JP2014198646A - Inorganic composite for inorganic powder dispersion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inorganic composite for inorganic powder dispersion capable of achieving excellent dispersibility in a simple process, and a method for producing the inorganic composite for inorganic powder dispersion, a method for producing a slurry composition, and a slurry composition.SOLUTION: There is provided an inorganic composite which is used for the dispersion of an inorganic powder and has a coating layer on the surface of the inorganic powder. The coating layer comprises: an inner layer composed of a polyvinyl acetal resin (A) having a hydroxyl group content of 20 to 50 mol% and a degree of polymerization of 20 to 500; and an outer layer composed of a polyvinyl acetal resin (B) having a hydroxyl group content of 20 to 45 mol% and a degree of polymerization of 600 to 4500. The degree of polymerization of the polyvinyl acetal resin (A) and the degree of polymerization of the polyvinyl acetal resin (B) satisfy a relation of the following expression (1). In expression (1), X represents the degree of polymerization of the polyvinyl acetal resin (A): and Y represents the degree of polymerization of the polyvinyl acetal resin (B).

Description

The present invention relates to an inorganic composite for dispersing an inorganic powder that can realize excellent dispersibility by a simple process. Moreover, it is related with the manufacturing method of this inorganic composite for inorganic powder dispersion | distribution, the manufacturing method of a slurry composition, and a 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, in such a method, when the compatibility with the binder resin is poor, there is a problem that the dispersibility is deteriorated or the dispersibility is lowered during long-term storage.
In order to solve the problem, Patent Document 3 describes a method in which an acetalization reaction is performed after a powder is dispersed in a polyvinyl alcohol solution. However, such a method has a problem that when the powder is extremely small, the powder cannot be finely dispersed in the polyvinyl alcohol.

On the other hand, the dispersibility is also improved by using a composite in which the surface of the inorganic powder is coated with a dispersant in advance, but a ceramic green sheet was prepared using such a composite. In this case, there is a problem that the dispersing agent on the surface of the composite melts and blocking occurs in the extrusion process in the feeder when the ceramic powder is charged into the disperser.

JP 2005-139034 A JP-A-6-325971 Japanese Patent No. 4828277

An object of this invention is to provide the inorganic composite for inorganic powder dispersion | distribution which can implement | achieve the outstanding dispersibility by a simple process in view of the said present condition. Moreover, it aims at providing the manufacturing method of this inorganic composite for inorganic powder dispersion | distribution, the manufacturing method of a slurry composition, and a slurry composition.

式（１）中、Ｘはポリビニルアセタール樹脂（Ａ）の重合度、Ｙはポリビニルアセタール樹脂（Ｂ）の重合度を表す。
以下に本発明を詳述する。 The present invention is an inorganic composite used for dispersion of inorganic powder, and has a coating layer on the surface of the inorganic powder, and the coating layer has a hydroxyl group content of 20 to 50 mol% and a polymerization degree of 20 to 500. An inner layer composed of a certain polyvinyl acetal resin (A), and an outer layer composed of a polyvinyl acetal resin (B) having a hydroxyl amount of 20 to 45 mol% and a polymerization degree of 600 to 4500, and the polyvinyl acetal resin (A) Is an inorganic composite for dispersing an inorganic powder in which the polymerization degree of the polyvinyl acetal resin (B) has a relationship represented by the following formula (1).

In formula (1), X represents the degree of polymerization of the polyvinyl acetal resin (A), and Y represents the degree of polymerization of the polyvinyl acetal resin (B).
The present invention is described in detail below.

The inventors of the present invention used an inorganic composite for dispersing an inorganic powder having a coating layer having a two-layer structure made of a polyvinyl acetal resin having a predetermined amount of hydroxyl group and polymerization degree. It has been found that excellent dispersibility can be realized by a simple process without using it separately.
In addition, such an inorganic composite for dispersing an inorganic powder is such that the inorganic powder and the polyvinyl acetal resin are firmly bonded to each other, so that the polyvinyl acetal resin easily stays around the inorganic powder. In this case, it was found that thermal deformation hardly occurs, and the present invention has been completed.

The inorganic composite for inorganic powder dispersion described in the present invention has a coating layer on the surface of the inorganic powder.
The inorganic powder is not particularly limited, and examples thereof include conductive powder, magnetic powder, ceramic powder, and glass powder.

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.

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 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.

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.

The average particle size of the inorganic powder is preferably 0.01 to 10 μm.
When the average particle size is less than 0.01 μm, dispersibility becomes insufficient, and the resin may not be sufficiently adsorbed on the surface of the inorganic powder. When the average particle size exceeds 10 μm, the mass of the inorganic powder becomes large, and adhesion is caused. The effect of the polyvinyl acetal resin may not be sufficiently exhibited.

The inorganic composite for dispersing inorganic powder of the present invention has an inner layer made of a polyvinyl acetal resin (A) having a hydroxyl group content of 20 to 50 mol% and a polymerization degree of 20 to 500, a hydroxyl group content of 20 to 45 mol%, and a polymerization amount. And a coating layer having an outer layer made of a polyvinyl acetal resin (B) having a degree of 600 to 4500.

In the present invention, the coating layer is formed of polyvinyl acetal resins having different properties such as a polyvinyl acetal resin (A) and a polyvinyl acetal resin (B).
The two types of polyvinyl acetal resins have the property of easily loosening the aggregate of the inorganic powder and the property of easily adhering to the surface of the inorganic powder. It becomes possible to improve.
Moreover, the sheet | seat strength of the ceramic green sheet obtained can be raised by the effect of the entanglement by the high polymerization degree of polyvinyl acetal resin (B). Furthermore, since the surface of the inorganic composite for dispersing inorganic powder can be stabilized, blocking when temperature or pressure is applied from the outside can be prevented.

The said coating layer has an inner layer which consists of a polyvinyl acetal resin (A) whose hydroxyl amount is 20-50 mol% and whose polymerization degree is 20-500. By comprising the polyvinyl acetal resin (A), the polyvinyl acetal resin (A) penetrates faster to the surface of the inorganic powder, and the aggregates of the inorganic powder are easily loosened.

The minimum of the amount of hydroxyl groups of the said polyvinyl acetal resin (A) is 20 mol%, and an upper limit is 50 mol%. When the amount of the hydroxyl group is less than 20 mol%, the affinity to the surface of the inorganic powder is almost eliminated and the surface does not adhere to the surface of the inorganic powder, and does not contribute to the improvement of dispersibility. Adhesion to the surface becomes excessive, adheres only to the surface of the inorganic powder aggregate, and it becomes difficult to loosen. A preferred lower limit of the hydroxyl group content is 26 mol%, and a preferred upper limit is 45 mol%.

The lower limit of the degree of polymerization of the polyvinyl acetal resin (A) is 20, and the upper limit is 500. When the polymerization degree is less than 20, the bulkiness is insufficient, and even when adsorbed on the surface of the inorganic powder, other inorganic powders cannot be excluded, and sufficient dispersibility may not be obtained. When the said polymerization degree exceeds 500, it may become difficult to osmose | permeate the inorganic powder surface by polyvinyl acetal resin (A) itself bulkiness. The preferable lower limit of the polymerization degree is 100, and the preferable upper limit is 300.

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 derived from a methine group to which a carboxy group is bonded by dissolving a polyvinyl acetal resin (A) in DMSO-d ₆ (dimethylsulfoxide) and measuring a ¹³ C-NMR spectrum. It can be calculated from the peak area and the peak area derived from the methine group of the acetalized portion.

The coating layer has an outer layer made of a polyvinyl acetal resin (B) having a hydroxyl group content of 20 to 45 mol% and a polymerization degree of 600 to 4500. By containing the polyvinyl acetal resin (B), the distance between the inorganic powders can be maintained due to steric hindrance due to the high degree of polymerization of the polyvinyl acetal resin (B). Further, the surface of the inorganic composite for dispersing inorganic powder can be stabilized by the entanglement effect, and as a result, blocking when temperature or pressure is applied from the outside can be prevented.

The minimum of the amount of hydroxyl groups of the said polyvinyl acetal resin (B) is 20 mol%, and an upper limit is 45 mol%. When the amount of the hydroxyl group is less than 20 mol%, the adhesion to the inner layer is insufficient, so that the adhesion cannot be sufficiently achieved, and the strength is not improved. If it exceeds 45 mol%, the solubility in the solvent will be insufficient, and the molecules will not be able to spread sufficiently and will not adhere to the surface of the inner layer. The preferable lower limit of the amount of hydroxyl group is 28 mol%, and the preferable upper limit is 42 mol%.

The minimum of the polymerization degree of the said polyvinyl acetal resin (B) is 600, and a preferable upper limit is 4500. When the polymerization degree is less than 600, the molecular entanglement is reduced and the polymer is easily loosened, so that the stability of the surface of the inorganic composite for dispersing the inorganic powder becomes insufficient. When the degree of polymerization exceeds 4500, the solution viscosity becomes too high, and it becomes difficult to disperse the fine inorganic powder. The preferable lower limit of the polymerization degree is 800, and the preferable upper limit is 3500.

The degree of polymerization of the polyvinyl acetal resin (A) and the degree of polymerization of the polyvinyl acetal resin (B) have the relationship of the following formula (1).

式（１）中、Ｘはポリビニルアセタール樹脂（Ａ）の重合度、Ｙはポリビニルアセタール樹脂（Ｂ）の重合度を表す。

In formula (1), X represents the degree of polymerization of the polyvinyl acetal resin (A), and Y represents the degree of polymerization of the polyvinyl acetal resin (B).

By having the above relationship between the polyvinyl acetal resin (A) and the polyvinyl acetal resin (B), not only the aggregate of the inorganic powder is effectively loosened, but also the surface of the inorganic composite for dispersing the inorganic powder is stabilized. It becomes possible to do.
In the formula (1), the upper limit of Y-X is not particularly limited, but when it is far away, the bulky polyvinyl acetal resin (B) is strongly adsorbed to the inorganic powder, so that the polyvinyl acetal resin (A) having a low polymerization degree. In this case, the steric hindrance is insufficient, and the inorganic powder dispersed by the polyvinyl acetal resin (A) may be re-agglomerated by the polyvinyl acetal resin (B), so 3000 is preferable and 2000 is more preferable.

In the polyvinyl acetal resin (A) and the polyvinyl acetal resin (B), 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.

In the said polyvinyl acetal resin (A) and polyvinyl acetal resin (B), the minimum with preferable content of an acetyl unit is 0.5 mol%, and a preferable upper limit is 20 mol%. When the content of the acetyl unit is less than 0.5 mol%, the polyvinyl acetal intermolecular distance is decreased, and the intermolecular hydrogen bonding force is increased, which may make it difficult to adhere to the surface of the inorganic powder. If it exceeds 20 mol%, the polyvinyl acetal intermolecular distance increases and the intermolecular hydrogen bonding force decreases, so that sufficient strength may not be obtained.

The polyvinyl acetal resin (A) and the polyvinyl acetal resin (B) are preferably polyvinyl acetal resins obtained by acetalizing a polyvinyl alcohol resin with an aldehyde.

The acetalization method is not particularly limited, and a conventionally known method can be used. For example, an aqueous solution of polyvinyl alcohol, an alcohol solution, a water / alcohol mixed solution, a dimethyl sulfoxide (DMSO) solution in the presence of an acid catalyst. Examples thereof include a method of adding various aldehydes.

The aldehyde used for the acetalization is not particularly limited. For example, formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, amylaldehyde, hexylaldehyde, heptylaldehyde, 2-ethylhexylaldehyde, cyclohexylaldehyde, furfural, glyoxal, glutaraldehyde, benzaldehyde 2-methylbenzaldehyde, 3-methylbenzaldehyde, 4-methylbenzaldehyde, p-hydroxybenzaldehyde, m-hydroxybenzaldehyde, phenylacetaldehyde, β-phenylpropionaldehyde and the like. Among them, it is preferable to use acetaldehyde and butyraldehyde alone or to use acetaldehyde and butyraldehyde in combination.

The acid catalyst is not particularly limited, and either an organic acid or an inorganic acid can be used. Examples thereof include acetic acid, paratoluenesulfonic acid, nitric acid, sulfuric acid, and hydrochloric acid.

In order to stop the acetalization reaction, neutralization with an alkali is preferably performed. It does not specifically limit as said alkali, For example, sodium hydroxide, potassium hydroxide, ammonia, sodium acetate, sodium carbonate, sodium hydrogencarbonate, potassium carbonate, potassium hydrogencarbonate etc. are mentioned.
Moreover, it is preferable to wash | clean the polyvinyl acetal resin obtained using water etc. before and after the said neutralization process. In order to prevent impurities contained in the cleaning water from being mixed, it is more preferable to perform the cleaning with pure water.

The polyvinyl alcohol resin is preferably a polyvinyl alcohol resin obtained by saponifying a polymer of vinyl ester such as vinyl formate, vinyl acetate, vinyl propionate or vinyl pivalate. From the economical viewpoint, the vinyl ester is more preferably vinyl acetate.

The polyvinyl alcohol resin is also preferably a polyvinyl alcohol resin obtained by saponifying a copolymer of the vinyl ester and the α-olefin.
Examples of the α-olefin include ethylene, propylene, isopropylene, butylene, isobutylene, pentylene, hexylene, cyclohexylene, cyclohexylethylene, and cyclohexylpropylene. Of these, ethylene is preferable.
Further, as the polyvinyl alcohol resin, a terminal-modified polyvinyl alcohol resin obtained by copolymerizing the vinyl ester and ethylene in the presence of a thiol compound such as thiol acetic acid or mercaptopropionic acid, and then saponifying is then used. May be.

When the polyvinyl alcohol resin is copolymerized, the content of the α-olefin is preferably 1 mol% at a preferable lower limit and 20 mol% at a preferable upper limit. When the content of the α-olefin is less than 1 mol%, the effect of adding the α-olefin may not be obtained. When the content of the α-olefin exceeds 20 mol%, the solubility of the obtained polyvinyl alcohol resin in water decreases, making it difficult to perform the acetalization reaction, or the hydrophobicity of the obtained polyvinyl acetal resin. May become too strong and the solubility in organic solvents may decrease.

The polyvinyl alcohol resin is a polyvinyl alcohol resin obtained by copolymerizing other ethylenically unsaturated monomers in addition to the vinyl ester and the α-olefin within a range not impairing the effects of the present invention. There may be.
Examples of the other ethylenically unsaturated monomers include acrylic acid, methacrylic acid, (anhydrous) fumaric acid, (anhydrous) maleic acid, (anhydrous) itaconic acid, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, and 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, vinyl fluoride, Examples include vinylidene chloride, vinylidene fluoride, tetrafluoroethylene, sodium vinyl sulfonate, and sodium allyl sulfonate.

When the polyvinyl alcohol resin is copolymerized, the content of the other ethylenically unsaturated monomers is preferably 1 mol% at the preferred lower limit and 30 mol% at the preferred upper limit. If the content of the other ethylenically unsaturated monomer is less than 1 mol%, the effect of adding the other ethylenically unsaturated monomer may not be obtained. When content of the said other ethylenically unsaturated monomer exceeds 30 mol%, properties, such as adhesiveness of a polyvinyl acetal resin obtained, coating-film strength, and thermal decomposability, may fall.

The polyvinyl alcohol resin has a preferred lower limit of the saponification degree of 80 mol%. If the degree of saponification is less than 80 mol%, the solubility of the resulting polyvinyl alcohol in water may be reduced, making it difficult to carry out the acetalization reaction. If the amount is small, it may be difficult to proceed with the acetalization reaction itself.

In the inorganic composite for dispersing an inorganic powder of the present invention, the total amount of the polyvinyl acetal resin (A) and the polyvinyl acetal resin (B) is preferably 3 parts by weight, preferably a lower limit of the content with respect to 100 parts by weight of the inorganic powder. The upper limit is 30 parts by weight. When the content is less than 3 parts by weight, the polyvinyl acetal resins (A) and (B) are not sufficiently adsorbed on the surface of the inorganic powder, and the dispersibility of the inorganic powder may be insufficient. When the said content exceeds 30 weight part, a viscosity will become high too much and a handleability may worsen. A more preferred lower limit is 5 parts by weight, and a more preferred upper limit is 20 parts by weight.
The weight ratio of the polyvinyl acetal resin (A) and the polyvinyl acetal resin (B) is preferably 5:95 to 50:50. By setting it within the above range, the effects of the polyvinyl acetal resin (A) and the polyvinyl acetal resin (B) can be sufficiently exhibited.

A preferable lower limit of the thickness of the entire coating layer is 0.1 nm, and a preferable upper limit is 1000 nm. When the thickness is less than 0.1 nm, the binder may not be sufficiently removed when the binder is added, and the ceramic may aggregate. When the thickness exceeds 1000 nm, the ceramic is adsorbed. The ceramic may not move easily due to the dispersant, and may not be sufficiently dispersed. A preferable lower limit of the thickness of the entire coating layer is 1 nm, and a preferable upper limit is 200 nm.
The thickness of the coating layer can be measured by a dry density measurement method. Moreover, the thickness of the inner layer is measured using a dry automatic densimeter after preparing an inorganic powder composite that covers only the inner layer, and the thickness of the coating layer after forming the inner layer and the outer layer is measured. The thickness of the outer layer can be calculated by calculating the difference between the two.
Moreover, it is preferable that the film thickness ratio of the inner layer which comprises the said coating layer, and an outer layer is 5: 95-50: 50. By setting it within the above range, the effects of the polyvinyl acetal resin (A) and the polyvinyl acetal resin (B) can be sufficiently exhibited.
Furthermore, the ratio between the average particle diameter of the inorganic powder and the thickness of the coating layer is preferably 1: 1 to 5: 1.

The coating layer may contain, for example, an acrylic resin such as polymethyl methacrylate, a cellulose resin such as ethyl cellulose, and a resin such as polyethylene oxide.

The average particle diameter of the inorganic composite for dispersing inorganic powder of the present invention is preferably 0.02 to 10 μm.
When the average particle size is less than 0.02 μm, the surface area becomes too large, and when added to a solvent, the dispersibility of the particles may be insufficient. When the average particle size exceeds 10 μm, the mass of the particles is large. The effect of adhering the resin may not be sufficiently obtained.
In addition, the said average particle diameter can be measured with a laser diffraction type particle diameter distribution measuring apparatus (SALD-2300, Shimadzu Corporation Corp.) etc., for example.

As a method for producing an inorganic composite for dispersing an inorganic powder of the present invention, for example, a step of adding and mixing an inorganic powder, a polyvinyl acetal resin (A) and an organic solvent for an inner layer to prepare an inorganic dispersion for coating an inner layer, Adding and mixing the polyvinyl acetal resin (B) and the outer layer organic solvent to prepare an outer layer coating resin solution; and adding and mixing the outer layer coating resin solution to the inner layer coating inorganic dispersion; The method of performing the process of producing the slurry for body preparation, and the process of drying the organic solvent in the said slurry for inorganic composite preparation is mentioned.

The organic solvent for the inner layer and the organic solvent for the outer layer 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, etc. Ketones, alcohols such as methanol, ethanol, isopropanol, butanol, aromatic hydrocarbons such as toluene, xylene, methyl propionate, ethyl propionate, butyl propionate, methyl butanoate, ethyl butanoate, butyl butanoate , Esters such as methyl pentanoate, ethyl pentanoate, butyl pentanoate, methyl hexanoate, ethyl hexanoate, butyl hexanoate, 2-ethylhexyl acetate, 2-ethylhexyl butyrate, terpineol, dihydroterpineol, terpineol acetate , 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.

In the method for producing an inorganic composite for dispersing an inorganic powder of the present invention, it is preferable to add 5 to 35 parts by weight of the polyvinyl acetal resin (A) and the polyvinyl acetal resin (B) with respect to 100 parts by weight of the inorganic powder. . When the addition amount is less than 5 parts by weight, the amount of the adhering resin may be insufficient, and thus dispersibility may be insufficient. When the addition amount exceeds 35 parts by weight, the amount of the adhering resin In some cases, the strength is insufficient.

The inorganic composite for dispersing inorganic powder of the present invention is used for dispersion of inorganic powder. In particular, the inorganic composite for dispersing inorganic powder of the present invention is added to and mixed with an organic solvent for slurry. Excellent dispersibility can be achieved in the process.
The method for producing such a slurry composition is also one aspect of the present invention.

In the manufacturing method of the slurry composition of this invention, it has the process of adding and mixing the inorganic composite for inorganic powder dispersion of this invention to the organic solvent for slurry.
In the present invention, in the above step, the polyvinyl acetal resin (A) and the polyvinyl acetal resin (B) of the inorganic composite for dispersing the inorganic powder have a role as a dispersant by dissolving the polyvinyl acetal resin (A). And the polyvinyl acetal resin (B) is more firmly bound to the inorganic powder than when the inorganic powder composite was not produced. In this step, the polyvinyl acetal resin (A) and the polyvinyl acetal resin (B) are made of an inorganic powder by acting as a dispersant in a state where the polyvinyl acetal resin (A) and the polyvinyl acetal resin (B) are more firmly bound. As a result, the surface is more firmly attached, and as a result, the dispersibility of the inorganic powder can be improved. And, by the entanglement effect due to the high degree of polymerization of the polyvinyl acetal resin (B), not only can the sheet strength when made into a ceramic green sheet be increased, but also the surface of the resulting inorganic composite for dispersing inorganic powder can be stabilized. It is possible to prevent blocking when temperature or pressure is applied from the outside.
Therefore, since the high intensity | strength which the polyvinyl acetal resin for binders expresses without inhibiting the outstanding dispersibility of polyvinyl acetal resin (A) and polyvinyl acetal resin (B), the outstanding dispersibility of inorganic powder and Thus, a slurry composition having the effect of obtaining a film having high strength can be produced.

In the present invention, in the above step, the polyvinyl acetal resin (A) and the polyvinyl acetal resin (B) act as a dispersant. As a result, it is not necessary to consider the adverse effects due to the addition of a dispersant as in the prior art. This is because the dispersant and the binder resin are the same type, so the compatibility is good and the dispersant and the binder can be mixed without separation. Moreover, the sheet | seat intensity | strength at the time of making it a green sheet can be raised according to the effect of the entanglement by the high polymerization degree of polyvinyl acetal resin (B).
In the present specification, the polyvinyl acetal resin (A) and the polyvinyl acetal resin (B) are also simply referred to as a polyvinyl acetal resin when there is no need to particularly distinguish the polyvinyl acetal resin for binders described later.

The preferred lower limit of the amount of the organic solvent for slurry in the step of adding and mixing the inorganic composite for dispersing inorganic powder of the present invention to the organic solvent for slurry is 20 parts by weight with respect to 100 parts by weight of the inorganic composite for dispersing inorganic powder. The preferred upper limit is 60 parts by weight. When the addition amount of the organic solvent for slurry is less than 20 parts by weight, the viscosity of the inorganic dispersion liquid becomes high, the movement of the inorganic powder is restricted, and sufficient dispersibility may not be obtained, and it exceeds 60 parts by weight. In addition, the inorganic powder concentration of the inorganic dispersion is lowered, and the number of collisions between the inorganic powders is reduced, so that sufficient dispersibility may not be obtained.

In the above step, the water content of the slurry composition is preferably less than 3% by weight. When the water content of the slurry composition 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.

In the present invention, after the step of adding and mixing the inorganic composite for dispersing inorganic powder of the present invention to the organic solvent for slurry, the polyvinyl acetal resin for binder and the organic solvent for resin solution are added and mixed to prepare a resin solution. You may perform the process and the process of adding a resin solution.
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.

The minimum with a preferable polymerization degree of the said polyvinyl acetal resin for binders is 800, and a preferable upper limit is 4000. When the degree of polymerization is less than 800, the sheet strength may be insufficient when used for a green sheet, and when the degree of polymerization exceeds 4000, the viscosity of the slurry composition becomes too high and the coating may not be performed. It can be difficult. The more preferable lower limit of the degree of polymerization is 1200, and the more preferable upper limit is 3,500.

The minimum with the preferable amount of hydroxyl groups of the said polyvinyl acetal resin for binders is 43 mol%, and a preferable upper limit is 60 mol%. When the amount of the hydroxyl group is less than 43 mol%, when a green sheet is produced using a slurry containing the polyvinyl acetal resin, the sheet attack property may be insufficient. When the amount exceeds 60 mol%, Not only the solubility in the organic solvent for the resin solution is remarkably lowered but also aggregation of the inorganic powder particles may be caused. A preferable lower limit of the hydroxyl group content is 46 mol%, and a preferable upper limit is 56 mol%.

The preferable lower limit of the addition amount of the polyvinyl acetal resin for binder in the step of preparing the resin solution is 5 parts by weight with respect to 100 parts by weight of the inorganic composite for dispersing inorganic powder, and the preferable upper limit is 20 parts by weight. When the added amount of the polyvinyl acetal resin for the binder is less than 5 parts by weight, for example, the dispersibility of the inorganic powder is insufficient, or the strength, flexibility, adhesiveness and the like 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 deteriorate, and the handleability may deteriorate.
In particular, in a thin-layer ceramic green sheet for which strength is required, by containing a polyvinyl acetal resin for a binder having a high degree of polymerization with respect to the polyvinyl acetal resin (A) and the polyvinyl acetal resin (B) having a low degree of polymerization, A ceramic green sheet having sufficient dispersibility and sheet strength can be produced.

The preferable lower limit of the addition amount of the organic solvent for resin solution in the step of preparing the resin solution is 70 parts by weight and the preferable upper limit is 130 parts by weight with respect to 100 parts by weight of the inorganic composite for dispersing inorganic powder. 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.

In the present invention, a step of adding a resin solution 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 slurry 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, etc. Ketones, alcohols such as methanol, ethanol, isopropanol, butanol, aromatic hydrocarbons such as toluene, xylene, methyl propionate, ethyl propionate, butyl propionate, methyl butanoate, ethyl butanoate, butyl butanoate , Esters such as 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 slurry 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 for the binder, whereas toluene contributes to the adhesion of the polyvinyl acetal resin (A) and the polyvinyl acetal resin (B) to the inorganic powder surface. This is probably because the dispersibility of the slurry composition is greatly improved by the effect.

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.

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.

ADVANTAGE OF THE INVENTION According to this invention, the inorganic composite for inorganic powder dispersion | distribution which can implement | achieve the outstanding dispersibility by a simple process can be provided. Moreover, the manufacturing method of this inorganic composite for inorganic powder dispersion | distribution, the manufacturing method of a slurry composition, and a 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 (A9)])
350 parts by weight of polyvinyl alcohol having a polymerization degree of 250 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. Then, the liquid temperature was lowered to 0 ° C., and 212 parts by weight of n-butyraldehyde was added to maintain the temperature. 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). The obtained polyvinyl acetal resin was dissolved in DMSO-d ₆ (dimethylsulfoxaside), and the butyralization degree, the amount of hydroxyl groups and the amount of acetyl groups were measured using ¹³ C-NMR (nuclear magnetic resonance spectrum). The degree of conversion was 69 mol%, the amount of hydroxyl groups was 30 mol%, and the amount of acetyl groups was 1 mol%.
Further, polyvinyl acetal resins (A2) to (A9) were synthesized in the same manner as the polyvinyl acetal resin (A1) except that the conditions shown in Table 1 were used. The polyvinyl acetal resin (A8) is anion-modified with a carboxyl group.

(Synthesis of polyvinyl acetal resin (B) [(B1) to (B6)])
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 is cooled to 10 ° C., 200 parts by weight of hydrochloric acid having a concentration of 35% by weight and 155 parts by weight of n-butyraldehyde are added thereto, the liquid temperature is lowered to 1 ° C., and this temperature is maintained to perform 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 (B6) 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 for inner layer coating)
In addition to 1 part by weight of polyvinyl acetal resin (A1) shown in Table 3, a mixed solvent of 25 parts by weight of toluene and 25 parts by weight of ethanol, the mixture was stirred and dissolved. Next, 100 parts by weight of barium titanate powder (manufactured by Sakai Chemical Co., Ltd., BT01, average particle size 0.15 μm) was added to the obtained solution, 300 parts by weight of ceramic balls having a diameter of 0.5 mm were added, and a bead mill ( An inorganic dispersion for coating the inner layer was prepared by stirring for 100 minutes at a rotational speed of 1500 rpm using a ready mill manufactured by IMEX.

(Preparation of outer layer coating resin solution)
8 parts by weight of the obtained polyvinyl acetal resin (B1) was added to a mixed solvent of 45 parts by weight of ethanol and 45 parts by weight of toluene and dissolved by stirring to prepare an outer layer coating resin solution.

(Preparation of slurry for preparing inorganic composite)
98 parts by weight of the obtained outer layer coating resin solution is added to the inorganic dispersion for preparing the inorganic composite, and the slurry for preparing the inorganic composite is stirred by using a bead mill (Ready Mill manufactured by IMEX Co., Ltd.) for 100 minutes at a rotational speed of 1900 rpm. Produced.

(Preparation of inorganic composite)
The obtained slurry for preparing an inorganic composite was poured into an aluminum tray and dried at 70 ° C. for 6 hours to obtain a block-shaped inorganic composite. Thereafter, the block-like inorganic composite was crushed with a coffee mill to obtain an inorganic composite. The obtained inorganic composite had an average particle diameter of 0.64 μm, the inner layer of the coating layer had a thickness of 25 nm, and the outer layer had a thickness of 186 nm. Moreover, the weight ratio of the polyvinyl acetal resin (A) to the inorganic powder was 5.2% by weight.

(Preparation of slurry composition)
To 100 parts by weight of the obtained inorganic composite, 220 parts by weight of a mixed solvent of ethanol and toluene (mixing ratio 5: 5) and 2 parts by weight of DOP were mixed, and 300 parts by weight of ceramic balls having a diameter of 0.5 mm were added and rotated in a bead mill. The slurry composition was obtained by stirring for 120 minutes at several 1900 rpm.

(Examples 2 to 13)
An inorganic composite and a slurry composition were 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.

(Examples 14 to 15)
In place of barium titanate as the 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 3 were used. A composition was obtained.

(Examples 16 to 17)
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 3 were used. Thus, a slurry composition was obtained.

(Comparative Example 1)
An inorganic composite and a slurry composition were obtained in the same manner as in Example 1 except that an inorganic composite was produced using only the polyvinyl acetal resin (B).

(Comparative Example 2)
An inorganic composite and a slurry composition were obtained in the same manner as in Example 1 except that an inorganic composite was produced using only the polyvinyl acetal resin (A).

(Comparative Example 3)
An inorganic composite and a slurry composition were obtained in the same manner as in Example 1 except that the polyvinyl acetal resin (A) was dissolved together with the polyvinyl acetal resin (B) to prepare an outer layer coating resin solution.

(Comparative Examples 4 to 8)
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 9)
Instead of the polyvinyl acetal resin (A), a bisphenol A type epoxy resin (Japan Epoxy Resin, Epicoat 1001) was used, and the polyvinyl acetal resin (B) shown in Table 3 and an organic solvent were used. A slurry composition was obtained in the same manner as in Example 1.

(Comparative Example 10)
Instead of the polyvinyl acetal resin (A), an MDI reaction type urethane resin (Cosmonate M-200, manufactured by Mitsui Chemicals, Inc.) and the polyvinyl acetal resin (B) shown in Table 3 and an organic solvent were used. Except for this, a slurry composition was obtained in the same manner as in Example 1.

(Comparative Example 11)
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.

(Comparative Examples 12-13)
A slurry composition was obtained in the same manner as in Example 1 except that the inorganic powder, binder resin and organic solvent shown in Table 3 were used at the time of preparing the slurry composition without preparing the inorganic composite.

(Comparative Example 14)
In place of barium titanate as the inorganic powder, aluminum nitride powder was used, polyvinyl acetal resin (A) was not added, and polyvinyl acetal resin (B) shown in Table 3 and an organic solvent were used. Thus, a slurry composition was obtained.

(Comparative Example 15)
Example in place of barium titanate instead of barium titanate as inorganic powder, using polyvinyl acetal resin (B) and organic solvent shown in Table 3 without adding polyvinyl acetal resin (A) and adding polyvinyl acetal resin (A). In the same manner as in No. 1, a slurry composition was obtained.

(Evaluation)
The following evaluation was performed about the obtained slurry composition.

(1) Evaluation of ceramic green sheet (production of ceramic green sheet)
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.
Generally, the higher the dispersibility of the slurry composition, the smaller the surface roughness of the ceramic green sheet.

(Examples 1-13, Comparative Examples 1-13)
◎ Less than 0.030μm ○ 0.030μm or more, less than 0.040μm △ 0.040μm or more, less than 0.050μm × 0.050μm or more

(Examples 14-17, Comparative Examples 14-15)
◎ Less than 0.25 μm ○ 0.25 μm or more, less than 0.35 μm Δ 0.35 μm or more, less than 0.45 μm × 0.45 μm or more

(1-2) Tensile modulus About the ceramic green sheet obtained above, in accordance with JIS K 7113, using AUTOGRAPH (manufactured by Shimadzu Corporation, “AGS-J”) under the condition of a tensile speed of 20 mm / min. The tensile elastic modulus (MPa) was measured.

(Examples 1-13, Comparative Examples 1-13)
◎ 1800 MPa or more ○ 1600 MPa or more, less than 1800 MPa Δ 1400 MPa or more, less than 1600 MPa × less than 1400 MPa

(Examples 14-17, Comparative Examples 14-15)
◎ 1700 MPa or more ○ 1500 MPa or more, less than 1700 MPa Δ 1300 MPa or more, less than 1500 MPa × less than 1300 MPa

(1-3) Evaluation of Thermal Deformation Rate The ceramic green sheet obtained above was cut into a 10 cm square to obtain a green sheet piece. A thermal deformation rate was calculated by applying a pressure of 100 kg / cm ² at 60 ° C. for 10 minutes to the green sheet piece and measuring the subsequent dimensions.

(Examples 1-13, Comparative Examples 1-13)
◎ Less than 3.0% ○ 3.0% or more, less than 5.0% △ 5.0% or more, less than 7.0% × 7.0% or more

(Examples 14-17, Comparative Examples 14-15)
◎ Less than 4.0% ○ 4.0μm or more, less than 6.0μm △ 6.0μm or more, less than 8.0μm × 8.0μm or more

(2) Evaluation of dispersibility (production of a solution for evaluating dispersibility)
0.1 part by weight of the obtained slurry composition is added to a mixed solvent of 5 parts by weight of ethanol and 5 parts by weight of toluene, and stirred for 10 minutes with an ultrasonic disperser (“US-303” manufactured by SNDI). As a result, a dispersion evaluation solution was prepared.

(Dispersibility evaluation)
The obtained dispersion evaluation solution was subjected to particle size distribution measurement using a laser diffraction particle size distribution analyzer (Horiba, Ltd., LA-910), and the position of the maximum particle diameter peak and the average dispersion diameter were measured. . The average dispersion diameter was evaluated according to the following criteria.

(Examples 1-13, Comparative Examples 1-13)
◎ Less than 0.4μm ○ 0.4μm or more, less than 0.5μm △ 0.5μm or more, less than 0.6μm x 0.6μm or more

(Examples 14-17, Comparative Examples 14-15)
◎ Less than 2.5μm ○ 2.5μm or more, less than 3.5μm △ 3.5μm or more, less than 4.5μm x 4.5μm or more

ADVANTAGE OF THE INVENTION According to this invention, the inorganic composite for inorganic powder dispersion | distribution which can implement | achieve the outstanding dispersibility by a simple process can be provided. Moreover, the manufacturing method of this inorganic composite for inorganic powder dispersion | distribution, the manufacturing method of a slurry composition, and a slurry composition can be provided.

Claims (7)

An inorganic composite used for dispersion of inorganic powder,
Having a coating layer on the surface of the inorganic powder;
The coating layer has an inner layer made of the polyvinyl acetal resin (A) having a hydroxyl group content of 20 to 50 mol% and a polymerization degree of 20 to 500, a hydroxyl group amount of 20 to 45 mol%, and a polymerization degree of 600 to 4500. An outer layer made of a polyvinyl acetal resin (B), and the degree of polymerization of the polyvinyl acetal resin (A) and the degree of polymerization of the polyvinyl acetal resin (B) have the relationship of the following formula (1): An inorganic composite for dispersing an inorganic powder.

In formula (1), X represents the degree of polymerization of the polyvinyl acetal resin (A), and Y represents the degree of polymerization of the polyvinyl acetal resin (B). The inorganic composite for preparing an inorganic slurry according to claim 1, wherein the weight ratio of the polyvinyl acetal resin (A) to the polyvinyl acetal resin (B) is 5:95 to 50:50. The inorganic composite for dispersing an inorganic powder according to claim 1 or 2, wherein the polyvinyl acetal resin (A) has an anionic group. A method for producing an inorganic composite for dispersing an inorganic powder according to claim 1, 2 or 3,
Step of adding and mixing inorganic powder, polyvinyl acetal resin (A) and organic solvent for inner layer to produce inorganic dispersion for inner layer coating, adding and mixing polyvinyl acetal resin (B) and organic solvent for outer layer to coat outer layer A step of preparing a resin solution for coating, and a step of adding and mixing an outer layer coating resin solution to the inorganic dispersion for coating an inner layer to prepare a slurry for preparing an inorganic composite, and in the slurry for preparing an inorganic composite The manufacturing method of the inorganic composite for inorganic powder dispersion characterized by having the process of drying the organic solvent of this. The inorganic composite for dispersing inorganic powder according to claim 4, wherein 5 to 35 parts by weight of polyvinyl acetal resin (A) and polyvinyl acetal resin (B) are added to 100 parts by weight of the inorganic powder. Method. A method for producing a slurry composition comprising a step of adding and mixing the inorganic composite for dispersing an inorganic powder according to claim 1, 2 or 3 to an organic solvent for slurry. A slurry composition obtained by using the method for producing a slurry composition according to claim 6.