| 摘要 |
The swelling of bentonite particles is retarded by coating them with the product obtained by treating with sodium hydroxide a graft copolymer of an alkyl substituted acrolein and an organic polymeric material (in the form of an aqueous dispersion) of at least one monomer having one or two ethylenically unsaturated bonds and being free of reactive hydroxyl groups, e.g. polyvinyl chloride and butadienestyrene copolymers.ALSO:Graft copolymers are made by mixing and graft copolymerizing (A) at least one alkyl alpha-substituted acrolein monomer with (B) an aqueous dispersion of an organic polymeric material of at least one monomer having one or two ethylenic bonds and being free of reactive hydroxyl groups, in admixture with (C) a free radical initiator. Monomers (A) specified are methacrolein and ethacrolein, which may be used in admixture with other monomers, e.g. butadiene, isoprene, chloroprene, cyanoprene, dimethyl butadiene, styrene, acrylonitrile and methyl isopropenyl ketone. Polymers (B) specified are polyvinyl chloride, copolymers of vinyl chloride and vinyl acetate, polydiolefines and copolymers of butadiene or dimethyl butadiene with styrene, substituted styrenes or an ester or nitrile of acrylic or methacrylic acid. Initiators (C) specified are potassium persulphate, hydrogen peroxide, benzoyl peroxide and air. The resulting graft copolymer latices may be reacted with a strong base, e.g. an alkali metal hydroxide, diisopropylamine, diisobutylamine or piperidine, whereby the aldehyde groups of the grafted monomer are converted to methylol and carboxyl salt groups. The said carboxyl salt groups may be converted to the free acid form by treatment with acetic acid, and the ammonium salt of the copolymer may then be obtained by treatment with ammonium hydroxide. Films made from the graft copolymer in the free acid or ammonium salt form are rendered hydrophobic by heating. |
