DE3416855A1 - Fibre composite materials - Google Patents

Abstract

The invention relates to a process for producing fibre composite materials, in which a heat-resistant thermoplastic polymer A containing reactive groups, preferably nitrile and/or arylthio or alkylthio groups, is applied, if appropriate together with a heat-resistant thermoplastic polymer B containing no reactive groups, to reinforcing fibres, the resulting semi-finished product is moulded and the plastics matrix in the moulding thus obtained cross-linked such that its glass transition temperature increases and it becomes virtually insoluble.

Description

Fiber composite materials

The invention relates to molded parts made of temperature-resistant, with oriented Fibers reinforced plastics and processes for the production of such fiber composites by applying the plastics to reinforcing fibers.

For the production of high performance composite materials has been practical so far worked exclusively with epoxy resins as matrix material.

These resins offer the advantage because of their low viscosities the good impregnability of the reinforcing fibers, but they have the disadvantage that semifinished product made therefrom cannot be stored indefinitely, so that shaping and hardening must take place at the same time. This disadvantage does not apply to use of temperature-resistant thermoplastics as matrix material; here However, other problems arise: If one uses soluble, amorphous thermoplastics, such as polysulfones or polyethersulfones, molded parts are obtained which, because of the Solubility of the matrix material in organic solvents sensitive to stress cracking are, which is particularly opposed to their use in the automotive sector.

If you try insoluble, partially crystalline thermoplastics, such as polyether ketones or to apply polysulfide ketonet as a melt to reinforcing fibers there is insufficient wetting of the fibers because of the high viscosity of the melt.

EP-A-56 703 proposes “fiber structures with melts to impregnate low molecular weight, low viscosity thermoplastic polymers.

The resulting fiber composite materials show, however - in particular with partially crystalline thermoplastics - unsatisfactory toughness and elongation behavior. In EP-A-56 703 there is the possibility of subsequently increasing the molecular weight indicated; the recommended methods (solid phase condensation, addition of crosslinking agents and irradiation) lead to uncontrollable polymers in the case of the polymers described there and undesirable side reactions and thus a reduction in the mechanical properties the prefabricated parts. Furthermore, they require a high outlay in terms of equipment.

The invention was based on the object of creating fiber composite materials with high toughness, good heat resistance and resistance to solvents and stress cracking to manufacture. According to the invention, this object is achieved by a reactive Group-containing, crosslinkable thermoplastic polymer A with a glass transition temperature above 80 "C, optionally together with one containing no reactive groups Polymers B with a glass transition temperature above 80 "C, on reinforcement fibers applies, forms the resulting semi-finished product and in the resulting molded part the Plastic matrix cross-linked in such a way that its glass temperature increases by at least 20 * C, and that they practically no longer exist in the low-boiling chlorinated hydrocarbon is soluble.

Polymers in the context of the invention are those with a degree of polymerization of at least 5, preferably at least 10 and especially at least 20.

Preferred crosslinkable polymers A are those which are nitrile and / or Wear arylthio or alkylthio groups. Under arylthio is the group -S-R to be understood, where R is an optionally substituted aryl radical, for example a phenyl, naphthyl or pyridyl radical, for example halogen, aryl or alkyl substituents can carry, under alkylthio the group -S-R ', where R' is an alkyl radical with 1 to 6 carbon atoms.

The groupings mentioned can on the one hand the solubility of the Improve polymer A in organic solvents, on the other hand can use it the crosslinking reaction go out. The crosslinking reaction creates covalent bonds knotted.

Furthermore, the solubility of polymer A can be influenced by the presence of heterocyclic groups in the polymer molecule, e.g. the group -N =, be improved or through a meta-linking of the individual links within the Polymer chain.

The following groups can also function as reactive groups from which a crosslinking reaction can start: -NC -NCO -NCS -SCN -OCN -C = CH Furthermore, the following groups in the polymer chain: Under certain circumstances, alkyl radicals and halogen substituents can also function as reactive groups.

Because of the presence of the reactive groups in polymer A is a Addition of chemical crosslinking agents in the method according to the invention is not absolutely necessary.

Particularly preferred polymers A are aromatic polyethers of the general formula -XOPO-, in which X and Y have the following meanings: X is an aryl radical which carries at least one nitrile and / or one arylthio group; Y is a diphenol radical, preferably the bisphenol-S radical or the bisphenol A residue The residues of the following diphenols are also suitable: Suitable aryl radicals X are, for example: Mixtures of two or more different types of polymers A can also be used, as well as copolymers which contain different types of monomer units X and Y, respectively.

The polymer A is a temperature-resistant plastic, i.e. its Glass transition temperature is above 80 "C, preferably above 100" C and in particular above 1300C.

In the process according to the invention, either polymer A alone can be applied to the reinforcing fibers or a mixture of polymer A with a temperature-resistant thermoplastic polymer B which does not contain any reactive groups and which also has a glass transition temperature above 80 ° C., preferably above 1000 ° C. and in particular above 130 ° 'C has. The polymers B are preferably amorphous and soluble in organic solvents. Polyether sulfones are preferred Polysulfones in addition, polyetherimides, such as

Polycarbonates and aromatic polyethers.

The polymers A and B are used in a weight ratio of 100: 0 to 1:99. The polymers B do not contain any reactive groups themselves, but during the crosslinking reaction they are incorporated into the crosslinked structure so that they are practically insoluble and lose their susceptibility to stress cracking. This is particularly the case when components A and B form a molecularly disperse, single-phase mixture, such as, for example, in the case of mixtures of A. 2 to 20 parts by weight of the aromatic polyether of the formula and B. 98 to 80 parts by weight of polyether sulfone or polysulfone, and in the case of mixtures of A. 98 to 80 parts by weight of said aromatic polyether and B. 2 to 20 parts by weight of polyether sulfone or polysulfone.

The reinforcing fibers are conventional continuous fiber strands (rovings), e.g.

made of glass, carbon or aromatic polyamides ((R) aramid fibers) in Question. They can be used as a single roving or as a parallel fiber structure or used as a fabric. The volume ratio of plastic to reinforcing fibers is preferably between 70:30 and 15:85, in particular between 55:45 and 35:65.

In a preferred manufacturing process, the reinforcing fibers impregnated with a solution of thermoplastic polymers. Come as a solvent preferably low-boiling organic liquids in question, in particular chlorinated hydrocarbons with a boiling point below 80 "C.

Dichloromethane and a mixture of dichloromethane are particularly suitable and chloroform in a volume ratio of about 1: 1. There are also trichloroethane, Chloroform, hexafluorobenzene, fluorinated aliphatic hydrocarbons and higher chlorinated hydrocarbons suitable.

In principle, higher-boiling solvents can also be used, such as dimethylformamide or N-methylpyrrolidone. But these solvents are difficult to remove from the semi-finished product. It is preferred to impregnate with 5 to 40, in particular with 10 to 30% strength by weight solutions. The solutions should have a viscosity below of 10,000 mPas, preferably below 5000 mPas and in particular between 50 and 1000 mPas. When soaking, the rovings are made individually or in ribbon form pulled side by side through the solvent bath. The rovings should be there Spread out as well as possible, i.e. be pulled apart flat, which is known from known Devices can be accomplished.

The fiber content of the soaked roving can be determined by the concentration the impregnation solution, the dwell time in the bath, as well as by a arranged after the impregnation bath Squeeze roller pair are influenced. Then go through the soaking bath soaked rovings a drying section where the solvents, preferably at temperatures above 60 "C, in particular between 80 and 1500C are evaporated.

The impregnated, synthetic resin-bonded prepreg rovings can - in In the form of single threads or 0.5 to 2 cm wide tapes - non-sticky on spools to be wrapped. They represent a storage-stable semi-finished product that is thermoplastic can be further processed. You can e.g. - if necessary also directly after the Impregnation and drying - after passing through a preheating section on cores Wind up, connect there by heating to temperatures between 160 and 300 "C and in this way produce rotationally symmetrical molded parts, e.g. pipes.

Furthermore, the impregnated roving can be placed directly on a winding core position and only then remove the solvent.

Flat prepregs can be made by going a wide variety of rovings in parallel through the impregnation bath and the resulting, preferably 2 to 150 cm wide impregnated, synthetic resin-bonded roving tape after drying cuts into plate-shaped pieces or winds endlessly on spools.

These preferably 0.1 to 0.5 mm thick, unidirectionally fiber-reinforced Prepregs can be stacked in layers, with the individual prepregs can be placed at any angle to each other. The stacks can then go through Pressing, preferably at temperatures above the melting range of the polymers, be formed into finished parts.

In doing so, the pile is heated, e.g. outside of the press, and then placed then in the press, which is at a temperature below the glass transition point of the polymer is held.

Furthermore, fabrics can be soaked with solutions of the polymers. By evaporating the solvent, flat semi-finished products are obtained, which are further processed as above can be.

The plastic matrix is finally in the molded parts obtained so crosslinked that their glass transition temperature is at least 20 "C, preferably at least 50 "C to a value above 100" C, preferably above 1800C, and that they are practically absent in low-boiling chlorinated hydrocarbons is more soluble. It should not be ruled out that - in the case of a large Excess of polymer B - not all of the polymer B is also completely crosslinked. Included However, the soluble plastic content (measured by one-hour extraction in dichloromethane at 35 [deg.] C.) 5%, preferably 1%.

The crosslinking of the plastic matrix is expediently carried out by heating the molded parts, optionally in the presence of crosslinking catalysts. Lewis acids, such as zinc chloride, are particularly useful as crosslinking catalysts or aluminum chloride in question, which the polymers in amounts of preferably 0.5 up to 5% by weight had been mixed in, furthermore metal oxides such as aluminum oxide and ferrous oxide.

The molded parts are preferably at least 5 minutes long, in particular 1 to 10 hours at temperatures above 200 "C, in particular between 2500 and 450 "C heated.

In this way, infusible, solvent-resistant moldings are obtained, which still have good mechanical properties even at high temperatures, e.g. from 3000C exhibit. After curing, the finished parts are resistant to the solvents previously used - e.g. chlorinated hydrocarbons - stable.

In another preferred method, the reinforcing fibers are used impregnated with a melt of the thermoplastic polymers. This should melt The viscosity should be as low as possible, i.e. it should have a viscosity below 100,000 have mPas. The viscosity should preferably be below 20,000 mPas and in particular between 1,000 and 10,000 mPas.

According to this process, nitrile and / or arylthio or. Crosslinkable thermoplastic polymers A carrying alkylthio groups and having a glass transition temperature processed above 80 "C. They cannot carry any reactive side groups thermoplastic polymers B be mixed, in addition to the amorphous polysulfones and polyethersulfones also partially crystalline and thus insoluble temperature-resistant Polymers such as polyether ketones, polyphenylene sulfide, polysulfide ketones or polyamides come into question. The process steps of soaking, shaping and crosslinking correspond to those described above.

Another method is plastic powder, consisting of polymers A and optionally polymer B applied to reinforcing fibers. The powder preferably has an average particle size of 5 to 15 μm. The Blowing air or other known devices as well as possible Rovings preheated and pulled through a fluidized bed with the plastic powder. Included the plastic powder has a temperature just below the glass point or melting point. Then the plastic powder adhering to the reinforcing fibers is melted, whereby the fibers are soaked. These are then followed by those described above further procedural steps.

Another method is based on plastic fibers, which consist of polymers A and, if appropriate, polymers B and constitutes tissue from these Fibers and reinforcing fibers, for example one type of fiber being warp threads and the other types of fibers are wefts. The plastic fibers are used in the molding process melted and the resulting semi-finished products processed as described above.

Finally, you can also use a plastic film made of polymer A and optionally polymer B run out and such films in one or more Drape layers with flat structures made of reinforcing fibers on top of each other. The locations are then pressed at temperatures above the melting range of the plastics, the resulting semi-finished product is further processed in the manner described.

Another subject matter of the invention are fiber composites, containing a temperature-resistant thermoplastic polymer A, the nitrile and / or arylthio or alkylthio groups, optionally together a temperature-resistant thermoplastic polymer B, which carries no reactive groups, and 30 to 80% by volume of oriented reinforcing fibers, with the plastic matrix having a glass transition temperature of more than 100 etc, preferably of more than 1300C and especially of more than 1800C and practical in a low boiling chlorinated hydrocarbon is insoluble.

Such fiber composite materials, which are characterized by high toughness, good Heat resistance and resistance to solvents and stress cracking, are used as automotive parts, as well as in the aerospace industry.

The parts and percentages given in the examples relate to the weight.

Examples a) Preparation of the polymer A 1 54.57 g (0.25 mol) 4,4'-thiodiphenol and 43.0 g (0.25 mol) of 2,6-dichlorobenzonitrile are in 420 ml of N-methylpyrrolidone and 190 ml of toluene and dissolved with 35.88 g (0.26 mol) of anhydrous potassium carbonate offset. The reaction mixture is azeotropic with constant distillation Mixture of water and toluene heated to 1500C within 2 hours. To complete removal of the toluene, the temperature is increased to 1800C and leave the reaction mixture at this temperature for 5 hours. Through 30 minutes The polycondensation is terminated by introducing a stream of methyl chloride.

The inorganic constituents are after adding 300 ml of chlorobenzene filtered off and the polymer in a mixture of equal parts 1Xiger acetic acid and methanol precipitated. After careful washing with water and methanol, it becomes 12 Dried in vacuo at 100 ° C. for hours.

The polymer has an intrinsic viscosity [#] NMP25 ° C = 0.59 dl. g-1, a glass transition temperature Tg = 153 ° C, and the K value 52.

b) Preparation of the polymer A 2 0.25 mol of 4,4'-thiodiphenol and 0.25 Moles of 2,5-dichloro-3-cyano-4-methylpyridine are polycondensed as described under a), however, the polycondensation time is 5 hours.

The polymer A 2 obtained has a glass transition temperature of 154 "C, a reduced viscosity [2'25'C of 0.21 dl.g 1 and a K value of 29.

c) Preparation of the copolymer A 3 The procedure is as described under b) worked, but 0.125 mol of 2,6-dichlorobenzonitrile and 0.125 mol of 2,5-dichloro-3-cyano-4-methyl - pyridine were used. The copolymer A 3 obtained has a glass transition temperature Tg of 148 "C, a K-value of 26.

Example 1 A 20% solution of the polymer A 1 in CH2Cl2 with a Viscosity of 800 mPa.s at room temperature is used to impregnate glass fibers (1200 tex - roving from Gewetex).

Several fibers are passed through a bath with the polymer solution in parallel drawn, then the solvent is drawn off at 80 to 1300C and you contains flat, still thermoplastic, unidirectionally reinforced prepregs. Respectively four of them are draped on top of each other so that all fibers are parallel. That The scrim is heated in a press at 300 ° C and light pressure for about 1 hour. The temperature is then increased up to 400 ° C. The entire curing process takes about 7 hours. The cross-linked plate can, however, already after 1 - 2 Hours under the press for 8-15 hours in an oven at 350-400 ° C to end the networking.

The finished panel is metallic black, while the prepreg scrim was almost colorless. The cross-linked plate is resistant to CH2C12.

The glass transition temperature Tg of the plastic matrix has risen to 300 ° C.

The shear modulus at 20 "C is 5000 N / mm2 and drops at 200 ° C 4000, at 300 ° C only to 3000 N / mm2. The fiber content is 75 t by volume. Example 2 The procedure is as in Example 1, but only one glass fiber roving is soaked will.

After passing through the drying section, the soaked "prepreg roving" wound on a spool. It has a glass fiber content of 70 Vol.-X and represents a storable semi-finished product.

The prepreg roving is wound on a conventional winding machine a cylindrical mandrel that has been tempered to approx. 200 ° C. The layer structure is 90 ° / 90 ° / + 45s / -45e / -45 ° / + 45 ° / 90 ° / 90 °, the mandrel diameter is 70 mm, the Tube is 100 mm long. After being completely wrapped, the tube will last for 20 hours cross-linked to the finished part in an oven at 350 - 400 "C.

Example 3 A 20 Die solution is prepared, the same parts of the polymer A 1 and polyethersulfone with a glass transition temperature of 220 "C in CH2Cl2 contains. The viscosity of the solution is 800 mPas at room temperature. With this Solution are glass fibers (1200 tex. Roving from Fa.

Gevetex) soaked. There are several fibers running parallel through one Bath with the polymer solution drawn, then the solvent is at 80 to 130iC peeled off and flat, unidirectionally reinforced prepregs are obtained.

4 of them are draped on top of each other in such a way that all fibers are parallel lie. The scrim is heated in a convection oven at 350 "C for 2 hours, then the plate is heated in a press to 350 ° C. for 2 hours.

The cross-linked plate is then placed in a convection oven for 12 hours post-crosslinked for a long time at 350 ° C.

The finished panel is metallic black, while the prepreg scrim was almost colorless. The glass transition temperature Tg of the plastic matrix is 280 ° C. Of the The shear modulus is 4500 N at 20 ° C. mm 2 and drops at 200 "C on 3900, with 30000 only to 3000 N. mm-2 from. The fiber content is 65% by volume.

An extraction experiment with CH2C12 shows that the plastic matrix has become practically insoluble, i.e. that the polyethersulfone is also crosslinked became.

Example 4 A 100 cm wide glass fabric with a weight per unit area from 296 g. m-2 is impregnated with a 20% solution of the polymer A 2 in CH2Cl2, by running it continuously through a soaking bath. It then goes through a vertical drying tower, with the solvent evaporated at 130-150 "C will. The fabric prepreg obtained is cut into lengths of 1 m and used as a semi-finished product stored.

16 fabric prepregs are placed on top of each other in a press and at 340 "C and 10 bar pressed for 4 hours. The finished molded part is placed in a convection oven Postcrosslinked at 340 ° C. for 10 hours.

The resulting plate is solvent-resistant against Cd2012; the Due to the crosslinking, the glass transition temperature Tg of the plastic matrix is from 150 ° C to 300 ° C increased.

Example 5 A 30% strength solution of the copolymer A 3 in CH2Cl2 is used produced, which has a viscosity of 60 mPas at room temperature. By this solution becomes 100 carbon fibers (T 300 from TORAY) at one speed of 5 m. s-1 pulled through in parallel, then the solvent is at 13000 to 180 "C evaporated and you get a flat, thermoplastic unidirectional Reinforced prepreg 300 mm wide, from which pieces 100 cm long were cut will. 8 of these pieces are stacked on top of each other so that all fibers are parallel are aligned. The scrim is in a press at 320 "C and 10 bar for 10 hours cured for a long time to a test plate with a fiber content of 60% by volume. Afterward is post-tempered at 320 ° C for 12 hours. The plate is resistant to solvents. The glass transition temperature of the plastic matrix has risen from 148 to 260 ° C.

Example 6 20 rovings made of carbon fibers (T 300 from TORAP) are spread well and at a speed of 0.5 m. s 1 through a melt pool drawn with the polymer A 1. The bath temperature was 280 "C. After cooling the 6 cm wide prepreg tape is wound onto a spool. It represents a storable thermoplastic semi-finished product, which is deformed into finished parts if necessary and at can be crosslinked at elevated temperatures. The plastic matrix is in CH2C12 insoluble and the glass temperature Tg increases depending on the crosslinking conditions of 153 ° to 250 to 350es.

Claims (15)

Claims i) \ Process for the production of molded parts from temperature-resistant, plastics reinforced with oriented fibers by impregnating reinforcing fibers with a solution of A. a crosslinkable thermoplastic containing reactive groups Polymers with a glass temperature above 80 "C and optionally B. a thermoplastic polymers containing no reactive groups and having a glass transition temperature above 80 ° C, the solution having a viscosity below 10,000 mPas, Evaporation of the solvent and shaping of the resulting semi-finished product, characterized in that that in the molded part obtained in this way, the plastic matrix is crosslinked in such a way that their glass transition temperature rises by at least 20 "C, and that they are low-boiling chlorinated hydrocarbons is practically no longer soluble. 2. The method according to claim 1, characterized in that a 5 to 40 Gew.Xige solution is used in an organic solvent. 3. The method according to claim 2, characterized in that the organic Solvent a chlorinated hydrocarbon with a boiling point below 80 "C is. 4. Process for the production of molded parts from temperature-resistant, plastics reinforced with oriented fibers by impregnating reinforcing fibers with a melt of A. a nitrile and / or arylthio or alkylthio group load-bearing crosslinkable thermoplastic polymers with a glass transition temperature above of 80 ° C and possibly B. a thermoplastic which does not carry any reactive side groups Polymers with a glass transition temperature above 80 ° C, the melt preferably has a viscosity below 100,000 mPas, and shapes the resulting Semi-finished product, thereby characterized in that in the molded part obtained thereby the plastic matrix is crosslinked in such a way that its glass transition temperature is at least 20 "C. increases, and that they are useful in low-boiling chlorinated hydrocarbons is no longer soluble. 5. Process for the production of molded parts from temperature-resistant, plastics reinforced with oriented fibers by applying a plastic powder, consisting of A. a crosslinkable thermoplastic containing reactive groups Polymers with a glass transition temperature above 80 "C and optionally B. a thermoplastic polymers containing no reactive groups with a glass temperature above 80 "C, on reinforcing fibers, melting of the plastic and shaping of the resulting semi-finished product, characterized in that in this obtained molded part, the plastic matrix is crosslinked so that its glass transition temperature by at least 20'C, and that they are in low-boiling chlorinated hydrocarbons is practically no longer soluble. 6. Process for the production of molded parts from temperature-resistant, plastics reinforced with oriented fibers by creating a fabric Basis of reinforcement fibers and synthetic fibers from A. one reactive groups containing, crosslinkable thermoplastic polymers with a glass transition temperature above 80 "C and possibly B. one containing no reactive groups, thermoplastic polymers with a glass transition temperature above 80 ° C, melt on the plastic fibers and forms of the resulting semi-finished product, characterized in that in the molded part obtained in this way, the plastic matrix is crosslinked in such a way that their glass transition temperature rises by at least 200C, and that they are low-boiling chlorinated raw hydrogen is practically no longer soluble. 7. Process for the production of molded parts from temperature-resistant, with oriented fibers reinforced plastics by draping over one another in each case one or more layers of a flat structure made of reinforcing fibers and a plastic film, consisting of A. containing reactive groups, crosslinkable thermoplastic polymers with a glass transition temperature above 80 "C and optionally B. a thermoplastic which does not contain reactive groups Polymers with a glass transition temperature above 80 "C, pressing the layers underneath Melting the plastic film and shaping the resulting material, thereby characterized in that the plastic matrix is crosslinked in the molded part obtained in this way that their glass transition temperature increases by at least 20 "C, and that they are in low-boiling chlorinated hydrocarbons is practically no longer soluble. 8. The method according to claims 1 to 7, characterized in that that the polymers A are aromatic polyethers, the at least one nitrile and / or carry an arylthio group. 9. The method according to claims 1 to 7, characterized in that that the polymer B is a polyether sulfone, a polysulfone, a polyetherimide, a polycarbonate or an aromatic polyether. 10. The method according to claims 1 to 7, characterized in that that the polymers A and B are used in a weight ratio of 100: 0 to 1:99. 11. The method according to claims 1 to 7, characterized in that that the reinforcing fibers in the form of single rovings, parallel fiber fabrics or can be used as a fabric. 12. The method according to claims 1 to 7, characterized in that that the volume ratio of plastic to reinforcing fibers between 70:30 and 15: 85 lies. 13. The method according to claims 1 to 7, characterized in that that the crosslinking of the plastic matrix by heating, optionally in the presence of crosslinking catalysts, preferably Lewis acids, is carried out. 14. The method according to claim 13, characterized in that the molded part is heated to temperatures above 2000C for at least 5 minutes. 15. Fiber composite material containing a temperature-resistant thermoplastic Polymer A bearing nitrile and / or arylthio or alkylthio groups, if appropriate together with a temperature-resistant thermoplastic that does not carry any reactive groups Polymers B, as well as 30 to 85 volumes; oriented reinforcing fibers, characterized in that that the plastic matrix has a glass transition temperature of more than 100eC and in is practically insoluble in a low-boiling chlorinated hydrocarbon.