Additional curable liquid conductive silicone rubber composition and electrophotographic image forming member

Abstract

To provide an electroconductive highly heat-conductive silicone rubber composition that comprises a heat conductive powder and a carbon material for imparting electroconductivity, the silicone rubber composition having improved storage stability, particularly less tendency to decrease in hardness over time.SOLUTION: An addition reaction-curable liquid electroconductive silicone rubber composition includes: (A) liquid organopolysiloxane having two or more silicon atom-bonded alkenyl groups in one molecule; (B) organohydrogenpolysiloxane having two or more silicon atom-bonded hydrogen atoms in one molecule; (C) a platinum group metal-based catalyst; (D) a carbon material; (E) a heat conductive powder having an average primary particle diameter of 30 μm or less, and a heat conductivity of 10 W / m K or more; and (F) organosilane and / or organopolysiloxane having one or more alkoxysilyl group(s) in one molecule.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an addition-curable liquid conductive silicone rubber composition and an electrophotographic image forming member.

Background Art

[0002] Conventionally, various conductive rubbers in which a conductive material is blended with a rubbery substance exhibiting electrical insulation properties are known. For example, conductive rubbers blended with carbon black or the like as a conductive material are applied in a wide range of fields. Among them, silicone rubber is excellent in heat resistance, cold resistance, and weather resistance, and is widely used as an electrical insulating rubber. On the other hand, by adding a conductive material as with other rubbery substances, it has also been put into practical use as a conductive rubber.

[0003] In this case, examples of the conductive material added to the conductive silicone rubber include carbon black, graphite, various metal powders such as silver, nickel, and copper, various non-conductive powders and those obtained by treating the surface of short fibers with a metal such as silver, carbon fibers, and mixtures of metal fibers. These are frequently used because they can lower the volume resistivity of silicone rubber depending on the type and filling amount of the conductive material without impairing the specific properties of the rubber. In particular, addition-curable liquid silicone rubber is widely used as an electrophotographic image forming member because it has a low viscosity, excellent moldability, and can be cured in a short time even when a conductivity-imparting material such as carbon black is blended.

[0004] In addition, silicone rubber has been used as a coating material for heat dissipation components of computers, fixing devices of copiers and laser beam printers, specifically for fixing rollers such as heater rollers and pressure rollers, taking advantage of its heat resistance. In particular, for the rubber used for heater rollers, as printing speeds increase and energy conservation progresses, there is a demand for high thermal conductivity in order to reduce power consumption and shorten the waiting time during machine startup. However, since the thermal conductivity of silicone rubber itself is not high, a method of adding fillers with high thermal conductivity is commonly used. Examples of the above-mentioned thermal conductivity fillers include silica, alumina, magnesium oxide, and the like.

[0005] In addition, since the surface layer of the heating member comes into contact with the paper and then peels off, the faster the peeling speed, the greater the static electricity generated on the surface layer of the heating member. Due to such static electricity, there is a problem that the paper or the toner electrostatically adhered to the paper is subjected to an external force, resulting in image distortion.

[0006] On the other hand, in recent years, with the increasing precision and speed of image formation, more refined printing characteristics are required for image forming apparatuses. Colorant particles called toner are used in copiers and electrophotographic printers. These toners need to melt quickly in order to speed up printing, and also tend to have a lower designed melting point of the toner from the perspective of energy conservation of the apparatus itself.

[0007] Conventionally, in order to cope with the high speed of printing required for the developing member, it was necessary to lower the hardness of the rubber and improve the surface smoothness. However, in recent years, with the lowering of the melting point of the toner, the influence of the frictional heat generated in the developing member on the toner has become greater, and the low temperature management of the surface of the developing roller has become important.

[0008] Therefore, silicone rubber used in image forming apparatuses is required to have high heat dissipation, high thermal conductivity, and conductivity. In this specification, high thermal conductivity means that the thermal conductivity is higher than 0.16 W / m·K of silicone oil.

[0009] In response to such problems, there is a method that uses metal silicon powder to exhibit good thermal conductivity and, moreover, significantly improves the compression set (Patent Document 1).

[0010] Also, a method of adding carbon black and iron oxide (red iron oxide) to a thermally conductive silicone rubber material containing metal silicon powder is also known (Patent Document 2). It is said that the appearance defect (color unevenness) of the metal silicon-containing material can be eliminated by mixing carbon black and red iron oxide. However, although these methods solve problems such as thermal conductivity, the problem of the hardness reduction of the cured product caused by the change over time of the composition remains.

[0011] Also, as a thermally conductive silicone rubber material for a developing rubber member, there is a method of adding a thermally conductive powder with a small particle size and carbon black for imparting conductivity (Patent Document 3). It discloses that the thermally conductive powder is surface-treated with a silane-based coupling agent or its partial hydrolyzate, an alkylalkoxysilane or its partial hydrolyzate, an organosilazane, a titanate-based coupling agent, an organopolysiloxane oil, a hydrolyzable functional group-containing organopolysiloxane, etc. for the purpose of improving thermal stability and compounding properties.

[0012] Also, in a high thermal conductivity silicone rubber composition, in order to stably add a large amount of a thermally conductive filler, it is well known to use an organopolysiloxane having a silicon atom-bonded hydrolyzable group as a surface treatment agent (Patent Documents 4 to 8). There is a description about the fluidity that affects the handleability and moldability such as suppressing the increase in viscosity and the increase in plasticity by using a surface treatment agent.

[0013] There is also a description that after forming a natural oxide film with few defects on the metal silicon powder by heat treatment and wet treatment, it is further surface-treated with a silane-based coupling agent or its partial hydrolyzate, an alkylalkoxysilane or its partial hydrolyzate, a hydrolyzable functional group-containing organopolysiloxane, etc. (Patent Document 9).

[0014] Even with these methods, the problem of the change over time of the composition has not been solved, and there has been a demand for the development of a silicone rubber composition that has excellent storage stability and has electrical conductivity and high thermal conductivity.

Prior Art Documents

Patent Documents

[0015]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Patent Document 8

Patent Document 9

Summary of the Invention

Problems to be Solved by the Invention

[0016] An object of the present invention is to provide a conductive and highly thermally conductive silicone rubber composition containing a thermally conductive powder and a carbon material for imparting conductivity, in which the storage stability is improved, particularly a silicone rubber composition in which the decrease in hardness over time is suppressed, and an electrophotographic image forming member having a cured product of the composition as an elastic layer.

Means for Solving the Problems

[0017] In order to solve the above problems, in the present invention, (A) A liquid organopolysiloxane containing two or more alkenyl groups bonded to silicon atoms in one molecule: 100 parts by mass, (B) An organohydrogenpolysiloxane containing two or more hydrogen atoms bonded to silicon atoms in one molecule: an amount such that the number of hydrogen atoms bonded to silicon atoms contained in the component (B) is 0.5 to 10 with respect to one alkenyl group bonded to a silicon atom contained in the component (A), (C) A platinum group metal-based catalyst as an addition reaction catalyst: an amount such that it is 0.5 to 1,000 ppm in terms of platinum group metal with respect to the total mass of the component (A), (D) A carbon material: 1 to 50 parts by mass, (E) A thermally conductive powder having an average primary particle diameter of 30 μm or less and a thermal conductivity of 10 W / m·K or more: 10 to 400 parts by mass, and (F) An organosilane and / or organopolysiloxane having one or more alkoxysilyl groups in one molecule: an amount such that it is 0.05 to 30 parts by mass, provided is an addition-curing type liquid conductive silicone rubber composition containing the above.

[0018] With such a composition, good storage stability can be achieved, and a cured product with suppressed hardness reduction over time can be obtained.

[0019] Further, it is preferable that the component (E) is metal silicon powder.

[0020] When the thermally conductive powder is metal silicon powder, the storage stability becomes particularly good.

[0021] Further, the component (F) is represented by the following general formula (1) R 1 d SiX 4-d (1) (In the formula, R 1 is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 20 carbon atoms, d is an integer of 1 to 3, and X is an alkoxy group having 1 to 4 carbon atoms.) and is preferably an organosilane having one or more alkoxysilyl groups in one molecule.

[0022] In the general formula (1), it is preferable that X is a methoxy group or an ethoxy group, and d is 1 or 2.

[0023] In the present invention, such an organosilane can be used as the component (F).

[0024] Further, the component (F) has the following average composition formula (2) R 1 e X f SiO {4-(e+f)} / 2 (2) (In the formula, R 1 is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 20 carbon atoms, X is an alkoxy group having 1 to 4 carbon atoms, and e and f are positive numbers satisfying e = 1.0 to 2.8, f = 0.01 to 0.5, and e + f = 1.5 to 3.) and is preferably an organopolysiloxane having one or more alkoxysilyl groups in one molecule.

[0025] In the average composition formula (2), it is preferable that X is a methoxy group or an ethoxy group, and f is 0.02 to 0.3.

[0026] In the average composition formula (2), R 1 is preferably a methyl group or a phenyl group.

[0027] In the present invention, such an organopolysiloxane can be used as the component (F).

[0028] Further, the present invention provides an electrophotographic image forming member having an elastic layer made of a cured product of the above addition-curable liquid conductive silicone rubber composition.

[0029] The addition-curable liquid conductive silicone rubber composition of the present invention can be suitably used for an electrophotographic image forming member.

[0030] Further, it is preferable that the electrophotographic image forming member is a member selected from a developing roll and a developing belt.

[0031] The addition-curable liquid conductive silicone rubber composition of the present invention can be particularly preferably used for such applications.

Advantages of the Invention

[0032] According to the present invention, it is possible to provide an addition-curable liquid conductive silicone rubber composition that gives a cured product having good storage stability, particularly hardness stability over time. In particular, an addition-curable liquid conductive high thermal conductivity silicone rubber composition for an electrophotographic image forming member and an electrophotographic image forming member having a cured product of the composition as an elastic layer can be obtained.

Embodiments for Carrying Out the Invention

[0033] As described above, there has been a demand for the development of a conductive high thermal conductivity composition that gives a cured product having good storage stability, and an electrophotographic image forming member having a cured product of the composition as an elastic layer.

[0034] As a result of intensive studies to achieve the above object, the present inventors have found that in an addition-curable liquid high thermal conductivity conductive silicone rubber composition containing components (A) to (F) described below, particularly in addition to carbon black as component (D), a thermally conductive powder as component (E) and an organopolysiloxane having an alkoxysilyl group as component (F) are blended to form a conductive thermally conductive silicone rubber composition, which can suppress a decrease in hardness over time and has good storage stability. They have also found that a thermally conductive silicone rubber member (such as a roll or a belt) having a silicone rubber layer formed by curing the composition has suitable conductivity and excellent thermal conductivity and can be effectively used as a rubber member for a high-speed copying machine or a printer, thus leading to the present invention.

[0035] That is, the present invention relates to (A) A liquid organopolysiloxane containing two or more alkenyl groups bonded to silicon atoms in one molecule: 100 parts by mass, (B) Organohydrogenpolysiloxane containing hydrogen atoms bonded to two or more silicon atoms in one molecule: The amount of hydrogen atoms bonded to the silicon atoms contained in the component (B) is 0.5 to 10 with respect to one alkenyl group bonded to the silicon atoms contained in the component (A). (C) Platinum group metal-based catalyst as an addition reaction catalyst: The amount is 0.5 to 1,000 ppm in terms of platinum group metal with respect to the total mass of the component (A). (D) Carbon material: 1 to 50 parts by mass (E) Thermally conductive powder having an average primary particle diameter of 30 μm or less and a thermal conductivity of 10 W / m·K or more: 10 to 400 parts by mass, and (F) Organosilane and / or organopolysiloxane having one or more alkoxysilyl groups in one molecule: The amount is 0.05 to 30 parts by mass. It is an addition-curing type liquid conductive silicone rubber composition containing the above.

[0036] Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.

[0037] <Addition-curing type liquid conductive silicone rubber composition> The addition-curing type liquid conductive silicone rubber composition (addition-curing type liquid conductive high thermal conductivity silicone rubber composition) of the present invention contains the following components (A) to (F).

[0038] [Component (A)] Component (A) is a liquid (particularly liquid at 25°C) organopolysiloxane containing two or more alkenyl groups bonded to silicon atoms in one molecule, and is the base polymer (main agent) of the composition according to the present invention.

[0039] (A) The molecular structure of the component includes, for example, linear, cyclic, branched, three-dimensional network (resin-like), etc. However, the main chain basically consists of repeating units of diorganosiloxane, and a linear diorganopolysiloxane with both ends of the molecular chain blocked by triorganosiloxy groups is preferred. Further, when the molecular structure of the organopolysiloxane of component (A) is linear or branched, the position of the silicon atom to which the alkenyl group is bonded in the molecule of the organopolysiloxane may be either at the end of the molecular chain (i.e., the triorganosiloxy group) or in the middle of the molecular chain (i.e., a bifunctional diorganosiloxane unit or a trifunctional monoorganosilsesquioxane unit located at a non-terminal position of the molecular chain), or both. Particularly preferably, component (A) is a linear diorganopolysiloxane containing alkenyl groups bonded to silicon atoms at both ends of the molecular chain.

[0040] As the alkenyl group bonded to the silicon atom in component (A), for example, those having 2 to 8 carbon atoms, preferably 2 to 4 carbon atoms are usually mentioned. Specific examples thereof include vinyl group, allyl group, butenyl group, pentenyl group, hexenyl group, cyclohexenyl group, heptenyl group, etc., and particularly preferably a vinyl group.

[0041] The content of the alkenyl group bonded to the silicon atom in component (A) is preferably 0.001 to 10 mol / 100 g, particularly preferably 0.01 to 5 mol / 100 g, based on the total monovalent hydrocarbon groups bonded to the silicon atom.

[0042] As the monovalent hydrocarbon group bonded to the silicon atom other than the alkenyl group in component (A), for example, monovalent hydrocarbon groups having 1 to 12 carbon atoms, preferably 1 to 10 carbon atoms are mentioned. Specific examples of the monovalent hydrocarbon group include alkyl groups such as methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, cyclohexyl group, heptyl group; aryl groups such as phenyl group, tolyl group, xylyl group, naphthyl group; aralkyl groups such as benzyl group, phenethyl group, etc. Among these, particularly preferably, it is a methyl group.

[0043] (A) component has a viscosity at 25 °C of preferably 50 to 500,000 mPa·s, more preferably 500 to 200,000 mPa·s. When the viscosity is within this range, the handleability of the resulting silicone rubber composition is good, and the mechanical properties of the cured product of the resulting silicone rubber composition are good. In this specification, the viscosity refers to the value measured by a rotational viscometer at 25 °C by the method described in JIS K 7117-1:1999.

[0044] Specific examples of the organopolysiloxane of component (A) include dimethylsiloxane·methylvinylsiloxane copolymer blocked with trimethylsiloxy groups at both ends of the molecular chain, methylvinylpolysiloxane blocked with trimethylsiloxy groups at both ends of the molecular chain, dimethylsiloxane·methylvinylsiloxane·methylphenylsiloxane copolymer blocked with trimethylsiloxy groups at both ends of the molecular chain, dimethylpolysiloxane blocked with dimethylvinylsiloxy groups at both ends of the molecular chain, methylvinylpolysiloxane blocked with dimethylvinylsiloxy groups at both ends of the molecular chain, dimethylsiloxane·methylvinylsiloxane copolymer blocked with dimethylvinylsiloxy groups at both ends of the molecular chain, dimethylsiloxane·methylvinylsiloxane·methylphenylsiloxane copolymer blocked with dimethylvinylsiloxy groups at both ends of the molecular chain, dimethylpolysiloxane blocked with divinylmethylsiloxy groups at both ends of the molecular chain, dimethylsiloxane·methylvinylsiloxane copolymer blocked with divinylmethylsiloxy groups at both ends of the molecular chain, dimethylpolysiloxane blocked with trivinylsiloxy groups at both ends of the molecular chain, dimethylsiloxane·methylvinylsiloxane copolymer blocked with trivinylsiloxy groups at both ends of the molecular chain, and mixtures composed of two or more of these organopolysiloxanes.

[0045] The organopolysiloxane of component (A) may be used alone or in combination of two or more. Among them, it is preferable to use two or more in combination because it is easy to adjust the composition of the present invention to a preferable viscosity range.

[0046] [Component (B)] (B) component of organohydrogenpolysiloxane undergoes a hydrosilylation addition reaction with the alkenyl group in (A) component and acts as a crosslinking agent (hardening agent). There is no particular restriction on its molecular structure, and various conventionally manufactured ones can be used, such as those with linear, cyclic, branched, three-dimensional network (resin-like) structures, etc. However, it is necessary to have hydrogen atoms (hydrosilyl groups represented by SiH) bonded to two or more silicon atoms in one molecule.

[0047] (B) component of organohydrogenpolysiloxane may be used alone or in combination of two or more.

[0048] As this organohydrogenpolysiloxane, those represented by the following average composition formula (3) can be used. R 2 a H b SiO (4-a-b) / 2 (3) (In the formula, R 2 is independently a group selected from alkyl groups having 1 to 10 carbon atoms, aryl groups having 6 to 10 carbon atoms, and aralkyl groups having 7 to 10 carbon atoms. Also, a is 0.7 to 2.1, b is 0.001 to 1.0, and a + b is a positive number satisfying 0.8 to 3.0.)

[0049] In the above formula (3), R 2 is independently a monovalent hydrocarbon group bonded to a silicon atom, excluding aliphatic unsaturated bonds such as alkenyl groups, preferably having 1 to 10 carbon atoms. Examples of the monovalent hydrocarbon group in this R 2 include alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, cyclohexyl group, octyl group, nonyl group, decyl group; aryl groups such as phenyl group, tolyl group, xylyl group, naphthyl group; aralkyl groups such as benzyl group, phenylethyl group, phenylpropyl group, etc. R 2The monovalent hydrocarbon group is preferably an alkyl group or an aryl group, more preferably a methyl group. Also, a is 0.7 to 2.1, b is 0.001 to 1.0, and a + b is a positive number satisfying 0.8 to 3.0. Preferably, a is 1.0 to 2.0, b is 0.01 to 1.0, and a + b is a positive number satisfying 1.5 to 2.5.

[0050] The SiH groups contained in one molecule may be located at either the molecular chain end or in the middle of the molecular chain, or may be located at both. Also, the molecular structure of this organohydrogenpolysiloxane may be any of linear, cyclic, branched-chain, and three-dimensional network structures. However, the number of silicon atoms (or degree of polymerization) in one molecule is usually 2 to 300, preferably 3 to 150, more preferably about 4 to 100. Those having a viscosity at 25°C of usually 0.1 to 1,000 mPa·s, preferably about 0.5 to 500 mPa·s and being liquid at 25°C are used. In this specification, the degree of polymerization can be determined, for example, as the number average degree of polymerization (number average molecular weight) or weight average degree of polymerization (weight average molecular weight) in terms of polystyrene in GPC (gel permeation chromatography) analysis using toluene as the developing solvent.

[0051] Examples of such organohydrogenpolysiloxanes as component (B) include 1,1,3,3 - tetramethyldisiloxane, 1,3,5,7 - tetramethylcyclotetrasiloxane, tris(hydrogendimethylsiloxy)methylsilane, tris(hydrogendimethylsiloxy)phenylsilane, methylhydrogencyclopolysiloxane, methylhydrogensiloxane - dimethylsiloxane cyclic copolymer, trimethylsiloxy - terminated methylhydrogenpolysiloxane at both ends of the molecular chain, trimethylsiloxy - terminated dimethylsiloxane - methylhydrogensiloxane copolymer at both ends of the molecular chain, trimethylsiloxy - terminated dimethylsiloxane - methylhydrogensiloxane - methylphenylsiloxane copolymer at both ends of the molecular chain, trimethylsiloxy - terminated dimethylsiloxane - methylhydrogensiloxane - diphenylsiloxane copolymer at both ends of the molecular chain, dimethylhydrogensiloxy - terminated methylhydrogenpolysiloxane at both ends of the molecular chain, dimethylhydrogensiloxy - terminated dimethylpolysiloxane at both ends of the molecular chain, dimethylhydrogensiloxy - terminated dimethylsiloxane - methylhydrogensiloxane copolymer at both ends of the molecular chain, dimethylhydrogensiloxy - terminated dimethylsiloxane - methylphenylsiloxane copolymer at both ends of the molecular chain, dimethylhydrogensiloxy - terminated dimethylsiloxane - diphenylsiloxane copolymer at both ends of the molecular chain, dimethylhydrogensiloxy - terminated methylphenylpolysiloxane at both ends of the molecular chain, dimethylhydrogensiloxy - terminated diphenylpolysiloxane at both ends of the molecular chain, and those in which part or all of the methyl groups in each of these exemplified compounds are substituted with other alkyl groups such as ethyl group and propyl group, the formula: R 3 3SiO 1 / 2 The siloxane unit represented by and the formula: R 3 2HSiO 1 / 2 The siloxane unit represented by and the formula: SiO 4 / 2 An organosiloxane copolymer composed of the siloxane unit represented by, the formula: R 3 2HSiO 1 / 2 The siloxane unit represented by and the formula: SiO 4 / 2 An organosiloxane copolymer composed of the siloxane unit represented by, the formula: R3 HSiO 2 / 2 The siloxane unit represented by and the formula: R 3 SiO 3 / 2 The siloxane unit represented by or the formula: HSiO 3 / 2 An organosiloxane copolymer composed of the siloxane unit represented by, and a mixture composed of two or more of these organopolysiloxanes can be mentioned. Note that the above R 3 Is a group selected from an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 10 carbon atoms, and particularly preferably a methyl group.

[0052] (B) The blending amount of the component is such that the silicon atom-bonded hydrogen atom in the (B) component is 0.5 to 10 (or moles) with respect to 1 (or mole) of the silicon atom-bonded alkenyl group in the (A) component, preferably 0.6 to 5 (or moles), and more preferably 0.7 to 2.0 (or moles).

[0053] If the silicon atom-bonded hydrogen atom in the (B) component is less than 0.5 with respect to 1 silicon atom-bonded alkenyl group in the (A) component, the silicone rubber composition may not cure sufficiently and the desired strength may not be obtained. Also, if this exceeds 10, the heat resistance of the cured product of the silicone rubber composition may deteriorate extremely.

[0054] [(C) component] As the addition reaction catalyst of the (C) component, platinum black, platinum dichloride, chloroplatinic acid, a reaction product of chloroplatinic acid and a monohydric alcohol, a complex of chloroplatinic acid and olefins, platinum group metal catalysts such as platinum bisacetylacetate, palladium-based catalysts, rhodium-based catalysts, etc. can be mentioned.

[0055] (C) The blending amount of the component can be an amount that is a catalyst amount, that is, 0.5 to 1,000 ppm in terms of platinum group metal with respect to the total mass of the (A) component, and particularly 1 to 500 ppm may be sufficient. If the addition amount is too small, the curability will decrease, and if the addition amount is too large, the cost will increase and it will be uneconomical.

[0056] [(D) component] (D) The carbon material is necessary to obtain the conductivity (or volume resistivity) of a specific region, and known manufacturing methods and types of carbon materials can be used. Here, the "conductivity of a specific region" specifically means that the volume resistivity of the cured product of the obtained silicone rubber composition is usually designed to be 0.1 to 10,000,000 Ω·m, preferably 1 to 10,000,000 Ω·m, more preferably 10 to 1,000,000 Ω·m. Although the conductivity of the carbon material varies depending on its manufacturing method, in the present invention, any carbon material can be used as long as it can obtain the desired conductivity when compounded and kneaded.

[0057] The carbon material is not particularly limited. For example, acetylene black, conductive furnace black (CF), super conductive furnace black (SCF), extra conductive furnace black (XCF), conductive channel black (CC), carbon black such as furnace black and channel black heat-treated at a high temperature of about 1,500 to 3,000 °C, carbon nanoparticles, carbon nanofibers, carbon nanotubes, graphene, graphite, fibrous graphite, etc. can be mentioned. Among these, one kind can be used alone or two or more kinds can be used in combination. Note that among the above examples, graphite and fibrous graphite also have the effect as the (E) heat conductive powder described later. In the present invention, when using graphite or fibrous graphite, the blending amount shall be adjusted as the one blended as the (D) carbon material.

[0058] Specifically, examples of acetylene black include Denka Black (manufactured by Denka Co., Ltd.), Shawinigan Acetylene Black (manufactured by Shawinigan Chemicals, Inc.), etc.; examples of conductive furnace black include Continex CF (manufactured by Continental Carbon Company), Vulcan C (manufactured by Cabot Corporation), etc.; examples of super conductive furnace black include Continex SCF (manufactured by Continental Carbon Company), Vulcan SC (manufactured by Cabot Corporation), etc.; examples of extra conductive furnace black include Asahi HS-500 (manufactured by Asahi Carbon Co., Ltd.), Vulcan XC-72 (manufactured by Cabot Corporation), etc.; examples of conductive channel black include Kuraray L (manufactured by Degussa), etc. In addition, Ketjen Black EC-350 and Ketjen Black EC-600JD (manufactured by Ketjen Black International), which are a type of furnace black, and ENSACO260G, ENSACO250G, and SUPER P Li for batteries (manufactured by Imerys), which are manufactured by an oil combustion method that does not include a rapid cooling step with water in the oil combustion reaction stopping step, can also be used.

[0059] For carbon black produced by the furnace process, the amount of impurities, particularly sulfur and sulfur compounds, is desirably 6,000 ppm or less, more preferably 3,000 ppm or less, in terms of the concentration of sulfur element. Note that acetylene black and oil furnace carbon with high carbon crystallinity are particularly preferably used in the present invention because they have a low impurity content.

[0060] (D) The compounding amount of the carbon material is 1 to 50 parts by mass, preferably 1 to 30 parts by mass, and more preferably 1 to 20 parts by mass, based on 100 parts by mass of the organopolysiloxane as the component (A).

[0061] If the compounding amount of the carbon material is too large, the mechanical properties of the cured product of the silicone rubber composition may deteriorate, and the viscosity of the silicone rubber composition may increase, resulting in deterioration of workability such as moldability and coating properties when making rolls. If the compounding amount of the carbon material is too small, the conductivity of the target product may not be obtained.

[0062] This method of adding and mixing the carbon material can be added and mixed simultaneously with the components (A) to (C) and the components (E) and (F) described below. However, preferably, a method of adjusting the viscosity by adding liquid oil (the liquid organopolysiloxane of component (A)) to a previously dispersed state with a higher viscosity so as to be easily molded is preferred.

[0063] Specifically, first, a part of the liquid organopolysiloxane of component (A) is added to and mixed with the total amount of the carbon material of component (D) to sufficiently disperse the carbon material. At this time, a surface treatment agent may be added or the mixture may be heated to about 100 to 180 °C while mixing. After mixing, the remaining component (A) and components (B), (C), (E), and (F) are added and stirred sufficiently again to obtain a liquid silicone rubber composition having a desired viscosity.

[0064] In order to further impart conductivity to the cured product (elastic layer) of the silicone rubber composition, other conductive agents can be used in combination with the carbon material of (D) as necessary. Examples of such other conductive agents include various conductive metals or alloys such as aluminum, copper, tin, and stainless steel, and metal oxides obtained by subjecting various conductive treatments to tin oxide, zinc oxide, indium oxide, titanium oxide, and a tin oxide-antimony oxide solid solution.

[0065] [Component (E)] Component (E) is a thermally conductive powder for imparting thermal conductivity to the silicone rubber composition of the present invention, having an average primary particle diameter of 30 μm or less and a thermal conductivity of 10 W / m·K or more. The silicone rubber composition of the present invention is a composition in which the specific (E) thermally conductive powder is blended with the above-mentioned (A) organopolysiloxane.

[0066] The thermally conductive powder used in the present invention has a thermal conductivity of 10 W / m·K or more, preferably 20 W / m·K or more, and more preferably 40 W / m·K or more. If the thermal conductivity of the thermally conductive powder is less than 10 W / m·K, it is necessary to incorporate a large amount of the thermally conductive powder into the silicone rubber composition, which causes a decrease in the elastic modulus and an increase in the hardness in the cured silicone rubber, so it is unsuitable.

[0067] The average primary particle diameter of the thermally conductive powder used in the present invention is 30 μm or less, usually 15 μm or less, preferably 0.1 to 12 μm, more preferably 0.5 to 10 μm, and particularly preferably 2 to 8 μm. Particles with an average primary particle diameter of 0.1 μm or more are easy to manufacture, have good dispersibility in silicone polymers (for example, the alkenyl group-containing organopolysiloxane of component (A) which is the base polymer), are easy to disperse primary particles, and are also easy to blend in large amounts. If it exceeds 30 μm, not only the mechanical strength of the rubber cured product is impaired, but also the surface becomes uneven particularly when used as a developing rubber member such as a developing roll or a developing belt, which may cause problems in performance such as image characteristics and toner transferability.

[0068] In the present invention, the average primary particle diameter can be determined as the cumulative weight average value D50 (or median diameter) using a particle size distribution measuring device such as a laser light diffraction method.

[0069] Specific examples of the thermally conductive powder include thermally conductive inorganic powders such as metal silicon powder, alumina, aluminum, silicon carbide, silicon nitride, magnesium oxide, magnesium carbonate, zinc oxide, and aluminum nitride.

[0070] Among them, the metallic silicon powder can be most preferably used in the present invention. Metallic silicon has good thermal conductivity and a low Mohs hardness. As a characteristic of metallic silicon, it is easily crushed when struck and has low malleability, so it has the property that the metal powder itself is not easily aggregated even when subjected to high shear. Therefore, it is easy to form fine particles by pulverization and has excellent dispersibility in organopolysiloxane. Therefore, when polishing an electrophotographic image forming member containing metallic silicon powder, good polishability can be obtained, and it is possible to obtain a rubber member having excellent surface smoothness.

[0071] Further, the thermal conductive powder of component (E) may be surface-treated with a silane coupling agent or its partial hydrolyzate, an alkylalkoxysilane or its partial hydrolyzate, an organosilazane, a titanate coupling agent, an organopolysiloxane oil, a hydrolyzable functional group-containing organopolysiloxane, etc. for the purpose of improving the thermal stability of the silicone rubber composition and the compatibility of the thermal conductive powder. These treatments may be performed by pre-treating the thermal conductive powder itself, or by performing surface treatment under heating during the mixing of component (A) and component (E). Incidentally, as will be described later, surface treatment may be performed under heating during the mixing of component (A), component (E), and the reinforcing silica fine powder described later.

[0072] The blending amount of the thermal conductive powder of component (E) is 10 to 400 parts by mass, preferably 40 to 400 parts by mass, more preferably 50 to 300 parts by mass with respect to 100 parts by mass of component (A). If it is less than 10 parts by mass, the desired high thermal conductivity cannot be obtained, and if it exceeds 400 parts by mass, it will cause a decrease in rubber elasticity and significantly deteriorate physical properties such as rubber strength.

[0073] Incidentally, the conductive high thermal conductivity silicone rubber member obtained from the silicone rubber composition of the present invention is used in an image forming apparatus using an electrophotographic method, and since good rubber elasticity and good compression set are particularly required, it is desirable to adjust the addition amount of the thermal conductive powder so as to optimize the above characteristics.

[0074] [Component (F)] (F) component is an organosilane and / or organopolysiloxane having one or more alkoxy groups (alkoxysilyl groups) bonded to silicon atoms in one molecule. As the organosilane, for example, those represented by the following general formula (1) can be used. R 1 d SiX 4-d (1) (In the formula, R 1 is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 20 carbon atoms, d is an integer of 1 to 3, and X is an alkoxy group having 1 to 4 carbon atoms.)

[0075] Here, d in the above formula is an integer of 1 to 3, preferably 1 or 2. R 1 is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 20 carbon atoms, particularly 1 to 10 carbon atoms. Specifically, alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, cyclohexyl group, octyl group, nonyl group, decyl group, dodecyl group, etc., aryl groups such as phenyl group, tolyl group, xylyl group, naphthyl group, etc., aralkyl groups such as benzyl group, phenylethyl group, phenylpropyl group, etc., alkenyl groups such as vinyl group, allyl group, propenyl group, isopropenyl group, butenyl group, hexenyl group, cyclohexenyl group, octenyl group, etc., and those in which some or all of the hydrogen atoms of these groups are substituted with halogen atoms such as fluorine, bromine, chlorine, etc., cyano group, epoxy group, glycidoxy group, (meth)acryloxy group, amino group, β-aminoethyl-substituted amino group, mercapto group, etc., for example, chloromethyl group, chloropropyl group, bromoethyl group, trifluoropropyl group, cyanoethyl group, γ-(meth)acryloxypropyl group, β-(3,4-epoxycyclohexyl)ethyl group, γ-glycidoxypropyl group, N-β(aminoethyl)-γ-aminopropyl group, γ-aminopropyl group, γ-mercaptopropyl group, etc. When d is 2 or more, R 1They may be the same or different. X is an alkoxy group having 1 to 4 carbon atoms, specifically, a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, an isobutoxy group, a tert-butoxy group, etc. When d is 2 or less, X may be the same or different.

[0076] In addition, as the organopolysiloxane having an alkoxy group bonded to one or more silicon atoms in one molecule, for example, a partial hydrolysis condensate of the above-described organoalkoxysilane (that is, an organopolysiloxane having one or more, preferably two or more residual alkoxy groups in the molecule) or a compound represented by the following average composition formula (2) can be used. R 1 e X f SiO {4-(e+f)} / 2 (2) (In the formula, R 1 is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 20 carbon atoms, X is an alkoxy group having 1 to 4 carbon atoms, and e and f are positive numbers satisfying e = 1.0 to 2.8, f = 0.01 to 0.5, and e + f = 1.5 to 3.)

[0077] In the above formula, R 1 , X are the same as those exemplified for the above R 1 , X, and R 1 is particularly preferably a methyl group or a phenyl group. e and f are positive numbers satisfying e = 1.0 to 2.8, preferably 1.4 to 2.5, f = 0.01 to 0.5, preferably 0.02 to 0.3, and e + f = 1.5 to 3, preferably 1.8 to 2.5.

[0078] The above organopolysiloxane preferably has one or more, preferably 1 to 8, more preferably 2 to 6 alkoxy groups bonded to silicon atoms in one molecule. Also, the molecular structure of this organopolysiloxane may be any of linear, cyclic, branched, three-dimensional network, etc. The number of silicon atoms (or degree of polymerization) in one molecule is preferably, for example, 2 to 100, particularly 5 to 50. Incidentally, the alkoxy group bonded to the silicon atom may be located at either the molecular chain end or in the middle of the molecular chain, or may be located at both positions.

[0079] (F) component is compounded in an amount of 0.05 to 30 parts by mass, preferably 0.1 to 20 parts by mass, more preferably 1 to 20 parts by mass, extremely preferably 1 to 15 parts by mass, particularly preferably 1 to 10 parts by mass, and even more preferably 1 to 5 parts by mass, based on 100 parts by mass of the organopolysiloxane of the (A) component. If the compounding amount exceeds 30 parts by mass, the rubber physical properties of the cured product may deteriorate. On the other hand, if the compounding amount is less than 0.05 parts by mass, the effect of improving the storage stability of the composition cannot be obtained.

[0080] [Reinforcing silica fine powder] The addition of inorganic fillers other than the above (A) to (F) components to the silicone rubber composition according to the present invention is optional, and it is possible to add reinforcing silica fine powder.

[0081] The reinforcing silica fine powder has a specific surface area measured by the BET adsorption method of 10 m 2 / g or more, particularly preferably 50 to 400 m 2 / g in order to obtain a silicone rubber composition with excellent mechanical strength. Examples of the reinforcing silica fine powder include fumed silica (dry silica) and precipitated silica (wet silica), and among them, fumed silica (dry silica) is preferred.

[0082] Examples of these commercially available reinforcing silica fine powders include Aerosil 130, 200, 300 (trade names of products manufactured by Nippon Aerosil Co., Ltd.), Cab-O-sil MS-5, MS-7, HS-5, HS-7 (trade names of products manufactured by Cabot Corporation), Santocel FRC, CS (trade names of products manufactured by Monsanto Company), Nipsil VN-3 (trade name of a product manufactured by Nippon Silica Industry Co., Ltd.), and the like. Further, the surfaces of these may be hydrophobically treated with organopolysiloxanes, organopolysilazanes, chlorosilanes, alkoxysilanes, etc. These silicas may be used alone or in combination of two or more kinds.

[0083] From the viewpoint of better compression set and further suppressing the increase in volume resistivity over time, it is desirable that the addition amount of the above reinforcing silica fine powder to the silicone rubber composition is small.

[0084] In order to obtain better volume resistivity and compression set while blending the above reinforcing silica fine powder, it is preferably blended in an amount of 0 to 5 parts by mass, particularly 0 to 3 parts by mass, based on 100 parts by mass of the organopolysiloxane as the component (A) in the silicone rubber composition. Note that the lower limit value of the blending amount can be 0.1 part by mass or more.

[0085] [Other inorganic fillers, etc.] Examples of inorganic fillers other than the reinforcing silica fine powder include diatomaceous earth, perlite, mica, calcium carbonate, glass flakes, hollow fillers, and the like.

[0086] These inorganic fillers may be those surface-treated with a silane-based coupling agent or its partial hydrolyzate, an alkylalkoxysilane or its partial hydrolyzate, organosilazanes, a titanate-based coupling agent, an organopolysiloxane oil, a hydrolyzable functional group-containing organopolysiloxane, etc. These treatments may be performed by pretreating the inorganic filler itself or by performing the treatment at the time of mixing with the oil.

[0087] The compounding amount is preferably about 0 to 30 parts by mass with respect to 100 parts by mass of the organopolysiloxane as the component (A) in the silicone rubber composition.

[0088] Also, if necessary, it is optional to compound hydrosilylation reaction control agents such as nitrogen-containing compounds, acetylene compounds, phosphorus compounds, nitrile compounds, carboxylates, tin compounds, mercury compounds, sulfur compounds, various additives, flame retardants, heat-resistant agents, etc.

[0089] [Preparation and Molding of Addition-Curing Type Liquid Conductive Silicone Rubber Composition] The addition-curing type liquid conductive silicone rubber composition of the present invention can be prepared by uniformly mixing the above components (A) to (F) and, if necessary, other components (reinforcing silica fine powder and other inorganic fillers) using an ordinary mixing and stirring device, kneading device, etc., such as a kneader, planetary mixer.

[0090] The molding method of the silicone rubber composition of the present invention includes methods such as casting molding, injection molding, coating, etc. As the curing conditions, a press cure in the range of 100 to 300°C for 10 seconds to 1 hour is preferably employed. Also, for the purpose of reducing the low molecular weight siloxane component that causes an increase in compression set, after molding, a post-cure (secondary cure) may be carried out in an oven at 120 to 250°C for about 30 minutes to 70 hours.

[0091] The volume resistivity of the cured product may have any range of conductivity. It is usually designed to be 0.1 to 10,000,000,000,000 Ω·m, preferably 1 to 10,000,000 Ω·m, more preferably 10 to 1,000,000 Ω·m. Here, the volume resistivity can be measured according to JIS K 6249:2003.

[0092] <Electrophotographic Image Forming Member> The present invention also provides an electrophotographic image forming member having an elastic layer made of a cured product of the above-described addition-curing type liquid conductive silicone rubber composition. Such an electrophotographic image forming member is preferably a member selected from a developing roll and a developing belt.

[0093] For example, it may be used as a single-layer roll in which the outer peripheral surface of a core bar is coated with a silicone rubber layer that is a cured product of the silicone rubber composition of the present invention, or as a single-layer belt in which the front and back surfaces of a base material made of a heat-resistant resin or metal are coated with a silicone rubber layer that is a cured product of the silicone rubber composition of the present invention. Alternatively, it may be used as a roll or a belt in which a resin such as a polyimide resin, a urethane resin, or a fluorine-based resin is further coated on the silicone rubber layer. In that case, the silicone rubber layer may be coated only in one layer on the surface (outer peripheral surface), or may be a multi-layer coating of two or more layers. Among them, those in which the outermost surface of the roll or belt is coated with a urethane resin, a fluorine-based resin, etc. are preferable from the viewpoint of durability such as abrasion resistance.

[0094] Here, the material of the core bar or the base material is preferably selected from iron, stainless steel, aluminum, polyamide / polyimide resin, and PEEK (polyetheretherketone). [[ID=⑨]]

[0095] Also, as the fluorine-based resin, a fluorine-based resin coating material, a fluorine-based resin tube, etc. can be used. Examples of the fluorine-based resin coating material include a latex of polytetrafluoroethylene resin (PTFE), Dai-el latex (manufactured by Daikin Industries, Ltd., fluorine-based latex), etc. As the fluorine-based resin tube, commercially available products can be used. Examples include polytetrafluoroethylene resin (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin (PFA), ethylene fluoride-polypropylene copolymer resin (FEP), polyvinylidene fluoride resin (PVDF), polyvinyl fluoride resin, etc. Among these, PFA and PTFE latex are particularly preferable.

Examples

[0096] Hereinafter, examples and comparative examples will be shown to specifically describe the present invention. However, the present invention is not limited to the following examples. The viscosity described below is a value at 25°C measured by a rotational viscometer described in JIS K 7117-1:1999. However, Examples 6 to 9 are reference examples.

[0097] [Example 1] 35 parts by mass of dimethylpolysiloxane (A) in which both ends of the molecular chain are blocked with vinyldimethylsiloxy groups, the alkenyl group content is 0.015 mol / 100 g, and the viscosity is 500 mPa·s, and 6.7 parts by mass of acetylene black (Denka Black, manufactured by Denka Co., Ltd.) (D) were mixed in a planetary mixer for 30 minutes and then passed through a three-roll mill twice. After returning this to the planetary mixer, 65 parts by mass of the above dimethylpolysiloxane (A), dimethylsiloxane-methylhydrogensiloxane copolymer (B) in which both ends of the molecular chain are blocked with trimethylsiloxy groups and which has a silicon atom-bonded hydrogen atom in the side chain (silicon atom-bonded hydrogen atom content = 0.0032 mol / g) 2.7 parts by mass, the following general formula (I)

Chemical formula

[0098] Next, in order to confirm the storage stability, Composition A was mixed at a mass ratio of 1 to 1 as follows so that the catalyst and the crosslinking agent were separated into two liquids of Material 1 and Material 2 in the following blending amounts so as to become Composition A.

[0099] [Preparation of Material 1] 35 parts by mass of dimethylpolysiloxane (A) having vinyl dimethylsiloxy groups blocking both ends of the molecular chain, an alkenyl group content of 0.015 mol / 100 g, and a viscosity of 500 mPa·s, 6.7 parts by mass of acetylene black (Denka Black, manufactured by Denka Co., Ltd.) (D) were mixed with a planetary mixer for 30 minutes and then passed through a three-roll mill twice. After returning this to the planetary mixer, further 67.59 parts by mass of the above dimethylpolysiloxane (A), 0.42 parts by mass of a dimethylpolysiloxane solution (C) containing 1% by mass of platinum atom content as chloroplatinic acid / 1,3-divinyltetramethyldisiloxane complex, BET specific surface area of 110 m 2 0.67 parts by mass of hydrophobized fumed silica (R-972 manufactured by Nippon Aerosil Co., Ltd.) which is / g, 110 parts by mass of pulverized metallic silicon powder (E) (average primary particle diameter 5 μm), 2.0 parts by mass of the above alkoxy group-containing siloxane compound (F), were mixed at room temperature with a planetary mixer for 30 minutes to prepare Composition A1 as Material 1.

[0100] [Preparation of Material 2] Next, 35 parts by mass of dimethylpolysiloxane (A) with vinyl dimethylsiloxy groups blocking both ends of the molecular chain, an alkenyl group content of 0.015 mol / 100 g, and a viscosity of 500 mPa·s, and 6.7 parts by mass of acetylene black (Denka Black, manufactured by Denka Co., Ltd.) (D) were mixed in a planetary mixer for 30 minutes and then passed through a three-roll mill twice. After returning this to the planetary mixer, further 62.41 parts by mass of the above dimethylpolysiloxane (A), 5.4 parts by mass of a dimethylsiloxane-methylhydrogensiloxane copolymer (B) with trimethylsiloxy groups blocking both ends of the molecular chain and having silicon atom-bonded hydrogen atoms in the side chain (silicon atom-bonded hydrogen atom content = 0.0032 mol / g), 0.2 part by mass of 1-ethynylcyclohexanol, and 0.67 part by mass of hydrophobized fumed silica (R-972 manufactured by Nippon Aerosil Co., Ltd.) with a BET specific surface area of 110 m 2 / g, 110 parts by mass of pulverized metallic silicon powder (E) (average primary particle diameter 5 μm), and 2.0 parts by mass of the above alkoxy group-containing siloxane compound (F) were mixed at room temperature in a planetary mixer for 30 minutes to prepare a composition A2 as Material 2.

[0101] [Evaluation of Storage Stability] Next, Composition A1 and Composition A2 were each sealed and stored at 25°C for 4 months, at 25°C for 12 months, at 70°C for 7 days, at 80°C for 3 days, and at 80°C for 5 days. After storage, Composition A1 and Composition A2 were mixed at a ratio of 1:1, press-cured at 120°C for 10 minutes to form a silicone rubber sheet, and then post-cured at 200°C for 4 hours. The hardness was measured according to JIS K 6249:2003, and the hardness difference from the initial value was determined. The results are shown in Tables 1 and 3.

[0102] [Example 2] In Example 1, Composition B was prepared with the same formulation except that 2.7 parts by mass of the dimethylsiloxane-methylhydrogensiloxane copolymer (B) was replaced with 2.54 parts by mass and 110 parts by mass of the pulverized metallic silicon powder (E) (average primary particle diameter: 5 μm) was replaced with 80 parts by mass, and the same evaluation as in Example 1 was performed. Table 1 shows the results of confirming only the condition of 80°C for 3 days regarding the storage stability.

[0103] [Example 3] In Example 1, Composition C was prepared with the same formulation except that 2.0 parts by mass of the siloxane compound (F) was replaced with 0.05 parts by mass, and Table 1 shows the results of performing the same evaluation as in Example 2.

[0104] [Example 4] In Example 1, Composition D was prepared with the same formulation except that 2.0 parts by mass of the siloxane compound (F) was replaced with 0.7 parts by mass, and Table 1 shows the results of performing the same evaluation as in Example 2.

[0105] [Example 5] In Example 1, Composition E was prepared with the same formulation except that 2.0 parts by mass of the siloxane compound (F) was replaced with 14 parts by mass, and Table 1 shows the results of performing the same evaluation as in Example 2.

[0106] [Example 6] In Example 1, Composition F was prepared with the same formulation except that 2.0 parts by mass of the siloxane compound (F) was replaced with 0.67 parts by mass of 3-glycidoxypropyltrimethoxysilane, and Table 1 shows the results of performing the same evaluation as in Example 2.

[0107] [Example 7] In Example 1, Composition G was prepared with the same formulation except that 2.0 parts by mass of the siloxane compound (F) was replaced with 0.45 parts by mass of methyltrimethoxysilane, and Table 1 shows the results of performing the same evaluation as in Example 2.

[0108] [Example 8] In Example 1, Composition H was prepared with the same formulation except that 2.0 parts by mass of the above siloxane compound (F) was replaced with 0.71 parts by mass of hexyltrimethoxysilane, and the results of the same evaluation as in Example 2 are shown in Table 1.

[0109] [Example 9] In Example 1, Composition I was prepared with the same formulation except that 2.0 parts by mass of the above siloxane compound (F) was replaced with 0.79 parts by mass of 1,6-bis(trimethoxysilyl)hexane, and the results of the same evaluation as in Example 2 are shown in Table 1.

[0110] [Comparative Example 1] 35 parts by mass of dimethylpolysiloxane (A) with vinyl dimethylsiloxy groups blocking both ends of the molecular chain, an alkenyl group content of 0.015 mol / 100 g, and a viscosity of 500 mPa·s, and 6.7 parts by mass of acetylene black (Denka Black, manufactured by Denka Co., Ltd.) (D) were mixed in a planetary mixer for 30 minutes and then passed through a three-roll mill twice. After returning this to the planetary mixer, 65 parts by mass of the above dimethylpolysiloxane (A), a dimethylsiloxane-methylhydrogensiloxane copolymer (B) with trimethylsiloxy groups blocking both ends of the molecular chain and having silicon atom-bonded hydrogen atoms in the side chain (silicon atom-bonded hydrogen atom content = 0.0032 mol / g) 2.7 parts by mass, 0.1 part by mass of 1-ethynylcyclohexanol, a dimethylpolysiloxane solution (C) containing 1% by mass of platinum as platinum atoms in a chloroplatinic acid / 1,3-divinyltetramethyldisiloxane complex 0.21 parts by mass, and a BET specific surface area of 110 m 2 / g of hydrophobized fumed silica (R-972 manufactured by Nippon Aerosil Co., Ltd.) 0.67 parts by mass, and pulverized metallic silicon powder (E) (average primary particle diameter 5 μm) 110 parts by mass were mixed in a planetary mixer at room temperature for 30 minutes to prepare Composition J, and the same evaluation as in Example 1 was performed. The results are shown in Table 1.

[0111] Next, in order to confirm the storage stability, Composition J was divided into two liquids, Material 1 and Material 2, with the following blending amounts so that the catalyst and the crosslinking agent were separated so that Composition J would be obtained when they were mixed at a mass ratio of 1 to 1.

[0112] [Preparation of Material 1] 35 parts by mass of dimethylpolysiloxane (A) with vinyl dimethylsiloxy groups blocking both ends of the molecular chain, an alkenyl group content of 0.015 mol / 100 g, and a viscosity of 500 mPa·s, and 6.7 parts by mass of acetylene black (Denka Black, manufactured by Denka Co., Ltd.) (D) were mixed in a planetary mixer for 30 minutes and then passed through a three-roll mill twice. After returning this to the planetary mixer, 67.59 parts by mass of the above dimethylpolysiloxane (A), 0.42 parts by mass of a dimethylpolysiloxane solution (C) containing 1% by mass of platinum atoms as a chloroplatinic acid / 1,3-divinyltetramethyldisiloxane complex, and hydrophobic fumed silica (R-972 manufactured by Nippon Aerosil Co., Ltd.) with a BET specific surface area of 110 m 2 / g and 110 parts by mass of pulverized metallic silicon powder (E) (average primary particle diameter: 5 μm) were mixed in a planetary mixer at room temperature for 30 minutes to prepare a composition J1 as Material 1.

[0113] [Preparation of Material 2] Next, 35 parts by mass of dimethylpolysiloxane (A) with vinyl dimethylsiloxy groups blocking both ends of the molecular chain, an alkenyl group content of 0.015 mol / 100 g, and a viscosity of 500 mPa·s, and 6.7 parts by mass of acetylene black (Denka Black, manufactured by Denka Co., Ltd.) (D) were mixed in a planetary mixer for 30 minutes and then passed through a three-roll mill twice. After returning this to the planetary mixer, 62.41 parts by mass of the above dimethylpolysiloxane (A), 5.4 parts by mass of a dimethylsiloxane-methylhydrogensiloxane copolymer (B) with trimethylsiloxy groups blocking both ends of the molecular chain and having silicon atom-bonded hydrogen atoms in the side chain (silicon atom-bonded hydrogen atom content = 0.0032 mol / g), 0.2 parts by mass of 1-ethynylcyclohexanol, and hydrophobic fumed silica (R-972 manufactured by Nippon Aerosil Co., Ltd.) with a BET specific surface area of 110 m 2 / g and 110 parts by mass of pulverized metallic silicon powder (E) (average primary particle diameter: 5 μm) were mixed in a planetary mixer at room temperature for 30 minutes to prepare a composition J2 as Material 2.

[0114] [Evaluation of storage stability] Next, Component J1 and Composition J2 were each sealed and stored at 25°C for 4 months, 25°C for 12 months, 70°C for 7 days, 80°C for 3 days, and 80°C for 5 days. After storage, Composition J1 and Composition J2 were mixed at a ratio of 1:1 and press-cured at 120°C for 10 minutes to form a silicone rubber sheet, followed by post-curing at 200°C for 4 hours. The hardness was measured according to JIS K 6249:2003, and the hardness difference from the initial value was determined. The results are shown in Tables 2 and 3.

[0115] [Comparative Example 2] In Example 2, Composition K was prepared with the same formulation except that 2.0 parts by mass of the above siloxane compound (F) was not added, and the results of the same evaluation as in Example 2 are shown in Table 2.

[0116] [Comparative Example 3] In Comparative Example 2, Composition L was prepared with the same formulation except that the pulverized metallic silicon powder (E) (average primary particle diameter 5 μm) was additionally heat-treated in a stainless steel container with an open upper part in a thermostatic and humidistatic chamber at a temperature of 80°C and a humidity of 30% for 24 hours, and the results of the same evaluation as in Example 2 are shown in Table 2.

[0117] [Comparative Example 4] 65 parts by mass of dimethylpolysiloxane (A) with vinyl dimethylsiloxy groups blocking both ends of the molecular chain, an alkenyl group content of 0.015 mol / 100 g, and a viscosity of 500 mPa·s, and a BET specific surface area of 110 m 20.67 parts by mass of hydrophobized fumed silica (R-972 manufactured by Nippon Aerosil Co., Ltd.) with a specific surface area of [[ID=]], 80 parts by mass of pulverized metallic silicon powder (E) (average primary particle diameter: 5 μm) were mixed using a planetary mixer for 30 minutes, heat-treated at 150 °C for 2 hours under normal pressure, and then cooled to room temperature to prepare Composition F1. On the other hand, 35 parts by mass of the above dimethylpolysiloxane (A) and 6.7 parts by mass of acetylene black (Denka Black, manufactured by Denka Co., Ltd.) (D) were mixed using a planetary mixer for 30 minutes and then passed through a three-roll mill twice. After returning this to the planetary mixer, 2.54 parts by mass of Composition F1, a dimethylsiloxane-methylhydrogensiloxane copolymer (B) in which both ends of the molecular chain are blocked with trimethylsiloxy groups and which has silicon atom-bonded hydrogen atoms in the side chains (content of silicon atom-bonded hydrogen atoms = 0.0032 mol / g), 0.1 part by mass of 1-ethynylcyclohexanol, and 0.21 part by mass of a dimethylpolysiloxane solution (C) containing 1% by mass of platinum atoms as a chloroplatinic acid / 1,3-divinyltetramethyldisiloxane complex were mixed using a planetary mixer at room temperature for 30 minutes to prepare Composition M, and the results of the same evaluation as in Example 2 are shown in Table 2.

[0118] 〔Comparative Example 5〕 In Example 1, 2.7 parts by mass of the dimethylsiloxane-methylhydrogensiloxane copolymer (B) was replaced with 2.4 parts by mass, and 110 parts by mass of the pulverized metallic silicon powder (E) (average primary particle diameter: 5 μm) was replaced with 190 parts by mass. Composition N was prepared with the same formulation except that 0.67 part by mass of hydrophobized fumed silica (R-972 manufactured by Nippon Aerosil Co., Ltd.) with a BET specific surface area of [[ID=]] / g, 2.0 parts by mass of the above siloxane compound (F), and 6.7 parts by mass of acetylene black (D) were not added, and the results of the same evaluation as in Example 2 are shown in Table 2. 2 / g, 0.67 parts by mass of hydrophobized fumed silica (R-972 manufactured by Nippon Aerosil Co., Ltd.), 2.0 parts by mass of the above siloxane compound (F), and 6.7 parts by mass of acetylene black (D) were not added, and the results of the same evaluation as in Example 2 are shown in Table 2.

[0119] 〔Comparative Example 6〕 In Comparative Example 1, Composition O was prepared with the same formulation except that 6.7 parts by mass of acetylene black (D) was replaced with 4.3 parts by mass, and the results of the same evaluation as in Example 2 are shown in Table 2.

[0120]

Table 1

[0121]

Table 2

[0122]

Table 3

[0123] In Examples 1 to 9, sufficient component (F) was included in all cases, so the storage stability was good, and while having good thermal conductivity, volume resistivity, and compression set, the hardness did not decrease after storage. In comparison, in Comparative Examples 1, 2, 3, 4, and 6 that did not contain component (F), a significant decrease in hardness occurred after storage. In Comparative Example 5 where only (E) thermally conductive powder was blended and (D) carbon material was not blended, no decrease in hardness occurred.

[0124] Note that the present invention is not limited to the above-described embodiments. The above-described embodiments are examples, and any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits the same operational effects is included in the technical scope of the present invention.

Claims

1. An addition-curing type liquid conductive silicone rubber composition used for an electrophotographic image forming member, (A) A liquid organopolysiloxane containing two or more alkenyl groups bonded to silicon atoms in one molecule: 100 parts by mass, (B) An organohydrogenpolysiloxane containing hydrogen atoms bonded to two or more silicon atoms in one molecule: an amount such that the number of hydrogen atoms bonded to the silicon atoms contained in the component (B) is 0.5 to 10 with respect to one alkenyl group bonded to the silicon atoms contained in the component (A), (C) A platinum group metal-based catalyst as an addition reaction catalyst: an amount such that it is 0.5 to 1,000 ppm in terms of platinum group metal with respect to the total mass of the component (A), (D) A carbon material: 1 to 50 parts by mass, (E) A thermally conductive powder having an average primary particle diameter of 30 μm or less and a thermal conductivity of 10 W / m·K or more: 10 to 400 parts by mass, and (F) The following average composition formula (2) R １ ｅ X ｆ SiO ｛４－（ｅ＋ｆ）｝／２ (2) (In the formula, R １ is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 20 carbon atoms, X is an alkoxy group having 1 to 4 carbon atoms, and e and f are positive numbers satisfying e = 1.0 to 2.8, f = 0.01 to 0.5, and e + f = 1.5 to 3.) An organopolysiloxane represented by the formula, having one or more alkoxysilyl groups in one molecule and the number of silicon atoms in one molecule being 5 or more (however, excluding those corresponding to the component (A)): an amount of 0.05 to 30 parts by mass, and containing, The addition-curing type liquid conductive silicone rubber composition, wherein the component (E) is a metal silicon powder.

2. The addition-curing type liquid conductive silicone rubber composition according to claim 1, wherein in the average composition formula (2), X is a methoxy group or an ethoxy group, and f is 0.02 to 0.

3.

3. In the average compositional formula (2), the R １ The addition-curing type liquid conductive silicone rubber composition according to claim 1 or claim 2, wherein is a methyl group or a phenyl group.

4. An electrophotographic image forming member having an elastic layer made of a cured product of the addition-curing type liquid conductive silicone rubber composition according to any one of claims 1 to 3.

5. The electrophotographic image forming member according to claim 4, wherein the electrophotographic image forming member is a member selected from a developing roll and a developing belt.

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