| 摘要 |
<p>In a process for preparing a pressure sensitive adhesive emulsion containing a polymer having a Tg of-10°C or below which comprises polymerizing in an aqueous emulsion (a) an alkyl acrylate or vinyl ester, (b) an olefinically unsaturated carboxylic acid and (c) a polyolefinically unsaturated monomer for enhancing cohesive strength of the polymer, the method for enhancing the shear resistance of the pressure sensitive adhesive polymer which comprises
<UnorderedLists id="ula01" listStyle="none"><ListItem>(1) forming an aqueous suspension reaction mixture comprising a stabilizing agent and at least a portion of the alkyl acrylate or vinyl ester,</ListItem><ListItem>(2) initiating the reaction mixture by the addition of a free radical source at a temperature from about 10-40°C and bringing the reaction mixture to a reaction temperature of from 45-85°C within a period of not more than 2 hours with the reaction temperature exceeding the initiation temperature by at least 15°C,</ListItem><ListItem>(3) adding the olefinically unsaturated carboxylic acid monomer and the polyotefinically unsaturated monomer at a substantially uniform rate such that the major portion of the carboxylic acid and polyolefinically unsaturated monomers has been added by the time the alkyl acrylate and vinyl ester content as free monomer in the reaction mixture has been reduced to a level of less than about 10 wt% of the mixture, and</ListItem><ListItem>(4) continuing polymerization of the reaction mixture until the alkyl acrylate and vinyl ester content as free monomer in the reaction mixture is reduced below about 1 wt%.</ListItem></UnorderedLists></p> |
