Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
2000-08-18
2001-12-25
Edwards, N. (Department: 1774)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S375000, C428S394000
Reexamination Certificate
active
06333107
ABSTRACT:
TECHNICAL FIELD
With a recent spread of portable electronic gears, a proposal was made to line the pockets of a suit with a fabric capable of shielding against the electromagnetic waves generated by the electronic gears to mitigate the influence of electromagnetic waves on the human body. The electroconductive materials proposed for control of electricity, imparting electroconductivity or shielding against electromagnetic wave include, for example, surfactants, carbon-type or tin antimony-type electroconductive fillers, metallic fibers and metal-plated fibers.
BACKGROUND ART
However, when a surfactant is used, a sufficient electroconductivity is not imparted and its use is limited. When metallic fibers or metal-plated fibers are used, the electroconductivity is impaired by oxidation and the design is limited due to metallic luster.
On the other hand, carbon-type or tin antimony-type electroconductive fillers pose problems of having low whiteness degree and poor dispersibility and producing dust, so that they are singly usable only for limited purposes. Nevertheless, electroconductive fillers useful for coating potassium titanate fibers, titania fibers, silica or like inorganic fillers show a high resin-reinforcing ability, and the obtained electroconductive compositions have various excellent properties such as superior strength, high electroconductivity, proper surface properties and uniform electroconductivity. Consequently these fillers are now in wide use to render resins electroconductive. Further, it has been proposed to spin a resin composition containing a resin and such electroconductive fillers for the production of electroconductive threads (JP-A-63-196717). However, the proposed method poses a problem of entailing a difficulty in continuous spinning because the filter and nozzles are clogged with large-size fillers in the spinning operation, thereby increasing the back pressure of the nozzles.
An object of the present invention is to provide fine electroconductive fibers and an electroconductive thread prepared from the fibers which thread is excellent in strength and electroconductivity.
Another object of the present invention is to provide an electroconductive thread having a high whiteness degree.
A further object of the present invention is to provide an electroconductive resin composition suitably usable as a raw material for the electroconductive thread.
DISCLOSURE OF THE INVENTION
The present invention provides an electroconductive fiber comprising a fibrous core material whose surface is coated with an electroconductive substance, the fibrous core material having an average fiber length of 1 to 5 &mgr;m, an average fiber diameter of 0.01 to 0.5 &mgr;m and an aspect ratio of 3 or more.
According to the present invention, there is provided an electroconductive resin composition containing a resin and the electroconductive fibers.
According to the present invention, there is provided an electroconductive thread prepared by spinning the electroconductive resin composition.
The electroconductive fiber of the present invention comprises a fibrous core material having a surface coated with an electroconductive substance, the fibrous core material possessing an average fiber length of 1 to 5 &mgr;m, an average fiber diameter of 0.01 to 0.5 &mgr;m and an aspect ratio of 3 or more.
The core material used herein for the electroconductive fiber has an average fiber length of 1 to 5 &mgr;m, preferably 1 to 4 &mgr;m, an average fiber diameter of 0.01 to 0.5 &mgr;m, preferably 0.01 to 0.2 &mgr;m, and an aspect ratio of 3 or more. Since the core material may be broken to a shorter length in a processing procedure to be described later, it is possible to use a core material having a fiber length longer than said range in the initial stage but falling within said range in the final stage.
Preferred core materials include a titania compound represented by the formula mK
2
O.nTiO
2−x
.yH
2
O wherein m is 0 or 1, n is 1 or a number of 4 to 8, x is a number in the range of 0≦x<2, y is a number of 0 to 10, provided that when m is 0, n is 1, whereas when m is 1, n is a number of 4 to 8.
Preferred examples of the core material to be used herein are potassium, tetratitanate fibers, potassium, hexatitanate fibers, potassium, octatitanate fibers and monoclinic titania fibers.
Of the core materials, those consisting essentially of a compound represented by K
2
O.4TiO
2
.yH
2
O wherein y is as defined above can be prepared by baking at 870 to 970° C. at least one species selected from titanium, compounds capable of producing titanium, dioxide by, e.g., heating, potassium compounds capable of producing potassium oxide by heating, potassium halide, metallic oxide and metal-containing compounds capable of producing metallic oxide by heating (the metal being e.g., at least one species selected from Mg, Al, Si, Fe, Ni and Mn). When the fibrous core material is treated with an acid or otherwise for removal of potassium, and is baked, the procedure gives a core material having a specific shape and comprising a potassium hexatitanate of the formula K
2
O.6TiO
2
.yH
2
O, potassium octatitanate of the formula K
2
O.8TiO
2
.yH
2
O, monoclinic titania of the formula TiO
2
.yH
2
O or the like.
Of the compounds of the formula mK
2
O.nTiO
2−x
.yH
2
O, those wherein x is <2 are obtained by baking in a non-oxidizing or reducing atmosphere or by heat treatment in a non-oxidizing or reducing atmosphere in a step of forming an electroconductive coating as described later. These core materials are electroconductive themselves and thus preferable. The electroconductive fibers of the present invention can be prepared by coating the surface of core material with carbon, tin oxide or like electroconductive substances. When the desired fibers are required to have whiteness, a core material coated with tin oxide or the like is preferable. When the color of desired product is not important, a core material coated with carbon which is available at relatively low costs is preferable. The surface of the core material can be coated with carbon by the steps of placing the core material into a rotary kiln or a rolling firing furnace or the like in which the atmosphere can be adjusted, supplying a compound in a liquid, gaseous or solid form which decomposes on heating to produce carbon, such as benzene, toluene, pyridine, butane gas, melamine or the like, and heat-treating the compound at higher than the decomposition temperature of the compound, e.g. 350 to 1,000° C.
The amount of the carbon to be coated on the surface of core material is 10 to 200 parts by weight per 100 parts by weight of the core material.
Such method and similar methods are described in detail in JP-B-7-111026, JP-B-7-111027, JP-B-7-111028, etc.
A coating method using tin oxide comprises, for example, the steps of dispersing the core material in water to give a slurry, adding dropwise to the slurry a hydrochloric acid solution of tin chloride, optionally a hydrochloric acid solution of a metal compound capable of forming a metallic oxide to be coated concurrently with tin oxide, for example, a hydrochloric acid solution of antimony chloride and an aqueous solution of sodium, hydroxide, removing the insolubles and heat-treating the residue. Examples of the metallic oxide to be coated concurrently with tin oxide include oxides of indium, bismuth, cobalt, molybdenum or the like as well as the antimony described above. These oxides may account for about 0.01 to about 75% by weight of the oxides to be coated. These metals other than tin may be doped to increase the electroconductivity and whiteness. The amount of tin oxide or the like to be coated on the core material is 50 to 300 parts by weight calculated as a metal oxide per 100 parts by weight of the core material.
Such method and similar methods are described in detail in JP-B-62-4328, JP-A-2-149424, JP-B-7-23221, etc.
The electroconductive resin composition of the invention can be prepared by adding the foregoing electroconductive fibers to a resin. There is no limitation on t
Monde Hiroyuki
Ogawa Hiroshi
Ogawa Jun
Edwards N.
Kubovcik & Kubovcik
Otsuka Kagaku Kabushiki Kaisha
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