CA1263338A - Metal coated filaments, process for their production, and articles made therefrom - Google Patents
Metal coated filaments, process for their production, and articles made therefromInfo
- Publication number
- CA1263338A CA1263338A CA000457206A CA457206A CA1263338A CA 1263338 A CA1263338 A CA 1263338A CA 000457206 A CA000457206 A CA 000457206A CA 457206 A CA457206 A CA 457206A CA 1263338 A CA1263338 A CA 1263338A
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Abstract
METAL COATED FILAMENTS, PROCESS
FOR THEIR PRODUCTION, AND ARTICLES
MADE THEREFROM
ABSTRACT OF THE DISCLOSURE
Filaments comprising a rough, sensitized core of non-conductive polymer, e.g., aramid, or the like, a firmly bonded conductive metallic interlayer chemi-cally deposited on the core,alone, or in combination with a uniform, electrically conductive overlayer of an electrodepositable metal, such as nickel or the like.
FOR THEIR PRODUCTION, AND ARTICLES
MADE THEREFROM
ABSTRACT OF THE DISCLOSURE
Filaments comprising a rough, sensitized core of non-conductive polymer, e.g., aramid, or the like, a firmly bonded conductive metallic interlayer chemi-cally deposited on the core,alone, or in combination with a uniform, electrically conductive overlayer of an electrodepositable metal, such as nickel or the like.
Description
~2633~3 ~,~1 ~ 1 METAL CCATED FILAMENTS, PROCESS
FOR THEIR PRODUCTION, AND ARTICLES
MADE THEREFROM
The present invention relates to filaments comprising filaments having rough, non-conductive polymeric cores coated with thin adherent layers of metals, to methods for their production, and to articles made from them.
12~3338 BACKGROUND OF THE INVENTION
Fllaments of normally non-electrically-conductive materials, bundles, e.g., yarns, tows, mats, cloths and chopped strands are known to be useful in reinforclng plastics and rubber. Some have normally smooth surfaces, such as polyesters and polyamides, and some have surfaces which are normally rough, such as cotton, rayon and wool. Articles comprising plastics and rubber reinforced with such filaments find wide-spread use in replacing heavier components made of lower strength conventional materials such as aluminum, steel, titanium, as well as glass, asbestos, etc., in aircraft, automobiles, office equipment, sporting goods, and in many other fields.
A common problem in the use of such filaments, is a seeming lack of ability to fully translate the properties, especially strength, to the material to which ultimate and intimate contact is to be made.
The problem is manifested in a variety of ways: for example, if a length of high strength yarn comprising filaments of a long chain synthetic polyamide in which 85% of the amide linkages are attached directly to two aromatic rings is mixed with an epoxy resin and the resin is cured, and if the workpiece is pulled until broken, the breaking strength will be less than expected because of bonding difficulties. The lack of reinforcement capability seems to be entirely due to poor translation of strength between the slippery plastic filaments and the plastic matrix. Compressive strength too is unexpectedly poor when some types of polyester and polyamide r - 2 filaments, and the like in the form of strands, chopped strands, nvn-woven mats, felts, papers, etc., or woven fabrics are mixed with organic polymeric substances, such as phenolics, styrenics, epoxy resins, polycarbonates, and the like, because they seem merely to fill the plastics without providing any reinforcement, and in many cascs even cause physical properties to deteriorate.
Continuous fi]aments of electrically conductive semi-metallic cores having at least one thin, uniforrn, firmly adherent, electrically conductive layer of at least one electrodeposited metal on the cores have been described elsewhere. Such filaments are useful to reinforce plastics or metals to an unparalleled degree because the strength of the core is directly translated through the firmly bonded metallic layer into the plastic or metal matrix. Unfortunately, however, the methods proposed in Canadian application 457,193* require that the core material be semi-metallic (and therefore electrically conductive, e.g., carbon) so that normally non-conductive materials such as nylon, polyester and/or aramids, cotton, rayon, wool and the like, cannot be electroplated directly into high strength coated fibers.
In Stuetz, United States 3,495,940, continuous filaments of high temperature resistant carbonaceous fibers are produced by forming a thin film of a sensitizing metal on an organic fiber precursor, e.g., acrylics, polybenzimidazoles, nylons or on a carbon fiber, electrolessly plating copper on the sensitized surface and electrodepositing additional copper on top of this think copper layer. Thereafter an electric current is passed across the plated fiber to *See also United States Patent 4,661,403 iL263338 - 4 - 6LlOg-7292 pyrolyze the core. The plating is then removed, and the filament is used as the filament winding, etc. Alternatively, the core is burned out leaving hollow metal filaments which can be used to weave light weight space suits. In any event, reinforcing filaments having a strongly adherent metal coating are not produced by such a process.
It has now been discovered that if the surfaces only of filaments comprising a rough non-conduc-tive core is sensitized and finally rendered conductive, by chemical deposition of a thin metallic interlayer, useful materials are ob-tained. Moreover, if then such yarns and tows are subjected to theunique processing conditions set forth in Canadian application 457,193, then metal coated filaments will also be obtained in which the bond between the coating and the filament is so strong that bending the fiber, as in weaving or knitting, may rupture the coat-ing, but it will not peel away. If a smooth surface core is provi-ded, e.g., aramid, it is necessary to roughen the surface before sensitizing the roughened surface with a salt of a noble metal, e.g., palladium. If a rough surface is normally present, e.g., then the roughening can be omitted. Next there is deposited a metal, such as nickel, silver, or copper on the rough, sensitized surface. More-over, the surface can be electroplated, e.g., with nickel or silver using a high external voltage. In either case, there will be pro-vided uniform, continuous, adherent, thin metal coatings on the sur-face of the filaments. It is believed that high voltage provides energy sufficient to provide uniform nucleation, especially if a plurality of filaments is used. Furthermore, the high voltage ~263~3~3 61109-~292 provides an even distribution of each fiber. Filaments comprising thin metal coatings on the metallized cores, and yarns, cloths, felts and the like, according to this invention can be knotted or folded without the metal substantially flaking off.
Articles made by adding the filaments of the present invention to a matrix forming material also are highly advantageous because they are strongly reinforced. In addition, these articles possess other advantages, for example, they dissipate electrical charges making them useful as shielding devices, and provide a degree of protection against lightning strikes. Aramid fibers, especially, when metal coated according to this process are not substantially degraded by ultraviolet light.
Therefore, according to the present invention there is provided a continuous metal-coated filament comprising an electrically non-conductive polymeric core having a mechanically roughened surface sensitized to the chemical deposition of a metal, an electrically conductive metallic interlayer chemically deposited on the rough surface of said core and firmly bonded thereto, and at least one thin, uniform, firmly adherent, electrically conductive layer of at least one metal electrodeposited on said interlayer.
` '' 3331~ 110-023 _ 6 BRIEF DESCRIPTION OF THE DRAWINGS
The invention may be more readily understood by reference to the accompanying drawings in which:
Fig. l is a transverse cross sectional view of a metal coated rough-surfaced filament of this invention.
Fig. 2 lS a longitudinal cross sectional view of a metal coated rough-surfaced filament according to this invention.
Fig. 3 is a magnified view of a portion of Fig. 2.
Fig. 4 is a partial sectional view of a metal coated filament-reinforced polymer matrix obtained by using this invention; and Fig. 5 is a view showing an apparatus for carrying out the process of the present invention.
All the drawings represent schematics of the articles described.
SU~I~IARY OF THE INVENTION
According to the present invention, continuous metal-coated filaments are provided having a rough, electrically non-conductive polymeric core, the rough surface of which is sensitized to the chemical deposition of a metal, an electrically conductive metallic interlayer chemically deposited on the sensitized rough surface of said core and firm]y bonded thereto, alone, or in combination with at least one thin, uniform, firmly adherent, electrically conductive layer of at least one metal electrodeposited on said interlayer. The bond strength of the coated filament is at least sufficient to provide that when the coated filament is bent the coating may fracture, but it will not peel off.
In preferred features the core comprises polyesters, polyamides, cotton or wool, and especially polyamides in which at least 85 percent of the amide linkages are attached directly to two aromatic rings (aramids).
Among the features of the invention are knottable filaments, fabrics woven from such filaments, non-woven sheets, mats and papers laid up from such filaments, chopped strands of such filaments and articles comprising such filaments uniformly dispersed in a matrix comprising an organic polymeric material.
In preferred embodiments, interlayers will comprise nickel, silver, copper, etc., and coating metals will be nickel, silver, zinc, copper, lead, cadmium, tin, cobalt, gold, indium, iron, palladium, platinum, tellurium, or an alloy of any of the foregoing, without limitation, preferably in crystalline form.
If the surface of the core is smooth, i.e., not normally . ~,,,~, ~26333~3 ~ 61109-7292 rough, such as a smooth filament of polyester, nylon or aramid, etc., it is a feature of the invention to roughen the surface, e.g., by solve~t treatment or treatment with a chemical, but preferably by mechanical abrading it, e.g., by use of slurried silica, sand, etc., e.g., of 60-320 mesh, preferably 120-1~0, size, conveniently in a fluidized bed abrader. Sensitization of the roughened surface will be by conventional methods, e.g., first by treatment with a stannous salt solution, then with a precious metal salt, e.g., palladium halide or sulfate. A single bath can instead be used for sensitization. Suitable techniqucs are well known to those skilled in this art and will be exemplified hereinafter. Especially preferred for the metallic interlayer is silver chemically deposited by reduction with alkaline hydrazine or a borohydride.
In another principal aspect, the present invention contemplates a process for the production of a metal-coated filament comprising:
(a) providing a continuous length of filament comprising a rough surfaced electrically non-conductive polymeric core and mechanically roughening said ~i~amont;
~:~r~
(b) sensitizing the rough surfaced fila~ent to the chemical deposition of a metal;
(c) chemically depositing a firmly adherent electrically conductive metal interlayer on the sensitized surface of ~o~
the core to yield a filamen-t coated with an electrically conductive metal interlayer; and, optionally, (d) continuously immersing at least a portion of the length of a filament resulting from step (c) in a solution ~L263~3~3 capable of electrolytically depositing at least one metal;
(e) providing a quantity of electricity and applying an external voltage betwcen the filament resulting from step (d) and an electrode immersed in the solution, which voltage is in cxcess of what is normally required to cause metal deposition, whereby (i) the metal nucleates substantially uniformly on the surface of the filaments and (ii) produces a substantially uniform, firmly adherent layer of metal on said interlayer, thereby yielding said continuous metal-coated filament.
In preferred features, the process will use core filaments of a number of organic polymeric materials, all of which will be electrically non-conductive. Included will be polyolefin filaments, e.g., polypropylene, polyacrylonitrile, wool, cotton, rayon and the like. Especially contemplated are polyester filaments, such as poly(ethylene terephthalate) and polyamide filaments such as nylons, e.g., poly(caprolactam) and poly(l,6-hexamethylenediamine adipate), and the so-called aramids, which are long chain synthetic polyamides in which at least ~5~ of the amide linkages are attached directly to two aromatic rings. The latter are described, together with methods for their production, in the Encyclopedia of Chemical Technology, 3rd Edition, Volume 3, John Wiley, New York, 1978, pages 213-242.
Especially suitable as core materials are aramid filaments made by polycondensing diacid chlorides and diamines in amide solvents, such as dimethylacetamide ~26~33~
and N-methylpyrrolidone. High strength filaments can be made by solvent spinning the condensation product of p-aminobenzoyl chloride hydrochloride, the product being known as poly (p~benzamide) or PPB.
Another condensation product is made from p-phenylenediamine and terephthaloyl chloride. It is known as poly(paraphenyleneterephthal-amide) or PPD-T. Fibers comprising the latter are available from the DuPont Company, Wilmington, Delaware 19898 under its trademark KEVLAR 29 and 49, the latter being a hot drawn fiber. Typical bundles of filaments used in this invention will average 4 thousand filaments per yarn bundle, each of which filaments has an average 12 micron diameter.
In one preferred embodiment the core filaments comprise a tow of filaments and the product of the process is a tow of coated filaments which can be knotted without substantial separation of the ~layers of metal or portions thereof from the core. Some small amounts of separation can be tolerated but generally more than about 90 percent, and especially more than about 95 percent, of the metal coating will remain attached.
Other preferred features comprise the steps of weaving or knitting filaments produced by the process into a fabric, laying them up into non-woven sheets, or chopping them into shortened lengths.
Other preferred features including carrying out the process in an electrolytic solution which is recycled into contact with the filaments immediately prior to immersion in the solution so as to provide increased carrying capacity to the filaments and replenish-ment of the electrolyte on the surface thereof.
,~ -- 10 --33~
DETAILED DESCRIPTION OF THE INVENTION
Referring to Figures 1 and 2 continuous yarns and tows for use in the core 2 according to the present invention are available commercially. For example, suitable aramid fiber yarns are available from DuPont Company, under the trademark KEVLAR-29 and KEVLAR-49 and suitable polyester fiber yarns are available from DuPont Company un-der the trademark DACRON Polyester (Type 68). Suitable nylon poly-amide yarns are available from DuPont (Type 728) for example. Cotton thread and wool fibers can be used. As mentioned above, all such fibers will be non-conductive and sensitized to chemical deposition of a metallic interlayer 3. The cotton threads and wool fibers are naturally rough; the others must be made rough.
Surface roughening is carried out in any normal way, but preferred is abrading the filaments with finely divided silica, alu-minum oxide, sand, etc. In conventional filaments, e.g., those 4 to 15 microns thick, 120 mesh abrasive will produce a suitably roughened surface. The roughened surfaces provide essential anchoring sites for interlayer 3, as shown in Figure 3, providing an enhanced mecha-nical grip. In continuous production, roughening is facilitated in a fluidized bed mechanical abrader, e.g., a Cole-Parmer-type appara-tus.
The roughened filaments are then treated with materials to produce a sensitized and activated surface, e.g., by continuously passing them through a stannous chloride, or stannous sulfate solu-tion and then through a solution of a salt of a noble metal. Wetting of the roughened filaments can be facilitated in the stannous A _ ' ~L26~3;38 chloride solution by the addition of a small amount of a cleaning agent. The preferred noble metal salt is a water-soluble palladium salt, such as palladium chloride.
Salts of gold, platinum and rhodium can also be used.
The sensitized rough surface presents outwardly a thin layer of metal which catalyzes the chemical deposition of metal from ions in the solution used to form the metal interlayer, e.g., silver metal from silver nitrate solution, then, without rinsing, into a solution of hydrazine, a hydrazine compound or a borohydride, at a high reducer to low metal ratio, to reduce silver ion to silver metal, well-bonded to the surface. The thickness of interlayer 3 builds up with time and it is sufficiently thick when conductivity (or decrease in resistance) is sufficient to permit electrodeposition in subsequent steps. This can be measured in known ways.
For further details on this aspect, reference is made to the above-mentioned, U.S. 3,495,940, the procedure of which does not, however, use a roughened fiber surface.
Metal layer ~ will be of any electrodepositable metal, and it will be electrically conductive. Two layers, or even more, of metal can be applied and metal can be the same or different, as will be shown in working examples.
The metal coated filaments of this invention can be assembled by any conventional means into composites represented in Fig. 4 ln which matrix 6 is a plastic, e.g., an epoxy resin, or a phenolic resin, or the like, the matrix being reinforced by virtue of the presence of metal coated cores 2.
_ 13_ 110-023 O
For those embodiments using one, formation of the outermost metal coating layer 4 by the electro-deposition process of this invention can be carried out in a number of ways. For example, a monofilament or a plurality of metallized core filaments can be immersed in an electrolytic solution and through suit-able electrical connections the required high external voltage can be applied. Because the filaments are so small, e.g., 5 to 50 microns in diameter, and because the innermost fibers can be surrounded by hundreds or _ even thousands of others, massive amounts of external voltage are used (even though only 0.5 to 2.6 volts are needed to dissociate the electrolyticl metal to ions, e.g., nickel, gold, silver, copper depending on the salt used), of the order of 5 times the dissociation values, to uniformly nucleate the metal onto the innermost filaments. Preferred external voltages of e.g., 10 to 50, or even more, volts are used.
Although non-continuous processes can be used, it is preferred to carry this part of the procedure out in a continuous fashion on a moving filament or bundle of filaments.
Shown schematically in Fig. 5 are components of a continuous processing a?paratus comprising in series a filament transport section 29, feeding a fluid-ized bed mechanical abrader means 30 in which surface roughening filament 24 is accomplished, e.g., with a slurry of 120 mesh silica. This is not used if the filament has a normally rough surface. Then after sensitization, e.g., by transporting and dipping first into tank 32 holding a SnC12 solution, rinsing, and ~Z6~33~3 then into tank 34 holding a PdC12 so]ution, and rinsing, filament 24 having a rough, sensitized surface is passed into tank 36 holding chemical metal deposition bath containing, e.g., silver nitrate and finally, without rinsing, into reducing bath tank 38, containing, e.g., hydrazine hydrate (alkaline). A thin coating of silver is deposited, sufficient to reduce electrical resistance to the point where the filament can be used in composites or, optionally, sent to e]ectrolytic tank 8.
To overcome the problem of filament burnout because of high voltages, to keep them cool enough outside the baths, one can blow air or pour water on them, for example, but it is preferred to operate in an apparatus also shown schematically in Figure 5.
Electrolytic solution 8 is maintained in tank 10. Also included are anode baskets 12 and idler rollers 14 near the bottom of tank 10. Two electrical contact rollers 16 are located above the tank.
Filament 24 is pulled by means not shown off feed rollers 26, over first contact rollers 16 down into the bath under idler rollers 14~ up through the bath, over second contact rollers 16 and into take up rollers 28. Optional, but very much preferred, is a simple loop comprising pump 18, conduit 20, and feed head 22.
This permits recirculation of the plating solution at a large flow rate and pumping it onto contact rollers 16. As the plating solution is discharged just above the rolls, the sections of filament 24 entering and leaving the solution are totally bathed, and thus cooled. At the high current carried by the filament, the heat generated in some cases might destroy it before it reaches or ,, . ~,, ~263~38 14a 61lO9-7292 after it leaves the bath surface without such coo].ing. Of course, more than one plating bath can be used in ser,ies, preferably 3 to 4 baths, for economy, . ~
:, .. ..
~i i333~3 and the filaments can be rin~ed free of electrolyte solution, dried, chopped, woven into fabric, all in accordance with conventional procedures.
DESCRIPTION OF THE PREFERRED E~IBODIMENTS
The following Examples illustrate the present invention, but are not intended to limit it.
A continuous tow comprised of smooth surfaced aramid filaments (4,000 fibers per bundle, average 12 microns in diameter, poly(paraphenylene terephthalamide), DuPont KEVLAR 49) was mechanically abraded with 120 mesh size silica slurried in water in a gas-fluidized bed until the surface of each fiber was roughened. The tow was dipped in an aqueous solution of 10 g/l stannous chloride and 10 ml/l of concentrated hydrochloric acid heated to 140F. and permitted to reside therein for one minute, and rinsed. The tow was then dipped into an aqueous solution of 2.8 g. of palladium chloride and 10 ml. of concentrated aqueous hydrochloric acid per liter, heated to 140F. and permitted to reside therein for one minute, and ri~sed. This technique was repeated and a rough, sensitized surface was produced on the filaments. Next the tow was immersed in an aqueous solution of 31 g./l silver nitrate and then without rinsing, into a solution of 85% aqueous hydrazine h~drate (Hummel Chemical Corp., No. 85). A silver inter-layer was adherently deposited thereby. A specimen was taken, washed and dried and resistance was measured with an ohmeter. If necessary, the silver deposition pro-cedure was repeated until the resistance of the 4K, 12 micron tow was reduced to 20 ohms per foot, at which time it was suitable for electroplating.
~263338 110-023 In a continuous electroplating system, a bath is provided having the following composition:
INGREDIENT AMOUNT
nickel sulfate ~NiSO4.6H2O) 40 ounces/gallon nickel chloride (NiC12.6H2O3 12-20 ounces/gallon boric acid (H3BO3) 5-8 ounces/gallon The bath is heated to 140-160F. and has a pH of 3.8 - 4.2.
The anode baskets are kept filled with electrolytic nickel pellets and 4 tows (fiber bundles) of 4,000 strands each of 12 micron metallized aramid filaments are continuously drawn through the bath at 5 ft./min. while an external voltage of 30 volts is applied at a current of 160 amps. At the same time, electrolytic solution is recycled through a loop into contact with the entering and leaving parts of the tow.
The tow is next passed continuously through an identical bath, also at a tow speed of 5.0 ft./min. with 160 amps current. The final product is a tow of high strength composite fibers according to this invention comprising a 12 micron fiber core, a thin silver interlayer and about 50% by weight of the composite of crystalline electrodeposited nickel adhered firmly to the core through the interlayer.
~Z~3338 _17 _ If a length of the filament is sharply bent, as in weaving or knitting, then examined, the metal coating may fracture, but it will not peel off.
If the procedure of Example 1 is repeated, substituting two baths of the following compositions, in series, and using silver in the anode baskets, crystal-line silver electrocoated over silver metallized aramid filaments according to this invention will be obtained.
INGREDIENT FIRST BATH SECOND sATH
Silver Cyanide 0.1 - 0.3 oz./gal 7 - 11 oz./gal.
15 Potassium Cyanide 12 - 20 oz./gal. 12 - 20 oz./gal.
Potassium Hydroxide --- 1 - 2 oz./gal.
The first bath is to be operated at room temperature and about 12-36 volts; the second at room temperature and about 6-18 volts.
The procedure of Example 2 can be modified, by substituting nickel or copper metallized aramid filaments for the feed, and the voltage in the first bath is reduced to about 18 volts. There are obtained high strength coated filaments according to this invention in which a crystalline silver coating surrounds a nickel or copper interlayer on a rough surfaced aramid core.
~;~63338 o The procedure of Example 1 can be modified by substituting for the nickel bath a bath of the following composition, using zinc in the anode baskets, and zinc coated silver-metallized aramid filaments according to this invention will be obtained:
INGREDIENT AMOUNT
Zinc sulfate 8 oz./gal.
Ammonium alum 3 - 4 oz./gal.
Potassium hydroxide 16 oz./gal.
Potassium cyanide 3 oz./gal.
The bath is run at 100F. and 18 volts are externally applied.
EXAMPLE 5_ The procedure of Example 1 can be modified by substituting for the nickel bath a bath of the following composition, using copper in the anode baskets, and copper coated silve-r-metallized filaments according to this invention will be obtained:
INGREDIENT AMOUNT
Copper cyanide 3.5 oz./gal.
sodium cyanide 4.6 oz./gal.
Sodium carbonate 4 oz./gal.
Sodium hydroxide 0.5 oz./gal.
Rochelle salt 6 oz./gal.
~2~333~ 110-023 _ 19_ The bath is run at 140~. and 18 volts are externally applied. The copper plated fibers should be rinsed and then washed with sodium dichromate solution immediately after plating to prevent tarnishing, if required. If the procedure of Example 3 is repeated, substituting the copper bath of this example for the silver bath, there will be obtained high strength fila-ments according to this invention in which a copper coating surrounds a nickel or copper interlayer an aramid core.
The procedure of Example 1 can be modified by substituting for the nickel bath two baths of the follow-ing composition, using standard 80% Cu/20% zinc anodes, and brass coated silver-metallized aramid filaments according to this invention will be obtained.
INGREI:~IENTAMOUNT
Copper cyanide4 ounce/gallon Zinc cyanide1.25 ounce/gallon Sodium cyanide7.5 ounce/gallon Sodium carbonate 4 ounce/gallon Both baths are run at 110 - 120F. Since one-third of the brass is plated in the first bath, at 24 volts, and two-thirds in the second at 15 volts, the current is proportioned accordingly. Following two water rinses, the bxass plated filaments are washed with a solution of sodium dichromate, to prevent tarnishing, and then rinsed twice again with water, if required.
1;2~i3338 _ 20_ The procedure of Example 1 can be modified by substituting for the nickel bath a bath of the following composition, using solid lead bars in the anode baskets, and lead coated silver-metallized aramid filaments according to this invention will be obtained:
INGREDIENT AMOUNT
Lead acetate (Pb(OAC)2 14 oz. Pb/gal.
Fluoboric acid, HBF4 13 oz./gal.
Optionally, about 2.g./1. of beta-naphthol and of gelatine are added. The pH is less than 1, the bath is operated at 80F, and an external voltage of 12 volts is applied. If the coating thickness exceeds 0.5 microns, there is a tendency for the lead to bridge between individual filaments.
By the general procedure of Example 1, and substituting a conventional gold bath for the nickel electroplating bath and applying sufficient external voltage, coated high strength filaments comprising gold on silver-metallized aramid filaments are obtained.
llO-023 ~263~3~3 By the general procedure of Example l, sub-stituting cotton thread for the aramid fibers, and omitting the surface roughening step, there are produced nickel on silver-metallized cotton filaments according to this invention.
Aramid filaments comprising poly(p-benzamide) are metallized with copper or nickel electrolessly and then coated with nickel by placing them in cathodic contact with a nickel plating bath of Example 1 and applying an external voltage of about 30 volts.
A composition is prepared by chopping the coated filaments of Example 1 into short lengths, 1/8" to 1" long then thoroughly mixing 30 wt. % with thermoplastic nylon polyamide in an extruder, and chopping the extrudate into molding pellets in accordance with conventional proced-ures. The pellets are injection molded into plaques 4" x 8" x l/8" in size. The plaque is reinforced by the coated filaments. By virtue of the metal content, it also does not build up static charge, and it can act as an electrical shield in electronic assemblies.
~ ~.
lZ6333t3 E~AMPLE 12 Bundles of nickel plated aramid filaments of about one inch in length prepared according to the procedure of Example 1 are mixed 1:9 with uncoated graphite filaments and laid up into a non woven mat, at 1 oz./l sq. yard. The mat has a metal content of about 5% by weight of nickel and can be impregnated with thermo-setting resin varnishes and consolidated under heat and pressure into reinforced laminates having high strength and excellent electrical dissipation properties.
Many variations of the present invention will suggest themselves to those skilled in this art in light of the above, detailed description. For example, poly(ethylene terephthalate) polyester fibers, nylon fibers, wool fibers and asbestos filaments can be substituted for the aramid and cotton filaments. Other reducing agents can be used. All such variations are within the full intended scope of the invention as defined in the appended claims.
',~
FOR THEIR PRODUCTION, AND ARTICLES
MADE THEREFROM
The present invention relates to filaments comprising filaments having rough, non-conductive polymeric cores coated with thin adherent layers of metals, to methods for their production, and to articles made from them.
12~3338 BACKGROUND OF THE INVENTION
Fllaments of normally non-electrically-conductive materials, bundles, e.g., yarns, tows, mats, cloths and chopped strands are known to be useful in reinforclng plastics and rubber. Some have normally smooth surfaces, such as polyesters and polyamides, and some have surfaces which are normally rough, such as cotton, rayon and wool. Articles comprising plastics and rubber reinforced with such filaments find wide-spread use in replacing heavier components made of lower strength conventional materials such as aluminum, steel, titanium, as well as glass, asbestos, etc., in aircraft, automobiles, office equipment, sporting goods, and in many other fields.
A common problem in the use of such filaments, is a seeming lack of ability to fully translate the properties, especially strength, to the material to which ultimate and intimate contact is to be made.
The problem is manifested in a variety of ways: for example, if a length of high strength yarn comprising filaments of a long chain synthetic polyamide in which 85% of the amide linkages are attached directly to two aromatic rings is mixed with an epoxy resin and the resin is cured, and if the workpiece is pulled until broken, the breaking strength will be less than expected because of bonding difficulties. The lack of reinforcement capability seems to be entirely due to poor translation of strength between the slippery plastic filaments and the plastic matrix. Compressive strength too is unexpectedly poor when some types of polyester and polyamide r - 2 filaments, and the like in the form of strands, chopped strands, nvn-woven mats, felts, papers, etc., or woven fabrics are mixed with organic polymeric substances, such as phenolics, styrenics, epoxy resins, polycarbonates, and the like, because they seem merely to fill the plastics without providing any reinforcement, and in many cascs even cause physical properties to deteriorate.
Continuous fi]aments of electrically conductive semi-metallic cores having at least one thin, uniforrn, firmly adherent, electrically conductive layer of at least one electrodeposited metal on the cores have been described elsewhere. Such filaments are useful to reinforce plastics or metals to an unparalleled degree because the strength of the core is directly translated through the firmly bonded metallic layer into the plastic or metal matrix. Unfortunately, however, the methods proposed in Canadian application 457,193* require that the core material be semi-metallic (and therefore electrically conductive, e.g., carbon) so that normally non-conductive materials such as nylon, polyester and/or aramids, cotton, rayon, wool and the like, cannot be electroplated directly into high strength coated fibers.
In Stuetz, United States 3,495,940, continuous filaments of high temperature resistant carbonaceous fibers are produced by forming a thin film of a sensitizing metal on an organic fiber precursor, e.g., acrylics, polybenzimidazoles, nylons or on a carbon fiber, electrolessly plating copper on the sensitized surface and electrodepositing additional copper on top of this think copper layer. Thereafter an electric current is passed across the plated fiber to *See also United States Patent 4,661,403 iL263338 - 4 - 6LlOg-7292 pyrolyze the core. The plating is then removed, and the filament is used as the filament winding, etc. Alternatively, the core is burned out leaving hollow metal filaments which can be used to weave light weight space suits. In any event, reinforcing filaments having a strongly adherent metal coating are not produced by such a process.
It has now been discovered that if the surfaces only of filaments comprising a rough non-conduc-tive core is sensitized and finally rendered conductive, by chemical deposition of a thin metallic interlayer, useful materials are ob-tained. Moreover, if then such yarns and tows are subjected to theunique processing conditions set forth in Canadian application 457,193, then metal coated filaments will also be obtained in which the bond between the coating and the filament is so strong that bending the fiber, as in weaving or knitting, may rupture the coat-ing, but it will not peel away. If a smooth surface core is provi-ded, e.g., aramid, it is necessary to roughen the surface before sensitizing the roughened surface with a salt of a noble metal, e.g., palladium. If a rough surface is normally present, e.g., then the roughening can be omitted. Next there is deposited a metal, such as nickel, silver, or copper on the rough, sensitized surface. More-over, the surface can be electroplated, e.g., with nickel or silver using a high external voltage. In either case, there will be pro-vided uniform, continuous, adherent, thin metal coatings on the sur-face of the filaments. It is believed that high voltage provides energy sufficient to provide uniform nucleation, especially if a plurality of filaments is used. Furthermore, the high voltage ~263~3~3 61109-~292 provides an even distribution of each fiber. Filaments comprising thin metal coatings on the metallized cores, and yarns, cloths, felts and the like, according to this invention can be knotted or folded without the metal substantially flaking off.
Articles made by adding the filaments of the present invention to a matrix forming material also are highly advantageous because they are strongly reinforced. In addition, these articles possess other advantages, for example, they dissipate electrical charges making them useful as shielding devices, and provide a degree of protection against lightning strikes. Aramid fibers, especially, when metal coated according to this process are not substantially degraded by ultraviolet light.
Therefore, according to the present invention there is provided a continuous metal-coated filament comprising an electrically non-conductive polymeric core having a mechanically roughened surface sensitized to the chemical deposition of a metal, an electrically conductive metallic interlayer chemically deposited on the rough surface of said core and firmly bonded thereto, and at least one thin, uniform, firmly adherent, electrically conductive layer of at least one metal electrodeposited on said interlayer.
` '' 3331~ 110-023 _ 6 BRIEF DESCRIPTION OF THE DRAWINGS
The invention may be more readily understood by reference to the accompanying drawings in which:
Fig. l is a transverse cross sectional view of a metal coated rough-surfaced filament of this invention.
Fig. 2 lS a longitudinal cross sectional view of a metal coated rough-surfaced filament according to this invention.
Fig. 3 is a magnified view of a portion of Fig. 2.
Fig. 4 is a partial sectional view of a metal coated filament-reinforced polymer matrix obtained by using this invention; and Fig. 5 is a view showing an apparatus for carrying out the process of the present invention.
All the drawings represent schematics of the articles described.
SU~I~IARY OF THE INVENTION
According to the present invention, continuous metal-coated filaments are provided having a rough, electrically non-conductive polymeric core, the rough surface of which is sensitized to the chemical deposition of a metal, an electrically conductive metallic interlayer chemically deposited on the sensitized rough surface of said core and firm]y bonded thereto, alone, or in combination with at least one thin, uniform, firmly adherent, electrically conductive layer of at least one metal electrodeposited on said interlayer. The bond strength of the coated filament is at least sufficient to provide that when the coated filament is bent the coating may fracture, but it will not peel off.
In preferred features the core comprises polyesters, polyamides, cotton or wool, and especially polyamides in which at least 85 percent of the amide linkages are attached directly to two aromatic rings (aramids).
Among the features of the invention are knottable filaments, fabrics woven from such filaments, non-woven sheets, mats and papers laid up from such filaments, chopped strands of such filaments and articles comprising such filaments uniformly dispersed in a matrix comprising an organic polymeric material.
In preferred embodiments, interlayers will comprise nickel, silver, copper, etc., and coating metals will be nickel, silver, zinc, copper, lead, cadmium, tin, cobalt, gold, indium, iron, palladium, platinum, tellurium, or an alloy of any of the foregoing, without limitation, preferably in crystalline form.
If the surface of the core is smooth, i.e., not normally . ~,,,~, ~26333~3 ~ 61109-7292 rough, such as a smooth filament of polyester, nylon or aramid, etc., it is a feature of the invention to roughen the surface, e.g., by solve~t treatment or treatment with a chemical, but preferably by mechanical abrading it, e.g., by use of slurried silica, sand, etc., e.g., of 60-320 mesh, preferably 120-1~0, size, conveniently in a fluidized bed abrader. Sensitization of the roughened surface will be by conventional methods, e.g., first by treatment with a stannous salt solution, then with a precious metal salt, e.g., palladium halide or sulfate. A single bath can instead be used for sensitization. Suitable techniqucs are well known to those skilled in this art and will be exemplified hereinafter. Especially preferred for the metallic interlayer is silver chemically deposited by reduction with alkaline hydrazine or a borohydride.
In another principal aspect, the present invention contemplates a process for the production of a metal-coated filament comprising:
(a) providing a continuous length of filament comprising a rough surfaced electrically non-conductive polymeric core and mechanically roughening said ~i~amont;
~:~r~
(b) sensitizing the rough surfaced fila~ent to the chemical deposition of a metal;
(c) chemically depositing a firmly adherent electrically conductive metal interlayer on the sensitized surface of ~o~
the core to yield a filamen-t coated with an electrically conductive metal interlayer; and, optionally, (d) continuously immersing at least a portion of the length of a filament resulting from step (c) in a solution ~L263~3~3 capable of electrolytically depositing at least one metal;
(e) providing a quantity of electricity and applying an external voltage betwcen the filament resulting from step (d) and an electrode immersed in the solution, which voltage is in cxcess of what is normally required to cause metal deposition, whereby (i) the metal nucleates substantially uniformly on the surface of the filaments and (ii) produces a substantially uniform, firmly adherent layer of metal on said interlayer, thereby yielding said continuous metal-coated filament.
In preferred features, the process will use core filaments of a number of organic polymeric materials, all of which will be electrically non-conductive. Included will be polyolefin filaments, e.g., polypropylene, polyacrylonitrile, wool, cotton, rayon and the like. Especially contemplated are polyester filaments, such as poly(ethylene terephthalate) and polyamide filaments such as nylons, e.g., poly(caprolactam) and poly(l,6-hexamethylenediamine adipate), and the so-called aramids, which are long chain synthetic polyamides in which at least ~5~ of the amide linkages are attached directly to two aromatic rings. The latter are described, together with methods for their production, in the Encyclopedia of Chemical Technology, 3rd Edition, Volume 3, John Wiley, New York, 1978, pages 213-242.
Especially suitable as core materials are aramid filaments made by polycondensing diacid chlorides and diamines in amide solvents, such as dimethylacetamide ~26~33~
and N-methylpyrrolidone. High strength filaments can be made by solvent spinning the condensation product of p-aminobenzoyl chloride hydrochloride, the product being known as poly (p~benzamide) or PPB.
Another condensation product is made from p-phenylenediamine and terephthaloyl chloride. It is known as poly(paraphenyleneterephthal-amide) or PPD-T. Fibers comprising the latter are available from the DuPont Company, Wilmington, Delaware 19898 under its trademark KEVLAR 29 and 49, the latter being a hot drawn fiber. Typical bundles of filaments used in this invention will average 4 thousand filaments per yarn bundle, each of which filaments has an average 12 micron diameter.
In one preferred embodiment the core filaments comprise a tow of filaments and the product of the process is a tow of coated filaments which can be knotted without substantial separation of the ~layers of metal or portions thereof from the core. Some small amounts of separation can be tolerated but generally more than about 90 percent, and especially more than about 95 percent, of the metal coating will remain attached.
Other preferred features comprise the steps of weaving or knitting filaments produced by the process into a fabric, laying them up into non-woven sheets, or chopping them into shortened lengths.
Other preferred features including carrying out the process in an electrolytic solution which is recycled into contact with the filaments immediately prior to immersion in the solution so as to provide increased carrying capacity to the filaments and replenish-ment of the electrolyte on the surface thereof.
,~ -- 10 --33~
DETAILED DESCRIPTION OF THE INVENTION
Referring to Figures 1 and 2 continuous yarns and tows for use in the core 2 according to the present invention are available commercially. For example, suitable aramid fiber yarns are available from DuPont Company, under the trademark KEVLAR-29 and KEVLAR-49 and suitable polyester fiber yarns are available from DuPont Company un-der the trademark DACRON Polyester (Type 68). Suitable nylon poly-amide yarns are available from DuPont (Type 728) for example. Cotton thread and wool fibers can be used. As mentioned above, all such fibers will be non-conductive and sensitized to chemical deposition of a metallic interlayer 3. The cotton threads and wool fibers are naturally rough; the others must be made rough.
Surface roughening is carried out in any normal way, but preferred is abrading the filaments with finely divided silica, alu-minum oxide, sand, etc. In conventional filaments, e.g., those 4 to 15 microns thick, 120 mesh abrasive will produce a suitably roughened surface. The roughened surfaces provide essential anchoring sites for interlayer 3, as shown in Figure 3, providing an enhanced mecha-nical grip. In continuous production, roughening is facilitated in a fluidized bed mechanical abrader, e.g., a Cole-Parmer-type appara-tus.
The roughened filaments are then treated with materials to produce a sensitized and activated surface, e.g., by continuously passing them through a stannous chloride, or stannous sulfate solu-tion and then through a solution of a salt of a noble metal. Wetting of the roughened filaments can be facilitated in the stannous A _ ' ~L26~3;38 chloride solution by the addition of a small amount of a cleaning agent. The preferred noble metal salt is a water-soluble palladium salt, such as palladium chloride.
Salts of gold, platinum and rhodium can also be used.
The sensitized rough surface presents outwardly a thin layer of metal which catalyzes the chemical deposition of metal from ions in the solution used to form the metal interlayer, e.g., silver metal from silver nitrate solution, then, without rinsing, into a solution of hydrazine, a hydrazine compound or a borohydride, at a high reducer to low metal ratio, to reduce silver ion to silver metal, well-bonded to the surface. The thickness of interlayer 3 builds up with time and it is sufficiently thick when conductivity (or decrease in resistance) is sufficient to permit electrodeposition in subsequent steps. This can be measured in known ways.
For further details on this aspect, reference is made to the above-mentioned, U.S. 3,495,940, the procedure of which does not, however, use a roughened fiber surface.
Metal layer ~ will be of any electrodepositable metal, and it will be electrically conductive. Two layers, or even more, of metal can be applied and metal can be the same or different, as will be shown in working examples.
The metal coated filaments of this invention can be assembled by any conventional means into composites represented in Fig. 4 ln which matrix 6 is a plastic, e.g., an epoxy resin, or a phenolic resin, or the like, the matrix being reinforced by virtue of the presence of metal coated cores 2.
_ 13_ 110-023 O
For those embodiments using one, formation of the outermost metal coating layer 4 by the electro-deposition process of this invention can be carried out in a number of ways. For example, a monofilament or a plurality of metallized core filaments can be immersed in an electrolytic solution and through suit-able electrical connections the required high external voltage can be applied. Because the filaments are so small, e.g., 5 to 50 microns in diameter, and because the innermost fibers can be surrounded by hundreds or _ even thousands of others, massive amounts of external voltage are used (even though only 0.5 to 2.6 volts are needed to dissociate the electrolyticl metal to ions, e.g., nickel, gold, silver, copper depending on the salt used), of the order of 5 times the dissociation values, to uniformly nucleate the metal onto the innermost filaments. Preferred external voltages of e.g., 10 to 50, or even more, volts are used.
Although non-continuous processes can be used, it is preferred to carry this part of the procedure out in a continuous fashion on a moving filament or bundle of filaments.
Shown schematically in Fig. 5 are components of a continuous processing a?paratus comprising in series a filament transport section 29, feeding a fluid-ized bed mechanical abrader means 30 in which surface roughening filament 24 is accomplished, e.g., with a slurry of 120 mesh silica. This is not used if the filament has a normally rough surface. Then after sensitization, e.g., by transporting and dipping first into tank 32 holding a SnC12 solution, rinsing, and ~Z6~33~3 then into tank 34 holding a PdC12 so]ution, and rinsing, filament 24 having a rough, sensitized surface is passed into tank 36 holding chemical metal deposition bath containing, e.g., silver nitrate and finally, without rinsing, into reducing bath tank 38, containing, e.g., hydrazine hydrate (alkaline). A thin coating of silver is deposited, sufficient to reduce electrical resistance to the point where the filament can be used in composites or, optionally, sent to e]ectrolytic tank 8.
To overcome the problem of filament burnout because of high voltages, to keep them cool enough outside the baths, one can blow air or pour water on them, for example, but it is preferred to operate in an apparatus also shown schematically in Figure 5.
Electrolytic solution 8 is maintained in tank 10. Also included are anode baskets 12 and idler rollers 14 near the bottom of tank 10. Two electrical contact rollers 16 are located above the tank.
Filament 24 is pulled by means not shown off feed rollers 26, over first contact rollers 16 down into the bath under idler rollers 14~ up through the bath, over second contact rollers 16 and into take up rollers 28. Optional, but very much preferred, is a simple loop comprising pump 18, conduit 20, and feed head 22.
This permits recirculation of the plating solution at a large flow rate and pumping it onto contact rollers 16. As the plating solution is discharged just above the rolls, the sections of filament 24 entering and leaving the solution are totally bathed, and thus cooled. At the high current carried by the filament, the heat generated in some cases might destroy it before it reaches or ,, . ~,, ~263~38 14a 61lO9-7292 after it leaves the bath surface without such coo].ing. Of course, more than one plating bath can be used in ser,ies, preferably 3 to 4 baths, for economy, . ~
:, .. ..
~i i333~3 and the filaments can be rin~ed free of electrolyte solution, dried, chopped, woven into fabric, all in accordance with conventional procedures.
DESCRIPTION OF THE PREFERRED E~IBODIMENTS
The following Examples illustrate the present invention, but are not intended to limit it.
A continuous tow comprised of smooth surfaced aramid filaments (4,000 fibers per bundle, average 12 microns in diameter, poly(paraphenylene terephthalamide), DuPont KEVLAR 49) was mechanically abraded with 120 mesh size silica slurried in water in a gas-fluidized bed until the surface of each fiber was roughened. The tow was dipped in an aqueous solution of 10 g/l stannous chloride and 10 ml/l of concentrated hydrochloric acid heated to 140F. and permitted to reside therein for one minute, and rinsed. The tow was then dipped into an aqueous solution of 2.8 g. of palladium chloride and 10 ml. of concentrated aqueous hydrochloric acid per liter, heated to 140F. and permitted to reside therein for one minute, and ri~sed. This technique was repeated and a rough, sensitized surface was produced on the filaments. Next the tow was immersed in an aqueous solution of 31 g./l silver nitrate and then without rinsing, into a solution of 85% aqueous hydrazine h~drate (Hummel Chemical Corp., No. 85). A silver inter-layer was adherently deposited thereby. A specimen was taken, washed and dried and resistance was measured with an ohmeter. If necessary, the silver deposition pro-cedure was repeated until the resistance of the 4K, 12 micron tow was reduced to 20 ohms per foot, at which time it was suitable for electroplating.
~263338 110-023 In a continuous electroplating system, a bath is provided having the following composition:
INGREDIENT AMOUNT
nickel sulfate ~NiSO4.6H2O) 40 ounces/gallon nickel chloride (NiC12.6H2O3 12-20 ounces/gallon boric acid (H3BO3) 5-8 ounces/gallon The bath is heated to 140-160F. and has a pH of 3.8 - 4.2.
The anode baskets are kept filled with electrolytic nickel pellets and 4 tows (fiber bundles) of 4,000 strands each of 12 micron metallized aramid filaments are continuously drawn through the bath at 5 ft./min. while an external voltage of 30 volts is applied at a current of 160 amps. At the same time, electrolytic solution is recycled through a loop into contact with the entering and leaving parts of the tow.
The tow is next passed continuously through an identical bath, also at a tow speed of 5.0 ft./min. with 160 amps current. The final product is a tow of high strength composite fibers according to this invention comprising a 12 micron fiber core, a thin silver interlayer and about 50% by weight of the composite of crystalline electrodeposited nickel adhered firmly to the core through the interlayer.
~Z~3338 _17 _ If a length of the filament is sharply bent, as in weaving or knitting, then examined, the metal coating may fracture, but it will not peel off.
If the procedure of Example 1 is repeated, substituting two baths of the following compositions, in series, and using silver in the anode baskets, crystal-line silver electrocoated over silver metallized aramid filaments according to this invention will be obtained.
INGREDIENT FIRST BATH SECOND sATH
Silver Cyanide 0.1 - 0.3 oz./gal 7 - 11 oz./gal.
15 Potassium Cyanide 12 - 20 oz./gal. 12 - 20 oz./gal.
Potassium Hydroxide --- 1 - 2 oz./gal.
The first bath is to be operated at room temperature and about 12-36 volts; the second at room temperature and about 6-18 volts.
The procedure of Example 2 can be modified, by substituting nickel or copper metallized aramid filaments for the feed, and the voltage in the first bath is reduced to about 18 volts. There are obtained high strength coated filaments according to this invention in which a crystalline silver coating surrounds a nickel or copper interlayer on a rough surfaced aramid core.
~;~63338 o The procedure of Example 1 can be modified by substituting for the nickel bath a bath of the following composition, using zinc in the anode baskets, and zinc coated silver-metallized aramid filaments according to this invention will be obtained:
INGREDIENT AMOUNT
Zinc sulfate 8 oz./gal.
Ammonium alum 3 - 4 oz./gal.
Potassium hydroxide 16 oz./gal.
Potassium cyanide 3 oz./gal.
The bath is run at 100F. and 18 volts are externally applied.
EXAMPLE 5_ The procedure of Example 1 can be modified by substituting for the nickel bath a bath of the following composition, using copper in the anode baskets, and copper coated silve-r-metallized filaments according to this invention will be obtained:
INGREDIENT AMOUNT
Copper cyanide 3.5 oz./gal.
sodium cyanide 4.6 oz./gal.
Sodium carbonate 4 oz./gal.
Sodium hydroxide 0.5 oz./gal.
Rochelle salt 6 oz./gal.
~2~333~ 110-023 _ 19_ The bath is run at 140~. and 18 volts are externally applied. The copper plated fibers should be rinsed and then washed with sodium dichromate solution immediately after plating to prevent tarnishing, if required. If the procedure of Example 3 is repeated, substituting the copper bath of this example for the silver bath, there will be obtained high strength fila-ments according to this invention in which a copper coating surrounds a nickel or copper interlayer an aramid core.
The procedure of Example 1 can be modified by substituting for the nickel bath two baths of the follow-ing composition, using standard 80% Cu/20% zinc anodes, and brass coated silver-metallized aramid filaments according to this invention will be obtained.
INGREI:~IENTAMOUNT
Copper cyanide4 ounce/gallon Zinc cyanide1.25 ounce/gallon Sodium cyanide7.5 ounce/gallon Sodium carbonate 4 ounce/gallon Both baths are run at 110 - 120F. Since one-third of the brass is plated in the first bath, at 24 volts, and two-thirds in the second at 15 volts, the current is proportioned accordingly. Following two water rinses, the bxass plated filaments are washed with a solution of sodium dichromate, to prevent tarnishing, and then rinsed twice again with water, if required.
1;2~i3338 _ 20_ The procedure of Example 1 can be modified by substituting for the nickel bath a bath of the following composition, using solid lead bars in the anode baskets, and lead coated silver-metallized aramid filaments according to this invention will be obtained:
INGREDIENT AMOUNT
Lead acetate (Pb(OAC)2 14 oz. Pb/gal.
Fluoboric acid, HBF4 13 oz./gal.
Optionally, about 2.g./1. of beta-naphthol and of gelatine are added. The pH is less than 1, the bath is operated at 80F, and an external voltage of 12 volts is applied. If the coating thickness exceeds 0.5 microns, there is a tendency for the lead to bridge between individual filaments.
By the general procedure of Example 1, and substituting a conventional gold bath for the nickel electroplating bath and applying sufficient external voltage, coated high strength filaments comprising gold on silver-metallized aramid filaments are obtained.
llO-023 ~263~3~3 By the general procedure of Example l, sub-stituting cotton thread for the aramid fibers, and omitting the surface roughening step, there are produced nickel on silver-metallized cotton filaments according to this invention.
Aramid filaments comprising poly(p-benzamide) are metallized with copper or nickel electrolessly and then coated with nickel by placing them in cathodic contact with a nickel plating bath of Example 1 and applying an external voltage of about 30 volts.
A composition is prepared by chopping the coated filaments of Example 1 into short lengths, 1/8" to 1" long then thoroughly mixing 30 wt. % with thermoplastic nylon polyamide in an extruder, and chopping the extrudate into molding pellets in accordance with conventional proced-ures. The pellets are injection molded into plaques 4" x 8" x l/8" in size. The plaque is reinforced by the coated filaments. By virtue of the metal content, it also does not build up static charge, and it can act as an electrical shield in electronic assemblies.
~ ~.
lZ6333t3 E~AMPLE 12 Bundles of nickel plated aramid filaments of about one inch in length prepared according to the procedure of Example 1 are mixed 1:9 with uncoated graphite filaments and laid up into a non woven mat, at 1 oz./l sq. yard. The mat has a metal content of about 5% by weight of nickel and can be impregnated with thermo-setting resin varnishes and consolidated under heat and pressure into reinforced laminates having high strength and excellent electrical dissipation properties.
Many variations of the present invention will suggest themselves to those skilled in this art in light of the above, detailed description. For example, poly(ethylene terephthalate) polyester fibers, nylon fibers, wool fibers and asbestos filaments can be substituted for the aramid and cotton filaments. Other reducing agents can be used. All such variations are within the full intended scope of the invention as defined in the appended claims.
',~
Claims (37)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A continuous metal-coated filament comprising an electrically non-conductive polymeric core having a mechanically roughened surface sensitized to the chemical deposition of a metal, an electrically conductive metallic interlayer chemically deposited on the rough surface of said core and firmly bonded thereto, and at least one thin, uniform, firmly adherent, electrically conductive layer of at least one metal electrodeposited on said interlayer.
2. A metal-coated filament as defined in claim 1 wherein the bond strength of said interlayer to said core is at least sufficient to provide that when the filament is bent, the layer may fracture, but it will not peel off.
3. A metal-coated filament as defined in claim 1 wherein said core comprises a polyester or a polyamide.
4. A metal-coated filament as defined in claim 3 wherein said core comprises a polyamide in which at least 85 percent of the amide linkages are attached directly to two aromatic rings.
5. A metal-coated filament as defined in claim 4 wherein said core comprises poly(p-benzamide) or poly(paraphenylene-terephthalamide).
6. A metal-coated filament as defined in claim 5 wherein said core comprises poly(paraphenyleneterephthalamide).
7. A metal-coated filament as defined in claim 5 wherein said metal-coated filament comprises a hot drawn core of poly-(paraphenyleneterephthalamide).
8. A metal-coated filament as defined in claim 1 wherein said metallic interlayer comprises a compound of a metal chemically reducible with hydrazine, a hydrazine compound or a borohydride compound.
9. A metal-coated filament as defined in claim 8 wherein said metallic interlayer comprises nickel, silver or copper.
10. A metal-coated filament as defined in claim 9 wherein said metallic interlayer comprises silver.
11. A metal-coated filament as defined in claim 1 wherein the metal interlayer has been deposited by chemical reduction on a roughened, stannous halide-palladium halide-sensitized core.
12. A metal-coated filament as defined in claim 11 wherein the interlayer is silver chemically deposited with alkaline hydrazine on a stannous halide-palladium halide-sensitized mechanically abraded core comprising poly(paraphenylenetereph-thalamide).
13. A metal-coated filament as defined in claim 1 wherein said metal deposited on said interlayer is crystalline.
14. A continuous metal-coated filament comprising an electrically non-conductive polymeric core having a rough surface sensitized to the chemical deposition of a metal, an electrically conductive metallic interlayer chemically deposited on the rough surface of said core and firmly bonded thereto, and at least one thin, uniform, firmly adherent, electrically conductive layer of at least one metal electrodeposited on said interlayer and wherein said filament can be knotted without substantial separation and loss of the metal coating.
15. A fabric woven or knitted from metal-coated filaments defined in claim 1, alone, or in combination with filaments which are of different material.
16. A non-woven sheet laid up from lengths of metal-coated filaments as defined in claim 1, alone, or in combination with filaments of different material.
17. A three-dimensional article of manufacture produced by weaving, knitting or laying up a mat comprised of metal-coated filaments as defined in claim 1, alone, or in combination with filaments of different material.
18. A composition of matter comprising a plurality of chopped continuous metal-coated filaments according to claim 1.
19. A composition of matter comprising metal-coated fila-ments as defined in claim 1, disposed in a matrix comprising an organic material.
20. A metal-coated filament as defined in claim 1 wherein said metal which has been deposited on said metal interlayer comprises nickel, silver, zinc, copper, lead, arsenic, cadmium, tin, cobalt, gold, indium, iron, palladium, platinum, tellurium, or an alloy of any of the foregoing.
21. A process for the production of a continuous metal-coated filament comprising:
(a) providing a continuous length of at least one rough, electrically non-conductive polymeric core and mechanically roughening said core;
(b) sensitizing said core to the chemical deposition of a metal;
(c) chemically depositing a firmly adherent electrically conductive metal interlayer on the rough, sensitized surface of said core to yield a core coated with an electrically conductive metal interlayer;
(d) continuously immersing at least a portion of the length of a filament resulting from step (c) in a solution capable of electrolytically depositing at least one metal; and (e) providing a quantity of electricity and applying an external voltage between a filament resulting from step (d) and an electrode immersed in the solution, which voltage is in excess of what is normally required to cause metal deposition, whereby (i) the metal nucleates substantially uniformly on the surface of the filament and (ii) there is produced a substantially uniform, firmly adherent layer of metal on said interlayer, thereby yielding said continuous metal-coated filament.
(a) providing a continuous length of at least one rough, electrically non-conductive polymeric core and mechanically roughening said core;
(b) sensitizing said core to the chemical deposition of a metal;
(c) chemically depositing a firmly adherent electrically conductive metal interlayer on the rough, sensitized surface of said core to yield a core coated with an electrically conductive metal interlayer;
(d) continuously immersing at least a portion of the length of a filament resulting from step (c) in a solution capable of electrolytically depositing at least one metal; and (e) providing a quantity of electricity and applying an external voltage between a filament resulting from step (d) and an electrode immersed in the solution, which voltage is in excess of what is normally required to cause metal deposition, whereby (i) the metal nucleates substantially uniformly on the surface of the filament and (ii) there is produced a substantially uniform, firmly adherent layer of metal on said interlayer, thereby yielding said continuous metal-coated filament.
22. A process as defined in claim 21 wherein the bond strength of said interlayer to said core in the filament is at least sufficient to provide that when the coated filament is bent, the layer may fracture, but it will not peel off.
23. A process as defined in claim 21 wherein said core comprises a polyester or a polyamide.
24. A process as defined in claim 23 wherein said core comprises a polyamide in which at least 85 percent of the amide linkages are attached to two aromatic rings.
25. A process as defined in claim 24 wherein said core comprises poly(b-benzamide) or poly(paraphenyleneterephthalamide).
26. A process as defined in claim 25 wherein said core comprises poly(paraphenyleneterephthalamide).
27. A process as deEined in claim 26 wherein said core comprises a hot drawn filament of poly(paraphenyleneterephthal-amide).
28. A process as defined in claim 21 wherein step (c) comprises chemically depositing nickel, silver, or copper over the mechanically roughened, sensitized core to provide said metallic interlayer.
29. A process as defined in claim 21 wherein said metal deposited on said interlayer is crystalline.
30. A process as defined in claim 21 including the step of weaving knitting metal-coated filaments produced by the process, alone, or in combination with filaments of a different material into a fabric.
31. A process as defined in claim 21 including the step of laying up the metal-coated filaments produced by the process alone, or in combination with filaments of a different material into a non-woven sheet.
32. A process as defined in claim 30 including laying up the fabric into a three-dimensional article of manufacture.
33. A process as defined in claim 31 including laying up the sheet into a three-dimensional article of manufacture.
34. A process as defined in claim 21 including the step of chopping the metal-coated filaments produced by the process into shortened lengths.
35. A process as defined in claim 21 including the further step of forming a reinforced composite by intimately contacting a liquid organic polymeric material with at least a reinforcing amount of said metal-coated filaments, a fabric or non-woven sheet comprised of said metal-coated filaments, or chopped fibers comprising said metal-coated filaments.
36. A process as defined in claim 21 including recycling the contents of a bath of the solution capable of electrolytically depositing at least one metal into contact with the filament immediately prior to immersion therein so as to provide increased current carrying capacity to the filament and replenishment of the electrolyte on the surface therein.
37. A process as defined in claim 35 wherein the amount of fabric sheet or chopped metal-coated filaments is at least sufficient to provide an electrostatically shielded reinforced composite.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US50743983A | 1983-06-24 | 1983-06-24 | |
| US507,439 | 1983-06-24 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1263338A true CA1263338A (en) | 1989-11-28 |
Family
ID=24018653
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000457206A Expired CA1263338A (en) | 1983-06-24 | 1984-06-22 | Metal coated filaments, process for their production, and articles made therefrom |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPS6059096A (en) |
| CA (1) | CA1263338A (en) |
| ZA (1) | ZA844770B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP6805424B2 (en) * | 2015-10-15 | 2020-12-23 | ウラセ株式会社 | Method of manufacturing conductive yarn |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6036479B2 (en) * | 1981-06-24 | 1985-08-20 | 日立電線株式会社 | Method of metal plating carbon fiber bundle or cloth |
-
1984
- 1984-06-22 CA CA000457206A patent/CA1263338A/en not_active Expired
- 1984-06-22 ZA ZA844770A patent/ZA844770B/en unknown
- 1984-06-23 JP JP59129911A patent/JPS6059096A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6059096A (en) | 1985-04-05 |
| ZA844770B (en) | 1985-02-27 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |