| abstract |
A disk stacker for inverting and stacking sheets has a stacking tray and registration member and a paddle wheel wiper having semicircular blades made of a polyurethane elastomer obtained by the reaction of a polytetramethylene ether glycol having the formula HO[(CH2)4O]nH where n is from 10 to 60, preferably 55 to 60, and from about 20 to about 95 parts preferably 22 to 26 parts, by weight per 100 parts by weight of said glycol of a diisocyanate selected from the group consisting of diphenylmethane diisocyanates, toluene diisocyanates, naphthalene diisocyanates and blends thereof and a sufficient amount of cross linking agents to provide a crosslinked elastomer, said cross linking agents comprising a mixture of from about 75% to 60% by weight of a diol having the formula HO(R1)OH where R1 is a straight or branched chain alkyl group having from 2 to 12 carbon atoms and from about 25% to 40% by weight of a triol having the formula: R'-C-[(OH)a(CH2OH)b] where R' is H, CH3 or C2H5, a is 0 or 1, b is 2 or 3 and a+b=3. |