| 摘要 |
1491437 Bisulphite adducts of polyisocyanate prepolymers BAYER AG 23 Sept 1976 [26 Sept 1975] 39484/76 Heading C3R A process for the production of a bisulphite addition product of a polyisocyanate prepolymer comprises reacting in an organic solvent free aqueous medium, a water soluble bisulphite, e.g. sodium potassium or ammonium bisulphite with a polyisocyanate prepolymer having free isocyanate groups, the polyisocyanate prepolymer being the reaction product of an excess of an organic polyisocyanate with an organic polyhydroxy compound having nonionic hydrophilic groups incorporated in such a way that the resulting prepolymer may be emulsified in water. The prepolymer may be represented by the general formula wherein A represents a radical obtained by removing the hydroxyl groups from an n-functional polyalkylene oxide polyol Mol. Wt. 500- 8,000 in which from 5 to 100% of the alkylene oxide units are ethylene oxide units; R represents a divalent radical obtained by removing the isocyanate groups from an organic diisocyanate having a Mol. Wt. of from 112 to 1,000 and n represents an integer of from 2 to 4. Suitable polyols are those comprising from 8 to 70% of ethylene oxide units and from 92 to 30% of propylene oxide units. In a typical example a trifunctional polyether, 17% of whose alkylene oxide segments consist of terminal ethylene oxide segments and 83% consist of propylene oxide segments is reacted with hexamethylene diisocyanate and unreacted diisocyanate subsequently removed from the reaction product by thin layer distillation in vacuo to give the prepolymer (NCO content 3À6%) which is mixed in water containing emulsifying agents, with sodium bisulphite to yield a water dilutable 30% bisulphite adduct solution. The aqueous adduct solutions may be used for treating textiles of natural or synthetic fibres and as binders for chip board, as adhesives and as crosslinking agents in emulsions of isocyanatereactive precondensates. |
