The polyalkylene imine that is'employed is a lower alkyl substitute of polyethylene imine, that is a polyethylene imine in which one or more of the hydrogens is substituted by a lower alkyl, such as a one to three carbon alkyl radical, such. as methyl, ethyl, and n-propyl or isopropyl and including the substitution derivatives in which one or more alkyl hydrogen is substituted by a bath compatible