JP7685945B2 - Method for producing toner for developing electrostatic images - Google Patents

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.

As a binder resin for toner, crystalline polyester resin is known to be effective in improving the low-temperature fixing properties of toner, and its use in combination with amorphous resin is being considered.

Patent Document 1 discloses a toner for developing electrostatic images, which contains an amorphous polyester resin A and a crystalline polyester resin C, in which the amorphous polyester resin A has a constituent part derived from a polyester resin and a constituent part derived from a modified polyolefin polymer A having a reactive functional group, the constituent part derived from the polyester resin and the constituent part derived from the modified polyolefin polymer A are linked via a covalent bond, and the amount of the constituent part derived from the modified polyolefin polymer A is 5% by mass or more and 30% by mass or less with respect to the total amount of resin components in the toner.

Patent document 2 discloses a toner containing a crystalline resin and a non-crystalline resin, characterized in that in a reflected electron image of a cross section of the toner stained with ruthenium tetroxide taken with a scanning electron microscope, the proportion of the area stained with ruthenium tetroxide is 50 area % or more and 80 area % or less, and in a reflected electron image of the surface of the toner stained with ruthenium tetroxide taken with a scanning electron microscope, the proportion of the area stained with ruthenium tetroxide is 10 area % or more and 40 area % or less.

Patent document 3 discloses a toner that has a crystalline resin and an amorphous resin, and that has a diffraction peak at least at 2θ = 20° to 25° in X-ray diffraction measurement, and that is characterized in that the difference between the glass transition temperature observed in the final heating step after heating and cooling under a predetermined heating and cooling condition 1 using a differential scanning calorimeter (DSC) and the glass transition temperature observed in the final heating step after heating and cooling under a predetermined heating and cooling condition 2 is within 10°C.

JP 2020-86459 A JP 2014-77987 A JP 2016-206632 A

However, when pulverized toner is produced using crystalline polyester resin, if the crystalline polyester resin is not sufficiently dispersed in the amorphous resin by melt kneading, the dispersibility will be insufficient even after it is cooled and made into toner, and the low-temperature fixability characteristic of crystalline polyester resin will not be fully exhibited. In addition, durability will also be poor, possibly because the crystalline polyester resin with reduced dispersibility hinders the dispersion of the release agent.

The present invention relates to a method for producing a toner for developing electrostatic images that has excellent low-temperature fixing properties and durability.

The present invention relates to a method for producing a toner for developing electrostatic images, which contains crystalline polyester resin C, amorphous resin A, and a release agent, and the crystalline polyester resin C is a polycondensate of an alcohol component containing an aliphatic diol having 8 to 10 carbon atoms and a carboxylic acid component containing an aliphatic dicarboxylic acid compound having 6 to 10 carbon atoms, and the method includes a step of melt-kneading a mixture containing crystalline polyester resin C, amorphous resin A, and a release agent using an open-roll type twin-screw kneader equipped with two rolls having different peripheral speeds, and the temperature of the kneaded product discharge side of the high-speed rotation roll of the open-roll type twin-screw kneader is from -20°C to +15°C, which is the melting point of the crystalline polyester resin C.

The toner for developing electrostatic images obtained by the method of the present invention is excellent in terms of improving low-temperature fixing properties and durability.

The present invention is characterized in that, when producing a toner for developing electrostatic images containing a crystalline polyester resin, an amorphous resin, and a release agent, the crystalline polyester resin is a polycondensation product of raw material monomers including specific aliphatic monomers, and an open-roll type twin-screw kneader in which a high-speed rotation roll is adjusted to a predetermined temperature is used in the melt-kneading process. The reason why the toner for developing electrostatic images obtained by the method of the present invention has excellent low-temperature fixing properties and durability is not clear, but is presumed to be as follows.

In the present invention, the dispersibility of the crystalline polyester resin in the amorphous resin is improved by using an open-roll type twin-screw kneader with high kneading strength and easy temperature control. However, when an open-roll type twin-screw kneader is used for melt kneading the raw material mixture, if the temperature of the kneaded product discharge side of the high-speed rotation roll is too low, the dispersibility in the amorphous resin decreases, possibly because a part of the crystalline polyester resin crystallizes during kneading. On the other hand, if the temperature of the kneaded product discharge side of the high-speed rotation roll is too high, the dispersibility in the amorphous resin decreases, possibly because the viscosity of the crystalline polyester resin decreases, and in either case, this is not reflected in the improvement of low-temperature fixability. Furthermore, the durability also decreases, possibly because the crystalline polyester resin with reduced dispersibility hinders the dispersion of the release agent.
In contrast, in the present invention, the temperature of the discharge side of the kneaded product of the open roll type twin-screw kneader is controlled to be close to the melting point of the crystalline polyester resin. Furthermore, the crystalline polyester resin contains an aliphatic diol having 8 to 10 carbon atoms as an alcohol component and an aliphatic dicarboxylic acid compound having 6 to 10 carbon atoms as a carboxylic acid component, which increases hydrophobicity and improves dispersibility in the amorphous resin. It is believed that this improves the dispersibility of the hydrophobic release agent as well, resulting in a toner with excellent low-temperature fixing ability and durability.

In the present invention, the crystalline polyester resin C is a polycondensation product of an alcohol component containing an aliphatic diol having 8 to 10 carbon atoms and a carboxylic acid component containing an aliphatic dicarboxylic acid compound having 6 to 10 carbon atoms.

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, i.e., the value of [softening point/maximum endothermic peak temperature]. A 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 crystallinity index is greater than 1.4, preferably greater 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.

Examples of aliphatic diols having 8 to 10 carbon atoms include 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol.

The content of the aliphatic diol having 8 to 10 carbon atoms 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%.

Examples of alcohol components other than aliphatic diols having 8 to 10 carbon atoms include aliphatic diols having 7 or less carbon atoms, such as 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and 1,7-heptanediol, aliphatic diols having 11 or more carbon atoms, aromatic diols such as alkylene oxide adducts of bisphenol A, bisphenol A, hydrogenated bisphenol A, sorbitol, pentaerythritol, glycerin, and trimethylolpropane or higher alcohols.

Examples of aliphatic dicarboxylic acid compounds with 6 to 10 carbon atoms include adipic acid (carbon number: 6), suberic acid (carbon number: 8), azelaic acid (carbon number: 9), sebacic acid (carbon number: 10), anhydrides of these acids, and alkyl esters of these acids with carbon numbers of 1 to 3. Note that 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 content of the aliphatic dicarboxylic acid compound having 6 to 10 carbon atoms in the carboxylic acid 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%.

Examples of carboxylic acid components other than aliphatic dicarboxylic acid compounds having 6 to 10 carbon atoms include aliphatic dicarboxylic acid compounds having 5 or less or 11 or more carbon atoms, aromatic dicarboxylic acid compounds, and trivalent or higher carboxylic acid compounds.

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

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

Crystalline polyester resin C 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 an esterification promoter, a polymerization inhibitor, etc., at a temperature preferably between 120°C and 230°C.

Examples of the esterification catalyst include tin compounds such as dibutyltin oxide and tin(II) 2-ethylhexanoate, and titanium compounds such as titanium diisopropylate bistriethanolamine. The amount of the esterification catalyst used is preferably 0.01 parts by mass or more, more preferably 0.1 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 esterification promoter include gallic acid. The amount of the esterification promoter 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 t-butylcatechol. The amount of the 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 C is preferably 50°C or higher, more preferably 55°C or higher, and even more preferably 60°C or higher, and from the viewpoint of low-temperature fixability, it is preferably 120°C or lower, and more preferably 110°C or lower.

The melting point of crystalline polyester resin C is preferably 60°C or higher, more preferably 65°C or higher, from the viewpoint of durability, and is preferably 130°C or lower, more preferably 120°C or lower, from the viewpoint of low-temperature fixability.

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

The content of crystalline polyester resin C in the total amount of crystalline polyester resin C and amorphous resin A is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 4% by mass or more, from the viewpoint of low-temperature fixability, and is preferably 45% by mass or less, more preferably 40% by mass or less, even more preferably 30% by mass or less, and even more preferably 20% by mass or less, from the viewpoint of durability.

Examples of the amorphous resin A include amorphous polyester resin, composite resin in which polyester resin is combined with a styrene-based resin, polyamide resin, vinyl-based resin, epoxy resin, polycarbonate resin, polyurethane resin, etc., but in the present invention, from the viewpoint of improving durability, amorphous polyester resin or composite resin is preferred, and amorphous polyester resin is more 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.

Carboxylic acid components include aliphatic dicarboxylic acid compounds, aromatic dicarboxylic acid compounds, trivalent or higher carboxylic acid compounds, etc.

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

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.

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 the present invention, from the viewpoint of durability, it is preferable that the carboxylic acid component of the amorphous polyester resin contains a succinic acid derivative substituted with a hydrocarbon group.

The hydrocarbon group in the succinic acid derivative substituted with a hydrocarbon group is preferably an alkyl group or an alkenyl group. Therefore, specific examples of succinic acid derivatives substituted with a hydrocarbon group include dodecylsuccinic acid, dodecenylsuccinic acid, tetrapropenylsuccinic acid, decenylsuccinic acid, their acid anhydrides, and their alkyl esters having 1 to 3 carbon atoms. Among these, from the viewpoint of low-temperature fixability, dodecenylsuccinic acid, tetrapropenylsuccinic acid, or their acid anhydrides are preferred, and dodecenylsuccinic anhydride is more preferred.

From the viewpoint of hydrophobicity, the number of carbon atoms in the hydrocarbon group in the succinic acid derivative is preferably 8 or more, more preferably 10 or more, even more preferably 12 or more, and is preferably 20 or less, more preferably 18 or less, even more preferably 16 or less.

From the viewpoint of hydrophobicity, the succinic acid derivative preferably contains at least one or more types selected from the group consisting of succinic acid substituted with an alkyl group having 10 to 18 carbon atoms and succinic acid substituted with an alkenyl group having 10 to 18 carbon atoms, and more preferably contains at least one or more types selected from the group consisting of succinic acid substituted with an alkyl group having 12 to 16 carbon atoms and succinic acid substituted with an alkenyl group having 12 to 16 carbon atoms.

The content of the succinic acid derivative in the carboxylic acid component is preferably 1 mol% or more, more preferably 5 mol% or more, and even more preferably 7 mol% or more from the viewpoint of hydrophobicity, and is preferably 40 mol% or less, more preferably 35 mol% or less, even more preferably 20 mol% or less, and even more preferably 15 mol% or less from the viewpoint of durability.

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 group of the carboxylic acid component to the hydroxyl group of the alcohol component (COOH group/OH group) is preferably 0.6 or more, more preferably 0.7 or more, even more preferably 0.75 or more, and is preferably 1.2 or less, more preferably 1.15 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 suitable reaction temperature is preferably 130°C or higher, more preferably 170°C or higher, and preferably 250°C or lower, more preferably 240°C or lower.

In the composite resin containing the polyester resin and the styrene-based resin, the polyester resin is the same as the amorphous polyester resin, and the styrene-based resin is an addition polymer of raw material monomers containing at least styrene or a styrene derivative such as α-methylstyrene or 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 durability, 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 polymerization inhibitor, 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, more preferably 170°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 the resin is 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 group, carboxyl group, epoxy group, primary amino group, and secondary amino group, preferably a hydroxyl group and/or a 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 of polycondensation reaction and addition polymerization reaction, at least one selected from the group consisting of acrylic acid, methacrylic acid, and fumaric acid is even more preferable. 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, and more preferably 2 mol or more, relative to 100 mol of the total of the alcohol components of the polyester resin, from the viewpoint of low-temperature fixability, 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 dispersibility of the styrene-based resin and the polyester resin and improving the durability of the toner.
From the viewpoint of low-temperature fixability, the amount of the bireactive monomer used is preferably 1 part by mass or more, more preferably 2 parts by mass or more, relative to 100 parts by mass of the total of the raw material monomers of the styrene resin, and from the viewpoint of improving the dispersibility of the styrene resin and the polyester resin and improving the durability of the toner, it is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less. Here, the polymerization initiator is included in the total of the raw material monomers of the styrene resin.

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 in an addition polymerization reaction together with the raw material monomer of the styrene-based resin from the viewpoint of improving the durability and low-temperature fixability of the toner.

(i) A method of carrying out step (A) of polycondensation reaction with raw material monomers of polyester resin, followed by step (B) of addition polymerization reaction with raw material monomers of styrene resin and bireactive monomers. In this method, step (A) is carried out under reaction temperature conditions suitable for polycondensation reaction, the reaction temperature is lowered, and step (B) is carried out under temperature conditions suitable for addition polymerization reaction. The raw material monomers of styrene resin and bireactive monomers are preferably added to the reaction system at a temperature suitable for addition polymerization reaction. The bireactive monomers carry out addition polymerization reaction and also react with polyester resin.
After step (B), the reaction temperature is increased again, and if necessary, a raw material monomer of a polyester resin having a valence of three or more and serving as a crosslinking agent is added to the polymerization system, 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 of raw material monomers of a styrene-based resin and a bireactive monomer is followed by step (A) of a polycondensation reaction of raw material monomers of a polyester resin. In this method, step (B) is carried out under reaction temperature conditions suitable for an addition polymerization reaction, and the reaction temperature is raised to carry out the polycondensation reaction of step (A) under temperature conditions suitable for a polycondensation reaction. The bireactive monomer is involved in both the addition polymerization reaction and the 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 of the raw material monomer of the polyester resin and the step (B) of the addition polymerization reaction of the raw material monomer of the styrene resin and the bireactive monomer proceed in parallel. In this method, it is preferable to carry out the steps (A) and (B) in parallel under reaction temperature conditions suitable for the addition polymerization reaction, raise the reaction 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. The bireactive monomer is involved in the polycondensation reaction as well as the addition polymerization reaction.

In the above method (i), a prepolymerized polycondensation 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 resin may be dripped 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 polyester resin to 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 smearing, 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 polyester resin is the mass of the raw material monomer of the polyester resin used minus the amount of reaction water dehydrated by the polycondensation reaction (calculated value), and the amount of bireactive monomer is included in the amount of raw material monomer of the polyester resin. The amount of styrene resin is the total amount of raw material monomer of the styrene resin and polymerization initiator.

From the viewpoint of durability, the softening point of the amorphous resin A is preferably 90°C or higher, more preferably 100°C or higher, and from the viewpoint of low-temperature fixability, it is preferably 150°C or lower, more preferably 140°C or lower.

From the viewpoint of low-temperature fixing property and fixing width, the amorphous resin A 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 12°C or more, and is preferably 60°C or less, more preferably 30°C or less, and even more preferably 20°C or less.

The softening point of the amorphous resin with the higher softening point (resin AH) 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 180°C or lower, more preferably 160°C or lower, and even more preferably 140°C or lower, from the viewpoint of low-temperature fixing ability.

The softening point of the amorphous resin with the lower softening point (resin AL) is preferably 70°C or higher, more preferably 90°C or higher, and even more preferably 100°C or higher, from the viewpoint of durability, 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 fixability.

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 70/30 or less.

From the viewpoint of durability, the glass transition temperature of the amorphous resin A 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, and even more preferably 65°C or lower.

From the viewpoint of low-temperature fixability, the acid value of the amorphous resin A 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.

From the viewpoint of durability, the number average molecular weight of the amorphous resin A is preferably 1,000 or more, more preferably 1,500 or more, and even more preferably 2,000 or more, and from the viewpoint of low-temperature fixability, it is preferably 6,000 or less, more preferably 5,000 or less, and even more preferably 4,000 or less.

From the viewpoint of durability, the weight average molecular weight of the amorphous resin A is preferably 5,000 or more, more preferably 6,000 or more, and even more preferably 8,000 or more, and from the viewpoint of low-temperature fixability, it is preferably 500,000 or less, more preferably 200,000 or less, and even more preferably 150,000 or less.

The mass ratio of crystalline polyester resin C to amorphous resin A (crystalline polyester resin C/amorphous resin A) is preferably 1/99 or more, more preferably 3/97 or more, and even more preferably 5/95 or more, from the viewpoint of low-temperature fixability, and is preferably 40/60 or less, more preferably 35/65 or less, and even more preferably 30/70 or less, from the viewpoint of durability.

In the toner, crystalline polyester resin C and amorphous resin A are contained as binder resins.

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 crystalline polyester resin C and amorphous resin A 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, even more preferably 80% by mass or more, and is preferably less than 100% by mass, more preferably 98% by mass or less, even more preferably 95% by mass or less.

Examples of release agents include hydrocarbon waxes such as polypropylene wax, polyethylene wax, polypropylene-polyethylene copolymer wax, microcrystalline wax, paraffin wax, and Fischer-Tropsch wax, and oxides thereof; ester waxes such as carnauba wax, montan wax, and deacidified waxes thereof, and fatty acid ester wax; fatty acid amides, fatty acids, higher alcohols, and fatty acid metal salts; and the like, which can be used alone or in combination of two or more.

From the viewpoint of durability, the melting point of the release agent is preferably 60°C or higher, more preferably 70°C or higher, and from the viewpoint of low-temperature fixability, it is preferably 160°C or lower, more preferably 140°C or lower, even more preferably 120°C or lower, and even more preferably 110°C or lower.

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, relative to 100 parts by mass of the binder resin, from the viewpoints of the low-temperature fixability and durability of the toner and dispersibility in the binder resin, and is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 7 parts by mass or less.

In addition to the binder resin and release agent, the toner may contain additives such as colorants, charge control agents, magnetic powders, flow improvers, conductivity adjusters, reinforcing fillers such as fibrous substances, antioxidants, and cleaning improvers.

As colorants, dyes, pigments, magnetic materials, etc. used as toner colorants can be used. Examples 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, isoindoline, disazo yellow, etc. In the present invention, the toner may be either a black toner or a color toner.

From the viewpoint of improving the image density and low-temperature fixability of the toner, the content of the colorant is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and preferably 40 parts by mass or less, more preferably 20 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 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", and "Bontron N-11" (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 chargeable 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" (both 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 charge 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.

In the present invention, a mixture containing crystalline polyester resin C, amorphous resin A, and a release agent, and further additives such as a colorant and a charge control agent, as necessary, is subjected to a process of melt kneading using an open-roll type twin-screw kneader.

The mixture to be melt kneaded may be kneaded all at once or in portions, but it is preferable to mix the mixture in advance in a mixer such as a Henschel mixer or ball mill, and then feed it to an open-roll type twin-screw kneader.

An open-roll type twin-screw kneader is one that has two rolls and the melt-kneading section is open, not sealed, and can easily dissipate the heat of kneading that occurs during melt-kneading. The open-roll type twin-screw kneader used in the present invention has multiple raw material supply ports and kneaded material discharge ports arranged along the axial direction of the rolls, and from the viewpoint of production efficiency, it is preferable that it is a continuous open-roll type twin-screw kneader.

The open-roll type twin-screw kneader used in the present invention is a kneader equipped with two rolls with different peripheral speeds, i.e., a high-speed roll with a high peripheral speed and a low-speed roll with a low peripheral speed. In the present invention, from the viewpoint of improving the dispersibility of the crystalline polyester resin, it is preferable that the high-speed roll is a heating roll and the low-speed roll is a cooling roll.

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

From the viewpoint of improving the dispersibility of the crystalline polyester resin, the temperature of the discharge side of the kneaded material of the high-speed rotation roll is -20°C or more, preferably -15°C or more, more preferably -10°C or more, even more preferably -5°C or more, and even more preferably above the melting point of the crystalline polyester resin C, and is +15°C or less, preferably +13°C or less, and more preferably +12°C or less than the melting point of the crystalline polyester resin C.

On the other hand, the temperature of the raw material input side of the high speed roll is, from the viewpoint of melting the crystalline polyester resin, preferably +5°C or more, more preferably +15°C or more, even more preferably +25°C or more, even more preferably +40°C or more of the melting point of crystalline polyester resin C, and is preferably +65°C or less, more preferably +60°C or less, even more preferably +55°C or less of the melting point of crystalline polyester resin C.

The temperature of the discharge side of the low rotation roll of the kneaded material is preferably 25°C or higher, more preferably 30°C or higher, from the viewpoint of improving the dispersibility of the crystalline polyester resin, and is preferably 80°C or lower, more preferably 50°C or lower.

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, from the viewpoint of reducing the mechanical force during melt kneading and suppressing heat generation, and is preferably 80°C or lower, more preferably 70°C or lower.

In both the high-speed and low-speed rolls, the temperature of the raw material input side is preferably higher than that of the kneaded material discharge side, and the temperature difference between the raw material input side and the kneaded material discharge side of the high-speed roll is preferably 5°C or more, more preferably 20°C or more, even more preferably 25°C or more, and preferably 60°C or less, more preferably 55°C or less, from the viewpoint of preventing the kneaded material from coming off the roll, and from the viewpoint of reducing the mechanical force during melt kneading and suppressing heat generation. In the low-speed roll, the temperature difference between the raw material input side and the kneaded material discharge side is preferably 5°C or more, and preferably 50°C or less, from the viewpoint of improving the dispersibility of the crystalline polyester resin, and from the viewpoint of 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 improving the dispersibility of the crystalline polyester resin, and from the viewpoint of reducing the mechanical force during melt 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 appropriately cool the kneaded material until it reaches a pulverizable hardness, and if necessary, toner particles are obtained by performing a pulverization process and classification. Here, cooling refers to cooling the kneaded material to a temperature between 0°C and 50°C, or to cooling below the glass transition temperature of the binder resin in the kneaded material.

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 coarse pulverization, it is preferable to pulverize until the maximum diameter is 3 mm or less. For example, pulverized material with a maximum diameter of 3 mm or less can be obtained by coarsely pulverizing the kneaded material until the particle size is about 0.05 mm or more and 3 mm or less, and then passing the kneaded material through a sieve with 3 mm openings.

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 include an external addition step in which the obtained toner particles are mixed with an external additive.

External additives include inorganic fine particles such as silica, alumina, titania, zirconia, tin oxide, and zinc oxide, and organic fine particles such as resin 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 durability of the toner, hydrophobic silica that has been hydrophobized is more preferred.

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 and fluidity of the toner, the average particle size of the external additive is preferably 5 nm or more, more preferably 10 nm or more, and even 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.

From the viewpoint of the chargeability and fluidity 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, per 100 parts by mass of the toner particles before being treated 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 can be measured by the following methods.

[Softening point of resin]
Using a flow tester "CFT-500D" (Shimadzu Corporation), 1g of sample is heated at a temperature increase rate of 6℃/min while applying a load of 1.96MPa with the plunger, and extruding the sample from a nozzle with a diameter of 1mm and length of 1mm. The plunger descent distance 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 sample is weighed into an aluminum pan and cooled from room temperature (25°C) to 0°C at a rate of 10°C/min, and maintained at 0°C for 1 minute. Then, measurements are performed at a rate of 10°C/min. The temperature of the peak with the largest peak area among the observed endothermic peaks is regarded as the maximum endothermic peak temperature.

[Glass transition temperature of amorphous resin]
Using a differential scanning calorimeter "Q-100" (manufactured by TA Instruments Japan), 0.01 to 0.02 g of sample is weighed into an aluminum pan, heated to 200°C, and cooled from that temperature to 0°C at a rate of 10°C/min. The sample is then 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 top of the peak.

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

[Number average molecular weight and weight average molecular weight of resin]
The number average molecular weight and the weight average molecular weight are determined by gel permeation chromatography (GPC) according to the following method.
(1) Preparation of sample solution The resin was dissolved in tetrahydrofuran to a concentration of 0.5 g/100 mL. The solution was then filtered through a fluororesin filter (manufactured by Sumitomo Electric Industries, Ltd., product name: FP-200) with a pore size of 2 μm to remove insoluble components, and the sample solution was prepared.
(2) Molecular weight measurement Using the following measuring device and analytical column, tetrahydrofuran was used as the eluent at a flow rate of 1 mL per minute, and the column was stabilized in a thermostatic bath at 40°C. 100 μL of the sample solution was injected into the column for measurement. The molecular weight of the sample was calculated based on a calibration curve prepared in advance. For the calibration curve, several types of monodisperse polystyrene with known molecular weights (Tosoh Corporation: 2.63×10 ³ , 2.06×10 ⁴ , 1.02×10 ⁵ , GL Sciences Corporation: 2.10×10 ³ , 7.00×10 ³ , 5.04×10 ⁴ ) were used as standard samples.
Measuring device: CO-8010 (product name, manufactured by Tosoh Corporation)
Analytical column: GMH _XL + G3000H _XL (both product names, manufactured by Tosoh Corporation)

[Melting point of release agent]
Using a differential scanning calorimeter "Q-100" (manufactured by TA Instruments Japan, Inc.), 0.02 g of the sample is weighed into an aluminum pan and heated to 200°C, then cooled from 200°C to 0°C at a rate of 10°C/min. The sample is then heated at a rate of 10°C/min, the amount of heat is 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 calculated by measuring the particle sizes (average of major and minor axes) 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: 50 μm
・Analysis software: "Multisizer (registered trademark) III version 3.51" (Beckman Coulter, Inc.)
・Electrolyte: "Isoton (registered trademark) II" (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 dispersed for 1 minute using an ultrasonic disperser (machine name: US-1, manufactured by SND Corporation, output: 80 W). Thereafter, 25 mL of 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 where the particle size of 30,000 particles can be measured in 20 seconds, and then the 30,000 particles are measured and the volume median particle size ( _D50 ) is calculated from the particle size distribution.

Preparation of alkenyl succinic anhydride 1
(1) Propylene tetramer (manufactured by Nippon Oil Corporation, trade name: "Light Tetramer") was used and fractionated under heating conditions of 183 to 208°C to obtain an alkylene compound (a). The obtained alkylene compound (a) had 40 peaks in gas chromatography mass spectrometry described later. The distribution of the alkylene compounds was measured according to the analysis of alkylene compound A by mass spectrometry gas chromatography in JP 2014-013384 A, and was C ₉ H ₁₈ : 0.5 mass%, C ₁₀ H ₂₀ : 4 mass%, C ₁₁ H ₂₂ : 20 mass%, C ₁₂ H ₂₄ : 66 mass%, C ₁₃ H ₂₆ : 9 mass%, and C ₁₄ H ₂₈ : 0.5 mass% (6 peaks corresponding to alkylene compounds having 9 to 14 carbon atoms).

(2) 542.4 g of alkylene compound (a), 157.2 g of maleic anhydride, 0.4 g of antioxidant "Chelex-O" (SC Organic Chemicals, Triisooctyl phosphite), and 0.1 g of butylhydroquinone as a polymerization inhibitor were charged into a 1-liter autoclave manufactured by Nitto Koatsu Co., Ltd., and pressurized nitrogen replacement (0.2 MPaG) was repeated three times. After stirring was started at 60°C, the temperature was raised to 230°C over one hour and the reaction was carried out for six hours. The pressure when the reaction temperature was reached was 0.3 MPaG. After the reaction was completed, the mixture was cooled to 80°C, returned to normal pressure (101.3 kPa), and transferred to a 1-liter four-neck flask. The temperature was raised to 180°C with stirring, and the remaining alkylene compound was distilled off at 1.3 kPa for one hour. The mixture was then cooled to room temperature (25°C) and returned to normal pressure (101.3 kPa) to obtain 406.1 g of the desired alkenyl succinic anhydride A. The average molecular weight of alkenyl succinic anhydride A, calculated from the acid value, was 268.

Resin Production Example 1
The alcohol component and carboxylic acid component shown in Table 1 were placed in a 5-liter four-neck flask equipped with a thermometer, a stainless steel stirring rod, a downflow condenser, and a nitrogen inlet tube, and the temperature was raised to 200°C over 8 hours in a nitrogen atmosphere in a mantle heater. Then, an esterification catalyst was added, and the reaction was carried out at 8.0 kPa until the softening point shown in Table 1 was reached, obtaining crystalline polyester resins (resins C1 to C7). The physical properties are shown in Table 1.

Resin Production Example 2
The raw material monomers of polyester resin other than trimellitic anhydride, esterification catalyst and esterification promoter shown in Table 2 were placed in a 5-liter four-neck flask equipped with a nitrogen inlet tube, a stirrer and a thermocouple, and the temperature was raised to 235°C under a nitrogen atmosphere, and polycondensation was carried out at 235°C for 6 hours. The temperature was then lowered to 210°C, trimellitic anhydride was added, and the reaction was carried out at 210°C for 1 hour, and the reaction was further carried out at 210°C under a reduced pressure of 10 kPa until the softening point shown in Table 2 was reached, to obtain an amorphous polyester resin (resin AH1). The physical properties are shown in Table 2.

Resin Production Example 3
The raw material monomers of polyester resin other than trimellitic anhydride and fumaric acid shown in Table 2, the esterification catalyst and the esterification promoter were placed in a 5-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 235°C under a nitrogen atmosphere, and then polycondensation was carried out at 235°C for 6 hours. The temperature was then lowered to 160°C, and a mixture of the bireactive monomer, the raw material monomer of the styrene resin and the polymerization initiator was dropped over 1 hour using a dropping funnel. After the dropping, the addition polymerization reaction was matured for 1 hour while maintaining the temperature at 160°C, and then the temperature was raised to 200°C and reduced pressure at 10 kPa for 1 hour. After opening the pressure, the temperature was lowered to 180°C, and the trimellitic anhydride, fumaric acid and polymerization inhibitor shown in Table 2 were added, and the temperature was kept at 180°C for 1 hour, and then the temperature was raised from 180°C to 210°C at 10°C/h, and the reaction was carried out at 210°C for 1 hour. The reaction was further carried out at 210° C. under a reduced pressure of 10 kPa until the softening point shown in Table 2 was reached, to obtain an amorphous composite resin (Resin AH2).

Resin Production Example 4
The raw material monomers of polyester resin other than trimellitic anhydride and fumaric acid shown in Table 2, esterification catalyst and esterification promoter were placed in a 5-liter four-neck flask equipped with a nitrogen inlet tube, a stirrer and a thermocouple, and heated to 235°C under a nitrogen atmosphere, and then polycondensed at 235°C for 6 hours. The temperature was then lowered to 180°C, trimellitic anhydride, fumaric acid and a polymerization inhibitor were added, and the mixture was kept at 180°C for 1 hour, after which the temperature was raised from 180°C to 210°C at a rate of 10°C/h, and reacted at 210°C for 1 hour. The reaction was further carried out at 210°C under a reduced pressure of 10 kPa until the softening point shown in Table 2 was reached, to obtain an amorphous polyester resin (resin AH3). The physical properties are shown in Table 2.

Resin Production Example 5
The raw material monomers, esterification catalyst and esterification promoter for the polyester resin shown in Table 2 were placed in a 5-liter four-neck flask equipped with a nitrogen inlet tube, a stirrer and a thermocouple, and the temperature was raised to 235°C under a nitrogen atmosphere, followed by polycondensation at 235°C for 6 hours. The temperature was then lowered to 210°C, and the reaction was continued under a reduced pressure of 10 kPa until the softening point shown in Table 2 was reached, yielding amorphous polyester resins (resins AL1 and AL3). The physical properties are shown in the table.

Resin Production Example 6
The raw material monomers of polyester resin other than fumaric acid shown in Table 2, the esterification catalyst and the esterification promoter were placed in a 5-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 235°C under a nitrogen atmosphere, and then polycondensation was carried out at 235°C for 6 hours. The temperature was then lowered to 160°C, and a mixture of the bireactive monomer, the raw material monomers of the styrene resin and the polymerization initiator was dropped over 1 hour using a dropping funnel. After the dropping, the addition polymerization reaction was matured for 1 hour while maintaining the temperature at 160°C, and then the temperature was raised to 200°C and reduced pressure at 10 kPa for 1 hour. After opening the pressure, the temperature was lowered to 180°C, and the fumaric acid and polymerization inhibitor shown in Table 2 were added, and the mixture was kept at 180°C for 1 hour, and then the temperature was raised from 180°C to 210°C at 10°C/h, and reacted at 210°C for 1 hour. The reaction was further carried out at 210° C. under a reduced pressure of 10 kPa until the softening point shown in Table 2 was reached, to obtain an amorphous composite resin (Resin AL2).

Examples 1 to 10 and Comparative Examples 1 to 5
100 parts by mass of the binder resin shown in Table 3, 5 parts by mass of a colorant "ECB-301" (manufactured by Dainichi Seika Chemicals Co., Ltd., phthalocyanine blue (PB15:3)), 3 parts by mass of a release agent "Carnauba Wax C1" (manufactured by Kato Yoko Co., Ltd., melting point: 83° C.), 3 parts by mass of a release agent "HNP-9" (manufactured by Nippon Seiro Co., Ltd., paraffin wax, melting point: 75° C.), and 0.5 parts by mass of a charge control agent "Bontron E-304" (manufactured by Orient Chemical Co., Ltd.) were mixed in a Henschel mixer.

The obtained raw material mixture was fed to a continuous open-roll type twin-screw kneader "Kneedex" (manufactured by Mitsui Mining Co., Ltd.) by a table feeder and kneaded to obtain a kneaded product. The continuous open-roll type twin-screw kneader used here had an outer diameter of 0.14 m and an effective roll length of 0.8 m, and the operating conditions were a rotation speed of the high-speed roll (front roll) of 75 r/min (circumferential speed 33 m/min), a rotation speed of the low-speed roll (rear roll) of 50 r/min (circumferential speed 22 m/min), and a roll gap of 0.1 mm. The heating and cooling medium temperatures in the rolls were set to the temperatures shown in Table 3 for the raw material input side (IN) and the kneaded material discharge side (OUT) of the high-speed roll, and 65°C for the raw material input side and 30°C for the kneaded material discharge side of the low-speed roll. The raw material mixture was fed at a rate of 10 kg/h, and the average residence time was about 5 minutes.

The resulting kneaded material was cooled to 25°C and coarsely pulverized using a pulverizer "Rotoplex" (manufactured by Toa Machinery Co., Ltd.) and a coarsely pulverized material with a particle size of 2 mm or less was obtained using a sieve with a mesh size of 2 mm. Fine pulverization and upper limit classification (removal of coarse powder) were performed using a counter jet mill "400AFG" (manufactured by Hosokawa Alpine Co., Ltd.). Furthermore, lower limit classification (removal of fine powder) was performed using a classifier "TTSP" (manufactured by Hosokawa Alpine Co., Ltd.), and toner particles with a volume median particle size of 6.5 μm were obtained.

100 parts by mass of the obtained toner particles were mixed with 1.0 part by mass of hydrophobic silica "R972" (manufactured by Nippon Aerosil Co., Ltd., hydrophobic treatment agent: DMDS, average particle size: 16 nm) and 1.0 part by mass of hydrophobic silica "RY-50" (manufactured by Nippon Aerosil Co., Ltd., hydrophobic treatment agent: silicone oil, average particle size: 40 nm) as external additives in a Henschel mixer (manufactured by Mitsui Mining Co., Ltd.) at a rotation speed of 3000 r/min (circumferential speed: 32 m/sec) for 3 minutes to obtain a toner.

Test Example 1 [Low temperature fixability of toner]
The toner was loaded into a copy machine "AR-505" (manufactured by Sharp Corporation) with a modified fixing machine that allows fixing outside the machine, and a printout was obtained in an unfixed state (print area: 2cm x 12cm, adhesion amount: 0.5mg/ ^cm2 ). Then, using a fixing machine (fixing speed 300mm/sec) adjusted to a total fixing pressure of 40kgf, the temperature of the fixing roll was raised from 100°C to 200°C in 5°C increments, and a fixing test was performed on the unfixed printout at each temperature. A cellophane adhesive tape "UNICEF Cellophane" (manufactured by Mitsubishi Pencil Co., Ltd., width: 18mm, JIS Z1522:2009) was attached to the image portion of the printout, and the printout was passed through a fixing roller set at 30°C, separate from the fixing roll of the fixing machine, and the tape was then peeled off. The optical reflection density before and after the tape was applied was measured using a reflection densitometer "RD-915" (manufactured by GretagMacbeth), and the temperature of the fixing roll at which the ratio of the two (after peeling/before application x 100) first exceeded 90% was determined as the minimum fixing temperature. The results are shown in Table 3. The lower the minimum fixing temperature, the better the low-temperature fixing properties. The fixing paper used was "CopyBond SF-70NA" (manufactured by Sharp Corporation, 75g/ ^m2 ).

Test Example 2 [Toner Durability]
The toner was mounted on a printing machine "Page Presto N-4" (manufactured by Casio Computer Co., Ltd., fixing: contact fixing method, development: non-magnetic one-component development method, developing roll diameter: 2.3 cm), and a pattern of diagonal stripes with a blackening rate of 5.5% was continuously printed under an environment of a temperature of 32°C and a humidity of 85%. During the printing, a black solid image was printed every 500 sheets, and the presence or absence of streaks on the image was confirmed. Printing was stopped when streaks appeared on the image, and printing was continued up to a maximum of 9000 sheets. The number of printed sheets until streaks were visually observed on the image was regarded as the number of sheets on which streaks occurred due to the toner fusing and adhering to the developing roll, and durability was evaluated. The results are shown in Table 3. The greater the number of printed sheets until streaks appeared, that is, the greater the number of printed sheets without streaks, the higher the durability of the toner can be judged to be. In the table, ">9000" means that no streaks were observed at the time of printing 9000 sheets.

The above results show that the toners of Examples 1 to 10 have good low-temperature fixability and durability, in comparison with Comparative Examples 1 and 2, in which the temperature of the kneaded material discharge side of the high-speed rotation roll of the open-roll type twin-screw kneader is outside the specified range, and Comparative Examples 3 to 5, in which a crystalline polyester resin that does not use the specified raw material monomer is used.

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

Claims (2)

A method for producing a toner for developing electrostatic images, comprising crystalline polyester resin C, amorphous resin A, and a release agent, the crystalline polyester resin C being a polycondensate of an alcohol component containing an aliphatic diol having 8 to 10 carbon atoms and a carboxylic acid component containing an aliphatic dicarboxylic acid compound having 6 to 10 carbon atoms, the method comprising melt-kneading a mixture containing crystalline polyester resin C, amorphous resin A, and a release agent using an open-roll type twin-screw kneader having two rolls with different peripheral speeds, the temperature of the kneaded product discharge side of the high-speed rotation roll of the open-roll type twin-screw kneader being between -20°C and +15°C, the melting point of the crystalline polyester resin C. The manufacturing method according to claim 1, wherein the content of crystalline polyester resin C is 3% by mass or more and 40% by mass or less in the total amount of crystalline polyester resin C and amorphous resin A.