JP2007206614A - Processing method for electrophotographic carrier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a processing method for rapidly and effectively removing a predetermined resin that coats the surface of a magnetic material without giving any adverse influence on the characteristics of the magnetic material constituting a carrier, and to provide a method for advantageously recycling the carrier by taking out the magnetic material with the coating resin removed from the carrier, reusing the magnetic material as it is and again coating the surface with a predetermined resin. <P>SOLUTION: The carrier comprising a magnetic material the surface of which is coated with a predetermined resin layer is brought into contact with sub-critical water containing hydrogen peroxide at a temperature of 280°C or lower and a pressure of at least 0.1 MPa or more so as to remove the resin that coats the surface of the magnetic material of the carrier. The magnetic material with the coating resin layer removed is used as it is, and a predetermined resin is applied on the surface of the magnetic material to obtain a desired carrier. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for treating an electrophotographic carrier, and more particularly to an effective method for treating a used carrier having a surface coated with a predetermined resin such as a fluorine resin.

  In recent years, awareness of environmental conservation has increased rapidly. In the fields of electrophotographic copying machines, laser printers, facsimiles, printing machines, etc., various improvements have been made to reuse recovered parts in order to meet such environmental conservation requirements. It has been. For example, in a copying machine, various devices arranged so as to surround a photosensitive member can be easily attached and detached, and various devices after a certain use state are removed. Each part is collected, and after its function is restored through processes such as disassembly and cleaning, it is again attached to the copying machine. In this way, recently, the cycle of reuse has been slow, leading to an improvement in the recovery rate and consequently to environmental conservation.

  However, in a copying machine or the like, an electrophotographic carrier that constitutes a two-component developer together with a toner is configured by firmly coating a predetermined resin on the surface of fine particles. From some places, it is difficult to reuse and recycle, and even if it is collected, it has been taken up without being treated in any way, such as being landfilled or incinerated at high temperatures. It also causes a reduction in the recycling rate of parts. Among them, in particular, in a carrier in which the surface of fine magnetic particles is coated with a fluororesin, it is preferably used from the viewpoint of favorably controlling the chargeability. When a carrier coated with a fluororesin is treated at high temperature in the furnace, an acid gas is generated and the furnace material is damaged. In addition, a decomposition gas generated by the high temperature treatment, particularly hydrofluoric acid (hydrofluoric acid), is not suitable. Have problems such as being extremely toxic.

  On the other hand, an electrophotographic carrier is one of the basic materials in copying technology, and its powder characteristics including its electromagnetic characteristics, mechanical characteristics, and surface characteristics need to be controlled severely. is there. For this reason, when recycling the carrier, it is necessary to avoid adverse effects on these characteristics, which is also one of the causes of reluctance to recycle the carrier for electrophotography. It is.

  By the way, as one of the techniques used for carrier recovery, a resin coated with a magnetic material can be melted, carbonized, decomposed, etc. in an oxygen-containing or non-oxygen atmosphere using a high-temperature firing furnace. There is a method of peeling by a method. This method is inexpensive in terms of equipment, and can treat together toner that is electrostatically attached to the carrier surface, toner that is firmly attached to the carrier surface, so-called impacted toner, and so on. There is an advantage. However, in this processing method by high-temperature firing, various problems occur due to the action of high temperature and the decomposition of the coating resin. For example, in the case of a carrier coated with a fluorine resin, as described above. In addition to damaging the furnace due to the generated gas, it is necessary to treat hydrofluoric acid, and there is a possibility that the magnetic body itself, which is the core of the carrier, may be denatured due to high temperature treatment, etc. The problem was inherent.

  As another method, there is a method of recycling the carrier by mechanically peeling the coat resin on the surface of the magnetic material using a ball mill or the like. Specifically, the carrier recovered from the market is housed in a container together with hard balls such as alumina balls, and a small amount of solvent and water are added to rotate the carrier resin so that the coating resin on the carrier surface is physically In such a method, the coating resin can be peeled to some extent, but the peeling action causes the carrier itself (specifically, the magnetic substance itself). ) Are crushed, and after the peeling step, there is still a problem that a step of separating organic substances such as a coating resin adhering to and remaining on the surface of the magnetic particles is necessary.

  Furthermore, as another technique used for carrier recovery, there is a so-called wet peeling method in which the coating resin is removed by bringing the carrier into contact with an organic solvent or a release agent. By adopting such a method, there is an advantage that the quality of the recovered magnetic material to be obtained can be secured to a high level without inviting the modification of the magnetic material, but it is necessary to recover the solvent or the release agent. In addition, the apparatus becomes complicated, and there are concerns about the risk of ignition and explosion and the environmental impact due to the use of flammable organic solvents.

  On the other hand, Patent Documents 1 to 4 disclose a method for separating a coating resin and a magnetic material of an electrophotographic carrier using water in a supercritical state or a subcritical state. However, in the methods described in these patent documents, even in the supercritical state or the subcritical state, the conditions of temperature: 300 ° C. or higher and pressure: 20 MPa or higher are adopted. The magnetic substance itself is eluted by the water in the subcritical state (this fact can be easily recognized from the increase in Fe or Mn ions contained in the treated water), and a resin such as a fluorine resin. The magnetic body itself (particularly the surface of the magnetic body), which is the carrier core coated with, may be modified and the magnetic body may not be able to exhibit the desired characteristics. There is a problem that the magnetic material from which the coating resin is removed by the method cannot be reused as it is as the carrier core. Further, in the high temperature and high pressure regions as described above, a large and complicated device with pressure resistance is required for the separation operation, and the processing concentration of the carrier cannot be increased. In reality, water / magnetic material (weight ratio) can only be used up to about 2.5, so the amount of treatment per treatment is small and the treatment is inexpensive. There is an inherent disadvantage of not being able to do it.

  In addition, by directly processing such an electrophotographic carrier with water under subcritical conditions, there is also a technique for recovering the core magnetic material without changing any other powder characteristics in addition to the electromagnetic characteristics. Even in the present inventors, a method for treating a carrier for electrophotography employing subcritical water treatment, which can be treated at a low temperature, has been previously proposed in Patent Document 5. Then, since no organic solvent is used at all, it is an environmentally friendly treatment method, and since the treatment temperature is 280 ° C. or less, the treatment temperature is applied to the magnetic body itself. Although there is no influence, since the treatment medium is merely water, removing the coating resin to some extent requires at least 2 hours or 3 hours or more as the treatment time. Furthermore, in order to sufficiently remove the coating resin, there is a problem that a long time is required for the treatment, for example, a treatment time of 5 hours or more is required. Even in the processing apparatus used, it is only necessary to form a coating layer made of fluorine resin (PTFE) inside, but for the above-mentioned sufficient processing, a carrier is left in the apparatus for a long time. Since it is required to stay, such a long stay causes a problem such as damage caused by the magnetic powder wearing the processing apparatus itself.

JP 2003-98762 A JP 2003-96198 A JP 2001-290311 A JP 2002-244351 A JP 2005-242237 A

  Here, the present invention has been made in the background of such circumstances, and the problem to be solved is to cover the surface of the magnetic material without adversely affecting the characteristics of the magnetic material constituting the carrier. Another object of the present invention is to provide a treatment method capable of quickly and effectively removing a predetermined resin that has been removed, and another problem is that a magnetic material from which the coating resin has been removed from the carrier. An object of the present invention is to provide a method in which a carrier can be advantageously recycled by taking out a body and reusing it as it is and coating the surface with a predetermined resin again.

  And, as a result of intensive studies to solve such problems, the present inventors adopted a water treatment in a subcritical state, which can be processed at a low temperature, previously proposed by the present inventors. Based on the processing method of the carrier for electrophotography, as a result of earnestly examining a more practical coating resin from such a carrier, in particular, a resin containing a fluorine resin, water in a subcritical state as a processing medium, By using hydrogen peroxide as water containing hydrogen peroxide, the coating time on the carrier surface can be reduced without significantly affecting the magnetic material after the treatment, while enabling a significant reduction in the treatment time. It has been found that it can be decomposed and peeled off effectively, and it has been found that the processing apparatus and processing technology are simple and economically advantageous, and the present invention has been completed. Because .

  Therefore, in order to solve the above-described problems, the present invention provides, as a first aspect thereof, a method for treating a carrier constituting an electrophotographic developer together with a toner, wherein the magnetic surface is formed on a predetermined resin layer. The carrier coated with the magnetic substance surface of the carrier is brought into contact with the hydrogen peroxide-containing water in a subcritical state at a temperature of 280 ° C. or lower and a pressure of at least 0.1 MPa or higher. An electrophotographic carrier processing method characterized in that it is removed is adopted.

  In the second embodiment of the electrophotographic carrier processing method according to the present invention, the hydrogen peroxide-containing water has a hydrogen peroxide concentration of 0.1 to 10%.

  Furthermore, in the third aspect of the method for processing an electrophotographic carrier according to the present invention, when removing the resin coated on the surface of the magnetic material of the carrier, the hydrogen peroxide-containing water under the subcritical state and the carrier Are contacted at a ratio of 0.5: 1 to 40: 1 on a weight basis.

  In addition, according to the fourth aspect of the present invention, the resin layer is composed of a fluorine resin alone, or (A) a fluorine resin, (B) a polyester resin, an acrylic resin, and a silicone resin. A blend of at least one resin selected from the group consisting of polyethylene resin, polypropylene resin, polystyrene resin, polyacrylonitrile resin, polyurethane resin and epoxy resin, or (A) resin component and (B) resin component It is comprised from the copolymer of this, a graft copolymer, or a block copolymer.

  In the fifth aspect of the present invention, the resin layer is made of polyester resin, acrylic resin, silicone resin, polyethylene resin, polypropylene resin, polystyrene resin, polyacrylonitrile resin, polyurethane resin, and epoxy resin. At least one resin or blend selected from the group, or a copolymer, block copolymer, or graft copolymer of these resin components will be used.

Furthermore, in the sixth aspect of the present invention, a magnetic material represented by the following composition formula (I) is employed as the magnetic material of the carrier.
(MeO) _1-n (Fe ₂ O ₃ ) _{n + 1} (I)
[However, in composition formula (I), Me represents Co, Ni, Mn, Zn, Mg, or Fe, while n satisfies 0 ≦ n ≦ 1. ]

  In addition, in the seventh aspect of the present invention, the carrier is treated with the hydrogen peroxide-containing water under the subcritical state, and the magnetic material constituting the carrier is present to perform such peroxidation. Hydrogen-containing water is brought into direct contact with the magnetic material.

  In addition, the present invention is also directed to the method for recycling the electrophotographic carrier as described above, and the magnetic material from which the coating resin layer has been removed from the electrophotographic carrier by the method as described above. The gist of the method is a method for recycling a carrier for electrophotography using a magnetic material, which is used as it is, in which a predetermined resin is coated on the surface of the magnetic material to obtain a target carrier.

  Thus, according to the method for processing an electrophotographic carrier according to the present invention, a carrier coated with a predetermined resin layer using hydrogen peroxide-containing water as a processing medium in a subcritical state at a low temperature of 280 ° C. or lower. The processing time for removing the coating resin from the carrier can be greatly shortened by directly processing, and in addition to the electromagnetic characteristics, other powder characteristics are not changed at all. Thus, the core magnetic body can be recovered advantageously.

  In addition, according to the present invention, there is provided a method for recycling an electrophotographic carrier that can be carried out economically advantageously in a short time without deteriorating the functions required of the carrier, having an excellent cleaning effect, and having no environmental impact. It was realized.

  Incidentally, the electrophotographic carrier to be processed in the present invention is a component constituting a developer together with toner in a copying machine or the like, and is generally composed of fine magnetic particles and a resin. The body surface has a structure coated with a predetermined resin. In the present invention, particularly, the surface of the magnetic particles coated with a resin layer containing a fluorine resin is advantageously processed. The electrophotographic carrier includes a magnetic substance alone, a magnetic substance surface coated with a resin, and a carrier having various particle diameters. The present invention can be applied to any structure of the carrier. Is possible.

  More specifically, the magnetic body constituting the electrophotographic carrier is not particularly limited, for example, a ferromagnetic metal such as iron, cobalt, nickel, ferrite powder such as zinc, manganese, magnesium, etc. A conventionally well-known thing can be mentioned. Among these, since ferrite can arbitrarily control its magnetic properties, a metal oxide magnetic material represented by the composition formula (I) is particularly preferably employed. In such a composition formula (I), Me represents Co, Ni, Mn, Zn, Mg, or Fe, while n is a number satisfying 0 ≦ n ≦ 1, and the composition formula (I) Typical examples of the magnetic material represented by the above include magnetite, hematite, and jacobsite, and these are usually sintered bodies. Moreover, generally the average particle diameter of this magnetic body shall be about 1-100 micrometers.

  On the other hand, in the present invention, as the predetermined resin constituting the surface of the electrophotographic carrier to be processed, that is, the resin coated on the surface of the magnetic body, various conventionally known resins are targeted. In general, as described above, a resin or a resin composition containing a resin (fluorine resin) containing at least a fluorine atom is preferably used. Examples of such a fluorine resin include polytetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer resin, tetrafluoroethylene / hexafluoropropylene copolymer (PFEP), and polyvinylidene fluoride. (PVDF), perfluoroacrylate resin, etc. can be mentioned. In addition, a carrier coated with a resin containing at least one of these known fluorine resins is effectively treated in the present invention.

  In addition, as for the thing which consists only of a fluorine resin as a thing which contains the above-mentioned fluorine resin suitably which forms the coating resin layer of the magnetic body surface, or (A) fluorine resin and (B) conventional Used in electrophotographic carriers, blends of at least one resin selected from resins other than fluorine resins, or a copolymer or graft of (A) resin component and (B) resin component It may be made of a copolymer or block copolymer, and further formed by sequentially applying a plurality of resins (A) resin component and (B) resin component to the surface of the magnetic material. (A) A layer structure in which a layer composed of a resin component and (B) a layer composed of a resin component are laminated may be employed. Here, the resin component (B) is not particularly limited, and specific examples include polyester resins, acrylic resins, silicone resins, polyolefin resins (for example, polyethylene resins, polypropylene resins, polystyrene resins). , Polyacrylonitrile resin, polyurethane resin, epoxy resin and the like. Of course, in the present invention, an electron formed by forming on the surface of the magnetic body a resin other than those containing at least such a fluorine resin, for example, a coating resin layer composed of the resin component (B) described above. It goes without saying that photographic carriers are also targeted.

  Furthermore, the coating resin layer as described above may have any known various additives evenly contained in the same manner as in the conventional carrier. For example, the conductivity of the carrier itself may be controlled. For the purpose, a conductive material such as carbon black may be contained. Needless to say, when various additives such as a conductive material are added, they are appropriately contained in a normal addition amount.

  And, such an electrophotographic carrier is to be processed according to the present invention. At that time, as a carrier to be processed, a non-standard product excluded in the factory or a product distribution Even if it is unused (recovered) returned for some reason in the process, there is no problem. Generally, however, the carrier in the collected developer is mainly used as a developer. It will be the subject and will be treated according to the present invention.

  When processing a used carrier, the collected developer contains a large amount of toner in addition to the carrier, and such toner is electrostatically attached to the carrier. Therefore, it is desirable to first perform a pretreatment for roughly removing the toner adhering to the carrier by a known separation operation such as air blowing, sieving, or a combination thereof.

  Then, according to the present invention, the carrier thus obtained is brought into contact with hydrogen peroxide-containing water under a predetermined subcritical state to thereby form a predetermined coating resin formed on the surface of the magnetic material constituting the carrier. The layer will advantageously be removed.

  More specifically, the hydrogen peroxide-containing water under the subcritical state employed in the present invention is a subcritical state satisfying the conditions that the temperature is 280 ° C. or lower and the pressure is at least 0.1 MPa or higher. It is the water containing hydrogen peroxide in (refer FIG. 1). In addition, hydrogen peroxide-containing water in such a subcritical state has characteristics such as low ionic product, relative dielectric constant, and density compared to the case of normal water, and exhibits acid / base catalytic functions. In addition, in the present invention, a coating resin layer made of a fluorine resin or the like is effectively used by oxidative decomposition or dissolution using the high reactivity. It can be removed. The subcritical state employed in the present invention is selected so as to satisfy the conditions of temperature: 100 to 280 ° C. and pressure: 0.1 to 20 MPa among the temperature and pressure ranges as described above. .

  Moreover, in the present invention, not only mere water but also water containing hydrogen peroxide is used as the subcritical processing medium, and this has no influence on the magnetic material after processing. The coating resin on the surface of the carrier can be decomposed and peeled off in a very short time without giving it, so that in addition to economic advantages, damage to the processing equipment is also effective. In other words, it is possible to suppress or avoid the problem, and it has become possible to treat the carrier more advantageously, and to recycle or reuse it.

  Here, the mechanism by which the presence of hydrogen peroxide in the treatment medium has an advantageous effect on the decomposition of the coating resin on the carrier surface has not yet been fully elucidated. It is inferred that. That is, due to the water treatment in the subcritical state, the ionic product is increased and hydrolysis is caused. In addition, because the reaction atmosphere is a high temperature and high pressure, a thermal decomposition reaction of the resin occurs, and Since it is in an oxygen-rich state due to the decomposition of hydrogen peroxide, and there is a magnetic powder that is a core component of the carrier in the vicinity, a metal oxide that gives such magnetic powder is present. As a catalyst, the oxidizing action by hydrogen peroxide proceeds rapidly and effectively, and the coating resin component of the carrier can be easily oxidized and dissolved. It is believed that the clothes resin melts away and the peeling and removal is completed.

  In the case where a processing medium such as water in a subcritical state or supercritical state exceeding the above range is used, it is possible to remove the coating resin layer made of fluorine resin or the like formed on the carrier surface. However, since the magnetic body (particularly the surface of the magnetic body) that is the carrier core tends to be denatured, the treated magnetic body cannot be reused as a carrier as it is, This is because operations such as heat treatment of the obtained magnetic material again are required. In addition, there is a problem that a processing vessel made of a material such as SUS is corroded due to generation of acidic gas such as hydrofluoric acid having high reactivity in the decomposition process of the resin from the high temperature treatment. There is a fear. In particular, when a carrier to which toner is attached is processed, various fragments are generated, and the processing container is easily corroded.

  By the way, according to the present invention, in order to treat the electrophotographic carrier as described above with hydrogen peroxide-containing water under a subcritical state under specific conditions, first, the carrier to be treated is placed in a predetermined treatment container. And the water containing hydrogen peroxide will be accommodated.

  In this case, the processing vessel is not particularly limited as long as it can withstand a temperature of at least 280 ° C. and a high pressure for forming a subcritical state, and SUS that has been used conventionally. For example, a pressure vessel made of metal can be used. In particular, in the present invention, since the above-described conditions are adopted, a PTFE container having excellent heat resistance and chemical resistance and a container whose surface is coated with such PTFE is used. Is also possible. As described above, if a processing container in which the inner surface of the processing container (the surface to be processed comes into contact with) is made of PTFE, deterioration due to corrosion of the processing container is effective even if acid gas is generated. As a result, the wear due to the contact between the carrier and the inner surface of the processing container is further advantageously suppressed in addition to the contribution based on a significant reduction in processing time. Incidentally, in the case of processing at higher temperature and higher pressure than the above-mentioned conditions, the use of PTFE is difficult due to problems such as the melting point of PTFE, and higher energy costs and expensive equipment are required.

  In addition, according to the present invention, hydrogen peroxide-containing water is accommodated in the processing container, but the water that is a medium for such hydrogen peroxide is not particularly limited, and is distilled. Any ordinary water such as water, purified water or tap water can be used. In addition, in the case of tap water, it is desirable to use purified water treated with a commercial water purifier or the like because there is a concern about the influence of chlorine or the like contained for disinfection. Then, hydrogen is contained at a predetermined concentration with respect to water as such a medium, and the concentration is appropriately selected according to the processing conditions and the like. Especially, in this invention, what was prepared in accordance with the conventional method in the form of about 0.1-20%, preferably about 1-10% aqueous solution will be used advantageously. However, if the concentration of hydrogen peroxide is too low, it will be difficult to expect a sufficient shortening of the processing time. If the concentration of hydrogen peroxide is too high, the safety of the work will be reduced. In addition, there is a problem that the apparatus is corroded or the recovered magnetic substance is easily denatured.

  Furthermore, in the present invention, a metal oxide serving as a catalyst that promotes the oxidizing action of hydrogen peroxide is preferably added to the hydrogen peroxide-containing water contained in such a processing vessel, and the carrier treatment system is thus added. It is desirable that it be present. This is because the coexistence of such a metal oxide makes it possible to further shorten the processing time. However, since such a metal oxide is generally used in the form of a powder and is mixed with a carrier, in order to maintain the quality of the final recovered core magnetic material, such a metal oxide is used. As the metal oxide, a magnetic material constituting the carrier itself is used, and hydrogen-containing water is directly brought into contact with such a magnetic material. In addition, such a metal oxide such as a carrier-constituting magnetic body is generally 0.1 parts by weight or more, preferably 1 part by weight with respect to 100 parts by weight of the carrier, in order to sufficiently exert its effect of use. In more than part, it will be used. The upper limit is generally about 20 parts by weight, preferably about 10 parts by weight.

  Then, after sealing the processing vessel containing the carrier, hydrogen peroxide-containing water, and if necessary, a metal oxide such as a magnetic material constituting the carrier, the inside of the vessel is set to a desired temperature and pressure. By heating the processing container under a general temperature rising condition, the hydrogen peroxide-containing water stored in the processing container is brought into a subcritical state. In this way, when the carrier is brought into contact with the hydrogen peroxide-containing water in a predetermined subcritical state, the coating resin that is firmly firmly fixed to the magnetic surface of the carrier peels off, dissolves or melts. It can be advantageously removed from the surface of the magnetic material by being caulked or decomposed. In addition, since the reaction conditions at this time are milder than the case where a processing medium such as supercritical water is used, the influence on the magnetic particles is further suppressed as much as possible. Powder characteristics such as electromagnetic characteristics, mechanical characteristics, and surface characteristics are sufficiently maintained. When processing the carrier in contact with hydrogen peroxide-containing water in a subcritical state, in order to accelerate the reaction, a stirring shaft is inserted into the processing container, the processing container itself is rotated, It is also effective to stir the carrier in the container by stirring with a magnet or the like.

  In addition, the amount of hydrogen peroxide-containing water that gives a subcritical state according to the present invention is not particularly limited, and is appropriately set according to the type of coating resin, and thus the type of carrier, etc. The ratio by which the weight ratio of hydrogen-containing water to the carrier to be treated is generally about hydrogen peroxide-containing water: carrier = about 0.1: 1 to 40: 1, preferably about 0.5: 1 to 20: 1. It is desirable to be used in In other words, the hydrogen peroxide-containing water and the carrier are mixed so that the liquid-solid ratio (weight ratio of hydrogen peroxide-containing water / carrier) is about 0.1 to 40, preferably about 0.5 to 20. It is desirable to put it in the processing container. This is because if the hydrogen peroxide-containing water present in the system is less than the above ratio, the coating resin on the carrier surface may not be sufficiently removed, and more than the above ratio. This is because the amount of carrier accommodated in the processing container is extremely small, and the processing cost increases. And among the above-mentioned ranges, the ratio of hydrogen peroxide-containing water: carrier = about 0.5: 1 to 2: 1 can be more suitably employed, and by adopting such a ratio, The amount of carriers that can be processed at a time increases, and the processing cost can be further advantageously reduced.

  Further, depending on the type of the coating resin, the liquid-solid ratio, etc., even when it is in the time (treatment time or reaction time) in which the carrier to be treated is contacted and treated with hydrogen peroxide-containing water in a subcritical state. In particular, in the present invention, by using hydrogen peroxide-containing water as the treatment medium, the contact time is greatly shortened and is usually 10 minutes to 12 minutes. It is desirable that the time is about 30 minutes to 8 hours. If the contact time is too short, the coating resin on the carrier surface tends not to be sufficiently removed. If the contact time is too long, the surface of the magnetic material is denatured. This is because there is fear and it is also economically disadvantageous.

  Thereafter, when the treatment with hydrogen peroxide-containing water in the subcritical state as described above is completed, the treatment container is cooled, and the treatment medium (aqueous solution) in the treatment container is subjected to contact with a predetermined coating resin such as a fluorine resin. The magnetic material from which strong adhesion has been eliminated is taken out. The magnetic material separated from the processing medium and taken out is usually subjected to a cleaning process using water or a drying process.

  In the magnetic material thus obtained, the coating resin is effectively removed and the desired characteristics can be advantageously ensured, so that the virgin core material (uncoated resin, uncoated) is obtained. As with the magnetic particles used), it can be advantageously reused as it is as a carrier core material. In addition, if such a magnetic material surface is coated with a carrier resin such as a fluorine resin or a silicone resin by a conventionally known method, an electrophotographic carrier as one component of the developer can be advantageously regenerated. Thus, recycling of the electrophotographic carrier can be realized extremely well.

  In addition, by effectively decomposing, removing and removing the surface resin of the carrier in this way, the carrier particles in the developer once used and recovered from the market can be chemically or physically treated. It has been possible to take advantage of this to restore its function and to bring it to a state where it can be reused, and it is possible to find great practical significance there.

  Hereinafter, some experimental examples including examples of the present invention will be shown to clarify the present invention more specifically. However, the present invention is not limited by the description of such experimental examples. It goes without saying that it is not something that you receive. In addition to the following examples, the present invention includes various changes, modifications, and modifications based on the knowledge of those skilled in the art without departing from the spirit of the present invention, in addition to the above specific description. It should be understood that improvements and the like can be added.

  In the following experimental examples, the amount of residual carbon in the magnetic material was analyzed by SEM / EDS (JEOL JSM-6330F / JED-2140) and CHN coder (Yanaco Analytical Chemicals MT-6). Evaluation was made by both methods. Here, the accelerating voltage: 15 kV and the imaging magnification: 1000 were adopted as the quantitative conditions using an EDS (Energy Dispersion Spectrometer). For trace elemental analysis, ICP-AES (OPTIMA3300V manufactured by Perkin Elmer Japan) was used. Furthermore, the surface state of the magnetic material was measured using XPS (ESCA-3300 manufactured by Shimadzu Corporation), while the crystal structure of the magnetic material was measured using an X-ray diffractometer (RINT-2500 manufactured by Rigaku Corporation).

<Experimental example 1>
First, a carrier for a copying machine having a structure in which the surface of magnetic particles (average particle diameter: about 50 μm) having the following composition was coated with a resin layer having the following composition was prepared.
-Carrier composition-
Magnetic material: Fe ₂ O ₃ 63 parts by weight
MnO 17 parts by weight Resin layer: Perfluoroacrylate resin 5 parts by weight
14.5 parts by weight of polyester resin
Carbon black 0.5 parts by weight

  Next, 5% hydrogen peroxide water is used as a treatment medium, and 10 g of the 5% hydrogen peroxide water and 5 g of the above carrier are mixed so that the liquid-solid ratio is 2. After putting in an ethylene-lined pressure vessel and sealing, heat to 250 ° C. at a rate of 1 ° C./min and treat for 2 hours under subcritical conditions of such temperature: 250 ° C. and pressure: 3 MPa. Thus, the treatment with hydrogen peroxide solution in a subcritical state was carried out. During such processing, stirring of the contents in the pressure vessel was continued. Then, after cooling to room temperature and solid-liquid separation according to a conventional method, the magnetic material constituting the carrier was recovered as a solid.

-Morphological observation of recovered magnetic material-
The magnetic material thus obtained was observed for its morphology using a scanning electron microscope (SEM), and the SEM photograph is shown in FIG. As is clear from the SEM photograph shown in FIG. 2, it was confirmed that the resin layer on the surface of the magnetic material could be effectively peeled compared to the carrier before treatment, and the treatment medium (aqueous catalyst) Was transparent, and it was confirmed that the carbon black contained in the carrier was also decomposed, and ultrasonic cleaning was not necessary.

-Evaluation of residual carbon-
Further, in order to evaluate the remaining amount of the coating resin on the surface of the magnetic material recovered by such treatment, the carbon content of the magnetic material obtained by treatment with hydrogen peroxide solution in such a subcritical state, The carbon content of the treated carrier was measured using a CHN coder. And from the obtained value, the following formula:
Carbon residual rate (%) = [Measured carbon content after subcritical treatment (wt%)]
÷ [Measured carbon amount of untreated carrier (wt%)] × 100
The carbon residual rate (%) was calculated using the following formula: The treatment time: 2 hours, the carbon residual rate of the obtained magnetic material was 0.5% or less, and this value is the carbon residual rate of the virgin magnetic material. It was confirmed that the coating resin on the surface of the magnetic material was completely removed.

-Crystal structure analysis-
Furthermore, the crystal structure analysis of the magnetic material obtained above was performed, and the obtained X-ray diffraction graph is shown in FIG. The X-ray diffraction conditions were Cu Kα 50 kV-100 mA. In addition to the recovered magnetic material, FIG. 3 also shows an X-ray diffraction pattern of a virgin magnetic material that is not coated with a resin layer for comparison. From FIG. 3, the crystal form of the magnetic material obtained by recovery is all Jacobsite. Compared to the virgin magnetic material, there is no difference in crystal size and interplanar spacing. It was found that the crystal form and crystal form were not affected at all by the treatment with hydrogen peroxide solution under the critical condition.

-Analysis of surface condition-
Further, the surface state analysis (XPS analysis) of the magnetic material obtained by the above recovery was performed, and the XPS spectrum is shown in FIG. FIG. 4 also shows an XPS spectrum of a virgin magnetic material not coated with a resin for comparison, in addition to the magnetic material obtained by the above recovery. As is apparent from FIG. 4, it is recognized that the magnetic substance recovered by treating the carrier with the hydrogen peroxide solution in the subcritical state has no change in Fe2p and is not denatured at all.

  From the above results, the magnetic material obtained by removing the coating resin from the carrier as described above has been completely removed without modification, and thus the carrier is provided. It has been found that the magnetic material can be used advantageously as it is or after the surface is coated with a resin.

  Therefore, using the magnetic powder recovered from the carrier as described above, a blend of a ratio of perfluoroacrylate resin: polyester resin = 30: 70 is applied to the surface, and the weight ratio is 20%. A coat layer was formed to prepare a carrier. Next, using this carrier, copying with a normal electrophotographic copying machine was carried out, and the image quality was examined. As a result, a good quality copy without any problem could be obtained.

<Experimental example 2>
The developer collected from the market is passed through a 20-micron mesh sieve to separate the toner and carrier, while the electrostatically attached toner is removed by vacuum suction from the bottom of the mesh, and the recovered carrier Prepared. The recovered carrier was an overcoat of a blend of a silicone resin and a polyester resin.

  Then, 5 g of the recovered carrier is weighed, and it is put into a pressure-resistant treatment vessel lined with fluororesin with 10 g of 5% hydrogen peroxide water or normal water so that the liquid-solid ratio is 2. After sealing, the treatment for 3 hours was carried out under the subcritical condition of 250 ° C. and 3 MPa.

  The evaluation of residual carbon, crystal structure analysis, and surface state analysis of the magnetic material thus obtained were carried out in the same manner as in Experimental Example 1, and when hydrogen peroxide was used as the treatment medium, The residual ratio was as extremely low as 0.5%, and no change was observed in the X-ray diffraction pattern and XPS spectrum. On the other hand, in the treatment under the subcritical state using the treatment medium of only water, the residual carbon amount is as high as 8%, and it is recognized that carbon black remains on the surface of the magnetic material. It was determined that further processing was necessary.

<Experimental example 3>
Using the developer recovered from the market, the toner and the carrier were separated in the same manner as in Experimental Example 2, and 10 g of the taken-out carrier (clothing resin: fluorine-based resin) was weighed to obtain a liquid. It is housed in a pressure-resistant container together with 5% hydrogen peroxide water so that the solid ratio is 2, and is 0.5 hours, 1 hour, 2 hours, 4 hours, or 6 hours in a subcritical state at 260 ° C. and 5 MPa. The process of was carried out.

  And the carbon residual amount of the magnetic substance obtained in each processing time was measured similarly to the said Experimental example 1, and the result was shown in FIG. As can be seen from FIG. 5, even when the processing time is 0.5 hours, the coating resin can be effectively removed from the recovered carrier, so that it can be sufficiently reused. Is understood.

<Experimental example 4>
In Experimental Example 2, a carrier prepared from the collected developer was used, and 5% hydrogen peroxide water was used as a processing medium, and these were mixed with various liquid-solid ratios (0.3, 0.5, 5, 10). Alternatively, in 30), the coating resin was removed from the carrier by storing in a pressure vessel and treating for 0.5 hour in a subcritical state at a temperature of 270 ° C. and a pressure of 6 MPa. And about the collection | recovery magnetic body obtained by each process, the amount of residual carbon was measured and the result was shown in FIG. As can be seen from FIG. 6, until the liquid-solid ratio is 0.5, the amount of residual carbon is 4% or less, and it is recognized that the coating resin can be effectively removed and removed from the carrier. However, if the liquid-solid ratio becomes lower than that, the amount of residual carbon increases rapidly, and it is considered that it is difficult to remove the coating resin by a single treatment, and repeated treatment is required.

<Experimental example 5>
Using a carrier in which a coating resin layer made of a blend of a polyester resin and a perfluoroacrylate resin is formed on the surface of a magnetic material, 5 g of the carrier together with 2.5 ml of 10% hydrogen peroxide water and a pressure resistance of 80 ml in volume It was accommodated in a container (liquid / solid ratio: 0.5), and the treatment was carried out for 2 hours under a subcritical state of temperature: 280 ° C. and pressure: 18 MPa.

  Subsequently, the carbon residue on the surface of the magnetic material taken out by such treatment was measured and found to be 3%, and it was recognized that sufficient removal of the coating resin layer could be realized. Further, when such a recovered magnetic material was observed with an SEM at an acceleration voltage of 10 kV, no residual resin was observed, and no abnormality was observed in terms of form.

<Experimental example 6>
In Experimental Example 1, a virgin magnetic material (Fe ₂ O ₃ + MnO) that is not coated with a resin together with a carrier and 5% hydrogen peroxide solution having a liquid-solid ratio of 2 is 5% of the carrier. In the ratio, it was accommodated in a pressure resistant container, and the treatment in the subcritical state similar to Experimental Example 1 was performed.

  And when the carbon residual rate was measured about the obtained collection | recovery magnetic body, it became 0.5% or less, and the removal effect | action of the coating resin layer which was excellent was recognized. Further, it was recognized that even if the treatment time was shortened from 2 hours to 1 hour, the carbon residual ratio was low, and the effect of removing the coating resin could be improved by adding and blending the virgin magnetic material separately.

<Experimental example 7>
The carrier prepared in Experimental Example 1 was used to remove the coating resin of the carrier at a liquid-solid ratio: 2 using water as the treatment medium. However, as the processing conditions, the conditions under which water becomes supercritical (temperature: 380 ° C., pressure: 25 MPa) are adopted, and the carrier is kept under such temperature and pressure conditions for 24 hours, thereby using supercritical water. The treatment was performed, and then the same operation as in Experimental Example 1 was performed to recover the magnetic material.

  Then, the evaluation of residual carbon, crystal structure analysis, and surface state analysis of the recovered magnetic material were performed in the same manner as in Experimental Example 1. As a result, the carbon residual ratio was 2%, and SEM observation was performed. Although no abnormal form was observed, it was confirmed that a new peak appeared at a location where the binding energy of Fe2p was about 715 eV in the XPS spectrum. Although the cause of the appearance of such a peak is not clear, it is considered that supercritical water treatment is not suitable for reusing a magnetic material as it is by changing the surface state of the magnetic material. Moreover, in such supercritical water treatment, the peak area increases at the same time as the peak area around 711 eV, compared to the water treatment product in the subcritical state or the magnetic material before treatment, and at the same time shifts to the higher energy side. It was recognized that the surface condition was changed.

<Experimental Example 8>
The carrier used in Experimental Example 1 was treated under the same subcritical condition as in Experimental Example 1 using only water as the processing medium, and the coating resin of the carrier was removed. The processing time was 2 hours.

  And about the magnetic substance obtained by such a process, as a result of observing the form, compared with the SEM photograph before the process, it was recognized that the resin layer on the surface was almost peeled off and removed, It was confirmed that deposits that seemed to be part of the resin remained on the surface of the magnetic material. The residual carbon amount was 5.2%, and it was found that cleaning was necessary. Moreover, when the obtained magnetic material was collected using a magnet and ultrasonically cleaned in pure water, there was no abnormality in the shape of the magnetic material, and the magnetic material that can be reproduced in that form is still available. The powder was recognized.

<Experimental example 9>
The market-collected product used in Experimental Example 2 was treated at 280 ° C. and 18 MPa for 2 hours using pure water as a treatment medium and adjusting the liquid-solid ratio to 0.4. And when the carbon residual rate was investigated about the magnetic body obtained in this way, it was 15%, and it became clear that the reuse was impossible. At the same time, SEM observation was carried out. As a result, it was confirmed that some forms of residual resin were observed, and that the coating resin layer was not sufficiently peeled off.

It is a state diagram of water for explaining a subcritical state adopted in the present invention. 2 is a SEM photograph of a magnetic material obtained in Experimental Example 1. 2 is an X-ray diffraction diagram showing the results of crystal structure analysis obtained in Experimental Example 1. FIG. 3 is an XPS spectrum showing the result of surface state analysis performed in Experimental Example 1. 10 is a graph showing the relationship between the processing time and the amount of residual carbon obtained in Experimental Example 3. 6 is a graph showing the relationship between the liquid-solid ratio and the amount of residual carbon obtained in Experimental Example 4.

Claims (8)

  A method for treating a carrier constituting an electrophotographic developer together with a toner, wherein a carrier having a magnetic surface coated with a predetermined resin layer is heated to a temperature of 280 ° C. or lower and a pressure of at least 0.1 MPa or higher. A method for treating an electrophotographic carrier, wherein the resin coated on the surface of the magnetic material of the carrier is removed by contacting with hydrogen peroxide-containing water in a subcritical state.   The method for treating an electrophotographic carrier according to claim 1, wherein the hydrogen peroxide-containing water has a hydrogen peroxide concentration of 0.1 to 10%.   When removing the resin coated on the surface of the magnetic material of the carrier, the hydrogen peroxide-containing water under the subcritical state and the carrier are contacted at a ratio of 0.5: 1 to 40: 1 on a weight basis. 3. The method for processing an electrophotographic carrier according to claim 1, wherein the processing method is performed.   The resin layer is composed of a fluorine resin alone, or (A) a fluorine resin, and (B) a polyester resin, an acrylic resin, a silicone resin, a polyethylene resin, a polypropylene resin, a polystyrene resin, a polyacrylonitrile resin, A blend of at least one resin selected from the group consisting of polyurethane resins and epoxy resins, or a copolymer, graft copolymer, or block copolymer of (A) resin component and (B) resin component The method for processing an electrophotographic carrier according to any one of claims 1 to 3, wherein the processing method is composed of a united body.   The resin layer is at least one resin or blend selected from the group consisting of polyester resins, acrylic resins, silicone resins, polyethylene resins, polypropylene resins, polystyrene resins, polyacrylonitrile resins, polyurethane resins, and epoxy resins. The electrophotographic carrier according to any one of claims 1 to 3, wherein the carrier is composed of a copolymer, a block copolymer, or a graft copolymer of the resin components. Processing method. The method of processing a carrier for electrophotography according to any one of claims 1 to 5, wherein the magnetic substance of the carrier is represented by the following composition formula (I).
(MeO) _1-n (Fe ₂ O ₃ ) _{n + 1} (I)
[However, in composition formula (I), Me represents Co, Ni, Mn, Zn, Mg, or Fe, while n satisfies 0 ≦ n ≦ 1. ]   The magnetic substance constituting the carrier is present in the carrier treatment system using the hydrogen peroxide-containing water under the subcritical state, and the hydrogen peroxide-containing water is brought into direct contact with the magnetic substance. The method for processing an electrophotographic carrier according to claim 1, wherein the electrophotographic carrier is processed. The magnetic material from which the coating resin layer has been removed from the electrophotographic carrier by the method according to any one of claims 1 to 7 is used as it is, and a surface of the magnetic material is coated with a predetermined resin. A method for recycling an electrophotographic carrier using a magnetic material, wherein the carrier is a target carrier.

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