| 摘要 |
The present invention relates to a free radical emulsion polymerization process. The latex is prepared by polymerizing (a) at least one conjugated diene, (b) at least one non-carboxylic vinyl aromatic or aliphatic comonomer selected from the group consisting of styrene, .alpha.-methyl styrene, p-methyl styrene, vinyl toluene, acrylonitrile, methacrylonitrile, vinylidene chloride, ethyl acrylate; butyl acrylate, vinyl pyridine, methylmethacrylate, hexylacrylate, 2-ethyl hexyl acrylate or mixtures thereof, and (c) at least one ethylenically unsaturated carboxylic acid monomer selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, fumaric acid, 3- carboxyethylacrylate, itaconic acid or mixtures thereof. The process of the present invention is characterized by (a) initially polymerizing the non- carboxylic comonomer in the presence of the unsaturated carboxylic acid and in the absence of any conjugated diene to a conversion of 3 to 12 percent to form a partially polymerized latex; and thereafter (b) copolymerizing the conjugated diene with the unreacted non-carboxylic comonomer in the partially polymerized latex. The present process mitigates the formation of codimers of the conjugated diene and non-carboxylic comonomer. The present process also provides a latex having unique film forming characteristics and polymer morphology leading to unique film stiffness and stress-strain relationship.
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