JP7797117B2 - Method for producing a slurry composition - Google Patents

Description

The present invention relates to a method for producing a slurry composition, a slurry composition, and a dispersant.

Slurried powders for electronic materials are used in the production of electronic components such as multilayer ceramic capacitors. For example, a slurry composition of dielectric ceramic powder is used as a material for forming the dielectric ceramic layers of multilayer ceramic capacitors. As electronic devices, such as mobile phones, and their electronic components become more compact and perform better, there is a demand for slurry compositions with improved handleability. For example, the miniaturization of multilayer ceramic capacitors requires thinner dielectric ceramic layers, and there is a demand for slurry compositions of dielectric ceramic powder with improved dispersibility and workability.
In addition, a slurry composition in which a catalyst for treating automobile exhaust gas is dispersed in a dispersion medium is used in the manufacture of an automobile exhaust gas purification device. As regulations on automobile exhaust gases become stricter, there is a demand for a slurry composition with improved dispersibility.

Polycarboxylic acid (co)polymers are known as one of the dispersants for powders.
Patent Document 1 discloses a viscosity reducer for a slurry of an exhaust gas purification catalyst, which contains a copolymer composed of (meth)acrylic acid (A) units and (meth)acrylic acid alkoxypolyoxyalkylene ester (B) units, and the content of (A) units is 50 to 70 mol % and the content of (B) units is 50 to 30 mol %.
Patent Document 2 discloses a viscosity reducer for a slurry of an exhaust gas purification catalyst, which contains a copolymer composed of (meth)acrylic acid (A) units and (meth)acrylic acid alkoxypolyoxyalkylene ester (B) units, and the content of (A) units is 80 to 97 mol % and the content of (B) units is 3 to 20 mol %.
Patent Document 3 discloses a cement additive that contains a carboxylic acid copolymer having a structural unit (I) derived from an unsaturated polyalkylene glycol monomer (a) and a structural unit (II) derived from an unsaturated carboxylic acid monomer (b), and an alkanolamine compound, in which the content of the structural unit (I) and the structural unit (II) is 60 mol % or less.
Patent Document 4 discloses a method for producing a polycarboxylic acid polymer, which comprises a step of polymerizing a polyoxyalkylene monoalkyl ether with (meth)acrylic acid to obtain a polycarboxylic acid polymer.
Patent Document 5 discloses a method for producing a hydrophilic copolymer for a cement admixture, which includes a reaction step of reacting a predetermined unsaturated acid compound with a predetermined polyether compound to obtain a hydrophilic polymer for a cement admixture.
Patent Document 6 discloses that a copolymer mixture obtained by copolymerizing a monomer (A1) such as an ethylenically unsaturated carboxylic acid derivative having a polyoxyalkylene group with a monomer (A2) such as (meth)acrylic acid is used as a dispersant for coal slurry.

JP 2014-105222 A JP 2017-148780 A International Publication No. 2017/033590 JP 2014-152187 A JP 2011-213537 A Japanese Patent Application Laid-Open No. 2003-003180

For example, in fields such as fine ceramics applied to electronic components, attempts are being made to achieve miniaturization, higher speed, lower power consumption, higher efficiency, and higher capacity of electronic components by controlling their nanoscale microstructure. Also, in the field of catalysts, such as catalysts for treating automobile exhaust gases, attempts are being made to improve catalytic activity by controlling their nanoscale microstructure. In these fields, there is a high demand for nano-dispersion technology of powders in dispersion media such as water, and further improvements in the performance of dispersants are being sought.
Therefore, the present invention provides a slurry composition that exhibits excellent dispersion effects over a wide pH range, maintains these effects over time, and enables control of the fine structure of the powder.

The present invention provides a method for producing a slurry composition by mixing a dispersant, a powder, and a dispersion medium,
The dispersant relates to a method for producing a slurry composition, wherein the dispersant comprises a copolymer containing a structural unit derived from an (alkoxy)polyalkylene glycol (meth)acrylate [hereinafter referred to as structural unit (I)] and a structural unit derived from (meth)acrylic acid [hereinafter referred to as structural unit (II)], wherein the proportion of structural unit (II) is more than 10 mass% and less than 50 mass%, where the total of structural units (I) and (II) is 100 mass%, and the metal ion content in the copolymer is 100 ppm or less.

The present invention provides a slurry composition comprising a dispersant, a powder, and a dispersion medium,
The dispersant comprises a copolymer containing a structural unit derived from an (alkoxy)polyalkylene glycol (meth)acrylate [hereinafter referred to as structural unit (I)] and a structural unit derived from (meth)acrylic acid [hereinafter referred to as structural unit (II)], wherein the proportion of structural unit (II) is more than 10% by mass and less than 50% by mass, where the total of structural units (I) and (II) is 100% by mass, and the metal ion content in the copolymer is 100 ppm or less,
The slurry composition relates to a slurry composition in which the blending amount of the dispersant relative to the powder is 0.05% by mass or more and 3.0% by mass or less, calculated as the copolymer contained in the dispersant.

The present invention relates to a dispersant that includes a copolymer containing a structural unit derived from an (alkoxy)polyalkylene glycol (meth)acrylate [hereinafter referred to as structural unit (I)] and a structural unit derived from (meth)acrylic acid [hereinafter referred to as structural unit (II)], wherein the proportion of structural unit (II) is more than 10% by mass and less than 50% by mass, where the total of structural units (I) and (II) is 100% by mass, and the metal ion content in the copolymer is 100 ppm or less.

The present invention provides a slurry composition that exhibits excellent dispersion effects over a wide pH range, maintains these effects over time, and enables control of the powder microstructure.

The reason why the dispersant of the present invention can disperse powders well in a dispersion medium such as water is not clear, but the reason is thought to be as follows.
The copolymer contained in the dispersant of the present invention is thought to exhibit electrostatic repulsion at the (meth)acrylate moiety and further exhibit steric repulsion at the (alkoxy)polyalkylene glycol (meth)acrylate moiety. In the present invention, by setting the mass ratio of the (meth)acrylic acid moiety to the (alkoxy)polyalkylene glycol (meth)acrylate moiety in the copolymer within the optimal mass ratio range, it is thought that efficient dispersion stabilization can be achieved over a wide range, for example, from the acid side of pH 4 to 10 to the basic side. Within this optimal mass ratio range, dispersion stabilization of the powder can be achieved, and as a result, change in slurry viscosity over time is thought to be extremely small.
On the other hand, even if the copolymer is within this optimum mass ratio range, when the dispersant containing more than 100 ppm of metal ions in the copolymer is used to make a slurry composition, the dispersant containing the copolymer is adsorbed on the powder surface such as alumina powder immediately after the production of the slurry composition, and maintains dispersibility, but as time passes, the metal ions in the system approach the anion part (methacrylic acid) of the dispersant and become hydrated, so that the dispersant is removed from the powder, and the slurry composition is thought to thicken.However, these are only speculations, and the present invention is not limited to these mechanisms.

The present invention provides a method for producing a slurry composition (hereinafter referred to as the slurry composition of the present invention) by mixing a dispersant, a powder, and a dispersion medium,
The dispersant relates to a method for producing a slurry composition, wherein the dispersant comprises a copolymer containing a structural unit derived from an (alkoxy)polyalkylene glycol (meth)acrylate [hereinafter referred to as structural unit (I)] and a structural unit derived from (meth)acrylic acid [hereinafter referred to as structural unit (II)], wherein the proportion of structural unit (II) is more than 10 mass% and less than 50 mass%, where the total of structural units (I) and (II) is 100 mass%, and the metal ion content in the copolymer is 100 ppm or less.
In addition, (meth)acrylic acid means acrylic acid or methacrylic acid, (alkoxy) means a structure that includes or does not include an alkoxy group, and (meth)acrylate means acrylate or methacrylate (the same applies hereinafter).

First, we will provide a detailed description of the dispersant, powder, and dispersion medium that are mixed into the slurry composition of the present invention.

<Dispersant>
The dispersant of the present invention contains a copolymer containing structural units (I) and (II) (hereinafter also referred to as the copolymer of the present invention), in which the proportion of structural unit (II) is more than 10% by mass and less than 50% by mass, where the total of structural units (I) and (II) is 100% by mass, and the metal ion content in the copolymer of the present invention is 100 ppm or less.

The structural unit (I) is a structural unit derived from (alkoxy)polyalkylene glycol (meth)acrylate (hereinafter sometimes referred to as monomer (I)).

The alkoxy group of monomer (I) has, for example, one or more carbon atoms and preferably eight or fewer, more preferably six or fewer. Incidentally, alkoxy groups include unsaturated groups. The alkylene oxide in the polyalkylene glycol of monomer (I) preferably has two or more and four or fewer carbon atoms, and is more preferably ethylene oxide. The average number of added moles of alkylene oxide in the polyalkylene glycol is preferably four or more, more preferably six or more, even more preferably eight or more, even more preferably 12 or more, even more preferably 13 or more, and preferably 90 or fewer, more preferably 70 or fewer, even more preferably 50 or fewer, even more preferably 45 or fewer, even more preferably 35 or fewer, and even more preferably 25 or fewer.

Examples of monomer (I) include (alkoxy)polyethylene glycol (meth)acrylate. From the viewpoint of reducing the viscosity of the slurry composition, the average number of moles of ethylene oxide added to the polyethylene glycol in the (alkoxy)polyethylene glycol (meth)acrylate is preferably 4 or more, more preferably 6 or more, even more preferably 8 or more, even more preferably 12 or more, even more preferably 13 or more, and preferably 90 or less, more preferably 70 or less, even more preferably 50 or less, even more preferably 45 or less, even more preferably 35 or less, even more preferably 25 or less.

Examples of the monomer (I) include a monomer represented by the following general formula (I).
R ¹¹ -O-(AO) _n -CO-C(R ¹² )=CH ₂ (I)
[In the formula, R ¹¹ is a hydrogen atom or a hydrocarbon group having from 1 to 8 carbon atoms, preferably an alkyl group or an alkenyl group, more preferably an alkyl group; R ¹² is a methyl group or a hydrogen atom; AO is an alkyleneoxy group having from 2 to 4 carbon atoms, preferably 2 or 3 carbon atoms; and n is the average number of moles of AO added, which is from 4 to 90.]

In general formula (I), the average number of moles of AO added, n, is 4 or more, preferably 6 or more, more preferably 8 or more, even more preferably 12 or more, even more preferably 13 or more, and is 90 or less, preferably 70 or less, more preferably 50 or less, even more preferably 45 or less, even more preferably 35 or less, even more preferably 25 or less.

The structural unit (II) in the copolymer is a structural unit derived from (meth)acrylic acid (hereinafter sometimes referred to as monomer (II)).

The (meth)acrylic acid monomer (II) may be a compound represented by the following general formula (II). The carboxy group of the monomer (II) may be an acid, or a portion of the carboxy group may be a salt. When the monomer (II) is a salt, examples of the salt include an ammonium salt and an alkanolammonium salt. The alkanolammonium salt is formed, for example, by neutralizing the monomer (II) whose carboxy group is an acid with an alkanolamine.
CH ₂ =C(R ²¹ )-COOM (II)
[In the formula, ^R21 represents a methyl group or a hydrogen atom, and M represents a hydrogen atom or a counter ion.]

In general formula (II), when M is a counter ion, M may be one or more selected from inorganic ions such as alkali metal ions, alkaline earth metal ions, and ammonium ions, and organic amine ions, and is preferably one or more selected from ammonium ions and alkanolammonium ions. Monomer (II) may be a salt with an inorganic base or a salt with an organic base. However, when monomer (II) is a salt with an inorganic base, the metal ion content in the copolymer is 100 ppm or less, preferably 50 ppm or less, and more preferably 10 ppm or less.

In the copolymer of the present invention, the proportion of structural unit (I) is preferably more than 50% by mass, more preferably 53% by mass or more, even more preferably 60% by mass or more, and preferably less than 90% by mass, more preferably 88% by mass or less, even more preferably 85% by mass or less, based on the total of structural units (I) and (II) being 100% by mass.

In the copolymer of the present invention, the proportion of structural unit (II) is greater than 10% by mass, preferably 12% by mass or more, more preferably 15% by mass or more, and less than 50% by mass, preferably 47% by mass or less, more preferably 40% by mass or less, based on the total of structural units (I) and (II) being 100% by mass.

The copolymer of the present invention may contain a structural unit derived from a monomer other than the monomers (I) and (II) (hereinafter referred to as "monomer (III)"). Examples of the monomer (III) include α-olefins, styrenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyl alcohol, maleic anhydride, maleic acid, itaconic acid, styrene, benzyl methacrylate, and vinylbenzyl alcohol.
When the copolymer of the present invention contains a structural unit derived from monomer (III), the amount of monomer (III) is preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 15% by mass or less, still more preferably 1% by mass or less, and more preferably more than 0% by mass, of all structural units.
Furthermore, when the copolymer of the present invention contains a structural unit containing an aromatic group, the content of the structural unit containing an aromatic group in the copolymer of the present invention is preferably 3% by mass or less, and more preferably a copolymer in which the content of the structural unit containing an aromatic ring is 3% by mass or less and the weight average molecular weight is 10,000 or more and 80,000 or less.

In the copolymer of the present invention, the total proportion of structural units (I) and (II) among all structural units is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 85% by mass or more, and preferably 100% by mass or less, and may even be 100% by mass.

From the viewpoint of reducing the viscosity of the slurry composition and improving the dispersibility of the powder particles used during charging, the weight-average molecular weight (Mw) of the copolymer of the present invention is preferably 10,000 or more, more preferably 14,000 or more, even more preferably 18,000 or more, and preferably 80,000 or less, more preferably 70,000 or less, even more preferably 60,000 or less. The weight-average molecular weight of the copolymer is a value measured by GPC (gel permeation chromatography). Specifically, the weight-average molecular weight of the copolymer can be measured under the following conditions.

[Method for measuring weight average molecular weight of copolymer]
Column: TSK (α-M) + (α-M) (both manufactured by Tosoh Corporation)
Column temperature: 40°C
Detector: RI or UV (210 nm)
Eluent: 60 mmol/L phosphate buffer/dimethylformamide (1/9)
Flow rate: 1.0mL/min
Injection volume: 0.1mL
Standard: Polystyrene (molecular weight: 2,000 to 10,000,000)

In order to maintain dispersibility over time, the content of metal ions in the copolymer of the present invention is 100 ppm or less (mass ratio, the same applies hereinafter), preferably 50 ppm or less, more preferably 10 ppm or less.
Examples of metal ions include alkali metal ions, alkaline earth metal ions, and light metal ions such as aluminum ions, and more specifically, sodium ions, potassium ions, calcium ions, magnesium ions, and aluminum ions.

The copolymer of the present invention is in the form of an acid or a salt. When the copolymer of the present invention is in the form of a salt, at least the structural unit (II) is in the form of a salt. The copolymer of the present invention may be one or more salts selected from inorganic base salts such as ammonium salts and organic base salts such as organic amine salts. However, when the copolymer is in the form of an inorganic base salt, the metal ion content in the copolymer satisfies the above range.
From the viewpoint of improving dispersibility, the degree of neutralization of the copolymer of the present invention is preferably 40 mol % or more, more preferably 50 mol % or more, and even more preferably 60 mol % or more, where the degree of neutralization is expressed as [molar equivalent of neutralized acid groups in the copolymer/molar equivalent of all acid groups that can be neutralized in the copolymer]×100 (mol %).
As long as the above-mentioned condition for the degree of neutralization is satisfied, the degree of neutralization or excess alkalinity when multiple salts of the copolymer of the present invention are used is not particularly limited, but from the viewpoint of chemical decomposition resistance and odor resistance of the powder component, it is preferably 45 mol% or more, more preferably 55 mol% or more, even more preferably 65 mol% or more, and preferably 120 mol% or less, more preferably 110 mol% or less, and even more preferably 105 mol% or less. Here, the excess alkalinity indicates that [the molar equivalents of neutralized acid groups in the copolymer/the molar equivalents of all acid groups that can be neutralized in the copolymer] is greater than 1. A range in which the mol% is greater than 100 mol% is indicated as excess alkalinity.

The dispersant of the present invention may be in liquid form, or may be in liquid form containing the copolymer of the present invention in water. Examples of dispersants include liquid dispersants containing the copolymer of the present invention and water.

When the dispersant of the present invention is a liquid dispersant, for example, a liquid dispersant containing water, the pH of the dispersant of the present invention at 20°C is preferably 1.5 or higher, more preferably 1.7 or higher, even more preferably 2.0 or higher, and preferably 11.0 or lower, more preferably 10.0 or lower, even more preferably 9.0 or lower, from the viewpoint of chemical decomposition resistance and odor resistance of the powder component.

From the viewpoint of reducing the viscosity of the slurry composition, the dispersant of the present invention preferably contains 20% by mass or more, more preferably 25% by mass or more, even more preferably 30% by mass or more, and preferably 55% by mass or less, more preferably 50% by mass or less, even more preferably 45% by mass or less, of the copolymer of the present invention. The dispersant may be a dispersant consisting of the copolymer of the present invention.

The dispersant of the present invention may contain the copolymer of the present invention in a proportion of 30% by mass or more, more preferably 35% by mass or more, even more preferably 40% by mass or more, and preferably 100% by mass or less, more preferably 80% by mass or less, even more preferably 70% by mass or less, of the solid content of the dispersant. The dispersant of the present invention may contain 100% by mass of the copolymer of the present invention in a proportion of the solid content of the dispersant. Here, the solid content of the dispersant may include components other than water.

In addition to the copolymer of the present invention, the dispersant of the present invention can contain optional components such as nonionic surfactants, anionic surfactants, inorganic salts, and organic salts. However, when the dispersant contains these optional components, the metal ion content in the copolymer is used in a range of 100 ppm or less, preferably 50 ppm or less, and more preferably 10 ppm or less. Similarly, the slurry composition of the present invention can contain these optional components. However, when the slurry composition contains these optional components, the metal ion content in the slurry composition is used in a range of preferably 1 ppm or less, more preferably 0.7 ppm or less, and even more preferably 0.5 ppm or less.

<Powder>
The powder may be a water-insoluble powder. The term "water-insoluble" refers to a powder that dissolves in 100 g of water at 20° C. in an amount of 0.1 g or less. Examples of the powder include water-insoluble salts such as carbonates, phosphates, titanates, silicates, and manganates; metal oxides such as zinc oxide, iron oxide, titanium oxide, alumina (aluminum oxide), silica (silicon oxide), magnesium oxide, zirconium oxide, and cerium oxide; metal hydroxides such as nickel hydroxide; carbon black, silicon carbide, aluminum nitride, and boron nitride.
The powder may vary depending on the application of the slurry composition, but examples thereof include powders for electronic materials, catalyst powders, abrasive powders, and powders for manufacturing primary or secondary batteries.
Examples of electronic material powders include powders used in the production of electronic components such as IC packages, wiring boards, insulators, sensors, electrodes, magnetic materials, semiconductors, capacitors, and optical fibers. Examples of catalyst powders include catalyst powders for treating automobile exhaust gases that treat exhaust gases from gasoline-powered vehicles, diesel-powered vehicles, and hybrid vehicles (for example, catalyst powders in which a noble metal such as platinum, palladium, or rhodium is attached to the surface of a carrier such as cerium oxide or alumina). Examples of abrasive powders include powders of silica or cerium oxide, and examples of powders for producing primary or secondary batteries include powders of manganate, cobaltate, and nickel hydroxide.

From the viewpoint of improving dispersibility, the average particle size of the powder is preferably 60 nm or more, more preferably 80 nm or more, and even more preferably 100 nm or more. From the viewpoint of improving dispersibility, it is preferably 700 nm or less, more preferably 600 nm or less, and even more preferably 500 nm or less. The average particle size of the powder can be measured using a laser scattering particle size analyzer (LA-920, manufactured by Horiba, Ltd.).

<Dispersion medium>
The dispersion medium is preferably water. The dispersion medium is preferably a dispersion medium containing water. Examples of the dispersion medium include water and a mixed solution of water and a water-soluble organic compound. The water-soluble organic compound may be an organic compound that dissolves in an amount of 100 g or more in 100 g of water at 20°C.
The content of water in the dispersion medium is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and may be 100% by mass or less, 98% by mass or less, or 95% by mass or less. Examples of water include distilled water, ion-exchanged water, and ultrapure water. Examples of water-soluble organic compounds include ethyl alcohol and ethylene glycol.

<Slurry Composition>
The slurry composition of the present invention is a slurry composition comprising the above-mentioned dispersant, powder, and dispersion medium, wherein the dispersant comprises a copolymer containing structural units (I) and (II), and the proportion of structural unit (II) is greater than 10% by mass and less than 50% by mass, where the total of structural units (I) and (II) is 100% by mass. The metal ion content in the copolymer is 100 ppm or less, and the amount of dispersant relative to the powder is 0.05% by mass or more and 3.0% by mass or less, calculated as the copolymer contained in the dispersant. The slurry composition of the present invention may be a slurry composition containing the above-mentioned dispersant, powder, and dispersion medium. The preferred amount of the slurry composition can be considered as the preferred content of the slurry composition.

From the viewpoint of reducing the viscosity of the slurry composition, the amount of dispersant blended relative to the powder, calculated as the copolymer contained in the dispersant, is 0.05% by mass or more, preferably 0.07% by mass or more, more preferably 0.1% by mass or more, and 3.0% by mass or less, preferably 1.0% by mass or less, more preferably 0.4% by mass or less.

In the slurry composition of the present invention, the amount of powder blended into all components in the slurry composition is not particularly limited, but from the viewpoint of improving drying efficiency and productivity, it is preferably 68% by mass or more, more preferably 72% by mass or more, even more preferably 76% by mass or more, and preferably 85% by mass or less. The powder may be a raw material powder blended into the slurry composition.

In the slurry composition of the present invention, the content of dispersed particles is preferably 68% by mass or more, more preferably 72% by mass or more, even more preferably 76% by mass or more, and preferably 85% by mass or less, from the viewpoint of improving drying efficiency and productivity. The content of dispersed particles may be the content of the raw material powder. Furthermore, in a slurry composition, the remainder of the dispersed particles can usually be considered to be the content of the dispersion medium.

In order to maintain dispersibility over time, the metal ion content in the slurry composition of the present invention is preferably 1 ppm or less, more preferably 0.7 ppm or less, even more preferably 0.5 ppm or less, and even more preferably 0.15 ppm or less.

The viscosity of the slurry composition of the present invention at 25°C may be, for example, 60 mPa·s or more, further 70 mPa·s or more, further 100 mPa·s or more, and 890 mPa·s or less, further 600 mPa·s or less, and further 400 mPa·s or less. This viscosity can be measured using a B-type viscosity measuring device TVB-10 manufactured by Toki Sangyo Co., Ltd. at a rotor rotation speed of 3 to 60 rpm. If the viscosity of the slurry composition is within the above range, it can be preferably used as a slurry composition for producing electronic components, catalysts for treating automobile exhaust gases, etc., enabling the production of high-quality electronic components, catalysts for treating automobile exhaust gases, etc.

<Method of producing dispersant>
The dispersant of the present invention and the method for producing the copolymer contained in the dispersant will be described in detail. Note that the method for producing the dispersant and copolymer of the present invention are not limited to the described embodiments. Preferred embodiments of the dispersant and copolymer in the method for producing the dispersant and copolymer of the present invention are the same as the preferred embodiments of the dispersant and copolymer of the present invention described above. The preferred content of the copolymer, etc. in the dispersant of the present invention can be applied by replacing it with the preferred blending amount in the production of the dispersion medium. Furthermore, the preferred ratio of the structural units constituting the copolymer of the present invention can be applied by replacing it with the preferred blending amount of the monomer in the production of the copolymer of the present invention.

Here, we will explain in detail the method for producing the copolymer of the present invention. The copolymer of the present invention can be produced in a reaction system containing water as a reaction medium. After the reaction, the resulting mixture containing the copolymer of the present invention can be used as is as the dispersant of the present invention.

First, ion-exchanged water is charged as a solvent into a reaction vessel equipped with a stirrer, thermometer, reflux condenser, nitrogen inlet tube, and dropping funnel. The mixture is heated under a nitrogen stream and then maintained at the temperature. Next, the monomers, persulfate aqueous solution, and chain transfer agent, which have been mixed and dissolved in advance, are added dropwise from separate dropping funnels over a predetermined time period to carry out the polymerization reaction. After the addition is complete, the mixture is aged for a predetermined time (the persulfate aqueous solution is added after a predetermined time has elapsed since the start of aging, for example, 15 minutes), and the polymerization reaction is completed. Subsequently, while maintaining the temperature, a neutralizing agent is added dropwise to neutralize the mixture to a pH of 6-7, thereby obtaining the copolymer of the present invention. When the copolymer is used in the form of an acid, the acid copolymer can be used as the dispersant of the present invention without adding the neutralizing agent dropwise. In this case, the pH of the dispersant is, for example, about 2.

The polymerization reaction is preferably carried out using a polymerization initiator to easily initiate and accelerate the polymerization, such as hydrogen peroxide or ammonium persulfate.
A chain transfer agent may be further added to the polymerization reaction, such as isopropyl alcohol, 2-mercaptoethanol, mercaptomalic acid, mercaptoglycerol, 3-mercaptopropionic acid, butyl mercaptan, and ammonium hypophosphite.

From the viewpoint of ease of control of the molecular weight of the copolymer, a polymerization method in which each agent is charged into a dropping funnel and added dropwise at a predetermined time is preferred. To facilitate the reaction, the temperature during polymerization and subsequent aging is preferably 75°C or higher, more preferably 78°C or higher, even more preferably 81°C or higher, and preferably 110°C or lower, more preferably 105°C or lower, and even more preferably 100°C or lower.

Neutralizing agents added to neutralize the copolymer to form a salt include, for example, amines and ammonium compounds. Examples of amine and ammonium compounds include monoethanolamine, diethanolamine, triethanolamine, ethylenediamine, diethylenetriamine, triethylamine, tributylamine, tetramethylammonium hydroxide, triethylmethylammonium hydroxide, and aqueous ammonia solution.

The dispersant of the present invention reduces the viscosity of a slurry composition containing a powder and a dispersion medium, and provides excellent long-term stability for a slurry composition containing fine dispersed particles. The dispersant of the present invention can be used to disperse, for example, powders for electronic materials, powders for abrasives, catalyst powders for automobile exhaust gas treatment, and powders for primary or secondary batteries in a dispersion medium. The dispersant of the present invention is particularly suitable for dispersing powders used as powders for electronic materials.

<Method for producing slurry composition>
The method for producing a slurry composition of the present invention will be described in detail. The above-mentioned dispersant, powder, and dispersion medium can be preferably used for producing the slurry composition. The preferred blending amount of the slurry composition is the preferred blending amount in the method for producing the slurry composition, and the preferred content of the slurry composition can be applied by replacing the blending amount in the method for producing the slurry composition.

The present invention provides a method for producing a slurry composition, which includes the steps of mixing the dispersant of the present invention, a powder, and a dispersion medium, and dispersing the powder in the dispersion medium. The present invention also provides a method for producing a slurry composition, which includes the steps of mixing the copolymer of the present invention, a powder, and the dispersion medium of the present invention, and dispersing the powder in the dispersion medium.

The slurry composition of the present invention can be produced, for example, by adding a powder to an aqueous solution containing the dispersant of the present invention, followed by stirring and mixing, or by adding a dispersion medium and the dispersant of the present invention to the powder, followed by stirring and mixing. A common stirring device can be used to stir and mix the slurry composition of the present invention. Examples of stirring devices include a homodisper, homomixer, ball mill, bead mill, or paint shaker. The stirring temperature of the slurry composition is preferably 20°C or higher, more preferably 23°C or higher, even more preferably 25°C or higher, and preferably 60°C or lower, more preferably 50°C or lower, and even more preferably 40°C or lower, from the viewpoint of easily mixing the dispersant of the present invention and the powder.

The method for producing the slurry composition of the present invention may be a method for producing a slurry composition by simultaneously grinding and slurrying coarse powder particles having a number-average particle size of 10 μm or more. Specifically, one example is a method in which a dispersion medium and the dispersant of the present invention are added to the coarse powder particles, and the particles are simultaneously ground and slurried. A typical stirring device can be used in the method for simultaneously grinding and slurrying the coarse powder particles. Examples of stirring devices include a bead mill or a paint shaker. The stirring temperature for the slurry composition is preferably 20°C or higher, more preferably 23°C or higher, even more preferably 25°C or higher, and preferably 60°C or lower, more preferably 50°C or lower, and even more preferably 40°C or lower, from the viewpoint of easily mixing the aqueous dispersant of the present invention with the powder.

In the slurry composition of the present invention, the average particle size of the powder is preferably 70 nm or more, more preferably 100 nm or more, and even more preferably 200 nm or more, from the viewpoint of improving dispersibility. Also, from the viewpoint of improving dispersibility, it is preferably 1000 nm or less, more preferably 800 nm or less, and even more preferably 700 nm or less. The average particle size of the powder in the slurry composition can be measured using a laser scattering particle size analyzer (LA-920, manufactured by Horiba, Ltd.). The average particle size of the powder in the slurry composition may be the average particle size of dispersed particles in the slurry composition.

<Method for dispersing powder>
The present invention provides a method for dispersing a powder, the method comprising the step of dispersing the powder in a dispersion medium using a dispersant that includes a copolymer containing structural units (I) and (II), wherein the proportion of structural unit (II) is more than 10 mass% and less than 50 mass%, where the total of structural units (I) and (II) is 100 mass%, and the metal ion content in the copolymer is 100 ppm or less.

Preferred embodiments of the dispersant, powder, dispersion medium, etc. in the powder dispersion method of the present invention are the same as those described above for the dispersant, powder, dispersion medium, slurry composition, and method for producing a slurry composition of the present invention.

As described above, the dispersant of the present invention can, for example, improve the dispersibility of powders in a slurry composition and reduce the viscosity of the slurry composition, thereby improving the workability of operations using the slurry composition. This can contribute, for example, to improved productivity in each manufacturing process, improved catalytic activity, and the miniaturization, speedup, reduced power consumption, increased efficiency, and increased capacity of electronic components.

The slurry composition, dispersant, method for producing a slurry composition, method for producing a dispersant, and method for dispersing powder of the present invention can be used in applications such as semiconductor manufacturing processes, electronic material manufacturing processes, fine ceramic manufacturing processes, automobile exhaust gas treatment device manufacturing processes, catalyst manufacturing processes, primary or secondary battery manufacturing processes, and water-soluble printing ink manufacturing processes.

The slurry composition of the present invention may be a slurry for chemical mechanical polishing (CMP), a slurry for electronic materials, a slurry for manufacturing automobile exhaust gas treatment devices, a slurry for manufacturing catalysts, a slurry for manufacturing primary or secondary batteries, or a slurry for manufacturing water-soluble printing inks.
Examples of slurries for chemical mechanical polishing include slurries containing silica powder or cerium oxide powder. Examples of slurries for electronic materials include slurries containing dielectric ceramic powder. Examples of slurries for automobile exhaust gas treatment include slurries containing powders in which a noble metal catalyst is attached to a support such as alumina (catalyst powders for automobile exhaust gas treatment). Examples of slurries for manufacturing primary or secondary batteries include slurries containing carbon nanotubes (CNTs) or positive or negative electrode active materials. The dispersant of the present invention can be used as a dispersant for these slurries.

The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[Method for measuring weight average molecular weight of copolymer]
In the examples and comparative examples, the weight-average molecular weight of the copolymer was measured by GPC (gel permeation chromatography). Specifically, the weight-average molecular weight of the copolymer was measured using a measuring device HLC-8120GPC (manufactured by Tosoh Corporation) under the above-mentioned conditions.

[Method for measuring metal ion content in copolymer]
The amount of sodium ions in the copolymer was measured, and the metal ion content in the copolymer was calculated. The amount of sodium ions was measured by flameless atomic absorption spectrometry. The specific conditions are as follows. The sodium ion content in the copolymer can be considered as the metal ion content in the copolymer. The metal ion content in the copolymer in the table is the content of metal ions relative to the mass of the copolymer.
Frameless atomic absorption spectrometer (Agilent Technologies)
Lamp current: 5.0mA
Measurement wavelength: 589.0nm
Gas pressure: argon supply pressure 0.2 MPa
Sample injection volume: 20 μL

[Preparation of Dispersants (Examples 1 to 15, Comparative Examples 1 to 8)]
The dispersants shown in Table 1 (Examples 1 to 15, Comparative Examples 1 to 8) were prepared by the following method.

Example 1
A reaction vessel equipped with a stirrer, thermometer, reflux condenser, nitrogen inlet tube, and dropping funnel was charged with 72.8 g of ion-exchanged water. Next, after heating to 100 ° C. under a nitrogen stream, while maintaining this temperature, 85.0 g of methoxypolyethylene glycol (EO 23 mol) methacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.) and 15.0 g of methacrylic acid (manufactured by Mitsubishi Chemical Corporation), 60.0 g of a 2.9 mass% 2-mercaptoethanol aqueous solution (manufactured by Tokyo Chemical Industry Co., Ltd.), and 17.0 g of a 2 mass% ammonium persulfate aqueous solution (manufactured by Mitsubishi Gas Chemical Company, Inc.) were each added dropwise from separate dropping funnels over 2 hours to carry out a polymerization reaction. After completion of the dropwise addition, the mixture was aged at 100 ° C. for 3 hours (1.5 g of a 2 mass% ammonium persulfate aqueous solution was added 15 minutes after the start of aging) to complete the polymerization reaction. Next, to prevent discoloration of the dispersant, 3.3 g of 35% by mass hydrogen peroxide solution (manufactured by Mitsubishi Gas Chemical Company, Inc.) was added dropwise, and the mixture was further aged for 1 hour. After cooling to 40°C, the concentration was adjusted with ion-exchanged water to obtain a dispersant containing a copolymer. The weight average molecular weight (Mw) of the copolymer was then measured by GPC. The Mw of the copolymer was 19,600. The sodium ion concentration in the copolymer was 51 ppm.

(Comparative Example 1)
A reaction vessel equipped with a stirrer, thermometer, reflux condenser, nitrogen inlet tube, and dropping funnel was charged with 72.8 g of ion-exchanged water. Next, after heating to 100 ° C. under a nitrogen stream, while maintaining this temperature, 85.0 g of methoxypolyethylene glycol (EO 23 mol) methacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.) and 15.0 g of methacrylic acid (manufactured by Mitsubishi Chemical Corporation) were dissolved and mixed in advance. 60.0 g of a 2.9 mass% 2-mercaptoethanol aqueous solution (manufactured by Tokyo Chemical Industry Co., Ltd.), and 17.0 g of a 2 mass% sodium persulfate aqueous solution (manufactured by Mitsubishi Gas Chemical Company, Inc.) were each added dropwise from separate dropping funnels over 2 hours to carry out a polymerization reaction. After completion of the dropwise addition, the mixture was aged for 3 hours at 100 ° C. (1.5 g of a 2 mass% sodium persulfate aqueous solution was added 15 minutes after the start of aging) to complete the polymerization reaction. Next, to prevent discoloration of the dispersant, 3.3 g of 35% by mass hydrogen peroxide solution (manufactured by Mitsubishi Gas Chemical Company, Inc.) was added dropwise, and the mixture was further aged for 1 hour. After cooling to 40°C, the concentration was adjusted with ion-exchanged water to obtain a dispersant containing a copolymer. The weight average molecular weight (Mw) of this copolymer was measured by GPC. The Mw of the copolymer was 19,700. The sodium ion concentration in the copolymer was 730 ppm.

(Comparative Example 2)
A reaction vessel equipped with a stirrer, thermometer, reflux condenser, nitrogen inlet tube, and dropping funnel was charged with 72.8 g of ion-exchanged water. Next, after heating to 100 ° C. under a nitrogen stream, while maintaining this temperature, 85.0 g of methoxypolyethylene glycol (EO 23 mol) methacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.) and 15.0 g of methacrylic acid (manufactured by Mitsubishi Chemical Corporation) dissolved and mixed in advance, 60.0 g of 2.9 mass% 2-mercaptoethanol aqueous solution (manufactured by Tokyo Chemical Industry Co., Ltd.), and a mixture of 3.5 g of 2 mass% sodium persulfate aqueous solution and 13.6 g of 2 mass% ammonium persulfate aqueous solution (all manufactured by Mitsubishi Gas Chemical Company, Inc.) were added dropwise from separate dropping funnels over 2 hours to carry out a polymerization reaction. After completion of the dropwise addition, the mixture was aged for 3 hours at 100 ° C. (a mixture of 0.3 g of 2 mass% sodium persulfate aqueous solution and 1.2 g of 2 mass% ammonium persulfate aqueous solution was added 15 minutes after the start of aging) to complete the polymerization reaction. Next, to prevent discoloration of the dispersant, 3.3 g of 35% by mass hydrogen peroxide solution (manufactured by Mitsubishi Gas Chemical Company, Inc.) was added dropwise, and the mixture was further aged for 1 hour. After cooling to 40°C, the concentration was adjusted with ion-exchanged water to obtain a dispersant containing a copolymer. The weight average molecular weight (Mw) of the copolymer was then measured by GPC. The Mw of the copolymer was 19,700. The sodium ion concentration in the copolymer was 150 ppm.

(Examples 2 to 15, Comparative Examples 3 to 8)
Dispersants containing the monomer composition ratio, weight average molecular weight (Mw), and neutralized salt shown in Table 1 were prepared in the same manner as in Example 1. Comparative Example 8 is a polyacrylic acid ammonium salt.

In Table 1, the methacrylic acid and acrylic acid in the monomer composition ratios (mass ratios) are listed in their acid forms. The symbols in Table 1 have the following meanings, and the n in parentheses in the symbols below and the number in parentheses in Table 1 represent the average number of moles of ethylene oxide (EO) added.

MePEG(n)MA: methoxypolyethylene glycol methacrylate (Shin-Nakamura Chemical Co., Ltd.)
MePEG(n)AA: methoxypolyethylene glycol acrylate (Shin-Nakamura Chemical Co., Ltd.)
PEG(n)MA: Polyethylene glycol methacrylate (Shin-Nakamura Chemical Co., Ltd.)
MAA: Methacrylic acid (Mitsubishi Chemical Corporation)
AA: Acrylic acid (manufactured by Nippon Shokubai Co., Ltd.)
_NH3 : ammonium salt (neutralizer: 28% by mass aqueous ammonia solution (Sigma-Aldrich, special grade reagent))
MEA: Monoethanolamine salt (neutralizer: monoethanolamine (manufactured by Nippon Shokubai Co., Ltd.))

[Dispersibility test]
Regarding dispersibility, the dispersants were evaluated based on whether they could achieve a viscosity range suitable for a slurry composition used in the production of a catalyst for treating automobile exhaust gases.
Slurry compositions shown in Table 1 were prepared using the dispersants of Examples 1 to 15 and Comparative Examples 1 to 8, and the viscosities of the resulting slurry compositions were measured. Maintaining the viscosity of a slurry composition reduces concentration differences within the slurry composition, and so if the viscosity of a slurry composition is maintained, the composition can be said to have excellent dispersibility over time. Note that if the viscosity of a slurry composition is as shown in the Examples, it is preferable not only for producing catalysts for treating automobile exhaust gases, but also for use as a slurry composition in the production of electronic components and the like.

First, 117 g of alumina powder (AES-12, manufactured by Sumitomo Chemical Co., Ltd.) with an average particle size of 400 nm, a dispersant containing each copolymer shown in Table 1, and ion-exchanged water were added to a 500 mL disposable beaker, and the mixture was stirred (2,500 rpm x 2 minutes) using a Primix Homodisper to prepare a 78% by mass powder slurry (slurry composition). The dispersant was added so that the blend amount relative to the alumina powder was 0.2% by mass, calculated as the copolymer contained in the dispersant.

Slurry compositions were prepared using dispersants containing the copolymers of each example, with pH adjusted to pH 4, pH 7, and pH 10. The pH of the slurry compositions was adjusted by adding acetic acid or aqueous ammonia solution dropwise to the slurry composition while measuring the pH of the slurry composition with a pH meter (F-21, manufactured by Horiba, Ltd.) before stirring the slurry composition with a homodisper. For example, when preparing a slurry with a pH of 4, the pH of the slurry composition was adjusted by adding 99.5% by mass of acetic acid (manufactured by Daicel Corporation) dropwise to the slurry composition. Furthermore, when preparing a slurry with a pH of 10, the pH of the slurry composition was adjusted by adding 28% by mass of aqueous ammonia dropwise to the slurry composition. The pH of the slurry composition was adjusted with the slurry composition at 25°C.

The viscosity of each pH-adjusted slurry composition was measured immediately after preparation and after storage at 25°C for 30 days after preparation. The viscosity of the slurry composition was measured using a B-type viscometer TVB-10 manufactured by Toki Sangyo Co., Ltd., at a rotor rotation speed of 3 to 60 rpm and 25°C. The results are shown in Table 1. The metal ion content in all of the slurry compositions of the examples was less than 0.15 ppm.
The viscosity was measured by changing the rotor rotation speed depending on the viscosity of the slurry composition. In the comparative examples, "more than 100,000" means a value exceeding 100,000, that is, exceeding the upper limit of measurement by the viscometer.

The slurry compositions using the dispersants of Examples 1 to 15 were found to have lower viscosity immediately after preparation in the pH range of 4 to 10 compared to slurry compositions with the same powder content but using the dispersants of Comparative Examples 1 to 8, and this effect was maintained even after 30 days, demonstrating excellent powder dispersibility.
Furthermore, alumina powder is a powder used, for example, as a support for catalysts for treating automobile exhaust gases, and it is believed that a slurry composition having similar properties (viscosity, dispersibility, etc.) can be obtained even when a catalyst such as a precious metal is attached to the surface of the powder.

Thus, the dispersants of Examples 1 to 15 provided excellent dispersing effects (low viscosity, long-term stability of slurries containing fine dispersed particles) over a wide range of pH ranges with a small amount of addition.

Claims (11)

A method for producing a slurry composition by mixing a dispersant, a powder, and a dispersion medium, comprising:
The dispersant comprises a copolymer containing a structural unit derived from an (alkoxy)polyalkylene glycol (meth)acrylate [hereinafter referred to as structural unit (I)] and a structural unit derived from a compound represented by the following general formula (II) [hereinafter referred to as structural unit (II)], wherein the content of structural units other than structural units (I) and structural units (II) among all structural units in the copolymer is 1 mass% or less , the proportion of structural units (II) is more than 10 mass% and 40 mass% or less, where the total of structural units (I) and (II) is 100 mass%, and the metal ion content in the copolymer is 10 ppm or more and 63 ppm or less.
Method for producing a slurry composition.

[In the formula, R21 ^represents a methyl group or a hydrogen atom, and M represents a hydrogen atom or a counter ion.] The method for producing a slurry composition according to claim 1, wherein the weight average molecular weight of the copolymer is 10,000 or more and 80,000 or less. The method for producing a slurry composition according to claim 1 or 2, wherein the (alkoxy)polyalkylene glycol (meth)acrylate is an (alkoxy)polyethylene glycol (meth)acrylate, and the average number of moles of ethylene oxide added in the polyethylene glycol is 4 or more and 90 or less. The method for producing a slurry composition according to claim 3, wherein the average number of moles of ethylene oxide added is 6 or more and 45 or less. The method for producing a slurry composition according to any one of claims 1 to 4, wherein the metal ion content in the slurry composition is 1 ppm or less. The method for producing a slurry composition according to any one of claims 1 to 5, wherein the amount of powder in the slurry composition is 55% by mass or more and 85% by mass or less. The method for producing a slurry composition according to any one of claims 1 to 6, wherein the metal ions are light metal ions. The method for producing a slurry composition according to any one of claims 1 to 7, wherein the amount of dispersant blended relative to the powder is 0.05% by mass or more and 3.0% by mass or less, calculated as the copolymer contained in the dispersant. A slurry composition comprising a dispersant, a powder, and a dispersion medium,
The dispersant comprises a copolymer containing a structural unit derived from an (alkoxy)polyalkylene glycol (meth)acrylate [hereinafter referred to as structural unit (I)] and a structural unit derived from a compound represented by the following general formula (II) [hereinafter referred to as structural unit (II)], wherein the content of structural units other than structural units (I) and structural units (II) among all structural units in the copolymer is 1 mass% or less , and the proportion of structural unit (II) is more than 10 mass% and 40 mass% or less, where the total of structural units (I) and (II) is 100 mass%, and the metal ion content in the copolymer is 10 ppm or more and 63 ppm or less,
The blending amount of the dispersant relative to the powder is 0.05% by mass or more and 3.0% by mass or less, calculated as the copolymer contained in the dispersant.
Slurry composition.

(In the formula, R21 ^represents a methyl group or a hydrogen atom, and M represents a hydrogen atom or a counter ion.) The slurry composition of claim 9, wherein the powder is a metal oxide. A dispersant comprising a copolymer containing a structural unit derived from an (alkoxy)polyalkylene glycol (meth)acrylate [hereinafter referred to as structural unit (I)] and a structural unit derived from a compound represented by the following general formula (II) [hereinafter referred to as structural unit (II)], wherein the content of structural units other than structural units (I) and structural units (II) among all structural units in the copolymer is 1 mass% or less , and the proportion of structural unit (II) is more than 10 mass% and 40 mass% or less, where the total of structural units (I) and (II) is 100 mass%, and the metal ion content in the copolymer is 10 ppm or more and 63 ppm or less.

[In the formula, R21 ^represents a methyl group or a hydrogen atom, and M represents a hydrogen atom or a counter ion.]