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A specific class of thermoplastic polymers with improved processability resulting from initial partial degradation of high molecular weight polymers using a chemical prodegradant present in excess of the amount reacted during pelletization. This class of polymers includes polymers and copolymers of

A specific class of thermoplastic polymers with improved processability resulting from initial partial degradation of high molecular weight polymers using a chemical prodegradant present in excess of the amount reacted during pelletization. This class of polymers includes polymers and copolymers of polypropylene and butylene. After pelletizing, the polymer including unreacted prodegradant can be safely handled and shipped without difficulty. When remelted by extruding or the like, the prodegradant in the pellets reacts, further reducing the molecular weight as well as narrowing the molecular weight distribution of the polymer to a point where high capacity production of quality fibers and extruded products can be obtained. The prodegradant is preferably of the type that predictably and controllably affects the polymer molecular properties without being significantly affected by minor fluctuations in the polymer producer's or processor's manufacturing steps. Specific preferred embodiments include 2,5-dimethyl - 2,5 bis-(t-butylperoxy) hexyne-3; 3,6,6,9,9-pentamethyl-3-(ethyl acetate)-1,2,4,5-textraoxy cyclononane; α,α'-bis (t-butylperoxy) diispropyl benzene and 2, 5-dimethyl-2, 5-di (t-butylperoxy) hexane as the prodegradant added in an amount providing an amount of unreacted prodegradant after pelletizing of about 0.01 to 10.0 percent based on the weight of polymer. The present invention reduces the safety hazards present when handling free radical prodegradants by the polymer processor and avoids the need for multiple addition of prodegradants while still producing a material that can be processed easily by the polymer producer and processor.

대표청구항 ▼

1. Method of producing polymer pellets having improved extrusion characteristics comprising the steps of: (a) providing a high weight average molecular weight polymer selected from the group consisting of polymers and copolymers of propylene and butylene, (b) adding to said polymer a free radica

1. Method of producing polymer pellets having improved extrusion characteristics comprising the steps of: (a) providing a high weight average molecular weight polymer selected from the group consisting of polymers and copolymers of propylene and butylene, (b) adding to said polymer a free radical generating prodegradant having a half-life in said polymer of at least about one-half minute at pelletizing extrusion temperatures, and (c) pelletizing said polymer under conditions wherein greater than about 50% of that added and at least about 0.01% by weight of said prodegradant remains available for further degradation after pelletizing. 2. Method of claim 1 including the additional step of rapidly cooling said pellets to stop the reaction of said prodegradant. 3. Method of claim 1 wherein said prodegradant is selected from the group consisting of 2, 5-dimethyl-2,5 bis(t-butylperoxy) hexyne -3; 3, 6, 6, 9, 9 -pentamethyl-3-(ethyl acetate) - 1, 2, 4, 5 -tetraoxy cyclononane; 4 methyl 4 t-butylperoxy -2 pentanone; α,α'-bis (t-butylperoxy) diispropyl benzene; and 2,5-dimethyl -2, 5-di (t-butylperoxy) hexane. 4. Method of claim 1 wherein said polymer is polypropylene. 5. Method of claim 3 wherein said polymer is polypropylene. 6. Method of claim 4 wherein said polymer has a weight average molecular weight in the range of from about 250,000 to 1,000,000. 7. Method of claim 4 wherein said prodegradant is added in an amount in the range of from about 0.01 to 10% based on the polymer weight and said prodegradant remaining available is at least 75% of that added. 8. Method of claim 4 including the additional step of reextrusion wherein the polymer produced has a weight average molecular weight in the range of from about 40,000 to 130,000 with a molecular weight distribution in the range of from about 2.5 to 4.5 upon reextrusion. 9. Method of claim 7 wherein said prodegradant remaining is at least 90%. 10. Pellets of a polymer selected from the group consisting of polymers and copolymers of propylene and butylene having dispersed therein a free radical source prodegradant having a half-life in said polymer of at least about one-half minute at pelletizing extrusion temperatures in an amount of at least 0.01% unreacted. 11. Pellets of claim 10 wherein said prodegradant is selected from the group consisting of 2, 5-dimethyl -2, 5 bis(t-butylperoxy) hexyne -3; 3, 6, 6, 9, 9 - pentamethyl - 3 -(ethyl acetate) -1, 2, 4, 5 - tetraoxy cyclononane; 4 methyl 4 t-butylperoxy -2 pentanone; α,α' -bis (t-butylperoxy) diispropyl benzene; and 2, 5-dimethyl -2, 5-di (t-butylperoxy) hexane. 12. Pellets of claim 11 wherein said polymer is polypropylene. 13. Pellets of claim 10 wherein said prodegradant is present in an amount in the range of from about 0.4 to 10% by weight forming a concentrate for addition to non-prodegradant containing polymer pellets. 14. Pellets of claim 13 wherein said polymer is polypropylene. 15. Pellets of claim 13 wherein said polymer is polybutylene. 16. The pellets of claim 13 wherein said polymer is a copolymer of propylene. 17. Pellets of claim 13 wherein said polymer is a copolymer of butylene. 18. Method of claim 1 wherein said polymer is a copolymer of propylene. 19. Method of claim 1 wherein said polymer is a copolymer of butylene.