Polyurea-urethane cord treatment for power transmission belt and belt
View Patent ↗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 or water. 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 twisted tensile cord embedded in the elastomeric body;
with the tensile cord impregnated with a crosslinked polyurea-urethane composition different from said elastomeric body comprising the polyurea reaction product of:
a polyurethane prepolymer; and
a curative selected from the group consisting of diamines and water.
2. 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; and wherein said curative is water.
3. The belt of claim 2 wherein said diisocyanate is selected from the group consisting of para-phenylene diisocyanate, toluene diisocyanate, and 4,4′-methylene diphenyl diisocyanate.
4. The belt of claim 3 wherein said one or more polyols is selected from the group consisting of polycarbonate polyols and polycaprolactone polyols.
5. The belt of claim 4 wherein said one or more polyols comprises a mixture of a diol and a triol.
6. The belt of claim 5 wherein said tensile cord comprises a filament yarn with interstices between fibers and said composition impregnates at least a portion of said interstices and coats said fibers.
7. The belt of claim 6 wherein said impregnated portion is from about 20% to about 100% of the volume of the interstices.
8. The belt of claim 5 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.
9. The belt of claim 1 wherein said prepolymer comprises the reaction product of para-phenylene diisocyanate and one or more polycaprolactone polyols; and wherein said curative comprises water.
10. The belt of claim 1 wherein said composition consists essentially of the polyurea reaction product of:
the polyurethane prepolymer; and
water.
11. The belt of claim 1 wherein said elastomeric body comprises cast polyurethane elastomer, and said elastomer is in intimate contact with said composition.
12. The belt of claim 11 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.
13. The belt of claim 1 wherein said elastomeric body comprises vulcanized rubber.
14. The belt of claim 13 wherein said tensile cord comprises an overcoat adhesive layer disposed between said polyurea-urethane composition and said vulcanized rubber.
15. 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.
16. The belt of claim 15 wherein said elastomer is a thermoplastic polyurethane.
17. The belt of claim 16 wherein said belt has a first end and a second end.
18. The belt of claim 1 wherein said belt is an endless, power transmission belt.
19. The belt of claim 18 wherein said belt is a toothed belt.
20. A twisted tensile cord wound on a spool for subsequent use in reinforcing an elastomeric article; with at least a portion of said cord impregnated with a crosslinked polyurea-urethane composition comprising the reaction product of:
a polyurethane prepolymer comprising the reaction product of a polyisocyanate and at least one polyol selected from polyester polyols, polycarbonate polyols, and polyether polyols; and
a chain extender selected from diamines and water.
21. The tensile cord of claim 20 wherein said polyol is selected from the group consisting of polycarbonate polyols and polycaprolactone polyols and includes a mixture of a diol and a triol; said polyisocyanate is selected from the group consisting of para-phenylene diisocyanate, 2,6-toluene diisocyanate, and 4,4′-diphenyl methane diisocyanate; and said chain extender is water.
22. The tensile cord of claim 21 wherein said tensile cord comprises a filament 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.
23. A method comprising:
mixing a dip comprising a polyurethane prepolymer in an inert non-aqueous solvent;
dipping a filament yarn in said dip;
drying said dipped filament yarn to remove said solvent; and
curing to some degree said prepolymer in the presence of water;
whereby is provided a tensile cord at least partially impregnated with a crosslinked polyurea-urethane composition; and
embedding said tensile cord in an elastomeric power transmission belt body.
24. The method of claim 23 wherein said elastomeric power transmission belt body is of a second polyurea-urethane composition of a different composition than said crosslinked polyurea-urethane composition.
25. The method of claim 23 further comprising:
wherein said filament yarn is of carbon fiber in twisted form, and
whereby said tensile cord is a twisted tensile cord.
26. The method of claim 23 further comprising:
twisting said dipped filament yarn; and
whereby said tensile cord is a twisted tensile cord.
27. The tensile cord of claim 20 wherein the curative is diamine, and the polyurethane prepolymer has isocyanate end groups that are blocked.
28. The belt of claim 1 wherein the curative is diamine, and the polyurethane prepolymer has isocyanate end groups that are blocked with a blocking agent.
29. A method comprising:
mixing in an inert non-aqueous solvent a dip comprising: a polyurethane prepolymer with blocked isocyanate end groups, and a polyamine curative;
dipping a filament yarn in said dip;
drying said dipped filament yarn to remove said solvent; and
curing to some degree said prepolymer;
whereby is provided a tensile cord at least partially impregnated with a crosslinked polyurea-urethane composition; and
embedding said tensile cord in an elastomeric power transmission belt body.
30. The method of claim 29 wherein said filament yarn comprises carbon fiber.
31. The method of claim 30 wherein said elastomeric belt body comprises a polyurethane elastomer different in composition from said crosslinked polyurea-urethane composition.