EP1106724B1 - Process for pre-binding fibrous materials - Google Patents

Description

The invention relates to a method for Manufacture of molded plastic parts made of fiber-reinforced, unsaturated polyester resins or epoxy resins by laying out the pre-bonded fiber material, Soak the fiber material with the unsaturated polyester resin or epoxy resin and molding the molded part.

The production of high-strength, flat plastic parts, such as for example automotive body parts, boat shells, aircraft fuselages, is known to occur frequently from so-called unsaturated Polyester resins (UP resins), which are made of glass, aramid or carbon fibers are mechanically reinforced. The Fibers are in the form of woven, laid or pre-tied Fiber mats (= nonwovens) used. In the manufacturing process the textile structures into the molds draped and impregnated with the reaction resin, the in of the fiber mat existing prebinder by the existing in the UP resin Styrene is dissolved or dissolved. Consequently the mats lose their inherent stiffness and become adapt better to the tool contours, while at the same time the impregnation of the fiber mats with the resin is accelerated becomes.

So far, thermoplastic materials have been used in the production process mentioned Polyester powder, in particular polyester powder based Bisphenol-A, used as a pre-binder for the fiber mats. For this purpose, the bisphenol A polyester powder is placed on a previously deposited one Sprinkled glass fleece and at the subsequent Furnace run melted, so that the glass fibers at their crossing points bound by the molten polymer powder become. The pre-bound glass mats then become Reinforcement of UP resins used. A disadvantage of these However, the prebinder is, for certain applications, insufficient kinetics of solubility in monomeric styrene.

Another important area of application for polymer powder is the pre-binding of textile fabrics for the purpose of Shaping fiber mats before applying injection resin is used, for example, for preforming before an RTM process (= Resin Transfer Molding). The main thing here is to minimize the fraying of the assembled fiber mat, the dimensional stability of an optionally preformed fiber mat to ensure and incompatibility between preform binders and to avoid injection resin.

AU-A 36659/89 describes a process for the production of pre-bonded fiber materials in the glass fibers with two different Lengths with a triple combination as a binder which styrene-soluble polyester powder, Contains polystyrene powder and polyvinyl acetate dispersion.

DE-A 2604544 styrene-soluble binders are unsuitable Binder for the consolidation of fiber materials described, which is further processed with a thermoplastic melt become. For this application the use of hydroxyl groups or polyacrylates containing carboxyl groups recommended, which by means of solvent or bulk polymerization getting produced. Emulsion polymers become explicit discouraged, as the surface-active contained therein Substances contaminate the binder and lead to undesirable side effects such as discoloration or thermal degradation.

EP-A 894888 discloses textile binders based on carboxyl-functional ones Polymers, which in combination with Epoxy or isocyanate crosslinkers are used, known. On processes for the preparation of pre-bound, styrene-soluble Molded fiber parts are not received.

The task was to use a powdery prebinder To provide, which is in a styrene-containing UP resin resolves as quickly as possible, but also for pre-binding in processes is suitable, especially where the tolerance of the prebinder with the polyester resin in the foreground.

The invention relates to a method for Manufacture of fiber reinforced Plastic molded parts made of reactive resins such as Epoxy resins or unsaturated polyester resins.

Suitable copolymers are those based on one or more monomers from the group comprising vinyl esters of unbranched or branched alkyl carboxylic acids 1 to 15 carbon atoms, methacrylic acid ester and acrylic acid ester of Alcohols with 1 to 10 carbon atoms, vinyl aromatics such as styrene and Vinyl chloride. Preferred vinyl esters are vinyl acetate, vinyl propionate, Vinyl butyrate, vinyl 2-ethylhexanoate, vinyl laurate, 1-methyl vinyl acetate, vinyl pivalate and vinyl ester of alpha-branched Monocarboxylic acids with 5 to 11 carbon atoms, for example VeoVa5 or VeoVa9. Preferred methacrylic acid esters or acrylic acid esters are methyl acrylate, methyl methacrylate, Ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, n-butyl acrylate, n-butyl methacrylate, 2-ethylhexyl acrylate.

It is essential that the composition of the copolymer be chosen so that a glass transition temperature Tg or a melting point of greater than 35 ° C, preferably from 55 ° C to 150 ° C results. The glass transition temperature Tg and the melting point of the polymers can be determined in a known manner by means of differential scanning calorimetry (DSC). The Tg can also be roughly predicted using the Fox equation. According to Fox TG, Bull. Am. Physics Soc. 1 , 3, page 123 (1956) applies: 1 / Tg = x ₁ / Tg ₁ + x ₂ / Tg ₂ + ... + x _n / Tg _n , where x _n for the mass fraction (% by weight / 100 ) of the monomer n, and Tg _{n is} the glass transition temperature in degrees Kelvin of the homopolymer of the monomer n. Tg values for homopolymers are listed in Polymer Handbook 2nd Edition, J. Wiley & Sons, New York (1975).

Vinyl ester copolymers, styrene copolymers are preferred and acrylic acid ester copolymers. Especially preferred copolymers are vinyl acetate / ethylene copolymers, Vinyl acetate / vinyl chloride-, vinyl acetate / VeoVa5-, Vinyl acetate / VeoVa9 copolymers, each of 0.01 to 25% by weight of the above-mentioned monomer units containing carboxyl groups contain, and the composition of which is chosen so that the above-mentioned glass temperatures Tg or melting points result. Methyl methacrylate / butyl acrylate are also particularly preferred. and styrene / butyl acrylate copolymers, which each 0.01 to 25 wt .-% of the carboxyl-containing Contain monomer units, and their composition is chosen so that the above-mentioned glass temperatures Tg or melting points result.

Suitable ethylenically unsaturated monomers containing carboxyl groups are ethylenically unsaturated mono- or dicarboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid. The content of carboxyl groups is preferably Comonomer units containing 0.01 to 10 wt .-%, based on the total weight of the copolymer.

If necessary, the copolymers 0.01 to 10.0 % By weight, based on the total weight of the copolymer, auxiliary monomers from the group of ethylenically unsaturated Carboxamides, preferably acrylamide, from the group the ethylenically unsaturated sulfonic acids or their salts, preferably vinyl sulfonic acid, from the group of multiple ethylenically unsaturated comonomers, for example divinyl adipate, Diallyl maleate, allyl methacrylate or triallyl cyanurate and / or from the group of N-methylol (meth) acrylamides and whose ethers such as isobutoxy or n-butoxy ether contain. In a preferred embodiment contain the copolymers each 0.01 to 2 wt .-% acrylic acid and / or acrylamide.

The copolymers are prepared in a manner known per se Way after the emulsion polymerization process in Presence of emulsifier, as for example in WO-A 94/20661, the disclosure of which is part of the present application. To make the powder the resulting polymer dispersion is dried. Drying can be done by spray drying, drum drying, Freeze drying or by coagulation of the dispersion and subsequent Fluid bed drying take place. To be favoured spray drying and roller drying. Preferably done the preparation of the copolymer and its drying without Protection colloid added.

Suitable crosslinkers are powdered compounds which contain two or more reactive groups with carboxylic acid groups form a covalent bond with a melting point from 40 ° C to 150 ° C. Epoxides, isocyanates, Primides, organohalogen compounds, aziridines, carbodiimides, Oxazolines, alcohols, amines, aminosilanes, aminoformaldehydes. Compounds which are two or more reactive are preferred Groups from the group of epoxides, isocyanates or primides contain.

Examples of suitable epoxy crosslinkers are those from Bisphenol A type, that is, condensation products of bisphenol A and epichlorohydrin or methylepichlorohydrin. such Epoxy crosslinkers are commercially available, for example under the trade names Epicote or Eurepox available. Suitable diisocyanates are also common commercial products, for example m-tetramethylxylene diisocyanate (TMXDI), methylene diphenyl diisocyanate (MDI). The crosslinker content is generally from 0.1 to 25% by weight, preferably from 4 to 12% by weight, based on the powdery copolymer.

Combinations of the copolymer a) are usually and the crosslinker b) used. This is especially true for applications in which high mechanical strength is required. In contrast, in applications where the styrene solubility is paramount can also be used without the addition of a crosslinker.

In a preferred embodiment, the powdered Binder composition still a crosslinking catalyst based on organic compounds, which are quaternary Groups of elements of the 5th main group of the PSE included. Powdered catalysts are preferred, which differ from Triphenylphosphonium halides or quaternary ammonium compounds derived. Examples include methyl, ethyl, Propyl, butyl triphenylphosphonium bromide or the corresponding Iodides and chlorides. Triphenylphosphonium halides are also suitable with substituted alkyl radical such as 2-carboxyethyl, 3-bromopropyl or formylmethyl triphenylphosphonium bromide. Suitable quaternary ammonium compounds are tetrabutylammonium, Benzyltrimethylammonium, methyltributylammonium salts. The compounds mentioned are commercially available and are preferably obtained in amounts of 0.1 to 5% by weight on the powdery copolymer, used.

In applications where it depends on the melt flow characteristics arrives, have proven as polymers a) those which have a molecular weight Mw of 60,000 to 300,000. The molecular weight can be known in the art and Way by means of regulators, such as dodecyl mercaptan, during the polymerization can be set.

The preparation of the powdered binder composition is done by mixing the powdered components in the specified mixing ratios. For this, the known Devices for mixing powders are used.

All fibers, which are usually suitable, are suitable as fiber material used to reinforce fiber-reinforced plastics become. These include in particular glass fibers, polyamide fibers and carbon fibers. The polyamide fibers are aramid fibers prefers. The fiber materials can be used as single filaments or as yarns, so-called rovings, or as fleeces, tangles or scrim can be used. The fibers can both both individually and in the form of combinations with each other are used, for example in the form of blended yarns or blended fabrics.

The powder composition is generally used for fiber binding in an amount of 1 to 50% by weight, preferably 4 to 15% by weight, particularly preferably 3 to 8 wt .-%, each based on the Fiber weight used.

It can be used to manufacture the molded parts or fabrics be proceeded so that the fiber materials with the powder composition be mixed and the mixture of fiber and powder before solidification by the usual methods nonwoven technology, for example by means of an air laying, Wet laying, direct spinning or carding device becomes. The fiber / powder mixture can optionally be carded become. Then by means of temperature increase, preferably to 130 ° C to 250 ° C, if necessary using Pressure and / or superheated steam bound the fiber material.

It can also be done so that before solidification the fibers are spread out area-wide, the fiber-powder mixture can still be carded if necessary, or a fiber scrim, fabric or fleece is laid out. Subsequently is the powder mixture in the laid fiber material interspersed; powder spreaders, roller application systems and electrostatic spraying methods are preferred. Then, if necessary, by increasing the temperature by means of infrared radiation source or microwave, preferably to 130 ° C to 250 ° C, if necessary using pressure and / or superheated steam, the fiber material bound.

The pre-bonded fiber materials available in this way are suitable to manufacture fiber reinforced Plastics, which is particularly characterized by a good and characterized by rapid solubility in styrene. In this application is used to manufacture plastic molded parts from fiber-reinforced, unsaturated polyester resins the pre-bonded fiber material designed, then with the unsaturated polyester resin soaked and finally molded the molded part,

Another preferred area of application is solidification of glass, aramid or carbon fiber mats in the form of laid or woven fabrics, mixed beds or mixed fabrics by means of the powder composition, analogous to the process description above can be worked. The available pre-bonded fiber materials are, for example for the production of fiber-reinforced, epoxy-bonded RTM molded parts (RTM = Resin Transfer Molding) or SMC molded parts (SMC = Sheet Molding Composites). For the production of preformed fabrics ("preforming") can the pre-bound Fiber material in a suitable mold, if necessary using elevated temperature and pressure be shaped.

The following examples serve for further explanation the invention.

Example 1:

Monomerdosierung 1 mit 67.3 g Methacrylsäure, 403.7 g Butylacrylat, 861.3 g Styrol und 6.7 g Dodecylmercaptan.

Monomerdosierung 2 mit 67.3 g Wasser, 44.9 g Acrylamid (30 %).

Initiatordosierung mit 217.6 g Wasser und 6.7 g Kaliumperoxodisulfat.

Nach den Dosierungen wurde ca. 2 Stunden bei 80°C nachpolymerisiert. Nach dem Abkühlen und dem Einstellen des pH-Wertes auf 8 mittels Ammoniak wurde die Dispersion sprühgetrocknet. Die Glastemperatur dieses Produktes lag bei 59°C.

Production of a polymer powder containing carboxylic acid groups:
838.8 g of deionized water and 6.7 g of sodium lauryl sulfate were placed in a reactor with a volume of 3 liters and heated to 80 ° C. with nitrogen and stirring. At this temperature, the initiator solution (6.7 g of potassium peroxodisulfate and 218.4 g of water) was added to the reactor and the following compositions were metered into the reactor over the course of 4 hours from separate containers:

Monomer dosage 1 with 67.3 g methacrylic acid, 403.7 g butyl acrylate, 861.3 g styrene and 6.7 g dodecyl mercaptan.

Monomer dosage 2 with 67.3 g water, 44.9 g acrylamide (30%).

Initiator dosage with 217.6 g water and 6.7 g potassium peroxodisulfate.

After the metered additions, the polymerization was continued at 80 ° C. for about 2 hours. After cooling and adjusting the pH to 8 using ammonia, the dispersion was spray-dried. The glass temperature of this product was 59 ° C.

Example 2:

Monomerdosierung 1 mi 67.2 g Methacrylsäure, 403.4 g Butylacrylat, 860.5 g Styrol, 6.7 g Dodecylmercaptan.

Monomerdosierung 2 mit 67.3 g Wasser und 28.0 g N-Methylolacrylamid (48 %).

Initiatordosierung mit 217.4 g Wasser und 6.6 g Kaliumperoxodisulfat.

Nach den Dosierungen wurde ca. 2 Stunden bei 80°C nachpolymerisiert. Nach dem Abkühlen und dem Einstellen des pH-Wertes auf 8 mittels Ammoniak wurde die Dispersion sprühgetrocknet. Die Glastemperatur dieses Produktes lag bei 59°C.

Production of a polymer powder containing carboxylic acid groups:
855 g of deionized water and 6.7 g of sodium lauryl sulfate were placed in a reactor with a volume of 3 liters and heated to 80 ° C. with nitrogen and stirring. At this temperature, the initiator solution (6.7 g of potassium peroxodisulfate and 217.4 g of water) was added to the reactor and the following compositions were metered into the reactor from separate containers within 4 hours:

Monomer dosage 1 ml 67.2 g methacrylic acid, 403.4 g butyl acrylate, 860.5 g styrene, 6.7 g dodecyl mercaptan.

Monomer dosing 2 with 67.3 g water and 28.0 g N-methylolacrylamide (48%).

Initiator dosage with 217.4 g water and 6.6 g potassium peroxodisulfate.

After the metered additions, the polymerization was continued at 80 ° C. for about 2 hours. After cooling and adjusting the pH to 8 using ammonia, the dispersion was spray-dried. The glass temperature of this product was 59 ° C.

Example 3:

Production of the powder mixture: 98 g of the polymer powder containing carboxylic acid groups from Example 1 was in a powder mixer with 2 g of a powder, multifunctional epoxy compound mixed.

Example 4:

Production of the powder mixture: 98 g of the polymer powder containing carboxylic acid groups from Example 2 was in a powder mixer with 2 g of a powdery, multifunctional epoxy compound mixed.

Comparative Example 5:

A commercial polyester powder based on an unsaturated Ester.

Comparative Example 6:

A commercial polyester powder based on a bisphenol A fumarate.

Comparative Example 7:

A commercial polyester powder based on an unsaturated Bisphenol polyester.

Production of a glass fiber mat:

To produce a glass fiber mat, glass rovings were statistical spread out on a carrier plate and evenly with a powder from the examples or comparative examples sprinkled. The powder application was 5% by weight in each case, based on the fiber weight. The carrier plate was used for solidification with the fiber / powder mixture for 3 minutes at 210 ° C heated, melting the powder, soaking the fibers and joined together at the crossing points. The received with it Fiber mats showed no discoloration.

Application tests: styrene solubility:

The fiber mats were used to test the styrene solubility cut a test specimen of size 10 x 15 cm, with 100 g weight and hung vertically in monomeric styrene dipped. The styrene solubility was characterized by the time span (in seconds) from the time of immersion to to tear off the fiber mat.

The results of the application test are summarized in Table 1. pinafores Styrene solubility [s] example 1 8th Example 2 12 Example 3 13 Example 4 14 Comparative Example 5 130 Comparative Example 6 31 Comparative Example 7 34

The table shows that the procedure according to the invention is clear better styrene solubility is obtained than with conventional Vorbindern.

Processing according to the RTM process:

A carbon fiber fabric was laid out, grounded and the powder from example 1 by means of electrostatic spray application in an amount of 5 wt .-%, based on fiber weight, applied. In a subsequent oven run at 150 ° C / 20 sec the mat was pre-consolidated. Then the pre-consolidated Mat in a crimping tool into a hemispherical Formed.

This experiment was repeated with the powder from Example 3, with a glass fiber fabric instead of a carbon fiber fabric has been used.

The pre-bound and pre-formed scrims or fabrics were dimensionally stable and can be easily integrated without loss of shape Transfer the appropriately shaped injection tool.

Claims (7)

1. Process for producing plastics mouldings, which comprises a first step of mixing a pulverulent binder composition comprising

   a) a pulverulent interpolymer, obtainable by emulsion polymerization and subsequent drying, of one or more monomers from the group consisting of vinyl esters, acrylic esters, methacrylic esters, vinylaromatics and vinyl chloride and 0.01 to 25% by weight, based on the total weight of the interpolymer, of one or more ethylenically unsaturated carboxyl-containing monomers, the interpolymer having a glass transition temperature Tg or a melting point of above 35°C, and optionally

   b) at least one pulverulent compound containing at least two reactive groups capable of reaction with the carboxyl groups mentioned under a), and having a melting point of 35°C to 150°C,

   and spreading out the mixture,
   or sprinkling the pulverulent binder on the spread-out fibre material and then binding the fibre material by raising the temperature to 50°C to 250°C,
   and a second step of laying up the prebound fibre material, saturating said fibre material with unsaturated styrene-containing polyester resin or with epoxy resin, and forming the plastics moulding.
2. Process according to Claim 1, characterized in that the interpolymer used is selected from vinyl acetate-ethylene, vinyl acetate-vinyl chloride, vinyl acetate-VeoVa5, vinyl acetate-VeoVa9, methyl methacrylate-butyl acrylate and styrene/butyl acrylate interpolymers which each contain 0.01 to 25% by weight of carboxyl-containing monomer units.
3. Process according to Claim 1 or 2, characterized in that said one or more ethylenically unsaturated carboxyl-containing monomers are selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, fumaric acid and itaconic acid.
4. Process according to any of Claims 1 to 3, characterized in that the one or more pulverulent compounds containing two or more reactive groups are selected from the group consisting of epoxides, isocyanates, Primids, organohalogens, aziridines, carbodiimides, oxazolines, alcohols, amines, aminosilanes and aminoformaldehydes.
5. Process according to any of Claims 1 to 4, characterized in that the fibre material used is glass fibre, polyamide fibre or carbon fibre.
6. Process according to any of Claims 1 to 5, which comprises the prebound fibre material also being preformed.
7. Process according to Claim 6, which comprises the prebound fibre material being formed in a suitable mould, if necessary by the application of heat and pressure.