Dihydroxyalkyl substituted polygalactomannan, and methods for producing and using the same

A method for making a non-hydrophobically modified dihydroxypropyl- and cationic-substituted-polygalactomannan comprising:

• a) combining an aqueous caustic solution with polygalactomannan comprising mannose and galactose at a molar ratio of mannose to galactose of at least about 2.0:1 to form a first mixture wherein at least a portion of the polygalactomannan is alkalized;
• b) adding a compound selected from the group consisting of 3-chloro-1,2-propanediol, 3-bromo-1,2-dihydroxypropanediol, 3-iodo-1,2-dihydroxypropanediol, 3-tosyl-1,2-dihydroxypropanediol, 3-chloro-2-hydroxypropyl phenyl/alkyl ether, 2,3-epoxy propyl phenyl ether, glycidol, and combinations thereof, to the first mixture to form a second mixture;
• c) heating the second mixture to a temperature of from about 40° C. to about 140° C. for a period of about 1 to about 4 hours to substitute at least one dihydroxypropyl moiety onto the polygalactomannan to form the dihydroxypropyl-substituted-polygalactomannan;
• d) cooling the second mixture to a temperature of from about 10° to about 60° C. and adjusting the pH of the second mixture to about 6.0 to 8.5;
• e) recovering the dihydroxypropyl-substituted-polygalactomannan from the second mixture;
• f) combining the dihydroxypropyl-substituted-polygalactomannan with a second aqueous caustic solution wherein at least a portion of the dihydroxypropyl-substituted-polygalactomannan is alkalized to form a third mixture;
• g) adding a cationic compound to the third mixture to form a fourth mixture;
• h) heating the fourth mixture to a temperature of from about 30° C. to about 100° C. for a period of about 1 to about 4 hours to substitute at least one cationic moiety onto the dihydroxypropyl-substituted-polygalactomannan to form a cation-and-dihydroxypropyl-substituted-polygalactomannan;
• i) cooling the fourth mixture to a temperature of from about 10° C. to about 50° C. and adjusting the pH of the fourth mixture to about 6.0 to 8.5;
• and
• j) recovering the cation-and-dihydroxypropyl-substituted-polygalactomannan from the fourth mixture.