Water-clear aliphatic polyurethane pultrusion formulations and processes

Abstract

Clear polyurethane fiber reinforced composites are produced by a pultrusion process with a polyurethane-forming system that includes: (a) a clear, aliphatic polyisocyanate having a viscosity at 25° C. of no more than 1000 centipoise, (b) a colorless polyol component comprising an amine-initiated polyol having a molecular weight of from about 150 to about 400 and an OH functionality greater than or equal to 3, and (c) a catalyst. These fiber-reinforced composites are characterized by both excellent weathering characteristics and excellent physical properties.

What is claimed is: 
     
         1 . A clear polyurethane-forming system for the preparation of a fiber reinforced composite by a pultrusion process comprising:
 (a) a clear, aliphatic polyisocyanate having a viscosity at 25° C. of no more than 1000 centipoise, and   (b) a colorless polyol component comprising an amine-initiated polyol having a molecular weight of from about 150 to about 400 and an OH functionality greater than or equal to 3, and   (c) a catalyst.   
     
     
         2 . The system of  claim 1  in which (a) is HMDI. 
     
     
         3 . The system of  claim 1  in which the amine-initiated polyol has an OH functionality of at least 4. 
     
     
         4 . The system of  claim 1  in which (a) is IPDI. 
     
     
         5 . The system of  claim 1  in which (b) further comprises a colorless, short-chained polyether polyol that is not amine-initiated having an OH functionality of at least 3. 
     
     
         6 . A reaction system for the preparation of a fiber reinforced composite by a pultrusion process comprising:
 (a) a clear, aliphatic polyisocyanate having a viscosity at 25° C. of no more than 1000 centipoise,   (b) a colorless polyol component comprising an amine-initiated polyol having a molecular weight of from about 150 to about 400 and an OH functionality greater than or equal to 3,   (c) a catalyst, and   (d) a fiber reinforcing material.   
     
     
         7 . The reaction system of  claim 6  in which (d) is selected from the group consisting of single strands, braided strands, woven mat structures, non-woven mat structures and combinations thereof. 
     
     
         8 . The reaction system of  claim 6  in which (d) comprises one or more of glass fibers, glass mats, carbon fibers, polyester fibers, natural fibers, aramid fibers, basalt fibers and nylon fibers. 
     
     
         9 . The reaction system of  claim 6  in which (d) comprises glass fibers. 
     
     
         10 . The reaction system of  claim 6  in which (a) is selected from the group consisting of ethylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,12-dodecane diisocyanate, cyclobutane-1,3-diisocyanate, cyclohexane-1,3- and -1,4-diisocyanate, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane (“isophorone diisocyanate”), 2,4- and 2,6-hexahydrotoluene diisocyanate, dicyclohexylmethane-4,4′-diisocyanate (“hydrogenated MDI”, or “HMDI”), isocyanate-terminated prepolymers and mixtures thereof. 
     
     
         11 . The reaction system of  claim 6  in which (a) is HMDI. 
     
     
         12 . The reaction system of  claim 6  in which the amine-initiated polyol has an OH functionality of at least 4. 
     
     
         13 . The reaction system of  claim 6  in which (a) is IPDI. 
     
     
         14 . The reaction system of  claim 6  in which (b) further comprises a colorless, short-chained polyether polyol that is not amine-initiated having an OH functionality of at least 3. 
     
     
         15 . A pultrusion process for preparing a fiber reinforced polyurethane composite comprising:
 (a) continuously pulling a roving or tow of continuous fiber reinforcing material successively through an impregnation chamber and a die;   (b) continuously feeding the polyurethane-forming system of  claim 1  to the impregnation chamber;   (c) contacting the fiber reinforcing material with the polyurethane-forming system in the impregnation chamber such that substantially complete wetting of the material by the formulation occurs;   (d) directing the fiber reinforcing material through a die heated to reaction temperature to form a solid composite; and   (e) drawing the composite from the die,   
       wherein conditions in the impregnation chamber are such that substantially no polymerization takes place. 
     
     
         16 . The pultrusion process of  claim 15  in which the fiber reinforcing material is selected from the group consisting of single strands, braided strands, woven mat structures, non-woven mat structures and combinations thereof. 
     
     
         17 . The pultrusion process of  claim 15  in which the fiber reinforcing material comprises one or more of glass fibers, glass mats, carbon fibers, polyester fibers, natural fibers, aramid fibers, basalt fibers and nylon fibers. 
     
     
         18 . The pultrusion process of  claim 15  in which the fiber reinforcing material comprises glass fibers. 
     
     
         19 . The pultrusion process of  claim 15  in which (a) is chosen from 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane (“isophorone diisocyanate”) and dicyclohexylmethane-4,4′-diisocyanate (“hydrogenated MEN”, or “HMDI”). 
     
     
         20 . A fiber reinforced polyurethane composite made by the process of  claim 15 .