Copolymer, dispersant for inorganic powder, and slurry composition

Abstract

To provide a copolymer capable of well dispersing an inorganic powder and adjusting the viscosity of a slurry composition to a low level even when water or an organic solvent is used as a solvent or the powder concentration is increased.SOLUTION: A copolymer comprising the following as constituent units; Component (a): Formula (1) A polyoxyethylene compound represented by R1O(C2H4O)mR2; Component (b): a polyoxyalkylene compound represented by Formula (2) R3O(AO)nR4; and Component (c): A copolymer containing a maleic acid-based compound as a constituent unit, wherein the total proportion of the component (a) and the component (b) in the copolymer is 40 mol% or more, and the molar ratio of the component (a) to the component (b) ((a):(b)) is 97:3 to 50:50.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a copolymer, a dispersant for inorganic powder, and a slurry composition. [Background technology]

[0002] Copolymers are products obtained by polymerizing two or more types of monomers, and by changing the type and arrangement of the monomers, they can have a variety of functions. For this reason, they are used in a variety of applications, including synthetic rubber, synthetic fibers, surfactants, and dispersants.

[0003] On the other hand, inorganic powders often have insufficient dispersibility when used alone, and therefore, when preparing a slurry containing these, a dispersant is used to improve the fluidity and storage stability of the dispersion composition. Inorganic powders are used in various industrial fields, and are used as materials for paints, abrasives, electronic components, etc. Examples of inorganic powders include aluminum oxide and barium titanate. When using these inorganic powders as materials, a milling process is carried out in which mechanical milling is repeated in a mill such as a ball mill in an initial step to make the inorganic powder particles fine and uniform.

[0004] Furthermore, pulverized inorganic powders are used in electronic components such as dielectric layers of multilayer ceramic capacitors, semiconductor substrates, sensors, liquid crystal display elements, etc. In the manufacturing process of electronic components, inorganic powders are processed by various molding methods to give them a shape, resulting in inorganic powder compacts (Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2023-23701 Summary of the Invention [Problem to be solved by the invention]

[0006] Dispersants are used in multiple processes, such as the pulverization process and molding process of inorganic powders. However, when different types of dispersants are used in each process, interactions between the dispersants occur, resulting in problems such as poor dispersion of the inorganic powder. Furthermore, even when the same type of dispersant is used, water is often used as the solvent in the pulverization process of inorganic powders and an organic solvent is often used as the solvent in the molding process, and the different solvents used can sometimes result in poor dispersion of the inorganic powder. Therefore, there is a need for a dispersant that can well disperse inorganic powders not only in the pulverization process of inorganic powders but also in the molding process of inorganic powders.

[0007] Furthermore, in recent years, efforts have been made to increase the powder concentration in each process in order to improve productivity. When the powder concentration is increased, conventional polymer surfactants, such as polyacrylic acid and salts of their copolymers, sometimes fail to provide sufficient dispersibility. Therefore, there is a demand for dispersants that can disperse inorganic powders well, even when the powder concentration is increased.

[0008] The present invention has been made in view of the above circumstances, and the problem to be solved by the present invention is to provide a copolymer that can disperse inorganic powders well and adjust the viscosity of a slurry composition to a low level even when water or an organic solvent is used as a solvent or when the powder concentration is increased. [Means for solving the problem]

[0009] As a result of extensive research in light of the above circumstances, the present inventors have found that the above object can be achieved by using a copolymer composed of specific components.

[0010] That is, the present invention relates to the following [1] to [3]. [1] Component (a): Formula (1) R 1 O(C2H4O) m R 2 (In formula (1), R 1 represents a hydrocarbon group having 1 to 4 carbon atoms, and R 2represents an unsaturated hydrocarbon group having 2 to 5 carbon atoms, and m represents the average number of moles of oxyethylene groups added, which is 1 to 15; Component (b): Formula (2) R 3 O(AO) n R 4 (In formula (2), R 3 represents a hydrocarbon group having 1 to 4 carbon atoms, and R 4 represents an unsaturated hydrocarbon group having 2 to 5 carbon atoms, AO represents an oxyalkylene group having 2 to 4 carbon atoms, and n is the average number of moles of the oxyalkylene group added, which is 16 to 70; and Component (c): A copolymer containing a maleic acid compound as a constituent unit, The copolymer has a total content of the component (a) and the component (b) of 40 mol % or more, and a molar ratio of the component (a) to the component (b) ((a):(b)) of 97:3 to 50:50. [2] A dispersant for inorganic powders, comprising the copolymer described in [1] above. [3] A slurry composition comprising: component (A): the dispersant for inorganic powders according to claim 2; component (B): an inorganic powder; and component (C): a dispersion medium, wherein the slurry composition contains 0.01 to 10.0% by weight of component (A), 5 to 80% by weight of component (B), and 15 to 90% by weight of component (C). [Effects of the Invention]

[0011] The copolymer of the present invention, when used as a dispersant for inorganic powders, exhibits a good dispersing effect and can reduce the viscosity of a slurry composition in a process using water or an organic solvent as a solvent or when the powder concentration is increased. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the embodiments described herein and various modifications can be made without departing from the spirit of the present invention. In this specification, a numerical range defined using the symbol "to" includes the numerical values ​​on both ends (upper and lower limits) of the symbol "to." For example, "2 to 5" means 2 or more and 5 or less.

[0013] [Copolymer] The copolymer of the present invention is a copolymer containing structural units derived from component (a), structural units derived from component (b), and structural units derived from component (c). The copolymer may also contain structural units derived from component (d). Component (d) is optional, and the copolymer may be composed only of structural units derived from component (a), structural units derived from component (b), and structural units derived from component (c).

[0014] (Component (a)) Component (a) is a compound represented by the formula (1) R 1 O(C2H4O) m R 2 It is a polyoxyethylene compound represented by the formula: (In formula (1), R 1 represents a hydrocarbon group having 1 to 4 carbon atoms, and R 2 represents an unsaturated hydrocarbon group having 2 to 5 carbon atoms, and m is the average number of moles of oxyethylene groups added, which is 1 to 15.

[0015] In formula (1), R 1 R represents a hydrocarbon group having 1 to 4 carbon atoms, and may be either linear or branched. 1 is preferably a linear hydrocarbon group, more preferably a hydrocarbon group having one carbon atom. 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 even more preferred.

[0016] In formula (1), R 2R represents an unsaturated hydrocarbon group having 2 to 5 carbon atoms, and may be either linear or branched. 2 is preferably an unsaturated hydrocarbon group having 3 to 4 carbon atoms. 2 Examples of the unsaturated hydrocarbon 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, and allyl and methallyl groups are more preferred.

[0017] In formula (1), m represents an oxyethylene group, specifically, the average number of moles of oxyethylene groups added represented by (C2H4O) in formula (1), and represents 1 to 15. The polyoxyethylene compound acts as a steric repulsion site in the structure of the dispersant when adsorbed to powder. When m is 0, dispersibility and water solubility are low. From this viewpoint, m is 1 or more, preferably 2 or more, and more preferably 3 or more. Furthermore, when m exceeds 15, dispersibility is reduced. From this viewpoint, m is 15 or less, preferably 13 or less, and more preferably 10 or less.

[0018] The component (a) may be used alone or in combination of two or more.

[0019] Component (a) may be obtained, for example, by introducing an unsaturated hydrocarbon group into a polyoxyethylene monoalkyl ether, or by introducing a hydrocarbon group into a polyoxyethylene monoalkenyl ether. There are no particular limitations on the method for introducing the unsaturated hydrocarbon group into a polyoxyethylene monoalkyl ether. For example, it can be obtained by adding an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide to a polyoxyethylene monoalkyl ether and then subjecting the resulting mixture to 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 polyoxyethylene monoalkenyl ether. For example, it can be obtained by adding an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide to a polyoxyethylene monoallyl ether or polyoxyethylene monomethallyl ether and then subjecting the resulting mixture to an etherification reaction with a monohalogenated hydrocarbon such as methyl chloride, methyl bromide, butyl chloride, or butyl bromide.

[0020] (ingredient (b)) Component (b) is a compound represented by the formula (2) R 3 O(AO) n R 4 It is a polyoxyalkylene compound represented by the formula: (In formula (2), R 3 represents a hydrocarbon group having 1 to 4 carbon atoms, and R 4 represents an unsaturated hydrocarbon group having 2 to 5 carbon atoms, AO represents an oxyalkylene group having 2 to 4 carbon atoms, and n is the average number of moles of the oxyalkylene group added, which is 16 to 70.

[0021] In formula (2), R 3 R represents a hydrocarbon group having 1 to 4 carbon atoms, and may be either linear or branched. 3 is preferably a linear hydrocarbon group, more preferably a hydrocarbon group having one carbon atom. 1Examples 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 even more preferred.

[0022] In formula (2), R 4 R represents an unsaturated hydrocarbon group having 2 to 5 carbon atoms, and may be either linear or branched. 4 is preferably an unsaturated hydrocarbon group having 3 to 4 carbon atoms. 4 Examples of the unsaturated hydrocarbon 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, and allyl and methallyl groups are more preferred.

[0023] In formula (2), AO is an oxyalkylene group having 2 to 4 carbon atoms, preferably 2 to 3 carbon atoms. The form of AO may be linear or branched. AO may be one type or two or more types, but it is preferable to use one type. When two or more types of AO are used, the addition form may be random or block.

[0024] In formula (2), AO includes an oxyethylene group (EO), an oxypropylene group (PO), and an oxybutylene group. From the viewpoint of dispersibility, it is preferable to use one or two selected from oxyethylene groups and oxypropylene groups, more preferably one, and particularly preferably an oxyethylene group. On the other hand, when two types are used, it is preferable to use an oxyethylene group and an oxypropylene group. When two or more AOs are used in combination, the ratio can be appropriately determined depending on the type of AO, etc. For example, when EO and PO are combined, the composition ratio of EO to PO is preferably EO:PO=10:90 to 90:10 in mole fraction (mol %), more preferably 40:60 to 90:10.

[0025] In formula (2), n is the average number of moles of oxyalkylene groups added, and represents 16 to 70. The polyoxyalkylene compound acts as a steric repulsion site in the structure of the dispersant when adsorbed to the powder. If n is less than 16, dispersibility is low. From this viewpoint, n is set to 16 or more, preferably 18 or more, and more preferably 20 or more. Furthermore, if n exceeds 70, dispersibility is reduced. From this viewpoint, n is set to 70 or less, and preferably 60 or less.

[0026] Furthermore, component (b) can be used alone or in combination of two or more types.

[0027] Component (b) 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. There are no particular limitations on the method for introducing the unsaturated hydrocarbon group into a polyoxyalkylene monoalkyl ether. For example, it can be obtained by adding an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide to a polyoxyalkylene monoalkyl ether and then subjecting the resulting mixture to 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, it can be obtained by adding an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide to a polyoxyalkylene monoallyl ether or a polyoxyalkylene monomethallyl ether and then subjecting the resulting mixture to an etherification reaction with a monohalogenated hydrocarbon such as methyl chloride, methyl bromide, butyl chloride, or butyl bromide.

[0028] (component (c)) Component (c) is a maleic acid compound. A maleic acid compound is a compound that has a maleic acid structure in its molecule. Examples of maleic acid compounds include maleic anhydride, maleic acid, maleate salts, and maleate esters.

[0029] 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.

[0030] 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.

[0031] Component (c) may be used alone or in combination of two or more. From the viewpoint of dispersibility, component (c) is preferably maleic anhydride, maleic acid, or ammonium maleate, more preferably maleic anhydride or ammonium maleate.

[0032] (ingredient (d)) Component (d) is a monomer copolymerizable with components (a), (b), and (c). 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.

[0033] The composition ratio of each component (monomer) in the copolymer of the present invention will be explained below. The composition ratio of each component (monomer) corresponds to the proportion in the copolymer.

[0034] In the copolymer, the total proportion of the component (a) and the component (b) is 40 mol % or more, and the molar ratio of the component (a) to the component (b) ((a):(b)) is 97:3 to 50:50. From the viewpoint of solubility in a solvent, the total proportion of the component (a) to the component (b) in the copolymer is preferably 42 mol % or more. From the viewpoint of dispersibility, the molar ratio of the component (a) to the component (b) ((a):(b)) is preferably 97:3 to 60:40, more preferably 95:5 to 60:40, and even more preferably 95:5 to 80:20.

[0035] In the copolymer, the proportion of the component (c) is preferably 40 mol% or more, more preferably 45 mol% or more, from the viewpoint of dispersibility, and is preferably 60 mol% or less, more preferably 55 mol% or less, from the viewpoint of solubility in solvents.

[0036] In the copolymer, the total proportion of the components (a), (b), and (c) is preferably 80 mol% or more, more preferably 90 mol% or more, even more preferably 95 mol% or more, and even more preferably 98 mol% or more.

[0037] In addition, in the copolymer of the present invention, the ratio m / n of the average number of moles of oxyethylene groups added in component (a) to the average number of moles of oxyalkylene groups added in component (b) is preferably less than 0.8, more preferably less than 0.6, and even more preferably less than 0.4, from the viewpoint of dispersibility.

[0038] The polymerization of the 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% by weight, preferably 5 to 30% by weight, based on the total weight of the monomers. The solution polymerization can be carried out batchwise or continuously.

[0039] Examples of the polymerization initiator 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 be used in combination, if necessary. The polymerization temperature is usually 50 to 130°C, preferably 60 to 90°C, and the polymerization time is usually 5 to 25 hours, preferably 5 to 10 hours. From the viewpoint of dispersibility, it is preferable to use an azo-based polymerization initiator, and dimethyl 2,2'-azobis(isobutyrate) is particularly preferable. The amount of the azo-based initiator used is usually 1 to 10 mol%, preferably 2 to 5 mol%, based on the total moles of the monomers.

[0040] If desired, a chain transfer agent can be used. Examples of the chain transfer agent include dodecyl mercaptan and α-methylstyrene dimer. The amount of the chain transfer agent used is usually 1 to 20 mol% based on the total moles of the monomers. The chain transfer agent can be used alone or in combination of two or more.

[0041] The weight average molecular weight (Mw) of the copolymer is preferably 40,000 or less, more preferably 30,000 or less. If Mw exceeds 40,000, dispersibility decreases and the copolymer cannot fully exhibit its performance. Furthermore, Mw is preferably 4,000 or more, more preferably 8,000 or more. If Mw is less than 4,000, dispersibility decreases and the copolymer cannot fully exhibit its performance. 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).

[0042] (Dispersant for inorganic powder and slurry composition) The copolymer of the present invention can be used as a component (A): a dispersant for inorganic powders, either as a single compound or mixed with other additives commonly used in the art (thickeners, plasticizers, antistatic agents, etc.). The dispersant for inorganic powders of the present invention may also be referred to simply as a "dispersant."

[0043] The inorganic powder dispersant of the present invention is used as a dispersant to disperse a dispersion target (powder) in a solvent (component (C): dispersion medium) by a method commonly used in the art, thereby obtaining a slurry composition. The dispersion target of the dispersant of the present invention can be component (B): inorganic powder.

[0044] Examples of the component (B): inorganic powder include metal powder, alloy powder consisting of two or more types of metals or metal and nonmetal, composite powder of metal powder or alloy powder, and mixed powder of two or more types of inorganic powder or inorganic powder mixed with other powder. Other examples of the inorganic powder include silicate compounds, carbonate compounds, sulfate compounds, hydroxide compounds, oxide compounds, carbide compounds, nitride compounds, titanate compounds, etc. Preferred examples of the component (B): inorganic powder include metal powders such as nickel, cobalt, palladium, copper, silver, gold, and platinum; oxide compound powders such as zirconium oxide, magnesium oxide, aluminum oxide, iron oxide, zinc oxide, indium tin oxide, and titanium oxide; and titanate compound powders such as barium titanate, calcium titanate, and strontium titanate.

[0045] Examples of solvents (component (C): dispersion medium) for dispersing component (B): inorganic powder using the dispersant of the present invention include aromatic hydrocarbon solvents such as toluene and xylene, hydrocarbon solvents such as cyclohexane, ketone solvents such as acetone and methyl ethyl ketone, ester solvents such as ethyl acetate and n-propyl acetate, glycol ether solvents such as ethylene glycol monoethyl ether and ethylene glycol monoisopropyl ether, glycol ether ester solvents such as ethylene glycol monoethyl ether acetate and ethylene glycol monoisopropyl ether acetate, terpene solvents such as terpineol and dihydroterpineol, alcohol solvents such as methanol, ethanol, and n-propanol, and water, and one or more selected from these can be used.

[0046] In the slurry composition, the component (A) is preferably 0.01 to 10.0% by weight, the component (B) is 5 to 80% by weight, and the component (C) is 15 to 90% by weight, and more preferably the component (A) is 0.1 to 10.0% by weight, the component (B) is 10 to 80% by weight, and the component (C) is 15 to 70% by weight. [Example]

[0047] The present invention will be described in more detail below with reference to examples and comparative examples.

[0048] <Examples 1 to 9 and Comparative Examples 1 to 4> <Production of copolymer> (GPC measurement conditions) The GPC system used was a Showa Denko Shodex GPC-101, and the differential refractive index detector was a Showa Denko Shodex RI-71S. The columns were connected to Showa Denko Shodex OHpak SB-802HQ and Shodex OHpak SB-806M HQ columns and a guard column. The column temperature was 40°C. A 0.1M sodium chloride solution was used as the developing solvent at a flow rate of 1 mL / min. 0.1 mL of 0.1% by mass of the sample was injected. A chromatogram was obtained using the Borwin GPC calculation program, plotting the refractive index versus elution time. Sample peaks were detected in the chromatogram, and the weight-average molecular weight was calculated using the Borwin GPC calculation program based on a calibration curve constructed from polyethylene glycol standards.

[0049] (Polyoxyethylene compound (a)-1) A 5-liter pressure reactor was charged with 160 g (5.0 mol) of methanol and 5 g of sodium methylate as a catalyst. The air in the system was replaced with nitrogen gas, and then 880 g (20.0 mol) of ethylene oxide was gradually added at approximately 0.05 to 0.5 MPa (gauge pressure) at 100 to 120 °C to carry out an addition reaction. After the reaction was completed, the mixture was cooled to 50 °C. Next, 280 g of potassium hydroxide was added, and the air in the system was replaced with nitrogen gas. 383 g (5.0 mol) of allyl chloride was gradually added with stirring at 80 °C, and the reaction was carried out for 6 hours. The by-product salt was then removed to obtain polyoxyethylene compound (a)-1.

[0050] (Polyoxyethylene compound (a)-2) Polyoxyethylene compound (a)-2 was obtained in the same manner as polyoxyethylene compound (a)-1, except that the amounts of methanol, ethylene oxide, and allyl chloride were changed to 32 g (1.0 mol), 484 g (11.0 mol), and 77 g (1.0 mol), respectively.

[0051] (Polyoxyethylene compound (a)-3) Polyoxyethylene compound (a)-3 was obtained in the same manner as polyoxyethylene compound (a)-1, except that methanol was replaced with 370 g (5.0 mol) of butanol and 1100 g (25.0 mol) of ethylene oxide.

[0052] (Polyoxyalkylene compound (b)-1) Polyoxyalkylene compound (b)-1 was obtained in the same manner as polyoxyethylene compound (a)-1, except that the amounts of methanol, ethylene oxide, and allyl chloride were changed to 32 g (1.0 mol), 1452 g (33.0 mol), and 77 g (1.0 mol), respectively.

[0053] (Polyoxyalkylene compound (b)-2) Polyoxyalkylene compound (b)-2 was obtained in the same manner as polyoxyethylene compound (a)-1, except that the amounts of methanol, ethylene oxide, and allyl chloride were changed to 32 g (1.0 mol), 968 g (22.0 mol), and 77 g (1.0 mol), respectively.

[0054] (Polyoxyalkylene compound (b)-3) Polyoxyalkylene compound (b)-3 was obtained in the same manner as polyoxyethylene compound (a)-1, except that the amounts of methanol used were changed to butanol (74 g, 1.0 mol), ethylene oxide (704 g, 16.0 mol), propylene oxide (928 g, 16.0 mol), and allyl chloride (77 g, 1.0 mol).

[0055] (Copolymer 1) A 5-liter flask equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet was charged with 944 g (3.8 mol) of (a)-1 from Table 1, 305 g (0.20 mol) of (b)-1 from Table 2, 412 g (4.2 mol) of (c) maleic anhydride, 38 g (0.36 mol) of a chain transfer agent (NOF Corporation's "Nofumer MSD"), and 535 g of toluene. Under a nitrogen gas atmosphere, 83 g (0.36 mol) of 2,2'-azobis(isobutyric acid) dimethyl ester was added as a polymerization initiator. 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 to obtain Copolymer 1.

[0056] (Copolymer 2) After obtaining a copolymer in the same manner as in Copolymer 1, 150 g of ion-exchanged water was added and stirred for 2 hours at 85±5° C. Then, 511 g of ammonia water (8.4 mol as ammonia) was added for neutralization, and the ion-exchanged water was removed under reduced pressure to obtain Copolymer 2.

[0057] (Copolymer 3) Copolymer 3 was obtained in the same manner as for copolymer 1, except that (a)-1 in Table 1 was changed to 696 g (2.8 mol) and (b-2 in Table 2 was changed to 1250 g (1.20 mol).

[0058] (Copolymer 4) A 1-liter flask equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet was charged with 116 g (0.47 mol) of (a)-1 from Table 1, 305 g (0.20 mol) of (b)-1 from Table 2, 67 g (0.70 mol) of maleic anhydride, 3 g (0.027 mol) of a chain transfer agent (NOF Corporation's "Nofumer MSD"), and 153 g of toluene. Under a nitrogen gas atmosphere, 14 g (0.060 mol) of 2,2'-azobis(isobutyrate)dimethyl ester was added as a polymerization initiator. 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. 41 g of ion-exchanged water was added, and the mixture was stirred at 85±5°C for 2 hours. The ion-exchanged water was removed under reduced pressure, yielding Copolymer 4.

[0059] (Copolymer 5) A 1-liter flask equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet was charged with 116 g (0.47 mol) of (a)-1 from Table 1, 305 g (0.20 mol) of (b)-1 from Table 2, 67 g (0.70 mol) of maleic anhydride, 3 g (0.027 mol) of a chain transfer agent (NOF Corporation's "Nofumer MSD"), and 153 g of toluene. Under a nitrogen gas atmosphere, 14 g (0.060 mol) of 2,2'-azobis(isobutyric acid) dimethyl ester was added as a polymerization initiator. 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. 41 g of ion-exchanged water was added and stirred at 85±5°C for 2 hours. Subsequently, 85 g of ammonia water (1.4 mol as ammonia) was added for neutralization, and the ion-exchanged water was removed under reduced pressure to obtain Copolymer 5.

[0060] (Copolymer 6) A 1-liter flask equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet was charged with 116 g (0.47 mol) of (a)-1 from Table 1, 305 g (0.20 mol) of (b)-1 from Table 2, 67 g (0.70 mol) of maleic anhydride, 3 g (0.027 mol) of a chain transfer agent (NOF Corporation's "Nofumer MSD"), 0.4 g (0.0038 mol) of styrene, and 153 g of toluene. Under a nitrogen gas atmosphere, 14 g (0.060 mol) of 2,2'-azobis(isobutyric acid)dimethyl ester was added as a polymerization initiator. 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 to obtain Copolymer 6.

[0061] (Copolymer 7) A 3-liter flask equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet was charged with 1003 g (1.8 mol) of (a)-2 from Table 1, 305 g (0.20 mol) of (b)-1 from Table 2, 206 g (2.1 mol) of maleic anhydride, 19 g (0.08 mol) of a chain transfer agent (NOF Corporation's "Nofumer MSD"), and 472 g of toluene. Under a nitrogen gas atmosphere, 41 g (0.18 mol) of 2,2'-azobis(isobutyric acid)dimethyl ester was added as a polymerization initiator. 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, 147 g of ion-exchanged water was added and the mixture was stirred at 85±5°C for 2 hours. Thereafter, 131 g of ammonia water (4.2 mol as ammonia) was added to neutralize the mixture, and the ion-exchanged water was removed under reduced pressure to obtain Copolymer 7.

[0062] (Copolymer 8) Copolymer 8 was obtained in the same manner as for copolymer 2, except that (a)-1 in Table 1 was changed to 944 g (3.8 mol) and (b-3 in Table 2 was changed to 354 g (0.20 mol).

[0063] (Copolymer 9) Copolymer 9 was obtained in the same manner as for copolymer 2, except that (a)-3 in Table 1 was changed to 1123 g (3.2 mol) and (b-1 in Table 2 was changed to 1221 g (0.8 mol).

[0064] (Comparative copolymer 1) (b) Comparative Copolymer 1 was obtained in the same manner as Copolymer 2, except that no polyoxyalkylene compound was used and (a)-1 in Table 1 was changed to 994 g (4.0 mol).

[0065] (Comparative copolymer 2) Comparative Copolymer 2 was obtained in the same manner as Copolymer 2, except that (a) polyoxyethylene compound was not used and (b)-1 in Table 2 was changed to 6107 g (4.0 mol).

[0066] (Comparative copolymer 3) Comparative copolymer 3 was obtained in the same manner as copolymer 2, except that (a)-1 in Table 1 was changed to 199 g (0.8 mol) and (b-1 in Table 2 was changed to 4886 g (3.20 mol).

[0067] (Comparative copolymer 4) Comparative Copolymer 4 was obtained by mixing 10 g of Comparative Copolymer 1 and 10 g of Comparative Copolymer 2.

[0068] [Table 1]

[0069] [Table 2]

[0070] [Table 3]

[0071] (Dispersion Test 1) 0.02 g of each copolymer (dispersant), 2.0 g of barium titanate, and 2.0 g of the following solvent were weighed into a 50 mL screw tube and stirred at 2000 rpm for 2 minutes using a planetary centrifugal mixer to obtain a slurry. The solvent used was either ion-exchanged water or a 1:1 (wt%) mixture of toluene and ethanol. The content of each component is shown in Table 4. The viscosity of each slurry composition was measured as follows, and the results are shown in Table 5. Using a dynamic viscoelasticity 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), and was evaluated according to the following criteria. ◎: Shear viscosity is less than 50 mPa·s 〇: Shear viscosity is 50 mPa·s or more and less than 200 mPa·s ×: Shear viscosity is 200 mPa·s or more

[0072] (Distributed Test 2) 0.1 g of each copolymer (dispersant), 2.0 g of barium titanate, and 0.5 g of the following solvent were weighed into a 50 mL screw tube and stirred at 2000 rpm for 2 minutes using a planetary centrifugal mixer to obtain a slurry. The solvent used was either ion-exchanged water or a 1:1 (wt%) mixture of toluene and ethanol. The content of each component is shown in Table 4. The viscosity of each slurry composition was measured as follows, and the results are shown in Table 5. Using a dynamic viscoelasticity 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), and was evaluated according to the following criteria. ◎: Shear viscosity is less than 1,000 mPa·s Good: Shear viscosity is 1,000 mPa·s or more and less than 20,000 mPa·s ×: Shear viscosity is 20,000 mPa·s or more

[0073] [Table 4]

[0074] [Table 5]

[0075] The slurry compositions of the examples using copolymers 1 to 9 showed low viscosity even when the dispersion medium or powder concentration was changed.

[0076] In contrast, Comparative Polymer 1, which contains only component (a) as a constituent unit, had a high slurry viscosity in organic solvents and poor dispersibility. Comparative Polymer 2, which contains only component (b) as a constituent unit, had a high slurry viscosity when the powder concentration was increased and poor dispersibility. Comparative Polymer 3, which has a molar ratio of component (a) to component (b) ((a):(b)) of 20:80, had a high slurry viscosity in organic solvents and poor dispersibility. Comparative Polymer 4, which is a mixture of Comparative Polymer 1, which contains only component (a) as a constituent unit, and Comparative Polymer 2, which contains only component (b) as a constituent unit, had a high slurry viscosity when the powder concentration was increased and poor dispersibility.

Claims

1. Component (a): Formula (1) R １ O(C) ２ H ４ O) ｍ R ２ (In formula (1), R １ represents a hydrocarbon group having 1 to 4 carbon atoms, and R ２ represents an unsaturated hydrocarbon group having 2 to 5 carbon atoms, and m represents the average number of moles of oxyethylene groups added, which is 1 to 15; Component (b): Formula (2) R ３ O (AO) ｎ R ４ (In formula (2), R ３ represents a hydrocarbon group having 1 to 4 carbon atoms, and R ４ represents an unsaturated hydrocarbon group having 2 to 5 carbon atoms, AO represents an oxyalkylene group having 2 to 4 carbon atoms, and n is the average number of moles of the oxyalkylene group added, which is 16 to 70; and Component (c): maleic acid-based compound, A copolymer containing as a constituent unit The copolymer is characterized in that the total proportion of the component (a) and the component (b) in the copolymer is 40 mol % or more, and the molar ratio of the component (a) to the component (b) ((a):(b)) is 97:3 to 50:

50.

2. A dispersant for inorganic powders, comprising the copolymer according to claim 1.

3. A slurry composition comprising: component (A): the inorganic powder dispersant according to claim 2; component (B): an inorganic powder; and component (C): a dispersion medium, The slurry composition comprises 0.01 to 10.0% by weight of the component (A), 5 to 80% by weight of the component (B), and 15 to 90% by weight of the component (C).

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