JP2010192550A - Electromagnetic wave shielding composition, molded body of electromagnetic wave shielding composition, electromagnetic wave shielding sheet, and electric wire for electromagnetic wave shielding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electromagnetic wave shielding composition that is high in electromagnetic wave shielding efficiency even when it is a thin film and has high flame retardancy even when it is thin as well as of high strength enough to be handled without crack or breakage even when it is bent. <P>SOLUTION: The electromagnetic wave shielding composition contains 50-200 pts.mass of carbon fiber and 100-350 pts.mass of metal hydroxide to 100 pts.mass of compound polymer containing a proportion of 5-30 pts.mass of thermoplastics, 45-85 pts.mass of thermoplastic elastomer and 5-30 pts.mass of rubber. The electromagnetic wave shielding sheet is made by molding the electromagnetic wave shielding composition into a sheet of 0.05-0.30 mm in thickness, and a coaxial cable uses the electromagnetic wave shielding composition. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a composition that shields electromagnetic noise generated from electronic components and the like. More specifically, it excels in electromagnetic shielding performance that efficiently shields electromagnetic noise generated from semiconductor elements in electronic and electrical equipment, and effectively diffuses heat generated from power sources and light sources used in electronic and electrical products. Excellent thermal conductivity, excellent flame retardancy, and further in the form of a sheet, the composition for shielding electromagnetic waves having such a strength that it can be handled such that it does not break even if bent and does not generate cracks or cracks, and It relates to a molded body.

  In electronic and electrical equipment, electromagnetic noise is generated from electronic components such as semiconductor elements incorporated in the electronic equipment and power supplies. In recent years, electronic and electrical equipment has become more sophisticated and faster, and electromagnetic noise generated from electronic components and power supplies has increased. This causes malfunctions and malfunctions of electronic and electrical equipment. Has become important.

  One of the countermeasure parts is an electromagnetic shielding sheet. As the electromagnetic wave shielding sheet, a metal foil or mesh such as copper or aluminum is known, and the electromagnetic wave noise generated inside is effectively shielded by sticking it to a generating part of a semiconductor element or the like in an electronic / electric device. It is a member for doing.

  Further, an electromagnetic wave absorbing sheet has been developed in which a soft magnetic alloy powder mainly composed of iron is dispersed in a polymer compound such as rubber or thermoplastic elastomer. (For example, see Patent Document 1)

JP 2002-299112 A

  However, the metal foil or mesh electromagnetic wave shielding sheet has a drawback that the mass is increased due to its high density and the rigidity of the electromagnetic wave shielding sheet is high due to the metal and the flexibility is impaired.

  In addition, the invention described in Patent Document 1 is required to perform a strong press in order to increase the magnetic permeability of the flat-shaped soft magnetic alloy powder and increase the density by compression in order to increase the magnetic permeability. There was a problem that the sheet became hard.

  The present invention has been made paying attention to the above-described problems, and its purpose is to have a high electromagnetic shielding performance, high flame retardancy, and a sheet shape of 0.05 mm to 0.30 mm. It is an object to provide an electromagnetic wave shielding composition that is excellent in flexibility that does not crack or crack even if bent at the same time and that also has strength.

The inventors have included a high concentration of carbon fibers and metal hydroxides in a composite polymer in which a specific number of types of polymers are combined in a specific amount, and the carbon fibers are oriented in a certain direction, whereby A molded article having a large dielectric constant was obtained. The molded article having a large relative dielectric constant has a large refractive index, and has been found to reflect and shield electromagnetic waves, and based on the knowledge, the present invention has been made.
That is, the present invention
(1) 50 to 200 parts by mass of carbon fiber and metal water with respect to 100 parts by mass of the composite polymer contained in a ratio of 5 to 30 parts by mass of thermoplastic, 45 to 85 parts by mass of thermoplastic elastomer, and 5 to 30 parts by mass of rubber. An electromagnetic shielding composition obtained by mixing 100 to 350 parts by mass of an oxide;
(2) The electromagnetic shielding composition according to (1), wherein the thermoplastic plastic is polyethylene or polypropylene having a melting point of 120 to 150 ° C,
(3) The electromagnetic shielding composition according to (1) or (2), wherein the thermoplastic elastomer is ethylene vinyl acetate having a vinyl acetate group content of 40 to 60%,
(4) The electromagnetic wave shielding composition according to any one of (1) to (3), wherein the rubber is an ethylene / methyl acrylate copolymer of a binary copolymer,
(5) The electromagnetic shielding composition according to any one of (1) to (4), wherein the carbon fiber is a carbon fiber having an average diameter of 4 to 12 μm and an average length of 25 to 200 μm,
(6) The electromagnetic wave shielding composition according to any one of (1) to (5), wherein an average particle diameter of the metal hydroxide is 10 μm or less,
(7) A molded article obtained by molding the electromagnetic wave shielding composition according to any one of (1) to (6),
(8) An electromagnetic wave shielding sheet formed by molding the electromagnetic wave shielding composition according to any one of (1) to (6) into a sheet shape having a thickness of 0.05 to 0.30 mm,
(9) An electromagnetic shielding wire, wherein the electromagnetic shielding composition according to any one of (1) to (6) is extrusion-coated between layers of the coating layer of the wire,
(10) An electromagnetic wave shielding method comprising placing the electromagnetic wave shielding sheet according to (8) on a cable,
Is to provide.

  According to the present invention, electromagnetic waves generated by semiconductor elements and the like in electronic and electrical equipment are efficiently reflected and shielded, so that electromagnetic noise is not radiated into and out of the equipment, and the cause of malfunction or malfunction can be eliminated. . Furthermore, it is lighter than metal, has flame retardancy even if it is thin, and has excellent strength for electromagnetic wave shielding such that it can be handled without tearing or cracking or cracking even if bent. Can be obtained.

It is a schematic diagram which shows typically the cross section of the electromagnetic wave shielding sheet which concerns on this invention. It is a figure which shows the method of the electromagnetic wave shielding performance test in the Example which concerns on this invention. It is a figure which shows the result of the electromagnetic wave shielding performance test of Example 1 which concerns on this invention. It is a figure which shows the shielding characteristic of the coaxial cable of Example 9 which concerns on this invention.

Hereinafter, embodiments of the present invention will be described in detail.
The electromagnetic wave shielding composition of the present invention is a composition containing carbon fiber and metal hydroxide in a composite polymer obtained by mixing several kinds of polymers such as thermoplastic, thermoplastic elastomer and rubber in a specific ratio. By using the composite polymer, it becomes possible to contain the carbon fiber having electromagnetic shielding properties and the metal hydroxide powder of the flame retardant at a high concentration, and even at a high content of 0.05 to 0. The thin film sheet having a thickness of 30 mm has an electromagnetic wave shielding performance, a flame retardance, and a strength capable of handling such that no tearing or cracking or cracking occurs even when bent.

  First, the composite polymer used in the present invention includes several kinds of polymers such as thermoplastics, thermoplastic elastomers, and rubbers in a predetermined ratio, that is, 5-30 parts by mass of thermoplastics, 45-85 parts by mass of thermoplastic elastomers. The ratio of rubber is 5 to 30 parts by mass, and the total amount is 100 parts by mass.

  Content of the thermoplastic in 100 mass parts of composite polymers used for this invention is 5-30 mass parts, Preferably it is 10-25 mass parts, More preferably, it is 15-25 mass parts. If the proportion of thermoplastic is too small, the content of thermoplastic that greatly contributes to sheet strength will be low, and handling such as being easily broken at thicknesses from 0.05 mm to 0.30 mm will be difficult. Come. On the other hand, if the proportion of the thermoplastic is too high, the composition becomes too hard, for example, a sheet having a thickness of 0.05 mm to 0.30 mm becomes brittle, and cracks and cracks may occur during bending. .

  Examples of the thermoplastic used in the present invention include polypropylene, polyethylene, polyethylene terephthalate, and polybutylene terephthalate. Among them, a melting point of 120 to 150 ° C., which enables mixing at a minimum temperature as the mixing temperature of the polymer such as around 160 ° C. so as to prevent dehydration of the metal hydroxide contained as a flame retardant as much as possible, preferably Polyethylene or polypropylene at 120 to 130 ° C. is preferred. Among them, polypropylene having higher strength is more preferable because of high crystallinity.

  The polyethylene suitably used in the present invention has the above-mentioned melting point, and the high-density polyethylene or the repeating unit having a high density due to the fact that the ethylene of the repeating unit has almost no branch and is linearly bonded. Low-density polyethylene with low density due to ethylene being randomly branched and bonded, and linear low-density with low density and linear units copolymerized with repeating units of ethylene and a small amount of α-olefin Any of polyethylene may be sufficient. Furthermore, modified polyethylene to which a special functional group or acid is added can also be used.

  Polypropylene suitably used in the present invention has the above melting point, and is a homopolymer of a homopolymer, a block type in which ethylene and propylene are block-copolymerized, and a copolymer of ethylene and propylene at random. Any of the random types may be used.

  Polyethylene and polypropylene may be used alone or in combination with any of several kinds.

When the melting point of the thermoplastic is too low, for example, when polyethylene having a melting point of less than 120 ° C. is included and a heat history of 120 ° C. or higher is given, there is a problem that the heat resistance is inferior such that deterioration tends to proceed. is there. In that case, there is a possibility that the sheet becomes hard and brittle due to the heat generated from the heat radiating body when it is incorporated and used in an actual electronic / electrical device, and there is a possibility that it may fall off from the incorporated part. Absent.
On the other hand, when the melting point of the thermoplastic is too high, for example, when polypropylene or the like having a melting point exceeding 150 ° C. is contained, a mixing temperature of 200 ° C. or higher is required when the material of the composition is mixed with a Banbury mixer or a kneader. It becomes. If it does so, dehydration will start in the metal hydroxide which contributes to a flame retardance by the mixing temperature of 200 degreeC or more, and as a result, the flame retardance of the material of the composition may fall and it is unpreferable.

  The content of the thermoplastic elastomer in 100 parts by mass of the composite polymer used in the present invention is 45 to 85 parts by mass, preferably 50 to 80 parts by mass, and more preferably 60 to 70 parts by mass. Thermoplastic elastomers contribute to the inclusion of high concentrations of carbon fiber in electromagnetic shielding powder and metal hydroxide powder of flame retardant, and if the proportion of thermoplastic elastomer is too small, carbon fiber and metal hydroxide powder High concentration is also difficult. If it does so, desired electromagnetic wave shielding property and a flame retardance cannot be acquired, or even if it can be contained, if the obtained thin film sheet is bent very brittle, a crack and a crack may generate | occur | produce. Furthermore, since the thermoplastic elastomer forms a carbonized layer at the time of ignition and thus its ignitability is low, it greatly contributes to the improvement of flame retardancy. Even if its content is reduced, the flame retardancy is also lowered. On the other hand, when the ratio of the thermoplastic elastomer is too large, the content of the thermoplastic elastomer that is inferior in strength to that of the thermoplastic plastic increases, so that the strength of the material having the composition decreases. Then, in the case of a thin film sheet having a thickness of 0.05 mm to 0.30 mm, it may be broken, and there may be a problem that it cannot be handled.

  Examples of the thermoplastic elastomer used in the present invention include ethylene vinyl acetate and ethylene ethyl acrylate. Among them, ethylene vinyl acetate having a vinyl acetate group content of 40 to 60%, preferably 40 to 50%, which is effective for imparting flame retardancy and strength, is suitable.

  If the vinyl acetate group content is too small, 20mm vertical combustion test 94V-2 or higher in UL94 "Plastic material flammability test for equipment parts" at 0.05mm to 0.30mm thickness or thin material vertical combustion test 94VTM It is not preferable because it becomes impossible to obtain a vertical flame retardancy of −2 or more. This is because if the vinyl acetate group content is low, the crystallinity increases and the behavior becomes similar to that of thermoplastics such as polyethylene and polypropylene, and the formation of a carbonized layer during ignition is reduced, making it more flammable and flame retardant. This is because the property decreases. When the vinyl acetate group content is large, the rubber is close to an amorphous and flexible rubber, and the formation of a carbonized layer at the time of ignition increases, so that the ignitability is lowered and the flame retardancy is improved.

  On the other hand, if the vinyl acetate group content is too large, a thin film sheet having a thickness of 0.05 mm to 0.30 mm may be broken and cannot be handled. This is because, if the vinyl acetate group content is large, as described above, it becomes a behavior close to that of an amorphous and flexible rubber, and the strength is lowered.

The rubber content in 100 parts by mass of the composite polymer used in the present invention is 5 to 30 parts by mass, preferably 5 to 25 parts by mass, and more preferably 10 to 20 parts by mass. When the proportion of rubber is too small, the rubber contributes greatly to the inclusion of high concentrations of carbon fiber in the electromagnetic shielding powder and metal hydroxide powder of the flame retardant. When the proportion decreases, the carbon fiber and the metal hydroxide It becomes difficult to contain a high concentration of the powder of the product. If it does so, desired electromagnetic wave shielding property and flame retardance cannot be obtained, or even if it can be contained, the obtained thin film sheet is very brittle, and if bent, cracks and cracks may occur and handling may not be possible. On the other hand, when the ratio of rubber is too large, the content ratio of rubber inferior in strength compared to thermoplastics and thermoplastic elastomers increases, and the strength of the composition decreases, resulting in a thin film sheet having a thickness of 0.05 mm to 0.30 mm. There are cases where problems arise, such as being broken and unable to be handled.
In the present invention, the “rubber” does not include a thermoplastic elastomer.

  Examples of the rubber suitably used in the present invention include acrylic rubber, ethylene propylene rubber, and ethylene / methyl acrylate copolymer. Of these, an ethylene / methyl acrylate copolymer is preferable. The reason for this is that during the mixing of materials, thermoplastics and thermoplastic elastomers plasticize and decrease in viscosity when heated, but rubber only softens and has a relatively high viscosity. This is because the temperature is likely to rise due to heat generation, whereas the ethylene / methyl acrylate copolymer is suitable because it has low viscosity and green strength and thus has low shear heat generation during mixing of materials.

  The ethylene / methyl acrylate copolymer includes a binary copolymer and a ternary copolymer, either of which may be used, but the binary copolymer is more preferable. The reason is that, in the case of a ternary copolymer, it has a carboxylic acid monomer that reacts with a specific amine to become a crosslinking point, and therefore, if necessary, an ethylene / methyl acrylate copolymer containing an amine material. This is because the strength of the thin film sheet is excessively increased and the thin film sheet becomes brittle. Even when other polymers or powders contain trace amounts of amines as impurities or when such amines do not exist, the carboxylic acid monomer is used as a crosslinking point in high temperature and high humidity environments. However, there is a concern that the crosslinking may proceed. On the other hand, since the binary copolymer does not have a carboxylic acid monomer serving as a crosslinking point, such a concern is eliminated.

  The polymer in the present invention is a composite polymer obtained by mixing a plurality of types of polymers such as the above-described thermoplastics, thermoplastic elastomers, and rubbers at a predetermined ratio.

  In the electromagnetic wave shielding composition of the present invention, the carbon fiber contains 50 to 200 parts by mass, preferably 75 to 175 parts by mass, and more preferably 100 to 150 parts by mass with respect to 100 parts by mass of the composite polymer. If the carbon fiber content is too small, the distance between the carbon fibers inside the sheet is too large, and the desired electromagnetic shielding performance cannot be obtained. On the other hand, when the carbon fiber content is too high, the content ratio of the powder material including both the carbon fiber powder and the metal hydroxide powder with respect to the composite polymer is too high, and mixing becomes difficult or mixing was possible. However, if the powder cannot be sufficiently bound with the polymer and the thin film sheet becomes very brittle and bent, cracks and cracks may occur.

  Carbon fibers are made by firing organic fibers such as heating and oxidation, but the carbon fibers used in the present invention may be coal tar pitch or petroleum, even if they are PAN-based polyacrylonitrile as a raw material. Any pitch system using pitch or coal pitch as a raw material may be used. The average diameter of the carbon fibers is preferably 4 to 12 μm, more preferably 6 to 10 μm. The average length of the carbon fiber is preferably 25 to 200 μm, more preferably 30 to 70 μm.

  When the average diameter of the carbon fiber is too thin or the average length is too short, the bulk density of the carbon fiber is increased, it is difficult to mix, the compound is hardened, and the flexibility is impaired.

  On the other hand, when the average diameter of the carbon fibers is too large or the average length is too long, if the thin film sheet is bent brittlely, it becomes unpreferable because cracks and cracks are generated and the film cannot be handled. This is because thick or long fibrous powders are less likely to be bound because the polymer is less likely to cling to the surroundings.

  In the electromagnetic wave shielding composition of the present invention, the metal hydroxide contains 100 to 350 parts by mass, preferably 200 to 300 parts by mass, and more preferably 240 to 300 parts by mass with respect to 100 parts by mass of the composite polymer. The If the metal hydroxide content is too low, the thin flame of 0.05mm to 0.30mm and the vertical flame retardant of ULV94 20mm vertical combustion test 94V-2 or more or thin material vertical combustion test 94VTM-2 or more High flame retardance cannot be obtained. On the other hand, if the content of the metal hydroxide is too high, the content ratio of the powder material including both the metal hydroxide powder and the carbon fiber powder with respect to the composite polymer is too high, and mixing becomes difficult or cannot be mixed. Even if these powders cannot be sufficiently bound with the polymer and the thin film sheet is bent very brittle, cracks and cracks may occur.

Examples of the metal hydroxide suitably used in the present invention include magnesium hydroxide and aluminum hydroxide, and the surface thereof may be subjected to fatty acid treatment, titanate treatment or silane treatment. The average particle size of the metal hydroxide is preferably 10 μm or less, and more preferably 0.8 to 2.0 μm.
When the average particle size is too large, there are particles with a particle size of 50 μm or more depending on the particle size distribution, and particles with a particle size exceeding the thickness of the sheet when the thickness is 0.05 mm to 0.05 mm. This is not preferable because the metal hydroxide powder having a particle size larger than the sheet thickness is broken off.

  The electromagnetic wave shielding composition of the present invention may contain an anti-aging agent, a lubricant, a colorant, a plasticizer, an oil and the like as necessary within the range not impairing the characteristics of the present invention.

  According to this embodiment, the electromagnetic wave shielding composition according to this embodiment has a high relative dielectric constant because it contains carbon fiber at a high concentration. Further, by orienting the carbon fibers in a certain direction, the electromagnetic shielding composition according to the present embodiment can achieve a larger relative dielectric constant. The electromagnetic wave shielding composition according to this embodiment has a high relative dielectric constant, and thus can totally reflect electromagnetic waves and has high electromagnetic wave shielding performance.

  Moreover, since the composition for electromagnetic wave shielding which concerns on this embodiment contains a metal hydroxide compound in high concentration, it has high flame retardance.

  Moreover, the electromagnetic wave shielding composition according to the present embodiment has such a strength that it can be handled such that even if it is bent as a thin film sheet having a thickness of 0.05 mm to 0.30 mm, it will not be broken or cracked or cracked.

  Moreover, since the composition for electromagnetic wave shielding which concerns on this embodiment contains the carbon fiber of heat conductive powder in high concentration, it has high heat conductivity.

  In addition, the electromagnetic wave shielding composition according to the present embodiment is halogen-free because no substance containing a halogen element is used.

  In addition, since the electromagnetic wave shielding composition according to this embodiment can produce a molded body without using silicone rubber, siloxane is not generated from the molded body, and the electrical contact portion is not adversely affected.

  Another embodiment of the present invention is an electromagnetic wave shielding sheet obtained by molding the electromagnetic wave shielding composition according to the present invention into a sheet shape having a thickness of 0.05 to 0.30 mm. The thickness of the sheet is preferably 0.08 to 0.20 mm, and more preferably 0.08 to 0.12 mm. When the sheet thickness is too thin, even a predetermined composition material may be broken and difficult to handle. On the other hand, if the sheet thickness is too thick, the arrangement of the carbon fibers in the sheet is randomly arranged in the surface direction and the thickness direction, which is not preferable because the electromagnetic wave shielding property is lowered.

  FIG. 1 is a schematic view schematically showing a cross section of an electromagnetic wave shielding sheet according to the present invention. The illustrated electromagnetic wave shielding sheet 1 is molded in a state where the carbon fibers 3 and the metal hydroxides 4 are almost uniformly dispersed in the composite polymer 2, and the carbon fibers 3 are arranged in a substantially constant direction. . In particular, when the electromagnetic wave shielding sheet is formed by calendar roll molding or extrusion molding, the carbon fiber 3 has high orientation, the relative dielectric constant of the electromagnetic wave shielding sheet 1 is higher, and the electromagnetic wave shielding performance is higher.

  Another embodiment of the present invention is an electromagnetic wave shielding electric wire coated with the electromagnetic wave shielding composition according to the present invention. The electromagnetic wave shielding composition according to the present invention can cover general electric wires and cables. Since the carbon fibers are oriented in the longitudinal direction of the electromagnetic shielding wire, the electromagnetic shielding wire according to the present invention has higher electromagnetic shielding performance.

  The method for molding the electromagnetic wave shielding molded product of the present invention is not particularly limited. For example, the materials are mixed using a commonly used Banbury mixer, kneader, etc., and the mixture is calendered by an ordinary method, open roll It can be formed into a sheet by molding, press molding, extrusion molding or the like. In addition, these shapes can be formed into a different shape, a line shape, a tube shape, a coating on an electric wire, or the like by a single or a combination.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example and a comparative example, this invention is not limited to this.

(Example 1 to Example 8)
Novatec FX4G manufactured by Nippon Polypro Co., Ltd., which has a melting point of 125 ° C., is used for polypropylene, which is a thermoplastic plastic, and is made by Bayer Co., Ltd., which has a 40% vinyl acetate group content in an ethylene-vinyl acetate copolymer, which is a thermoplastic elastomer. Tevajin using Revaprene 400HV, a binary copolymer, Baymac DP manufactured by Mitsui DuPont Polychemical Co., Ltd., as the rubber ethylene-methyl acrylate copolymer, with carbon fiber having an average diameter of 8 μm and an average length of 50 μm Lacima R-A201 manufactured by Co., Ltd. was used, and Mag Seeds N-4 manufactured by Kamishima Chemical Co., Ltd. having an average particle size of 1.1 μm was used for magnesium hydroxide, which is a metal hydroxide. Compounding amounts (parts by mass) in each example shown in Tables 1 and 2 were kneaded with a Banbury mixer to obtain an electromagnetic wave shielding composition. This electromagnetic wave shielding composition was molded into a sheet shape with a calender roll, Sheets having thicknesses of 0.05 mm to 0.30 mm shown in Table 1 were obtained.

(Comparative Examples 1 to 10)
Except for the mixing ratios shown in Table 2, the same materials as in Examples 1 to 7 were used and molded by the same method to obtain sheets having thicknesses of 0.05 mm to 0.30 mm shown in Table 2. It was.

(Measurement of noise reduction)
A sample sheet was placed on a flat cable as shown in FIG. 2, and noise was measured with a spectrum analyzer. First, a signal (Po) is input from a transmitter (tracking generator) to the BNC connector 1 (hereinafter referred to as BNC1), and the output of the BNC2 is read by a spectrum analyzer 100 to 1000 MHz. This value is Pin. At this time, BNC3 and BNC4 terminate with a BNC connector incorporating 50 ohms. (Hereafter referred to as “50Ω termination”)
Input the same signal as the Pin measurement to BNC1. BNC2 and BNC3 are 50Ω terminated. Similarly, the output of BNC4 is measured with an analyzer, and this value is defined as FEPout. The far end crosstalk (FEXT) is obtained by the following equation.
FEXT [dB] = (FEPout) − (Pin)
Measure FEXT for both the case where the sample sheet is not placed on the flat cable and the case where the sample sheet is placed. FIG. 3A shows FEXT characteristics when the sample sheet according to Example 1 is not placed. FIG. 3B shows FEXT characteristics when the sample sheet according to Example 1 is placed. Comparing FIG. 3 (a) and FIG. 3 (b), a sample sheet having a reduction effect of 10 dB or more in the 100 to 1000 MHz region with a far-end crosstalk characteristic is acceptable.

(UL94 thin material vertical combustion test)
UL94, which is evaluated and evaluated by Underwriters Laboratories, an organization that grants approval for products that meet product safety standards aimed at standardization of functions and safety, from materials, equipment, parts, tools, etc. to products. It conformed to the thin material vertical combustion test in "Flammability test of plastic materials for equipment parts". This test is also performed for a material that is distorted, shrunk, or burns out to the clamp because the material is thin when the 20 mm vertical combustion test in UL94 is performed. Since the electromagnetic wave shielding thin film sheet of the present invention is as thin as 0.05 mm to 0.30 mm, this thin material vertical combustion test was performed.
It is 94VTM-2 or higher.

(Sheet winding test)
For example, there is a situation where a specified sheet must be bent when it is set in an electronic or electrical device. At this time, if the piece is broken or cracked or cracked even if it is bent slightly, the productivity of assembling the electrical and electronic equipment is greatly reduced, and the product cannot be realized. Having strength that can be handled means strength that does not cause tearing or cracking or cracking even if it is bent.
In response to this, the winding additional heat test of the JIS C 3005 rubber / plastic insulated wire test method was referred to. That is, a wire sample is tightly wound or bent around a cylinder with a specified diameter for a specified number of times, and is left as it is for 1 hour after being heated in a constant temperature bath and cracked and cracked on the surface of the sample. It is to check whether it is visually. In this test, when a specified sheet was wound around a cylindrical rod having a diameter of 1.0 mm, it was determined whether it was torn or cracked or cracked. This was carried out with the actual product, and the same test was carried out with a specified sheet in which no tearing or cracking or cracking occurred and a thermal history of 1000 hours at 120 ° C.
Those that do not tear or crack or crack are acceptable.

  As shown in Table 1, the electromagnetic wave shielding sheets of Examples 1 to 8 have a noise reduction effect of 10 dB or more. In the UL94 thin material vertical combustion test, Example 6 containing 100 parts by mass of magnesium hydroxide having an average diameter of 1.1 μm was 94 VTM-2, and Examples 1 to 5 containing 270 parts by mass and 350 parts by mass were used. Examples 6 through 8 have 94VTM-0. Furthermore, in the sheet winding test, it has a strength that does not cause tearing or cracking or cracking even when it is wound around the actual product and a cylindrical rod having a diameter of 1.0 mm after a heat history of 120 ° C. for 1000 hours. As described above, it is confirmed that the electromagnetic wave shielding thin film sheet of the present invention is excellent in electromagnetic wave shielding properties and has high flame resistance even when it is thinner, and also has a strength that can be handled.

On the other hand, the 0.15 mm thick sheet of Comparative Example 1 in which the thermoplastic plastic of Table 2 is less than 5 parts by mass has low strength and is broken when handled around a cylindrical rod having a diameter of 1.0 mm. It turns out that is difficult.
The 0.15 mm thick sheet of Comparative Example 2 in which the thermoplastic plastic of Table 2 exceeds 30 parts by mass was cracked and cracked when wound around a cylindrical rod having a diameter of 1.0 mm because the composition was too hard. It turns out that it is difficult to handle.
The 0.15 mm thick sheet of Comparative Example 3 with less than 45 parts by mass of ethylene vinyl acetate, which is the thermoplastic elastomer of Table 2, is brittle, and cracking and cracking occur when wound around a cylindrical rod with a diameter of 1.0 mm, making it difficult to handle I understand that.
The 0.15 mm thick sheet of Comparative Example 4 in which ethylene vinyl acetate, which is the thermoplastic elastomer of Table 2, exceeds 90 parts by mass, has low strength and is broken when handled around a cylindrical rod having a diameter of 1.0 mm. I find it difficult.
The 0.15 mm thick sheet of Comparative Example 5 in which the ethylene / methyl acrylate copolymer, which is the rubber of Table 2, is less than 5 parts by mass is brittle, and when wound around a cylindrical rod having a diameter of 1.0 mm, cracks and cracks are generated and handled. It turns out that is difficult.

The 0.15 mm thick sheet of Comparative Example 6 in which the ethylene / methyl acrylate copolymer, which is the rubber of Table 2, exceeds 30 parts by mass has low strength and is broken when wound on a cylindrical rod having a diameter of 1.0 mm. It turns out that handling is difficult.
It can be seen that the 0.15 mm thick sheet of Comparative Example 7 in which the carbon fiber of Table 2 is less than 50 parts by mass has a low noise reduction amount of 5 dB and is inferior in electromagnetic wave shielding.
It can be seen that the 0.15 mm thick sheet of Comparative Example 8 in which the carbon fiber in Table 2 exceeds 200 parts by mass is brittle and cracks and cracks occur when wound around a cylindrical rod having a diameter of 1.0 mm, making it difficult to handle.
The 0.30 mm thick sheet of Comparative Example 9 in which magnesium hydroxide, which is the metal hydroxide of Table 2, is less than 100 parts by mass does not have vertical flame retardancy such as the UL94 thin material vertical combustion test 94 VTM-2 or higher. Recognize.
The 0.15 mm thick sheet of Comparative Example 10 in which magnesium hydroxide, which is the metal hydroxide of Table 2, exceeds 350 parts by mass is brittle, and when wound around a cylindrical rod having a diameter of 1.0 mm, cracks and cracks are generated and handled. I find it difficult.

Example 9
A coaxial cable coated with the electromagnetic wave shielding composition described in Example 1 was prototyped. An annealed copper wire having a diameter of 0.65 mm is used as the conductor, and the conductor is covered with a crosslinked polyethylene having a thickness of 1.69 mm as an insulator, and the electromagnetic shielding described in Example 1 having a thickness of 0.50 mm is used as a first shield. The coaxial cable, which is covered with a composition for use, further covered with a braid of an annealed copper wire with a braid density of 85% and a diameter of 0.12 mm as a second shield, and further with a black non-halogen sheath having a thickness of 1.0 mm as a sheath, was made as an experiment.

(Evaluation of shielding characteristics of coaxial cable)
The shielding characteristics of the coaxial cable in the frequency region of 30 MHz or higher were evaluated by the absorbing clamp method. The result is shown in FIG.

  As shown in FIG. 4, the coaxial cable according to Example 9 exhibited a shielding characteristic of −50 dBm or more in a frequency region of 30 MHz or more. On the other hand, when the coating with the electromagnetic wave shielding composition is not performed, that is, when shielding is performed only with a braid of an annealed copper wire having a braid density of 85%, it is known that a shielding characteristic of about −30 dBm is exhibited. Therefore, a noise reduction effect of 20 dB or more was obtained by coating with the electromagnetic wave shielding composition according to Example 1.

DESCRIPTION OF SYMBOLS 1 ......... Electromagnetic wave shielding sheet 2 ......... Composite polymer 3 ......... Carbon fiber 4 ......... Metal hydroxide

Claims (10)

  Carbon fiber 50-200 parts by mass and metal hydroxide 100 with respect to 100 parts by mass of the composite polymer contained in a proportion of 5-30 parts by mass of thermoplastic, 45-85 parts by mass of thermoplastic elastomer, 5-30 parts by mass of rubber. The composition for electromagnetic wave shielding characterized by including -350 mass parts.   The electromagnetic shielding composition according to claim 1, wherein the thermoplastic plastic is polyethylene or polypropylene having a melting point of 120 to 150 ° C.   The electromagnetic shielding composition according to claim 1 or 2, wherein the thermoplastic elastomer is an ethylene-vinyl acetate copolymer having a vinyl acetate group content of 40 to 60 mass%.   The electromagnetic wave shielding composition according to any one of claims 1 to 3, wherein the rubber is an ethylene / methyl acrylate copolymer of a binary copolymer.   5. The electromagnetic wave shielding composition according to claim 1, wherein the carbon fibers are carbon fibers having an average diameter of 4 to 12 μm and an average length of 25 to 200 μm.   6. The electromagnetic wave shielding composition according to claim 1, wherein the metal hydroxide has an average particle size of 10 μm or less.   The molded object which consists of a composition for electromagnetic wave shielding of any one of Claims 1-6.   An electromagnetic wave shielding sheet formed by molding the electromagnetic wave shielding composition according to any one of claims 1 to 6 into a sheet shape having a thickness of 0.05 to 0.30 mm.   An electromagnetic wave shielding electric wire obtained by extrusion coating the electromagnetic wave shielding composition according to any one of claims 1 to 6 between layers of an electric wire covering layer.   An electromagnetic wave shielding method comprising placing the electromagnetic wave shielding sheet according to claim 8 on a cable.