Polyurea-urethane cord treatment for power transmission belt and belt
A belt with a tensile cord embedded in an elastomeric body, having a polyurea-urethane adhesive composition impregnating the cord and coating the fibers. The composition is reaction product of a polyurethane prepolymer and a diamine curative. The prepolymer is a reaction product of a compact, symmetric diisocyanate and a polyester, polyether, or polycarbonate polyol. The belt body may be of cast polyurethane, vulcanized rubber, or thermoplastic elastomer. The cord may have an adhesive overcoat.
1. A power transmission belt comprising: an elastomeric body, and a tensile cord embedded in the elastomeric body;
with the tensile cord impregnated with a polyurea-urethane composition different from said elastomeric body, said said polyurea-urethane composition consisting of the polyurea reaction product of:
a polyurethane prepolymer; and
a curative selected from the group consisting of diamines and water;
said tensile cord obtained by impregnation with said polyurethane prepolymer and said curative, followed by reaction to form said polyurea reaction product, optionally in the presence of non-reactive ingredients.
2. The belt of claim 1 wherein said polyurea-urethane composition is a crosslinked polyurea-urethane composition.
3. The belt of claim 2 wherein said tensile cord is a twisted tensile cord and said curative is a diamine.
4. The belt of claim 1 wherein said prepolymer comprises the reaction product of a diisocyanate and one or more polyols selected from the group consisting of polyester polyols, polycarbonate polyols and polyether polyols.
5. The belt of claim 4 wherein said diisocyanate is selected from the group consisting of para-phenylene diisocyanate, toluene diisocyanate, and 4,4′-methylene diphenyl diisocyanate.
6. The belt of claim 5 wherein said one or more polyols is selected from the group consisting of polyether polyols.
7. The belt of claim 6 wherein said tensile cord comprises a yarn comprising a plurality of carbon fibers with interstices between said carbon fibers, and wherein said composition impregnates from 20% to 100% of the volume of said interstices and coats said carbon fibers.
8. The belt of claim 1 wherein said prepolymer comprises the reaction product of para-phenylene diisocyanate and a polyether polyol.
9. The belt of claim 8 wherein said curative is 4,4′-methylenebis(3-chloro-2,6-diethylaniline).
10. The belt of claim 9 wherein said elastomeric body comprises cast polyurethane elastomer, and said elastomer is in intimate contact with said polyurea-urethane composition.
11. The belt of claim 10 wherein said tensile cord comprises a yarn comprising a plurality of carbon fibers with interstices between said carbon fibers, and wherein said composition impregnates from 20% to 99% of the volume of said interstices and coats said carbon fibers; and wherein said elastomer impregnates at least a portion of the remainder of said interstices.
12. The belt of claim 1 wherein said elastomeric body comprises vulcanized rubber.
13. The belt of claim 1 wherein said elastomeric body comprises a thermoplastic elastomer and said elastomer is in intimate contact with said polyurea-urethane composition.
14. The belt of claim 13 wherein said elastomer is a thermoplastic polyurethane.
15. The belt of claim 1 wherein the polyurethane prepolymer has isocyanate end groups that are blocked with a blocking agent.
16. The belt of claim 4 wherein said diisocyanate comprises para-phenylene diisocyanate, toluene diisocyanate, or both, and wherein said polyol comprises a polyether polyol.
17. The belt of claim 16 , wherein said polyether polyol comprises polytetramethylene ether glycol.
18. The belt of claim 4 , wherein said diisocyanate comprises isophorone diisocyanate, hexamethylene diisocyanate, or both, and wherein said polyol comprises a polyether polyol.
19. The belt of claim 18 , wherein said polyether polyol comprises polytetramethylene ether glycol.