JP2007335570A - Rubber composition for shielding electromagnetic wave - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide rubber composition for shielding electromagnetic wave which has achieved the reduction of a hardness thereof without deteriorating electromagnetic wave shielding property. <P>SOLUTION: The rubber composition for shielding electromagnetic wave includes ethylene-α-olefin-non-conjugated polyene copolymer which shows the shear viscosity of lower than 10<SP>8</SP>(Pa sec) (40°C, strain 1%), and preferably Ketjenblack contained in EPDM. The electromagnetic wave shielding characteristic in a cured material produced by the composition is not lower than 10 dB in 1 GHz with respect to a rubber sheet whose hardness (Duro-A) is not more than 80 and whose thickness is 2 mm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rubber composition for electromagnetic wave shielding. More specifically, the present invention relates to a rubber composition for electromagnetic wave shielding containing a carbon filler.

  In recent years, when electronic devices and the like have been digitized and the degree of integration has increased to operate with a very small current, electromagnetic interference (Electro Electromagnetic interference) in which the signal is disturbed by electromagnetic waves generated from the main body of the device or disturbing radio waves from other electronic devices, etc. Magnetic Interference (EMI) occurs frequently. This EMI is mainly caused by noise generated from the switching power supply. This noise is divided into conductive noise that flows in the circuit of electronic equipment and radiation noise that propagates in the air. Conductive noise can be removed through a filter or the like in the circuit, whereas radiation noise is a conductive material. It is removed by covering the electronic device and the like to be shielded and not transmitting electromagnetic waves.

  As an electromagnetic wave shielding material, a conventional method using a metal plate such as an aluminum plate, a method using a metal fiber wire mesh such as a stainless steel fiber wire mesh, a method of applying a plating coating to a housing, a conductive surface treatment, etc. There are methods of covering with applied materials, etc., which are properly used depending on the purpose and cost. The method of imparting electrical conductivity to the rubber material and exhibiting the shielding effect is slightly inferior to the electromagnetic wave shielding effect (attenuation effect), but on the other hand, it is excellent in low cost, durability and light weight, and also has a sealing property at the mounting site. Since it has an effect that can be added, it has begun to be applied to a joint portion of a casing or a wire covering.

Due to recent demands for weight reduction and downsizing, metal plates are heavy, and space efficiency is problematic, so the casing is being converted from metal plates to composite materials such as resin and metal fibers or metal plating. Here, in the case of a metal casing, since the strength is large, even a conventional electromagnetic shielding rubber material can maintain a sufficient sealing performance. However, in the case of a resin casing, the conventional electromagnetic shielding rubber material has a rubber itself. There is a problem that the reaction force causes a problem such as deformation of the resin, and a low hardness is strongly demanded as a rubber material for electromagnetic wave shielding. However, conventional electromagnetic wave shielding rubber requires the addition of a large amount of a conductivity-imparting agent, which results in a high-hardness material. Therefore, in order to compensate for this, it is necessary to take measures such as adding a softening agent and reducing fillers. However, such a method is not suitable as a measure for reducing the hardness because the electromagnetic wave shielding property is greatly lowered.
JP 2000-332483 Japanese Patent Laid-Open No. 11-167825 Japanese Patent Laid-Open No. 10-298355

As a countermeasure, a method has been proposed in which a large amount of both high-conductivity carbon fibers and softening agents, which have weak reinforcement properties, are blended. There is a problem that quality is difficult to maintain due to change, inferior properties required for sealing materials such as compression set, and high cost. In addition, the addition of a softening agent (plasticizer) causes an increase in outgas, leading to an adverse effect on electronic devices and the like.
JP 2002-167474 A

In addition, there is a method of mixing two or more types of polymers and reducing the amount of the conductivity-imparting agent to make it low hardness by unevenly distributing the conductivity-imparting agent in one polymer, but there is a problem in workability .
JP 2002-309107 A

  An object of the present invention is to provide a rubber composition for electromagnetic wave shield that achieves low hardness without deteriorating electromagnetic wave shielding properties.

An object of the present invention is to provide an ethylene / α-olefin / non-conjugated polyene copolymer having a shear viscosity of 10 ⁸ Pa · sec (40 ° C., strain 1%) or less, preferably EPDM containing ketjen black. This is achieved by a rubber composition for electromagnetic wave shielding that gives a cured product having an electromagnetic wave shielding property at 1 GHz of 10 dB or more for a rubber sheet having a hardness (Duro-A) of 80 or less and a thickness of 2 mm.

  The molded product obtained from the rubber composition for electromagnetic wave shielding of the present invention has excellent electromagnetic wave shielding properties and, of course, does not contain a plasticizer, reducing outgas that adversely affects electronic devices compared to conventional products. The value of compression set, which is an essential property as a sealing material for preventing the entry of water, dust, etc. into the resin casing that houses the parts required to have low hardness, for example, electronic / electric devices, etc. Has an excellent effect of being good. In addition, mold contamination can be reduced and low-temperature rapid curing can be performed.

As the ethylene / α-olefin / non-conjugated polyene copolymer, for example, the shear viscosity using an Anton Paar product viscoelastic device MCR301 is 10 ⁸ Pa · sec (40 ° C., strain 1%) or less, preferably 10 ⁵ Those showing Pa · sec or less are used. Use of a material having a shear viscosity higher than this is not preferable because when the ketjen black is highly filled and blended so as to obtain desired electromagnetic wave shielding characteristics, the rubber composition becomes high in hardness and its workability deteriorates.

  The ethylene / α-olefin / non-conjugated polyene copolymer is a copolymer of ethylene, an α-olefin having 3 to 20 carbon atoms and a non-conjugated polyene, preferably an ethylene / propylene / non-conjugated polyene copolymer. A polymer (EPDM) is used. The ethylene / α-olefin / non-conjugated polyene copolymer is preferably a random copolymer.

  Specific examples of the α-olefin having 3 to 20 carbon atoms include propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-nonene, Decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-nonadecene, 1-eicosene, 9-methyl-1-decene, 11-methyl- 1-dodecene, 12-ethyl-1-tetradecene, and the like, preferably α-olefins having 3 to 10 carbon atoms, more preferably propylene, 1-butene, 1-hexene, 1-octene and the like are used. These α-olefins may be used alone or in combination of two or more.

または

ｎ：0ないし10の整数
R¹：水素原子またはC1〜10のアルキル基
R²、R³：水素原子またはC1〜5のアルキル基
で表わされるノルボルネン化合物である。 The non-conjugated polyene used in the present invention is preferably a norbornene compound having an unsaturated group-containing substituent, more preferably a general formula

Or

n: integer from 0 to 10
R ¹ : hydrogen atom or C1-10 alkyl group
R ² and R ³ are norbornene compounds represented by a hydrogen atom or a C1-5 alkyl group.

  Specific examples of the norbornene compound having an unsaturated group-containing substituent including the norbornene compound represented by the above general formula [I] or [II] include 5-methylene-2-norbornene, 5-vinyl-2-norbornene, 5 -(2-propenyl) -2-norbornene, 5- (3-butenyl) -2-norbornene, 5- (1-methyl-2-propenyl) -2-norbornene, 5- (4-pentenyl) -2-norbornene 5- (1-methyl-3-butenyl) -2-norbornene, 5- (5-hexenyl) -2-norbornene, 5- (1-methyl-4-pentenyl) -2-norbornene, 5- (2, 3-Dimethyl-3-butenyl) -2-norbornene, 5- (2-ethyl-3-butenyl) -2-norbornene, 5- (6-heptenyl) -2-norbornene, 5- (3-methyl-5- (Hexenyl) -2-norbornene, 5- (3,4-dimethyl-4-pentenyl) -2-norbornene, 5- (3-ethyl-4-pentenyl) -2-norbornene, 5- (7-octenyl) -2 -Norbornene, 5- (2-methyl-6- Heptenyl) -2-norbornene, 5- (1,2-dimethyl-5-hexesyl) -2-norbornene, 5- (5-ethyl-5-hexenyl) -2-norbornene, 5- (1,2,3- Trimethyl-4-pentenyl) -2-norbornene, 5-ethylidene-2-norbornene, 5-methylene-2-norbornene, 5-isopropylidene-2-norbornene, 5-vinylidene-2-norbornene, 6-chloromethyl-5 -Isopropenyl-2-norbornene and the like, preferably 5-vinyl-2-norbornene, 5-methylene-2-norbornene, 5- (2-propenyl) -2-norbornene, 5- (3-butenyl)- 2-norbornene, 5- (4-pentenyl) -2-norbornene, 5- (5-hexenyl) -2-norbornene, 5- (6-heptenyl) -2-norbornene, 5- (7-octenyl) -2- Norbornene is used, and these are used alone or in combination of two or more.

  In addition to the norbornene compounds as described above, other non-conjugated polyenes can be used in combination as long as the physical properties of the present invention are not impaired. Specific examples of such non-conjugated polyenes include 1,4-hexadiene, 3-methyl-1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene, 4,5- Chain non-conjugated dienes such as dimethyl-1,4-hexadiene and 7-methyl-1,6-octadiene, cyclic non-conjugated dienes such as methyltetrahydroindene, dicyclopentadiene and norbornadiene, 2,3-diisopropylidene-5 And trienes such as -norbornene, 2-ethylidene-3-isopropylidene-5-norbornene, 2-propenyl-2,2-norbornadiene, and the like.

As the ethylene / α-olefin / non-conjugated polyene copolymer comprising the above components, those having the following characteristics are used.
(i) Mass ratio of ethylene to α-olefin (ethylene / α-olefin):
The ethylene / α-olefin / non-conjugated polyene copolymer comprises (a) a unit derived from ethylene and (b) a unit derived from an α-olefin, 35/65 to 95/5, preferably 40/60. To 90/10, more preferably 45/55 to 85/15, particularly preferably 50/50 to 80/20 in a mass ratio [(a) / (b)].
When this mass ratio is within the above range, a rubber composition capable of providing a crosslinked rubber molded article having excellent heat aging resistance, strength characteristics and rubber elasticity, and excellent cold resistance and processability is formed.
(ii) Iodine number:
The iodine value of the ethylene / α-olefin / non-conjugated polyene copolymer is 0.5 to 50 (g / 100 g), preferably 1 to 45 (g / 100 g), more preferably 1 to 43 (g / 100 g), particularly Preferably it is 3-40 (g / 100g).
When the iodine value is within the above range, a rubber composition having high crosslinking efficiency can be obtained, and a crosslinked rubber molded article having excellent resistance to compression set and excellent environmental degradation resistance (= heat aging resistance) is provided. Can be obtained. If the iodine value exceeds the above range, the crosslink density becomes too high, and mechanical properties such as tensile elongation may deteriorate.
(iii) Intrinsic viscosity:
The intrinsic viscosity [η] of the ethylene / α-olefin / non-conjugated polyene copolymer measured in decalin at 135 ° C. is 0.01 to 5.0 dl / g, preferably 0.03 to 4.0 dl / g, more preferably 0.05 to 3.5 dl. / G, particularly preferably 0.07 to 3.0 dl / g. When the rubber composition according to the present invention is applied to LIM molding, 0.01 to 1.5 dl / g, preferably 0.03 to 1.3 dl / g, more preferably Is 0.05 to 1.2 dl / g, particularly preferably 0.07 to 1.1 dl / g. An embodiment in which the upper limit of the intrinsic viscosity is 0.5 dl / g or less, preferably less than 0.3 dl / g, is one preferred embodiment particularly for LIM molding. When the intrinsic viscosity [η] is within the above range, a rubber composition that can provide a crosslinked rubber molded article having excellent strength characteristics and compression set resistance and excellent processability is formed.

The ethylene / α-olefin / non-conjugated polyene copolymer used in the present invention can be produced by a conventionally known method as described in the following documents.
Polymer production process (published by Industrial Research Council) 365-378 pages JP-A-9-71617 JP-A-9-71618 Japanese Patent Laid-Open No. 9-208615 Japanese Patent Laid-Open No. 10-67823 Japanese Patent Laid-Open No. 10-67824 Japanese Patent Laid-Open No. 10-110054 WO 2003/057777

The SiH group-containing compound reacts with the ethylene / α-olefin / non-conjugated polyene copolymer to act as a crosslinking agent. This SiH group-containing compound is not particularly limited in its molecular structure, and can be used in conventionally produced resinous materials such as linear, cyclic, branched or three-dimensional network structures, but one molecule It is necessary to contain at least two hydrogen atoms directly bonded to silicon atoms, that is, SiH groups. Such SiH group-containing compounds usually have a general formula
R ⁴ _b H _c SiO _{(4-bc) / 2}
The compound represented by these can be used. Here, R ⁴ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 10, preferably 1 to 8 carbon atoms excluding an aliphatic unsaturated bond, and as such a monovalent hydrocarbon group, In addition to the alkyl group, a phenyl group and a halogen-substituted alkyl group such as a trifluoropropyl group can be exemplified. Of these, a methyl group, an ethyl group, a propyl group, a phenyl group, and a trifluoropropyl group are preferable, and a methyl group and a phenyl group are particularly preferable. Further, b is 0 ≦ b <3, preferably 0.6 <b <2.2, more preferably 1.5 ≦ b ≦ 2, and c is 0 <c ≦ 3, preferably 0.002 ≦ c <2, more preferably 0.01 ≦ c ≦ 1, and b + c is 0 <b + c ≦ 3, preferably 1.5 <b + c ≦ 2.7.

This SiH group-containing compound is preferably an organohydrogenpolysiloxane having preferably 2 to 1000, particularly preferably 2 to 300, and most preferably 4 to 200 silicon atoms in one molecule. Siloxane oligomers such as 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethyltetracyclosiloxane, 1,3,5,7,8-pentamethylpentacyclosiloxane, molecular chain Both ends trimethylsiloxy group-blocked methylhydrogenpolysiloxane, molecular chain both ends trimethylsiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane copolymer, molecular chain both-end silanol group-blocked methylhydrogenpolysiloxane, molecular chain both-end silanol group Blocked dimethylsiloxane / methylhydrogensiloxane copolymer, dimethylhydrogensiloxy at both ends of the molecular chain Blocked dimethylpolysiloxane, molecular chain both ends dimethylhydrogensiloxy group blocked methylhydrogenpolysiloxane, molecular chain both ends dimethylhydrogensiloxy group blocked dimethylsiloxane / methylhydrogensiloxane copolymer, R ⁴ ₂ (H) SiO _{Consists of 1/2} units and SiO _4/2 units, optionally R ⁴ ₃ SiO _1/2 units, R ⁴ ₂ SiO _2/2 units, R ⁴ (H) SiO _2/2 units, (H) SiO _{3 Examples} include silicone resins that may contain _{/ 2} or R ⁴ SiO _3/2 units.

Examples of the methyl hydrogen polysiloxane blocked with trimethylsiloxy groups at both ends of the molecular chain include (CH ₃ ) ₃ SiO-[-SiH (CH ₃ ) -O-] _d -Si (CH ₃ ) ₃ (d is an integer of 2 or more. And a compound in which part or all of the methyl group of this compound is substituted with an ethyl group, a propyl group, a phenyl group, a trifluoropropyl group, or the like.

Examples of the dimethylsiloxane / methylhydrogensiloxane copolymer blocked with trimethylsiloxy group at both ends of the molecular chain include, for example, (CH ₃ ) ₃ SiO-[-Si (CH ₃ ) ₂ -O-] _e -[-SiH (CH ₃ ) -O-] _f -Si (CH ₃ ) ₃ (e is an integer of 1 or more, f is an integer of 2 or more), and further, a part or all of the methyl group of this compound is ethyl group, propyl And a compound substituted with a group, a phenyl group, a trifluoropropyl group, and the like.

Examples of the methyl hydrogen polysiloxane blocked with silanol groups at both ends of the molecular chain include HOSi (CH ₃ ) ₂ O-[-SiH (CH ₃ ) -O-] ₂ -Si (CH ₃ ) ₂ OH, Examples include compounds in which part or all of the methyl group is substituted with an ethyl group, a propyl group, a phenyl group, a trifluoropropyl group, or the like.

Examples of dimethylsiloxane / methylhydrogensiloxane copolymers blocked with silanol groups at both ends of the molecular chain include, for example, HOSi (CH ₃ ) ₂ O-[-Si (CH ₃ ) ₂ -O-] _e -[-SiH (CH ₃ ) -O-] _f -Si (CH ₃ ) ₂ OH (e is an integer of 1 or more, f is an integer of 2 or more), and further, part or all of the methyl group of this compound is an ethyl group, Examples include compounds substituted with a propyl group, a phenyl group, a trifluoropropyl group, and the like.

Examples of dimethylpolysiloxane blocked with dimethylhydrogensiloxy group at both ends of the molecular chain include, for example, HSi (CH ₃ ) ₂ O-[-Si (CH ₃ ) ₂ -O-] _e -Si (CH ₃ ) ₂ H (in the formula e is an integer of 1 or more.) Further, a compound in which part or all of the methyl group of this compound is substituted with an ethyl group, a propyl group, a phenyl group, a trifluoropropyl group, or the like can be given.

Examples of the dimethylhydrogensiloxy group-blocked methylhydrogenpolysiloxane at both molecular chain ends include HSi (CH ₃ ) ₂ O-[-SiH (CH ₃ ) -O-] _e -Si (CH ₃ ) ₂ H (wherein E is an integer of 1 or more.) Further, a compound in which part or all of the methyl group of this compound is substituted with an ethyl group, a propyl group, a phenyl group, a trifluoropropyl group, or the like can be given.

Examples of dimethylsiloxane / methylhydrogensiloxane copolymers blocked with dimethylhydrogensiloxy groups at both ends of the molecular chain include, for example, HSi (CH ₃ ) ₂ O-[-Si (CH ₃ ) ₂ -O-] _e -[-SiH ( CH ₃ ) —O—] _h —Si (CH ₃ ) ₂ H (wherein e and h are each an integer of 1 or more), and a part or all of the methyl group of this compound is converted to an ethyl group. , Propyl group, phenyl group, trifluoropropyl group and the like.

  Such a compound can be produced by a known method, for example, octamethylcyclotetrasiloxane and / or tetramethylcyclotetrasiloxane and hexamethyldisiloxane or 1,3-dihydro-1,1 which can be a terminal group. , 3,3-tetramethyldisiloxane and other compounds containing a triorganosilyl group or a diorganohydrogensiloxy group in the presence of a catalyst such as sulfuric acid, trifluoromethanesulfonic acid or methanesulfonic acid at -10 ° C It can be easily obtained by equilibrating at a temperature of about ~ 40 ° C.

  The SiH group-containing compound is 0.1 to 100 parts by weight, preferably 0.1 to 75 parts by weight, more preferably 0.1 to 50 parts by weight, and still more preferably 100 parts by weight of the ethylene / α-olefin / non-conjugated polyene copolymer. Is used in a proportion of 0.2-30 parts by weight, still more preferably 0.2-20 parts by weight, particularly preferably 0.5-10 parts by weight, most preferably 0.5-5 parts by weight. When the SiH group-containing compound is used in a proportion within the above range, a rubber composition capable of forming a crosslinked rubber molded article having excellent compression set resistance, moderate crosslinking density and excellent strength characteristics and elongation characteristics can be obtained. On the other hand, when the SiH group-containing compound is used in a proportion exceeding 100 parts by weight, it is not preferable because it is disadvantageous in terms of cost.

  In addition, the SiH group-containing compound is a hydrogen atom bonded to a silicon atom (≡SiH group) for one aliphatic unsaturated bond (alkenyl group, etc.) contained in the ethylene / α-olefin / non-conjugated polyene copolymer. Is suitable in the range of 0.2 to 10, preferably in the range of 0.7 to 5. If it is less than 0.2, crosslinking may not be sufficient and sufficient mechanical strength may not be obtained. On the other hand, if it is more than 10, physical properties after curing will deteriorate, particularly heat resistance and compression set resistance will deteriorate significantly. Sometimes.

  The addition reaction catalyst promotes an addition reaction (such as alkene hydrosilylation reaction) between an alkenyl group of an ethylene / α-olefin / non-conjugated polyene copolymer and a SiH group of a SiH group-containing compound, for example, An addition reaction catalyst comprising a platinum group element such as a platinum-based catalyst, a palladium-based catalyst, or a rhodium-based catalyst, preferably a platinum-based catalyst is used. As a catalyst including a platinum-based catalyst, it is desirable to use a complex of a group 8 element metal of the periodic table, particularly preferably platinum and a compound containing a vinyl group and / or a carbonyl group. As the compound containing this carbonyl group, carbonyl, octanal and the like are preferable, and as a complex of these with platinum, specifically, a platinum-carbonyl complex, a platinum-octanal complex, a platinum-carbonylbutyl cyclic siloxane complex, a platinum- And carbonylphenyl cyclic siloxane complex. The vinyl group-containing compound is preferably a vinyl group-containing organosiloxane. Specific examples of complexes of these with platinum include platinum-divinyltetramethyldisiloxane complex, platinum-divinyltetraethyldisiloxane complex, platinum. -Divinyltetrapropyldisiloxane complex, platinum-divinyltetrabutyldisiloxane complex, platinum-divinyltetraphenyldisiloxane complex.

  Among the vinyl group-containing organosiloxanes, vinyl group-containing cyclic organosiloxanes are preferable, and platinum-vinylmethyl cyclic siloxane complexes, platinum-vinylethyl cyclic siloxane complexes, and platinum-vinylpropyl cyclic siloxane complexes are examples of complexes of these with platinum. It is done.

  The vinyl group-containing organosiloxane itself may be a ligand for a metal, but may be used as a solvent for coordinating other ligands. A complex in which a vinyl group-containing organosiloxane is used as a solvent and the aforementioned compound containing a carbonyl group is a ligand is particularly preferable as an addition reaction catalyst. Specific examples of such complexes include a platinum-carbonyl complex vinylmethyl cyclic siloxane solution, a platinum-carbonyl complex vinylethyl cyclic siloxane solution, a platinum-carbonyl complex vinylpropyl cyclic siloxane solution, and a platinum-carbonyl complex divinyl. Tetramethyldisiloxane solution, platinum-carbonyl complex divinyltetraethyldisiloxane solution, platinum-carbonyl complex divinyltetrapropyldisiloxane solution, platinum-carbonyl complex divinyltetrabutyldisiloxane solution, platinum-carbonyl complex divinyltetraphenyldi A siloxane solution is mentioned.

  The addition reaction catalyst comprising these complexes may further contain components other than the compound containing a vinyl group and / or a carbonyl group. For example, a solvent other than the compound containing a vinyl group and / or a carbonyl group may be contained. Examples of these solvents include, but are not limited to, various alcohols and xylene. Specific examples of the alcohol include methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, n-amyl alcohol, isoamyl alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol. , Aliphatic saturated alcohols such as capryl alcohol, nonyl alcohol, decyl alcohol, undecyl alcohol, lauryl alcohol, tridecyl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, eicosyl alcohol, fats such as allyl alcohol, crotyl alcohol, etc. Unsaturated alcohols, cycloaliphatic alcohols such as cyclopentanol and cyclohexanol, benzyl alcohol, cinnamyl alcohol Aromatic alcohols such as Lumpur, and the like heterocyclic alcohols such as furfuryl alcohol.

  Examples of using alcohol as a solvent include platinum-octanol / octanol complexes. By including these solvents, there are advantages such as easy handling of the addition reaction catalyst and easy mixing with the rubber composition.

Among the various addition reaction catalysts listed above, a platinum-carbonyl complex, preferably a vinylmethyl cyclic siloxane solution of Pt ⁰ · CO · [CH ₂ = CH (Me) SiO] ₄ , a platinum-vinylmethyl cyclic siloxane complex, Pt ⁰ · (CH ₂ = CH (Me) SiO) ₄ , platinum-divinyltetramethyldisiloxane complex, preferably Pt ⁰ -1.5 [(CH ₂ = CH (Me) ₂ Si) ₂ O], platinum- Octal / octanol complexes are practically preferred, and among them, platinum-carbonylvinylmethyl cyclic siloxane complexes are particularly preferred.

  The proportion of Group 8 element metal, preferably platinum, contained in these addition reaction catalysts is usually 0.1 to 10% by weight, preferably 1 to 5% by weight, more preferably 2 to 4% by weight, particularly preferably. 2.5 to 3.5% by weight.

  The addition reaction catalyst is 0.1 to 100,000 ppm by weight, preferably 0.1 to 10,000 ppm by weight, more preferably 1 to 5,000 ppm by weight, and particularly preferably 5 to 1,000 ppm with respect to the ethylene / α-olefin / non-conjugated polyene copolymer. Used in a weight ppm ratio. When the addition reaction catalyst is used in a proportion within the above range, a rubber composition capable of forming a crosslinked rubber molded article having a moderate crosslinking density and excellent strength properties and elongation properties can be obtained. On the other hand, if the addition reaction catalyst is used in a proportion exceeding 100,000 ppm by weight, it is not preferable because it is disadvantageous in terms of cost.

  The addition reaction catalyst is an optional component, and it is also possible to obtain a crosslinked rubber molded article by irradiating an uncrosslinked rubber molded article of a rubber composition not containing it with light, γ-rays, electron beams or the like.

  Reaction inhibitors used as optional components together with the addition reaction catalyst include ethynyl group-containing alcohols such as benzotriazole and ethynylcyclohexanol, N, N-diallylacetamide, N, N-diallylbenzamide, N, N, N ′, N Amide compounds such as' -tetraallyl-o-phthalic acid diamide, N, N, N ', N'-tetraallyl-m-phthalic acid diamide, N, N, N', N'-tetraallyl-p-phthalic acid diamide, Examples thereof include organic peroxides such as acrylonitrile, sulfur, phosphorus, nitrogen, amine compounds, sulfur compounds, phosphorus compounds, tin, tin compounds, tetramethyltetravinylcyclotetrasiloxane, and hydroperoxide.

  The reaction inhibitor is 0 to 50 parts by weight, usually 0.0001 to 50 parts by weight, preferably 0.0001 to 30 parts by weight, more preferably 0.0001 to 100 parts by weight of the ethylene / α-olefin / non-conjugated polyene copolymer. It is used in a proportion of 20 parts by weight, more preferably 0.0001 to 10 parts by weight, particularly preferably 0.0001 to 5 parts by weight. When the reaction inhibitor is used in a proportion of 50 parts by weight or less, a rubber composition having a high crosslinking speed and excellent productivity of a crosslinked rubber molded product can be obtained. On the other hand, if the reaction inhibitor is used in a proportion exceeding 50 parts by weight, it is not preferable because it is disadvantageous in terms of cost.

Ketjen Black is a highly conductive carbon black having a primary particle size of 50 nm or less, a DBP oil absorption of 300 ml / 100 g or more, and a BET specific surface area of 500 m ² / g or more, preferably a primary particle size of 40 nm or less, DBP oil absorption A product having an amount of 400 ml / 100 g or more and a BET specific surface area of 1000 m ² / g or more, for example, a commercial product, Lion product EC600JD or the like is used. Ketjen black is used in a proportion of 5 to 50 parts by weight, preferably 10 to 25 parts by weight, more preferably 12 to 18 parts by weight, per 100 parts by weight of the ethylene / α-olefin / non-conjugated polyene copolymer. If ketjen black is used in a proportion below this, the desired electromagnetic shielding properties cannot be obtained, while if it is used in a proportion above this, scorching occurs due to shear heat generation during kneading, and the processability is remarkably inferior.

  When a rubber composition having these components is used as a molding material for a sealing material, a cured product having a hardness (Duro A) of 80 or less, preferably 60 or less is used. Conventionally, such adjustment to hardness has been performed by, for example, further blending 30 parts by weight or more of a plasticizer or paraffinic oil per 100 parts by weight of rubber. However, the addition of a plasticizer causes an increase in outgas. There was a problem of causing adverse effects on electronic devices. On the other hand, in the present invention, by using a low-viscosity EPDM, a rubber having a hardness that can be sufficiently used as a sealing material can be prepared even when a plasticizer is not added.

  The rubber composition for electromagnetic shielding comprising the above components usually includes flaky inorganic fillers usually blended with rubber and thermoplastic elastomer, specifically clay, diatomaceous earth, talc, mica, graphite, etc. Can be used as a filler by blending barium sulfate, calcium carbonate, magnesium carbonate and metal oxide. Further, carbon fiber, carbon fiber, single-walled carbon nanotube (SWCNT), multi-walled carbon nanotube (MWCNT) or the like can be added as long as it is 10 parts by weight or less.

  Further, various solid powders such as metal powders, glass powders, ceramic powders, and powdered polymers, and waxes, and anti-aging agents such as phenols and derivatives thereof are used as long as the performance is not impaired. Here, when an amine, its derivative, or an imidazole anti-aging agent is used, it becomes a catalyst poison for condensation addition crosslinking, so that these anti-aging agents and additives belonging thereto cannot be used.

  A small amount of a thermoplastic resin may be added to improve the stabilizer, tackifier, release agent, pigment, flame retardant, lubricant, moldability and the like.

  The rubber composition is prepared using a kneading apparatus such as a three-roll mill, an open roll, a kneader, an internal mixer, a planetary mixer, a Banbury mixer, a high-shear mixer, or a two-open roll. The molded product should be molded at 50 to 200 ° C., preferably 100 to 180 ° C. after uniformly dispersing the SiH group-containing compound and the condensation addition catalyst together with other components such as a polymer, a reinforcing agent, an inorganic filler, and a softening agent. Can be obtained. Here, the molding is performed by LIM molding, injection molding, injection molding, compression molding or the like.

  The molded product formed into a predetermined shape is further heat-treated at about 100 to 200 ° C., preferably about 120 to 150 ° C. for about 0.5 to 24 hours, preferably about 1 to 15 hours using an air oven or the like. A heat treatment temperature lower than this is not preferable because curing does not reach the end point and compression set deteriorates, while a temperature higher than this promotes softening deterioration.

  When the rubber composition for electromagnetic wave shielding according to the present invention is molded into a rubber sheet having a thickness of 2 mm, the electromagnetic wave shielding characteristic at 1 GHz shows a value of 10 dB or more.

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

Example 1
100 parts ethylene / propylene / 5-vinyl-2-norbornene random copolymer
(E content 52.7 wt%, VNB content 4.7 wt%, shear viscosity 1100 Pa · sec (40 ° C))
C ₆ H ₅ Si (OSi (CH ₃ ) ₃ ) ₃ 5 parts
1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane platinum catalyst 0.2 parts
1-ethynyl-1-cyclohexanol 0.4 parts Ketjen black (Lion product EC600JD) 15 parts or more of each component (parts by weight) are kneaded and mixed with a three-mill roll, and the mixture is made into a test sheet type of 140 x 100 x 2 mm After casting, a rubber sheet was obtained by compression molding under conditions of a hot platen set temperature of 150 ° C. and a mold compression of 80 MPa for 6 minutes, and then heat treatment was performed in an air oven at 150 ° C. for 1 hour.

Example 2
In Example 1, the ketjen black amount was changed to 20 parts by weight.

Comparative Example 1
In Example 1, 20 parts by weight of acetylene black (electrochemical product) was used instead of ketjen black.

Comparative Example 2
In Example 1, 50 parts by weight of artificial graphite fine powder (Showa Denko product UFG30: flake graphite, average particle size 10 μm, specific surface area 15 m ² / g) was used instead of ketjen black.

With respect to the rubber sheets obtained in the above examples and comparative examples, the following items were measured.
Normal physical properties: Compliant with JIS K6253, K6251 Compression set: Compliant with JIS K6262 (150 ° C, 70 hours), 3 layers of 13mm diameter, 2mm thick rubber sheets Volume resistance: Compliant with JIS K6271, Mitsubishi Chemical Measured by the four-terminal method using the Loresta EP (MCP-T360) product Shield characteristics: Measures shielding performance (attenuation effect) at 1 GHz using Advantest's plastic shield evaluation device TR17301A

The measurement results obtained are shown in the following table.
table
Measurement Item Example 1 Example 2 Comparative Example 1 Comparative Example 2
Normal physical properties Hardness (Duro-A) 55 71 64 68
Tensile strength (MPa) 4.9 6.8 3.9 4.5
Elongation (%) 230 200 140 210
Compression set (%) 26 28 48 42
Volume resistance (Ω ・ cm) 4 1.5 15 7
Shield characteristics (dB) 12 28 <1 8

The rubber composition for electromagnetic shielding according to the present invention is an electromagnetic shielding material, for example, an electromagnetic shielding material for outdoor installation devices (a rubber packing used for the purpose of waterproofing / dustproofing used for relay equipment such as measuring equipment and CATV). And gaskets), electromagnetic shielding materials for covering long objects such as connectors and cables, and electromagnetic shielding materials for shutting out electromagnetic waves generated from the engine of hybrid vehicles. Such electromagnetic shielding materials include antistatic rubber products, electronic devices such as mobile phones and wireless devices / measurement devices, microwave ovens, medical devices, polarized electrodes of electric double layer capacitors of electric vehicles, battery electrode materials, conductive films It is used for building materials that require EMI countermeasures, such as machine tools and robots that cause malfunctions due to external electromagnetic interference, TVs and radios that cause malfunctions in AV equipment and personal computers.

Claims (8)

An ethylene / α-olefin / non-conjugated polyene copolymer with a shear viscosity of 10 ⁸ Pa · sec (40 ° C., strain 1%) or less is made to contain ketjen black and has a hardness (Duro-A) of 80 or less. A rubber composition for electromagnetic wave shielding, which gives a cured product having an electromagnetic wave shielding characteristic at 1 GHz of a rubber sheet having a thickness of 2 mm of 10 dB or more.   The rubber composition for electromagnetic wave shielding according to claim 1, wherein Ketjen black is used in a proportion of 5 to 50 parts by weight with respect to 100 parts by weight of the ethylene / α-olefin / non-conjugated polyene copolymer.   The rubber composition for electromagnetic wave shielding according to claim 1, wherein the ethylene / α-olefin / non-conjugated polyene copolymer is EPDM.   The rubber composition for electromagnetic wave shielding according to claim 1 or 3, further comprising a SiH group-containing compound and an addition reaction catalyst.   Furthermore, the rubber composition for electromagnetic wave shields of Claim 1, 3 or 4 formed by containing a reaction inhibitor.   The rubber composition for electromagnetic wave shielding according to claim 1, 3, 4, or 5, wherein the molding is performed by LIM molding, injection molding, injection molding or compression molding.   The rubber composition for electromagnetic wave shielding according to any one of claims 1 to 6, which is used as a molding material for a sealing material. The sealing material shape | molded from the rubber composition for electromagnetic wave shields of Claim 7.