Patent Application
20220308481
This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2021-054286 filed Mar. 26, 2021.
The present disclosure relates to a method for producing a resin particle dispersion, to a method for producing a toner for electrostatic image development, and to a toner for electrostatic image development.
For example, Japanese Unexamined Patent Application Publication No. 2010-6976 discloses “a method for producing a polyester dispersion including: (1) the step of obtaining a polyester solution by dissolving a polyester having a Log P value of 3.0 to 5.0 in an organic solvent; (2) the step of neutralizing the polyester by adding a neutralizer to the polyester solution obtained in step (1) such that 10.A×B 18 is satisfied (where A is the neutralization equivalent of the polyester in the polyester solution, and B is the acid value (mg KOH/g) of the polyester; and (3) the step of emulsifying the polyester by adding water in the polyester solution neutralized in step (2).”
Japanese Unexamined Patent Application Publication No. 2016-210969 discloses “a method for producing crystalline resin particles by phase inversion emulsification (PIE) including: (a) the step of dissolving a crystalline resin having an acid value in a mixture of at least two solvents, a first amount of base, and water to form an emulsion; (b) the step of adding a second amount of base to the emulsion to obtain a neutralization rate of about 100% to about 200%; and (c) the step of converting the emulsion of step (b) into latex particles having a size of less than about 200 nm by the addition of water.”
Aspects of non-limiting embodiments of the present disclosure relate to a method for producing a resin particle dispersion including: preparing a phase-inverted emulsion by phase inversion emulsification of a resin using a neutralizer, an organic solvent, and an aqueous medium; and removing the organic solvent from the phase-inverted emulsion. With this method, the yield of the resin particle dispersion is higher than that of a resin particle dispersion produced by a method wherein the acid value A of the resin is less than 8 mg KOH/g or more than 20 mg KOH/g, wherein the rate of neutralization of the resin with the neutralizer is less than 60% or higher than 150%, wherein the organic solvent includes at least one organic solvent B selected from the group consisting of esters and ketones and an organic solvent C selected from alcohols, and wherein, in the phase-inverted emulsion, the relations among the mass Wr (kg) of the resin, the mass Wb (kg) of the organic solvent B, and the mass Wc (kg) of the organic solvent C do not satisfy any of formulas 1 to 6. Moreover, the resin particle dispersion contains resin particles having a narrower particle size distribution.
Aspects of certain non-limiting embodiments of the present disclosure address the above advantages and/or other advantages not described above. However, aspects of the non-limiting embodiments are not required to address the advantages described above, and aspects of the non-limiting embodiments of the present disclosure may not address advantages described above.
According to an aspect of the present disclosure, there is provided a method for producing a resin particle dispersion, the method including:
preparing a phase-inverted emulsion by phase inversion emulsification of a resin using a neutralizer, an organic solvent, and an aqueous medium; and removing the organic solvent from the phase-inverted emulsion to thereby obtain a resin particle dispersion, wherein the acid value A of the resin is from 8 mg KOH/g to 20 mg KOH/g inclusive, wherein the rate of neutralization of the resin with the neutralizer is 60% or more and less than 150%, wherein the organic solvent contains at least one organic solvent B selected from the group consisting of esters and ketones and at least one organic solvent C selected from alcohols, and
wherein, in the phase-inverted emulsion, the acid value A of the resin, the mass Wr (kg) of the resin, the mass Wb (kg) of the organic solvent B, and the mass Wc (kg) of the organic solvent C satisfy relations represented by the following formulas 1 to 6:
30≤(Wb+Wc)/(Wr/100) 250, formula 1
0.67 Wb/(Wb+Wc) 0.85, formula 2
K1=(Wb×100)/(A×Wr), formula 3
4: 2≤K1≤16.5, formula 4
K2=(Wc×100)/(A×Wr), and formula 5
0.5≤K2≤5.5. formula 6
Exemplary embodiments of the present disclosure will be described below. The description and Examples are illustrative of the present disclosure and are not intended to limit the scope of the present disclosure.
In the present specification, a numerical range represented using “to” means a range including the numerical values before and after the “to” as the minimum value and the maximum value, respectively.
In a set of numerical ranges expressed in a stepwise manner in the present specification, the upper or lower limit in one numerical range may be replaced with the upper or lower limit in another numerical range in the set. Moreover, in a numerical range described in the present specification, the upper or lower limit in the numerical range may be replaced with a value indicated in an Example.
In the present specification, the term “step” is meant to include not only an independent step but also a step that is not clearly distinguished from other steps, so long as the prescribed purpose of the step can be achieved.
In the present specification, when an exemplary embodiment is explained with reference to the drawings, the structure of the exemplary embodiment is not limited to the structure shown in the drawings. In the drawings, the sizes of the components are conceptual, and the relative relations between the components are not limited to these relations.
In the present specification, any component may contain a plurality of materials corresponding to the component. In the present disclosure, when reference is made to the amount of a component in a composition, if the composition contains a plurality of materials corresponding to the component, the amount means the total amount of the plurality of materials, unless otherwise specified.
In the present specification, the “toner for electrostatic image development” may be referred to simply as a “toner.”
A resin particle dispersion production method according to an exemplary embodiment includes the steps of: preparing a phase-inverted emulsion by phase inversion emulsification of a resin using a neutralizer, an organic solvent, and an aqueous medium; and removing the organic solvent from the phase-inverted emulsion. In the production method, the following conditions (1) to (4) are satisfied:
(1) the acid value of the resin is from 8 mg KOH/g to 20 mg KOH/g inclusive;
(2) the rate of neutralization of the resin with the neutralizer is 60% or more and less than 150%;
(3) the organic solvent contains at least one organic solvent B selected from the group consisting of esters and ketones and at least one organic solvent C selected from alcohols; and
(4) in the phase-inverted emulsion, the acid value A of the resin, the mass Wr (kg) of the resin, the mass Wb (kg) of the organic solvent B, and the mass Wc (kg) of the organic solvent C satisfy relations represented by the following formulas 1 to 6:
30≤(Wb+Wc)/(Wr/100) 250, formula 1
0.67 Wb/(Wb+Wc) 0.85, formula 2
K1=(Wb×100)/(A×Wr), formula 3
4: 2≤K1≤16.5, formula 4
K2=(Wc×100)/(A×Wr), and formula 5
0.5≤K2≤5.5. formula 6
With the resin particle dispersion production method according to the present exemplary embodiment, a resin particle dispersion containing resin particles having a narrow size distribution can be obtained with a high yield. The reason for this may be as follows.
The resin particle dispersion is produced, for example, by dissolving the resin in an organic solvent, mixing the resulting solution with water to cause phase inversion emulsification to occur to thereby disperse the resin finely in the aqueous medium, and then removing the organic solvent by reduced pressure distillation.
In the production of the resin particle dispersion, the particle size distribution of the resin particles is controlled by adjusting the amount of the solvent or the rate of neutralization according to the properties of the resin.
However, the size distribution of the resin particles obtained may be nonuniform in some cases depending on the amount of the organic solvent or the type of organic solvent. In this case, dissolution of the resin in the organic solvent may be insufficient, and the yield of the resin particle dispersion may decrease.
The resin is well dissolved in the at least one organic solvent B selected from the group consisting of esters and ketones, but the hydrophilicity of the at least one organic solvent B is low.
The solubility of the resin in the at least one organic solvent C selected from alcohols is low, but the hydrophilicity of the at least one organic solvent C is high.
If the amount of the organic solvent B is small, the dissolving power of the organic solvent is low, and some of the resin is not dissolved in the solvent, so that the yield decreases. If the amount of the organic solvent B is large, the dissolving power of the organic solvent is excessively high. In this case, the phase change from an oil phase dispersion to a water phase dispersion occurs non-uniformly, and a narrow size distribution may not be obtained.
If the amount of the organic solvent C is small, the hydrophilicity of the organic solvent is insufficient, and a narrow particle size distribution may not be obtained. If the amount of the organic solvent C is large, the hydrophilicity of the organic solvent is excessively high. In this case, the dissolving power of the organic solvent is low, and some of the resin is not dissolved in the solvent, so that the yield decreases.
“(Wb+Wc)/(Wr/100)” in formula 1 represents the amount of the organic solvent relative to the resin. If the total amount of the organic solvent relative to the amount of the resin is small, the amount of the organic solvent is not large enough to dissolve the resin. In this case, some of the resin is not dissolved in the solvent, so that the yield decreases. If the total amount of the organic solvent relative to the amount of the resin is large, the dissolving power of the organic solvent is excessively high. In this case, the phase change from the oil phase dispersion to the water phase dispersion tends to occur non-uniformly, and a narrow size distribution may not be obtained.
“Wb/(Wb+Wc)” in formula 2 represents the ratio in the organic solvent. If the mass ratio of the organic solvent B to the organic solvent C (the organic solvent B/the organic solvent C) is small, the hydrophilicity of the organic solvent is excessively high, and therefore some of the resin is not dissolved in the solvent, so that the yield decreases. If the mass ratio of the organic solvent B to the organic solvent C (the organic solvent B/the organic solvent C) is large, the hydrophilicity of the organic solvent is insufficient. In this case, the phase change from the oil phase dispersion to the water phase dispersion tends to occur non-uniformly, and a narrow size distribution may not be obtained.
K1 in formula 3 is an indicator indicating the ratio of the mass of the organic solvent B relative to the acid value A and the mass of the resin. If K1 is small, the mass of the organic solvent B relative to the acid value A is small. In this case, the dissolving power of the organic solvent is highly insufficient, and some of the resin is not dissolved in the solvent, so that the yield decreases. If K1 is large, the amount of the organic solvent B relative to the acid value A is large. In this case, the dissolving power of the organic solvent is excessively high, and the phase change from the oil phase dispersion to the water phase dispersion tends to occur non-uniformly, so that a narrow size distribution may not be obtained.
K2 in formula 6 is an indicator indicating the ratio of the mass of the organic solvent C relative to the acid value A and the mass of the resin. If K2 is small, the amount of the organic solvent C relative to the acid value A is small, and the hydrophilicity of the organic solvent is highly insufficient, so that a narrow size distribution may not be obtained. If K2 is large, the amount of the organic solvent C relative to the acid value A is large, and the hydrophilicity of the organic solvent is high. In this case, the dissolving power of the organic solvent is highly insufficient, and some of the resin is not dissolved in the solvent, so that the yield decreases.
Therefore, by adjusting the amount of the resin, the amount of the organic solvent B, and the amount of the organic solvent C to appropriate ranges such that formulas 1 to 6 are satisfied, the solubility of the resin in the organic solvent is increased, and the yield is improved. Moreover, the hydrophilicity of the organic solvent as a whole is appropriate, and a narrow particle size distribution is obtained.
Even when the amount of the organic solvent and the type of organic solvent are changed within the range where formulas 1 to 6 are satisfied, the self-emulsification ability of the resin is sufficient, so long as the acid value of the resin and the neutralization rate of the resin are in the above ranges. Therefore, the yield is high, and a narrow particle size distribution is obtained.
It is inferred from the above that, with the resin particle dispersion production method according to the present exemplary embodiment, a resin particle dispersion containing resin particles having a narrow particle size distribution is obtained with a high yield.
In the resin particle dispersion obtained by the resin particle dispersion production method according to the present exemplary embodiment, the resin particles have a narrow particle size distribution. Therefore, when the resin particle dispersion is used for a toner (particularly for an emulsification aggregation method used as a toner production method), a toner having a narrow particle size distribution is obtained.
The resin particle dispersion production method according to the present exemplary embodiment will be described in detail.
In the phase-inverted emulsion preparation step, the phase-inverted emulsion is prepared by subjecting the resin to phase inversion emulsification using the neutralizer, the organic solvent, and the aqueous medium.
The phase-inverted emulsion is obtained by a phase inversion emulsification method.
In the phase inversion emulsification method, the aqueous medium (i.e., the W phase) is added to an oil phase dispersion (i.e., a resin solution used as the O phase) that is a continuous phase containing the resin dissolved in an organic solvent capable of dissolving the resin to thereby subject the resin to conversion (i.e., phase inversion) from W/O to O/W. The oil phase dispersion is thereby converted to a discontinuous phase, and the resin is dispersed as particles in the aqueous medium.
Examples of the method for producing the phase-inverted emulsion include the following methods.
1) The resin is dissolved in the organic solvent, and the neutralizer is added to the obtained resin solution to neutralize the resin. Then the aqueous medium is added to the resin solution to perform phase inversion emulsification.
2) The resin is dissolved in a solvent containing the organic solvent and the neutralizer to neutralize the resin, and the aqueous medium is added to the resin solution to perform phase inversion emulsification.
3) The resin is dissolved in a solvent containing water, the neutralizer, and the aqueous medium to neutralize the resin, and then the aqueous medium is added to the resin solution to perform phase inversion emulsification.
The phase-inverted emulsion is produced using a well-known emulsification device such as an emulsification tank equipped with agitation impellers.
When the resin is dissolved in the organic solvent, the aqueous medium and the neutralizer may be mixed with the resin and the organic solvent.
No particular limitation is imposed on the order of addition of the resin and the organic solvent to the emulsification tank. When the resin easily dissolves in the organic solvent, the resin may be added after all the organic solvent or part of the organic solvent has been added, from the viewpoint of dissolving time.
A tube used to add the resin to the emulsification tank can be freely selected in consideration of, for example, the diameter of the pulverized resin to be added. For example, to prevent dust particles from flying during addition of the resin, a tube that can be lowered to a lower portion of the emulsification tank may be used.
No particular limitation is imposed on the position, number, and shape of nozzles used to add water to the resin solution obtained by dissolving the resin to the organic solvent. For example, the nozzles may be immersed in the solution. When a large-scale facility is used, two or more tubes may be used to add water, or a nozzle having a showerhead may be used to add water from an upper portion of the emulsification tank such that the water is sprayed over the surface of the solution.
Any resin that can undergo phase inversion emulsification can be used.
However, from the viewpoint of improving the yield and narrowing the particle size distribution, the resin used may have an acid value of from 8 mg KOH/g to 20 mg KOH/g inclusive (preferably from 10 mg KOH/g to 16 mg KOH/g inclusive).
The acid value is determined by a neutralization titration method specified in JIS K0070 (1992). Specifically, the acid value is determined as follows.
An appropriate amount of a sample is collected, and 100 mL of a solvent (a solution mixture of diethyl ether/ethanol) and a few drops of an indicator (phenolphthalein solution) are added. Then the mixture is well-shaken in a water bath until the sample is completely dissolved. The mixture is titrated with a 0.1 mol/L potassium hydroxide ethanol solution. The point when the light red color of the indicator does not disappear for 30 seconds is defined as the end point. The acid value is denoted as A, and the weight of the sample is denoted as S (g). The volume of the 0.1 mol/L potassium hydroxide ethanol solution used for the titration is denoted as B (mL), and the factor of the 0.1 mol/L potassium hydroxide ethanol solution is denoted as f. Then the acid value is computed as A=(B x f x 5.611)/S.
The glass transition temperature (Tg) of the resin is preferably from 50° C. to 80° C. inclusive and more preferably from 50° C. to 65° C. inclusive.
The glass transition temperature is measured using a differential scanning calorimeter (DSC3110 manufactured by Mac Science Co., Ltd., thermal analysis system 001) according to JIS 7121-1987. The melting point of a mixture of indium and zinc is used to correct the temperature of a detection unit of the above apparatus, and the heat of fusion of indium is used to correct the amount of heat. A sample is placed in an aluminum pan. The aluminum pan with the sample placed therein and an empty reference pan are set in the apparatus, and the measurement is performed at a heating rate of 10° C/min.
The glass transition temperature is defined as the temperature at the intersection of the base line in an endothermic portion in the DSC curve obtained by the measurement and an extension of a rising line.
The weight average molecular weight (Mw) of the resin is preferably from 5000 to 1000000 inclusive and more preferably from 7000 to 500000 inclusive.
The number average molecular weight (Mn) of the resin may be from 2000 to 100000 inclusive.
The molecular weight distribution Mw/Mn of the resin is preferably from 1.5 to 100 inclusive and more preferably from 2 to 60 inclusive.
The weight average molecular weight and the number average molecular weight are measured by gel permeation chromatography (GPC). In the molecular weight measurement by GPC, a GPC measurement apparatus HLC-8120GPC manufactured by TOSOH Corporation is used. A TSKgel Super HM-M (15 cm) column manufactured by TOSOH Corporation and a THF solvent are used. The weight average molecular weight and the number average molecular weight are computed from the measurement results using a molecular weight calibration curve produced using monodispersed polystyrene standard samples.
No particular limitation is imposed on the amount of the resin used, and the amount may be appropriately selected according to the concentration of solids in the resin particle dispersion to be obtained.
Examples of the resin include: vinyl-based resins composed of homopolymers of monomers such as styrenes (such as styrene, p-chlorostyrene, and a-methylstyrene), (meth)acrylates (such as methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate, and 2-ethylhexyl methacrylate), ethylenically unsaturated nitriles (such as acrylonitrile and methacrylonitrile), vinyl ethers (such as vinyl methyl ether and vinyl isobutyl ether), vinyl ketones (such as vinyl methyl ketone, vinyl ethyl ketone, and vinyl isopropenyl ketone), and olefins (such as ethylene, propylene, and butadiene); and vinyl-based resins composed of copolymers of combinations of two or more of the above monomers.
Other examples of the resin include: non-vinyl-based resins such as epoxy resins, polyester resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, and modified rosins; mixtures of the non-vinyl-based resins and the above-described vinyl-based resins; and graft polymers obtained by polymerizing a vinyl-based monomer in the presence of any of these resins.
One of these resins may be used alone, or two or more of them may be used in combination.
The resin may have a polar group such as a carboxyl group, a sulfonic acid group, or a hydroxy group.
The resin used may be an amorphous resin.
The amorphous resin exhibits only a stepwise endothermic change instead of a clear endothermic peak in thermal analysis measurement using differential scanning calorimetry (DSC), is a solid at room temperature, and is thermoplastic at temperature equal to or higher than its glass transition temperature.
The crystalline resin exhibits a clear endothermic peak instead of a stepwise endothermic change in the differential scanning calorimetry (DSC).
Specifically, the crystalline resin means that, for example, the half width of the endothermic peak measured at a heating rate of 10° C/minute is 10° C. or less, and the amorphous resin means a resin in which the half width exceeds 10° C. or a resin in which a clear endothermic peak is not observed.
Examples of the amorphous resin include well-known amorphous resins such as amorphous polyester resins, amorphous vinyl resins (such as styrene-acrylic resins), epoxy resins, polycarbonate resins, and polyurethane resins. Of these, amorphous polyester resins, and amorphous vinyl resins (particularly styrene-acrylic resins) resins are preferred, and amorphous polyester resins are more preferred.
The amorphous resin may be a combination of an amorphous polyester resin and a styrene-acrylic resin. Moreover, the amorphous resin used may be an amorphous resin having an amorphous polyester resin segment and a styrene acrylic resin segment.
The amorphous polyester resin is, for example, a polycondensation product of a polycarboxylic acid and a polyhydric alcohol. The amorphous polyester resin used may be a commercial product or a synthesized product.
Examples of the polycarboxylic acid include aliphatic dicarboxylic acids (such as oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, alkenyl succinic acids, adipic acid, and sebacic acid), alicyclic dicarboxylic acids (such as cyclohexanedicarboxylic acid), aromatic dicarboxylic acids (such as terephthalic acid, isophthalic acid, phthalic acid, and naphthalenedicarboxylic acid), anhydrides thereof, and lower alkyl (having, for example, 1 to 5 carbon atoms) esters thereof. In particular, the polycarboxylic acid may be an aromatic dicarboxylic acid.
The polycarboxylic acid used may be a combination of a dicarboxylic acid and a tricarboxylic or higher polycarboxylic acid having a crosslinked or branched structure. Examples of the tricarboxylic or higher polycarboxylic acid include trimellitic acid, pyromellitic acid, anhydrides thereof, and lower alkyl (having, for example, 1 to 5 carbon atoms) esters thereof.
One of these polycarboxylic acids may be used alone, or two or more of them may be used in combination.
Examples of the polyhydric alcohol include aliphatic diols (such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, and neopentyl glycol), alicyclic diols (such as cyclohexanediol, cyclohexanedimethanol, and hydrogenated bisphenol A), and aromatic diols (such as an ethylene oxide adduct of bisphenol A and a propylene oxide adduct of bisphenol A). In particular, the polyhydric alcohol is, for example, preferably an aromatic diol or an alicyclic diol and more preferably an aromatic diol.
The polyhydric alcohol used may be a combination of a diol and a trihydric or higher polyhydric alcohol having a crosslinked or branched structure. Examples of the trihydric or higher polyhydric alcohol include glycerin, trimethylolpropane, and pentaerythritol.
One of these polyhydric alcohols may be used alone, or two or more of them may be used in combination.
Among these amorphous polyesters, an amorphous polyester resin obtained by polycondensation of a polycarboxylic acid containing dodecenyl succinic acid and a polyhydric alcohol may be used. This amorphous polyester resin has good compatibility with the organic solvent, and the oil phase containing the resin dissolved therein is stabilized, so that a narrow particle size distribution can be easily obtained by converting the oil phase dispersion to the water phase dispersion.
The amorphous polyester resin is obtained by a well-known production method. Specifically, the amorphous polyester resin is obtained, for example, by the following method. The polymerization temperature is set to from 180° C. to 230° C. inclusive. If necessary, the pressure inside the reaction system is reduced, and the reaction is allowed to proceed while water and alcohol generated during condensation are removed. When the raw material monomers are not dissolved or not compatible with each other at the reaction temperature, a high-boiling point solvent may be added as a solubilizer to dissolve the monomers. In this case, the polycondensation reaction is performed while the solubilizer is removed by evaporation. When a monomer with poor compatibility is present during the copolymerization reaction, the monomer with poor compatibility and an acid or an alcohol to be polycondensed with the monomer are condensed in advance, and then the resulting polycondensation product and the rest of the components are subjected to polycondensation.
Examples of the neutralizer include basic compounds capable of neutralizing polar groups in the resin such as carboxyl groups, sulfonic acid groups, or hydroxy groups.
Specific examples of the neutralizer include organic bases and inorganic alkalis.
Examples of the organic base include triethanolamine, diethanolamine, N-methyldiethanolamine, and dimethylethanolamine.
Examples of the inorganic alkali include hydroxides of alkali metals (such as sodium hydroxide, lithium hydroxide, and potassium hydroxide), carbonates (such as sodium carbonate and sodium hydrogencarbonate), and ammonia.
To prevent hydrolysis of the resin, the neutralizer is preferably an amine, which is a weak base, and more preferably ammonia. Particularly preferably, ammonia in the form of an aqueous ammonia solution is added.
The rate of neutralization of the resin with the neutralizer is 60% or more and less than 150%. From the viewpoint of improving the yield and narrowing the size distribution, the neutralization rate is preferably 60% or more and less than 145% and still more preferably 65% or more and less than 140%.
Specifically, the neutralizer is used such that the rate of neutralization of the resin falls within the above range.
The rate of neutralization of the resin is measured as follows.
The acid value of the resin is denoted as AV [mg-KOH/g-resin], and the valence of the neutralizer (i.e., the basic material) added is denoted as n. The molecular weight of the neutralizer (i.e., the basic material) added is denoted as Mwb. The amount of the neutralizer (i.e., the basic material) added per 1 g of the resin is denoted as mb [g]. Then the acid value is computed using the following formula.
The rate of neutralization of the resin [%]=mb×n×56.1/Mwb/AV×1000
The organic solvent contains at least one organic solvent B selected from the group consisting of esters and ketones and at least one organic solvent C selected from alcohols.
An organic solvent other than the organic solvent B and the organic solvent C may also be used. However, the ratio of the amount of the organic solvents B and C to the total amount of the organic solvent may be 90% by mass or more and is preferably 95% by mass or more and particularly preferably 100% by mass.
Examples of the esters include ethyl acetate, butyl acetate, propyl acetate, and isopropyl acetate.
Examples of the ketones include acetone, methyl ethyl ketone, cyclohexanone, butanone, and methyl isobutyl ketone.
Examples of the alcohols include methanol, ethanol, isopropyl alcohol, n-propanol, n-butanol, diacetone alcohol, and 2-ethylhexanol.
In the phase-inverted emulsion, the acid value A of the resin, the mass Wr(kg) of the resin, the mass Wb (kg) of the organic solvent B, and the mass Wc (kg) of the organic solvent C satisfy relations represented by the following formulas 1 to 6:
30≤(Wb+Wc)/(Wr/100) 250, formula 1
0.67 Wb/(Wb+Wc) 0.85, formula 2
K1=(Wb×100)/(A×Wr), formula 3
4: 2≤K1≤16.5, formula 4
K2=(Wc×100)/(A×Wr), and formula 5
0.5≤K2≤5.5. formula 6
The amount of the resin, the amount of the organic solvent B, and the amount of the organic solvent C are adjusted to appropriate ranges such that formulas 1 to 6 are satisfied. The solubility of the resin in the organic solvent is thereby increased, and the yield is improved. Moreover, the hydrophilicity of the organic solvent as a whole is appropriate, and a narrow particle size distribution is obtained.
From the viewpoint of improving the yield and narrowing the particle size distribution, the value of “(Wb +Wc)/(Wr/100)” in formula 1 is preferably from 40 to 200 inclusive and more preferably from 45 to 170 inclusive.
From the viewpoint of improving the yield and narrowing the particle size distribution, the value of “(Wb/(Wb+Wc)” in formula 2 is preferably from 70 to 85 inclusive and more preferably from 72 to 83 inclusive.
From the viewpoint of improving the yield and narrowing the particle size distribution, K1 in formula 4 is preferably from 3 to 14.5 inclusive and more preferably from 3.5 to 13.5 inclusive.
From the viewpoint of improving the yield and narrowing the particle size distribution, K2 in formula 6 is preferably from 1 to 4.5 inclusive and more preferably from 1.5 to 4 inclusive.
From the viewpoint of improving the yield and narrowing the particle size distribution, the content of the organic solvent B in the phase-inverted emulsion with respect to the mass of the resin is preferably from 25% by mass to 150% by mass inclusive and more preferably from 40% by mass to 130% by mass inclusive.
From the viewpoint of improving the yield and narrowing the particle size distribution, the content of the organic solvent C in the phase-inverted emulsion with respect to the mass of the resin is preferably from 10% by mass to 50% by mass inclusive and more preferably from 10% by mass to 40% by mass inclusive.
The aqueous medium used is, for example, water (such as distilled water or ion exchanged water).
The amount of water added to the oil phase medium prepared by dissolving the resin in the organic solvent is set to, for example, an amount that allows phase inversion emulsification to proceed and the amount of waste generated to decrease.
Specifically, the amount of water added is preferably from 50% by mass to 2000% by mass inclusive and more preferably from 100% by mass to 1000% by mass inclusive based on the mass of the resin.
In the organic solvent removal step, the organic solvent is removed from the phase-inverted emulsion.
To remove the organic solvent, a method in which the organic solvent is removed from the phase-inverted emulsion by reduced pressure distillation (a reduced pressure distillation method) may be used.
A well-known reduced pressure distillation method may be used, such as a method in which a reduced pressure distillation bath equipped with an agitating unit is used to perform reduced pressure distillation while the phase-inverted emulsion is bubbled with an inert gas or a method in which a so-called wall wetter is used to draw up the phase-inverted emulsion in the reduced pressure distillation bath to an upper portion of the bath to form a liquid film on a heat transfer surface of the bath in a portion above the liquid level to thereby perform reduced pressure distillation.
A well-known organic solvent removal method may be used, such as a method in which a gas (an inert gas such as nitrogen or air) is introduced into the phase-inverted emulsion under stirring to evaporate the organic solvent at the air-liquid interface (an exhaust-drying method) or a method in which the phase-inverted emulsion is repeatedly discharged in the form of a shower from small holes down to, for example, a receiving tray to evaporate the organic solvent (a shower-type solvent removal method).
By removing the organic solvent from the phase-inverted emulsion, a resin particle dispersion containing the resin particles dispersed therein is obtained.
After the removal of the organic solvent, the collected organic solvent, the collected neutralizer, the collected aqueous medium, etc. may be re-used for the production of the phase-inverted emulsion. In this manner, the cost and the environmental load may be reduced.
A surfactant may be added to the obtained resin particle dispersion.
When the resin particle dispersion contains a surfactant, the dispersibility of the resin particles may be increased, and the storage stability of the dispersion may be improved.
Examples of the surfactant include various surfactants such as anionic surfactants, amphoteric surfactants, cationic surfactants, and nonionic surfactants.
Of these, anionic surfactants may be used from the viewpoint of improving the storage stability of the resin particle dispersion.
Examples of the anionic surfactant include carboxylic acid-type anionic surfactants, sulfate-type anionic surfactants, sulfonate-type anionic surfactants, and phosphate-type anionic surfactants.
Specific examples of the anionic surfactant include fatty acid salts, rosin acid salts, naphthenic acid salts, ether carboxylic acid salts, alkenyl succinic acid salts, primary alkyl sulfates, secondary alkyl sulfates, polyoxyethylene alkyl sulfates, polyoxyethylene alkylphenyl sulfates, monoacylglycerol sulfates, acylamino sulfates, sulfated oils, sulfated fatty acid alkyl esters, a-olefin sulfonates, secondary alkane sulfonates, a-sulfofatty acid salts, acyl isethionates, dialkyl sulfosuccinates, alkylbenzenesulfonates, alkylnaphthalenesulfonates, alkyl diphenyl ether disulfonates, petroleum sulfonates, lignin sulfonates, alkyl phosphates, polyoxyethylene alkyl phosphates, polyoxyethylene alkylphenyl phosphates, perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, and perfluoroalkyl phosphates.
Of these, sulfate-type or sulfonate-type anionic surfactants are more preferable, and sulfonate-type anionic surfactants are particularly preferable, from the viewpoint of improving the storage stability of the resin particle dispersion.
From the viewpoint of improving the storage stability of the resin particle dispersion, the content of the surfactant is preferably from 0.1% by mass to 10% by mass inclusive and more preferably from 0.5% by mass to 5% by mass inclusive based on the mass of the resin.
The volume average particle diameter of the resin particles in the resin particle dispersion according to the present exemplary embodiment is preferably from 65 nm to 220 nm inclusive and more preferably from 90 nm to 200 nm inclusive.
In the resin particle dispersion according to the present exemplary embodiment, even when the volume average particle diameter of the resin particles is in the above range, the yield is high, and the resin particle dispersion has a narrow particle size distribution.
The volume average particle diameter of the resin particles is measured as follows. A particle size distribution measured using a laser diffraction particle size measurement apparatus (e.g., LA-700 manufactured by HORIBA Ltd.) is used and divided into different particle diameter ranges (channels), and a cumulative volume distribution is computed from the small particle diameter side. The particle diameter at which the cumulative frequency is 50% relative to the total number of particles is measured as the volume average particle diameter D50v.
In the resin particle dispersion according to the present exemplary embodiment, the content of the residual organic solvent is preferably 3000 ppm or lower and more preferably 1500 ppm or lower. The lower limit of the content of the residual organic solvent is 0 ppm. However, from the viewpoint of reducing the cost for reducing the amount of the residual organic solvent, the lower limit is, for example, 25 ppm or more. The term “ppm” means the mass ratio in the resin particle dispersion after the organic solvent removal step.
When the content of the residual organic solvent in the resin particle dispersion is in the above range, aggregation of the resin particles may be prevented, and the storage stability of the resin particle dispersion may be improved.
To adjust the content of the residual organic solvent to the above range, for example, a method may be used in which the amount of the distillate to be collected is computed in advance using the amount of the phase-inverted emulsion before distillation and the amount of the organic solvent component contained in the phase-inverted emulsion.
The concentration of solids in the resin particle dispersion according to the present exemplary embodiment may be appropriately selected as needed. The solid concentration is preferably from 1% by mass to 60% by mass inclusive, more preferably from 5% by mass to 50% by mass inclusive, and particularly preferably from 10% by mass to 50% by mass inclusive.
The resin particle dispersion production method according to the present exemplary embodiment is typically used as a method for producing a resin particle dispersion for a toner.
Other examples of the application of the method include methods for producing resin particle dispersions for inkjet inks, cosmetics, powder coatings, various coatings, and electronic paper inks.
A toner production method according to an exemplary embodiment includes the steps of:
forming aggregated particles by aggregating, in a dispersion containing resin particles in a resin particle dispersion obtained by the resin particle dispersion production method according to the preceding exemplary embodiment, at least the resin particles (this step is hereinafter referred to as an aggregated particle forming step);
and fusing and coalescing the aggregated particles by heating an aggregated particle dispersion containing the aggregated particles dispersed therein to thereby form toner particles (this step is hereinafter referred to as a fusion/coalescence step).
A toner according to an exemplary embodiment contains toner particles obtained by the toner production method according to the above exemplary embodiment.
The above steps will next be described in detail. In the following description, a method for obtaining toner particles containing a coloring agent and a release agent will be described, but the coloring agent and the release agent are used optionally. Of course, additional additives other than the coloring agent and the release agent may be used.
In a resin particle dispersion preparing step, a resin particle dispersion, a coloring agent particle dispersion, and a release agent particle dispersion are prepared.
The resin particle dispersion is produced using the resin particle dispersion production method according to the preceding exemplary embodiment.
However, a resin particle dispersion other than the resin particle dispersion obtained using the resin particle dispersion production method according to the preceding exemplary embodiment may also be used.
The coloring agent particle dispersion is a dispersion obtained by dispersing a coloring agent in at least an aqueous medium.
Examples of the coloring agent include: various pigments such as carbon black, chrome yellow, Hansa yellow, benzidine yellow, threne yellow, quinoline yellow, pigment yellow, permanent orange GTR, pyrazolone orange, vulcan orange, watchung red, permanent red, brilliant carmine 3B, brilliant carmine 6B, DuPont oil red, pyrazolone red, lithol red, rhodamine B lake, lake red C, pigment red, rose bengal, aniline blue, ultramarine blue, calco oil blue, methylene blue chloride, phthalocyanine blue, pigment blue, phthalocyanine green, and malachite green oxalate; and various dyes such as acridine-based dyes, xanthene-based dyes, azo-based dyes, benzoquinone-based dyes, azine-based dyes, anthraquinone-based dyes, thioindigo-based dyes, dioxazine-based dyes, thiazine-based dyes, azomethine-based dyes, indigo-based dyes, phthalocyanine-based dyes, aniline black-based dyes, polymethine-based dyes, triphenylmethane-based dyes, diphenylmethane-based dyes, and thiazole-based dyes.
One of these coloring agents may be used alone, or two or more of them may be used in combination.
The coloring agent is dispersed in an aqueous medium using a well-known method. For example, a rotary shearing-type homogenizer, a media-type disperser such as a ball mill, a sand mill, or an attritor, or a high-pressure counter collision-type disperser may be used. The coloring agent may be dispersed in the aqueous medium using a polar ionic surfactant and using a homogenizer to thereby produce the coloring agent particle dispersion.
The volume average particle diameter of the coloring agent is preferably 1 μm or less, more preferably 0.5 μm or less, and particularly preferably from 0.01 μm to 0.5 μm inclusive.
A dispersant may be added in order to improve the dispersion stability of the coloring agent in the aqueous medium to thereby reduce the energy of the coloring agent in the toner, and examples of the dispersant include rosin, rosin derivatives, coupling agents, and polymeric dispersants.
The release agent particle dispersion is a dispersion obtained by dispersing a release agent in at least an aqueous medium.
Examples of the release agent include: hydrocarbon-based waxes; natural waxes such as carnauba wax, rice wax, and candelilla wax; synthetic and mineral/petroleum-based waxes such as montan wax; and ester-based waxes such as fatty acid esters and montanic acid esters. The release agent used is not limited to the above release agents.
One of these release agents may be used alone, or two or more of them may be used in combination.
The melting temperature of the release agent is preferably from 50° C. to 110° C. inclusive and more preferably from 60° C. to 100° C. inclusive.
The melting temperature is determined using a DSC curve obtained by differential scanning calorimetry (DSC) from “peak melting temperature” described in melting temperature determination methods in “Testing methods for transition temperatures of plastics” in JIS K7121-1987.
The release agent is dispersed in the aqueous medium using a well-known method. For example, a rotary shearing-type homogenizer, a media-type disperser such as a ball mill, a sand mill, or an attritor, or a high-pressure counter collision-type disperser may be used. The release agent may be dispersed in the aqueous medium using a polar ionic surfactant and using a homogenizer to thereby produce the release agent particle dispersion.
The volume average particle diameter of the release agent particles is preferably 1 μm or less and more preferably from 0.01 μm to 1 μm inclusive.
Next, the resin particle dispersion, the coloring agent particle dispersion, and the release agent particle dispersion are mixed.
Then the resin particles, the coloring agent particles, and the release agent particles are hetero-aggregated in the dispersion mixture to form aggregated particles containing the resin particles, the coloring agent particles, and the release agent particles and having diameters close to the diameters of target toner particles.
Specifically, for example, a flocculant is added to the dispersion mixture, and the pH of the dispersion mixture is adjusted to acidic (for example, a pH of from 2 to 5 inclusive). Then a dispersion stabilizer is optionally added, and the resulting mixture is heated to the glass transition temperature of the resin particles (specifically, for example, a temperature equal to higher than the glass transition temperature of the resin particles −30° C. and equal to or lower than the glass transition temperature −10° C.) to aggregate the particles dispersed in the dispersion mixture to thereby form aggregated particles.
In the aggregated particle forming step, for example, the flocculant is added at room temperature (e.g., 25° C.) while the dispersion mixture is agitated in a rotary shearing-type homogenizer. Then the pH of the dispersion mixture is adjusted to acidic (e.g., a pH of from 2 to 5 inclusive), and the dispersion stabilizer is optionally added. Then the resulting mixture is heated in the manner described above.
Examples of the flocculant include a surfactant with a polarity opposite to the polarity of the surfactant added to the dispersion mixture, inorganic metal salts, and divalent or higher polyvalent metal complexes. In particular, when a metal complex is used as the flocculant, the amount of the surfactant used can be reduced, and charging characteristics may be improved.
An additive that forms a complex with a metal ion in the flocculant or a similar bond may be optionally used. The additive used may be a chelating agent.
Examples of the inorganic metal salts include: metal salts such as calcium chloride, calcium nitrate, barium chloride, magnesium chloride, zinc chloride, aluminum chloride, and aluminum sulfate; and inorganic metal salt polymers such as polyaluminum chloride, polyaluminum hydroxide, and calcium polysulfide.
The chelating agent used may be a water-soluble chelating agent. Examples of the chelating agent include: oxycarboxylic acids such as tartaric acid, citric acid, and gluconic acid; iminodiacetic acid (IDA); nitrilotriacetic acid (NTA); and ethylenediaminetetraacetic acid (EDTA).
The amount of the chelating agent added is, for example, preferably from 0.01 parts by mass to 5.0 parts by mass inclusive and more preferably 0.1 parts by mass or more and less than 3.0 parts by mass based on 100 parts by mass of the resin particles.
—Fusion/Coalescence step—
Next, the aggregated particle dispersion containing the aggregated particles dispersed therein is heated, for example, to a temperature equal to or higher than the glass transition temperature of the resin particles (e.g., a temperature higher by 10° C. to 30° C. than the glass transition temperature of the resin particles) to fuse and coalesce the aggregated particles to thereby form toner particles.
The toner particles are obtained through the above-described steps.
Alternatively, the toner particles may be produced through: the step of, after the preparation of the aggregated particle dispersion containing the aggregated particles dispersed therein, mixing the aggregated particle dispersion further with the resin particle dispersion containing the resin particles dispersed therein and then causing the resin particles to adhere to the surface of the aggregated particles to aggregate them to thereby form second aggregated particles; and the step of heating a second aggregated particle dispersion containing the second aggregated particles dispersed therein to fuse and coalesce the second aggregated particles to thereby form toner particles having a core-shell structure.
After completion of the fusion/coalescence step, the toner particles formed in the solution are subjected to a well-known washing step, a solid-liquid separation step, and a drying step to obtain dried toner particles.
From the viewpoint of chargeability, the toner particles may be subjected to displacement washing with ion exchanged water sufficiently in the washing step. No particular limitation is imposed on the solid-liquid separation step. From the viewpoint of productivity, suction filtration, pressure filtration, etc. may be performed in the solid-liquid separation step. No particular limitation is imposed on the drying step. From the viewpoint of productivity, freeze-drying, flash drying, fluidized drying, vibrating fluidized drying, etc. may be performed in the drying step.
The toner according to the present exemplary embodiment is produced, for example, by adding an external additive to the dried toner particles obtained and mixing them. The mixing may be performed, for example, using a V blender, a Henschel mixer, a Loedige mixer, etc. If necessary, coarse particles in the toner may be removed using a vibrating sieving machine, an air sieving machine, etc.
Examples of the external additive include inorganic particles. Examples of the inorganic particles include particles of SiO2, TiO2, Al2O3, CuO, ZnO, SnO2, CeO2, Fe2O3, MgO, BaO, CaO, K2O, Na2O, ZrO2, CaO·SiO2, K2O. (TiO2) n, Al2O3·2SiO2, CaCO3, MgCO3, BaSO4, and MgSO4.
The surface of the inorganic particles used as the external additive may be subjected to hydrophobic treatment. The hydrophobic treatment is performed, for example, by immersing the inorganic particles in a hydrophobic treatment agent. No particular limitation is imposed on the hydrophobic treatment agent, and examples of the hydrophobic treatment agent include silane-based coupling agents, silicone oils, titanate-based coupling agents, and aluminum-based coupling agents. One of these may be used alone, or two or more of them may be used in combination.
The amount of the hydrophobic treatment agent is generally, for example, from 1 part by mass to 10 parts by mass inclusive based on 100 parts by mass of the inorganic particles.
Other examples of the external additive include resin particles (particles of resins such as polystyrene, polymethyl methacrylate (PMMA), and melamine resins) and cleaning activators (such as metal salts of higher fatty acids typified by zinc stearate and fluorine-based polymer particles).
The amount of the external additive added externally is, for example, preferably from 0.01% by mass to 5% by mass inclusive and more preferably from 0.01% by mass to 2.0% by mass inclusive relative to the mass of the toner particles.
In the toner according to the present exemplary embodiment, the toner particles may have a single layer structure or may be toner particles each having a so-called core-shell structure including a core (core particle) and a coating layer (shell layer) covering the core.
The toner particles having the core-shell structure may each include, for example: a core containing the binder resin and optional additives such as the coloring agent and the release agent; and a coating layer containing the binder resin.
The volume average particle diameter (D50v) of the toner particles is preferably from 2 μm to 10 μm inclusive and more preferably from 4 μm to 8 μm inclusive.
The volume average particle diameters of the toner particles and their grain size distribution indexes are measured using Coulter Multisizer II (manufactured by Beckman Coulter, Inc.), and ISOTON-II (manufactured by Beckman Coulter, Inc.) is used as an electrolyte.
In the measurement, 0.5 mg to 50 mg of a measurement sample is added to 2 mL of a 5% aqueous solution of a surfactant (preferably sodium alkylbenzenesulfonate) serving as a dispersant. The mixture is added to 100 mL to 150 mL of the electrolyte.
The electrolyte with the sample suspended therein is subjected to dispersion treatment for 1 minute using an ultrasonic dispersion apparatus, and then the particle size distribution of particles having diameters within the range of 2 μm to 60 μm is measured using the Coulter Multisizer II with an aperture having an aperture diameter of 100 μm. The number of particles sampled is 50,000.
The particle size distribution measured and divided into particle size ranges (channels) is used to obtain volume-based and number-based cumulative distributions computed from the small diameter side. In the computed volume-based cumulative distribution, the particle diameter at a cumulative frequency of 16% is defined as a volume-based particle diameter D16v, and the particle diameter at a cumulative frequency of 50% is defined as a volume average particle diameter D50v. The particle diameter at a cumulative frequency of 84% is defined as a volume-based particle diameter D84v. In the number-based cumulative distribution, the particle diameter at a cumulative frequency of 16% is defined as a number-based particle diameter D16p, and the particle diameter at a cumulative frequency of 50% is defined as a number average cumulative particle diameter D50p. Moreover, the particle diameter at a cumulative frequency of 84% is defined as a number-based particle diameter D84p.
These are used to compute a volume-based grain size distribution index (GSDv) defined as (D84v/D16v)1/2 and a number-based grain size distribution index (GSDp) defined as (D84p/D16p)1/2.
The average circularity of the toner particles is preferably from 0.94 to 1.00 inclusive and more preferably from 0.95 to 0.98 inclusive.
The circularity of a toner particle is determined as (the peripheral length of an equivalent circle of the toner particle)/(the peripheral length of the toner particle) [i.e., (the peripheral length of a circle having the same area as a projection image of the particle)/(the peripheral length of the projection image of the particle)]. Specifically, the average circularity is a value measured by the following method.
First, the toner particles used for the measurement are collected by suction, and a flattened flow of the particles is formed. Particle images are captured as still images using flashes of light, and the average circularity is determined by subjecting the particle images to image analysis using a flow-type particle image analyzer (FPIA-3000 manufactured by SYSMEX Corporation). The number of particles sampled for determination of the average circularity is 3500.
When the toner contains the external additive, the toner (developer) for the measurement is dispersed in water containing a surfactant, and the dispersion is subjected to ultrasonic treatment. The toner particles with the external additive removed are thereby obtained.
An electrostatic image developer according to an exemplary embodiment contains at least the toner according to the preceding exemplary embodiment.
The electrostatic image developer according to the present exemplary embodiment may be a one-component developer containing only the toner according to the preceding exemplary embodiment or a two-component developer containing the toner and a carrier.
No particular limitation is imposed on the carrier, and a well-known carrier may be used. Examples of the carrier include: a coated carrier prepared by coating the surface of a core material formed of a magnetic powder with a coating resin; a magnetic powder-dispersed carrier prepared by dispersing a magnetic powder in a matrix resin; and a resin-impregnated carrier prepared by impregnating a porous magnetic powder with a resin.
In each of the magnetic powder-dispersed carrier and the resin-impregnated carrier, the particles included in the carrier may be used as cores, and the cores may be coated with a coating resin.
Examples of the present disclosure will be described. However, the present disclosure is not limited to these
Examples. In the following description, “parts” and “%” are all based on mass, unless otherwise specified.
The above materials are placed in a flask equipped with a stirrer, a nitrogen introduction tube, a temperature sensor, and a rectifying column. The temperature of the mixture is increased to 220° C. in a nitrogen flow over 1 hour, and 1 part of titanium tetraethoxide is added to 100 parts of the above materials. While water generated is removed by evaporation, the temperature of the mixture is increased to 240° C. over 0.5 hours. A dehydration condensation reaction is continued at 240° C. for 1 hour, and the reaction product is cooled. An amorphous polyester resin (1) having an acid value of 8.0 mg KOH/g, a weight average molecular weight of 139000, and a glass transition temperature of 60° C. is thereby obtained. <Synthesis of amorphous polyester resin (2)>
The same procedure as for the amorphous polyester resin (1) is repeated except that the amount of the ethylene glycol is changed to 40 parts and the amount of the 1,5-pentanediol is changed to 45 parts to thereby obtain an amorphous polyester resin (2) having an acid value of 12.0 mg KOH/g, a weight average molecular weight of 127000, and a glass transition temperature of 59° C.
The same procedure as for the amorphous polyester resin (1) is repeated except that the amount of the ethylene glycol is changed to 36 parts and the amount of the 1,5-pentanediol is changed to 39 parts to thereby obtain an amorphous polyester resin (3) having an acid value of 20.0 mg KOH/g, a weight average molecular weight of 116000, and a glass transition temperature of 58° C.
<Synthesis of amorphous polyester resin (4)>
The same procedure as for the amorphous polyester resin (1) is repeated except that the amount of the ethylene glycol is changed to 50 parts and the amount of the 1,5-pentanediol is changed to 48 parts to thereby obtain an amorphous polyester resin (4) having an acid value of 7.5 mg KOH/g, a weight average molecular weight of 142000, and a glass transition temperature of 62° C. <Synthesis of amorphous polyester resin (5)>
The same procedure as for the amorphous polyester resin (1) is repeated except that the amount of the ethylene glycol is changed to 34 parts and the amount of the 1,5-pentanediol is changed to 38 parts to thereby obtain amorphous polyester resin (5) having an acid value of 20.5 mg KOH/g, a weight average molecular weight of 114000, and a glass transition temperature of 57° C.
The above materials are placed in a flask equipped with a stirrer, a nitrogen introduction tube, a temperature sensor, and a rectifying column. The temperature of the mixture is increased to 220° C. in a nitrogen flow over 1 hour, and 1 part of titanium tetraethoxide is added to 100 parts of the above materials. While water generated is removed by evaporation, the temperature of the mixture is increased to 240° C. over 0.5 hours. A dehydration condensation reaction is continued at 240° C. for 1 hour, and the reaction product is cooled. An amorphous polyester resin (6) having an acid value of 12.5 mg KOH/g, a weight average molecular weight of 131000, and a glass transition temperature of 60° C. is thereby obtained.
A reaction bath equipped with a stirrer, a condenser, and a thermometer is charged with 60 kg of ethyl acetate used as the organic solvent B, 24 kg of isopropanol used as the organic solvent C, and 100 kg of the polyester resin (2) used as the resin. Then the mixture is stirred at 50° C. for 30 minutes to dissolve the resin. 3.3 kg of 10% by mass ammonia water used as the neutralizer is added to the obtained solution such that the rate of neutralization is 90%. Then 500 kg of pure water at 40° C. is gradually added to the resulting mixture to subject the mixture to phase inversion emulsification to thereby obtain a phase-inverted emulsion (1). After completion of the dropwise addition, the phase-inverted emulsion is returned to 25° C., and the organic solvent is removed from the phase-inverted emulsion under reduced pressure. Then the resulting phase-inverted emulsion is caused to pass through a sieve to thereby obtain an amorphous polyester resin particle dispersion (1-1).
Amorphous polyester resin particle dispersions in Examples are obtained using the same procedure as in Example 1 except that conditions shown in Table 1 are used.
An amorphous polyester resin particle dispersion is obtained using the same procedure as in Examples 1 except that the organic solvent B is changed to methyl ethyl ketone.
An amorphous polyester resin particle dispersion is obtained using the same procedure as in Example 1 except that 15 kg of a 20% aqueous sodium dodecylbenzene sulfonate solution is added to the amorphous polyester resin particle dispersion caused to pass through the sieve.
The volume average and number average particle diameters of the resin particles in the resin particle dispersion in each of the Examples are measured as follows. A particle size distribution measured using a laser diffraction particle size measurement apparatus (LA-700 manufactured by HORIBA Ltd.) is used and divided into different particle diameter ranges (channels), and volume-based and number-based cumulative distributions are computed from the small diameter side. The particle diameter at which the cumulative frequency is 50% relative to the total volume of the particles is defined as a volume average particle diameter D50v, and the particle diameter at which the cumulative frequency is 50% relative to the total number of particles is defined as a number average particle diameter D50p.
The particle size distribution is computed as the ratio of the volume average particle diameter D50v to the number average particle diameter D50p (D50v/D50p) and evaluated according to the following criteria.
A◯: The ratio of the volume average particle diameter D50v to the number average particle diameter D50p is 1 or more and less than 1.3.
BΔ: The ratio of the volume average particle diameter D50v to the number average particle diameter D50p is 1.3 or more and less than 1.5.
C×: The ratio of the volume average particle diameter D50v to the number average particle diameter D50p is 1.5 or more.
The weight of the resin particle dispersion caused to pass through the sieve with a mesh size of 20 μm and the concentration of solids are used to compute the amount of the resin particles, and the amount of the resin particles is divided by the amount of the resin used for the phase inversion emulsification to compute the yield. The yield is evaluated according to the following criteria.
A◯: The yield is 99% or more.
BΔ: The yield is 98% or more.
C×: The yield is less than 98%.
The storage stability of the resin particle dispersion is evaluated as follows. The resin particle dispersion placed in a sealed container is stored in a thermostatic bath at 50° C. and left to stand for one month. Then the temperature is reduced to 30° C., and the pH of the resin particle dispersion is reduced to 3. The storage stability is evaluated according to the following criteria.
A+⊙: The particle size distribution is not changed even after the pH has been reduced to 3.
A◯: The particle size and the particle size distribution are not changed after the resin particle dispersion has been stored and left to stand for one month.
BΔ: The ratio of the volume average particle diameter D50v to the number average particle diameter D50p after the resin particle dispersion has been stored and left to stand for one month is 1.3 or more and less than 1.5.
C×: The ratio of the volume average particle diameter D50v to the number average particle diameter D50p after the resin particle dispersion has been stored and left to stand for one month is 1.5 or more.
As can be seen from the above results, in each of the Examples, the yield is higher than that in the Comparative Examples, and the resin particle dispersion obtained contains resin particles having a narrower particle size distribution.
The foregoing description of the exemplary embodiments of the present disclosure has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the disclosure and its practical applications, thereby enabling others skilled in the art to understand the disclosure for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the disclosure be defined by the following claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-054286 | Mar 2021 | JP | national |
