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1. (WO2019005237) EPOXY-FIBER REINFORCED COMPOSITES, METHOD TO FORM THE COMPOSITES AND EPOXY RESIN COMPOSITION USED THEREFOR
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CLAIMS:

1. An epoxy resin composition comprising

An epoxy resin comprised of at least one solid epoxy resin; a liquid polyurethane toughener that is dissolved in the epoxy resin and, upon curing of the epoxy resin, the liquid polyurethane toughener phase separates into particles having a particle size of 50 nm to 2 micrometers;

an epoxy hardener; and

an epoxy soluble latent catalyst.

2. The epoxy resin composition of claim 1 , wherein the epoxy hardener is dicyandiamide particles having a particle distribution in which 98 percent of the dicyandiamide particles have a diameter less than 10 microns, and at least 35% of the dicyandiamide particles have a particle size of less than 2 microns.

3. The epoxy resin composition of claim 1, wherein the epoxy resin is further comprised of a liquid epoxy resin and the solid epoxy resin is comprised of an epoxy resin containing oxazolidone.

4. The epoxy resin composition of Claim 3, wherein the solid epoxy resin comprises from 19 to 54 weight percent, the amount of liquid epoxy resin is from 11 to 61 weight percent based on the total weight of all epoxy resin components in the epoxy resin composition.

5. The epoxy resin composition of either Claim 3 or 4, wherein the liquid epoxy resin is comprised of at least one of a diglycidyl ether of bisphenol A and an epoxy novolac resin.

6. The epoxy resin composition of claim 1 , wherein the liquid polyurethane toughener phase separates into particles having a particle size of 50 nm to 1.5 micrometers.

7. The epoxy resin composition of claim 1, wherein the liquid polyurethane toughener is present in an amount of 1% to 10% by weight of the epoxy resin composition.

8. The epoxy resin composition of claim 1, wherein the epoxy resin

composition as an uncured glass transition temperature (Tg,o) from 5 to 15 °C, and a cured glass transition temperature (Tg,c) from 150 to 160 °C.

9. The epoxy resin composition of claim 1 further comprising a solid rubber toughener having a particle size between 25 nm to 500 nm.

10. The epoxy resin of composition of claim 9, wherein the solid rubber toughener has a particle size distribution that is bimodal or multimodal.

11. The epoxy resin composition of claim 1 , wherein the amount of the latent catalyst in the epoxy resin composition is present at a level of 1 to 7 parts per hundred parts epoxy resin, and the latent hardener is present in an amount relative to the total amount of epoxy components in the epoxy resin composition corresponding to an epoxy/hardener equivalent ratio from 0.5 to 3.

12. The epoxy resin composition of claim 1, wherein the viscosity of the epoxy resin composition is less than 100 Pa*s at 100°C.

13. The epoxy resin composition of claim 12, wherein the viscosity of the epoxy resin composition has a viscosity less than a corresponding epoxy resin composition failing to contain the liquid polyurethane toughener.

14. A prepreg comprising the epoxy resin composition of any one of the preceding claims impregnated into a fibrous material wherein the fibrous material comprises greater than 50% of the prepreg by volume.

15. The prepreg of claim 14, wherein the fibrous material comprises carbon fibers.

16. The prepreg of claim 15, wherein the fibrous material comprises a plurality of stacked layers of non-crimped fabrics.

17. The prepreg of claim 16, wherein the prepreg has been partially cured so that the glass transition temperature of the prepreg (Tg,p) is from 12 to 25°C.

18. The prepreg of claim 14, wherein the prepreg has a total void volume that is less than 1% by volume.

19. An epoxy fiber reinforced composite comprising a cured epoxy resin matrix having therein reinforcing fibers, wherein the fibers comprise greater than 50% by volume of said composite and the epoxy resin matrix has a phase that is comprised of liquid polyurethane toughener that has been reacted with the epoxy resin matrix and said liquid polyurethane toughener has phase separated into particles ranging in size between 50 nm and 2 micrometers dispersed within the cured epoxy matrix.

20. The epoxy fiber reinforced composite of claim 19, wherein the cured epoxy resin also has therein a solid rubber toughener having a particle size between 50 nm and 500 nm.

21. The epoxy fiber reinforced composite of claim 20, wherein the solid rubber toughener has a bimodal or multimodal size distribution.

22. The epoxy fiber reinforced composite of claim 19, wherein the solid rubber toughener is a core shell rubber toughener.

23. The epoxy fiber reinforced composite of claim 20, wherein the solid rubber is present in an amount of 1.0% to 7.5% by weight of the cured epoxy resin matrix and the liquid polyurethane rubber is present in an amount of 1% to 7.5% by weight of the cured epoxy resin matrix.

24. The epoxy fiber reinforced composite of claim 19, wherein the reinforcing fibers comprise carbon fibers.

25. The epoxy fiber reinforced composite of claim 24, wherein the reinforcing fibers are a plurality of stacked layers of non-crimped fabrics.

26. The epoxy fiber reinforced composite of claim 25, wherein the liquid polyurethane toughener particles are uniformly dispersed throughout the epoxy resin matrix including between the fibers in the stacked layers and between the stacked layers.

27. The epoxy fiber reinforced composite of any one of claims 19 to 26, wherein said composite has a total void volume of at most about 1%