JP2025088993A - Method for producing toner for developing electrostatic images - Google Patents

Abstract

To provide a manufacturing method of an electrostatic charge image developing toner excellent in heat-resistant storage stability.SOLUTION: A manufacturing method of an electrostatic charge image developing toner includes a process of fusing and kneading a mixture which contains a binder resin, colorant, and a release agent. The binder resin contains a crystalline polyester resin with ester group concentration of 5.0 mmol/g or more and 10.0 mmol/g or less. When a value obtained by dividing the total number of -NH-groups and -NH2 groups in one molecule by molecular weight is set as NH group amount, the colorant contains an organic yellow pigment with the NH group amount of 3.0 mmol/g or more. The release agent contains a paraffin wax. The fusion and kneading of the mixture are performed by using an open-roll kneader.SELECTED DRAWING: None

Description

The present invention relates to a method for producing a toner for developing electrostatic images, which is used to develop latent images formed in electrophotography, electrostatic recording, electrostatic printing, etc.

In the field of electrophotography, with the development of electrophotographic systems, there is a demand for the development of toners for developing electrostatic images that can handle higher image quality and faster speeds. For example, as machine speeds increase, the amount of heat applied to the toner applied to the recording paper during fixing decreases, so there is a demand for toners with better low-temperature fixing properties.

Therefore, crystalline polyester resins have been considered as binder resins that are effective in improving the low-temperature fixing properties of toner (see Patent Documents 1 and 2).

JP 2013-24985 A JP 2012-78423 A

However, toners containing crystalline polyester resins have the problem that their heat-resistant storage stability is unstable.

The present invention relates to a method for producing a toner for developing electrostatic images that has excellent heat resistance and storage stability.

The present invention relates to a method for producing a toner for developing electrostatic images, the method including a step of melting and kneading a mixture containing a binder resin, a colorant, and a release agent, the binder resin containing a crystalline polyester resin having an ester group concentration of 5.0 mmol/g or more and 10.0 mmol/g or less, the colorant containing an organic yellow pigment having an NH group amount of 3.0 mmol/g or more when the NH group amount is the value obtained by dividing the total number of -NH- groups and -NH2 _groups in one molecule by the molecular weight, the release agent containing paraffin wax, and the melting and kneading of the mixture is performed using an open roll type kneader.

The method of the present invention allows for the production of a toner for developing electrostatic images that has excellent heat resistance and storage stability.

The present invention is a method for producing a toner for developing electrostatic images (hereinafter also simply referred to as "toner") through a process of melting and kneading a mixture containing a binder resin, a colorant, and a release agent, and is a method for melting and kneading a mixture containing a specific crystalline polyester resin, an organic yellow pigment, and a release agent using an open roll type kneader. The reason why a toner with excellent heat resistance and storage stability can be obtained by the method of the present invention is not clear, but is presumed to be as follows. Note that the following mechanism is merely presumed and is not limited thereto.

As a result of extensive investigations, the inventors of the present invention believed that the deterioration of heat-resistant storage stability was due to insufficient control of crystal domain formation of the crystalline polyester resin in the toner after melt-kneading (enlargement of domains, poor dispersion, etc.).
Therefore, by using an open roll type kneader with a strong kneading shear for melt kneading the raw materials, and increasing the dispersibility of the hydrophobic components, crystalline polyester resin and wax (releasing agent), in the toner particles, the domains of the hydrophobic components in the toner particles can be made fine. As a result, the crystalline polyester resin, which has been made fine, gathers on the surface (hydrophobic field) of the wax domain, which has been increased by the fineness, and crystallization is promoted. Therefore, paraffin wax, which has a higher hydrophobicity, is preferable as the wax. Furthermore, by using an organic yellow pigment with a large amount of amino groups and controlling the ester group concentration of the crystalline polyester resin to a specific range, the interaction between the ester group of the crystalline polyester resin and the amino group of the yellow pigment is significantly activated, and the affinity between the crystalline polyester resin and the yellow pigment is improved, so that the yellow pigment is also finely dispersed in the toner together with the crystalline polyester resin. Then, this yellow pigment acts as a crystal nucleating agent, further promoting the crystal recovery of the crystalline polyester resin. It is considered that these actions quickly form fine crystal domains of the crystalline polyester resin, thereby improving the heat-resistant storage stability of the resulting toner.

In the present invention, the binder resin contains a crystalline polyester resin having a specific ester group concentration from the viewpoint of interaction with the organic yellow pigment, as described above.

The ester group concentration of the crystalline polyester resin is 5.0 mmol/g or more, preferably 5.3 mmol/g or more, more preferably 5.6 mmol/g or more, and 10.0 mmol/g or less, preferably 9.5 mmol/g or less, more preferably 9.0 mmol/g or less. When two or more types of crystalline polyester resins are used, the weighted average of the ester group concentrations of the respective crystalline polyester resins is regarded as the ester group concentration of the crystalline polyester resin.

In the present invention, the ester group concentration of the polyester resin is calculated using the following formula:

[In the formula, A is the total amount of ester bonds (mol) generated when all the raw monomers of the polyester resin have reacted, and B is the total mass (g) of the raw monomers that make up the polyester resin. The numbers in parentheses in the formula indicate the units of each value.]

In the present invention, the crystalline polyester resin is preferably a polycondensation product of an alcohol component containing an aliphatic diol and a carboxylic acid component containing an aliphatic dicarboxylic acid compound.

Examples of aliphatic diols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-butenediol, 1,7-heptanediol, 1,8-octanediol, neopentyl glycol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, and 1,12-dodecanediol.

The carbon number of the aliphatic diol is 2 or more, and from the viewpoint of adjusting the ester group concentration, is preferably 14 or less, more preferably 10 or less, and even more preferably 8 or less.

From the viewpoint of improving the low-temperature fixing property of the toner, the aliphatic diol preferably has a hydroxyl group at the end of the carbon chain, and is more preferably an α,ω-linear alkanediol.

The content of the aliphatic diol in the alcohol component is preferably 80 mol% or more, more preferably 90 mol% or more, and even more preferably 95 mol% or more, and 100 mol% or less.

Examples of alcohol components other than aliphatic diols include alkylene oxide adducts of bisphenol A, aromatic diols such as bisphenol A, hydrogenated bisphenol A, sorbitol, pentaerythritol, glycerin, trihydric or higher alcohols such as trimethylolpropane, etc.

Examples of aliphatic dicarboxylic acid compounds include succinic acid (carbon number: 4), fumaric acid (carbon number: 4), adipic acid (carbon number: 6), suberic acid (carbon number: 8), azelaic acid (carbon number: 9), sebacic acid (carbon number: 10), dodecanedioic acid (carbon number: 12), tetradecanedioic acid (carbon number: 14), anhydrides of these acids, and alkyl esters of these acids having 1 to 3 carbon atoms. Here, when the aliphatic dicarboxylic acid compound is an alkyl ester, the number of carbon atoms of the alkyl group is not included in the above carbon number.

The carbon number of the aliphatic dicarboxylic acid compound is preferably 4 or more, more preferably 6 or more, and even more preferably 8 or more, and from the viewpoint of adjusting the ester group concentration, is preferably 14 or less.

The content of the aliphatic dicarboxylic acid compound in the carboxylic acid component is preferably 50 mol% or more, more preferably 60 mol% or more, even more preferably 70 mol% or more, even more preferably 80 mol% or more, and 100 mol% or less, from the viewpoint of hydrophobicity.

Other carboxylic acid components include aromatic dicarboxylic acid compounds such as phthalic acid, isophthalic acid, and terephthalic acid, and trivalent or higher carboxylic acid compounds such as trimellitic acid and pyromellitic acid.

Furthermore, from the viewpoint of durability, it is preferable that the alcohol component and/or carboxylic acid component of the crystalline polyester resin contain a monofunctional monomer.

Examples of monofunctional monomers contained in the alcohol component include aliphatic monoalcohols such as capryl alcohol, lauryl alcohol, myristyl alcohol, palmityl alcohol, stearyl alcohol, and behenyl alcohol.

From the viewpoint of hydrophobicity, the carbon number of the aliphatic monoalcohol is preferably 10 or more, more preferably 12 or more, and even more preferably 14 or more, and from the viewpoint of low-temperature fixability, it is preferably 22 or less, more preferably 20 or less, and even more preferably 18 or less.

Examples of monofunctional monomers contained in the carboxylic acid component include aliphatic monocarboxylic acids such as capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and behenic acid, and aliphatic monocarboxylic acid compounds such as alkyl esters of these acids in which the alkyl group has 1 to 3 carbon atoms.

The number of carbon atoms in the aliphatic monocarboxylic acid compound is preferably 10 or more, more preferably 12 or more, and even more preferably 14 or more, from the viewpoint of hydrophobicity, and is preferably 22 or less, more preferably 20 or less, and even more preferably 18 or less, from the viewpoint of low-temperature fixability. Here, when the aliphatic monocarboxylic acid compound is an alkyl ester, the number of carbon atoms in the alkyl group is not included in the above carbon number.

The content of monofunctional monomers in the total amount of alcohol components and carboxylic acid components is preferably 1 mol% or more, more preferably 3 mol% or more, and even more preferably 5 mol% or more, and from the viewpoint of low-temperature fixability, is preferably 30 mol% or less, more preferably 20 mol% or less, and even more preferably 15 mol% or less.

In this specification, macromonomers and hydroxycarboxylic acids are not included in the alcohol component and carboxylic acid component.

The equivalent ratio of the carboxyl groups of the carboxylic acid component to the hydroxyl groups of the alcohol component (COOH groups/OH groups) is preferably 0.8 or more, more preferably 0.9 or more, from the viewpoint of charging stability, and is preferably 1.2 or less, more preferably 1.1 or less, from the viewpoint of low-temperature fixability.

Crystalline polyester resins can be produced, for example, by polycondensing an alcohol component and a carboxylic acid component in an inert gas atmosphere, preferably in the presence of an esterification catalyst, and, if necessary, in the presence of a cocatalyst, polymerization inhibitor, etc., at a temperature of preferably 120°C or higher, more preferably 180°C or higher, and preferably 230°C or lower, more preferably 220°C or lower.

Examples of the esterification catalyst include tin compounds such as dibutyltin oxide and tin(II) 2-ethylhexanoate, and titanium compounds such as titanium diisopropoxybis(triethanolamine). The amount of the esterification catalyst used is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, and preferably 1.5 parts by mass or less, and more preferably 1 part by mass or less, relative to 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component. Examples of the co-catalyst for the esterification catalyst include gallic acid. The amount of the co-catalyst used is preferably 0.001 parts by mass or more, more preferably 0.01 parts by mass or more, and preferably 0.5 parts by mass or less, and more preferably 0.1 parts by mass or less, relative to 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component. Examples of the polymerization inhibitor include tert-butylcatechol. The amount of polymerization inhibitor used is preferably 0.001 parts by mass or more, more preferably 0.01 parts by mass or more, and preferably 0.5 parts by mass or less, more preferably 0.1 parts by mass or less, per 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component.

In the present invention, the polyester resin may be modified to such an extent that its properties are not substantially impaired. Examples of modified polyester resins include polyester resins grafted or blocked with phenol, urethane, epoxy, or the like, by the methods described in JP-A-11-133668, JP-A-10-239903, JP-A-8-20636, and the like. Among the modified polyester resins, urethane-modified polyester resins in which polyester resins are urethane-extended with a polyisocyanate compound are preferred.

From the viewpoint of durability, the softening point of the crystalline polyester resin is preferably 50°C or higher, more preferably 55°C or higher, and even more preferably 65°C or higher, and from the viewpoint of low-temperature fixability, it is preferably 140°C or lower, more preferably 120°C or lower, and even more preferably 100°C or lower.

The crystallinity of a resin is represented by a crystallinity index defined as the ratio of the softening point to the maximum endothermic peak temperature measured by a differential scanning calorimeter, that is, the value of [softening point/maximum endothermic peak temperature].
The crystalline resin is a resin having a crystallinity index of 0.6 or more, preferably 0.7 or more, more preferably 0.9 or more, and 1.4 or less, preferably 1.2 or less, more preferably 1.1 or less.
On the other hand, an amorphous resin is a resin in which no endothermic peak is observed, or if an endothermic peak is observed, the resin has a crystallinity index of more than 1.4, preferably more than 1.5, more preferably 1.6 or more, or less than 0.6, preferably 0.5 or less.
The crystallinity of the resin can be adjusted by the type and ratio of the raw material monomers, and the production conditions (e.g., reaction temperature, reaction time, cooling rate), etc. The maximum endothermic peak temperature refers to the temperature of the peak with the largest peak area among the observed endothermic peaks. In the case of a crystalline resin, the maximum endothermic peak temperature is the melting point.

From the viewpoint of durability, the melting point of the crystalline polyester resin is preferably 50°C or higher, more preferably 55°C or higher, and even more preferably 65°C or higher, and from the viewpoint of low-temperature fixability, it is preferably 130°C or lower, more preferably 120°C or lower, and even more preferably 100°C or lower.

From the viewpoint of low-temperature fixability, the acid value of the crystalline polyester resin is preferably 1 mgKOH/g or more, more preferably 3 mgKOH/g or more, and from the viewpoint of durability, it is preferably 20 mgKOH/g or less, more preferably 15 mgKOH/g or less.

The content of the crystalline polyester resin in the binder resin is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more, from the viewpoint of low-temperature fixability, and is preferably 35% by mass or less, more preferably 30% by mass or less, and even more preferably 25% by mass or less, from the viewpoint of durability.

From the viewpoint of heat-resistant storage stability, it is preferable that the binder resin further contains an amorphous polyester resin.

As the amorphous polyester resin, an amorphous polyester resin or an amorphous composite resin in which a polyester resin is combined with a styrene resin is preferred.

As the amorphous polyester resin, a polycondensation product of an alcohol component and a carboxylic acid component, including an alkylene oxide adduct of bisphenol A, is preferred.

The alkylene oxide adduct of bisphenol A is represented by the formula (I):

(In the formula, OR and RO are oxyalkylene groups, R is an ethylene group and/or a propylene group, x and y are the average number of moles of alkylene oxide added, each of which is a positive number, and the sum of x and y is 1 or more, preferably 1.5 or more, and 16 or less, preferably 8 or less, more preferably 6 or less, and even more preferably 4 or less.)
Preferred is a compound represented by the following formula:

From the viewpoint of low-temperature fixability, the content of the alkylene oxide adduct of bisphenol A in the alcohol component is preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, even more preferably 95 mol% or more, and even more preferably 100 mol%.

Other alcohol components include aliphatic diols, bisphenol A, hydrogenated bisphenol A, sorbitol, pentaerythritol, glycerin, trimethylolpropane, and other trihydric or higher alcohols.

Examples of carboxylic acid components include aromatic dicarboxylic acid compounds, aliphatic dicarboxylic acid compounds, and trivalent or higher carboxylic acid compounds.

Examples of aromatic dicarboxylic acid compounds include phthalic acid, isophthalic acid, terephthalic acid, anhydrides of these acids, and alkyl esters of these acids having 1 to 3 carbon atoms.

Aliphatic dicarboxylic acid compounds include fumaric acid, maleic acid, succinic acid, succinic acid derivatives substituted with a hydrocarbon group, glutaric acid, adipic acid, sebacic acid, anhydrides of these acids, and alkyl esters of these acids having 1 to 3 carbon atoms.

Examples of trivalent or higher carboxylic acid compounds include trimellitic acid, pyromellitic acid, anhydrides of these acids, and alkyl esters of these acids having 1 to 3 carbon atoms.

In addition, the alcohol component may contain a monohydric alcohol, and the carboxylic acid component may contain a monovalent carboxylic acid compound, as appropriate.

From the viewpoint of adjusting the softening point of the polyester resin, the equivalent ratio of the carboxyl groups of the carboxylic acid component to the hydroxyl groups of the alcohol component (COOH groups/OH groups) is preferably 0.6 or more, more preferably 0.7 or more, even more preferably 0.8 or more, and is preferably 1.3 or less, more preferably 1.2 or less.

The polycondensation reaction conditions of the alcohol component and the carboxylic acid component of the amorphous polyester resin are the same as those of the crystalline polyester resin, except that the preferred reaction temperature is 160°C or higher, more preferably 180°C or higher, and 250°C or lower, more preferably 240°C or lower.

The polyester resin in the composite resin is the same as the amorphous polyester resin described above, and the styrene-based resin is an addition polymer of raw material monomers that contain at least styrene or styrene derivatives such as α-methylstyrene and vinyltoluene (hereinafter, styrene and styrene derivatives are collectively referred to as "styrene compounds").

The content of the styrene compound, preferably styrene, in the raw material monomer of the styrene-based resin is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more, from the viewpoint of storage stability, and is preferably 95% by mass or less, more preferably 93% by mass or less, and even more preferably 90% by mass or less, from the viewpoint of low-temperature fixability.

The styrene-based resin may also contain, as a raw material monomer, an alkyl (meth)acrylate ester having an alkyl group with 7 or more carbon atoms. Examples of alkyl (meth)acrylate esters include 2-ethylhexyl (meth)acrylate, (iso)octyl (meth)acrylate, (iso)decyl (meth)acrylate, and (iso)stearyl (meth)acrylate. It is preferable to use one or more of these. In this specification, "(iso)" means that both the case where this group is present and the case where it is not present are included, and when these groups are not present, it indicates that it is normal. Furthermore, "(meth)acrylic acid" refers to acrylic acid, methacrylic acid, or both.

The number of carbon atoms in the alkyl group in the (meth)acrylic acid alkyl ester as a raw material monomer for the styrene-based resin is preferably 7 or more, more preferably 8 or more, from the viewpoint of improving the low-temperature fixing property of the toner, and is preferably 12 or less, more preferably 10 or less. The number of carbon atoms in the alkyl ester refers to the number of carbon atoms derived from the alcohol component that constitutes the ester.

The raw material monomers for styrene-based resins may include raw material monomers other than styrene compounds and (meth)acrylic acid alkyl esters, for example, ethylenically unsaturated monoolefins such as ethylene and propylene; diolefins such as butadiene; halovinyls such as vinyl chloride; vinyl esters such as vinyl acetate and vinyl propionate; ethylenically monocarboxylic acid esters such as dimethylaminoethyl (meth)acrylate; vinyl ethers such as methyl vinyl ether; vinylidene halides such as vinylidene chloride; and N-vinyl compounds such as N-vinylpyrrolidone.

The addition polymerization reaction of the raw material monomers for styrene-based resins can be carried out in the presence of a polymerization initiator such as dibutyl peroxide or dicumyl peroxide, a chain transfer agent, a crosslinking agent, etc., in the presence of an organic solvent or without a solvent, by a conventional method, and the temperature conditions are preferably 110°C or higher, more preferably 140°C or higher, and preferably 200°C or lower.

When an organic solvent is used in the addition polymerization reaction, xylene, toluene, methyl ethyl ketone, acetone, etc. can be used. The amount of the organic solvent used is preferably 10 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the raw material monomer of the styrene-based resin.

The composite resin is preferably a resin in which a polyester resin and a styrene-based resin are bonded together, and more preferably a resin in which a polyester resin and a styrene-based resin are chemically bonded together via a bireactive monomer that can react with both the raw material monomers of the polyester resin and the raw material monomers of the styrene-based resin.

The bireactive monomer is preferably a compound having at least one functional group selected from the group consisting of hydroxyl, carboxyl, epoxy, primary amino, and secondary amino groups, preferably a hydroxyl and/or carboxyl group, more preferably a carboxyl group, and an ethylenically unsaturated bond in the molecule, more preferably at least one selected from the group consisting of acrylic acid, methacrylic acid, fumaric acid, maleic acid, and maleic anhydride, and from the viewpoint of reactivity in polycondensation reactions and addition polymerization reactions, still more preferably at least one selected from the group consisting of acrylic acid, methacrylic acid, and fumaric acid. However, when used together with a polymerization inhibitor, a polyvalent carboxylic acid compound having an ethylenically unsaturated bond such as fumaric acid functions as a raw material monomer for polyester resin. In this case, fumaric acid, etc. is not a bireactive monomer, but a raw material monomer for polyester resin.

The amount of the bireactive monomer used is preferably 1 mol or more, more preferably 2 mol or more, per 100 mol of the total alcohol components of the polyester resin, from the viewpoint of increasing the dispersibility of the styrene resin and the polyester resin and improving the dispersibility of the raw materials in the toner, and is preferably 30 mol or less, more preferably 20 mol or less, and even more preferably 10 mol or less, from the viewpoint of improving the low-temperature fixing property of the toner.

Specifically, the composite resin is preferably produced by the following method. When a bireactive monomer is used, it is preferable to use the bireactive monomer together with the raw material monomer of the polyester resin from the viewpoint of improving the dispersibility of the pigment and the crystalline polyester resin in the toner.

(i) A method of carrying out a polycondensation reaction step (A) using raw material monomers for a polyester resin followed by an addition polymerization reaction step (B) using raw material monomers for a styrene-based resin. In this method, the step (A) is carried out under temperature conditions suitable for the polycondensation reaction, the temperature is lowered, and the step (B) is carried out under temperature conditions suitable for the addition polymerization reaction. The raw material monomers for the styrene-based resin are preferably added to the reaction system at a temperature suitable for the addition polymerization reaction.
After step (B), the temperature is increased again, and a raw material monomer of a polyester resin having a valence of three or more and serving as a crosslinking agent, etc., is added to the polymerization system as necessary, so that the polycondensation reaction of step (A) and the reaction with the bireactive monomer can be further promoted.

(ii) A method in which step (B) of an addition polymerization reaction using raw material monomers for a styrene-based resin is followed by step (A) of a polycondensation reaction using raw material monomers for a polyester resin. In this method, step (B) is carried out under temperature conditions suitable for an addition polymerization reaction, the temperature is raised, and the polycondensation reaction of step (A) is carried out under temperature conditions suitable for a polycondensation reaction.
The raw material monomers of the polyester resin may be present in the reaction system during the addition polymerization reaction, or may be added to the reaction system under temperature conditions suitable for the polycondensation reaction. In the former case, the progress of the polycondensation reaction can be controlled by adding an esterification catalyst at a temperature suitable for the polycondensation reaction.

(iii) A method of carrying out the reaction under conditions in which the step (A) of the polycondensation reaction by the raw material monomer of the polyester resin and the step (B) of the addition polymerization reaction by the raw material monomer of the styrene resin proceed in parallel. In this method, it is preferable to carry out the steps (A) and (B) in parallel under temperature conditions suitable for the addition polymerization reaction, raise the temperature, add a raw material monomer of the polyester resin having a valence of 3 or more as a crosslinking agent to the polymerization system as necessary under temperature conditions suitable for the polycondensation reaction, and further carry out the polycondensation reaction of step (A). At that time, under temperature conditions suitable for the polycondensation reaction, it is also possible to add a polymerization inhibitor to proceed with only the polycondensation reaction. When a bireactive monomer is used, the bireactive monomer is involved in the polycondensation reaction as well as the addition polymerization reaction.

In the above method (i), a prepolymerized polyester resin may be used instead of step (A) in which a polycondensation reaction is carried out. In the above method (iii), when the reaction is carried out under conditions in which steps (A) and (B) proceed in parallel, a mixture containing raw material monomers for a styrene-based resin may be dropped into a mixture containing raw material monomers for a polyester resin to cause the reaction.

The above methods (i) to (iii) are preferably carried out in the same container.

The mass ratio of the polyester resin to the styrene resin in the composite resin (polyester resin/styrene resin) is preferably 98/2 or less, more preferably 95/5 or less, and even more preferably 90/10 or less, from the viewpoint of improving the dispersibility of the raw materials in the toner, and is preferably 60/40 or more, more preferably 70/30 or more, and even more preferably 75/25 or more, from the viewpoint of low-temperature fixability. In the above calculation, the mass of the polyester resin is the amount obtained by subtracting the amount of reaction water dehydrated by the polycondensation reaction (calculated value) from the mass of the raw material monomers of the polyester resin used, and the amount of the bireactive monomer is included in the amount of raw material monomers of the polyester resin. In addition, the amount of the styrene resin is the total amount of the raw material monomers of the styrene resin.

From the viewpoint of charging stability, the softening point of the amorphous polyester resin is preferably 70°C or higher, more preferably 90°C or higher, and even more preferably 100°C or higher, and from the viewpoint of low-temperature fixability, it is preferably 170°C or lower, more preferably 160°C or lower, and even more preferably 150°C or lower.

From the viewpoint of low-temperature fixing property and fixing width, the amorphous polyester resin may be made of resins with different softening points. The difference in softening points between the two types of resins is preferably 10°C or more, more preferably 20°C or more, and is preferably 60°C or less, more preferably 40°C or less.

The softening point of the amorphous polyester resin (resin AH) having a higher softening point is preferably 100°C or higher, more preferably 110°C or higher, and even more preferably 120°C or higher, from the viewpoint of fixing width, and is preferably 170°C or lower, more preferably 160°C or lower, and even more preferably 150°C or lower, from the viewpoint of low-temperature fixing ability.

The softening point of the amorphous polyester resin (resin AL) having a lower softening point is preferably 70°C or higher, more preferably 90°C or higher, and even more preferably 100°C or higher, from the viewpoint of charging stability, and is preferably 130°C or lower, more preferably 125°C or lower, and even more preferably 120°C or lower, from the viewpoint of low-temperature fixing ability.

The mass ratio of resin AH to resin AL (resin AH/resin AL) is preferably 10/90 or more, more preferably 20/80 or more, even more preferably 30/70 or more, and is preferably 90/10 or less, more preferably 80/20 or less, even more preferably 75/25 or less.

From the viewpoint of heat-resistant storage stability, the glass transition temperature of the amorphous polyester resin is preferably 40°C or higher, more preferably 50°C or higher, and from the viewpoint of low-temperature fixability, it is preferably 80°C or lower, more preferably 70°C or lower.

The acid value of the amorphous polyester resin is preferably 5 mgKOH/g or more, more preferably 10 mgKOH/g or more, from the viewpoint of pigment dispersibility, and is preferably 50 mgKOH/g or less, more preferably 40 mgKOH/g or less, from the viewpoint of charge stability.

From the viewpoint of charging stability, the content of the amorphous polyester resin in the total amount of the crystalline polyester resin and the amorphous polyester resin is preferably 65% by mass or more, more preferably 70% by mass or more, even more preferably 75% by mass or more, and is preferably 95% by mass or less, more preferably 90% by mass or less, even more preferably 85% by mass or less.

From the viewpoint of low-temperature fixability and heat-resistant storage stability, the mass ratio of the amorphous polyester resin to the crystalline polyester resin (amorphous polyester resin/crystalline polyester resin) is preferably 65/35 or more, more preferably 70/30 or more, even more preferably 75/25 or more, and is preferably 95/5 or less, more preferably 90/10 or less, even more preferably 85/15 or less.

Other binder resins include vinyl resins such as styrene acrylic resin, epoxy resin, polycarbonate, polyurethane, and composite resins containing two or more of these resins.

The total content of the crystalline polyester resin and the amorphous polyester resin in the binder resin is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 100% by mass.

The content of the binder resin in the toner is preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more, and is preferably less than 100% by mass, more preferably 98% by mass or less, and even more preferably 95% by mass or less.

The colorant includes an organic yellow pigment having a specific amount of NH groups in view of its interaction with the crystalline polyester resin.

The NH group amount of the organic yellow pigment is 3.0 mmol/g or more, preferably 5.0 mmol/g or more, more preferably 7.0 mmol/g or more, even more preferably 10.0 mmol/g or more, and is preferably 15.0 mmol/g or less, more preferably 13.0 mmol/g or less, even more preferably 12.5 mmol/g or less. Here, the NH group amount is the value obtained by dividing the total number of -NH- groups and _-NH2 groups in one molecule by the molecular weight.

As the organic yellow pigment, at least one selected from the group consisting of benzimidazolone pigments, isoindoline pigments, and condensed disazo pigments is preferred.

Examples of benzimidazolone pigments include C.I. Pigment Yellow 180 (total number of -NH- groups and _-NH2 groups in one molecule = 6, molecular weight = 733, NH group amount = 8.2 mmol/g).

Examples of isoindoline pigments include C.I. Pigment Yellow 185 (total number of -NH- groups and -NH2 _groups in one molecule = 4, molecular weight = 337, NH group amount = 11.9 mmol/g).

Examples of condensed disazo pigments include C.I. Pigment Yellow 93 (total number of -NH- groups and -NH ₂ groups in one molecule = 4, molecular weight = 937, NH group amount = 4.3 mmol / g), C.I. Pigment Yellow 95 (total number of -NH- groups and -NH ₂ groups in one molecule = 4, molecular weight = 917, NH group amount = 4.4 mmol / g), and the like.

From the viewpoint of heat-resistant storage stability of the toner, the organic yellow pigment used in the present invention is preferably at least one selected from benzimidazolone pigments and isoindoline pigments, more preferably at least one selected from C.I. Pigment Yellow 180 (PY180) and C.I. Pigment Yellow 185 (PY185), and even more preferably C.I. Pigment Yellow 185.

The content of the organic yellow pigment is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, and is preferably 15 parts by mass or less, more preferably 12 parts by mass or less, and even more preferably 10 parts by mass or less, per 100 parts by mass of the binder resin.

The mass ratio of the crystalline polyester resin to the organic yellow pigment (crystalline polyester resin/organic yellow pigment) is preferably 20/80 or more, more preferably 40/60 or more, even more preferably 50/50 or more, and is preferably 90/10 or less, more preferably 85/15 or less, even more preferably 80/20 or less.

The colorant may contain other colorants as long as the effect of the present invention is not impaired, but the content of the organic yellow pigment in the colorant is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 100% by mass. Examples of other colorants include carbon black, phthalocyanine blue, permanent brown FG, brilliant fast scarlet, pigment red 122, pigment green B, rhodamine B base, solvent red 49, solvent red 146, solvent blue 35, quinacridone, carmine 6B, disazo yellow, etc.

The content of the colorant is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, and is preferably 15 parts by mass or less, more preferably 12 parts by mass or less, and even more preferably 10 parts by mass or less, per 100 parts by mass of the binder resin.

The release agent contains paraffin wax. In the present invention, paraffin wax refers to paraffin wax as defined in JIS K2235. The paraffin wax in the present invention may be either one made from petroleum (petroleum-based paraffin wax) or one made from coal (coal-based paraffin wax). For example, paraffin wax made from petroleum includes paraffin wax obtained by refining petroleum, such as high-purity refined paraffin wax obtained by further separating and refining petroleum wax extracted from petroleum using vacuum distillate distillate to increase the ratio of linear hydrocarbons. On the other hand, paraffin wax made from coal includes Fischer-Tropsch wax obtained by hydrogenating distillation components by-produced during the production of synthetic petroleum by the Fischer-Tropsch process to remove unsaturated hydrocarbons and oxygen compounds. In the present invention, paraffin wax obtained by refining petroleum is preferred from the viewpoint of heat-resistant storage stability.

From the viewpoint of heat resistance storage stability and low-temperature fixability, the melting point of the paraffin wax is preferably 60°C or higher, more preferably 65°C or higher, and is preferably 110°C or lower, more preferably 100°C or lower.

The mass ratio of the crystalline polyester resin to the paraffin wax (crystalline polyester resin/paraffin wax) is preferably 10/90 or more, more preferably 30/70 or more, even more preferably 40/60 or more, and is preferably 95/5 or less, more preferably 90/10 or less, even more preferably 85/15 or less.

The content of paraffin wax is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 1.5 parts by mass or more, and is preferably 15 parts by mass or less, more preferably 12 parts by mass or less, and even more preferably 9 parts by mass or less, per 100 parts by mass of binder resin.

The release agent may contain other release agents within the range that does not impair the effects of the present invention, but the content of paraffin wax in the release agent is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 100% by mass. Examples of other release agents include polypropylene wax, polyethylene wax, ethylene propylene copolymer wax; aliphatic hydrocarbon waxes such as microcrystalline wax and Fischer-Tropsch wax, or oxides thereof; ester waxes such as carnauba wax, montan wax, or deoxidized waxes thereof, and fatty acid ester wax; fatty acid amides, fatty acids, higher alcohols, and fatty acid metal salts.

The content of the release agent is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 1.5 parts by mass or more, and is preferably 15 parts by mass or less, more preferably 12 parts by mass or less, and even more preferably 9 parts by mass or less, per 100 parts by mass of the binder resin.

The mixture to be melt-kneaded may contain additives such as charge control agents, magnetic powders, flow improvers, conductivity adjusters, reinforcing fillers such as fibrous substances, antioxidants, and cleaning improvers, in addition to the binder resin, colorant, and release agent.

The charge control agent is not particularly limited, and may contain either a positively charged charge control agent or a negatively charged charge control agent.

Positively charged charge control agents include nigrosine dyes such as "Nigrosine Base EX", "Oil Black BS", "Oil Black SO", "Bontron N-01", "Bontron N-04", "Bontron N-07", "Bontron N-09", "Bontron N-11", and "Bontron N-79" (all manufactured by Orient Chemical Industries Co., Ltd.); triphenylmethane dyes containing a tertiary amine as a side chain; quaternary ammonium salt compounds such as "Bontron P-51" (manufactured by Orient Chemical Industries Co., Ltd.), cetyltrimethylammonium bromide, and "COPY CHARGE PX" VP435 (Clariant), etc.; polyamine resins, such as AFP-B (Orient Chemical Industries, Ltd.); imidazole derivatives, such as PLZ-2001 and PLZ-8001 (both manufactured by Shikoku Chemical Industries, Ltd.); styrene-acrylic resins, such as FCA-701PT and FCA-201-PS (Fujikura Chemical Industries, Ltd.), etc.

Examples of negatively charged charge control agents include metal-containing azo dyes, such as "Varifast Black 3804", "Bontron S-31", "Bontron S-32", "Bontron S-34", and "Bontron S-36" (all manufactured by Orient Chemical Industry Co., Ltd.), "Aizen Spiron Black TRH", and "T-77" (manufactured by Hodogaya Chemical Co., Ltd.); metal compounds of benzilic acid compounds, such as "LR-147" and "LR-297" (all manufactured by Nippon Carlit Co., Ltd.); metal compounds of salicylic acid compounds, such as "Bontron E-81", "Bontron E-84", "Bontron E-88", and "Bontron E-304" (all manufactured by Orient Chemical Industry Co., Ltd.), and "TN-105" (manufactured by Hodogaya Chemical Co., Ltd.); copper phthalocyanine dyes; and quaternary ammonium salts, such as "COPY CHARGE NX" VP434" (Clariant), nitroimidazole derivatives, etc.; organometallic compounds, etc.

From the viewpoint of the charging stability of the toner, the content of the charge control agent is preferably 0.01 parts by mass or more, more preferably 0.2 parts by mass or more, and preferably 10 parts by mass or less, more preferably 5 parts by mass or less, even more preferably 3 parts by mass or less, and even more preferably 2 parts by mass or less, per 100 parts by mass of the binder resin.

It is preferable that the mixture to be melt-kneaded is mixed in advance in a mixer such as a Henschel mixer or ball mill, and then fed to an open roll type kneader.

An open-roll type kneader is one in which the kneading section is open and not sealed, and the heat of kneading generated during melt kneading can be easily dissipated. The open-roll type kneader used in the present invention is equipped with a raw material supply port and a kneaded material discharge port provided along the axial direction of the roll, and from the viewpoint of production efficiency, it is preferable that it is a continuous open-roll type kneader.

The open-roll type kneader used in the present invention is preferably a kneader equipped with two rolls with different peripheral speeds, i.e., a roll with a high peripheral speed (high rotation roll) and a roll with a low peripheral speed (low rotation roll). In the present invention, from the viewpoint of dispersibility of the kneaded material, it is preferable that the high rotation roll functions as a heating roll and the low rotation roll functions as a cooling roll, i.e., the set temperature of the high rotation roll is preferably higher than the set temperature of the low rotation roll. When the set temperatures of the rolls are different on the raw material input side and the kneaded material discharge side, it is preferable that the set temperature of the high rotation roll is higher than the set temperature of the low rotation roll at least on the raw material input side, and it is more preferable that the set temperature of the high rotation roll is higher than the set temperature of the low rotation roll on both the raw material input side and the kneaded material discharge side.

The temperature of the rolls can be adjusted, for example, by the temperature of the heat medium passed through the inside of the rolls, and each roll may be divided into two or more sections to pass heat mediums of different temperatures through them.

The temperature of the raw material input side of the high rotation roll is preferably 80°C or higher, more preferably 100°C or higher, and even more preferably 120°C or higher, from the viewpoint of reducing the mechanical force during melt kneading and suppressing heat generation, and is preferably 160°C or lower, and more preferably 150°C or lower. From the same viewpoint, the temperature of the raw material input side of the low rotation roll is preferably 25°C or higher, more preferably 40°C or higher, and preferably 90°C or lower, and more preferably 80°C or lower.

For both the high-speed and low-speed rolls, it is preferable that the temperature on the raw material input side is higher than that on the kneaded material discharge side, and the temperature difference between the raw material input side and the kneaded material discharge side is preferably 20°C or more, more preferably 30°C or more, and is preferably 60°C or less, more preferably 50°C or less, from the viewpoint of preventing the kneaded material from detaching from the rolls, reducing the mechanical force during melt kneading, and suppressing heat generation.

The temperature of the raw material inlet side of the high rotation roll and low rotation roll refers to the set temperature of the raw material inlet end, and the temperature of the kneaded material discharge side refers to the set temperature of the kneaded material discharge end.

From the viewpoint of reducing the mechanical force during kneading and suppressing heat generation, the peripheral speed of the high rotation roll is preferably 2 m/min or more, more preferably 10 m/min or more, even more preferably 25 m/min or more, and preferably 100 m/min or less, more preferably 75 m/min or less, and even more preferably 50 m/min or less. From the same viewpoint, the peripheral speed of the low rotation roll is preferably 1 m/min or more, more preferably 5 m/min or more, even more preferably 15 m/min or more, and preferably 90 m/min or less, more preferably 60 m/min or less, and even more preferably 30 m/min or less. In addition, the ratio of the peripheral speeds of the two rolls (low rotation roll/high rotation roll) is preferably 1/10 or more, more preferably 3/10 or more, and preferably 9.9/10 or less, more preferably 8/10 or less.

There are no particular limitations on the structure, size, material, etc. of each roll. The roll surface has grooves used for kneading, and the shape of these grooves can be linear, spiral, wavy, uneven, etc.

After melt kneading, it is preferable to cool the kneaded mixture appropriately until it reaches a pulverizable hardness, and then perform a pulverization and classification process to obtain toner particles. Here, cooling refers to cooling the kneaded mixture to a temperature between 0°C and 50°C, or to cooling below the glass transition temperature of the binder resin in the kneaded mixture.

When grinding the kneaded material, the kneaded material may be ground to the desired particle size all at once or in stages, but from the viewpoint of efficient and more uniform grinding, it is preferable to grind the material in two stages: coarse grinding and fine grinding.

Mills used for coarse grinding include hammer mills, cutter mills, atomizers, and rotoplexes.

In the coarse grinding process, the kneaded material is coarsely ground until the particle size is approximately 0.1 to 3 mm, and then passed through a sieve with mesh size of approximately 2 to 3 mm. The ground material that passed through the sieve is preferably subjected to fine grinding as ground material with a maximum diameter of 2 to 3 mm or less.

Mills used for fine grinding include jet mills such as fluidized bed jet mills and collision plate jet mills, mechanical mills, etc.

It is preferable to adjust the degree of pulverization appropriately depending on the particle size of the desired toner particles.

Classifiers used for classification include airflow classifiers, inertial classifiers, and sieve classifiers. During the classification process, the pulverized material that is removed due to insufficient pulverization may be subjected to the pulverization process again, and the pulverization and classification processes may be repeated as necessary.

In the present invention, it is preferable to further carry out a step of mixing the obtained toner particles with an external additive from the viewpoint of improving transferability.

External additives used in the external addition step include inorganic fine particles such as silica, alumina, titania, zirconia, tin oxide, and zinc oxide, and organic fine particles such as melamine-based resin fine particles and polytetrafluoroethylene resin fine particles, and two or more types may be used in combination. Among these, silica is preferred, and from the viewpoint of the transferability of the toner, hydrophobic silica that has been subjected to a hydrophobic treatment is more preferred.

Examples of hydrophobic treatment agents for hydrophobizing the surface of silica particles include hexamethyldisilazane (HMDS), dimethyldichlorosilane (DMDS), cyclic silazane, silicone oil, aminosilane, octyltriethoxysilane (OTES), methyltriethoxysilane, etc.

From the viewpoint of the chargeability, fluidity, and transferability of the toner, the average particle size of the external additive is preferably 10 nm or more, more preferably 15 nm or more, and is preferably 250 nm or less, more preferably 200 nm or less, and even more preferably 90 nm or less.

The toner particles and the external additives can be mixed in the usual manner, using a mixer such as a Henschel mixer.

From the viewpoint of the chargeability, fluidity, and transferability of the toner, the content of the external additive is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and even more preferably 0.3 parts by mass or more, relative to 100 parts by mass of the toner particles before treatment with the external additive, and is preferably 5 parts by mass or less, and more preferably 3 parts by mass or less.

The volume median particle diameter ( _D50 ) of the toner obtained by the method of the present invention is preferably 3 μm or more, more preferably 4 μm or more, and preferably 15 μm or less, more preferably 10 μm or less. In this specification, the volume median particle diameter ( _D50 ) means the particle diameter at which the cumulative volume frequency calculated by volume fraction is 50% calculated from the smallest particle diameter. In addition, when the toner is treated with an external additive, the volume median particle diameter of the toner particles before treatment with the external additive is taken as the volume median particle diameter of the toner.

The toner obtained by the method of the present invention can be used as it is as a single-component developing toner, or mixed with a carrier as a two-component developing toner, in image forming devices using a single-component developing method or a two-component developing method, respectively.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. The physical properties of the resins and the like were measured by the following methods.

[Softening point of resin]
Using a flow tester "CFT-500D" (manufactured by Shimadzu Corporation), 1 g of the sample is heated at a temperature increase rate of 6°C/min while applying a load of 1.96 MPa with the plunger, and extruded from a nozzle with a diameter of 1 mm and a length of 1 mm. The plunger descent amount of the flow tester is plotted against the temperature, and the temperature at which half of the sample flows out is taken as the softening point.

[Maximum endothermic peak temperature of resin]
Using a differential scanning calorimeter "Q-100" (manufactured by TA Instruments Japan, Inc.), 0.01 to 0.02 g of a sample is weighed into an aluminum pan and cooled from room temperature (25°C) to 0°C at a temperature drop rate of 10°C/min, and maintained at 0°C for 1 minute. Thereafter, measurements are performed at a temperature increase rate of 10°C/min. The temperature of the peak with the largest peak area among the observed endothermic peaks is taken as the maximum endothermic peak temperature. For crystalline resins, the maximum endothermic peak temperature is taken as the melting point.

[Glass transition temperature of resin]
Using a differential scanning calorimeter "Q-100" (manufactured by TA Instruments Japan, Inc.), 0.01 to 0.02 g of a sample is weighed into an aluminum pan, heated to 200°C, and cooled from that temperature at a rate of 10°C/min to 0°C. Next, the sample is heated at a rate of 10°C/min, and the endothermic peak is measured. The glass transition temperature is the temperature at the intersection of an extension of the baseline below the maximum endothermic peak temperature and a tangent line showing the maximum slope from the rising part of the peak to the apex of the peak.

[Acid value of resin]
Measurement is performed based on the method of JIS K 0070: 1992. However, only the measurement solvent is changed from the mixed solvent of ethanol and ether specified in JIS K 0070 to a mixed solvent of acetone and toluene (acetone:toluene = 1:1 (volume ratio)) for amorphous resins, and a mixed solvent of chloroform and dimethylformamide (chloroform:dimethylformamide = 7:3 (volume ratio)) for crystalline resins.

[Melting point of release agent]
Using a differential scanning calorimeter "Q-100" (manufactured by TA Instruments Japan, Inc.), 0.01 to 0.02 g of a sample is weighed into an aluminum pan, heated to 200°C at a heating rate of 10°C/min, and cooled from that temperature to 0°C at a heating rate of 10°C/min. The sample is then heated to 200°C at a heating rate of 10°C/min and measured, and the maximum endothermic peak temperature is taken as the melting point.

[Average particle size of external additives]
The average particle size refers to the number-average particle size, and is determined by measuring the particle sizes (average of major and minor diameters) of 500 particles in a scanning electron microscope (SEM) photograph and averaging these by number.

[Volume Median Particle Size ( _D50 ) of Toner]
Measuring instrument: "Coulter Multisizer (registered trademark) III" (manufactured by Beckman Coulter, Inc.)
Aperture diameter: 100 μm
Analysis software: "Multisizer (registered trademark) III version 3.51" (Beckman Coulter, Inc.)
Electrolyte: "Isoton (registered trademark) II" (manufactured by Beckman Coulter, Inc.)
Dispersion: Polyoxyethylene lauryl ether "EMULGEN (registered trademark) 109P" [manufactured by Kao Corporation, HLB (Griffin) = 13.6] was dissolved in the electrolyte to adjust the concentration to 5% by mass. Dispersion conditions: 10 mg of a measurement sample was added to 5 mL of the dispersion, and the mixture was dispersed for 1 minute using an ultrasonic disperser (machine name: US-1, manufactured by SND Corporation, output: 80 W). Thereafter, 25 mL of the electrolyte was added, and the mixture was further dispersed for 1 minute using the ultrasonic disperser to prepare a sample dispersion.
Measurement conditions: The sample dispersion is added to 100 mL of the electrolyte to adjust the concentration to a level that allows the particle sizes of 30,000 particles to be measured in 20 seconds. The 30,000 particles are then measured, and the volume median particle size ( _D50 ) is determined from the particle size distribution.

Resin Production Example 1
The alcohol components, fumaric acid, esterification catalyst, and polymerization inhibitor shown in Table 1 were placed in a 10-liter four-neck flask equipped with a dehydration tube equipped with a nitrogen inlet tube, a stirrer, and a thermocouple, and the temperature was raised to 230°C in a mantle heater under a nitrogen atmosphere, and polycondensation was carried out for 7 hours. The temperature was then lowered to 200°C, trimellitic anhydride was added, and the temperature was raised to 210°C to carry out a polycondensation reaction, thereby obtaining an amorphous polyester resin (resin A1). The physical properties of the obtained resin are shown in Table 1.

Resin Production Example 2
The raw material monomers of the polyester resin other than trimellitic anhydride shown in Table 2, the bireactive monomers and the esterification catalyst were placed in a 10-liter four-neck flask equipped with a dehydration tube equipped with a nitrogen inlet tube, a stirrer and a thermocouple, and heated to 160 ° C. in a mantle heater under a nitrogen atmosphere. Then, a mixture of the raw material monomers of the styrene-based resin and the polymerization initiator was dropped over 1 hour to perform polymerization. Then, the temperature was raised to 200 ° C. and the mixture was allowed to mature for 1 hour to generate a styrene-based resin in the reaction system. Then, the temperature was raised to 230 ° C. over 1 hour, and after confirming that all the solid monomers had melted and reacted, the pressure was reduced to 8 kPa and dehydration condensation was performed for 1 hour. Then, the temperature was lowered to 210 ° C., trimellitic anhydride was added, and the reaction was continued for another 1 hour, after which the pressure was reduced to 8 kPa and the reaction was continued until the softening point shown in Table 2 was reached to obtain an amorphous composite resin (resin A2). The physical properties of the obtained resin are shown in Table 2.

Resin Production Example 3
The alcohol component, carboxylic acid component and esterification catalyst shown in Tables 3 and 4 were placed in a 10-liter four-neck flask equipped with a dehydration tube equipped with a nitrogen inlet tube, a stirrer and a thermocouple, and the temperature was raised to 200°C over 8 hours in a mantle heater under a nitrogen atmosphere. Thereafter, the reaction was carried out at 8 kPa until the softening points shown in Tables 3 and 4 were reached, thereby obtaining crystalline polyester resins (resins C1 to C4, C6, C7 and C9). The physical properties of the obtained resins are shown in Tables 3 and 4.

Resin Production Example 4
The alcohol component, carboxylic acid component, esterification catalyst, and polymerization inhibitor shown in Tables 3 and 4 were placed in a 10-liter four-neck flask equipped with a dehydration tube equipped with a nitrogen inlet tube, a stirrer, and a thermocouple, and the temperature was raised to 200° C. over 8 hours in a mantle heater under a nitrogen atmosphere. Thereafter, the reaction was continued at 8 kPa until the softening points shown in Tables 3 and 4 were reached, to obtain crystalline polyester resins (resins C5 and C8). The physical properties of the obtained resins are shown in Tables 3 and 4.

Examples 1 to 8 and Comparative Examples 1 to 3
40 parts by mass of Resin A1, 40 parts by mass of Resin A2, 20 parts by mass of a crystalline polyester resin shown in Table 5, a colorant shown in Table 5, 4 parts by mass of a release agent "HNP-9" (manufactured by Nippon Seiro Co., Ltd., paraffin wax, melting point: 80°C), and 0.5 parts by mass of a charge control agent "Bontron E-304" (manufactured by Orient Chemical Industries Co., Ltd.) were thoroughly mixed in a Henschel mixer and then melt-kneaded under the conditions shown below.

A continuous open-roll type twin-screw kneader "Kneedex" (manufactured by Mitsui Mining Co., Ltd., roll outer diameter: 14 cm, effective roll length: 80 cm) was used. The operating conditions of the continuous open-roll type twin-screw kneader were high rotation roll (front roll) peripheral speed 32.4 m/min, low rotation roll (back roll) peripheral speed 21.7 m/min, roll gap 0.1 mm. The heating medium temperature and cooling medium temperature in the rolls were 145°C on the raw material input side of the high rotation roll and 100°C on the kneaded material discharge side, and 75°C on the raw material input side of the low rotation roll and 35°C on the kneaded material discharge side. The raw material mixture was supplied at a rate of 10 kg/h, and the average residence time was about 3 minutes.

The kneaded product obtained was cooled and coarsely pulverized using a pulverizer "Rotoplex" (manufactured by Hosokawa Micron Co., Ltd.), and a coarsely pulverized product having a maximum diameter of 2 mm or less was obtained using a sieve with a mesh size of 2 mm. The coarsely pulverized product obtained was finely pulverized using an air classifier "DS2 type" (impingement plate type, manufactured by Nippon Pneumatic Co., Ltd.) by adjusting the pulverization pressure so that the volume median particle diameter ( _D50 ) was 5.5 μm. The finely pulverized product obtained was classified using an air classifier "DSX2 type" (manufactured by Nippon Pneumatic Co., Ltd.) by adjusting the static pressure (internal pressure) so that the volume median particle diameter ( _D50 ) was 6.0 μm, to obtain toner particles.

1.0 part by mass of "R972" (hydrophobic silica, manufactured by Nippon Aerosil Co., Ltd., hydrophobic treatment agent: DMDS, average particle size: 16 nm) and 1.0 part by mass of "RX50" (hydrophobic silica, manufactured by Nippon Aerosil Co., Ltd., hydrophobic treatment agent: HMDS, average particle size: 40 nm) were added as external additives to 100 parts by mass of the obtained toner particles, and the mixture was mixed in a Henschel mixer at 3700 rpm for 3 minutes to perform external additive treatment and obtain a toner.

Comparative Example 4
A toner was obtained in the same manner as in Example 3, except that a co-rotating twin-screw extruder "PCM-30" (manufactured by Ikegai Corporation, shaft diameter 2.9 cm, shaft cross-sectional area 7.06 ^cm2 ) was used in the melt-kneading step. The operating conditions of the twin-screw extruder were barrel set temperature 100°C, shaft rotation speed 200 r/min (shaft rotation peripheral speed 0.30 m/sec), and mixture supply rate 10 kg/h.

Comparative Example 5
The crystalline polyester resin and the colorant were melt-kneaded in advance in a continuous open-roll type twin-screw kneader "Kneedex" (manufactured by Mitsui Mining Co., Ltd., roll outer diameter: 14 cm, effective roll length: 80 cm) (the melt-kneading conditions were the same as above) to prepare a pigment master batch. Thereafter, a toner was obtained in the same manner as in Comparative Example 4, except that the pigment master batch was used instead of the crystalline resin and the colorant.

Comparative Example 6
A toner was obtained in the same manner as in Example 3, except that 4 parts by mass of carnauba wax (Carnauba Wax No. 1, manufactured by Kato Yoko Co., Ltd., melting point: 88° C.) was used as the release agent instead of the paraffin wax.

The colorants used in the examples are as follows:
C.I. Pigment Yellow 180: "TONER YELLOW HG" (manufactured by Heubach Color Japan Co., Ltd.)
C.I. Pigment Yellow 185: "Paliothol Yellow D1155" (manufactured by DIC Corporation (BASF Color & Effects Japan Co., Ltd.))
C.I. Pigment Yellow 155: "TONER YELLOW 3GP-CT" (manufactured by Heubach Color Japan Co., Ltd.)

Test example [Heat resistance storage]
5 g of toner was placed in a 20 mL polypropylene container. The container containing the toner was placed in a thermohygrostat at 48° C. and a relative humidity of 60%, and stored for 120 hours with the lid of the container open. The degree of aggregation of the toner after storage was measured by the following method and used as an index of heat-resistant storage stability. The results are shown in Table 5. The smaller this value, the better the heat-resistant storage stability.

(Cohesion degree)
The degree of cohesion is measured using a powder tester (manufactured by Hosokawa Micron Corp.).
Sieves with 150 μm, 75 μm, and 45 μm openings are stacked, 5 g of toner is placed on the top, and the sieves are vibrated with a vibration amplitude of 1 mm for 60 seconds. After the vibration, the amount of toner remaining on the sieve is measured, and the degree of cohesion is calculated using the following formula.

The above results show that the toners of Examples 1 to 8 have good heat-resistant storage stability compared to Comparative Examples 1 to 6. The decrease in heat-resistant storage stability in Comparative Example 5 is thought to be due to the fact that even though the crystalline polyester resin and colorant were pre-mixed in a continuous open-roll type twin-screw kneader, no wax (release agent) was added at this time, resulting in insufficient refinement of the wax domains and failure to promote crystallization of the crystalline polyester resin.

The electrostatic image developing toner obtained by the method of the present invention is suitable for use in developing latent images formed in electrostatic image developing methods, electrostatic recording methods, electrostatic printing methods, etc.

Claims (4)

A method for producing a toner for developing electrostatic images, comprising a step of melting and kneading a mixture containing a binder resin, a colorant, and a release agent, the binder resin containing a crystalline polyester resin having an ester group concentration of 5.0 mmol/g or more and 10.0 mmol/g or less, the colorant containing an organic yellow pigment having an NH group amount of 3.0 mmol/g or more when the NH group amount is the total number of -NH- groups _{and -NH2} groups contained in one molecule divided by the molecular weight, the release agent containing paraffin wax, and the melting and kneading of the mixture is carried out using an open roll type kneader. The method for producing a toner for developing electrostatic images according to claim 1, wherein the content of the crystalline polyester resin in the binder resin is 5% by mass or more and 35% by mass or less. The method for producing a toner for developing electrostatic images according to claim 1 or 2, wherein the mass ratio of the crystalline polyester resin to the paraffin wax is 10/90 or more and 95/5 or less. The method for producing a toner for developing electrostatic images according to any one of claims 1 to 3, wherein the mass ratio of the crystalline polyester resin to the organic yellow pigment is 20/80 or more and 90/10 or less.