JP6521239B2 - Hydrophobic magnetic iron oxide particle powder and method for producing the same - Google Patents

Description

  The present invention is a hydrophobic magnetic iron oxide particle powder, the surface of which is coated with a silane compound, which contains less volatile organic compounds emitted from the magnetic iron oxide particle powder when heated, and is in a nonpolar solvent. The present invention provides a hydrophobic magnetic iron oxide particle powder for magnetic toner, which has good dispersibility in the above.

  Conventionally, as one of electrostatic latent image development methods, so-called one-component using composite particles in which black magnetic iron oxide particles such as magnetite particles are mixed and dispersed in a resin without using a carrier as a developer A developing method using a magnetic toner is widely known and widely used.

  Recently, as the image quality of laser beam printers and digital copiers has been improved, there has been a strong demand for improvement in the characteristics of magnetic toners as developers. For this purpose, magnetic iron oxide particles are contained as much as possible in the toner. It is desirable to have a distributed and distributed state.

  In addition, with the increase in speed of laser beam printers and digital copiers, the amount of use of magnetic toner as a developer per unit time also increases, so there is a demand for suppression of the emission of volatile organic compounds. It is desirable to suppress the emission of volatile organic compounds of raw materials used for toners.

  The magnetic toner is manufactured by a pulverizing method, but is being transferred to a polymerization method toner in the function imparting such as the reduction of the particle diameter, the equalization, the low temperature fixing property and the like.

  Since the polymerization toner is prepared by dispersing magnetic iron oxide particles in a polymerizable monomer, it is important to hydrophobize the magnetic iron oxide particles as a hydrophilic surface to disperse in the polymerizable monomer. It will be

  As a means for hydrophobizing magnetic iron oxide particles in a wet manner, methods for hydrophobizing alkylalkoxysilane in an aqueous medium are disclosed (see Patent Documents 1, 2 and 3).

  After adding reactive silicone oil and / or silane coupling agent to core particles using a Henschel mixer etc. as means for hydrophobizing magnetic iron oxide particles in a dry state, and after performing mechanical mixing and stirring Subsequently, after adding an aluminum-based coupling agent and mechanically mixing and stirring, a method of removing the heating 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, there is disclosed a method in which a treating agent is brought into contact for reaction to cause a reaction (see Patent Document 5).

JP, 2008-282002, A JP, 2005-263619, A Unexamined-Japanese-Patent No. 2010-100464 official law JP 2003-183027 A JP 2000-327948 A

  Patent documents 1 and 2 have good dispersibility in nonpolar solvents, but volatile organic compounds which are thermally decomposed products of alkyl alkoxysilanes used for a hydrophobization treatment remain, and thus heating is carried out. Sometimes it may have an unpleasant odor. Further, Patent Document 3 sets the carbon number of the hydrophobic group of the silane coupling agent to 3 or 4 in order to reduce the particle size of magnetic iron oxide particles in an organic solvent, and a thermally decomposed product of alkyl alkoxysilane Volatile organic compounds remain, which may have an unpleasant odor on heating. Furthermore, since the degree of hydrophobicity is low, when suspending the resin monomer in water, the hydrophobic magnetic iron oxide particle powder is transferred to the aqueous phase, and the dispersibility in the toner can not be said to be sufficient.

  Further, in the technology described in Patent Document 4, the dispersibility in a nonpolar solvent is not necessarily good, and it is a thermally decomposed product of an aluminum-based coupling agent used for a hydrophobizing agent. Volatile organic compounds may remain and may have an unpleasant odor when heated.

  Further, in the technique described in Patent Document 5, since the heat treatment is performed at a high temperature, the particles are easily aggregated, and the dispersibility in the nonpolar solvent is not sufficient.

  Therefore, the present invention is to provide a hydrophobized magnetic iron oxide particle powder which emits little volatile organic compounds at the time of heating and has good dispersibility in a nonpolar solvent.

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

  That is, the present invention is a magnetic iron oxide the surface of which is coated with a silane compound, and the silane which is 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 having a total of 15 ppm or less of a volatile organic compound selected from aliphatic hydrocarbons having 2 or more and 16 or less carbon atoms, aliphatic aldehydes, aliphatic ketones and aliphatic alcohols as decomposition products of the compound Powder (Invention 1).

Also, 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 a linear organopolysiloxane represented by the following chemical formula 1 and a silazane represented by the chemical formula 2. Particle powder (Invention 2).

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

  The hydrophobic magnetic iron oxide particle powder (Invention 4) according to Claim 1, wherein the glossiness of the coating film dispersed in styrene / n-butyl acrylate is 60% or more.

  Further, according to the present invention, the magnetic iron oxide particles serving as nuclei are subjected to a hydrophobization treatment in a dry state, and then heat treatment is performed while rotating in a temperature range of 80 to 120 ° C. and a circumferential speed of 0.01 to 10.0 m / sec. A method of producing a hydrophobic magnetic iron oxide particle powder according to claim 1, characterized in that the method (Invention 5).

  According to the present invention, it is a hydrophobic magnetic iron oxide particle powder having high hydrophobicity and good dispersibility in styrene / n-butyl acrylate, and the content of volatile organic compound having an unpleasant odor 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 in which the particle surface is coated with a silane compound, and when the magnetic iron oxide particle powder is kept at 120 ° C. for 30 minutes, the magnetic oxidation occurs. The total amount of volatile organic compounds selected from aliphatic hydrocarbons having 2 to 16 carbon atoms or aliphatic aldehydes, aliphatic ketones and aliphatic alcohols as decomposition products of silane compounds dissipated from iron particle powder is 15 ppm or less It is. If the total amount of volatile organic compounds exceeds 15 ppm, it is perceived as an unpleasant odor. Preferably it is 12 ppm or less, more preferably 10 ppm or less.

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

  Specific examples of linear organopolysiloxanes include methyltriethoxysilane oligomer, methyltrimethoxysilane oligomer, ethyltriethoxysilane oligomer, ethyltrimethoxysilane oligomer, propyltriethoxysilane oligomer, propyltrimethoxysilane oligomer, Examples of the silazane include hexamethyldisilazane, hexaethyldisilazane, and hexapropyldisilazane.

  As the carbon number of the alkyl chain of the hydrophobic group of the silane compound which is a hydrophobizing agent increases, the odor intensity of the volatile organic compound which is its thermally decomposed product also increases, so the carbon number of the alkyl chain is 3 or less Is preferred. Preferably it is 2 or less, More preferably, it is 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. If the BET specific surface area is less than 3.0 m ² / g, the dispersibility in styrene / n-butyl acrylate tends to be poor because of aggregation. When the BET specific surface area exceeds 13.0 m ² / g, the hydrophobization treatment is insufficient, the degree of hydrophobization is low, and the dispersibility in styrene / n-butyl acrylate tends to be poor. 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, which is evaluated by the measurement method described later. If the BET retention rate is less than 60%, it means that the dispersibility in styrene / n-butyl acrylate is poor because of aggregation. Preferably, it is 63% or more, more preferably 65 to 80%.

  The hydrophobic magnetic iron oxide particle powder according to the present invention preferably has an adhesion amount of 0.10 to 1.00 wt% as a carbon amount of a silane compound evaluated by a measurement method described later, and more preferably 0.15 to 0. It is 90 wt%.

  The hydrophobic magnetic iron oxide particle powder according to the present invention preferably has a sticking amount of 0.08 to 1.00 wt% as a carbon amount of a silane compound evaluated by a measuring method described later, and more preferably 0.12 to 0. It is 72 wt%.

  The hydrophobic magnetic iron oxide particle powder according to the present invention preferably has a sticking rate of 80% or more of a silane compound evaluated by the measurement method described later. If the fixation rate is less than 80%, the amount of the eluted hydrophobizing agent increases, and the dispersibility tends to be poor. 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, which is evaluated by the measurement method described later. When the degree of hydrophobization is less than 60%, the hydrophobic magnetic iron oxide particle powder tends to shift to the aqueous phase when suspension polymerization of the resin monomer in water is performed, and the dispersibility in the toner tends to be deteriorated. . Preferably it is 62% or more, more preferably 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%, the dispersibility in the resin monomer is poor, which means that 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 which becomes the nucleus in the present invention will be described.

The magnetic iron oxide particles as the core 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 cohesion between the magnetic iron oxide particles is large and the dispersion becomes difficult, which is also disadvantageous for the hydrophobic treatment. When it exceeds 0.5 μm, the coloring power is inferior and the hiding power is also low. It is preferably 0.1 to 0.3 μm, more preferably 0.15 to 0.25 μm. The BET specific surface area is 5 to 15 m ² / g.

Magnetic iron oxide particles serving as nuclei in the present invention are composed of magnetite particles ((FeO) _x · Fe ₂ O ₃ , 0 <x 1 1), and if necessary, elements Si, Al, P, Mn, Ni other than iron You may contain 1 type, or 2 or more types of metallic elements chosen from Zn, Cu, Mg, Co, and Ti.

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

  By covering the core magnetic iron oxide particles in the present invention with the intermediate coating, the detachment of the hydrophobizing agent can be further suppressed.

  The particle shape of the primary particles of the magnetic iron oxide particle powder to be the core in the present invention is an octahedral, hexahedral, granular, spherical or other isotropic shape. Spherical shape is preferable in consideration of dispersibility.

  The coercive force of the magnetic iron oxide particle powder to be a core 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 particle powder to be the core in the present invention is preferably 81.1 to 90.0 Am ^{2 /} kg (81.0 to 90.0 emu / g). More preferably, it is 84.0 to 90.0 Am ^{2 /} kg (84.0 to 90.0 emu / g).

  The magnetic iron oxide particles in the present invention are a ferrous salt reaction aqueous solution containing ferrous hydroxide colloid obtained by neutralizing and mixing a ferrous salt aqueous solution and an aqueous alkali hydroxide solution, preferably an oxygen-containing gas, The air can be oxidized while being blown into the slurry, and the slurry after the completion of the oxidation reaction can be 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, but considering that the hydrophobization treatment is carried out in an aqueous medium, the magnetic iron oxide particles are subjected as they are without passing through the drying step. It is preferable to carry out a hydrophobization process using the contained slurry.

  The amount of the alkali solution in forming the ferrous hydroxide colloid may be adjusted according to the shape of the magnetic iron oxide particles to be obtained. Specifically, spherical particles are obtained by adjusting the pH of ferrous hydroxide colloid to be less than 8.0, and hexahedral particles are obtained by adjusting the pH to be 8.0 to 9.5. If adjustment is made so as to exceed 9.5, octahedral particles are obtained, and accordingly adjustment is made.

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

  In the present invention, the aqueous alkali hydroxide solution may be an aqueous solution of an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide, or an alkaline earth metal hydroxide such as magnesium hydroxide or calcium hydroxide. Can.

  The oxidation reaction temperature in the present invention is 85 to 100 ° C. When the temperature is less than 85 ° C., needle-like hydrous iron oxide particles tend to be by-produced. When the temperature exceeds 100 ° C., magnetic iron oxide particles are formed, but they are not industrially suitable.

  Next, the method for producing 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 dry-hydrophobicized by adding a silane compound to magnetic iron oxide particle powder serving as a core, and then the temperature range of 80 to 120 ° C. and the peripheral speed 0.01 to 0.01 It can be obtained by heat treatment while rotating in the range of 10.0 m / sec.

  Specifically, the hydrophobization treatment is carried out by adding a silane compound which is a hydrophobizing agent while sufficiently dispersing the magnetic iron oxide particles in a dry mixing and stirring apparatus.

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

  For mixing of the core particles and the silane compound by a dry method, a known mixing and stirring apparatus can be used. For example, a Henschel mixer, a high speed mixer, a wheel type kneader, a Nauta mixer, etc. can be used. As operating conditions of these apparatuses, it is preferable to set the temperature at the time of mixing and stirring to 10 to 60 ° C., particularly 10 to 50 ° C. By this, it is possible to prevent self-condensation and volatilization before the silane compound is sufficiently mixed with the core particles, and to promote a hydrolysis reaction or a dehydrogenation reaction of the silane compound.

  When dry mixing is completed, in order to cause dehydration condensation of the silane compound, it is preferable to perform heat treatment by heating to a temperature of 80 to 120 ° C., preferably 90 to 110 ° C. during mixing and stirring. By carrying out heating in this temperature range, aggregation of core particles can be prevented and dehydration condensation of a silane compound can be performed. When the temperature of the heat treatment exceeds 120 ° C., the dehydration condensation reaction proceeds too much, the magnetic iron oxide particles become easy to unite with each other, the dispersibility is deteriorated, and the hydrophobicity can not be said to be sufficient. If the temperature is less than 80 ° C., the sticking rate of the silane compound is lowered and the dispersibility is deteriorated.

  In the present invention, it is preferable to perform heat treatment while rotating at a circumferential speed of 0.01 to 10.0 m / sec after hydrophobizing treatment in a dry state. 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 power is too strong, so the silane compound is volatilized and the self condensation reaction is promoted before the dehydration condensation reaction is performed on the surface of the core particle. The fixation rate is lowered, and the dispersibility is deteriorated. In addition, when the circumferential speed is 0.00 m / sec, the magnetic iron oxide particles are easily integrated with each other, and the dispersibility is deteriorated. As the heat treatment apparatus, a rotary furnace or the like can be used instead of the above-mentioned mixing and stirring apparatus. For example, a retort rotary furnace, a rotary kiln, a 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 core.

  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 suspension polymerization. In the suspension polymerization method, a mixture obtained by adding a polymerizable monomer and magnetic iron oxide particle powder and, if necessary, a colorant, a polymerization initiator, a crosslinking agent, a charge control agent and other additives is dissolved or The dispersed monomer composition is obtained by granulating with stirring into an aqueous phase containing a suspension stabilizer and polymerizing to a desired particle size.

  Of course, it can also be carried out 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 mixing a magnetic iron oxide particle powder and a binder resin with a mixture, to which a mold release agent, a colorant, a charge control agent, other additives and the like are further added if necessary, with a mixer The magnetic iron oxide particles and the like are dispersed in a binder resin by a heating kneader, and then solidified by cooling to obtain a resin kneaded product, and the resin kneaded product is pulverized and classified to obtain a desired particle size Obtained by

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

  The inventors consider these facts as follows.

  The magnetic iron oxide particle powder in which the surface of the present invention is coated with a silane compound is limited to 3 or less carbon atoms of the hydrophobic group of the linear organopolysiloxane or silazane used for the silane compound which is a hydrophobizing agent. And hydrophobize the magnetic iron oxide particles to be used as nuclei, and then heat treat 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 fat as a decomposition product of the silane compound dissipated from the magnetic iron oxide particle powder And the total content of volatile organic compounds selected from aliphatic aldehydes, aliphatic ketones and aliphatic alcohols is reduced to 15 ppm or less, making it possible to contain no unpleasant odorous components, and Dispersibility in styrene / n-butyl acrylate are also considered to be good.

  Next, the present invention will be described by way of examples and comparative examples.

<Average particle size>
The average particle diameter of the magnetic iron oxide particle powder is a value obtained by multiplying a photograph (magnification of 10,000 times) taken by a transmission electron microscope by a factor of 4 and obtaining about 300 particles by the Martin diameter.

<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 BET method using Mono Sorb MS-II (manufactured by Yuasa Ionix Co., Ltd.).

<BET maintenance rate>
The BET retention rate was determined by the following equation.
BET retention ratio (%) = BET of hydrophobized magnetic iron oxide particle powder / BET of magnetic iron oxide particle powder × 100

<Attachment amount, adhesion amount, adhesion ratio>
The amount of adhesion of hydrophobic magnetic iron oxide particles powder, the amount of adhesion and the adhesion 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 particle powder was measured to determine the amount of adhesion. Next, 10 g of hydrophobic magnetic iron oxide particle powder and 100 g of toluene were placed in a 100 ml beaker, and ultrasonic waves were irradiated for 30 minutes using an ultrasonic cleaner BRANSONIC 5510 (manufactured by Yamato Scientific Co., Ltd.). Thereafter, the amount of carbon in the filtered and dried powder was measured to obtain a fixed amount. The sticking rate was determined by the following equation.
Fixation rate (%) = fixed amount / adhesion amount × 100

<Magnetic characteristics>
The magnetic properties of the magnetic iron oxide particle powder are shown by values measured at an external magnetic field of 796 kA / m using a vibrating sample magnetometer VSM-3S-15 (manufactured by Toei Kogyo Co., Ltd.).

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

<Glossiness of styrene / n-butyl acrylate dispersion coating>
A paste containing 45 g of magnetic iron oxide particle powder, 37 g of styrene and 13 g of n-butyl acrylate in a 100 ml beaker, and a disperser dispersion speed of 1500 rpm for 15 minutes is placed on a PET film, and a WET film thickness 24 μm bar coater The glossiness (60 °) of the coated and dried coated film surface was measured with a digital variable gloss meter UGV-5D (manufactured by Suga Test Instruments Co., Ltd.).

<Main component and total amount of volatile organic compounds emitted from magnetic iron oxide particle powder>
Aliphatic hydrocarbon having a carbon number of 2 or more and 16 or less, which is a decomposition product of the silane compound dissipated from the magnetic iron oxide particle powder, or a volatile organic compound selected from aliphatic aldehydes, aliphatic ketones, and aliphatic alcohols Qualitative and quantitative determination is performed by the following GC-MS analysis by headspace method.

Device Name: PERKIN ELMER Claus 500
PERKIN ELMER HS-TurboMatrix 40
Measuring method:
100 mg of magnetic iron oxide particle powder was enclosed in a head space vial, heated (120 ° C. × 30 min) with a head space sampler, and GC-MS analysis of generated gas was performed.
Headspace sampler requirements:
Sample heating temperature 120 ° C
Sample heating time 30 minutes GC-MS conditions:
Capillary column GL science TC-1
Carrier gas He
Column oven Hold at 40 ° C / 2 minutes and heat to 230 ° C at 10 ° C / min.
analysis method:
As a standard substance for calibration, toluene is used, and measurement is performed by sealing 0.000 μL, 0.025 μL, 0.050 μL, and 0.075 μL in a head space vial. A peak is observed at around 7.05 minutes for toluene, and a calibration curve is prepared from the area area value.
Alkenes, aldehydes and the like are observed as the thermally decomposed material of the alkyl chain which is a hydrophobic group in the silane compound. For example, when the alkyl group is C10, 1-decene and decanal are formed, C8 generates 1-octene and octanal, and C6 generates 1-hexene and hexanal. By measuring the mass spectrum obtained by measurement, the main component of the odor can be identified. For example, a peak is observed around 11.8 minutes for 1-decene derived from C10, a peak is observed around 7.7 minutes for 1-octene derived from C8, and 1-hexene derived from C6 is A peak is observed around 3.6 minutes. The amount of volatile organic compound per unit weight of magnetic iron oxide is calculated by converting the area area value of the obtained peak from a toluene calibration curve.

<Dispersibility in magnetic toner>
The dispersibility of the hydrophobic magnetic iron oxide particle powder in the magnetic toner is obtained by slicing the magnetic toner with an ultramicrotome MT2C (manufactured by RESEACH MANFACTURING), and observing the cross section with a transmission electron microscope (magnification of 10000). The aggregation state of the magnetic iron oxide particle powder was observed and evaluated in four steps. The less the aggregates, the better the dispersibility.
Aggregate: 0 to 1 Dispersion degree ◎
2 to 5 ○
5 to 10 pieces
11 or more ×

<Production 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 (equivalent ratio = 0.95) and water 17. Air was blown into 396 l at 90 ° C. to form core particles of magnetic iron oxide particles. Next, NaOH is added so that the equivalent ratio is 1.0 or more, and the remaining ferrous sulfate is reacted, and then it is washed with water and dried by a conventional method to obtain magnetic iron oxide particles (core particles A). The The magnetic iron oxide particles obtained were spherical in particle shape, and had 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
The conditions were changed variously based on the production conditions of the core particle A, and core particles B, D and E were produced.

(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 magnetic iron oxide particles obtained were octahedral in particle shape, and had an average particle diameter of 0.24 μm and a BET specific surface area of 9.5 m ² / g.

  Various properties of the magnetic iron oxide particles to be core particles obtained are shown in Table 1.

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

Examples 2 to 8
A hydrophobic magnetic iron oxide particle powder was obtained in the same manner as in Example 1 except that the type of core particles, the type and amount of silane compound, and the heat treatment conditions were variously changed. In Example 3, after the dry mixing, the mixture was charged into a rotary furnace, and heat treatment was performed for 2 hours at a peripheral speed of 0.31 m / sec. In Examples 7 and 8, the silane compound was added after being diluted beforehand with an equal volume of ethanol.

Comparative Example 1 (Supplementary 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 number of the homomixer was 500 rpm. The pH was adjusted to 6.4 and sufficiently dispersed, n-decyltrimethoxysilane was added, and hydrophobization treatment was performed while performing hydrolysis. The generated hydrophobic magnetic iron oxide particles were filtered, washed with water and dried at 80 ° C. Thereafter, the dried product was charged into a Henschel mixer, heated to 100 ° C., and heat-treated while stirring at a circumferential speed of 15 m / sec for 1 hour to obtain hydrophobic magnetic iron oxide particle powder.

Comparative example 2 (follow-up experiment of Example 2 of Unexamined-Japanese-Patent No. 2010-100464)
The solid content concentration of the slurry containing the core particle D obtained was 10 wt%, and the rotation number of the homomixer was 5000 rpm. The slurry is adjusted to a pH of 6 and the temperature of the slurry is adjusted to 40 ° C. and dispersed sufficiently, isobutyltrimethoxysilane is added, and the hydrophobization treatment is carried out while performing hydrolysis, the generated surface-treated magnetic iron oxide particle powder-containing slurry Fluidized bed drying is carried out at 150 ° C. using a spray dryer (solid content: 10 wt%), and then heat treatment is carried out at 100 ° C. for 2 hours using a constant temperature dryer FS-420 (Toyo Seisakusho Co., Ltd.) A surface-treated magnetic iron oxide particle powder was obtained.

Comparative Example 3 (Supplementary Experiment of Example 1 of Japanese Patent Application Laid-Open No. 2003-183027)
The obtained core particles E of 5 kg are charged 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 in 100 g of ethanol was gradually added, and stirring was performed for 2 hours. Subsequently, 25 g of hexane diluted with 25 g of acetyl acetate aluminum diisopyrate, which is an aluminum coupling agent, was gradually added, and stirring was performed for 1 hour to obtain surface-treated magnetic iron oxide particle powder.

Comparative example 4
A hydrophobic magnetic iron oxide particle powder was obtained in the same manner as in Example 1 except that the type of core particles, the type and amount of silane compound, and the heat treatment conditions were variously changed.

Tables 2 and 3 show various properties of the obtained hydrophobic magnetic iron oxide particle powder.

Use example 1
<Manufacture of magnetic toner>
An aqueous medium was obtained by adding 5 parts by weight of colloidal silica S-150 (manufactured by Shoto Kagaku Co., Ltd.) as a suspension stabilizer to 500 parts by weight of ion exchange water and heating to 70 ° C.
Styrene: 80 parts by weight n-butyl acrylate: 20 parts by weight Divinylbenzene: 0.3 parts by weight Hydrophobic magnetic iron oxide powder powder 82 parts by weight

The above mixture was dispersed using a paint conditioner. Thereto, 1.5 parts by weight of a polymerization initiator 2,2'-azobis (2,4 dimethyl valeronitrile) was dissolved.
The polymerizable monomer was charged into the aqueous medium and stirred at 8000 rpm for 10 minutes with a homomixer at 70 ° C. under an N ₂ atmosphere to form droplets. Then, it 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 a magnetic toner 1. The weight average particle size was 7.5 μm.

Use example 2-12
A magnetic toner was obtained in the same manner as in Use Example 1 except that the type of the hydrophobic magnetic iron oxide particles was variously changed.

  Various properties of the obtained magnetic toner are shown in Table 4.

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

Claims (4)

Hydrophobic magnetic iron oxide particle powder wherein the particle surface is coated with a silane compound , wherein the silane compound is at least one selected from the linear organopolysiloxanes shown in Chemical formula 1 or the silazane shown in Chemical formula 2 is two, when the magnetic iron oxide particles were held for 30 minutes at 120 ° C., the number of carbon atoms as a decomposition product of the silane compound is dissipated from the magnetic iron oxide particles is 2 to 16 aliphatic hydrocarbon Alternatively, the hydrophobic magnetic iron oxide particle powder is characterized in that the total amount of volatile organic compounds selected from aliphatic aldehydes, aliphatic ketones and aliphatic alcohols is 15 ppm or less.

Hydrophobic magnetic iron oxide particles according to claim 1, wherein the degree of hydrophobicity of 60% or more. The hydrophobic magnetic iron oxide particle powder according to claim 1 or 2, wherein the glossiness of the coating film dispersed in styrene / n-butyl acrylate is 60% or more. The magnetic iron oxide particles to be the nucleus are subjected to a hydrophobization treatment in a dry state, and then heat treatment is performed while rotating in a temperature range of 80 to 120 ° C. and a circumferential speed of 0.01 to 10.0 m / sec. The manufacturing method of the hydrophobic magnetic iron oxide particle powder of a claim | item 1 aspect.