JP6624517B2 - Sponge roller, method of manufacturing the same, 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 high durability, excellent surface smoothness, and low compression set, a method of manufacturing the sponge roller, and a method of manufacturing the sponge roller. The present invention relates to an image forming apparatus including a sponge roller.

  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 by, for example, 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 the conductive compressible layer 23” 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, A foaming method in which a rubber is foamed during vulcanization to form a compressible layer having cells, a hollow microsphere mixing method in which hollow microspheres are blended in place of a foaming agent to form independent cells, or water. A powder that can be eluted into an eluate such as methanol, for example, sodium chloride, sugar, etc., is compounded in a synthetic rubber compound, and the vulcanized vulcanized powder is eluted with a compressible layer having cells. 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 cored bar", The elastic layer heats 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. It is characterized by the fact that the voids are formed by breaking. "

  Patent Document 3 discloses a “water-in-oil type emulsion composition capable of forming a porous silicone elastomer having uniform fine cells (bubbles) without a foaming phenomenon” using a “copier, laser printer, etc. "Substantially closed-cell porous silicone elastomer" which can be used for an image forming part or the like.

  In addition to various rollers for an image forming apparatus, for example, Patent Document 4 relating to a “sponge rubber print” as a stamping material discloses “rubber, water-soluble fine powder, vulcanizing agent, filler, and fiber length of 0.2 to 2 mm. A sponge rubber printed body having open cells obtained by kneading a staple of organic synthetic fibers thus kneaded to form a master batch, vulcanizing the staple, and then washing away a water-soluble fine powder ”(claim 1). .

  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 an inflated resin microballoon with a low molecular weight silicone rubber is higher than the softening point of the resin microballoon. A silicone rubber sponge obtained by curing silicone rubber by heating at a low temperature is disclosed (see claim 1).

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

  An object of the present invention is to provide a sponge roller having high durability and excellent surface smoothness, a method of manufacturing the sponge roller, and an image forming apparatus provided with the sponge roller.

Means for solving the above-mentioned problem are:
(1) A sponge roller having a shaft and an elastic layer formed on an outer peripheral surface of the shaft,
The elastic layer, the difference between the maximum expansion rate and the expansion rate in the last round of expansion rate measurement among expansion rates measured every predetermined time after heating the elastic layer to 180 ° C. is 0 to 1.5. A sponge roller characterized by being within a range,
(2) The elastic layer is formed of a millable silicone rubber, an unexpanded microballoon, and a chemical foaming agent, and in the cross section of the elastic layer, a large-diameter cell derived from the chemical foaming agent and at least two adjacent large-diameter cells. A sponge roller comprising a small-diameter cell derived from an unexpanded micro-balloon that makes
(3) A mixture is prepared by mixing a millable silicone rubber, a crosslinking agent, a chemical foaming agent, and an unexpanded microballoon that expands at a temperature higher than the decomposition temperature of the chemical foaming agent. A method for producing a sponge roller, characterized in that the chemical blowing agent is decomposed but heated to a temperature at which the unexpanded microballoons do not expand, and then heated to a temperature at which the unexpanded microballoons expands,
(4) An image forming apparatus comprising the sponge roller according to any one of (1) and (2).

According to the present invention, the difference between the maximum expansion coefficient (RE1) of the expansion coefficients measured every predetermined time after the elastic layer is heated to 180 ° C. and the expansion coefficient (RE2) in the final round of the expansion coefficient measurement (RE2). RE1-RE2) is in the range of 0 to 1.5, so that the surface of the elastic layer becomes smooth, and the image formed by the sponge roller has no distortion even at a high temperature in the image forming apparatus. And a high quality image is formed. A high-quality image can be formed by the sponge roller according to the present invention because a large-diameter cell derived from a chemical foaming agent and an adjacent large-diameter cell are connected by a small-diameter cell derived from an unexpanded microballoon. According to the state, it is considered.
According to the present invention, by having an elastic layer including a large-diameter cell derived from a chemical foaming agent and a small-diameter cell derived from an unexpanded microballoon that brings at least two adjacent large-diameter cells into communication, high-temperature However, since the air existing in the elastic layer is discharged outside the elastic layer, the expansion of the elastic layer is suppressed, and as a result, the image formed by the sponge roller at a high temperature may be distorted. And a high quality image can be formed.
Thus, according to the present invention, a sponge roller having a smooth surface can be provided, and an image forming apparatus capable of realizing a high quality image can be provided. Further, it is possible to provide a method for producing a sponge roll with a smooth surface capable of providing a high-quality image.

FIG. 1 is an explanatory view showing a sponge roller showing one embodiment of the present invention. FIG. 2 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. FIG. 3 is a schematic view showing a durability test apparatus suitably used for performing a durability test of an elastic roller in the embodiment.

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

  The shaft body is usually a long cylindrical body called a core metal formed 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 to 40 mm, and a shaft length from one end to the other end is usually 150 to 1000 mm.

  The elastic layer is formed of a millable silicone rubber, unexpanded microballoons, and a chemical foaming agent.

  The millable silicone rubber is similar to a natural rubber or an unvulcanized compound rubber of a general synthetic rubber before being cured, and can be plasticized and mixed by a kneading roll machine or a closed mixer. It is a silicone rubber compound that can be used.

A suitable millable silicone rubber is
(A) 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.)
An organopolysiloxane having a degree of polymerization of 100 or more,
(B) a reinforcing silica having a specific surface area of 50 m ² / g or more by a BET adsorption method,
(C) 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 the same or different unsubstituted or substituted alkyl group, and m is 0, 1, 2, or 3)
An alkoxysilane represented by
(D) water,
(E) The following general formula (III)
_{^{R 4 3 SiNHSiR 4 3 (III}} )
(In the formula, R ⁴ represents the same or different monovalent hydrocarbon groups.)
And a hexaorganodisilazane represented by the formula:

R ¹ in the formula (I) representing the organopolysiloxane preferably has 1 to 12 carbon atoms, particularly preferably 1 to 8 carbon atoms. Specifically, methyl, ethyl, propyl, butyl, hexyl Alkyl group such as octyl group, cyclopentyl group, cycloalkyl group such as cyclohexyl group, vinyl group, allyl group, alkenyl group such as propenyl group, cycloalkenyl group, phenyl group, aryl group such as tolyl group, benzyl group, An aralkyl group such as a 2-phenylethyl group, or a hydrogen atom of these groups, in which a part or all of the hydrogen atoms are substituted with a halogen atom such as fluorine or chlorine or a cyano group, for example, a chloromethyl group, a trifluoropropyl group, a cyanoethyl group And the like, and a methyl group, a vinyl group, a phenyl group, and a trifluoropropyl group are preferable. Vinyl group is preferred.

In particular, the organopolysiloxane as the component (A) has two or more, usually about 2 to 50, and especially about 2 to 20 aliphatic unsaturated groups such as alkenyl groups and cycloalkenyl groups in one molecule. Those having a vinyl group are particularly preferable. In this case, it is preferable that 0.01 to 20 mol%, particularly 0.02 to 10 mol%, of all R ¹ is an aliphatic unsaturated group. The aliphatic unsaturated group may be bonded to a silicon atom at a molecular chain terminal, may be bonded to a silicon atom in the middle of the molecular chain (non-molecular chain terminal), or may be both. Is preferably bonded to at least the silicon atom at the terminal of the molecular chain.

In particular, the organopolysiloxane as the component (A) has two or more, usually about 2 to 50, and especially about 2 to 20 aliphatic unsaturated groups such as alkenyl groups and cycloalkenyl groups in one molecule. Those having a vinyl group are particularly preferable. In this case, it is preferable that 0.01 to 20 mol%, particularly 0.02 to 10 mol%, of all R ¹ is an aliphatic unsaturated group. The aliphatic unsaturated group may be bonded to a silicon atom at a molecular chain terminal, may be bonded to a silicon atom in the middle of the molecular chain (non-molecular chain terminal), or may be both. Is preferably bonded to at least the silicon atom at the terminal of the molecular chain.

A is a positive number of 1.95 to 2.05, preferably 1.98 to 2.02, and more preferably 1.99 to 2.01. Further, it is desirable that 90 mol% or more, preferably 95 mol% or more, of all R ¹ , and more preferably all R ¹ except an aliphatic unsaturated group is an alkyl group, especially a methyl group.

The molecular structure of the organopolysiloxane as the component (A) is preferably a straight chain or a straight chain having a partially branched structure. Specifically, diorganosiloxane units constituting the main chain of the organopolysiloxane ^{_{(R 1 2 SiO 2/2, R}} 1 is as defined above, hereinafter the same) is repeated structures, repeating only dimethylsiloxane units Or a diphenylsiloxane having a phenyl group, a vinyl group, a 3,3,3-trifluoropropyl group, etc. as a substituent as a part of a dimethylpolysiloxane structure composed of repeating dimethylsiloxane units constituting the main chain It is preferable that a diorganosiloxane unit such as a unit, a methylphenylsiloxane unit, a methylvinylsiloxane unit, or a methyl-3,3,3-trifluoropropylsiloxane unit is introduced.
Further, the both ends of the molecular chain, for example, trimethylsiloxy groups, dimethylphenylsiloxy groups, vinyldimethylsiloxy group, divinyl trimethylsiloxy groups, triorganosiloxy groups such as tri-siloxy group (R ¹ ₃ SiO _1/2) or hydroxy it is preferable that the blocked with dimethyl siloxy-hydroxy diorganosiloxy group such as _{^{(R 1 2 (HO) SiO}} 1/2).

The organopolysiloxane of the component (A), as described above, both ends of the molecular chain triorganosiloxy groups (R ¹ ₃ SiO _1/2) or hydroxy diorgano siloxy group _{^{(R 1 2 (HO) SiO}} 1/2 ) blocked with the main chain can be exemplified preferably a straight-chain, which comprises repeating diorganosiloxane units (R ¹ ₂ SiO _2/2). Particularly preferred are methylvinylpolysiloxane, methylphenylvinylpolysiloxane, methyltrifluoropropylvinyl as the type of substituent in the molecule (ie, an unsubstituted or substituted monovalent hydrocarbon group bonded to a silicon atom). Polysiloxane and the like can be mentioned.
Such an organopolysiloxane can be obtained, for example, by subjecting one or more of organohalogenosilanes to (co) hydrolytic condensation, or by converting a cyclic polysiloxane (siloxane trimer, tetramer, etc.) to alkaline or It can be obtained by ring-opening polymerization using an acidic catalyst.

  The degree of polymerization of the organopolysiloxane is 100 or more (usually 100 to 100,000), preferably 1,000 to 100,000, more preferably 2,000 to 50,000, and particularly preferably 3,000 to 50,000. It is preferably 20,000 and has no self-flowing property at room temperature (25 ° C.). If the degree of polymerization is too small, when the compound is used, problems such as roll adhesion may occur, and the roll workability will deteriorate. The degree of polymerization can be measured as a weight-average degree of polymerization in terms of polystyrene by gel permeation chromatography (GPC) analysis.

As the component (A), one type may be used alone, or a mixture of two or more types having different molecular weights (degrees of polymerization) and molecular structures may be used.
The reinforcing silica as the component (B) is a filler added to obtain a silicone rubber composition having excellent mechanical strength, and for this purpose, the specific surface area (BET adsorption method) is 50 m ² / g. It is necessary to be at least 100 to 450 m ² / g, more preferably 100 to 300 m ² / g. If the specific surface area is less than 50 m ² / g, the mechanical strength of the cured product will be low.

  Examples of such reinforcing silica include fumed silica (fumed silica), precipitated silica (wet silica), and the like, and those obtained by hydrophobizing their surfaces with chlorosilane, hexamethyldisilazane, or the like are also suitable. Used for Of these, fumed silica having excellent dynamic fatigue characteristics is preferred. As the component (B), one type or two or more types may be used in combination.

The compounding amount of the reinforcing silica of the component (B) is 5 to 100 parts by mass, preferably 10 to 50 parts by mass, per 100 parts by mass of the organopolysiloxane of the component (A). If the blending amount of the component (B) is too small, no reinforcing effect can be obtained, and if it is too large, workability deteriorates, mechanical strength decreases, and dynamic fatigue durability also deteriorates. I will.
Examples of the alkoxysilane of the component (B) represented by the formula (II) include organoalkoxysilanes such as organotrialkoxysilane, diorganodialkoxysilane, and triorganoalkoxysilane, and m = 1 and R ² is hydrogen. Examples of the atom are trialkoxysilane and m = 0 tetraalkoxysilane.

Here, R ² is a hydrogen atom or the same or different unsubstituted or substituted monovalent hydrocarbon group. Examples of the unsubstituted or substituted monovalent hydrocarbon group include those represented by the formula (I) of the component (A). The same as R ^{1 in the} above are exemplified, but usually those having 1 to 8 carbon atoms, particularly those having 1 to 4 carbon atoms, are preferred. Specifically, methyl, ethyl, propyl, butyl, hexyl Groups, alkyl groups such as octyl group, cycloalkyl groups such as cyclopentyl group and cyclohexyl group, alkenyl groups such as vinyl group, allyl group and propenyl group, cycloalkenyl groups such as cyclohexenyl group, and aryl groups such as phenyl group and tolyl group An aralkyl group such as a benzyl group or a 2-phenylethyl group, or a halogen atom such as fluorine, chlorine or bromine or a cyano group And the like, chloromethyl group, 3,3,3-trifluoropropyl group, 2-cyanoethyl group, and the like, and a methyl group, a vinyl group, a phenyl group, and a trifluoropropyl group are preferable, and a methyl group and a vinyl group are particularly preferable. And a phenyl group is preferred. Further, it is preferably the same as the unsubstituted or substituted monovalent hydrocarbon group R ^{1 of the} component (A) from the viewpoint of compatibility with the organopolysiloxane of the component (A).

Examples of the unsubstituted or substituted alkyl group for R ³ include, for example, an alkyl group having usually about 1 to 4 carbon atoms, such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, and a tert-butyl group. Examples thereof include an alkoxy-substituted alkyl group such as a methoxymethyl group, a methoxyethyl group, an ethoxymethyl group, and an ethoxyethyl group, and a methyl group and an ethyl group are preferred from the viewpoint of hydrolyzability and the like. M in the formula is 0, 1, 2, or 3, and preferably 1 or 2.

  Examples of such an alkoxysilane include dimethoxydimethylsilane, diethoxydimethylsilane, dimethoxydiethylsilane, diethoxydiethylsilane, dimethoxymethylvinylsilane, dimethoxydiphenylsilane, dimethoxymethylphenylsilane, trimethoxymethylsilane, and triethoxymethylsilane. And trimethoxyvinylsilane, trimethoxyphenylsilane, trimethoxysilane, triethoxysilane, tetramethoxysilane, tetraethoxysilane, and the like. Among them, diorganodialkoxysilanes such as dialkyldialkoxysilanes having m = 2 can be used. Preferred, especially preferred is dimethoxydimethylsilane.

  These alkoxysilanes are relatively inexpensive, and using them as starting materials is extremely economically advantageous. The above-mentioned alkoxysilanes can be used alone or in combination of two or more. However, when using a mixture of a plurality of alkoxysilanes, care must be taken because they may not react uniformly because the hydrolysis rates of the two are different.

  Component (C) is used in an amount of 0.1 to 20 parts by mass, preferably 1 to 15 parts by mass, per 100 parts by mass of component (A). If the amount of the alkoxysilane is too small, the plasticity of the compound becomes too high, and the plastic reversion (creep hardening) becomes large. If the amount is too large, the plasticity of the compound becomes too low. And the roll workability deteriorates.

The pH of the water as the component (D) is not particularly limited. However, if the pH is too high or too low, the equipment used at the time of compounding is corroded, so that the pH is 1.0 to 12.0. Is more preferable, more preferably 2.0 to 10.0, and still more preferably 2.0 to 7.0.
Here, the water as the component (D) may be an aqueous acidic solution prepared using an inorganic acid such as hydrochloric acid, sulfuric acid, or nitric acid, or an organic acid such as formic acid or acetic acid, or sodium hydroxide, so as to have a pH within the above range. It can also be used as a basic aqueous solution prepared using potassium hydroxide, aqueous ammonia or the like.

The amount of water used is preferably 0.3 to 10 times, more preferably 0.5 to 2.0 times, especially 1.0 to 1.5 times the mol of the alkoxy group of the alkoxysilane. If the amount is less than the above range, there arises a problem that the alkoxy group is not completely hydrolyzed and a small amount of hydroxyl group is generated. Even with large additions, excess water must be removed.
In the formula (III) representing the hexaorganodisilazane as the component (E), R ⁴ may be the same as R ^{1 in the} component (A). Alkyl groups having a number of about 1 to 6 are preferable, and an alkenyl group such as a vinyl group may be contained in the molecule.

  (E) As components, hexamethyldisilazane, 1-vinylpentamethyldisilazane, 1,3-divinyl-1,1,3,3-tetramethyldisilazane, 1,3-dimethyl-1,1,3 , 3-tetravinyldisilazane and the like are exemplified, and hexamethyldisilazane and 1,3-divinyl-1,1,3,3-tetramethyldisilazane are preferred, and hexamethyldisilazane is more preferred.

  As the component (E), ammonia water can be used in addition to the above-mentioned hexaorganodisilazane. The concentration of the ammonia water is not particularly limited, but usually about 1 to 30% by mass, preferably about 10 to 28% by mass, and more preferably about 15 to 28% by mass can be used.

  The amount of the component (E) is 0.01 to 1 part by mass, preferably 0.02 to 1 part by mass in the case of hexaorganodisilazane with respect to 100 parts by mass of the organopolysiloxane of the component (A). More preferably 0.05 to 0.5 part by mass, and in the case of ammonia water, 0.01 to 1 part by mass, preferably 0.05 to 1 part by mass, more preferably 0.1 to 1 part by mass. It is. When the amount of the component (E) is too small, the effect of shortening the compounding time is small, and the effects of improving compression set and dynamic fatigue durability are not obtained. Is too high in hardness and is not economically preferable.

  The component (E) needs to be added after the hydrolysis of the component (C) with the alkoxysilane and the component (D) with water is sufficiently performed. Specifically, the production of the composition When each component is uniformly mixed and kneaded in the process, the component (B) is added to the components (A), (C), and (D) in an amount of 25% by mass or more (25 to 100% by mass) of the required addition amount, preferably It is necessary to add (E) component after adding 50 to 100% by mass and uniformly mixing.

  If the component (E) is added when the hydrolysis of the component (C) with the alkoxysilane and the component (D) is insufficiently hydrolyzed, the plastic reversion resistance before curing and the compression set resistance after curing are reduced. The composition becomes inferior to

  The millable silicone rubber of the present invention is obtained by uniformly kneading a predetermined amount of the above-mentioned components (A) to (E) in a predetermined blending order (blending time) using a two-roll (roll mill), kneader, Banbury mixer, or the like. Can be obtained by mixing.

  That is, the components (A), (C) and (D) are mixed with 25 to 100% by mass, preferably 50 to 100% by mass, of the required addition amount of the component (B). During this mixing, the alkoxysilane as the component (C) and the water as the component (D) undergo a hydrolysis reaction, and the hydrolysis reaction product acts as a wetter for the silica as the component (B), thereby shortening the mixing time. Is done. In this case, the mixing and kneading are preferably performed at 0 to 100 ° C, more preferably at 10 to 90 ° C, and still more preferably at 30 to 80, in order to sufficiently achieve the hydrolysis reaction of the component (C) with the component (D). It is desirable that the temperature is preferably set to 1 to 120 minutes, more preferably 10 to 60 minutes at ℃.

  Next, after the hydrolysis reaction of the component (C) and the component (D) has sufficiently proceeded, the component (E), hexaorganodidisilazane or aqueous ammonia, is added. This further reduces the mixing time. When the total amount of the component (B) silica is not used in the previous mixing and kneading steps, the remainder of the component (B) silica is added during the mixing and kneading steps. The temperature when adding the remaining amounts of the components (E) and (B) and mixing and kneading is preferably 0 to 100 ° C, particularly preferably 10 to 90 ° C, particularly preferably 40 to 80 ° C. It is preferably from 1 to 120 minutes, especially from 3 to 60 minutes.

  The total mixing time of the components (A) to (E) is preferably 5 minutes to 5 hours, more preferably 10 minutes to 3 hours.

  The millable silicone rubber according to the present invention includes, 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.

  The unexpanded microballoon according to the present invention may be a resin microballoon that has 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 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.
The 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 blowing agent used to form 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, and examples thereof include sodium bicarbonate and ammonium carbonate as inorganic foaming agents, and diazoamino derivatives as organic foaming agents. 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.
The chemical blowing agent suitable for the present invention has a function of decomposing at a temperature lower than the temperature at which the unexpanded microballoon expands to generate gas.

The sponge roller of the present invention has an elastic layer formed of the above-mentioned millable silicone rubber, unexpanded microballoons, and a chemical foaming agent. In 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, a communicating cell in which large-diameter cells derived from unexpanded microballoons communicate with small-diameter cells derived from a chemical foaming agent. Is observed. The total area of the communication cells in a state where the large-diameter cells communicate with each other by the small-diameter cells is much larger than the total area of the independent small-diameter cells and the independent large-diameter cells. The ratio of the total area of the communication cells to the total of the total area of the communication cells and the total area of the independent cells is usually 0.05 to 10%.
The average cell diameter of the independent cells formed by the unexpanded microballoons is 150 μm or less, preferably 150 μm or less, 20 μm or more, and particularly preferably 120 μm or less and 30 μm or more. The average cell diameter of the independent cells formed by the chemical foaming agent is 300 μm or less, preferably 300 μm or less, 50 μm or more, particularly preferably 250 μm or less and 60 μm or more.
In the present invention, the average cell diameter of the independent cells formed by the chemical foaming agent is larger than the average cell diameter of the independent cells formed by the unexpanded microballoons.

  The cell area ratio between the communicating cells and the independent cells is, on the outer surface of the elastic layer, or on the cut surface when cut in any direction, when magnified 200 times with an optical microscope, the total area of cells by microballoons and , The ratio to the total area of the cells by the chemical blowing agent. 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 cells by the uninflated microballoons can be determined by the presence of microballoon shells or shrunken debris inside the cells. The average cell diameter can be adjusted by appropriately setting the vulcanization conditions of the mixture containing the millable silicone rubber for forming the elastic layer and the unexpanded microballoon and the chemical foaming agent.

  The elastic layer preferably has Asker C hardness of 20 to 60. Further, 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. The small difference in Asker C hardness of the elastic layer in the sponge roller is advantageous in that the pressed elastic layer is uniformly deformed, and the bias of the stress distribution is reduced.

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

  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.

  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, the millable silicone rubber, 0.2 to 3.0 parts by mass of the uninflated microballoon with respect to 100 parts by mass of the millable silicone rubber, and 100 parts by mass of the millable silicone rubber And 0.05 to 3.0 parts by mass of a chemical foaming agent and a crosslinking agent.

  The type of the unexpanded microballoon and the chemical foaming agent have been described above. Examples of the crosslinking agent include an addition reaction crosslinking agent and an organic peroxide crosslinking agent.

  As the addition reaction crosslinking agent, for example, an organohydrogenpolysiloxane known as an addition reaction type crosslinking agent having two or more SiH groups (SiH bonds) in one molecule is preferably exemplified. 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 to 3.0 parts by mass 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 alone can crosslink the millable silicone rubber, but when used as an auxiliary cross-linking agent for the addition reaction cross-linking agent, the resulting sponge is used. Physical properties such as strength and distortion of the 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, 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 to 5.0 parts by mass 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. The addition reaction catalyst is platinum black, platinum chloride, chloroplatinic acid, a reaction product of chloroplatinic acid and a monohydric alcohol, a complex of chloroplatinic acid and olefins, platinum bisacetoacetate, a palladium-based catalyst, and a rhodium-based catalyst. And the like. 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, unexpanded microballoons, a chemical foaming agent, and a cross-linking agent are added to a millable silicone rubber sequentially or all at once, and are uniformly mixed with a stirrer, kneader, or the like. And the like. 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 and crosslinking agents, catalysts, dispersants, foaming agents, antioxidants, antioxidants, fillers, pigments, colorants, processing aids, softeners, plasticizers Agents, an emulsifier, 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.
In the present invention, it is important to appropriately control the heating temperature when performing heat molding.

  After the mixture is formed in a cylindrical shape on the outer peripheral surface of the shaft, the cylindrical mixture, in other words, the cylindrical molded body, is heated and vulcanized together with the shaft. 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.

  In the present invention, it is important to appropriately control the heating temperature when performing heat molding. That is, after the heating is started, the columnar mixture is allowed to reach a temperature lower than the temperature at which the unexpanded microballoon expands and higher than the decomposition temperature of the chemical blowing agent (primary heating temperature: T1). In the mixture maintained at the primary heating temperature (T1), large-diameter cells are formed by gas generated by decomposition of the chemical blowing agent. The temperature (T1) is usually 100 to 300 ° C., particularly 150 to 250 ° C., and the time for maintaining the mixture at the primary heating temperature (T1) is usually 5 to 30 minutes. Next, the mixture maintained at the primary heating temperature is heated to a temperature (secondary heating temperature: T2) sufficient to expand the unexpanded microballoons. The secondary heating temperature (T2) is usually from 180 to 250C, particularly from 200 to 230C. The heating time for maintaining the mixture at the secondary heating temperature (T2) is usually 1 to 10 hours. Under the heating condition in the primary heating, a large-diameter cell is formed by chemical foaming, but the outer shell of the unexpanded microballoon is not easily broken. Therefore, the large-diameter cell is independent and not in communication only by the primary heating. Then, under the heating condition in the secondary heating, the outer shell of the unexpanded microballoon is broken, so that the large-diameter cells communicate with each other. In addition, such heating controls expansion of unexpanded microballoons, decomposition of chemical foaming agent, hardening of millable silicone rubber, removal of residual low molecular siloxane, and heat shrinkage of expanded microballoons as necessary. It becomes possible.

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. However, a heating furnace is preferable as the heating means used for the primary heating, and a hot air drying furnace is preferable as the heating means used for the secondary heating.
After the primary heating, the mixture becomes an expanded material including a small-diameter cell and a large-diameter cell around the shaft body, and the large-diameter cells communicate with each other by the secondary heating performed thereafter. However, not all of the large-diameter cells may be in a communicating state, but may be partially in an inflated state.In the present invention, the sponge roller precursor containing the inflated part in this part is used. Further, it is subjected to post-processing.
The post-processing is a continuous process in which the large-diameter cells and the small-diameter cells communicate with each other by breaking the cell wall separating the large-diameter cells and the small-diameter cells existing in a part of the expanded material contained in the sponge roller precursor. Various techniques can be adopted as long as the cells are formed.
As such a post-treatment, for example, the shell of the outer shell is broken by placing it in a hot air dryer heated to a temperature higher than the temperature at which the shell of the outer shell is broken. Alternatively, destruction of the outer shell due to the resonance wavelength of a magnetic field or an electromagnetic wave can be mentioned.

What is important in the present invention is that the difference between the maximum expansion rate and the expansion rate in the final round of expansion rate measurement among the expansion rates measured every predetermined time after heating the elastic layer to 180 ° C. is zero. １．５1.5. When the difference in expansion is in the above range, a sponge roller having excellent durability and excellent surface smoothness is formed.
The expansion coefficient of the elastic layer is usually an expansion coefficient measured at a predetermined time after heating to 180 ° C. and stopping the heating. The measurement interval for measuring the expansion rate is usually equal to 10 minutes, preferably equal to 5 minutes. When the difference in expansion coefficient is within the above range, the object of the present invention can be achieved.
The final measurement of the expansion coefficient is a time when 50 minutes have elapsed since the sponge roller was heated and the sponge roller was stopped after the temperature of the sponge roller reached 180 ° C.
The expansion rate is calculated by the following formula.
[(PE2-PE1) / PE1] × 100
Here, PE1 is the outer diameter of the elastic layer that does not include the core before heating, and PE2 is the outer diameter of the elastic layer that does not include the core during any measurement.
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 to both ends of the shaft, that is, an inverted crown shape or a straight shape.

  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 (hereinafter, sometimes referred to as an image forming apparatus according to the present invention) having a fixing device provided with a sponge roller according to the present invention will be described with reference to FIG. .

  As shown in FIG. 3, the 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. The image forming apparatus includes a charging unit 32 such as a charging roller, an exposure unit 33, a developing unit 40, a transfer unit 34 such as a transfer roller and a cleaning unit 37, and a fixing device 35 on the downstream side in the conveyance 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 pressing roller 56. That is, as shown in FIG. 3, the fixing device 35 includes a fixing roller 53 and an endless end 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 57 for externally heating the fixing roller 53 via an endless belt 55 so that the fixing roller 53 and the pressing roller 56 abut or press against each other via the endless belt 55. This is a pressure heat fixing device rotatably supported by the device.

  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 polyamideimide, and its thickness and the like can be appropriately adjusted so as to be suitable for the fixing device 35. The pressure roller 56 is pressed against the fixing roller 53 via an endless belt 55 by a biasing means (not shown) such as a spring. In the fixing device 35, the sponge roller according to the present invention is mounted as a pressure roller 56. As the heating means 57, a radiant heating method using a halogen heater, a reflection plate, or the like, a direct contact heating method in which a heater or the like is brought into direct contact for heating, an induction heating method, or the like is adopted. The heating unit 57 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 devices 35. However, as shown in FIG. It is preferable that the fixing roller 53 be disposed substantially in parallel with the fixing roller 53 at a fixed distance from the surface. 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 is formed by winding a conductive wire. 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 device 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 device 35 and the image forming device 30, the fixing device 35 and the image forming device 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-described embodiment, and various modifications are possible within a range where the object of the present invention can be achieved.

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

  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 device 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, 2 Comparative Examples 1 to 3)
In Examples 1-2 and Comparative Examples 1-3, the base rubber material shown in Table 1, the crosslinking agent shown in Table 1, the catalyst shown in Table 1, and the unexpanded material shown in Table 1 The microballoons and the chemical blowing agents shown in Table 1 were sufficiently kneaded with two rolls in the amounts shown in Table 1 to obtain a mixture.

  The base rubber material used in Examples 1 and 2 and Comparative Examples 1 to 3 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 cross-linking agent is a combination of Shin-Etsu Chemical Co., Ltd. trade name C-25B described as "addition cross-linking" and C-3 manufactured by Shin-Etsu Chemical Co., Ltd. described as "peroxide cross-linking". "Catalyst" described in No. 1 is a platinum catalyst having a trade name of C-25A manufactured by Shin-Etsu Chemical Co., Ltd. "Chemical blowing agent" described in Table 1 is a trade name of AZO series manufactured by Otsuka Chemical Co., Ltd. AIBN. The uninflated microballoons described in Table 1 are Matsumoto Microspheres manufactured by Matsumoto Yushi-Seiyaku Co., Ltd.

In Comparative Example 1, no unexpanded microballoons were blended, and only a chemical foaming agent was used.
Next, a shaft body having a 19.5 mm outer shape and a primer layer formed thereon and the mixture were integrally separated by an extruder. In Examples 1 to 7 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 and 2 and Comparative Examples 1 to 3 had a straight shape with an outer diameter of 27.5 mm and an axial length of 340 mm, and had a rubber thickness of 4 mm.

  The average cell diameter of the manufactured sponge roller and the hardness (Asker C hardness) on the surface side and the shaft side of the elastic layer after polishing were measured. The results are shown in Table 1.

The expansion coefficient of the sponge roller during heating was measured and evaluated.
(Heat expansion coefficient)
The sponge roll prepared in a hot-air drying furnace heated to 180 ° C. was charged, the outer diameter was measured every 10 minutes, and the results are shown in Table 2.
The expansion coefficient during heating was calculated from the following equation.

Outer diameter PE1 of elastic layer not containing core metal before heating
Outer diameter of elastic layer not containing core metal for arbitrary time PE2
[(PE2-PE1) / PE1] × 100

REFERENCE SIGNS LIST 1 developer transport roller 2 shaft 3 foam elastic layer 4 silicone coat layer 6 cell 30 image forming device 31 image carrier 32 charging means 33 exposure means 34 transfer means 35 fixing means 36 transferred object 37 cleaning means 40 developing means 41 development Agent storage section 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 20 Iron plate 21 Spacer 70 Durability tester 71 Heating roller 72 Internal heater 73 Heat insulating material 74 Test roller mounting part 75 Pressing force adjusting means

Claims (3)

A sponge roller having a shaft and an elastic layer formed on an outer peripheral surface of the shaft,
The elastic layer is formed of a millable silicone rubber, an unexpanded microballoon, a cross-linking agent, and a chemical foaming agent, and appears when the elastic layer is cut in a direction perpendicular to a center axis of the elastic layer. In the cross section of the elastic layer, comprising a large-diameter cell derived from the chemical foaming agent, and a small-diameter cell derived from the unexpanded micro-balloon that makes at least two adjacent large-diameter cells communicate with each other,
After the elastic layer is heated to 180 ° C., the difference between the maximum expansion rate and the expansion rate in the final round of expansion rate measurement within the range of 0 to 1.5 out of the expansion rates measured every predetermined time after the elastic layer is heated to 180 ° C. Wherein the expansion coefficient is represented by the following equation:
[(PE2-PE1) / PE1] × 100
Here, PE1 is the outer diameter of the elastic layer that does not include the core before heating, and PE2 is the outer diameter of the elastic layer that does not include the core during any measurement. A method for manufacturing a sponge roller having a shaft and an elastic layer formed on an outer peripheral surface of the shaft,
A millable silicone rubber, a crosslinking agent, a chemical foaming agent, and an unexpanded microballoon that expands at a temperature higher than the decomposition temperature of the chemical foaming agent are mixed to prepare a mixture, and the mixture is mixed with a chemical foaming agent. Decomposes but heats to a temperature at which the unexpanded microballoons do not expand, and then heats to a temperature at which the unexpanded microballoons expands to form the elastic layer, wherein the elastic layer is orthogonal to the central axis of the elastic layer. In the cross section of the elastic layer that appears when the elastic layer is cut in the direction, the large-diameter cell derived from the chemical foaming agent and the unexpanded microballoon derived from at least two adjacent large-diameter cells communicate with each other. A method for manufacturing a sponge roller, comprising: a small-diameter cell . An image forming apparatus comprising the sponge roller according to claim 1 .

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