US2986115A - Gas plating of synthetic fibers - Google Patents

Description

May 30, 1961 H A. TOULMlN, JR

GAS PLATING OF SYNTHETIC FIBERS Filed May 14, 1958 INVENTOR HA REY A. TOL/LM/N JR.

Q BY

ATTORNEY5 United States Patent GAS PLATIN G 0F SYNTHETIC FIBERS Harry A. Toulmin, Jr., Dayton, Ohio, assignor, by mesne assignments, to Union Carbide Corporation, New York, N.Y., a corporation of New York Filed Mar. 14, 1958, 'Ser. No. 735,193

2 Claims. (Cl. 118-48) This invention relates to the metal plating of fibers, fabrics and the like, and particularly to fibers and fabrics which are made of natural or synthetic resins and which fibers tend to. soften or change physically when subjected to temperatures ordinarily required for effecting the metal plating operation.

This application is a continuation-in-part of application Serial No. 437,085 filed on June 16, 1954 now Patent No. 2,859,130.

This invention is especially adapted for metal plating of natural and/or synthetic resin fibers or mixtures thereof, or fabrics woven or fabricated therefrom, and which fibers or fabric tend to deteriorate, discolor or otherwise change physically when subjected to relatively high temperatures, and such as are generally employed in gaseous metal plating.

The invention is of particular utility for gaseous metal plating of synthetic fibers or fibrous masses such as are made principally of synthetic fibers or filaments, for example, nylon, Dacron, Orlon, Dynel, Acrilan, Saran, Vinyon and the like.

The invention will be described with more particularity as fibers or filaments of continuous length,'but it will be understood as aforementioned that such fibers or filaments may be in the form of fabricated products such as fabrics, mats, either woven, matted or otherwise formed into articles which can be subjected to gaseous metal plating.

It is an object of the invention to provide a method and apparatus which can be employed to effect metal plating of fibers, filaments and the like by bringing the same in contact with a suitable heat-decomposable gaseous metal compound or mixture of such compounds and employing temperatures sufiiciently high to cause decomposition of the gaseous metal compound and deposition of the metal constituents thereof onto the surface of the fibers without causing softening or injury to the fibers thus treated.

Another object of the invention is to provide a method of treating fibers composed of synthetic resins and the like and which have a relatively low softening or melting point whereby the same can be gaseous metal plated even at temperatures above their softening point.

Another object of the invention is to provide an improved method of treating fibers, especially synthetic resinous fibers, so as to make. it possible to gasous metal plate them by limiting the period of time that the synthetic resinous fibers are in contact with the heatdecom-.

posable gaseous metal plating compound, and whereby the fibers are not subjected to a temperature for long enough time to cause softening or melting of the fibers.

Another object of the invention is to provide an apparatus wherein fibers of the character described can be gaseous metal plated, such apparatus comprising a chamber for carrying out gaseous metal deposition in combination with means for drawing the fibers through the chamber at a predetermined rate which may 1. varied depending upon the fiber being'plated,

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A still further object of the invent-ion is to provide an apparatus through which fibers may be drawn as a continuous length fiber and subjected to gaseous metal plating, provision being made to move one or more fibers, filaments, or fabric formed of the fibers, therealong through said chamber at a predetermined speed, the duration of exposure of the fiber to the temperature in the gas plating chamber, and which temperature may be above the established softening point of the particular fiber, being controlled and limited so as to prevent deterioration of the fiber during gaseous metal plating.

A still further object of the invention is to provide an improved apparatus and method for treating the fibers, both synthetic and natural, to gaseous metal'plating and wherein the heating of the heat-decomposable gaseous metal compound in contact with the fibers, and time of exposure thereto is controlled so as to prevent softening or deterioration of the fiber or fibers during gaseous metal plating of the same. i

This and other objects and advantages will become apparent from the following description and reference to the drawing, wherein one embodiment of the apparatus and method of gas plating fibers is illustrated. A

In the drawings Figure 1 illustrates, in perspective and diagrammatically, a suitable apparatus for gaseous metal plating continuous fiber lengths in accordance with this invention;

Figure 2 is a vertical sectional view taken through the apparatus illustrated in Figure 1, being taken substantially on the line 2-2 of Figure 1;

Figure 3 is a cross-sectional view taken substantially on the line 3-3 of Figure 2;

Figure 4 is a cross-sectional view taken substantially on the line 4-4 of Figure 2; and

Figure 5 is a view in perspective, similar to Figure l, with the omission of the fiber drawing mechanism and illustrating a modification thereof wherein multiple gaseous metal plating chambers and cooling means are provided for carrying out successive and continuous gas plating treatments.

Attempts heretofore made to metal plate fibers, both natural and synthetic, have been unsuccessful, particularly where the fiber is composed of material such as synthetic resin or organic or animal substances which tend to soften or deteriorate at the temperature required for effecting the gaseous metal plating. The plating operation utilizing heat-decomposable metal compounds requires that the temperature be raised high enough to cause the gaseous metal compound to decompose and deposit the metal constituent on the fibers. Each heatdecomposable metal compound has a temperature at which decomposition takes place. However, decomposition may take place slowly at a somewhat lower temperature or while the vapors are being heated up through a particular range. For example, nickel carbonyl almost completely decomposes at a temperature in the range ,of about 375 F. to 400 F. This carbonyl, however, starts to decompose slowly at about F. and decomposition continues during the time of heating from about 200 F. to 380 F. A large number of metal carbonyls and hydrides also become effectively and eflici'ent- 1y decomposed at a temperature in the range of 350 to 400 F. When working with most metal carbonyis it is preferred to operate. in a temperature range of about 3,7:5" F. to 450 F.

As will be seen, in order to deposit metal coatings on the fiber or fabric materials exposed thereto, it is necessary that the same be subjected to a temperature in the general decomposition range of the gaseous metal compound used to 'efiect the metal plating, a f

This has presented a very difliclilt. Problem which, insofar as is known, has not been solved heretofore.

The present invention provides an apparatus and method for achieving this.

In accordance with the preferred method the fiber, either in the form of continuous length filaments of fabric, is subjected to a pro-warming treatment and then drawn through a gaseous metal plating chamber wherein the same is subjected to gaseous metal plating and immediately thereafter the fiber is cooled by moving the same through a refrigerating chamber. The fiber or fabric which may be made of synthetic resin having a softening or melting point below the temperature of gaseous metal plating, is prevented from deteriorating during the gaseous metal plating by limiting the period of time in which the fiber is subjected to gaseous metal plating. Thus, by subjecting the fibers to a controlled time of treatment a flash gaseous metal deposition may be effected without bringing about injury or physical change of the fibers or fabric material being treated.

In accordance with the process, a stream of gaseous material is brought in contact with the fiber, preferably pre-warmed and the gaseous metal plating carried out before the fiber becomes heated to a temperature high enough to cause deterioration. The gaseous plating atmosphere may be formed by mixing an inert gas with the vapors of a volatile metal compound which is heatdecomposable or by atomizing a liquid metal compound into a blast of hot inert gas or other equivalent method which provides a substantially gaseous metal for deposition onto the fibers.

As the inert gas there may be used carbon dioxide, helium, nitrogen or the like which is inert to the gaseous metal compound and to the fibers being treated.

Metal to be deposited may be introduced as gaseous metal carbonyls or vaporized solutions of the metal carbonyls, in readily vaporizable solvents, for example, petroleum ether or the like, also nitroxyl compounds or hydrides may be used such as nitrosyl carbonyls, metal hydrides, metal alkyls, metal halides, and the like.

Illustrative compounds of the carbonyl type are nickel, iron, chromium, molybdenum, cobalt, titanium, zirconium, and mixed carbonyls.

Illustrative compounds of other groups are the nitroxyls, such as copper nitroxyl; nitrosyl canbonyls, for example, cobalt nitrosyl carbonyl; hydrides, such as antimony hydride, tin hydride; metal alkyls, such as chromyl chloride; and carbonyl halogens for example, osmium carbonyl bromide, ruthenium carbonyl chloride, and the like.

An important factor which results in the successful operation of the method and apparatus for gaseous metal plating the fibers and fabrics of the character afore- .mentioned, is that of controlling the speed of the passage of the fiber material through the gaseous plating chamber. For example, nylon softens at about 320 F. whereas Orlon softens at a higher temperature, for instance about 450 F. Saran becomes soft at about 260 F. Accordingly, the speed of travel of the fibers through the apparatus, especially through the gaseous metal plating chamber, is controlled so that at no time do the fibers themselves reach a temperature such as to cause them to soften or deteriorate.

The speed or duration of time in which the fibers. are subjected to gaseous metal plating depends upon the fiber being treated. Further, where the time allowed for gaseous metal plating of the fiber is insutficient to deposit the required thickness of metal coating on the fiber, then the fiber is returned for successive plating treatments and passed through multiple gaseous metal plating chambers, as illustrated in the drawings.

Referring to the drawing, and particularly to Figures 1 and 2, there is disclosed an embodiment of the invention wherein the fibers to 'be plated are drawn from one or more spools 12 and moved first through a preheatingchamber 14. This chamber is suitably heated,

as by the electrical heating elements 16, arranged around the walls of the chamber and so as to encompass the fiber drawn therethrough. Heating elements 16 are connected to a source of electric current by leads 18 and 19. The temperature of the pre-heating is preferably controlled by a rheostat 20 actuated by a thermocouple 21 disposed in the chamber 14 and electrically connected thereto. After the fiber has been drawn through the preliminary heating chamber 14 it is passed into the gaseous decomposition metal plating chamber 24 wherein the same is subjected to gaseous metal deposition. Thereafter the fiber is moved along through the cooling chamber 26 and thence over the guide pulleys 28, 29, 31 to the storage spools 33 and 34.

To control the speed at which the fibers are drawn through the gaseous metal chamber and associated heating and cooling chambers, a variable speed motor 40 is utilized. This motor is arranged for variable speed operation which may be accomplished by the use of a temperature actuated rheostat 42. The speed or r.p.m. of the motor 40, as thus controlled, is arranged to drive the pulley 44 through the V-belt 45. Difierent speeds may also be provided through the use of different diameter driven pulleys operated by the motor 40 if desired. Pulley 44 is, in turn, drivingly connected to the pulleys 46 and 48 by means of the V-belts 50 and 51 respectively.

The temperature and speed control means 42 are connected to the thermocouple 60 which is arranged in the gaseous metal plating chamber, as illustrated in Figure 1 and Figure 2, whereby the speed of the motor may be increased or decreased depending upon the temperature in the gaseous plating chamber. Thus, by setting the temperature control mechanism 42 in accordance with the temperature desired in the gaseous metal plating chamber,

,the apparatus may be operated so as to maintain the temperature and speed of movement of the fiber through the gaseous chamber substantially constant for any particular setting.

The gaseous metal deposition chamber 24 is suitably heated as by the use of resistance coil 65, the same being arranged around the chamber so as to evenly heat the same and bring about decomposition of the gaseous metal compound introduced therein. The gaseous metal compound admixed with inert carrier gas, e.g. carbon dioxide,

nitrogen, helium or the like, are introduced to the plating chamber 24 through a conduit 68 and the spent gases, including unused metal compound, are withdrawn through a conduit 70 and to a condenser 79, the gaseous metal compound being restored as a liquid in a tank or container 78 which is connected through conduit 80 to the vaporizer 75 from which it is returned through the conduit 68 to the gaseous metal plating chamber, as described.

The cooling chamber 26 comprises a coil which is arranged in the chamber 87 through which the fiber is drawn after its passage through the gaseous plating chamber. Arranged around the cooling coil 85 is insulating material 89 which may consist of mineral glass wool or the like insulating material. Cooling fiuid is admitted to the coil 85 through the conduit 91 and withdrawn therefrom through the conduit 93.

To prevent seepage of gaseous metal compound from the plating chamber 24 through apertures at the opposite ends, as at 95 and 96, which permits the entrance and egress of the fibers, inert gas such as carbon dioxide is admitted through the conduits and 102 to the closure chambers 103 and 104 which are arranged about these apertures. This inert gas is maintained at a slightly higher pressure than that inside the gaseous plating chamber, thus preventing the gaseous metal compound from passing out through these apertures.

In the modification illustrated in Figure 5, the apparatus is of similar construction as illustrated and described in Figures 1 and 2, and the same reference characters are pp ie tad s snate t e me- IP h Parti ul r m ifi cation three gaseous plating chambers 24a, 241;,and, 24c are utilized toef fect a triple flash metal plating of the fibers. Whereadditional gaseous metal treatment is desired, a plurality of gaseous metalplating chambers may be employed with interposed cooling chambers whereby the process may be carfied out to provide multiple-gaseous plating treatment. In this manner, the fibers may be subjected to any desired number of gaseous metal plating treatments to produce metal coating of a predetermined thickness. 7

In a plat ng with nick ar on l to p s t nickel me on o g nic q filame ts. ncr n th mperature of the Ni(CO) vapor up to about 350 F. (maximum) increases the thermal decomposition rate of Ni(CO) Above 350 F. (approximately) no significant decomposition rate increaseoccurs, e.g. it can be regarded practically as an instantaneous reaction.

On an organic fiber, as in the process of this invention, at 350 F. the endothermic instantaneous" decomposition of Ni(CO) to give Ni thereon results in a cooling of the fiber or loss of fiber heat so that the decomposition of Ni(CO) Ni+CO gradually decreases to a very low impractical rate. Accordingly, since only a small amount of heat (particularly at 350 F.) can be put into a filamentous organic fiber, it follows that only a very minute amount of Ni(CO) will be decomposed for this quantity of filament heat.

It is, therefore, necessary to reheat and replate onto the fibers by alternately moving them through a series of heater-plater chambers or assembly, as illustrated in the drawings, where the amount of nickel deposited onto the fibers and the fiber temperature are directly related to the number of alternate heating and plating chambers. This relationship may be indicated as follows- Amount of nickel per unit weight of fiber=Number of alternate heating and plating chambers multiplied by the fiber temperature It is, therefore, apparent that by increasing the number of alternate heating and plating chambers to a large figure (50-200) the fiber temperature may be lowered to a point where thermally delicate fibers such as Dynel, or nylon can be satisfactorily plated with adequate amounts of nickel. This is based on a constant through-put rate through the plating apparatus.

The following examples illustrate the process of gaseous metal plating different fibers with various heat-decomposable gaseous metal compounds as described.

Example I Fibers of nylon were drawn through the apparatus as described, and subjected to a preliminary heat treatment of 250 F. Thereafter the synthetic fibers are drawn through the gaseous metal plating chamber and subjected to a temperature of 375 F. The gaseous metal plating material constitutes nickel carbonyl diluted with carbon dioxide gas, the rate of gas fiow being maintained at approximately 4 liters per minute at a temperature of 78 F. and 125 mm. Hg. The fiber in the gaseous metal chamber was drawn through the chamber at a rate of 1 linear foot per second, and such as to expose the ,fiber to gaseous metal treatment for approximately 3 seconds. Where the plating chamber is of a length of approximately 3 feet, this provides a gaseous plating time of 3 seconds, being insutficient to heat up the fiber to a temperature such as to cause it to soften. Thereafter the gaseous metal treated fiber is drawn through the cooling chamber so as to quickly cool the fiber and prevent it from retaining the residual heat and causing distortion or deterioration thereof. The cooling chamber was maintained at a temperature of approximately 32 F. by cireulating brine through the cooling coil.

The process p ovide nylon fibers havin a c at ng o n cke metal, h hi ne s t h seat ng b insibttwss about 0.00002-0.00004 inch. Where a greater thickness of the metal coating is desired, the fiber is subiected to repeated gaseous metal plating cycles of tieatnients as aforementioned, For carrying out a plurality of succw sive gaseous metal treatments, the apparatus illustrated in Figure 5 may be used.

Example II In this instance Orlonfiber iscoated with iron utilizing ron carbony s he heat d comp able aseonsmetal mpound. The fiber s rawn h o s he apparatus similarly as described in Example I, being subjected ma preliminary heat treatment of 350 F.- The gaseous metal deposition in the plating chamber is conducted in this instance at 475 F. The atmosphere in the plating chamber consists of nitrogen containing about 2% by volume of iron carbonyl. The duration exposure of the fiber in the gaseous metal plating chamber to this temperature is held to approximately 10 seconds and the speed of the fiber was accordingly adjusted so as to provide for this plating time in the gaseous metal plating chamber.

Inasmuch as Orlon has a higher softening temperature, namely about 450 F. as compared with'about 320 F. for nylon, accordingly Orlon fibers may be exposed for a somewhat longer length of time in the plating chamber without injury.

After passing the fibers through the plating chamber and cooling chamber as in Example I, the resultant Orlon fibers are provided with a metal coating of iron having a film thickness approximately 0.00004 to 0.00006 inch.

Example III In this instance a fabric made of Saran is nickel coated utilizing nickel carbonyl similarly as in Example I, by passing the same through the heating and gaseous metal plating chamber at a speed such as to complete the exposure of the fiber in the gaseous metal chamber in 5 seconds. The temperature for carrying out the gaseous metal deposition of the nickel being held at approximately 375 F.

In this instance the thickness of the nickel metal coating on the fiber approximates 00004-000006 inch.

As will be understood, other gaseous metal compounds may be employed, or mixtures thereof, to produce the desired metal coating on the fiber or fabric being treated.

It will be understood that this invention is not to be restricted to the specific fibers mentioned and examples given above, but that it is susceptible to various modifications and changes which come within the spirit and scope of this disclosure and as more particularly set forth in the appended claims.

What is claimed is:

1. Apparatus for gas plating metal on heat sensitive organic fiber material, and which tend to soften under prolonged heating at 350 to 475 F., said apparatus comprising a series of gas plating and cooling chambers, means including a variable speed motor for advancing said fiber material through said series of chambers, each of said gas plating chambers being connected directly with a cooling chamber whereby said fiber is quickly cooled following the gas plating operation, a source of heat-decomposable metal bearing compound admixed with inert carrier gas, means for heating said organic fiber material, means for directing a blast of said inert carrier gas containing the heat-decomposable metal compound onto said fiber, and means for controlling the speed of operation of said variable speed motor and resultant speed at which said fiber material is moved through said apparatus.

2. Apparatus for gas plating metal on heat-sensitive organic fiber material, and which tend to soften under prolonged heating at 350 to 475 F., said apparatus comprising a plurality of gas plating chambers with interposed cooling chambers, means including a variable Speed main,

mechanismfor advancing said fiber material through said plurality of chambers, each of said gas plating chambers .bcing contiguously connected with a cooling chamber whereby said fiber is immediately cooled following the gas plating operation, a source of heat-decomposable metalbearing compound-admixed withinert carrier gas, means for heating said organic fiber material, means for introducing said inert-carrier gas containing the heatdecornposable metal compound into said plating chamspeed at which said fiber material is moved; through said apparatus. 1

References Cited in the file of tliisipatent UNITED STATES PATENTS Aug. 13, 1946 2,616,165 Brennan Nov, 4, 1952 2,656,283 Fink et a1. Oct. 20, 1953 2,785,651 Pawlyk Mar. 19, 1957 2,789,064 Schladitz Apr. 16, 1957 2,859,130 Toulmin Nov. 4, 1958 2,884,337 Homer et al. Apr. 28, 1959 2,897,091

Homer et a1. July 28, 1959

Claims (1)

1. APPARATUS FOR GAS PLATING METAL ON HEAT-SENITIVE ORGANIC FIBER MATERIAL, AND WHICH TEND TO SOFTEN UNDER PROLONGED HEATING AT 350 TO 475*F., SAID APPARATUS COMPRISING A SERIES OF GAS PLATING AND COOLING CHAMBERS, MEANS INCLUDING A VARIABLE SPEED MOTOR FOR ADVANCING SAID FIBER MATERIAL THROUGH SAID SERIES OF CHAMBERS, EACH OF SAID GAS PLATING CHAMBERS BEING CONNECTED DIRECTLY WITH A COOLING CHAMBER WHEREBY SAID FIBER IS QUICKLY COOLED FOLLOWING THE GAS PLATING OPERATION, A SOURCE OF HEAT-DECOMPOSABLE METAL BEARING COMPOUND ADMIXED WITH INERT CARRIER GAS, MEANS FOR HEATING SAID ORGANIC FIBER MATERIAL, MEANS FOR DIRECTING A BLAST OF SAID INERT CARRIER GAS CONTAINING THE HEAT-DECOMPOSABLE METAL COMPOUND ONTO SAID FIBER, AND MEANS FOR CONTROLLING THE SPEED OF OPERATION OF SAID VARIABLE SPEED MOTOR AND RESULTANT SPEED AT WHICH SAID FIBER MATERIAL IS MOVED THROUGH SAID APPARATUS.

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