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    • 专利摘要:
    The invention is aimed primarily at a process for preparing a semi-finished product comprising a PAEK-based resin and reinforcing fibers, comprising the steps of: a. Preparation of a dispersion comprising a powder-based PAEK-based resin dispersed in an aqueous phase comprising a surfactant; b. Contacting the reinforcing fibers with said aqueous dispersion; vs. Drying of the dispersion-impregnated fibers; and D. Heating the impregnated fibers to a temperature sufficient for melting the resin, so as to form a semi-product, characterized in that the surfactant is a thermally stable surfactant. It also aims at the dispersion useful in said process. Finally, it targets the semi-products that can be obtained as well as their use for the manufacture of composite materials.
    公开号:FR3065002A1
    申请号:FR1752951
    申请日:2017-04-05
    公开日:2018-10-12
    发明作者:Benoit Brule；Henri-Alexandre Cayzac；Guillaume Le；Jerome Pascal；Fabien Sguerra
    申请人:Arkema France SA；
    IPC主号:
    专利说明:

    [Technical area]
    The present patent application relates to the field of manufacturing semi-finished products comprising a thermoplastic matrix and reinforcing fibers. It also relates to such semi-products as well as their use for the manufacture of composite parts.
    [Prior art]
    Due to their excellent mechanical properties at low weight, composite materials combining a thermoplastic resin with reinforcing fibers are of great interest in many fields, particularly in the aeronautics and space industry, but also in the automotive and sports equipment.
    These composite materials are generally produced by consolidating semi-products made of reinforcing fibers coated with resin such as prepregs in the form of unidirectional sheets, wicks or woven fabrics.
    These semi-products can be obtained by impregnating the fibers with the resin. There are different methods, in which the resin can be melted, dissolved in a solvent, or even in the form of a powder, either in a fluidized bed or dispersed in an aqueous solution. The impregnated fibers are then optionally freed from the solvent or the aqueous solution and then heated in order to melt the retained resin and form the semi-finished product.
    For polymers with a high melting point such as polyaryletherketones (PAEK), the impregnation in an aqueous dispersion bath is advantageous from an economic and environmental point of view.
    However, in order to obtain a uniform charge of the resin fibers, this process requires ensuring a homogeneous distribution of the resin in the dispersion.
    Thus, patent application WO 88/03468 proposes to stabilize the suspension by making it very viscous (at least 50 Pa-s) and by addition, if necessary, adding a surfactant.
    With a similar approach, US Patent 5,236,972 proposes to add a water-soluble polymer, a wetting agent, and in addition a biocide, a plasticizer and an anti-foaming agent to the dispersion.
    US Patent 5,888,580 proposes, on the contrary, to use a dispersion with low viscosity and containing little dispersing agent, and to regulate the charge of the resin fibers by means of the resin concentration of the dispersion and the residence time. However, the composite parts made from such semi-finished products have a high porosity and non-optimal mechanical properties.
    In order to remedy this problem, application FR 3 034 425 proposes to disperse the thermoplastic resin by means of a specific surfactant alkoxylated alcohol, namely stearyl alcohol ethoxylated 100 times, and to associate a stirring device to maintain the homogeneous suspension. Thus, the authors claim to be able to consolidate composite products without porosities. However, this invention does not solve all the difficulties associated with the viscosity of the resin, and can lead to subsequent forming defects. In fact, in the molten state, the too viscous polymeric resin is no longer able to flow properly. Therefore, it is difficult to obtain composite parts having the desired shape and surface appearance.
    In particular, it is common to observe the appearance of wrinkling on the surface and problems with the strength of the welds produced during the assembly of the composite parts into complex parts. These defects are exacerbated when consolidation is carried out at a pressure below 5 bars.
    In general, it is advantageous to be able to manufacture composite parts without having to use high pressure, since this requires the use of very expensive autoclaves.
    The object of the invention is to remedy these problems and to propose a process for the preparation of semi-finished products capable of being transformed into composite parts not exhibiting the defects mentioned above.
    It also aims to propose a process for the preparation of semi-products capable of being consolidated under low vacuum, outside of an autoclave.
    More specifically, the object of the invention is to propose such a process for the preparation of semi-products in which the resin has a viscosity and a molecular mass which changes little following the thermal cycles required for the manufacture of composite parts.
    [Summary of the invention]
    The objects mentioned above have been achieved by a method according to the invention, in which the reinforcing fibers are impregnated in an aqueous dispersion of pulverulent resin comprising at least one thermally stable surfactant.
    Indeed, the present invention is based on the observation that the quality of composite parts based on PAEK resins depends in particular on the viscosity of the resin in the semi-finished product and on its subsequent development. However, the high temperatures necessary for the manufacture and consolidation of semi-finished products based on PAEK (temperatures generally above 300 ° C.) can cause the decomposition of compounds introduced during the process into reactive species, which can lead to reactions PAEK chain extension which can lead to connections. The resulting increase in molecular weight then increases the viscosity of the resin.
    However, the systematic study of the various agents likely to be present in the PAEK-based semi-product has revealed on the one hand that the surfactant used in the dispersion constitutes a main factor in the increase in viscosity after a thermal cycle and on the other hand, this effect was very variable depending on the surfactant chosen.
    On this basis, it has been validated that the use of a thermally stable surfactant makes it possible to limit the evolution of the viscosity of the resin and to obtain composite parts of the required quality.
    Without wishing to be bound by this hypothesis, it is assumed that many surfactants decompose in the PAEK resin under the effect of the high temperature required to melt the PAEK polymers. The reactive species formed during decomposition, in particular radicals, can then react with the polymer and cause chain extension or branching reactions, which increase the molecular weight of the polymer and therefore also its viscosity. However, when the resin has a high viscosity, it is no longer able to properly impregnate and coat the fibers, to ensure good adhesion of the semi-finished products, or to marry the mold walls, this which affects the quality of the composite products obtained.
    Also, according to a first aspect, the subject of the invention is a process for the preparation of a semi-finished product comprising a resin based on PAEK and reinforcing fibers, comprising the steps of:
    at. Preparation of a dispersion comprising a resin based on PAEK in pulverulent form dispersed in an aqueous phase comprising at least one surfactant;
    b. Contacting the reinforcing fibers with said aqueous dispersion;
    vs. Drying of fibers impregnated with dispersion; and
    d. Heating the impregnated fibers to a temperature sufficient for the melting of the resin, so as to form a semi-finished product, characterized in that the surfactant is a thermally stable surfactant.
    Advantageously, the surfactant comprises aromatic groups. According to another embodiment of the invention, the surfactant comprises a phosphate group.
    Preferably, the reinforcing fibers are carbon fibers. Preferably, the reinforcing fibers used in the process of the invention are non-sized fibers.
    When the reinforcing fibers are sized fibers, they are preferably sized with a thermally stable size.
    Preferably, the PAEK resin is chosen from the group consisting of poly-ether-ketone (PEK), polyether-ether-ketone (PEEK), poly-ether-ether-ketone-ketone (PEEKK), poly-ether-ether- ketone ketone (PEKK), poly-ether-ketone-ether-ketone-ketone (PEKEKK), poly-ether-ether-ketone-ether ketone (PEEKEK), poly-ether-ether-ether-ketone (PEEEK), and poly-ether -diphenyl-ether-ketone (PEDEK), their mixtures and their copolymers with each other or with other members of the PAEK family.
    When it is a PEKK resin, the PAEK resin is preferably a PEKK having a mass percentage of terephthalic units relative to the sum of the terephthalic and isophthalic units of between 50 and 90%.
    Advantageously, the pulverulent PAEK resin in the dispersion has a median diameter D50 of 1 to 300 μm, preferably of 5 to 100 and very particularly of 10 to 50 μm as measured according to standard ISO 13 320.
    According to a preferred embodiment, the semi-product is chosen from a prepreg or a tape.
    Furthermore, according to a second aspect, the invention relates to a semi-product capable of being obtained by said process.
    Preferably, the weight average molecular weight Mw of the PAEK resin in the semi-finished product, as measured by steric exclusion chromatographic analysis, does not increase by more than 100%, in particular not more than 50% and all especially not more than 20% after heat treatment at 375 ° C for 20 minutes.
    According to a third aspect, the subject of the invention is a dispersion useful in the preparation of a semi-product comprising a resin based on PAEK and reinforcing fibers, comprising:
    at. 1 and 50% by weight of PAEK-based resin having a number average particle size of between 1 and 300 μm;
    b. 0.001 to 5% by weight, calculated relative to the weight of the resin, of at least one thermally stable surfactant;
    vs. 0 - 1% by weight of other additives; and
    d. the rest of the water.
    According to a fourth aspect finally, the invention relates to the use of a semi-finished product as described above for the manufacture of composites.
    In the manufacturing processes of composite parts, the semi-products are subjected to different thermal cycles under pressure or under vacuum in order to assemble them together to form the composite part and / or to shape it.
    [Brief description of the figures]
    The invention will be better understood with reference to the description which follows and the figure, which shows:
    Fig. the evolution of the viscosity of a sample of PEKK resin with variable mass content of fibers in only 20 minutes at 375 ° C. under 1 Hz under nitrogen, according to Example 2.
    [Description of the embodiments]
    Definition of terms
    The term “semi-finished product” is intended to denote products comprising a resin and reinforcing fibers used as intermediate products in the manufacture of composite materials. These products can be in particular prepregs in the form of unidirectional sheets of wicks, woven fabrics, or even fiber-matrix mixtures.
    The semi-finished products can then be assembled, for example by manual or automated draping or by automated fiber placement, and shaped by consolidation, for the manufacture of composite parts. The composite parts thus produced can be further processed, in order to obtain assemblies of complex composite parts. Thus, it is possible to co-consolidate composite parts, a process generally carried out in an autoclave by means of a new thermal cycle, or to weld parts to each other by local heating.
    The term “resin” is intended to denote a composition mainly comprising one or more polymers added, where appropriate, with conventional additives, in particular fillers and functional additives.
    The term “dispersion” is intended to denote a heterogeneous composition comprising a liquid phase and a solid phase. In the dispersion used in the process of the invention, the liquid phase is aqueous and contains a thermally stable surfactant as well as other additives, if necessary. The solid phase essentially comprises or consists of the PAEK resin in powder form.
    The term "surfactant" is intended to denote a compound having a hydrophilic part and a lipophilic part, and capable of dispersing the resin powder in the liquid phase and of maintaining it in suspension in the presence or in the absence of agitation. This compound can also assist in wetting the fibers through dispersion.
    The term “thermally stable surfactant” means a surfactant, which does not generate, when it is subjected to temperatures exceeding 300 ° C., in particular exceeding 350 ° C. and in particular of 375 ° C., for at least 20 min. , reactive species capable of reacting significantly with the PAEK resin.
    This property is evaluated by the following test: The PAEK resin in powder form (median diameter D50 = 20 μm) is introduced into an aqueous solution containing 1% by weight relative to the quantity of resin of the surfactant to be evaluated. The mixture obtained is stirred for 30 minutes using a magnetic stirrer. The water is then evaporated in an oven at 90 ° C for 48 h. A dry residue of PAEK resin with surfactant is obtained. Then, a sample of the PAEK resin supplemented with surfactant is subjected to a heat treatment at a temperature of 375 ° C. for a period of 20 minutes under nitrogen sweeping.
    It has proved difficult to measure the viscosity of these samples. Also, the viscosity of the PAEK resin supplemented with surfactant was evaluated by means of the molecular weight distribution, measured by steric exclusion chromatographic analysis, according to the following protocol.
    About 30 mg of PAEK resin with added surfactant to be evaluated are introduced into 1 ml of 4chlorophenol and stirred for 24 h at 150 ° C. After the solution has cooled to room temperature, 14 ml of hexafluoroisopropanol (HFIP) are added, then the solution is filtered through a syringe filter of Acrodisc type comprising a polytetrafluoroethylene (PTFE) membrane with a diameter of 25 mm and a porosity 0.2 pm.
    The molecular weights of the resin are determined by size exclusion chromatography using a Waters Alliance 2695 type instrument using the conditions below:
    Flow rate: 1.00 ml / min. Eluent: HFIP. Volume injected: 100.00 pl. Set of columns PSS PFG (1000 + 100 Â) 2 * 30cm. Temperature 40 ° C. Detection mode: differential refractometer. Calibration: PMMA with a range of molecular weights from 402g / mol to 1900000g / mol to be updated during each analysis series.
    The rate of soluble is measured by the ratio between the areas of the chromatograms of the sample analyzed on the one hand, and of a soluble reference compound on the other hand prepared at the same concentration and injected in the same amount into the apparatus for chromatography.
    When the weight average molecular weight Mw of the PAEK resin increases by more than 100%, preferably 50%, and in particular 20% relative to the resin before the heat treatment, the surfactant studied is classified as not thermally stable. Conversely, when the weight average molecular weight Mw of the PAEK resin increases by 100%, preferably 50% and in particular 20% or less, the surfactant studied is classified as thermally stable.
    A “thermally stable size” is understood to mean a size which does not generate, when it is subjected to temperatures exceeding 300 ° C., in particular exceeding 350 ° C. and in particular of 375 ° C., for at least 20 min, reactive species capable of reacting significantly with the PAEK resin.
    This property is evaluated by the following test: An intimate mixture of 70% by weight of PAEK resin and 28% by weight of sized fibers to be evaluated in a mortar is prepared. Next, a sample of this mixture of PAEK resin and sized fibers is introduced into a plane-plane rheometer and the change in viscosity is measured over 20 min. When the viscosity of the mixture increases by more than 100%, preferably 50%, in particular 20%, the size is classified as not thermally stable. Conversely, when the weight average molecular weight Mw of the size increases by 100%, preferably 50% and in particular 20% or less, the size studied is classified as thermally stable.
    The dispersion
    The dispersion used in the proposed process comprises, according to the invention, an aqueous phase comprising the PAEK resin in powder form as well as at least one thermally stable surfactant.
    The PAEK resin essentially comprises at least one polyaryletherketone polymer (PAEK). The poly- (aryl-ether-ketones) (PAEK) have the following formula units:
    (-Ar-X-) and (-Ari-Y-) in which:
    Ar and Ari each denote a divalent aromatic radical;
    Ar and Ari may be chosen, preferably, from 1,3-phenylene, 1,4-phenylene, 4,4'biphenylene, 1,4-naphthylene, 1,5-naphthylene and 2,6- naphthylene, optionally substituted;
    X denotes an electron-withdrawing group; it can preferably be chosen from the carbonyl group and the sulfonyl group,
    Y denotes a group chosen from an oxygen atom, a sulfur atom, an alkylene group, such as -CH2- and isopropylidene.
    In these units X and Y, at least 50%, preferably at least 70% and more particularly, at least 80% of the groups X are a carbonyl group, and at least 50%, preferably at least 70% and more particularly at at least 80% of the Y groups represent an oxygen atom. According to a preferred embodiment, 100% of the groups X denote a carbonyl group and 100% of the groups Y represent an oxygen atom.
    More preferably, the poly-arylene ether-ketone (PAEK) can be chosen from:
    a polyether ketone ketone, also called PEKK, comprising units of formula I A, of formula I B and their mixture:

    Formula I A
    a polyether ether ketone, also called PEEK, comprising units of formula II:
    The sequences can be totally para (Formula II). Similarly, we can introduce, partially or totally, meta sequences in these structures at the level of ethers and ketones according to the two examples of formulas III and IV below:
    Formula III
    Or :
    Formula IV
    Or ortho sequences according to formula V:

    Formula V a polyether ketone, also called PEK, comprising units of formula VI:
    Formula VI
    In the same way, the sequence can be totally para but we can also introduce meta sequences partially or totally (formulas VII and VIII):

    or ίο ü-

    Formula VIII a poly-ether-ether-ketone-ketone, also called PEEKK, comprising units of formulas IX:
    \ //
    o
    Formula IX
    In the same way we can introduce meta sequences in these structures at the level of ethers and ketones.
    a poly-ether-ether-ether-ketone, also called PEEEK, comprising units of formulas X:
    //
    In the same way we can introduce meta sequences in these structures at the level of ethers and ketones but also biphenol or diphenyl sequences according to formula XI (D type motifs in the next names, formula XI thus corresponds to the name PEDEK):
    Other arrangements of the carbonyl group and the oxygen atom are also possible.
    Preferably, the PAEKs used in the invention are chosen from the group consisting of polyetherketone (PEK), polyetheretheretherketone (PEEK), polyetheretheretherketone ketone (PEEKK), polyetherether- ketone-ketone (PEKK), poly-ether-ketone-ether-ketone-ketone (PEKEKK), poly-ether-etherketone-ether-ketone (PEEKEK), poly-ether-ether-ether-ketone (PEEEK), and poly -ether-diphenyl-etherketone (PEDEK), their mixtures and their copolymers with each other or with other members of the PAEK family. PEEK and PEKK as well as their mixtures are particularly preferred.
    Advantageously, the stability of the PAEK in the molten state can be improved by adding one or more phosphates or phosphate salts.
    Preferably, the PAEK resin comprises at least one polyether-ketone-ketone (PEKK) which represents more than 50%, preferably more than 60%, in particular more than 70%, more preferably more than 80% and in particular more than 90 % by mass of the resin, terminal included. The remaining 10 to 50% by mass can consist of other polymers, whether or not belonging to the PAEK family.
    More preferably, the PAEK resin consists essentially of PEKK.
    Advantageously, the PEKK has a mass percentage of terephthalic units relative to the sum of the terephthalic and isophthalic units of between 50 and 90% and preferably between 60 and 80%, and very particularly, this ratio is 65 to 75%.
    The resin can also, as discussed above, additionally contain other usual additives such as fillers. Furthermore, the resin may optionally contain minor amounts of functional additives. Preferably, the resin is nevertheless devoid of additives capable of decomposing under the effect of heat in order to limit the risk of change in viscosity.
    The particle size of the PAEK resin powder can have an impact on the stability of the suspension. It can also influence the quality of resin impregnation of the reinforcing fibers. In order to ensure optimal homogeneity of the suspension and good impregnation, it is preferred that the resin powder is finely divided. More specifically, it is preferred that the PAEK powder has a median diameter D50 is situated in a range from 1 to 300 μm, preferably from 5 to 100 and more particularly from 10 to 50 μm as measured according to standard ISO 13 320 .
    Preferably, the content of PAEK resin powder in the dispersion is advantageously between 0.1 and 50%, preferably between 1 and 40% by weight relative to the weight of the finished dispersion.
    As mentioned above, the method according to the invention is characterized in that the dispersion also comprises at least one thermally stable surfactant. In fact, the studies carried out have made it possible to demonstrate that the surfactant was the main factor in the increase in the viscosity of the PAEK resin contained in a semi-product observed following the thermal cycle required for its consolidation.
    The test described above makes it possible to evaluate a surfactant in terms of its ability to withstand the temperatures required without forming reactive species capable of reacting significantly with PAEK resins. It is thus possible to quickly and simply determine whether a surfactant is thermally stable within the meaning of the present invention.
    As a thermally stable surfactant, one can choose an ionic or nonionic surfactant. Preferably, it is an ionic surfactant, and in particular an anionic surfactant.
    Preferably, the thermally stable surfactant is a surfactant comprising at least one aromatic entity, in particular one or more phenyl groups.
    According to a particularly preferred embodiment, the thermally stable surfactant comprises a phosphate group. In fact, phosphates seem less prone to react with PAEK resins than other surfactants when they are used in the aqueous dispersion impregnation process.
    More specifically, mention may in particular be made of surfactants from the family of phosphoric acid esters. Preferably, these are monoesters of phosphoric acid. They may especially be phosphoric acid esters with alcohols, in particular alcohols having 6 to 24 and in particular 10 to 16 carbon atoms. Particularly preferred are alkyl ether phosphates and alkylaryl ether phosphates.
    Mention may in particular be made, as compounds of this family, of the surfactants sold under the name Lanphos PE35 by the company Lankem, Cecabase RT by the company CECA France and Klearfac AA270 by the company DeWolf.
    This surfactant can be used in the form of free acid, but it is preferably neutralized. Neutralization can be carried out beforehand or in situ in the dispersion by adding an appropriate quantity of sodium or potassium hydroxide.
    The dispersion preferably contains no more than the minimum content of surfactant required to adequately stabilize the suspension. This content depends on factors such as the particle size of the PAEK resin, the quantity of particles to be dispersed and the nature of the surfactant.
    It may be advantageous to add several thermally stable surfactants. In particular, it is possible to choose a thermally stable surfactant making it possible to ensure good dispersion of the PAEK resin powder and another thermally stable surfactant in order to improve the affinity of the reinforcing fibers with the PAEK resin powder.
    However, most often, a surfactant content of 0.001 to 5% by weight, preferably 0.01 to 2, and very particularly 0.1 - 1% by weight relative to the weight of resin makes it possible to ensure the stability of the suspension and good wetting of the fibers.
    The aqueous phase of the dispersion can, if necessary, contain minor amounts of other conventional additives such as thickening agents, anti-foaming agents, biocidal agents. In order to limit the presence of additives in the semi-finished products and the potential problems associated therewith, the dispersion nevertheless contains a minimum content preferably of other additives. Preferably, the amount of other additives will not exceed 1% by weight, and in particular not 0.5% by weight of the finished dispersion.
    Preferably, the additives present in the dispersion will be thermally stable, as determined by the test described above. However, it is preferred that the aqueous phase of the dispersion comprises a minimum of additives, and in particular only comprises the thermally stable surfactant.
    The water used to prepare the dispersion is preferably demineralized water.
    The process for preparing the dispersion can be carried out in a manner known per se. More specifically, the dispersion can be prepared by introducing the quantity of water required into a container of suitable volume and fitted with an appropriate stirring device, then adding the surfactant as well as the other additive (s), if necessary. If necessary, the mixture is stirred until a homogeneous solution is obtained. The pulverulent PAEK resin is then introduced into the aqueous solution and then stirred until a stable dispersion is obtained.
    Reinforcement fibers
    The reinforcing fibers can in principle be any fibers usually used in the manufacture of semi-finished products.
    According to the invention, the reinforcing fibers can be chosen from all the fibers capable of being used as reinforcement in the manufacture of parts made of composite materials.
    Thus, it may especially be glass fibers, quartz fibers, carbon fibers, graphite fibers, silica fibers, metallic fibers such as steel fibers, aluminum fibers or boron fibers, ceramic fibers such as silicon carbide or boron carbide fibers, synthetic organic fibers such as aramid fibers or poly (p-phenylene benzobisoxazole) fibers, better known by the acronym PBO, or PAEK fibers, or mixtures of such fibers.
    Preferably, these are carbon fibers or glass fibers, and more particularly carbon fibers.
    According to a preferred embodiment, the fibers do not induce, in combination with the other compounds, a significant change in the viscosity of the PAEK in the semi-finished product and in the composite.
    The fibers are preferably not sized. If they are sized, they are preferably sized by a thermally stable size as defined above.
    The reinforcing fibers used for the manufacture of semi-finished products by impregnation by aqueous dispersion are generally continuous.
    Preferably, they are in the form of unidirectional fibers, for example in the form of threads grouping together several thousand elementary filaments (typically from 3000 to 48000) measuring, for example, 6 to 10 μm in diameter for carbon fibers. This type of fiber is known under the name of wick (in English "rovings").
    The fibers can nevertheless also be organized in a different way, for example in the form of a mat, or else of textiles obtained by weaving wicks.
    The manufacturing process for semi-finished products
    The manufacturing process according to the invention can be carried out in a conventional manner, on the usual equipment, by implementing the dispersion as described above. As indicated above, the presence in the dispersion of a thermally stable surfactant makes it possible to limit the formation of reactive species capable of increasing the molecular mass of the resin and therefore its viscosity, and thereby reducing the appearance defects in composite parts.
    More specifically, the semi-products are obtained by introduction and circulation of the reinforcing fibers in an aqueous dispersion bath as described above. The fibers impregnated with PAEK resin are then removed from the bath and freed from water, for example by drying in an infrared oven. The dried impregnated fibers are then heated until the resin melts, in order to allow the fibers to be coated with the PAEK resin. The coated fibers obtained are then optionally shaped, for example by calendering, in order to shape and size the semi-finished product.
    Preferably, the semi-products according to the invention comprise from 1 to 99% by weight, preferably 30 to 90%, in particular 50 to 80% by weight, and in particular 60 to 70% by weight of reinforcing fibers.
    The semi-products obtained according to the process of the invention can be used in particular for the manufacture of composite parts.
    The composite parts are obtained for example by first manufacturing a preform, in particular by placing or draping the semi-finished products prepreg in a mold. The composite part is then obtained by consolidation, a stage during which the preform is heated, generally under pressure in an autoclave, so as to assemble the semi-finished products by fusion. Preferably, the semi-products manufactured according to the invention can be consolidated outside of an autoclave, for example under a vacuum cover placed in an oven.
    The semi-products manufactured according to the process of the invention are characterized in particular by a resin whose viscosity has changed little despite the high temperatures required for their manufacture in order to melt the resin.
    The composite products manufactured according to the process of the invention are characterized in particular by a resin whose viscosity has changed little despite the high temperatures required for their manufacture.
    During these stages, a not too high viscosity of the matrix is essential in order to ensure that the semi-finished products conform to the shapes of the mold. The viscosity of the matrix also ensures good flow during consolidation and thus avoids surface defects such as wrinkling.
    The invention will be explained in more detail in the following examples.
    [Examples]
    Example 1 to 3: Evolution of the viscosity according to the manufacturing process of the semi-finished product
    The impact of the thermal cycle on the evolution of viscosity has been studied for a PEKK resin (Kepstan 7003, marketed by Arkema France) and for semi-products made from this resin and carbon fibers according to different methods.
    The prepregs were produced on a laboratory scale with 70% by weight of Kepstan resin
    7003 and 30% by weight of carbon fibers on the one hand according to a molten method and on the other hand by dispersion method, according to the following respective protocols:
    1) Method of impregnation by melt:
    Approximately 8 g of wicks of carbon fibers (12K fiber with size Μ0Ε marketed under the name T700S by the company Toray) are placed on a polyimide sheet (Upilex film 50 μm thick marketed by the company UBE). using a temperature-resistant aluminum adhesive.
    The carbon fiber locks are then sprinkled with 20g of PEKK powder (sold under the name of Kepstan 7003 by the company Arkema France, D50 = 300pm) homogeneously using a vibrating screen. The surface of the PEKK powder is then covered with a second polyimide sheet.
    The assembly is then placed between two steel sheets and passed through a CARVER press at 375 ° C for 1 minute at 5 bars. The assembly is then removed from the press and allowed to cool to room temperature.
    After peeling off the polyimide sheets and cutting the aluminum adhesives, a prepreg prepared by melt is obtained. The prepreg obtained is divided into two parts.
    2) Method of impregnation by aqueous dispersion:
    An aqueous solution of surfactant is prepared by introduction into a flask of 1000g of water as well as 0.1g of an alcohol C16-C18 ethoxylated as surfactant (marketed under the name of Cremophor® A25 by the company BASF). The aqueous solution is homogenized for 10 minutes using a magnetic stirrer.
    Then 4g of non-sized carbon fibers (HexTow AS4 sold by the company Hexcel) cut to a length of 1 cm are gradually introduced into the flask containing the aqueous solution with vigorous stirring with a Ultra-turrax type homogenizer. The dispersion obtained is finally homogenized for 10 minutes. At the end of this step, the carbon fibers have been ground uniformly and are suspended in the aqueous solution.
    Then, 10 g of PEKK powder (sold under the name of Kepstan 7003 by the company Arkema France, D50 = 20 pm) are added and the mixture obtained is stirred for 30 minutes using a magnetic stirrer.
    The water is then evaporated in an oven at 90 ° C for 48 h.
    This gives a homogeneous mixture of PEKK powder added with surfactant and carbon fibers. A prepreg is then produced by compression at 375 ° C. at 5 bars for 1 minute as described above.
    The two prepregs produced respectively by the melt and by aqueous dispersion are then subjected to a thermal cycle reproducing that required for the consolidation of the semi-products. The thermal cycle consists of passing through an oven at 375 ° C for 20 minutes with nitrogen sweeping.
    The weight average molecular mass M w of the PEKK resin is then measured by steric exclusion chromatography, according to the protocol below for:
    the unprocessed PEKK resin (example 1) the sample obtained by the molten route (example 2) and the sample brought into contact with a surfactant as in an impregnation process by the aqueous dispersion route (example 3).
    For examples 2 and 3, the measurement is carried out for the sample before and after the thermal cycle.
    About 30 mg of the sample are introduced into 1 ml of 4-chlorophenol and stirred for 24 h at 150 ° C. After the solution has cooled to room temperature, 14 ml of hexafluoroisopropanol (HFIP) are added, then the solution is filtered through a syringe filter of Acrodisc type comprising a polytetrafluoroethylene (PTFE) membrane with a diameter of 25 mm and a porosity 0.2 pm.
    The molecular weights of the resin in the sample are determined by size exclusion chromatography using a Waters Alliance 2695 type instrument using the conditions below:
    Flow rate: 1.00 ml / min. Eluent: HFIP. Volume injected: 100.00 pl. Set of columns PSS PFG (1000 + 100 Â) 2 * 30cm. Temperature 40 ° C. Detection mode: differential refractometer. Calibration: PMMA with a range of molecular weights from 402g / mol to 1900000g / mol to be updated during each analysis series.
    The rate of soluble is measured by the ratio between the areas of the chromatograms of the sample analyzed on the one hand, and of a soluble reference compound prepared at the same concentration and injected in the same quantity into the chromatography apparatus on the other go. The rate of insolubles then consists of the rate of carbon fibers and the rate of insoluble polymer. Care will then be taken to subtract the level of carbon fibers to obtain only the level of insoluble polymer.
    The results are collated in Table 1 below.
    Table 1: Evolution of the weight average molecular mass Mw of the PEKK resin
    Ex Material before thermal cycle after thermal cycle Evolutionon Mw(%) Mw(g / mol) Insoluble(%) Mw (g / mol) Insoluble(%) 1 PEKK resin (Kepstan7003) (reference) 54000 58000 7.5% 2 Sample obtained bymelted track 54000 69000 <5% 28% 3 Sample obtained bydispersal route 59000 98000 7% 66%
    The results in Table 1 demonstrate that the evolution of the weight average molecular weight Mw of the resin in the sample containing a surfactant as necessary in the dispersion route is more than twice that in a semi-finished product manufactured by the route. fondue.
    In addition, in example 3 made by dispersion, a notable increase in the fraction of insolubles is noted, indicating that part of the polymer can no longer be dissolved under the experimental conditions.
    Example 4 to 12: Evolution of the viscosity according to the nature of the carbon fibers
    The impact of the thermal cycle on the evolution of viscosity was studied for samples containing carbon fibers from different manufacturers and sized or not. The fibers used here are:
    HexTow AS4 fiber sold by Hexcel (not sized).
    - HexTow AS4D fiber sold by Hexcel (not sized).
    Tenax HTS45 P12 fiber sold by Toho-Tenax (with thermoplastic compatible size).
    Tenax HTA40 E13 fiber sold by Toho-Tenax (with epoxy compatible size).
    Mixtures of PEKK resin and these carbon fibers were produced according to the following protocol:
    A quantity of 2g of PEKK resin powder (Kepstan 7002, marketed by Arkema France, D50 = 20pm) is introduced into a mortar. 14, 28 and 43% by weight, relative to the total weight of the sample, of fibers cut to a length of 0.5 cm are added.
    Mechanical mixing is carried out in the mortar in the presence of a few drops of water making it possible to aid in the wettability and in the good dispersion of the fibers in the resin.
    The mixtures thus produced are then dried for 12 hours under vacuum at 120 ° C.
    The viscosity is then measured for each sample in a plane-plane rheometer under nitrogen (1 Hz) at 375 ° C. as a function of time for 20 minutes.
    The change in viscosity (in%) under the effect of the thermal cycle reproducing that required for the consolidation of the semi-finished products can be evaluated by comparing the viscosity value measured at the initial instant and after 20 minutes of testing. .
    The results for the various mixtures produced are collated in table 2 below and in FIG. 1.
    Table 2: Composition of the examples, and evolution of the viscosity
    Ex PEKK resin[% in weight] AS4 fibers[% in weight] AS4D fibers [%in weight] FibersP12[% in HTS45 Fibers HTA40 Evolution ofviscosity(%) weight] E13[% in weight] 4 100% 0% 5 72% 28% 16% 6 57% 43% 3% 7 72% 28% 12% 8 57% 43% 14% 9 86% 14% 27% 10 72% 28% 33% 11 86%14% 21% 12 72% 28% 110%
    The results in Table 2 and FIG. 1 show that the presence of carbon fibers has a notable effect on the evolution of the viscosity of the PAEK resin. Furthermore, it is noted that this effect is very variable depending on the nature of the fibers used. In particular, it is found that the non-sized fibers have a lesser effect in comparison with the sized fibers. Among the sized fibers, it is finally noted that certain sizes can have a very harmful effect on the viscosity of the PAEK resin.
    Also, we can deduce from this study the link between the increase in viscosity and the presence of exogenous species, after heat treatment. We also conclude that it is advantageous to use non-sized fibers.
    Example 13-15: Evolution of the viscosity according to the surfactant
    The impact of the thermal cycle on the evolution of the average molecular mass by weight Mw has been studied for a PEKK resin (Kepstan 7002, marketed by Arkema France) with various surfactants, in the presence of non-sized carbon fibers AS4D marketed by Hexcel .
    The samples were made according to the protocol of Example 3 above, with the surfactants indicated below.
    The Cremophor® A25 surfactant sold by BASF.
    The Lanphos PE35 surfactant sold by the company Lankem.
    A part of the prepared samples is subjected to a thermal cycle and then the weight average molecular mass M w of the PEKK resin of the samples is measured before and after the thermal cycle as described in Example 3.
    The results are collated in Table 3 below.
    Table 3: Weight-average molecular mass Mw of PEKK resin containing different surfactants
    Ex Material Beforethermiqi cycleI Afterthermal cycle Evolution[%] Mw[g / mol] Insoluble(%) Mw[g / mol] Insoluble(%) 13 PEKK resin only(reference) 65000 68000 5% 14 PEKK resin with 30%AS4D fibers and 1% ofCremophor® surfactantA25 65000 > 100,000 > 50% > 50% 15 PEKK resin with 30%AS4D fibers and 1% ofPE35 surfactant 65000 73000 <5% 12%
    The results in Table 3 demonstrate a marked effect of the choice of surfactant on the evolution of the viscosity of the PAEK resin.
    Indeed, the PE35 surfactant is more stable with PEKK under the test conditions than the Cremophor® A25 surfactant. The change in average molecular weight by weight Mw of Example 14 produced with the Cremophor® A25 surfactant is very significantly greater than that measured on the sample of Example 15 produced using the PE35 surfactant.
    In addition, there is a significant fraction of insolubles in the sample, reflecting the presence of polymer which cannot be dissolved by the experimental protocol.
    It can be seen from all of the studies reported above that the nature of the surfactant constitutes an essential factor concerning the evolution of the viscosity and of the weight-average molecular mass Mw of a PAEK resin subjected to a thermal cycle representative of that required for the consolidation of a semi-finished product into composite parts.
    This effect can nevertheless be significantly attenuated by a suitable choice of surfactant. In particular, the use of a thermally stable surfactant at the melting temperatures of the PAEK polymers makes it possible to limit the formation of reactive species.
    Furthermore, the choice of suitable reinforcing fibers, sized or not, further reduces the increase in viscosity.
    The use of a thermally stable surfactant during the manufacture of semi-products according to the process of the invention therefore makes it possible, while preserving the viscosity of the PAEK resin, to ensure good quality of the composite parts obtained from those -this.
    [List of cited documents]
    WO 88/03468
    US 5,236,972
    US 5,888,580
    FR 3 034 425
    权利要求:
    Claims (14)
    [1" id="c-fr-0001]
    Claims
    1. Process for the preparation of a semi-finished product comprising a resin based on PAEK and reinforcing fibers, comprising the steps of:
    at. Preparation of a dispersion comprising a resin based on PAEK in pulverulent form dispersed in an aqueous phase comprising at least one surfactant;
    b. Contacting the reinforcing fibers with said aqueous dispersion;
    vs. Drying of fibers impregnated with dispersion; and
    d. Heating the impregnated fibers to a temperature sufficient for the melting of the resin, so as to form a semi-finished product, characterized in that the surfactant is a thermally stable surfactant.
    [2" id="c-fr-0002]
    2. Preparation process according to claim 1, in which the surfactant contains aromatic groups.
    [3" id="c-fr-0003]
    3. Method of preparation according to one of claims 1 to 2, wherein the surfactant comprises a phosphate group.
    [4" id="c-fr-0004]
    4. Preparation process according to one of claims 1 to 3, wherein the reinforcing fibers are carbon fibers.
    [5" id="c-fr-0005]
    5. Preparation process according to one of claims 1 to 4, wherein the reinforcing fibers are non-sized fibers.
    [6" id="c-fr-0006]
    6. Preparation process according to one of claims 1 to 4, in which the reinforcing fibers are sized fibers with a thermally stable size.
    [7" id="c-fr-0007]
    7. Preparation process according to one of claims 1 to 6, in which the PAEK resin is chosen from the group consisting of poly-ether-ketone (PEK), polyether-ether-ketone (PEEK), poly-ether-ether -ketone-ketone (PEEKK), poly-ether-ether-ketone-ketone (PEKK), poly-etherketone-ether-ketone-ketone (PEKEKK), poly-ether-ether-ketone-ether-ketone (PEEKEK), polyether -ether-ether-ketone (PEEEK), and poly-ether-diphenyl-ether-ketone (PEDEK), their mixtures and their copolymers with each other or with other members of the PAEK family.
    [8" id="c-fr-0008]
    8. Preparation process according to one of claims 1 to 7, in which the PAEK resin is a PEKK having a mass percentage of terephthalic units relative to the sum of the terephthalic and isophthalic units of between 50 and 90%.
    [9" id="c-fr-0009]
    9. Preparation process according to one of claims 1 to 8, in which the pulverulent PAEK resin in the dispersion has a median diameter D50 of 1 to 300 μm, preferably of 5 to 100 and very particularly of 10 to 50 μm such than measured according to ISO 13 320.
    [10" id="c-fr-0010]
    10. Preparation process according to one of claims 1 to 9, in which the semi-finished product is chosen from a prepreg or a strip.
    [11" id="c-fr-0011]
    11. Dispersion useful in the preparation of a semi-finished product comprising a PAEK-based resin and reinforcing fibers, comprising:
    at. 1 and 50% by weight of PAEK-based resin having a number average particle size of between 1 and 300 μm;
    b. 0.001 to 5% by weight, calculated relative to the weight of the resin, of at least one thermally stable surfactant;
    vs. 0 -1% by weight of other additives; and
    d. the rest of the water.
    [12" id="c-fr-0012]
    12. Semi-finished product comprising a resin based on a PAEK and reinforcing fibers, obtained by the process as defined in claims 1 to 10.
    [13" id="c-fr-0013]
    13. The semi-finished product according to claim 12, in which the weight average molecular weight Mw of the PAEK resin, as measured by steric exclusion chromatographic analysis, does not increase by more than 100% after heat treatment at 375 °. C for 20 minutes.
    [14" id="c-fr-0014]
    14. Use of a semi-finished product according to one of claims 12 or 13 for the manufacture of composite materials.
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    公开号 | 公开日
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    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    US4894105A|1986-11-07|1990-01-16|Basf Aktiengesellschaft|Production of improved preimpregnated material comprising a particulate thermoplastic polymer suitable for use in the formation of substantially void-free fiber-reinforced composite article|
    US5063265A|1988-05-02|1991-11-05|Amoco Corporation|Stabilized poly compositions|
    WO2016156325A1|2015-03-31|2016-10-06|Airbus Defence And Space Sas|Aqueous impregnation bath for reinforcement fibres and uses thereof|
    US5236972A|1989-07-05|1993-08-17|The United States Of America As Represented By The Secretary Of The Air Force|Thermoplastic powder slurry for fiber impregnation and film formation|
    US5888580A|1991-07-03|1999-03-30|Hoechst Aktiengesellschaft|Production of composites from polymer powder dispersions|
    US7267782B2|2003-06-19|2007-09-11|Owens-Corning Fiberglas Technology Ii, Llc|Two-part combination of compositions for forming substantially colorless thermoplastic reinforcements|FR3093666B1|2019-03-15|2022-01-14|Arkema France|Process for the manufacture by sintering of a powder based on partly recycled poly-aryl-ether-ketone|
    WO2021066438A1|2019-10-02|2021-04-08|한국화학연구원|Polymer composite material comprising aramid nanofiber, and method for preparing same|
    WO2021132416A1|2019-12-27|2021-07-01|三菱ケミカル株式会社|Member for composite materials, composite material, moving body and method for producing film for composite materials|
    FR3112307A1|2020-07-10|2022-01-14|Arkema France|Method for analyzing semi-finished products comprising a thermoplastic resin|
    WO2022012908A1|2020-07-17|2022-01-20|Solvay Specialty Polymers Usa, Llc|Process for preparing a continuous fiber filament, continuous fiber filament and use thereof|
    法律状态:
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    2018-10-12| PLSC| Search report ready|Effective date: 20181012 |
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    优先权:
    申请号 | 申请日 | 专利标题
    FR1752951A|FR3065002B1|2017-04-05|2017-04-05|PROCESS FOR IMPREGNATION OF REINFORCING FIBERS WITH POLYARYLETHERCETONES AND SEMI-PRODUCTS THUS OBTAINED|
    FR1752951|2017-04-05|FR1752951A| FR3065002B1|2017-04-05|2017-04-05|PROCESS FOR IMPREGNATION OF REINFORCING FIBERS WITH POLYARYLETHERCETONES AND SEMI-PRODUCTS THUS OBTAINED|
    KR1020197031725A| KR20190128081A|2017-04-05|2018-04-05|Method of impregnating fibers with polyaryletherketone and semifinished product obtained therefrom|
    PCT/FR2018/050856| WO2018185440A1|2017-04-05|2018-04-05|Method for impregnating reinforcing fibres with polyaryletherketones and semi-products obtained therefrom|
    US16/500,160| US20210130557A1|2017-04-05|2018-04-05|Method for impregnating reinforcing fibres with polyaryletherketones and semi-products obtained therefrom|
    BR112019020190A| BR112019020190A2|2017-04-05|2018-04-05|process of impregnation of reinforcing fibers with polyarylether ketones and semi-products obtained by the same|
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    JP2019554911A| JP2020513052A|2017-04-05|2018-04-05|Method for impregnating reinforcing fibers with polyaryl ether ketone and semi-finished products obtained therefrom|
    EP18718898.2A| EP3606984A1|2017-04-05|2018-04-05|Method for impregnating reinforcing fibres with polyaryletherketones and semi-products obtained therefrom|
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