JPH11116739A - Rubber composition for fixing roll - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for a fixing roll which can be used for forming a fixing roll excellent in toner releasing properties, low hardness, low compression set, mechanical strengths and silicone oil resistance. SOLUTION: There is provided a rubber composition comprising (A) crosslinked rubber particles having a number average particle size of 20 μm or less and comprising a crossliked silicone rubber with a toluene-insoluble content of 30 wt.% or more, (B) an oil-resistant rubber containing the crosslinked rubber particles (A) dispersed therein and (C) a silica filler having an average primary particle size of not less than 1 nm and not more than 50 nm which is contained in at least one of the crosslinked rubber particles (A) and the oil-resistant rubber (B). The wt. ratio of the crosslinked rubber particles (A) to the oil resistant rubber (B) in the rubber component ranges from 5/95 to 80/20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition for a fixing roll, that is, a fixing roll used as a material of a fixing roll constituting a toner fixing device in a printer or a copying machine by an electrophotographic method or an electrostatic recording method. It relates to a rubber composition.

[0002]

2. Description of the Related Art Generally, in an electrophotographic process, an electrostatic latent image formed on a photoreceptor is formed by executing steps such as charging, exposure, development, transfer, fixing and charge removal of the photoreceptor. The toner image is developed by the toner, and the resulting toner image is transferred and fixed to a transfer sheet to form a visible image. Various rolls are used in a mechanism for executing each step in such an electrophotographic process, and in these rolls, a request to precisely control an object to be processed in contact with the roll in accordance with a purpose is required. In recent years, the required characteristics of rubber materials have become increasingly severe.

[0003] In particular, the toner fixing device is constituted by a heating roll having a heat source and a pressure roll pressed against the heating roll, between which a recording material having an unfixed toner image is passed to record the unfixed toner image. In the fixing roll of such a fixing device, a toner material, a silicone oil resistance, a compression resistance, and a rubber material forming the roll are applied to a fixing roll of such a fixing device so that the toner can be satisfactorily fixed. Characteristics that are excellent in permanent set and mechanical strength are required.

Conventionally, a fixing roll has a rubber layer provided so as to cover the surface of a hollow metal core made of, for example, aluminum or the like, and a single-layer roll having a single layer of silicone rubber as the rubber layer. A two-layer roll having a lower non-addition type silicone rubber layer and an upper additional silicone rubber layer, such as a fluorine-modified silicone rubber between the lower and upper layers of such a two-layer roll,
A three-layer roll formed by forming a barrier layer for silicone oil applied to the surface of a fixing roll is used. The outer surface is coated with a release agent such as fluororesin or silicone rubber, a material having good heat resistance and abrasion resistance, or the outermost layer is coated with silicone rubber via an intermediate layer made of fluororubber. A fixing roll having a three-layer rubber layer having a lower layer is also known.
In particular, when an image forming apparatus using an electrophotographic method is a color copying machine in which control of image quality is important,
Fixing rolls having an outermost surface layer formed of silicone rubber have been suitably used.

On the other hand, in order to improve the physical strength of the silicone rubber, a means for dispersing an inorganic powder such as silica in the silicone rubber is known. In this means, the content ratio of the inorganic powder is practically used. Since it is necessary to set the fixing roll to a considerably high value of 20% by weight or more, the fixing roll obtained by the silicone rubber reinforced by such a means has an extremely high toner releasability even though its physical strength is good. As a result, there occurs a problem that the recording material is wrapped and the service life is shortened.

For the purpose of suppressing the decrease in the toner releasability, it has been proposed to improve the physical strength and the toner releasability by using a resinous polyorganosiloxane as a reinforcing agent. It is proposed by Japanese Patent Publication No. However, in recent years, with the spread of color copiers, there has been a demand for an increase in image forming speed, and as a result, the fixing temperature of the heating roll of the fixing device has been increasing, and the running cost has been reduced. As the life of the fixing roll is desired to be extended in accordance with the demand, the fixing set temperature is relatively high,
When used for a long period of time at a temperature set to 70 ° C. or higher, a fixing roll having a rubber layer made of an addition type silicone rubber mixed with a reinforcing material made of the above-mentioned resin-like polyorganosiloxane, There is a problem that the strength is reduced due to the deterioration and the life of the roll is significantly shortened.

As described above, in all of the conventional fixing rolls, the properties of the material of the rubber layer are insufficient, so that a single rubber layer alone cannot sufficiently satisfy the required performance.
For this reason, a method of providing a multi-layer rubber layer of a plurality of types of rubber has been adopted.However, a fixing roll having a multi-layer rubber layer naturally has a complicated manufacturing process and a high cost. Problem.

[0008]

As described above, the rubber material for forming the rubber layer of the fixing roll, which can exhibit good characteristics even with a single layer, has great advantages. Nevertheless, at present, there are no products with sufficient characteristics. An object of the present invention is to provide a rubber composition for a fixing roll capable of forming a fixing roll excellent in toner release property, low hardness, low compression set, mechanical strength and silicone oil resistance. Aim.

[0009]

Means for Solving the Problems The rubber composition for a fixing roll according to the present invention comprises crosslinked rubber particles (A) having a number average particle diameter of 20 μm or less, comprising a crosslinked silicone rubber having a toluene insoluble content of 30% by weight or more. An oil resistant rubber (B) in which the crosslinked rubber particles (A) are dispersed, and an average primary particle diameter of at least one of the crosslinked rubber particles (A) and the oil resistant rubber (B) of 1 to 50 nm or less. It is characterized by comprising a silica filler (C). Here, the ratio of the crosslinked rubber particles (A) to the oil-resistant rubber (B) may be in the range of 5/95 to 80/20 in terms of the weight of the crosslinked rubber particles (A) / oil-resistant rubber (B). preferable.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described specifically. The rubber composition for a fixing roll of the present invention comprises a crosslinked rubber particle (A) composed of a specific crosslinked silicone rubber and an oil resistant rubber (B) in which the crosslinked rubber particle (A) is dispersed, and a rubber component is constituted. This rubber component further contains a specific silica filler (C). Here, the silica filler (C) may be contained in only one of the crosslinked rubber particles (A) and the oil resistant rubber (B), or may be contained in both.

In the rubber composition of the present invention, the ratio of the crosslinked rubber particles (A) and the oil-resistant rubber (B) constituting the rubber component is 5% by weight of the crosslinked rubber particles (A) / oil-resistant rubber (B).
/ 95 to 80/20, preferably 10 /
90-70 / 30, more preferably 20 / 80-60
/ 40. If the proportion of the crosslinked rubber particles (A) is too small, the fixing roll made of the obtained rubber composition has insufficient toner release properties, while the crosslinked rubber particles (A)
If the ratio is too large, the fixing roll will have poor silicone oil resistance.

As a raw material of the crosslinked rubber particles (A) composed of a crosslinked silicone rubber, an uncrosslinked silicone rubber is used, and the kind thereof is not particularly limited. Examples thereof include polydimethylsiloxane, polymethylvinylsiloxane, and polymethylsiloxane. Examples include phenyl vinyl siloxane, polymethyl p-vinyl phenyl siloxane, polymethyl trifluoropropyl vinyl siloxane, silicone rubber comprising a modified form of these polyorganosiloxanes, and the like. These silicone rubbers can be used alone or in combination of two or more.

The crosslinked rubber particles (A) are particles having specific properties due to a crosslinked product of silicone rubber, and are contained in the oil resistant rubber (B) in a dispersed state. The crosslinked rubber particles (A) have a number average particle diameter of 20 μm or less, preferably 10 μm or less, more preferably 5 μm or less.
The crosslinked silicone rubber forming the crosslinked rubber particles (A) must have a toluene insoluble content of 30% by weight or more, preferably 50% by weight or more, more preferably 70% by weight or more.

The number average particle diameter of the crosslinked rubber particles (A) is 20
When the particle size exceeds μm, the resulting rubber composition has poor abrasion resistance. On the other hand, when the toluene-insoluble content is less than 30% by weight, the degree of crosslinking of the crosslinked silicone rubber is low. In the obtained rubber, a part of the uncrosslinked silicone rubber bleeds out on the surface. As a result, in the obtained fixing roll, the formed toner image may be unclear.

The number average particle diameter of the crosslinked rubber particles (A) is determined by freeze-cutting the rubber composition, observing the cut surface with a transmission electron microscope, and finding that the number of crosslinked rubber particles (A) is about 50 to 100. Arbitrarily selecting three existing surface regions, examining the major axis and number of the crosslinked rubber particles (A) for each of them, calculating the number average particle diameter from the results, and calculating the number for the three regions obtained. It is determined as the average of the average particle diameter values.

The toluene-insoluble content of the crosslinked silicone rubber is an index indicating the degree of crosslinking, and a sample is precisely weighed and placed in a basket of 325 mesh wire mesh, and left in a large excess of boiling toluene for 6 hours. It is a value obtained by taking out the basket later, drying the insoluble matter, weighing the cage, and dividing the weight by the total weight of the sample before melting. When the silicone rubber is crosslinked after blending with the oil resistant rubber (B),
A sample of the blended rubber composition was precisely weighed and placed in a 325 mesh wire mesh, left in a large excess of boiling toluene, taken out after 6 hours, and the toluene solution portion was treated with a rotary evaporator. By removing the toluene and drying with a vacuum dryer, the polymer in the toluene solution is taken out and precisely weighed, and the polymer in the toluene solution is measured by nuclear magnetic resonance (NMR) to obtain a crosslinked silicone. Determine the composition ratio of the rubber component and the oil-resistant rubber component to determine the weight of the dissolved silicone rubber component,
This value is a value obtained by a method of calculating the ratio of the insolubilized silicone rubber from this value, the weight of the sample, and the blend ratio of the silicone rubber.

The oil-resistant rubber (B) in the present invention includes:
For example, chloroprene rubber, acrylic rubber, acrylonitrile-butadiene rubber or hydrogenated acrylonitrile-butadiene rubber, chlorosulfonated polyethylene rubber, ethylene-acrylate ester rubber, epichlorohydrin rubber, epichlorohydrin-ethylene oxide rubber, fluorine rubber and the like can be mentioned. Among them, preferred are acrylic rubber, fluoro rubber, acrylonitrile-butadiene rubber and hydrogenated acrylonitrile-butadiene rubber, and more preferred are acrylic rubber and fluoro rubber. These can be used alone or 2
More than one species can be used in combination.

The acrylic rubber is obtained by copolymerizing a polymer of an alkyl (meth) acrylate or an alkyl (meth) acrylate as a main component with a crosslinkable monomer having an active group. Copolymers can be mentioned. Here, specific examples of the alkyl ester of (meth) acrylic acid include ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, methoxyethyl (meth) acrylate, and (meth) acrylate.
One or more kinds such as ethoxyethyl acrylate can be mentioned. The acrylic rubber may be, for example, one obtained by copolymerizing one or more monomers such as acrylonitrile, styrene, 1,3-butadiene, isoprene, chloroprene, ethylene, propylene, vinyl acetate, and acrylic acid. Good.

As described above, the acrylic rubber may be a copolymer of a crosslinkable monomer having an active group. Examples of such a crosslinkable monomer include an epoxy group, a halogen atom and a carboxy group. Or a monomer having a carbon-carbon double bond in the side chain, for example, dihydrodicyclopentenyl acrylate, dihydrodicyclopentenyl methacrylate, dihydrodicyclopentenyl itaconate, dihydrodicyclopentenyl maleate, dihydrodicyclo fumarate Pentenyl, dihydrodicyclopentenyloxyethyl acrylate, dihydrodicyclopentenyloxyethyl methacrylate, dihydrodicyclopentenyloxyethyl itaconate, dihydrodicyclopentenyloxyethyl maleate, dihydrodicyclopentenyloxyethyl fumarate, 2-methyl Methacryloyloxyethyl, vinyl methacrylate, vinyl acrylate, allyl acrylate, allyl methacrylate, dicyclopentadiene, methyl dicyclopentadiene, ethylidene norbornene,
1,1-dimethylpropenyl methacrylate, 1,1-
Dimethylpropenyl acrylate, 3,3-dimethylbutenyl methacrylate, 3,3-dimethylbutenyl ether, 1-acryloyloxy-1-phenylethene,
Examples thereof include 1-acryloyloxy-2-phenylethene, 1-methacryloyloxy-2-phenylethene, and 1-methacryloyloxy-2-phenylethene. These can be used alone or in combination of two or more.

As a preferred fluororubber as the oil-resistant rubber (B), a polymer obtained from a fluoromonomer or a copolymer of a fluoromonomer and a monomer copolymerizable therewith is used. it can. Here, preferred fluorine-containing monomers include vinylidene fluoride, hexafluoropropene, pentafluoropropene, trifluoroethylene, trifluorochloroethylene, tetrafluoroethylene, vinyl fluoride, perfluoro (methyl vinyl ether), perfluoro (Propylvinylidene) and the like can be used. Examples of the monomer copolymerizable with the fluorine-containing monomer include vinyl compounds such as acrylic acid esters, olefin compounds such as propylene or diene compounds, and halogen-containing vinyl compounds containing a chlorine atom, a bromine atom or an iodine atom. And the like. Examples of preferred copolymer fluororubbers as the oil-resistant rubber (B) include vinylidene fluoride-propylene hexafluoride copolymer, vinylidene fluoride-propylene hexafluoride-tetrafluoroethylene terpolymer, and tetrafluoride. Examples include an ethylene-propylene copolymer and an ethylene tetrafluoride-vinylidene fluoride-propylene terpolymer.

In order to produce a rubber mixture comprising a rubber component in the rubber composition for a fixing roll of the present invention, that is, a crosslinked rubber particle (A) having the above-mentioned properties and an oil-resistant rubber (B) in which the rubber component is dispersed. Can preferably utilize any of the following [Method 1] to [Method 3].

[Method 1] A crosslinked silicone having a toluene insoluble content of 30% by weight or more is obtained by uniformly blending an uncrosslinked silicone rubber and an oil-resistant rubber (B) and then crosslinking the uncrosslinked silicone rubber. A method in which crosslinked rubber particles (A) made of rubber and having a number average particle diameter of 20 μm or less are formed in oil-resistant rubber (B). [Method 2] A crosslinked rubber particle (A) having a number average particle diameter of 20 µm or less made of a crosslinked silicone rubber having a toluene-insoluble content of 30% by weight or more is independently produced, and this is mixed with an oil-resistant rubber (B) by a mixer. A method of mixing using a roll or the like. [Method 3] An emulsion of crosslinked rubber particles (A) having a number-average particle diameter of 20 μm or less made of a crosslinked silicone rubber having a toluene insoluble content of 30% by weight or more was produced. A method of graft-polymerizing the monomer for (B).

As specific means of the above [Method 1],
The following method is preferred. (Method 1A) The uncrosslinked silicone rubber and the oil resistant rubber (B) are kneaded using a kneader until the kneading torque becomes constant, and in that state, a silicone rubber crosslinking agent is added while kneading. A method of generating a crosslinked rubber particle (A) in the oil-resistant rubber (B) by proceeding a crosslinking reaction of the silicone rubber while maintaining the temperature at an appropriate temperature.

Here, as the kneading machine, a usual kneading machine such as a roll, an internal mixer, a Banbury mixer and a kneader can be used. As the crosslinking agent for silicone rubber, a combination of a polyvalent hydrosilyl compound and a catalyst of a transition metal compound of Group VIII of the periodic table (for example, preferably a platinum catalyst), peroxide, sulfur, a sulfur compound, etc. are used. When the silicone rubber is a modified silicone rubber into which carbinol or the like is introduced, a polyfunctional isocyanate, an epoxy compound or the like is used.

The polyhydric hydrosilyl compound used as a crosslinking agent for the silicone rubber is not particularly limited in its chemical structure, but causes a hydrosilylation reaction with the polyorganosiloxane to form a crosslinked structure. Need to be something. Specifically, a polyorganohydrogensiloxane having at least two hydrogen atoms bonded to a silicon atom in one molecule is preferably used. Such polyorganohydrogensiloxanes are well known, and specific examples thereof include the following (formula 1)
To (Equation 7).

[0026]

Embedded image (Wherein, R ¹ is an alkyl group having 1 to 18 carbon atoms, m ≧
0, n ≧ 2. )

[0027]

Embedded image (In the formula, R ¹ is an alkyl group having 1 to 18 carbon atoms.)

[0028]

Embedded image (In the formula, R ¹ represents an alkyl group having 1 to 18 carbon atoms, and R ² represents a butyl group or a phenyl group.)

[0029]

Embedded image (Wherein, R ¹ is an alkyl group having 1 to 18 carbon atoms, m ≧
0 and two n are values whose sum is 2 or more. )

[0030]

Embedded image (In the formula, R ¹ represents an alkyl group having 1 to 18 carbon atoms, R ³ represents a methyl group or a phenyl group, and p ≧ 0.)

[0031]

Embedded image (Wherein, R ¹ is an alkyl group having 1 to 18 carbon atoms, q ≧
0, r ≧ 1. )

[0032]

Embedded image (Wherein, R ¹ is an alkyl group having 1 to 18 carbon atoms, s ≧ 1
It is. )

(Method 1B) An uncrosslinked silicone rubber having a silanol group and the oil-resistant rubber (B) are kneaded using a kneading machine, and a crosslinking component that undergoes hydrolysis and condensation reaction with the silanol group is subjected to the condensation. Together with the catalyst for the reaction,
A method of producing crosslinked rubber particles (A) composed of a crosslinked silicone rubber in an oil resistant rubber (B) by subjecting a silicone rubber to hydrolysis and condensation reaction at an appropriate temperature. Here, as the crosslinkable component, a silicon compound containing two or more hydrolyzable groups in the molecule that hydrolyze and undergo a condensation reaction with a silanol group is used. Examples of the catalyst for this reaction include heavy metal compounds, amines and quaternary ammonium salts.

In the above (method 1B), the silicon compound used as a crosslinkable component includes, for example, a compound of the formula R _a
SiX _4-a (Formula 8) (where R is a monovalent hydrocarbon group,
X is a hydrolyzable group bonded to a silicon atom. )
Or a partially hydrolyzed condensate thereof. In the case of a silane, a is 0 or 1, and in the case of a partially hydrolyzed condensate, a is 0.
It is an appropriate value selected from the range of ~ 3, but in any case, it is necessary to have two or more X in one molecule.

Examples of X include an acyloxy group such as an acetoxy group; an alkoxy group such as an isopropoxy group and a butoxy group; an oxime group such as an acetone oxime group and a methyl ethyl ketoxime group; a dimethylamino group and a diethylamino group. An amino group such as a group; an aminooxy group such as a dimethylaminooxy group or a diethylaminooxy group; an amide group such as a methylcarbonylmethylamino group; an isocyanate group; a group or an atom selected from a hydroxyl group and a chlorine atom.

In the kneading steps of (Method 1A) and (Method 1B), the kneading torque increases with the progress of the crosslinking reaction of the silicone rubber, but the kneading may be continued until the kneading torque becomes constant. preferable. As a result, the silicone rubber is divided into a sufficiently small particle size and the crosslinking reaction proceeds sufficiently, so that the crosslinked rubber particles (A) to be produced surely have the desired property, that is, the toluene-insoluble content is reduced. It can be 30% by weight or more and the number average particle diameter is 20 μm or less. In kneading, a third component such as a usual filler and processing aid can be added before the step or during the kneading step.

As a specific means for producing the crosslinked rubber particles (A) used in the above [Method 2], the following method can be mentioned. (Method 2A) A method in which an uncrosslinked silicone rubber is crosslinked with a crosslinking agent for silicone rubber to produce a crosslinked silicone rubber, which is mechanically pulverized at a low temperature or a normal temperature with a ball mill or the like. Here, as the crosslinker for silicone rubber, the one shown in the above (Method 1A) can be used.

(Method 2B) To an uncrosslinked silicone rubber having a silanol group, a crosslinkable component which hydrolyzes and condenses with the silanol group is added together with a catalyst for the reaction, and the silicone rubber undergoes hydrolysis and condensation reaction. A cross-linked silicone rubber is manufactured by mechanically pulverizing the crosslinked silicone rubber at a low or normal temperature with a ball mill or the like. Here, as the crosslinkable component and the catalyst, those shown in the above (Method 1B) can be used. (Method 2C) A latex made of uncrosslinked silicone rubber particles having a number average particle diameter of 20 μm or less is produced, and the latex is treated with a peroxide or an electron beam to crosslink the silicone rubber to form crosslinked rubber particles. A method for obtaining (A).

In the above (method 2C), the latex composed of uncrosslinked silicone rubber particles is obtained by dissolving a solution obtained by dissolving uncrosslinked silicone rubber in a solvent such as toluene or hexane in water in which an emulsifier is dispersed. Into an emulsion, and the solvent can be removed from the emulsion to produce the emulsion. In order to obtain an emulsion, a method using a homomixer having a high-speed stirring blade or a high-speed pipe emulsifier, or other known methods can be used.

In order to produce the above-mentioned latex, a method of treating uncrosslinked silicone rubber with an organic solvent, an emulsifier and about 20% by weight or less of water using a multi-screw extruder is adopted. Can also.
Further, a cyclic siloxane oligomer such as octamethylcyclotetrasiloxane and a gelling agent such as a polyfunctional alkoxysilane are emulsified using a known anionic or cationic surfactant in the presence of an acid or alkaline siloxane polymerization catalyst. Silicone rubber latex can also be obtained by polymerization.

In the above method for producing latex,
In any case, a stable latex can be obtained by adding a partially saponified polyvinyl alcohol, an ethylene-vinyl acetate copolymer, a modified polyethylene wax, or the like as an emulsification aid.

As specific means of the above [Method 3],
An ordinary organosiloxane and a graft-linking agent having both an atomic group containing an ethylenically unsaturated group and an alkoxysilyl group are polycondensed in the presence of a catalyst, and the resulting modified silicone rubber emulsion is added to an oil-resistant rubber ( Examples of the method include a method for obtaining the monomer for B) by graft polymerization using a polymerization initiator.

The rubber composition for a fixing roll of the present invention comprises a rubber component in which crosslinked rubber particles (A) are dispersed in an oil resistant rubber (B) and a silica filler (C). is there. Specifically, the silica filler (C) is contained in one or both of the crosslinked rubber particles (A) and the oil-resistant rubber (B) constituting the rubber component. As described above, when the silica filler (C) is contained in the rubber component, the mechanical strength of the obtained rubber is increased, and the effect of preventing the roll surface from being damaged in the fixing step is obtained.

In the present invention, as the silica filler (C), those having an average primary particle diameter of 1 nm or more and 50 nm or less are used. When a silica filler having a primary particle average diameter of more than 50 nm is used, the finally obtained rubber has a small mechanical strength, whereas a silica filler having a primary particle diameter of less than 1 nm is liable to be scattered. It is not preferable because there is a problem. As specific examples of the silica filler (C), fumed silica and precipitated silica can be used, and those obtained by hydrophobizing these silicas with various surface treatment agents can also be used. Among these, fumed silica is preferable, and fumed silica obtained by subjecting the fumed silica to a hydrophobic treatment is particularly preferable. According to these silica fillers (C), a rubber excellent in mechanical strength, low in hardness and excellent in low compression set can be formed.

As surface treatment agents for hydrophobizing silica, for example, (CH ₃ ) ₃ SiCl, (CH ₃ ) ₂
SiCl ₂ , [(CH ₃ ) ₃ Si] ₂ NH, [(C
H ₃ ) ₂ SiO] ₄ and RSi (OR ¹ ) ₃ . Here, R represents an alkyl group. Silica hydrophobized by such a surface treatment agent has high affinity for the rubber component.

The method of adding the silica filler (C) is a method of previously mixing the uncrosslinked silicone rubber with a closed kneader, an open roll machine, or the like, or a method of mixing the silicone rubber and the oil resistant rubber (B). Alternatively, a method of adding after mixing can be used. The ratio of the silica filler (C) is 0.1 to 100 parts by weight of the rubber component composed of the crosslinked rubber particles (A) and the oil-resistant rubber (B).
To 20 parts by weight, preferably 0.5 to 15 parts by weight, more preferably 1 to 10 parts by weight. If the proportion of the silica filler (C) is too small, the resulting rubber will have low mechanical strength, while if too large, the resulting rubber will have poor compression set resistance.

The above silica filler (C) is mixed with the rubber component obtained by the above [Method 1] to [Method 3], in which crosslinked rubber particles (A) are dispersed in oil resistant rubber (B). For example, by kneading using an ordinary open roll or a closed kneader, the silica filler (C) is dispersed and contained in the oil resistant rubber (B) together with the crosslinked rubber particles (A). A rubber composition is obtained. Further, the rubber composition in which the silica filler (C) is contained in the crosslinked rubber particles (A) is obtained by mixing the silica filler (C) in the uncrosslinked silicone rubber for obtaining the crosslinked rubber particles (A).
Is dispersed and kneaded with the oil-resistant rubber (B), followed by crosslinking the uncrosslinked silicone rubber, or by crosslinking the uncrosslinked silicone rubber in which the silica filler (C) is dispersed. The crosslinked rubber particles (A) can be manufactured by kneading them into the oil-resistant rubber (B).

In order to crosslink (vulcanize) the rubber composition according to the present invention, a sulfur-based vulcanizing agent, an organic peroxide, a quinoid vulcanizing agent, a resin may be used depending on the type of rubber constituting the oil-resistant rubber (B). Vulcanizing agents, metal oxide vulcanizing agents, sulfur-containing organic compounds, amine vulcanizing agents, triazine vulcanizing agents, polyol vulcanizing agents, metal soap vulcanizing agents, crosslinkers such as maleimide vulcanizing agents are appropriately selected. Used as When a sulfur-based vulcanizing agent is used as a cross-linking agent, a vulcanization accelerator can be used in combination, and when an organic peroxide is used, a co-cross-linking agent can be used in combination. it can.

In the rubber composition for a fixing roll of the present invention, various additives used in a usual rubber composition can be blended as long as the properties of the fixing roll are not impaired. Examples of such additives include carbon black such as conductive carbon black, a conductivity-imparting substance composed of an electron-conductivity imparting substance or an ionic-conductivity imparting substance, a white filler, a lubricant, a metal oxide, a softener, Plasticizers, anti-aging agents, pigments, dyes, processing aids, activators, coupling agents, internal mold release agents, anti-scorch agents, foaming agents, foaming assistants, antibacterial agents and the like can be mentioned.

The rubber obtained from the rubber composition of the present invention comprises
Rolls that make up the toner fixing unit in printers and copiers using electrophotographic processes, electrostatic recording processes, etc.
That is, the fixing roll is used as a material of a heating roll or a pressure roll, whereby a fixing roll excellent in toner releasing property, low hardness, low compression set, mechanical strength and silicone oil resistance can be obtained. Specifically, a fixing roll having a rubber layer of the rubber composition of the present invention is used under conditions where silicone oil is always applied, even if it has a single rubber layer, due to its properties. thing,
Alternatively, it is suitable for use at a relatively high fixing set temperature, and particularly suitable as a heating roll. Of course,
The rubber composition of the present invention is not limited to a constitution of a fixing roll having a single rubber layer, but can be used to constitute one layer of a multilayer constitution.

[0051]

The present invention will now be described in more detail with reference to Examples, but it should not be construed that the invention is limited thereto. In addition, "part" means "part by weight". Example 1 2.0 parts of p-vinylphenylmethyldimethoxysilane and 98.0 parts of octamethylcyclotetrasiloxane were mixed, and this was placed in 300 parts of distilled water in which 2.0 parts of dodecylbenzenesulfonic acid was dissolved. It was emulsified and dispersed by stirring with a homomixer for 3 minutes. The mixed solution was transferred to a separable flask equipped with a condenser, a nitrogen inlet and a stirrer, heated at 90 ° C. for 6 hours while stirring and mixing, and cooled at 5 ° C. for 24 hours to complete the condensation to thereby obtain the modified polyorgano-organo. A siloxane was produced. The condensation rate of octamethylcyclotetrasiloxane in the modified polyorganosiloxane was 89.5%.

This modified polyorganosiloxane emulsion was neutralized to pH 7 with an aqueous sodium carbonate solution to obtain a crosslinked silicone rubber emulsion. This is designated as Emulsion E-1. In addition, when the polymer of this emulsion E-1 was measured by salting out, the average degree of polymerization was 5000 in terms of the number of silicon atoms, and the ratio of p-vinylphenyl groups in the organic groups of the polymer was 0.3%. .

Next, according to the polymerization recipe shown in Table 1, 30 parts of the above-mentioned emulsion E-1, 69 parts of ethyl acrylate as a monomer for oil resistant rubber and allyl methacrylate 1 were placed in an autoclave having an internal volume of 6 liters. Department,
0.3 part of potassium phosphate, 0.005 part of ferrous sulfate and 0.02 part of paramenthane hydroperoxide as a radical polymerization initiator and 0.1 part of sodium dodecylbenzenesulfonate as an emulsifier were added, and the reaction temperature was increased. Polymerization was performed at 30 ° C. After the polymerization conversion reached 90%, 0.2 part of N-diethylhydroxyamine was added to terminate the polymerization. Next, 1 part of alkylated diphenylamine was added as a stabilizer to the reaction solution, unreacted monomers were removed by steam distillation, and aluminum sulfate was added to coagulate the resulting polymer.

[0054]

[Table 1]

The polymer obtained here is washed with water and then dried using a vacuum drier to obtain a mixed rubber comprising crosslinked rubber particles (A) made of crosslinked silicone rubber dispersed in oil resistant rubber (B). Was manufactured. This is designated as Sample S-1. And about the crosslinked rubber particle (A) in this sample S-1,
The toluene insoluble content and the number average particle size were determined. Table 2 shows the results.

Next, with respect to 100 parts of the sample S-1,
According to the formulation shown in Table 3, stearic acid 1 as a lubricant
Parts, 5 parts of a silica filler C1, 1 part of a crosslinking agent and 1 part of a crosslinking aid 1 were blended to prepare a rubber composition. Here, the silica filler C1 is hydrophobic silica “Aerosil R972” (manufactured by Nippon Aerosil Co., Ltd.) having a primary particle average diameter of 20 nm and surface-treated with dimethyldichlorosilane, and the crosslinking agent is 1,3-bis (t- Butyl peroxyisopropyl) benzene “Percadox 14/40”
(Nippon Kayaku Akzo Co., Ltd.), and the crosslinking assistant 1 is N, N'-metaphenylenebismaleimide "Barnock PM" (Ouchi Shinko Chemical Co., Ltd.). Further, the rubber composition thus obtained was subjected to a primary treatment of heating at 170 ° C. for 20 minutes and a crosslinking treatment by a secondary treatment of heating at 200 ° C. for 4 hours to produce a vulcanized rubber.

Example 2 100 parts of linear polymethylvinylsiloxane having an average degree of polymerization of 5500 and 1 mol% of organic groups bonded to silicon atoms being vinyl groups and the remainder being methyl groups, and an average primary particle diameter Surface treatment of fine powder silica “Aerosil 130” (manufactured by Nippon Aerosil Co., Ltd.) with a diameter of 20 nm [(CH ₃ ) ₂ Si
O] ₄ and 15 parts of silica filler C2 hydrophobized to obtain an uncrosslinked silicone rubber composition by kneading until uniform. Next, 34.5 parts of this uncrosslinked silicone rubber composition and 70 parts of a fluoro rubber "Afras 150E" (manufactured by Asahi Glass Co., Ltd.) were used as the oil-resistant rubber, and the terminal was blocked with a trimethylsilyl group as a crosslinking agent for the silicone rubber. Then, 2 parts of a linear polymethyl hydrogen siloxane composed of 20 methyl hydrogen siloxane units are used, and these are sequentially put into a rubber mixer set at a temperature of 60 to 80 ° C. and a rotation speed of 60 rpm to be mixed. When it is kneaded and becomes homogeneous, chloroplatinic acid 1% by weight
And further kneaded by adding an isopropanol solution containing
After about 80 minutes had passed and the state became uniform again, the contents were discharged. The composition obtained here is a composition in which crosslinked rubber particles (A) are dispersed in oil-resistant rubber (B) and silica filler (C) is contained in the crosslinked rubber particles (A). This is designated as Sample S-2. For the crosslinked rubber particles (A) in this sample S-2, the toluene insoluble content and the number average particle size were determined. Table 2 shows the results.

Next, with respect to 100 parts of the sample S-2,
According to the formulation shown in Table 3, 1 part of stearic acid, 5 parts of silica filler C2, and 1 part of a crosslinking agent and 3 parts of a crosslinking aid 2 were blended to prepare a rubber composition. Here, the crosslinking assistant 2 is triallyl isocyanurate “Taiku” (manufactured by Nippon Kasei Co., Ltd.). In the obtained product, the crosslinked rubber particles (A) and the silica filler (C) are dispersed in the oil resistant rubber (B), and the silica filler (C) is further included in the crosslinked rubber particles (A). The composition contained. The rubber composition thus obtained was subjected to a crosslinking treatment under the same conditions as in Example 1 to produce a vulcanized rubber.

Example 3 100 parts of linear polydimethylsiloxane having a hydroxyl group bonded to a silicon atom at both ends and having an average degree of polymerization of 100, and fine powder silica "Aerosil 130" having an average primary particle diameter of 20 nm A non-crosslinked silicone rubber composition was obtained by kneading 15 parts of silica filler C2 whose surface was hydrophobized with a treating agent [(CH ₃ ) ₂ SiO] ₄ with a Henschel mixer until the surface became uniform. I got something.
Next, an acrylic rubber “AREX1” was used as the oil-resistant rubber (B).
00 "(manufactured by Nippon Synthetic Rubber Co., Ltd.), 57.5 parts of the uncrosslinked silicone rubber composition, and a partially hydrolyzed / condensed product of ethyl silicate" ethyl silicate-40 "(silicon dioxide 40 0.5% by weight (manufactured by Union Carbide Co.)
° C., and kneaded sequentially in a rubber mixer set at a rotation speed of 60 rpm, and kneaded. When the mixture became uniform, 0.1 part of dibutyltin laurate was further added and kneaded. The contents were discharged. The composition obtained here is a composition in which the crosslinked rubber particles (A) are dispersed in the oil-resistant rubber (B) and the silica filler (C) is contained in the crosslinked rubber particles (A). This is designated as Sample S-3. For the crosslinked rubber particles (A) in this sample S-3, the toluene insoluble content and the number average particle size were determined. Table 2 shows the results.

Next, for 100 parts of this sample S-3,
According to the formulation shown in Table 3, 1 part of stearic acid, 2 parts of silica filler C1, and 1 part of crosslinking agent and 1 part of crosslinking aid 1 were blended to produce a rubber composition. The rubber composition thus obtained was subjected to a crosslinking treatment under the same conditions as in Example 1 to produce a vulcanized rubber.

Comparative Example 1 A millable silicone rubber "K" containing finely divided silica
E8751-U ”(Shin-Etsu Chemical Co., Ltd.) and acrylic rubber“ AREX100 ”(oil-resistant rubber) (Nippon Synthetic Rubber Co., Ltd.)
And, by weight, silicone rubber / acrylic rubber = 40/6
By mixing at a mixing ratio of 0, a rubber component for comparison was produced.
This is designated as Sample R-1. The insoluble content and the average particle size of the silicone rubber of this comparative sample R-1 were determined. Table 2 shows the results. Next, a rubber composition was prepared in the same manner as in Example 1 except that the sample R-1 was used instead of the sample S-1 as a rubber component. Crosslinking treatment was performed under the same conditions as in the above to prepare a vulcanized rubber.

Comparative Example 2 A rubber composition was prepared in the same manner as in Example 1 except that diatomaceous earth (average structure particle diameter: 30 nm, manufactured by Nippon Talc) was used instead of the silica filler C1. Further, the obtained rubber composition was subjected to a crosslinking treatment under the same conditions as in Example 1 to produce a vulcanized rubber.

Comparative Example 3 A millable silicone rubber "KE875" was used as a rubber component.
Using only 1-U (manufactured by Shin-Etsu Chemical Co., Ltd.), 1 part of stearic acid and 1 part of a cross-linking agent were blended according to the formulation shown in Table 3 to produce a rubber composition. The rubber composition thus obtained was subjected to a crosslinking treatment under the same conditions as in Example 1 to produce a vulcanized rubber.

Using each of the vulcanized rubbers obtained in Examples 1 to 3 and Comparative Examples 1 to 3 as samples, the presence or absence of bleed-out of silicone rubber, tensile strength, elongation at break, compression set and resistance to silicone The oil properties were examined under the following conditions. Table 4 shows the results. <Hardness> Measured according to JIS K6301.
(JIS-A) <Compression set> Measured at a temperature of 180 ° C. for a period of 22 hours in accordance with JIS K6301. <Silicone oil resistance> (In Table 4, it is described as "oil resistance".) Silicone oil for release agent "TSF451-
Using "1000" as the immersion oil, the sample was immersed at a temperature of 220 ° C for 22 hours, and the volume change before and after the immersion was measured.

[0065]

[Table 2]

[0066]

[Table 3]

[0067]

[Table 4]

From Table 4, it can be seen that the rubbers of the rubber compositions according to Examples 1 to 3 have no mechanical bleed-out of silicone rubber, high mechanical strength, low hardness, low compression set, and silicone-resistant oil. It is clear that the sex is great. On the other hand, in Comparative Example 1 using the comparative sample R-1 in which the number average particle diameter of the crosslinked rubber particles was large, bleed out of the silicone rubber occurred, the tensile strength was small, the compression set was large, and Comparative Example 2 using diatomaceous earth as an agent also has a low tensile strength and a large compression set. In Comparative Example 3 containing no oil-resistant rubber, the silicone oil resistance was very poor.

Further, Example 1 obtained as described above was used.
A fixing roll having a single rubber layer was manufactured using each of the rubber compositions according to Example 3 and the same fixing roll 2
Using the books as a heating roll and a pressure roll, a fixing device was constructed. Then, using a color copier equipped with this fixing device, the set fixing temperature of the heating roll was set to 180 ° C.
When a color image forming test was performed a large number of times (20,000 times in total) at an image forming speed of 30 times / min while constantly applying silicone oil as a releasing agent to the heating roll, a very good image quality was obtained. It was confirmed that a color image was formed stably over a long period of time, and that the phenomenon of winding of the recording material did not occur.

[0070]

According to the rubber composition for a fixing roll of the present invention, it has excellent silicone oil resistance, low compression set, low hardness, no bleed-out, and sufficient opportunity strength. Is obtained, and a fixing roll having excellent characteristics can be provided.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toru Hasegawa 2--11-24 Tsukiji, Chuo-ku, Tokyo Inside Nippon Gosei Rubber Co., Ltd. (72) Kenji Yasuda 2-11-24 Tsukiji, Chuo-ku, Tokyo Nippon Synthetic Rubber Co., Ltd.

Claims (2)

[Claims] 1. A crosslinked rubber particle (A) comprising a crosslinked silicone rubber having a toluene insoluble content of 30% by weight or more and having a number average particle size of 20 μm or less, and an oil-resistant rubber (A) in which the crosslinked rubber particle (A) is dispersed. B) and the crosslinked rubber particles (A)
And 1 contained in at least one of the oil-resistant rubber (B)
A rubber composition for a fixing roll, comprising a silica filler (C) having an average secondary particle diameter of 1 to 50 nm. 2. The ratio of the crosslinked rubber particles (A) to the oil-resistant rubber (B) is within the range of 5/95 to 80/20 by weight of the crosslinked rubber particles (A) / oil-resistant rubber (B). Claim 1
The rubber composition for a fixing roll according to the above.