Poly glycol terephthalate system

Those polymers which are the condensation product of two different monomers are named by applying the preceding rules to the repeat unit. For example, the polyester formed by the condensation of ethylene glycol and terephthalic acid is called poly(oxyethylene oxyterphthaloyl) according to the lUPAC system, as well as poly (ethylene terephthalate) or polyethylene terephthalate. 

The separation of methanol from ethylene glycol is an important industrial process in the synthesis of poly(ethylene terephthalate). The methanol/ethylene glycol system has been extensively studied using various analytical methods and pervaporation experiments as well. The methanol selectivity reaches up to 250 at low methanol concentrations, however, the total flux decreases in this region. 

Poly(ethylene terephthalate) (PET) is commonly prepared by melt-phase polycondensation reactions. Bis(hydroxyethyl) terephthalate (BHET) was converted to PET under a variable flow (2-10 mL/min) of CO2 at 20.7 MPa (207 bar) (95). Molecular weights were obtained over the range 3 x 10 to 6.3 x 10 g/mol and increased significantly with flow rate and/or reaction time. These values are low compared to normal molecular weights obtained in commercial processes (approx. 2 X 10 g/mol) and may be attributed to the decreased solubility of the ethylene glycol condensate in CO2 compared with phenol in the polycarbonate system. 

Cyclic oligomer formation during polycondensation has been studied for the ethylene glycol-adipic acid system and oxycycloeicosanone has been identified. Similarly, oligomers have been isolated and identified from the preparation of poly(butylene glycol terephthalate). ... 

If the liberated alcohol is distilled from the system as it is formed, the reaction may be taken to completion. In the preparation of poly(ethylene terephthalate) two successive ester interchange reactions are performed. In the first step, dimethyl terephthalate is heated with an excess of ethylene glycol (the molar ratio is 1 2.1-2.2) at 150-210 C in the presence of a catalyst (see later). Ester interchange occurs, the principal product being bis(2-hydroxyethyl) terephthalate ... 

An approach related to the use of emulsions as a raw material for scaffolding is the use of emulsions for coating. Sohier et al. [221] used a W/O emulsion of poly(ethylene glycol) terephthalate/poly(butylene terephthalate) multiblock copolymer loaded with lysozyme as a model protein to coat porous scaffolds made of the same material. They could release the protein over several days and were able to show that the activity of lysozyme was maintained. While the use of emulsions has the advantage of creating an even distribution of drugs inside the material, in some cases, sensitive drugs may not be stable in such an emulsion system [222-224]. 

Oku, A. Ebisu, R. Yamada, E. Recovery of terephthalic acid and ethylene glycol by hydrolysis of poly(ethylene terehthalate) in alcohol-ether mixed solvent system. Japanese Patent JP 10,087,529. 

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