JP2016025288A - Ferrite magnetic material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the influence of a minor element which makes a factor obstructing the high-level stabilization of the quality of a carrier core making the core of a magnetic carrier, thereby meeting the rising demand for achievement of a higher performance of a magnetic carrier with the increase in the printing speed.SOLUTION: A ferrite magnetic material comprises, as primary components, Fe, and an additive element including at least one of Mn, Mg, Ti, Cu, Zn, Ni, Sr and Ca. The ferrite magnetic material has an average particle diameter of 1-100 μm. In the ferrite magnetic material, the total amount of impurities except Fe, the additive element and oxygen is 0.5 mass% or less. The impurities include at least two kinds of elements of Si, Al, Cr, Cu, P, Cl, Ni, Mo, Zn, Ti, sulfur, Ca, Mn and Sr.SELECTED DRAWING: None

Description

  The present invention relates to a magnetic material made of magnetic powder or particles. The magnetic material is used for magnets and magnetic recording media, and in particular, a magnetic carrier core material used for an electrophotographic developer, a magnetic carrier coated with a resin using the magnetic carrier core material, and toner And the like.

  The electrophotographic dry development method is a method in which powder toner from an electrophotographic developer is attached to an electrostatic latent image on a photoreceptor, and the attached toner is transferred to a medium such as predetermined paper for development. . This method is roughly divided into a method using a one-component developer containing only toner as an electrophotographic developer and a method using a two-component developer containing toner and a magnetic carrier. In recent years, a two-component development method that can easily control charging of toner, obtain a stable high image quality, and can perform high-speed development has become the mainstream of the electrophotographic development method.

  In recent years, with the increase in printing speed, the stirring speed of magnetic carriers in an electrophotographic developing machine tends to increase. There are many technical problems such as crushing of magnetic carrier powder particles, generation of irregular fine powder due to the crushing, and further increase in carrier scattering resulting from the generation of irregular fine powder. As the speed and image quality of electrophotographic development increases, and the performance and versatility of electrophotographic developing machines, magnetic carriers are also attracting attention as factors that influence the quality and performance. With the advancement of technology, attention has also been paid to minute phenomena that have not occurred in the past.

For example, in Patent Document 1, by controlling the valence state of Fe in the core material of the magnetic carrier, fine graining on the developing sleeve is achieved, so that the particle diameter of the magnetic carrier is reduced. Even when the magnetic carrier is reduced in size, the magnetic force per particle is sufficiently high, and the technology is disclosed in which the magnetic carrier is prevented from scattering onto the image carrier and the image is deteriorated. . In addition, a technique is disclosed in which a magnetic carrier powder composition that does not contain elements with high environmental impact such as Cu (copper), Zn (zinc), Mn (manganese), Co (cobalt), and Cr (chromium) is disclosed.

  In addition to iron oxide powder as a raw material, the magnetic material (for example, carrier core material) includes elements that greatly affect magnetism such as Mn (manganese) and Mg (magnesium) as additive elements, as well as C (carbon), B (boron), Nonmetals, metal elements, and organic substances such as Ca (calcium), Sr (strontium), and Al (aluminum) are added in accordance with required performance. The additive elements are often added in a plurality of types, and each element alone causes various interactions and the like at the manufacturing stage, affecting the superiority of each characteristic of the magnetic carrier core material and the magnetic carrier.

The magnetic material is prepared for each metal element, and is mixed according to the desired component. Compounds such as oxides and carbonates are used as raw materials for the magnetic material. Naturally, the raw material of the magnetic material is of a certain quality or higher, but the raw material of the metal component is smelted from ore and contains inevitable trace elements that cannot be controlled by the supply side. This inevitable trace element is not known unless it is analyzed in detail, and the influence of the trace element is unknown. For this reason, since the raw material which further reduced the content of trace elements is expensive and the supply amount in the market is not sufficient, it is avoided to use it. Moreover, although it could be predicted that some trace elements were included, analysis costs were incurred to analyze unknown trace elements, and no response was made due to the ambiguity of the effects.

  However, in order to cope with an advanced image quality, high quality stability is desired, and measures for quality stability are highly desired. However, the problem of quality is that factors consisting of a plurality of elements overlap, and the magnetic carrier core material is a powder in which fine particles having a particle size of about several tens of μm are aggregated, and is practically used. In terms of quantity, the number was enormous, and it was difficult to pursue individual defects at the particle level, and it was difficult to investigate the true cause and take countermeasures.

JP 2009-157078 A

In order for magnetic carriers according to the conventional technology to meet the demands for higher image quality and the like, in order to stabilize the high quality of the carrier core material, to control the obstruction factor even if it is a minute amount, We focused on the need to suppress the influence of elemental obstruction factors.
In recent years, with the increase in printing speed, the stirring speed of magnetic carriers in an electrophotographic developing machine tends to increase. There are many technical problems such as crushing of magnetic carrier powder particles, generation of irregular fine powder due to the crushing, and further increase in carrier scattering resulting from the generation of irregular fine powder.

  The present invention has been made under such circumstances, and the problem to be solved is due to a trace element that becomes an obstructive factor even if it is a trace amount in order to stabilize the high quality of the carrier core material. It is to suppress the influence of characteristic deterioration.

  In order to solve the above-mentioned problems, the present inventors have conducted intensive research. As a result, in the magnetic material manufacturing process, the trace element is most exposed at the stage of pulverizing the raw material of the magnetic material. The time was considered to be suitable for processing to suppress the influence of elements. Therefore, by controlling the slurry state in which the raw material and water are brought into contact with each other at the time of pulverization, the knowledge that the trace elements are reacted with or eluted from the water and the influence on the magnetic material can be suppressed, and the magnetic properties of the present invention are obtained. Invented the material.

That is, the first invention for solving the above-described problem is:
In the ferrite magnetic material which is an additive element composed of Fe and at least one of Mn, Mg, Ti, Cu, Zn, Ni, Sr and Ca, the average particle diameter is 1 to 100 μm. The total amount of impurities excluding Fe, additive elements and oxygen in the ferrite magnetic material is 0.5 mass% or less, and the impurities are Si, Al, Cr, Cu, P, Cl, Ni, Mo , A ferrite magnetic material containing at least two of any one of Zn, Ti, sulfur, Ca, Mn, and Sr. Moreover, it is a ferrite magnetic material of Claim 1 whose saturation magnetization (sigma) s is 50 emu / g or more. This magnetic material can be used as a magnetic carrier core material for an electrophotographic developer, and further becomes a magnetic carrier for electrophotographic development in which a magnetic carrier core material for an electrophotographic developer is filled or coated with a resin. . By including the magnetic carrier for electrophotographic developer and toner, an electrophotographic developer is obtained. Moreover, as said magnetic carrier core material, saturation magnetization (sigma) s is 50 emu / g or more and 95 emu / g or less.

  The phylite magnetic material according to the present invention can be used in various industrial applications. When the ferrite magnetic material is ferrite particles, the magnetic carrier used as the magnetic carrier core material for the electrophotographic developer is a ferrite magnetic material in which the influence of impurities in the raw material is suppressed, and has a high magnetic force, Carrier scattering is suppressed.

Hereinafter, the present invention will be described in detail.
The inventors of the present invention have conducted intensive research on the magnetic force adjustment of ferrite magnetic materials. As a result of the study, the present inventors have found that even if the raw material contains a trace element, it is mixed with moisture at the time of pulverization, and is pulverized under pressure by a ball mill or the like to obtain a raw material slurry. A method for obtaining a ferrite magnetic material with suppressed influence and a ferrite magnetic material were found. Moreover, it discovered that the ferrite magnetic material concerning this invention was used suitably as a magnetic carrier core material for electrophotographic development. In addition, the present inventors have found a carrier powder that is an electrophotographic developer using the magnetic carrier core material.

Hereinafter, specific embodiments will be described in detail by taking a magnetic carrier core material as an example.
[Raw material for magnetic carrier core]
The composition of the magnetic carrier core material according to the present invention is an oxide of Fe. Therefore, the raw material of the magnetic carrier core material is preferably Fe ₂ O ₃ that exists stably at normal temperature and pressure. In addition, Mn, Mg, Ca, Sr, Si, B (boron), C (carbon), P (phosphorus), etc. are added elements as main components added to prepare the composition of the magnetic material according to the required characteristics. It is as. The form of the additive element is oxide powder, carbonate or the like. For example, MnCO ₃ , Mn ₃ O ₄ or the like can be suitably used as the Mn component raw material.

  The raw material of the ferrite magnetic material is an iron oxide and often contains a small amount of impurities. This is the same for other additive elements. Moreover, the kind and amount of impurities differ depending on the raw material and manufacturing method of the manufacturer. Since the impurities as the magnetic material are defined by the main component, they are other than the main component element. That is, which element is an impurity is determined by the main component. As a ferrite magnetic material, Si, Al, Cr, Cu, P, Cl, Ni, Mo, Zn, Ti, S, Ca, Mn, Sr, vanadium, and the like are contained as trace elements that are impurities. These trace elements are often not controllable at the raw material acquisition stage. In addition, the content of impurities in each raw material is 0.1% by mass or less, and in order to remove these, the raw material supply side must be further supplied with an additional cost for refining, and be supplied industrially. It is difficult. However, it is desirable that the amount of trace elements is as small as possible. The magnetic carrier core material preferably has a total amount of trace elements of 0.5% by mass or less, regardless of the form of alloy or simple substance.

[Slurry process]
Next, the calcined raw material is pulverized and charged into a dispersion medium to prepare a slurry. Water is preferred as the dispersion medium used in the present invention. Alternatively, warm water may be used. This is because trace elements are eluted or reacted, and the influence of characteristic deterioration can be suppressed. In the dispersion medium, the Fe component raw material, a main component raw material such as Mn, and in addition, a binder, a dispersing agent and the like may be blended if necessary. For example, polyvinyl alcohol can be suitably used as the binder. The blending amount of the binder is preferably about 0.5 to 2% by mass in the slurry. Moreover, as a dispersing agent, polycarboxylate ammonium etc. can be used conveniently, for example. As the blending amount of the dispersant, the concentration in the slurry is preferably about 0.5 to 2% by mass. In addition, you may mix | blend a lubricant, a sintering accelerator, etc. The solid content concentration of the slurry is desirably in the range of 50 to 90% by mass.

  Next, the slurry produced as described above is wet pulverized. For example, wet grinding is performed for a predetermined time using a ball mill or a vibration mill. The average particle size of the raw material after pulverization is preferably 10 μm or less, more preferably 2 μm or less. The vibration mill or ball mill preferably contains a medium having a predetermined particle diameter. Examples of the material of the media include iron-based chromium steel and oxide-based zirconia, titania, and alumina. As a form of a grinding | pulverization process, any of a continuous type and a batch type may be sufficient. The particle size of the pulverized product is adjusted depending on the pulverization time and rotation speed, the material and particle size of the media used, and the like.

[Granulation process]
Then, the pulverized slurry is spray-dried and granulated. Specifically, the slurry is introduced into a spray dryer such as a spray dryer, and granulated into a spherical shape by spraying into the atmosphere. The atmospheric temperature during spray drying is preferably in the range of 100 to 300 ° C. Thereby, a spherical granulated product having a particle size of 10 to 200 μm is obtained. In addition, it is desirable that the obtained granulated product has a sharp particle size distribution by removing coarse particles and fine powder using a vibration sieve or the like. The preferable average particle diameter of the granulated product is in the range of 10 μm to 200 μm.

[Baking process]
Next, the granulated powder is put into a furnace heated to 950 to 1200 ° C. and fired for synthesizing soft ferrite to produce a magnetic carrier core material.
In order to adjust the average valence number of Fe to a predetermined value, carbon may be added to the raw material as a reducing agent. If the oxygen concentration in the furnace is too high, the added reducing agent may be oxidized. If the added reducing agent is oxidized, the reduction of iron oxide, which is the original purpose, cannot be adjusted. Therefore, the oxygen concentration in the firing furnace is controlled to 1% by volume or less.

  Regarding the firing temperature, if it is 700 ° C. or higher, sufficient productivity can be secured at the time of industrialization. On the other hand, if it is 1500 degrees C or less, oversintering of particle | grains can be avoided and a baked product can be obtained with the form of a powder. Furthermore, it is preferable to fire at 950 to 1200 ° C. from the viewpoint of ensuring the magnetic properties and crushing strength of the produced magnetic carrier core material.

  It is desirable to adjust the particle size of the obtained fired product at this stage. For example, the baked product is coarsely pulverized with a hammer mill, etc., then subjected to primary classification with an airflow classifier, and further subjected to a process of aligning the particle size with a vibration sieve or an ultrasonic sieve, whereby the baked product with adjusted particle size is used. A certain magnetic carrier core material can be manufactured. In addition, after the said particle size adjustment, it is desirable to perform the process by a magnetic separator further and to remove a nonmagnetic particle.

[Manufacture of magnetic carrier]
A magnetic carrier can be obtained by applying a resin coating to the obtained magnetic carrier core material. As a coating method, a dry method, a fluidized bed method, a dipping method, or the like can be used. Among these, from the viewpoint of filling the resin inside the magnetic carrier core material, an immersion method and a dry method are more preferable.
Here, the dipping method will be described as an example. As the coating resin, a silicone resin or an acrylic resin is preferable. About 20 to 40% by mass of the coating resin is dissolved in a solvent (toluene or the like) to prepare a resin solution. The coating operation can be performed by heating and stirring at 150 to 250 ° C. after mixing in a container so that the solid content is 0.7 to 10% of the magnetic carrier core material. The coating amount of the resin can be controlled by the concentration of the resin solution and the mixing ratio of the resin solution and the magnetic carrier core material. After the resin coating, a heat treatment is further performed to cure the resin coating layer, whereby a magnetic carrier (powder) is obtained.

(Magnetic property measurement)
The magnetic properties of the magnetic carrier core material according to the present invention were measured using VSM (manufactured by Toei Kogyo Co., Ltd., VSM-P7). An external magnetic field is continuously applied to the magnetic carrier core material from 0 to 10000 (Oe), and the magnetization is measured to obtain magnetizations σ500 (emu / g), σ1000 (emu / g), σs (emu / g) was obtained. Further, the saturation magnetization σs is expressed by magnetization when the applied magnetic field is 10000 Oe.

[Crush strength test]
In the crushing strength test of the magnetic carrier core material according to the present invention, 100 g of the magnetic carrier core material according to the present invention was put into a sample mill (SK-M10 type, Kyoritsu Riko Co., Ltd.), and the crushing test was performed at a rotational speed of 16000 rpm for 120 seconds It went by. And the generation amount of fine powder having a particle size of 22 μm or less after the crushing test was measured by a laser diffraction type particle size distribution measuring device (Microtrack, Model 9320-X100 manufactured by Nikkiso Co., Ltd.). Then, the generation rate of fine powder having a particle size of 22 μm or less relative to the weight of the magnetic carrier core material before the crushing test is calculated, and the generation rate of powder having a particle size of 22 μm or less before and after the crushing test is calculated. (Hereinafter, it may be described as an occurrence rate of −22 μm).
According to the study by the present inventors, from the results of Examples described later, when the 22 μm generation rate is 6% or less, the carrier scattering amount is 10 ppm or less.

[Evaluation of carrier scattering]
An evaluation test was performed to confirm that the magnetic carrier core material according to the present invention hardly causes carrier scattering.
Specifically, a carrier core material was filled in a magnetic drum having a diameter of 50 mm and a surface magnetic force of 1000 Gauss, and the magnetic drum was rotated at 270 rpm for 30 minutes. And the particle | grains which scattered from the said magnetic drum were collect | recovered, the weight was measured, and the ratio of the particle | grains which scattered from the carrier core material with which it initially filled was calculated as carrier scattering amount.
Of course, the carrier scattering amount is most preferably 0 ppm. However, according to the study by the present inventors, it has been confirmed that when the carrier scattering amount is 10 ppm or less, no particular problem occurs in actual electrophotographic development.

In the examples, three types of iron raw materials were prepared. That is, raw materials of two companies with different ores and processes are prepared, and it is referred to as Example 1 or 2, and about one company is Example 2 and the same company, but raw materials of different production lots with different manufacturing dates are described in Example 3. Prepared as. The raw materials in different production lots have different trace components depending on the raw material components that are the sources of the raw materials.
Example 1
MnMg ferrite particles were produced by the following method. As starting materials, Fe ₂ O ₃ (average particle size: 0.6 μm) is dispersed in 10.05 kg, Mn ₃ O ₄ (average particle size: 2 μm) is dispersed in 4.72 kg, and water 3.8 kg. As a mixture, 90 g of an ammonium polycarboxylate-based dispersant, MgCO ₃ as an Mg source, SrCO ₃ as an Sr raw material, and CaCO ₃ as a Ca raw material were added. The solid content concentration of this mixture was 80% by weight. This mixture was pulverized by a wet ball mill (media diameter 2 mm) to obtain a mixed slurry. After stirring for a while, it was sprayed into hot air at 190 ° C. with a spray dryer to obtain a dry granulated product having a particle size of 10 to 200 μm.

  Coarse particles and fine particles were separated from the obtained dried granulated product using a sieve mesh having a mesh size of 80 μm and 25 μm. The granulated product after separation of the coarse particles and fine particles is fired for 5 hours at 1000 ° C. in a nitrogen atmosphere (a nitrogen atmosphere in which the measured value of the oxygen concentration by a zirconia oxygen sensor is 450 ppm) to obtain a fired product. It was. The fired product was pulverized with a hammer mill, fine powder was removed using an air classifier, and the particle size was adjusted with a vibrating screen having a mesh size of 45 μm to obtain a magnetic carrier core material according to Example 1 having an average particle size of 35 μm. The composition of the main components is shown in Table 1.

(composition)
(Analysis of Fe)
Ferrite particles containing iron element were weighed and dissolved in a mixed acid water of hydrochloric acid and nitric acid. After evaporating this solution to dryness, sulfuric acid water is added and redissolved to volatilize excess hydrochloric acid and nitric acid. Solid Al is added to this solution to reduce all Fe ³⁺ in the solution to Fe ²⁺ . Subsequently, the amount of Fe ²⁺ ions in the solution was quantitatively analyzed by potentiometric titration with a potassium permanganate solution to obtain a titer of Fe (Fe ²⁺ ).
(Analysis of Mn)
The Mn content of the ferrite particles was quantitatively analyzed according to the ferromanganese analysis method (potentiometric titration method) described in JIS G1311-1987. The Mn content of the ferrite particles described in the present invention is the amount of Mn obtained by quantitative analysis by this ferromanganese analysis method (potentiometric titration method).
(Ca analysis)
The Ca content of the ferrite particles was analyzed by the following method. The ferrite particles according to the present invention were dissolved in an acid solution, and quantitative analysis was performed by ICP. The Ca content of the ferrite particles described in the present invention is the amount of Ca obtained by this quantitative analysis by ICP. Similarly, the Mg content can be obtained by quantitative analysis by ICP.
(Analysis of trace components)
In the obtained magnetic carrier core material according to Example 1, 51.1% by mass of iron as a main component, 18.6% by mass of Mn as an additive element, 2.16% by mass of Mg, 0.50% by mass of Sr, Ca 0 0.062% by mass. Other trace elements were analyzed by ICP-MS. Trace elements are 0.016 mass% Si, 0.024 mass% Al, 0.035 mass% Cr, 0.013 mass% Cu, 0.012 mass% P, less than 0.002 mass% Cl, and Ni 0.007. % By mass, 0.002% by mass of Mo, 0.003% by mass of Zn, 0.004% by mass of Ti, and sulfur were not detected. The total content of trace elements was 0.117% by mass or less. Less than chlorine indicates that it was below the detection limit. Except for the main components of iron, additive elements, and trace elements, oxygen is mainly used. Li (lithium), B (boron), K (potassium), and Na (sodium) are also about 20 to 100 ppm each. It was included.

  Here, the results of measuring the magnetic properties of the magnetic carrier core material according to Example 1 are as follows: σs: 69.1 (emu / g), σ1k: 58.8 (emu / g), σ500: 37.8 (emu) / G). When the carrier scattering amount was measured, it was 10 ppm or less, and it was found that all of them were practically satisfactory. Trace elements other than those described here can be assumed, but as a result, since they are not affected, it can be said that the trace elements of 0.001% by mass or less are not present or the influence of the trace remaining can be suppressed. In addition, it turned out that the influence of Ni, Mo, etc. was able to be suppressed.

(Example 2)
A magnetic carrier core material was prepared in the same manner as in Example 1 except that the raw material of iron was changed (the manufacturing company was different). The content of each element was measured by the same analysis. The total Fe amount was 51.3% by mass. The main component was 51.3 mass% iron, the additive element Mn was 18.7 mass%, Mg was 1.39 mass%, Sr was 0.14 mass%, and Ca was 0.12 mass%. Trace elements are 0.04 mass% Si, 0.039 mass% Al, 0.022 mass% Cr, 0.006 mass% Cu, 0.016 mass% P, less than 0.002 mass% Cl, 0.01 Ni % By mass, 0.002% by mass of Mo, 0.006% by mass of Zn, 0.008% by mass of Ti, and sulfur were not detected. The total content of trace elements was 0.148% by mass or less. Less than chlorine indicates that it was below the detection limit. Except for the main components of iron, additive elements, and trace elements, oxygen is mainly used, and B (boron), K (potassium), and Na (sodium) are also contained in about 20 to 100 ppm each.
Here, the result of measuring the magnetic properties of the magnetic carrier core material according to Example 2 was σs: 68 (emu / g). When the carrier scattering amount was measured, it was 10 ppm or less, and it was found that all of them were practically satisfactory. Trace elements other than those described here can be assumed, but as a result, since they are not affected, trace elements of 0.001% by mass or less do not exist, or it can be said that the effects of trace residuals can be suppressed. .

(Example 3)
A magnetic carrier core material was prepared in the same manner as in Example 2 except that the raw material for iron was the same as that of Example 2 except that the lot number was changed. The content of each element was measured by the same analysis as in Example 1. The total amount of Fe was 51.4% by mass. The additive elements were Mn 18.4 mass%, Mg 1.39 mass%, Sr 0.14 mass%, and Ca 0.10 mass%. Trace elements are 0.020 mass% of Si, 0.033 mass% of Al, 0.018 mass% of Cr, 0.005 mass% of Cu, 0.014 mass% of P, 0.002 mass% of Cl or less, Ni 0.006 % By mass, 0.002% by mass of Mo, 0.001% by mass of Zn, 0.004% by mass of Ti, and sulfur were not detected. The total content of trace elements was 0.251% by mass or less. Less than chlorine indicates that it was below the detection limit. Except for the main components of iron, additive elements, and trace elements, oxygen is mainly used, and B (boron), K (potassium), and Na (sodium) are also contained in about 20 to 100 ppm each.
Here, the result of measuring the magnetic properties of the magnetic carrier core material according to Example 3 was σs: 68 (emu / g). When the carrier scattering amount was measured, it was 10 ppm or less, and it was found that all of them were practically satisfactory. Trace elements other than those described here can be assumed, but as a result, since they are not affected, trace elements of 0.001% by mass or less do not exist, or it can be said that the effects of trace residuals can be suppressed. . It can be seen that the content of trace elements varies depending on the type of raw material and the date of acquisition.

Claims (2)

  In the ferrite magnetic material which is an additive element composed of Fe and at least one of Mn, Mg, Ti, Cu, Zn, Ni, Sr and Ca, the average particle diameter is 1 to 100 μm. The total amount of impurities excluding Fe, additive elements and oxygen in the ferrite magnetic material is 0.5 mass% or less, and the impurities are Si, Al, Cr, Cu, P, Cl, Ni, Mo , A ferrite magnetic material containing at least two of any one of Zn, Ti, sulfur, Ca, Mn, and Sr. The ferrite magnetic material according to claim 1, wherein the saturation magnetization σs is 50 emu / g or more.