Abstract: This invention relates generally to insolubilizers for use with binders in paper coating compositions. There is provided a process for preparing both an insolubilizer and paper coating composition containing the insolubilizer and a binder which, when applied onto paper products, significantly enhances their wet-rub resistance.The insolubilizer is prepared by:(a) forming a glyoxal-urea adduct by reacting from about 1.0 to about 4.0 moles of glyoxal with about 1.0 mole of urea, at an elevated temperature,(b) cooling the glyoxal-urea adduct to room temperature,(c) adding from about 0.5 to about 2.0 moles of free glyoxal to the glyoxal-urea adduct to form an oligomer, and(d) adjusting the pH of the oligomer to from about 5 to about 7.