JP2016210629A - Hydrophobic magnetic iron oxide particle powder, and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide hydrophobic magnetic iron oxide particle powder for a magnetic toner high in hydrophobic properties and good in dispersibility in styrene/n-butylacrylate, and also having a reduced content of volatile organic compounds having unpleasant odor.SOLUTION: Provided is magnetic iron oxide particle powder in which the surfaces of particles are covered with a silane compound, in which the magnetic iron oxide particle powder is retained at 120°C for 30 min, the total of the volatile organic compounds selected from 2 to 16C aliphatic hydrocarbon, aliphatic aldehyde, aliphatic ketone and aliphatic alcohol as the decomposition products of the silane compound diffused from the magnetic iron oxide particle powder is 15 ppm or lower.SELECTED DRAWING: None

Description

  The present invention is a hydrophobic magnetic iron oxide particle powder whose surface is coated with a silane compound, and has little volatile organic compound released from the magnetic iron oxide particle powder when heated, and in a nonpolar solvent. The present invention provides a hydrophobic magnetic iron oxide particle powder for a magnetic toner having good dispersibility in

  Conventionally, as one of the electrostatic latent image developing methods, a so-called one-component using a composite particle in which black magnetic iron oxide particle powder such as magnetite particle powder is mixed and dispersed in a resin without using a carrier as a developer. Development methods using magnetic toners are widely known and widely used.

  Recently, with the improvement in image quality of laser beam printers and digital copying machines, there has been a strong demand for improvement in the characteristics of magnetic toner as a developer. For this purpose, magnetic iron oxide particles are included as much as possible in the toner. And a dispersed state is desirable.

  In addition, with the increase in the speed of laser beam printers and digital copying machines, the amount of magnetic toner used as a developer increases per unit time, and therefore, suppression of the emission of volatile organic compounds is required. It is desirable to suppress the emission of volatile organic compounds as raw materials used for toner.

  Magnetic toner is manufactured by a pulverization method, but is shifting to a polymerization method toner in order to provide functions such as finer and uniform particle diameter and further low-temperature fixability.

  Since the polymerized toner is made by dispersing magnetic iron oxide particles in a polymerizable monomer, it is important to make the magnetic iron oxide particles, which are hydrophilic surfaces, hydrophobic and disperse in the polymerizable monomer. It becomes.

  As means for hydrophobizing magnetic iron oxide particles in a wet process, a method of hydrophobizing alkylalkoxysilane in an aqueous medium has been disclosed (see Patent Documents 1, 2, and 3).

  After adding a reactive silicone oil and / or silane coupling material to the core particles using a Henschel mixer as a means of hydrophobizing the magnetic iron oxide particles in a dry manner, and after mechanical mixing and stirring Subsequently, after adding an aluminum-based coupling agent and performing mechanical mixing and stirring, a method of removing the heated solvent and forming the first and second coating layers is disclosed (see Patent Document 4). .

  As a means for hydrophobizing magnetic iron oxide particles in the gas phase, a method is disclosed in which a treatment agent is reacted by vaporization contact (see Patent Document 5).

JP 2008-282002 A JP 2005-263619 A JP 2010-1000046 Public Law JP 2003-183027 A JP 2000-327948 A

  In Patent Documents 1 and 2, although dispersibility in a nonpolar solvent is good, a volatile organic compound, which is a thermal decomposition product of alkylalkoxysilane used in the hydrophobizing agent, remains, and heating is performed. Sometimes it can have an unpleasant odor. Patent Document 3 discloses that the number of carbon atoms of the hydrophobic group of the silane coupling agent is 3 or 4 in order to reduce the behavior particle diameter of the magnetic iron oxide particles in the organic solvent, and the thermal decomposition product of the alkylalkoxysilane. The volatile organic compound may remain and have an unpleasant odor when heated. Furthermore, since the degree of hydrophobicity is low, when the resin monomer is suspended in water, the hydrophobic magnetic iron oxide particle powder moves to the aqueous phase, and it is difficult to say that the dispersibility in the toner is sufficient.

  Further, in the technique described in Patent Document 4, it is difficult to say that dispersibility in a nonpolar solvent is always good, and it is a thermal decomposition product of an aluminum-based coupling agent used in a hydrophobizing agent. Volatile organic compounds may remain and have an unpleasant odor upon heating.

  Moreover, in the technique of patent document 5, since it heat-processes at high temperature, it is easy to aggregate and it is hard to say that the dispersibility in a nonpolar solvent is enough.

  Therefore, the present invention provides a hydrophobized magnetic iron oxide particle powder that has little emission of volatile organic compounds during heating and has good dispersibility in a nonpolar solvent.

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

  That is, the present invention provides a magnetic iron oxide having a surface coated with a silane compound, and the silane released from the magnetic iron oxide particle powder when the magnetic iron oxide particle powder is held at 120 ° C. for 30 minutes. Hydrophobic magnetic iron oxide particles in which the total of volatile organic compounds selected from aliphatic hydrocarbons having 2 to 16 carbon atoms or aliphatic aldehydes, aliphatic ketones, and aliphatic alcohols is 15 ppm or less as a decomposition product of the compound Powder (Invention 1).

Further, in the present invention, the hydrophobic magnetic iron oxide according to claim 1, wherein the silane compound is at least one or two selected from linear organopolysiloxane represented by the following chemical formula 1 or silazane represented by the chemical formula 2. Particle powder (Invention 2).

  The hydrophobic magnetic iron oxide particle powder according to claim 1, wherein the present invention has a degree of hydrophobicity of 60% or more (Invention 3).

  The hydrophobic magnetic iron oxide particle powder according to claim 1, wherein the gloss of the coating film dispersed in styrene / n-butyl acrylate is 60% or more.

  In the present invention, the magnetic iron oxide particles serving as nuclei are hydrophobized by a dry process and then heat-treated while rotating at a temperature range of 80 to 120 ° C. and a peripheral speed of 0.01 to 10.0 m / sec. The method for producing hydrophobic magnetic iron oxide particles according to claim 1 (Invention 5).

  According to the present invention, the hydrophobic magnetic iron oxide particles having high hydrophobicity and good dispersibility in styrene / n-butyl acrylate, and the content of volatile organic compounds having an unpleasant odor is high. A small amount of hydrophobic magnetic iron oxide particle powder for magnetic toner can be produced.

  Hereinafter, the present invention will be described in detail.

  First, the hydrophobic magnetic iron oxide particle powder according to the present invention will be described.

  The hydrophobic magnetic iron oxide particle powder according to the present invention is a magnetic iron oxide particle powder whose particle surface is coated with a silane compound. When the magnetic iron oxide particle powder is held at 120 ° C. for 30 minutes, The total amount of volatile organic compounds selected from aliphatic hydrocarbons having 2 to 16 carbon atoms, aliphatic aldehydes, aliphatic ketones and aliphatic alcohols as decomposition products of silane compounds diffused from the iron particle powder is 15 ppm or less. It is. If the total amount of volatile organic compounds exceeds 15 ppm, it is recognized as an unpleasant odor. Preferably it is 12 ppm or less, More preferably, it is 10 ppm or less.

  As the silane compound used in the hydrophobic magnetic iron oxide particles according to the present invention, linear organopolysiloxane represented by Chemical Formula 3 or silazane represented by Chemical Formula 4 is preferable.

  Specific examples of the linear organopolysiloxane include methyltriethoxysilane oligomer, methyltrimethoxysilane oligomer, ethyltriethoxysilane oligomer, ethyltrimethoxysilane oligomer, propyltriethoxysilane oligomer, propyltrimethoxysilane oligomer, Examples thereof include hydroxyl-modified silicone oils at both ends and methyl hydrogen silicone oil. Specific examples of silazane include hexamethyldisilazane, hexaethyldisilazane, hexapropyldisilazane, and the like.

  As the carbon number of the alkyl chain of the hydrophobic group of the silane compound that is a hydrophobizing agent increases, the odor intensity of the volatile organic compound that is the thermal decomposition product also increases, so the carbon number of the alkyl chain is 3 or less. It is preferable that Preferably it is 2 or less, more preferably 1.

The BET specific surface area of the hydrophobic magnetic iron oxide particle powder according to the present invention is preferably 3.0 to 13.0 m ² / g. When the BET specific surface area is less than 3.0 m ² / g, the dispersibility in styrene / n-butyl acrylate tends to deteriorate due to aggregation. When the BET specific surface area exceeds 13.0 m ² / g, the hydrophobization treatment is insufficient, the degree of hydrophobization becomes low, and the dispersibility in styrene / n-butyl acrylate tends to deteriorate. More preferably, it is 4.0-12.0 m < ² > / g.

  The hydrophobic magnetic iron oxide particle powder according to the present invention has a BET retention rate of 60% or more evaluated by a measurement method described later. When the BET retention rate is less than 60%, it means that the dispersibility in styrene / n-butyl acrylate is poor due to aggregation. Preferably, it is 63% or more, more preferably 65 to 80%.

  In the hydrophobic magnetic iron oxide particle powder according to the present invention, the adhesion amount as the carbon amount of the silane compound evaluated by the measurement method described later is preferably 0.10 to 1.00 wt%, more preferably 0.15 to 0.00. 90 wt%.

  The hydrophobic magnetic iron oxide particle powder according to the present invention preferably has a fixed amount as a carbon amount of a silane compound evaluated by a measurement method described later of 0.08 to 1.00 wt%, more preferably 0.12 to 0.0. 72 wt%.

  The hydrophobic magnetic iron oxide particles according to the present invention preferably have a silane compound sticking rate of 80% or more evaluated by a measurement method described later. When the fixing rate is less than 80%, the amount of the eluted hydrophobizing agent increases, and thus the dispersibility tends to deteriorate. More preferably, it is 82% or more, and the upper limit is 100%.

  The hydrophobic magnetic iron oxide particle powder according to the present invention has a degree of hydrophobicity of 60% or more evaluated by a measurement method described later. When the degree of hydrophobicity is less than 60%, when the resin monomer is subjected to suspension polymerization in water, the hydrophobic magnetic iron oxide particle powder moves to the aqueous phase, and the dispersibility in the toner tends to deteriorate. . Preferably it is 62% or more, More preferably, it is 64% or more.

The hydrophobic magnetic iron oxide particle powder according to the present invention has a glossiness of 60% or more when dispersed in styrene / n-butyl acrylate to form a coating film. When the glossiness of the coating film is less than 60%, it means that the dispersibility in the resin monomer is poor and the dispersion state in the toner is poor. Preferably it is 64% or more, More preferably, it is 64 to 80%.

  Next, the magnetic iron oxide particle powder as the core of the present invention will be described.

The magnetic iron oxide particles serving as the nucleus in the present invention have an average particle diameter of 0.05 to 0.5 μm. When the average particle size is less than 0.05 μm, the cohesive force between the magnetic iron oxide particles is large, making it difficult to disperse, which is disadvantageous for the hydrophobic treatment. When it exceeds 0.5 μm, the coloring power is inferior and the hiding power is low. Preferably it is 0.1-0.3 micrometer, More preferably, it is 0.15-0.25 micrometer. The BET specific surface area is 5 to 15 m ² / g.

The magnetic iron oxide particles serving as the nucleus in the present invention are composed of magnetite particles ((FeO) _x .Fe ₂ O ₃ , 0 <x ≦ 1). If necessary, elements other than iron, Si, Al, P, Mn, Ni , Zn, Cu, Mg, Co, or Ti may contain one or more metal elements.

  In the magnetic iron oxide particles serving as the core in the present invention, the particle surface may be coated in advance with an intermediate coating comprising at least one selected from Si, Al, and Ti compounds, if necessary.

  By covering the magnetic iron oxide particles serving as the nucleus in the present invention with the intermediate coating, the desorption of the hydrophobizing agent can be further suppressed.

  In the present invention, the primary particle shape of the magnetic iron oxide particle powder serving as the nucleus is an isotropic shape such as an octahedral shape, a hexahedral shape, a granular shape, and a spherical shape. In consideration of dispersibility, a spherical shape is preferable.

  The coercive force of the magnetic iron oxide particle powder as a nucleus in the present invention is preferably 2.4 to 15.9 kA / m (30 to 200 Oe). More preferably, it is 3.2 to 13.5 kA / m (40 to 170 Oe).

The saturation magnetization value of the magnetic iron oxide particles used as the core in the present invention is preferably 81.0-90.0 Am ^{2 /} kg (81.0-90.0 emu / g). More preferably, it is 84.0-90.0 Am < ² > / kg (84.0-90.0 emu / g).

  In the present invention, the magnetic iron oxide particles are prepared by neutralizing and mixing a ferrous salt aqueous solution and an alkali hydroxide aqueous solution, and a ferrous salt reaction aqueous solution containing a ferrous hydroxide colloid obtained by oxygen-containing gas, preferably Oxidation is performed while blowing air into the slurry, and the slurry after the oxidation reaction is filtered and washed to obtain magnetic iron oxide particles. The obtained magnetic iron oxide particle slurry may be dried according to a conventional method and subjected to a hydrophobization treatment. However, considering that the hydrophobization treatment is performed in an aqueous medium, the magnetic iron oxide particles can be directly used without passing through a drying step. It is preferable to hydrophobize using the contained slurry.

  What is necessary is just to adjust the quantity of the alkaline solution at the time of producing | generating a ferrous hydroxide colloid according to the shape of the magnetic iron oxide particle calculated | required. Specifically, spherical particles can be obtained by adjusting the pH of the ferrous hydroxide colloid to be less than 8.0, and hexahedral particles can be obtained by adjusting the pH to 8.0 to 9.5. If it is adjusted to exceed 9.5, octahedral particles can be obtained.

  As the ferrous salt aqueous solution in the present invention, ferrous sulfate aqueous solution, ferrous chloride aqueous solution and the like can be used.

  The alkali hydroxide aqueous solution in the present invention uses aqueous solutions of alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, alkaline earth metal hydroxides such as magnesium hydroxide and calcium hydroxide, and the like. Can do.

  The oxidation reaction temperature in this invention is 85-100 degreeC. When the temperature is lower than 85 ° C., acicular hydrous iron oxide particles are easily produced as a by-product, and when the temperature is higher than 100 ° C., magnetic iron oxide particles are produced but are not industrial.

  Next, a method for producing hydrophobic magnetic iron oxide particles according to the present invention will be described.

  The hydrophobic magnetic iron oxide particle powder according to the present invention is obtained by adding a silane compound to the core magnetic iron oxide particle powder and subjecting it to a hydrophobization treatment, followed by a temperature range of 80 to 120 ° C. and a peripheral speed of 0.01 to It can be obtained by heat treatment while rotating in the range of 10.0 m / sec.

  Specifically, the hydrophobizing treatment is performed by adding a silane compound as a hydrophobizing agent while sufficiently dispersing the magnetic iron oxide particles in a dry mixing and stirring device.

  In order to suppress aggregation of the magnetic iron oxide particles in the hydrophobization treatment, the silane compound may be diluted with a small amount of alcohol and added.

  A known mixing and stirring device can be used for mixing the core particles and the silane compound by a dry method. For example, a Henschel mixer, a high speed mixer, a wheel kneader, a nauta mixer, or the like can be used. As operating conditions of these apparatuses, it is preferable to set the temperature during mixing and stirring to 10 to 60 ° C, particularly 10 to 50 ° C. This prevents self-condensation and volatilization before the silane compound is sufficiently mixed with the core particles, and promotes hydrolysis and dehydrogenation of the silane compound.

  When dry mixing is completed, in order to cause dehydration condensation of the silane compound, heat treatment is preferably performed by heating the temperature at the time of mixing and stirring to 80 to 120 ° C, preferably 90 to 110 ° C. By performing heating in this temperature range, the core particles can be prevented from aggregating and dehydration condensation of the silane compound can be performed. When the temperature of the heat treatment exceeds 120 ° C., the dehydration condensation reaction proceeds so much that the magnetic iron oxide particles are easily united with each other, dispersibility is deteriorated, and hydrophobicity is not sufficient. When the temperature is less than 80 ° C., the fixing rate of the silane compound is lowered and the dispersibility is deteriorated.

  In the present invention, it is preferable to perform a heat treatment while rotating at a peripheral speed of 0.01 to 10.0 m / sec after hydrophobizing by a dry process. More preferably, it is 0.10-10.0 m / sec. When the peripheral speed of the heat treatment exceeds 10.0 m / sec, the crushing force is too strong, so that the silane compound volatilizes before the dehydration condensation reaction is performed on the surface of the core particles, and the self-condensation reaction is accelerated. , The fixing rate is lowered, and the dispersibility is deteriorated. Moreover, when peripheral speed is 0.00 m / sec, it becomes easy to unite magnetic iron oxide particles, and dispersibility deteriorates. As the heat treatment apparatus, a rotary furnace or the like can be used instead of the above-described mixing and stirring apparatus. For example, a retort rotary furnace, rotary kiln, paddle dryer or the like may be used.

  The addition amount of the silane compound is 0.1 to 2.5% by weight with respect to the magnetic iron oxide particles serving as the nucleus.

  Next, the magnetic toner containing the magnetic iron oxide particle powder according to the present invention will be described.

  The magnetic toner according to the present invention can be obtained by a suspension polymerization method. In the suspension polymerization method, a polymerizable monomer and magnetic iron oxide particle powder are dissolved or mixed with a colorant, a polymerization initiator, a crosslinking agent, a charge control agent, and other additives as necessary. The dispersed monomer composition is added to an aqueous phase containing a suspension stabilizer while stirring, granulated, and polymerized to obtain a desired particle size.

  Of course, it can also be performed by a known method of mixing, kneading, and pulverizing a predetermined amount of binder resin and a predetermined amount of magnetic iron oxide particle powder. Specifically, after the magnetic iron oxide particle powder and the binder resin are mixed sufficiently with a mixer, a mixture further containing a release agent, a colorant, a charge control agent, and other additives as necessary. The magnetic iron oxide particles and the like are dispersed in the binder resin by a heat kneader, and then cooled and solidified to obtain a resin kneaded product. The resin kneaded product is pulverized and classified to obtain a desired particle size. Can be obtained.

<Action>
In the present invention, the most important point is a magnetic iron oxide particle powder whose particle surface is coated with a silane compound, and when the magnetic iron oxide particle powder is held at 120 ° C. for 30 minutes, the magnetic iron oxide particle The total of volatile organic compounds selected from aliphatic hydrocarbons having 2 to 16 carbon atoms, aliphatic aldehydes, aliphatic ketones, and aliphatic alcohols as a decomposition product of the silane compound emitted from the powder is 15 ppm or less. This is the fact that the magnetic iron oxide particle powder does not contain an unpleasant odor.

  The present inventor considers these facts as follows.

  The magnetic iron oxide particle powder having the surface of the present invention coated with a silane compound limits the number of carbon atoms of the hydrophobic group of the linear organopolysiloxane or silazane used in the silane compound as a hydrophobizing agent to 3 or less. The core magnetic iron oxide particles are hydrophobized by a dry process and then heat treated while rotating at a temperature range of 80 to 120 ° C. and a peripheral speed of 0.01 to 10.0 m / sec. Since the compound adheres firmly to the magnetic iron oxide particles and has a high fixation rate, an aliphatic hydrocarbon having 2 to 16 carbon atoms or a fatty acid as a decomposition product of the silane compound released from the magnetic iron oxide particle powder, The total amount of volatile organic compounds selected from the group aldehydes, aliphatic ketones, and aliphatic alcohols can be suppressed to 15 ppm or less, making it possible to contain no unpleasant odor components, and Dispersibility in styrene / n-butyl acrylate are also considered to be good.

  Next, the present invention will be described with reference to examples and comparative examples.

<Average particle size>
The average particle diameter of the magnetic iron oxide particle powder is a value obtained by magnifying a photograph taken with a transmission electron microscope (magnification 10,000 times) four times by the Martin diameter for 300 particles.

<BET specific surface area>
The BET specific surface areas of the magnetic iron oxide particle powder and the hydrophobic magnetic iron oxide particle powder were determined by the BET method using Mono Sorb MS-II (manufactured by Yuasa Ionics Co., Ltd.).

<BET maintenance rate>
The BET maintenance rate was calculated by the following formula.
BET retention rate (%) = BET of hydrophobized magnetic iron oxide particles / BET × 100 of magnetic iron oxide particles

<Adhesion amount / Adhesion amount / Adhesion rate>
The amount of adhering hydrophobic magnetic iron oxide particles, the amount of sticking, and the sticking rate were evaluated by measuring the amount of carbon using a carbon analyzer EMIA-80 (manufactured by Horiba, Ltd.).
First, the amount of carbon in the hydrophobic magnetic iron oxide particles was measured and used as the amount of adhesion. Next, 10 g of hydrophobic magnetic iron oxide particles and 100 g of toluene were placed in a 100 ml beaker and irradiated with ultrasonic waves for 30 minutes using an ultrasonic cleaner BRANSONIC 5510 (manufactured by Yamato Scientific Co., Ltd.). Thereafter, the carbon content of the filtered and dried powder was measured and used as the fixed amount. The fixing rate was obtained by the following formula.
Adhesion rate (%) = Adhesion amount / Adhesion amount × 100

<Magnetic properties>
The magnetic properties of the magnetic iron oxide particles were shown by values measured with an external magnetic field of 796 kA / m using a vibrating sample magnetometer VSM-3S-15 (manufactured by Toei Industry Co., Ltd.).

<Hydrophobicity>
The hydrophobicity of the hydrophobic magnetic iron oxide sulfide powder was determined by adding 100 mg of the hydrophobic magnetic iron oxide particle powder to 70 ml of aqueous methanol solution having a volume concentration of 50% using a powder wettability tester (WET101P manufactured by Reska Co., Ltd.) Stir with a stirring blade. Under this condition, methanol is dropped, and the aqueous methanol solution is irradiated with laser light having a wavelength of 780 nm, and the transmittance is measured. The volume concentration of the aqueous methanol solution at which the hydrophobic magnetic iron oxide particle powder wets, settles and suspends and the transmittance becomes 50% is defined as the degree of hydrophobicity.

<Glossiness of styrene / n-butyl acrylate dispersed coating film>
45 g of magnetic iron oxide particle powder, 37 g of styrene, and 13 g of n-butyl acrylate were placed in a 100 ml beaker, and a paste in which the number of revolutions of the disperser was dispersed at 1500 rpm for 15 minutes was placed on a PET film. The gloss (60 °) of the coated and dried coating film surface was measured with a digital variable gloss meter UGV-5D (manufactured by Suga Test Instruments Co., Ltd.).

<Main components and total amount of volatile organic compounds released from magnetic iron oxide particles>
A volatile organic compound selected from aliphatic hydrocarbons having 2 to 16 carbon atoms, aliphatic aldehydes, aliphatic ketones, and aliphatic alcohols, which are decomposition products of the silane compound diffused from the magnetic iron oxide particle powder Qualitative and quantitative determination is performed by the following GC-MS analysis by the headspace method.

Device name: Claus 500 manufactured by PERKIN ELMER
HS-TurboMatrix40 manufactured by PERKIN ELMER
Measuring method:
100 mg of magnetic iron oxide particle powder was sealed in a headspace vial, heated with a headspace sampler (120 ° C. × 30 min), and GC-MS analysis of the generated gas was performed.
Headspace sampler requirements:
Sample heating temperature 120 ° C
Sample heating time 30 minutes GC-MS conditions:
Capillary column TC-1 made by GL Sciences
Carrier gas He
Column oven Hold at 40 ° C / 2 minutes and heat up to 230 ° C at 10 ° C / minute.
analysis method:
Toluene is used as a calibration standard, and 0.000 μL, 0.025 μL, 0.050 μL, and 0.075 μL are sealed in a headspace vial for measurement. A peak of toluene is observed around 7.05 minutes, and a calibration curve is created from the area area value.
Alkenes, aldehydes, and the like are observed as thermal decomposition products of alkyl chains that are hydrophobic groups in the silane compound. For example, when the alkyl group is C10, 1-decene and decanal are produced, when C8 is produced, 1-octene and octanal are produced, and when C6 is used, 1-hexene and hexanal are produced. The main component of odor can be specified by confirming the obtained mass spectrum by measurement. For example, 1-decene derived from C10 has a peak observed around 11.8 minutes, 1-octene derived from C8 has a peak observed around 7.7 minutes, and 1-hexene derived from C6 is A peak is observed around 3.6 minutes. The amount of volatile organic compounds per unit weight of magnetic iron oxide is calculated by converting the area area value of the obtained peak from the toluene calibration curve.

<Dispersibility in magnetic toner>
The dispersibility of the hydrophobic magnetic iron oxide particles in the magnetic toner was determined by slicing the magnetic toner with an ultramicrotome MT2C (manufactured by RESEACH MANFACTURERING) and observing the cross section with a transmission electron microscope (magnification 10,000 times). The aggregation state of the magnetic iron oxide particle powder was observed and evaluated in four stages. It shows that dispersibility is so good that there are few aggregates.
Aggregate: 0 to 1 Dispersion degree ◎
2-5 pieces ○
5-10 pieces △
11 or more ×

<Manufacture of magnetic iron oxide particles>
(Nuclear particle A)
Ferrous sulfate solution (Fe ²⁺ concentration; 1.723 mol / l, specific gravity; 1.248 g / cc) 31.942 kg, NaOH (18.5 N) 4.806 l (equivalent ratio = 0.95) and water 17. Air was blown into 396 l at 90 ° C. to produce core particles of magnetic iron oxide particles. Next, NaOH is added so that the equivalent ratio becomes 1.0 or more, and the remaining ferrous sulfate is reacted, and then washed with water and dried by a conventional method to obtain magnetic iron oxide particles (nuclear particles A). It was. The obtained magnetic iron oxide particles had a spherical particle shape, an average particle diameter of 0.24 μm, and a BET specific surface area of 7.5 m ² / g.

Nuclear particles B, D and E
Based on the manufacturing conditions of the core particle A, the core particles B, D, and E were generated by changing the conditions.

(Nuclear particle C)
Ferrous sulfate solution (Fe ²⁺ concentration; 1.723 mol / l, specific gravity; 1.248 g / cc) 31.942 kg, NaOH (18.5 N) 5.068 l (equivalent ratio = 1.06) and water 17. Air was blown into 396 l at 90 ° C. to produce magnetic iron oxide particles. The obtained magnetic iron oxide particles had an octahedral particle shape, an average particle diameter of 0.24 μm, and a BET specific surface area of 9.5 m ² / g.

  Table 1 shows various characteristics of the magnetic iron oxide particles to be the obtained core particles.

Example 1
<Production of hydrophobic magnetic iron oxide particle powder>
3 kg of core particles A shown in Table 1 are put into a Henschel mixer, and stirring is started while adjusting the product temperature to 50 ° C. 36 g of methyl hydrogen polysiloxane was gradually added and stirred for 30 minutes. Subsequently, the mixture was stirred for 1 hour at a peripheral speed of 5.39 m / sec while adjusting the product temperature to 120 ° C. by heating. Thereafter, cooling was performed to obtain hydrophobic magnetic iron oxide particles.

Examples 2-8
Hydrophobic magnetic iron oxide particles were obtained in the same manner as in Example 1 except that the types of the core particles, the types and amounts of the silane compounds, and the heat treatment conditions were variously changed. In Example 3, after dry mixing, the mixture was put into a rotary furnace and heat-treated at a peripheral speed of 0.31 m / sec for 2 hours. In Examples 7 and 8, the silane compound was added after diluting with an equal amount of ethanol in advance.

Comparative Example 1 (Follow-up experiment of Example 7 of Japanese Patent Application No. 20008-282002)
The solid content concentration of the obtained core particle D slurry was 10 wt%, and the rotation speed of the homomixer was 500 rpm. The mixture was adjusted to pH 6.4 and sufficiently dispersed, n-decyltrimethoxysilane was added, and hydrophobization was performed while performing hydrolysis. The produced hydrophobizing magnetic iron oxide particles were filtered, washed with water, and dried at 80 ° C. Thereafter, the dried product was put into a Henschel mixer, heated to 100 ° C., and heat-treated with stirring at a peripheral speed of 15 m / sec for 1 hour to obtain hydrophobic magnetic iron oxide particles.

Comparative Example 2 (Follow-up experiment of Example 2 of JP 2010-100144 A)
The solid content concentration of the obtained slurry containing the core particles D was 10 wt%, and the rotation speed of the homomixer was 5000 rpm. The resulting surface-treated magnetic iron oxide particle powder-containing slurry that was adjusted to pH 6 and the slurry temperature was adjusted to 40 ° C. and sufficiently dispersed, and hydrophobized while adding isobutyltrimethoxysilane and hydrolyzing. (Solid content concentration: 10 wt%) is fluidized bed dried at 150 ° C. using a spray dryer, and then heat treated at 100 ° C. for 2 hours using a constant temperature dryer FS-420 (Toyo Seisakusho). A surface-treated magnetic iron oxide particle powder was obtained.

Comparative example 3 (follow-up experiment of Example 1 of JP2003-183027A)
The obtained core particle E5 kg is put into a Henschel mixer, and stirring is started while adjusting the temperature of the powder to 70 ° C. with a heating jacket. A reactive silicone oil, 100 g of methyl hydrogen polysiloxane diluted with 100 g of ethanol, was gradually added and stirred for 2 hours. Subsequently, a solution obtained by diluting 25 g of acetyl acetate aluminum diisopyrate, which is an aluminum coupling agent, into 25 g of hexane was gradually added and stirred for 1 hour to obtain a surface-treated magnetic iron oxide particle powder.

Comparative Example 4
Hydrophobic magnetic iron oxide particles were obtained in the same manner as in Example 1 except that the types of the core particles, the types and amounts of the silane compounds, and the heat treatment conditions were variously changed.

Tables 2 and 3 show properties of the obtained hydrophobic magnetic iron oxide particles.

Example 1
<Manufacture of magnetic toner>
5 parts by weight of colloidal silica S-150 (manufactured by Hakuto Chemical Co., Ltd.) as a suspension stabilizer was added to 500 parts by weight of ion-exchanged water and heated to 70 ° C. to obtain an aqueous medium.
Styrene: 80 parts by weight n-butyl acrylate: 20 parts by weight Divinylbenzene: 0.3 part by weight Hydrophobic magnetic iron oxide particle powder 82 parts by weight

The mixture was dispersed using a paint conditioner. Into this, 1.5 parts by weight of a polymerization initiator 2,2′-azobis (2,4 dimethylvaleronitrile) was dissolved.
The polymerizable monomer was put into the aqueous medium, and stirred at 8000 rpm for 10 minutes with a homomixer in an N ₂ atmosphere at 70 ° C. to form droplets. Thereafter, the mixture was reacted at 70 ° C. for 8 hours while stirring with a paddle. After completion of the reaction, the suspension stabilizer was removed by adjusting the pH to 12 with NaOH, followed by filtration, washing with water, and drying to obtain magnetic toner 1. The weight average particle diameter was 7.5 μm.

Examples of use 2-12
A magnetic toner was obtained in the same manner as in Use Example 1 except that the kind of the hydrophobic magnetic iron oxide particle powder was variously changed.

  Table 4 shows various properties of the obtained magnetic toner.

  The hydrophobic magnetic iron oxide particle powder according to the present invention is a magnetic iron oxide particle powder whose particle surface is coated with a silane compound, and when the magnetic iron oxide particle powder is held at 120 ° C. for 30 minutes, A total of volatile organic compounds selected from aliphatic hydrocarbons having 2 to 16 carbon atoms, aliphatic aldehydes, aliphatic ketones, and aliphatic alcohols as decomposition products of the silane compound emitted from the iron oxide particle powder. Since it is suppressed to 15 ppm or less, it is possible to contain no unpleasant odor components and good dispersibility in styrene / n-butyl acrylate, so it is suitable as a hydrophobic magnetic iron oxide particle powder for magnetic toner. is there.

Claims (5)

  Hydrophobic magnetic iron oxide particle powder whose particle surface is coated with a silane compound, and the silane compound released from the magnetic iron oxide particle powder when the magnetic iron oxide particle powder is held at 120 ° C. for 30 minutes Hydrophobic, characterized in that the total of volatile organic compounds selected from aliphatic hydrocarbons having 2 to 16 carbon atoms or aliphatic aldehydes, aliphatic ketones, and aliphatic alcohols is 15 ppm or less Magnetic iron oxide particle powder. The hydrophobic magnetic iron oxide particle powder according to claim 1, wherein the silane compound is at least one selected from linear organopolysiloxane represented by Chemical Formula 1 or silazane represented by Chemical Formula 2.

  The hydrophobic magnetic iron oxide particle powder according to claim 1 or 2, having a degree of hydrophobicity of 60% or more.   The hydrophobic magnetic iron oxide particle powder according to any one of claims 1 to 3, wherein the gloss of the coating film dispersed in styrene / n-butyl acrylate is 60% or more.   The magnetic iron oxide particles serving as nuclei are hydrophobized by a dry process and then heat-treated while being rotated in a temperature range of 80 to 120 ° C. and a peripheral speed of 0.01 to 10.0 m / sec. Item 2. A method for producing hydrophobic magnetic iron oxide particles according to Item 1.