| 摘要 |
A composition used to opacify paper (see Division D2) comprises a solution of polyvinyl chloride in a mixture of two parts of acetone and one part of isopropanol.ALSO:Light-weight paper is made opaque by impregnating an absorbent fibrous web with a solution of a solid organic polymeric material in a volatile organic solvent, incorporating in the solution a volatile organic liquid that is miscible with the solvent and can, when present in sufficient amount, precipitate the polymeric material as fine particles between the fibres of the web, causing the concentration of the precipitant liquid to attain a value at which the polymeric material so precipitates, and evaporating off the solvent and the precipitant liquid at a temperature below that at which the particles of polymeric material coalesce. The precipitant liquid may be less voltaile than the solvent and present with it in the solution as applied, in such proportions that the polymeric material is in solution, as applied, but is precipitated during the evaporation. The polmeric material may be a cellulose ester, cellulose ether, addition polymer or condensation polymer. The specification lists examples of each, and also suitable solvents and precipitants. The solution may also contain a dye or pigment. |
