JP4973845B2 - Addition-curable liquid conductive silicone rubber composition for roller and developing roller - Google Patents

Description

  The present invention provides an addition curable liquid conductive silicone rubber composition for a roller that is easy to mold and has a volume resistivity of 10 kΩ · m or less and a cured product having a small compression set, and the composition. The present invention relates to the formed developing roller.

Conventionally, various conductive rubbers in which a conductive material is blended with a rubbery substance exhibiting electrical insulation properties are known. For example, carbon black or the like is blended as a conductive material, and the volume resistivity is 10 ⁻³ to 10 ^−1. Conductive rubber in the range of Ω · m is applied in a wide range of fields. On the other hand, silicone rubber, which is one of the electrically insulating rubbery substances, is excellent in heat resistance, cold resistance and weather resistance, and is widely used as an electrically insulating rubber, but it is conductive like other rubbery substances. It is also put into practical use as a conductive rubber by adding materials.

  In this case, as the conductive material added to the conductive silicone rubber, for example, various metal powders such as carbon black, graphite, silver, nickel and copper, various nonconductive powders and the surface of short fibers are treated with a metal such as silver. The mixture of carbon fiber, metal fiber, etc. reduces the volume resistivity of silicone rubber to 10 kΩ · m or less depending on the type and filling amount of the conductive material without impairing the unique properties of the rubber. Used frequently from getting.

  In particular, liquid addition-curing type silicone rubber is widely used as a roll material because of its low viscosity and excellent moldability even when blended with a conductivity imparting material such as carbon black, and because it can be cured in a short time. Has been.

  However, just adding conductive carbon black such as ketjen black and acetylene black to liquid silicone rubber rubber, the strength of silicone rubber is insufficient, and when it is incorporated into an electrophotographic apparatus as a roll, rubber breakdown occurs during durability. End up. In order to improve this, if the amount of carbon black is increased or a large amount of fumed silica is added, the compression set is deteriorated. Therefore, there is a method of blending inorganic powders such as quartz powder, diatomaceous earth, precipitated silica, and pearlite that have a relatively small effect on compression set. However, since these fillers have hydrophilic groups such as silanol groups on the surface, they have a property of easily adsorbing moisture in the air. Moisture adsorbed in this way volatilizes when the rubber is cured and remains as bubbles inside, or volatilizes when the silicone rubber is aftercured and the roll shrinks, which may affect the roll dimensions. is there. In particular, in the case of a developing roll, since toner is transferred in contact with a photoreceptor, a slight difference in roll diameter affects toner transferability, that is, an image.

  JP-A-2000-9129 and JP-A-2002-338808 (Patent Documents 1 and 2) exemplify the use of diatomaceous earth as a filler for roll materials. No mention is made of liquid addition curing using only millable silicone rubber. Japanese Patent Laid-Open No. 9-222770 (Patent Document 3) describes that diatomaceous earth may be added to the liquid silicone rubber, but no filler is described in the examples. On the other hand, Japanese Patent Application Laid-Open No. 2005-82617 (Patent Document 4) exemplifies addition-curing liquid conductive silicone blended with an inorganic filler defined by an average particle diameter and a bulk density. There is no mention of rate or weight loss on heating.

JP 2000-9129 A JP 2002-338808 A JP-A-9-222770 JP 2005-82617 A

  The present invention has been made in view of the above circumstances, and is formed using an addition-curing liquid conductive silicone rubber composition for a roller having a low viscosity, excellent moldability, and a small compression set of the cured product, and the composition. It is an object to provide a developed developing roller.

  As a result of intensive studies in order to achieve the above object, the present inventor blended a conductivity-imparting material such as conductive carbon black with the addition-curable liquid silicone rubber composition, and further added this conductive silicone rubber composition. By blending an inorganic filler with an average particle size of 50 μm or less and a heating loss at 200 ° C. for 4 hours of 1% or less with respect to the product, there is no generation of voids due to bubbles or the like during molding, and curing It was found that a roller having a small compression set of the product can be obtained, and the present invention has been made.

Accordingly, the present invention provides the following addition curable liquid conductive silicone rubber composition and developing roller for a roller.
[1] (A) Polystyrene conversion number average degree of polymerization by gel permeation chromatography (GPC) is 100 to 800, and alkenyl group content is 1.0 × 10 ⁻⁶ mol / g to 5.0 × 10 ^{−. 3} mol / g of an organopolysiloxane containing an alkenyl group bonded to at least two silicon atoms in one molecule: 100 parts by mass
(B) Organohydrogen containing at least two hydrogen atoms bonded to silicon atoms in one molecule, and the content of silicon-bonded hydrogen atoms (Si—H) is 0.001 to 0.017 mol / g Polysiloxane: 0.1 to 30 parts by mass,
(C) Inorganic filler selected from diatomaceous earth, pearlite, quartz powder and precipitated silica having an average particle size of 50 μm or less and a mass loss of 0.5 % or less when left in an oven at 200 ° C. for 4 hours: 3 to 100 parts by mass,
(D) Conductive carbon black: 5 to 50 parts by mass,
(E) addition reaction catalyst: and also contains a catalytic amount of a viscosity at 25 ° C. The following 10 Pa · s or more 200 Pa · s, the volume resistivity after curing Ri 0.1~290Ω · m der, developing roll An addition curable liquid conductive silicone rubber composition for a roller for use in a charging roll or a transfer roll .
[2] Tensile strength of the cured rubber and wherein the at least 2.0MPa (1) Symbol mounting rollers for addition curable liquid conductive silicone rubber composition.
[ 3 ] The addition-curable liquid conductive silicone rubber composition for rollers according to [1] or [2], further containing 5 parts by mass or less of fumed silica with respect to 100 parts by mass of component (A).
[ 4 ] A roll having a conductive elastic layer as a surface layer on the outer periphery of a conductive shaft or a roll having a surface layer made of an organic resin on the outer periphery of the elastic layer, wherein the elastic layer is [1] to [ 3 ] A developing roller for an electrophotographic image forming apparatus, which is obtained by curing the addition-curable liquid conductive silicone rubber composition according to any one of [ 3 ].

  The conductive silicone rubber composition of the present invention is not only good in moldability because it is a liquid material and excellent in fluidity, but also has few voids during molding, and after curing, the volume resistivity depends on the time and molding conditions. It is a stable material that does not change, has a small compression set, and is excellent in roll durability.

Hereinafter, the present invention will be described in more detail. The addition curable liquid conductive silicone rubber composition for rollers of the present invention is:
(A) an organopolysiloxane containing an alkenyl group bonded to at least two silicon atoms in one molecule;
(B) an organohydrogenpolysiloxane containing at least two hydrogen atoms bonded to silicon atoms in one molecule;
(C) an inorganic filler having an average particle size of 50 μm or less and a mass loss of 1% or less when left in an oven at 200 ° C. for 4 hours;
(D) conductivity imparting material,
(E) An addition reaction catalyst is contained.

  The organopolysiloxane containing an alkenyl group bonded to at least two silicon atoms in one molecule of the component (A) is the main agent (base polymer) of the present composition. As the alkenyl group-containing organopolysiloxane, What is shown by the following average compositional formula (1) can be used.

R ¹ _a SiO _{(4-a) / 2} (1)
In the formula, R ¹ is an unsubstituted or substituted monovalent hydrocarbon group having the same or different carbon number of 1 to 10, preferably 1 to 8, and a is 1.5 to 2.8, preferably 1.8. It is a positive number in the range of ˜2.5, more preferably 1.95 to 2.02.

Here, as the unsubstituted or substituted monovalent hydrocarbon group bonded to the silicon atom represented by R ¹ , a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, Pentyl group, neopentyl group, hexyl group, cyclohexyl group, octyl group, nonyl group, alkyl group such as decyl group, aryl group such as phenyl group, tolyl group, xylyl group, naphthyl group, benzyl group, phenylethyl group, phenylpropyl Aralkyl groups such as groups, vinyl groups, allyl groups, propenyl groups, isopropenyl groups, butenyl groups, hexenyl groups, cyclohexenyl groups, octenyl groups and other alkenyl groups, and some or all of the hydrogen atoms of these groups are fluorine. Substituted with a halogen atom such as bromine, chlorine, cyano group, etc., such as chloromethyl group, chloro Propyl group, bromoethyl group, trifluoropropyl group, but cyanoethyl group and the like, Preferably, at least 90% of all R ¹ is a methyl group. In addition, at least two of R ¹ must be alkenyl groups (preferably those having 2 to 8 carbon atoms, more preferably those having 2 to 6 carbon atoms, and particularly preferably vinyl groups). .

The alkenyl group content in the organopolysiloxane is 1.0 × 10 ⁻⁶ mol / g to 5.0 × 10 ⁻³ mol / g, particularly 5.0 × 10 ⁻⁶ mol / g to 1.0. It is preferable to set it as x10 < ^-3 > mol / g. If the amount of the alkenyl group is less than 1.0 × 10 ⁻⁶ mol / g, crosslinking may be insufficient and gelation may occur, and if it exceeds 5.0 × 10 ⁻³ mol / g, compression set Not only gets worse, but also may become brittle rubber.
This alkenyl group may be bonded to a silicon atom at the end of the molecular chain, may be bonded to a silicon atom in the middle of the molecular chain, or may be bonded to both.

  The structure of this organopolysiloxane basically has a linear structure in which the main chain is composed of repeating diorganosiloxane units, and both ends of the molecular chain are blocked with triorganosiloxy groups, but partially branched. The structure may be a ring structure or a ring structure. The degree of polymerization may be liquid at room temperature, but preferably, the number average degree of polymerization in terms of polystyrene by gel permeation chromatography (GPC) is usually 100 to 800, more preferably 150 to 600. If it is less than 100, rubber elasticity may be insufficient, and if it is more than 800, compression set may be deteriorated.

  The component (B) is an organohydrogenpolysiloxane having at least 2, preferably 3 or more hydrogen atoms (Si-H groups) bonded to silicon atoms in one molecule, and the Si-H groups in the molecule are The alkenyl group bonded to the silicon atom in the component (A) is cross-linked by a hydrosilyl addition reaction, and acts as a cross-linking agent for curing the composition.

This (B) component organohydrogenpolysiloxane has the following average composition formula (2)
R ² _b H _c SiO _{(4-bc) / 2} (2)
(In the formula, R ² is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 10 carbon atoms, b is 0.7 to 2.1, c is 0.001 to 1.0, and b + c. Is a positive number satisfying 0.8 to 3.0.)
And those having at least 2, preferably 3 to 100, more preferably 3 to 50 silicon-bonded hydrogen atoms in one molecule are suitably used.

Here, examples of the monovalent hydrocarbon group for R ² include the same groups as those exemplified for R ¹ , but those having no aliphatic unsaturated group are preferred. Further, b is preferably 0.8 to 2.0, c is preferably 0.01 to 1.0, b + c is preferably 1.0 to 2.5, and the molecular structure of the organohydrogenpolysiloxane is: The structure may be any of linear, cyclic, branched, and three-dimensional network. In this case, the number of silicon atoms in one molecule (or the degree of polymerization) is preferably 2 to 300, particularly about 4 to 150 at room temperature (25 ° C.), and the liquid one is preferably used. The ratio of the component to the total amount of alkenyl groups is 0.3 to 10.0, preferably 0.5 to 3.0.

  The silicon atom-bonded hydrogen atom (Si—H) content is preferably 0.001 to 0.017 mol / g, particularly 0.002 to 0.015 mol / g in the organohydrogenpolysiloxane. If the amount of silicon atom-bonded hydrogen atoms (Si—H) is too small, the crosslinking may be insufficient and gelation may occur, and if the amount is too large, the crosslinking density may become too high, resulting in brittle rubber. There is.

In addition, the hydrogen atom couple | bonded with a silicon atom may be located in any of the molecular chain terminal and the middle of a molecular chain, and may be located in both. Examples of the organohydrogenpolysiloxane of the component (C) include 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, tris (hydrogendimethylsiloxy) methylsilane, Tris (hydrogendimethylsiloxy) phenylsilane, methylhydrogencyclopolysiloxane, methylhydrogensiloxane / dimethylsiloxane cyclic copolymer, trimethylsiloxy group-blocked methylhydrogenpolysiloxane at both ends, trimethylsiloxy group-blocked dimethylsiloxane at both ends Methyl hydrogen siloxane copolymer, both ends dimethyl hydrogen siloxy group-capped dimethyl polysiloxane, both ends dimethyl hydrogen siloxy group capped dimethyl siloxane methyl high Rogen siloxane copolymer, trimethylsiloxy group-blocked methylhydrogensiloxane / diphenylsiloxane copolymer, trimethylsiloxy group-blocked methylhydrogensiloxane / diphenylsiloxane / dimethylsiloxane copolymer, both-end trimethylsiloxy group-blocked Methylhydrogensiloxane / methylphenylsiloxane / dimethylsiloxane copolymer, both ends dimethylhydrogensiloxy group-blocked methylhydrogensiloxane / dimethylsiloxane / diphenylsiloxane copolymer, both ends dimethylhydrogensiloxy group-blocked methylhydrogensiloxane / dimethylsiloxane-methylphenylsiloxane copolymer, (CH _{3) 2} HSiO _1/2 units and (CH _{3) 3} SiO _1/2 units and SiO _4/2 Position and a copolymer, (CH ₃₎ a copolymer consisting of ₂ HSiO _1/2 units and SiO _4/2 units, and (CH _{3) 2} HSiO _1/2 units and SiO _4/2 units (C ₆ H ₅ ) Copolymers consisting of ₃ SiO _1/2 units and in these exemplified compounds, some or all of the methyl groups are substituted with other alkyl groups such as ethyl groups, propyl groups, and aryl groups such as phenyl groups. And the like.

  The compounding amount of the organohydrogenpolysiloxane is 0.1 to 30 parts by mass, preferably 0.3 to 20 parts by mass with respect to 100 parts by mass of the component (A). If the amount is less than 0.1 parts by mass, the curing is insufficient and a gel is formed, and a rubber-like elastic cured product cannot be obtained. If the amount exceeds 30 parts by mass, the strength of the cured product and the compression set resistance are reduced. Is significantly reduced (compression set becomes large). For the same reason as described above, the molar ratio of the component (A) to the silicon-bonded hydrogen atom to the alkenyl group is preferably in the range of 0.3 to 5.0, more preferably 0.5 to 2.5. is there.

  Next, the inorganic filler of component (C) is an essential component for obtaining sufficient roll durability by imparting strength to the cured product with low compression set. The inorganic filler has an average particle size of 50 μm or less, preferably 1 to 30 μm, more preferably 2 to 20 μm. If the average particle size is smaller than 1 μm, the volume resistance may change with time, and if it is larger than 50 μm, irregularities are generated on the surface or the durability as a roll is lowered.

Furthermore, the essential property as these inorganic fillers is that the weight loss upon heating (mass loss by heating) when left in an oven at 200 ° C. for 4 hours is 1% by mass or less, preferably 0.8% by mass or less. Preferably it is 0.5 mass% or less. If the loss on heating exceeds 1% by mass, water and the like are generated during molding, and voids are generated in the molded product. In this heating loss, about 100 g of filler is put into a 1,000 cc beaker, put into an oven at 200 ° C., taken out after 4 hours, cooled in a desiccator for 1 hour, and the mass is measured. When the filler amount in the beaker is Ag, and the filler amount after heating and cooling (mass minus the beaker mass) is Bg,
Loss on heating (mass%) = [(A−B / A)] × 100
Calculated by

  These fillers may use what passed the drying process previously at the time of purchase, and may use what was heat-dried at 30-100 degreeC for about 30 minutes-24 hours before mixing | blending. When using a product that has undergone a drying process at the time of purchase, it is necessary to consider such as a packaging form with low moisture permeability so as not to absorb moisture during subsequent transportation and storage, or packaging with a moisture absorbent. Furthermore, even if the filler is insufficiently dried, after mixing with the component (A), take a step of removing volatile components such as mixing at 100 to 200 ° C. for 30 minutes to 8 hours under normal pressure or reduced pressure. Also good.

  Examples of such inorganic fillers include quartz powder, diatomaceous earth, pearlite, mica, calcium carbonate, glass flakes, glass beads, and precipitated silica. Among them, diatomaceous earth, pulverized perlite and foamed pearlite, and quartz powder are preferable. It is.

  As a compounding quantity of an inorganic filler, it is 3-100 mass parts with respect to 100 mass parts of (A) component, Preferably it is 5-50 mass parts. When the blending amount is less than 3 parts by mass, the roll durability is insufficient, and when it exceeds 100 parts by mass, not only the compression set is deteriorated, but blending becomes difficult.

  The mixing method of these inorganic fillers may be mixed with the components (A) and (B) using equipment such as a planetary mixer and a kneader at room temperature, or at a high temperature of 100 to 200 ° C. as described above. You may mix.

  These inorganic fillers include silane coupling agents or partial hydrolysates thereof, alkylalkoxysilanes or partial hydrolysates thereof, organic silazanes, titanate coupling agents, organopolysiloxane oils, and hydrolyzable functional groups. The surface may be treated with an organopolysiloxane or the like. In these treatments, the inorganic filler itself may be treated in advance, or may be performed at the time of mixing with oil. However, when these surface treatment agents remain, if the heating loss at 200 ° C. for 4 hours exceeds 1% by mass, the intended effect cannot be obtained.

  In addition to these inorganic fillers, inorganic powders such as fumed silica, precipitated silica, titanium oxide, alumina, aluminum hydroxide, etc., have low compression set, which is a feature of this material, and stable volume resistance over time. You may add in the range which does not impair a rate and roll durability.

As the conductive material of component (D), the following are preferably used.
As the conductive carbon black, those usually used in a conductive rubber composition can be used. For example, acetylene black, conductive furnace black (CF), super conductive furnace black (SCF), and extra conductive furnace black (XCF). Conductive channel black (CC), furnace black and channel black heat-treated at a high temperature of about 1500 ° C. Specifically, as acetylene black, electrified acetylene black (manufactured by Electrochemical Co., Ltd.), Shaunigan acetylene black (manufactured by Shaunigan Chemical Co., Ltd.), etc., and as conductive furnace black, Continex CF (manufactured by Continental Carbon) , Vulcan C (manufactured by Cabot Corp.), etc., Superconductive Furnace Black, Connexex SCF (Continental Carbon Corp.), Vulcan SC (Cabot Corp.), etc., Extra Conductive Furnace Black, Asahi HS-500 ( Asahi Carbon Co., Ltd.), Vulcan XC-72 (Cabot Co., Ltd.), etc., examples of the conductive channel black include Kourax L (Degussa Co., Ltd.), and Ketjen, a kind of furnace black. It is also possible to use a rack EC and Ketchen black EC-600JD (manufactured by Ketchen Black International Co., Ltd.). Of these, acetylene black and a mixture of acetylene black and the above carbon are particularly preferably used in the present invention.

The blending amount of the component (D) is such that the volume resistivity of the cured product of the silicone rubber composition is 10 kΩ · m or less, preferably 0.1Ω · m to 10 kΩ · m, particularly 1Ω · m to 5 kΩ · m. Amount.
Specifically, the addition amount of the conductive carbon black is preferably 0.5 to 50 parts by mass, particularly 1 to 20 parts by mass with respect to 100 parts by mass of the component (A) described above. If the addition amount is less than 0.5 parts by mass, desired conductivity may not be obtained, and if it exceeds 50 parts by mass, compression set may be deteriorated.

  (E) Component addition reaction catalysts include platinum black, platinous chloride, chloroplatinic acid, a reaction product of chloroplatinic acid and a monohydric alcohol, a complex of chloroplatinic acid and olefins, platinum bisacetoacetate, A palladium catalyst, a rhodium catalyst, etc. are mentioned. In addition, the compounding quantity of this addition reaction catalyst can be made into a catalyst quantity, and is about 0.5-1,000 ppm with respect to the total mass of (A) and (B) component as a platinum group metal normally, Especially about 1-500 ppm. It is.

  In the silicone rubber composition, a low molecular siloxane ester, a silanol, for example, a dispersant such as diphenylsilanediol, a heat resistance improver such as iron oxide, cerium oxide, and iron octylate, as long as the object of the present invention is not impaired. Reaction control agents such as ethynylcyclohexanol and tetravinyltetramethylcyclotetrasiloxane, various carbon functional silanes for improving adhesion and moldability, halogen compounds that impart flame retardancy, etc. may be added and mixed. .

  The composition of this material can be used at any viscosity as long as it is liquid at 25 ° C., but the viscosity at 25 ° C. is preferably 10 Pa · s or more and 200 Pa · s or less, more preferably 20 Pa · s. The pressure is 150 Pa · s or less. If it is less than 10 Pa · s, the strength of the cured product may be low and roll durability may be insufficient. If it is more than 200 Pa · s, pressure may be required for molding, and roll dimensions may not be stable.

  The cured product of this material preferably has a volume resistivity of 0.1 Ω · m to 10 kΩ · m, particularly 1 Ω · m to 5 kΩ · m. If it is less than 0.1 Ω · m, the blending amount of the conductivity-imparting agent may be too large to obtain roll durability. If it is greater than 10 kΩ · m, the volume resistance is not stable and a clear image is obtained. It may not be possible. Moreover, it is preferable that the tensile strength of hardened | cured material is 2.0 Mpa or more, especially 2.5 Mpa or more, and if it is less than 2.0 Mpa, the durability as a roll may become inadequate.

  The addition curable liquid conductive silicone rubber composition of this material is used for rolls in electrophotographic devices such as charging rolls, developing rolls, paper feed rolls, toner transport rolls, transfer rolls, especially developing rolls, charging rolls, transfer rolls. And particularly suitable for a developing roll. In addition, this material may be used as a single-layer roll in which a silicone rubber layer is coated as a surface layer on a core metal for these rolls, or a resin such as polyimide, urethane, or fluorine is further added to a silicone rubber layer. You may use as a roll coat | covered on. The thickness is preferably in the range of 0.5 to 50 mm, particularly 1 to 20 mm as the silicone rubber layer, and 1 to 300 μm, particularly 2 to 100 μm, as the surface layer.

  In the present invention, in particular, a developing roller for an electrophotographic image forming apparatus having a conductive elastic layer as a surface layer on the outer periphery of a conductive shaft, and a surface layer made of an organic resin on the outer periphery of the conductive elastic layer. It is preferable to use a material obtained by curing the addition-curable liquid conductive silicone rubber composition as the material for the elastic layer of the developing roller for an electrophotographic image forming apparatus.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not limited to the following Example. In the following examples, all parts are parts by mass.

[Example 1]
80 parts of dimethylpolysiloxane blocked at both ends with dimethylvinylsiloxy groups (degree of polymerization 250), 20 parts of dimethylpolysiloxane blocked at both ends with dimethylvinylsiloxy groups (degree of polymerization 800), average particle size 6 μm A certain diatomaceous earth (Oplite W-3005S, manufactured by Hokuaki Diatomaceous Earth Co., Ltd.) left in an oven at 150 ° C. for 8 hours (200 ° C. × 4 hours heat loss 0.1% by mass), 30 parts, acetylene black (DENKA BLACK HS (-100, manufactured by Denki Kagaku Kogyo Co., Ltd.) 5 parts were put into a planetary mixer and stirred for 30 minutes, and then passed once through three rolls. This was returned to the planetary mixer, and 2.7 parts of methylhydrogenpolysiloxane having a Si—H group at both ends and side chains (polymerization degree 17, Si—H amount 0.0060 mol / g) as a crosslinking agent was reacted. A composition obtained by adding 0.1 part of ethynylcyclohexanol, 0.1 part of platinum catalyst (Pt concentration 1% by mass) and 0.2 part of tetravinyltetramethylcyclotetrasiloxane as control agents and stirring for 15 minutes. Was a silicone rubber composition (1). It was 95 Pa.s as a result of measuring the viscosity at 25 degrees C of this silicone rubber composition (1) with the rotational viscometer (BH type | mold rotor 7 20 rpm).

  This silicone rubber composition (1) was press-cured at 150 ° C. for 5 minutes within 30 minutes after stirring, and further post-cured at 200 ° C. for 4 hours to obtain a silicone rubber sheet having a thickness of 2 mm and a thickness of 6 mm, a thickness of 12 A 5 mm cylinder was obtained. Table 1 shows the results of measuring hardness (durometer type A) and tensile strength with a sheet having a thickness of 2 mm, measuring volume resistivity with a sheet having a thickness of 6 mm, and compression set with a cylinder having a thickness of 12.5 mm. I wrote. The hardness, tensile strength and compression set were measured according to JIS K 6249, and the volume resistivity was measured between the electrodes A and B (2, 3) as shown in FIG. Contact was made and the resistance between the electrodes was measured. The measurement voltage was 100 V, measured at 12 points, and the average value was recorded. The measuring instrument 4 used was an ultrahigh resistance meter R8340 manufactured by Advanced Digital Corporation.

  Subsequently, primer No. 4 (manufactured by Shin-Etsu Chemical Co., Ltd.), an iron core shaft with a diameter of 6 mm and a length of 300 mm was placed in the center of the mold, and this silicone rubber composition (1) was injected around the core shaft at 140 ° C. for 30 After partial curing, it was removed from the mold and left in an oven at 200 ° C. for 4 hours to obtain a conductive roller elastic layer having a diameter of 14 mm and a rubber part length of 240 mm. The section of the rubber cut in the circumferential direction was visually observed from the periphery of the elastic layer and every 10 mm from the shaft end. As a result, no void was found.

[ Reference Example 1 ]
Both ends are blocked with trimethylsiloxy groups, 80 parts of dimethylpolysiloxane having a vinyl group in the side chain and a polymerization degree of 480 (vinyl group content 0.00008 mol / g), both ends blocked with dimethylvinylsiloxy groups 20 parts of dimethylpolysiloxane (degree of polymerization 250) and 30 parts of diatomaceous earth (Radiolite F, Showa Chemical Industry Co., Ltd., 200 ° C. × 4 hours heat loss 1.2% by mass) having an average particle size of 7 μm are room temperature. After stirring for 30 minutes, the temperature was raised to 180 ° C. and stirring was continued for 2 hours. After returning to room temperature, 4.5 parts of acetylene black (Denka Black HS-100, manufactured by Denki Kagaku Kogyo Co., Ltd.) was added, and the mixture was stirred for 30 minutes, and then passed once through three rolls. This was returned to the planetary mixer, and 1.5 parts of methylhydrogenpolysiloxane (polymerization degree 17, Si—H amount 0.0060 mol / g) having Si—H groups at both ends and side chains as a cross-linking agent, 0.3 parts of methylhydrogenpolysiloxane (polymerization degree 12, Si—H content 0.013 mol / g) having a terminal end blocked with a trimethylsiloxy group and all Si atoms having Si—H bonds, and ethynyl as a reaction control agent A silicone rubber composition (2) was prepared by adding 0.05 part of cyclohexanol and 0.1 part of platinum catalyst (Pt concentration 1% by mass) and continuing stirring for 15 minutes. It was 140 Pa.s as a result of measuring the viscosity at 25 degrees C of this silicone rubber composition (2) with the rotational viscometer (BH type | mold rotor 7 20 rpm).

  This silicone rubber composition (2) was press-cured at 150 ° C. for 5 minutes within 30 minutes after the completion of stirring, and further post-cured at 200 ° C. for 4 hours to obtain a silicone rubber sheet having a thickness of 2 mm and a thickness of 6 mm, a thickness of 12 A 5 mm cylinder was obtained. In the same manner as in Example 1, hardness (durometer type A), tensile strength, volume resistivity and compression set were measured, and the results are shown in Table 1.

  Subsequently, primer No. 4 (manufactured by Shin-Etsu Chemical Co., Ltd.), an iron core shaft having a diameter of 6 mm and a length of 300 mm was placed in the center of the mold, and this silicone rubber composition (2) was injected around the core shaft, and the temperature was increased at 140 ° C. After partial curing, it was removed from the mold and left in an oven at 200 ° C. for 4 hours to obtain a conductive roller elastic layer having a diameter of 14 mm and a rubber part length of 240 mm. The section of the rubber cut in the circumferential direction was visually observed from the periphery of the elastic layer and every 10 mm from the shaft end. As a result, no void was found.

[Example 2 ]
50 parts of dimethylpolysiloxane (vinyl group content 0.00012 mol / g) having both ends capped with dimethylvinylsiloxy groups and having vinyl groups in the side chains and a polymerization degree of 550, both ends being dimethylvinylsiloxy groups 50 parts of blocked dimethylpolysiloxane (polymerization degree 250), 30 parts of dimethylpolysiloxane (polymerization degree 100) blocked at both ends with trimethylsiloxy groups, and a hydrophobized fume having a specific surface area of 110 m ² / g 2 parts of dosilica (R-972 manufactured by Nippon Aerosil Co., Ltd.) and pearlite (LocaHelp 4209, manufactured by Mitsubishi Metal Industries, Ltd.) having an average particle size of 17 μm are left in an oven at 250 ° C. for 2 hours (200 ° C. × 4 hours) Loss of heat of 0.05% by mass), acetylene black (Denka Black HS-100, Electrochemical Industry) 5.5 parts) was put into a planetary mixer, stirred for 30 minutes, and then passed once through three rolls. This is returned to the planetary mixer, and 2.6 parts of methylhydrogenpolysiloxane having a Si—H group at both ends and side chains (polymerization degree 17, Si—H amount 0.0060 mol / g) as a crosslinking agent is reacted. As a control agent, 0.1 part of ethynylcyclohexanol and 0.1 part of platinum catalyst (Pt concentration: 1% by mass) were added, and a composition obtained by continuing stirring for 15 minutes was designated as a silicone rubber composition (3). It was 66 Pa.s as a result of measuring the viscosity at 25 degrees C of this silicone rubber composition (3) with the rotational viscometer (BH type | mold rotor 7 20 rpm).

  This silicone rubber composition (3) was press-cured at 150 ° C. for 5 minutes within 30 minutes after completion of stirring, and further post-cured at 200 ° C. for 4 hours to obtain a silicone rubber sheet having a thickness of 2 mm and a thickness of 6 mm, a thickness of 12 A 5 mm cylinder was obtained. In the same manner as in Example 1, hardness (durometer type A), tensile strength, volume resistivity and compression set were measured, and the results are shown in Table 1.

  Subsequently, primer No. An iron core shaft having a diameter of 6 mm and a length of 300 mm coated with 4 (manufactured by Shin-Etsu Chemical Co., Ltd.) is placed in the center of the mold, and this silicone rubber composition (3) is injected around the core shaft, at 30 ° C. After partial curing, it was removed from the mold and left in an oven at 200 ° C. for 4 hours to obtain a conductive roller elastic layer having a diameter of 14 mm and a rubber part length of 240 mm. The section of the rubber cut in the circumferential direction was visually observed from the periphery of the elastic layer and every 10 mm from the shaft end. As a result, no void was found.

[Comparative Example 1]
80 parts of dimethylpolysiloxane blocked at both ends with dimethylvinylsiloxy groups (degree of polymerization 250), 20 parts of dimethylpolysiloxane blocked at both ends with dimethylvinylsiloxy groups (degree of polymerization 800), average particle size 6 μm 30 parts of a certain diatomaceous earth (Oplite W-3005S, loss of heating at 200 ° C. × 4 hours, 1.2% by mass) and 5 parts of acetylene black (Denka Black HS-100, manufactured by Denki Kagaku Kogyo Co., Ltd.) are placed in a planetary mixer. After stirring for a minute, the mixture was passed once through three rolls. This was returned to the planetary mixer, and 2.1 parts of methyl hydrogen polysiloxane (polymerization degree 17, Si—H amount 0.0060 mol / g) having Si—H groups at both ends and side chains as a crosslinking agent was reacted. A composition obtained by adding 0.1 part of ethynylcyclohexanol, 0.1 part of platinum catalyst (Pt concentration 1% by mass) and 0.2 part of tetravinyltetramethylcyclotetrasiloxane as control agents and stirring for 15 minutes. Was made into the silicone rubber composition (4). It was 93 Pa.s as a result of measuring the viscosity at 25 degrees C of this silicone rubber composition (4) with the rotational viscometer (BH type | mold rotor 7 20 rpm).

  This silicone rubber composition (4) was press-cured at 150 ° C. for 5 minutes within 30 minutes after completion of stirring, and further post-cured at 200 ° C. for 4 hours to obtain a silicone rubber sheet having a thickness of 2 mm and a thickness of 6 mm, a thickness of 12 A 5 mm cylinder was obtained. In the same manner as in Example 1, hardness (durometer type A), tensile strength, volume resistivity and compression set were measured, and the results are shown in Table 1.

  Subsequently, primer No. 4 (manufactured by Shin-Etsu Chemical Co., Ltd.), an iron core shaft with a diameter of 6 mm and a length of 300 mm was placed in the center of the mold, and this silicone rubber composition (4) was injected around the core shaft, and the temperature was increased at 140 ° C. After partial curing, it was removed from the mold and left in an oven at 200 ° C. for 4 hours to obtain a conductive roller elastic layer having a diameter of 14 mm and a rubber part length of 240 mm. The section of the rubber cut in the circumferential direction was visually observed from the periphery of the elastic layer and every 10 mm from the shaft end. As a result, a total of eight voids having a diameter of about 0.5 to 1 mm were confirmed on the surface and inside.

[Comparative Example 2]
Both ends are blocked with trimethylsiloxy groups, 80 parts of dimethylpolysiloxane having a vinyl group in the side chain and a polymerization degree of 480 (vinyl group content 0.00008 mol / g), both ends blocked with dimethylvinylsiloxy groups 20 parts of dimethylpolysiloxane (degree of polymerization 250) and 30 parts of diatomaceous earth (Radiolite F, 1.1% by mass at 200 ° C. × 4 hours) having an average particle size of 7 μm were stirred at room temperature for 30 minutes, and then acetylene After adding 4.5 parts of black (Denka Black HS-100, manufactured by Denki Kagaku Kogyo Co., Ltd.) and continuing stirring for 30 minutes, it was passed once through three rolls. This was returned to the planetary mixer, and 1.5 parts of methylhydrogenpolysiloxane (polymerization degree 17, Si—H amount 0.0060 mol / g) having Si—H groups at both ends and side chains as a cross-linking agent, 0.3 parts of methylhydrogenpolysiloxane (polymerization degree 12, Si—H content 0.013 mol / g) having a terminal end blocked with a trimethylsiloxy group and all Si atoms having Si—H bonds, and ethynyl as a reaction control agent A composition obtained by adding 0.05 part of cyclohexanol and 0.1 part of platinum catalyst (Pt concentration 1% by mass) and continuing stirring for 15 minutes was designated as a silicone rubber composition (5). It was 155 Pa.s as a result of measuring the viscosity at 25 degrees C of this silicone rubber composition (5) with the rotational viscometer (BH type | mold rotor 7 20 rpm).

  This silicone rubber composition (5) was press-cured at 150 ° C. for 5 minutes within 30 minutes after stirring, and further post-cured at 200 ° C. for 4 hours to obtain a silicone rubber sheet having a thickness of 2 mm and a thickness of 6 mm, a thickness of 12 A 5 mm cylinder was obtained. In the same manner as in Example 1, hardness (durometer type A), tensile strength, volume resistivity and compression set were measured, and the results are shown in Table 1.

  Subsequently, primer No. 4 (manufactured by Shin-Etsu Chemical Co., Ltd.), an iron core shaft having a diameter of 6 mm and a length of 300 mm was placed in the center of the mold, and the silicone rubber composition (5) was injected around the core shaft, and the temperature was increased at 140 ° C. After partial curing, it was removed from the mold and left in an oven at 200 ° C. for 4 hours to obtain a conductive roller elastic layer having a diameter of 14 mm and a rubber part length of 240 mm. The section of the rubber cut in the circumferential direction was visually observed from the periphery of the elastic layer and every 10 mm from the shaft end. As a result, a total of five voids having a diameter of 0.5 to 2 mm were confirmed on the surface and inside.

[Comparative Example 3]
50 parts of dimethylpolysiloxane (vinyl group content 0.00012 mol / g) having both ends capped with dimethylvinylsiloxy groups and having vinyl groups in the side chains and a polymerization degree of 550, both ends being dimethylvinylsiloxy groups 50 parts of blocked dimethylpolysiloxane (polymerization degree 250), 30 parts of dimethylpolysiloxane (polymerization degree 100) blocked at both ends with trimethylsiloxy groups, and a hydrophobized fume having a specific surface area of 110 m ² / g 2 parts of dosilica (R-972 manufactured by Nippon Aerosil Co., Ltd.), 20 parts of pearlite (LocaHelp 4209, loss of heat of 2.9% by mass at 200 ° C. for 4 hours) having an average particle diameter of 17 μm, acetylene black (DENKA BLACK HS-100) (Manufactured by Denki Kagaku Kogyo Co., Ltd.) 5.5 parts in a planetary mixer, and after stirring for 30 minutes, One pass through the roll. This is returned to the planetary mixer, and 2.6 parts of methylhydrogenpolysiloxane having a Si—H group at both ends and side chains (polymerization degree 17, Si—H amount 0.0060 mol / g) as a crosslinking agent is reacted. As a control agent, 0.1 part of ethynylcyclohexanol and 0.1 part of platinum catalyst (Pt concentration: 1% by mass) were added, and a composition obtained by continuing stirring for 15 minutes was designated as a silicone rubber composition (6). As a result of measuring the viscosity at 25 ° C. of this silicone rubber composition (6) with a rotational viscometer (BH type rotor No. 7 20 rpm), it was 69 Pa · s.

  This silicone rubber composition (6) was press-cured at 150 ° C. for 5 minutes within 30 minutes after the completion of stirring, and further post-cured at 200 ° C. for 4 hours to obtain a silicone rubber sheet having a thickness of 2 mm and a thickness of 6 mm, a thickness of 12 A 5 mm cylinder was obtained. In the same manner as in Example 1, hardness (durometer type A), tensile strength, volume resistivity and compression set were measured, and the results are shown in Table 1.

  Subsequently, primer No. 4 (manufactured by Shin-Etsu Chemical Co., Ltd.), an iron core shaft having a diameter of 6 mm and a length of 300 mm was installed in the center of the mold, and this silicone rubber composition (6) was injected around the core shaft, and was heated at 140 ° C. for 30 After partial curing, it was removed from the mold and left in an oven at 200 ° C. for 4 hours to obtain a conductive roller elastic layer having a diameter of 14 mm and a rubber part length of 240 mm. The section of the rubber cut in the circumferential direction was visually observed from the periphery of the elastic layer and every 10 mm from the shaft end. As a result, many (20 or more) voids having a diameter of 0.5 to 2 mm were confirmed on the surface and inside.

It is the schematic explaining the measuring method of the volume resistivity in the Example of this invention.

Explanation of symbols

1 Rubber sheet 2 Electrode A
3 Electrode B
4 Measuring equipment

Claims (4)

(A) The number average polymerization degree in terms of polystyrene by gel permeation chromatography (GPC) is 100 to 800, and the alkenyl group content is 1.0 × 10 ⁻⁶ mol / g to 5.0 × 10 ⁻³ mol /. g, an organopolysiloxane containing an alkenyl group bonded to at least two silicon atoms in one molecule: 100 parts by mass,
(B) Organohydrogen containing at least two hydrogen atoms bonded to silicon atoms in one molecule, and the content of silicon-bonded hydrogen atoms (Si—H) is 0.001 to 0.017 mol / g Polysiloxane: 0.1 to 30 parts by mass,
(C) Inorganic filler selected from diatomaceous earth, pearlite, quartz powder and precipitated silica having an average particle size of 50 μm or less and a mass loss of 0.5 % or less when left in an oven at 200 ° C. for 4 hours: 3 to 100 parts by mass,
(D) Conductive carbon black: 5 to 50 parts by mass,
(E) addition reaction catalyst: and also contains a catalytic amount of a viscosity at 25 ° C. The following 10 Pa · s or more 200 Pa · s, the volume resistivity after curing Ri 0.1~290Ω · m der, developing roll An addition curable liquid conductive silicone rubber composition for a roller for use in a charging roll or a transfer roll . Claim 1 Symbol placement roller for addition curable liquid conductive silicone rubber composition, wherein the tensile strength of the cured rubber is not less than 2.0 MPa. The addition-curable liquid conductive silicone rubber composition for rollers according to claim 1 or 2 , further comprising 5 parts by mass or less of fumed silica with respect to 100 parts by mass of component (A). A roll having a conductive elastic layer as a surface layer on the outer periphery of a conductive shaft, or a roll having a surface layer made of an organic resin on the outer periphery of the elastic layer, wherein the elastic layer is any one of claims 1 to 3 . A developing roller for an electrophotographic image forming apparatus, which is obtained by curing the addition-curable liquid conductive silicone rubber composition according to item 1.

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