Color stabilized acrylonitrile polymers

A method of making a polymer composition stabilized against thermal discoloration, said composition comprising a homopolymer of acrylonitrile or a copolymer comprising at least 20 percent by weight of acrylonitrile, the balance being one or more monomers copolymerizable with acrylonitrile, which method comprises dissolving an effective amount of at least one stabilizer selected from the group consisting of nitroalkanes having 1 to 8 carbon atoms, nitrocycloalkanes having 5 or 6 carbon atoms in the cycloalkane ring, alkyl isocyanates having up to 8 carbon atoms, cycloalkyl isocyanates having 5 or 6 carbon atoms in the cycloalkyl ring, aryl isocyanates having 6 to 22 carbon atoms in the aryl group, and pyrocarbonic acid dialkyl esters wherein each alkyl group has from 1 to 8 carbon atoms, in monomeric acrylonitrile or in a monomer mixture comprising at least 20 percent by weight of acrylonitrile, which monomer or monomer mixture may be partially polymerized, and then polymerizing the resultant mixture by pearl polymerization in an aqueous phase.

A method of making a polymer composition stabilized against thermal discoloration, said composition comprising a homopolymer of acrylonitrile or a copolymer comprising at least 20 percent by weight of acrylonitrile, the balance being one or more monomers copolymerizable with acrylonitrile, which method comprises adding an effective amount of at least one stabilizer selected from the group consisting of nitroalkanes having 1 to 8 carbon atoms, nitrocycloalkanes having 5 or 6 carbon atoms in the cycoalkane ring, alkyl isocyanates having up to 8 carbon atoms, cycloalkyl isocyanates having 5 or 6 carbon atoms in the cycloalkyl ring, aryl isocyanates having 6 to 22 carbon atoms in the aryl group, and pyrocarbonic acid dialkyl esters wherein each alkyl group has from 1 to 8 carbon atoms, to a solution of said homopolymer or copolymer of acrylonitrile in an organic solvent therefor and then removing said solvent.

A method of making a polymer composition stabilized against thermal discoloration, said composition comprising a homopolymer of acrylonitrile or a copolymer comprising at least 20 percent by weight of acrylonitrile, the balance being one or more monomers copolymerizable with acrylonitrile, which method comprises forming a homogeneous mixture of said homopolymer or copolymer with from 0.1 to 2 percent, by weight thereof, of at least one stabilizer selected from the group consisting of nitroalkanes having a 1 to 8 carbon atoms, nitrocycloalkanes having 5 or 6 carbon atoms in the cycloalkane ring, alkyl isocyanates having up to 8 carbon atoms, cycloalkyl isocyanates having 5 or 6 carbon atoms in the cycloalkyl ring, aryl isocyanates having 6 to 22 carbon atoms in the aryl group, and pyrocarbonic acid dialkyl esters wherein each alkyl group has from 1 to 8 carbon atoms.