JP2011227144A - Treating method for electrophotographic carrier, recycling method, and electrophotographic carrier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a treating method and a recycling method for an electrophotographic carrier, by which a coating resin is removed from a core material of an electrophotographic carrier, characteristics of the core material are not influenced after removing the coating resin, and even when a coating resin is again applied, sufficient performances as an electrophotographic carrier are imparted to the carrier.SOLUTION: The treating method for a used electrophotographic carrier, where in the electrophotographic carrier comprises a core material and a coating resin coating the core material, and comprises treating of the electrophotographic carrier with a supercritical methanol or sub-critical methanol in a supercritical state so as to remove the coating resin from the core material.

Description

  The present invention is a processing method for recycling and reusing a core material constituting a carrier for electrophotography used in an electrostatic image two-component dry developer used for electrophotography, electrostatic recording, and the like, The present invention relates to a recycling method and an electrophotographic carrier that can be used for reuse.

  The two-component dry developer used in electrophotography is composed of toner and an electrophotographic carrier (hereinafter, sometimes simply referred to as “carrier”). In this two-component dry developer (hereinafter, simply referred to as “developer”), minute toner particles are held on the surface of relatively large carrier particles by electrostatic force generated by friction between both particles. . Then, when approaching the electrostatic latent image, the attractive force in the direction of the electrostatic latent image with respect to the toner particles by the electric field formed by the electrostatic latent image overcomes the binding force between the toner particles and the carrier particles, and the toner particles are electrostatically charged. The electrostatic latent image is visualized by sucking and adhering onto the latent image.

  As the carrier used for the developer, a resin-coated (coated) carrier formed from magnetic particles (core material) and a resin is widely used. This includes a configuration in which a layer mainly composed of a coating resin is formed on the surface of relatively large magnetic particles, and a configuration in which relatively small magnetic powder is uniformly dispersed in the resin. The developer is used repeatedly while replenishing the toner consumed by the development. Therefore, the carrier must be triboelectrically charged with a desired polarity and a sufficient charge amount at all times during long-term use.

  However, conventional developers tend to change their charging characteristics due to mechanical collision such as collision between particles or collision between particles and a developing machine. For example, there may be a case where the surface state changes due to cracking, chipping, peeling or the like on the carrier surface, or a toner film is formed on the carrier surface due to heat generated by the frictional action, so-called spent. In such a case, the charging characteristics of the carrier deteriorate with use time, and the entire developer needs to be replaced. Various improvements have been proposed for the deterioration of the charging characteristics of the carrier. For example, in order to increase the mechanical strength such as cracking, chipping, and peeling of the carrier surface, the coating resin has been improved and the adhesion between the magnetic surface and the coating resin has been improved.

Various resins have been proposed as the coating resin, and there are many proposals of a crosslinkable resin capable of increasing mechanical strength. In general, acrylic resins, polyester resins, silicon resins and the like are used, and are used together with various crosslinking systems and additives.
For example, a method of crosslinking a resin containing a polycarbodiimide resin (for example, see Patent Document 1), a method of crosslinking an acrylic resin having specific physical properties or structure (for example, see Patent Documents 2 and 3), and a coating resin as urethane A method of providing a composite cross-linking structure composed of a bond and a urea bond (for example, see Patent Document 4), a method of using a silicon resin using a specific silane coupling agent (for example, see Patent Document 5), and an alcoholic coating resin A method of crosslinking a resin having a hydroxyl group with a compound having a phenolic hydroxyl group (for example, see Patent Document 6) has been proposed. In addition to this, a method of directly polymerizing a resin on the surface of a magnetic material serving as a core material has also been proposed. For example, a method of interfacial polymerization of a coating resin on the surface of a core material, and a method of crosslinking this (for example, , See Patent Document 7).

  Further, in order to prevent spent, a method of coating various resins on the carrier surface has been proposed. For example, a higher degree of curing is proposed by defining the degree of curing of the silicon resin to be coated (for example, , See Patent Document 8).

  However, these proposals all improve the mechanical strength and stability against heat stress, or prevent spent, so a cross-linked resin is used as the coating resin, and the coating state is the core. It is very strong against the material. For this reason, it is generally difficult to separate the core material from the coating resin, and no consideration is given to such separation between the core material and the coating resin.

  Conventionally, the developer deteriorated by use has been collected and discarded, but recently, environmental destruction due to industrial waste has become a problem, and reuse of the developer has become one of the problems. Regarding the regeneration of the developer, a method (Method A) for removing spent toner on the carrier surface to restore the performance and a carrier coating resin are peeled to obtain a core material, and the coating resin is applied to the core material. A method (method B) for re-installing and restoring performance is known.

  As an example of the former method (Method A), a method is proposed in which the toner that has been spent on the carrier surface is removed by heating, solvent washing, or the like, and the core material is recycled (for example, see Patent Document 9). This method is a method for recycling the resin coated on the core as it is, and according to such a method, it is possible to recycle a carrier whose characteristics are deteriorated mainly due to spent.

  However, if the deterioration of properties is not only spent but also cracking, chipping or peeling of the carrier coating resin, the carrier properties cannot be recovered and reused simply by removing the spent toner. In addition, there are spent toners that are difficult to remove even with the technique described in Patent Document 9, and a more powerful removal method is required. Further, in the case of washing with a solvent, a method with less environmental influence is required in consideration of the post-treatment of the solvent itself.

  On the other hand, as an example of the latter method (Method B), a method in which the recovered developer is heated and regenerated at a high temperature of about 1000 ° F. has been proposed (see, for example, Patent Document 10). According to this method, in a carrier coated with a thermoplastic resin such as an acrylic resin, it is possible to remove the coating resin by the heat treatment as described above. Even in the case of cracking, chipping or peeling, it is possible to reuse the core material by coating again when reused.

  However, when the core material is regenerated by heating the toner using the ferrite-based material provided with the required magnetic properties with the metal suboxide as the core material at a high temperature as described above, the characteristics of the core material are the original. There was a drawback of not returning to. In addition, if this regeneration method by high-temperature heating is a method that reuses heat, the environmental impact can be improved to some extent, but since there are few combustibles such as resins that generate combustion heat among the substances that make up the carrier, efficiency is improved. Thermal recycling cannot be expected.

  Furthermore, even when the above-described regeneration technique using high-temperature heating is applied to a system in which a thermosetting resin is used as the carrier coating resin, there is a drawback that the coating resin cannot be sufficiently peeled from the core material. The inventors have confirmed. In addition, the present inventors, when the coated resin or the product produced by the above-described high-temperature heat treatment remains attached to the core material, the case where the regenerated core material is again coated with the resin as a carrier Comparing the case where a non-recycled new core material coated with resin is used as a carrier, the former is clearly inferior, and the difference in performance is due to the coating resin peeling off. I verified that it was so small. Therefore, in order for the former to exhibit the same performance as the latter, the smaller the residual resin in the recycled core material, that is, the higher the degree of coating peeling is desirable.

For the above reasons, with respect to the conventional two-component developer carrier, the method of separating the coating resin and the core material (magnetic material) and the recycling method cannot reliably remove the coating resin having little influence on the environment. Since the characteristics of the core material are deteriorated, it is not satisfactory in practice.
In fact, the conventional technology can achieve both the conditions for removing the coating resin of the carrier that is chemically and mechanically robust and the conditions that do not impair the performance of the magnetic material imparted with the desired magnetic properties. It was not. In particular, it is applied to granular magnetic materials consisting of predetermined crystal particles of metal suboxide and coating resin, and does not involve oxidation to the oxide or reverse reduction, and does not disturb the crystalline state, thus deteriorating the magnetic properties. There is no prior art relating to the recovery of magnetic material particles. In other words, since the magnetic material used as the core material of the carrier is a suboxide having a specific crystal structure, it is necessary to avoid chemical changes such as oxidation and changes in the crystal structure in the recycling process.

  By the way, as for the decomposition of the resin, a method of decomposing a thermosetting resin in supercritical or subcritical water (for example, see Patent Document 11), chlorine-containing plastic waste is decomposed using water in a supercritical region as a reaction medium. However, a method for converting to oil (for example, see Patent Document 12) has been proposed. These are performed mainly for the purpose of making a large amount of resin waste into a monomer, making it harmless and making it into a raw material, and have proposed conditions suitable for the target object.

  On the other hand, for the purpose of carrier recycling, proposals have been made in which the resin decomposition conditions are defined as subcritical conditions and the fluid used is hydrogen peroxide (see, for example, Patent Document 13). In this method, the specific resin film can be removed to some extent, but the oxidizing action is advanced by the hydrogen peroxide solution, and the characteristics of the granular magnetic material composed of predetermined crystal particles of the metal suboxide are greatly impaired. In particular, the resistance, which is a characteristic of the granular magnetic material, is higher than that of the unused core material due to the influence of the hydrogen peroxide solution, and there is a change (decrease) in the magnetic characteristics, which is not necessarily suitable for recycling. Further, since the hydrogen peroxide solution has a corrosive action, it brings about an undesirable phenomenon that the carrier surface is corroded.

  Also, a method of removing a resin by bringing a carrier whose magnetic surface is coated with a resin layer containing at least a fluororesin into contact with subcritical water so that the subcritical water and carrier are in a specific ratio, and contacting the carrier. Has been proposed (see, for example, Patent Document 14). The releasability of the coating resin with subcritical water and supercritical water is quite good, but variations in the collected developer remain in the core material after peeling. The variation is the usage situation of the user, and the recovery agent of the user with a lot of copy volume (hereinafter recovery agent K) has almost no coating resin, and the recovery agent of the user with less copy volume (hereinafter recovery agent S) The coating resin remains sufficiently. Subcritical water and supercritical water have very good solubility, and the recovery agent K has few coating resins and can be completely peeled off directly. However, the recovery agent S cannot be completely peeled off because the coating resin is thick. In the developer collected from the market, the collecting agent K and the collecting agent S are mixed, and both can be dealt with by reducing the processing amount in order to completely peel off. However, the developer such as the recovery agent K contained in the recovered developer is peeled off directly, and even the oxide film on the core material surface is dissolved. When the oxide film dissolves, the core material resistance value changes.

The present applicant has also proposed a method of separating the coating resin from the magnetic material by treating the carrier composed of the magnetic material and the coating resin under supercritical water or subcritical water conditions (for example, (See Patent Documents 15 to 16).
That is, in the method described in Patent Document 15, the condition is supercritical water or subcritical water, and hydrogen peroxide is used as the water. For this reason, there is a tendency that the characteristics of the granular magnetic material composed of predetermined crystal particles of the metal suboxide are greatly impaired by the use of hydrogen peroxide water.
In the method described in Patent Document 16, distilled water is used as a processing solvent under supercritical or subcritical conditions. This method is effective for the coating film having a uniform residual film amount, but the above-mentioned ones containing the collecting agent K and the collecting agent S such as a developer collected from the market are mixed. Thus, even the oxide film on the surface of some core materials is dissolved. When the oxide film dissolves, the core material resistance value changes.

The first object of the present invention is to remove a resin (coating resin) firmly covering a magnetic material as a core material from the magnetic material in an electrophotographic carrier of a two-component dry developer for electrophotography, and Provided is an electrophotographic carrier processing method and recycling method that does not affect the properties of the core material after removal and can provide sufficient performance as an electrophotographic carrier even if it is coated with a coating resin again. is there. That is, a method for processing an electrophotographic carrier that can reliably remove the coating resin by a method with little environmental impact, can recycle the core material by coating the coating resin again without deteriorating the properties of the core material, and To provide a recycling method.
The second object of the present invention is to provide an electrophotographic carrier core material from which the coating resin is removed, and an electrophotographic carrier in which the electrophotographic carrier core material from which the coating resin is removed is coated with a new coating resin. It is to provide.

  As a result of intensive investigations to achieve the above object, the present inventors have unexpectedly found that the use of supercritical pure methanol is effective in achieving the above object, leading to the present invention. It was. That is, the said objective is achieved by following (1)-(6).

(1): A method for treating a used electrophotographic carrier, wherein the electrophotographic carrier includes a core material and a coating resin for coating the core material, An electrophotographic carrier processing method, wherein the coating resin is removed from the core material by processing with supercritical methanol or subcritical methanol in a critical state.
According to the configuration described in (1) above (that is, a method for separating the coating resin and the core material made of a magnetic material), supercritical methanol or a supercritical methanol in which the electrophotographic carrier in the developer after use is in a supercritical state. It is treated with subcritical methanol, and the coating resin is separated from the core material by solvolysis and / or thermal decomposition, and it is reliably and efficiently separated by a method with less environmental impact compared to the conventional method. Not only can the treatment with a higher removal rate be possible, but the core material itself is not altered.

(2): The method for treating an electrophotographic carrier according to (1), wherein the coating resin is not completely removed from the core material.

(3): In the above (1) or (2), the supercritical methanol has a supercritical temperature in a range of 239 ° C. or more and 320 ° C. or less and a supercritical pressure in a range of 6 MPa or more and 12 MPa or less. It is a processing method of the electrophotographic carrier described.
According to the configuration described in (3) above, there is an effect that decomposition can be performed more efficiently.

(4): A core material from which the coating resin is removed after the coating resin is removed from the core material by the electrophotographic carrier processing method according to any one of (1) to (3) above. An electrophotographic carrier recycling method, wherein the coating resin is re-coated.
According to the configuration described in (4) above, the core material and the coating resin are separated. At the same time or thereafter, the core material is washed, and after drying, the core material is subjected to recycling for the carrier. Previously discarded core material can be reused, which can contribute from the viewpoint of protecting the global environment. In addition, it is possible to recycle an active ingredient such as a resin monomer from the treatment liquid, which also has an effect of protecting the environment by recycling.

(5): The electrophotographic carrier, wherein the coating resin is removed from the core material by the electrophotographic carrier processing method according to any one of (1) to (3) above. It is a core material.

(6): A carrier for electrophotography, wherein the carrier core material for electrophotography described in (5) above is recoated with a coating resin.

According to the present invention, the coating resin is removed from the core material of the electrophotographic carrier, and even after the removal, the coating resin is coated again without affecting the various properties of the core material. It is possible to provide a method for processing and recycling an electrophotographic carrier capable of providing performance.
Further, according to the present invention, it is possible to provide a carrier core material from which the coating resin has been removed, and an electrophotographic carrier in which the carrier core material from which the coating resin has been removed is coated with a new coating resin.

It is a reaction vessel used in the practice of the present invention, (A) is its overall view, (B) shows a state in which a processing sample (electrophotographic carrier) and a fluid (methanol) are accommodated in the reaction vessel. FIG. It is a figure which shows the fluid sand bath for heating the fluid in the said reaction container to predetermined temperature.

An electrophotographic carrier processing method according to the present invention is a used electrophotographic carrier processing method, wherein the electrophotographic carrier includes a core material and a coating resin that covers the core material. The electrophotographic carrier is treated with supercritical methanol or subcritical methanol in a supercritical state to remove the coating resin from the core material.
Next, the electrophotographic carrier processing method according to the present invention will be described in more detail.
Although the embodiments described below are preferred embodiments of the present invention, various technically preferable limitations are attached thereto, but the scope of the present invention is intended to limit the present invention in the following description. Unless otherwise described, the present invention is not limited to these embodiments.

  The method for processing an electrophotographic carrier of the present invention (hereinafter sometimes simply referred to as a carrier) is a supercritical state in which an electrophotographic carrier (treated carrier) composed of at least a core material and a coating resin is in a supercritical state. The coating resin is removed (separated) from the core material by treatment with critical methanol or subcritical methanol. That is, the method of removing (separating) the coating resin and the core material (magnetic material) of the carrier to be treated according to the present invention separates the carrier to be treated in a used developer under supercritical methanol or subcritical methanol conditions. Then, the coating resin is separated from the magnetic substance by the action and dissolution action by solvolysis and / or thermal decomposition.

  Methanol used for supercritical methanol in the present invention is not particularly problematic as long as it is at a reagent level, but when impurities are included, there is a concern about damage to the core material quality during supercritical processing, and Depending on the object, the resin removal (separation) effect is weakened. For example, it is not preferable to use a water (water) or hydrogen peroxide solution having a strong sterilizing and decomposing action because the carrier core material quality is impaired by the oxidizing action in addition to the removal and separation of the coating resin film.

  The mixing ratio of the carrier to be processed and the fluid (methanol) in contact with the supercritical state at the time of the separation process is not generally determined, but when the separation process is completed by one operation, the fluid ( The weight of methanol) is preferably equal to or greater than the weight of the carrier to be treated, so that good coating removal can be performed.

  However, if all the coating layers are removed, an extra coating solution is required for re-coating, resulting in an extra cost. One reason for using methanol is that if a highly soluble solvent such as water or hydrogen peroxide is used in a supercritical state, the solvent is peeled regardless of the remaining film state. The recovery agent for users with a large amount of copy volume (hereinafter referred to as recovery agent K) has less coating resin, so it can be completely peeled off directly. Cannot be peeled off. In the developer collected from the market, the collecting agent K and the collecting agent S are mixed, and both can be dealt with by reducing the processing amount in order to completely peel off. However, the developer such as the recovery agent K contained in the recovered developer is peeled off directly, and even the oxide film on the core material surface is dissolved. When the oxide film dissolves, the core material resistance value changes.

  Considering the above background, the mixing ratio of the carrier to be treated and the fluid (methanol) in contact with the supercritical state during the separation treatment is such that the weight of the fluid (methanol) is equal to or more than the weight of the carrier to be treated. It is preferable that the ratio is less than twice, so that even if there are variations in the recovery agent, uniform coating removal can be performed and the core material characteristics are not affected. Methanol is not highly soluble compared to water or hydrogen peroxide solution, and it cannot remove even the coating film (coating resin) of the recesses against the unevenness of the core material surface. Although it is preferable if the remaining film (remaining coating resin) can be uniformly peel-controlled with a thin layer, it is technically difficult. By leaving the coating resin in the recesses, in other words, by not completely removing the coating resin, the coating liquid on the recesses becomes unnecessary, depending on the coating thickness, but rather than coating from the beginning. , About 1/3 to 1/5 can reduce the coating liquid.

  In the electrophotographic carrier processing method of the present invention, it is preferable that the separation process with supercritical methanol is performed for 1 to 90 minutes. Although depending on the properties of the resin used for coating and the temperature and pressure conditions of supercritical methanol, it is preferably 1 to 60 minutes.

  Furthermore, the electrophotographic carrier processing method of the present invention is a structure in which a carrier to be processed is coated with a coating resin crosslinked to a core material, and a coating resin that is difficult to dissolve in a solvent or the like is supercritical or subcritical. This is a method for separating a coating resin and a magnetic material (core material) by performing a separation treatment in methanol.

  Furthermore, in the method for processing an electrophotographic carrier of the present invention, the carrier to be processed has a structure in which a core material made of a magnetic material is coated with a silicon resin alone or a silicon / acrylic resin combination, and is easily decomposed by combustion or the like. By treating a difficult coating resin (silicone resin or the like) in methanol in a supercritical state, the coating resin and the magnetic material are separated.

  Furthermore, the electrophotographic carrier processing method of the present invention is a structure in which a resin film composed of a silicon resin alone or a silicon / acrylic resin combination is coated on at least a core material of a carrier to be processed, which is a magnetic material, This is a method of reliably separating a magnetic material by treating a silicon-coated resin, which is difficult to separate with various separation means such as a solvent, an acid, a base and combustion, with methanol in a supercritical state.

  The composite form of the electrophotographic carrier and the magnetic material targeted by the present invention includes a structure in which a layer mainly composed of a coating resin is formed on the surface of a relatively large magnetic particle, and a relatively small magnetic material in the resin. There is a configuration in which the powder is uniformly dispersed. The present invention can be applied to any configuration.

  The magnetic material (core material) contained in the electrophotographic carrier targeted by the present invention may be a conventionally known magnetic material such as a ferromagnetic metal such as iron, cobalt and nickel, magnetite, hematite, ferrite and the like. Examples include alloys and composites of the ferromagnetic fine particles and a resin. The average particle diameter of these magnetic particles is usually 10 to 1000 μm. However, depending on the magnetic material, it is subject to oxidation and hydrolysis under supercritical methanol conditions, and therefore a magnetic material that is more stable in such an environment is preferable. For example, suitable target magnetic materials include metal oxides. Among them, typical ones include ferrite and magnetite. Since ferrite is stable in supercritical methanol, the separation operation can be performed without altering the core material itself. However, even if it is a magnetic substance that is susceptible to alteration by methanol in the supercritical state, this can be avoided by setting the remaining film state of the coating resin to an appropriate temperature, pressure, treatment time, additives, etc. It is.

  In the separation operation, the treatment with supercritical methanol is preferably performed under non-acidic conditions, and more preferably under non-oxidizing and non-reducing conditions in order to prevent alteration of the magnetic substance.

  The carrier magnetic material recycling method of the present invention comprises treating the carrier under supercritical methanol conditions, separating the coating resin from the core material by the action of solvolysis and / or thermal decomposition and dissolution, and simultaneously with this. Alternatively, after that, the core material is separated, and at the same time or thereafter, the core material is washed, dried, and then recycled to the carrier.

  In the process of recovering, washing and drying the core material, it passes through a sieve having a coarse screen, for example, the coated resin layer is not yet separated, or a magnetic material having a large particle size exceeding the desired particle size due to unintentional reasons. It is possible to remove and pass a sieve having a fine screen to remove a magnetic substance having a small particle diameter that has become smaller than a desired particle diameter due to, for example, wear or collision.

  Of course, when the core material is recycled again as the carrier core material, a virgin core material may be mixed and used. Furthermore, it is possible to recycle active ingredients such as resin monomers from the treatment liquid. In addition, the method for separating the coating resin and the core material of the carrier of the present invention is a decomposition product of substances constituting the developer (toner and electrophotographic carrier) contained in supercritical methanol brought into contact with the carrier to be processed. Alternatively, by reducing the dissolved matter with time, it is possible to reliably separate the coating resin from the carrier, which is an object to be processed with a large amount of non-decomposed matter, and to perform heat-efficient treatment. The carrier core material from which the coating resin is separated can be coated with a new resin (preferably a silicone resin) to form a carrier.

  Silicone resin as used in the present invention refers to all generally known silicon resins, such as straight silicon consisting only of organosilosan bonds and silicon resins modified with alkyd, polyester, epoxy, acrylic, urethane, etc. Although it is mentioned, it is not restricted to this. For example, as commercially available products, straight silicone resins include KR271, KR255, KR152 manufactured by Shin-Etsu Chemical, SR2400, SR2406, SR2410 manufactured by Toray Dow Corning Silicone. In this case, it is possible to use the silicon resin alone, but it is also possible to simultaneously use other components that undergo a crosslinking reaction, charge amount adjusting components, and the like. Further, as modified silicone resins, KR206 (alkyd modified), KR5208 (acrylic modified), ES1001N (epoxy modified), KR305 (urethane modified) manufactured by Shin-Etsu Chemical, SR2115 (epoxy modified) manufactured by Toray Dow Corning Silicone Co., Ltd. , SR2110 (alkyd modified) and the like.

  Moreover, an acrylic resin may be used in combination with the coating resin. Acrylic resin has strong adhesiveness and low brittleness, so it has very excellent properties in terms of wear resistance, and it is difficult for deterioration such as coating film scraping and film peeling to occur. In addition, the particles contained in the coating layer such as conductive particles can be firmly held due to the strong adhesiveness. In particular, a powerful effect can be exhibited in holding particles having a particle size larger than the coating layer thickness.

  The acrylic resin referred to in the present invention refers to all resins having an acrylic component, and is not particularly limited. In addition, it is possible to use the acrylic resin alone, but it is also possible to use at least one other component that undergoes a crosslinking reaction at the same time. Examples of other components that undergo a crosslinking reaction include amino resins and acidic catalysts, but are not limited thereto. The amino resin here refers to guanamine, melamine resin and the like, but is not limited thereto. Moreover, what has a catalytic action can be used with an acidic catalyst here. For example, it has a reactive group such as a fully alkylated type, a methylol group type, an imino group type, and a methylol / imino group type, but is not limited thereto.

  Acrylic resin has excellent adhesion properties and low brittleness, so it has excellent wear resistance. On the other hand, its surface energy is high, so when it is combined with easily spent toner, toner component spent accumulates. In some cases, problems such as a decrease in charge amount due to the occurrence of charging. In this case, the problem can be solved by using a silicone resin that has an effect that it is difficult to spend the toner component because the surface energy is low and film accumulation occurs and the accumulation of the spent component is difficult to proceed. However, since silicon resin has weak adhesiveness and high brittleness, it also has a weak point that it has poor wear resistance. Therefore, it is important to obtain a good balance between the properties of these two types of resins, which makes it difficult to spend. It is possible to obtain a coating film having wear characteristics.

  In addition, in the carrier used in the present invention, a conductivity imparting material may be dispersed in the coating layer in order to control the volume resistivity. The conductivity imparting agent to be dispersed may be a conventionally known one, and the surface treated fine particles such as carbon black, titanium oxide, zinc oxide, indium oxide, tin oxide-antimony oxide, tin oxide-indium oxide as conductive fine particles, etc. The conductive fine particles can be used. When the conductive fine particles are other than colorless or white, the conductive fine particles are mixed in the toner due to the scraping of the coating layer, which causes color smearing in the color image.

  In addition, in the carrier coating layer, a silane coupling agent, a titanium coupling agent, etc. are added for the purpose of improving the adhesiveness with the core particles (nuclear particles) or improving the dispersibility of the conductivity-imparting agent. It may be added.

As the coupling agent used in the present invention, a coupling agent such as a silane coupling agent, a titanate coupling agent, and an aluminum coupling agent can be used.
As the silane coupling agent, one having a hydrophobic group, an amino group or an epoxy group can be used. Examples of the silane coupling agent having a hydrophobic group include vinyltrichlorosilane, vinyltriethoxysilane, and vinyltris (β-methoxy) silane. Examples of silane coupling agents having an amino group include γ-aminopropylethoxysilane, N-β (aminoethyl) -γ-aminopropyltrimethoxysilane, and N-β (aminoethyl) -γ-aminopropylmethyldimethoxysilane. N-phenyl-γ-aminopropyltrimethoxysilane and the like. Examples of the silane coupling agent having an epoxy group include γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltriethoxysilane, β- (3,4-epoxycyclohexyl) trimethoxysilane, and the like. .
Examples of the titanium coupling agent include isopropyl triisostearoyl titanate, isopropyl tridodecylvinsen sulfonyl titanate, isopropertris (dioctyl pyrophosphate) titanate, and the like.

  The carrier targeted by the present invention is actually recovered as a developer after use. Although this is a mixture of toner and carrier, supercritical processing may be performed in the state of this mixture, but it is desirable to separate toner that can be easily separated in advance. As this separation method, a mesh having a mesh size smaller than that of the carrier may be used, and the toner may be separated by air blowing and suction. However, toner spent on the carrier cannot be easily separated. About this, you may combine with the pre-process which carries out a supercritical process. For example, cleaning with a solvent or heat treatment may be performed. However, even if a small amount of toner is mixed at the time of supercritical processing, the coating resin and the magnetic material can be separated without any problem.

In the present invention, the supercritical methanol for treating the carrier may be appropriately adjusted at least in the range of temperature: 230 to 320 ° C. and pressure: 6 to 12 MPa, preferably temperature: 239 to 320 ° C., pressure: 6 to 12 MPa, more preferably temperature: 280 to 320 ° C., pressure: 8 to 12 MPa. By satisfying such conditions, the coating resin can be efficiently decomposed.
Among these ranges, a more preferable range is adjusted by the thickness of the coating resin of the target carrier and the configuration of the magnetic body (core material). That is, the conditions are suitable such that the coating resin decomposes rapidly but the magnetic material does not change in quality. Further, the temperature and pressure conditions of supercritical methanol are preferably as high as possible so that the treatment time can be shortened.

  In the method for separating the carrier coating resin and the magnetic material of the present invention, it is not necessary to separate all the coating resins contained in the carrier. As described above, even if there is a variation in the recovery agent, it is sufficient that uniform coating removal can be performed. In this state, the film of the convex part is removed with respect to the irregularities on the surface of the core material, and is removed to the extent that the film of the concave part remains. The degree is difficult to express numerically and varies depending on the unevenness of the core material to be reused. That is, it is necessary to remove the coating layer to such an extent that the coating layer does not vary when the coating is applied. When there is a variation in the coating layer, it is a variation in individual particles, and the resistance value changes. This causes problems such as initial carrier adhesion.

  In addition, after the carrier is supercritically processed, the magnetic material used for the carrier can be coated with the resin again by performing the steps of washing the magnetic material to remove deposits, and then drying it. It becomes. In the step of cleaning the magnetic material and removing the adhering matter, the adhering matter can be more reliably removed by applying mechanical friction to the surface of the core material, for example, while stirring. Further, an ultrasonic cleaner or the like may be used.

1 and 2 show an example of an apparatus suitably used for carrying out the method of the present invention.
FIG. 1A is an overall view of the reaction vessel 1, for example, material: SUS316, inner diameter: 8.5 mm, wall thickness: 2.1 mm, and internal volume: 6 cc. The upper and lower sides of the container are screwed and fixed so that the internal pressure does not fluctuate. FIG. 1B shows a state in which the reaction container 1 is filled with the processing sample S and the fluid L (methanol).

  FIG. 2 is an overall view of the fluidized sand bath 2, and the upper part is opened when the reaction vessel 1 is charged and taken out, but at other times the lid is closed and the peripheral wall is doubled. The cylindrical state of the structure is exhibited. A fluidized sand 2a such as alumina powder is accommodated in the bath 2, and a heater 21 is disposed in the double wall so as to heat the fluidized sand 2a. On the other hand, heated air is blown from the bottom of the fluid sand bath 2 so that the fluid sand 2a flows. In the figure, 3 is a compressor and 22 is a heater.

  When the fluid sand 2a of the fluid sand bath 2 reaches the set temperature, the reaction vessel 1 filled with the processing sample S and the fluid L is put into the fluid sand 2a for a predetermined time. Then, when the heating set time is reached, the reaction vessel 1 filled with the processing sample S and fluid L is taken out from the fluid sand 2a, put into a cooling tank containing ice or the like (not shown), and rapidly cooled. Return to. Through these processes, the coating resin in the processed sample S is separated from the core material.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.
[Example 1]
The manufacture example of the carrier for electrophotography which this invention makes object is shown.
<Prescription of carrier coating resin layer>
Silicone resin solution 432.2 parts by weight [solid content 23% by weight (SR2410: manufactured by Toray Dow Corning Silicone)]
-Titanium chelate catalyst 1.0 part by weight [solid content 100% by weight (TC-750: manufactured by Matsumoto Fine Chemical Co., Ltd.)]
Aminosilane 1.50 parts by weight [solid content 100% by weight (SH6020: manufactured by Toray Dow Corning Silicone)]
Filler: 110 parts by weight of conductive alumina EC-700 [manufactured by Titanium Industry Co., Ltd., particle size 0.40 μm, true specific gravity 4.2, particle powder specific resistance 5 Ω · cm]
・ 900 parts by weight of toluene

The carrier coating resin layer formulation was dispersed with a homomixer for 10 minutes to obtain a silicon resin coating film forming solution A. Using an average particle diameter of 5000 parts by weight as an average particle diameter: 35 μm sintered ferrite powder (magnetization: 68 Am ² / kg) as a core material, the above-mentioned coating film forming solution A is coated on a surface of the core material with a spiral coater (0.30 μm). Applied to the coater at a temperature of 40 ° C. and dried. The obtained carrier was fired in an electric furnace at 200 ° C. for 1 hour. After cooling, the ferrite powder bulk was crushed using a sieve having an aperture of 63 μm to obtain [Carrier A] having a volume resistivity of 13.9 [Log (Ω · cm)] and a magnetization of 64 Am ² / kg. A method for measuring magnetization (magnetic characteristics) will be described later.

  The developer A was obtained by mixing 93 parts by weight of the carrier particles A and 7 parts by weight of a commercially available toner (manufactured by RICOH, imgio toner type 7). Using this developer A in a copying machine imgio MP5000 (manufactured by Ricoh), running evaluation of 300,000 sheets was performed on an image chart having a 50% image area in a single color mode to obtain a deterioration agent AS. On the other hand, 300,000 running evaluations were performed using an image chart with an image area of 0.5% in the monochromatic mode to obtain a deterioration agent AK. At this time, the thickness of the coating layer of the deterioration agent AS was 0.25 μm with respect to the initial carrier A: 0.30 μm. Moreover, the coating layer thickness of the deterioration agent AK was 0.10 μm excluding the portion where the core material was exposed.

  In addition, the thickness of the coating layer of the carrier is obtained from the average value by observing the cross section of the carrier using a transmission electron microscope (TEM), measuring the thickness of the resin portion of the coating layer covering the carrier surface. Specifically, only the thickness of the resin part existing between the surface of the carrier core material and the particles is measured. The thickness of the resin part existing between the particles and the thickness of the resin part on the inorganic fine particles are not included in the measurement.

(Treatment with supercritical methanol)
Into a pressure resistant reaction vessel (internal volume 10 ml) made of SUS316, 0.5 part by weight of the processing sample (deteriorating agent) AK, 0.5 part by weight of the processing sample (deteriorating agent) AS, and 2.7 parts by weight of the methanol reagent are charged. Pressurized argon gas of 1 Mpa was supplied from the upper part of the pressure-resistant reaction vessel, pressurized, allowed to stand for 1 minute, and then depressurized to atmospheric pressure over about 30 seconds. This pressurization and depressurization operation was repeated three times, and after replacing the gas in the pressure resistant reactor with argon gas, the vessel was sealed. The container was then placed in a fluidized sand bath heated to 230 ° C. Thereby, the temperature in the pressure resistant reactor reaches 230 ° C. and the pressure reaches 6.6 MPa. After 1 hour, it was taken out, put into ice water and rapidly cooled.

  The pressure-resistant reaction container was opened and the reaction product was taken out into a glass container. In the reaction product taken out into the glass container, relatively large black-gray particles settled, and these were ferrite particles. In addition, methanol was suspended in a cloudy color, and this was the dissolution of the coating layer and filler (conductive alumina) particles in the coating layer. In addition, a slightly oily component adhered to the wall surface of the glass container.

  After removing the supernatant liquid in the glass container, 100 ml of pure water having an electric conductivity of 0.98 μS · cm was added to the glass container, and after washing for 5 minutes in an ultrasonic washing machine, only settled particles (black gray particles) Was taken out and dried in a constant temperature dryer at 100 ° C. for 1 hour to obtain an evaluation sample AH.

As a result, the resin film was removed to some extent when the evaluation sample AH was observed with a scanning electron microscope. The thickness of the coating layer in the evaluation sample AH (observation with the above-mentioned TEM) was 0.12 μm on average. Actual measurement data varied from 0.08 to 0.18 μm. The magnetic properties of AH were 66 Am ² / kg.

(Coating layer thickness variation)
The thickness of the coating layer was observed by the above-mentioned TEM, but the difference between the maximum value and the minimum value of the thickness data was 0.05 μm or less, ◯, and more than 0.05 μm and 0.10 μm or less Δ And those larger than 0.10 μm were evaluated as x. As a result, in Example 1, as described above, the difference between the maximum value and the minimum value of the thickness data was 0.10 μm. ○ △ was accepted and × was rejected.

(Evaluation of magnetic properties)
In order to confirm the change in magnetic characteristics, magnetic characteristics were measured. The measuring instrument measured saturation magnetization, residual magnetization, and coercive force with a small fully automatic vibrating sample magnetometer: VSM-C7-10A (manufactured by Toei Kogyo Co., Ltd.).
For magnetic property evaluation, the change rate is 3% or less with respect to the saturation magnetization value of the core material before coating (when 1 KOe is applied), the change rate is over 3% to 6% or less, and the change rate. A value exceeding 6% was evaluated as x. ○ △ was accepted and × was rejected.
As a result, in Example 1, as described above, the rate of change was 2.94%.

Using AH obtained by peeling off the coating layer, coating treatment was performed in the same manner as when [Carrier A] was obtained. At this time, the amount of the silicon resin coating film forming solution A was reduced to 2/3 for coating treatment. As the core surface coating layer, [Carrier A1] having 0.30 μm, volume resistivity: 13.8 [Log (Ω · cm)], and magnetization: 64 Am ² / kg was obtained.

  A developer A1 was obtained by mixing 93 parts by weight of the carrier particles A1 and 7 parts by weight of a commercially available toner (manufactured by RICOH, imgio toner type 7). Carrier adhesion evaluation was performed using this developer A1 in a copying machine imgio MP5000 (manufactured by Ricoh Co., Ltd.). The number of edge carriers attached on the photosensitive member was 61, and the number of white spots (image portions) was 15.

[Carrier adhesion]
The developer is set in the copier imagio MP5000 (manufactured by Ricoh), and the charging potential is set to DC 740 V and the developing bias is set to 600 V (the background potential is fixed to 140 V), and the dot forming halftone is adhered to the developed photoreceptor surface. The number of carriers was counted in five fields of view by magnifying glass, and the average number of adhered carriers per 100 cm ² was taken as the edge carrier adhesion amount. Evaluation was as follows: ○: 60 or less, Δ: 61 or more and 80 or less, ×: 81 or more, ○ △ was accepted and x was rejected.

  Further, white spots (image part) were set to a charging potential of DC 740 V and a developing bias of 600 V (the background potential was fixed to 140 V), a full-color image (A3 size) was output, and the number of white spots on the image was counted. Evaluation was as follows: ○: 10 or less, Δ: 11 or more and 20 or less, ×: 21 or more, ○ △ was accepted and x was rejected.

[Example 2]
0.5 parts by weight of the treated sample AK obtained in the same manner as in Example 1 and 0.5 parts by weight of the treated sample AS were charged with 0.9 parts by weight of a methanol reagent, and 1 Mpa of pressurized argon gas was added from the upper part of the pressure resistant reactor. After supplying and pressurizing for 1 minute, the pressure was released to atmospheric pressure over about 30 seconds. This pressurization and depressurization operation was repeated three times, and after replacing the gas in the pressure resistant reactor with argon gas, the vessel was sealed. The container was then placed in a fluidized sand bath heated to 300 ° C. Thereby, the temperature in the pressure resistant reactor reaches 300 ° C. and the pressure reaches 10 MPa. Thereafter, the same processing as in Example 1 was performed to obtain an evaluation sample BH.

As a result, when the evaluation sample BH was observed with a scanning electron microscope, the resin film was removed to some extent. The thickness of the coating layer in the evaluation sample BH (observation by the above-mentioned TEM) was 0.08 μm on average. Actual measurement data varied from 0.05 to 0.10 μm. The magnetic property of BH was 67 Am ² / kg. As described above, the difference between the maximum value and the minimum value of the thickness data was 0.05 μm. The magnetic property evaluation was 67 Am ² / kg against the saturation magnetization value of the core material before coating (when 1 KOe was applied) 68 Am ² / kg, so the rate of change was 1.47%.

Using BH obtained by peeling off the coating layer, coating treatment was performed in the same manner as when [Carrier A] was obtained. At this time, the amount of the silicon resin coating film forming solution A was reduced to 7/10 for coating. A core surface coating layer of 0.30 μm, volume resistivity: 13.7 [Log (Ω · cm)], and magnetization: 64 Am ² / kg [Carrier B1] was obtained.
In the same manner as in Example 1, the carrier adhesion was evaluated using [Carrier B1].

Example 3
Volume specific resistance: 13.1 [Log (Ω · cm)], Magnetization: 65 Am, except that the coating resin layer formulation is changed to the acrylic resin and silicon resin formulations described below. ² / kg of [Carrier C] was obtained.

<Prescription of carrier coating resin layer>
-Acrylic resin solution 17.1 parts by weight [solid content 50% by weight]
-Guanamine solution 4.85 parts by weight [solid content 70% by weight]
Acid catalyst 0.10 parts by weight [solid content 40% by weight]
・ Silicon resin solution 216.2 parts by weight [solid content 23 wt% (SR2410: manufactured by Toray Dow Corning Silicone)]
Aminosilane 1.68 parts by weight [solid content 100% by weight (SH6020: manufactured by Toray Dow Corning Silicone)]
-Titanium chelate catalyst 0.5 part by weight [solid content 100% by weight (TC-750: manufactured by Matsumoto Fine Chemical Co., Ltd.)]
Inorganic oxide fine particles B Aluminum oxide 97 parts by weight [particle size: 0.37 μm, true specific gravity 3.9]
・ Toluene 1600 parts by weight

  A developer C was obtained by mixing 93 parts by weight of [Carrier C] thus obtained and 7 parts by weight of a commercially available toner (manufactured by RICOH, imagio toner type 7). Running was performed in the same manner as in Example 1 to obtain a deterioration agent. The coating layer thickness of the deterioration agent CS was 0.17 μm with respect to the initial carrier C: 0.22 μm. Moreover, the coating layer thickness of the deterioration agent CK was 0.06 μm except for the portion where the core material was exposed.

  0.5 parts by weight of the treated sample CK and 0.5 parts by weight of the treated sample CS are charged with 0.9 parts by weight of a methanol reagent, 1 Mpa of pressurized argon gas is supplied from the upper part of the pressure-resistant reaction vessel, and after pressurization and left for 1 minute The pressure was released to atmospheric pressure over about 30 seconds. This pressurization and depressurization operation was repeated three times, and after replacing the gas in the pressure resistant reactor with argon gas, the vessel was sealed. The container was then placed in a fluidized sand bath heated to 300 ° C. Thereby, the temperature in the pressure resistant reactor reaches 300 ° C. and the pressure reaches 10 MPa. Thereafter, the same processing as in Example 1 was performed to obtain an evaluation sample CH.

As a result, the resin film was removed to some extent when the evaluation sample CH was observed with a scanning electron microscope. The thickness of the coating layer in the evaluation sample CH (observation by the above-mentioned TEM) was 0.06 μm on average. Actual measurement data varied from 0.05 to 0.10 μm. The magnetic property of CH was 67 Am ² / kg. As described above, the difference between the maximum value and the minimum value of the thickness data was 0.05 μm. The magnetic property evaluation was 67 Am ² / kg against the saturation magnetization value of the core material before coating (when 1 KOe was applied) 68 Am ² / kg, so the rate of change was 1.47%.

Using CH obtained by peeling off the coating layer, coating treatment was performed in the same manner as when [Carrier C] was obtained. At this time, the amount of the coating film forming solution containing the silicon resin and the acrylic resin was reduced to ½ to perform the coating treatment. A core surface coating layer of 0.23 μm, volume resistivity: 13.3 [Log (Ω · cm)], and magnetization: 65 Am ² / kg [Carrier C1] was obtained.
As in Example 1, the carrier adhesion was evaluated using [Carrier C1].

[Comparative Example 1]
The processing sample put into the pressure-resistant reaction vessel is the same processing sample AK 0.2 part by weight as in Example 1, and the processing sample AS 0.2 part by weight hydrogen peroxide water (concentration 3%) 0.9 part by weight, In the same manner as in Example 1, an evaluation sample DH was obtained. At this time, the temperature in the pressure resistant reactor reaches 380 ° C. and the pressure reaches 25 MPa.

As a result, the observation result of the evaluation sample DH with a scanning electron microscope (SEM) was that the coating layer on the particle surface was completely removed, and observation with TEM was not performed. However, the magnetic property result was 60 Am ² / kg, which was a very large drop of 11.76% compared to the physical properties of the carrier core material before use.

Using DH obtained by peeling off the coating layer, coating treatment was performed in the same manner as when [Carrier A] was obtained. The amount of the silicon resin coating film forming solution A at this time was not reduced, but the same amount was coated. [Carrier D1] having a core surface coating layer of 0.30 μm, volume resistivity: 11.7 [Log (Ω · cm)], and magnetization: 57 Am ² / kg was obtained.
As in Example 1, the carrier adhesion was evaluated using [Carrier D1].

[Comparative Example 2]
As in Comparative Example 1, under the supercritical processing conditions, except that the hydrogen peroxide water of the supercritical processing fluid was replaced with distilled water (electrical conductivity: 1.6 μS · cm), the same as in Comparative Example 1, An evaluation sample EH was obtained.
As a result, in the observation of the evaluation sample EH scanning electron microscope (SEM), the surface coating layer of the particles was completely removed, and the observation by TEM was not performed. However, the magnetic property result was 63 Am ² / kg, which was a significant decrease of 7.35% compared to the physical properties of the carrier core material before use.

Using EH obtained by peeling off the coating layer, coating treatment was performed in the same manner as when [Carrier A] was obtained. The amount of the silicon resin coating film forming solution A at this time was not reduced, but the same amount was coated. The core material surface coating layer was 0.30 μm, volume resistivity: 12.5 [Log (Ω · cm)], and magnetization: 60 Am ² / kg [Carrier E1].
As in Example 1, the carrier adhesion was evaluated using [Carrier E1].

  Regarding the carriers A1 to E1 of Examples 1 to 3 and Comparative Examples 1 and 2, Table 1 shows the carrier used and the characteristic values after the run, Table 2 shows the characteristic values after the peeling treatment, 3 shows the characteristic value after re-coating and the obtained carrier evaluation (results of evaluation of the physical properties of the carrier core material and the carrier).

  As is clear from the results of the above evaluation, according to the method for removing (separating) the core material composed of the coating resin of the carrier and the magnetic material of the present invention, the resin is reused again without affecting the properties of the core material after the removal. Even if it coats, there exists an effect which brings sufficient performance as a carrier.

1 Reaction vessel 2 Fluid sand bath 2a Fluid sand (alumina powder)
3 Compressor 22 Heater

JP 05-127432 A JP 05-216282 A JP 05-216283 A Japanese Patent Laid-Open No. 05-197211 Japanese Patent Laid-Open No. 07-114221 Japanese Patent Application Laid-Open No. 08-87137 Japanese Patent Laid-Open No. 06-194881 Japanese Examined Patent Publication No. 62-61948 Japanese Patent Laid-Open No. 06-149132 JP-A-47-12286 Japanese Patent Laid-Open No. 10-24274 Japanese Patent Laid-Open No. 09-111249 JP 2007-206614 A Japanese Patent No. 4244197 Japanese Patent No. 3847534 Japanese Patent No. 3853159

Claims (6)

A method for processing a used electrophotographic carrier,
The electrophotographic carrier includes a core material and a coating resin that covers the core material,
A method for processing an electrophotographic carrier, comprising: treating the electrophotographic carrier with supercritical methanol or subcritical methanol in a supercritical state to remove the coating resin from the core material.   The method for processing an electrophotographic carrier according to claim 1, wherein the coating resin is not completely removed from the core material.   3. The electrophotographic carrier according to claim 1, wherein the supercritical methanol has a supercritical temperature in a range of 239 ° C. or more and 320 ° C. or less and a supercritical pressure in a range of 6 MPa or more and 12 MPa or less. Processing method.   After removing the said coating resin from the said core material with the processing method of the carrier for electrophotography of any one of Claims 1-3, the coating resin is recoated on the core material from which the said coating resin was removed. A method for recycling an electrophotographic carrier characterized by the above.   An electrophotographic carrier core material, wherein the coating resin is removed from the core material by the electrophotographic carrier processing method according to claim 1.   An electrophotographic carrier, wherein the carrier core material for electrophotography according to claim 5 is coated again with a coating resin.