| 摘要 |
944,686. Treating polyvinyl butyral films. DYNAMIT NOBEL A.G. June 21, 1962 [June 26, 1961], No. 23998/62. Heading B5B. The surface-tackiness of plasticizer-containing polyvinyl butyral film is reduced by immersing the film in a solution of polyvinyl butyral containing a precipitant for polyvinyl butyral, having a higher boiling point than the solvent, and in a concentration insufficient to cause precipitation of the polyvinyl butyral, and thereafter drying the film in a stream of warm air. The preferential evaporation of the solvent results in an increase in the concentration of precipitant in the applied solution, thereby causing precipitation of polyvinyl butyral on the film as a uniform, fine surface matting. The immersion bath is prepared by forming a solution of polyvinyl butyral with or without plasticizer, in, e.g., methanol and methyl acetate, in presence of a precipitant such as water, glycerine, an ether, an ethylene glycol, or an aliphatic hydrocarbon, e.g. benzine. Preferably, the concentration of precipitant is as close as possible to the precipitation point without actually precipitating the polyvinyl butyral. The film to be treated suitably contains 30% of plasticizer, e.g. triethylene glycol or diethylene butyral. In an example, a highly tacky plasticizer containing polyvinyl butyral film is briefly dipped into a mixture of methanol (100 parts), methyl acetate (100 parts), benzene B.P. 100-140‹ C. (150 parts) and plasticizer containing polyvinyl butyral (10 parts), and then dried in a stream of warm air. |
