. . "Specifically, the polyether diamine of the formula (2) may, for example, be a polyoxypropylene diamine (a compound wherein R1 and R2 are propylene groups and m is at least 1), polyoxyethylene diamine (a compound wherein R1 and R2 are ethylene groups and m is at least 1), or 4,7,10-trioxa-tridecane-1,13-diamine (a compound wherein R1 is an ethylene group, R2 is a trimethylene group and m is 2)." . . .