JPS6187716A - Electromagnetic shielding material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electromagnetic shielding material. For more details,
The present invention relates to an electromagnetic shielding material having a coating layer with excellent weather resistance and corrosion resistance.

(Prior Art) In recent years, plastic materials have been widely used for housings of computers and other electronic devices.

Plastic housings do not conduct electricity, so if used as is, they will cause electromagnetic interference.In other words, high-frequency pulses generated by ICs and LSIs built into electronic devices may cause other computers and digital electronic devices to malfunction. In addition, natural and artificial noises are reflected by high-rise structures such as high-rise buildings, bridges, large tanks, chimneys, communication bases, etc., causing radio wave interference, which interferes with the reception of television, radar, etc. It has a negative impact on.

To prevent such electromagnetic interference, acrylic resin,
The method used is to paint the housing etc. with conductive paint, which is a mixture of urethane resin, vinyl chloride resin, synthetic rubber, etc., and conductive materials such as gold, silver, copper, iron, nickel, carbon black, and graphite.

[Problem that the invention seeks to solve]

Although conventional conductive paints are effective in preventing electromagnetic interference, they have the disadvantage of poor durability such as weather resistance and corrosion resistance.

An object of the present invention is to provide an electromagnetic shielding material that is excellent not only in electromagnetic shielding properties but also in weather resistance and anticorrosion properties.

[Means for solving problems].

The present invention provides ωchlorotrifluoroethylene (hereinafter referred to as CTFE) or tetrafluoroethylene (hereinafter referred to as TFE), (b>fluoro lower alkyl vinyl ether and (C
) It relates to an electromagnetic shielding material having a coating layer containing a crosslinked copolymer mainly composed of hydroxyalkyl vinyl ether.

[Function and Examples]

The coating layer in the present invention consists of (ω component and (b+acid component (C
) and a crosslinking agent (hereinafter referred to as fluorine-containing copolymer) and a crosslinking agent. , n.

The fluorine-containing copolymer has properties that conventional fluororesins do not have, namely, it cures at room temperature to form a hard film, and the formed coating film has properties such as corrosion resistance and weather resistance that fluorine-based polymers have. It is kept as is. It also has good adhesion to plastics. Regarding each component, composition, etc. of such a fluorine-containing copolymer, please refer to Japanese Patent Application No. 58-633.
It is explained in detail in the specification of No. 99 and the specification of Japanese Patent Application No. 175123/1982. Among them, particularly preferred as the ttn component are alkyl vinylethers in which the alkyl group has 1 to 10 carbon atoms, and in which the hydrogen atoms of the alkyl group are partially or completely substituted with fluorine atoms. Specific examples include 2,2,2-trifluoroethyl vinyl ether, 2,2,3,3-tetrasulfopropyl vinyl ether, 2,2,3,3,3-pentafluoropropyl vinyl ether, 2,2,3 ,3,
4,4,5.5-octafluoropentyl vinyl ether, 2,2,3,3,4°4, 5.5.6.6.7.7
．． 8.8.9.9-hexadecafluorononyl vinyl ether and the like.

In addition, as component (C), the alkyl group has 2 to 10 carbon atoms.
Particularly preferred is one. Specific examples include hydroxybutyl vinyl ether, hydroxybutyl vinyl ether, hydroxypropyl vinyl ether, 1
-Methyl-3-hydroxypropyl vinyl ether and the like.

The fluorine-containing copolymer in the present invention has (ω component unit 40
~60 mol%, (b) component unit 5-50 mol%, (C)
Those containing 0.5 to 40 mol% of component units are preferable, particularly (40 to 60 mol% of (ω) component units, (b) 20 to 40 mol% of component units).
45 mol% and 1 to 30 mol% of (C) component units are preferred. In addition, as long as the desired characteristics are not impaired,
Other ethylenically unsaturated monomers may be copolymerized.

Examples of copolymerizable ethylenically unsaturated monomers include ethylene, propylene, imbutylene, vinyl acetate,
Vinyl chloride, vinylidene chloride, (meth)acrylic acid, (
Examples include meth)acrylic acid esters.

The method for producing the fluorine-containing copolymer used in the present invention includes, for example, using a polymerization catalyst in the presence of a solvent, at -20 to 150°C, preferably at -20 to 150°C. Temperature of 5-95℃ and 0-30Kg/ca2
A method such as emulsion polymerization, suspension polymerization or solution polymerization in an aqueous medium under a pressure condition of G, preferably 10 to 0/cm2Q or less may be employed.

The coating wA layer in the present invention is usually prepared by blending a crosslinking agent with a fluorine-containing copolymer as described above and uniformly mixing it in an appropriate solvent.
It is formed by applying a coating composition obtained by dissolving it onto a shield base material such as a plastic housing, and crosslinking and curing it at room temperature. Curing proceeds quickly at room temperature, and a hard coating film is usually obtained in 1 to 10 days, but the time required for curing can be shortened by raising the temperature to a level that does not adversely affect the substrate.

Examples of the crosslinking agent include compounds having two or more functional groups that can react with the hydroxyl groups contained in the fluorine-containing copolymer, and cure the copolymer by reacting with the hydroxyl groups.

Specific examples of the crosslinking agent include hexamethylene diisocyanate, derivatives such as its trimer, xylylene diisocyanate, tolylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated -4,4゛-diphenylmethane diisocyanate, block type isocyanate, etc. Examples include isocyanates, acid anhydrides, polyvalent amines, amino resins, and compounds having epoxy groups. The amount of the crosslinking agent blended is preferably adjusted to 0.5 to 2 equivalents relative to the hydroxyl groups in the fluorine-containing copolymer.

As the solvent, unlike conventional fluorine-containing copolymers, a wide variety of ordinary solvents can be used. Specific examples include esters such as ethyl acetate, butyl acetate, isobutyl acetate, and cellosolve acetate; acetone, methyl ethyl ketone,
Ketones such as methyl isobutyl ketone; cyclic ethers such as tetrahydrofuran; amides such as todimethylformamide and todimethylacetamide; alcohols such as methyl alcohol, ethyl alcohol, and butyl alcohol; aromatic hydrocarbons such as toluene and xylene One or more types of these can be mentioned.

The concentration of the fluorine-containing copolymer varies depending on the coating method, coating manufacturing method, etc., but is usually 5 to 70% by weight, preferably 20 to aoia m%.

The fluorine-containing copolymer coating composition may be coated on a conventional conductive coating film provided on a shielding substrate to form a protective layer, or the fluorine-containing copolymer coating composition may be coated with a conductive material. may be blended to form a conductive paint and applied to the shielding substrate directly or via another layer such as a general-purpose conductive paint or primer to form a conductive coating layer. As the conductive material to be mixed, conventionally used conductive materials can be used. Crosslinking and curing is performed at room temperature or under elevated temperature.

The fluorine-containing copolymer coating composition may further contain other polymers, curing accelerators, dyes, pigments, viscosity modifiers,
Leveling agents, anti-gelling agents, ultraviolet absorbers, light stabilizers, anti-scald agents, dispersants, antifoaming agents, etc. may be added.

Application to the housing etc. can be done by spray method, spacing method,
This can be carried out by a conventional method such as a dipping method, a roll coating method, or a knife coating method.

Next, the present invention will be explained with reference to Examples, but the present invention is not limited to these Examples.

Example 1 50 parts (parts by weight, the same shall apply hereinafter) of a fluorine-containing copolymer consisting of 5 parts mol% CTFE, 40 mol% 2,2,3.3-tetrafluoropropyl vinyl ether, and 10 mol% hydroxybutyl vinyl ether were dissolved in acetic acid. n-butyl 35
10 parts of xylene, and 50 parts of a mixed solvent of 5 parts of methyl isobutyl ketone. 9 parts were added and mixed uniformly to prepare a coating composition.

On the other hand, a conductive paint consisting of 1 part by weight of thermoplastic acrylic resin, 55 parts by weight of nickel flakes, 20 parts by weight of toluene, and 15 parts by weight of methyl isobutyl ketone was coated on an ABS resin molded plate (15011X 75111X 2g1m) so that the film thickness was 27JJM. It was spray coated and dried at 25°C for 60 minutes to obtain a substrate.

The coating composition was applied to the surface of the substrate using butyl acetate for 35 minutes.
It was diluted to % by weight, spray coated to a film thickness of 20%, and dried and cured at 25° C. for 7 days to obtain a test piece.

Examples 2 to 6 Test pieces were obtained in the same manner as in Examples using the coating compositions shown in Table 1.

Examples 7 to 8 200 parts by weight of the coating composition shown in Table 1 was blended with 500 parts by weight of oxidized nickel flakes, and the mixture was spray applied to the ABS resin molded plate to a film thickness of 29 mm. The sample was dried and cured at 25° C. for 7 days to obtain a test piece.

[Margin below]

In addition, each abbreviation in Table 1 represents the following compound.

3FVE: 2,2,2-trifluoroethyl vinyl ether 4FVE: 2,2,3,3-tetrafluoropropyl vinyl ether 5FVE: 2,2,3,3.3-hentafluoro070
Rubinyl ether 8FVE: 2,2,3,3,4,4,5.5-t 7A/olopentyl vinyl ether HBVE: Hydroxybutyl vinyl ether Comparative example 1 A substrate obtained in the same manner as in Example 1 was used as a test piece. .

The following tests were conducted on the test pieces obtained in Examples 1 to 8 and Comparative Example 1. The results are shown in Table 2.

〔Weatherability〕

Continuous irradiation, rainfall cycle 18 minutes 7120 minutes, humidity 6 using Sunshine Weather Meter made by Suga Test i side
0%, black panel temperature: 4000 hours accelerated weathering test was conducted and the appearance was observed.

Note that O in Table 2 indicates no abnormality, and × indicates that the surface is rough.

[Corrosion resistance]

Using a salt water spray tester manufactured by Suga Test Instruments ■, a test was conducted for 2000 hours on a test piece with scratches marked with an X mark, and the surface condition was observed after the test. In Table 2, O indicates no abnormality, and × indicates occurrence of blisters.

(Electromagnetic wave shielding property) The volume resistivity values of Examples 7 to 8 and Comparative Example 1 were measured by a potential drop method. The sample was coated on the surface of a fluororesin film and then allowed to smudge. The lower the volume resistivity value, the better the electromagnetic wave shielding property.

[Margin below]

Table 2 [Effects of the Invention] As described above, the fluorine-containing copolymer containing the (ω, (b+, and C) components as main components) can be cured at room temperature, has excellent electromagnetic shielding properties, and Since a coating layer with excellent weather resistance and corrosion resistance can be formed on any type of housing, etc., the electromagnetic shielding material of the present invention having the coating layer has extremely excellent electromagnetic shielding properties, corrosion resistance, It is weather resistant and has excellent durability.

Claims (1)

[Claims] 1. A coating layer containing a crosslinked product of a copolymer mainly composed of (a) chlorotrifluoroethylene or tetrafluoroethylene, (b) fluoro lower alkyl vinyl ether, and (c) hydroxyalkyl vinyl ether. Electromagnetic shielding material with 2. The electromagnetic shielding material according to claim 1, wherein the coating layer is a protective layer laminated on a coating of conductive paint. 3. The electromagnetic shielding material according to claim 1, wherein the coating layer is a conductive coating layer.