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| Magnetic recording medium |
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| Magnetic recording medium |
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| Process for producing crystal-oriented permanent magnets |
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| Apparatus and process for automatic control of the production of optical fiber |
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| Method of supplying fluid to a rotating tube |
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| Process and furnace for heat application |
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| Process for manufacturing liquefied methane |
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| Nitrogen-methane separation process and system |
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High strength polyacrylonitrile fiber and method of producing the same
| Details |
Inventors: Kobashi, Toshiyuki; Takao, Seiji;
Assignee: Japan Exlan Company Limited (Osaka, JP)
Primary Examiner:
Assistant Examiner:
Attorney, Agent or Firm:
Polyacrylonitrile (PAN) fiber of high strength (tensile strength.gtoreq.20 g/d) produced from a polymer composed mainly of acrylonitrile (AN) and having a weight average molecular weight not less than 400,000, and a method of producing said fiber characterized by a multistage stretching step and a drying step under particular conditions. |
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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In the production of the PAN fiber having a tensile strength not less than 20 g/d, the object of the present invention, the molecular weight of the polymer is important.
It is necessary to use a polymer having a weight average molecular weight not less than 400,000, preferably not less than 800,000.
As detailed in Journal of Polymer Science (A-1) Vol.
6, pp 147-159 (1968), said molecular weight is obtained by measuring the intrinsic viscosity, [.
eta.
], of the polymer in dimethylformamide (DMF) and calculated by the following formula: [.
eta.
]=3.
35.
times.
10.
sup.
-4 M.
sub.
w.
sup.
0.
72 wherein M.
sub.
w represents weight average molecular weight.
To produce such a high molecular weight polymer, any method can be used without limitation as long as the polymer has a molecular weight of not less than 400,000.
However the polymer can be produced advantageously on an industrial scale by suspension polymerization of the monomer in an aqueous medium containing a water-soluble polymer, in the presence of an oil-soluble initiator, while maintaining an unreacted monomer concentration higher than 9 weight % in the reaction system.
As the monomer is used AN alone or a monomer, there mixture composed of more than 85 weight % AN, preferably more than 95 weight % AN and a known comonomer copolymerizable with AN.
The production of a high strength fiber depends on to what extent it is possible to bring all the molecular chains forming the fiber near to the state of the chains extended in the fiber direction to their full length.
For the attainment of such a state, it is important to produce a polymer solution (spinning solution) in which the polymer chains are sufficiently disentangled so that the molecular chains can be easily arranged in parallel and oriented in the fiber direction in the steps of spinning and stretching.
As examples of the solvents for producing such a polymer solution, there may be mentioned organic solvents such as DMF, dimethylacetamide, dimethyl sulfoxide, etc
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Manufacturing Materials 
