The Dow Chemical Company

Steven Rosenberg

Chieh-Chun Chau

Thomas D Gregory

Harvey D Ledbetter

Kenneth J Quackenbush

Carl W Hurtig

Myrna Serrano

Zenon Lysenko

William J Harris

Mark D Newsham

Ming-Biann Liu

Robert A Bubeck

Stephen J Nolan

Luke R Kleiss

George J Quarderer, Jr

Richard C Krauss

Ying Hung So

Yoshihiko Teramoto

Gary J Schulz

Timothy L Faley

Katsuya Tani

Willard E Alexander

Ashish Sen

Masaru Nakagawa

Michael V Spencer

A process for making a low molecular weight cellulose ether has the following steps: a) providing a high molecular weight cellulose ether; b) contacting it with acid to partially depolymerize it to a cellulose ether of a viscosity of about 100 cP or less; c) neutralizing the acid; d) repeating steps a)-c) to produce two or more discrete product batches of low molecular weight cellulose ether and produce at least one discrete product batch which is partially neutralized; and e) blending the two or more discrete product batches to form a combined product batch of low molecular weight cellulose ether of a pH of 4 to 6.8. The process provides a cellulose ether with reduced yellowing and discoloration.

Process for making cellulose ethers having reduced yellowing and discoloration

A process for making PBZ fibers of ultra-high physical properties is given. Polybenzoxazole fibers made by the process of this invention have tensile strengths nearly double in value from what has been reported previously.

Polybenzazole fibers with ultra-high physical properties and method for

Polybenzazole polymer dopes are spun through a spinneret having more than 2 per cm.sup.2, of orifices in relatively close proximity. The dope filaments formed, then pass through an air gap which has a temperature of 50.degree. to 100.degree. C. and a gas flow sufficient to uniformly reduce the temperature of the dope filaments. The filaments cool in the air gap and are then coagulated.

Method for rapid spinning of a polybenzazole fiber

This invention aims at improvement of heat-treatment technology for manufacture of large amounts of polybenzazole fibers. The fibers are heat treated in a device that provides for a rapid, cocurrent, countercurrent or both cocurrent and countercurrent flow of heat treatment gas.

Rapid heat-treatment method for polybenzaole fiber

Polybenzazole fiber with ultra-high physical properties

Salts that contain AA-PBZ monomer ions and BB-PBZ monomer ions can be precipitated from an aqueous solution by contacting soluble salts of the monomers in an aqueous solution. The monomer salt can be polymerized by ordinary techniques to form polybenzazole polymers without the need for devolatilization and with very accurate stoichiometric control.

Salts of polybenzazole monomers and their use

The invention is a condensation polymerization reaction in which functionally terminated polybenzazole ligomers are reacted in a solvent acid at a temperature of at least 150.degree. C. and a shear of at least about 10 sec..sup.-1 under conditions so that the desired molecular weight is reached in no more than about 4 hours. The oligomers may be, for example, derived from the reaction of 4,6-diaminoresorcinol bis(hydrochloride) and terephthalic acid. The concentration of oligomers is high enough so that the reaction mixture contains liquid crystalline domains.

Rapid advancement of molecular weight in polybenzazole oligomer dopes

Polybenzazole polymers can be synthesized rapidly in large quantities at high molecular weight and high concentration by a two-step process of forming oligomers in a batch reactor and advancing the molecular weight of the polymer in an extruder.

Semi-continuous process for synthesis of polybenzazole polymers

It is advantageous to prepare oligomers of polybenzazole polymers by reaction of AA-PBZ monomer with an excess of BB-PBZ monomer. The resulting oligomer dopes may be stored at a temperature at which they remain pumpable until such time as the dope can be advanced to higher molecular weight by adding additional AA-PBZ monomer. The molecular weight of the polymer may be adjusted by controlling the amount of chain extender and/or chain terminator added to oligomer mixtures as they are advanced to final molecular weight.

Staged polymerization of polybenzazole polymers

Polybenzazole polymers are conveniently synthesized in the presence of a reducing agent, such as tin (II) chloride.

Use of reducing agents in polybenzazole synthesis

PBZ polymers are synthesized by the reaction of AA- and BB-monomers. The BB-monomer is conveniently synthesized and isolated as a phosphate salt having a uniform number of phosphate ions associated with each BB-monomer ion. Such high purity monophosphate and diphosphate salts can be obtained by precipitating the monomer from an aqueous acid solution by adjusting the pH balance or from a mixture of phosphoric acid and a volatile, polar, saturated organic liquid at a relatively low temperature.

Phosphate salts of monomers for PBZ and their use in preparing PBZ

Polybenzazole polymers can be advanced rapidly to high molecular weight at relatively high temperatures and high shear in a dehydrating solvent acid.

Growing community of inventors

Midland, MI, United States of America

Steven Rosenberg