Method of controlling the particle size in the crystallization of dimethylol alkanoic acids

Abstract

Polymethylolalkanoic or monomethylolalkanoic acids of the formula (I) 1 where R are identical or different and are each a methylol group or a substituted or unsubstituted aliphatic hydrocarbon radical, are selectively crystallized to give crystals having an essentially monomodal particle size distribution. This is achieved by crystallization in a temperature range from 85° C. to 50° C. and at a cooling rate of <10 K/h, giving essentially trigonally symmetric crystals. Furthermore, polymethylolalkanoic or monomethylolalkanoic acids of the formula (I) 2 where R are identical or different and are each a methylol group or a substituted or unsubstituted aliphatic hydrocarbon radical, are selectively crystallized to give crystals having an essentially monomodal particle size distribution by carrying out the crystallization at ≦50° C. or in a temperature range from 50° C. to 5° C. and at a cooling rate of <15 K/h.

Dependencies are inferred from the claim text.