FLEXIBLE POLYUREA SEALANT COMPOSITIONS
Disclosed are polyurea compositions and methods for using such composition as sealants, such as construction sealants.
1 . A sealant composition comprising:
(A) a component comprising a polyisocyanate; and
(B) a component comprising:
(B1) a polyaspartic ester and/or polyether diol, and
(B2) a blend of at least two different polyetheraspartic esters each having the formula (VI):
wherein X is the residue of a polyether polyamine and has a repeat unit of the structure:
wherein m is different in each polyetheraspartic ester and wherein m is in the range of 2 to 35.
2 . The sealant composition according to claim 1 , wherein the polyisocyanate comprises a 2,4- and/or 4,4′-diphenylmethane diisocyanate terminated polyether prepolymer based on polypropylene ether glycol having an isocyanate content of greater than 12.5%.
3 . The sealant composition according to claim 2 , wherein the isocyanate content is greater than 16%.
4 . The sealant composition according to claim 1 , wherein (B) comprises a polyoxypropylene diol having a molecular weight of 2500 to 5000.
5 . The sealant composition according to claim 1 , wherein (B) comprises a polyaspartic ester of the formula:
wherein: n is an integer of 2 to 6; Z represents an aliphatic residue; and R 1 and R 2 represent the same or different organic groups and are inert to isocyanate groups under reaction conditions.
6 . The sealant composition according to claim 1 , wherein (B1) comprises a polyaspartic ester selected from the group consisting of formulae (III), (IV) and (V):
7 . The sealant composition according to claim 6 , wherein (B) further comprises a polyether diol.
8 . The sealant composition according to claim 7 , wherein a relative weight ratio of the polyether diol to the polyaspartic ester in the mixture is 1:1: to 1:2.
9 . The sealant composition according to claim 6 , wherein the polyaspartic ester is present in component (B) in an amount 30 to 50 percent by weight, based on the total weight of reactants in component (B).
10 . The sealant composition according to claim 1 , wherein a ratio of isocyanate groups of component (A) to isocyanate-reactive groups of component (B) is 1:1 to 1.5:1.