JP7570187B2 - Sponge Roller - Google Patents

Description

The present invention relates to a sponge roller.

Laser printers, copiers, video printers, facsimiles, and all-in-one machines employ various image forming devices that use electrophotography. Electrophotographic image forming devices are equipped with various printing sponge rollers, such as cleaning rollers, charging rollers, developing rollers, transfer rollers, pressure rollers, paper feed rollers, and fixing rollers, that have a shaft body and an elastic layer formed on the outer circumferential surface of the shaft body.

The fixing means in the image forming apparatus described above is, for example, 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 the basic configuration, and the toner image is generally fixed to the recording material (transfer material sheet, fax paper, printing paper, etc.) carrying the toner image by introducing the recording material (transfer material sheet, fax paper, printing paper, etc.) into the pressure nip of the pair of rollers. 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.

The foamed elastic layer is generally formed by vulcanizing and foaming millable silicone rubber containing organopolysiloxane and a filler. The fixing or pressure roller having the foamed elastic layer is mounted in a pressure-contact state and functions by rotating continuously or intermittently, so it is prone to loads due to heat and friction, and the hardness of the foamed elastic layer decreases over time, so it is required to have high durability.
As a silicone rubber composition capable of forming a rubber member for feeding paper that has high abrasion resistance even after repeated use, for example, Patent Document 1 proposes a silicone rubber composition in which a vinyl group-containing silicone raw rubber is added to a rubber compound that forms a rubber member for feeding paper, and in which the loss factor tan δ after vulcanization of the rubber compound is 0<tan δ≦1.

Japanese Patent Application Publication No. 10-182977

However, in order to meet the recent demand for high-speed, high-definition, and high-quality image forming apparatuses, there is a demand for further improvement in durability of the fixing roller or pressure roller.
The present invention has been made in consideration of the above circumstances, and has an object to provide a sponge roller having high durability.

The present invention is a sponge roller having 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 millable type silicone rubber composition, a vinyl group-containing silicone raw rubber, a foaming agent, and a crosslinking agent, and the 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 measurement conditions described below.
<Measurement conditions>
Frequency 8Hz, temperature 100℃, distortion control 5μm

It is preferable that the foamed elastic layer has an Asker C hardness of 15 degrees or more and 40 degrees or less.

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

The present invention makes it possible to obtain a highly durable sponge roller.

FIG. 2 is a perspective view showing a sponge roller of the present invention. 10 is a graph showing the amount of change in hardness of sponge rollers of an example and a comparative example.

The following describes in detail the embodiments of the present invention. However, the following embodiments are presented for illustrative purposes, and the present invention is not limited to the embodiments described below.

[Sponge roller]
As shown in FIG. 1, the sponge roller 1 of the present invention is a sponge roller 1 including a shaft body 2 and a foamed elastic layer 3 formed on the outer periphery of the shaft body 2 in this order.
Hereinafter, the sponge roller 1 of the present invention will be described in detail with reference to FIG.

(Shaft body)
The shaft body 2 may preferably be a conductive shaft body used in a conventionally known developing 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. The shaft body 2 made of such a metal is generally known as a "core metal."

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 may 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 metal in order to obtain good electrical conductivity.

The shape of the shaft body 2 is preferably, for example, rod-like or tubular. The cross-sectional shape of the shaft body 2 may be, for example, circular or elliptical, or may be non-circular, such as polygonal. The outer peripheral surface of the shaft body 2 may be subjected to a cleaning treatment, a degreasing treatment, a primer treatment, or the like, in order to improve adhesion with the foamed elastic layer 3.

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 device in which it is installed. For example, when the printing target is A4 size, the axial length of the shaft body 2 is preferably 250 mm or more and 320 mm or less, and more preferably 260 mm or more and 310 mm or less. The diameter of the shaft body 2 (diameter of the circumscribing circle) is also not particularly limited, and may be adjusted as appropriate depending on the type of the image forming device in which it is installed. For example, the outer diameter (diameter of the circumscribing circle) of the shaft body 2 is preferably 4 mm or more and 14 mm or less, and more preferably 6 mm or more and 10 mm or less.

(Foamed Elastic Layer)
The foamed elastic layer 3 is formed by foaming and vulcanizing a foamed elastic layer composition containing (A) a millable type silicone rubber composition, (B) a vinyl group-containing silicone raw rubber, (C) a foaming agent, and (D) a crosslinking agent.

The foamed elastic layer 3 has a loss factor tan δ of 0.035 or less, preferably 0.025 or less, as measured in dynamic viscoelasticity measurement at a frequency of 8 Hz, a temperature of 100° C., and a strain control of 5 μm.
The loss factor tan δ was measured for the cured product of the rubber composition containing (A) the millable type silicone rubber composition, (B) the vinyl group-containing silicone raw rubber, and (D) the crosslinking agent, excluding (C) the foaming agent from the foamed elastic layer composition. That is, 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 resistant to fatigue deterioration can be obtained, and as a result, a sponge roller with high durability can be obtained.
The components of the foamed elastic layer composition will be described below.

(A) Millable silicone rubber composition As the millable silicone rubber composition, an addition curing type millable silicone rubber composition is preferable. The addition curing type millable silicone rubber composition preferably contains at least (a) an organopolysiloxane and (b) a filler.

(a) Organopolysiloxane (a) Organopolysiloxane is represented by the following average composition formula (1).
R _a SiO _(4-a)/2 (1)
(In the formula, R may be the same or different and 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. a is a positive number ranging from 1.5 to 2.8, preferably 1.8 to 2.5, more preferably 1.95 to 2.05, and even more preferably 1.98 to 2.01.)
R ¹ _n SiO _(4-n)/2 ...(1)
In formula (1), n is a positive number of 1.95 to 2.05. R ¹ 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 to 12, more preferably 1 to 8.

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 of these hydrocarbon groups have been substituted with a substituent. The substituent may be, for example, a halogen atom or a cyano group. Examples of the hydrocarbon group having a substituent include a chloromethyl group, a trifluoropropyl group, and a cyanoethyl group.

(A) The molecular chain terminals of the organopolysiloxane 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 triarylalkylsilyl group such as a trivinylsilyl group.

The organopolysiloxane (A) preferably has two or more alkenyl groups in the molecule. The organopolysiloxane (A) preferably has 0.001 mol % or more and 5 mol % or less (more preferably 0.01 mol % or more and 0.5 mol % or less) of alkenyl groups in ^R1 . The alkenyl groups contained in the organopolysiloxane (A) are particularly preferably vinyl groups.

(A) Organopolysiloxane can be obtained, for example, by cohydrolytic condensation of one or more organohalosilanes, or by ring-opening polymerization of cyclic polysiloxanes such as siloxane trimers or tetramers. (A) Organopolysiloxane may basically be a linear diorganopolysiloxane, or may be partially branched. (A) Organopolysiloxane may also be a mixture of two or more types having different molecular structures.

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

(b) Filler Examples of the filler (b) include silica-based fillers. Examples of the silica-based fillers include fumed silica and precipitated silica.

As the silica-based filler, a surface-treated silica-based filler that has been surface-treated with a silane coupling agent represented by R ² Si(OR ³ ) ₃ can be suitably used. Here, R ² 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. ^{R 3} may be an alkyl group, for example, a methyl group, an ethyl group, etc. Silane coupling agents are easily 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, the trade name "Zeothix 95" manufactured by J. M. HUBER Co., Ltd.

The amount of silica-based filler is preferably 11 parts by weight or more and 39 parts by weight or less, and more preferably 15 parts by weight or more and 35 parts by weight or less, per 100 parts by weight of the organopolysiloxane (A). The average particle size of the silica-based filler is preferably 1 μm or more and 80 μm or less, and more preferably 2 μm or more and 40 μm or less. 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.

As examples of millable silicone rubber in the present invention, 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. can be used. In addition, as millable silicone rubber containing a conductivity imparting agent, KE-87C-40PU, etc. can be used.

(B) Vinyl-containing silicone raw rubber (B) The vinyl-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.

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

(C) Foaming Agent As the foaming agent, a known foaming agent used for forming the foamed elastic layer 3 can be used. For example, a chemical foaming agent or unexpanded microballoons can be used. As for the chemical foaming agent, examples of the inorganic foaming agent include sodium bicarbonate and ammonium carbonate, and examples of the organic foaming agent include organic azo compounds such as diazoamino derivatives, azonitrile derivatives, and azodicarboxylic acid derivatives. Among the organic azo compounds, azodicarboxylic acid amide, azobis-isobutyronitrile, and the like are preferably used. In particular, azobis-isobutyronitrile is preferably used.

Resin microballoons can be cited as examples of unexpanded microballoons. Resin microballoons that use a thermoplastic resin for the outer shell are preferably used. Examples of the thermoplastic resin that constitutes the outer shell include vinylidene chloride/acrylonitrile copolymer, methyl methacrylate/acrylonitrile copolymer, and methacrylonitrile/acrylonitrile copolymer. It is preferable to use resin microballoons whose shell resin has a softening temperature within an appropriate range in accordance with the curing temperature of the silicone rubber. Examples of evaporative substances to be encapsulated include hydrocarbons such as butane and isobutane.
The average particle size of the unexpanded microballoons is preferably from 5 μm to 50 μm, more preferably from 5 μm to 25 μm.

Unexpanded microballoons can also be used as the foaming agent. Unexpanded microballoons suitable for the present invention are commercially available as "Matsumoto Microsphere F Series" (manufactured by Matsumoto Yushi Seiyaku Co., Ltd.) and "Expancel Series" (manufactured by Expancel Co., Ltd.). Unexpanded resin microballoons suitable for the present invention are selected from resin microballoons that have the function of expanding at a temperature higher than the decomposition temperature of the chemical foaming agent used to form the elastic layer.
The blending amount of the foaming agent is preferably 0.5% by mass or more and 6% by mass or less, from the viewpoint of obtaining cells of uniform size while having a low specific gravity relative to 100 parts by mass of the foamed elastic layer composition.

(D) Crosslinking Agent Examples of the crosslinking agent include addition reaction crosslinking agents, organic peroxide crosslinking agents, and the like.
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 kinds.
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.

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 with the addition reaction crosslinking agent as an auxiliary crosslinking agent, the physical properties such as strength and distortion of the obtained toner supply roller can be further improved. Examples of the organic peroxide crosslinking agent include benzoyl peroxide, bis-2,4-dichlorobenzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, etc.
The amount of the organic peroxide crosslinking agent is usually 0.1 parts by mass or more and 7 parts by mass or less per 100 parts by mass of the foamed elastic layer composition. The organic peroxide crosslinking agent may be used alone or in combination of two or more kinds.

It is preferable to use an addition reaction catalyst in combination with the addition reaction crosslinking agent. Examples of addition reaction catalysts include platinum black, platinic chloride, chloroplatinic acid, reaction products of chloroplatinic acid and monohydric alcohols, complexes of chloroplatinic acid and olefins, platinum bisacetoacetate, palladium catalysts, and rhodium catalysts. The amount of addition reaction catalyst used can be a catalytic amount.

The foamed elastic layer composition may further contain additives in addition to the above. Examples of additives include conductive materials, auxiliaries (chain extenders, crosslinking agents, etc.), catalysts, dispersants, antioxidants, antioxidants, pigments, colorants, processing aids, softeners, plasticizers, emulsifiers, heat resistance improvers, flame retardant improvers, acid acceptors, thermal conductivity improvers, release agents, solvents, etc.

The foamed elastic layer 3 is formed on the outer circumferential surface of the shaft body 2 by simultaneously or successively performing heat curing and molding using a known molding method. The rubber composition may be cured by any method that can apply the heat required for hardening the rubber composition. The molding method of the foamed elastic layer 3 is not particularly limited, and may include continuous vulcanization by extrusion molding, pressing, mold molding by injection, etc. For example, extrusion molding, etc. may be selected. The foamed elastic layer 3 formed on the shaft body 2 may also be ground or polished, etc.

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. If necessary, secondary vulcanization may be performed. The rubber composition can also be foamed and cured by a known method to easily form a foamed elastic layer 3 having bubbles.

The hardness (Asker C hardness) of the foamed elastic layer 3 is preferably 15 degrees or more and 40 degrees or less. For such a low-hardness foamed elastic layer, it is effective to use a rubber material that exhibits the above-mentioned tan δ.

The sponge roller of the present invention is suitable for use as a pressure roller or a fixing roller in various image forming apparatuses that utilize an electrophotographic system.
Although the present invention has been described above using the embodiments, it goes without saying that the technical scope of the present invention is not limited to the scope of the invention described in the above embodiments, and it is clear to those skilled in the art that various modifications and improvements can be made to the above embodiments. Furthermore, it is clear from the description of the claims that inventions with such modifications or improvements can also be included in the technical scope of the present invention.

The present invention will now be described in detail with reference to examples.
[Example 1]
(Preparation of foamed elastic layer composition)
A foamed elastic layer composition was prepared using the following materials.
(A) Addition-curing millable silicone rubber composition (X-30-4037U, manufactured by Shin-Etsu Chemical Co., Ltd.) 80 parts by mass (B) Vinyl-containing silicone raw rubber (KE-77VB, manufactured by Shin-Etsu Chemical Co., Ltd.)
20 parts by weight (C) Chemical foaming agent 5 parts by weight (D) Crosslinking agent 3 parts by weight

(Formation of primer layer)
An electroless nickel-plated shaft (made of SUM22, diameter 10 mm, length 275 mm) was washed with ethanol, and its surface was coated with a silicone-based 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.

(Formation of foamed elastic layer)
Next, the shaft body on which the primer layer was formed and the foamed elastic layer composition were extruded as one unit using an extruder, and the mixture was heated at 250°C for 20 minutes in an infrared heating furnace (IR furnace) for primary vulcanization, and then the mixture was secondary vulcanized for 10 hours at 210°C in a hot air drying furnace to produce a foamed roller base body. The circumferential surface of this foamed roller base body was polished at high speed with a metal grindstone using a polishing machine manufactured by Mizuguchi Seisakusho Co., Ltd., to produce a sponge roller with an outer diameter of 32 mm.

[Examples 2 and 3, and Comparative Examples 1 to 3]
The preparation was carried out in the same manner as in Example 1, except that the type and composition of the vinyl group-containing silicone rubber was changed as shown in Table 1.

[evaluation]
The following durability evaluation was carried out for the above-mentioned Examples and Comparative Examples. The evaluation results are shown in Table 1.
(Change in hardness)
For durability evaluation, the change in hardness was measured by the following evaluation method.
A roller with a product diameter of φ32 mm was produced using a shaft diameter of φ22.0 mm. The roller was compressed to 35% of the rubber thickness and fixed to a metal roller with a diameter of φ40.0 mm. In this state, the roller was rotated for 200 hours while being heated to 180°C. The hardness before the start of the measurement (0 hours) was set to 0, and the hardness after 100 hours of rotation and after 200 hours of rotation was measured using an ASKER rubber hardness tester C type (manufactured by Kobunshi Keiki Co., Ltd.) with a measurement load of 9.8 N. The hardness change over time is shown in Table 2 and a graph is shown in Figure 2.

(Loss factor tan δ)
Next, in the above-mentioned Examples and Comparative Examples, a foamed elastic layer composition containing no foaming agent was prepared and vulcanized to prepare a sample having a length of 20 mm, a width of 5 mm, and a thickness of 2 mm, and the loss factor tan δ was measured using a viscoelasticity spectrometer (manufactured by Rheology Co., Ltd.). The measurement conditions were as follows.
<Measurement conditions>
A dynamic viscoelasticity measuring instrument (product name "Pheogel-E4000", UBM Corporation) was used to measure 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, strain control of 5 μm, and a chuck distance of 10 mm.

As shown in Tables 1 and 2 and FIG. 2, the sponge roller of the present invention can suppress tan δ to 0.035 or less and hardness change (degrees) to within -3 by incorporating a silicone raw rubber having a vinyl group in the side chain into the foamed elastic layer composition.
On the other hand, Comparative Example 3, which contained a silicone raw rubber that did not contain vinyl groups in the side chains, had a larger change in tan δ and hardness than the Examples, and Comparative Examples 1 and 2, which contained only the millable silicone composition and no other silicone raw rubber, showed even larger changes in tan δ and hardness.

1 Sponge roller 2 Shaft body 3 Foamed elastic layer

Claims (3)

A sponge roller having a shaft body and a foamed elastic layer formed on the outer periphery of the shaft body,
the foamed elastic layer is formed by foaming and vulcanizing a foamed elastic layer composition containing a millable type silicone rubber composition, a vinyl group-containing silicone raw rubber, a foaming agent, and a crosslinking agent;
The foaming agent includes a chemical foaming agent and a resin microballoon, or includes only a resin microballoon;
a rubber composition obtained by removing the foaming agent from the foamed elastic layer composition, the rubber composition being cured, has a loss factor tan δ of 0.020 or less under the following measurement conditions.
<Measurement conditions>
Frequency 8Hz, temperature 100℃, distortion control 5μm the hardness change amount of the foamed elastic layer is within −2.5,
2. The sponge roller according to claim 1, wherein the foamed elastic layer has an Asker C hardness of 15 degrees or more and 40 degrees or less. 3. The sponge roller according to claim 1, which is a pressure roller.

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