Fremgangsmåde til fremstilling af et bøjeligt polyurethanskumstof

Polyurethane foam is prepared by admixing (a) a diisocyanate, (b) a mixture of polyether polyols consisting of 50 to 90% by weight of a polyoxyalkylene triol having a molecular weight of 1000 to 5000 and an -OH number of 30 to 170 and 10 to 50% by weight of a polyoxyalkylene diol having a molecular weight of 1000 to 3000 and an -OH number of 40 to 110, the mixture having a primary hydroxyl group content of 10 to 65% and (c) water. Suitable diisocyanates (a) are m-phenylene diisocyanate, 2,4- and 2,6-tolylene diisocyanates, naphthalene 1,5- and naphthalene 1,8-diisocyanates, 4,41-methylene - bis - (phenylisocyanate), 4,41-methylene - bis - (tolylisocyanate) 4,41 - methylene - bis - (cyclohexylisocyanate) and 1,6-hexamethylene diisocyanate. A mixture of polyoxyalkylene triols and diols is utilized at least one of which preferably contains terminal hydroxyethylene or hydroxypropylene groups and which is preferably prepared by using 1,2-propylene oxide or a mixture of 1,2-propylene oxide and ethylene oxide in the initial condensation and thereafter to condense ethylene oxide or less preferably 1,3-propylene oxide with the initial condensation product to provide terminal hydroxyalkylene groups and primary hydroxyl groups in the required amount. The preferred polyoxypropylene triol has a primary hydroxyl content of 25 to 50% and the preferred polyoxypropylene diol has a primary hydroxyl content of 0 to 30%. Auxiliary blowing agents such as fluorocarbons, catalysts such as tertiary amines, organo-tin compounds and organic tin salts, and dispersing agents such as silicone-oxyalkylene block copolymers may also be incorporated into the foam forming reaction mixture. At least 5% of a filler having a particle size of below 50 microns in the largest dimension may also be incorporated into the reaction mixture. Barium sulphate is the preferred filler.