JP5544066B2 - Dielectric elastomer composition and antenna member - Google Patents

Description

  The present invention relates to a dielectric elastomer composition having both excellent flame retardancy and dielectric properties, and an antenna member formed by molding the composition.

  In recent years, with the remarkable spread of patch antennas used for mobile phones, cordless phones, RFID, etc., lens antennas such as radio telescopes and millimeter wave radars, and the remarkable development of satellite communication equipment, the frequency of communication signals has been increased and the frequency of communication equipment has increased. Further downsizing is desired. In the communication device, when the relative dielectric constant of the antenna material incorporated in the communication device is increased, the frequency can be further reduced and the size can be reduced. The relative dielectric constant is a parameter indicating the degree of polarization inside the dielectric. Therefore, if an antenna material having a high relative dielectric constant can be used, high frequency can be increased, and therefore the circuit can be shortened and the communication device can be miniaturized. In addition, as the usage modes of communication devices diversify, antenna materials are also required to have little change in electrical characteristics from low temperature to high temperature and to be excellent in flame retardancy.

Conventionally, as a material for obtaining an antenna having a high relative dielectric constant and a low dielectric loss tangent over a wide temperature range from a low temperature to a high temperature, an elastomer such as ethylene propylene rubber is used in a temperature range of −40 ° C. to 100 ° C. A dielectric elastomer composition containing a barium-neodymium ceramic powder or the like having a relative dielectric constant temperature coefficient α (unit: 1 / ° C.) in the range of (−200 to 100) × 10 ⁻⁶ is known ( Patent Document 1).
On the other hand, as a measure for improving flame retardancy in antenna materials and the like, it is known to blend a bromine-based or chlorine-based halogen-based flame retardant (for example, see Patent Document 2). In general, in order to improve flame retardancy in an elastomeric material, it is known to blend a metal hydroxide, expanded graphite and the like in addition to the halogen flame retardant. It is known that the metal hydroxide is blended in, for example, an elastomer material constituting a transfer belt of an electrophotographic apparatus (see Patent Document 3).

However, the dielectric elastomer composition of Patent Document 1 has excellent dielectric properties with little change in electrical properties from low temperature to high temperature, but does not contain a flame retardant and is used for applications where flame retardancy is required. There is a problem that it cannot be used.
In order to improve the flame retardancy of such a dielectric elastomer composition, when the halogen flame retardant is used as a flame retardant, there is a concern that dioxins may be generated from a brominated flame retardant or a chlorine flame retardant at the time of disposal. And environmentally unfavorable.
In addition, when using a metal hydroxide, it is difficult to produce a flame retardant effect unless it is contained in a large amount, and when it is contained in a large amount, the dielectric loss tangent generally increases, so a low dielectric loss tangent is required as in antenna materials. It is not known for use in certain applications.
Further, when the expanded graphite is blended in the antenna material, the flame retardancy is improved, but the dielectric property is extremely deteriorated, which is not preferable.
JP 2006-1989 JP 2005-333516 A JP 2005-97493 A

  The present invention has been made in order to cope with such problems, and has excellent flame retardancy while considering the influence on the environment, and has sufficient dielectric characteristics as an antenna material over a wide temperature range from low temperature to high temperature. It is an object of the present invention to provide a dielectric elastomer composition having an antenna member and an antenna member formed by molding the composition.

The dielectric elastomer composition of the present invention is a dielectric elastomer composition obtained by blending 100 parts by weight to 600 parts by weight of a metal hydroxide with respect to 100 parts by weight of an elastomer, and has a frequency of 400 MHz and a temperature of 30 ° C. The dielectric elastomer composition has a relative dielectric constant of 3 or more and a dielectric loss tangent of 0.02 or less.
The dielectric elastomer composition is characterized in that 5 to 40 parts by weight of carbon black is blended with 100 parts by weight of the elastomer.

  The dielectric elastomer composition is characterized in that a relative dielectric constant at an arbitrary temperature within a temperature range of −10 ° C. to 70 ° C. is a value within ± 0.4 of a relative dielectric constant based on 30 ° C.

  The dielectric elastomer composition is characterized by blending dielectric ceramic powder. The metal hydroxide is at least one selected from aluminum hydroxide and magnesium hydroxide. The elastomer is ethylene propylene rubber.

  The antenna member of the present invention is formed by molding a dielectric elastomer composition, and the dielectric elastomer composition is the dielectric elastomer composition described above.

  The dielectric elastomer composition of the present invention comprises 100 to 600 parts by weight of a metal hydroxide as a flame retardant with respect to 100 parts by weight of the elastomer, and the dielectric elastomer composition described above at a frequency of 400 MHz and a temperature of 30 ° C. Since the relative dielectric constant of an object is 3 or more and the dielectric loss tangent is 0.02 or less, it has excellent flame resistance while maintaining sufficient dielectric properties as an antenna material.

  In the dielectric elastomer composition, since 5 to 40 parts by weight of carbon black is blended with 100 parts by weight of the elastomer, there is no bleed of process oil on the surface of the molded body, and adhesion with the electrode does not decrease. Change of dielectric properties of the elastomeric molded article can be suppressed.

  In addition, by blending the metal hydroxide as a flame retardant at the above blending ratio, the dielectric elastomer composition has a relative dielectric constant of 30 ° C. at an arbitrary temperature within a temperature range of −10 ° C. to 70 ° C. Therefore, it is suitable as an antenna material because the temperature change of the dielectric constant is small over a wide temperature range from low temperature to high temperature.

  Moreover, since the said dielectric elastomer composition mix | blends dielectric ceramic powder, it can make a dielectric constant higher than the case where it is not mix | blended.

  Since the antenna member of the present invention is formed by molding the above dielectric elastomer composition, it has excellent flame retardancy while maintaining a high relative dielectric constant and low dielectric loss tangent over a wide temperature range from low temperature to high temperature.

As described above, when a metal hydroxide is used as a flame retardant, a flame retardant effect is difficult to obtain unless it is contained in a large amount, and generally a dielectric loss tangent increases when contained in a large amount. Hydroxide was not used. As a result of actually carrying out tests with various blending ratios, it was confirmed that the dielectric constant was slightly improved but the dielectric loss tangent was increased. On the other hand, it was newly found out that the change in the temperature of the relative dielectric constant is less when the metal hydroxide is added than when the metal hydroxide is not added (see Table 1 described later). Reducing the temperature change of the dielectric constant is preferable as an antenna material.
From these facts, the present inventors have used metal hydroxide as a flame retardant, and variously studied the blending ratio with respect to the elastomer, while achieving both dielectric properties sufficient as an antenna material and flame retardancy, A dielectric elastomer composition having a reduced dielectric constant temperature change was obtained. The present invention is based on the above findings.

  Examples of the metal hydroxide that can be used in the present invention include magnesium hydroxide, aluminum hydroxide, dawsonite, calcium aluminate, calcium hydroxide, barium hydroxide, and hydrotalcite. These metal hydroxides can absorb heat and release water molecules by causing an endothermic dehydration reaction under high heat, thereby reducing the temperature and imparting flame retardancy. In addition, the above-mentioned metal hydroxide improves dispersibility, processability, etc., so that silane coupling agents, titanate coupling agents, epoxy surface treatment agents, higher fatty acids or salts thereof, higher alcohols, surfactants, etc. The surface treatment may be performed.

  These metal hydroxides may be used alone or in combination of two or more. When two or more kinds of metal hydroxides are used in combination, more excellent flame retardancy can be imparted because each metal hydroxide starts an endothermic dehydration reaction at a different temperature.

Among the above metal hydroxides, at least one selected from magnesium hydroxide and aluminum hydroxide is preferable because it is inexpensive and has a high hydrate content. Magnesium hydroxide and aluminum hydroxide preferably have a BET specific surface area of 1 to 20 m ² / g or less and an average particle size of 0.1 to 50 μm. The decomposition temperatures are 300 to 350 ° C. for magnesium hydroxide and 200 to 230 ° C. for aluminum hydroxide.

For magnesium hydroxide or aluminum hydroxide, a dry method or a wet slurry method can be employed as a surface treatment method using a silane coupling agent. In addition to performing surface treatment in advance as described above, a silane coupling agent can also be added to the dielectric elastomer composition and surface treatment can be performed while mixing.
Further, when magnesium hydroxide or aluminum hydroxide is surface-treated with a higher fatty acid or a salt thereof, a method in which the higher fatty acid or a salt thereof is dissolved and sprayed, and the surface is treated by a dry method using a Henschel mixer or the like can be employed. Examples of higher fatty acids and salts thereof include stearic acid, oleic acid, palmitic acid, lauric acid, and sodium and potassium salts thereof.

  As commercial products of magnesium hydroxide that can be used in the present invention, manufactured by Kamishima Chemical Industries: WX-3 (average particle size 2.5 μm, surface treatment: none), WH-3 (average particle size 2.5 μm, surface treatment: present) ), N-4 (average particle size 1.1 μm, surface treatment: present) and N-6 (average particle size 1.3 μm, surface treatment: present), manufactured by Kyowa Chemical Co., Ltd .: Kisuma 5A (average particle size 0.85 μm, surface treatment) : Yes) and Kisuma 5B (average particle size 0.87 μm, surface treatment: yes), manufactured by Sakai Chemical Industry Co., Ltd .: MGZ-1 (average particle size 0.8 μm, surface treatment: yes) and MGZ-3 (average particle size 0.1 μm) , Surface treatment: yes), manufactured by Tateho Chemical Co., Ltd .: Echo Mug Z-10 and the like. Moreover, as a commercial item of aluminum hydroxide, Nippon Light Metal Co., Ltd. product: B703S (average particle diameter 2 micrometers) etc. are mentioned.

  Further, in consideration of environmental load and imparting flame retardancy, a flame retardant having a large flame retardant effect may be added in the minimum necessary amount in addition to the metal hydroxide.

The compounding ratio of the metal hydroxide in the dielectric elastomer composition of the present invention is 100 to 600 parts by weight with respect to 100 parts by weight of the elastomer. More preferably, it is 100 to 300 parts by weight.
When the amount is less than 100 parts by weight, sufficient flame retardancy (specifically, tests described in Examples described later) cannot be obtained. In addition, the effect of reducing the temperature change of the dielectric constant is reduced. On the other hand, if it exceeds 600 parts by weight, the dielectric loss tangent may be 0.02 or more depending on the temperature, or molding may not be possible.
Moreover, the temperature change of a dielectric constant can be made small by mix | blending a metal hydroxide in the said range. Specifically, the relative dielectric constant of the dielectric elastomer composition at an arbitrary temperature within a temperature range of −10 ° C. to 70 ° C. can be a value within ± 0.4 of the relative dielectric constant based on 30 ° C. Here, the reference frequency may be any frequency as long as the comparison target is the same.

  The elastomer constituting the dielectric elastomer composition of the present invention has a relative dielectric constant of 3 or more and a dielectric loss tangent of 0.02 or less when the metal hydroxide is blended at a frequency of 400 MHz and a temperature of 30 ° C. Any natural rubber-based elastomer and synthetic rubber-based elastomer can be used.

  Natural rubber-based elastomers include natural rubber, chlorinated rubber, hydrochloric acid rubber, cyclized rubber, maleated rubber, hydrogenated rubber, and vinyl monomers such as methyl methacrylate, acrylonitrile, and methacrylic acid ester grafted onto the double bond of natural rubber. Examples thereof include a graft-modified rubber, a block polymer obtained by roughening natural rubber in the presence of a monomer in a nitrogen stream. These include natural rubber as a raw material, and elastomers from synthetic cis-1,4-polyisoprene as a raw material.

  Synthetic rubber elastomers include isobutylene rubber, ethylene propylene rubber, ethylene propylene diene rubber, ethylene propylene terpolymer, polyolefin elastomer such as chlorosulfonated polyethylene rubber, styrene-isoprene-styrene block copolymer (SIS), styrene-butadiene- Styrene elastomers such as styrene copolymer (SBS), styrene-ethylene-butylene-styrene block copolymer (SEBS), isoprene rubber, urethane rubber, epichlorohydrin rubber, silicone rubber, nylon 12, butyl rubber, butadiene rubber, polynorbornene rubber, acrylonitrile- Examples thereof include butadiene rubber.

  These elastomers can be used alone or in combination of two or more. Further, one or two thermoplastic resins can be blended and used within a range that does not impair the elasticity of the elastomer. When one or more kinds selected from natural rubber elastomers and / or synthetic nonpolar elastomers are used as the elastomer of the present invention, a dielectric elastomer having excellent electrical insulation can be obtained. Examples of the synthetic non-polar elastomer include ethylene propylene rubber, ethylene propylene diene rubber, isobutylene rubber, isoprene rubber, and silicone rubber. In particular, ethylene propylene rubber and ethylene propylene diene rubber have a very low dielectric loss tangent, and can be preferably used as a material for an antenna member.

Examples of the carbon black that can be used in the present invention include pigments such as hard carbon and soft carbon, and carbon black used for improving wear resistance. However, acetylene-based carbon black having good conductivity is not preferable because the amount of increase in dielectric loss tangent is large. As a commercial product of carbon black, for example, Tokai Carbon Co., Ltd .: Seast S can be mentioned.
The blending ratio of the carbon black is 5 to 40 parts by weight with respect to 100 parts by weight of the elastomer. If the amount is less than 5 parts by weight, the oil retaining effect of carbon black is small, so that process oil bleeds to the surface of the molded body occurs, the adhesion to the electrode is lowered, and the dielectric properties change greatly, which is not preferable. On the other hand, when the amount exceeds 40 parts by weight, the dielectric loss tangent increases, which is not preferable. The optimum amount for high dielectric constant and low dielectric loss tangent is 10 to 35 parts by weight.

In order to improve the dielectric constant of the dielectric elastomer composition of the present invention, it is preferable to blend a dielectric ceramic powder.
The dielectric ceramic powder that can be used in the present invention is a group IIa, IVa, IIIb, IVb group oxide, carbonate, phosphate, silicate, or a complex oxide containing group IIa, IVa, IIIb, group IVb. It is preferable that at least one selected. Specifically, TiO ₂ , CaTiO ₃ , MgTiO ₃ , Al ₂ O ₃ , BaTiO ₃ , SrTiO ₃ , Ca ₂ P ₂ O ₇ , SiO ₂ , Mg ₂ SiO ₄ , Ca ₂ MgSi ₂ O ₇ , or relative dielectric In order to improve the temperature dependency of the rate, BaO—TiO ₂ —Nd ₂ O ₃ based ceramics containing an alkaline earth metal and a rare earth oxide can be used. The dielectric ceramic powder to be blended is not particularly limited as long as it exhibits dielectric properties. Moreover, you may mix | blend trace compositions, such as Al and Zr, for a characteristic improvement.

  The average particle size of the dielectric ceramic powder is preferably about 0.01 to 100 μm. If it is smaller than 0.01 μm, it is difficult to handle and unfavorable because binding properties are inhibited. If it is larger than 100 μm, it is not preferable because it may cause variation in dielectric properties in the molded body. A more practical range is about 0.1 to 20 μm.

  The blending ratio of the dielectric ceramic powder in the dielectric elastomer composition of the present invention is preferably 50 to 1000 parts by weight with respect to 100 parts by weight of the elastomer. By blending the dielectric ceramic powder in the above range, the relative dielectric constant can be improved by about 2 to 20 as compared with the case of not blending.

  In the present invention, in order to improve the mechanical strength by improving the affinity and bondability of the interface between the elastomer and the ceramic powder within the range not hindering the effects of the present invention, a silane coupling agent, Coupling agents such as titanate coupling agents, zirconia aluminate coupling agents, etc. (2) In order to improve plating properties for electrode formation, particulate fillers such as talc and calcium pyrophosphate (3 ) Antioxidants to further improve thermal stability, (4) Light stabilizers such as UV absorbers to improve light resistance, and (5) Impact resistance to improve impact resistance. (6) Colorants such as dyes and pigments for coloring, (7) Plasticizers for adjusting physical properties, cross-linking agents such as sulfur and peroxides, (8) For proceeding with vulcanization Each vulcanization accelerator It can be formulated.

  In addition, the dielectric elastomer composition of the present invention includes glass fibers, alkali metal titanate fibers such as potassium titanate whiskers, titanium oxide fibers, magnesium borate whiskers and aluminum borate within a range not impairing the object of the present invention. Various organic or inorganic fillers such as metal borate fibers such as um whisker, metal silicate fibers such as zinc silicate whisker and magnesium silicate whisker, carbon fiber, alumina fiber, and aramid fiber can be used in combination.

  The method for producing the dielectric elastomer composition of the present invention is not particularly limited, and various mixed molding methods can be used. For example, the above-mentioned carbon black, metal hydroxide, dielectric ceramic powder, various additives, vulcanizing agents, etc. are blended in an elastomer and kneaded with a Banbury mixer, roller, twin screw extruder, etc. The method etc. are mentioned.

  The antenna member of the present invention can be obtained by molding the dielectric elastomer composition obtained above into a predetermined shape, for example, a flat plate shape or a disk shape. As a molding method, any method such as heat compression molding, injection molding, transfer molding, and extrusion molding can be adopted. In the present invention, it is preferable to employ heat compression molding because it contains a large amount of metal hydroxide and ceramic powder.

Reference Example 1 to Reference Example 6, Example 1 to Example 8, and Comparative Example 1 to Comparative Example 15
Ethylene propylene rubber (Mitsui Chemical Co., Ltd .: EPT-3095), magnesium hydroxide (Kamishima Chemical Industry Co., Ltd .: WX-3) or aluminum hydroxide (Nihon Light Metal Co., Ltd .: B703S), and dielectric ceramic powder (Kyoritsu Material) Company :: HF-120) and carbon black (manufactured by Tokai Carbon Co., Ltd .: Seest S) were mixed in the blending ratios shown in Table 1, respectively, and further a vulcanization accelerator and process oil (manufactured by Idemitsu Kosan Co., Ltd .: PW380) A processing aid containing was added, kneaded with a pressure kneader, and then a compact of 80 mm × 80 mm × 1.5 mm was obtained by heat compression molding. The vulcanization conditions are 170 ° C x 20 minutes each.
With respect to the molded bodies of the dielectric elastomer compositions obtained in the respective Reference Examples, Examples and Comparative Examples, the flame retardancy, relative dielectric constant, dielectric loss tangent, and presence / absence of bleed were measured by the following methods. The results are also shown in Table 1.

<Flame retardance test>
The obtained molded product and the flame of an alcohol lamp are brought into contact with each other, and are kept stationary for 10 seconds. The state of combustion was confirmed by separating immediately. If the flame disappeared within 10 seconds, “○” was recorded as being sufficiently flame retardant, and “×” was recorded as being insufficient when burned for 10 seconds or longer.

<Measurement of relative dielectric constant and dielectric loss tangent>
The obtained molded body was processed into 20 mm × 20 mm × t1.5 mm, and the relative dielectric constant and dielectric loss tangent were measured at −10, 30, and 70 ° C. in the frequency band of 400 MHz by the capacitance method. The measurement apparatus used for the capacitance method was an impedance analyzer: E4991A (manufactured by Agilent Technologies), and the electrode was 16453A (manufactured by Agilent Technologies).
As for the relative permittivity, when the values at -10 ° C and 70 ° C are within ± 0.4 of the value at 30 ° C, the temperature change of the relative permittivity is small, and “○” is exceeded. Recorded “x” respectively.
Regarding the dielectric loss tangent, when the temperature was 0.02 or less at 30 ° C., “X” was recorded as the dielectric loss tangent being small, and “X” was recorded when exceeding this.

<Bleed presence / absence confirmation test>
The surface of a 100 mm × 80 mm × 2.0 mm molded body obtained by heat compression molding was visually observed, and the presence or absence of process oil bleed was observed.

As shown in Table 1, Reference Examples 1 to 6 and Examples 1 to 8 were excellent in flame retardancy, had a small temperature change in relative permittivity, and had a low dielectric loss tangent. In addition, no bleeding occurred.
On the other hand, Comparative Examples 1 to 3 were inferior in flame retardancy because the compounding amount of the metal hydroxide was less than the predetermined amount. In Comparative Examples 4 to 6, Comparative Example 14 and Comparative Example 15, the amount of metal hydroxide was larger than the predetermined amount, and therefore the dielectric loss tangent at 30 ° C. was larger than 0.02. Comparative Examples 7 and 12 had good dielectric properties, but bleed occurred because carbon black was not blended. In Comparative Example 8 and Comparative Example 13, the amount of carbon black was greater than the predetermined amount, so the dielectric loss tangent at 30 ° C. was greater than 0.02. In Comparative Example 9 to Comparative Example 11, the amount of metal hydroxide blended was less than a predetermined amount, so the amount of change in temperature of the dielectric constant was greater than ± 0.4.

  The dielectric elastomer composition of the present invention has a low environmental impact, has excellent flame retardancy, and has a low temperature dependence of relative permittivity, so that it can be used for antennas, circuit boards, filters, resonances of high frequency communication devices. It can be suitably used as a material for electronic parts such as a container, a capacitor, and a piezoelectric element.

Claims (5)

A dielectric elastomer composition comprising 200 to 600 parts by weight of a metal hydroxide based on 100 parts by weight of an elastomer,
The dielectric elastomer composition comprises 50 to 1000 parts by weight of dielectric ceramic powder and 5 to 40 parts by weight of carbon black, respectively, with respect to 100 parts by weight of the elastomer .
The metal hydroxide is at least one selected from aluminum hydroxide and magnesium hydroxide,
A dielectric elastomer composition, wherein the dielectric elastomer composition has a relative dielectric constant of 3 or more and a dielectric loss tangent of 0.02 or less at a frequency of 400 MHz and a temperature of 30 ° C. The dielectric elastomer composition according to claim 1, wherein 600 parts by weight of the dielectric ceramic powder is blended with 100 parts by weight of the elastomer in the dielectric elastomer composition.   The dielectric elastomer composition has a relative dielectric constant at an arbitrary temperature within a temperature range of -10 ° C to 70 ° C, which is a value within ± 0.4 of a relative dielectric constant based on 30 ° C. Item 3. The dielectric elastomer composition according to item 1 or 2. The dielectric elastomer composition according to any one of claims 1 to 3 , wherein the elastomer is ethylene propylene rubber. An antenna member formed by molding a dielectric elastomer composition,
5. The antenna member according to claim 1, wherein the dielectric elastomer composition is the dielectric elastomer composition according to any one of claims 1 to 4 .