JP2008096758A - Iron-based black particle powder for toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide iron-based black particle powder which is superior in staining power and of which magnetization intensity is, as low as possible, and make it possible to use the iron-based black particle powder as a coloring material for a black pigment, dye, and resin composition, etc. <P>SOLUTION: The present invention is the iron-based black particle powder for toner, comprising iron-titanium composite oxides, in which the iron-based black particle is 0.05-0.4 μm for the average particle size of the primary particle (Dp), and is 0.06-1.0 μm in the average particle size of the secondary particle (Da), and the ratio of the average particle size of the secondary particle (Da) to the average particle size of the primary particle (Dp), or (Da/Dp), is 1.1-2.8. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention provides a toner iron-based black particle powder having excellent coloring power and having a magnetization value as low as possible.

  The iron-based black particle powder according to the present invention can be used as a pigment and paint exhibiting black color, a coloring material for a resin composition, and the like, and particularly when used for a non-magnetic black toner, it has a high coloring power. And having a low magnetization value and uniform black particle dispersion in the binder resin composition, it is possible to provide a non-magnetic black toner with high durability development.

  Black pigments such as magnetite particle powder, ilmenite particle powder, and carbon black have been widely used as colorants for paints, printing inks, cosmetics, rubber / resin compositions, and the like.

  In particular, composite particles obtained by mixing and dispersing black magnetic iron oxide particles such as magnetite particles in a resin are frequently used in magnetic toners used as electrophotographic developers.

  However, since magnetite particles have magnetism, they tend to be magnetically aggregated between the particles, and it is difficult to say that they are excellent in dispersibility.

  Recently, with the increase in the speed and image quality of laser beam printers and digital copying machines, there has been a strong demand for improving the characteristics of black toner as a developer. For this purpose, black toner has sufficient blackness. It is strongly required to have it.

  Furthermore, in recent years, full-color printing has been promoted, and non-magnetic toner is used as a corresponding printer or copying machine.

  Therefore, there is a demand for black toner that is non-magnetic or has a magnetization value as small as possible and can be adapted to the current system.

  As described above, improvement of various characteristics of the black nonmagnetic toner is strongly demanded. In black nonmagnetic toner, it is known that the characteristics of the black pigment contained in the toner have a great influence on the development characteristics, and various characteristics of the black nonmagnetic toner are mixed and dispersed in the black nonmagnetic toner. There is a close relationship with various characteristics of black pigments, and there is a strong demand for further improvements in characteristics of black pigments used in black nonmagnetic toners.

  That is, in order to obtain a black non-magnetic toner with excellent blackness, it is required that the black particle powder has sufficient blackness and better dispersibility. Furthermore, in order to adapt to the current system using non-magnetic toner, as the black particle powder, non-magnetic or particle powder having a magnetization value as low as possible is required.

On the other hand, although carbon black is non-magnetic, it is a fine particle powder having an average particle size of about 0.005 to 0.05 μm, so that it is difficult to disperse in a vehicle or a resin composition. It is known that the powder is bulky with a density of about 0.1 g / cm ³ , so that it is difficult to handle and the workability is poor.

  Therefore, there is a demand for black particle powder that is excellent in blackness and has a magnetization value as low as possible and excellent in dispersion in a resin composition.

Ilmenite particle powder (Patent Document 1) obtained by hydrothermal treatment as a black iron-based particle powder, a black pigment comprising a mixed composition of Fe ₂ TiO ₅ and Fe ₂ O ₃ —FeTiO ₃ solid solution (patent) Document 2), iron-based black particle powder (Patent Document 3) comprising a mixed composition of Fe ₂ O ₃ —FeTiO ₃ solid solution or Fe ₂ O ₃ —FeTiO ₃ solid solution and an iron-based oxide having a spinel structure is known. ing.

JP-A-1-298028 JP-A-3-2276 JP 2004-161608 A

  An iron-based black particle powder that is excellent in coloring power and has a magnetization value as low as possible is currently most demanded, but has not yet been obtained.

That is, in the above-mentioned Patent Document 1, it is described that ilmenite particle powder is obtained by hydrothermal treatment using Ti ³⁺ , but it is manufactured by hydrothermal treatment and is not industrially useful.

The non-magnetic particle powder described in Patent Document 2 contains Fe ₂ TiO ₅ and thus has a low magnetization value. However, the particle size distribution is not taken into consideration, the coloring power is low, and the blackness is satisfied. It is hard to say.

The iron-based black particle powder described in the above-mentioned Patent Document 3 does not consider the particle size distribution, and has a high saturation magnetization value of 5 to 40 Am ² / kg and can be easily adapted to a non-magnetic system. It's hard to say.

  Then, this invention makes it a technical subject to obtain the iron-type black particle powder which is excellent in coloring power, and has a low magnetization value.

  The technical problem can be achieved by the present invention as follows.

  That is, the present invention is iron-based black particles having an average primary particle diameter (Dp) of 0.05 to 0.4 μm, and an average particle diameter (Da) of secondary particles of the iron-based black particles is 0.00. Iron-titanium composite oxide having a ratio (Da / Dp) of the average particle diameter (Da) of the secondary particles to the average particle diameter (Dp) of the primary particles of 1.1 to 2.8. An iron-based black particle powder for toner, which is characterized by comprising a product. (Invention 1).

Further, the present invention is the iron-based black particle powder for toner according to the present invention 1, wherein the saturation magnetization value is less than 5 Am ² / kg. (Invention 2)

  The present invention is the iron-based black particle powder for toner according to the first or second aspect of the present invention, wherein the L * value representing the coloring power is 44.5 or less. (Invention 3)

  The present invention is the iron-based black particle powder for toner according to any one of the iron-titanium composite oxide particle powders of the present invention 1 to 3, wherein the Ti content is 10 to 38 atomic%. (Invention 4)

Further, the present invention is the iron-based black particle powder for toner, wherein the constituent phase of the iron-titanium composite oxide particle powder has at least a FeTiO ₃ —Fe ₂ O ₃ solid solution. (Invention 5)

Further, the present invention provides the toner iron-based toner according to the fifth invention, further comprising at least one selected from an iron-based oxide having a spinel structure, a Na—Fe—Ti compound, and Fe ₂ TiO _5. Black particle powder. (Invention 6)

  The iron-based black particle powder according to the present invention is excellent as a coloring power and has a magnetization value as low as possible, and thus is suitable as a coloring material for black toner.

  In particular, when used for a non-magnetic black toner, it has a high coloring power, a low magnetization value, and a uniform dispersion of black particles in the binder resin. Become.

  Further, since the iron-based black particle powder according to the present invention has excellent coloring power and has a magnetization value as low as possible, it is also suitable as a pigment and paint exhibiting black, a coloring material for a resin composition, a filler, and the like. is there.

  The configuration of the present invention will be described in more detail as follows.

  First, the iron-based black particle powder according to the present invention will be described.

  When the average particle diameter (Dp) of the primary particles of the iron-based black particle powder according to the present invention is less than 0.05, the desired blackness cannot be obtained. The cohesive force between the particles is large, making dispersion difficult. If it exceeds 0.40 μm, the desired coloring power cannot be obtained. Preferably it is 0.10-0.40 micrometer, More preferably, it is 0.10-0.35 micrometer.

  The iron-based black particle powder according to the present invention controls the average particle diameter (Da) of secondary particles to 0.06 to 1.0 μm. When the average particle diameter (Da) of the secondary particles is less than 0.06 μm, it is difficult to produce industrially, and when it exceeds 1.0 μm, the desired coloring power cannot be obtained. The agglomerated particle size is increased and the dispersion in the toner is deteriorated. Preferably it is 0.11-0.648 micrometer.

  In addition, the particle diameter of the secondary particle in this invention is calculated | required by laser diffraction type particle size distribution measurement as mentioned later, and let the average particle diameter by a volume reference | standard be Da.

  In the iron-based black particle powder according to the present invention, the ratio (Da / Dp) of the average particle diameter (Da) of the secondary particles to the average particle diameter (Dp) of the primary particles is 1.1 to 2.8. When the ratio (Da / Dp) of the average particle diameter (Da) of the secondary particles to the average particle diameter (Dp) of the primary particles is less than 1.1, it is difficult to produce industrially. If it exceeds .8, the sintered portion due to the heat treatment increases, and the desired coloring power cannot be obtained. In addition, when used in a non-magnetic toner, the dispersibility in the resin becomes poor and it becomes difficult to obtain a desired image density. Preferably it is 1.1-2.7.

The saturation magnetization value of the iron-based black particle powder according to the present invention is preferably less than 5 Am ² / kg. When the saturation magnetization value exceeds 5 Am ² / kg, it is difficult to easily adapt to the current system using non-magnetic toner, it becomes difficult to obtain a desired image density, and the possibility of fogging is high. Tend to be. More preferably, it is 3 Am ² / kg or less.

  The coloring power (L * value) of the iron-based black particle powder according to the present invention is preferably 35 to 44 when shown by the color development of the evaluation method described later. When the coloring power exceeds 44, it is difficult to obtain a sufficient image density when the non-magnetic black toner using the iron-based black particle powder is used. Iron-based black particle powder having a coloring power of less than 35 cannot be produced industrially. More preferably, it is 35-43.

The BET specific surface area value of the iron-based black particle powder according to the present invention is preferably 3 to 15 m ² / g. When the BET specific surface area value is less than 3 m ² / g, the iron-based black particle powder is coarse or becomes coarse particles in which the particles and particles are sintered together, and the coloring power is reduced. When it exceeds 15 m ² / g, it becomes difficult to obtain a desired blackness. More preferably, it is 6-12 m < ² > / g, More preferably, it is 6.5-11 m < ² > / g.

  The titanium content of the iron-based black particle powder according to the present invention is preferably 10 to 38 atomic%, more preferably 12 to 33.3 atomic%.

The constituent phase of the iron-based black particle powder according to the present invention has at least a FeTiO ₃ —Fe ₂ O ₃ solid solution, and further includes Fe ₂ TiO ₅ , Fe ₂ TiO ₄ —Fe ₃ O ₄ solid solution, and FeTiO _3. Iron-titanium composite oxides such as Fe ₂ TiO ₄ and Na—Fe—Ti compounds such as NaFeTi ₃ O ₈ , Na ₂ Fe ₂ Ti ₃ O ₁₀ and NaFeTiO ₄ , and mixtures of two or more of the above compounds It may be. Also, _Fe 3 _{O 4} and a raw material, spinel iron oxide such as _γ-Fe 2 _{O 3} may be present.

  The iron-based black particle powder according to the present invention contains one or more elements selected from Mg, Al, Si, P, Mn, Co, Ni, Cu and Zn in addition to iron and titanium. It may be contained in an amount of 0 to 10 atomic% based on the total amount.

  Next, a method for producing the iron-based black particle powder according to the present invention will be described.

  The iron-based black particle powder according to the present invention can be obtained by firing and firing titanium-containing magnetite particles in a non-oxidizing atmosphere at a temperature range of 650 to 850 ° C.

  The titanium-containing magnetite particle powder is obtained, for example, by aerating an oxygen-containing gas to a ferrous salt reaction solution containing a ferrous hydroxide colloid obtained by reacting a ferrous salt aqueous solution and an alkaline aqueous solution. In the production method for obtaining magnetite, a titanium compound may be added to a ferrous salt reaction solution containing a ferrous hydroxide colloid while an oxygen-containing gas is being passed.

  The aqueous ferrous salt solution used in the present invention is preferably an aqueous iron sulfate solution.

  Examples of the titanium compound used in the present invention include titanyl sulfate, titanium tetrachloride, and titanium trichloride.

  The titanium compound is preferably added simultaneously with the addition of the titanium compound by adding an alkali hydroxide aqueous solution, an alkali carbonate aqueous solution or the like to maintain the pH value of the aqueous suspension at 6.0 or more.

  In the present invention, the surface of the titanium-containing magnetite particles may be further coated with a titanium compound.

  The titanium-containing magnetite particle powder is coated with a titanium compound by adding an aqueous alkali hydroxide solution, an aqueous alkali carbonate solution, or the like to the water suspension containing the titanium-containing magnetite particles before adding the titanium compound. At the same time as the addition, an aqueous alkali hydroxide solution, an aqueous alkali carbonate solution or the like is preferably added to maintain the pH value of the aqueous suspension.

The titanium content of the titanium-containing magnetite particle powder is preferably 10 to 38 atomic%. When it is out of the above range, the number of sintered parts due to heat treatment increases and the coloring power decreases. More preferably, it is 12-33.3 atomic%.
The magnetite particles preferably contain at least 3 atomic% or more of titanium. If it is less than 3 atomic%, the number of sintered parts due to the heat treatment increases and the coloring power decreases. More preferably, it is 5 atomic% or more.

  When the different metal element is contained, it may be previously contained in the magnetite particles, or a salt composed of various metal elements in an aqueous solution in which a titanium compound is coated on the surface of the magnetite particles, or various metals. A solution containing an element may be added.

  Further, when the Na-Fe-Ti compound is contained, a sodium compound may be added to the titanium-containing magnetite particles, the titanium-containing magnetite particles coated with the titanium compound, or the water suspension containing them. . Examples of the sodium compound include sodium hydroxide, sodium sulfate, sodium carbonate, and sodium chloride.

  The heating and firing atmosphere in the present invention is preferably a non-oxidizing atmosphere, and it is difficult to obtain an iron-based black particle powder having high blackness under an oxidizing atmosphere.

  The temperature range of the heating and baking in the present invention is preferably 650 to 850 ° C. When the temperature is less than 650 ° C., the solid phase reaction between the magnetite particles and the Ti compound becomes insufficient, and the intended iron-based black particle powder can be obtained. It is difficult, and when it exceeds 850 ° C., an unnecessary phase is generated, which is not preferable. More preferably, it is 680-830 degreeC.

  What is necessary is just to grind | pulverize the particle powder after heat-firing by a conventional method.

<Action>
The reason for the low saturation magnetization value of the iron-based black particle powder according to the present invention is that by containing a titanium compound in the magnetite, the reactivity between the magnetite and the titanium compound during the heat treatment is increased, and the remaining magnetite is made possible. The present inventor presumes that this is due to a decrease in the number of times.

  The present inventors presume that the reason why the iron-based black particle powder according to the present invention is excellent in particle size distribution is that the reactivity during the heat treatment is increased and a uniform solid-phase reaction proceeds.

  The reason why the iron-based black particle powder according to the present invention is excellent in coloring power is that the magnetic agglomeration is suppressed due to the low saturation magnetization value, and sintering between particles is suppressed and the particle size distribution is excellent. The present inventors presume that the iron-based black particle powder is excellent in dispersibility.

  A typical embodiment of the present invention is as follows.

  The average particle diameter of the primary particles was measured by measuring the particle diameters of 350 particles shown in the electron micrograph, and the average value (Dp) was indicated.

  The average particle size of the secondary particles was determined by adding 400 ml of water and 20 mg of iron-based black particle powder as a dispersant to 1 ml of sodium dodecylbenzenesulfonate as a dispersant using a laser diffraction particle size distribution measuring device (SYMPatec GmbH's HELOS & SUCELL). It is an average particle diameter (Da) based on volume measured by irradiating for 5 minutes.

  The constituent phases of the particles were identified using “X-ray diffractometer RINT-2500” (manufactured by Rigaku Corporation, tube: Cu).

BET specific surface area using the "Mono Sorb MS-II" (manufactured by Yuasa Ionics Co.), expressed by the value measured by the BET method by _{N 2} adsorption.

  The magnetic characteristics of the iron-based black particle powder are values measured under a magnetic field of 796 kA / m (10 kOe) using a “vibrating sample magnetometer VSM-3S-15” (manufactured by Toei Industry Co., Ltd.).

  The content of Ti in the iron-based black particle powder was measured by a calibration curve method using a “fluorescence X-ray analyzer RIX-2100 type” (manufactured by Rigaku Corporation).

The coloring power of the iron-based black particle powder is as follows: 0.5 g of sample, 0.5 ml of castor oil and 1.5 g of titanium dioxide are kneaded with a Hoover type Mahler to form a paste, and 4.5 g of clear lacquer is added to this paste, An application piece (coating thickness: about 30 μm) was prepared by applying a 150 μm (6 mil) applicator on cast-coated paper, and a spectrocolorimeter color guide (manufactured by BYK-Gardner GmbH) was applied to the application piece. The color was used and measured, and the color index (L ^* value) was indicated according to JIS Z 8729.

  The gloss representing the dispersibility of the iron-based black particle powder is obtained by kneading 0.5 g of a sample and 0.5 ml of castor oil with a Hoover-type Mahler to form a paste, adding 4.5 g of clear lacquer to this paste, and kneading it into a paint. Then, a coated piece (coating thickness: about 30 μm) coated on a cast-coated paper using a 150 μm (6 mil) applicator is prepared, and a digital gonio-gloss meter (manufactured by UGV-5D Suga Test Instruments) is used for the coated piece. The light reflectance (%) measured at an incident angle of 60 °.

Example 1
<Manufacture of iron-based black particle powder>
17.8 L of a 1.8 mol / L ferrous sulfate aqueous solution was added to 22.2 L of a 2.76 N NaOH solution to obtain a reaction solution containing a total amount of 40 L and a pH 6.5 iron hydroxide colloid. Thereafter, the temperature of the reaction solution was raised to 90 ° C., air was passed through for 100 minutes, and 20 L of a 0.48 mol / L titanyl sulfate aqueous solution was added to form a black precipitate. During this time, the temperature was maintained at 90 ° C. and pH 6.5.
The black precipitate was separated by filtration, washed with water, dried at 60 ° C., further heated and fired at 730 ° C. under a N ₂ gas flow, and then pulverized to obtain iron-based black particle powder.

The average particle diameter (Dp) of the primary particles of the obtained iron-based black particle powder is 0.11 μm, the average particle diameter (Da) of the secondary particles is 0.29 μm, the average particle diameter (Da) of the secondary particles and the primary particle the ratio of the average particle diameter of the particles (Dp) (Da / Dp) is 2.64, BET specific surface area is 12.8m ² / g, a saturation magnetization value σs is 1.2Am ² / kg, the total The titanium content with respect to iron was 29.7 atomic%, and the L ^* value representing the coloring power was 39.2. The constituent phase was FeTiO ₃ —Fe ₂ O ₃ solid solution.

Examples 2 and 3
An iron-based black particle powder was obtained in the same manner as in Example 1 except that the type and addition amount of the titanium compound, the pH of the reaction solution, and the temperature of the heat treatment were varied.

Example 4
In the same manner as in Example 1, a reaction solution containing an iron hydroxide colloid having a total amount of 40 L and a pH of 6.5 was obtained. Thereafter, the temperature of the reaction solution was raised to 90 ° C., and air was passed through for 100 minutes, and 3.3 L of 0.48 mol / L titanyl sulfate aqueous solution was added to form a black precipitate. During this time, the temperature was maintained at 90 ° C. and pH 6.5.
Subsequently, 16.7 L of 0.48 mol / L titanyl sulfate aqueous solution was added to the aqueous solution containing this black precipitate. In addition, NaOH was added to this aqueous solution so that the pH of the aqueous solution at the time of addition was maintained at 8.5 or more. Thereafter, the pH of the aqueous solution was adjusted to 8.0.
The black particle powder coated with the hydrated titanium oxide was filtered, washed with water, dried, further heated and fired at 790 ° C. under a N ₂ gas flow, and then pulverized to obtain iron-based black particle powder.

The average particle diameter (Dp) of the primary particles of the obtained iron-based black particle powder is 0.31 μm, the average particle diameter (Da) of the secondary particles is 0.48 μm, the average particle diameter (Da) of the secondary particles and the primary particle The ratio (Da / Dp) to the average particle diameter (Dp) of the particles is 1.55, the BET specific surface area value is 5.2 m ² / g, the saturation magnetization value σs is 4.7 Am ² / kg, The titanium content with respect to iron was 29.9 atomic%, and the L ^* value representing the coloring power was 42.9. The constituent phase was a mixture of FeTiO ₃ —Fe ₂ O ₃ solid solution and Fe ₃ O ₄ —γ-Fe ₂ O ₃ solid solution.

Examples 5 and 6
The same as in Example 4 except that the type and amount of the titanium compound added at the time of magnetite formation, the pH of the reaction solution, the type and amount of the titanium compound used for the coating treatment, and the temperature of the heat-firing treatment were variously changed. An iron-based black particle powder was obtained.

  The production conditions at this time are shown in Table 1, and various characteristics of the obtained iron-based black particle powder are shown in Table 2.

Example 7
17.8 L of a 1.8 mol / L ferrous sulfate aqueous solution was added to 22.2 L of a 2.76 N NaOH solution to obtain a reaction solution containing a total amount of 40 L and a pH 6.5 iron hydroxide colloid. Thereafter, the temperature of the reaction solution was raised to 90 ° C., air was passed through for 100 minutes, and 20 L of a 0.48 mol / L titanyl sulfate aqueous solution was added to form a black precipitate. Thereafter, an NaOH solution was added, and the temperature was maintained at 90 ° C. and pH 12.0.
This black precipitate was separated by filtration, washed with water, dried at 60 ° C., further heated and fired at 810 ° C. under a N ₂ gas flow, and then pulverized to obtain iron-based black particle powder.

The average particle size (Dp) of the primary particles of the obtained iron-based black particle powder is 0.23 μm, the average particle size (Da) of the secondary particles is 0.52 μm, the average particle size (Da) of the secondary particles and the primary particle the ratio of the average particle diameter of the particles (Dp) (Da / Dp) is 2.26, BET specific surface area is 6.9 m ² / g, a saturation magnetization value σs is 1.0Am ² / kg, the total The titanium content with respect to iron was 30.8 atomic%, and the L ^* value representing the coloring power was 38.2. The constituent phase was a mixture of FeTiO ₃ —Fe ₂ O ₃ solid solution and NaFeTi ₃ O ₈ .

Example 8
As in Example 1, 17.8 L of a 1.8 mol / L ferrous sulfate aqueous solution is added to 22.2 L of a 2.76N NaOH solution, and the total amount of the iron hydroxide colloid includes pH 6.5 and pH 6.5. A reaction solution was obtained. Thereafter, the temperature of the reaction solution was raised to 90 ° C., air was passed through for 100 minutes, and 20 L of a 0.48 mol / L titanyl sulfate aqueous solution was added to form a black precipitate. During this time, the temperature was maintained at 90 ° C. and pH 6.5.
The black precipitate was separated by filtration, washed with water, and then dried at 60 ° C. to obtain black magnetic iron oxide particles having a particle surface coated with a hydrated titanium oxide.
100 g of sodium sulfate was added to and mixed with 2 kg of black magnetic iron oxide particles whose surface was coated with a hydrous oxide of titanium. Next, 2 kg of the obtained mixture was heated and fired at 750 ° C. under a N ₂ gas flow, and then pulverized to obtain iron-based black particle powder.

The average particle size (Dp) of the primary particles of the obtained iron-based black particle powder is 0.13 μm, the average particle size (Da) of the secondary particles is 0.34 μm, the average particle size (Da) of the secondary particles and the primary particle The ratio (Da / Dp) to the average particle diameter (Dp) of the particles is 2.62, the BET specific surface area value is 10.7 m ² / g, the saturation magnetization value σs is 1.0 Am ² / kg, The titanium content with respect to iron was 29.6 atomic%, and the L ^* value representing the coloring power was 38.5. The constituent phase was a mixture of FeTiO ₃ —Fe ₂ O ₃ solid solution and NaFeTi ₃ O ₈ .

Comparative Example 1
17.8 L of a 1.8 mol / L ferrous sulfate aqueous solution was added to 22.2 L of a 2.76 N NaOH solution to obtain a reaction solution containing a total amount of 40 L and a pH 6.5 iron hydroxide colloid. Thereafter, the temperature of the reaction solution was raised to 90 ° C., and air was passed through for 100 minutes to produce a black precipitate. During this time, the temperature was maintained at 90 ° C. and pH 6.5.
Next, 20 L of a 0.48 mol / L aqueous solution of titanyl sulfate was added to the aqueous solution containing the black precipitate. In addition, NaOH was added to this aqueous solution so that the pH of the aqueous solution at the time of addition was maintained at 8.5 or more. Thereafter, the pH of the aqueous solution was adjusted to 8.0.
The black particle powder coated with the hydrated titanium oxide was filtered off, washed with water, dried, heated and fired at 730 ° C. under N 2 gas flow, and then pulverized to obtain iron-based black particle powder.

The average particle diameter (Dp) of the primary particles of the obtained black particle powder is 0.15 μm, the average particle diameter (Da) of the secondary particles is 0.55 μm, the average particle diameter (Da) of the secondary particles and the primary particles The ratio (Da / Dp) to the average particle diameter (Dp) is 3.67, the BET specific surface area value is 10.3 m ² / g, and the saturation magnetization value σs is 14.3 Am ² / kg. The titanium content was 29.8 atomic%, and the L ^* value representing the coloring power was 44.8. The constituent phase was a mixture of FeTiO ₃ —Fe ₂ O ₃ solid solution and Fe ₃ O ₄ —γ-Fe ₂ O ₃ solid solution.

Comparative Examples 2 and 3
The iron system was the same as in Comparative Example 1 except that the amount of titanium compound added at the time of magnetite formation, the pH of the reaction solution, the amount of titanium compound used for the coating treatment, and the temperature and time of the heating and firing treatment were variously changed. Black particle powder was obtained.

  The production conditions at this time are shown in Table 1, and various characteristics of the obtained iron-based black particle powder are shown in Table 2.

Example 1
<Manufacture of toner for electrophotography>
Using the iron-based black particle powder obtained in Example 1, the composition mixed by the Henschel mixer at the following mixing ratio was melt-kneaded using a biaxial extrusion kneader (trade name: S-1 manufactured by Kurimoto Steel). The kneaded product was cooled and then finely pulverized. This was classified into a volume average particle diameter of 8 to 10 μm (trade name manufactured by Colecounter, Inc., measured by Multisizer). Further, 100 parts by weight of the obtained toner powder was used to produce a hydrophobic silica fine powder (trade name manufactured by Nippon Aerosil Co. : RX-200) 0.5 part by weight was externally added to obtain an electrophotographic toner.

100 parts by weight of styrene-acrylic copolymer resin,
(Heimer SB-308: Sanyo Chemical Industries, Ltd.)
25 parts by weight of iron-based black particle powder,
0.5 parts by weight of negative charge control agent,
(BONTRON E-84: manufactured by Orient Chemical Co., Ltd.)
5 parts by weight of low molecular weight wax.
(Biscol 550-P: Sanyo Chemical Industries, Ltd.)

  The obtained electrophotographic toner had an initial image density of 1.55 and no fogging (◎ out of 4 steps).

Example 2
A nonmagnetic toner was obtained in the same manner as in Use Example 1 except that the black particle powder was changed to that obtained in Comparative Example 1.

  Table 3 shows the treatment conditions and various characteristics of the obtained nonmagnetic black toner.

  Since the iron-based black particle powder according to the present invention has a high coloring power and a magnetization value as low as possible, it is suitable as a pigment and paint exhibiting black, a coloring material for a resin composition, a filler, and the like.

The black nonmagnetic toner produced using the iron-based black particle powder according to the present invention has a high blackness and a low magnetization value, and therefore is suitable as a nonmagnetic toner.

Claims (6)

The primary particles are iron-based black particles having an average particle diameter (Dp) of 0.05 to 0.4 μm, and the secondary particles of the iron-based black particles have an average particle diameter (Da) of 0.06 to 1.0 μm. And a ratio of the average particle diameter (Da) of the secondary particles to the average particle diameter (Dp) of the primary particles (Da / Dp) is made of an iron-titanium composite oxide having a ratio of 1.1 to 2.8. An iron-based black particle powder for toner. The iron-based black particle powder for toner according to claim 1, wherein the saturation magnetization value is less than 5 Am ² / kg. 3. The iron-based black particle powder for toner according to claim 1, wherein an L * value representing a coloring power is 44.5 or less. 6. The iron-based black particle powder for toner according to claim 1, wherein the content of Ti is 10 to 38 atomic%. 6. The iron-based black particle powder for toner according to claim 1, wherein the constituent phase has at least a FeTiO ₃ —Fe ₂ O ₃ solid solution. 6. The iron-based black particle powder for toner according to claim 5, further comprising at least one selected from an iron-based oxide having a spinel structure, a Na—Fe—Ti compound, and Fe ₂ TiO ₅ .