DE1926520A1 - Process for the production of bodies with electrically conductive coatings - Google Patents

Description

DR. BERG DIPL.-ING. STAPF

PATENT LAWYERS

β MUNICH 2. HIUBLESTRASSE 2O

Dr. Berg Dipl.-Ing. Stapf, 8 Munich 2, HilblestraBe 20 «

our reference X / X 18 4 ₉₉ D _atate 23-May 1969

Attorney's file number: 18 499

CHOMERICS ING. Arlington, Mass ,, USA

"Process for the production of bodies with electrically conductive coatings"

The present invention relates to a method for Manufacture of bodies which have an electrically conductive coating which is flexible and resilient

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and especially the coating of substrates such as plates, wires, fabrics and seals with an electrically conductive, flexible, resilient and deformable polymeric coating. The present invention also includes heat shrink capable articles which have at least one side coated with a flexible, resilient, electrically conductive polymeric substance, in particular tubular An article comprising an outer wall of a heat shrinkable material and an inner wall of a flexible one and resilient electrically conductive polymers.

It has long been known to cover current-carrying cables with an insulating material in order to prevent an undesired short circuit or grounding of the wire cable impede. Where it is desired to form an electrical connection, insulation from the wire can be used subtracted from. Although conventional coatings are effective are electrical insulators, they usually are ineffective as insulators from electromagnetic energy. if When electrons move from one place to another, an electromagnetic field is built up, which is acts outwards from the point of its formation, and this field influences the electrons in every neighboring conductive material. It would therefore be preferable to to use insulation that is electromagnetic

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Prevents energy from influencing other systems and at the same time also acts as normal electrical insulation works.

Electronic equipment is shielded by being completely enclosed in a metal "container" or case that is conductive throughout and none-discontinuities in its mahing points or the doors. The shielding of wires and cables was made in one similar titmouse carried out. by cutting the wires and cables, which are provided with an electrically insulating coating, leads inside metal tubes, the metal tube for provides the necessary shielding. Such shields are ex: rera cumbersome "since they are rigid" and the system do not give ilexibility. A more flexible shielding cable can be made from woven metal strands, metal strips in Shape of a spiral bellows or any other Spirals are placed., Which interlock of "allow adjacent strips. Although such tubes are more flexible than Iletall tubes, they are for some applications not flexible enough, and they suffer from the extra Disadvantage that a loss of electromagnetic energy through breaks, joints and other openings occurs found in this type of tube. This loss of effectiveness increases when

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the frequency increases and the shielding effectiveness is negligible at high frequencies.

There is therefore a need for a flexible and resilient insulation material for forming electrical connections or connections, and, more recently, for applications requiring shielding from electromagnetic Require energy, which is to a high degree electrically conductive and its flexibility and conductivity over a longer period of time Maintains duration. It is essential that the material is stable and remains conductive, even if it is exposed to weather conditions, particularly high temperatures. However, many of the known electrically conductive plastic materials suffer from one or more of the following listed disadvantages: They are not highly conductive; they lose their conductivity when they are elevated in temperature are exposed; and they do not work satisfactorily when used for shielding electromagnetic energy be used. For example, plastic materials with carbon as a filler material have only a small amount or no value at all for shielding applications, and plastic gaskets reinforced with wire mesh are included higher frequencies are ineffective, as the energy of small wavelengths easily penetrates the gaps in the wire mesh.

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Plastic solders were made by filling epxy adhesives with silver powder. · These solders were made for Purposes such as linking lines and connections, or for filling in voids and cracks in waveguides 'and metal housings used for electronic equipment. However, such solders harden to a hard one and brittle resin which, for example, does not adhere to a ribbed surface without damaging the ribbed surface or the resin.

The manufacture of soft, flexible and resilient seals and closures which will readily adapt to ribbed surfaces and which are very good electrical conductors is described in US Pat. No. 3,140,312. The seals disclosed there are stable and contain a binding agent made of a flexible and compressible plastic material which contains from 10 to 80 % by volume of metal particles, which are kept in electrical particle-to-particle contact by the plastic binding agent. The metal particles are dispersed throughout the binder. Although such seals are flexible and effective as electrical conductors and as a shield against electromagnetic energy, they are expensive and can pose a weight problem in view of the high metal concentration they usually contain.

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interpret. A less expensive and lighter seal * which has the desired properties was once a desirable, desirable goal.

For certain applications such as the strip seals described in U.S. Patent 3,140,342, the Metal particles concentrated on or near one of the surfaces of the seal. These seals are made according to the U.S. Patent 3,140,342 prepared by making a plastisol underfilled with metal, so that the heavy metal particles are removed during the heat-plasticization of the plastisol set down in the desired position. Such strip seals create limited protection in terms of electromagnetic energy shielding, although they are "necessary" Ensure electrical conductivity through part of the plastisol. This shortcoming is due to the fact due to the fact that the metal particles are concentrated in a certain layer, and therefore large proportions the strip seal and its exposed surface are free of metal particles.

Thin metal coatings have been painted onto objects the surfaces with a dispersion of fine metal flakes in a liquid medium, which when dry evaporated, applied. Such coatings are stiff and

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have a strong tendency to peel off when bent.

According to the present invention, an electrically conductive coating is applied to a substrate by applying a liquid preparation containing from 2 to 6 parts by volume of a polymeric material which forms a flexible, resilient and deformable film and from ¹ J to 8 parts by volume of electrically conductive particles with a average particle size of 0.00254 to 2.54 mm (0.1 to 100 mils) and an outer surface of metal on the substrate and hardening of the formulation. The preparation can be hardened by evaporation of any solvents contained therein and then post-hardened. The coating is electrically conductive and is effective as a shield for electromagnetic energy and magnetic energy when certain metals are used. The particles having at least one outer surface of a noble metal are preferred and, if electromagnetic shielding is desired, the particles are preferably non-planar, ie, granular, spherical or generally spherical. Non-planar particles, especially those which are granular or generally spherical in shape, are preferred because such particles provide better contact between the particles as well as with the surfaces being contacted, and because these particles - as found

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- for an effective shielding against electromagnetic Provide energy over a wide range of wavelengths, including the higher frequencies. About that In addition, the use of non-planar particles allows a higher weight loading of metal without affecting the machinability of the polymeric material is disturbed. For certain reasons, planar or flake-like par-. Article not be incorporated in high concentrations because the polymeric material is extremely difficult can be processed when the particle concentration increases *

The term "polymeric material" is intended to include resins and elastomers as well as common plastic materials such as e.g. Include polyolefins. Asphalts, polyurethanes, polyesters such as those sold under the trade name "Mylar" by E.I. du Pont de Nemours & Co., Inc. Polyacrylates, polyamides, natural rubber, polyvinyl chloride and Silicones are additional examples of suitable materials. alien. The polymeric material can be thermosetting or thermoplastic and it can be either a liquid or a rubber before curing; curing can through Catalysts, irradiation or by heating. Particularly preferred polymeric materials include Polyvinyl chloride plastisols, the room temperature curing silicone polymers and the polyolefins. One by reaction

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butadiene polymer bonded with styrene, which under the Trade name "Thermoplastic 125" sold by the Shell Oil Company is also suitable. Numerous silicone rubber gum resin mater Italy are sold by Dow Corning Corporation under the trademark "Silastic". These materials are dimethyl polysiloxanes with vinyl, bonded to them to modify their properties. Phenyl, methyl or trifluoropropyl groups. Recommended curing agents include peroxides such as benzoyl peroxide, Dicumyl peroxide and di-tert-butyl peroxide. Room temperature vulcanizing Silicone rubber compounds which are liquids or pastes and after adding a hardening agent Cure into firm, durable, resilient silicone rubbers, are manufactured by the Silicone Products Department of General Electric sold under the trade name "RTV Silicone Rubber". DieSf Silicone rubbers are also of the methyl-phenyl type. Suitable Hardening agents include tin octoate, dibutyltin, dilaurate, and lead octoate.

The polymeric material may be an adhesive type resin such as the silicone adhesive resin disclosed by General Electric is sold. Adhesive Resins SR-529 and SR-585 are examples of flexible silicone resins.

The electrically conductive particles that enter the poly-

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meric material to be incorporated must be continuous outer surface area of, metal and an average particle size of about 0.00254 to 2.54 mm (OjI to 100 mils). Such particles can solid metal particles or non-metal particles coated with a metal. Examples of non- Metal particles include glass beads as well as hard polymeric substances such as epoxy resin beads. These non-metal particles can be coated with the desired metal by any of the well known methods will. Examples of suitable metals which can be used for coating the non-metallic particles or as Solid metal particles that can be used include aluminum, nickel, lead, zinc, cadmium, copper, and iron the precious metals such as silver and gold. Alloys of such metals can also be used. Because In response to the problem of oxide formation, it is preferred to use particles which have an outer surface made of a noble metal to have. These particles can be solid precious metal particles. Non-precious metal particles coated with a precious metal are coated, or be non-metallic particles, which are coated with a noble metal with or without an intervening Coating made of a non-precious metal. The manufacture of silver-plated copper powders, which preferred in the present invention is in the

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U.S. Patent No. 3,220,488. Copper-plated. Iron powder as such, or silver-coated, can also be used, the manufacture of silver-coated powders being described in copending application Serial No. 227 755j filed October 2, 1962 and assigned to the same assignee as the present invention.

Although an average particle size of about 0.00254 to 2.54 mm (0.1 to 100 mils) in the process is useful in the present invention, it is preferred that the particles have an average particle size of 0.00254 to 0.623 now (0.1 to 25 mils), and most commonly the average size of 0.00254 to 0.38 mm (0.1 to 15 mils).

The liquid preparation of the present invention comprises from 2 to 6 parts by volume of the polymeric material and from 4 to 8 parts by volume of the electrically conductive particles. Preferably used for greater shielding effectiveness high concentrations, such as 50 to 80 volume # of metal particles incorporated into the polymeric material.

In addition to the electrically conductive particles, the liquid preparation can also contain fillers for enhancement

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the strength and other properties of the resulting film. Correctly selected fillers lower furthermore the cost of creating a larger volume without undesirable side effects and they have to be taken off consist of fine particles and be heat-stable and chemically inert. Synthetic, fine silica particles are the main reinforcing fillers and also commercially available.

The liquid preparations can by means of known methods such as by coating with a knife, coating can be applied by rolling, dipping, spraying, cushioning and extrusion. The special method of application is not critical, but it is determined by the consistency of the preparations and the desired thickness of the coating, Low viscosity preparations are preferred, and the viscosity of the preparation prior to application to the Substrate can be reduced by known methods, such as by heating or by diluting with solvents. Suitable solvents include organic solvents such as toluene and xylene, which are found to be particularly useful were found.

After the liquid preparation has been applied to the substrate, it becomes flexible and resilient

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Film hardened. This is achieved by evaporation of the solvent, if one has been used, and / or by post-curing the polymeric material, which leads to the formation of an electrically conductive, flexible and resilient coating, which is either tight or loose on the substrate depending on the nature of the polymeric material adheres ". The choice of adhesive-type polymeric materials results in tighter bonds. Significantly, no pressure is required to achieve the particle-to-particle contact that is required in order for the resulting film to be conductive.

The coatings formed could be of any desired thickness , although for economy and convenience of handling, the thickness are generally less than 1.27 mm (50 mils) and preferably less than 0.623 mm (25 mils). Such thin coatings have been found to be sufficient to provide the necessary electrical conductivity and ensure the electromagnetic energy shielding properties.

The objects of the present invention can be freely selected by applying a coating of the polymeric Material containing the electrically conductive particles onto the substrate without the use of solvents

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getting produced. This can be done by any of the known methods such as knife coating and roller coating, or, if the formulation is of suitable consistency, it can be applied over the substrate cast and then post-hardened or hardened. The particular method of application isn't critical to them ^ is however determined by the consistency of the preparation and the desired thickness of the coating. The consistency the preparation before application to the substrate can be done by known methods such as z3. reduced by heating will. The selection of adhesive-type polymeric materials results in tighter bonds.

The substrate which is produced by the method of the invention can be coated, can be made of any material, as long as it is not through the liquid preparation or is attacked by any solvent which may be contained therein. A wide variety of shapes and materials can be coated, although the shape of the substrate and the location to be coated are particular Determine the method of application. For example, insulated wire cables can be immersed in the liquid preparation be coated, since a complete coating of the surface is desired, but the coating is the Inside of pre-formed, tubular profiles through

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Extrusion, spraying or slow pouring of the liquid preparation through the inside of the tube is carried out.

In those cases in which post-curing is required in order to obtain a flexible and resilient film, the curing catalysts, as described earlier, are incorporated into the liquid preparation at the time of Application incorporated. The coated substrate is freely selectable in the dose required to form a film subjected to the desired properties when the polymeric material is to be cured by irradiation.

A particularly valuable application of this invention lies in the production of electrically conductive coatings on heat-shrinkable substrates, the coating then preferably containing from 20 to 80 volume percent of a polymeric material and from 80 to 20 volume percent electrically conductive particles having an average particle size of 0.0025 ¹ to 2.54 mm (0.1 to 100 mils) and an outer metal layer. When such a coated substrate is placed tightly around an insulated wire or cable with the coating inward and heated, the shrinkage of the substrate will force the coating to contact the insulation of the wire or cable, and thus a tight fitting jacket will be obtained. The one obtained in this way: ^

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shielded wire or cable is impervious to atmospheric components and electromagnetic energy.

The heat-shrinkable substrate can be any of known ones Be heat-shrinkable materials, e.g. thermoplastics like the polyolefins (polyethylene, polypropylene and

^ Polystyrene) and suitable oriented polyesters such as polyethylene terephthalate. The orientation of these thermoplastic preparations is generally achieved by stretching the material by at least 25 % and up to 100 % or more in at least one direction, and preferably in both longitudinal and transverse directions. If the production of shrinkable tubes is desired, the stretching should only take place in the transverse or radial direction, since longitudinal stretching on heating would result in undesired longitudinal shrinkage. This stretching can be done in space

w temperature or at higher temperatures, but it must be done at a temperature below the melting point of the polymeric material.

Orientation of polyolefins such as polyethylene generally involves stretching the polyolefin either after, during or before the irradiation of the same with electrons of high energy to cross-link the polyolefin Orientation can also be combined with chemically transverse

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crosslinked polyolefins are exercised.

The polyethylene for use as heat-shrinkable Substrates are solid polymeric materials made by polymerizing ethylene at various temperatures and printing. Such materials are in "Modern Plastics Encyclopedia" 1§68, New York 1967, pages 205 to 210. Specific examples of commercially available polyethylenes are those described by E.I. du Pont de Nemours & Co., Inc., Wilmington, Delaware under the Tradenames "Alathon" and. Sold by Phillips Petroleum Company under the trademarks "Marlex 20" and "Marlex 50" Polyethylene. Other polyethylenes which can be used, which can be obtained by either “polymerisation at high or low Prints are described in U.S. Patents 2,816,883 and 2,882,357.

In addition to the thermoplastic polyethylenes described above are also cross-linked polyethylene, e.g. polyethylene, which is one of the essentially infusible and insoluble form is crosslinked, such as by irradiation with high energy electrons, is also useful. To achieve this cross-linking, a dose of about 4 × 10 to 5 × 10 rep is usually used. About that in addition, the polyethylene, usually in situ, with

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Using a specific class of organic peroxides such as dicumyl peroxide, in amounts ranging from about 0.1 to 10 wt -.% Of polyethylene, be chemically cross-linked. Chemically crosslinked polyethylenes are described in U.S. Patents 2,826,570 and 3,079,370.

will.

Oriented polyethylene terephthalate sold under the trade name "Mylar" by EI du Pont de Nemours & Co, Inc. This commercially available film can be even higher oriented when stretched it in one axis by 3 to 24% at room temperature or elevated temperatures, and then heated for 30 minutes at 25 to 15O ⁰ C. This post-orientation process is described in U.S. Patent 2,993,820. Oriented polyethylene terephthalates exhibit great springback when subsequently heated, and the riach-oriented material P is particularly useful where a material is desired which has an exceptionally high degree of shrinkage when heated.

The heat-shrinkable substrates can be in the form of a Flat film or a tube. In those cases in which the substrate is tubular, a flat film of the material is produced simply by rolling in, forming a butt seam and suitable welding of the joint

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will. There where greater pressure forces than those which one by heating a single layer of the heat-shrinkable Substrate can be obtained, if desired, a flat sheet can be rolled into a tube in such a way that formed a series of spirally wound layers The compressive forces when shrinking are considerably greater than those caused by a single layer of the shrinkable substrate.

A tubular article can be made by one first takes a tube of heat-shrinkable substrate by extrusion or pressing, or by any one known method and then coated the inside of the tube with an electrically conductive coating, the from 20 to 80 vol. -5? of a polymeric material and of 80 to 20 vol .- / l> electrically conductive particles with a average particle size from 0.00254 to 2.54 mm (0.1 to 100 mils) and an outer metal layer. The method used to coat the tube is not critical. Such an internal coating can be carried out, for example, by using the tube a suitable formulation of polymeric material and particles (with or without solvent) and fill in the excess allowed to flow out of the tube, leaving a coherent film within the tube. Based on

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Alternatively, the preparation can be poured slowly into the tube, the tube rotating around a knee and so safely is made so that the preparation touches the entire inner surface, udd an adherent layer * on the wall the tube leaves behind. For applications that require a greater thickness of the coating, the casting and turning procedure be repeated until the desired thickness is obtained or a more viscous formulation can be used.

In the accompanying drawings, Pig. 1 illustrates a foam-like plastic material 10 covered with a metal-filled polymeric material 11; ^ Fig.2 illustrates a plate 15 of a material containing a layer of a polymeric material 17, covered with a metal-filled polymeric material 16 ψ;

Fig. 3 is a side view of a cylinder section of an insulated 21 wire cable 20 covered with a Metal-filled polymeric material 22; Figure 4A illustrates a strip material which has a Nose 27, suitably fitting for a recess 28 on the opposite end of the strip. The strip contains a layer of flexible poly-ethereal Material 26 covered with a layer

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metal-filled polymeric material 25;
Figure 4B illustrates the tubular shape obtained
of that the nose 27 fits by bending in the strip shown Fig ¹ IA in the way into the recess 28;. ·

Figure 5 illustrates a tube containing an outer layer 30 made of a flexible plastic material and an inner layer 31 of conductive metal-filled polymeric material;

Fig.öA illustrates a normal, pressed O-ring 35; Figure 6b illustrates the pressed O-ring 35 of Figure 6A coated with metal-filled polymeric material

Figure 7 illustrates a bundle of insulated wires 40 coated with a metal-filled polymeric material 41;

Fig. 8 is an enlarged cross-sectional view of an article according to the present invention;
including a heat-shrinkable substrate 50 and a metal-filled polymeric material 51;
Fig.9 is a side view of a cylinder section
a heat shrinkable tubular article according to the present invention around a wire or
a cable 64 around which carries insulation 65; and
Fig.10 is a cylinder section in side view of a

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Bundle of insulated wires encased in a heat-shrinkable tubular article according to of the present invention.

Some examples are now given:

For example

A liquid preparation was made from 72.5 parts of "SR-529 Adhesive", a pressure-sensitive silicone polymer of low molecular weight in a 50 # dispersion in toluene, from 200 parts of a silver-coated copper powder (granular), made in accordance with made by the method of example 1 of US Patent 3202 (having an average particle size of about φ508 to 0.0762 (2 to 3 mils)), and of 54 parts of toluene manufacturing ψ. This liquid preparation was poured onto a bundle of insulated wires, and the preparation adhering to the bundle was allowed to dry. After the toluene was removed by evaporation, the coating on the wire bundle was electrically conductive and had a resistance of 10 ohms over a distance of 76.2 cm (2.5 feet) when the process was repeated a second time to deposit a more stable Layer was repeated, the resistance of the coating was 2.5 ohms over a span of 76.2 cm (2.5

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feet). The wire bundle coated in this way is illustrated in FIG. 7 of the accompanying drawings.

Example 2

A liquid formulation was prepared containing 85 parts of the silver-coated copper powder used in Example 1 and 15 parts of the polybutadiene-styrene copolymer in 30 parts of toluene sold under the trade name "Thermolastic 125". This formulation was applied to an extruded neoprene foam stick by dipping the stick into the solution. After drying the toluene by evaporation of the coating had on the rod a thickness of approximately 0.25 to 0.381 mm I ¹ (10 to 15 mils) and exhibited a elkjetrische conductivity. Fig.l of the drawings illustrates the product thus obtained, in which 10 represents the foam rod and 11 the conductive coating.

Example 3

The procedure of Example 2 was repeated with the exception that the neoprene foam rod was replaced by a neoprene foam sheet material was replaced. The electrically conductive coated product obtained in this way becomes explained in Fig.2, wherein the layer 17 is the foam

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Plate material and 16 represents the conductive coating.

Example 4

A liquid formulation was prepared containing 22 parts of a liquid silicone gum sold by the General Electric Company under the trade name "RTV-615A"; 2 parts of a hardener sold by General Electric under the trade name ^t; RTV-615B ", 76 parts of silver scales, sold by Handy and Harmon under the trade name SiIflake 135" and 30 parts of xylene. This preparation was put on one side of a piece of a "zipper?" final tube "^ Zipper Tubing") made of plastic, explained in FIG. ¹ IA, applied; the coating was cured at room temperature and was found to be electrically conductive.

Example 5

A liquid formulation was prepared in accordance with the procedure of Example 4, except that the silver scales by 96 parts of a silver-copper-coated iron powder, made in the manner as it is described in the pending application Serial No. 227 755, have been replaced. The base iron powder had one effective surface area of about 14.34 m / kg (about 70 sq. ft.

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per pound) and an average particle diameter of about O _a O762 mm (3 mils). It was first additionally coated with 18 mol # copper from a copper sulfate solution, and then 12 mol # of the copper was replaced by silver from a silver cyanide solution. The silver-coated powder in loose form had a volume specific electrical resistivity below 0.5 ohm / cm.

This liquid preparation was applied to a standard rubber O-ring seal applied by dipping the seal into the liquid preparation. The coated in this way The seal, illustrated in Fig. 6B, was electrically conductive and worked satisfactorily as a shield against electromagnetic Energy.

Example 6

A polymeric blend was made from 20 parts of "SR-585 Adhesive ", a pressure-sensitive silicone polymer with low molecular weight in a 50 wt .- # - dispersion in toluene, 80 parts of a granular, silver-coated copper powder made in accordance with the procedure described in Example 1 of U.S. Patent 3,202,488 (having an average particle size of 0.0508 to 0.0762 mm (2 to 3 mils) and 30 parts of toluene

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manufactured. This mixture was converted into a conventional, Heat-shrinkable polyethylene pipe of approximately 30 cm Poured in length and about 2.5 cm in diameter with a wall thickness of about 0.1 cm. The tube was turned slowly as long as the metal-filled adhesive moved to the opposite end of the tube until it was all inside the polyethylene outer wall was covered with the mixture. Rotation of the tube was continued until the toluene took under Leaving behind a flexible and resilient elastomer Coating on the inside of the tube had evaporated. The elastomeric coating was found to be electrically conductive.

A wooden spatula handle was placed within the tube prepared above and the tube heated to effect the shrinkage. The diameter of the tube was reduced to about 1.5 to cm 2 and the resistance measured by ψ placement of the viewfinder of a volt meter QHM 9 cm apart, was found to be 0.4 ohms. This value was essentially constant over the entire tube.

Example 7

The procedure of Example 6 was repeated with the exception that the polymer mixture 13> 7 parts (solid) "SR-585 Adhesive", 71.8 parts of the silver-coated

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Copper powder and 14.5 parts of toluene. The film deposited on this way contained 16 % adhesives and 84 % powder, was 0.254 mm (10 mils) thick, shrunk to 54 % of its original dimensions, and resisted over a span of 30.48 cm (1 st foot), before shrinking, of 2 ohms.

Example 8

A strip of oriented "Mylar" (polyethylene terephthalate) of 3 cm 30 cm was coated on one side with a polymeric mixture consisting of 60 parts Silflake 135 in 22 parts ^!! RTV-615A "and 2 parts ^{: I} RTV-615B" knife-coated. The metal-filled, polymeric coating was cured at room temperature and found to be electrically conductive. The coated strip was wound around an insulated electrical wire with the polymer coating on the inside. Heat was then applied to shrink the outer layer of the strip and to force the inner polymer coating to come into contact with the insulation. The electric wire made in this way was shielded from electromagnetic energy.

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Example'9

The procedure of Example 8 was repeated with the Except that the silver scales are made from an equivalent amount of a silver-copper-coated iron powder in the manner described in Example 5 were replaced. '

Example Io

The procedure of Example 6 was repeated with the Exception that the polymer mixture contains 85 parts of the silver-coated copper powder and 15 parts of "Thermolastic 125", dissolved in 30 parts of toluene. The inner layer of the tubular article thus obtained showed excellent electrical conductivity properties and shielded electromagnetic energy.

Fig.9 illustrates the product thus obtained when the tubular The subject of this example is wrapped around an insulated cable and then for the purpose of shrinking the Object is heated around the insulated cable. The tubular article comprises an outer layer of a Heat-swellable polyethylene 62 and an inner layer of metal-filled polybutadiene-styrene copolyperen 63. The

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insulated cable contains a core of an electrically-conductive Wire, es or cable 64 and an insulating coating 65

Fig. 10 illustrates the product thus obtained when the insulated cables 64 and 65 by a bundle of insulated ürähten 70 is replaced. It should be recognized that the The shape of the insulated cable is not critical and that it can be either flat or circular tubular article comprises an inner layer of conductive material 71 and an outer layer of heat shrink capable material 72.

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Spherical copper powder with an apparent density of 5.0 to 5.5 s as shown on the Hall Plometer according to ASTM-B 212 bis. 48 was determined, was replacement-coated with silver from a silver cyanide solution as described in Example 1 of US Pat. No. 3,202,488. The silver-plated copper powder thus obtained had an average

Particle size of et, a 0.254 to 0.382 mm (10 to 15 mils). This powder (240 parts) was mixed with 53 parts of a dimethyl-polysiloxane rubber containing vinyl and phenyl groups, sold under the trade name "Silastic 440, Gum" and 1.08 parts of 2,5-dimethyl-2,5-di- (tert-butylperoxy) -hexane by mixing at room temperature for

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mixed in a Banbury mixer for about 3 minutes. This mixture was then knife-coated onto a plate made of very swellable polyethylene. This plate could be used as such or cut into narrow strips. The plates or strips were electrically insulated cable has been to _a wound whereupon heat (170 ° C) to shrink the outer layer of polyethylene and curing of the inner layer of the metal-filled silicone rubber used. At your option, the polyethylene could be heat-shrunk at a lower temperature and the silicone could be cured by irradiation. Regardless of which way ₃ the electrical wires were now provided with an electromagnetic energy shield.

As can be seen from the preceding examples, the method of the present invention is particularly useful in providing substrates with a conductive coating ₃ which is effective as a shield for electromagnetic and magnetic energy. Such coatings are further characterized in ₃ that they are flexible, resilient and deformable. These coatings are also useful in providing a method of grounding part or all of the substrate. For example, where a bundle of insulated wires is coated in accordance with the method of the present invention, the insulation can

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partially stripped from one of the wires in the bundle to ensure an earth connection for the coating.

Electronic parts such as Capacitors and resistors, can be made in accordance with the method of the present Invention to form a shield around which items are coated to avoid interference from within of the constituent or other constituents in the vicinity of the coated items with prevent electromagnetic energy.

It can be seen from the above examples that the objects of the present invention include first link of heat-shrinkable material and a second link of conductive material, particularly valuable to create electromagnetic and magnetic

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Shielding is required if flexibility is required. These Objects are also useful for the creation of suitable ones Grounding for electrical and electronic equipment in view of the conductive nature of the second link If, for example, on an insulated, current-carrying cable to carry out an electrical connection its insulation is stripped off, it can with the subject of the present - Efifldung be enveloped to the desired Provide shielding for electromagnetic energy,

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and the second member (conductive) can, if desired Earth to be connected. The articles of the present invention, particularly the tubular articles, can used to provide tools for connecting cables or wires together in such a way that a dense, intimate and impermeable bandage and coating is formed. Capacitors can also through an electronic enclosure made by heat shrinking an article of the present invention Invention around a normal capacitor.

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909848/1178

Claims (1)

192652Q Claims Soldering process for producing an electrically conductive coating on a substrate, characterized in that a liquid preparation containing 2 to 6 parts by volume of a polymeric material forms soft, flexible, resilient and deformable films on the substrate and 4 to 8 parts by volume of electrically conductive films Particles having an average particle size of 0.00254 to 2.54 mm (0.1 to 100 mils) and an outer surface of metal, is applied and cured. 2p method according to claim 1, characterized in that that the preparation is hardened by evaporation of any solvent present and then post-hardened wi ^ -d. - 3β method according to any one of claims 1 and 2, characterized Tekann notes that the particles are granular, spherical, round or are generally spherical, 4ο Method according to one of claims 1 to 3, characterized characterized ·: that the particles of silver-coated Made of copper «, 909848/1178 _ 34 - 5. The method according to any one of claims 1 to 3 »characterized that the Teilchan by silver coating made of copper coated iron powder 0.00254 having 6 _e method of any one of claims 1 to 5, characterized in that the particles τοη an average particle size up to 0.623 ^ m (0.1 to 25 mils) " 7. The method according to claim 6, characterized in that the particles have an average particle size from 0.0254 to 0.381 (1 to 15 mils) mm, 8. The method according to any one of claims 1 to 7, characterized in " characterized in that 50 to 80 percent by volume of metal particles are incorporated into the polymeric material, 9. The method of claim 1 substantially as described with reference to any one of Examples 1-11 _β 10 substrate carrying an electrically conductive coating, made by a method according to any one of Claims 1 to 9. 11. Heat-shrinkable substrate, carrying an electrically- 909848/1178 BAD Gfl _IQINAL -35- 192652Q conductive coating characterized by a content of 20 "to 80 percent by volume of a polymeric material and from 80 "to 20 percent by volume of electrically-conductive particles having an average particle size of 0.00254 to 2.54 mm (0.1 to 100 mils) and an exterior surface area of metal « Ι2β tubular object comprising a tube of a Heat-shrinkable material, bearing on its inner Surface an electrically conductive coating containing from 20 "to 80 percent by volume of a polymeric material and from 80 to 20 volume percent electrically conductive particles having an average particle size of 0.00254 up to 2.5 mm (0.1 to 100 mils) and an outer metal surface « 13. Insulation-supporting wire or cable, characterized by an object according to claim 12 _{e which is shrunk onto its surface} BATH 909848/1178