Patent GB-1036572-A (GB)
Title: Improvements in or relating to translucent paper
Inventor: STONE JAMES BRYAN
IPC: D21H17/57
Filed: 1961-12-29
Abstract: Translucent is produced by applying a polyisocyanate component, a polyhydroxy component and an organic solvent inert to both components to absorbent paper and allowing the two components to react together in the paper to form a translucent macromolecular polyurethane.  The polyhydroxy component may be a polyester containing free hydroxyl groups, e.g. a polyester produced from a dibasic carboxylic acid, a diol and a triol, a polyether containing free hydroxyl groups, ethylene glycol or trimethylol propane and the polyisocyanate component may be a compound derived from toluylene 2, 4-diisocyanate and timethylol propane.  Suitable organic solvents are ethylene glycol acetate, xylene, xylol and butyl acetate.  The treating composition may also contain a catalyst, e.g. a zinc solution in mineral spirits, and the components may be allowed to react together at an elevated temperature.  The paper is preferably treated with the composition comprising the polyisocyanate, polyhydroxy compound, organic solvent and, if desired, catalyst, wound on to a spindle, allowed to stand for a sufficient time to enable the required degree of absorption by the material to be effected and for the reaction of the two components to occur in the paper, unwound and the solvent evaporated.  The paper may subsequently be coated with an aqueous composition comprising isopropyl alcohol, urea, thio urea, tartaric acid, magnesium chloride, resorcinol, 4(N: N-diethylamino) benzene diazonium chloride zinc salt, polyvinylacetate, polyvinyl alcohol and rice starch, and dried at a temperature of 130 DEG C.ALSO:Translucent paper is produced by applying a polyisocyanate component, a polyhydroxy component and an organic solvent inert to both components to absorbent paper and allowing the two components to react together in the paper to form a translucent macromolecular polyurethane.  The polyhydroxy component may be a polyester containing free hydroxyl groups, e.g. a polyester produced from a dibasic carboxylic acid, a diol and a triol, apolyether containing free hydroxyl groups, ethylene glycol or trimethylol propane and the polyisocyanate component may be a compound derived from toluylene, 2, 4-diisocyanate and trimethylol propane.  Suitable organic solvents are ethylene glycol acetate, xylene, xylol and butyl acetate.  The treating composition may also contain a catalyst, e.g. a zinc solution in mineral spirits, and the components may be allowed to react together at an elevated temperature.  The paper is preferably treated with the composition comprising the polyisocyanate, polyhydroxy compound, organic solvent and, if desired, catalyst, wound on to a spindle, allowed to stand for a sufficient time to enable the required degree of absorption by the paper to be effected and for the reaction of the two components to occur in the paper, unwound and the solvent evaporated.  The paper may subsequently be coated with an aqueous composition comprising isopropyl alcohol, urea, thiourea, tartaric acid, magnesium chloride, resorcinol, 4(N : N-diethylamino) benzene diazonium chloride zinc salt, polyvinylacetate, polyvinyl alcohol and rice starch, and dried at a temperature of 130 DEG C.