| 摘要 |
A polymeric emulsion comprising a (i) polymer, (ii) water, and (iii) a surfactant is useful as a binder for a water-based varnish that is resistant to water, 50% ethanol, and alkali. The polymer comprises about 20 to about 40 weight percent of a soft monomer whose homopolymer has a Tg of less than about -20 DEG C. and about 60 to about 80 weight percent of a mixture of hard monomers each of whose homopolymer has a Tg of greater than about 30 DEG C. As part of the hard monomer comonent of the polymer, the polymer comprises about 5 to about 25 weight percent acrylonitrile and about 1 to about 5 weight percent of an olefinic carboxylic acid. Typically, the polymer comprises less than about 1 weight percent surfactant and has a calculated Tg of about 25 DEG to about 60 DEG C., an actual Tg of about 30 DEG to about 70 DEG C., and an average particle size of less than about 250 nm. The emulsion generally comprises at least about 40 weight percent solids and has a surface tension of at least about 45 dynes/cm.
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