Process for making wood laminate

Claim 2

A process according to claim 2 wherein the adhesive mixture is acidified by the addition of a salt selected from the group consisting of aluminum and ammonium salts of sulfuric, hydrochloric, and nitric acids.

Claim 3

A process according to claim 3 wherein the salt is aluminum sulfate.

Claim 4

In a process for the manufacture of plywood, wherein the wood plies are bonded by a urea-formaldehyde adhesive composition comprising a urea-formaldehyde resin and an extender, and wherein the adhesive is applied by spraying, and wherein the surface ply is less than 1/16 inch in thickness and the assembled panel prepressed prior to hot pressing, the improvement which comprises using a modified urea-formaldehyde adhesive composition in bonding the wood plies, said modified urea-formaldehyde adhesive composition being a urea-formaldehyde adhesive composition containing a phenol-formaldehyde resin in an amount of from 10 to 90 weight percent of the urea-formaldehyde resin in the adhesive, and acidified with an acid salt to a pH in the range of 5 to 7, said phenol-formaldehyde resin being condensed under alkaline conditions in a mole ratio of 0.8 to 3.0 moles of formaldehyde per mole of phenol until a 40 percent aqueous solution of the resin has a viscosity in the range of from 10 to 200 centipoises at 25* C, and said modified urea-formaldehyde adhesive composition being prepared by intermixing the constituents in an order such that the acidification and the addition of the urea-formaldehyde resin are made after the other constituents have been intermixed.

Claim 5

A process according to claim 5 wherein the phenol-formaldehyde resin is pre-condensed under alkaline conditions in a mole ratio of from 1.6 to 2.5 moles of formaldehyde per mole of phenol until the 40 weight percent aqueous solution of the resin has a viscosity in the range of 25 to 100 centipoises.

Claim 6

A process according to claim 6 wherein the adhesive mixture is acidified by the addition of aluminum sulfate prior to the addition of the urea-formaldehyde resin to the adhesive mixture.

Claim 7

A process according to claim 7 wherein the amount of phenol-formaldehyde resin added is in the range of from 25 to 40 percent of the urea-formaldehydE resin.

Claim 8

A process according to claim 7 wherein the modified urea-formaldehyde adhesive composition is prepared by intermixing the constituents in an order such that the phenol-formaldehyde resin is intermixed with constituents under alkaline conditions and subsequently the urea-formaldehyde resin is added and the adhesive acidified, said urea-formaldehyde resin being pre-condensed in a mole ratio of 0.8 to 3.0 moles of formaldehyde per mole of urea under acid conditions until the viscosity of a 65 weight percent aqueous solution of the resin has a viscosity in the range of from 100 to 1,500 centipoises at 25* C.

Claim 9

A process according to claim 9 wherein the urea-formaldehyde resin is pre-condensed until the viscosity of the 65 weight percent aqueous solution is in the range of 300 to 1,000 centipoises.