JP2013160796A - Manufacturing method of toner particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of toner particles for reducing scale adhesion to the inner wall of a polymerization container or the surface of a stirring blade or the like, or generation of coarse particles, and accordingly, providing toner particles with high yield and ensuring high process operation rate; and stably providing toner particles having excellent heat characteristics.SOLUTION: A manufacturing method of toner particles includes a step of adding an organic solvent having vapor pressure at polymerization temperature T1 higher than vapor pressure of styrene at polymerization temperature T1 by 15kPa or more, in the amount of molar number 0.06 times or more and 0.20 times or less relative to the total molar number of a polymerizable monomer, until the polymerization rate of the polymerizable monomer reaches 50% in a polymerization process.

Description

  The present invention relates to a method for producing toner particles for developing an electrostatic latent image.

  In electrophotography, a method for developing an electrostatic latent image is currently used in various fields. In electrophotography, an electrostatic latent image is formed on an image carrier by a charging process and an exposure process. Next, a developer for developing an electrostatic latent image (hereinafter sometimes simply referred to as “developer”) including a toner for developing an electrostatic latent image (hereinafter sometimes simply referred to as “toner”). A fixed image is formed on the transfer material through a development process, a transfer process, and a fixing process for developing the electrostatic charge latent image. As the developer, there are a two-component developer having a toner and a carrier and a one-component developer using a magnetic toner or a nonmagnetic toner alone. The production method of the toner particles used for the toner is roughly classified into a dry production method and a wet production method, and the configurations of the production apparatus and the production method are greatly different.

  A pulverization method is mentioned as a dry manufacturing method. In this manufacturing method, a thermoplastic resin, a colorant, a release agent, and the like are melted and mixed in a kneader to generate a melt-kneaded product. Further, the obtained melt-kneaded product is cooled and solidified, then finely pulverized by a fine pulverizer, and classified to obtain toner particles having a desired particle diameter. Thereafter, a predetermined additive is added to the toner particles to produce a toner.

  On the other hand, the wet manufacturing method is a method of forming toner particles in an aqueous medium. Depending on the material constituting the toner particles and the desired shape of the toner particles, a suitable production method can be selected from various toner particle production methods such as suspension polymerization, emulsion polymerization, dissolution suspension, and dispersion polymerization. Is done.

  Among these wet production methods, in the suspension polymerization method, a composition containing a polymerizable monomer is dispersed in an aqueous medium, and toner particles are generated by a polymerization reaction, whereas in the emulsion polymerization method, a polymerizable monomer is used. The composition containing the body is dispersed in an aqueous medium to obtain resin particles constituting the toner particles by a polymerization reaction, and then the toner particles are produced from the resin particles.

  In Patent Document 1, in the suspension polymerization method, a polymerizable monomer composition containing a polymerizable monomer, a colorant, a release agent and the like is dispersed in an aqueous medium and granulated to a desired particle size. Then, particles of the polymerizable monomer composition are generated in the aqueous medium. Next, in the suspension polymerization method, a method for producing toner particles by polymerizing a polymerizable monomer in particles of a polymerizable monomer composition is described.

  In such a production method including a polymerization reaction in an aqueous medium, scale is likely to adhere to the inner wall of the polymerization vessel or the surface of the stirring blade in the polymerization step, and irregular coarse particles are likely to be generated in the aqueous medium. The generation of scales and coarse particles reduces the yield of toner particles. Further, since the scale removal work is required, the operation rate of the toner particle production plant is lowered. Furthermore, if the reaction vessel with the scale attached is used continuously, the wettability increases due to the reduction in the difference in surface free energy between the scale and the reactant in the aqueous medium, and the anchor effect of the irregularities formed by the scale further increases. The adhesion of the scale is promoted, and a thick scale film may be formed on the inner wall of the reaction vessel. As a result, the heat transfer performance of the polymerization vessel is lowered, and the temperature increase rate and reaction temperature control are not stable. If adjustment of the heating rate and reaction temperature is not stable, the polymerizable monomer cannot be polymerized at a stable reaction rate, and the molecular weight of the resin component of the toner particles varies, and toner particles having stable thermal characteristics can be obtained. Becomes difficult.

  For this reason, in the wet production method, measures for adhesion of scale to the inner wall of the polymerization vessel in the polymerization step and methods for suppressing the generation of coarse particles have been proposed.

  Patent Document 2 describes a method for suppressing the adhesion of the polymerization scale and easily removing the attached polymerization scale by forming a coating film of a polymerization scale inhibitor on the inner wall of the polymerization vessel and performing the polymerization. ing.

  In addition, cited document 3 proposes a method for suppressing the generation of coarse particles by removing deposits on the inner wall of the polymerization vessel with high-pressure water after the polymerization reaction.

  Further, in the cited document 4, generation of coarse irregular shaped particles is carried out by spraying water or an aqueous dispersion obtained by mixing water and a dispersion stabilizer on the inner wall of the gas phase part of the polymerization vessel or the gas phase part of the shaft of the stirrer. There has been proposed a method for suppressing the generation of polymerization scale.

  However, with respect to Patent Document 2, the production method for polymerizing by forming a coating film of a polymerization scale inhibitor on the inner wall of the polymerization vessel requires a process for forming the coating film, and the production line is in operation. The ratio (hereinafter also referred to as process operation rate) decreases. Furthermore, although there is an effect of delaying the adhesion in several batches at the initial stage of production, the growth of adhesion becomes remarkable due to the anchor effect due to the unevenness when cracks enter the coating film. Since the polymerization vessel raises and lowers the temperature for each reaction batch, the coating film is easily cracked due to the difference in thermal expansion coefficient between the inner wall of the polymerization vessel and the scale inhibitor, and further improvement is desired.

  Further, with respect to Patent Document 3, the method of removing deposits on the inner wall of the polymerization vessel with high-pressure water cannot prevent the deposits themselves. Therefore, there is a possibility that the composition of the product (toner particles) may change due to the adhesion of the specific component, and a method for suppressing the adhesion is preferable.

  Further, with respect to Patent Document 4, in the method in which water or an aqueous dispersion medium in which water and a dispersion stabilizer are mixed is sprayed on the inner wall of the vapor phase portion of the polymerization vessel and / or its auxiliary equipment, the adhesion of the vapor phase portion is suppressed. However, it is difficult to suppress adhesion of the liquid phase part.

  Furthermore, in any of the techniques of Patent Documents 2 to 4, the evaporated polymerizable monomer is liquefied by condensation and refluxed to form an aggregate of polymerizable monomers that cannot be dispersed and stabilized in an aqueous medium. However, it is difficult to prevent the formation of coarse particles that are generated by the progress of polymerization.

  As described above, in the prior art, a method for fundamentally solving the scale adhesion and the generation of coarse particles on the inner wall of the polymerization vessel, the surface of the stirring blade, or the like is expected. In particular, a method for producing toner particles having stable thermal characteristics is desired for the production of toner particles in recent years where low-temperature fixing is progressing.

JP-A-8-314195 JP 2009-230058 A JP 2005-171062 A JP-A-10-153878

  An object of the present invention is a method for producing toner particles having a step of polymerizing a polymerizable monomer containing styrene in an aqueous medium, and adhesion of scale to the inner wall of a polymerization vessel or the surface of a stirring blade, An object of the present invention is to provide a toner particle production method capable of suppressing the generation. An object of the present invention is to provide a toner particle production method for obtaining toner particles with high yield, ensuring a high process operating rate, and obtaining toner particles having stable thermal characteristics.

The above problems can be solved by the following manufacturing method.
The present invention relates to a method for producing toner particles, which comprises a step of polymerizing a polymerizable monomer containing styrene in an aqueous medium in a polymerization container, wherein the polymerizable monomer is transferred to the aqueous medium in the polymerization container. And the polymerizable monomer is polymerized at a polymerization temperature T1, and 0.06 times or more and 0.20 times or less with respect to the total number of moles of the polymerizable monomer when added to the polymerization vessel. An organic solvent in an amount of the number of moles is added until the polymerization rate of the polymerizable monomer reaches 50%. At the polymerization temperature T1, the organic solvent is at least 15 kPa higher than the vapor pressure of styrene at the polymerization temperature T1. The present invention relates to a method for producing toner particles characterized by having a vapor pressure.

  According to the present invention, in a method for producing toner particles having a step of polymerizing a polymerizable monomer containing styrene in an aqueous medium, adhesion of scale to the inner wall of a polymerization vessel or the surface of a stirring blade and generation of coarse particles are performed. It is possible to suppress. As a result, toner particles can be obtained in a high yield, a high process operation rate can be ensured, and toner particles having excellent thermal characteristics can be stably obtained.

  The method for producing toner particles of the present invention includes a step of polymerizing a polymerizable monomer containing styrene in an aqueous medium. Examples of a method for performing a polymerization reaction of the polymerizable monomer include a polymerization method such as a suspension polymerization method and an emulsion polymerization method.

  In a method for producing toner particles that undergoes a polymerization reaction, scale adhesion and generation of coarse particles are likely to occur on the inner wall of the polymerization vessel and the surface of the stirring blade in the polymerization step.

  In order to solve this problem, the present inventors have studied the mechanism of scale adhesion and generation of coarse particles. As a result, it was found that polymerizable monomers whose dispersion state could not be stabilized in the aqueous medium gathered, and the aggregate formed was the main cause. That is, the polymerization proceeds in the non-dispersed polymerizable monomer assembly, and the product of this polymerization reaction adheres as a scale to the stirring blade or the inner wall of the polymerization vessel at the time when the product is sticky. Further, it was found that the product solidified as the polymerization progressed became coarse particles. In addition, this non-dispersed polymerizable monomer aggregate is a product that is liquefied by evaporating the polymerizable monomer in the reaction solution and cooling it at the top of the polymerization vessel with the lid and condenser. It was found to occur by refluxing to an aqueous medium. That is, the present inventors have found that a technique for suppressing evaporation of a polymerizable monomer such as styrene is important in order to prevent scale adhesion and generation of coarse particles.

  As a technique for suppressing the evaporation of a liquid such as a polymerizable monomer, a technique in which a gas phase part is pressurized with a gas such as air or nitrogen to a pressure higher than the vapor pressure of the liquid is known. The present inventors paid attention to this technology, and studied conditions for pressurizing the inside of the polymerization vessel with gas. As a result, although scale adhesion and generation of coarse particles can be suppressed, it has been difficult to stably obtain toner particles having excellent thermal characteristics. This is considered to be the result of the polymerization temperature fluctuating due to compression or expansion due to pressure fluctuation in the polymerization vessel, and the molecular weight of the binder resin of the toner particles obtained is fluctuated. This is considered to be due to the influence of the polymerization initiator. In the polymerization reaction, it is common to use a polymerization initiator, but when the molecular chain of the polymerization initiator is cleaved and a radical is generated, a gas may be generated as a by-product. The pressure in the polymerization vessel fluctuates.

  Based on the above situation, the present inventors have studied a technique for suppressing evaporation of a polymerizable monomer such as styrene. As a result, by performing a polymerization reaction in a state where a predetermined amount of an organic solvent whose vapor pressure at the polymerization temperature is higher than a certain level than the vapor pressure of styrene is added, evaporation of the polymerizable monomer can be suppressed and the problem can be solved. I found out.

  It is presumed that the evaporation of the polymerizable monomer could be suppressed by reducing the vapor partial pressure of the polymerizable monomer. That is, according to Raoul's law and Henry's law, when the mixed solution is in equilibrium with the gas phase, the vapor partial pressure of a certain component is Proportional to vapor pressure and mole fraction. When the mixed solution is in gas-liquid equilibrium under a constant pressure, if there are many components having a high vapor pressure in the mixed solution, the vapor partial pressure of the other components decreases. As a result, components with high vapor pressure are likely to evaporate, and the evaporation of other components is hindered.

  Hereinafter, although the form for implementing this invention is demonstrated in detail, this invention is not limited to this.

  Examples of the method for producing toner particles having a step of polymerizing a polymerizable monomer containing styrene in an aqueous medium include polymerization methods such as a suspension polymerization method and an emulsion polymerization method. Here, a method for obtaining a toner particle dispersion by suspension polymerization will be described as a representative example.

  First, a release agent, a colorant, a charge control agent, a polymerization initiator, a crosslinking agent, and other additives are added to a polymerizable monomer containing styrene as necessary, such as a homogenizer or an ultrasonic disperser. A polymerizable monomer composition that is uniformly dissolved or dispersed by a stirrer is prepared. Next, by using a stirrer having a high shearing force such as CLEARMIX or a homomixer in an aqueous phase containing a dispersion stabilizer, droplets of the polymerizable monomer composition are obtained to obtain a desired toner particle size. Granulate to size. In the suspension polymerization method, it is usually preferable to use 100 to 3000 parts by mass of water as a dispersion medium with respect to 100 parts by mass of the polymerizable monomer composition. Thereafter, the polymerizable monomer composition is maintained in a particle state by the action of the dispersion stabilizer, and therefore, stirring may be performed to such an extent that sedimentation of the particles is prevented. Polymerization is carried out by setting the polymerization temperature T1 to 40 ° C. or higher, generally 50 to 90 ° C. When adding a polymerization initiator, it can be carried out at an arbitrary time and required time as long as the polymerizable monomer composition is being prepared or after the polymerizable monomer composition is prepared. In addition, the temperature may be raised in the latter half of the polymerization reaction for the purpose of obtaining a desired molecular weight distribution. Further, in order to remove unreacted polymerizable monomers and by-products from the system, the latter half of the reaction or the completion of the reaction. Later, part of the aqueous medium may be distilled off by distillation. The distillation operation can be performed under normal pressure or reduced pressure.

In the present invention, the amount of the organic solvent having a vapor pressure higher than the vapor pressure of styrene at the polymerization temperature T1 by a predetermined value relative to the sum of the number of moles of the polymerizable monomer is It is characterized in that it is added up to the polymerization rate to carry out the polymerization reaction.
The organic solvent to be added will be described.

  According to Raoul's law, the vapor partial pressure of a component in a mixed solution is proportional to its molar fraction and the vapor pressure of a pure substance. Therefore, the vapor pressure of the organic solvent added to lower the vapor partial pressure of the polymerizable monomer needs to be higher than a certain level than the vapor pressure of the polymerizable monomer.

  In the study by the present inventors, in a system containing styrene, as an organic solvent to be added, an organic solvent having a vapor pressure higher by 15 kPa or more than the vapor pressure of styrene at the polymerization temperature T1 is used, so that scale adhesion and coarseness are used. The effect of reducing the generation of particles was obtained. Moreover, the higher the vapor pressure of the organic solvent to be added, the better, but if the vapor pressure is too high, evaporation may be too fast and the added organic solvent may be lost from the reaction solution. Therefore, the vapor pressure at the polymerization temperature T1 of the organic solvent to be added is preferably 250 kPa or less.

  Specifically, when the polymerization temperature T1 is 65 ° C., toluene, n-heptane, n-hexane, cyclohexane, butanol, propanol, ethanol, and acetone are exemplified. Moreover, you may use it in combination of 2 or more type as needed.

  The vapor pressure at an arbitrary temperature of each organic solvent is calculated using the Antoine equation and the Antoine constant (see Chemical Engineering Handbook, Revised 6th edition, Maruzen, pages 18 to 45, page 52).

  Further, the organic solvent to be added may be heated and added as necessary. In order to avoid an unintended chain transfer reaction, the organic solvent to be added is preferably an organic solvent having no allyl group or benzyl group. Moreover, it is preferable from the viewpoint of sharpening the particle size distribution that the organic solvent to be added is an organic solvent having an action of lowering the surface tension of the continuous phase.

  The amount of organic solvent added will be described.

  As described above, according to Raoul's law, the vapor partial pressure of a certain component in the mixed solution is proportional to the molar fraction and the vapor pressure in the case of a pure substance. Therefore, from the viewpoint of suppressing the evaporation of the polymerizable monomer, the amount of the organic solvent to be added needs to be an amount that is a certain number of moles greater than the sum of the number of moles of the polymerizable monomer. However, if it is added in a large amount, the polymer produced by the polymerization reaction is dissolved, and scale adhesion and generation of coarse irregular shaped particles are likely to occur.

  In the study by the present inventors, the amount of the organic solvent to be added is 0.06 times or more and 0.20 times in terms of the number of moles relative to the total number of moles of the polymerizable monomer at the time of addition to the polymerization vessel. Must be: If it is not 0.06 times or more, the effect of suppressing the evaporation of the polymerizable monomer is small, and if it exceeds 0.20 times, there may be a case where an adverse effect due to dissolution of the polymer occurs.

The timing for adding the organic solvent will be described.
In the present invention, one of the points is to suppress the evaporation of the polymerizable monomer, so that the effect cannot be sufficiently obtained after the polymerization proceeds and the polymerizable monomer is solidified. Therefore, it is important to add the organic solvent from the time when the polymerizable monomer composition is prepared until the polymerization rate of the polymerizable monomer reaches 50%. The organic solvent may be added into the polymerizable monomer composition or may be added into an aqueous medium.

  In addition, the addition speed at the time of addition is not particularly limited, and it may be added all at once, or may be added continuously by dividing or adding up to 50% polymerization rate.

The environment for conducting the polymerization reaction will be described.
The environment for carrying out the polymerization reaction is not particularly limited, but if the polymerization reaction is carried out in a pressurized environment using a sealed polymerization vessel, adhesion and generation of coarse particles can be suppressed, but toner having excellent thermal characteristics It is difficult to obtain particles stably. This is considered to be due to pressure fluctuations and temperature fluctuations in the polymerization vessel due to the gas generated during the polymerization reaction.

  Therefore, it is preferable to polymerize the polymerizable monomer in a polymerization vessel communicating with the atmosphere because the generated gas can be easily removed and the pressure can be easily controlled.

  As the polymerizable monomer used in the toner particles of the suspension polymerization method, a vinyl polymerizable monomer capable of radical polymerization is preferably used. As the vinyl polymerizable monomer, a monofunctional polymerizable monomer or a polyfunctional polymerizable monomer can be used.

  For example, styrene derivatives such as styrene and 2,4-dimethylstyrene, and acrylic polymerizable monomers such as n-butyl acrylate are preferably used. Other examples include methacrylic polymerizable monomers such as methyl methacrylate and vinyl esters such as vinyl acetate. Among these, in the present invention, it is preferable to use styrene alone or in combination of two or more polymerizable monomers other than styrene and styrene. Moreover, when using combining a polymerizable monomer other than styrene and styrene as a polymerizable monomer, it is preferable that styrene is 50 mass% or more with respect to the whole quantity of a polymerizable monomer.

  A known colorant can be used as the colorant. For example, C.I. I. Direct Red 1, C.I. I. Direct Blue 1, C.I. I. Examples thereof include dyes such as basic green 6; pigments such as carbon black, mineral fast yellow, cadmium red, brilliant carmine 3B, and phthalocyanine blue.

  As a release agent, a wax in a solid state at room temperature is preferable in terms of blocking resistance, durability of a large number of sheets, low-temperature fixability, and offset resistance of a toner having toner particles. Examples thereof include paraffin wax, microcrystalline wax, Fischer-Tropsch wax, and ester wax. In order to improve the translucency of the image fixed on the OHP, a linear ester wax is particularly preferably used.

  The charge control agent can be externally added to the toner particles, but is preferably added to the surface layer portion and inside of the toner particles by dispersion in the polymerizable monomer composition. Examples of the charge control agent imparting negative chargeability include organometallic compounds and chelate compounds, and examples of the charge control agent imparting positive chargeability include amine compounds.

  Polymerization initiators used for the suspension polymerization toner particles include potassium peroxodisulfate, hydrogen peroxide, 2,2′-azobis- (2,4-dimethylvaleronitrile), benzoyl peroxide, t-butylperoxy Laurate.

  Examples of the crosslinking agent include polyfunctional compounds such as divinylbenzene, 4,4'-divinylbiphenyl, and ethylene glycol di (meth) acrylate.

  In addition, as a dispersion stabilizer for dispersing a polymerizable monomer composition in an aqueous medium in a suspension polymerization method, a water-soluble polymer that generally develops a repulsive force due to steric hindrance and an electrostatic repulsive force. They are roughly classified into poorly water-soluble inorganic compounds that aim to stabilize dispersion. The fine particles of the hardly water-soluble inorganic compound are preferably used because they are dissolved by an acid or an alkali and can be easily removed by washing with an acid or an alkali after polymerization. Among the hardly water-soluble inorganic compounds, metal phosphates are preferably used. Among these, alkaline earth metal phosphates such as calcium phosphate are preferable. For example, in the case of tricalcium phosphate, a dispersion stabilizer suitable for the suspension polymerization method can be obtained by charging and mixing a trisodium phosphate aqueous solution and a calcium chloride aqueous solution with sufficient stirring.

  In the case of a polymerization method using an aqueous medium such as a suspension polymerization method, the inclusion of a release agent can be promoted by adding a polar resin to the polymerizable monomer composition. When a polar resin is present in the polymerizable monomer composition in the aqueous medium, the polar resin moves to the vicinity of the interface between the aqueous medium and the polymerizable monomer composition due to the difference in hydrophilicity. Polar resin is unevenly distributed. As a result, the toner particles have a capsule structure having a core / shell structure, and even when a large amount of the release agent is contained in the core portion, the inclusion property of the release agent is improved.

  In addition, if a polar resin with a high melting temperature is selected for the shell, blocking is prevented during storage even when the core binder is designed to melt at a lower temperature for the purpose of low-temperature fixing. can do. As such a polar resin, a saturated or unsaturated polyester resin is preferable.

  The produced dispersion of toner particles is subjected to solid-liquid separation, and the separated toner particles are washed. At that time, the dispersion of the toner particles may be treated with an acid or an alkali in order to remove the dispersion stabilizer attached to the surface of the toner particles. Thereafter, the toner particles are separated by a general solid-liquid separation method. In order to completely remove the acid or alkali and the dispersion stabilizer dissolved therein, water is again added to wash the toner particles. This process is repeated several times, and after sufficient cleaning is performed, an aggregate of toner particles (hereinafter also referred to as toner wet cake) is obtained. The obtained toner wet cake is dried by a known drying means, and if necessary, a particle group having a particle size outside the predetermined range is separated by classification. The non-predetermined particle group separated at this time may be reused to improve the final yield.

  As the toner particles obtained by the method for producing toner particles of the present invention, only the toner particles obtained by the above-described polymerization method may be used, or an external additive is added to the toner particles for the purpose of imparting various properties to the toner particles. It may be externally added to the particles.

  The external additive preferably has a particle size of 1/10 or less of the number average particle size of the toner particles from the viewpoint of durability after external addition to the toner particles. Examples of the external additive include metal oxide fine particles such as aluminum oxide, nitride fine particles such as silicon nitride, carbide fine particles such as silicon carbide, inorganic metal salt fine particles such as calcium sulfate, and fatty acids such as zinc stearate. Metal salt fine particles and silica fine powder are used.

  The toner particles produced according to the present invention are used in a one-component developer and a two-component developer. For example, in the case of a magnetic toner having magnetic toner particles in which a magnetic material is contained in toner particles as a one-component developer, a magnet built in the developing sleeve is used to convey and frictionally charge the magnetic toner. There is a way. In addition, when using a non-magnetic toner that does not contain a magnetic material, there is a method of using a blade or a fur brush to forcibly frictionally charge the developing sleeve and transport the non-magnetic toner on the developing sleeve. . On the other hand, in the case of a two-component developer, a carrier is used together with the toner. As the carrier, composite ferrite particles formed of iron and copper, zinc, nickel, cobalt, manganese, and / or chromium are used. In general, a resin-coated carrier in which a carrier core particle is formed and then coated with a resin is used. In order to reduce the load on the toner of the carrier, the low-density carrier and the mixture of inorganic oxide and monomer produced by pulverization and classification after kneading the inorganic oxide and resin are suspended in an aqueous medium. A polymerized carrier may be used after polymerization.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, the embodiment of this invention is not limited to these. The measurement method used in the present invention will be described below.

(1) Measurement of polymerization rate The polymerization rate of the polymerizable monomer is calculated by measuring the amount of unreacted styrene by gas chromatography (GC) as follows.

  In the polymerization step, a dispersion of the polymerizable monomer composition is sampled, 0.4 g is precisely weighed and placed in a sample bottle. A well-balanced 15 g of acetone is added to this and the lid is capped, followed by thorough mixing. A tabletop ultrasonic cleaner with an oscillation frequency of 42 kHz and an electrical output of 125 W (for example, “B2510J-MTH”, manufactured by Branson) Irradiate with ultrasonic waves for 30 minutes. Thereafter, filtration is performed using a solvent-resistant membrane filter “Maysho Disc” (manufactured by Tosoh Corporation) having a pore diameter of 0.2 μm, and 2 μl of the filtrate is analyzed by gas chromatography. Then, the amount of unreacted styrene is calculated from a calibration curve prepared in advance using styrene, and the polymerization rate is measured by the ratio with the total amount of styrene extracted with acetone.

The measurement apparatus and measurement conditions are as follows.
GC: HP 6890GC
Column: HP INNOWax (200 μm × 0.40 μm × 25 m)
Carrier gas: He (constant pressure mode: 20 psi)
Oven: (1) Hold at 50 ° C for 10 minutes, (2) Increase to 200 ° C at 10 ° C / minute, (3) Hold at 200 ° C for 5 minutes Inlet: Temperature at 200 ° C, pulsed splitless mode
(20 → 40 psi, until 0.5 min)
Split ratio: 5.0: 1.0
Detector: Temperature 250 ° C (FID)

(2) Measurement of scale deposit amount In order to quantify the scale deposit amount, a test piece is placed in the polymerization vessel. An aluminum plate (length 100 mm × width 50 mm × thickness 2 mm) is used as a test piece. Four test pieces are placed on a stirring blade, and one batch of toner particles is produced. Then, the toner particles are removed from the polymerization vessel, immersed in water, washed lightly with water, dried, and weighed. The difference from the weight of the test piece before manufacturing the toner particles is taken, and the total amount of change in the weight of the four test pieces is taken as the amount of scale deposit. The evaluation is obtained by calculating the ratio of the amount of scale deposit to the total weight of the charged polymerizable monomer composition.
A: Ratio of scale deposit amount less than 500 ppm B: Scale deposit amount ratio of 500 ppm or more and less than 1000 ppm C: Scale deposit amount ratio of 1000 ppm or more and less than 2000 ppm D: Scale deposit amount ratio of 2000 ppm or more and less than 4000 ppm E: Scale deposit The ratio of the amount is 4000ppm or more

(3) Measurement of the amount of coarse particles The amount of coarse particles is measured by filtering the toner particle dispersion obtained through the polymerization reaction before sending it to the solid-liquid separation step, and evaluating it by the amount filtered off on the filter. To do. Specifically, the obtained dispersion of toner particles is filtered through a metal mesh mesh filter having a mesh size of 53 μm, and the ratio of the amount of particles filtered on the filter to the total amount of toner particles is calculated. .
A: Coarse particle amount ratio of less than 100 ppm B: Coarse particle amount ratio of 100 ppm or more and less than 300 ppm C: Coarse particle amount ratio of 300 ppm or more and less than 500 ppm D: Coarse particle amount ratio of 500 ppm or more and less than 1000 pm E: Coarse particles The amount ratio is 1000ppm or more

(4) Evaluation of Stability of Thermal Characteristics of Toner Particles As an index of thermal characteristics of toner particles, a melt index value at a temperature of 110 ° C. and a load of 10 kg is used. The melt index value represents the ease of melting of toner particles at an arbitrary temperature and load, and can be used as an index of thermal characteristics when fixing toner at an arbitrary temperature and load. Here, a method for measuring the melt index of the toner particles is described below.

<Measurement of melt index>
The melt index indicates the discharge amount from the orifice in 10 minutes at an arbitrary temperature and load. In this embodiment, the value is measured under the following conditions. This basically conforms to JIS standard K-7210.

  Semi-automatic 2-A Melt Index (Toyo Seiki Co. Ltd) is used as a measuring device.

  An orifice having a cavity inner diameter of 2.095 mm is put, and the temperature is adjusted to 110 ° C. in advance, and 3 to 8 g of toner particle samples are weighed and put therein. At this time, set the metal piston while being careful not to enter air bubbles, and keep the temperature for 5 minutes or more. Thereafter, measurement is performed while applying a constant load so that the sum of the piston and the weight is 10 kg. The measurement may be performed at an arbitrary time and converted to a discharge amount of 10 minutes.

<Evaluation of stability of thermal characteristics of toner particles by melt index value>
Evaluation of the stability of the thermal characteristics of the toner particles is carried out by preparing toner particles while depositing scale deposits by preparing toner batches of 10 batches using the same polymerization container. The melt index value of each of 10 batches of toner particles thus obtained is measured and evaluated by the standard deviation.
A: Standard deviation of melt index value is less than 0.5 B: Standard deviation of melt index value is 0.5 or more and less than 1.0 C: Standard deviation of melt index value is 1.0 or more and less than 2.0 D: Melt Standard deviation of index value is 2.0 or more and less than 4.0 E: Standard deviation of melt index value is 4.0 or more

[Example 1]
<Preparation process of polymerizable monomer composition>
The following materials were heated to a temperature of 60 ° C. and mixed for 30 minutes.
Styrene (vapor pressure 7 kPa at a temperature of 65 ° C.) 70 parts by mass n-butyl acrylate 30 parts by mass : 12), glass transition temperature Tg = 68 ° C., weight average molecular weight Mw = 10000, molecular weight distribution Mw / Mn = 5.12) 8 parts by mass Carbon black (BET specific surface area = 80 m ² / g, oil absorption = 120 ml / 100 g) 8 parts by mass / salicylic acid compound (E-88, manufactured by Orient Chemical Industries) 1 part by mass / zinc phthalocyanine 0.1 part by mass After mixing for 30 minutes, the following materials were mixed to obtain a polymerizable monomer composition.
Polymerization initiator 2,2′-azobis (2,4-dimethylvaleronitrile) 8 parts by mass Cyclohexane 8 parts by mass (vapor pressure 62 kPa at 65 ° C., 0 with respect to the total number of moles of polymerizable monomers .10 times the number of moles)

<Dispersing process>
5 parts by weight of Na ₃ PO ₄ · 12H ₂ O is charged into 332 parts by weight of ion-exchanged water and heated to 60 ° C., and then 58.3 revolutions per second using a stirrer (CLEAMIX, manufactured by M Technique). The mixture was stirred at (3500 rpm). To this, 27 parts by mass of a 1.0 mol / liter-CaCl ₂ aqueous solution was added to obtain an aqueous medium containing Ca ₃ (PO ₄ ) ₂ .

A polymerizable monomer composition is put into an aqueous medium, and stirred at 75 ° C. (4500 rpm) for 15 minutes with a stirrer (CLEARMIX) at a temperature of 60 ° C. in an N ₂ atmosphere to polymerize in the aqueous medium. The functional monomer composition was dispersed.

<Polymerization process>
The polymerization monomer composition dispersion is introduced into a polymerization vessel communicating with the atmosphere through a condenser, and stirred at a full zone stirring blade (manufactured by Shinko Pantech Co., Ltd.) at a temperature of 65 ° C. (polymerization temperature T1). The temperature was raised to 10 minutes and the polymerization reaction was carried out for 10 hours. After completion of the polymerization reaction, saturated water vapor (steam pressure: 205 kPa / temperature: 120 ° C.) was introduced while stirring was continued with a full zone stirring blade. Due to the introduction of saturated steam, the temperature of the reaction solution reached 100 ° C., and a distillation fraction began to come out. Residual monomers were distilled off by obtaining a predetermined amount of fractions, and cooled to obtain a toner particle dispersion.

<Washing / solid-liquid separation / drying process>
Hydrochloric acid was added to the obtained dispersion of toner particles and stirred to dissolve Ca ₃ (PO ₄ ) ₂ covering the toner particles, followed by solid-liquid separation with a pressure filter to obtain a toner wet cake. . This was put into water and stirred to obtain a dispersion again, followed by solid-liquid separation with the above-mentioned filter. The re-dispersion of toner wet cake in water and solid-liquid separation are repeated until Ca ₃ (PO ₄ ) ₂ is sufficiently removed, and finally solid-liquid separation is performed to obtain a toner wet cake. It was.

The resulting toner wet cake was crushed and dried with an air dryer (manufactured by Seishin Corporation: flash jet dryer: pipe diameter 0.1016 m) to obtain toner particles. The drying conditions were a blowing temperature of 90 ° C., a blowing air volume of 10 m ³ / min, a dryer outlet temperature of 40 ° C., and a toner wet cake feed rate that deviated from 40 ° C. depending on the moisture content of the toner wet cake. Adjusted to no speed.

<Evaluation>
The above process was repeated 10 batches, and the obtained toner particles were evaluated according to the above-described thermal particle stability evaluation method. The evaluation results are shown in Table 2.

  Moreover, after completion | finish of the polymerization process of 1st batch, it evaluated according to the measuring method of the amount of scale deposits mentioned above, and the measuring method of the amount of coarse particles. The evaluation results are shown in Table 2.

[Examples 2-7 and Comparative Examples 1-5]
Toner particles were produced in the same manner as in Example 1 except that the production conditions were changed as described in Table 1. The evaluation results are shown in Table 2.

  As is clear from Table 2, “Examples 1 to 7”, which are the toner particle production methods of the present invention, are less likely to cause scale adhesion and produce coarse particles compared to “Comparative Examples 1 to 5”. Was suppressed. The toner particles obtained by the method for producing toner particles of the present invention had stable thermal characteristics.

Claims (3)

A method for producing toner particles comprising a step of polymerizing a polymerizable monomer containing styrene in an aqueous medium in a polymerization container,
Adding the polymerizable monomer to the aqueous medium in the polymerization vessel;
Polymerizing the polymerizable monomer at a polymerization temperature T1,
An organic solvent having an amount of moles of 0.06 to 0.20 times the total number of moles of the polymerizable monomer at the time of addition to the polymerization vessel is added to the polymerizable monomer. Add until the polymerization rate reaches 50%,
The method for producing toner particles, wherein the organic solvent has a vapor pressure of 15 kPa or more higher than a vapor pressure of styrene at the polymerization temperature T1 at the polymerization temperature T1.   The method for producing toner particles according to claim 1, wherein the polymerizable monomer is polymerized in the polymerization vessel communicating with the atmosphere. The method for producing toner particles according to claim 1 or 2, wherein the vapor pressure of the organic solvent at the polymerization temperature T1 is 250 kPa or less.