JPH0934175A - Method for making electrostatic charge image developing toner spherical - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a uniform surface form of a toner even when the processing time is short by using a heating gas flow containing vapor of a solvent which swells or dissolves a binder resin. SOLUTION: Particles of an irregular electrostatic charge image developing toner produced by kneading at least a coloring agent, binder resin and release agent while heating, then cooling and pulverizing, are made spherical by heating the toner at a temp. higher than the softening temp. of the binder resin in a heating gas flow. In this method, the heating gas flow contains vapor of a solvent which swells or dissolves the binder resin. As for the solvent vapor used, lower alcohols such as methanol and ethanol, or acetone, toluene, methylethylketone or mixture of these can be used. Moreover, the amt. of the solvent vapor is controlled to 50-80% of the saturated vapor amt. The solvent to be used is selected to satisfy the relation of P1 /P2 >1, wherein P1 is the solubility of the binder resin in the solvent and P2 is the solubility of the release agent which is added to prevent offset.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention spheroidizes an irregular electrostatic charge developing toner produced by an ordinary pulverizing method (a method of kneading a toner raw material under heating, cooling and pulverizing for classification). Regarding the method.

[0002]

2. Description of the Related Art Toners used in a dry development method are mainly composed of a thermoplastic resin (binder resin), a dye / pigment (coloring material), a release agent, etc., and if necessary, magnetic powder and charge control. It is manufactured by adding agents and fluidity improvers. Then, as a method for producing these toners, the raw materials are mixed and heated, melted and dispersed by a kneader or the like to obtain a uniform composition, which is then cooled, pulverized and classified to obtain a volume average particle size. A method for producing a toner having a diameter of about 10 μm is generally adopted. However, since the toner particles produced by such a kneading and pulverizing method have irregular shapes, the toner characteristics vary. This especially deteriorates the fluidity of the toner, makes it difficult to convey the toner in the developing machine, and since the charging characteristics of each toner particle are different, scumming and toner scattering easily occur, and the developing characteristics There is a problem that it adversely affects.

In order to solve such a problem, it is effective to make the toner spherical. Therefore, the following techniques have been proposed so far as means for making the spherical shape. (1) A technique for producing a toner by a polymerization method so as to make it spherical (JP-A-61-18965, JP-A-61-19602).
No.), (2) a resin containing a toner blending component and a medium are mixed and stirred at the softening point temperature of the resin and the medium, and then the medium is removed (JP-A-60-57350), (3) toner blending component A technique for atomizing a resin containing a resin in a molten state and cooling the resin to form a sphere (Japanese Patent Laid-Open No. 54-80752).
(4) A technique of redispersing the particles obtained through the steps of kneading, pulverizing and classifying in a solvent, and melting the surface of the particle powder with hot air or the like using a spray dryer to achieve spheroidization (JP-A-56) -52758, JP-A-59-127662
(5) Kneading and coarsely pulverizing the particle powder obtained by finely pulverizing the powder by adjusting the temperature of the inflowing air (JP-A-61-61627),
(6) A technique for dispersing the particle powder obtained through the steps of kneading, pulverizing, and classifying in a hot air stream to melt the surface of the powder to make it spherical (JP-A-58-134650, 59-127).
640, 61-249710, JP-A-3-1793.
No. 63), (7) Particle powder obtained through the steps of kneading, crushing, and classifying is subjected to mechanical impact in a solid-gas two-phase flow to smooth the surface and to make it spherical (Japanese Patent Application Laid-Open No. 2003-242242). 63-23
5957, JP-A-63-249155, JP-A-2-
167566).

[0004]

However, the above method (1) requires an apparatus completely different from the conventional crushing method,
New capital investment is required. Further, since the methods (2) and (4) both use a large amount of solvent for the particles, a large amount of energy is required to remove the solvent and obtain a dry powder, It will not be worth the cost. Further, in the method (3), if the resin is directly atomized, it is difficult to obtain a desired particle size of about 10 μm due to its characteristics, and if a solvent is added to reduce the viscosity to obtain a desired particle size, (2) ) And (4), the solvent evaporates from inside the particles at the same time as the drying energy increases, so-called dents occur and spherical particles cannot be obtained. Further, in the above method (5), since the internal temperature of the pulverizer approaches the softening point of the resin, not only the pulverizability of the resin is deteriorated, but also the inside of the pulverizer is adhered and the particles are aggregated. The above methods (6) and (7) can be applied to the existing process as compared with the other methods, and therefore, the cost is low, and some methods have been actually tried. However, in the method (6) of melting the resin surface with heat, it is necessary to lengthen the average residence time to some extent in order to uniformly treat all particles. However, when the residence time is lengthened, there arises a problem that particles are aggregated and united. Also in the method (7) of using mechanical impact force, a continuous method for uniformly treating all particles requires a single treatment, and several treatments are required. It was necessary to lengthen the processing time. Further, the methods (6) and (7) uniformly act on all the constituent components present on the toner surface, and therefore, when the particles having a release agent are treated, the release agent is not There is also a problem in that the surface characteristics of the particles are changed by bleeding out.

An object of the present invention is to solve these problems and to achieve a short processing time (or a small number of processing times).
It is an object of the present invention to provide a spheroidizing method which can obtain a spherical toner for electrostatic charge development having a uniform surface shape and can suppress the exudation of internal constituent components of a particle to the surface of the particle.

[0006]

DISCLOSURE OF THE INVENTION The inventors of the present invention have included an amorphous (non-uniform) electrostatic charge developing toner produced by a pulverizing method in a solvent vapor in which a binder resin in the toner swells or dissolves. Sphericalization by heat treatment in a heated air stream or by containing a solvent vapor that causes the binder resin of the toner to swell or dissolve as a gas when applying a mechanical impact force to the toner in a solid-gas two-phase flow Have been found to be performed well. The present invention has been made based on this.

Therefore, according to the present invention, (1) an irregular (uneven) electrostatic charge developing toner produced by heating and kneading at least a coloring material, a binder resin and a release agent, cooling and pulverizing. In a method of spheroidizing by heating to a temperature above the softening point of the binder resin in a heated air stream, a solvent vapor that swells or dissolves the binder resin is used as the heated air stream and is used. Method for spheroidizing electrostatic charge developing toner, (2) Amorphous (uneven) electrostatic charge developing toner produced by heating and kneading at least a colorant, a binder resin and a release agent, cooling and pulverizing the toner. In a method of imparting a mechanical impact force in a solid-gas two-phase flow to spheroidize, a static method characterized in that a solvent vapor that swells or dissolves a binder resin as a gas of the solid-gas two-phase flow is used. A method for spheronizing a charge developing toner is provided.

According to the present invention, (3) in the above (1) or (2), the content of the solvent vapor is set to 50% to 80% of the saturated vapor amount of the solvent. spheronization method charge developing toner, in (4) above (3), as the solvent, the solubility P ₁ of the binder resin of the toner, when the solubility P ₂ of the release agent, the P ₁ / P _2> 1 A method of spheroidizing a toner for electrostatic charge development, characterized in that a solvent satisfying the relationship is used, (5) In the above (1), (2), (3) or (4), the solvent vapor is circulated in a closed circuit. A method for spheroidizing a toner for electrostatic charge development, which is characterized by being used.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The method of the present invention will be described in more detail below. In the present invention, the toner for electrostatic charge development which is to be spheroidized is all the irregular toners produced by the usual heat kneading and pulverization methods, and can be applied to both one-component developer and two-component toner. is there. These irregular toners are
Most of the conventional methods have been made spherical by a method of heating to a temperature near the softening point of the resin in a heated air stream, a method of repeatedly applying a mechanical impact force in a solid-gas two-phase flow, etc. However, it was not possible to efficiently obtain a high quality spherical toner. Therefore, in the present invention, solvent vapor that swells or dissolves the binder resin is used as the heated gas and the gas phase. Any solvent vapor may be used as long as it swells or dissolves the binder resin, but from the viewpoint of safety, it is desirable that it is not explosive or corrosive to equipment materials. For general toners, lower alcohols such as methanol and ethanol, acetone, toluene, methyl ethyl ketone, and mixed solvents thereof can be applied.

Further, the solvent vapor in the present invention can be more efficiently spheroidized by adjusting the saturated vapor amount to 50 to 80%. 50 of saturated steam
If it is less than 80%, the effect is small, and if it is more than 80%, there is a problem that the cohesiveness and adhesiveness of the particles increase.

The reason why the efficiency of spheroidization is improved by using a solvent vapor in the present invention has not always been clarified, but the solvent vapor used here is a binder resin which is one of the main components of the toner. Since a solvent that can swell or dissolve is used, the surface of the toner particles present in this solvent vapor is softened in the vicinity of the surface as compared with the toner particle surface present in the vapor without solvent. . Therefore, in the method of the present invention in which heat is applied to make the temperature higher than the softening point of the binder resin to make the toner particles spherical, the surface conditions of all the toner particles are uniform in a short time, and the same spherical shape is obtained. Is achieved. Therefore, in the conventional method, in order to promote the spheroidization, the temperature of the hot air is increased or
It was necessary to lengthen the residence time in the hot air, and therefore, the aggregation and coalescence of the particles occurred, but the method according to the present invention significantly shortens the time, so that the aggregation and coalescence are small. Become. Further, in the method in which the toner particles are repeatedly subjected to a mechanical impact force to smooth the convex portions of the surface, the energy required to smooth the convex portions is small because the surface of the toner particles is softened. It seems that even if the number of repeated collisions is small, the spheroidization similar to the conventional method can be achieved.

As the solvent used in the present invention, when the solubility of the binder resin is P ₁ and the solubility of the release agent added mainly for preventing offset is P ₂ , P ₁ / P ₂ > 1 By making the solvent satisfying the relationship of, the release agent is spheroidized,
It is possible to reduce the phenomenon of seeping on the particle surface. Any solvent may be used as long as it satisfies the relation of P ₁ / P ₂ > 1, but generally, the binder resin is polystyrene and its substitutes, and the release agent is carnauba wax. A mixed solvent of the above-mentioned solvent such as methanol and water can be applied to the toner. The mixing ratio at this time may be set to be optimum depending on the constituent components of the toner.

Furthermore, in the method of the present invention, the spheroidization can be performed more efficiently by using the solvent vapor in a closed circuit. FIG. 1 is a system flow diagram in the case where the present invention is applied as it is, except that a solvent vapor that swells or dissolves a binder resin is contained in a conventional hot-air type sphering device. Although achieved, this makes the solvent vapor disposable. Further, even if a solvent recovery device is provided, it is necessary to heat from a gas at room temperature in order to obtain hot air, and there is room for improvement in efficiency. When the spheroidizing technique of the present invention is applied, the problem is solved by forming the system as a closed circuit and capable of continuous treatment as shown in FIG. Processing becomes possible.

[0014]

The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. The parts here are based on weight.

Comparative Example 1 Binder resin (styrene-acrylic copolymer) 100 parts Binder (carbon black) 10 parts Charge control agent (nigrosine) 2 parts Release agent (carnauba wax) 5 parts Mix by mixer and 1 by kneader
Melt kneading was carried out under the condition of 50 ° C. After cooling this, coarsely crushed with a hammer mill, and further with a jet airflow type crusher,
The particles were finely pulverized and classified by a wind-powered classifier to obtain amorphous particles. The volume average particle diameter of these particles is 8.1μ.
m, and the aggregation rate was 2%. The method for making the particles spherical was performed by spraying the powder in a hot air stream as shown in FIG. The processing conditions at this time are: hot air temperature; 200 ° C.,
The average residence time was 1.1 seconds. Table 3 shows the sphericity, the volume average particle diameter, and the agglomeration rate of the obtained powder.

The sphericity is the Wader's true sphericity (Ψ)
Was determined by Wader's true sphericity (Ψ) = specific surface area when processed as a sphere / BET specific surface area In the above formula, the specific surface area assuming a spherical shape is measured by a Coulter Multisizer (manufactured by Nikkaki Co., Ltd.), BET
Specific surface area is Flowsorb type 2300 (manufactured by Shimadzu Corporation)
Measured using The volume average particle diameter is a value measured using a Multisizer, and the agglomerated particles are 20% by weight or more in the steam measurement result.

Further, 1 part of hydrophobic silica was added to the obtained powder and mixed by a mixer to obtain a comparative toner.
2.5 parts of this toner is used as a silicone resin coated carrier 9
A two-component developer was prepared by mixing with 7.5 parts. This developer was set in an electrophotographic copying machine (FT3300) manufactured by Ricoh Co., Ltd., and the transfer rate, background stain and offset property were evaluated. The results are also summarized in Table 3. Here, the transfer rate was obtained by measuring the toner weight before transfer and the toner weight after transfer on the photoconductor.

Comparative Example 2 Spherical particles were obtained by treating under the same conditions as Comparative Example 1 except that the conditions for sphering were different. That is, the treatment conditions at this time were a hot air temperature of 200 ° C. and an average residence time of 3.0 seconds. The obtained powder was treated in the same manner as in Comparative Example 1 and evaluated in the same manner. Table 3 shows the obtained results.

Examples 1 to 3 Amorphous particles were obtained in the same manner as in Comparative Example 1. The apparatus for spheroidizing the obtained amorphous particles was the one shown in FIG. 1, but the one containing the solvent vapor shown in Table 1 as the hot air flow and the amount shown in Table 1 with respect to the saturated vapor amount was used. did. Then, the obtained powder was treated in the same manner as in Comparative Example 1 and evaluated in the same manner. Table 3 shows the obtained results.

[0020]

[Table 1]

Comparative Example 3 The same treatment as in Comparative Example 1 was carried out to obtain amorphous particles. The method of spheroidizing the obtained particles was a method by mechanical impact force, and specifically, it was treated by hybridization (manufactured by Nara Machinery Co., Ltd.) at a rotation speed of 12000 rpm for 1 minute. The obtained powder was treated in the same manner as in Comparative Example 1 and evaluated in the same manner. Table 3 shows the obtained results.

Comparative Example 4 Spherical particles were obtained by the same treatment as in Comparative Example 3 except that the conditions of the sphering treatment were different. The processing condition is 1200 rpm.
It was processed at 0 rpm for 5 minutes. The obtained powder was treated in the same manner as in Comparative Example 1 and evaluated in the same manner. Table 3 shows the obtained results.

Examples 4 to 6 Amorphous particles were obtained in the same manner as in Comparative Example 3. The same apparatus as in Comparative Example 3 was used as the apparatus for spheroidizing the obtained particles, but at the same time as the start of operation, the solvent shown in Table 2 was atomized and supplied in an amount shown in Table 2 with respect to the saturated vapor amount, Processed.
Then, the obtained powder was treated in the same manner as in Comparative Example 1 and evaluated in the same manner. Table 3 shows the obtained results.

[0024]

[Table 2]

Example 7 Amorphous particles were obtained in the same manner as in Comparative Example 1. The apparatus for spheroidizing the obtained particles was the apparatus of the system shown in FIG. 2, but the processing conditions such as hot air temperature, solvent species, content, and average residence time were the same as in Example 3, and a total of 1 kg of spherical shape was used. A treated powder was obtained. The solvent amount ratio used at this time was 1/20 as compared with that in Example 3, and the spheroidization could be achieved with a small heat amount ratio of 1/15. The obtained powder was treated in the same manner as in Comparative Example 1 and evaluated in the same manner. Table 3 shows the obtained results.

[0026]

[Table 3]

[0027]

According to the first and second aspects of the present invention, since the treatment is performed in a solvent vapor atmosphere that swells or dissolves the binder resin, which is the main constituent component of the toner, as compared with the conventional method, the surface of the toner particle is conventionally treated. Even if the method is softer than the conventional method and the treatment time is short (or the number of treatments is small), it is possible to obtain a more uniform surface state and spherical particles as compared with the conventional method. Further, since the processing time is shorter than that of the conventional method, it is possible to reduce aggregation and coalescence of particles. Furthermore, by limiting the solvent species used in the present invention, it is possible to control the phenomenon in which the specific component oozes out from the inside of the toner to the surface with the spheroidization. According to the invention of claim 3, the spheroidization can be performed more efficiently. According to the invention of claim 4, it is possible to reduce the phenomenon that the release agent seeps out to the surface of the toner particles due to the spheroidization. According to the invention of claim 5, by continuously treating the heated solvent vapor in a closed loop, it is possible to realize an efficient spheronization device with a small amount of solvent used and a required amount of heat.

[Brief description of drawings]

FIG. 1 is a system flow diagram of a hot air flow spheronizer useful in practicing the present invention.

FIG. 2 is a system flow diagram of another hot air spheronizer useful in practicing the present invention.

FIG. 3 is a system flow diagram of a conventional hot-air type spheronizer.

[Explanation of symbols]

 1 Heat treatment container 2 Swirling mechanism 3 Heating mechanism 4 Solvent supply mechanism 5 Cyclone 6 Dust collector 7 Exhaust mechanism 31 Air supply blower 32 Heating heater 33 Heating air flow introducing section 34 Rectifying section 35 Solvent supply pump 36 Mixer

Claims (5)

[Claims] 1. An amorphous electrostatic development toner produced by heating and kneading at least a coloring material, a binder resin and a release agent, and cooling and pulverizing the toner in a heated air stream to a softening point of the binder resin or higher. A method for spheroidizing a toner for electrostatic charge development, which comprises using a solvent vapor that swells or dissolves the binder resin as a heating air stream in the method of spheroidizing by heating to the temperature of 1. 2. An amorphous toner for electrostatic charge development, which is produced by heating and kneading at least a coloring material, a binder resin, and a release agent, and cooling and then pulverizing the toner to obtain a mechanical impact force in a solid-gas two-phase flow. A method of sphering an electrostatic charge image developing toner, characterized in that a solvent vapor that swells or dissolves a binder resin is contained as a gas of the solid-gas two-phase flow in the method of giving and sphering. 3. The method for spheroidizing a toner for electrostatic charge development according to claim 1, wherein the content of the solvent vapor is 50% to 80% of the saturated vapor amount of the solvent. 4. The solvent according to claim 3, wherein the solvent has a solubility P ₁ of the binder resin of the toner and a solubility P ₂ of the release agent, the solvent satisfying the relationship of P ₁ / P ₂ > 1 is used. A method for spheroidizing a toner for electrostatic charge development, which comprises: 5. The method for spheroidizing a toner for developing an electrostatic charge image according to claim 1, 2, 3 or 4, wherein solvent vapor is circulated and used in a closed circuit.