Sponge roller

Abstract

To provide a highly durable sponge roller.SOLUTION: The present invention relates to a sponge roller 1 comprising a shaft 2 and a foamed elastic layer 3 provided around an outer periphery of the shaft 2. The foamed elastic layer 3 is composed of a foamed elastic layer-producing resin composition containing a millable silicone rubber, a vulcanizing agent, and a foaming agent, and a difference in cell density between a surface layer side and an inner layer side of the foamed elastic layer 3 is ±7% or less with respect to a cell density of the surface layer side.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a sponge roller. [Background technology]

[0002] Various image forming devices using electrophotography are employed in printers such as laser printers and video printers, copiers, facsimiles, and multifunction machines thereof. Electrophotographic image forming devices are equipped with various printing sponge rollers, such as cleaning rollers, charging rollers, developing rollers, transfer rollers, secondary transfer rollers, pressure rollers, paper feed rollers, and fixing rollers, each having a shaft body and an elastic layer formed on the outer circumferential surface thereof.

[0003] Among these sponge rollers, for example, pressure rollers, fixing rollers, etc., apply pressure to fix toner to the recording medium, so it is desirable that distortion of the sponge be applied uniformly throughout. However, when a foamed elastic layer is vulcanized by infrared heating, the foamed elastic layer is heated from its rubber surface, and heat is absorbed by the core bar near the core bar, resulting in uneven heating throughout the layer. As a result, the sponge on the surface layer has a large cell diameter and a low specific gravity, while the sponge on the inner layer has a small cell diameter and a high specific gravity. If the cells in the layer are uneven, it is difficult to respond to external stress with a consistent repulsive force, resulting in deformation of the sponge and poor durability.

[0004] To solve these problems, for example, Patent Document 1 discloses a silicone rubber sponge containing carbon black that is obtained by hot air vulcanization or ultra-high frequency vulcanization (hereinafter sometimes referred to as UHF vulcanization) to have excellent compression set, a low specific gravity, and fine cells with an average cell diameter of 200 μm or less. Furthermore, Patent Document 2 discloses that by vulcanizing an ionically conductive rubber composition containing acrylonitrile rubber and epichlorohydrin rubber using a microwave irradiation device, it is possible to form a conductive rubber roller having a foamed rubber layer with a small aspect ratio of the inner and outer diameters, a stable inner diameter dimension, a uniform cell distribution, and no unevenness in hardness or resistance in the circumferential direction. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 11-130896 [Patent Document 2] International Publication No. 2006 / 085696 Summary of the Invention [Problem to be solved by the invention]

[0006] In order to provide high quality images, a sponge roller having more uniform cells and higher durability than the technology disclosed in the above patent document is desired. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a sponge roller with high durability. [Means for solving the problem]

[0007] The present invention is a sponge roller comprising a shaft body and a foamed elastic layer on the outer periphery of the shaft body, wherein the foamed elastic layer is formed by vulcanizing a resin composition for a foamed elastic layer containing millable silicone rubber, a vulcanizing agent, and a foaming agent using microwaves, and the difference in cell density between the surface side and the inner side of the foamed elastic layer is ±7% or less, based on the cell density of the surface side.

[0008] The blowing agent preferably includes at least one of a chemical blowing agent and unexpanded microballoons.

[0009] The difference in specific gravity between the surface layer side and the inner layer side of the foamed elastic layer is preferably ±3% or less, based on the specific gravity of the surface layer side.

[0010] The sponge roller is preferably a fixing roller or a pressure roller. [Effects of the Invention]

[0011] According to the present invention, a highly durable sponge roller can be provided. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a perspective view showing an embodiment of a sponge roller of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. [Sponge roller] As shown in FIG. 1, the sponge roller 1 of the present invention is a sponge roller that includes a shaft 2 and a foamed elastic layer 3 on the outer periphery of the shaft 2. Each component will be described in detail below.

[0014] <Shaft> The shaft 2 may preferably be a conductive shaft used in conventional sponge rollers. The shaft 2 is preferably made of at least one metal selected from the group consisting of iron, aluminum, stainless steel, and brass. Such a shaft 2 is also generally known as a "core metal."

[0015] The shape of the shaft 2 is preferably, for example, rod-like or tubular. The cross-sectional shape of the shaft 2 may be, for example, circular or elliptical, or may be non-circular such as polygonal. The shaft 2 may be solid or hollow. The outer peripheral surface of the shaft 2 may be subjected to treatment such as cleaning, degreasing, or primer treatment.

[0016] The axial length of the shaft 2 is not particularly limited and may be adjusted appropriately depending on the type of the image forming apparatus in which it is installed. The diameter of the shaft 2 (diameter of the circumscribing circle) is also not particularly limited and may be adjusted appropriately depending on the type of the image forming apparatus in which it is installed.

[0017] <Foamed elastic layer> The foamed elastic layer 3 is provided to give the sponge roller 1 hardness and elasticity that allows it to be pressed against an object with an appropriate nip width and nip pressure. The foamed elastic layer 3 is formed by applying a resin composition for a foamed elastic layer to the outer peripheral surface of the shaft 2 and vulcanizing it with microwaves. The resin composition for a foamed elastic layer contains (A) millable silicone rubber, (B) a vulcanizing agent, and (C) a foaming agent.

[0018] (A) Millable silicone rubber The millable silicone rubber is preferably an addition-curing type millable silicone rubber, which preferably contains, for example, at least (a) an organopolysiloxane and (b) a filler.

[0019] (a) Organopolysiloxane (a) Organopolysiloxane is represented by the following average composition formula (1): R 1 n SiO (4-n) / 2 …(1) In formula (1), n ​​is a positive number between 1.95 and 2.05. 1 represents a substituted or unsubstituted monovalent hydrocarbon group, which may be the same or different. The hydrocarbon group preferably has 1 or more and 12 or less carbon atoms, more preferably 1 or more and 8 or less carbon atoms.

[0020] R 1Examples of the R include alkyl groups such as methyl, ethyl, propyl, butyl, hexyl, and dodecyl groups, cycloalkyl groups such as cyclohexyl groups, alkenyl groups such as vinyl, allyl, butenyl, and hexenyl groups, aryl groups such as phenyl and tolyl groups, and aralkyl groups such as β-phenylpropyl groups. 1 may be groups in which some or all of the hydrogen atoms of these hydrocarbon groups have been substituted with a substituent. The substituent may be, for example, a halogen atom, a cyano group, etc. Examples of hydrocarbon groups having a substituent include a chloromethyl group, a trifluoropropyl group, and a cyanoethyl group.

[0021] The (a) organopolysiloxane is preferably one whose molecular chain terminals are blocked with a trialkylsilyl group such as a trimethylsilyl group, a dialkylaralkylsilyl group such as a dimethylvinylsilyl group, a dialkylhydroxysilyl group such as a dimethylhydroxysilyl group, or a trialalkylsilyl group such as a trivinylsilyl group.

[0022] (a) Organopolysiloxane preferably has two or more alkenyl groups in the molecule. (A) Organopolysiloxane preferably has two or more alkenyl groups in the molecule. 1 Of these, it is preferable that the alkenyl group account for 0.001 mol % or more and 5 mol % or less (more preferably 0.01 mol % or more and 0.5 mol % or less).Vinyl groups are particularly preferable as the alkenyl groups contained in (A) organopolysiloxane.

[0023] (a) Organopolysiloxane can be obtained, for example, by cohydrolytic condensation of one or more organohalosilanes, or by ring-opening polymerization of a cyclic polysiloxane such as a siloxane trimer or tetramer. (a) Organopolysiloxane may be essentially a linear diorganopolysiloxane, or may be partially branched. (a) Organopolysiloxane may also be a mixture of two or more types with different molecular structures.

[0024] The organopolysiloxane (a) preferably has a kinematic viscosity at 25°C of 100 cSt or more, and more preferably 100,000 cSt or more and 10,000,000 cSt or less. The degree of polymerization of (a) organopolysiloxane is preferably, for example, 100 or more, and more preferably 3,000 or more and 10,000 or less.

[0025] (b) Filler (b) Examples of fillers include silica-based fillers, such as fumed silica and precipitated silica.

[0026] Silica-based fillers include R 2 Si(OR 3 A surface-treated silica-based filler that has been surface-treated with a silane coupling agent represented by formula (R) 3 can be preferably used. 2 may be a group having a vinyl group or an amino group, such as a glycidyl group, a vinyl group, an aminopropyl group, a methacryloxy group, an N-phenylaminopropyl group, or a mercapto group. 3 may be an alkyl group, such as a methyl group or an ethyl group. Silane coupling agents are readily available, for example, under the trade names "KBM1003" and "KBE402" manufactured by Shin-Etsu Chemical Co., Ltd. The surface-treated silica-based filler can be obtained by treating the surface of a silica-based filler with a silane coupling agent according to a standard method. Commercially available surface-treated silica-based fillers may be used, such as "Zeothix 95" manufactured by JMHUBER Corporation.

[0027] The amount of silica-based filler blended is preferably 11 to 39 parts by mass, and more preferably 15 to 35 parts by mass, per 100 parts by mass of (a) organopolysiloxane. The average particle size of the silica-based filler is preferably 1 to 80 μm, and more preferably 2 to 40 μm. The average particle size of the silica-based filler can be measured as the median size using a particle size distribution analyzer based on laser diffraction.

[0028] Examples of the millable silicone rubber that can be used in the present invention include KE-571-U, KE-1571-U, KE-951-U, KE-541-U, KE-551-U, KE-561-U, KE-961T-U, KE-1541-U, KE-1551-U, KE-941-U, and KE-971T-U manufactured by Shin-Etsu Chemical Co., Ltd. Furthermore, examples of millable silicone rubber that can be used include KE-87C-40PU and the like, which contain a conductivity-imparting agent.

[0029] (B) Vulcanizing agent Examples of the vulcanizing agent include an addition reaction vulcanizing agent and an organic peroxide vulcanizing agent. Suitable examples of the addition reaction vulcanizing agent include organohydrogenpolysiloxanes, which are known as addition reaction vulcanizing agents having two or more SiH groups (SiH bonds) in one molecule. These addition reaction vulcanizing agents can be used alone or in combination. The amount of the addition reaction vulcanizing agent added is usually 0.1 parts by mass or more and 7 parts by mass or less per 100 parts by mass of the resin composition for the foamed elastic layer. When an addition reaction vulcanizing agent is used, the organic peroxide vulcanizing agent can crosslink the millable silicone rubber by itself, but when used in combination with the addition reaction vulcanizing agent as an auxiliary vulcanizing agent, the physical properties such as strength and distortion of the resulting fixing roller or pressure roller can be further improved.

[0030] Examples of organic peroxide vulcanizing agents include benzoyl peroxide, bis-2,4-dichlorobenzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, and 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane. The amount of the organic peroxide vulcanizing agent is usually 0.1 to 7 parts by mass per 100 parts by mass of the resin composition for the foamed elastic layer. The organic peroxide vulcanizing agents can be used alone or in combination of two or more.

[0031] The addition reaction vulcanizing agent is preferably used in combination with an addition reaction catalyst. Examples of the addition reaction catalyst include platinum black, platinic chloride, chloroplatinic acid, reaction products of chloroplatinic acid and monohydric alcohols, complexes of chloroplatinic acid and olefins, platinum bisacetoacetate, palladium-based catalysts, and rhodium-based catalysts. The amount of the addition reaction catalyst to be added can be a catalytic amount.

[0032] (C) Foaming agent The foaming agent may be any known foaming agent used in forming the foamed elastic layer 3. For example, at least one of a chemical foaming agent and unexpanded microballoons may be used. As for chemical foaming agents, inorganic foaming agents include sodium bicarbonate and ammonium carbonate, while organic foaming agents include organic azo compounds such as diazoamino derivatives, azonitrile derivatives, and azodicarboxylic acid derivatives. Among organic azo compounds, azodicarboxylic acid amide and azobis-isobutyronitrile are preferably used. Azobis-isobutyronitrile is particularly preferably used.

[0033] Examples of unexpanded microballoons include resin microballoons. Resin microballoons preferably have a thermoplastic resin outer shell. Examples of thermoplastic resins constituting the outer shell include vinylidene chloride / acrylonitrile copolymer, methyl methacrylate / acrylonitrile copolymer, and methacrylonitrile / acrylonitrile copolymer. Resin microballoons whose shell resin softening temperature is within an appropriate range in accordance with the curing temperature of the silicone rubber are preferably used. Examples of evaporative substances to be encapsulated include hydrocarbons such as butane and isobutane. The average particle size of the unexpanded microballoons is preferably 5 μm or more and 50 μm or less, and more preferably 5 μm or more and 25 μm or less.

[0034] Unexpanded microballoons suitable for the present invention are commercially available as the "Matsumoto Microsphere F Series" (manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.) and the "Expancel Series" (manufactured by Expancel Co., Ltd.), etc. Unexpanded resin microballoons suitable for the present invention are selected from resin microballoons that have the function of expanding at a temperature higher than the decomposition temperature of the chemical foaming agent used to form the foamed elastic layer 3. The amount of foaming agent added is preferably 0.5% by mass or more and 6% by mass or less, from the viewpoint of obtaining cells with a low specific gravity and uniform size relative to 100 parts by mass of the resin composition for foamed elastic layer.

[0035] (D) Other ingredients The resin composition for the foamed elastic layer may contain various additives, such as conductive agents, auxiliary agents such as chain extenders, catalysts, dispersants, antioxidants, antioxidants, non-silica fillers such as glass beads, pigments, colorants, processing aids, softeners, plasticizers, emulsifiers, heat resistance improvers, flame retardancy improvers, acid acceptors, thermal conductivity improvers, mold release agents, and solvents.

[0036] (Method for forming foamed elastic layer) The foamed elastic layer 3 is formed on the outer peripheral surface of the shaft 2 by simultaneously or successively carrying out heat curing and molding using a known molding method. From the viewpoint of forming uniform cells, the resin composition for the foamed elastic layer is preferably vulcanized using a microwave vulcanizer. In addition to vulcanization using microwaves, it is also preferable to use hot air in combination. When a microwave vulcanizing device is used, the output is preferably in the range of 4 kW to 8 kW, and the vulcanization time is preferably 5 minutes to 15 minutes. The microwaves penetrate into the foamed elastic layer 3 molded around the shaft 2 and heat it evenly, so that uniform cells can be formed.

[0037] The heating temperature during vulcanization of the resin composition for the foamed elastic layer is preferably 100°C to 500°C, more preferably 120°C to 300°C. The heating time is preferably several seconds to 1 hour, more preferably 10 seconds to 35 minutes. If necessary, secondary vulcanization may be performed. Tertiary vulcanization may be performed at 180 to 280°C, particularly 200 to 250°C, for 1 to 15 minutes. This multiple heating step is preferable because it allows for the expansion of unexpanded microballoons, the curing of the millable silicone rubber, the removal of residual low-molecular-weight siloxanes, and the thermal shrinkage of expanded microballoons to be controlled as needed. By performing this multiple heating step, the unexpanded microballoons expand while the silicone rubber simultaneously hardens, forming cell walls. Only the expanded microballoons subsequently undergo thermal shrinkage, allowing the average cell diameter to be adjusted to 150 μm or less. The rubber composition can also be foamed and cured by known methods to easily form a foamed elastic layer 3 containing cells.

[0038] The method for forming the foamed elastic layer 3 is not particularly limited and may include continuous vulcanization by extrusion molding, pressing, injection molding, etc. For example, extrusion molding may be selected. The foamed elastic layer 3 formed on the shaft 2 may also be ground or polished.

[0039] The sponge roller thus obtained may be further subjected to a polishing process, in which the shape of the sponge roller formed on the outer peripheral surface of the shaft body 2 is adjusted to a shape in which the thickness of the sponge roller in the axial direction of the shaft body 2 gradually increases toward the center of the shaft body and gradually decreases from the center of the shaft body 2 toward the tip of the shaft body, i.e., a crown shape, or a shape in which the thickness of the sponge roller increases from the center of the shaft body 2 toward both ends of the shaft body, i.e., an inverted crown shape.

[0040] The thickness of the foamed elastic layer 3 is not particularly limited, but is preferably 0.1 mm to 6 mm, and more preferably 1 mm to 4 mm. Note that the thickness in this specification refers to the thickness in the direction perpendicular to the axial direction of the sponge roller 1.

[0041] The outer diameter of the foamed elastic layer 3 is not particularly limited, and is preferably, for example, 6 mm or more and 25 mm or less, and more preferably 7 mm or more and 21 mm or less.

[0042] The outer peripheral surface of the foamed elastic layer 3 may be subjected to a surface treatment such as primer treatment, corona treatment, plasma treatment, excimer treatment, UV treatment, itro treatment, or flame treatment in order to improve adhesion to the coating layer.

[0043] (cell density) The difference in cell density between the surface layer side and the inner layer side of the foamed elastic layer 3 is ±7% or less, preferably ±3% or less, and more preferably ±1.2% or less, based on the cell density on the surface layer side. The cell density can be measured by the following measurement method. -Measurement method- Images are taken of the surface 50% and inner 50% regions of the foamed elastic layer, and the cell density is calculated using a cell structure analysis system, Porescan (manufactured by Goldluck BmbH).

[0044] (specific gravity) The difference in specific gravity between the surface layer side and the inner layer side of the foamed elastic layer is preferably ±3% or less, and more preferably ±1.1% or less, based on the specific gravity of the surface layer side. The specific gravity can be measured by the following method. -Measurement method- A sample was prepared by cutting the silicone rubber sponge into a size of 50 mm x 20 mm x t (thickness) 5 mm, and measurements were taken at three points using a hydrometer (product name "MDS-300", manufactured by Alpha Mirage) to obtain the arithmetic average.

[0045] (cell diameter) The difference in cell diameter between the surface layer side and the inner layer side of the foamed elastic layer is preferably ±7% or less, and more preferably ±1% or less, based on the cell diameter on the surface layer side. The cell diameter can be measured by the following method. -Measurement method- Images are taken of the surface 50% and inner 50% regions of the foamed elastic layer, and the cell diameter is calculated using a cell structure analysis system, Porescan (manufactured by Goldluck BmbH).

[0046] <Other configurations> The sponge roller of the present invention may have a covering layer provided on the outer periphery of the foamed elastic layer 3. The covering layer is preferably a resin tube. Materials that can be used for the resin tube include polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, FEP (tetrafluoroethylene-hexafluoropropylene copolymer), PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), ETFE (tetrafluoroethylene-ethylene copolymer), PVDF (polyvinylidene fluoride), polyethylene terephthalate, polyamide, polyimide, polycarbonate, polystyrene, ABS, polyurethane, etc. Among these, PFA is preferred. More preferably, the resin tube is made of PFA. The resin tube can be produced by melt extrusion of a resin composition, etc. The resin tube can be attached to the foamed elastic layer 3 provided with the adhesive layer by a known pressurized insertion method or reduced pressure insertion method. The thickness of the resin tube is preferably 30 μm or more and 60 μm or less from the viewpoint of providing a conductive layer on the inner surface.

[0047] In the sponge roller of the present invention, cells are uniformly formed on the surface and inner layer sides of the foamed elastic layer 3. As a result, the sponge roller has excellent compression set and high durability, and when incorporated into an image forming apparatus as a fixing roller or pressure roller, it can provide high-quality images. [Example]

[0048] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the examples shown below.

[0049] [Example 1] The sponge roller of Example 1 was produced by the following procedure. (Formation of primer layer) An electroless nickel-plated shaft (made of SUM23, diameter 10 mm, length 274.2 mm) was washed with ethanol, and its surface was coated with a silicone primer (product name "Primer No. 16", manufactured by Shin-Etsu Chemical Co., Ltd.). The primer-treated shaft was baked in a gear oven at 150°C for 10 minutes and then cooled at room temperature for at least 30 minutes, forming a primer layer on the outer surface of the shaft.

[0050] (Formation of foamed elastic layer) The resin composition for the foamed elastic layer described below was molded onto the outer circumferential surface of the shaft by extrusion molding, and vulcanization was carried out by heating for 12 minutes using microwaves and hot air at 200°C using a wide continuous heating device (manufactured by Micro Electronics Co., Ltd.) This formed a foamed elastic layer containing silicone rubber on the outer circumferential surface of the primer-treated shaft.

[0051] Details of the resin composition for the foamed elastic layer are as follows. (A) Millable silicone rubber KE-571-U (Shin-Etsu Chemical Co., Ltd.) 100 parts by mass (B) Vulcanizing agent: Product name "C-25B" (manufactured by Shin-Etsu Chemical Co., Ltd.) 1.0 part by mass (C) Foaming agent Chemical foaming agent: Product name "AIBN" (Otsuka Chemical Co., Ltd.) 0.5 parts by mass (D) Colorant Product name "KE-Color BR" (manufactured by Shin-Etsu Chemical Co., Ltd.) 0.5 parts by mass (E) Catalyst Product name "C-25A" (manufactured by Shin-Etsu Chemical Co., Ltd.) 0.5 parts by mass

[0052] A sponge roller was produced in the same manner as in Example 1, except that the vulcanization conditions were microwave and hot air at 230° C. for 12 minutes.

[0053] [Comparative Example 1] A sponge roller was produced in the same manner as in Example 1, except that the vulcanization conditions were set to 200° C. for 25 minutes in an infrared heating furnace (IR furnace).

[0054] [evaluation] For the above-mentioned Examples and Comparative Examples, the cell density, specific gravity, and number of cells were measured by the above-mentioned measuring methods. The evaluation results are shown in Table 1.

[0055] [Table 1]

[0056] As shown in Table 1, in Examples 1 and 2, the foamed elastic layer was formed by microwave vulcanization of a resin composition for foamed elastic layers containing Millable silicone rubber, a vulcanizing agent, and a foaming agent, and the difference in cell density between the surface and inner side of the foamed elastic layer was ±7% or less. A difference in cell density between the surface and inner side of the foamed elastic layer of ±7% or less means that the cells of the foamed elastic layer are formed uniformly throughout, and since the compression set is excellent, a highly durable sponge roller can be obtained. [Explanation of symbols]

[0057] 1 sponge roller 2-axis body 3. Foam elastic layer

Claims

1. A sponge roller having a shaft body and a foamed elastic layer on the outer periphery of the shaft body, The foamed elastic layer is formed by vulcanizing a resin composition for foamed elastic layer, the resin composition including a millable silicone rubber, a vulcanizing agent, and a foaming agent, using microwaves; A sponge roller, wherein the difference in cell density between the surface layer side and the inner layer side of the foamed elastic layer is ±7% or less based on the cell density of the surface layer side.

2. 2. The sponge roller according to claim 1, wherein the foaming agent comprises at least one of a chemical foaming agent and unexpanded microballoons.

3. 2. The sponge roller according to claim 1, wherein a difference in specific gravity between the surface layer side and the inner layer side of the foamed elastic layer is within ±3% based on the specific gravity of the surface layer side.

4. 2. The sponge roller according to claim 1, wherein the sponge roller is a fixing roller or a pressure roller.

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