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Publication numberUS2845962 A
Publication typeGrant
Publication date5 Aug 1958
Filing date28 Jun 1954
Priority date14 Jul 1953
Publication numberUS 2845962 A, US 2845962A, US-A-2845962, US2845962 A, US2845962A
InventorsBulgin Douglas
Original AssigneeDunlop Rubber Co
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Antistatic fabrics
US 2845962 A
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Description  (OCR text may contain errors)

ANTlSTATl-Q FABRICS No Drawing. Application June 2%, 1954 Serial No. 439,917

Claims priority, application Great Britain Iiuly 14, 1953 18 Claims. (Cl. 139-420} This invention relates to the production of fabrics having antistatic electrical properties.

The conductivity that is desirable in an antistatic fabric depends on the application for which the fabric is intended. An antistatic fabric which is to be used in circumstances in which the risks arising from the generation of static electrical charges are not very serious may quite satisfactorily have a relatively high resistance, that is to say, a resistance up to about 100,000 megohms per unit square. A lower resistance of the order of magnitude of to 100 megohms per unit square is desirable in a fabric which is intended for use in the presence of inflammable vapours, e. g. in operating theatres, where it is a matter of vital importance that. no static electrical charges should be generated. Megohms per unit square is the resistance in megohms to the passage of electricity on or parallel to a surface between two electrodes placed to form opposite sides of a square and is independent of the dimensions of the square. Otherwise stated, if the length of two parallel electrodes is always equal to the distance between them it is immateral what the length of these elec trodes is as the resistance increases directly proportional to the distance between the electrodes and inversely proportional to the length of the electrodes, that is, to the width of the electrical path.

For this reason only cotton and viscose rayon are generally considered suitable for use in operating theatres, but even these materials are likely to be unsuitable in dry weather or conditions of low relative humidity. Experience has shown that the relative humidity of air should not be lower than 65% for safe use of cotton and viscose rayon fabrics. it is of course not always possible to keep the relative humidity of the atmosphere above 65%, and accordingly there is a need for a fabric in which there can be virtually no generation of static charges by movement at any atmospheric humidity. It is among the objects of the present invention to provide such a fabric.

According to the invention, an antistatic fabric is made up of fibrous material containing electrically conductive carbon black and fibrous material free from such black in such proportions that the electrical resistance of the fabric as a whole is less than 100,000 megohms per unit square at all humidities.

Carbon black is a product result ng from the incomplete combustion of hydrocarbon gas such as acetylene or natural gas and is generally deposited by actual contact of a flame upon a metallic surface. Normally carbon black is a non-conductor of electricity but is made conductive by treatment for that purpose and is known in the trade as electrically conductive carbon black.

Normal fibrous material free from carbon black, such as viscose rayon or cotton, has a high electrical resistance at low relative humidity and a lower resistance at high relative humidity. It has been found that, whereas fibrous material containing a relatively small proportion of carbon black has the same characteristic, fibrous material containing more than a certain critical proportion atent ice of carbon black has a resistance which varies to a very much smaller extent with humidity and which in any case does not rise as its humidity falls. In the case of acetylene black this critical proportion is usually around 25%, but it varies somewhat with the particular fibres used.

The fabrics of the present invention, i. e. fabrics having a resistance less than 100,000 megohms per unit square at all humidities, may be satisfactorily produced using a fibrous material containing a proportion of carbon black that is not less than the critical proportion referred to above. Even if only a small proportion of the black-containing fibrous material is used, it is this material rather than the fibrous material free from black which makes the more important contribution to the conductivity of the fabric as a whole, and it is therefore possible to make the resistance of the present fabrics more or less independent of humidity by using a suitable proportion of the black-containing fibrous material. In general the use of about 10% of the black-containing fibrous material referred to gives the fabric a resistance which is substantially independent of humidity, that is to say, a resistance which does not, at any humidity, depart from its means value by any factor greater than about ten. Such a substantially constant resistance may be contrasted with the resistances of fabrics free from black, which at certain humidities may depart from their mean values by factors as great as ten thousand.

In general the proportion of black-containing fibrous material used in the present fabrics is not substantially less than 2%. Preferably the proportion used is from 5 to 20%. If the fabric has substantially less than 2% of the black-containing fibrous material, its resistance will be undesirably high; while if it has substantially more than 20% the resistance will (at some humidities at least) be undesirably low, and a fire risk and also an electric-shock risk may be introduced if the fabric is to be used in proximity to apparatus connected with the electric means for instance. With higher proportions of black-containing material, moreover, the mechanical strength of the fabric is impaired appreciably, a fibre containing carbon black being much weaker than a similar fibre free from black.

The proportion of black-containing fibrous material and the proportion of black in this material do not by themselves exclusively determine the resistance-humidity characteristics of the fabrics. Other factors which affect these characteristics are the denier of the fibres, their lengths (if they are used in staple form), and the nature of the weave.

The fabric may be woven from a mixed yarn spun from the two fibrous materials together, or it may be woven from two types of yarn, one of the two types being spun from the fibrous material free from black and the other being spun from the fibrous material containing electrically conductive carbon black. In the latter case the fabric may be so woven as to have a fine black-and- White chequered pattern, which by virtue of its distinctive appearance facilitates identification of the fabric.

It is not essential, where one yarn containing black and another yarn free from black are used, that the fabric should have both black-containing warp threads and black-containing weft threads. Even if the black-containing threads do not cross each other, the antistatic properties of the fabric may be entirely satisfactory, provided the black threads are reasonably close together.

A number of suitable types of conductive carbon black are available including acetylene black, which is generally known as Shawinigan black; reinforcing furnace black, for example those commercially available under the names Philblack 0, Vulcan 3, and Vulcan XXX; channel black for example Spheron C; and channel black that has been submitted to heat treatment, e. u. at 1000 C.

The black which is preferred for the present purpose is Shawinigan black.

The fibrous material that contains the carbon black may be a regenerated cellulose, such as a viscose rayon obtained by extruding a solution of cellulose Xanthate in aqueous sodium hydroxide containing dispersed carbon black into a coagulating bath of a suitable aqueous mineral acid, e. g. sulphuric acid.

Instead of a regenerated cellulose containing carbon black, there may be used such other fibrous materials as nylon or polyester fibres spun from a nylon or polyester melt in which carbon black has been incorporated.

The fibrous material free from black may be a cellulosic fibrous material such as cotton or viscose rayon. Other materials which may be used include nylon and polyester fibrous materials. A mixture of fibrous materials free from black may be used.

As an example of a particularly suitable fabric having the desired antistatic properties reference is made to a fabric containing 10% by weight of threads of viscose rayon containing 30% of Shawinigan black together with 90% of viscose rayon threads free from carbon black and having a resistance not less than 0.5 megohm per unit square not greater than megohms per unit square at any humidity. This fabric may be contrasted with a similar fabric free from black, whose resistance varies with humidity between 0.5 and megohms per unit square.

The fabrics of the present invention are valuable not only for use in goods intended to be employed in operating theatres and the like; examples of other applications are their use in the manufacture of transmission belting and conveyor belting, and, after proofing, in the production of garments of various kinds.

Having now described my invention, what I claim is:

1. An antistatic fabric made up of fibrous material having electrically conductive carbon black dispersed throughout the fibre and fibrous material free from such black in such proportions that the electrical resistance of the fabric as a whole is less than 100,000 megohms per unit square at all humidities.

2. A fabric according to claim 1, in which the fibrous material having electrically conductive carbon black dispersed throughout the fibre is fibrous regenerated cellulose.

3. A fabric according to claim 1, in which the fibrous material free from black is a cellulosic fibrous material.

4. A fabric according to claim 1 in which the weight of the fibrous material having electrically conductive carbon black dispersed throughout the fibre is at least 2% of the total weight of the fabric.

5. A fabric according to claim 4, in which the weight of the fibrous material containing electrically conductive carbon black is from 5% to of the total Weight of the fabric.

6. A fabric according to claim 1, in which the two fibrous materials are present in such proportions that the electrical resistance of the fabric as a whole is substantially independent of its humidity.

7. A fabric according to claim 1, in which the fibrous material containing electrically conductive carbon black contains such a proportion of the black that its resistance does not rise as its humidity falls.

8. A fabric according to claim 1, in which the electrically conductive carbon black present is acetylene black.

9. A fabric accordin to claim 1, in which the weight of the electrically conductive carbon black is or more of the total weight of the fibrous material in which it is present.

10. A fabric according to claim 1, which is woven from a mixed yarn spun from the two fibrous materials together.

11. A fabric according to claim 1, which is woven from two types of yarn, one of the two types being spun from the fibrous material free from black and the other being spun from the fibrous material containing electrically conductive carbon black.

12. A fabric according to claim 11, which is so woven as to have a fine black-and-white chequered pattern.

13. An antistatic fabric which contains about 90% by weight of viscose rayon free from carbon black and correspondingly about 10% by weight of viscose rayon containing about by weight of electrically conductive acetylene black.

14. An antistatic fabric made of fibrous yarns, said yarns made up of from 2% to 20% of fibres having electrically conductive carbon black dispersed throughout the fibres, the balance of the fibres of the yarn being substantially without electrically conductive carbon black.

15. An antistatic fabric made of fibrous yarns, from 2% to 20% of said yarns having electrically conductive carbon black dispersed throughout the fibres, the balance of the yarns being substantially without electrically conductive carbon black.

16. An antistatic fabric made of woven yarns, the yarns Woven in one direction containing from 2% to 20% of fibres having electrically conductive carbon black dispersed throughout the fibres, the balance of the fibres of said fabric being substantially without electrically conductive carbon black.

17. An antistatic fabric having an electric surface resistance not less than 0.5 megohm per unit square nor greater than 5 megohrns per unit square at any humidity which contains about by weight of viscose rayon free from carbon black and correspondingly about 10% by weight of viscose rayon containing about 30% by weight of electrically conductive acetylene black.

18. An antistatic fabric having an electrical resistance less than 100,000 megohms per unit square at any atmospheric humidity comprising from 5 to 20 percent by weight of artificial fibrous material containing not less than 25 percent by weight of electrically conductive carbon black dispersed throughout the fibers, said fibers being woven with a fibrous material free from carbon black.

References Cited in the file of this patent UNITED STATES PATENTS 2,078,886 Weinberg Apr. 27, 1937 2,302,003 Cadwell Nov. 17, 1942 2,443,782 Barnard et al June 22, 1948

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2078886 *26 Jul 193427 Apr 1937Celanese CorpMixed textile material and method of making same
US2302003 *2 Aug 194017 Nov 1942Us Rubber CoStatic discharging floor covering
US2443782 *7 Apr 194422 Jun 1948Pacific MillsTextile material of comparatively low electric resistance and method of producing the same
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3007083 *28 Aug 195731 Oct 1961Int Shoe CoPerforated conductive insole
US3011188 *31 May 19605 Dec 1961Vorwerk & Co Elektrowerke KgAppliance for cleaning floors and coverings thereof
US3166824 *5 Jul 196026 Jan 1965Cleanese Corp Of AmericaProcess of shrink-proofing fabrics
US3196315 *29 Aug 196220 Jul 1965Thomas F PetersonCarpet underlay
US3206923 *16 May 196321 Sep 1965Russell W PriceReinforced conductive yarn
US3386797 *19 Jul 19654 Jun 1968Rohm & HaasFibrous textile products
US3590570 *2 Jan 19696 Jul 1971Teijin LtdSewing thread
US3706195 *8 Feb 197119 Dec 1972Ici LtdSynthetic yarns
US3955022 *16 Oct 19724 May 1976E. I. Du Pont De Nemours And CompanyAntistatic tufted carpet
US4064075 *11 Aug 197220 Dec 1977E. I. Du Pont De Nemours And CompanyConductive, extrudable polymer composition of poly(ε-caproamide) and carbon black
US4107129 *24 Feb 197715 Aug 1978Toray Industries, Inc.Acrylonitrile polymer, polymer cn on black
US4232082 *11 Jul 19794 Nov 1980Nippon Keori Kabushiki KaishaAnti-electrostatically guarded worsted suiting
US4242382 *26 May 197830 Dec 1980Imperial Chemical Industries LimitedBy adsorption of particles in component of lower melting point
US4753088 *14 Oct 198628 Jun 1988Collins & Aikman CorporationMesh knit fabrics having electrically conductive filaments for use in manufacture of anti-static garments and accessories
US4856299 *14 Dec 198715 Aug 1989Conductex, Inc.Knitted fabric having improved electrical charge dissipation and absorption properties
US4902562 *7 Jul 198820 Feb 1990Courtaulds PlcElectrically conductive materials
US5091130 *29 May 199025 Feb 1992Courtaulds PlcProcess for the production of highly filled yarns
US5368913 *12 Oct 199329 Nov 1994Fiberweb North America, Inc.Antistatic spunbonded nonwoven fabrics
US5412013 *20 Jul 19932 May 1995Mitsubishi Gas Chemical Company, Inc.Polyamide resin composition
US5482773 *9 Mar 19959 Jan 1996E. I. Du Pont De Nemours And CompanyActivated carbon-containing fibrids
US5763069 *28 Apr 19979 Jun 1998Amoco CorporationElectrically conductive tapes and processes
US5876849 *2 Jul 19972 Mar 1999Itex, Inc.Cotton/nylon fiber blends suitable for durable light shade fabrics containing carbon doped antistatic fibers
US6057032 *10 Oct 19972 May 2000Green; James R.Yarns suitable for durable light shade cotton/nylon clothing fabrics containing carbon doped antistatic fibers
DE2528189A1 *24 Jun 197522 Jan 1976Kuraray CoGewirktes oder gewebtes tuch mit antistatischen eigenschaften
EP0580387A1 *19 Jul 199326 Jan 1994Mitsubishi Gas Chemical Company, Inc.Polyamide resin composition
WO1994005841A1 *31 Aug 199217 Mar 1994Du PontActivated carbon-containing fibrids
Classifications
U.S. Classification139/420.00R, 174/47, 427/122, 427/121, 260/DIG.150, 57/901, 474/90
International ClassificationC08K3/04, D06M11/74, D01F1/09
Cooperative ClassificationC08K3/04, Y10S57/901, D06M11/74, Y10S260/15, D01F1/09
European ClassificationD01F1/09, D06M11/74, C08K3/04