JPH02223960A - Production of toner - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing a toner used as a developer for electrostatic latent images in electrophotography.

(Prior art) Toners currently used as developers for electrostatic latent images in electrophotography are generally made by melt-kneading binder resin, carbon black, colorants such as dyes, and charge control agents. The toner is produced by a pulverization method in which the toner is then pulverized and classified, and the average particle size of the toner is 12 to 13 μm. In order to obtain reproduced images with good resolution and gradation, fine particles of 5μ or less and coarse particles of 20μ or more must be removed from the product by classification, resulting in a very low yield. have.

On the other hand, as a method for producing toner having a relatively small particle size without using a pulverization method and with a high yield, a method has been proposed in which a coloring agent or the like is contained in a polymerizable monomer and the toner is obtained by suspension polymerization.

In the monomer suspension polymerization method, water or an aqueous dispersion medium mainly composed of water is used as the dispersion medium. In order to stabilize the dispersion of the particles, it is usually necessary to include a dispersant in the dispersion medium.

This dispersant generally forms a protective colloid film,
They are broadly divided into two types: water-soluble polymers that exhibit repulsive force due to steric hindrance, and poorly water-soluble inorganic substances that express electrostatic repulsive force and aim to stabilize dispersion.

As the former, dispersants such as polyvinyl alcohol, methylcellulose, and gelatin are known.

Proposals have been made regarding toner manufacturing methods using suspension polymerization using these dispersants. However, in this method, the particles obtained by polymerization contain many small particles and have a wide particle size distribution. Furthermore, it is difficult to remove the dispersant attached to the particle surface, and the particles have electrical properties (electrical properties). At present, the toner has very poor resistance (resistance, chargeability) and cannot be used in practical use as a toner.

On the other hand, the latter dispersants include poorly water-soluble salts such as calcium phosphate, barium sulfate, calcium sulfate, barium carbonate, calcium carbonate, and magnesium carbonate, inorganic polymer substances such as talc and silicic acid, and metal oxides such as aluminum oxide and titanium oxide. Dispersants such as metal hydroxides such as aluminum hydroxide and ferric hydroxide are known. Proposals have been made regarding toner manufacturing methods using suspension polymerization using these dispersants (Japanese Patent Publication No. 58-49863, Japanese Patent Publication No. 18697-1982, Japanese Patent Publication No. 33910-1982, Japanese Patent Publication No. 45101-1982). Publications, JP-A No. 61-22354, etc.) These methods may result in a relatively narrow particle size distribution, but when trying to control the particle size to a size that can be used as a toner, a large amount of dispersant is used. There are problems in particle size distribution control, such as the generation of microparticles due to the surfactant (emulsifier) used as a dispersion aid, as well as problems with the dispersant used and surface activity due to pickling and water washing after polymerization. There are problems in that the removal of the agent is insufficient and sufficient electrical properties are not developed, and the current situation is that toners with excellent developability that can be put to practical use as toners have not yet been obtained.

(Problems to be Solved by the Invention) An object of the present invention is to provide a novel method for producing toner for electrostatic images that overcomes the drawbacks of toners produced by pulverization methods and conventional polymerization methods.

Another object of the present invention is to provide a method for producing toner for electrostatic images which has excellent image quality characteristics such as resolution and capri because the toner has an extremely sharp particle size distribution and good electrical properties. be.

(Means for Solving the Problems) The object of the present invention is to combine a colorant and a vinyl monomer in an aqueous dispersion medium in which a water-soluble inorganic acid and/or a water-soluble inorganic salt, and an anionic surfactant are present. Adding a homogeneous mixture of the above inorganic acid and/or inorganic salt under high shearing, precipitating the inorganic acid and/or inorganic salt in the form of a poorly water-soluble inorganic salt, and then proceeding with polymerization. By a method for producing a toner, characterized in that the average particle size of the colorant contained in the particles is 3 to 20 μ-1 and the particle size distribution (ratio of volume average particle size/number average particle size) is 1.6 or less. achieved.

In the present invention, when a homogeneous mixture of a colorant and a vinyl monomer is subjected to high shear force in an aqueous dispersion medium and becomes small droplets, at the same time the water-soluble inorganic acid and/or water-soluble It is characterized by precipitating a highly water-soluble inorganic salt as a poorly water-soluble inorganic salt. That is, in the above step, the poorly water-soluble inorganic salt is selectively and densely precipitated on the surface of the small droplets, and the droplets are sufficiently stabilized in dispersion with a relatively small amount of the poorly water-soluble inorganic salt.

Another feature of the present invention is that a small amount of an anionic surfactant is used in conjunction with the formation of small droplets mainly composed of vinyl monomers. The function of the surfactant is to enhance the dispersion stabilizing effect of the precipitated poorly water-soluble inorganic salt, and to significantly reduce the amount of the poorly water-soluble inorganic salt precipitated in the dispersion medium system, and to perform subsequent steps. Coalescence and aggregation of particles during polymerization can be prevented as much as possible. Furthermore, the surfactant is partially salted out during the above process in which water-soluble inorganic acids and/or water-soluble inorganic salts are turned into poorly water-soluble inorganic salts, resulting in the generation of emulsified fine particles by the surfactant. can be prevented.

(As a result, the toner obtained by this manufacturing method can easily remove the above-mentioned dispersion stabilizer by pickling or washing with water, which is usually carried out after polymerization, and has extremely good electrical properties. Furthermore, the toner obtained has an average particle size of has a small particle size of 3 to 20μI,
and particle size distribution (volume average particle size/number average particle size) is 1.6
It is extremely narrow as below, and the image quality characteristics such as resolution and fog are extremely good.

Examples of water-soluble inorganic acids and inorganic salts include phosphoric acid, pyrophosphoric acid, sulfuric acid, sodium carbonate, sodium hydrogen carbonate, potassium carbonate, sodium phosphate, disodium hydrogen phosphate,
Examples include sodium birophosphate, potassium phosphate, sodium sulfate, potassium sulfate, and sodium metasilicate.

There are various methods for converting the above-mentioned water-soluble inorganic acids and inorganic salts into poorly water-soluble inorganic salts in an aqueous dispersion medium in the presence of droplets mainly composed of vinyl monomers. For example, a method is effective in which metal ions of divalent or higher valence are present in the system, the pH of the system is adjusted to an appropriate range, and the metal ions are precipitated as poorly water-soluble inorganic salts.

Examples of divalent or higher metal ions include Ca”, Baz*H
g12 Mn! +, zfl! +, S%*, 11
'J+ etc., for example, metal chlorides in the aqueous dispersion medium,
It can be added in the form of a metal sulfide or the like.

When using phosphoric acid, sodium phosphate dodecahydrate, or sodium carbonate as a water-soluble inorganic acid or inorganic salt, Ca'' ions and Ba'' ions are present as divalent or higher metal ions, and vinyl-based Calcium phosphate, barium phosphate, calcium carbonate, The method of effectively precipitating a sparingly water-soluble inorganic salt such as barium carbonate on the surface of the droplets is a preferred method for stabilizing the dispersion of the droplets and further stabilizing the dispersion of the particles formed during polymerization. A toner with an extremely narrow particle size distribution can be obtained.

On the other hand, anionic surfactants used for the purpose of increasing particle dispersion stability include fatty acid salt types such as potassium oleate, sodium oleate, sodium beef tallow fatty acid, potassium tallow fatty acid, sodium stearate, and sodium dialkyl sulfosuccinate. alkyl sulfate salts such as sodium lauryl sulfate, triethanolamine lauryl sulfate, ammonium lauryl sulfate, and alkyl sulfonate salts such as sodium dodecylbensulfonate and sodium alkylnaphthalene sulfonate. Can be mentioned. Among them, the use of fatty acid salt type surfactants such as potassium oleate and sodium oleate is particularly preferred from the viewpoint of dispersion stabilization and prevention of emulsified fine particles.The above anionic surfactants may be used alone or in combination. Alternatively, a nonionic surfactant may be used in combination if necessary.

The concentration of the water-soluble inorganic acid or inorganic salt and the divalent or higher-valent metal ion in the aqueous dispersion medium is selected depending on the desired particle size, but preferably the poorly water-soluble inorganic salt produced is a monomer. It is within the range of 0.1 to 20 parts by weight per 100 parts by weight. The amount of the anionic surfactant used is preferably 0.001 to 0.00% per 100 parts by weight of monomer.
The range is 1 part by weight.

Also, high shear stirring is required to disperse the mixture of colorant and vinyl monomer in the aqueous dispersion medium as small droplets, but this can be done with any homomixer homogenizer, etc. It is sufficient to simply apply a shearing force that divides the droplet into a desired size range.

Examples of the vinyl monomer used in the present invention include:
Styrene, α-methylstyrene, p-methylstyrene,
Aromatic vinyl monomers such as p-chlorostyrene, unsaturated nitriles such as acrylonitrile, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, ethylhexyl (meth)acrylate, lauryl (meth)acrylate Acrylate, stearyl (meth)
Examples include unsaturated acrylic esters such as acrylate, unsaturated methacrylic esters, and conjugated diolefins such as butadiene and isoprene. The above monomers can be used alone or in combination of two or more.

In addition, in the present invention, any oil-soluble initiator,
Molecular weight regulators and crosslinkable monomers can be used.

The oil-soluble polymerization initiator used in the present invention may be one that is soluble in the organic solvent used, such as methyl ethyl ketone peroxide, di-t-butyl peroxide, dicumyl peroxide, acetin Peroxides such as Zhenzero kineperoxide, lauroyl peroxide, benzoyl peroxide, di-t-butylshiba-oxyisophthalate, 2,2'azobis(4-methoxy-2,4-dimethylvaleronitrile) , 2.2
'-azobis(2,4-dimethylvaleronitrile)
, 2.2'-azobisisobutyronitrile, 1.1
Examples include azo compounds such as '-azobis(1-cyclohexanecarbonitrile).

Examples of molecular weight modifiers used as necessary in the present invention include mercaptans such as L-dodecylmercaptan and n-dodecylmercaptan, and halogenated hydrocarbons such as carbon tetrachloride and carbon tetrabromide. be able to. These molecular weight regulators are added before the start of polymerization or
It can be added during the polymerization.

Examples of crosslinking monomers used as necessary in the present invention include polyfunctional monomers such as divinylbenzene, ethylene glycol di(meth)acrylate, and glycidyl(meth)acrylate. . These crosslinking monomers can be added before the start of polymerization or during the polymerization.

Examples of the coloring agent used in the present invention include pigments such as carbon black, silicon dioxide, zinc oxide, and titanium oxide, nigrosine base, aniline blue, calco oil blue, chrome yellow ultramarine blue, orient oil red, and phthalocyanine. Examples include dyes such as blue and malachite green offsalate, and magnetic particles such as iron, cobalt, nickel, iron sesquioxide, triiron tetroxide, iron manganese oxide, iron zinc oxide, and iron nickel oxide.

There is no particular limitation on the ratio of the dispersoid consisting of the colorant and monomer, etc. to the aqueous dispersion medium, but it depends on the ease of forming droplets in the dispersion medium and the dispersion stability of the particles during the polymerization reaction. Considering this, the concentration of dispersoid in the system is preferably in the range of about 5 to 50% by weight.

Furthermore, in addition to colorants and vinyl monomers, polyolefins, various polyester waxes, and various low-temperature softening polymers are present as dispersoids in order to improve the fixing properties of the resulting toner. Also good. Further, for the purpose of uniformly dispersing the colorant in the particles, a dispersion aid such as a lubricant such as oleic acid or stearic acid, or a silane-based or titanium-based coupling agent may be present.

After the polymerization reaction is completed, a toner is obtained by removing poorly water-soluble inorganic salts, surfactants, etc. remaining on the particle surfaces by conventional post-treatments, such as pickling and water washing, if desired, followed by dehydration and drying.

(Effects of the Invention) Thus, according to the present invention, poorly water-soluble inorganic salts are selectively and densely precipitated on the surface of dispersoid droplets mainly composed of vinyl monomers, and the anionic surfactant is This action enhances the dispersion stabilizing effect, and the subsequent polymerization makes it possible to obtain a toner containing a colorant, having small particles, an extremely narrow particle size distribution, and excellent electrical properties and developability.

(Example) The present invention will be described in more detail with reference to Examples below. Note that parts and percentages in Examples and Comparative Examples are based on weight unless otherwise specified.

Example 1 2.5 parts of sodium carbonate, 0.02 parts of potassium oleate
70 parts of styrene, 30 parts of butyl methacrylate, 8 parts of carbon black, and 0.2 parts of Cr-based dye were added to an aqueous solution in which 1 part was dissolved in 350 parts of pure water with normal stirring at room temperature.
1 part, 2.2'-azobis(2,4-dimethylvaleronitonyl), which had been uniformly mixed in advance, was added to obtain an aqueous dispersion.

Next, the aqueous dispersion was subjected to high shear stirring at a rotation speed of 6000 rpm using a rotor-stator type homomixer, and 4.0% of calcium chloride dihydrate was added to the aqueous dispersion.
Add 10 parts of an aqueous solution containing 1% of the solution, and then adjust the pH of the aqueous dispersion.
Aqueous ammonia was added so that the ratio was 9 or higher, and high shear stirring was continued for 10 minutes.

It was confirmed by a Coulter counter that the monomer droplets in water obtained by the above operation had a volume average particle size of 12.2 μm and a particle size distribution (dv/dρ ratio) of 1.32.

Next, the aqueous dispersion of this monomer was poured into a volume 41 equipped with a stirring blade.
The mixture was placed in a reactor and a polymerization reaction was carried out at 65°C for 4 hours with stirring.

The volume average particle size of the particles (toner) after the polymerization reaction is 12
．． Its particle size distribution (dv/dp) was 1.28 at 0 μm, and it contained carbon black inside.

Next, while stirring the polymer dispersion, hydrochloric acid was added to the system to make the pi
After acid washing was carried out to reduce the water content to 4 or less and the water was separated, 500 parts of pure water was newly added to form a reslurry, which was then washed with water. Thereafter, dehydration and water washing were repeated several times, and the solid content was separated by filtration, followed by drying in a dryer all day and night to obtain a toner.

Externally adding 0.3 parts of hydrophobic silica to 100 parts of the above toner,
A developer having a toner concentration of 5% was prepared by mixing with a carrier.

The electrical resistance (30°C, 1 kHz) of the obtained toner was 1
1.1j! ogΩ・C1l, and the amount of charge is -15μc
/g.

When the developer was image-evaluated using a commercially available copying machine, clear images without fog or unevenness were obtained.

Example 2 A toner was obtained in the same manner as in Example 1 except that 7 parts of sodium phosphate dodecahydrate was used instead of sodium carbonate.

The volume average particle size of the obtained toner was 8.1 tIm, and the particle size distribution (dv/dp) was 1.23.

0.2 parts of hydrophobic silica was externally added to 100 parts of the above toner and mixed with a carrier to prepare a developer having a toner concentration of 7%.

The electrical resistance of toner (30℃, 1kHz) is 10.9fo
gΩ·C■, and the amount of charge was -18 μc/g.

When the image was evaluated using a commercially available copying machine using the above developer, an image with no fogging or unevenness and with extremely good resolution was obtained.

Example 3 7 parts of sodium phosphate dodecahydrate, 3 parts of magnesium chloride
An aqueous solution was prepared by adding 0.05 parts of potassium tallow fatty acid to 350 parts of pure water and adjusting the pH to 3 with hydrochloric acid.Next, 8 parts of styrene was added to this aqueous solution with stirring at room temperature.
5 parts, butyl acrylate 15 parts, divinylbenzene 0
．． 2 parts, Zn dye 0.5 parts, carbon black 5 parts,
A homogeneous mixture of 3 parts of benzoyl peroxide was added.

Next, caustic soda-water was added to the obtained aqueous dispersion of Natsuma while applying high shear stirring at a rotation speed of 7000 rpm using a rotor-stator type homomixer to adjust the pH of the aqueous dispersion to 9 or higher. A dispersion of droplets containing the monomer as the main component was created by doing this.

The above operation results in a particle size distribution (dv/d) with a volume average diameter of 9 μm.
It was confirmed that droplets with p) of 1.20 were dispersed.

Next, this aqueous dispersion was put into a reactor equipped with stirring blades, and the
The polymerization reaction was carried out under stirring at °C for 5 hours.

Further, after the reaction was completed, washing and drying were performed in the same manner as in Example 1 to obtain a toner.

The volume average particle diameter of the obtained toner was 8.8 μm, the particle size distribution (dv/dp) was 1.18, carbon black was uniformly contained inside the particles, and the electrical resistance (30
°C11kHz) is 11.2J! ogΩ・1, and the blow-off charge amount after mixing with the carrier is -12pc/
It became g.

Externally adding 0.2 parts of hydrophobic silica to 100 parts of the above toner,
Image evaluation was performed using a commercially available copying machine using a developer with a toner concentration of 5%.

The resulting image had high density in solid areas and good quality gradation.

Example 4 Magnetite 5 was used instead of carbon black in Example 1.
0 parts, titanium-based coupling agent as lipophilic agent 0.5
A magnetic toner was obtained in the same manner except that the same amount was used.

The obtained toner had a volume average particle size of 13 μm and a particle size distribution (dv/dp) of 1.20.

The electrical resistance (30°C, 1kHz) of 100 parts of the above toner with external addition of 0.2 parts of hydrophobic silica is 10.81 parts gΩ・cm, and the amount of charge using an iron powder carrier is -15 p.
c/g.

The image quality obtained by a commercially available copying machine was clear with no fog.

Comparative Example 1 2.5 parts of sodium carbonate, 0.02 parts of potassium oleate
was dissolved in 350 parts of pure water, 4.0 parts of calcium chloride dihydrate was added under stirring at room temperature, and the pH of the aqueous solution was adjusted to 9 or higher with aqueous ammonia to dissolve poorly water-soluble carbonic acid in the aqueous solution. Calcium was precipitated and dispersed.

Next, in the aqueous dispersion medium, 70 parts of styrene, 30 parts of butyl methacrylate, 8 parts of carbon black, and 0 parts of Cr-based dye were added.
．． 2 parts of 2.2' azobis(2,4-dimethylvaleronitrile) were mixed uniformly in advance, and the mixture was heated at 6000 r using a rotor-stator type homomixer.
High shear stirring was continued for 10 minutes at a rotation speed of p-.

The volume average diameter of the droplets mainly composed of monomers in water obtained by the above operation was 25 μm, and the distribution (dv/dp
) was 2.7.

Next, polymerization was carried out under the same conditions as in Example 1.

The volume average particle size of the obtained toner was 28 μ-, and its distribution (
dv/dp) was 3.21, which had a wide distribution, and some carbon black had separated from the particles.

Comparative Example 2 A toner was prepared in the same manner as in Example 3 except that potassium tallow fatty acid was not used.

The volume average particle size of the obtained toner was 26 μ..., and its distribution (dv/dp) was 1.7, indicating that the particle size was large, and some particles appeared to be aggregates during the polymerization reaction. generated by something.

Comparative Example 3 A toner was prepared in the same manner as in Example 3, except that the beef tallow fatty acid potassium used in Example 3 was added to the polymerization system immediately before the polymerization reaction.

The volume average particle diameter of the obtained toner was 27 μm, and its distribution (dv/dp) was 2.1. Moreover, there were a large number of ultrafine particles with a size of 1 μm or less, which were thought to have been produced during the polymerization reaction.

Comparative Example 4 A toner was obtained in the same manner as in Example 3, except that 20 parts of sodium phosphate dodecahydrate and 9 parts of magnesium chloride were used, and potassium tallow fatty acid was not used.

The volume average particle diameter of the obtained toner was 14μ noodles, and its distribution (
dv/dp) was 2.1. The electrical resistance (30''C, 1kHz) of the toner was lO,1j!ogΩ·l, and the amount of charge after mixing with the carrier was as low as -3 μc/g.

A developer was prepared by externally adding hydrophobic silica in the same manner as in Example 3, and image evaluation was performed using a commercially available copying machine.

The resulting image had a lot of fog, the density of solid areas was extremely low, and the image was overall unclear.

Patent applicant: Zeon Corporation

Claims (1)

[Claims] A homogeneous mixture of a colorant and a vinyl monomer is added to an aqueous dispersion medium containing a water-soluble inorganic acid and/or a water-soluble inorganic salt, and an anionic surfactant under pressure, followed by high shearing. After the inorganic acid and/or inorganic salt is precipitated in the form of a poorly water-soluble inorganic salt under stirring, the polymerization is continued to proceed, and the average particle size of the colorant contained in the particles is A method for producing a toner having a particle size distribution (ratio of volume average particle size/number average particle size) of 3 to 20 μm and 1.6 or less.