Production of solutions of formaldehyde-urea reaction products

Claim 1

THE PROCESS FOR THE PRODUCTION OF A STABLE, AQUEOUS SOLUTION OF FORMALDEHYDE-UREA REACTION PRODUCTS WHICH COMPRISES INCORPORATING WITH AN AQUEOUS FORMALDEHYDE SOLUTION CONTAINING FROM 30% TO 50% BY WEIGHT FORMALDEHYDE, AT A TEMPERATURE NO HIGHER THAN 60* C., UREA IN AMOUNT SUCH THAT THE RESULTING MIXTURE CONTAINS A MOL RATIO OF 4.4 TO 7.3 MOLS FORMALDEHYDE FOR EVERY 1 MOL UREA, ADJUSTING THE PH OF THE REACTION MIXTURE THUS PREPARED TO WITHIN THE RANGE PH 8.8 TO 9.5 AND THEREAFTER HEATING SAID REACTION MIXTURE AT TEMPERATURE IN THE RANGE 30* C. TO 60* C. FOR AT LEAST 15 MINUTES, THEREAFTER EVAPORATING WATER FROM SAID MIXTURE BY SIMPLE DISTILLATION AT TEMPERATURES IN THE RANGE OF ABOUT 45* TO 60* C. UNDER REDUCED PRESSURE BELOW ATMOSPHERIC AT WHICH WATER IS VAPORIZED FROM THE MIXTURE UNTIL THE LIQUID RESIDUE OF THE EVAPORATION CONTAINS 60% TO 90% BY WEIGHT TOTAL SOLIDS, THE PERIODS OF TIME OF INITIALLY HEATING THE REACTION MIXTURE AND THEREAFTER OF EVAPORATING WATER THEREFROM BEING SO CORRELATED WITH THE TEMPERATURE AT WHICH THE REACTION MIXTURE IS INITIALLY HEATED THAT WHEN THE PERIOD OF EVAPORATION AT 45* TO 60* C. IS SUBSTANTIALLY LESS THAN ONE HOUR, THE REACTION MIXTURE IS INITIALLY HEATED FOR A PERIOD OF AT LEAST 15 MINUTES AT ABOUT 50* TO 60* C. AND FOR PROGRESSIVELY LONGER PERIODS AT LOWER TEMPERATURES WHICH INCREASE TO AT LEAST ABOUT 30 MINUTES AT TEMPERATURES OF 30* TO ABOUT 35* C., WHEN SAID REACTION MIXTURE CONTAINS A CONCENTRATION OF FORMALDEHYDE, UREA AND WATER SUCH THAT THE FORMALDEHYDE-WATER RATIO IS GREATER THAN 0.67:1, FURTHER LIMITING THE TIME OF HEATING IT AT TEMPERATURE IN THE RANGE 30* TO 60* C., INCLUDING THE TIME IT IS AT SAID TEMPERATURE WHILE EVAPORATING WATER THEREFROM, TO NO MORE THAN ABOUT 14 HOURS, AND DURING SAID EVAPORATION OF WATER LIMITING THE LOSS OF FORMALDEHYDE FROM THE LIQUID UNDERGOING DISTILLATION BY RAPIDLY DISTILLING SAID LIQUID TO FORM A RESIDUE CONTAINING 4.0 TO 6.5 MOLS FORMALDEHYDE FOR EVERY 1 MOL UREA.