WO2013050074A1 - Method for producing fiber-reinforced composite materials - Google Patents

Abstract

The present invention relates to a method for producing molded parts from fiber-reinforced composite materials and to binders for preforming textile structures in the production of structural materials according to the RIM or RTM method.

Description

 Description: The present invention relates to a method for producing molded parts from fiber-reinforced composite materials and to binders for pre-forming textile structures in the production of structural materials by the RIM or RTM method. A known process for the production of fiber-reinforced sandwich components based on cast polyamide is based on the so-called RTM process (resin transfer molding). In this process, the core is provided with layers of dry, ie. H. non-preimpregnated fiber material arranged in a sealable form. The mold consists of two heatable mold halves whose inner contour corresponds to the outer contour of the finished component. In the closed mold space, liquid resin is supplied to the dry fiber material. The resin is cured by heating the mold. In this case, the resin can be supplied either at overpressure in the RTM form or at vacuum in the RTM form. The respective pressure difference is u. a. the avoidance of unwanted air pockets in the cover layer. By means of dry fiber scrims various disadvantages of the prepreg technique are avoided. In the literature, the term RIM method is often used synonymously with the RTM method. For the purposes of the present invention, the RIM method is synonymous with the RTM method. From EP-A-722 825 an RTM process is known which uses overpressure in the mold.

Corresponding RTM processes which suggest vacuum in the mold are known from EP-A-770 472, EP-A-786 330 and EP-A-1 281 505.

An RTM process, in which under pressure is injected resin and supporting a vacuum in the gas-tight closed mold is made, is from the

WO-A-02/074469 known. However, the aforementioned methods leave something to be desired. In particular, it is difficult in this way fiber-reinforced composites with consistent To produce quality. In particular, it is difficult to ensure consistent mechanical properties reproducible.

The present invention was therefore based on the object to remedy the aforementioned disadvantages. Surprisingly, it has now been found that this object is achieved by first pretreating a textile structure with a polymeric binder and subjecting it to a shaping step, and bringing the binder-containing, shaped textile structure thus obtained into contact with a polymerizable composition and polymerizing it.

A first subject of the invention is therefore a process for producing molded parts from fiber reinforced composites, comprising: a1) impregnating a textile structure with at least one liquid binder composition in the form of a solution or dispersion of a polymeric binder in a solvent, a2) forming the textile Structure wherein steps a1) and a2) may be performed in any order to obtain an impregnated formed textile structure, b) at least partially removing the solvent from the impregnated molded textile structure to obtain a binder-containing molded texti - len structure, c) impregnating the obtained in step b), binder-containing, shaped textile structure with a polymerizable composition and polymerization of the polymerizable composition.

Another object of the invention is a composite molding obtainable by the process as defined above and hereinafter.

Another object of the invention is the use of such a composite material molding as a shell for safety helmets, z. B. as a head protection for persons. Another object of the invention is a liquid binder composition consisting of an amorphous polyamide and a solvent or a solvent mixture. Another object of the invention is the use of a liquid binder composition as defined above and for pre-forming textile structures in the production of composites by the RIM or RTM process. In the context of the present invention, a "fiber reinforced composite molding" means an article comprising a fiber reinforced composite material or made of a fiber reinforced composite material having a shape suitable for a desired application. For impregnation in step a1), the textile structure can be brought into contact with the at least one liquid binder composition by customary methods known to the person skilled in the art. For impregnation in step c), the binder-containing, shaped, textile structure obtained in step b) can be brought into contact with the polymerisable composition by customary methods known to the person skilled in the art. The impregnation in steps a1) and c) can each independently, z. Example, by conventional application methods such as spraying, brushing, pouring, dipping, printing, etc., take place. The impregnation can be carried out using reduced pressure. Optionally, a phase of reduced pressure may be followed by a phase of reduced pressure.

For impregnation, the textile structure is preferably sprayed with the liquid binder composition in step a1).

The process according to the invention makes it possible to produce molded parts from fiber-reinforced composite materials of consistent quality. In particular, it is possible to provide fiber-reinforced composite materials with constant mechanical properties. These include, for example, tensile strength, modulus of elasticity, impact resistance and the like. The textile structure used in the method according to the invention serves as a reinforcing material for the production of the composite molded parts. In principle, fibers or fiber structures are suitable as a textile structure. The textile structure is preferably selected from rovings, fabrics (including microfiber fabrics), knits (knitwear), knits, mats, mats, nonwovens, felts, etc., and combinations thereof. To provide the fiber structure textile fabrics can be used from fibers, for. In the form of linen, strings, ropes, yarns or threads.

The fibers may be of natural or synthetic origin. To provide the textile structures, fibers of inorganic materials and fibers of organic materials can be used. Fibers of organic materials may include natural polymers, synthetic polymers, or combinations thereof, or may consist of natural polymers, synthetic polymers, or combinations thereof. Suitable fibers include inorganic materials such as high modulus carbon fibers, silicate and non-silicate glasses of various types, carbon, boron, silicon carbide, metals, metal alloys, metal oxides, metal nitrides, metal carbides and silicates and organic materials such as natural and synthetic polymers, for example polyacrylonitriles, polyesters , ultra-high-elongation polyolefin fibers, polyamides, polyimides, aramids, liquid-crystal polymers, polyphenylene sulfides, polyether ketones, polyether ether ketones, polyetherimides, cotton, cellulose and other natural fibers such as flax, sisal, kenaf, hemp, abaca. Preference is given to high-melting materials, for example glasses, carbon, aramids, liquid-crystal polymers, polyphenylene sulfides, polyether ketones, polyether ether ketones and polyetherimides. The fibers used according to the invention are particularly preferably selected from glass fibers, carbon fibers, aramid fibers, steel fibers, ceramic fibers, various temperature-resistant polymeric fibers and combinations thereof.

Particularly suitable textile structures are rovings of the abovementioned fibers, preferably nonlinear and linear structures, particularly preferably flat shaped bodies such as fibers, yarns, threads, ropes and textile structures such as woven, knitted, knitted, braided and nonwoven fabrics. Nonwovens, felts, fabrics, rovings, roving fabrics and mats are particularly suitable as a textile structure. Tissues, nonwovens and scrims are particularly suitable as textile structures. The textile structure preferably comprises or consists of glass fibers, carbon fibers and / or fibers of temperature-resistant plastics. Particularly preferred are textile structures based on glass, carbon or aramid fibers, especially glass or carbon fibers. The composite moldings according to the invention preferably have a content of fibers of 20 to 85 vol .-%, particularly preferably 40 to 70 vol .-%, based on the total volume of the composite molding on. A special embodiment are composite moldings with purely unidirectional reinforcement. Composite moldings with purely unidirectional reinforcement preferably have a content of fibers of 30 to 90% by volume, particularly preferably 40 to 80% by volume, based on the total volume of the composite molding. The reinforcing material may be evenly distributed in the composite molding according to the invention, but it may also be used in certain parts of the composite material, for. B. in the edge regions and / or particular reinforcement zones, be present in a greater proportion than in other parts of the composite material.

Preferably, the liquid binder composition used in step a1) contains from 1 to 30% by weight, especially from 2 to 20% by weight, based on its total weight, of the polymeric binder. The polymeric binder contained in the binder composition preferably comprises at least one thermoplastic polymer.

In a specific embodiment, the polymeric binder contained in the binder composition consists of a thermoplastic polymer or a mixture of thermoplastic polymers.

Preferably, the thermoplastic polymer is selected from polyamides and blends of polyamides. Suitable z. As polyamides derived from lactams with 7 to 13 ring members such as polycaprolactam, polycapryllactam and polylaurolactam and polyamides obtained by reacting dicarboxylic acids with diamines. As dicarboxylic acids z. B. alkanedicarboxylic acids having 6 to 12, in particular 6 to 10 carbon atoms and aromatic dicarboxylic acids, in particular adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, terephthalic acid and / or isophthalic acid.

Particularly suitable diamines are alkanediamines having 6 to 12 carbon atoms and aromatic diamines such as m-xylylenediamine, di (4-aminophenyl) methane,

Di (4-aminocyclohexyl) methane, 2,2-di (4-aminophenyl) propane, 2,2-di- (4-aminocyclohexyl) propane or 1,5-diamino-2-methyl pentane. Furthermore, polyamides which are obtainable by copolymerization of two or more of the abovementioned monomers or mixtures of a plurality of polyamides are suitable, the mixing ratio being arbitrary. The following non-exhaustive list contains suitable polyamides and their monomers.

AB-polymers:

PA 4 pyrrolidone, PA 6 ε-caprolactam, PA 7 ethanolactam, PA 8 capryllactam, PA 9 9-aminopelargonic acid, PA 1 1 1 1 -aminoundecanoic acid, PA 12 laurolactam.

AA / BB-polymers: PA 46 tetramethylenediamine, adipic acid,

 PA 66 hexamethylenediamine, adipic acid,

 PA 69 hexamethylenediamine, azelaic acid,

PA 610 hexamethylenediamine, sebacic acid,

 PA 612 hexamethylenediamine, decanedicarboxylic acid,

 PA 613 hexamethylenediamine, undecanedicarboxylic acid,

 PA 1212 1, 12-dodecanediamine, decanedicarboxylic acid,

 PA 1313 1, 13-diaminotridecane, undecanedicarboxylic acid,

PA 6T hexamethylenediamine, terephthalic acid,

 PA 9T nonyldiamine / terephthalic acid,

 PA MXD6 m-xylylenediamine, adipic acid,

 PA 6I hexamethylenediamine, isophthalic acid,

 PA 6-3-T trimethylhexamethylenediamine, terephthalic acid,

PA 6 / 6T (see PA 6 and PA 6T),

 PA 6/66 (see PA 6 and PA 66),

 PA 6/12 (see PA 6 and PA 12),

 PA 66/6/610 (see PA 66, PA 6 and PA 610),

 PA 6I / 6T (see PA 61 and PA 6T),

PA PACM 12 diaminodicyclohexylmethane, laurolactam,

 PA 6I / 6T / PACM such as PA 6I / 6T + diaminodicyclohexylmethane,

 PA 12 / MACMI laurolactam, dimethyldiaminodicyclohexylmethane, isophthalic acid,

PA 12 / MACMT laurolactam, dimethyldiaminodicyclohexylmethane, terephthalic acid,

PA PDA-T phenylenediamine, terephthalic acid.

It is also possible to use mixtures of the above polyamides.

Specifically, the thermoplastic polymer is selected from amorphous polyamides and blends of amorphous polyamides.

Preferably, the thermoplastic polymer is selected from polyamide 6, polyamide 66, polyamide 6/66, and blends containing polyamide 6, polyamide 66, and / or polyamide 6/66 as the major component. A "main constituent" is understood to mean that a thermoplastic polymer composition containing at least 50% by weight, based on the total weight, of polyamide 6, polyamide 66 and / or nylon 6/66 is used.

As a commercially available polymeric binder is particularly suitable Ultramid® 1 C BASF SE, a polyamide 6/66/136.

Suitable solvents for the liquid binder composition are water, alkanols, such as C 1 - to C 20 -alkanols, methanol, ethanol, n-propanol, isopropanol, n-butanol, Tanol, iso-butanol, tert-butanol, n-pentanol, iso-pentanol, n-hexanol, isohexanol, n-heptanol, iso-heptanol, n-octanol, iso-octanol, ketones such as acetone, methyl ethyl ketone , Esters, such as ethyl acetate and halogenated solvents, such as methylene chloride, chloroform and carbon tetrachloride, or mixtures thereof, preferably water, C 1 -C 12 -alkanols, such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec. Butanol, tert-butanol, n-pentanol, iso-pentanol, n-hexanol, iso-hexanol, n-heptanol, iso-heptanol, n-octanol, iso-octanol or mixtures thereof, particularly preferably water, d- to C4 Alkanols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol, or mixtures thereof.

The solvent used is preferably water or an aqueous-alcoholic solvent. Particularly preferred solvents are water / ethanol or water / propanol mixtures. In a preferred embodiment, the liquid binder composition used is a solution of a polyamide or polyamide blend in a water / ethanol or water / propanol mixture.

In step b) of the process according to the invention, the solvent is at least partially removed. In this case, a binder-containing, shaped, textile structure is obtained, which is then impregnated in step c) with a polymerizable composition and subjected to polymerization.

The partial removal of the solvent in step b) can be carried out by customary methods known to the person skilled in the art. This preferably includes evaporation under reduced pressure and / or elevated temperature.

The solvent is preferably removed in step b) to at least 30% by weight, preferably at least 50% by weight, in particular at least 70% by weight, based on the original amount of solvent. Specifically, the solvent is at least 80 wt .-%, more preferably at least 90 wt .-%, based on the amount originally used, removed.

In step c) of the process according to the invention, the binder-containing, shaped textile structure obtained in step b) is impregnated with a polymerizable composition and subsequently subjected to a polymerization.

The polymerizable composition is preferably selected from polyamide resins, epoxy resins or polyurethane resins.

Preferably, the polymerizable composition contains as polymerizable constituents a lactam or lactam resin. Specially suitable polymerizable compositions are available under the name "cast polyamides". The polymerizable composition used in step c) preferably contains ε-caprolactam as the polymerizable constituent. Suitable is the use of ε-caprolactam as the sole polymerizable component and of mixtures containing ε-caprolactam and at least one component copolymerizable therewith. Up to 20 wt .-%, that is 0 to 20 wt .-%, preferably 0 to 17 wt .-%, particularly preferably 0 to 15 wt .-% of caprolactam can by co-monomers from the group of lactams with at least 4 C atoms are used. Particularly preferred as a comonomer is o-lauryl lactam.

In a preferred embodiment, the polymerizable composition used is a mixture of ε-caprolactam and ω-laurolactam. The mixing ratio of ε-caprolactam and ω-laurolactam is generally from 1000: 1 to 1: 1000, preferably 100: 1 to 1: 100, more preferably 10: 1 to 1:10, in particular 2: 1 to 1: 2. Other components (activators) of the polymerizable composition are compounds which can be prepared by reacting isocyanates, for example HDI (hexamethylene diisocyanate) with lactams, for example ε-caprolactam, and blocked isocyanates, isophthaloylbiscaprolactam, terephthaloyl-biscaprolactam, esters, such as dimethylphthalate-polyethylene glycol , Polyols or polydienes in combination with acid chlorides, carbonylbiscaprolactam, hexamethylene diisocyanate or acyl lactamate, preferably isocyanates, hexamethylene diisocyanate or acyl lactamate, more preferably hexamethylene diisocyanate or acyl lactamate and alkaline catalysts such as magnesium halo lactamates, alkali caprolactamates, aluminum or magnesium lactam, sodium caprolactamate or magnesium Bromide lactamate, preferably alkali caprolactamate, aluminum or magnesium lactam, sodium caprolactamate or magnesium bromide lactamate, more preferably sodium caprolactam or magnesium bromide lactamate.

As activators, all activators that are used for the activated anionic polymerization can be used, such. N-acyl lactams, such as N-acetyl caprolactam, substituted triazines, carbodiimides, cyanamides, mono- and polyisocyanates and the corresponding masked isocyanate compounds. The activators are preferably used in concentrations of 0.1 to 1 mol%, based on the Lammenammenge. With the catalysts of the invention lactams with at least five ring members, such as. As caprolactam, laurolactam, capryllactam, Önanthlac- tam, the corresponding C-substituted lactams or mixtures of said lactams are polymerized. The polymerization can be carried out in the presence of at least one alkaline catalyst. Suitable alkaline catalysts can be prepared by reacting a polyether with the corresponding alkali or alkaline earth metal compound, such as. As the alkoxide, amide, hydride, Grignard compounds and the alkali or alkaline earth metals. The catalysts are generally added in amounts of from 0.1 to 40% by weight, preferably from 0.2 to 15% by weight, based on the polymerisable components. Suitable catalysts for the polymerization are potassium or sodium lactamates. Particularly suitable is sodium caprolactamate, which can be easily prepared from NaH and ε-caprolactam.

The mixing ratio of caprolactam, activator and alkaline catalyst can be varied within wide limits, as a rule, the molar ratio of caprolactam to activator to alkaline catalyst is 1000: 1: 1 to 1000: 200: 50.

The polymerization is preferably carried out at a temperature in a range of 50 to 250 ° C, more preferably 70 to 200 ° C, especially 100 to 190 ° C.

In a particularly preferred embodiment, the binder composition used is a thermoplastic polymer selected from polyamides and blends of polyamides and a polymerizable composition containing as polymerizable constituents a lactam or lactam resin. Such a system is characterized by excellent compatibility of the components used. In particular, the binder composition shows little or no inhibiting effect on the polymerizable composition.

If, in the method according to the invention, step a2) is carried out before step a1), the already deformed fabric remains in the mold after evaporation of the solvent. However, the tissues treated in this way can also be deformed by heating in a second step. The deformation can be carried out in the injection molding tool, but also in an upstream step. Processes for the production of structural components are known, for example, from the plastics manual "Duroplast 10", Hanserverlag 1988 on page 825 et seq.

The pre-formed textile can either be left in the heated mold after drying of the binder or introduced into the final polymerization tool. There, according to the described method, the caprolactam can be introduced together with the activators and catalysts, saturates the textile structure and hardens. It can be polymerized at mold temperatures of 100 to 190 ° C and optionally postpolymerized at temperatures of 80 to 150 ° C. A suitable sequence of processing steps is:

1 . Cutting the fabric or tissues

 2. Place the tissue in the pre-tool or RTM tool, possibly deform

3. Spraying with dissolved thermoplastic

 4. Evaporate solvent

 5. Close the tool

 6. Pre-deformation step

 7. Removal of the fabric part and transfer to RTM tool or further processing in the tool

The inventive method is particularly simple and cheap and therefore suitable for large series. The process according to the invention can be carried out as follows:

In a preferred embodiment, it is possible to work according to the so-called RTM (resine transfer molding) or RIM (reaction injection molding) method. In this process, the core can be arranged in a sealable form with layers of binder-containing, dried, textile structures arranged thereon. The mold usually consists of two heatable mold halves whose inner contour and their outer contour correspond to the finished components. In the closed mold space molten lactam can be supplied to the dry pre-formed fiber material with the additives required for the polymerization. The lactam can be cured by heating the mold. Here, the resin at atmospheric pressure (atmospheric pressure), preferably at a pressure of 1, 1 to 20 bar, preferably 1, 5 to 5 bar, more preferably 1, 0 to 3.0 bar or at a pressure of 0.001 to 0.9 bar, preferably 0.1 to 0.8 bar, more preferably 0.2 to 0.6 bar in the RTM or RIM form are supplied.

The invention also generally relates to the use of a liquid binder composition, as defined above, for pre-forming textile structures in the production of composites. Preferably, the composite materials are then produced by the RIM or RTM process. The term composite material is then generally understood as meaning materials made of two or more bonded materials, such as particle composite materials (dispersion materials, fiber composite materials, laminates, and interpenetration composite materials.) Preference is given to fiber composites and layered composites (laminates); fiber composites are particularly preferred.

The composite parts produced according to the invention are preferably suitable for use as a shell for safety helmets as head protection for persons. These include z. B. safety helmets for persons who drive or drive a motor vehicle, motorcycle, bicycle, etc., safety helmets for sporting activities such as mountaineering, roller skating, etc., safety helmets for children, safety helmets as protection against injury for disabled persons, safety helmets for occupational safety, z. B. in construction, mining, etc.

The invention will be further illustrated by the following non-limiting examples.

Examples

The fabric or textile structures used to reinforce the component are either pre-loaded into the mold, impregnated with the binder and pre-formed by closing the tool and evaporating the solvent and injecting the activated and catalyzed lactam, or they are pre-formed in a second heated tool and then into introduced the polymerization.

Starting Materials:

Polyamide: Ultramid® 1 C (BASF SE)

Catalyst: 17 to 19% strength by weight sodium caprolactamate in caprolactam: Brüggolene® C10 (Brüggemann, Heilbronn)

 Activator: 17% strength by weight blocked diisocyanate in caprolactam: Brüggolene® C20 (Brüggemann, Heilbronn)

 Cast polyamide: caprolactam: AP-Nylon® caprolactam (Brüggemann, Heilbronn)

example 1

5 layers of a glass fiber mat (manufacturer: Saertex) 5 x 90/10 (basis weight 424 g / m ² ) were placed in the tool (hat shape) and adapted by hand to the contours and with 50 ml of a solution of 10 wt. % Polyamide in ethanol / water at a volume ratio of 9: 1 sprayed. After drying the solvent at 30 to 150 ° C, the tool was closed and at 150 ° C Werkzeugtempe- poured with a cast polyamide based on caprolactam. The activator and the catalyst were used according to the data sheet. The cast polyamide was fed in two streams which were mixed immediately prior to their use. The first stream contained about 1 to 3 wt% activator and the second stream about 1.5 to 3 wt% catalyst. After 4 minutes, the molding was removed.

The resulting molded article was perfect and showed no surface disorder.

Comparative Example A

The glass fiber mats used for reinforcement (manufacturer: Saertex) 5 x 90/10 (basis weight 424 g / m ² ) were placed in the tool (hat shape) and adapted by hand to the contours. At 150 ° C tool temperature, the tool was poured out with a cast polyamide system from Brüggemann (Heilbronn) as described above.

The inserted fabrics had slipped, the quality of the resulting molding unsatisfactory because of surface noise.

Claims

PF 70600 2013/050074 PCT / EP2011 / 067411 13 Claims 1 . A process for the production of molded parts from fiber reinforced composites, comprising: a1) impregnating a textile structure with at least one liquid binder composition in the form of a solution or dispersion of a polymeric binder in a solvent, a2) shaping the textile structure, wherein steps a1) and a2) can be carried out in any order and obtaining an impregnated molded textile structure, b) removing the solvent from the impregnated, molded, textile structure to obtain a binder-containing, shaped, textile structure, c) impregnating the in step b ), binder-containing molded textile structure having a polymerizable composition and polymerizing the polymerizable composition. 2. The method of claim 1, wherein the binder contained in the binder composition is a thermoplastic polymer or a mixture of thermoplastic polymers. 3. The method of claim 2, wherein the thermoplastic polymer is selected from polyamides and blends of polyamides. 4. The method of claim 2, wherein the thermoplastic polymer is selected from amorphous polyamides and blends of amorphous polyamides. 5. The method according to claim 4, wherein the thermoplastic polymer is selected from polyamide 6, polyamide 66, polyamide 6/66 and blends containing polyamide 6, polyamide 66 and / or polyamide 6/66 as the main constituent. PF 70600  2013/050074 PCT / EP2011 / 067411  14  6. The method according to any one of the preceding claims, wherein the solvent is water or an aqueous-alcoholic solvent. A method according to claim 6, wherein the liquid binder composition used is a solution of a polyamide or polyamide blend in a water / ethanol or water / propanol mixture. 8. The method according to any one of the preceding claims, wherein the liquid binder composition contains 2 to 20 wt .-%, based on their total weight, of the polymeric binder. 9. The method according to any one of the preceding claims, wherein for impregnating the textile structure in step a1) sprayed with the liquid binder composition. 10. The method according to any one of the preceding claims, wherein the steps a1), a2) and b) is carried out so that the binder-containing, shaped textile structure contains 5 to 200 g / kg of polymeric binder. Method according to one of the preceding claims, wherein the polymerizable composition contains as the polymerizable constituents a lactam or lactam resin. 12. The method according to any one of the preceding claims, wherein one carries out step c) as a RIM or RTM method. 13. Composite moldings, obtainable by a process according to one of claims 1 to 12. 14. Use of the composite moldings according to claim 13 as a shell for safety helmets as head protection for persons. 15. Use of the composite molded parts, produced according to one of claims 1 to 12 as a shell for safety helmets as head protection for persons. PF 70600  2013/050074 PCT / EP2011 / 067411  15  16. Liquid binder composition consisting of an amorphous polyamide and a solvent or a solvent mixture. A binder composition according to claim 16 wherein the amorphous polyamide is selected from polyamide 6, polyamide 66, polyamide 6/66 and blends containing polyamide 6, polyamide 66 and / or polyamide 6/66 as the major component. 18. A binder composition according to claim 16 or 17, wherein the solvent is water or an aqueous-alcoholic solvent. 19. Use of a liquid binder composition according to any one of claims 16 to 18 for pre-forming textile structures in the production of composites by the RIM or RTM process.