Process for the preparation of aluminum oxide carboxylate polymers containing at most two percent by weight of ester

A process for the preparation of an aluminum oxide carboxylate polymer of the Formula (I) ##STR6## wherein X is an organic acid radical of a C.sub.8 to C.sub.22 aliphatic monocarboxylic acid;

• and
• n is a number that is at least 16 designating the degree of polymerization, said aluminum oxide carboxylate polymer containing not more than 2% by weight of an ester by-product, which comprises the steps of:
• (a) providing a solution of a C.sub.8 to C.sub.22 aliphatic monocarboxylic acid and water in a C.sub.2 to C.sub.5 alkanol;
• (b) introducing a solution of an aluminum alkoxide of the Formula
• wherein
• R is C.sub.2 to C.sub.5 alkyl, dissolved in an aromatic or aliphatic hydrocarbon, into a tank reactor kept under a pressure of 0.2 to 0.7.times.10.sup.5 Pa, wherein the aromatic or aliphatic hydrocarbon must have a boiling point that is at least 80.degree. C. higher than the boiling points of each of the C.sub.2 to C.sub.5 alkanol used as a solvent for the carboxylic acid and for the C.sub.2 to C.sub.5 alkanol which corresponds to the alkoxide component of the aluminum alkoxide;
• (c) leading, as a circulated flow at a temperature exceeding by 15.degree. to 50.degree. C. the boiling point of the higher boiling alcohol between the first C.sub.2 to C.sub.5 alkanol employed as the solvent in step (a) and the second C.sub.2 to C.sub.5 alkanol corresponding to the alkoxide component of the aluminum alkoxide employed according to step (b), the solution of the aluminum alkoxide to a tube reactor having a 10 to 200 length/diameter ratio and connected to the tank reactor;
• (d) simultaneously to step (c), feeding into the tube reactor the solution of the C.sub.8 to C.sub.22 aliphatic monocarboxylic acid and water in a C.sub.2 to C.sub.5 alkanol to react same with the solution of the aluminum alkoxide, whereby the aluminum/monocarboxylic acid molar ratio is at least 10:1 to form a foam phase reaction mixture containing the aluminum oxide carboxylate polymer of the Formula (I) and the C.sub.2 to C.sub.5 alkanols;
• (e) leading the foam phase reaction mixture obtained in step (d) through the tube reactor at a rate of 1 to 10 m/sec back to the tank reactor and stirring said foam phase reaction mixture;
• (f) removing the alkanols from the reaction mixture;
• (g) returning the reaction mixture to the tube reactor;
• (h) repeating steps (a) through (g) until the monocarboxylic acid/aluminum molar ratio reaches 0.95 to 1.05 and the water/aluminum molar ratio reaches 0.9 to 1.0 in the tank reactor;
• and
• (i) removing any additional alkanol present to obtain the desired product.