US3864148A

US3864148A - Process for production of metal-plated fibers

Info

Publication number: US3864148A
Application number: US296021A
Authority: US
Inventors: Minoru Maeawa; Hiroka Morioka
Original assignee: Kuraray Co Ltd
Current assignee: Kuraray Co Ltd
Priority date: 1971-10-14
Filing date: 1972-10-10
Publication date: 1975-02-04
Anticipated expiration: 1992-02-04
Also published as: NL7213967A; JPS4943518B2; JPS4844599A; DE2250309C3; GB1406102A; DE2250309A1; DE2250309B2

Abstract

A process for the production of metal-plated fibers by electrolessly plating pre-treated fibers, which comprises reeling the fibers into hanks, hanging the fibers in the hank form on a rotary cylinder having projection holes to suspend the fibers in the air, allowing the fibers to move rotatively around the cylinder by rotation of the cylinder, projecting a plating solution at a rate of 5 to 50 cm/sec from said projection holes against the rotatively moving fibers and thereby effecting the electroless plating of the fibers.

Description

United States Patent 11 1 1111 3,864,148 Maeawa et a1. Feb. 4, 1975 1 PROCESS FOR PRODUCTION OF 2,425,214 8/1947 Voelkeret a1. 7. 118/315 METALPLATED FIBERS 3,663,242 5/1972 Gulla 117/47 A [75] inventors: Minoru Maeawa; Morioka, Hiroka,

b th fOk ,J o 0 ayama apan Primary Examiner-William D. Martln Asslgnefil y -,1 Kllfashlkl, Assistant Examiner-Janyce A. Bell Okayama Prefecture, Japan Attorney, Agent, or Firm-Sherman & Shalloway [22] Filed: Oct. 10, 1972 [21] Appl. N0.: 296,021

57 ABSTRACT [30] Foreign Application Priority Data 1 14,1 71 46-81135 Oct 9 Japan A process for the product1on of metal-plated f1bers by 52 us. c1 117/47 A 8/115.6 117/1053 electrolessly Plating PIE-treated fibers which 117/1'054 117/133'8 Pv117/160 prises reeling the fibers into hanks, hanging the fibers 118/305 1l8/307 H8/315 118/320 in the hank form on a rotary cylinder having projec- [51] Int CL B44d 1/092 tion holes to suspend the fibers in the air, allowing the [58] Field R 1054 fibers to move rotatively around the cylinder by rota- 11771053 1388 118/307 tion of the cylinder, projecting a plating solution at a 6 rate of 5 to 50 cm/sec from said projection holes against the rotatively moving fibers and thereby effect- [56] References Cited ing the electroless plating of the fibers.

UNITED STATES PATENTS 2,410,626 11/1946 Boudreau 118/315 6 Claims, 3 Drawing Figures 5 M to I f I 1 2:. l" l 1.: Z: I. 9

PROCESS FUR PRODUCTION OF METAL-PLATED FIBERS This invention relates to a process for the production of metal-plated fibers by the electroless plating method.

In conventional methods of the electroless plating of fibers, fibers which have been subjected to such pretreatments as deoiling, etching, activation and the like are generally dipped in electroless plating solutions containing metallic ions, reducing agents, complexing agents, hydrogen ion-adjusting agents, stabilizers and other additives. In the case of fibers the surface area is much greater than in the case of molded articles of plastics having the same weight, and in threads the distances between individual fibers are very short and they are very close to one another. Further, in the electroless plating of threads, fine bubbles of hydrogen and other gases are generated from the fiber surfaces as the plating reaction advances. For these reasons, penetration of a plating solution into fibers is inhibited and unevenness of plating is brought about between the surface layer and inner layer of a thread. Accordingly, in conventional methods of the electroless plating of fibers, it is impossible to obtain metal-plated fibers having uniform plating layers.

It is therefore a primary object of this invention to provide an economical process which can overcome such defects of the conventional methods and can provide metal-plated fibers having uniform plating layers.

In accordance with this invention, there is provided a process for the production of metal-plated fibers by electrolessly plating pre-treated fibers, which comprises reeling the fibers into hanks, hanging the fibers in the hank form on a rotary cylinder having projection holes to suspend the fibers in the air, allowing the fibers to move rotatively around the cylinder by rotation of the cylinder, projecting a plating solution from said projection holes at a rate of to 50 cm/sec against the rotatively moving fibers and thereby effecting the electroless plating of the fibers.

This invention will now be detailed by reference to the accompanying drawings in which:

FIG. 1 is a diagram illustrating one embodiment of apparatus for use in the practice of the electroless plating according to this invention;

FIG. 2 is a sectional view illustrating the state in the fibers of the hank form being hung on the rotary cylinder of the apparatus illustrated in FIG. 1; and

FIG. 3 is a diagram illustrating the state where the fibers in the hank form to be subjected to the electroless plating treatment are tied by lea threads and divided into several portions.

Any chemical fibers such as polyamide fibers, polyester fibers, polyolefin fibers, polyvinyl alcohol fibers, polyacrylonitrile fibers, acetate fibers and rayon fibers and natural fibers such as cotton and wool fibers may be electrolessly plated according to this invention. Among these fibers, polyvinyl alcohol fibers are most preferably treated according to the process of this invention, because polyvinyl alcohol fibers have the property that metal-plated fibers excellent in durability of adherence between the plating layer and fibers can be obtained, even if the etching pre-treatment is not effected. In the case of other fibers, the etching pretreatment is indispensable because without the etching pre-treatment the adherence durability is much lowered and it is impossible to obtain metal-plated fibers of practical value. Further, as is illustrated in the Examples given hereinbelow, in the case of polyvinyl alcohol fibers the surprising result is obtained that the adherence durability of metal-plated fibers derived from polyvinyl alcohol fibers which have not been subjected to the etching pre-treatment is superior to the adherence durability of metal-plated fibers derived from other fibers which have been subjected to the etching pretreatment. Polyacrylonitrile fibers are most preferred among fibers other than polyvinyl alcohol fibers, but omission of the etching pre-treatment is not permissible in polyacrylonitrile fibers.

The fibers to be metal-plated according to the process of this invention may take any form. For instance, they may be a monofilament, multi-filament yarn, spun yarn, split yarn, tape yarn, cord, tape, etc. In the instant specification and claims, the term fiber" or fibers is used to mean all of these fibrous articles inclusively.

The process of this invention will now be explained by referring, for conveniences sake, to an embodiment where multi-filament yarn is treated as a typical instance of such fibrous articles.

Methods for the electroless plating of fibers and molded articles of plastics have been known in the art. in general, articles to be treated are subjected successively to such pre-treatments as deoiling, etching and activation, and then they are dipped in an electroless plating solution to effect the electroless plating. In this invention, these pre-treatments may be conducted according to customary procedures and no modification is necessary. More specifically, in the deoiling treatment fibers are treated with a neutral detergent or warm water to remove oils applied to fiber surfaces. After this deoiling treatment, the etching treatment is conducted in the case of other fibers than polyvinyl alcohol fibers. For instance, polyester and polyacrylonitrile fibers are treated with etching agents such as alkali metal hydroxides and polyolefin and polyamide fibers are treated with such etching agents as solutions of the chromic acid-sulfuric acid type. Other fibers are subjected to the etching treatment with use of appropriate etching agents such as alkaline substances, chromic acid, etc. As described hereinabove, this etching treatment can be omitted in the case of polyvinyl alcohol fibers, which results in an industrial advantage of reduction of the manufacturing cost. After the etching treatment, the activation treatment is conducted. This activation treatment is also accomplished according to customary procedures. For instance, fibers are activated by a method comprising treating fibers with a hydrochloric aqueous solution of stannous chloride, washing the fibers with water, treating the fibers with a hydrochloric aqueous solution of palladium chloride, and washing the fibers with water to remove unreacted palladium chloride remaining on fiber surfaces or in voids formed among the fibers. Fibers may be subjected to these pre-treatments in the form of cheese, cone or hank, but it is preferred that these pre-treatments are effected on fibers in the hank form.

Fibers which have been subjected to these pretreatments are then the electroless plated. As will be apparent from the description given below, the electroless plating process of this invention is unique and different from electroless plating techniques heretofore adopted in the art. Furthermore, the electroless plating process of this invention can give a plating layer which is superior in its uniformity and evenness over plating layers formed by the. conventional electroless plating techniques.

In FIGS. 1 and 2, fibers 1 in the hank form ready to be plated, which have passed through the steps of the abovementioned pre-treatments, are hung on a rotary cylinder in a uniform thickness with no overlapping of hanks. This cylinder 5 is driven by a motor 10, and the fibers 1 are moved rotatively around the rotary cylinder 5 by rotation thereof. The rotary cylinder 5 is provided with partition plates 2 for preventing the overlapping of hanks during the operation and with forwarding plates 3 for conducting the rotary movement of the hanks smoothly. Projecting holes 4 are mounted on the rotary cylinder 5 to project a plating solution against the fibers 1. In FIG. 1, a plating solution 7 contained in a plating solution tank 11 is fed to the cylinder 5 by means of a pump 8 after its temperature has been adjusted to a prescribed level by a heating or cooling device, and the solution 7 is projected against the fibers l of the hank form through projection holes 4. The adjustment in the feed rate of the plating solution and the agitation of the plating solution are accomplished by means of a valve 9. Thus, the fibers l in the hank form are contacted with the plating solution projected through the projection holes 4 and the electroless plating is accomplished. The plating solution flows downwardly along the fibers in the hank form suspended in the air, and is returned to the tank 11. In this treatment, in order to obtain a uniform plating layer, it is important that the lower ends of the hanks of the fibers I hung on the cylinder 5 do not contact the liquid face of the plating solution contained in the tank 11. It is desirable that the system for circulation (i.e. tank or cylinder) of the plating solution be lined with glass or plastic so as to prevent occurrence of the plating reaction by contact with the plating solution. Occurrence of the undesired plating of the circulation system may also be prevented if the system is constructed of stainless steel.

The most important feature of the process of this invention reside, as described above, in that the electroless plating is effected while projecting a plating solution against fibers hung (in the form of hanks) on the rotary cylinder which is provided with plating solutionprojecting holes. In this electroless treatment, it is important that the fibers in the hank form are hung on the rotary cylinder uniformly in either the lateral direction or the thickness direction, and the overlapping of the hanks of fibers or unequal distribution of the fibers hung on the rotary cylinder must be avoided as much as possible. For this purpose, partition plates 2 are mounted on the rotary cylinder 5. The uniform hanging of the fiber hanks can be effectively attained by tying the hanks with the use of lea threads and dividing each hank into several portions, which feature is illustrated in FIG. 3. The plating solution is then projected through the projection holes against the fibers hung in the form of hanks uniformly on the rotary cylinder. By

adopting such unique electroless plating means accord plating solution is prevented by fine bubbles formed with the advance of the plating reaction, which results in occurrence of unevenness of the plating layer. At a projection rate exceeding 50 cm/sec, although a uniform plating layer is obtainable, the hanks become greatly disordered and are difficult to reel. Moreover, when the plating solution is projected at a rate exceeding 50 cm/sec, the plating layers formed on the fibers tend to peel offeasily, the reason for which is unknown. Accordingly, too high a projection rate is not preferred, In view of the durability of adherence between the plating layer and the fibers, the flexibility of the resulting plated fibers, and the effects on the resulting plated fibers when used for antistatic purposes, it is desired that each individual filament has a denier of from 0.l to l5, and especially from I to 6. In the case of fibers having a filament denier of less than 0.1 good durability of adherence can be attained between the plating and the fibers, however the flexibility inherent in the fibers is lost when the metal is plated to a thickness of about 1 a, and the surface area per unit weight is increased, resulting in an economic disadvantage. In the case of fibers having a filament denier exceeding 15, the durability of adherence between the plating layer and the fibers is reduced because of swelling and expansion of the fibers brought about during the plating step or shrinkage of the fibers caused during the drying or cooling step. Furthermore, cracks are readily formed in the metal plating layer by mechanical deformation or the like. Additionally, plated fibers derived from fibers having a filament denier exceeding 15 exhibit low antistatic activity. For these reasons, the use of fibers having a filament denier exceeding 15 is not preferred.

Where the electroless plating process of this invention is applied to monofilaments, cords and the like, it is preferred that the total denier of the fibers to be plated is more than 20. The upper limit of the total denier is not particularly critical and even fibers having a total denier of about l,000 can be conveniently treated according to the electroless plating process of this invention.

The size of the hank to be used in this invention is determined appropriately depending on the amount of the fiber treated, of the fiber, the form of the fiber, the size of the electroless plating apparatus and other factors, but it is generallypreferred that a hank has a weight of from 30 to 500 g per 1.5 m circle. In case the hank has a weight of less than 30 g per 1.5 m circle, it takes a long time to effect the reeling and the use of such hank is not economical. Use of a hank having a weight of greater than 500 g per 1.5 m circle is also undesired because the penetration of the plating solution into the hank fibers is insufficient.

It is preferred that the lea thread to be used for tying the hanks exhibits a shrinkage not exceeding 5 percent during the plating step, When the lea thread shrinks by more than 5 percent during the plating step, the part tied by the lea thread undergoes contraction and penetration of the plating solution into the fibers of this part is insufficient, with the result that unevenness is brought about in the resulting plating layer.

It is desired that the hank be divided into 3 to 6 portions per 1.5 m with the lea thread. In case the number of leas is less than 3 per l.5 m. the hanks become disor dered during the plating step and consequently. the hanks are difficult to reel. Penetration of the plating solution is insufficient when the number of leas exceeds 6 per 1.5 m.

in a preferable embodiment of this invention, one bank of fibers is hung on each section of the rotary cylinder such section being partitioned by two partition plates. The distance between two adjoining partition plates is varied depending on the size of the hank, but it is generally preferable that the distance be within a range of from 5 to 10 cm. A preferable amount of fibers hung on one section partitioned by the two adjoining partition plates is within a range of from 30 to 500 g, especially 50 to 200 g.

The rate of rotation of the fibers hung in the hank form on the rotary cylinder is not critical but a rotation rate of about 9 to about 18 m/min is usually adopted. The rotation direction may be reversed at suitable intervals, for instance, every two minutes.

It is preferred that the projection holes for projecting a plating solution have a diameter of from 2 to 5 mm and that such projection holes are distributed on the rotary cylinder to such an extent that to 150 projection holes are present per 100 cm of the surface of the rotary cylinder In case the number of projection holes is less than 25 per 100 cm the thickness of the plating layer differs in the outer and interior portions of the plated thread and it is difficult to obtain metal-plated fibers having a uniform plating layer. In case the number of projection holes is more than l50 per 100 em it is difficult to maintain the constant flow rate of the plating solution at a prescribed level.

It is preferred that the plating reaction is carried out at a temperature ranging from 40 to 100C. The reaction time varies depending on the amount of fibers to be treated and the intended amount of the metal to be plated on the fibers, but generally, the reaction is conducted for from 5 to minutes.

In this invention it is possible to use a conventional solution for electroless plating which contains, in addition to ions of a metal to be plated on the fibers, a reducing agent, a complexing agent, a hydrogen ionadjusting agent and other additives. The plating solution may further contain a stabilizer according to need. As the metal to be plated on fibers, there may be mentioned nickel, copper, cobalt, chromuim, tin, etc. The metals be used singly or in the form of mixtures of two or more (for instance, a mixture of nickel and cobalt). In view of the stability of the plating solution and the rate of the plating reaction, the use of nickel and copper, especially nickel, is preferred. In this invention, an electrolytic plating may be formed on the resulting electroless plating layer, if desired.

In a very preferable embodiment of this invention, the plating reaction is conducted by employing a plating solution containing at least one stabilizer selected from: guanidines such as diphenyl guanidine and diortho-tolyl guanidine; thiourea derivatives such as thioearbanilide; imidazoline derivatives such as 2- mercaptoimidazoline; dithiocarbamic acid salts such as sodium dimethyldithiocarbamate and sodium dibutyldithiocarbamate; thiurams such as tetramethyl thiuram disulfide; thiazoles such as mercaptobenzthiazole; and imidazoles such as mercaptobenzimidazole. It is possible to conduct the electroless plating process of this invention by employing a plating solution free of such stabilizer, but that causes the undesired phenomenon of blacking ofthe plating solution in a short time from initiation of the plating reaction.

Once blacking occurs in the plating solution, the plating reaction does not proceed on the material to be plated and a black substance is deposited on the plating surface, which results in degradation of the appearance of the product. Accordingly, in this invention it is preferable to employ a plating solution containing a stabilizer such as mentioned above. It is considered that this undesired phenomenon of blacking is due to the selfdecomposition of the plating solution, and it has been known to avoid occurrence of this phenomenon by incorporation of a stabilizer such as sodium thiosulfate. However, known stabilizers lose their stabilizing activity in a relatively short time when incorporated in a plating solution maintained at high temperatures, and they cannot be used for a long time or continuously. By contrast, the specific stabilizers exemplified above are advantageous over known stabilizers in that their stabilizing activity undergoes no change even if they are used at high temperatures for a long time. The specific stabilizer to be used in this invention is incorporated preferably in an amount of 0.5 to 20 mg per liter of the plating solution. Among the stabilizers exemplified above, mercapto group-containing stabilizers such as mercaptobenzimidazole, mercaptobenzthiazole and 2- mercaptoimidazoline exhibit particularly great stabilizing effects. Since many of these stabilizers are difficultly soluble in the plating solution when it is necessary to incorporate them in great quantities, it is preferred that these stabilizers are used in the form of an aqueous solution of caustic alkali, e.g., an aqueous solution of sodium hydroxide of 0.05 l N.

The metal-plated fibers obtained according to the process of this invention usually have a metal plating layer with a thickness ranging from 0.01 to 15 microns, and preferably from 0.05 to 2.0 microns.

The metal-plated fibers obtained according to the process of this invention are superior to metal-plated fibers formed by conventional methods where fibers to be plated are dipped in plating solutions in that the thickness of the plating layer is highly uniform and hence, the deviation of the electric resistance in the longitudinal direction is very small.

The metal-plated fibers, as they are or after incorporation with unplated fibers, are used in the form of knitted fabrics, woven fabrics, non-woven fabrics, cords or tapes, and as electric heaters, protective suits for high voltage linemen, electromagnetic shieldings, and the like. Further, when they are incorporated in fibrous and plastic products in which static charges are readily generated and accumulated, an antistatic effect is attained in these products.

This invention will now be illustrated more detailedly by reference to Examples, but it is of course not limited by these Examples.

Values of the thickness of the plating layer of the metal plated fibers are those calculated by the weight method or microscope method. The values measured by the two methods agree with each other quite well.

EXAMPLE 1 A hank of a circle of 1.5 m was prepared from g of filaments of 250 denier/36 filaments (which will be abbreviated as 250 dr/36 f below) having a twist number of turns per meter and composed of a polyvinyl alcohol having a degree of formalization of 20 mole percent (sold under the trademark "Vinylon"), and the hank was tied with a lea thread and divided into lution consisting of l [of water, l6 g of stannous chloride and 20 m1 of 36 percent by weight hydrochloric acid at room temperature for 3 minutes, and washed Table 1-c0miHIIJ Amount of plating solution 200 l p 5.0 Plating time 20 minutes Plating temperature 80C.

varied within a Rate of projection of plating range of 2 to solution 60 with water. The hanks were further dipped in a solution cm sec Table 2 Rate of Thickness of Plating LZiyBl'(]-L)* Projection of Reel- Adherence plating solu- Outer portion inner portion ability durabition(cm/sec.) of hank of hank of hank lity 2(comparison) 0.14 0.22 0.18 0.22 good relatively ood 0.21 0.23 0.22 0.23 good good 40 0.23 0.25 0.24 0.25 good good 60(comparison) 0.24 0.26 0.24 0.26 poor not good Dipping method (conventional 0.18 0.32 0.l6 0.27 extremely method) poor good Note: the thickness was measured with respect to 10 hanks.

consisting of l [of water incorporated with 0.3 g of palladium chloride and 3 m I of 36 percent by weight hydrochloric acid at room temperature for 3 minutes, and washed with water sufficiently. The thus activated hanks of polyvinyl alcohol filaments were hung on a cylinder providedwith forwarding plates having 50 per 100 cm of projection holes of a diameter of 3 mm and 10 partition plates. One hank was hung on one section formed between the two adjoining partition plates (the total length of the cylinder being I m and the diameter of the cylinder being 5 cm). The cylinder was rotated at a rate of 60 rotations per minute, and the direction of rotation was reversed every 2 minutes. The electroless nickel-plating was conducted under conditions indicated in Table l. The state of the plating layer of the resulting plated filaments and the properties of the plated fibers are shown in Table 2.

For comparison, Vinylon filaments were activated under the same conditions as described above and the plating was conducted at 80C. for minutes by dip- 'Tiieictrbi's's plating was th en conducteti according to the process of this invention in the same manner as described above except that mercaptoimidazole was not incorporated in the plating solution (the rate of projection of the plating solution being 40 cm/sec). In about 3 minutes from the initiation of the plating reaction, the plating solution was blackened, and the plating ratio was only 12 percent.

On the other hand, where mercaptobenzimidazole was added as the stabilizer, even after 20 minutes had passed from the initiation of the plating reaction, no

blackening of the plating solution was observed, and at 0 3. In each run, even after 20 minutes from the initiation of the plating reaction (the rate of projection of the plating solution being cm/sec.), the plating solution was not blackened. The plating ratios obtained after 20 minutes from the initiation of the plating reaction in ping the filaments in 200 l of a plating solution as indieach run are shown in Table 3.

cated in Table I. Results are also shown in Table 2.

-- Table 3 Stabilizer Plating Kind Amount Ratio(%) 0.2 Z-mercaptoimidazoline 0.05 g of stabilizer 25 0.2 diphenyl guanidine solution in 0.2-N NaOH EXAMPLE 2 V 7 Ten hanks of 250 dr/36 f polyester filaments having a twistnumber of 150 turns per meter, each having a weight of g, were reeled and deoiled according to Table 1 Composition of Plating Solution N' k l lft 0.10 l l f j i' s 010 $2 3 customary procedures. Then, each hank was dipped in gog um citrate 0.10 mole/l an aqueous solution of sodium hydroxide having a conf g iggf centration of 100 g/l at 60C. for 30 minutes and then solution (in 0.2-N NaOH) 0.! g/l washed with water to remove the alkali therefrom, follec Plating Conditions lowing which the activation treatment was carried out in the same manner as in Example 1. The hanks were hung on a cylinder having a total length of l m and a diameter of cm and being provided with forwarding plates having 120 per 100 cm of holes for projection of a plating solution having a diameter of 2 mm and partition plates, one hank being hung on one section formed between the two adjoining partition plates. The cylinder was rotated at a rate of 60 rotations per minute and the rotation direction was reversed every two minutes. The plating was carried out at 80C. for 20 minutes while projecting a plating solution having the same composition as illustrated in Table l of Example 1 at a flow rate of 30 cm/sec. The thickness of the plating layer was 0.23-0.25 p. in the outer portion of the hank and 0.24 0.26 p. in the interior portion. Thus, nickelplated polyester filaments having a uniform plating layer were obtained.

EXAMPLE 3 Five hanks of Vinylon spun yarn (count No. 20; monofilament denier l; degree of formalization 30 mole percent), each having a weight of 100 g, were reeled and activated in the same manner as in Example 1. Then. the hanks were plated under the same conditions as shown in Table l of Example I. Namely, the hanks were hung on a cylinder having a total length of 0.5 m and a diameter of 5 cm and being provided with forwarding plates having 76 per 100 cm of projection holes of a diameter of 4 mm, one hank being hung on one section formed between the two adjoining partition plates. The electroless plating was effected at 87C. for 25 minutes at a rate of projection of the plating solution of 25 cm/sec. The thickness of the resulting plating layer was 0.40 0.43 p. in the outer portion of the hank and 0.42 0.43 p. in the interior portion of the hank. Thus, a nickel-plated Vinylon spun yarn having a uniform plating layer was obtained. For comparison, a nickel-plated Vinylon spun yarn was prepared according to the conventional dipping plating method. in this comparative yarn. the thickness ofthe plating layer was 0.15 0.50 a in the interior portion of the hank and 0.32 0.47 t in the outer portion thereof.

EXAMPLE 4 Ten hanks, each having a weight of 50 g, were reeled from 210 dr/24 nylon filaments having a twist number of 100 turns per meter and deoiled according to customary procedures. Then, the hanks were etched with a solution consisting of l [of water, 30 g of chromic anhydride, 150 g of concentrated sulfuric acid and 100 g of phosphoric acid at 40C. for 3 minutes, and washed with water. Then the activation treatment was carried out in the same manner as described in Example 1, and the activated hanks were electrolessly plated by employing the same plating solution and plating apparatus as in Example 1, at 80C. for 20 minutes while projecting the plating solution at a flow rate of 30 cm/sec. As a result, nickel-plated nylon filaments with a uniform plating having a thickness of 0.35 0.37 ,u. in the outer portion of the hank and 0.36 0.38 p. in the interior portion of the hank were obtained. Comparative nickel-plated nylon filaments prepared by the conventional dipping plating method had a plating layer with a thickness of 0.25 0.39 p. in the outer portion of the hank and 0.19 0.32 ,u in the interior portion of the bank.

EXAMPLE 5 Ten hanks of the same Vinylon filaments as used in Example 1, each hank having a weight of g, were subjected to the deoiling and activation treatments in the same manner as in Example 1. The activated hanks were then subjected to the electroless copper-plating using the same plating apparatus as used in Example 1. The composition of the plating solution used and the plating conditions adopted are shown below:

Composition of Plating Solution Copper sulfate 17.5 /l Roe elle salt 85 g/? Sodium hydroxide 25 g/l Formalin (37%) 50 ml/l Merca tobenzthiazole 15 mg/l Electroless P ating Conditions Amount of plating solution 200 l Plating time l5 minutes Plating temperature 25C. Flow rate of projected plating solution 35 cm/sec As a result, copper-plated Vinylon filaments with a uniform plating layer having a thickness of 0.27 0.3l u in the outer portion of the hank and 0.29 0.32 p. in the interior portion of the hank were obtained.

In comparative copper-plated Vinylon filaments obtained according to the conventional dipping method,

unplated parts were observed here and there in the product, and it was impossible to obtain a plated product having a uniform plating.

EXAMPLE 6 ments having a uniform plating were obtained.

EXAMPLE 7 This Example illustrates that metal-plated filaments having a very excellent adherence durability can be obtained from polyvinyl alcohol filaments without conducting the etching treatment.

Polyvinyl alcohol filaments as used in Example 1 were subjected to the deoiling and activation treatments conducted in the same manner as in Example 1 without performing the etching treatment as in Example l. The electroless plating was effected on the thus treated polyvinyl alcohol filaments under the same conditions as shown in Table l of Example 1 by employing the plating solution shown in Table l of Example 1.

Ten hanks, each having a weight of l00 g, were reeled from 250 dr/36 f polyester filaments having a twist number of turns per meter, and were deoiled according to customary procedures. Then, they were dipped for 30 minutes in an aqueous solution of sodium hydroxide having a concentration of 20 g/l which was Table 4 untreated (before Electrical Resistance Sample washing or washing(times) bending (times) bending) l 5 l0 50 100 200 Vinylon (250 dr/36 f) 37 32 35 42 48 6i Polyester (250 dr/36 f) 28 67 120 350 182 490 57] 797 Nylon (210 dr/34 f) 35 60 l I6 290 43 12l 216 364 572 maintained at C. to effect the etching and washed with water to remove the alkali therefrom. Then, the hanks were activated in the same manner as in Example 1 and subjected to the electroless plating under the conditions indicated in Table l of Example 1 with use of the plating solution shown in Table l of Example 1.

Ten hanks, each having a weight of 50 g, were reeled from 210 dr/34 fnylon filaments, and were deoiled according to customary procedures. Then, the hanks were etched with a solution containing 1 l of water, 20 g of chromic anhydride, 300 g of concentrated sulfuric acid and g of phosphoric acid and washed with water. Then, the hanks were subjected to the activation treatment conducted in the same manner as in Example I, and the electroless plating was effected on the banks under the same conditions as illustrated in Table l of Example I with use of the same plating solution as employed in Example I.

Three kinds of the thus obtained metal-plated fibers were subjected to the following test to compare them to each other with respect to the durability of adherence between the metal layer and the filament. Each sample of the three kinds of the plated filaments was subjected to the bending test using a custom bending tester, and the electrical resistance was measured after the bending was conducted a prescribed number of times. The measured value was compared with the value of the electrical resistance of the sample before the bending test. Further, each sample was subjected to the washing test. One cycle of washing treatment comprised washing the sample with a rinsing liquor containing 1 g/l of a surface active agent (sold under the trademark Monogen Uni at 40C. for 12.5 minutes by employing an ordinary electric washing machine. This washing treatment was repeated a prescribed number of times, and the electrical resistance was measured. The measured value was then compared with the value of the electrical resistance of the untreated sample. The smaller the increase of electrical resistance after the washing or bending treatment, the better the durability of adherence between the plating layer and filaments. Results are shown in Table 4, where the electrical resistance is expressed in the unit of (L/3 cm.

What we claim is:

1. A process for the production of metal-plated fibers by electrolessly plating pre-treated fibers, which comprises reeling the fibers into hanks, hanging the fibers in the hank form on a rotary cylinder having projection holes to suspend the fibers in the air, wherein the projection holes are from about 2 to about 5 mm in diameter and present in from about 25 to about holes per 100 cm of the cylinder surface, and wherein the fibers have a denier of from about 0.1 to about 15, allowing the fibers to move rotatively around the cylinder by rotation of the cylinder, projecting an electroless metal plating solution at a rate of 5 to 50 cm/sec from said projection holes against the rotatively moving fibers and thereby effecting the electroless plating of the fibers.

2. A process set forth in claim 1, wherein the fibers are polyvinyl alcohol fibers.

3. A process set forth in claim 1, wherein a plating layer which nickel or copper is formed on the fiber by the electroless plating.

4. A process set forth in claim 1, wherein the rate of projection of the plating solution is within a range of from 15 to 35 cm/sec.

5. A process set forth in claim 1, wherein the plating solution contains as a stabilizer at least one member selected from the group consisting of guanidines, thiourea derivatives, imidazolines, dithiocarbamic acid salts, thiurams, thiazoles and imidazoles.

6. A process set forth in claim 1, wherein a stabilizer is incorporated in the plating solution at a concentra tion of from 0.5 to 20 mg per liter of the plating solution.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,864, 148 Dated February 4, 1975 Inventofls) Minoru Maekawa et al It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the Heading, correct the spelling of the Invehtors' names to read as follows:

-- Minoru Maekawa; Hiroaki Morioka Signed and sealed this 3th day of April 1'375.

(SEAL) Attest:

l C. I'MRSHALL DAN-N RUTH C. EiASON Commissioner of Patents Attesting Officerand Trademarks FORM PC3-1050 (10-59)

Claims

2. A process set forth in claim 1, wherein the fibers are polyvinyl alcohol fibers.
3. A process set forth in claim 1, wherein a plating layer which nickel or copper is formed on the fiber by the electroless plating.
4. A process set forth in claim 1, wherein the rate of projection of the plating solution is within a range of from 15 to 35 cm/sec.
5. A process set forth in claim 1, wherein the plating solution contains as a stabilizer at least one member selected from the group consisting of guanidines, thiourea derivatives, imidazolines, dithiocarbamic acid salts, thiurams, thiazoles and imidazoles.
6. A process set forth in claim 1, wherein a stabilizer is incorporated in the plating solution at a concentration of from 0.5 to 20 mg per liter of the plating solution.