JP5109276B2 - Slurry composition for ceramic production - Google Patents

Description

  The present invention relates to a slurry composition for producing ceramics, and more particularly to a slurry composition for producing ceramics useful for the production of ceramic electronic parts such as ceramic capacitors, varistors, thermistors, dielectric filters and sensors.

For the production of ceramic electronic parts, a slurry composition for ceramic production is used, and the slurry composition for ceramic production contains, for example, a ceramic raw material powder and a dispersant in a dispersion medium. Examples of the ceramic raw material powder include fine metal particles, and generally used are those having a particle size of about submicron to several microns. Moreover, the dispersing agent is used in order to improve the dispersibility of the ceramic raw material powder in a dispersion medium.
Various dispersing agents have been proposed for dispersing metal fine particles in a dispersion medium, such as lignin sulfonate, naphthalene sulfonate formaldehyde condensate, melamine sulfonate formaldehyde condensate, polystyrene sulfonate, etc. Aromatic sulfonic acid dispersants, polyacrylates, salts of copolymers of maleic anhydride and α-olefins, polycarboxylic acid dispersants such as polyacrylic acid partial alkyl esters, and the like. Among them, there are many occasions where a polycarboxylic acid-based dispersant is used from the viewpoints of dispersion power and stability of the slurry composition (for example, see Patent Documents 1 and 2).
Japanese Patent Laid-Open No. 7-25665 JP 2000-185226 A

  In recent years, it has become possible to produce ultrafine particles having an average particle size of 0.01 to 0.1 μm by a direct current arc plasma method, and it is said that electronic parts having a further excellent function can be obtained by using this as a ceramic raw material powder. Yes. Therefore, if a very fine powder of submicron or nano size is used as the ceramic raw material powder and the slurry composition for ceramic production containing this in a high concentration is used, it can be densified at a lower temperature during ceramic sintering shrinkage. Is expected to be possible.

  However, conventional polycarboxylic acid-based dispersants may take time to act on the ceramic raw material powder. Thus, if the original dispersing power cannot be exhibited immediately after the addition of the dispersant, a stable slurry is obtained. For this reason, not only does the operation take longer than necessary, but the working efficiency is deteriorated, and the dispersant is excessively added, and when the dispersion force is exerted, the slurry is separated. Further, according to the study by the present inventors, as the particle size of the ceramic raw material powder is finer, the dispersibility (initial dispersibility) tends to be hardly exhibited immediately after the addition of the dispersant. When a polycarboxylic acid-based dispersant is used to prepare a slurry composition for producing ceramics containing a body at a high concentration, there has been a problem that the desired slurry composition for producing ceramics cannot be obtained due to an increase in viscosity. The inventors of the present invention have conducted further detailed research on the dispersant, and it is difficult to obtain a dispersion effect with the conventional polycarboxylic acid-based dispersant, and there is a limit to increasing the concentration of the slurry composition for producing ceramics. The conclusion was reached.

  The present invention has been made in view of such circumstances, and the problem to be solved includes an extremely fine ceramic raw material powder and a polycarboxylic acid-based dispersant, and has excellent dispersion stability and high concentration. An object of the present invention is to provide a slurry composition for producing ceramics that can be converted into a ceramic.

  As a result of intensive studies in view of the above problems, the present inventors have used a polycarboxylic acid-based copolymer composed of a specific component and having a predetermined weight average molecular weight as a dispersant. It has been found that even when a ceramic raw material powder is contained, the dispersion stability is excellent and a high concentration can be achieved, and the present invention has been completed.

That is, the present invention is as follows.
(1) The following (A) component and (B) component are included in the dispersion medium, and the content of (B) component is 0.5 to 5.0% by weight with respect to the total weight of (A) component. A slurry composition for producing ceramics, which is characterized in that it exists.

(A) Ceramic raw material powder having an average particle diameter of 0.01 to 1.0 μm (B) (a) General formula [I];
R ¹ O (AO) _n R ² [I]
(In the formula, R ¹ represents a hydrocarbon group having 1 to 18 carbon atoms, R ² represents an unsaturated hydrocarbon group having 2 to 5 carbon atoms, and AO is one kind of oxyalkylene group having 2 to 4 carbon atoms. Or 2 or more, and n is the average addition mole number of the oxyalkylene group and represents a positive number of 1 to 100).
(B) a maleic acid compound;
(C) A dispersant comprising a polycarboxylic acid copolymer having a weight average molecular weight of 14,000 or less, containing a monomer copolymerizable with the component (a) and the component (b) as a constituent unit.

(2) The slurry composition for producing ceramics according to (1) above, wherein the polycarboxylic acid copolymer has a weight average molecular weight of less than 10,000.
(3) The polycarboxylic acid copolymer is obtained by polymerizing the component (a), the component (b) and optionally the component (c) in the presence of an azo polymerization initiator and a chain transfer agent. The slurry composition for producing a ceramic according to the above (1) or (2), wherein
(4) The slurry composition for producing a ceramic according to any one of (1) to (3) above, wherein the content of the component (A) is more than 60% by weight based on the total weight of the dispersion medium. object.

  According to the present invention, a slurry composition for producing ceramics which is excellent in dispersion stability without gelation or rapid viscosity increase even when containing a ceramic raw material powder having a particle size of several tens to several hundreds of nanometers at a high concentration Things can be provided. In addition, the slurry composition for producing ceramics of the present invention can prepare a slurry composition having a low viscosity in a short time and with a low addition amount. In addition, a ceramic molded body having excellent dimensional stability can be obtained. Therefore, the slurry composition for producing ceramics of the present invention is useful for producing ceramic electronic parts such as ceramic capacitors, varistors, thermistors, dielectric filters and sensors.

Hereinafter, the present invention will be described in detail with reference to preferred embodiments thereof.
The slurry composition for producing a ceramic of the present invention contains the component (A) and the component (B) in the dispersion medium, and the content of the component (B) is 0 with respect to 100 parts by weight of the component (A). .5 to 5.0 parts by weight.

(A) component Although it will not specifically limit if (A) component is generally used as a ceramic raw material, For example, an inorganic powder can be used.
Examples of the inorganic powder include silicates such as kaolin, aluminum silicate, clay, talc, mica, calcium silicate, sericite, and bentonite; carbonates such as calcium carbonate, magnesium carbonate, barium carbonate, and basic lead carbonate. Salts; sulfates such as calcium sulfate and barium sulfate; chromates such as strontium chromate and pigment yellow; magnesium molybdate such as zinc molybdate and calcium zinc molybdate; alumina, antimony oxide, titanium oxide, cobalt oxide, tetraoxide Metal oxides such as triiron, ferric trioxide, trilead tetraoxide, lead monoxide, chromium oxide green, tungsten trioxide, yttrium oxide; aluminum hydroxide, magnesium hydroxide, calcium hydroxide, iron hydroxide, metatitanium Metal hydroxide such as acid Metal carbides such as silicon carbide, tungsten carbide, boron carbide, titanium carbide; aluminum nitride, silicon nitride, boron nitride, zirconia, barium titanate, satin white, carbon black, graphite, chrome yellow, mercury sulfide, ultramarine, Paris Examples thereof include powders of blue, titanium yellow, chromium vermillion, lithopone, copper acetoarsenite, nickel, silver, palladium, lead zirconate titanate, and the like.

  Although the average particle diameter of the ceramic raw material powder varies greatly depending on the type, ultrafine particles having an average particle diameter of usually 0.01 to 1.0 μm, preferably 0.01 to 0.5 μm are used. Further, as the ceramic raw material powder, two or more kinds of different kinds of particles may be used in combination as long as the average particle diameter is in the range of 0.01 to 1.0 μm. The average particle size (D50) can be obtained by measuring the ceramic raw material powder to be used with a particle size distribution meter (dynamic light scattering method, NICOMP 370A, manufactured by Particle Sizing Systems).

Component (B) The component (B) is a polycarboxylic acid copolymer containing the components (a) and (b) as essential structural units and the component (c) as optional structural units. A terpolymer having the component (b) and the component (b) and the component (c) as essential structural units is also used. Hereinafter, each component will be described.

The component (a) is a compound represented by the above general formula [I].
In the formula, R ¹ represents a hydrocarbon group having 1 to 18 carbon atoms, and such a hydrocarbon group may be in any form of linear, branched, and cyclic. Examples of R ¹ include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, tert-butyl group, pentyl group, isopentyl group, neopentyl group, hexyl group, heptyl group, Examples include octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, cyclohexyl group, phenyl group, benzyl group, etc. 1-4 hydrocarbon groups are preferable, and a methyl group, an ethyl group, a propyl group, and a butyl group are more preferable.
R ² represents an unsaturated hydrocarbon group having 2 to 5 carbon atoms, and the unsaturated hydrocarbon group may be in a linear or branched form. Examples of R ² include a vinyl group, an allyl group, an isopropenyl group, a 1-propenyl group, a methallyl group, and a 3-butenyl group. Among these, an unsaturated hydrocarbon group having 3 to 4 carbon atoms is preferable. An allyl group and a methallyl group are more preferable in that they have moderate polymerizability and are easy to copolymerize with the component (a).
AO represents an oxyalkylene group having 2 to 4 carbon atoms, and the oxyalkylene group may be either linear or branched. Further, AO may be one type or two or more types, and when AO is two or more types, the addition form may be random or block. Examples of AO include an oxyethylene group, an oxypropylene group, an oxybutylene group, and an oxytetramethylene group. Among them, an oxyethylene group and an oxypropylene group are preferable.
n is an average addition mole number of the oxyalkylene group and represents a positive number of 1 to 100, and a positive number of 10 to 60 is preferable. If n is less than 1, sufficient dispersion performance may not be exhibited. On the other hand, when n exceeds 100, there is a possibility that the viscosity becomes high and the handling becomes difficult.

The polyoxyalkylene derivative represented by R ¹ O (AO) _n R ^{2 as} component (a) is a polyoxyalkylene derivative represented by R ¹ O (AO) _n H (n is as defined above; hereinafter the same). be introduced unsaturated hydrocarbon group represented by R ² in the polyoxyalkylene derivatives, it is introduced hydrocarbon group represented by R ¹ in the polyoxyalkylene derivative represented by R 2 ^{O (AO)} _n H Good.
There is no particular limitation on the method for introducing the unsaturated hydrocarbon group represented by R ² into the polyoxyalkylene derivative represented by R ¹ O (AO) _n H. For example, sodium hydroxide is added to polyoxyalkylene monoalkyl ether. It can be obtained by adding an alkali metal hydroxide such as potassium hydroxide and etherification reaction with monohalogenated unsaturated hydrocarbon such as allyl chloride, allyl bromide, allyl iodide, methallyl chloride, methallyl bromide. .
Further, the polyoxyalkylene derivative represented by _{^{R 2 O (AO) n H}} , no particular limitation on the method of introducing the hydrocarbon group represented by R ^1, for example, polyoxyalkylene monoallyl ether, or poly Obtained by adding an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide to oxyalkylene monomethallyl ether and etherification with monohalogenated hydrocarbons such as methyl chloride, methyl bromide, butyl chloride, butyl bromide You can also
In addition, (a) component can be used individually or in combination of 2 or more types.

  The component (b) is a maleic acid compound. In this specification, a maleic acid compound is a concept including maleic acid and its derivatives, and examples of maleic acid derivatives include maleic anhydride and maleate. Examples of maleates include alkali metal salts, alkaline earth metal salts, ammonium salts, and organic amine salts. These salts may be mono-substituted or di-substituted. Examples of alkali metal salts include monolithium salts, dilithium salts, monosodium salts, disodium salts, monopotassium salts, and dipotassium salts. Alkaline earth metal salts include calcium salts and magnesium salts, and ammonium salts. Examples of the organic amine salt include alkylamine salts such as methylamine salt, dimethylamine salt, and ethylamine salt, monoethanolamine salt, diethanolamine salt, triethanolamine salt, and methylethanol. Examples thereof include alkanolamine salts such as amine salts. In addition, (b) component can be used individually or in combination of 2 or more types.

  Component (c) is a monomer copolymerizable with components (a) and (b). Examples of such monomers include styrene, vinyl acetate, vinyl sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, acrylic acid, methacrylic acid, acrylic acid ester, methacrylic acid ester, acrylonitrile, methacrylonitrile, acrylamide, methacrylic acid. Examples thereof include compounds having an ethylenically unsaturated bond such as amide, isobutylene, diisobutylene and vinylcyclohexane. Among them, styrene, isobutylene, diisobutylene and vinyl acetate are preferable.

In order to obtain a polycarboxylic acid-based copolymer, the above-described monomer components may be polymerized. In this case, the blending ratio of each monomer can be appropriately selected. The blending ratio of each monomer is preferably (a) component: (b) component: (c) component = 35 to 65 mol%: 35 to 65 mol%: 0 to 30 mol%, more preferably (a). Component: (b) Component: (c) Component = 45 to 55 mol%: 45 to 55 mol%: 0 to 10 mol%, and in the case of a terpolymer, (a) component: (b) Component: (c) Component = 45 to 54.8 mol%: 45 to 54.8 mol%: 0.2 to 5 mol% is preferable.
The polymerization type can be carried out by a known method such as solution polymerization or bulk polymerization, and is not particularly limited. That is, the polymerization reaction can be performed in the absence of a solvent or in the presence of a solvent, but when the polymerization reaction is performed in the presence of a solvent, water; alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol; acetone, Uses ketones such as 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 Among these, toluene and methylcyclohexane are preferably used. The usage-amount of a solvent is 1-50 weight% normally with respect to the total weight of a monomer, Preferably it is 5-30 weight%. The solution polymerization can be carried out batchwise or continuously.

As polymerization initiators, peroxide initiators such as benzoyl peroxide; azo polymerization initiators such as 2,2′-azobisisobutyronitrile; persulfate initiators such as ammonium persulfate and sodium persulfate, etc. Is mentioned. Moreover, you may use a chain transfer agent together as needed. In that case, the ratio of the polymerization initiator (C) to the chain transfer agent (D) is a molar ratio (D / C), usually 0.1 ≦ (D) / (C) ≦ 20, preferably 0.4 ≦. (D) / (C) ≦ 5. The polymerization temperature is usually 50 to 100 ° C., preferably 60 to 90 ° C., and the polymerization time is usually 5 to 25 hours, preferably 5 to 10 hours.
In the present invention, in order to obtain a polycarboxylic acid copolymer having excellent dispersibility and a high concentration, it is preferable to perform polymerization in the presence of an azo initiator and a chain transfer agent.

  Examples of the azo initiator include 2,2′-azobis-2-methylpropionamidine hydrochloride, 2,2′-azobis-N- (2-hydroxyethyl) -2-methylpropionamidine hydrochloride, 2, 2'-azobis-2-methyl-N-phenylpropionamidine hydrochloride, 2,2'-azobis-N- (4-chlorophenyl) -2-methylpropionamidine hydrochloride, 2,2'-azobis-N- ( 4-hydroxyphenyl) -2-methylpropionamidine hydrochloride, 2,2'-azobis-2-methyl-N-phenylmethylpropionamidine hydrochloride, 2,2'-azobis-2-methyl-N-2-propenyl Propionamidine hydrochloride, 2,2′-azobis-2-methyl-N-[(1,1-bishydroxymethyl) -2-hydroxyethyl] propiona Midine, 2,2′-azobis-2-methyl-N-[(1,1-bishydroxymethyl) ethyl] propionamidine, 2,2′-azobis-2-methyl-N- (2-hydroxyethyl) propion Azoamidine compounds such as amidine, 2,2′-azobis-2-methylpropionamidine dihydrate; 2,2′-azobis-2- (2-imidazolin-2-yl) propane hydrochloride, 2, 2′- Azobis-2- (5-methyl-2-imidazolin-2-yl) propane hydrochloride, 2,2′-azobis-2- [1- (2-hydroxyethyl) -2-imidazolin-2-yl] propane hydrochloride Salt, 2,2'-azobis-2- (2-imidazolin-2-yl) propane, 2,2'-azobis-2- (3,4,5,6-tetrahydropyrimidin-2-yl) propane hydrochloride 2,2′-azobis-2- (5-hydroxy-3,4,5,6-tetrahydropyrimidin-2-yl) propane hydrochloride, 2,2′-azobis-2- (4,5,6, Cyclic azoamidine compounds such as 7-tetrahydro-1H-1,3-diazepin-2-yl) propane hydrochloride; aqueous azo initiators such as azonitrile compounds such as 2-carbamoylazoisobutyronitrile; 2,2′- Azobisisobutyronitrile, 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis- 2-methylbutyronitrile, 1,1′-azobis (cyclohexane-1-carbonitrile), 2,2′-azobis (dimethyl isobutyrate), 1,1′-azobis- (cyclohexane-1-carbonitri) ) And the like oily azo initiators such. Among them, in the present invention, it is preferable to use an oily azo polymerization initiator, and 2,2′-azobisisobutyronitrile is particularly preferable. The usage-amount of an azo initiator is 1-10 mol% normally with respect to the total weight of a monomer, Preferably it is 2-5 mol%.

  Examples of the chain transfer agent include mercaptoethanol, mercaptoacetic acid, dodecyl mercaptan, thioglycerol, thioglycolic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, thiomalic acid, octyl thioglycolate, and 3-mercaptopropion. Examples include octyl acid, 2-mercaptoethanesulfonic acid, and 2-benzothiazole thiol. Among them, mercaptoethanol, mercaptoacetic acid, dodecyl mercaptan, and 2-benzothiazole thiol are preferable. The usage-amount of a chain transfer agent is 1-20 mol% normally with respect to the total weight of a monomer, Preferably it is 2-10 mol%. In addition, a chain transfer agent can be used individually or in combination of 2 or more types.

  The polycarboxylic acid copolymer thus obtained can be converted into a hydrolyzate of the copolymer or a salt of the hydrolyzate as necessary. For example, when maleic anhydride is used as the component (b), a part or all of maleic anhydride units can be opened by hydrolysis after the polymerization reaction to obtain a hydrolyzate of a polycarboxylic acid copolymer. . Furthermore, a salt of the polycarboxylic acid copolymer hydrolyzate can be obtained by neutralizing part or all of the maleic acid units of the hydrolyzate of the polycarboxylic acid copolymer with an alkali. Examples of the alkali used for neutralization include hydroxides, carbonates or bicarbonates of alkali metals such as lithium, sodium, and potassium; hydroxides of alkaline earth metals such as magnesium and calcium; methylamine, dimethylamine, ethylamine, etc. Alkanolamines such as alkylamine, monoethanolamine, diethanolamine, triethanolamine and methylethanolamine; ammonia and the like. In addition, these can be used individually or in combination of 2 or more types.

  The weight average molecular weight (Mw) of the polycarboxylic acid copolymer is 14,000 or less, preferably 12,000 or less, more preferably less than 10,000, and particularly preferably 8,000 or less. In the present invention, the lower the Mw, the higher the slurry concentration becomes possible, and a high dispersion effect is expressed even at a high concentration. However, those having an Mw of less than 3000 may be difficult to manufacture. The lower limit of Mw is preferably 3,000 because it tends to be disadvantageous in terms of cost. In addition, in this specification, a weight average molecular weight means the weight average molecular weight of standard polyethyleneglycol conversion by gel permeation chromatography (GPC).

(Dispersion medium)
The dispersion medium is not limited to water, and an organic solvent can also be used. Examples of the organic solvent include fuel oils such as kerosene, light oil, and kerosene; aliphatic hydrocarbons such as hexane, isohexane, cyclohexane, methylcyclohexane, and isooctane; aromatic hydrocarbons such as benzene, toluene, xylene, and cresol; Alcohols such as ethanol, methanol, isopropyl alcohol; esters such as ethyl acetate, dioctyl phthalate, soybean oil, linseed oil; polyethylene glycol, polypropylene glycol, carbitol, monoglyme, diglyme, tetraglyme, methyl cellosolve, butyl cellosolve Ethers such as 1,1,1-trichloroethane, trichloroethylene, dichloroethylene, chlorodifluoromethane and the like halogenated hydrocarbons; acetone, methyl ethyl ketone, etc. Ton class; terpineol, liquid paraffin, mineral spirits, or the like can be used glycerin. As the dispersion medium, it is preferable to use an organic solvent. In addition, you may use a dispersion medium individually or in combination of 2 or more types.

  In the present invention, conventionally known various additives such as other dispersants, viscosity modifiers, surfactants, antifoaming agents, etc., in the slurry composition for producing ceramics, as long as the object of the present invention is not impaired. Can be contained.

The slurry composition for producing ceramics can be prepared by adding the component (B) and various additive components used as desired in a predetermined ratio and uniformly dispersing the component (A) according to a conventionally known method. In that case, it is preferable to use 0.5 to 5 weight% of (B) component with respect to the total weight part of (A) component, More preferably, it is 0.5 to 3 weight part, More preferably, it is 0.5. ~ 2% by weight. If the amount of the component (B) used is less than 0.5% by weight, the effect of improving the dispersion stability is hardly exhibited, and if it exceeds 5% by weight, the physical properties of the resulting ceramic are impaired.
In addition, the concentration of the component (A) is usually 40% by weight or more, preferably 50% by weight or more with respect to the total weight of the dispersion medium, from the viewpoints of handleability, moldability, sinterability, etc. Is 90% by weight or less, preferably 80% by weight or less. In addition, in this specification, the ratio (weight%) of (A) component with respect to the total weight of a dispersion medium is called slurry concentration.
Furthermore, in the present invention, since the component (B) described above is contained as a dispersant, even if the slurry concentration is as high as more than 60% by weight (more than 65% by weight), gelation and viscosity Thus, it is possible to obtain a slurry composition for producing ceramics which is excellent in dispersion stability without causing a rapid increase in the temperature. Here, in this specification, a viscosity means what was measured using the dynamic viscoelasticity apparatus (25 degreeC, Paar Physica MCR300, Nihon Shibel Hegner company make).

By firing the slurry composition for producing ceramics of the present invention, a ceramic molded body can be obtained. Before firing the ceramics, the slurry composition for producing ceramics is desired according to a known method such as extrusion molding or rolling roll molding. The green molded product may be fired after forming into a green molded product.
The ceramic molded body obtained from the slurry composition for producing a ceramic according to the present invention is dense and excellent in dimensional stability, and thus is useful as a ceramic electronic component such as a ceramic capacitor, a varistor, a thermistor, a dielectric filter, and a sensor.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not restrict | limited at all by these Examples. In Examples,% is% by weight unless otherwise specified.

(Preparation of dispersant)
(Synthesis Example 1)
A 5-liter pressurized reactor was charged with 160 g (5.0 mol) of methanol and 6.0 g of sodium methylate as a catalyst, and the air in the system was replaced with nitrogen gas. 0.0 mol) was gradually injected at about 0.05 to 0.5 MPa (gauge pressure) to carry out the addition reaction. After completion of the reaction, the inside of the reaction vessel was cooled to 50 ° C. Next, 280 g of potassium hydroxide was added to the reaction solution, the air in the system was replaced with nitrogen gas, and then 382.5 g (5.0 mol) of allyl chloride was gradually added while stirring at 80 ° C. Thereafter, the reaction was performed for 6 hours to remove the by-produced salt to obtain a polyoxyalkylene derivative.

  Subsequently, 2,224 g (4 moles) of the polyoxyalkylene derivative obtained above and 392 g (4 moles) of maleic anhydride were added to a 5 liter flask equipped with a stirrer, thermometer, nitrogen gas inlet tube, dropping funnel and reflux condenser. Mol), 4.16 g (0.04 mol) of styrene, 48.5 g (0.24 mol) of dodecyl mercaptan, and 400 g of toluene. A solution of 39.4 g (0.24 mol) of 2,2′-azobisisobutyronitrile as a polymerization initiator dissolved in 132 g of toluene was added dropwise at 85 ± 2 ° C. over 3 hours under a nitrogen gas atmosphere. did. After completion of dropping, the reaction was further continued at 85 ± 2 ° C. for 3 hours. Toluene was distilled off under reduced pressure, and the molecular weight of the resulting polycarboxylic acid copolymer was measured by GPC. As a result, the weight average molecular weight was 12,000.

(Synthesis Examples 2 to 4)
A polyalkylene derivative was synthesized by the same method as in Synthesis Example 1 except that the blending ratio shown in Table 1 was changed, and then a polycarboxylic acid copolymer was obtained.

(Synthesis Example 5)
The polyalkylene derivative was synthesized by the same method as in Synthesis Example 1. Next, in a 5 liter flask equipped with a stirrer, a thermometer, a nitrogen gas inlet tube, a dropping funnel and a reflux condenser, 2,604 g of a polyoxyalkylene derivative, 323.4 g of maleic anhydride (3.3 mol), styrene 3 .12 g (0.03 mol), mercaptoethanol 16.6 g (0.54 mol), and toluene 400 g were added. Next, in a nitrogen gas atmosphere, 29.5 g (0.18 mol) of AIBN as a polymerization initiator dissolved in 140 g of toluene was dropped into a reaction vessel at 85 ± 2 ° C. over 3 hours. After completion of dropping, the reaction was further continued at 85 ± 2 ° C. for 3 hours. Toluene was distilled off under reduced pressure and neutralized with triethanolamine (1.65 mol). As a result of measuring the molecular weight of the obtained polycarboxylic acid copolymer by GPC, the weight average molecular weight was 6,000.

(Synthesis Example 6)
A polyoxyalkylene derivative was synthesized in the same manner as in Synthesis Example 1. Next, in a 5-liter flask equipped with a stirrer, a thermometer, a nitrogen gas introduction tube, a dropping funnel and a reflux condenser, 2,780 g of a polyoxyalkylene derivative, 400 g of toluene, 490 g (5 mol) of maleic anhydride and styrene 5. 2 g (0.05 mol) was added, and 64.8 g (0.3 mol) of BPH as a polymerization initiator was added at 35 ° C. The air in the system was replaced with nitrogen gas, and then reacted at 50 ± 2 ° C. for 16 hours. Toluene was distilled off under reduced pressure, and the molecular weight of the resulting polycarboxylic acid copolymer was measured by GPC. As a result, the weight average molecular weight was 15,000.

(Synthesis Example 7)
A polyoxyalkylene derivative was synthesized by the same method as in Synthesis Example 6 except that the blending ratio shown in Table 1 was changed, and then a polycarboxylic acid copolymer was obtained.

(Synthesis Example 8)
An acrylic resin which is a known dispersant was synthesized by the following method. That is, 1 kg of deionized water was put into a five-necked flask equipped with a stirrer, a thermometer, a dropping funnel, a nitrogen gas inlet tube and a reflux condenser, and the temperature was raised to 70 ° C. under a nitrogen gas stream. Subsequently, while maintaining the temperature at 70 to 75 ° C., 200 g of polyoxyethylene monomethyl methacrylate (average molecular weight 540), 50 g of acrylic acid, 500 g of methyl acrylate and 2,2′-azobis [2-methyl-N-2-propenylpropionamidine] An aqueous solution in which 3.0 g of dihydrochloride was dissolved in 200 g of deionized water was added dropwise over 5 hours, and then kept at 75 ° C. for 2 hours. After the polymerization reaction, a 30% aqueous ammonia solution was added for neutralization to obtain an aqueous acrylic resin solution. As a result of measuring the molecular weight of the obtained acrylic resin by GPC, the weight average molecular weight was 60,000.

(Preparation of slurry composition for ceramic production)
(Examples 2, 3, 5, Reference Examples 1-2 and Comparative Examples 1-2)
Using a mixed solution of toluene: ethanol = 1: 1 as a dispersion medium and alumina having an average particle size of 0.1 μm as a ceramic raw material powder, a slurry composition for producing ceramics was prepared as follows. That is, 300 g of alumina was weighed into a 1 L beaker, and 3.0 g of the dispersant shown in Table 2 (1.0 wt% with respect to the ceramic raw material powder), 300 g of dispersion medium (slurry concentration 50%), 162 g (Slurry concentration 65%) and 100 g (slurry concentration 75%) were added, respectively, and stirred at 120 rpm for 1 minute using a four-blade impeller to prepare a slurry composition for producing ceramics. And the fluidity | liquidity of the obtained slurry composition for manufacture of ceramics was evaluated by the following reference | standard, and the viscosity in 25 degreeC was measured using the dynamic viscoelasticity apparatus (Paar Physica MCR300, Nihon Shibel Hegner company make). The results are shown in Table 2.

(Fluidity test)
Evaluation criteria:
A: All powders are uniformly dispersed in the dispersion medium.
○: Most of the powder is uniformly dispersed in the dispersion medium, but remains slightly at the bottom.
Δ: About half of the powder is dispersed in the dispersion medium, but aggregation is also observed.
X: The powder is not dispersed at all in the dispersion medium.

4) Slurry concentration: (A) component / dispersion medium x 100 (wt%)
5) Impossible to measure: The viscosity of the slurry composition is 10,000 (mPa · s) or more.

(Examples 6-8 and Comparative Examples 3-4)
A slurry composition for producing ceramics was prepared as follows using terpineol as a dispersion medium and silicon nitride having an average particle size of 0.2 μm as a ceramic raw material powder. That is, weigh 250 g of silicon nitride into a 1 L beaker, add 2.5 g of the dispersant shown in Table 3 (1.0% by weight with respect to the ceramic raw material powder) and 250 g of the dispersion medium, and add a four-blade impeller. The resulting mixture was stirred at 120 rpm for the time shown in Table 3 to prepare a slurry composition for producing ceramics. And the fluidity | liquidity and viscosity of the obtained slurry composition for ceramics manufacture were evaluated on the basis similar to the above. The results are shown in Table 3.

5) Impossible to measure: The viscosity of the slurry composition is 10,000 (mPa · s) or more.

(Examples 9 to 10 and Comparative Example 5)
A slurry composition for producing ceramics was obtained as follows using water as a dispersion medium and two kinds of alumina having an average particle diameter of 0.1 μm and 1.2 μm as ceramic raw material powders. That is, 250 g of alumina was weighed into a 1 L beaker, 2.5 g of the dispersant shown in Table 4 (1.0% by weight with respect to the ceramic raw material powder) and 130 g of the dispersion medium were added, and a four-blade impeller was used. The slurry was stirred at 120 rpm for the time shown in Table 4 to prepare a slurry composition for producing ceramics. And the fluidity | liquidity and viscosity of the obtained slurry composition for ceramics manufacture were evaluated on the basis similar to the above. The results are shown in Table 4.

Claims (3)

The dispersion medium contains the following component (A) and component (B), and the content of component (B) is 0.5 to 5.0% by weight with respect to the total weight of component (A). A slurry composition for producing ceramics, which is characterized.
(A) Ceramic raw material powder having an average particle diameter of 0.01 to 1.0 μm (B) (a) General formula [I];
R ¹ O (AO) _n R ² [I]
(In the formula, R ¹ represents a hydrocarbon group having 1 to 18 carbon atoms, R ² represents an unsaturated hydrocarbon group having 2 to 5 carbon atoms, and AO is one kind of oxyalkylene group having 2 to 4 carbon atoms. Or 2 or more, and n is the average addition mole number of the oxyalkylene group and represents a positive number of 1 to 100).
(B) a maleic acid compound;
(C) optionally containing a monomer copolymerizable with component (a) and component (b) as constituent units; (a) component, component (b) and optionally component (c) starting azo-based polymerization A dispersant comprising a polycarboxylic acid copolymer having a weight average molecular weight of 8,000 or less , obtained by polymerization in the presence of an agent . The polycarboxylic acid copolymer is obtained by polymerizing the component (a), the component (b) and optionally the component (c) in the presence of an azo polymerization initiator and a chain transfer agent. to claim 1 Symbol placement of the ceramic-forming slurry composition. The slurry composition for producing ceramics according to claim 1 or 2 , wherein the content of the component (A) is more than 60% by weight based on the total weight of the dispersion medium.