Organic Builders. XX.

Biodegradability and Building Performance of Poly (sodium β-malate)

Abstract

Poly (β-DL-malic acid) sodium salt (PMLA) with a number average molecular weight (Mn) of 30006000 was prepared by the ring-opening polymerization of benzyl malolactonate. Poly (DL-malic acid) sodium salt with both α and β ester linkages of malic acid (PMLA-D) was prepared by the direct polymerization of DL-malic acid in dimethylsulfoxide under reduced pressure at 90°C. The biodegradability of the polymer was studied under aerobic conditions using activated sludge, soil bacteria and poly (malic acid) assimilable bacteria obtained by enrichment culture techniques. The enzymatic degradation of poly (malic acid) was carried out so as to elucidate the mechanism of the biodegradation. The sequestration capacity for Ca (II) ions and dispersion capacity for MnO₂ of both these salts were determined and compared in these respects with sodium tripolyphosphste (STPP), disodium 3-oxapentanedioate (ODA) and trisodium citrate. Their building performance in detergents was also examined.
Poly (malic acid) s obtained both by ring-opening and direct polymerization showed excellent biodegradability with activated sludge and soil bacteria. The biodegradation of poly (malic acid) appeared to occur first by the enzymatic hydrolysis of the terminal ester group of the polymer by bacteria, giving monomeric malic acid. The malic acid was metabolized in an usual manner. The polymers examined in this report showed the comparable detergency building performance to that of trisodium citrate and ODA.