JP2007153961A - Elastomer with high dielectric constant - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dielectric elastomer which requires no application of a large force for deformation, shows a sufficient strength and has no risk of breaking or powder fall by deformation, even when it is largely deformed before use. <P>SOLUTION: The elastomer with a high dielectric constant is obtained by dispersing particles of a dielectric in a crosslinked rubber such as ethylene propylene. The dielectric has a particle size of 30-500 nm and a relative dielectric constant of ≥1,000 and is obtained by treating a metal titanate etc. to which a bismuth oxide is added with a silane coupling agent. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a high dielectric constant elastomer.

  Conventionally, as high dielectric elastomers, additives such as barium titanate, carbon black, metal oxides and metal powders are added to polar synthetic rubbers having polar components such as halogen atoms and acrylonitrile for electric field relaxation applications such as radio wave absorption. An added composition (for example, Patent Document 1) is known.

  On the other hand, attempts have been made to combine a fibrous material with an organic polymer material as a dielectric. For example, Patent Documents 2 to 4 disclose a method for producing fibrous barium titanate or polycrystalline barium titanate fibers. However, since these dielectric fibers are fibers with insufficient strength or small aspect ratios, they are difficult to apply for the purpose of blending with an elastomer to produce a flexible high dielectric material. It was a material.

Further, for the purpose of providing a durable high dielectric elastomer composition having excellent mechanical strength such as tear strength, the general formula MO.TiO ₂ (wherein M is Ba, Sr, Ca) is included in the elastomer matrix. , Mg, Co, Pd, Zn, Be, or Cd represents a metal element selected from the group consisting of two or more metal elements) and / or the metal titanate. A high dielectric elastomer composition (Patent Document 5) obtained by blending 5 to 80% by weight of a composite fiber that is composite-integrated in a form in which amorphous titanium oxide is encapsulated, and an electronic device using the same The material is known.

For example, by sandwiching the elastomer described in Patent Document 6 between two electrodes and applying a DC voltage between the electrodes, the elastomer is compressed by the Coulomb force between the electrodes, and the compressed elastomer protrudes from between the electrodes. A mechanism for generating elongation and force is disclosed.
Japanese Patent Publication No.58-24455 Japanese Examined Patent Publication No. 62-7160 Japanese Examined Patent Publication No. 62-55243 JP-A-63-260822 Japanese Patent No. 348391 US Pat. No. 6,812,624

  However, since an appropriate size and particle size distribution are not selected for the dielectric, when the elastomer is used with a large deformation, the strength is insufficient, and there is a possibility that the dielectric will be damaged if deformed. Furthermore, there was a possibility of causing powder falling.

  When the fibrous dielectric material is filled, the expansion and contraction of the elastomer is interrupted, so that a large force is required for the deformation, and there is a possibility of being damaged when the deformation is performed.

  If an appropriate dielectric material is not selected, the dielectric constant is low and the dielectric constant of the elastomer may not be sufficiently improved. In addition, changes in the dielectric constant of the dielectric due to temperature and changes due to an electric field are large, and there is a possibility that the usable temperature range and the electric field range may be limited.

  Therefore, the present invention is to improve the performance of the dielectric elastomer.

  The present invention relates to a high dielectric constant elastomer obtained by dispersing dielectric particles having a relative dielectric constant of 1,000 or more and a particle size in the range of 30 to 500 nm in a crosslinked rubber.

  According to the high dielectric constant elastomer of the present invention, the dielectric itself can be used as a reinforcing material, and the relative dielectric constant and the amount of deformation during compression can be improved.

  In the present invention, a dielectric elastomer is sandwiched between two electrodes, and a voltage is applied between the electrodes, so that the elastomer is compressed by a Coulomb force between the electrodes, and the compressed elastomer extends so as to protrude from between the electrodes. The present invention relates to an elastomer used in a mechanism that generates

  In such a mechanism, when an electric field is applied, (1) it is required to be greatly deformed with a relatively small repulsive force, and high durability is required for repeated operation. The Coulomb force between the electrodes is proportional to the dielectric constant of the elastomer and proportional to the square of the applied electric field. For this reason, (2) the generated force increases when the dielectric constant of the elastomer is high. Further, since the force generated when a high electric field is loaded increases, (3) When the dielectric strength of the elastomer is increased, the loadable electric field can be increased, thereby increasing the generated force.

  In order to achieve (1), it is necessary to put an appropriate amount of an appropriately sized reinforcing filler. In order to make the elastomer easily stretched, the filler is required to be granular. On the other hand, if the size is too large, the durability may be lowered.

  Normally, the dielectric constant of an elastomer is not as high as about 8 at most, so in order to improve the dielectric performance of the elastomer, it is necessary to fill the elastomer with as much dielectric material as possible.

  This time, the shape of the dielectric with a high dielectric constant is granular, the size is 30 to 500 nm, and the filling amount is usually set to 5 to 20% by volume based on the volume of the crosslinked rubber. Can be used for the purpose of reinforcing / durability and providing a dielectric constant, and an elastomer having a high dielectric constant and excellent durability can be developed.

  The high dielectric constant elastomer of the present invention is characterized in that dielectric particles having a relative dielectric constant of 1,000 or more and a particle size of 30 to 500 nm are dispersed in a crosslinked rubber. Here, the high dielectric constant means a dielectric having a dielectric constant of 1,000 or more. The high dielectric constant elastomer of the present invention can be said to be a composition comprising a crosslinked rubber and the dielectric.

  The crosslinked rubber that can be used in the present invention is not particularly limited, and may be an organic or inorganic substance as long as it is a substance having rubber-like elasticity at room temperature, and may be a natural product or a synthetic product. .

  Natural cross-linked rubbers include chlorinated rubber, hydrochloric acid rubber, cyclized rubber, maleated rubber, hydrogenated rubber, and graft-modified rubber made by grafting vinyl monomers such as PMMA, PAN and acrylate to the double bond of natural rubber. And a block copolymer formed by masticating natural rubber in the presence of a monomer in a nitrogen stream. These include those made from synthetic cis-1,4-polyisoprene as well as those made from natural rubber.

  Synthetic crosslinked rubber includes fluorine rubber such as VDF-HFP, VDF-CTFE, VDF-PFVE, fluorosilicone rubber, TFE-PFVE, PTFE-P, fluoroalkoxypolyphosphazene, isobutylene rubber, ethylene propylene rubber, ethylene propylene diene Polyolefin elastomers such as rubber, ethylene propylene terpolymer, chlorosulfonated polyethylene rubber, styrene-isoprene-styrene block copolymer (SIS), styrene-butadiene-styrene copolymer (SBS), styrene-ethylene-butylene-styrene block copolymer (SEBS) ) Styrene elastomer, isoprene rubber, urethane rubber, epichlorohydrin rubber, chloroprene rubber, silicone rubber, nylon 12 Butyl rubber, butadiene rubber, fluorine rubber, polynorbornene rubber, A chloronitrile - butadiene rubber and the like. Here, VDF: vinylidene fluoride, HFP: hexafluoropropylene, CTFE: chlorotrifluoroethylene, PFVE: perfluoromethylvinyl ether, TFE: tetrafluoroethylene, PTFE-P: polytetrafluoroethylene-propylene. .

  These crosslinked rubbers may be used alone or in combination of two or more. Further, one or two or more thermoplastic resins can be blended and used within a range that does not impair the elasticity of the crosslinked rubber.

  As the crosslinked rubber that can be used in the elastomer of the present invention, when one or two or more kinds selected from the group consisting of natural crosslinked rubber and synthetic non-polar elastomer are used, a highly dielectric elastomer excellent in electrical insulation. This is particularly suitable for applications requiring insulation. Examples of synthetic nonpolar elastomers include ethylene propylene rubber, ethylene propylene diene rubber, isobutylene rubber, isoprene rubber, and silicone rubber.

The dielectric that can be used in the present invention has a relative dielectric constant of 1,000 or more and a particle size in the range of 30 to 500 nm. By filling and dispersing a predetermined amount of the granular dielectric in the crosslinked rubber, the dielectric itself can be used as a reinforcing material, and the relative dielectric constant and the amount of deformation during compression can be improved. Specifically, it is possible to produce an elastomer having a characteristic that the relative dielectric constant is 8 or more and the amount of change in the compression direction and the vertical direction during compression is 20% or more. Further, when the particle diameters of the dielectrics are not uniform, it is considered that the particles interfere with each other at the time of deformation, thereby preventing the deformation. In the dispersion state, it is preferable that the crosslinked rubber and the dielectric are sufficiently stirred to disperse the dielectric in the crosslinked rubber almost uniformly. By being dispersed in this manner, the effect of adding the dielectric can be sufficiently exhibited. Specific examples of the dielectric include a general formula MO · TiO ₂ (wherein M is one or more selected from the group consisting of Ba, Sr, Ca, Mg, Co, Pd, Zn, Be, and Cd). shows a metal element. metal titanate represented by), in said metal titanate was added _Bi 2 _{O 3} in _{(Sr 1-x M x)} TiO 3 -Bi 2 O 3 -nTiO 2 ( wherein, M represents one or two or more metal elements selected from the group consisting of Ba, Ca, Mg, Pb, Zn, and Cu. In addition, niobium, tantalum, iron, aluminum And at least one selected from the group consisting of phosphorous, sodium and silicon. This is because, for example, in the case of a titanate composed of only one metal element such as BaTiO ₃ , the change in relative permittivity due to temperature and electric field is large, so that these Bi ₂ O ₃ -nTiO ₂ with less change are changed. The inclusion is preferred. As a high dielectric constant material whose change in relative dielectric constant due to temperature and electric field is small, nickel oxide, such as BaTiO ₃ (Japanese Patent No. 334003) or Li _(1-xy) Ti _y Ni _x O, A material doped with titanium, lithium, or the like can also be used. Among the above compounds, (Sr _1-x M _x ) TiO ₃ —Bi ₂ O ₃ —nTiO ₂ (wherein M is a kind selected from the group consisting of Ba, Ca, Mg, Pb, Zn, Cu) Or two or more kinds of metal elements.) Or a compound obtained by adding at least one selected from the group consisting of niobium, tantalum, iron, aluminum, sodium, and silicon to the compound represented by This is preferable from the viewpoint of improving the relative permittivity and displacement. The relative dielectric constant is preferably in the range of 1000 to 8000. Considering the use in a wider temperature range, a dielectric having a relative dielectric constant exceeding 8000 has a large change in the relative dielectric constant depending on the temperature, which may cause a problem depending on the application.

  Next, the dielectric particles are treated with a silane coupling agent by the following method.

  The silane coupling agent is used as a dilute aqueous solution. The aqueous solution concentration of the silane coupling agent is generally about 0.1 to 2.0%. In the case of a silane coupling agent having poor compatibility with water, it is diluted with about 0.1 to 2.0% acetic acid water or a water-alcohol (acetic acid water-alcohol) mixture. Acetic acid has two effects in the pH range that enhances the hydrolysis of the silane coupling agent and the stability of silanol.

Specifically, it is prepared by the following method.
(1) Prepare an aqueous solution with an acetic acid concentration of 1.0%.
When the solubility of the silane coupling agent is good, the acetic acid concentration can be lowered. In the case of an aminosilane coupling agent, it is not necessary to add acetic acid.
(2) A silane coupling agent is dropped while thoroughly stirring the aqueous acetic acid solution.
The concentration of the silane coupling agent is usually 1.0%. The stirring speed is as fast as possible without splashing the liquid. On the other hand, when the dropping time is short, the dispersion of the silane coupling agent becomes poor, and the gel-like generation increases.
(3) After the completion of dripping, stirring is continued for another 50 minutes.
When the aqueous solution becomes almost transparent, the hydrolysis of the silane coupling agent is completed.
(4) The prepared powder is mixed with dielectric powder, stirred and separated by a centrifugal separator, and the dielectric part is taken out and dried in a drying furnace.

  Silane coupling agents include 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, vinyltrichlorosilane, vinyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacrylic Roxypropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, N-2 (aminoethyl) 3-aminopropylmethyldimethoxysilane, N-2 (aminoethyl) 3-aminopropylmethoxysilane, N 2 (aminoethyl) 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, N -Phenyl-3-aminopropyltrimethoxysilane, 3-chloropropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, bis (triethoxysilylpropyl) tetrasulfide, 3-isocyanatopropyltri And ethoxysilane. When the rubber is EPDM, 3-methacryloxypropylmethyldiethoxysilane or 3-methacryloxypropyltriethoxysilane is preferred.

  By treating the dielectric with a silane coupling agent, the effect of reinforcing the dielectric elastomer is enhanced, and the durability during compression is increased.

  Thus, by filling and dispersing a predetermined amount of the granular dielectric, the dielectric itself can be used as a reinforcing material, and the relative dielectric constant is 8 or more, and the compression direction and the vertical direction during compression are increased. An elastomer having a change amount of 20% or more can be produced.

  The added amount of the dielectric occupies a range of 5 to 20% by volume based on the volume of the crosslinked rubber, and the aspect ratio between the maximum diameter and the minimum diameter of the dielectric particles is 3 or less. Is preferred. Regarding the aspect ratio, when the maximum diameter and the minimum diameter are the same, the aspect ratio is 1, and this value is the minimum value. Thereby, in the mechanism using the elastomer of the present invention, the output is enhanced. In addition, since the amount of deformation is large in the embodiment, when the same amount of deformation is used, there is a margin for the amount of deformation, and durability can be ensured.

  The high dielectric constant elastomer of the present invention is preferably a reinforcing filler other than the dielectric and does not include those having a particle size of 10 nm or more. The upper limit is a range usually used as a reinforcing material, for example, 10 μm. It is desirable not to include those up to. By not including the reinforcing filler, the elongation of the elastomer during compression can be further increased, and the elastomer can be stretched with a lower force. In general, the reinforcing filler for the rubber material is not particularly limited as long as it is added for the purpose of hardening the rubber, and examples thereof include carbon black and calcium carbonate.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited to an Example.

(Examples and Comparative Examples)
As the elastomer, ethylene propylene was used, and the following composition was used except for the dielectric.

  JSR ethylene propylene raw rubber EP93 100 parts by mass, 20 parts by mass of naphthenic process oil, 1 part by mass of stearic acid, 5 parts by mass of zinc oxide, tetramethylthiuram disulfide (TT), tetraethylthiuram disulfide (TET) as vulcanization system ), 2 parts by mass of N-cyclohexylbenzothiazylsulfenamide (CZ) and a dielectric.

  The dielectric was added by mastication, and then the above vulcanization system was added and kneaded, then formed into a sheet and vulcanized.

(Examples 1, 3, 4, and 5)
The dielectrics were made with different particle sizes by referring to the method of Japanese Patent Application Laid-Open No. 2004-161533 under the following conditions.

  0.01 to 0.05 mol / liter of barium nitrate and 0.01 to 0.05 mol / liter of titanium tetraisopropoxide are dissolved in 1 mol / liter of nitric acid solution (Ba / Ti ratio = 1). 075 to 0.1 mol / liter of potassium nitrate and 0.075 to 0.1 mol / liter of sodium nitrate were added (nitrate with respect to Ti in a molar ratio of 4 to 15).

  This solution is sprayed with an ultrasonic atomizer to form droplets, and 1 to 10 liters / min. Was supplied as a carrier gas to the heating furnace. The heating furnace was a five-stage furnace, and the core tube was a ceramic tube having an inner diameter (D) and a ratio L / D of the length (L) of the heated portion of 15 to 77. The heating temperature was 1,000 ° C.

  The particles exiting the heating furnace were collected by an electrostatic collector, and the produced particles were washed by ultrasonic washing and centrifugation and then dried.

  In Example 5, a silane coupling agent treatment was further performed. As the type of silane coupling agent, 3-methacryloxypropylmethyldiethoxysilane, an aqueous solution having an acetic acid concentration of 1.0%, and an silane coupling agent having a concentration of 1.0% were used.

(Example 2)
As the dielectric, BaTiO ₃ (granular) (manufactured by Kyoritsu Material) having an average particle diameter of 410 nm was used.

(Example 6)
The dielectric was prepared by the following method.

(Sr _1-x Ba _x ) TiO ₃ (x = 0.5) is composed of 1 mol of 0.05 mol / liter of barium nitrate, 0.05 mol / liter of strontium nitrate, 0.1 mol / liter of titanium tetraisopropoxide. / Liter of nitric acid solution (Ba: Sr: Ti ratio = 1: 1: 2), and 0.75 mol / liter of potassium nitrate and 0.75 mol / liter of sodium nitrate were added (nitrate relative to Ti 15) in molar ratio.

  This solution was sprayed with an ultrasonic atomizer to form droplets, and 1 liter / min. Was supplied as a carrier gas to the heating furnace. The heating furnace was a five-stage furnace, and the core tube was a ceramic tube having an inner diameter (D) and a ratio L / D of the length (L) of the heated portion of 15 to 77. The heating temperature was 1,000 ° C.

  The particles exiting the heating furnace were collected by an electrostatic collector, and the produced particles were washed by ultrasonic washing and centrifugation and then dried.

(Example 7)
The dielectric was prepared by the following method with reference to Japanese Patent No. 334003.

As starting materials, 100 mol of main component materials (BaTiO ₃ ) each having an average particle size of 0.1 to 1 μm and as the first to fifth subcomponent materials, carbonate (first subcomponent: MgCO ₃ is 1) 0.0 mol, the fourth subcomponent: 0.374 mol of MnCO ₃ , and the other raw materials are oxide (second subcomponent: Y ₂ O ₃ of 2.0 mol, third subcomponent: (Ba _0.6) Ca _0.4 ) SiO ₃ (3 mol) and _fifth subcomponent: V ₂ O ₅ (0.1 mol) were used. The third subcomponent (Ba _0.6 Ca _0.4 ) SiO ₃ is obtained by wet-mixing BaCO ₃ , CaCO ₃ and SiO ₂ with a ball mill for 16 hours, drying, and firing in air at 1150 ° C., It was manufactured by wet grinding with a ball mill for 100 hours. These raw materials were blended, wet mixed by a ball mill for 16 hours, and dried to obtain a dielectric material.

  100 parts by weight of the obtained dielectric material after drying, 4.8 parts by weight of acrylic resin, 40 parts by weight of methylene chloride, 20 parts by weight of ethyl acetate, 6 parts by weight of mineral spirit, and 4 parts by weight of acetone The paste was mixed by a ball mill to obtain a dielectric layer paste.

  Next, a green sheet having a thickness of 5 μm was formed on the PET film using the dielectric layer paste, and the green sheet was peeled off from the PET film. Next, 50 layers of these green sheets were laminated and pressed to obtain a green chip.

The green chip was cut into a predetermined size and subjected to binder removal processing, firing and annealing to obtain a multilayer ceramic fired body. The binder removal treatment was performed under the conditions of a heating rate of 15 ° C./hour, a holding temperature of 350 ° C., a holding time of 2 hours, and a humidified N ₂ + H ₂ mixed gas atmosphere (oxygen partial pressure of 10 to 31 Pa). Firing is performed under conditions of a temperature rising rate of 200 ° C./hour, a holding temperature of 1260 to 1340 ° C., a holding time of 2 hours, a cooling rate of 300 ° C./hour, and a humidified N ₂ + H ₂ mixed gas atmosphere (oxygen partial pressure is 10 to 6 Pa). I went there. The annealing was performed under the conditions of a holding temperature of 1050 ° C., a temperature holding time of 2 hours, a cooling rate of 300 ° C./hour, and a nitrogen atmosphere. Note that a wetter was used at a water temperature of 35 ° C. for humidifying the atmosphere during binder removal and firing.

  The obtained chip was pulverized to obtain dielectric particles having an average particle diameter of 80 nm.

(Comparative Examples 2, 4, 5)
The dielectrics were made with different particle sizes by referring to the method of Japanese Patent Application Laid-Open No. 2004-161533 under the following conditions.

  0.01 to 0.05 mol / liter of barium nitrate and 0.01 to 0.05 mol / liter of titanium tetraisopropoxide are dissolved in 1 mol / liter of nitric acid solution (Ba / Ti ratio = 1). 075 to 0.1 mol / liter potassium nitrate and 0.075 to 0.1 mol / liter sodium nitrate were added (nitrate is 4 to 15 in molar ratio to Ti).

  This solution is sprayed with an ultrasonic atomizer to form droplets, and 1 to 10 liters / min. Was supplied as a carrier gas to the heating furnace. The heating furnace was a five-stage furnace, and the core tube was a ceramic tube having an inner diameter (D) and a ratio L / D of the length (L) of the heated portion of 15 to 77. The heating temperature was 1,000 ° C.

  The particles exiting the heating furnace were collected by an electrostatic collector, and the produced particles were washed by ultrasonic washing and centrifugation and then dried.

(Comparative Example 3)
As the dielectric, BaTiO ₃ (granular) (manufactured by Kyoritsu Material) having an average particle diameter of 800 nm was used.

(Comparative Example 6)
The dielectric was obtained by the following method with reference to JP-A-9-31244.

Fibrous (Sr _1-x Ba _x ) TiO ₃ was prepared with reference to Reference Example 1 of JP-A-9-31244 to obtain an average fiber diameter of 0.4 μm and an average fiber length of 7 μm.

  In Examples 1-7 and Comparative Examples 1-6, the ratio of the component mix | blended and the obtained result are shown in Table 1. Here, the aspect ratio of the dielectric was measured by TEM observation. The dielectric constant of each dielectric was measured at room temperature using 1296 + 1260 manufactured by Toyo Technica after firing and before pulverization. The performance of the product was compared by relative permittivity (1296 + 1260 manufactured by Toyo Technica) and crack initiation displacement (Δx / x) when a compressive load was applied (see FIG. 1).

  FIG. 1 is a schematic view for explaining a displacement measuring method. FIG. 1A shows a state before compression, and FIG. 1B shows a state after load compression. The sample is an elastomer cylinder diameter x = 6 mm and a height of 2 mm. The measurement was performed using calipers.

In Table 1 *: Fiber diameter 0.4 μm, length 7 μm
**: Unmeasured due to displacement NG Comparative Example 1 is ethylene propylene rubber.

  Addition amount of dielectric: vol% of dielectric = dielectric volume × 100 / (rubber volume + dielectric volume), where rubber volume = rubber mass / rubber specific gravity, dielectric mass / dielectric Specific gravity.

  From Table 1, it can be seen that the elastomers of Examples 1 to 7 have a relative dielectric constant in the range of 8.6 to 33 and a deformation amount in the range of 0.21 to 0.33. On the other hand, the elastomers of Comparative Examples 1 to 6 had relatively low durability values except for Comparative Example 1.

It is a schematic drawing explaining the measuring method of displacement.

Explanation of symbols

1: elastomer cylinder,
2: Disc jig.

Claims (4)

  A high dielectric constant elastomer obtained by dispersing dielectric particles having a relative dielectric constant of 1,000 or more and a particle size in the range of 30 to 500 nm in a crosslinked rubber.   The added amount of the dielectric occupies a range of 5 to 20% by volume based on the volume of the crosslinked rubber, and the aspect ratio between the maximum diameter and the minimum diameter of the dielectric particles is 3 or less. The elastomer according to claim 1.   The elastomer according to claim 1 or 2, wherein the filler is a reinforcing filler other than the dielectric and does not contain a particle having a particle diameter of 10 nm or more.   The elastomer particles according to claim 1, wherein the dielectric particles are treated with a silane coupling agent.

Images