JP2023060579A - Addition-curable liquid silicone composition - Google Patents

Abstract

To provide an addition-curable liquid silicone composition capable of producing a silicone rubber excellent in heat resistance at a high temperature of 200°C or higher, specifically as high as 300°C, as well as excellent in thermal conductivity, and in particular, to provide a silicone composition for an image formation apparatus, and a fixation roll and a belt using a cured product (that is, a silicone rubber) obtained by curing the composition.SOLUTION: An addition-curable silicone composition, being a liquid at 25°C, includes components: (A) 100 pts.mass of organopolysiloxane having two or more alkenyl groups bonded to a silicon atom in one molecule with an average degree of polymerization of less than 1,000; (B) organohydrogenpolysiloxane having two or more hydrogen atoms bonded to a silicon atom in one molecule, in an amount at which a ratio of the number of the silicon atom-bonded hydrogen atoms in the component (B) to the number of the silicon atom-bonded alkenyl group in the component (A) is 0.3 to 3; (C) 40 to 800 pts.mass of a heat-conductive inorganic filler with an average particle diameter of 1 to 50 μm; (D) a catalyst quantity of a hydrosilylation reaction catalyst; (E) 0.1 to 10 pts.mass of a yellow iron oxide; and (F) 0.1 to 10 pts.mass of at least one kind selected from a cerium oxide and a cerium hydroxide.SELECTED DRAWING: None

Description

The present invention relates to addition-curable liquid silicone compositions. More particularly, it relates to addition-curable liquid silicone compositions that provide thermally conductive silicone rubbers. In particular, it relates to an addition-curable liquid silicone composition that provides a thermally conductive silicone rubber that is useful as a member for an image forming apparatus.

Silicone rubber is excellent in electrical insulation, heat resistance, weather resistance, and flame retardancy, and is used in various fields such as electrical and electronic equipment, parts for transportation equipment, OA equipment, and construction. In particular, it has been used as a coating material for fixing members such as heater rolls, belts and pressure rolls of members for image forming apparatuses such as copiers and laser beam printers, taking advantage of its heat resistance. In particular, with the increase in speed and resolution of color copying, the fixing rollers and fixing belts are required to have low hardness and high thermal conductivity, as well as improved heat resistance and toner releasability. Therefore, a construction in which a base material is provided with a highly thermally conductive silicone rubber layer and a fluororesin is further coated thereon is often employed.

Silicone rubber is generally made to have a high thermal conductivity by adding a filler having high thermal conductivity to the silicone polymer. Specifically, silica, alumina, magnesium oxide, metal silicon, etc. are blended as thermally conductive fillers with conventionally used silicone rubber. However, large amounts of filler are required to obtain the necessary thermal conductivity. As a result, as the filler ratio of the silicone composition increases, metallic impurities, hydroxyl groups, organic functional groups, etc. derived from the filler increase, and the heat resistance required for rubber rollers and belts decreases. There were drawbacks.

As a method for improving the heat resistance of silicone rubber, it is known to add additives such as cerium oxide, cerium hydroxide, iron oxide and carbon black. As such silicone rubber, Patent Documents 1 to 3 disclose a method of adding titanium oxide and iron oxide, a method of adding hydrous cerium oxide and/or hydrous zirconium oxide, and a method of adding aluminate or aluminate as a solid solution. A method of adding yellow iron oxide is described. However, the fixing roll and belt may be subjected to a heat history of 250° C. or higher when the apparatus is started. In addition, when the fixing roll or belt is to be heat-melted with fluororesin powder on the surface layer thereof, it is necessary to bake them at a high temperature of 320° C. or higher. Under these conditions, conventional methods are not sufficiently effective, and silicone rubbers with improved heat resistance are desired.

Japanese Patent Publication No. 2016-518461 Japanese Unexamined Patent Application Publication No. 2014-031408 JP-A-7-292256

Accordingly, an object of the present invention is to provide an addition-curable liquid silicone composition, especially an image forming agent, which provides a silicone rubber having excellent heat resistance at high temperatures of 200° C. or higher, particularly 300° C. or higher, and also having excellent thermal conductivity. An object of the present invention is to provide a fixing roll and a belt using a silicone composition for devices and a cured product obtained by curing the composition (that is, silicone rubber).

As a result of intensive research to achieve the above object, the present inventors have found that an addition-curable liquid silicone composition containing a high proportion of a thermally conductive inorganic filler contains yellow iron oxide and cerium oxide or cerium hydroxide. As a result, the inventors have found that the heat resistance of the highly thermally conductive silicone rubber is improved, and have completed the present invention.
That is, the present invention
(A) an organopolysiloxane having two or more silicon-bonded alkenyl groups per molecule and an average degree of polymerization of less than 1,000: 100 parts by mass;
(B) Organohydrogenpolysiloxane having two or more silicon-bonded hydrogen atoms per molecule: Silicon atom bonds in component (B) relative to the number of silicon-bonded alkenyl groups in component (A) an amount such that the ratio of the number of hydrogen atoms is 0.3 to 3,
(C) a thermally conductive inorganic filler having an average particle size of 1 to 50 μm: 40 to 800 parts by mass;
(D) hydrosilylation reaction catalyst: catalytic amount,
(E) yellow iron oxide: 0.1 to 10 parts by mass, and (F) at least one selected from cerium oxide and cerium hydroxide: 0.1 to 10 parts by mass, addition liquid at 25 ° C. A curable silicone composition is provided.

Further, the present invention provides the addition-curable liquid silicone composition for use in an image forming apparatus, a cured product obtained by curing the composition (i.e., silicone rubber), and a fixing roll and a fixing belt using the cured product. I will provide a.

ADVANTAGE OF THE INVENTION According to this invention, the highly heat-conductive silicone rubber excellent in heat resistance can be obtained. That is, the silicone rubber obtained by curing the addition-curable liquid silicone composition of the present invention exhibits excellent heat resistance at 230°C or higher, particularly at 350°C, excellent heat durability, flexibility and retention over time. To provide a fixing roll and a fixing belt excellent in properties. Therefore, the obtained silicone rubber can be suitably used as a member for an image forming apparatus.

The composition of the present invention is described in detail below.
[(A) Component]
Component (A) is an organopolysiloxane that is liquid at 25°C and has two or more silicon-bonded alkenyl groups per molecule and an average degree of polymerization of less than 1,000. It is the base polymer (main agent) of the product.

The molecular structure of the component (A) may satisfy the above requirements, and examples thereof include straight-chain and branched-chain structures. A linear diorganopolysiloxane whose main chain basically consists of repeating diorganosiloxane units and whose molecular chain ends are blocked with triorganosiloxy groups is preferred. In addition, the position of the silicon atom to which the alkenyl group is bonded in the molecule of the organopolysiloxane may be either or both of the molecular chain terminal and the molecular chain middle. A particularly preferred component (A) is a linear diorganopolysiloxane containing at least alkenyl groups bonded to silicon atoms at both ends of the molecular chain.

The alkenyl group bonded to the silicon atom preferably has 2 to 8 carbon atoms, more preferably 2 to 4 carbon atoms. Examples include vinyl group, allyl group, propenyl group, butenyl group, pentenyl group, hexenyl group, cyclohexenyl group, and heptenyl group, and vinyl group is particularly preferred.

Component (A) is characterized by having two or more silicon-bonded alkenyl groups, preferably from 2 to 50, more preferably from 2 to 20. The content of alkenyl groups is preferably 0.001 to 10 mol%, particularly 0, relative to the total number of monovalent organic groups bonded to silicon atoms. It is preferably from 0.01 to 5 mol %.

Component (A) preferably has a monovalent hydrocarbon group having 1 to 12 carbon atoms, more preferably 1 to 10 carbon atoms, as a monovalent organic group other than an alkenyl group bonded to a silicon atom. Examples of the monovalent hydrocarbon group include alkyl groups such as methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, cyclohexyl group, and heptyl group; phenyl group, tolyl group, xylyl group, and aryl groups such as naphthyl group; aralkyl groups such as benzyl group and phenethyl group; halogen-substituted alkyl groups such as chloromethyl group, 3-chloropropyl group and 3,3,3-trifluoropropyl group; A methyl group is preferred.

The component (A) is characterized by having an average degree of polymerization of less than 1,000. It preferably has an average degree of polymerization of 50 or more and less than 1,000, and more preferably has an average degree of polymerization of 100 or more and 800 or less. If the degree of polymerization is less than the above lower limit, the resulting silicone rubber may have insufficient mechanical properties. If the average degree of polymerization is 1,000 or more, the viscosity of the obtained silicone composition is too high, and the filling property of the thermally conductive inorganic filler may deteriorate. In addition, when (A) component is a mixture of multiple components, let the sum total of the product of the polymerization degree of each component and a mass fraction be the polymerization degree of (A) component.
In the present specification, the "degree of polymerization" is the average degree of polymerization, which can be obtained from the weight average molecular weight using polystyrene as a standard material by gel permeation chromatography (GPC) measured under the following conditions (hereinafter the same ).
[Measurement condition]
Developing solvent: toluene Flow rate: 1 mL/min
Detector: Differential Refractive Index Detector (RI)
Column: KF-805L x 2 (manufactured by Shodex)
Column temperature: 25°C
Sample injection volume: 20 μL (toluene solution with a concentration of 0.1% by mass)

Examples of the component (A) include dimethylsiloxane-methylvinylsiloxane copolymer with trimethylsiloxy group-blocked at both molecular chain ends, methylvinylpolysiloxane with trimethylsiloxy group-blocked at both molecular chain ends, and dimethyl with both molecular chain ends blocked with trimethylsiloxy groups. Siloxane/methylvinylsiloxane/methylphenylsiloxane copolymer, dimethylpolysiloxane with dimethylvinylsiloxy group-blocked at both molecular chain terminals, methylvinylpolysiloxane with dimethylvinylsiloxy group-blocked at both molecular chain terminals, dimethylvinylsiloxy group-blocked at both molecular chain terminals Siloxane-methylvinylsiloxane copolymer, dimethylvinylsiloxy group-blocked dimethylsiloxane at both molecular chain ends, methylvinylsiloxane-methylphenylsiloxane copolymer, divinylmethylsiloxy-blocked dimethylpolysiloxane at both molecular chain ends, divinyl at both molecular chain ends methylsiloxy group-blocked dimethylsiloxane/methylvinylsiloxane copolymer, both molecular chain ends blocked trivinylsiloxy group dimethylpolysiloxane, molecular chain both ends trivinylsiloxy group-blocked dimethylsiloxane/methylvinylsiloxane copolymer, and organo- Mixtures of two or more polysiloxanes are included.

The above organopolysiloxanes may be used alone or in combination of two or more. A combination of a straight-chain organopolysiloxane having alkenyl groups at both ends and a straight-chain organopolysiloxane having two or more alkenyl groups in side chains is particularly preferred. The ratio of combined use is not particularly limited. A linear organopolysiloxane having alkenyl groups at both ends and a linear organopolysiloxane having two or more alkenyl groups in side chains may be in a mass ratio of 1:99 to 99:1. It is preferably 20:80 to 80:20, more preferably 30:70 to 70:30.

[(B) Component]
Component (B) is mainly an organohydrogenpolysiloxane that undergoes a hydrosilylation addition reaction with the alkenyl groups in component (A) and acts as a cross-linking agent (curing agent). As the molecular structure of component (B), for example, various structures such as linear, cyclic, branched, and three-dimensional network (resinous) structures can be mentioned. Component (B) must have at least 2, preferably 3 or more silicon-bonded hydrogen atoms (hydrosilyl groups) in one molecule, usually 2 to 300, preferably 3 to 200. , more preferably 4 to 100 hydrosilyl groups. Such hydrosilyl groups may be located either at the end of the molecular chain, in the middle of the molecular chain, or both. Also, the component (B) is preferably liquid at 25°C. Most preferred is a linear organohydrogenpolysiloxane that has hydrosilyl groups at both ends and side chains and is liquid at 25°C.

The organohydrogenpolysiloxane can be represented, for example, by the following average compositional formula (1).

In formula (1), each R ¹ is independently a monovalent hydrocarbon group having no aliphatic unsaturated bond such as an alkenyl group, preferably having 1 to 10 carbon atoms. Examples of the monovalent hydrocarbon group include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, cyclohexyl group, octyl group and nonyl. Alkyl groups such as decyl group, aryl groups such as phenyl group, tolyl group, xylyl group and naphthyl group, aralkyl groups such as benzyl group, phenylethyl group and phenylpropyl group, and part of the hydrogen atoms of these groups Alternatively, all of them are substituted with halogen atoms such as fluorine, bromine and chlorine, such as chloromethyl, chloropropyl, bromoethyl and trifluoropropyl groups. R ¹ is preferably an alkyl group or an aryl group, more preferably a methyl group. In addition, a is 0.7 to 2.1, b is 0.001 to 1.0, and a + b is preferably a positive number satisfying 0.8 to 3.0, more preferably a is 1.0 ~2.0, b is a positive number satisfying 0.01 to 1.0, and a+b satisfies 1.5 to 2.5.

Examples of the organohydrogenpolysiloxane include 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, tris(hydrogendimethylsiloxy)methylsilane, tris(hydrogendimethylsiloxy)methylsilane, dimethylsiloxy)phenylsilane, methylhydrogencyclopolysiloxane, methylhydrogensiloxane/dimethylsiloxane cyclic copolymer, methylhydrogenpolysiloxane with trimethylsiloxy group-blocked at both molecular chain ends, dimethylsiloxane with trimethylsiloxy group-blocked at both molecular chain ends・Methylhydrogensiloxane copolymer, dimethylsiloxane blocked with trimethylsiloxy groups at both molecular chain ends・Methylhydrogensiloxane・methylphenylsiloxane copolymer, dimethylsiloxane blocked with trimethylsiloxy groups at both molecular chain ends・methylhydrogensiloxane・diphenylsiloxane Copolymer, dimethylhydrogensiloxy-blocked methylhydrogenpolysiloxane at both molecular chain ends, dimethylpolysiloxane blocked at both molecular chain ends dimethylhydrogensiloxy group, dimethylsiloxane/methylhydrogen blocked at both molecular chain ends dimethylhydrogensiloxy group-blocked Siloxane copolymer, dimethylsiloxane/methylphenylsiloxane copolymer with dimethylhydrogensiloxy group-blocked at both molecular chain ends, dimethylsiloxane/diphenylsiloxane copolymer with dimethylhydrogensiloxy group-blocked at both molecular chain ends, dimethylhydrogen at both molecular chain ends Gensiloxy group-blocked methylphenylpolysiloxane, dimethylhydrogensiloxy group-blocked diphenylpolysiloxane at both ends of the molecular chain, and in each of these exemplary compounds, some or all of the methyl groups are other alkyl groups such as ethyl groups and propyl groups. Organo consisting of a siloxane unit represented by the formula: R ² ₃ SiO _1/2 , a siloxane unit represented by the formula: R ² ₂ HSiO _1/2 , and a siloxane unit represented by the formula: SiO _4/2 Siloxane copolymer, an organosiloxane copolymer composed of siloxane units represented by the formula: R ² ₂ HSiO _1/2 and siloxane units represented by the formula: SiO _4/2 , represented by the formula: R ² HSiO _2/2 Organosiloxane copolymers comprising siloxane units and siloxane units represented by the formula: R ² SiO _3/2 or siloxane units represented by the formula: HSiO _3/2 , and mixtures of two or more of these organopolysiloxanes mentioned. R ² in the above formula is a monovalent hydrocarbon group other than an alkenyl group.

The amount of component (B) to be blended is such that the number of hydrosilyl groups contained in the composition is 0.3 to 3 per 1 total number of silicon-bonded alkenyl groups contained in the composition. In particular, the ratio of the number of hydrosilyl groups contained in component (B) to the number of silicon-bonded alkenyl groups contained in component (A) is 0.3 to 3, preferably 0.4 to 2. , more preferably 0.4 to 1.6. If the number of hydrosilyl groups is less than the lower limit, the composition will not cure sufficiently. On the other hand, if the number of hydrosilyl groups exceeds the above upper limit, the hardness of the resulting silicone rubber cured product may become extremely hard and the heat resistance may be extremely poor. It is preferably 0.1 to 20 parts by mass, more preferably 0.2 to 15 parts by mass, per 100 parts by mass of component (A).

The organohydrogenpolysiloxane may be used alone or in combination of two or more.

[(C) component]
Component (C) is a thermally conductive inorganic filler having an average particle size of 1 to 50 μm. The component (C) acts to impart thermal conductivity to the obtained silicone rubber. In order to improve the heat resistance of silicone rubber, the thermal conductivity of the thermally conductive inorganic filler is preferably 5 W/m·K or more. If the thermally conductive inorganic filler has a thermal conductivity of 5 W/m·K or more, a composition containing a large amount of the thermally conductive filler can impart an excellent effect of improving heat resistance to silicone rubber. .

The amount of the thermally conductive filler in the silicone composition of the present invention is 40 to 800 parts by mass, preferably 100 to 500 parts by mass, more preferably 180 to 180 parts by mass per 100 parts by mass of component (A). 480 parts by mass. If it is less than the above lower limit, the thermal conductivity of the cured product of the silicone composition will be insufficient, which is not preferable. On the other hand, when the amount is more than the above upper limit, the viscosity of the composition becomes too high, which may deteriorate the handleability. Within the above range, the cured product has a thermal conductivity of 0.4 W/m·K or more, which is preferable.

The thermally conductive inorganic filler is characterized by having an average particle size of 1-50 μm, preferably 2-20 μm. If the average particle size is smaller than the above lower limit, the hardness of the silicone rubber may increase significantly, or the electrical resistance may change over time. On the other hand, when it is larger than the above upper limit, it causes irregularities on the rubber surface. In the present invention, the average particle size refers to the d50 particle size measured by weight average value (i.e., median size) using a particle size distribution measuring device such as laser light diffraction method (hereinafter the same ).

Examples of the thermally conductive inorganic filler include quartz powder, alumina, metal oxides such as zinc oxide, metal particles such as silver, copper, and metal silicon, and composite metals such as boron nitride, aluminum nitride, silicon nitride, and silicon carbide. In the present invention, crystalline silica, alumina, metallic silicon and zinc oxide are particularly preferred. The above thermally conductive inorganic fillers may be used singly or in combination of two or more.

The thermally conductive inorganic fillers include silane coupling agents or partial hydrolysates thereof, alkylalkoxysilanes or partial hydrolysates thereof, organic silazanes, organopolysiloxane oils, hydrolyzable functional group-containing organopolysiloxanes, and the like. It may be surface-treated by The surface treatment method is not particularly limited. The thermally conductive inorganic filler may be surface-treated in advance before being mixed with other components. Alternatively, surface treatment may be carried out during mixing with the organopolysiloxane of component (A).

The thermally conductive inorganic filler may be mixed with component (A) at room temperature using a device such as a planetary mixer or kneader, or may be mixed at a high temperature of 100 to 200°C.

In addition to the thermally conductive inorganic filler, the silicone composition of the present invention contains reinforcing silica such as fumed silica and precipitated silica for the purpose of improving rubber strength and preventing sedimentation of the thermally conductive inorganic filler. It may be further contained within a range that does not impair the heat conduction properties. The reinforcing silica preferably has a specific surface area of 50 m ² /g to 300 m ² /g according to the BET method. Examples of the reinforcing silica include fumed silica (fumed silica, dry silica) and precipitated silica (precipitated silica, wet silica). Among them, fumed silica (dry silica) whose surface is hydrophobized with organopolysiloxane, organopolysilazane, chlorosilane, alkoxysilane or the like is more preferable. Moreover, these silicas may be used singly or in combination of two or more.

The content of the reinforcing silica in the silicone composition of the present invention is 0 to 20 parts by weight per 100 parts by weight of component (A), and when blended, it is preferably 0.5 to 10 parts by weight. If the content of this reinforcing silica exceeds the above upper limit, the hardness of the obtained silicone rubber may increase, or the blendability of the thermally conductive inorganic filler may deteriorate.

[(D) Hydrosilylation reaction catalyst]
Component (D) is a hydrosilylation reaction catalyst, which promotes the addition reaction between silicon-bonded alkenyl groups contained in the composition and hydrosilyl groups contained in the composition. It mainly promotes the addition reaction between the silicon-bonded alkenyl groups in component (A) and the hydrosilyl groups in component (B). This hydrosilylation reaction catalyst is not particularly limited, and examples thereof include platinum group metals such as platinum, palladium and rhodium; chloroplatinic acid; alcohol-modified chloroplatinic acid; Coordination compound; platinum group metal compounds such as tetrakis(triphenylphosphine)palladium, chlorotris(triphenylphosphine)rhodium, etc., and the like, preferably platinum group metal compounds.

The amount of component (D) to be blended should be an effective amount (catalytic amount) as a catalyst. For example, it is preferably 1 to 500 ppm, more preferably 5 to 100 ppm in terms of mass of the catalytic metal element relative to the total mass of component (A). If it is less than the above lower limit, the addition reaction may be significantly slowed down, and the composition may not cure. On the other hand, when the above upper limit is exceeded, the heat resistance of the cured product may be lowered.

The component (D) hydrosilylation reaction catalyst may be used alone or in combination of two or more.

[(E) yellow iron oxide]
Component (E) is yellow iron oxide, and when used together with component (F), which will be described later, suppresses an increase in the hardness of silicone rubber when heated and maintains the flexibility of the rubber.

Examples of yellow iron oxide include iron (III) oxide monohydrate represented by the chemical formula Fe ₂ O ₃ ·H ₂ O and α-iron oxyhydroxide represented by α-FeOOH. The appearance is yellow to yellowish brown, and the shape is generally needle-like to spindle-like particles. It can be obtained by pulverizing natural minerals such as goethite or by adding a base to a solution containing trivalent iron ions to precipitate it. to obtain a compound. Commercially available products include Todacolor TSY series (manufactured by Toda Kogyo Co., Ltd.) and TAROX-LL series (manufactured by Titan Kogyo Co., Ltd.). Although the particle size is not particularly limited, it is preferred that the 45 μm sieve residue is 0.01% or less and that there are few aggregates.

The amount of yellow iron oxide to be added is 0.1 to 10 parts by mass, preferably 0.2 to 6 parts by mass, per 100 parts by mass of component (A). If the added amount is less than the above lower limit, the heat resistance of the silicone rubber will not be improved, and if the added amount exceeds the above upper limit, the mechanical properties of the silicone rubber may be remarkably deteriorated.

[(F) Cerium compound]
Component (F) is one or more cerium compounds selected from cerium oxide and cerium hydroxide. The component (F) significantly improves the heat resistance of the silicone rubber when used in combination with the component (E).
Cerium oxide and cerium hydroxide may be commercially available. Commercially available products of cerium oxide include Shorox FL-2 (manufactured by Showa Denko KK), SN-2 (manufactured by Nikki Corporation), and cerium oxide S (manufactured by Anan Kasei Co., Ltd.). Commercially available products of cerium hydroxide include cerium hydroxide (manufactured by Nikki Co., Ltd.) and Cerhydrate 90 (manufactured by Treibach Industrie AG).

The amount of component (F) added is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 6 parts by mass, per 100 parts by mass of component (A). Below the above lower limit, the heat resistance of the silicone rubber is not improved. Moreover, if it is added in excess of the above upper limit, the mechanical properties of the silicone rubber may significantly deteriorate.

Component (F) may be either one of cerium oxide and cerium hydroxide, or a combination of cerium oxide and cerium hydroxide. When cerium oxide and cerium hydroxide are used together, the total amount should satisfy the above range.

A preferable compounding ratio of (E) the yellow iron oxide and (F) the cerium compound is 10:90 to 95:5, more preferably 50:50 to 80:20 in mass ratio.

[Other ingredients]
In addition to the above components (A) to (F), the silicone composition of the present invention may optionally contain other optional components. Examples include reaction control agents.

Reaction Control Agent The reaction control agent is not particularly limited as long as it is a compound having a curing inhibitory effect on the (D) hydrosilylation reaction catalyst, and known ones can be used. For example, phosphorus-containing compounds such as triphenylphosphine; nitrogen-containing compounds such as tributylamine, tetramethylethylenediamine and benzotriazole; sulfur-containing compounds; acetylenic compounds such as acetylene alcohols; compounds containing two or more alkenyl groups; oxy compounds; maleic acid derivatives; The degree of curing inhibition effect of the reaction control agent varies depending on the chemical structure of the reaction control agent. Therefore, it is preferable to adjust the amount of the reaction control agent to be added to the optimum amount for each reaction control agent used. By adding an optimum amount of the reaction control agent, the composition has excellent long-term storage stability and curability at room temperature.

• Other Additives The silicone composition of the present invention may contain fillers other than component (C) as long as they do not impair the effects of the present invention. Other fillers may be known fillers used in silicone compositions. For example, organic resin hollow fillers for density adjustment, polymethylsilsesquioxane fine particles (so-called silicone resin powder) and spherical rubber powder for improving surface smoothness, fumed titanium dioxide, magnesium oxide, oxide as flame retardants and coloring agents. Iron (II), diatomaceous earth, talc, kaolinite, glass fiber, aluminum hydroxide, magnesium carbonate, calcium carbonate, zinc carbonate as fillers, carbon black as conductivity enhancer, thermal conductivity and conductivity enhancer Examples include carbon fiber powder and graphite having a fiber length of 20 to 500 μm. In addition, fillers obtained by subjecting these fillers to a surface hydrophobizing treatment with an organosilicon compound such as an organoalkoxysilane compound, an organochlorosilane compound, an organosilazane compound, or a low-molecular-weight siloxane compound can also be used.

Other additives include, for example, organopolysiloxanes containing one silicon-bonded hydrogen atom per molecule and no other functional groups, and one silicon-bonded alkenyl group per molecule. organopolysiloxanes containing no other functional groups, non-functional organopolysiloxanes containing no silicon-bonded hydrogen atoms, silicon-bonded alkenyl groups or other functional groups (so-called dimethyl silicone oils), organic Solvents, anti-creep hardening agents, plasticizers, thixotropic agents, pigments, dyes, antifungal agents and the like can be blended.

Each of the other components described above may be used alone or in combination of two or more. Moreover, the blending amount is not particularly limited, and may be appropriately adjusted within a range that does not impair the effects of the present invention. For example, when a conductivity imparting agent such as carbon black is blended, it may be 3 to 20 parts by mass per 100 parts by mass of component (A).

<Preparation of addition-curable liquid silicone composition>
An addition-curable liquid silicone composition can be prepared by uniformly mixing the above components (A) to (F) and, if necessary, other components. Mixing of each component can be carried out using a known method and apparatus for producing a liquid silicone composition. Examples of the apparatus include known kneading apparatuses such as two-roll, three-roll, kneader mixers, planetary mixers, Ross mixers, acoustic vibration mixers, and the like. Components (A)-(F) may all be mixed together at ambient temperature. Alternatively, when heat treatment is performed, for example, components (A) and (C), and optionally other fillers such as finely powdered silica-based fillers, are mixed in advance and heated at 100 to 200 ° C. for 10 minutes to After preparing a heat-treated compound by heat-treating and mixing for 3 hours, components (B), (D), (E) and (F), and other additives described above may be mixed in a kneader to prepare a heat-treated compound. . In addition, components (E) and (F) are mixed in advance with a small amount of component (A) for the purpose of improving dispersibility in the silicone composition, and are mixed in a paint mill, a centrifugal mixer or an ultrasonic disperser. It may be added to the mixture of components (A) to (D) after preparation of a paste dispersed by using, for example.

The silicone composition of the present invention may be a two-part silicone composition for cast molding or injection molding. Specifically, (D) a hydrosilylation reaction catalyst is added to one half of a mixture of components (A) and (C) in advance and mixed. To the other mixture, (B) organohydrogenpolysiloxane and a reaction control agent are added and mixed. The preparation of the silicone composition can be easily prepared by mixing both just before use. At that time, the other components (E) and (F) may be added to either side or both sides.

The silicone composition of the present invention is a liquid composition at 25°C. Preferably, the silicone composition of the present invention has a viscosity at 25° C. of 1 to 2,000 Pa s, more preferably 5 ∼1,000 Pa·s. If the viscosity is within this range, when casting a fixing roll for an image forming apparatus or applying a thin film to the shape of a fixing belt, there may be problems with casting, unevenness in coating, and post-curing core bars and belts. Since insufficient adhesion to the base is less likely to occur, it can be preferably used.

The silicone composition of the present invention can be molded into the required applications by a variety of molding methods in which silicones are commonly molded, such as cast molding, LIM injection molding, and mold pressure molding. Although the molding conditions are not particularly limited, it is preferable to cure with a heat history of 100 to 400° C. for several seconds to 1 hour. In the case of secondary vulcanization after molding, the secondary vulcanization is preferably carried out at 150 to 250° C. for 1 to 30 hours. A cured product obtained by curing the silicone composition of the present invention (that is, silicone rubber) can have high thermal conductivity and heat resistance.

A cured product layer (silicone rubber layer) obtained from the silicone composition of the present invention has high thermal conductivity. Silicone rubbers used for fixing rolls and belts preferably have a thermal conductivity of 0.4 W/mK or more, preferably 0.5 to 3.0 W/mK.

The present invention further provides a fixing roll or fixing belt having the cured product (ie, silicone rubber). The fixing roll forms the cured product layer (silicone rubber layer) on the metal core. The material, dimensions, etc. of the cored bar may be appropriately selected according to the type of roll. For example, as the core bar, aluminum, iron, stainless steel (SUS), polyetheretherketone (PEEK) of heat-resistant thermoplastic resins, and the like are used. The surface of these metal cores is preferably treated with a primer such as a silane coupling agent or a silicone adhesive for the purpose of strengthening the adhesion to the silicone rubber layer. The method of molding and curing the silicone composition may be appropriately selected. For example, it can be molded by injection molding, transfer molding, injection molding, ring coating molding, knife coating, etc., and cured by heating. The silicone rubber layer may be a single layer of silicone rubber, or may be multiple layers of two or more silicone rubber layers with different types and amounts of (C) the thermally conductive inorganic filler.
In the fixing roll, the total thickness of the silicone rubber layer is preferably 50 μm to 20 mm, especially 0.2 mm to 6 mm. If the thickness is too thin, sufficient rubber elasticity may not be obtained. On the other hand, if it is too thick, the heat transfer properties between the metal core and the surface of the rubber roll may be impaired.

The fixing roll may be further provided with a fluororesin layer or a fluororubber layer on the outer surface of the silicone rubber layer for the purpose of releasing the melted toner. The fluororesin layer is formed of a fluororesin coating material, a fluororesin tube, or the like, and covers the silicone rubber layer. Here, as the fluororesin coating material, for example, latex of polytetrafluoroethylene resin (PTFE) or powder coated by baking and melting at 300° C. or higher is used. For example, DAI-EL latex (manufactured by Daikin Industries, fluorine-based latex) and the like can be mentioned. The fluororubber layer can be obtained by applying an uncrosslinked fluororubber composition to the outer surface of the silicone rubber layer and bonding it to the silicone rubber layer by, for example, cross-linking reaction. Moreover, by covering the outside of the silicone composition with a fluororesin tube, the fluororesin can be adhered to the surface layer of the silicone rubber at the same time as the silicone composition is cured. Alternatively, the fixing roll can be obtained by molding the silicone composition into a roll shape on the surface of the core metal and curing it, and then adhering the fluororesin tube to the surface layer of the silicone rubber using an adhesive or a primer.

As the fluororesin, commercially available products can be used, such as polytetrafluoroethylene resin (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin (PFA), fluoroethylene-polypropylene copolymer resin (FEP ), polyvinylidene fluoride resin (PVDF), and polyvinyl fluoride resin. A PFA tube is particularly preferred.

The thickness of the fluororesin or fluororubber layer formed on the outer surface of the silicone rubber layer is preferably 1 μm to 500 μm, particularly 10 μm to 100 μm. If the roll is too thin, it may break, wrinkle, or peel off when external stress is applied to it. sometimes.

The present invention further provides a fixing belt having the above silicone rubber layer. The fixing belt is obtained by laminating the silicone rubber layer on a belt base material. As the belt base material, known materials such as metal belts such as electroformed nickel, SUS, and aluminum, and organic resin films such as polyimide resin, polyamide resin, and polyamide-imide resin can be used. Also, the shape, dimensions, etc. thereof can be appropriately selected according to the type of the belt.

Methods for molding and curing the silicone composition are described above. The silicone rubber layer formed on the fixing belt base material may be a layer consisting of one type, or may be a plurality of layers consisting of two or more layers of silicone rubbers having different amounts of the thermally conductive inorganic filler of component (C). The total thickness of the silicone rubber layer is preferably 30 μm to 5 mm, especially 50 μm to 800 μm. If it is too thin, rubber elasticity may not be obtained, and if it is too thick, the heat transfer properties between the belt surface/substrate may be impaired.

It is desirable to laminate a fluororesin or fluororubber layer on the silicone rubber layer for the purpose of releasing the melted toner. The types of fluororesin and fluororubber are the same as those described for the fixing roll. In the case of the fixing belt, it is preferable to use a fluororesin layer so as not to impair the thermal conductivity of the cured rubber layer as much as possible. A belt with a curved or PFA tube disposed around its circumference is preferred. The thickness of the fluororesin layer is preferably 1 μm to 100 μm, particularly 2 μm to 70 μm. If the belt is too thin, it may tear, wrinkle or peel when external stress is applied to the belt. If it is too thick, the heat conductivity in the vertical direction of the belt axis may be lowered, resulting in lowered toner melting performance, loss of surface rubber elasticity, and appearance defects such as cracks and folds.

EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

Evaluation tests conducted in the following examples and comparative examples are as follows. In addition, the average particle size described in the examples and comparative examples refers to the d50 particle size measured as a weight average value using a particle size distribution measuring device such as a laser beam diffraction method.

Thermal conductivity measurement:
Thermal conductivity (W/m·K) was measured with a rapid thermal conductivity meter (QTM-700, manufactured by Kyoto Electronics Co., Ltd.) using a sheet with a thickness of 12 mm.

Measurement of volume resistivity:
The volume resistivity (insulation) (Ω·m) of silicone rubber was measured based on the JIS K6271:2008 double ring electrode method. The measurement conditions for the volume resistivity are a sample shape of 1 mm thickness×100 mm width×100 mm length, and a voltage of 500V.
The volume resistivity (conductivity) (Ω·m) of the silicone rubber was measured based on the JIS K6271:2008 parallel terminal electrode method. The measurement conditions for the volume resistivity were as follows: sample shape: 1 mm thick x 20 mm wide x 150 mm long; distance between current electrodes: 100 mm; distance between potential difference electrodes: 50 mm; current supply: 1 mA.

Measurement of rubber physical properties:
Using a 2 mm thick test sheet, hardness (durometer A), tensile strength (MPa), and elongation at break (%) were measured according to JIS K 6249:2003.
Next, the 2 mm thick test sheet was placed in a dryer at 230°C for 21 days and in a dryer at 350°C for 2 hours. Tensile strength (MPa) and elongation at break (%) were measured.

Bending test:
A sheet with a thickness of 1 mm was cut into a shape of 20 mm×100 mm and bent at an angle of 180° with a radius of curvature of 1 mm.
Next, the 1 mm thick test sheet was placed in a dryer at 230° C. for 21 days and in a dryer at 350° C. for 2 hours, and then subjected to a bending test by the same method as above.

The organopolysiloxane, organohydrogenpolysiloxane, and fumed silica used in the following examples and comparative examples are as follows.
Organopolysiloxane A1: A linear dimethylpolysiloxane that is liquid at 25° C., having both ends blocked with dimethylvinylsiloxy groups, a degree of polymerization of 200, and a vinyl value of 0.00013 mol/g.
Organopolysiloxane A2: a linear dimethylpolysiloxane that is liquid at 25° C., having both ends blocked with trimethylsiloxy groups and having vinyl groups in side chains, a degree of polymerization of 700 and a vinyl value of 0.000075 mol/g.
Organohydrogenpolysiloxane B: linear methylhydrogenpolysiloxane having hydrosilyl groups at both ends and side chains, liquid at 25°C, degree of polymerization 17, hydrosilyl content 0.0038 mol/g
Fumed silica: Hydrophobized fumed silica with a specific surface area of 110 m ² /g, R-972 (manufactured by Nippon Aerosil Co., Ltd.)

[Example 1]
40 parts by mass of organopolysiloxane A1, 60 parts by mass of organopolysiloxane A2, 1 part of fumed silica R-972, M-Si #600 (Kinsei Matec Co., Ltd.), which is a pulverized metal silicon powder with an average particle size of 6 μm (Heat conductivity of filler: 160 W/m·K) was placed in a planetary mixer and stirred at room temperature (23° C.) for 2 hours. Subsequently, the material was heat-treated at 150° C. for 2 hours in a planetary mixer, and then cooled to room temperature to obtain a heat-conducting base 1 .
Next, 1.0 parts by mass of Todacolor TSY-1 (Fe ₂ O ₃ ·H ₂ O 86% or more, yellow iron oxide, manufactured by Toda Kogyo Co., Ltd.) and cerium oxide are added to the heat conductive base 1 obtained above. 0.5 parts by mass of certain SN-2 (manufactured by Nikki Co., Ltd.) was added, and the mixture was further stirred for 1 hour using a planetary mixer. To the resulting mixture were added 2.2 parts by mass of organohydrogenpolysiloxane B, 0.05 parts by mass of ethynylcyclohexanol as a reaction controller, and 0.1 part by mass of a platinum catalyst (Pt concentration: 1% by mass). Stirring was continued for 15 minutes to obtain a liquid product at 25°C. This product was designated as a silicone composition (Example-1).
The viscosity at 25° C. of the silicone composition (Example-1) obtained above was measured with a B-type rotational viscometer according to JIS K7117-1:1999.

The above silicone composition (Example-1) was press-cured at 120°C for 10 minutes and then post-cured in an oven at 200°C for 4 hours to obtain a silicone rubber having a thickness of 1 mm, 2 mm, or 12 mm ( A test sheet) was prepared. Thermal conductivity, volume resistivity, rubber physical properties, and heat resistance were evaluated for each test sheet according to the evaluation methods described above.
Table 1 shows the results.

[Example 2]
The steps of Example 1 were repeated except that the cerium oxide in Example 1 was replaced with Cerhydrate 90 (manufactured by Treibach Industrie AG), which is cerium hydroxide, to prepare a silicone composition that is liquid at 25 ° C. ). The viscosity of the silicone composition at 25° C. was measured with a B-type rotational viscometer according to JIS K7117-1:1999.
The silicone composition was cured by the same method as in Example 1 to obtain silicone rubbers (test sheets) having a thickness of 1 mm, 2 mm or 12 mm. The thermal conductivity, volume resistivity, rubber physical properties, and heat resistance of the obtained silicone rubber were evaluated according to the evaluation methods described above. Table 1 shows the results.

[Example 3]
40 parts by mass of organopolysiloxane A1, 60 parts by mass of organopolysiloxane A2, 1 part by mass of fumed silica R-972, and Crystalite VXS-2, which is a pulverized crystalline silica powder with an average particle size of 5 μm (manufactured by Co., Ltd. Thermal conductivity of filler: 7 W/m·K) (250 parts by mass, manufactured by Tatsumori) was placed in a planetary mixer and stirred at room temperature for 2 hours to obtain a thermally conductive base 2 .
Next, on the heat conductive base 2 obtained above, 0.3 parts by mass of TAROX-LL-XLO (α-FeOOH 87.5% or more, yellow iron oxide, manufactured by Titan Kogyo Co., Ltd.), 0.3 parts of cerium oxide SN-2 .2 parts by mass were added, and the mixture was further stirred for 1 hour using a planetary mixer. To the resulting mixture were added 2.2 parts by mass of organohydrogenpolysiloxane B, 0.05 parts by mass of ethynylcyclohexanol as a reaction controller, and 0.1 part by mass of a platinum catalyst (Pt concentration: 1% by mass). Stirring was continued for 15 minutes to obtain a liquid product at 25°C. This product was designated as a silicone composition (Ex-3). The viscosity of the silicone composition at 25° C. was measured with a B-type rotational viscometer according to JIS K7117-1:1999.
The silicone composition (Example-3) was cured in the same manner as in Example 1 to obtain silicone rubbers (test sheets) having a thickness of 1 mm, 2 mm or 12 mm. The thermal conductivity, volume resistivity, rubber physical properties, and heat resistance of the obtained silicone rubber were evaluated according to the evaluation methods described above. Table 1 shows the results.

[Example 4]
40 parts by mass of organopolysiloxane A1, 60 parts by mass of organopolysiloxane A2, 1 part of fumed silica R-972, AS-40 spherical alumina powder with an average particle size of 12 μm (manufactured by Showa Denko KK, filler Thermal conductivity: 21 W/m·K) 450 parts by mass were placed in a planetary mixer and stirred at room temperature (23°C) for 2 hours. Subsequently, the material was heated to 150° C. with a planetary mixer, heat-treated for 2 hours, and then cooled to room temperature to obtain a heat-conducting base 4 .
Next, on the heat conductive base 4 obtained above, 6.0 parts by mass of Todacolor TSY-1 (Fe ₂ O ₃ ; H ₂ O 86% or more, yellow iron oxide, manufactured by Toda Kogyo Co., Ltd.) and cerium oxide 0.5 parts by mass of SN-2 was added, and the mixture was further stirred for 1 hour using a planetary mixer. To the resulting mixture were added 2.2 parts by mass of organohydrogenpolysiloxane B, 0.05 parts by mass of ethynylcyclohexanol as a reaction controller, and 0.1 part by mass of a platinum catalyst (Pt concentration: 1% by mass). Stirring was continued for a minute to obtain a liquid product at 25°C. This product was designated as a silicone composition (Ex-4). The viscosity of the silicone composition at 25° C. was measured with a B-type rotational viscometer according to JIS K7117-1:1999.
The silicone composition (Example-4) was cured by the same method as in Example 1 to obtain silicone rubbers (test sheets) having a thickness of 1 mm, 2 mm or 12 mm. The thermal conductivity, volume resistivity, rubber physical properties, and heat resistance of the obtained silicone rubber were evaluated according to the evaluation methods described above. Table 1 shows the results.

[Example 5]
40 parts by mass of organopolysiloxane A1, 60 parts by mass of organopolysiloxane A2, and calcined oxide powder, which is zinc oxide powder with an average particle size of 10 μm (manufactured by Hakusui Tech Co., Ltd., thermal conductivity of filler: 54 W / m K ) and 5 parts by mass of electrically conductive carbon powder, Denka Black powder (manufactured by Denka Co., Ltd.), were placed in a planetary mixer and stirred at room temperature (23° C.) for 2 hours. Subsequently, the above material was heated to 150° C. with a planetary mixer, heat-treated for 2 hours, and then cooled to room temperature to obtain a heat-conducting base 5 .
Next, 1.0 parts by mass of TAROX-LL-XLO (α-FeOOH 87.5% or more, yellow iron oxide, manufactured by Titan Kogyo Co., Ltd.) and Cerhydrate 90 of cerium hydroxide are added to the heat conductive base 5 obtained above. 6.0 parts by mass was added, and the mixture was further stirred for 1 hour using a planetary mixer. To the resulting mixture were added 2.2 parts by mass of organohydrogenpolysiloxane B, 0.05 parts by mass of ethynylcyclohexanol as a reaction controller, and 0.3 parts by mass of a platinum catalyst (Pt concentration: 1% by mass). Stirring was continued for 15 minutes to obtain a liquid product at 25°C. This product was designated as a silicone composition (Ex-5). The viscosity of the silicone composition at 25° C. was measured with a B-type rotational viscometer according to JIS K7117-1:1999.
The silicone composition (Example-5) was cured in the same manner as in Example 1 to obtain silicone rubbers (test sheets) having a thickness of 1 mm, 2 mm or 12 mm. The thermal conductivity, volume resistivity, rubber physical properties, and heat resistance of the obtained silicone rubber were evaluated according to the evaluation methods described above. Table 1 shows the results.
The silicone rubber obtained in Example 5 is electrically conductive and has a volume resistivity of 11 Ω·m as shown in Table 1 below.

[Comparative Example 1]
Instead of the iron (III) oxide monohydrate used in Example 1, Bayferrox 110M (Fe ₂ O ₃ , red iron oxide, manufactured by LANXESS Corporation) 1, which is iron (III) oxide containing no hydrate, was used. Example 1 was repeated except that 0.0 part by mass was used to obtain a silicone composition (ratio -1) that is liquid at 25°C and a silicone rubber. The viscosity of the silicone composition at 25° C. was measured with a B-type rotational viscometer according to JIS K7117-1:1999. In addition, thermal conductivity, volume resistivity, rubber physical properties, and heat resistance of the obtained silicone rubber were evaluated according to the evaluation methods described above. Table 2 shows the results.

[Comparative Example 2]
Example 1 was repeated except that the cerium oxide used in Example 1 was not used to obtain a liquid silicone composition (ratio -2) and silicone rubber at 25°C. The viscosity of the silicone composition at 25° C. was measured with a B-type rotational viscometer according to JIS K7117-1:1999. In addition, thermal conductivity, volume resistivity, rubber physical properties, and heat resistance of the obtained silicone rubber were evaluated according to the evaluation methods described above. Table 2 shows the results.

[Comparative Example 3]
Example 1 was repeated except that the iron (III) oxide monohydrate used in Example 1 was not used to obtain a silicone composition (ratio -3) and a silicone rubber that were liquid at 25°C. The viscosity of the silicone composition at 25° C. was measured with a B-type rotational viscometer according to JIS K7117-1:1999. In addition, thermal conductivity, volume resistivity, rubber physical properties, and heat resistance of the obtained silicone rubber were evaluated according to the evaluation methods described above. Table 2 shows the results.

[Comparative Example 4]
Example 1 was repeated except that the amount of iron (III) oxide monohydrate used in Example 1 was changed to 12 parts by mass and the amount of cerium oxide was changed to 12 parts by mass to prepare a silicone composition (ratio - 4) was prepared. However, the resulting composition was lumpy and could not be made into a liquid paste, so the sheet preparation was abandoned.

[Comparative Example 5]
Bayferrox 110M (Fe ₂ O ₃ , red iron oxide, manufactured by Lanxess KK), which is a hydrate-free iron (III) oxide instead of the iron (III) oxide monohydrate used in Example 4.1. Example 4 was repeated except that 0 parts by mass was used to obtain a liquid silicone composition (ratio -5) and silicone rubber at 25°C. The viscosity of the silicone composition at 25° C. was measured with a B-type rotational viscometer according to JIS K7117-1:1999. The thermal conductivity, volume resistivity, rubber physical properties, and heat resistance of the obtained silicone rubber were evaluated according to the evaluation methods described above. Table 2 shows the results.

[Example 6]
Primer No. 1 for addition reaction type liquid silicone rubber was applied to the surface of an aluminum shaft having a diameter of 12 mm and a length of 300 mm. 31A/B (manufactured by Shin-Etsu Chemical Co., Ltd.) was applied, and after 30 minutes of air-drying, baking was performed in a hot air dryer at 150° C. for 15 minutes. This aluminum shaft was fixed in a mold, and the silicone composition (Example-1) of Example 1 was filled in the mold at a pressure of 10 kgf/cm ² and cured by heating at 180°C for 30 minutes to form a silicone rubber layer. A silicone rubber roll (outer diameter 16 mm) with a thickness of 2 mm was obtained. Next, as a release layer for this roll, the silicone rubber roll was covered with a 30 μm thick PFA tube whose inner surface was treated with primer X-33-173A/B (manufactured by Shin-Etsu Chemical Co., Ltd.). Heat treatment was performed for 2 hours in a hot air dryer at 200° C. for both secondary cross-linking and adhesion of the primer.
After the roll obtained above was subjected to heat deterioration for 21 days in a hot air dryer at 230°C, it was mounted on an electrophotographic copier and 1,000 sheets of A4 size copy paper were continuously printed. However, no wrinkles or cracks were observed on the roll surface, and all the printed images were clear.

[Comparative Example 6]
Example 6 was repeated except that the silicone rubber composition of Comparative Example 1 (Comparative-1) was used in place of the silicone rubber composition of Example 1 (Comparative-1) to produce a roll. . As in Example 6, heat deterioration was carried out for 21 days in a hot air dryer at 230°C. After that, when 1,000 sheets of A4 size copying paper were continuously printed by mounting it on a thermoelectric copier, the image became unclear from the 350th sheet. When the surface of the roll was checked, it was confirmed that scale-like patterns had occurred on the surface of the roll, and that the rubber portion under the PFA was cracked.

[Example 7]
Addition reaction type liquid silicone rubber primer No. 1 was applied to the outer peripheral surface of a belt base material made of nickel (thickness: 30 μm, shape: inner diameter: φ30 mm, width: 250 mm). 101A/B (manufactured by Shin-Etsu Chemical Co., Ltd.) was applied, dried, and baked (150° C.×15 minutes). The silicone composition of Example 4 (Example-4) was knife-coated thereon and heated at 200° C. for 30 minutes to form a silicone layer having a thickness of about 300 μm. GLP-103SR primer for fluorine (manufactured by Daikin Industries, Ltd.) is evenly applied to the surface of the cured silicone rubber, dried, and then water-based PFA Dispersion EJ-CL500 (manufactured by Mitsui Chemours Fluoro Products Co., Ltd.) is applied. bottom. A 30 μm PFA release layer was formed by heating at 350° C. for 2 hours to prepare a fluororesin-coated silicone rubber fixing belt.
The fixing belt obtained above was installed in an electrophotographic copying machine, and 1,000 sheets of A4 size copying paper were continuously copied. After continuous printing of 1,000 sheets, the surface condition of the belt was checked. No wrinkles or cracks were observed on the roll surface, and all printed images were clear. It was confirmed that the material was able to withstand the PFA film forming conditions of °C/2 hours.

[Comparative Example 7]
A fixing belt was produced by repeating Example 7 except that the silicone composition of Comparative Example 5 (Comparative-5) was used in place of the silicone composition (Comparative-4). In the same manner as in Example 7, when A4 size copy paper was continuously passed through an electronic copying machine, the image became unclear after the 50th copy. When the printing was stopped and the belt surface was checked, a wavy pattern was generated on the surface in parallel with the belt axial direction, and it was confirmed that the rubber portion of the PFA lower layer was cracked.

As described above, the silicone rubber of the present invention has excellent heat resistance that can maintain rubber elasticity even at high temperatures of 230° C. or higher, particularly 350° C., and is excellent as a high thermal conductive silicone rubber for fixing rolls and fixing belts. there is

The silicone rubber obtained by curing the addition-curable liquid silicone composition of the present invention exhibits excellent high-temperature heat resistance, and can provide fixing rolls and fixing belts with excellent flexibility and retention over time. Therefore, it can be suitably used as a member for an image forming apparatus.

Claims (8)

(A) an organopolysiloxane having two or more silicon-bonded alkenyl groups per molecule and an average degree of polymerization of less than 1,000: 100 parts by mass;
(B) Organohydrogenpolysiloxane having two or more silicon-bonded hydrogen atoms per molecule: Silicon atom bonds in component (B) relative to the number of silicon-bonded alkenyl groups in component (A) an amount such that the ratio of the number of hydrogen atoms is 0.3 to 3,
(C) a thermally conductive inorganic filler having an average particle size of 1 to 50 μm: 40 to 800 parts by mass;
(D) hydrosilylation reaction catalyst: catalytic amount,
(E) yellow iron oxide: 0.1 to 10 parts by mass, and (F) at least one selected from cerium oxide and cerium hydroxide: 0.1 to 10 parts by mass, addition liquid at 25 ° C. A curable silicone composition. 2. The addition-curable silicone composition according to claim 1, wherein said (C) thermally conductive inorganic filler is at least one selected from crystalline silica, alumina, metallic silicon, and zinc oxide. The addition-curable silicone composition according to claim 1 or 2, which has a viscosity of 1 to 2,000 Pa·s at 25°C. 4. The addition-curable silicone composition according to any one of claims 1 to 3, which is used in an image forming apparatus. A cured silicone rubber obtained by curing the addition-curable silicone composition according to any one of claims 1 to 4. 6. The silicone rubber cured product according to claim 5, having a thermal conductivity of 0.4 W/mK or more. A roll shaft, at least one layer made of the cured silicone rubber according to claim 5 or 6 in contact with the outer peripheral surface of the roll shaft, and a fluororesin layer in contact with one surface of the layer made of the cured silicone rubber. and a fixing roll for an image forming apparatus. A cylindrical belt, at least one layer comprising the cured silicone rubber according to claim 5 or 6 in contact with the outer peripheral surface of the cylindrical belt, and a fluororesin layer in contact with one surface of the layer comprising the cured silicone rubber. and a fixing belt for an image forming apparatus.