Dispersant for inorganic powder and slurry composition

Abstract

A dispersant for an inorganic powder according to the present invention is characterized by comprising a polycarboxylic acid-based copolymer which contains, as constituent units, (a) a polyoxyalkylene compound represented by formula 1 [R1O(C2H4O)nR2] and (b) a maleic acid-based compound, wherein the composition ratio ((a):(b)) of (a) the component and (b) the component is 30:70 to 70:30 in terms of mol%, the weight-average molecular weight of the copolymer is 4,000 to 20,000, and an acid value is 200-350 mgKOH / g. In formula 1, R1 represents a C1-4 hydrocarbon group, R2 represents a C2-5 unsaturated hydrocarbon group, and n is the average number of moles of an oxyalkylene group added and represents 1-10.　The present invention makes it possible to provide a dispersant which can exhibit a good dispersion effect and reduce the viscosity of a slurry composition even when the ratio of an inorganic powder is varied or the dispersant is added in a small amount.

Description

Dispersant for inorganic powder and slurry composition

[0001] The present invention relates to a dispersant for inorganic powder, and more particularly to a dispersant that can satisfactorily disperse a slurry composition containing inorganic powder.

[0002] Inorganic powders are used in various industrial fields, including as materials for paints, abrasives, electronic components, etc. Examples of inorganic powders include aluminum oxide and barium titanate. When these inorganic powders are used as materials, they are subjected to a grinding process in which mechanical grinding is repeated in a grinder such as a ball mill in an initial step to make the inorganic powder particles fine and uniform.

[0003] Typically, inorganic powders are pulverized by uniformly dispersing them in water to prepare a slurry composition. Inorganic powders pulverized in this manner are used in electronic components such as dielectric layers of multilayer ceramic capacitors, semiconductor substrates, sensors, and liquid crystal display elements. In recent years, the development of various electronic components has seen remarkable progress, resulting in demands for higher performance, miniaturization, and higher capacity. To meet these demands, inorganic powders need to be micronized, and extremely fine powders of submicron or nanosize are used (Patent Document 1). Meanwhile, many slurry compositions contain two or more types of inorganic powders. For example, a mixture of titanium oxide powder and barium carbonate powder is used in the production of barium titanate, a dielectric material for multilayer ceramic capacitors (Patent Document 2). When preparing a slurry composition, inorganic powders often lack sufficient dispersibility on their own. Therefore, dispersants are used to disperse the inorganic powder in water in a short time and maintain a stable dispersion state without aggregation for a long period of time. As such dispersants, many polymer surfactants have been proposed so far, such as salts of polyacrylic acids and copolymers thereof, and salts of copolymers of maleic anhydride and α-olefins.

[0004] JP 2007-261911 A JP 2014-24750 A JP 2022-23548 A

[0005] However, a dispersant is required to stably disperse inorganic powders. The finer the powder, the greater the amount of dispersant needed. This increases the risk of residual organic matter remaining during sintering, potentially reducing the performance of the inorganic powder. Furthermore, adding a small amount increases the viscosity of the resulting slurry composition, potentially reducing productivity and ease of handling. Therefore, there is a need for a dispersant for inorganic powders that can achieve low viscosity with a low amount of dispersant. Furthermore, in recent years, for example, in the production of barium titanate, various changes in the ratio of composite metal oxides have been made to improve the dielectric constant and mechanical strength (Patent Document 3). There is a need for a dispersant for inorganic powders that can achieve low viscosity with a low amount of dispersant, even when the ratio of composite metal oxides is changed. Conventional polymer surfactant-based dispersants, such as polyacrylic acid, sometimes fail to exhibit sufficient dispersibility depending on the ratio of composite metal oxides.

[0006] The object of the present invention is to provide a dispersant having a predetermined structure that can disperse inorganic powders well even when the ratio of inorganic powders is varied or even when added in small amounts, thereby adjusting the viscosity of a slurry composition to a low level.

[0007] The present inventors have conducted extensive research to solve the above problems and have found that the use of a polycarboxylic acid copolymer composed of specific components as a dispersant can provide a good dispersion effect even when the amount added is low and the composition ratio of the inorganic powder is different, thereby completing the present invention. That is, the present invention is as follows: [1] to [2].

[0008] [1] A dispersant for inorganic powders, characterized in that it comprises a polycarboxylic acid copolymer containing (a) a polyoxyalkylene compound represented by the following formula (1) and (b) a maleic acid compound as structural units, the composition ratio ((a):(b)) of the component (a) to the component (b) being 30:70 to 70:30 in mol %, the weight average molecular weight of the copolymer being 4,000 to 20,000, and the acid value being 200 to 350 mgKOH / g. １ O (C ２ H ４ O) ｎ R ２ ....(1) R １represents a hydrocarbon group having 1 to 4 carbon atoms, R ２ represents an unsaturated hydrocarbon group having 2 to 5 carbon atoms, and n is the average number of moles of the oxyalkylene group added, which is 1 to 10. [2] A slurry composition containing 0.01 to 6.0 wt % of the following component (A), 10 to 80 wt % of component (B), and 15 to 85 wt % of component (C): Component (A): The dispersant for inorganic powders according to claim 1; Component (B): Inorganic powder in which the weight ratio (d):(e) of (d) oxide-based ceramic to (e) metal carbonate is 100:0 to 10:90; Component (C): Dispersion medium

[0009] According to the present invention, it is possible to provide a dispersant that exhibits a good dispersing effect even when the ratio of inorganic powder is changed or even when added in a small amount, and that can reduce the viscosity of a slurry composition.

[0010] The following describes in more detail the embodiments of the present invention. The dispersant for inorganic powders of the present invention comprises a polycarboxylic acid copolymer containing, as structural units, (a) a polyoxyalkylene compound represented by the following formula (1), (b) a maleic acid compound, and (c) optionally a monomer copolymerizable with components (a) and (b), wherein the composition ratio of components (a) to (b) ((a):(b)) is 30:70 to 70:30 in mole %, the weight average molecular weight of the copolymer is 4,000 to 20,000, and the acid value is 200 to 350 mgKOH / g.

[0011] The dispersant for inorganic powders of the present invention may be simply referred to as a “dispersant.” Furthermore, (a) the polyoxyalkylene compound represented by the following formula (1) may be referred to as “component (a),” (b) the maleic acid compound may be referred to as “component (b),” and (c) the monomer copolymerizable with component (a) and component (b) may be referred to as “component (c).”

[0012] [Dispersant for inorganic powder] The dispersant for inorganic powder of the present invention comprises a polycarboxylic acid copolymer containing structural units derived from component (a) and structural units derived from component (b). The carboxylic acid copolymer may contain structural units derived from component (c). Component (c) is optional, and the polycarboxylic acid copolymer may be composed only of structural units derived from component (a) and structural units derived from component (b).

[0013] (Component (a)) Component (a) is a polyoxyalkylene compound represented by formula (1). R １ O (C ２ H ４ O) ｎ R ２ ...Formula (1)

[0014] Here, R １ represents a hydrocarbon group having 1 to 4 carbon atoms, which may be either linear or branched. １ Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group. Of these, a linear methyl group, an ethyl group, a propyl group, or a butyl group is preferred, and a methyl group is more preferred.

[0015] R ２ represents an unsaturated hydrocarbon group having 2 to 5 carbon atoms, and may be either linear or branched. ２ Examples of the alkyl group include vinyl, allyl, isopropenyl, 1-propenyl, methallyl, and 3-butenyl groups. Among these, unsaturated hydrocarbon groups having 3 to 4 carbon atoms are preferred, with allyl and methallyl groups being more preferred.

[0016] n is an oxyalkylene group, specifically, (C ２ H ４O), and represents the average number of moles of oxyethylene groups added, which is 1 to 10. In the structure of the dispersant, the polyoxyalkylene compound acts as a steric repulsion site when adsorbed to the powder. When n is 0, dispersibility and water solubility are low. From this viewpoint, n is 1 or more, preferably 2 or more, and more preferably 3 or more. Furthermore, when n exceeds 10, dispersibility decreases. From this viewpoint, n is 10 or less, preferably 8 or less, and more preferably 6 or less.

[0017] Component (a) may be obtained, for example, by introducing an unsaturated hydrocarbon group into a polyoxyalkylene monoalkyl ether, or by introducing a hydrocarbon group into a polyoxyalkylene monoalkenyl ether.

[0018] There are no particular limitations on the method for introducing an unsaturated hydrocarbon group into a polyoxyalkylene monoalkyl ether. For example, an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide can be added to a polyoxyalkylene monoalkyl ether, followed by an etherification reaction with a monohalogenated unsaturated hydrocarbon such as allyl chloride, allyl bromide, allyl iodide, methallyl chloride, or methallyl bromide. There are also no particular limitations on the method for introducing a hydrocarbon group into a polyoxyalkylene monoalkenyl ether. For example, an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide can be added to a polyoxyalkylene monoallyl ether or a polyoxyalkylene monomethallyl ether, followed by an etherification reaction with a monohalogenated hydrocarbon such as methyl chloride, methyl bromide, butyl chloride, or butyl bromide. The component (a) can be used alone or in combination of two or more.

[0019] (Component (b)) Component (b) is a maleic acid compound. A maleic acid compound is a compound having a maleic acid structure in its molecule. Examples of maleic acid compounds include maleic anhydride, maleic acid, maleate salts, and maleate esters.

[0020] Examples of maleate salts include alkali metal salts, alkaline earth metal salts, ammonium salts, and organic amine salts, and these salts may be mono- or di-substituted. Examples of alkali metal salts include monolithium salt, dilithium salt, monosodium salt, disodium salt, monopotassium salt, and dipotassium salt. Examples of alkaline earth metal salts include calcium salt and magnesium salt. Examples of ammonium salts include ammonium salt and diammonium salt. Examples of organic amine salts include alkylamine salts such as methylamine salt, dimethylamine salt, and ethylamine salt, and alkanolamine salts such as monoethanolamine salt, diethanolamine salt, triethanolamine salt, and methylethanolamine salt.

[0021] Examples of maleic acid esters include esters of maleic acid with saturated alcohols such as methanol and ethanol; unsaturated alcohols such as allyl alcohol and methallyl alcohol; and polyalkylene glycol derivatives such as polyalkylene glycol, polyoxyalkylene monomethyl ether, and polyoxyalkylene monoallyl ether. Component (b) can be used alone or in combination of two or more. From the viewpoints of grindability and dispersion stability, component (b) is preferably maleic anhydride, maleic acid, or ammonium maleate, more preferably ammonium maleate.

[0022] (Component (c)) Component (c) is a monomer copolymerizable with components (a) and (b). Examples of such a monomer include compounds having an ethylenically unsaturated bond, such as styrene, vinyl acetate, vinyl sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, acrylic acid, methacrylic acid, acrylic acid esters, methacrylic acid esters, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, isobutylene, diisobutylene, and vinylcyclohexane. Among these, styrene, isobutylene, diisobutylene, and vinyl acetate are preferred, and styrene is more preferred.

[0023] The polycarboxylic acid copolymer of the present invention contains the component (a), the component (b), and, if necessary, the component (c) as structural units, but from the viewpoint of dispersibility, it is preferable that the copolymer contains only the component (a) and the component (b) as structural units.

[0024] The polycarboxylic acid copolymer of the present invention can be obtained by copolymerizing the above-mentioned components (a), (b), and (c), which is used as needed.

[0025] In the polycarboxylic acid copolymer of the present invention, the composition ratio of component (a) to component (b) ((a):(b)) is, in mol %, 30:70 to 70:30, preferably 40:60 to 60:40, and more preferably 45:55 to 55:45. The composition ratio of each monomer in the polycarboxylic acid copolymer of the present invention corresponds to the charging ratio during copolymerization.

[0026] When the component (c) is used, the composition ratio of the component (c) to the total of the components (a) and (b) is, for example, 0.01 to 5 mol, and preferably 0.1 to 0.5 mol, of the component (c) relative to 100 mol of the total of the components (a) and (b).

[0027] The polymerization of the polycarboxylic acid copolymer of the present invention can be carried out by known methods such as solution polymerization or bulk polymerization, and is not particularly limited. That is, the polymerization reaction can be carried out in the absence of a solvent or in the presence of a solvent. However, when the polymerization reaction is carried out in the presence of a solvent, solvents that can be used include water; alcohols such as methyl alcohol, ethyl alcohol, and isopropyl alcohol; ketones such as acetone and methyl ethyl ketone; cyclic ethers such as tetrahydrofuran and dioxane; aliphatic hydrocarbons such as n-hexane, 2-ethylhexane, and methylcyclohexane; and aromatic hydrocarbons such as toluene and xylene. Of these, toluene and methylcyclohexane are preferred. The amount of solvent used is usually 1 to 50 wt %, preferably 5 to 30 wt %, based on the total weight of the monomers. The solution polymerization can be carried out batchwise or continuously.

[0028] Examples of polymerization initiators include peroxide-based initiators such as benzoyl peroxide, azo-based polymerization initiators such as dimethyl 2,2'-azobis(isobutyrate), and persulfate-based initiators such as ammonium persulfate and sodium persulfate. A chain transfer agent may also be used if necessary. The polymerization temperature is typically 50 to 130°C, preferably 60 to 90°C, and the polymerization time is typically 5 to 25 hours, preferably 5 to 10 hours. From the perspective of dispersibility, it is preferable to use an azo-based polymerization initiator, with dimethyl 2,2'-azobis(isobutyrate) being particularly preferred. The amount of the azo-based initiator used is typically 1 to 10 mol%, preferably 2 to 5 mol%, based on the total moles of the monomers. A chain transfer agent can also be used if desired. Examples of chain transfer agents include dodecyl mercaptan and α-methylstyrene dimer. The amount of the chain transfer agent used is typically 1 to 20 mol%, based on the total moles of the monomers. The chain transfer agents may be used alone or in combination of two or more.

[0029] The weight average molecular weight (Mw) of the polycarboxylic acid copolymer is 20,000 or less, preferably 15,000 or less. If Mw exceeds 20,000, dispersibility decreases and the performance cannot be fully exhibited. Furthermore, Mw is 4000 or more, preferably 8000 or more. If Mw is less than 4000, dispersibility decreases and the performance cannot be fully exhibited. In this specification, the weight average molecular weight refers to the weight average molecular weight calculated as standard polyethylene glycol by gel permeation chromatography (GPC).

[0030] The acid value of the polycarboxylic acid copolymer is 200 mgKOH / g or more, more preferably 220 mgKOH / g or more, and even more preferably 230 mgKOH / g or more. If the acid value is less than 200 mgKOH / g, the dispersibility decreases and the performance cannot be fully exhibited. The acid value of the polycarboxylic acid copolymer is 350 mgKOH / g or less, preferably 330 mgKOH / g or less, more preferably 300 mgKOH / g or less, and even more preferably 260 mgKOH / g or less. If the acid value is greater than 350 mgKOH / g, the dispersibility decreases and the performance cannot be fully exhibited.

[0031] (Slurry Composition) The slurry composition of the present invention contains the following component (A) in an amount of 0.01 to 6.0 wt %, component (B) in an amount of 10 to 80 wt %, and component (C) in an amount of 15 to 85 wt %. Note that wt % means mass %. Component (A): The above-described inorganic powder dispersant Component (B): Inorganic powder in which the weight ratio (d):(e) of (d) oxide ceramic to (e) metal carbonate is 100:0 to 10:90 Component (C): Dispersion medium

[0032] The content of component (A) (dispersant for inorganic powder) in the slurry composition is 0.01 to 6.0 wt %. The content of component (A) is preferably 0.1 wt % or more, more preferably 0.2 wt % or more, and particularly preferably 0.3 wt % or more. The content of component (A) is more preferably 5.0 wt % or less, and particularly preferably 4.0 wt % or less. However, the total content of components (A), (B), and (C) is 100 wt %.

[0033] Component (B) is an inorganic powder, and the inorganic powder is composed of (d) oxide ceramics or a mixture of (d) oxide ceramics and (e) metal carbonate. Of these, component (B) is preferably an inorganic powder composed of a mixture of (d) oxide ceramics and (e) metal carbonate.

[0034] (d) Examples of oxide ceramics include powders of silicate minerals, other silicate compounds, oxide compounds, titanate compounds, etc. Examples include powders of kaolin, clay, talc, mica, bentonite, dolomite, calcium silicate, aluminum silicate, magnesium silicate, zirconium oxide, magnesium oxide, aluminum oxide, titanium oxide, iron oxide, zinc oxide, antimony trioxide, tricobalt tetroxide, lead monoxide, indium oxide, indium tin oxide, barium titanate, calcium titanate, strontium titanate, etc. Particularly preferred oxide ceramics are powders of oxide compounds such as zirconium oxide, magnesium oxide, aluminum oxide, titanium oxide, iron oxide, zinc oxide, antimony trioxide, tricobalt tetroxide, lead monoxide, indium oxide, and indium tin oxide, with titanium oxide being more preferred.

[0035] (e) Examples of metal carbonates include powders of potassium carbonate, calcium carbonate, sodium carbonate, barium carbonate, magnesium carbonate, lithium carbonate, iron carbonate, silver carbonate, strontium carbonate, manganese carbonate, cobalt carbonate, nickel carbonate, copper carbonate, zinc carbonate, rubidium carbonate, cadmium carbonate, etc. Particularly preferred metal carbonates are powders of calcium carbonate, strontium carbonate, barium carbonate, lithium carbonate, etc., and more preferred is barium carbonate.

[0036] The weight ratio of (d) oxide ceramic to (e) metal carbonate in the inorganic powder of the present invention is (d):(e)=100:0 to 10:90, preferably (d):(e)=80:20 to 20:80, more preferably 30:70 to 70:30, and particularly preferably 50:50 to 30:70.

[0037] The dispersion medium, which is component (C), can be water or an organic solvent. Examples of the organic solvent that can be used include aliphatic hydrocarbons, aromatic hydrocarbons, alcohols, esters, ethers, and ketones. Water is preferably used as the dispersion medium. The dispersion medium may be used alone or in combination of two or more.

[0038] In the present invention, various conventionally known additives such as dispersants other than the above-described dispersant for inorganic powders of the present invention, viscosity modifiers, surfactants, and antifoaming agents may be added to the slurry composition as desired, within the scope of not impairing the object of the present invention.

[0039] The present invention will be described in more detail below with reference to examples and comparative examples.

[0040] (GPC Measurement Conditions) A Showa Denko "Shodex GPC-101" GPC system was used, a Showa Denko "Shodex RI-71S" differential refractive index detector was used, and Showa Denko "Shodex OHpak SB-802HQ" and "Shodex OHpak SB-806M HQ" columns and a guard column were connected. The column temperature was 40°C. A 0.1M sodium chloride aqueous solution was run as the developing solvent at a flow rate of 1 mL / min, and 0.1 mL of a 0.1% by mass 0.1M sodium chloride aqueous solution was injected. A chromatogram was obtained using the BORWIN GPC calculation program, which shows the refractive index intensity and elution time. The sample peak was detected in the resulting chromatogram, and the weight-average molecular weight was calculated using the BORWIN GPC calculation program based on a calibration curve prepared from polyethylene glycol standards.

[0041] (Conditions for measuring acid value) Measurement was carried out in accordance with JIS K 0070-1992.

[0042] (Compound 1) A 3-liter flask equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet tube was charged with 1,000 g (3.7 mol) of the polyoxyalkylene compound shown in Table 1, 383 g (3.9 mol) of maleic anhydride, 35 g (0.15 mol) of a chain transfer agent (NOF Corporation's "Nofumer MSD"), and 600 g of toluene. Under a nitrogen gas atmosphere, 34 g (0.15 mol) of 2,2'-azobis(isobutyrate)dimethyl ester was added as a polymerization initiator, and the reaction was carried out at 75±5°C for 5 hours in the first stage and at 85±5°C for 3 hours in the second stage. The toluene was removed under reduced pressure, and the reaction mixture was cooled to 60°C. Then, 960 g of ion-exchanged water was added, and the mixture was stirred at 85±5°C for 2 hours. Subsequently, 274 g of ammonia water (4.5 mol as ammonia) was added for neutralization, yielding a polycarboxylic acid ammonium salt (Compound 1). The obtained compound 1 is a polycarboxylic acid copolymer having the polyoxyalkylene compound and ammonium maleate shown in Table 1 as constituent units.

[0043] (Compounds 2 and 3) Polycarboxylic acid copolymers were obtained in the same manner as Compound 1, except that the raw materials were changed to those shown in Table 1. Compound 2 is a polycarboxylic acid copolymer having a polyoxyalkylene compound and maleic acid shown in Table 1 as structural units. Compound 3 is a polycarboxylic acid copolymer having a polyoxyalkylene compound, ammonium maleate, and styrene as structural units shown in Table 1.

[0044] (Compound 4) 250 g (0.93 mol) of a polyoxyalkylene compound shown in Table 1 and 120 g of toluene were added to a 1-liter flask equipped with a stirrer, thermometer, condenser, nitrogen gas inlet tube, and dropping funnel. After heating to 130°C, 150 g (0.56 mol) of a polyoxyalkylene compound shown in Table 1, 94 g (0.96 mol) of maleic anhydride, 60 g of toluene, and 21.1 g (0.09 mol) of 2,2'-azobis(isobutyrate)dimethyl as a polymerization initiator were added dropwise to the flask over 2 hours. After completion of the dropwise addition, polymerization was carried out at 130°C for 30 minutes, after which the toluene was removed under reduced pressure. The reaction mixture was cooled to 60°C, and 330 g of ion-exchanged water was added, followed by stirring at 85±5°C for 2 hours. Subsequently, 60 g of ammonia water (0.99 mol as ammonia) was added for neutralization, yielding an ammonium polycarboxylate salt. The obtained compound 4 is a polycarboxylic acid copolymer having the polyoxyalkylene compound and ammonium maleate shown in Table 1 as constituent units.

[0045] (Compound 5) A 3-liter flask equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet tube was charged with 1,000 g (3.7 mol) of the polyoxyalkylene compound shown in Table 1, 383 g (3.9 mol) of maleic anhydride, 18 g (0.08 mol) of a chain transfer agent (NOF Corporation's "Nofumer MSD"), and 600 g of toluene. Under a nitrogen gas atmosphere, 34 g (0.15 mol) of 2,2'-azobis(isobutyrate)dimethyl ester was added as a polymerization initiator, and the reaction was carried out at 75±5°C for 5 hours in the first stage and at 85±5°C for 3 hours in the second stage. The toluene was removed under reduced pressure, and the reaction mixture was cooled to 60°C. Then, 960 g of ion-exchanged water was added, and the mixture was stirred at 85±5°C for 2 hours. Subsequently, 274 g of ammonia water (4.5 mol as ammonia) was added for neutralization, yielding an ammonium polycarboxylate salt. The obtained compound 5 is a polycarboxylic acid copolymer having the polyoxyalkylene compound and ammonium maleate shown in Table 1 as constituent units.

[0046] (Compounds 6 to 9, Comparative Compounds 1 to 4) Polycarboxylic acid copolymers were obtained by a method similar to that for Compound 1, except that the polyoxyalkylene compounds were changed to those shown in Table 1. Compounds 6 to 8 and Comparative Compounds 2 and 4 are polycarboxylic acid copolymers having the polyoxyalkylene compound and ammonium maleate salt shown in Table 1 as structural units. Compound 9 is a polycarboxylic acid copolymer having the polyoxyalkylene compound and maleic anhydride shown in Table 1 as structural units. Comparative Compounds 1 and 3 are polycarboxylic acid copolymers having the polyoxyalkylene compound and maleic acid shown in Table 1 as structural units.

[0047]

[0048] Examples 1 to 9, Comparative Examples 1 to 4 Slurry compositions were obtained by the following slurry preparation method 1 and slurry preparation method 2, and the shear viscosity was measured and evaluated.

[0049] (Slurry Preparation Method 1) Using ion-exchanged water as a dispersion medium and titanium oxide powder (TiO ２ ) and barium carbonate powder (BaCO ) as a metal carbonate ３ A slurry composition was prepared as follows using an inorganic powder mixture (weight ratio = 50:50) of the inorganic powder and the inorganic powder. 1.0 g of the inorganic powder was weighed into each of two 50 mL screw tubes, to which 1.0 g of the dispersion medium and 0.01 g (1.0 wt % relative to the inorganic powder) and 0.03 g (3.0 wt % relative to the inorganic powder) of the dispersant shown in Table 2 were added, respectively. The mixture was stirred at 2000 rpm for 2 minutes using a planetary mixer to obtain two slurry compositions with different dispersant concentrations.

[0050] (Slurry Viscosity 1) The viscosity of each slurry composition obtained by the above-mentioned slurry preparation method 1 was measured as follows. The results are shown in Table 2. Using a dynamic viscoelasticity measuring device (Paar Physica MCR-300, manufactured by Anton Paar), the viscosity was measured at a temperature of 20°C and a shear rate of 1 (1 / s). Vx1: Slurry viscosity when the amount of dispersant added was 1 wt% Vx2: Slurry viscosity when the amount of dispersant added was 3 wt% Evaluation was based on the following criteria: A: Shear viscosity less than 2.0 Pa s, very good dispersibility. B: Shear viscosity less than 8.0 Pa s, good dispersibility. C: Shear viscosity 8.0 Pa s or more, poor dispersibility.

[0051]

[0052] (Slurry Preparation Method 2) Ion-exchanged water was used as a dispersion medium, and titanium oxide powder (TiO ２ ) and barium carbonate powder (BaCO ) as a metal carbonate ３ A slurry composition was prepared as follows using an inorganic powder mixture (weight ratio = 30:70) containing 1.0 g of inorganic powder. To each of two 50 mL screw tubes, 1.0 g of dispersion medium and 0.01 g (1.0 wt % relative to the inorganic powder) and 0.03 g (3.0 wt % relative to the inorganic powder) of a dispersant shown in Table 3 were added, and the mixture was stirred at 2000 rpm for 2 minutes using a planetary mixer to obtain two slurry compositions with different dispersant concentrations.

[0053] (Slurry Viscosity 2) The viscosity of each slurry composition obtained by the above-mentioned slurry preparation method 2 was measured as follows. The results are shown in Table 3. A dynamic viscoelasticity apparatus (Paar Physica MCR-300, manufactured by Anton Paar) was used to measure the viscosity at a temperature of 20°C and a shear rate of 1 (1 / s). Vy1: Slurry viscosity when the amount of dispersant added was 1 wt% Vy2: Slurry viscosity when the amount of dispersant added was 3 wt% Evaluation was based on the following criteria. The results are shown in Table 3. A: Shear viscosity less than 1.0 Pa s, very good dispersibility. B: Shear viscosity less than 2.0 Pa s, good dispersibility. C: Shear viscosity 2.0 Pa s or more, poor dispersibility.

[0054]

[0055] The slurry compositions of each Example using Compounds 1 to 9, which are dispersants satisfying the requirements of the present invention, resulted in low viscosity even when the amount of dispersant added was small or the ratio of inorganic powder was varied. In contrast, the slurry compositions of each Comparative Example using Comparative Compounds 1 to 4, which are dispersants not satisfying the requirements of the present invention, had higher viscosity than the Examples, and were inferior in productivity and handleability.

Claims

1. A dispersant for inorganic powders, comprising a polycarboxylic acid copolymer containing as structural units (a) a polyoxyalkylene compound represented by the following formula (1), and (b) a maleic acid compound, wherein the composition ratio ((a):(b)) of the (a) component to the (b) component is 30:70 to 70:30 in mol %, the weight average molecular weight of the copolymer is 4,000 to 20,000, and the acid value is 200 to 350 mgKOH / g. １ O (C ２ H ４ O) ｎ R ２ ....(1) R １ represents a hydrocarbon group having 1 to 4 carbon atoms; R ２ represents an unsaturated hydrocarbon group having 2 to 5 carbon atoms; and n is the average number of moles of the oxyalkylene group added, which is 1 to 10.

2. A slurry composition containing 0.01 to 6.0 wt% of the following component (A), 10 to 80 wt% of component (B), and 15 to 85 wt% of component (C): Component (A): The dispersant for inorganic powders according to claim 1; Component (B): Inorganic powder in which the weight ratio (d):(e) of (d) oxide ceramics and (e) metal carbonate is 100:0 to 10:90; Component (C): Dispersion medium

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