JP7630892B2 - Addition-curable liquid silicone rubber composition and electrophotographic image forming member - Google Patents

Description

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

Taking advantage of its heat resistance, silicone rubber has been used as a coating material for the fixing rolls of copiers and laser beam printers, which require high thermal conductivity, especially higher than the 0.16 W/m·K of silicone oil.

In response to these demands, a method has been proposed in which metal silicon powder is used to improve thermal conductivity and dramatically improve compression set (Patent Document 1).

A technique has also been proposed in which metal silicon powder is subjected to heat treatment and wet processing to form a native oxide film with few defects, and then the surface is further treated with an organosilicon compound such as a silane coupling agent (Patent Document 2).

JP 2007-171946 A JP 2013-216576 A

However, when metallic silicon powder is added to addition-curing liquid silicone rubber, the metallic silicon powder adversely affects the addition-curing catalyst. This problem of delayed curing over time has not been resolved, and there has been a demand for the development of a silicone rubber composition that has high thermal conductivity and excellent storage stability.

The present invention aims to provide an addition-curing liquid silicone rubber composition with improved storage stability, particularly in terms of a highly thermally conductive addition-curing liquid silicone rubber composition containing a thermally conductive powder, which exhibits reduced delay in curing over time, and an electrophotographic image forming member having an elastic layer made of the cured product of the composition.

As a result of intensive research conducted by the present inventors to achieve the above object, they discovered that, in an addition-curing liquid silicone rubber composition containing the components (A) to (E) described below, a thermally conductive silicone rubber composition containing an addition reaction catalyst (C), a thermally conductive powder (D), and an alkenyl-containing organopolysiloxane having a specific structure (E) can suppress the delay in curing over time and has good storage stability, and they discovered that a thermally conductive silicone rubber member (roll, belt, etc.) having a silicone rubber layer formed by curing the composition has excellent thermal conductivity and can be effectively used as a rubber member for high-speed copying machines and printers, which led to the creation of the present invention.

（式中、Ｒ¹はメチル基又はビニル基であり、ｐは３～３０である。）
で表され、（Ｅ）成分中のアルケニル基含有鎖状オルガノポリシロキサンは下記一般式（２）

（式中、Ｒは独立して炭素数１～１０の１価炭化水素基であり、ｑは０以上、ｒは２以上、ｑ＋ｒが２～２００である。）
で表される〔１〕から〔３〕のいずれか１項に記載の付加硬化型液状シリコーンゴム組成物。
〔５〕〔１〕から〔４〕のいずれか１項に記載の付加硬化型液状シリコーンゴム組成物の硬化物からなる弾性層を有する電子写真式画像形成部材。
〔６〕電子写真式画像形成部材が、定着ロール及び定着ベルトから選ばれる部材である〔５〕に記載の電子写真式画像形成部材。 Accordingly, the present invention provides an addition-curable liquid silicone rubber composition and an electrophotographic imaging member as described below.
[1] (A) 100 parts by mass of a liquid organopolysiloxane containing two or more alkenyl groups bonded to silicon atoms in each molecule, the content of alkenyl groups bonded to silicon atoms being 1.0×10 ^-7 to 1.0×10 ^-3 mol/g based on the total amount of monovalent hydrocarbon groups bonded to silicon atoms;
(B) an organohydrogenpolysiloxane containing two or more hydrosilyl groups per molecule: the number of hydrosilyl groups contained in component (B) is 0.4 to 10 per alkenyl group bonded to a silicon atom contained in component (A);
(C) a platinum group metal catalyst as an addition reaction catalyst: an amount equivalent to 0.5 to 1,000 ppm in terms of platinum group metal based on the total mass of component (A);
An addition-curable liquid silicone rubber composition comprising: (D) 10 to 1,000 parts by mass of a thermally conductive powder having an average primary particle size of 75 μm or less and a thermal conductivity of 10 W/m·K or more; and (E) one or more selected from alkenyl-group-containing cyclic organopolysiloxanes having one or more alkenyl groups on all silicon atoms, and alkenyl-group-containing linear organopolysiloxanes in which the content of alkenyl groups bonded to silicon atoms is 1.1× ^10-3 to 1.0× ^10-1 mol/g relative to the total amount of monovalent hydrocarbon groups bonded to silicon atoms, in an amount of 0.1 to 500 mol per 1 mol of platinum group metal atoms in component (C).
[2] The addition-curable liquid silicone rubber composition according to [1], wherein component (D) is metallic silicon powder.
[3] The addition-curing liquid silicone rubber composition according to [1], wherein component (D) is a metallic silicon powder or a thermally conductive powder having a Mohs hardness higher than that of the metallic silicon powder.
[4]
The alkenyl group-containing cyclic organopolysiloxane in component (E) is represented by the following general formula (1):

(In the formula, R ¹ is a methyl group or a vinyl group, and p is an integer from 3 to 30.)
The alkenyl group-containing linear organopolysiloxane in component (E) is represented by the following general formula (2):

(In the formula, R is independently a monovalent hydrocarbon group having 1 to 10 carbon atoms, q is 0 or more, r is 2 or more, and q+r is 2 to 200.)
The addition-curable liquid silicone rubber composition according to any one of [1] to [3], wherein the formula (I) is
[5] An electrophotographic image forming member having an elastic layer made of a cured product of the addition-curable liquid silicone rubber composition according to any one of [1] to [4].
[6] The electrophotographic image forming member according to [5], wherein the electrophotographic image forming member is a member selected from a fixing roll and a fixing belt.

When the addition-curable liquid silicone rubber composition is as described above in [1], it is possible to obtain a cured product that has good storage stability and suppresses delay in curing over time.
By using the organopolysiloxane of the above formula (4), it is possible to maintain the storage stability of the addition reaction catalyst of the component (C).
The addition-curable liquid silicone rubber composition of the present invention can be particularly suitably used in applications such as the above items [5] and [6].

According to the present invention, it is possible to provide an addition-curing liquid silicone rubber composition that gives a cured product with good storage stability, particularly curing stability over time, and in particular, it is possible to obtain an addition-curing liquid silicone rubber composition for electrophotographic image forming members and an electrophotographic image forming member having a cured product of the composition as an elastic layer.

The present invention will be described in detail below.

<Addition-curable liquid silicone rubber composition>
The addition-curable liquid silicone rubber composition of the present invention (addition-curable highly thermally conductive silicone rubber composition) comprises the following components (A) to (E).

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

The molecular structure of component (A) may be, for example, linear, cyclic, branched, or three-dimensional network (resinous), but a linear diorganopolysiloxane in which the main chain is basically composed of repeated diorganosiloxane units and both ends of the molecular chain are blocked with triorganosiloxy groups is preferred. In addition, 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 organopolysiloxane molecule may be either or both of the molecular chain end (i.e., triorganosiloxy group) and the middle of the molecular chain (i.e., difunctional diorganosiloxane unit or trifunctional monoorganosilsesquioxane unit located at the non-terminal of the molecular chain). Particularly preferred as component (A) is a linear diorganopolysiloxane containing alkenyl groups bonded to silicon atoms at both ends of the molecular chain.

The alkenyl group bonded to the silicon atom in component (A) typically has 2 to 8 carbon atoms, and preferably has 2 to 4 carbon atoms. Specific examples include vinyl groups, allyl groups, butenyl groups, pentenyl groups, hexenyl groups, cyclohexenyl groups, and heptenyl groups, with vinyl groups being particularly preferred.

The content of alkenyl groups bonded to silicon atoms in component (A) is from 1.0×10 ^-7 to 1.0×10 ^-3 mol/g, and preferably from 1.0×10 ^-6 to 5.0×10 ^-4 mol/g, based on all monovalent hydrocarbon groups bonded to silicon atoms.

Examples of monovalent hydrocarbon groups bonded to silicon atoms other than alkenyl groups in component (A) include monovalent hydrocarbon groups having 1 to 12 carbon atoms, preferably 1 to 10 carbon atoms. Specific examples of monovalent hydrocarbon groups include alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, cyclohexyl, and heptyl; aryl groups such as phenyl, tolyl, xylyl, and naphthyl; and aralkyl groups such as benzyl and phenethyl. Of these, methyl groups are particularly preferred.

The viscosity of component (A) at 25°C is preferably 50 to 500,000 mPa·s, and more preferably 500 to 200,000 mPa·s. If the viscosity is within this range, the resulting silicone rubber composition is easy to handle and has good mechanical properties when cured. In this specification, the term "viscosity" refers to the value measured at 25°C using a rotational viscometer according to the method described in JIS K 7117-1:1999.

Specific examples of the organopolysiloxane of component (A) include dimethylsiloxane-methylvinylsiloxane copolymers capped with trimethylsiloxy groups at both molecular chain ends, methylvinylpolysiloxane capped with trimethylsiloxy groups at both molecular chain ends, dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymers capped with trimethylsiloxy groups at both molecular chain ends, dimethylpolysiloxane capped with dimethylvinylsiloxy groups at both molecular chain ends, methylvinylpolysiloxane capped with dimethylvinylsiloxy groups at both molecular chain ends, dimethylsiloxane-methylvinylpolysiloxane capped with dimethylvinylsiloxy groups at both molecular chain ends, Examples of the organopolysiloxane include a dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymer, a dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymer capped at both molecular chain terminals with dimethylvinylsiloxy groups, a dimethylpolysiloxane capped at both molecular chain terminals with divinylmethylsiloxy groups, a dimethylsiloxane-methylvinylsiloxane copolymer capped at both molecular chain terminals with divinylmethylsiloxy groups, a dimethylpolysiloxane capped at both molecular chain terminals with trivinylsiloxy groups, a dimethylsiloxane-methylvinylsiloxane copolymer capped at both molecular chain terminals with trivinylsiloxy groups, and a mixture of two or more of these organopolysiloxanes.

The organopolysiloxane of component (A) may be used alone or in combination of two or more. In particular, the use of two or more types in combination is preferred because it makes it easier to adjust the viscosity of the composition of the present invention to a preferred range.

[Component (B)]
The organohydrogenpolysiloxane of component (B) undergoes a hydrosilylation addition reaction with the alkenyl groups in component (A) and acts as a crosslinking agent (curing agent). There are no particular limitations on its molecular structure, and various types of conventionally produced structures, such as linear, cyclic, branched, and three-dimensional network (resinous) structures, can be used; however, it is necessary for each molecule to contain two or more hydrosilyl groups.

The organohydrogenpolysiloxane of component (B) may be used alone or in combination of two or more types.

As this organohydrogenpolysiloxane, one represented by the following average composition formula (3) can be used.
R ² _a H _b SiO _(4-ab)/2 (3)
(In the formula, ^R2 is independently a group selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms. In addition, a is a positive number that satisfies 0.7 to 2.1, b is a positive number that satisfies 0.001 to 1.0, and a+b is a positive number that satisfies 0.8 to 3.0.)

In the above formula (3), R ² is independently a group selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms, and examples of the monovalent hydrocarbon group in R ² include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyl, and decyl; aryl groups such as phenyl, tolyl, xylyl, and naphthyl; and aralkyl groups such as benzyl, phenylethyl, and phenylpropyl. R ² is preferably an alkyl group or an aryl group, and more preferably a methyl group. Furthermore, a is a positive number that satisfies 0.7 to 2.1, b is a positive number that satisfies 0.001 to 1.0, and a+b is a positive number that satisfies 0.8 to 3.0, and preferably a is a positive number that satisfies 1.0 to 2.0, b is a positive number that satisfies 0.01 to 1.0, and a+b is a positive number that satisfies 1.5 to 2.5.

The hydrosilyl groups contained in one molecule may be located at either the terminal or the middle of the molecular chain, or may be located at both. The molecular structure of this organohydrogenpolysiloxane may be linear, cyclic, branched, or a three-dimensional network structure, but the number of silicon atoms (or degree of polymerization) in one molecule is usually 2 to 300, preferably 3 to 150, and more preferably 4 to 100. The viscosity at 25°C is usually 0.1 to 1,000 mPa·s, preferably 0.5 to 500 mPa·s, and the polymer is liquid at 25°C. 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) converted into polystyrene in GPC (gel permeation chromatography) analysis using toluene as a developing solvent.

Examples of such organohydrogenpolysiloxanes of component (B) include 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, tris(hydrogendimethylsiloxy)methylsilane, tris(hydrogendimethylsiloxy)phenylsilane, methylhydrogencyclopolysiloxane, methylhydrogensiloxane-dimethylsiloxane cyclic copolymers, methylhydrogenpolysiloxanes capped at both molecular chain terminals with trimethylsiloxy groups, dimethylsiloxane-methylhydrogensiloxane copolymers capped at both molecular chain terminals with trimethylsiloxy groups, dimethylsiloxane-methylhydrogensiloxane-methylphenylsiloxane copolymers capped at both molecular chain terminals with trimethylsiloxy groups, dimethylsiloxane-methylhydrogensiloxane-diphenylsiloxane copolymers capped at both molecular chain terminals with trimethylsiloxy groups, and dimethylsiloxane-methylhydrogensiloxane-diphenylsiloxane copolymers capped at both molecular chain terminals with trimethylsiloxy groups. and compounds of the formula: R Examples of _such organosiloxane copolymers include those comprising siloxane units represented by the formula: ^{R33SiO1 /} _{2 ,} siloxane units represented by the formula: _{R32HSiO1 /2 ,} and siloxane units represented by the formula: SiO4 ^/ ₂ , organosiloxane copolymers comprising siloxane units represented by the formula: R32HSiO1 _/2 and siloxane units represented by the formula: SiO4 ^/ ₂ , organosiloxane copolymers comprising siloxane units represented by the formula: ^R3HSiO2 _/2 and siloxane units represented by the formula: R3SiO3 _{/2 or siloxane units represented by the formula: HSiO3/2} , and mixtures of two or more of these organopolysiloxanes. The above R ³ is a group selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms, and is particularly preferably a methyl group.

The amount of component (B) to be blended is such that there are 0.4 to 10 (or moles), preferably 0.5 to 5 (or moles), and more preferably 0.5 to 2.0 (or moles) hydrosilyl groups in component (B) per one (or mole) silicon-bonded alkenyl group in component (A).

If there are less than 0.4 hydrosilyl groups in component (B) per silicon-bonded alkenyl group in component (A), the silicone rubber composition may not cure sufficiently and may not achieve the desired strength. If there are more than 10 hydrosilyl groups, the heat resistance of the cured product of the silicone rubber composition may deteriorate significantly.

[Component (C)]
Examples of the addition reaction catalyst of component (C) include platinum group metal catalysts such as platinum black, platinic chloride, chloroplatinic acid, reaction products of chloroplatinic acid and monohydric alcohols, complexes of chloroplatinic acid and olefins, platinum bisacetoacetate, etc., palladium catalysts, and rhodium catalysts.

The amount of component (C) can be a catalytic amount, i.e., an amount equivalent to 0.5 to 1,000 ppm of platinum group metal relative to the total mass of component (A), and is preferably 1 to 500 ppm. If the amount is too small, curability will decrease, and if the amount is too large, the cost will increase and it will be uneconomical. The platinum group metal catalyst of component (C) may be used alone or in combination of two or more types.

[Component (D)]
Component (D) is a thermally conductive powder for imparting thermal conductivity to the silicone rubber composition of the present invention, and has an average primary particle size of 75 μm or less and a thermal conductivity of 10 to 5,000 W/m K. The silicone rubber composition of the present invention is obtained by blending the above-mentioned organopolysiloxane (A) with a specific thermally conductive powder (D).

The thermally conductive powder used in the present invention has a thermal conductivity of 10 to 5,000 W/m·K, preferably 20 to 5,000 W/m·K, and more preferably 40 to 5,000 W/m·K. If the thermal conductivity of the thermally conductive powder is less than 10 W/m·K, it would be necessary to add a large amount of thermally conductive powder to the silicone rubber composition, which would cause a decrease in the elastic modulus and an increase in hardness in the cured silicone rubber, making this unsuitable.

The average primary particle size of the thermally conductive powder used in the present invention is 75 μm or less, and is usually 50 μm or less, preferably 0.1 to 30 μm, more preferably 0.5 to 20 μm, and particularly preferably 2 to 15 μm. Particles with an average primary particle size of 0.1 μm or more are easy to manufacture, have good dispersibility in silicone polymers (for example, the alkenyl-containing organopolysiloxane of component (A), which is the base polymer), and are easy to disperse primary particles and to incorporate in large quantities. If the particle size exceeds 75 μm, not only will the mechanical strength of the cured rubber be impaired, but the surface will become uneven, especially when used as a developing rubber member such as a developing roll or developing belt, which may cause problems with performance such as image characteristics and toner transferability.

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

Specific examples of thermally conductive powders include thermally conductive inorganic powders such as metallic silicon powder, alumina, aluminum, silicon carbide, silicon nitride, magnesium oxide, magnesium carbonate, zinc oxide, and aluminum nitride.

Among them, metal silicon powder is most suitable for use in the present invention. Metal silicon has good thermal conductivity and low Mohs hardness. Metal silicon has the characteristics of being easily broken down when struck and having low malleability, so that the metal powder itself does not easily aggregate even when subjected to high shear. Therefore, it is easy to pulverize into fine particles and has the characteristics of excellent dispersibility in organopolysiloxane. Therefore, when polishing an electrophotographic image forming member containing metal silicon powder, it is possible to obtain a rubber member with good polishing properties and excellent surface smoothness.
It is also more preferable to use metallic silicon powder in combination with another thermally conductive powder, since this makes it possible to obtain a silicone rubber composition that has the properties of both the thermally conductive powders.
Examples of thermally conductive powders having a Mohs hardness higher than that of metallic silicon powder include silicon carbide, alumina, aluminum nitride, and silicon nitride.

In addition, the thermally conductive powder of component (D) is preferably surface-treated with a surface treatment agent such as a silane coupling agent or a partial hydrolyzate thereof, an alkylalkoxysilane or a partial hydrolyzate thereof, an organic silazanes, a titanate coupling agent, an organopolysiloxane oil, or an organopolysiloxane containing a hydrolyzable functional group, in order to improve the thermal stability of the silicone rubber composition and the compoundability of the thermally conductive powder.

The amount of the thermally conductive powder of component (D) is 10 to 1,000 parts by mass, preferably 40 to 600 parts by mass, and more preferably 50 to 400 parts by mass, per 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 1,000 parts by mass, the rubber elasticity is reduced and physical properties such as rubber strength are also significantly reduced.

The highly thermally conductive silicone rubber member obtained from the silicone rubber composition of the present invention is used in image forming devices that utilize electrophotography, and since good rubber elasticity and good compression set are particularly required, it is desirable to adjust the amount of thermally conductive powder to optimize the above characteristics.

（式中、Ｒ¹はメチル基またはビニル基であり、ｐは３～３０である。）
ｐは３～３０であり、好ましくは、ｐは４～２０であり、より好ましくは、ｐは４～１０である。上記範囲内である構造によって、（Ｃ）成分と、（Ｄ）成分と、（Ｅ）成分とが混合され、（Ｄ）成分が（Ｃ）成分に悪影響を及ぼす状態でも（Ｃ）成分が失活することなく経時での保存安定性を得ることができる。具体例として、下記のものが挙げられる。 [Component (E)]
Component (E) functions as a protective agent for the platinum catalyst of component (C) and is different from component (A). Component (E) is one or more types selected from the following alkenyl group-containing polysiloxanes:
(E-1) An alkenyl-group-containing cyclic organopolysiloxane in which all silicon atoms have one or more alkenyl groups. (E-2) An alkenyl-group-containing linear organopolysiloxane in which the content of alkenyl groups bonded to silicon atoms is 1.1 x ^10-3 to 1.0 x ^10-1 mol/g. The aforementioned component (E) is characterized by its good storage stability and does not act as a catalyst poison when added to the same composition.
Reaction inhibitors generally used in addition-curing organopolysiloxane compositions are intended to suppress the catalytic activity of the addition reaction catalyst, thereby preventing the hydrosilylation reaction from proceeding, thereby improving storage stability.
On the other hand, the protective agent, which is the component (E) of the present invention, is intended to protect the (C) addition reaction catalyst from the cure retardation action of the component (D), and to prevent the cure characteristics of the silicone rubber composition of the present invention from slowing down over time. Specifically, it is presumed that the (E) component prevents the (D) component from absorbing the (C) component. In addition, this cure retardation suppression effect was discovered for the first time by the present inventors. Since the metal silicon powder of the (D) component has a low Mohs hardness, when other thermally conductive powders are used in combination, the thermally conductive powders are often high in Mohs hardness. When a thermally conductive powder with a higher Mohs hardness than the metal silicon powder is used in combination with metal silicon, the metal silicon surface is scraped and broken. Therefore, a new metal silicon surface appears, which may easily absorb the addition cure catalyst. Even in such a case, the protective agent, which is the component (E) of the present invention, protects the (C) addition reaction catalyst from the cure retardation action of the component (D).
The alkenyl-containing cyclic organopolysiloxane of component (E-1) is a cyclic organopolysiloxane having one or more alkenyl groups on all silicon atoms, and is particularly preferably represented by the following general formula (1):

(In the formula, R ¹ is a methyl group or a vinyl group, and p is an integer from 3 to 30.)
p is 3 to 30, preferably 4 to 20, and more preferably 4 to 10. With a structure within the above range, even when components (C), (D), and (E) are mixed and component (D) has an adverse effect on component (C), component (C) is not inactivated and storage stability over time can be obtained. Specific examples include the following.

The alkenyl-containing linear organopolysiloxane of component (E-2) is an alkenyl-containing linear organopolysiloxane in which the content of alkenyl groups bonded to silicon atoms is 1.1× ^10-3 to 1.0× ^10-1 mol/g, based on all monovalent hydrocarbon groups bonded to silicon atoms, and is, for example, represented by the average composition formula (a) below, with a structure represented by general formula (2) below being particularly preferred.
R _c Vi _d SiO _(4-cd)/2 (a)
(In the formula, R is independently a monovalent hydrocarbon group having 1 to 10 carbon atoms, preferably 1 to 8 carbon atoms, not containing an aromatic group, and Vi is a vinyl group. In addition, c is 0.7 to 2.1, d is 0.001 to 1.0, and c+d is a positive number satisfying 0.8 to 3.0.)

（式中、Ｒは独立して炭素数１～１０の１価炭化水素基であり、ｑは０以上、ｒは２以上、ｑ＋ｒが２～２００である。）

(In the formula, R is independently a monovalent hydrocarbon group having 1 to 10 carbon atoms, q is 0 or more, r is 2 or more, and q+r is 2 to 200.)

Examples of monovalent hydrocarbon groups having 1 to 10 carbon atoms represented by R include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyl, and decyl, and alkenyl groups such as vinyl, allyl, propenyl, isopropenyl, butenyl, hexenyl, cyclohexenyl, and octenyl. In addition, groups in which some or all of the hydrogen atoms have been replaced with halogen atoms such as fluorine or chlorine, such as chloromethyl, chloropropyl, and trifluoropropyl, may also be used.

In the case of the general formula (2) above, in the formula, q is 0 or more, r is 2 or more, and q+r is 2 to 200, preferably q is 0 or more, r is 4 or more, and q+r is 4 to 100, and more preferably q is 0 or more, r is 4 or more, and q+r is 4 to 50. The content of alkenyl groups bonded to silicon atoms is 1.1×10 ^-3 to 1.0×10 ^-1 mol/g, and preferably 2.0×10 ^-3 to 1.0×10 ^-1 mol/g, based on the total number of monovalent hydrocarbon groups bonded to silicon atoms.
The structure within the above range allows the components (C), (D), and (E) to be mixed together, and even in a state in which the component (D) adversely affects the component (C), the component (C) is not inactivated and storage stability over time can be obtained. Specific examples include the following.

The amount of the (E) component is 0.1 to 500 mol/mol, preferably 0.1 to 300 mol/mol, and more preferably 0.1 to 200 mol/mol, of the platinum group metal catalyst (C) component (E)/platinum group metal atom (Pt, Pd, Rh, etc.). If the amount is 0.1 to 500 mol/mol, the (C) component is not deactivated and storage stability over time can be obtained even when the (C), (D) and (E) components are mixed and the (D) component has a negative effect on the (C) component. If the amount is less than 1 mol/mol, the (C) component is deactivated and storage stability over time cannot be obtained. If the amount is more than 500 mol/mol, the silicone rubber cured product becomes brittle. The (E) component may be used alone or in combination of two or more types.

[Reinforcing silica fine powder]
The silicone rubber composition of the present invention may optionally contain inorganic fillers other than the above-mentioned components (A) through (E), and a reinforcing silica fine powder may also be added.

In order to obtain a silicone rubber composition having excellent mechanical strength, the reinforcing silica fine powder preferably has a specific surface area measured by the BET adsorption method of 10 ^m2 /g or more, particularly 50 to 400 ^m2 /g. Examples of reinforcing silica fine powder include fumed silica (dry silica) and precipitated silica (wet silica), with fumed silica (dry silica) being preferred.

Examples of commercially available reinforcing silica powders that can be used include Aerosil 130, 200, 300 (trade names manufactured by Nippon Aerosil Co., Ltd.), Cab-O-sil MS-5, MS-7, HS-5, HS-7 (trade names manufactured by Cabot Corporation), Santocel FRC, CS (trade names manufactured by Monsanto Co., Ltd.), and Nipsil VN-3 (trade name manufactured by Nippon Silica Kogyo Co., Ltd.). The surfaces of these silicas may also be hydrophobized with organopolysiloxane, organopolysilazane, chlorosilane, alkoxysilane, etc. These silicas may be used alone or in combination of two or more kinds.

The amount of the reinforcing silica fine powder added to the silicone rubber composition is preferably small in order to improve compression set and further suppress the increase in volume resistivity over time.

To obtain better volume resistivity and compression set while incorporating the reinforcing silica fine powder, it is preferable to incorporate 0 to 5 parts by mass, and more preferably 0 to 3 parts by mass, per 100 parts by mass of the organopolysiloxane of component (A) in the silicone rubber composition. The lower limit of the amount incorporated can be 0.1 parts by mass or more.

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

These inorganic fillers may be surface-treated with a silane coupling agent or a partial hydrolyzate thereof, an alkylalkoxysilane or a partial hydrolyzate thereof, an organic silazanes, a titanate coupling agent, an organopolysiloxane oil, an organopolysiloxane containing a hydrolyzable functional group, or the like. These treatments may be performed by pretreating the inorganic filler itself, or may be performed when it is mixed with the oil.

The amount of the compounded resin is preferably about 0 to 400 parts by mass per 100 parts by mass of the organopolysiloxane (A) in the silicone rubber composition.

If necessary, it is optional to add hydrosilylation reaction inhibitors such as nitrogen-containing compounds such as amine compounds, acetylene compounds such as acetylene alcohols having an ethynyl group, organic phosphorus compounds such as phosphines, and organic sulfur compounds such as sulfides, various additives, flame retardants, heat resistance agents, etc.

[Preparation of addition-curable liquid silicone rubber composition and molding thereof]
The addition-curable liquid silicone rubber composition of the present invention can be prepared by uniformly mixing the above components (A) through (E), as well as other components (reinforcing silica fine powder and other inorganic fillers) as necessary, using a conventional mixer/stirrer or kneader such as a kneader or planetary mixer.

The silicone rubber composition of the present invention can be molded by cast molding, injection molding, coating, etc., and the curing conditions preferably include press curing at a temperature of 100 to 300°C for 10 seconds to 1 hour. In addition, after molding, a post cure (secondary cure) may be performed in an oven at 120 to 250°C for about 30 minutes to 70 hours in order to reduce low molecular weight siloxane components that cause a decrease in compression set.

Electrophotographic Imaging Members
The present invention also provides an electrophotographic image forming member having an elastic layer made of a cured product of the above-mentioned addition-curable liquid silicone rubber composition. Such an electrophotographic image forming member is preferably a member selected from a fixing roll and a fixing belt.

For example, it may be used as a single-layer roll in which the outer periphery of a core metal 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 substrate 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, or it may be used as a roll or belt in which a resin such as polyimide resin, urethane resin, or fluorine-based resin is further coated on the silicone rubber layer. In this case, the silicone rubber layer may be a single layer coating on the surface (outer periphery) or a multi-layer coating of two or more layers. Among these, rolls and belts coated with urethane resin, fluorine-based resin, etc. on the outermost surface are preferred from the standpoint of durability such as abrasion resistance.

Here, the material of the core or substrate is preferably selected from iron, stainless steel, aluminum, polyamide/polyimide resin, and PEEK (polyether ether ketone).

As the fluorine-based resin, a fluorine-based resin coating material or a fluorine-based resin tube can be used. Examples of the fluorine-based resin coating material include polytetrafluoroethylene resin (PTFE) latex and Daiel latex (fluorine-based latex, manufactured by Daikin Industries, Ltd.). As the fluorine-based resin tube, commercially available products can be used, such as polytetrafluoroethylene resin (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin (PFA), fluorinated ethylene-polypropylene copolymer resin (FEP), polyvinylidene fluoride resin (PVDF), and polyvinyl fluoride resin. Of these, PFA and PTFE latex are particularly preferred.

The present invention will be specifically explained below with examples and comparative examples, but the present invention is not limited to the following examples. Note that the viscosity described below is the value at 25°C measured using a rotational viscometer as described in JIS K 7117-1:1999.

Example 1
83 parts by mass of dimethylpolysiloxane (A1) having both molecular chain terminals blocked with vinyldimethylsiloxy groups, an alkenyl group amount of 1.5×10 ^-4 mol/g, and a viscosity of 500 mPa·s, 20 parts by mass of dimethylpolysiloxane (A2) having both molecular chain terminals blocked with trimethylsiloxy groups, an alkenyl group amount of 1.0×10 ^-4 mol/g, and a viscosity of 15,000 mPa·s and having vinyl groups on the side chains, 0.16 parts by mass of 1-ethynylcyclohexanol, 0.3 parts by mass of a dimethylpolysiloxane solution (C) containing chloroplatinic acid/1,3-divinyltetramethyldisiloxane complex with a platinum atom content of 1% by mass, and a BET specific surface area of 110 ^m2. Composition A was prepared by blending in this order 1 part by mass of hydrophobized fumed silica (R-972 manufactured by Nippon Aerosil Co., Ltd.) having a molecular weight of 1000 to 15000 kcal/g, 200 parts by mass of pulverized metallic silicon powder (D1) (average primary particle size 5 μm, thermal conductivity 168 W/m·K), 60 parts by mass of pulverized silicon carbide powder (D2) (average primary particle size 9 μm, thermal conductivity 270 W/m·K), 0.01 part by mass (2 moles per Pt atom) of 1,3,5,7-tetravinyltetramethylcyclotetrasiloxane (E1), and 4.02 parts by mass of dimethylsiloxane-methylhydrogensiloxane copolymer (B) (silicon-bonded hydrogen atom content=3.2× ¹⁰ mol/g) having both molecular chain terminals blocked with trimethylsiloxy groups and having silicon-bonded hydrogen atoms in the side chains, and mixing them for 30 minutes with a planetary mixer at room temperature (25° C.). Next, the prepared composition A was press-cured at 120° C. for 10 minutes to form a silicone rubber sheet, which was then post-cured at 200° C. for 4 hours, and the hardness was measured in accordance with JIS K 6249: 2003. The results are shown in Table 2.

Next, to confirm the storage stability, compositions A1 and A2 were prepared as follows. The compositions A1 and A2 were prepared with separate catalysts and crosslinking agents, with the (E) and (C) components being the same, in the amounts listed below so that when mixed in a 1:1 mass ratio, they would become composition A.

[Preparation of Composition A1]
44 parts by mass of dimethylpolysiloxane (A1) in which both molecular chain terminals are blocked with vinyldimethylsiloxy groups, 10 parts by mass of dimethylpolysiloxane (A2) in which both molecular chain terminals are blocked with trimethylsiloxy groups and which has vinyl groups on the side chains, 0.3 parts by mass of dimethylpolysiloxane solution (C) containing 1% by mass of chloroplatinic acid/1,3-divinyltetramethyldisiloxane complex as platinum atom content, 100 parts by mass of pulverized metallic silicon powder (D1), 30 parts by mass of pulverized silicon carbide powder (D2), 0.01 parts by mass of 1,3,5,7-tetravinyltetramethylcyclotetrasiloxane (E1) (2 moles per mole of Pt atom, BET specific surface area of 110 ^m2 0.5 parts by mass of hydrophobized fumed silica (R-972 manufactured by Nippon Aerosil Co., Ltd.) having a molecular weight of 1/g was mixed with a planetary mixer at room temperature (25° C.) for 30 minutes to prepare composition A1.

[Preparation of Composition A2]
Next, 39 parts by mass of dimethylpolysiloxane (A1) whose molecular chain terminals are blocked with vinyldimethylsiloxy groups, 10 parts by mass of dimethylpolysiloxane (A2) whose molecular chain terminals are blocked with trimethylsiloxy groups and have vinyl groups on the side chains, 4.02 parts by mass of dimethylsiloxane-methylhydrogensiloxane copolymer (B) whose molecular chain terminals are blocked with trimethylsiloxy groups and have silicon-bonded hydrogen atoms on the side chains, 100 parts by mass of pulverized metallic silicon powder (D1), 30 parts by mass of pulverized silicon carbide powder (D2), 0.16 parts by mass of 1-ethynylcyclohexanol, and 0.5 parts by mass of hydrophobized fumed silica (R-972, manufactured by Nippon Aerosil Co., Ltd.) having a BET specific surface area of 110 ^m2 /g were mixed for 30 minutes at room temperature (25°C) in a planetary mixer to prepare composition A2.

[Evaluation of storage stability]
Next, composition A1 and composition A2 were each sealed and stored at 25° C. for 12 months or at 80° C. for 3 days. Composition A was prepared by mixing composition A1 and composition A2 at a mass ratio of 1:1 at the initial preparation stage (3 days at 25° C.) or after storage, and then the curability T10 and T90 at 130° C. were measured using a rheometer MDR2000 (manufactured by Alpha Technologies), and the results were shown in Table 1. Curability T10 and T90 refer to the time required to reach 10% of the maximum torque value measured by the rheometer, T10, and the time required to reach 90% of the maximum torque value, T90, when the maximum torque value measured by the rheometer is taken as 100.

Example 2
Composition B was prepared according to the same recipe as in Example 1, except that the 4.02 parts by mass of dimethylsiloxane-methylhydrogensiloxane copolymer (B) was replaced by 4.3 parts by mass, and the 0.01 parts by mass of 1,3,5,7-tetravinyltetramethylcyclotetrasiloxane (E1) was replaced by 0.1 parts by mass (19 moles relative to Pt atoms), and evaluation was performed in the same manner as in Example 1. The storage stability was confirmed only under the condition of 80°C for 3 days, and the results are shown in Table 2.

Example 3
Composition C was prepared according to the same recipe as in Example 1, except that the 4.02 parts by mass of the dimethylsiloxane-methylhydrogensiloxane copolymer (B) was replaced by 4.14 parts by mass, and the 0.01 parts by mass of the 1,3,5,7-tetravinyltetramethylcyclotetrasiloxane (E1) was replaced by 0.05 parts by mass (9 moles relative to the Pt atom), and evaluation was performed in the same manner as in Example 1. The storage stability was confirmed only under the condition of 80°C for 3 days, and the results are shown in Table 2.

Example 4
Composition D was prepared according to the same recipe as in Example 1, except that the 4.02 parts by mass of the dimethylsiloxane-methylhydrogensiloxane copolymer (B) was replaced by 3.99 parts by mass, and the 0.01 parts by mass of the 1,3,5,7-tetravinyltetramethylcyclotetrasiloxane (E1) was replaced by 0.005 parts by mass (1 mole per Pt atom), and evaluation was performed in the same manner as in Example 1. The storage stability was confirmed only under the condition of 80°C for 3 days, and the results are shown in Table 2.

で示されるアルケニル基含有鎖状オルガノポリシロキサン（Ｅ２）０．３質量部（Ｐｔ原子に対し、１３モル）に置き換えたこと以外は全て同一の処方で組成物Ｅを調製し、実施例１と同様の評価を行った。保存安定性については８０℃３日の条件のみを確認した結果を表２に示す。 Example 5
In Example 1, 4.02 parts by mass of dimethylsiloxane-methylhydrogensiloxane copolymer (B) was mixed with 4.14 parts by mass of 1,3,5,7-tetravinyltetramethylcyclotetrasiloxane (E1) and 0.01 parts by mass of a compound represented by the following general formula (I):

Composition E was prepared using the same formulation, except that 0.3 parts by mass (13 moles per Pt atom) of an alkenyl group-containing linear organopolysiloxane (E2) represented by the following formula was substituted, and evaluations were carried out in the same manner as in Example 1. The storage stability was confirmed only under the condition of 80° C. for 3 days, and the results are shown in Table 2.

Example 6
Composition F was prepared according to the same recipe as in Example 1, except that the 4.02 parts by mass of the dimethylsiloxane-methylhydrogensiloxane copolymer (B) was replaced by 3.99 parts by mass, and 0.01 parts by mass of the 1,3,5,7-tetravinyltetramethylcyclotetrasiloxane (E1) was replaced by 0.03 parts by mass (1 mole per Pt atom) of the alkenyl-containing linear organopolysiloxane (E2) represented by the above general formula (I), and evaluated in the same manner as in Example 1. The storage stability was confirmed only under the condition of 80°C for 3 days, and the results are shown in Table 2.

Example 7
In Example 1, 83 parts by mass of dimethylpolysiloxane (A1) whose molecular chain ends are blocked with vinyldimethylsiloxy groups was replaced with 62 parts by mass, 20 parts by mass of dimethylpolysiloxane (A2) whose molecular chain ends are blocked with trimethylsiloxy groups and have vinyl groups on the side chains was replaced with 38 parts by mass, 0.16 parts by mass of 1-ethynylcyclohexanol was replaced with 0.17 parts by mass, and a BET specific surface area of 110 ^m2 was replaced with 0.2 parts by mass. /g hydrophobized fumed silica (R-972 manufactured by Nippon Aerosil Co., Ltd.) 1 part by mass was not added, 200 parts by mass of crushed metal silicon powder (D1) (average primary particle size 5 μm) was replaced with 105 parts by mass, 60 parts by mass of crushed silicon carbide powder (D2) (average primary particle size 9 μm) was not added, 0.01 parts by mass of 1,3,5,7-tetravinyltetramethylcyclotetrasiloxane (E1) was replaced with 0.005 parts by mass (1 mole per Pt atom), and 4.02 parts by mass of dimethylsiloxane-methylhydrogensiloxane copolymer (B) having silicon atom-bonded hydrogen atoms in the side chains blocked with trimethylsiloxy groups was replaced with 3.25 parts by mass. Composition G was prepared with the same formulation as in Example 1, and the same evaluation was performed. The results of confirming only the condition of 80 ° C. for 3 days for storage stability are shown in Table 2.

Example 8
In Example 1, 83 parts by mass of dimethylpolysiloxane (A1) whose molecular chain ends are blocked with vinyldimethylsiloxy groups was replaced with 62 parts by mass, 20 parts by mass of dimethylpolysiloxane (A2) whose molecular chain ends are blocked with trimethylsiloxy groups and have vinyl groups on the side chains was replaced with 38 parts by mass, 0.16 parts by mass of 1-ethynylcyclohexanol was replaced with 0.17 parts by mass, and a BET specific surface area of 110 ^m2 was replaced with 0.2 parts by mass. Composition H was prepared according to the same recipe as in Example 1, except that 1 part by mass of hydrophobized fumed silica (R-972 manufactured by Nippon Aerosil Co., Ltd.) having a molecular weight of 1000 to 10000 g/g was not added, 200 parts by mass of pulverized metallic silicon powder (D1) (average primary particle size 5 μm) was not added to 105 parts by mass, and 60 parts by mass of pulverized silicon carbide powder (D2) (average primary particle size 9 μm) was not added to 100 parts by mass, 0.01 parts by mass of 1,3,5,7-tetravinyltetramethylcyclotetrasiloxane (E1) was replaced by 0.03 parts by mass (1 mole per Pt atom) of alkenyl group-containing linear organopolysiloxane (E2) represented by the above general formula (I), and 4.02 parts by mass of dimethylsiloxane-methylhydrogensiloxane copolymer (B) having silicon atom-bonded hydrogen atoms in its side chains, was replaced by 3.25 parts by mass, and evaluation was performed in the same manner as in Example 1. The storage stability was confirmed only under the condition of 80° C. for 3 days, and the results are shown in Table 2.

Comparative Example 1
83 parts by mass of dimethylpolysiloxane (A1) whose molecular chain ends are blocked with vinyldimethylsiloxy groups, 20 parts by mass of dimethylpolysiloxane (A2) whose molecular chain ends are blocked with trimethylsiloxy groups and which has vinyl groups on its side chains, 0.16 parts by mass of 1-ethynylcyclohexanol, 0.3 parts by mass of a dimethylpolysiloxane solution (C) containing chloroplatinic acid/1,3-divinyltetramethyldisiloxane complex with a platinum atom content of 1% by mass, and a BET specific surface area of 110 m2 ^. Composition I was prepared by mixing 1 part by mass of hydrophobically treated fumed silica (R-972 manufactured by Nippon Aerosil Co., Ltd.) having a molecular weight of 1.001 mg/g, 200 parts by mass of pulverized metallic silicon powder (D1), 60 parts by mass of pulverized silicon carbide powder (D2), and 3.99 parts by mass of a dimethylsiloxane-methylhydrogensiloxane copolymer having silicon-bonded hydrogen atoms in its side chains (B) in a planetary mixer at room temperature for 30 minutes, and evaluations were carried out in the same manner as in Example 1. The results are shown in Table 2.

Next, to confirm the storage stability, compositions I1 and I2 were prepared as follows. The catalyst and crosslinking agent were prepared separately and in the amounts listed below so that when they were mixed in a 1:1 mass ratio, the composition I would be obtained.

[Preparation of composition I1]
Composition I1 was prepared by blending 44 parts by mass of dimethylpolysiloxane (A1) whose molecular chain terminals are blocked with vinyldimethylsiloxy groups, 10 parts by mass of dimethylpolysiloxane (A2) whose molecular chain terminals are blocked with trimethylsiloxy groups and have vinyl groups on the side chains, 0.3 parts by mass of dimethylpolysiloxane solution (C) containing chloroplatinic acid/1,3-divinyltetramethyldisiloxane complex at 1 mass% platinum atom content, 100 parts by mass of pulverized metallic silicon powder (D1), 30 parts by mass of pulverized silicon carbide powder (D2), and 0.5 parts by mass of hydrophobized fumed silica (R-972, manufactured by Nippon Aerosil Co., Ltd.) having a BET specific surface area of 110 ^m2 /g in this order and mixing them for 30 minutes with a planetary mixer at room temperature.

[Preparation of Composition I2]
Next, 39 parts by mass of dimethylpolysiloxane (A1) whose molecular chain terminals are blocked with vinyldimethylsiloxy groups, 10 parts by mass of dimethylpolysiloxane (A2) whose molecular chain terminals are blocked with trimethylsiloxy groups and have vinyl groups on the side chains, 3.99 parts by mass of dimethylsiloxane-methylhydrogensiloxane copolymer (B) whose molecular chain terminals are blocked with trimethylsiloxy groups and have silicon-bonded hydrogen atoms on the side chains, 100 parts by mass of pulverized metallic silicon powder (D1), 30 parts by mass of pulverized silicon carbide powder (D2), 0.16 parts by mass of 1-ethynylcyclohexanol, and 0.5 parts by mass of hydrophobized fumed silica (R-972, manufactured by Nippon Aerosil Co., Ltd.) having a BET specific surface area of 110 ^m2 /g were mixed for 30 minutes at room temperature in a planetary mixer to prepare composition I2.

[Evaluation of storage stability]
Next, composition I1 and composition I2 were each sealed and stored at 80° C. for 3 days. Composition I1 and composition I2 were mixed in a 1:1 ratio at the initial stage of preparation (3 days at 25° C.) or after storage to prepare composition I, and the curability T10 and T90 at 130° C. were measured using a rheometer MDR2000 (manufactured by Alpha Technologies). The results are shown in Table 1.

Comparative Example 2
Composition J was prepared using the same recipe as in Comparative Example 1, except that 0.16 parts by mass of 1-ethynylcyclohexanol was replaced by 0.32 parts by mass, and 0.3 parts by mass of the dimethylpolysiloxane solution (C) containing chloroplatinic acid/1,3-divinyltetramethyldisiloxane complex at 1% by mass in terms of platinum atom content was replaced by 0.75 parts by mass, and evaluation was performed in the same manner as in Example 1. Regarding storage stability, the results of checking only the condition of 80°C for 3 days are shown in Table 2.

で示されるアルコキシ基含有シロキサン化合物８質量部、を添加したこと以外は全て同一の処方で組成物Ｋを調製し、実施例１と同様の評価を行った。保存安定性については８０℃３日の条件のみを確認した結果を表２に示す。 Comparative Example 3
In Comparative Example 1, the compound represented by the following general formula (II)

Composition K was prepared in the same manner as in Example 1, except that 8 parts by mass of an alkoxy group-containing siloxane compound represented by the following formula was added, and evaluated in the same manner as in Example 1. The storage stability was confirmed only under the condition of 80° C. for 3 days, and the results are shown in Table 2.

Comparative Example 4
Composition L was prepared according to the same recipe as in Comparative Example 1, except that 60 parts by mass of the pulverized silicon carbide powder (D2) was replaced with 75 parts by mass of pulverized alumina (D3) (average primary particle size 3 μm, thermal conductivity 36 W/m·K), and evaluated in the same manner as in Example 1. The storage stability was confirmed only under the condition of 80° C. for 3 days, and the results are shown in Table 2.

Comparative Example 5
Composition M was prepared according to the same recipe as in Comparative Example 1, except that 60 parts by mass of the pulverized silicon carbide powder (D2) was replaced with 75 parts by mass of spherical alumina (D4) (average primary particle size 3 μm, thermal conductivity 36 W/m·K), and evaluated in the same manner as in Example 1. The storage stability was confirmed only under the condition of 80° C. for 3 days, and the results are shown in Table 2.

Comparative Example 6
In Comparative Example 1, 83 parts by mass of dimethylpolysiloxane (A1) in which both molecular chain terminals are blocked with vinyldimethylsiloxy groups was replaced with 62 parts by mass, 20 parts by mass of dimethylpolysiloxane (A2) in which both molecular chain terminals are blocked with trimethylsiloxy groups and which has vinyl groups on the side chains was replaced with 38 parts by mass, 0.16 parts by mass of 1-ethynylcyclohexanol was replaced with 0.17 parts by mass, and a BET specific surface area of 110 ^m2 was replaced with 0.2 parts by mass. Composition N was prepared with the same formulation as in Example 1, except that 1 part by weight of hydrophobized fumed silica (R-972 manufactured by Nippon Aerosil Co., Ltd.) having a molecular weight of 1000000000/g was not added, 105 parts by weight of pulverized metal silicon powder (D1) was not added, and 60 parts by weight of pulverized silicon carbide powder (D2) was not added, and 3.99 parts by weight of dimethylsiloxane-methylhydrogensiloxane copolymer (B) having silicon atom-bonded hydrogen atoms in the side chain was replaced with 3.25 parts by weight. The results of the same evaluation as in Example 1 were carried out. Regarding storage stability, the results of checking only the condition of 80 ° C. for 3 days are shown in Table 2.

In Examples 1 to 8, a sufficient amount of component (E) was included, preventing the adverse effects of component (D) on component (C), resulting in good storage stability and good thermal conductivity, while not deteriorating curing properties after storage. In contrast, Comparative Examples 1 to 6, which did not include component (E), showed a noticeable delay in curing properties after storage.

Claims (5)

(A) 100 parts by mass of a liquid organopolysiloxane containing two or more alkenyl groups bonded to silicon atoms in each molecule, the content of alkenyl groups bonded to silicon atoms being 1.0×10 ⁻⁷ to 1.0×10 ⁻³ mol/g based on the total number of monovalent hydrocarbon groups bonded to silicon atoms,
(B) an organohydrogenpolysiloxane containing two or more hydrosilyl groups per molecule: the number of hydrosilyl groups contained in component (B) is 0.4 to 10 per alkenyl group bonded to a silicon atom contained in component (A);
(C) a platinum group metal catalyst as an addition reaction catalyst: an amount equivalent to 0.5 to 1,000 ppm in terms of platinum group metal based on the total mass of component (A);
(D) 10 to 1,000 parts by mass of a thermally conductive powder having an average primary particle size of 75 μm or less and a thermal conductivity of 10 W/m·K or more, and (E ) an alkenyl -containing linear organopolysiloxane having an alkenyl group-bonded silicon atom content of 1.1×10 ⁻³ to 1.0×10 ⁻¹ mol/g based on the total amount of monovalent hydrocarbon groups bonded to silicon atoms , the alkenyl group being represented by the following general formula (2):

(In the formula, R is independently a monovalent hydrocarbon group having 1 to 10 carbon atoms, q is 0 or more, r is 2 or more, and q+r is 2 to 200.)
an alkenyl-containing linear organopolysiloxane represented by the formula: The addition-curable liquid silicone rubber composition according to claim 1, in which component (D) is metallic silicon powder. The addition-curing liquid silicone rubber composition according to claim 1, wherein component (D) is a metal silicon powder and a thermally conductive powder having a Mohs hardness higher than that of the metal silicon powder. 4. An electrophotographic image forming member having an elastic layer made of a cured product of the addition-curable liquid silicone rubber composition according to claim 1. 5. The electrophotographic imaging member of claim 4 , wherein said electrophotographic imaging member is a member selected from a fuser roll and a fuser belt.