| 摘要 |
A thin layer of polyvinyl alcohol is rendered insoluble in water by heating it to a temperature of incipient dehydration to effect at least partial cross-linking. In one example a hydrophilic coating on a base of paper or a foil of metal or plastic material comprises 100 parts by weight of titanium dioxide, 40 parts by weight of polyvinyl alcohol, 3 parts by weight of "Tergitol" (Registered Trade Mark) and 1.5 parts by weight of tributyl phosphate, together with water to make the solids content 21%. The coating is dried and heated to above 175 DEG C. to insolubilise the polyvinyl alcohol. At least 98% hydrolysed polyvinyl alcohol is preferably used. A barrier coat between a paper base and the hydrophilic coating may comprise 100 parts by weight of Rhoplea, 80 parts by weight of polystyrene, 80 parts by weight of a clay slip, 2.5 parts by weight of sulphonated tallow, and 1.5 parts by weight of ammonia water, water being provided to make the solids content about 30%. Specification 936,569 is referred to.ALSO:A hydrophilic coating on a base of paper, metal foil, or plastic material such as cellulose acetate, and suitable for imaging to form a lithographic printing plate, comprises 100 parts by weight of titanium dioxide, 40 parts by weight of polyvinyl alcohol, 3 parts by weight of "Tergitol" (Registered Trade Mark), and 1,5 parts by weight of tributyl phosphate, together with water to make the solids content 21%. The coating is dried p and heated to above 175 DEG C. to render the polyvinyl alcohol insoluble in water. At least 98% hydrolyzed polyvinyl alcohol is preferably used. In the case of a paper base it may be coated on both sides initially with cloy bound by starch or casein. A barrier coat comprising 160 parts by weight of Rhoplex, 80 parts by weight polystyrene, 80 parts by weight of a cloy slip, 2,5 parts by weight of sulphonated tallow, and 1,5 parts by weight of ammonia water, water being provided to make the solids content about 30%. Specification 936,569 is referred to.
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