Methods of concentrating solutions

Claim 1

A METHOD OF PREPARING A CLEAR, CONCENTRATED SOULUTION OF HYDROPHILIC METHYL ETHERS OF MELAMINE-FORMALDEHYDE OR METHYL ETHERS OF UREA-FORMALDEHYDE CONDENSATION PRODUCTS WHICH COMPRISES HEATING UNDER CONDITIONS OF TURBULENT FLOW AN ALKALINE REACTING SOLUTION CONSISTING ESSENTIALLY OF WATER, FREE FORMALDEHYDE, UNREACTED METHYLATING AGENT AND LESS THAN 70% BY WEIGHT OF SOLIDS WHICH CONSISTS ESSENTIALLY OF A HYDROPHILIC CONDENSATION PRODUCT SELECTED FROM THE GROUP CONSISTING OF HYDROPHILIC METHYL ETHERS OF MELAMINE-FORMALDEHYDE CONDENSATION PRODUCTS,HYDROPHILIC METHYL ETHERS OF UREA-FORMALDEHYDE CONDENSATION PRODUCTS AND MIXTURES OF SUCH CONDENSATION PRODUCTS, TO A TEMPERATURE OF AT LEAST 100* C BUT NOT IN EXCESS OF 125* C. UNTIL THE SOLUTION IS CONCENTRATED TO A SOLIDS CONTENT OF ABOUT 70 TO 95% BY WEIGHT WITHIN A PERIOD OF 5 MINUTES WHILE MAINTAINING THE INTERFACE OF THE SOLUTION IN INTIMATE CONTACT WITH THE VAPORS EVOLVED FROM THE SOLUTION DURING THE HEATING PERIOD, DISCONTINUING THE HEATING OF THE SOLUTION BEFORE THE REACTION PRODUCT IS CONVERTED TO THE HYDROPHOBE STATE, SEPARATING THE SOLUTION FROM THE VAPORS IN CONTACT THEREWITH BEFORE APPRECIABLE AMOUNTS OF THE VAPOR CONDENSE, ALLOWING THE SOLUTION TO STAND FOR A PERIOD OF AT LEAST 12 HOURS AT A CONCENTRATION OF ABOUT 70 TO 85% BY WEIGHT OF SOLIDS AND THEN SEPARATING THE WATER-INSOLUBLE IMPURITIES IN THE SOLUTION FROM THE REMAINDER OF THE SOLUTION.