DETAILED DESCRIPTION I claim: 1.
Composition comprising polypropylene, about 10-60% by weight based on the weight of polypropylene, of talc, and about 0.
5-3.
0% based on the weight of polypropylene of an amorphous copolyester derived from at least 50 mole percent terephthalic acid, and at least 50 mole percent ethylene glycol and about 20-50 mole percent diethylene glycol or 1,4-cyclohexanedimethanol, said copolyester characterized by having a glass transition temperature of about 40.
degree.
-85.
degree.
C.
and an inherent viscosity of about 0.
2-10.
2.
Composition according to claim 1 wherein said polypropylene has a density of about 0.
902 to about 0.
920 and a Flow Rate of about 0.
5 to about 12.
3.
Composition according to claim 1 wherein said copolyester is derived from terephthalic acid, ethylene glycol, 1,4-butanediol, 1,6-hexanediol and diethylene glycol.
4.
Composition according to claim 1 wherein said copolyester is derived from terephthalic acid, ethylene glycol and 1,4-cyclohexanedimethanol.
Description:
DESCRIPTION TECHNICAL FIELD This invention relates to compositions of plastic grade, semi-crystalline, polypropylene containing an inert filler material, and having improved heat stability.
BACKGROUND ART In the past, it has been conventional practice to include in molding and extrusion grade polypropylene various additives which give heat stability to the polymer.
Normally, about 0.
5% by weight of the additives is used.
The additives include antioxidants such as dilaurylthiodipropionate, Irganox 1010 (tetrakis[methylene(3,5-di-tert-butyl-4-hydroxyhydrocinnamate)methane]), and Naugard PHR (tris-[mixed mono- and dinonylphenyl phosphite), sometimes in a mixture.
It has now been found that the quantity of such antioxidants may be reduced by 50% or more, by the incorporation into the polypropylene, of a small amount of a less expensive copolyester.
My copending U.
S.
patent application Ser.
No.
202,403 filed Oct.
31, 1980, Pat.
No.
4,341,690, relates to stabilized polypropylene compositions containing talc and a semi-crystalline, low glass transition temperature copolyester derived from terephthalic acid and 1,6-hexanediol
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Adhesives and Rubbers 
