| 摘要 |
<p>A copolymer of (a) acrylonitrile, (b) at least one polymerizable neutral ester of a carboxylic acid having a , b unsaturation with a monohydric alcohol which is free of polymerizable unsaturation and is composed of C, H and O atoms, and (c) at least one a , b mono-olefinically unsaturated mono or dicarboxylic acid is made by a two-stage aqueous dispersion process which comprises polymerizing monomers (a), (b) and (c) in a first stage, said monomer (c) being present in an amount sufficient to provide an acid number of at least 15, in the presence of a water-soluble initiator to a conversion of at least 85%; then adding a second batch which comprises monomers (a) and (b) and optionally (c) wherein the relative proportions of the respective comonomers (a) and (b) in the two batches are from 0.8 to 1.2 times the relative proportions of the comonomers in the final polymer, the relative proportion of (c) in the second batch, if any, being no greater than 2 times the proportion in the first batch, the ratio of the second charge being from 0.67 to 1.5 parts per part by wt. of first charge, the amount of monomer (c) being sufficient to provide an acid number of 15 to 80 in the final polymer; initiating polymerization of the second batch with further initiator and continuing polymerization to at least 95% conversion. Exemplified monomers (b) are butyl acrylate, glycidyl methacrylate and ethyl acrylate. Exemplified monomers (c) are acrylic, methacrylic and itaconic acids and mono butyl itaconate. Polymerization may take place in the presence of an aquasol of silica. The copolymers produced may be neutralised with ammonia, mixed with water-soluble heat-reactive phenol/formaldehyde condensation products, cooled on wires and heat-coalesced. Specifications 761,928, 826,455 and 870,945 are referred to.</p> |
