US3586597A - Cloth having durable antistatic properties for use in garments and underwear - Google Patents

Abstract

A KNITTED OR WOVEN CLOTH HAVING DURABLE ANTISTATIC PROPERTIES FOR USE IN GARMENTS AND UNDERWEAR, SAID CLOTH CONTAINING ABOUT 0.005 TO ABOUT 10% BY WEIGHT OF AN ELECTRICALLY-CONDUCTIVE FIBER, CHARACTEIZED IN THAT SAID ELECTRICALLY-CONDUCTIVE FIBER COMPRISES A SUBSTRATE OF CHEMICAL FIBER AND AN ELECTICALLY-CONDUCTIE COATING FORMED THEREON, SAID COATING CONSISTING OF A BINDER PLYMER MATRIX HAVING DISPERSED THEREIN FINELY DIVIDED POWDER OF AN ELECTRICALLY CONDUCTIVE MATERIAL SUFFICIENT TO RENDER THE ELECTRICAL RESISTANCE OF THE ELECTRICALLY-CONDUCTIVE FIBER SO AS NOT TO EXCEED ABOUT 10**9 $/CM., AND SAID ELECTRICALLY-CONDUCTIVE FIBER HAVING THE FUNCTIONAL PROPERTIES OF TEXTILE FIBERS.

Description

United States Patent US. Cl. 16187 4 Claims ABSTRACT OF THE DISCLOSURE A knitted or woven cloth having durable antistatic properties for use in garments and underwear, said cloth containing about 0.005 to about by weight of an electrically-conductive fiber, characterized in that said electrically-conductive fiber comprises a substrate of chemical fiber and an electrically-conductive coating formed thereon, said coating consisting of a binder polymer matrix having dispersed therein finely divided powder of an electrically conductive material sufficient to render the electrical resistance of the electrically-conductive fiber so as not to exceed about 10 Q/cm., and said electrically-conductive fiber having the functional properties of textile fibers.

This invention relates to cloth having durable antistatic properties for use in garments and underwear.

The organic textile fibers have generally the drawback of becoming charged with static electricity upon being subjected to friction, especially when they are used at low humidity. This tendency is especially marked in the case of hydrophobic fibers, for example, synthetic fibers such as polyamide, polyester, acrylic and polyolefinic fibers and semi-synthetic fibers such as acetate and triacetate fibers. This electrification phenomenon causes troubles such as the occurrence of sound of electrostatic discharge, clinging of garments to a human body and electric shock.

As one method of solving these problems, there is a proposal to incorporate a small quantity of metallic fibers in the textile fiber material (US. Pat. 3,288,175). However, in using this method, it is necessary to use a metallic fiber having a minimum fineness of denier. Despite the use of a metallic fiber of fine denier there still remain problems during the mixing and processing steps as well as problems in the hand of the product. This is due to the fact that the usual textile fibers and the metallic fibers are essentially heterogeneous. Moreover, since the manufacture of metallic fibers of fine denier is not simple and metallic fibers are expensive, this method is not a desirable one from the standpoint of the quality and cost of the product obtained. There is also a proposal of preventing the electrostatic build-up by incorporating the usual textile fibers with an electrically conductive fiber which contains carbon black dispersed throughout the fiber (US. Pat. 2,845,962). However, in the case of a carbon black-incorporated conductive fiber such as this, the desired conductivity cannot be obtained unless the carbon black of a substantial amount is dispersed throughout the interior of the fiber. Therefore, its mechanical strength is low and Patented June 22, 1971 ice it has a tendency to break during the processing step. As a result, the manufacture of antistatic textile materials and products according to this method is difiicult. In addition, the appearance and hand of the product are not satisfactory since it is necessary to use a relatively large proportion of the conductive fiber black in color, which results from the incorporation and the dispersion in the fiber of the aforesaid carbon black for achieving the antistatic effect.

According to the present invention, there is provided a knitted or woven cloth having durable antistatic properties for use in garments and underwear, said cloth containing about 0.005 to about 10% by weight of an electrically conductive fiber, characterized in that said electrically conductive fiber comprises a substrate of chemical fiber and an electrically conductive coating formed thereon, said coating consisting of a binder polymer matrix having dispersed therein finely divided powder of an electrically conductive material sufficient to adjust the electrical resistance of the electrically-conductive fiber so as not to exceed about 10 SZ/cm., and said electrically conductive fiber having the functional properties of textile fibers.

Unless otherwise specified, the term fiber used in the specification and appended claims includes both staple fibers and continuous filaments.

The electrically conductive fiber to be incorporated into a knitted or woven cloth according to the invention comprises a substrate of chemical fiber and an electrically conductive coating formed thereon, and has the functional properties of textile fibers.

By the term functional properties of textile fibers, as here used, is meant, in general, the possession of mechanical properties by which a fiber can be subjected to the usual spinning, twisting, crimp-imparting, weaving and knitting operation and can stand such conditions which a fiber usually encounters during these processing steps as well as during its used, i.e. such conditions as abrasion, tensile stress, bending stress, repetitive fiexure, repetitive elongation and relaxation, and repetitive compression and relaxation; and the possession of compatibility and coprocessability With the usual organic textile fibers. The electrically conductive fiber to be used in the knitted and woven cloths according to the present invention should possess mechanical properties which are about comparable to those of the substrate of the chemical fiber. It should generally possess a tensile strength of at least about 1 g./den., preferably at least about 2 g./den., an elongation at break of at least about 3%, preferably about 10%, and an initial modulus not exceeding about 3000 kg./ rnmfi, preferably not exceeding about 2000 kg./mm. The electrically conductive fiber used should preferably possess not only the foregoing mechanical properties along the longitudinal direction but also its mechanical properties along the lateral direction such as flexibility and also its chemical properties such as its property to withstand the usual scouring, dyeing and washing operations. In addition, the electrically conductive fiber to be used in the present invention should generally possess a low density of less than 2.5 g./cc., and preferably a low density of less than 2.0 g./cc.

As the chemical fiber used as the substrate of the elec trically conductive fiber, fibers of linear synthetic polyamides such as nylon 6 and nylon 66 are preferably from the standpoint of mechanical properties and adhesiveness to the eltctrically-conductive coating. Also from the standpoint of mechanical properties fibers of polyesters such as polyethylene terephthalate are preferable. But fibers of other synthetic polymers are also usable such as those of polyolefinic polymers, acrylic polymers, polyvinyl acetal, polyurea, polyimide and blends thereof and cellulosic fibers composed of cellulose acetate or regenerated cellulose. The fineness of fibers is usually about to 50 denier, preferably about 10 to denier. Furthermore, the chemical fiber used as the substrate may be either in the form of monofilament or multifilament.

The electrically conductive coating can be formed on the substrate fiber in the following manner. A solution or an emulsion of a binder polymer which contains dispersed therein finely divided metals, for example, silver, gold, platinum, copper, brass, nickel, aluminum, tungsten, as well as other finely divided electrically conductive materials such as copper oxide and carbon black is applied to the surface of the substrate fiber, following which the coating is dried and, as desired, the binder polymer is cured. As the electrically-conductive finely divided powder, finely divided powder of silver and carbon black are especially preferable in view of resistance to scouring, dyeing, Washing, and chemicals and in view of electrical conductivity.

Usable as the binder polymer are various synthetic resins such as acrylic, epoxy, phenolic, urethane, melamine, urea, polyester, vinyl and silicone resins, natural and synthetic rubbers, and mixtures of these. However, in each individual case, choice should be suitably made, taking into consideration the characteristics of binders such as their adhesiveness to the substrate fiber, the abrasion resistance and chemical resistance of the coating, and flexibility of the coated substrate fiber. Further, this liquid composition can be incorporated with a thickening agent, an anti-aging agent, a modifier for imparting flexibility to the coating, a curing agent for the binder polymer as well as other additives. As examples of suitable binder polymers, included are the combinations of the oil-soluble phenolic resins with chloroprene polymer, styrene/butadiene copolymer, acrylonitrile/butadiene copolymer and other synthetic rubbers; the combinations of a bisphenol/epichlorohydrin type epoxy resin having an epoxy equivalent of about 170 to 250 with a polyamide resin, an epoxidized vegetable oil or liquid polyalkylene sulfide; a relatively low molecular weight polyurethane urea having terminal N,N-disubstituted ureylene groups; the combination of a partially saponified vinyl chloride/ vinyl acetate copolymer and a melamine resin modified by n-butanol; and the combination of ethyl acrylate/ styrene/hydroxyethyl acrylate copolymer with a melamine resin modified by n-butanol.

The electrically-conductive fibers used in the invention should have an electrical resistance not in excess of about 10 Q/cm., because if the electrical resistance exceeds this limit, the woven or knitted cloth having antistatic properties as contemplated by the invention cannot be obtained. To manufacture electrically-conductive fibers having an electrical resistance not in excess of about 10 Q/cm., it is necessary to adjust the amount of finely divided powder of an electrically-conductive material present in the electrically-conductive coating, and the thickness of the coating.

In order to attain an electrical resistance not exceeding about 10 t'Z/cm., the content of metal in the coating must generally be at least by weight, preferably at least 75% by weight when the finely divided electrically conductive material is a metal such as silver, whereas the carbon content must be at least 5% by weight, preferably 10% by weight when it is carbon. Further, it is preferred, from the standpoint of stable conductivity, that the thickness of the coating should be at least about 0.3 micron in the case of finely divided metals, and at least about 0.5

micron in the case of carbon. On the other hand, the upper limit of the thickness of the electrically conductive coating and the upper limit of the amount contained in the coating of the finely divided particles of the electricallyconductive material are restricted in actual use in view of the above-mentioned properties as the textile fiber, i.e., the functional properties as the textile fiber such as mechanical properties of the fiber and flexibility. A coating of excessive thickness is not only unnecessary from the standpoint of conductivity but also undesirable especially from the standpoint of fiexibiliy. A coating containing finely divided metals as its electrically-conductive material preferably should have an average thickness not exceding about 10 microns, preferably not exceeding about 5 microns. It is further necessary that a coating containing carbon should have an average thickness not exceeding about 15 microns, preferably not exceeding 10 microns. Again, coatings containing the finely divided metals in an amount exceeding about by weight or the carbon in an amount exceeding about 60% by weight are in general poor in their tenacity and their adhesiveness to the substrate and hence easily tend to become separated from the substrate during the procesing steps and in use.

The knitted or woven cloth for use in garments and underwear according to the invention consists of organic textile fibers and a minor amount of said electrically-conductive fibers. For achieving notable antistatic effects, the electrically-conductive fiber must be present in the knitted or woven cloth in an amount of at least 0.005% by Weight. Although it is possible at times to achieve the antistatic effects even with smaller amounts than indicated above, the effects are frequently not stable. On the other hand, when the electrically-conductive fiber is incorporated at the ratio of about 2% to about 10% by weight, the degree of improvement in the antistatic effects corresponding to the increase of the electrically conductive fiber gradually decreases as the ratio approaches the latter value. Hence, the use of the electrically-conductive fiber in an amount in excess of about 10% by weight is unnecessary for practical purposes. Therefore, from a practical standpoint, the electrically-conductive fiber should be incorporated in the knitted or woven cloth at the ratio of about 0.005% to about 10% by weight, and preferably about 0.01% to about 2% by weight.

The electrically-conductive fiber can be incorporated in a knitted or woven cloth for garments and underwears by mix spinning, doubling, mix twisting, mix weaving, mix knitting and other optional means. Generally, an electrically-conductive yarn containing an electrically-conductive fiber is prepared from the electrically-conductive fiber and an ordinary organic textile fiber. It is convenient to prepare a knitted or woven cloth by using only the electrically-conductive yarn or to prepare it from the electrically-conductive yarn and an ordinary non-electricallyconductive weaving or knitting yarn by an ordinary mix weaving or mix knitting. Depending upon the applications of a final product, it is possible to produce the intended woven or knitted cloth by mix weaving or mix knitting of an electrically-conductive spun or filamentary yarn consisting only of electrically-conductive fibers with an ordinary non-electrically-conductive weaving or knitting yarn. It has been found that it is advantageous and preferable to incorporate the electrically-conductive fiber in the form of continuous filaments. For instance, when the knitting or weaving yarns are spun yarns, the incorporation of electrically-conductive fibers can also be efiected by using spun yarns containing electrically-conductive fibers as part of these knitting or weaving yarns. Even when the knitting or weaving yarns are spun yarns, it is advantageous to use electrically-conductive fibers in the form of continuous filaments and to associate them with separately produced non-electrically-conductive spun yarns. One advantageous method of producing a knitted or woven cloth according to the invention includes conducting weaving or knitting while paralleling continuous electrically-conductive filaments, advantageously paralleling one electrically-conductive monofilament, with part or whole of non-electricallyconductive weaving or knitting yarns to be made into the knitted or woven cloth. It has been confirmed that a more excellent and more stable antistatic effect can be obtained by incorporating the electrically-conductive fibers in the form of continuous filaments than by doing it in the form of staple fibers. As a matter of course, the form of continuous filament is more advantageous for producing such an antistatic cloth. Especially when weaving or knitting yarns are continuous filaments, it is also possible to associate an electrically-conductive filament in the form of at least one, advantageously one, monofilament with an ordinary organic textile filament bundle, subjecting them to a mechanical crimping, and to use them as a part or whole of the weaving or knitting yarns.

It was unexpected that the electrically-conductive filament as used in the present invention could stand twisting, crimp-imparting, weaving and knitting.

As previously mentioned, it is not necessary that all the weaving and knitting yarns should contain an electricallyconductive filament. So long as the content of the electrically-conductive fiber in the knitted or woven cloth is at least about 0.005% by weight, a remarkable antistatic effect can be achieved, even if the distance between an electrically-conductive yarn and an adjacent electricallyconductive yarn is considerably large. The distance between electrically-conductive yarns should be chosen according to the purpose of using the knitted or woven cloth and the desired antistatic effect. Like the content of the electrically conductive fiber as mentioned above, this distance is an important factor for giving an antistatic effect to a knitted or woven cloth for garments and underwear. If the distance between electrically-conductive yarns in a knitted or woven cloth is less than cm., preferably less than 10 em, all of the garments sewn from this cloth are almost free from a phenomenon of the bottom flaring or sound of static discharge when putting off the garments. In the case of slips or skirts, clinging to the human body during wearing is hardly seen if this distance is less than 10 cm., preferably less than 5 cm. A cloth having electrically-conductive yarns incorporated therein at shorter intervals gives an increased antistatic effect. If a person wearing a working garment made from this cloth, the charged voltage of the garment and the wearer during wearing and at the time of putting off is restrained very low without worry about discharge or shock. Thus, he can safely work in a dangerous place such as in an inflammable atmosphere. Furthermore, if electrically-conductive yarns are incorporated at intervals of 1 cm. or less in parallel fashion or in cross stripes, the obtained cloth possesses not only an excellent antistatic effect but also a shielding effect of electro-static flux lines. Thus, it can be made into working wears for persons dealing with electronics and with high voltage live lines.

The electrically-conductive fibers used in the present invention include not only those in which an electric resistance is in the region of an ordinary conductor, but also those in which an electric resistance is very high such as 10 .Q/cm. It is surprising that a marked antistatic effect is exhibited even when a small amount of a fiber having such high electric resistance is incorporated. It is not easy to explain the mechanism of prevention of electrification with simplicity. Generally, a high voltage above 1000 volts poses a problem in an unfavorable electrification of ordinary organic textile fibers, and a quantity of electrostaticity generated at this time is very small. Hence, it is presumed that even in the case of such high electric resistance, a local intrinsic electric breakdown of the coating occurs under such 'high voltage, and electrostatic charge is easily dissipated with this electrically-conductive fiber by such effects as gaseous corona discharge, surface flashover and tracking and leakage, thus preventing the accumulation of electrostatic charge. This seems to contribute greatly to the prevention of electrostatic charge.

6 Further, the dispersion of electrostatic charge through the electrically-conductive fiber as well as the shielding effect of the fiber seem to contribute to the antistatic efiect.

The electrically-conductive fibers used in the present invention retain the functional properties of textile fibers and have durability against various conditions that are usually encountered during the manufacture of woven or knitted cloths for use in garments and undewear and during their use, such as abrasion, repetitive flexure, repetitive elongation and relaxation, scouring, dyeing and Washing. The electrically-conductive fibers of this invention can be incorporated in the knitted or woven cloth very readily during their manufacture. The cloths according to the present invention which contain a small amount of the electrically-conductive fibers have durable antistatic properties, and their appearance and hand are also highly satisfactory. Further, these electrically-conductive fibers are compatible with the other fibers that make up the cloths, and therefore, their tendency to separate from the surface during the use of the cloth is slight.

The knitted or woven cloths for garments and underwear according to the invention may be either weave cloth such as plain weave cloth, twill cloth, satin cloth and other fancy weave cloth, or knitted cloth such as weft knitted cloth and warp knitted cloth. Outer garments, shirts, blouses, underwear, lingeries and other wearing cloths made from these woven or knitted cloths possess durable antistatic properties.

The following examples are given for further illustration of the invention. The resistance of the electricallyconductive fiber shown in the eamples was determined by using an FM tester, Model L-19-B and an automatic insulation-ohmmeter, Model L-68, manufactured by Yokogawa Electric Works, Japan, and breakage tenacity, breakage elongation and initial Youngs modulus were measured using a sample of 5 cm. of gauge length with a stretching speed of 5 cm./min. The value of the electrification voltage was measured by means of a collecting type potentiometer, Model K-325, manufactured by Kasuga Electric Company, Japan. The content of the electrically-conductive fiber is presented in percentage by weight of the electrically-conductive fiber based on the organic textile fiber which constitutes the knitted or woven cloth.

Unless otherwise specified, the parts and percentages of composition in the examples are on a weight basis.

EXAMPLE 1 (A) A IS-denier nylon-6 monofilament was passed through a paste consisting of a mixture of finely divided flasky silver having an average particle size of 1.5 microns and a nitrile rubber-phenol type adhesive (solid content 24%) in the ratio respectively as indicated in Table A, at a feed rate of 25 m./min., and then passed through a slit to adjust its coating thickness. Thereafter, the monofilament was passed through a hot air oven at 70 C. for 6 seconds, and then through an air bath at C. for 6 seconds. An electrically-conductive monofilament having an electrical resistance indicated in Table A was obtained respectively.

(B) A IS-denier nylon-6 monofilament was passed through a paste consisting of a mixture of acetylene black and a nitrile rubber-phenol type adhesive (solid content 24%) in the ratio respectively as indicated in Table B, at a feed rate of 25 m./min., and then passed through a slit to adjust its coating thickness. Thereafter, the monofilament was passed through a hot air oven at 70 C. for 6 seconds, and then through an air bath at 190 C. for 6 seconds. An electrically-conductive monofilament having an electrical resistance indicated in Table B Was obtained respectively.

As shown in Tables A and B, all the obtained electrically-conductive filaments possess properties as weaving and knitting fibers and retain tenacity, pliability and flexibility which hardly differ from those of the substrate filament. In addition, they are light in weight.

TABLE A Properties of the electrically-enductive filament Compound'ng ratio Breakage of paste tenacity Thickness based on Finely Adhesive of the the denier divided (part elcctricallyof sub- Initial llaky calculated conductive Electrical Breakage strate Breakage Youngs Specific silver as solid coating resistance tenacity filament elongation modulus gravity Specimen Number (part) content) (micron) (Q/em.) (g./den.) (g./den.) (percent) (kg/mm?) (g./cc.)

100 2!) 3. S 2. 5X10 2 2. 6 5. 4 42 280 1. 7 100 24 2. 3 1. 2X10 3 3. 3 5. 6 43 250 1. 6 100 24 1.0 5. 0X10 G 4. 2 5. 5 41 200 1.6 100 ll) 2. 0 8. 0X10 3. 3 5. (l 42 240 1. 0

TABLE B Properties of the elcetrieally-conductive filament Compounding ratio Breakage of paste tenacity Thickness based on Finely Adhesive of the the denier divided (part clectricallyof sub- Initial flaky calculated conductive Electrical Breakage strate Breakage Youngs Specific silver as solid coating resistance tenacity filament elongation modulus gravity Specimen Number (part) content) (micron) (Q/em.) (g./den.) (g./den.) (percent) (kg/111111. (g./cc.

15 85 7. 0 8. 0X10 9 3. 3 5. 3 38 240 1. 1 10 24 4. 3 3. 0X10 4. 0 5. G 40 230 1. 2 10 24 2. 5 6. 0X10 7 4. 5 5. 5 42 210 1. 2 45 55 3.0 4. 0X10 4 4. 2 5. 5 41 220 1. 2

For the manufacture of a plain weave cloth wherein both warps and wcfts consist of 75 denier/36 filament polyethylene terephthalate yarns, each of the said electrically-conductive monofilamtnts was doubled with 75 denier/36 filament polyethylene tercphthalatc multifilamcnts, and the resulting filament bundles were woven in so that they were arranged at intervals of 2 cm. in the warp and weft directions. The ratio of the electricallyconductive filament incorporated into the plain weave (emulsion type; solid content 42% 3.5 parts of an aqueous solution of melamine resin (solid content 50%) and a small amount of a catalyst was prepared.

Each of the so prepared pastes was coated using a rotary roller on a -denicr polyethylene tcrephthalate monofilamerit, and cured by heating with an infrared ray lamp. Electrically-conductive monofilamcnts (A) and (B) having the properties indicated in the following table were obtained respectively.

Properties of the electrically-conductive filaments Breakage tenacity Thickness based on of the the denier electricallyof sub- Breakage Initial conductive Electrical Breakage strata elonga- Young's Specific coatin resistance tenacity filament tion modulus gravity Specimen Number (micron (SI/cm.) (g./den.) (g./den.) (percent) (kg/mm. (g./cc.)

A 1. .l 5. 0X10 Z 3. 3 4. 9 24 860 l. 8 B 3. 5 2. 0X10 5 3. 6 4. 5 21 760 1. 3

cloth was 0.080.l3% for the electrically-conductive filaments (A), and 0.070.l% for the electrically-conductive filaments (B).

These electrically conductive filament incorporated cloths and cloths having no electrically-conductive filament were each scoured, and rubbed with a cloth of polyacrylonitrile fiber at C. and a relative humidity of at a speed of 6 cm./sec. The electrification voltage of each of these cloths was measured 30 seconds after the electrification voltage reached saturation. Consequently, it was found that the cloths having no electrically-conductive filament produced the sound of discharge during rubbing and exhibited an electrification voltage as high as +7,300 volts, but that the cloths containing these electrically-conductive filaments all exhibited an electrification voltage of only +430 to +550 volts.

It was noted that both an electrically-conductive filament having a very high electrical resistance such as specimen B-1 and a well conductive filament, when incorporated, exhibited the same excellent antistatic effect.

EXAMPLE 2 and a small amount of a catalyst was prepared.

(B) A well mixed paste consisting of 10 parts of acctylene block, parts of an acrylic ester type adhesive These electrically-conductive filaments have the propcrtics indicated in the foregoing table, and have tenacity, pliability and flexibility which are little ditferent from those of the substrate filament. Moreover, they are light in weight.

After the above-mentioned electrically-conductive monofilamcnts were repeatedly bended times with a bonded angle of 90, their electrical resistance hardly changed. Furthermore even after they were rubbed for 5 minutes by a nylon gear (rotation speed r.p.m.; module 3.61; the number of teeth 40) under a load of 0.33 g./den. calculated on the basis of the substrate fiber, there was little change in their electrical resistance, and the electrically-conductive coating was not stripped off.

The above-mentioned electrically-conductive monofilament was doubled with a 50 denier/24 filament polyethylene tcrephthalate multifilamcnt to form an electricallyconductive yarn. A tricot fabric for shirts was knitted from the resulting electrically-conductive yarn and the said polyethylene terephthalate multifilamcnt yarn so that the electrically-conductive yarn was arranged in the warps at intervals of 5 cm. Mcns shirts were sown by using the resulting fabric. The content of the electricallyconductive filament incorporated was 0.06% for (A) and 0.05% for (B).

With respect to shirts having incorporated therein these electrically-conductive filaments and shirts containing no electrically-conductive filament, wearing and undressing tests were conducted at 24 C. and 10% RH. In the case of the shirts containing no electrically-conductive filament, they clung to the wearer on putting off, and the sound of static discharge was heard. Further, when the wearer, after putting off the shirt, touched a conductive material such as metal, he got a violent electric shock. The electrification voltages of the shirt and the human body after undressing reached +8000 volts and 4700 volts, respectively. But in the case of the shirt containing the electrically-conductive filament (A), the electrification voltage was only +300 volts and -400 volts respectively, and in the case of the shirt containing the electrically-conductive filament (B), it was only +350 volts and 400 volts respectively. The above-mentioned electrostatic troubles did not at all occur in any of these shirts, and they had an excellent antistatic effect.

EXAMPLE 3 A -denier polyethylene terephthalate filament was passed through a well mixed paste consisting of 10 parts of finely divided copper having an average particle size of about 10 microns and parts of an acrylic resin type adhesive (solvent type; solid content 10%), and passed through a slit to adjust its coating thickness, followed by hardened by heating it in hot air. There was obtained an electrically-conductive filament having an average electrical resistance of 1000 MQ/cm. and an average coating thickness of 1.4 microns.

The obtained electrically-conductive filament had a breakage tenacity of 3.6 g./den. (4.9 g./den. calculated on the basis of the denier of the substrate filament), a breakage elongation of and an initial Youngs modplus of 1100 kg./mm. It had tenacity, pliability and flexibility which are little different from those of the substrate filament, and was light in weight as demonstrated by a specific gravity of 1.6.

For the manufacture of a plain Weave cloth wherein both warps and wefts consist of 100 denier/ 84 filament polyethylene terephthalate multifilaments, the above-mentioned electrically-conductive monofilament was doubled with a 100 denier/48 filament polyethylene terephthalate multifilament, and the resulting filament bundle was woven in so that it was arranged at intervals of 1 cm. in the warp and weft directions. The content of the electrically-conductive filament incorporated was 0.18%.

A cloth having incorporated herein this electricallyconductive filament and a cloth containing no electricallyconductive filament were each scoured, and their electrification voltage was measured in the same manner as in Example 1 by rubbing them with a cloth of an acrylic fiber. The cloth having no electrically-conductive filament exhibited an electrification voltage of +7,300 volts, whereas the cloth containing the electrically-conductive filament showed only +350 volts, exhibiting a very excellent antistatic effect.

A skirt sewn by using the cloth obtained in this example did not cling to legs nor flare at all, and beautiful proportions could be retained. On the other hand, a skirt sewn by using the plain weave cloth containing no electrically-conductive filament violently clung to legs or creep up legs, so that it was very uncomfortable to the wearer.

EXAMPLE 4 An electrically-conductive monofilament (specimen A 2 obtained in Example 1) was laid together with two polyethylene terephthalate/cotton blend yarns (blend ratio being 65/35) of count and subjected to a final twist to form a ply yarn having electrically-conductivity. Using this yarn and an ordinary 30-count ply yarn having no electrically-conductivity, a polyethylene terephthalate/cotton twill cloth was woven by arranging the electrically-conductive yarn in the warp direction at various intervals indicated in the following table. Working wears were sewn by using the resulting twill cloths.

Each of these working wears was Washed for 20 minutes in a warm water at 60 C. containing 1 g. per liter of a nonionic detergent, and dried after removing the de- 10 tergent thoroughly. A person wearing insulated shoes put off each of these wears, and an undressing test was conducted at 24 C. and RH.

At the time of undressing the working Wears Interval of Ratio of the the eleetrieleetrically- Electrificacally-conconductive Electn'fication voltage ductive yarn filament tion voltage of the incorporated incorporated of the human working Specimen No. (cm.) (percent) body (kv.) wear (kv.)

l N 0t incorporated.

One part of acetylene black and 12 parts of chloroprenephenol type adhesive (polychloroprene/p-t-butylphenol-formaldehyde resin: 100/ solvent toluene; solid content 24%) were thoroughly mixed to prepare a paste. A plurality of S-denier nylon 6 monofilaments were paralleled as slightly spaced from each other, and simultaneously immersed in the paste while retained in the paralleled state. Then the filaments were passed through a slit to adjust the coating thickness, and cured by heating while retained at the small intervals to prevent their mutual adhesion. Thus they were covered with electrically-conductive coating. The filaments were bundled into one strand and taken up onto a winder, to provide an electrically conductive multi-filament yarn having an average electrically-conductive coating thickness of 1.2 microns, and an average resistance of l0MQ/cm. per single yarn. This electrically-conductive filament had a breakage tenacity of 4.5 g./den. (5.4 g./den. on the basis of the denier fineness of the substrate filament), a breakage elongation of 40%, an initial Youngs of 250 kg./mm. and a density of 1.2 g./cc.

This electrically conductive multifilament yarn was mixed with an acrylic tow in advance of preparing therefrom acrylic staple fiber for making a plain weave cloth, andsubsequently the tow and the yarn were together subjected to a crimper to be crimped, followed by cutting to the length of 76 mm., to obtain a stable fiber incorporated with the electrically conductive fiber of the invention. The so incorporated electrically-conductive fiber showed crimpability similarly to acrylic fiber, but still retained suflicient electrically-conductivity.

Thus, acrylic staple fibers (5 d. x 76 mm.) containing about 10% of the electrically-conductive staple fiber were obtained. Using the so obtained staple fibers, 30-count spun yarns were prepared. This electrically-conductive spun yarn and 30-count ordinary spun yarn were woven to make a plain weave acrylic cloth was arranged in the warp and weft directions at intervals of 5 cm. The content of the electrically conductive fiber in the cloth was 0.08%. A test piece with a size of 10 cm. x 10 cm. was prepared from the obtained cloth. When this test piece was scoured, and then rubbed vigorously with a cloth of polyvinyl chloride fiber at 24 C. and a relative humidity of 40%, a sound of static discharge was not heard at all and its electrification voltage was only +5.0 kv., exhibiting a very excellent antistatic elfect. On the other hand, a plain weave acrylic cloth not containing the electrically-conductive fiber produced a sound of static discharge upon rubbing, and its electrification voltage reached +60 kv.

We claim:

1. A knitted or woven cloth having durable antistatic properties for use in garments and underwear, said cloth consisting of a yarn of elecrtrically non-conductive fiber and a yarn comprising said non-conductive fiber and an electrically conductive filament, said electrically conductive filament comprising a substrate of an organic synthetic filament of -50 denier and an electrically conductive coating formed thereon in a thickness of 0.3 to microns, said coating consisting of a resinous matrix and a material selected from the group consisting of finely divided silver, finely divided electrically conductive carbon black and mixtures thereof dispersed in said matrix in an amount suflicient to render the electrical resistance of said electrically conductive filament less than about 10 ohms/cm., said electrically conductive filament being present in an amount of about 0.0052% by weight of the entire knitted or woven cloth in the form of at least one continuous filament incorporated with said non-conductive yarn.

2. The cloth according to claim 1 wherein at least one of said continuous, electrically conductive filament is contained at intervals of cm. or less in the warp or weft direction of said cloth or in both the warp and weft direction.

3. The cloth according to claim 1 wherein said electrically conductive coating has an average thickness of 12 about 0.5 to 10 microns and contains dispersed therein about to by weight of finely divided powder of silver.

4. The cloth according to claim 1, wherein said electrically conductive coating has an average thickness of about 0.7 to 10 microns, and contains dispersed therein about 5 to 60% by weight of finely divided powder of electrically conductive carbon.

References Cited UNITED STATES PATENTS 2,150,570 3/1939 Whitehead 57157AS 2,302,003 8/1940 Cadwell 139420 2,443,782 6/1948 Barnard 117160A 2,845,962 6/1954 Bulgin 139-420 3,008,215 1/1958 Pitts 161-175 3,030,237 9/1959 Price 117160 3,129,487 4/1964 Whitacre 57157AS 3,278,455 10/1966 Feather 117-227 3,288,175 11/1966 Valko 57139 3,399,079 8/1968 Harris 117-138.8U 3,412,043 11/1968 Gilliland 117-227 ROBERT F. BURNETT, Primary Examiner I. J. BELL, Assistant Examiner U..S. Cl. X.R.