JPH04303849A - Production of resin particles - Google Patents

Abstract

PURPOSE:To produce resin particles of several to several ten mum uniform particle size from an emulsion by utilizing phase inversion phenomenon. CONSTITUTION:An aq. soln. optionally contg. an auxiliary emulsifier is added to a resin soln. contg. a hydrophobic solvent as a medium and having 50cPs viscosity. Phase inversion is caused, an oil-in-water type emulsion is prepd. and the solvents in the solns. are removed to produce resin particles of 3-8mum average particle size.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing resin particles, and more particularly to a method for producing resin particles such as toner particles used in copying machines.

0002

[Prior Art] Methods using suspension polymerization or emulsion polymerization are known as methods for producing fine resin particles with relatively uniform particle sizes, but the types of monomers that can be used are limited. The types of resin particles that can be obtained are limited. As a method of obtaining various resin particles without such problems, there is a method of obtaining an emulsion formed by dispersing or emulsifying a resin solution in a solution that is incompatible with the resin solution.

However, even if an emulsion is simply formed by dispersing and emulsifying a resin solution in a dispersion solvent, the resulting resin particles tend to have a wide particle size distribution and are likely to generate fine powder. be. As a technique to solve such problems, for example, Japanese Patent Publication No. 61-28688
However, strict settings of various conditions are required, and resin particles having a uniform particle size cannot be easily obtained.

0004

SUMMARY OF THE INVENTION The present invention was made in view of the above circumstances, and relates to a method for producing resin particles from an emulsion. It is an object of the present invention to provide a method for obtaining resin particles having a uniform diameter.

[0005]

[Means for Solving the Problems] That is, the present invention involves adding an aqueous solution II to a resin solution I using a hydrophobic solvent as a medium to cause a phase inversion, forming an O/W emulsion, and then forming an O/W emulsion. The present invention relates to a method for producing resin particles by removing the solvent of solution II and producing resin particles.

In the present invention, first, a solution (hereinafter referred to as "solution I") in which a resin etc. of a specific viscosity is dissolved and an aqueous solution (hereinafter referred to as "solution II") which may contain an emulsification aid are prepared. do.

The resin that can be made into granules by the method of the present invention is not particularly limited as long as it is insoluble in the aqueous solution II. Therefore, most resins can be used depending on the desired purpose as long as there is a solvent that can dissolve the resin and has the following properties. For example, when producing toner particles using the present invention, styrene resins, ester resins, styrene-acrylic resins, etc., which are known as toner constituent resins, may be used.

The solvent used in solution I is selected to be one that dissolves the desired resin and is substantially insoluble in aqueous solution II. Furthermore, when removing the solvent by heating in the final step of the present invention, it is preferable to use a solvent that has a melting point lower than the melting point of the resin used and lower than the boiling point of the aqueous solvent of Solution II. Even if the boiling point is slightly higher than that of the aqueous solvent of II, it can be used because it is azeotropic. Specific examples of solvents that can be used in solution I are hydrocarbons such as hexane, cyclohexane, benzene, tetralin, etc., halogenated hydrocarbons such as chloroform, carbon tetrachloride, methylene chloride, etc. A mixed solvent of these may also be used.

Solution I is prepared by dissolving 5 to 50% by weight, preferably 10 to 40% by weight, of the desired resin in the above-mentioned solvent, and maintaining the temperature at the time of emulsion preparation, preferably 5 to 30°C.
, more preferably viscosity at 15 to 25°C (hereinafter referred to as “cp
) is 50 cp or less, preferably 3 to 30 cp,
More preferably, it is 5 to 20 cp. This viscosity may be tentatively indicated, for example, as a viscosity of 23°C. The viscosity of this solution I is made higher than that of solution II, which will be described later. Preferably 1 to 20 cp, more preferably 2 to 15 cp
Make it expensive. If a solution adjusted to have a viscosity outside the above range is used, fine powder is likely to be generated in the resin particles that are the final product.

Various additives can be added to the solution I depending on the use of the resin particles. For example, when the purpose is to prepare a toner, a colorant, a charge control agent and other desired additives may be added. may be added in a predetermined amount.

Next, the preparation of solution II will be explained. Solution II is a solvent that is incompatible with solution I, typically water or an aqueous solution of an emulsification aid. A hydrophilic solvent such as methanol, ethanol, isopropanol, acetone, etc. may be used in combination. In addition, a charge control agent,
If it is desired to attach or coat a colorant, antioxidant, etc., these components may be dissolved and used. Examples of emulsification aids include surfactants and dispersion stabilizers. Surfactants contribute to stabilizing the emulsion after phase inversion. As the surfactant, ionic surfactants are particularly preferred.

Examples of the ionic surfactant include anionic surfactants such as carboxylic acid salts, sulfuric acid ester salts, sulfonic acid salts, and phosphoric acid ester salts, or primary amine salts,
Examples include cationic surfactants such as secondary amine salts, tertiary amine salts, and quaternary ammonium salts. The amount added is 0.5 to 3% by weight of solution II, preferably 1 to 2%.
Weight%. If the amount is less than 0.5% by weight, the emulsion after phase inversion becomes unstable. If the amount is more than 3% by weight, problems such as bubbling of the solution will occur.

The dispersion stabilizer applies heat to the emulsion after the phase inversion, evaporates the solvent from the droplets of the resin solution, and contributes to stabilizing the suspension state (solid-liquid). Preferred dispersion stabilizers are polymeric dispersion stabilizers. Examples of the polymeric dispersion stabilizer include methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, carboxymethylcellulose, polyvinyl alcohol, and gum arabic. The amount added is 0.1 to 10% by weight of solution II, preferably 0.5 to 5% by weight. When the amount is less than 0.1% by weight, it does not contribute to stabilization, and when it is more than 10% by weight, there is a problem that the viscosity of the solution becomes too high.

Solution II has a lower viscosity than solution I. Preferably it is 1 to 20 cp, more preferably 1 to 10 cp. Solution II is used in combination with solution I in which the difference in viscosity is 10 cp or less, preferably 10 cp or less. If the difference is greater than 20 cp, vigorous high-speed stirring is required to obtain the desired particle size, which places high shear forces on the solution and forms an emulsion with a broad particle size distribution. As a result, the resulting resin particles contain a large amount of fine powder. Note that the viscosity of both may be the same.

Solution I obtained as described above is added to solution II while stirring. At the beginning of the addition, solution I is
It becomes turbid and dispersed in the form of particles in I. The state is shown in FIG. In FIG. 1, solution I corresponds to a water droplet, and solution II corresponds to an oil phase. As the addition progressed and the amount of solution II increased, both phases passed through the states shown in Figures 2 and 3, a phase inversion phenomenon occurred, and finally the droplets of solution I became emulsified in solution II. The state shown in FIG. 4 is reached. The amount of solution II added, stirring conditions, temperature conditions, the size of each viscosity of solutions I and II, the viscosity difference between both solutions, etc. are such that the particle size of solution I after phase inversion is 1 to 15 μm, preferably 2 to 10 μm, More preferably, the thickness is adjusted to 3 to 8 μm. Usually solutions I and I
The ratio of I is 100 parts by weight of the former to 100 to 5 parts by weight of the latter.
00 parts by weight, more preferably 100 to 300 parts by weight. The emulsion creation temperature is room temperature, usually 5 to 35°C.
Preferably it is 15-25°C. According to the present invention, by using Solution I and Solution II as described above, it becomes easy to prepare an emulsion with relatively uniform particle size. Phase inversion may be carried out by increasing the amount of solution II added, or by changing the temperature of the emulsion, separately adding a surfactant with a high HLB, or adding a hydrophilic solvent. It's okay.

To obtain resin particles from an emulsion, the emulsion obtained as described above is heated to a temperature above the boiling point of solution I and below the boiling point of solution II, or heated to the azeotropic temperature of both, and then The solvent is removed from the resin solution particles. Removal of the solvent results in a suspension of resin particles in solution II. By separating the resin particles from solution II by means such as filtration, washing with a solvent that does not dissolve the resin, and drying, it is possible to obtain resin particles having a uniform particle size with an average particle size of several μm to 9 μm. The present invention will be explained below with reference to Examples.

Example 1 Polyester resin (Mn:
2980, Mw/Mn: 3.4) was dissolved to obtain a solution with a viscosity of 9.3 cp. The resulting solution will be referred to as Solution I. 100 parts by weight of distilled water, 2 parts by weight of polyvinyl alcohol (2% aqueous solution; viscosity 15 cp) and 2 parts by weight of sodium laurate were mixed to obtain a solution with a viscosity of 4.1 cp. The resulting solution will be referred to as Solution II.

Note that the viscosity is a value measured at 230C using an Ostwald viscometer. The viscosities described below also indicate similar measured values unless otherwise specified.

[0019] With a homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.),
Solution II was gradually added to 50 parts by volume of solution I while stirring at 00C and 4000 rpm. Phase inversion occurred upon addition of 100 parts by volume of solution II. At that point, addition of Solution II was stopped and stirring continued for an additional 10 minutes. After the stirring was completed, the obtained dispersion was poured into distilled water. The system was stirred at about 500 rpm while maintaining the temperature at 500C to evaporate methylene chloride.

Subsequently, the particles in the aqueous solution were filtered out. Further washing was repeated to wash away dispersion stabilizers and the like adhering to the particle surfaces. The obtained particles were vacuum dried to obtain resin particles.

Example 2 Polyester resin (Mn:
2980, Mw/Mn: 3.4) was dissolved to obtain a solution with a viscosity of 9.3 cp. This solution will be referred to as Solution I. 100 parts by weight of distilled water, 1 part by weight of methyl cellulose (2% aqueous solution; viscosity 15 cp) and 1 part by weight of sodium laurate were mixed to obtain a solution with a viscosity of 5.8 cp. This solution will be referred to as solution II.

Resin particles were obtained in the same manner as in Example I except that Solution I and Solution II were used.

Comparative Example 1 Resin particles were prepared in the same manner as in Example 1, except that the order of adding Solution II to Solution I was changed to the order of adding Solution I to Solution II. That is, with a homo mixer (manufactured by Tokushu Kika Kogyo Co., Ltd.), 200C, 400
50 parts by volume of solution II stirring at 0 rpm
100 parts by volume of Solution I were slowly added to the mixture. After the addition was complete, stirring was continued for an additional 10 minutes. After the stirring was completed, the obtained dispersion was poured into distilled water. The system was stirred at about 500 rpm while maintaining the temperature at 500C to evaporate methylene chloride.

[0024] Subsequently, the particles in the aqueous solution were filtered out. Further washing was repeated to wash away dispersion stabilizers and the like adhering to the particle surfaces. Vacuum dry the obtained particles,
Resin particles were obtained.

Comparative Example 2 Solutions I and II similar to those used in Example 2 were prepared. 50 parts by volume of Solution I and 100 parts by volume of Solution II were placed in a beaker at the same time and stirred for 10 minutes at 200C and 4000 rpm using a homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.). After the stirring was completed, the obtained dispersion was poured into distilled water. The system was stirred at about 500 rpm while maintaining the temperature at 500C to evaporate methylene chloride.

[0026] Subsequently, the particles in the aqueous solution were filtered out. Further washing was repeated to wash away dispersion stabilizers and the like adhering to the particle surfaces. The obtained particles were vacuum dried to obtain resin particles.

Example 3 Methylene chloride
400 parts by weight polyester resin
100 parts by weight
(Mn: 2980, Mw/Mn: 3.4, Softening point:
1030C, Tm: 580C) Phthalocyanine pigment
5 parts by weight Charge control agent: Bontron (P-51): (manufactured by Orient Chemical Co., Ltd.)
3 parts by weight of the above materials were mixed and uniformly dispersed and dissolved. The resulting solution will be referred to as Solution I. Solution I has a viscosity of 10.2 cp
Met.

Distilled water
100
Part by weight Polyvinyl alcohol (degree of polymerization approximately 500)
2 parts by weight Sodium laurate
2 parts by weight of the above materials were mixed and uniformly dissolved. The obtained solution will be referred to as solution II. Solution II
had a viscosity of 4.1 cp.

[0029] Homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.)
Solution II was slowly added to 50 parts by volume of solution I while stirring at 0C and 4000 rpm. When 100 parts by volume of solution II was added, a phase inversion occurred. At that point, the addition of Solution II was stopped and stirring continued for an additional 10 minutes. After the stirring was completed, the obtained dispersion was poured into distilled water. The system was stirred at about 500 rpm while maintaining the temperature at 500C to evaporate methylene chloride.

Subsequently, the particles in the aqueous solution were filtered out. Further washing was repeated to wash away dispersion stabilizers and the like adhering to the particle surfaces. The obtained particles were vacuum dried to obtain a toner.

Example 4 Methylene chloride
400 parts by weight polyester resin
100 parts by weight
(Mn: 2980, Mw/Mn: 3.4, Softening point:
1030C, Tm: 580C) Phthalocyanine pigment
5 parts by weight Charge control agent: Bontron (P-51): (manufactured by Orient Chemical Co., Ltd.)
3 parts by weight of the above materials were mixed and uniformly dispersed and dissolved. The resulting solution will be referred to as Solution I. Solution I has a viscosity of 10.2 cp
Met.

Distilled water
100
Parts by weight Methyl cellulose (2% aqueous solution; 15 cp
1 part by weight Sodium lauryl sulfate
2 parts by weight of the above materials were mixed and uniformly dissolved. The resulting solution will be referred to as Solution II. Solution II had a viscosity of 5.8 cp.

Toner particles were obtained in the same manner as in Example I except that Solution I and Solution II were used.

Comparative Example 3 A toner was prepared in the same manner as in Example 3, except that the order of adding Solution II to Solution I was changed to the order of adding Solution I to Solution II.

That is, 100 parts by volume of Solution I was heated at 200C and 4000C in a homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.).
It was slowly added to 50 parts by volume of solution II while stirring under rpm conditions. After the addition was complete, stirring was continued for an additional 10 minutes. After the stirring was completed, the obtained dispersion was poured into distilled water. The system was stirred at about 500 rpm while maintaining the temperature at 500C to evaporate methylene chloride.

Subsequently, the particles in the aqueous solution were filtered out. Further washing was repeated to wash away dispersion stabilizers and the like adhering to the particle surfaces. Vacuum dry the obtained particles,
Toner particles were obtained.

Comparative Example 4 Solutions I and II similar to those used in Example 4 were prepared. 50 parts by volume of Solution I and 100 parts by volume of Solution II were placed in a beaker at the same time and stirred for 10 minutes at 200C and 4000 rpm using a homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.). After the stirring was completed, the obtained dispersion was poured into distilled water. The system was stirred at about 500 rpm while maintaining the temperature at 500C to evaporate methylene chloride.

[0038] Subsequently, the particles in the aqueous solution were filtered out. Further washing was repeated to wash away dispersion stabilizers and the like adhering to the particle surfaces. Vacuum dry the obtained particles,
Toner particles were obtained.

Particle Size Evaluation The particle size distribution of the particles obtained in Examples 1 to 4 and Comparative Examples 1 to 4 was measured using SALD-1100 (manufactured by Shimadzu Corporation). The results are shown in Table 1 below.

[0040]

[Table 1]
Table 1------------
−−−−−−−−−−−−−−−−−
Average particle size (μm) 2 μm or less (%) 1
6 μm or more (%)
−−−−−−−−−−−−−−−−−−Example 1
6.0 1.3
1.4 Example 2 5.
2 7.4
3.8 Comparative Example 1 6.3
6.4 13
．． 8 Comparative Example 2 5.6
19.0 7.8 Example 3
6.4 1.4
2.5 Example 4
5.4 7.2
4.3 Comparative Example 3 6.9
5.3
18.6 Comparative Example 4 6.2
16.0 9.9-
−−−−−−−−−−−−−−−−−−−−−−−−−
−−−−−−−−−

As is clear from Table 1, by producing particles using the phase inversion phenomenon, it is possible to obtain particles with less fine powder and coarse powder and a sharp particle size distribution.

Evaluation of charging rise First, a carrier was manufactured as follows. polyester resin
100 parts by weight
(Softening point 1230C, glass transition point 650C,
AV23, OHV40) Fe-Zn ferrite fine particles 50
0 parts by weight MPP-2 (manufactured by TDK) Carbon black (MA#8; manufactured by Mitsubishi Chemical Industries, Ltd.)
2 parts by weight The above materials were thoroughly mixed and pulverized using a Henschel mixer, and then melted and kneaded using an extrusion kneader set at a cylinder section 1800C and a cylinder head section 1700C. After cooling the kneaded product, it was coarsely ground using a feather mill, further finely ground using a jet mill, and then classified using a classifier to obtain a carrier having an average particle size of 60 μm.

The obtained carrier was mixed with the toner obtained in Examples 3 and 4 and Comparative Examples 3 and 4 at a ratio of 10% by weight of the toner. 30 g of the obtained mixture was placed in a 50 cc polyethylene bottle, and mixed by rotation with a paint conditioner (manufactured by Red Devil Co., Ltd.) at 1200 rpm for 30 minutes. The amount of charge at that time is measured and taken as the amount of charge at the time of initial mixing.

Thereafter, the toner and carrier are separated by applying an electric field, and 10% by weight of new toner is added to the separated carrier.
30 g of the mixture was placed in a 50 cc polyethylene bottle and rotated at 1200 rpm. The toner charge amount at that time is set as the charge amount at the time of additional mixing. The above results are summarized in Table 2 below.

[0045]

[Table 2]
Table 2 ----------
−−−−−−−−−−−−−−−−−−−
Charge amount during initial mixing
Charge amount during additional mixing
(μC/g) (μC
/g) −−−−−−−−−−−−−−
−−−−−−−−−−−−− Example 3 +22
+20 Example 4
+25 +22
Comparative example 3 +20
+12 Comparative example 4 +23
+ 8 −−−−−−−−−
−−−−−−−−−−−−−−−−−

Table 2
It can be seen from the above that as the amount of fine powder of 2 μm or less or the amount of large particles of 16 μm or more increases, the amount of charge during additional mixing tends to be smaller than the amount of charge during initial mixing. This shows that as the number of copies actually increases, the toner charge amount decreases. This is thought to be because the fine powder clings to the carrier and cannot be separated from the carrier, preventing contact between the additional toner and the carrier. If there are many large particles, the toner charge amount will decrease during additional mixing because the mixing and stirring performance with the carrier will be worse than at the initial stage.

[0047]

According to the present invention, by utilizing the phase inversion phenomenon of an emulsion, resin particles having a uniform average particle size of 3 to 9 μm can be obtained. The present invention can be applied to a method for producing toner particles.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram conceptually showing the turbid state of a W/O emulsion.

FIG. 2 is a schematic diagram conceptually showing a phase inversion process.

FIG. 3 is a schematic diagram conceptually showing a phase inversion process.

FIG. 4 is a schematic diagram conceptually showing the turbid state of an O/W emulsion.

Claims (1)

[Claims] Claim 1: Adding an aqueous solution II to a resin solution I using a hydrophobic solvent as a medium to cause phase inversion to form an O/W emulsion, and then removing the solvents of solutions I and II,
A method for producing resin particles.