Patent ID: 7507361

Claim:
A pultrusion process for preparing a fiber reinforced composite comprising the steps of: (a) pulling continuous fibers through an impregnation die while contacting the fibers with a reaction mixture comprising an isocyanate reactive composition and a polyisocyanate composition, sufficient to cause substantial polymerization of the reaction mixture within the impregnation die to produce a composite of fibers coated by the reaction mixture, which is not fully cured; (b) directing the composite of fibers coated by the reaction mixture through a heated curing die to further advance the cure of the reaction mixture so as to produce a solid fiber reinforced composite; and (c) withdrawing the solid fiber reinforced composite from the curing die; wherein the reaction mixture initially contains both free alcoholic —OH groups and free isocyanate (—NCO) groups, has a gel time of greater than 768 seconds at 25° C., and a gel time of less than 120 sec at 175° C., wherein the isocyanate reactive composition comprises a mixture of (i) 60 to 100% weight of at least one polyol having a number averaged molecular weight between 250 and 750 and a number averaged functionality of 3 to 4, and (ii) 2 to about 30% by weight of a least one polyol having a number averaged functionality of 2 to 3 and a number averaged molecular weight of less than 200; wherein the weights of (i)+(ii) total 100% of said isocyanate reactive composition.