JPH0711716B2 - Method for producing polymerized toner - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to improvements in the production of polymerized toners, and more particularly to a method for producing a polymerized toner excellent in moisture resistance, storability and triboelectrification.

[Conventional technology]

Conventionally, toners used for electrophotography and the like are generally kneaded with a thermoplastic resin and additives such as a coloring agent such as carbon black and a charge control agent, and after uniformly dispersing, pulverized by a pulverizer and then classified by a classifier. It is manufactured by a so-called pulverization method in which particles are classified into a particle size suitable for toner. However, the toner produced by this kneading and pulverizing method has the following problems.

That is, when manufacturing a toner using a pulverization method, the material must have brittleness so that it can be pulverized to some extent. However, if a material having too high brittleness is used, the toner is too finely pulverized, and the fine powder must be removed in order to finally obtain a toner having an appropriate particle size distribution, which increases the manufacturing cost. Further, such toner may be further pulverized in the developing device of the copying machine during the continuous copying process. Further, in order to improve the heat fixing property, when a toner having a low melting point is used or a material having a pressure fixing property is used, the toner is fused and developed in a crushing device or a classifying device and continuously There are cases where it cannot be produced.

In order to solve the problems of such a pulverization method, it has been proposed to produce a polymerized toner from a polymerizable monomer by a suspension polymerization method (Japanese Patent Publication No. 51-14895 and Japanese Patent Publication No. 57-5376). etc). When a developing toner is obtained by a conventional general suspension polymerization method, a monomer composition containing at least a polymerizing monomer and a colorant mainly composed of carbon black is used as an aqueous solution containing a suspension stabilizer. In a medium or the like, a suitable stirrer is used to granulate to a particle size of the toner, and a radical that is generated when the pre-added polymerization initiator or the newly added polymerization initiator is decomposed by heat, The polymerizable monomer is polymerized to form a polymer to produce a polymerized toner. That is, since this suspension polymerization method does not include a pulverizing step, it is not necessary to select a material having brittleness as the polymerized toner, and since the shape is spherical, the polymerized toner has excellent fluidity and triboelectrification property. Are uniform. However, since the polymerized toner is produced in an aqueous medium containing a suspension stabilizer, a washing step for removing the suspension stabilizer and the like is required after the suspension polymerization is completed. The washing step is usually performed using a solvent such as water that dissolves a suspension stabilizer, but since the particle size of the polymerized toner is as small as 10 μm or less, operability is poor with methods such as filtration and centrifugation, and also in terms of cost. It is difficult to perform sufficient washing. That is,
After the completion of the polymerization, the excess suspension stabilizer present in the aqueous phase can be easily removed by washing with a solvent such as water, but the suspension stabilizer coating the surface of the polymer particles is It is very difficult to remove due to its strong affinity with the particle surface. In addition, since some suspension stabilizer molecules may be embedded in particles and physically fixed on the particle surface, it is considered that removal of such suspension stabilizer by washing is almost impossible. ing.

Further, when water-soluble acrylic acid esters are used in combination with styrene as a polymerizable monomer, acrylic acid esters move to the aqueous phase during the granulation process, so these do not participate in the polymerization reaction and the polymerization is completed. After that, they remain in the aqueous phase.
In addition, there are also low-polymerized products of these acrylic acid esters, so that there is a drawback that the polymerized particles are contaminated with the low-polymerized products of these acrylic acid esters. Furthermore, these low-polymerization products of acrylic acid esters have low solubility in water, and therefore are difficult to remove in the washing step.

When a suspension stabilizer, etc. adheres to and remains on the surface of polymerized toner particles, the hydrophilic group portion of the suspension stabilizer adsorbs moisture in the air. It is a cause of marked deterioration of storability and the like, and adverse effects on other physical properties of the toner such as triboelectric charging property, developing property and durability.

Further, in the drying step, a large amount of energy is required to dry the powder containing water, which is a cost disadvantage.

[Problems to be Solved by the Invention]

The present invention has the above-mentioned problems in the production of a polymerized toner by the suspension polymerization method, that is, it effectively removes the suspension stabilizer and the like, and also has moisture resistance, fluidity, storability, triboelectric chargeability, durability, etc. It is an object of the present invention to easily provide a good polymerized toner.

[Means and Actions for Solving the Problems]

In order to solve the problems of the conventional techniques as described above, the present inventors have earnestly studied, as a result of suspension polymerization of a monomer composition containing at least a polymerizable monomer and a colorant,
It has been found that it is effective to use a washing agent used in the step of washing the obtained polymerized toner after separation with a concentration gradient of a water-miscible organic solvent.

That is, by repeatedly performing washing treatment with a concentration gradient such that the concentration of the water-miscible organic solvent is gradually increased, the suspension stabilizer and the like are effectively removed, and moisture resistance, fluidity, storage stability, etc. are improved, and It was found that the drying energy in the drying process is reduced.

That is, the suspension stabilizer adhering to the particle surface of the resulting polymerized toner obtained by suspension-polymerizing a monomer composition containing a polymerizable monomer and a colorant can be removed to some extent with water or warm water. Since impurities such as low-polymerization products derived from acrylic acid esters have low solubility in water, they cannot be removed by water alone. On the other hand, impurities consisting of low-polymerization products derived from acrylates dissolve in organic solvents,
Suspension stabilizers are generally insoluble in organic solvents. That is,
When the organic solvent is added after washing with water, the remaining suspension stabilizer deposits and adheres to the surface of the polymerized toner, which may contaminate the particles. Also, depending on the type of organic solvent, some may dissolve the polymerized toner itself, so washing with water alone or with an organic solvent alone may result from the suspension stabilizer or acrylic ester remaining on the particle surface of the polymerized toner. It is not possible to effectively remove the impurities that occur.

Therefore, if a water-miscible organic solvent-water mixed solvent is washed by applying a concentration gradient, it is possible to very effectively remove the impurities derived from the suspension stabilizer or acrylic ester remaining on the surface of the particles of the polymerizable toner. It turns out that it can be removed. The water-miscible organic solvent used in the present invention is an organic solvent that dissolves in water at an arbitrary ratio and can be adjusted to any concentration. That is, when the concentration of the water-miscible organic solvent is low, highly hydrophilic compounds such as suspension stabilizers are removed, and as the concentration of the water-miscible organic solvent is increased, it is likely that impurities derived from acrylate ester Compounds with low hydrophilicity are removed. At this time, water-miscible organic solvent
Since a mixed solution of water (also referred to as an aqueous solution) is used with a concentration gradient, precipitation of a suspension stabilizer or the like due to a difference in concentration is prevented.

Further, simply, when a saturated aqueous solution of an organic solvent capable of swelling polymer particles is used together with a water-miscible organic solvent, the particles swell, and the hydrophilic group moiety on the particle surface faces the inside of the surface, that is, the center of the particle , The particle surface is more hydrophobic.

The method for producing the polymerized toner of the present invention can be carried out as follows, but is not limited thereto. After suspension polymerization of a monomer composition containing at least a polymerizable monomer and a colorant, the suspension is filtered and washed briefly with water to obtain a slurry of polymerized toner. A 5% aqueous solution of a water-miscible organic solvent such as methanol or acetone is added to this, and the mixture is stirred and filtered again to obtain a slurry of polymerized toner. A 10% aqueous solution of a water-miscible organic solvent is added to the slurry of the polymerized toner, stirred and filtered again to obtain a slurry of the polymerized toner. Further, if necessary, the concentration of the water-miscible organic solvent is changed to 100% to prepare a water-miscible organic solvent aqueous solution having a concentration gradient, and the above operation is repeated using this. Finally, the solvent was removed using a centrifugal filter, etc., and the surface-treated toner was obtained by leaving it at room temperature for one day and drying.

Further, it is more effective to add a small amount of a saturated aqueous solution of a non-water-miscible organic solvent to the water-miscible organic solvent-water mixed solvent used in the present invention. The non-water-miscible organic solvent used in the present invention is a solvent capable of dissolving or swelling the polymerized toner particles and having a relatively low solubility in water.
That is, when a saturated aqueous solution such as toluene is used in combination, the surface of the polymerized toner particles swells and the hydrophobicity is further improved, which is preferable. At this time, swollen particles tend to aggregate, so
Drying by spray drying or the like is preferable from the viewpoint of preventing aggregation of particles. Further, at this time, when the surface is treated with an organic solvent in which a charge control agent is dissolved, the charge control agent is adsorbed on the surface of the particles, and a polymerized toner having a uniform and high charge amount can be obtained.

Generally, increasing the temperature increases the solubility of the compound,
The dissolution time will also be shorter. Therefore, by heating, the treatment can be performed in a short time with a smaller amount of solvent.

As the alcohol used as the water-miscible organic solvent used in the present invention, a commercially available alcohol can be used as it is, and specifically, for example, methyl alcohol, ethyl alcohol, n-propyl alcohol, 1-methylethyl alcohol. , N-butyl alcohol, 1-methylpropyl alcohol, t-butyl alcohol, 2-methoxyethyl alcohol and the like are preferable.

Further, as the ketones used in the water-miscible organic solvent, commercially available ketones can be used as they are, and specifically, for example, acetone, methyl ethyl ketone and the like are preferable.

It is not preferable to use a water-miscible organic solvent that may dissolve polymerized toner particles such as ketones in a high concentration. In this case, the resin composition of the polymerized toner, the molecular weight, etc. must be taken into consideration to set the concentration to an appropriate level.

Further, as the organic solvent capable of swelling the polymer particles, a commercially available solvent can be used as it is, and specifically, for example,
Aromatic organic solvents such as benzene and toluene, ethers such as diethyl ether and dioxane are preferable.

These water-miscible organic solvents and organic solvents capable of swelling polymer particles can be used alone or in combination of two or more kinds in various compositions as required.

The suspension stabilizer used in the present invention will be described.

Generally, as a suspension stabilizer used in suspension polymerization, a surfactant having a hydrophilic group and a hydrophobic group in its molecule is often used. The suspension stabilizer is composed of a hydroxyl group as a hydrophilic group, a carboxyl group and a salt thereof, a polar group such as a sulfone group and a salt thereof, and a non-polar group such as an aliphatic and aromatic group as a hydrophobic group. , A compound having an ability to prevent and stabilize coalescence of particles of the monomer assembly product formed in the granulation step.

Such suspension stabilizers include, for example, polyvinyl alcohol, casein, gelatin, methyl cellulose, methyl hydroxypropyl cellulose, ethyl cellulose and other cellulose derivatives, starch and its derivatives, poly (meth) acrylic acid and salts thereof, polystyrene sulfonic acid. And their salts, etc., and these suspension stabilizers serve to coat the surface of the droplets during polymerization and prevent coalescence and agglomeration of the droplets.

Next, materials other than the above, which constitute the monomer composition for producing the polymerized toner of the present invention, will be described.

That is, as the main component of the monomer composition used in the polymerized toner of the present invention, for example, the following polymerizable polymerizable monomers can be used.

Styrene, o-methylstyrene, m-methylstyrene,
p-methylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, p-ethylstyrene, 2,4-dimethylstyrene, pn-butylstyrene, p-tert. -Styrene and its derivatives such as butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene and pn-decyl styrene; ethylene unsaturated such as ethylene, propylene, butylene and isobutylene Mono-olefins; vinyl halides such as vinyl chloride, vinylidene chloride, vinyl bromide, vinyl fluoride, etc .; organic acid vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate; methacrylic acid, methyl methacrylate, methacryl Ethyl acid, propyl methacrylate, n-butyl methacrylate, methacrylic acid n-octyl, dodecyl methacrylate, 2-ethylhexyl methacrylate,
Methacrylic acid and its derivatives such as stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate and diethylaminoethyl methacrylate; acrylic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate. , N-octyl acrylate, dodecyl acrylate,
Acrylic acid and its derivatives such as 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether; vinyl methyl ketone, vinyl hexyl ketone , Vinyl isopropenyl ketone, and other vinyl ketones; N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole, N-vinyl pyrrolidone, and other N-vinyl compounds; vinyl naphthalene compounds; acrylonitrile, methacrylonitrile, acrylamide, etc. There is a monomer.

These monomers may be used alone or in combination of two or more as needed in various compositions.

Among the above-mentioned monomers, it is preferable to use styrene or a styrene derivative alone or in combination with other monomers as a polymerizable monomer in order to improve the developing characteristics and durability of the toner.

Next, the colorant constituting the present invention will be described.

Carbon black is suitable as the colorant in the present invention.

That is, as the carbon black used in the present invention, the number average particle diameter, oil absorption amount, pH and the like can be used without limitation, and the following are commercially available products.

For example, US Cabot Corp. Regal 400, 66
0, 330, 300, SRF-S, STERLING SO,
V, NS, R; Raven H20, MT-P, 410, 420, 430, 450, 500, 76 manufactured by Columbia Carbon Japan Co., Ltd.
0,780,1000,1035,1060,1080; Mitsubishi Kasei Co., Ltd.
Manufactured by # 10B, # 5B, # 40, # 2400B, MA-100; and the like.

These carbon blacks may be used alone or in combination of two or more in various compositions.

As the colorant other than carbon black, a colorant that is dispersible in the monomer composition and exhibits a clear and stable color with time when used as a toner is used.
Examples of such colorants include phthalocyanine pigments, rhodamine lake pigments, azo lake pigments, iron oxide, titanium oxide, alumina, barium sulfate and the like.

The amount of colorant added is 1 with respect to 100 parts by weight of the polymerizable monomer.
-40 parts by weight, preferably 5-20 parts by weight.

Further, in the present invention, in order to improve heat fixing property and offset resistance, waxes such as paraffin wax, low molecular weight polyolefins such as low molecular weight polyethylene and low molecular weight polypropylene, and the like, having a low softening point having releasability. The compound may be added to the monomer composition.

Further, in the present invention, in order to improve blocking resistance and durability, a crosslinking agent may be added to carry out suspension polymerization. As such a cross-linking agent, a known cross-linking agent such as divinylbenzene can be added to the monomer composition.

Further, in the present invention, if necessary, a known charge control agent may be added to the monomer composition, or the surface of the polymerized toner particles may be treated with a solution prepared by dissolving it in an organic solvent. Examples of such a charge control agent include a metal complex of an organic compound having a carboxyl group, a sulfonate ester, or a nitrogen-containing group, a metal-containing dye, and the like.

The polymerization initiator used in the present invention is preferably soluble in the polymerizable monomer.

Examples of such a polymerization initiator include 2,2'-azobisisobutyronitrile, 2,2'-azobis- (2,4-dimethylvaleronitrile) and 2,2'-azobis-4-methoxy-2. ,Four
-Dimethylvaleronitrile, other azo or diazo polymerization initiators; benzoyl peroxide, methyl ethyl ketone peroxide, isopropyl peroxycarbonate, other peroxide polymerization initiators and the like.

However, a benzoyl peroxide-based polymerization initiator or the like may have a bad influence on the preservability of the toner for decomposing and forming a carboxylic acid such as benzoic acid as a by-product.
In addition, it is preferable to use an azo-based polymerization initiator because it has a drawback that an aromatic odor is generated.

In the present invention, for the purpose of controlling the molecular weight and molecular weight distribution of the polymer, or for controlling the reaction time, it is preferable to use two or more of the above-mentioned polymerization initiators in combination in various compositions. Further, if necessary, a water-soluble initiator such as ammonium persulfate or potassium persulfate may be used in combination.

The amount of the polymerization initiator used is usually 0.1 to 20 parts by weight, preferably 1 to 10 parts by weight, based on 100 parts by weight of the polymerizable monomer. If the amount of the polymerization initiator is less than 0.1 parts by weight, the polymerization time will be long and the molecular weight of the polymerization product will be too high. On the other hand, if the polymerization initiator exceeds 20 polymerized parts, the molecular weight of the polymerized part becomes too low, which is not preferable.

In the present invention, the suspension polymerization reaction is usually carried out at a polymerization temperature of 50.
The temperature is set in consideration of the decomposition temperature of the polymerization initiator. If the set temperature is too high, a rapid decomposition of the polymerization initiator occurs, which affects the molecular weight and the like, which is not preferable.

A neutral salt such as sodium chloride or sodium sulfate may be added to the continuous phase (aqueous phase) for the purpose of preventing emulsification. Furthermore,
A thickener such as glycerin or ethylene glycol may be added for the purpose of preventing coalescence of the monomer composition particles formed in the granulation step.

〔Example〕

 Hereinafter, the present invention will be specifically described based on Examples.

<Example 1> 90 g of styrene, 10 g of n-butyl acrylate and 20 g of carbon black (# 40 manufactured by Mitsubishi Kasei Co., Ltd.) were mixed and dispersed for about 1 hour at room temperature using a paint conditioner, and then placed in a separable flask. After replacing with nitrogen gas for about 30 minutes,
Surface-treated carbon black was obtained by surface-treating carbon black with the above-mentioned polymerizable monomer at 100 ° C. or higher.

To the above monomer mixture, 5 g of 2,2'-azobisisobutyronitrile was added and dissolved to prepare a monomer composition.

Next, polyacrylic acid aqueous solution (manufactured by Wako Pure Chemical Industries, about 25%,
8000-12000cP) 8g, sodium sulfate 4g, distilled water 500
g was dissolved and added to a separable flask with a capacity of 1 L, the monomer composition prepared above was added, and the mixture was produced at 60 ° C. for about 20 minutes at 10000 rpm using a TK homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.). After granulating, the monomer composition was polymerized under conditions of 60 ° C. for 6 hours and then 80 ° C. for 1 hour using a turbine with a flat plate.

The polymer composition obtained above was cooled and filtered, and then washed with water until the washing liquid became neutral to obtain a slurry of polymerized toner.

A 10% aqueous methanol solution was added to the slurry of the polymerized toner, and the mixture was stirred and then filtered.

Furthermore, the concentration of methanol is 20%, 40%, 60%, 80%,
The above operation was repeated using an aqueous methanol solution having a concentration gradient of 100%. Finally, after removing the solvent using a centrifugal dehydrator, the polymerized toner of the present invention was obtained by leaving it at room temperature for one day and drying.

When the particle size of the obtained polymerized toner was measured using a Coulter counter (aperture 100 μm), the volume average particle size of the toner was 8.0 μm.

When this polymerized toner was observed with an optical microscope (450 ×), each particle of the toner showed a substantially completely spherical spherical shape, and uneven distribution of carbon black in the toner particle was not recognized. Further, the fluidity of this polymerized toner was excellent as compared with the polymerized toners obtained in Comparative Examples.

Further, using this toner, an image forming test was carried out under the conditions of room temperature of 30 ° C. and humidity of 80% RH using a commercially available copying machine (SF-8260, manufactured by Sharp Corporation), and an image with good density and image quality was obtained. Was given.

<Example 2> To the above-mentioned monomer mixture, 5 g of 2,2'-azobisisobutyronitrile was added and dissolved to prepare a monomer composition.

The suspension stabilizer was changed to the polyacrylic acid aqueous solution of Example 1, and polyvinyl alcohol (manufactured by Tokyo Kasei Co., polymerization degree about 2000,
Using the same saponification degree of about 80% and 2 g), the above monomer composition was treated in the same manner as in Example 1 to obtain a slurry of polymerized toner.

A 5% aqueous acetone solution was added to the slurry of the polymerized toner, and the mixture was stirred and then filtered.

Further, the above operation was repeated using an acetone aqueous solution having a gradient in the concentration of acetone such as 10%, 15% and 20%. Finally, after removing the solvent using a centrifugal dehydrator, the polymerized toner of the present invention was obtained by allowing to stand overnight at room temperature and drying.

When the particle size of the obtained polymerized toner was measured using a Coulter counter (aperture 100 μm), the volume average particle size of the toner was 8.0 μm.

When this polymerized toner was observed with an optical microscope (450 ×), each particle of the toner showed a substantially completely spherical spherical shape, and uneven distribution of carbon black in the toner particle was not recognized. Further, the fluidity of this polymerized toner was excellent as compared with the polymerized toners obtained in Comparative Examples.

Further, using this toner, an image forming test was carried out under the conditions of room temperature of 30 ° C. and humidity of 80% RH using a commercially available copying machine (SF-8260, manufactured by Sharp Corporation), and an image with good density and image quality was obtained. Was given.

<Example 3> The above monomer mixture was mixed and dispersed at room temperature for about 1 hour using a paint conditioner, and then 5 g of 2,2'-azobisisobutyronitrile was added and dissolved to prepare a monomer composition.

A slurry of polymerized toner was obtained from the monomer composition by the same operation as in Example 1.

A 10% aqueous methanol solution was added to the slurry of the polymerized toner, and the mixture was stirred and then filtered.

Furthermore, the concentration of methanol is 20%, 40%, 60%, 80%,
The above operation was repeated using an aqueous methanol solution having a concentration gradient of 100%.

At this time, in the above operation, a saturated aqueous solution of toluene was added to a solution having a methanol concentration of 100%, mixed and stirred to slightly swell the particle surface. Then, a saturated aqueous solution of toluene was removed with a large amount of methanol, and finally, the solvent was removed using a centrifugal dehydrator, and then spray drying was performed to obtain a polymerized toner of the present invention.

When the particle size of the obtained polymerized toner was measured using a Coulter counter (aperture 100 μm), the volume average particle size of the toner was 8.0 μm.

When the polymerized toner was observed with an optical microscope (450 ×), each particle of the toner showed a spherical shape, and the phthalocyanine pigment in the toner particle was uniformly dispersed and uneven distribution was not observed. Further, the fluidity of this polymerized toner was excellent as compared with the polymerized toners obtained in Comparative Examples.

Further, using this toner, an image forming test was carried out under the conditions of room temperature of 30 ° C. and humidity of 80% RH using a commercially available copying machine (SF-8260, manufactured by Sharp Corporation), and an image with good density and image quality was obtained. Was given.

<Comparative Example> Suspension polymerization was carried out in the same manner as in the method described in Example 1 to obtain a slurry of polymerized toner.

The polymerized toner slurry was thoroughly washed with water, dehydrated using a centrifugal dehydrator, and dried under reduced pressure at 40 ° C. overnight.

When the particle size of the obtained polymerized toner was measured using a Coulter counter (aperture 100 μm), the volume average particle size of the toner was 8.0 μm.

When the polymerized toner was observed with an optical microscope (450 ×), each particle of the toner showed a substantially completely spherical spherical shape, and uneven distribution of carbon black in the toner particles was not observed, but a commercially available copying machine ( Sharp, SF-
8260), the image formation test was conducted at room temperature of 30 ° C and humidity of 80% RH. As a result, the density and the image quality were deteriorated as the number of copies increased.

〔The invention's effect〕

The polymerized toner of the present invention, after polymerization, is subjected to repeated washing treatment with a mixed soot of a water-miscible organic solvent having a concentration gradient-water, and therefore has excellent fluidity, exhibits uniform triboelectricity, and has a high image density. A stable image can be given. Further, since the hydrophobicity of the surface of the polymerized toner particles is improved, it is possible to obtain a toner having improved storage stability and offset resistance.

Furthermore, it is possible to reduce the drying energy in the step of drying the polymerized toner.

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Claims (2)

[Claims] 1. A monomer composition containing at least a polymerizable monomer and a colorant is subjected to suspension polymerization, and the obtained polymerized toner is separated, and then a water-miscible organic solvent-water mixed solvent is added. A method for producing a polymerized toner, characterized in that the washing treatment is repeated with a concentration gradient in which the concentration of the water-miscible organic solvent is gradually increased. 2. A method for producing a polymerized toner, wherein a saturated aqueous solution of a non-water-miscible organic solvent is added to the water-miscible organic solvent-water mixed solvent of claim 1.