Thermoplastic olefin compositions of EPDM rubber and ethylene copolymer resin

Abstract

Heat shrinkable thermoplastic compositions are prepared by blending an ethylene copolymer resin with an EPDM rubber and dynamically vulcanizing the rubber. The ethylene copolymer resin is a copolymer of ethylene with an alkyl ester of an alpha, beta monoethylenically unsaturanated monocarboxylic acid as well as copolymers of ethylene with the acid per se. The preferred copolymer is ethylene-vinylacetate copolymer. Uncured rubber can be included in the composition.

What is claimed is: 
     
       1. A thermoplastic olefin composition comprising an EPDM rubber fully cured by dynamic vulcanization .Iadd.with a phenolic resin cure system .Iaddend.in a thermoplastic resin consisting of (A) from 25 to 100 wt% of an ethylene copolymer resin selected from the group consisting of copolymers of ethylene with vinylacetate, copolymers of ethylene with alpha, beta monoethylenically unsaturated monocarboxylic acids and copolymers of ethylene with alkyl esters of said acids and (B) from 0 to 75 wt% of at least one additional polyolefin resin selected from the group consisting of polybutylene, low density polyethylene, very low density polyethylene, and linear low density polyethylene. 
     
     
       2. The composition of claim 1 wherein the ethylene copolymer resin comprises from about 20 to about 90 wt.% of the resin/rubber component of the composition. 
     
     
       3. The composition of claim 1 wherein the vulcanized EPDM rubber comprises about 10 to about 80 wt.% of the resin/rubber component of the composition. 
     
     
       4. The composition according to claim 1 wherein the vulcanized EPDM rubber comprises from about 20 to about 75 wt.% of the resin/rubber component of the composition. 
     
     
       5. The composition according to claim 4 wherein the vulcanized EPDM rubber comprises from about 40 to about 60 wt.% of the resin/rubber component. 
     
     
       6. The composition according to claim 1 wherein an inorganic filler is incorporated therein. 
     
     
       7. The composition according to claim 6 wherein the inorganic filler is calcium carbonate or clay. 
     
     
       8. The composition according to claim 1 wherein the ethylene copolymer resin is an ethylene-vinylacetate copolymer resin. 
     
     
       9. The composition according to claim 8 wherein the vinylacetate content of the copolymer is from about 2 to about 30 wt.%. 
     
     
       10. The composition according to claim 8 wherein the vinylacetate content of the copolymer is from about 9 to about 29 wt.%. 
     
     
       11. The composition according to claim 1 wherein the ethylene copolymer resin is an ethylene-methylacrylate copolymer resin. 
     
     
       12. The composition according to claim 1 having incorporated therein from 0 to about 50 wt.%, based on total rubber, of an uncured rubber. 
     
     
       13. The composition according to claim 12 wherein the uncured rubber comprises from about 5 to about 20 wt.% of the total rubber in the composition. 
     
     
       14. The composition according to claim 12 wherein the uncured rubber is selected from EP copolymer rubber and polyisobutylene rubber. 
     
     
       15. The composition according to claim 12 wherein the uncured rubber is styrene ethylene-butene block copolymer. 
     
     
       16. A process for preparing a DVA composition comprising the steps of (a) blending a thermoplastic resin consisting of (A) from 25 to 100 wt% of an ethylene copolymer resin selected from the group consisting of copolymers of ethylene with vinylacetate, copolymers of ethylene with alpha, beta monoethylenically unsaturated monocarboxylic acids and copolymers of ethylene with alkyl esters of said acids and (B) from 0 to 75 wt% of at least one additional polyolefin resin selected from the group consisting of polybutylene, low density polyethylene, very low density polyethylene, and linear low density polyethylene and an EPDM rubber at a temperature above the melting point of the resin;   (b) adding a .[.non-peroxide.]. .Iadd.phenolic resin .Iaddend.cure system for the rubber to the resin/rubber blend; and   (c) vulcanizing the rubber under dynamic vulcanization conditions for a time sufficient to fully vulcanize the rubber.   
     
     
       17. The process according to claim 16 wherein an additional rubber not vulcanizable by the .[.vulcanizing agent.]. .Iadd.phenolic resin cure system .Iaddend.is incorporated. 
     
     
       18. The process according to claim 17 wherein the additional rubber is introduced during the blending of the resin and rubber and prior to dynamic vulcanization. 
     
     
       19. The process according to claim 17 wherein the additional rubber is added after the rubber to be vulcanized is fully vulcanized, blending being continued until the additional rubber is uniformly dispersed in the resin/vulcanized rubber blend. 
     
     
       20. The process according to claim 16 wherein an additional rubber is added to the composition after the rubber to be vulcanized is fully vulcanized; said additional rubber being vulcanizable by the .[.vulcanization agent.]. .Iadd.phenolic resin cure system.Iaddend.; provided, however, that the .[.vulcanizing agent.]. .Iadd.phenolic resin cure system .Iaddend.is fully consumed during the dynamic vulcanization step and is unavailable to vulcanize any part of the additional rubber. 
     
     
       21. The process according to claim 16 wherein an additional rubber which is vulcanizable by the .[.vulcanizing agent.]. .Iadd.phenolic resin cure system .Iaddend.is added to the rubber/resin blend after the rubber to be vulcanized is fully vulcanized; said .[.vulcanizing agent.]. .Iadd.phenolic resin cure system .Iaddend.being present in an amount sufficient to at least partially cure the additional rubber, but insufficient to fully vulcanize the additional rubber. 
     
     
       22. The process according to claim 17 wherein the additional rubber is selected from EP copolymer rubber and polyisobutylene rubber. 
     
     
       23. The process according to claim 20 wherein the additional rubber is a styrene ethylene-butene block copolymer.