JPH103181A - Electrostatic charge image developing toner and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic charge image developing toner which is uniform in particle size, by using an arbitrary polymer contg. a polymer with which the pulverization of its particles is heretofore difficult, and an easy process for producing the same. SOLUTION: A binder resin and coloring agent are mixed in a solvent having solubility in water of <=1wt.%. The resulted compsn. is dispersed and suspended in an aq. medium in the presence of an inorg. dispersant coated with the polymer having a carboxyl group. Next, the resulted dispersion particles are heated to 91 to 150 deg.C or are subjected to a pressure reduction under 10 to 200mmHg at 0 to 50 deg.C, by which the solvent in the dispersion particles is removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic image developing toner used for developing an electrostatic latent image formed by an electrostatographic method or an electrostatic recording method, and a method for producing the same.

[0002]

2. Description of the Related Art There are conventionally known several methods for producing fine polymer particles containing a toner for developing an electrostatic image. Among them, there is a method of directly producing polymer fine particles by a polymerization reaction such as a suspension polymerization method, an emulsion polymerization method, a seed polymerization method or a dispersion polymerization method using a monomer as a starting material. However, polymer fine particles produced by these polymerization methods are difficult to remove residual monomers and surfactants, difficult to internally add insoluble materials such as colorants, charge control agents and release agents, There are problems such as that the type and particle size range are limited, and that it is necessary to study a particle formulation every time the material composition is changed.

[0003] There is also a method for producing polymer fine particles by making a polymer prepared in advance by polymerization into fine particles. Among them, the melt-kneading and pulverizing method is a method in which a coarsely pulverized polymer is pulverized using a fine pulverizer such as a mechanical rotary type or a jet type, and then classified to obtain fine polymer particles. This method is the most frequently used method for producing a toner for developing an electrostatic image, and the obtained polymer fine particles are irregular and have a nonuniform particle size. Has a problem that a classification step is required, and polyolefins and the like cannot be employed as a polymer used in these polymers because the particles are difficult to pulverize.

[0004] The dissolved polymer spray method is a method in which a polymer solution previously dissolved in a solvent is atomized to form particles, and the polymer fine particles produced by this method do not have a uniform particle size and a manufacturing apparatus. However, there are drawbacks such as an increase in size. The dissolved polymer precipitation method is a method in which a fine solvent is added to a polymer solution previously dissolved in a solvent, or a polymer solution previously heated and dissolved in a solvent is cooled to precipitate polymer fine particles. This method has problems that it is difficult to control the shape and it is difficult to select the type of polymer and the type of solvent for it. The molten polymer suspension method is a method of obtaining polymer fine particles by dispersing a heated and melted polymer in a medium heated to a temperature higher than its melting point and cooling the polymer. In such a case, pressurization is required, and if an oil system is used, there are problems that cleaning becomes difficult and shape control becomes difficult.

Further, the dissolved polymer suspension method (dissolved suspension method) is disclosed in JP-B-38-2095 and JP-B-61-2.
As disclosed in JP-A-8688 and JP-A-63-25664, a polymer solution (a toner composition mixed solution) previously dissolved in a solvent is dispersed in an aqueous medium, and this is heated or depressurized or the like. This is a method of forming particles by removing the solvent, and is considered to be the most suitable method for industrialization among the above-mentioned conventional methods. However, the above-mentioned dissolution suspension method is still insufficient in making the obtained polymer fine particles (toner for developing an electrostatic image) uniform in particle size. In addition, since it is necessary to provide a classification step after the particles are produced, the number of manufacturing steps is increased and the cost is increased.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances in the prior art.
That is, an object of the present invention is to provide an electrostatic charge image having a uniform particle size containing a polymer and a colorant without using a classification step, using any polymer including a polymer that has conventionally been difficult to pulverize. An object of the present invention is to provide a developing toner and a method for easily manufacturing the same.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies on a method for producing a toner for developing an electrostatic image containing a polymer and a colorant by a solution suspension method, and as a result, in the process of producing toner particles, By mixing the toner material with a specific solvent, suspending the resulting mixed solution in a specific aqueous medium, and then removing the solvent in the formed particles at specific temperature and / or pressure conditions, The inventors have found that the present invention is effective in producing a toner for developing an electrostatic charge image having a uniform particle size, and have completed the present invention.

That is, according to the method for producing a toner for developing an electrostatic image of the present invention, the binder resin and the colorant have a solubility in water of 1
Mixing in a solvent of not more than 1% by weight, dispersing and suspending the obtained composition in an aqueous medium in the presence of an inorganic dispersant coated with a polymer having a carboxyl group, and obtained dispersed particles Is heated to a temperature of 91 to 150 ° C. to remove the solvent in the dispersed particles. Another method for producing a toner for developing an electrostatic image according to the present invention is a method for preparing a binder resin and a colorant having a solubility in water of 1% by weight.
A step of mixing in the following solvent, a step of dispersing and suspending the obtained composition in an aqueous medium in the presence of an inorganic dispersant coated with a polymer having a carboxyl group, and The method is characterized by comprising a step of removing the solvent in the dispersed particles by reducing the pressure to 10 to 200 mmHg at a temperature of ５０50 ° C.

[0009]

Embodiments of the present invention will be described below in detail. In the present invention, in the first step (mixing step), a polymer and a colorant as a binder resin,
Further, it is necessary to appropriately mix a release agent, a charge control agent, and the like, which are usually added to toner particles, with a solvent having a solubility in water of 1% by weight or less.
The mixing may be carried out by melting and kneading a colorant, a release agent, a charge controlling agent, and the like in advance with the polymer, and then dissolving the polymer in a solvent having a solubility in water of 1% by weight or less. After being dissolved in a solvent having a solubility of 1% by weight or less in a solvent, a colorant, a release agent, a charge control agent, and the like are added to a ball mill.
Dispersion and mixing may be performed using a disperser containing a medium such as a sand mill or a high-pressure disperser. In this mixing step, the polymer may be mixed by any method, provided that the polymer is dissolved in a solvent having a solubility in water of 1% by weight or less.

The polymer used in the present invention has a solubility in water of not more than 1% by weight among any polymer including polymers which have been considered difficult to pulverize in the prior art. Any solvent can be used as long as it dissolves in a solvent.Specifically, styrene-acryl copolymer, polyester resin, ketone resin, epoxy resin, polyolefin resin and other thermoplastic resins known as binder resins for toners Is raised. Examples of the colorant used in the present invention include carbon black, magnetic powder, cyan, magenta, yellow and other known colorants for toner particles. As the release agent, polyethylene, low-molecular-weight polyolefins such as polypropylene, and other known release agents for toner particles are used. Further, as the charge control agent, a quaternary ammonium salt compound, other A known charge control agent for the toner particles is used.

In the present invention, the solubility in water is 1% by weight.
The following solvents need to be able to dissolve the polymer, ester solvents such as butyl acetate, ether solvents such as diisopropyl ether, toluene,
Hydrocarbon solvents such as benzene and cyclohexane, and halogenated hydrocarbon solvents such as dichloromethane, chloroform and trichloroethylene are used. Above all, the boiling point is 80 ℃ like cyclohexane and trichloroethylene
It is preferable to use the above solvents. Note that these solvents cannot be sufficiently removed if contained in particles under slow conditions such as normal temperature and normal pressure, so that aggregation of particles is likely to occur. The amount of the solvent used is such that the viscosity of the mixed solution of the toner composition is 1 to 10,000 mPa · s at 20 ° C. or 40 ° C., and particularly preferably 1 to 2,000 mPa · s. It is.

The second step of the present invention is a step of dispersing and suspending the mixed solution of the toner composition obtained in the above mixing step in an aqueous medium. In the dispersion suspension step, the mixed solution of the toner composition is dispersed and suspended in an aqueous medium using an apparatus capable of applying a strong shearing force. As this aqueous medium, it is necessary to use a dispersion of inorganic dispersant particles whose surface is coated in water. Inorganic dispersants include media-containing dispersers such as ball mills, ultrasonic dispersers,
Disperse in water using a high-pressure emulsifier or the like. As the water, ion-exchanged water, distilled water or pure water is usually used.

The inorganic dispersant used in the present invention is preferably a hydrophilic one. Specifically, silica, alumina,
Titania, calcium carbonate, magnesium carbonate, tricalcium phosphate, clay, diatomaceous earth, bentonite and the like can be mentioned, with calcium carbonate being particularly preferred. As these inorganic dispersants, those whose particle surfaces are coated with a polymer having a carboxyl group are used. By using an inorganic dispersant having the coating,
Particles can be stably manufactured. As the polymer having a carboxyl group used for coating the particle surface of the inorganic dispersant, the number average molecular weight by VPO method or the like is 1,
Typical examples thereof include acrylic acid resins, methacrylic acid resins, fumaric acid resins, maleic acid resins, and the like. Examples include homopolymers of monomers such as acrylic acid, methacrylic acid, fumaric acid, and maleic acid, copolymers of these, and copolymers of these with other vinyl monomers. Further, the carboxyl group may be a metal salt such as a sodium salt, a potassium salt, and a magnesium salt. These inorganic dispersants have an average particle diameter in the range of 1 to 1,000 nm,
Particularly preferably, it is in the range of 5 to 100 nm. Further, these inorganic dispersants are used in an amount of 1 to 500 parts by weight, preferably 10 to 300 parts by weight, based on 100 parts by weight of the toner.

The apparatus used in the second dispersion and suspension step, which can apply a strong shearing force, is not particularly limited as long as it is generally available as an emulsifier or disperser. , Homogenizer (IKA
Batch emulsifiers such as Polytron (Kinematica), TK Auto Homomixer (Toki Kika), Ebara Milder (Ebara Seisakusho), TK Pipeline Homomixer (Toki Kika Kogyo) Continuous emulsification such as colloid mill (manufactured by Shinko Pantech), slasher, trigonal wet pulverizer (manufactured by Mitsui Miike Kakoki), Cavitron (manufactured by Eurotec), fine flow mill (manufactured by Taiheiyo Kiko) Machine, Microfluidizer (manufactured by Mizuho Industries), Nanomizer (manufactured by Nanomizer), A
High pressure emulsifier such as PV Goulin (manufactured by Goulin Co.), membrane emulsifier such as membrane emulsifier (manufactured by Reika Kogyo), vibrating emulsifier such as Vibromixer (manufactured by Reika Kogyo), ultrasonic homogenizer (Branson) Ultrasonic emulsifiers and the like can be used.

[0015] The third step of the present invention is a step of removing the solvent in the dispersion suspension generated in the second dispersion suspension step. In this solvent removal step, (1) the dispersion suspension produced in the dispersion suspension step is heated to a temperature range of 91 to 150 ° C. and held for 1 to 6 hours, or (2) the dispersion suspension produced in the dispersion suspension step is produced. The dispersed suspension thus obtained is cooled at a temperature of 0 to 50 ° C. for 10 minutes.
By reducing the pressure to ~ 200 mmHg and maintaining the pressure for 1 to 6 hours, particles from which the solvent in the particles of the dispersion suspension has been removed can be easily obtained. In the third step, before, simultaneously with, or after the processing operation of (1) or (2),
If necessary, (3) water is added to the dispersion suspension produced in the dispersion suspension step, or (4) an inert gas is blown into the dispersion suspension produced in the dispersion suspension step, thereby dispersing. The treatment operation of removing the solvent in the particles of the suspension may be arbitrarily combined. The solvent is extracted from the toner droplets into the aqueous medium and evaporates from the surface of the dispersion suspension. In the case of (1), at 90 ° C. or lower, the partial pressure of the vapor pressure of the solvent becomes extremely small, and the solvent is removed. On the other hand, when the temperature is 151 ° C. or higher, the pressure for pressurizing the aqueous medium to suppress boiling is increased, which is not preferable. In the case of (2), if the pressure is 200 mmHg or more, the partial pressure of the vapor pressure of the solvent becomes extremely small, and it takes time to remove the solvent, which is not preferable. On the other hand, if it is 10 mmHg or less, the aqueous medium boils.

In the present invention, the following steps are further performed as necessary. First, this is a step of removing the aqueous medium from the fine particle suspension generated in the third solvent removing step, washing and dewatering. In this washing and dehydration step, the fine particle suspension generated in the solvent removal step is acid-treated to dissolve the inorganic dispersant, and then washed with water and dehydrated, but after the acid treatment, an alkali treatment is added. You may. Further, the next step is a step of drying, sieving, and externally adding. In these steps, the fine-particle cake generated in the dehydration step is dried, sieved, and externally added to obtain a toner for developing an electrostatic image. In these steps, drying, sieving, and external addition may be performed by any method as long as the method does not cause aggregation and pulverization of the toner.

[0017]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. In the following description, "parts" means "parts by weight". The particle size and distribution of the toner particles were measured using a Coulter Multisizer II (manufactured by Coulter Inc.). The particle size is a weight average particle size, and a measure of the breadth of the distribution is GSD (Geometric Sta.).
ndard Deviation), (weight 50% diameter)
/ (Weight 84% diameter). As this value approaches 1, the particle size becomes monodisperse. What is generally referred to as monodisperse particles has a GSD value of about 1.1.

Example 1 [Mixing process] 95 parts of trans-polyisoprene resin (crystallinity: 36%, glass transition point: -68 ° C, melting point: 67 ° C, manufactured by Kuraray Co.) carbon black (Cabot) 5 Part The above components were kneaded with a Banbury mixer (manufactured by Kobe Steel) to form a dispersion. 5 parts of this dispersion was treated with trichloroethylene (solubility in water at 20 ° C. 0.0011).
(% By weight) and stirred at 90 ° C. for 3 hours to obtain 100 parts of a mixed solution of the toner composition in which the trans-polyisoprene resin was dissolved. [Dispersion / suspension step] Calcium carbonate (average particle size: 80 μm) coated with an acrylic acid-maleic acid copolymer (number average molecular weight: 10,000) 10 parts Ion-exchanged water 100 parts The above components were introduced into an ultrasonic dispersing machine. Then, a solution produced by stirring this was used as an aqueous medium. The obtained aqueous medium 220
g with a homogenizer (manufactured by IKA) at 10,000.
While stirring at rpm, mixed solution 1 of the above polymer
Then, 00 g was slowly charged, and the mixture was stirred for 2 minutes, and then stopped to obtain 320 g of a dispersion suspension.

[Solvent Removal Step] The temperature of the dispersion suspension produced in the dispersion suspension step was raised to 95 ° C. with stirring, and then maintained at 95 ° C. for 6 hours, followed by cooling to room temperature. [Washing and Dehydration Step] To 200 g of the fine particle suspension obtained in the solvent removal step, 40 g of 10 N hydrochloric acid was added, and washing with ion-exchanged water was repeated four times by suction filtration, followed by dehydration. [Drying and Sieving Step] The fine particle cake obtained in the dehydration step was dried by a vacuum drier and sieved with a 45 μm mesh to obtain a toner for developing an electrostatic image. When copying was performed using the obtained toner, a clear quality image could be obtained. [Measurement] As a result of measuring the particle size of the toner particles obtained in the sieving step, the average particle size was 9.5 μm, and the GSD was 1.
It was 31.

Example 2 [Mixing step] Polypropylene resin (molecular weight: about 8,000, manufactured by Mitsui Petrochemical Co., Ltd.) 95 parts Carbon black (manufactured by Cabot) 5 parts The above components were kneaded with a Banbury mixer (manufactured by Kobe Steel). To obtain a dispersion. 5 parts of this dispersion was put into 95 parts of cyclohexane (solubility in water at 20 ° C .: 0% by weight), and the mixture was stirred at 70 ° C. for 3 hours to obtain a mixed solution of a toner composition in which a polypropylene resin was dissolved. 100 parts were obtained. [Dispersion and Suspension Step] Calcium carbonate (average particle size: 80 μm) coated with acrylic acid-maleic acid copolymer (number average molecular weight: 10,000) 10 parts Ion-exchanged water 100 parts The above components were introduced into an ultrasonic dispersing machine. Then, a solution produced by stirring this was used as an aqueous medium. The obtained aqueous medium 220
g with a homogenizer (manufactured by IKA) at 10,000.
While stirring at rpm, mixed solution 1 of the above polymer
Then, 00 g was slowly charged, and the mixture was stirred for 2 minutes, and then stopped to obtain 320 g of a dispersion suspension.

[Solvent Removal Step] The dispersion suspension produced in the dispersion suspension step was reduced in pressure to 40 mmHg at 20 ° C. while stirring, and the state of 40 mmHg was maintained for 6 hours. [Washing and Dehydration Step] To 200 g of the fine particle suspension obtained in the solvent removal step, 40 g of 10 N hydrochloric acid was added, and washing with ion-exchanged water was repeated four times by suction filtration, followed by dehydration. [Drying and Sieving Step] The fine particle cake obtained in the dehydration step was dried by a vacuum drier and sieved with a 45 μm mesh to obtain a toner for developing an electrostatic image. When copying was performed using the obtained toner, a clear quality image could be obtained. [Measurement] As a result of measuring the particle size of the toner particles obtained in the sieving step, the average particle size was 10 μm, and the GSD was 1.3.
It was 0.

Comparative Example 1 The same operation as in Example 1 was performed, except that the solvent removing step was changed as follows. [Solvent Removal Step] The temperature of the dispersion suspension produced in the dispersion suspension step was raised to 70 ° C. while stirring, and then the temperature was maintained at 70 ° C. for 6 hours, followed by cooling to room temperature. In this case, since the solvent was not completely removed in the solvent removing step, when hydrochloric acid was added in the next step, the toner particles aggregated.

Comparative Example 2 The same operation as in Example 2 was performed, except that the solvent removal step was changed as follows. [Solvent Removal Step] The dispersion suspension generated in the dispersion suspension step was reduced in pressure to 400 mmHg at 20 ° C. while stirring.
The state of 00 mmHg was maintained for 6 hours. In this case, since the solvent was not completely removed in the solvent removing step, when hydrochloric acid was added in the next step, the toner particles aggregated.

Comparative Example 3 A conventional melt-kneaded and pulverized toner,
0 (manufactured by Fuji Xerox Co., Ltd.), the particle size distribution was measured. As a result of measuring the particle size of the toner particles, the average particle size was 10.3 μm.
SD was 1.39.

[0025]

According to the method of the present invention, an arbitrary polymer including a polymer that has been difficult to pulverize in a conventional method can be used without classifying compared with a toner obtained by a conventional melt-kneading pulverization method. With a simple operation, it is possible to easily form a toner for developing an electrostatic image having a narrow particle size distribution and a uniform particle size.

Claims (4)

[Claims] 1. A binder resin and a coloring agent having a solubility in water of 1
Mixing in a solvent of not more than 1% by weight, dispersing and suspending the obtained composition in an aqueous medium in the presence of an inorganic dispersant coated with a polymer having a carboxyl group, and obtained dispersed particles Wherein the solvent in the dispersed particles is removed by heating the toner to a temperature of 91 to 150 ° C. 2. A binder resin and a coloring agent having a solubility in water of 1
Mixing in a solvent of not more than 1% by weight, dispersing and suspending the obtained composition in an aqueous medium in the presence of an inorganic dispersant coated with a polymer having a carboxyl group, and obtained dispersed particles At a temperature of 0 to 50 ° C. and 10 to 200 mmH
g. A method for producing a toner for developing an electrostatic image, comprising a step of removing the solvent in the dispersed particles by reducing the pressure to g. 3. An electrostatic image developing toner comprising particles obtained by the production method according to claim 1. 4. An electrostatic image developing toner comprising particles obtained by the production method according to claim 2.