Patent ID: 7872088

Claim:
A method for preparing an aqueous binder, said method comprising: (a) selecting an aqueous resole resin having a pH greater than about 7, said resin prepared by reacting phenol with excess formaldehyde under alkaline conditions, wherein the free formaldehyde content of the resole resin is about 7.5% by weight, based on the total weight of the resole resin; (b) adding to said aqueous resole resin and reacting therewith aqueous urea in an amount to produce a premix containing about 70 parts by weight of resole resin solids and about 30 parts by weight of urea solids, wherein the free formaldehyde content of the premix is about 0.5% by weight, based on the total weight of the premix; (c) mixing into said premix a melamine-containing resin and aqueous urea such that resole resin solids, urea solids, and melamine solids are present in said aqueous binder in the range from about 45 to about 50 parts by weight, about 35 to about 45 parts by weight, and about 10 to about 15 parts by weight, respectively, based on the total of resole resin solids, urea solids, and melamine solids; and (d) mixing into said premix a latent acid catalyst, wherein said catalyst is generated in situ in said premix from aqueous ammonia and an aqueous organic acid.