Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Patent
1983-09-15
1985-08-06
Schofer, Joseph L.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
524706, 528176, 528183, 528184, 528185, 528186, 528188, 528327, 528330, 528331, 528337, 528341, 528342, 528346, 528347, 528348, 528352, 528353, 528364, C08K 332
Patent
active
045336938
DESCRIPTION:
BRIEF SUMMARY
2. Technical Field of Invention
The present invention relates broadly to novel anisotropic (liquid-crystalline) extended chain polymerpolyphosphoric acid compositions, to the production of high molecular weight extended chain polymers by polycondensation of selected monomers in certain polyphosphoric acids, and especially to the production of highly concentrated polymer compositions from which industrially useful polymeric articles such as fibers and films are readily produced.
Among some of the most serious difficulties encountered in the production of thermally stable articles such as fibers and films from extended chain polymers are described in the Background Art below.
3. Reference to Related Applications
Reference is made to another United States patent application filed concurrently with the present application, both being assigned to SRI International and having as one of their inventors, James F. Wolfe. Said other application is entitled: "Liquid Crystalline Poly(2,6-benzothiazole) Compositions, Process, and Products" and is herein incorporated by reference.
4. Background Art
In general, the class of aromatic heterocyclic extended chain polymers are well known for their outstanding thermal, physical, and chemical properties. Unfortunately, these polymers are essentially non-melting and have proven very difficult to economically process into articles. In order to fashion such polymers into desired articles of commerce, for example fibers, films, fibrids, and the like, it is necessary that they be in solution or dope form. Although such polymers can be dissolved in various acidic solvents, such as sulfuric acid, methanesulfonic acid, chlorosulfonic acid, polyphosphoric acid, and the like, difficulty is often experienced in preparing and using the polymer-acid compositions or dopes because of poor polymer-acid solubility.
Normally, a precipitated or dried particulate form of the polymer is dissolved in a strong acidic solvent by mixing the (isolated) polymer particles at elevated temperatures and/or under high pressures for a period from several hours to several days. If the polymer is insoluble in the particular solvent, other solvents or various solvent mixtures are employed. Usually, heating and cooling cycles are applied and repeated to obtain a useful dope.
The resulting dopes often contain undissolved polymer and must be filtered before further processing into articles.
Although spinning dopes of polybenzobisoxazole, polybenzimidazole and polybenzobisthiazole in sulfuric acid and/or methanesulfonic acid and/or chlorosulfonic acid with polymer concentrations above about 10 percent are known in the art, the intrinsic viscosity of these polymers is for the most part below 5dL/g and oftentimes less than 3dL/g. The cohesive strength of such dopes is inherently weak and economically less desirable for use in dry-jet wet spinning. In the case of polybenzobisoxazole, numerous attempts of dry-jet wet spinning an approximately 10% polybenzobisoxazole/methane sulfonic acid-dope into fibers were not successful (E. W. Choe, et al., in Macromolecules 1981, 14, pp. 920-924).
In the case of polybenzimidazole, prior art dopes of this polymer lack adequate strength to maintain filament integrity while dropping through the air-gap. In order to overcome this problem U.S. Pat. No. 4,263,245 teaches dissolving a high concentration (up to 30%) of this polymer into suitable solvents such as concentrated sulfuric acid. At such high polymer concentrations lithium chloride is required to prevent the polybenzimidazole from phasing out of solution.
In the case of polybenzobisthiazole, U.S. Pat. No. 4,225,700 teaches the formation of a liquid crystalline composition of this polymer at concentrations near 10% in methane sulfonic acid and chlorosulfonic acid and at about 6% in polyphosphoric acid. Concentrations of polybenzobisthiazole in polyphosphoric acid above about 10% by weight are difficult, if indeed possible to achieve. One difficulty encountered is that the solution of the 2,5-diamino-1,4-benzenedithiol monomer in p
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Sybert Joanne R.
Sybert Paul D.
Wolfe James F.
Chen John Y.
Sarofim N.
Schofer Joseph L.
SRI - International
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