| 摘要 |
<p>A sheet material such as paper is provided with a coating of gum capable of being rendered adhesively tacky by moistening with water, which, while appearing megascopically homogeneous (i.e. as observed with the naked eye, or with the aid of a small pocket lens) consists of the solidified gum having a multiplicity of microscopic air spaces therein. It may be produced by emulsifying in an aqueous solution of the gum, serving as the continuous phase, a volatile liquid which is substantially insoluble in water and a non-solvent for the gum, applying a film of the emulsion to the sheet material, and drying to set the gum and evaporate the water and the volatile liquid, substantially in that order, to reproduce in solid form the spatial disposition of the continuous phase of the liquid film. Examples of such gum compositions are given in which (1) "Solvesso" (Registered Trade Mark) Xylol (a mixture of dimethylbenzenes) is emulsified in aqueous solutions of bone glue, in some cases using an emulsifier, Aerosol OT, stated to be di-octyl sodium sulphosuccinate; (2) "Solvesso" Xylol is emulsified in an aqueous solution of partially converted starch, using alkali lignin as emulsifier; (3) "Solvesso" Xylol is emulsified in a solution of dextrin, using Aerosol OT as emulsifier; (4) "Solvesso" Xylol is emulsified, using Aerosol OT, in an aqueous solution of Elvanol 51 A-05, a low viscosity cold water soluble polyvinyl alcohol; (5) Varsol No. 2, a petroleum solvent having a boiling range of about 305 DEG to 397 DEG F., and a flash-point of about 110 DEG to 114 DEG F., is emulsified, using Indoil Sulphonate B, Purified, a petroleum sulphonate, in a solution of Rhotex size, stated to be a polymerized sodium acrylate; (6) Varsol No. 2 is emulsified, using Indoil Sulphonate T-16, a petroleum sulphonate, in a solution of Methocel, a methyl cellulose of 25 centipoises viscosity; (7) "Solvesso" Xylol is dispersed, using alkali lignin, in a solution of gum arabic. Other volatile liquids which may be used are methyl hexyl ketone, diphenyl ether, o-dichlorbenzene, solvent naphtha Nos. 3 and 6, butyl acetate, cyclohexanol and carbon tetrachloride. The compositions were coated on paper in accordance with usual practices, and the products dried, first at room temperature and then on a drum heated to 220 DEG F., but similar results are obtained by drying throughout at 140 DEG F., or at room temperature. Attainment of the final porous condition is indicated by the coating acquiring an opaque, white, glossy appearance.</p> |
