Heat resistant thermoplastic copolymers

Abstract

Thermoplastic copolymers having excellent tensile and heat resistance properties are obtained by copolymerization of a monovinyl aromatic monomer, an α,β-unsaturated dicarboxylic acid anhydride, an α, β-unsaturated carboxylic acid, and a C 1 -C 4 alkyl ester of methacrylic acid. In a preferred embodiment, a styrene/maleic anhydride/methacrylic acid/methyl methacrylate random copolymer is prepared. Impact properties are improved by incorporation of an elastomer.

I claim: 
     
       1. A thermoplastic copolymer comprised of (a) from about 40 to 97 weight percent of recurring units of a monovinyl aromatic monomer;   (b) from about 1 to 30 weight percent of recurring units of an α,β-unsaturated dicarboxylic acid anhydride;   (c) from about 1 to 30 weight percent of recurring units of an α,β-unsaturated carboxylic acid; and   (d) from about 1 to 40 weight percent of recurring units of a C 1  -C 4  alkyl ester of methacrylic acid; wherein the thermoplastic copolymer has a substantially random structure.     
     
     
       2. The thermoplastic copolymer of claim 1 wherein the monovinyl aromatic monomer is selected from the group consisting of styrene, α-methylstyrene, ar-methyl styrene, ar-ethyl styrene, ar-chlorostyrene, ar-bromostyrene, ar-(t-butyl)styrene, ar-cyano-styrene, ar-vinyl naphthalene, and mixtures thereof. 
     
     
       3. The thermoplastic copolymer of claim 1 wherein the α,β-unsaturated dicarboxylic acid anhydride is selected from the group consisting of maleic anhydride, chloromaleic anhydride, citraconic anhydride, tetrahydrophthalic anhydride, itaconic anhydride, ethyl maleic anhydride, bromomaleic anhydride, methyl itaconic anhydride, and mixtures thereof. 
     
     
       4. The thermoplastic copolymer of claim 1 wherein the α,β-unsaturated carboxylic acid is selected from the group consisting of acrylic acid and methacrylic acid. 
     
     
       5. The thermoplastic copolymer of claim 1 wherein the C 1  -C 4  alkyl ester of methacrylic acid is selected from the group consisting of methyl methacrylate, ethyl methacrylate, propyl methacrylate, iso-propyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, t-butyl methacrylate and mixtures thereof. 
     
     
       6. A thermoplastic copolymer comprised of (a) from about 40 to 74 weight percent of recurring units of styrene;   (b) from about 5 to 20 weight percent of recurring units of maleic anhydride;   (c) from about 3 to 12 weight percent of recurring units of methacrylic acid; and   (d) from about 18 to 35 weight percent of recurring units of methyl methacrylate; wherein the thermoplastic copolymer has a substantially random structure.     
     
     
       7. A molded article produced by molding the thermoplastic copolymer of claim 1. 
     
     
       8. A molded article produced by molding the thermoplastic copolymer of claim 6. 
     
     
       9. A process for producing a thermoplastic copolymer having a substantially random structure comprising copolymerizing a monovinyl aromatic monomer, an α,β-unsaturated dicarboxylic acid anhydride, an α,β-unsaturated carboxylic acid, and a C 1  -C 4  alkyl ester of methacrylic acid, wherein the resulting thermoplastic copolymer is comprised of (a) from about 40 to 97 weight percent of recurring units of the monovinyl aromatic monomer;   (b) from about 1 to 30 weight percent of recurring units of the α,β-unsaturated dicarboxylic acid anhydride;   (c) from about 1 to 30 weight percent of recurring units of the α,β-unsaturated carboxylic acid; and   (d) from about 1 to 40 weight percent of recurring units of the C 1  -C 4  alkyl ester of methacrylic acid.   
     
     
       10. The process of claim 9 wherein the copolymerization is carried out in the presence of an effective amount of a free-radical initiator. 
     
     
       11. The process of claim 9 wherein the monovinyl aromatic monomer is selected from the group consisting of styrene, α-methylstyrene, ar-methyl styrene, ar-ethyl styrene, ar-chlorostyrene, ar-bromostyrene, ar-(t-butyl)styrene, ar-cyanostyrene, ar-vinyl naphthalene, and mixtures thereof. 
     
     
       12. The process of claim 9 wherein the α,β-unsaturated dicarboxylic acid anhydride is selected from the group consisting of maleic anhydride, chloromaleic anhydride, citraconic anhydride, tetrahydrophthalic anhydride, itaconic anhydride, ethyl maleic anhydride, bromomaleic anhydride, methyl itaconic anhydride, and mixtures thereof. 
     
     
       13. The process of claim 9 wherein the α,β-unsaturated carboxylic acid is selected from the group consisting of acrylic acid and methacrylic acid. 
     
     
       14. The process of claim 9 wherein the C 1  -C 4  alkyl ester of methacrylic acid is selected from the group consisting of methyl methacrylate, ethyl methacrylate, propyl methacrylate, iso-propyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, t-butyl methacrylate and mixtures thereof. 
     
     
       15. A process for producing a thermoplastic copolymer having a substantially random structure comprising copolymerizing styrene, maleic anhydride, methacrylic acid, and methyl methacrylate in the presence of an effective amount of a free-radical initiator, wherein the resulting thermoplastic copolymer is comprised of (a) from about 40 to 74 weight percent of recurring units of styrene;   (b) from about 5 to 20 weight percent of recurring units of maleic anhydride;   (c) from about 3 to 12 weight percent of recurring units of methacrylic acid; and   (d) from about 18 to 35 weight percent of recurring units of methyl methacrylate.   
     
     
       16. The process of claim 9 wherein the copolymerization is performed in a continuous manner. 
     
     
       17. A process for producing a molded article comprising molding the thermoplastic copolymer of claim 1.