multilayer heat shrink film, packaging article, packaging process and process to produce an annular

专利摘要:
DELAMINATION RESISTANT MULTILAYER HEAT-SHRINKABLE OXYGEN BARRIER FILM CONTAINING POLYESTER. It is a first multilayer heat shrink film that has an outer polyester layer, an O2 barrier layer and a bonding layer between the polyester layer and the barrier layer. The second multilayer film, an outer polyester layer, an inner polyamide layer and a bonding layer between the polyester and polyamide layers. The binding layer comprises a styrene based polymer and the binding layer in the second film comprises a functional anhydride styrene based copolymer. Included are a packaging article comprising the film, a packaging process using the film, a process for making the film, and a packaged product comprising a packaging article produced from the film, with a product within the packaging.
公开号:BR112016009511B1
申请号:R112016009511-1
申请日:2014-11-01
公开日:2021-05-11
发明作者:Michael E. Broadus；Bryan FREEMAN；Randall L. Brush；J. Doug WILSON；Donny S. Kay；Kevin L. Mccormick；Sumita S. Ranganathan
申请人:Cryovac, Inc；
IPC主号:

专利说明:

[001] This application claims priority to the provisional application at USSN 61/976,850, filed on April 8, 2014, entitled "Heat-Shrinkable Multilayer Barrier Film Containing High Melt Point Polyester", which is incorporated herein in its entirety by way of reference. This application also claims priority to the provisional application at USSN 61/898,757, filed November 1, 2013, also entitled "Heat-Shrinkable Multilayer Barrier Film Containing High Melt Point Polyester", which is also incorporated herein in its entirety. by way of reference. This application also claims priority from the provisional application at USSN 62/055144, filed September 25, 2014, also entitled "Heat-Shrinkable Multilayer Film with Tie Layer Bonding Polyester to Polyamide", which is also incorporated herein in its all for reference. BACKGROUND
[002] Multilayer heat shrink films that have an oxygen barrier layer have been used for the vacuum packaging of oxygen sensitive products, including food products and particularly meat products. Upon evacuation of the atmosphere from the package, followed by sealing the closed package while under evacuation, the resulting closed package is then shrunk around the meat product. Shrinkage causes the film to shrink against the meat product, reducing the amount of excess film that projects away from the meat product, improving the appearance and function of the package.
[003] Meat and cheese products, as well as other food and non-food products, generate abrasion violation and perforation violation of the films in which the products are packaged. As a result, abrasion resistant tenacious films are needed to package many food and non-food products, particularly dense products and/or products with sharp edges, such as bone-in meat products.
[004] Heat-shrinkable oxygen barrier films that are shrinkable at relatively low temperature, have good heat sealability and relatively high strength, have been developed and used to package a wide variety of products, including meat products. However, these ethylene-based shrink films have been found to lack the abrasion and puncture resistance needed to package products that produce high levels of package tampering when handled, such as meat and cheese products. As a result, there is a need for more tamper resistant heat shrinkable multilayer films that have an oxygen barrier layer.
[005] The amount of tampering by abrasion and puncture varies with the product being packaged. Some products are highly tamper-evident due to the combination of product weight and shape, as well as any particularly sharp and/or hard portion locations on the product. Recently, patchless polyamide-based shrink bags have been marketed, these bags provide sufficient tamper resistance to package meat and cheese products, including some bone-in meat products. However, polyamide based heat shrink films have proven to be unstable during storage, transport and use. More particularly, polyamide-based films tend to shrink upon exposure to atmospheric moisture and/or heat experienced during storage and/or transport. This instability is problematic for subsequent use in packaging meat and other products. SUMMARY
[006] In an effort to develop a multilayer heat shrink oxygen barrier film that has improved tamper resistance and temperature stability for packaging meat and cheese products and other oxygen-sensitive food and non-food products, the inventors of the present invention conducted the research in an effort to develop a suitable packaging film that utilizes a film containing polyester in place of some or all of the polyamide used in prior art heat shrink oxygen barrier films. It was found that by replacing the polyester with some or all of polyamide, the polyester layers had the ability to provide adequate toughness and abrasion resistance and dimensional stability over time, along with a temperature stability superior to films with corresponding polyamide base.
[007] However, it has been found that it is difficult to bond polyester to other thermoplastic film layers for use in a heat shrink film. Most of the coextrudable bonding layers that have been used for bonding to the polyester are made up of ethylene copolymer grafted with maleic anhydride/methylacrylate (gEMA). It was found that bonding layers produced from g-EMA are not sufficient to prevent delamination between the polyester layer and (i) an inner layer comprising polyamide or (ii) an oxygen barrier layer produced from of ethylene/vinyl alcohol copolymer (EVOH). In such films, delamination has occurred at the interface between the polyester layer and the bonding layer. Delamination occurred through shrinkage of the film, and sometimes even during film manufacturing.
[008] A solution to the delamination problem was sought in the development of a film containing tenacious and tamper resistant heat shrinkable polyester that also exhibits the desired additional features of: (i) linear and total unrestricted shrinkage at 85°C of at least 10% using ASTM D 2732, (ii) low oxygen transmission rate, and (iii) heat sealing capability. This shear strength can produce delamination if it exceeds the level of adhesion to the adjacent layer.
[009] The investigation revealed that the reason for delamination during shrinkage was that, upon immersion in water at 85°C, the outer polyester layer was shrinking faster and with greater shrinkage resistance than the bonding layer and additional film layers. The sub-optimal bond strength between the inner bonding layer and the outer polyester layer was overcome by differences in the shrinkage rates of the layers, in combination with the high shrinkage strength of the polyester layer, resulting in delamination.
[0010] It has been found that the problem of delamination by shrinkage can be overcome by providing the inner bonding layer with a styrene-based polymer, such as styrene-ethylene-butylene-styrene copolymer. In multilayer shrink films that have an outer polyester layer and an inner oxygen barrier layer produced from EVOH, with no polyamide between the polyester layer and the EVOH layer, it was found that delamination can be avoided with use of a styrene-based polymer that does not need to contain anhydride functionality. However, in films in which the bonding layer was directly adhered to both the outer polyester layer and the inner polyamide layer, it was found that an anhydride-functional styrene-based polymer was necessary to prevent delamination of the film by shrinkage.
[0011] It is not known exactly why the styrene-based polymer avoids delamination. However, factors that can encompass this result include providing the inner bonding layer with greater elasticity, as well as providing the inner bonding layer with greater bond strength to the outer polyester layer.
[0012] A first aspect relates to a multilayer heat shrink film comprising: (i) a first layer comprising a first polyester, (ii) a second layer serving as an O2 barrier layer, and (iii) a third layer between the first layer and the second layer. The first layer is an outer film layer. The second layer comprises at least one member selected from the group consisting of saponified ethylene/vinyl acetate copolymer, polyamide MXD6, polyamide 6I/6T, polyamide 6, polyvinylidene chloride, polyethylene naphthalate, polytrimethylene terephthalate, polyamide polymer. liquid crystal and O2 sequestrant. The third layer serves as a binding layer and comprises at least one styrene-based copolymer. The multilayer heat shrink film exhibits a total linear shrinkage at 85°C of at least 10% measured according to a linear shrinkage test modified otherwise according to ASTM D 2732. Polyester is present in the film in an amount of at least 2% by volume, based on total film volume.
[0013] In one embodiment, the third layer (ie, the bonding layer) is directly adhered to the first layer.
[0014] In one embodiment, the film does not have a layer comprising a polyamide between the first layer and the second layer.
[0015] In one embodiment, the styrene-based polymer constitutes from 10 to 100% by weight of the weight of the third layer.
[0016] In one embodiment, the third layer comprises the styrene-based polymer in an amount of at least 5% by weight, based on the weight of the layer; or from 5 to 100% by weight, or from 8 to 100% by weight, or from 10 to 100% by weight, or from 10 to 90% by weight, or from 10 to 80% by weight, or from 10 to 60 % by weight, or from 10 to 40% by weight, or from 10 to 30% by weight, or from 10 to 25% by weight, or from 10 to 20% by weight, or from 10 to 15% by weight, or from 50 to 100% by weight, or from 60 to 90% by weight, based on the weight of the layer.
[0017] In one embodiment, the styrene-based polymer comprises at least one member selected from the group consisting of styrene-ethylene-butylene-styrene copolymer, styrene-butadiene-styrene copolymer, styrene-isoprene copolymer- styrene, styrene-ethylene-butadiene-styrene copolymer, styrene-(ethylene-propylene rubber)-styrene copolymer and polystyrene-poly(ethylene-propylene)-polystyrene copolymer.
[0018] In one embodiment, the third layer comprises a combination of the styrene-based copolymer and at least one member selected from cyclic olefin copolymer and ethylene/unsaturated ester copolymer.
[0019] In one embodiment, the third layer comprises a combination of a styrene-based polymer and an acrylate-based polymer. In one embodiment, the styrene-based polymer constitutes from 5 to 95% by weight of the blend, and the acrylate-based polymer constitutes from 5 to 95% by weight of the blend, and the styrene-based polymer and the acrylate-based polymer acrylate base together constitute at least 70% by weight of the combination.
[0020] In one embodiment, the styrene-based polymer constitutes from 5 to 40% by weight of the blend, and the acrylate-based polymer constitutes from 60 to 95% by weight of the blend.
[0021] In one embodiment, the styrene-based polymer constitutes from 10 to 20% by weight of the blend, and the acrylate-based polymer constitutes from 80 to 90% by weight of the blend.
[0022] In an embodiment in which the third layer comprises a combination of the styrene-based polymer and a cyclic polymer, the styrene-based polymer may constitute 5 to 95% by weight of the combination, and the cyclic polymer constitutes 5 to 95% by weight of the blend, the styrene-based polymer and the cyclic polymer together making up at least 70% by weight of the blend. In one embodiment, the styrene-based polymer constitutes from 60 to 95% by weight of the blend, and the cyclic polymer constitutes from 5 to 40% by weight of the blend. In one embodiment, the styrene-based polymer constitutes from 80 to 90% by weight of the blend, and the cyclic polymer constitutes from 10 to 20% by weight of the blend.
[0023] In one embodiment, the third layer comprises a combination of the styrene-based polymer and the modified polyolefin. In one embodiment, the styrene-based polymer constitutes from 5 to 95% by weight of the blend, and the modified polyolefin constitutes from 5 to 95% by weight of the blend, and the styrene-based polymer and the modified polyolefin together, constitute at least 70% by weight of the combination. In one embodiment, the styrene-based polymer constitutes from 5 to 40% by weight of the blend, and the modified polyolefin constitutes from 60 to 95% by weight of the blend. In one embodiment, the styrene-based polymer constitutes from 10 to 20% by weight of the blend, and the modified polyolefin constitutes from 80 to 90% by weight of the blend.
[0024] In one embodiment, the third layer comprises a combination of a styrene-based polymer, an acrylate-based polymer and a cyclic polymer. In one embodiment, the styrene-based polymer constitutes from 5 to 90% by weight of the blend, the acrylate-based polymer constitutes from 5 to 90% by weight of the blend, and the cyclic polymer constitutes from 5 to 90% by weight of the blend. of the combination, and the styrene-based polymer, the acrylate-based polymer, and the cyclic polymer together constitute at least 70% by weight of the combination. The styrene-based polymer constitutes from 5 to 40% by weight of the blend, the acrylate-based polymer constitutes from 20 to 90% by weight of the blend, and the cyclic polymer constitutes from 5 to 40% by weight of the blend. The styrene-based polymer constitutes from 10 to 20% by weight of the blend, the acrylate-based polymer constitutes from 30 to 80% by weight of the blend, and the cyclic polymer constitutes from 10 to 20% by weight of the blend.
[0025] In one embodiment, the third layer comprises a combination of the styrene-based polymer, an acrylate-based polymer and the modified polyolefin. In one embodiment, the styrene-based polymer constitutes from 5 to 90% by weight of the blend, the acrylate-based polymer constitutes from 5 to 90% by weight of the blend, and the modified polyolefin constitutes from 5 to 90% by weight. of the combination, and the styrene-based polymer, the acrylate-based polymer and the modified polyolefin together constitute at least 70% by weight of the combination. The styrene-based polymer constitutes from 5 to 40% by weight of the blend, the acrylate-based polymer constitutes from 20 to 90% by weight of the blend, and the modified polyolefin constitutes from 5 to 40% by weight of the blend. The styrene-based polymer constitutes from 10 to 20% by weight of the blend, the acrylate-based polymer constitutes from 30 to 80% by weight of the blend, and the modified polyolefin constitutes from 10 to 20% by weight of the blend.
[0026] In one embodiment, the third inner layer comprises a combination of the styrene-based polymer, a cyclic polymer and a modified olefin copolymer. In one embodiment, the styrene-based polymer constitutes from 5 to 90% by weight of the blend, the cyclic polymer constitutes from 5 to 90% by weight of the blend, and the modified olefin copolymer constitutes from 5 to 90% by weight of the combination, and the styrene-based polymer, the cyclic polymer and the modified polyolefin together constitute at least 70% by weight of the combination. The styrene-based polymer constitutes from 5 to 40% by weight of the blend, the cyclic polymer may constitute from 20 to 90% by weight of the blend, and the modified olefin copolymer constitutes from 5 to 40% by weight of the blend. The styrene-based polymer constitutes from 10 to 20% by weight of the blend, the cyclic polymer constitutes from 30 to 80% by weight of the blend, and the modified olefin copolymer constitutes from 10 to 20% by weight of the blend.
[0027] In one embodiment, the third inner layer comprises a combination of a styrene-based polymer, an acrylate-based polymer, a cyclic polymer and a modified polyolefin. In one embodiment, the styrene-based polymer constitutes from 5 to 85% by weight of the blend, the acrylate-based polymer constitutes from 5 to 85% by weight of the blend, the cyclic polymer constitutes from 5 to 85% by weight of the blend. blend, and the modified polyolefin constitutes from 5 to 85% by weight of the blend, whereby the styrene-based polymer, the acrylate-based polymer, the cyclic polymer and the modified polyolefin together constitute at least 70% by weight of the combination. In one embodiment, the styrene-based polymer constitutes from 10 to 40% by weight of the blend, the acrylate-based polymer constitutes from 10 to 40% by weight of the blend, the cyclic polymer constitutes from 10 to 40% by weight of the blend. blend, and the modified polyolefin constitutes from 10 to 40% by weight of the blend. In one embodiment, the styrene-based polymer constitutes from 10 to 20% by weight of the blend, the acrylate-based polymer constitutes from 10 to 80% by weight of the blend, the cyclic polymer constitutes from 5 to 20% by weight of the blend. blend, and the modified polyolefin constitutes from 10 to 80% by weight of the blend.
[0028] In one embodiment, the cyclic olefin copolymer comprises ethylene/norbornene copolymer.
[0029] In one embodiment, the combination further comprises at least one member selected from the group consisting of a second polyester and a modified polyolefin.
[0030] In one embodiment, the second polyester comprises a copolyester, and the combination comprises: (i) at least one member selected from the group consisting of styrene-ethylene-butylene-styrene block copolymer and styrene block copolymer. styrene-butadiene, (ii) ethylene/acrylate copolymer; and (iii) at least one member selected from the group consisting of copolyester and anhydride modified polyolefin.
[0031] In one embodiment, the combination comprises: (i) from 10 to 90% by weight, based on the total weight of the combination, of at least one member selected from the group consisting of styrene-ethylene triblock copolymer -butylene-styrene and styrene-butadiene multiblock copolymer; (ii) ethylene/methyl acrylate copolymer in an amount of 10 to 90% by weight, based on the total weight of the combination; and (iii) from 5 to 30% by weight, based on the total weight of the blend, of at least one member selected from the group consisting of amorphous copolyester having a melting point of 100°C to 185°C, and anhydride-modified ethylene/alpha-olefin copolymer.
[0032] In one embodiment, the copolyester is a linear, saturated, thermoplastic, semi-crystalline copolyester that has a density of 1.15 to 1.30 g/cm3, a melting point of 115°C to 125°C, and an index pour from 0.5 to 2 g/10 min.
[0033] In one embodiment, the blend comprises from 5 to 15% by weight, based on the total weight of the blend, of at least one member selected from the group consisting of copolyester having a melting point of 105°C at 140°C and anhydride modified linear low density polyethylene.
[0034] In an embodiment wherein the binding layer comprises a modified polyolefin, the modified polyolefin may comprise at least one member selected from the group consisting of a grafted anhydride functionality, a copolymerized anhydride functionality and a combination of the polyolefin and another polymer that has an anhydride functionality.
[0035] In an embodiment wherein the binding layer comprises an acrylate-based polymer, the acrylate-based polymer may comprise at least one member selected from the group consisting of ethylene/methyl acrylate copolymer, copolymer of ethylene/ethyl acrylate, ethylene/butyl acrylate copolymer and ethylene/vinyl acetate copolymer.
[0036] In an embodiment wherein the binding layer comprises a cyclic polymer, the cyclic polymer may comprise at least one member selected from the group consisting of ethylene/norbornene copolymer and ethylene/tetracyclododecene copolymer and cyclic olefin polymer .
[0037] In one embodiment, the second layer comprises saponified ethylene vinyl acetate copolymer.
[0038] In one embodiment, the first polyester comprises at least one semi-crystalline polyester selected from the group consisting of polyethylene terephthalate homopolymer, polyethylene terephthalate copolymer, polybutylene terephthalate homopolymer, polybutylene terephthalate copolymer, polybutylene terephthalate homopolymer. polynaphthalene terephthalate, polynaphthalene terephthalate copolymer, polyethylene furanoate homopolymer and polyethylene furanoate copolymer, wherein the semicrystalline polyester has a melting point of 80°C to 265°C.
[0039] In one embodiment, the first polyester comprises polyethylene terephthalate homopolymer having a melting point of at least 240°C.
[0040] In one embodiment, the polyethylene terephthalate homopolymer has a melting point of at least 240°C and is present in the first layer in an amount of at least 95% by weight, based on the weight of the first layer.
[0041] In one embodiment, the first polyester comprises amorphous polyester.
[0042] In one embodiment, the polyester has a melting point of at least 240°C and is present in the film in an amount that constitutes at least 25% by volume of the film and comprises at least one member selected from the group that consists of polyethylene terephthalate and polyethylene furanoate.
[0043] In one embodiment, at least 50% by weight of polyester in the film is present in the outer film layer, based on the total polyester in the film, or at least 60% by weight of the polyester is present in the outer film layer, or at least 70% by weight of the polyester is present in the outer film layer, or at least 80% by weight of the polyester is present in the outer film layer, or at least 90% by weight of the polyester is present in the outer film layer , or at least 95% by weight of the polyester is present in the outer film layer, or 100% by weight of the polyester is present in the outer film layer, based on the total polyester in the film.
[0044] In one embodiment, the film does not have an inner layer comprising polyester. In one embodiment, polyester is a copolyester.
[0045] In one embodiment, the film has an inner layer comprising polyester, and the polyester is in an interpenetrating polymer network. In an alternative embodiment, the film has an inner layer that comprises polyester, but polyester that is not in an interpenetrating polymer network.
[0046] In one embodiment, the multilayer heat shrink film has a thickness of 17.78 µm to 254 µm (0.7 mil to 10 mils), or 25.4 µm to 203.2 µm (1 mil to 8 mils). ), or from 27.94 μm to 177.8 μm (1.1 thousand to 7 mils), or from 30.48 μm to 152.4 μm (1.2 mil to 6 mils), or 30.48 μm to 127 μm (1.2 mil to 5 mils), or from 33.02 μm to 101.6 μm (1.3 to 4 mils), or from 35.56 μm to 88.9 μm (1.4 to 3 .5 mils), or from 33.02 μm to 43.18 μm (1.3 to 1.7 mils), or from 50.8 μm to 101.6 μm (2 to 4 mils), or 63.5 µm to 76.2 µm (2.5 to 3 mils) or from 30.48 µm to 101.6 µm (1.2 to 4 mils).
[0047] In one embodiment, polyester that has a melting point of at least 240°C constitutes from 25 to 80% by volume of the film, or from 25 to 70% by volume of the film, or from 25 to 60% by volume film volume, or 25 to 50% by film volume, or 27 to 49% by film volume, or 28 to 47% by film volume, or 29 to 46% by film volume.
[0048] In one embodiment, the multilayer heat shrink film has a total linear shrinkage at 85°C from 10% to 130%, measured according to a modified linear shrinkage test, otherwise according to ASTM D 2732, or a total linear shrinkage at 85°C from 20% to 100%, or a total linear shrinkage at 85°C from 70% to 110%, or a total linear shrinkage at 85°C from 30% to 90%, or a total linear shrinkage at 85°C from 40% to 80%, or a total linear shrinkage of at least 15% at 85°C, or a total linear shrinkage of at least 20% at 85°C, or a total linear shrinkage of at least 30% at 85°C, or a total linear shrinkage of at least 40% at 85°C, or a total linear shrinkage of at least 50% at 85°C.
[0049] In one embodiment, the multilayer film does not exhibit visible delamination when subjected to linear and unrestricted shrinkage upon immersion in water at 85°C for 8 seconds, using ASTM D 2736.
[0050] In one embodiment, the film exhibits a total linear shrinkage at 85°C of at least 30% measured according to the modified linear shrinkage test, otherwise according to ASTM D 2732, and the first polyester is present in the film in an amount of at least 15% by volume, based on the total film volume.
[0051] In one embodiment, the multilayer heat shrink film exhibits a total linear shrinkage at 85°C of 40% to 90% measured in accordance with the modified linear shrinkage test, otherwise in accordance with ASTM D 2732, and the first polyester is present in the film in an amount of at least 20% by volume, based on total film volume.
[0052] In one embodiment, the multilayer film exhibits a shrinkage stress of at least 3.1 MPa measured in accordance with ASTM D2838-09, or at least 3.5 MPa, or at least 4 MPa, or at least 5 MPa, measured in accordance with ASTM D2838-09.
[0053] In one embodiment, the multilayer heat shrink film further comprises a fourth layer which is the second outer layer and which serves as a heat seal layer and which comprises at least one member selected from the group consisting of polyolefin, polyamide , polyester, polyvinyl chloride and ionomer resin.
[0054] In one embodiment, the heat seal layer comprises at least one member selected from the group consisting of polyolefin, polyamide 6/12, polyamide 12, ionomer resin, ethylene/unsaturated acid copolymer, ethylene/ethylene copolymer. unsaturated ester, polyester having a melting point of up to 150°C, homogeneous ethylene/alpha-olefin copolymer, heterogeneous ethylene/alpha-olefin copolymer, ethylene homopolymer, ethylene/vinyl acetate copolymer, and ionomer resin .
[0055] In one embodiment, the thermal seal layer constitutes from 5 to 40 percent by volume, based on the volume of the total film, or from 10 to 30 percent by volume, from 15 to 25 percent by volume, or from 10 to 60 percent by volume, based on total movie volume, or 15 to 55 percent by volume, or 17 to 50 percent by volume, or 19 to 46 percent by volume, based on total movie volume.
[0056] In one embodiment, the thermal sealing layer additionally comprises a slip agent and an anti-blocking agent.
[0057] In one embodiment, the heat seal layer comprises a combination of a homogeneous ethylene/alpha-olefin copolymer (eg having a density of 0.89 to 0.91 g/cm3) and an ethylene copolymer /heterogeneous alpha-olefin (eg LLDPE).
[0058] In one embodiment, the heat seal layer comprises a combination of 75 to 90% by weight of homogeneous ethylene/alpha-olefin copolymer having a density of 0.895 to 0.905 g/cm3, and 10 to 25% in weight of a heterogeneous ethylene/alpha-olefin copolymer having a density of 0.915 to 0.925 g/cm3.
[0059] In one embodiment, the third layer is a first third layer and the multilayer heat shrink film additionally comprises a fifth layer that is between the fourth layer and the second layer, with the fifth layer serving as a second bonding layer, wherein the fifth layer comprises at least one member selected from the group consisting of modified polyolefin, modified ethylene/unsaturated acid copolymer, ethylene/modified unsaturated ester copolymer and polyurethane. In one embodiment, the second tie layer can comprise an anhydride modified linear low density polyethylene.
[0060] In one embodiment, the second bonding layer comprises a combination of 50 to 85% by weight of a modified ethylene/alpha-olefin copolymer with 50 to 15% by weight of a modified ethylene/vinyl acetate copolymer having a vinyl acetate content of 6 to 15% by weight.
[0061] In one embodiment, the multilayer heat shrink film additionally comprises a sixth layer that is between the second layer and the fifth layer, the sixth layer comprising at least one member selected from the group consisting of (i) a amorphous polyamide, (ii) a combination of a semicrystalline polyamide and amorphous polyamide, and (iii) a combination of 6/12 polyamide and a different semicrystalline polyamide. The sixth layer gives the multi-layer heat shrink film toughness and additional impact strength.
[0062] In one embodiment, the sixth layer comprises a combination of amorphous polyamide and polyamide 6, or a combination of amorphous polyamide and polyamide 6/66.
[0063] In one embodiment, the sixth layer comprises a combination of (i) from 60 to 95% by weight of at least one member selected from the group consisting of polyamide 6 and polyamide 6/66, and (ii) of 5 to 40% by weight of 6I/6T polyamide.
[0064] In one embodiment, the sixth layer constitutes 1 to 40 percent of the total film thickness, or 3 to 20 percent of the total film thickness, or 3 to 10 percent of the total film thickness, or 4 to 6 percent of total film thickness.
[0065] In one embodiment, the sixth layer comprises a combination of polyamide 6/66 or polyamide 6 and polyamide 6I/6T. The combination may comprise from 50 to 95% by weight of polyamide 6/66 or polyamide 6 and from 5 to 50% by weight of polyamide 6I/6T, or from 60 to 95% by weight of polyamide 6/66 or polyamide 6 and from 5 to 40% by weight of polyamide 6I/6T, or from 70 to 95% by weight of polyamide 6/66 or polyamide 6 and from 5 to 30% by weight of polyamide 6I/6T, or from 80 to 95% in weight of polyamide 6/66 or polyamide 6 and from 5 to 20% by weight of polyamide 6I/6T, or from 85 to 95% by weight of polyamide 6/66 or polyamide 6 and from 5 to 15% by weight of polyamide 6I /6T.
[0066] In one embodiment, the film contains polyamide in an amount less than 10 percent by weight, based on the weight of the total film, based on the weight of the total film, or in an amount less than 9 percent by weight, or in an amount less than 8 percent by weight, or in an amount less than 7 percent by weight, or in an amount less than 6 percent by weight, or in an amount of 1 to 6 percent by weight, based in total film weight.
[0067] In one embodiment, the film does not contain polyamide.
[0068] In one embodiment, the film does not comprise an inner layer comprising polyamide.
[0069] In one embodiment, the film does not comprise an outer layer comprising polyamide.
[0070] In one embodiment, the third layer is the only layer on the film that comprises a styrene-based polymer.
[0071] In one embodiment, the film has only one layer comprising a styrene-based polymer.
[0072] In one embodiment, the multilayer heat shrink film further comprises a complementary bonding layer between the second layer and the third layer, wherein the complementary bonding layer comprises at least one member selected from the group consisting of modified polyolefin , modified acid copolymer, modified ester copolymer and polyurethane.
[0073] In one embodiment, the complementary bonding layer comprises a combination of 50 to 85% by weight of a modified ethylene/alpha-olefin copolymer with 50 to 15% by weight of a modified ethylene/vinyl acetate copolymer having a vinyl acetate content of 6 to 15% by weight. In one embodiment, the complementary bonding layer is directly adhered to the third layer and directly adhered to the second layer.
[0074] In one embodiment, the complementary binding layer comprises at least one member selected from the group consisting of ethylene/modified alpha-olefin copolymer, ethylene/modified unsaturated ester copolymer, and ethylene/modified unsaturated acid copolymer.
[0075] In one embodiment, the modified polyolefin comprises anhydride modified linear low density polyethylene. The anhydride modified linear low density polyethylene may constitute at least 80% by weight of the complementary tie layer, or at least 90% by weight of the complementary tie layer, or at least 95% by weight of the complementary tie layer or 100 % by weight of the complementary bonding layer.
[0076] In one embodiment, the multilayer heat shrink film is a seamless tubing that has an extended flat width of 40 to 1,000 millimeters, a thickness of 25.4 to 50.8 μm (1 to 2 mils), and a shrinkage total linear at 85°C from 40% to 90% measured in accordance with a modified linear shrinkage test otherwise in accordance with ASTM D 2732.
[0077] In one embodiment, the multilayer heat shrink film is a seamless tubing that has an extended flat width of 300 to 1000 millimeters, a thickness of 50.8 to 127 µm (2 to 5 mils), and a total linear shrinkage at 85°C from 40% to 90% measured according to a modified linear shrinkage test otherwise according to ASTM D 2732.
[0078] A second aspect relates to an article of packaging comprising a heat-shrinkable multilayer film thermally sealed thereto. The multilayer film conforms to the first aspect, described above, as well as any and all combinations of non-conflicting modalities of the first aspect, described above. The packaging article is a member selected from the group consisting of end seal bag, side seal bag, L-seal bag, back seam bag and bag.
[0079] A third aspect relates to a packaging process comprising: (a) providing a filament of a flat, heat shrinkable multilayer film, in accordance with the first aspect described above (as well as any and all combination of non-conflicting modalities of the first aspect described above), (b) using the film in a flow wrap process to produce a partially packaged product comprising a back-seamed packaging article having a bottom seal and an open top, the article The packaging article has a product therein, (c) evacuating the atmosphere from within the packaging article and sealing the open top of the packaging article closed so that the product is surrounded by the packaging article, and (d) shrinking the article around the product.
[0080] In one embodiment, the process is performed intermittently, and the packaging article has a first portion of the back seam produced before the process is stopped, and a second portion of the back seam produced after the process is stopped, and the packaging article has a breaking strength as high as the breaking strength of a corresponding packaging, where the entire back seam has been produced continuously without interruption.
[0081] In one embodiment, the process is performed intermittently, and the packaging article has a first portion of the back seam produced before the process is stopped, and a second portion of the back seam produced after the process is stopped, and the packaging article has a tear strength at least 95 percent as high as the tear strength of a corresponding packaging, where the entire back seam has been produced continuously without interruption, or at least 90 percent as high, or at least 85 percent as high, or at least 80 percent as high, or at least 75 percent as high, or at least 70 percent as high as the tear strength of a corresponding package, where the entire back seam was produced continuously without interruption.
[0082] A fourth aspect relates to a process for producing an annular heat shrink film comprising: (I) coextruding an annular multilayer extrudate down from an annular matrix, (II) quenching the annular extrudate by applying a liquid quenching the annular extrudate, (III) reheating the extrudate to an orientation temperature of 54°C to 99°C, which results in a reheated annular extrudate, and (IV) orienting the reheated annular extrudate while the reheated annular extrudate is in solid state, the orientation being performed with a total orientation factor of at least 2, so that an oriented multilayer heat shrink film is produced. The coextruded annular extrudate comprises: (a) a first layer comprising a first polyester, the first layer being an outer layer, (b) a second layer serving as an O2 barrier layer, the second layer comprising at least one member selected from the group consisting of saponified ethylene/vinyl acetate copolymer, polyamide MXD6, polyamide 6I/6T, polyamide 6, polyvinylidene chloride, polyethylene naphthalate, polytrimethylene terephthalate, liquid crystal polymer and scavenger of O2, and (c) a third layer between the first layer and the second layer, the third layer serving as a binding layer, the third layer comprising at least one styrene-based copolymer. The orientation is performed so that the oriented multilayer heat shrink film exhibits a total linear shrinkage at 85°C of at least 10 percent, measured in accordance with a modified linear shrinkage test otherwise in accordance with ASTM D 2732, and the first polyester is present in the film in an amount of at least 2% by volume, based on the total film volume. The process can be carried out such that the oriented multilayer heat shrink film conforms to the first aspect, described above, including any and all combinations of non-conflicting embodiments of the first aspect, described above.
[0083] In one embodiment, the quench liquid absorbs heat from the annular extrudate as at least 50% of the quench liquid falls below the annular extrudate for a distance of at least 5.08 cm (2 inches), being that the sudden coolant makes initial contact with the annular extrudate at a distance of 0.254 to 20.32 cm (0.1 to 8 inches) downstream of a point at which the annular extrudate emerges from the annular die. This process can be performed as illustrated in Figure 15, described below.
[0084] Alternatively, the process may be carried out as illustrated and described in USPN 7,744,806, to Broadus et al, entitled "Process for Making Shrink Film Compressing Rapidly-Quenched Semi-Crystalline Polyamide", which is incorporated herein. in its entirety as a reference. Refer particularly to the apparatus illustrated in Figures 2A, 2C, 3 and 4 thereof, and portions of the specification describing the same.
[0085] In one embodiment, the process further comprises annealing the multilayer heat shrink film after it has been oriented in the solid state.
[0086] In one embodiment, all layers of the multilayers are simultaneously co-extruded.
[0087] A fifth aspect relates to a packaged product comprising a packaging article produced from a multilayer heat shrink film and a product comprising food within the package. The multilayer heat shrink film conforms to the first aspect, described above, including any and all combinations of non-conflicting modalities of the first aspect described above.
[0088] A sixth aspect relates to a multilayer heat shrink film that has (A) a first outer layer that contains polyester, (B) a second outer layer that serves as a heat seal layer, (C) a first inner layer which comprises a polyamide, and (D) a second inner layer which is between the first inner layer and the first outer layer and which serves as a bonding layer for bonding the first outer layer to the inner polyamide layer. The second inner layer comprises a combination of: (i) a first combination component comprising an anhydride functional polyolefin; (ii) a second combination component comprising at least one member selected from the group consisting of styrene/maleic anhydride copolymer, anhydride-functional styrene-ethylene-butylene-styrene copolymer, anhydride-functional styrene-butylene-styrene copolymer as anhydride, anhydride functional styrene-isoprene-styrene copolymer, anhydride functional styrene-ethylene-butadiene-styrene copolymer and anhydride functional styrene(ethylene-propylene rubber)-styrene graft copolymer; and (iii) a third blending component comprising a second polyester. The multilayer heat shrink film exhibits a total linear shrinkage at 85°C of at least 10 percent measured according to an otherwise modified shrinkage test in accordance with ASTM D 2732. The first polyester is present in the film in an amount of at least 5% by volume, based on total film volume.
[0089] In one embodiment, the first inner layer comprises at least one member selected from the group consisting of: (a) a combination of a semicrystalline polyamide and an amorphous polyamide; (b) a combination of a semicrystalline polyamide and 6/12 polyamide; and (c) 100% amorphous polyamide.
[0090] In one embodiment, the first combination component comprises an anhydride functional ethylene/alpha-olefin copolymer and the anhydride functional second combination component comprises anhydride functional styrene/butadiene block copolymer.
[0091] In one embodiment, the third component of the blend comprises a linear, thermoplastic, semi-crystalline saturated polyester resin having a density of 1.15 to 1.30 g/cm3, a melting point of 150°C to 160° C, and a melt index of 0.5 to 2 g/10 min.
[0092] In one embodiment, the first outer layer constitutes from 5 to 20% by volume based on the volume of the total film, the second outer layer constitutes from 15 to 40% by volume based on the volume of the total film, the first layer inner layer constitutes 10-30% by volume based on total film volume, and the second inner layer constitutes 10-30% by volume based on total film volume.
[0093] In one embodiment, the film has a total thickness of 38.1 µm to 101.6 µm (1.5 mils to 4 mils), or from 50.8 µm to 88.9 µm (2 to 3.5 mils) or from 63.5 µm to 76.2 µm (2.5 to 3 mils).
[0094] In one embodiment, the first component of the combination constitutes from 30 to 80% by weight based on the weight of the total layer, the second component of the combination constitutes from 10 to 50% by weight based on the weight of the total layer, and the third component of the blend constitutes from 2 to 20% by weight based on the weight of the total layer.
[0095] In one embodiment, the first combination component constitutes from 40 to 70% by weight based on the weight of the total layer, the second combination component constitutes from 20 to 40% by weight based on the weight of the total layer, and the third component of the blend constitutes from 5 to 15% by weight based on the weight of the total layer.
[0096] In one embodiment, the first polyester comprises polyethylene terephthalate that has a melting point of at least 240°C.
[0097] In one embodiment, the second inner layer is directly adhered to both the first outer layer and the first inner layer.
[0098] In one embodiment, the film exhibits a total linear shrinkage at 85°C of at least 20 percent measured in accordance with a modified shrinkage test (disclosed below), otherwise in accordance with ASTM D 2732; or at least 30 percent, or at least 40 percent, or at least 50 percent, or at least 55 percent, or at least 60 percent, in accordance with the otherwise modified shrinkage test in accordance with ASTM D 2732.
[0099] In one embodiment, the second outer layer that serves as the heat seal layer comprises at least one member selected from the group consisting of polyolefin, polyamide 6/12, polyamide 12, ionomer resin, ethylene copolymer/ unsaturated acid, ethylene/unsaturated ester copolymer and polyester which has a melting point of up to 150°C.
[00100] In one embodiment, the thermal sealing layer additionally comprises a slip agent and an anti-blocking agent.
[00101] In one embodiment, the second outer layer comprises a homogeneous ethylene/alpha-olefin copolymer having a density of 0.89 to 0.91 g/cm3.
[00102] In one embodiment, the film further comprises (E) a third inner layer that serves as an O2 barrier layer, the third inner layer comprising at least one member selected from the group consisting of ethylene/copolymer saponified vinyl acetate, polyamide MXD6, polyamide 6I/6T, polyamide 6, polyvinylidene chloride, polyethylene naphthalate, polytrimethylene terephthalate, liquid crystal polymer, and O2 scavenger. The third inner layer is between the first inner layer and the second outer layer.
[00103] In one embodiment, the film further comprises (F) a fourth inner layer that serves as a second bonding layer, the fourth inner layer being between the second outer layer and the third inner layer, and (G) a fifth inner layer between the third inner layer and the fourth inner layer, the fifth inner layer comprising a combination of at least one member selected from the group consisting of: (a) a combination of a semi-crystalline polyamide and an amorphous polyamide, (b) a combination of a semicrystalline polyamide and 6/12 polyamide, and (c) 100% amorphous polyamide.
[00104] In an embodiment, the first inner layer and the fifth inner layer have the same composition. In one embodiment, the first inner layer and the fifth inner layer have different compositions.
[00105] In one embodiment, the first inner layer and the fifth inner layer have the same thickness. In one embodiment, the first inner layer and the fifth inner layer have different ones.
[00106] In one embodiment, the first inner layer and the fifth inner layer have the same composition and have the same thickness.
[00107] In one embodiment, the third inner layer, which is an O2 barrier layer, is directly adhered to both the first inner layer and the fifth inner layer.
[00108] In one embodiment, the polyester in the first outer layer comprises polyethylene terephthalate copolymer in an amount of at least 95% by weight, based on the weight of the total layer. In combination therewith, the second outer layer may comprise a blend of 75 to 90% by weight of homogeneous ethylene/alpha-olefin copolymer having a density of 0.895 to 0.905 g/cm3 and 10 to 25% by weight of a heterogeneous ethylene/alpha-olefin copolymer having a density of 0.915 to 0.925 g/cm3. In combination therewith, the first inner layer may comprise a combination of (a) from 60 to 95% by weight of at least one member selected from the group consisting of polyamide 6 and polyamide 6/66, and (b) from 5 to 40% by weight of 6I/6T polyamide. In combination therewith, the second inner layer may comprise (i) from 50 to 70% by weight of an anhydride functional ethylene/alpha-olefin copolymer, (ii) from 20 to 40% by weight of styrene block copolymer /butadiene functional as anhydride; and (iii) from 5 to 15% by weight of polyester. In combination therewith, the third inner layer may comprise saponified ethylene-vinyl acetate copolymer. In combination therewith, the fourth inner layer may comprise an anhydride grafted ethylene/alpha-olefin copolymer. In combination therewith, the inner fifth layer may comprise a combination of (i) from 60 to 95% by weight of at least one member selected from the group consisting of polyamide 6 and polyamide 6/66, and (ii) from 5 to 40% by weight of 6I/6T polyamide.
[00109] In one embodiment, the first outer layer constitutes 5 to 15% in volume based on the volume of the total film, the second outer layer constitutes 15 to 25% in volume based on the volume of the total film, the first layer inner layer is 10 to 20% by volume based on total film volume, second inner layer is 10 to 20% by volume based on total film volume, third inner layer is 2 to 10% by volume with Based on total film volume, the inner fourth layer constitutes 20-30% by volume based on the total film volume, and the inner fifth layer constitutes 10-20% by volume based on the total film volume.
[00110] A seventh aspect refers to a process for producing a fully coextruded heat shrink annular film. The process comprises (I) co-extruding through layers of annular matrix film (A), (B), (C) and (D), i.e. the layers according to the sixth aspect, (II) abruptly cooling the extrudate , (III) reheating the extrudate, and (IV) orienting the extrudate. The quenching (II) of the annular extrudate is carried out by applying a coolant to the annular extrudate. Reheating (III) of the extrudate is accomplished by reheating the extrudate to an orientation temperature of 54.44°C to 98.88°C (130°F to 210°F), which results in a reheated annular extrudate. Orientation (IV) of the annular extrudate is performed by orienting the reheated annular extrudate while the reheated annular extrudate is in the solid state, with the orientation being performed with a total orientation factor of at least 2, so that a thermally heated film of Oriented multilayer is produced. The orientation is performed so that the oriented multilayer heat-heated film exhibits a total linear shrinkage at 85°C of at least 40 percent measured according to an otherwise modified shrinkage test in accordance with ASTM D 2732. The first Polyester is present in the film in an amount of at least 5% by volume, based on the total film volume. Extrusion can be carried out according to any of the modalities of the sixth aspect described herein.
[00111] In one embodiment, the coextrusion may include layers (A), (B), (C) and (D) in combination with layer (E). In an alternative embodiment, the coextrusion may include layers (A), (B), (C) and (D) in combination with layers (E), (F) and (G).
[00112] In one mode, the orientation is performed with a total orientation factor of at least 5, or at least 6, or at least 7 or at least 8. The total orientation factor is the orientation factor in the machine direction multiplied by the orientation factor in the transverse direction. For example, if the reheated extrudate is stretched 2.5X in the machine direction and 2.7X in the cross direction, the total orientation factor is about 6.75X.
[00113] In one embodiment, the quench liquid absorbs heat from the annular extrudate as at least 50% of the quench liquid falls below the annular extrudate for a distance of at least 5.08 cm (2 inches), with the sudden coolant making initial contact with the annular extrudate at a distance of 0.254 to 20.32 cm (0.1 to 8 inches) downstream of a point at which the annular extrudate emerges from the annular die.
[00114] An eighth aspect relates to a packaging process comprising: (A) providing a filament of a flat, heat shrinkable multilayer film according to the sixth aspect, described above; (B) using the film in a flow wrap process to produce a partially packaged product comprising a back-seamed packaging article that has a bottom seal and an open top, the packaging article having a product therein. ; (C) evacuating the atmosphere from within the packaging article and sealing the open top of the packaging article closed so that the product is surrounded by the packaging article; and (D) shrink the packaging article around the product.
[00115] In one embodiment, the process is carried out intermittently, and the packaging article has a first portion of the back seam produced before the process is interrupted and a second portion of the back seam produced after the process is interrupted.
[00116] A ninth aspect refers to an article of packaging produced from a film according to the sixth aspect. The packaging article is a member selected from the group consisting of end seal bag, side seal bag, L-seal bag and bag.
[00117] A tenth aspect refers to a packaged product comprising a packaging article produced from a film according to the sixth aspect. The packaging article surrounds a product comprising food. In one embodiment, the packaging article conforms to the ninth aspect. BRIEF DESCRIPTION OF THE FIGURES
[00118] Figure 1 is a schematic plan view of a bag with an end seal.
[00119] Figure 2 is a cross-sectional view of the bag with end seal of Figure 1, taken through section 2-2 of Figure 1.
[00120] Figure 3 is a schematic plan view of the bag with side seal.
[00121] Figure 4 is a cross-sectional view of the bag with side seal of Figure 3, taken through section 4-4 of Figure 3.
[00122] Figure 5 is a schematic plan view of an L-shaped sealing bag.
[00123] Figure 6 is a cross-sectional view of the L-shaped sealing bag of Figure 5, taken through section 6-6 of Figure 5.
[00124] Figure 7 is a longitudinal cross-sectional view of the L-shaped sealing bag of Figure 5, taken through section 7-7 of Figure 5.
[00125] Figure 8 is a schematic plan view of a backseam bag that has a flap seal backseam.
[00126] Figure 9 is a cross-sectional view of the back-seamed bag of Figure 8.
[00127] Figure 10 is a schematic plan view of a backseam bag that has an overlapping backseal seam.
[00128] Figure 11 is a cross-sectional view of the back-seamed bag of Figure 10.
[00129] Figure 12 is a schematic plan view of a tote bag.
[00130] Figure 13 is a cross-sectional view of the tote bag of Figure 12, taken through section 13-13 of Figure 12.
[00131] Figure 14 is a longitudinal cross-sectional view of the bag-type bag of Figure 12, taken through section 14-14 of Figure 12.
[00132] Figure 15 is a schematic of a process used to produce a heat shrink film as it can be used to produce a heat shrink bag or for use in a flow wrap type packaging process.
[00133] Figure 16 is a schematic of a flow wrap type horizontal process for packaging products with the use of a heat shrink film according to the invention. DETAILED DESCRIPTION
[00134] As used herein, the term "film" is used in a generic sense to include a plastic sheet, regardless of whether it is a film or sheet. Preferably, e-films used in the present invention have a thickness of 0.25 mm or less. The film can be of any desired total thickness, as long as the film provides the desired properties for the particular packaging operation in which the film is used.
[00135] As used herein, the term "packaging" refers to packaging materials used in the packaging of a product, as well as the way the film was placed in preparing the packaging article that partially or fully surrounds the product. inside. As used in this document, the term "packaged product" refers to the packaging that has the product in it.
[00136] As used in this document, the terms "sealing layer", "sealing layer", "thermal sealing layer" and "sealing layer" refer to an outer layer, or layers, involved in sealing the film itself, another layer of the same or another film, and/or another article that is not a film. While it should also be recognized that up to the outer 76.2 µm (3 mils) of a film may be involved in sealing the film to the same or another layer, the term "sealing layer", and the like, is referred to herein. only to the outer layer(s) that should be heat sealed to them, to another film, etc. Any inner layers that contribute to the sealing performance of the film are herein referred to as "seal aid" layers. With regard to packages that have only flap-type seals, as opposed to overlap-type seals, the term "sealing layer" generally refers to the inner layer of a package, the inner layer being an outer layer that often also serves as a a food contact layer on the food packaging.
[00137] The sealing layers employed in packaging techniques include the thermoplastic polymer genre, which includes thermoplastic polyolefin, polyamide, polyester, polyvinyl chloride and ionomer resin. For low temperature end use, preferred polymers for the sealing layer include low melting point polymers such as homogeneous ethylene/alpha-olefin copolymer, heterogeneous ethylene/alpha-olefin copolymer, ethylene homopolymer, ethylene/acetate copolymer vinyl and ionomer resin.
[00138] As used herein, the term "heat seal", and the term "thermal seal", refer to any sealing of a first region of a film surface to a second region of a film surface, in that the seal is formed by heating the regions to at least their respective seal initiation temperatures. Heating can be accomplished in any one or more of a wide variety of ways, such as using a heated bar, hot wire, hot air, infrared radiation, ultrasonic sealing, etc. Thermal sealing is the process of joining two or more thermoplastic films or sheets by heating areas in contact with each other to the temperature at which fusion occurs, usually with the aid of pressure. Thermal sealing includes heat sealing, cast ball sealing, impulse sealing, dielectric sealing and ultrasonic sealing.
[00139] As used herein, the term "barrier", and the expression "barrier layer", as applied to a film and/or layers, is used with reference to the ability of a film or layer to serve as a barrier to one or more gases. The term "thermoplastic oxygen barrier" refers to any thermoplastic polymeric material that controls the oxygen permeability of the entire film. In a multilayer oxygen barrier film, the layer that provides the lowest oxygen transmission rate (OTR) controls the oxygen barrier property of the entire film. For perishable food packaging applications, OTR should be minimized.
[00140] In packaging techniques, oxygen barrier layers (i.e., O2 barrier layers) may include, for example, saponified ethylene/vinyl acetate copolymer (also called ethylene/vinyl alcohol copolymer, i.e. , EVOH), polyvinylidene chloride (PVDC), polyalkylene carbonate, polyamide, polyethylene naphthalate, polyester, polyacrylonitrile etc., as known to those skilled in the art. In the film of the present invention, the O2 barrier layer preferably comprises EVOH or polyvinylidene chloride. PVDC may comprise a thermal stabilizer (i.e., HCl sequestrant, for example, epoxidized soybean oil) and a lubrication processing aid which, for example, comprises one or more acrylates.
[00141] The term "oxygen transmission rate" ("OTR") is defined herein as the amount of oxygen (O2) in cubic centimeters (cm3) that will pass through 645.16 square centimeters (100 square inches) of film in 24 hours at 0% relative humidity and at 23°C. The thickness (caliper) of the O2 barrier layer has a direct relationship to the oxygen transmission rate. Packaging films that are useful as an oxygen barrier are required to have an OTR value of about 0 to 10.0 cm3/645.16 cm2 (100 in2) for 24 h at 0% relative humidity and 23° C at 25.4 µm (1.0 mils) or less. OTR can be measured in accordance with ASTM D-3985-81, which is incorporated herein by reference.
[00142] In all aspects and embodiments set forth above, the thermoplastic oxygen barrier film may include, but are not limited to, ethylene/vinyl alcohol copolymer, polyamide, polyvinylidene chloride and combinations thereof. The thermoplastic oxygen barrier can be a combination of polyamides. The oxygen barrier layer may include a polyamide blend of about 85% by weight of a polyamide selected from the group consisting of nylon 4.6 (polytetramethylene adipamide), nylon 6 (polycaprolactam), nylon 6.6 ( polyhexamethylene adipamide), nylon 6.9 (polyhexamethylene nonanediamide), nylon 6.10 (polyhexamethylene sebacamide), nylon 6.12 (polyhexamethylene dodecandiamide), nylon 6/12 copolymer (polycaprolactam/dodecanediamide), nylon 6.6/6 copolymer ( polyhexamethylene adipamide/caprolactam), nylon 11 (polyundecanolactam), nylon 12 (polyaurylactam) or combinations thereof, and about 15% by weight of an amorphous polyamide.
[00143] As used herein, the term "ethylene/vinyl alcohol copolymer" or EVOH, refers to polymerized ethylene/vinyl alcohol. The ethylene/vinyl alcohol copolymer is saponified or hydrolyzed ethylene/vinyl acrylate copolymer. In all aspects and embodiments presented above, the degree of hydrolysis can be at least 50%, or at least 85%. The ethylene/vinyl alcohol copolymer may comprise from about 28 to 48 mol% ethylene, or from about 32 to 44 mol% ethylene, or from about 38 to 44 mol% ethylene.
[00144] As used herein, the term "bonding layer" refers to any inner layer that has the primary purpose of adhering two layers of film together. Binding layers can be used to adhere a barrier layer (such as EVOH) to a polyolefin heat seal layer, or to adhere a polyamide layer to a polyolefin layer. Such binding layers can comprise any polymer which has a polar group grafted onto it. Polymers for use in binder layers to bond polyolefin to polyamide or EVOH include, but are not limited to: modified and unmodified ethylene/unmodified unsaturated acid copolymer, modified and unmodified ethylene/unmodified unsaturated ester copolymer, anhydride grafted polyolefin , polyurethane, modified and unmodified acrylate-based polymer and mixtures thereof.
[00145] Binding layers for binding polyester to EVOH or PVDC or polyamide or polyolefin include: styrene-based polymers modified or unmodified alone or in combinations with unsaturated ester copolymer (particularly unsaturated acrylate copolymer) and/or cyclic olefin copolymer and optionally additionally in combination with anhydride and/or polyester modified polyolefin.
[00146] As used herein, the term "adhesive" refers to a polymeric material that serves a primary function or purpose of adhering two surfaces together. In the present invention, the adhesive can adhere one film layer surface to another film layer surface or an area of one film layer surface to another area of the same film layer surface. The adhesive can comprise any polymer, copolymer or combination of polymers that have a polar group thereon, or any other polymer, homopolymer, copolymer or combination of polymers including modified and unmodified polymers, e.g., graft copolymers, that provide sufficient intercoat adhesion to adjacent layers that otherwise comprise non-stick polymers. The adhesive compositions of the present invention may include, but are not limited to, modified and unmodified polyolefins, including ethylene homopolymers and copolymers, ethylene/α-olefin copolymer, modified and unmodified acrylate copolymers such as ethylene/acrylate copolymer. vinyl, ethylene/methyl acrylate copolymer, ethylene/butyl acrylate copolymer, ethylene/ethyl acrylate, or combinations thereof.
[00147] As used herein, the term "adhered" includes films that are directly adhered together using a heat seal or other means, as well as films that are adhered to each other using an adhesive that is between the two movies. As used herein, the term "directly adhered" as applied to the layers is defined as the adhesion of the subjective layer to the objective layer, without a bonding layer, adhesive or other layer in between. In contrast, as used herein, the term "between", as applied to a layer expressed as being between two other specific layers, includes both direct adhesion of the layer in question between the two other layers between which it is, as well as including a lack of direct adhesion to one or two other layers between which the layer in question is located, i.e. one or more additional layers may be imposed between the layer in question and one or more of the layers between which the layer in question is question.
[00148] As used herein, the expressions "polymer functional as anhydride" and "modified polymer", as well as more specific expressions such as "modified ethylene/vinyl acetate copolymer", "modified polyolefin" and "styrene copolymer anhydride functional" refers to such polymers as having an anhydride functionality associated with them, irrespective of whether the anhydride functionality is grafted thereto, and/or copolymerized with and/or in combination thereto. Modified polymers can have the anhydride functionality grafted or polymerized therewith, as opposed to merely in combination therewith.
[00149] As used herein, the term "modified" refers to a chemical derivative, for example, one that has any form of anhydride functionality, such as maleic acid anhydride, crotonic acid, citraconic acid, de itaconic acid, fumaric acid etc., whether grafted onto a polymer, copolymerized with a polymer or in combination with one or more polymers, and which also includes derivatives of such functionalities, such as acids, esters and metal salts derived therefrom.
[00150] The anhydride functionality can be an anhydride of maleic acid, crotonic acid, citraconic acid, itaconic acid, fumaric acid etc., and includes derivatives of such functionalities, such as acids, esters and metal salts derived therefrom. As used herein, the terms "anhydride-containing polymer" and "anhydride-modified polymer" refer to one or more of the following: (i) polymers obtained by copolymerizing an anhydride-containing monomer with a second different monomer , and (ii) anhydride grafted copolymers and (iii) a mixture of a polymer and an anhydride-containing compound.
[00151] As used herein, the term "acrylate-based resin" refers to homopolymers, copolymers, including, for example, bipolymers, terpolymers etc., which have a chemical moiety of acrylate in at least one of the units of repeat (ie, "mer" units) that form the backbone of the polymer. Acrylate-based resins include polyalkyl acrylates. Acrylate-based resins can be prepared by any method known to those skilled in the art. Suitable examples of such resins for use in the present invention include ethylene/vinyl acrylate (EVA) copolymers, ethylene/methacrylate (EMA) copolymers, ethylene/butyl acrylate (EBA) copolymers, and the like.
[00152] As used herein, the term "styrene-based polymer" refers to at least one polymer selected from the group consisting of styrene-ethylene-butylene-styrene copolymer, styrene-butadiene-styrene copolymer styrene-isoprene-styrene copolymer, styrene-ethylene-butadiene-styrene copolymer and styrene(ethylene-propylene rubber)-styrene copolymer. As used herein, the term "styrene-based polymer" includes anhydride-modified copolymers of all styrene-based polymers identified herein. Unless otherwise indicated, as used herein, the use of a "hyphen" (ie, the "-") in a styrene-based polymer formula includes both block copolymers and random copolymers. More particularly, the term "styrene-based polymer" includes either copolymers in which (i) all recited monomers are present as a block, or (ii) any subset of recited monomers is present as a block, with the remaining monomers are randomly arranged, or (iii) all the monomers cited are randomly arranged.
[00153] Styrene-based polymers include hydrogenated block copolymers including: (a) polystyrene-poly(ethylene-propylene) diblock copolymer, e.g., KRATON G1701 and G1702 available from Kraton Polymers; (b) polystyrene-poly(ethylene-butylene)-polystyrene triblock copolymer, for example, KRATON G1641, G1650, G1651, G1654, G1657, G1726, G4609,G4610, GRP-6598, RP-6924, MD-6932M, MD-6933 and MD-6939 available from Kraton Polymers; (c) polystyrene-poly(ethylene-butylene-styrene)-polystyrene (S-EB/S-S) triblock copolymer, e.g., KRATON RP-6935 and RP-6936 available from Kraton Polymers; (d) polystyrene-poly(ethylene-propylene)-polystyrene triblock copolymer, e.g., KRATON G1730 available from Kraton Polymers; (e) polystyrene-poly(ethylene-butylene)-polystyrene triblock copolymer grafted with maleic anhydride, e.g., KRATON G1901, G1924 and MD-6684, available from Kraton Polymers; and (f) polystyrene-poly(ethylene-butylene-styrene)-polystyrene triblock copolymer grafted with maleic anhydride, e.g., KRATON MD-6670 available from Kraton Polymers.
[00154] Other styrene-based hydrogenated block copolymers include: (g) polystyrene-poly(ethylene-butylene)-polystyrene triblock copolymer, such as polystyrene-poly(ethylene-butylene)-polystyrene triblock copolymer comprising 67 weight percent polystyrene available from Asahi Kasei Elastomer as TUFTEC H1043; (h) polystyrene-poly(ethylene-butylene)-polystyrene triblock copolymer, such as polystyrene-poly(ethylene-butylene)-polystyrene triblock copolymer comprising 42 weight percent polystyrene available from Asahi Kasei Elastomer as TUFTEC H1051; (i) polystyrene-poly(butadiene-butylene)-polystyrene triblock copolymer, such as TUFTEC P1000 and P2000 available from Asahi Kasei Elastomer as: (j) polystyrene-polybutadiene-poly(styrene-butadiene)-block copolymer- polystyrene such as SOE-SS L601 available from Asahi Kasei Elastomer as SOE-SS L601; (k) hydrogenated radial block copolymer such as K-Resin KK38, KR01, KR03 and KR05 available from Chevron Phillips Chemical Company as: (1) polystyrene-poly(ethylene-butylene)-polystyrene triblock copolymer such as polystyrene-poly(ethylene-butylene)-polystyrene triblock copolymer comprising 60 by weight of polystyrene available from Kuraray as SEPTON 58104; (m) polystyrene-poly(ethylene-ethylene/propylene)-polystyrene triblock copolymer, such as SEPTON S4044, S4055, S4077 and S4099 available from Kuraray; (n) polystyrene-poly(ethylene-propylene)-polystyrene triblock copolymer, such as polystyrene-poly(ethylene-propylene)-polystyrene triblock copolymer comprising 65 weight percent polystyrene available from Kuraray as SEPTON S2104. Blends of two or more hydrogenated block copolymers can be used.
[00155] As used herein, the term "compatibilization layer" refers to a film layer that has its first major surface directly adhered to a primary layer, with its second major surface offering greater bond strength for direct bonding with a tertiary layer than if the tertiary layer were directly attached to the primary layer. The compatibilization layer is present on many of the films in Table 2 below. The compatibilization layer contains a combination of 90% polyamide 6/66 and 10% polyamide 6I/6T. A first main surface of the compatibilization layer is directly adhered to the barrier layer, which is EVOH in the films in Table 2. The second main surface of the compatibilization layer is directly adhered to a bonding layer produced from a low linear polyethylene modified density. The bond between the linear low density modified polyethylene and the polyamide blend is stronger than the bond strength that would be present if the linear low density modified polyethylene were bonded to the EVOH. Thus, the compatibilization layer improves the interlaminar strength in the multilayer film, but it does not need to be a thick layer, as its compatibilization advantage is based on chemistry, not volume.
[00156] As used herein, the term "oriented" refers to a polymer-containing material that has been stretched at an elevated temperature (the orientation temperature), followed by being "hardened" in the stretched configuration by cooling the material while substantially retain the stretched dimensions. Upon subsequent unrestricted heating, of the unannealed, oriented polymer-containing material at its orientation temperature, heat shrinkage is produced almost to the original unstretched dimension, i.e., pre-oriented dimensions. More particularly, the term "oriented", as used herein, refers to oriented films, in which orientation can be produced in one or more of a variety of ways.
[00157] As used herein, the term "orientation ratio" refers to the product of the multiplication of the extent to which the plastic material film is expanded in various directions, usually two directions perpendicular to each other. The expansion in the machine direction is hereby called "stretching", while the expansion in the transverse direction is hereby called "stretching". For films extruded through an annular die, stretching is usually achieved by "blowing" the film to produce the bubble. For such films, stretch is normally achieved by passing the film through two sets of fed choke cylinders, the downstream set having a higher surface velocity than the upstream set, with the resulting stretch rate being the surface velocity of the downstream set of choke cylinders divided by the surface velocity of the upstream set of choke cylinders. The degree of orientation is also called the rate of orientation or sometimes the "displacement rate".
[00158] As used herein, the term "machine direction", herein abbreviated as "MD", refers to a direction "along the length" of the film, ie, in the direction of the film as it the film is formed during extrusion and/or coating. As used herein, the term "transverse direction", herein abbreviated as "TD", refers to a direction through the film, perpendicular to the machine or longitudinal direction.
[00159] As used in this document, the expressions "heat shrink", "thermal shrink" and the like refer to the tendency of a film, usually an oriented film, to shrink upon the application of heat, i.e., to contract when being heated, so that the size (area) of the film decreases while the film is in an unrestricted state. Likewise, the tension of a heat shrink film increases upon the application of heat if the film is prevented from shrinking. Consequently, the term "thermally shrunk" refers to a heat shrink film, or a portion thereof, that has been exposed to heat such that the film or portion thereof is in a heat shrink state, i.e., reduced in size (unhindered) or under increased stress (hindered).
[00160] As used herein, the term "linear shrinkage" refers to the percentage of dimensional change in a 10 cm by 10 cm film specimen when subjected to selected heat (i.e., at a certain temperature), being that the quantitative determination is performed in accordance with ASTM D 2732, as set forth in the 1990 Annual Book of ASTM Standards, Vol. 08.02, pages 368 to 371, which is incorporated herein in its entirety by reference. As used herein, the term "@STP" refers to testing that is performed under standard test conditions, ie, an atmosphere of pressure, 23°C, and 0% relative humidity.
[00161] Although the linear shrinkage test disclosed above is a standard ASTM linear shrinkage test for use in analyzing the degree of shrinkage exhibited by a heat shrink film, the linear shrinkage of the films in Table 2, and the linear shrinkage values cited in the claims below, were measured by an "otherwise modified linear shrinkage test in accordance with ASTM D2732". The modified test was performed due to the film's tendency to curl during the linear shrinkage test, making measurement difficult due to the difficulty of measuring the uncurled film sample after shrinkage.
[00162] The otherwise modified linear shrinkage test according to ASTM D2732 was performed by marking a sample with a 10 cm by 10 cm square and then cutting the sample so that the entire sample had an edge 25 mm outside the 10 cm marking. In other words, the sample was 15 cm by 15 cm, with the central 10 cm by 10 cm being marked before shrinkage. Shrinkage was otherwise performed in accordance with ASTM D2732, except that the percentage of linear shrinkage in each direction was calculated by measuring the marked area after shrinkage, rather than measuring the total sample dimensions after the shrinkage. In all other situations, the actual shrinkage of the sample was conducted in accordance with ASTM D2732, but the shrinkage measurement was produced by measuring the marking after shrinkage, with excess film being used to retain the film during unwinding, so that the film can be kept flat for post-shrinkage measurement to be obtained.
[00163] As used herein, the term "heat shrink" is used with reference to all films that exhibit a total linear shrinkage (ie, L+T) of at least 10 percent at 85°C.
[00164] The "total linear shrinkage" is determined by adding the linear shrinkage percentage in the machine direction with the linear shrinkage percentage in the transverse direction. For example, a film that exhibits, at 85°C, 30 percent linear shrinkage in the transverse direction, and 20 percent linear shrinkage in the machine direction, has a "total linear shrinkage" at 85°C of 50 percent.
[00165] As used herein, the term "monomer" refers to a relatively simple compound, which usually contains carbon and of low molecular weight, which can react to form a polymer by combining with the same or other compounds or similar molecules.
[00166] As used herein, the term "comonomer" refers to a monomer that is copolymerized with at least one different monomer in a copolymerization reaction, the result of which is a copolymer.
[00167] As used herein, the term "polymer" refers to the product of a polymerization reaction, and includes homopolymers, copolymers, terpolymers etc. The film layer can consist of a single polymer (with or without non-polymeric additives), or it can have further polymers together with it, i.e. in combination with it.
[00168] As used herein, the term "homopolymer" is used with reference to a polymer that results from the polymerization of a single monomer, i.e., a polymer consisting essentially of a single type of mer, i.e., unit of repetition.
[00169] As used herein, the term "copolymer" refers to polymers formed by the polymerization reaction of at least two different monomers. For example, the term "copolymer" includes the copolymerization reaction product of ethylene and an alpha-olefin, such as 1-hexene. However, the term "copolymer" also includes, for example, the copolymerization of a mixture of ethylene, propylene, 1-hexene and 1-octene. The term copolymer also includes polymers produced by reaction, such as graft copolymer, block copolymer and random copolymer.
[00170] As used herein, the term "polymerization" includes homopolymerizations, copolymerizations, terpolymerizations etc., and includes all types of copolymerizations such as random, graft, block etc. Polymers in films used in accordance with the present invention can be prepared according to any suitable polymerization process, including slurry polymerization, gas phase polymerization, and high pressure polymerization processes.
[00171] As used herein, the term "copolymerization" refers to the simultaneous polymerization of two or more monomers to result in a copolymer. As used herein, a copolymer identified in terms of a plurality of monomers, e.g., "propylene/ethylene copolymer"", refers to a copolymer in which each monomer can copolymerize at a higher molar percentage or by weight than than the other monomer or monomers. However, the first listed monomer preferably polymerizes at a higher weight percentage than the second listed monomer, and, for copolymers that are terpolymers, quadripolymers, etc., preferably the first monomer copolymerizes at a percentage by weight higher than the second monomer, and the second monomer copolymerizes at a percentage by weight higher than the third monomer, etc.
[00172] For addition polymers, copolymers are identified, that is, named, in terms of the monomers from which the copolymers are produced. For example, the term "propylene/ethylene copolymer" refers to a copolymer produced by copolymerizing either propylene or ethylene, with or without additional comonomer(s). A copolymer comprises recurring "mers" derived from the monomers from which the copolymer is produced, for example a propylene/ethylene copolymer" comprises propylene mer units and ethylene mer units.
[00173] As used herein, terminology employing a "/" in relation to the chemical identity of a copolymer (eg, "an ethylene/alpha-olefin copolymer"), identifies the comonomers that are copolymerized to produce the copolymer. As used herein, "ethylene alpha-olefin copolymer" is the equivalent of "ethylene/alpha-olefin copolymer".
[00174] As used herein, the term "polyester" refers to homopolymers or copolymers that have an ester bond between monomer units that can be formed, for example, by condensation polymerization reactions between a dicarboxylic acid and a glycol. The dicarboxylic acid can be linear or aliphatic, that is, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and the like; or it may be aromatic or aromatic substituted by alkyl, i.e., various isomers of phthalic acid (i.e., ortho-phthalic acid), such as isophthalic acid (i.e., meta-phthalic acid) and terephthalic acid (i.e., acid para -phthalic acid) as well as naphthalic acid. Specific examples of alkyl substituted aromatic acids include the various isomers of dimethylphthalic acid, such as dimethylisophthalic acid, dimethylorthophthalic acid, dimethylterephthalic acid, the various isomers of diethylphthalic acid, such as diethylophthalic acid, diethylophthalic acid, the various isomers of such dimethylnaphthalic acid, such as 2,6-dimethylnaphthalic acid and 2,5-dimethylnaphthalic acid and the various isomers of diethylnaphthalic acid. The dicarboxylic acid can alternatively be 2,5-furandicarboxylic acid (FDCA). Glycols can be straight chain or branched. Specific examples include ethylene glycol, propylene glycol, trimethylene glycol, 1,4-butane diol, neopentyl glycol and the like. Glycols include modified glycols such as cyclohexane dimethanol. The polyester in the outer layer of the film can comprise any of the above polyesters. The first layer may comprise copolymer of polyethylene terephthalate, polybutylene terephthalate, polynaphthalene terephthalate, and/or polyethylene furanoate, any of which may be biaxially oriented. As used herein, the term "polyester" includes both polyethylene terephthalate homopolymer and copolymers thereof.
[00175] In one embodiment, the outer layer comprises polyethylene furanoate. Avantium® biobased polyester is a polyethylene furanoate that, by unit thickness, exhibits only one-tenth the oxygen transmission rate of polyethylene terephthalate (PET); a quarter of the carbon dioxide transmission rate of PET, and half of the water vapor transmission rate of PET. Polyethylene furanoate is more heat resistant than PET (Tg 12°C higher than PET). In addition, polyethylene furanoate is recyclable on its own or in combination with PET. Polyethylene furanoate can be extruded to form films. Polyethylene furanoate is produced by polymerizing ethylene glycol and 2,5-furandicarboxylic acid (FDCA). Polyethylene furanoate is renewable due to the fact that it is biobased.
[00176] As used herein, the term "polyamide" refers to homopolymers, copolymers, or terpolymers that have an amide bond between monomer units that can be formed by any method known to those skilled in the art. Useful polyamide homopolymers include nylon 6 (polycaprolactam), nylon 11 (polyundecanolactam), nylon 12 (polylauryllactam), and the like. Other useful polyamide homopolymers also include nylon 4.2 (polytetramethylene ethylenediamide), nylon 4.6 (polytetramethylene adipamide), nylon 6.6 (polyhexamethylene adipamide), nylon 6.9 (polyhexamethylene azelamide), nylon 6.10 (polyhexamethylene sebacamide) ), nylon 6.12 (polyhexamethylene dodecandiamide), nylon 7.7 (polyheptamethylene pimelamide), nylon 8.8 (polyoctamethylene suberamide), nylon 9.9 (polynonamethylene azelamide), nylon 10.9 (polydecamethylene azelamide), nylon 12, 12 (polydodecamethylene dodecanediamide) and the like. Useful polyamide copolymers include nylon 6.6 copolymer (polyhexamethylene adipamide/caprolactam copolymer), nylon 6/6.6 copolymer (polycaprolactam/hexamethylene adipamide copolymer), nylon 6.2/6,2 copolymer ( polyhexamethylene ethylenediamide/hexamethylene ethylenediamide copolymer), nylon 6.6/6.9/6 copolymer (polyhexamethylene adipamide/hexamethylene azelaamide/caprolactam copolymer), as well as other nylons which are not particularly mentioned here. Additional polyamides include nylon 4.1, nylon 6.I, nylon 6.6/6I copolymer, nylon 6.6/6T copolymer, MXD6 (poly-m-xylylene adipamide), nylon 6T/6I copolymer, nylon copolymer nylon 6/MXDT/I, nylon MXDI, poly-p-xylylene adipamide, polyhexamethylene terephthalamide, polydodecamethylene terephthalamide, and the like.
[00177] The multilayer heat shrink film may have a polyamide layer consisting of any one or more of the polyamides in the paragraph above. Furthermore, the polyamide may be in combination with another polymer such as ionomer resin, polyether block amide copolymer (eg PEBAX® polyether block amide), maleic anhydride graft polymer (eg monoxide terpolymer carbon ethylene acrylate grafted, ethylene vinyl acetate grafted, grafted homogeneous polyethylene, grafted homogeneous polyethylene (eg, metallocene catalyzed), grafted ethylene propylene rubber, and grafted polypropylene, grafted butaniene styrene copolymer, and styrene ethylene copolymer grafted styrene. Furthermore, the polyamide or polyamide combination may constitute at least 60% by weight of the layer, based on the weight of the layer, or at least 80% by weight, based on the weight of the layer, or at least 90% by weight, based on layer weight, or at least 95% by weight, based on layer weight, or 100% by weight, based on layer weight
[00178] As used herein, the term "amorphous polyamide" refers to polyamides or nylons with an absence of a three-dimensional array of molecules or subunits of molecules that span distances that are large relative to atomic dimensions. However, structure regularity exists on a local scale. See, "Amorphous Polymers", in Encyclopedia of Polymer Science and Engineering, 2nd Ed., pages 789 to 842 (J. Wiley & Sons, Inc. 1985). This document has a Library of Congress Catalog Card Number 84-19713. In particular, the term "amorphous polyamide" refers to a material recognized by one skilled in the technique of differential scanning calorimetry (DSC) as having no measurable melting point (less than 0.5 cal/g) or no heat of melting. as measured by DSC using ASTM 3417-83. Such nylons include those amorphous nylons prepared from the condensation polymerization reactions of diamines with dicarboxylic acids. For example, an aliphatic diamine is combined with an aromatic dicarboxylic acid, or an aromatic diamine is combined with an aliphatic dicarboxylic acid to generate suitable amorphous nylons. As used herein, the term "amorphous polyamide" includes (i) the copolymer of hexamethylene diamine and isophthalic acid and terephthalic acid, i.e., polyamide 6I6T, and (ii) the homopolymer of meta-xylene diamine and adipic acid, i.e. is, polyamide MXD6.
[00179] As used herein, the term "heterogeneous polymer" refers to polymerization reaction products of relatively wide variation in molecular weight and relatively wide variation in composition distribution, that is, typical polymers prepared, for example, with the use of conventional Ziegler-Natta catalysts. Heterogeneous polymers are useful in various layers of the film used in the present invention. Although there are some exceptions (such as TAFMERTM linear homogeneous ethylene/alpha-olefin copolymers produced by Mitsui Petrochemical Corporation using Ziegler-Natta catalysts), heterogeneous polymers typically contain a relatively wide range of chain lengths and comonomer percentages .
[00180] As used herein, the term "homogeneous polymer" refers to polymerization reaction products of relatively narrow molecular weight distribution and relatively narrow composition distribution. Homogeneous polymers are useful in the various layers of the multilayer film used in the present invention. Homogeneous polymers are structurally different from heterogeneous polymers in that homogeneous polymers exhibit relatively uniform sequencing of comonomers within a chain, a mirroring of sequence distribution across all chains, and a similarity in length of all chains. is, a narrower molecular weight distribution. In addition, homogeneous polymers are typically prepared using metallocene, or other single-site type catalysts, rather than using Ziegler Natta catalysts.
[00181] More particularly, homogeneous ethylene/alpha-olefin copolymers can be distinguished by one or more methods known to those skilled in the art, such as molecular weight distribution (Mw/Mn), composition distribution amplitude index (CDBI) ) and narrow melting point range and unique melting point behavior. Molecular weight distribution (Mw/Mn), also known as polydispersity, can be determined by gel permeation chromatography. The homogeneous ethylene/alpha-olefin copolymers useful in the present invention generally have a Mw/Mn of less than 2.7; preferably from about 1.9 to about 2.5; more preferably, from about 1.9 to about 2.3. The composition span of distribution index (CDBI) of such homogeneous ethylene/alpha-olefin copolymers will generally be greater than about 70 percent. CDBI is defined as the percentage by weight of copolymer molecules that have a comonomer content of 50 percent (ie, plus or minus 50%) of the average total molar comonomer content. The linear polyethylene CDBI, which does not contain a comonomer, is defined to be 100%. The Composition Distribution Amplitude Index (CDBI) is determined using the Raising Temperature Elution Fractionation (TREF) technique. The CDBI determination clearly distinguishes the homogeneous copolymers used in the present invention (restricted composition distribution as assessed by CDBI values generally above 70%) from commercially available VLDPEs that generally have a broad composition distribution as assessed by generally lower CDBI values than 55%. The CDBI of a copolymer is readily calculated from data obtained from techniques known in the art, such as, for example, fractionation by temperature rise elution as described, for example, in Wild et. al., J. Poly. Sci. Poli. Phys. Ed., Vol. 20, page 441 (1982). Preferably, the homogeneous ethylene/alpha-olefin copolymers have a CDBI of greater than about 70%, i.e. a CDBI of about 70% to about 99%. The homogeneous ethylene/alpha-olefin copolymers in the multilayer films to be used in the present invention also exhibit a relatively narrow melting point range compared to "heterogeneous copolymers", i.e. polymers that have a CDBI of less than 55%. Preferably, homogeneous ethylene/alpha-olefin copolymers exhibit an essentially unique melting point characteristic, with a peak melting point (Tm), as determined by Differential Scanning Calorimetry (DSC), of about 60°C at about 105°C. Preferably, the homogeneous copolymer has a DSC Tm peak of about 80°C to about 100°C. As used herein, the term "essentially singular melting point" means that at least about 80% by weight of the material corresponds to a single peak Tm at a temperature in the range of from about 60°C to about 105°C. °C, and essentially no substantial fraction of the material has a peak melting point in excess of about 115 °C, as determined by DSC analysis. DSC measurements are produced on a Perkin Elmer System 7 Thermal Analysis System. The fusion information reported is second fusion data, ie the sample is heated at a programmed rate of 10°C/min to a temperature below its critical range. The sample is then reheated (2nd melting) at a programmed rate of 10°C/min. The presence of higher melting peaks is detrimental to film properties such as opacity, and compromises the chances of a significant reduction in the final film seal initiation temperature.
[00182] A homogeneous ethylene/alpha-olefin copolymer can be prepared by copolymerizing ethylene and any one or more alpha-olefins. Preferably, the alpha-olefin is a C3-20 α-monoolefin, more preferably a C4-12 α-monoolefin, even more preferably a C4-8 α-monoolefin. Even more preferably, the alpha-olefin comprises at least one member selected from the group consisting of butene-1, hexene-1 and octene-1, i.e., 1-butene, 1-hexene, and 1-octene, respectively. . Most preferably, the alpha-olefin comprises octene-1 and/or a combination of hexene-1 and butene-1.
[00183] Processes for the preparation and use of homogeneous polymers are disclosed in US Patent No. 5,206,075, US Patent No. 5,241,031 and International PCT Application No. WO 93/03093, each of which is incorporated herein by way of reference in its entirety. Additional details regarding the production and use of homogeneous ethylene/alpha-olefin copolymers are disclosed in PCT International Publication number WO 90/03414, and PCT International Publication number WO 93/03093, both of which designate Exxon Chemical Patents, Inc. as the Applicant, and both of which are incorporated herein by reference in their respective entireties.
Yet another genus of homogeneous ethylene/alpha-olefin copolymers is disclosed in U.S. Patent 5,272,236, to LAI, et. al., and U.S. Patent 5,278,272, to LAI, et. al., both of which are incorporated herein by reference in their respective entireties.
[00185] As used herein, terms that identify polymers such as "polyamide", "polyester", "polyurethane" etc. include not only polymers comprising repeating units derived from monomers known to polymerize to form a polymer of the named type, but also include comonomers, derivatives etc. which can copolymerize with unpolymerized monomers to produce the named polymer, including modified polymers such as anhydride modified polymers. For example, the term "polyamide" encompasses both polymers comprising repeating units derived from monomers, such as caprolactam, which polymerize to form a polyamide, as well as copolymers derived from copolymerization of caprolactam with a comonomer which, when polymerized by itself, , does not result in the formation of a polyamide. In addition, terms that identify polymers also include blends, blends, etc. of such polymers with other polymers of a different type.
[00186] As used herein, the term "cyclic polymer" includes cyclic olefin copolymer, whether aliphatic or phenolic, i.e. including ethylene/norbornene copolymer, polycyclododecene, polyester and cyclic olefin polymer.
As used herein, the term "polyolefin" refers to any polymerized olefin, which may be linear, branched, cyclic, aliphatic, aromatic, substituted or unsubstituted. More specifically, included within the term polyolefin are olefin homopolymers, olefin copolymers, copolymers of an olefin and a non-olefinic comonomer copolymerizable with the olefin, such as vinyl monomers, modified polymers thereof, and the like. Specific examples include polyethylene homopolymer, polypropylene homopolymer, polybutene, ethylene/alpha-olefin copolymer, ethylene/propylene copolymer, propylene/alpha-olefin copolymer, butene/alpha-olefin copolymer, low density polyethylene, linear polyethylene low density polyethylene, very low density polyethylene, ultra low density polyethylene, medium density polyethylene, high density polyethylene, polyethylenes comprising copolymers of ethylene with one or more alpha-olefins (α-olefins) such as butene-1, hexene -1, octene-1, or the like such as a comonomer, linear low density polyethylene, very low density polyethylene, ultra low density polyethylene, ethylene/propylene copolymer, polypropylene, propylene/ethylene copolymer, polyisoprene, polybutylene, polybutene, poly-3-methylbutene-1, poly-4-methylpentene-1, ethylene/unsaturated ester copolymer, ethylene/unsaturated acid copolymer, (especially ethyl acrylate copolymer, ethylene/butyl acrylate copolymer, ethylene/methyl acrylate copolymer, ethylene/acrylic acid copolymer, ethylene/methacrylic acid copolymer), modified polyolefin resin, ionomer resin, polymethylpentene etc. Modified polyolefin resin includes modified polymer prepared by copolymerizing the olefin homopolymer or copolymer thereof with an unsaturated carboxylic acid, for example, maleic acid, fumaric acid or the like, or a derivative thereof such as anhydride, ester or salt of metal or similar. It can also be obtained by incorporating into the olefin copolymer or homopolymer an unsaturated carboxylic acid, for example maleic acid, fumaric acid or the like, or a derivative thereof such as the anhydride, ester or metal salt or the like.
[00188] As used herein, the expression "ethylene alpha-olefin copolymer" and "ethylene/alpha-olefin copolymer" refer to such heterogeneous materials as linear low density polyethylene (LLDPE), and high density polyethylene very low and ultra low (VLDPE and ULDPE); and homogeneous polymers such as linear homogeneous ethylene/alpha-olefin copolymer resins EXACT.TM. metallocene catalyzed resins obtainable from Exxon Chemical Company of Baytown, Tex., and TAFMERTM linear homogeneous ethylene/alpha-olefin copolymer resins obtainable from Mitsui Petrochemical Corporation. All such materials generally include ethylene copolymers with one or more comonomers selected from a C4-10 α-olefin such as butene-1 (ie, 1-butene), hexene-1, octene-1 etc., where as Copolymer molecules comprise long chains with relatively few side chain branches or crosslinked structures. This molecular structure must be contrasted with conventional low and medium density polyethylenes that are more highly branched than their respective counterparts. Heterogeneous ethylene/alpha-olefin commonly known as LLDPE has a density typically in the range of about 0.91 grams per cubic centimeter to about 0.94 grams per cubic centimeter. Other ethylene/alpha-olefin copolymers, such as the long chain homogeneous ethylene/alpha-olefin copolymers available from The Dow Chemical Company, known as AFFINITYTM resins, are also included as another type of ethylene/alpha copolymer. homogeneous olefin useful in the present invention.
[00189] The ethylene/alpha-olefin copolymer comprises a copolymer that results from the copolymerization of about 80 to about 99 weight percent ethylene and 1 to about 20 weight percent alpha-olefin. Preferably, the ethylene/alpha-olefin copolymer comprises a copolymer that results from the copolymerization of from about 85 to about 95 weight percent ethylene and from about 5 to about 15 weight percent alpha-olefin.
[00190] As used herein, the expressions "inner layer" and "inner layer" refer to any layer of a multilayer film that has both of its main surfaces directly adhered to another layer of the film.
[00191] As used herein, the term "outer layer" refers to any layer of film that has fewer than two of its major surfaces directly adhered to another layer of film. The term includes both monolayer and multilayer films. In multilayer films, there are two outer layers, each of which has a main surface adhered to just one other layer of the multilayer film. In monolayer films, there is only one layer, which, of course, is an outer layer where neither of its two main surfaces is adhered to another layer of the film.
[00192] As used herein, the term "inner layer" refers to the outer layer, of a multilayer film that packages a product, which is closer to the product, in relation to the other layers of the multilayer film. "Inner layer" is also used with reference to the innermost layer of a plurality of concentrically disposed layers simultaneously co-extruded through an annular die.
[00193] As used herein, the term "outer layer" refers to the outer layer, of a multilayer film that packages a product, which is further away from the product in relation to the other layers of the multilayer film. The term "outer layer" is also used with reference to the outermost layer of a plurality of concentrically disposed layers co-extruded through an annular die.
[00194] As used herein, the term "extrusion" is used with reference to the process of forming continuous shapes by forcing a molten plastic material through a die, followed by chemical cooling or hardening. Immediately prior to extrusion through the die, the relatively high viscosity polymeric material is fed to a variable pitch rotating screw, i.e., an extruder, which forces the polymeric material through the die.
[00195] As used herein, the term "co-extrusion" refers to the process of extrusion of two or more materials through a single die with two or more holes arranged so that the extrudates merge and fuse into a laminar structure before cooling, that is, cooling off sharply. Co-extrusion can be employed in film blowing, linear film extrusion and extrusion coating processes.
[00196] The multilayer heat shrink film of the invention can be fully coextruded, in contrast to being the lamination of two films produced by separate extrusion processes. In a fully co-extruded film, all layers of the film are extruded simultaneously. A fully co-extruded film is free of lamination adhesive, the film layers being fused together.
[00197] At least a portion of the multilayer film of the present invention may optionally be irradiated to induce crosslinking. In the irradiation process, the film is subjected to one or more energetic radiation treatments, such as corona discharge, plasma, flame, ultraviolet, X-ray, gamma ray, beta ray and high energy electron treatment, each of which induces crosslinking between molecules of the irradiated material. Irradiation of polymeric films is disclosed in US Patent No. 4,064,296, to BORNSTEIN, et. al., which is incorporated herein by reference in its entirety. BORNSTEIN, et. al. disclose the use of ionizing radiation to crosslink the polymer present in the film.
[00198] To produce crosslinking, an adequate radiation dosage of high energy electrons is employed, preferably with the use of an electron accelerator, with a dosage level that is determined by means of standard dosimetry methods. Other accelerators such as a Van de Graaf or resonant transformer can be used. Radiation is not limited to electrons from an accelerator as any ionizing radiation can be used. Ionizing radiation can be used to crosslink polymers in the film. Preferably, the film is irradiated at a level from about 30,000 J/kg to about 207,000 J/kg, more preferably from about 30,000 J/kg to about 140,000 J/kg. As can be seen from the descriptions of preferred films for use in the present invention, the most preferred amount of radiation depends on the film and its end use.
[00199] As used in this document, the expressions "corona treatment" and "corona discharge treatment" refer to the fact of subjecting the surfaces of thermoplastic materials, such as polyolefins, to corona discharge, that is, the ionization of a gas such as air in close proximity to a film surface, ionization initiated by a high voltage passed through a nearby electrode, and causing oxidation and other changes to the film surface, such as surface roughness.
[00200] The corona treatment of polymeric materials is disclosed in Patent No. US 4,120,716, of BONET, issued on October 17, 1978, incorporated herein by reference in its entirety. BONET reveals improved adhesion characteristics of the polyethylene surface through corona treatment to oxidize the polyethylene surface. Patent No. US 4,879,430, by HOFFMAN, also incorporated herein by reference in its entirety, discloses the use of corona discharge for the treatment of plastic blankets for use in packaging for cooking meat within it, with corona treatment on the inside surface of the mat to increase meat adhesion to meat adhesion to proteinaceous material. The films of this invention can be corona treated in a preferred modality.
[00201] Figure 1 is a schematic of a bag with a preferred end seal 10, in an extended flat position; Figure 2 is a cross-sectional view of bag 10 taken through section 2-2 of Figure 1. Seeing Figures 1 and 2 together, bag 10 comprises bag film 11, top edge 12 defining a open top, first bag side edge 13, second bag side edge 14, bottom edge 15 and end seal 16.
[00202] Figures 3 and 4 illustrate the side seal bag 18. Figure 3 illustrates a schematic of the side seal bag 18, in an extended view; Figure 4 illustrates a cross-sectional view taken through section 4-4 of Figure 3. Referring to Figures 3 and 4 together, the side seal bag 18 is comprised of bag film 19, top edge 20 defining a open top, bottom edge 21, first side seal 22 and second side seal 23.
[00203] Figure 5 is an extended view of a preferred L-shaped sealing bag 26, in an extended flat position. Figure 6 is a cross-sectional view of the L-seal bag 26 taken through section 6-6 of Figure 5. Figure 7 is a longitudinal cross-sectional view of the L-seal bag 26 taken through section 7 -7 of Figure 5. Seeing Figures 5, 6, and 7 together, the L-shaped bag 26 has side seal 28, bottom seal 30, open top 32, seamless folded bag side edge 34, and side edges of stitched bag 36.
[00204] The flap seal back seam bag 38 of Figures 8 and 9 has open top 40, bottom seal 42, first folded side edge 44, second folded side edge 46, bottom edge 48, back seam seal 50 (within the film layer heat is sealed thereto) and back seam fins 52.
[00205] The bag with lap seam back seam 54 of Figures 10 and 11 has open top 55, bottom seal 56, first folded side edge 58, second folded side edge 60, bottom edge 62 and back seam seal 64 ( inside the film layer heat is sealed to the outside of the film layer).
[00206] Figures 12, 13 and 14 illustrate a bag-type bag 66 produced by sealing two separate pieces of flat film together. In Figures 12, 13 and 14, bag 66 has open top 68, bottom heat seal 70 and bottom edge 72, first side seal 74 and first side edge 76, second side seal 78 and second side edge 80. Together, the first and second side seals 74 and 76 connect with the bottom seal 70 to form a "U-shaped" seal that connects the two pieces of flat film together to form the bag-type bag 66.
[00207] In Figure 15, solid polymer microspheres (not shown) are provided for a plurality of extruders 100. For simplicity, only one extruder 100 is illustrated in Figure 15. Within each extruder 100, the microspheres of polymer are advanced, melted and degassed, then the resulting stream of bubble-free molten material emitted from each extruder 100 is advanced to the annular multilayer matrix 102.
[00208] The molten material streams from the extruders 100 are supplied to the annular multilayer die 102, pass through the annular multilayer die 102, and are emitted from the annular die 102 in the form of discrete layers, resulting in an extrudate of annular multilayer 104, also referred to as a "ribbon". The number of extruders 100 may correspond to the number of discrete layers in the annular multilayer extrudate 104 or may be less than the number of film layers if the extrudate from a single extruder 100 is divided into two or more streams, each stream being used to form a distinct layer of multilayer annular extrudate 104.
[00209] As the annular extrudate 104 emerges from the annular die 102, the annular extrudate 104 passes into the gauge 106, which is positioned below the annular die 102 so that the upper edge of the gauge 106 is about 5.08 to 6.35 cm (2 to 2.5 inches) below the point at which the annular extrudate 104 emerges from the annular die 102. The gauge 106 has a length of 30.48 to 45.72 cm (12 to 18 inches). Gauge 106 is essentially a pipe with an outer surface and an inner surface. The inner surface controls the diameter of the extrudate 104. Furthermore, the gauge 106 supplies the quench liquid to the annular extrudate 104, as the gauge 106 itself is hollow and connected to a source of cold water (not shown ) which is pumped into the walls of the calibrator 106 from a chiller (not shown). A plurality of annular slits (not shown) in the inner surface of the caliper 106 provide cold water streams between the inner surface of the caliper 106 and the outer surface of the annular extrudate 104, to quench the annular extrudate 104 as it emerges from the annular matrix 102. In making the films in Table 2, below, calibrator 106 was supplied with water at 43°C, which was probably 46°C to 48°C before the water came into contact with annular extrudate 104. Caliper 106 serves to control the size of the outer diameter of the annular extrudate 104, as well as the quenching of the annular extrudate 104.
The gauge 106, as well as about 1.2 m (four feet) from the uppermost portion of the annular extrudate 104, are surrounded by the vacuum chamber 108. Complementary cold water sprinklers 110 are provided within the vacuum chamber 108. Vacuum chamber 108 is connected to a vacuum source (not shown). The bottom edge of the vacuum chamber 108 is provided with a sealing ring 112 so that water emitted from the slots in the gauge 106, as well as water from the sprinklers 110, can be evacuated, recirculated through the chiller and back to the sprinklers 110 of the calibrator 106.
[00211] The collapse of the annular extrudate 104 is prevented by maintaining a slight superatmospheric pressure within the annular extrudate by means of the centrally positioned pipe 114 which passes through the center of the annular die 102 and which extends below the annular die 102. Alternative or in addition to maintaining a slightly positive pressure within the annular extrudate 104 (i.e., within the "first bubble"), a slight vacuum, i.e., from 0.0015 to 0.0018 MPa (15 to 18 millibar), is maintained by evacuating the water and atmosphere from the inner region 116 within the vacuum chamber 108. In this way, the diameter of the annular extrudate 104 is strictly controlled while the thermoplastic resins emitted from the annular matrix 102 are quenched by extrusion. Furthermore, the resin extrusion rate of the annular matrix 102, in combination with control over the downward velocity of the annular extrudate 104 through the regulation of the speed on the surface of nip rollers 118, determines the amount of strangulation of the annular extrudate 104 as it emerges from the annular die 102. The extrusion rate and velocity at the cylinder surface have been controlled so that the annular extrudate 104 has an outside diameter suitable for the inside diameter of the caliper 106.
[00212] The annular extrudate 104 moves down to the water bath 120, and is compacted to the flat extended configuration as it passes through the choke cylinders 118 in the water bath 120. The resulting flat extended pipe 122 emerges from the water bath 120 and passes over inactive cylinders 124 and 126 and then through optional irradiation chamber 128 and around inactive cylinder 130 and then through upper choke cylinders 132. Annular extrudate 104 can remain at an elevated temperature by the time it reaches choke cylinders 132 (for example, a °Ct of about 73°C to 93°C in Table 2 below).
[00213] Immediately on passing through the upper choke cylinders 132, the annular extrudate 122 is re-inflated to its extruded diameter (i.e., a first portion of the "second bubble") as it passes through the four sets of heaters 134 positioned around the entire annular extrudate 136. Heaters 134 progressively heat the inflated annular extrudate 136 to its softening point (eg a °Cb of 56°C to 130°C in Table 2 below), after which the inflated and softened annular extrudate 138 passes through a set of support guide rollers 140. The guide rollers 140 hold the inflated annular extrudate 136 and bubble 142 in a central position in the oven so that the annular extrudate 136 and the bubble 142 can be uniformly heated by the various heaters surrounding the second bubble. After passing through the guide rollers 140, the annular extrudate 138 is blown into the oriented bubble 142 (i.e., the second portion of the second bubble).
[00214] The entire second bubble contains trapped air 144 between the upper choke cylinders 132 and the lower choke cylinders 146. The lower choke cylinders 146 have a greater surface velocity than the upper choke cylinders 132, stretching, of that Thus, the softened extrudate 138 in the machine direction. Furthermore, the larger diameter of the oriented bubble 142 provides the transverse solid state orientation of the extrudate 138. Three sets of complementary heaters 147 are provided along the oriented bubble 142. The result is biaxially oriented film tubing 148 at the end a downstream of the oriented bubble 142.
[00215] Thereafter, the lower choke cylinders 146 form the biaxially oriented film tubing 148 in an extended flat configuration, with the resulting extended flat tubing 150 passing over the idle cylinders 152 and 154, and through the choke cylinders 156, after which the extended flat tubing 150 is inflated again into the third bubble 158 which surrounds the trapped air 160. The trapped air 160 is held within the third bubble 158 by upper choke cylinders 156 and lower choke cylinders 164. As the third biaxially oriented bubble 158 passes downward, it is annealed by three sets of infrared annealing heaters that surround the bubble 158. The surface velocity of the upper choke cylinders 156 is nearly the same as the surface velocity of the lower choke cylinders 164. When passing through the choke cylinders On the lower rolls 164, the resulting annealed, biaxially oriented film 166 is returned to the extended flat configuration and is wound onto roll 168.
[00216] Figure 16 illustrates the use of a heat shrink film, such as the films in Table 2, below. The process illustrated in Figure 16 is a type of horizontal forming, filling and sealing process known in the packaging art as a "flow wrap" type process. The process of Figure 16 uses a continuous roll of flat film to pack a product into a packaging article as illustrated in Figures 8 and 9 (or Figures 10 and 11), rather than pre-produced bags or sacks as illustrated in the Figures 1 to 9 and 12 to 14.
[00217] Although the process of Figure 16 has, at least theoretically, the ability to run continuously, in actual use the process is intermittent, with different packers having different frequency and duration of process interruption. The process of Figure 16 does not produce a fully closed package. Instead, the product of the packaging operation illustrated in Figure 16 results in a product within the open packaging article illustrated in Figures 8 to 9 (described above), with the product within the open packaging article being advanced downstream in the additional machinery (described below) to complete the packaging process.
[00218] In Figure 16, products 302 are supplied to the packaging machine 303 via conveyor 304. Although product 302 can be any product to be packaged, a preferred product is a meat product, such as a roast, steak , chops, ribs, etc. Each product 302 can be an individual piece of meat or a set of a plurality of pieces of meat.
[00219] Conveyor 304 ends up as the inlet end of forming horn 306. Product 302 is pushed onto forming horn 306 by a pusher (not shown). Product 302 is pulled onto the top surface of continuous film filament 308 as product 302 is pushed to and through forming horn 306. Continuous film filament 308 (supplied from a roll of film, not illustrated ) is advanced to, through, and past forming horn 306 as a continuous stream of products 302 is individually pushed to forming horn 306. Once on film 308, products 302 are advanced through forming horn 306 by advancing film filament 308, that is, at the same rate as film 308 passes to, through and beyond forming horn 306. Once at film 308, film advancing 308 advances products 302 with it.
[00220] Film 308 is folded as it passes through forming horn 306, so that as product 302 emerges from forming horn 306, film 308 is folded around product 302. product 302 is now inside a tube 312 of film 308. Above forming shoe 306, edges of film 308 are folded up and a sealing apparatus (not shown) forms a continuous fin type heat seal 310 at the along the upwardly folded longitudinal film edges 308. The heat seal can be formed using, for example, three sets of seal heads, i.e. three sets of heat seal throttling cylinders. The first (upstream) set of heat seal choke cylinders can have a temperature of 65°C. The second (intermediate) set of heat seal choke cylinders can have a temperature of 90°C. The third (downstream) set of heat seal choke cylinders can have a temperature of 150°C. The inlet pressure of the seal heads was 0.2 MPa (2 bar). The web speed was 1.032 km/h (1.032 km/h (17.2 meters per minute). During the formation of the thermal seal with back seam 310, the film 308 surrounding the products 302 is routed by a second conveyor (not illustrated) on which the film 308 and the products 302 rest.
[00221] During process interruption in which the flow of products is temporarily stopped, the seal heads are pulled away from the film so that the film is not burned for a long period of contact with the hot seal heads. As the process continues, the seal heads are re-applied to the film and back sewing is continued. Logically, it is desirable for the carton to be provided with a strong back-seam seal even if a portion of the back-seam seal is produced before the process is stopped and a portion of the back-seam seal is produced after the process continues. It is desirable for such a package to exhibit a tear strength of at least 95 percent as high as the tear strength of a package produced from the same film, but in which the backseam seal was produced continuously, i.e., without interruption. Alternatively, packaging that has a back seam with portions produced before and after stopping the process may have a tear strength of at least 90 percent, or at least 85 percent, or at least 80 percent, or at least 75 percent as high as to the breaking strength of a corresponding package in which the back seam was continuously produced, i.e. without interruption.
[00222] The product stream 302 within the now sealed film tubing 312 is advanced to a seal and cross cutter that includes upper seal/cutter member 314 and lower seal/cutter member 316, which work together to produce cross seals between the products 302, and to cut the separate film tubing 312 to produce individual packaged products 318. The temperatures for each of the two transverse sealing bars on members 314 and 316 can be, for example, 105°C and 105°C, the dwell time of the sealing bar being, for example, 350 milliseconds. The top and bottom seal/cutter bars 314, 316 swing up and down as the 312 film tubing is advanced. By being sealed at the downstream end and cut from the backseamed film tubing, the result is a partially packaged product 318 that has a backseam below its length, a closed bottom seal and an open top end, as illustrated in Figures 8 and 9, described above.
[00223] Upon leaving the packaging machine 303, the partially packaged products 318 are forwarded to a vacuum chamber machine in which the atmosphere is evacuated from inside the package and the open end of the package is closed by thermal sealing, so that the product is completely enveloped by the shrink wrapping article. The closed and evacuated packaged product is then forwarded to a shrinking machine in which the film is shrunk against the product by passing the closed packaged product and evacuated through a hot air tunnel or by immersing the closed packaged product and evacuated in a hot water bath.
[00224] The process of Figure 16 is but a modality of the way in which film can be used. The process in Figure 16 is called "flow wrap" and is a type of process known in the art as "horizontal forming, filling and sealing". When used in conjunction with downstream vacuum packaging, it is called the "flow vac process". The film may also be used for packaging by forming, filling, and vertical sealing, as described in USPN 5,491,019, by Kuo, which is incorporated herein in its entirety by way of reference hereto. The film can be used to manufacture packaging items such as bags and bags, including the bags and bags illustrated in Figures 1 to 14. EXAMPLES
[00225] The present invention may be further understood by reference to the Examples below, which are merely illustrative and should not be construed as a limitation on the scope of the present invention which is defined by the appended claims. The Examples films contained various resins identified in Table 1, below.



[00226] The resins identified in Table 1, above, were used in the preparation of the films in Table 2, below. The films in Table 2, below, were prepared using the process illustrated in Figure 15, described above.


















[00227] Films 1 to 90 are directed to films that have an outer polyester layer, a barrier layer and at least one bonding layer between the outer polyester layer and the barrier, without a polyamide layer between the polyester layer outer shell and the barrier layer. An analysis of these films reveals the effect of having a styrene-based polymer in the binding layer between the outer polyester layer and the barrier layer: of the ninety films lacking a styrene-based polymer in this binding layer, the recorded data indicate the presence of delamination are shown for eleven of these films (ie, films 1, 2, 3, 6, 7, 8, 10, 12, 15, 18, and 74). This delamination was delamination by conducting free shrinkage unimpeded by immersion in water at 85°C for 8 seconds, using ASTM D2732 (stage 2 delamination), or delamination by handling the film after orientation and annealing (delamination of stage 3), or strip extrusion delamination, ie before orienting (stage 4 delamination). There was no indication of whether or not delamination occurred for the remaining eight films (ie, films 4, 5, 9, 11, 16, 17, 52 and 72) which were devoid of a bonding layer containing a polymer to the styrene base. Each of the eighteen films devoid of a styrene-based polymer in the binding layer is designated as a Comparative Example ("C") in the second column of Table 2.
[00228] In contrast, in each of the remaining eighty-one films in Table 2, the binding layer between the outer polyester layer and the barrier layer contained a styrene-based polymer. Thirty-four of the eighty-one movies (ie, movies 13, 14, 24-31, 33, 43-45, 49, 50, 56, 58, 60, 61, 63, 64, 65, 69, 72, 75 -80, 82, 83 and 86) included an express comment indicating that these films did not exhibit any delamination. Twenty-five of the eighty-one movies (ie, movies 22, 23, 32, 34-42, 46-48, 53-55, 57, 59, 62, 81, and 88 to 90) did not include any express commentary on the presence or absence of delamination. However, if stage 2, 3, or 4 delamination had occurred in any of these films, it is believed that data would have been recorded about such delamination if, in fact, it had occurred, as the "delaminated" comment was registered for multiple samples outside that group. Since no such comments were recorded, it is believed that these twenty-five samples also did not experience stage 2, 3 or 4 delamination.
[00229] Six of the eighty-one films (ie, films 51, 70, 71, 84, 85 and 87) could not be produced for various reasons such as unstable process and bursts. Another six films (i.e. films 19, 20, 21, 66, 67 and 68) exhibited delamination even though they have a styrene based polymer in the tie layer adjacent to the outer polyester layer. For three of these films, ie, films 19, 20 and 21, the data indicate that the potential reason for delamination is that the process conditions were not optimized. In the three remaining films that delaminated, ie, films 66, 67 and 68, it is not known why the delamination occurred.
[00230] In summary, it was found that, of the ninety heat shrink films, the totality of the data supports the conclusion that the presence of a binding layer containing a styrene-based copolymer between the PET layer and the barrier layer decreased or eliminated film delamination from stage 2 to stage 4. In contrast, heat shrink films lacking a styrene-based copolymer between the PET layer and the barrier layer were found to be substantially more likely to exhibit stage delamination 2 through stage 4.
[00231] Fourteen films (i.e. films 64, 69, 70, 79, 80 and 82 to 90) had a bonding layer that contains a combination of the styrene-based polymer with a copolyester that has a low melting point in (121°C). Some of these films were used to produce packaging articles that exhibited superior tear strength due to their improved delamination resistance.
Films which delaminated by shrinkage exhibited visible signs of delamination. These visible signs of delamination included, among other visible signs, one or more of (i) delaminated layers on the edge of the sample (ii) "white spots" into the edge of the sample, caused by layer delamination, (iii) an appearance of highly wrinkled film in distinct areas or across the specimen, sometimes only on a major surface of the specimen, and (iv) areas of diminished or diminished film transparency across the entire transparency film.
[00233] Films 91 to 93 are directed to multilayer heat shrink coextruded films having an outer polyester layer, a first inner layer comprising a polyamide and a second inner layer between the polyester layer and the layer comprising the polyamide. Film 91 and Film 92 above are practical examples in accordance with the present invention. Film 91 and Film 92 each had an outer layer comprising a polyethylene terephthalate copolymer having a melting point of 255°C and a first inner polyamide layer comprising a combination of 90% by weight of semi-crystalline polyamide (PA6) and 10% by weight amorphous polyamide (PA 6I/6T). Between the outer polyester layer and the polyamide layer was a tie layer comprising a combination of (i) 60 wt% anhydride grafted LLDPE, 30 wt% ethylene styrene triblock copolymer and anhydride grafted butylene and 10% by weight of polyester.
[00234] During production, both Film 91 and Film 92 were produced as a film tubing with no significant process instability, ie, no melt ripples and no bubble breaks. Furthermore, after production, the film 91 and Film 92 heat shrink film pipes were each cut and wound like a roll of flat film. Samples of Film 91 and Film 92 each were shrunk into a hot water bath by immersing themselves in 85°C water for 8 seconds. Neither Film 91 nor Film 92 experienced delamination during production or during shrinkage.
[00235] After that, the roll was used in a horizontal forming, filling and sealing machine, as illustrated in Figure 16, described above. After sealing through the pipe upstream of the meat product, the resulting open package (318) having the meat inside it was routed to a vacuum chamber machine. While in the vacuum chamber, the atmosphere was evacuated from inside the package and the package was sealed. The excess film was then cut above the heat seal and the resulting packaging product was sent to a hot water bath to shrink the film tightly around the meat product. Neither Film 91 nor Film 92 experienced delamination during production or during shrinkage.
[00236] Film 93 was a Comparative Example. Film 93 was a heat shrink film produced in the same manner as used for the production of Film 91 and Film 92. Film 93 differed from Film 91 only in that the bonding layer between the outer polyester layer and the polyester layer inner polyamide comprised a combination of 60% by weight anhydride grafted LLDPE, 30% by weight ungrafted styrene-ethylene-butylene copolymer and 10% by weight polyester. That is, the 3-component combination in the bonding layer of Film 93 used 30% by weight ungrafted terpolymer instead of the 30% by weight styrene-ethylene-butylene anhydride grafted copolymer used in Film 91 and Film 92 .
[00237] Unlike Film 91, during production, Film 93 exhibited process instability with the formation of melt ripples. Furthermore, after production, Film 93 delaminated by immersion for 8 seconds in water at 85°C.
[00238] Although the present invention has been described with reference to preferred embodiments, it is to be understood that modifications and variations of the invention exist without departing from the principles and scope of the invention, as those skilled in the art will readily understand. Accordingly, such modifications are in accordance with the claims set out below.

权利要求:
Claims (30)
[0001]
1. Multilayer heat shrink film characterized in that it comprises: (A) a first layer comprising a first polyester, the first layer being an outer layer; (B) a second layer that serves as an O2 barrier layer, the second layer comprising at least one member selected from the group consisting of saponified ethylene/vinyl acetate copolymer, polyamide MXD6, polyamide 6I/6T, polyamide 6, polyvinylidene chloride, polyethylene naphthalate, polytrimethylene terephthalate and liquid crystal polymer; (C) a third layer between the first layer and the second layer, the third layer serving as a tie layer, the third layer comprising at least one styrene-based copolymer; and wherein the tie layer comprises an anhydride functional styrene-based polymer if the tie layer is directly adhered to both the outer polyester layer and an inner polyamide layer, and wherein the multilayer heat shrink film exhibits a total linear shrinkage at 85°C of at least 10% measured according to an otherwise modified linear shrinkage test in accordance with ASTM D 2732, and the polyester is present in the film in an amount of at least 2% by volume , based on total movie volume.
[0002]
2. Multilayer heat shrink film according to claim 1, characterized in that the styrene-based polymer constitutes up to 10 to 100% by weight of the weight of the third layer, and the styrene-based polymer comprises at least one member selected from the group consisting of styrene-ethylene-butylene-styrene copolymer, styrene-butadiene-styrene copolymer, styrene-isoprene-styrene copolymer, styrene-ethylene-butadiene-styrene copolymer, styrene copolymer-( ethylene-propylene rubber)-styrene, and polystyrene-poly(ethylene-propylene)-polystyrene copolymer.
[0003]
3. Multilayer heat shrink film according to claim 2, characterized in that the third layer comprises a combination of styrene-based copolymer and at least one member selected from cyclic olefin copolymer and ethylene/ester copolymer unsaturated.
[0004]
4. Multilayer heat shrink film according to claim 3, characterized in that the combination additionally comprises at least one member selected from the group consisting of a second polyester and a modified polyolefin.
[0005]
5. Multilayer heat shrink film according to claim 4, characterized in that the second polyester comprises a copolyester, and the combination comprises: (i) at least one member selected from the group consisting of a block copolymer. styrene-ethylene-butylene-styrene and styrene-butadiene block copolymer; (ii) ethylene/acrylate copolymer; and (iii) at least one member selected from the group consisting of copolyester and anhydride modified polyolefin.
[0006]
6. Multilayer heat shrink film according to claim 5, characterized in that the combination comprises from 5 to 15% by weight, based on the total weight of the combination, of at least one member selected from the group consisting of in copolyester having a melting point of 105°C to 140°C and anhydride modified linear low density polyethylene.
[0007]
7. Multilayer heat shrink film according to claim 1, characterized in that the first polyester comprises at least one semi-crystalline polyester selected from the group consisting of polyethylene terephthalate homopolymer, polyethylene terephthalate copolymer, polyethylene homopolymer. polybutylene terephthalate, polybutylene terephthalate copolymer, polynaphthalene terephthalate homopolymer, polynaphthalene terephthalate copolymer, polyethylene furanoate homopolymer, and polyethylene furanoate copolymer, wherein the semicrystalline polyester has a melting point of 80°C at 265°C.
[0008]
8. Multilayer heat shrink film, according to claim 1, characterized in that the first polyester comprises amorphous polyester.
[0009]
9. Multilayer heat shrink film according to claim 1, characterized in that the film exhibits a total linear shrinkage at 85°C from 40% to 90% measured according to the otherwise modified linear shrinkage test , according to ASTM D 2732, and the first polyester is present in the film in an amount of at least 20% by volume, based on the volume of the total film.
[0010]
10. Multilayer heat shrink film according to claim 1, characterized in that the multilayer heat shrink film further comprises a fourth layer which is a second outer layer and which serves as a heat seal layer and which comprises at least one member selected from the group consisting of polyolefin, polyamide, polyester, polyvinyl chloride, and ionomer resin; and wherein the third layer is a first bonding layer and the multilayer heat shrink film further comprises a fifth layer which is between the fourth layer and the second layer, the fifth layer serving as a second bonding layer, the fifth layer comprising atr. minus one member selected from the group consisting of modified polyolefin, ethylene/modified unsaturated acid copolymer, ethylene/modified unsaturated ester copolymer, and polyurethane.
[0011]
11. Multilayer heat shrink film according to claim 10, characterized in that it further comprises a sixth layer which is between the second layer and the fifth layer, the sixth layer comprising at least one member selected from the group consisting of in (i) an amorphous polyamide, (ii) a combination of a semicrystalline polyamide and amorphous polyamide, and (iii) a combination of 6/12 polyamide and a different semicrystalline polyamide.
[0012]
12. Multilayer heat shrink film according to claim 11, characterized in that it further comprises a complementary bonding layer between the second layer and the third layer, with the complementary bonding layer comprising at least one member selected from the group consisting of modified polyolefin, modified ethylene/unsaturated acid copolymer, modified ethylene/unsaturated ester copolymer, and polyurethane.
[0013]
13. Multilayer heat shrink film according to claim 1, characterized in that it further comprises a complementary bonding layer between the second layer and the third layer, with the complementary bonding layer comprising at least one member selected from the group consisting of modified polyolefin, modified ethylene/unsaturated acid copolymer, modified ethylene/unsaturated ester copolymer, and polyurethane.
[0014]
14. Multilayer heat shrink film according to claim 1, characterized in that the film is in the form of a seamless pipe that has an extended flat width of 40 to 1000 millimeters, a thickness of 25.4 to 50, 8 µm (1 to 2 mils), and a total linear shrinkage at 85°C of 40% to 90% measured according to an otherwise modified linear shrinkage test in accordance with ASTM D 2732.
[0015]
15. Multilayer heat shrink film according to claim 1, characterized in that the film is in the form of a seamless pipe that has an extended flat width of 300 to 1,000 millimeters, a thickness of 50.8 to 127 μm (2 to 5 mils), and a total linear shrinkage at 85°C of 40% to 90% measured according to an otherwise modified linear shrinkage test in accordance with ASTM D 2732.
[0016]
16. An article of packaging characterized in that it comprises a multilayer heat shrink film thermally sealed thereto, the multilayer heat shrink film comprising: (A) a first layer comprising a first polyester, the first layer being an outer layer; (B) a second layer that serves as an O2 barrier layer, the second layer comprising at least one member selected from the group consisting of saponified ethylene/vinyl acetate copolymer, polyamide MXD6, polyamide 6I/6T, polyamide 6, polyvinylidene chloride, polyethylene naphthalate, polytrimethylene terephthalate, and liquid crystal polymer; (C) a third layer between the first layer and the second layer, the third layer serving as a tie layer, the third layer comprising at least one styrene-based copolymer; and wherein the binding layer comprises an anhydride functional styrene-based polymer if the binding layer is directly adhered to both an outer polyester layer and an inner polyamide layer, and wherein the multilayer heat shrink film exhibits shrinkage total linear at 85°C of at least 10% measured in accordance with a modified linear shrinkage test otherwise in accordance with ASTM D 2732, and the polyester is present in the film in an amount of at least 2% by volume , based on total movie volume; and wherein the packaging article is a member selected from the group consisting of end seal bag, side seal bag, L-seal bag, back seam bag, and bag.
[0017]
17. A packaging process characterized in that it comprises: (A) providing a filament of a flat, heat shrinkable multilayer film comprising: (i) a first layer comprising a first polyester, the first layer being an outer layer; (ii) a second layer that serves as an O2 barrier layer, the second layer comprising at least one member selected from the group consisting of saponified ethylene/vinyl acetate copolymer, polyamide MXD6, polyamide 6I/6T, polyamide 6, polyvinylidene chloride, polyethylene naphthalate, polytrimethylene terephthalate, and liquid crystal polymer; (iii) a third layer between the first layer and the second layer, the third layer serving as a binding layer, the third layer comprising at least one styrene-based copolymer; and wherein the binding layer comprises an anhydride functional styrene-based polymer if the binding layer is directly adhered to both an outer polyester layer and an inner polyamide layer, and wherein the multilayer heat shrink film exhibits shrinkage total linear at 85°C of at least 10% measured according to an otherwise modified linear shrinkage test in accordance with ASTM D 2732, and the polyester is present in the film in an amount of at least 10% by volume, based on total movie volume; (B) using the film in a flow wrap type process to produce a partially packaged product comprising a back-seamed packaging article having a bottom seal and an open top, the packaging article having a product therein; (C) evacuating atmosphere from within the packaging article and sealing the open top of the packaging article closed so that the product is surrounded by the packaging article; and (D) shrink the packaging article around the product.
[0018]
18. A process for producing an annular heat shrink film characterized in that it comprises: (I) coextruding an annular multilayer extrudate downwardly from an annular matrix, the annular multilayer extrudate comprising: (A) a first layer comprising a first polyester, the first layer being an outer layer; (B) a second layer that serves as an O2 barrier layer, the second layer comprising at least one member selected from the group consisting of saponified ethylene/vinyl acetate copolymer, polyamide MXD6, polyamide 6I/6T, polyamide 6, polyvinylidene chloride, polyethylene naphthalate, polytrimethylene terephthalate, and liquid crystal polymer; (C) a third layer between the first layer and the second layer, the third layer serving as a tie layer, the third layer comprising at least one styrene-based copolymer; and wherein the tie layer comprises an anhydride functional styrene-based polymer if the tie layer is directly adhered to both an outer polyester layer and an inner polyamide layer; (II) quenching the annular extrudate by applying a quench liquid to the annular extrudate; (III) reheating the extrudate to an orientation temperature of 54°C to 99°C, resulting in a reheated annular extrudate; and (IV) orienting the reheated annular extrudate while the reheated annular extrudate is in the solid state, the orientation being performed with a total orientation factor of at least 2, so that an oriented multilayer heat shrink film is produced; and wherein the orientation is performed such that the oriented multilayer heat shrink film exhibits a total linear shrinkage at 85°C of at least 10% measured in accordance with an otherwise modified linear shrinkage test in accordance with ASTM D 2732, and the first polyester is present in the film in an amount of at least 2% by volume, based on the total film volume.
[0019]
19. Process according to claim 18, characterized in that the quench liquid absorbs heat from the annular extrudate as at least 50% of the quench liquid falls below the annular extrudate by a distance of at least 5 .08 cm (2 inches), the quench liquid making initial contact with the annular extrudate at a distance of 0.254 to 20.32 cm (0.1 to 8 inches) downstream of a point at which the annular extrudate emerges from the annular array.
[0020]
20. Process according to claim 18, characterized in that it further comprises reheating the multilayer heat shrink film after it has been oriented in the solid state.
[0021]
21. A multilayer heat shrink film, characterized in that it comprises: (A) a first outer layer comprising a first polyester; (B) a second outer layer that serves as a heat seal layer; (C) a first inner layer comprising a polyamide; (D) a second inner layer between the first inner layer and the first outer layer, the second inner layer serving as a tie layer, the second inner layer comprises a combination of: (i) a first combination component comprising a polyolefin of functional anhydride; (ii) a second combination component comprising at least one member selected from the group consisting of styrene/maleic anhydride copolymer, styrene-ethylene-butylene-styrene anhydride functional copolymer, styrene-butadiene-styrene anhydride copolymer functional, styrene-isoprene-styrene functional anhydride copolymer, styrene-ethylene-butadiene-styrene functional anhydride copolymer, and styrene(ethylene-propylene rubber)-styrene functional anhydride graft copolymer; and (iii) a third blend component comprising a second polyester; and wherein the multilayer heat shrink film exhibits a total linear shrinkage at 85°C of at least 10 percent measured in accordance with an otherwise modified linear shrinkage test in accordance with ASTM D 2732, and the first polyester is present in the film in an amount of at least 5% by volume, based on the total film volume.
[0022]
22. Multilayer heat shrink film according to claim 21, characterized in that: the first combination component comprises an ethylene/alpha-olefin functional anhydride copolymer; the second combination component comprises anhydride functional styrene/butadiene block copolymer; and the third blending component comprises a linear, thermoplastic, semi-crystalline saturated polyester resin having a density of 1.15 to 1.30 g/cm3, a melting point of 150 °C to 160 °C and a melt index from 0.5 to 2 g/10 min; wherein the first outer layer constitutes from 5 to 20% by volume based on the total film volume, the second outer layer constitutes from 15 to 40% by volume based on the total film volume, the first inner layer constitutes from 10 to 30% by volume based on total film volume, and the second inner layer constitutes 10 to 30% by volume based on total film volume, and the film has a total thickness of 38.1 to 101.6 µm ( 1.5 mils to 4 mils); and wherein the first combination component constitutes from 30 to 80% by weight based on the total layer weight, the second combination component constitutes from 10 to 50% by weight based on the total layer weight, and the third component of blend constitutes from 2 to 20% by weight based on total layer weight.
[0023]
23. Multilayer heat shrink film according to claim 21, characterized in that: the first combination component constitutes from 40 to 70% by weight based on the total layer weight, the second combination component constitutes from 20 to 40% by weight based on total layer weight, and the third blend component constitutes from 5 to 15% by weight based on total layer weight; and the first combination component comprises an anhydride functional ethylene/alpha-olefin copolymer, and the second combination component comprises anhydride functional styrene/butadiene block copolymer, and the third combination component comprises a linear saturated polyester resin , thermoplastic, semi-crystalline which has a density of 1.15 to 1.30 g/cm3, a melting point of 150°C to 160°C, and a melt index of 0.5 to 2 g/10 min.
[0024]
24. Multilayer heat shrink film according to claim 21, characterized in that the polyamide in the first inner layer comprises at least one member selected from the group consisting of: (a) a combination of a semi-crystalline polyamide and a amorphous polyamide; (b) a combination of a semicrystalline polyamide and 6/12 polyamide; and (c) 100% amorphous polyamide.
[0025]
25. Multilayer heat shrink film according to claim 21, characterized in that the film exhibits a total linear shrinkage at 85°C of at least 40% measured according to a modified linear shrinkage test, otherwise according to ASTM D 2732.
[0026]
26. Multilayer heat shrink film according to claim 21, characterized in that the film exhibits a total linear shrinkage at 85°C of at least 60% measured according to a modified linear shrinkage test, otherwise according to ASTM D 2732.
[0027]
27. Multilayer heat shrink film according to claim 21, characterized in that the second outer layer that serves as the heat seal layer comprises at least one member selected from the group consisting of polyolefin, polyamide 6/12 , polyamide 12, ionomer resin, ethylene/unsaturated acid copolymer, ethylene/unsaturated ester copolymer, polyester having a melting point of up to 150°C; and wherein the second outer layer comprises a homogeneous ethylene/alpha-olefin copolymer having a density of 0.89 to 0.91 g/cm 3 .
[0028]
28. Multilayer heat shrink film according to claim 21, characterized in that the film further comprises (E) a third inner layer that serves as an O2 barrier layer, the third inner layer comprising at least one selected member from the group consisting of saponified ethylene/vinyl acetate copolymer, polyamide MXD6, polyamide 6I/6T, polyamide 6, polyvinylidene chloride, polyethylene naphthalate, polytrimethylene terephthalate, liquid crystal polymer, and O2 scavenger, the third inner layer being between the first inner layer and the second outer layer.
[0029]
29. Multilayer heat shrink film according to claim 28, characterized in that the film further comprises: (F) a fourth inner layer which serves as a bonding layer, the fourth inner layer being between the second outer layer and the third inner layer; and (G) a fifth inner layer between the third inner layer and the fourth inner layer, the fifth inner layer comprising a combination of at least one member selected from the group consisting of: (a) a combination of a semi-crystalline polyamide and an amorphous polyamide, (b) a combination of a semicrystalline polyamide and 6/12 polyamide, and (c) 100% amorphous polyamide.
[0030]
30. Multilayer heat shrink film according to claim 29, characterized in that: (A) the polyester in the first outer layer comprises polyethylene terephthalate copolymer in an amount of at least 95% by weight, based on weight full layer; (B) the second outer layer comprises a blend of 75 to 90% by weight of homogeneous ethylene/alpha-olefin copolymer having a density of 0.895 to 0.905 g/cm3, and from 10 to 25% by weight of a copolymer of heterogeneous ethylene/alpha-olefin which has a density of 0.915 to 0.925 g/cm3; (C) the first inner layer comprises a combination of (i) from 60 to 95% by weight of at least one member selected from the group consisting of polyamide 6 and polyamide 6/66, and (ii) from 5 to 40 % by weight 6I/6T polyamide; (D) the second inner layer comprises (i) from 50 to 70% by weight of an ethylene/alpha-olefin anhydride functional copolymer, (ii) from 20 to 40% by weight of styrene/butadiene block copolymer of functional anhydride; and (iii) from 5 to 15% by weight of polyester; (E) the third inner layer comprises saponified ethylene vinyl acetate copolymer; (F) the fourth inner layer comprises an anhydride grafted ethylene/alpha-olefin copolymer; and (G) the inner fifth layer comprises a combination of (i) from 60 to 95% by weight of at least one member selected from the group consisting of polyamide 6 and polyamide 6/66, and (ii) from 5 to 40% by weight 6I/6T polyamide; and wherein the first outer layer is 5 to 15% by volume based on the total film volume, the second outer layer is 15 to 25% by volume based on the total film volume, the first inner layer is 10 at 20% by volume based on total film volume, second inner layer constitutes 10 to 20% by volume based on total film volume, third inner layer constitutes 2 to 10% by volume based on total film volume. total film, the inner fourth layer constitutes 20-30% by volume based on the total film volume, and the inner fifth layer constitutes 10-20% by volume based on the total film volume.

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同族专利:

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公开号 | 公开日

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AU2014341952A1|2016-05-05|

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AU2018208651A1|2018-08-09|

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MX2016005175A|2016-08-12|

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CN105658430A|2016-06-08|

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AU2018208651B2|2019-05-23|

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EP3063004A1|2016-09-07|

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NZ719181A|2020-12-18|

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CA2927107C|2018-07-31|

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US11020944B2|2021-06-01|

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EP3063004B1|2018-02-28|

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CA2927107A1|2015-05-07|

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AU2014341952B2|2018-08-09|

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US10843443B2|2020-11-24|

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WO2015066570A1|2015-05-07|

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US20170144416A1|2017-05-25|

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KR20160078492A|2016-07-04|

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US20190291396A1|2019-09-26|

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ES2669219T3|2018-05-24|

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KR102151839B1|2020-09-03|

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CN105658430B|2020-03-31|

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法律状态:
2020-02-18| B06U| Preliminary requirement: requests with searches performed by other patent offices: procedure suspended [chapter 6.21 patent gazette]|

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2021-04-20| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|

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2021-05-11| B16A| Patent or certificate of addition of invention granted|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 01/11/2014, OBSERVADAS AS CONDICOES LEGAIS. |

优先权:

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申请号 | 申请日 | 专利标题

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US201361898757P| true| 2013-11-01|2013-11-01|

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US61/898,757|2013-11-01|

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US201461976850P| true| 2014-04-08|2014-04-08|

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US61/976,850|2014-04-08|

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US201462055144P| true| 2014-09-25|2014-09-25|

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US62/055,144|2014-09-25|

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PCT/US2014/063600|WO2015066570A1|2013-11-01|2014-11-01|Delamination-resistant heat-shrinkable multilayer oxygen barrier film containing polyester|

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