EFFICIENT PRODUCTION OF COMPOSITE SEMIFINISHED PRODUCTS AND COMPONENTS IN A WET PRESSING METHOD USING HYDROXY FUNCTIONALIZED (METH)ACRYLATES WHICH ARE DUROPLASTICALLY CROSSLINKED USING ISOCYANATES OR URETDIONES

Abstract

The invention relates to a process for producing semi-finished composites and composite components. For production of the semi-finished products or components, (meth)acrylate monomers, (meth)acrylate polymers, polyfunctionalized (meth)acrylates, hydroxy-functionalized (meth)acrylate monomers and/or hydroxy-functionalized (meth)acrylate polymers are mixed with di- or polyisocyanates or with uretdione materials. This liquid mixture is applied by known processes to fibre material, for example carbon fibres, glass fibres or polymer fibres, and polymerized with the aid of a first temperature increase or of a redox accelerator or by means of photoinitiation. Polymerization, for example at room temperature or at up to 120° C., gives rise to thermoplastics which can still be subjected to a forming operation. The hydroxy-functionalized (meth)acrylate constituents can subsequently be crosslinked in a press with isocyanates or uretdiones already present in the system at a second temperature at least 20° C. above the polymerization temperature. In this case, the shaping to give the final component is effected simultaneously in this press. In this way, dimensionally stable thermosets or crosslinked composite components can be produced.

Claims

1. A process for producing a semi-finished composite and further processing thereof to give a moulding, comprising: I. producing a liquid reactive composition, II. directly impregnating a fibrous carrier with the composition from I., III. polymerizing a monomer constituent in the liquid composition at a temperature T.sub.1, to give a polymerized composition, IV. shaping the polymerized composition from III. in a press and/or another mould to give the moulding and V. simultaneously curing the isocyanate component in the composition in the press and/or mold at a temperature T.sub.2, wherein the composition comprises the following components: A) a (meth)acrylate-based reactive resin component containing at least one (meth)acrylate monomer and at least one poly(meth)acrylate, wherein at least one constituent of the resin component has a hydroxyl group, B) at least one blocked di- or polyisocyanate and/or at least one uretdione as isocyanate component, and wherein the temperature T.sub.2 is at least 20° C. higher than the temperature T.sub.1.

2. The process as claimed in claim 1, wherein the ratio of the resin component to the isocyanate component is between 90:10 and 40:60.

3. The process as claimed in claim 1, wherein the temperature T.sub.1 in III. is between 20 and 120° C.

4. The process as claimed in claim 1, wherein the resin component A) comprises at least 20% by weight to 100% by weight of a monomer, and 0% by weight to 70% by weight of a prepolymer.

5. The process as claimed in claim 4, wherein the resin component A) comprises at least 0% by weight to 10% by weight of a crosslinker, 30% by weight to 90% by weight of a monomer, 0% by weight to 20% by weight of an urethane (meth)acrylate, 0% by weight to 40% by weight of a prepolymer, 0% by weight to 10% by weight of one or more initiators, and 5% by weight to 50% by weight of one or more polyols.

6. The process as claimed in claim 5, wherein the initiator is present and comprises hydroxy ketones and/or bisacylphosphines as photoinitiator and/or a peroxide as thermally activatable initiator and/or a redox accelerator, and wherein the sum total of the initiators is present in the composition in a concentration between 0.2% and 6.0% by weight.

7. The process as claimed in claim 1, wherein the fibrous carrier comprises for the most part glass, carbon, a polymer, a natural fiber, or mineral fiber material, and wherein the fibrous carrier takes the form of a textile structure in the form of a sheet and made from nonwoven fabric, of a knitted fabric, of a non-knitted structure, or of long fiber or short fiber material.

8. The process as claimed in claim 1, wherein di- or polyisocyanate of component B) is selected from the group consisting of isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), diisocyanatodicyclohexylmethane (H.sub.12MDI) 2-methylpentane diisocyanate (MPDI), 2,2,4-trimethylhexamethylene diisocyanate/2,4,4-trimethylhexamethylene diisocyanate (TMDI) and/or norbornane diisocyanate (NBDI), including the isocyanurates, and wherein the di- or polyisocyanate has been blocked with an external blocking agent selected from the group consisting of ethyl acetoacetate, diisopropylamine, methyl ethyl ketoxime, diethyl malonate, ε-caprolactam, 1,2,4-triazole, phenol or a substituted phenol, 3,5-dimethylpyrazole and mixtures thereof.

9. The process as claimed in claim 1, wherein the isocyanate component additionally contains 0.01% of 5.0% by weight of a catalyst.

10. The process as claimed in claim 1, wherein the isocyanate component used is uretdione prepared from isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), diisocyanatodicyclohexylmethane (H.sub.12MDI), 2-methylpentane diisocyanate (MPDI), 2,2,4-trimethylhexamethylene diisocyanate/2,4,4-trimethylhexamethylene diisocyanate (TMDI) and/or norbornane diisocyanate (NBDI).

11. The process as claimed in claim 10, wherein the pure isocyanate component is in solid form below 40° C. and in liquid form above 125° C., has a free NCO content of less than 5% by weight and a uretdione content of 3% to 60% by weight, and wherein the isocyanate component additionally contains 0.01% to 5% by weight of at least one catalyst selected from quaternary ammonium salts and/or quaternary phosphonium salts with halogens, hydroxides, alkoxides or organic or inorganic acid anions as counterion.

12. The process as claimed in claim 10, wherein the isocyanate component additionally contains 0.1% to 5% by weight of at least one cocatalyst selected from either at least one epoxide and/or at least one metal acetylacetonate and/or quaternary ammonium acetylacetonate and/or quaternary phosphonium acetylacetonate, and optionally an auxiliary and/or an additive known from polyurethane chemistry.

13. The process as claimed in claim 1, wherein the resin component and the isocyanate component are present in such a ratio to one another that there is 0.3 to 1.0 uretdione group for every hydroxyl group in the resin component.

14. The process as claimed in claim 5, wherein the resin component contains 10% by weight to 30% by weight of the additional polyol, and wherein the polyol is a low molecular weight polyol having 3 to 6 OH functionalities, a polyester having a molecular weight M.sub.n between 200 and 4000 g/mol, an OH number between 25 and 800 mg KOH/g and an acid number less than 2 mg KOH/g, a polyether having an OH number between 25 and 1200 mg KOH/g and a molar mass M.sub.n between 100 and 2000 g/mol, or a mixture of at least two of these polyols.

15. The process as claimed in claim 14, wherein the polyester is a polycaprolactone having an OH number between 25 and 540, an acid number between 0.5 and 1 mg KOH/g and a molar mass between 240 and 2500 g/mol.

16. Use of A moulding obtained by the process as claimed in claim 1.

17. A semi-finished product, comprising: a fibrous carrier and a matrix material, wherein the matrix material comprises a cured resin component and an unreacted isocyanate component in a ratio between 90:10 and 40:60, wherein the resin component comprises at least 30% by weight of a cured (meth)acrylate-based reactive resin, and in that the resin component has an OH number between 10 and 600 mg KOH/g.

Description

EXAMPLES

[0111] The following glass fibre scrims or fabrics were used in the examples: Glass filament fabric 296 g/m.sup.2- Atlas, Finish FK 144 (Interglas 92626)

Preparation of the Uretdione-Containing Curing Agent CA:

[0112] 119.1 g of IPDI uretdione (Evonik Industries) were dissolved in 100 ml of methyl methacrylate, and 27.5 g of propanediol and 3.5 g of trimethylolpropane were added. After adding 0.01 g of dibutyltin dilaurate, the mixture was heated to 80° C. while stirring for 4 h. Thereafter, no free NCO groups were detectable any longer by titrimetric methods. The curing agent CA, based on solids, has an effective NCO latency content of 12.8% by weight.

[0113] For Examples 1 and 2, two of these curing agents a) and b) were produced by an identical procedure.

Reactive Polyurethane Composition

[0114] Reactive polyurethane compositions having the formulations which follow were used for production of the prepregs and the composites.

Example 1

[0115]

TABLE-US-00001 TABLE 1 Curing agent CA (60% in uretdione-containing 40% by wt. MMA) (effective NCO: 7.7%) curing agent component a) 3-Hydroxypropyl OH-functional monomer 11% by wt. methacrylate (HPMA) of the resin component Methyl methacrylate monomer of the 47% by wt. (MMA) resin component Dibenzoyl peroxide initiator  1% by wt. N,N-bis(2-Hydroxyethyl)- accelerator  1% by wt. p-toluidine

[0116] To produce the component, 10 plies of glass fibre fabric were stacked one on top of another in a metal mould of size 25×25 cm, which was purged with nitrogen.

[0117] The feedstocks from the table were mixed in a premixer and then dissolved. This mixture can be used within about 15 min at RT before it gelates.

[0118] The matrix was subsequently applied to the fibres. During the closure operation, the matrix is distributed within the mould and wets the reinforcing fibres. After 20 min, the reaction at RT is complete and it was possible to remove the preform (synonymous here with semi-finished product) from the mould. The preform of Example 1, after the reaction, showed a weight loss based on matrix of about 2% by weight.

[0119] The preform was subsequently compressed in a further mould at 180° C. and 50 bar for 1 h, and the matrix material was crosslinked completely in the process. The hard, stiff, chemical-resistant and impact-resistant composite components (sheet material) had a glass transition temperature T.sub.g of 118° C.

Example 2

[0120] Example 2 was conducted analogously to Example 1. The only difference was that a resin component which additionally contained non-(meth)acrylic polyols was used. The composition is shown in Table 2.

[0121] The procedure for Example 2 was according to Example 1. A weight loss of the preform after the reaction of 1% by weight was measured, rather than 2% by weight in Example 1. The hard, stiff, chemical-resistant and impact-resistant composite components (sheet material) had a glass transition temperature T.sub.g of 80° C. and were somewhat more flexible overall than the sheets from Example 1.

TABLE-US-00002 TABLE 2 Curing agent CA (60% in uretdione-containing curing 54% by wt. MMA) (effective NCO: 7.9%) agent component b) 3-Hydroxypropyl OH-functional monomer of  6% by wt. methacrylate (HPMA) the resin component Methyl methacrylate monomer of the 22% by wt. (MMA) resin component Polyol R3215 polyol in resin component 16% by wt. Dibenzoyl peroxide initiator  1% by wt. N,N-bis(2-Hydroxyethyl)- accelerator  1% by wt. p-toluidine