Hoechst Celanese Corporation

Celanese Gmbh

Sunil K Garg

Tai-Shung Chung

Samuel Kenig

Robert M Mininni

Henry H George, Jr

Steven B Warner

Anne Holt

Daniel Palangio

An improved method of bonding a polymeric composition comprised of a thermotropic liquid crystalline polymer to a substrate is provided. It has been determined that the adhesion of a thermotropic liquid crystalline polymer to a substrate is enhanced if the absolute difference between the surface pH of the substrate to which the polymer is to be bonded and the pH of the polymer itself is at least approximately 1.0 pH unit as measured by the method described herein.

Method of adhesive bonding by use of thermotropic liquid crystal polymers

An improved technique is provided to melt-extrude a liquid crystalline polymer to form large elongated solid shaped articles which exhibit significantly improved polymeric orientation. The molten polymer which is capable of forming an anisotropic melt phase is extruded through a converging die that is provided with at least one enclosed cooling zone at an interior location within the flowing molten polymer wherein a cooling fluid is circulated. This cools the molten polymer adjacent the cooling zone with the concomitant increase in its melt viscosity. Such increased melt viscosity at the interior of the stream of the molten polymer contributes to the uniformity of the polymeric orientation imparted within the converging die as well as during subsequent drawdown outside the extrusion orifice. Such improved polymeric orientation leads to the formation of an improved product (e.g., a three-dimensional rod) which exhibits an unusually high tensile modulus in the direction of its length. The present invention accordingly overcomes difficulties encountered in the prior art wherein melt-extruded shaped articles significantly larger than fibers heretofore often have exhibited substantial internal heterogeneity and a highly oriented skin and a core of a substantially lesser polymeric orientation.

Melt-extrusion of polymer which is capable of forming an anisotropic

Improved pellets comprising a melt-processable thermotropic liquid crystalline polymer (e.g., a wholly aromatic polyester) are provided. The molten anisotropic melt-forming polymer, while present as a thin film of the specified thickness at an appropriate temperature, is subjected to reduced pressure conditions whereby residual volatiles are evolved and removed, and the polymer thereby is densified to the specified degree prior to pellet formation. The resulting densified polymer next is melt-extruded and is cut to form pellets while at an appropriate temperature. It surprisingly has been found to be of prime importance that the resulting pellets possess a density of at least 95 percent of the theoretical maximum (e.g., a polymer density of approximately 1.35 to 1.4 gram/cc.) if the advantages of the present invention are to be fully realized. These pellets have been found to be capable of undergoing melt processing to form shaped articles having improved physical properties. For instance, such shaped articles exhibit markedly smoother surface characteristics and can be used at elevated temperatures for extended periods of time while better retaining the desired surface characteristics.

Production of improved pellets from melt-processable polymer which is

Provided is a process for melt spinning a partially oriented yarn of increased birefringence, and hence higher orientation, for a given wind-up speed. The process comprises extruding a molten fiber forming polyester through a shaped orifice to form a molten filamentary material, which is then passed in the direction of its length into a quench zone wherein the filamentary material is contacted with a first gaseous quenching medium. While the filamentary material is still in a deformable state, however, it is passed through a hot zone provided with an atmosphere having a temperature greater than the first gaseous quenching medium and greater than the glass transition temperature of the molten polyester filamentary material. The filamentary material is then withdrawn from the hot zone and contacted with a second gaseous quenching medium at a temperature below the glass transition temperature of the filamentary material until the filamentary material is no longer deformable, after which the filamentary material is withdrawn from the quench zone.

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Summit, NJ, United States of America

Sunil K Garg