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 about 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, wherein the improvement comprises carrying out the polymerization in the presence of about 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 said 1,2-dichloroethane results.

Claim 3

An improved process for preparing a sulfonated copolymer of styrene and maleic anhydride by polymerizing styrene and maleic anhydride monomers in a molar ratio of about 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 of styrene and maleic anhydride in said 1,2-dichloroethane, and recovering the resultant precipitated sulfonated copolymer, wherein the improvement comprises carrying out the polymerization in the presence of about 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 and soluble copolymer of styrene and maleic anhydride is formed and results in a substantially odorless copolymer after sulfonation.

Claim 4

An improved process for preparing a sulfonated copolymer of styrene and maleic anhydride by polymerizing styrene and maleic anhydride monomers in a molar ratio of about 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 of styrene and maleic anhydride in said 1,2-dichloroethane, and recovering the resultant precipitated sulfonated copolymer, wherein the improvement comprises carrying out the polymerization in the presence of about 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 and soluble copolymer of styrene and maleic anhydride is formed and results in a substantially odorless copolymer after sulfonation.

Claim 5

The process of claim 1 wherein the polymerization is conducted between 85°-95° C.

Claim 6

The process of claim 1 wherein said chain transfer agent is used in an amount of 1-3% based on the weight of the monomers and the copolymer has a molecular weight of from 1,000 to 4,000.

Claim 7

The process of claim 1 wherein said free radical generating polymerization catalyst is azoisobutyronitrile.

Claim 8

The process of claim 1 wherein said free radical generating polymerization catalyst is 2,2'-azobis (2-methyl-pentanenitrile).

Claim 9

The process of claim 1 wherein said molar ratio of styrene to maleic anhydride is 1:1 to 3:1.

Claim 10

The process of claim 1 wherein the styrene is α-methyl styrene.

Claim 11

The process of claim 1 wherein the styrene is vinyl toluene.

Claim 12

The process of claim 1 wherein the copolymer is recovered by distilling off the dichloroethane solvent.

Claim 13

The process of claim 2 wherein the polymerization is conducted between 85°-95° C.

Claim 14

The process of claim 2 wherein said chain transfer agent is used in an amount of 1-3% based on the weight of the monomers and the copolymer prior to sulfonation has a molecular weight of from 1,000 to 4,000.

Claim 15

The process of claim 2 wherein said free radical generating polymerization catalyst is azoisobutyronitrile.

Claim 16

The process of claim 2 wherein said free radical generating polymerization catalyst is 2,2'-azobis (2-methyl-pentanenitrile).

Claim 17

The process of claim 2 wherein said molar ratio of styrene to maleic anhydride is 1:1 to 3:1.

Claim 18

The process of claim 2 wherein the styrene is α-methyl styrene.

Claim 19

The process of claim 2 wherein the styrene is vinyl toluene.

Claim 20

The process of claim 2 wherein said sulfonated copolymer is neutralized with sodium carbonate and recovered by filtration.

Claim 21

The process of claim 2 wherein 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.