JP2636234B2 - Powder toner for developing an electrostatic image and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a powder toner for dry developing an electrostatic latent image such as electrophotography and ion flow recording.

(Prior Art) As a method for producing a powder toner for dry developing an electrostatic image, a dye, a pigment, a magnetic powder, etc. are dispersed in a resin for a toner by melt-kneading, and this is mechanically pulverized and classified. The method of obtaining is common.

However, the toner obtained by this method is indefinite and it is difficult to obtain a uniform charge.

Further, the consumption of electric energy required for melt kneading and pulverization is enormous, and various methods for producing a toner by a method other than the so-called pulverization method have been proposed.

As a method other than the pulverization method, a spray drying method, an emulsion polymerization method, an interfacial polymerization method, a suspension polymerization method and the like are known.

However, in the spray drying method, a uniform charge is obtained because spherical toner is generated, and the fluidity is improved.
There are drawbacks such as the need for explosion-proof measures and the need to recover the solvent, the enormous consumption of heat energy required for drying, and the fact that the solvent remains in the toner after drying and is difficult to remove.

Therefore, for example, JP-A-36-10231, 47-51830, 51-14895
Various methods for producing spherical toner particles in water by the suspension polymerization method disclosed in each of the publications have been studied. In this method, it is easy to obtain particles having a particle size suitable for the toner, and it is easy to incorporate a compounding agent necessary for the toner such as a colorant, a wax, and a magnetic powder. However, the dispersant and stabilizer of the toner particles in water remain on the toner surface and are difficult to remove, and this adsorbs moisture in the air and lowers the electrical resistance of the toner. Such toner has the drawback that it is difficult to copy plain paper and that the charge on the surface becomes uneven. Further, instead of the suspension polymerization method, for example, JP-A-51-14895, 55-5096
Although it is possible to use the emulsion polymerization method disclosed in each gazette of US Pat. No. 2,59-152459, etc., it is generally easy to adjust the molecular weight distribution which has an effect on the fixability, etc. There is a problem that the toner particles are too small and it is difficult to contain other toner components inside. Further, similarly to the suspension polymerization method, there is a problem that the electric resistance is reduced due to the adsorption of moisture in the air.

As described above, powder toner has advantages and disadvantages in each method, but a common problem is that when the particle size distribution is adjusted to a range suitable for toner, a large number of particles that cannot be used particularly on the fine particle side are generated. I do. They are,
It is mixed with the raw materials again for reuse.
Those based on emulsion polymerization, suspension polymerization, etc. cannot be reused.

Further, a method of using a toner material which has been made fine in advance and aggregating the toner material to granulate the toner is disclosed in, for example,
-185, 60-220358, 61-167956, 61-167957 and the like. However, this method has the following problems, and has not been sufficiently commercialized.

The finely divided toner material is partially secondary-agglomerated and difficult to disintegrate, so that the composition of each toner particle is not uniform.

The granulated material has a severe surface irregularity and becomes porous, has poor fluidity as a powder, and is bulky, so that triboelectric charging does not occur uniformly.

Since the cohesive force is weak, the toner particles are broken by a relatively weak impact.

(Problems to be Solved by the Invention) Based on the above situation, the present inventors have conducted intensive studies. As a result, instead of the conventionally complicated and energy-consuming toner manufacturing method, all of the toner components have been finely divided. The particles are coated with a resin, and the coated resin is agglomerated as a binder. Thereafter, a desired particle size distribution is obtained in a crushing process.
In addition, the present inventors have found a method for producing a powder toner which is excellent in function as a toner by adjusting the shape, and which simplifies the production process and reduces energy consumption.

[Configuration of the invention]

(Means for Solving the Problem) That is, the first invention essentially comprises spherical resin fine particles (A) having a hydrophobic resin coating and having an average particle size of 10 μm or less and produced by an emulsion polymerization method or a suspension polymerization method. ), Wherein either the upper air coating or the resin fine particles (A) contains a coloring agent or other necessary fine particles, and the surface of the aggregate is smoothened by heat melting. It is a powder toner for developing an electrostatic image, characterized by being
The second invention is to provide a spherical resin fine particle (A) having an average particle size of 10 μm or less produced by an emulsion polymerization method or a suspension polymerization method containing a colorant and other necessary fine particles as necessary, and optionally a colorant or At the same time as coating with a hydrophobic resin together with other necessary fine particles, an aggregate of the coated fine particles is obtained, and then the aggregate is crushed into an aggregate containing a plurality of spherical resin fine particles (A). This is a method of producing a powder toner for developing an electrostatic image, wherein the hydrophobic resin is thermally melted by mechanical strain to smooth the surface of the aggregate.

The present invention will be described more specifically. A coloring agent and other necessary fine particles are added to an aqueous dispersion of spherical resin fine particles (A) obtained by an emulsion polymerization method or a suspension polymerization method, if necessary, and a homogenizer, a colloid The other fine particles are uniformly adhered to the surface of the resin fine particles (A) by applying a strong shearing force with a mill or the like. Here, other fine particles include dyes, pigments, charge control agents, waxes, magnetic powder fine particles, and the like. At this time, the aggregation of the resin fine particles (A) is also broken. (When no fine particles other than the resin fine particles (A) are used, the above operation is performed using the resin fine particles (A)
The main purpose is to disintegrate. Next, replace water with a solvent, or once dry with a spray dryer, vacuum dryer, etc., and then immerse in the solvent. Thereafter, the resin is coated with a hydrophobic resin by a coacervation method, and dried by a spray drier, a vacuum drier, or the like, to obtain an aggregate of toner raw materials.

The aggregate of the toner raw material is a brittle lump that is agglomerated by coating the resin fine particles (A) with a hydrophobic resin. For this reason, it is easily crushed by a relatively light impact force. However, ordinary crushing results in extremely broad particles having a particle size distribution including fine powder to considerably coarse powder.
The shape is porous and there are many irregularities. Therefore, in the present invention, for example, a mode of volume-based particle size distribution can be obtained by using a pulverizer such as a hammer mill, a rotary pulverizer such as a coffee mill, or a driven pulverizer or a cone pulverizer. Diameter 10 ~
After about 25μ, for example, by airflow classification
The particles having a size of 25 μ or more are removed, and the volume-based median diameter (hereinafter, referred to as an average particle size) is adjusted to 5 to 15 μ.

At this stage, the toner particles still have a porous shape with many irregularities, and have an unsuitable particle size of 5 μm.
Many of the following particles are included. Next, a relatively strong impact force is applied to the particles to apply a mechanical strain under the condition that the average particle size of the particles is in the range of 8 to 20 μ.
It is possible to obtain toner particles having a smooth surface without substantially fine particles. The number of resin fine particles (A) contained in each toner particle is a few to several hundreds.

It is to be noted that if the above processing conditions are grasped, it is possible to remove the coarse particles after smoothing the surface of the toner and removing the fine particles in advance.

The reason why applying a mechanical strain force to the toner particles has the effect of smoothing the toner surface and removing fine particles is considered as follows. It is considered that the toner particles collide with each other or with a dispersing medium such as a wall or a blade, so that the temperature is instantaneously and partially increased to a considerably high temperature, and the toner surface is considered to be in a heat-melted state. At this time, it is considered that the fine particles are easily aggregated, so that the fine particles generally adhere to each other or the fine particle surface, and the resin is softened and fused by the heat generated by the impact force, so that the above-described effect is obtained. This can be understood by observing electron micrographs before and after the treatment. That is, before the treatment, the toner particles have a relatively large particle size, are mixed with porous toner particles, and a part of the fine toner particles are agglomerated on the surface of the large toner particles. After the treatment, the toner surface is smooth. Almost no fine particles of toner are seen.

In addition, the particles are hard to break even in a running test in a copying machine. As described above, the present method has a great feature in that processing can be continuously performed at room temperature without particularly heating the machine.

Although various factors can be considered as factors for obtaining the above-described effects, according to the study of the present inventors, the influence of the speed of the toner particles in the crusher is the largest. Specifically, in a hammer mill, coffee mill, etc., it is the number of rotations of the internal rotating plate.
It is desirable that the airflow velocity be about the same as above. Also,
At the same rotation speed (or air velocity), the longer the residence time of the particles in the machine, the greater the effect. Therefore, if necessary, the crusher may be recycled as a closed circuit.

In the present invention, the average particle size of the toner is in the range of several μm to 20 μm, and fine particles are sized. Therefore, special classification is not required. The toner contains, as necessary, fine particles having an average particle size of 2 μm or less, that is, a coloring material, a magnetic powder, a wax, a charge control material, and the like, in addition to the resin as the binder. These fine particles may be aggregated together with the resin fine particles (A), or may be previously contained in the resin fine particles (A).

The resin that can be used in the resin fine particles (A) of the present invention has a function of retaining a colorant, magnetic powder, and the like and fixing a visible image on paper, and includes ethylene-vinyl acetate copolymer, polystyrene-based resin. Styrene, acrylate or methacrylate, acrylonitrile or maleate copolymer containing styrene, polyacrylate, polymethacrylate, polyester, polyamide, polyvinyl acetate, epoxy Phenol-based, hydrocarbon-based, and petroleum-based resins. These can be used alone or in combination.

In the present invention, a coacervation method that can be preferably used for coating the resin fine particles (A) with a hydrophobic resin is as follows.
First, after dissolving the hydrophobic resin in a good solvent, the spherical resin fine particles (A) are dispersed in this solution, and a poor solvent for the hydrophobic resin or a phase-separating organic agent is added to the dispersion to cause phase separation to perform resin separation. This coats the surface of (A). Examples of the combination of hydrophobic resin / good solvent / poor solvent (phase separation inducing agent) include, for example, polyvinyl acetate / methyl ethyl ketone / n-hexane, polyvinyl acetate / chloroform / isopropanol, styrene-maleic acid copolymer / ethanol / Isopropyl ether, polyethylene / xylene / ethanol, polystyrene / benzene / polydimethylsiloxane, polystyrene / xylene / petroleum ether,
Ketone resin / ethanol / water, polymethyl methacrylate / benzene / polydimethylsiloxane, acrylonitrile-styrene copolymer / methyl ethyl ketone / polybutadiene, epoxy resin / toluene / polybutadiene,
Examples include polystyrene / benzene / poly p-chlorostyrene.

The coloring material is a dye / pigment and is not necessarily limited thereto, but examples include the following.

Yellow pigments and dyes Zinc yellow, yellow iron oxide, Hansa yellow, disazo yellow, quinoline yellow, permanent yellow.

Red pigment / dye Bengala, permanent red, lithol red, pyrazolone red, watchjan red Ca salt, watchjan red Mn salt, lake red C, lake red D, brilliant carmine 6B, brilliant carmine 3B.

Blue pigments and dyes Navy blue, phthalocyanine blue, metal-free phthalocyanine.

In addition, colored pigments such as orange, purple, and green, and white or black pigments or dyes such as titanium oxide and oil black can be used as necessary.

Various types of ferrite, magnetite,
Alloys or compounds of iron, zinc, cobalt, nickel, manganese, etc. such as hematite can be used. Their magnetic properties are those with a saturation magnetization of 70 emu / g or more and a coercive force of 200 Oe or less under a magnetic field of 5 kOe. Is particularly preferred. These magnetic powders can be used in any of crystalline forms (cubic, octahedral, needle-like, etc.), amorphous, spherical, and rice-granular forms. Depending on the purpose, it may be classified or a surface treatment known per se. For example, it may be subjected to a hydrophobic treatment or a silane coupling agent treatment.

Examples of the wax include polyolefin wax such as polyethylene wax and polypropylene wax, petroleum wax such as paraffin wax and microcrystalline wax, and natural wax such as carnauba wax, montan wax and rice wax.

Charge control agents include dyes and alloy dyes such as fettschwarz-HBN, nigrosine base, brilliant spirit, zavonschwartz X, cellschschwarz RG, copper phthalocyanine dye, and other CI solvent black 1,2,3,5, 7, CI Acid Black 123,22,23,8,42,43,
Dyes such as oil black (CI6150) and spiron black, quaternary ammonium salts, metal salts of naphthenic acids, metal soaps of aliphatic or resin acids, and colloidal silica.

Hereinafter, the present invention will be described in detail with reference to examples. The middle part in the examples indicates parts by weight.

Example 1 A separable flask equipped with a stirrer, a thermometer, a condenser, a dropping funnel, and a gas inlet tube was previously heated to 80 ° C.
0% polyvinyl alcohol (Nippon Synthetic Chemical Industry Co., Ltd. product name G
H-20) An aqueous solution (1500 g) and a liquid previously mixed in accordance with the following formulation were charged, and the mixture was stirred at 10,000 rpm for 10 minutes using an Ultra Homomixer (manufactured by Nippon Seiki Co., Ltd.) in Container 3.

Styrene 240g Methyl methacrylate 60g Benzoyl peroxide 60% xylene solution 12g After stirring was stopped, the above emulsion was replaced with nitrogen for 9 hours.
The mixture was stirred at 0 ° C for 7 hours at low speed to continue the polymerization reaction.
μ spherical resin particles were obtained. This is referred to as resin fine particles (A1). Next, the resin fine particles (A1) were once filtered, the resulting cake was poured into n-hexane, water was replaced with n-hexane, and then filtered again.

Next, the raw materials are weighed according to the following recipe and then premixed, and 100 g of this mixture is mixed with a ketone resin (trade name: Hilac 110H,
Hitachi Chemical Co., Ltd. 10% ethyl alcohol solution 30
The mixture was charged into 0 g, and stirred for 5 minutes with a TK homomixer (manufactured by Tokushu Kika Co., Ltd.).

Resin fine particles (A1) 60 parts Iron tetroxide powder (particle size 0.3μ) 40 parts Polypropylene wax (trade name: Viscol 550P, manufactured by Sanyo Chemical Industries, Ltd.) 2 parts Charge control agent (trade name: Spiron Black TRH) , Hodogaya Chemical Co., Ltd.) 0.5 parts Carbon black (trade name; Mogul-L, manufactured by Cabot Corporation, USA) 1 part 100 g of n-hexane was added to this slurry with a dropping funnel while stirring at low speed. Add slowly over 5 minutes. By this operation, an aggregate covered with the ketone resin was obtained. From this, the solvent was removed by filtration and dried.

Next, this was introduced into a hammer mill (sample mill, manufactured by Hoskawa Micron Corp.) and processed at high speed. The product discharged to the collection device was repeatedly treated a total of eight times by the same operation to obtain the desired toner particles having an average particle diameter of 13 μm. It contains virtually no particles less than 5μ, and
These particles were hardly contained. The surface was smooth and rounded by visual observation with an electron microscope. This was subjected to a classification process to completely remove particles having a particle size of 25 μm or more, and then 0.3 parts of colloidal silica (trade name: R-972, manufactured by Nippon Aerosil Co., Ltd.) was added to 100 parts of the toner to commercialize the toner. Copier (Product name; NP-300Z,
(Manufactured by Canon Inc.).

In this copy, charge stability, blocking resistance and image quality were extremely good.

COMPARATIVE EXAMPLE 1 A sample which had been subjected to the treatment by the sample mill only once in Example 1 was taken out. This was a porous surface with many irregularities by visual observation with an electron microscope, and many fine powders of 5 μm or less were observed. A colloidal silica was added thereto in the same manner as in Example 1, and a copying test was performed. As a result, blocking occurred in the toner hopper, and the image density was extremely light and unsuitable.

Example 2 Using a pressurized reactor having a capacity of 10 while purging with nitrogen
The polymerization reaction was carried out at 20 ° C. according to the following formulation by an emulsion polymerization method.

Styrene 80 parts Butyl methacrylate 20 parts Divinylbenzene 0.2 parts This was dispersed in 200 parts of water. Further, 2 parts of a fatty acid potassium salt and 0.5 part of potassium phosphate were used as an emulsifier. The polymerization reaction was continued with low-speed stirring for 24 hours.
8μ latex was obtained. This is referred to as resin fine particles (A2). Thereafter, n-hexane substitution was performed in the same manner as in Example 1, and the same coating treatment as in Example 1 was performed using a mixture having the following formulation.

Resin fine particles (A2) 60 parts Iron tetroxide powder (particle size 0.3μ) 40 parts Polypropylene wax (trade name: Viscol 550P, manufactured by Sanyo Chemical Industries, Ltd.) 2 parts Charge control agent (trade name: Spiron Black TRH) , Manufactured by Hodogaya Chemical Co., Ltd.) 0.5 parts Carbon black (trade name; Mogul-L, manufactured by Cabot Corporation, USA) 1 part The obtained aggregates are first crushed by a sample mill and then circulated by an impact type 150 g was introduced into a pulverizer (trade name type NHS-1; manufactured by Nara Machinery Co., Ltd.) and treated at 6000 rpm for 2 minutes. Example 1 was applied to the thus obtained toner having an average particle diameter of 12 μm.
An image test was performed by applying the same processing to that described above, and good images could be obtained without blocking.

〔The invention's effect〕

The electrostatic toner according to the present invention consumes less energy for manufacturing than before, and the post-treatment according to the present invention efficiently obtains toner particles having a target particle diameter.
It is possible to improve the particle shape of the toner.

[Brief description of the drawings]

FIG. 1 is a scanning electron micrograph (× 1500) showing the structure of the particles of the powder toner according to the present invention, and FIG. 2 is the particle structure of the aggregate of coated spherical resin fine particles before applying mechanical strain. 5 is a scanning electron micrograph (× 1500) showing the above.

Claims (3)

(57) [Claims] 1. An aggregate comprising a plurality of spherical resin fine particles (A) formed by an emulsion polymerization method or a suspension polymerization method having an average particle size of 10 μm or less and having a coating of a hydrophobic resin. Either the coating or the resin fine particles (A) contains a coloring agent or other necessary fine particles, and the surface of the aggregate is smoothed by heat melting, thereby developing an electrostatic image. For powder toner. 2. Spherical resin fine particles (A) having an average particle size of 10 μm or less produced by an emulsion polymerization method or a suspension polymerization method containing a coloring agent and other necessary fine particles as necessary, and optionally a coloring agent or other fine particles. At the same time as coating with a hydrophobic resin together with the necessary fine particles, to obtain an aggregate of the coated fine particles, and then crushing the aggregate into an aggregate containing a plurality of spherical resin fine particles (A), A method for producing a powder toner for developing an electrostatic image, wherein the hydrophobic resin is thermally melted by a mechanical strain to smooth the surface of the aggregate. 3. The static resin according to claim 2, wherein the hydrophobic resin is coated on the surface of the spherical resin fine particles (A) by a coacervation method in an organic solvent which does not dissolve or swell the spherical resin fine particles (A). A method for producing a powder toner for developing a charge image.