Amoco Corporation

Standard Oil Company (indiana)

Lawrence G Packer

David E James

Allen B Mossman

John A Macek

Edward J Schlossmacher

High quality linear polyester resin is prepared by reacting in a first step or zone 2,6-naphthalene dicarboxylic acid with a molten prepolymer derived from a glycol and 2,6-naphthalene dicarboxylic acid to form a low molecular weight product of the first step or zone; reacting this resultant product with a glycol in at least two successive steps or zones of glycol addition to form prepolymer; and polymerizing at least a portion of the resulting prepolymer to form polyester resin which exhibits midpoint glass transition temperatures above about 123.degree. C. The resulting prepolymer is particularly suitable for reaction with the 2,6-naphthalene dicarboxylic acid in the first step or zone. Advantageously, at least a portion of the prepolymer is, therefore, returned to the first step or zone.

Process for manufacture of high molecular weight polyester resins from

An improved method for producing purified terephthalic acid by catalytic hydrogenation is disclosed. Control of the reduction of colored compounds during the production of purified terephthalic acid is effected by modulating solution hydrogen concentration during hydrogenation.

Purification of terephthalic acid

Fiber-grade quality terephthalic acid can be obtained by dissolving partially purified terephthalic acid: the product separated from catalyst components and impurities in acetic acid solvent portion of oxidation effluent, acetic acid washed and dried: either in deionized water or acetic acid at temperatures from 250.degree. C. and upward, contacting the solution and hydrogen gas with a hydrogenation catalyst preferably a platinum family metal disposed on an insoluble support followed by separation of the solution from catalyst, cooling the separated solution to precipitate terephthalic acid, recovering, washing and drying the precipitate. The use of deionized water in the purification route, with respect to the oxidative preparation of terephthalic acid, has the drawback of maintaining two distinctly different solvent systems and tolerating the rather limited water solubility of the p-toluic acid. While the use of acetic acid as solvent in the purification route makes use of a solvent having a greater capacity to dissolve p-toluic acid (an oxidation co-product impurity and the reduction product of 4-carboxybenzaldehyde also a co-oxidation product), such use of acetic acid has the drawback of decreasing the hydrogenation rate as well as having some inherent decomposition of the acetic acid solvent. The aforementioned drawbacks are avoided by heating the oxidation effluent's suspension of impure solid terephthalic acid to a temperature of 250.degree. C. and upward in the presence of sufficient acetic acid to dissolve all the solids of the total solids content of said effluent, contacting such solution and hydrogen gas with the above platinum family hydrogenation catalyst, then precipitating, recovering, acetic acid washing, and drying terephthalic acid so purified. Such purification and recovery route also provides a less yellow purified product than that produced when the same process is conducted but in the absence of the platinum family metal hydrogenation catalyst.

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Lisle, IL, United States of America

Lawrence G Packer