Reaction with polyols

The foams can be obtained by the action of a diiscyanate on a polyol and water. The reaction with water forms carbon dioxide and the reaction with polyol forms a urethane polymer. Catalysts play a crucial role in the process. Tin octeate and dibutyl tin dilaurate are preferred catalysts along with tertiary amines. 

Some of the major copolymerization reactions of isocyanates are shown in Scheme 2. Only the reaction with epoxides is discussed in this chapter. The reaction with polyols to give polyurethanes and with amines to give polyureas is discussed in Vol. I of this series [2]. Ulrich [2a] has briefly reviewed these and other reactions and this review should be consulted for additional material and references. 

Toluene diisocyanate is used in the manufacture of polyurethanes, which are produced by reaction with polyols and polyesters. 

Then the original weight of phenyl isocyanate present W fg) in the total reaction flask charge W ig) (i.e., before reaction with polyol commences) is given by ... 

FIGURE 17.5 Chemical equilibria giving rise to the borate cross-linking reaction with polyols. 

For these oligomers, it is preferred that n have a value of about 1 to 6. Modified block copolymers have been synthesized by coupling the above products with difunctional isocyanates (193) and with cycloaliphatic diepoxides (194). They were also used to synthesize radiation-curable diacrylates by means of a condensation reaction with acrylic acid (195). Other modifications of the oligomeric compounds include end capping with anhydrides to form acid-terminated oligomers (196) and reaction with polyols, anhydrides, and carboxylic acids to form low-viscosity, oil-free alkyds that are useful as coating intermediates (197). 

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