Sponge roller

Abstract

To provide a sponge roller having high durability even when a foamed elastic layer has low hardness.SOLUTION: The sponge roller includes an axial body 2 and a foamed elastic layer 3 on the outer periphery of the axial body 2, wherein the foamed elastic layer 3 is formed from a foamed elastic layer composition containing (a) an organopolysiloxane, (b) a silicone ball, (c) a conductivity-imparting agent, (d) a filler, (e) a vulcanizing agent, and (f) a foaming agent. In the sponge roller 1, the content of the silicone balls (b) in the composition for the foamed elastic layer is 3 mass% or more and 24 mass% or less, and the foamed elastic layer 3 has an Asker C hardness according to JISK7312 of 45 or less and a surface-roughness Ra of 1 μm or more and 5 μm or less.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 include various elastic rollers, such as developing rollers, transfer rollers, toner supply rollers, and cleaning rollers, each having an elastic layer provided on the outer periphery of a shaft. The elastic layer can be formed by coating the outer periphery of the shaft with a rubber composition using, for example, a crosshead extrusion molding machine, followed by vulcanization (see, for example, Patent Document 1).

[0003] For example, since the developing roller rotates in contact with the image carrier, if the hardness of the elastic layer is too high, the developer may be damaged between the developing roller and the image carrier. To address this problem, it is conceivable to add a silicone rubber to the composition for the elastic layer to reduce the hardness of the elastic layer and thereby reduce damage to the developer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-224378 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the case of a roller having a foamed elastic layer such as a fixing roller or a pressure roller, if the hardness of the foamed elastic layer composition is to be reduced, the foaming ratio is increased, which results in the formation of more cells, which may deteriorate the surface smoothness during extrusion molding and reduce durability, resulting in a problem of reduced image quality. 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 that has high durability even when the foamed elastic layer has a low hardness. [Means for solving the problem]

[0006] As a result of extensive research, the inventors discovered that by incorporating low-hardness, high-resilience silicone balls into a foamed elastic layer composition, it is possible to reduce the hardness of the foamed elastic layer while maintaining surface smoothness during extrusion molding, and thus arrived at the present invention.

[0007] That is, 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 from a foamed elastic layer composition containing (a) organopolysiloxane, (b) silicone balls, (c) a conductivity imparting agent, (d) a filler, (e) a vulcanizing agent, and (f) a foaming agent, and the content of (b) silicone balls in the foamed elastic layer composition is 3% by mass or more and 24% by mass or less, the foamed elastic layer has an Asker C hardness in accordance with JIS K 7312 of 45 or less, and the surface roughness Ra is 1 μm or more and 5 μm or less.

[0008] (b) The average particle size of the silicone balls is preferably 2 μm or more and 20 μm or less. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a sponge roller that has high durability even though the foamed elastic layer has a low hardness. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a perspective view showing an embodiment of a sponge roller of the present invention. [Figure 2] FIG. 1 is a schematic diagram showing a compression set measuring device. DETAILED DESCRIPTION OF THE INVENTION

[0011] 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.

[0012] (shaft body) The shaft 2 can preferably be a conductive shaft used in a conventionally known sponge roller. 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."

[0013] The shaft 2 may contain an insulating resin. The insulating resin may be, for example, a thermoplastic resin or a thermosetting resin. The shaft 2 may include, for example, a core made of an insulating resin and a plating layer provided on the core. Such a shaft 2 can be obtained, for example, by plating the core made of an insulating resin to make it conductive. The shaft 2 is preferably a cored bar in order to obtain good electrical conductivity.

[0014] 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 outer peripheral surface of the shaft 2 may be subjected to treatment such as cleaning, degreasing, or primer treatment.

[0015] 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.

[0016] (foam elastic layer) The foamed elastic layer 3 is preferably made of silicone rubber. For example, the foamed elastic layer composition described below is extruded onto the outer peripheral surface of the shaft 2, followed by vulcanization and polishing. The foamed elastic layer composition contains at least (a) organopolysiloxane, (b) silicone balls, (c) a conductivity imparting agent, (d) a filler, (e) a vulcanizing agent, and (f) a foaming agent.

[0017] (a) Organopolysiloxane The organopolysiloxane is preferably an organopolysiloxane having a degree of polymerization of 100 or more and represented by the following average composition formula (I). R 1 a SiO (4-a) / 2 (I) (In the formula, R 1 represent the same or different unsubstituted or substituted monovalent hydrocarbon groups, and a is a positive number of 1.95 or more and 2.05 or less.

[0018] R 1 Examples of the alkyl group 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.

[0019] The molecular chain terminals of the organopolysiloxane are preferably 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.

[0020] The 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 the organopolysiloxane.

[0021] Organopolysiloxanes can be obtained, for example, by co-hydrolysis and condensation of one or more organohalosilanes, or by ring-opening polymerization of cyclic polysiloxanes such as siloxane trimers or tetramers. The organopolysiloxane may basically be a linear diorganopolysiloxane, or may be partially branched. Furthermore, the organopolysiloxane may be a mixture of two or more organopolysiloxanes with different molecular structures.

[0022] The organopolysiloxane preferably has a kinematic viscosity of 100 cSt or more, more preferably 100,000 cSt or more and 10,000,000 cSt or less at 25° C. The degree of polymerization of the organopolysiloxane is preferably, for example, 100 or more, more preferably 3,000 or more and 10,000 or less.

[0023] (b) Silicone ball In this specification, silicone balls refer to fine particles made of silicone. The average particle size of the silicone balls is preferably 5 μm or more and 20 μm or less. The hardness (Durometer A) of the silicone balls is preferably 25 or more and 75 or less, and more preferably 30 or more and 75 or less. An example of a commercially available product is "KMP-598" (manufactured by Shin-Etsu Chemical Co., Ltd.).

[0024] In the present invention, the content of silicone balls in the foamed elastic layer composition is 3% by mass or more and 24% by mass or less, and more preferably 5% by mass or more and 23% by mass or less. The content of silicone balls within the above range results in low hardness and good surface smoothness during extrusion molding. As a result, a highly durable sponge roller can be obtained, and when incorporated into an image forming apparatus, high-quality images can be obtained.

[0025] (c) Conductive agent Examples of the conductivity imparting agent include conductive powders containing conductive carbon, rubber carbons, metals, conductive polymers, etc. Carbon black is preferably used as the conductive powder, and examples of carbon black include furnace black such as Ketjenblack (registered trademark), acetylene black, channel black, and thermal black. The resistance value of the foamed elastic layer is preferably adjusted to the range of 4 to 9 (log Ω).

[0026] (d) Filler Examples of the filler include silica-based fillers, such as fumed silica and precipitated silica.

[0027] 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. 3may 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.

[0028] The amount of silica-based filler blended is preferably 11 parts by mass or more and 39 parts by mass or less, and more preferably 15 parts by mass or more and 35 parts by mass or less, per 100 parts by mass of (a) organopolysiloxane. The average particle size of the silica-based filler is preferably 1 μm or more and 80 μm or less, and more preferably 2 μm or more and 40 μm or less. The average particle size of the silica-based filler can be measured as the median size using a particle size distribution measuring device based on the laser diffraction method.

[0029] (e) Vulcanizing agent Examples of the vulcanizing agent include an addition vulcanizing agent and an organic peroxide vulcanizing agent. Suitable examples of the addition vulcanizing agent include organohydrogenpolysiloxanes, which are known as addition reaction type vulcanizing agents having two or more SiH groups (SiH bonds) in one molecule. The addition vulcanizing agents can be used alone or in combination of two or more. The amount of the addition vulcanizing agent is usually preferably 0.1 to 10 parts by mass, more preferably 2 to 5 parts by mass, per 100 parts by mass of the foamed elastic layer composition.

[0030] When an addition vulcanizing agent is used, the organic peroxide vulcanizing agent can crosslink the millable silicone rubber alone, but when used in combination with the addition vulcanizing agent as an auxiliary vulcanizing agent, the physical properties of the resulting roller, such as strength and distortion, can be further improved.

[0031] 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 preferably 0.1 to 10 parts by mass, more preferably 2 to 8 parts by mass, per 100 parts by mass of the foamed elastic layer composition.

[0032] The addition 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 with monohydric alcohols, complexes of chloroplatinic acid with 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.

[0033] (f) Foaming agent (f) The foaming agent may be either a chemical foaming agent or unexpanded microballoons. Examples of chemical foaming agents include inorganic foaming agents such as sodium bicarbonate and ammonium carbonate. Examples of 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.

[0034] Examples of unexpanded microballoons include resin microballoons. Resin microballoons with a thermoplastic resin outer shell are preferably used. Examples of thermoplastic resins constituting the outer shell include vinylidene chloride / acrylonitrile copolymer, methyl methacrylate / acrylonitrile copolymer, and methacrylonitrile / acrylonitrile copolymer. Resin microballoons with a softening temperature of the outer shell resin within an appropriate range, matching 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 particle size of the unexpanded microballoons is preferably 30 μm or less, and more preferably 5 μm or more and 30 μm or less.

[0035] 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.

[0036] The amount of foaming agent to be added is preferably 0.5 parts by mass or more and 6 parts by mass or less, based on 100 parts by mass of the foamed elastic layer composition, from the viewpoint of obtaining cells with a low specific gravity and uniform size.

[0037] (Other ingredients) (g) Reaction inhibitor The foamed elastic layer composition may contain a reaction inhibitor. The reaction inhibitor is a component that inhibits the crosslinking reaction of the silicone raw rubber at room temperature (e.g., 23°C). The reaction inhibitor may be, for example, a component that is deactivated or volatilized by heating. The inclusion of a reaction inhibitor extends the pot life of the foamed elastic layer composition, making the foamed elastic layer composition easier to work with.

[0038] The reaction inhibitor can be appropriately selected from components capable of inhibiting the crosslinking reaction of the silicone raw rubber at room temperature, depending on the types of silicone raw rubber, vulcanizing agent, and curing accelerator blended in the foamed elastic layer composition. For example, when the foamed elastic layer composition contains a platinum catalyst, suitable reaction inhibitors include methylvinylcyclotetrasiloxane, acetylene alcohols, siloxane-modified acetylene alcohols, and hydroperoxides.

[0039] The amount of the reaction inhibitor is not particularly limited and can be adjusted appropriately depending on the desired pot life, curing temperature, curing speed, etc. The amount of the reaction inhibitor is, for example, preferably 0.5% by mass or more and 8.0% by mass or less, and more preferably 1.0% by mass or more and 6.0% by mass or less, based on the total amount of the foamed elastic layer composition.

[0040] The foamed elastic layer composition may also contain various additives. Examples of the various additives include auxiliary agents such as chain extenders, catalysts, dispersants, antioxidants, antioxidants, and 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. These various additives may be commonly used additives or may be specially used additives depending on the application.

[0041] The heating temperature when vulcanizing the foamed elastic layer composition is preferably 100°C or higher and 500°C or lower, more preferably 120°C or higher and 300°C or lower. The heating time is preferably several seconds to 1 hour, more preferably 10 seconds to 35 minutes. If necessary, secondary vulcanization may be performed. Further, tertiary vulcanization may be performed at 180 to 280°C, particularly 200 to 250°C, for 1 to 15 minutes.

[0042] The sponge roller thus obtained is polished to the desired product outer diameter. In the polishing process, the shape of the sponge roller formed on the outer surface of the shaft is adjusted to a straight shape, a shape in which the thickness of the sponge roller gradually increases in the axial direction of the shaft toward the center and gradually decreases from the center to the tip of the shaft (i.e., an inverted crown shape), or a shape in which the thickness of the sponge roller increases from the center of the shaft toward both ends of the shaft (i.e., an inverted crown shape).

[0043] 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.

[0044] 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.

[0045] (Asker C hardness of foam elastic layer) The foamed elastic layer 3 in the sponge roller of the present invention has an Asker C hardness of 45 or less, more preferably 30 or less, and even more preferably 26.5 or less. The lower limit is preferably 10 or more, and more preferably 20 or more. The Asker C hardness of the foamed elastic layer is measured by the measurement method in the examples described later.

[0046] (Surface roughness of foamed elastic layer) The surface roughness Ra of the foamed elastic layer 3 is preferably 1 μm or more and 5 μm or less. When the surface roughness Ra is in the above range, the smoothness is high, and therefore the durability is high and high-quality images can be provided. The surface roughness Ra is measured by the measurement method in the examples described later.

[0047] The sponge roller of the present invention has excellent flatness and smoothness, and can be used as a pressure roller or a fixing roller of an image forming apparatus, and can provide high durability. [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: Table 1 shows the formulation of the foamed elastic layer composition of each Example and Comparative Example. (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) First, a foamed elastic layer composition was prepared. Details of the foamed elastic layer composition are as follows. Silicone compound (product name "KE-931", manufactured by Shin-Etsu Chemical Co., Ltd.) 95 parts by mass Silicone ball (manufactured by Shin-Etsu Chemical Co., Ltd.) 5 parts by weight Peroxide vulcanizing agent (product name "C-3", manufactured by Shin-Etsu Chemical Co., Ltd.) 3.0 parts by mass Foaming agent product name: "AZO series AIBN" (manufactured by Otsuka Chemical Co., Ltd.) 1.5 parts by mass

[0051] The foamed elastic layer composition was used to form a foamed elastic layer on the outer peripheral surface of the foamed elastic layer using an extrusion molding machine, and the layer was heated in an infrared heating furnace (IR furnace) at 270°C for 5 minutes, and then heated in a gear oven at 200°C for 4 hours for vulcanization. In this way, a foamed elastic layer was formed on the outer peripheral surface of the foamed elastic layer, and a sponge roller was produced. The thickness of the foamed elastic layer was 4 mm.

[0052] [Examples 2 to 4, Comparative Examples 1 to 4] A sponge roller was produced in the same manner as in Example 1, except that the composition of the components for the foamed elastic layer was changed as shown in Table 1.

[0053] [evaluation] The sponge rollers produced in the above Examples and Comparative Examples were evaluated for the following items. The evaluation results are shown in Table 1.

[0054] (Asker C hardness) The Asker C hardness of the foamed elastic layer was measured in accordance with JIS K 7312 using an Asker C hardness tester (manufactured by Kobunshi Keiki Co., Ltd.).

[0055] (Initial plasticity) After compounding with weighting agents, etc., the plasticity of the unvulcanized rubber was measured in accordance with JIS 6249. The instrument used was a Williams Plastometer No. 105 (manufactured by Yasuda Seiki Seisakusho Co., Ltd.). The volume was 2±0.02 cm. 3 A cylindrical sample piece was prepared and sandwiched between two sheets of cellophane paper for measurement. The measurement time was 3 minutes, and the value after 3 minutes was taken as the initial plasticity.

[0056] (surface roughness Ra) The surface roughness Ra of the foamed elastic layer was measured in the circumferential direction of the sponge roller at a measurement length of 2.4 mm and a measurement speed of 0.15 mm / s in accordance with JIS-1994.

[0057] (superficial) The surfaces of the sponge rollers of the examples and comparative examples were observed and evaluated according to the following criteria. ○: The surface is smooth and glossy ×: The surface is very rough and lacks gloss.

[0058] (Compression set) As shown in Figure 2, the sponge roller 1 is sandwiched between iron plates 20 at the top and bottom and fixed in a vice. At this time, a spacer 21 is sandwiched between the upper and lower iron plates 20 to adjust the distance between the iron plates to maintain a constant distance. In this state, it is left in a dryer at 180°C for 5 hours. It is then removed from the dryer and left at room temperature for 16 hours. After that, the iron plates that were sandwiching the sponge roller 1 are removed, the diameter of the sponge roller 1 is measured, and the compression set is calculated using the following formula. Compression set (%) = (D1-D2) / (D1-H) x 100 Diameter of sponge roller 1 before test D1 Diameter of sponge roller 1 after test D2 Shaft diameter L Spacer 21 height H Product outer diameter φ34mm, shaft diameter φ22, thickness 6mm Compression rate 25% → Pushed in 1.5mm

[0059] [Table 1]

[0060] As shown in Table 1, the sponge rollers of the examples have a foamed elastic layer with low hardness, and are therefore good in compression set and excellent in durability. [Explanation of symbols]

[0061] 1 sponge roller 2-axis body 3. Foam elastic layer

Claims

1. A sponge roller comprising a shaft body and a foamed elastic layer on the outer periphery of the shaft body, the foamed elastic layer is formed from a foamed elastic layer composition containing (a) organopolysiloxane, (b) silicone balls, (c) a conductivity imparting agent, (d) a filler, (e) a vulcanizing agent, and (f) a foaming agent; the content of the (b) silicone balls in the foamed elastic layer composition is 3% by mass or more and 24% by mass or less, The foamed elastic layer has an Asker C hardness in accordance with JIS K 7312 of 45 or less, and a surface roughness Ra of 1 μm or more and 5 μm or less.

2. 2. The sponge roller according to claim 1, wherein the average particle size of the silicone balls (b) is 2 [mu]m or more and 20 [mu]m or less.

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