Compositions containing impact copolymers made from a blend...

Details Compositions containing impact copolymers made from a blend... Compositions containing impact copolymers made from a blend...

1997-10-24

2001-03-06

Wilson, Donald R. (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

C525S240000, C525S323000

Reexamination Certificate

active

06197886

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to polypropylene impact copolymer compositions having improved film properties, including balance of tensile and tear properties.
BACKGROUND OF THE INVENTION
Impact polypropylene has seen wide use over the years with many applications. For example, EP Patent No. 557853 discloses compositions that comprise 25-95 parts crystalline random propylene-ethylene copolymer having a propylene content greater than 85% and haze less than 25%, and 5-75 parts of an elastomeric copolymer of ethylene with propylene.
However, the known impact copolymers do have physical property limitations. For example. with cast films made from known impact copolymers, the films are relatively hard, noisy, and tear readily. Thus, impact copolymers which rectify these physical shortcomings are desirable.
SUMMARY OF THE INVENTION
The present invention teaches propylene-ethylene impact copolymers of about 5 to about 50 g/10 min melt flow index that have a propylene homopolymer phase combined with a copolymer rubber phase in which the ethylene content of the rubber (E
c
) is between about 78 to about 95% w. The rubber content of the copolymer (F
c
) being ranges between about 25% w to about 60% w. The higher rubber crystallinity provides improvement in and balance of film tensile properties in the machine and transverse directions.


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