Sponge roller

Abstract

A sponge roller 1 is provided with a shaft body 2, and a foam elastic layer 3 provided the outer circumference of the shaft body 2. An average cell diameter of the foam elastic layer 3 is 20-100 μm. In the foam elastic layer 3, distribution of an inclination value of an approximate straight line in a load-displacement curve of a rebound load measurement result obtained by a predetermined calculation method is 0.005 or less.

Description

Sponge roller

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

[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 rollers, each having a shaft body and an elastic layer formed on the outer circumferential surface thereof, such as a cleaning roller, a charging roller, a developing roller, a transfer roller, a secondary transfer roller, a pressure roller, a paper feed roller, and a fixing roller.

[0003] The fixing means in the image forming apparatus described above employs a heat roller fixing system. The heat roller fixing system generally comprises a pair of a heating roller (fixing roller) and a pressure roller, and the toner image is fixed to the recording material (transfer sheet, fax paper, printing paper, etc.) by introducing the recording material carrying the toner image into the pressure-contact nip between the pair of rollers. The fixing roller or pressure roller used in the fixing means typically employs a foamed elastic layer (sponge layer) to adjust the nip pressure appropriately.

[0004] The foamed elastic layer is generally formed by vulcanizing and foaming a millable silicone rubber containing an 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 susceptible to heat and friction loads and is required to have high durability. To improve durability, for example, Patent Document 1 discloses a sponge roller whose foamed elastic layer contains a chemical foaming agent and a pre-expanded resin balloon that expands at a higher temperature than the chemical foaming agent.

[0005] JP 2018-36611 A

[0006] The foamed elastic layer is formed, for example, by extrusion molding. However, with the technology described in Patent Document 1, after vulcanization, the size and shape of the cells in the foamed elastic layer differ between the vicinity of the shaft and the surface of the foamed elastic layer. Specifically, the cell shape near the shaft is elliptical, while the cell shape on the surface side is close to a perfect circle. Such a foamed elastic layer has the problem of stress concentration in a portion of the foamed elastic layer, resulting in reduced durability. The present invention was made in consideration of the above circumstances, and aims to provide a sponge roller with high durability.

[0007] The inventors discovered that forming a foamed elastic layer with uniform hardness in the thickness direction reduces stress concentration and results in a sponge roller with high durability, leading to the present invention. Specifically, the present invention relates to a sponge roller comprising a shaft and a foamed elastic layer disposed on the outer periphery of the shaft, wherein the foamed elastic layer has an average cell diameter of 20 μm to 100 μm, and the foamed elastic layer exhibits a variance of 0.005 or less in the slope of an approximated line in a load-displacement curve of rebound load measurements, as calculated using the following calculation method. <Calculation Method> 1. Two incisions are made in the foamed elastic layer at a distance t of 15 mm inward from both axial ends of the layer, and then the layer is cut parallel to the axial direction so that the length L from the curved surface is 10 mm, to prepare a semi-cylindrical sample. 2. The rebound load is measured at five cross-shaped points in the short and long axis directions on the radially parallel surface of the semi-cylindrical sample using a microload measuring device, up to a maximum load of 5 N. 3. Slope of the approximate line of the load-displacement curve at five points X １ , X ２ , X ３ , X ４ , and X ５ 4. Five slopes X １ From X ５ 5. Calculate the average value A of the above. 6. Calculate the variance using the following formula (1).

[0008]

[0009] The foamed elastic layer is formed from a foamed elastic layer composition containing a millable silicone rubber composition, a vinyl group-containing silicone raw rubber, a foaming agent, and a crosslinking agent, and it is preferable that only a pre-expanded resin balloon is used as the foaming agent.

[0010] The foamed elastic layer is preferably formed by extrusion molding.

[0011] The blending mass of the expanded resin balloons in the foamed elastic layer composition is preferably 5 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the foamed elastic layer composition.

[0012] The particle diameter of the expanded resin balloon is preferably 20 μm or more and 100 μm or less.

[0013] According to the present invention, a highly durable sponge roller can be obtained.

[0014] 1 is a perspective view showing an embodiment of the sponge roller of the present invention; 2 is a diagram showing a method for measuring the hardness of a foamed elastic layer; 3 is a graph showing an approximation line of the load-displacement curve of Example 1 (n=1); 4 is a graph showing an approximation line of the load-displacement curve of Comparative Example 1 (n=1);

[0015] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. [Sponge Roller] As shown in Figure 1, the sponge roller of the present invention is a sponge roller comprising a shaft 2 and a foamed elastic layer 3 provided on the outer periphery of the shaft 2. The foamed elastic layer 3 is formed from a foamed elastic layer composition containing a millable silicone rubber composition, a vinyl group-containing silicone raw rubber, a foaming agent, and a crosslinking agent, and only pre-expanded resin balloons are used as the foaming agent.

[0016] That is, the sponge roller 1 of the present invention has high durability because the repulsive load is uniform in the thickness direction of the foamed elastic layer 3, and therefore stress is applied evenly. The structure of the sponge roller will be described below.

[0017] <Shaft> The shaft 2 may preferably be a shaft having conductive properties and used in conventionally known 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."

[0018] 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, for example, include 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 to obtain good conductive properties.

[0019] The shape of the shaft 2 is preferably, for example, rod-like, tubular, or the like. The cross-sectional shape of the shaft 2 may be, for example, circular, elliptical, or 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.

[0020] The axial length of the shaft 2 is not particularly limited and may be adjusted as appropriate depending on the type of image forming apparatus in which it is installed.Furthermore, the diameter of the shaft 2 (diameter of the circumscribed circle) is also not particularly limited and may be adjusted as appropriate depending on the type of image forming apparatus in which it is installed.

[0021] <Foamed Elastic Layer> The foamed elastic layer 3 is formed by vulcanizing a foamed elastic layer composition containing (A) a millable silicone rubber composition, (B) a vinyl group-containing silicone raw rubber, (C) a pre-expanded resin balloon, and (D) a crosslinking agent. The components of the foamed elastic layer composition are described below.

[0022] (A) Millable 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 and (b) a filler.

[0023] (a) Organopolysiloxane (a) The organopolysiloxane is represented by the following average composition formula (1): １ ｎ SiO （４－ｎ）／２ ... (1) In formula (1), n ​​represents a positive number of 1.95 or more and 2.05 or less. 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.

[0024] 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.

[0025] The molecular chain terminals of the organopolysiloxane (a) 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.

[0026] 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 (a) organopolysiloxane, vinyl groups are particularly preferable.

[0027] 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 basically be a linear diorganopolysiloxane, or may be partially branched. The (a) organopolysiloxane may also be a mixture of two or more types having different molecular structures.

[0028] (a) The organopolysiloxane has a kinematic viscosity of 1×10 at 25° C. －４ m ２ / s or more, and 1×10 －１ m ２ / s or more 1×10 １ m ２ The degree of polymerization of the organopolysiloxane (a) is preferably, for example, 100 or more, and more preferably 3,000 or more and 10,000 or less.

[0029] (b) Filler Examples of the filler (b) include silica-based fillers, such as fumed silica and precipitated silica.

[0030] As the silica-based filler, R ２ Si(OR ３ ) ３ A surface-treated silica-based filler that has been surface-treated with a silane coupling agent represented by the formula: 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, 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. Surface-treated silica-based fillers can be obtained by treating the surface of a silica-based filler with a silane coupling agent according to a standard method. Commercially available products may be used as the surface-treated silica-based filler, for example, under the trade name "Zeothix 95" manufactured by J. M. HUBER Corporation.

[0031] The amount of silica-based filler blended is preferably 11 to 39 parts by mass, 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, 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.

[0032] (B) Vinyl Group-Containing Silicone Raw Rubber (B) is a rubber containing at least one vinyl group per molecule, and may contain two vinyl groups per molecule. Examples of vinyl group-containing silicone raw rubbers include vinylmethylsilicone raw rubber, phenylmethylsilicone raw rubber, and fluorosilicone raw rubber.

[0033] The blending mass ratio of (A) the addition-curing millable silicone rubber composition to (B) the vinyl group-containing silicone raw rubber is preferably in the range of 50:50 to 80:20, and more preferably in the range of 60:40 to 70:30.

[0034] (C) Pre-expanded Resin Balloons The foamed elastic layer composition contains only pre-expanded resin balloons as a foaming agent. By using pre-expanded resin balloons as a foaming agent, fine cells can be uniformly formed throughout the foamed elastic layer, resulting in a highly durable sponge roller. Examples of pre-expanded resin balloons include composite-type pre-expanded resin balloons in which calcium carbonate powder is coated around the balloon shell. Pre-expanded resin balloons suitable for the present invention are commercially available as the "Matsumoto Microsphere MFL Series" (manufactured by Matsumoto Yushi Seiyaku Co., Ltd.) and "Expancel DE Grade" (manufactured by Nippon Phillite Co., Ltd.).

[0035] The average particle size of the expanded resin balloons is preferably 20 μm or more and 100 μm or less, and more preferably 40 μm or more and 80 μm or less. By having the average particle size of the expanded resin balloons in this range, fine cells can be formed uniformly.

[0036] The pre-expanded resin balloons are preferably contained so that the blending mass ratio of pre-expanded resin balloons to vinyl group-containing silicone raw rubber is from 1: 4 to 1: 6. The blending mass of the pre-expanded resin balloons is preferably from 5 to 30 parts by mass, and more preferably from 5 to 25 parts by mass, per 100 parts by mass of the foamed elastic layer composition.

[0037] (D) Crosslinking Agent The foamed elastic layer composition contains a crosslinking agent. Examples of crosslinking agents include addition reaction crosslinking agents and organic peroxide crosslinking agents. Suitable examples of the addition reaction crosslinking agent include organohydrogenpolysiloxanes, which are known as addition reaction crosslinking agents having two or more SiH groups (SiH bonds) in one molecule. The addition reaction crosslinking agents can be used alone or in combination of two or more. The amount of the addition reaction crosslinking agent is usually 0.1 to 7 parts by mass per 100 parts by mass of the foamed elastic layer composition.

[0038] When an addition reaction crosslinking agent is used, the organic peroxide crosslinking agent can crosslink the millable silicone rubber alone, but when used in combination as an auxiliary crosslinking agent for the addition reaction crosslinking agent, the physical properties of the resulting toner supply roller, such as strength and distortion, can be further improved. Examples of organic peroxide crosslinking 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 organic peroxide crosslinking agent blended is typically 0.1 to 7 parts by weight per 100 parts by weight of the foamed elastic layer composition. The organic peroxide crosslinking agents can be used alone or in combination.

[0039] 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, reaction products of chloroplatinic acid with monohydric alcohols, complexes of chloroplatinic acid with olefins, platinum bisacetoacetate, palladium catalysts, and rhodium catalysts. The amount of the addition reaction catalyst to be added can be a catalytic amount.

[0040] (Other Components) The foamed elastic layer composition may further contain various additives. Examples of the various additives include auxiliary agents such as conductive agents and chain extenders, 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] 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, all 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.

[0042] The foamed elastic layer 3 is formed on the outer peripheral surface of the shaft body 2 by simultaneously or successively performing heat curing and molding using a known molding method. The molding method for 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 or the like can be selected.

[0043] The method for curing the foamed elastic layer composition may be any method that can apply the heat required for curing (vulcanization) the foamed elastic layer composition. The heating temperature when vulcanizing the foamed elastic layer composition is preferably 100°C or higher and 500°C or lower, and more preferably 120°C or higher and 300°C or lower. The heating time is preferably several seconds or higher and 1 hour or lower, and more preferably 10 seconds or higher and 35 minutes or lower. Furthermore, secondary vulcanization may be performed as necessary.

[0044] (Dispersion of the slope of the approximate line in the load-displacement curve of the rebound load measurement results for the foamed elastic layer) The dispersion of the slope of the approximate line in the load-displacement curve of the rebound load measurement results for the foamed elastic layer 3 can be measured by the following method (see Figure 2): 1. In a region 10 mm or more inward from both ends (31, 32) of the foamed elastic layer 3 in the axial direction (Z direction), two notches (A, B) are made with a spacing t of 15 mm (Figure 2(a)), and then a cut is made parallel to the axial direction so that the length L from the curved surface 33a is 10 mm to prepare a semi-cylindrical sample 33 (Figure 2(b)). 2. On a surface (XY surface) 33b parallel to the radial direction (X direction or Y direction) of the semi-cylindrical sample 33, the repulsion load is measured at five points (a, b, c, d, e) in a cross shape in the short side direction (X direction) and the long side direction (Y direction) using a microload measuring device up to a maximum load of 5 N ( FIG. 2(c) ). As the microload measuring device, a product name "MODEL-1305VR" (manufactured by Aiko Engineering Co., Ltd.) can be used.

[0045] From the rebound load measured as above, the variance is calculated as follows: 3. The slope X of the approximate line of the load-displacement curve at five points １ , X ２ , X ３ , X ４ , and X ５ 4. Five slopes X １ From X ５ 5. Calculate the average value A of the above. 6. Calculate the variance using the following formula (1).

[0046]

[0047] In the foamed elastic layer 3 of the sponge roller 1 of the present invention, the variance calculated by the above calculation method is 0.005 or less. The variance is preferably 0.003 or less, and more preferably 0.002 or less. Since the repulsion load of the foamed elastic layer 3 is measured in the depth direction from the XY plane of the semi-cylindrical sample, as shown in the above measurement method, a variance of the repulsion load of 0.005 or less means that the repulsion load of the foamed elastic layer 3 is uniform in the thickness direction of the foamed elastic layer 3. The sponge roller 1 of the present invention equipped with such a foamed elastic layer 3 has high durability because stress is applied evenly.

[0048] (Rebound Load of Foamed Elastic Layer) The rebound load of the foamed elastic layer 3 can be measured by the above-mentioned procedures 1 and 2. At any of the five points, the slope X of the approximate line of the load-displacement curve is １ From X ５ is preferably 0.5 or more and 3.0 or less, more preferably 0.8 or more and 1.8 or less, and even more preferably 1.0 or more and 1.6 or less.

[0049] (Hardness of Foamed Elastic Layer) The A-hardness of the foamed elastic layer 3, both in the surface and depth directions, is preferably 10 or more and 30 or less, and more preferably 15 or more and 22 or less. The A-hardness of the foamed elastic layer 3 can be measured at the above five points using an ASKER micro rubber hardness meter MD-1capa Type A (manufactured by Kobunshi Keiki Co., Ltd.) in the same manner as in steps 1 and 2 of the above-mentioned method for measuring rebound load.

[0050] (Average Cell Diameter of Foamed Elastic Layer) The average cell diameter of the foamed elastic layer 3 is from 20 μm to 100 μm, preferably from 40 μm to 80 μm, and more preferably from 50 μm to 70 μm. When the average cell diameter of the foamed elastic layer 3 is within the above range, the cells become fine and uniform, which can reduce stress concentration and result in a highly durable foamed elastic layer 3. The average cell diameter of the foamed elastic layer 3 can be measured using a polyurethane foam / elastomer testing machine called PORE SCAN (trade name, manufactured by Goldlucke GmbH).

[0051] <Method for measuring average cell diameter of foamed elastic layer> The average cell diameter was determined in the region including the above five points (a, b, c, d, and e) by the following method. ２ The area A and the circle diameter d of 1000 or more cells are calculated within the region. 2. The area-weighted average of the circle diameters is calculated and used as the average cell diameter L.

[0052] <Other Configurations> A resin tube may be provided on the outer peripheral surface of the foamed elastic layer 3. 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 preferred. The resin tube can be produced by melt extrusion of a resin composition, or the like. The resin tube can be attached by known methods such as pressurized insertion and reduced pressure insertion.

[0053] The sponge roller 1 of the present invention uses expanded resin balloons with a particle diameter of 20 μm or more and 100 μm or less, thereby forming a foamed elastic layer 3 having uniform cells with an average cell diameter of 20 μm or more and 100 μm or less. The uniform cells in the foamed elastic layer 3 can reduce the amount of hardness loss due to use over time, resulting in high durability.

[0054] 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.

[0055] [Example 1] A sponge roller of Example 1 was produced by the following procedure. (Formation of Primer Layer) An electroless nickel-plated shaft (made by 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 30 minutes or more to form a primer layer on the outer peripheral surface of the shaft.

[0056] (Formation of Foamed Elastic Layer) First, a foamed elastic layer composition was prepared. -Foamed Elastic Layer Composition- (A) Addition-curing Millable type silicone rubber (KE-951-U, manufactured by Shin-Etsu Chemical Co., Ltd.) 50 parts by mass (B) Vinyl group-containing silicone raw rubber (KE-77VBS, manufactured by Shin-Etsu Chemical Co., Ltd.) 50 parts by mass) 100 parts by mass (C) Pre-expanded resin balloon (Matsumoto Microsphere MFL series, manufactured by Matsumoto Yushi Seiyaku Co., Ltd.) 10 parts by mass (D) Crosslinking agent 3 parts by mass

[0057] The foamed elastic layer composition was extruded onto the outer circumferential surface of the primer layer to form a foamed elastic layer. In the extrusion process, the composition was heated at 250°C for 15 minutes in an infrared oven (IR oven), and then cured at 225°C for 7 hours in a gear oven. This resulted in the formation of a foamed elastic layer on the outer circumferential surface of the primer layer.

[0058] The foamed elastic layer had a thickness of 10 mm. The foamed elastic layer had an average cell diameter of 60.8 μm. The average cell diameter was measured using a polyurethane foam / elastomer testing machine, PORE SCAN (trade name, manufactured by Goldlucke GmbH). The foamed elastic layer had an A-hardness of 16.8. The A-hardness was measured using an ASKER micro rubber hardness tester, MD-1capa Type A (manufactured by Kobunshi Keiki Co., Ltd.).

[0059] (Method for calculating the variance of the slope of the approximation line in the load-displacement curve of the repulsion load measurement results for the foamed elastic layer) The variance was determined by the following method (see Figure 2). The results are shown in Table 1. <Calculation method> First, the repulsion load of the foamed elastic layer 3 was measured using the following procedures 1 and 2. 1. Two notches (A, B) were made in a region 10 mm or more inward from both ends (31, 32) of the foamed elastic layer 3 in the axial direction (Z direction) with a distance t of 15 mm, and then a semi-cylindrical sample was cut parallel to the axial direction (Z direction) so that the length L from the curved surface 33a was 10 mm, to prepare a semi-cylindrical sample. 2. The repulsion load was measured at five points in the short side direction and long side direction in a cross shape on the surface 33b of the semi-cylindrical sample parallel to the radial direction (X direction or Y direction) using a microload measuring device.

[0060] Next, the dispersion value of the rebound load was calculated according to the following steps 3 to 5. Figures 3 and 4 show the approximate straight line of the load-displacement curve. Example 1-1 in Figure 3 shows the sample of Example 1 where n=1, and Comparative Example 1-1 in Figure 4 shows the sample of Comparative Example 1 where n=1. The slope X of the approximate straight line of the load-displacement curve at 3.5 points １ , X ２ , X ３ , X ４ , and X ５ 4. Five slopes X １ From X ５ 5. Calculate the average value A of the above. 6. Calculate the variance using the following formula (1).

[0061]

[0062] The equipment and conditions used to measure the rebound load are as follows: (1) Microload measuring device: MODEL-1305VR (manufactured by Aiko Engineering Co., Ltd.) (2) Microload measuring device amplifier: MODEL-1016BASIC (manufactured by Aiko Engineering Co., Ltd.) (3) Precision load displacement measuring device data collection system (data acquisition software: FS-301v, manufactured by Aiko Engineering Co., Ltd.) (4) Measurement terminal tip shape: circular, φ2.5 mm

[0063] Next, the dispersion was calculated in the same manner for another location on the same sponge roller as in Example 1. The calculation results are shown in Table 1 with n=2.

[0064] [Example 2] (B) A sponge roller was produced in the same manner as in Example 1, except that the amount of pre-expanded resin balloons was 12 parts by mass. The average cell diameter of the foamed elastic layer in Example 2 was 58.3 μm.

[0065] The slope and variance were calculated in the same manner for another location on the same sponge roller as in Example 2. The calculation results are shown in Table 1 with n=2.

[0066] [Example 3] (B) A sponge roller was produced in the same manner as in Example 1, except that the amount of pre-expanded resin balloons was 14 parts by mass. The average cell diameter of the foamed elastic layer in Example 3 was 57.1 μm.

[0067] The slope and variance were calculated in the same manner for another location on the same sponge roller as in Example 3. The calculation results are shown in Table 1 with n=2.

[0068] Comparative Example 1 A sponge roller was prepared in the same manner as in Example 1, except that 2 parts by mass of unexpanded microballoons (Matsumoto Microsphere F Series, manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.) and 2 parts by mass of a chemical foaming agent were used as the foaming agent instead of the (C) expanded resin balloons.

[0069] The inclination and its variance were calculated in the same manner for another location on the same sponge roller as in Comparative Example 1. The calculation results are shown in Table 1 with n=2.

[0070] Comparative Example 2 A sponge roller was prepared in the same manner as in Example 1, except that 3 parts by mass of unexpanded microballoons (Matsumoto Microsphere F Series, manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.) and 2 parts by mass of a chemical foaming agent were used as the foaming agent instead of the (C) expanded resin balloons.

[0071] The inclination and its variance were calculated in the same manner for another location on the same sponge roller as in Comparative Example 2. The calculation results are shown in Table 1 with n=2.

[0072] Comparative Example 3 A sponge roller was prepared in the same manner as in Example 1, except that 4 parts by mass of unexpanded microballoons (Matsumoto Microsphere F Series, manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.) and 2 parts by mass of a chemical foaming agent were used as the foaming agent instead of the (C) expanded resin balloons.

[0073] The inclination and its variance were calculated in the same manner for another location on the same sponge roller as in Comparative Example 3. The calculation results are shown in Table 1 with n=2.

[0074]

[0075] REFERENCE SIGNS LIST 1 Sponge roller 2 Shaft 3 Foamed elastic layer 31, 32 Ends (of foamed elastic layer) 33 Semi-cylindrical sample 33a Curved surface (of semi-cylindrical sample) 33b Parallel surface (in the radial direction of the semi-cylindrical sample)

Claims

1. A sponge roller comprising a shaft and a foamed elastic layer provided on the outer periphery of the shaft, the foamed elastic layer having an average cell diameter of 20 μm or more and 100 μm or less, and the foamed elastic layer having a variance of the slope of an approximate straight line in a load-displacement curve of a repulsive load measurement result, calculated by the following calculation method, of 0.005 or less. <Calculation method> 1. In an area 10 mm or more inside from both ends in the axial direction of the foamed elastic layer, two cuts are made with a distance t of 15 mm, and then cut parallel to the axial direction so that the length L from the curved surface is 10 mm, to prepare a semi-cylindrical sample.

2. On a surface of the semi-cylindrical sample parallel to the radial direction, the repulsive load is measured at five points in total in the short side direction and the long side direction in a cross shape up to a maximum load of 5 N using a microload measuring device.

3. The slope X of the approximate straight line of the load-displacement curve at five points is calculated by the following calculation method. １ , X ２ , X ３ , X ４ , and X ５ 4. Calculate the five slopes X １ From X ５ 5. Calculate the average value A of the above.

6. Calculate the variance using the following formula (1).

2. The sponge roller according to claim 1, wherein the foamed elastic layer is formed from a foamed elastic layer composition comprising a millable type silicone rubber composition, a vinyl group-containing silicone raw rubber, a foaming agent, and a crosslinking agent, and wherein only pre-expanded resin balloons are used as the foaming agent.

3. The sponge roller according to claim 1, wherein said foamed elastic layer is formed by extrusion molding.

4. A sponge roller as described in claim 2, wherein the blending mass of the expanded resin balloons in the foamed elastic layer composition is 5 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the foamed elastic layer composition.

5. A sponge roller according to claim 2, wherein the particle diameter of the expanded resin balloons is 20 μm or more and 100 μm or less.

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