JP4616680B2 - Method for producing hydrophobized magnetite particle powder - Google Patents

Description

  The present invention relates to a method for producing a magnetite particle powder having excellent dispersibility and hydrophobicity at a low environmental load.

  Magnetite particle powder is widely used in electrostatic copying magnetic toner material powder, electrostatic latent image developing carrier material powder, etc., but with the recent development of electrophotographic technology, in particular, a copying machine using digital technology, Printers are rapidly developing and the required characteristics are becoming more sophisticated.

  Magnetite particle powder is generally hydrophilic because it contains hydroxyl groups and adsorbed moisture on the particle surface, poorly lipophilic, and difficult to disperse in organic media and knead into resin. There is a demand for magnetite particle powders that are hydrophobized and excellent in dispersion in organic media and resins.

  Furthermore, in recent years, a wet process using a chemical reaction in an organic solvent or the like has attracted attention as a toner manufacturing process instead of the conventional dry process using heat kneading. The chemical toner obtained by the wet method is not treated with a strong dispersion force as compared with the kneaded toner obtained by the dry method, and therefore it is not easy to uniformly disperse the magnetite particles in the toner.

  On the other hand, environmental regulations are becoming stricter in recent years, and it is demanded not to discharge harmful substances with a low environmental load even in the manufacturing process of magnetite particle powder.

  Conventionally, as a method for hydrophobizing the surface of hydrophilic magnetite particles, a method is generally known in which magnetite particle powder and a hydrophobizing agent are mixed in a wet or dry manner and then heat-treated.

  As a method for hydrophobizing the surface of magnetite particles by dry method, a method using a mixer-type mixer or a wheel-type mixer using magnetite particle powder and a hydrophobizing agent as raw materials is disclosed (see Patent Documents 1 and 2). ). However, the magnetite particle powder has strong cohesiveness, and the simple dry mixing method makes it easy to coat the surface of the aggregated particle with the hydrophobization treatment agent, making uniform treatment difficult. Therefore, in the toner produced using such a treated powder, some of the magnetite particles contained are present in a coarse aggregate state, the dispersibility in the toner is poor, and the image characteristics are adversely affected. .

  In addition, as a method of hydrophobizing the surface of magnetite particles by wet, a method of performing heat treatment after mixing, dispersing, and filtering magnetite particle powder and a hydrophobizing treatment agent in an organic solvent is disclosed (see Patent Document 3). .

  Furthermore, as a method for hydrophobizing the surface of magnetite particles by wet, a method is disclosed in which magnetite particle powder is dispersed in water, mixed with a hydrophobizing agent, filtered, and then heat treated (Patent Documents 4 and 5). reference).

  When the surface of magnetite particles is hydrophobized by wet, the magnetite particles have strong magnetic cohesive properties, and it is difficult to obtain a good dispersion state even if simple stirring or the like is performed in the dispersion medium. Therefore, the hydrophobizing agent is unavoidably coated on the secondary particles aggregated to some extent, and uniform treatment is still difficult.

  Further, the surface treatment method using an organic solvent as in Patent Document 3 requires a waste liquid treatment of the organic solvent, and includes a risk of explosion and fire during the heat treatment. Furthermore, even in the surface treatment method in an aqueous medium such as Patent Documents 4 and 5, since the magnetite particle powder surface and the unadsorbed and unreacted treating agent flow out into the waste liquid, the waste liquid treatment is necessary, Is not preferable.

Japanese Patent Laid-Open No. 03-221965 Japanese Patent Laid-Open No. 2001-312095 Japanese Patent Laid-Open No. 59-200256 JP-A-11-314919 Japanese Patent Laid-Open No. 2002-72546

  Accordingly, it is an object of the present invention to provide a production method capable of solving the above-mentioned various disadvantages of the prior art and producing magnetite particle powder having excellent dispersibility and excellent hydrophobicity with a low environmental load. .

  As a result of intensive studies, the present inventors have identified a raw material to be subjected to a hydrophobization treatment and processing conditions, thereby producing a method for producing magnetite particle powder having excellent dispersibility and excellent hydrophobicity with a low environmental load. The headline and the present invention were completed.

That is, the method for producing magnetite particle powder according to the present invention includes a coupling containing one or more types of silicon, aluminum, or titanium to a magnetite cake obtained by iron salt aqueous solution neutralization-oxygen-containing gas oxidation method. agent is added and kneaded using a blade-type mixer, dry, a manufacturing method of a row horse Gunetaito particles heat treatment,
The viscosity during the magnetite cake kneading process is 500 kg / m · sec or more and 10 ⁴ kg / m · sec or less, and
The cake solid content concentration during the magnetite cake kneading process is set to 74% or more and 90% or less .

  According to the method for producing a magnetite particle powder of the present invention, a magnetite particle powder particularly suitable for producing a chemical toner excellent in dispersibility in a resin can be efficiently produced with a low environmental load.

  The magnetite particle powder production method of the present invention comprises a magnetite cake obtained by an iron salt aqueous solution neutralization-oxygen-containing gas oxidation method, and one or more silicon-, aluminum-, or titanium-containing coupling agents. In addition, it is characterized by kneading, drying, and heat treatment.

  The starting material used in the production is not particularly limited as long as it is a magnetite cake obtained by washing and dehydrating a reaction slurry obtained by a wet method, but by a method in which a known iron salt aqueous solution is neutralized with an alkali and then oxidized with an oxygen-containing gas. What is obtained is preferred. What is important is that a wet magnetite cake is used, and as a post-treatment after the wet reaction, if the hydrophobized treatment is performed on the product that has undergone the drying process, the particles are agglomerated due to water cross-linking during drying, and it is difficult to re-disperse. Thus, the surface of the particles cannot be uniformly hydrophobized.

The magnetite particles contained in the magnetite cake are preferably composed mainly of magnetite (Fe ₃ O ₄ ), and have an intermediate composition beltride compound (FeOx · Fe ₂ O ₃ , 0 <X < 1) and spinel ferrite particles containing at least one or more of Si, Al, Mn, Ni, Zn, Cu, Mg, Ti, Co, Zr, W, Mo, P, etc. Are selected depending on the required characteristics.

  The surface of the magnetite particles contained in the magnetite cake may be coated with one or more compounds of silicon, aluminum, and titanium. This is because, in general, the reactivity with a coupling agent is better for hydroxides and oxides made of silicon, aluminum and titanium than for iron oxide containing magnetite.

  The content of the elemental compound is preferably 0.05 to 5% by mass, more preferably 0.1 to 3% by mass in terms of element. If it is less than 0.05% by mass, the effect of inclusion cannot be expected, and if it exceeds 5% by mass, other properties required for the magnetite particle powder may be impaired, or the elemental compound may fall off from the surface of the magnetite particle. Is not preferable.

  The average particle size of the magnetite particles contained in the magnetite cake is 0.05 to 1 μm suitable for chemical toner production. Moreover, since the average particle diameter of recent chemical toners is becoming finer, 0.05 to 0.5 μm is preferable.

  Moreover, the chemical | medical agent used for a hydrophobization process is a 1 type, or 2 or more types of coupling agent containing silicon, aluminum, or titanium.

  The coupling agent preferably does not contain an organic solvent in order to avoid waste liquid treatment of an organic solvent with a high environmental load and to reduce the risk of explosion or fire during heat treatment.

  As the silane coupling agent, vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, methyltrimethoxysilane, methyltriethoxysilane, isobutyltrimethoxysilane, dimethyldimethoxysilane, Dimethyldiethoxysilane, trimethylmethoxysilane, hydroxypropyltrimethoxysilane, phenyltrimethoxysilane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane, n-octyltrimethoxysilane, n-octyltriethoxysilane, n- Examples include decyltrimethoxysilane, n-hexadecyltrimethoxysilane, and n-octadecyltrimethoxysilane.

  Examples of aluminate coupling agents include ethyl acetoacetate aluminum diisopropylate, methyl acetoacetate aluminum diisopropylate, ethyl acetate aluminum dibutyrate, alkyl acetoacetate aluminum diisopropylate, aluminum monoacetyl acetate bis (ethyl acetoacetate), etc. Can be mentioned.

  Examples of titanate coupling agents include isopropyl triisostearoyl titanate, isopropyl tridodecylbenzenesulfonyl titanate, bis (dioctyl pyrophosphate) oxyacetate titanate, isopropyl tris (dioctyl pyrophosphate) titanate, and bis (dioctyl pyrophosphate) ethylene titanate. be able to.

  The coupling agent is preferably added so as to have a content of 1 wt% or more and 10 wt% or less with respect to the obtained magnetite particles. When the coating amount of the coupling agent is 1% by weight or less, the surface of the magnetite particles not subjected to the hydrophobization treatment is exposed, and the hydrophobicity becomes insufficient, which is not preferable. On the other hand, when the coating amount of the coupling agent is 10% by weight or more, the coupling agent that cannot react with the surface of the magnetite particles increases, and the hydrophilic portion of the coupling agent inhibits hydrophobicity, which is not preferable.

Further, the method of producing magnetite particles of the present invention is carried out hydrophobic treatment by kneading, cakes viscosity at that time, Ru der below 500 kg / m · sec or more 10 ⁴ kg / m · sec. If it is less than 500 kg / m · sec, not only the shearing force of the kneader is transmitted to the dispersion of the particles, but also the particles are easily re-aggregated before the coupling agent is bonded to the particles, so that the hydrophobic treatment is uniformly performed. Can not. On the other hand, if the cake viscosity is 10 ⁴ kg / m · sec or more, it becomes difficult to disperse the aggregated particles, and the coupling agent is not distributed, so that the cake is not uniformly processed.

In the method of the present invention, the solid concentration in performing a hydrophobic treatment by kneading, and 90% or less 74% or more, preferably 85% or less than 74%. If the solid content concentration is less than 74 %, the shearing force of the kneader is dispersed, a uniform hydrophobization treatment cannot be performed, and the load in drying in a subsequent process is large, which is not industrially preferable. On the other hand, if it exceeds 90%, it becomes difficult to disperse the agglomerated particles, and the hydrophobic treatment cannot be performed uniformly. By kneading the magnetite particle powder and the hydrophobizing agent in a state where the solid content concentration is high, a solid-liquid separation step such as filtration becomes unnecessary, and the unadsorbed and unreacted coupling agent flows into the waste liquid. Therefore, waste liquid treatment is not necessary.

  In the present invention, it is preferable to perform the hydrophobization treatment while uniformly dispersing the particles mainly by the shearing action of the kneading apparatus. By adding the hydrophobizing agent to the magnetite cake separated into solid and liquid by the shearing action of the kneading machine while dispersing the particles one by one, the hydrophobizing agent is mixed uniformly and the kneader-specific shearing Due to the mechanochemical action, the reaction between the hydrophobizing agent and the magnetite particles is promoted, and a uniform hydrophobized surface treatment can be achieved.

As the kneader having the shearing action, an apparatus capable of applying shear to a mixture having a high solid content concentration such as a blade type kneader is used . This is because by adding a hydrophobizing agent while applying shear in a high-viscosity state, the hydrophobizing agent is distributed between the particles or is uniformly processed.

Examples of the blade-type kneader include a universal mixer, a planetary mixer, a trimix, a TK combination mix, a TK hibismix, and a TK hibissper mix .

  The magnetite particle powder and the hydrophobizing agent are treated with a kneader having shearing force, and then dried and heat-treated. The temperature during the heat treatment is preferably 60 ° C. or higher and 300 ° C. or lower. If the heat treatment temperature is less than 60 ° C., moisture may remain in the particle powder, making it difficult to obtain high hydrophobicity. Moreover, when it exceeds 300 degreeC, decomposition | disassembly of a hydrophobization processing agent may occur, and it becomes difficult to obtain high hydrophobicity similarly.

BEST MODE FOR CARRYING OUT THE INVENTION

  The characteristic evaluation of the magnetite cake used for manufacture of the magnetite particle powder of this invention and the magnetite particle powder was performed as follows.

(A) Particle shape and average particle diameter Using a scanning electron microscope, the particle shape was observed at a magnification of 20000 times, and the ferret diameter was measured for 200 particles to determine the average particle diameter.

(B) Analysis of silicon and aluminum content Samples were dissolved and measured by ICP.

(C) Solid content concentration The solid content concentration was determined from the weight change before and after drying when the magnetite cake was dried at 50 ° C for 10 hours.

(D) Carbon analysis In order to see the degree of coating of the coupling agent on the magnetite particles, the carbon in the magnetite particle powder subjected to the coupling agent treatment was analyzed. The amount of carbon in the sample was measured using a carbon analyzer (EMIA-110, manufactured by Horiba, Ltd.).

(E) Filter permeability 0.2 g of a sample and 10 g of a styrene monomer are placed in a test tube and treated with an ultrasonic homogenizer (BRANSON, SONIFIER 450) for 1 minute. The obtained suspension is passed through the membrane filter (Millipore) having a diameter of 25 mm and an opening of 1.2 μm while applying pressure. At this time, the filtrate did not become transparent and the whole suspension passed through was marked with ◯, and the others were marked with x.

(F) pH change value In 100 parts by mass of water, 1.01 part by mass of potassium nitrate and 1 part by mass of 0.1N nitric acid are added, dissolved and mixed. Set to 1. While stirring, 0.4 mL of 0.1 N potassium hydroxide is added dropwise to 100 g of the preparation solution 1 to prepare the preparation solution 2 having a pH of about 5. 1.6 g of the sample is added to the obtained preparation liquid 2 and stirred to obtain preparation liquid 3.
Also, 1.0 mL of 0.1N potassium hydroxide is dropped into Preparation Solution 1 to prepare Preparation Solution 4 having a pH of about 12. Similarly, 1.6 g of the sample is added to the obtained preparation liquid 4 and stirred to obtain preparation liquid 5.
The pH of the obtained preparation liquids 2 to 5 is measured, and the value obtained by the following formula (1) is defined as the pH change value. This value indicates that the closer to 0, the higher the hydrophobicity (when the hydrophobicity is high, the preparation solution is less likely to penetrate inside than the hydrophobic coating of the sample, and the fluctuation in pH is small).
pH change value = | A | + | B | (1)
A: Change in pH of preparation liquid 2 and preparation liquid 3
B: Change in pH of preparation liquid 4 and preparation liquid 5

(G) Dispersibility Unevenness in the kneaded product of the sample and the resin; the sample and the resin (TB-1000F manufactured by Sanyo Chemical Co., Ltd.) are used and mixed with a Henschel mixer at a mass ratio of 1: 1. After melt-kneading at 180 ° C. for 1 minute, it was molded into a plate shape using a roller and cooled. The plate-shaped molded product is cut, and the cut surface is observed with a scanning electron microscope (magnification: 5,000 times). The iron oxide particles in the cut surface are uniformly distributed. Evaluation was made with △ for those with a bias and × for those with a significant distribution bias.

Hereinafter, the present invention will be specifically described with reference to examples and the like. Of the following examples, Example 3 is outside the scope of the present invention.
[Magnetite cake production example 1]
A slurry containing magnetite particles was obtained by performing a known method of oxidizing an iron salt aqueous solution with an oxygen-containing gas after neutralization with an alkali. This slurry was washed with a filter press, filtered, and further air blown for 20 minutes to obtain a magnetite cake having a solid content concentration of 75% by mass.

[Magnetite cake production example 2]
A magnetite cake was obtained in the same manner as in Magnetite Cake Production Example 1 except that the air blowing time was 60 minutes. The solid content concentration of the obtained magnetite cake was 80% by mass.

[Magnetite cake production example 3]
A magnetite cake was obtained in the same manner as in Magnetite Cake Production Example 1 except that the air blowing time was 1 minute. The solid content concentration of the obtained magnetite cake was 64% by mass.

[Magnetite cake production example 4]
A magnetite cake was obtained in the same manner as in Magnetite Cake Production Example 1 except that sodium silicate was added so that the wet reaction was 0.2 wt% with respect to the magnetite particles in terms of Si. The solid content concentration of the obtained magnetite cake was 74% by mass.

[Magnetite cake production example 5]
Magnetite cake production example, except that the slurry after the wet reaction was mixed with an aqueous aluminum sulfate solution so that the slurry was 0.2 wt% in terms of Al with respect to the magnetite particles, and then the reaction was terminated by adjusting the pH to 6. In the same manner as in No. 1, a magnetite cake was obtained. The solid content concentration of the obtained magnetite cake was 75% by mass.

  Table 1 shows the characteristics of the magnetite cake of the obtained production example.

[Example 1]
While heating to 50 ° C. with Hibismix (made by Koki Kogyo Co., Ltd.), 2.7% by mass of decyltrimethoxysilane based on 100 parts by mass of the magnetite cake obtained in Production Example 1 and magnetite solids, The container was kneaded for 2 hours in a sealed state. The obtained kneaded material was heat-treated at 50 ° C. for 10 hours and at 90 ° C. for 2 hours and then pulverized to obtain magnetite particle powder having a hydrophobic particle surface. The viscosity of the magnetite cake during the kneading process was measured at a rotation speed of 2 rpm using a VISCOMETER, BH type (manufactured by TOKIMEC) and a rotor for measurement No. 7 and maintained at 500 kg / m · sec. .

[Example 2]
The same procedure as in Example 1 was performed except that the magnetite cake obtained in Production Example 2 was used and the viscosity was maintained at 1980 kg / m · sec during kneading.

Example 3
The same procedure as in Example 1 was performed except that the magnetite cake obtained in Production Example 3 was used and the viscosity was maintained at 120 kg / m · sec during kneading.

Example 4
The same procedure as in Example 1 was performed except that octyltriethoxysilane was used as the coupling agent.

Example 5
The same procedure as in Example 1 was performed, except that the magnetite cake obtained in Production Example 5 was used and the viscosity was maintained at 520 kg / m · sec during kneading.

Example 6
The same procedure as in Example 1 was performed, except that the magnetite cake obtained in Production Example 6 was used and the viscosity was maintained at 540 kg / m · sec during kneading.

[Comparative Example 1]
The magnetite cake obtained in Production Example 1 was dried and pulverized to obtain magnetite particle powder.

[Comparative Example 2]
2.7% by mass of decyltrimethoxysilane with respect to the magnetite solid content was added to the magnetite particle powder of Comparative Example 1 corresponding to 100 parts by mass of the magnetite cake of Production Example 1, and a Henschel mixer, FM20B type (Mitsui Miike Chemical) Machine), and processed for 30 minutes at a rotational speed of 2000 rpm. After heat treatment at 90 ° C. for 2 hours, the mixture was pulverized to obtain magnetite particle powder.

[Comparative Example 3]
650 parts by mass of water was added to 100 parts by mass of the hydrous magnetite cake obtained in Production Example 1, and slurried with a general-purpose stirrer. Thereto was added 2.7% by mass of decyltrimethoxysilane with respect to the solid content of magnetite, and the mixture was mixed for 2 hours while heating to 50 ° C. The obtained surface treatment slurry was solid-liquid separated with a filter paper, heat-treated at 50 ° C. for 10 hours, and at 90 ° C. for 2 hours, and then pulverized to obtain magnetite particle powder.

[Comparative Example 4]
The magnetite particle powder of Comparative Example 1 corresponding to 100 parts by mass of the magnetite cake of Production Example 1 has a solid content concentration of 2.7% by mass of decyltrimethoxysilane and the magnetite cake of Production Example 1 based on the solid content of magnetite. Such a considerable amount of water was added and the same kneading treatment and post-treatment as in Example 1 were performed to obtain magnetite particle powder.

[Comparative Example 5]
Magnetite particle powder was obtained in the same manner as in Comparative Example 4 except that water was changed to toluene.

  The above production conditions are shown in Table 2, and the characteristics of the obtained magnetite particle powder are shown in Table 3.

  As can be seen from Table 3, the magnetite particle powder of the example has a sufficiently low pH change value, so that the surface of the particle is sufficiently hydrophobized, and as a result, the dispersibility is extremely excellent. Is. In addition, it can be seen that filterability is good and aggregation is very small.

In comparison, the magnetite particle powder of the comparative example has a high pH change value, insufficient particle surface hydrophobization, and poor dispersibility. Filterability was poor and particle aggregation was remarkable.

Claims (3)

Iron salt aqueous solution neutralization-Add one or more silicon, aluminum, or titanium-containing coupling agents to the magnetite cake obtained by the oxygen-containing gas oxidation method, and knead using a blade-type mixer. , drying, a method of manufacturing the row horse Gunetaito powder particles heat treatment,
The viscosity during the magnetite cake kneading process is 500 kg / m · sec or more and 10 ⁴ kg / m · sec or less, and
A method for producing magnetite particle powder, characterized in that the solid content concentration of the cake during the magnetite cake kneading treatment is 74% or more and 90% or less . The manufacturing method of the magnetite particle powder of Claim 1 which knead | mixes with the said coupling agent, without performing a drying process with respect to a magnetite cake . One or more silicon to magnetite, aluminum or the content of the coupling agent titanium contained in, to claim 1 or 2, characterized in that added in an amount of 1 wt% to 10 wt% or less, The manufacturing method of the magnetite particle powder of description.