JPS61217247A - Electromagnetic-wave shield 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.

[Conventional technology]

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, the high frequency pulses generated by ICs and L-3Is built into electronic devices can cause other computers and digital electronic devices to malfunction or generate noise. Furthermore, natural and artificial noises are reflected by high-rise structures such as high-rise buildings, bridges, large tanks, chimneys, communication towers, etc., causing radio wave interference, which adversely affects the reception of television, radar, etc.

To prevent such electromagnetic interference, acrylic resin,
A method is used in which the housing is coated 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 blank, 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 corrosion resistance.

[Means for solving problems]

The present invention relates to an electromagnetic shielding material having a protective layer mainly composed of a vinylidene fluoride copolymer having a functional group and/or a crosslinked product of a vinylidene fluoride copolymer having a functional group.

[Function and Examples]

The coating layer in the present invention is usually made of a vinylidene fluoride copolymer having a functional group (hereinafter referred to as a fluorine-containing copolymer).
It consists of a polymer composition whose main components are: and a crosslinking agent.

It is obtained by applying a fluorine resin paint and crosslinking and curing it at room temperature, and has a film thickness of about 5 to 100 μm.

The fluorine-containing copolymer has properties that conventional fluorine-containing resins 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-containing polymers have. is kept as is. It also has good adhesion to plastics. Regarding each component and composition of such a fluorine-containing copolymer,
It is explained in detail in the specification of No. 5123.

The fluorine-containing copolymer is usually vinylidene fluoride 50 to 99
Mol% preferably 65-85 mol%, vinyl a-it derivatives having functional groups 1-50 mol%, preferably 1-10 mol%, or vinylidene fluoride 50-99 mol%, preferably 65-85 mol%, functional Vinyl monomers having groups 1-
50 mol%, preferably 1 to 10 mol%, and less than 30 mol% of fluoroolefins other than vinylidene fluoride, preferably 10 to 25 mol%.

The molecular weight measured by gel permeation chromatography (GPC, polystyrene standard) of the fluorine-containing copolymer containing vinylidene fluoride as the main component and having a functional group is as follows:
Usually in the range of 10,000 to 500,000.

The vinyl monomer having the above functional group usually has the formula: % formula %) (wherein, X is a hydroxyl group, carboxyl group or glycidyl group, k is 0 or 1, m is an integer of 0 to 10,
represents an integer of 0 to 4 [1 to 4 when X is a hydroxyl group]. ) Compound 2: CH2=CHO(CH2)-X (wherein, X and n are as above) Compound 2: CH2= CY COO(C, H2) p ,
Y is hydrogen or a methyl group, p is an integer of 1 to 4, and X is as defined above. ) A compound or a compound represented by the formula: %Formula% (wherein, Y is as defined above).

The fluoroolefins other than vinylidene fluoride mentioned above are usually tetrafluoroethylene, chlorotrifluoroethylene, monofluoroethylene, trifluoroethylene, hexafluoropropene, lower fluoroalkyl vinyl ether, etc., and preferably tetrafluoroethylene or chlorotrifluoroethylene. be.

As a method for preparing the fluorine-containing copolymer used in the present invention, for example, each component is combined with a polymerization catalyst in the presence of a solvent,
-20 to 150 °C, preferably 5 to 95 °C and O to 30 kg/cf C, preferably 10 kg/
Methods such as emulsion polymerization, suspension polymerization, or solution polymerization in an aqueous medium under pressure conditions of ct G or less may be employed.

Further, the fluorine-containing copolymer of the present invention has good compatibility with an acrylic resin, and can be used in combination with an acrylic resin.

The above-mentioned acrylic resin refers to a single or copolymer of acrylate or methacrylate containing an alkyl group having 1 to 8 carbon atoms. For example, single or copolymers of methyl methacrylate, ethylmethacrylate, tacrylate I, butyl methacrylate, cyclohexyl acrylate, copolymers of the above acrylates or methacrylates with hydroxyethyl methacrylate, methacrylic acid, glycidyl methacrylate, styrene, acrylonitrile, etc.
Commercially available acrylic resins include Hyfroid 3004, Hyfroid 3018, Hyfroid 3046C (all manufactured by Hitachi Chemical), Acridic A 810-45, Acridic ABI4, and Acridic 47-540.
(all manufactured by Dainippon Ink & Chemicals), but are not limited to these.

The acrylic resin is preferably one containing 50% by weight or more of methyl methacrylate and a molecular weight of 1t (C1, PC) of 5,000 to 300,000 from the viewpoint of compatibility with the fluorine-containing copolymer. The blending ratio of the above-mentioned fluorine-containing copolymer and acrylic resin is usually 10 to 10 parts by weight of the acrylic resin to 100 parts by weight of the fluorine-containing copolymer.
The amount is 1900 parts by weight, preferably 25 to 400 parts by weight. When blended within this range, the weather resistance, translucency, pigment dispersibility, etc. of the paint are good.

The coating layer in the present invention is usually prepared by blending a fluorine-containing copolymer with a crosslinking agent as described above, uniformly mixing and dissolving it in an appropriate solvent, and applying the coating composition to a plastic housing or the like. It is formed by applying it to a shield base material, crosslinking and curing it at room temperature.

Curing proceeds rapidly 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 leave any negative impression on the substrate.

The crosslinking agent is a functional group (
Hydroxyl group, carboxyl group or glycidyl group′
) is a compound having two or more groups capable of crosslinking a fluorine-containing copolymer. When the functional group is a hydroxyl group, the crosslinking agent is usually an isocyanate, acid anhydride, or the like. When the functional group is a carboxyl group, it is usually an isocyanate, an amine, an amino resin, a compound containing a glycidyl group, etc. When the functional group is a glycidyl group, it is usually an amine. Examples of isocyanates include, but are not limited to, hexamethylene diisocyanate, tolylene diisocyanate, hydrogenated tolylene diisocyanate, and block isocyanates thereof. Examples of amines include diethylenetriamine,
Examples include, but are not limited to, triethylenetetramine, xylenediamine, metaphenylenediamine, benzyldimethylamine, bisaminopropyltetraoxaspiroundecane, and the like. Examples of acid anhydrides include, but are not limited to, phthalic anhydride, pyromellitic anhydride, and mellitic anhydride. Examples of amino resins include, but are not limited to, alkyl etherified methylol melamine, alkyl etherified methylol urea, alkyl etherified benzoylguanamine, and the like. An example of a compound containing a glycidyl group is the formula: %Formula% (wherein, Z represents a glycidyl group, and R1 represents an alkylene group having 2 to 10 carbon atoms or a divalent aromatic group having 6 to 10 carbon atoms. ) aliphatic diepoxides or aromatic dieboxides represented by the formula: (In the formula, R2 is a trivalent aromatic group and Z is the same as above.) Not done.

The amount of the crosslinking agent is preferably adjusted to 0.5 to 2 equivalents based on all the functional groups in the fluorine-containing copolymer and the acrylic resin.

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,
Ketone necks such as methyl isobutyl ketone; cyclic ethers such as tetrahydrofuran; amides such as N-dimethylformamide and N-dimethylacetamide; alcohols such as methyl alcohol, ethyl alcohol, and butyl alcohol; toluene, xylene, etc. One or more kinds of aromatic hydrocarbons may be used.

The concentration of the fluorine-containing copolymer varies depending on the coating method and coating manufacturing method, but is usually 5 to 70% by weight, preferably 20 to 600 to 60% by weight.

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 a primer to form an electrically sensitive 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 housing etc. can be done by spray method, brush 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 I 70 mol% VdF, 20 mol% CTFE and M5FP
50 parts (parts by weight,
The same applies below) was added to 50 parts of methyl isobutyl ketone and mixed uniformly, and furthermore, as a crosslinking agent, Coronet) EH (polyisocyanate crosslinking agent manufactured by Nippon Polyurethane Kogyo A2A) was added to OHHI3 of the fluorine-containing copolymer and Coronet 1-
An amount equivalent to E HONCO value of 1.1 and 0.05 g of dibutyl tin dilaure as a curing accelerator were added and mixed uniformly to prepare a coating composition.

On the other hand, a conductive paint consisting of 10 parts by weight of thermoplastic acrylic resin, 55 parts by weight of nickel flakes, 20 parts by weight of toluene and 50 parts of methyl isobutyl ketone was coated on an ABS resin molded plate (150 Dragon x 7511 x 2 pieces) to a film thickness of 27 μm.
The substrate was coated with a brush and dried at 25°C for 60 minutes.

The coating composition was diluted to 35% by weight with methyl isobutyl ketone and applied to the surface of the substrate with a brush to a thickness of 20 μm, and dried and cured at 25° C. for 7 days to obtain a test piece.

Examples 2 to 10 A fluorine-containing copolymer or a fluorine-containing copolymer and an acrylic resin (the proportions are shown in Table 1) having the compositions shown in Table 1 were dissolved in methyl isobutyl ketone, and the solid content concentration was 35
It was adjusted to be % by weight.

Coronate EH to OHHI3 of the solid content of the solution
An amount equivalent to NC0 value of 1.1 and dibutyltin dilaurate were added to 10-3 g of I

A test piece was obtained in the same manner as in Example 1 using the above coating composition.

Experimental Examples 11 to 15 350 parts by weight of oxidized nickel flakes were blended with 200 parts by weight of each of the coating compositions of Examples 2 to 10, and applied to the ABS resin molded plate so that the film thickness was about 35 μm. It was applied with a brush and dried and cured at 25° C. for 7 days to obtain a test piece.

In addition, each abbreviation showing a monomer shows the following compound.

VdF: vinylidene fluoride CTFE: chlorotrifluoroethylene TFE: tetrafluoroethylene M5F'P: CF2=CFCFz, CH'zOH3
FHA: CF2=CFCH2CH20H)TBVE
: Hydroxybutyl vinyl ether 7 F, HA :
CF! =CFCFICF2CH2CH20HMMA
: Methyl methacrylate EMA : Ethyl methacrylate HEHA : Hydroxyethyl methacrylate 8-bar A Nibutyl methacrylate-1 MA: Methacrylic acid 5FBA: CFz=CFCF2COOH 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 15 and Comparative Example 1. The results are shown in Table 1.

〔Weatherability〕

Continuous irradiation, rainfall cycle 18 minutes 7120 minutes, humidity 6 using Sunshine Weather Meter manufactured by Suga Test Instruments ■
0%, black panel temperature: 4000 hours accelerated weathering test was conducted and the appearance was observed. In Table 1, ◎ indicates no abnormality, and × indicates that the surface is rough.

[Corrosion resistance]

Using a salt spray tester manufactured by Suga Test Instruments ■, a test was conducted for 2000 hours on a test piece marked with an x mark, and the surface condition was observed after the test. In Table 1, ◎ indicates no abnormality, and × indicates occurrence of blisters.

[Electromagnetic shielding]

The volume resistivity values of Examples 11 to 15 and Comparative Example 1 were measured by a potential drop method. The sample was coated on the surface of a fluorine resin film and then allowed to smudge. The lower the volume resistivity value, the better the electromagnetic wave shielding property.

〔Effect of the invention〕

As described above, a polymer composition whose main component is a fluorinated vinylizone copolymer having a functional group can be cured at room temperature, has excellent electromagnetic shielding properties, and is a coating with excellent weather resistance and corrosion resistance. Since the film layer can be formed on any type of housing etc., the electromagnetic wave shielding material of the present invention having the film layer has extremely excellent electromagnetic shielding properties, anti-corrosion properties, and excellent durability. .

Claims (1)

[Claims] 1. Vinylidene fluoride copolymer having a functional group and/or
Or an electromagnetic shielding material having a coating layer mainly composed of a crosslinked vinylidene fluoride copolymer having a functional group. 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.