Conductive urethane foam, method for producing conductive urethane foam, and conductive roller

Abstract

To provide a conductive urethane foam which requires less burden on a conductive agent impregnation process and offers a stable chargeability imparting effect, and to provide a conductive roller.SOLUTION: A conductive urethane foam of the present invention has an impregnation solution, containing a conductive agent and a binder resin, impregnated in a surface layer of a urethane foam base material, where the binder resin contains at least one selected from an acrylic resin and silicone resin, and the impregnation solution contains a low molecular weight siloxane compound.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a conductive urethane foam, a method for producing the conductive urethane foam, and a conductive roller. [Background technology]

[0002] Generally, as shown in FIG. 1, the developing section of an electrophotographic image forming apparatus such as a copying machine or a printer is provided with an image forming body 11 such as a photosensitive body that holds an electrostatic latent image, a developing roller 12 that comes into contact with the image forming body 11 and causes toner 20 carried on its surface to adhere to make the electrostatic latent image visible, and a toner supply roller 13 that supplies toner to the developing roller 12. An image is formed through a series of processes in which toner 15 is transported from a toner storage section 14 to the image forming body 11 via the toner supply roller 13 and the developing roller 12.

[0003] Of these, the toner supply roller 13 may have a conductive elastic material such as urethane foam formed on the outer periphery of the shaft via an adhesive layer in order to avoid damaging the developing roller 12 that it comes into contact with and to increase the contact area of ​​the roller to ensure a good grip. The functions required of the toner supply roller 13 include toner transportability and toner charging ability, and various measures are taken to satisfy these functions.

[0004] For example, Patent Documents 1 to 3 disclose a technology that reduces the electrical resistance of the toner supply roller, reduces the toner charge amount (Q / M), and increases the toner transport amount (M / A) by impregnating the polyurethane foam that makes up the toner supply roller with a treatment liquid containing a conductive agent such as conductive carbon black. Furthermore, Patent Document 4 discloses a conductive elastic roller in which a foamed polyurethane structure supported by a rotating shaft is impregnated with conductive liquid silicone rubber, with the aim of enhancing the stable charging effect and obtaining good images (improving the stability of the roller). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Unexamined Patent Publication No. 115433 / 1983 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-319315 [Patent Document 3] Japanese Patent Application Laid-Open No. 2003-215905 [Patent Document 4] Japanese Patent Application Laid-Open No. 2003-262997 Summary of the Invention [Problem to be solved by the invention]

[0006] The techniques disclosed in Patent Documents 1 to 4 have made it possible to enhance the electrostatic charge imparting effect to a certain extent. However, the techniques disclosed in Patent Documents 1 to 4 all require the process of impregnating the urethane foam with the conductive material to be carried out multiple times (six or more times), which increases the burden on the manufacturing process. Furthermore, in the techniques of Patent Documents 1 to 4, the process of impregnating the urethane foam with a conductive agent takes time and effort, which can result in variations in resistance depending on the part of the resulting urethane foam, and there is also the problem that a sufficient electrostatic charge imparting effect cannot be obtained.

[0007] Therefore, an object of the present invention is to provide a conductive urethane foam and a method for manufacturing the conductive urethane foam that achieves stable chargeability while minimizing the burden of the impregnation treatment with a conductive agent. Another object of the present invention is to provide a toner supply roller that has a high chargeability and excellent stability. [Means for solving the problem]

[0008] The present inventors conducted extensive research to solve the above-mentioned problems on conductive urethane foam, in which the surface layer of a urethane foam substrate is impregnated with an impregnation liquid containing a conductive agent and a binder resin. As a result, they found that by using at least one binder resin selected from the group consisting of an acrylic resin and a silicone resin and further including a low-molecular-weight siloxane compound in the impregnation liquid, the penetration rate of the impregnation liquid into the urethane foam substrate can be increased, the burden required for the impregnation process can be significantly reduced, and the impregnation process can be carried out more efficiently and stably, resulting in a conductive urethane foam with no variation in resistance and with a stable charge-imparting effect.

[0009] That is, the conductive urethane foam of the present invention is a conductive urethane foam in which the surface layer of a urethane foam substrate is impregnated with an impregnation liquid containing a conductive agent and a binder resin, characterized in that the binder resin contains at least one selected from acrylic resins and silicone resins, and the impregnation liquid further contains a low-molecular-weight siloxane compound. By providing the above-mentioned configuration, the burden required for the impregnation treatment of the conductive agent is reduced, and a stable chargeability imparting effect can be achieved.

[0010] Furthermore, in the conductive urethane foam of the present invention, the molecular weight of the siloxane compound is preferably 500 to 1,000, because this allows for more efficient and stable impregnation treatment while preventing elution from the urethane foam substrate.

[0011] Furthermore, in the conductive urethane foam of the present invention, the content of the siloxane compound in the impregnation liquid is preferably 2% by mass or more, because this allows the impregnation treatment to be carried out more efficiently and stably.

[0012] Furthermore, in the conductive urethane foam of the present invention, it is preferable that the binder resin contains at least an acrylic resin, because this allows the impregnation treatment to be carried out efficiently and increases the strength of the surface layer.

[0013] The method for producing a conductive urethane foam of the present invention comprises a step of impregnating the surface layer of a urethane foam substrate multiple times with an impregnation liquid containing a conductive agent and a binder resin, wherein the binder resin contains at least one selected from an acrylic resin and a silicone resin, and the impregnation liquid further contains a low molecular weight siloxane compound. By providing the above-mentioned configuration, a high charge imparting effect and excellent stability can be realized.

[0014] In addition, in the method for producing a conductive urethane foam of the present invention, the number of times that the urethane foam substrate is impregnated with the impregnation liquid is preferably three or less, because this allows the impregnation treatment to be carried out more efficiently.

[0015] Furthermore, in the method for producing a conductive urethane foam of the present invention, the molecular weight of the siloxane compound is preferably 500 to 1,000, because this allows the impregnation treatment to be carried out more efficiently and stably while preventing elution from the urethane foam substrate.

[0016] The conductive roller of the present invention is characterized by using the conductive urethane foam of the present invention described above. By providing the above-mentioned configuration, there is no variation in resistance, and a stable chargeability imparting effect can be realized.

[0017] Furthermore, in the conductive roller of the present invention, it is preferable that the conductive urethane foam constitutes the outermost layer of the conductive roller, because a stable chargeability-imparting effect can be achieved without providing an outermost layer such as a protective layer. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide a conductive urethane foam and a method for manufacturing the conductive urethane foam, which realize a stable chargeability-imparting effect with a small burden on the impregnation process of the conductive agent, and also to provide a toner supply roller with a high chargeability-imparting effect and excellent stability.

[0019] In addition, in the method for producing a conductive urethane foam of the present invention, the number of times that the urethane foam substrate is impregnated with the impregnation liquid is preferably three or less, because this allows the impregnation treatment to be carried out more efficiently. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a partial cross-sectional view schematically illustrating an example of an image forming apparatus. [Figure 2] 1 is a cross-sectional view schematically illustrating an embodiment of a toner supply roller of the present invention. [Figure 3] 1 is a graph showing the resistance values ​​and variations thereof of conductive urethane foams obtained in Examples and Comparative Examples. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, one embodiment of the present invention will be described with reference to the drawings as necessary. <Conductive urethane foam> The conductive urethane foam of the present invention is obtained by impregnating the surface layer of a urethane foam substrate with an impregnation liquid containing a conductive agent and a binder resin. By impregnating the surface layer of the urethane foam substrate with an impregnation liquid containing a conductive agent and a binder resin, a chargeability imparting effect can be exhibited, and a good image can be obtained.

[0022] (urethane foam base material) The urethane foam substrate constituting the conductive urethane foam of the present invention is not particularly limited, and known urethane foams can be used appropriately depending on the application and purpose.

[0023] The urethane foam base material can be produced, for example, by mixing and foaming a compound having two or more active hydrogens and a compound having two or more isocyanate groups together with additives such as a catalyst, a blowing agent, and a foam stabilizer, followed by foaming and curing. For example, the urethane foam base material can be produced by mixing a single diol mixture containing two single diols having an average molecular weight difference of 800 to 3600 with a polyether polyol containing a total amount of 50 mass% or more of the polyol component, an isocyanate, water, a catalyst, and a blowing agent, foaming the mixture, and leaving it to stand.

[0024] Here, the term "single diol" is used to collectively refer to one type of diol or two or more types of diols whose difference in average molecular weight is within 400. The term "difference in average molecular weight" refers to the difference in average molecular weight between the diols in question, and when there are many different combinations, it is used to particularly refer to the largest difference.

[0025] Examples of the polyol component used in producing the prepolymer include polyether polyols obtained by addition polymerization of ethylene oxide and propylene oxide, polytetramethylene ether glycol, polyester polyols obtained by condensation of an acid component and a glycol component, polyester polyols obtained by ring-opening polymerization of caprolactone, and polycarbonate diols.

[0026] In the present invention, examples of the polyether polyol used in producing the urethane foam substrate include (A) a polyether polyol of the type in which only propylene oxide is added to diethylene glycol, (B) a polyether polyol of the type in which propylene oxide and ethylene oxide are block or randomly added to diethylene glycol, and (C) a polyether polyol of the type in which, for example, acrylonitrile or styrene is grafted onto the (A) or (B). Among these, the (A) type polyether polyol is preferred in order to exert a greater effect.

[0027] Examples of initiators used to produce the polyether polyol include polyhydric alcohols, polyhydric phenols, mono- or polyamines, and others. Polyhydric alcohols and polyhydric phenols are preferred, and polyhydric alcohols are more preferred. Examples include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-butanediol, and 1,4-butanediol. Of these, diethylene glycol is particularly preferred.

[0028] The polyether polyol component may also contain polyol components other than diols. Examples of such polyol components include trifunctional polyols typically used in the production of urethane foam substrates, such as those obtained by adding an alkylene oxide such as propylene oxide to a glycerin base, or those obtained by randomly or block-adding two alkylene oxides such as propylene oxide and ethylene oxide, and examples of multifunctional polyether polyols include those obtained by adding the same compounds as those described above to a sucrose base.

[0029] Examples of polyether polyols obtained by addition polymerization of ethylene oxide and propylene oxide include those obtained by addition polymerization of ethylene oxide and propylene oxide using starting materials such as water, propylene glycol, ethylene glycol, glycerin, trimethylolpropane, hexanetriol, triethanolamine, diglycerin, pentaerythritol, ethylenediamine, methyl glucoside, aromatic diamines, sorbitol, sucrose, and phosphoric acid. However, those using water, propylene glycol, ethylene glycol, glycerin, trimethylolpropane, and hexanetriol as starting materials are particularly preferred. Regarding the ratio of ethylene oxide and propylene oxide added and the microstructure, the ratio of ethylene oxide is preferably 2 to 95% by mass, more preferably 5 to 90% by mass, and ethylene oxide is preferably added to the terminal. Furthermore, the arrangement of ethylene oxide and propylene oxide in the molecular chain is preferably random.

[0030] When water, propylene glycol, or ethylene glycol is used as the starting material, the polyether polyol is bifunctional, with a weight-average molecular weight preferably in the range of 300 to 6000, and more preferably in the range of 3000 to 5000. When glycerin, trimethylolpropane, or hexanetriol is used as the starting material, the polyether polyol is trifunctional, with a weight-average molecular weight preferably in the range of 900 to 9000, and more preferably in the range of 4000 to 8000. Furthermore, a bifunctional polyol and a trifunctional polyol can also be blended as appropriate.

[0031] Polytetramethylene ether glycol can be obtained, for example, by cationic polymerization of tetrahydrofuran, and one having a weight-average molecular weight in the range of 400 to 4,000, particularly 650 to 3,000, is preferably used. It is also preferable to blend polytetramethylene ether glycols with different molecular weights. Furthermore, polytetramethylene ether glycol obtained by copolymerizing alkylene oxides such as ethylene oxide and propylene oxide can also be used.

[0032] Furthermore, it is also preferable to blend polytetramethylene ether glycol with a polyether polyol obtained by addition polymerization of ethylene oxide and propylene oxide, in which case the blend ratio by mass is preferably in the range of 95:5 to 20:80, and more preferably in the range of 90:10 to 50:50.

[0033] In addition to the polyol component, polymer polyols obtained by modifying polyols with acrylonitrile, polyols obtained by adding melamine to polyols, diols such as butanediol, polyols such as trimethylolpropane, and derivatives thereof can also be used in combination.

[0034] The polyisocyanate component may be an aromatic isocyanate or a derivative thereof, an aliphatic isocyanate or a derivative thereof, or an alicyclic isocyanate or a derivative thereof. Among these, aromatic isocyanates or derivatives thereof are preferred, and tolylene diisocyanate (TDI) or a derivative thereof, diphenylmethane diisocyanate (MDI) or a derivative thereof, or polymethylene polyphenyl polyisocyanate or a derivative thereof is particularly preferred, and may be used alone or in combination.

[0035] Examples of tolylene diisocyanate or its derivatives include crude tolylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, mixtures of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, and urea-, biuret-, and carbodiimide-, and urethane-modified products with polyols. Examples of diphenylmethane diisocyanate or its derivatives include diphenylmethane diisocyanate or its derivatives obtained by phosgenating diaminodiphenylmethane or its derivatives. Derivatives of diaminodiphenylmethane include polynuclear compounds, such as pure diphenylmethane diisocyanate obtained from diaminodiphenylmethane and polymeric diphenylmethane diisocyanate obtained from polynuclear compounds of diaminodiphenylmethane. Regarding the number of functional groups in the polymeric diphenylmethane diisocyanate, a mixture of pure diphenylmethane diisocyanate and polymeric diphenylmethane diisocyanates with various functionalities is typically used. The average functionality is preferably 2.05 to 4.00, more preferably 2.50 to 3.50. Derivatives obtained by modifying these diphenylmethane diisocyanates or their derivatives, such as urethane-modified products with polyols, dimers formed by uretidione formation, isocyanurate-modified products, carbodiimide / uretonimine-modified products, allophanate-modified products, urea-modified products, and biuret-modified products, can also be used. Blends of several diphenylmethane diisocyanates and their derivatives can also be used.

[0036] The prepolymerization method includes placing a polyol and an isocyanate in a suitable container, thoroughly stirring them, and incubating the mixture at 30 to 90°C, preferably 40 to 70°C, for 6 to 240 hours, more preferably 24 to 72 hours. In this case, the ratio of the amounts of polyol and isocyanate is preferably adjusted so that the isocyanate content of the resulting prepolymer is 4 to 30% by mass, more preferably 6 to 15% by mass. If the isocyanate content is less than 4% by mass, the stability of the prepolymer may be impaired, causing the prepolymer to harden during storage, making it unusable. If the isocyanate content exceeds 30% by mass, the content of unprepolymerized isocyanate increases, and this polyisocyanate hardens via a reaction mechanism similar to that of a one-shot process, which does not involve a prepolymerization reaction with the polyol component used in the subsequent polyurethane curing reaction, thereby reducing the benefits of using the prepolymer method.

[0037] The catalyst used in the curing reaction of the urethane foam substrate is not particularly limited, and examples thereof include monoamines such as triethylamine and dimethylcyclohexylamine, diamines such as tetramethylethylenediamine, tetramethylpropanediamine, and tetramethylhexanediamine, triamines such as pentamethyldiethylenetriamine, pentamethyldipropylenetriamine, and tetramethylguanidine, cyclic amines such as triethylenediamine, dimethylpiperazine, methylethylpiperazine, methylmorpholine, dimethylaminoethylmorpholine, and dimethylimidazole, dimethylaminoethanol, dimethylaminoethoxyethanol, and trimethylaminoethanol. Examples of suitable catalysts include alcohol amines such as aminoethylethanolamine, methylhydroxyethylpiperazine, and hydroxyethylmorpholine, ether amines such as bis(dimethylaminoethyl)ether and ethylene glycol bis(dimethyl)aminopropyl ether, and organometallic compounds such as stannous octoate, dibutyltin diacetate, dibutyltin dilaurate, dibutyltin mercaptide, dibutyltin thiocarboxylate, dibutyltin dimaleate, dioctyltin mercaptide, dioctyltin thiocarboxylate, phenylmercury propionate, and lead octenate. These catalysts may be used alone or in combination of two or more.

[0038] (binder resin) In the conductive urethane foam of the present invention, the impregnation liquid that impregnates the surface layer contains a binder resin, and the binder resin contains at least one selected from the group consisting of an acrylic resin and a silicone resin. By using these resins as binder resins, impregnation into the urethane foam substrate after impregnation can be carried out efficiently, and changes in the hardness and rebound resilience of the urethane foam can also be suppressed.

[0039] Here, the surface layer of the urethane foam substrate refers to a layer formed by coating the skeleton of the urethane foam with an impregnation liquid containing a conductive agent and a binder resin. In the present invention, a certain level of chargeability can be achieved as long as at least the surface is impregnated with the impregnation liquid, so there are no particular restrictions on the thickness of the surface layer (the layer impregnated with the impregnation liquid). Furthermore, the impregnation liquid may be impregnated into at least a portion of the surface layer of the urethane foam, but from the viewpoint of minimizing changes in the hardness and impact resilience of the urethane foam, it is preferable to impregnate the surface layer of the entire urethane foam substrate.

[0040] The content of at least one resin selected from the group consisting of acrylic resin and silicone resin contained in the binder resin is not particularly limited as long as it allows the surface layer of the urethane foam substrate to be impregnated with the resin. For example, the content (total content) of at least one resin selected from the group consisting of acrylic resin and silicone resin can be 50% by mass or more, 70% by mass or more, or 100% by mass of the binder resin. The content of the binder resin in the impregnation liquid is not particularly limited, and can be, for example, about 20 to 30% by mass.

[0041] Furthermore, the content of at least one resin selected from acrylic resin and silicone resin in the conductive urethane foam of the present invention is preferably 0.3 to 20 mass% and more preferably 5 to 10 mass% relative to 100 mass parts of the urethane foam base material. This is because changes in the hardness and resilience of the urethane foam can be further suppressed. If the content of the silicone resin is less than 0.3 mass parts relative to 100 mass parts of the urethane foam base material, the carbon may not adhere to the urethane foam and may fall off. If the content exceeds 20 mass%, the physical properties of the conductive urethane foam may change, and changes in hardness and resilience may not be sufficiently suppressed.

[0042] The binder resin preferably contains at least an acrylic resin, because this allows the impregnation treatment to be carried out efficiently and increases the strength of the surface layer. The acrylic resin is not particularly limited as long as it is a polymer of acrylic acid ester or methacrylic acid ester, but an acrylonitrile-alkyl acrylate copolymer is preferably used. Furthermore, the acrylic resin may be a commercially available acrylic resin, and may be used alone or in combination.

[0043] Furthermore, the type of silicone resin contained in the binder resin is not particularly limited as long as it is a polymer compound having a main skeleton formed by siloxane bonds, and a suitable silicone resin can be selected and used according to the purpose and application.For example, from the viewpoint of improving the processability and adhesion for impregnating the silicone resin into the urethane foam substrate, it is preferable that the silicone resin is a silicone resin composed of a liquid silicone gel base material and a curing agent.Examples of such silicone resins include addition reaction type liquid silicone resins and heat vulcanization type millable silicone resins that use peroxide for vulcanization. Furthermore, from the viewpoint of further suppressing changes in the hardness and impact resilience of the urethane foam, it is preferable that the silicone resin be at least one selected from the group consisting of peroxide-cured silicones, condensation-type thermosetting silicones, addition-type thermosetting silicones, and cationic UV-cured silicones. The silicone resin is a polymer compound having a main skeleton formed by siloxane bonds, and is different from the low-molecular-weight siloxane compounds described below.

[0044] Furthermore, the binder resin may further contain, in addition to the above-mentioned acrylic resin and silicone resin, acrylic resins such as acrylic acid-styrene copolymer resin and acrylic acid-vinyl acetate copolymer resin, polyvinyl alcohol, polyacrylamide, polyvinyl chloride resin, urethane resin, vinyl acetate resin, butadiene resin, epoxy resin, alkyd resin, melamine resin, chloroprene rubber, etc., within the range that does not impair the effects of the present invention. These components may be used alone or as a mixture of two or more.

[0045] The impregnation liquid may contain an appropriate amount of water or a solvent such as toluene or ethyl acetate in addition to the binder resin. The solvent is preferably added so that the viscosity of the impregnation liquid is about 5 to 300 cps (25°C). By adjusting the viscosity of the impregnation liquid to fall within the above range, the impregnation and adhesion process becomes easier.

[0046] (Conductive agent) The impregnation liquid further contains a conductive agent. The conductive agent is a material that can impart conductivity to the urethane foam substrate by impregnating the urethane foam substrate with the binder resin. Specific examples of the conductive agent include carbon conductive agents, ionic conductive agents, and electronic conductive agents, and these can be used alone or in combination. Among the above-mentioned conductive agents, it is preferable to use a carbon conductive agent, since it can provide an excellent chargeability-imparting effect while keeping costs down.

[0047] Examples of the carbon conductive agent include gas blacks such as denka black, ketjen black, and acetylene black, oil furnace blacks including ink blacks, thermal blacks, channel blacks, and lamp blacks.

[0048] Furthermore, the content of the carbon conductive agent in the conductive urethane foam of the present invention is preferably 5 to 25 parts by mass, and particularly preferably 10 to 20 parts by mass, per 100 parts by mass of the urethane foam base material, because this can further suppress changes in the hardness and impact resilience of the urethane foam while imparting good conductivity.

[0049] Examples of the ion conductive agent include ammonium salts such as perchlorates, chlorates, hydrochlorides, bromates, iodates, hydrofluoroborates, sulfates, alkyl sulfates, carboxylates, and sulfonates of tetraethylammonium, tetrabutylammonium, dodecyltrimethylammonium (e.g., lauryltrimethylammonium), hexadecyltrimethylammonium, octadecyltrimethylammonium (e.g., stearyltrimethylammonium), benzyltrimethylammonium, and modified fatty acid dimethylethylammonium; and perchlorates, chlorates, hydrochlorides, bromates, iodates, hydrofluoroborates, trifluoromethyl sulfates, and sulfonates of alkali metals and alkaline earth metals such as lithium, sodium, potassium, calcium, and magnesium.

[0050] Examples of the electronic conductive agent include conductive metal oxides such as tin oxide, titanium oxide, and zinc oxide, and metals such as nickel, copper, silver, and germanium.

[0051] (Siloxane compounds) The conductive urethane foam of the present invention is characterized in that the impregnation liquid further contains a low molecular weight siloxane compound. The impregnation liquid contains a low-molecular-weight siloxane compound, which reduces the surface tension and increases the rate at which the impregnation liquid penetrates the urethane foam substrate. This increases the efficiency of the impregnation process, thereby reducing the burden on the impregnation process. Furthermore, because the impregnation process is carried out stably and efficiently, the resulting conductive urethane foam of the present invention exhibits consistent resistance and exhibits a stable chargeability-imparting effect.

[0052] The siloxane compound must have a low molecular weight, preferably 300 to 1,500, and more preferably 500 to 1,000. When the molecular weight of the siloxane compound is 300 or more, the impregnation liquid does not elute from the urethane foam substrate, and when the molecular weight of the siloxane compound is 1,500 or less, the surface tension can be further reduced, allowing the impregnation process to be carried out more efficiently and stably.

[0053] The siloxane compound may be any compound having a siloxane bond, and may be unmodified or modified. Examples of the siloxane compound include polydimethylsiloxane, polyether-modified polydimethylsiloxane, and polymethylalkylsiloxane. These siloxane compounds may be used singly or in combination of two or more.

[0054] The content of the siloxane compound in the impregnation liquid is preferably 2% by mass or more, more preferably 5% by mass or more, and even more preferably 8% by mass or more, from the viewpoint of performing the impregnation treatment more efficiently and stably. Furthermore, the content of the siloxane compound in the impregnation liquid is preferably 40% by mass or less, from the viewpoint of preventing saturation of the effect.

[0055] The impregnation liquid may further contain other additives as needed. Examples of such additives include antifoaming agents, surfactants, and charge control agents. The content of these additives is preferably 0.001 to 10 parts by mass, and more preferably 0.001 to 1 part by mass, per 100 parts by mass of the impregnation liquid.

[0056] <Method of manufacturing conductive urethane foam> Next, a method for producing the conductive urethane foam of the present invention will be described. The method for producing a conductive urethane foam of the present invention includes a step of impregnating a surface layer of a urethane foam substrate with an impregnation liquid containing a conductive agent and a binder resin multiple times, The binder resin contains at least one selected from an acrylic resin and a silicone resin, and the impregnation liquid further contains a low-molecular-weight siloxane compound. By using at least one binder resin selected from the group consisting of acrylic resin and silicone resin, and further including a low-molecular-weight siloxane compound in the impregnation liquid, the rate at which the impregnation liquid penetrates the urethane foam substrate can be increased, significantly reducing the burden required for the impregnation process and enabling the impregnation process to be carried out more efficiently and stably. As a result, the resulting conductive urethane foam has no variation in resistance and achieves a stable charge-imparting effect.

[0057] The conditions for the urethane foam substrate, the conductive agent, the binder resin, the siloxane compound, etc. are the same as those explained in the conductive urethane foam of the present invention.

[0058] Furthermore, as described above, the method for producing a conductive urethane foam of the present invention can significantly reduce the burden of the impregnation treatment, i.e., the number of times the urethane foam substrate is impregnated with the impregnation liquid can be reduced. Specifically, from the viewpoint of performing the impregnation treatment more efficiently and reducing the burden, the number of times is preferably three or less, and more preferably two or less.

[0059] <Conductive roller> The toner conductive roller of the present invention is characterized by using the conductive urethane foam of the present invention described above. By using the conductive urethane foam of the present invention, a toner supply roller that is highly effective in providing chargeability and has excellent stability can be realized.

[0060] The conductive roller is a roller member that has conductivity and exhibits a chargeability-imparting effect, and examples thereof include a toner supply roller, a charging roller, a developing roller, a transfer roller, etc. Among these, the conductive roller of the present invention is preferably used as a toner supply roller.

[0061] The toner supply roller is, for example, a roller 13 for supplying toner 15 to a developing roller 12, as shown in FIG. 1, and has electrical conductivity. Fig. 2 is a schematic diagram showing an example of the toner supply roller of the present invention, which comprises a shaft 1 and a conductive urethane foam 3 of the present invention supported on the outer periphery of the shaft 1 via an adhesive layer 2.

[0062] The shaft 1 used in the toner supply roller is not particularly limited and can be any material. Examples include metal shafts such as those made of sulfur-free cutting steel or other steel plated with nickel or zinc, solid metal cores made of iron, stainless steel, aluminum, or other metals, and hollowed-out metal cylinders. In the present invention, it is preferable that the diameter of the shaft 1 be less than 6 mm, e.g., 5.0 mm, and the thickness of the conductive urethane foam 3 of the present invention be less than 4.5 mm, e.g., 4.0 mm. This not only reduces the weight of the roller, but also increases the macroscopic elastic modulus of the urethane foam due to the thin layer of the conductive urethane foam 3 of the present invention, thereby improving toner scraping performance. Furthermore, the thin layer of the conductive urethane foam 3 of the present invention reduces the volume of the urethane foam, thereby reducing the amount of toner contained in the conductive urethane foam 3 of the present invention during endurance printing, thereby reducing toner consumption.

[0063] 2, it is preferable that the toner supply roller has an adhesive layer 2 between the shaft 1 and the charge-controlled conductive urethane foam 3. The adhesive used for the adhesive layer 2 is preferably a hot-melt polymer adhesive having a melting point of 120°C or higher, particularly 130°C to 200°C, and containing an adipate-based polyurethane resin as its main component. The adhesive may be in any form, such as a film or pellets. The thickness of the adhesive layer 2 is preferably 20 to 300 μm; if it is too thin, poor adhesion occurs, and if it is too thick, suitable roller resistance cannot be obtained, so neither is preferable. The melting temperature of the adhesive during adhesion is preferably 100°C or higher, particularly 130°C to 200°C, which is lower than the melting point of the adhesive. This puts the adhesive layer 2 into a semi-molten state, and reduces the roller resistance when 5 V is applied to 10 6 ~10 8 Ω, the roller resistance when 100V is applied is 10 2 ~10 4 It becomes easier to control the Ω and voltage dependency, and it becomes possible to increase the density at the beginning of printing durability.

[0064] The toner supply roller 13 can be manufactured, for example, by forming the conductive urethane foam 3 of the present invention on the outer periphery of the shaft 1, optionally via an adhesive, and then heat-bonding the shaft 1 and the conductive urethane foam 3 of the present invention at a predetermined temperature. For example, first, an impregnation solution containing a binder resin and additives is prepared. A block of urethane foam (16 mm x 1000 mm x 2000 mm) that has not been subjected to membrane removal treatment is immersed in a bath filled with this impregnation solution, compressed between two rolls, and then released to impregnate the urethane foam with the impregnation solution. The foam is then guided above the bath and passed through nip rolls to squeeze out and remove excess impregnation solution. The foam is then heated and dried in a hot air oven at 110°C for 10 minutes to produce a charge-controlled urethane foam 3. The conductive urethane foam 3 of the present invention that can be molded using this method has a lower hardness than that obtained by mechanical gas injection, specifically, an Asker F hardness of 30 to 90°.

[0065] An adhesive film is formed around the outer periphery of shaft 1 by wrapping a film adhesive around it or by melting and applying a pellet-like adhesive. A hole is then drilled in conductive urethane foam 3 of the present invention, and shaft 1 with the adhesive is inserted into the hole. Heating is then performed at a predetermined temperature to integrate shaft 1 and conductive urethane foam 3 of the present invention via adhesive layer 2. The surface of conductive urethane foam 3 of the present invention is polished to form the desired cylindrical shape, and the ends of conductive urethane foam 3 of the present invention are then cut to form the desired shape, thereby obtaining toner supply roller 13. [Example]

[0066] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0067] (Samples 1-8) Under the conditions shown in Table 1, a polyurethane foam substrate (manufactured by Bridgestone Corporation, density 55 kg / m 3 , hardness 80 (Ask-F), breathability 100cc / cm 2 Conductive urethane foam samples were produced by impregnating the surface layer of a 1000-kJ / sec (1000-kJ / sec) sheet with an impregnation solution containing 18% by mass of conductive agent (carbon black: Mikuni Pigment Co., Ltd.'s "PSM Black A898," solids content 40%), 7% by mass of binder resin (acrylic resin (acrylonitrile-alkyl acrylate copolymer emulsion): Enex Co., Ltd.'s "BS-050301-1," solids content 50%), and additives as shown in Table 1. The number of times the impregnation process was performed is shown in Table 1. Thereafter, the following evaluations were carried out on each of the prepared conductive urethane foam samples of the Examples and Comparative Examples.

[0068] (Evaluation of the effect of imparting chargeability) For each sample of conductive urethane foam, the resistance value (Log Ω·cm) was measured using a Loresta GX MCP-T700 manufactured by Mitsubishi Chemical Analytech Co., Ltd., at an applied voltage of 90 V. Measurements were taken five times for each sample, and the average values ​​are shown in Figure 3.

[0069] [Table 1]

[0070] *1 Polyoxyethylene alkyl ether, "Leocol SC-90" manufactured by Lion Specialty Chemicals Co., Ltd., molecular weight: 923 *2 Polyether-modified polydimethylsiloxane, BYK "BYK349", molecular weight: 901-1640 *3 Polyether-modified polydimethylsiloxane, BYK "BYK3450", molecular weight: 808 *4 Polyether-modified polydimethylsiloxane, BYK "BYK3451", molecular weight: 941

[0071] The results in Table 1 and Figure 3 show that the conductive urethane foams of each Example, despite being impregnated twice, have lower resistance and better conductivity than the conductive urethane foam of Comparative Example 1. On the other hand, for each sample of the Comparative Examples, although a certain level of conductivity was achieved by performing the impregnation process nine times (Sample 2), it was found that good conductivity was not achieved by performing the impregnation process two times. [Industrial Applicability]

[0072] According to the present invention, it is possible to provide a conductive urethane foam and a method for manufacturing the conductive urethane foam, which realize a stable chargeability-imparting effect with a small burden on the impregnation process of the conductive agent, and also to provide a toner supply roller with a high chargeability-imparting effect and excellent stability. [Explanation of symbols]

[0073] 1 axis 2 Adhesive layer 3 Conductive urethane foam 11 Image forming body 12 Developing roller 13 Toner supply roller 14 Toner storage compartment 15 Toner

Claims

1. A conductive urethane foam obtained by impregnating a surface layer of a urethane foam substrate with an impregnation liquid containing a conductive agent and a binder resin, the binder resin includes at least one selected from an acrylic resin and a silicone resin, The conductive urethane foam is characterized in that the impregnation liquid further contains a siloxane compound having a molecular weight of 500 to 1,000.

2. 2. The conductive urethane foam according to claim 1, wherein the content of the siloxane compound in the impregnation liquid is 2% by mass or more.

3. 3. The conductive urethane foam according to claim 1, wherein the binder resin contains at least an acrylic resin.

4. A method for producing a conductive urethane foam, comprising a step of impregnating a surface layer of a urethane foam substrate with an impregnation liquid containing a conductive agent and a binder resin multiple times, the binder resin includes at least one selected from an acrylic resin and a silicone resin, A method for producing a conductive urethane foam, wherein the impregnation liquid further contains a siloxane compound having a molecular weight of 500 to 1,000.

5. 5. The method for producing a conductive urethane foam according to claim 4, wherein the number of times the urethane foam substrate is impregnated with the impregnation liquid is three or less.

6. A conductive roller, characterized by using the conductive urethane foam according to any one of claims 1 to 3.

7. 7. The conductive roller according to claim 6, wherein the conductive urethane foam constitutes an outermost layer of the conductive roller.

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