Patent GB-849155-A (GB)
Title: Improvements in or relating to permeable polymeric coatings and films
IPC: D06N3/14
Filed: 1958-01-15
Abstract: Microporous films are produced by coating an impervious substrate with a polymeric solution having as essential constituents a hygroscopic solvent and up to 30% by weight of a polymer formed by chain-extending an isocyanate-group terminated reaction product of at least one polyalkylene ether glycol and at least one diisocyanate with at least one chain-extending agent in the form of a compound having two active hydrogen atoms, exposing the coated substrate to an atmosphere having a relative humidity of 15 to 100% at a dry bulb temperature of from 50 DEG  to 100 DEG F., removing the residual hygroscopic solvent from the resulting microporous coating, and stripping the coating from the impervious substrate.  The reaction product may have a molecular weight of 750 to 10,000 and the solvent may be removed from the coating by washing with water or by air drying at room or elevated temperature.  The polymeric solution may be applied by spraying, roller coating, casting, brushing or knife coating.  Specified impervious substrates are glass and stainless steel.  specified hygroscopic solvents are N,N1 dimethyl formamide, dimethyl sulphoxide, tetrahydrofuran, tetramethylurea, N,N1-dimethylacetamide, and mixtures of acetone and N,N1dimethylformamide.  Chain-extending agents disclosed are water, hydrazine, diamines, e.g. 4-methyl-m-phenylene diamine, dimethyl piperazine, m-phenylene-diamine, 3,31-dichlorobenzidine or 4,41-diaminodiphenylmethane, amino alcohols, e.g. 2-amino ethanol, amino acids, e.g. m-amino-benzoic acid, hydroxy acids, glycols, e.g. ethylene glycol, or mixtures thereof.  Polyalkylene ether glycols specified are polyethylene ether glycol, polypropylene ether glycol, polytetramethylene ether glycol, polyhexamethylene ether glycol, polyoctamethylene ether glycol, polynonomethylene ether glycol, polydecamethylene ether glycol, or mixtures thereof, and compounds of the formula HO(CH2OC2H4O)nH, where n is an integer greater than 1. Aromatic, e.g. arylene, aliphatic or cycloaliphatic diisocyanates or mixtures thereof may be used in forming the polymers, e.g. 4-methyl-m-phenylene diisocyanate, m-phenylene diisocyanate, 4,41biphenylene diisocyanate, methylene bis (4phenyl isocyanate), 4-chloro-1,3-phenylene diisocyanate, 1,5-naphthalene diisocyanate, 1,4tetra-methylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,10-decamethylene diisocyanate, 1,4-cyclohexylene diisocyanate, 4,41-methylenebis (cyclohexylene isocyanate) and 1,5-tetrahydronaphthalene diisocyanate.  The polymers may be prepared as described in Specifications 731,071, 796,041, and 849,154.  Vinyl polymers, e.g. polyvinyl chloride, polymethyl methacrylate, polyvinyl butyral, polyacrylonitrile, and copolymers thereof, in an amount of up to 50% of the polymer mixture, may be dissolved in the polymeric solution.  The films can also be laid down as permanent coatings on a variety of substrates (see Group VIII).ALSO:Microporous coating films are produced by coating a substrate with a polymeric solution having as essential constituents a hygroscopic solvent and up to 30% by weight of a polymer formed by chain-extending an isocyanate-group terminated reaction product of at least one polyalkylene ether glycol and at least one diisocyanate with at least one chain-extending agent in the form of a compound having two active hydrogen atoms, exposing the coated substrate to an atmosphere having a relative humidity of 15 to 100% at a dry bulb temperature of from 50 to 100 DEG F. removing the residual hygroscopic solvent from the resulting microporous coating, and if necessary stripping the coating from the substrate.  The reaction product may have a molecular weight of 750 to 10,000 and the solvent may be removed from the coating by washing with water or by air drying at room or elevated temperature.  The polymeric solution may be applied by spraying, roller coating, casting, brushing or knife coating.  Specified impervious substrates are glass and stainless steel.  Specified hygroscopic solvents are N, N1-dimethyl formamide, dimethyl sulphoxide, tetrahydrofuran, tetramethylurea, N,N1-dimethylacetamide and mixtures of acetone and N,N1-dimethylformamide.  Chain-extending agents disclosed are water, hydrazine, diamines, e.g. 4-methyl-m-phenylene diamine, dimethyl piperazine, m-phenylene-diamine, 3,31-dichlorobenzidine or 4,41-diaminodiphenyl methane, amino alcohols, e.g. 2-amino ethanol, amino acids, e.g. m-amino-benzoic acid, hydroxy acids, glycols, e.g. ethylene glycol, or mixtures thereof.  Polyalkylene ether glycols specified are polyethylene ether glycol, polypropylene ether glycol, polytetramethylene ether glycol, polyhexamethylene ether glycol, polyoctamethylene ether glycol, polymonomethylene ether glycol, polydecamethylene ether glycol, or mixtures thereof, and compounds of the formula HO (CH2OC2H4O)nH, where n is an integer greater than 1. Aromati, e.g. arylene, aliphatic or cycloaliphatic diisocyanates or mixtures thereof may be used in forming the polymers, e.g. 4-methyl-m-phenylene diisocyanate, m-phenylene diisocyanate, 4,41-biphenylene diisocyanate, methylene bis (4-phenyl isocyanate), 4-chloro-1, 3-phenylene diisocyanate, 1,5-naphthalene diisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,10-decamethylene diisocyanate, 1,4-cyclohexylene diisocyanate, 4,41-methylene-bis (cyclohexylene isocyanate) and 1,5-tetrahydronaphthalene diisocyanate.  The polymers may be prepared as described in Specifications 731,071, 796,041 and 849,154.  Vinyl polymers, e.g. polyvinyl chloride, polymethyl methacrylate, polyvinyl butyral, polyacrylonitrile, and copolymers thereof, in an amount of up to 50% of the polymer mixture, may be dissolved in the polymeric solution.