JPH09230626A - Toner for development of electrostatic charge image and manufacture of toner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To establish a manufacturing method for a toner for electrostatic charge image development, which can easily control the form of particles amorphous and make uniform the particle size. SOLUTION: Polymer and pigment are mixed with a solvent A which can be dissolved in water to a minor extent, and the obtained composition is dispersed in an aqueous medium containing inorganic dispersing agent, and thereupon either water is added to the suspension liquid prepared in this manner or a medium B soluble both in the waterand solvent A is added so as to remove the solvent A from oil drops. Thus a toner for electrostatic charge image development having amorphous form is manufactured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner for developing an electrostatic image containing a polymer and a colorant 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 using a monomer as a starting material and performing a polymerization reaction such as a suspension polymerization method, an emulsion polymerization method, a seed polymerization method or a dispersion polymerization method. However, in the polymer fine particles produced by these polymerization methods, it is difficult to remove the residual monomer and the surfactant, it is difficult to internally add the insoluble material, and the kind and particle size range of the obtained polymer are limited. There is a drawback of.

There is also a method of producing fine polymer particles by making fine particles of a polymer prepared by polymerization in advance. Among them, the melt-kneading and pulverization method is a method in which a polymer that has been coarsely pulverized in advance is pulverized by using a fine pulverizer such as a mechanical rotary type or a jet type and then classified to obtain polymer fine particles. This method is the most widely used method for producing toner at present, and the polymer fine particles obtained have drawbacks such as non-uniform particle size.

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 production apparatus. Has the drawback of becoming larger. The dissolved polymer precipitation method is a method of precipitating polymer particles by adding a poor solvent to a polymer solution previously dissolved in a solvent or by cooling a polymer solution previously heated and dissolved in a solvent. This method has drawbacks such as difficulty in controlling the shape and selection of polymer species and solvent species. The molten polymer suspension method is a method of obtaining polymer particles by dispersing and cooling a heat-melted polymer in a medium heated to a temperature higher than its melting point. In this method, in most cases, the medium is an aqueous medium. However, there are drawbacks such as the need for pressurization and the difficulty of cleaning and the difficulty of controlling the shape of the oil type.

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 (toner solution) previously dissolved in a solvent is dispersed in an aqueous medium, and the solvent is removed by heating or reducing pressure. By doing
It is a method of forming particles, and among the conventional methods described above,
It is considered to be the most suitable method for industrialization. However, the above-mentioned dissolution suspension method is still not sufficient in controlling the shape of the obtained polymer fine particles and making the particle diameter uniform.

[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 use a mixed solution containing a polymer and a colorant to easily control the shape of the fine particles and make the particle diameter uniform, and a toner for developing an electrostatic latent image and a method for producing the same. To provide.

[0007]

DISCLOSURE OF THE INVENTION The inventors of the present invention have diligently studied a method for producing a toner for developing an electrostatic charge image containing a polymer and a colorant by a dissolution suspension method, and as a result, control the shape of those particles. In the process, (1) it is effective to control the shape of the particles by adding excess water to the dispersion suspension obtained in the suspension process to extract all the solvent in the oil droplet particles. And (2)
By adding a solvent that is soluble in both water and a solvent that is slightly soluble in water to the dispersion suspension obtained in the suspension step and extracting all the solvent in the oil droplet particles, the shape of the particles can be made uniform. The inventors have found that it is effective for controlling to a fixed form, and completed the present invention.

That is, the method for producing a toner for developing an irregular electrostatic image according to the present invention comprises a step of mixing a polymer and a colorant in a solvent A which is slightly soluble in water, and the obtained composition containing an inorganic dispersant. The method is characterized by having a step of dispersing in an aqueous medium and a step of adding water to the obtained mixed liquid to remove the solvent A. Further, another method for producing the toner for developing an irregular electrostatic image of the present invention is the solvent A slightly soluble in water.
To a polymer and a colorant, a step of dispersing the obtained composition in an aqueous medium containing an inorganic dispersant, and a solvent B dissolved in both the water and the solvent A in the obtained mixed solution.
Is added to remove the solvent A.

[0009]

Embodiments of the present invention will be described below in detail. The method for producing the toner for developing an irregular electrostatic image according to the present invention will be described. In the present invention, in the first step, a polymer and a colorant, and a release agent and a charge control agent which are usually added to toner particles are appropriately blended with a solvent A which is slightly soluble in water. is required. The blend may be a polymer in which a colorant, a release agent, a charge control agent, and the like are melt-kneaded in advance, or after the polymer is melted, a media-containing disperser such as a ball mill or a sand mill may be used. It may be dispersed and used. In this mixing step, mixing may be carried out by any method as long as the polymer is dissolved in a solvent which is slightly soluble in water.

The polymers used in the present invention include styrene-acrylic copolymers, polyester resins, ketone resins, epoxy resins, polyolefin resins and other known thermoplastic resins used as binder resins for toners for developing electrostatic images. Resin can be used. 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, low molecular weight polyolefins such as polyethylene and polypropylene, and other known release agents for toners for developing electrostatic images can be used. Further, as the charge control agent, a quaternary ammonium salt compound and other known compounds for toners for developing electrostatic image can be used.

In the present invention, as the solvent A which is slightly soluble in water (hereinafter, simply referred to as “solvent A”), a solvent having a solubility in water of about 0 to 30% by weight is used.
Specifically, methyl acetate, ethyl acetate, ester solvents such as propyl acetate, ether solvents such as diethyl ether, methyl ethyl ketone, methyl isopropyl ketone,
A ketone-based solvent such as methyl isobutyl ketone, a hydrocarbon-based solvent such as toluene, a halogenated hydrocarbon-based solvent such as dichloromethane, chloroform, trichloroethylene or the like is used. When water is used as a solvent and shape control is performed by solvent extraction, the solvent A used has a solubility in water of about 0.5 to 30% by weight.
When a shape other than water is used as a solvent and the shape is controlled by solvent extraction, the solvent A has a proportion of 0 in water.
About 30% by weight is used. Of these solvents, those having a water-soluble ratio of about 0 to 30% by weight are preferable for industrialization, and ethyl acetate is particularly preferable in consideration of safety and productivity.

The second step of the present invention is a step of dispersing and suspending the toner mixture mixed solution obtained in the above mixing step in an aqueous medium. In this dispersion and suspension step, the toner formulation mixed solution is dispersed and suspended in the aqueous medium using an apparatus capable of imparting a strong shearing force. As the aqueous medium in the present invention, it is necessary to use one in which an inorganic dispersant is dispersed in water. The inorganic dispersant is dispersed in water by using a media-containing disperser such as a ball mill or an ultrasonic disperser. As the inorganic dispersant, hydrophilic ones are preferable, and specifically, silica, alumina, titania, calcium carbonate, magnesium carbonate, tricalcium phosphate, clay, diatomaceous earth, bentonite and the like can be used. In particular, calcium carbonate, magnesium carbonate,
Tricalcium phosphate is preferred. As these inorganic dispersants, those having an average particle diameter in the range of 10 to 1000 nm are used, and particularly preferably in the range of 20 to 500 nm. Further, these inorganic dispersants are used in the range of 1 to 500 parts by weight, and particularly preferably in the range of 1 to 300 parts by weight, relative to 100 parts by weight of the toner.

In the present invention, the surface of the particles of these inorganic dispersants is preferably coated with a polymer having a carboxyl group, and the coating enables stable production of the particles. As the polymer having a carboxyl group, a polymer having a number average molecular weight of about 1,000 to 200,000 according to the VPO method or the like can be used. If the molecular weight is higher than this, the adherence to the surface of the suspended particles is too strong to be embedded in the particles, and if the molecular weight is too low, the contribution to the dispersibility is reduced. Specific examples of the polymer having a carboxyl group used in the present invention include acrylic acid-based resins, methacrylic acid-based resins, fumaric acid-based resins, maleic acid-based resins, and the like, which constitute these. Homopolymers of monomers such as acrylic acid, methacrylic acid, fumaric acid, maleic acid and the like and copolymers thereof with other vinyl monomers can also be used.
Further, the carboxyl group may be a metal salt such as a sodium salt, a potassium salt, and a magnesium salt.

The device for applying a strong shearing force used in the second dispersion / suspension step is not particularly limited as long as it is commercially available as an emulsifying machine or a dispersing machine. , Homogenizer (IKA
Company), Polytron (Kinematica), TK Auto Homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.), batch type emulsifier, Ebara Milder (manufactured by EBARA CORPORATION), TK Pipeline homomixer (Tokushu Koki Kogyo) Co., Ltd.), colloid mill (Shinko Pantech Co., Ltd.), slasher (Mitsui Miike Kakoki Co., Ltd.), trigonal wet milling machine, Cavitron (Eurotec Co., Ltd.), fine flow mill (Pacific Machine Co., Ltd.), etc. Type emulsifier, high pressure emulsifier such as Microfluidizer (manufactured by Mizuho Industry Co., Ltd.), Nanomizer (manufactured by Nanomizer Co., Ltd.), APV Goulin (manufactured by Gorin Co., Ltd.), film emulsifier such as membrane emulsifier (manufactured by Chilling Industry Co., Ltd.) Examples thereof include a vibrating emulsifier such as a Vibro mixer (manufactured by Cryogenic Industry Co., Ltd.) and an ultrasonic emulsifier such as an ultrasonic homogenizer (manufactured by Branson).

The third step of the present invention is a step of controlling the shape of the particles, and the solvent in the dispersion suspension produced in the dispersion suspension step is removed. In this shape control step, water is added to the dispersion suspension obtained in the dispersion suspension step in an amount equal to or more than that necessary for extracting all the solvent in the oil droplet particles, or in the dispersion suspension step. The solvent in the particles of the dispersion suspension is removed by adding the solvent B, which is soluble in both water and the solvent, to the dispersion suspension thus obtained. It is removed from the particles by extraction into a mixture of solvents. In the present invention, when excess water or solvent B is added to the dispersion suspension, the solvent A in the droplet is extracted at a high speed. At this time, the volume of the particles shrinks, but it is considered that the inorganic dispersant on the surface of the particles remains and forms an uneven shape.

In the present invention, as the solvent B which is soluble in both water and solvent A, methanol, ethanol, 1-
Propanol, t-butyl alcohol, acetone or the like is used. The solvent in the oil droplet particles is all the water extracted,
Alternatively, the amount of the solvent B dissolved in both water and the solvent A is preferably about 20 times or more that of the dispersion suspension as in the known method used for reprecipitation of a general polymer.
In particular, it is preferable to use water as the water-based medium or water-based solvent, because the particle size becomes uniform when water is used. When water is used, ion exchange water, distilled water or pure water is generally used.

In the present invention, the following steps are carried out if necessary. First, there is a step of removing and washing the aqueous medium from the product obtained through the above steps. In this washing step, the toner particle suspension generated in the previous step (third step) is treated with an acid to dissolve the inorganic dispersant, and then washed with water, but an alkali treatment is added after the acid treatment. May be.
Further, the next step is a step of dehydration, drying, sieving and external addition. In these steps, the dispersion suspension produced in the previous step is dehydrated, dried, sieved and externally added to obtain a toner for developing an electrostatic image. In these steps, any method may be used for dehydration, drying, sieving and external addition as long as the toner does not cause aggregation. Further, as the external additive, a fluidizing agent such as silica, titania, and alumina having an average particle diameter of 5 to 50 nm, resin fine particles such as styrene, methyl methacrylate, and vinylidene fluoride of 0.05 to 5 μm, and cerium oxide, A cleaning aid such as molybdenum sulfide, an abrasive, a lubricant or the like can be used.

[0018]

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". A Coulter Multisizer II (manufactured by Coulter, Inc.) was used to measure the particle size and distribution of the particles. The particle size is the weight average particle size, and the scale of the distribution is
GSD (Geometrical Standard)
Deviation) (weight 50% diameter) / (weight 84%
(Diameter). As this value approaches 1, the particle size becomes monodisperse. What is generally called monodisperse particles is GSD
The value is around 1.1. The shape of the obtained particles was observed with a scanning electron microscope (SEM).

Example 1 [Mixing step] Styrene-n-butyl acrylate resin 90 parts (copolymerization ratio 77:23, Mn = 14000, Mw = 26000, prepared by solution polymerization) Carbon black (manufactured by Cabot) 5 parts Polypropylene (Molecular weight: about 8,000, manufactured by Mitsui Petrochemical Co., Ltd.) 5 parts The above components were kneaded with a Banbury mixer (manufactured by Kobe Steel) to give a dispersion. 100 parts of this dispersion was put into 400 parts of ethyl acetate, and this was stirred at 20 ° C. for 2 hours to obtain 500 parts of a toner formulation mixed solution in which a styrene-n-butyl acrylate resin was dissolved.

[Dispersion and Suspension Step] Calcium carbonate coated with an acrylic acid-maleic acid copolymer (number average molecular weight 4000) (average particle diameter 80 nm, manufactured by Maruo Calcium Co., Ltd.) 10 parts Ion-exchanged water 100 parts The solution was introduced into an ultrasonic disperser and stirred to form a solution as an aqueous medium. The obtained aqueous medium 220
g with a homogenizer (manufactured by IKA) at 10,000 r.
While stirring at pm, 100 parts of the above polymer mixed solution
g was slowly added, the mixture was stirred for 2 minutes after the addition, and then stopped to obtain 320 g of a dispersed suspension solution.

[Shape Control Process] 30 g of the dispersion suspension produced in the dispersion suspension process is used in an amount of ion-exchanged water 57 which is more than the amount necessary to extract all the ethyl acetate in the oil droplet particles.
Add 0 g and dilute to 1/20 and stir at room temperature for 10
It was kept for a minute to obtain 600 g of a toner suspension. [Washing Step] 40 g of 10 N hydrochloric acid was added to 600 g of the fine particle suspension obtained in the above shape control step, and washing with ion-exchanged water by suction filtration was repeated 4 times. [Drying Step] The fine particle cake obtained in the washing step was crushed with a vacuum dryer and sieved with a 45 μm mesh to obtain a toner for developing an electrostatic charge image. The shape of the obtained toner is shown in FIG.

Example 2 The same operation as in Example 1 was carried out except that the shape control process was changed as follows. The shape of the obtained toner is shown in FIG. [Shape Control Process] To 30 g of the dispersion suspension generated in the dispersion suspension process, 570 g of methanol dissolved in both water and ethyl acetate was added and diluted to 1/20, and the mixture was stirred at room temperature and kept for 10 minutes. Then, 600 g of a toner suspension was obtained.

Comparative Example 1 The same operation as in Example 1 was carried out except that the shape control process was changed as follows. The shape of the obtained toner is shown in FIG. [Shape Control Step] 240 g of the dispersion suspension produced in the dispersion suspension step was heated to 50 ° C. with stirring and held for 2 hours, and then cooled to obtain 240 g of a toner suspension. Comparative Example 2 A general melt-kneading and pulverizing toner, which is Vivace 40
The shape and particle size distribution of the toner used in No. 0 (manufactured by Fuji Xerox Co., Ltd.) were measured.

Table 1 shows the measurement results of the polymer-containing toner fine particles obtained in each of the above Examples and Comparative Examples.

[Table 1]

[0025]

According to the present invention, the shape of the toner particles for developing an electrostatic charge image can be easily controlled to a desired irregular shape by a simple operation, and the toner particles can be controlled to have a desired amorphous shape as compared with the conventional pulverization method. In addition, it is possible to easily form the toner for developing an irregular electrostatic image having a narrow particle size distribution.

[Brief description of drawings]

1 is an electron micrograph showing the shape of a toner for developing an electrostatic charge image obtained by the manufacturing method of Example 1. FIG.

2 is an electron micrograph showing the shape of the toner for developing an electrostatic charge image obtained by the manufacturing method of Example 2. FIG.

3 is an electron micrograph showing the shape of a toner for developing an electrostatic charge image obtained by the manufacturing method of Comparative Example 1. FIG.

Claims (3)

[Claims] 1. A step of mixing a polymer and a colorant in a solvent A which is slightly soluble in water, a step of dispersing the obtained composition in an aqueous medium containing an inorganic dispersant, and a water mixture in the obtained mixed solution. A method for producing a toner for developing an irregular electrostatic image, comprising the step of adding the solvent A to remove the solvent A. 2. A step of mixing a polymer and a colorant in a solvent A which is slightly soluble in water, a step of dispersing the obtained composition in an aqueous medium containing an inorganic dispersant, and a mixed solution obtained by adding water to the mixture. And a solvent B which is soluble in both the solvent A and the solvent A, and the step of removing the solvent A is included. 3. A toner for developing an amorphous electrostatic image, which is obtained by the manufacturing method according to claim 1.