Method for forming an adhesive layer using hydrophilic polyurethanes related applications

A method for forming an adhesive layer on a substrate which comprises:

• applying to the substrate a nonlonic, water-soluble polyurethane consisting essentially of the groups:
• (a) —O—(OH2—OH2 O—)n, wherein n is a number of 8-500;
• (b) —CO—NH—X—NH—CO— wherein X is an aliphatic or cycloeliphatic group;
• and
• (c) —O—Y—O—, wherein Y comprises a hydrophobic moiety selected from the group consisting of
• (—CH2—CH(CH3)—O)m—CH2—CH(CH3)—,
• (CH2 CH(C2H5)—O)m—CH2—CH(C2H5)—,
• (CH2—CH2—CH2—CH2 O)m—CH2 CH2 CH2 CH2—,
• alkylene groups having from 2 to 44 carbon atoms, cyoloalkylene groups having from 6 to 44 carbon atoms and mixtures thereof wherein m is a number of 8 to 500, the nonionic polyurethane forms a homogenous mixture with water;
• the mixture having a specific viscosity of at least 0.4 at a 1% by weight solution in water at 20° C. wherein (c) comprises from 2% to 40% by weight, based on (a)+(c) of the polyurethane and wherein at least one of the following conditions is met:
• (i) the nonionic polyurethane is soluble in water at any mixing ratio at 20° C.;
• (ii) n is 20 to 300 and m is 20 to 300
• (iii) (c) comprises residues of a diol having a solubility in water not greater than 2 grams/100 grams of water;
• (iv) the equivalent ratio of (a) to (c) is greater than 1:1;
• (v) (c) comprises a hydrophobic polyoxyalkylene moiety wherein the alkylene group contains 3 or 4 atoms.