JP2013100389A - Binder for producing inorganic sintered body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a binder for producing an inorganic sintered body excellent in thermally-degradable properties at calcination, wherein a ceramic green sheet can be obtained which has sufficient sheet strength even if made in a thin film when the binder is used especially as the binder for the ceramic green sheet.SOLUTION: A binder for producing an inorganic sintered body contains a block copolymer that has a unit comprising a polyvinyl butyral and a unit comprising poly (meth)acrylic acids.

Description

The present invention relates to a binder for producing an inorganic sintered body that can obtain a ceramic green sheet having a sufficient sheet strength even in a thin film and is excellent in thermal decomposability during firing, particularly when used as a binder for a ceramic green sheet.

As a method for producing various inorganic sintered bodies, various thermoplastic resins and organic compounds are mixed with inorganic powders such as alumina, silica, zirconia, mullite, silicon carbide, silicon nitride, and barium titanate. A method is widely used in which a green molded body is obtained, and the obtained molded body is fired to sinter the inorganic powder while decomposing and scattering the binder.

For example, when manufacturing a ceramic circuit board, a multilayer ceramic capacitor, a separation plate for thin layer chromatography, etc., a ceramic green sheet formed into a thin film into a sheet shape is used.
The ceramic green sheet was prepared by uniformly mixing a ceramic raw material powder and a binder resin, a plasticizer, an antifoaming agent, a dispersant and an organic solvent with a mixing device such as a ball mill, and applying the slurry to a support. Thereafter, it is produced by removing the solvent by drying.

In particular, when a multilayer ceramic capacitor is manufactured, a PET film that has been subjected to a release treatment is used as a support, and a conductive paste serving as an internal electrode is applied on a ceramic green sheet by screen printing or the like. It is manufactured by peeling from a certain PET film, laminating a plurality of these films and heating and pressing to produce a laminate, and then thermally decomposing and removing the binder resin by heating and baking.

The binder used for such a ceramic green sheet is required to be excellent in thermal decomposability during firing and to exhibit sufficient sheet strength when formed into a ceramic green sheet. In particular, in recent years, multilayer ceramic capacitors are required to be smaller and have a larger capacity, and in order to produce a laminate having a thinner inter-electrode distance, a binder having higher performance in the above characteristics is required. For example, Patent Document 1 discloses a method for producing a ceramic green sheet having a thickness of 5 μm or less by using a polyvinyl acetal resin having a polymerization degree of 1200 to 2400.

However, when the thickness of the ceramic green sheet is further reduced, there is a problem that when the molding is performed using a conventional binder, sufficient sheet strength cannot be obtained, and the ceramic green sheet is damaged at the time of peeling. In addition, because it is inferior in thermal decomposability, a part of the binder does not decompose and burn and remains as residual carbide in the sintered body, or cracks, warps, bulges, etc. in the molded body due to rapid decomposition and scattering in the sintering process. However, a satisfactory binder has not been obtained.

For example, when a polyvinyl butyral resin is used as a binder, there is a problem that the produced ceramic green sheet is inferior in thermal decomposability when fired, and there is a large amount of residual carbon after firing.
On the other hand, acrylic resin is excellent in thermal decomposability, and residual carbon after firing is reduced. However, the ceramic green sheet produced using this acrylic resin as a binder has the disadvantage of low strength. It was necessary to add a large amount. Therefore, in the baking treatment, there is a problem that cracks and cracks accompanying rapid volume shrinkage of the obtained degreased body are likely to occur, and that baking also takes a long time.

For these problems, for example, Patent Document 2 discloses a binder excellent in decomposability and sheet strength during firing from a graft copolymer obtained by polymerizing alkyl (meth) acrylate in an environment where polyvinyl butyral resin exists. The binder is described. However, the copolymer produced by such a production method has a very low grafting rate, so that the target sheet strength may not be obtained. Patent Document 3 describes a binder containing a graft copolymer obtained by grafting a (meth) acrylate ester using a polyvinyl butyral resin having a vinyl group introduced into a polyvinyl butyral resin. However, in order to increase the grafting rate using such a method, it is necessary to introduce a large amount of vinyl groups into the polyvinyl butyral resin. In the presence of such a polyvinyl butyral resin (meth) When the acrylic ester is polymerized, a crosslinking reaction occurs, and the resulting binder resin solution has a significantly increased viscosity or gelation, which makes it difficult to obtain a uniform thin film sheet or a firing step. There is a problem that the degreasing property of the ceramic capacitor decreases, and the electrical characteristics of the ceramic capacitor deteriorate.

Japanese Patent No. 3193022 Japanese Patent No. 4737985 JP 2004-331413 A

The present invention provides a binder for producing an inorganic sintered body that is excellent in thermal decomposability during firing, while providing a ceramic green sheet having sufficient sheet strength even in a thin film, particularly when used as a binder for ceramic green sheets. The purpose is to do.

The present invention is a binder for producing an inorganic sintered body containing a block copolymer having a unit made of polyvinyl butyral and a unit made of poly (meth) acrylic acid.
The present invention is described in detail below.

The binder for producing an inorganic sintered body of the present invention contains a block copolymer having a unit made of polyvinyl butyral and a unit made of poly (meth) acrylic acid.
In the present invention, the “unit consisting of polyvinyl butyral” and the “unit consisting of poly (meth) acrylic acid” are mainly used in the state where the commonly used “polyvinyl butyral” and “poly (meth) acrylic acid” are blocked. It is present in the chain.
That is, in the block copolymer having a unit made of polyvinyl butyral and a unit made of poly (meth) acrylic acid, the unit made of polyvinyl butyral and the unit made of poly (meth) acrylic acid are bonded to the main chain in the copolymer. It has the structure connected by.

The block copolymer having a unit made of polyvinyl butyral and a unit made of poly (meth) acrylic acid is a block copolymer, which is used as a binder for ceramic green sheets compared to a graft copolymer. In this case, a green sheet having high sheet strength can be obtained, and a uniform thin film sheet can be obtained. This is because the block copolymer has a portion having a polyvinyl butyral structure and a portion having a poly (meth) acrylic acid structure contained in the binder resin, and does not phase-separate macroscopically, and is uniformly present in the binder. Because it can. In addition, the block copolymer tends to increase the main chain length of the polymer compared to the graft copolymer, and the binder molecules in the stress direction when stress such as tension is applied to the sheet. On the other hand, it is considered that high strength is expressed by orientation.
The structure as the block copolymer is not particularly limited, and examples thereof include a diblock structure, a triblock structure, and a multiblock structure.

The molecular weight of the block copolymer is not particularly limited, but the number average molecular weight (Mn) is 10,000 to 400,000 and the weight average molecular weight (Mw) is 20,000 to 800,000. (Mw / Mn) is preferably 2.0 to 40. When Mn, Mw, and Mw / Mn are within such ranges, the sheet strength increases when the block copolymer is used as a binder for a ceramic green sheet. Moreover, since the slurry viscosity does not become too high and the dispersibility of the inorganic powder is improved, a uniform ceramic green sheet can be formed, which is preferable.

The unit made of polyvinyl butyral (hereinafter also referred to as polyvinyl butyral unit) has a vinyl acetate unit, a vinyl alcohol unit, and a vinyl butyral unit that are usually contained in polyvinyl butyral.

The content of vinyl butyral unit (butyralization degree) in the polyvinyl butyral unit is not particularly limited, but considering the solvent solubility during slurry adjustment when used as a raw material for the ceramic green sheet, it may be 40 mol% or more. preferable.

The vinyl acetate unit content (acetyl group amount) in the polyvinyl butyral unit is not particularly limited, but it is preferably 30 mol% or less in view of sheet strength when used as a raw material for a ceramic green sheet.

Although the polymerization degree of the said polyvinyl butyral unit is not specifically limited, Generally, the thing of 200-4000 is used suitably. When the polymerization degree of the polyvinyl butyral unit is less than 200, the sheet strength of the resulting ceramic green sheet is weak, and when it exceeds 4000, the viscosity when it is made into a slurry is increased, and coating unevenness when applied to a support. It may cause.

The content of the polyvinyl butyral unit contained in the block copolymer is not particularly limited because it is designed according to the use, but it is preferably 10 to 80% by weight with respect to the entire block copolymer.

The unit composed of the poly (meth) acrylic acid (hereinafter also referred to as a poly (meth) acrylic acid unit) is obtained by polymerizing the monomer (meth) acrylic acid.
In the present invention, “(meth) acrylic acids” refers to at least one selected from the group consisting of (meth) acrylic acid esters and (meth) acrylic acid.

Among the above (meth) acrylic acids, the (meth) acrylic acid ester is not particularly limited, but is not particularly limited, but monofunctional (meth) acrylic acid alkyl ester, monofunctional (meth) acrylic acid cyclic alkyl ester and monofunctional It is preferable to contain at least one selected from the group consisting of (meth) acrylic acid aryl esters.
Thereby, when it uses as a binder for ceramic green sheets, the decomposability at the time of baking becomes high and the binder with few residual carbides can be obtained. Moreover, when it is set as a slurry, it can be set as a moderate viscosity.

Examples of the monofunctional (meth) acrylic acid alkyl ester include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, and isobutyl. (Meth) acrylate, t-butyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) ) Acrylate, isodecyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, isotetradecyl (meth) acrylate, and the like.
Examples of the monofunctional (meth) acrylic acid cyclic alkyl ester include cyclohexyl (meth) acrylate and isobornyl (meth) acrylate.
Examples of the monofunctional (meth) acrylic acid aryl ester include phenyl (meth) acrylate and benzyl (meth) acrylate.
The said (meth) acrylic acid ester may be used independently and may use 2 or more types together. In the present specification, the (meth) acrylic acid is a generic term for acrylic acid and methacrylic acid, and the (meth) acrylate is a generic term for acrylate and methacrylate.

Among the above (meth) acrylic acid esters, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate It is preferable to contain at least one selected from the group consisting of t-butyl (meth) acrylate and 2-ethylhexyl (meth) acrylate.
Of these, methacrylic acid esters are preferred because they have a particularly high decomposability during firing and a very small amount of residual carbides, and are further selected from the group consisting of methyl methacrylate, isobutyl methacrylate and n-butyl methacrylate. It is particularly preferable to include at least one selected from the above as a structural unit.
In addition, as said (meth) acrylic acid ester, the kind, compounding quantity, etc. of (meth) acrylic acid ester are set so that the glass transition temperature of the polymer which consists only of (meth) acrylic acid ester may be below room temperature. Thus, even when no plasticizer is added, an appropriate sheet strength can be obtained.

The (meth) acrylic acid constituting the poly (meth) acrylic acid unit preferably contains 80% by weight or more of methacrylic acid, more preferably 90% by weight or more, and 95% by weight or more. Further preferred. Thereby, when this block copolymer is used as a binder for a ceramic green sheet, it is possible to obtain a ceramic green sheet having high decomposability at the time of firing and low residual carbides.

The (meth) acrylic acids preferably contain those having at least one polar group selected from the group consisting of a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, and an ether group in the molecule.
Specifically, for example, (meth) acrylic acid, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, (meth) acrylamide, amino (meth) acrylate Examples thereof include ethyl, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, glycidyl (meth) acrylate, and (meth) acrylate having a polyethylene glycol chain in the ester side chain.

The content of the poly (meth) acrylic acid unit contained in the block copolymer is not particularly limited because it is designed according to the use, but is 20 to 90% by weight with respect to the entire block copolymer. Is preferred.

The ratio of the polyvinyl butyral unit and the poly (meth) acrylic acid unit contained in the block copolymer is not particularly limited because it is designed according to the use, but with respect to 100 parts by weight of the polyvinyl butyral unit, The (meth) acrylic acid unit is preferably 25 to 900 parts by weight. By using it as the said range, when using as a binder for ceramic green sheets, the thermal decomposability of the binder at the time of baking and sheet | seat strength can be made compatible.

The block copolymer may further have units composed of other monomers.
When the block copolymer has units composed of the other monomers, the intermolecular interaction of the obtained block copolymer is increased, and by using the block copolymer as a binder, a ceramic having high sheet strength is obtained. A green sheet can be formed. Furthermore, when the other monomer has a polar group, the polar group and the surface of the inorganic powder cause an interaction such as a hydrogen bond, thereby improving the dispersibility of the resulting slurry of the inorganic powder and Even when no agent is blended, a uniform ceramic green sheet can be formed.

The other monomer is not particularly limited, but includes at least one polar group selected from the group consisting of a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, and an ether group in the molecule, and one olefinic double bond. Monomers having are preferred. Examples of such monomers include crotonic acid, maleic acid, fumaric acid, citraconic acid, mesaconic acid, itaconic acid, allyl alcohol, vinyl ether, allylamine, and the like. Among these other monomers, when a ceramic green sheet is produced using a binder containing the obtained block copolymer, a higher sheet strength can be obtained. A monomer having a hydroxyl group therein is more preferred.

The content of units composed of other monomers contained in the block copolymer is not particularly limited because it is designed according to the use, but is preferably 20% by weight or less based on the entire block copolymer. 10 weight% or less is more preferable, and 5 weight% or less is further more preferable.

The method for producing the block copolymer is not particularly limited. For example, vinyl acetate and (meth) acrylic acid are polymerized by a living polymerization method, and a block copolymer of polyvinyl acetate and poly (meth) acrylic acid is obtained. After being obtained, the polyvinyl acetate site is saponified and converted into a polyvinyl alcohol unit, and a method of producing a polyvinyl alcohol unit by butyralization using butyraldehyde, a polyvinyl alcohol having a reactive group at the terminal is prepared in advance. A method of producing polyvinyl butyral by polymerizing (meth) acrylic acids from reactive end groups and then making polyvinyl alcohol units, producing polyvinyl butyral having reactive groups at the ends, and polymerizing (meth) acrylic acids from reactive end groups And a method of obtaining a block copolymer.
Among these, the method of polymerizing (meth) acrylic acid using polyvinyl butyral having a reactive group at the terminal is easy to control the degree of butyralization and the amount of acetyl group of the polyvinyl butyral unit of the resulting block copolymer. Further, it can be suitably used because the variation in composition between molecules is reduced.

Examples of the reaction between the polyvinyl butyral having a reactive group at the terminal and (meth) acrylic acid include, for example, reacting a polyvinyl butyral having a mercapto group at the terminal and a radical initiator in an environment where a (meth) acrylic acid monomer is present. Can be done. In this reaction, a hydrogen atom of a mercapto group is pulled out by a radical generated by a radical initiator or the like to generate a radical at a polymer terminal, from which the polymerization of (meth) acrylic acid proceeds to form the block copolymer. Can be obtained.
The polymerization method of polyvinyl butyral having a mercapto group at the terminal and a (meth) acrylic acid monomer is not particularly limited. For example, conventionally known polymerization methods such as solution polymerization, emulsion polymerization, suspension polymerization, bulk polymerization, and the like can be used. Can be mentioned. The solvent used for the solution polymerization is not particularly limited, and examples thereof include ethyl acetate, toluene, methanol, ethanol, dimethyl sulfoxide, acetone, diethyl ether, tetrahydrofuran, and a mixed solvent thereof.

The radical initiator is not particularly limited. For example, 1,1-bis (t-hexylperoxy) -3,3,5-trimethylcyclohexane, t-hexylperoxypivalate, t-butylperoxypivalate, Lauroyl peroxide, 2,5-dimethyl-2,5-bis (2-ethylhexanoylperoxy) hexane, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate , Organic peroxides such as t-butylperoxyisobutyrate, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxylaurate, 2,2′-azobisiso Butyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 4,4′-azobis (4-cyanopentanoic acid), 2, '- azobis (2-methylbutyronitrile), azo compounds such as azo-bis-cyclohexane carbonitrile and the like.
These radical initiators may be used alone or in combination of two or more.

In addition, polyvinyl butyral having a mercapto group at the end is obtained by saponifying polyvinyl acetate obtained by polymerizing vinyl acetate in the presence of thiolic acid such as thioacetic acid using an alkali and further converting the obtained polyvinyl alcohol to butyraldehyde. Can be obtained by butyralization in the presence of an acid catalyst.
The polymerization of vinyl acetate in the presence of the thiolic acid can be carried out by any method such as bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization in the presence of a radical polymerization initiator. A solution polymerization method using is preferably used. Examples of radical polymerization initiators include polymerization initiation of t-hexylperoxypivalate, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), and the like. An azo initiator such as 2,2′-azobisisobutyronitrile is preferably used.

Moreover, as another method of obtaining a block copolymer, it can carry out by making polyvinyl butyral and a tetravalent cerium ion react in the environment where a (meth) acrylic acid monomer exists, for example. In this reaction, the main chain corresponding to the 1,2-glycol moiety contained in polyvinyl butyral is cleaved by cerium ions to generate polyvinyl butyral having a radical at the end of the main chain, from which (meth) acrylic acids As the polymerization proceeds, a block copolymer can be obtained.
The polymerization method of the polyvinyl butyral and the (meth) acrylic acid monomer using the cerium ion is not particularly limited, and examples thereof include conventionally known polymerization methods such as solution polymerization, emulsion polymerization, suspension polymerization, and bulk polymerization. It is done.
The solvent used for the solution polymerization is not particularly limited, and examples thereof include methanol, ethanol, dimethyl sulfoxide, N, N-dimethylformamide, acetone, diethyl ether, tetrahydrofuran, water, and a mixed solvent thereof.

A ceramic green sheet can be produced by using the binder for producing an inorganic sintered body of the present invention as a binder for molding a ceramic green sheet.
The method for producing the ceramic green sheet is not particularly limited, and is formed by a known forming method. For example, if necessary, additives such as plasticizers, dispersants and antifoaming agents are blended into the binder for producing the inorganic sintered body of the present invention, and the organic solvent and ceramic powder are mixed uniformly with a mixing device such as a ball mill. Then, a slurry is prepared, and the slurry is wet-applied on a support such as a PET film by a known method such as a doctor blade method, and the organic solvent is removed by drying. In addition, there may be mentioned a method in which the slurry is granulated by a spray dryer method or the like and then the granule is molded by a dry press method.

The ceramic green sheet thus obtained is subjected to various processes such as punching as necessary, and used for manufacturing various ceramic products. For example, in the case of manufacturing a multilayer ceramic capacitor, a PET film that has been subjected to a release treatment is used as a support, and the support is formed by applying a conductive paste serving as an internal electrode on a green sheet by screen printing or the like. It is manufactured by peeling from a PET film, laminating a plurality of the films and heating and pressing to produce a laminate, followed by overheating and thermal decomposition to remove the binder resin.

According to the binder for producing an inorganic sintered body of the present invention, particularly when used as a binder for a ceramic green sheet, a ceramic green sheet having sufficient sheet strength even with a thin film can be obtained, and the thermal decomposability at the time of firing can be obtained. It will be excellent.

Examples of the present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1
(1) Preparation of block copolymer In a reaction vessel equipped with a thermometer, stirrer, nitrogen introduction tube, and cooling tube, polyvinyl butyral having a mercapto group at the end (polymerization degree 800, butyralization degree 68.0 mol%, 25 parts by weight of acetyl group (1.2 mol%), 25 parts by weight of methyl methacrylate, and 100 parts by weight of ethyl acetate were added, and polyvinyl butyral was dissolved while stirring. Next, nitrogen gas was blown for 30 minutes to replace the inside of the reaction vessel with nitrogen, and then the inside of the reaction vessel was heated to 75 ° C. while stirring. After 30 minutes, 0.5 part by weight of AIBN as a polymerization initiator was diluted with 16 parts by weight of ethyl acetate, and the resulting polymerization initiator solution was added dropwise to the reactor over 5 hours. Thereafter, the mixture was further reacted at 75 ° C. for 3 hours.
Next, the reaction solution was cooled to obtain a block copolymer solution A having a solid content of 30% by weight and containing a block copolymer. In addition, it was 200,000 when the weight average molecular weight by polystyrene conversion was measured by GPC method using "2690 Separations Model" made from Waters, using the weight average molecular weight of the obtained block copolymer as a column.

(2) Preparation of ceramic green sheet The obtained block copolymer solution A was diluted with a diluting solvent (a mixed solvent of ethanol and toluene, and the weight ratio of ethanol and toluene was 1: 1) to obtain a solution having a solid content of 10% by weight. It was. Next, 20 parts by weight of this solution is 20 parts by weight of barium titanate powder (BT-03, average particle size 0.3 μm, manufactured by Sakai Chemical Industry Co., Ltd.) as a ceramic powder, and 0.4 parts by weight of dioctyl phthalate as a plasticizer. Part thereof was added and kneaded for 48 hours using a ball mill to obtain a ceramic green sheet slurry.
Next, the obtained slurry for ceramic green sheets was applied onto a PET film that had been subjected to a release treatment so that the thickness after drying was 3 μm using a coater, air-dried at room temperature for 1 hour, and then heated with a hot-air dryer. A ceramic green sheet was obtained by drying at 80 ° C. for 1 hour and then at 120 ° C. for 1 hour.

(Example 2)
In Example 1, “(1) Preparation of block copolymer”, in place of 25 parts by weight of methyl methacrylate, 50 parts by weight of methyl methacrylate and 50 parts by weight of n-butyl methacrylate were used. The block copolymer solution B containing a block copolymer and having a solid content of 50% by weight was obtained. In addition, it was 350,000 when the weight average molecular weight by polystyrene conversion was measured by GPC method using "2690 Separations Model" made from Waters, using the weight average molecular weight of the obtained block copolymer as a column.
Next, a ceramic green sheet was obtained in the same manner as in “(2) Preparation of ceramic green sheet” in Example 1 except that the block copolymer solution B was used and dibutyl phthalate was used as a plasticizer.

(Example 3)
In Example 1, “(1) Preparation of block copolymer”, the same operation as in Example 1 was carried out except that 10 parts by weight of isobutyl methacrylate was used instead of 25 parts by weight of methyl methacrylate. A block copolymer solution C having a solid content of 23% by weight containing the coalesced was obtained. In addition, it was 170,000 when the weight average molecular weight by polystyrene conversion was measured by GPC method using "2690 Separations Model" made from Waters, using the weight average molecular weight of the obtained block copolymer as a column.
Next, a ceramic green sheet was obtained in the same manner as “(2) Preparation of ceramic green sheet” in Example 1 except that the block copolymer solution C was used.

Example 4
The same operation as in Example 1 except that instead of 25 parts by weight of methyl methacrylate, 24 parts by weight of methyl methacrylate and 1 part by weight of methacrylic acid were used in “(1) Preparation of block copolymer” in Example 1. And a block copolymer solution D having a solid content of 30% by weight containing the block copolymer was obtained. In addition, it was 200,000 when the weight average molecular weight by polystyrene conversion was measured by GPC method using "2690 Separations Model" made from Waters, using the weight average molecular weight of the obtained block copolymer as a column.
Next, a ceramic green sheet was obtained in the same manner as “(2) Production of ceramic green sheet” in Example 1 except that the block copolymer solution D was used.

(Example 5)
(1) Preparation of block copolymer In a reaction vessel equipped with a thermometer, a stirrer, a nitrogen introduction tube, and a cooling tube, 20 parts by weight of polyvinyl butyral (polymerization degree 1700, butyralization degree 65.0 mol%) and methyl 40 parts by weight of methacrylate and 40 parts by weight of dimethyl sulfoxide were added, and polyvinyl butyral was dissolved while stirring. Next, nitrogen gas was blown for 30 minutes to replace the inside of the reaction vessel with nitrogen, and then the inside of the reaction vessel was heated to 50 ° C. with stirring. After 30 minutes, 0.8 part by weight of ceric ammonium nitrate as a polymerization initiator was added and reacted at 50 ° C. for 5 hours while stirring in the reaction vessel.
Thereafter, the reaction solution was cooled to obtain a block copolymer solution E having a solid content of 60% by weight and containing a block copolymer. In addition, it was 120,000 when the weight average molecular weight by polystyrene conversion was measured by GPC method using "2690 Separations Model" made from Waters, using the weight average molecular weight of the obtained block copolymer as a column.

(2) Preparation of ceramic green sheet The obtained block copolymer solution E was precipitated in water and re-dissolved in THF three times and then sufficiently dried, and then a mixed solvent of ethanol and toluene (ethanol: toluene) = 1: 1) was redissolved so that the solid content was 30 wt%.
20 parts by weight of barium titanate powder (BT-03, average particle size 0.3 μm, manufactured by Sakai Chemical Industry Co., Ltd.) as ceramic powder, 6.7 parts by weight of the obtained block copolymer ethanol / toluene solution, Then, 15 parts by weight of a mixed solvent of ethanol and toluene (ethanol: toluene = 1: 1) as a solvent and 0.4 parts by weight of dibutyl phthalate as a plasticizer are added, and kneaded for 48 hours using a ball mill. A slurry was obtained.
Next, the obtained slurry for ceramic green sheets was applied onto a PET film that had been subjected to a release treatment so that the thickness after drying was 3 μm using a coater, air-dried at room temperature for 1 hour, and then heated with a hot-air dryer. A ceramic green sheet was obtained by drying at 80 ° C. for 1 hour and then at 120 ° C. for 1 hour.

(Comparative Example 1)
Polyvinyl butyral resin (polymerization degree 800, butyralization degree 68.0 mol%, acetyl group amount 1.2 mol%) is dissolved in a mixed solvent of ethanol and toluene (ethanol: toluene = 1: 1) at a solid content of 10% by weight. A polyvinyl butyral resin solution was prepared. In addition, it was 150,000 when the weight average molecular weight by polystyrene conversion was measured by GPC method using "2690 Separations Model" made from Waters, using this polyvinyl butyral resin as a column.
Next, in “(2) Production of ceramic green sheet” in Example 1, the same operation as in Example 1 was performed except that the obtained polyvinyl butyral resin solution was used in place of the block copolymer solution A. A ceramic green sheet was obtained.

(Comparative Example 2)
A polymethyl methacrylate solution was prepared by dissolving polymethyl methacrylate (weight average molecular weight 80,000) in a mixed solvent of ethanol and toluene (ethanol: toluene = 1: 1) at a solid content of 10% by weight.
Next, in “(2) Production of ceramic green sheet” in Example 1, the same operation as in Example 1 was performed except that the obtained polymethyl methacrylate solution was used in place of the block copolymer solution A. A ceramic green sheet was obtained.

(Comparative Example 3)
A mixture of polyvinyl butyral resin (degree of polymerization 800, degree of butyralization 68.0 mol%, acetyl group amount 1.2 mol%) and polymethyl methacrylate (weight average molecular weight 80,000) (1: 1 by weight). A mixed resin solution dissolved in a mixed solvent of ethanol and toluene (ethanol: toluene = 1: 1) at a solid content of 10% by weight was prepared.
Next, in “(2) Production of ceramic green sheet” in Example 1, the same operation as in Example 1 was performed except that the obtained mixed resin solution was used instead of the block copolymer solution A. A ceramic green sheet was obtained.

(Comparative Example 4)
In a reaction vessel equipped with a thermometer, a stirrer, a nitrogen introduction tube, and a cooling tube, 25 parts by weight of polyvinyl butyral (degree of polymerization 800, degree of butyralization 68.0 mol%, acetyl group amount 1.2 mol%) and methyl 25 parts by weight of methacrylate and 100 parts by weight of ethyl acetate were added, and polyvinyl butyral was dissolved while stirring. Next, nitrogen gas was blown for 30 minutes to replace the inside of the reaction vessel with nitrogen, and then the inside of the reaction vessel was heated to 75 ° C. while stirring. After 30 minutes, 0.5 part by weight of AIBN as a polymerization initiator was diluted with 16 parts by weight of ethyl acetate, and the resulting polymerization initiator solution was added dropwise to the reactor over 5 hours. Thereafter, the mixture was further reacted at 75 ° C. for 3 hours.
Thereafter, the reaction solution was cooled to obtain a binder resin solution A having a solid content of 30% by weight partially containing the graft polymer. In addition, it was 90,000 when the weight average molecular weight by polystyrene conversion was measured by GPC method using "2690 Separations Model" made from Waters, using the weight average molecular weight of the obtained binder resin as a column.
Next, in “(2) Production of ceramic green sheet” in Example 1, the same operation as in Example 1 was performed except that the obtained binder resin solution A was used instead of the block copolymer solution A. A ceramic green sheet was obtained.

(Comparative Example 5)
In a reaction vessel equipped with a thermometer, a stirrer, a nitrogen introduction tube, and a cooling tube, 20 parts by weight of polyvinyl butyral (degree of polymerization 800, degree of butyralization 68.0 mol%, acetyl group amount 1.2 mol%) and acetic acid 80 parts by weight of ethyl was added, and polyvinyl butyral was dissolved while stirring. Next, 0.6 parts by weight of 2-isocyanatoethyl methacrylate and 1 part by weight of trimethylamine were added, and the mixture was reacted at 75 ° C. for 10 hours while stirring in the reaction vessel.
Next, 40 parts by weight of methyl methacrylate was added to the reaction solution. Next, 0.5 part by weight of AIBN as a polymerization initiator was diluted with 16 parts by weight of ethyl acetate, and the resulting polymerization initiator solution was added dropwise to the reactor over 5 hours. Thereafter, the mixture was further reacted at 75 ° C. for 3 hours.
Thereafter, the reaction solution was cooled to obtain a binder resin solution B having a solid content of 38 wt% partially containing the graft polymer. In addition, it was 110,000 when the weight average molecular weight by polystyrene conversion was measured by GPC method using "2690 Separations Model" made from Waters, using the weight average molecular weight of the obtained binder resin as a column.
Next, in “(2) Production of ceramic green sheet” in Example 1, the same operation as in Example 1 was performed except that the obtained binder resin solution B was used instead of the block copolymer solution A. A ceramic green sheet was obtained.

(Evaluation method)
The performance of the ceramic green sheet obtained above was evaluated by the following method. The results are shown in Table 1.

(Strength evaluation)
The obtained ceramic green sheet was peeled from the polyester film, the state of the ceramic green sheet was visually observed, and the strength was evaluated according to the following criteria.
A: No cutting or tearing was observed on the ceramic green sheet.
○: A small cut was observed in a small part of the ceramic green sheet.
X: The ceramic green sheet could not be peeled from the polyester film, or cuts and tears were observed on the majority of the peeled sheet.

(Pyrolysis evaluation)
The obtained various resin solutions were applied onto a PET film that had been subjected to a release treatment so that the thickness after drying was 100 μm using a coater, air-dried at room temperature for 1 hour, and then heated at 80 ° C. for 1 hour with a hot-air dryer. Then, it was dried at 120 ° C. for 1 hour to produce a film. This was heated to 600 ° C., and observed whether or not it was completely decomposed, and the thermal decomposability was evaluated according to the following criteria.
(Double-circle): There was no residue and it decomposed | disassembled completely.
○: Almost no residue and almost completely decomposed.
X: There was a clear residue.

(Sheet uniformity)
The state of the obtained ceramic green sheet was visually observed, and the sheet uniformity was evaluated according to the following criteria.
A: A uniform sheet was obtained with no unevenness in the ceramic green sheet.
○: There was almost no unevenness in the ceramic green sheet, and a substantially uniform sheet was obtained.
X: There was clear unevenness in the ceramic green sheet.

According to the present invention, especially when used as a binder for a ceramic green sheet, a ceramic green sheet having sufficient sheet strength even in a thin film can be obtained, and the binder for producing an inorganic sintered body having excellent thermal decomposability upon firing. Can be provided.

Claims (5)

A binder for producing an inorganic sintered body, comprising a block copolymer having a unit made of polyvinyl butyral and a unit made of poly (meth) acrylic acid. (Meth) acrylic acids constituting units composed of poly (meth) acrylic acids are methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) 2. The inorganic sintered material according to claim 1, comprising at least one selected from the group consisting of) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate and 2-ethylhexyl (meth) acrylate. Binder for body production. The binder for producing an inorganic sintered body according to claim 1 or 2, wherein the (meth) acrylic acid constituting the unit composed of poly (meth) acrylic acid contains 80% by weight or more of methacrylic acid. 2. The (meth) acrylic acid constituting the unit composed of poly (meth) acrylic acid contains at least one selected from the group consisting of methyl methacrylate, isobutyl methacrylate and n-butyl methacrylate. 2. A binder for producing an inorganic sintered body according to 2 or 3. The (meth) acrylic acid constituting the unit composed of poly (meth) acrylic acid has at least one polar group selected from the group consisting of a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, and an ether group in the molecule. The binder for manufacturing an inorganic sintered body according to claim 1, 2, 3 or 4, further comprising: