JP2007293135A - Method for manufacturing toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a toner capable of preventing the desorption of a release agent at the time of obtaining toner particles by dispersing a kneaded material in a molten state or softened state into an aqueous medium. <P>SOLUTION: In a step s1, the kneaded material is created by kneading the toner raw material containing an admixture having polarity between the polarity of a binder and the polarity of a release agent and to mix the binder and the release agent, in addition to the binder, a colorant and the release agent in the molten or softened state of the binder. In a step s2, the aqueous medium containing water is prepared. In a step s3, the toner particles are obtained by dispersing the kneaded material created in the step s1 in a molten or softened state into the aqueous medium prepared in the step s2 to make the material into particles. Since the admixture is contained in the kneaded material, the desorption of the release agent from the binder can be prevented at the time of dispersing the kneaded material in the molten or softened state into the aqueous medium in the step s3. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a toner, for example, a toner used for developing an electrostatic image in an image forming process by electrophotography.

  An image forming apparatus that forms an image by electrophotography forms an electrostatic image on the surface of an electrophotographic photosensitive member (hereinafter, simply referred to as “photosensitive member”) that is an image carrier, and then supplies toner. Then, the electrostatic charge image is developed, and the formed toner image is transferred to a recording medium such as paper (hereinafter sometimes referred to as “transfer material”) and fixed to form an image. Toner used for developing an electrostatic image (hereinafter, sometimes referred to as “electrostatic image developing toner”) is a toner material other than the binder resin such as a colorant and a release agent. Etc. are distributed. The toner is charged by frictional charging, is carried on a developing roller, and is supplied to the surface portion of the photoreceptor.

  As a toner production method, there are a dry method in which granulation is performed without using a medium and a wet method in which toner particles are generated in the medium. In the pulverization method, which is one of the dry methods, a toner is obtained by kneading a toner raw material containing a binder and a colorant, and then pulverizing the obtained kneaded material with a pulverizer or the like (for example, Patent Documents). 1). In order to increase the definition of the image, it is preferable to reduce the particle diameter of the toner particles constituting the toner to, for example, about 7.0 μm or less. However, in the pulverization method, toner particles having such a small particle diameter are manufactured. It is difficult. In order to reduce the particle size of the toner particles in the pulverization method, it is necessary to perform classification after pulverization of the kneaded product. However, classification causes a problem that the yield of the toner decreases and the manufacturing cost increases. Further, in the pulverization method, the shape of the toner particles obtained is indefinite, so that the toner charging performance varies.

  Examples of the wet method include a polymerization method and an emulsion dispersion aggregation method. In the polymerization method, for example, a binder resin monomer is polymerized in a state in which a binder resin monomer and a toner raw material other than the binder resin such as a colorant are dispersed in water, and the resulting binder resin particles are colored. A toner is obtained by including a toner raw material such as an agent. In the emulsion dispersion aggregation method, for example, a toner raw material containing a binder resin and a colorant is dissolved in a water-insoluble organic solvent in which the binder resin can be dissolved, and the obtained resin solution is emulsified and dispersed in an aqueous medium. After removing the organic solvent from the obtained dispersion liquid, the resin particles in the dispersion liquid are aggregated to obtain toner particles (see, for example, Patent Document 2).

  In the polymerization method, since a polymerization reaction is performed in water, there is a problem that a resin that can be used as a binder resin is limited to a vinyl polymer that can be generated by radical polymerization. In addition, the polymerization method has a problem that the monomer of the binder resin, the polymerization initiator, the suspension stabilizer and the like remain in the toner particles, and the charging performance of the toner varies. In order to suppress variations in charging performance, it is necessary to remove these residues, but it is very difficult to remove monomers, polymerization initiators, suspension stabilizers, etc. that have entered the toner particles. It is.

  In the emulsification dispersion aggregation method, an organic solvent is used to dissolve or disperse the binder resin. Therefore, the organic solvent remains in the toner particles to be produced, and the dispersion state and composition of each component in the toner particles are changed for each preparation. There is a problem of changing. In addition, when an organic solvent is used, the amount of each component contained in the toner particles to be produced varies depending on the solubility of the binder resin in the organic solvent, so that it is possible to manufacture a toner having desired characteristics with good reproducibility. Have difficulty. In addition, from the viewpoint of worker safety, a solvent recovery device is required, and the manufacturing facility becomes large. Also, equipment for treating the recovered solvent is required. There is also a problem that the resin that can be used as the binder resin is limited to a resin that is soluble in an organic solvent. In addition, since the toner particles are produced by aggregating the resin particles after the organic solvent is removed, there is a problem that the toner particles having a uniform composition cannot be stably formed.

  As a technique for solving these problems, a kneaded material obtained by kneading a toner raw material containing a binder and a colorant is dispersed in an aqueous medium in a state where the binder is melted or softened. There has been proposed a toner production method (hereinafter referred to as “melt emulsification method”) in which toner particles are formed by the above-described method (see, for example, Patent Document 3).

Japanese Patent Laid-Open No. 6-186872 (pages 2, 8) JP 2004-195105 (Pages 2, 22-23) JP-A-2005-148406 (pages 12-13)

  The toner contains a release agent such as wax for the purpose of increasing the temperature at which the high temperature offset phenomenon starts to occur (hereinafter referred to as “high temperature offset generation start temperature”). The high temperature offset phenomenon means that the toner is excessively melted when it is fixed by heating and pressing the toner with a fixing member, as in the heat roller fixing method in which the toner is heated and pressed with a fixing heating roller. This is a phenomenon in which a part of the melted toner is fused and removed from the fixing member.

  In the melt emulsification method, the release agent is contained in the toner raw material, and is kneaded together with the binder resin and the colorant and dispersed in the binder resin. When the kneaded product produced by kneading is dispersed in an aqueous medium to form particles, the binder resin is heated to melt or soften (hereinafter, unless otherwise specified, “melting” includes “softening”). Not only the binder resin but also the release agent melts. As the binder resin, for example, a polyester resin is used. When a polyester resin is used as the binder resin, the melted release agent is easily separated from the binder resin and easily detached into the aqueous medium.

  When the release agent is desorbed, the content of the release agent contained in the manufactured toner becomes lower than the content of the release agent contained in the kneaded material before particle formation. When this occurs, the high temperature offset phenomenon starts to occur at a lower heating temperature than when the release agent does not desorb. Further, the content of the release agent contained in each toner particle differs among the toner particles, and the dispersibility of the release agent in the toner becomes low. For example, the fixability on the recording medium becomes non-uniform and constant. A quality image cannot be formed stably.

  Patent Documents 1 to 3 do not disclose a method for preventing the release agent from being detached when the kneaded product is granulated in the melt emulsification method. Patent Document 1 discloses using a polyester resin and a styrene acrylic copolymer resin as a binder resin in order to realize a positively chargeable toner. In the technique disclosed in Patent Document 1, since the toner is manufactured by a pulverization method, it is difficult to manufacture a toner having a small particle diameter as described above, and the shape of the toner particle becomes indeterminate and charging performance is improved. Variation occurs.

  Patent Document 2 discloses the use of a styrene acrylic copolymer resin together with a polyester resin in order to improve the stability of the charge amount of a toner using only a polyester resin as a binder resin. In the technique disclosed in Patent Document 2, the release agent is dissolved in an organic solvent and dispersed in an aqueous medium together with the polyester resin and the styrene acrylic copolymer resin. Since the toner is produced by agglomerating resin particles after removing the organic solvent, the toner particles cannot contain a release agent at a desired content. As a result, there is a problem that the fixing property of the toner is lowered and the temperature at which the high temperature offset is generated is lowered. Further, since toner particles having a uniform composition cannot be stably produced, the properties of the toner become non-uniform. For example, since the content of the release agent becomes non-uniform, the fixability to the recording medium becomes non-uniform, and an image with a certain quality cannot be stably formed.

  Patent Document 3 does not describe that the release agent is detached when the kneaded product is granulated. The technique disclosed in Patent Document 3 has room for improvement.

  An object of the present invention is to provide a toner production method capable of preventing the release agent from being detached when obtaining toner particles by dispersing the kneaded material in an aqueous medium in a melted or softened state. That is.

In addition to the binder, the colorant, and the release agent, the present invention has a polarity between the polarity of the binder and the polarity of the release agent. A kneading step for producing a kneaded product by kneading a toner raw material containing an admixture to be mixed in a state where the binder is melted or softened; and
A kneaded product obtained in the kneading step is granulated by dispersing it in an aqueous medium containing water in a melted or softened state to obtain toner particles. It is a manufacturing method.

  According to the present invention, in the kneading step, the toner raw material containing the colorant, the binder, the release agent and the admixture is kneaded in a state where the binder is melted or softened, and the colorant, the release agent is mixed with the binder. A kneaded product in which the mold and admixture are dispersed is produced. The kneaded product obtained in the kneading step is converted into particles by being dispersed in an aqueous medium in a state of being melted or softened in the granulation step, and becomes toner particles. Since the kneaded material contains an admixture that has a polarity between the polarity of the binder and the polarity of the release agent and mixes the binder and the release agent, the granulation step When the kneaded material is melted or softened and the release agent in the kneaded material is melted or softened, the release agent is held in the binder via the admixture. “Polarity” refers to the degree of charge bias within a molecule, and the greater the degree of polarity, the greater the degree of charge bias within a molecule.

In the present invention, the release agent is contained in the toner raw material in a weight ratio of 1 part by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the toner raw material.
The admixture is contained in the toner raw material in a weight ratio of 0.1 to 3 parts by weight with respect to 1 part by weight of the release agent.

  According to the present invention, the toner raw material contains a release agent in a weight ratio of 1 to 10 parts by weight with respect to 100 parts by weight of the toner raw material, and the admixture is 0 parts by weight with respect to 1 part by weight of the release agent. .1 parts by weight or more and 3 parts by weight or less. When the release agent is contained in the toner raw material in a weight ratio of less than 1 part by weight with respect to 100 parts by weight of the toner raw material, the effect of including the release agent is not sufficiently exerted, and the fixing member is heated and heated. When the toner is fixed to the recording medium by pressing, there is a possibility that the high temperature offset generation start temperature cannot be increased. When the release agent is contained in the toner raw material at a weight ratio exceeding 10 parts by weight with respect to 100 parts by weight of the toner raw material, the storage stability of the toner is lowered, and the toner is stored while being stored in the storage container. Aggregation between particles tends to occur. When the admixture is contained in the toner raw material in a weight ratio of less than 0.1 with respect to 1 part by weight of the release agent, the effect of including the admixture is not sufficiently exhibited, and the release agent is used in the granulation step. May occur. When the admixture is contained in the toner raw material in a weight ratio exceeding 3 parts by weight with respect to 1 part by weight of the release agent, the properties of the toner imparted by the binder may be inhibited by the admixture. Fixability of toner to the recording medium is reduced. Inclusion of a release agent in the toner raw material at a weight ratio of 1 part by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the toner raw material increases the high temperature offset generation start temperature without lowering the storage stability. be able to. Further, when the admixture is contained in the toner raw material at a weight ratio of 0.1 parts by weight or more and 3 parts by weight or less with respect to 1 part by weight of the release agent, for example, in the granulation step without reducing the fixability. The release of the release agent from the adhesive can be prevented more reliably.

  In the invention, the admixture is contained in the toner raw material in a weight ratio of 1 part by weight or more and 20 parts by weight or less with respect to 100 parts by weight of the binder.

  According to the present invention, the toner raw material contains the admixture in a weight ratio of 1 to 20 parts by weight with respect to 100 parts by weight of the binder. When the admixture is contained in the toner raw material in a weight ratio of less than 1 part by weight with respect to 100 parts by weight of the binder, the effect of containing the admixture is not sufficiently exhibited, and the release agent is used in the granulation process. May occur. If the admixture is contained in the toner raw material in a weight ratio exceeding 20 parts by weight with respect to 100 parts by weight of the binder, the properties of the toner imparted by the binder may be inhibited by the admixture. Fixability of toner to the recording medium is reduced. When the admixture is contained in the toner raw material in a weight ratio of 1 part by weight or more and 20 parts by weight or less with respect to 100 parts by weight of the binder, the release agent is prevented from being detached in the granulation step and the binder is bonded. The influence of the admixture on the characteristics of the toner imparted by the adhesive, for example, the fixability to the recording medium can be suppressed.

In the present invention, the binder is made of a polyester resin.
According to the invention, the binder comprises a polyester resin. Since the polyester resin includes an ester bond which is a bond having polarity in the main chain and includes a carboxyl group and a hydroxyl group which are polar groups at the terminal, the binder has polarity. Since the toner raw material contains an admixture having a polarity between that of the binder and that of the release agent, the kneaded product is melted or softened in the granulation step, and the release material in the kneaded product is released. When the mold is melted or softened, the release agent is held in the binder composed of the polyester resin through the admixture.

In the present invention, the admixture is composed of a styrene acrylic copolymer resin.
According to the present invention, the admixture comprises a styrene acrylic copolymer resin. The styrene acrylic copolymer resin contains a styrene structural unit derived from a styrene monomer and an acrylic structural unit derived from an acrylic monomer. Since the acrylic structural unit includes a carboxyl group or an ester group which is a polar group in the side chain, it has polarity. Styrene-based structural units are less polar than acrylic structural units. Since the polyester resin contains a polar ester bond in the main chain and has a polar carboxyl group and a hydroxyl group at the terminal, the admixture made of styrene acrylic copolymer resin is compared with the binder made of polyester resin. The degree of polarity is small. By using a binder composed of a polyester resin and using an admixture composed of a styrene acrylic copolymer resin, when using a mold release agent having a lower degree of polarity than the styrene acrylic copolymer resin as a mold release agent, Release of the release agent in the granulation step can be prevented.

In the present invention, the aqueous medium contains a dispersant,
The dispersant is a water-soluble dispersant.

  According to the present invention, the aqueous medium in which the kneaded material is dispersed in the granulation step contains a water-soluble dispersant as a dispersant. As a result, the dispersion of the concentration of the dispersant in the aqueous medium can be suppressed as compared with the case where a dispersant insoluble in water is used, and thus the kneaded material can be more uniformly dispersed in the aqueous medium. Therefore, it is possible to narrow the width of the particle size distribution of the generated toner particles. In addition, since the kneaded product can be dispersed in an aqueous medium so that each toner particle to be produced contains an admixture, it is possible to more reliably prevent the release agent from being detached from the binder. .

  According to the present invention, the kneaded product contains an admixture that has a polarity between the polarity of the binder and the polarity of the release agent and mixes the binder and the release agent. Therefore, when the kneaded material is melted or softened in the granulation step and the release agent in the kneaded material is melted or softened, the release agent is held in the binder via the admixture. As a result, it is possible to more reliably prevent the release agent from being released from the binder in the granulation step as compared with the case where no admixture is contained in the toner raw material. The residual ratio of the agent can be increased. Accordingly, it is possible to prevent a decrease in the start temperature of occurrence of high temperature offset when the toner is fixed to the recording medium by, for example, a heat roller fixing method. Further, since the dispersibility of the release agent in the toner can be improved, an image with a certain quality can be stably formed.

  According to the present invention, since the release agent is contained in the toner raw material in a weight ratio of 1 part by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the toner raw material, the storage stability is not lowered. The high temperature offset generation start temperature can be increased. In addition, since the admixture is contained in the toner raw material in a weight ratio of 0.1 to 3 parts by weight with respect to 1 part by weight of the release agent, it does not deteriorate the fixability and does not deteriorate in the granulation step. The release of the release agent from the adhesive can be prevented more reliably.

  According to the present invention, since the admixture is contained in the toner raw material at a weight ratio of 1 part by weight or more and 20 parts by weight or less with respect to 100 parts by weight of the binder, the release agent is removed in the granulation step. In addition to preventing separation, the effect of the admixture on the properties of the toner imparted by the binder can be suppressed. Accordingly, it is possible to more reliably prevent the release agent from being detached from the binder in the granulating step without deteriorating the properties of the toner imparted by the binder, for example, the fixing property to the recording medium.

  Further, according to the present invention, the release agent is held in the binder made of the polyester resin through the admixture in the granulation step, so that when the toner containing the binder made of the polyester resin is manufactured. The release of the release agent can be prevented. Therefore, for example, a toner containing a binder composed of a polyester resin can be produced without reducing the high temperature offset generation start temperature when the toner is fixed to the recording medium by a hot roller fixing method.

  Further, according to the present invention, since the admixture made of styrene acrylic copolymer resin has a lower degree of polarity than the binder made of polyester resin, the degree of polarity is higher than that of styrene acrylic copolymer resin as a release agent. When using a release agent having a small size, release of the release agent in the granulation step can be prevented.

  Further, according to the present invention, the aqueous medium in which the kneaded product is dispersed in the granulation step contains a water-soluble dispersant as a dispersant, so that the aqueous medium is more water-soluble than when a water-insoluble dispersant is used. Variation in the concentration of the dispersant in the medium can be reduced, and the kneaded material can be more uniformly dispersed in the aqueous medium. Therefore, it is possible to narrow the width of the particle size distribution of the generated toner particles. In addition, since the kneaded product can be dispersed in an aqueous medium so that each toner particle to be produced contains an admixture, it is possible to more reliably prevent the release agent from being detached from the binder. .

  FIG. 1 is a flowchart showing a procedure of a toner manufacturing method according to an embodiment of the present invention. The toner manufacturing method of the present embodiment includes a kneading step (step s1), an aqueous medium preparation step (step s2), a granulating step (step s3), a cooling step (step s4), and a cleaning step (step s5). ), A separation step (step s6), a drying step (step s7), and an external addition processing step (step s8). The production of the toner according to the present embodiment is started in step s0 and proceeds to the kneading step in step s1.

[Kneading process]
In the kneading step of step s1, in addition to the binder, the colorant and the release agent, the toner raw material containing the admixture is kneaded in a state where the binder is melted or softened to generate a kneaded product. As a result, a kneaded product in which the colorant, the release agent and the admixture are dispersed in the binder is generated. The admixture has a polarity between the polarity of the binder and the polarity of the release agent, and the binder and the release agent are mixed. By including the admixture in the toner raw material, the binder and the release agent can be mixed, so when the release agent melts or softens as the binder melts or softens, the release agent is released. Aggregation of agents can be prevented. Therefore, the dispersibility of the release agent in the binder can be improved.

  The toner raw material may contain an additive such as a charge control agent in addition to the binder, the colorant, the release agent and the admixture. The additive is kneaded together with a colorant, a binder, a release agent, and an admixture and dispersed in the binder.

(A) Binder As the binder, any material that has binding properties and can be melted or softened by heating can be used without particular limitation. In the following, unless otherwise specified, “melting” means fluidizing and includes “softening”. The binder is made of, for example, a resin material. As the binder made of a resin material (hereinafter sometimes referred to as “binder resin”), any resin that can be melted by heating can be used without particular limitation.

  The softening point Tm of the binder is 150 ° C. or lower in this embodiment, and more specifically 60 ° C. or higher and 150 ° C. or lower. The softening point Tm of the binder is not limited to the above range, but is preferably 150 ° C. or lower, more preferably 60 ° C. or higher and 150 ° C. or lower as in the present embodiment. When the softening point Tm of the binder exceeds 150 ° C., kneading with the colorant and the additive becomes difficult, and the dispersibility of the colorant and the additive may be lowered. Further, the fixing property of the toner to the transfer material is lowered, and there is a possibility that fixing failure occurs. If the softening point of the binder is less than 60 ° C., the glass transition point Tg of the binder is likely to be close to room temperature, so that the toner causes thermal aggregation inside the image forming apparatus, resulting in poor printing. There is a risk of causing failure.

  The glass transition point Tg of the binder is 30 ° C. or higher and 80 ° C. or lower in this embodiment. The glass transition point Tg of the binder is not limited to the above range, but is preferably 30 ° C. or higher and 80 ° C. or lower as in the present embodiment in consideration of the fixing property and storage stability of the obtained toner. When the glass transition point Tg of the binder is less than 30 ° C., the storage stability becomes insufficient, the toner tends to agglomerate inside the image forming apparatus, and printing failure may occur. When the glass transition point Tg of the binder exceeds 80 ° C., the fixability is lowered and fixing failure may occur.

  The weight average molecular weight of the binder is 5000 or more and 500000 or less in this embodiment. Although the weight average molecular weight of a binder is not limited to the said range, it is preferable that it is 5000 or more and 500000 or less like this embodiment. When the weight average molecular weight of the binder is less than 5000, the mechanical strength of the binder is lower than that required for the binder for toner, and the resulting toner particles are stirred inside the developing device. There is a possibility that the charging performance may vary due to pulverization and deformation. When the weight average molecular weight of the binder exceeds 500,000, kneading with the colorant and the additive becomes difficult, and the dispersibility of the colorant and the additive may be lowered. Further, since the glass transition point Tg of the binder is likely to exceed 80 ° C., the fixability may be deteriorated and fixing failure may occur. The weight average molecular weight of the binder is a value in terms of polystyrene measured by gel permeation chromatography (abbreviation: GPC).

  In the present embodiment, the binder is made of a polyester resin. By using a binder made of a polyester resin, it is possible to improve the powder fluidity and fixability of the manufactured toner as compared with the case of using a binder made of another resin material. In addition, since the polyester resin is excellent in translucency, a color toner having excellent secondary color reproducibility can be realized by using a binder composed of a polyester resin.

  In this embodiment, the acid value of the polyester resin is 5 mgKOH / g or more and 40 mgKOH / g or less, and more specifically 10 mgKOH / g or more and 20 mgKOH / g or less. Although the acid value of a polyester resin is not limited to the said range, it is preferable that they are 5 mgKOH / g or more and 40 mgKOH / g or less like this embodiment. If the acid value of the polyester resin is less than 5 mgKOH / g, it is difficult to disperse the colorant in the binder resin, and sufficient coloring power may not be obtained. When the acid value of the polyester resin exceeds 40 mgKOH / g, the environmental stability of the toner is lowered, and the toner cannot be stably charged to a constant charge amount, and for example, the toner may be scattered.

  In this embodiment, the hydroxyl value of the polyester resin is 5 mgKOH / g or more and 40 mgKOH / g or less, and more specifically, 5 mgKOH / g or more and 25 mgKOH / g or less. Although the hydroxyl value of a polyester resin is not limited to the said range, it is preferable that they are 5 mgKOH / g or more and 40 mgKOH / g or less like this embodiment. When the hydroxyl value of the polyester resin is less than 5 mgKOH / g, it is difficult to disperse the colorant in the binder resin, and there is a possibility that sufficient coloring power cannot be obtained. When the acid value of the polyester resin exceeds 40 mgKOH / g, the environmental stability of the toner is lowered, and the toner cannot be stably charged to a constant charge amount, and for example, the toner may be scattered.

  Examples of the polyester resin include polycondensation products of polybasic acids and polyhydric alcohols. “Polybasic acids” are polybasic acids and derivatives of polybasic acids, and include, for example, acid anhydrides and esterified products of polybasic acids. “Polyhydric alcohols” are compounds having two or more hydroxyl groups, and include both alcohols and phenols.

  Examples of polybasic acids include aromatic carboxylic acids such as terephthalic acid, isophthalic acid, phthalic anhydride, trimellitic anhydride, pyromellitic acid, naphthalenedicarboxylic acid, maleic anhydride, fumaric acid, succinic acid, adipic acid, etc. Examples thereof include aliphatic carboxylic acids. One type of polybasic acids may be used alone, or two or more types may be used in combination.

  Examples of polyhydric alcohols include aliphatic polyhydric alcohols such as ethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol, and glycerin, and alicyclic compounds such as cyclohexanediol, cyclohexanedimethanol, and hydrogenated bisphenol A. Examples thereof include aromatic diols such as polyhydric alcohols, ethylene oxide adducts of bisphenol A, and propylene oxide adducts of bisphenol A. “Bisphenol A” is 2,2-bis (p-hydroxyphenyl) propane. Examples of the ethylene oxide adduct of bisphenol A include polyoxyethylene-2,2-bis (4-hydroxyphenyl) propane. Examples of the propylene oxide adduct of bisphenol A include polyoxypropylene-2,2-bis (4-hydroxyphenyl) propane. One type of polyhydric alcohols may be used alone, or two or more types may be used in combination.

  The polyester resin can be synthesized by subjecting a polybasic acid and a polyhydric alcohol to a condensation polymerization reaction. More specifically, it can be synthesized by, for example, subjecting a polybasic acid and a polyhydric alcohol to a polycondensation reaction, specifically a dehydration condensation reaction in the presence of a catalyst in an organic solvent or in the absence of a solvent. At this time, a demethanol polycondensation reaction may be carried out using a methyl esterified product of a polybasic acid as part of the polybasic acid. The polycondensation reaction between the polybasic acid and the polyhydric alcohol may be terminated when the acid value and softening point of the polyester resin to be produced reach predetermined values. In this polycondensation reaction, by appropriately changing the blending ratio of polybasic acids and polyhydric alcohols, the reaction rate, etc., for example, adjusting the number of carboxyl groups and hydroxyl groups bonded to the terminal of the polyester resin to be produced, The acid value and hydroxyl value of the polyester resin can be adjusted. In addition, other physical property values such as a softening point can be adjusted.

(B) Colorant As the colorant, any of known organic dyes, organic pigments, inorganic pigments and the like used as toner colorants can be used. Specific examples of the colorant include the following colorants. In the following, C.I. I. Is a color index.

  Examples of the black colorant include carbon black, copper oxide, manganese dioxide, aniline black, activated carbon, nonmagnetic ferrite, magnetic ferrite, and magnetite.

  Examples of yellow colorants include C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 155, C.I. I. Pigment yellow 180, C.I. I. And CI Pigment Yellow 185.

  Examples of the orange colorant include red chrome yellow, molybdenum orange, permanent orange GTR, pyrazolone orange, vulcan orange, indanthrene brilliant orange RK, benzidine orange G, indanthrene brilliant orange GK, C.I. I. Pigment orange 31, C.I. I. And CI Pigment Orange 43.

  Examples of the red colorant include C.I. I. Pigment red 19, C.I. I. Pigment red 48: 3, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 150, C.I. I. And CI Pigment Red 184.

  Examples of purple colorants include manganese purple, fast violet B, and methyl violet lake.

  Examples of the blue colorant include C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 16, C.I. I. And CI Pigment Blue 60.

  Examples of the green colorant include chrome green, chromium oxide, pigment green B, micalite green lake, final yellow green G, C.I. I. And CI Pigment Green 7.

  Examples of the white colorant include compounds such as zinc white, titanium oxide, antimony white, and zinc sulfide.

  One of these colorants may be used alone, or two or more of different colors may be used in combination. Also, a plurality of colorants of the same color can be used in combination. The use ratio of the colorant in the toner raw material is not particularly limited and can be appropriately selected from a wide range according to various conditions such as the types of the binder and the colorant and the properties required for the toner particles to be obtained. The weight ratio is preferably 0.1 parts by weight or more and 20 parts by weight or less, and more preferably 5 parts by weight or more and 15 parts by weight or less with respect to 100 parts by weight of the binder. If the amount of the colorant used is less than 0.1 parts by weight, sufficient coloring power cannot be obtained, the amount of toner required to form an image having a desired image density increases, and toner consumption increases. There is a risk. When the ratio of the colorant used exceeds 20 parts by weight, the dispersibility of the colorant in the kneaded product is lowered, and there is a possibility that a uniform toner cannot be obtained.

(C) Release agent Examples of the release agent include wax. “Wax” includes substances that exhibit waxy physical properties. Examples of the wax include polyolefin wax such as polypropylene wax and polyethylene wax, synthetic wax such as Fischer-Tropsch wax, alcohol wax and ester wax, coal-based wax such as montan wax, petroleum-based wax such as paraffin wax, and carnauba wax. And natural waxes such as vegetable waxes such as rice wax. A mold release agent may be used individually by 1 type, and 2 or more types may be used together.

  The release agent has no polar groups or polar bonds, or has a small number of polar groups or polar bonds. The “polar group” is a group having polarity, and the “polar bond” is a bond having polarity. Examples of the polar group include a carboxyl group and a hydroxyl group. Examples of the polar bond include an ester bond.

  For example, polyolefin waxes are nonpolar compounds that do not have polar groups and polar bonds. Fischer-Tropsch wax is a wax-like hydrocarbon synthesized by catalytic hydrogenation of carbon monoxide using the Fischer-Tropsch method, and is structurally a linear paraffin wax with few methyl branches. And a nonpolar compound having no polar bond. Alcohol wax is an aliphatic alcohol having about 14 to 30 carbon atoms and has a hydroxyl group as a polar group. However, since the carbon chain is long, the contribution of the polar group is small and the degree of polarity is small. The ester wax is, for example, an ester of a linear saturated carboxylic acid having about 14 to 30 carbon atoms and a linear saturated monohydric alcohol having about 14 to 30 carbon atoms, and has an ester bond as a polar bond, but has a long carbon chain. Therefore, the contribution of the polar bond is small and the degree of polarity is small. Carnauba wax has the same structure as ester wax.

  In this embodiment, a release agent having a melting point lower than the softening point of the binder is used. The melting point of the release agent is not limited to this, but preferably has a melting point lower than the softening point of the binder as in this embodiment. By using such a release agent, the melt viscosity of the toner can be reduced, and the temperature at which the low temperature offset phenomenon starts to occur (hereinafter referred to as “low temperature offset generation start temperature”) can be reduced. The “low temperature offset phenomenon” means that when the toner is heated and pressed by a fixing member as in the heat roller fixing method, the toner is not sufficiently melted, and the adhesive force between the toner and the fixing member is This is a phenomenon that exceeds the adhesive force with the recording medium and a part of the toner adheres to the fixing member and is removed.

  In this embodiment, the release agent is contained in the toner material in a weight ratio of 1 part by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the toner material. The amount of the release agent used is not limited to the above range, but is preferably 1 to 10 parts by weight with respect to 100 parts by weight of the toner raw material as in this embodiment. In other words, the content of the release agent in the toner material is preferably 1% by weight or more and 10% by weight or less. Inclusion of a release agent in the toner raw material at a weight ratio of 1 part by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the toner raw material increases the high temperature offset generation start temperature without reducing storage stability. Can do. When the release agent is contained in the toner raw material in a weight ratio of less than 1 part by weight with respect to 100 parts by weight of the toner raw material, the effect of including the release agent is not sufficiently exerted, and the fixing member is heated and heated. When the toner is fixed to the recording medium by pressing, there is a possibility that the high temperature offset generation start temperature cannot be increased. When the release agent is contained in the toner raw material at a weight ratio exceeding 10 parts by weight with respect to 100 parts by weight of the toner raw material, the storage stability of the toner is lowered, and the toner is stored while being stored in the storage container. Aggregation between particles tends to occur.

(D) Admixture As the admixture, those having a polarity between the polarity of the binder and the polarity of the release agent are used. The admixture is selected according to the kind of the binder and the release agent. In this embodiment, the binder is made of a polyester resin and has a higher degree of polarity than the release agent. Therefore, the binder has a degree of polarity smaller than that of the binder and greater than that of the release agent. An agent is used. In this embodiment, the admixture is made of a resin material.

  The amount of admixture used is selected according to the amount of mold release agent used. In the present embodiment, the admixture is contained in the toner raw material in a weight ratio of 0.1 to 3 parts by weight with respect to 1 part by weight of the release agent. The amount of the admixture used is not limited to the above range, but is preferably a weight ratio of 0.1 parts by weight or more and 3 parts by weight or less with respect to 1 part by weight of the release agent as in this embodiment. Influence of the admixture on the properties of the toner imparted by the binder by incorporating the admixture in the toner raw material in a weight ratio of 0.1 to 3 parts by weight with respect to 1 part by weight of the release agent. And the release of the release agent from the binder in the granulation step described later can be prevented. For example, detachment of the release agent from the binder can be prevented without lowering the fixability.

  If the admixture is contained in the toner raw material at a weight ratio of less than 0.1 parts by weight with respect to 1 part by weight of the release agent, the effect of containing the admixture is not sufficiently exhibited, and the binder is separated from the binder. There is a possibility that it cannot be mixed with the mold. This may reduce the dispersibility of the release agent in the binder. In addition, the release agent may be detached in the granulation process. If the admixture is contained in the toner raw material in a weight ratio exceeding 3 parts by weight with respect to 1 part by weight of the release agent, the properties of the toner imparted by the binder may be hindered by the admixture. For example, when a binder made of a polyester resin is used as in this embodiment, if the admixture is contained in the toner raw material in a weight ratio exceeding 3 parts by weight with respect to 1 part by weight of the release agent, the recording medium There is a possibility that the fixing property of the toner to the toner will be lowered, and the low temperature offset generation start temperature will rise.

  The amount of admixture used is selected according to the amount of binder used. In this embodiment, the admixture is contained in the toner raw material at a weight ratio of 1 part by weight or more and 20 parts by weight or less with respect to 100 parts by weight of the binder. The amount of the admixture used is not limited to the above range, but is preferably 1 part by weight or more and 20 parts by weight or less with respect to 100 parts by weight of the binder as in this embodiment. By setting the amount of the admixture used within this range, it is possible to more reliably prevent the properties of the toner imparted by the binder from being hindered by the admixture. For example, it is possible to prevent the toner fixing property from being lowered. Further, the binder and the release agent can be mixed more reliably.

  When the admixture is contained in the toner raw material in a weight ratio of less than 1 part by weight with respect to 100 parts by weight of the binder, the effect of containing the admixture is not sufficiently exhibited, and the binder and the release agent May not be sufficiently mixed. As a result, the dispersibility of the release agent in the binder is lowered, and the release agent may be detached in the granulation step. If the admixture is contained in the toner raw material in a weight ratio exceeding 20 parts by weight with respect to 100 parts by weight of the binder, the properties of the toner imparted by the binder may be inhibited by the admixture. For example, the fixability of the toner to the recording medium is lowered, and even if a binder made of a polyester resin is used as the binder, the minimum fixing temperature described later may exceed 170 ° C.

  In the present embodiment, the admixture is in a weight ratio range of 0.1 to 3 parts by weight with respect to 1 part by weight of the release agent, and 1 part by weight or more with respect to 100 parts by weight of the binder. It is contained in the toner material in a weight ratio range of 20 parts by weight or less. As a result, it is possible to prevent the properties of the toner imparted by the binder from being hindered by the admixture, and to more reliably mix the binder and the release agent.

  The softening point Tm of the admixture is preferably selected according to the softening point Tm of the binder. In this embodiment, the softening point Tm (2) of the admixture is different from the softening point Tm (1) of the binder (| Tm (2) −Tm (1) | Is selected to be not more than 5 ° C. The difference between the softening point Tm (2) of the admixture and the softening point Tm (1) of the binder is not limited to this, but 10 ° C. as in this embodiment. Preferably, the temperature is 5 ° C. or less, for example, when the softening point Tm (2) of the admixture is higher than the softening point Tm (1) of the binder. When the difference between (2) and the softening point Tm (1) of the binder exceeds 10 ° C., the admixture is melted when the binder is melted or softened in the kneading step and the granulation step described later. Or it is not softened, and it becomes difficult to mix the release agent and the binder by the admixture. Further, the dispersibility of the release agent may decrease, and the release agent may be detached during the granulation process, and the softening point Tm (2) of the admixture is the softening point Tm (1) of the binder. If the difference between the softening point Tm (2) of the admixture and the softening point Tm (1) of the binder exceeds 10 ° C., the admixture will melt too much when the toner is fixed. There is a possibility that an offset phenomenon may occur, and there is a risk that the start temperature of occurrence of high temperature offset may decrease, and either the softening point Tm (2) of the admixture or the softening point Tm (1) of the binder may be higher. .

  The softening point Tm of the admixture is 150 ° C. or lower in this embodiment, and more specifically 60 ° C. or higher and 150 ° C. or lower. The softening point Tm of the admixture is not limited to the above range, but is preferably 150 ° C. or lower, more preferably 60 ° C. or higher and 150 ° C. or lower as in this embodiment. When the softening point Tm of the admixture exceeds 150 ° C., kneading with the binder, colorant, release agent and additive becomes difficult, and the release agent and binder are sufficiently mixed by the admixture. The dispersibility of the release agent in the binder may be reduced. In addition, the release agent may be detached in the granulation process. In addition, the fixability of the toner to the recording medium is lowered, and there is a possibility that fixing failure occurs. If the softening point of the admixture is less than 60 ° C., the glass transition point Tg of the admixture tends to be close to room temperature, so that the toner causes heat aggregation inside the image forming apparatus, printing failure, apparatus failure, etc. May be induced.

  The glass transition point Tg of the admixture is 30 ° C. or higher and 80 ° C. or lower in the present embodiment. The glass transition point Tg of the admixture is not limited to the above range, but is preferably 30 ° C. or higher and 80 ° C. or lower as in the present embodiment in consideration of the fixing property and storage stability of the obtained toner. When the glass transition point Tg of the admixture is less than 30 ° C., the storage stability becomes insufficient, the toner tends to agglomerate inside the image forming apparatus, and printing failure may occur. When the glass transition point Tg of the admixture exceeds 80 ° C., the fixability is lowered and fixing failure may occur.

  The weight average molecular weight of the admixture is 5000 or more and 500000 or less in this embodiment. The weight average molecular weight of the admixture is not limited to the above range, but is preferably 5000 or more and 500000 or less as in the present embodiment. When the weight average molecular weight of the admixture is less than 5,000, the mechanical strength of the admixture becomes low, the mechanical strength of the obtained toner particles becomes low, and the toner particles are deformed by being pulverized by stirring inside the developing device. However, the charging performance may vary. When the weight average molecular weight of the admixture exceeds 500,000, it becomes difficult to knead with the binder, colorant, release agent and additive, and the binder and the release agent are not sufficiently mixed, and the binder is not mixed. There is a possibility that the dispersibility of the release agent in the adhesive may be lowered. In addition, the release agent may be detached in the granulation process. Further, since the glass transition point Tg of the admixture tends to exceed 80 ° C., the fixability may be lowered, and fixing failure may occur. The weight average molecular weight of the admixture is a value in terms of polystyrene measured by gel permeation chromatography (abbreviation GPC).

  In the present embodiment, the admixture is made of a styrene acrylic copolymer resin. Examples of the styrene acrylic copolymer resin include a copolymer of an acrylic monomer and a styrene monomer. The styrene acrylic copolymer resin contains a styrene structural unit derived from a styrene monomer and an acrylic structural unit derived from an acrylic monomer. Since the acrylic structural unit includes a carboxyl group or an ester group which is a polar group in the side chain, it has polarity. The styrenic structural unit does not contain a polar group, or the polarity of an alkyl group such as a methyl group such as a methyl group contained in the structural unit is different from that of a polar group such as a carboxyl group or an ester group contained in an acrylic structural unit. Since it is smaller than the degree of polarity, the degree of polarity is smaller than that of the acrylic structural unit. Since the polyester resin constituting the binder in the present embodiment contains a polar ester bond in the main chain and has a polar carboxyl group and a hydroxyl group at the terminal, the degree of polarity compared to the styrene acrylic copolymer resin. Is big. In addition, the release agent does not contain polar groups and polar bonds like polyolefin wax, or has less polar groups and polar bonds than ester wax, and therefore has a degree of polarity compared to styrene acrylic copolymer resin. small.

  Thus, the admixture made of styrene acrylic copolymer resin has a polarity between the polarity of the binder made of polyester resin and the polarity of the release agent. More specifically, the admixture made of styrene acrylic copolymer resin has a polarity smaller than that of the binder made of polyester resin and larger than that of the release agent. Therefore, by using an admixture made of styrene acrylic copolymer resin, the binder made of polyester resin and the release agent can be mixed, so the dispersibility of the release agent in the binder is improved. Can be made. In addition, it is possible to prevent the release agent from being detached in the granulation step described later.

  The proportion of structural units derived from acrylic monomers in the styrene acrylic copolymer resin (hereinafter referred to as “acrylic structural units”) is 10 mol% or more and 50 mol% or less in this embodiment. The ratio of the acrylic structural unit is not limited to the above range, but is preferably 10 mol% or more and 50 mol% or less in the present embodiment. When a polyester resin having an acid value of 5 mgKOH / g or more and 40 mgKOH / g or less is used as the binder, the proportion of the acrylic structural unit contained in the styrene acrylic copolymer resin constituting the admixture is less than 10 mol%. And the polarity of the admixture is too close to that of the mold release agent, and the difference between the polarities of the binder and the binder becomes too large, and the binder and mold release agent may not be mixed. There is. When the proportion of acrylic structural units exceeds 50 mol%, the polarity of the admixture becomes too close to that of the binder, and the difference from the polarity of the release agent becomes too large. There is a possibility that the agent and the release agent cannot be mixed. By setting the ratio of the acrylic structural unit to 10 mol% or more and 50 mol% or less, the binder and the release agent can be more reliably mixed. In the present embodiment, the ratio of the acrylic monomer contained in the raw material monomer of the styrene acrylic copolymer resin is the ratio of the acrylic structural unit contained in the styrene acrylic copolymer resin.

  Examples of acrylic monomers include acid monomers and ester monomers. Examples of the acid monomer include acrylic acid and methacrylic acid. Examples of ester monomers include methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, Acrylic acid ester monomers such as n-octyl acrylate, decyl acrylate and dodecyl acrylate, and methyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, n-methacrylate And methacrylic acid ester monomers such as hexyl, 2-ethylhexyl methacrylate, n-octyl methacrylate, decyl methacrylate and dodecyl methacrylate. Among these acrylic monomers, it is preferable to use ester monomers. By using an ester monomer, the polarity of the admixture can be close to that of the mold release agent, so that the mold release agent and the binder can be mixed more reliably. The acrylic monomer may have a substituent. Examples of the acrylic monomer having a substituent include an acrylic ester type or a methacrylic ester type having a hydroxyl group such as hydroxyethyl acrylate and hydroxypropyl methacrylate. And monomers. One type of acrylic monomer may be used alone, or two or more types may be used in combination.

  Examples of the styrene monomer include aromatic vinyl monomers such as styrene and α-methylstyrene. A styrene-type monomer may be used individually by 1 type, and 2 or more types may be used together.

  Styrene acrylic copolymer resin is, for example, a solution polymerization method or suspension of one or more acrylic monomers and one or more styrene monomers in the presence of a radical polymerization initiator. It can be produced by polymerizing by a polymerization method, an emulsion polymerization method or the like.

  Specific examples of the styrene acrylic copolymer resin constituting the admixture include styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-propyl acrylate copolymer. Examples thereof include a polymer, a styrene-methyl methacrylate copolymer, a styrene-ethyl methacrylate copolymer, and a styrene-butyl methacrylate copolymer.

  The material of the admixture is not limited to the styrene acrylic copolymer resin, and may be a polyol resin or a mixture of the styrene acrylic copolymer resin and the polyol resin. Examples of the polyol resin include a bisphenol A type epoxy resin synthesized from bisphenol A and epichlorohydrin, a phenol novolak that is a reaction product of phenol and formaldehyde, a phenol novolak type epoxy resin synthesized from epichlorohydrin, and cresol. Examples thereof include a cresol novolak type epoxy resin synthesized from cresol novolak, which is a reaction product with formaldehyde, and epichlorohydrin. Since the polyol resin contains an epoxy group which is a polar group and an ether bond which is a polar bond, and contains a benzene ring in the main chain, the degree of polarity of a binder composed of a polyester resin is the same as that of a styrene acrylic copolymer resin. And the degree of polarity of the release agent. Therefore, by using an admixture composed of a polyol resin or an admixture composed of a polyol resin and a styrene acrylic copolymer resin, the release agent is combined with the release agent in the same manner as when an admixture composed of a styrene acrylic copolymer resin is used. The dispersibility of the release agent in the binder can be improved by mixing with the adhesive. In addition, it is possible to prevent the release agent from being detached in the granulation step described later.

(E) Additives As additives, general toner additives such as charge control agents can be used. As the charge control agent, those commonly used in this field can be used. For example, calixarenes, quaternary ammonium salt compounds, nigrosine compounds, organometallic complexes, chelate compounds, salicylic acid metal salts such as zinc salicylate, sulfones, etc. Examples thereof include a polymer compound obtained by homopolymerizing or copolymerizing a monomer having an ionic group such as an acid group or an amino group. One charge control agent may be used alone, or two or more charge control agents may be used in combination. The blending amount of the charge control agent is not particularly limited, and is appropriately selected from a wide range according to various conditions such as the type and content of other components such as a binder and a colorant, and characteristics required for the toner to be produced. Although it can be selected, it is preferably 0.5 parts by weight or more and 5 parts by weight or less with respect to 100 parts by weight of the binder.

  The kneaded product is, for example, a toner containing appropriate amounts of the above-mentioned binder, colorant, release agent and admixture, and various additives such as the above-described charge control agent. After the raw materials are dry-mixed with a mixer, the binder is heated to a temperature not lower than the softening point of the binder and lower than the thermal decomposition temperature, specifically about 80 to 200 ° C., preferably about 100 to 150 ° C. It can be obtained by melting or softening the agent and kneading. The toner raw material may be kneaded as it is without being dry-mixed, but is preferably kneaded after being dry-mixed as in this embodiment. As a result, the dispersibility of each component such as the release agent in the binder can be improved, and variations in the properties of the obtained toner, such as release properties and charging performance, can be suppressed.

  As a mixer used for dry mixing, a known mixer can be used. For example, Henschel mixer (trade name, manufactured by Mitsui Mining Co., Ltd.), super mixer (trade name, manufactured by Kawata Co., Ltd.), mechano mill ( Henschel type mixers such as trade name, manufactured by Okada Seiko Co., Ltd., Ongmill (trade name, manufactured by Hosokawa Micron Co., Ltd.), hybridization system (trade name, manufactured by Nara Machinery Co., Ltd.), Cosmo system (trade name, Kawasaki) Heavy Industries, Ltd.). For melt kneading, a general kneader such as a kneader, a twin-screw extruder, a two-roll mill, a three-roll mill, or a lab blast mill can be used. As such a kneader, for example, TEM-100B ( 1-axis or 2-axis extruder such as trade name, manufactured by Toshiba Machine Co., Ltd., PCM-65 / 87, PCM-30 (all of which are trade names, manufactured by Ikegai Co., Ltd.), Niedix (trade name, Mitsui Mining Co., Ltd.) Open roll type kneaders, etc.). The melt kneading may be performed using a plurality of kneaders.

[Aqueous medium preparation step]
In the aqueous medium preparation step of step s2, an aqueous medium containing water is prepared. In the aqueous medium, the kneaded material is dispersed in the granulation step of step s3 described later. The aqueous medium preparation step in step s2 may be performed before the kneading step in step s1.

  The aqueous medium more particularly contains water and a dispersant. In the present embodiment, the dispersant is a water-soluble dispersant. When a water-insoluble dispersant is used, the dispersant is not uniformly dispersed in the aqueous medium, and the concentration of the dispersant in each part of the aqueous medium may vary and become non-uniform. If the concentration of the dispersant in the aqueous medium is non-uniform, the dispersion stabilizing effect of the kneaded product by the dispersant becomes non-uniform, making it difficult to uniformly disperse the kneaded product. Further, there is a possibility that toner particles containing no admixture may be generated, and the release agent may be detached from the binder. Therefore, the dispersant is preferably a water-soluble dispersant.

  In the present embodiment, the water-soluble dispersant is a water-soluble polymer dispersant composed of a water-soluble polymer compound. The weight average molecular weight Mw of the water-soluble polymer dispersant is preferably 1000 or more and 20000 or less. By setting the weight average molecular weight Mw of the water-soluble polymer dispersant to 1000 or more and 20000 or less, an increase in the viscosity of the aqueous solution of the water-soluble polymer dispersant can be suppressed. As a result, the kneaded material can be more uniformly dispersed in the aqueous medium, so that the release of the release agent from the binder can be more reliably prevented. Further, since the spread of the particle size distribution of the toner particles can be suppressed, the toner charge amount can be prevented from becoming non-uniform. Further, since the kneaded material can be efficiently dispersed in the aqueous medium, toner particles having a small particle size of, for example, 10 μm or less can be easily generated.

  When the weight average molecular weight Mw of the water-soluble polymer dispersant exceeds 20000, the viscosity of the aqueous medium increases and it becomes difficult to disperse the kneaded product in the granulation step described later. Further, since the shearing force generated by stirring the mixture is applied to the aqueous medium and is difficult to be applied to the kneaded product, granulation of the kneaded product is inhibited, and it becomes difficult to disperse the kneaded product in the aqueous medium. As a result, the particle diameter of the toner particles tends to increase, and it becomes difficult to produce small toner particles having a volume average particle diameter of 10 μm or less. Even if toner particles having a desired particle size can be generated, the particle size distribution of the toner particles tends to be wide, and the particle size may be non-uniform. Further, there is a possibility that toner particles containing no admixture may be generated, and the release agent may be detached from the binder.

  When the weight average molecular weight Mw of the water-soluble polymer dispersant is less than 1000, the water-soluble polymer dispersant contains an oligomer or an unreacted monomer, and the water-soluble polymer dispersant has a property close to that of the oligomer or monomer. Therefore, the function as a dispersant cannot be exhibited in the granulation step, and it becomes difficult to disperse the kneaded material in the aqueous medium.

  The weight average molecular weight Mw of the water-soluble polymer dispersant can be adjusted by, for example, the type of monomer that is a raw material of the water-soluble polymer dispersant, the degree of polymerization, and the like. Moreover, when a water-soluble polymer dispersing agent consists of a copolymer, it can adjust with a copolymerization ratio, for example. The weight average molecular weight Mw of the water-soluble polymer dispersant is a value in terms of polystyrene measured by GPC.

  As the water-soluble polymer dispersant, a dissociable polymer dispersant having a dissociating group is preferable. Dissociative polymer dispersants are superior in solubility in water compared to non-dissociable polymer dispersants that do not have a dissociative group. Therefore, by using a dissociative polymer dispersant, The concentration can be made more uniform, and the spread of the particle size distribution and the release of the release agent from the binder can be prevented more reliably. Examples of the non-dissociable polymer dispersant include polyvinyl alcohol, polyvinyl pyrrolidone, and hydroxycellulose.

  Examples of the dissociative polymer dispersant include polyacrylic acids and salts thereof, and styrene acrylic copolymers and salts thereof. Examples of polyacrylic acids include polyacrylic acid and polymethacrylic acid. Examples of the salts of polyacrylic acids include ammonium salts of polyacrylic acids such as ammonium polyacrylate and ammonium polymethacrylate, and alkali metal salts of polyacrylic acids such as sodium polyacrylate and sodium polymethacrylate.

  Examples of the styrene acrylic copolymer include a copolymer of a styrene monomer and an acrylic monomer. Examples of the styrenic monomer include styrene and α-methylstyrene. A styrene-type monomer may be used individually by 1 type, and 2 or more types may be used together. Examples of acrylic monomers include acid monomers such as acrylic acid and methacrylic acid, and acrylic acid ester monomers such as methyl acrylate and ethyl acrylate, and methacrylic acid ester monomers such as methyl methacrylate and propyl methacrylate. And ester monomers such as One type of acrylic monomer may be used alone, or two or more types may be used in combination.

  Specific examples of the styrene acrylic copolymer include, for example, a styrene-acrylic acid copolymer that is a copolymer of styrene and acrylic acid, and a styrene-α that is a copolymer of styrene, α-methylstyrene, and acrylic acid. -Methylstyrene-acrylic acid copolymer etc. are mentioned. Examples of styrene-acrylic copolymer salts include styrene-acrylic acid copolymer ammonium salts, styrene-acrylic acid copolymer ammonium salts such as styrene-α-methylstyrene-acrylic acid copolymer ammonium salts, and styrene-acrylic. Examples thereof include sodium styrene-acrylic acid copolymers such as sodium acid copolymer and sodium styrene-α-methylstyrene-acrylic acid copolymer.

  Polyacrylic acids can be produced, for example, by polymerizing acrylic acids such as acrylic acid or methacrylic acid in the presence of a radical polymerization initiator by a solution polymerization method, a suspension polymerization method, an emulsion polymerization method, or the like. . The styrene acrylic copolymer is prepared by, for example, using a solution polymerization method, suspension weight, or the like in the presence of a radical polymerization initiator by using one or more acrylic monomers and one or more styrene monomers in the presence of a radical polymerization initiator. It can be produced by polymerization by a combination method, an emulsion polymerization method or the like.

  Among the dissociative polymer dispersants described above, styrene acrylic copolymer salts are preferred. By using the salt of the styrene acrylic copolymer, the kneaded product can be more uniformly dispersed in the aqueous medium, so that a toner having a narrower particle size distribution can be produced. One type of water-soluble polymer dispersant may be used alone, or two or more types may be used in combination.

  The concentration of the dispersant in the aqueous medium is not particularly limited, and is appropriately selected from a wide range according to the types and contents of the binder, colorant, release agent, admixture and additive contained in the kneaded product. However, considering the ease of mixing operation of the kneaded material and the aqueous medium, the dispersion stability of the produced toner particles, etc., in an aqueous medium at a temperature of 25 ° C., it is 5 wt% or more and 40 wt% or less. It is preferable that When the concentration of the dispersant is less than 5% by weight, a large amount of an aqueous medium is required to realize a suitable use ratio of the dispersant to the kneaded product in the granulation step described later. The mixing operation becomes complicated. If the concentration of the dispersant exceeds 40% by weight, the viscosity of the aqueous medium increases, and therefore mixing with the kneaded product in the granulation step may be difficult. Further, granulation of the kneaded product is hindered, and the kneaded product cannot be uniformly dispersed in the aqueous medium, and the particle size distribution of the produced toner particles may be widened.

  The aqueous medium can be prepared, for example, by dissolving an appropriate amount of the aforementioned dispersant in water. As water, it is preferable to use water having an electrical conductivity of 20 μS / cm or less. Water whose conductivity is within the above range can be prepared by, for example, an activated carbon method, an ion exchange method, a distillation method, a reverse osmosis method, or the like. Moreover, you may prepare the water whose electrical conductivity is in the said range by combining 2 or more types among these methods. Moreover, it can also prepare using a commercially available pure water manufacturing apparatus, for example, Minipure TW-300RU (trade name) manufactured by Nomura Micro Science Co., Ltd.

[Granulation process]
In the granulation step of step s3, the kneaded product obtained in the kneading step of step s1 is granulated by being dispersed in the aqueous medium prepared in the aqueous medium preparation step of step s2, in a molten or softened state, Toner particles are obtained. More specifically, after mixing the kneaded material and the aqueous medium, the resulting mixture is stirred under heating or heating and pressurizing to disperse the kneaded material in the form of particles in the aqueous medium. Some toner particles are produced. The generated toner particles become toner particles constituting the toner. “Toner” is an aggregate of toner particles. The “toner particles” include toner particles to which an external additive has been added in an external addition process described later.

  In the granulation step, the mixture of the kneaded product and the aqueous medium is heated in order to melt or soften the kneaded product. At this time, the release agent in the kneaded material is melted or softened and becomes fluid. The polyester resin as the binder has a high degree of polarity, and the release agent is nonpolar or has a very low degree of polarity, so that the binder and the release agent are difficult to mix. If the admixture is not contained in the kneaded product, the release agent that is in a fluid state is easily detached from the binder due to the difference in the degree of polarity from the binder.

  In the present embodiment, since the admixture is contained in the kneaded product, the release agent and the binder can be mixed with the admixture interposed. Accordingly, when the kneaded material is dispersed in the aqueous medium, the release agent can be held in the binder via the admixture, and thus the release agent is prevented from being detached from the binder. be able to.

  Also, when a highly polar resin having a large number of polar groups such as a polyester resin is used as a binder, if the toner raw material does not contain an admixture, it melts when the toner raw material is kneaded in the kneading step. The release agents aggregate with each other in the binder to form a domain. Thus, when the binder is a resin having a high degree of polarity, the release agents are aggregated with each other, so that it is difficult to disperse the release agent in the binder. The agglomerated release agent is easily detached from the binder in the granulation step.

  In this embodiment, since the admixture is contained in the toner material, aggregation of the release agents in the kneading step can be prevented, and the dispersibility of the release agent can be improved. This can more reliably prevent the release agent from being detached from the binder in the granulation step.

  The heating temperature of the mixture in the granulation step is not particularly limited, and the particle size of the toner particles to be finally obtained, such as the type and characteristics of the binder contained in the kneaded product, such as the weight average molecular weight and softening point, etc. However, the temperature is preferably not lower than the softening point of the binder contained in the kneaded material and not higher than the thermal decomposition temperature.

  The stirring speed of the mixture of the kneaded product and the aqueous medium is not particularly limited, and the stirring operation can be easily carried out according to the kind and content of the binder, colorant and additive in the kneaded product. The value for obtaining toner particles having the following particle diameter, particle size distribution and shape may be appropriately selected. Further, the stirring time of the mixture of the kneaded product and the aqueous medium is not particularly limited, and the type and content of the binder, colorant and additive in the kneaded product, the type and concentration of the dispersant in the aqueous medium, Depending on various conditions such as the heating temperature of the mixture, it can be appropriately selected from a wide range, for example, 10 minutes or more and 20 minutes or less.

  In the present embodiment, the mixture is heated and stirred while the inside of the mixing container in which the mixture of the kneaded material and the aqueous medium is accommodated is pressurized. Although the inside of the mixing vessel does not necessarily need to be in a pressurized state, the boiling point of water contained in the aqueous medium can be increased by heating and stirring the mixture in the pressurized state. The mixture can be heated to 100 ° C. or higher without boiling. Accordingly, it is possible to prevent the shearing force from being reduced due to the generation of bubbles and to granulate the kneaded material more efficiently.

  The pressure of the gas in the mixing container (hereinafter referred to as “pressure in the mixing container”) is not particularly limited, and the type and content of the binder, colorant and additive in the kneaded product, and dispersion in the aqueous medium Depending on the type and concentration of the agent, the heating temperature of the mixture, etc., the mixing operation can be easily carried out, and the pressure at which toner particles having a desired particle diameter and shape can be obtained may be appropriately selected. The pressure in the mixing container is, for example, 0.1 MPa (about 1 atm) or more and 1 MPa (about 10 atm) or less. The “pressurized state” is a state where the pressure is higher than the atmospheric pressure.

  More specifically, the pressure in the mixing vessel is preferably a minimum pressure that can suppress boiling of the mixture at a desired heating temperature. If the pressure in the mixing vessel becomes too high, bubbles generated in the mixture may not be lost, but may be refined by pressure and contained in the system, and granulation of the kneaded product may be hindered. Therefore, the pressure in the mixing vessel is appropriately selected particularly in consideration of the heating temperature of the mixture. For example, when the heating temperature of the mixture is 150 ° C., the pressure in the mixing container is about 0.5 MPa (about 5 atm).

  The kneaded product may be used as it is without cooling a kneaded binder, colorant, additive, etc., and the solidified product obtained by cooling after kneading is heated as it is or again to a molten state. You may use what was returned.

  The mixing ratio of the kneaded material and the aqueous medium is not particularly limited, and can be appropriately selected from a wide range according to various conditions such as the content of the binder in the kneaded material and the type and content of the dispersant in the aqueous medium. However, from the viewpoint of efficiently performing the mixing operation, the subsequent toner particle cleaning operation, the toner particle isolation operation, and the like, 100 parts by weight or more of the aqueous medium to 500 parts by weight or more with respect to 100 parts by weight of the kneaded product. It is preferable to use less than or equal to parts by weight.

  More specifically, the kneaded product and the aqueous medium are mixed using, for example, an emulsifier or a disperser. As the emulsifier and the disperser, the kneaded product and the aqueous medium can be received batchwise or continuously, and have a heating means or a heating means and a pressurizing means, and the kneaded product and the aqueous medium are heated or An apparatus capable of mixing under heating and pressurization to produce toner particles and discharging the toner particles in a batch or continuous manner is preferable. Moreover, it is preferable that an emulsifier and a disperser have a stirring means and can mix a kneaded material and an aqueous medium under stirring. In the emulsifier and the disperser, the mixing container for mixing the kneaded material and the aqueous medium preferably has a temperature adjusting means. The mixing vessel preferably has pressure resistance, and more preferably has pressure resistance and is provided with a pressure regulating valve and the like. If such a mixing container is used, the temperature of the mixture in the container is kept almost constant, and the pressure in the container is also controlled to a constant pressure in consideration of the softening point of the binder and the vapor pressure of the aqueous medium. In addition, when mixing the kneaded material and the aqueous medium at a heating temperature of 100 ° C. or higher, the emulsifier and the disperser are equipped with a mechanical seal, and the mixing container can be sealed because it is used in a pressurized state. It is desirable that

  Such emulsifiers and dispersers are commercially available. Specific examples thereof include Ultra Tarrax (trade name, manufactured by IKA Japan Co., Ltd.), Polytron Homogenizer (trade name, manufactured by KINEMATICA), T. K. Batch type emulsifiers such as auto homomixer (trade name, manufactured by Special Machine Industries Co., Ltd.), Ebara Milder (trade name, manufactured by Ebara Corporation), T. K. Pipeline homomixer, T.W. K. Homomic line flow, T.W. K. Fill mix (all are trade names, manufactured by Koki Kogyo Co., Ltd.), colloid mill (trade names, manufactured by Shinko Pantech Co., Ltd.), slasher, trigonal wet pulverizer (all are trade names, Mitsui Miike Chemical Machinery Co., Ltd.) Co., Ltd.), Cavitron (trade name, manufactured by Eurotech Co., Ltd.), Fine Flow Mill (manufactured by Taiheiyo Kiko Co., Ltd.), etc. (Trade name, manufactured by Special Machine Industries Co., Ltd.).

  By heating and stirring the mixture of the kneaded product and the aqueous medium as described above, the kneaded product is dispersed in the aqueous medium, and contains at least a binder, a colorant, a release agent, and an admixture. Particles are generated.

[Cooling process]
In the cooling step of step s4, the mixture containing the granulated toner particles (hereinafter also referred to as an aqueous slurry) is cooled. Cooling of the aqueous slurry may be performed by forced cooling in which heating is stopped after the toner particles are generated in the granulation process in step s3 and forcibly cooled with a refrigerant, or natural cooling in which the toner is allowed to cool as it is. preferable.

  In the granulation step, granulation is performed by heating a mixture of the kneaded product and the aqueous medium and melting and dispersing the kneaded product, so that the toner particles immediately after being produced are in a molten state and have adhesiveness. . In this state, the toner particles tend to adhere to each other and become coarse. In the present embodiment, since the dispersant is contained in the aqueous medium together with the toner particles, the toner particles are stabilized by the dispersant and dispersed in the aqueous medium. As a result, the toner particles are not coarsened in the cooling step, and the toner particles can be cooled while maintaining their shape and size while being dispersed in the aqueous medium. Therefore, a toner having a narrow particle size distribution with a volume average particle size as small as 10 μm or less and a coefficient of variation of 35 or less can be produced.

  The mixture (aqueous slurry) is preferably cooled with stirring. When the mixture is cooled without stirring, when the temperature of the mixture is equal to or higher than the softening point of the binder contained in the toner particles, the dispersion stabilizing effect by the water-soluble polymer dispersant is not sufficiently exhibited, and the toner There is a possibility that the particles are fused to each other. Therefore, it is preferable to continue stirring of the mixture (aqueous slurry) also in the cooling step.

  Moreover, when the kneaded material is granulated under pressure at a heating temperature of 100 ° C. or higher, it is preferable to continue the pressure in the cooling step. When the temperature of the mixture is 100 ° C. or higher, when the pressurization is stopped and the pressure in the mixing container is returned to the atmospheric pressure, the aqueous slurry boils and a large number of bubbles are generated, which makes subsequent processing difficult. . The pressure in the mixing container is preferably returned to atmospheric pressure when the temperature of the mixture in the mixing container becomes 50 ° C. or lower, and the atmospheric pressure after the mixture in the mixing container is cooled to room temperature (about 25 ° C.). It is further preferable to return to.

[Washing process]
In the washing process of step s5, the toner particles contained in the cooled aqueous medium are washed. The toner particles are washed to remove the dispersant and impurities derived from the dispersant. If the dispersant and the impurities remain in the toner particles, the charging performance of the obtained toner particles may become unstable. In addition, the chargeability may be lowered due to the influence of moisture in the air.

  The toner particles can be washed, for example, by adding water to the mixture, stirring and washing. The toner particles are washed with water repeatedly using a conductivity meter until the conductivity of the supernatant liquid separated from the mixture by centrifugation or the like becomes 100 μS / cm or less, preferably 10 μS / cm or less. As a result, it is possible to more reliably prevent the dispersant and impurities from remaining and to make the charge amount of the toner particles more uniform.

  The water used for washing is preferably water having a conductivity of 20 μS / cm or less. Such water can be prepared, for example, by an activated carbon method, an ion exchange method, a distillation method, a reverse osmosis method, or the like. Moreover, you may prepare water combining 2 or more types among these methods. The toner particles may be washed with water either batchwise or continuously. The temperature of the washing water is not particularly limited, but is preferably in the range of 10 to 80 ° C.

[Separation process]
In the separation step of step s6, the toner particles are separated and recovered from the aqueous medium containing the washed toner particles. Separation of the toner particles from the aqueous medium can be performed according to a known method, for example, filtration, suction filtration, centrifugation, or the like.

  The cleaning process in step s5 may be performed after the separation process in step s6 and before the drying process in step s7. When the washing step of step s5 is performed after the separation step of step s6, for example, the toner particles can be washed by washing the separated toner particles with water. The toner particles are washed with water repeatedly using a conductivity meter or the like until the conductivity of the washing water after washing the toner particles is 100 μS / cm or less, preferably 10 μS / cm or less. As a result, it is possible to more reliably prevent the dispersant and impurities from remaining and to make the charge amount of the toner particles more uniform.

[Drying process]
In the drying step of step s7, the washed toner particles are dried. The toner particles can be dried according to a known method such as a freeze drying method or an airflow drying method.

  The dried toner particles can be used as toner particles as they are, but in this embodiment, an external additive is externally added in the external addition processing step of step s8.

[External addition process]
In the external addition processing step of step s8, an external additive is externally added to the dried toner particles to obtain toner particles to which the external additive has been added. The external additive may be attached to the surface of the toner particles, or a part or all of the external additive may be embedded in the surface of the toner particles. Examples of the external additive include a fluidity improver. By externally adding a fluidity improver to the toner particles, the powder fluidity of the toner can be improved. Examples of the fluidity improver include metal oxide particles such as silicon dioxide (silica) and titanium oxide (titania). The metal oxide particles may be used after being subjected to a surface modification treatment such as a hydrophobic treatment with a surface modifier such as a silane coupling agent.

  The use ratio of the external additive to the toner particles is not particularly limited, but is preferably 0.1 parts by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the toner particles. If the use ratio of the external additive is less than 0.1 parts by weight with respect to 100 parts by weight of the toner particles, the fluidity improving effect may not be sufficiently exhibited. When the use ratio of the external additive exceeds 10 parts by weight with respect to 100 parts by weight of the toner particles, the external additive is present in the toner in a free state, and the image carrier such as a photoconductor by the free external additive. May be damaged and image defects may occur.

  As described above, a toner composed of toner particles is obtained. When the toner is manufactured in this way, the process proceeds to step s9, and the manufacture of the toner according to the present embodiment is completed. In this embodiment, since the admixture is contained in the toner material, the admixture is contained in the kneaded product. In the granulation step of step s3, the release agent can be held in the binder via this admixture, so that the binder in the granulation step can be compared with the case where no admixture is contained. Detachment of the release agent can be prevented more reliably, and the residual rate of the release agent after the granulation step can be increased. Accordingly, it is possible to prevent a decrease in the start temperature of occurrence of high temperature offset when the toner is fixed to the recording medium by, for example, a heat roller fixing method. Further, since the dispersibility of the release agent in the toner can be improved, an image with a certain quality can be stably formed.

  In this embodiment, since the aqueous medium contains a water-soluble dispersant, the kneaded material is dispersed in the aqueous medium in a more uniform size in the granulation step than in the case of not containing the water-soluble dispersant. Can do. As a result, a toner having a narrow particle size distribution with a coefficient of variation of 35 or less can be obtained without classification. Therefore, it is possible to prevent the toner charge amount from becoming non-uniform, and to prevent a decrease in image density, occurrence of white background fog, a decrease in transferability, and the like. Further, since toner particles having a volume average particle diameter of 10 μm or less can be easily generated, a toner capable of realizing a high-definition image can be obtained.

  Further, in the present embodiment, toner particles are produced by dispersing the kneaded product in an aqueous medium in the granulation step in a melted or softened state, so that a resin other than a resin that can be synthesized by radical polymerization is used as a binder. For example, a toner can be manufactured using a polyester resin. Further, it is possible to prevent the binder monomer from remaining in the toner. Further, since the toner can be produced without using an organic solvent, it is possible to prevent the organic solvent from remaining in the toner. Thus, since the binder monomer and the organic solvent can be prevented from remaining in the toner, variation in charging performance can be more reliably suppressed. In addition, since the waste liquid containing the organic solvent is not discharged, the cost required for processing the waste liquid can be reduced.

  The toner obtained by the toner manufacturing method according to the present embodiment can be used for developing an electrostatic image when an image is formed by, for example, electrophotography or electrostatic recording. Further, by containing a magnetic material in the toner material, the produced toner can be used for developing a magnetic latent image when an image is formed by a magnetic recording method. The toner produced in this embodiment is suitable as an electrostatic image developing toner used for developing an electrostatic image because it has a narrow particle size distribution and a constant charging performance. By using the toner manufactured in this embodiment as a toner for developing an electrostatic image, it is possible to suppress variations in the charge amount of the toner, thereby suppressing a decrease in image density, generation of white background fog, a decrease in transferability, and the like. High quality images without image defects can be formed. The toner produced in this embodiment may be used alone as a one-component developer, or may be mixed with a carrier and used as a two-component developer.

  EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples. In the following, “parts” and “%” mean “parts by weight” and “% by weight”, respectively, unless otherwise specified.

[Preparation of water]
In the following Examples and Comparative Examples, water having an electrical conductivity of 0.5 μS / cm was used as water for preparing an aqueous medium and water for cleaning toner particles. This washing water was prepared from tap water using an ultrapure water production apparatus (trade name: Minipure TW-300RU, manufactured by Nomura Micro Science Co., Ltd.). The electrical conductivity of water was measured using Lacom Tester EC-PHCON10 (trade name, manufactured by Seiei Iuchi (currently As One Co., Ltd.)).

[Volume average particle size and coefficient of variation]
The volume average particle diameter of the toner particles was calculated from the result of measurement using Coulter Multisizer II (trade name, manufactured by Coulter, Inc. (currently Beckman Coulter, Inc.). The number of measured particles was 50,000 counts, and the aperture diameter was 100 μm. The coefficient of variation was calculated based on the following formula (1) from the volume average particle diameter obtained from the measured particle diameter and its standard deviation.
Coefficient of variation = standard deviation / volume average particle diameter (1)

[Weight average molecular weight Mw of binder, admixture and water-soluble polymer dispersant]
The weight average molecular weight Mw of the binder, the admixture, and the water-soluble polymer dispersant is a sample solution using a column set at a temperature of 40 ° C. with a GPC apparatus (trade name: HLC-8220 GPC, manufactured by Tosoh Corporation). Was measured with an injection amount of 100 mL. As the sample solution, a 0.25 wt% (solid content concentration) tetrahydrofuran solution of the sample obtained by drying the binder, admixture or water-soluble polymer dispersant was used overnight. The molecular weight calibration curve was prepared using standard polystyrene (monodisperse polystyrene).

[Softening point of binder]
The softening point of the binder was measured as follows. Using a flow characteristic evaluation apparatus (trade name: Flow Tester CFT-100C, manufactured by Shimadzu Corporation), a load of 10 kgf / cm ² (9.8 × 10 ⁵ Pa) was applied so that 1 g of a sample was extruded from a die (nozzle). ), The temperature at a heating rate of 6 ° C. per minute was obtained, and the temperature at which half of the sample flowed out of the die was determined as the softening point. A die having a diameter of 1 mm and a length of 1 mm was used.

[Glass transition point of binder (Tg)]
The glass transition point (Tg) of the binder was measured as follows. Using a differential scanning calorimeter (trade name: DSC220, manufactured by Seiko Denshi Kogyo Co., Ltd.), according to Japanese Industrial Standard (substantially JIS) K7121-1987, 1 g of a sample was heated at a heating rate of 10 ° C./min to obtain a DSC curve. Was measured. Draw at the point where the slope is maximum with respect to the straight line obtained by extending the base line on the high temperature side of the endothermic peak corresponding to the glass transition of the obtained DSC curve to the low temperature side and the curve from the peak rising part to the peak. The temperature at the intersection with the tangent was determined as the glass transition point (Tg).

[Melting point of release agent]
The melting point of the release agent was measured as follows. Using a differential scanning calorimeter (trade name: DSC220, manufactured by Seiko Denshi Kogyo Co., Ltd.), 1 g of the sample was heated from a temperature of 20 ° C. to 150 ° C. at a heating rate of 10 ° C. per minute, and then rapidly cooled from 150 ° C. to 20 ° C. The operation was repeated twice and the DSC curve was measured. The temperature at the top of the endothermic peak corresponding to the melting of the DSC curve measured in the second operation was determined as the melting point of the release agent.

[Residual rate of release agent]
The ratio of the content of the release agent in the toner particles to the content of the release agent in the toner material was calculated as the residual rate of the release agent. The content of the release agent in the toner particles is the same as that when the melting point of the release agent is measured using a differential scanning calorimeter (trade name: DSC220, manufactured by Seiko Denshi Kogyo Co., Ltd.) using the toner as a measurement sample. The DSC curve is measured, the endothermic amount of the release agent in the toner is obtained from the area of the endothermic peak attributed to the release agent of the obtained DSC curve, and the release agent obtained from the obtained endothermic amount of the release agent And the amount of toner as a measurement sample were compared.

Example 1
[Melting and kneading process]
220 parts of polyoxypropylene (2.0) -2,2-bis (4-hydroxyphenyl) propane, 90 parts of polyoxyethylene (2.0) -2,2-bis (4-hydroxyphenyl) propane and terephthalic acid A polyester resin (glass transition point Tg 62 ° C., softening point Tm 130 ° C., acid value 15 mgKOH / g, hydroxyl value 21 mgKOH / g) synthesized using 200 parts as a raw material monomer and 3 parts of dibutyltin oxide as a catalyst Copper phthalocyanine (C.I. Pigment Blue 15: 3) was added and melt-kneaded for 40 minutes in a kneader set at a temperature of 140 ° C. to prepare a master batch having a colorant concentration of 40% by weight. “Polyoxypropylene (2.0) -2,2-bis (4-hydroxyphenyl) propane” means that propylene oxide has an average of 1.0 mol of 2,2-bis (4-hydroxyphenyl) propane. It is a compound with 2.0 mol added. “Polyoxyethylene (2.0) -2,2-bis (4-hydroxyphenyl) propane” is an average of ethylene oxide with respect to 1.0 mol of 2,2-bis (4-hydroxyphenyl) propane. It is a compound with 2.0 mol added.

  As the toner material, 68.5 parts of the same polyester resin (glass transition point Tg 62 ° C., softening point Tm 130 ° C., acid value 15 mgKOH / g, hydroxyl value 21 mgKOH / g) used for preparing the master batch, as described above. 12.5 parts of the prepared master batch (colorant concentration 40% by weight), 7 parts of polyethylene wax (trade name: PW-655N, manufactured by Toyo Petrolite Co., Ltd., melting point 100 ° C.) as a release agent, styrene acrylic as an admixture 10 parts of a copolymer resin (glass transition point Tg 64 ° C., softening point Tm 132 ° C.) and 2 parts of a charge control agent (trade name: TN105, Hodogaya Chemical Co., Ltd.) are mixed and dispersed in a Henschel mixer for 3 minutes to obtain a toner raw material (Hereinafter referred to as “raw material mixture”). For the styrene acrylic copolymer resin, which is an admixture, styrene-butyl acrylate copolymer obtained by reacting 1000 g of styrene and 200 g of n-butyl acrylate as raw material monomers and using azobisisobutylnitrile as a catalyst. A coalesced resin (glass transition point Tg 64 ° C., softening point Tm 132 ° C., ratio of acrylic structural unit 14 mol%) was used.

  The obtained raw material mixture was melt-kneaded and dispersed using a twin-screw extruder (trade name: PCM-30, manufactured by Ikegai Co., Ltd.) to produce a kneaded product. The operating conditions of the twin screw extruder were a cylinder set temperature of 110 ° C., a barrel rotation speed of 300 rotations / minute (300 rpm), and a raw material mixture supply speed of 20 kg / hour.

[Aqueous medium preparation step]
As a dispersant, 100 parts (solid content) of water-soluble polymer compound styrene-α-methylstyrene-acrylic acid copolymer ammonium salt (trade name: John Crill 61J, manufactured by Johnson Polymer Co., Ltd.) and 900 parts of water And an aqueous medium having a dispersant concentration of 10% by weight was prepared.

[Granulation process]
In a metal mixing vessel equipped with a pressure regulating valve, heating means and rotor-stator stirring means (caliber 30 mm), 100 parts of the kneaded material prepared as described above and 550 parts of an aqueous medium (dispersant concentration 10% by weight) Was stirred and mixed for 10 minutes with a rotor-stator stirring means while heating so that the temperature of the mixture in the mixing vessel became 120 ° C. under a pressure of 5 atm (5 atm), thereby generating toner particles. The rotational speed of the rotor of the rotor stator type stirring means at this time was set to 15,000 revolutions / minute (15000 rpm).

[Cooling process]
After producing the toner particles as described above, heating was stopped, and the mixture containing the produced toner particles was cooled to 20 ° C. while stirring the mixture. The rotational speed of the rotor of the rotor stator type stirring means at this time was set to 15,000 revolutions / minute (15000 rpm).

[Washing process]
Next, water having a conductivity of 0.5 μS / cm (temperature of 20 ° C.) was added to the mixture to clean the toner particles. Toner particles are washed by adding water (conductivity 0.5 μS / cm) to the mixture and adjusting the amount of solids to 10% by weight depending on the amount of water added, and then using a turbine-type stirring blade. Was carried out by stirring for 30 minutes at a rotation speed of 300 rpm / 300 rpm. This washing operation was repeated until the electrical conductivity of the supernatant liquid separated from the stirred mixture by centrifugation was 10 μS / cm or less.

[Separation process]
The solid content containing toner particles was separated from the washed mixture by centrifugation.

[Drying process]
The collected solid content was lyophilized to obtain toner particles. The obtained toner particles had a volume average particle diameter of 6.5 μm and a coefficient of variation of 31.

[External addition process]
To 100 parts of the obtained toner particles, 0.7 part of silica particles having an average primary particle size of 20 nm hydrophobized with a silane coupling agent and 1 part of titanium oxide were mixed to obtain a toner.

(Example 2)
As a styrene acrylic copolymer resin as an admixture, styrene-methyl acrylate copolymer resin (1000 g of styrene and 200 g of methyl acrylate were used as raw material monomers and reacted using azobisisobutylnitrile as a catalyst ( A toner of Example 2 was produced in the same manner as in Example 1 except that the glass transition point Tg was 59 ° C., the softening point Tm was 132 ° C., and the proportion of acrylic structural units was 19 mol%. The toner particles of Example 2 have a volume average particle size of 6.4 μm and a coefficient of variation of 32.

(Example 3)
Styrene-acrylic resin obtained by reacting styrene-acrylic copolymer resin as admixture with 1000 g of styrene, 200 g of n-butyl acrylate and 200 g of methyl methacrylate as raw material monomers and azobisisobutylnitrile as a catalyst. Example 3 toner in the same manner as in Example 1 except that butyl acid-methyl methacrylate copolymer resin (glass transition point Tg 62 ° C., softening point Tm 132 ° C., acrylic structural unit ratio 27 mol%) is used. Manufactured. The toner particles of Example 3 had a volume average particle size of 6.8 μm and a coefficient of variation of 33.

Example 4
The blending amount of the polyester resin (glass transition point Tg 62 ° C., softening point Tm 130 ° C., acid value 15 mgKOH / g, hydroxyl value 21 mgKOH / g) when preparing the raw material mixture was changed to 64.5 parts, and styrene as an admixture A toner of Example 4 was produced in the same manner as in Example 1 except that the amount of the acrylic copolymer resin was changed to 14 parts. The volume average particle size of the toner particles of Example 4 was 6.8 μm, and the coefficient of variation was 32.

(Comparative Example 1)
The blending amount of the polyester resin (glass transition point Tg 62 ° C., softening point Tm 130 ° C., acid value 15 mgKOH / g, hydroxyl value 21 mgKOH / g) when preparing the raw material mixture was changed to 58.5 parts, and styrene as an admixture A toner of Comparative Example 1 was produced in the same manner as in Example 1 except that the amount of the acrylic copolymer resin was changed to 20 parts. The volume average particle diameter of the toner particles of Comparative Example 1 was 7.8 μm, and the coefficient of variation was 33.

(Comparative Example 2)
A toner of Comparative Example 2 was produced in the same manner as in Example 1 except that the toner raw material did not contain a styrene acrylic copolymer resin as an admixture. The volume average particle size of the toner particles of Comparative Example 2 was 6.0 μm, and the coefficient of variation was 31.

(Characteristic evaluation)
To each of the toners obtained in Examples 1 to 4 and Comparative Examples 1 and 2, a ferrite core carrier having a volume average particle size of 60 μm as a carrier was adjusted and mixed so that the toner concentration would be 4% by weight. A two-component developer having a concentration of 4% by weight was prepared. An image for evaluation was formed as follows using the obtained two-component developer, and the following evaluation was performed.

[Formation of image for evaluation]
The obtained two-component developer was put into a developing device of a test printer obtained by removing a fixing device from a commercially available printer (trade name: LIBRE AR-S505, manufactured by Sharp Corporation), and was subjected to Japanese Industrial Standard (JIS). ) On the A4 size recording paper defined in P0138, the toner adhesion amount is adjusted to 0.6 mg / cm ^2, and the rectangular solid image portion 20 mm long and 50 mm wide is unfixed. Formed. An unfixed toner image formed was fixed by using an external fixing machine at a recording paper passing speed of 120 mm / sec (120 mm / sec) to form an evaluation image. For the external fixing machine, an oil-less fixing device taken out from a commercially available full-color copying machine (trade name: LIBRE AR-C260, manufactured by Sharp Corporation) can set the surface temperature of the fixing heating roller to an arbitrary value. The one modified as described above was used. The “oilless fixing device” is a fixing device that performs fixing without applying a release agent such as silicone oil to the heating roller.

[Evaluation of high temperature offset resistance]
The formed evaluation image is visually observed to check whether or not the toner is retransferred from the fixing heating roller to the white background portion of the recording paper. It was determined that a high temperature offset phenomenon did not occur when the image was not retransferred.

  This operation is repeated by gradually increasing the surface temperature of the fixing heating roller from 100 ° C. to 210 ° C. in increments of 5 ° C., and the maximum temperature of the fixing heating roller surface temperature (hereinafter referred to as “the highest fixing”). Temperature)). The high temperature offset resistance was evaluated as good (◯) when the maximum fixing temperature was 190 ° C. or higher, and evaluated as poor (×) when the maximum fixing temperature was less than 190 ° C.

[Evaluation of non-offset area]
Similarly to the evaluation of the high temperature offset resistance, the surface temperature of the fixing heating roller is sequentially increased from 100 ° C. to 210 ° C. by 5 ° C. to form an image, and the toner image is not fixed on the recording paper. A fixing heating roller in which neither a low-temperature offset phenomenon in which a portion to be an image portion becomes a white background nor a high-temperature offset phenomenon in which a toner image is re-transferred from the fixing heating roller to a white background portion to be a white background of a recording sheet. The non-offset region which is the range of the surface temperature of was obtained. The non-offset range is the lowest fixing temperature (° C), which is the lowest temperature of the fixing heating roller where the low temperature offset phenomenon does not occur, and the highest fixing temperature (the highest temperature of the surface temperature of the fixing heating roller, where the high temperature offset phenomenon does not occur) ° C) as a temperature difference.

Using the non-offset area as an evaluation index, the non-offset area was evaluated based on the following evaluation criteria.
○: Good. The non-offset region is 40 ° C. or higher.
X: Defect. The non-offset region is less than 40 ° C.

(Evaluation of image density)
For an image formed when the surface temperature of the fixing heating roller is 180 ° C., the optical reflectance density of the solid image portion is measured using a reflection densitometer (trade name: RD918, manufactured by Macbeth Co., Ltd.). The image density was used. A case where the image density was 1.4 or higher was evaluated as good (◯), and a case where the image density was less than 1.4 was evaluated as poor (×).

〔Comprehensive evaluation〕
From the above evaluation results of the high-temperature offset resistance, non-offset region and image density, comprehensive evaluation was performed based on the following evaluation criteria.
○: Good. There is no item evaluated as defective (x).
X: Defect. There is one or more items evaluated as defective (x).

The above evaluation results are shown in Table 1. In Table 1, the volume average particle diameter of the toner particles is expressed as “D ₅₀ ”.

  From Table 1, a toner raw material containing a polyester resin as a binder and a polyethylene wax as a release agent has a styrene-acrylic copolymer having a polarity between that of the polyester resin and that of the polyethylene wax. The toners of Examples 1 to 4 manufactured by the toner manufacturing method of the present invention in which a coalesced resin is contained as an admixture and mixed and kneaded are mixed in the toner particles with respect to the content of the release agent in the toner raw material. The release agent residual ratio, which is the ratio of the release agent content, was as high as 100%. The toners of Examples 1 to 4 had a maximum fixing temperature of 200 ° C. or higher and excellent high-temperature offset resistance.

  Further, like the toners of Examples 1 to 4, the toner of Comparative Example 1 has a high release agent residual ratio of 100%, the maximum fixing temperature of 200 ° C. or higher, and is excellent in high temperature offset resistance. there were. This is presumably because, in Comparative Example 1, the toner was produced by adding the styrene acrylic copolymer resin as the admixture to the toner raw material, as in Examples 1 to 4.

  The toners of Examples 1 to 4 had a minimum fixing temperature of 160 ° C. or lower, and a wide non-offset region of 40 ° C. or higher could be secured. In Examples 1 to 4, a release agent having a melting point lower than the softening point of the binder was used, and the residual rate of the release agent could be increased to 100%. This is probably because the softening point of the toner can be lowered, and a toner having excellent high temperature offset resistance and low temperature offset resistance has been realized.

  It can also be seen that the toners of Examples 1 to 4 have a small coefficient of variation of 33 or less, a narrow particle size distribution and a uniform particle size, and a volume average particle size of 6.8 μm or less. It can be understood that the toners of Examples 1 to 4 have uniform charging performance, excellent transferability, and can form an image having a high image density of 1.4 or more in terms of optical reflectance density.

  On the other hand, the toner of Comparative Example 2 produced by granulating in an aqueous medium without containing the styrene acrylic copolymer resin as an admixture in the toner raw material is granulated in the aqueous medium. As a result, it was found that an image having a high image density can be formed, which is not inferior to the toners of Examples 1 to 4 in terms of coefficient of variation and toner diameter reduction. However, the toner of Comparative Example 2 has a lower residual ratio of the release agent than the toners of Examples 1 to 4, and is inferior to the toners of Examples 1 to 4 in terms of high-temperature offset resistance and a wide non-offset region. It was a thing.

  Further, from comparison between Examples 1 to 4 and Comparative Example 1, Examples 1 to 4 in which the admixture is contained in the toner material in a weight ratio of 1 part by weight or more and 20 parts by weight or less with respect to 100 parts by weight of the binder. The toner of this example has a minimum fixing temperature lower than that of the toner of Comparative Example 1 in which the admixture is contained in the toner material in a weight ratio exceeding 20 parts by weight with respect to 100 parts by weight of the binder. It can be seen that this is excellent in terms of the size of the offset area.

  As described above, the toner raw material contains the styrene acrylic copolymer resin which is an admixture having a polarity between the polarity of the polyester resin as the binder and the polarity of the polyethylene wax as the release agent. According to the method for producing a toner of the present invention in which particles obtained by melting and kneading and dispersing the obtained kneaded material in an aqueous medium are used, the release agent is prevented from being detached when the particles are formed in an aqueous medium. In addition, a toner having excellent high-temperature offset resistance and a narrow particle size distribution could be obtained.

3 is a flowchart illustrating a procedure of a toner manufacturing method according to an embodiment of the present invention.

Claims (6)

In addition to the binder, the colorant, and the release agent, the admixture has a polarity between the polarity of the binder and the polarity of the release agent and mixes the binder and the release agent. A kneading step for producing a kneaded product by kneading a toner raw material containing a binder in a melted or softened state; and
A kneaded product obtained in the kneading step is granulated by dispersing it in an aqueous medium containing water in a melted or softened state to obtain toner particles. Production method. The release agent is contained in the toner raw material in a weight ratio of 1 to 10 parts by weight with respect to 100 parts by weight of the toner raw material,
2. The toner production method according to claim 1, wherein the admixture is contained in the toner raw material in a weight ratio of 0.1 part by weight or more and 3 parts by weight or less with respect to 1 part by weight of the release agent.   The method for producing a toner according to claim 1, wherein the admixture is contained in the toner raw material at a weight ratio of 1 part by weight or more and 20 parts by weight or less with respect to 100 parts by weight of the binder.   The toner manufacturing method according to claim 1, wherein the binder is made of a polyester resin.   The toner manufacturing method according to claim 4, wherein the admixture comprises a styrene acrylic copolymer resin. The aqueous medium contains a dispersant,
The method for producing a toner according to claim 1, wherein the dispersant is a water-soluble dispersant.

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