sponge roller

Abstract

The present invention provides a highly durable sponge roller. The sponge roller (1) of the present invention comprises a shaft (2) and a foamed elastic layer (3) formed on the outer periphery of the shaft (2). The foamed elastic layer (3) is formed by foaming and vulcanizing a foamed elastic layer composition containing a kneaded silicone rubber composition, a vinyl-containing organic silicone raw rubber, a foaming agent, and a crosslinking agent. The loss factor tanδ of the cured product of the rubber composition obtained by removing the foaming agent from the foamed elastic layer composition is 0.035 or less under the following measurement conditions. <Measurement conditions> Frequency 8 Hz, temperature 100°C, distortion control 5 μm.

Description

Technical Field

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

[0002] Laser printers, copiers, video printers, fax machines, and other multifunction devices employ various electrophotographic image forming devices. These devices include various printing sponge rollers, such as cleaning rollers, charging rollers, developing rollers, transfer rollers, pressure rollers, paper feed rollers, and fuser rollers, with shafts and elastic layers formed on their outer circumferences.

[0003] As the fixing device in the above-mentioned image forming apparatus, for example, a heat roller fixing method is employed. In this method, a pair of heated rollers (fusing rollers) and a pressure roller are generally used as a basic structure. A recording medium (transfer material sheet, fax paper, printer paper, etc.) carrying a toner image is introduced into the pressure nip of the roller pair, whereupon the toner image is fixed to the recording medium by heat pressure. The fixing roller or pressure roller used in the fixing device utilizes a foamed elastic layer (sponge layer) to adjust the nip pressure to an appropriate level.

[0004] The foamed elastic layer is typically formed by vulcanizing and foaming a kneaded silicone rubber containing an organopolysiloxane and a filler. The fixing or pressure roller with the foamed elastic layer is attached in a pressure-contacted state and functions by rotating continuously or intermittently. Therefore, it is susceptible to heat and friction loads. Since the hardness of the foamed elastic layer decreases over time, it is required to have high durability.

[0005] As a silicone rubber composition capable of forming a paper feeding rubber member having high wear resistance even after repeated use, Patent Document 1, for example, proposes a silicone rubber composition obtained by adding a vinyl-containing organic silicone raw rubber to a rubber compound forming a paper feeding rubber member, wherein the loss factor tan δ of the rubber compound after vulcanization is 0 <tanδ≤1。

[0006] Existing technology

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 10-182977 Summary of the Invention

[0009] Technical problem to be solved by the invention

[0010] However, in order to meet the recent demand for high-speed, high-definition, and high-quality image forming apparatuses, it is necessary to further improve the durability of the fixing roller or the pressure roller.

[0011] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a sponge roller having high durability.

[0012] Technical means to solve technical problems

[0013] An embodiment of the present invention is a sponge roller comprising: a shaft; and a foamed elastic layer formed on the outer periphery of the shaft; wherein the foamed elastic layer is formed by foaming and vulcanizing a foamed elastic layer composition containing a kneaded silicone rubber composition, a vinyl-containing organic silicone raw rubber, a foaming agent, and a crosslinking agent; and wherein a cured product of the rubber composition obtained by removing the foaming agent from the foamed elastic layer composition has a loss factor tan δ of 0.035 or less under the following measurement conditions.

[0014] <Measurement Conditions>

[0015] Frequency 8Hz, temperature 100℃, distortion control 5μm.

[0016] The Asker C hardness of the foamed elastic layer is preferably 15 degrees or more and 40 degrees or less.

[0017] The sponge roller of the present invention is preferably a pressure roller.

[0018] Effects of the Invention

[0019] According to the present invention, a sponge roller having high durability can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a perspective view showing the sponge roller of the present invention.

[0021] Figure 2 This is a graph showing the changes in hardness of sponge rollers in Examples and Comparative Examples.

[0022] Description of Reference Numerals

[0023] 1 sponge roller

[0024] 2-axis

[0025] 3 Foam elastic layer DETAILED DESCRIPTION

[0026] Hereinafter, embodiments of the present invention will be described in detail. However, the following embodiments are shown for illustrative purposes, and the present invention is not limited to the following embodiments.

[0027] [Sponge roller]

[0028] like Figure 1 As shown, the sponge roller 1 of the present invention includes a shaft 2 and a foamed elastic layer 3 sequentially formed on the outer periphery of the shaft 2 .

[0029] Below, refer to Figure 1 The sponge roller 1 of the present invention will be described in detail.

[0030] (Axis)

[0031] The shaft 2 can preferably be a conductive shaft used in conventional developing rollers. The shaft 2 is preferably made of metal, such as at least one selected from the group consisting of iron, aluminum, stainless steel, and brass. A shaft 2 made of such a metal is often referred to as "core gold."

[0032] The shaft body 2 may also include 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 may be obtained, for example, by electroplating the core body made of an insulating resin to impart conductivity.

[0033] In order to obtain good electrical conductivity, the shaft body 2 is preferably made of core gold.

[0034] The shaft body 2 is preferably shaped like a rod or a tube, for example. The cross-sectional shape of the shaft body 2 may be circular, elliptical, or non-circular, such as a polygon. The outer peripheral surface of the shaft body 2 may be treated, such as by cleaning, degreasing, or priming, to improve adhesion to the foamed elastic layer 3.

[0035] The length of the shaft body 2 in the axial direction is not particularly limited and can be appropriately adjusted according to the type of image forming device provided. For example, when the printing object is A4 size, the length of the shaft body 2 in the axial direction is preferably not less than 250 mm and not more than 320 mm, and more preferably not less than 260 mm and not more than 310 mm. In addition, the diameter of the shaft body 2 (the diameter of the circumscribed circle) is not particularly limited and can be appropriately adjusted according to the type of image forming device provided. For example, the outer diameter of the shaft body 2 (the diameter of the circumscribed circle) is preferably not less than 4 mm and not more than 14 mm, and more preferably not less than 6 mm and not more than 10 mm.

[0036] (Foamed elastic layer)

[0037] The foamed elastic layer 3 is formed by foaming and vulcanizing a foamed elastic layer composition containing (A) a kneading type silicone rubber composition, (B) a vinyl group-containing silicone raw rubber, (C) a foaming agent, and (D) a crosslinking agent.

[0038] In a dynamic viscoelasticity measurement, the loss factor tan δ of the foamed elastic layer 3 measured under the conditions of a frequency of 8 Hz, a temperature of 100° C., and a strain control of 5 μm is 0.035 or less, preferably 0.025 or less.

[0039] The loss factor tan δ is obtained by measuring a cured product of a rubber composition comprising (A) a kneadable silicone rubber composition, (B) a vinyl-containing silicone raw rubber, and (D) a crosslinking agent, after removing (C) the blowing agent from the foamed elastic layer composition. Specifically, by using a rubber composition having a cured product tan δ of 0.035 or less as the rubber material for the foamed elastic layer, a foamed elastic layer that is less susceptible to fatigue degradation can be obtained, resulting in a highly durable sponge roller.

[0040] Hereinafter, the components of the composition for the foamed elastic layer will be described.

[0041] (A) Millable Silicone Rubber Composition

[0042] The kneadable silicone rubber composition is preferably an addition-curing kneadable silicone rubber composition. The addition-curing kneadable silicone rubber composition preferably contains, for example, at least (a) an organopolysiloxane and (b) a filler.

[0043] (a) Organopolysiloxane

[0044] (a) The organopolysiloxane is represented by the following average composition formula (1).

[0045] R a SiO (4-a) / 2 (1)

[0046] (wherein, R is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, preferably 1 to 10 carbon atoms, and more preferably 1 to 8 carbon atoms, which is the same or different from each other; a is a positive number within the range of 1.5 to 2.8, preferably 1.8 to 2.5, more preferably 1.95 to 2.05, and further preferably 1.98 to 2.01).

[0047] R 1 n SiO (4-n) / 2 ...(1)

[0048] 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 number of carbon atoms in the hydrocarbon group is preferably 1 to 12, more preferably 1 to 8.

[0049] As R 1 Examples 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. 1Alternatively, some or all of the hydrogen atoms of these hydrocarbon groups may be replaced by substituents. Examples of the substituents include halogen atoms, cyano groups, and the like. Examples of hydrocarbon groups having substituents include chloromethyl, trifluoropropyl, and cyanoethyl.

[0050] The molecular chain ends of the organopolysiloxane (A) are preferably capped with trialkylsilyl groups such as trimethylsilyl, dialkylaralkylsilyl groups such as dimethylvinylsilyl, dialkylhydroxysilyl groups such as dimethylhydroxysilyl, or trialkylsilyl groups such as trivinylsilyl.

[0051] (A) The organopolysiloxane preferably has two or more alkenyl groups in the molecule. (A) The organopolysiloxane preferably has two or more alkenyl groups in the molecule. 1 The organopolysiloxane (A) contains 0.001 mol% to 5 mol% (more preferably 0.01 mol% to 0.5 mol%) of alkenyl groups. The alkenyl groups contained in the organopolysiloxane are particularly preferably vinyl groups.

[0052] The organopolysiloxane (A) can be obtained, for example, by co-hydrolysis and condensation of one or more organohalosilanes, or by ring-opening polymerization of cyclic polysiloxanes such as trimers or tetramers of siloxanes. The organopolysiloxane (A) can be a substantially linear diorganopolysiloxane or a partially branched one. Furthermore, the organopolysiloxane (A) can be a mixture of two or more different molecular structures.

[0053] The dynamic viscosity of the organopolysiloxane (A) at 25° C. is preferably 100 cSt or more, more preferably 100,000 cSt or more and 10,000,000 cSt or less.

[0054] 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.

[0055] (b) Filler

[0056] Examples of the filler (b) include silica-based fillers, such as fumed silica and precipitated silica.

[0057] As the silica filler, preferably used is a filler made of R 2 Si(OR 3 ) 3 is a surface-treated silica filler having a surface-treated silane coupling agent. 2 It may be a group having a vinyl group or an amino group, for example, a glycidyl group, a vinyl group, an aminopropyl group, a methacryloxy group, an N-phenylaminopropyl group, a mercapto group, etc. 3The silane coupling agent may be an alkyl group, such as a methyl group or an ethyl group. Silane coupling agents are readily available, for example, those manufactured by Shin-Etsu Chemical Co., Ltd. under the trade names "KBM1003" and "KBE402." Surface-treated silica fillers can be obtained by treating the surface of a silica filler with a silane coupling agent according to conventional methods. Commercially available surface-treated silica fillers, such as those manufactured by JMHUBER Co., Ltd. under the trade name "Zeothix 95," can be used as surface-treated silica fillers.

[0058] The amount of the silica filler blended per 100 parts by mass of the organopolysiloxane (A) is preferably from 11 parts by mass to 39 parts by mass, more preferably from 15 parts by mass to 35 parts by mass. Furthermore, the average particle size of the silica filler is preferably from 1 μm to 80 μm, more preferably from 2 μm to 40 μm. The average particle size of the silica filler can be measured as the median particle size using a particle size distribution analyzer using a laser diffraction method.

[0059] As the kneadable silicone rubber of the present invention, 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, KE-971T-U, etc. manufactured by Shin-Etsu Chemical Co., Ltd. In addition, as the kneadable silicone rubber containing a conductivity-imparting agent, KE-87C-40PU, etc. can be used.

[0060] (B) Vinyl-containing silicone rubber

[0061] (B) The vinyl-containing silicone rubber contains at least one vinyl group in one molecule, and may contain two vinyl groups in one molecule.

[0062] Examples of the vinyl group-containing silicone raw rubber include vinylmethyl silicone raw rubber, benzyl silicone raw rubber, and fluorosilicone raw rubber.

[0063] The blending ratio of (A) the addition-curing millable silicone rubber composition to (B) the vinyl-containing silicone raw rubber is preferably in the range of 50:50 to 80:20, more preferably in the range of 60:40 to 70:30.

[0064] (C) Foaming agent

[0065] As the foaming agent, any existing foaming agent used to form the foamed elastic layer 3 can be used. For example, chemical foaming agents and unexpanded microspheres can be used. Among chemical foaming agents, inorganic foaming agents include sodium bicarbonate and ammonium carbonate, while organic foaming agents include organic azo compounds such as diazoamino derivatives, azonitrile derivatives, and azodicarboxylic acid derivatives. Among organic azo compounds, azodicarbonamide and azobisisobutyronitrile are preferred. Azobisisobutyronitrile is particularly preferred.

[0066] Examples of unexpanded microspheres include resin microspheres. Resin microspheres preferably have a thermoplastic resin shell. Examples of thermoplastic resins constituting the shell include vinylidene chloride / acrylonitrile copolymers, methyl methacrylate / acrylonitrile copolymers, and methacrylonitrile / acrylonitrile copolymers. Resin microspheres preferably have a shell resin whose softening temperature is within an appropriate range, depending on the curing temperature of the silicone rubber. Examples of volatile substances to be encapsulated include hydrocarbons such as butane and isobutane.

[0067] The average particle size of the unexpanded microspheres is preferably 5 μm or more and 50 μm or less, and more preferably 5 μm or more and 25 μm or less.

[0068] Unexpanded microspheres can also be used as the blowing agent. Commercially available unexpanded microspheres suitable for use in the present invention include the "Matsumoto Microsphere F Series" (manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.) and the "Expancel Series" (manufactured by Expancel). Unexpanded resin microspheres suitable for use in the present invention are selected from resin microspheres that expand at a temperature higher than the decomposition temperature of the chemical blowing agent used to form the elastic layer.

[0069] The amount of the foaming agent blended is preferably 0.5% by mass or more and 6% by mass or less relative to 100 parts by mass of the composition for the foamed elastic layer, from the viewpoint of obtaining cells of low specific gravity and uniform size.

[0070] (D) Cross-linking agent

[0071] Examples of the cross-linking agent include addition reaction cross-linking agents and organic peroxide cross-linking agents.

[0072] Examples of the addition reaction crosslinking agent include conventional organohydrogen polysiloxanes, which are addition reaction type crosslinking agents having two or more SiH groups (SiH bonds) in one molecule. The addition reaction crosslinking agent may be used alone or in combination of two or more.

[0073] 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 relative to 100 parts by mass of the composition for the foamed elastic layer.

[0074] When using an addition reaction crosslinking agent, the organic peroxide crosslinking agent can crosslink with the millable silicone rubber alone. However, when the organic peroxide crosslinking agent is used in conjunction with the addition reaction crosslinking agent as an auxiliary crosslinking agent, the physical properties of the resulting toner supply roller, such as strength and deformation, can be further improved. Examples of the organic peroxide crosslinking agent include benzoyl peroxide, bis-2,4-dichlorobenzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, and 2,5-dimethyl-2,5-bis(tert-butylperoxide)hexane.

[0075] The amount of the organic peroxide crosslinking agent added is usually 0.1 to 7 parts by mass per 100 parts by mass of the composition for the foamed elastic layer. The organic peroxide crosslinking agent may be used alone or in combination of two or more.

[0076] The addition reaction crosslinking agent is preferably used in combination with an addition reaction catalyst. Examples of the addition reaction catalyst include platinum black, platinum chloride, chloroplatinic acid, a reaction product of chloroplatinic acid and a monovalent alcohol, a complex of chloroplatinic acid and an olefin, bisacetoacetic acid platinum, a palladium catalyst, and a rhodium catalyst. The addition reaction catalyst may be used in a catalytic amount.

[0077] In addition to the above, the composition for the foamed elastic layer may further contain additives. Examples of such additives include conductive materials, auxiliary agents (chain extenders, crosslinking agents, etc.), catalysts, dispersants, anti-aging agents, antioxidants, pigments, colorants, processing aids, softeners, plasticizers, emulsifiers, heat resistance improvers, flame retardant improvers, acid acceptors, thermal conductivity improvers, release agents, and solvents.

[0078] The foamed elastic layer 3 is formed on the outer peripheral surface of the shaft body 2 by simultaneously or continuously heat-curing and molding using existing molding methods. The rubber composition can be cured by any method that can apply the heat required to cure the rubber composition. Furthermore, the molding method for the foamed elastic layer 3 is not particularly limited and may include continuous vulcanization (extrusion molding), press molding, injection molding, and the like. For example, extrusion molding can be selected. Furthermore, the foamed elastic layer 3 formed on the shaft body 2 may be subjected to grinding or polishing.

[0079] The heating temperature during vulcanization of the composition for the foamed elastic layer is preferably from 100°C to 500°C, more preferably from 120°C to 300°C. The heating time is preferably from several seconds to 1 hour, more preferably from 10 seconds to 35 minutes. Furthermore, secondary vulcanization may be performed as needed. Furthermore, by foaming and curing the rubber composition using conventional methods, a foamed elastic layer 3 having cells can be easily formed.

[0080] The hardness (Asker C hardness) of the foamed elastic layer 3 is preferably 15 to 40. For such a low-hardness foamed elastic layer, it is effective to use a rubber material having tan δ as described above.

[0081] The sponge roller of the present invention is suitable for use as a pressure roller or a fixing roller in various image forming apparatuses utilizing an electrophotographic system.

[0082] While the present invention has been described above using embodiments, it goes without saying that the technical scope of the present invention is not limited to the invention described in the above embodiments. It is obvious to those skilled in the art that various modifications or improvements can be made to the above embodiments. Furthermore, according to the claims, such modified or improved inventions are also encompassed within the scope of the claims.

[0083] Example

[0084] Hereinafter, the present invention will be described in detail by giving examples.

[0085] [Example 1]

[0086] (Preparation of composition for foamed elastic layer)

[0087] A composition for a foamed elastic layer was prepared using the following materials.

[0088] (A) Addition-curing millable silicone rubber composition (X-30-4037U, manufactured by Shin-Etsu Chemical Co., Ltd.): 80 parts by mass

[0089] (B) Vinyl-containing silicone raw rubber (KE-77VB, manufactured by Shin-Etsu Chemical Co., Ltd.): 20 parts by mass

[0090] (C) Chemical foaming agent: 5 parts by mass

[0091] (D) Cross-linking agent: 3 parts by mass

[0092] (Formation of Primer Layer)

[0093] A shaft (SUM22, 10 mm diameter, 275 mm long) that had been electrolessly nickel-plated was cleaned with ethanol and coated with a silicone primer (trade name "Primer No. 16," manufactured by Shin-Etsu Chemical Co., Ltd.). The primed shaft was baked in a Gir oven at 150°C for 10 minutes and then cooled at room temperature for at least 30 minutes to form a primer layer on the outer circumference of the shaft.

[0094] (Formation of Foamed Elastic Layer)

[0095] Next, the shaft with the primer layer formed thereon and the composition for the foamed elastic layer were extruded integrally using an extruder. The mixture was heated at 250°C for 20 minutes in an infrared oven (IR oven) for primary vulcanization. Subsequently, the mixture was secondary vulcanized in a hot air drying oven at 210°C for 10 hours to produce a foamed roller blank. The circumferential surface of the foamed roller blank was high-speed polished using a metal grinding wheel using a polishing machine manufactured by Mizuguchi Seisakusho Co., Ltd., to produce a sponge roller with an outer diameter of 32 mm.

[0096] [Examples 2, 3 and Comparative Examples 1 to 3]

[0097] As shown in Table 1, a sponge roller was prepared in the same manner as in Example 1 except that the type and ratio of the vinyl-containing silicone rubber were changed.

[0098] [evaluate]

[0099] The durability evaluations of the above-mentioned Examples and Comparative Examples were performed as follows. The evaluation results are shown in Table 1.

[0100] (Hardness change)

[0101] As a durability evaluation, the hardness change amount was measured by the following evaluation method.

[0102] A roller with a product diameter of 32 mm was made using a shaft with a diameter of 22.0 mm. The roller was fixed to a metal roller with a diameter of 40.0 mm by compressing an amount equivalent to 35% of the thickness of the rubber. In this state, the roller was rotated for 200 hours while applying a temperature of 180°C. The hardness before the start of the measurement (0 hour) was set to 0, and the hardness after 100 hours of rotation and after 200 hours of rotation was measured using an ASKER rubber hardness tester type C (manufactured by Kobunsu Keiki Co., Ltd.) with a measurement load of 9.8 N. Table 2 shows the change in hardness over time, and the graph shows Figure 2 The hardness change at each measurement time is shown in Table 2, and the graph is as follows Figure 2 shown.

[0103] (loss factor tanδ)

[0104] Next, compositions for foamed elastic layers without adding a foaming agent were prepared and vulcanized in the aforementioned Examples and Comparative Examples. Samples measuring 20 mm long, 5 mm wide, and 2 mm thick were prepared and their loss factor, tan δ, was measured using a viscoelasticity spectrometer (manufactured by Rheology Co., Ltd.). The measurement conditions were as follows.

[0105] <Measurement Conditions>

[0106] The measurement was performed using a dynamic viscoelasticity tester (trade name "Pheogel-E4000", UBM Co., Ltd.) at a frequency of 8 Hz, a starting temperature of 30°C, an ending temperature of 100°C, a heating rate of 5°C / min, a strain control of 5 μm, and a chuck distance of 10 mm.

[0107] [Table 1]

[0108]

[0109] [Table 2]

[0110]

[0111] As shown in Tables 1 and 2, Figure 2 As shown, the sponge roller of the present invention can suppress tan δ to 0.035 or less and hardness variation (degrees) to within -3 by containing a silicone raw rubber having a vinyl group in a side chain in the composition for the foamed elastic layer.

[0112] On the other hand, in Comparative Example 3 containing silicone raw rubber without a vinyl group on the side chain, the changes in tan δ and hardness are greater than those in the examples; and in Comparative Examples 1 and 2 containing only a kneaded silicone composition without other silicone raw rubber, the changes in tan δ and hardness are even greater.

Claims

1. A sponge roller comprising: Axis; and A foamed elastic layer is formed on the outer periphery of the shaft; The foamed elastic layer is formed by foaming and vulcanizing a composition for a foamed elastic layer containing a kneading type silicone rubber composition, a vinyl-containing organic silicone raw rubber, a foaming agent, and a crosslinking agent; The cured product of the rubber composition obtained by removing the blowing agent from the composition for the foamed elastic layer has a loss factor tan δ of 0.035 or less under the following measurement conditions, <Measurement Conditions> Frequency 8Hz, temperature 100℃, distortion control 5μm.

2. The sponge roller according to claim 1, wherein The Ascar C hardness of the foamed elastic layer is not less than 15 degrees and not more than 40 degrees.

3. The sponge roller according to claim 1 or 2, wherein: The sponge roller is a pressure roller.

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