Process for stabilizino an aqueous formaldehyde solution

Claim 1

PROCESS FOR PREPARING A CONCENTRATED FORMALDEHYDE SOLUTION, SUITED AS STARTING MATERIAL IN THE PREPARATION OF FORMALDEHYDE-CYANURIC ACID SYNTHETIC RESINS, BY ABSORPTION OF FORMALDEHYDE FROM FORMALDEHYDE CONTAINING GAS IN AN ABSORPTION SYSTEM COMPRISING MORE THAN ONE ABSORPTION STAGES WHEREIN THE FORMALDEHYDE GAS IS PASSED INTO A FIRST STAGE THROUGH WHICH AN AQUEOUS ABSORPTION LIQUID IS CIRCULATED COMPRISING IN ADDITION TO 15-60% BY WEIGHT OF WATER, FORMALDEHYDE AND CYANURIC ACID IN THE RATIO OF 3-8 MOLES OF FORMALDEHYDE PER MOLE OF CYANURIC ACID, A PORTION OF THIS CIRCULATING SOLUTION BEING DISCHARGED CONTINUOUSLY FROM THE SYSTEM TO GIVE THE DESIRED PRODUCT WHEREIN THE AMOUNT OF DISCHARGED SOLUTION IS SUCH THAT THE AMOUNT OF FORMALDEHYDE ENTRAINED THEREIN PER UNIT TIME CORRESPONDS TO THE QUANTITY OF GASEOUS FORMALDEHYDE SUPPLIED TO SAID FIRST STAGE AND WHEREIN FORMALDEHYDE GAS NOT ABSORBED IN THE FIRST STAGE IS SUBSEQUENTLY ABSORBED IN A FINAL ABSORPTION STAGE BY MEANS OF A CONTINUOUS FLOW OF WATER RUNNING IN COUNTERFLOW TO THE GAS AND CYANURIC ACID IS ADDED TO THE RESULTING SOLUTION IN AN AMOUNT SUCH THAT PER UNIT TIME THE AMOUNT OF ADDED CYANURIC ACID CORRESPONDS WITH THE AMOUNT OF ACID DISCHARGED IN THE DESIRED PRODUCT RECOVERED FROM THE FIRST STAGE, THE RESULTING MIXTURE OF FORMALDEHYDE, CYANURIC ACID AND WATER BEING ADDED AS MAKE-UP LIQUID TO THE LIQUID CIRCULATING THROUGH THE FIRST STAGE.