JPH02153361A - Manufacture of toner - Google Patents

Abstract

PURPOSE:To uniformize dispersion of toner additives by the solution method by melting and kneading toner components and dissolving or dispersing it into a prescribed solvent, and then dispersing it into an aqueous system. CONSTITUTION:The spherical toner particles are prepared by melting and kneading the toner components comprising a binder resin (A) and the toner additives (B) in advance, and dissolving or dispersing them in a solvent substantially incompatible with water, such as a mixture of toluene and chloroform, to obtain a toner preparation solution, dispersing this solution into an aqueous system, and next, heating and stirring them to evaporate the solvent. A styrene type copolymer and the like can be used for the resin A, and a colorant, an electric charge control agent, a wax, and the like can be used for the additives B, thus permitting the additives B to be well and finely dispersed and the toner particles uniform in composition to be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a method for producing toner. More specifically, the present invention relates to a method for producing toner for developing electrostatic images used in electrophotography, electrostatic recording, and the like.

(B) Conventional technology In recent years, an electrostatic charge image of the image to be transferred is formed using electrophotography or electrostatic recording, and this is made microscopic with developing toner, transferred to transfer paper, etc., and then fixed. A method of converting images into visible images is widely adopted.

The above toners used for developing electrostatic images include two-component toners that are mixed with a carrier such as iron powder or glass beads, and one-component toners that do not require a carrier. All of these toners are usually made by adding carbon black, coloring agents such as dyes and pigments, and charge control agents to a thermoplastic resin as a binder, and in the case of magnetic toners, further adding a magnetic substance, etc., and mixing. It is manufactured by melting, kneading, pulverizing, and classifying.

The toner produced through the pulverization process as described above has an amorphous shape and therefore has poor fluidity, resulting in undesirable results in terms of storage stability. For this reason, a method has been adopted in which a fine powder such as silica is added to the toner surface as an external additive. However, since the step of adding the external additive described above is a separate step, it increases the cost and the resulting toner does not have sufficient fluidity. Therefore, recently, in-liquid drying methods that do not require the above-mentioned pulverization process and external additive addition process,
Research has been conducted into methods for producing spherical toner using solution-based production methods (hereinafter referred to as solution methods) such as suspension polymerization, and attempts are being made to improve storage stability and other properties and to reduce costs.

In addition, the most common fixing method is to melt and fix toner using a heated roller, but fixing using a heating method requires a heat source, which has disadvantages such as high power consumption and the need for warm-up. are doing. In order to address these drawbacks, much research is being conducted to save energy by using toner with a low fixing temperature, to save energy by adopting a pressure fixing method, and to eliminate warm-up time.

All of these toners use low molecular weight polymers and waxes, and undergo plastic deformation at low temperatures or pressure. If such a toner is produced by a pulverization method, the binder tends to be fused due to heat during pulverization, making stable production very difficult. For this reason, the production of these toners has mainly been studied using solution methods such as submerged drying methods and suspension polymerization methods.

(c) Problems to be Solved by the Invention The principle of the toner manufacturing method using the above solution method is to dissolve or disperse the binder resin and toner additives in a water-insoluble solvent, disperse this mixed solution in water, and then The solvent is vaporized by heating and stirring. Accordingly, this makes it possible to obtain spherical toner particles.

However, in the production of toner by the above-mentioned solution method, a major problem is the dispersibility of toner additives dispersed in the finally obtained toner.

For example, the surface of carbon black is oxidized to form hydroxyl groups, carbonyl groups, and carphoquinol groups on the surface, and therefore exhibits hydrophilicity. For this reason, they tend to aggregate in the hydrophobic medium used in the solution method and do not exhibit good dispersibility during toner production, resulting in non-uniform toners. Further, due to its hydrophilic nature, carbon black transitions to an aqueous dispersed phase during production, causing generation of fine powder, force on the toner surface, and aggregation of carbon black, resulting in disadvantages in terms of toner properties. This also applies to magnetic materials.

In addition, although polyethylene and polypropylene are often used in wax, they often do not dissolve in hydrophobic solvents, so they are dispersed in the toner with the same particle size as the raw material, which limits the particle size of the raw material. There is a problem that the amount becomes large.

As described above, in the production of toner by the solution method, good and fine dispersion of the above-mentioned toner additives that are insoluble in the solution has become an important issue.

(d) Means for Solving the Problems The present invention has been made in view of the above situation, and it uses the solution method, which is a highly versatile method for producing spherical toner, to add the above-mentioned toner additives to the toner. It is an object of the present invention to provide a method for producing a toner that can provide good dispersibility.

The inventors of this invention discovered that among toner additives that are insoluble in hydrophobic solvents, carbon black and magnetic substances, which are hydrophilic and have poor separation properties in hydrophobic solvents, can be melted and kneaded on the surface by melt-kneading with a binder resin. It was found that the dispersibility was improved by modification. The present invention was also completed based on the fact that organic additives such as wax are pulverized by melt mixing with a binder resin, resulting in a reduction in particle size.

Thus, according to the present invention, toner components are prepared by melt-kneading the toner components consisting of a binder resin and toner additives in advance, and then dissolving or dispersing them in a solvent that is substantially incompatible with water. A method for producing a toner is provided in which spherical toner particles are obtained by preparing the toner as a liquid, dispersing the toner preparation liquid in an aqueous system, and then heating and stirring to volatilize the solvent.

The method of the present invention is a method for producing toner particles using a solution method, and is characterized in that toner components are melt-kneaded prior to mixing into a solution.

In the method of this invention, the toner component refers to one consisting of a binder resin and a toner additive. The above-mentioned toner additives refer to those commonly added to binder resins in the art, such as colorants, charge control agents, and waxes. Typical toner components include 80 to 90% by weight of binder resin, 5 to 1% of colorant such as dye and pigment.
5% by weight, 1 to 5% by weight of a charge control agent, and 1 to 5% by weight of a wax added as necessary. The above binder resins include polystyrenes, styrene copolymers such as styrene-methacrylic acid esters and acrylic acid ester copolymers, polyvinyl chloride, polyvinyl acetate, polymethacrylic esters, epoxy resins, polyester resins, and polyamides. resin, polyethylene, polyurethane, ethylene-vinyl acetate copolymer,
Thermoplastic resins such as petroleum resins and paraffin wax are used alone or in combination. As the coloring agent, conventionally known dyes and pigments such as carbon black, nigrosine dyes, and phthalocyanine pigments can be used alone or in combination. Examples of charge control agents include electron-donating nigrosine dyes, quaternary ammonium salts, etc. for positive polarity toners, and electron-accepting organometallic complexes, aliphatic metal salts, etc. for negative polarity toners. It will be done. In addition, the above toner components may further contain ordinary fluidizing agents, magnetic substances, and the like. Examples of the fluidizing agent include colloidal silica, while examples of the magnetic material include metals, alloys, or compounds containing ferromagnetic elements such as iron, cobalt, and nickel, including ferrite and magnetite. Can be mentioned.

The particle size of the colorant used above ranges from 10 to several 100.
It is preferable to have the size of a human being.

In the method of this invention, the toner components as described above are prepared by melt-kneading. For this melt-kneading, it is preferable to use a pressurized Ni-Goo or the like, and the melt-kneading temperature is higher than the softening point of the resin, preferably 100 to 300°C.

In the present invention, the toner components prepared by melt-kneading as described above are dissolved or dispersed in a hydrophobic solvent that is substantially incompatible with water and can be volatilized relatively easily to prepare the toner. It is considered a liquid. The hydrophobic solvent in this toner preparation solution includes toluene, chloroform,
Organic solvents such as diethyl ether are suitable, and these can be used alone or in any desired mixture. This hydrophobic solvent is used in an amount sufficient to form toner particles during dispersion in water, which will be described later.

In other words, ordinary solution methods (in-liquid drying method, suspension polymerization method, etc.)
It is used in an amount sufficient to produce, in solution, a particulate solid having any desired particle size and surface morphology and having suitable strength as toner particles.

In the present invention, the toner preparation liquid is dispersed in an aqueous system in the form of oil droplets of a predetermined size, and is manufactured into spherical toner particles by a known method such as a so-called submerged drying method. In dispersing into the above aqueous system, a dispersion stabilizer known in the art may be used. The dispersion stabilizer is added to the aqueous system so that the oil droplets of the toner preparation liquid can be stably dispersed in the aqueous system, and includes commonly used water-soluble polymers such as polyvinyl alcohol and polyvinylpyrrolidone, carbonic acid, etc. Insoluble inorganic salts such as calcium and tricalcium phosphate can be used. The above-mentioned dispersion stabilizer is usually used so that it can be contained in the aqueous system in an amount of % to several 10% by weight.

In the above dispersion, the size of each oil droplet-like toner preparation liquid formed in the aqueous system is usually adjusted to several micrometers to several tens of micrometers. It is preferable to use a homogenizer for this adjustment. In this case, 5000-110000 rp.

The above-mentioned size adjustment and uniform dispersion can be achieved by high-speed rotation, preferably 7000-8000 rpm. The dispersion liquid in which the above-mentioned uniform dispersion has been achieved is subjected to drying conditions. This drying is achieved by heating the dispersion liquid at a predetermined temperature for a predetermined time while maintaining stirring. The above temperature is below the boiling point of the dispersion medium and the hydrophobic solvent used, and preferably below the glass transition temperature of the binder resin used. For example, when toluene is used as the hydrophobic solvent and a binder resin with a glass transition temperature of 60°C is used, the drying temperature is 50°C.
~60°C, and the heating time may be 1 to 3 hours. It should be noted that the stirring speed during this drying does not need to be particularly high, but may be at a speed of 100% to facilitate volatilization of the hydrophobic solvent.
~1o00rp is preferred.

(E) Effect According to the present invention, by melt-kneading the toner component consisting of the binder resin and the toner additive in advance,
The surface of the additive is modified by mechanochemical action, and the particle size of the additive is reduced to make the composition uniform, and it is stable in solvents that are substantially incompatible with water. It will be distributed to

The present invention will be described in detail below with reference to Examples, but the present invention is not limited thereby.

(f) Example An example of manufacturing the toner according to the present invention using an in-liquid drying method is as follows.

The apparatus used in the submerged drying method has a water tank 1, as shown in FIG. Disperse the homogenizer 4, stirrer 5, and water I! A device equipped with a heater 6 for heating the liquid in the container 1 is used.

A method for manufacturing toner using the above-mentioned apparatus will be explained based on the flowchart shown in FIG.

First, a styrene-butyl methacrylate copolymer (glass transition temperature = 60°C) as a binder resin, carbon black (particle size: 250 ℃) as a colorant, nigrosine dye as a charge control agent, and polyethylene wax. The following weight ratio: Styrene-butyl methacrylate copolymer 85° 5 parts by weight Carbon black 10 parts by weight Nigrosine dye 3 parts by weight Polyethylene wax ... 15 parts by weight was weighed out and melted and kneaded for 5 minutes at 200° C. in a pressurized Ni-Goo 7 equipped with a heater 8 as shown in FIG. 3 to obtain a kneaded toner component.

The above-mentioned toner component kneaded product was cooled, and dissolved and dispersed in a mixed organic solvent of toluene:chloroform=4:l (volume ratio) to a total concentration of 10% by weight (see the figure);
A toner preparation liquid was obtained.

Next, the above toner preparation liquid was dropped into water containing 0.5% by weight of gelatin and being stirred at high speed by a homogenizer 4 rotating at a high speed of 7,500 rpm, and dispersed into oil droplets with a particle size of about lθμm. Figure C).

After that, by heating with a heater in the aquarium, 5
While raising the temperature to 0 °C, the stirring speed was 800 rpm.
The mixed organic solvent was evaporated from the oil droplets by stirring at a speed of .

After that, the solid matter was removed from the water (Fig. 2), the dispersant was removed with hydrochloric acid, and the average particle size was 10 μm.
spherical toner particles were obtained.

When the toner particles obtained as described above were subjected to internal observation under a transmission electron microscope after being sliced, it was found that the dispersibility of additives including carbon black was very good.

Comparative Example Spherical toner particles were obtained in the same manner as in the above Example, except that the same toner components as in the above Example were directly dissolved and dispersed in a mixed organic solvent without melt-kneading. When this toner particle was observed using a transmission electron microscope in the same manner as above, it was found that the carbon black was aggregated to a size of 0.1 to 1 μm, indicating that the dispersibility of the additive was extremely poor.

According to the method of the present invention, spherical toner particles in which additives are well dispersed can be obtained by an in-liquid drying method.

(G) Effects of the Invention According to the present invention, when producing spherical toner particles by a solution method, it is possible to obtain toner particles having a uniform composition in which additives, which are problematic in terms of dispersibility, are uniformly dispersed.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an apparatus used in the submerged drying method, FIG. 2 is a flowchart for producing toner by the submerged drying method, and FIG. 3 is a schematic diagram of a pressurized type secondary generator.

Claims (1)

[Claims] 1. Toner components consisting of a binder resin and toner additives are melt-kneaded in advance, then dissolved or dispersed in a solvent that is substantially incompatible with water to form a toner preparation liquid, and then this toner After dispersing the prepared liquid in an aqueous system,
A method for producing a toner, which obtains spherical toner particles by heating and stirring to volatilize the solvent.