Liquid isocyanate-terminated prepolymer

In two-component sealants the components consist of a base, a hydroxyl-terminated compound and a liquid isocyanate-terminated prepolymer. The prepolymer reacts with the base in the presence of a catalyst to form the polyurethane ... 

Chain extenders are used by polyurethane fabricators to cure a liquid isocyanate-terminated prepolymer into a useful product. Typically this chain extender can be a... 

Ex. 2. Liquid, isocyanate-terminated prepolymers prepared from diisocyanates such as TDI (I) and Poly B-D glycol (XXVII), a polybutadiene glycol, may be placed on an adherend directly or from solution and permitted to cure via the action of moisture in the air. Useful as rubber-fabric adhesive. 

There are many different formulations for two component polyurethane sealants dependent of the sealant properties required. The usual NCO/OH equivalent ratio is 1.05 to 1.10. One component is a liquid isocyanate-terminated prepolymer containing pigments, fillers such as calcimn carbonate or talc, and an antisag agent such as fimied silica. The second component is a hydroxyl terminated polymer, pigment, and a catalyst such as methylene dianiline. The individual components are mixed at elevated temperatures under dry conditions so that premature crosslinking does not occur. Prior to use, the two components are mixed well and have a pot life of about 1 to 4 hours. Cure time to develop full sealant properties is 1 to 2 days. 

Recently, hot melt PSA systems have been introduced and radiation curable PSA systems are at the commercial development stage. High solids (50%-70% by wt.) nonaqueous dispersion acrylic PSA systems have also been reported(1). Unlike the hot melt and radiation cured systems which require new capital outlay in coating head and/or curing (drying) equipment, BFG has developed PSA systems, based on Hycar 2100R reactive acrylic liquid polymers and isocyanate terminated prepolymer, which can be processed at 80% solids (by wt.) with equipment presently used in the PSA industry, namely, the reverse roll and knife-over-roll coater. 

W. J. McKillip and C. N. Impola, Compositions made from (A) Isocyanate-Terminated Prepolymers and (B) Polyesters Prepared from Polyols and a, Ethylenically Unsaturated Monocarboxylic Acids, U.S. Pat. 3,396,210 (1968). IPN-type compositions. P. Mendoyanis, Thermosetting Compositions Containing a Liquid Rubber Selected from Polysulfide, Polymercaptan, and Chlorinated Polyethylene. Together with an Epoxide and Curing Agent, U.S. Pat. 3,316,324 (1967). SIN compositions of epoxy and polysulfide rubber. 

Liquid polybutadienes, especially those with OH terminal groups, can be modified with isocyanates. Already known is the commercial product NISSO-TP-1000, produced by the reaction with isocyanate of telechelic polybutadiene with OH groups [256]. Copolymeric resins can also be modified with polyisocyanates and urethanic prepolymers [257]. 

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