Polyesters ester interchange method

Polyesters are made in one of two ways by either direct reaction of a diacid and a diol or ester interchange of a diester and a diol. By far the most commercially useful polyester is poly(ethylene terephthalate) (PET). Both methods are illustrated here. 

Introduction of these photocrosslinkable structures in macro-molecular chains can be performed by esterification of hydroxyla-ted polymers with cinnamoyl chloride. Cellulose Q).condensation products (4, ) and mainly poly(vinyl alcohol) have Been treated( by this method. Other chemical modifications have been studied as ester interchange of poly(vinyl acetate) 7) and Knoevenagel reaction on polyesters (8). Very few results on the synthesis of such photocrosslinkable polymers by polymerization have been reported. Therefore free radical polymerization of cinnamic acid vinyl derivatives did not lead to the expected polymers, but to insolubilization reactions. Howewer cationic procedure can be a good way in some cases since Kato et al. could polymerize by this way with high yields p-vinyl phenylcinnamate (9) and B-vinyloxyethyl cinnamate (10). 

Polyesters were historically the first synthetic condensation polymers studied by Carothers in his pioneering work in the early 1930s. Commercial polyesters [30] were manufactured by polycondensation reactions, the methods commonly used being melt polymerization of diacid and diol, ester interchange of diester and diol, and interfacial polymerization (Schotten-Baumann reaction) of diacid chloride and diol. In a polycondensation reaction a by-product is generated which has to be removed as the reaction progresses. 

The polymerization step is chosen appropriate to the monomers used and products produced. Solution pol3nnerization, interfacial condensation, and ester interchange can be used to produce polyesters for example. References 27 and 29 should be consulted to locate specific reaction conditions and methods for a given polymer class. 

Polycarbonate resin (PC) n. Any of a family of special polyesters in which groups of dihydric phenols are joined through carbonate linkages. They can be produced by a variety of methods, of which the most commercially important are (1) Phosogen-eration of dihydric alcohols, usually bisphenol A. (2) Ester interchange between... 

Whinfield and Dixon, in UK, developed polyethylene terephthalate fibers (Dacron, Terylene). This first Dacron polyester plant went into operation in 1953. Ester interchange (also known as ester exchange or alcoholysis) was once the preferred method for making polyethylene terephthalate (PET) because... 

TPEs associating both rigid and soft polyester blocks have also been described. They cannot be obtained by the melt polyesterification used for polyesterether TPEs, since interchange reactions would yield random—rather than block — copolyesters. The preferred method involves the reaction of OH-terminated aliphatic and aromatic-aliphatic polyesters with chain extenders such as diisocyanates and results in copoly(ester-ester-urethane)s. 

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