GB828718A - Stable, curable polyurethane compositions and method of making same - Google Patents

Abstract

A polyurethane composition comprises a reaction product of a polyether, other than one consisting solely of isopropylene ether groups, or a polyester or a mixture of a polyether and a polyester and a polyisocyanate, the reaction product having mixed therewith as a curing agent 0.2 to 8 parts by weight for every 100 parts of the reaction product of an organic peroxide of the general formula R1-OOR, where R and R1 are organic groups of at least 3 carbon atoms and at least one of the groups R and R1 is an araliphatic group having a tertiary aliphatic carbon atom, an aliphatic carbon atom of the araliphatic group being attached to the peroxide oxygen group and being connected directly to but one oxygen atom. The amount of polyisocyanate is preferably equal to or only slightly in excess (6% to 15%) of that necessary to react with all the polyether and/or polyester. For rubbery products the molecular weight of the polyester or polyether is preferably above 1000. Rigid products are obtained when the polyethers or polyesters have molecular weights below 500 or 600 or by using a cross-linking agent such as trimethylol propane. Suitable polyethers are mixed poly-(ethylene-propylene) ether glycols, poly tri-, tetra- or penta-methylene ether glycols and polyneopentylene ether glycol. The peroxide is incorporated suitably by milling, and carbon black, synthetic wax, silicon dioxide and calcium carbonate can also be incorporated. Examples illustrate the use of di-cumyl peroxide in the curing of polyesters (polyethylenepropylene adipate) and polytetramethylene ether glycol. Comparison figures are given of the physical properties of a polyester urethane rubber (in some cases incorporating carbon black) with di-t-butyl peroxide, di-2,2-bis-(t-butyl peroxy) butane, t-butyl hydroperoxide, cumene hydroperoxide, methane hydroperoxide, t-butyl isopropyl benzene hydroperoxide, t-butyl perbenzoate, benzoyl peroxide, lauroyl peroxide, methyl ethyl ketone peroxide, cyclohexanone peroxide, methyl amyl ketone peroxide and bis-azoisobutyronitrile as curing catalysts.