Fast-cure polyurethane sealant composition containing silyl-substituted guanidine accelerators

A one-component, moisture-curable sealant composition comprising a mixture of

• (a) a silane-terminated polyurethane polymer of the formula ##STR12## wherein R is lower alkyl of from 1 to 6 carbon atoms;
• R.sup.1 is a divalent bridging radical selected from the group consisting of a divalent hydrocarbon radical, a divalent hydrocarbon ether radical, and a divalent hydrocarbon amino radical;
• A is selected from the group consisting of --S-- and --NR.sup.2 -- where R.sup.2 is hydrogen or alkyl of from one to six carbon atoms;
• (b) from 0.2 to 1.0 parts by weight of an aminosilane per 100 parts by weight of said silane-terminated polyurethane polymer, said aminosilane having the structure ##STR13## wherein x is an integer of from one to three;
• R.sup.3 and R.sup.4 may be the same or different and are selected from alkyl of from one to four carbon atoms;
• R.sup.5 is alkyl of from one to four carbon atoms or alkoxyl of from one to four carbon atoms;
• R.sup.6 is hydrogen or --(CH.sub.2).sub.y NHR.sup.7 wherein R.sup.7 is hydrogen or 13 (CH.sub.2).sub.z NH.sub.2 and wherein y and z may be the same or different and are integers of from one to three;
• (c) from 0.2 to 1.0 parts by weight of an accelerator per 100 parts by weight of said silane-terminated polyurethane polymer, said accelerator selected from the group consisting of compounds or mixtures thereof having the structure ##STR14## where x and R are as previously defined;
• R.sup.8, is hydrogen or ##STR15## where R.sup.3, R.sup.4, R.sup.5, and x are as defined above;
• R.sup.9 and R.sup.10 are hydrogen or, when taken together with the carbon atoms to which they are attached, form a saturated six-membered carbocyclic ring;
• and
• R.sup.11, R.sup.12, R.sup.13, and R.sup.14 are independently hydrogen or alkyl of from one to four carbon atoms.