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 an elastic layer 3 provided around an outer periphery of the shaft 2. The elastic layer 3 is composed of a rubber composition containing a millable silicone rubber, unexpanded microballoons, and cross-linker, where the unexpanded microballoons have particle diameters of 30 μm or less and the elastic layer 3 has an area average cell diameter of 90 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 apparatuses using electrophotography are used in printers such as laser printers and video printers, copiers, facsimiles, and multifunction machines thereof. The image forming apparatuses using electrophotography are equipped with various printing rollers, such as cleaning rollers, charging rollers, developing rollers, transfer rollers, secondary transfer rollers, pressure rollers, paper feed rollers, and fixing rollers, each of which has a shaft body and an elastic layer formed on its outer circumferential surface.

[0003] The fixing means in the image forming apparatus adopts a heat roller fixing method. In the heat roller fixing method, a pair of a heating roller (fixing roller) and a pressure roller is used as a basic configuration, and a recording material (transfer material sheet, fax paper, printing paper, etc.) carrying a toner image is generally introduced into the pressure nip of the pair of rollers to fix the toner image to the recording material by heat and pressure. A foamed elastic layer (sponge layer) is used in the fixing roller or pressure roller used as the fixing means to adjust the nip pressure to an appropriate level.

[0004] The foamed elastic layer is generally formed by vulcanizing and foaming millable silicone rubber containing organopolysiloxane and a filler. A fixing or pressure roller having a foamed elastic layer is mounted in a pressure-contact state and functions by rotating continuously or intermittently, so it is prone to loads due to heat and friction, and the hardness of the foamed elastic layer decreases over time, so it is required to have high durability. For example, Patent Document 1 discloses a sponge roller in which a chemical foaming agent and unexpanded microballoons that expand at a higher temperature than the chemical foaming agent are contained in the elastic layer in order to improve durability. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2018-36611 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, in order to meet the recent demand for high-speed, high-definition, and high-quality image forming apparatuses, there is a demand for even greater durability than the technology described in Patent Document 1. The present invention has been made in consideration of the above circumstances, and has an object to provide a sponge roller having excellent durability. [Means for solving the problem]

[0007] As a result of intensive research, the inventors found that when unexpanded microballoons were used, there were some lots in which the sponge roller had coarse cells. They also found that this was due to the presence of microballoons with somewhat large particle diameters, which resulted in the sponge cells being non-uniform, and thus arrived at the present invention. In other words, the present invention is a sponge roller comprising a shaft body and an elastic layer provided on the outer periphery of the shaft body, wherein the elastic layer is formed from a rubber composition containing millable type silicone rubber, unexpanded microballoons, and a crosslinking agent, wherein the particle diameter of the unexpanded microballoons is 30 μm or less, and the area average cell diameter of the elastic layer is 90 μm or less.

[0008] The Asker C hardness of the elastic layer is preferably 10° or more and 80° or less.

[0009] The maximum cell diameter of the elastic layer is preferably 200 μm or less.

[0010] The specific gravity of the elastic layer is preferably 0.3 or more and 0.8 or less.

[0011] The open cell ratio of the elastic layer is preferably 20% or more and 90% or less. Effect of the Invention

[0012] According to the present invention, a sponge roller having excellent durability can be obtained. [Brief description of the drawings]

[0013] [Figure 1] 1 is a perspective view showing an embodiment of a sponge roller of the present invention. [Diagram 2] 1 is a graph showing the particle size distribution of unexpanded microballoons. [Diagram 3] 1 is a graph showing the area average cell diameter distribution of an elastic layer. [Figure 4] 1 is a graph showing the results of a durability test. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment 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 comprising a shaft 2 and an elastic layer 3 provided on the outer periphery of the shaft 2, in which the elastic layer 3 is formed from a rubber composition containing millable silicone rubber, unexpanded microballoons, and a crosslinking agent, the particle diameter of the unexpanded microballoons being 30 μm or less, and the area average cell diameter of the elastic layer 3 being 90 μm or less. Each component will be described in detail below.

[0015] <Shaft body> The shaft body 2 may preferably be a shaft body having conductive properties and used in a conventionally known sponge roller. The shaft body 2 is preferably made of at least one metal selected from the group consisting of iron, aluminum, stainless steel, and brass. Such a shaft body 2 is generally also known as a "core metal."

[0016] The shaft body 2 may contain an insulating resin. The insulating resin may be, for example, a thermoplastic resin or a thermosetting resin. The shaft body 2 may include, for example, a core body made of an insulating resin and a plating layer provided on the core body. Such a shaft body 2 can be obtained, for example, by plating a core body made of an insulating resin to make it conductive. The shaft body 2 is preferably a core bar in order to obtain good electrical conductivity.

[0017] The shape of the shaft body 2 is preferably, for example, rod-like, tubular, etc. The cross-sectional shape of the shaft body 2 may be, for example, circular, elliptical, or non-circular, such as polygonal. The outer peripheral surface of the shaft body 2 may be subjected to treatment such as cleaning treatment, degreasing treatment, and primer treatment.

[0018] The axial length of the shaft body 2 is not particularly limited, and may be adjusted as appropriate depending on the type of the image forming apparatus in which it is installed. The diameter (diameter of the circumscribing circle) of the shaft body 2 is also not particularly limited, and may be adjusted as appropriate depending on the type of the image forming apparatus in which it is installed.

[0019] <Elastic layer> The elastic layer 3 can be formed by curing a composition for elastic layer containing (A) a millable type silicone rubber composition, (B) unexpanded microballoons, and (C) a crosslinking agent. The components of the composition for elastic layer are described below.

[0020] (A) Millable type silicone rubber composition The millable silicone rubber composition is preferably an addition-curing millable silicone rubber composition. The addition-curing millable silicone rubber composition preferably contains, for example, at least (a) an organopolysiloxane, (b) a filler, and (c) a conductivity imparting agent.

[0021] (a) Organopolysiloxane The organopolysiloxane (a) 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 number of carbon atoms in the hydrocarbon group is preferably 1 or more and 12 or less, more preferably 1 or more and 8 or less.

[0022] 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 a group in which some or all of the hydrogen atoms of these hydrocarbon groups are substituted with a substituent. The substituent may be, for example, a halogen atom, a cyano group, etc. Examples of the hydrocarbon group having a substituent include a chloromethyl group, a trifluoropropyl group, a cyanoethyl group, etc.

[0023] 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 triarylalkylsilyl group such as a trivinylsilyl group.

[0024] The organopolysiloxane (a) 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).As the alkenyl group contained in the (a) organopolysiloxane, a vinyl group is particularly preferable.

[0025] The (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. The (a) organopolysiloxane may be a basically linear diorganopolysiloxane, or may be partially branched. The (a) organopolysiloxane may also be a mixture of two or more types having different molecular structures.

[0026] The (a) organopolysiloxane 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 the (a) organopolysiloxane is, for example, preferably 100 or more, and more preferably 3,000 or more and 10,000 or less.

[0027] (b) Filler (b) Examples of the filler include silica-based fillers, such as fumed silica and precipitated silica.

[0028] Silica-based fillers include R 2 Si(OR 3 A surface-treated silica-based filler having a surface treated with a silane coupling agent represented by the 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, a mercapto group, etc. 3may be an alkyl group, for example, a methyl group, an ethyl group, etc. 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. As the surface-treated silica-based filler, a commercially available product may be used, for example, under the trade name "Zeothix 95" manufactured by JMHUBER Co., Ltd.

[0029] The amount of the silica-based filler is preferably 11 to 39 parts by mass, more preferably 15 to 35 parts by mass, per 100 parts by mass of the (a) organopolysiloxane. The average particle size of the silica-based filler is preferably 1 to 80 μm, 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 measuring device using a laser light diffraction method.

[0030] (c) Conductive agent Examples of the conductivity imparting agent include conductive powders including conductive carbon, carbons for rubber, metals, conductive polymers, etc. As the conductive powder, it is preferable to use carbon black, and examples of the carbon black include furnace black such as Ketjen Black (registered trademark), acetylene black, channel black, thermal black, etc. The resistance value of the elastic layer is preferably adjusted to the range of 4 to 9 (log Ω).

[0031] (B) Unexpanded microballoons The elastic layer composition contains at least unexpanded microballoons as a foaming agent. Examples of unexpanded microballoons include resin microballoons. Resin microballoons that use a thermoplastic resin for the outer shell are preferably used. Examples of the thermoplastic resin that constitutes the outer shell include vinylidene chloride / acrylonitrile copolymer, methyl methacrylate / acrylonitrile copolymer, and methacrylonitrile / acrylonitrile copolymer. It is preferable to use resin microballoons whose shell resin has a softening temperature within an appropriate range in accordance with the curing temperature of the silicone rubber. 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. The particle size of the unexpanded microballoons is a value measured by the measuring method in the Examples described later.

[0032] Unexpanded 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 Expansel 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 elastic layer 3.

[0033] The foaming agent may further contain a chemical foaming agent. Examples of the chemical foaming agent include inorganic foaming agents such as sodium bicarbonate and ammonium carbonate. Examples of the organic foaming agent include organic azo compounds such as diazoamino derivatives, azonitrile derivatives, and azodicarboxylic acid derivatives. Among the organic azo compounds, azodicarboxylic acid amide and azobis-isobutyronitrile are preferably used. In particular, azobis-isobutyronitrile is preferably used.

[0034] The blending amount of the foaming agent is preferably 0.5% by mass or more and 6% by mass or less, from the viewpoint of obtaining cells of uniform size while having a low specific gravity relative to 100 parts by mass of the elastic layer composition.

[0035] (C) Crosslinking agent The composition for the elastic layer contains a crosslinking agent. Examples of the crosslinking agent include an addition reaction crosslinking agent and an organic peroxide crosslinking agent. As the addition reaction crosslinking agent, for example, organohydrogenpolysiloxane, which is known as an addition reaction type crosslinking agent having two or more SiH groups (SiH bonds) in one molecule, can be preferably used. The addition reaction crosslinking agent can be used alone or in combination of two or more. The amount of the addition reaction crosslinking agent is usually 0.1 parts by mass or more and 7 parts by mass or less per 100 parts by mass of the composition for the elastic layer.

[0036] When an addition reaction crosslinking agent is used, the organic peroxide crosslinking agent can crosslink the millable silicone rubber by itself, but when used in combination as an auxiliary crosslinking agent for the addition reaction crosslinking agent, the physical properties such as strength and distortion of the obtained toner supply roller can be further 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, etc. The amount of the organic peroxide crosslinking agent is usually 0.1 parts by mass or more and 7 parts by mass or less per 100 parts by mass of the composition for the elastic layer. The organic peroxide crosslinking agent may be used alone or in combination of two or more kinds.

[0037] The addition reaction crosslinking agent is preferably used in combination with an addition reaction catalyst. Examples of the addition reaction catalyst include platinum black, platinic chloride, chloroplatinic acid, a reaction product of chloroplatinic acid with a monohydric alcohol, a complex of chloroplatinic acid with an olefin, platinum bisacetoacetate, a palladium catalyst, a rhodium catalyst, etc. The amount of the addition reaction catalyst to be used may be a catalytic amount.

[0038] (Other Ingredients) The elastic layer composition may further contain various additives. Examples of the various additives include auxiliary agents such as chain extenders, crosslinking agents, catalysts, dispersants, antioxidants, antioxidants, and fillers other than silica-based materials such as glass beads, pigments, colorants, processing aids, softeners, plasticizers, emulsifiers, heat resistance improvers, flame retardant improvers, acid acceptors, thermal conductivity improvers, release agents, and solvents. These various additives may be additives that are commonly used, or may be additives that are specially used depending on the application.

[0039] Examples of the millable silicone rubber 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. Also, examples of the millable silicone rubber that contains a conductivity imparting agent include KE-87C-40PU.

[0040] The elastic layer 3 is formed on the outer peripheral surface of the shaft body 2 by simultaneously or successively carrying out heat curing and molding using a known molding method. The molding method of the elastic layer 3 is not particularly limited and may be continuous vulcanization by extrusion molding, pressing, molding by injection, etc. For example, extrusion molding, etc. may be selected. The method for curing the composition for elastic layer may be any method that can apply heat required for curing (vulcanization) the composition for elastic layer. The heating temperature when vulcanizing the composition for elastic layer is preferably 100°C or more and 500°C or less, more preferably 120°C or more and 300°C or less. The heating time is preferably several seconds or more and 1 hour or less, more preferably 10 seconds or more and 35 minutes or less. In addition, secondary vulcanization may be performed as necessary.

[0041] (area average cell diameter of elastic layer) The area average cell diameter of the elastic layer 3 is preferably 90 μm or less. When the area average cell diameter of the elastic layer is within the above range, the cells are fine and uniform, the amount of reduction in hardness can be reduced, and an elastic layer with high durability can be obtained. The area average cell diameter is a value measured by the measuring method in the Examples described later.

[0042] (Hardness of elastic layer) The Asker C hardness of the elastic layer 3 is preferably 10° or more and 80° or less, and more preferably 20° or more and 60° or less. The method for measuring the hardness of the elastic layer 3 is to press the center of the presser of a hardness meter against the curved surface of a roller to be measured, and to read the scale at the moment when the reference surface comes into contact with the surface of the roller. In practice, the Asker C hardness meter can be set to a load of 9.8 N, dropped from a distance of about 10 mm, and measured by reading the peak value after the hardness meter comes into contact with the roller surface. As the hardness meter, an ASKER Rubber Hardness Tester Type C (manufactured by Kobunshi Keiki Co., Ltd.) can be used. The elastic layer of the sponge roller of the present invention exhibits a hardness reduction of 10% or less in a 200-hour durability test.

[0043] (Specific gravity of elastic layer) From the viewpoint of durability, the specific gravity of the elastic layer 3 is preferably 0.3 or more and 0.8 or less, and more preferably 0.3 or more and 0.6 or less. The specific gravity was measured as follows. A high-precision electronic specific gravity meter, MDS-300, manufactured by ALFA MIRAGE, was used. First, about 2.0 g of the foamed elastic layer was cut out in air, and then the weight in air and in water were measured to calculate the specific gravity. The mass of the cut foamed elastic layer in air was W (g), and the mass in water was Ww (g), and the specific gravity (SG) of the foamed elastic layer was calculated from SG = W / (W-Ww).

[0044] (Open cell ratio of elastic layer) The open cell ratio of the elastic layer 3 is preferably 20% to 90%, and more preferably 30% to 85%. When the open cell ratio of the elastic layer 3 is within the above range, even if the sponge roller 1 is compressed during use, stress can be alleviated, and deformation can be suppressed. The open cell ratio of the elastic layer 3 can be calculated as follows. First, a test piece is prepared by cutting out all or a part of the elastic layer 3. The mass W (g) and density D (g / cm 3 ) is measured in the usual way, and the volume V (cm3) of the test piece is calculated by W / D. The test piece is then immersed in water filled in a container placed in a vacuum chamber, and the pressure inside the vacuum chamber is reduced to 30 mmHg or less for 2 minutes until no more air bubbles emerge from the test piece, and the reduced pressure is released and the test piece is left to stand at normal pressure for 5 minutes. The test piece is then removed from the water, the water adhering to the test piece is wiped off, the mass Wi (g) of the test piece after immersion is measured, and the mass Ww (g) of the water absorbed by the test piece is calculated by Wi-W. Note that the density of water is assumed to be 1 (g / cm 3 ), then Ww and the volume of water absorbed by the test piece Vw (cm 3 ) of the rubber composition forming the elastic layer 3. 3 From this, the open cell ratio (%) of the elastic layer 3 can be calculated by the formula: {(Wi-W) / specific gravity of water} / {(1-D / Dc)×(W / D)}×100(%).

[0045] <Other configurations> A resin tube may be provided on the outer peripheral surface of the elastic layer 3. Examples of 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, and polyurethane. Among these, PFA is preferable. The resin tube can be prepared by melt extrusion of a resin composition, etc. The resin tube can be attached by a known pressurized insertion method, reduced pressure insertion method, etc.

[0046] The sponge roller of the present invention can have an elastic layer with uniform cells having an area average cell diameter of 90 μm or less by using unexpanded microballoons with a particle diameter of 30 μm or less. The uniform cells in the elastic layer can reduce the amount of hardness loss caused by use over time, resulting in high durability. EXAMPLES

[0047] The present invention will be described in detail below with reference to examples. However, the present invention is not limited to the examples shown below.

[0048] [Example 1] The sponge roller of Example 1 was produced by the following procedure. (Formation of primer layer) The 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", made 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 30 minutes or more to form a primer layer on the outer circumferential surface of the shaft.

[0049] (Formation of elastic layer) First, a composition for the elastic layer was prepared. -Composition for elastic layer- (A) 100 parts by mass of an addition-curing millable silicone rubber composition (KE-951-U, manufactured by Shin-Etsu Chemical Co., Ltd., 70 parts by mass and vinyl group-containing silicone raw rubber (KE-77VBS, manufactured by Shin-Etsu Chemical Co., Ltd., 30 parts by mass) (B) Unexpanded microballoons (Matsumoto Microsphere F Series, manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.) 5 parts by mass (C) Crosslinking agent 3 parts by mass Incidentally, for the (B) unexpanded microballoons, those with a particle size of 30 μm or less were used after sieving.

[0050] The elastic layer composition was extrusion molded on the outer circumferential surface of the shaft. In the extrusion molding, the composition was heated at 270°C for 15 minutes in an infrared heating oven (IR oven), and then heated at 200°C for 4 hours in a gear oven to harden. The thickness of the elastic layer was 5 mm.

[0051] [Comparative Example 1] A sponge roller was produced in the same manner as in Example 1, except that the particle size of the unexpanded microballoons used was 10 μm or more and 50 μm or less.

[0052] [evaluation] The following evaluations were carried out for the above-mentioned Examples and Comparative Examples. The evaluation results are shown in Table 1.

[0053] (Maximum cell diameter of elastic layer) The maximum cell diameter of the elastic layer in Example 1 was 162.7 μm, and the maximum cell diameter of the elastic layer in Comparative Example 1 was 337.0 μm. The maximum cell diameter was determined by observing the cut surface of the elastic layer under a microscope at 50 to 200 times magnification, measuring the cell diameters of 10 cells selected in descending order of size, and recording the maximum value.

[0054] (Asker C hardness) The Asker C hardness of Example 1 was 41.3°, and the Asker C hardness of Comparative Example 2 was 44.0°. The hardness was measured with an ASKER rubber hardness tester C type (manufactured by Kobunshi Keiki Co., Ltd.).

[0055] (specific gravity) The specific gravity of the elastic layers in Example 1 and Comparative Example 1 was both 0.4.

[0056] (Open cell ratio of elastic layer) The open cell ratio of the elastic layer in Example 1 was 80.7%, while the open cell ratio of the elastic layer in Comparative Example 1 was 71.9%. The open cell ratio was measured by the method described above.

[0057] (Particle size of unexpanded microballoons) The particle size of the unexpanded microballoons was measured by the following method for Example 1 and Comparative Example 1. The particle size distribution of the unexpanded microballoons is shown in FIG. In Example 1, D10=10.65 μm, D50=15.27 μm, and D90=21.69 μm. In Comparative Example 1, D10=10.88 μm, D50=18.91 μm, and D90=27.60 μm. The particle size of the unexpanded microballoons was measured by dropping microballoons diluted with thinner onto a scattering method particle size distribution measuring device.

[0058] (Area-average cell size distribution of elastic layer) The area average cell diameter of the elastic layer was measured for Example 1 and Comparative Example 1. The area average cell diameter distribution is shown in Figure 3. The measurement method is as follows. The area-average cell diameter La was measured using a polyurethane foam / elastomer testing machine "PORE!SCAN" (product name, manufactured by Goldlucke GmbH) with a scale of 531.861 [pix] and a photographing area of ​​13.154 [mm 2 ] was measured. The area average cell diameter of the elastic layer in Example 1 was 77 μm, while the area average cell diameter of the elastic layer in Comparative Example 1 was 132 μm.

[0059] (Durability test: hardness change) For durability evaluation, the change in hardness was measured by the following evaluation method. A roller with a product diameter of φ32 mm was produced using a shaft with a diameter of φ22.0 mm. The roller was compressed to 35% of the rubber thickness and fixed to a metal roller with a diameter of φ40.0 mm. In this state, the roller was rotated for 200 hours while being heated to 180°C. The hardness before the start of the measurement (0 hours) was set to 0, and the hardness after 100 hours of rotation and 200 hours of rotation was measured using an ASKER rubber hardness tester Type C (manufactured by Kobunshi Keiki Co., Ltd.) with a measurement load of 9.8 N. The change in hardness over time is shown in Figure 4.

[0060] 4, it can be seen that the amount of reduction in hardness is smaller in Example 1 than in Comparative Example 1. That is, the sponge roller of the present invention has high durability because the elastic layer is uniformly formed with small cells of 90 μm or less. [Explanation of symbols]

[0061] 1 Sponge roller 2-axis body 3 Elastic layer

Claims

1. A sponge roller comprising a shaft body and an elastic layer provided on an outer periphery of the shaft body, the elastic layer is formed from a rubber composition containing millable silicone rubber, unexpanded microballoons, and a crosslinking agent; The particle size of the unexpanded microballoons is 30 μm or less; A sponge roller, wherein the elastic layer has an area average cell diameter of 90 μm or less.

2. 2. The sponge roller according to claim 1, wherein the elastic layer has an Asker C hardness of 10 degrees or more and 80 degrees or less.

3. 2. The sponge roller according to claim 1, wherein the maximum cell diameter of the elastic layer is 200 [mu]m or less.

4. 2. The sponge roller according to claim 1, wherein the specific gravity of the elastic layer is 0.3 or more and 0.8 or less.

5. 2. The sponge roller according to claim 1, wherein the open cell ratio of the elastic layer is 20% or more and 90% or less.

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