| 摘要 |
<p>The wearing properties of leather are improved by partial impregnation with a polyurethane prepolymer comprising the reaction product of (1) a polyisocyanate or iso-thiocyanate, and (2) a polyhydroxy glycol ether comprising block copolymers of ethylene and propylene oxides with poly-hydric alcohols, containing at least 3 hydroxyl groups in which 80 to 97% of the alkylene oxide is propylene oxide and at least 3% of the propylene oxide is present as terminal blocks. The pre-polymer in part reacts with groups of the leather fibre, and in part is cross-linked by reaction with water.ALSO:The invention comprises polyhydroxy glycol ethers and polyurethanes therefrom. The glycol ethers have a molecular weight of 1000 to 6000, and comprise block copolymers of ethylene and propylene oxides with a poly-hydric alcohol having at least 3 hydroxyl groups, of which 80 to 97% of the alkylene oxides is propylene oxide and at least 3% of the propylene oxide is present as terminal blocks. Specified initiators are trimethylol propane, hexane-triol, pentaerythritol, a -methyl glucoside, and sorbitol. Suitable reaction catalysts are alkalimetals and their hydroxides and alkoxides. Polyurethanes are prepared by reacting the above polyhydroxyglycol ethers with a polyfunctional isocyanate or isothiocyanate. Specified isocyanates are a mixture of toluene 2:4-and 2:6-diisocyanates, polymethylene di-isocyanate and di-thio-isocyanate, hexamethylene di-isocyanate, xylene di-isocyanate, napthylene diisocyanate, 1 - methyl - 2:4 - phenylenediisocyanate, mixed isomers of 1-methyl-2:4- and 2:6-phenylene di-isocyanate and 4,41-di-isocyanato-diphenylmethane. Polyurethane prepolymers are prepared by using an excess of isocyanate such that the ratio of NCX to OH groups is at least 1.5 to 1. Preferred conditions are 80-120 DEG C., a reaction time of 30 to 240 minutes and the presence of 0.1% by weight of water. They may be hardened by addition of minor amounts of low-molecular weight polyhydric alcohols or softened by addition of an alcohol R1(OC2H4)a(OC3H6)bOH where a and b are integers or zero and R1 is a hydrocarbyl radical. Prepolymers may be stabilized by addition of an acyl chloride. Suitable curing agents contain two or more of the groups: hydroxyl, primary or secondary amine carboxyl. The prepolymer may be foamed by reaction with water with or without auxilliary blowing agents, e.g. halogenated hydrocarbons, a tertiary amine catalyst and a water-insoluble silicone oil foam stabilizer, e.g. polysiloxane polyalkylene block copolymers. Polyurethane foams may also be prepared by a one-shot process. Specified catalysts are 1,4-diazabicyclo-octane; N,N1-tetramethyl-1,3-butanediamine; N-methyl morpholine, dibutyl-tindilaurate, stannous octoate and mixtures thereof. The examples describe the preparation of polyethers by reacting, (1)-(6), glycerol with, in turn, propylene oxide, ethylene oxide, propylene oxide; (7)-(9) glycerol with, in turn, a mixture of ethylene and propylene oxides, propylene oxide. The product of (1) is reacted with a mixture of 2:4- and 2:6-toluene diisocyanates to form, (10) a polyurethane foam by a one-shot process, (11) a prepolymer which is subsequently foamed. Uses.-The prepolymer is used as a surface-coating agent for wood, metals and leather (see Divisions C6 and B2). The foams may be used in crash-parts on cars.ALSO:Polyurethanes suitable for surface-coating wood, metal and leather are prepared by reacting (1) a polyisocyanate or iso-thiocyanate, and (2) a polyhydroxy glycol ether comprise block copolymers of ethylene and propylene oxides with a polyhydric alcohol containing at least three hydroxy groups, in which 80 to 97% of the alkylene oxide is propylene oxide and at least 3% of the propylene oxide is present as terminal blocks. The prepolymer is dissolved in a solvent (e.g. toluene, xylenes, mixed hydrocarbon fractions, carbon tetrachloride, ethyl acetate or the acetate of ethylene glycol ether). The solution is applied to the surface and the solvent evaporated. The resulting film is cured by reaction with atmospheric moisture either with or without catalysts.</p> |
