Urea-thiourea formaldehyde resins

Claim 1

A PROCESS FOR PREPARING A WATER-SOLUBLE RESINOUS PRODUCT, SAID PROCESS COMPRISING REACTING IN AQUEOUS MEDIUM RELATIVE PROPORTIONS OF 1 MOLE OF UREA WITH FROM 1.5 TO 2.4 MOLES OF FORMALDEHYDE AT A PH OF 7 TO 10, AND AT A TEMPERATURE BETWEEN 70* AND 100*C. FOR 0.25 TO 2.0 HOURS, ADJUSTING THE PH OF THE REACTION MIXTURE TO BETWEEN 4.0 TO 6.0, PARTIALLY POLYMERIZING THE UREA-FORMALDEHYDE CONDENSATE AT TEMPARATURE OF 70* TO 100*C. UNTIL THE VISCOSITY AT 25*C. OF A RESIN SOLUTION CONTAINING 40-60% SOLIDS IS 25-40 CENTIPOISES, ADJUSTING THE PH TO BETWEEN 7.2 AND 9.0, CONCENTRATING THE REACTION MIXTURE TO A SOLIDS CONTENT OF AT LEAST 70%, ADDING BETWEEN 0.2 AND 0.6 MOLE OF THIOUREA AND REACTING SAID THIOUREA IN SAID CONCENTRATED SOLIDS AND IN THE PRESENCE OF THE PARTIALLY POLYMERIZED UREA-FORMALDEHYDE CONDENSATE REACTION MIXTURE WITH 0.7 TO 1.3 MOLES OF FORMALDEHYDE PER MOLE OF THIOUREA AT A TEMPERATURE OF 20* TO 70*C. FOR 5 TO 250 MINUTES AT A PH PH OF ABOUT 5.0-9.0.