Method for producing polyvinyl acetal resin and polyvinyl acetal resin solution

Abstract

To provide: a polyvinyl acetal resin which contains little foreign matter and enables the production of a ceramic green sheet having high mechanical strength, and with which it is possible to produce a multilayer ceramic capacitor having excellent reliability; a method for producing a polyvinyl acetal resin solution using the polyvinyl acetal resin; slurry for a ceramic green sheet; a ceramic green sheet; and a multilayer ceramic capacitor.SOLUTION: In the polyvinyl acetal resin, if P(MIX) is the number of particles having a size of 0.5-1.0 μm in a 0.2 mass% ethanol-toluene mixed solution (ethanol:toluene=50:50), and P(EOH) is the number of particles having a size of 0.5-1.0 μm in a 0.2-mass% ethanol solution, then P(MIX) is 1-20,000 particles / 10 ml and P(EOH) / P(MIX) is 1.2-7.0. In addition, in an IR absorption spectrum measured using an infrared spectrophotometer, among wavenumbers exhibiting transmittance a (%) satisfying [100-(100-X) / 2], where X (%) refers to the minimum transmittance of a peak in the wavenumber range of 3050-3750 cm-1, the wavenumber on the lower wavenumber side is represented by A and the wavenumber on the higher wavenumber side is represented by B; and then the hydroxyl-group-content-converted wavenumber width obtained by formula (1) using the wavenumbers A and B and the hydroxyl group content measured by 1H-NMR is 8.31 or more, where formula (1) is defined by [hydroxyl-group-content-converted wavenumber width (cm-1 / mol%)]=[(B-A) / (hydroxyl group content)].SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to polyvinyl acetal resin, a method for producing a polyvinyl acetal resin solution, a slurry for ceramic green sheets, ceramic green sheets, and multilayer ceramic capacitors. [Background technology]

[0002] In recent years, electronic components used in various electronic devices have become smaller and more layered, and multilayer electronic components such as multilayer circuit boards, multilayer coils, and multilayer ceramic capacitors are widely used. In particular, multilayer ceramic capacitors are generally manufactured through the following process. First, a binder resin such as polyvinyl butyral resin or poly(meth)acrylic acid ester resin is dissolved in an organic solvent, and plasticizers, dispersants, etc., are added to the solution. Then, ceramic raw material powder is added and the mixture is uniformly mixed using a mixing device such as a bead mill or ball mill. After degassing, a ceramic slurry composition with a constant viscosity is obtained. This slurry composition is cast onto a support surface such as a release-treated polyethylene terephthalate film or a SUS plate using a doctor blade, reverse roll coater, etc. After heating or otherwise removing volatile components such as solvents, it is peeled off from the support to obtain a ceramic green sheet. Next, multiple sheets of the obtained ceramic green sheet, onto which conductive paste that will serve as the internal electrodes is screen-printed, are stacked alternately and heated and pressed together to create a laminate. After that, a process called degreasing is performed to remove binder resin components and other substances contained in the laminate, and then the ceramic sintered body is fired and external electrodes are sintered onto the end face to obtain a multilayer ceramic capacitor.

[0003] For example, Patent Document 1 describes a polyvinyl acetal resin suitable as a ceramic binder, having a predetermined degree of polymerization, vinyl ester unit content, and degree of acetalization, and having a predetermined molar ratio of the portion acetalized by acetaldehyde to the portion acetalized by butyraldehyde. Furthermore, Patent Document 2 describes a polyvinyl acetal resin having a predetermined degree of polymerization, vinyl ester unit content, and degree of acetalization, and having specific constituent units. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2011-236304 [Patent Document 2] International Publication No. 2012 / 023517 [Overview of the project] [Problems that the invention aims to solve]

[0005] On the other hand, in recent years, with the increasing multi-functionality and miniaturization of electronic devices, there has been a demand for multilayer ceramic capacitors to be both high-capacity and small-sized, and further thinning of ceramic green sheets is also required. However, when conventional polyvinyl acetal resin is used in thin-layer ceramic green sheets, the presence of foreign matter in the resin can lead to problems such as short-circuit failures in multilayer ceramic capacitors and a decrease in various electrical characteristics. Furthermore, there is the problem that the resulting ceramic green sheet may have insufficient strength.

[0006] The present invention aims to provide a polyvinyl acetal resin capable of obtaining a ceramic green sheet with less foreign matter in the resin and high mechanical strength, and capable of producing a laminated ceramic capacitor with excellent reliability, a method for producing a polyvinyl acetal resin solution using the polyvinyl acetal resin, a slurry for a ceramic green sheet, a ceramic green sheet, and a laminated ceramic capacitor.

Means for Solving the Problems

[0007] In the present disclosure 1, when the number of particles with a size of 0.5 to 1.0 μm in a 0.2 mass% ethanol-toluene (ethanol:toluene = 50:50) mixed solution is P(MIX), and the number of particles with a size of 0.5 to 1.0 μm in a 0.2 mass% ethanol solution is P(EOH), P(MIX) is 1 to 20,000 particles / 10 ml, and P(EOH) / P(MIX) is 1.2 to 7.0. In the IR absorption spectrum measured by an infrared spectrophotometer, when the minimum transmittance of the peak within the range of wavenumbers 3050 to 3750 cm 4 is X (%), and among the wavenumbers showing the transmittance a (%) that satisfies [100 - (100 - X) / 2], when the wavenumber on the low wavenumber side is A and the wavenumber on the high wavenumber side is B, using the hydroxyl group amount measured by 1 1H-NMR, the hydroxyl group amount conversion wavenumber width obtained by formula (1) is 8. 42 or more The ratio is 9.65 or less, and the acetyl group content is 0.1 mol% or more and 22.0 mol% or less. This is a polyvinyl acetal resin. Hydroxyl group amount conversion wavenumber width (cm -1 / mol%) = [(B - A) / hydroxyl group amount] (1) Disclosure 2 is the polyvinyl acetal resin described in Disclosure 1, wherein the P(MIX) is 2926 to 18243 particles / 10 ml and the P(EOH) / P(MIX) is 1.81 to 5.85. The present disclosure 3 is the polyvinyl acetal resin according to the present disclosure 1, where P(EOH) is 4000 to 60,000 particles / 10 ml. The present disclosure 4 is the polyvinyl acetal resin according to the present disclosure 1, where the wavenumber width obtained by formula (1) is 8.45 or more. ~3 of the above The present disclosure is the polyvinyl acetal resin according to the present disclosure 1, where the differential refractive 5 is OccasionallyIn GPC measurement using a rate detector, when the z-average molecular weight obtained using THF as the mobile phase is denoted as Mz(THF) and the z-average molecular weight obtained using NMP as the mobile phase is denoted as Mz(NMP), Mz(THF) / Mz(NMP) is 1.7 to 2.0, as described in any one of Disclosures 1 to 4 It is the polyvinyl acetal resin described in any one of them. This disclosure 6 is a method for producing a polyvinyl acetal resin solution using the polyvinyl acetal resin described in any one of Disclosures 1 to 5 which comprises dissolving the polyvinyl acetal resin using an ethanol / toluene mixed solvent having an ethanol content of 70% by weight or more, removing particles by a filtration step, and then adding toluene. This disclosure 7 is a slurry for a ceramic green sheet containing the polyvinyl acetal resin described in any one of Disclosures 1 to 5 and an organic solvent and ceramic powder. This disclosure 8 is a ceramic green sheet obtained using the slurry for a ceramic green sheet described in this disclosure 7 as described. This disclosure 9 is a multilayer ceramic capacitor obtained using the ceramic green sheet described in this disclosure 8 as described. The present invention will be described in detail below.

[0008] As a result of intensive studies, the present inventors have found that the number of particles having a size of 0.5 to 1.0 μm in an ethanol solution with respect to the number of particles having a size of 0.5 to 1.0 μm in an ethanol-toluene mixed solution is within a predetermined range, and in the IR absorption spectrum measured by an infrared spectrophotometer, the peak wave number width within the range of 3050 to 3750 cm -1 is within a predetermined range, and a polyvinyl acetal resin can provide a ceramic green sheet with few foreign substances in the resin and high mechanical strength, and a multilayer ceramic capacitor with excellent reliability can be produced, thus completing the present invention.

[0009] In the present invention, the polyvinyl acetal resin has a ratio of P(EOH) / P(MIX) of 1.2 to 7.0, where P(MIX) is the number of particles of size 0.5 to 1.0 μm in a 0.2% by mass ethanol-toluene (ethanol:toluene = 50:50) mixed solution, and P(EOH) is the number of particles of size 0.5 to 1.0 μm in a 0.2% by mass ethanol solution. The number of particles with a diameter of 0.5 to 1.0 μm is determined by preparing a predetermined solution (0.2% by mass ethanol-toluene mixed solution, 0.2% by mass ethanol solution) and then measuring the number of particles with a diameter of 0.5 to 1.0 μm using a particle counter. When the P(EOH) / P(MIX) ratio is within the above range, the uniformity of the slurry is improved, allowing for the production of smoother ceramic green sheets, and reducing the likelihood of sheet defects such as cracks. In other words, this has the advantage of improving the reliability of the resulting multilayer ceramic capacitors. The above P(EOH) / P(MIX) ratio is preferably 3.3 or higher, and more preferably 4.3 or higher. Furthermore, the above P(EOH) / P(MIX) ratio is preferably 6.5 or lower, and more preferably 6.5 or lower. In this invention, P(EOH) / P(MIX) serves as an indicator of the ease with which particles precipitate in ethanol. For example, the "KS-42C" manufactured by Rion Co., Ltd. can be used as the particle counter mentioned above. For example, particle measurements using the above-mentioned particle counter are preferably performed in a cleanroom at 23°C.

[0010] The polyvinyl acetal resin of the present invention preferably has a particle count P(EOH) of 0.5 to 1.0 μm size in a 0.2% by mass ethanol solution of 4,000 to 60,000 particles / 10 ml, and more preferably 5,000 particles / 10 ml or more and 50,000 particles / 10 ml or less. By keeping it within the above range, particles in the resin solution can be efficiently removed. The above P(EOH) is even more preferably 7,000 particles / 10 ml or more, and even more preferably 40,000 particles / 10 ml or less.

[0011] The polyvinyl acetal resin of the present invention has a particle count P(MIX) of 0.5 to 1.0 μm size in a 0.2% by mass ethanol-toluene (ethanol:toluene = 50:50) mixed solution of 1 to 20,000 particles / 10 ml. Preferably, P(MIX) is between 10 particles / 10 ml and 15,000 particles / 10 ml. By keeping it within this range, particles in the resin solution can be efficiently removed. More preferably, P(MIX) is 100 particles / 10 ml or more, and even more preferably 8,000 particles / 10 ml or less.

[0012] The above P(EOH) / P(MIX), P(EOH), and P(MIX) can be adjusted, for example, by changing the average degree of polymerization and saponification of the raw material polyvinyl alcohol resin, as well as the temperature and time conditions of the acetalization reaction, and by appropriately setting the amount of acetal groups, hydroxyl groups, acetyl groups, etc., of the polyvinyl acetal resin. In particular, the P(EOH) / P(MIX) ratio described above can be adjusted by changing the hydrolysis temperature, hydrolysis time, aldehyde input temperature, heating time, reaction temperature, reaction time, holding (aging) temperature, and holding (aging) time during the acetalization reaction described later. Specifically, it can be adjusted by changing the hydrolysis temperature, hydrolysis time, holding (aging) temperature, and holding (aging) time.

[0013] The polyvinyl acetal resin of the present invention exhibits an IR absorption spectrum measured by an infrared spectrophotometer with wavenumbers of 3050 to 3750 cm⁻¹. -1When the minimum peak transmittance within the range is X (%), and among the wavenumbers that show a transmittance a (%) satisfying [100 - (100 - X) / 2], if the wavenumber on the lower wavenumber side is A and the wavenumber on the higher wavenumber side is B, then the hydroxyl group equivalent wavenumber width calculated by the above formula (1) is 8.31 or greater. By keeping the range within the above limits, it is possible to obtain a ceramic green sheet with even higher mechanical strength. The preferred lower limit for the above hydroxyl group-based wavenumber width is 8.45, a more preferred lower limit is 8.70, an even more preferred lower limit is 8.84, a preferred upper limit is 10.00, and a more preferred upper limit is 9.70. In the present invention, the above-mentioned hydroxyl group amount-based wavenumber width serves as an indicator of the continuity of the positions of the hydroxyl groups. The above IR absorption spectrum can be measured, for example, by transmission using a Fourier transform infrared spectrophotometer (such as HORIBA's "FT-720" or JASCO's "FT / IR-4000") at a temperature of 20°C.

[0014] The polyvinyl acetal resin of the present invention is the same as A, B and 1 It is preferable that the hydroxyl group and acetyl group equivalent wavenumber width, calculated using the following formula (2) based on the amount of hydroxyl groups and acetyl groups measured by 1H-NMR, is between 6.5 and 18.0. Wavewidth converted to hydroxyl group / acetyl group amount = [(BA) / hydroxyl group amount / acetyl group amount] (2) By keeping the range within the above limits, a ceramic green sheet with high mechanical strength can be obtained. A more preferred lower limit for the above hydroxyl group acetyl group equivalent wavenumber width is 10.5, an even more preferred lower limit is 11.0, a more preferred upper limit is 16.0, and an even more preferred upper limit is 14.0.

[0015] Analysis of polyvinyl acetal resin using the above infrared spectrophotometer revealed that the spectrum originating from the stretching vibrations of the CH bond in the polyvinyl acetal resin was 2980 cm⁻¹. -1 It appears in the vicinity. The peak analysis above first determines that the minimum transmittance of the peak originating from the stretching vibration of this CH bond is 2500 cm. -1 and 3050cm-1 When measuring, adjust the film thickness of the measurement sample so that it becomes 20 to 25% when connected to form a baseline. Further, for the peak that appears within the range of the above wavenumber 3050 to 3750 cm -1 draw a baseline for the peak that appears within the range, and perform it on the corrected data such that the transmittance at both ends of the peak becomes 100%.

[0016] The wavenumber width in terms of the hydroxyl group amount can be adjusted, for example, by changing the average degree of polymerization, saponification degree of the raw material polyvinyl alcohol resin, and temperature and time conditions of the acetalization reaction, and appropriately setting the amount of acetal groups, hydroxyl groups, acetyl groups, etc. of the polyvinyl acetal resin. In particular, the above wavenumber width can be adjusted by changing the hydrolysis temperature, hydrolysis time, aldehyde charging temperature, temperature rising time, reaction temperature, reaction time, holding (aging) temperature, and holding (aging) time during the acetalization reaction described later. In particular, it can be adjusted by changing the temperature rising rate, holding (aging) temperature, and holding (aging) time.

[0017] An example of the IR absorption spectrum measured by an infrared spectrophotometer under the condition of 20 °C for the polyvinyl acetal resin of the present invention is shown in FIG. 1. FIG. 1 has the transmittance on the vertical axis and the wavenumber on the horizontal axis. In the IR absorption spectrum shown in FIG. 1, the minimum transmittance X is 65.7%. Also, the transmittance a (%) satisfying [100 - (100 - X) / 2] is 82.85%, and the wavenumber A on the low wavenumber side is 3297 cm -1 and the wavenumber B on the high wavenumber side is 3557 cm -1 is. In the above case, if the amount of hydroxyl groups is 30 mol%, the wavenumber width in terms of the hydroxyl group amount [(B - A) / hydroxyl group amount] is 8.67 (cm -1 / mol%). The above wavenumber A is preferably 3250 cm -1 or more, and more preferably 3270 cm -1 or more. Also, it is preferably 3350 cm -1 or less, and more preferably 3330 cm -1 or less. The above wavenumber B is 3530 cm-1 The above is preferable, 3550cm -1 The above is preferable. Also, 3600cm -1 The following is preferable: 3580cm -1 The following are preferable. The above transmittance a is preferably 80% or more, and preferably 85% or less.

[0018] The polyvinyl acetal resin of the present invention has differential refractive index Occasionally In GPC measurements using a rate detector, when the z-average molecular weight obtained using THF as the mobile phase is denoted as Mz(THF) and when the z-average molecular weight obtained using NMP as the mobile phase is denoted as Mz(NMP), it is preferable that Mz(THF) / Mz(NMP) is between 1.7 and 2.0. By keeping it within this range, a ceramic green sheet with high mechanical strength can be obtained. The above Mz(THF) / Mz(NMP) is preferably 1.75 or higher, and more preferably 1.80 or higher. Furthermore, the above Mz(THF) / Mz(NMP) is preferably 1.95 or lower, and more preferably 1.90 or lower. In this invention, Mz(THF) / Mz(NMP) serves as an indicator of the intermolecular interactions of polyvinyl acetal resin. The above Mz(THF) / Mz(NMP) uses tetrahydrofuran as the mobile phase and solvent, and differential refractometer as the detector. Occasionally After measuring Mz(THF) obtained using gel permeation chromatography (GPC) with a rate detector, using THF as the mobile phase, N-methylpyrrolidone was used as the mobile phase and solvent, and a differential refractometer was used as the detector. Occasionally By measuring Mz(NMP) using NMP as the mobile phase via GPC measurement with a rate detector, it can be calculated by determining Mz(THF) / Mz(NMP).

[0019] The above Mz(THF) is preferably 400,000 or more, more preferably 700,000 or more, preferably 6,000,000 or less, and more preferably 2,000,000 or less. The above Mz(NMP) is preferably 200,000 or more, more preferably 400,000 or more, preferably 4,200,000 or less, and more preferably 1,200,000 or less.

[0020] The above Mz(THF) / Mz(NMP) ratio can be adjusted, for example, by changing the average degree of polymerization and saponification of the raw material polyvinyl alcohol resin, as well as the temperature and time conditions of the acetalization reaction, and by appropriately setting the amount of acetal groups, hydroxyl groups, acetyl groups, etc., in the polyvinyl acetal resin. In particular, the above Mz(THF) / Mz(NMP) ratio can be adjusted by changing the aldehyde input temperature, number of inputs, input interval, heating time, reaction temperature, reaction time, holding (aging) temperature, and holding (aging) time during the acetalization reaction described later. Specifically, it can be adjusted by changing the aldehyde input temperature, reaction time, heating rate, holding (aging) temperature, and holding (aging) time.

[0021] The polyvinyl acetal resin of the present invention preferably has a solution viscosity of 30 mPa·s or more and 600 mPa·s or less when a 5% by mass solution, prepared by dissolving it in a 1:1 mixed solvent of ethanol and toluene, is measured using a B-type viscometer at a solution temperature of 20°C. From the viewpoint of improving tensile strength, the viscosity is more preferably 50 mPa·s or higher, and even more preferably 65 mPa·s or higher. From the viewpoint of improving the viscosity stability of the ceramic slurry composition, it is more preferably 400 mPa·s or lower, and even more preferably 200 mPa·s or lower. As the above-mentioned Type B viscometer, for example, the TVB-10 viscometer manufactured by Toki Sangyo Co., Ltd. can be used. Furthermore, it is preferable to adjust the rotor and rotation speed appropriately depending on the viscosity of the solution when measuring viscosity. For example, it is preferable to measure using SPINDLE No. M1 to M4 at a rotation speed in the range of 0.3 to 100 rpm.

[0022] The viscosity can be adjusted, for example, by changing the average degree of polymerization and saponification of the raw material polyvinyl alcohol resin, as well as the temperature and time conditions of the acetalization reaction, and by appropriately setting the amount of acetal groups, hydroxyl groups, acetyl groups, etc., of the polyvinyl acetal resin.

[0023] The polyvinyl acetal resin of the present invention preferably has a structural unit having an acetal group represented by the following formula (3), a structural unit having a hydroxyl group represented by the following formula (4), and a structural unit having an acetyl group represented by the following formula (5).

[0024] [ka]

[0025] In the above equation (3), R 1 represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.

[0026] In the above equation (3), R 1 When the alkyl group has 1 to 20 carbon atoms, examples of the alkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl, iso-butyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, 2-ethylhexyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, and octadecyl groups. Among these, methyl and n-propyl groups are preferred.

[0027] In the polyvinyl acetal resin of the present invention, the preferred lower limit of the content of constituent units having an acetal group represented by the above formula (3) (hereinafter also referred to as "acetal group content") is 50 mol%, and the preferred upper limit is 83 mol%. If the amount of acetal groups is 50 mol% or more, solubility in organic solvents can be improved. If the amount of acetal groups is 83 mol% or less, a polyvinyl acetal resin with excellent tensile strength can be obtained. The above acetal group content has a more preferable lower limit of 55 mol% and a more preferable upper limit of 80 mol%. That is, the above acetal group content is preferably 50 to 83 mol%, and more preferably 55 to 80 mol%. The above amount of acetal groups is, for example, 1 It can be measured by 1H-NMR. Regarding the calculation method for the amount of acetal groups, since the acetal groups in polyvinyl acetal resin are obtained by acetalizing two hydroxyl groups of polyvinyl alcohol, the method of counting the two acetalized hydroxyl groups is adopted.

[0028] In the polyvinyl acetal resin of the present invention, the preferred lower limit of the content of constituent units having a hydroxyl group represented by the above general formula (4) (hereinafter also referred to as "hydroxyl group content") is 18 mol%, and the preferred upper limit is 40 mol%. When the amount of hydroxyl groups is 18 mol% or more, a highly tough polyvinyl acetal resin can be obtained. When the amount of hydroxyl groups is 40 mol% or less, the solubility in organic solvents can be sufficiently improved. The above hydroxyl group content has a more preferable lower limit of 22 mol% and a more preferable upper limit of 38 mol%. That is, the above hydroxyl group content is preferably 18 to 40 mol%, and more preferably 22 to 38 mol%. By using the above-mentioned amount of hydroxyl groups, the wavenumber width converted to the amount of hydroxyl groups and the wavenumber width converted to the amount of hydroxyl groups and acetyl groups can be set to a predetermined range. The amount of hydroxyl groups mentioned above is, for example, 1 It can be measured by 1H-NMR.

[0029] In the polyvinyl acetal resin of the present invention, the preferred lower limit of the content of the constituent unit having an acetyl group represented by the above general formula (5) (hereinafter also referred to as "acetyl group content") is 0.1 mol%, and the preferred upper limit is 22.0 mol%. When the amount of acetyl groups is 0.1 mol% or more, it is possible to suppress the increase in viscosity of the slurry composition for ceramic green sheets due to intramolecular and intermolecular hydrogen bonding of hydroxyl groups in the polyvinyl acetal resin. When the amount of acetyl groups is 22.0 mol% or less, it is possible to improve handling properties without increasing the flexibility of the polyvinyl acetal resin too much. The above acetyl group content has a more preferable lower limit of 0.5 mol% and a more preferable upper limit of 15.0 mol%. That is, the above acetyl group content is preferably 0.1 to 22.0 mol%, and more preferably 0.5 to 15.0 mol%. By using the above amount of acetyl groups, the hydroxyl group-acetyl group-equivalent wavenumber width can be set to a predetermined range. The above amount of acetyl groups is, for example, 1 It can be measured by 1H-NMR.

[0030] The polyvinyl acetal resin of the present invention, when used to produce thin-film ceramic green sheets, has a preferred lower limit of 500 and a more preferred lower limit of 600 in terms of maintaining mechanical strength, and a preferred upper limit of 10,000 and a more preferred upper limit of 5,000 in terms of solubility in organic solvents and dissolution viscosity. In other words, the above average degree of polymerization is preferably 500 to 10,000 and more preferably 600 to 5,000. Furthermore, the average degree of polymerization of the polyvinyl acetal resin is the same as that of the raw material polyvinyl alcohol. The average degree of polymerization can also be measured in accordance with JIS K 6726.

[0031] The polyvinyl acetal resin of the present invention can typically be produced by acetalizing a polyvinyl alcohol resin.

[0032] As the polyvinyl alcohol resin mentioned above, conventionally known polyvinyl alcohol resins can be used, such as resins produced by saponifying polyvinyl acetate resins with alkali, acid, ammonia water, etc. The polyvinyl alcohol resin described above may be fully saponified, but it does not need to be fully saponified as long as there is at least one unit having a double hydroxyl group at the meso or racemo position at least one location in the main chain; it may be a partially saponified polyvinyl alcohol resin. In addition, as the polyvinyl alcohol resin, copolymers of vinyl alcohol and monomers copolymerizable with vinyl alcohol, such as ethylene-vinyl alcohol copolymer resins and partially saponified ethylene-vinyl alcohol copolymer resins, can also be used. Examples of the polyvinyl acetate resins mentioned above include ethylene-vinyl acetate copolymers.

[0033] The polyvinyl alcohol resin described above preferably has a degree of saponification of 70 mol% or more. The degree of saponification is more preferably 76 mol% to 99.4 mol%, and even more preferably 78 mol% to 99.2 mol%. That is, the degree of saponification is more preferably 76 to 99.4 mol%, and even more preferably 78 to 99.2 mol%. By using the above-mentioned polyvinyl alcohol resin, the above-mentioned Mz can be set to a predetermined range.

[0034] The above acetalization is preferably carried out in an aqueous solvent, in a mixed solvent of water and a water-compatible organic solvent, or in an organic solvent. As the above-mentioned organic solvent that is compatible with water, for example, an alcohol-based organic solvent can be used. Examples of the above-mentioned organic solvents include alcohol-based organic solvents, aromatic organic solvents, aliphatic ester-based solvents, ketone-based solvents, lower paraffin-based solvents, ether-based solvents, amide-based solvents, and amine-based solvents. Examples of the above-mentioned alcohol-based organic solvents include methanol, ethanol, n-propanol, isopropanol, n-butanol, and tert-butanol. Examples of the above-mentioned aromatic organic solvents include xylene, toluene, ethylbenzene, and methyl benzoate. Examples of the above-mentioned aliphatic ester solvents include methyl acetate, ethyl acetate, butyl acetate, methyl propionate, ethyl propionate, methyl butyrate, ethyl butyrate, methyl acetoacetate, and ethyl acetoacetate. Examples of the ketone-based solvents mentioned above include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methylcyclohexanone, benzophenone, and acetophenone. Examples of the lower paraffinic solvents mentioned above include hexane, pentane, octane, cyclohexane, and decane. Examples of the above-mentioned ether-based solvents include diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol diethyl ether. Examples of the above-mentioned amide solvents include N,N-dimethylformamide, N,N-dimethyltesetamide, N-methylpyrrolidone, and acetanilide. Examples of the above-mentioned amine-based solvents include ammonia, trimethylamine, triethylamine, n-butylamine, di-n-butylamine, tri-n-butylamine, aniline, N-methylaniline, N,N-dimethylaniline, and pyridine. These can be used individually or as a mixture of two or more solvents. Among these, ethanol, n-propanol, isopropanol, and tetrahydrofuran are particularly preferred from the viewpoint of solubility in resins and ease of purification.

[0035] The above acetalization is preferably carried out in the presence of an acid catalyst. The above-mentioned acid catalysts are not particularly limited and include mineral acids such as sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid; carboxylic acids such as formic acid, acetic acid, and propionic acid; and sulfonic acids such as methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, and p-toluenesulfonic acid. These acid catalysts may be used alone or in combination of two or more compounds. Among these, hydrochloric acid, nitric acid, and sulfuric acid are preferred, with hydrochloric acid being particularly preferred.

[0036] Examples of aldehydes used in the above acetalization include aldehydes having a chain-like aliphatic group, a cyclic aliphatic group, or an aromatic group having 1 to 10 carbon atoms. Conventionally known aldehydes can be used as these aldehydes. The aldehydes used in the above acetalization reaction are not particularly limited and include, for example, aliphatic aldehydes and aromatic aldehydes. Examples of the above-mentioned aliphatic aldehydes include formaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, n-valeraldehyde, n-hexylaldehyde, 2-ethylbutyraldehyde, 2-ethylhexylaldehyde, n-heptylaldehyde, n-octylaldehyde, n-nonylaldehyde, n-decylaldehyde, and amylaldehyde. Examples of the above aromatic aldehydes include benzaldehyde, cinnamaldehyde, 2-methylbenzaldehyde, 3-methylbenzaldehyde, 4-methylbenzaldehyde, p-hydroxybenzaldehyde, m-hydroxybenzaldehyde, phenylacetaldehyde, and β-phenylpropionaldehyde. These aldehydes may be used individually or in combination of two or more. Among the aldehydes, formaldehyde, acetaldehyde, butyraldehyde, 2-ethylhexylaldehyde, and n-nonylaldehyde are preferred because they exhibit excellent acetalization reactivity, provide sufficient internal plasticity to the resulting resin, and consequently impart good flexibility. Furthermore, formaldehyde, acetaldehyde, and butyraldehyde are more preferred because they yield an adhesive composition with particularly excellent impact resistance and adhesion to metals.

[0037] The amount of aldehyde added can be appropriately set according to the amount of acetal groups in the target polyvinyl acetal resin. In particular, a value of 50 mol% to 95 mol%, more preferably 55 mol% to 90 mol%, relative to 100 mol% of polyvinyl alcohol is preferable because it allows the acetalization reaction to proceed efficiently and makes it easier to remove unreacted aldehydes.

[0038] In the above acetalization reaction, it is preferable to perform a hydrolysis step with hydrochloric acid or sodium hydroxide before the acetal reaction, and in particular, the hydrolysis step with hydrochloric acid is preferred. By performing the hydrolysis step with hydrochloric acid, P(EOH), P(MIX), and P(EOH) / P(MIX) can be set to a predetermined range. For example, the hydrolysis step with hydrochloric acid is a step in which polyvinyl alcohol is heated and dissolved in water, then hydrochloric acid is added and heated and stirred for a certain period of time to hydrolyze the acetyl groups contained in the polyvinyl alcohol to hydroxyl groups. The temperature (hydrolysis temperature), time (hydrolysis time), and amount of hydrochloric acid in the hydrolysis step can be appropriately adjusted according to the degree of saponification of the raw material polyvinyl alcohol and the desired degree of saponification after hydrolysis.

[0039] The hydrolysis temperature is preferably 50°C or higher, and preferably 90°C or lower. More preferably 53°C to 85°C, even more preferably 55°C to 80°C, and particularly preferably 60°C to 75°C. In other words, the hydrolysis temperature is preferably 50 to 90°C, more preferably 53 to 85°C, even more preferably 55 to 80°C, and particularly preferably 60 to 75°C. The hydrolysis time is preferably 30 minutes or more, and preferably 10 hours or less. More preferably 45 minutes or more and 8 hours or less, even more preferably 1 hour or more and 7 hours or less, and particularly preferably 2 hours or more and 6 hours or less. In other words, the hydrolysis time is preferably 30 minutes to 10 hours, more preferably 45 minutes to 8 hours, even more preferably 1 to 7 hours, and particularly preferably 2 to 6 hours. The amount of hydrochloric acid is preferably 10 parts by weight or more, and preferably 250 parts by weight or less, per 100 parts by weight of polyvinyl alcohol. More preferably, it is 15 parts by weight or more, and 200 parts by weight or less, and even more preferably 30 parts by weight or more, and 120 parts by weight or less. In other words, the amount of hydrochloric acid is preferably 10 to 250 parts by weight, more preferably 15 to 200 parts by weight, and even more preferably 30 to 120 parts by weight, per 100 parts by weight of polyvinyl alcohol.

[0040] In the above acetalization process, it is preferable to add the aldehyde at a predetermined temperature, carry out the reaction for a predetermined time (reaction step), and then maintain the temperature at a predetermined temperature (aging step). The aldehyde introduction temperature is preferably 5°C or higher and 35°C or lower, and more preferably 15°C or higher and 25°C or lower. The time from the addition of the aldehyde to the start of heating (heating start time or reaction time) is preferably 150 minutes or more and 420 minutes or less, and more preferably 180 minutes or more and 360 minutes or less. Furthermore, the heating time is preferably 330 minutes or more and 520 minutes or less, and more preferably 400 minutes or more and 510 minutes or less. Furthermore, if the temperature at the time of aldehyde addition (introduction) is below 35°C, it is preferable to change the heating rate from the temperature at the time of aldehyde addition to 35°C (heating rate 1) and the heating rate from 35°C to the holding temperature for the maturation process (heating rate 2) to increase the temperature. The above heating rate 1 is preferably 0.02°C / min or more and 0.06°C / min or less. By keeping the above heating rate 1 within the above range, the THF viscosity can be set to a predetermined range. The above heating rate 2 is preferably 0.10°C / min or more and 0.30°C / min or less. By setting the above heating rate 2 within the above range, the hydroxyl group amount-based wavenumber width and the hydroxyl group amount-acetyl group amount-based wavenumber width can be set within a predetermined range.

[0041] The holding time in the above maturation process is preferably 1 hour or more and 5 hours or less, and more preferably 2.5 hours or more and 3 hours or less. The holding temperature in the above maturation process is preferably 50°C or higher and 70°C or lower, and more preferably 55°C or higher and 65°C or lower. By setting the above-mentioned holding time and holding temperature, the above-mentioned wavenumber width converted to hydroxyl group amount and wavenumber width converted to hydroxyl group amount and acetyl group amount can be set to a predetermined range.

[0042] A method for producing a polyvinyl acetal resin solution using the polyvinyl acetal resin of the present invention is also one of the present invention, which comprises dissolving the polyvinyl acetal resin in an ethanol / toluene mixed solvent having an ethanol content of 70% by weight or more, removing particles by a filtration step, and then adding toluene. By using this manufacturing method, it is possible to produce a polyvinyl acetal resin solution with even fewer particles. The above-mentioned filtration process may include filtration using metal mesh, ceramic filters, nonwoven fabrics, resin filters, centrifugal separation, etc.

[0043] The present invention provides a resin composition for ceramic green sheets by including the polyvinyl acetal resin and a plasticizer. The above-mentioned resin composition for ceramic green sheets may contain components such as antioxidants, surfactants, ultraviolet absorbers, and defoamers, as long as they do not hinder the effects of the present invention.

[0044] As a method for producing the above-mentioned resin composition for ceramic green sheets, for example, a polyvinyl acetal resin obtained by acetalizing a polyvinyl alcohol resin with an aldehyde can be mixed with a plasticizer and other additives as needed to produce the resin composition for ceramic green sheets.

[0045] The above-mentioned resin composition for ceramic green sheets contains a plasticizer. By adding the above-mentioned plasticizer, the mechanical strength and flexibility of the resulting ceramic green sheet can be significantly improved. Examples of the above-mentioned plasticizers include phthalate diesters such as dioctyl phthalate (DOP) and dibutyl phthalate (DBP), adipic acid diesters such as dioctyl adipate, and alkylene glycol diesters such as triethylene glycol-di-2-ethylhexanoate, tetraethylene glycol-di-2-ethylhexanoate, triethylene glycol-di-2-ethyl butyrate, tetraethylene glycol-di-2-ethyl butyrate, tetraethylene glycol-di-heptanoate, and triethylene glycol-di-heptanoate.

[0046] In the above-mentioned resin composition for ceramic green sheets, the content of the plasticizer is preferably 7 parts by weight, more preferably 8.5 parts by weight, preferably 18 parts by weight, and more preferably 13.5 parts by weight per 100 parts by weight of polyvinyl acetal resin.

[0047] A slurry for ceramic green sheets can be prepared by mixing the polyvinyl acetal resin of the present invention with an organic solvent and ceramic powder.

[0048] The above organic solvents are not particularly limited, and are not particularly limited as long as they can dissolve the polyvinyl acetal resin. For example, ketones such as acetone, methyl ethyl ketone, dipropyl ketone, and diisobutyl ketone are examples. Other examples include alcohols such as methanol, ethanol, isopropanol, and butanol, and aromatic hydrocarbons such as toluene and xylene. Furthermore, esters such as methyl propionate, ethyl propionate, butyl propionate, methyl butanoate, ethyl butanoate, butyl butanoate, methyl pentanoate, ethyl pentanoate, butyl pentanoate, methyl hexanoate, ethyl hexanoate, butyl hexanoate, 2-ethylhexyl acetate, and 2-ethylhexyl butyrate are examples. Also, methyl cellsolve, ethyl cellsolve, butyl cellsolve, terpineol, dihydroterpineol, butyl cellsolve acetate, butyl carbitol acetate, terpineol acetate, and dihydroterpineol acetate are examples. In particular, alcohols, ketones, aromatic hydrocarbons, and mixed solvents thereof are preferred in terms of coating properties and drying properties. Among these, mixed solvents of ethanol and toluene, and mixed solvents of methyl ethyl ketone and toluene are more preferred.

[0049] The content of the organic solvent in the above-mentioned slurry for ceramic green sheets is determined by the type of polyvinyl acetal resin used, etc., and is not particularly limited. However, if the amount is too small, it will be difficult to achieve the solubility necessary for mixing. On the other hand, if the amount is too large, the viscosity of the slurry composition for ceramic green sheets may become too low, resulting in poor handling when producing ceramic green sheets. For this reason, the content of the organic solvent is preferably 20% by weight or more and 80% by weight or less.

[0050] The above-mentioned ceramic powders include metal or nonmetal oxide or non-oxide powders used in the manufacture of ceramics. These powders may be used individually or in combination as single compositions or compounds. The constituent elements of the metal oxide or non-oxide may consist of a single element or multiple elements, both as cations or anions, and may also contain additives to improve the properties of the oxide or non-oxide. Specifically, examples include oxides, carbides, nitrides, borides, and sulfides of Li, K, Mg, B, Al, Si, Cu, Ca, Sr, Ba, Zn, Cd, Ga, In, Y, lanthanides, actinides, Ti, Zr, Hf, Bi, V, Nb, Ta, W, Mn, Fe, Co, and Ni. Furthermore, when classifying specific oxide powders containing multiple metal elements, commonly referred to as complex oxides, based on their crystal structure, examples of perovskite-type structures include NaNbO3, SrZrO3, PbZrO3, SrTiO3, BaZrO3, PbTiO3, and BaTiO3. Examples of spinel-type structures include MgAl2O4, ZnAl2O4, CoAl2O4, NiAl2O4, and MgFe2O4. Examples of ilmenite-type structures include MgTiO3, MnTiO3, and FeTiO3. Examples of garnet-type structures include GdGa5O 12 Y6Fe5O 12 These are some examples. Among these, the modified polyvinyl acetal resin of the present invention exhibits superior properties when mixed with BaTiO3 powder to form a ceramic green sheet.

[0051] The average particle size of the above ceramic powder is not particularly limited, but for example, for the production of thin-layer ceramic green sheets (thickness of 5 μm or less), it is preferably 0.5 μm or less.

[0052] The above-mentioned slurry for ceramic green sheets may contain other polyvinyl acetal resins other than the polyvinyl acetal resin of the present invention, as well as other resins such as acrylic resins and ethylcellulose, to the extent that the effects of the present invention are not impaired. In such cases, it is preferable that the content of the polyvinyl acetal resin of the present invention relative to the total binder resin is 50% by weight or more.

[0053] The above-mentioned slurry for ceramic green sheets may contain, as needed, dispersants, antioxidants, UV absorbers, surfactants, fillers, etc., and in some cases, small amounts of other resins such as acrylic resin or urethane resin may also be added.

[0054] The method for producing the above-mentioned slurry for ceramic green sheets is not particularly limited, and examples include mixing the polyvinyl acetal resin, organic solvent, ceramic powder, and various additives as needed using various mixers such as ball mills, blender mills, and three-roll mills.

[0055] After applying the above-mentioned slurry for ceramic green sheets, the ceramic green sheet is obtained by heating and drying. Ceramic electronic components can be manufactured using the above-mentioned ceramic green sheets. For example, ceramic electronic components can be manufactured by applying an electrode layer paste to the surface of the ceramic green sheets, and then degreasing and firing the laminate obtained by laminating and heat-pressing the ceramic green sheets on which the electrode layers have been formed.

[0056] The method for applying the above-mentioned slurry for ceramic green sheets is not particularly limited and includes methods such as roll coaters, die coaters, and curtain coaters. Furthermore, conventionally known methods can be used for other specific applications.

[0057] The ceramic electronic components mentioned above are not particularly limited and include, for example, multilayer ceramic capacitors, multilayer ceramic inductors, capacitors, piezoelectric actuators, multilayer varistors, multilayer thermistors, EMI filters, aluminum nitride multilayer substrates, alumina multilayer substrates, and the like. Such multilayer ceramic capacitors are also one of the present inventions.

[0058] In the above-described method for manufacturing ceramic electronic components, a step is performed to apply an electrode layer paste to the surface of the ceramic green sheet. Electrode layer pastes can be obtained, for example, by dissolving polyvinyl acetal resin, ethyl cellulose, acrylic resin, etc., as a binder resin in an organic solvent and dispersing conductive powder, etc. These resins may be used individually or in mixtures of two or more. Electrode layer pastes containing polyvinyl acetal resin are preferred because they exhibit excellent adhesion to ceramic green sheets during the heat-pressing process.

[0059] In the above-described method for manufacturing ceramic electronic components, after producing ceramic green sheets with electrode layers formed on them as described above, the laminates obtained by stacking and heat-pressing these similarly produced ceramic green sheets are degreased and fired, thereby obtaining multilayer ceramic electronic components in which problems such as sheet attack and cracking are resolved. Furthermore, the above-mentioned heating and pressing process and the process of degreasing and firing the laminate are not particularly limited, and conventionally known methods can be used. [Effects of the Invention]

[0060] According to the present invention, it is possible to obtain a ceramic green sheet with fewer foreign matter in the resin and high mechanical strength, and to provide a polyvinyl acetal resin that can be used to manufacture a highly reliable multilayer ceramic capacitor, as well as a method for producing a polyvinyl acetal resin solution using the polyvinyl acetal resin, a slurry for ceramic green sheets, a ceramic green sheet, and a multilayer ceramic capacitor. [Brief explanation of the drawing]

[0061] [Figure 1] This figure shows an example of an IR absorption spectrum of the polyvinyl acetal resin of the present invention, measured using an infrared spectrophotometer at 20°C. [Modes for carrying out the invention]

[0062] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0063] (Example 1) 260 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 88.1 mol%) was added to 3000 g of pure water and stirred at 90°C for approximately 2 hours to dissolve. This solution was cooled to 70°C, 200 g of 35 wt% hydrochloric acid was added, and the mixture was held for 3 hours. The mixture was cooled to 20°C, and 145 g of n-butyraldehyde was added. After 180 minutes, the temperature was increased to 35°C at a heating rate [heating rate 1] of 0.06°C / min, and from 35°C, the temperature was increased at a heating rate [heating rate 2] of 0.22°C / min (heating time 340 minutes). The reaction was completed by holding at 55°C for 2.5 hours, neutralization, washing with water, and drying by conventional methods to obtain a white powder of polyvinyl acetal resin. Note that the heating time is the time from the start of heating to reaching the holding temperature.

[0064] (Preparation of ceramic green sheets) [Preparation of resin solution] Eight parts by weight of the obtained polyvinyl acetal resin and 2.1 parts by weight of a plasticizer (G260, manufactured by Sekisui Chemical Co., Ltd.) were added to a mixed solvent of 45 parts by weight of ethanol and 19 parts by weight of toluene, and the mixture was stirred and dissolved to prepare a solution. Next, the above solution was filtered using a ceramic filter with a pore size of 0.5 μm to obtain a filtered solution. 74.1 parts by weight of the filtered solution was mixed with 26 parts by weight of toluene and stirred to prepare a resin solution. [Preparation of inorganic powder dispersion] One part by weight of polyvinyl acetal resin (BL-1, manufactured by Sekisui Chemical Co., Ltd.) was added to a mixed solvent of 20 parts by weight of toluene and 20 parts by weight of ethanol, and dissolved by stirring. Next, 100 parts by weight of barium titanate powder (BT01, manufactured by Sakai Chemical Industry Co., Ltd.) was added to the resulting solution, and an inorganic powder dispersion was prepared by stirring for 180 minutes using a bead mill (Ready Mill, manufactured by AIMEX Co., Ltd.). [Preparation of slurry for ceramic green sheets] 141 parts by weight of the obtained inorganic powder dispersion was mixed with 100.1 parts by weight of the resin solution and stirred in a bead mill for 90 minutes to obtain a slurry for ceramic green sheets. The obtained slurry was coated onto a PET film that had been released using a coater to a thickness of 20 μm after drying, and then heated and dried to produce a ceramic green sheet.

[0065] (Example 2) 260 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 88.1 mol%) was added to 3000 g of pure water and stirred at 90°C for about 2 hours to dissolve. This solution was cooled to 70°C, 200 g of 35 wt% hydrochloric acid was added, and the mixture was held for 3 hours. The mixture was cooled to 20°C, and 145 g of n-butyraldehyde was added. After 180 minutes, the temperature was increased to 35°C at a heating rate [heating rate 1] of 0.06°C / min, and from 35°C the temperature was increased at a heating rate [heating rate 2] of 0.22°C / min (heating time 340 minutes). The reaction was completed by holding at 55°C for 3.0 hours, neutralization, washing with water, and drying by conventional methods to obtain a white powder of polyvinyl acetal resin. Furthermore, a ceramic green sheet was prepared in the same manner as in Example 1.

[0066] (Example 3) 260 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 88.1 mol%) was added to 3000 g of pure water and stirred at 90°C for about 2 hours to dissolve. This solution was cooled to 70°C, 200 g of 35 wt% hydrochloric acid was added, and the mixture was held for 3 hours. The mixture was cooled to 20°C, and 145 g of n-butyraldehyde was added. After 180 minutes, the temperature was increased to 35°C at a heating rate [heating rate 1] of 0.06°C / min, and from 35°C the temperature was increased at a heating rate [heating rate 2] of 0.22°C / min (heating time 363 minutes). The reaction was completed by holding at 60°C for 3.0 hours, neutralization, washing with water, and drying by conventional methods to obtain a white powder of polyvinyl acetal resin. Furthermore, a ceramic green sheet was prepared in the same manner as in Example 1.

[0067] (Example 4) 260 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 88.1 mol%) was added to 3000 g of pure water and stirred at 90°C for about 2 hours to dissolve. This solution was cooled to 70°C, 200 g of 35 wt% hydrochloric acid was added, and it was held for 2.5 hours. It was cooled to 20°C, and 145 g of n-butyraldehyde was added. After 180 minutes, the temperature was raised to 35°C at a heating rate [heating rate 1] of 0.06°C / min, and from 35°C the temperature was raised at a heating rate [heating rate 2] of 0.22°C / min (heating time 340 minutes). The reaction was completed by holding at 55°C for 3.0 hours, neutralization, washing with water, and drying by conventional methods to obtain a white powder of polyvinyl acetal resin. Furthermore, a ceramic green sheet was prepared in the same manner as in Example 1.

[0068] (Example 5) 260 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 88.1 mol%) was added to 3000 g of pure water and stirred at 90°C for about 2 hours to dissolve. This solution was cooled to 60°C, 200 g of 35 wt% hydrochloric acid was added, and it was held for 5.0 hours. It was cooled to 20°C, and 145 g of n-butyraldehyde was added. After 180 minutes, the temperature was raised to 35°C at a heating rate [heating rate 1] of 0.06°C / min, and from 35°C the temperature was raised at a heating rate [heating rate 2] of 0.22°C / min (heating time 340 minutes). The reaction was completed by holding at 55°C for 3.0 hours, neutralization, washing with water, and drying by conventional methods to obtain a white powder of polyvinyl acetal resin. Furthermore, a ceramic green sheet was prepared in the same manner as in Example 1.

[0069] (Example 6) 260 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 88.1 mol%) was added to 3000 g of pure water and stirred at 90°C for about 2 hours to dissolve. This solution was cooled to 80°C, 200 g of 35 wt% hydrochloric acid was added, and it was held for 1.0 hour. It was cooled to 20°C, and 145 g of n-butyraldehyde was added. After 180 minutes, the temperature was raised to 35°C at a heating rate [heating rate 1] of 0.06°C / min, and from 35°C the temperature was raised at a heating rate [heating rate 2] of 0.22°C / min (heating time 340 minutes). The reaction was completed by holding at 55°C for 3.0 hours, neutralization, washing with water, and drying by conventional methods to obtain a white powder of polyvinyl acetal resin. Furthermore, a ceramic green sheet was prepared in the same manner as in Example 1.

[0070] (Example 7) 260 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 88.1 mol%) was added to 3000 g of pure water and stirred at 90°C for about 2 hours to dissolve. This solution was cooled to 60°C, 200 g of 35 wt% hydrochloric acid was added, and it was held for 5.0 hours. It was cooled to 20°C, and 145 g of n-butyraldehyde was added. After 180 minutes, the temperature was raised to 35°C at a heating rate [heating rate 1] of 0.06°C / min, and from 35°C the temperature was raised at a heating rate [heating rate 2] of 0.22°C / min (heating time 363 minutes). The reaction was completed by holding at 60°C for 3.5 hours, neutralization, washing with water, and drying by conventional methods to obtain a white powder of polyvinyl acetal resin. Furthermore, a ceramic green sheet was prepared in the same manner as in Example 1.

[0071] (Example 8) 260 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 88.1 mol%) was added to 3000 g of pure water and stirred at 90°C for about 2 hours to dissolve. This solution was cooled to 70°C, 200 g of 35 wt% hydrochloric acid was added, and it was held for 3.0 hours. It was cooled to 20°C, and 145 g of n-butyraldehyde was added. After 180 minutes, the temperature was raised to 35°C at a heating rate [heating rate 1] of 0.06°C / min, and from 35°C the temperature was raised at a heating rate [heating rate 2] of 0.22°C / min (heating time 363 minutes). The reaction was completed by holding at 60°C for 3.5 hours, neutralization, washing with water, and drying by conventional methods to obtain a white powder of polyvinyl acetal resin. Furthermore, a ceramic green sheet was prepared in the same manner as in Example 1.

[0072] (Example 9) 260 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 88.1 mol%) was added to 3000 g of pure water and stirred at 90°C for about 2 hours to dissolve. This solution was cooled to 80°C, 200 g of 35 wt% hydrochloric acid was added, and it was held for 1.0 hour. It was cooled to 20°C, and 145 g of n-butyraldehyde was added. After 180 minutes, the temperature was raised to 35°C at a heating rate [heating rate 1] of 0.06°C / min, and from 35°C the temperature was raised at a heating rate [heating rate 2] of 0.22°C / min (heating time 363 minutes). The reaction was completed by holding at 60°C for 3.0 hours, neutralization, washing with water, and drying by conventional methods to obtain a white powder of polyvinyl acetal resin. Furthermore, a ceramic green sheet was prepared in the same manner as in Example 1.

[0073] (Example 10) 260 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 88.1 mol%) was added to 3000 g of pure water and stirred at 90°C for about 2 hours to dissolve. This solution was cooled to 60°C, 200 g of 35 wt% hydrochloric acid was added, and it was held for 5.0 hours. It was cooled to 20°C, and 145 g of n-butyraldehyde was added. After 180 minutes, the temperature was raised to 35°C at a heating rate [heating rate 1] of 0.06°C / min, and from 35°C the temperature was raised at a heating rate [heating rate 2] of 0.15°C / min (heating time 420 minutes). The reaction was completed by holding at 60°C for 3.0 hours, neutralization, washing with water, and drying by conventional methods to obtain a white powder of polyvinyl acetal resin. Furthermore, a ceramic green sheet was prepared in the same manner as in Example 1.

[0074] (Example 11) 260 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 88.1 mol%) was added to 3000 g of pure water and stirred at 90°C for about 2 hours to dissolve. This solution was cooled to 60°C, 200 g of 35 wt% hydrochloric acid was added, and it was held for 5.0 hours. After cooling to 20°C, 145 g of n-butyraldehyde was added. After 360 minutes, the temperature was raised to 35°C at a heating rate [heating rate 1] of 0.06°C / min, and from 35°C the temperature was raised at a heating rate [heating rate 2] of 0.22°C / min (heating time 340 minutes). The reaction was completed by holding at 55°C for 3.0 hours, neutralization, washing with water, and drying by conventional methods to obtain a white powder of polyvinyl acetal resin. Furthermore, a ceramic green sheet was prepared in the same manner as in Example 1.

[0075] (Example 12) 260 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 88.1 mol%) was added to 3000 g of pure water and stirred at 90°C for about 2 hours to dissolve. This solution was cooled to 85°C, 200 g of 35 wt% hydrochloric acid was added, and it was held for 0.5 hours. It was cooled to 20°C, and 145 g of n-butyraldehyde was added. After 360 minutes, the temperature was raised to 35°C at a heating rate [heating rate 1] of 0.06°C / min, and from 35°C the temperature was raised at a heating rate [heating rate 2] of 0.22°C / min (heating time 340 minutes). The reaction was completed by holding at 55°C for 2.5 hours, neutralization, washing with water, and drying by conventional methods to obtain a white powder of polyvinyl acetal resin. Furthermore, a ceramic green sheet was prepared in the same manner as in Example 1.

[0076] (Comparative Example 1) 300 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 99.2 mol%) was added to 3100 g of pure water and stirred at 90°C for about 2 hours to dissolve. This solution was cooled to 40°C, and 200 g of 35 wt% hydrochloric acid and 160 g of n-butyraldehyde were added to it. Furthermore, a ceramic green sheet was prepared in the same manner as in Example 1.

[0077] (Comparative Example 2) 260 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 99.2 mol%) was added to 3000 g of pure water and stirred at 90°C for about 2 hours to dissolve. This solution was cooled to 20°C, and 200 g of 35 wt% hydrochloric acid and 147 g of n-butyraldehyde were added to it. 30 minutes after addition, the temperature was increased at a rate of 0.22°C / min (heating time 45 minutes), and the acetalization reaction was carried out at 40°C for 3 hours. Neutralization, washing with water, and drying were performed by conventional methods to obtain a white powder of polyvinyl acetal resin. Furthermore, a ceramic green sheet was prepared in the same manner as in Example 1.

[0078] (Comparative Example 3) 260 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 99.1 mol%) was added to 3000 g of pure water and stirred at 90°C for about 2 hours to dissolve. This solution was cooled to 20°C, and 200 g of 35 wt% hydrochloric acid and 147 g of n-butyraldehyde were added to it. 60 minutes after addition, the temperature was increased at a rate of 0.3°C / min (heating time 150 minutes), and the acetalization reaction was carried out at 60°C for 2.2 hours. Neutralization, washing with water, and drying were performed by conventional methods to obtain a white powder of polyvinyl acetal resin. Furthermore, a ceramic green sheet was prepared in the same manner as in Example 1.

[0079] (Comparative Example 4) 300 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 98.7 mol%) was added to 3100 g of pure water and stirred at 90°C for about 2 hours to dissolve. This solution was cooled to 40°C, and 200 g of 35 wt% hydrochloric acid and 160 g of n-butyraldehyde were added to it. Subsequently, the acetalization reaction was carried out by holding the mixture at 40°C for 3 hours, followed by neutralization, washing with water, and drying using conventional methods to obtain a white powder of polyvinyl acetal resin. Furthermore, a ceramic green sheet was prepared in the same manner as in Example 1.

[0080] (evaluation) The polyvinyl acetal resin and ceramic green sheets obtained in the examples and comparative examples were evaluated as follows. The results are shown in Table 1.

[0081] (1) Evaluation of polyvinyl acetal resin (1-1) Amount of acetal group, hydroxyl group, acetyl group The obtained polyvinyl acetal resin was analyzed using an AV400 spectrometer (manufactured by Bruker). 1 ¹H-NMR measurements were performed to calculate the amount of acetal groups, hydroxyl groups, and acetyl groups. The obtained polyvinyl acetal resin was dissolved in DMSO-D6 to a concentration of 1.6% by weight to prepare the measurement solution. 1 1H-NMR measurements were performed at 80°C.

[0082] (1-2) IR absorption spectrum The obtained polyvinyl acetal resin was dissolved in a 1:1 weight-ratio ethanol-toluene mixed solution, and then coated onto a PET film, resulting in a 2980 cm² vibration derived from the stretching vibration of the CH bond. -1 The film thickness of the measurement sample was adjusted so that the minimum transmittance of the peak appearing in the vicinity was 22%, and a polyvinyl acetal resin sheet was obtained. The IR absorption spectrum of the obtained polyvinyl acetal resin sheet was measured at 20°C using an infrared spectrophotometer (HORIBA FT-720). The measurement results were obtained for wavenumbers 3050~3750 cm⁻¹. -1 A baseline was drawn for the peaks that appeared within the specified range, and peak analysis was performed on the data corrected so that the transmittance at both ends of the peaks was 100%, to measure the minimum transmittance X, transmittance a, and peak wavenumbers A and B. Subsequently, 1 Using the amount of hydroxyl groups determined by H-NMR measurement, the wavewidth (cm) converted to the amount of hydroxyl groups was calculated. -1 The formula / mol%) = [(BA) / hydroxyl group amount] was calculated. 1 Using the amount of acetyl groups determined from 1H-NMR measurements, the hydroxyl group-acetyl group-reduced wavenumber width = [(BA) / hydroxyl group amount / acetyl groups] was calculated.

[0083] (1-3) Particles The obtained polyvinyl acetal resin was added to an ethanol-toluene (ethanol:toluene = 50:50) mixed solvent so that the solid content concentration of the polyvinyl acetal resin was 0.2% by mass. The mixture was then stirred and dissolved using a mix rotor at 60 rpm for 24 hours to prepare an ethanol-toluene mixed solution. For 10 mL of the resulting ethanol-toluene mixture, the number of particles between 0.5 and 1.0 μm in size was measured three times using a particle counter (RION Corporation, KS-42C, KE-40B1), and the average value was defined as D1. Separately, the ethanol-toluene (ethanol:toluene = 50:50) mixed solvent used as the solvent for the ethanol-toluene mixed solution was measured three times using a particle counter (RION Corporation, KS-42C, KE-40B1), and the average value was defined as C1. From the obtained C1 and D1, P(MIX) was calculated using the following formula. P(MIX) = D1 - C1

[0084] Similarly, an ethanol solution was prepared by adding the obtained polyvinyl acetal resin to ethanol so that the solid content concentration of the polyvinyl acetal resin was 0.2% by mass, and then stirring and dissolving it using a mixing rotor at 60 rpm for 24 hours. For 10 mL of the obtained ethanol solution, the number of particles between 0.5 and 1.0 μm in size was measured three times using a particle counter (RION Corporation, KS-42C, KE-40B1), and the average value was defined as D2. Separately, the number of particles in the ethanol used as the solvent for the ethanol solution was measured three times using a particle counter (RION Corporation, KS-42C, KE-40B1), and the average value was defined as C2. From the obtained C2 and D2, P(EOH) was calculated using the following formula. Furthermore, P(EOH) / P(MIX) was calculated from the obtained P(MIX) and P(EOH). P(EOH) = D2 - C2

[0085] (1-4) Viscosity measurement The obtained polyvinyl acetal resin was dissolved in a 1:1 ethanol-toluene mixed solution to a concentration of 5% by mass to prepare a viscosity measurement sample. The viscosity of the obtained viscosity measurement sample was measured using a B-type viscometer at a solution temperature of 20°C. For the B-type viscometer, a TVB-10 viscometer (manufactured by Toki Sangyo Co., Ltd.) was used, and the rotation speed and rotor were set as follows for the measurements. Examples 1-12, Comparative Examples 1-4: Rotation speed 30 rpm, SPINDLE No. M1

[0086] (1-5)z average molecular weight [Mz(THF), Mz(NMP)] measurement The obtained polyvinyl acetal resin was dissolved in tetrahydrofuran (THF) at a concentration of 0.2% by weight, passed through a PTFE filter with a pore size of 0.45 μm, and measured at a flow rate of 0.35 mL / min using an HLC-8420 GPC instrument (Tosoh Corporation), THF as the mobile phase, a Blythe-type double-pass differential refractive index detector (Tosoh Corporation), and a TSKgelSuperHZM-H column (Tosoh Corporation). The obtained measurement results were calibrated using a molecular weight calibration curve prepared with monodisperse polystyrene standard samples to obtain the z-average molecular weight Mz(THF). Similarly, the obtained polyvinyl acetal resin was dissolved in N-methylpyrrolidone (NMP) at a concentration of 0.2% by weight, passed through a PTFE filter with a pore size of 0.45 μm, and measured at a flow rate of 0.5 mL / min using a GPC-101 (Shodex) GPC instrument, NMP as the mobile phase, a differential refractive index detector RI-715 (Shodex) as the detector, and an LF-804 (Shodex) as the column. The obtained measurement results were calibrated using a molecular weight calibration curve prepared with monodisperse polystyrene standard samples to obtain the z-average molecular weight Mz(NMP). From the obtained Mz(THF) and Mz(NMP), "Mz(THF) / Mz(NMP)" was calculated. Then, using the THF viscosity obtained from the viscosity measurement above, "[THF viscosity / Mz(NMP)] × 10000" was calculated.

[0087] (2) Evaluation of ceramic green sheets (2-1) Surface roughness The obtained ceramic green sheets were measured for a ten-point average roughness (Rz) based on JIS B 0601 (1994) and evaluated according to the following criteria. AA: Rz is 0.25 μm or less A: Rz is greater than 0.25 μm and less than 0.30 μm. B: Rz is 0.30 μm or greater and less than 0.40 μm. C:Rz is 0.40 μm or larger

[0088] (2-2) Stress and strain at fracture point The obtained ceramic green sheet was cut into 5cm x 1cm pieces to serve as test specimens. A tensile testing machine (Shimadzu Corporation, AUTOGRAPH AGS-J) was used to pull the sheet at a tensile speed of 500% / min, and the breaking tensile strength (kg / cm²) was measured at a temperature of 20°C. 2 The stress σ (MPa) - strain ε (%) was measured. From the obtained values, a stress σ (MPa) - strain ε (%) curve was obtained. Note that 500% / min means a speed at which the specimen is moved a distance five times the distance between the chucks per minute. The fracture stress and fracture strain were determined from the obtained stress-strain curve and judged according to the evaluation criteria below. (Stress at fracture point) AA:34MPa or more A: 33 MPa or higher, less than 34 MPa B: 30 MPa or higher, less than 33 MPa C: Less than 30 MPa (Fracture point strain) AA: 22% or higher A: 21% or more, less than 22% B: 17% or more, less than 21% C: Less than 17%

[0089] [Table 1] [Industrial applicability]

[0090] According to the present invention, it is possible to obtain a ceramic green sheet with fewer foreign matter in the resin and high mechanical strength, and to provide a polyvinyl acetal resin that can be used to manufacture a highly reliable multilayer ceramic capacitor, as well as a method for producing a polyvinyl acetal resin solution using the polyvinyl acetal resin, a slurry for ceramic green sheets, a ceramic green sheet, and a multilayer ceramic capacitor.

Claims

1. When the number of particles of size 0.5 to 1.0 μm in a 0.2% by mass ethanol-toluene (ethanol:toluene = 50:50) mixed solution is denoted as P(MIX), and the number of particles of size 0.5 to 1.0 μm in a 0.2% by mass ethanol solution is denoted as P(EOH), then P(MIX) is 1 to 20,000 particles / 10 ml, and P(EOH) / P(MIX) is 1.2 to 7.

0. In the IR absorption spectrum measured by an infrared spectrophotometer, wavenumbers 3050–3750 cm⁻¹ －１ When the minimum peak transmittance within the range is X (%), and among the wavenumbers that show a transmittance a (%) that satisfies [100 - (100 - X) / 2], if the wavenumber on the lower wavenumber side is A and the wavenumber on the higher wavenumber side is B, then A, B and １ A polyvinyl acetal resin having a hydroxyl group equivalent wavenumber width of 8.42 or more and 9.65 or less, calculated using formula (1) based on the amount of hydroxyl groups measured by H-NMR, and an acetyl group content of 0.1 mol% or more and 22.0 mol% or less. Hydroxyl group-based wavewidth (cm) －１ / mol%) = [(B - A) / amount of hydroxyl groups] (1)

2. The polyvinyl acetal resin according to claim 1, wherein the P(MIX) is 2926 to 18243 particles / 10 ml, and the P(EOH) / P(MIX) is 1.81 to 5.

85.

3. The polyvinyl acetal resin according to claim 1, wherein the P(EOH) content is 4,000 to 60,000 units / 10 ml.

4. The polyvinyl acetal resin according to claim 1 or 2, wherein the wavewidth calculated by formula (1) is 8.45 or greater.

5. The polyvinyl acetal resin according to claim 1 or 2, wherein, in GPC measurement using a differential refractive index detector, when the z-average molecular weight obtained using THF as the mobile phase is Mz(THF) and when the z-average molecular weight obtained using NMP as the mobile phase is Mz(NMP), the ratio Mz(THF) / Mz(NMP) is 1.7 to 2.

0.

6. A method for producing a polyvinyl acetal resin solution using the polyvinyl acetal resin described in claim 1 or 2, A method for producing a polyvinyl acetal resin solution, comprising the steps of dissolving the polyvinyl acetal resin using an ethanol / toluene mixed solvent having an ethanol content of 70% by weight or more, removing particles by filtration, and then adding toluene.

7. A slurry for ceramic green sheets, comprising the polyvinyl acetal resin according to claim 1 or 2, an organic solvent, and ceramic powder.

8. A ceramic green sheet made using the ceramic green sheet slurry described in claim 7.

9. A multilayer ceramic capacitor obtained using the ceramic green sheet described in claim 8.

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