JPS60135958A - Spherical magnetic carrier particles and their manufacture - Google Patents

Abstract

PURPOSE:To prepare spherical magnetic carrier particles having magnetic characteristics of a coercive force of <=15Oe, and a saturation magnetization of >=50emu/g, and having an average particle diameter of 50-200mum and superior surface property and to provide their manufacturing method by using a mixture of Fe2O3, MgO, ZnO, and CuO specified in compsn. CONSTITUTION:The spherical magnetic carrier particles are obtained by preparing a mixture of ferrite-forming metal oxides of an iron compd. and/or iron oxide contg. an amt. of 44.5-52.5mol% as Fe2O3, and Mg, Zn, and Cu oxides or such compds. capable of forming the oxides upon heating in an amt. of 55.5- 47.5mol% in terms of MO, M meaning Mg, Zn, and Cu; adding the obtained mixture into a aq. soln. dissolving polycarboxylic acid Na salt in an amt. of 0.2-1.0wt% of said mixture to form a slurry so as to adjust the concn. of said ferrite forming metal oxide to 50-80wt%; and burning the obtained substantially spherical metal oxide obtained by spray drying the slurry in the temp. range of 1,100-1,350 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides magnetic carrier particles, particularly magnetic carrier particles having magnetic properties of 1500 or less coercive force, 5Q em'mVg or more, average particle size 50 to 200 μm, and excellent surface properties. The present invention relates to magnetic carrier particles exhibiting a spherical shape and a method for producing the same.

Various developing methods have been known in the past, and can be broadly classified into wet developing methods and dry developing methods. Since the former uses an organic solvent as a carrier, problems such as operability and odor pollution have been pointed out, and as a result, dry developing methods have become mainstream at present. As this method, a magnetic brush development method, a cascade development method, etc. are well known.

The developer used in the above-mentioned magnetic brush development, cascade development, etc. is a one-component developer that uses magnetic powder in the toner particles itself, or a toner that is composed of a binder resin, carbon black, dye, etc. There are two-component developers consisting of a mixture of particles and gearia.

Currently, various materials such as spherical and amorphous glass, silica sand, and iron powder are used as carriers in these two-component developers, and the most commonly used material is iron. There is powder.

Iron powder has a large saturation magnetization value and is suitable as a carrier for two-component developers, but the surface of iron powder is easily oxidized by moisture and oxygen in the atmosphere, forming a thin monoxide layer.
This oxidized layer itself is easily worn and peeled off, and its oxidation state changes according to changes in the environmental conditions, and oxidation progresses inside the particles in the form of rust, making it extremely unstable. , tends to weaken the magnetic adsorption to the magnet roll, and peeled off rust tends to compete with toner particles, resulting in image unevenness and fogging.

In addition, when using a two-component developer, there is a drawback that the bulk specific gravity of iron powder is large, making it difficult for the toner particles to mix with the carrier. It is difficult to make the toner spherical, and it is often difficult to make it spherical. For this reason, when the carrier and toner are mixed, the so-called spent toner fuses to the carrier, deteriorating the properties of the developer and shortening its lifespan. I kept it short.

For this reason, it has recently been proposed to use ferrite-based materials as carriers instead of iron powder.

The characteristics required for a carrier are that it has appropriate triboelectric charging properties and attracts toner particles, that the particles have good fluidity, that the particles are uniform, and that they have excellent surface properties.
It also has appropriate coercive force and saturation magnetization.

Conventionally, Kakinada's ferrite gears have been used as carrier particles, especially soft ferrite, and these ferrite gears are not necessarily satisfactory in terms of image characteristics or lifespan.

It is known that the condition of the surface of carrier particles is a cause of deterioration of image characteristics or shortening of lifespan.

This fact is evidenced, for example, by [
...The shape of the carrier needs to be approximately spherical. Even if they are spherical, they have a rough surface or are irregularly shaped, and have poor fluidity, making it easy for toner to stick to or be packed into the carrier, as well as toner shattering or abrasion. becomes difficult to achieve. It is clear from the statement "...".

In recent years, as office automation has progressed, there has been a demand for faster development, and the carrier particles used for dry development in high-speed copying machines have correspondingly large saturation magnetization (σI+). There is a need for the development of such ferrite carrier particles, which are required to have a particle morphology that is spherical and has an appropriate coercive force and excellent surface properties.

In the present invention, the term ``elite carrier particles with excellent surface properties'' refers to ferrite carrier particles that have no irregularities on the particle surface and have fewer pores and grain boundaries.

The present inventor has systematically examined the relationship between the coercive force, saturation magnetization, and surface properties of ferrite carrier particles and ferrite composition.

And when converted into Fe2O3 amount, it is 44.5-452.
5 moles of iron compounds and/or oxidation and MO (
M represents Mg, Zn, Ou) when converted to 5
Magnesium, zinc in an amount of 55 to 47.5 mol%,
A mixture of a ferrite-forming metal oxide with a copper oxide or a compound that becomes an oxide by heating is prepared, and the mixture is mixed with a ferrite-forming metal oxide of 02 to 1.
The weight concentration of the ferrite-forming metal oxide was brought to 5 by adding it into an aqueous solution in which 0% by weight of polycarboxylic acid Na4 was dissolved.
A substantially spherical metal oxide obtained by spray-drying a slurry adjusted to 0 to 80%
When firing in the temperature range of 50°C, the coercive force is 15
0e or less, saturation magnetization of 53 emVg or more, an average particle size of 50 to 200 μm, and a spherical shape with excellent surface properties.The present invention was completed based on the discovery that it is possible to obtain magnetic carrier particles having a spherical shape with excellent surface properties. This is what I did.

That is, the present invention consists of 44.5 to 52.5 moles of Fe20B, 24 to 51 moles of Mg, 12 to 22 moles of ZnO, and 4 to 15 moles of ZnO, and has a coercive force of 1508 or less and a saturation magnetization of 5Q @mu/g or more. The present invention provides spherical magnetic carrier particles having magnetic properties, an average particle size of 50 to 200 μm, and excellent surface properties, and a method for producing the same.

Next, the configuration and effects of the present invention will be explained in detail.

The present inventors first investigated various ferrite compositions.

Then, the present inventors discovered Ni-Zn-based ferrite carrier particles that have been conventionally used as ferrite carrier particles.
For Zn-based ferrite, it is not economically preferable to use expensive N1-based raw materials, and when using Mn-based materials, it is necessary to limit the atmosphere when firing to form ferrite, resulting in operational clutter. Since this upper root is essential, we focused on Mg-Zn thread ferrite particles among other soft ferrite particles.

Subsequently, the present inventor studied the magnetic properties of ferrite carrier particles used as magnetic carrier particles, particularly the coercive force HC1 saturation magnetization σS and the ferrite composition that imparts carvings to the surface properties of the particles.

In order to obtain satisfactory magnetic properties such as coercive force and saturation magnetization value of the Mg-Zn-based ferrite carrier particles of the present invention as a carrier, it is necessary to increase the amount of Fe2O3. In order to obtain excellent Mg-Zn based ferrite carrier particles, it is necessary to reduce the amount of FezO5, and in order to satisfy the basic properties such as coercive force, saturation magnetization value and surface properties, the above θ2054
4.5-525 mol%, MgO24-61 mol%, Zn
It was discovered that a composition ratio of 012 to 2222 mol% uo and 4 to 75 mol% is required.

Next, specific conditions for implementing the present invention will be described.

As the iron oxide in the present invention, α-Fe20!57-
Fe2O3 or Fe3O4, α as an iron compound
-yeo(oH) and 1-FeO(OH) can be used.

Most preferred is α-p'e203.

As the magnesium compound in the present invention, Mg (
OH)2, MgO, Mg0Q3, etc. can be used. ZnO as a zinc compound, 0uO10u2 as a copper compound
0 etc. can be used.

The magnetic carrier particles in the present invention are FezO3:44
．． 5-525 mol%, MgO: 24-51 mol%, Z
It consists of ferrite particles with a composition represented by nO: 12 to 22 mol%, QuO: 4 to 7.5 mol%, and outside this range, the magnetic property values and surface properties as a ferrite carrier, which are the objects of the present invention, are Spherical magnetic carrier particles having both properties cannot be obtained.

The average particle size of the magnetic carrier particles in the present invention is 50 to 2
00μ〃! must be done. If it is less than 50 μm, it is not preferable because there is a possibility that a large amount of carrier scratching and toner staining may occur.

In this way, the average particle size of the magnetic gearia particles is set to 50 to 200.
In order to control μtn within the range U1+, the weight concentration of the ferrite-forming metal oxide in the ferrite-forming metal oxide mixture slurry, which is the slurry to be treated when performing the spray drying treatment, must be adjusted to 02 ~1.
0% by weight (relative to the ferrite-forming metal oxide) must be added to yield 50-80% by weight. If the weight concentration of the ferrite-forming metal oxide outside this range is 50% by weight or less, the spray drying effect will be poor and the productivity will be low.

On the other hand, if it is more than 80% by weight, supply becomes difficult and spray drying becomes impossible, making the magnetic carrier particles that are the object of the present invention profitable.

The firing temperature in the present invention must be in the range of 1100 to 1650°C.

The present invention of the f'i# precept as described above achieves the following effects.

That is, according to the present invention, the ferrite composition range Fe2O
344.5 to 52.5 mol%, MgO 24 to 61 mol, ZnO 12-22 mol, Ouo 4 to 7.5 mol, coercive force 1500 or less, saturation magnetization 5Q em
Has magnetic properties of u/g or more, average particle size 50-200μ
m, and it is possible to obtain spherical magnetic carrier particles with excellent surface properties, which prevents the toner from fusing to the carrier and forming spent toner when mixed with the toner, and also prevents the toner from becoming spent toner. It is suitable as a carrier for two-component developers for dry development, which are currently required, since no deterioration of properties occurs and the life of the developer can be extended.

Next, the present invention will be explained with reference to Examples and Comparative Examples.

Example 1 Magnesium hydroxide (Mg(OH)z) 6.84 k
g, zinc oxide 6.57kg and copper oxide 2.49kl? and 34.52 kg of iron oxide (α-Fe2O3) to give MgO: 26.6 mol%, ZnO: 17.7 mol%,
OuO near, 1 mol, Fe2O3: 48.6 mol%
A mixture of ferrite-forming metal oxides with the composition was prepared. Then, the mixture was mixed with polycarboxylic acid Na salt 0.3
5% by weight (based on the mixture of ferrite-forming metal oxides) was added to an aqueous solution of 1671, and after adjusting the concentration of the ferrite-forming metal oxide to 751% (5%), it was blown and dried to form a spherical shape. A ferrite-forming metal oxide was obtained.Subsequently, the obtained spherical ferrite-forming metal oxide was
It was fired at a temperature of 0°C for 3.5 hours to form ferrite. Next, this material was agglomerated and classified to obtain an average particle size of 9.
Magnetic carrier particles exhibiting a spherical shape of 0 μm were obtained.

As a result of magnetic observation, it was confirmed that the obtained spherical magnetic carrier particles had excellent surface properties, with no irregularities on the particle surface, and few pores and grain boundaries. .

Examples 2 to 7 Same as Example 1 except that the raw materials for the 7 erite-forming metal oxides, the composition ratio, the amount of polycarboxylic mNa salt, the concentration of the ferrite-forming metal oxide mixed slurry, and the firing temperature were varied. Magnetic carrier particles exhibiting a spherical shape with excellent surface properties were obtained.

Table 1 shows the main manufacturing conditions and characteristics of the magnetic carrier particles.

Note that the iron oxide raw material used in Example 5 was Fe3O4. Further, a scanning electron micrograph (X700) of the magnetic carrier particles obtained in Example 7 is shown in FIG.

Comparative Examples 1 to 5 Composition ratio of ferrite-forming metal oxide, polycarboxylic acid N
Magnetic carrier particles were obtained in the same manner as in Example 1, except that the amount of a salt, the concentration of the ferrite metal oxide mixed slurry, and the firing temperature were varied.

A scanning electron micrograph (X700) of the magnetic carrier particles obtained in Comparative Example 1 is shown in FIG. As is clear from the scanning electron micrograph shown in FIG. 6, the particle surface was uneven and the magnetic carrier particles had many pores and grain boundaries. In addition, the magnetic carrier M:<j obtained in Comparative Example 3 was produced by using polycarboxylic acid Na salt, and this Na or the magnetic carrier had a negative effect. The particle surface was uneven, and there were many pores and grain boundaries.

[Brief explanation of drawings]

Figures 1 to 6 are all scanning electron micrographs (X7
DO), FIG. 1 shows the magnetic carrier particles obtained in Example 1, FIG. 2 shows the magnetic carrier particles obtained in Example 7, and FIG. 6 shows the magnetic carrier particles obtained in Comparative Example 1. Patent applicant: Toda Kogyo Co., Ltd.

Claims (1)

[Claims] 1) Fe20B 44.5-52.5 mol%, MgO
24-51 mo/l/%, ZnO12-22 mo/l/%,
It consists of 7.5 moles of OuO, has magnetic properties of less than 1500 coercive force, more than 50 mu/g saturation magnetization, and has an average particle size of 50 to 200 μ! A spherical magnetic carrier particle characterized by excellent surface properties. 2) When converted to Fe2O3, the amount of iron compounds and H- or ferric oxides is 44.5-52.5 mol%, and when converted to MO (M represents Mg, Zn, Ou), Ki555
475 mole % of magnesium, zinc, copper oxides or heating to form a mixture of ferrite-forming metal oxides with compounds that become oxides, and then converting the mixture into a mixture of ferrite-forming metal oxides. Against 02-1
0% by weight of polycarboxylic acid Na salt dissolved in an aqueous solution, and the weight concentration of the ferrite-forming metal oxide was increased to 5% by weight.
After adjusting the concentration to 0 to 80% by weight, it is spray-dried to form a substantially spherical metal oxide, and fired in a temperature range of 1100 to 1350°C to create a magnetic field with a coercive force of 1500 or less and a saturation magnetization of 5Q emVg or more. with the average particle size of 5
A method for producing spherical magnetic carrier particles characterized by excellent surface properties.