JP7726091B2 - Wax composition for toner - Google Patents

Description

The present invention relates to a toner wax composition that is suitable for use in toners used to develop electrostatic images recorded by electrophotography or electrostatic recording methods in copiers, laser printers, etc.

Toners used in image forming devices such as copiers and printers contain a thermoplastic resin as a binder resin, a colorant (carbon black, magnetic powder, pigment, etc.), a charge control agent, and wax, and may further contain a fluidity additive, a cleaning aid, and a transfer aid, as necessary.
Among these, wax functions as a release agent that prevents the toner from remaining on the fixing roll (filming) during fixing, and also has the function of promoting the softening of the thermoplastic resin to improve fixing properties.

On the other hand, since bleeding of wax during toner storage can cause blocking between toner particles, studies are being conducted to improve the storage stability of toner.
For example, Patent Document 1 describes a method for producing an ester wax for toner, which comprises condensing a linear saturated monocarboxylic acid selected from those having 14 to 30 carbon atoms or a mixture thereof with a linear saturated monohydric alcohol selected from those having 14 to 30 carbon atoms or a mixture thereof, or a dihydric to hexahydric polyhydric alcohol selected from those having 2 to 30 carbon atoms or a mixture thereof, followed by neutralizing the reaction mixture with an aqueous alkali solution and removing the neutralized salt by centrifugation. It also describes that the use of this wax provides a toner with excellent storage stability.

Furthermore, in recent years, copying machines such as multifunction machines and commercial printing machines have been required to have toners that are adaptable to ultra-high speed printing, which is faster than conventional toners, from the viewpoint of improving production efficiency and saving energy.
For example, Patent Document 2 introduces a toner that can produce printed matter with excellent abrasion resistance by mixing a hydrocarbon wax such as a microcrystalline wax with an ester wax such as behenyl behenate. When such a wax composition is used, the improved abrasion resistance makes it possible to handle high-speed printing.

Furthermore, in the commercial printing field where these devices are used, there is a demand for the stable production of high-quality prints equivalent to photographs and posters obtained by silver halide photography or gravure printing, even under the aforementioned ultra-high-speed printing conditions. However, there are issues with wax, such as excessive aggregation and uneven distribution within toner particles, which inhibits the dispersion of colorants, and differences in the crystalline state of wax on the surface of printed materials, which causes uneven gloss. A wax that can solve these issues is needed.
For example, Patent Document 3 describes that a toner excellent in image fixation and colorant dispersibility can be obtained by using a mixed wax containing a monoester of a linear monocarboxylic acid and a linear monoalcohol, and an ester of glycerin with a mixed carboxylic acid consisting of a linear monocarboxylic acid having 12 to 24 carbon atoms and one hydroxyl group and a linear monocarboxylic acid having 12 to 24 carbon atoms. However, when an ester having a glycerol skeleton is used in combination with another wax in this way, the freezing point of the wax composition is significantly lowered, which causes differences in the way the wax solidifies and therefore differences in the crystalline state depending on the printed area on the printed material during high-speed printing, and this may cause blocking between printed materials and uneven gloss.

In addition, Patent Document 4 introduces a toner that uses an ester wax in which the difference between the endothermic peak temperature when the wax is heated and the exothermic peak temperature when the wax is cooled, i.e., the difference between the melting point and the freezing point, falls within a specific range as measured by differential scanning calorimetry (DSC), thereby adjusting the affinity between the wax and the polyester resin binder resin, thereby suppressing the amount of wax bleeding during image fixation and making it possible to suppress gloss unevenness caused by the wax. However, even when such an ester is used, it is not sufficient to suppress gloss unevenness caused by differences in the crystalline state of the wax, and there is a risk that the amount of wax bleeding will be insufficient during high-speed printing, or that the wax will not melt and solidify sufficiently due to the large difference between the melting point and the freezing point, making it difficult to stably supply high-quality printed matter.
As described above, there are many required properties for toner, and there is a demand for a toner wax that can simultaneously satisfy all of these required properties.

JP 2012-32479 A Japanese Patent Application Laid-Open No. 2020-187270 WO2020/022351 Japanese Patent Application Laid-Open No. 2021-170100

The object of the present invention is to provide a wax composition for toner that has excellent storage stability and colorant dispersibility in toner, and can suppress uneven gloss in printed materials even during high-speed printing.

The present inventors have conducted extensive research to solve the above-mentioned problems, and as a result have found that when a composition containing the following monoester compound A and monoester compound B in a specific ratio is used as a toner wax, the storage stability and dispersibility of a colorant in the toner are excellent and gloss unevenness in printed matter can be suppressed even during high-speed printing, thereby completing the present invention.
That is, the toner wax composition of the present invention contains a monoester compound A represented by the following structural formula (1) and a monoester compound B represented by the following structural formula (2), and the mass ratio of the monoester compound A to the monoester compound B is 99.9:0.1 to 30:70.
Monoester Compound A:

(In the formula, ^R1 represents a linear saturated alkyl group having 15 to 24 carbon atoms, and ^R2 represents a linear saturated alkyl group having 16 to 24 carbon atoms.)
Monoester Compound B:

(In the formula, ^R3 represents a linear saturated alkyl group having 15 to 24 carbon atoms, and n represents an integer of 2 to 6.)

The toner wax composition of the present invention has excellent storage stability and improved colorant dispersibility in toner, and can suppress uneven gloss in printed materials even during high-speed printing.

Hereinafter, an embodiment of the present invention will be described.
The toner wax composition of the present invention contains, as essential components, a monoester compound A and a monoester compound B shown below.
In this specification, a numerical range defined using the symbol "to" is intended to include both the upper and lower limits of the symbol "to." For example, "2 to 5" represents a range from 2 to 5.

[Monoester Compound A]
The monoester compound A is a fatty acid ester wax obtained from at least one linear saturated monocarboxylic acid selected from linear saturated monocarboxylic acids having 16 to 24 carbon atoms and at least one linear saturated monoalcohol selected from linear saturated monoalcohols having 16 to 24 carbon atoms, and is represented by the following structural formula (1):

(In the formula, ^R1 represents a linear saturated alkyl group having 15 to 24 carbon atoms, and ^R2 represents a linear saturated alkyl group having 16 to 24 carbon atoms.)

The raw carboxylic acid for monoester compound A is a linear saturated monocarboxylic acid having a carbon number of 16 to 24, preferably 18 to 22. If the raw carboxylic acid has too few carbon atoms, the wax may melt at a low temperature, resulting in a significant decrease in storage stability in the toner. If the raw carboxylic acid has too many carbon atoms, the wax may become less dispersible in the toner, adversely affecting the dispersion of the colorant.
Specific examples of the raw material carboxylic acid include palmitic acid, stearic acid, arachidic acid, behenic acid, etc. Among these, stearic acid and behenic acid are particularly preferred.

The raw material alcohol for monoester compound A is a linear saturated monoalcohol having a carbon number of 16 to 24, preferably 18 to 22. If the carbon number of the raw material alcohol is too small, the wax may melt at a low temperature, resulting in a significant decrease in storage stability in the toner. If the carbon number is too large, the dispersibility of the wax in the toner may deteriorate, adversely affecting the dispersion of the colorant.
Specific examples of the raw material alcohol include palmityl alcohol, stearyl alcohol, arachidyl alcohol, and behenyl alcohol. Of these, stearyl alcohol and behenyl alcohol are particularly preferred. The monoester compound A obtained from the above-mentioned linear saturated monocarboxylic acid and the above-mentioned linear saturated monoalcohol preferably has a total carbon number of 36 to 44, and particularly preferably has a total carbon number of 40 to 44. Of these, a monoester compound formed from stearic acid or behenic acid and behenyl alcohol is preferred.

In view of storage stability and compatibility with high-speed printing, the monoester compound A in the present invention preferably has an acid value of 5 mgKOH/g or less, more preferably 3 mgKOH/g or less, and particularly preferably 1 mgKOH/g or less.
From the same viewpoint, the hydroxyl value is preferably 10 mgKOH/g or less, more preferably 5 mgKOH/g or less, and particularly preferably 3 mgKOH/g or less.
The acid value can be measured in accordance with JOCS (Japan Oil Chemists' Society) 2.3.1-1996, and the hydroxyl value can be measured in accordance with JOCS (Japan Oil Chemists' Society) 2.3.6.2-1996.

The melting point of the monoester compound A in the present invention is preferably 60 to 80° C., more preferably 65 to 75° C. If the melting point is less than 60° C., the storage stability may be deteriorated, and if it is higher than 80° C., the monoester compound A may not dissolve during high-speed printing, and may not be effective as a toner wax.
The melting point of the monoester compound A can be measured by differential scanning calorimetry (DSC) at a temperature rise rate of 10°C per minute, and the temperature of the top peak of the endothermic peak measured by DSC analysis can be taken as the melting point.

[Monoester Compound B]
The monoester compound B of the present invention is a monoester compound obtained from at least one linear saturated monocarboxylic acid selected from linear saturated monocarboxylic acids having 16 to 24 carbon atoms and at least one aliphatic alcohol selected from linear saturated alkylene glycols having 2 to 6 carbon atoms, and is represented by the following structural formula (2):

(In the formula, ^R3 represents a linear saturated alkyl group having 15 to 24 carbon atoms, and n represents an integer of 2 to 6.)

The raw carboxylic acid of monoester compound B is a linear saturated monocarboxylic acid having a carbon number of 16 to 24, preferably 18 to 22. If the raw carboxylic acid has too few carbon atoms, the wax may melt at a low temperature, resulting in a significant decrease in storage stability in the toner. If the raw carboxylic acid has too many carbon atoms, the wax may become less dispersible in the toner, adversely affecting the dispersion of the colorant.
Specific examples of the raw material carboxylic acid include palmitic acid, stearic acid, arachidic acid, behenic acid, etc. Among these, stearic acid is particularly preferred.

The raw material alcohol for monoester compound B is a linear saturated alkylene glycol having 2 to 6 carbon atoms, preferably 2 to 4 carbon atoms. If the carbon number is outside the above range, the melting point of the wax may be significantly lowered, resulting in a loss of storage stability. Furthermore, if the alkyl group of the raw material alcohol has a branched structure, such as 1,2-propanediol, or is a trivalent or higher alcohol, such as glycerin or pentaerythritol, blending with the above-mentioned monoester compound A may significantly reduce the crystallinity of the wax, making it difficult to achieve high-speed printing and causing gloss unevenness due to the crystalline state of the wax. From these perspectives, specific examples of the raw material alcohol include ethylene glycol, 1,4-butanediol, and 1,6-hexanediol. Among these, ethylene glycol and 1,4-butanediol are particularly preferred.
The monoester compound B obtained from the linear saturated monocarboxylic acid and the linear saturated alkylene glycol preferably has a total carbon number of 20 to 26, and particularly preferably has a total carbon number of 20 to 24. Among these, a monoester compound formed from stearic acid and ethylene glycol is preferred.

From the viewpoint of storage stability, the monoester compound B in the present invention preferably has an acid value of 5 mgKOH/g or less, more preferably 3 mgKOH/g or less, and particularly preferably 1 mgKOH/g or less.
From the viewpoint of pigment dispersion and suppression of uneven gloss during high-speed printing, the hydroxyl value is preferably 140 mgKOH/g to 190 mgKOH/g, and more preferably 160 mgKOH/g to 180 mgKOH/g.
The acid value can be measured in accordance with JOCS (Japan Oil Chemists' Society) 2.3.1-1996, and the hydroxyl value can be measured in accordance with JOCS (Japan Oil Chemists' Society) 2.3.6.2-1996.

The melting point of the monoester compound B in the present invention is preferably 60 to 80° C., more preferably 65 to 75° C. If the melting point is less than 60° C., the storage stability may be deteriorated, and if it is higher than 80° C., the monoester compound B may not dissolve during high-speed printing, and may not be effective as a toner wax.
The melting point of the monoester compound B can be measured by differential scanning calorimetry (DSC) at a temperature rise rate of 10°C per minute, and the temperature of the top peak of the endothermic peak measured by DSC analysis can be taken as the melting point.

[Wax composition for toner]
The toner wax composition of the present invention contains the above-mentioned monoester compound A and monoester compound B, and the mass ratio (A):(B) of monoester compound A to monoester compound B is 99.9:0.1 to 70:30, and preferably 99:1 to 85:15. If the mass ratio of monoester compound A to monoester compound B does not satisfy the range of 99.9:0.1 to 70:30, the effects of the present invention cannot be obtained, but if the range is 99:1 to 85:15, the effects of the present invention can be obtained more significantly.

From the viewpoint of suppressing gloss unevenness during high-speed printing, it is preferable that the toner wax composition of the present invention has small differences in crystallization behavior caused by differences in cooling rate. As an index of this, the ratio (ΔH _R /ΔH _S ) of the crystallization enthalpy ΔH _S when the toner wax composition is slowly cooled from a molten state to the crystallization enthalpy ΔH _R when the toner wax composition is rapidly cooled from a molten state is preferably 0.70 or more, more preferably 0.75 or more, and particularly preferably 0.80 or more.
In the present invention, the crystallization enthalpy ΔH _S of the toner wax composition when it is slowly cooled from a molten state is determined by calculating the integral of the exothermic peak when the temperature is decreased from 130° C. to 30° C. by differential scanning calorimetry (DSC) at a temperature decrease rate of 2° C. per minute, and the obtained integral value is designated as ΔH _S. Furthermore, the crystallization enthalpy ΔH _R of the toner wax composition when it is rapidly cooled from a molten state is determined by calculating the integral of the exothermic peak when the temperature is decreased from 130° C. to 30° C. by differential scanning calorimetry (DSC) at a temperature decrease rate of 10° C. per minute, and the obtained integral value is designated as ΔH _S.

The toner wax composition of the present invention can be produced by a known method. For example, the monoester compound A and the monoester compound B may be synthesized separately and then blended to produce the toner wax. Alternatively, the amounts of the synthesis materials may be adjusted so that the mass ratio (A):(B) of the monoester compound A to the monoester compound B falls within the above range, and the toner wax composition may be produced by simultaneous synthesis.
In the method of producing a toner wax composition by separately synthesizing a monoester compound A and a monoester compound B and then blending them, it is preferable to heat the monoester compound A and the monoester compound B to a temperature equal to or higher than their melting points, mix them uniformly, and then cool and atomize the mixture, from the viewpoint of preventing variations in quality.

The toner wax composition of the present invention is blended with a binder resin, a colorant, a charge control agent, etc., and a toner is produced by a conventional manufacturing method. The amount of the toner wax composition of the present invention blended in the toner is typically 1 to 10 parts by mass per 100 parts by mass of the binder resin. The toner may contain a single toner wax composition of the present invention, or two or more types may be blended together.

The present invention will be explained in more detail below by showing examples of the production of the toner wax composition of the present invention and the evaluation method thereof.
[Preparation Example of Monoester Compound A]
The acid value, hydroxyl value, and melting point of the monoester compound A used in the examples and comparative examples are shown in Table 1. The preparation method is as follows.
[Preparation of monoester compound A-1]
1090.9 g (3.8 mol) of stearic acid and 1200 g (3.7 mol) of behenyl alcohol were placed in a 3 L four-neck flask equipped with a thermometer, a nitrogen inlet tube, a stirring blade, and a condenser, and the mixture was reacted under a nitrogen stream at 220° C. The obtained crude ester product weighed 2228.5 g and had an acid value of 5.0 mgKOH/g.
To this crude ester product, 700 g of toluene and 150 g of 2-propanol were added, and a 10% by mass aqueous potassium hydroxide solution containing potassium hydroxide in an amount equivalent to 2.0 times the residual acid value of the crude ester product was added, followed by stirring at 70°C for 30 minutes. The mixture was then allowed to stand for 30 minutes, and the aqueous layer (lower layer) was separated and removed. Washing with water was repeated four times until the pH of the wastewater became neutral. The solvent from the remaining ester layer was distilled off under reduced pressure conditions of 180°C and 1 kPa, followed by filtration, yielding 2072.5 g of Wax A-1.

[Preparation of Monoester Compound A-2]
A 3 L four-neck flask equipped with a thermometer, a nitrogen inlet tube, a stirring blade, and a condenser was charged with 1226.2 g (3.6 mol) of behenic acid, 1200 g (3.7 mol) of behenyl alcohol, and 4.4 g (0.1 mol) of paratoluenesulfonic acid, and the mixture was reacted under a nitrogen stream at 220° C. The obtained crude ester product weighed 2360.5 g and had an acid value of 1.0 mgKOH/g.
[Preparation of monoester compound A-3]
Monoester Compound A-3 shown in Table 1 was obtained in the same manner as in the preparation of Monoester Compound A-2, except that behenic acid was used as the linear saturated fatty acid and palmityl alcohol was used as the linear saturated fatty alcohol, and the amounts of raw materials charged were changed.

[Preparation Example of Monoester Compound B]
Table 2 shows the acid value, hydroxyl value, and melting point of the monoester compound B used in the examples and comparative examples.
[Preparation of Monoester Compound B-1]
800.0 g (12.9 mol) of ethylene glycol and 1,834.6 g (6.4 mol) of stearic acid were placed in a 3 L four-neck flask equipped with a thermometer, a nitrogen inlet tube, a stirring blade, and a condenser, and the mixture was reacted at 200° C. under a nitrogen stream, followed by distillation at 250° C. under reduced pressure of 30 kPa. The obtained crude ester product weighed 2,058.0 g and had an acid value of 2.0 mgKOH/g.
500 g of this crude ester product was completely dissolved in a mixed solvent of 1000 g of heptane and 1000 g of 2-propanol at 70°C, and then recrystallized by slow cooling, and the resulting precipitate was recovered by filtration. Recrystallization was repeated three times in the same manner, and the recovered precipitate was dried in vacuo at 40°C to obtain 200 g of monoester compound B-1.

[Preparation of Monoester Compound B-2]
Monoester Compound B-2 shown in Table 2 was obtained in the same manner as in the preparation of Monoester Compound B-1, except that 1,4-butanediol was used as the linear saturated alkylene glycol and the amounts of raw materials charged were changed.
[Preparation of Monoester Compound B-3]
Monoester Compound B-3 shown in Table 2 was obtained in the same manner as in the preparation of Monoester Compound B-1, except that 1,6-hexanediol was used as the linear saturated alkylene glycol and the amounts of raw materials charged were changed.
[Preparation of Monoester Compound B-4]
Monoester compound B-4 shown in Table 2 was obtained in the same manner as in the preparation of monoester compound B-1, except that behenic acid was used as the linear saturated fatty acid and the amounts of raw materials charged were changed.
[Preparation of Monoester Compound B-5]
Monoester Compound B-5 shown in Table 2 was obtained in the same manner as in the preparation of Monoester Compound B-1, except that palmitic acid was used as the linear saturated fatty acid and the amounts of raw materials charged were changed.
[Preparation of Monoester Compound B-6]
Monoester Compound B-6 shown in Table 2 was obtained in the same manner as in the preparation of Monoester Compound B-1, except that 1,10-decanediol was used as the linear saturated alkylene glycol and the amounts of raw materials charged were changed.
[Monoester compound B-7]
Monoester compound B-7 shown in Table 2 was obtained in the same manner as monoester compound B-1, except that glycerin (NOF Corporation's product "Monoglyc D") was used instead of linear saturated alkylene glycol and the amounts of raw materials charged were changed.

[Preparation Example of Toner Wax Composition]
Table 3 shows the compositions of the wax compositions used in the examples and comparative examples, and the ratio of the crystallization enthalpy ΔH _S during slow cooling from a molten state to the crystallization enthalpy ΔH _R during rapid cooling (ΔH _R /ΔH _S ). The preparation methods are as follows.
In a 0.3 L separable flask equipped with a stirring blade and a nitrogen inlet tube, monoester compound A and monoester compound B were melt-mixed in the mass ratio shown in Table 3, and stirred under a nitrogen stream at 150° C. for 1 hour. The mixture was then cooled, solidified, and pulverized to obtain a toner wax composition.

[Evaluation method]
The various tests and evaluation methods carried out in the examples and comparative examples are as follows.
[Testing of Monoester Compounds A and B]
(1) Measurement of Acid Value The acid value was measured in accordance with JOCS (Japan Oil Chemists' Society) 2.3.1-1996.
(2) Measurement of hydroxyl value: Measurement was carried out in accordance with JOCS (Japan Oil Chemists' Society) 2.3.6.2-1996.

(3) Measurement of Melting Point A "DSC-7000X" manufactured by Hitachi High-Tech Science Corporation was used as a differential scanning calorimeter. Measurements were performed by placing approximately 10 mg of ester in a sample holder and using 10 mg of alumina as a reference material, and heating from 30°C to 180°C at a heating rate of 10°C per minute. Prior to measurement, a sample was used as the measurement sample, which had undergone a heating step from 30°C to 180°C and a cooling step from 180°C to 30°C. The temperatures of the top peaks of the endothermic peaks measured by the DSC were taken as the melting points of monoester compounds A and B.

[Measurement of Crystallization Enthalpy of Toner Wax Composition and Calculation of Ratio (ΔH _R /ΔH _S )]
Using the same apparatus and procedure as in "(3) Measurement of Melting Point" above, the crystallization enthalpy was measured when the toner wax composition was slowly or rapidly cooled from a molten state. The crystallization enthalpy during slow cooling, ΔH _S , was determined by calculating the integral of the exothermic peak of the toner wax composition when the temperature was decreased from 130° C. to 30° C. using differential scanning calorimetry (DSC) at a temperature decrease rate of 2° C. per minute, and the obtained integral was designated as ΔH _S. The crystallization enthalpy during rapid cooling, ΔH _R , was determined by calculating the integral of the exothermic peak of the toner wax composition when the temperature was decreased from 130° C. to 30° C. using differential scanning calorimetry (DSC) at a temperature decrease rate of 10° C. per minute, and the obtained integral was designated as ΔH _S. From the obtained measured values, the ratio (ΔH _R /ΔH _{S ) of the crystallization enthalpy during slow cooling (ΔH S )} to the crystallization enthalpy during rapid cooling (ΔH _R ) was calculated.

[Evaluation of Toner Wax Composition]
(1) Storage Stability of Toner Wax Composition The storage stability when the wax composition was mixed with a binder resin was evaluated by the following method. Evaluation samples were prepared for each of Examples 1 to 8 and Comparative Examples 1 to 6. Specifically, 95 parts by mass of polyester resin (product name: Diaclone ER-508, manufactured by Mitsubishi Rayon Co., Ltd.) and 5 parts by mass of the wax composition shown in Table 3 were mixed, and melt-kneaded using a twin-screw kneader "Labo Plastomill" (manufactured by Toyo Seiki Seisakusho Co., Ltd.) to obtain a resin kneaded product. The melt-kneading was performed at 120°C and 80 rpm for approximately 5 minutes, and the obtained resin kneaded product was pulverized and molded into particles with a particle size of 50 μm or less to obtain an evaluation sample.
For each evaluation sample, 5 g of the resin kneaded sample was placed in a glass vial, and left to stand for 2 weeks in a thermostatic chamber maintained at 45° C. The vial was then turned upside down and the sample was removed without applying force. When the sample was removed, the mass of the sample that flowed out without depositing in the vial and whose particle size was maintained at 50 μm or less was taken as X. The blocking resistance rate R was calculated by the following calculation formula (I).
Calculation formula (I): R=X(g)/5(g)
The storage stability was evaluated based on the calculated blocking resistance rate R according to the following evaluation criteria. The larger the value of the blocking resistance rate R calculated in this way, the more excellent the storage stability is evaluated to be.
<Evaluation criteria>
◎ (excellent storage stability): 0.95≦R
Good (excellent storage stability): 0.90<R<0.95
× (insufficient storage stability): 0.90≧R

(2) High-Speed Printing Responsivity of Toner Wax Compositions Because a wax composition must melt and solidify quickly during high-speed printing, it is preferable for the wax composition to have a small difference between its melting point and freezing point. Therefore, in this invention, the difference ΔT between the melting point and freezing point of the wax composition was calculated, and the responsiveness of the wax composition to high-speed printing was evaluated using ΔT as an index. Specifically, a Hitachi High-Tech Science DSC-7000X differential scanning calorimeter was used. Measurements were performed by placing approximately 10 mg of the wax composition in a sample holder and using 10 mg of alumina as a reference material. The sample was heated from 30°C to 180°C at a heating rate of 10°C per minute, and then cooled from 180°C to 30°C. The sample used for measurement had undergone a heating process from 30°C to 180°C and a cooling process from 180°C to 30°C prior to measurement. The temperature of the top peak of the endothermic peak during temperature increase measured by the DSC was taken as the melting temperature (Tpm), and the temperature of the top peak of the exothermic peak during temperature decrease was taken as the solidification temperature (Tec).
Using the melting temperature (Tpm) and solidification temperature (Tec) of the obtained toner wax composition, the difference ΔT between the melting temperature and the solidification temperature was calculated according to the following calculation formula (II).
Calculation formula (II): ΔT=Tpm-Tec
Based on the calculated ΔT value, the responsiveness of the wax composition to high speed printing was evaluated according to the following criteria.
<Evaluation criteria>
◎ (Also compatible with ultra-high speed printing): 12 ≥ ΔT
Good (capable of handling high-speed printing without problems): 12<ΔT≦15
× (not suitable for high-speed printing): 15<ΔT

(3) Effect of Toner Wax Composition on Improving Pigment Dispersibility The effect of the toner wax composition on improving pigment dispersibility was evaluated by the following method.
Evaluation samples were prepared for each of Examples 1 to 8 and Comparative Examples 1 to 6. Specifically, 94 parts by mass of polyester resin (product name: Diaclone ER-508, manufactured by Mitsubishi Rayon Co., Ltd.), 5 parts by mass of the wax shown in Table 2, and 1 part by mass of colorant (product name: PV-FAST BLUE BG, manufactured by Clariant) were mixed and melt-kneaded using a twin-screw kneader (product name "Laboplastomill", manufactured by Toyo Seiki Co., Ltd.) to obtain a resin kneaded product. The melt-kneading was performed at 120 ° C. and 80 rpm / min for about 5 minutes, and the obtained resin kneaded product was pelletized using a tablet molding machine (product name "Tabletop Hydraulic Molding Machine MP250", manufactured by Maassen Co., Ltd.) to obtain a sample. For each evaluation sample, 10 different points on the sample surface were measured in reflection mode using a color difference meter (Color Difference Meter ZE6000, manufactured by Nippon Denshoku Industries Co., Ltd.), and the color a* and b* values for each hue in the CIE 1976 (L*, a*, b*) color space (also known as CIELAB) were obtained. Using the obtained measurements, the chroma C of the evaluation sample was calculated using the following calculation formula (III).
Calculation formula (III): C=(a* ² + b* ² ) ^1/2
The difference ΔC between the maximum saturation value _Cmax and the minimum saturation value _Cmin measured within the same sample was calculated using the following calculation formula (IV): The smaller the value of the saturation difference ΔC calculated in this way, the better the dispersion of the colorant is evaluated to be.
Calculation formula (IV): ΔC=C _max - C _min
<Evaluation criteria>
◎ (Excellent colorant dispersion): 0.5≧ΔC
Good (excellent colorant dispersion): 0.5<ΔC≦1.0
× (not excellent in dispersibility of colorant): 1.0<ΔC

(4) Effect of Toner Wax Composition on Suppressing Gloss Unevenness The effect of suppressing gloss unevenness during high-speed printing was evaluated using the following method. For each of Examples 1 to 8 and Comparative Examples 1 to 6, 10 g of the wax composition was melted at a temperature above the melting point, a 2 mm thick frame was sandwiched between mirror-finished metal plates with a diameter of 20 cm, and the molten liquid was poured into the frame. The wax plate was then sandwiched between the metal plates from above and below and slowly or rapidly cooled to prepare a wax plate. The resulting wax plate was measured (10 measurement areas were evaluated) using a Gloss Checker IG-320 manufactured by Horiba, Ltd., at an incident angle of 60°C, and the average value was taken as the gloss value. The smaller the absolute value ΔG of the difference between the gloss value G _S after slow cooling and the gloss value G _R after rapid cooling, calculated using formula (V), the better the gloss unevenness suppression effect was evaluated.
Calculation formula (V): ΔG=｜G _R −G _S |
<Evaluation criteria>
◎ (Excellent in suppressing uneven gloss due to differences in cooling speed): 1.0≧ΔG
Good (Excellent in suppressing uneven gloss due to differences in cooling rate): 1.0<ΔG≦2.0
× (not excellent in suppressing uneven gloss due to differences in cooling rate): 2.0<ΔG

[Evaluation results]
The evaluation results for the above Examples and Comparative Examples are shown in Tables 4 and 5.

In Examples 1 to 8, which used wax compositions W1 to 8, the blocking resistance rate R was high, and therefore it can be said that the storage stability in the toner during storage is also excellent. Furthermore, wax compositions W1 to 8 have a small difference between their melting point and freezing point, making them suitable for high-speed printing, and also have excellent pigment dispersion in the toner, since the saturation difference ΔC is ΔC<1.0, and the absolute value ΔG of the difference between the gloss value G _S during slow cooling and the gloss value G _R during rapid cooling is ΔG<2.0, so it can be said that gloss unevenness in printed matter can be suppressed even during high-speed printing.

On the other hand, in Comparative Example 1, which used wax composition W9 in which the number of carbon atoms n of the linear saturated alkylene glycol constituting monoester compound B was larger than the range of the present invention, the effect of suppressing gloss unevenness was confirmed, but the storage stability was deteriorated, the difference between the melting point and freezing point of the wax composition was large, making it unsuitable for high-speed printing, and the effect of improving pigment dispersibility was not obtained.
In Comparative Example 2, in which wax composition W10 in which the alcohol constituting monoester compound B was a trihydric alcohol was used, the effect of improving pigment dispersibility was confirmed, but storage stability deteriorated, the difference between the melting point and freezing point of the wax composition was large, making it unsuitable for high-speed printing, and the effect of suppressing gloss unevenness was not obtained.
In Comparative Examples 3 and 4, which used wax compositions W11 and W12 that did not contain monoester compound B, storage stability and compatibility with high-speed printing were confirmed, but the effect of improving pigment dispersibility and the effect of suppressing gloss unevenness were not obtained.
In Comparative Example 5, which used wax composition W13 in which the blending amount of monoester compound B was higher than the range of the present invention, the effect of improving pigment dispersibility was confirmed, but the storage stability was deteriorated, the difference between the melting point and freezing point of the wax composition was large, making it unsuitable for high-speed printing, and the effect of suppressing gloss unevenness was not obtained.
In Comparative Example 6, which did not contain monoester compound A, the effect of improving pigment dispersibility was confirmed, but the storage stability was deteriorated, the difference between the melting point and freezing point of the wax composition was large, making it unsuitable for high-speed printing, and the effect of suppressing gloss unevenness was not obtained.

Claims (1)

A toner wax composition comprising a monoester compound A represented by the following structural formula (1) and a monoester compound B represented by the following structural formula (2), wherein the mass ratio of the monoester compound A to the monoester compound B (A):(B) is 99.9:0.1 to 70:30.
Monoester Compound A:
(In the formula, ^R1 represents a linear saturated alkyl group having 15 to 24 carbon atoms, and ^R2 represents a linear saturated alkyl group having 16 to 24 carbon atoms.)
Monoester Compound B:
(In the formula, ^R3 represents a linear saturated alkyl group having 15 to 24 carbon atoms, and n represents an integer of 2 to 6.)