Fiber Industries, Inc.

Nicolai A Favstritsky

Ronald L Griffith

A method of reducing the number of free carboxyl end groups present in a fiber-forming polymer is given whereby to the polymer minor amounts of a low-boiling oxirane compound such as ethylene oxide are added.

Esterification of carboxyl end groups employing addition of oxirane

A novel polyester is provided which has been found to exhibit an anisotropic melt phase at a temperature which enables it readily to undergo melt processing to form quality fibers, molded articles, etc. The polyester of the present invention includes as essential ingredients moieties derived from para-hydroxy benzoic acid, 2,6-naphthalene dicarboxylic acid, terephthalic acid, and methylhydroquinone in the proportions indicated. In a preferred embodiment the polyester is capable of undergoing melt processing at a temperature below approximately 320.degree. C., and in a particularly preferred embodiment at a temperature below approximately 300.degree. C. (e.g., with standard equipment commonly used to melt process polyethylene terephthalate). Fibers conveniently can be melt spun from the polyester of the present invention which exhibit tenacity values which are enchanced upon thermal treatment. It surprisingly has been found that the polyester of the present invention exhibits a hydrolytic stability which is substantially greater than that of the polyester of U.S. Pat. No. 4,083,829.

Polyester of para-hydroxy benzoic acid, 2,6-naphthalene dicarboxylic

A novel polyester is provided which has been found to exhibit an anisotropic melt phase at a temperature which enables it readily to undergo melt processing to form quality fibers, molded articles, etc. The polyester of the present invention is different in character than polyesters of the prior art and includes as essential ingredients moieties derived from para-hydroxy benzoic acid, 1,2-bis(para-carboxy phenoxy)ethane, terephthalic acid, and unsubstituted hydroquinone in the proportions indicated. The polyester of the present invention can be produced on a relatively economical basis and has been found capable of yielding an anisotropic melt of relatively low viscosity at a desirable temperature for melt processing. In a preferred embodiment the polyester is capable of undergoing melt processing at a temperature below approximately 300.degree. C., and in a particularly preferred embodiment at a temperature below approximately 290.degree. C. (e.g., with standard equipment commonly used to melt process polyethylene terephthalate). Fibers conveniently can be melt spun from the polyester of the present invention which exhibit tenacity values which are enhanced to a surprisingly great extent upon thermal treatment.

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Broomall, PA, United States of America

Nicolai A Favstritsky