| abstract |
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 ot 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 °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 °C. As part of the hard monomer component 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° to about 60 °C, an actual Tg of about 30° to about 70 °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. |