JPH0241748B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a toner for developing an electrostatic latent image or the like.

Conventionally, toners have generally been melt-mixed in thermoplastic resins, uniformly dispersed, and then used in a pulverizer classifier to produce toners having a desired particle size.
Although this method of manufacturing can produce fairly good toners, it does have certain limitations, namely the range of selection of materials for the toner. For example, the resin pigment dispersion must be sufficiently brittle that it can be milled at economically viable production rates. From this request,
Since the resin pigment dispersion is sufficiently brittle, when it is actually pulverized at high speed, particles with a wide range of particle sizes are likely to be formed by pulverization, and a relatively large proportion of fine particles are included. . Furthermore, such highly brittle materials are often further pulverized or pulverized when used for development in copying machines. Other requirements for toners include being stable on storage and not coagulating.
This toner must have triboelectric properties suitable for development, form excellent images, not coat or stain the photoreceptor, and have a low melting point suitable for thermal fusing. Combined with additional requirements imposed by law.

Toners for developing electrostatic images obtained by suspension polymerization overcome the drawbacks of the pulverization method. In other words, since there is no pulverization process involved, there is no need for brittleness, and the spherical shape provides excellent fluidity. Furthermore, by appropriately controlling polymerization or using crosslinking agents, toners with excellent heat fixing properties can be created. Obtainable.

Therefore, attempts have been made to directly produce toners for electrostatic charge development by emulsification or suspension polymerization. These polymerization methods have been proposed in JP-A-53-17735 and other publications. These are monomeric polymerization initiators,
A toner is obtained directly by dispersing a colorant, a magnetic substance, and other components in water. In other words, there is no need for brittleness because there is no pulverization process involved, and the spherical shape has excellent fluidity. Furthermore, by appropriately controlling polymerization or using crosslinking agents, it has excellent heat fixing properties. toner.

However, the requirements for electrophotography are becoming more and more stringent, and are compatible with being stable during storage, not solidifying, and having a low melting point suitable for heat fixing.

The present invention provides a novel method for producing toner for developing electrostatic images, etc., which satisfies such requirements.

Specifically, the present invention provides a toner material containing a vinyl monomer or a mixture of vinyl monomers, an oil-soluble polymerization initiator, and a colorant that is substantially miscible with the vinyl monomer. It is dispersed in an aqueous dispersion medium that does not contain any emulsifier or contains a dispersion stabilizer or a surfactant below the critical micelle concentration using a high-shear mixing device, and is subjected to suspension polymerization. A vinyl monomer system containing an oil-soluble polymerization initiator and a vinyl monomer having a glass transition temperature higher than the glass transition temperature of the polymer particles is combined with the polymer particles. The present invention relates to a method for producing a toner, characterized in that the toner is produced by a polymerization method in which the toner is adsorbed onto particles and grown.

When growing polymer particles, the formula (1) Tg=
A monomer system with a glass transition temperature expressed as V ₁ Tg ₁ +V ₂ Tg ₂ , 1/Tg=W ₁ /Tg ₁ +W ₂ /Tg ₂ that is higher than that of the seed polymer particles is carefully controlled and injected. Let it absorb. At this time, it is important to carefully control the monomer addition rate to obtain the best results. If the addition rate is too low, the polymerization time will be unduly long; if the addition rate is too high, not only will a large amount of fine particles be produced, but the seed particles will tend to coalesce and form agglomerates.

Generally, monomer should be added at approximately the same rate as the monomer is adsorbed by the particles. Therefore, preferably the Tg of the seed polymer particles is 80.
of the monomer system used for growth below ℃.
Tg is 80℃ or higher. The surface of the seed polymer particles adsorbs the monomer, causing the surface to swell.
If this swelling occurs only on the surface, it will be coated with monomer and polymerized by the initiator, so it will have a smooth surface that is not contaminated with colorants or magnetic substances, or with little stain. Can be done. Furthermore, by adjusting the amount of monomer in the seed polymer particles, it is possible to control the particle size to a desired value.

The seeding polymer particles are a monomer-based toner in which a vinyl monomer or a mixture of vinyl monomers, an oil-soluble polymerization initiator, a colorant, a magnetic substance, an additive, etc. are uniformly dissolved or dispersed. Homomixer the material into an aqueous or continuous phase containing suspension stabilizers;
Disperse using a high shear mixing device such as a homogenizer. Preferably, the stirring speed and time are adjusted so that the monomer droplets have the desired toner particle size, generally 30 μm or less, and thereafter this state is maintained approximately by the action of the dispersion stabilizer. Stirring may be carried out to the extent that sedimentation of particles is prevented.
The polymerization temperature is set at 50°C or higher, generally from 70°C to 90°C.

Suitable dispersion media used in the present invention include, for example, any suitable stabilizer, such as polyvinyl alcohol, gelatin, methyl cellulose, methyl hydropropyl cellulose, ethyl cellulose, sodium salt of carboxymethyl cellulose, polyacrylic acid and their like. Salt, starch, gum alginate, zein, casein, tricalcium phosphate, talc, barium sulfate, pentonite, aluminum hydroxide, ferric hydroxide, titanium hydroxide, thorium hydroxide, etc. are included in the aqueous phase. It can be used as The stabilizer is in a stabilizing amount in the continuous phase, preferably in the range of about 0.1 to 10% by weight.

Further, the inorganic dispersion stabilizer is finely dispersed,
In order to promote the action of the inorganic dispersion stabilizer, a surfactant may be used at a concentration of 0.001 to 0.1% by weight below the critical micelle concentration. Specific examples of surfactants include sodium dodecylbenzenesulfonate, sodium tetradecylsulfate, sodium pentadecylsulfate, sodium octylsulfate, sodium allyl-alkyl-polyethersulfonate, sodium oleate, sodium laurate, sodium caprate, and caprylic. sodium acid, sodium caproate, potassium stearate, calcium oleate, sodium 3,3'-disulfone diphenyl urea-4,4'-diazo-bis-amino-8-naphthol-6-sulfonate, ortho-carboxybenzene -Azo-dimethylaniline, 2,2',5,5'-tetramethyl-triphenylmethane-4,4'-diazo-bis-β-
Naphthol-sodium disulfonate, and others can be mentioned.

In addition, water-soluble monomers undergo emulsion polymerization simultaneously in water, and the resulting suspension polymer is contaminated with small emulsion polymer particles. It is also good to prevent emulsion polymerization.
Furthermore, glycerin, glycol, etc. may be added to the water in order to increase the viscosity of the medium and prevent coalescence of particles. It is also possible to use salts such as NaCl, KCl, Na ₂ SO ₄ to reduce the solubility of easily soluble monomers in water.

As the polymerization initiator, any suitable oil-soluble polymerization initiator such as azobisisobutyronitrile (AIBN), benzoyl peroxide, methyl ethyl ketone peroxide, isopropyl peroxy carbonate, kinimen hydroperoxide, 2,4-dichloro Monomer polymerization can be carried out using lylbenzoyl peroxide, lauroyl peroxide, or the like. Generally about 0.5 to 5% initiator by weight of monomer is sufficient.

The polymerization temperature is usually 50°C to 120°C, but uniform polymerization is more likely to occur at lower temperatures. Examples of vinyl monomers include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-n-butylstyrene, p-tert-butyl Styrene, p-n-hexylstyrene, p-
n-octylstyrene, p-n-nonylstyrene, p-n-decylstyrene, p-n-dodecylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, etc. styrene and its derivatives, among which styrene monomer is most preferred. Examples of other vinyl monomers include ethylenically unsaturated monoolefins such as ethylene, propylene, butylene, and isobutylene; vinyl chloride;
Vinyl halides such as vinylidene chloride, vinyl bromide, and vinyl fluoride; Vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate, and vinyl butyrate; Methyl acrylate, ethyl acrylate, n-butyl acrylate, Isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, α-
Methyl chloroacrylate, methyl methacrylate,
Ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate,
α-methylene aliphatic monocarboxylic acid esters such as dimethylaminoethyl methacrylate and diethylaminoethyl methacrylate; acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, and acrylamide; vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether Vinyl ethers such as; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, methyl isopropenyl ketone;
N-vinylpyrrole, N-vinylcarbazole,
Examples include N-vinyl compounds such as N-vinylindole and N-vinylpyrrolidone; vinylnaphthalenes and the like.

The polymer according to the present invention may be polymerized in the presence of a crosslinking agent to form a crosslinked polymer. Preferably used crosslinking agents are mainly compounds having two or more polymerizable double bonds, such as aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene and derivatives thereof, such as ethylene glycol dimethacrylate and diethylene glycol methacrylate. , diethylene glycol methacrylate, trimethylolpropane triacrylate, allyl methacrylate, t-butylaminoethyl methacrylate, totera ethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate, etc., N,N-divinyl All divinyl compounds such as aniline, divinyl ether, divinyl sulfide, divinyl sulfone, and compounds having three or more vinyl groups are selected singly or as a mixture.

The amount of the crosslinking agent added to the monomer is selected to be in the range of 0.005 to 20% by weight, preferably 0.1 to 5% by weight. If the amount added is too large, the toner will not melt and will tend to lose its fixing properties as a toner. In addition, if the amount is too low, it becomes difficult to impart toner properties such as durability, storage stability, and abrasion resistance.Especially in hot roll fixing copiers, etc., the molecular weight distribution of the polymer expands due to crosslinking, and as a result, Due to the properties of the toner itself, it becomes difficult to achieve the effect of preventing the offset phenomenon during fixing.

As the coloring agent, any one selected from pigments, dyes, etc. can be used. For example, carbon black,
Nigrosine dye, oil black, etc. can be used alone or in combination. A magnetic material may also be used as a coloring agent.

The magnetic material used in the toner material may be any material as long as it is strongly magnetized in that direction by a magnetic field. Preferably magnetite is used. Typical magnetic or magnetic materials include metals such as cobalt, iron, and nickel; aluminum, cobalt, steel, iron,
Alloys and mixtures of metals such as lead, magnesium, nickel, tin, zinc, antimony, beryllium, bismuth, iodium, calcium, manganese, selenium, titanium, tungsten, vanadium; aluminum oxide, iron oxide, copper oxide, nickel oxide , metal compounds including metal oxides such as zinc oxide, titanium oxide and magnesium oxide; refractory titides such as vanadium titride, chromium titide; carbides such as tungsten carbide and silica carbide; ferrites and mixtures thereof. etc. can be used.

The monomer used in the method for growing polymer particles can be the same compound as the monomer used in the seed polymerization described above.

The polymerization initiator used in the growth method is preferably oil-soluble, as described in the Examples below. As the oil-soluble polymerization initiator, an oil-soluble free radical initiator is used, specifically, t
-butyl hydroperoxide, diternary butyl peroxide, dibenzoyl peroxide, perbenzoic acid, tert-butyl peracetate, azobisisobutyronitrile, etc. are used. Initiator concentration is generally relative to monomer
It is in the range of 0.3-0.8wt%.

In the growth process, surfactants can be used to stabilize the polymerized particles. for example,
Examples of anionic activators include potassium palmitate, potassium stearate, potassium caprate, potassium oleate, sodium dodecylsulfonate, sodium laurate, sodium rosinate, alkyl sodium sulfosuccinate, and the like. Examples of cationic activators include long-chain quaternary amine salts. Examples of the nonionic surfactant include ethylene oxide condensates of linoleic acid, lauric acid, ricinoleic acid, caproic acid, ethylene oxide condensates of oleyl alcohol, cetyl alcohol, lauryl alcohol, and the like. The above surfactants can be used alone or in combination. When a surfactant is used, it must be used at a concentration below the critical micelle concentration, as shown in Example 2 below, in order to prevent the occurrence of emulsion polymerization.

After the reaction is completed, the produced toner particles are recovered by a suitable method such as washing, filtration, decantation, centrifugation, etc., and dried.

[Example 1] 320 g of styrene, 80 g of ethyl acrylate, 240 g of magnetite EPT-1000 having a particle size of Fischer diameter 0.4 μBET specific surface area 6.0 m ² /g, and petrolactam oxide metal salt (OX- manufactured by Nippon Seiro Co., Ltd.)
0851) 24g and 8g of chromium acetylsalicylate complex
were uniformly mixed for about 20 minutes in a container equipped with a high shear mixing device such as a TK-Homo mixer (manufactured by Tokushu Kogyo Co., Ltd.). During that time, the temperature rose to about 50°C.
During this time, the magnetite was dispersed in the styrene monomer. 30 g of lauroyl peroxide was stirred and mixed into the magnetite-containing styrene monomer. 600 g of water in which 9.0 g of polyvinyl alcohol was dissolved was kept at 70° C., and the slurry was put into a homomixer with stirring, followed by stirring at 4000 rpm for 30 minutes. This reaction mixture system was stirred with paddle blade stirring to complete the polymerization. The glass transition temperature of this product was 67°C.

Thereafter, 100 g of styrene (glass transition temperature: 100° C.) in which 1 g of benzoyl peroxide was dissolved was added dropwise over a period of 2 hours, followed by polymerization for 3 hours to complete the polymerization.

After washing with water and drying, a toner with a number average diameter of 10.1 μ, a number distribution of 6.35 μ or less of 15%, and a volume distribution of 20.2 μ or more of 1% (using a Coulter counter 100 μ aperture) was obtained. It was confirmed by a scanning electron microscope that it had a smooth surface.

This toner is applied to a commercially available dry type electrophotographic copying machine NP-
The image was created using 400RE. As a result, clear images without fog could be obtained. The image density was 1.20 in solid black areas using a reflection densitometer. Furthermore, the toner properties were also satisfactory, and the fluidity and continuous image printing durability were particularly excellent.

[Example 2] Styrene 80g, n-butyl acrylate 20g,
Trimethylolpropane triacrylate 0.2g,
10 g of β-type phthalocyanine pigment and 2 g of chromium acetylsalicylate complex were uniformly dispersed and mixed using a ball mill. Thereafter, 3 g of 2,2'-azobis-(2,4-dimethylvaleronitrile) was added and dissolved. 3g tricalcium phosphate and
The above slurry was added to an aqueous phase of 300 g of water to which 0.05 g of sodium dodecylbenzenesulfonate was added.
The mixture was added to the TK-homogenizer while stirring at a stirring speed of 5000 rpm. Thereafter, polymerization was carried out at 60° C. for 7 hours to complete the polymerization reaction. The glass transition temperature of this product was 55°C. After that, the temperature was raised to 70℃ and
50g of styrene in which 1g of 2,2'-azobisisobutyronitrile is dissolved (glass transition temperature: 100℃)
was added dropwise over 4 hours, and then polymerization was completed for 5 hours. After cooling, it was filtered and dried to obtain a toner having a number average diameter of 9.2 μm (using a Coulter counter with an aperture of 100 μm).

This toner is applied to a commercially available dry type electrophotographic copying machine NP-
Images were produced using 5000 machines. As a result, a clear image without fogging was obtained.

[Comparative Example 1] In the same manner as in Example 2, 80 g of styrene, 20 g of n-butyl acrylate, 0.2 g of trimethylolpropane triacrylate, 10 g of β-type phthalocyanine pigment, and 2 g of chromium acetylsalicylate complex were uniformly dispersed using a ball mill. Mix and then add and dissolve 3 g of 2,2'-azobis-(2,4-dimethylvaleronitrile) to prepare a slurry, then add 3 g of tricalcium phosphate and 0.05 g of dodecylbenzenesulfonic acid. The above slurry was poured into an aqueous phase of 300 g of water to which sodium had been added while being stirred using a TK-homogenizer at a stirring speed of 5000 rpm, then suspension polymerized at 60°C for 7 hours, and after cooling,
It was filtered and dried to obtain a toner.

When the obtained toner was imaged in the same manner as in Example 2, the fluidity was poor, and as the toner wore on, aggregates were formed and fogging was observed.

Further, 10 g of the above toner was placed in a 100 c.c. plastic container and left open at 50° C. for 7 days to examine blocking properties. As a result, formation of aggregates was observed, and visual fluidity was also significantly reduced. On the other hand, in the case of the toner of Example 2, which was tested at the same time, no aggregates were observed.

[Example 2] The first stage suspension polymerization (60
℃ for 7 hours) to form polymer particles in the aqueous phase, and then add 1.5 g of sodium dodecylbenzenesulfonate and 3 g of potassium persulfate, a water-soluble polymerization initiator, to the aqueous phase to reach a critical micelle concentration or higher. After the temperature was raised to 70° C., 50 g of styrene monomer was added dropwise in the same manner as in Example 2 to perform emulsion polymerization. After emulsion polymerization, the mixture was cooled, filtered, and dried to obtain a toner.

The obtained toner contained many fine particles smaller than the particle size of the polymer particles prepared by suspension polymerization in the first stage of polymerization, and had inferior fluidity compared to the toner obtained in Example 2. was.

When image formation was carried out in the same manner as in Example 2 using the obtained toner, the image density was lower and there was more fog than in Example 2. Furthermore, when image printing was performed under a high temperature and high humidity environment, the image density was significantly lower than that in Example 2.

[Comparative Example 3] Suspension polymerization (60° C., 7 hours) was carried out in the same manner as in Example 2 to produce polymer particles. After cooling,
It was filtered and dried to obtain polymer particles. Approximately 110 g of the obtained polymer particles were added to a xylene solution in which 50 g of polystyrene resin with a glass transition temperature of 100°C was dissolved.
A dispersion liquid was prepared by dispersing in 100 ml, and the prepared dispersion liquid was sprayed with a spray dryer to produce a toner.

The obtained toner contained many fine particles smaller in diameter than the polymer particles prepared by suspension polymerization, and had poor fluidity compared to the toner obtained in Example 2.

When image formation was carried out in the same manner as in Example 2 using the obtained toner, the image density was lower and there was more fog than in Example 2.

Claims (1)

[Scope of Claims] 1. A toner material containing a vinyl monomer or a mixture of vinyl monomers, an oil-soluble polymerization initiator, and a colorant that is substantially incompatible with the vinyl monomer and Contains no emulsifier or
A dispersion stabilizer or surfactant is dispersed in an aqueous dispersion medium containing less than the critical micelle concentration using a high shear force mixing device, and suspension polymerized to form polymer particles. A toner is produced by a polymerization method in which a vinyl monomer system containing a vinyl monomer that produces a vinyl polymer having a glass transition temperature higher than the glass transition temperature of the combined particles is adsorbed onto the polymer particles and grown. A method for producing a toner, characterized by: 2. The method for producing a toner according to claim 1, wherein the vinyl monomer is styrene, a styrene derivative, or an α-methylene aliphatic monocarboxylic acid ester. 3. The method for producing a toner according to claim 2, wherein the α-methylene aliphatic monocarboxylic acid ester is an acrylic ester. 4. The method for producing a toner according to claim 1, wherein the mixture of vinyl monomers is a mixture of styrene and acrylic ester.