Natural fiber plastic composite product and method for preparing thereof

专利摘要:
The present application relates to a method for preparing a natural fiber plastic composite board the method comprising forming a mixture comprising 25–35% (w/w) recycled polyethylene, 25–35% (w/w) recycled label material, 25–35% (w/w) organic filler comprising wood powder, 5–10% (w/w) inorganic filler, and 2.0–4.0% % (w/w) coupling agent, and forming the mixture into a natural fiber plastic composite board. The present application also provides a natural fiber plastic composite board.
公开号:FI20195613A1
申请号:FI20195613
申请日:2019-07-05
公开日:2020-07-15
发明作者:Juha Nikkola；Kalle-Pekka Niipala
申请人:Upm Kymmene Corp；
IPC主号:

专利说明:

Natural fiber plastic composite product and method for preparing thereof Field of the application The present application relates to natural fiber plastic composite materials, composite products such as composite boards made thereof, and to methods for preparing the products. Background Natural fiber plastic composite products typically comprise fiber material, such as cellulose, and at least one kind of plastic polymer. The composite products may be provided as boards or planks which may be used for several purposes, for example for furniture, deck floors, fences, window frames, and door frames.
To support circular economy it is desired to manufacture environment-friendly and sustainable composite products utilizing recycled materials. However, the quality of the recycled material is usually not as high as corresponding virgin materials, so the obtained products may suffer from instable quality problems, and using the recycled materials may also make the manufacturing process challenging. Therefore there is a need to develop better manufacturing methods and higher quality composite products utilizing recycled raw materials. Summary = It was found out how to prepare natural fiber plastic composite products from N recycled plastics and label materials, which composite products exhibit high S guality in respect of mechanical strength and other properties. Especially 3 30 composite boards, such as decking boards, planks and the like, could be I prepared. The composite products can be prepared by using mainly recycled N raw materials, and it is not necessary to add any virgin plastic, cellulose and/or © wood material.
O N 35 The present application provides a method for preparing a natural fiber plastic composite products the method comprising forming a mixture comprising -15—35% (w/w) recycled polyethylene,
-25—35% (w/w) recycled label material, -25—45% (w/w) organic filler comprising wood powder, -5-10% (w/w) inorganic filler, -2.0-4.0% % (w/w) coupling agent, and -optionally 0.5-4% lubricant, and forming the mixture into a natural fiber plastic composite product. The present application also provides a natural fiber plastic composite products comprising -20-45% (w/w) recycled thermoplastic polymer(s) comprising polyethylene, such as recycled high density polyethylene (HDPE), -20-30% (w/w) recycled cellulosic fibers from recycled label material, -25—45% (w/w) organic filler comprising wood powder, -5-10% (w/w) inorganic filler, such as talcum or calcium carbonate, -optionally 0.5-4% lubricant, and -2.0—4.0% (w/w) coupling agent, wherein the product comprises impurities comprising silicone(s), adhesive(s) and optionally printing ink(s). The natural fiber plastic composite products may be prepared with the method disclosed herein. The present application also provides use of the natural fiber plastic composite product, such as board, as a building element, a facade, a floor element, such as a decking board, a landscaping element, a furniture, a window frame or a door frame or profile, a cover strip, a support rail, a railing, a fence, a noise = barrier, and/or a part thereof.
N S The main embodiments are characterized in the independent claims. Various 3 30 embodiments are disclosed in the dependent claims. The embodiments and I examples recited in the claims and in the description are mutually freely N combinable unless otherwise explicitly stated. i, O When recycled plastics and label materials are included in composite N 35 materials, the mechanical and structural properties of the final products may be weaker compared to products made from corresponding virgin materials. However, it was found out that by including specific fillers in the composite material and using specific amounts of the ingredients, these properties could be maintained, and even enhanced. Mechanical properties such as flexural strength, flexural modulus, impact strength and linear shrinkage could be improved, especially in extruded products. In addition thermal properties, such as heat reversion and thermal expansion, and properties such as moisture absorption were also improved. Such properties are especially important in products designed for outdoor use.
Especially in elongated composite products, such as composite boards, it is desired to obtain a certain stiffness, hardness and tensile or flexural properties of the product to avoid bending and wearing during storing, handling and use. These properties can be enhanced by applying a polymeric coating. However, when using the composition disclosed herein there is no or less need for such coating. For example a partial coating may be used.
Further, when recycled label material is used as raw material it may not be necessary to dry the raw material as the plastic present in the material lowers the moisture variation.
It is therefore possible to use inexpensive and readily available recycled materials in composite products without compromising the quality and other properties of the obtained products. Such products are useful for example as composite boards, which may be exposed to weather and other challenging conditions, so they may be used outdoors.
Brief description of the drawings oO N Figure 1 shows a cross section of a schematic board of an embodiment
S 3 30 Figure 2 shows a cross section of a schematic board of an embodiment x containing apertures inside the body along the lengthwise direction of the body
O o Figure 3 shows a cross section of a schematic installation of two boards 3 on a support by using a fastener clip & 35 Figure 4 shows test results for different compositions for the effect of flexural strength and flexural modulus
Figure 5 shows test results for the effect of fiber dosage on impact strength Figure 6 shows test results for the effect of fiber dosage on linear shrinkage % Figure 7 shows test results for the effect of wood powder on moisture absorption Figure 8 shows test results for the effect of coupling agent dosage on flexural strength and modulus Figure 9 shows test results for the effect of LDPE blending on flexural strength and modulus Figure 10 shows test results for the effect of fiber source to flexural strength and modulus Figure 11 shows a graph presenting the particle diameter (size) distribution for Sample 1 Figure 12 shows a graph presenting the particle diameter (size) distribution for Sample 2 Figure 13 shows a graph presenting the particle diameter (size) distribution > for Sample 3O
N S Figure 14 shows a graph presenting the particle diameter (size) distribution 3 30 for Sample 4
I = n Figure 15 shows a comparison of saw dust (15A) and sanding dust (15B) o visualized microscopically. 3 Detailed description
All the percentage values disclosed herein refer to percentages by weight (w/w) of dry weights unless otherwise mentioned. The sum of the ingredients, such as polymers, fillers and additives, in the embodiments and examples disclosed herein adds up to 100% (w/w). The open term “comprise” also 5 includes the closed term “consisting of” as one option. The present application provides a method for preparing a natural fiber plastic composite products, such as composite bodies, for example composite boards or the like. The present application also provides composite products, which may be obtained by the method, and products including such composite products.
The method comprises forming a mixture comprising the ingredients, and forming the mixture into a natural fiber plastic composite product, such as a composite board. Preferably only recycled polymers and cellulosic materials are used, i.e. the composite material may not contain virgin plastic polymers, cellulosic material and/or wood material. However the composite material may be coated by using virgin materials, if necessary.
The composite product comprises polyolefin(s) as polymeric matrix material. Especially recycled polyolefins are desired in the method and product. It was found out that recycled polyethylene could be used to form desired composite products, especially composite boards. Even though different polyolefins could be used in composite products, and for example polypropylene could provide better properties in many respect, recycled polyethylene is highly available and reasonably priced and therefore it may be a desired raw material. On the other = hand, recycled polyethylene could have a negative effect to the properties of N the final composite product, especially to the structural and mechanical S properties. However, when the composite product was prepared as described 3 30 herein, also with recycled polyethylene it was possible to obtain desired x structural and mechanical properties of the final product.
O o Polyethylene is a thermoplastic polymer which may be classified into several O different categories based on density and branching. Examples of such | 35 categories include ultra-high-molecular-weight polyethylene (UHMWPE), ultra-low-molecular-weight polyethylene (ULMWPE or PE-WAX), high- molecular-weight polyethylene (HMWPE), high-density polyethylene (HDPE),
high-density cross-linked polyethylene (HDXLPE), cross-linked polyethylene (PEX or XLPE), medium-density polyethylene (MDPE), linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), very-low-density polyethylene (VLDPE) and chlorinated polyethylene (CPE). The melting point and glass transition temperature may vary depending on the type of polyethylene. For virgin medium and high-density polyethylene the melting point is typically in the range of 120-180°C, and for average low-density polyethylene in the range of 105-115°C. However, in the case of recycled polymers the melting point may be even lower.
Recycled polyethylene is commercially available, usually as different grades. For example recycled polyethylene may be provided as separate products containing LLDPE, LDPE or HDPE only.. Such recycled material contains impurities such as pigments and/or dyes, carbon black pigments, remains of mineral fillers such as talc or CaCO3, remains of cellulose and/or adhesives, and it may also contain other thermoplastic polymers and/or reagents used in the recycling process as well as unwanted reaction products, which may be also considered as impurities. The recycled polyethylene may contain 0.1— 10% (w/w) of the impurities, such as 0.5-5% (w/w) or 0.5-3% (w/w). The material may have been recycled several times which deteriorates the polymer structure and the properties of the material, such as density and melt index, and raises the ash content. For example recycled polyethylene may be recognized by studying the impurity content and/or melt index and/or density of the material. Further, recycled polyethylene may have been dyed to mask the coloured impurities, so the material may be black or grey, and therefore the appearance thereof may not be appealing and desired in final products. = However it was found out that it was possible to include relatively large amount N of such material in a composite product. The mixture comprising the S ingredients comprises 15-35% (w/w) of the recycled polyethylene, such as 3 30 27-33% (w/w), for example about 30% (w/w). This does not include I polyethylene from other sources, such as from the label waste. The “recycled N polyethylene is this context refers to a recycled product containing o substantially or mainly polyethylene, in general from plastic recycling, 3 preferably obtained from polyethylene waste. The recycled plastics may have been sorted, and the sorted polyethylene material may have been shredded. These shredded fragments may then undergo processes to eliminate impurities like paper labels.
This material may be melted and optionally extruded into the form of pellets or granules.
The obtained final product may contain the same amount of recycled polyethylene, or more, if recycled polyethylene is applied also from other sources and/or if the polyethylene is reacted with coupling agent(s), in case where covalently bound coupling agent increases the mass of the polymer.
Therefore the final product may contain thermoplastic polymer comprising recycled polyethylene, or recycled polyethylene, up to 51% (w/w), up to 50% (w/w), up to 47% (w/w), or up to 44% (w/w), such as 25-50% (w/w), 25-47% (w/w), for example 32-44% (wiw). In one embodiment the recycled polyethylene comprises or is recycled high density polyethylene (HDPE). High density polyethylene was found to enhance the mechanical properties of the obtained composite.
It was found out that recycled low density polyethylene, or a mixture of recycled low and high density polyethylenes, did not provide as good mechanical properties as high density polyethylene alone.
Another ingredient of the composite material mixture is recycled label material.
The mixture comprising the ingredients comprises 25-35% (w/w) of recycled label material, such as 27-33% (w/w), for example about 30% (w/w). The recycled label material may include recycled adhesive laminate, face material, adhesive material, and/or release material.
In general recycled label material(s) are based on label laminate manufacturing, converting, dispensing and/or recycling of label waste materials produced thereof.
The label material = may contain or refer to label laminate material, such as paper or plastic N laminates, which contain one or more layer(s) of paper and/or plastic and one S or more layer(s) of other material(s), such as adhesive(s), release agent(s), 3 30 printing(s) and/or the like.
Also this recycled label material could have a I negative effect to the properties of the final composite product, but it was still N possible to use relatively high amount of such material in the composite. i, O In general the recycled label material comprises mainly cellulosic material and N 35 synthetic polymers, such as plastic(s), raw material(s) of plastic, silicone- based compound(s), and adhesive material, such as dispersion adhesive(s), latex, adhesive resin(s) and derivative(s) thereof.
The synthetic polymer may refer to any fully or semi synthetic polymer. The recycled label material may comprise thermoplastic polymer(s) and cellulosic material(s), and impurities comprising silicone(s) adhesive(s) and optionally printing ink(s). Also pigments, dyes, reagents or other materials or agents considered as impurities may be included. The recycled label material may contain 0.1-10% (w/w) of the impurities, such as 0.5-5% (w/w) or 0.5-3% (w/w). The exact composition of the recycled label materials may vary depending on the source, but when preparing the composite products the total composition of the recycled label material may be adjusted by combining different recycled materials to obtain a desired composition and/or to provide the recycled label material described herein. The impurities may be detected from the final composite products by studying the product visually, such as by microscopically, to detect the coloured impurities, or the chemical composition of the product may be analysed.
The thermoplastic polymers, also called as plastics or plastic polymers, may comprise polyolefins, such as polyethylene, polypropylene, polymethylpentene or polybutene-1, or polyamide, polystyrene, polyethylene terephthalate (PET), polyvinyl chloride (PVC) or polycarbonate. Preferably the thermoplastic polymers comprise mainly polyolefins, such as polyethylene and/or polypropylene. The cellulosic material in the recycled labels comprises cellulosic fibers, which do not include the wood particles, i.e. the cellulosic material is not wood material. However, the cellulosic material may be derived from wood. The cellulosic material, which is material comprising cellulosic fiber, may originate = from pulp, such as mechanical, chemical or chemithermomechanical pulp, N preferably chemically treated pulp. The cellulosic material may originate from S recycled papers, cardboards, labels, release liners, and the like, which may be 3 30 included in the recycled label material. Preferably the obtained mixture or the I final composite material does not contain virgin cellulosic material(s) or virgin N cellulosic fibers. > O In one example the recycled label material, such as face and/or release N 35 material, comprises paper, paperboard or the like. In one example the recycled label material comprises fine paper, such as a wood-free or lignin-free paper. In one example the recycled label material is formed of substantially plastic and/or cellulosic material. The recycled label material, or the paper, paperboard or other cellulosic fibers therein, may be lignin-free, or the lignin content may be low, such as less than 1% (w/w), less than 0.5% (w/w) or less than 0.1% (w/w). Such lignin-free or low-lignin material, which usually contain cellulose obtained from chemical pulping, such as from kraft pulping, is homogenous, stabile and resilient, and it has a longer fiber length when compared to mechanically refined fiber material. Therefore it enhances the structural and mechanical properties of the composite material.
The recycled label material may comprise 70-90% (w/w) of cellulosic material, such as paper or paperboard, for example 75-85% (w/w), and 10-30% (w/w) of thermoplastic polymer(s), such as 15-25% (w/w).
The final composite product may comprise 17.5-31.5% (w/w), such as 20- 30% (w/w), of cellulosic material, or cellulose, more particularly recycled cellulosic fibers. The recycled label material raises the total thermoplastic polymer content of the final product, for example by 2.5-10 or 5-10 percentage units.
The recycled label material may act as filler, and it provides polymer(s), natural fibers and optionally also inorganic filler(s) to the composite material. The recycled label material may be obtained from discarded face materials or adhesive label laminates, liners, trimmings, waste matrix, printings and the like, for example from processes of manufacturing label laminates and the like.
A label structure comprising a face layer, an adhesive layer and a release liner may be called as an adhesive label laminate.
oO N The recycled label material may comprise adhesive label laminate waste S material. Alternatively or in addition the recycled label material may comprise 3 30 release liner material. Release liner typically includes a substrate, such as a I plastic film or a paper, which is coated with silicone or other release agent. The N release liner is subseguently contacted with an adhesive layer, such as a o pressure-sensitive adhesive, and laminated with the face material layer so as 3 to form an adhesive label laminate. Release liner is to be removed from the label laminate structure to expose the adhesive surface so that the label may be attached to a target. An adhesive label usually contains one or more layers of paper and/or plastic film(s) and one or more layer(s) of adhesive(s). The label and/or the release liner may be printed, dyed, pigmented or they may contain any other additional agents. The paper(s) may include coating(s), filler(s) and the like additives.
The recycled label material, such as label laminate waste, may include adhesive material(s), glue(s), ink(s), dye(s), pigment(s), inorganic filler(s), and/or release agent(s), such as silicone-based agent(s), and/or other agents or components considered as impurities. The recycled label material may be obtained for example from label laminate production, label laminate press facilities and/or label laminate end users. In other words, the recycled label material may be obtained from label conversion and/or dispensing steps. The recycled label material may comprise for example coated and/or uncoated papers, comprising cellulose fibers and possibly inks or pigments, inorganic filler(s), and/or adhesive(s), such as water-based acrylic polymer adhesives, hotmelt adhesives, and/or rubber adhesives. In one example the recycled label material is provided as chaff, which may refer to shredded material. The chaff may be used in the mixture or in the composite material. More particularly the recycled label material, such as adhesive laminate waste, may be chopped or shredded and screened into chaff material of a desired particle size before making the composite material. In one example the particle size of the chaff is in the range of 1-10 mm, such as 3-5mm. Any other recycled material may be formed into chaff material in similar way. It is not necessary to form granules from the recycled material(s) but the material(s) can be used as ungranulated. oO N Recycling refers to new use of material, wherein the material to be recycled is S recovered and provided for a new use, such as for the manufacture of 3 30 composite materials disclosed herein. The “recycled material’ discussed x herein may be also called material to be recycled or recyclable material.
O o If necessary, the materials, such as recycled materials and/or non-plastic 3 materials, used in the composites are dried before usage, and they are provided as dry. The water or moisture content of the dry material, especially the cellulosic fibers and/or the wood powder, may be 10% (w/w) or less, 7% (w/w) or less, 5% (w/w) or less, or 3% (w/w) or less, such as in the range of
0.1-10% (w/w), such as 0.1—-7% (w/w), such as 0.1-5% (w/w), or 0.1-3% (w/w). The method may comprise setting the moisture content into said range. However, recycled materials may already have a relatively low moisture content, for example compared to never-dried pulp or fresh wood material, so obtaining the desired dry content is easy and does not require much energy or special equipment. Further, when dry materials are used, the wetting of the fiber material and mixing and adhesion between the matrix material and the fiber material can be improved and the flocculation of the fiber material can be avoided because in this case the coupling agent may not react first with water but it reacts with the fiber material.
To compensate the negative effects of the recycled raw materials, specific fillers were introduced to the composite material. One filler is organic filler comprising wood powder. In one embodiment the organic filler is wood powder. The addition of wood powder improved the processability of the formed mixture. In general the organic filler comprises or is cellulosic material containing lignin, such as having a lignin content in the range of 5-30% (w/w), or 10-30% (w/w), calculated as dry weight. Such material may be wood. The wood material is not pulped material. Wood material may contain cellulose in the range of 38-45% (w/w), such as 38-42% (w/w), and it may contain hemicelluloses in the range of 25-35% (w/w). Delignified cellulose pulp based materials, wherein the lignin has been removed or the content thereof is lowered, are excluded. On the contrary, lignin as such does not provide such preferable properties either. The lignin content in the final product may be in the range of 0.25—5.25% (w/w), such as 0.75-5.25% (w/w). = The mixture comprising the ingredients comprises 25-45% (w/w) organic filler N comprising wood powder, such as 27-43% (w/w), for example about 30% S (w/w). This content was found to optimal in respect of the mechanical 3 30 properties. Too high content of the organic filler could enhance water I absorption in the final product, which is not desired especially in outdoor N products It was also possible to affect to the linear shrinkage of the composite o product with the amount and the type of the wood powder, which has especially 3 great effect to elongated products, such as boards and the like. It was also found out that when using wood powder in the amounts presented in the embodiments, the water absorption was less than 10%. This is at an acceptable level and does not have remarkable impact to the structural properties and durability of the composite product. In one example the organic filler consist of wood, such as wood powder. The wood material may be softwood, such as spruce, pine, fir, larch, douglas-fir or hemlock, or hardwood, such as birch, aspen, poplar, alder, eucalyptus, or acacia, or a mixture of softwood and hardwood. Especially birch, spruce, pine and beech were found suitable, birch and spruce being preferable. Preferably the wood material is dried, such as having a moisture content of 10% (w/w) or less, such as 7% (w/w) or less, 5% (w/w) or less, or 3% (w/w) or less, for example in the range of 0.1-10% (w/w), 0.1-5% (w/w), or 0.1-3% (w/w). The method may comprise setting the moisture content into said range, for example by drying. The wood powder may be obtained from plywood grinding or sanding, which may contain birch, beech or spruce, and/or it may be commercial wood powder, such as spruce. The wood powder may be also considered as recycled material, especially if it is a by-product of a process such as grinding, sanding or other processing of wood products. It was found preferable that the wood powder has a bulk density of 200 g/l (kg/m ) or less, such as in the range of 150-200 g/l. Wood powder having such a bulk density was found to provide such filler properties that supported the mechanical and structural properties of the obtained composite material, such as flexural strength, flexural modulus, heat reversion, linear shrinkage and thermal expansion.
Bulk density is a property of dust, powders, granules or other solids, which is = defined as the mass of many particles of the material divided by the total N volume they occupy. The total volume includes particle volume, inter-particle S void volume, and internal pore volume. Bulk density may be divided into three 3 30 classes, aerated, poured and tap. Each of these depends on the treatment to I which the sample is subjected. Aerated bulk density is when the volume of the N powder is at a maximum, caused by aeration, just prior to complete breakup o of the bulk. Poured bulk density is when the volume is measured after pouring 3 powder into a cylinder, creating a relatively loose structure. Tapped bulk density is, in theory, the maximum bulk density that can be achieved without deformation of the particles. In practice, it is generally unrealistic to attain this theoretical tapped bulk density, and a lower value obtained after tapping the sample in a standard manner is used. Bulk density may be measured by ASTM D 6111 "Standard Test Method for Bulk Density and Specific Gravity of Plastic Lumber and Shapes by Displacement”. The test method covers the determination of the bulk density and specific gravity of materials in their “as manufactured” form. Therefore, this test method evaluates a product, not an inherent material property. The wood powder, which may be also called wood dust, may be a by-product or waste product of woodworking operations such as sanding or other suitable mechanical treatment, so it may be considered as a recycled material. Preferably the present compositions do not contain saw dust. Wood powder differs from saw dust (sawings) for example in size, composition and moisture content. In this application, wood powder may also be called as sanding dust. Saw dust is formed for example in sawing of wood material such as logs. When such fresh wood material is sawn, the obtained saw dust is usually present in its natural moisture content. The moisture content may be for example 20— 100% (w/w). Also the average particle size of saw dust is usually 0.5 mm or more, or 1.0 mm or more, such as 1-5 mm. Saw dust was analyzed for particle size distribution in separate tests, and it was found out that the analyzed samples contained 37.3% or 42.5% of particles with a size of 2 mm or more. In further fractionating tests it was found out that saw dust contained 24.5% of particles having size over 4 mm, 18.0% of particles having size in the range of 2-4mm and 57.5% of particles with size of less than 2 mm. The size may refer to the largest dimension of a particle. The average aspect ratio of saw dust, which may be in the range of 1:1 to 1:4, isremarkably smaller than with sanding = dust, which may be in the range of 1:5 to 1:22, such as 1:7 to 1:22, 1:10 to N 1:22 or 1:10 to 1:20.
S 3 30 The analysis of particle or fiber length and width distributions can be carried I Out for example by using tube-flow fractionation methods, which can be used N to fractionate particles over the wide size range of particles (such as 1-5000 o um) with high selectivity. The classification of particles in different size 3 categories enables fractional analysis of samples. The particle length is probably the most significant individual shape factor in particle classification for different size categories using tube flow fractionation. Particle size distribution may be determined also for example by using a laser diffraction particle size distribution analyzer device. Saw dust obtained from spruce was analyzed by screening, and the tests revealed that the screen rejects were distributed as follows: >2.00 mm 37.3%, >1.00 mm 37.9%, >500 pm 20.0%, >200 um 3.9%, >100 um 0.6% and >45 um 0.17% (by weight). When wood powder is obtained from sanding operations of already processed wood materials, such as plywood and the like, the starting material is already different. For example plywood is obtained from logs which have been soaked in warm water, rotary cut into plies, heated/dried at hot oven at a temperature of from 100 to 220 °C, stacked and glued into slabs, and hot pressed at a temperature of from 120 to 150 °C, for example at about 135 into plywood sheets. In an example, the warm water for soaking the logs has temperature between 15 and 50 °C. The above disclosed heat treatment, referred as heating/drying, at a temperature of from 100 to 220 °C, for example at about 180°C, may last for at least 1 minute, preferably at least 2 minutes, for example between 5 and 15 minutes. In this way, the heat treatment (heating/drying) can be seen as a primary way for heat treating the plywood material (first heat treatment step). Hot pressing at the temperature of from 120 to 150 °C can be seen as a secondary way for heat treating the plywood material (second heat treatment step). Finally the sheets are sanded, especially at the largest surfaces of the sheets. Therefore the surface plies have already undergone two phases at high temperatures so emissions have been evaporated from the wood material at these temperatures. Therefore the obtained sanding dust no = longer contains as much volatile compounds as for example sawdust. Such N volatile compounds may be volatile organic compounds (VOC), which are not S desired in materials, such as composite materials. The volatile compounds 3 30 may provide smell problems and/or health risks. Therefore when using sanding I dust obtained from already processed wood materials, it is possible to obtain N products with lowered VOC content and health risk, and which do not produce © undesired smell.
O N 35 The sanding dust of plywood or other processed wood products is very dry, because the plies have undergone drying process and hot press. Further, during sanding of the already dry wood products heat is produced which further enhances the drying of the wood powder and may be considered as a heat treatment. Therefore the moisture content of sanding dust may be 5% (w/w) or less, even 3% (w/w) or less. Providing the wood powder in dry form saves energy and time as there is no need to provide drying equipment and dry the product before the use. However wood powder is hygroscopic material so it absorbs moisture from ambient atmosphere, so in practice the moisture content of wood powder may be 10% or less. In one embodiment the method comprises providing the wood powder in a moisture content of 10% (w/w) or less, or 7% (w/w) or less, such as in the range of 0.1-10% (w/w), for example 1-10% (w/w) or 1-7% (w/w). Preferably the wood powder is obtained from soaked and heat-treated wood, such as wood treated at least once at a temperature of about 100°C or more, such as at a temperature in the range of 100-220°C, for example at the one or more heat treatment(s) discussed in previous.
Saw dust is usually obtained as wood chips with relatively high particle size. Wood chips can be furthermore grinded down to smaller particle size to enable processing of WPC products. However, in the process of obtaining the sanding dust, the grinding step can be avoided, because the desired particle size is obtained in the specific sanding process. Further, wood powder with different properties is obtained. The average particle diameter of the wood powder may be 400 um or less, 300 um or less, 260 um or less or 200 um or less, such as 100-300 um, 100-250 pm, 100-200 um, 150-300 um, 150-260 um or 150-250 um. In the tests it was found out that for birch and spruce over half of the particles had a diameter = of 260 um or less, or 200 um or less, or even 150 um or less or 125 um or less. N In the tests the mean particle diameter was in the range of 150-260 um for S birch and spruce. Wood powder may contain particles even down to 1 um, or 3 30 down to 5 um or 10 um. This particle diameter facilitated obtaining the bulk x density discussed in previous.
O o A fiber width of wood powder, such as sanding dust, may be in the range of 3— 3 10 um and an average aspect ratio (length/diameter) may be in the range of N 35 1:10—1:22, such as 1:15—1:22. The percentage of fines (particles shorter than 20 um) may be at least 14%, at least 20%, at least 30% or at least 40% or 45%, by weight, such as 14-60%, 20-60%, 30-60% or 40-60%.
The sanding wood powder contains cellulose, hemicellulose, lignin and extractives. It was noticed that during the plywood preparation process including heat and drying treatments, the extractive content of the wood is lowered. On the other hand the sanding dust contains more extractives than the ply itself, so it is assumed that extractives are transferred to the surface in heat pressing and/or other preparation step. Sawdust contains significantly higher amount of extractives. On the contrary pulp mainly contains cellulose as the hemicellulose, lignin and extractives have been removed or the content thereof has been lowered in pulping processes. However lignin has an ability to bind fibers together with the effect of heat and moisture. Lignin may therefore facilitate the processability of the wood powder in injection molding and extrusion.
In one embodiment the wood powder is sanding dust, preferably obtained from sanding of heat-treated wood, such as plywood. The wood used for obtaining the wood powder may comprise hardwood and/or softwood, such as birch, spruce, pine, beech or a combination thereof, preferably birch and/or spruce. Different wood sources contain different agents, such as extractives. For example spruce contains extractives with antimicrobial properties, which may be utilized for example in medical applications and medical products. Spruce material also does not mold or decay as fast as for example birch material. The wood powder being a recycled material also enables manufacturing environment-friendly and sustainable products. On the other hand, too high amount of extractives is avoided when using the heat-treated wood powder, which could have a negative impact to the other properties of the obtained > products.
& S The composite product also comprises inorganic filler. Without inorganic filler 3 30 the mechanical properties of the composite product would be much inferior.
= N The mixture comprising the ingredients, or the final product, comprises 5-10% co (w/w) inorganic filler, such as 5-8% (w/w) or 6-8% (w/w). The inorganic filler 3 may comprise one or more inorganic filler(s), such as mineral filler(s). The inorganic filler may comprise kaolin clay, ground calcium carbonate, precipitated calcium carbonate, titanium dioxide, wollastonite, talcum, mica, silica, or a mixture thereof. Preferably the inorganic filler is selected from talcum and calcium carbonate.
The inorganic filler may be provided as a separate source, but a part of the inorganic filler may originate from the recycled label material, especially from the paper or paperboard present in the label material.
It was found out that by including said amount of inorganic filler, especially talcum, it was possible to enhance mechanical properties of the products and lower the water absorption in the final product.
This compensates the water-absorbing tendency of wood powder, and the inorganic and organic fillers can support each other.
Part of the inorganic filler may originate from the recycled label material, wherein the paper or paperboard contained therein contains few percent of inorganic filler.
This may lower the amount of the added inorganic filler needed to obtain the amounts disclosed herein by about 0.5—1 percentage units.
The composite material contains one or more coupling agent(s), or coupling agent(s) is/are used for preparing the composite material.
The thermoplastic polymer(s) together with the coupling agent(s) may form the matrix material present in the composite material, and/or the coupling agent may react with the cellulosic fibers, such as with the OH groups present in the cellulose.
The coupling agent may modify the thermoplastic polymer and/or cellulosic fibers by grafting.
The mixture comprising the ingredients may comprise 2.0-4.0% (w/w) of the coupling agent, such as 2.5-3.5% (w/w). Depending on the type of coupling agent, the coupling agent may be present in the final product as such, or it may have reacted with the ingredient(s), such as thermoplastic polymers or fibers, covalently or non-covalently, and therefore may be integrated in the polymers or in the fibers, such as covalently bound.
The coupling agent may be a cross-linking agent, which may provide covalent or = non-covalent cross-linking.
The coupling may be carried out by using a suitable N grafting method, such as graft copolymerization, for example by xanthation, S high energy radiation, maleation, or acetylation. 3 30 I The coupling agent may be a polymeric coupling agent.
Preferably a coupling N agent which is compatible with the used polymer(s) is selected.
Polymeric o coupling agent preferably contains moiety or moieties, which are reactive or at 3 least compatible with the thermoplastic polymer material and moiety or moieties, which are reactive or at least compatible with the cellulosic fiber material.
Preferable polymeric coupling agent contains the same repeat units as the thermoplastic material used.
Advantageously at least 30% (w/w) or at least 40% (w/w), more preferably at least 50% (w/w) or at least 60% (w/w), and most preferably at least 80% (w/w) or at least 85% (w/w) of the moieties of the polymeric coupling agent are chemically the same as in the thermoplastic material. Advantageously said moiety or moieties which is/are reactive or at least compatible with the cellulosic fiber material comprise(s) anhydride(s), acid(s), alcohol(s), isocyanate(s), and/or aldehyde(s). In one example the coupling agent is acrylic acid grafted polymer and/or the coupling agent is methacrylic acid grafted polymer. Preferably the coupling agent comprises or consists of maleic acid anhydride grafted polymer, such as maleic anhydride grafted or functionalized polyolefin. The coupling agent may, in principle, be any chemical which is able to improve the adhesion between two main components. This means that it may contain moieties or components, which are reactive or compatible with thermoplastic material and moieties or components, which are reactive or compatible with the cellulosic fiber material. Examples of coupling agent comprise or consists of anhydrides, preferably maleic anhydride (MA) polymers and/or copolymers, such as maleic anhydride functionalized HDPE, maleic anhydride functionalized LDPE, maleic anhydride-modified polyethylene (MAHPE), maleic anhydride functionalized EP copolymers, maleated polyethylene (MAPE), maleated polypropylene (MAPP), acrylic acid functionalized PP, HDPE, LDPE, LLDPE, and EP copolymers, styrene/maleic anhydride copolymers, such as styrene-ethylene- butylene-styrene/maleic anhydride (SEBS-MA) and/or styrene/maleic anhydride (SMA), and/or organic-inorganic agents, preferably silanes and/or alkoxysilanes such as vinyl trialkoxy silanes, or combinations thereof.
The coupling agent may be or comprise a maleic anhydride based coupling = agent, such as thermoplastic polymer graft maleic anhydride copolymer, N preferably olefin-graft maleic anhydride copolymer especially in the case S wherein the thermoplastic polymer comprises olefin. Specific examples of 3 30 coupling agents include polyethylene graft maleic anhydride to be used with I polyethylene and polypropylene graft maleic anhydride to be used with N polypropylene. The amount of the coupling agent may be in the range of 3— o 7% (w/w) in the final mixture, such as 4-7% (w/w), 5—7% (w/w) or 5-6% (w/w), 3 for example about 5% (w/w). & 35 The coupling agent may be called a thermoplastic compatibilizer, or a thermoplastic compatibilizer may comprise the coupling agent(s) and optionally thermoplastic polymer(s), or it may be formed of coupling agent(s) and thermoplastic polymer(s), more particularly polyethylene.
The coupling agent(s) and the thermoplastic polymer(s) may be provided as a thermoplastic compatibilizer, or coupling agent(s) and the thermoplastic polymer(s) may be reacted to obtain a thermoplastic compatibilizer, or the matrix material, so the amount of the thermoplastic compatibilizer or the matrix material, for example in the final product, would be the sum of the amounts of the thermoplastic polymer(s) and the coupling agent used for preparing the product.
In one embodiment the formed mixture comprises -15—35% (w/w) recycled high density polyethylene (HDPE), -25—35% (w/w) recycled face laminate material comprising adhesive laminate waste and/or release material, -25—45% (w/w) wood powder having an average particle diameter in the range of 400 um or less, such as 300 um or less, or 260 um or less, for example 200 um or less , -6—-8% (w/w) inorganic filler comprising talcum, and -2.0-4.0% (w/w) coupling agent.
The formed mixture or the obtained composite material may further comprise additives, such as one or more additive(s) selected from foaming agents (blowing agents), such as chemical or physical foaming agents, binders, cross- linking agents, pigments, dyes, UV protective agents, lubricants and/or other additives customary in the art of natural fiber plastic composites.
The content of the additives in the composite product may be in the range of 1-10% (w/w), such as in the range of 1-5% (w/w) or 1-3% (w/w), for example 1-3% (w/w) = of one or more pigment(s) and/or 1-3% (w/w) one or more UV protective N agent(s). The additive(s), such as one or more of the additives, may be added S initially or later in the process, for example after the basic mixture discussed in 3 30 previous has been formed. = N The mixture or the obtained composite material may comprise also other o additives, such as one or more lubricant(s) and/or one or more wax(es). The 3 lubricant(s) may be wax-based lubricant(s). Preferably the mixture comprises one or more wax(es) and/or one or more wax-based lubricant(s). Alternatively the mixture does not contain other additives besides the lubricant and/or wax.
In one example the mixture or the formed composite material contains only lubricant(s) or only wax(es), but not both, and optionally one or more other additive(s). The lubricant(s) and/or wax(es) may be added and mixed last to the mixture, for example in a heating, molding and/or extrusion step, so the other ingredients may be combined and mixed first.
Lubrication is a technique of using a lubricant to reduce friction and/or wear in a contact between two surfaces. Typically lubricants contain 90% base oil and less than 10% additives. Due to their efficient lubricating effect, the lubricants significantly improve the flow characteristics and process behavior of compounds during extruding, molding, etc. Lubricants reduce viscosity, promote dispersion, shorten mixing times and lower mixing temperatures and energy requirements. Examples of lubricants suitable for the present applications include hydrocarbons, stearates, fatty acids, esters and amides, which may be modified with functional groups.
Lubricants and the like agents are often used in forming composite materials for facilitating the process, for example to enhance the process speed. However, when the recycled label materials are used as raw material, the label materials contain different dispersion and melt adhesives and silicones, which can act as lubricants. Extrusion-coated laminates may also contain extrusion grades of polyolefines, which have high melt index and which therefore form a fluidic layer enhancing the lubrication. However, it was noticed that it may be necessary to add lubricants to the mixture when recycled plastics and label laminate waste was used.
In one embodiment however the mixture further comprises one or more = lubricants, such as 0.5—-4% (w/w) of one or more lubricant(s). Also wax may be N used instead or in addition in the same amounts.
S 3 30 In general the material may further include a carrier such as a wax (universal I carrier) or a specific polymer, identical or compatible with the polymer(s) used N (polymer-specific). When a carrier different than the base plastic is used, the o carrier material may modify the resulting plastic's properties. > N 35 The wax may comprise a modified wax, for example oxidized or functionalized, natural wax, or a synthetic or a speciality wax such as amide wax or metallocene wax, or a mixture thereof. In addition, the wax may be a paraffin wax, micro-crystalline wax, polyolefin wax, such as polyethylene, and/or polypropylene wax. The wax may comprise polar wax and/or non-polar wax, and it may be reactive wax. Examples of suitable waxes include reactive wax comprising modified polypropylene, such as silane-modified polypropylene, and polypropylene wax, which may be provided for example in powdery form or in granulate form. The wax is then mixed and melted. The obtained natural fiber plastic composite material may be obtained from a mixture comprising -15—35% (w/w) recycled polyethylene, such as about 30% (w/w), -25—35% (w/w) recycled label material comprising thermoplastic polymer and cellulosic material, and impurities comprising silicone, adhesive and optionally printing ink, such as about 30% (w/w), -25—45% (w/w) organic filler comprising wood powder, such as about 30% (w/w), and -5-10% (w/w) inorganic filler. The amount 2.0-4.0% (w/w) for the coupling agent may be included separately or it may be integrated with the percentages of recycled polyethylene or thermoplastic polymer(s) in the recycled label material. The wood powder having a bulk density of 200 g/l or less. The wood powder preferably having an average particle diameter of 400 um or less, such as 300 um or less, or 260 um or less, for example 200 um or less. In one example the obtained natural fiber plastic composite material comprises -15—35% (w/w) recycled thermoplastic polymer(s) comprising polyethylene, -25—35% (w/w) recycled cellulosic fibers from recycled label material, -25—35% (w/w) wood powder, such as about 30% (w/w), preferably having an = average particle diameter of 400 um or less, such as 300 um or less, or 260 N um or less, for example 200 um or less, S -5-10% (w/w) inorganic filler, 3 30 -optionally 0.5-4% lubricant, and x -2.0-4.0% (w/w) coupling agent.
O o In one example the obtained natural fiber plastic composite material comprises 3 -27.5-51% (w/w) recycled thermoplastic polymer(s) comprising polyethylene, -17.5—31.5% (w/w) recycled cellulosic fibers from recycled label material,
-25—35% (w/w) wood powder, such as about 30% (w/w), preferably having an average particle diameter of 400 um or less, such as 300 um or less, or 260 um or less, for example 200 um or less, -5-10% (w/w) inorganic filler, -optionally 0.5-4% lubricant, and -2.0-4.0% (w/w) coupling agent. In one example the obtained natural fiber plastic composite material comprises -29.5-55% (w/w) matrix material comprising recycled thermoplastic polymer(s) comprising polyethylene, -17.5—31.5% (w/w) recycled cellulosic fibers from recycled label material, -25—35% (w/w) wood powder, such as about 30% (w/w), preferably having an average particle diameter of 400 um or less, such as 300 um or less, or 260 um or less, for example 200 um or less, -5-10% (w/w) inorganic filler, and -optionally 0.5-4% lubricant. In one embodiment the obtained natural fiber plastic composite material comprises -30—45% (w/w) recycled thermoplastic polymer(s) comprising polyethylene, -20-30% (w/w) recycled cellulosic fibers from recycled label material, -25—35% (w/w) wood powder, such as about 30% (w/w), preferably having an average particle diameter of 400 um or less, such as 300 um or less, or 260 um or less, for example 200 um or less, -5—10% (w/w) inorganic filler, -optionally 0.5-4% lubricant, and = -2.0-4.0% (w/w) coupling agent, wherein the product comprises impurities N comprising silicone(s), adhesive(s) and optionally printing ink(s).
S 3 30 In one embodiment the obtained natural fiber plastic composite material I comprises N -32-49% (w/w) matrix material comprising recycled thermoplastic polymer(s) o comprising polyethylene, 3 -20-30% (w/w) recycled cellulosic fibers from recycled label material, -25—35% (w/w) wood powder, such as about 30% (w/w), preferably having an average particle diameter of 400 um or less, such as 300 um or less, or 260 um or less, for example 200 um or less,
-5-10% (w/w) inorganic filler, and -optionally 0.5-4% lubricant, wherein the product comprises impurities comprising silicone(s), adhesive(s) and optionally printing ink(s). In one embodiment the obtained natural fiber plastic composite material comprises -30—40% (w/w) recycled thermoplastic polymer(s) comprising polyethylene, -20—25% (w/w) recycled cellulosic fibers from recycled label material, -25-35% (w/w), such as about 30% (w/w), wood powder, preferably having an average particle diameter of 400 um or less, such as 300 um or less, or 260 um or less, for example 200 um or less, -5-10% (w/w) inorganic filler, -optionally 0.5-4% lubricant, and -2.0-4.0% (w/w) coupling agent, wherein the product comprises impurities comprising silicone(s), adhesive(s) and optionally printing ink(s). In one embodiment the obtained natural fiber plastic composite material comprises -32—-44% (w/w) matrix material comprising recycled thermoplastic polymer(s) comprising polyethylene, -20-25% (w/w) recycled cellulosic fibers from recycled label material, -25—35% (w/w), such as about 30% (w/w), wood powder, preferably having an average particle diameter of 400 um or less, such as 300 um or less, or 260 um or less, for example 200 um or less, -5-10% (w/w) inorganic filler, -optionally 0.5-4% lubricant, wherein the product comprises impurities = comprising silicone(s), adhesive(s) and optionally printing ink(s).
N S The recycled thermoplastic polymer(s) comprise mainly polyethylene, which is 3 30 originated from the recycled polyethylene and also from the recycled labels. I However the thermoplastic polymer(s) may also contain other polymers, such N as polyolefins, which are originated from the recycled labels. The content of o these polymers is usually lower than the content of polyethylene, such as 1— O 40%, 1-20%, 1-20% or 1-10% (w/w). In one example the recycled N 35 thermoplastic polymer(s) comprise(s) at least 60% (w/w) of polyethylene, such as at least 70% (w/w), at least 80% (w/w) or at least 90% (w/w). In most cases the final composite product contains about 30-35% (w/w) of polyethylene.
The percentages provided for the formed mixture and for the composite material are with the proviso that the sum of ingredients in the composition does not exceed 100%. In one example the natural fiber plastic composite does not contain metals, such as aluminum, which could be originated for example from recycled milk or juice cartons or the like packages. Such recycled materials are however excluded from the present embodiments. The composite products may be provided as elongated boards having a composite body. The board may be obtained with the methods described herein. The body 10 has a first side 12 and a second side 14, which is opposite to the first side. These sides are the largest sides of the board, i.e. the sides with largest surface areas. The first side is the side which is visible when the final product is installed, for example the upper side or the outer side. The second side is the side which is not visible when the final product is installed, for example the bottom side or the inner side. The board has also a third side 16 and a fourth side 18, which have smaller surface areas, and they are practically perpendicular to the first side and to the second side. The third side and/or the fourth side(s) may contain further shapes, for example one or more installation groove(s) 26 and/or one or more protrusion(s), for example arranged to fit to one or more installation groove(s). The board also has a fifth side and a sixth side, which are the end sides of the elongated board.
The board is elongated, which means that it has one dimension, a length, which is greater than any other dimension. The board has also a width and at least one height, wherein the width is greater than the at least one height. The = length of the board is greater than the width, such as at least two times the N width, for example at least three, four, five, six, ten or more times the width. S The first and the second sides may be defined by the length and the width. 3 30 The third and the fourth sides may be defined by the length and the height. I The fifth and the sixth sides may be defined by the width and the height(s). N The length of the board may be at least 500 mm, at least 1000 mm, such as at o least 2000 mm, at least 3000 mm or at least 4000 mm, for example in the range 3 of 1000-10000 mm, 1000-6000 mm, or 1000-5000 m. The width of the board may be in the range of 50-500 mm, such as in the range of 50-300 mm, in the range of 100-500 mm, or in the range of 100-300 mm. The height of the board may be in the range of 5-50 mm, such as in the range of 5-40 mm, in the range of 5-30 mm, in the range of 10-50 mm, in the range of 10-40 mm, or in the range of 10-30 mm.
The board may have more than one height, for example when there are one or more protrusions on the second side of the board.
There may be two or three heights, for example, the first height being the lowest, and the second and/or third height being higher than the first height, for example 3-20 mm higher, such as 5-10 mm higher.
Figure 1 shows a cross-section of an example of the board having a width and two different heights.
The dimensions and ranges disclosed herein are mutually combinable.
In one embodiment the board has a width in the range of 50-300 mm, height in the range of 5-50 mm and/or a length of at least 1000 mm, such as in the range of 1000-10000 mm.
The obtained composite boards, even without a polymeric coating, exhibited high flexural strength (bending strength) and flexural modulus.
Flexural strength is a material property, defined as the stress in a material just before it yields in a flexure test.
The flexural modulus (bending modulus) is computed as the ratio of stress to strain in flexural deformation, or the tendency for a material to resist bending.
It is determined from the slope of a stress-strain curve produced by a flexural test, and uses units of force per area.
These may be determined according to ASTM D790 or EN15534. The flexural strength of the composite product, such as a composite board, may be in the range of 40-55 MPa, such as 40-55 MPa, or 45-55 MPa.
The flexural modulus of the composite product, such as a composite board, may be in the range of 3000-3800 N/mm , such as in the range of 3300-3700 N/mm , for example 3300-3600 N/mm . These values indicate that the product = exhibits stiffness and resist bending, which is especially advantageous for N elongated products, which easily are prone to bend and even break during S handling, storing and use.
Also when installing board-like elongated products 3 30 it is important that the products are not bent to ensure true installation. = N The composite materials may shrink, and the shrinkage is an irreversible o process and therefore not desired especially in products used in constructions. 3 With the present composition it was possible to obtain a low shrinkage while maintaining other advantageous properties of the composites.
The linear shrinkage of the composite product may be in the range of 0.05-0.12%, such as 0.05-0.1%.
The moisture absorption by composites containing natural fibers has several adverse effects on their properties and thus affects their long-term performance. For example, increased moisture decreases their mechanical properties, provides the necessary condition for biodegradation, and changes their dimensions. However in the present composite materials it was possible to maintain the water or moisture adsorption at a tolerable level, which is advantageous especially for products designed for outdoor uses, such as decking boards and the like. Moisture absorption can be determined by the weight gain relative to the dry weight of the samples during a specified time. The water adsorption of the composite products (in 28 days) may be in the range of 4.0-6.5% (w/w), such as 4.5-6.5% (w/w). This may be measured according to EN317.
The composite body may comprise more than one composite material, such as mixed or as layers, or it may consist of one composite material. The composite body or the composite product may contain foamed and/or non- foamed composite material(s). In one example the composite body is non- foamed. In one example the composite body contains or comprises a foamed composite core completely or partially coated with a non-foamed composite layer and/or polymeric layer.
In general a method for manufacturing natural fiber plastic composite product comprises providing one or more thermoplastic polymer(s) and one or more filler(s), and optionally one or more additive(s), mixing the materials, preferably into a homogenous mixture, and forming the mixture into a composite product. = More particularly the present method may comprise providing recycled N polyethylene, recycled label material, organic filler comprising wood powder, S inorganic filler, and coupling agent, mixing the materials, and forming the 3 30 mixture into a composite product. These ingredients may be considered as the I basic ingredients, and further additives may be provided and mixed. One or N more of these steps may be carried out for example by using an extruder or o an extrusion system, or by injection molding. The one or more thermoplastic 3 polymer(s) and one or more filler(s), including the recycled materials, and optionally one or more additive(s), may be provided as a mixture, for example as a mixture of chaff, shredded material, granules, pellets or other pieces of the materials. In one example all the materials are conveyed as a single flow to extrusion, or to an extruder. In another example two or more of the recycled polyethylene, the recycled label material, the organic filler and the inorganic filler, optionally also other additives, are conveyed to the extrusion, or to an extruder, as two or more separate flows. The ratio of the ingredients in the formed mixture may be adjusted to obtain a desired composition. The method may comprise providing a system comprising a forming device, which may be called as thermoplastic forming device. The compounding and/or forming may be carried out in the system or in the forming device. The system, or the forming device may comprise for example an extruder and/or other device disclosed herein. The ingredients are combined to form a mixture. The raw materials comprising the fibers and plastic polymers are provided in amounts resulting in desired fiber and/or plastic content in the final product. Therefore the content of the mixture and the final product may be controlled by adjusting the amounts of the materials dosed to the system or to the forming device. The system or the forming device may comprise a mixer for mixing the materials. The mixing is carried out in one or more mixing stage(s) or step(s). This mixer may be a first mixer and the mixing stage may be a first mixing stage or a primary mixing stage. The system or the forming device may contain also a second mixer or further mixer(s), such as for mixing one or more of the additives in a further mixing step(s), for example lubricant(s), filler(s), and/or other additive(s) disclosed herein. One or more, or all, of the additives may be also provided to the first mixer and mixed in the first mixer. A mixing step comprises introducing the ingredients to a mixer and mixing with the mixer to = form a mixture. The mixer may be a hot-cold mixer. The ingredients may be N melt processed during mixing and/or after mixing.
S 3 30 Forming the mixture into a composite product may be carried out by melt I processing, such as melt processing the mixture or one or more ingredients of N the mixture. It may include heating the mixture above the melting point of the co one or more thermoplastic polymer(s), such as the melting point of the 3 polyethylene, such as HDPE. Therefore in one example forming the mixture into composite product comprises melt processing the mixture. In one example forming the mixture into composite product also include foaming the mixture. In such case one or more foaming agent(s) is/are included in the mixture. In some embodiments the method comprises forming the mixture into a natural fiber plastic composite product by extruding, by injection molding, by pultrusion, and/or by compression molding.
Wetting of the fiber material with the plastic material can be secured during a primary mixing stage. Therefore, the fiber material can be spread evenly among the plastic matrix material and the fibers can be wetted evenly with the matrix material. Forming of covalent or strong physical bonds or strong mechanical attachment between the fibers of the fiber material during the primary mixing stage can be prevented. Further, adhesion of the fibers of the fiber material to the matrix material can be secured and a composite product without fiber agglomerates can be obtained. The primary mixing stage is preferably a part of a continuous process. However, the primary mixing stage may also be implemented in a batch process.
In the method the thermoplastic polymer material, i.e. the plastic material, is provided in melt form, either fully or partly melt. The thermoplastic polymer material is, at least partly, in melt form, when the cellulosic fiber material can adhere to the thermoplastic polymer material, and/or the melt flow index of the material can be measured (according to standard ISO 1133 (valid in 2011)), and/or the cellulosic fiber material can adhere to the surfaces of thermoplastic polymer material particles.
Preferably at least 10% or at least 30%, more preferably at least 50% or at least 70% and most preferably at least 80% or at least 90% of the thermoplastic polymer material is in melt form in the contacting step of the = primary mixing stage. Preferably, at least 20% or at least 40%, more preferably N at least 60% or at least 80% and most preferably at least 90% or at least 95% S of the thermoplastic polymer material is in melt form at least momentarily 3 30 during the primary mixing stage.
= N The melting point of the thermoplastic polymer material may be under 250°C, © such as under 220°C, and for example under 190°C. The glass transition 3 temperature of the thermoplastic polymer material may be under 250°C, such as under 210°C, and for example under 170°C.
The melting temperature or melting point of the thermoplastic polymer may be for example about 120°C, about 130°C, about 150°C, about, 155°C, about 160°C, about 170°C, about 180°C, about 190°C, about 200°C, about 220°C. "Above the melting point of the thermoplastic polymer” refers to a temperature wherein the thermoplastic polymer melts at least partially and can be processed, for example extruded, and it may include the melting point. The temperature used for melting the thermoplastic polymer may be for example in the range of 120-200°C, such as 120—190*C. As the composite mixture contains wood, the use of temperatures above 200°C may not be desired to avoid damaging the wood material. At lower temperatures, such as 180°C or less or 160°C or less, polyethylene is preferred. A temperature for example in the range of 120—190*C or 120—180*C may be used. The melt flow rate, MFR, of the thermoplastic polymer material may be under 1000 g/10 min (230°C, 2.16 kg defined by ISO 1133, valid 2011), such as 0.1— 200 g/10 min, for example 0.3—150 g/10 min. Preferably the melt flow rate of the thermoplastic polymer material is over 0.1 g/10 min (230°C, 2.16 kg defined by ISO 1133, valid 2011), such as over 1 g/10 min, for example over 3 g/10 min. The composite product comprising the mixture may be formed by means of a mixing device, an internal mixer, a kneader, a pelletizer, a pultrusion method, a pull drill method, and/or an extrusion device. In one embodiment the method comprises forming the materials, more particularly the mixture of the materials, into a composite product by extruding and/or by injection moulding. The = forming the materials into a composite product may be carried out as a N continuous process or as a batch process, or as a combination thereof.
S 3 30 The method for preparing the natural fiber plastic composite product may I further comprise providing one or more additives, such as one or more N lubricant(s), wax(es), inorganic fillers, fire retardant(s), pigment(s), o surfactant(s), adsorption agent(s), property enhancer(s), adhesion 3 promoter(s), rheology modifier(s), fire retardant(s), coloring agent(s), anti- mildew compound(s), antioxidant(s), uv-stabilizer(s), foaming agent(s), curing agent(s), coagent(s), catalyst(s) or combinations thereof. The additive(s) may be mixed with other ingredients at any suitable stage or place.
In one example the primary mixing stage is implemented with an extruder. In this case, after the primary mixing stage, the extruder is preferably also used to form the composite product.
Extrusion is a process used to create objects of a fixed cross-sectional profile. A material is pushed or drawn through a die of a desired cross-section and profile to obtain a product with desired shape. The product may be cooled and cut into a desired length. The two main advantages of this process over other manufacturing processes are its ability to create very complex cross-sections, and to work materials that are brittle, because the material only encounters compressive and shear stresses. It also forms parts with an excellent surface finish. In an extrusion process thermoplastic polymer and filler and/or reinforcement material are provided, mixed if necessary, and fed to an extruder, wherein the materials are heated to a desired temperature and pushed through a die to obtain an extrudate. Extrusion may be continuous (theoretically producing indefinitely long material) or semi-continuous (producing many pieces). One example of the extrusion process is extrusion molding.
In one example the mixture containing at least the fiber material and the plastic material, or all the ingredients, is extruded. In one example, the mixture is extruded after at least one pre-treatment. In one example the ingredients are supplied into the extrusion directly. In one example the plastic material is mixed with the fiber material in connection with the extrusion, preferably without any pre-treatment stage. 2 N In the case of the extrusion, any suitable single-screw extruder or twin-screw N extruder, such as a counter-rotating twin-screw extruder or a co-rotating twin- 0 30 screw extruder, may be used. The twin-screw extruder may have parallel or I conical screw configuration. a = In one example, the melt of the mixture is conveyed to a co-rotating parallel S twin screw extruder, through melt pump to die plate to form strand of the > 35 mixture. In one example, a co-rotating conical twin-screw extruder is used for the composite production. The screw volume may be, for example, from 4 to 8 times bigger at the beginning of the screw than in the end of the extruder.
One example of the extrusion comprises compounding with a co-rotating twin screw extruder. One example of the extrusion comprises compounding with a conical counter-rotating twin screw extruder. In this case, material components are fed into main feed of the compounding extruder at the beginning of the screws so melting can start as soon as possible. One example of the extrusion comprises compounding with a single screw extruder with screening unit. In this case, the material components are fed into main feed of the extruder at the beginning of the screws so melting can start as soon as possible.
The obtained composite products have a good dispersion. Dispersion is a term that describes how well other components are mixed with the matrix material, preferably with the polymer matrix. Good dispersion means that all other components are evenly distributed into material and all solid components are separated from each other i.e. all particles or fibers are surrounded by matrix material, i.e. the plastic. The inks, dyes, pigments, adhesives, silicones, lignins, fillers and other impurities in the recycled materials or other materials may affect the appearance and the mechanical and chemical properties of the final composite product. Usually colored material originated from the recycled materials can be seen from the final composite product even by naked eye, for example from a cross-section. Also the color of the product may fade especially in outdoor use or storage. There may also be variations in the color and in the composition of the filler which may affect to the appearance of the product. Further, the composite comprising recycled materials, especially paper or the O like, may not tolerate moisture as well as pure plastic in respect of the N mechanical properties. Therefore it may be desired to apply a covering layer N on a composite product containing recycled materials, such as a non- 0 30 transparent covering layer. The covering layer is preferably also weather I resistant. The covering layer may be called a coating, a first layer or an outer + layer, and the other layer containing the composite material may be called a = second layer, a body, an inner layer, or an inner composite. In one embodiment S the composite product comprises a polymeric coating layer comprising at least > 35 one thermoplastic polymer, such as polyolefin. The composite product may be fully or partly coated. The manufacturing method may comprise forming a polymeric coating layer comprising at least one thermoplastic polymer, such as polyolefin, onto the composite product. The coating layer may comprise polyethylene to ensure compatibility with the composite product. The composite body and the coating layer may be formed or obtained in a lamination process, a gluing process, a molding process, an extrusion process, or a welding process, preferably in a coextrusion process, especially by providing a coextruder or a coextrusion system. Coextrusion process is an effective way to manufacture a product comprising two layers with different raw materials. For example, the flow properties of the raw materials may be separately controlled during the co-extrusion process, and the different layers can be effectively attached together. Other methods for forming polymeric coatings include applying paint and/or varnish, such as polyurethane paint or polyurethane varnish or coating. The composite product may be first coated with a primer, such as a polyurethane primer. Thereafter a paint coating may be applied, such as polyurethane paint. Also printing may be applied onto the primer, such as by printing for example by digital printing, or by laminating a printed film. Finally a top coating may be applied, such as varnish, finish or coating, for example polyurethane varnish or coating.
In such case at least the first side of the composite product, such as a board, is completely coated with a polymeric coating layer 20. The first side may be the only side of the product completely coated with the polymeric coating layer. However, it is also possible to coat the other sides of the composite product as well, even the whole composite product may be completely coated. As the polymeric coating layer is more shrinkable than the composite body, it causes = bending force affecting especially to elongated products, such as to a board, N which bends the product if the coating is applied only on one side of the S product. When a coating or a partial coating is applied to the product, it 3 30 balances the structure and enhances the mechanical properties of the product, I such as stiffness, hardness and tensile or flexural properties, such as tensile N strength, flexural modulus and/or bending/flexural strength, and therefore o prevents deformation of the product, for example deflections in the longitudinal 3 and crosswise direction. & 35 As the first side is completely coated, no composite body is directly visible or accessible at the first side of the product. The applied coating usually defines the appearance of the product as the first side is the side which is usually visible when the product is installed in the target. The coating may be colored, for example with one or more pigment(s), and it may contain for example patterns or figuration, such as patterns mimicking the appearance of wood. The coating may enhance the mechanical properties of the product, but it may also provide other properties, such as properties relating to friction. For example the coating may provide higher wet friction compared to the composite body, which is important especially when the products such as boards are used as outdoor floor materials. The coating layer may have a thickness in the range of 0.5-5 mm, such as 0.5-3 mm, or 0.5-2 mm, for example 0.6—1.2 mm. The thickness of the coating layer may depend on the desired mechanical properties, but also the need to mask the composite layer may also have an effect to the reguired thickness of the coating layer. For example if the color of the composite layer differs significantly from the color of the coating layer, it may be necessary to apply a thicker coating layer to prevent the color of the composite being visible through the coating layer, for example 1-3 mm. On the other hand, in some cases a thinner coating layer may be desired, such as one having a thickness of 0.6-1.0 mm, for example about 0.8 mm.
The coating layer may comprise one or more polymer(s), such as plastic polymers. The polymers may be thermoplastic polymer(s). As the coating layer is visible during the use and is exposed to mechanical wear and probably also to sunlight and weather, it is preferable that the coating layer is made of high guality material. The coating layer may comprise only plastic polymer(s), meaning that no or substantially no fillers are included, such as fibers or = mineral fillers. Preferably the coating layer is not a fiber-plastic composite N layer. The plastic polymer(s) may be virgin polymer(s). The coating layer may S contain minor amount of additives, such as 0.5-5% (w/w), or 0.5-2% (w/w), or 3 30 about 1%, of one or more pigment(s), one or more binder(s), one or more UV I protecting agent(s), one or more coupling or cross-linking agent(s) and/or the N like. The coating layer may comprise at least 95% (w/w) of polymer(s), such o as at least 98% (w/w), at least 99% (w/w) or at least 99.5% (w/w) of polymer(s). 3 Preferably the coating layer is not a composite layer, such as a fiber-plastic composite layer. However, in some examples it is possible to include filler to the coating layer, such as any filler disclosed herein, for example an inorganic filler, for example in the range of 1-30% (w/w), 1-20% (w/w) or 1-10% (w/w).
In such case the filler content in the coating layer is lower than in the body, such as 50% or less, or 30% or less, or 10% or less of the filler content of the body.
The coating layers of the embodiments are suitable for versatile use, for example outdoor use.
The coating layer is hard and durable and therefore it provides for example scratch resistance.
The polymers, such as thermoplastic polymers, in the composite material and in the coating layer may be same or different.
However, when same polymer(s) is/are used, the body and the coating layer are more compatible with each other and will be strongly attached to each other.
This enhances the mechanical properties of the product.
In one embodiment the natural fiber plastic composite and the polymeric coating layers comprise the same at least one polymer(s). In one embodiment the polymeric coating layers comprises at least one thermoplastic polymer, such as one or more polyolefin(s), such as polyethylene.
In one example wherein the product is a board, as shown in Figure 1, the second side of the body comprises at least two elongated protrusions 30, 31, 32 along the lengthwise direction of the body.
The protrusions are preferably continuous along the lengthwise direction of the body.
Such protrusions, which may also be called as projections, may be included in elongated boards to provide stiffness.
It is also possible to save in material costs and to obtain a lighter product, but maintain larger overall outer dimensions of the product, such as height.
A board may contain for example two, three, four or more elongated protrusions.
It is also possible to include one or more apertures inside the body, for example four apertures as illustrated in Figure 2. In one = example the body contains at least one elongated aperture inside the body N along the lengthwise direction of the body, such as two, three, four or more S apertures.
One or more side(s), such as the first side, of the board may be 3 30 grooved. = N The body of the product, especially a board, may contain one or more co installation groove(s) 26 or one or more protrusion(s), for example one or more 3 protrusion(s) arranged to fit to one or more installation groove(s) in another board or other product.
These may be on the third and/or fourth side(s) of the body.
When two or more similar boards are installed, for example in a form of decking boards when building a deck, the boards may be installed next to each other. In one example the separate boards touch each other and the boards may contain compatible parts, such as shapes, on the third and the fourth sides. In one example an installation groove on a third side of a board is designed to fit to an installation protrusion on a fourth side of another board. In another example, as illustrated in Figure 3, a gap is left between two adjacent boards 42, 44 and an installation fastener 40 is placed between the two boards in such way that protruding parts of the fastener 40 will enter the installation grooves on the both third and the fourth sides of the boards 42, 44, and the fastener 40 is attached to a background or a support. An example of such a fastener is a T-clip used for installing decking boards, which clip 40 may be secured to a support with a screw 46. The gap between the two adjacent boards may be in the range of 5-10 mm, such as about 6 mm. In one embodiment the body contains at least one installation groove on at least one side. In one embodiment the body contains at least one installation protrusion on at least one side. The installation grooves and/or protrusions are directed along the lengthwise direction of the body. In one example the body contains at least one installation groove on the third side and at least one installation groove on the fourth side, as shown in Figure 1.
The present application also provides use of the composite products, such as boards, in the final products disclosed herein, such as in the following. The composite product may be used or be present for example as a building element, a facade, a floor element, such as a decking board, a landscaping element, a furniture, a window or a door frame or profile, a cover strip, a support rail, a railing, a fence, a noise barrier, or a part thereof. oO N The product, which may be in a form of a board, may be a building element, S such as a decking board, other floor element or a facade panel, or a 3 30 landscaping element. Also furniture, window frames and door frames may be I obtained from the boards. In an example, the board is a railing, a fence, or a N noise barrier. The board may also be a product that is used to cover the surface o of another product, such as a cover strip. The board may be an outdoor 3 element. In one embodiment the board is a decking board. & 35 One example provides a building comprising an elongated board comprising the natural fiber plastic composite body described herein. The building may comprise the board, wherein the board is fastened by a fastener in order to form a part of the building.
A building may be a structure with a roof and walls, preferably standing permanently in one place, such as a house, shed, garage, factory, or the like.
The board may be used as a facade element or panel in the building.
One example provides a terrace comprising an elongated board comprising the natural fiber plastic composite body described herein.
A terrace is an external, raised, open, flat area in either a landscape near a building or as a roof terrace on a flat roof.
A terrace may protrude from a building.
The terrace may comprise the board, wherein the board is fastened by the fastener in order to form a part of the terrace.
The board may be used as a floor element in the terrace.
Examples Example 1: Compounding Composite board products with different compositions were prepared and tested for flexural strength (the bars) and flexural modulus (the line). Label waste obtained from Raflatac (“RAF”) was used amounts in the range of 30-57% (w/w), wood powder obtained from birch sanding wood powder (“WD”) was used in amounts in the range of 0-37% (w/w), talc as inorganic filer was used in amounts in the range of 0-10% (w/w), recycled HDPE (rHDPE) was present as 30% (w/w) and maleic anhydride based coupling = agent was present as 3% (w/w). The ingredients were combined and mixed.
If N lubricant was included, it was added last, for example in the extrusion or S molding step. 3 30 I The raw materials were mixed and extruded or injection molded into elongated N composite products.
Products obtained by injection molding were tested for o properties presented in Figures 4-10. The ingredients and percentages 3 thereof are indicated below each test point in the graphs. & 35 It can be seen that with the combination 30% (w/w) label waste, 30% (w/w) wood powder, 30% (w/w) recycled HDPE, 7% (w/w) talc and 3% (w/w) coupling agent yielded the highest flexural strength (up to about 50 MPa) and flexural modulus (up to about 3700 N/mm ). The effect of fiber dosage on impact strength was tested and the results are presented in Figure 5. The effect of fiber dosage on linear shrinkage percentage was tested and the results are presented in Figure 6. The linear shrinkage may be in the range of 0.05-0.12%, such as 0.05—0.1%. The effect of wood powder on moisture/water absorption was tested and the results are presented in Figure 7. Including high amount of wood powder will increase the water absorption. The water adsorption in 28 days may be in the range of 4.0-6.5% (w/w), such as 4.5-6.5% (w/w). The effect of coupling agent dosage on flexural strength and modulus was tested and the results are presented in Figure 8. The effect of LDPE blending on flexural strength and modulus was tested and the results are presented in Figure 9. The effect of wood fiber source to flexural strength and modulus was tested and the results are presented in Figure 10. Wood powder (WD), softwood (pine/spruce) wood powder (SWD) and commercial products Arbocel (powdery water-insoluble fibrous cellulose) and Lignocel (wood fiber/ lignocellulose product) were tested. The particle sizes of the wood fiber sources were similar. = Example 2: Properties of wood powder particles
N S Two particle size measurements were carried out for birch sanding dust 3 30 (samples from two factories) and two particle size measurements were carried I out for spruce sanding dust (samples from two sanding machines). The n samples for spruce included a “rough” sanding carried out using sanding paper o grade 60 and “fine” sanding carried out using sanding paper grade 80. For
LO O birch the samples were sanded by using sanding paper grades 80 and/or 100, N 35 so these sanding are both considered “fine” sandings.
The measurements were carried out using Beckman Coulter LS 13 320 particle size analyzer, which is based on light scattering measurements. Sample 1: Birch mill 1 Table 1 presents fiber size distribution in the sample. Disp. Sokalan CP5, dilution 0.2%, Magnetic stirrer 30 min, US 37 kHz Pulse 100% 6 min, Optical model: Fraunhofer.rfd PIDS included Volume statistics (Arithmetic) Calculations from 0.040 um to 2000 um Volume: 100% Mean: 168.0 um Median: 117.5 um Mean/Median ratio: 1.430 Mode: 140.1 um S.D: 187.4 um — Variance: 35117 um CV: 112% Skewness: 3.080 Right skewed Kurtosis: 12.54 Leptokurtic Table 1 : & N 21.50 57.28 117.5 210.0 | 242.0 344.0 | 476.0 1085 O um um um um um um um um n um um um um um um um um >N
Figure 6 is a graph showing the particle diameter (size) distribution for Sample
1. Sample 2: Birch mill 2 Table 2 presents fiber size distribution in the sample. Disp. Sokalan CP5, dilution 0.2%, Magnetic stirrer 30 min, US 37 kHz Pulse 100% 6 min, Optical model: Fraunhofer.rfd PIDS included Volume statistics (Arithmetic) Calculations from 0.040 um to 2000 um Volume: 100% Mean: 157.5 um Median: 107.6 um Mean/Median ratio: 1.464 Mode: 140.1 um S.D: 187.1 um Variance: 35011 um CV: 119% Skewness: 3.408 Right skewed Kurtosis: 14.65 Leptokurtic Table 2. o 25 |
K <Q 21.27 52.56 107.6 192.1 2209 | 3157 | 4324 1108 3 um um um um um um um um ™ um um um um um um um um O 14.8% | 212% | 30.2% | 42.7% | 56.5% | 83.9% | 96.1% | 98.4% oO
N Figure 7 is a graph showing the particle diameter (size) distribution for Sample
2.
Sample 3: Spruce fine Table 3 presents fiber size distribution in the sample.
Disp. Sokalan CP5, dilution 0.3%, Magnetic stirrer 30 min, US 37 kHz Pulse 100% 6 min, Optical model: Fraunhofer.rfd PIDS included Volume statistics (Arithmetic) Calculations from 0.040 um to 2000 um Volume: 100% Mean: 190.6 um Median: 120.6 um Mean/Median ratio: 1.581 Mode: 127.6 um S.D: 214.3 um Variance: 45927 um CV: 112% Skewness: 2.542 Right skewed Kurtosis: 7.656 Leptokurtic Table 3. o 28.09 61.28 120.6 233.8 277.0 425.0 638.0 1113 N pm pm pm pm pm pm pm pm ; S um um um = 7.31% | 11.4% | 17.0% | 259% | 38.3% | 42.5% | 51.5% | 77.0%
O O Figure 8 is a graph showing the particle diameter (size) distribution for Sample 2 25 3.O
N Sample 4: Spruce rough
Table 4 presents fiber size distribution in the sample. Disp. Sokalan CP5, dilution 0.3%, Magnetic stirrer 30 min, US 37 kHz Pulse 100% 6 min, Optical model: Fraunhofer.rfd PIDS included Volume statistics (Arithmetic) Calculations from 0.040 um to 2000 um Volume: 100% Mean: 256.2 um Median: 156.5 um Mean/Median ratio: 1.637 Mode: 153.8 um S.D: 299.2 um Variance: 89505 um CV: 117% Skewness: 2.659 Right skewed Kurtosis: 8.528 Leptokurtic Table 4.
35.08 78.01 156.5 311.0 368.6 589.7 862.0 1588 um um um um um um um um oO N um um um LO 6.00% | 9.15% | 13.2% | 19.6% | 29.4% | 33.0% | 41.2% | 68.0%O
I = = Figure 9 is a graph showing the particle diameter (size) distribution for Sample S 4. > 25 Table 5 present a comparison of the properties of different samples.
Table 5 Sample | Fractionation Fiber Fiber width| Aspect Fines method length [um] ratio [I/d]*** | [%]**** [um]* Small fractionator Small fractionator 3 [Large fractionator | 136.5 4 — |Largefractionator | 1465 | 69 | 212 | 144 | * Length weighted average fiber length ** Average fiber width *** Average particle length versus width **** Percentage of measured particles shorter than 20 um Extractives The total amount of extractives from different materials were determined by acetone extraction using Soxhlet eguipment and GC-FID analysis. The results are shown in Table 6. The following materials were tested: spruce saw dust, which is an example of wood based material that has been neither soaked nor heat treated (i.e. virgin wood material); spruce veneer which is an example of wood based material that has been soaked and dried at elevated temperature; and spruce plywood sanding dust, which is an example of wood based material that has been soaked, dried, and hot-pressed. Table 6. = Spruce saw [Spruce plywood! Spruce veneer . dust sanding dust 3 Fatty acidsLO
S o Betulinol maa] 023 | 0 | 0 | 3 Steryl esters > Triglycerides |mglg| 040 [| 0 | 0 Extractives totalma/g — 331 | 140 | 075 |
Comparison of saw dust and sanding dust Figure 15 shows a comparison of saw dust (15A) and sanding dust (15B) visualized microscopically. The saw dust was visualized with stereo microscope and it can be seen that the particle size (length, or the largest diameter) varies in the range from about 500 um to several millimeters. The aspect ratio is approximately in the range of 1:1 to 1:4.
The sanding dust was visualized with electron microscopy and the particles size of the marked particles varies in the range of 61-966 um. However it can be seen that the average aspect ratio of the particles is significantly higher than for example in saw dust, approximately in the range of 1:5 to 1:22 or higher.
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权利要求:
Claims (16)
[1] 1. A method for preparing a natural fiber plastic composite product the method comprising forming a mixture comprising -15—35% (w/w) recycled polyethylene, -25—35% (w/w) recycled label material, -25—45% (w/w) organic filler comprising wood powder, -5-10% (w/w) inorganic filler, -2.0-4.0% % (w/w) coupling agent, and -optionally 0.5-4% lubricant, and forming the mixture into a natural fiber plastic composite product.
[2] 2. The method of claim 1, wherein the recycled polyethylene is recycled high density polyethylene (HDPE).
[3] 3. The method of any of the preceding claims, wherein the recycled label material comprises recycled adhesive laminate and/or release material.
[4] 4. The method of any of the preceding claims, wherein the recycled label material comprises thermoplastic polymer and cellulosic material, and impurities comprising silicone(s), adhesive(s) and optionally printing ink(s).
[5] 5. The method of any of the preceding claims, wherein the recycled label material comprises 70-90% (w/w) of cellulosic material, such as paper or paperboard, such as 75-85% (w/w), and 10-30% (w/w) of thermoplastic polymer(s), such as 15-25% (w/w). oO N
[6] 6. The method of any of the preceding claims, wherein the inorganic filler S comprises talcum, kaolin clay, calcium carbonate, such as ground calcium S 30 carbonate or precipitated calcium carbonate, titanium dioxide, wollastonite, x mica, and/or silica, preferably talcum or calcium carbonate.
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[7] 7. The method of preceding claims, wherein the wood powder has a bulk 3 density of 200 g/l or less, and/or wherein the wood powder has an average particle diameter of 400 um or less, such as 300 um or less, or 260 um or less, for example 200 um or less.
[8] 8. The method of preceding claims, wherein the wood powder is obtained from sanding of soaked and heat treated wood, such as plywood.
[9] 9. The method of preceding claims, comprising forming the mixture into a natural fiber plastic composite product by melt processing, such as by extruding and/or by injection moulding.
[10] 10. The method of any of the preceding claims, wherein the formed mixture comprises -15—35% (w/w) recycled high density polyethylene (HDPE), -25—35% (w/w) recycled label material comprising adhesive laminate waste and/or release material, -25—45% (w/w) organic filler comprising wood powder having a bulk density of 200 g/l or less, -6-8% (w/w) inorganic filler comprising talcum, and -2.0-4.0% (w/w) coupling agent.
[11] 11. A natural fiber plastic composite product, such as a board, comprising -20-45% (w/w) recycled thermoplastic polymer(s) comprising polyethylene, such as recycled high density polyethylene (HDPE), -20-30% (w/w) recycled cellulosic fibers from recycled label material, -25—45% (w/w) wood powder, preferably having an average particle diameter of 400 um or less, such as 300 um or less, or 260 um or less, for example 200 um or less -5-10% (w/w) inorganic filler, such as talcum or calcium carbonate, -optionally 0.5-4% lubricant, and = -2.0—4.0% (w/w) coupling agent, N wherein the product comprises impurities comprising silicone(s), adhesive(s) S and optionally printing ink(s). 3 30 I
[12] 12. The natural fiber plastic composite product of claim 11 obtained with the N method of any of the claims 1—10. i, O
[13] 13. The natural fiber plastic composite product of any of the claims 11-12 N 35 having a flexural strength in the range of 40-55 MPa, such as in the range of 40—55 MPa, orin the range of 45-55 MPa and/or flexural modulus in the range of 3000-3800 N/mm , such as in the range of 3300-3700 N/mm .
[14] 14. The natural fiber plastic composite product of any of the claims 11-13 having a linear shrinkage in the range of 0.05-0.12%, such as 0.05—0.1% and/or water adsorption in 28 days measured according to in the range of 4.0—
6.5% (w/w), such as 4.5-6.5% (w/w).
[15] 15. The natural fiber plastic composite product of any of the claims 11-14, comprising a polymeric coating layer comprising at least one thermoplastic polymer, such as polyolefin.
[16] 16. The natural fiber plastic composite product of any of the claims 11-15, wherein the product is in a form of a board, such as a building element, a facade, a floor element, such as a decking board, a landscaping element, a furniture, a window frame or a door frame or profile, a cover strip, a support rail, a railing, a fence, a noise barrier, and/or a part thereof.
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