Plastic and nonmetallic article shaping or treating: processes – Forming continuous or indefinite length work – Shaping by extrusion
Reexamination Certificate
1999-08-04
2001-09-18
Tentoni, Leo B. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Forming continuous or indefinite length work
Shaping by extrusion
C264S210700, C264S210800, C264S211150, C264S211160
Reexamination Certificate
active
06290888
ABSTRACT:
The present invention relates to polymer fibers and a method for making the fibers from a polymer solution. More particularly, the present invention relates to improvements in the method for making polymer fibers known as “dry-jet wet spinning.”
Polymers can be spun into fibers having a variety of uses. In particular, liquid crystalline main chain polymers, such as poly(p-phenyleneterephthalamide), have unique physical characteristics making them useful in the production of high-strength fibers. For example, aramid fibers (fibers made from aromatic polyamides) are well known for their strength.
One method of processing linear polymers into fibers is known as dry-jet wet spinning. In this procedure a solution of the polymer, commonly referred to as a “spinning dope,” is extruded from a die first through a layer of non-coagulating fluid and then into a coagulating bath. While in the coagulating bath, the solvent is removed from the dope so as to form the fiber. Tension is applied to the fiber as it leaves the coagulating bath. This stretches the fiber, which improves the degree of orientation of polymer molecules in the lengthwise direction of the fiber.
While processes such as dry-jet wet spinning produce fibers having good tensile strength, they result in fiber having less than optimum tensile modulus.
In accordance with the present invention there is provided a process for making polymer fibers so as to improve their properties, that is, high tensile strength, high tensile modulus, and low breakage elongation.
In order to achieve the above-mentioned aims, the highly oriented polymer fiber of the present invention is characterized in that the tensile strength ranges from 1500 to 5000 MPa, the tensile modulus ranges from 200 to 500 GPa, and the breakage elongation ranges from 0.8 to 1.4%.
In the fibers, the polymer is preferably aromatic polyamide. The tensile strength is preferably 2500-4500 MPa, and the tensile modulus ranges 200-300 GPa.
It is also preferable in the fibers that stripe patterns are not seen in the direction perpendicular to the fiber axis when the orientation of the passing axes of the polarizer and the analizer of the highly oriented polyamide fibers is observed by using a polarizing microscope.
It is preferable in the fibers that the fibril will not be generated substantially when the highly oriented polyamide fiber is stretched until it is broken.
The method for producing the highly oriented polymer fibers of the present invention comprises the sequential steps of:
a) extruding as a stream a solution of a polymer having a polymer concentration of 4-24 weight % into a first non-coagulating fluid;
b) stretching the stream while in the non-coagulating flue at a spinning draft of 25-2000;
c) passing the stream through a first coagulating bath in order to increase the polymer concentration by at least 2 weight % to a concentration of 20-65 weight %;
d) stretching the stream at a stretch ratio 1.3-8 in a second non-coagulating fluid; and
e) passing the stream through a second coagulating bath and increasing the polymer concentration in the stream sufficiently to form a fiber.
In these steps, “stream” means the intermediate of the highly oriented fibers. In the method, the polymers are preferably aromatic polyamides. In the b) step, the “non-coagulating flue” indicates, for example, the area between the spinning cap and an optional point in the first coagulating bath. In the d) step, drafting is carried out inside or adjacent to the first coagulating bath. In the e) step, the polymer can be maintained to be a predetermined length, otherwise it is strained, or stretched.
The highly oriented polymer fibers of the present invention are made in the above-mentioned method, and have tensile strength of 1500-5000 MPa, tensile modulus of 200-500 GPa, and breakage elongation of 0.8-1.4%.
It is preferable in the process that the stream passes between a first driven roller and a cooperating press roller before stretching, and then passing over a second driven roller followed by a third driven roller.
It is preferable in the process that the process of the invention further comprises a fourth driven roller that contacts the fiber in a manner to effect a tension ratio of 0.8-1.2 in the filament passing through the second coagulating bath.
It is preferable that the stream is passed through the second coagulating bath at a tension ratio of 0.8-1.2.
It is also preferable that the stream is passed through the second coagulating bath at a tension ratio of 0.9-1.2.
The present invention includes a method for making a fiber comprising the sequential steps of: a) extruding as a stream a solution of a polymer having a polymer concentration of 4-24 weight % into a non-coagulating fluid; b) stretching the stream while in the non-coagulating fluid at a spinning draft of 25-2000; c) increasing the polymer concentration by at least 2 weight % to a concentration of 20-65 weight %; d) stretching the stream at a stretch ratio of 1.3-10, preferably 1.5-8; and e) increasing the polymer concentration in the stream sufficiently to form a fiber. The present invention also includes a polymer made by a claimed process as well as a polyamide fiber having a tensile strength of at least 1210 MPa and a tensile modulus of at least 145 GPa.
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Fibres From Synthetic Polymers, Rowland Hill, Ed., Aug. 1953, pp. 382-387.*
Li, L-S et al. “On the Morphology of Aromatic Polyamide Fibers (Kevlar, Kevlar-49-and PRD-49”, Journal of Macro-Molecular Science-Physics B 22(2), pp. 269-290 (1983).*
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Jacobson & Holman PLLC
Kansai Research Institute (KRI)
Tentoni Leo B.
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