Gas plating electrically conductive metals on fibers for antistatic purposes

United States Patent Office „ ₄ 3,129,487

Patented Apr. 21, 1964

3,129,487

GAS PLATING ELECTRICALLY CONDUCTIVE METALS ON FIBERS FOR ANTISTATIC PURPOSES

John R, Whitacre, Dayton, and Jack J, Bnlloff, Columbus, ® Ohio, assignors to The CommonweaSth Engineering Company of Ohio, Dayton, Ohio

No Drawing. Filed Apr. 12, 1961, Ser. No. 102,379

Claims. (Cl. 28—75) ¹⁰

This invention relates to antistatic materials and the method of rendering antistatic materials which tend to accumulate electrostatic charges, especially where accumulation interferes with use.

The invention is concerned more particularly with a 15 method of conditioning a shaped article, for example fiber, film or the like, in non-woven condition or as a fabric, such as clothing, canvas, draperies, paper and the like, to produce a material which does not tend to accumulate electrostatic charges. 20

An object of this invention is to provide a method of treating materials, for example natural fibers such as cotton, wool, etc., and synthetic fibers such as nylon (polyamide synthetic), Dacron, saran (vinylidine chloride polymer), Vinyon, Velon, Dynel, Orlon and Acrilan, 25 in woven or unwoven condition, and products made therefrom, such as belting and the like, so as to provide a filament or product which has less tendency to accumulate static charges of electricity thereon. The material thus treated can be used in fabricating processes without en- 30 countering the hazards and disadvantages ordinarily attending these materials which have not been treated and which tend to develop or accumulates charges of static electricity.

It is a further object of the invention to provide a 35 treatment whereby an antistatic coating is applied to the material either in a dry or wet state, and wherein the coating eliminates the tendency for the material to build up or accumulate static charges of electricity. The invention is applicable for the treatment of pre-woven ma- ⁴θ terials, as well as one or more strands of fibers in a roving or fabric so as to provide a product which prevents the accumulation of electrostatic charges on the surface.

These and other objects and advantages will become apparent as the description proceeds.

In accordance with the invention, the fiber, fabric or material to be rendered anti-electrostatic is coated uniformly with an electro-conductive substance or film thereof. The coating may be very thin, for example one atomic thickness of metal being enough to provide sufficient con- ⁵⁰ductance to prevent static electricity accumulation. Where metal or the like substance thus applied is desired to be removed subsequently after further processing of the fiber or fabric, the same may be achieved by subjecting the material to a carbon monoxide treatment at a ⁵⁵temperature of approximately 60-70° C. and under a pressure of 50 atmospheres to form the corresponding volatilizable carbonyl. This treatment brings about removal of the metal in the form of gaseous metal carbonyl. If desired, however, the metal coating may be removed ⁶⁰by dissolving the metal employing liquid solvents which do not attack the fibers.

The following examples are given as illustrative of the method and product of the present invention, the same being merely exemplary of the invention and not limita- ⁶⁵five thereof.

Example 1

Dynel fibers are subjected to gas plating at reduced atmospheric pressures, utilizing nickel carbonyl Ni(CO)₄, 70 to produce a fiber having an outer thin continuous film of nickel. The nickel coating which is on the order of

0.00005 inch in thickness is electrically conductive and the fiber can then be woven, belted or processed in any desired manner without having a tendency to accumulate static electrical charges.

Where it is desired to restrict the metal coating to one or more molecular layers in thickness, the gaseous plating will be carried out under strict control so that the material will be subjected to gas plating just sufficient time to deposit a very thin film of electrically conducting metal as a continuous un-broken film on the surface of the material.

When using metal carbonyls in general, and where the fiber or fabric or belting is drawn through the gaseous metal plating chamber, the speed of drawing the material through the gaseous metal plating chamber will be regulated so as to limit the time in which the material is exposed to gaseous metal plating to thus control the thickness of the coating. By thus controlling the metal deposit the original flexibility of the fiber, filament or fabric treated is retained. Ordinarily only sufficient metal is deposited on the material to give the material the desired antistatic properties. Such material may be subjected to gas plating for a time such as to deposit a coating film of between 0.00001 to 0.00025 inch, preferably of 0.00005 to 0.00015 inch in depth. Of course, this film thickness may be varied upwardly or downwardly somewhat depending upon the particular metal employed.

Example II

In this example nylon fibers are treated similarly as in Example I using nickel carbonyl. The gaseous plating is conducted at relatively low temperature just sufficient to cause heat decomposition of the nickel carbonyl in the presence of the fiber.

The product in the form of fibers can then be woven, or formed into a desired material without encountering electrostatic charges on the fibers or material.

Example III

In this example glass fibers are gaseously plated with chromium carbonyl Cr(CO)₆. The chromium metal is deposited on the fibers by heat decomposing the chromium compound and depositing the chromium metal onto the fibers to a .thickness of 0.00008 inch. The glass fibers are thus rendered antistatic.

After processing the glass fibers in this manner to provide the same with a .thin coating or film of chromium metal, the fibers are woven into a fabric. During the weaving operation the fibers are rendered free of any tendency to develop electrostatic charges and thus loom trouble from this source is eliminated. After weaving the metal coated glass fibers into the final cloth product, the chromium is then removed by washing the same in acid solution.

Example IV

Rayon fabric is gas plated in this example using acetylacetonate of rhodium to render the same anti-electrostatic. The decoratively, permanently coated fiber is further processed by being woven into a fabric to provide an antistatic material.

In the treatment of .the fibers the antistatic coating need only be applied to selected areas of the fiber and in an amount sufficient to produce a microscopic film of metal over the surface of the fiber and thus prevent .the accumulation of static electricity. One or two coated fibers may be thus treated to render them non-static and these fibers woven into a pack or roving containing a large number of uncoated fibers to render the whole pack conductive to electricity and thus prevent the building up of static charges of electricity. The product or fiber can then be woven or felted into the desired prod3,139,487 uct while obtaining the beneficial results with respect to the antistatic properties of the fibers.

As aforementioned, where it is not desired or . applicable for treating a heavy matt of fibers, such as in a roving or bolt, one or more of the fibers or filaments may be selectively treated to provide it with a thin superficial metal coating and thus prevent the entire bolt or roving of fibers from accumulating static electrical charges. A permanent or temporary antistatic coating may be thus applied to one or more strands of the fibers •to produce the desired non-static condition. In this manner no noticeable alteration of the color or physical properties of the rovings or fabric is produced.

The antistatic treatment is applicable, as forementioned, through the treatment of filaments, fibers, yarns, film woven, knitted, felted, laid and built-up fibers as in the formation of fabrics and mats. Articles made from such fibers or filaments are also amenable for treatment in accordance with this process. The invention is especially useful in the treatment of thermoplastic and synthetic fibers and fabricated articles from synthetic fibers which have a persistent tendency to build up electrostatic charges during their manufacture or processing.

An important advantage of employing gaseous metal depositions for coating and conditioning materials which have a tendency to accumulate static electrical charges to substantially eliminate this tendency is that a very thin, microscopic thickness coating of the electrical conducting metal can be deposited upon the surface of. the material. Thus for example, by gaseous metal deposition a thickness represented by one molecular layer thickness may be effected. This very thin coating is readily removed after the material has been processed or fabricated to a point where it is not necessary or is not desired to leave the antistatic coating on the fiber or material treated. This is an important advantage where fibers such as synthetic fibers are being processed in the dry state and where it is a decided disadvantage, to allow the accumulation of static charges of electricity on -the fibers. Where it is desired or is beneficial to leave the antistatic coating on the material, this of course is done, and thus eliminates the extra steps of its removal. In general, the removal of the antistatic coating is unnecessary since the flexibility, feel and other physical characteristic properties of the material thus treated are not altered. .

The process of gaseous metal plating utilizing carbonyls and the like as described hereinbefore is carried out similarly as described in the U.S. Patents 2,344,138 and 2,638,423 to which reference may be made. In the use of metal carbonyls and hydrides the process may be effectively and efficiently carried out by moving the material through a chamber or atmosphere containing the desired metal compound and which is heat decomposable and heating the atmosphere in a temperature range of about 350-450° F. When working with most metal carbonyls it is preferred to provide an atmospheric temperature in the chamber of between about 375-425° F. In this connection nickel carbonyl heat decomposes at a temperature in the range of about 375-400 F.

The terms “fibers” and “yarns” as generally referred to in this application and in the appended claims is intended to include and encompass a single filament, a plurality of filaments, drawn or twisted together in the 5 form of a thread, and which may be either made up single or multiple threads associated together as by twisting, to produce a thread or multiple threads. Also, these terms include staple fibers produced from filaments or threads which may be spun into yam or felted to 10 produce a mat.

It will be understood that while the method has been described and specific coating compositions set forth herein as a preferred form of the invention and its manner of using, modifications obviously can be made with15 out departing from the spirit and scope of the disclosure and that such modifications and substitutions which fall within the scope of the appended claims are to be included herein.