反应详情

Suitable blocking agents or example, an oxime (preferably butanone oxime), a lactam (preferably ε caprolactam), an acetoacetate (preferably ethyl acetate), a malonate (preferably diethyl malonate), or a substituted phenol. Within the substitued phenols, p-hydroxybenzoic acid esters (e.g. p-hydroxybenzoic acid ethyl ester) are particularly preferred. They have low cleavage temperatures (less than 150° C.), and the ester eliminated has a low volatility and no unpleasant odor. In one preferred embodiment of the invention, component III may be obtained by reaction of the trimer (i.e. isocyanurate) of 1,6-hexamethylene diisocyanate with a hydroxyfunctional polyester, especially a polyadipate having a melting range of no more than 100° C. In another embodiment of the invention, 1,3-bis-(isocyanato-organo)-2,4-dioxo-1,3-diazetidines or 3,5-bis-(isocyanato-organo)-2,4,6-trioxotetrahydro-1,3,5-oxadiazines, such as, e.g., the adduct of 2 moles 1,6-hexamethylene diisocyanate and 1 mole carbon dioxide, may also be used as blocked polyisocyanates.

1. customcleavage temperatures (less than 150° C.)