Making paper using a modified ureaformaldehyde resin

Claim 2

IN A PROCESS FOR THE MANUFACTURE OF PAPER HAVING IMPROVED STRENGTH PROPERTIES THE STEPS WHICH COMPRISE IMPREGNATING CELLULOSIC PAPER MATERIAL WITH FROM 0.5% TO ABOUT 25%, BASED ON THE DRY WEIGHT OF THE PAPER, OF A UREA-FORMALDEHYDE CONDENSATION PRODUCT, MODIFIED WITH HEXAMETHYLENE DIAMINE, SHEETING THE RESULTING MIXTURE, AND POLYMERIZING THE SAID CONDENSATION PRODUCT IN THE SHEET IN THE PRESENCE OF AN ACIDIC UREA-FORMALDEHYDE POLYMERIZATION CATALYST, SAID MODIFICATION WITH HEXAMETHYLENE DIAMINE RESULTING FROM THE ADDITION OF HEXAMETHYLENE DIAMINE TO UREA-FORMALDEHYDE PRIOR TO POLYMERIZATION, THE QUANTITY OF HEXAMETHYLENE DIAMINE BEING FROM 5 TO 30 PARTS BY WEIGHT PER 100 PARTS OF COMBINED UREA AND FORMALDEHYDE, SAID IMPREGNATING BEING ACCOMPLISHED BY ADMIXING THE CELULOSIC PAPER MATERIAL WITH A LIQUID COMPOSITION IN WHICH THE SOLE FORMALDEHYDE-REACTIVE RESIN-FORMING INGREDIENTS ARE UREA AND HEXAMETHYLENE DIAMINE.

Claim 3

IN A PROCESS FOR PREPARING A PAPER-TREATING COMPOSITION WHICH IS USEFUL AS AN IMPREGNATING AGENT FOR IMPARTING HIGH WET-STRENGTH TO PAPER THE STEPS WHICH COMPRISE ADMIXING 5 TO 30 PARTS BY WEIGHT OF HEXAMETHYLENE DIAMINE WITH 100 PARTS BY WEIGHT OF UREA-FORMALDEHYDE IN AN AQUEOUS MEDIUM WHILE CONTROLLING THE PH SO THAT IT DOES NOT DROP BELOW 3, THE PH OF THE UREA-FORMALDEHYDE COMPOSITION BEING INITIALLY WITHIN THE RANGE OF 7.0 TO 9.0, SAID UREA-FORMALDEHYDE COMPOSITION BEING A CLEAR STABLE LIQUID OBTAINED BY LIQUEFYING AMIXTURE OF GASEOUS FORMALDEHYDE AND WATER VAPOR HAVING A TEMPERATURE ABOVE 90* C. BY COOLING TO A TEMPERATURE OF 60* TO 90* C., THE WEIGHT OF THE FORMALDEHYDE BEING FROM 50% TO 70% OF THE WEIGHT OF THE RESULTANT AQUEOUS LIQUID MIXTURE, KEEPING THE TEMPERATURE OR THE SAID AQUEOUS LIQUID CONTINUOUSLY AT 60* TO 90* C. UNTIL THE SAID LIQUID IS BROUGHT INTO CONTACT WITH UREA, ADMIXING UREA WITH THE SAID LIQUID IN THE PRESENCE OF A BUFFER WHICH MAINTAINS THE PH WITHIN THE RANGE OF 7.0 TO 9.0, THE AMOUNT OF THE SAID UREA BEING IN THE PROPORTION OF 1 MOL PER 4.5 TO 7 MOLS OF THE SAID FORMALDEHYDE, AND MAINTAINING THE TEMPERATURE OF THE RESULTANT LIQUID AT LEAST MOMENTARILY AT FROM 70* TO 90* C., WHEREBY THE SAID CLEAR STABLE UREA-FORMALDEHYDE LIQUID COMPOSITION IS OBTAINED, THE FORMALDEHYDE: UREA MOL RATIO IN THE SAID COMPOSITION BEING ADJUSTED TO FROM 1.5:1 TO 3:1 BY ADDITION OF UREA PRIOR TO THE ADDITION OF THE HEXAMETHYLENE DIAMINE.

Claim 4

IN A PROCESS FOR PREPARING A PAPER-TREATING COMPOSITION WHICH IS USEFUL AS AN IMPREGNATING AGENT FOR IMPARTING HIGH WET-STRENGTH TO PAPER THE STEPS WHICH COMPRISE ADMIXING 5 TO 30 PARTS BY WEIGHT OF HEXAMETHYLENE DIAMINE WITH 100 PARTS BY WEIGHT OF UREA-FORMALDEHYDE IN AN AQUEOUS MEDIUM WHILE CONTROLLING THE PH SO THAT IT DOES NOT DROP BELOW 3, THE PH OF THE UREA-FORMALDEHYDE COMPOSITION BEING INITIALLY WITHIN THE RANGE OF 7.0 TO 9.0, SAID UREA-FORMALDEHYDE COMPOSITION BEING A CLEAR STABLE LIQUID OBTAINED BY LIQUEFYING AMIXTURE OF GASEOUS FORMALDEHYDE AND WATER VAPOR HAVING A TEMPERATURE ABOVE 90* C. BY COOLING TO A TEMPERATURE OF 60* TO 90* C., THE WEIGHT OF THE FORMALDEHYDE BEING FROM 50% TO 70% OF THE WEIGHT OF THE RESULTANT AQUEOUS LIQUID MIXTURE, KEEPING THE TEMPERATURE OR THE SAID AQUEOUS LIQUID CONTINUOUSLY AT 60* TO 90* C. UNTIL THE SAID LIQUID IS BROUGHT INTO CONTACT WITH UREA, ADMIXING UREA WITH THE SAID LIQUID IN THE PRESENCE OF A BUFFER WHICH MAINTAINS THE PH WITHIN THE RANGE OF 7.0 TO 9.0, THE AMOUNT OF THE SAID UREA BEING IN THE PROPORTION OF 1 MOL PER 4.5 TO 7 MOLS OF THE SAID FORMALDEHYDE, AND MAINTAINING THE TEMPERATURE OF THE RESULTANT LIQUID AT LEAST MOMENTARILY AT FROM 70* TO 90* C., WHEREBY THE SAID CLEAR STABLE UREA-FORMALDEHYDE LIQUID COMPOSITION IS OBTAINED, THE FORMALDEHYDE: UREA MOL RATIO IN THE SAID COMPOSITION BEING ADJUSTED TO FROM 1.5:1 TO 3:1 BY ADDITION OF UREA PRIOR TO THE ADDITION OF THE HEXAMETHYLENE DIAMINE.