Storage stable activated prepolymer composition
The addition of a small amount of an alkyl sulfoxide, e.g., DMSO, to an isocyanate capped prepolymer provides a storage stable prepolymer composition in which the prepolymer is also highly activated towards curing with certain blocked curing agents such as methylenedianiline metal salt coordination complexes. The prepolymer/alkyl sulfoxide compositions are cured by said blocked curing agents at lower temperatures and/or at an accelerated rate compared to similar compositions lacking the alkyl sulfoxide providing high performance polyurethane elastomers.
1. A method of preparing a polyurethane elastomer, the method comprising the steps of:
i) adding dimethyl sulfoxide to an isocyanate terminated prepolymer formed by reaction of one or more diisocyanate monomers selected from the group consisting of diphenylmethane diisocyanate, toluene diisocyanate and para-phenylene diisocyanate, with one or more polyols selected from the group consisting of polyether polyol, polyester polyol and polycaprolactone polyol; to form a prepolymer composition comprising from 0.1 to 1.5 wt % dimethyl sulfoxide based on the combined weight of the prepolymer and dimethyl sulfoxide,
ii) storing the prepolymer composition formed in step i) at temperatures in the range from 20° C. to 70° C. for at least 168 hours
iii) combining the prepolymer composition of step ii) with a polyamine metal salt coordination complex to form a curable composition, and
iv) heating the curable composition to effect cure.
2. The method according to claim 1 , wherein the dimethyl sulfoxide is present at from about 0.25 to about 1.0 wt %, based on the combined weight of the prepolymer and the dimethyl sulfoxide.