JP3127649B2 - Method for producing encapsulated resin particles and method for producing toner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing encapsulated resin particles.

[0002]

2. Description of the Related Art In recent years, low-temperature fixability of toner has been improved,
Due to the demand for improving the translucency of full color toners and the like, the glass transition temperature and the molecular weight of the resin for toner tend to decrease. However, a toner having a high glass transition temperature or a high molecular weight is preferable in consideration of the storage stability, environmental resistance, and chargeability of the toner. In order to satisfy these requirements, it has been proposed to provide a relatively hard outer layer, that is, a capsule, on the toner surface.

On the other hand, in order to satisfy the demand for higher image quality, the particle size of the toner has been reduced. However, the toner obtained by the conventional pulverization method has a wide particle size distribution of the toner particles, and the toner has a small particle size. There is a limit in terms of technology and the productivity such as yield. Wet granulation method such as suspension polymerization method and suspension granulation method is a method that is small particle size and relatively narrow particle size distribution is obtained, and is more advantageous than grinding method in terms of productivity. . This method involves adding a polymerizable monomer, a colorant, and other additives, synthesizing the toner in a suspended state, and granulating the toner. It is difficult to produce a toner having a uniform and small particle size (about 6 μm) by the conventional pulverization method, which is a method of producing a toner, because the pulverization efficiency is very poor, and it is overwhelming to produce by a wet method. Is advantageous.

Conventionally, as a method of providing an outer shell layer on a resin particle having a small particle diameter such as a toner, a hybridization device or the like is used to deposit resin fine particles on the resin particle, and this is formed by heating under dry conditions or the like. A method of forming a film is used. However, it is difficult to obtain uniform capsules under dry conditions.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for obtaining resin particles satisfying the above two contradictory properties under wet conditions.

[0006]

That is, according to the present invention, the resin fine particles are uniformly fixed on the resin base particles, then mixed and stirred with the beads in a wet system, and stress is applied to the resin fine particles to thereby obtain the surface of the resin base particles. The present invention relates to a method for producing encapsulated resin particles, characterized in that a film-like outer shell layer is formed thereon.

In the present specification, the term “base particles” means particles serving as a core, and the term “resin fine particles” means that particles adhere to the base particles,
Fine particles which are further formed into a film as an outer shell layer.

The base particles used in the present invention are resin or resin particles obtained by blending various additives such as a pigment, a charge controlling agent, a wax and the like into the resin, and include, for example, suspension polymerization, seed polymerization, emulsion polymerization, and emulsion dispersion. Although it may be produced by any method such as a wet production method such as granulation, a spray granulation method, a dry production method such as a kneading and pulverizing method, uniform spherical resin particles can be obtained at a high yield. The suspension method is most preferred.

The resin constituting the base particles is not particularly limited, but is preferably a styrene acrylic resin, a styrene resin, a (meth) acrylic resin, an olefin resin,
Polyester resin, amide resin, carbonate resin, polyether resin, thermoplastic resin such as polysulfone resin, or epoxy resin, urea resin, thermosetting resin such as urethane resin and These copolymers and polymer blends can be used. Further, for example, in the case of producing an electrophotographic toner, the resin constituting the base particles is not particularly limited as long as it is generally used as a binder in a toner, and the above-described resins can be used. .

In recent years, there has been a demand for a technique capable of copying at a higher speed. For a toner used in such a high-speed system, the fixability of the toner to transfer paper or the like in a short period of time, and the use of a fixing roller. It is necessary to improve the separability. Therefore, when attempting to obtain a toner used in such a high-speed system, the resin constituting the spherical resin particles is synthesized from a styrene monomer, a (meth) acrylic monomer, and a (meth) acrylate monomer. It is preferable to use a homopolymer or copolymer, or a polyester resin, which has a number average molecular weight (Mn), a weight average molecular weight (Mw),
The relationship with the average molecular weight (Mz) is 1,000 ≦ Mn ≦ 7.0
00, 40 ≦ Mw / Mn ≦ 70, 200 ≦ Mz / Mn ≦ 50
0, and the number average molecular weight (Mn) is further 2,000.
It is desirable to use those in which 0 ≦ Mn ≦ 7,000. When used as an oilless fixing toner, the glass transition temperature is 55 to 80 ° C. and the softening point is 80 to 1
It is desirable that the composition further contains 5 to 20% by weight of a gelling component at 50 ° C. Further, in order to improve the vinyl chloride resistance, it is preferable to use a polyester resin, and it is particularly preferable to use a polyester resin containing 5 to 20% by weight of a gelling component.

In order to obtain a translucent color toner used for OHP or full color,
As a resin constituting spherical resin particles, vinyl chloride resistance,
It is desirable to use a polyester resin from the viewpoints of light transmission as a light-transmitting color toner and adhesion to an OHP sheet, and in this case, the glass transition temperature is 55 to 7
0 ° C, softening point 80-150 ° C, number average molecular weight (Mn) of 1,000-15,000, molecular weight distribution
(Mw / Mn) is preferably a linear polyester of 4 or less. Further, as a binder resin for obtaining a translucent color toner, a linear urethane-modified polyester (C) obtained by reacting a linear polyester resin (A) with a diisocyanate (B) is also preferably used. Can be The linear urethane-modified polyester mentioned here is composed of a dicarboxylic acid and a diol, and has a number average molecular weight of 1,000 to 15,000.
A linear urethane-modified polyester resin obtained by reacting 0.3 to 0.95 moles of diisocyanate (B) per mole of a linear polyester resin having an end group of hydroxyl group having an oxidation of 5 or less. Further, the resin (C) has a glass transition temperature of 40 to 80 ° C. and an oxidation of 5 or less as a main component. Furthermore, it is a polymer modified by grafting a styrene-based, acrylic-based, aminoacrylic-based monomer, etc. to a linear polyester by a method such as block polymerization or the like, and has the same glass transition temperature, softening point, and molecular weight characteristics as above. Those are also preferably used.

The resin fine particles used in the present invention preferably have a glass transition temperature of less than 100 ° C., more preferably 50 ° C.
These are fine particles composed of a resin having a temperature of less than 80 ° C. If the glass transition temperature of the resin constituting the resin fine particles is 100 ° C. or higher, the resin particles are not sufficiently melted even by mixing and stirring with beads, and the film formation is insufficient, which is not preferable. Specifically, polystyrene, PMMA, polyester and the like are exemplified.

When used in an electrophotographic toner, the fine resin particles have a glass transition temperature of 50 ° C. to 80 ° C. and a weight average molecular weight (Mw) of 5,000 to 20.
A resin of 000 or less is preferably used.

The particle size of the base particles of the present invention may be selected according to the purpose and application. Assuming that the particle diameter of the base particles is D _A and the particle diameter of the fine particles is D _B , 5 <D _A / D _B <1
0000, is preferred particularly that the _{10 <D A / D B <} 100. If D _A / D _B is 5 or less, the amount of the attached fine particles will vary, making it difficult to control the physical properties. Further, the fine particles do not uniformly adhere to the surface of the base particles, resulting in incomplete film formation. If D _A / D _B is 10,000 or more, the effect cannot be obtained even if a film is formed.

The addition amount of the resin fine particles is 2 to the base particles.
It may be added in an amount of 5 to 50 parts by weight, preferably 5 to 20 parts by weight. When the addition amount of the resin fine particles exceeds 50 parts by weight, there are a large number of resin fine particles that do not form the film-like outer shell layer, which affects the chargeability. If the amount is less than 2 parts by weight, the surface of the base particles cannot be completely covered with the resin fine particles, so that a uniform film cannot be formed.

In the method for producing the encapsulated resin particles of the present invention, the resin fine particles are uniformly fixed on the resin base particles, and then mixed and stirred with the beads in a wet system to form a film-like outer layer on the surface of the resin base particles. It is formed. As a method for uniformly fixing the resin fine particles on the resin base particles, any conventionally used method may be used. For example, the base particles and the fine particles are mixed in a dry or wet process to form an ordered mixture with the fine particles adhered on the surface of the base particles, and then the fine particles are fixed to the surface of the base particles by a method such as a high shear force. It is preferred that

In the present invention, the resin particles produced by the wet granulation method are encapsulated by uniformly mixing the resin fine particles on the resin base particles and then mixing and stirring with the beads in a wet system. In the case of performing immobilization treatment after forming ordered mixture in a wet process as particles, it can be processed in a wet process without drying in the middle of the process, shortening the overall manufacturing process, Cost can be reduced.

As a method of forming the ordered mixture, for example, the resin base particles and the resin fine particles are dispersed in a solvent that swells without dissolving the resin constituting the base particles, and the fine particles adhere to the base particles uniformly. What is necessary is just to obtain the ordered mixture. Solvents for dispersing the base particles and the resin fine particles and swelling without dissolving the resin constituting the base particles are methanol, ethanol, n-propyl alcohol, isopropyl alcohol, ethylene glycol, diethylene glycol, acetone, methyl ethyl ketone, tetrahydrofuran, 1, 4-dioxane,
Water-soluble low dielectric constant solvents such as acetonitrile, formamide, acetic acid, and pyridine are preferable, and a mixed solvent of these and water is particularly preferably used. When the base particles are easily compatible with water, that is, when the resin is a resin with good wettability, only water or a mixed solvent containing water as a main component is also a resin that is not easily compatible with water, that is, a resin with poor wettability. A mixed solvent having a low ratio of water is preferably used. The base particles are 10
It is added at a concentration of about 30% by weight.

In dispersing the base particles and resin fine particles in the above-mentioned dispersion solvent, it is preferable to add an electrolyte. Such an electrolyte is not particularly limited, but aluminum oxide, a metal salicylate complex, or the like is particularly preferably used. The addition of the electrolyte causes hetero (heterogeneous) aggregation of the base particles and the resin fine particles, thereby making it possible to more easily obtain an ordered mixture in which the resin fine particles uniformly adhere to the base particles. At this time, an adhesive such as methylcellulose may be supplementarily added.

The electrolyte is used in an amount of from 0.1% by weight to
It is preferable to add 2% by weight. 0.1% by weight
In the following cases, the effects of the present invention cannot be obtained due to incomplete heteroaggregation. On the other hand, if the amount exceeds 2% by weight, the electrolyte is unnecessarily taken into the obtained toner particles, and the environmental stability and the chargeability are undesirably reduced.

The ordered mixture in which the fine particles are uniformly attached to the base particles is stirred while applying a high shearing force to fix the fine particles on the base particles. Since the surface of the base particles is swollen, the fine particles can be fixed uniformly and firmly on the surface of the base particles, and the fine particles are not easily displaced from the surface of the base particles even if a strong stress is applied in a subsequent step. The high shearing force can be applied, for example, by performing high-speed stirring using a high shearing force emulsifying and dispersing machine. Specific examples of the apparatus include a TK auto homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) and an ultra disperser (LK-41, manufactured by Yamato Scientific Co., Ltd.).

The ordered mixture obtained as described above is stirred in the presence of beads, and the resin fine particles on the base particles are melted by the stress to form a film. By using the beads, uniform and strong stress is applied to the resin fine particles, and a uniform outer shell layer can be obtained on the surface of the base particles.

The beads used in the method of the present invention are spherical, relatively hard materials such as glass, ferrite, zirconia, steel and the like having a specific gravity of 1.5 to 10.0, preferably 1.5 to 5.0. Are preferred. When the specific gravity exceeds 10.0, it is difficult to stir with a bead mill. When the specific gravity is less than 1.5, the stress at the time of stirring is weak, and it is difficult to melt the resin fine particles to form a film.

As for the size of the beads, assuming that the particle size of the beads is D _C , the relationship with the particle size D _A of the base particles is as follows: 3 <D _C / D _A <1000, preferably 10 <D _C / It satisfies D _A <200. If the particle size of the beads is smaller than this, the stress during stirring is weak, and it is difficult to form a film. On the other hand, if it is large, the film-like outer shell layer is not formed even though the stress is uniform, which is not preferable.

The amount of beads to be added is preferably about the same as that of a dispersion containing 10 to 30% by weight of ordered mixture, that is, 80 to 120% by volume of the dispersion. When the added amount of the beads is too large, the stirring by the bead mill becomes difficult to perform, and when the added amount is too small, the application of the stress is uneven and the film formation is incomplete.

The stirring may be performed using a commercially available bead mill. The temperature at this time may be appropriately selected depending on the resin constituting the base particles and the resin fine particles, and may be a temperature equal to or higher than the glass transition temperature of the resin or a lower temperature equal to or lower than the glass transition temperature. It is preferably carried out at around the glass transition temperature. In addition, this step is performed in the above-described water-soluble low-dielectric solvent, and good film formation can be performed even when stress is applied while the surface of the resin fine particles is softened to some extent.

The base particles that have been deformed or broken due to excessive stress can be restored to a substantially spherical shape by stirring at a temperature higher than the glass transition temperature of the constituent resin.

After the film formation is completed, the particles are washed and dried. The particles are preferably prepared in a solution prepared by adjusting the pH of an aqueous solvent of a lower alcohol such as methanol, ethanol or isopropyl alcohol to about 3 with an acid such as hydrochloric acid, acetic acid or formic acid. It is convenient to use a decantation method for washing. The decantation method is a method in which the solution from which the solvent has been distilled off is left to stand for 24 hours after stirring, and then the supernatant is removed to remove the precipitated solid. According to this method, particles having a small particle size are removed, and washing and classification can be performed at the same time.

The resin particles thus obtained are finally dried. As a drying method, any of known methods and apparatuses such as air drying, vacuum drying, and spray drying may be used.
By the encapsulation method of the present invention, an outer shell layer having a thickness of about 0.1 to 2 μm can be formed on the base particles.

The resin particles having an outer shell layer on the surface obtained by the method of the present invention can be applied to toners used in developing electrophotography and the like, printers, cosmetics, pharmaceuticals and the like. Hereinafter, the present invention will be described in more detail with reference to Examples. In the following examples, “parts” means “parts by weight” unless otherwise specified.

[0031]

Example 1 Low molecular weight polyester resin (Mw = 600)
(0, Mn = 3500) was completely dissolved in methylene chloride so as to be 20% by weight. Here, 6 parts of carbon black (Mogar L) as a coloring agent and 4 parts of Bontron E-84 (manufactured by Orient Chemical Industries) as a charge controlling agent were dispersed to obtain a resin solution (I).

The resin solution (I) was added to Metroose 65SH-5.
0 (manufactured by Shin-Etsu Chemical Co., Ltd.) and 1% sodium lauryl sulfate in an aqueous dispersion using a homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) at room temperature for 10 minutes at 3800 rpm for 3 minutes. An o / w emulsion was obtained. Next, replace the stirring blade with four blades and raise the temperature to 40 to 45 ° C.
Methylene chloride was distilled off with stirring for 3 hours to obtain an aqueous suspension of toner particles.

After the methylene chloride was completely distilled off, the mixture was allowed to stand for 24 hours, and then the solid content that had settled out was removed by decantation. This operation was repeated twice more.
The toner having a size of 2 to 3 μm or less is separated and removed together with the supernatant, and plays a role of both classification and washing. The solid content of the toner particles thus taken out was washed twice with a washing solution adjusted to pH 3 with a mixed solvent of water / methanol (5/5: weight ratio) with hydrochloric acid to obtain toner mother particles having an average particle diameter of 6 μm (collected). Rate 90
%).

Polystyrene fine particles (average particle size 0.2 μm)
m, Mw = 50,000, Mn = 20,000, glass transition temperature: 65 ° C.), 7% by weight with respect to the toner base particles, dispersed in methanol by ultrasonic waves, and further added water equivalent to methanol to obtain polystyrene. 50% of fine particles
A dispersion in a methanol solution was obtained. The toner base particles were adjusted to have a solid content of 10% by weight in the dispersion, and the base particles were swollen by applying ultrasonic waves. To this, 2 g of aluminum sulfate was added to aggregate the fine particles on the base particles to form an ordered mixture.

This ordered mixture was subjected to high shear stirring at 10,000 revolutions per minute at room temperature for 10 minutes at room temperature using a homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) to fix resin fine particles on the toner surface. The toner to which the resin fine particles are fixed is strongly mixed with glass beads (particle diameter: 1.0 mm) at 3,000 revolutions per minute by using an Eiger motor mill (manufactured by Eiger Japan Co., Ltd.) to apply strong stress, thereby applying toner mother particles. A film-like polystyrene resin shell layer was formed on the surface of. According to the first embodiment, the thickness is set to 0.
A toner having an average particle size of 7.0 μm having an outer shell layer as a uniform capsule of 5 μm was obtained.

[0036]

Example 2 70 parts of styrene, 30 parts of n-butyl methacrylate, 3 parts of low molecular weight polypropylene wax (Viscol 660P: manufactured by Sanyo Chemical Industries), 8 parts of carbon black (MA-8: manufactured by Mitsubishi Kasei Industries) And 2,2'-
Azobis- (2,4-dimethylvaleronitrile) (3 parts) was sufficiently mixed with a sand stirrer to prepare a polymerizable composition containing a polymerization initiator. This polymerizable composition was used for 1.
In a 25% by weight aqueous solution of polyvinyl alcohol, TK.
Using an auto homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.), the mixture was added with stirring at a rotation speed of 6000 rpm. Then 3
6 while stirring at 500 rpm using a single turbine blade
The polymerization reaction was carried out at 0 ° C. for 6 hours to obtain an aqueous suspension of toner particles.

After the completion of the polymerization reaction, the reaction system was cooled, hydrochloric acid was added, and decantation, filtration and washing were carried out in the same manner as in Example 1 to obtain toner base particles having an average particle diameter of 6 μm.
To the obtained toner base particles, in the same manner as in Example 1, 0.7% by weight of polystyrene fine particles (average particle size: 0.2 μm).
m, Mw = 50,000, Mn = 20,000) is adsorbed on the toner base particles, and the mixture is fixed by high-shear stirring, and mixed and stirred with glass beads to form a film on the surface of the toner base particles. A polystyrene resin outer shell layer was formed.
The toner deformed or destroyed by the strong stress was restored to a substantially spherical shape by stirring at a temperature equal to or higher than the Tg (glass transition point) of the base particles to obtain the toner of Example 2. According to Example 2, a toner having an average particle size of 7.0 μm and an outer shell layer as a uniform capsule having a thickness of 0.5 μm was obtained.

[0038]

Comparative Example The base particles of the toner of Example 1 were used as comparative example toners.

To each of the toners of Examples 1 and 2 and Comparative Example, 0.2% by weight of hydrophobic silica R-974 (manufactured by Nippon Aerosil Co., Ltd., average particle size: 6 mμ) was added, and a Henschel mixer was used. Processing was performed at 3000 rpm for 1 minute. A two-component developer was prepared using each of the post-processed toners and the following carriers, and the following tests were performed.

Production parts by weight of carrier : polyester resin 100 (softening point 123 ° C., glass transition temperature 65 ° C., AV23, OHV 40) Fe—Zn ferrite fine particles 500 (MFP-2: manufactured by TDK) ・ carbon black 2 ( MA-8: manufactured by Mitsubishi Chemical Corporation)

The above-mentioned materials were sufficiently mixed and pulverized by a Henschel mixer, and then melted and kneaded using an extruder kneader set at a cylinder portion of 180 ° C. and a cylinder head portion of 170 ° C. The kneaded product was left to cool, coarsely pulverized using a feather mill, further finely pulverized using a jet mill, and then classified using a classifier to obtain a carrier having an average particle diameter of 60 μm.

Test Fluidity Test Using the toners of Example 1 and Comparative Example, a toner / carrier mixing ratio of 7%, a ball mount, and a rotation speed of 1000 r.
The specific gravity of the developer obtained by mixing and stirring at pm was measured. The measurement conformed to JIS standard Z2504. The bulk specific gravity of the developer of Example 1 was 2.3 g / cm ³ , while the bulk specific gravity of the developer of the comparative example was 1.6 g / cm ³ .

Blocking Resistance Test The toner was stored for 24 hours in an environment of a temperature of 45 ° C. and a humidity of 80%, and was then sieved with a 40 μm mesh, and the ratio of the residue to the whole was measured. The sieving residue of the toner of Example 1 was 2.1%, whereas the sieving residue of the toner of Comparative Example was 10.3%.

Time-dependent change of charge and environmental fluctuation Toner / carrier mixing ratio of Examples 1 and 2 and Comparative Example 5
% Of the developer was prepared and used. Prepared developer at temperature 2
The chargeability was measured after mixing and stirring for 3 minutes, 90 minutes, and 900 minutes at 1,000 rpm using a ball mount under an environment of 5 ° C. and 60% humidity. In order to check the environmental resistance, the following conditions were used: NN: temperature 25 ° C., humidity 60% HH: temperature 30 ° C., humidity 85% LL: temperature 10 ° C., humidity 15% at a rotation speed of 1000 rpm with a ball mount. 9 each
The chargeability after mixing and stirring for 0 minutes was measured. The measurement was carried out using a blow-off powder charge meter (manufactured by Toshiba Chemical Corporation). Table 1 shows the results.

[0045]

[Table 1]

[0046]

The encapsulated resin particles obtained by the method of the present invention are excellent in fluidity and charge stability, and even when a resin having a low glass transition temperature is used as a base particle, blocking resistance and environmental resistance are obtained. The toner has good properties and can be fixed at a low temperature.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroki Nagai Osaka International Building Minolta Camera Co., Ltd. 2-3-13 Azuchicho, Chuo-ku, Osaka-shi, Osaka In-house (72) Inventor Junji Machida Azuchi, Chuo-ku, Osaka-shi, Osaka 2-3-3, Osaka-cho, Osaka International Building Minolta Camera Co., Ltd. In-house (56) References JP-A-2-160038 (JP, A) JP-A-62-278547 (JP, A) JP-A-63-240937 (JP) JP-A-61-64326 (JP, A) JP-A-6-234863 (JP, A) JP-A-1-184034 (JP, A) JP-A-63-256128 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C08J 3/12 C08L 1/00-101/16 G03G 9/08

Claims (5)

(57) [Claims] After the resin fine particles are uniformly fixed on the resin base particles, they are mixed and stirred with the beads in a wet system, and stress is applied to the resin fine particles to form a film-like outer shell layer on the surface of the resin base particles. A method for producing encapsulated resin particles, comprising: 2. The specific gravity of the beads is greater than 1.5.
The method for producing encapsulated resin particles according to claim 1, which is less than 0. 3. A particle diameter D _A of the mother particle, the particle diameter D _B of the resin particles, when the particle size of the beads was D _C tripartite relationship following formula: 5.0 <D _A / The method for producing encapsulated resin particles according to claim 1, wherein the following condition is satisfied: D _B <1000 3.0 <D _C / D _B <1000. 4. The glass transition temperature of the resin fine particles is 100 ° C.
The process for producing encapsulated resin particles according to claim 1, wherein 5. A method for producing toner particles, wherein resin particles containing a coloring agent are used as the resin particles, and the resin particles are produced by applying the method according to claim 1.