JPH01187706A - Electromagnetic shielding material - Google Patents

Abstract

PURPOSE:To increase shielding effect and reduce the weight by doping dopant to polyacethylene. CONSTITUTION:For doping dopant, polyacetylene is exposed in gas dopant, polyacetylene is immersed in solution including dopant, or ion implantation method is taken. Dopant is doped to polyacethylene for increasing its conductivity, and the dopant can be any if it increases the conductivity. Obtained material has a large conductivity and a good shielding effect, and because it consists of polyacethylene, its specific gravity is extremely small compared to metal filler, thereby the weight can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an electromagnetic shielding material, and more particularly to an electromagnetic shielding material used for the casing of electrical equipment and components within the electrical equipment.

<Conventional technology> Conventionally, casings for electrical equipment such as televisions, video table recorders, word processors, personal computers, industrial robots, and vending machines, as well as parts within electrical equipment, have been used to reduce weight and cost. Plastic molded products are widely used.

However, since plastic is an electrical insulator and has almost no shielding function against electromagnetic waves, the above plastic molded products are unable to prevent interference, such as malfunctions, caused by electromagnetic waves generated by other electrical equipment. Therefore, it is not possible to prevent leakage of electromagnetic waves generated from parts housed within the plastic molded product.

In view of the above points, a technique for preventing interference caused by electromagnetic waves by imparting conductivity to plastic is being considered. In other words, methods for imparting conductivity to a plastic casing include applying a conductive paint containing a conductive material to the surface of the plastic casing to form a conductive film; The method of molding plastics has been mainly studied, and the conductive material used is a conductive filler made of copper, silver, nickel, etc. in the form of powder, flakes, fibers, etc.

More specifically, the conductive paint usually contains the conductive filler, a resin such as an acrylic resin, an epoxy resin, a polyester, and optionally additives such as an antioxidant and an antisettling agent. After applying the conductive paint to the plastic casing, it is cured at a temperature between room temperature and about 800°C to form a conductive film on the surface of the plastic casing, imparting conductivity to the plastic casing. are doing. In particular, when using a conductive paint containing silver as a conductive filler,
A conductive film of conductive dust I X 103 to I X 105 S/c+a is obtained, and is said to have the greatest shielding effect at present.

On the other hand, when a conductive plastic containing a conductive material is molded, the maximum amount of conductive dust in the conductive plastic casing is approximately 1×10 3 S/cm.

However, according to the above-mentioned conductive paints and conductive plastics, the conductive filler is a metal filler and not only has a high specific gravity but also requires a large amount of conductive filler to obtain a certain amount of conductive dust, so it has no shielding effect. When a large amount of conductive filler is added to increase the conductive filler, especially in the case of conductive plastic molded products, the weight increases and handling becomes complicated. In addition, if the amount of conductive filler added increases, the film forming properties of conductive paint and the moldability of conductive plastic will be impaired, so there is a certain limit to the amount of conductive filler added, and the shielding effect It is difficult to increase

Therefore, even if electromagnetic shielding is processed using conventional technology,
Powerful electromagnetic waves can cause computers and other devices to malfunction, so there is a need to further improve shielding effectiveness. In particular, electrical equipment for aviation and space applications is required not only to improve the shielding effect but also to be lightweight, and these requirements cannot be met.

<Objective of the Invention> The present invention has been made in view of the above-mentioned problems, and an object thereof is to provide an electromagnetic shielding material that has an excellent shielding effect and can be lightweight.

Means and Effects for Solving the Problems> In order to achieve the above object, the electromagnetic shielding material of the present invention is made of polyacetylene doped with a dopant.

According to the electromagnetic shielding material with the above configuration, since polyacetylene is doped with a dopant, conductive dust is large and
Great shielding effect.

Furthermore, since it is made of polyacetylene, its specific gravity is significantly lower than that of the metal filler, and it can be made lighter.

In addition, electromagnetic shielding materials whose dopant is iodine are
Especially conductive dust is large. The polyacetylene doped with Donivant is preferably in the form of a thin film, powder, granules, flakes or fibers.

The present invention will be explained in detail below.

The above-mentioned polyacetylene may be either cis-type or trans-type, and the polyacetylene can be produced by a conventional method, using a Ziegler-Natsuta type catalyst, for example, an AJ(C2H5) s・T i CJa type catalyst. ,
AJ (C2Hs) 3 ・Ti(OC4Hs)
4-based catalyst, AJ(C2Hs) s ・V O(CH
3COCHCOCH3) 2-system catalyst, NaBH3・N
Polyacetylene can be produced by introducing acetylene gas under normal pressure or reduced pressure in the presence of a 1CJ2 .P (Ce Hs ) 3-based catalyst, or by polymerizing acetylene with radiation. In order to form an electromagnetic shielding material on the surface of the shielded member, the catalyst composition is adjusted by adding silicone oil, n-butyllithium, etc. to the various catalysts mentioned above, and the catalyst composition is applied to the shielded member. It may be applied and polymerized on the surface of the shielded member. Although the polyacetylene produced by the above method may be amorphous, crystalline polyacetylene is preferable from the viewpoint of stability.

By controlling the polymerization conditions, polyacetylene in the form of powder, flakes, fibers, or thin film can be obtained.

The above polyacetylene is doped with a dopant to increase its electrical conductivity. The above-mentioned dopant is not particularly limited, and any dopant can be used as long as it increases the electrical conductivity. Such dopants include electron-accepting dopants, such as CJ2, Br2.12, ICJ
, ICJ3, halogen or interhalogen compounds such as IBr, PF5, AsF5, SbF5, FeC15
, FeCl2, AJCJ3, N1CJz, BF3,
BCno3, BBr3, AgCJO4, AgBF4,
FSO200SO2FSH2S04, HCno04, H
3PO4, (NO2)(SbFe), (No)(Sb
CJs), (NO2) (BF4), S03, HNO
3. Electron donating dopants such as Lewis acids or protic acids such as FSO3H, CF3SO3H, e.g. N
a5KSLi, Rh.

Examples include alkali metals such as Cs. Note that among the above-mentioned dopants, iodine is preferable because of its high electrical conductivity and electromagnetic shielding effect. One or more of the above dopants may be used.

The doping amount of the above-mentioned dopant is not particularly limited, and can be set as appropriate depending on the type of dopant, etc.
Usually, about 0.01 to 0.5 mol per +CH+ unit constituting the polyacetylene is preferable, and particularly when the dopant is iodine, it is preferably doped with 0.01 to 0.25 mol per unit constituting the polyacetylene. When the amount of dopant is less than 0.01 mol, it is difficult to sufficiently increase the conductivity. In addition, the above-mentioned dopant is usually 10 to 25 with respect to polyacetylene.
0% by weight, preferably 50-200% by weight.

Doping with the dopant is carried out by conventional methods, such as exposing the polyacetylene to a gaseous dopant, immersing the polyacetylene in a solution containing the dopant, or ion implantation. Note that the gaseous dopant can be obtained at room temperature or under heating conditions and under normal pressure or reduced pressure depending on the vapor pressure of the dopant, and the solution containing the dopant can be obtained as an aqueous solution or an organic solvent solution depending on the type of dopant. can be used. The concentration and immersion time of the gaseous dopant and solution dopant are as follows:
The doping amount can be set as appropriate depending on the desired doping amount, and doping may be performed under heating.

The shape and size of the polyacetylene doped with a dopant are not particularly limited, and any suitable shape can be used depending on the form of use, but powder/body, flake, fiber, or thin film shapes are preferred.

When the polyacetylene is in the form of powder, flakes or fibers, it can be mixed into the molding resin or paint and used as a conductive plastic or paint. Examples of the molding resin include polyolefins such as polyethylene, polypropylene, and ionomers, ethylene-vinyl acetate copolymers, acrylic resins,
Examples include thermoplastic resins such as styrene resin, polyester, polycarbonate, polyamide, styrene-butadiene copolymer, and styrene-acrylonitrile copolymer, and thermosetting resins such as epoxy resin, urethane resin, and phenol resin. The above resins may be used alone or in combination of two or more.

Note that the conductive plastic containing polyacetylene may be used to form a casing for an electrical device or a component in an electrical device, or may be formed into a film or sheet that can cover the casing or the like.

In addition, the conductive paint is made of polyacetylene, synthetic resins such as the above resins and alkyd resins, solvents such as water and organic solvents, various additives such as plasticizers, antioxidants, and leveling materials, and colorants if necessary. , fillers, etc. Furthermore, since the specific gravity of the polyacetylene is small, it is not necessarily necessary to add an anti-settling agent as in the past.

In addition, when polyacetylene is in the form of fibers, since the polyacetylene is entangled in the conductive plastic casing and the paint film, conductive dust can be increased with a small amount added.

The content of the polyacetylene is used in an appropriate amount depending on the type of dopant, the shape and size of the polyacetylene, and is usually 1 to 50% by weight, preferably 5 to 30% by weight.

If the content of doped polyacetylene is less than 1% by weight, the shielding effect will not be sufficient, and if it exceeds 50% by weight, moldability etc. will be insufficient. Note that doped polyacetylene not only has a low specific gravity but also has a large amount of conductive dust, so it is lightweight and can enhance the shielding effect with a small amount of content.

Further, when the polyacetylene is in the form of a thin film, the shielding efficiency can be increased by covering the plastic casing of an electrical device with the thin film of polyacetylene by means such as adhesion, without using it in combination with the above-mentioned resin or the like.

Hereinafter, a method for producing the doped thin film polyacetylene using a polymerization catalyst will be described with reference to the accompanying drawings.

First, a substrate (2) coated with a polymerization catalyst, for example, a coating solution containing the catalyst, is placed in a reaction vessel (1) that can be depressurized, and the reaction vessel (1) is depressurized to a predetermined pressure. The raw material acetylene gas (4
) is introduced and polymerized on the substrate (2) for a predetermined period of time.

The polyacetylene (3a) polymerized on the base material (2) is stretched together with the base material (2), and after washing with a solvent such as toluene, the polyacetylene (3a) is peeled off from the base material (2) to form a polyacetylene film (3b). get.

Next, the polyacetylene film (3b) is doped by immersing it in a dopant solution or exposing it to a gaseous dopant to obtain a dopant-doped polyacetylene film (5).

The acetylene polymerization reaction can be carried out at an appropriate temperature, under reduced pressure conditions, and at an appropriate amount of acetylene feed, and by controlling the polymerization conditions, the various forms of polyacetylene can be produced. In addition, there is no need to use a substrate coated with a coating solution containing a catalyst,
The catalyst is used in an appropriate form depending on the desired form of polyacetylene.

As mentioned above, the electromagnetic shielding material of the present invention is lightweight,
Furthermore, since the conductive dust is large, it is possible to prevent problems such as malfunctions caused by electromagnetic waves between electrical devices or between parts within the device, and it is also possible to reduce the weight of the casing, which can be used for aircraft, rockets, etc. Fuel consumption can be saved by using it in mobile electrical equipment such as.

<Examples> The present invention will be described in more detail below based on Examples.

Example Using the polymerization reactor shown in the figure, a thin film of polyacetylene was prepared and doped with iodine in the following manner.

That is, 50 ml of silicone oil (polydimethylsiloxane, manufactured by Shin-Etsu Chemical Co., Ltd., trade name KF96) and AJ
(C2H5) 330m1 and T i (OC4H9
) After aging and degassing a catalyst consisting of 440 ml at 120°C for 2 hours, 30% by weight of n-butyllithium was added to this catalyst to prepare a coating solution containing the catalyst, and the coating solution was used as a base. It was coated on a high-density polyethylene film (2).゛The above polyethylene film (2) is placed in a reaction vessel (1) made of Pyrex glass, and after the pressure is evacuated to 10-2 Torr, acetylene gas (4) as a raw material is introduced into the reaction vessel (1). Polymerization was carried out on the polyethylene film (2) for 5 hours. After synthesizing polyacetylene (3a), it was stretched 5 times along with the polyethylene film, washed with toluene, and then peeled off from polyethylene film (3) to obtain polyacetylene film (3b).

Next, the polyacetylene film (3b) was immersed in a solution of 2.65 g of iodine/100 ml of carbon tetrachloride for 1 hour to obtain a polyacetylene film (5) doped with iodine.

- Comparative Example 1 Contains toluene as an organic solvent, 15% by weight of acrylic resin in solid content, and 50% by weight of copper powder as metal filler
A conductive paint was prepared by mixing and dispersing a conductive paint containing trace amounts of an antioxidant and an antisettling agent.

Comparative Example 2 A conductive paint was prepared in the same manner as in Comparative Example 1, except that silver powder was used in place of the copper powder in Comparative Example 1.

Then, when a conductive film was formed using the conductive paints of Comparative Examples 1 and 2 and the conductivity and density of the conductive film were measured, the conductive film of Comparative Example 1 had a conductivity of 5X
102S/cm, density 5, Og/aA, and the conductive film of Comparative Example 2 has a conductivity of about I×104S/cII1
1 density was approximately 6.0 g/-. On the other hand, the conductivity and density of the doped polyacetylene film (5) of Example are 1.7×105 SΔh density 1.1
5 g/cj, which revealed that it not only had higher conductivity and greater shielding effect than the conductive paint of the comparative example, but was also significantly lighter.

<Effects of the Invention> As described above, since the electromagnetic shielding material of the present invention is made of polyacetylene doped with a dopant, it has high conductivity and excellent shielding effect, and since it is made of polyacetylene, it has a higher electrical conductivity than the metal filler. It has an extremely low specific gravity and has the unique effect of being lightweight.

[Brief explanation of the drawing]

The figure is a process diagram showing one method for producing doped polyacetylene. Patent applicant Sumitomo Electric Industries, Ltd. (and 2 others) I Stretching, cleaning ↓ Doping procedure Correction Book σ 0

Claims (4)

[Claims] 1. Polyacetylene doped with dopants Electromagnetic shielding material consisting of 2. The dopant according to claim 1 is iodine. An electromagnetic shielding material. 3. The polyacetylene according to claim 1 is thin Membrane, powder, flake or fiber Electromagnetic shielding material. 4. An electromagnetic shielding material in which the dopant according to claim 1 or 2 is doped in an amount of 0.01 to 0.5 mol per unit (CH) constituting polyacetylene.