Method for manufacturing regenerated conductive roller

Abstract

Provided is a method for manufacturing a regenerated conductive roller, the method contributing to good image formation by effectively removing contaminants attached to the surface of a conductive roller, which is used over a long period of time and to which contaminants remarkably adhere, without impairing conductivity. This method for manufacturing a regenerated conductive roller comprises a contaminant removal step for removing contaminants adhering to the outer surface of a conductive roller. The conductive roller has a support having a conductive outer surface, and a conductive layer on the outer surface of the support. The conductive layer has a matrix containing a first rubber, and a domain containing a second rubber and an electronic conductive agent. When the Young's modulus of the matrix is denoted by G1 (MPa) and the Young's modulus of the domain is denoted by G2 (MPa), G1 and G2 satisfy G1 < G2. The contaminant removal step includes a step for spraying a liquid on the surface of the conductive roller to which the contaminants adhere.

Description

Manufacturing method for recycled conductive rollers

[0001] The present disclosure relates to a method for manufacturing a recycled conductive roller.

[0002] Electrophotographic image forming apparatuses use electrophotographic rollers such as charging rollers, transfer rollers, developing rollers, fixing rollers, and cleaning rollers. As images are output, contaminants such as developer, external additives derived from the developer, and paper dust adhere to and gradually accumulate on the surfaces of these electrophotographic rollers. As a result, the performance of the electrophotographic rollers may deteriorate, and they may need to be replaced as consumable parts. In recent years, from the perspective of reducing environmental impact, there has been an increasing need to develop technologies for recovering used electrophotographic rollers and cleaning and regenerating the roller surfaces using various cleaning means. Patent Document 1 discloses a cleaning device that sprays pressurized water onto the surface of a rubber roller and removes surface dirt with a brush.

[0003] Japanese Patent Application Laid-Open No. 2001-327932

[0004] With the recent trend toward longer lifespans of electrophotographic devices, contaminants on electrophotographic rollers may increase and adhere, and the contaminants may form a film. The present inventors have recognized that, in the case of electrophotographic rollers, particularly conductive rollers, the recycling method of Patent Document 1 poses the following problems.

[0005] When the adhesive force between the conductive roller surface and the contaminants is strong, if the water pressure is increased too much to remove the highly adhesive contaminants, a large pressure is applied to the conductive roller surface, causing a change in conductivity. This change in conductivity is particularly noticeable in roller configurations where the surface is made conductive by an electronic conductive agent.

[0006] Furthermore, in order to achieve conductivity, a typical conductive roller requires a quantity of carbon black (hereinafter also referred to as CB) that causes the percolation phenomenon, which means that there is no wide area without CB, making it difficult for water to penetrate the interface between the contaminants and the roller, making it difficult to remove the contaminants.

[0007] The present disclosure is directed to a method for manufacturing a recycled conductive roller that effectively removes contaminants adhering to the surface of a conductive roller that has been used for a long period of time and has developed a significant buildup of contaminants without impairing conductivity, thereby contributing to good image formation.

[0008] The present disclosure relates to a method for manufacturing a recycled conductive roller, the method including a contaminant removal step of removing contaminants adhering to the outer surface of the conductive roller, wherein the conductive roller has a support having a conductive outer surface and a conductive layer on the outer surface of the support, the conductive layer having a matrix containing a first rubber and domains containing a second rubber and an electronic conductive agent, wherein when the Young's modulus of the matrix is ​​G1 (MPa) and the Young's modulus of the domain is G2 (MPa), G1 and G2 satisfy G1 < G2, and the contaminant removal step includes a step of spraying a liquid onto the surface of the conductive roller to which the contaminants have adhered.

[0009] According to the present disclosure, it is possible to provide a method for manufacturing a recycled conductive roller that effectively removes contaminants adhering to the surface of a conductive roller that has been used for a long period of time and has developed a significant buildup of contaminants without impairing conductivity, thereby contributing to good image formation.

[0010] Fig. 1 is an example of a cross-sectional view of a conductive roller. Figs. 2A and 2B are schematic diagrams of the deformation of the surface when liquid pressure is applied to a used conductive roller. Figs. 3A and 3B are schematic diagrams of the cross-sectional structure of a conductive roller. Fig. 4 is an example of an apparatus for spraying liquid to remove adhered contaminants.

[0011] In the present disclosure, expressions such as "XX or more and YY or less" or "XX to YY" representing a numerical range mean a numerical range including the lower and upper limits, which are the endpoints, unless otherwise specified. Furthermore, when a numerical range is described in stages, the upper and lower limits of each numerical range can be arbitrarily combined. Furthermore, in the present disclosure, expressions such as "at least one selected from the group consisting of XX, YY, and ZZ" mean any of XX, YY, ZZ, a combination of XX and YY, a combination of XX and ZZ, a combination of YY and ZZ, or a combination of XX, YY, and ZZ. Note that when XX is a group, multiple XXs may be selected, and the same applies to YY and ZZ.

[0012] When the amount of contaminants on the conductive roller increases, especially when the contaminants have formed a film, the inventors have recognized the following problem with the regeneration method disclosed in Patent Document 1. When the adhesive force between the conductive roller surface and the contaminants is strong, if the pressure applied to spray the liquid (hereinafter also referred to as liquid pressure) to remove the highly adhesive contaminants is increased too much, a large pressure is applied to the conductive roller surface, causing a change in conductivity. This change in conductivity is particularly noticeable in roller configurations in which the surface is made conductive by an electronic conductive agent.

[0013] On the other hand, if the liquid pressure is reduced so as not to impair the conductivity of the conductive roller, the contaminant removal performance will be reduced. If the conductivity of the conductive roller changes after regeneration or if the contaminants are not completely removed, it may not be possible to form good images when the roller is reused.

[0014] To effectively remove adhered contaminants using liquid pressure, the sprayed liquid must efficiently penetrate the interface between the contaminant and the conductive roller. However, in the case of film-like contaminants, the sprayed liquid does not effectively penetrate the interface unless cracks occur in the film. Furthermore, in order for a typical conductive roller to exhibit conductivity, a CB amount that reaches the percolation region is required. Therefore, the uniform dispersion of CB can make it difficult for the liquid to penetrate the interface between the contaminant and the roller.

[0015] Therefore, the inventors have conducted extensive research into a method that can effectively remove contaminants, particularly film-like contaminants, by effectively creating cracks in them even at low liquid pressure, and that is less likely to cause changes in conductivity even when subjected to liquid pressure.

[0016] As a result, the inventors discovered that when the conductive roller to be regenerated has the following configuration, it is possible to effectively remove adhered contaminants, particularly film-like contaminants, even at low liquid pressures, and that changes in conductivity with pressure are suppressed. The conductive roller has a support having a conductive outer surface and a conductive layer on the outer surface of the support. The conductive layer has a matrix including a first rubber and domains including a second rubber and an electronic conductive agent. Furthermore, when the Young's modulus of the matrix is ​​G1 (MPa) and the Young's modulus of the domain is G2 (MPa), G1 and G2 satisfy the relationship G1 < G2.

[0017] The reason for this is presumed to be as follows. First, an example of the layer structure of a conductive roller having a matrix domain structure is shown in Fig. 1. Fig. 1 shows the cross-sectional structure perpendicular to the longitudinal direction, which is the axial direction of the conductive roller. The conductive roller has a support 11 having a conductive outer surface, and a conductive layer 10 provided on the outer surface of the support 11. The conductive layer 10 is composed of a matrix 12 containing a first rubber, and domains containing a second rubber 13 and an electronic conductive agent 14.

[0018] Next, Fig. 2A shows the deformation of a typical conductive roller when liquid pressure is applied to the conductive roller. Contaminants 23 (adherents 23) are adhered to the conductive roller. When liquid is sprayed onto the conductive roller, liquid pressure 24 causes the surface of the conductive layer 22 of the conductive roller to deform by an amount 25 toward the support 21. On the other hand, Fig. 2B shows the deformation when the conductive layer is composed of a matrix 12 containing a first rubber, a domain containing a second rubber 13 and an electronic conductive agent 14, and the Young's modulus G2 of the domain is larger than the Young's modulus G1 of the matrix.

[0019] 2B , the deformation amount 26 of the matrix portion is greater than the deformation amount 27 of the domain portion. At this time, the contaminants 23 adhering to the domain portion follow the deformation of the domain, and the contaminants 23 adhering to the matrix portion follow the deformation of the matrix. Because the deformation of the domain portion and the matrix portion in the conductive layer differs, cracks are generated in the contaminants 23 adhering across the domain portion and the matrix portion, starting from the domain-matrix interface. As a result, liquid enters through the generated cracks and penetrates into the interface between the conductive layer and the contaminants, making it possible to effectively peel off the adhering contaminants.

[0020] In addition, in the case of a typical conductive roller, particularly one that exhibits conductivity through electronic conduction, the conductive path formed by the conductive agent changes when the conductive agent moves due to liquid pressure. However, in a configuration comprising a matrix made of the first rubber, a domain containing the second rubber, and an electronic conductive agent, where the Young's modulus G2 of the domain is greater than the Young's modulus G1 of the matrix, the matrix can be preferentially deformed by liquid pressure. Therefore, deformation of the domain containing the electronic conductive agent is suppressed, and therefore, changes in conductivity are unlikely to occur. On the other hand, when G1 = G2 or G1 > G2, the domain containing the electronic conductive agent is more likely to deform, and therefore, changes in conductivity are more likely to occur.

[0021] The relationship between G1 and G2 is preferably such that G2 / G1 is 1.1 or greater. Furthermore, it is more preferable that G2 / G1 ≥ 3.0, even more preferable that G2 / G1 ≥ 4.5, and even more preferable that G2 / G1 ≥ 5.0. When G2 / G1 is 3.0 or greater, it becomes possible to more effectively generate cracks in adhered contaminants, and in addition, deformation of the domain portion is further suppressed, thereby further suppressing changes in electrical conductivity. There is no particular upper limit for G2 / G1. G2 / G1 is preferably 3.0 to 40.0, 4.5 to 30.0, or 5.0 to 22.0.

[0022] G1 is preferably 1 to 20 MPa, more preferably 1 to 15 MPa, and even more preferably 3 to 10 MPa. G2 is preferably 5 to 100 MPa, more preferably 20 to 100 MPa. Within this range, contaminants can be removed more effectively. In particular, when G2 is 100 MPa or less, the matrix located directly below the domains is less likely to deform significantly due to deformation of the domains caused by liquid pressure. Therefore, a difference in deformation between the matrix and the domains is more likely to occur, and cracks can be more effectively generated in the contaminants.

[0023] G1 can be controlled by the viscoelastic properties of the first rubber in the matrix and the addition of other fillers, while G2 can be controlled by the viscoelastic properties of the second rubber forming the domains, the amount of electronic conductive agent, and the addition of other fillers.

[0024] On the surface of the conductive roller, a thin conductive resin layer may be formed on the conductive layer, which is an elastic layer. Even in this case, the effect of causing cracks in contaminants due to the difference in deformation between the matrix and domains in the conductive layer underlying the conductive resin layer can be obtained. From the viewpoint of making cracks more likely to occur, it is preferable that the matrix and domains of the conductive layer are exposed on the outer surface of the conductive roller.

[0025] A larger amount of the electronic conductive agent present in the domain is preferable because the conductivity of the domain is less likely to change even if the conductive path changes due to liquid pressure. Specifically, when observing a cross section of the conductive layer in the thickness direction, the ratio of the total cross-sectional area of ​​the electronic conductive agent contained in the domain to the total cross-sectional area of ​​the domain is preferably 10 to 45 area %, and more preferably 20 to 40 area %.

[0026] In addition, from the viewpoint of allowing the liquid to more easily penetrate the interface between the conductive layer and the contaminant, the more matrix there is, the better. Therefore, when observing the outer surface of the conductive roller, the ratio of the total area of ​​the matrix to the area of ​​the observation region is preferably 60 to 80 area %, and more preferably 70 to 80 area %.

[0027] In addition, it is preferable that the liquid contains water as a main component. From the viewpoint of affinity between the outer surface of the conductive roller and the liquid, it is preferable that at least one group selected from the group consisting of an acidic functional group and a carbonyl group is present on the outer surface of the conductive roller. Specific examples of means for generating these functional groups include UV treatment.

[0028] There are no particular limitations on the UV treatment, and known means can be used. For example, a low-pressure mercury lamp or the like can be used as a UV light source. The cumulative light dose is not particularly limited as long as it is within a range that can generate the desired functional groups. The cumulative light dose is preferably 1,000 to 15,000 mJ / cm. ２ , 5000~10000mJ / cm ２ Examples include:

[0029] Furthermore, from the viewpoint of further improving the affinity between the surface of the conductive roller and the liquid, when an acidic functional group or a carbonyl group is present on the outer surface of the conductive roller, the liquid is preferably a basic solution. Specifically, the basic solution may be at least one selected from the group consisting of an aqueous sodium hydroxide solution, an aqueous sodium hydrogen carbonate solution, an aqueous potassium hydroxide solution, an aqueous calcium hydroxide solution, etc. The concentration of the basic solution is not particularly limited, and may be, for example, 0.1 to 5.0 mass %, or 0.2 to 2.0 mass %.

[0030] It is also preferable that acidic functional groups are present on the outer surface of the conductive roller and that the liquid contains an aqueous solution of sodium bicarbonate. It is presumed that the aqueous solution of sodium bicarbonate reacts with the acidic functional groups between the contaminants and the surface of the conductive roller to generate carbon dioxide, which makes the contaminants more likely to peel off.

[0031] When a cross section of the conductive layer is observed in the thickness direction, the number average circle-equivalent diameter of the domains is, for example, 0.3 to 7.0 μm, and preferably 0.5 to 5.0 μm. When the number average circle-equivalent diameter of the domains is in the above range, cracks can be more effectively generated in the contaminants.

[0032] Furthermore, when observing a cross section of the conductive layer in the thickness direction, the number-average equivalent circle diameter of the aggregates of the electronic conductive agent in the domains is preferably less than 0.50 μm. The average value is preferably 0.05 to 0.50 μm, and more preferably 0.05 to 0.20 μm. When the number-average equivalent circle diameter of the aggregates is less than 0.50 μm, the Young's modulus G2 value of the domains is stable, and the effect of causing cracks in contaminants due to the difference in deformation between the matrix and the domains is more likely to be exhibited.

[0033] Furthermore, the ratio of the total cross-sectional area of ​​the electronic conductive agent contained in the matrix to the cross-sectional area of ​​the matrix is ​​preferably 5 area % or less. This area ratio is preferably 0 to 5 area %, and more preferably 0 to 2 area %. It has been found through extensive research that within this range, oxidized functional groups are more likely to be generated during UV treatment, etc., which is thought to facilitate the penetration of liquids and make it easier for contaminants to be removed.

[0034] <Conductive Roller> The conductive roller and recycled conductive roller can be used as a conductive roller for an electrophotographic image forming apparatus, specifically as a developing roller, charging roller, transfer roller, fixing roller, cleaning roller, etc.

[0035] An example of a recycled conductive roller is shown in Fig. 3A. Note that a recycled conductive roller is a conductive roller from which dirt such as developer and external additives has been removed due to image formation or the like, and therefore a conductive roller without dirt on its surface has the same configuration as a recycled conductive roller. The configuration of a conductive roller will be described below using a recycled conductive roller as an example.

[0036] Fig. 3A is a cross-sectional view showing the configuration of a cross section perpendicular to the longitudinal direction, which is the axial direction, of the conductive roller. The conductive roller has a cylindrical support 11 having a conductive outer surface, and a conductive layer 10 provided on the outer peripheral surface of the support 11, i.e., on the outer surface of the support. However, the shape of the support in the conductive roller is not particularly limited. Fig. 3B is a cross-sectional view showing the configuration of a conductive roller having a surface layer 33 on the conductive layer 10.

[0037] <Support> The material constituting the support 11 can be appropriately selected from materials known in the field of electrophotographic conductive members and materials usable as conductive members. Examples include metals or alloys such as aluminum, stainless steel, conductive synthetic resins, iron, steel, and copper alloys.

[0038] Furthermore, these may be subjected to an oxidation treatment or a plating treatment with chromium, nickel, or the like. As the type of plating, either electroplating or electroless plating can be used. Electroless plating is preferred from the viewpoint of dimensional stability. Examples of the electroless plating used here include nickel plating, copper plating, gold plating, and various other alloy platings. Of these, electroless nickel plating is preferred. The plating thickness is preferably 0.05 μm or more, and considering the balance between work efficiency and rust prevention ability, the plating thickness is preferably 0.10 μm or more and 30.00 μm or less.

[0039] The cylindrical support 11 may have a solid cylindrical shape or a hollow cylindrical shape. The outer diameter of the support is preferably 3 mm or more and 10 mm or less. The length of the support in the longitudinal direction is not particularly limited, but is preferably, for example, 200 mm or more and 300 mm or less. Furthermore, if necessary, the support may be partially processed for installation in an electrophotographic apparatus.

[0040] From the viewpoint of supplying electric charges, it is preferable that the conductive layer is provided directly on the support in a manner that the conductive layer is in contact with the support. Another preferable embodiment is that the conductive layer is provided on the outer surface of the support via an intermediate layer made of a conductive resin layer such as a primer layer. It is more preferable that the primer layer is a thin film.

[0041] As the primer, a known material can be selected and used depending on the rubber material for forming the conductive layer and the material of the support. Examples of the primer material include thermosetting resins and thermoplastic resins, and specific examples of known materials that can be used include phenolic resins, urethane resins, acrylic resins, polyester resins, polyether resins, and epoxy resins. Among these, phenolic resins are preferred, and for example, Metalock U-20 (manufactured by Toyo Kagaku Kenkyusho Co., Ltd.) can be used.

[0042] <Conductive Layer> The conductive roller has a conductive layer on the outer surface of the support. The conductive layer formed on the support may be a conductive elastic layer. The conductive layer is preferably configured to consist of only the conductive elastic layer. A surface layer may be formed on the conductive elastic layer as long as the effects of the present disclosure are not impaired. The outer surface of the conductive layer preferably corresponds to the outer surface of the conductive roller.

[0043] The conductive layer has a matrix containing at least a first rubber and domains containing a second rubber and an electronic conductive agent. The matrix and domains form a phase-separated structure. That is, the conductive layer has a matrix-domain structure with multiple domains dispersed in the matrix.

[0044] For example, the first rubber that forms the matrix is ​​the component with the highest compounding ratio in the rubber composition for forming the conductive layer, and it provides the required mechanical strength, such as abrasion resistance and low settling. In other words, it is resistant to scratches and deformation even during the contamination removal process, resulting in a higher quality recycled conductive roller.

[0045] It is preferable to use a rubber with good dispersibility of the electronic conductive agent for the second rubber forming the domain, and to disperse the electronic conductive agent therein. This is because uniform dispersion of the electronic conductive agent in the rubber can impart excellent electrical properties. If the domain contains an electronic conductive agent, the uniform dispersion of the electronic conductive agent suppresses aggregation of the electronic conductive agent contained in the rubber in the conductive layer due to external stresses such as stress received in the contaminant removal process and friction, thereby suppressing a decrease in conductivity.

[0046] The conductive layer may contain a rubber other than the first rubber and the second rubber as long as the effects of the present disclosure are not impaired. In this case, the top two rubbers in terms of content, in no particular order, are designated as the first rubber and the second rubber. For example, the conductive layer may contain a third rubber other than the first rubber and the second rubber.

[0047] In the present disclosure, a phase-separated structure containing three or more rubber components, having a core-shell domain configuration in a matrix, and in which the matrix and domains are formed from a first rubber and a second rubber, respectively, is also referred to as a matrix-domain structure. For example, the domain may include a core containing the second rubber and an electronic conductive agent, and a shell of a third rubber. When the third rubber is used as the shell, for example, the third rubber may be selected to have an SP value between the SP values ​​of the first rubber and the second rubber.

[0048] <Method for Confirming Phase Separation Structure> The phase separation structure can be confirmed, for example, by the following method. That is, a thin piece of the conductive layer is cut out from the conductive layer to prepare an observation sample. Examples of means for cutting out the thin piece include a razor, a microtome, and an FIB. If necessary, the observation sample is subjected to a treatment (e.g., a staining treatment or a vapor deposition treatment) that makes it easy to distinguish between the first rubber phase and the second rubber phase. The observation sample is then observed using a laser microscope, SEM, or TEM. A more specific procedure will be described later.

[0049] <First Rubber> A specific example of the first rubber is preferably at least one selected from the group consisting of natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), acrylonitrile butadiene rubber (NBR), styrene butadiene rubber (SBR), butyl rubber (IIR), ethylene propylene rubber (EPM), ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), nitrile rubber (NBR), hydrogenated nitrile rubber (H-NBR), silicone rubber, and urethane rubber (U).

[0050] The first rubber is more preferably at least one selected from the group consisting of isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), and ethylene propylene diene rubber (EPDM), and even more preferably at least one selected from the group consisting of isoprene rubber (IR), styrene-butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), and butadiene rubber (BR).

[0051] The glass transition temperature Tg1 of the first rubber is preferably lower than −15° C. This is because, when the glass transition temperature Tg1 is lower than −15° C., the roller hardness can be kept low and the change in hardness of the conductive roller is small under usage environments such as high-temperature, high-humidity environments and low-temperature, low-humidity environments. This is because conductive rollers used in electrophotographic image forming apparatuses are usually used in contact with other members, and therefore it is necessary to maintain an appropriate nip width.

[0052] It is preferable that the first rubber has a diene bond. As a result of extensive research, it has been found that the presence of a diene bond makes it easier for oxidized functional groups to be generated when UV treatment or the like is performed, which is presumed to make it easier for liquids to penetrate and therefore easier for contaminants to peel off.

[0053] <Second Rubber> Specific examples of the second rubber include at least one selected from the group consisting of natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), acrylonitrile butadiene rubber (NBR), styrene butadiene rubber (SBR), butyl rubber (IIR), ethylene propylene rubber (EPM), ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), nitrile rubber (NBR), hydrogenated nitrile rubber (H-NBR), silicone rubber, and urethane rubber (U).

[0054] The second rubber more preferably contains at least one selected from the group consisting of isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), and ethylene propylene diene rubber (EPDM), and further preferably contains at least one selected from the group consisting of isoprene rubber (IR), styrene-butadiene rubber (SBR), and acrylonitrile butadiene rubber (NBR). Furthermore, the second rubber is preferably different from the first rubber.

[0055] The glass transition temperature Tg2 of the second rubber is preferably lower than −15° C. This is because, when the glass transition temperature Tg2 is lower than −15° C., the roller hardness can be kept low and the change in hardness of the conductive roller is small under usage environments such as high-temperature, high-humidity environments and low-temperature, low-humidity environments. This is because conductive rollers used in electrophotographic image forming apparatuses are usually used in contact with other members, and therefore it is necessary to maintain an appropriate nip width.

[0056] The first rubber and the second rubber are preferably, for example, any of the following combinations: The first rubber is styrene butadiene rubber (SBR) and the second rubber is acrylonitrile butadiene rubber (NBR). The first rubber is acrylonitrile butadiene rubber (NBR) and the second rubber is styrene butadiene rubber (SBR). The first rubber is isoprene rubber (IR) and the second rubber is acrylonitrile butadiene rubber (NBR). The first rubber is butadiene rubber (BR) and the second rubber is acrylonitrile butadiene rubber (NBR).

[0057] The mass ratio of the second rubber to the first rubber in the conductive layer (second rubber:first rubber) is preferably 10:90 to 40:60, and more preferably 20:80 to 40:60.

[0058] When a third rubber is used, preferred examples of the third rubber include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), butyl rubber (IIR), ethylene-propylene rubber (EPM), ethylene propylene diene rubber (EPDM), and silicone rubber. The third rubber preferably contains SBR. The content of the third rubber is, for example, 1 to 25 parts by mass, or 5 to 20 parts by mass, per 100 parts by mass of the first rubber.

[0059] <Electron-conductive agent> The conductive layer contains an electronic conductive agent. The electronic conductive agent is preferably conductive particles. Examples of electronic conductive agents include: fine particles and fibers of metals such as aluminum, palladium, iron, copper, and silver; metal oxides such as titanium oxide, tin oxide, and zinc oxide; composite materials in which the surfaces of the above-mentioned metal-based fine particles, fibers, and metal oxides are surface-treated by electrolysis, spray coating, or mixing and shaking; carbon black and carbon-based fine particles. The electronic conductive agent preferably contains carbon black.

[0060] Examples of carbon black include black furnace black, thermal black, acetylene black, and ketjen black. Examples of furnace black include SAF-HS, SAF, ISAF-HS, ISAF, ISAF-LS, I-ISAF-HS, HAF-HS, HAF, HAF-LS, T-HS, T-NS, MAF, FEF, GPF, SRF-HS-HM, SRF-LM, ECF, and FEF-HS. Examples of thermal black include FT and MT. Examples of carbon-based fine particles include PAN (polyacrylonitrile)-based carbon particles and pitch-based carbon particles.

[0061] By incorporating such a conductive agent, the conductive layer can be ４ ~1 x 10 １０ A conductive roller having a conductive layer with a volume resistivity in this range can impart a uniform charge to the surface of a photoreceptor. The volume resistivity of the conductive layer of the conductive roller is more preferably 1×10 ４ ~1 x 10 ９ It is Ω·cm.

[0062] Furthermore, fillers, processing aids, crosslinking aids, crosslinking accelerators, crosslinking accelerator aids, crosslinking retarders, softeners, plasticizers, dispersants, and the like, which are commonly used as compounding agents for rubber, may be added to the rubber composition for forming the conductive layer as needed.

[0063] <Roughening Particles> The rubber composition forming the conductive layer may contain spherical particles having a particle diameter in the range of 1 μm to 90 μm. Examples of the spherical particles include at least one selected from the following: phenolic resin particles, silicone resin particles, polyacrylonitrile resin particles, polystyrene resin particles, polyurethane resin particles, nylon resin particles, polyethylene resin particles, polypropylene resin particles, acrylic resin particles, silica particles, and alumina particles. By using such a rubber composition, convex portions derived from the spherical particles can be formed on the outer surface of the conductive layer.

[0064] Examples of methods for mixing these raw materials include a mixing method using a closed type mixer such as a Banbury mixer or a pressure kneader, and a mixing method using an open type mixer such as an open roll.

[0065] The conductive layer can be formed, for example, as follows: An unvulcanized rubber composition for forming the conductive layer is prepared. The unvulcanized rubber composition for forming the conductive layer can be formed, for example, via a method including the following steps (I) to (III). Step (I): A step of preparing an unvulcanized domain rubber composition (hereinafter also referred to as "CMB") containing an electronic conductive agent and a second rubber. Step (II): A step of preparing an unvulcanized matrix rubber composition (hereinafter also referred to as "MRC") containing a first rubber. Step (III): A step of kneading the CMB and MRC to prepare an unvulcanized rubber composition for forming the conductive layer having a matrix-domain structure. The mass-based mixing ratio of CMB to MRC (CMB:MRC) in the unvulcanized rubber composition for forming the conductive layer is preferably 10:90 to 40:60, more preferably 20:80 to 40:60. When a third rubber is used, it is preferable to incorporate the third rubber into the MRC.

[0066] Next, a layer of unvulcanized rubber composition for forming a conductive layer is formed on the conductive support. Examples of methods for forming such a rubber composition layer include the following methods (i) to (iii): (i) a method in which the unvulcanized rubber composition is extruded into a tube using an extruder and a core is inserted into the tube; (ii) a method in which the unvulcanized rubber composition is co-extruded into a cylindrical shape around a core using an extruder equipped with a crosshead to obtain a molded product with a desired outer diameter; (iii) a method in which the unvulcanized rubber composition is injected into a mold with a desired outer diameter using an injection molding machine to obtain a molded product. Among these, method (ii) is preferred because it allows for easy continuous production of conductive rollers, requires fewer steps, and is suitable for low-cost production.

[0067] Next, the unvulcanized composition layer is vulcanized. Vulcanization is carried out by heating, and examples of heating devices include hot air oven heating using a gear oven, heat vulcanization using far infrared rays, and steam heating using a vulcanization can. Among these, hot air oven heating and far infrared heating are preferred because they allow continuous production. The surface of the vulcanized rubber layer, i.e., the conductive layer, can also be ground if necessary.

[0068] Methods for grinding the roller surface include, for example, a traverse grinding method in which a grinding stone or roller is moved in the thrust direction of the roller to grind. Another method is a plunge-cut grinding method in which a grinding stone wider than the roller length is cut into the roller without reciprocating while the roller is rotated around the center of the core shaft. The plunge-cut cylindrical grinding method has the advantage that the entire width of the conductive roller can be ground at once, and is more preferable than the traverse cylindrical grinding method because it can shorten the processing time.

[0069] The conductive roller may be surface-modified to the extent that it does not affect the glass transition temperature of the rubber forming the conductive layer. Surface modification methods include ultraviolet irradiation, electron beam irradiation, plasma treatment, and corona discharge treatment. These surface treatments may also be combined.

[0070] <Surface Layer> A surface layer such as a conductive resin layer may be provided on the conductive layer, provided that the effect of the difference in deformation between the matrix and domain of the conductive layer when liquid pressure is applied to cause cracks in the contaminant is not significantly impaired. The surface layer contains, for example, a binder resin and an electronic conductive agent. The surface layer contains an electronic conductive agent. If the surface layer is formed in a form in which the electronic conductive agent is dispersed in the binder resin, dispersion proceeds sufficiently, which is also preferable in terms of the physical durability of the surface layer. The surface layer may contain roughening particles, a surface release agent, etc., as necessary.

[0071] Furthermore, the surface layer may be subjected to UV treatment or the like as described above. The UV treatment generates acidic functional groups or carbonyl groups, which improves the affinity of the surface layer with water and makes it easier to remove contaminants.

[0072] <Electron Conductive Agent> Examples of the electron conductive agent contained in the surface layer include conductive particles such as conductive carbon black, metal oxide conductive particles such as titanium oxide, tin oxide, and zinc oxide, and metal conductive particles such as aluminum, iron, copper, and silver. These conductive particles can be used alone or in combination of two or more. Furthermore, composite particles in which silica particles are coated with conductive particles can also be used as the conductive particles.

[0073] Carbon black is preferred as the conductive particles used in the surface layer. Carbon black has a low specific gravity and high conductivity, so adding a small amount of carbon black to the binder resin can ensure sufficient conductivity for the surface layer. In the present disclosure, it is preferable to maintain the hardness of the surface layer at a low level, so carbon black suitable for addition in small amounts is preferred.

[0074] <Binder Resin> Known binder resins can be used as the binder resin. Examples include various synthetic resins, natural rubber and vulcanized natural rubber, synthetic rubber, and other rubbers. Examples of binder resins that can be used include fluororesins, polyamide resins, acrylic resins, polyurethane resins, silicone resins, butyral resins, styrene-ethylene-butylene-olefin copolymers, and olefin-ethylene-butylene-olefin copolymers.

[0075] The binder resin can be used alone or in combination of two or more. The binder resin is preferably a resin containing a polycarbonate structure. The polycarbonate structure has low polarity, so the volume resistivity of the binder resin itself can be maintained high. Specifically, a polycarbonate-based polyurethane obtained by copolymerizing polycarbonate polyol and polyisocyanate is preferred.

[0076] Examples of polycarbonate polyols include polynonamethylene carbonate diol, poly(2-methyl-octamethylene) carbonate diol, polyhexamethylene carbonate diol, polypentamethylene carbonate diol, poly(3-methylpentamethylene) carbonate diol, polytetramethylene carbonate diol, polytrimethylene carbonate diol, poly(1,4-cyclohexanedimethylene carbonate) diol, poly(2-ethyl-2-butyl-trimethylene) carbonate diol, and random / block copolymers thereof.

[0077] The polyisocyanate may be selected from commonly used known isocyanates, such as toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), polymeric diphenylmethane polyisocyanate, hydrogenated MDI, xylylene diisocyanate (XDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), etc. Among these, aromatic isocyanates such as toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and polymeric diphenylmethane polyisocyanate are more preferably used.

[0078] <Step of Removing Adhered Contaminants> The method for manufacturing a recycled conductive roller includes a step of removing contaminants adhering to the outer surface of the conductive roller. The contaminant removal step includes a step of spraying a liquid onto the surface of the conductive roller to which the contaminants are adhering. In the contaminant removal step, a liquid such as water is sprayed onto the surface of the used conductive roller.

[0079] The equipment used in this step may be a known cleaning equipment that removes adhered contaminants by spraying a liquid under pressure. The liquid preferably contains water as a main component. The main component means that the content is 50% by mass or more. Examples of the liquid include water, a basic solution, and an acidic solution. The liquid is preferably a basic solution, and more preferably a basic aqueous solution. It is preferable to change the liquid temperature depending on the situation.

[0080] Figure 4 shows an example of an apparatus for spraying a liquid onto the outer surface of a conductive roller to remove adhering contaminants. In Figure 4, a liquid such as water pressurized by a compressor (not shown) is sprayed from a spray nozzle 42. Meanwhile, a conductive roller 41 is supported by a rotatable support base so as to rotate in the direction of arrow 43. The accelerated liquid collides with the surface of the rotating conductive roller 41, removing contaminants, such as those originating from the developer, that have adhered to the surface of the conductive roller 41. Furthermore, the spray nozzle 42 moves back and forth from side to side in the direction of arrow 44, spraying the liquid over the entire outer surface of the conductive roller 41.

[0081] To effectively obtain the deformation difference between the matrix and the domain by the liquid pressure described above, it is preferable to set the pressure P when the liquid collides with the outer surface of the conductive roller within an appropriate range. The pressure P is adjusted by the pressure of the ejected liquid, the distance between the ejection nozzle and the surface of the conductive roller, etc. The pressure applied to the outer surface of the conductive roller is measured by, for example, fixing a commercially available pressure sensor to the surface of the conductive roller.

[0082] The pressure P of the liquid that collides with the conductive roller surface when the liquid is sprayed can be measured using a pressure measurement film prescale. Pressure from the liquid is applied to the prescale, and then the change in color of the prescale can be converted into pressure P using a pressure image analysis system. The specific procedure will be described later. The pressure P is, for example, 0.1 to 120.0 MPa, preferably 0.2 to 100.0 MPa, more preferably 0.2 to 10.0 MPa, and even more preferably 0.7 to 10.0 MPa.

[0083] The present disclosure will be described below based on examples, but the present disclosure is not limited to these examples.

[0084] The conductive roller was produced using the materials shown below. <Conductive Elastic Layer Forming Materials> <Acrylonitrile Butadiene Rubber NBR> NBR (trade name: NBR N230SV, acrylonitrile content: 35%, Mooney viscosity ML （１＋４） 100℃: 32, manufactured by ENEOS Material Co., Ltd., abbreviation: N230SV)

[0085] <Styrene butadiene rubber SBR> SBR (1) (product name: ESBR1507, styrene content: 23.5%, Mooney viscosity ML （１＋４） 100°C: 35, manufactured by ENEOS Materials Corporation, abbreviation: 1507) SBR (2) (trade name: Asaprene 303, styrene content: 46%, Mooney viscosity ML （１＋４） 100°C: 45, manufactured by Asahi Kasei Corporation, abbreviation: 303) <Isoprene rubber IR> Isoprene rubber (trade name: Nipol 2200L, Mooney viscosity ML （１＋４） 100°C: 70, manufactured by Zeon Corporation, abbreviation: 2200L) <Butadiene rubber BR> Butadiene rubber (trade name: UBEPOL BR130B, Mooney viscosity ML （１＋４） 100°C: 29, manufactured by Ube Industries, abbreviated name: BR130B)

[0086] <Electronic conductive agent> Carbon black (1) (product name: Toka Black #7270SB, DBP absorption: 62 cm ３ / 100g, manufactured by Tokai Carbon Co., Ltd., abbreviation: #7270) <Vulcanizing agent> Vulcanizing agent (trade name: SULFAX PMC, sulfur content 97.5%, manufactured by Tsurumi Chemical Industry Co., Ltd., abbreviation: sulfur)

[0087] <Vulcanization accelerators> Vulcanization accelerator (1) (trade name: Suncerar TBZTD, tetrabenzyl thiuram disulfide, manufactured by Sanshin Chemical Industry Co., Ltd., abbreviation: TBzTD) Vulcanization accelerator (2) (trade name: Noccela TET, tetraethyl thiuram disulfide, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., abbreviation: TET) Vulcanization accelerator (3) (trade name: ACCEL CZ, N-cyclohexyl-2-benzothiazolylsulfenamide, manufactured by Kawaguchi Chemical Industry Co., Ltd., abbreviation: Cz) <Fillers> Filler (1) (trade name: Nanox #30, calcium carbonate, manufactured by Maruo Calcium Co., Ltd., abbreviation: #30)

[0088] <Example 1> <Production of conductive roller 1> [1-1. Preparation of unvulcanized domain rubber composition CMB1] The types and amounts of materials shown in Table 1 were mixed in a pressure kneader to obtain unvulcanized domain rubber composition CMB1. The mixing conditions were a filling rate of 70 vol%, a blade rotation speed of 30 rpm, and 18 minutes.

[0089]

[0090] [1-2. Preparation of Unvulcanized Matrix Rubber Composition MRC1] The materials shown in Table 2 were mixed in the amounts and types shown in Table 2 using a pressure kneader to obtain Unvulcanized Matrix Rubber Composition 1. The mixing conditions were a filling rate of 70 vol%, a blade rotation speed of 30 rpm, and 18 minutes.

[0091]

[0092] [1-3. Preparation of Unvulcanized Rubber Composition 1 for Forming Conductive Layer] The types and amounts of materials shown in Table 3 were mixed using an open roll to prepare unvulcanized rubber composition 1 for forming a conductive layer. An open roll with a roll diameter of 12 inches was used as the mixer. The mixing conditions were a front roll rotation speed of 10 rpm, a rear roll rotation speed of 8 rpm, a roll gap of 2 mm, and a total of 20 left and right turns, followed by 10 thin passes with a roll gap of 1.0 mm.

[0093]

[0094] [2. Formation of Conductive Layer] A round bar with a total length of 252 mm and an outer diameter of 6 mm was prepared, the surface of which was made of free-cutting steel and electroless nickel-plated. Next, using a roll coater, an adhesive, Metalock U-20 (trade name, manufactured by Toyo Kagaku Kenkyusho Co., Ltd.), was applied to the entire circumference of the round bar over a range of 230 mm, excluding 11 mm at each end. In this example, the adhesive-coated round bar was used as a conductive support.

[0095] Next, a die with an inner diameter of 10.4 mm was attached to the tip of a crosshead extruder having a mechanism for feeding the conductive support and a mechanism for discharging the unvulcanized rubber roller, and the temperatures of the extruder and the crosshead were adjusted to 80° C., and the conveying speed of the conductive support was adjusted to 60 mm / sec. Under these conditions, unvulcanized rubber composition 1 for forming a conductive layer was fed from the extruder, and the outer periphery of the conductive support was coated with unvulcanized rubber composition 1 for forming a conductive layer in the crosshead, thereby obtaining an unvulcanized rubber roller 1.

[0096] The unvulcanized rubber roller 1 was then placed in a hot-air vulcanizing furnace at 170°C and heated for 60 minutes to vulcanize the unvulcanized rubber composition 1, thereby obtaining a roller having a conductive layer formed on the outer periphery of the conductive support. Then, both ends of the conductive layer were cut off to make the longitudinal length of the conductive layer portion 231 mm.

[0097] Next, the surface of the conductive layer was polished with a rotary grindstone. This resulted in a conductive roller 1 having a diameter of 9.62 mm at positions 90 mm from the center to both ends, a central diameter of 9.7 mm, and a crown amount of 80 μm. Next, the current value of this conductive roller 1 was measured under the conditions described below, and this was taken as the initial current value.

[0098] <Current Measurement Method> A 500 g weight was applied to each exposed support portion at both ends of the conductive roller, and the outer surface of the conductive roller was abutted against a 40 mm diameter SUS cylindrical electrode. The cylindrical electrode was rotated in this state, causing the conductive roller to rotate along with the electrode. Once the rotation stabilized, a voltage was applied to the support from a DC power source, and a voltage of 200 V was applied between the support and the cylindrical electrode. The environment during this period was 20°C and 50% RH (relative humidity). The current value at this time was measured using an ammeter for one rotation of the conductive roller, and the average value was calculated to obtain the current value of the conductive roller. The volume resistivity ρ was calculated using the measured current value I, internal resistance R, applied voltage V, nip area S between the SUS cylindrical electrode and the conductive roller, and the total thickness t of the conductive layer and surface layer of the conductive roller, using the following formula: ρ=(V / I-R)×S / t

[0099] <Confirmation of the Phase Separation Structure of the Matrix Containing the First Rubber and the Domain Containing the Second Rubber and the Electronic Conductive Agent in the Conductive Layer> The matrix domain structure in the conductive layer was confirmed as follows. Specifically, ultrathin slices with a thickness of 1 μm were cut from a cross section in the thickness direction of the conductive layer, including the surface of the conductive roller 1, using a microtome (trade name: Leica EM FCS, manufactured by Leica Microsystems) at a cutting temperature of −100°C. When cutting the slices, the cross section was oriented perpendicular to the longitudinal direction of the conductive member, taking into account the direction in which charge is transported for conductivity. The prepared slices were stained using a staining agent and photographed at 10,000x magnification using a scanning electron microscope (SEM) (trade name: S-4800, manufactured by Hitachi High-Technologies Corporation) to obtain backscattered electron images of the cross section. Examples of staining agents include osmium tetroxide, ruthenium tetroxide, and phosphotungstic acid. Staining agents that can distinguish the first rubber and the second rubber were selected. When a cross-sectional image showed that multiple domains were dispersed in a matrix and existed independently without being connected to each other, it was determined that the structure was a matrix domain structure. The phase-separated structure consisting of the first rubber and the second rubber in the conductive layer of the conductive roller 1 was a matrix-domain structure, and the carbon black, which is an electronic conductive agent, was present in the domains.

[0100] (Measurement of the ratio of the sum of the cross-sectional areas of the electronic conductive agent contained in the domains to the sum of the cross-sectional areas of the domains) The backscattered electron image of the cross section obtained by the above-mentioned SEM observation was converted to 8-bit grayscale using image processing software (product name: ImageProPlus, manufactured by Media Cybernetics) to obtain a monochrome image with 256 gradations. Next, the black and white of the image were inverted and binarized so that the domains in the cross section became white, and the domain parts were extracted, and the sum of the cross-sectional areas of the domains was calculated. Next, the secondary electron image obtained simultaneously with the backscattered electron image acquisition was converted to 8-bit grayscale to obtain a monochrome image with 256 gradations. Next, the black and white of the image were inverted and binarized so that the electronic conductive agent in the cross section became white. At this time, the total area of ​​the electronic conductive agent present in the parts corresponding to the domain parts divided by the binarization of the backscattered electron image was calculated. The ratio of the total cross-sectional area of ​​the electronic conductive agent contained in the domains to the total cross-sectional area of ​​the domains was calculated based on the total cross-sectional area of ​​the domains calculated above and the total cross-sectional area of ​​the electronic conductive agent present in the locations corresponding to the domain portions.

[0101] (Proportion of the sum of the cross-sectional areas of the electronic conductive agent present in the matrix based on the cross-sectional area of ​​the matrix) The backscattered electron image of the cross section obtained by the above-mentioned SEM observation was converted to 8-bit grayscale using image processing software (product name: ImageProPlus, manufactured by Media Cybernetics) or the like to obtain a monochrome image with 256 gradations. Next, the image was inverted and binarized so that the matrix in the cross section became white, and the matrix portion was extracted, and the sum of the cross-sectional areas of the matrix was calculated. Next, the secondary electron image obtained simultaneously with the backscattered electron image acquisition was converted to 8-bit grayscale to obtain a monochrome image with 256 gradations. Next, the image was inverted and binarized so that the electronic conductive agent in the cross section became white. At this time, the total area of ​​the electronic conductive agent present in the portions corresponding to the matrix portion divided by binarizing the backscattered electron image was calculated. The ratio of the total cross-sectional area of ​​the electronic conductive agent present in the matrix to the cross-sectional area of ​​the matrix was calculated using the total cross-sectional area of ​​the matrix calculated above and the total cross-sectional area of ​​the electronic conductive agent present in the portion corresponding to the matrix portion.

[0102] (Measurement of the number average value of the circle equivalent diameter of the domains) The backscattered electron image of the cross section obtained by the above-mentioned SEM observation was converted to an 8-bit grayscale using image processing software (trade name: ImageProPlus, manufactured by Media Cybernetics, Inc.) to obtain a monochrome image with 256 gradations. Next, the image was inverted and binarized so that the domains in the cross section became white, and the domain portions were extracted. The number average value of the circle equivalent diameter of the domains was calculated using image analysis software (trade name: LUZEX, manufactured by Nireco Corporation).

[0103] (Measurement of the number average value of the circle-equivalent diameter of aggregates of electronic conductive agent in domains) The backscattered electron image of the cross section obtained by the above-mentioned SEM observation was converted to 8-bit grayscale using image processing software (trade name: ImageProPlus, manufactured by Media Cybernetics) to obtain a monochrome image with 256 gradations. Next, the black and white of the image were inverted and binarized so that the domains in the cross section became white, and the domain portions were extracted. Next, the secondary electron image obtained simultaneously with the acquisition of the backscattered electron image was converted to 8-bit grayscale to obtain a monochrome image with 256 gradations. Next, the black and white of the image were inverted and binarized so that the electronic conductive agent in the cross section became white. Thereafter, image analysis software (trade name: LUZEX; manufactured by Nireco Corporation) was used to calculate the circle-equivalent diameter of aggregates of electronic conductive agent present in the locations corresponding to the domain portions separated by binarization of the backscattered electron image. Note that, when the area is 5000 nm ２ The electronic conductive agent portion having a diameter equal to or larger than this was defined as an aggregate, and the number average value of the equivalent circle diameter of the aggregate was calculated.

[0104] <Calculation of the ratio of the total area of ​​the matrix to the area of ​​the observation region in observation of the outer surface of the conductive roller> A backscattered electron image of the outer surface of the conductive roller obtained by SEM observation was converted to an 8-bit grayscale using image processing software (product name: ImageProPlus, manufactured by Media Cybernetics, Inc.) or the like to obtain a monochrome image with 256 gradations. Next, the image was inverted and binarized so that the matrix in the cross section became white, and the matrix portion was extracted and the total area of ​​the matrix portion was calculated, thereby calculating the ratio of the total area of ​​the matrix portion to the whole.

[0105] <Calculation of Young's Modulus of Matrix and Domain> The method for measuring the Young's modulus of the matrix and domain is described below. In this example, first, a cross section of the conductive roller was taken with a razor, and then a 1 μm-thick thin section was cut out using a microtome (trade name: Leica EM FCS, manufactured by Leica Microsystems) at a cutting temperature of -100°C. One side of the thin section (hereinafter also referred to as the "ground surface") was grounded on a silicone wafer, and a surface topography image was measured at 10 μm square using the SPM imaging function of a nanoindenter (trade name: Hysitron TI980 Nanoindenter, manufactured by Bruker). Subsequently, measurement positions for the matrix and domain were specified from the acquired surface topography image, and nanoindentation measurement was performed to measure the Young's modulus G1 of the matrix and the Young's modulus G2 of the domain. Fifty points were acquired for each of the matrix and domain, and the arithmetic average values ​​were used. The surface topography image and Young's modulus measurements were performed using a Vickers indenter.

[0106] The obtained conductive roller was evaluated according to the following procedure. <Method for forming developer-derived contaminants> The conductive roller 1 obtained above was incorporated into an electrophotographic process cartridge as a charging roller, and an image was output using an electrophotographic image forming apparatus. The electrophotographic image forming apparatus used was an electrophotographic laser printer (product name: LaserJetProM203dw, manufactured by HP Corporation), and the electrophotographic process cartridge used was one specifically for this electrophotographic image forming apparatus.

[0107] An electrophotographic process cartridge incorporating the charging roller was left in an environment at a temperature of 15°C and a relative humidity of 10% for 24 hours, and then installed in an electrophotographic apparatus main body in the same environment. Then, 60,000 sheets were continuously output until the developer adhered to the surface of the conductive roller 1, causing density unevenness and image streaks in images with a print rate of 1%. Next, the charging roller with the developer-derived contaminants adhered thereto was removed, and the surface of the charging roller was observed with an optical microscope. It was confirmed that a large amount of developer-derived contaminants had adhered to the entire surface of the charging roller. Using the above method, a used conductive roller 1 with developer-derived contaminants adhered thereto was obtained.

[0108] <Preparation of a recycled conductive roller by removing adhered contaminants> A used conductive roller 1 was attached to the device shown in Fig. 4. A spray nozzle 42 was installed at a distance of 2 cm from the surface of the used conductive roller 1 (41 in the figure) so as to face the center of rotation of the conductive roller. The roller was rotated at 60 rpm, and the spray nozzle 42 was moved back and forth in the longitudinal direction of the roller at a speed of 1.3 cm / s while spraying water, thereby obtaining a recycled conductive roller 1.

[0109] The pressure P at which the liquid impacted the conductive roller surface was measured using a pressure measurement film prescale (manufactured by Fujifilm Corporation). Specifically, a prescale was attached to the outer surface of a portion of the conductive roller's longitudinal axis, and liquid pressure was applied to the prescale by spraying it from above. The change in color of the prescale was then converted into pressure using the pressure image analysis system FPD-8010. As a result, the pressure P applied to the conductive roller 1 was 1.0 MPa. The conditions for the pressure image analysis system FPD-8010 were temperature, humidity, and continuous pressure during measurement, and automatic analysis was performed, with the calculated average pressure being taken as the pressure P. A sheet with an appropriate pressure range was used for the prescale, ranging from ultra-low pressure (measurable range 0.6 to 2.5 MPa) to high pressure (50 to 130 MPa), depending on the conditions.

[0110] <Evaluation of characteristics of recycled conductive roller> <Level of removal of contaminants from the surface of the conductive roller by surface observation> The level of removal of contaminants from the surface of the recycled conductive roller after the above-mentioned contaminant removal process was confirmed by visual observation and observation using an optical microscope. "A": No contaminants were observed even under a microscope. "B": Contaminants were confirmed under a microscope, but not by visual observation. "C": Slight contaminants were observed by visual observation. "D": Contaminants were observed visually over the entire area of ​​the roller. The results are shown in Table 7.

[0111] <Current Recovery Rate> The ratio of the post-regeneration current value to the initial current value was calculated as the current recovery rate. Contaminants derived from the developer generally have a higher resistance than conductive rollers, and the conductive roller's resistance increases with the amount of contaminants attached. Furthermore, repeated stress during the regeneration process can change the distance between the electronic conductive agents dispersed in the conductive layer, resulting in increased resistance. Therefore, the current recovery rate can be used as an indicator of the degree of removal of developer-derived contaminants and the change in the distance between the electronic conductive agents on the surface of the conductive layer. The current recovery rate was evaluated according to the following criteria: "A": Current recovery rate of 90% or more; "B": Current recovery rate of 80% or more but less than 90%; "C": Current recovery rate of 60% or more but less than 80%; "D": Current recovery rate of 40% or more but less than 60%. The results are shown in Table 7.

[0112] <Charge Stability Evaluation> When a recycled conductive roller is used as a charging roller, if the removal of developer-derived contaminants is insufficient, further developer-derived contaminants will accumulate on the charging roller surface during reuse, causing minute white spots in the image. The recycled conductive roller 1 obtained above was incorporated into an electrophotographic process cartridge as a charging roller, and an image was output using an electrophotographic image forming apparatus. The electrophotographic image forming apparatus used was an electrophotographic laser printer (product name: LaserJet Pro M203dw, manufactured by HP Corporation), and the electrophotographic process cartridge used was one specifically designed for this electrophotographic image forming apparatus.

[0113] An electrophotographic process cartridge incorporating the charging roller was left in an environment at a temperature of 15°C and a relative humidity of 10% for 24 hours, and then installed in an electrophotographic apparatus in the same environment. Next, 24,000 images were printed on A4-size paper, each with a 4-point "E" printed at a coverage rate of 1%. The electrophotographic image was output in an intermittent mode, in which the rotation of the electrophotographic photosensitive member was stopped for 7 seconds after each image was output. Image output in the intermittent mode involves more friction between the charging roller and the electrophotographic photosensitive member than when electrophotographic images are output continuously, which can be considered a more severe evaluation condition for the charging roller. Next, a halftone image was output, and the resulting image was observed visually and with a magnifying glass and evaluated according to the following criteria: "A": No white dots were observed even with a magnifying glass. "B": No white dots were observed visually. "C": Slight white dots were observed visually. "D": White spots were visually observed over the entire area. The results are shown in Table 7.

[0114] <Examples 2 to 15> [Preparation of conductive rollers 2 to 4 and 6 to 11] Conductive rollers 2 to 4 and 6 to 11 were prepared in the same manner as for conductive roller 1, except that the formulations of the unvulcanized domain rubber composition CMB, the unvulcanized matrix rubber composition MRC, and the unvulcanized rubber composition for forming the conductive layer were changed to the types, types, and amounts of materials shown in Tables 4 to 6.

[0115] [Preparation of Conductive Roller 5] Conductive roller 5 was prepared by using conductive roller 3 and applying a surface layer coating liquid prepared as described below to the outer periphery of the roller to form a surface layer.

[0116] [Preparation of Surface Layer Coating Liquid] Surface layer coating liquid 1 for forming a surface layer was prepared as follows. Under a nitrogen atmosphere, 100 parts by mass of polyester polyol (product name: P3010, manufactured by Kuraray Co., Ltd.) was slowly added dropwise to 27 parts by mass of polymeric MDI (product name: Millionate MR200, manufactured by Nippon Polyurethane Industry Co., Ltd.) in a reaction vessel while maintaining the temperature inside the reaction vessel at 65°C. After completion of the addition, the mixture was allowed to react at 65°C for 2 hours. The resulting reaction mixture was cooled to room temperature to obtain an isocyanate-terminated prepolymer with an isocyanate group content of 4.3%.

[0117] Next, 57.0 parts by mass of the isocyanate-terminated prepolymer, 43.0 parts by mass of the same polyester polyol (trade name: P2010, manufactured by Kuraray Co., Ltd.), and 23 parts by mass of carbon black (trade name: MA230, manufactured by Mitsubishi Chemical Corporation, number average particle diameter 30 nm) were dissolved in methyl ethyl ketone (MEK) to adjust the solids content to 27% by mass. Then, 0.1 parts by mass of modified dimethyl silicone oil (trade name: SH-28PA, manufactured by Dow Corning Toray Silicone Co., Ltd.) was added to prepare a mixed liquid.

[0118] [Formation of Surface Layer by Coating with Surface Layer Coating Liquid] 270 g of the mixed liquid and 200 g of glass beads with an average particle size of 0.8 mm were placed in a 450 mL glass bottle and dispersed for 12 hours using a paint shaker disperser. After dispersion, 15 parts by mass of urethane particles with an average particle size of 7.0 μm (product name: Dimic Beads UCN-5070D, manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.) were added. The mixture was then further dispersed for 15 minutes, and the glass beads were removed to obtain a surface layer coating liquid.

[0119] The conductive roller 5 was oriented with its longitudinal direction in the vertical direction, and its upper end was gripped and immersed (dipped) in the surface layer coating liquid and then pulled up. The immersion time for the dip coating was 9 seconds, and the roller pull-up speed was adjusted so that the initial speed was 20 mm / sec and the final speed was 2 mm / sec, and the speed was changed linearly with time between 20 mm / sec and 2 mm / sec.

[0120] After coating, the coating was air-dried at 23° C. for 30 minutes. Next, the coating was dried in a hot air circulation dryer at 80° C. for 1 hour and then at 160° C. for 1 hour to form a dried film of the surface layer coating liquid on the conductive layer, thereby obtaining a conductive roller 5. Measurement of the current value, confirmation of the phase separation structure and the electronic conductive agent, and measurements of the Young's moduli of the matrix and domain were performed in the same manner as in Example 1. The results are shown in Table 7.

[0121] Example 16 Example 16 was prepared in the same manner as Example 2, except that sodium hydroxide was mixed with the water used in Example 2 to prepare a 0.3 mass % aqueous sodium hydroxide solution.

[0122] Example 17: The roller produced in Example 2 was irradiated with ultraviolet light having a wavelength of 254 nm at an integrated light intensity of 9000 mJ / cm ２ The binder resin on the outermost surface of the surface layer was decomposed by irradiating the surface with ultraviolet light so that the binder resin on the outermost surface of the surface layer was decomposed. A low-pressure mercury lamp (manufactured by Harrison Toshiba Lighting Co., Ltd.) was used for ultraviolet irradiation, and this was used as the conductive roller 12. Example 17 was prepared in the same manner as Example 2, except that the conductive roller 12 was used.

[0123] Example 18 Sodium hydroxide was mixed with the water used in Example 2 to prepare a 0.3% by mass aqueous sodium hydroxide solution. The roller prepared in Example 2 was irradiated with ultraviolet light having a wavelength of 254 nm at an integrated light intensity of 9000 mJ / cm. ２ The binder resin on the outermost surface of the surface layer was decomposed by irradiating the surface with ultraviolet light in a manner such that the binder resin on the outermost surface of the surface layer was decomposed. A low-pressure mercury lamp (manufactured by Harrison Toshiba Lighting Co., Ltd.) was used for ultraviolet irradiation, and this was used as the conductive roller 12. Example 18 was prepared in the same manner as Example 2, except that the conductive roller 12 was used.

[0124] Example 19 Example 19 was prepared in the same manner as Example 2, except that sodium hydrogen carbonate was mixed with the water used in Example 2 to prepare a 1.0 mass % aqueous sodium hydrogen carbonate solution.

[0125] [Regenerated Conductive Rollers 2 to 19] Regenerated conductive rollers 2 to 19 were produced in the same manner as in Example 1, except that developer-derived contaminants were formed in the same manner as in Example 1, and the water pressure P during regeneration to remove the adhered contaminants was changed as shown in Table 7. The contaminant removal level, current value recovery rate, and charging stability of the regenerated conductive rollers were evaluated in the same manner as in Example 1. The results are shown in Table 7.

[0126]

[0127]

[0128]

[0129]

[0130] In Table 7, ECD indicates the ratio (area %) of the total cross-sectional area of ​​the electronic conductive agent contained in the domain based on the total cross-sectional area of ​​the domain. ECM indicates the ratio (area %) of the total cross-sectional area of ​​the electronic conductive agent present in the matrix based on the cross-sectional area of ​​the matrix. M indicates the ratio (area %) of the total area of ​​the matrix to the area of ​​the observation region in observation of the outer surface of the conductive roller. Domain D is the number-average circle-equivalent diameter of the domain, and aggregate D is the number-average circle-equivalent diameter of aggregates of the electronic conductive agent. In the conductive rollers of Examples 1 to 4 and 6 to 19, the matrix and domains were exposed on the outer surface of the conductive roller.

[0131] Table 8 shows whether each of the following conditions was used in each example: sodium hydroxide solution was used as the liquid, the conductive roller was subjected to UV treatment, or sodium bicarbonate solution was used as the liquid. Y indicates that each of the conditions was used.

[0132] Comparative Examples 1 to 3 [Preparation of Conductive Roller 13] Conductive roller 13 was prepared in the same manner as conductive roller 1, except that the unvulcanized rubber composition for forming the conductive layer was changed as shown in Table 9.

[0133]

[0134] [Preparation of Conductive Roller 14] Conductive roller 14 was prepared in the same manner as conductive roller 5, except that the unvulcanized rubber composition for forming the conductive layer was changed as shown in Table 10.

[0135]

[0136] [Recycled Conductive Roller] Recycled conductive rollers 20 to 22 were produced in the same manner as in Example 1, except that developer-derived contaminants were formed in the same manner as in Example 1, and the water pressure during recycling for removing the adhered contaminants was changed as shown in Table 11. The contaminant removal level, current value recovery rate, and charging stability of the recycled conductive rollers were evaluated in the same manner as in Example 1. The results are shown in Table 11.

[0137]

[0138] The raw materials in Table 11 above are as follows: ECO: epichlorohydrin rubber (EO-EP-AGE ternary compound) Epichromer CG102 (manufactured by Osaka Soda Co., Ltd.)

[0139] The present disclosure is not limited to the above-described embodiments, and various modifications and variations are possible without departing from the spirit and scope of the present disclosure. Therefore, the following claims are appended to clarify the scope of the present disclosure. This application claims priority based on Japanese Patent Application No. 2024-103354, filed June 26, 2024, the entire contents of which are incorporated herein by reference.

Claims

1. A method for manufacturing a recycled conductive roller, which includes a contaminant removal step of removing contaminants adhering to the outer surface of the conductive roller, wherein the conductive roller has a support having a conductive outer surface and a conductive layer on the outer surface of the support, the conductive layer having a matrix containing a first rubber and a domain containing a second rubber and an electronic conductive agent, wherein when the Young's modulus of the matrix is ​​G1 (MPa) and the Young's modulus of the domain is G2 (MPa), G1 and G2 satisfy the relationship G1 < G2, and the contaminant removal step includes a step of spraying a liquid onto the surface of the conductive roller to which the contaminants have adhered.

2. The method for producing a recycled conductive roller according to claim 1, wherein G1 and G2 satisfy the relationship G2 / G1≧3.

0.

3. The method for producing a recycled conductive roller according to claim 1 or 2, wherein G1 is 1 to 20 MPa, and G2 is 20 to 100 MPa.

4. A method for producing a recycled conductive roller according to any one of claims 1 to 3, wherein the matrix and the domains are exposed on the outer surface of the conductive roller.

5. A method for manufacturing a recycled conductive roller according to any one of claims 1 to 4, wherein, in cross-sectional observation of the conductive layer in the thickness direction, the ratio of the total cross-sectional area of ​​the electronic conductive agent contained in the domains to the total cross-sectional area of ​​the domains is 20 to 40 area %.

6. A method for manufacturing a recycled conductive roller according to any one of claims 1 to 5, wherein, when observed across a cross section of the conductive layer in the thickness direction, the number average circle-equivalent diameter of the domains is 0.5 to 5.0 μm.

7. A method for manufacturing a recycled conductive roller according to any one of claims 1 to 6, wherein, when a cross section of the conductive layer is observed in the thickness direction, the number average circle-equivalent diameter of the aggregates of the electronic conductive agent in the domain is less than 0.50 μm.

8. A method for manufacturing a recycled conductive roller according to any one of claims 1 to 7, wherein, in the contaminant removal process, the pressure of the liquid colliding with the outer surface of the conductive roller is defined as pressure P, and the pressure P is 0.2 to 10.0 MPa.

9. A method for producing a recycled conductive roller according to any one of claims 1 to 8, wherein at least one group selected from the group consisting of an acidic functional group and a carbonyl group is present on the outer surface of the conductive roller.

10. The method for producing a recycled conductive roller according to claim 9, wherein the liquid is a basic solution.

11. The method for producing a recycled conductive roller according to any one of claims 1 to 10, wherein an acidic functional group is present on the outer surface of the conductive roller, and the liquid contains an aqueous solution of sodium bicarbonate.

12. A method for manufacturing a recycled conductive roller according to any one of claims 1 to 11, wherein, when observing the outer surface of the conductive roller, the ratio of the total area of ​​the matrix to the area of ​​the observation region is 60 to 80 area %.

13. A method for manufacturing a recycled conductive roller according to any one of claims 1 to 12, wherein, when observing a cross section of the conductive layer in the thickness direction, the ratio of the total cross-sectional area of ​​the electronic conductive agent contained in the matrix to the cross-sectional area of ​​the matrix is ​​5 area % or less.

14. A method for producing a recycled conductive roller according to any one of claims 1 to 13, wherein the first rubber has a diene bond.

15. A method for manufacturing a recycled conductive roller according to any one of claims 1 to 14, wherein the first rubber and the second rubber are any of the following combinations: the first rubber is styrene butadiene rubber (SBR) and the second rubber is acrylonitrile butadiene rubber (NBR); the first rubber is acrylonitrile butadiene rubber (NBR) and the second rubber is styrene butadiene rubber (SBR); the first rubber is isoprene rubber (IR) and the second rubber is acrylonitrile butadiene rubber (NBR); the first rubber is butadiene rubber (BR) and the second rubber is acrylonitrile butadiene rubber (NBR).

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