US3590570A

US3590570A - Sewing thread

Info

Publication number: US3590570A
Application number: US788570A
Authority: US
Inventors: Tomomi Okuhashi; Kinichi Kumura
Original assignee: Teijin Ltd
Current assignee: Teijin Ltd
Priority date: 1968-03-14
Filing date: 1969-01-02
Publication date: 1971-07-06
Anticipated expiration: 1988-07-06
Also published as: SE356081B; GB1257709A; NL6901300A; DE1902647A1; DE1902647B2; BE727326A; FR2003846A1

Abstract

A sewing thread which comprises an organic textile fiber and an electrically conductive filament, the amount of said electrically conductive filament being sufficient to impart to said sewing thread an electrical resistance of less than about 2,000 megohms per centimeter, and said electrically conductive filament having the functional properties of textile fibers and comprising a substrate of chemical fiber and an electrically conductive coating thereon.

Description

United States Patent Inventors Tomoml Okuhashi Tokyo; Klnichl Kumura. Amagasaki-shi, both of, Japan Appl. No. 788,570 Filed Jan. 2, 1969 Patented July 6, 1971 Assignee Teijin Limited Osaka, Japan Priority Mar. 14, 1968, Mar. 14, 1968, June 18,

1968 Japan 43/20417, 43/211418 and 43/51397 SEWING THREAD 3 Clalms,3 Drawing Figs.

11.8. CI 57/140, 5 7/153 lnt. D023 3/02, D02g 3/04, D02g 3/12 Field 01 Search 57/140,

139,157 AS, 140 C, 153; 139/425; 2/73; 117/107, 28,138.8 A, 227, 160; 28/75, 76

56 RGIBIGBCQS Cited UNITED STATES PATENTS 2,443,782 6/1948 Barnard 61 a1. 57/157 ux 2,473,183 6/1949 Watson 57/157 ux 2,845,962 8/1958 19111 111 57/157 ux 2,897,098 7/1959 1161116161 61. 57/157 ux 3,288,175 11/1966 V6116 139/425 5,530,935 4/1968 Ring.... 117/227 x 3,422,460 1/1969 Burke 61 a]. 2/73 Primary Examiner-Donald E. Watkins Attorney-Wenderoth, Lind & Ponack ABSTRACT: A sewing thread which comprises an organic textile fiber and an electrically conductive filament, the amount of said electrically conductive filament being sufficient to impart to said sewing thread an electrical resistance of less than about 2,000 megohms per centimeter, and said electrically conductive filament having the functional properties of textile fibers and comprising a substrate of chemical fiber and an electrically conductive coating thereon.

PATENTED JUL 6 IHYI F/gZ INVENTORS TOMOM/ OKUHASH/ KIN/CHI KUMURA Fig.3

' SEWWG TllllltlEAD This invention relates to an electrically conductive sewing thread comprising an organic textile fiber and an electrically conductive filament, and to woven and knitted goods having durable antistatic properties obtained by using this sewing thread.

Generally, woven or knitted good consisting of organic textile fibers have an undesirable property of becoming charged with static electricity on being subjected to friction, particularly at low humidity. Woven or knitted goods made of hydrophobic chemical fibers such as synthetic fibers, for instance, polyamides, polyesters, polyacrylonitrile and polyolefins, and semisynthetic fibers, for instance, acetate and triacetate fibers tend to be electrostatically charged, and undergo such troubles as the occurrence of sound of electrostatic discharge, clinging of these goods to a human body and electric shock.

As an attempt to overcome these difficulties, U.S. Pat. No. 3,288,175 discloses the incorporation of a small quantity of metallic fibers into woven goods. In this patent, it is necessary to use a metallic fiber having as fine a denier as possible. Because the metallic fibers are essentially difierent in nature from ordinary textile fibers, these two kinds of fibers are hardly compatible with each other. Therefore difficulties are encountered in the steps of mixing metallic fibers of fine denier with textile fibers, spinning, weaving, processing, dyeing and finishing, and the hand of the obtained woven materials is not good. In addition, it is difficult to manufacture metallic fibers of fine denier, and the metallic fibers are expensive.

As another method of overcoming these difficulties, Japanese Patent Application Publication No. 4196/57 and U.S. Pat. No. 2,845,962 disclose a method of preventing electrostatic charge of woven goods by incorporating into textile fibers electrically conductive fibers with carbon black being dispersed throughout their interior. In order, however, for the electrically conductive fibers containing carbon black to have the desired electric conductivity, they must contain carbon black in a great quantity, i.e., at least 20 percent by weight. Moreover, because of low mechanical strength, these fibers tend to be broken in the steps of spinning, weaving and processing.

The present invention has made it possible to solve the aforesaid problems by making woven and knitted goods with the use of a sewing thread comprising organic textile fibers and an electrically conductive filament.

According to the invention, there is provided a sewing thread which comprises at least one organic textile yarn and at least one electrically conductive filament, characterized in that said electrically conductive filament comprises a sub strate of at least one continuous organic synthetic filament, the total denier of said substrate being -50, and an electri cally conductive coating on said substrate filament, said electrically conductive coating having an average thickness of about 0.3 to microns and comprising about 10 to 50 per cent by weight of a polymer binder matrix and about 50 to 90 percent by weight of finely divided silver dispersed therein so that said electrically conductive filament has an electrical re sistance of less than 2,000 megohms per centimeter.

The term sewing thread," as used herein and the appended claims, unless otherwise specified, includes a machine sewing thread and a hand sewing thread.

The term filament, as used herein and the appended claims, includes continuous monofilament and multifilaments.

The electrically conductive filament used in the sewing thread according to the present invention comprises a substrate of at least one continuous organic synthetic filament consisting of a polymer such as nylon, polyester, acrylic, polypropylene, on which substrate is formed an electrically conductive coating comprising a polymeric binder matrix having dispersed therein finely divided particles of silver and the filament thus formed possesses the functional properties of textile fibers. The terminology, functional properties of textile fibers," as used herein, is meant, in general, to be the possession of mechanical properties whereby a fiber can be submitted to the usual spinning, twisting, crimp-imparting, weaving and knitting operations and stand such conditions which it will usually encounter during these processing steps as well as in its use, i.e. such conditions as abrasion, tensile stress, bending stress, repetitive fiexure, repetitive elongation and relaxation; and the possession of compatibility and coprocessability with the usual organic textile fibers. The electrically conductive filament to be used in the sewing thread according to the present invention should possess mechanical properties which are about comparable to those of the substrate organic filament. it should generally possess a tensile strength of at least about 1 g./denier, preferably at least about 2 g./denier, an elongation at break of at least about 3 percent, preferably about 10 percent, and an initial modulus not exceeding about 3,000 kg/rnrn. preferably not exceeding about 2,000 kg/rnrnP. The electrically conductive filament used should preferably excel not only in the foregoing mechanical proper ties in the longitudinal direction but also in its mechanical properties in the lateral direction such as flexibility and also in its chemical properties such as its property to withstand the usual scouring, dyeing and washing operations. In addition, the electrically conductive filament 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.

The electrically conductive coating can be formed on the substrate fiber in the following manner. A polymeric binder solution or emulsion which contains dispersed therein finely divided silver, is applied to the surface of the substrate filament, after which the coating is dried and, if desired, the polymeric binder is cured. The electrically conductive filament to be used in the present invention should be one having an electrical resistance not exceeding about 2,000 megohms per centimeter.

The desirable electrically conductive filament used in the sewing thread according to the present invention comprises a substrate of at least one continuous organic synthetic filament with a total denier of about 5 to 50 and an electrically conductive coating thereon consisting of a polymeric binder matrix having dispersed therein finely divided particles of silver sufficient to render the electrical resistance of said filament less than about 2,000 megohms per centimeter, the thickness of which coating averages about 0.3 to about 10 microns. Moreover, said electrically conductive filament possesses the functional properties of textile fibers. An electrically conductive filament of this kind can be conveniently produced by applying to the substrate filament either a solution or emulsion of 'a polymeric binder in which finely divided silver particles are dispersed, followed by drying and, if required, curing of the polymeric binder. As the substrate filament, particularly preferred from the standpoint of their a-dhesiveness of the conductive coating and mechanical strength are filaments of synthetic linear polyamides such as nylon 6 and 66, those of about 5 to 50 denier, and preferably about 10 to 30 denier, being advantageously used. The substrate filament if preferably of monofilament form.

Finely divided particles of silver are advantageously used in the invention in view of their resistance to scouring and dyeing treatments, resistance to washing, weatherability, chemical resistance and electrical conductivity. These finely divided particles of silver are mixed and dispersed in an adhesive composition, i.e. a liquid composition containing a suitable polymeric binder, and this dispersion is applied to the substrate filament.

Usable as the polymeric binder are the various synthetic resins of the acrylic, epoxy, phenolic, urethane, melamine, urea, polyester, vinyl and silicone types, the natural and synthetic rubbers, and the mixtures of these. However, in each individual case, a 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 cured coating, and flexiblity of the coated substrate fiber. This liquid composition can be incorporated with a thickening agent, an antioxidant, a modifier for imparting flexibility to the coating, a curing agent for the polymeric binder as well as other additives. Examples of suitable polymeric binders include the combinations of the oilsoluble 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 and a melamine resin modified by n-butanol.

The lower limit of the amount of the finely divided particles of silver to be present in the electrically conductive coating is imposed a limitation in view of the conductivity of the resulting electrcially conductive filament. The content of the silver in the coating must be made at least 50 percent by weight.

It is preferred from the standpoint of the stability of the conductivity that the thickness of the coating be at least 0.3 micron. 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 silver are imposed a practical limitation in view of the mechanical properties, especially flexibility of the filament, the tenacity of the coating and the adhesiveness between the coating and the substrate. A coating of excessive thickness is not only unnecessary from the standpoint of conductivity but also undesirable from the standpoint of flexibility. A coating containing finely divided silver should have average thickness not exceeding about microns. The coatings containing the finely divided silver in an amount exceeding about 90 percent 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 processing steps and in use.

The electrically conductive filaments 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 sewing thread and during their use such as abrasion, repetitive fiexurc, repetitive elongation and relaxation, scouring, dyeing and washing. The conductive filaments of the invention are compatible with the textile fibers which are used in the sewing thread. These conductive filaments can be incorporated into the sewing thread very readily during their manufacture. The conductive sewing thread obtained has sewability comparable to that of a sewing thread containing no conductive filament, and also has durable electric conductivity.

The invention will now be described with reference to the accompanying drawings in which:

FIG. 1 is an enlarged view of the sewing thread of the invention; and,

FIGS. 2 and 3 are front elevations of garments sewn by using the sewing thread ofthe invention.

In FlG. ll,

reference numerals

2, 2 and 21" represent yarns consisting of textile fibers preliminarily twisted. Reference numeral 1 represents an electrically conductive filament which has been preliminarily twisted together with a yarn 2 consisting of ordinary textile fibers. As shown in the drawings, the sewing thread of the invention can be very easily produced by preliminarily twisting an electrically conductive filament with a yarn consisting of ordinary textile fibers, and then finally twisting the resulting yarn together with one or a plurality of other twisted yarns. It is preferred from the viewpoint of sewability that the electrically conductive filament be given a preliminary twist together with the yarn. This is, however, not restrictive. The sewing thread of the invention can also be made by twisting the electrically conductive filament together with a plurality of preliminarily twisted yarns. in this case, the

electrically conductive filament can be twisted together with the preliminarily twisted yarns while the conductive filament is being tensioned, thereby producing a sewing thread in which the electrically conductive filament is not visible from without.

An amount of the electrically conductive filament to be contained in the sewing thread of the invention is such that at least one electrically conductive filament is present along the entire length of the sewing thread. If at least one of such an electrically conductive continuous filament is present in the sewing thread along its entire length, the sewing thread has an electrical resistance not in excess of 2,000 megohms/cm. There is no particular upper limit to the amount of the electrically conductive filament contained in the sewing thread of the invention.

Since the sewing thread of the invention has an excellent durability in electric conductivity, woven and knitted goods such as garments sewn by using the sewing thread have excellent antistatic properties.

FIG. 2 shows a skirt consisting of synthetic fibers which has been sewn by using the sewing thread 3 of the invention.

Even if the sewing thread of the invention is used only in the seams as shown in the drawing, the clinging of the skirt to legs does not occur.

H6. 3 shows a mans shirt sewn by using the sewing thread 42 of the invention. The presence of this sewing thread can prevent the sound of electrostatic discharge and flaring at the time of putting off the shirt, and also soiling owing to attraction of dust. in sewing this shirt, an ordinary sewing thread can be used as upper thread with the sewing thread of the invention used as lower thread. The antistatic effect is the same as in the case of using the sewing thread of the invention both as upper thread and lower thread.

A marked antistatic effect can be imparted to ordinary garments if the ordinary sewing parts are sewn with the sewing thread of the invention. Thus, electrostatic troubles such as clinging, sound of electrostatic discharge, flaring, soiling owing to attraction of dust, and electric shock can be drastically reduced.

A higher antistatic effect can be imparted by quilting woven and knitted goods at optional intervals such as l0 cm., 5 cm., or 1 cm., by using the electrically conductive sewing thread of the invention.

The electrically conductive sewing threads 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 2,000 mil/cm. it is surprising that a marked antistatic effect is exhibited even when a very small amount ofa sewing thread having such high electric resistance is incorporated. It is not easy to explain the mechanism of prevention of electrification. Generally, a high voltage above 1,000 v. poses the problem of 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, the local intrinsic electric breakdown of the coating occurs under such high voltage, and the electrosta ic charge is easily dissipated with this electrically conductive filament 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. Further, the dispersion of electrostatic charge through the electrically conductive filament as well as the shielding effect of the filament seem to contribute to the antistatic effect.

The sewing thread of the invention can be used in various woven and knitted goods, for instance, garments, interior decorating fiber products such as curtain and covering cloth of chairs and sofas, beddings such as blankets, and other products such as mailbags and parachutes. Woven and knitted fabrics sewn, quilted or embroidered by using the sewing thread of the invention have excellent durable antistatic propertles.

The following examples are given for further illustration of the invention. The resistance of the electrically conductive filament and the electrically conductive sewing thread shown in the examples was determined by using an FM tester, Model L-l9-B and an automatic insulation-ohrnmeter, Model L-68, manufactured by Yokogawa Electric Works, Japan, and breakage tenacity, breakage elongation and initial Young's modulus were measured using a sample of 5 cm. of gauge length with a stretching speed of 5 cm./rnin. The value of the electrification voltage was measured by means of a collecting type potentiometer, Model K-325, manufactured by lfiasuga Electric Company, Japan. The content of the electrically conductive filament is presented in percentage by weight of the electrically conductive filament based on the organic textile fiber.

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

Example 1 A IS-denier nylon 6 monofilament was immersed in, and passed at a rate of 25 mJmin. through a paste obtained by well mixing l00,parts of flaky fine powder of silver (having an average diameter of 1.5 ,u), 100 parts of an adhesive of the nitrile rubber-phenol type (having a solid content of 24 percent), and 5 parts of methyl isobutyl ketone. The monofilament was passed through a slit to adjust its coating thickness, and then passed through a hot air drier at 120 C. for 6 seconds. Subsequently, it was further passed through an air bath at 195 C. for 6 seconds. An electrically conductive monofilament having an electrical resistance of 120 (l/cm. and an average thickness of the electrically conductive coating of2.3 p. was obtained.

This electrically conductive filament has a tenacity at break of 3.3 g./denier (5.6 g./denier calculated as the substrate fiber), an elongation at break of 43 percent and an initial Young's modulus of 250 ltgJmmF, and has a tenacity, pliability and flexibility much the same as those of the substrate filament. Also, it has a low density of about 1.6 g./cc.

One electrically conductive monofilament was doubled with one 75 denier/36 filament polyethylene terephthalate multifilament, and the resulting yarn was imparted a twist of 830 turns/m. by an Italian-type twister. The electrically conductive yarn thus obtained was doubled with two preliminarily twisted 75 denier/36 filament polyethylene terephthalate yarns not containing an electrically conductive fiber, and the resulting yarn was imparted a twist of 530 turns/m. Thereafter, the resulting yarn was heat set in vacuo for 20 minutes at 130 C. in the form of skein, scoured, and dyed.

According to the processes mentioned above the sewing thread containing an electrically conductive filament was easily obtained as in the production of ordinary sewing threads.

The only necessity was to pay an appropriate attention to the control of tension of the yarn in doubling and twisting steps.

The electrically conductive sewing thread thus obtained has an average electrical resistance of about 100 kQ/cm., and the ratio of the electrically conductive filament contained in the sewing thread is 10 percent. The physical properties of the electrically conductive sewing thread and an ordinary polyethylene terephthalate sewing thread of 50 count containing no electrically conductive filament, and the results of testing their sewability are shown in the following table.

Physical properties lt is seen from these tables that the sewing thread of the invention exhibits much the same physical properties and sewability as the ordinary sewing thread containing no electrically conductive filament.

Using the electrically conductive sewing thread as lower thread and an ordinary polyethylene terephthalate sewing thread containing no electrically conductive filament as upper thread, a tricot shirt consisting of percent polyethylene terephthalate fibers was sewn in accordance with the usual sewing specification. The ratio of the electrically conductive monofilament contained in the shirt was about 0.05 percent. The shirt thus obtained and a shirt sewn with an ordinary sewing thread were washed with a nonionic detergent for 5 minutes in an electric washer.

These shirts were subjected to wearing and undressing electrification tests at 25 C. and 25 percent Rl-l. A person put on an undershirt made of polyvinyl chloride fibers, and then a shirt containing no electrically conductive filament. After rubbing them vigorously, he put off the shirt. There was a hissing sound of electrostatic discharge. The shirt clung to his body, and flared. When he touched a conductive material such as metal, he received an unpleasant electrical shock. At this time, the shirt exhibited an electrification voltage of +50 kv., and the human body, *9 kv. On the other hand, when he wore the shirt sewn with the electrically conductive sewing thread of the invention, the electrification voltage of the shirt and the human body were only +9 kv., and 2 kv., respectively. Moreover, the electrostatic troubles above mentioned were almost obviated. It was recognized therefore that the incorporation of a very small amount of the electrically conductive filament had a marked antistatic effect.

The shirt was repeatedly washed 100 times, but its antistatic effect was hardly lost, showing an excellent durability. Example 2 A lS-denier polyethylene terephthalate monofilament was immersed in, and passed at a rate of 25 mJmin. through a paste consisting of flaky fine powder of silver having an average particle diameter of 1.5 p. and an adhesive of the nitrile rubber/phenol type having a solid content of 24 percent in the ratios indicated in the table below, and passed through a slit to adjust its coating thickness. The monofilament was passed through a hot air drier at 70 C. for 6 seconds, and then through an air bath at 220 C. for 6 seconds. Electrically con ductive filaments having various electrical resistance values were obtained. I

All of the electrically conductive filaments shown in the table possess excellent fiber properties for spinning and weaving, and also much the same tenacity, pliability and flexibility as the substrate filament. Moreover, their densities are low.

One electrically conductive monofilament was doubled with a 30 denier/l2 filament polyethylene multifilament, and the resulting yarn was imparted an S twist of 930 turns/m. by an Italian-type twister. The electrically conductive yarn thus obtained was doubled with two 50 denier/24 filament polyethylene terephthalate yarn (primarily given an S twist of 930 turns/m.). The resulting yarn was imparted a Z twist of 580 turns/m. Thereafter, it was heat set in vacuo in the form of skein at C. for 20 minutes, scoured, and dyed. A sewing thread containing an electrically conductive filament was obtained, as shown in the following table.

Sewability test Initial Shrinkage Coefficient Sewability" Skipping Tenacity gation Youngs in boiling of friction oi seam Fineness at break at break modulus water (-300 cm./ 3,000 3,500 (number! (denier) (g./den.) (percent) (kg/mm?) (percent) min.) r.p.m. r.p.m. 50 cm.)

Ordinary sewing thread (ii 50) (control) 258 3. 9 35 620 0 0.21 10 8 0 Electrically conductive sewing thread... 288 3. J 34 510 0 0. 25 10 8 0 The sewability is a time period during which four polyester/rayon clothes can be continuously sewn by a sewing machine driven at 3,000 r.p.m. and 3,500 r.p.m., using the sewing threads as upper thread, expressed by the following grades.

Time in second during which the sewing could be continuously efiected es L than 6.

O In

Sewability grade 1 2 Blend ratio of paste Properties of electrically conductive filaments Adhesive Thickness of Tenacity Fine (part electrically at break Elon- Initial powder calculated conductive Electrical Tenacity calculated cation Young's of silver as solid coating resistance at break as substrate at break modulus Density (part) conti-ni) (micron) (!Z,'c1n.) Lftlen.) fiber (g./den.) (percent) (kgq'innifi) g.,"cc.)

7 I2 3.b 4.5)(10 2.4 4.8 23 740 2.0 80 20 3.2 1.1!)(10 2.6 4.0 25 7250 1.) 80 20 1.5 x10 2.!) 4.9 25 820 1.9 84 16 1.0 X10 3.8 5.1 24 1,000 1.6

Ratio of m? Physical mommies of the M80 The ratio of the electrically conductive filament incorporated Electrically electrically trieully conductive sewing thread in the sewing thread was 25.6 percent. conductive cont uctive filament mama, Average With the use of this electrically conductive sewing thread as forploratedi incorporated in electrical lower thread a mailbag (37X49 cm.) made of a nylon 6 cloth n t e sew mg the sewing Fineness resistance thread thread (percent) (denier) (mam) l of plain weave was sewn at the opening part and both sides. I j 1 r6 O With the use of the electrically conductive sewing thread as 3 21 55 4 lower thread, the above-mentioned plain cloth was quilted at 3 is 170 J. 0X10 parallel intervals of 5 cm., 3 cm., and 1 cm. Mailbags made of 4 13 165 5. 0X10 in the manufacture of the above-mentioned sewing thread containing an electrically conductive filament, no problems occurred as in the case of producing an ordinary sewing thread, and the only necessity was to pay an appropriate attention to the control of tension on the yarn in doubling and twisting operations. The electrically conductive sewing threads obtained were subjected to the sewability test as in example i, and it was found that their scwability was almost the same as that of an ordinary sewing thread containing no electrically conductive filament.

With the use of the electrically conductive sewing thread as lower thread and an ordinary polyethylene terephthalate sewing thread as upper thread, slips consisting only of nylon 6 fiber were sewn in accordance with the usual sewing specification. The ratios of the electrically conductive monofilament contained in the slips were about 0.14 to 0.25 percent. The slips and a slip sewn with an ordinary sewing thread were washed with a nonionic detergent for 5 minutes in an electric washer, and thereafter, these slips were subjected to the wearing electrification test at 25 C. and 35-percent RH. The wearer put on one ofthe slips and stockings made of nylon 6 fiber, and a skirt made of polyethylene terephthalate fiber,

and violently rubbed by hand the skirt against the thighs. in

the case of an ordinary slip not subjected to an antistatic treatment, it clung tightly to the thighs, giving a pressed feeling. The electrification voltage of the slip after putting ofi the skirt was as high as +23 kv. On the other hand, in the case of the slips sewn with the above-mentioned electrically conductive sewing thread, there were no such electrostatic troubles, and the electrification voltages of the slips after putting off the skirt were +7 to +9 kv., exhibiting a very excellent antistatic effect.

Example 3 A IS-denier nylon 6 monofilament was immersed in a paste obtained by intimately mixing 100 parts ofa flaky fine powder of silver and 120 parts of an adhesive of the chloroprenephenol type having a solid content of 24 percent. it was passed through a slit to adjust its coating thickness, and dried by an infrared ray lamp, followed by heat-curing in a hot air bath. An electrically conductive filament having an average electrical resistance of 150 Q/cm. and an average thickness of the electrically conductive coating of 3.0 u.

The electrically conductive filament obtained had a tenacity at break of 3.3 gJdenier (6.0 gJdenier when calculated as the substrate fiber), an elongation at break of 42 percent and an initial Youngs modulus of 230 kg./mm. They had much the same tenacity, pliability and flexibility as the substrate filament, and had a low density of about 1.6 g./cc.

these cloths were sewn by using the electrically conductive sewing thread.

These mailbags and a mailbag containing no electrically conductive fiber were washed, and thereafter subjected to an electrification test at 25 C. and 25-percent RH. Each of the mailbags was placed on a polyvinyl chloride cloth spread on a desk, and was rubbed violently with other polyvinyl chloride cloth to electrify it to saturation. Thereafter, the opening part was separated part by hand, and the electrification voltage was measured. The results are shown in the following table. it is seen from the table that the mailbags sewn with the sewing One electrically conductive monofilament was doubled with 70 a yarn of 64 count spun from polyethylene terephthalate staple (1.25 denier X 38 mm.) and imparted an S twist of 26.4 turns/inch. Two of the electrically conductive yarns were imparted a final Z twist of 26.4 turns/inch to make a sewing thread of the invention are very low in electrification voltage, and exhibit an excellent antistatic effect.

Ratio of the electrically conductive filament Electrificaincorporated tion voltage in the mail of the mail Mail bag bag (percent) bag (kv.)

Bag containing no electrically conductive monofilziment (control) 0 +61 40 Bag made of a plain weave cloth and sewn with the electrically conductive sewing thread 0.02 +8 Bag made of a plain weave cloth quil d at intervals of 5 cm. with the electrically conductive sewing thread, and sewn with the electrically conductive sewing thread 0.07 +6 Bag made of a plain weave cloth quilted at intervals of 3 cm. with the electrically conductive sewing thread, and sewn with the electrically conductive sewing thread 0. 14 +5 Bag made of a plain weave cloth quilted at intervals of 1 cm. with the electrically conductive sewing thread, and sewn with the electrically conductive sewing thread 0. 39 +5 Example 4 With the use of the sewing thread containing one electrically conductive monofilament obtained in example i as lower thread, and a polyethylene terephthalate sewing thread as upper thread, a working wear consisting of a polyethylene terephthalate/rayon blend cloth of plain weave (blend ratio 0 being /35) was sewn in accordance with the usual sewing specification.

The above-mentioned plain weave cloth was quilted at intervals of 3 cm. and 1 cm. with the use of the electrically conductive sewing thread as lower thread and a polyethylene 65 tercphthalate sewing thread as upper thread. Working wears made of these plain cloths were sewn with an ordinary polyethylene terephthalate sewing thread.

These working wears were washed, and thereafter subject to the wearing and undressing electrification test at 23 C. and 40-percent RH. The wearer put on a wool sweater, and one of the above-mentioned working wears on it. The working wear was rubbed violently with the sweater. The electrification voltages of the human body and the working wear were measured immediately after putting off the working wear and the results thread having an average electrical resistance of 900 kQ/cm. are shown in the following table.

Ratio of 1m; i-Ilectri Elem-tn mention iluntloh ioltagvoltagof tin of the monnfilahuman working inent body Wear Working wear .perct-ntl (av) (kv; Wear containing no electrically conductlte mouofilament control) u -9. -15. 0 Wear sewn with the electrically conductlve sewing thread u. 04 1. -5. 5 Wear quilted at intervals of 3 cm. with the electrically conductive sewing thread 0. 1': +0. 2 3. 5 Wear quilted at intervals or 1 cm. with the electrically conductive sewing thread 0. 4 +0.1 0. 3

The working wear containing no electrically conductive monofilament made a sound of discharge at the time of undressing, and exhibited an electrification voltage of -45 kv. The human body then showed an electrification voltage of +9 kv., and received a violent shock when touching a conductive material such as metal. On the other hand, as is seen in the table, the working wears containing the electrically conductive monofilament hardly undergo electrostatic troubles, and exhibit excellent antistatic efi'ect.

These working wears were repeatedly washed times in an automatic washer (washing continued for 20 minutes in a l g./l. aqueous solution of soap at 60 C., followed by rinsing in wann water at 40 C.). The antistatic effect was hardly lost, showing an excellent durability.

Example 5 A IS-denier nylon 6 monofilament was immersed and.

passed through a mixture consisting of 100 parts of a fine powder of silver having an average particle diameter of about 1.5 p, 50 parts of an acrylic adhesive (emulsion type; solid content 42 percent), 2.5 parts of an aqueous solution of a melamine resin (solid content 50 percent), and a minor amount of a catalyst, and thereafter passed through a slit to adjust its coating thickness, followed by curing in hot air. An electrically conductive monofilament having an average electrical resistance of 350 u/cm. and an average thickness of the electrically conductive coating of 2.8 p. was obtained.

This electrically conductive filament had a tenacity at break of 3.4 g./denier (5.9 gJdenier calculated as the substrate fiber), an elongation at break of 42 percent, an initial Young's modulus of 260 kgJmmF, and a density of 1.6 g./cc.

One electrically conductive monofilament was doubled with a 75 denier/36 filament polyethylene terephthalate multifilament, and the resulting yarn was imparted a Z twist of 800 tums/m One electrically conductive yarn was doubled with ISO denier/72 filament polyethylene terephthalate yarn with primary twist. and the resulting yarn was imparted an S twist of 500 turns/m. to form a sewing thread containing the electrically conductive filament.

The electrically conductive sewing thread thus obtained had an average electrical resistance of IO mil/cm, and the ratio of the electrically conductive filament incorporated in the sewing thread was I I percent.

With the use of this electrically conductive sewing thread, a Japanese kimono consisting of polyethylene terephthalate fiber was sewn by hand in accordance with the usual sewing specification. The ratio of the electrically conductive filament incorporated in the kimono was about 0.02 percent. The soobtained kimono and a kimono sewn with a thread containing no electrically conductive filament were subjected to the wearing test at 25 C. and 30-percent RH. In this test, the wearer put on an underwear made of polyethylene terephthalate fiber. In the case of the kimono containing no electrically conductive filament, the bottom thereof clung frequently to the wearers body when the wearer stepped 100 times at the same place. The electrification voltage of the bottom was found to be 35 kv. On the other hand, the kimono sewn with the electrically conductive sewing thread of the invention hardly clung to legs during walking, and exhibited an electrification voltage of only -l0 kv.

We claim:

I. A sewing thread which comprises at least one organic textile yarn and at least one electrically conductive filament, characterized in that said electrically conductive filament comprises a substrate of at least one continuous organic synthetic filament, the total denier of said substrate being 5- 50, and an electrically conductive coating on said substrate filament, said electrically conductive coating having an average thickness of about 0.3 to 10 microns and comprising about 10 to 50 percent by weight of a polymer binder matrix and about 50 to percent by weight of finely divided silver dispersed therein so that said electrically conductive filament has an electrical resistance of less than 2,000 megohms per centimeter.

2. A sewing thread according to claim 1 which comprises at least two primary twist yarns wherein said at least one electrically conductive filament is present in at least one of said primary twist yarns.

3. A. sewing thread according to claim 1 which comprises at least two primary twist yarns, one of said primary twist yarns containing one said electrically conductive filament.

Claims

2. A sewing thread according to claim 1 which comprises at least two primary twist yarns wherein said at least one electrically conductive filament is present in at least one of said primary twist yarns.
3. A sewing thread according to claim 1 which comprises at least two primary twist yarns, one of said primary twist yarns containing one said electrically conductive filament.