High performance polyurethane prepolymer and curing compositions
View Patent ↗Compositions comprising isocyanate capped polyurethane prepolymers and select mono-benzyl phthalate plasticizers, e.g., 7-(2,6,6,8-tetramethyl-4-oxa-3-oxo-nonyl) benzylphthalate, exhibit better isocyanate stability than prepolymer compositions comprising other plasticizers common in polyurethane systems. Curing compositions comprising these prepolymers, the select mono-benzyl phthalate plasticizers, and methylenedianiline coordination complex curing agents exhibit improved processing characteristics and yield elastomeric polyurethanes with lower compression set, higher break strength and lower color than similar composition comprising plasticizers such as benzoate plasticizers.
1. A composition comprising:
(a) an isocyanate capped prepolymer prepared from a diisocyanate monomer and a polyol; and
(b) from about 1 to about 50 wt % of a mono-benzyl phthalate plasticizer of formula (I), based on the combined weight of the prepolymer and mono-benzyl phthalate,
wherein n is a number from 0 to 4, each R is independently selected from C 1-4 alkyl, and R 1 is a C 2-24 alkyl group substituted by a C 2-12 , alkylcarbonyloxy group.
2. The composition according to claim 1 wherein R 1 in formula I is a group of formula (IIa):
wherein * marks the point of attachment of R 1 to the phthalate oxygen of formula (I), each R 2 is independently selected from the group consisting of H and C 1-6 alkyl, R 3 is C 1-11 alkyl, and m is a number of from 1 to 6.
3. The composition according to claim 1 wherein the mono-benzyl phthalate plasticizer is a compound of formula (IV):
wherein each R 2 is independently selected from the group consisting of H and C 1-6 alkyl and R 3 is C 1-11 alkyl.
4. The composition according to claim 3 wherein in formula (IV) R 3 is C 1-5 alkyl.
5. The composition according to claim 4 wherein each R 2 is methyl, and R 3 is C 1-4 alkyl.
6. The composition according to claim 1 wherein the isocyanate capped prepolymer comprises less than 5 wt % free isocyanate monomer.
7. The composition according to claim 1 wherein the isocyanate capped prepolymer is prepared from diphenylmethane diisocyanate and a polyol.
8. The composition according to claim 7 further comprising a curing agent.
9. The composition according to claim 8 wherein the curing agent is a metal salt coordination complex of methylene dianiline.
10. The composition according to claim 1 further comprising a curing agent.
11. The composition according to claim 10 wherein the curing agent is a metal salt coordination complex of methylene dianiline.
12. An elastomeric polyurethane obtained by curing the composition of claim 8 .
13. An elastomeric polyurethane obtained by curing the composition of claim 9 .
14. The elastomeric polyurethane according to claim 13 having a Shore hardness of from 50A to 85 A.
15. An elastomeric polyurethane obtained by curing the composition of claim 10 .
16. An elastomeric polyurethane obtained by curing the composition of claim 11 .
17. The elastomeric polyurethane according to claim 16 having a Shore hardness of from 50A to 85 A.
18. A method of preparing a polyurethane elastomer, the method comprising the steps of preparing a composition according to claim 9 and heating the composition to deblock the methylenedianiline/metal salt coordination complex and cure the composition to form the polyurethane elastomer.
19. The method according to claim 18 wherein the elastomeric polyurethane has a Shore hardiness of from 50A to 85A.
20. A method of preparing a polyurethane elastomer, the method comprising the steps of preparing a composition according to claim 11 and heating the composition to deblock the methylenedianiline/metal salt coordination complex and cure the composition to form the polyurethane elastomer.