JP2748188B2 - Method for producing polymerization toner - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrostatic image developer, and more particularly, to a method for producing a polymerization toner for developing an electrostatic image formed in electrophotography.

[Background Art] As described in U.S. Pat. No. 2,297,691 and the like, a large number of methods are known for electrophotography. Generally, a photoconductor is used by various means using a photoconductive substance. An electric latent image is formed thereon, the latent image is developed using toner, a toner image is transferred to a transfer member such as paper as necessary, and then fixed by heating, pressure, solvent vapor, or the like to obtain a copy. Is a way to get As a method of developing using toner or a method of fixing a toner image, various methods have been conventionally proposed, and a method suitable for each image forming process is adopted.

In general, as a method for producing a toner, a colorant such as a dye or pigment, and an additive such as a charge control agent are melt-mixed in a thermoplastic resin and uniformly dispersed, and then the desired particles are dispersed with a fine pulverizer and a classifier. A method for producing a toner having a diameter is known.

In these pulverized toners, the binder resin must be brittle in order to impart sufficient pulverizability. In addition, the pulverized toner has fine projections, so it is further pulverized in a developing device. Or susceptible to powdering. As a result, an increase in fog, scattering in the machine, and the like occur, which is not preferable.

Generally, the addition of a crosslinking agent is used as a method for imparting brittleness, but this is a method that goes against the low-temperature fixing of the toner and is not appropriate. Furthermore, since the toner obtained by the pulverization method is generally in an irregular shape, there is a limit in performing faithful reproduction with respect to a latent image, which is disadvantageous for high image quality. In order to achieve high image quality in the pulverization method, it is necessary to pulverize the particles into smaller particles. However, it has been difficult to achieve both the brittleness relating to the pulverization efficiency of the binder resin and the thermal properties relating to the fixability and storage stability, and it has been impossible to sufficiently satisfy these performances.

Spherical toners have been proposed for these irregular toners. For example, Japanese Patent Publication No. 56-13945 discloses a method of obtaining a spherical toner by a melt spray method.
Japanese Patent No. 51676 discloses a method of obtaining a spherical toner by adding a small amount of an organic solvent to an irregular toner and performing a stirring process under cooling, and further includes JP-B-36-10231 and JP-A-59-53856. JP-A-59-61842 and the like disclose a method for obtaining a spherical toner using a polymerization method.

Since these spherical toners have a uniform shape, a latent image,
Particularly, since the edge portion is faithfully developed, it is suitable for high image quality. Further, when a spherical toner is obtained by the polymerization method, it is easy to reduce the particle size of the particles, which is more suitable for higher image quality.

Thus, it has been found that the polymerized toner solves some of the disadvantages of the pulverized toner, but causes new disadvantages. Polymerization method toner, polymerizable monomer, colorant,
A polymerization initiator, further a crosslinking agent as needed, a charge control agent, etc.
After uniformly dissolving or dispersing other additives into a monomer composition, the monomer composition is dispersed in a continuous phase containing a dispersion stabilizer, for example, an aqueous phase using a suitable stirrer. It is obtained by simultaneously performing a polymerization reaction. Therefore, in the initial stage of the polymerization reaction, the viscosity of the polymerizable monomer composition is extremely low, so that the colorant once dispersed in the particles may re-aggregate. This undesirably causes a decrease in the colorant of the toner.

[Problem to be Solved by the Invention] An object of the present invention is to solve the problems as described above. That is, the present invention provides a method for producing a toner having high coloring power by preventing re-aggregation of a colorant in suspension particles during polymerization of suspension particles.

[Means and Actions for Solving the Problems] Specifically, the present invention provides a method for suspending a polymerizable monomer composition containing at least a polymerizable monomer, a release agent and a colorant in an aqueous dispersion medium. In a method for producing a polymerization toner in which toner particles are produced by turbid polymerization, a polymerizable monomer composition containing at least a polymerizable monomer, a release agent and a colorant is heated to release a release agent. Is dissolved or melted, and the heated polymerizable monomer composition in which the release agent is dissolved or melted is heated to a liquid temperature capable of maintaining a state in which the release agent is dissolved or melted. Is added to the aqueous dispersion medium, and the polymerizable monomer composition is granulated in the heated aqueous dispersion medium to produce particles of the polymerizable monomer composition. Lower the liquid temperature of the medium to a temperature below the temperature at which the release agent precipitates, and polymerize the polymerizable monomer in the particles of the polymerizable monomer composition. To produce toner particles by polymerization.

 Hereinafter, the present invention will be described in detail.

As a result of intensive studies, the present inventors have found that a polymerized monomer system containing at least a polymerizable monomer, a release agent, and a colorant is suspension-polymerized in an aqueous medium to produce a polymerized toner. In the method, the polymerizable monomer system is suspended in an aqueous medium at a temperature at which the release agent dissolves or melts in the polymerizable monomer system, and then suspended to a temperature below the temperature at which the release agent precipitates. By lowering the temperature of the suspension and conducting polymerization at the temperature of the suspension, it was found that reaggregation of the colorant in the particles was prevented, and a polymerization toner having excellent coloring power was obtained.

That is, the polymerized toner is prepared by adding various additives such as a colorant to a polymerizable monomer from the characteristics of the manufacturing method, dispersing the same in an aqueous medium, and forming a suspended particle to perform a polymerization reaction. Therefore, at the initial stage of the polymerization reaction, the viscosity of the suspended particles is very low, so that the colorant dispersed in the particles tends to re-aggregate. Therefore, the temperature of the suspension is lowered to a temperature at which the release agent dissolved or melted in the particles after suspension is deposited or lower. As a result, the viscosity of the particles increases due to the effect of the separated release agent, and the colorant once dispersed is less likely to re-aggregate. Therefore, even during the polymerization reaction, the initial dispersion state of the colorant is maintained, and a toner having a large coloring power can be obtained.

The polymerized toner used in the present invention is obtained by the following method. That is, for example, additives such as a release agent, a colorant, a charge control agent, etc. are added to the polymerizable monomer, and the release agent is heated until dissolved or melted, and homogenized by a homogenizer, an ultrasonic disperser, or the like. A polymerizable monomer composition obtained by dissolving or dispersing a release agent in a water-based dispersion medium containing a dispersion stabilizer heated to the same temperature as the polymerizable monomer composition, Granulate using a stirrer, homomixer, or homogenizer. Preferably, the stirring speed and time are adjusted so that the droplets of the polymerizable monomer composition have a predetermined toner particle size, generally a particle size of 30 μm or less, and then the liquid temperature of the aqueous dispersion medium is adjusted to a release agent. If the stirring is performed to such an extent that the state of the particles of the polymerizable monomer composition is maintained and the sedimentation of the particles in the aqueous dispersion medium is prevented by the action of the dispersion stabilizer, good. The polymerization temperature is set to a temperature equal to or lower than the precipitation temperature of the release agent, and the polymerizable monomer in the particles is polymerized. After completion of the reaction, the generated toner particles are collected by washing and filtration, and dried. In the suspension polymerization method, it is usually preferable to use 300 to 3000 parts by weight of water as an aqueous dispersion medium based on 100 parts by weight of the monomer system.

As the polymerizable monomer that can be used in the above-mentioned polymerized toner,
Styrene, o-methylstyrene, m-methylstyrene,
p-methylstyrene, p-methoxystyrene, styrene monomers such as p-ethylstyrene, methyl acrylate,
Ethyl acrylate, n-butyl acrylate, isobutyl acrylate, n-propyl acrylate, n-acrylate
Acrylates such as octyl, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-methacrylate Methacrylates such as butyl, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, and diethylaminoethyl methacrylate; and acrylonitrile and methacrylic acid. Monomers such as lonitrile and acrylamide are exemplified.

These monomers can be used alone or as a mixture. Among the above-mentioned monomers, it is preferable to use styrene or a styrene derivative alone or in a mixture with another monomer, from the viewpoint of the developing characteristics and durability of the toner.

The dispersion medium used in the present invention is any suitable stabilizer, for example, polyvinyl alcohol, gelatin, methylcellulose, methylhydroxypropylcellulose,
Ethyl cellulose, sodium salt of carboxymethyl cellulose, polyacrylic acid and salts thereof, starch, starch, tricalcium phosphate, aluminum hydroxide, magnesium hydroxide, calcium metasilicate, barium sulfate, bentonite, etc. can be used by dispersing them in an aqueous phase. . The stabilizer is preferably used in an amount of 0.2 to 20 parts by weight based on 100 parts of the polymerizable monomer.

Also, for fine dispersion of these stabilizers, 0.001-0.1
Parts by weight of surfactant may be used. This is to promote the intended action of the dispersion stabilizer, and specific examples thereof include sodium dodecylbenzene sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate, sodium oleate,
Examples include sodium laurate, potassium stearate, calcium oleate and the like.

In the monomer system, a polymer having a polar group as an additive
It is more preferable to carry out polymerization by adding a copolymer. Further, in the present invention, a polymer / copolymer having a polar group or a monomer system to which a cyclized rubber is added is suspended in an aqueous phase in which the polar polymer and a reverse-charge dispersant are dispersed. It is preferable to carry out polymerization. That is, the cationic or anionic polymer / copolymer contained in the monomer system, or the cyclized rubber is polymerized with the reversely charged anionic or cationic dispersant dispersed in the aqueous phase. The surface of the particles serving as the toner inside is electrostatically attracted, and the dispersant covers the surface of the particles to prevent the particles from coalescing and stabilize, and the polar polymer added during polymerization collects on the surface layer of the toner particles. Therefore, it has a kind of shell-like form, and the obtained particles become pseudo capsules. Using a relatively high molecular weight polar polymer / copolymer or cyclized rubber, while imparting excellent properties to the toner particles in blocking properties and developer wear,
In the inside, polymerization is performed with a relatively low molecular weight so as to contribute to the improvement of the fixing property, whereby a toner satisfying the contradictory requirements of the fixing property and the blocking property can be obtained.
The polar polymer / copolymer and the reverse charge dispersant which can be used in the present invention are exemplified below.

(1) Examples of the cationic polymer include a polymer of a nitrogen-containing monomer such as dimethylaminoethyl methacrylate and diethylaminoethyl methacrylate, and a copolymer with styrene, an unsaturated carboxylic acid ester, and the like.

(2) Examples of the anionic polymer include nitrile monomers such as acrylonitrile, halogen-containing monomers such as vinyl chloride, unsaturated carboxylic acids such as acrylic acid and methacrylic acid,
Other examples include polymers such as unsaturated dibasic acids, unsaturated dibasic acid anhydrides, nitro monomers, and copolymers with styrene monomers. Further, a cyclized rubber may be used instead of these polar polymers.

(3) As the anionic dispersant, silica fine powder is preferably used, and in particular, colloidal silica having a BET specific surface area of 200 m ² / g or more is suitable.

(4) As the cationic dispersant, aminoalkyl-modified colloidal silica (preferably having a BET specific surface area of 200 m ² / g
And the like, and finely divided hydrophilic positively chargeable silica, aluminum hydroxide and the like.

It is preferable to use 0.2 to 20 parts by weight of such a dispersant based on 100 parts by weight of the polymerizable monomer. More preferably, it is 0.3 to 15 parts by weight.

In the present invention, it is desirable to add a charge control agent to the toner material in order to control the chargeability of the toner. Among these charge control agents, among known ones,
Those having little polymerization inhibitory property and water phase transfer property are used. Examples of the positive charge control agent include nigrosine dyes, triphenylmethane dyes, quaternary ammonium salts, amine and polyamine compounds, and the like. Examples of the control agent include a metal-containing salicylic acid-based compound, a metal-containing monoazo dye-based compound, a styrene-acrylic acid copolymer, and a styrene-methacrylic acid copolymer.

As the colorant used in the present invention, known colorants can be used. For example, in addition to carbon black and iron black, CI Direct Red 1, CI Direct Red 4, CI Acid Red 1, CI Basic Red 1, CI Modane Tread 30, CI Direct Blue 1, CI Direct Blue 2, CI Acid Blue 9, CI Acid Blue
15, CI Basic Blue 3, CI Basic Blue 5, CI Modant Blue 7, CI Direct Green 6, CI Basic Green 4, CI Basic Green 6, etc., dye, graphite, cadmium yellow, mineral fast yellow, navel yellow, naphthol Yellow S, Hansa Yellow G, Permanent Yellow NCG,
Tartrazine Lake, Molybdenum Orange, Permanent Orange GTR, Benzidine Orange G, Cadmium Red, Permanent Red 4R, Watching Red Calcium Salt, Brilliant Carmine 3B, Fast Violet B, Methyl Violet Lake, Navy Blue, Cobalt Blue, Alkaline Blue Lake, Victoria Blue Lake, quinacridone, rhodamine B, phthalocyanine blue, fast sky blue, pigment green B,
Pigments such as Macalite Green Lake and Final Yellow Green G are available. In the present invention, in order to obtain a toner using a polymerization method, it is necessary to pay attention to the polymerization inhibitory property and the aqueous phase migration property of the colorant, preferably, surface modification, for example, hydrophobicity by a substance without polymerization inhibition It is better to have a chemical treatment.

Examples of the release agent used in the present invention include paraffin / polyolefin-based waxes and modified products thereof, for example, oxides and grafted products, higher fatty acids, metal salts thereof, and amide waxes. These waxes have a softening point of 40 to 130 according to the ring and ball method (JISK 2531).
° C, preferably those having a temperature of 50 to 120 ° C. When the softening point is lower than 40 ° C, the blocking resistance and shape retention of the toner are insufficient, and when the softening point is higher than 130 ° C, the releasing effect is insufficient. Becomes

Such a release agent is preferably used in an amount of 5 to 30 parts by weight based on 100 parts by weight of the polymerizable monomer.

As the polymerization initiator, any suitable polymerization initiator, for example, 2,2'-azobis- (2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 1,1'- Azobis (cyclohexane-1-carbonitrile), 2,
2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, azo or diazo polymerization initiators such as azobisisobutyronitrile, benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate, cumene hydroperoxide, 2, Peroxide-based polymerization initiators such as 4-dichlorobenzoyl peroxide and lauroyl peroxide are exemplified. Further, the above-mentioned peroxides as redox initiators may be used in combination with reducing agents such as dimethylaniline, mercaptans, tertiary amines, iron (II) salts, and sodium bisulfite. These polymerization initiators are suitably used to obtain a desired molecular weight, but generally, 0.1 to 10
A weight percent addition is sufficient.

The release agent, polymerization initiator and polymerization temperature in the present invention will be described in more detail.

When a paraffin wax or the like having a low melting point or softening point is generally used as a release agent, the temperature at which the release agent precipitates from the polymerizable monomer system is lowered, so that the polymerization temperature is also lowered.
In such a case, it is preferable to use a redox initiator or 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile having a short half-life.

Conversely, when a polyolefin wax or the like having a high melting point or softening point is used, it is preferable to use an autoclave or the like in order to dissolve or melt the release agent in the polymerizable monomer system. Also, in this case, since the deposition temperature of the release agent is relatively higher than that of paraffin wax or the like, 2,2′-
Azobis (2,4-dimethylvaleronitrile), dimethyl
It is preferable to use a polymerizable initiator such as 2,2'-azobisisobutyrate.

Further, for the purpose of imparting various properties to the toner of the present invention,
Additives may be added. In addition, the additive has a volume average diameter of the toner particles from the viewpoint of durability when added to the toner.
The particle size is preferably 1/10 or less. The particle size of the additive means an average particle size obtained by observing the surface of the toner particles with an electron microscope. As additives for the purpose of imparting these properties, for example, the following are used.

1) Fluidity imparting agent: metal oxide (silicon oxide, aluminum oxide, titanium oxide, etc.), carbon black, carbon fluoride, etc. Those subjected to a hydrophobic treatment are more preferable.

2) Abrasives: metal oxides (strontium titanate, cerium oxide, aluminum oxide, magnesium oxide, chromium oxide, etc.), nitrides (silicon nitride, etc.), carbides (silicon carbide, etc.), metal salts (calcium sulfate, barium sulfate) , Calcium carbonate, etc.).

3) Lubricant: fluororesin powder (vinylidene fluoride, polytetrafluoroethylene, etc.), fatty acid metal salt (zinc stearate, calcium stearate, etc.).

4) Charge controllable particles: metal oxides (tin oxide, titanium oxide, zinc oxide, silicon oxide, aluminum oxide, etc.),
Such as carbon black.

These additives are used in an amount of 0.1 to 100 parts by weight of the toner particles.
10 parts by weight are used, preferably 0.1 to 5 parts by weight. These additives may be used alone or in combination of two or more.

 The measurement of the particle size distribution in the present invention will be described.

A Coulter Counter TA-II type (manufactured by Coulter) was used as a measuring device, and an interface (manufactured by Nikkaki) for outputting a number average distribution and a volume average distribution and a CX-1 personal computer (manufactured by Canon) were connected. A 1% aqueous NaCl solution is prepared using primary sodium chloride.

As a measurement method, 0.1 to 5 ml of a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant to 100 to 150 ml of the aqueous electrolytic solution, and 0.5 to 50 mg of a measurement sample is further added.

The electrolytic solution in which the sample was suspended was subjected to a dispersion treatment for about 1 to 3 minutes by an ultrasonic disperser, and a 100 μm aperture was used as the aperture by the Coulter Counter TA-II.
The volume average distribution and the number average distribution are determined by measuring the particle size distribution of the particles having a size of 〜40 μm.

The volume average particle size is obtained from the obtained volume average distribution and number average distribution.

Hereinafter, the present invention will be described in detail based on the present invention. still,
All parts are parts by weight.

Example 1 The above formulation was heated to 70 ° C. in a container to dissolve paraffin wax, and sufficiently dissolved and dispersed using a homomixer to prepare a heated polymerizable monomer composition.

Separately, 10 parts of aminoalkyl-modified colloidal silica were added to 1200 parts of ion-exchanged water, and the above polymerizable monomer composition heated to an aqueous dispersion medium adjusted to pH 6 with hydrochloric acid was added. The polymerizable monomer composition was granulated using a TK homomixer (manufactured by Tokushu Kika Kogyo). Thereafter, the temperature of the suspension was lowered to 20 ° C., paraffin wax was precipitated in the particles of the polymerizable monomer composition, and 10 parts of benzoyl peroxide (manufactured by Wako Pure Chemical Industries, Ltd.) was added thereto as a polymerization initiator. And 5 parts of ammonium thiocyanate (manufactured by Wako Pure Chemical Industries, Ltd.). Thereafter, the temperature of the suspension was heated to 40 ° C., and the polymerizable monomer was polymerized under a nitrogen atmosphere. After the polymerization was completed, sodium hydroxide was added to remove the dispersion medium, washed with water, filtered, and dried to obtain toner particles by a suspension polymerization method.

When the obtained toner particles were measured with a Coulter counter (aperture diameter 100 μm), the volume average diameter was 8.0 μm.
And had a sharp particle size distribution. The particles were dispersed in an epoxy resin, cured and then sliced to a thickness of 2 μm with a microtome. The dispersibility of the colorant was evaluated using an optical microscope. Was found to be well dispersed. Further, 0.5 part of silica fine powder subjected to hydrophobic treatment was mixed with 100 parts of the particles to obtain a toner. 94 parts of an acrylic-coated ferrite carrier was mixed with 6 parts of the toner to prepare a developer.

Using the thus obtained developer, CL manufactured by Canon Inc.
When the image output was evaluated using C-500, the copy was very clear.

Example 2 The above formulation was heated to 150 ° C. in an autoclave to dissolve the polyethylene wax, and sufficiently dissolved and dispersed using a homomixer to obtain a monomer composition.

Separately, in an autoclave, add 10 parts of amino-modified colloidal silica to 1200 parts of ion-exchanged water, and add the above monomer system to a dispersion medium system adjusted to pH 6 with hydrochloric acid. Was used to granulate the monomer system. Thereafter, the suspension was cooled to 80 ° C. to precipitate polyethylene wax, and then, as a polymerization initiator,
Dimethyl 2,2'-azobis-isobutyrate (10 parts) was added, and polymerization was carried out under a nitrogen atmosphere. After the polymerization is completed, sodium hydroxide is added, the dispersant is removed, and water washing, filtration,
Drying was performed to obtain polymer particles.

When the obtained particles were measured by a Coulter counter (aperture diameter: 100 μm), they had a volume average diameter of 8.2 μm and a sharp particle size distribution. The particles were dispersed in an epoxy resin, cured, sliced to a thickness of 2 μm with a microtome, and evaluated for dispersibility of the colorant using an optical microscope. The agent was found to be well dispersed. Also, this particle
0.5 part of silica fine powder subjected to hydrophobizing treatment was mixed with 100 parts to obtain a toner. 94 parts of an acrylic-coated ferrite carrier was mixed with 6 parts of the toner to prepare a developer.

Using the thus obtained developer, CL manufactured by Canon Inc.
When the image output was evaluated using C-500, the copy was very clear.

Example 3 Polymer particles were obtained by performing the same operation as in Example 1 except that

When the obtained particles were measured by a Coulter counter (aperture diameter: 100 μm), they had a volume average diameter of 8.8 μm and a sharp particle size distribution. These particles were dispersed in an epoxy resin, cured, sliced to a thickness of 2 μm with a microtome, and evaluated for dispersibility of the colorant using an optical microscope. As a result, no aggregates of the colorant were found. Was found to be well dispersed. In addition, 100 parts of the particles were mixed with 0.5 part of amino-modified silica fine powder to prepare a toner. 94 parts of an acrylic-coated ferrite carrier was mixed with 6 parts of the toner to prepare a developer.

Using the developer obtained in this way, Canon NP
When the image output was evaluated at -3525, the copy was very clear.

Comparative Example 1 Using the monomer composition having the same formulation as in Example 1 and a dispersion medium, granulation was performed at 70 ° C., and 10 parts of dimethyl 2,2′-azobis-isobutyrate was added thereto as a polymerization initiator. Was added and polymerization was carried out at the same temperature. After the completion of the polymerization, sodium hydroxide was added to remove the dispersant, and the polymer was washed with water, filtered, and dried to obtain polymer particles. When the obtained particles were measured by a Coulter counter (aperture diameter: 100 μm), they had a volume average diameter of 8.5 μm and a sharp particle size distribution. These particles are dispersed in an epoxy resin, and after curing,
When sliced to a thickness of 2 μm with a microtome and evaluated for dispersibility of the colorant using an optical microscope,
Some colorant aggregates were observed.

Comparative Example 2 The same operation as in Example 1 was performed without using paraffin wax to obtain polymer particles. When the obtained particles were measured by a Coulter counter (aperture diameter: 100 μm), they had a volume average diameter of 7.8 μm and a sharp particle size distribution. The particles were dispersed in an epoxy resin, cured, sliced to a thickness of 2 μm with a microtome, and evaluated for dispersibility of the colorant using an optical microscope. As a result, aggregates of the colorant were partially observed. .

[Effects of the Invention] As described above, according to the present invention, a toner having excellent dispersibility of a colorant in toner particles and high coloring power can be obtained.

Claims (1)

(57) [Claims] 1. A method for producing a polymerization toner, wherein toner particles are produced by suspension polymerizing a polymerizable monomer composition containing at least a polymerizable monomer, a release agent and a colorant in an aqueous dispersion medium. In, the polymerizable monomer composition containing at least a polymerizable monomer, a release agent and a colorant is heated to dissolve or melt the release agent, and to dissolve or melt the release agent. The heated polymerizable monomer composition is added to an aqueous dispersion medium that is heated to a liquid temperature capable of maintaining a state in which the release agent is dissolved or melted, and heated. The polymerizable monomer composition is granulated in an aqueous dispersion medium to form particles of the polymerizable monomer composition, and then the temperature of the aqueous dispersion medium is reduced to a temperature below the temperature at which the release agent is deposited. Polymerizing a polymerizable monomer in particles of the polymerizable monomer composition to form toner particles. Method of manufacturing over.