| 摘要 |
Gas-permeable, waterproof films and coatings having interconnecting pores comprise a polymerization product obtained from one or more organic isocyanates the molecule of each of which has at least two isocyanate groups directly attached to one or more aromatic nuclei, the polymerization having been carried out in the presence of a compound being an N,N-dialkyl or N,N-diaralkyl formamide the nitrogen atom of which is attached to at least one methyl or methylene group or being a pyrrolidone the nitrogen atom of which is attached to a methyl or methylene group, which compound is liquid in the temperature range applied and readily dissolves the isocyanate compounds used. The films and coatings may be prepared by mixing the organic isocyanates and the formamide or pyrrolidone compound and applying to a support in the form of one o more tin layers, the resulting layer being treated with water, if desired in the presence of a catalyst, during a period of time in which the number of free isocyanate groups which have not yet taken part in the resulting polymerization is in the range from 0.1 to 4% by weight, based on the total weight of the mixture, and in which the viscosity is 3 x 103 to 1 x 106 c.p. and, when a film is to be manufactured, the resultant coating being drawn off the support. Preferred isocyanates are diphenyl-methane-4,41-diisocyanate and a polyether diisocyanate obtained by the reaction of polypropylene glycol with an excess of diphenyl - methane - 4,41 - diisocyanate. The preferred dialkyl formamide is dimethyl formamide. The preferred catalysts are triethylamine, potassium permanganate and ultraviolet light. The water treatment may be carried out in a water bath. In examples are also used degassed carbon black and potassium permanganate, a polyester diisocyanate obtained by reaction of an adipic ethylene glycol polyester with an excess of toluene-2,4-diisocyanate and hexamethylene tetramine.ALSO:Gas-permeable, waterproof coatings having interconnecting pores are prepared by mixing, one or more organic isocyanates the molecule of each of which has at least two isocyanate groups directly attached to one or more aromatic nuclei and at least one compound being an N,N-dialkyl or N,N-diaralkyl formamide the nitrogen atom of which is attached to at least one methyl or methylene group, or being a pyrrolidone the nitrogen atom of which is attached to a methyl or methylene group, which compound is liquid in the temperature range applied and readily dissolves the isocyanate compounds used, and applying the mixture to a support in the form of one or more thin layers, treating the resulting layer with water, if desired in the presence of a catalyst, during a period of time in which the number of free isocyanate groups which have not yet taken part in the resulting polymerisation is in the range from 0.1 to 4% by weight, based on the total weight of the mixture, and in which the viscosity is 3 x 103 to 1 x 106 c.p. Supports coated are a tightly woven fabric of polyethylene terephthalate, a finely perforated water-permeable polyamide film and a fleece of synthetic fibres. |
