Anisotropic composite materials based on polyisocyanates
The present invention relates to novel anisotropic composite materials and processes for production thereof. The composite materials are based on the crosslinking of polyisocyanates and feature good weathering stability.
1. Process for producing a composite polyisocyanurate material, comprising the steps of
a) providing a reactive resin mixture comprising all compounds that react with each other during the process, the reactive resin mixture comprising:
at least one reactive polyisocyanate composition A consisting of at least 50% by weight of one or more aliphatic isocyanates, and at least one crosslinking catalyst B,
wherein the at least one crosslinking catalyst B comprises a trimerization catalyst;
b) providing a fibrous filler C, the fibres of which have an aspect ratio of at least 1000,
c) wetting the fibrous filler C with the reactive resin mixture from process step a), wherein the molar ratio of free isocyanate groups to the sum of hydroxyl, amino and thiol groups in the reactive resin mixture is at least 5.0:1.0,
d) curing the resin-impregnated fibrous filler, to give a profile by means of one or more chemical reactions, the curing comprising at least 50% of the free isocyanate groups in the polyisocyanate composition A being crosslinked on the resin-impregnated fibrous filler to form isocyanurate structures and optionally at least one structure selected from the group consisting of uretdione, allophanate, biuret, iminooxadiazinedione, oxadiazinetrione, and combinations thereof, the curing continued until at most 10% of the free isocyanate groups from the reactive resin mixture remain.
2. The process according to claim 1 , wherein the polyisocyanate composition A consists of at least 90% by weight of one or more aliphatic isocyanates.
3. The process according to claim 2 , wherein the at least one aliphatic isocyanate is selected from the group consisting of 1,4-diisocyanatobutane, 1,5-diisocyanatopentane, 1,6-diisocyanatohexane, isophorone diisocyanate and 4,4′-diisocyanatodicyclohexylmethane.
4. The process according to claim 1 , wherein the polyisocyanate composition A consists of at least 55% by weight of oligomeric polyisocyanates.
5. The process according to claim 1 , wherein the polyisocyanate composition A has a mean isocyanate functionality of >1.0 to 6.0.
6. The process according to claim 1 , wherein the fibrous filler is selected from the group consisting of glass fibres, basalt fibres, boron fibres, ceramic fibres, whiskers, silica fibres, metallic reinforcing fibres and mixtures thereof.
7. The process according to claim 1 , wherein the molar ratio of free isocyanate groups to the sum of hydroxyl, amino and thiol groups in the reactive resin mixture is at least 10:1.0.
8. The process according to claim 1 , wherein the crosslinking catalyst B is characterized in that the polyisocyanate composition A, after it has been added, has a pot life of at least 5 minutes at 23° C.
9. The process according to claim 1 , wherein the trimerization catalyst comprises an alkali metal compound, an alkaline metal compound, a quaternary ammonium salt, or phosphonium salt.
10. The process according to claim 1 , wherein the trimerization catalyst comprises a polyether, wherein the polyether comprises a polyethylene glycol.
11. The process according to claim 1 , wherein the process is conducted at a temperature of above 180° C. within less than 10 minutes at least up to a conversion level at which only at most 20% of the isocyanate groups originally present in the polyisocyanate composition A are still present.
12. The process according to claim 1 , wherein the trimerization catalyst comprises an alkali metal compound, an alkaline metal compound, a quaternary ammonium salt, or phosphonium salt dissolved in or at least suspended in a polyether.
13. The process according to claim 1 , wherein in method step d) at least 50% of the free isocyanate groups in the polyisocyanate composition A are crosslinked on the resin-impregnated fibrous filler to give isocyanurate groups.
14. The process according to claim 1 , wherein in method step d) at least 60% of the free isocyanate groups in the polyisocyanate composition A are crosslinked on the resin-impregnated fibrous filler to give isocyanurate structures and at least one structure selected from the group consisting of uretdione, allophanate, biuret, iminooxadiazinedione, oxadiazinetrione, and combinations thereof.