Process for producing synthetic tannins by dehydrating and sulfonating a novolak resin in a vacuum

Claim 1

A PROCESS FOR PRODUCING SYNTHETIC TANNINS WHICH COMPRISES DEHYDRATING A PHOSPHORIC ACIDCATALYST NOVOLAK RESIN OF 1 MOLECULAR PROPORTION OF PHENOL AND 0.65 TO 0.75 MOLECULAR PROPORTION OF FORALDEHYDE BY HEATING THE RESIN AT A PRESSURE BETWEEN ABOUT 38 AND 42 MILLIMETERS OF MERCURY (ABSOLUTE PRESSURE) UNTIL THE TEMPERATURE OF THE RESIN IS BETWEEN 90 AND 100* C., ADDING COMMERCIAL SULFURIC ACID OF 93% STRENGTH TO THE RESIN GRANUALLY AND CONCURRENTLY MAINTAINING THE REACTION MASS AT A PRESSURE BETWEEN ABOUT 38 AND 42 MILLIMETERS OF MERCURY (ABSOLUTE PRESSURE) AND ALSO MAINTAINING THE TEMPERATURE OF THE REACTION MASS BETWEEN 90 AND 100* C. UNTIL THE RESIN CONTAINS FROM 0.3 TO 0.35 MOL OF COMBINDED SO3 PER MOL OF PHENOL, THE AMOUNT OF ACID ADDED BEING 0.4 TO 0.5 MOLS OF SULFURIC ACID (CALCULATED AS 100% ACID) FOR EACH MOL OF PHENOL, ALLOWING THE PRESSURE SURROUNDING THE RESIN TO RISE TO THE PREVAILING ATMOSPHERIC PRESSURE AND SUBSTANTIALLY CONCURRENTLY ADDING BETWEEN 40 AND 150% BY WEIGHT OF WATER, BASED ON THE WEIGHT OF THE NOVALAK RESIN, SAID WATER BEING AT A TEMPERATE BETWEEN 75 AND 95* C., AND THEN NEUTRALIZING THE RESULTING MIXTURE WITH AN AQUEOUS SOLUTION OF AN ALKALINE SUBSTANCE AND AN ORGANIC ACID BUFFER TO FORM A SOLUTION HAVING A PH BETWEEN ABOUT 3 TO 4.7.