Quilted Fabric Containing High Surface Area Carbon Fibers

Abstract

A quilted fabric containing high surface area carbon fibers is made by uniting a central layer of flexible activated carbon fibers between a pair of outer layers of reinforcing fabric, positioned on each side of the layer of activated flexible carbon fibers, with a network of quilting stitching. The quilted fabric thus made is useful for fabricating protective clothing or gas masks for use by personnel who must enter areas which may contain noxious gases, or for face masks for combatting the air pollution problem. The quilted fabric makes possible the use of spun yarns of activated carbon fabric which have, per se, low tensile strength, but which can be made more economically than continuous filaments of higher tensile strength.

Description

BACKGROUND OF THE INVENTION

The possibility of using activated carbon for protective clothing has long been explored by military and other research laboratories. Because of the high surface area of activated carbon, it is an especially effective absorber or adsorber of poisonous or other noxious gases. Thus, clothing containing activated carbon can be used in combination with gas masks to provide protection for personnel who must enter areas which may contain such noxious gases.

One approach which has been considered is to bond granular activated carbon with a resin to a fabric backing from which clothing is made. This system has the disadvantage, however, that the resin which is used to bond the activated carbon particles can enter into the particles and in part destroy the high surface area which is desired in the activated carbon.

The use of activated carbon fibers for such purposes has been considered both from the viewpoint of continuous filaments and yarns spun from staple fibers. The continuous filaments are strong, if made of sufficient filament diameter, but are difficult and expensive to produce, and also are at larger filament diameters, relatively inflexible. Yarns of activated carbon spun from staple fibers are relatively weak, even though the individual filaments may have a high tensile strength, due to a variety of factors which influence the yarn strength, such as the tendency of activated carbon filaments to slip upon each other easily when spun into a yarn.

To overcome this weakness problem, it has been proposed to weave fabric using alternating activated carbon yarns and others yarns of higher strength. This system, however has the disadvantage that the activated carbon fibers are relatively far apart so that noxious fumes can penetrate the garment without coming into contact with an activated carbon surface, thereby causing the garment made from such a fabric to fail in its essential purpose of protecting the wearer from the noxious fumes.

It is therefore, an object of this invention to provide a fabric containing high surface area carbon fibers ("activated carbon" fibers), i.e., fibers having a surface area of at least 300 m.sup.2 /g, which overcomes these various disadvantages of the prior art.

SUMMARY OF THE INVENTION

According to the present invention, a quilted fabric containing high surface area carbon fibers comprises in combination (1) at least one central layer of flexible carbon fibers having a surface area of at least about 300 square meters per gram (m.sup.2 /g); (2) a pair of outer layers of reinforcing fabric, positioned on each side of the layer of flexible carbon fibers; and (3) a network of quilting stitching, uniting the central layer of flexible carbon fibers and the outer layers of reinforcing fabric into an integral quilted fabric.

BRIEF DESCRIPTION OF THE DRAWING

The single FIGURE of the drqwing illustrates a quilted fabric containing high surface area carbon fibers in accordance with the present invention.

DETAILED DESCRIPTION

According to the present invention, the quilted fabric containing high surface area carbon fibers begins with at least one central layer of flexible carbon fibers having a surface area of at least 300 m.sup.2 /g. It is convenient to use for this central layer of flexible carbon fibers a layer of woven carbon cloth; however, other forms of fibers can also be used, such as carbon felt, resin bonded carbon batting, or a multiplicity of loose staple fibers of carbon. For any of these four forms--cloth, felt, batting or staple fibers--a preferred method for producing the carbon fibers comprises the steps of (1) heating an infusible cured phenol-formaldehyde novolac (CA-0001) fiber in air from about room temperature up to an intermediate temperature in the range of from about 250.degree.C to about 450.degree.C, at a rate of temperature rise of from about 50.degree.C/hr to about 200.degree.C/hr, and (2) further heating said fiber in a nonoxidizing atmosphere from said intermediate temperature to a final temperature in the range of from about 700.degree.C to about 900.degree.C, at a rate of temperature rise of from about 50.degree.C/hr to about 200.degree.C/hr. Further details of this method of producing carbon fibers, and preferred features of the method of production, are set forth in commonly assigned, copending U.S. pat. application Ser. No. 182,865, filed Sept. 22, 1971, by J. Economy and R. Y. Lin, the disclosure of which is incorporated herein by reference. The starting material, namely the infusible cured (cross-linked) phenol-formaldehyde novolac fiber, is produced as described in U.S. pat. No. 3,650,102, issued Mar. 21, 1972 to J. Economy and R. Clark, assignors to The Carborundum Company of Niagara Falls, New York. The U.S. Federal Trade Commission has assigned the symbol "CA-0001" for temporary use in describing the cross-linked novolac fiber, and it is sold by The Carborundum Company of Niagara Falls, New York, as Kynol CA-0001 fiber. It is preferred to form the layer of woven carbon cloth, carbon felt, resin bonded carbon batting, or loose staple fibers of carbon by first forming the respective shape of CA-0001 fibers, and then applying the above-described carbonization and activation process to provide an activated carbon layer. Resin bonded carbon batting is preferably produced by bonding the cross-linked novolac fiber with melamine resin, prior to carbonization and activation.

Other methods of forming activated flexible carbon fibers can also be used. For example, carbon fibers made from pitch or mixtures of pitch and novolac can be activated by heating in steam (e.g., 20- 30 min. at 900.degree.C for carbon fibers made from pitch, or as little as 5 min. at 900.degree.C for carbon fibers made from combinations of pitch and novolac), and such fibers can also be used in the present invention. Other flexible carbon fibers having high surface area, if available, can also be used.

If desired, a plurality of central layers of flexible carbon fibers can be utilized, such as two or more layers of carbon cloth, or a layer of carbon cloth in combination with a multiplicity of loose staple fibers of carbon, or the like. The quilting stitching pattern should of course be chosen with the number and type of layers of flexible carbon fibers in mind. Thus, if a multiplicity of loose staple fibers of carbon is used, it is preferred that the quilting stitching be relatively close together, e.g., several centimeters apart. On the other hand, if felt, batting or woven carbon cloth is used, the quilting stitching can be somewhat further apart e.g., 5-10 cm apart.

The outer layers of reinforcing fabric can be any suitable material. Nylon cloth is a preferred material for this purpose, since it is a relatively strong fabric and can be formulated with a loose mesh and still retain a high degree of strength. Loose meshes are preferred for these outer reinforcing fabric layers for some applications, for ease of stitching. An especially preferred nylon for the outer layers of reinforcing fabric is that nylon which is a wholly aromatic polyamide. This type of fiber is available commercially under the trademark "NOMEX" (E. I. duPont de Nemours & Co.), and details of manufacture of such wholly aromatic polyamides are disclosed in U.S. pat. Nos. 3,063,966 and 3,287,324. A process for the dry spinning of such aromatic polyamides into fibers is disclosed in U.S. pat. No. 3,360,598.

Another fiber which is preferred for use in fabricating the outer layers of reinforcing fabric is uncarbonized Kynol CA-0001 cloth, described in U.S. pat. No. 3,650,102 and available commercially from The Carborundum Company. The use of wholly aromatic polyamides and uncarbonized CA-0001 cloth for the outer layers of reinforcing fabric have the advantage of providing a protective fabric for clothing which combines the heat resistance of wholly aromatic polyamide or CA-0001 cloth with the property of gas absorption and adsorption of high surface area flexible carbon fibers, so that an individual who may face one or both of these hazards can protect himself with a single garment.

Referring now to the drawing, the single figure of drawing illustrates a portion of quilted fabric containing high surface area carbon fibers in accordance with the present invention. This quilted fabric comprises in combination at least one central layer 11 of flexible carbon fibers having a surface area of at least about 300 m.sup.2 /g; and a pair of outer layers 12 of reinforcing fabric positioned on each side of the layer of flexible carbon fibers. A network of quilting stitching 13 unites the central layer of flexible carbon fibers and the outer layers of reinforcing fabric into an integral quilted fabric. As mentioned above, layer 11 of flexible carbon fibers, although illustrated as woven carbon cloth, can also be carbon felt, resin bonded carbon batting, or loose staple fibers of carbon. The network of a quilting stitching 13 will of course be modified to take into account the physical form of central layer 11 of flexible carbon fibers.

The invention will now be illustrated with an example.

EXAMPLE

An infusible cured phenol-formaldehyde novolac (CA-0001) fiber was produced in accordance with the teaching of U.S. pat. No. 3,650,102. The fiber was produced in staple filament form, the individual filaments being about 5 centimeters in average length. These filaments were then spun into a yarn about 17 microns in diameter, having a designation 12/1 (cc). This yarn was then woven into cloth having a 3 .times. 3 basket weave construction, having 49 warp ends per inch and 46 filling ends per inch, and weight of about 5.34 ounces per square yard. This woven cloth was then carbonized and activated in accordance with the teachings of U.S. pat. application Ser. No. 182,865, in the course of which the length and width of the fabric shrank about 21 percent, and the weight of the fabric was reduced about 50 percent. The resulting carbonized and activated carbon fabric had a weight of about 4.24 ounces per square yard, and a surface area of at least about 300 m.sup.2 /g. This activated carbon cloth constituting a layer 11 of flexible carbon fibers, was then placed between two layers 12 of nylon mesh fabric having a 27 .times. 48 square weave construction. The three layers were then united by a network of quilting stitching 13 into an integral quilted fabric. The quilted fabric was found to be substantially stronger than the carbonized activated carbon fabric layer 11 by itself, yet it retains its flexibility. The composite quilted fabric, as thus constituted, can be used to fabricate protective clothing, which is highly effective as a scavenger for poisonous or other noxious gases.

Claims

We claim:

1. A quilted fabric containing high surface area carbon fibers, comprising in combination

1. at least one central layer of flexible carbon fibers having a surface area of at least about 300 m.sup.2 /g;

2. a pair of outer layers of reinforcing fabric, one layer being positioned on each side of the layer of flexible carbon fibers; and

3. a network of quilting stitching, uniting the central layer of flexible carbon fibers and the outer layers of reinforcing fabric into an integral quilted fabric.

2. The quilted fabric of claim 1, wherein the central layer of flexible carbon fibers is woven carbon cloth.

3. The quilted fabric of claim 1, wherein the central layer of flexible carbon fibers is carbon felt.

4. The quilted fabric of claim 1, wherein the central layer of flexible carbon fibers is resin bonded carbon batting.

5. The quilted fabric of claim 1, wherein the central layer of flexible carbon fibers is a multiplicity of loose staple fibers of carbon.

6. The quilted fabric of claim 1, comprising a plurality of central layers of flexible carbon fibers.

7. The quilted fabric of claim 1, wherein the outer layers of reinforcing fabric are nylon cloth.

8. The quilted fabric of claim 7, wherein the nylon is a wholly aromatic polyamide.

9. The quilted fabric of claim 1, wherein the outer layers of reinforcing fabric are uncarbonized CA-0001 cloth.

10. The quilted fabric of claim 1, wherein the method of producing the central layer of flexible carbon fibers comprises the steps of

1. heating an infusible cured phenol-formaldehyde novolac fiber in air from about room temperature up to an intermediate temperature in the range of from 250.degree.C to about 450.degree.C, at a rate of temperature rise of from about 50.degree.C/hr to about 200.degree.C/hr, and

2. further heating said fiber in a nonoxidizing atmosphere from said intermediate temperature to a final temperature in the range of from about 700.degree.C to about 900.degree.C, at a rate of temperature rise of from about 50.degree.C/hr to about 200.degree.C/hr.