The Dow Chemical Company

Willard E Alexander

Louis C Rubens

Chieh-Chun Chau

Timothy L Faley

Steven Rosenberg

Katsuya Tani

Carl A Raeck

Improved polybenzoxazole fibers are made by a process for finishing a spun and drawn dope fiber, which contains polybenzoxazole polymer and polyphosphoric acid, including the steps of:

Process for post-spin finishing of polybenzoxazole fibers

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

Improved polybenzoxazole fibers are made by a process for finishing a spun and drawn dope fiber, which contains polybenzoxazole polymer and a solvent acid, including the steps of: (a) coagulating the dope fiber in an aqueous coagulant: (b) washing the coagulated fiber with an aqueous washing fluid for less than 72 hours under conditions such that the fiber contains no more than 8,000 ppm residual solvent acid (1 ppm=1 part per million, by weight); (c) drying the fiber at a temperature of no more than 300.degree. C. until it retains no more than about 2 weight percent residual moisture; and (d) heat-treating the fiber at a temperature of at least about 300.degree. C. under tension.

Pneumatic synthetic resinous foams are used as dunnage. Foams are added to a package under fluid pressure; the package closed, the pressure reduced to atmospheric, and particulate pneumatic foam expands to fill container.

Process and apparatus for packaging

Expandible synthetic resinous particles are molded by injecting heated air generally centrally into the mold cavity by means of a probe, withdrawing the probe and heating the surface of the mold. Low densities and rapid cycle times are obtained.

Method and apparatus for the preparation of foamed thermoplastic articles

Resilient foam particles and moldings are obtained employing a lightly crosslinked polymer such as a styrene polymer with volatile fluid foaming agent that has low permeability through the polymer. Multiple expansion will permit low density particles for molding.

Expandable synthetic resinous thermoplastic particles, method for the

Shaped articles of organic polymer resins having cellular (foamed) structure are made from heat-expandable normally solid thermoplastic resin compositions in permeable molds particularly characterized by flooding the mold cavity and the expandable material therein with molten salt as heating medium. For example, a permeable mold, charged with pieces of polyethylene containing azobisformamide and crosslinked by electron irradiation, is immersed into a molten salt eutectic mixture of KNO.sub.3, NaNO.sub.2 and NaNO.sub.3 at about 264.degree. C, removed, cooled and washed with water, thereby forming a coherent, unitary cellular resin molded article completely filling the mold cavity.

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Midland, MI, United States of America

Willard E Alexander