Anti-static Yarn And Fabrics

Abstract

The invention relates to the production of an anti-static yarn, especially useful in the making of carpets. The anti-static yarn is made by fibrillating into fibers a web comprising a monoaxially oriented film of synthetic material faced with metal, such as aluminum. The metallized fibers are blended with other fibers, such as wool and/or nylon and converted into an anti-static yarn, which has utility in forming the pile elements of a carpet.

Description

The present invention relates to a method of producing an anti-static yarn and to a method of producing an anti-static carpet made from said yarn and to an anti-static yarn and carpet made by said method.

Carpets tend to store and generate static electricity, which could be dangerous in certain areas, as for example, in hospitals, where ether or other explosive or highly inflammable materials may be present.

It has been proposed to make anti-static yarn by incorporating therein fibers of stainless steel to provide electrically conductive elements in the yarn. Such a yarn is very expensive.

Moreover, stainless steel fibers in the anti-static yarn described are comparatively short and tend to sift out during the processing of the yarn and the operation of making a fabric or carpet therefrom, and tend thereby to concentrate in spaced regions of the yarn. In the regions where these steel fibers concentrate, they are visible and unsightly. Also, the uneven distribution of conductive steel fibers in the yarn creates large gaps in the conductive network within the yarn, resulting thereby in loss of anti-static properties.

Moreover, the steel fibers do not lend themselves to coloration, but come in dark colors, such as steel gray, and in light shades are extremely unsightly.

It has also been proposed to incorporated a fine copper wire in a yarn for anti-static purposes. This copper wire is more noticeable in the yarn than are the steel fibers described, and since this copper wire must be in the yarn during the twisting of the yarn, it reduces the speed of twisting and poses some difficulty in the process of weaving the yarn incorporating the copper wire therein. Also, these wires pose the problem of increased wear and the dulling of expensive cutting blades in the manufacture of carpets.

One object of the present invention is to provide a new and improved method of producing an anti-static yarn and a new and improved anti-static yarn made by this method and a carpet containing such a yarn.

In accordance with certain features of the present invention, the electrically conductive elements incorporated in a yarn to give it anti-static properties are produced by fibrillating a monoaxially oriented fibrillatable film of synthetic material, coated with an extremely thin, flexible layer of metal, such as aluminum, deposited by suitable coating processes, such as the well-known vacuum or vapor deposition process. The film so metallized may be fibrillated in any of the well-known methods, but is desirably fibrillated by a method involving initial needling, to form continuous metallized fibers extending longitudinally along the direction of film orientation. The fibrillated film is desirably cut into staple length sections and after precarding or picking is blended with staple length natural fibers such as wool fibers and/or synthetic fibers, such as nylon, to produce a composite anti-static yarn having anti-static efficiency. These metallized fibers made by the fibrillation process present in the blended yarn a network of intersecting fibers affording a substantially uniform pattern of distribution in the conductivity of electric charges, and maintain this distribution pattern without sifting or bunching of the metallized fibers in spaced areas of the yarn. Also the metallized fibers may be colored to match or mix attractively with the basic color of the main component of the blended yarn, so as not to detract from the esthetic appearance of the yarn.

Other objects, features and advantages of the present invention are apparent from the following description and from the accompanying drawings, in which

FIG. 1 is a perspective showing a portion of a continuous composite web consisting of a film of polymeric synthetic material, monoaxially oriented along its length and metallized by metal layers on opposite faces of the film;

FIG. 2 is a section of the composite web taken on lines 2--2 of FIG. 1 but showing the web on a magnified scale;

FIG. 3 shows the composite metallized web of FIG. 1, fibrillated by the piercing of the web with needles into a coherent network of interconnected strips extending generally along the direction of orientation of the film in the web;

FIG. 4 shows the fibrillated web of FIG. 3 after it has been picked or pre-carded into a web of independent, intersecting fibers;

FIG. 5 is a view on an enlarged scale of an anti-static ply yarn formed by a blending of the metallic fibers shown in FIG. 4 and other non-conductive fibers, such as nylon, part of the view being shown within a magnification circle in which the metallized fibers are emphasized by a darkened showing thereof;

FIG. 6 is a diagrammatic illustration showing partly in cross-section and partly in side elevation a woven loop-pile carpet on an enlarged scale, having pile elements formed from the anti-static yarn shown in FIG. 5; and

FIG. 7 is similar view of a similar carpet, except that the carpet is of the woven cut-pile type.

Referring to the drawings, a continuous film or ribbon 10 of polymeric fibrillatable synthetic material is extruded and oriented monoaxially in the longitudinal direction of the film. This film 10 can be oriented by any of the processes well-known in the art for that purpose. For example, it can be oriented by supercooling the film and then orienting by stretching or by heating the film to a temperature below that at which the film is in molten state and then stretching it. This oriented film constitutes the basic component of a composite metal laminated web 11 from which the metallized fibers of the present are produced by fibrillation, and may consist of polymeric materials that can be oriented and fibrillated, as for example, polyolefins, such as polyethylene, polypropylene, and poly (butene-1), polyesters, such as polyethylene terephthalate, and polyamides, such as the nylons. In the specific embodiment of the invention illustrated, the film could be polypropylene and could have a thickness of about 1.5 mil.

The monoaxially oriented film 10 described is coated on opposite faces with metal layers 12 permanently applied thereto as to be incapable of delamination. The layers 12 may be of any suitable metal, as for example, aluminum, and may be applied to the faces of the basic film 10 in a conventional manner, as for example, by drawing the film from a supply roll and causing it to travel through a high vacuum chamber in which both surfaces of the film are metallized by vapor deposition of aluminum vapor. The aluminum may also be applied to the basic film 10, as for example, in the form of foils, secured thereto by adhesive.

The metal layers 12 applied to the basic polymeric film 10 are extremely thin, each being for example in a specific embodiment less than one-half mil. and being, therefore, almost molecular in thickness.

The metal layers 12 on the polymeric basic film 10 may be colored by dyeing or by any suitable technique known in the art, so that the metallized fibers formed from the composite web 11 will, when blended with the basic fibers in a yarn, present an esthetically pleasing appearance and will not make too visibly apparent the presence of conductive elements.

The composite web 11 described is fibrillated desirably by piercing the web while under tension longitudinally of the web by means of a plurality of needles movable transversely of the plane of the web. These needles may be of the barbed type conventionally employed as felting needles, and are caused to pierce the web 11 without moving longitudinally or laterally of the web. The density of the needles would depend on the type of synthetic basic film 10 employed and the type of fabric to be produced.

As the point of each needle strikes and pierces the web 11 under tension, the web is split along its axis of orientation for a substantial distance in either or both directions from a needle point impact. A large number of needles making substantially instantaneous impact on the web 11, cause the web to be initially fissured into a filigree network like expanded metal, comprising strips or fibers 13 extending generally along the longitudinal direction of the web, and integrally interconnected at intervals, as shown in FIG. 3. The needling operation in itself is sufficient to fibrillate the web 11 in the general form shown in FIG. 2, but the web continues to fibrillate in subsequent operations leading to the formation of the anti-static yarn to be described.

The metallized web 11, fibrillated as described and as shown in FIG. 3, is desirably cut into substantially uniform staple lengths ranging approximately from 3 to 6 inches in length at right angles to the orientation of the film 10, and the staple segments are then pre-carded or picked to change the network of interconnected fibrillated strips 13 into webs of separate, intersecting, individual, fine metallized conductive fibers 14, arranged substantially parallel, but in an intersecting relationship, as shown in FIG. 4. The fibrillated pre-carded web and the webs, tow strands or other forms of blending fibers 15, such as those made of nylon or wool, and desirably also in staple lengths, are then mixed and blended and fed to a mechanism for carrying out conventional carding operations, where the mix of metallized and basic fibers 14 and 15 are combed or brushed until they are straight and the separate fibers are interlocked into a soft web; the staple length of the metallized fibers 14 will vary in accordance with the staple length of the other fibers 15 blended therewith. At the finisher end of the card, the wide web of mixed fibers is divided into strands and rubbed into rovings or slivers. These rovings are then spun and twisted in a conventional manner into a singles yarn. A number of these singles yarn, as for example two, three or four are combined and twisted to produce the required ply yarn 16 shown in FIG. 5. The metallized conductive fibers 14 in this ply yarn 16 would make up at least 1 percent by weight of the yarn and could go up as high as 50 percent depending upon the acceptable cost of the yarn, the efficiency of manufacture and customer's requirements. If nylon is used as the basic fibers 15, these fibers could, for example, have a denier of between 8 and 15, but can vary from this range according to the nature of the carpet formed therefrom.

Although the metallized web 11, fibrillated as shown in FIG. 3, is preferably cut into staple lengths prior to carding as described, as far as certain aspects of the invention are concerned, the fibrillated web can be carded without being cut into staple lengths. However, under these conditions, the carding is harder to accomplish and is carried out less efficiently. Moreover, although the uncut metallized fibers will be broken into segments by the carding operation, these segments will vary widely in length, as for example, approximately from one-fourth inch to 9 inches in length. On the other hand, if the fibrillated web 11 shown in FIG. 3 is cut before carding to a 3 to 6 inches length, most of the individual metallized fibers 14 will, even after carding, remain in length within this range.

In the ply yarn 16, all of the fibers run generally in the longitudinal direction of the singles yarn, but the metallized fibers 14 are somewhat interengaged, interlaced, interlooped and interlocked, so as to maintain a substantially uniformly distributed conductive network along the ply yarn 16. The conductive fibers 14 in this network will not sift or bunch in different areas of the yarn 16 and non-conducting gaps will not readily be created in this network.

From the composite yarn 16 containing the metallized continuous fibers 14 produced by fibrillation of the metallized synthetic film 10, a fabric having highly efficient anti-static properties may be produced in the usual manner. This composite yarn 16 can, for example, be woven, tufted or knitted to produce an anti-static carpet.

FIG. 6 shows a woven, loop-pile carpet, that can be made with the anti-static yarns 16 of the present invention by conventional techniques on a longitudinal pile wire loom. These yarns 16 extend upwardly from the face of the carpet in the form of loops 17 to form the pile elements of the carpet. The loops 17 are arranged in rows and the loops in each row are interconnected by base portions 18 extending through the carpet to the rear face thereof. The pile loops 17 are held in place in the usual manner by filling yarns 20 and binder warp yarns 21 with a stuffer yarn 22 extending between adjacent rows of pile loops 17.

An adhesive backing 23 made essentially from a latex compound extends over the rear face of the carpet. The backing 23 spans the spaces between adjacent rows of the conductive pile loops 17 on the rear face of the carpet and thus is in intimate contact with the base portions of all of these loops on the rear face of the carpet. This backing 23 may be conductive, although it is not necessary and for that purpose, may contain particles of an electrically conductive material, such as carbon or graphite, to afford a conductive path connecting the electrically conductive yarns 16 in the many rows of the pile elements. This insures that the desired discharge will take place, even though the pile loops 17 may have been severed by wear or accident.

A suitable formulation for the latex compound for use as the carpet backing 23 may contain 66.5 pounds of dry acrylic latex (Polyco No. 2715) (46percent), 50 pounds of dry graphite flakes (Dixon No. 635) and 0.1 pound of dry polyacrylate (10percent) mixed with water to produce a mixture having a viscosity of 2,000 cps. In the manufacture of the carpet, the water-based latex flows around the yarn and inbetween the fibers of the yarn at the bases of the pile loops 17, and thereby establishes intimate contact between the backing 23 produced from this latex and the conductive fibers 14 in the yarn.

FIG. 7 shows a woven, cut-pile carpet containing the anti-static pile yarn 16 of the present invention. This carpet is similar in construction to that of FIG. 6, except that the crests of the pile loops formed from the pile yarns 16 have been cut above the face of the carpet to form cut-pile elements 24 extending upwardly from the face of the carpet. In connection with the woven cut-pile carpet of FIG. 7, the backing 23 is desirably electrically conductive, since the electrical path through the yarn is no longer continuously through each row of pile elements, as was the case with the loop-pile type of carpet shown in FIG. 6.

Besides the benefits described for the metallized fibers made by web fibrillation in the anti-static yarn, these fibers can be easily cut by the usual cutting devices employed in carpet making machines, and this advantage is especially useful in making cut-pile carpets, such as those shown in FIG. 7.

Although the invention has been described herein as involving the fibrillation of a metallized monoaxially oriented film made of synthetic material by initial needling of the film to produce electrically conductive fibers, as far as certain aspects of the invention are concerned, this film can be converted into long continuous conductive fibers by other conventional mechanical fibrillating techniques, which do not involve initial needling. For example, the metallized monoaxially oriented film may be converted into a fibrous product by twisting, brushing, or applying friction or forces transversely across the width of the film but without sufficient severity to destroy substantially the continuity of the fibers produced thereby.

Also, as far as certain aspects of the invention are concerned, the monaxially oriented metallized film can initially be fibrillated into a coherent network of interconnected strips extending along the direction of orientation by needling or the use of other suitable mechanical operations, and then forming a shed in said network by raising these strips out of the plane of the reticulated film to split the film into independent continuous fibers.

Claims

What is claimed is:

1. A method of producing an anti-static yarn which comprises preparing a composite web consisting of a monoaxially oriented film of fibrillatable synthetic material and a thin flexible coating of metal on the face of said film, fibrillating said web into metallized fibers extending along the direction of orientation of said film, blending said metallized fibers with non-conductive fibers and processing the blending fibers into a yarn having anti-static properties.

2. The method as described in claim 1, in which the metal coating is on both faces of the film and is produced by metal vapor deposition.

3. The method as described in claim 1, in which the metal coating is aluminum.

4. The method as described in claim 1, in which the metal coating is on both faces of the film and is produced by deposition of aluminum vapors on these faces.

5. The method as described in claim 1, in which the web is fibrillated by initially piercing the web with needles to fissure the web and the pierced web is converted into separate metallized fibers extending generally in a parallel direction along the web.

6. The method as described in claim 1, in which the metal coating is aluminum on both faces of the film, the web is fibrillated by initially piercing the web with needles to fissure the web, and the pierced web is converted into separate metallized fibers extending generally in a parallel direction along the web in the direction of the orientation of its film component.

7. The method as described in claim 1, in which the fibrillated web is subdivided into staple lengths before processing into a yarn.

8. The method as described in claim 1, in which the fibrillated web is cut into predetermined staple lengths before blending.

9. The method as described in claim 1, in which the fibrillated web is cut into predetermined staple lengths ranging from 3 to 6 inches before blending.