Sponge roller

Abstract

To provide a sponge roller with superior durability.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, where the foamed elastic layer 3 has an average cell diameter in a range of 20 μm to 100 μm, inclusive, and contains 60% or more cells with circularity in a range of 0.8 to 1.0, inclusive.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 likely to be subjected to loads due to heat and friction and is required to have high durability. For example, Patent Document 1 discloses a sponge roller in which a 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. [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] The foamed elastic layer is formed, for example, by an extrusion molding method, but in the technology described in the above Patent Document 1, after vulcanization, the size and shape of the cells in the foamed elastic layer are different between the vicinity of the shaft and the surface of the foamed elastic layer. Specifically, the shape of the cells is elliptical near the shaft and close to a perfect circle on the surface side. In such a foamed elastic layer, there is a problem that stress is concentrated in a part of the foamed elastic layer, resulting in low durability. The present invention has been made in consideration of the above circumstances, and has an object to provide a sponge roller having high durability. [Means for solving the problem]

[0007] The inventors discovered that by uniformly forming fine cells throughout the entire foamed elastic layer, stress concentration can be alleviated and a sponge roller with high durability can be obtained, leading to the present invention. That is, the present invention is a sponge roller comprising a shaft body and a foamed elastic layer provided on the outer periphery of the shaft body, wherein the foamed elastic layer is formed from a composition for a foamed elastic layer containing millable type silicone rubber, a foaming agent, and a crosslinking agent, and only pre-expanded resin balloons are used as the foaming agent, the average cell diameter of the foamed elastic layer is 20 μm or more and 100 μm or less, and the foamed elastic layer contains 60% or more of cells having a circularity of 0.8 or more and 1.0 or less.

[0008] The foamed elastic layer is preferably formed by extrusion molding.

[0009] The blending mass of the expanded resin balloon is preferably 5 parts by mass or more and 25 parts by mass or less per 100 parts by mass of the foamed elastic layer composition. Effect of the Invention

[0010] According to the present invention, a highly durable sponge roller can be obtained. [Brief description of the drawings]

[0011] [Figure 1] 1 is a perspective view showing an embodiment of a sponge roller of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] 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 comprises a shaft 2 and a foamed elastic layer 3 provided on the outer periphery of the shaft 2, the foamed elastic layer 3 being formed from a composition for foamed elastic layer containing millable type silicone rubber, a foaming agent, and a crosslinking agent, and only expanded resin balloons are used as the foaming agent, the average cell diameter of the foamed elastic layer 3 is 20 μm or more and 100 μm or less, and the foamed elastic layer 3 is a sponge roller containing 60% or more of cells having a circularity of 0.8 or more and 1.0 or less. Each component will be described in detail below.

[0013] <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."

[0014] 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.

[0015] 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.

[0016] 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.

[0017] <Foamed elastic layer> The foamed elastic layer 3 is obtained by vulcanizing a foamed elastic layer composition containing (A) a millable type silicone rubber composition, (B) a vinyl group-containing silicone raw rubber, (C) an expanded resin balloon, and (D) a crosslinking agent. The components of the foamed elastic layer composition will be described below.

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

[0019] (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.

[0020] 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.

[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 triarylalkylsilyl group such as a trivinylsilyl group.

[0022] The organopolysiloxane (a) preferably has two or more alkenyl groups in the molecule. 1 Of these, it is preferable that the alkenyl group is present in an amount of from 0.001 mol % to 5 mol % (more preferably from 0.01 mol % to 0.5 mol %). As the alkenyl group contained in the (a) organopolysiloxane, a vinyl group is particularly preferable.

[0023] 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.

[0024] 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.

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

[0026] Silica-based fillers include R 2 Si(OR 3 ) 3 A surface-treated silica-based filler having 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, a mercapto group, etc. 3 may 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.

[0027] 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.

[0028] (B) Vinyl-containing silicone rubber (B) The vinyl group-containing silicone raw rubber contains at least one vinyl group per molecule, and may contain two vinyl groups per molecule. Examples of vinyl group-containing silicone raw rubber include vinylmethylsilicone raw rubber, phenylmethylsilicone raw rubber, and fluorosilicone raw rubber.

[0029] 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.

[0030] (C) Expanded resin balloon The foamed elastic layer composition contains only expanded resin balloons as a foaming agent. By using expanded resin balloons as a foaming agent, fine cells can be uniformly formed throughout the foamed elastic layer, so that a sponge roller having high durability can be formed. The pre-expanded resin balloon may be a composite type pre-expanded resin balloon in which calcium carbonate powder is wrapped around the shell of the balloon. Pre-expanded resin balloons suitable for the present invention are commercially available as "Matsumoto Microsphere MFL Series" (manufactured by Matsumoto Yushi Seiyaku Co., Ltd.) and "Expancel DE Grade" (manufactured by Nippon Phillite Co., Ltd.).

[0031] 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 the above range, fine cells can be formed uniformly.

[0032] The expanded resin balloons are preferably contained such that the compounding mass ratio of the expanded resin balloons to the vinyl group-containing silicone raw rubber is 1:4 or more and 1:6 or less. The blending mass of the expanded resin balloon is preferably 5 parts by mass or more and 30 parts by mass or less, and more preferably 5 parts by mass or more and 25 parts by mass or less, per 100 parts by mass of the foamed elasticity composition. The blend ratio of (A) the millable type silicone rubber composition to (B) the vinyl group-containing silicone raw rubber is preferably in the range of 60:40 to 30:70.

[0033] (D) Crosslinking agent The foamed elastic layer composition 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 based on 100 parts by mass of the foamed elastic layer composition.

[0034] 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 to 7 parts by mass per 100 parts by mass of the foamed elastic layer composition. The organic peroxide crosslinking agent may be used alone or in combination of two or more kinds.

[0035] 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.

[0036] (Other Ingredients) 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, antiaging agents, 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.

[0037] The millable silicone rubber in the present invention may be, for example, 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, or KE-971T-U manufactured by Shin-Etsu Chemical Co., Ltd. Also, the millable silicone rubber containing a conductivity imparting agent may be, for example, KE-87C-40PU.

[0038] The foamed elastic layer 3 is formed on the outer circumferential surface of the shaft body 2 by simultaneously or successively carrying out heat curing and molding using a known molding method. The method of forming the foamed elastic layer 3 is not particularly limited and may be continuous vulcanization by extrusion molding, pressing, injection molding, etc. For example, extrusion molding, etc. may be selected.

[0039] The method for curing the foamed elastic layer composition may be any method that can apply 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, 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, more preferably 10 seconds or higher and 35 minutes or lower. In addition, secondary vulcanization may be performed as necessary.

[0040] (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, so that the concentration of stress can be alleviated, and a foamed elastic layer with high durability can be obtained. The average cell diameter of the foamed elastic layer 3 can be measured by a polyurethane foam / elastomer testing machine PORE SCAN (trade name, manufactured by Goldlucke GmbH).

[0041] (Circularity of foamed elastic layer) The foamed elastic layer 3 contains 60% or more of cells having a circularity of 0.8 or more and 1.0 or less, preferably 64% or more, and more preferably 80% or more. The circularity of the foamed elastic layer 3 is measured by the following method.

[0042] <Method of measuring cell roundness> Using the PORE SCAN, cut out any part of the sponge from the foamed elastic layer and measure the cell area and cell circumference until the number of observed cells reaches 10,000 or more. Next, calculate the circularity using the following formula. Circularity = 4π (cell area) / (cell circumference) 2

[0043] A cell with a circularity of 0.8 or more and 1.0 or less is almost a perfect sphere, and therefore can effectively reduce stress concentration. When the foamed elastic layer 3 contains 60% or more of cells that are nearly spherical, the cells of the foamed elastic layer 3 are uniformly formed, and stress concentration can be effectively alleviated.

[0044] (Hardness of foamed elastic layer) The Asker C hardness of the foamed elastic layer 3 is preferably 10 or more and 80 or less, and more preferably 20 or more and 60 or less. The hardness of the foamed elastic layer 3 is measured by pressing the center of a hardness meter's presser against the curved surface of a roller to be measured, and reading the scale at the moment when the reference surface comes into contact with the surface of the roller. In practice, the Asker C hardness can be measured by setting the Asker C hardness meter to a load of 9.8 N, dropping it from a distance of about 10 mm, and 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.

[0045] <Other configurations> A resin tube may be provided on the outer peripheral surface of the foamed 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 form a foamed elastic layer 3 having uniform cells with an average cell diameter of 20 μm to 100 μm by using expanded resin balloons with a particle diameter of 20 μm to 100 μm. Since the cells of the foamed elastic layer 3 are uniform, the amount of hardness loss caused by use over time can be reduced, and durability is high. 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 foamed elastic layer) First, a foamed elastic layer composition was prepared. -Composition for foamed elastic layer- (A) Addition-curing millable silicone rubber (KE-951-U, manufactured by Shin-Etsu Chemical Co., Ltd.) 50 parts by mass (B) Vinyl group-containing silicone 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 Pharmaceutical Co., Ltd.) 10 parts by mass (D) Crosslinking agent 3 parts by mass

[0050] The foamed elastic layer composition was extrusion molded on the outer peripheral surface of the foamed elastic layer. In the extrusion molding, the composition was heated at 270°C for 5 minutes using an infrared heating furnace (IR furnace), and further heated at 200°C for 4 hours using a gear oven to harden. This formed a foamed elastic layer on the outer peripheral surface of the foamed elastic layer. The thickness of the foamed elastic layer was 5 mm. The average cell diameter of the foamed elastic layer was 60.8 μm. The average cell diameter was measured using a polyurethane foam / elastomer testing machine, PORE SCAN (trade name, manufactured by Goldlucke GmbH).

[0051] [Example 2] (B) A sponge roller was produced in the same manner as in Example 1, except that the amount of the expanded resin balloon was changed to 11 parts by mass. The average cell diameter of the foamed elastic layer in Example 2 was 59.2 μm.

[0052] [Comparative Example] A sponge roller was produced in the same manner as in Example 1, except that unexpanded microballoons (Matsumoto Microsphere F Series, manufactured by Matsumoto Yushi Seiyaku Co., Ltd.) and a chemical foaming agent were used as the foaming agent instead of the expanded resin balloons (B).

[0053] [evaluation] The following evaluations were carried out for the above-mentioned Examples and Comparative Examples. The evaluation results are shown in Table 1.

[0054] (Cell roundness) The circularity of the cells of the foamed elastic layers of Example 1, Example 2 and Comparative Example was measured by the above-mentioned method. The circularity distribution of the cells is shown in Table 1, and the measurement results are shown in Table 2.

[0055] [Table 1]

[0056] [Table 2] As shown in Table 1, Examples 1 and 2, which used pre-expanded resin balloons, contain 60% or more of cells with a circularity of 0.8 to 1.0. The sponge roller of the present invention has a foamed elastic layer with fine cells uniformly distributed throughout the layer, which allows for good relaxation of stress concentration and provides high durability. On the other hand, in the comparative example, the percentage of cells with a circularity of 0.8 or more and 1.0 or less is less than 60%, and the variation is also large. [Explanation of symbols]

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

Claims

1. A sponge roller comprising a shaft body and a foamed elastic layer provided on an outer periphery of the shaft body, The average cell diameter of the foamed elastic layer is 20 μm or more and 100 μm or less, The foamed elastic layer contains 60% or more of cells having a roundness of 0.8 or more and 1.0 or less.

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

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

4. 3. The sponge roller according to claim 2, wherein the blending mass of the expanded resin balloons is 5 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the foamed elastic layer composition.

5. 3. The 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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