JPH0687516B2 - Electromagnetic wave shielding molding material and manufacturing method thereof - Google Patents

Description

The present invention relates to an electromagnetic wave shielding molding material and a method for producing the same. More specifically, the present invention provides a molding material having excellent electromagnetic wave shielding properties and bending resistance, particularly a sheet material, and a molding material such as this, which is reproducible and has a conductive property used therein. The present invention relates to a method for producing without breaking or miniaturizing a material and without dropping it.

[Conventional technology]

Conventionally known conductive materials include metallic fillers such as metal powders and metal flakes, non-metal inorganic fillers such as powders or flakes of carbon black and grafide, or a matrix made of a polymer material. , Metallized glass fibers (eg chemical vapor deposition,
There is also one in which metallized glass fibers by an electroplating method, an electroless plating method, or the like is dispersedly contained and kneaded and molded, for example, formed into a sheet shape.

Further, a composite sheet in which the above-mentioned conductive material and a base cloth made of a fiber material are combined is also known. Since such a conductive sheet or film has a matrix made of the polymer material which is easily stretched,
When it is repeatedly subjected to an extension load or an instantaneous load is applied, it tends to easily extend. in this way,
When the conductive sheet or film is stretched or deformed, the distribution of the conductive filler dispersed in the conductive sheet or film is changed, and as a result, its resistance value and electromagnetic wave shielding property are changed and its performance is lowered. And eventually lose its usefulness.

In order to solve the above drawbacks, it has been attempted to form or adhere a conductive sheet or film on one side or both sides of a base fabric made of a fibrous material. Such a conductive composite sheet substantially eliminates the above-mentioned drawbacks of conventional conductive sheets or films, and can be effectively used for static applications that are not subject to bending action.

[Problems to be Solved by the Invention]

However, when the above-mentioned conductive composite material is used in a simple warehouse, awning, etc., such as fluttering by wind,
Since the sheet or film containing the conventional conductive filler is subject to repeated bending action, it is easily damaged by the above-mentioned repeated bending action, and there is a problem that its resistance value and electromagnetic wave shielding property are significantly changed.

As a method for solving this problem, it has also been attempted to use an organic fiber having a high bending resistance as a base material and mixing the surface of the organic fiber with a conductive metal mixed with a polymer material. In this method, if a coating method or a casting method that does not relatively stress the surface of the metal-plated organic fiber is used, there is no particular problem in the production thereof, and the performance of the obtained product is good. However, when a considerably large stress is applied to the surface of the metal-plated organic fiber as in the calendering method or the injection molding method, the plating layer is easily peeled and removed.

Therefore, when producing a conductive / electromagnetic wave shielding molding material, a method in which a large shearing force acts on the inorganic conductive fibers or particles to be dispersed, such as a kneading step, for example, a calender kneading molding method, an extrusion molding method and When using the injection molding method, etc., develop a method that does not break the inorganic conductive fibers or particles during this process, or peel off the conductive coating layer on the surface of the metal-plated organic fibers. Was desired.

Further, it has been desired that the sheet material has excellent conductivity and electromagnetic wave shielding property, excellent flex resistance, and is not damaged by repeated bending action during use.

The present invention has excellent conductivity and electromagnetic wave shielding properties,
Further, the electromagnetic wave shielding molding material having high flexural strength, particularly the sheet-like material and the conductive material, can be uniformly dispersed in the matrix material without damaging it, and the above-mentioned excellent reproducibility can be obtained. An object of the present invention is to provide a method for producing an electromagnetic wave shielding molding material, particularly a sheet material.

[Means for Solving the Problems]

The electromagnetic wave shielding molding material of the present invention is a molded body molded from a composition containing a matrix made of a moldable polymer material and a large number of conductive material-containing dispersions kneaded and dispersed in the matrix. The conductive material-containing dispersion comprises (a) a base made of a polymer material having a melting point higher than the molding temperature of the molded body, and (b) a conductive material dispersed and held in the base. The conductive material is a granular, flake-shaped, foil-shaped and / or fibrous fine body, and contacts with each other in the substrate to form a network, and a part of this network is the dispersion. It is exposed on the outer surface of.

The method of the present invention for producing the above electromagnetic wave shielding molding material comprises preparing a composition by kneading and dispersing a large number of conductive material-containing dispersions in a matrix composed of a moldable polymer material, and molding the composition. In the method, the conductive material-containing dispersion is added to a polymer material having a melting point higher than the molding temperature of the molded body, and a granular, flaky, foil-shaped, and / or fibrous fine conductive material is used. To prepare a composition, which is then formed into a dispersion, in which the fine conductive materials dispersed in the substrate made of the polymer material are in contact with each other to form a network, and It is prepared by exposing a part of the network to the outer surface of the dispersion.

Another electromagnetic wave shielding molding material of the present invention has a substrate formed of a fibrous material and a conductive material-containing coating layer formed on at least one surface of the substrate. Is formed from a composition containing a matrix made of a flexible polymer material and a large number of conductive material-containing dispersions kneaded and dispersed in the matrix, wherein the conductive material-containing dispersion is (A) a base made of a polymer having a melting point higher than the molding temperature of the molded body, and (b) a conductive material dispersed and held in the base.
The conductive material is granular, flake-shaped, foil-shaped, and / or
Alternatively, it is a fibrous fine body, which forms a network by coming into contact with each other in the substrate, and a part of this network is exposed on the outer surface of the dispersion. .

The method of the present invention for producing the above-mentioned molding material comprises preparing a composition by kneading and dispersing a large number of conductive material-containing dispersions in a matrix made of a flexible polymer material, and molding the composition. Then, in the method of coating and adhering this molding on at least one surface of a base layer made of a fibrous material, the conductive material-containing dispersion is added to a polymer material having a melting point higher than the molding temperature of the molding, Granular, flake-shaped, foil-shaped and / or fibrous fine conductive materials are mixed and dispersed to prepare a composition, and the composition is formed into a dispersion, which is then added to a substrate made of the polymer material. The dispersed fine conductive materials contact each other to form a network,
It is prepared by exposing a part of this network to the outer surface of the dispersion.

[Action]

In the electromagnetic wave shielding molding material of the present invention, the molded body or the molded body coating layer contains a conductive material dispersedly held in a substrate made of a polymer material having a specific melting point, and kneaded with a matrix polymer material. An electrically conductive material-containing dispersion that is dispersed, wherein the electrically conductive material in the electrically conductive material-containing dispersion is in the form of particles, flakes, foil flakes, and / or
Alternatively, it is a fine fibrous substance, dispersed in a substrate made of a polymer material, and contacting each other to form a network, and a part of this network is exposed on the outer surface of the dispersion. It is characterized by being The polymer material constituting the substrate has a melting point higher than the molding temperature of the molded body or the molded body coating layer, and therefore, does not melt during molding of the molded body or the molded body coating layer and is dispersed. It can be dispersed almost uniformly as a body in the matrix polymer material.

Generally, the matrix-forming polymer material is preferably selected from those having a molding temperature of about 100 to 300 ° C., such as by an extrusion method or a rolling method.

The moldable polymer material forming the matrix as described above is composed of at least one of moldable synthetic rubber and synthetic resin.

Moldable synthetic resins include polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyvinyl acetate,
Polybutene, polyacrylic acid ester, polyvinyl butyral, polyvinylidene chloride, polyacrylonitrile,
Examples of the thermoplastic resin include ABS resin, acrylonitrile-styrene resin, ethylene-vinyl acetate resin, ionomer resin, fluorinated polyethylene, acetal resin, chlorinated polyether resin, fluorine-containing polymer resin and silicone resin.

As synthetic rubber, diene rubber such as styrene-butadiene copolymer, olefin rubber such as butyl rubber, fluorine-containing rubber such as fluorinated acrylate rubber, ether / thioether rubber, urethane rubber, silicone rubber and chlorosulfonated polyethylene. Rubbers such as can be mentioned.

Among these materials, polyvinyl chloride, ethylene-vinyl acetate copolymer and polyurethane are preferable, and they can be molded into a desired shape at a temperature of 150 to 250 ° C.

The polymer material constituting the substrate of the conductive material-containing dispersion is
It is selected from polymer materials having a melting point higher than the molding temperature of the above-mentioned molded article or molded article coating layer, preferably 10 ° C. or higher. As such a polymer material for a substrate, polyester resin (polyethylene terephthalate resin), polyamide resin (nylon 6, nylon 66, etc.) and the like can be used.

The conductive material contained in the conductive material-containing dispersion is fine carbon, graphite, conductive metal (for example, nickel, silver, copper, zinc, aluminum, etc.) conductive metal compound (for example, conductive compound of the above metal, etc.) ) Can be selected. As such a conductive material, the shape thereof is granular, flake-shaped, foil-shaped, and / or fibrous, and preferably has a size of 0.1 to 100 μm.

In the electroconductive material-containing dispersion used in the present invention, the electroconductive material is dispersed and held in the substrate, but it may be evenly distributed or locally distributed in the substrate. However, it is necessary that the conductive materials contact each other in the substrate to form a network, and a part of the conductive material is exposed on the outer surface of the dispersion. The conductive material held in such a dispersion is brought into contact with the conductive material held in another dispersion, thereby forming a conductive network in the molded body or the molded body coating layer. You can In order to expose a part of the conductive material to the surface of the dispersion as described above, a part of the polymer material forming the outer surface of the dispersion may be removed by a treatment such as melting, rubbing or burning if necessary. The conductive material dispersion contains 1 to 50% by weight of a conductive material, and its specific resistance value is preferably 10 ° Ω-cm or less, more preferably 10 ^-3 Ω-cm or less. As long as the dispersion meets the above requirements,
The shape and size are not particularly limited, and may have any shape such as fibrous shape, flake shape, foil piece shape, and granular shape. The length of the fibrous dispersion is preferably 0.1 to 5 mm, more preferably 0.3 to 3 mm, and even more preferably 0.5 to 2 mm. Further, it is preferable that the granular, flake-shaped or foil-shaped dispersion has a size of 0.1 mm or more.

The conductive material-containing dispersion of the present invention is preferably contained in the molded body or the molded body coating in a proportion of 1 to 70% by weight, and more preferably 5 to 30%.
This content rate takes into consideration the conductivity, electromagnetic wave shielding properties and strength characteristics required for the molded product, the types of conductive material, base forming material and matrix forming material, and the method for forming the molded product or the molded product coating layer and its conditions. Can be appropriately determined.

As described above, in the conductive material-containing dispersion contained in the molded body or molded body coating layer of the present invention, the conductive material,
Since the base material is dispersed and held in the base material and the base material does not melt during the molding process, the conductive material is broken, dropped, or separated even in the process of receiving shearing force such as kneading, extrusion or rolling. In addition, the dispersion can be easily dispersed and distributed in the matrix to form a desired conductive material network.

The electromagnetic wave shielding molding material comprising the polymer matrix of the present invention and the conductive material-containing dispersion dispersed therein is not particularly limited in its shape, but it is generally used as a sheet. There are no particular restrictions on the thickness, width, etc. of sheet-like materials, but generally 10-1000
Those having a weight of g / m ² and a thickness of 0.01 to 1.0 mm are practically convenient. Such a molding material can be molded by a general rolling method or an extrusion method.

The electromagnetic wave shielding molding material of the present invention may be a composite molding material in which a coating layer containing the conductive material-containing dispersion described above is formed on at least one surface of a base layer formed of a fiber material.

The fibers constituting the base layer of the composite molding material include natural fibers such as cotton and hemp; inorganic fibers such as glass fibers, carbon fibers and metal fibers; recycled fibers such as viscose rayon and cupra; Synthetic fibers such as cellulose and triacetate fibers, and synthetic fibers such as nylon 6, nylon 66, polyester (polyethylene terephthalate),
Aromatic polyamide, aromatic polyester, acrylic polymer, polyvinyl chloride, vinylon, and polyolefin fibers can be selected, especially high strength fibers (15 ~
50 g / d) and / or high heat resistant fibers and the like can also be used.

Preferred fibers for the present invention are polyester fibers, polyamide fibers, water insolubilized polyvinyl alcohol fibers, aromatic polyamide fibers, aromatic polyester fibers and the like.

The fibers in the base layer may be of any shape such as short fiber spun yarn, long fiber yarn, split yarn, tape yarn, etc., and the base fabric may be woven fabric, knitted fabric, non-woven fabric, paper-like product, and these. Any of two or more composite sheets of Generally, the fibers used in the sheet of the present invention are preferably polyester fibers, and the fibers are preferably in the form of long fibers (filaments). The fibrous base layer is useful for maintaining a high level of mechanical strength of the resulting molding material.

Generally, a sheet-like base fabric is often used as the fiber base layer, and useful sheet-like base fabrics include twill, plain weave, leno weave, warp weave, special knitted fabrics and other woven fabrics having a general structure. You can

There is no particular limitation on the weight or thickness of the base cloth, but in general
Those having a weight of 30 to 1,000 g / m ² and / or a thickness of 0.05 to 1.0 mm are preferred.

In the composite molding material of the present invention, the base layer made of a fibrous material can suppress the expansion and deformation of the conductive coating layer to stabilize the electromagnetic wave shielding property of the composite molding material,
It is effective in improving durability against fluttering and repeated bending.

In the matrix of the molded body or molded body coating layer of the present invention, in addition to the conductive material-containing dispersion, a known conductive material,
For example, metal fibers, metal coated glass fibers, metal flakes,
Contains metal powders, carbon fibers, carbon black, antimony chloride powders, copper iodide powders, etc., and matrix modifying materials such as colorants, plasticizers, stabilizers, fillers, etc. in appropriate amounts as necessary. You may stay.

In the composite molding material of the present invention, the weight and thickness of the conductive material-containing coating layer is not particularly limited, but generally 50 to
It preferably has a weight of 1,500 g / m ² and / or a thickness of 0.05 to 1.0 mm.

To produce the composite molding material of the present invention, a conductive molding comprising a flexible polymer material matrix and a conductive material-containing dispersion dispersed therein on a predetermined surface of the fiber base layer, For example, a film may be attached, or a working liquid having the above composition may be applied on a predetermined surface of the base cloth and solidified. In order to form such a conductive coating, known coating methods such as a calendar method, a laminating method, a topping method, a coating method and an impregnation method can be used.

〔Example〕

Example 1 In Example 1, 65 parts by weight of polyethylene terephthalate resin was mixed with 55 parts by weight of nickel powder (7.24 × 10 ⁻⁶ Ω-cm) having a particle size of 2.5 μm, and the mixture was melt extruded. A fibrous conductive material-containing dispersion having a diameter of 0.05 mm and a length of 1.2 mm was produced. Its specific resistance value is 3.0
It was × 10 ^-3 Ω-cm.

The conductive material-containing dispersion described above is used in the blending amount shown in Table 1,
It was mixed into a matrix polymer material having the composition shown in Table 1. The volume content of the conductive material-containing dispersion is approximately 5%.
Met. This mixture was kneaded using a calender machine at a temperature of 165 ° C. to form a sheet having a thickness of 0.3 mm. The specific resistance value of this sheet was measured by the voltage / current method described in SRIS, 2301 (1969) .3.1, and the measured value shown in Table 1 was 3.8 × 10 ^-2 Ω-cm.

Observation of the obtained sheet revealed that the nickel powder-containing fibrous dispersion was uniformly dispersed in the matrix by kneading and rolling forming a conductive network, and had a mechanical strength sufficient for practical use. Was.

For comparison, a viscous liquid was prepared by calcining the composition shown in Table 1 in 30 parts of Tokuren without calendering to the extent that the fibrous dispersion was not cut, and preparing this liquid on a glass plate. Then, it was cast on a plate, dried, and gelled at 180 ° C. to form a sheet having a thickness of 0.3 mm.

The specific resistance value of this sheet was about 4 × 10 ^-2 Ω-cm.

That is, it can be seen that by using the conductive material-containing dispersion in the present invention, it is possible to form and retain a practically sufficient conductive network in the sheet even when subjected to calendar kneading treatment.

Comparative Example 1 The same operation as in Example 1 was performed. However, in place of the conductive material-containing dispersion, 20 parts by weight of metallized fiber produced by the following method was used.

That is, in order to produce a metallized fiber, a length of 0.8 mm,
100 g of polyethylene terephthalate short fibers having a diameter of 15 μm (aspect ratio 53) are treated with 5 g / l of γ-aminopropyltriethoxysilane and dried, and then this is mixed with 10 ml of 0.1 g / l palladium chloride / hydrochloric acid solution, Add to an aqueous solution containing 990 ml of 10 ml / l hydrochloric acid and stir well at room temperature.
It was catalyzed for 30 minutes. This is filtered off, 11
It was dried in a dryer at 0 ° C.

This catalyzed polyester short fiber was put into a nickel plating bath having the following composition; component amount (g / l) nickel sulfate 25 sodium hypophosphite 30 malic acid 30 succinic acid 16 pH 4.5 to 5.0 Nickel plating was performed at a liquid temperature of ° C.

The metallization ratio of the obtained conductive polyester short fibers as the conductive material was 36%.

The resistivity value of this sheet could not be measured by the above method because no current flowed. In addition, when the metallized fibers in the obtained sheet were observed, it was confirmed that the metal plating layer was peeled off and separated. No formation of conductive network was observed.

However, the sheet produced by the same casting method as in Example 1 was 7.
It showed a good resistivity value of 8 × 10 ^-2 Ω-cm. This indicates that metallized fibers are unsuitable for molding processes where shear forces act violently.

Comparative Example 2 The same operation as in Example 1 was performed. However, SUS3161 stainless steel fiber (diameter 1
2 μm, length 0.8 mm) 50 parts by weight were used.

The specific resistance value of the obtained sheet could not be measured because current did not flow by the above method.

When the stainless steel fibers in this sheet were observed, they were finely broken and separated, and although a large amount of 50 parts by weight was added, formation of a conductive network was not observed.

However, the sheet prepared by the same casting method as in Example 1
A specific resistance value of 6.2 × 10 ^-2 Ω-cm was shown. This is
The continued use of stainless steel fibers has shown to be unsuitable for molding processes subject to harsh shear forces.

Comparative Example 3 The same operation as in Example 1 was performed. However, in place of the conductive material-containing dispersion, 55 parts by weight of nickel flakes (major axis: about 40 μm) were used as the conductive material.

The specific resistance value of the obtained sheet could not be measured by the above method because no current flowed.

Further, when flakes in the sheet were observed, formation of a conductive network was not observed, although the flakes were added in a large amount of 55 parts by weight.

However, the sheet prepared by the same casting method as in Example 1
A specific resistance value of 2.8 × 10 ^-1 Ω-cm was shown. This is
It has been shown that conductive flakes are still unsuitable for use in molding processes subject to harsh shear forces.

Example 2 (A) The following structure composed of polyethylene terephthalate multifilament yarn: And a plain woven fabric having a weight of 180 g / m ² were produced, and this was washed and dried by a conventional method to obtain a base fabric.

(B) Preparation of Conductive Material-Containing Dispersion As Described in Example 1 (C) Production of Composite Sheet A polyvinyl chloride sheet containing the conductive material-containing dispersion dispersed therein was produced by the method described in Example 1. While it was hot, both sides of the base cloth were pasted and pressure bonded to prepare a composite sheet.

The thickness of the obtained conductive coating layer was about 0.3 mm, and the total thickness of the obtained composite sheet was about 0.8 mm.

Each of these composite sheets exhibited a water resistance of 1500 mm or more of water column.

Tensile strength, elongation, and specific resistance of composite sheet (immediately after processing, after being subjected to 5,000 flexing operations, and 1
Those subjected to a bending action of 000 times) were measured, and the results are shown in Table 2.

The composite sheet of Example 2 exhibited the electromagnetic wave shielding properties shown in FIG. 1 (measurement method: ASTM method, ES 7-83 electric field shield test method).

As is clear from Table 2, the composite sheet of Example 2 according to the present invention has extremely good tensile strength and elongation, and can be used for applications such as a simple warehouse or awning which requires high load and waterproofness. Moreover, not only the mechanical durability against repeated bending but also the durability against changes in the specific resistance value and the electromagnetic wave shielding property was excellent. That is, the composite sheet of the present invention showed the same specific resistance value of the order of 10 ⁻² Ω-cm as before bending even after 10,000 times of bending. However, each of the sheets of Comparative Examples 1 to 3 had low electromagnetic wave shielding properties and was not practical.

Example 3 The same operation as in Example 2 was performed. However, the dispersion containing fibrous conductive material was treated with 3% caustic soda aqueous solution at 70 ° C, 3
A heating / stirring process was performed for 0 minutes to dissolve and remove a part of the polymer material on the outer surface of the dispersion to increase the exposed part of the conductive material particles.

The appearance of the obtained composite sheet was almost the same as that of Example 2, showing a water resistance of 1500 mm or more of water column. The specific resistance values of this composite sheet before bending and after 10,000 times of bending are 7.5 × 10 ^-3 Ω-cm and 4.5 × 10 ^-3 Ω-cm, respectively.
And it was excellent.

〔The invention's effect〕

The electromagnetic wave shielding molding material of the present invention has not only excellent electromagnetic wave shielding properties but also good mechanical strength, and in particular, an electromagnetic wave shielding composite of the present invention obtained by compounding a base fabric made of a fiber cloth. The molding material exhibits, in addition to excellent tensile strength, excellent resistance to repeated bending. According to the method of the present invention, the electromagnetic wave shielding molding material as described above can exhibit the above excellent performance even after undergoing a molding step which is subjected to a strong shearing force.

[Brief description of drawings]

FIG. 1 shows the electromagnetic wave frequency (MHz) and the electromagnetic wave shielding property (d) of one embodiment (Example 2) of the composite molding material of the present invention.
It is a graph which shows the relationship of B).

Claims (4)

[Claims] 1. A molded article molded from a composition comprising a matrix composed of a moldable polymer material and a large number of conductive material-containing dispersions kneaded and dispersed in the matrix, wherein the conductive material Conductive material-containing dispersion includes (a) a base made of a polymer material having a melting point higher than the molding temperature of the molded body, and (b) a conductive material dispersedly held in the base, The granular material is a granular, flake-shaped, foil-shaped and / or fibrous fine body, which contacts each other in the substrate to form a network, and a part of this network is formed on the outer surface of the dispersion. An electromagnetic wave shielding molding material characterized by being exposed. 2. A method for forming a composition by kneading and dispersing a large number of conductive material-containing dispersions in a matrix made of a moldable polymer material, wherein the conductive material-containing dispersion is formed. To a polymer material having a melting point higher than the molding temperature of the molded body, and mixed and dispersed a fine conductive material in the form of particles, flakes, foil pieces and / or fibers to prepare a composition, The composition is formed into a dispersion, and the fine conductive materials dispersed in the substrate made of the polymer material are in contact with each other to form a network,
Moreover, the method for producing an electromagnetic wave shielding molding material is characterized in that it is prepared by exposing a part of this network to the outer surface of the dispersion. 3. A base layer formed of a fibrous material, and a conductive material-containing coating layer formed on at least one surface of the base layer, wherein the conductive material-containing coating layer is a flexible polymer material. And a conductive material-containing dispersion which is kneaded and dispersed in the matrix, wherein the conductive material-containing dispersion is (a) the coating layer molding. A base made of a polymer having a melting point higher than the temperature of, and (b) a conductive material dispersed and held in the base, the conductive material is granular, flake-shaped, foil-shaped and / or A fibrous fine body, which forms a network by contacting each other in the base body, and a part of this network is exposed on the outer surface of the dispersion body. Material. 4. A composition is prepared by kneading and dispersing a large number of conductive material-containing dispersions in a matrix made of a flexible polymer material, molding the composition, and molding the molded article from a fiber material. In the method of coating and adhering on at least one surface of a base layer, the conductive material-containing dispersion is a polymer material having a melting point higher than the molding temperature of the molded body, in the form of granules, flakes, foil pieces, And / or fibrous fine conductive material is mixed and dispersed to prepare a composition, the composition is formed into a dispersion, and the fine conductive material dispersed in a substrate made of the polymer material is Contact each other to form a network,
And a part of this network is exposed on the outer surface of the dispersion to prepare the electromagnetic wave shielding molding material.