JP6624516B2 - Sponge roller, method of manufacturing sponge roller, and image forming apparatus - Google Patents

Description

  The present invention relates to a sponge roller, a method of manufacturing a sponge roller, and an image forming apparatus, and more particularly, a sponge roller having a low coefficient of thermal expansion, a method of manufacturing the sponge roller, and an image forming apparatus including the sponge roller. Equipment related.

  Rubber sponges having a porous structure are suitably used, for example, as various rollers for image forming apparatuses, sponges for cleaning, sponges for absorbing fluid such as water and oil, and stamping materials.

  Such a rubber sponge can be produced, for example, by a foam molding method using a foaming agent, a method using hollow fine particles, or an elution method of eluting soluble particles mixed in advance. For example, as a method for forming a conductive compressible layer of an image transfer roll for an image forming apparatus, Patent Document 1 discloses that a foaming agent is compounded in a synthetic rubber compound forming a compressible layer, and vulcanization of rubber is performed. Foam molding method to form a compressible layer having cells by foaming inside, hollow microspheres are blended in place of the foaming agent, and hollow microsphere mixing method to form independent cells, or water, methanol, etc. Powder eluting method in which a powder that can be eluted in the eluate, for example, sodium chloride, sugar, etc., is compounded in a synthetic rubber compound, and the powder is eluted after vulcanization to form a compressible layer having cells. And the like are known.

  More specifically, as a method using microballoons, Patent Document 2 discloses a pressure roller having an elastic layer dispersedly containing voids formed by resin microballoons around a core metal, and the elastic layer is Heating the liquid silicone rubber containing the inflated resin microballoon on the core metal at a temperature lower than the softening point of the resin microballoon to cure the liquid silicone rubber, and then breaking the resin microballoon. It is described that the voids are generated by the method.

  Patent Document 3 discloses that a water-in-oil emulsion composition capable of forming a silicone elastomer porous body having uniform fine cells (bubbles) without a foaming phenomenon is used to manufacture a copier, a laser printer, and the like. A substantially closed-cell-type silicone elastomer porous body that can be used for image parts and the like is described.

  In addition to various rollers for an image forming apparatus, for example, in Patent Document 4 relating to a sponge rubber printed body as a stamping material, rubber, a water-soluble fine powder, a vulcanizing agent, a filler, and a fiber length of 0.2 mm to 2 mm were used. A sponge rubber printed body having open cells obtained by kneading a staple of organic synthetic fibers to form a master batch, vulcanizing the master batch, and then washing away a water-soluble fine powder is described.

  Patent Document 5 discloses that a silicone rubber compound obtained by mixing a high molecular weight silicone rubber with a compound A obtained by mixing a low molecular weight silicone rubber with an inflated resin microballoon is lower than the softening point of the resin microballoon. A silicone rubber sponge obtained by curing a silicone rubber by heating at a temperature is disclosed.

JP 2005-24902 A Japanese Patent No. 3658305 Japanese Patent No. 4638714 Japanese Patent No. 3647110 Re-published patent WO2013 / 005613

  Here, with a conventional sponge roller such as the sponge roller described in Patent Document 1, when only microballoons are used as the foaming agent, the average cell diameter can be reduced, but the coefficient of thermal expansion may increase. When only a chemical foaming agent is used as a foaming agent, the coefficient of thermal expansion can be suppressed low, but the average cell diameter may be increased. Further, even when a microballoon and a chemical blowing agent are used in combination as the blowing agent, there is a problem that the coefficient of thermal expansion is relatively large. Accordingly, it is an object of the present invention to provide a sponge roller having a low coefficient of thermal expansion, a method of manufacturing the sponge roller, and an image forming apparatus including the sponge roller.

  The inventors of the present invention have intensively studied to solve the above problems. As a result, the present inventors have found that the above problem can be solved by a sponge roller having an elastic layer formed of a millable silicone rubber, an unexpanded microballoon, a chemical foaming agent, and a porous filler. Was completed. Specifically, the present invention provides the following.

  (1) A first aspect of the present invention is a sponge roller having a shaft and an elastic layer formed on the outer peripheral surface of the shaft, wherein the elastic layer is made of a millable silicone rubber and an unexpanded micro rubber. An oven formed from a balloon, a chemical foaming agent, and a porous filler, wherein an average cell diameter of cells formed by the unexpanded microballoons and the chemical foaming agent is 150 μm or less, and a sponge roller is heated to 180 ° C. In the case where the roller outer diameter was measured every 10 minutes until 60 minutes after the start of heating, and the coefficient of thermal expansion of the elastic layer measured every 10 minutes was calculated from the thickness of the elastic layer before heating, A sponge roller characterized in that the value obtained by subtracting the coefficient of thermal expansion of the elastic layer 60 minutes after the start of heating from the coefficient of thermal expansion of the elastic layer 10 minutes after the start of heating is -1.0 to 2.0. .

  (2) A second aspect of the present invention is the sponge roller according to (1), wherein a cell area ratio of the unexpanded microballoon and the chemical foaming agent (unexpanded microballoon: Foaming agent) is from 95: 5 to 10:90.

  (3) A third aspect of the present invention is the sponge roller according to (1) or (2), wherein the content of the porous filler in the elastic layer is 0.05% by mass to 50% by mass. It is characterized by the following.

  (4) In a fifth aspect of the present invention, a millable silicone rubber, an unexpanded microballoon, a chemical foaming agent, and a porous filler are mixed to prepare a mixture, and the mixture is mixed with a shaft. A sponge roller according to any one of (1) to (3), which is extruded on an outer surface of the sponge roller, and then heat-cured to produce the sponge roller according to any one of (1) to (3).

  (5) A sixth aspect of the present invention is an image forming apparatus comprising the sponge roller according to any one of (1) to (3).

  The sponge roller of the present invention uses a millable silicone rubber, an unexpanded microballoon, and a chemical foaming agent to form an elastic layer, and further uses a porous filler in addition to this. . By using an unexpanded microballoon and a chemical foaming agent together, the average cell diameter becomes relatively small, and the coefficient of thermal expansion of the elastic layer is also adjusted, but in addition to this, using a porous filler Accordingly, the pores on the surface of the porous filler function as air passages connecting the cells, and the substantial open cell rate is improved, so that the coefficient of thermal expansion of the elastic layer of the sponge roller is further suppressed. According to the present invention, it is possible to provide a sponge roller in which a change in shape due to heat is suppressed.

It is an explanatory view showing a sponge roller showing one example of the present invention. It is a schematic diagram which shows the measuring device which measures the compression set of the sponge roller concerning this invention. FIG. 1 is an explanatory diagram illustrating an example of an image forming apparatus in which a sponge roller according to an embodiment of the present invention is incorporated in a fixing device.

<Sponge roller>
As shown in FIG. 1, a sponge roller 1 as an example of the present invention includes a shaft 2 also called a core metal and an elastic layer 3 formed on an outer peripheral surface of the shaft. Reference numeral 4 denotes a fluororesin layer formed on the surface of the elastic layer 3 as needed.

  The shaft body is usually a long cylindrical body called a so-called core metal made of iron, aluminum, stainless steel, brass or the like. The shaft is adjusted to an appropriate diameter and an axial length according to the image forming apparatus to be mounted.

  When a sponge roller is incorporated in the image forming apparatus, the shaft has a diameter of usually 5.0 mm or more and 80 mm or less, and a shaft length from one end to the other end is usually 150 mm or more and 1500 mm or less.

[Elastic layer]
The elastic layer is formed of a millable silicone rubber, a crosslinking agent, an unexpanded microballoon, a chemical foaming agent, and a porous filler.

(Millable silicone rubber)
Millable silicone rubber is similar to uncured compound rubber of natural rubber or ordinary synthetic rubber before being cured, and can be plasticized and mixed with a kneading roll machine or a closed mixer. It is a silicone rubber compound.

  A preferred millable silicone rubber contains the following components (A) to (E).

(A) Organopolysiloxane having a polymerization degree of 100 or more represented by the following average composition formula (I) R ¹ _a SiO _{(4-a) / 2} (I)
(In the formula, R ¹ represents the same or different unsubstituted or substituted monovalent hydrocarbon group, and a is a positive number from 1.95 to 2.05.)
(B) Reinforcing silica having a specific surface area of 50 m ² / g or more by BET adsorption method (C) Alkoxysilane represented by the following general formula (II) R ² mSi (OR ³ ) _4-m (II)
(Wherein, R ² is independently a hydrogen atom or an unsubstituted or substituted monovalent hydrocarbon group, R ³ is an identical or different unsubstituted or substituted alkyl group, and m is 0, 1, 2, or 3)
(D) Water (E) represented by the following general formula hexaorgano represented by (III) disilazane _{^{R 4 3 SiNHSiR 4 3 (III}} )
(In the formula, R ⁴ represents the same or different monovalent hydrocarbon groups.)

  As the millable silicone rubber in the present invention, in addition to those described above, KE-571-U, KE-1571-U, KE-951-U, KE-541-U, and KE-551 manufactured by Shin-Etsu Chemical Co., Ltd. -U, KE-561-U, KE-961TU, KE-1541-U, KE-1551-U, KE-941-U, and KE-971TU can be used.

(Unexpanded micro balloon)
In the sponge roller of the present invention, an unexpanded microballoon is used for forming the elastic layer. The unexpanded microballoons in the present invention include resin microballoons that have not been expanded.

  As the resin microballoon, those using a thermoplastic resin for the outer shell are preferably used. Examples of the thermoplastic resin constituting the outer shell include vinylidene chloride / acrylonitrile copolymer, methyl methacrylate / acrylonitrile copolymer, and methacrylonitrile / acrylonitrile copolymer. It is preferable to use a resin microballoon in which the softening temperature of the resin serving as the outer shell is within an appropriate range according to the curing temperature of the liquid silicone rubber. In addition, examples of the evaporative substance included therein include hydrocarbons such as butane and isobutane.

  Unexpanded resin microballoons suitable for the present invention are commercially available as "Matsumoto Microsphere F Series" (manufactured by Matsumoto Yushi Seiyaku Co., Ltd.), "Expancel Series" (manufactured by Expancel), and the like.

  In addition, for unexpanded microballoons, it is preferable to use unexpanded microballoons that expand at the same temperature as the decomposition temperature of the chemical blowing agent, and when using azobis-isobutyronitrile as the chemical blowing agent, The expansion start temperature of the unexpanded microballoon is preferably 90 ° C. or lower, and the maximum expansion temperature is preferably about 110 ° C.

(Chemical blowing agent)
In the sponge roller of the present invention, a chemical foaming agent is used for forming the elastic layer. As the chemical foaming agent in the present invention, any foaming agent conventionally used for forming an elastic layer may be used. For example, inorganic foaming agents include sodium bicarbonate and ammonium carbonate, and organic foaming agents include diazoamino derivatives. And organic azo compounds such as azonitrile derivatives and azodicarboxylic acid derivatives. Among the organic azo compounds, azodicarboxylic amide, azobis-isobutyronitrile and the like are preferably used. In particular, azobis-isobutyronitrile can be suitably used.

(Porous filler)
In the present invention, a porous filler is used for forming the elastic layer of the sponge roller. By using the porous filler, the pores on the surface of the porous filler function as a passage for air connecting the cells and improve the substantial open cell rate of the elastic layer. The coefficient of thermal expansion is further suppressed.

  Examples of the porous filler that can be used in the present invention include, but are not particularly limited to, zeolite, porous silica, diatomaceous earth, and porous carbon particles. Among these, it is preferable to use porous silica and zeolite. As the porous filler, for example, when the integrated pore volume is measured by a mercury intrusion method or the like (an example of an apparatus used for this method is an automatic specific surface area measuring apparatus “GEMINI 2375” (manufactured by Shimadzu Corporation)). It is preferable to use an inorganic porous filler having a pore volume of 0.3 ml / g or more, and specifically, "CA-100P" (manufactured by Nippon Chemical Industry Co., Ltd.) which is a synthetic zeolite (zeostar), silica filler "Sunsphere H-33" (manufactured by ACG S-I-Tech Co., Ltd.).

The content of the porous filler is preferably not more than 0.05 part by weight to 50 parts by mass with respect millable silicone rubber 100 parts by mass or less 5.0 parts 0.5 parts by Is more preferred. By blending the porous filler with the content described above, the coefficient of thermal expansion of the elastic layer can be suppressed to a low level while maintaining good processability of the silicone rubber.

[Cell area ratio, average cell diameter]
The sponge roller of the present invention has an elastic layer formed of a millable silicone rubber, an unexpanded microballoon, a chemical foaming agent, and a porous filler. The cross section of the elastic layer that appears when the elastic layer is cut in a direction perpendicular to the center axis of the elastic layer has an area ratio between the unexpanded microballoon and the cell formed by the chemical blowing agent (unexpanded microballoon: chemical blowing agent). ) Is preferably from 95: 5 to 10:90, more preferably from 90:10 to 50:50, even more preferably from 90:10 to 55:45. When the cell area ratio is within the above range, the cell diameter of the chemical foaming agent does not become excessively large due to the effect of the unexpanded microballoons, and an elastic layer having excellent surface smoothness can be obtained.

  Furthermore, in the present invention, the average cell diameter of the cells formed by the unexpanded microballoons and the chemical foaming agent in the elastic layer is 150 μm or less, and preferably 50 μm or more and 250 μm or less. In the present invention, by using an unexpanded microballoon and a chemical foaming agent in combination, the average cell diameter of the cells formed in the elastic layer is adjusted, and a sponge roller excellent in surface smoothness can be provided.

  The elastic layer preferably has an average cell diameter of 200 μm or less, more preferably 10 μm or more and 20 μm or less, particularly preferably 30 μm or more and 150 μm or less. A composite cell with a cell having a cell diameter of preferably 300 μm or less, more preferably 30 μm or more and 80 μm or less, and particularly preferably 40 m or more and 60 μm or less.

  The cell area ratio, the outer surface of the elastic layer, or the cut surface when cut in any direction, when magnified 200 times with an optical microscope, the total area of the cells by micro-balloon, the cell by the chemical blowing agent It is the ratio to the total area. The average cell diameter is an average value of 10 randomly selected cells when enlarged by 100 to 200 times with an optical microscope on the outer surface of the elastic layer or on a cut surface when cut in any direction. . The identification of the cells by the uninflated microballoons can be determined by the presence of microballoon shells or shrunk debris inside the cells. In the present invention, the average cell diameter can be adjusted by adding a porous filler to a mixture containing a millable silicone rubber for forming an elastic layer, an unexpanded microballoon, and a chemical foaming agent. it can.

  The elastic layer having cells generated by the chemical foaming agent by containing the chemical foaming agent but not having cells by the unexpanded microballoons by not containing the unexpanded microballoons has a larger cell diameter. Surface smoothness decreases. The elastic layer in the sponge roller of the present invention suppresses the expansion of the cell derived from the chemical foaming agent due to the cell derived from the unexpanded microballoon, thereby improving the surface smoothness of the sponge roller.

  Further, it is preferable to adjust the compounding amount of the unexpanded microballoon and the compounding amount of the chemical blowing agent to the amounts described in the description of the production method according to the present invention.

[Coefficient of thermal expansion]
In the present invention, since the substantial open cell rate of the elastic layer is maintained high, when the sponge roller is heated, the air inside the cell is easily released to the outside, and the thermal expansion due to heating tends to be suppressed. It is in. In general, a sponge roller having a low open cell rate shows an increase in volume at the initial stage of heating, but this volume increase tends to be eliminated over time due to the permeability of the silicone rubber itself. Since the sponge roller of the present invention has substantially high open-cell properties, the volume of the elastic layer does not significantly increase at the initial stage of heating, and the coefficient of thermal expansion is kept low.

  More specifically, the sponge roller is put into an oven heated to 180 ° C., and the roller outer diameter is measured every 10 minutes until 60 minutes after the start of heating, and every 10 minutes from the thickness of the elastic layer before heating. When the coefficient of thermal expansion of the elastic layer was calculated, the value obtained by subtracting the coefficient of thermal expansion of the elastic layer 60 minutes after the start of heating from the coefficient of thermal expansion of the elastic layer 10 minutes after the start of heating was -1.0 or more. 2.0 or less, preferably 0 or more and 2.0 or less, more preferably 0 or more and 1.0 or less. When the coefficient of thermal expansion falls within the above range, the volume change due to the time change after heating is small, so that paper wrinkling during fixing can be suppressed.

  The coefficient of thermal expansion of the sponge roller is measured as follows. First, a roller left at a normal temperature of 23 ° C. is measured by an outer diameter measuring device, and then the roller is put into an oven heated to 180 ° C., taken out every 10 minutes, and taken out 2 seconds later by an automatic outer diameter measuring device. The roll outer diameter is measured at three locations, and immediately after the measurement, the roll is again placed in a 180 ° C. oven. The time required for measurement at three locations by the automatic outer diameter measuring machine is 20 seconds on average. This operation is repeated every 10 minutes, and the measurement is performed up to 60 minutes.

The thermal expansion coefficient of the elastic layer is calculated from the following equation based on the measurement results. The thickness of the elastic layer is a value obtained by removing the core diameter from the value measured by the automatic outer diameter measurement.

Elastic layer thickness before heating PE0
Elastic layer thickness at each time PE (T)
Time T = 10, 20, 30, 40, 50, 60
Thermal expansion coefficient (U) = (PE (T) -PE0) / PE0 × 100

A sponge roller satisfying −1.0 ≦ U ( 10 ) −U ( 60 ) ≦ 2.0 was a roll having a low coefficient of thermal expansion.

[Compression permanent set, Asker C hardness]
The compression set can be evaluated as follows.

<Evaluation method of 25% compression set>
As shown in FIG. 2, the upper and lower sides of the sponge roller 1 are sandwiched between iron plates 20 and fixed with a vice. At that time, a spacer 21 is sandwiched between the upper and lower iron plates 20 and the distance between the iron plates is adjusted to maintain a constant distance. In this state, it is left in a dryer at 180 ° C. for 5 hours. Thereafter, the iron plate sandwiching the sponge roller 1 is removed and left at room temperature for 16 hours. The diameter of the sponge roller 1 is measured, and the compression set is calculated by the following equation.

Diameter of sponge roller 1 before test D1
Diameter of sponge roller 1 after test D2
Core metal diameter L
Height H of spacer 21

Compression set (%) = (D1−D2) / (D1−H) × 100
Compression rate (%) = (D1−H) / (D1−L) × 100

  The elastic layer preferably has Asker C hardness of 20 or more and 60 or less. In the sponge roller according to the present invention, the Asker C hardness of the elastic layer surface is such that the difference between both ends in the axial direction is 1 or less. It is preferable that the difference in Asker C hardness of the elastic layer in the sponge roller is small because there is an advantage that the pressed elastic layer is uniformly deformed and the bias of the stress distribution is reduced.

[Dimensions of elastic layer, etc.]
The elastic layer is formed in a cylindrical shape on the outer peripheral surface of the shaft body, and the thickness of the elastic layer is usually 0.5 mm to 30 mm, preferably 1 mm to 15 mm.

[Others]
In this elastic layer, as long as the object of the present invention can be achieved, a low molecular weight siloxane ester, a silanol, for example, a dispersant such as diphenylsilanediol, and a heat resistance improver such as iron oxide, cerium oxide, and iron octylate. In addition, various carbon functional silanes for improving adhesiveness and moldability, halogen compounds for imparting flame retardancy, and the like may be contained within a range not to impair the object of the present invention.

<Production method of sponge roller>
The sponge roller according to the present invention can be manufactured by the manufacturing method according to the present invention.

  In the production method according to the present invention, first, 0.5 to 5.0 parts by mass of the non-expandable microballoon and 100 parts by mass of the millable silicone rubber and 100 parts by mass of the millable silicone rubber, 0.1 part by mass or more and 2.0 parts by mass or less of a chemical foaming agent with respect to parts, and 0.05 part by mass or more and 50 parts by mass or less of a porous filler with respect to 100 parts by mass of a millable silicone rubber, Mix.

  The types of unexpanded microballoons, chemical foaming agents, porous fillers and the like have already been described. Examples of the crosslinking agent include an addition reaction crosslinking agent and an organic peroxide crosslinking agent.

  Examples of the addition reaction crosslinking agent include an organohydrogenpolysiloxane known as an addition reaction type crosslinking agent having two or more SiH groups (SiH bonds) in one molecule. The addition reaction crosslinking agent can be used alone or in combination of two or more. The compounding amount of the addition reaction crosslinking agent is usually 0.1 part by mass or more and 3.0 parts by mass or less based on 100 parts by mass of the millable silicone rubber.

  When this addition reaction cross-linking agent is used, the organic peroxide cross-linking agent can independently cross-link the millable silicone rubber, but when used as an auxiliary cross-linking agent for the addition reaction cross-linking agent, a sponge roller obtained is used. Physical properties such as strength and strain 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, and 2,5-dimethyl-2,5-bis (T-butylperoxy) hexane and the like. The compounding amount of the organic peroxide crosslinking agent is usually 0.1 part by mass or more and 5.0 parts by mass or less based on 100 parts by mass of the millable silicone rubber. The organic peroxide crosslinking agent can be used alone or in combination of two or more.

  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 and a monohydric alcohol, a complex of chloroplatinic acid and an olefin, platinum bisacetoacetate, a palladium-based catalyst, and a rhodium-based catalyst. A catalyst and the like can be mentioned. The amount of the addition reaction catalyst can be a catalytic amount.

  The method of mixing is not particularly limited.For example, under normal temperature and normal pressure, an unexpanded microballoon, a chemical foaming agent, a porous filler, and a cross-linking agent are sequentially or at a time put into a millable silicone rubber, and a stirrer, A method of uniformly mixing with a kneader or the like may be used. Thus, the step of preparing the mixture is completed.

  The mixture can include various additives. As various additives, for example, auxiliaries such as chain extenders, catalysts, dispersants, foaming agents, antioxidants, antioxidants, fillers, pigments, colorants, processing aids, softeners, plasticizers, emulsifiers , A heat resistance improver, a flame retardant improver, an acid acceptor, a thermal conductivity improver, a release agent, a solvent and the like. These various additives may be commonly used additives, or may be specially used additives depending on applications.

  The mixture is uniformly mixed using a rubber kneader such as a two-roll, three-roll, roll mill, Banbury mixer, dough mixer (kneader) or the like, for example, for several minutes to several hours, preferably for five minutes. It can be obtained by kneading at room temperature or under heating for 1 hour or less.

  Next, the obtained mixture is heat-formed on the outer peripheral surface of a shaft for constituting a sponge roller by continuous heat forming by extrusion, pressing, molding by injection, or the like.

  After the mixture is formed into a cylindrical shape on the outer surface of the shaft, the cylindrical mixture, in other words, the cylindrical molded body is heated and vulcanized together with the shaft (heat curing). Conditions for performing this heat vulcanization, such as the type and amount of unexpanded microballoons and chemical blowing agents, the type and amount of cross-linking agents, the average cell diameter of the large-diameter cells and the small-diameter cells after foaming depending on the heating temperature, etc. Can be adjusted to a predetermined range.

  It is particularly preferable that the heating at the time of heating and vulcanizing the molded body is as follows. That is, as primary vulcanization, it is heated from 100 ° C to 300 ° C, especially from 150 ° C to 250 ° C for 5 minutes to 30 minutes, and then as secondary vulcanization, from 180 ° C to 250 ° C, particularly from 200 ° C to 230 ° C, from 1 hour. It is preferable to heat for 10 hours. Heating multiple times in this way controls expansion of unexpanded microballoons, decomposition of chemical blowing agent, hardening of millable silicone rubber, removal of residual low molecular siloxane, and heat shrinkage of expanded microballoons as necessary. It is possible because it is possible. By performing the heating operation a plurality of times in this manner, a small-diameter cell having an average cell diameter of 150 μm or less and a large-diameter cell having an average cell diameter of 300 μm or less are derived from unexpanded microballoons. It can be adjusted to a composite cell having cells. Note that the average cell diameter of the large-diameter cells does not become smaller than the average cell diameter of the small-diameter cells.

  The heating required for vulcanization can be performed by a heating furnace such as an infrared heating furnace or a hot blast furnace, or a heating machine such as a dryer.

  The sponge roller thus obtained may be further subjected to a polishing step. In the polishing step, the shape of the sponge roller formed on the outer peripheral surface of the shaft body is gradually increased in the axial direction of the shaft body toward the center of the shaft body. This is a step of adjusting to a shape that gradually decreases toward the tip, that is, a crown shape, or a shape that increases the thickness of the sponge roller from the center of the shaft body toward both ends of the shaft body, that is, an inverted crown shape, or a straight shape.

  Further, the outer surface of the sponge roller obtained by the vulcanization or the sponge roller adjusted to a predetermined shape by a polishing step may be covered with a tube, for example, a fluororesin tube. Coating with a fluororesin tube includes, for example, a pressure insertion method in which a sponge roller is compressed under pressure and inserted into the fluororesin tube, a decompression insertion method in which the fluororesin tube is compressed under pressure and inserted into the fluororesin tube, and a decompression method. This can be performed by a reduced-pressure expansion method or the like in which a fluororesin tube is radially expanded below and a sponge roller is inserted therein.

  The sponge roller according to the present invention can be incorporated in, for example, a fixing device of an image forming apparatus.

  Next, an example of an image forming apparatus equipped with a fixing device including a sponge roller according to the present invention (hereinafter, may be referred to as an image forming apparatus according to the present invention) will be described with reference to FIG. .

  As shown in FIG. 3, an image forming apparatus 30 according to the present invention includes a rotatable image carrier 31 on which an electrostatic latent image is formed, for example, a photoconductor, and is disposed around the image carrier 31. And a charging unit 32, for example, a charging roller, an exposure unit 33, a developing unit 40, a transfer unit 34, for example, a transfer roller and a cleaning unit 37, and a fixing unit 35 on the downstream side in the transport direction of the recording medium. The developing unit 40 is formed basically in the same manner as the conventional developing unit. Specifically, as shown in FIG. 3, a developer 42 is supplied to the developer accommodating portion 41 and the image carrier 31. The image forming apparatus includes a developer carrier 44, a developer supply unit 43 that supplies the developer 42 to the developer carrier 44, and a developer regulating member 45 that charges the developer 42.

  A conventional fixing device in an image forming apparatus generally has a fixing roller having a low hardness and a pressing roller having a high hardness to secure a nip width and a nip pressure. As described above, the heat fixing device includes the low-hardness fixing roller 53 having the Asker C hardness (load of 1.0 kg) in the range of 20 to 35 and the low-hardness pressure roller 56. That is, as shown in FIG. 3, the fixing means 35 includes a fixing roller 53 and an endless endless member disposed near the fixing roller 53 in a housing 50 having an opening 52 through which the recording medium 36 passes. The belt support roller 54, the endless belt 55 wound around the fixing roller 53 and the endless belt support roller 54, the pressing roller 56 that is in pressure contact with the fixing roller 53 via the endless belt 55, And a heating means for heating the fixing roller 53 from outside via an endless belt 55 so that the fixing roller 53 and the pressure roller 56 abut or press against each other via the endless belt 55. This is a pressure heat fixing device rotatably supported.

  The endless belt support roller 54 may be a roller normally used in an image forming apparatus, and for example, an elastic roller is used. The endless belt 55 may be an endless belt made of, for example, a resin such as polyamide or polyamide imide, and its thickness and the like can be appropriately adjusted so as to be suitable for the fixing unit 35. The pressure roller 56 is pressed against the fixing roller 53 via an endless belt 55 by an urging means (not shown) such as a spring. In the fixing means 35, the sponge roller according to the present invention is mounted as a pressure roller 56. As the heating means, a radiant heating method using a halogen heater and a reflecting plate, a direct contact heating method in which a heater or the like is brought into direct contact for heating, an induction heating method, and the like are employed. The heating unit is a member having a length substantially the same as the length of the fixing roller 53 in the axial direction, and may be disposed in any of the fixing units 35. As shown in FIG. It is preferable that the fixing rollers 53 be disposed substantially parallel to the fixing roller 53 at a more constant interval. A heating coil is used in the induction heating method, and the heating coil is usually made of a ferromagnetic material such as ferrite, and is a typical shape used for a switching power supply, such as I type, E type, and U type. It is formed in a mold or the like, and the conductor is wound. When the recording medium 36 passes through the endless belt 55 and the pressure roller 56 that are pressed against each other, the recording medium 36 is heated simultaneously with pressurization, and the developer 42 (electrostatic latent image) transferred to the recording medium 36 is fixed. be able to.

  The image forming apparatus 30 according to the present invention operates as follows. First, in the image forming apparatus 30, the image carrier 31 is uniformly charged by the charging unit 32, and an electrostatic latent image is formed on the surface of the image carrier 31 by the exposure unit 33. Next, a developer 42 is supplied from the developing unit 40 to the image carrier 31 to develop the electrostatic latent image, and the developer image is transferred onto the recording medium 36 that is conveyed between the image carrier 31 and the transfer unit 34. Is transferred to The recording body 36 is conveyed to the fixing unit 35, and the developer image is fixed on the recording body 36 as a permanent image. Thus, an image can be formed on the recording body 36.

  Since the sponge roller according to the present invention is employed as the pressure roller 56 in the fixing unit 35 and the image forming apparatus 30, the fixing unit 35 and the image forming apparatus 30 are excellent in fixing property for fixing the developer onto the recording medium and have low power consumption.

  The sponge roller and the image forming apparatus according to the present invention are not limited to the above embodiments, and various modifications can be made within a range where the object of the present invention can be achieved.

  For example, in the sponge roller 1, the elastic layer 3 has a single-layer structure, but may have a multilayer structure of two or more layers in the present invention.

  Although the image forming apparatus 30 is an electrophotographic image forming apparatus, in the present invention, the image forming apparatus is not limited to the electrophotographic method, and may be, for example, an electrostatic image forming apparatus. Good. Further, the image forming apparatus 30 is a monochrome image forming apparatus in which only the single-color developer 42 is stored in the developing unit 40. However, in the present invention, the image forming apparatus is not limited to the monochrome image forming apparatus, and may be a color image forming apparatus. An image forming apparatus may be used. Examples of the color image forming apparatus include, for example, a four-cycle type color image forming apparatus that repeats primary transfer of a developer image carried on an image carrier to an intermediate transfer body sequentially, and a plurality of image carriers provided with developing means of each color. And a tandem type color image forming apparatus in which are arranged in series on an intermediate transfer member or a transfer conveyance belt. The image forming apparatus 30 is, for example, an image forming apparatus such as a copying machine, a facsimile, and a printer.

  In the fixing unit 35 and the image forming apparatus 30, a one-component developer is advantageously used as the developer 42, but a two-component developer containing a toner and a carrier such as iron or nickel is also used. can do.

(Examples 1 to 5, Comparative Examples 1 to 4)
In Examples 1 to 5 and Comparative Examples 1 to 4, the base rubber material shown in Table 1, the addition reaction crosslinking agent and the organic peroxide crosslinking agent shown in Table 1, and the catalyst shown in Table 1 And the unexpanded microballoons shown in Table 1, the chemical foaming agents shown in Table 1, and the porous fillers shown in Table 1 in a blending amount shown in Table 1 with two rolls. The mixture was kneaded to obtain a mixture.

  The base rubber material used in Examples 1 to 5 and Comparative Examples 1 to 4 was a millable silicone rubber having a trade name of KE-551U manufactured by Shin-Etsu Chemical Co., Ltd., and is shown in Table 1. The crosslinking agent is a combination of a product name C-25B manufactured by Shin-Etsu Chemical Co., Ltd. described as “addition cross-linking” and a product name C-3 manufactured by Shin-Etsu Chemical Co., Ltd. described as “peroxide cross-linking”. The "catalyst" described in Table 1 is a platinum catalyst having a trade name of C-25A manufactured by Shin-Etsu Chemical Co., Ltd. The "chemical blowing agent" described in Table 1 is a product manufactured by Otsuka Chemical Co., Ltd. The name AZO series is AIBN, and the porous fillers listed in Table 1 are Nippon Kagaku Kogyo Co., Ltd. brand name CA-100P described as "Zeostar", or ACG described as "silica filler". S eye Tsu is a trade name Sunsphere H-33 manufactured by click Corporation. The uninflated microballoons described in Table 1 are Matsumoto Microspheres manufactured by Matsumoto Yushi-Seiyaku Co., Ltd.

  In Comparative Example 1, no porous filler was blended in the elastic layer. In Comparative Example 2, only unexpanded microballoons were used, and no chemical foaming agent was blended. In Comparative Example 3, only the chemical foaming agent was used, and the unexpanded microballoons and the porous filler were not blended. In Comparative Example 4, the porous filler and the chemical foaming agent were blended, but the unexpanded microballoons were not blended.

  Next, the shaft on which the primer layer was formed and the mixture were integrally separated by an extruder. In Examples 1 to 5 and Comparative Examples 1 to 4, an infrared heating furnace (IR furnace) was used. The mixture was subjected to primary vulcanization by heating at 225 ° C. for 17 minutes, and then subjected to secondary vulcanization at 225 ° C. for 7 hours in a hot-air drying furnace to produce a foamed roller body. The circumferential surface of the foamed roller body was subjected to high-speed polishing with a metal grindstone using a polishing machine manufactured by Mizuguchi Seisakusho Co., Ltd.

  The sponge rollers obtained in Examples 1 to 5 and Comparative Examples 1 to 4 had a straight shape with an outer diameter of 30 mm and an axial length of 340 mm.

  The average cell diameter, the coefficient of thermal expansion, and the hardness (Asker C hardness) of the elastic layer after polishing on the surface side and the shaft body side after polishing were measured. The results are shown in Table 1.

  Further, the durability of the sponge roller was evaluated by the already described 25% compression set.

* Thermal expansion coefficient Thickness of elastic layer before heating PE0
Elastic layer thickness at each time PE (T)
Time T = 10, 20, 30, 40, 50, 60
Thermal expansion coefficient (U) = (PE (T) -PE0) / PE0 × 100

−1.0 ≦ U (10) −U (60) ≦ 2.0

  As is clear from Table 1, the sponge roller of the present invention has a relatively small average cell diameter due to the combined use of the microballoon and the chemical blowing agent (Examples 1 to 3 and Comparative Example 4). . Further, in the sponge roller of the present invention, since the porous filler is used, the coefficient of thermal expansion is adjusted to be low (Example 5 and Comparative Example 1). The effect of adjusting the coefficient of thermal expansion by the combination of the microballoon, the chemical foaming agent, and the porous filler was more preferable than the case where the microballoon and the porous filler were used in combination (Examples). 1 to 3 and Comparative Example 2).

DESCRIPTION OF SYMBOLS 1 Sponge roller 2 Shaft 3 Elastic layer 4 Fluororesin layer 6 Cell 20 Iron plate 21 Spacer 30 Image forming device 31 Image carrier 32 Charging means 33 Exposure means 34 Transfer means 35 Fixing means 36 Recording medium 37 Cleaning means 40 Developing means 41 Development Developer container 42 developer 43 developer supply means 44 developer carrier 45 developer regulating member 50 housing 52 opening 53 fixing roller 54 endless belt support roller 55 endless belt 56 pressure roller

Claims (5)

A sponge roller having a shaft and an elastic layer formed on an outer peripheral surface of the shaft,
The elastic layer is formed from a millable silicone rubber, an unexpanded microballoon, a chemical foaming agent, and a porous filler,
The average cell diameter of the cells formed by the unexpanded microballoons and the chemical blowing agent is 150 μm or less,
The sponge roller was put into an oven heated to 180 ° C., and the roller outer diameter was measured every 10 minutes until 60 minutes after the start of heating, and the elastic layer was measured every 10 minutes from the thickness of the elastic layer before heating. When the coefficient of thermal expansion is calculated by the following formula, a value obtained by subtracting the coefficient of thermal expansion U (60) of the elastic layer 60 minutes after the start of heating from the coefficient of thermal expansion U (10) of the elastic layer 10 minutes after the start of heating. U (10) -U (60) is -1.0 or more and 2.0 or less.
Thermal expansion coefficient (U) = (PE (T) -PE0) / PE0 × 100
Elastic layer thickness before heating PE0
Elastic layer thickness at each time PE (T)
Time T = 10, 20, 30, 40, 50, 60   2. The cross-section of the elastic layer, wherein the cell area ratio between the unexpanded microballoon and the chemical foaming agent (unexpanded microballoon: chemical foaming agent) is from 95: 5 to 10:90. 3. Sponge roller. Porous filler content in the elastic layer is not more than 50 parts by mass or more 0.05 part by mass relative to the millable silicone rubber 100 parts by weight, the sponge roller according to claim 1 or 2.   Millable silicone rubber, unexpanded microballoons, chemical blowing agent, and porous filler are mixed to prepare a mixture, and the mixture is extruded on the outer surface of the shaft, and then heat-cured. A method for manufacturing a sponge roller, comprising manufacturing the sponge roller according to any one of claims 1 to 3.   An image forming apparatus comprising the sponge roller according to claim 1.