Stabilized nitrile polymers

A polymer composition stable toward thermal discoloration containing from about 0.05 to 2.0 parts by weight per hundred parts of resin of an organic stabilizing agent selected from the group consisting of:

• ##EQU11## and ##EQU12## wherein X may be oxygen;
• and imide group, -NH-;
• or an N-substituted imide group, --NR--, wherein R may be an alkyl, or a phenyl alkyl group containing from 1 to 8 carbon atoms;
• Y may be an oxygen or a methylene group;
• and Z may be hydrogen or an alkyl group containing from 1 to 12 carbon atoms;
• and where said resin is composed of 100 parts by weight of:
• A. at least 50% by weight of at least one nitrile having the structure ##EQU13## wherein R is hydrogen, a lower alkyl group having from 1 to 4 carbon atoms, or a halogen, and
• B. up to 50% by weight based on the combined weight of (A) and (B) of at least one member selected from the group consisting of:
• 1. styrene,
• 2. an ester having the structure ##EQU14## wherein R.sub.1 is hydrogen, an alkyl group having from 1 to 4 carbon atoms, or a halogen, and R.sub.2 is an alkyl group having from 1 to 6 carbon atoms,
• 3. an alpha-olefin having the structure ##EQU15##
• wherein R' and R" are alkyl group having from 1 to 7 carbon atoms, 4. a vinyl ether selected from the group consisting of methyl vinyl ether, ethyl vinyl ether, the propyl vinyl ethers, and the butyl vinyl ethers, and
• 5. vinyl acetate, and
• wherein said monomers are copolymerized in the presence of from 0 to 40 parts by weight of:
• C. a rubbery polymer of a conjugated diene monomer selected from the group consisting of butadiene and isoprene and optionally a comonomer selected from the group consisting of styrene and a nitrile monomer having the structure ##EQU16## wherein R has the above designation, said rubbery polymer containing from 50 to 100% by weight of polymerized conjugated diene and from 0 to 50% by weight of comonomer.