JP2012072057A - Method for producing slurry composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a slurry composition by which a slurry composition keeping high dispersibility over a long period of time can be produced in a simple way, and to provide a slurry composition produced using the method for producing a slurry composition.SOLUTION: The method for producing a slurry composition containing an inorganic powder, a polyvinyl acetal resin and an organic solvent includes: a step of preparing an inorganic dispersion by adding and mixing the inorganic powder, a polyvinyl acetal resin (A) and an organic solvent for inorganic dispersion; a step of preparing a resin solution by adding and mixing a polyvinyl acetal resin (B) and an organic solvent for a resin solution; and a step of adding the resin solution to the inorganic dispersion. The polyvinyl acetal resin (A) has a polymerization degree of 20-600 and an amount of hydroxy groups of 27.5-37 mol%. The polyvinyl acetal resin (B) has a polymerization degree of 800-4,200 and an amount of hydroxy groups of 28-42 mol%. In the step of preparing the inorganic dispersion, the polyvinyl acetal resin (A) is added in an amount of 0.1-20 pts.wt. relative to 100 pts.wt. of the inorganic powder.

Description

The present invention relates to a method for producing a slurry composition capable of producing a slurry composition capable of maintaining high dispersibility over a long period of time by a simple method. Moreover, it is related with the slurry composition manufactured using the manufacturing method of this slurry composition.

Polyvinyl acetal resin is excellent in toughness, film-forming properties, inorganic pigments, dispersibility of organic powders, adhesion to coated surfaces, etc. And conductive paste, ink, paint, baking enamel, wash primer, etc.

In particular, a multilayer ceramic capacitor is generally manufactured through the following steps.
First, a ceramic raw material powder is added to a binder resin such as a polyvinyl butyral resin and mixed uniformly to obtain a slurry composition. The obtained slurry composition is applied to the support surface subjected to the mold release treatment. This is heated to remove volatile components such as a solvent, and then peeled off from the support to obtain a ceramic green sheet. Next, on the obtained ceramic green sheet, a plurality of sheets of conductive paste containing ethyl cellulose, polyvinyl butyral resin, etc. applied as a binder resin are alternately stacked, heated and pressed to produce a laminate, After performing the degreasing treatment, a multilayer ceramic capacitor is obtained through a step of sintering an external electrode on the end face of the fired ceramic product obtained by firing.

In recent years, there has been a demand for further downsizing and higher capacity of multilayer ceramic capacitors, and further multilayering and thinning have been studied. In such multilayer ceramic capacitors, a thin film of a ceramic green sheet is considered. Therefore, ceramic powders having a small particle diameter are demanded.

Generally, as a method of dispersing ceramic powder or the like in a slurry composition, as described in Patent Document 1, an inorganic dispersion composed of an inorganic powder, an organic solvent, etc. is prepared on the one hand, and a binder resin is dissolved on the other hand. A method of mixing the inorganic dispersion and the resin solution after preparing the prepared resin solution is used.
However, such a method has a problem that unless the mixed solution is stirred for a long time, the ceramic powder is not sufficiently dispersed, and stirring requires excessive energy and time.
As a method for ensuring the dispersibility of the ceramic powder in the slurry composition, as described in Patent Document 2, a method of adding a dispersant is also used. However, such a method has a problem in that the dispersibility is worsened if the compatibility with the binder resin is poor.
Furthermore, in the production of the multilayer ceramic capacitor, after preparing the ceramic slurry composition, there may be a storage period of several days before coating, and if the long-term slurry dispersion stability is insufficient, Due to the lowering of the dispersibility, the strength of the ceramic green sheet is reduced and the surface irregularities are increased, resulting in a problem that the electrical characteristics of the obtained multilayer ceramic capacitor are lowered.

JP 2005-139034 A JP-A-6-325971

An object of this invention is to provide the manufacturing method of the slurry composition which can manufacture the slurry composition which can maintain a high dispersibility over a long period of time by a simple method in view of the said present condition. Moreover, it aims at providing the slurry composition manufactured using the manufacturing method of this slurry composition.

The present invention relates to a method for producing a slurry composition containing an inorganic powder, a polyvinyl acetal resin and an organic solvent, wherein the inorganic powder, the polyvinyl acetal resin (A) and an organic solvent for inorganic dispersion are added and mixed to form an inorganic dispersion. A step of adding a polyvinyl acetal resin (B) and an organic solvent for a resin solution to prepare a resin solution, and a step of adding a resin solution to the inorganic dispersion, and the polyvinyl acetal The resin (A) has a degree of polymerization of 20 to 600 and a hydroxyl group amount of 27.5 to 37 mol%, and the polyvinyl acetal resin (B) has a polymerization degree of 800 to 4200 and a hydroxyl group amount of 28. In the step of preparing the inorganic dispersion, the polyvinyl acetal resin (A) is added in an amount of 0.1 to 100 parts by weight of the inorganic powder. 0 is a manufacturing method of parts added to the slurry composition.
Hereinafter, the present invention will be described in detail.

As a result of intensive studies, the inventor prepared an inorganic dispersion composed of inorganic powder, an organic solvent for inorganic dispersion, a dispersant, etc. on the one hand, and prepared a resin solution in which the binder resin was dissolved on the other hand, and then dispersed the inorganic dispersion. In the manufacturing method of the slurry composition in which the liquid and the resin solution are mixed, the dispersibility of the inorganic powder is greatly improved by adjusting the degree of polymerization and the amount of hydroxyl groups of the polyvinyl acetal resin used as the dispersant to a predetermined range. It was found that a slurry composition capable of maintaining high dispersibility over a long period of time can be produced.
Moreover, when producing a ceramic green sheet using the slurry composition obtained using such a manufacturing method, it discovered that it could peel easily from sheets, such as PET, with small force, and came to complete this invention.

In the present invention, an inorganic powder, a polyvinyl acetal resin (A) and an organic solvent for inorganic dispersion are added and mixed to prepare an inorganic dispersion, and a polyvinyl acetal resin (B) and an organic solvent for a resin solution are added and mixed. A step of preparing a resin solution, and a step of adding the resin solution to the inorganic dispersion.
In the present invention, the polyvinyl acetal resin (A) is used as a dispersant in the step of preparing the inorganic dispersion. Thus, in the process of producing the inorganic dispersion liquid, the polyvinyl acetal resin (A) adheres to the surface of the inorganic powder by using the polyvinyl acetal resin (A) as a dispersant, and as a result, the dispersibility of the inorganic powder is improved. Can be increased. After that, even if the resin solution containing the polyvinyl acetal resin (B) is added to the inorganic dispersion, the polyvinyl acetal resin (B) is adsorbed to the inorganic powder due to the steric hindrance of the polyvinyl acetal resin (A) attached earlier. Therefore, the strength of the sheet obtained, for example, in the case of using a green sheet can be increased without impairing the dispersibility of the inorganic powder.
Therefore, since the high intensity | strength which polyvinyl acetal resin (B) expresses, without inhibiting the outstanding dispersibility of polyvinyl acetal resin (A), the film | membrane which has the outstanding dispersibility of inorganic powder and high intensity | strength. A slurry composition having the effect of obtaining a shaped body can be produced.
On the other hand, when the polyvinyl acetal resin (A) and the polyvinyl acetal resin (B) are added at the same time, the polyvinyl acetal resin (B) adheres to the surface of the inorganic powder, and as a result, aggregation of the inorganic powder occurs. As a result, the dispersibility of the inorganic powder is greatly reduced.

In the step of preparing the inorganic dispersion, it is preferable to add the inorganic powder after previously mixing and dissolving the polyvinyl acetal resin (A) in the organic solvent for inorganic dispersion.

In the present invention, the polyvinyl acetal resin (A) is used as a dispersant in the step of preparing the inorganic dispersion. In the present invention, by using the same kind of polyvinyl acetal resin (A) as the binder resin as the dispersant, it is not necessary to consider the adverse effects due to the addition of the dispersant as in the prior art.
In the present specification, the polyvinyl acetal resin (A) and the polyvinyl acetal resin (B) described later are also simply referred to as a polyvinyl acetal resin when it is not necessary to distinguish between them.

The lower limit of the degree of polymerization of the polyvinyl acetal resin (A) is 20, and the upper limit is 600. When the degree of polymerization is less than 20, it is difficult to obtain industrially and is not practical. When the degree of polymerization exceeds 600, the cohesive force becomes too high, and it becomes difficult to develop sufficient dispersibility. The preferable lower limit of the polymerization degree is 100, and the preferable upper limit is 500.

The lower limit of the amount of hydroxyl groups in the polyvinyl acetal resin (A) is 27.5 mol%, and the upper limit is 37 mol%. When the amount of the hydroxyl group is less than 27.5 mol%, the polyvinyl acetal resin (A) is less likely to adhere to the surface of the inorganic powder, and does not contribute to the improvement of dispersibility. Not only is the synthesis of the acetal resin (A) difficult, but the solubility in the solvent is reduced. Moreover, when producing a ceramic green sheet using the slurry composition obtained by making the amount of hydroxyl groups into the said range, it can peel easily from sheets, such as PET, with small force. A preferable lower limit of the hydroxyl group content is 31 mol%, and a preferable upper limit is 35 mol%.

The polyvinyl acetal resin (A) preferably has an anionic group.
By having the anionic group, the polyvinyl acetal resin (A) can easily adhere to the surface of the inorganic powder, and the dispersibility of the inorganic powder can be improved.

The anionic group is not particularly limited as long as it is an anionic modifying group, and examples thereof include a carboxyl group, a sulfonic acid group, and a phosphoric acid group.

The preferable lower limit of the degree of modification of the anionic group is 0.1 mol%, and the preferable upper limit is 2 mol%.
When the degree of modification of the anionic group is less than 0.1 mol%, the polyvinyl acetal resin (A) is less likely to adhere to the surface of the inorganic powder, and may not contribute to improvement in dispersibility. If it exceeds 1, attractive interaction may work between the polyvinyl acetal resins (A), and it may be difficult to adhere to the surface of the inorganic powder. A more preferable lower limit of the degree of modification is 0.2 mol%, and a more preferable upper limit is 1 mol%.
The degree of modification is determined by dissolving the modified polyvinyl acetal resin in DMSO-d ₆ (dimethyl sulfoxide), measuring the ¹³ C-NMR spectrum, and determining the peak area derived from the methine group to which the carboxy group is bonded. And the peak area derived from the methine group of the acetalized portion.

In the polyvinyl acetal resin (A), the ratio of the portion acetalized with acetaldehyde and the portion acetalized with butyraldehyde is preferably 30/70 to 95/5. In the portion acetalized with the acetaldehyde, the length of the hydrocarbon group due to the aldehyde is shortened and the steric hindrance is lowered, so that the hydroxyl group may be easily adsorbed to the inorganic powder. Therefore, by setting the portion acetalized with acetaldehyde to be 30/70 or more, the dispersibility of the inorganic powder is improved and high dispersibility can be maintained over a long period of time. More preferably, the ratio of the portion acetalized with acetaldehyde and the portion acetalized with butyraldehyde is 40/60 to 80/20.

The inorganic powder is not particularly limited, and examples thereof include metal powder, conductive powder, ceramic powder, and glass powder.

When a conductive powder is used as the inorganic powder, it can be used as a conductive paste.
The conductive powder is not particularly limited as long as it exhibits sufficient conductivity, and examples thereof include powder made of nickel, palladium, platinum, gold, silver, copper, alloys thereof, and the like. These conductive powders may be used alone or in combination of two or more.

When ceramic powder is used as the inorganic powder, it can be used as a ceramic paste. The ceramic powder is not particularly limited. For example, a powder made of alumina, zirconia, aluminum silicate, titanium oxide, zinc oxide, barium titanate, magnesia, sialon, spinemullite, silicon carbide, silicon nitride, aluminum nitride, or the like. Is mentioned. Especially, it is preferable to consist of the same component as the ceramic powder contained in the ceramic green sheet to be used. These ceramic powders may be used alone or in combination of two or more.

When glass powder is used as the inorganic powder, it can be used as a glass paste. The glass powder is not particularly limited. For example, lead oxide-boron oxide-silicon oxide-calcium oxide glass, zinc oxide-boron oxide-silicon oxide glass, lead oxide-zinc oxide-boron oxide-silicon oxide glass. Etc. These glass powders may be used alone or in combination of two or more. Moreover, you may use aluminum oxide etc. together in the range which does not impair the objective of this invention.

When magnetic powder is used as the inorganic powder, it can be used as a magnetic material paste. The magnetic powder is not particularly limited, for example, ferrites such as manganese zinc ferrite, nickel zinc ferrite, copper zinc ferrite, barium ferrite and strontium ferrite, metal oxides such as chromium oxide, metal magnetic materials such as cobalt, amorphous Examples include magnetic materials. These magnetic powders may be used alone or in combination of two or more.

The lower limit of the amount of the polyvinyl acetal resin (A) added in the step of preparing the inorganic dispersion is 0.1 part by weight with respect to 100 parts by weight of the inorganic powder, and the upper limit is 20 parts by weight. When the added amount of the polyvinyl acetal resin (A) is less than 0.1 parts by weight, for example, the dispersibility of the inorganic powder may be insufficient, and when it exceeds 20 parts by weight, the viscosity becomes too high. , Handling may be worse. The minimum with said preferable addition amount is 0.6 weight part, and a preferable upper limit is 15 weight part. Furthermore, the more preferable minimum of the said addition amount is 1 weight part, and a more preferable upper limit is 10 weight part. In particular, when the addition amount is 0.6 parts by weight or more, the polyvinyl acetal resin (A) can be sufficiently adsorbed on the surface of the inorganic powder, so that the inorganic powder in the ceramic slurry is more finely dispersed. It becomes possible.

In the step of preparing the inorganic dispersion, the water content of the inorganic dispersion is preferably less than 3% by weight. When the water content of the inorganic dispersion is 3% by weight or more, high dispersibility may not be maintained over a long period of time. Preferably it is less than 1% by weight.

Next, in the present invention, a step of preparing a resin solution by adding and mixing the polyvinyl acetal resin (B) and the organic solvent for the resin solution is performed.
In the present invention, the resin solution is prepared as described above, and the step of adding the resin solution to the inorganic dispersion in the subsequent step is performed to prevent the aggregation of the inorganic powder and to disperse the inorganic powder more finely. It becomes possible.
On the other hand, when the polyvinyl acetal resin (B) is not dissolved in the organic solvent for the resin solution, that is, when the resin solution is not prepared, the polyvinyl acetal resin (B) becomes bulky and a plurality of inorganic powders As a result, the inorganic powder is agglomerated.

The lower limit of the degree of polymerization of the polyvinyl acetal resin (B) is 800, and the upper limit is 4200. When the degree of polymerization is less than 800, the sheet strength becomes insufficient when used for a green sheet, and when the degree of polymerization exceeds 4200, the viscosity of the slurry composition becomes too high and coating becomes difficult. The preferable lower limit of the polymerization degree is 1200, and the preferable upper limit is 3500.

The minimum of the amount of hydroxyl groups of the said polyvinyl acetal resin (B) is 28 mol%, and an upper limit is 42 mol%. When the amount of the hydroxyl group is less than 28 mol%, when a green sheet is produced using a slurry containing the polyvinyl acetal resin, the sheet strength may be insufficient. Aggregation of powder particles may occur. The minimum with said preferable amount of hydroxyl groups is 29 mol%, a preferable upper limit is 38 mol%, a more preferable minimum is 30 mol%, and a more preferable upper limit is 36 mol%.

The preferable lower limit of the addition amount of the polyvinyl acetal resin (B) in the step of preparing the resin solution is 5 parts by weight with respect to 100 parts by weight of the inorganic powder, and the preferable upper limit is 20 parts by weight. When the added amount of the polyvinyl acetal resin (B) is less than 5 parts by weight, for example, the dispersibility of the inorganic powder is insufficient, or the strength, flexibility, adhesiveness, etc. of the coating film after drying are insufficient. When the amount exceeds 20 parts by weight, the viscosity may become too high or the coatability may be lowered, resulting in poor handling.
In particular, in a thin-layer ceramic green sheet for which strength is required, a sheet having sufficient dispersibility and a sheet can be obtained by containing a polyvinyl acetal resin (B) having a high degree of polymerization relative to a polyvinyl acetal resin (A) having a low degree of polymerization. A ceramic green sheet having strength can be produced.

The polyvinyl acetal resin is obtained by acetalizing polyvinyl alcohol with an aldehyde.

The polyvinyl alcohol can be obtained, for example, by saponifying a copolymer of vinyl ester and ethylene. Examples of the vinyl ester include vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate and the like. Of these, vinyl acetate is preferred from the viewpoint of economy.

The polyvinyl alcohol may be a copolymer of an ethylenically unsaturated monomer as long as the effects of the present invention are not impaired. The ethylenically unsaturated monomer is not particularly limited, and examples thereof include acrylic acid, methacrylic acid, (anhydrous) phthalic acid, (anhydrous) maleic acid, (anhydrous) itaconic acid, acrylonitrile methacrylonitrile, acrylamide, and methacrylamide. , Trimethyl- (3-acrylamido-3-dimethylpropyl) -ammonium chloride, acrylamido-2-methylpropanesulfonic acid and its sodium salt, ethyl vinyl ether, butyl vinyl ether, N-vinyl pyrrolidone, vinyl chloride, vinyl bromide, fluorine Vinyl chloride, vinylidene chloride, vinylidene fluoride, tetrafluoroethylene, sodium vinyl sulfonate, sodium allyl sulfonate and the like. Also use terminal-modified polyvinyl alcohol obtained by copolymerizing vinyl ester monomer such as vinyl acetate with ethylene in the presence of thiol compounds such as thiol acetic acid and mercaptopropionic acid, and saponifying it. Can do.

The polyvinyl alcohol may be a saponified copolymer obtained by copolymerizing the vinyl ester and an α-olefin. Further, the above-mentioned ethylenically unsaturated monomer may be copolymerized to obtain polyvinyl alcohol containing a component derived from the ethylenically unsaturated monomer. Also used is a terminal polyvinyl alcohol obtained by copolymerizing a vinyl ester monomer such as vinyl acetate with an α-olefin in the presence of a thiol compound such as thiol acetic acid or mercaptopropionic acid, and saponifying it. be able to. The α-olefin is not particularly limited, and examples thereof include methylene, ethylene, propylene, isopropylene, butylene, isobutylene, pentylene, hexylene, cyclohexylene, cyclohexylethylene, and cyclohexylpropylene.

The polyvinyl acetal resin preferably has an acetalization degree of 40 to 80 mol%. When the degree of acetalization is less than 40 mol%, the solubility in an organic solvent is lowered, and thus it is difficult to use the slurry composition. If the degree of acetalization exceeds 80 mol%, it will be difficult to industrially produce a polyvinyl acetal resin. Preferably it is 50-75 mol%.
In this specification, the degree of acetalization is the ratio of the number of hydroxyl groups acetalized with butyraldehyde in the number of hydroxyl groups of polyvinyl alcohol, and the calculation method of the degree of acetalization is as follows. Since the acetal group is formed by acetalization from two hydroxyl groups, a method of counting the two acetal hydroxyl groups is employed to calculate the mol% of the degree of acetalization.

In the present invention, a step of adding a resin solution to the inorganic dispersion is then performed.
Thereby, a slurry composition is obtained.

In addition, in the manufacturing method of the slurry composition of this invention, in the range which does not impair the effect of this invention, other resins, such as polyvinyl acetal resins other than the said polyvinyl acetal resin, an acrylic resin, and ethyl cellulose, may be contained. . However, in such a case, the content of the polyvinyl acetal resin with respect to the total binder resin needs to be 50% by weight or more.

The organic solvent for inorganic dispersion and the organic solvent for resin solution are not particularly limited, and organic solvents generally used in slurry compositions can be used. For example, acetone, methyl ethyl ketone, dipropyl ketone, diisobutyl ketone Ketones such as methanol, ethanol, isopropanol, butanol, aromatic hydrocarbons such as toluene, xylene, methyl propionate, ethyl propionate, butyl propionate, methyl butanoate, ethyl butanoate, butanoic acid Esters such as butyl, methyl pentanoate, ethyl pentanoate, butyl pentanoate, methyl hexanoate, ethyl hexanoate, butyl hexanoate, 2-ethylhexyl acetate, 2-ethylhexyl butyrate, terpineol, dihydroterpineol, terpineol Seteto, terpineol and its derivatives such as dihydro terpineol acetate, and the like. These organic solvents may be used independently and 2 or more types may be used together.

As the organic solvent for inorganic dispersion and the organic solvent for resin solution, it is particularly preferable to use a mixed solvent composed of ethanol and toluene. By using the mixed solvent, the dispersibility of the slurry composition can be greatly improved. This is because ethanol contributes to the prevention of aggregation of the polyvinyl acetal resin (B), while toluene contributes to the adhesion of the polyvinyl acetal resin (A) to the inorganic powder surface. This is probably because the dispersibility is greatly improved.

When the mixed solvent is used, the mixing ratio of ethanol and toluene is preferably 5: 5 to 2: 8. By setting it within the above range, the dispersibility of the slurry composition can be greatly improved.

The preferable lower limit of the amount of the inorganic dispersion organic solvent added in the step of preparing the inorganic dispersion is 20 parts by weight with respect to 100 parts by weight of the inorganic powder, and the preferable upper limit is 60 parts by weight. When the addition amount of the organic solvent for inorganic dispersion is less than 20 parts by weight, the viscosity of the inorganic dispersion becomes high, the movement of the inorganic powder is restricted, and sufficient dispersibility may not be obtained. If it exceeds, the inorganic powder concentration of the inorganic dispersion liquid becomes low and the number of collisions between the inorganic powders decreases, so that sufficient dispersibility may not be obtained.
Moreover, the preferable minimum of the addition amount of the said organic solvent for resin solutions in the process of producing the said resin solution is 70 weight part with respect to 100 weight part of inorganic powder, and a preferable upper limit is 130 weight part. If the amount of the organic solvent for the resin solution is less than 70 parts by weight, the amount of the resin is not sufficient, so the strength of the green sheet may be insufficient. If the amount exceeds 130 parts by weight, the resin in the green sheet The amount of residue may increase in the baking process.
A more preferred lower limit is 90 parts by weight, and a more preferred upper limit is 110 parts by weight.

In the method for producing the slurry composition of the present invention, a plasticizer, a lubricant, an antistatic agent, and the like may be appropriately added as long as the effects of the present invention are not impaired.

By using the method for producing a slurry composition of the present invention, an extremely high dispersibility can be realized, and a slurry composition having a high strength can be produced. Such a slurry composition is also one aspect of the present invention.

In this invention, the manufacturing method of the slurry composition which can manufacture the slurry composition which can maintain a high dispersibility over a long period of time by a simple method can be provided. Moreover, the slurry composition manufactured using the manufacturing method of this slurry composition can be provided.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited only to these examples.

(Synthesis of polyvinyl acetal resin (A) [(A1) to (A10)])
350 parts by weight of polyvinyl alcohol having a polymerization degree of 320 and a saponification degree of 99 mol% was added to 3000 parts by weight of pure water, and stirred at a temperature of 90 ° C. for about 2 hours for dissolution. The solution was cooled to 40 ° C., and 230 parts by weight of hydrochloric acid having a concentration of 35% by weight was added thereto, the liquid temperature was lowered to 1 ° C., and 202 parts by weight of n-butyraldehyde was added to maintain the temperature, and the acetal was maintained. The reaction product was precipitated by the reaction. Then, the liquid temperature was kept at 20 ° C. for 3 hours to complete the reaction, and neutralized, washed with water and dried by a conventional method to obtain a white powder of polyvinyl acetal resin (A1). When the obtained polyvinyl acetal resin was dissolved in DMSO-d ₆ (dimethylsulfoxaside) and the degree of butyralization, the amount of hydroxyl groups and the amount of acetyl groups were measured using ¹³ C-NMR (nuclear magnetic resonance spectrum), butyral was measured. The degree of conversion was 66 mol%, the amount of hydroxyl groups was 33 mol%, and the amount of acetyl groups was 1 mol%.
In addition, it was 1 weight% when the moisture content of the obtained polyvinyl acetal resin (A1) was measured with the Kett moisture measuring device (the Kensei Kogyo company make, "MX-50").
Further, polyvinyl acetal resins (A2) to (A10) were synthesized in the same manner as the polyvinyl acetal resin (A1) except that the conditions shown in Table 1 were used.

(Synthesis of polyvinyl acetal resin (B) [(B1) to (B10)])
280 parts by weight of polyvinyl alcohol having a polymerization degree of 1700 and a saponification degree of 99 mol% was added to 3000 parts by weight of pure water, and the mixture was stirred for dissolution for 2 hours at a temperature of 90 ° C. The solution was cooled to 40 ° C., 200 parts by weight of hydrochloric acid having a concentration of 35% by weight and 155 parts by weight of n-butyraldehyde were added thereto, the liquid temperature was lowered to 1 ° C., and this temperature was maintained, thereby performing an acetalization reaction. And the reaction product was precipitated. Then, liquid temperature was hold | maintained at 40 degreeC for 3 hours, reaction was completed, and the white powder of polyvinyl acetal resin (B1) was obtained through neutralization, water washing, and drying by a conventional method. When the obtained polyvinyl acetal resin (B1) was dissolved in DMSO-d ₆ (dimethyl sulfoxide), the degree of butyralization, the amount of hydroxyl groups and the amount of acetyl groups were measured using ¹³ C-NMR (nuclear magnetic resonance spectrum). The degree of butyralization was 66 mol%, the amount of hydroxyl groups was 33 mol%, and the amount of acetyl groups was 1 mol%.
Further, polyvinyl acetal resins (B2) to (B10) were synthesized in the same manner as the polyvinyl acetal resin (B1) except that the conditions shown in Table 2 were used.

Example 1
(Preparation of inorganic dispersion)
1 part by weight of the obtained polyvinyl acetal resin (A1) was added to a mixed solvent of 24 parts by weight of toluene and 16 parts by weight of ethanol and dissolved by stirring. Next, 100 parts by weight of barium titanate powder (manufactured by Sakai Chemical Industry Co., Ltd., “BT02”) was added to the resulting solution, and stirred for 180 minutes in a bead mill (manufactured by Imex Co., Ltd., “Lady Mill”). An inorganic dispersion was prepared.

(Preparation of resin solution)
8 parts by weight of the obtained polyvinyl acetal resin (B1) and 2 parts by weight of DOP were added to a mixed solvent of 36 parts by weight of ethanol and 54 parts by weight of toluene, and dissolved by stirring to prepare a resin solution.

(Preparation of slurry composition)
A resin composition was added to the obtained inorganic dispersion and stirred for 90 minutes in the same bead mill to obtain a slurry composition.

(Examples 2 to 17)
A slurry composition was obtained in the same manner as in Example 1 except that the polyvinyl acetal resin (A), the polyvinyl acetal resin (B) and the organic solvent shown in Table 3 were used.

(Comparative Examples 1-2)
A slurry composition was obtained in the same manner as in Example 1 except that the polyvinyl acetal resin (A) was not added and the polyvinyl acetal resin (B) and the organic solvent were used in Table 3.

(Comparative Examples 3-5)
A slurry composition was obtained in the same manner as in Example 1 except that the polyvinyl acetal resin (A) was not added to the inorganic dispersion but dissolved in the resin solution together with the polyvinyl acetal resin (B).

(Comparative Examples 6-8)
A slurry composition was obtained in the same manner as in Example 1 except that the polyvinyl acetal resin (B) was not dissolved in the organic solvent and added to the inorganic dispersion.

(Comparative Examples 9-17)
A slurry composition was obtained in the same manner as in Example 1 except that the polyvinyl acetal resin (A), the polyvinyl acetal resin (B), and the organic solvent shown in Table 3 were used.

(Comparative Example 18)
In place of the polyvinyl acetal resin (A), a slurry composition was prepared in the same manner as in Example 1 except that a polyamine compound (“Hypermer KD-2” manufactured by Croda Co., Ltd.) having hydrocarbons grafted on the side chains of the dispersant was used. Obtained.

(Evaluation)
The following evaluation was performed about the obtained slurry composition.
(1) Evaluation of green sheets (production of green sheets)
On the polyethylene terephthalate (PET) film subjected to the release treatment, the slurry composition was applied and dried so that the film thickness after drying was 20 μm, and a ceramic green sheet was produced.

(1-1) Surface Roughness About the ceramic green sheet obtained above, the surface roughness Ra was measured based on JIS B 0601 (1994), and the surface roughness of the ceramic slurry was evaluated. Further, the surface roughness Ra after being allowed to stand at 23 ° C. for one week was also measured.
Generally, the higher the dispersibility of the slurry composition, the smaller the surface roughness of the ceramic green sheet. Further, the obtained surface roughness Ra was evaluated according to the following criteria.

◎ Less than 0.04 μm ○ 0.04 μm or more, less than 0.06 μm Δ 0.06 μm or more, less than 0.08 μm × 0.08 μm or more

(1-2) Tensile modulus In accordance with JIS K 7113, measurement of the tensile modulus (MPa) is performed using AUTOGRAPH (“AGS-J”, manufactured by Shimadzu Corporation) under the condition of a tensile speed of 20 mm / min. went. Moreover, it measured also about the tensile elasticity modulus (MPa) after leaving to stand at 23 degreeC for one week. Further, the obtained tensile elastic modulus was evaluated according to the following criteria.

◎ 1450 MPa or more ○ 1300 MPa or more, less than 1450 MPa Δ 1150 MPa or more, less than 1300 MPa × less than 1150 MPa

(1-3) Evaluation of peelability The ceramic green sheet formed on the obtained PET film was cut into 20 mm × 140 mm, and one end of the ceramic green sheet was removed using TENSILON (manufactured by Shimadzu Corporation, AUTOGRAPH AGS-J). The force acting when the green sheet was peeled from the PET film was measured (mN / cm) in the direction of 90 degrees with respect to the sheet surface and at a speed of 8 mm / min. Further, the obtained tensile elastic modulus was evaluated according to the following criteria.

◎ Less than 0.05 N / cm ○ 0.05 N / cm or more, less than 0.06 N / cm Δ 0.06 N / cm or more, less than 0.07 N / cm × 0.07 N / cm or more

(2) Dispersibility evaluation (Preparation of dispersibility evaluation solution)
0.1 part by weight of the obtained slurry composition was added to an ethanol / toluene mixed solvent having the same composition as the organic solvent used for the preparation of the inorganic powder dispersion, and an ultrasonic disperser (manufactured by SND, “US-303”). ) For 10 minutes to prepare a dispersion evaluation solution.
(Dispersibility evaluation)
The obtained dispersion evaluation solution was subjected to particle size distribution measurement using a laser diffraction particle size distribution analyzer (manufactured by Horiba, Ltd., LA-910), and the position of the maximum particle diameter peak and the average dispersion diameter were measured. Further, the position of the maximum particle diameter peak after being allowed to stand at 23 ° C. for one week and the average dispersion diameter were also measured. Further, the average particle diameter obtained was evaluated according to the following criteria.

◎ Less than 0.7μm ○ 0.7μm or more, less than 0.8μm △ 0.8μm or more, less than 0.9μm × 0.9μm or more

(Examples 18 to 20)
In place of barium titanate as inorganic powder, slurry was used in the same manner as in Example 1 except that aluminum nitride powder was used and the polyvinyl acetal resin (A), polyvinyl acetal resin (B) and organic solvent shown in Table 5 were used. A composition was obtained.

(Examples 21 to 23)
Instead of barium titanate as the inorganic powder, Ni—Zn ferrite powder was used, and the same procedure as in Example 1 was used except that the polyvinyl acetal resin (A), polyvinyl acetal resin (B) and organic solvent shown in Table 5 were used. Thus, a slurry composition was obtained.

(Comparative Example 19)
It replaces with barium titanate as an inorganic powder, uses aluminum nitride powder, does not add the polyvinyl acetal resin (A), and uses the polyvinyl acetal resin (B) and organic solvent shown in Table 1 as in Example 1. Thus, a slurry composition was obtained.

(Comparative Example 20)
Example except that Ni-Zn ferrite powder was used instead of barium titanate as the inorganic powder, the polyvinyl acetal resin (B) and the organic solvent shown in Table 1 were used without adding the polyvinyl acetal resin (A). In the same manner as in No. 1, a slurry composition was obtained.

(1) Evaluation of Green Sheet (1-1) Surface Roughness Surface roughness Ra was measured by the same method as “(1-1) Surface roughness” in “(1) Evaluation of green sheet” described above. Further, the obtained surface roughness Ra was evaluated according to the following criteria.

◎ Less than 0.2μm ○ 0.2μm or more, less than 0.3μm △ 0.3μm or more, less than 0.4μm × 0.4μm or more

(1-2) Tensile modulus The tensile modulus (MPa) was measured by the same method as “(1-2) Tensile modulus” in “(1) Evaluation of green sheet” described above. Further, the obtained tensile elastic modulus was evaluated according to the following criteria.

◎ 1200 MPa or more ○ 1000 MPa or more, less than 1200 MPa Δ 800 MPa or more, less than 1000 MPa × less than 800 MPa

(1-3) Evaluation of peelability The ceramic green sheet formed on the obtained PET film was cut into 20 mm × 140 mm, and one end of the ceramic green sheet was removed using TENSILON (manufactured by Shimadzu Corporation, AUTOGRAPH AGS-J). The force acting when the green sheet was peeled from the PET film was measured (mN / cm) in the direction of 90 degrees with respect to the sheet surface and at a speed of 8 mm / min. Further, the obtained tensile elastic modulus was evaluated according to the following criteria.

◎ Less than 0.1 N / cm ○ 0.1 N / cm or more, less than 0.15 N / cm Δ 0.15 N / cm or more, less than 0.2 N / cm x 0.2 N / cm or more

(2) Dispersibility evaluation The position of the maximum particle diameter peak and the average particle diameter were measured in the same manner as in the above-mentioned "(2) Dispersibility evaluation". Further, the average particle diameter obtained was evaluated according to the following criteria.

◎ Less than 2μm ○ 2μm or more, less than 3μm △ 3μm or more, less than 4μm × 4μm or more

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the slurry composition which can manufacture the slurry composition which can maintain a high dispersibility over a long term by a simple method can be provided. Moreover, the slurry composition manufactured using the manufacturing method of this slurry composition can be provided.

Claims (4)

A method for producing a slurry composition comprising an inorganic powder, a polyvinyl acetal resin and an organic solvent,
Adding inorganic powder, polyvinyl acetal resin (A) and organic solvent for inorganic dispersion and mixing to prepare an inorganic dispersion, adding polyvinyl acetal resin (B) and organic solvent for resin solution, and mixing to obtain a resin solution And a step of adding a resin solution to the inorganic dispersion,
The polyvinyl acetal resin (A) has a polymerization degree of 20 to 600 and a hydroxyl group amount of 27.5 to 37 mol%.
The polyvinyl acetal resin (B) has a polymerization degree of 800 to 4200 and a hydroxyl group content of 28 to 42 mol%.
In the step of preparing the inorganic dispersion, 0.1 to 20 parts by weight of the polyvinyl acetal resin (A) is added to 100 parts by weight of the inorganic powder. The method for producing a slurry composition according to claim 1, wherein the polyvinyl acetal resin (A) has an anionic group. The method for producing a slurry composition according to claim 1 or 2, wherein the organic solvent for inorganic dispersion and the organic solvent for resin solution are mixed solvents composed of ethanol and toluene. It manufactures using the manufacturing method of the slurry composition of Claim 1, 2, or 3. The slurry composition characterized by the above-mentioned.