EP0115661A1

EP0115661A1 - Electrically conducting material and method of preparing same

Info

Publication number: EP0115661A1
Application number: EP83300487A
Authority: EP
Inventors: Shinji Tomibe; Reizo Gomibuchi; Kiyofumi Takahashi
Original assignee: Nihon Sanmo Dyeing Co Ltd
Current assignee: Nihon Sanmo Dyeing Co Ltd
Priority date: 1983-01-31
Filing date: 1983-01-31
Publication date: 1984-08-15
Also published as: EP0115661B1; DE3377176D1

Abstract

An electrically conducting material including a polymeric material having adsorbed thereby sulphides of a first metal selected from copper, cobalt, tin, mercury and lead and a second metal selected from silver, gold and elements of the platinum group. The polymeric material is in the form of powder or a shaped body such as fibre, film or string and is formed of a synthetic polymer having no cyanic groups contained therein such as polyester or a polyamide or a naturally occurring polymeric substance such as silk or wool. The electrically conducting material may be prepared by treating the polymeric material with hydrogen sulphide, and then treating the resultat material having hydrogen sulphide adsorbed thereon with (a) a source of ions containing the first metal, (b) a source of ions containing the second metal and, optionally, (c) a sulphur-containing compound to form sulphides of the first and second metals adsorbed by the polymeric material.

Description

This invention relates to electrically conducting materials and a method of preparing such electrically conducting materials.
Numerous methods for imparting electrical conductivity to synthetic polymeric materials in the form of a shaped body are known in the art. For example, in United States patent No. 3,940,533, there is proposed a method for imparting electrical conductivity to polymeric shaped materials such as polyamide fibres, in which the fibres are first contacted with hydrogen sulphide and the resulting fibres having the hydrogen sulphide impregnated therewithin are then immersed in a metal salt solution such as an aqueous copper sulphate solution, to form a deposit of metal sulphide, such as copper sulphide, on the fibres. However, the copper sulphide deposited fibres obtained according to this process is poor in stability, especially in washability, so that the electrical conductivity is lost during storage or use. In British patent publication No. 2,078,545 A (published Jan. 13, 1982), theiu is proposed a method in which an electrically conducting, copper sulphide-deposited fibre, obtained by such a method as disclosed in the above-mentioned U.S. patent No. 3,940,533, is treated with a reducing agent such as ascorbic acid or hydrazine to increase the atomic ratio Cu/S of the copper sulphide to between 1.5 and 2.0. Although the thus treated electrically conducting fibre can exhibit superior washability in comparison with the non-treated starting fibre, the washability is still desired to be improved in practice.
In accordance with the present invention there is provided an electrically conducting material comprising a substantially cyanic group-free polymeric material having adsorbed thereby the sulphide of at least one first metal selected from the group consisting of copper, cobalt, tin, mercury and lead and the sulphide of at least one second metal selected from the group consisting of silver, gold and elements of the platinum group.
In another aspect of the present invention, there is provided a method of preparing an electrically conducting material, comprising treating a substantially cyanic group-free polymeric material having adsorbed thereby hydrogen sulfide with (a) a source of ions containing a first metal selected from the group consisting of copper, lead, tin, mercury and cobalt and (b) a source of ions containing a second metal selected from the group consisting of silver, gold and elements of the platinum group.
In a still further aspect, the present invention provides a method of improving the stability of an electrically conducting, first metal sulphide-carrying, substantially cyanic group-free polymeric material, comprising treating said polymeric material with a source of ions containing a second metal selected from the group consisting of silver, gold and elements of the platinum group.
The polymeric material to which an electrical conductivity is to be imparted includes both natural and synthetic polymers capable of adsorbing hydrogen sulphide. Thus, cyanic group-containing polymers, such as polyacrylonitrile, which have no affinity for hydrogen sulphide are not suitable for the purpose of the present invention. Illustrative of the synthetic polymers are polymers and copolymers based on polyesters, aromatic polyamides, polyurethanes, polycarbonates, polyamides, polyamide-imides, polyphenols, polyethers, polyvinylalcohols, and polyethylene oxides. Mixtures of these polymers with other polymers such as polyolefins may also be used. The synthetic polymers to be imparted with electrical conductivity may be in the form of powder or in the form of a shaped body such as a film, plate, fibre, fabric, paper, sheet, block, pellet, thread, string, rod or pipe and can contain customarily employed additives such as an ultraviolet ray-absorber and a molding aid. The natural polymeric materials include polypeptides such as wool and silk and may generally be used in the form of fibres.
The electrically conducting material of this invention is comprised of sulphides of a first metal selected from copper, cobalt, tin, mercury and lead and a second metal selected from the group consisting of silver, gold and elements of the platinum group, i.e. ruthenium, rhodium, palladium, osmium, iridium and platinum, supported by the above-mentioned polymeric material.
The amount of the first metal sulfide adsorbed by the polymeric material varies depending on the kind of the starting polymeric material and the intended electrical conductivity but is generally in the range of about 0.5 to 30 %, preferably 1 to 15 %, in terms of elemental metal based on the weight of the starting polymeric material.
The amount of the sulphide of the second metal in the electrically conducting material of this invention can be sufficiently low and is, in general, such that the atomic ratio M₂/M₁, where M_l stands for the first metal and M₂ stands for the second metal, is 0.0001 to 0.5, preferably 0.001 - 0.3, more preferably 0.01 - 0.2. Too small an amount of the second metal component is insufficient to attain an improvement in washability, whereas an amount of the second metal component in excess of 0.5 of the M 2_/M_l atomic ratio tends to lower the electrical conductivity and is also disadvantageous from the economic point of view since the second metal is very expensive.
The electrically conducting material of the present invention may be prepared with the use of, as the starting material, the above-mentioned polymeric material having deposited thereon the first metal sulphide or the above-mentioned polymeric material having adsorbed thereby hydrogen sulphide.
The first metal sulphide-deposited, electrically conducting polymeric material may be preferably prepared in accordance with the method described in United States patent No. 3,940,533. Briefly, the method includes treating the above-mentioned polymeric material with hydrogen sulphide under pressure, and treating the resulting material having adsorbed thereby hydrogen sulphide with first metal-containing ions to form the sulphide of the first metal adsorbed on or within the polymeric material. When copper is used as the first metal, the resulting product may be further treated with a reducing agent as suggested in British patent publication No. 2,078,545 A. Further, the treatment with the copper- containing ions may be performed in the presence of a polyphenol such as diphenol as a swelling agent. The electrically conducting, copper sulphide-carrying polymeric material is also commercially available under a trade mark of "Rhodiastat", which can be suitably employed as the starting material for the preparation of the electrically conducting material of this invention. Although there is no disclosure in U.S. patent No. 3,940,533 with respect to the use of cobalt to form the electrically conducting layer, it has been found that the treatment with cobalt ions can also give an electrically conducting material likewise copper and lead.
The polymeric material having adsorbed thereby first metal sulphide is treated, as such or after being washed with water, in a bath containing ions containing a source of the second metal. As the source of ions containing the second metal, a salt or complex of the second metal, such as a sulphate, nitrate, chloride, acetate, benzoate, a thiocyanate complex or a thiosulphate complex, may be suitably employed. The concentration of the second metal-containing ions in the bath is generally in the range of 0.005 - 10 g/2, preferably 0.01 - 6 g/Z in terms of the elemental metal. The treatment is performed at a temperature from room temperature to 100°C, preferably 30 - 80°C, for a period of 0.5 - 20 hours, preferably 1 - 10 hours with a ratio by weight of the bath to the material to be treated being in the range of 5:1 to 50:1, preferably 10:1 to 30:1.
It is preferred that the treatment with the second metal-containing ions be performed in the presence of a sulphur-containing compound or be followed by a treatment with the sulphur-containing compound to further improve both the stability and the electrical conductivity of-the resulting electrically conducting material.
The sulphur-containing compound is of a type which is capable of providing sulphur atoms and/or sulphur ions for reaction with the second metal to accelerate the formation of sulphides of the second metal. Illustrative of the sulphur-containing materials are sodium sulphide, sulphur dioxide, sodium hydrogen sulphite, sodium pyrosulphite, sulphurous acid, dithionous acid, sodium dithionite, sodium thiosulphate, thiourea dioxide, hydrogen sulphide, sodium formaldehyde sulphoxylate (rongalite C), zinc formaldehyde sulphoxylate (rongalite Z) and mixtures thereof. The sulphur-containing compound is geneiully used in an amount of 0.2 - 5 mols, preferably 0.4 - 3 mols per mol of the source of second metal-containing ions.
In the above embodiment, the modification with the second metal component is preceded by the formation of first metal sulphide. In an alternative embodiment, the sulphides of first and second metals are adsorbed simultaneously on the polymeric material. In this case, a polymeric material having adsorbed thereon hydrogen sulphide is used as the starting material. The hydrogen sulphide-adsorbed polymeric material may be obtained by contacting the polymeric material with hydrogen sulphide, preferably under pressure, for 0.5 to 2 hours.
The hydrogen sulphide-adsorbed polymeric material is treated in a bath containing both first metal-containing ions and second metal-containing ions. A water-soluble salt or complex such as a chloride, a sulphate and a nitrate of the first metal is generally used as the source of first metal-containing ions. The concentration of the first metal ions in the bath is generally in the range of 10 - 100 g/t, preferably 20 - 40 gjt, in terms of elemental metal. As the source of ions containing the second metal, any of the salts or complexes as exemplified previously may be used. The concentration of the second metal-containing ions in this embodiment is the same as in the previously described embodiment.
The treatment with the first and second metal ions is generally performed at a temperature in the range from 10 to 100°C, preferably from room temperature to 60°C. Similar to the previously described embodiment, it is preferred that the above treatment be carried out in the presence of or be followed by the treatment with a sulphur-containing compound of the above-mentioned type. The amount of the sulphur-containing compound used is also the same as described previously.
As a result of the foregoing treatments, there is obtained the electrically conducting material in which sulphides of the first and second metals are adsorbed by the polymeric material to form a continuous, electrically conducting layer or deposit at least on the surface thereof. The X-ray diffraction pattern of the electrically conducting material of this invention in which copper and silver are used as the first and second metals, respectively, has been found not to be the same as that deduced from the X-ray diffraction patterns of copper sulphide and silver sulphide. The analysis of the electrically conducting material by an X-ray microanalyzer indicates that the silver exists at the same locations as the copper and sulphur. Further, in view of'the fact that the electrically conducting material of this invention shows a property which is not expected from the properties of a polymeric material having either the sulphide of the first metal or the sulphide of the second metal, the electrically conducting layer is not considered to be formed of a mere mixture of the first metal sulphide and the second metal sulphide. Rather, it is believed that at least some of the first metal sulphide and the second metal sulphide should be present in a mixed crystal-like form in which the second metal is associated with the sulphur atom or atoms of the first metal sulphide.
In addition to the above-described second metal, iron or nickel has been found to be effective in improving the quality of the electrically conducting material, especially in lightening the color thereof. Such as auxiliary metal component may be incorporated into the electrically conducting material in the same manner as the second metal component. Thus, a source of ions containing the auxiliary metal, such as a salt or complex thereof is added to the bath which is used for treating the polymeric material with first metal-containing ions, the source of ions containing the second metal and/or the sulphur-containing compound. If desired, the incorporation of the auxiliary metal component can be done independently of the above treatments by treating the polymeric material in the same manner and conditions as in the case of the treatment with the source of ions containing the second metal. The amount of auxiliary metal-containing ions used in either case of treatment is generally 0.01 to 0.5 mol per mol of the first metal-containing ions.
The electrically conducting material of this invention, when in the form of fibres, may be advantageously utilized as clothes, carpets, interior decorative sheets, gloves or like by themselves or in combination with other fibres because of their freeness of static charging and easiness to be dyed. When in the form of a film or plate, the electrical conductivity and transparency of the materials of this invention allow the use thereof as a cover or enclosure for electric parts such as integrated circuits and large-scale integrated circuits which are required to be shielded from electrostatic charges during storage or transportation. The powdery, electrically conductive material of this invention may be incorporated into a coating composition to form electrically conductive coatings. Because of the excellent thermal stability of the sulphides, the powdery or granular, electrically conductive material of this invention formed from synthetic polymers, such as polyamide, can be subjected to thermal molding conditions to produce electrically conducting molded articles. Thus, the electrically conducting materials of this invention lend themselves to numerous-applications in many fields.
"The following examples will further illustrate the present invention. In the examples, the washability was determined according to the method speculated in Japanese Industrial Standard (JIS) L 1045. That is, a sample was added in a washing liquid containing 3 g/t of a commercially available detergent ("All Temperature Cheer" of Proctor & Gamble Inc.) with a ratio by weight of the sample to the washing liquid of 1:50. The liquid was charged in a dye- fastness testing device together with ten stainless balls and agitated at 50°C for 30 min followed by washing with water and drying. Such a procedure was repeated a number of times for the examination of the fastness to washing. The moisture resistance test was conducted by suspending the sample from the top of a closed glass vessel containing water, the vessel being placed in a thermostat oven to maintain the sample at 60°C and 100 % humidity for a given period of time for the examination of the change in its electrical resistivity.

Example 1

5 g of a commercially available, electrically conducting polyamide staple fibre having a deposit of copper sulphide (trade mark: "Rhodiastat", 7 denier, manufactured by Rhone Poulenc-Textile, FRANCE) were immersed in an aqueous solution containing 2 g/ℓ of silver nitrate and heat-treated therein at 45°C for 3 hours. The resultant fibre was washed with water and dried to obtain an electrically conducting fibre of this invention. The results of the washability test. are shown in Table 1 together with that of the non-treated, starting fibre.

Example 2

Example 1 was repeated in the same manner as that described therein except that the treatment bath further contained 5 g/ℓ of sodium thiosulphate and that the treatment time was reduced to 2 hours. The resultant fibre had an electrical resistivity of 1.18 x 10^-1 and no change in electrical conductivity was observed after 50 times washing operations.

Example 3

A polyamide knit (Toyobo Nylon, 70 denier, 24 filaments) weighing 5 g was suspended within an autoclave to which hydrogen sulphide was charged until the inside pressure reached 5 Kg/cm². The treatment of the knit with hydrogen sulphide was carried out at 20°C for 1 hour. The resulting knit having adsorbed thereby hydrogen sulphide was then immersed in 100 mi of an aqueous solution containing 30 g/i of cupric sulphate and 1 g/ℓ silver nitrate, and treated therein at 20°C for 30 min and then at 50°C for 1 hour.
The thus treated knit was olive-gray in color and had an electrical resistivity of 1.46 x 10^-1Ω-cm. The electrical conductivity remained unchanged through 100 days-moisture-resistance test.
For the purpose of comparison, the above procedure was repeated in the same manner as described above except that no silver nitrate was used. The resulting knit had an electrical resistivity.of 1.38 x 10^-1Ω-cm. However, the electrical conductivity was lost after 15 days from the initiation of the moisture-resistance test. The results of the washability test were as shown in Table 2.

Example 4

Example 3 was repeated in the same manner as that described therein except that the treatment bath contained 15 g/ℓ of sodium thiosulphate in addition to the cupric sulphate and silver nitrate, thereby to give a brown-gray, electrically conducting knit having an electrical resistivity of 1.18 x 10^-1Ω-cm. During the course of the treatment, there was observed a small amount of precipitates. No appreciable change was observed after 100 days-moisture-resistance test. The washability test gave the results shown in Table 2.

Example 5

Example 4 was repeated in the same manner as that described therein except that silver sulphate, palladium chloride, gold chloride and platinum chloride were used each in place of silver.nitrate, obtaining an improvement in moisture-resistance. Further,Example 4 was repeated using sodium dithionite in place of sodium thiosulphate, with the results similar to tne case of sodium thiosulphate.

Example 6

A polyamide knit (Toyobo Nylon, 70 deniers, 24 filaments) weighing 5 g was suspended within an autoclave to which was charged hydrogen sulphide until the inside pressure reached 5 Kg/cm², and treated therein at 20°C for 1 hour. The resulting knit with hydrogen sulphide being adsorbed thereby was then treated in an aqueous bath containing 30 g/2 of cupric sulphate at 20°C for 30 min. Subsequently, 0.2 g of palladium chloride and 2 g of sodium thiosulphate were added to the bath and the resulting mixture was heated at 50°C and maintained at that temperature for 2 hours, whereby to obtain an electrically conducting knit product having an electrical resistivity of 3.1 x 10^-1Ω-cm. The product withstood 30 times washing.

Example 6

Example 5 was repeated in the same manner as that described therein except that palladium chloride was replaced with various amounts of silver nitrate, whereby obtaining electrically conducting knit materials having various Ag/Cu atomic ratios as shown in Table 3. The washability test results are also shown in Table 3.

Example 7

Example 3 was repeated using a polyethylene terephthalate yarn (Trade mark: TETORON, 150 deniers, 30 filaments, manufactured by Toray Co., Ltd., JAPAN), an aromatic polyamide fibre (Trade mark: CONEX, manufactured by Teijn Co., Ltd., JAPAN), a polychlal fibre (Trade mark: CODELA_N, manufactured by Kojin Co., Ltd., JAPAN, a copolymer of vinyl alcohol and vinyl chloride), a polyurethane film (Trade mark: OPELON, manufactured by Toray Co., Ltd., JAPAN), a polyester powder and a polyamide film, respectively, in place of the polyamide knit, thereby giving electrically conducting materials which withstood 100 days-moisture-resistance test.

Example 8

A polyamide knit (Toyobo Nylon, 70 denier, 24 filaments) weighing 5 g was suspended within an autoclave to which hydrogen sulphide was charged until the inside pressure reached 5 Kg/cm². The treatment of the knit with hydrogen sulphide was carried out at 20°C for 1 hour. The resulting knit having adsorbed thereby hydrogen sulphide was then immersed in 100 mℓ of an aqueous solution containing 30 g/ℓ of cobalt acetate, and treated therein at 20°C for 30 min. Subsequently, 0_'.2 g of silver nitrate and 2 g of sodium thiosulphate were added to the reaction mixture for reaction therewith at 50°C for 2 hours. The thus treated knit was dark brown in color and had an electrical resistivity of 3.6 x 10^-1Ω-cm. The electrical conductivity remained unchanged through 100 days-moisture-resistance test.
For the purpose of comparison, the above procedure was repeated in the same manner as described above except that no silver nitrate was used. The resulting knit had an electrical resistivity of 3.2 x 10^-1Ω-cm. However, the electrical conductivity was lost after 15 days from the initiation of the moisture-resistance test. The results of the washability test were as shown in Table 4.

Example 9

Example 8 was repeated in the same manner as that described therein except that cobalt acetate was replaced with lead acetate, thereby to give a dark gray, electrically conducting knit having an electrical resistivity of 1.2 x 10⁴Ω-cm. No appreciable change was observed after 100 days-moisture-resistance test. The washability test gave the results shown in Table 4. For the purpose of comparison, the above procedure was repeated in the same manner as described above, except that no silver nitrate was used. The resultant knit had an electrical resistivity of 1.4 x 10⁴ Ω-cm. However, the electrical conductivity was lost after 15 days from the initiation of the moisture-resistance test. The results of the washability test are also shown in Table 4.

Claims

1. An electrically conducting material comprising a substantially cyanic group-free polymeric material having adsorbed thereby the sulphide of at least one first metal selected from the group consisting of copper, cobalt, tin, mercury and lead and the sulphide of at least one second metal selected from the group consisting of silver, gold and elements of the platinum group.

2. An electrically conducting material as claimed in claim 1, wherein said polymeric material is a polypeptide.

3. An electrically conducting material as claimed in claim 1, wherein said polymeric material includes a synthetic polymeric substance selected from the group consisting of polyamides, polyesters, polycarbonates, polyamide-imides, aromatic polyamides, polyurethanes, polyvinylalcohols, polychlals, polyethers, polyethylene oxides and polyphenols.

4. An electrically conducting material as claimed in claim 1, 2 or 3 wherein the amount of the sulphide of the first metal is about 0.5 to 30 % in terms of elemental metal based on the weight of the polymeric material.

5. An electrically conducting material as claimed in claim 4, wherein the amount of the sulphide of the second metal is such that the atomic ratio M2/M1, where M₁and M₂ stand for the first and second metals, respectively, is in the range of about 0.0001 to 0.5.

6. An electrically conducting material as claimed in claim 5, wherein the atomic ratio M₂/M_lis in the range of aLout 0.001 to 0.3.

7. An electrically conducting material as claimed in any of claims 1 to 6 wherein the second metal is silver.

8. An electrically conducting material as claimed in any of claims 1 to 7, further comprising the sulphide of iron or nickel adsorbed on the polymeric material. ,

9. An electrically conducting material as claimed in any of claims 1 to 8, wherein said polymeric material is in the form of powder or a shaped body.

10. A method of improving the stability of an electrically conducting, first metal sulphide-carrying, .substantially cyanic group-free polymeric material, comprising treating said polymeric material with a source of ions containing a second metal selected from the group consisting of silver, gold and elements of the platinum group.

ll. A method as claimed in claim 10, wherein said first metal is selected from the group consisting of copper, cobalt, tin, mercury and lead.

12. A method as claimed in claim 10 or 11, wherein said treatment is conducted in the presence of a sulphur-containing compound.

13. A method as claimed in claim 10 or 11, further comprising treating the product, obtained by treating said polymeric material with said source of ions containing the second metal, with a sulphur-containing compound.

14. A method as claimed in claim 12 or 13, wherein said sulphur-containing compound is selected from the group consisting of sodium sulphide, sulphur dioxide, sodium hydrogen sulphite, sodium pyrosulphite, sulphurous acid, dithionous acid, sodium dithionite, sodium thiosulphate, thiourea dioxide, hydrogen sulphide, sodium formaldehyde sulphoxylate, zinc formaldehyde sulphoxylate and mixtures thereof.

15. A method of preparing an electrically conducting material, comprising treating a substantially cyanic group-free polymeric material having adsorbed thereby hydrogen sulphide with (a) a source of ions containing a first metal selected from the group consisting of copper, lead, tin, mercury and cobalt and (b) a source of ions containing a second metal selected from the group consisting of silver, gold and elements of the platinum group.

16. A method as claimed in claim 15, wherein the treatment with components (a) and (b) is within the same treating bath.

17. A method as claimed in claim 15, wherein the treatment with component (b) is separate from and subsequent to the treatment with component (a).

18. A method as claimed in claim 16 or 17, wherein the treatment with component (b) is followed by a treatment with a sulphur-containing compound.

19. A method as claimed in claim 16 or 17, wherein the treatment with component (b) is carried out in the presence of a sulphur-containing compound.

20. A method as claimed in claim 18 or 19, wherein said sulphur-containing compound is selected from the group consisting of sodium sulphide, sulphur dioxide, sodium hydrogen sulphite, sodium pyrosulphite, sulphurous acid, dithionous acid, sodium dithionite, sodium thiosulphate, thiourea dioxide, hydrogen sulphide, sodium formaldehyde sulphoxylate, zinc formaldehyde sulphoxylate and mixtures thereof.