Production of polymers in powdered form which contain carboxylic acid or carboxylic anhydride groups

Claim 1

A PROCESS FOR THE PRODUCTION IN POWDERED FORM OF A POLYMER CONTAINING CARBOXYLIC ACID OR CARBOXYLIC ANHYDRIDE GROUPS WHICH COMPRISES POLYMERIZING ACRYLIC ACID, METHACRYLIC ACID OR MALEIC ANHYDRIDE WITH ONE OR MORE THAN ONE OTHER MONOMERS SELECTED FROM THE GROUP CONSISTING OF STYRENE AND ESTERS OF ACRYLIC ACID AND METHACRYLIC ACID WITH ALCOHOLS OF THE STRUCTURE HO-CH2-R WHEREIN R IS HYDROGEN, ALKYL OF FROM ONE TO FIVE CARBONS, BENZYL, CH2-NR2 OR CH2-CH2NR2, IN SUCH AMOUNTS THAT THE RESULTING COPOLYMERS CONTAIN FROM 5 TO 40% BY WEIGHT OF THE MONOMERS CONTAINING CARBOXYLIC ACID GROUPS OR FROM 10 TO 50% BY WEIGHT OF MALEIC ANHYDRIDE, SAID POLYMERIZATION BEING CONDUCTED AT A TEMPERATURE OF FROM 70* TO 150*C AND IN THE PRESENCE OF AN ALCOHOL OR HYDROCARBON AUXILIARY LIQUID HAVING A BOILING OF FROM 70* TO 150*C, WHEREIN THE RATIO BY WEIGHT OF MONOMERS TO AUXILIARY LIQUID IS FROM 0.5:1 TO 1.5:1, AND WHEREIN THE SURFACE AREA OF THE MIXTURE IN THE REACTION ZONE IS INCREASED BY MECHANICAL STIRRING TO AT LEAST TWENTY TIMES THAT OF THE UNSTIRRED MIXTURE AND DISTILLING OFF THE AUXILLIARY LIQUID WHILE STIRRING AFTER THE MIXTURE HAS REACHED A VISCOSITY OF AT LEAST 20,000 CENTIPOISES MEASURED AT 20*C.