Hydrolysis kinetics of terephthalic and 5‐sulfonatoisophthalic acid esters

Abstract

The saponification reaction of bis(2-hydroxyethyl) terephthalate (3) and sodium 3,5-bis(2-hydroxyethoxycarbony1)benzenesulfonate (6) was followed under pH-stat conditions in the alkaline pH range (pH 8 to 10 at 50 to 80°C) to determine the consecutive reaction rate constants for the hydrolysis of the diesters and the intermediate monoesters. The observed overall reaction rate constants were split into the individual rate constants for the hydrolysis catalyzed by the solvent, the O H -ions, the SO; groups and the COOgroups (ko. koH -, ksos. kroo-. respectively). No intermolecular catalysis by either the sulfonato or the carboxylato groups and no "autocatalysis" by the solvent was found. The activation parameters for the hydrolysis of the corresponding esters of both acids are equal; for the diesters 3 and 6: AH+=73,7 (72,O) kJ mol-' [17,6 (17,2) kcal mol-'1, AG*= 103,8 (104,7) kJ mol-' [24,8 (25,O) kcal mol-'1, AS* = -89,6 (-97,6) J mol-' K -' [-21,4(-23,3) cal mol-' K-'1; for the monoesters [terephthalic acid mono(2-hydroxyethyl) ester and 5-sodiumsulfonatoisophthalic acid mono(2-hydroxyethyl) ester]: AH*=80,4 (78,7) kJ mo1-l [19,2 (18,8) kcal mol-'1, AG+=109,3 (109,7)cal mo1-l K-'1. It is concluded that disorders in the fine structure of polyester fibers modified with sulfonato group containing comonomers may primarily be responsable for their lower hydrolytic stability and not any catalytic effects of these groups.kJ mol-' [26,1 (26,2) kcal mol-' 1, AS* = -86,3 (-93,O) J mol-' K ' [ -20,6 (-22,2) ZUSAMMENFASSUNG:Die Kinetik der Verseifungsreaktion von Terephthalsaure-bis(2-hydroxyathy1)ester (3) und Natrium-3,5-bis(2-hydroxyathoxycarbonyl)benzolsulfonat (6) wird mit Hilfe der pHstat-Technik im alkalischen pH-Bereich gemessen (pH 8 bis 10 bei 50 bis SO'C), um *) 14th communication in the series ,,Synthesefasern in der Wollindustrie"; for 13th communication see: V. Rossbach, H. Miiller, D. Nissen, Textilveredlung 9, 339 (1974).

Preparation and hydrolytic degradation of sulfonated poly(ethylene terephthalate) copolymers

“…Two groups of factors, one of chemical nature and the other related to the accessibility of the polymer to water were considered: (a) the ester hydrolysis reaction rate is higher in the sulfonated polyester due to the inductive and/or catalytic effect exerted by the sodio sulfonate group, and (b) the hydrolytic stability of the sulfonated polyester is lower because of the greater hydrophilicity, the lower crystallinity, and the high polarity of the ionic aggregated microdomains of these copolymers, all facilitating the penetrability of water. Grobe et al [14] reported that the inductive effect of the Na-SI group should be ignored since BHET and BHESI have the same hydrolysis rates under alkaline conditions. Chisholm et al [13] reached to similar conclusions from hydrolysis experiments carried out on DMT and Na-DMSI.…”

Study on degradation reactions in polyethylene terephthalate containing 5‐sulpho isophthalyl moieties

“…The copolymer structure breaks up the regularity of repeating ethylene terephthalate units of PET thereby inhibiting the formation of crystalline regions during fiber manufacture. These copolymers are known to be hydrolytically less stable compared with the homopolymer—polyethylene terephthalate 9, 10. The presence of isophthalate comonomer units also promote thermal degradation through increased chain flexibility and more favorable bond angles in the polymer chain.…”

“…These copolymers are known to be hydrolytically less stable compared with the homopolymer-polyethylene terephthalate. 9,10 The presence of isophthalate comonomer units also promote thermal degradation through increased chain flexibility and more favorable bond angles in the polymer chain.…”

The accessibility of sulphonic acid groups in basic dyeable polyester fibers. I. The prevention of fiber hydrolysis during dyeing

“…The course taken in the development of satisfactory dyeing conditions for experimental purposes is indicated in the experimental sections below. 4 denier semidull fibers with a staple length of 5 cm were supplied by E. I. Du Pont de Nemours Inc. (Leicester U.K. Division).…”