JP3370647B2 - Preparation of ferrite particles containing ammonium salt-based charge control agent - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing ammonium salt-based charge control agent-containing ferrite particles which prevents deterioration in image density and resolution and prevents fog in electrophotographic copying methods to improve transfer efficiency.

[0002]

2. Description of the Related Art At present, electrophotographic copying machines, which are becoming smaller and faster, are capable of enduring continuous operation for a long time under a bad environment of high temperature and high humidity and always producing stable and high quality clear images. Is required. Therefore, excellent environmental stability,
There is a need for an electrophotographic toner that has durability stability and suitable density, is free from black spots, and is capable of copying images with high resolution.

In the conventional technique of preliminary dry mixing, a resin, a coloring agent such as magnetite or carbon black, a charge control agent such as a metal-containing dye, wax and the like are mixed in a mixer such as a Henschel mixer at a time and cooled. , The shape of the rotating blade, the number of revolutions, the number of revolutions, etc. are changed and mixed. However, since the resin, the colorant such as magnetite or carbon black, the charge control agent such as a metal-containing dye, and the wax have different particle diameters, specific gravities, and charging characteristics, it is difficult to uniformly disperse them in the toner. In particular, since it is difficult to uniformly disperse a colorant such as magnetite or carbon black and a charge control agent such as a metal-containing dye, there is a tendency that the image density and resolution of the toner decrease and fog occurs, and the transfer efficiency decreases.

[0004]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a process for producing ferrite particles containing an ammonium salt-based charge control agent, which prevents deterioration of image density and resolution as well as generation of fog and improves transfer efficiency. .

[0005]

The ammonium salt-based charge control agent-containing ferrite particles according to the present invention are prepared by mixing an iron-containing salt, a solvent and an alkali metal hydroxide to oxidize iron in the salt. A step of obtaining a reaction mixture containing ferrite and a by-product, a step of dissolving and removing the by-product in the reaction mixture in a solvent to extract ferrite, an ammonium salt aqueous solution in the extracted ferrite, and a sulfonic acid compound , Metal acid, isopoly acid and heteropoly acid 1
And a step of mixing two or more kinds to obtain an ammonium salt-based charge control agent-containing ferrite, and a step of purifying the ammonium salt-based charge control agent-containing ferrite.

Oxidation of iron contained in the salt produces a reaction mixture containing a ferrite such as magnetite and a by-product such as a sulfate, and after removal of the by-product, ammonium salt-based charge control agent-containing ferrite particles. To generate. As a result, high-purity ferrite particles are obtained, and a small amount of ferrite sufficiently exhibits the function as a colorant. Further, ferrite conveys toner particles such as a binder resin as a carrier to a magnetic roll, but if the ferrite particles are of high purity, the toner particles adhere firmly and uniformly to the ferrite particles, and the toner particles together with the ferrite particles become toner particles. The particles are conveyed well to the magnetic roll. Further, since the ferrite is mixed at the stage of producing the ammonium salt-based charge control agent, not the ammonium salt-based charge control agent and the ferrite are mixed after the formation, the charge control agent and the ferrite particles are uniformly dispersed in the toner particles. And the charge control agents do not aggregate with each other, and charging unevenness does not occur.

In the embodiment according to the present invention, the ferrite and the ammonium salt-based charge control agent are uniformly mixed, and the ferrite and the ammonium salt-based charge control agent are integrally attached to form particles having an average particle size of 1.0 μm or less. And a step of forming.

The ammonium salt is an ammonium salt represented by the formula (I) (wherein R ₁ , R ₂ , R ₃ and R ₄ are hydrogen atoms, alkyl groups having 1 to 22 carbon atoms and 6 to 20 carbon atoms). Selected from aromatic groups, A is selected from sulfonic acids, metal acids, isopoly acids and heteropoly acids)

[Chemical 2] Consists of. The solvent is water or a mixed liquid of water and alcohol.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the method for producing ferrite particles containing an ammonium salt type charge control agent according to the present invention will be described below.

In the production method according to the present invention, a salt containing iron, a solvent, and a hydroxide of an alkali metal are mixed to oxidize iron in the salt to obtain ferrite (MO.Fe ₂ O ₃ ) and a by-product. To produce a reaction mixture containing. Oxidation is 2 at 70-120 ℃
Do it for 6 hours. The solvent is water or a mixture of water and alcohol, and the alcohol is selected from methyl alcohol, ethyl alcohol, butyl alcohol, propyl alcohol, isopropyl alcohol and the like. When alcohol is used as a solvent in addition to water, the viscosity is lowered and the reaction is carried out quickly. As the alkali metal hydroxide, sodium hydroxide, potassium hydroxide or lithium hydroxide can be used.
Since the reaction mixture contains by-products in addition to ferrite, the by-products are dissolved in a solvent and removed. This is repeated several times to extract highly pure ferrite.

Next, the extracted ferrite is mixed with an aqueous solution of ammonium salt and any one kind or two or more kinds of a sulfonic acid compound, a metal acid, an isopoly acid and a heteropoly acid, and reacted for 15 to 30 minutes. An ammonium salt-based charge control agent-containing ferrite is produced.

Finally, the produced ammonium salt-based charge control agent-containing ferrite is filtered, washed, dried and pulverized. As a result, as shown in FIG. 1, the ferrite (2) and the ammonium salt-based charge control agent (3) were uniformly mixed and the ferrite (2) and the ammonium salt-based charge control agent (3) were adhered together. Ferrite particles (1) containing an ammonium salt-based charge control agent and having an average particle size of 1.0 μm or less are obtained. Ammonium salt type charge control agent (3) and ferrite (2) are uniformly dispersed in the toner particles, and ammonium salt type charge control agent (3)
However, since they do not aggregate with each other and uneven charging does not occur, the decrease in image density and resolution and the occurrence of fog are prevented, and the transfer efficiency is improved. The average particle size is preferably 1.0 μm or less, and more preferably 0.01 μm or more. When the average particle size exceeds 1.0 μm, the dispersibility of the charge control agent in the toner is poor and the charge amount of the toner becomes uneven. It is difficult to uniformly pulverize particles of less than 0.01 μm, which causes a large variation in particle size, which is a drawback in manufacturing.

The ammonium salt-based charge control agent-containing ferrite and the purified ammonium salt-based charge control agent-containing ferrite particles (1) are

[Chemical 3] It includes an ammonium salt represented by the formula (I). R ₁ , R ₂ , R ₃ and R ₄ shown in formula (I) are selected from a hydrogen atom, an alkyl group having 1 to 22 carbon atoms and an aromatic group having 6 to 20 carbon atoms. The alkyl group is selected from methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl and octadecyl. The aromatic group is selected from phenyl, naphthyl, tolyl, benzyl, p-chlorobenzyl and phenethyl.

In the formula (I), the anion represented by A is sulfonic acid such as benzenesulfonic acid, naphthalenesulfonic acid and naphtholsulfonic acid, iron, chromium, nickel, cobalt, tin, manganese, cerium, silver, zinc, magnesium. , Zirconium, beryllium, copper, aluminum,
Metal acids such as barium, calcium, titanium, indium, lithium and cadmium, isopolytungstic acid,
It is selected from isopoly acids such as isopolyvanadate and isopolymolybdic acid and heteropoly acids such as silicon molybdic acid and phosphotungstic acid.

Specific examples of the ammonium salt used in the present invention are shown by the following chemical formulas.

[0016]

[Chemical 4]

The content of the ammonium salt type charge control agent (3) in the ferrite particles (2) is 0.1 to 10% by weight.
When the content is less than 0.1% by weight, the charge amount is low and the chargeability is not stable. If it exceeds 10% by weight, the charge amount becomes too high, and at the same time, the ferrite particles act as a colorant.
The ratio of (2) decreases and the toner concentration decreases. It is preferably 0.5 to 3% by weight.

The produced ammonium salt-based charge control agent-containing ferrite particles (1) are thoroughly mixed with a binder resin, wax and the like with a mixer such as a ball mill and a Henschel mixer, and then heated roll kneader, extruder and the like. Are kneaded by a kneading machine of No. 1 and cooled and solidified, pulverized, classified and post-treated (external addition). As a result, it is possible to obtain a toner having a high transfer efficiency by preventing a decrease in image density and resolution and the occurrence of fog. In addition, it can be obtained by a spraying method, a polymerization method or the like.

As a raw material of the toner, a binder resin, a colorant such as magnetite or carbon black, a charge control agent such as a metal-containing dye, and a wax are used. The binder resin is polystyrene, a styrene-styrene-acrylic acid copolymer, a styrene-methacrylic acid copolymer, a styrene-acrylic acid ester copolymer, a styrene-methacrylic acid ester copolymer, or a styrene-butadiene copolymer. Resin, saturated polyester resin, unsaturated polyester resin, epoxy resin, phenol resin, maleic acid resin, coumarone resin,
Chlorinated paraffin, xylene resin, vinyl chloride resin,
It is possible to use one kind or a mixture of two or more kinds of polypropylene and polyethylene.

As the colorant and the charge control agent, the above-mentioned ammonium salt-based charge control agent-containing ferrite particles (1) are used, and the content ratio with respect to the toner is 5 to 70%, preferably 25 to 55%. If it is less than 5%, the magnetic force is weak so that it cannot be supported on the magnetic roll, and if it exceeds 70%, the content of the resin is reduced and the fixing property is deteriorated.

The wax is low molecular weight polypropylene, low molecular weight polyethylene, microcrystalline wax,
Carnauba wax, Sazol wax, paraffin wax, aliphatic solid alcohol and the like can be used.

A fluidizing agent, a charging aid, an abrasive and the like may be added to the toner as needed.
Fine particles of silica, titanium oxide, alumina, etc., and fine particles obtained by hydrophobizing these with silicon oil, silicon varnish, silane coupling agent, etc., metal oxides such as calcium titanate, metal carbides, inorganics such as metal nitrides Fine particles, methyl methacrylate, polyvinylidene fluoride,
Organic fine particles such as polystyrene and fine particles of organic metal compounds such as zinc stearate and calcium stearate can be used.

[0023]

EXAMPLES The present invention will now be described in more detail by way of examples, which should not be construed as limiting the invention in any way. All parts in the following formulations are parts by weight.

Example 1 <Synthesis of Ferrite Particles Containing Quaternary Ammonium Salt-Based Charge Control Agent> A solution prepared by adding 3000 parts of ferrous sulfate to 3400 parts of water and 1000 parts of ethyl alcohol and dissolving them, and 1000 parts of sodium hydroxide. Parts were added to 1500 parts of water and dissolved and mixed and stirred. Next, while blowing in air, 9
The ferrite (F
eO.Fe ₂ O ₃ ) particles were precipitated and the supernatant was discarded. To this, 3000 parts of water was added and stirred, and decantation of precipitating ferrite particles and discarding the supernatant was repeated 7 times, sodium sulfate as a by-product was removed, and high-purity ferrite particles were extracted. To the extracted aqueous solution of ferrite particles, 4.9 parts of decylpentyl ammonium chloride dissolved in 20 parts of water was added, and subsequently, 4.6 parts of sodium 1-naphthol-5-sulfonate dissolved in 10 parts of water was added.
Parts were added and the reaction was allowed to stir for 30 minutes. Further, after filtering and washing with water, it is dried at 120 ° C. for 6 hours and pulverized to obtain 840 parts of ferrite particles uniformly containing 1.0% of a quaternary ammonium salt type charge control agent having an average particle size of 0.6 μm. It was

<Toner Production / Performance Confirmation> Styrene-acrylic acid ester copolymer 49 parts Low molecular weight polypropylene NP-505 (manufactured by Mitsui Petrochemical Co., Ltd.) 2 parts Ferrite particles containing quaternary ammonium salt type charge control agent 49 parts The materials were dry-mixed by a mixer (Henschel mixer), and then kneaded by a twin-screw kneader whose temperature was set at 130 ° C. The obtained kneaded product was cooled, coarsely pulverized to about 2 mm or less with a hammer mill, and then finely pulverized with a jet pulverizer having a coarse powder classification function. The obtained fine powder was classified by an airflow classifier to obtain a raw toner having an average particle size of 9.0 μm. To 100 parts of the obtained raw toner, 0.3 parts of hydrophobic colloidal silica and 1.0 part of calcium titanate were added and mixed with a mixer (Henschel mixer), and then aggregates were removed by a vibrating screen to obtain a toner. Use this toner on a commercial copying machine (trade name, NP-40
As a result of conducting a continuous copying test of 10,000 sheets by using 0RE, manufactured by Canon Inc.), as shown in Table 1, the image density and the resolution were not lowered, the fog was not generated, and the transfer efficiency was high.

Comparative Example 1 <Manufacture and Performance Confirmation of Toner> Styrene-acrylic acid ester copolymer 49 parts Low molecular weight polypropylene NP-505 (manufactured by Mitsui Petrochemical Co., Ltd.) 2 parts Ferrite particles 44.6 parts Quaternary ammonium Salt-based charge control agent 0.4 parts The above materials were dry-mixed by a mixer (Henschel mixer), and then kneaded by a twin-screw kneader whose temperature was set at 130 ° C. The obtained kneaded product is cooled and roughly crushed to about 2 mm or less with a hammer mill, then finely crushed with a jet crusher having a coarse powder classifying function, and classified with an air flow classifier to obtain an average particle size of 9.2 μm.
To obtain a raw toner of. To 100 parts of the obtained raw toner, 0.3 parts of hydrophobic colloidal silica and 1.0 part of calcium titanate were added and mixed with a mixer, and then aggregates were removed by a vibrating screen to obtain a toner. Use this toner on a commercial copying machine (trade name,
As a result of conducting a continuous copying test of 10,000 sheets with NP-400RE (manufactured by Canon Inc.), as shown in Table 1, the image density and resolution were low, fogging occurred frequently, and transfer efficiency was low.

Example 2 <Synthesis of Ferrite Particles Containing Quaternary Ammonium Salt Charge Control Agent> A solution prepared by adding 2640 parts of ferrous sulfate to 3870 parts of water and dissolving it, and 880 parts of sodium hydroxide in water 1320.
The liquid added to the parts was mixed and stirred. Next, while blowing air, an oxidation reaction was carried out at 115 ° C. for 6 hours to precipitate the obtained ferrite (FeO.Fe ₂ O ₃ ) particles, and the supernatant was discarded. To this, 3000 parts of water was added and stirred, and the decantation of precipitating the ferrite particles and discarding the supernatant was repeated 7 times, sodium sulfate as a by-product was removed, and high-purity ferrite particles were extracted. Next, acetic acid 45
Then, a solution prepared by dissolving 17 parts of a quaternary ammonium salt-based charge control agent consisting of hexadecylpentyl ammonium chloride and potassium ferrate in 50 parts of methanol is added and stirred for 15 minutes. Further, after filtering and washing with water, it is dried at 120 ° C. for 6 hours and crushed to obtain an average particle size of 0.0
740 parts of ferrite particles containing 2.0% of 5 μm quaternary ammonium salt type charge control agent uniformly were obtained.

<Manufacturing and Performance Check of Toner> Saturated polyester resin 67 parts Low molecular weight polypropylene NP-505 (manufactured by Mitsui Petrochemical Co., Ltd.) 3 parts Ferrite particles containing quaternary ammonium salt type charge control agent 30 parts Mixer ( After dry-mixing with a Henschel mixer, the mixture was kneaded with a twin-screw kneader whose temperature was set to 130 ° C. The obtained kneaded product is cooled, roughly crushed to about 2 mm or less with a hammer mill, finely crushed with a jet crusher having a coarse powder classifying function, and classified with an airflow classifier to obtain an average particle size of 9.4.
A raw toner of μm was obtained. To 100 parts of the obtained raw toner, 0.3 parts of hydrophobic colloidal silica and 0.5 part of methyl methacrylate fine particles were added and mixed with a mixer, and then aggregates were removed by a vibrating screen to obtain a toner. The toner was subjected to a continuous copying test of 10,000 sheets using a commercially available copying machine (trade name, NP-6062, manufactured by Canon Inc.). As a result, as shown in Table 1, the image density and resolution did not decrease, and fog There was no occurrence and the transfer efficiency was high.

Comparative Example 2 <Manufacture and Performance Confirmation of Toner> Saturated polyester resin 67 parts Low molecular weight polypropylene NP-505 (manufactured by Mitsui Petrochemical Co., Ltd.) 3 parts Ferrite particles 28 parts Quaternary ammonium salt type charge control agent 2 parts The above materials were dry-mixed with a mixer (Henschel mixer) and then kneaded with a twin-screw kneader whose temperature was set to 130 ° C. The obtained kneaded product is cooled and roughly crushed to about 2 mm or less with a hammer mill, then finely crushed with a jet crusher having a coarse powder classifying function, and classified with an airflow classifier to obtain an average particle size of 9.0 μm.
To obtain a raw toner of. To 100 parts of the obtained raw toner, 0.3 parts of hydrophobic colloidal silica and 0.5 part of methyl methacrylate fine particles were added and mixed with a mixer, and then aggregates were removed by a vibrating screen to obtain a toner. Use a commercially available copying machine (trade name, NP-6062, manufactured by Canon Inc.) to copy this toner 1
As a result of conducting a continuous copying test on ten thousand sheets, as shown in Table 1, the image density and resolution were low, fogging occurred frequently, and transfer efficiency was low.

Table 1 shows the results of evaluation of the copied image at the start of the continuous copying test and the copied image at the end of each continuous copying test for each item in each example and comparative example. The Electrophotographic Society Test Chart No. 1-R was used as a copy sample. As the image density, the density of the black solid portion of the copied image was measured with a Macbeth densitometer. The resolution was evaluated by visually observing the copied image with a magnifying glass and counting the number of individual thin lines. For fog, the density of the non-image portion of the copied image was measured with a Macbeth densitometer. For transfer efficiency, divide the amount of waste toner (increase in the amount of waste toner) by the amount of used toner (decrease in amount in the development unit), and multiply by 100
It is a value subtracted from 00.

[0031]

[Table 1]

[0032]

INDUSTRIAL APPLICABILITY According to the present invention, the transfer efficiency can be improved by the method of producing the ammonium salt type charge control agent-containing ferrite particles, preventing the image density and resolution of the toner from being deteriorated and preventing the occurrence of fog.

[Brief description of drawings]

FIG. 1 is an enlarged view of ferrite particles containing an ammonium salt-based charge control agent according to the present invention.

[Explanation of symbols]

(1) ・ ・ Ferrite particles containing ammonium salt type charge control agent, (2) ・ ・ Ferrite, (3) ・ ・ Charge control agent,

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-22673 (JP, A) JP-A-8-6295 (JP, A) JP-A-6-59518 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) G03G 9/083 G03G 9/097

Claims (4)

(57) [Claims] 1. A step of mixing a salt containing iron, a solvent and a hydroxide of an alkali metal to oxidize iron in the salt to obtain a reaction mixture containing ferrite and a by-product; A step of dissolving and removing the by-product of the above in a solvent to extract ferrite, an ammonium salt solution in the extracted ferrite, and any one or more of a sulfonic acid compound, a metal acid, an isopoly acid and a heteropoly acid. And a step of refining the ammonium salt-based charge control agent-containing ferrite, and a step of purifying the ammonium salt-based charge control agent-containing ferrite. . 2. A step of forming particles having an average particle diameter of 1.0 μm or less, in which ferrite and an ammonium salt-based charge control agent are uniformly mixed, and ferrite and an ammonium salt-based charge control agent are integrally attached. Item 2. A process for producing ferrite particles containing an ammonium salt-based charge control agent according to Item 1. 3. An ammonium salt is an ammonium salt represented by formula (I) (wherein R ₁ , R ₂ , R ₃ and R ₄ are a hydrogen atom, an alkyl group having 1 to 22 carbon atoms and a carbon atom having 6 to 20 carbon atoms). Selected from aromatic groups, A being selected from sulfonic acids, metal acids, isopoly acids and heteropoly acids) The process for producing ferrite particles containing an ammonium salt-based charge control agent according to claim 1 or 2. 4. The method for producing an ammonium salt-based charge control agent-containing ferrite particle according to claim 1, wherein the solvent is water or a mixed liquid of water and alcohol.