Preparation of low molecular weight styrene-maleic anhydride copolymers and sulfonated copolymers thereof

Claim 2

An improved process for preparing a copolymer of styrene and maleic anhydride in the molecular weight range of about 500 to 10,000 by polymerizing styrene and maleic anhydride monomers in a molar ratio of 1:1 to 9:1 in 1,2-dichloroethane at 70°-100°C. in the presence of a free radical generating polymerization catalyst and a mercaptan chain transfer agent, characterized in that the polymerization is carried out in the presence of 0.5-5%, based on the weight of the monomers, of 3-mercaptopropionic acid or methyl-3-mercaptopropionate as the chain transfer agent, whereby a substantially odorless copolymer which remains soluble in the 1,2-dichloroethane results.

Claim 3

The process of Claim 1, characterized in that the polymerization is carried out at 85°-95°C. in the presence of azoisobutyronitrile or 2,2'-azobis (2-methyl-pentanenitrile) as the catalyst and 1-3% of the chain transfer agent, whereby the copolymer has a molecular weight of from 1,000 to 4,000.

Claim 4

The process of Claim 1, characterized in that said molar ratio of styrene to maleic anhydride is 1:1 to 3:1.

Claim 5

The process of Claim 1, characterized in that the styrene is o(-methyl styrene or vinyl toluene.

Claim 6

The process of Claim 1, characterized in that the copolymer is recovered by distilling off the dichloroethane solvent.

Claim 7

An improved process for preparing a sulfonated copolymer of styrene and maleic anhydride by polymerizing styrene and maleic anhy- ride monomers in a molar ratio of 1:1 to 9:1 in 1,2-dichloroethane at 70°-100°C. in the presence of a free radical generating polymerization catalyst and a mercaptan chain transfer agent yielding a copolymer in the molecular weight range of about 500 to 10,000, sulfonating the resulting copolymer in the 1,2-dichloroethane, and recovering the resultant precipitated sulfonated copolymer, characterized in that the polymerization is carried out in the presence of from 0.5-5%, based on the weight of the monomers, of 3-mercaptopropionic acid or methyl-3-mercaptopropionate, whereby a substantially odorless and soluble copolymer of styrene and maleic anhydride is formed and results in a substantially odorless copolymer after sulfonation.

Claim 8

An improved process for preparing a sulfonated copolymer of styrene and maleic anhydride by polymerizing styrene and maleic anhy- ride monomers in a molar ratio of 1:1 to 9:1 in 1,2-dichloroethane at 70°-100°C. in the presence of a free radical generating polymerization catalyst and a mercaptan chain transfer agent yielding a copolymer in the molecular weight range of about 500 to 10,000, sulfonating the resulting copolymer in the 1,2-dichloroethane, and recovering the resultant precipitated sulfonated copolymer, characterized in that the polymerization is carried out in the presence of from 0.5-5%, based on the weight of the monomers, of 3-mercaptopropionic acid or methyl-3-mercaptopropionate, whereby a substantially odorless and soluble copolymer of styrene and maleic anhydride is formed and results in a substantially odorless copolymer after sulfonation.

Claim 9

The process of Claim 6, characterized in that the polymerization is carried out at 85-95°C in the presence of azoisobutyronitrile or 2,2'-azobis (2-methyl-pentanenitrile) as the free radical generating polymerization catalyst and 1-3% of the chain transfer agent using a 1:1 to 3:1 molar ratio of styrene to maleic anhydride, whereby the copolymer prior to sulfonation has a molecular weight of from 1,000 to 4,000.

Claim 10

The process of Claim 6, characterized in that the styrene is α-methyl sytrene or vinyl toluene.

Claim 11

9 . The process of Claim 6, characterized in that the sulfonated copolymer is neutralized with sodium carbonate and recovered by filtration.

Claim 12

The process of Claim 6, characterized in that water is added after sulfonation such that the sulfonated copolymer dissolves in the water and is separated and recovered in aqueous phase from the dichloroethane.