JP2019164244A - Sponge roller and image forming apparatus - Google Patents

Abstract

To provide a sponge roller excellent in durability and an image forming apparatus including the sponge roller.SOLUTION: There is provided a sponge roller that has a shaft body and an elastic layer formed on the outer peripheral surface of the shaft body, where the elastic layer is formed of a millable type silicone rubber, a crosslinking agent, and unexpanded micro balloon; the elastic layer contains filler; the content of the filler in the elastic layer is 1.0 mass% or more and 40.0 mass% or less; when the elastic modulus in the longitudinal direction of the elastic layer is MD, and the elastic modulus in the thickness direction is TD, MD/TD is 0.90 or more and less than 1.60. Also provided is an image forming apparatus including the sponge roller.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a sponge roller having excellent durability and an image forming apparatus including the sponge roller.

  Various types of image forming apparatuses using an electrophotographic system are employed in laser printers, copiers, video printers, facsimiles, and complex machines of these. An image forming apparatus using an electrophotographic system includes a shaft body and an elastic layer formed on an outer peripheral surface thereof. For example, a cleaning roller, a toner supply roller, a charging roller, a developing roller, a transfer roller, a pressure roller, paper Various printing sponge rollers such as a feed conveyance roller and a fixing roller are provided.

  In order to make the elastic layer in these sponge rollers have a porous structure, a foaming agent is used at the time of forming the elastic layer. As a method of using the foaming agent in forming the elastic layer of the sponge roller, for example, Patent Literature Reference numeral 1 denotes a fixing rotator having a built-in heat source, in which unfixed toner is carried in a nip portion between the fixing rotator and a pressure unit that is pressed against the fixing rotator via a recording medium. In a method for manufacturing a fixing member that constitutes a fixing rotating body that conveys the recorded recording medium and fixes the unfixed toner to the recording medium, the unvulcanized addition type silicone rubber contains a foaming agent or expanded particles, and A method for producing a fixing member is disclosed, which contains carbon fiber, performs primary vulcanization and foaming, and then performs secondary vulcanization.

  In addition, the elastic layer of the sponge roller generally contains a reinforcing filler to reinforce the elastic layer (see, for example, Patent Document 2).

JP 2011-227512 A JP 2005-292218 A

  Here, in a sponge roller in which cells are formed using a foaming agent as in Patent Document 1, it is preferable to use a filler as described in Patent Document 2 to reinforce the elastic layer. With the advancement of the forming apparatus, further improvement in durability is required. Accordingly, the present invention has been made in view of the above problems, and an object thereof is to provide a sponge roller excellent in durability and an image forming apparatus including the sponge roller.

  The inventors of the present invention have intensively studied to solve the above problems. As a result, it was found that the above problem can be solved by using an unexpanded microballoon as a foaming agent for forming the elastic layer, and further adjusting the filler content in the elastic layer and predetermined parameters of the elastic layer. The present invention has been completed. Specifically, the present invention provides the following.

  (1) A first aspect of the present invention is a sponge roller having a shaft body and an elastic layer formed on the outer peripheral surface of the shaft body, the elastic layer comprising a millable silicone rubber, a crosslinking agent, And the elastic layer contains a filler, and the content of the filler in the elastic layer is 1.0% by mass or more and 40.0% by mass or less, and the elasticity The sponge roller has MD / TD of 0.90 or more and less than 1.60, where MD is the elastic modulus in the longitudinal direction of the layer and TD is the elastic modulus in the thickness direction.

  (2) A second aspect of the present invention is the sponge roller according to (1), characterized in that the hardness decrease measured by a 25% compression durability test method is 8 points or less.

  (3) A third aspect of the present invention is an image forming apparatus including the sponge roller according to (1) or (2).

  The sponge roller of the present invention uses an unexpanded microballoon as a foaming agent, and further, the content of the filler in the elastic layer is 1.0% by mass or more and 40.0% by mass or less. When the elastic modulus is MD and the elastic modulus in the thickness direction is TD, MD / TD is 0.90 or more and less than 1.60, so that the durability is excellent.

It is explanatory drawing which shows the sponge roller of this invention. It is explanatory drawing which shows an example of the image forming apparatus formed by incorporating the sponge roller of this invention in the fixing device. It is a schematic diagram which shows the durability test apparatus used suitably for implementing the durability test of the sponge roller of this invention.

<Sponge roller>
As shown in FIG. 1, the sponge roller 1 as an example of the present invention includes a shaft body 2 also called a cored bar, and an elastic layer 3 formed on the outer peripheral surface of the shaft body. Reference numeral 4 denotes a coating layer such as a fluororesin layer provided on the surface of the elastic layer 3 as necessary.

[Shaft]
The shaft body is a long cylindrical body called a so-called metal core that is usually formed of iron, aluminum, stainless steel, brass, or the like. The shaft body is adjusted to an appropriate diameter and axial length according to the image forming apparatus to be mounted.

  When a sponge roller is incorporated in the image forming apparatus, the shaft body usually has a diameter of 4.0 mm or more and 60 mm or less, and the shaft length from one end to the other end is usually 120 mm or more and 1200 mm or less.

[Elastic layer]
The elastic layer is formed from millable silicone rubber, a crosslinking agent, and an unexpanded microballoon, and the elastic layer contains a filler. The elastic layer has a sponge-like form including cells formed by unexpanded microballoons.

(Millable silicone rubber)
Millable silicone rubber is similar to unvulcanized compounded rubber of natural rubber and ordinary synthetic rubber in a state before curing, and can be plasticized and mixed with a kneading roll machine or a closed mixer. Silicone rubber compound.

The millable silicone rubber contains at least the following components (A) and (B), and preferably further contains the following components (C) to (E).

Suitable millable silicone rubber is
(A) The following average composition formula (I)
R ¹ _a SiO _{(4-a) / 2} (I)
(In the formula, R ¹ represents the same or different unsubstituted or substituted monovalent hydrocarbon group, and a is a positive number of 1.95 to 2.05.)
An organopolysiloxane having a degree of polymerization represented by 100 or more,
(B) Filler (C) The following general formula (II)
R ² mSi (OR ³ ) _4-m (II)
Wherein R ² is independently a hydrogen atom or an unsubstituted or substituted monovalent hydrocarbon group, R ³ is the same or different unsubstituted or substituted alkyl group, and m is 0, 1, 2 or 3)),
(D) water,
(E) The following general formula (III)
R ⁴ ₃ SiNHSiR ⁴ ₃ (III)
(In the formula, R ⁴ represents the same or different monovalent hydrocarbon groups.)
It contains hexaorganodisilazane represented by

R ¹ in formula (I) representing an organopolysiloxane preferably has 1 to 12 carbon atoms, particularly 1 to 8 carbon atoms, and specifically includes a methyl group, an ethyl group, a propyl group, and a butyl group. Group, hexyl group, alkyl group such as octyl group, cycloalkyl group such as cyclopentyl group, cyclohexyl group, alkenyl group such as vinyl group, allyl group, propenyl group, aryl group such as cycloalkenyl group, phenyl group, tolyl group, Aralkyl groups such as benzyl group and 2-phenylethyl group, or some or all of hydrogen atoms of these groups are substituted with halogen atoms such as fluorine and chlorine or cyano groups, for example, chloromethyl group, trifluoropropyl group , Cyanoethyl group and the like, methyl group, vinyl group, phenyl group, trifluoropropyl group are preferable, Methyl group, a vinyl group preferred.

Particularly, the organopolysiloxane as the component (A) is 2 or more, usually 2 or more and 50 or less, particularly 2 or more and 20 or less alkenyl groups, cycloalkenyl groups, or the like in one molecule. Those having a group are preferred, and those having a vinyl group are particularly preferred. In this case, it is preferable that 0.01 mol% or more and 20 mol% or less, particularly 0.02 mol% or more and 10 mol% or less of all R ¹ are aliphatic unsaturated groups. The aliphatic unsaturated group may be bonded to the silicon atom at the molecular chain end, or may be bonded to the silicon atom in the middle of the molecular chain (molecular chain non-terminal), or both. Is preferably bonded to at least a silicon atom at the end of the molecular chain.

Further, a is a positive number of 1.95 or more and 2.05 or less, preferably 1.98 or more and 2.02 or less, more preferably 1.99 or more and 2.01 or less. The total R ¹ in 90 mol% or more, preferably 95 mol% or more, more preferably it is desirable that all of R ¹ except aliphatic unsaturated group is an alkyl group, especially a methyl group.

The molecular structure of the organopolysiloxane (A) is preferably linear or linear having a partially branched structure. Specifically, the repeating structure of the diorganosiloxane unit (R ¹ ₂ SiO _2/2 , R ¹ is the same as described above, the same applies hereinafter) constituting the main chain of the organopolysiloxane is repeated from only the dimethylsiloxane unit. Or diphenylsiloxane having a phenyl group, a vinyl group, a 3,3,3-trifluoropropyl group or the like as a substituent as a part of a dimethylpolysiloxane structure composed of repeating dimethylsiloxane units constituting the main chain Those having a diorganosiloxane unit introduced such as a unit, a methylphenylsiloxane unit, a methylvinylsiloxane unit, or a methyl-3,3,3-trifluoropropylsiloxane unit are preferred.

Further, both ends of the molecular chain are, for example, triorganosiloxy groups (R ¹ ₃ SiO _1/2 ) such as trimethylsiloxy group, dimethylphenylsiloxy group, vinyldimethylsiloxy group, divinylmethylsiloxy group, trivinylsiloxy group, hydroxy It is preferably blocked with a hydroxydiorganosiloxy group (R ¹ ₂ (HO) SiO _1/2 ) such as a dimethylsiloxy group.

As described above, the organopolysiloxane of the component (A) has a triorganosiloxy group (R ¹ ₃ SiO _1/2 ) or a hydroxydiorganosiloxy group (R ¹ ₂ (HO) SiO _{1/2 at} both ends of the molecular chain. ), And the main chain is preferably a straight chain composed of repeating diorganosiloxane units (R ¹ ₂ SiO _2/2 ). Particularly preferred are methyl vinyl polysiloxane, methyl phenyl vinyl polysiloxane, methyl trifluoropropyl vinyl as the types of substituents in the molecule (that is, unsubstituted or substituted monovalent hydrocarbon groups bonded to silicon atoms). Polysiloxane etc. can be mentioned. Such an organopolysiloxane can be obtained by, for example, cohydrolyzing and condensing one or more organohalogenosilanes, or by converting a cyclic polysiloxane (siloxane trimer, tetramer, etc.) into an alkaline or acidic solution. It can be obtained by ring-opening polymerization using a catalyst.

The degree of polymerization of the organopolysiloxane is 100 or more (usually 100 or more and 100,000 or less), preferably 1,000 or more and 100,000 or less, more preferably 2,000 or more and 50,000 or less, and particularly preferably 3 It is preferably in the form of a so-called raw rubber (non-liquid) that is not less than 20,000 and not more than 20,000 and has no self-fluidity at room temperature (25 ° C.). When the degree of polymerization is too small, problems such as roll adhesion occur when a compound is formed, and roll workability deteriorates. The degree of polymerization is determined by gel permeation chromatography (GP
C) It can be measured as a polystyrene-reduced weight average polymerization degree by analysis.

  (A) A component may be used individually by 1 type, or 2 types or 3 or more types of mixtures from which molecular weight (degree of polymerization) and molecular structure differ.

  The filler (B) is added to obtain a silicone rubber composition having excellent mechanical strength. The filler to be used is not particularly limited, and silica, diatomaceous earth, pearlite, mica, calcium carbonate, glass flake, hollow filler and the like can be used, but silica is preferably used from the viewpoint of reinforcement. Examples of the silica include fumed silica (fumed silica), precipitated silica (wet silica) and the like, and those whose surfaces are hydrophobized with chlorosilane, hexamethyldisilazane, or the like are also preferably used. Among these, fumed silica excellent in dynamic fatigue characteristics is preferable. (B) A component may use together 1 type (s) or 2 or more types.

When silica is used, in order to obtain a silicone rubber composition having excellent mechanical strength, the specific surface area (BET adsorption method) needs to be 50 m ² / g or more, preferably 100 m ² / g or more and 450 m ^2. / G or less, more preferably 100 m ² / g or more and 300 m ² / g or less. When the specific surface area is less than 50 m ² / g, the mechanical strength of the cured product is lowered.

  The blending amount of the component (B) filler is 5 parts by mass or more and 100 parts by mass or less, and preferably 10 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the organopolysiloxane of the component (A). . When the blending amount of the component (B) is too small, the reinforcing effect cannot be obtained, and when it is too large, the workability deteriorates, the mechanical strength decreases, and the dynamic fatigue durability also deteriorates. End up. The component (B) may be added not only when the millable silicone rubber is prepared, but also when the millable silicone rubber, the crosslinking agent, and the unexpanded microballoon are mixed.

Examples of the alkoxysilane of the component (C) represented by the above formula (II) include organoalkoxysilanes such as organotrialkoxysilane, diorganodialkoxysilane, and triorganoalkoxysilane, and m = 1 and R ² is hydrogen. Examples include trialkoxysilane as an atom and tetraalkoxysilane of m = 0.

Here, R ² is a hydrogen atom or the same or different unsubstituted or substituted monovalent hydrocarbon group, and the unsubstituted or substituted monovalent hydrocarbon group may be represented by the formula (I) of the component (A) above. while those in the same as R ¹ can be mentioned, usually 1 to 8 carbon atoms, particularly preferably those having 1 to 4 carbon atoms, specifically, methyl group, ethyl group, propyl group, butyl group Alkyl groups such as hexyl group and octyl group, cycloalkyl groups such as cyclopentyl group and cyclohexyl group, alkenyl groups such as vinyl group, allyl group and propenyl group, cycloalkenyl groups such as cyclohexenyl group, phenyl group and tolyl group Aryl groups such as aryl, benzyl and 2-phenylethyl groups, or some or all of the hydrogen atoms of these groups may be substituted with halogen atoms such as fluorine, chlorine and bromine. Or a chloromethyl group substituted with a cyano group, 3,3,3-trifluoropropyl group, 2-cyanoethyl group, and the like. A methyl group, a vinyl group, a phenyl group, and a trifluoropropyl group are preferable. Group, vinyl group and phenyl group are preferred. Further, it is preferably the same as organopolysiloxane unsubstituted or substituted monovalent hydrocarbon group from the viewpoint of compatibility of the component (A) and siloxane R ¹ in component (A).

As the unsubstituted or substituted alkyl group for R ³ , for example, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group or the like, usually an alkyl having 1 to 4 carbon atoms And alkoxy-substituted alkyl groups such as a methoxymethyl group, a methoxyethyl group, an ethoxymethyl group, and an ethoxyethyl group are exemplified, but a methyl group and an ethyl group are preferable from the viewpoint of hydrolyzability. M in the formula is 0, 1, 2 or 3, preferably 1 or 2.

  Examples of such alkoxysilane include dimethoxydimethylsilane, diethoxydimethylsilane, dimethoxydiethylsilane, diethoxydiethylsilane, dimethoxymethylvinylsilane, dimethoxydiphenylsilane, dimethoxymethylphenylsilane, trimethoxymethylsilane, and triethoxymethylsilane. , Trimethoxyvinyl silane, trimethoxyphenyl silane, trimethoxy silane, triethoxy silane, tetramethoxy silane, tetraethoxy silane, etc., and diorganodialkoxy silane such as dialkyl dialkoxy silane in which m = 2 Dimethoxydimethylsilane is particularly preferable.

  These alkoxysilanes are relatively inexpensive, and using them as starting materials is extremely advantageous economically. The above alkoxysilanes can be used alone or in combination of two or more. However, when a mixture of a plurality of alkoxysilanes is used, care must be taken because they may not react uniformly because the hydrolysis rates of the two differ.

  (C) The usage-amount of a component is 0.1 to 20 mass parts with respect to 100 mass parts of said (A) component, Preferably it is 1 to 15 mass parts. If the amount of alkoxysilane used is too small, the plasticity of the compound becomes too high, and the plastic return (creep hardening) also becomes large. If it is too much, the plasticity of the compound becomes too low, and the roll is mixed in a kneading means such as a roll mill. Stickiness occurs and roll workability deteriorates.

  The pH of water as component (D) is not particularly limited, but if the pH is too high or too low, the device used during compounding will corrode, so the pH is 1.0 or more and 12.0 or less. More preferably, it is 2.0 or more and 10.0 or less, More preferably, it is 2.0 or more and 7.0 or less.

  Here, the water of component (D) is an acidic aqueous solution prepared using an inorganic acid such as hydrochloric acid, sulfuric acid or nitric acid, and an organic acid such as formic acid or acetic acid, or sodium hydroxide in order to adjust the pH within the above range. It is also possible to use as a basic aqueous solution prepared using potassium hydroxide, aqueous ammonia or the like.

  Further, the amount of water used is 0.3 to 10 times mol, particularly 0.5 to 2.0 times mol, particularly 1.0 to 1 times mol to the alkoxy group of the alkoxysilane. .5 mol or less is preferable. When this amount is less than the above range, there is a problem that the alkoxy group is not completely hydrolyzed and only a few hydroxyl groups are formed. Even if a large amount is added, it is necessary to remove excess water.

In the formula (III) showing the hexaorganodisilazane as the component (E), R ⁴ may be the same as R ^{1 in the} component (A), but is particularly a carbon such as a methyl group or an ethyl group. An alkyl group having a number of 1 or more and 6 or less is preferable, and the molecule may have an alkenyl group such as a vinyl group.

  As the component (E), hexamethyldisilazane, 1-vinylpentamethyldisilazane, 1,3-divinyl-1,1,3,3-tetramethyldisilazane, 1,3-dimethyl-1,1,3 , 3-tetravinyldisilazane and the like are exemplified, but hexamethyldisilazane and 1,3-divinyl-1,1,3,3-tetramethyldisilazane are preferable, and hexamethyldisilazane is more preferable.

  As the component (E), ammonia water can be used in addition to the above hexaorganodisilazane. The concentration of the aqueous ammonia is not particularly limited, but it is usually 1% by mass to 30% by mass, preferably 10% by mass to 28% by mass, more preferably 15% by mass to 28% by mass.

  In the case of hexaorganodisilazane with respect to 100 parts by mass of the organopolysiloxane of component (A), the amount of component (E) is 0.01 to 1 part by mass, preferably 0.02 parts by mass. 1 part by mass or less, more preferably 0.05 part by mass or more and 0.5 part by mass or less. In the case of ammonia water, 0.01 part by mass or more and 1 part by mass or less, preferably 0.05 part by mass or more. 1 part by mass or less, more preferably 0.1 part by mass or more and 1 part by mass or less.

  When the amount of component (E) is too small, the effect of shortening the blending time is small, and the effect of improving compression set resistance and dynamic fatigue durability cannot be obtained. The hardness of the rubber becomes too high, and it is not economically preferable.

  The addition of the component (E) is necessary after the hydrolysis with the alkoxysilane of the component (C) and the water of the component (D) is sufficiently performed, and specifically, the production of the composition When mixing and kneading each component uniformly in the process, component (B) is added to component (A), (C), (D) at least 25% by mass (25% by mass to 100% by mass) ), Preferably 50 mass% or more and 100 mass% or less, and after mixing uniformly, it is necessary to add (E) component.

  When the (E) component is added at a time when hydrolysis of the (C) component alkoxysilane and the (D) component water is insufficient, the plastic return resistance before curing and the compression set resistance after curing. It becomes a composition inferior to.

  The millable silicone rubber in the present invention is uniformly kneaded with a predetermined amount of the components (A) to (E) described above in a predetermined blending order (blending time) with a two roll (roll mill), a kneader, a Banbury mixer, etc. It can be obtained by mixing. Moreover, the millable type silicone rubber to obtain | require can also be obtained by mixing (A) component with the millable type silicone rubber once adjusted.

  That is, 25% by mass or more and 100% by mass or less, preferably 50% by mass or more and 100% by mass or less of the necessary addition amount of the component (B), and the components (A), (C), and (D) are mixed. During this mixing, alkoxysilane as component (C) and water as component (D) undergo a hydrolysis reaction, and the hydrolysis reaction product acts as a wetter for the filler as component (B). Shortened. In this case, the mixing and kneading are preferably 0 ° C. or higher and 100 ° C. or lower, more preferably 10 ° C. or higher and 90 ° C. or lower, and still more preferably, in order to sufficiently achieve the hydrolysis reaction by the component (D) of the component (C). Is preferably from 1 minute to 120 minutes, more preferably from 10 minutes to 60 minutes at 30 ° C. to 80 ° C.

  Next, after the hydrolysis reaction of the component (C) and the component (D) has sufficiently proceeded in this way, the hexaorganodisilazane or ammonia water as the component (E) is added. This further shortens the mixing time. When the entire amount of the filler of component (B) is not used in the previous mixing and kneading step, the remainder of the filler of component (B) is added during the mixing and kneading step. The temperature in the case of adding the remaining amount of the component (E) and the component (B), mixing, and kneading is preferably 0 ° C. or higher and 100 ° C. or lower, particularly preferably 10 ° C. or higher and 90 ° C. or lower, particularly preferably 40 ° C. or higher and 80 ° C. or lower, The mixing and kneading time is preferably 1 minute to 120 minutes, particularly preferably 3 minutes to 60 minutes. The total blending time of the components (A) to (E) is preferably 5 minutes to 5 hours, more preferably 10 minutes to 3 hours.

  Specific examples of the millable silicone rubber in the present invention include KE-571-U, KE-1571-U, KE-951-U, KE-541-U, and KE-551 manufactured by Shin-Etsu Chemical Co., Ltd. U, KE-561-U, KE-961T-U, KE-1541-U, KE-1551-U, KE-941-U, KE-971T-U, KE-151-U, Toray Dow Corning Co., Ltd. SE 1184 U, SE 1188 U, RBB 2070 50 BASE, SE 4706 U, SE 4704 U, DY 32-152 U, ELASTOSIL (registered trademark) EL-1301, ELASTOSIL (registered trademark) manufactured by Asahi Kasei Wacker Silicone Co., Ltd. EL 4300, ELASTOSIL (registered trademark) EL 3630, etc. may be used. Kill.

(Crosslinking agent)
In the sponge roller of the present invention, a crosslinking agent is used for forming the elastic layer, and examples of the crosslinking agent include addition reaction crosslinking agents and organic peroxide crosslinking agents.

  Suitable examples of the addition reaction crosslinking agent include known organohydrogenpolysiloxanes as addition reaction type crosslinking agents having two or more SiH groups (SiH bonds) in one molecule. An addition reaction crosslinking agent can be used individually by 1 type or in mixture of 2 or more types. The addition amount of the addition reaction crosslinking agent with respect to 100 parts by mass of the millable silicone rubber is preferably 1 part by mass or more and 5 parts by mass or less, and more preferably 2 parts by mass or more and 4 parts by mass or less.

  When the above addition reaction crosslinking agent is used, the organic peroxide crosslinking agent can be used alone to crosslink the millable silicone rubber, but when used as an auxiliary crosslinking agent for the addition reaction crosslinking agent, a sponge is obtained. The strength of the roller can be made appropriate and the durability can be improved. Examples of the organic peroxide crosslinking agent include benzoyl peroxide, bis-2,4-dichlorobenzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-bis. (T-butylperoxy) hexane and the like. The amount of the organic peroxide crosslinking agent added to 100 parts by mass of the millable silicone rubber is preferably 1 part by mass or more and 5 parts by mass or less, and more preferably 2 parts by mass or more and 4 parts by mass or less. An organic peroxide crosslinking agent can be used individually by 1 type or in mixture of 2 or more types.

  The addition reaction crosslinking agent is preferably used in combination with an addition reaction catalyst. Addition reaction catalyst is platinum black, platinous chloride, chloroplatinic acid, reaction product of chloroplatinic acid and monohydric alcohol, complex of chloroplatinic acid and olefins, platinum bisacetoacetate, palladium catalyst, rhodium catalyst Etc. In addition, the compounding quantity of this addition reaction catalyst can be made into a catalyst quantity.

(Unexpanded micro-balloon)
In the sponge roller of the present invention, an unexpanded micro-balloon is used to form cells of the elastic layer. Examples of the unexpanded microballoon include an unexpanded resin microballoon. As the resin microballoon, those using a thermoplastic resin for the outer shell are preferably used. Examples of the thermoplastic resin constituting the outer shell include vinylidene chloride / acrylonitrile copolymer, methyl methacrylate / acrylonitrile copolymer, methacrylonitrile / acrylonitrile copolymer, and the like. It is preferable to use a resin microballoon in which the softening temperature of the resin serving as the outer shell is within an appropriate range in accordance with the curing temperature of the liquid silicone rubber. Moreover, hydrocarbons, such as butane and isobutane, can be mentioned as an evaporable substance included.

  Unexpanded resin microballoons suitable for the present invention are commercially available as “Matsumoto Microsphere F Series” (manufactured by Matsumoto Yushi Seiyaku Co., Ltd.), “Expansel Series” (manufactured by Expanscel Co., Ltd.), and the like. .

  In the elastic layer, the average cell diameter of the cells formed by the unexpanded microballoons is 150 μm or less, preferably 30 μm or more and 100 μm or less. When the average cell diameter of the cells contained in the elastic layer is within the above range, the elastic layer can suppress a decrease in hardness due to repeated compression, and can improve durability.

  The average cell diameter of the cells is an average value of 10 randomly selected cells when the surface of the elastic layer or a cut surface obtained by cutting an arbitrary surface is magnified 100 times with an optical microscope. This average cell diameter can be adjusted by appropriately setting the vulcanization conditions of the mixture containing the millable silicone rubber and the unexpanded microballoon for forming the elastic layer.

  The amount of the unexpanded microballoon with respect to 100 parts by mass of the millable silicone rubber before crosslinking and curing is preferably 0.5 parts by mass or more and 5 parts by mass or less, and 1.0 parts by mass or more and 4.0 parts by mass or less. More preferably, it is 1.1 parts by mass or more and 1.3 parts by mass or less. If the content of the unexpanded microballoon exceeds the upper limit of the above range, the number of cells becomes too large and the elasticity of the elastic layer itself is lost. If the value is less than the value, the elastic layer may become too hard to be used suitably for an image forming apparatus, for example.

  In addition, various additives can be further included in the mixture of the millable silicone rubber, the crosslinking agent, and the unexpanded microballoon. As various additives, for example, auxiliary agents such as chain extenders, catalysts, dispersants, anti-aging agents, antioxidants, fillers, pigments, colorants, processing aids, softeners, plasticizers, emulsifiers, heat resistance Examples include an improver, a flame retardant improver, an acid acceptor, a thermal conductivity improver, a release agent, and a solvent. These various additives may be commonly used additives or may be specially used additives depending on applications. In addition, about the filler, the silica etc. which were described as said (B) component of millable type silicone rubber can be used.

(Content of filler in elastic layer)
The elastic layer is filled with the component (B). The content of the filler in the elastic layer can be adjusted at the time of producing the millable silicone rubber as described above. For example, the component (A) is added to the millable silicone rubber containing the filler. It can also be adjusted when a certain kind of organopolysiloxane is separately mixed to finally produce a millable silicone rubber before crosslinking and curing. Moreover, in that case, (B) component can be mixed separately and can also be adjusted. Furthermore, it can be adjusted by adding a filler when mixing the millable silicone rubber, the crosslinking agent, and the unexpanded microballoon.
Here, in the sponge roller of the present invention, the content of the filler in the elastic layer is 1.0% by mass or more and 40.0% by mass or less. In the present invention, by using an unexpanded microballoon as a foaming agent, while improving the durability of the elastic layer, the content of the filler is in the above range, so that the hardness required for thermoforming described later can be obtained. While ensuring, durability of an elastic layer can be improved further. The content of the filler in the elastic layer is preferably 1.0% by mass or more and 30.0% by mass or less, and more preferably 1.0% by mass or more and 20.0% by mass or less.
In addition, content of the filler in an elastic layer can be measured with the thermogravimetry apparatus (Discovery TGA (TGA550)) by TA Instruments, and the mass of ash (remaining amount) can be measured. Measurement conditions 50 ° C / min Measured up to 1000 ° C. From the weight remaining at 1000 ° C., the content (% by mass) in the elastic layer can be calculated.

(Asker C hardness)
The elastic layer preferably has an Asker C hardness of 15 or more and 75 or less. In the sponge roller according to the present invention, the Asker C hardness of the elastic layer surface is such that the difference between the Asker C hardness on the outer surface and the Asker C hardness on the inner surface of the elastic layer is 1 or less in the axial direction. is there. A small difference in Asker C hardness of the elastic layer in the sponge roller is advantageous in that it has the advantage that the pressurized elastic layer is uniformly deformed and the stress distribution is less biased.

(Elastic modulus)
In the present invention, when the elastic modulus in the longitudinal direction of the elastic layer is MD and the elastic modulus in the thickness direction is TD, MD / TD is 0.90 or more and less than 1.60. By adjusting the MD / TD of the elastic layer within the above range, the durability of the sponge roller can be improved. The MD / TD is preferably 1.20 or more and 1.55 or less, and more preferably 1.30 or more and 1.55 or less. The thickness direction refers to a direction perpendicular to the shaft body.

The elastic modulus ratio can be obtained as follows. First, a measurement sample is cut out from the elastic layer of the pressure member with a razor. About this measurement sample, the elastic modulus MD in the longitudinal direction and the elastic modulus ND in the thickness direction of the elastic layer are measured by the following method. In addition, a measurement is performed 5 times about each elastic modulus, and elastic modulus ratio is calculated | required by making those average values into elastic modulus.
Each elastic modulus can be measured by a dynamic viscoelasticity measuring apparatus (trade name: DMA-Q800, manufactured by TA Instruments). The elastic modulus MD in the longitudinal direction is a value obtained by measuring the complex elastic modulus in an environment of a temperature of 200 ° C. with a chucking jig mounted on a measuring device, a distance between chucks of 20 mm, a frequency of 10 Hz. Note that the measurement sample is cut out so that the tensile direction of measurement is parallel to the longitudinal direction of the sample. The elastic modulus TD in the thickness direction is a value obtained by mounting a compression jig on a measuring apparatus and measuring the complex elastic modulus in an environment of a frequency of 10 Hz and 200 ° C. The measurement sample is cut out so that the compression direction of measurement and the thickness direction of the measurement sample are parallel.

(Decrease in hardness)
In the elastic layer of the present invention, the decrease in hardness measured by a 25% compression durability test method is preferably 8 points or less, and more preferably 3 points or less. It is preferable that the decrease in hardness is in the above numerical range because an image forming apparatus using a sponge roller can form a stable image over a long period of time.

[Dimensions of elastic layer, etc.]
The elastic layer is formed in a cylindrical shape on the outer peripheral surface of the shaft body, and the thickness of the elastic layer is usually 0.5 mm to 30 mm, preferably 1 mm to 15 mm.

[Others]
As long as the object of the present invention can be achieved, the elastic layer has a low molecular siloxane ester, a silanol, for example, a dispersant such as diphenylsilanediol, and a heat resistance improver such as iron oxide, cerium oxide, and iron octylate. Further, various carbon functional silanes for improving adhesiveness and moldability, halogen compounds for imparting flame retardancy, and the like may be contained within a range not impairing the object of the present invention.

<Manufacturing method of sponge roller>
The sponge roller according to the present invention can be manufactured by the manufacturing method according to the present invention.

  In the production method according to the present invention, millable silicone rubber, 1 to 6 parts by mass of a crosslinking agent and 100 parts by mass of millable silicone rubber, and an unexpanded microballoon are blended.

  The types of millable silicone rubber, crosslinking agent, unexpanded micro-balloon, etc. have already been described.

  The mixing method is not particularly limited. For example, under normal temperature and normal pressure, millable silicone rubber, unexpanded micro-balloon, and cross-linking agent are added sequentially or all at once and mixed uniformly with a stirrer, kneader or the like. Etc. In this way, the step of preparing the mixture is completed. In addition, said various additives can be included in a mixture.

  The above mixture is, for example, several minutes to several hours, preferably 5 minutes or more until it is uniformly mixed using a rubber kneader such as a two-roll, three-roll, roll mill, Banbury mixer, and dough mixer (kneader). It can be obtained by kneading at room temperature or under heating for 1 hour or less.

  Next, the obtained mixture is heat-molded on the outer peripheral surface of the shaft body constituting the sponge roller by continuous heat molding by extrusion molding, pressing, mold molding by injection, or the like.

  After the mixture is formed in a cylindrical shape on the outer surface of the shaft body, the cylindrical mixture, in other words, the cylindrical shaped body is heated and vulcanized together with the shaft body (heat curing).

  It is particularly preferable that the heating during vulcanization by heating the molded body is as follows. That is, as primary vulcanization, heating is performed at 100 ° C. to 300 ° C., particularly 150 ° C. to 250 ° C. for 5 minutes to 30 minutes, and then as secondary vulcanization, 180 ° C. to 250 ° C., particularly 200 ° C. to 230 ° C. for 1 hour. Heat for 10 hours. Heating in such a plurality of times is preferable because it is possible to control the curing of the millable silicone rubber and the removal of the remaining low-molecular siloxane as necessary.

  Heating necessary for vulcanization can be performed by a heating furnace such as an infrared heating furnace or a hot air furnace, a heating machine such as a dryer, or the like.

  The sponge roller thus obtained may be further subjected to a polishing process. In the polishing process, the thickness of the sponge roller formed on the outer peripheral surface of the shaft body is gradually increased in the axial direction of the shaft body toward the center of the shaft body. This is a process of adjusting to a shape that gradually decreases toward the tip, that is, a crown shape, or a shape that increases the thickness of the sponge roller from the center of the shaft toward both ends of the shaft, that is, a reverse crown shape or a straight shape. .

  Further, the outer surface of a sponge roller obtained by vulcanization or a sponge roller adjusted to a predetermined shape by a polishing process may be covered with a tube, for example, a fluororesin tube. Covering with a fluororesin tube is, for example, a pressure insertion method in which the sponge roller is compressed and inserted into the fluororesin tube under pressure, a vacuum insertion method in which the sponge roller is compressed and inserted into the fluororesin tube under reduced pressure, Can be carried out by a reduced-pressure expanding method or the like in which the diameter of the fluororesin tube is expanded in the radial direction and a sponge roller is inserted therein.

<Image forming apparatus>
An example of an image forming apparatus (hereinafter sometimes referred to as an image forming apparatus according to the present invention) having a fixing device including a sponge roller according to the present invention will be described with reference to FIG. The use of the sponge roller of the present invention is not particularly limited. For example, the fixing roller 53 and the pressure roller 56 incorporated in the fixing device, the cleaning unit 37 (for example, a cleaning roller), and the developer supply unit 43 (for example, a toner supply roller). Can be used as

  As shown in FIG. 2, the image forming apparatus 30 according to the present invention is arranged around a rotatable image carrier 31, for example, a photoreceptor, on which an electrostatic latent image is formed, and the image carrier 31. A charging unit 32 such as a charging roller, an exposure unit 33, a developing unit 40, a transfer unit 34 such as a transfer roller, a cleaning unit 37 such as a cleaning roller, and a fixing unit 35 are provided on the downstream side in the conveyance direction of the recording medium. The developing means 40 is formed basically in the same manner as the conventional developing means. Specifically, as shown in FIG. 2, the developer accommodating portion 41 and the developer 42 are supplied to the image carrier 31. A developer carrier 44, a developer supply means 43 for supplying the developer 42 to the developer carrier 44, for example, a toner supply roller, and a developer regulating member 45 that charges the developer 42 are provided.

  As shown in FIG. 2, the fixing unit 35 includes a fixing roller 53 and an endless belt support roller disposed in the vicinity of the fixing roller 53 in a housing 50 having an opening 52 through which the recording medium 36 passes. 54, an endless belt 55 wound around the fixing roller 53 and the endless belt support roller 54, a pressure roller 56 pressed against the fixing roller 53 via the endless belt 55, and the endless belt 55 in a non-contact manner. And a heating unit that heats the fixing roller 53 from the outside via the endless belt 55, and is rotatable so that the fixing roller 53 and the pressure roller 56 are in contact with or pressed against each other via the endless belt 55. This is a pressure heat fixing device supported.

  The endless belt support roller 54 may be a roller that is normally used in an image forming apparatus. For example, an elastic roller or the like is used. The endless belt 55 may be an endless belt formed of, for example, a resin such as polyamide or polyamideimide, and the thickness and the like of the endless belt 55 can be appropriately adjusted to match the fixing unit 35. The pressure roller 56 is in pressure contact with the fixing roller 53 via an endless belt 55 by a biasing means (not shown) such as a spring. As the heating means, a radiant heating method using a halogen heater, a reflector, or the like, a direct contact heating method in which heating is performed by directly contacting a heater or the like, an induction heating method, or the like is adopted. This heating means is a member having a length substantially the same as the length of the fixing roller 53 in the axial direction, and may be disposed in any of the fixing means 35. However, as shown in FIG. It is preferable that the fixing roller 53 be arranged substantially in parallel with a predetermined interval. A heating coil is used in the induction heating method, and this heating coil is usually a ferromagnetic material such as ferrite, and is a typical shape used for a switching power supply. I type, E type, and U type Etc., and a conducting wire is wound. By passing the recording medium 36 between the endless belt 55 and the pressure roller 56, the recording medium 36 is heated simultaneously with the pressurization, and the developer 42 (electrostatic latent image) transferred to the recording medium 36 is fixed. be able to.

  The image forming apparatus 30 according to the present invention operates as follows. First, in the image forming apparatus 30, the image carrier 31 is uniformly charged by the charging unit 32, and an electrostatic latent image is formed on the surface of the image carrier 31 by the exposure unit 33. Next, the developer 42 is supplied from the developing unit 40 to the image carrier 31 to develop the electrostatic latent image, and the developer image is conveyed between the image carrier 31 and the transfer unit 34 on the recording member 36. Is transcribed. The recording body 36 is conveyed to the fixing unit 35, and the developer image is fixed on the recording body 36 as a permanent image. In this way, an image can be formed on the recording body 36. The fixing roller 53 or the pressure roller 56 is excellent in fixability for fixing the developer onto the recording medium and consumes little power.

  The sponge roller and the image forming apparatus according to the present invention are not limited to the above-described embodiments, and various modifications can be made within a range in which the object of the present invention can be achieved.

  For example, in the sponge roller, the elastic layer has a single layer structure, but in the present invention, it may have a multilayer structure of two or more layers.

  The image forming apparatus 30 is an electrophotographic image forming apparatus. However, in the present invention, the image forming apparatus is not limited to the electrophotographic system, and may be, for example, an electrostatic image forming apparatus. Good. Further, the image forming apparatus 30 is a monochrome image forming apparatus in which the developing unit 40 contains only a single color developer 42. However, in this invention, the image forming apparatus is not limited to a monochrome image forming apparatus. It may be an image forming apparatus. As the color image forming apparatus, for example, a four-cycle color image forming apparatus that sequentially repeats primary transfer of a developer image carried on an image carrier to an intermediate transfer body, and a plurality of image carriers provided with developing means for each color And a tandem type color image forming apparatus in which the toner is disposed in series on an intermediate transfer member or a transfer conveyance belt. The image forming apparatus 30 is an image forming apparatus such as a copying machine, a facsimile machine, or a printer.

In the fixing unit 35 and the image forming apparatus 30, a one-component developer is advantageously used as the developer 42, but a two-component developer containing a toner and a carrier such as iron or nickel is also used. can do.

  As mentioned above, although this invention was demonstrated using embodiment, it cannot be overemphasized that the technical scope of this invention is not limited to the range of the invention as described in said embodiment, A various change or It will be apparent to those skilled in the art that improvements can be made. In addition, it is apparent from the scope of the claims that the invention to which such changes or improvements are added can also be included in the technical scope of the present invention.

  Hereinafter, the present invention will be described in detail with reference to examples. In addition, this invention is not limited to the Example shown below at all.

(Examples 1 to 7, Comparative Examples 1 to 4)
In Examples 1 to 7 and Comparative Examples 1 to 4, the base rubber material shown in Table 1, the cross-linking agent shown in Table 1, the catalyst shown in Table 1, and the unswelled shown in Table 1 Micro-balloons were sufficiently kneaded with two rolls at the blending amounts shown in Table 1 to obtain a mixture. The base rubber material is a millable silicone rubber (trade name KE-151U manufactured by Shin-Etsu Chemical Co., Ltd.) containing a filler (smokeous silica), and a raw rubber-like organopolysiloxane (Shin-Etsu Chemical Co., Ltd.) containing no filler. It is a millable silicone rubber mixed with a trade name KE-76VBS manufactured by Co., Ltd. The content of the filler in the elastic layer was adjusted by adjusting the mixing ratio of KE-151U and KE-76VBS.

  The cross-linking agents listed in Table 1 are trade name C-25B manufactured by Shin-Etsu Chemical Co., Ltd. described as “addition cross-linking”, and C-3 manufactured by Shin-Etsu Chemical Co., Ltd. described as “peroxide cross-linking”. The “catalyst” described in Table 1 is a platinum catalyst having the trade name C-25A manufactured by Shin-Etsu Chemical Co., Ltd., and “unexpanded microballoon” described in Table 1 is Matsumoto Yushi Seiyaku It is a trade name Matsumoto Microsphere made by Co., Ltd.

  Next, the shaft body on which the primer layer is formed and the mixture are integrally extracted with an extruder, and the mixture is primarily vulcanized by heating at 200 ° C. for 17 minutes using an infrared heating furnace (IR furnace), Thereafter, secondary foaming was carried out at 225 ° C. for 7 hours in a hot air drying furnace to produce a foam roller base. The circumferential surface of the foam roller base was subjected to high-speed polishing with a metal grindstone using a polishing machine manufactured by Mizuguchi Seisakusho.

  With respect to the obtained sponge rollers of Examples and Comparative Examples, the elastic modulus (MD / TD) and durability (decrease in hardness) of the elastic layer were evaluated, and the results are shown in Table 1.

(Durability evaluation: 25% compression durability test method)
Using the sponge roller thus manufactured and the durability test apparatus 70 shown in FIG. 3, the durability test of each sponge roller was performed to evaluate the decrease in hardness. Specifically, the durability test apparatus 70 is fixed to the lower surface inside the housing and is provided on both sides of the heating roller 71 provided with an internal heater 72 along the axial direction of the heating roller 71. A test roller mounting portion 74 provided on the upper surface inside the housing so as to be movable up and down so as to face the heat insulating material 73 and the heating roller 71, and a pressing force adjusting means 75 capable of moving the test roller mounting portion 74 up and down. For example, a pressure adjusting micrometer is provided. As the heating roller 71, a metal (stainless steel, SUS304) roller having a diameter of 20 mm was used.

The manufactured sponge roller is mounted on the bearing of the test roller mounting portion 74, and as shown in FIG. 3, the pressing force adjusting means 75 is operated to mount the mounted elastic roller (“elastic roller 76” in FIG. 3). The elastic roller 76 was fixed in contact with the heating roller 71 so that the foamed elastic layer of the elastic roller 76 was recessed 2 mm inside at the pressure contact portion between the heating roller 71 and the elastic roller 76 (that is, the radius of the elastic roller 76 and the heating). The distance d between the central axis of the elastic roller 76 and the central axis of the heating roller 71 was adjusted so as to be 2 mm shorter than the sum of the radii with the roller 71). Next, the internal heater 72 was started and the surface temperature of the heating roller 71 was adjusted to 180 ° C. Thereafter, the drive means (not shown) provided in the test roller mounting portion 74 was rotated at a rotation speed of 180 rpm for 100 hours. The elastic roller 76 was removed from the durability test apparatus 70, and Asker C hardness was measured. The Asker C hardness is measured at three locations in the axial direction and at four locations in the circumferential direction. Specifically, the three locations in the axial direction are a 30 mm portion and an axial line from both ends of the foamed elastic body toward the center. The central part of the direction is the four places in the circumferential direction, and the four places are equally spaced in the circumferential direction with a central angle of 90 ° in each of the three places in the axial direction. In addition, as a result of this durability test, the amount of hardness decrease is 8 points or less as OK.
About durability test Product outer diameter φ30, shaft outer diameter φ14, wall thickness 8mm
Compression rate 25% → 2mm indentation

DESCRIPTION OF SYMBOLS 1 Sponge roller 2 Shaft body 3 Elastic layer 4 Covering layer 30 Image forming apparatus 31 Image carrier 32 Charging means 33 Exposure means 34 Transfer means 35 Fixing means 36 Recording body 37 Cleaning means 40 Developing means 41 Developer accommodating part 42 Developer 43 Developer supply means 44 Developer carrier 45 Developer regulating member 50 Housing 52 Opening 53 Fixing roller 54 Endless belt support roller 55 Endless belt 56 Pressure roller 70 Durability test device 71 Heating roller 72 Internal heater 73 Insulating material 74 Test Roller mounting portion 75 Pressing force adjusting means 76 Pressure roller

Claims (3)

A sponge roller having a shaft body and an elastic layer formed on the outer peripheral surface of the shaft body,
The elastic layer is formed from a millable silicone rubber, a crosslinking agent, and an unexpanded microballoon,
The elastic layer contains a filler, and the content of the filler in the elastic layer is 1.0% by mass or more and 40.0% by mass or less,
A sponge roller, wherein MD / TD is 0.90 or more and less than 1.60, where MD is the elastic modulus in the longitudinal direction of the elastic layer and TD is the elastic modulus in the thickness direction.   The sponge roller according to claim 1, wherein the hardness decrease measured by a 25% compression durability test method is 8 points or less.   An image forming apparatus comprising the sponge roller according to claim 1.