Two step continuous polymerization method to form acrylonitrile copolymers

Claim 1

A method of polymerization comprising a. into a first reactor continuously feeding a free radical initiator and aqueous emulsified chain transfer agent, acrylonitrile and at least one monomer of styrene; 4-methyl styrene; 4-(t-butyl)styrene; 3-methyl styrene; 2,4-dimethyl styrene; 2,6-dimethyl styrene and 2,4-diisopropyl styrene or alpha-methyl styrene in combination with one of the above monomers; whereby at least 95% of the reaction time the monomer content relative to acrylonitrile in the reactor is maintained within 25% of a ratio required to be maintained to produce a polymer with an average composition of 65% to 85% by weight polymerized units of acrylonitrile and 35 to 15% by weight polymerized units of said monomer, said first reactor having a reaction temperature between 50 to 75°C., b. from said first reactor continuously withdrawing an outlet stream containing a polymer solids content of 15 to 20% by weight, an emulsifier content of 4 to 7% by weight of polymer, and unreacted acrylonitrile of 45 to 60% by weight of acrylonitrile feed to the first reactor; c. into a second reactor continuously feeding the outlet stream from step (b) together with free radical initiator and added aqueous emulsified chain transfer agent, acrylonitrile and said monomer with emulsifier present in an amount of at least 0.2% by weight of added water exclusive of water from step (b) whereby at least 95% of the reaction time a monomer content relative to acrylonitrile is maintained in the second reactor within 25% of a ratio required to be maintained to produce a polymer with an average composition of 65% to 85% by weight polymerized units of acrylonitrile and 35 to 15% polymerized units of said monomer, said second reactor having a reaction temperature between 50° to 75°C.; d. from said second reactor continuously withdrawing an outlet stream containing a polymer solids content of 20 to 30% by weight, an emulsifier content of 1.3 to 2.5% by weight of polymer, and unreacted acrylonitrile of 10 to 30% by weight of acrylonitrile feed to the second reactor, a ratio of polymer production in the second reactor to the first reactor maintained in a range of 1:1 to 6:1; the polymer possessing a melt stability of at least 10 minutes, an inherent viscosity of 0.3 to 1.0 deciliter/g as measured on a 0.5 g/deciliter solution of the polymer in gammabutyrolactone at 35°C., a melt viscosity of 10 4 to 10 6 poises at 220°C. and a carbon dioxide permeability of less than 0.045 barrer and containing 65 to 85% by weight polymerized units of acrylonitrile and 35 to 15% by weight polymerized units of said monomer.

Claim 2

A method of polymerization comprising a. into a first reactor continuously feeding a free radical initiator and aqueous emulsified chain transfer agent, acrylonitrile and at least one monomer of styrene; 4-methyl styrene; 4-(t-butyl)styrene; 3-methyl styrene; 2,4-dimethyl styrene; 2,6-dimethyl styrene and 2,4-diisopropyl styrene or alpha-methyl styrene in combination with one of the above monomers; whereby at least 95% of the reaction time the monomer content relative to acrylonitrile in the reactor is maintained within 25% of a ratio required to be maintained to produce a polymer with an average composition of 65% to 85% by weight polymerized units of acrylonitrile and 35 to 15% by weight polymerized units of said monomer, said first reactor having a reaction temperature between 50 to 75°C., b. from said first reactor continuously withdrawing an outlet stream containing a polymer solids content of 15 to 20% by weight, an emulsifier content of 4 to 7% by weight of polymer, and unreacted acrylonitrile of 45 to 60% by weight of acrylonitrile feed to the first reactor; c. into a second reactor continuously feeding the outlet stream from step (b) together with free radical initiator and added aqueous emulsified chain transfer agent, acrylonitrile and said monomer with emulsifier present in an amount of at least 0.2% by weight of added water exclusive of water from step (b) whereby at least 95% of the reaction time a monomer content relative to acrylonitrile is maintained in the second reactor within 25% of a ratio required to be maintained to produce a polymer with an average composition of 65% to 85% by weight polymerized units of acrylonitrile and 35 to 15% polymerized units of said monomer, said second reactor having a reaction temperature between 50° to 75°C.; d. from said second reactor continuously withdrawing an outlet stream containing a polymer solids content of 20 to 30% by weight, an emulsifier content of 1.3 to 2.5% by weight of polymer, and unreacted acrylonitrile of 10 to 30% by weight of acrylonitrile feed to the second reactor, a ratio of polymer production in the second reactor to the first reactor maintained in a range of 1:1 to 6:1; the polymer possessing a melt stability of at least 10 minutes, an inherent viscosity of 0.3 to 1.0 deciliter/g as measured on a 0.5 g/deciliter solution of the polymer in gammabutyrolactone at 35°C., a melt viscosity of 10 4 to 10 6 poises at 220°C. and a carbon dioxide permeability of less than 0.045 barrer and containing 65 to 85% by weight polymerized units of acrylonitrile and 35 to 15% by weight polymerized units of said monomer.