Process for producing concentrated urea-formaldehyde solutions by absorbing gaseous formaldehyde in aqueous urea solutions

Claim 1

A PROCESS FOR ABSORBING GASEOUS FORMALDEHYDE FROM A GASEOUS MEDIUM WHICH IS INERT TO A MIXTURE OF UREA AND FORMALDEHYDE WHICH CONTAINS FORMIC ACID VAPOR TO RESULT IN A HIGH ABSORPTION YIELD, COMPRISING THE STEPS OF FEEDING AN AQUEOUS UREA SOLUTION IN A MULTIPLE SERIES OF ABSORPTION STAGES OF DIMINISHING CONCENTRATION OF FORMALDEHYDE IN SAID MEDIUM SO AS TO FORM METHYLOL-UREAS IN AQUEOUS SOLUTION, SAID UREA SOLUTION BEING FED IN COUNTER-CURRENT FLOW TO SAID MEDIUM CONTAINING THE FORMALDEHYDE AT A TEMPERATURE OF FROM 30* TO 80*C, AND AT A PH OF SAID SOLUTION FROM 7 TO 9, MAINTAINING SAID TEMPERATURE RANGE AND PH VALUE IN THE AQUEOUS SOLUTION IN THE SUCCESSIVE STAGES, AND CONTINUOUSLY ABSORBING THE FORMALDEHYDE FROM SAID MEDIUM BY DISSOLVING IT INTO THE AQUEOUS UREA SOLUTION IN THE SUCCESSIVE STAGES WHEREBY METHYLOL-UREA IS PRESENT IN THE SOLUTION AT THE ABSORPTION STAGE, THE MOLAR RATIO OF UREA FED TO FORMALDEHYDE FED BEING MAINTAINED BETWEEN 1:4 AND 1:10.