Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Patent
1996-12-05
1999-01-12
Edwards, Newton
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
428373, 4234471, 4234473, D02G 300, D01F 912
Patent
active
058585303
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a flexible, ignition resistant biregional fiber derived from a precursor fiber preferably having a homogeneous polymeric composition throughout the cross-section of the precusor fiber, wherein the ignition resistant biregional fiber has an inner core region of a thermoplastic polymeric composition and a surrounding outer sheath region of a thermoset carbonaceous material. The invention also relates to a biregional precursor fiber having an inner core region of a thermoplastic polymeric composition and a surrounding oxidation stabilized outer sheath region, a method for the manufacture of the biregional fiber, and articles made from a multiplicity of said biregional fibers.
In both of the biregional precursor fiber and the biregional fiber, the ratio (r:R) of the radius of the core region (r) with respect to the total radius (R) of the biregional fiber is from 1:4 to 1:1.05, preferably from 1:3 to 1:1.12. Preferably, the biregional precursor fiber of the invention has a density of from 1.20 g/cm.sup.3 to 1.32 g/cm.sup.3, and a breaking twist angle of from about 17 to about 23 degrees, while the biregional fiber of the invention is ignition resistant and has an LOI value of greater than 40. The biregional fiber is flexible and lacks the brittleness normally associated with carbon and graphitic fibers of the prior art. The biregional fiber has a breaking twist angle of from 4 to 13 degrees, a density ranging from 1.45 to 1.85 g/cm.sup.3 and as high as 1.87 g/cm.sup.3, a bending strain value of from greater than 0.01 to less than 50%, preferably from 0.1 to 30%, and a Young's modulus of from less than 1 MM psi (<6.9 GPa) to 50 MM psi (345 GPa), preferably from 1 MM psi to 30 MM psi (207 GPa).
BACKGROUND OF THE INVENTION
Resilient and flexible, linear and non-linear carbonaceous fibers are now well known in the art. Representative of non-linear carbonaceous fibers is U.S. Pat. No. 4,837,076, issued Jun. 6, 1989 to McCullough et al. The fibers are produced by melt or wet spinning fibers from a thermoplastic polymeric composition and then stabilizing the fibers by treating them in an oxygen containing atmosphere and at an elevated temperature for a predetermined period of time. The oxidation stabilization treatment of the fibers is carried out to the extent such that the entire polymeric composition of the fibers, when viewed in cross-section, is oxidized. Although the stabilization process, to some extent, depends on the diameter of the fibers, the composition of the polymeric precursor composition, the level of oxygen in the atmosphere, and the treatment temperature, the process is extremely time consuming and costly in order to achieve complete stabilization of the fibers throughout their cross section.
Traditionally, the stabilization treatment of polymeric fibers under oxygen extends over at least several hours to in excess of 24 hours to completely permeate the fibers with oxygen and to achieve sufficient stabilization of the fibers in preparation for subsequent carbonization of the stabilized fibers to produce carbonaceous fibers for commercial end uses. The Encyclopedia of Polymer Science and Engineering, Vol. 2, A Wiley-Interscience Publication, 1985, pp. 641-659, reports that "current standard processing technology requires from 1 to 2 hours for adequate stabilization" of fibers, p.658. No other method of processing suitable for large or "heavy" 320 k tows is disclosed. Also, in "High Performance Fibers II, published by Battelle, esp. the chapter entitled "Process Technology-Oxidation/Stabilization", page 149 et seq. it is reported that oxidation and cyclization takes place between 150.degree. C.-300.degree. C. and that "the reaction must take place throughout the fiber and not be confined to the fiber surface." Accordingly, the lengthy stabilization treatment employed in present standard procedures reduces the productive output of stabilized fibers, requires substantial capital investment, and is therefor extremely costly and a major deterr
REFERENCES:
patent: 5700573 (1997-12-01), McCullough
Edwards Newton
Juhl Nis H.
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