Thermoplastic olefin compositions, processes and articles

Abstract

A thermoplastic olefin (TPO) composition comprises (1) a major amount by weight of (a) a substantially linear homopolymer or copolymer of a C 2 -C 10 ∀-olefin in major proportion to (b) a long chain branched a linear homopolymer or copolymer of a C 2 -C 10 ∀-olefin, (2) a minor amount by weight of a cross linkable elastomer, and (3) at least one thermally decomposing free radical generating agent present in an amount sufficient to promote an increase in melt strength of the composition over that of the melt strength of the linear homopolymer or copolymer of a C 2 -C 10 ∀-olefin alone and insufficient to substantially degrade the ∀-olefinic polymers. The TPO composition is prepared by melt blending the components at a temperature sufficient to melt said homopolymers or copolymers of a C 2 -C 10 ∀-olefin and thermally decompose said agent. Articles are thermoformed from the thermoplastic olefin.

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       33 . A process of manufacturing a thermoplastic olefin, comprising: 
 a) providing a composition comprising 
 i) from more than 50% up to about 90% by weight of polyolefins consisting of: 
 A) a substantially linear homopolymer of propylene and  
 B) a long chain branched linear homopolymer propylene,  
 
 ii) from about 10% to less than 50% by weight of a cross linkable ethylene α-olefin polymer elastomer, and  
 iii) a thermally decomposing free radical generating agent comprising at least an azo compound of the general formula R 1 —N═N—R 2  in which R 1  and R 2  can be the same or different alkane groups, present in an amount not exceeding about 1.0 phr of elastomer, and  
   b) melt blending said composition at a temperature sufficient to melt said polyolefins and elastomer and thermally decompose said free radical generating agent.    
   
   
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       35 . The process of  claim 33  in which in which said agent is an azoalkane.  
   
   
       36 . The process of  claim 35  in which said azoalkane is selected from azosilanes, azonitriles, and α-carbonyl azo compounds.  
   
   
       37 . The process of  claim 33  in which said agent comprises a combination of an azo compound and an organic peroxide in which the amount of organic peroxide does not substantially exceed the amount of azo compound.  
   
   
       38 . The process of  claim 37  in which said organic peroxide is included in said composition in an amount not in excess of about 0.3 phr of said elastomer.  
   
   
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       43 . The process of  claim 33  in which said elastomer comprises interpolymers and diene modified interpolymers, in either of which at least one monomer is ethylene.  
   
   
       44 . The process of  claim 33  in which said elastomer is selected from polymers prepared by polymerizing ethylene with at least one C 3 -C 20  comonomer.  
   
   
       45 . The process of  claim 33  in which said elastomer is selected from ethylene/propylene copolymers, ethylene/butylenes copolymers, ethylene/hexene-1 copolymers and ethylene/octene copolymers, ethylene/propylene/octene terpolymers, and terpolymers of ethylene, a C 3 -C 20  α-olefin and a diene.  
   
   
       46 . The process of  claim 45  in which said diene is dicyclopentadiene, 1,4-hexadiene, piperylene or 5-ethylidene-2-norbornene.  
   
   
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       49 . The process of  claim 33  in which said substantially linear polypropylene is included in an amount from about 20 to about 85 weight percent, said long chain branched polypropylene is included in an amount from about 5 to about 20 weight percent and said elastomer is included in an amount from about 10 to less than a majority weight percent of the process.  
   
   
       50 . The process of  claim 49  in which said azo compound is present in an amount not exceeding about 1.0 phr of elastomer.  
   
   
       51 . A process for forming an article from a thermoplastic olefin, comprising thermoforming a sheet extruded from a melt blended composition comprising