Preparation of polycondensates of citric acid and use thereof in detergents and cleaners

Abstract

Process for preparing polycondensates of citric acid and/or isocitric acid, by converting(a) citric acid, isocitric acid or mixtures thereof in an organic solvent in the presence of a water-withdrawing agent at least partially into the anhydride form and then condensing the reaction mixture, if desired after addition of two cocondensable compounds selected from the group consisting of(b) other hydroxycarboxylic acids and/or(c) amino acids, alcohols, amines and/or at least dibasic carboxylic acids other than carboxylic acids (a) and (b), at temperatures of at least 80.degree. C. to form polycarboxylates which have an average molecular weight of at least 500, polycondensates of citric acid and/or isocitric acid obtainable thereby, anduse of said polycondensates as ingredients in phosphate-free and reduced-phosphate detergents and cleaners, and also detergents and cleaners which contain at least one surfactant and optionally builders and other customary constituents with from 0.1 to 30% by weight of an abovementioned polyestercarboxylate.

Description

Claims

1. A process for preparing polyester carboxylate polycondensates of citric acid and/or isocitric acid, which comprises converting

(a) citric acid, isocitric acid or mixtures thereof in an organic solvent in the presence of a water-withdrawing agent at least partially into the anhydride form and then condensing by esterification the reaction mixture, optionally after addition of two cocondensable compounds selected from the group consisting of

(b) other hydroxycarboxylic acids and/or

(c) amino acids, alcohols, amines and/or at least dibasic carboxylic acids other than carboxylic acids (a) and (b),

at temperatures of at least 80.degree. C. to form polycarboxylates of citric acid and/or isocitric acid which have an average molecular weight of at least 500,

said polycarboxylates of citric acid containing units of the formula I and II or branched esterification condensates thereof ##STR1## and said polycarboxylates of isocitric acid containing units of the formulae III to V or branched esterification condensates thereof ##STR2##

2. A process as claimed in claim 1, wherein the amounts used

(a) per 1 mol of citric acid and/or isocitric acid are

(b) from 0 to 100 mol % of at least one other hydroxycarboxylic acid and/or

from 0 to 40 mol % of amino acids, alcohols, amines and/or at least dibasic carboxylic acids, which differ from the carboxylic acids (a) and (b).

3. A process as claimed in claim 1, wherein the anhydride formation from the compounds of component (a) and reaction of the anhydrides with compounds (a), the anhydrides obtained from (a) and optionally (b) and/or (c) is repeated one or more times.

4. A process as claimed in any of claims 1 to 3, wherein a solution of

(a) citric acid and/or isocitric acid in acetic acid is partially converted into citric anhydride and/or isocitric anhydride at temperatures up to 80.degree. C. by the addition of acetic anhydride as water-withdrawing agent and the reaction mixture is subsequently condensed by heating to a temperature within the range from 80.degree. to 150.degree. C.

5. A process as claimed in claim 1, wherein a solution of citric anhydride or of isocitric anhydride in acetic acid is admixed with

(b) malic acid, glycolic acid, lactic acid or mixtures thereof and condensed by heating to a temperature within the range from 80.degree. to 150.degree. C.

6. A process as claimed in claim 1, wherein the condensation is carried out in the additional presence of

(c) amino acids, alcohols, amines and/or at least dibasic carboxylic acids other than carboxylic acids (a) and (b).

7. Polycondensates of citric acid and/or isocitric acid prepared by the process of claim 1.