FULLY CAPPED POLYMETHYLENE POLYPHENYL ISOCYANATES

摘要

Fully capped polyisocyanates comprising a polymethylene polyphenyl mixture containing from 35 to 85% by weight of methylenebis-(phenyl isocyanates), the remainder of the polyisocyanate mixture being polymethylene polyphenyl isocyanates of functionality higher than 2.0, wherein each of the isocyanate groups has been capped with a thermally releasable capping agent containing an active hydrogen atom attached directly to nitrogen are prepared by direct reaction of the capping agent with the polyisocyanate, if desired in the presence of an inert organic solvent. Excess of capping agent is preferably employed. Said polyisocyanates can be represented by the general formula where n has an average value from 0.2 to 1.0 for mixtures containing from 85 to 35% by weight of methylenebis - (phenylisocyanate) respectively. Suitable capping agents specified are lactams, imides, N-monosubstituted aliphatic acid amides and secondary aromatic amines. Mixtures of capping agents may be used. The compounds are used in the treatment of paper and as promoters in the curing of hydrocarbon high polymers. They are also used in the preparation of elastomeric polyurethanes. The polyisocyanates are preferably obtained by phosgenation of the corresponding mixtures of methylene-bridged polyphenyl polyamines obtained by interaction of formaldehyde, hydrochloric acid and primary aromatic amines.