Sponge roller

Abstract

To provide a sponge roller with improved compressive permanent set.SOLUTION: The present invention relates to a sponge roller 1 comprising a shaft body 2 and a foamed elastic layer 3 provided on the outer periphery of the shaft body 2. The foamed elastic layer 3 is formed from a composition for a foamed elastic layer including a base rubber, a thermally expandable resin hollow filler or a pre-expanded resin hollow filler, and silazane.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Various image forming devices using electrophotography are employed in printers such as laser printers and video printers, copiers, facsimiles, and multifunction machines thereof. Electrophotographic image forming devices are equipped with various printing 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] In particular, sponge rollers such as fixing rollers having a foamed elastic layer are required to have a small compression set because they are compressed at high temperatures for a long period of time. The foamed elastic layer is generally formed by vulcanizing and foaming a millable silicone rubber containing an organopolysiloxane and a filler. For example, Patent Document 1 proposes a sponge roller in which the foamed elastic layer contains a chemical foaming agent and an unexpanded hollow filler that expands at a higher temperature than the chemical foaming agent in order to reduce the compression set of the foamed elastic layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-36611 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in order to provide a high-definition, high-quality image forming apparatus, a sponge roller with even smaller compression set than the technology described in Patent Document 1 is desired. The present invention has been made in view of the above circumstances, and has as its object to provide a sponge roller with improved compression set. [Means for solving the problem]

[0006] It is known that silica particles generated during the manufacturing process adhere to the surface of hollow resin fillers used as foaming agents. Silanol groups exist on the surface of silica particles, and the inventors suspected that these silanol groups adhere to the rubber substrate of the foamed elastic layer, thereby worsening the compression set of the foamed elastic layer. Therefore, they investigated whether the adhesion of hollow resin fillers to the rubber substrate could be reduced by replacing the silanol groups on the silica particle surface with trimethylsilyl groups using disilazane. They found that this problem could be solved, leading to the present invention.

[0007] That is, the present invention is a sponge roller having 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 foamed elastic layer-forming composition containing a base rubber, a thermally expandable resin hollow filler or a pre-expanded resin hollow filler, and silazane.

[0008] The content of silazane in the foamed elastic layer-forming composition is preferably 0.1 parts by mass or more and 2.0 parts by mass or less per 100 parts by mass of the base rubber.

[0009] The base rubber is preferably a millable type silicone rubber, and the silazane is preferably at least one of hexamethyldisilazane and tetramethyldisilazane.

[0010] The foamed elastic layer-forming composition preferably further contains water. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a sponge roller with improved compression set. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a perspective view showing an embodiment of a sponge roller of the present invention. [Figure 2] FIG. 1 is a cross-sectional view showing an apparatus for measuring compression set. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. [Sponge roller] As shown in Figure 1, the sponge roller 1 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, and the foamed elastic layer 3 is formed from a foamed elastic layer-forming composition containing a base rubber, a resin hollow filler, and silazane. Each component will be described in detail below.

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

[0015] The 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.

[0016] 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.

[0017] 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.

[0018] <Foamed elastic layer> The foamed elastic layer 3 is formed from a foamed elastic layer-forming composition containing (A) a base rubber, (B) a resin hollow filler, and (C) a silazane. The components of the foamed elastic layer-forming composition are described below.

[0019] (A) Base rubber Examples of the base rubber include silicone rubber, acrylonitrile-butadiene rubber (NBR), styrene-butadiene rubber (SBR), epichlorohydrin rubber, and urethane rubber. In the case of silicone rubber, millable silicone rubber can be used as the base rubber. The millable silicone rubber is preferably an addition-curing millable silicone rubber. The addition-curing millable silicone rubber may contain, for example, at least (a) an organopolysiloxane, (b) a filler, and (c) a conductivity-imparting agent.

[0020] (a) Organopolysiloxane (a) Organopolysiloxane is represented by the following average composition formula (1): R1nSiO(4-n) / 2 …(1) In formula (1), n ​​is a positive number of 1.95 or more and 2.05 or less. R1 may be the same or different and represents a substituted or unsubstituted monovalent hydrocarbon group. 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.

[0021] Examples of R1 include alkyl groups such as methyl, ethyl, propyl, butyl, hexyl, and dodecyl; cycloalkyl groups such as cyclohexyl; alkenyl groups such as vinyl, allyl, butenyl, and hexenyl; aryl groups such as phenyl and tolyl; and aralkyl groups such as β-phenylpropyl. R1 may also be a group in which some or all of the hydrogen atoms in these hydrocarbon groups have been substituted with a substituent. The substituent may be, for example, a halogen atom, a cyano group, or the like. Examples of hydrocarbon groups having a substituent include a chloromethyl group, a trifluoropropyl group, and a cyanoethyl group.

[0022] The (a) organopolysiloxane is preferably one whose molecular chain terminals are blocked with a trialkylsilyl group such as a trimethylsilyl group, a dialkylaralkylsilyl group such as a dimethylvinylsilyl group, a dialkylhydroxysilyl group such as a dimethylhydroxysilyl group, or a trialalkylsilyl group such as a trivinylsilyl group.

[0023] The (a) organopolysiloxane preferably has two or more alkenyl groups in the molecule. The (a) organopolysiloxane preferably has alkenyl groups in an amount of 0.001 mol % to 5 mol % (more preferably 0.01 mol % to 0.5 mol %) of R1. The alkenyl groups contained in the (a) organopolysiloxane are particularly preferably vinyl groups.

[0024] (a) Organopolysiloxane can be obtained, for example, by cohydrolytic condensation of one or more organohalosilanes, or by ring-opening polymerization of a cyclic polysiloxane such as a siloxane trimer or tetramer. (a) Organopolysiloxane may be essentially a linear diorganopolysiloxane, or may be partially branched. (a) Organopolysiloxane may also be a mixture of two or more types with different molecular structures.

[0025] The organopolysiloxane (a) preferably has a kinematic viscosity at 25°C of 100 cSt or more, and more preferably 100,000 cSt or more and 10,000,000 cSt or less. The degree of polymerization of (a) organopolysiloxane is preferably, for example, 100 or more, and more preferably 3,000 or more and 10,000 or less.

[0026] (b) Filling material (b) Examples of fillers include silica-based fillers, such as fumed silica and precipitated silica.

[0027] As the silica-based filler, a surface-treated silica-based filler that has been surface-treated with a silane coupling agent represented by R2Si(OR3)3 can be preferably used. Here, R2 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. R3 may be an alkyl group, such as a methyl group or an ethyl group. Silane coupling agents are readily available, for example, under the trade names "KBM1003" and "KBE402" manufactured by Shin-Etsu Chemical Co., Ltd. The surface-treated silica-based filler can be obtained by treating the surface of a silica-based filler with a silane coupling agent according to a standard method. Commercially available products may also be used as the surface-treated silica-based filler, such as "Zeothix 95" manufactured by JMHUBER Corporation.

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

[0029] (c) Conductive agent (c) 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 the carbon black include furnace black such as Ketjenblack (registered trademark), acetylene black, channel black, and thermal black.

[0030] The Millable type silicone rubber used 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. Furthermore, (c) as the millable type silicone rubber containing a conductivity imparting agent, KE-87C-40PU or the like can be used.

[0031] (B) Resin hollow filler The foamed elastic layer-forming composition contains a resin hollow filler, such as a thermally expandable resin hollow filler or a pre-expanded resin hollow filler. As the thermally expandable resin hollow filler, a microcapsule in which a liquid low-boiling hydrocarbon is encapsulated in a plastic polymer shell is preferably used. Examples of thermoplastic resins that make up the shell include vinylidene chloride / acrylonitrile copolymer, methyl methacrylate / acrylonitrile copolymer, and methacrylonitrile / acrylonitrile copolymer. It is preferable to use a resin hollow filler whose shell resin softening temperature is within an appropriate range to match the curing temperature of the silicone rubber. Examples of evaporative substances that can be encapsulated include hydrocarbons such as butane and isobutane.

[0032] Thermally expandable resin hollow fillers are commercially available as "Matsumoto Microsphere F Series" (manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.) and "Expancel Series" (manufactured by Expancel Co., Ltd.).

[0033] Examples of the expanded resin hollow filler include a composite type expanded resin hollow filler in which calcium carbonate powder is wrapped around the shell of a microcapsule. Pre-expanded hollow resin fillers are commercially available as "Matsumoto Microsphere FE Series" and "Matsumoto Microsphere F-DE Series" (manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.).

[0034] The particle size of the (B) resin hollow filler is preferably 30 μm or less, and more preferably 5 μm or more and 30 μm or less.

[0035] The blending amount of (B) resin hollow filler 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 foamed elastic layer-forming composition.

[0036] (C) Silazane Examples of the silazanes include hexamethyldisilazane and tetramethyldisilazane. By incorporating silazane into the foamed elastic layer-forming composition, silanol groups on the silica surface attached to the surface of the resin hollow filler can be substituted with trialkylsilyl groups, which is thought to reduce adhesion of the resin hollow filler to the rubber substrate and reduce compression set. The content of silazane in the foamed elastic layer-forming composition is preferably 0.1 to 2.0 parts by mass per 100 parts by mass of base rubber. By using a content of 0.1 or more parts by mass, silanol groups on the silica surface attached to the surface of the resin hollow filler can be sufficiently substituted with trialkylsilyl groups. Furthermore, by using a content of 2.0 or less parts by mass, residual silazane can be easily treated.

[0037] (D) Crosslinking agent The foamed elastic layer-forming composition may contain a crosslinking agent, such as an addition reaction crosslinking agent or an organic peroxide crosslinking agent. 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 added is usually 0.1 parts by mass or more and 7 parts by mass or less per 100 parts by mass of the foamed elastic layer-forming composition.

[0038] 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 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 the organic peroxide crosslinking agent is usually 0.1 to 7 parts by mass per 100 parts by mass of the foamed elastic layer-forming composition. The organic peroxide crosslinking agents can be used alone or in combination of two or more.

[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] (E)Water The foamed elastic layer-forming composition may contain water. By containing water, water molecules react with silanol groups on the surface of the silica particles, effectively preventing adhesion between the resin hollow filler and the rubber substrate. This improves the compression set of the foamed elastic layer 3.

[0041] (Other ingredients) The foamed elastic layer-forming composition may further 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.

[0042] The foamed elastic layer 3 is formed on the outer peripheral surface of the shaft body 2 by heat curing and molding simultaneously or successively using a known molding method. The method for 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 may be selected. The method for curing the foamed elastic layer-forming composition may be any method that can apply the heat required for curing (vulcanization) the foamed elastic layer-forming composition. The heating temperature when vulcanizing the foamed elastic layer-forming 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 to 1 hour or lower, and more preferably 10 seconds to 35 minutes or lower. Furthermore, secondary vulcanization may be performed as necessary.

[0043] After foaming and curing, the thickness of the foamed elastic layer 3 is preferably adjusted by polishing or grinding the outer peripheral surface.

[0044] (Hardness of foamed elastic layer) The Asker C hardness of the foamed elastic layer 3 is preferably 20 Hs or more and 50 Hs or less, and more preferably 25 Hs or more and 45 Hs or less. When the Asker C hardness of the foamed elastic layer 3 is within the above range, when the sponge roller 1 is installed in an image forming apparatus as a pressure roller or a fixing roller, a sufficient nip width can be ensured between the sponge roller 1 and a member that abuts or presses against it. The Asker C hardness of the foamed elastic layer 3 can be measured using an Asker C hardness tester in accordance with JIS K7312.

[0045] (Specific gravity of foam elastic layer) From the viewpoint of durability, the specific gravity of the foamed 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 can be measured as follows. An ALFA MIRAGE MDS-300 high-precision electronic specific gravity meter can be used. First, cut out a foamed elastic layer of approximately 2.0 g in air, and then measure its weight in air and in water to calculate its specific gravity. The mass of the cut foamed elastic layer in air is W (g), and its mass in water is Ww (g). Calculate the specific gravity (SG) of the foamed elastic layer using the formula SG = W / (W - Ww).

[0046] <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, polyurethane, etc. Among these, PFA is preferred. The resin tube can be produced by melt extrusion of a resin composition, etc. The resin tube can be attached by a known pressure insertion method, vacuum insertion method, etc.

[0047] In the sponge roller of the present invention, the silanol groups of the silica particles attached to the surface of the resin hollow filler are replaced with trialkylsilyl groups by silazane, thereby reducing adhesion to the rubber substrate and improving compression set. [Example]

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

[0049] [Example 1] The sponge roller of Example 1 was produced by the following procedure. (Formation of primer layer) An electroless nickel-plated shaft (made of SUM23, diameter 22 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 at least 30 minutes, forming a primer layer on the outer surface of the shaft.

[0050] (Formation of foamed elastic layer) A foamed elastic layer-forming composition 1 was prepared using the raw materials and blending ratios shown in Table 1. Details of the raw materials in Table 1 are as follows.

[0051] (A) Base rubber Silicone rubber (product name "KE-561-U", manufactured by Shin-Etsu Chemical Co., Ltd.) (B) Thermally expandable resin hollow filler (product name "Matsumoto Microsphere F Series", manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.) (C) Hexamethyldisilazane (D) Crosslinking agent (product name "C-25A", manufactured by Shin-Etsu Chemical Co., Ltd.) (E) Catalyst (product name "C-25B", manufactured by Shin-Etsu Chemical Co., Ltd.) (F) Colorant (product name "KE-ColorBR", manufactured by Shin-Etsu Silicone Co., Ltd.)

[0052] First, a thermally expandable resin hollow filler was placed in a sealable container, and hexamethyldisilazane (liquid) was added dropwise thereto. The container was then shook to mix the two components. The mass ratio of the thermally expandable resin hollow filler to hexamethyldisilazane was adjusted to 10:1. The remaining raw materials were then added, and the mixture was heated at 50°C for 2 hours. In this way, foamed elastic layer-forming composition 1 was prepared.

[0053] A sponge roller was produced by extrusion molding a foamed elastic layer on the outer peripheral surface of a shaft using the foamed elastic layer-forming composition 1. In the extrusion molding, the composition was heated at 180°C for 30 minutes using an infrared heating furnace (IR furnace), and then heated at 200°C for 240 minutes using a gear oven to harden it. The outer peripheral surface of this sponge roller was polished using a cylindrical grinder, and the thickness of the foamed elastic layer was set to 6 mm.

[0054] [Example 2] A foamed elastic layer-forming composition 2 was prepared using the formulation shown in Table 1, without base heating, and a sponge roller was produced in the same manner as in Example 1.

[0055] [Example 3] Base heating was carried out to prepare foamed elastic layer-forming composition 3, and a sponge roller was produced in the same manner as in Example 1.

[0056] [Comparative Example 1] A foamed elastic layer-forming composition 4 was prepared using the formulation shown in Table 1, without base heating, and a sponge roller was produced in the same manner as in Example 1.

[0057] [evaluation] The sponge rollers of the above-mentioned Examples and Comparative Examples were evaluated as follows.

[0058] (specific gravity) The specific gravity of the foamed elastic layer was determined using the method described above.

[0059] (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

[0060] [Table 1]

[0061] As shown in Table 1, the examples in which hexamethyldisilazane was added had a smaller compression set (%) after release than comparative example 1. A smaller value for compression set (%) after release indicates a higher return rate of the foamed elastic layer, and it can be seen that the sponge roller of the present invention has improved compression set. [Explanation of symbols]

[0062] 1 sponge roller 2-axis body 3. Foam elastic layer

Claims

1. A sponge roller having a shaft body and a foamed elastic layer provided on the outer periphery of the shaft body, The foamed elastic layer is formed from a foamed elastic layer-forming composition containing a base rubber, a thermally expandable resin hollow filler or a pre-expanded resin hollow filler, and a silazane.

2. 2. The sponge roller according to claim 1, wherein the content of the silazane in the foamed elastic layer-forming composition is 0.1 parts by mass or more and 2.0 parts by mass or less per 100 parts by mass of the base rubber.

3. the base rubber is a millable type silicone rubber, 2. The sponge roller according to claim 1, wherein the silazane is at least one of hexamethyldisilazane and tetramethyldisilazane.

4. 2. The sponge roller according to claim 1, wherein the foamed elastic layer-forming composition further contains water.

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