JPH0371699A - Electromagnetic shielding material and manufacture thereof - Google Patents

Abstract

PURPOSE:To enable the manufacture of a molding material, which has an electromagnetic shielding property and a flexing resistance and is excellent in reproducibility, by a method wherein a base body of polymer material whose molting point is higher than the molding temperature of a molded body and a conductive material contained in the base material are contained in conductive material containing dispersed material. CONSTITUTION:A molded body or a molded body coating layer contains conductive material contained and retained in a base body composed of polymer material which has a certain melting point and conductive material containing dispersed material which is dispersed by kneading in the matrix polymer material. A molding polymer material is, for instance, molding synthetic rubber or the like, the polymer material is, for instance, polyester resin or the like, and the conductive material is carbon or the like. The polymer material forming the base body concerned has a molting point higher than the molding temperature of the molded body or the molded body coating layer and is not melted at the molding of the molded body or the molded body coating layer, so that it can be uniformly dispersed into the matrix polymer material as dispersed material. By this setup, a molding material, which excellent in conductivity, electromagnetic shielding property, and bending strength, can be reproducible manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electromagnetic shielding molding material and a method for producing the same. More specifically, the present invention provides a molding material, particularly a sheet material, having excellent electromagnetic shielding properties and bending resistance, and a molding material having excellent electromagnetic shielding properties and bending resistance. The present invention relates to a method of manufacturing the material without breakage, miniaturization, or falling off of the material.

[Conventional technology]

Conventionally known electrically conductive materials include metallic fillers such as metal powders and metal flakes, non-metallic inorganic fillers such as carbon black and graphite powders or flakes, or , metallized glass fibers (e.g. chemical vapor deposition,
There are also products in which glass fibers (metalized by electroplating or electroless plating) are dispersed and kneaded and formed into, for example, a sheet shape.

Composite sheets are also known in which the above-mentioned conductive materials are combined with base fabrics made of fibrous materials.

Such a conductive sheet or film has a matrix made of a polymer material that is easily elongated, so that the conductive sheet or film as a whole easily elongates when a repeated elongation load is applied or an instantaneous load is applied. Tend.

In this way, when a conductive sheet or film is stretched or deformed, the distribution of the conductive filler dispersed therein changes, resulting in changes in its resistance value and electromagnetic shielding properties. It can degrade its performance and eventually lead to a loss of usefulness.

In order to eliminate the above-mentioned drawbacks, attempts have been made to form or adhere a conductive sheet or film on one 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 subjected to bending action.

[Problem to be solved by the invention]

However, when the above-mentioned conductive composite material is used for simple warehouses, tents, etc., it causes problems such as flapping due to wind.
Since it is subjected to repeated bending, conventional sheets or films containing conductive fillers are easily damaged by the repeated bending, and there is a problem in that their resistance value and electromagnetic shielding properties change significantly.

As a method to solve this problem, attempts have been made to use organic fibers with high bending strength as a base material, the surface of which is plated with a conductive metal, mixed with a polymer material. In this method, if a coating method or a casting method that does not cause stress on the surface of the metal-plated organic fiber is used, there will be no particular problem in its production, and the performance of the resulting product will be good. . However, like the calendar method, injection molding method, etc.
When a considerably large stress is applied to metal-plated organic fibers, a problem arises in that the plating layer is easily peeled off and removed.

Therefore, when producing conductive and electromagnetic shielding molding materials, methods such as kneading that apply large shearing forces to the inorganic conductive fibers and particles to be dispersed are used, such as calendering, extrusion molding, and injection molding. When using a method such as this, it is desirable to develop a method that does not break or 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 fiber. It was rare.

Further, it has been desired that the sheet material has excellent conductivity and electromagnetic shielding properties, as well as excellent bending resistance, and is not damaged by repeated bending during use.

The present invention has excellent conductivity and electromagnetic shielding properties,
In addition, electromagnetic wave shielding molding materials with high bending strength, especially sheet materials and conductive materials, can be uniformly dispersed in the matrix material without damaging them, resulting in excellent reproducibility. It is an object of the present invention to provide a method for producing the electromagnetic wave shielding molding material, particularly a sheet-like material.

[Means and actions to solve the problem]

The electromagnetic shielding molding material of the present invention is a molded article formed from a composition comprising: 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 contained and held in the base. It is characterized by comprising.

The method of the present invention for producing the above-mentioned electromagnetic shielding molding material involves preparing a composition by kneading and dispersing a large number of conductive material-containing dispersions in a matrix made of a moldable polymer material, and molding this composition. In the method, a composition is prepared by mixing and dispersing the conductive material in a polymer material having a melting point higher than the molding temperature of the molded body, and this composition is added to the dispersion. It is characterized in that it is prepared by molding into.

Another electromagnetic wave shielding molding material of the present invention has a base made of a fiber material, and a conductive material-containing coating layer formed on at least one surface of the base, the conductive material-containing coating layer a matrix consisting of a flexible polymeric material;
and a large number of conductive material-containing dispersions kneaded and dispersed in an IJ sock, and the conductive material-containing dispersion has (a) a melting point higher than the temperature of forming the coating layer. and (b) a conductive material held in the base.

In the method of the present invention for producing the above-mentioned molding material, a composition is prepared by kneading and dispersing a number of conductive material-containing dispersions in a matrix made of a flexible polymer material, and this composition is molded. In the method of coating and adhering this molded body onto one side of a substrate made of a fiber material, the conductive material-containing dispersion is coated with a polymer material having a melting point higher than the molding temperature of the molded body. The method is characterized in that it is prepared by mixing and dispersing a conductive material to prepare a composition, and then molding this composition into a dispersion.

In the electromagnetic wave shielding molding material of the present invention, the molded body or the molded body coating layer contains a conductive material contained and held in a substrate made of a polymer material having a specific melting point, and is kneaded and dispersed in the matrix polymer material. It is characterized by containing a conductive material-containing dispersion. The polymer material constituting this substrate has a melting point higher than the molding temperature of the molded article or the molded article coating layer, and therefore does not melt and disperse during the molding of the molded article or the molded article coating layer. They can be dispersed homogeneously in the matrix polymer material as a whole.

Generally, it is preferable to select the matrix-forming polymer material from those whose molding temperature by extrusion method, rolling method, etc. is about 100 to 300°C.

The moldable polymer material constituting the IJ hook as described above is made 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 include thermoplastic resins such as 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.

Synthetic rubbers include 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

Among these materials, polyvinyl chloride, ethylene-vinyl acetate copolymer and polyurethane are preferred, which can be molded into the desired shape at temperatures between 150 and 250°C.

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

The conductive materials contained in the conductive material-containing dispersion include powders of carbon, graphite, conductive metals (e.g., Nikkenope silver, copper, zinc, aluminum, etc.) and conductive metal compounds (e.g., conductive compounds of the above metals, etc.). You can choose from shapes. There is no particular restriction on the shape of such conductive material, and it may have any shape such as granules, flakes, foils, or fibers.
- is preferred.

In the conductive material-containing dispersion used in the present invention, the conductive material is held within the base, but it may be distributed uniformly or locally within the base. However, the conductive materials are in contact with each other within the base, and a portion thereof is exposed on the outer surface of the dispersion, and is in contact with the conductive material held in another dispersion, and the molded body or Preferably, a conductive network can be formed within the molded body coating layer. In order to expose a portion of the conductive material outside the dispersion in this manner, a portion of the polymer material constituting the outer surface portion of the dispersion may be removed by a process such as dissolving, rubbing, or burning. The conductive material dispersion is 1 to
Contains 50% by weight of conductive material and has a specific resistance of 10
It is preferably less than °Ω-Cm, and 10-'Ω-c
It is more preferable that it is less than m. There are no particular restrictions on the shape and dimensions of the dispersion as long as it satisfies the above requirements.
It may have any shape such as fibrous, flaky, foil, or granular. The length of the fibrous dispersion is 0.1 to 5+
It is preferable that it is n+n, it is more preferable that it is 0.3-3 mm, and it is still more preferable that it is 0.5-2 mm. Moreover, it is preferable that the granular, flake-like or foil-like 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 molded body coating layer in a proportion of 1 to 70% by weight, and this content is more preferably 5 to 30%. . This content is determined by the conductivity, electromagnetic shielding and strength characteristics required of the molded product, the type of conductive material, base forming material and IJ Fuchs constituent material, and the method and conditions for forming the molded product or molded product coating layer. It can be determined as appropriate, taking into account such factors as:

In the conductive material-containing dispersion contained in the molded body or molded body coating layer of the present invention as described above, the conductive material is
Since the conductive material is held in the base and does not melt during the molding process, the conductive material will not break, break, fall off, or separate even during processes that are subjected to shear forces such as kneading, extrusion, and rolling. Moreover, the dispersion can be easily dispersed in the matrix to form the desired conductive material network.

The electromagnetic shielding molding material of the present invention, which is composed of a polymer matrix (IJ hook) and a conductive material-containing dispersion dispersed therein, is generally used in the form of a sheet, although its shape is not particularly limited. In the case of sheet-like materials, there are no particular restrictions on the thickness, width, etc., but generally 10
It is practically convenient to have a weight of ~1000 g/m'' and a thickness of 0.01~1.Q mm.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 a conductive material-containing dispersion as described above is formed on at least one surface of a fiber substrate.

The fibers constituting the base of the composite molding material include natural fibers such as cotton and linen; inorganic fibers such as glass fiber, carbon fiber and metal fiber; recycled fibers such as viscose rayon and cupro; Semi-synthetic fibers such as cellulose di- and triacetate fibers, as well as synthetic fibers such as nylon 6, nylon 66, polyester (polyethylene terephthalate),
You can choose from fibers of aromatic polyamides, aromatic polyesters, acrylic polymers, polyvinyl chloride, vinylon, and polyolefins, especially high-strength fibers (15
~50g/d) and/or highly heat resistant fibers can also be used.

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

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

Generally, a sheet-like base fabric is often used as the fibrous base, and useful sheet-like bases include woven fabrics made of twill weave, plain weave, leno weave, leno weave, special knitted fabric, and other general structures. .

There are no particular limitations on the weight or thickness of the base fabric, but it generally has a weight of 30 to 1.000 g/m'' and/or
0.05~1. Preferably, the thickness is Ou.

In the composite molding material of the present invention, the base made of the fiber material can suppress the elongation and deformation of the conductive coating layer, thereby stabilizing the electromagnetic shielding properties of the composite molding material, and
It is effective in improving durability against flapping and repeated bending.

In addition to the conductive material-containing dispersion, the matrix of the molded body or molded body coating layer of the present invention contains known conductive materials such as metal fibers, metal-coated glass fibers, metal flakes, metal powders, carbon fibers, carbon black, antimony chloride powder, copper iodide powder, etc., as well as colorants, plasticizers,
Matrix modifying materials such as stabilizers, fillers, etc. may be included in appropriate amounts as required.

In the composite molding material of the present invention, there are no particular limitations on the weight, thickness, etc. of the conductive material-containing coating layer;
~1.500 g/m'' weight and/or 0.
05-1. Preferably, it has a thickness of On+m.

To produce the composite molding material of the present invention, a conductive molded body consisting of a flexible polymer material matrix and a conductive material-containing dispersion dispersed therein on a predetermined surface of a fibrous substrate; For example, a film may be attached, or a processing liquid having the above composition may be applied onto a predetermined surface of the base fabric and solidified. In order to form such a conductive coating layer, known coating methods such as a calendering method, a laminating method, a topping method, a coating method, and an impregnating method can be used.

〔Example〕

Example 1 In Example 1, 65 parts by weight of polyethylene terephthalate resin were mixed with 55 parts by weight of nickel powder (7,24 x 10-6 Ω-cm) having a particle size of 2.5μ, and the mixture was melt-extruded. , diameter 0.05mm,
A fibrous conductive material-containing dispersion with a length of 1.2 mm was produced. Its specific resistance value is 3. OXl0-'Ω-am.

The above-mentioned conductive material-containing dispersion is mixed in the amounts listed in Table 1,
Mixed into a matrix polymer material having the composition listed in Table 1. The volume content of the conductive material-containing dispersion is approximately 5%
Met. This mixture was heated to 165℃ using a calender machine.
The mixture was kneaded at a temperature of 0.3 mm and rolled into a sheet with a thickness of 0.3 mm. The specific resistance value of this sheet is 5RIS, 230H19
69), When measured by the voltage/current method described in Section 3.1, the measured values listed in Table i were 3 and 8 Xl0-"Ω-c
I got m.

When the obtained sheet was observed in Table 1, it was found that the nickel powder-containing fibrous dispersion was uniformly dispersed in the matrix by kneading and rolling forming, forming a conductive network, and that it had sufficient mechanical properties for practical use. It had strength.

For comparison, a viscous liquid was prepared by stirring and dispersing the composition listed in Table i in 30 parts of Trichlorene without calendering to the extent that the fibrous dispersion was not cut, and this liquid was poured onto a glass plate. The mixture was cast, dried, and gelled at 180°C to produce a sheet with a thickness of 0.3 m+n.

The specific resistance value of this sheet was about 4 xio-''o-Cm.

That is, it can be seen that by using the conductive material-containing dispersion in the present invention, a practically sufficient conductive network can be formed in the sheet even when calendering is performed.

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

That is, to produce metallized fibers, a length of 0.8 m
100 g of polyethylene terephthalate staple fibers (aspect ratio 53) with a diameter of 15 J-m and a diameter of 15 J-
treated with aminopropyltriethoxysilane, dried,
Next, this was mixed with 10 OAg/l of palladium chloride in hydrochloric acid solution.
m! and 10 m1/z of hydrochloric acid, and catalyzed it for 30 minutes at room temperature while thoroughly stirring and dispersing it. This was filtered and dried in a dryer at 110°C.

The catalyzed polyester short fibers were placed in a nickel plating bath with the following composition: (g/l) Nickel sulfate 25 Sodium hypophosphite 30 Malic acid 30 Succinic acid 16 pt (4.5-5.0 g/l) Then, nickel plating was performed at a liquid temperature of 60 to 95°C.

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

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

However, the sheet made by the same casting method as in Example 1 was 7.
．． It showed a good specific resistance of 8Xl0-2Ω-CIll. This indicates that metallized fibers are unsuitable for molding processes where shear forces are intense.

Comparative Example 2 The same operation as in Example 1 was performed. However, instead of the conductive material-containing dispersion, SO33161 stainless steel
Fifty parts by weight of fiber (diameter: 12 m, length: 0.8 mm) was used.

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

When the stainless steel fibers in this sheet were observed, they were found to be finely broken and separated, and even though a large amount of 50 parts by weight was added, no conductive network was observed to form.

However, the sheet made by the same casting method as in Example 1,
It showed a specific resistance value of 6.2 Xl0-"Ω-0m.

This indicates that the use of stainless steel fibers as such is inappropriate for molding processes subject to severe shear forces.

Comparative Example 3 The same operation as in Example 1 was performed. However, instead of the conductive material-containing dispersion, 55 parts by weight of nickel flakes (length: approximately 404 mm) were used as the conductive material.

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

Further, when observing the flakes during shifting, no formation of a conductive network was observed, even though a large amount of 55 parts by weight was added.

However, the sheet made by the same casting method as in Example 1,
It showed a specific resistance value of 2.8 Xl0-'Ω-cm.

This shows that it is inappropriate to use the conductive flakes directly in molding processes where they are subjected to severe shearing forces.

Example 2 (A) Preparation of base fabric The following structure consisting of polyethylene terephthalate multifilament yarns: 750d/250f x 750d/25Of 26 pieces/
Producing a plain weave fabric having 25.4 mtn x 27 pieces/25.4 mm and a weight of 180 g/m',
This was washed and dried in a conventional manner 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 a conductive material-containing dispersion dispersed therein was produced by the method described in Example 1. While it was still hot, a composite sheet was created by applying pressure to both sides of the base fabric.

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

All of these composite sheets exhibited water resistance of 1500 mm or more in the water column.

Tensile strength, elongation, and resistivity of composite sheets (immediately after processing, those subjected to 5,000 bending actions, and
The results are shown in Table 2.

Table 2 [Note] 11: Tensile strength and elongation measurements are based on JIS L 1096 (1
979), 6, Section 2, according to method A.

92: For bending, JIS P 8115 (1976)
The test was carried out with a load of 1 kg.

*3: Resistivity measurement is based on 5RIS 2301 (1969
), Section 3.1, according to the voltage and current method.

The composite sheet of Example 2 exhibited the electromagnetic shielding properties shown in FIG. 1 (measurement method: A37M 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 simple warehouses and awnings that can support high loads and require waterproof properties. Furthermore, it had excellent durability not only against repeated bending but also against changes in resistivity and electromagnetic shielding properties. That is, the composite sheet of the present invention, even after being bent 10,000 times,
The resistivity was on the order of 10-2 Ω-cm, which was the same as before bending.

However, the sheets of Comparative Examples 1 to 3 all had low electromagnetic shielding properties and could not be put to practical use.

Example 3 The same operation as in Example 2 was performed. However, for the fibrous conductive material-containing dispersion, 70°C with a 3% caustic soda aqueous solution
A heating and stirring treatment was performed for 30 minutes to dissolve and remove a portion of the polymer material on the outer surface of the dispersion, thereby increasing the exposed portion of the conductive material particles.

The appearance of the obtained composite sheet was the same as that of Example 2, and exhibited water resistance of 1500+nm water column or higher.

In addition, before bending and bending io of this composite sheet, 00
The resistivity after 0 cycles is 7.5 Xl0-3Ω-a, respectively.
m and 4.5 Xl0-'Ω-cm, which were excellent.

〔Effect of the invention〕

The electromagnetic shielding molding material of the present invention has excellent electromagnetic shielding properties and good mechanical strength, and in particular, the electromagnetic shielding composite of the present invention obtained by combining a base fabric made of fiber fabric. In addition to good tensile strength, the molding material exhibits good resistance to repeated bending. By the method of the present invention, the electromagnetic shielding molding material described above can exhibit the excellent performance described above even after undergoing a molding process that is subjected to severe shearing forces.

[Brief explanation of drawings]

Figure 1 shows the electromagnetic wave frequency (Mflz) and electromagnetic wave shielding property (dB) of one embodiment of the composite molding material of the present invention.
It is a graph showing the relationship between.

Claims (4)

[Claims] 1. A molded article formed from a composition comprising: a matrix made of a moldable polymer material; and a number of conductive material-containing dispersions kneaded and dispersed in the matrix, the conductive material-containing dispersion comprising: is characterized in that it comprises (a) a base made of a polymeric material having a melting point higher than the molding temperature of the molded body; and (b) an electrically conductive material contained and held in the base. Electromagnetic wave shielding molding material. 2. A method of preparing a composition by kneading and dispersing a large number of conductive material-containing dispersions in a matrix made of a moldable polymer material, and molding this composition, the conductive material-containing dispersion is added to the molded body. An electromagnetic wave shield, characterized in that it is prepared by mixing and dispersing a conductive material in a polymer material having a melting point higher than the molding temperature of the composition, and then forming the composition into a dispersion. A method for producing a synthetic molding material. 3. a matrix comprising a base made of a fibrous material and a conductive material-containing covering layer formed on at least one surface of the base, wherein the conductive material-containing covering layer is made of a flexible polymer material; and a large number of conductive material-containing dispersions kneaded and dispersed in the matrix, and the conductive material-containing dispersions are (a) heated to a temperature higher than the temperature of the coating layer molding; An electromagnetic shielding molding material comprising: a base made of a polymer having a melting point; and (b) a conductive material held in the base. 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, and this composition is molded, and this molded body is applied to at least one of a substrate made of a fiber material. In the method of coating and pasting on one surface, a composition is prepared by mixing and dispersing the conductive material in a polymer material having a melting point higher than the molding temperature of the molded body. A method for producing an electromagnetic shielding molding material, which is prepared by molding this composition into a dispersion.