JP2011023511A - Electromagnetic wave shielding fluoro-rubber and metal laminated board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electromagnetic wave shielding fluoro-rubber and metal laminated board allowing oven-vulcanization of a rubber layer, soft and excellent in electromagnetic wave shielding characteristics. <P>SOLUTION: In the electromagnetic wave shielding fluoro-rubber and metal laminated board, a conductive fluoro-rubber composition blended with a conductive carbon black which contains a polyester plasticizer of 5-40 pts.wt. and a polyol vulcanizing agent of 0.5-10 pst.wt. in 100 pts.wt. of polyol-vulcanizable fluoro-rubber, and which is at least 300 cm<SP>3</SP>/100g in DBP oil absorption and at least 700 m<SP>2</SP>/g in BET specific surface area so as to be 3-20 vol.% in the composition, is laminated on a metal board and the fluoro-rubber layer is vulcanized. In the above laminated board, the fluoro-rubber layer is vulcanized by oven-vulcanization. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an electromagnetic wave shielding fluororubber-metal laminate. More specifically, the present invention relates to an electromagnetic wave shielding fluororubber-metal laminate that can be oven vulcanized.

  As electronic devices become more sophisticated, each device operates with a minute current, and is equipped with an electromagnetic wave shield to prevent malfunctions and a seal to prevent intrusion of dust, dirt, moisture, etc. At the same time, there is a need for a sealing material, and a rubber material having electromagnetic shielding properties as described in Patent Documents 1 and 2 has been proposed. However, these proposals relate to the composition, and when a gasket material is molded using such a rubber composition, it is considered that the incorporation becomes difficult depending on the shape.

In order to improve assemblability, it is conceivable to laminate an electromagnetic wave shielding rubber layer on a metal plate or the like and use it as a gasket material. Patent Document 3 proposes such an electromagnetic wave shielding rubber laminate, and as its production means, an electromagnetic wave shielding rubber composition solution is applied to a metal plate, dried, press vulcanized, and formed into a gasket shape. The method of punching is shown. However, such a series of manufacturing procedures has the following problems.
(1) In press vulcanization, rubber flows during vulcanization.
(2) Since most of the electromagnetic shielding rubber laminate is discarded as scrap material, the material cost increases.
(3) Since the rubber layer is laminated, it is difficult to reuse the electromagnetic wave shielding rubber used as the end material.

JP 2002-105436 A JP 2002-359492 A JP 2003-232444 A

  An object of the present invention is to provide an electromagnetic wave shielding fluororubber-metal laminate that is capable of oven vulcanization of a rubber layer, is flexible, and has excellent electromagnetic wave shielding characteristics.

Such object of the present invention, and per 100 parts by weight of polyol-vulcanizable fluororubber polyester plasticizer 5-40 parts by weight, the polyol type vulcanizing agent 0.5 to 10 parts by weight of DBP oil absorption 300 cm ^3/100 g or more A conductive fluoro rubber composition containing conductive carbon black having a BET specific surface area of 700 m ² / g or more and 3 to 20% by volume in the composition is laminated on a metal plate, and the fluoro rubber layer is vulcanized. This is achieved by an electromagnetic wave shielding fluororubber-metal laminate. In this electromagnetic wave shielding fluororubber-metal laminate, the fluororubber layer is vulcanized by oven vulcanization.

  The electromagnetic wave shielding fluororubber-metal laminate according to the present invention is capable of oven vulcanization of the rubber layer, the rubber hardness is also flexible with a durometer A of 90 or less, and the S parameter measured value by the coaxial tube method is 7 dB. It is excellent also in the point of the above and electromagnetic shielding characteristics.

  Further, when the conductive fluororubber solution is applied to the metal plate by the screen printing method, the rubber solution is not wasted, and at the same time, the punched metal plate end material can be effectively used.

  Considering application to electronic equipment, it is not preferable to use sulfur as a vulcanizing agent, and in order to perform oven crosslinking using organic peroxides, equipment such as nitrogen substitution is required. There is a problem of rising. For this reason, polyol vulcanized fluororubber and amine vulcanized acrylic rubber can be considered as candidate polymers, but polyol vulcanized fluororubber with excellent water resistance and LLC (long life coolant) resistance is a polymer. Selected as

  Examples of the polyol-crosslinkable fluororubber include vinylidene fluoride, hexafluoropropene, pentafluoropropene, trifluoroethylene, trifluorochloroethylene, tetrafluoroethylene, vinyl fluoride, perfluoroacrylate, perfluoroalkyl acrylate, Homopolymers such as perfluoro (methyl vinyl ether), perfluoro (ethyl vinyl ether), perfluoro (propyl vinyl ether), and interpolymers or copolymers of these with propylene are preferred, preferably vinylidene fluoride-hexa Fluoropropene copolymer, vinylidene fluoride-hexafluoropropene-tetrafluoroethylene terpolymer, tetrafluoroethylene-propylene copolymer, etc. are used. Or it can be used.

  However, the hardness of fluororubber tends to increase, and the hardness increases only by adding a small amount of conductive filler for imparting electromagnetic wave shielding properties. Therefore, in order to satisfy both electromagnetic wave shielding properties and sealing properties at the same time, a plasticizer It is absolutely necessary to reduce the hardness of the base polymer.

  As the fluororubber plasticizer, liquid fluororubber is generally blended and used. However, if the liquid fluororubber is blended until the rubber hardness is sufficiently lowered, it becomes sticky and kneading becomes difficult. Further, when a polyether plasticizer is used, oven vulcanization cannot be performed. As a result of repeated studies to improve these points, it was found that only ester plasticizers achieve the desired effects.

  As the ester plasticizer, dibutyl phthalate, dioctyl phthalate, dioctyl adipate, dioctyl sebacate, polyazelenic acid neopentyl glycol, etc. are used. The use of 5 to 40 parts by weight, preferably about 5 to 25 parts by weight is effective in terms of characteristics. When used at a higher ratio, the flexibility is increased and the rubber hardness is lowered, but the plasticizer tends to bleed. On the other hand, when it is used at a lower ratio, the oven cannot be vulcanized or Even if vulcanization is possible, an increase in rubber hardness is inevitable.

  Examples of the polyol-based vulcanizing agent include 2,2-bis (4-hydroxyphenyl) propane (bisnor A), 2,2-bis (4-hydroxyphenyl) perfluoropropane (bisphenol AF), bis (4-hydroxy Phenyl) sulfone (bisphenol S), 2,2-bis (4-hydroxyphenyl) methane (bisphenol F), bisphenol A-bis (diphenyl phosphate), 4,4'-dihydroxydiphenyl, 2,2-bis (4- Hydroxyphenyl) butane, hydroquinone, catechol, resorcin, and the like, and bisphenol A, bisphenol AF, and the like are preferably used. These may also be in the form of alkali metal salts or alkaline earth metal salts. These polyol vulcanizing agents are generally used in a proportion of about 0.5 to 10 parts by weight, preferably about 0.5 to 6 parts by weight, per 100 parts by weight of the fluororubber.

  Along with the polyol vulcanizing agent, a quaternary phosphonium salt or a quaternary ammonium salt compound, preferably a quaternary phosphonium salt, is used as a vulcanization accelerator.

As the quaternary phosphonium salt, a compound represented by the following general formula is used.
_{(R 1 R 2 R 3 R} 4 P) + X -
R _{1 to} R ₄ : alkyl group having 1 to 25 carbon atoms, alkoxyl group, aryl group, alkyl
A ruaryl group, an aralkyl group or a polyoxyalkylene group,
Or two to three of these can form a heterocyclic structure with N or P.
Ru
^{X -: Cl -, Br -} , I -, HSO 4 -, H 2 PO 4 -, RCOO -, ROSO 2 -, CO 3 - , etc. anion of
N

  Specifically, tetraphenylphosphonium chloride, benzyltriphenylphosphonium bromide, benzyltriphenylphosphonium chloride, trioctylbenzylphosphonium chloride, trioctylmethylphosphonium chloride, trioctylethylphosphonium acetate, tetraoctylphosphonium chloride and the like are used. These quaternary phosphonium salts are used in a ratio of about 0.1 to 10 parts by weight, preferably about 0.5 to 5 parts by weight, per 100 parts by weight of the polyol vulcanizable fluororubber.

  Also, with polyol vulcanizing agent, o-, m- or p-cresol, 2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-dimethylphenol It is also effective to use monophenol compounds such as p-tert-butylphenol, pn-octylphenol, p-cumylphenol, p-methoxyphenol, 2,4,6-trimethylphenol, and p-phenylphenol.

  In addition to each of the above components, in order to impart electromagnetic shielding properties to the rubber material, an amount occupying 3 to 20% by volume, preferably 5 to 15% by volume in the rubber composition containing various compounding agents (see specific gravity) The conductive carbon black calculated as above is blended and used as an essential component. Such a volume% range of the conductive carbon black is selected from the viewpoint of securing the electromagnetic wave shielding property and securing the necessary rubber hardness that affects the sealing property.

The electrically conductive carbon black, DBP oil absorption of 300 cm ^3/100 g or more, preferably 400 cm ^3/100 g or more, and a BET specific surface area of 700 meters ² / g or more, preferably is used more than 1000 m ² / g. When a DBP oil absorption amount and BET specific surface area below this are used, a larger amount of addition is required to provide electromagnetic wave sealing properties. Actually, commercially available Lion products such as Ketjen Black EC and Ketjen Black EC600JD are used as they are.

  The required electromagnetic shielding property is preferably 7 dB or more in the S-parameter measurement by the coaxial tube method, and in order to satisfy the sealing property, the rubber hardness (based on JIS K6253) by durometer A is 90 or less. It is preferable.

  In the rubber composition containing the above components as essential components, an acid acceptor and other compounding agents are blended as necessary. Acid acceptors include divalent metal oxides or hydroxides that provide vulcanizate stability and appropriate vulcanization rates, such as magnesium oxide, magnesium hydroxide, barium hydroxide, calcium oxide, calcium hydroxide, Zinc white or the like or hydrotalcites are preferably used. In addition, carbonates of divalent metals such as magnesium carbonate and calcium carbonate are also used.

  Examples of compounding agents other than acid acceptors include stabilizers, lubricants, tackifiers, internal release agents, pigments, flame retardants, etc., which are usually compounded in rubber. A small amount of thermoplastic resin or rubber may be added for improvement, or short fibers may be added for improvement of strength and rigidity.

  The composition comprising these components is prepared by mixing with a rubber kneader such as a normal roll, kneader, intermix, etc., and the prepared conductive fluororubber composition includes methyl ethyl ketone, methyl isobutyl ketone, isophorone, etc. A conductive rubber solution is formed by dissolving and dispersing in a ketone polar organic solvent.

  The conductive rubber solution is applied to a metal plate punched into a predetermined shape such as a gasket shape and vulcanized to obtain a gasket material made of an electromagnetic wave shielding fluororubber-metal laminate.

  As the metal plate, a metal plate of iron, aluminum, copper or the like or a metal plate of these alloys is used, and generally a stainless steel plate such as SUS301, SUS301H, SUS304, SUS430 or the like is used. When the electromagnetic wave shielding fluororubber-metal laminated plate is used as a gasket material, the thickness of the metal plate is set to about 0.05 to 0.5 mm.

  The conductive rubber solution is applied to a metal plate that has been punched into a predetermined shape, such as a gasket shape, for a gasket material, the size is relatively small, the punched metal plate is flat and flat. In the case of having a surface, the screen printing method is applied because of the advantage that only a small amount of rubber solution is used, and for those having uneven beads on the surface of the metal plate after punching, for example, flow coating The law applies.

  Prior to the application of the conductive rubber solution to the metal plate, it is preferable to apply a primer to the metal plate. As the primer, for example, an organic solvent solution of cresol novolac-modified epoxy resin is used as a main agent, and bisphenol novolac phenol is added thereto. Resin curing agent and imidazole-based curing catalyst, preferably epoxy phenol resin to which 2-ethyl-4-methylimidazole is added and an organic solvent solution in which the conductive fluororubber composition used in the present invention is dissolved in an organic solvent are used. It is done. In this case, the organic solvent is preferably a ketone solvent such as methyl ethyl ketone, methyl isobutyl ketone or isophorone, and the epoxy phenol resin in the organic solvent solution is about 0.1 to 10% by weight, preferably about 0.3 to 7% by weight. The conductive fluororubber composition is used in an amount of about 1 to 40% by weight, preferably about 3 to 30% by weight.

  The primer is applied to the metal plate by a dipping method or the like, and a primer layer having a thickness of about 0.5 to 5 μm is formed by performing a baking process at about 100 to 180 ° C. for about 3 to 30 minutes. .

  As described above, the conductive rubber solution is applied onto the primer layer formed on the metal surface as described above. When the application is performed by a screen printing method, the organic solvent for the conductive rubber solution is used as an organic solvent. A high-boiling solvent such as isophorone is preferably used, and a low-boiling solvent such as methyl ethyl ketone is preferably used when the flow coating method is used.

  The conductive rubber solution applied on the primer layer is dried at about 80 to 150 ° C. for about 1 to 15 minutes, the thickness is set to about 20 to 100 μm, and then about 1 to 120 to about 120 to 220 ° C. An electromagnetic wave shielding fluororubber-metal laminate is formed by oven vulcanization for 60 minutes without pressure.

  Next, the present invention will be described with reference to examples.

Example 1
Polyol vulcanizable VdF-HFP copolymer rubber (Daikin G-701) 100 parts by weight Polyester plasticizer (ADEKA P-200) 10 部
Magnesium oxide 5 〃
Sodium stearate 0.5 〃
Benzyltriphenylphosphonium chloride 1 〃
(Rohm and Haas BTPPCl)
Bisphenol AF 3 〃
Ketjen Black (Lion product EC-600JD; 13.3 〃
DBP oil absorption 493cm ³ / 100g, BET specific surface area 1270m ² / g) (10% by volume)
The above components were kneaded with a 12-inch roll, and the resulting rubber composition was dissolved and dispersed in methyl ethyl ketone so that the solid content concentration was 20% by weight to prepare a conductive rubber solution.
On SUS steel plate (thickness 0.2mm)
Epoxy phenol resin 7% by weight
(Methyl ethyl ketone solution of cresol novolak modified epoxy resin as the main agent, with bisphenol novolac resin curing agent and 2-ethyl-4-methylimidazole curing catalyst added)
The conductive fluororubber composition 3
Methyl ethyl ketone 90 〃
A primer comprising the above was dip-coated on both sides of the steel sheet and heat-treated in an oven at 150 ° C. for about 5 minutes to form a primer layer having a thickness of 2.5 μm on one side.

  The conductive rubber solution was further applied on the primer layer, dried at 100 ° C. for 10 minutes, and the thickness was set to 50 μm. Thereafter, oven vulcanization at 180 ° C. for 10 minutes was performed to obtain an electromagnetic wave shielding fluororubber-metal laminate.

About the obtained electromagnetic wave shielding fluororubber-metal laminate, while evaluating or measuring the following items,
Oven vulcanizability: visually confirmed Surface condition: visually confirmed for plasticizer bleed Electromagnetic wave shielding characteristics: 1 mm thick shielding characteristics from S-parameter measurement by coaxial tube method
Converted to (S21) The conductive fluororubber composition was subjected to press vulcanization at 180 ° C. for 8 minutes to prepare a vulcanized sheet (150 × 150 × 2 mm), and the following items were measured.
Hardness: JIS K6253 compliant (durometer A)

Example 2
In Example 1, the amount of the polyester plasticizer (P-200) was changed to 20 parts by weight. Accordingly, the amount of ketjen black was changed to 14.4 parts by weight (10% by volume).

Example 3
In Example 1, 20 parts by weight of polyazenoic acid neopentyl glycol (UNICHEMA product Priplast3142) was used as a polyester plasticizer. Along with this, the amount of ketjen black was changed to 14.5 parts by weight (10% by volume).

Reference Example In Example 1, the same amount (100 parts by weight) of peroxide crosslinkable VdF-HFP copolymer rubber (Daikin product G-801) was used as the VdF-HFP copolymer rubber, and the quaternary onium salt and vulcanization system were used. Instead of bisphenol AF, 3 parts by weight of an organic peroxide (Nippon Oil Products Perhexa 25B40) and 3 parts by weight of triallyl isocyanurate (Nippon Kasei Kogyo Taik M60) were used.

Comparative Example 1
In Example 1, the same amount (10 parts by weight) of a polyether plasticizer (Asahi Denka ADEKA Sizer RS735) was used instead of the polyester plasticizer.

Comparative Example 2
In Example 1, the polyester plasticizer (P-200) was not used. Accordingly, the amount of ketjen black was changed to 12.2 parts by weight (10% by volume).

The results obtained in the above examples and comparative examples are shown in the following table.
table
Evaluation / Measurement Items Example 1 Example 2 Example 3 Reference Example Comparative Example 1 Comparative Example 2
Oven vulcanization Yes Yes Yes No No No Yes
Plasticizer bleed No No No No Yes No No
Electromagnetic shielding characteristics (dB) 12.6 9.4 8.6 Not measurable Not measurable 10.9
Hardness (Durometer A) 88 77 83 − − −

From this result, the following can be said.
Example 1: Oven vulcanization is possible, flexible, and high electromagnetic shielding characteristics are obtained. Examples 2, 3: Oven vulcanization is possible, and further, flexible, electromagnetic shielding characteristics are obtained.
Reference example: Rubber layer was not vulcanized because the vulcanizing agent was an organic peroxide. Comparative example 1: Plasticizer bleed and vulcanization inhibition was confirmed. Comparative example 2: Oven vulcanization possible. However, an electromagnetic shielding material with poor flexibility was obtained.
Was

Example 4
In Example 1, the solvent was changed from methyl ethyl ketone to isophorone to prepare a conductive rubber solution. Further, in the same manner as in Example 1, after applying a primer and baking treatment to a steel plate (SUS301) punched into a gasket shape, the conductive rubber solution was applied by screen printing, dried and oven vulcanized. Thus, a gasket-shaped electromagnetic wave shielding fluororubber-metal laminate was obtained. In the obtained electromagnetic wave shielding fluororubber-metal laminate, there was no rubber flow or exposed metal portion, and it was confirmed that a uniform conductive fluororubber layer was formed on the SUS steel plate.

Claims (5)

Polyol-vulcanizable fluororubber 100 parts by weight per ester plasticizer 5 to 40 parts by weight, the polyol type vulcanizing agent 0.5 to 10 parts by weight of DBP oil absorption 300 cm ^3/100 g or more and a BET specific surface area of 700 meters ² / An electromagnetic wave shielding fluororubber obtained by laminating a conductive fluororubber composition containing 3 to 20% by volume of conductive carbon black in an amount of g or more on a metal plate and vulcanizing the fluororubber layer -Metal laminate.   The electromagnetic wave shielding fluororubber-metal laminate according to claim 1, wherein the fluororubber layer is vulcanized by oven vulcanization.   3. The fluororubber layer is formed on a metal plate punched into a predetermined shape by using a conductive fluororubber solution in which a conductive fluororubber composition is dissolved and dispersed in an organic solvent. Electromagnetic shielding fluororubber-metal laminate.   The electromagnetic wave shielding fluororubber-metal laminate according to claim 3, wherein the conductive fluororubber solution is applied to the metal plate by a screen printing method. 5. The electromagnetic wave shielding fluororubber-metal laminate according to claim 1, wherein an S parameter measured value by a coaxial tube method is 7 dB or more and a rubber hardness is 90 or less by durometer A.