Polyvinyl acetal resin

Abstract

To provide: a polyvinyl acetal resin with which a ceramic green sheet having high mechanical strength and excellent sheet attack resistance can be obtained, and with which a multilayer ceramic capacitor having excellent reliability can be produced; and slurry for a ceramic green sheet, a ceramic green sheet and multilayer ceramic capacitor that use the polyvinyl acetal resin.SOLUTION: The polyvinyl acetal resin has one or more LS intensity peaks in a retention time region of 7-10 minutes in a chromatogram measured using GPC-MALS. 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 a polyvinyl acetal resin, a slurry for a ceramic green sheet, a ceramic green sheet, and a multilayer ceramic capacitor. [Background technology]

[0002] BACKGROUND ART In recent years, electronic components mounted in various electronic devices have become increasingly smaller and more laminated, and multilayer electronic components such as multilayer circuit boards, multilayer coils, and multilayer ceramic capacitors are widely used. Among these, multilayer ceramic capacitors are generally manufactured through the following process. First, a plasticizer, dispersant, etc. are added to a solution prepared by dissolving a binder resin such as polyvinyl butyral resin or poly(meth)acrylic ester resin in an organic solvent, followed by the addition of a ceramic raw material powder and uniform mixing using a mixing device such as a bead mill or ball mill to obtain a ceramic slurry composition with a certain viscosity after degassing. This slurry composition is then cast onto a support surface such as a release-treated polyethylene terephthalate film or SUS plate using a doctor blade, reverse roll coater, etc., and the volatile components such as the solvent are removed by heating or other methods, after which the sheet is peeled off from the support to obtain a ceramic green sheet. Next, a conductive paste that will become the internal electrodes is applied to the obtained ceramic green sheets by screen printing, and multiple sheets are stacked alternately and heated and pressed to form a laminate. After that, a process to thermally decompose and remove binder resin components and the like contained in the laminate, known as a degreasing process, is performed, and external electrodes are sintered onto the end faces of the ceramic sintered body obtained by firing, to obtain a multilayer ceramic capacitor.

[0003] For example, Patent Document 1 describes a polyvinyl acetal resin suitable as a ceramic binder, which has a predetermined degree of polymerization, vinyl ester unit content, and degree of acetalization, and in which the molar ratio of the portion acetalized with acetaldehyde to the portion acetalized with butylaldehyde is within a predetermined range. Furthermore, Patent Document 2 describes a polyvinyl acetal resin having a predetermined degree of polymerization, vinyl ester unit content, degree of acetalization, and specific structural units. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-236304 [Patent Document 2] International Publication No. 2012 / 023517 Summary of the Invention [Problem to be solved by the invention]

[0005] On the other hand, in recent years, with the trend toward multifunctionality and miniaturization of electronic devices, multilayer ceramic capacitors are being demanded to have larger capacitance and smaller size, and ceramic green sheets are also being demanded to be thinner. However, when the polyvinyl acetal resins described in Patent Documents 1 and 2 are used, the strength of the resulting ceramic green sheet is insufficient, and when peeled off from the release sheet, the sheet breaks due to insufficient strength, resulting in a problem of reduced yield. Furthermore, the sheet attack resistance of the resulting ceramic green sheet becomes insufficient, which causes a problem of a deterioration in the electrical properties of the multilayer ceramic capacitor and an increase in the defect rate.

[0006] The present invention aims to provide a polyvinyl acetal resin that can produce ceramic green sheets having high mechanical strength and excellent sheet attack resistance, and that can be used to fabricate highly reliable multilayer ceramic capacitors; and to provide a ceramic green sheet slurry, a ceramic green sheet, and a multilayer ceramic capacitor that use the polyvinyl acetal resin. [Means for solving the problem]

[0007] The present disclosure 1 is a compound having one or more LS intensity peaks in the retention time region of 7 to 10 minutes in a chromatogram measured using GPC-MALS, and having a wavenumber of 3050 to 3750 cm in an IR absorption spectrum measured using an infrared spectrophotometer. -1 When the minimum transmittance of the peak within the range is X (%), among the wave numbers showing transmittance a (%) that satisfies [100-(100-X) / 2], the wave number on the low wave number side is A and the wave number on the high wave number side is B. 1 A polyvinyl acetal resin having a hydroxyl group amount converted wavenumber width of 8.31 or more, calculated by formula (1) using the amount of hydroxyl groups measured by H-NMR. Hydroxyl group amount equivalent wavenumber width (cm -1 / mol%) = [(BA) / hydroxyl group content] (1) Disclosure 2 is the polyvinyl acetal resin according to Disclosure 1, which has three or more LS intensity peaks in the retention time region of 7 to 17 minutes in a chromatogram measured using GPC-MALS. Disclosure 3 is the polyvinyl acetal resin according to Disclosure 1 or 2, which has a z-average radius of gyration of 55 nm or more as measured using GPC-MALS. Disclosure 4 is the polyvinyl acetal resin according to any one of Disclosures 1 to 3, which has a hydroxyl group amount converted wavenumber width calculated by formula (1) of 8.45 or more. Disclosure 5 relates to the above A, B and 1The polyvinyl acetal resin according to any one of Disclosures 1 to 4, wherein the hydroxyl group-acetyl group amount converted wavenumber width calculated by the following formula (2) using the hydroxyl group amount and the acetyl group amount measured by H-NMR is 6.5 to 18.0: Hydroxyl group acetyl group amount converted wave number width (cm -1 / mol% / mol%) = [(BA) / hydroxyl group amount / acetyl group amount] (2) Disclosure 6 is the polyvinyl acetal resin according to any one of Disclosures 1 to 5, wherein, in GPC measurement using a differential refractive index detector, Mz(THF) / Mz(NMP) is 1.2 to 1.93, where Mz(THF) is the z-average molecular weight obtained using THF as the mobile phase and Mz(NMP) is the z-average molecular weight obtained using NMP as the mobile phase. Disclosure 7 is a polyvinyl acetal resin according to any one of Disclosures 1 to 6, wherein a 5% by mass solution of the polyvinyl acetal resin in a 1:1 mixed solvent of ethanol and toluene has a solution viscosity of 30 mPa s or more and 200 mPa s or less, as measured using a Brookfield viscometer at a solution temperature of 20°C. Disclosure 8 of the Present Invention is a slurry for a ceramic green sheet, containing the polyvinyl acetal resin according to any one of Disclosures 1 to 7 of the Present Invention, an organic solvent, and ceramic powder. Disclosure 9 is a ceramic green sheet obtained by using the ceramic green sheet slurry described in Disclosure 8. Disclosure 10 is a multilayer ceramic capacitor obtained using the ceramic green sheet according to Disclosure 9. The present invention will be described in detail below.

[0008] As a result of extensive investigations, the present inventors have found that a compound having a predetermined number of peaks or more in a chromatogram measured using GPC-MALS and a peak in the range of 3050 to 3750 cm in an IR absorption spectrum measured using an infrared spectrophotometer is -1The present inventors have found that a polyvinyl acetal resin having a hydroxyl group amount equivalent wavenumber width within a predetermined range, calculated based on peaks within the above range, can provide a ceramic green sheet having high mechanical strength and excellent sheet attack resistance, and can also produce a multilayer ceramic capacitor having excellent reliability, and have completed the present invention.

[0009] The polyvinyl acetal resin of the present invention has one or more LS intensity peaks in the retention time region of 7 to 10 minutes in a chromatogram measured using GPC-MALS. By using such a polyvinyl acetal resin, it is possible to obtain a ceramic green sheet that has high strength and excellent sheet attack resistance. The number of peaks in the chromatogram measured using GPC-MALS is preferably 1 or more. The number of peaks is preferably 3 or less. In the present invention, the number of peaks observed at a retention time of 7 to 10 minutes is an index of the number of associations formed by a plurality of polyvinyl acetal resins. Furthermore, the polyvinyl acetal resin of the present invention preferably has three or more LS intensity peaks in a retention time region of 7 to 17 minutes in a chromatogram measured using GPC-MALS. The number of peaks in the chromatogram measured using GPC-MALS can be measured by GPC-MALS using a multi-angle light scattering detector. Tetrahydrofuran can be used as the elution solvent (mobile phase). The types and conditions of the column, detector, etc. can be determined according to the methods described in the Examples below. Furthermore, the number of peaks can be counted using a predetermined data processing system (analysis software, etc.).

[0010] The LS intensity peak height in the chromatogram measured using the GPC-MALS is preferably 0.001 V or more, more preferably 0.002 V or more, and preferably 0.006 V or less, more preferably 0.005 V or less. When multiple peaks are detected in the region of retention times of 7 to 10 minutes, the peak with the greatest height is used. The LS intensity peak position in the chromatogram measured using the above GPC-MALS is preferably at a retention time of 7.5 minutes or more and 9.7 minutes or less, more preferably 8.0 minutes or more and 9.5 minutes or less. In the chromatogram measured using the above GPC-MALS, the peak width at an LS intensity value that is half the LS intensity peak value is preferably 2 minutes or less, more preferably 1.5 minutes or less, in terms of elution time.

[0011] The polyvinyl acetal resin of the present invention preferably has a z-average radius of gyration of 55 nm or more in a slope measurement of light scattering intensity measured using GPC-MALS. By using such a polyvinyl acetal resin, it is possible to obtain a ceramic green sheet that has high strength and excellent sheet attack resistance. The z-average radius of gyration is preferably equal to or greater than 59, and more preferably equal to or greater than 65. The z-average radius of gyration is preferably equal to or less than 75, and more preferably equal to or less than 70. The z-average radius of gyration can be calculated using analysis software based on a chromatogram measured using GPC-MALS.

[0012] The number of peaks and the z-average radius of gyration can be adjusted, for example, by changing the average degree of polymerization and degree of saponification of the raw material polyvinyl alcohol resin, and 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 number of peaks can be adjusted by changing the aldehyde introduction temperature, number of introductions, introduction interval, temperature rise time, temperature rise rate, reaction temperature, reaction time, holding (aging) temperature, and holding (aging) time during the acetalization reaction described below, and in particular, by changing the aldehyde introduction temperature, number of introductions, introduction interval, holding (aging) temperature, and holding (aging) time.

[0013] The polyvinyl acetal resin of the present invention has an IR absorption spectrum measured by an infrared spectrophotometer, which has a wave number of 3050 to 3750 cm -1 When the minimum transmittance of the peak within the range is X (%), among the wave numbers showing transmittance a (%) that satisfies [100-(100-X) / 2], the wave number on the low wave number side is A and the wave number on the high wave number side is B. 1 The hydroxyl group amount converted wavenumber width calculated by the above formula (1) using the hydroxyl group amount measured by H-NMR is 8.31 or more. By setting the thickness within the above range, it is possible to obtain a ceramic green sheet that has high strength and excellent sheet attack resistance. The lower limit of the hydroxyl group amount converted wavenumber width is preferably 8.45, more preferably 8.70, and even more preferably 8.84, and the upper limit is preferably 10.00, and more preferably 9.70. In the present invention, the hydroxyl group amount converted wavenumber width serves as an index of whether the positions of hydroxyl groups are continuous. The IR absorption spectrum can be measured by a transmission method using a Fourier transform infrared spectrophotometer (such as HORIBA's "FT-720" or JASCO's "FT / IR-4000") at 20°C.

[0014] The polyvinyl acetal resin of the present invention is 1 The wave number width of the hydroxyl group-acetyl group amount converted by the above formula (2) using the hydroxyl group amount and the acetyl group amount measured by 1 H-NMR is preferably 6.5 to 18.0. By setting the thickness within the above range, it is possible to obtain a ceramic green sheet that has high strength and excellent sheet attack resistance. The lower limit of the hydroxyl group-acetyl group converted wave number width is more preferably 10.5, and even more preferably 11.0, and the upper limit is more preferably 16.0, and even more preferably 14.0.

[0015] In the analysis of polyvinyl acetal resin using the above infrared spectrophotometer, the spectrum originating from the stretching vibration of the CH bond of polyvinyl acetal resin was observed at 2980 cm -1 The above peak analysis firstly revealed that the minimum transmittance of the peak due to the stretching vibration of the C-H bond is around 2500 cm -1 and 3050cm -1 The film thickness of the measurement sample is adjusted so that it is 20 to 25% of the baseline when the line connecting the two is connected. -1 A baseline is drawn for the peaks that appear within this range, and the data is corrected so that the transmittance at both ends of the peak is 100%.

[0016] The hydroxyl group amount-equivalent wavenumber width and the hydroxyl / acetyl group amount-equivalent wavenumber width can be adjusted, for example, by changing the average degree of polymerization and degree of saponification of the raw material polyvinyl alcohol resin, and the temperature and time conditions of the acetalization reaction, and by appropriately setting the amount of acetal groups, amount of hydroxyl groups, amount of acetyl groups, etc. of the polyvinyl acetal resin. In particular, the wavenumber width can be adjusted by changing the aldehyde introduction temperature, number of introductions, introduction interval, temperature rise time, temperature rise rate, reaction temperature, reaction time, holding (aging) temperature, and holding (aging) time during the acetalization reaction described below, and in particular, it can be adjusted by changing the aldehyde introduction temperature, number of introductions, and introduction interval.

[0017] An example of the IR absorption spectrum of the polyvinyl acetal resin of the present invention measured with an infrared spectrophotometer at 20° C. is shown in Fig. 1. In Fig. 1, the vertical axis represents transmittance and the horizontal axis represents wavenumber. In the IR absorption spectrum shown in Figure 1, the minimum transmittance X is 65.7%. The transmittance a (%) that satisfies [100-(100-X) / 2] is 82.85%, and the wavenumber A on the low wavenumber side is 3297 cm-1 , the wave number B on the high wave number side is 3557 cm -1 is. In the above case, 1 If the amount of hydroxyl groups measured by H-NMR is 30 mol%, the wavenumber width converted to the amount of hydroxyl groups [(BA) / amount of hydroxyl groups] is 8.67 (cm -1 / mol%). The wave number A is 3250 cm -1 More than 3270cm is preferable. -1 More than 3350cm is preferable. -1 The following is preferred: 3330cm -1 The following is more preferred: The wave number B is 3500 cm -1 More than 3530cm is preferable. -1 More than 3600cm is preferable. -1 The following is preferable: 3580cm -1 The following is preferred: The transmittance a is preferably 81% or more and 85% or less.

[0018] In the polyvinyl acetal resin of the present invention, when measured by GPC using a differential refractive index detector, Mz(THF) is the z-average molecular weight obtained using THF as the mobile phase, and Mz(NMP) is the z-average molecular weight obtained using NMP as the mobile phase, and the ratio Mz(THF) / Mz(NMP) is preferably 1.2 to 1.93. By keeping the ratio within the above range, a ceramic green sheet with high strength can be obtained. The ratio Mz(THF) / Mz(NMP) is preferably 1.40 or more, more preferably 1.50 or more, and is preferably 1.80 or less, more preferably 1.70 or less. In the present invention, Mz(THF) / Mz(NMP) is an index of the intermolecular interaction of the polyvinyl acetal resin. The above Mz(THF) / Mz(NMP) can be calculated by measuring Mz(THF) obtained by gel permeation chromatography (GPC) using tetrahydrofuran as the mobile phase and solvent and a refractive index detector as the detector, and then measuring Mz(NMP) obtained by GPC using N-methylpyrrolidone as the mobile phase and solvent and a refractive index detector as the detector, and then calculating Mz(THF) / Mz(NMP).

[0019] The Mz(THF) is preferably 500,000 or more, more preferably 700,000 or more, and even more preferably 800,000 or more. Also, it is preferably 2,000,000 or less, more preferably 1,400,000 or less, and even more preferably 1,000,000 or less. The Mz(NMP) is preferably 200,000 or more, more preferably 400,000 or more, and even more preferably 480,000 or more. Also, it is preferably 1,700,000 or less, more preferably 1,100,000 or less, and even more preferably 700,000 or less.

[0020] The above Mz(THF) / Mz(NMP) can be adjusted, for example, by changing the average degree of polymerization and degree of saponification of the raw material polyvinyl alcohol resin, and 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 above Mz(THF) / Mz(NMP) can be adjusted by changing the aldehyde introduction temperature, number of introductions, introduction interval, temperature rise time, temperature rise rate, reaction temperature, reaction time, holding (aging) temperature, and holding (aging) time during the acetalization reaction described below, and in particular, it can be adjusted by changing the aldehyde introduction temperature, number of introductions, introduction interval, 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 200 mPa s or less when a 5 mass % solution dissolved in a 1:1 mixed solvent of ethanol and toluene is measured using a Brookfield viscometer at a solution temperature of 20°C. In order to improve the tensile strength, the viscosity is more preferably 50 mPa·s or more, and even more preferably 72 mPa·s or more. In order to improve the viscosity stability of the ceramic slurry composition, the viscosity is more preferably 180 mPa·s or less, and even more preferably 150 mPa·s or less. The B-type viscometer may be, for example, a TVB-10 viscometer manufactured by Toki Sangyo Co., Ltd. The rotor and rotation speed during viscosity measurement are preferably adjusted appropriately depending on the viscosity of the solution, and for example, measurements are preferably performed using spindles 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 degree of saponification of the raw material polyvinyl alcohol resin, and 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 formula (3), R 1 represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.

[0026] In the above formula (3), R 1When is an alkyl group having 1 to 20 carbon atoms, examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, a heptyl group, a 2-ethylhexyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, an octadecyl group, etc. Of these, a methyl group and an n-propyl group are preferred.

[0027] In the polyvinyl acetal resin of the present invention, the content of the structural unit having the acetal group represented by the above formula (3) (hereinafter also referred to as "acetal group amount") is preferably 50 mol % in lower limit and 83 mol % in upper limit. When the amount of acetal groups is 50 mol % or more, the solubility in organic solvents can be improved, and when the amount of acetal groups is 83 mol % or less, the polyvinyl acetal resin can have excellent tensile strength. The acetal group amount has a more preferred lower limit of 55 mol % and a more preferred upper limit of 80 mol %. That is, the acetal group amount is preferably 50 to 83 mol %, and more preferably 55 to 80 mol %. The amount of acetal groups is, for example, 1 It can be measured by H-NMR. Regarding the method for calculating the amount of acetal groups, since the acetal groups of the 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 content of the structural unit having a hydroxyl group represented by the above general formula (4) (hereinafter also referred to as "hydroxyl group amount") is preferably 18 mol % in lower limit and 40 mol % in upper limit. When the amount of hydroxyl groups is 18 mol % or more, the polyvinyl acetal resin can have high toughness, and when the amount of hydroxyl groups is 40 mol % or less, the solubility in organic solvents can be sufficiently improved. The lower limit of the hydroxyl group amount is more preferably 22 mol % and the upper limit is more preferably 38 mol %. That is, the hydroxyl group amount is preferably 18 to 40 mol %, and more preferably 22 to 38 mol %. By setting the hydroxyl group amount within the above range, the hydroxyl group amount converted wave number width and the hydroxyl group amount converted acetyl group amount converted wave number width can be set within a predetermined range. The amount of hydroxyl groups is, for example, 1 It can be measured by H-NMR.

[0029] In the polyvinyl acetal resin of the present invention, the content of the structural unit having an acetyl group represented by the above general formula (5) (hereinafter also referred to as "acetyl group amount") is preferably 0.1 mol % in lower limit and 22.0 mol % in upper limit. When the acetyl group content is 0.1 mol% or more, 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 can be suppressed.When the acetyl group content is 22.0 mol% or less, the flexibility of the polyvinyl acetal resin is not excessively increased, and handling properties can be improved. The lower limit of the acetyl group amount is more preferably 0.5 mol % and the upper limit is more preferably 15.0 mol %. That is, the acetyl group amount is preferably 0.1 to 22.0 mol %, and more preferably 0.5 to 15 mol %. By setting the acetyl group amount within the above range, the wave number width of the hydroxyl group amount converted into the acetyl group amount can be set within a predetermined range. The amount of acetyl groups is, for example, 1 It can be measured by H-NMR.

[0030] From the viewpoint of maintaining mechanical strength when producing a thin film ceramic green sheet, the polyvinyl acetal resin of the present invention has an average degree of polymerization of preferably 500, more preferably 600, even more preferably 700, and particularly preferably 1000, and from the viewpoint of solubility in organic solvents and dissolution viscosity, the average degree of polymerization is preferably 10,000, more preferably 5,000, even more preferably 3500, and particularly preferably 2000. That is, the average degree of polymerization is preferably 500 to 10,000, more preferably 600 to 5,000, even more preferably 700 to 3500, and particularly preferably 1000 to 2000. The average degree of polymerization of the polyvinyl acetal resin is the same as that of the raw material polyvinyl alcohol, and can be measured in accordance with JIS K 6726.

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

[0032] As the polyvinyl alcohol resin, for example, a conventionally known polyvinyl alcohol resin such as a resin produced by saponifying a polyvinyl acetate resin with an alkali, an acid, aqueous ammonia, or the like can be used. The polyvinyl alcohol resin may be fully saponified, but does not need to be fully saponified as long as it has at least one unit having two consecutive hydroxyl groups at the meso and racemo positions at at least one location on the main chain, and may be a partially saponified polyvinyl alcohol resin. Furthermore, as the polyvinyl alcohol resin, a copolymer of vinyl alcohol and a monomer copolymerizable with vinyl alcohol, such as an ethylene-vinyl alcohol copolymer resin or a partially saponified ethylene-vinyl alcohol copolymer resin, may also be used. The polyvinyl acetate resin may be, for example, an ethylene-vinyl acetate copolymer.

[0033] The polyvinyl alcohol resin preferably has a degree of saponification of 75 mol % or more. The saponification degree is more preferably 76 mol % or more and 99.4 mol % or less, and even more preferably 78 mol % or more and 99.5 mol % or less. That is, the saponification degree is preferably 76 to 99.4 mol %, and more preferably 78 to 99.5 mol %. By using the polyvinyl alcohol resin, the Mz can be set within a predetermined range.

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

[0035] The acetalization is preferably carried out in the presence of an acid catalyst. The acid catalyst is not particularly limited, and examples thereof 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 paratoluenesulfonic 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, and hydrochloric acid is particularly preferred.

[0036] The aldehyde used in the acetalization reaction includes aldehydes having a chain aliphatic group, a cyclic aliphatic group, or an aromatic group having 1 to 10 carbon atoms. Any known aldehyde can be used as this aldehyde. The aldehyde used in the acetalization reaction is not particularly limited, and examples thereof include aliphatic aldehydes and aromatic aldehydes. Examples of the aliphatic aldehyde 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 aromatic aldehyde include benzaldehyde, cinnamaldehyde, 2-methylbenzaldehyde, 3-methylbenzaldehyde, 4-methylbenzaldehyde, p-hydroxybenzaldehyde, m-hydroxybenzaldehyde, phenylacetaldehyde, and β-phenylpropionaldehyde. These aldehydes may be used alone or in combination of two or more. Among them, formaldehyde, acetaldehyde, butylaldehyde, 2-ethylhexylaldehyde, and n-nonylaldehyde are preferred as aldehydes, as they have excellent acetalization reactivity, bring about a sufficient internal plasticizing effect in the resulting resin, and as a result, can impart good flexibility. Furthermore, formaldehyde, acetaldehyde, and butylaldehyde are more preferred, as they can provide an adhesive composition that is particularly excellent in impact resistance and adhesion to metals.

[0037] The amount of the aldehyde to be added can be appropriately determined depending on the amount of acetal groups in the target polyvinyl acetal resin. In particular, it is preferable to add the aldehyde in an amount of 50 mol % to 95 mol % and more preferably 55 mol % to 90 mol % relative to 100 mol % of polyvinyl alcohol, because this allows the acetalization reaction to proceed efficiently and makes it easy to remove unreacted aldehyde.

[0038] In the acetalization, the aldehyde is preferably added in several portions. The aldehyde is preferably added twice. When the aldehyde is added in multiple portions, the temperature during the first addition is preferably 40°C or higher and 55°C or lower, and more preferably 45°C or higher and 50°C or lower. By setting the temperature at the time of the initial addition as described above, it is possible to keep Mz(THF) and viscosity within the predetermined range. The temperature during the final addition is preferably 19°C or higher and 30°C or lower, and more preferably 20°C or higher and 27°C or lower. Furthermore, the interval between the first and last addition is preferably 4 hours or more and 12 hours or less, and more preferably 6 hours or more and 8 hours or less. By setting the interval between the first addition and the last addition as described above, the number of peaks in the chromatogram measured using GPC-MALS, the z-average radius of gyration, and Mz(THF) can be set within a predetermined range.

[0039] In the acetalization, it is preferable that the aldehyde is added at a predetermined temperature, the temperature is raised, the reaction is carried out for a predetermined time (reaction step), and the temperature is maintained at the predetermined temperature (aging step). The time from the addition of the final aldehyde to the start of temperature increase (temperature increase start time or reaction time) is preferably 150 minutes or more and 360 minutes or less, and more preferably 180 minutes or more and 300 minutes or less. By setting the temperature rise start time as described above, the number of peaks and z-average radius of gyration in a chromatogram measured using GPC-MALS can be set within a predetermined range. The temperature rise time is preferably 330 minutes or more and 485 minutes or less, and more preferably 340 minutes or more and 420 minutes or less.

[0040] Furthermore, when the temperature at the time of adding the final aldehyde is less than 35°C, it is preferable to increase the temperature by changing the rate of temperature increase from the temperature at the time of adding the final aldehyde to 35°C (temperature increase rate 1) and the rate of temperature increase from 35°C to the holding temperature in the aging step (temperature increase rate 2). The temperature rise rate 1 is preferably 0.02°C / min or more and 0.06°C / min or less. By setting the temperature rise rate 1 within the above range, the number of peaks and z-average radius of gyration in a chromatogram measured using GPC-MALS can be set within a predetermined range. The temperature rise rate 2 is preferably 0.10°C / min or more and 0.30°C / min or less. By setting the temperature rise rate 2 within the above range, the hydroxyl group amount equivalent wave number width and the hydroxyl group amount / acetyl group amount equivalent wave number width can be set within a predetermined range.

[0041] The retention time in the aging step 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 temperature maintained in the aging step 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 holding time and holding temperature as described above, the hydroxyl group amount equivalent wave number width and the hydroxyl group amount / acetyl group amount equivalent wave number width can be set within a predetermined range.

[0042] By containing the polyvinyl acetal resin of the present invention and a plasticizer, a resin composition for a ceramic green sheet can be obtained. The resin composition for a ceramic green sheet of the present invention may contain components such as an antioxidant, a surfactant, an ultraviolet absorber, and an antifoaming agent, as long as the effects of the present invention are not impaired.

[0043] As a method for producing the resin composition for a ceramic green sheet, for example, a plasticizer and other additives that are added as needed can be added to a polyvinyl acetal resin obtained by acetalizing a polyvinyl alcohol resin with an aldehyde, and then mixed to obtain a resin composition for a ceramic green sheet.

[0044] The resin composition for a ceramic green sheet contains a plasticizer. Addition of the plasticizer can significantly improve the mechanical strength and flexibility of the resulting ceramic green sheet. Examples of the plasticizer include phthalic acid 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-ethylbutyrate, tetraethylene glycol-di-2-ethylbutyrate, tetraethylene glycol-di-heptanoate, and triethylene glycol-di-heptanoate.

[0045] In the resin composition for a ceramic green sheet, the content of the plasticizer relative to 100 parts by weight of the polyvinyl acetal resin is preferably 7 parts by weight at its lower limit, more preferably 8.5 parts by weight at its upper limit, and preferably 18 parts by weight, more preferably 13.5 parts by weight at its upper limit.

[0046] 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.

[0047] The organic solvent is not particularly limited as long as it can dissolve the polyvinyl acetal resin, and examples thereof include ketones such as acetone, methyl ethyl ketone, dipropyl ketone, and diisobutyl ketone. Other examples include alcohols such as methanol, ethanol, isopropanol, and butanol, and aromatic hydrocarbons such as toluene and xylene. Further examples include 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. Other examples include methyl cellosolve, ethyl cellosolve, butyl cellosolve, terpineol, dihydroterpineol, butyl cellosolve acetate, butyl carbitol acetate, terpineol acetate, and dihydroterpineol acetate. In particular, alcohols, ketones, aromatic hydrocarbons and mixed solvents thereof are preferred in terms of coating and drying properties, with a mixed solvent of ethanol and toluene and a mixed solvent of methyl ethyl ketone and toluene being more preferred.

[0048] The content of the organic solvent in the ceramic green sheet slurry is determined depending on the type of polyvinyl acetal resin used and is not particularly limited. However, if the content is too low, the solubility required for kneading is difficult to achieve. On the other hand, if the content is too high, the viscosity of the ceramic green sheet slurry composition becomes too low, which can result in poor handling when producing ceramic green sheets. Therefore, the content of the organic solvent is preferably 20% by weight or more and 80% by weight or less.

[0049] The ceramic powders include metal or nonmetal oxide or non-oxide powders used in ceramic production. These powders may be single compositions, compounds, or mixtures. The constituent elements of the metal oxide or non-oxide, both cations and anions, may be single elements or multiple elements, and may further contain additives to improve the properties of the oxide or non-oxide. Specific examples include oxides, carbides, nitrides, borides, and sulfides of elements such as 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 specific oxide powders containing multiple metal elements, commonly called double oxides, are classified based on their crystal structure, those with a perovskite structure include NaNbO3, SrZrO3, PbZrO3, SrTiO3, BaZrO3, PbTiO3, BaTiO3, etc. Those with a spinel structure include MgAl2O4, ZnAl2O4, CoAl2O4, NiAl2O4, MgFe2O4, etc. Those with an ilmenite structure include MgTiO3, MnTiO3, FeTiO3, etc. Those with a garnet structure include GdGa5O 12 , Y6Fe5O 12 Among these, the modified polyvinyl acetal resin of the present invention exhibits excellent properties when mixed with BaTiO3 powder to form a ceramic green sheet.

[0050] The average particle size of the ceramic powder is not particularly limited, but for example, for producing a thin ceramic green sheet (thickness of 5 μm or less), it is preferably 0.5 μm or less.

[0051] The ceramic green sheet slurry 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 ethyl cellulose, within the range that does not impair the effects of the present invention. In such cases, the content of the polyvinyl acetal resin of the present invention relative to the total binder resins is preferably 50% by weight or more.

[0052] If necessary, a dispersant, an antioxidant, an ultraviolet absorber, a surfactant, a filler, etc. may be added appropriately to the above-mentioned slurry for the ceramic green sheet, and in some cases, a small amount of other resin such as an acrylic resin or a urethane resin may also be added.

[0053] The method for producing the slurry for the ceramic green sheet is not particularly limited, and examples thereof include a method in which the polyvinyl acetal resin of the present invention, an organic solvent, a ceramic powder, and various additives to be added as needed are mixed using various mixers such as a ball mill, a blender mill, and a three-roll mill.

[0054] After the slurry for the ceramic green sheet is applied, the slurry is heated and dried to obtain a ceramic green sheet. The ceramic green sheets can be used to manufacture ceramic electronic components, for example, by carrying out a step of applying an electrode layer paste to the surfaces of the ceramic green sheets, and a step of stacking the ceramic green sheets on which the electrode layers have been formed, and then heat-pressing and bonding the stacked body, and then degreasing and firing the resulting laminate.

[0055] The method for applying the slurry for the ceramic green sheet is not particularly limited, and examples thereof include methods using a roll coater, a die coater, a curtain coater, etc. As for other specific methods, conventionally known methods can be used.

[0056] The ceramic electronic component is not particularly limited, and examples thereof include a multilayer ceramic capacitor, a multilayer ceramic inductor, a capacitor, a piezoelectric actuator, a multilayer varistor, a multilayer thermistor, an EMI filter, an aluminum nitride multilayer substrate, an alumina multilayer substrate, etc. Such a multilayer ceramic capacitor also constitutes part of the present invention.

[0057] The method for producing a ceramic electronic component includes a step of applying a paste for electrode layers to the surfaces of the ceramic green sheets. The electrode layer paste can be obtained by dissolving, for example, polyvinyl acetal resin, ethyl cellulose, acrylic resin, or the like as a binder resin in an organic solvent and dispersing conductive powder, etc. These resins may be used alone or in combination of two or more. An electrode layer paste containing a polyvinyl acetal resin is preferred because it exhibits excellent adhesion to the ceramic green sheet in the thermocompression bonding process.

[0058] In the method for producing a ceramic electronic component, the ceramic green sheets having electrode layers formed thereon are produced as described above, and then ceramic green sheets having electrode layers formed thereon that are produced in the same manner are stacked and heated and pressed together to obtain a laminate, which is then degreased and fired, thereby obtaining a multilayer ceramic electronic component that solves problems such as sheet attack and cracking. The above-mentioned thermocompression bonding step and the steps of degreasing and firing the laminate are not particularly limited, and conventionally known methods can be used. [Effects of the Invention]

[0059] According to the present invention, it is possible to provide a polyvinyl acetal resin that can produce a ceramic green sheet having high mechanical strength and excellent sheet attack resistance, and that can produce a highly reliable multilayer ceramic capacitor, as well as a ceramic green sheet slurry, a ceramic green sheet, and a multilayer ceramic capacitor that use the polyvinyl acetal resin. [Brief explanation of the drawings]

[0060] [Figure 1] FIG. 1 is a diagram showing an example of an IR absorption spectrum of a polyvinyl acetal resin of the present invention measured with an infrared spectrophotometer at 20° C. DETAILED DESCRIPTION OF THE INVENTION

[0061] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0062] Example 1 3000 g of pure water was added to 260 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 99.2 mol%) and dissolved by stirring at 90°C for approximately 2 hours. This solution was cooled to 40°C, and 200 g of hydrochloric acid with a concentration of 35 wt% and 2 g of n-butylaldehyde were added to it (first addition). The solution was then cooled to 20°C, and 8 hours after the first addition, an additional 145 g of n-butylaldehyde was added (second addition). Then, 180 minutes after the second addition, the temperature was increased to 35°C at a rate of 0.06°C / min [temperature increase rate 1], and then increased from 35°C at a rate of 0.22°C / min [temperature increase rate 2] (temperature increase time: 340 minutes). The reaction was completed by maintaining the temperature at 55°C for 2.5 hours, and the mixture was neutralized, washed with water, and dried in a conventional manner to obtain a white powder of polyvinyl acetal resin. The temperature increase time was the time from the start of the temperature increase until the temperature reached the maintained temperature.

[0063] (Preparation of ceramic green sheets) (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 stirred for 180 minutes in a bead mill (Ready Mill, manufactured by Imex Co., Ltd.) to prepare an inorganic powder dispersion. (Preparation of resin solution) A resin solution was prepared by adding 8 parts by weight of polyvinyl acetal resin and 2.1 parts by weight of plasticizer (G260 manufactured by Sekisui Chemical Co., Ltd.) to a mixed solvent of 45 parts by weight of ethanol and 45 parts by weight of toluene and stirring to dissolve. (Preparation of slurry for ceramic green sheets) The resin solution was added to the obtained inorganic powder dispersion and stirred for 90 minutes in a bead mill to obtain a slurry for ceramic green sheets.

[0064] Example 2 3000 g of pure water was added to 260 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 99.2 mol%) and dissolved by stirring at 90°C for approximately 2 hours. This solution was cooled to 40°C, and 200 g of hydrochloric acid with a concentration of 35 wt% and 2 g of n-butylaldehyde were added to it (first addition). The solution was then cooled to 20°C, and 8 hours after the first addition, an additional 145 g of n-butylaldehyde was added (second addition). Thereafter, 180 minutes after the second addition, the temperature was increased to 35°C at a rate [temperature increase rate 1] of 0.06°C / min, and then increased from 35°C at a rate [temperature increase rate 2] of 0.22°C / min (temperature increase time: 340 minutes). The mixture was maintained at 55°C for 3 hours to complete the reaction, and the mixture was neutralized, washed with water, and dried in a conventional manner to obtain a white powder of polyvinyl acetal resin.

[0065] Example 3 3000 g of pure water was added to 260 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 99.2 mol%) and dissolved by stirring at 90°C for approximately 2 hours. This solution was cooled to 40°C, and 200 g of hydrochloric acid with a concentration of 35 wt% and 2 g of n-butylaldehyde were added to it (first addition). The solution was then cooled to 20°C, and 8 hours after the first addition, an additional 145 g of n-butylaldehyde was added (second addition). Thereafter, 180 minutes after the second addition, the temperature was increased to 35°C at a rate [temperature increase rate 1] of 0.06°C / min, and then increased from 35°C at a rate [temperature increase rate 2] of 0.22°C / min (temperature increase time: 363 minutes). The reaction was completed by maintaining the temperature at 60°C for 3 hours, and the mixture was neutralized, washed with water, and dried in a conventional manner to obtain a white powder of polyvinyl acetal resin.

[0066] Example 4 3000 g of pure water was added to 260 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 99.2 mol%) and stirred at 90°C for approximately 2 hours to dissolve. This solution was cooled to 40°C, and 200 g of hydrochloric acid with a concentration of 35 wt% and 2 g of n-butylaldehyde were added to it (first addition). The solution was then cooled to 30°C, and 4 hours after the first addition, an additional 145 g of n-butylaldehyde was added (second addition). Thereafter, 180 minutes after the second addition, the temperature was increased to 35°C at a rate [temperature increase rate 1] of 0.02°C / min, and then increased from 35°C at a rate [temperature increase rate 2] of 0.22°C / min (temperature increase time: 363 minutes). The reaction was completed by maintaining the temperature at 55°C for 3 hours, and the mixture was neutralized, washed with water, and dried in a conventional manner to obtain a white powder of polyvinyl acetal resin.

[0067] Example 5 3000 g of pure water was added to 260 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 99.2 mol%) and dissolved by stirring at 90°C for approximately 2 hours. This solution was cooled to 40°C, and 200 g of hydrochloric acid with a concentration of 35 wt% and 2 g of n-butylaldehyde were added to it (first addition). The solution was then cooled to 25°C, and 6 hours after the first addition, an additional 145 g of n-butylaldehyde was added (second addition). Thereafter, 180 minutes after the second addition, the temperature was increased to 35°C at a rate [temperature increase rate 1] of 0.04°C / min, and then increased from 35°C at a rate [temperature increase rate 2] of 0.22°C / min (temperature increase time 340 minutes). The reaction was completed by maintaining the temperature at 55°C for 3 hours, and the mixture was neutralized, washed with water, and dried in a conventional manner to obtain a white powder of polyvinyl acetal resin.

[0068] Example 6 3000 g of pure water was added to 260 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 98.7 mol%) and dissolved by stirring at 90°C for approximately 2 hours. This solution was cooled to 40°C, and 200 g of hydrochloric acid with a concentration of 35 wt% and 2 g of n-butylaldehyde were added to it (first addition). The solution was then cooled to 20°C, and 8 hours after the first addition, an additional 145 g of n-butylaldehyde was added (second addition). Thereafter, 180 minutes after the second addition, the temperature was increased to 35°C at a rate [temperature increase rate 1] of 0.06°C / min, and then increased from 35°C at a rate [temperature increase rate 2] of 0.22°C / min (temperature increase time: 363 minutes). The reaction was completed by maintaining the temperature at 60°C for 3 hours, and the mixture was neutralized, washed with water, and dried in a conventional manner to obtain a white powder of polyvinyl acetal resin.

[0069] Example 7 3000 g of pure water was added to 260 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 99.4 mol%) and stirred at 90°C for approximately 2 hours to dissolve. This solution was cooled to 50°C, and 200 g of 35 wt% hydrochloric acid and 2 g of n-butylaldehyde were added to it (first addition). The solution was then cooled to 20°C, and 12 hours after the first addition, 145 g of n-butylaldehyde was further added (second addition). Thereafter, 180 minutes after the second addition, the temperature was increased to 35°C at a rate [temperature increase rate 1] of 0.06°C / min, and then increased from 35°C at a rate [temperature increase rate 2] of 0.15°C / min (temperature increase time 420 minutes). The reaction was completed by maintaining the temperature at 60°C for 3 hours, and the mixture was neutralized, washed with water, and dried in a conventional manner to obtain a white powder of polyvinyl acetal resin.

[0070] Example 8 3000 g of pure water was added to 260 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 99.2 mol%) and stirred at 90°C for approximately 2 hours to dissolve. This solution was cooled to 40°C, and 200 g of hydrochloric acid with a concentration of 35 wt% and 2 g of n-butylaldehyde were added to it (first addition). The solution was then cooled to 30°C, and 4 hours after the first addition, an additional 145 g of n-butylaldehyde was added (second addition). Thereafter, 300 minutes after the second addition, the temperature was increased to 35°C at a rate [temperature increase rate 1] of 0.02°C / min, and then increased from 35°C at a rate [temperature increase rate 2] of 0.22°C / min (temperature increase time: 340 minutes). The reaction was completed by maintaining the temperature at 55°C for 3 hours, and the mixture was neutralized, washed with water, and dried in a conventional manner to obtain a white powder of polyvinyl acetal resin.

[0071] Example 9 3000 g of pure water was added to 260 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 99.2 mol%) and dissolved by stirring at 90°C for approximately 2 hours. This solution was cooled to 40°C, and 200 g of hydrochloric acid with a concentration of 35 wt% and 2 g of n-butylaldehyde were added to it (first addition). The solution was then cooled to 20°C, and 8 hours after the first addition, an additional 145 g of n-butylaldehyde was added (second addition). Thereafter, 180 minutes after the second addition, the temperature was increased to 35°C at a rate [temperature increase rate 1] of 0.04°C / min, and then increased from 35°C at a rate [temperature increase rate 2] of 0.22°C / min (temperature increase time 483 minutes). The reaction was completed by maintaining the temperature at 55°C for 3 hours, and the mixture was neutralized, washed with water, and dried in a conventional manner to obtain a white powder of polyvinyl acetal resin.

[0072] (Comparative Example 1) 3100 g of pure water was added to 300 g of polyvinyl alcohol resin (average polymerization degree 1700, saponification degree 98.0 mol%) and dissolved by stirring at 90°C for about 2 hours. This solution was cooled to 40°C, and 200 g of hydrochloric acid with a concentration of 35 wt% and 160 g of n-butylaldehyde were added thereto. Thereafter, the mixture was kept at 40°C for 3 hours to carry out an acetalization reaction, and then neutralized, washed with water and dried in a conventional manner to obtain a white powder of polyvinyl acetal resin.

[0073] (Comparative Example 2) 3000 g of pure water was added to 260 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 99.2 mol%) and dissolved by stirring at 90°C for approximately 2 hours. This solution was cooled to 20°C, and 200 g of hydrochloric acid with a concentration of 35 wt% and 147 g of n-butylaldehyde were added to it. 30 minutes after the addition, the temperature was increased at a rate of 0.22°C / min (heating time: 45 minutes), and the temperature was maintained at 40°C for 3 hours to carry out an acetalization reaction. The mixture was then neutralized, washed with water, and dried by conventional methods to obtain a white powder of polyvinyl acetal resin.

[0074] (Comparative Example 3) 3000 g of pure water was added to 260 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 99.1 mol%) and dissolved by stirring at 90°C for approximately 2 hours. This solution was cooled to 20°C, and 200 g of hydrochloric acid with a concentration of 35 wt% and 147 g of n-butylaldehyde were added to it. 60 minutes after the addition, the temperature was increased at a rate of 0.3°C / min (heating time: 150 minutes), and the temperature was maintained at 60°C for 2 hours to carry out an acetalization reaction. The mixture was then neutralized, washed with water, and dried in the usual manner to obtain a white powder of polyvinyl acetal resin.

[0075] Comparative Example 4 3100 g of pure water was added to 300 g of polyvinyl alcohol resin (average polymerization degree 1700, saponification degree 98.7 mol%) and dissolved by stirring at 90°C for about 2 hours. This solution was cooled to 40°C, and 200 g of hydrochloric acid with a concentration of 35 wt% and 160 g of n-butylaldehyde were added thereto. Thereafter, the mixture was kept at 40°C for 3 hours to carry out an acetalization reaction, and then neutralized, washed with water and dried in a conventional manner to obtain a white powder of polyvinyl acetal resin.

[0076] (evaluation) The polyvinyl acetal resins obtained in the examples and comparative examples were evaluated as follows, and the results are shown in Table 1.

[0077] (1) Evaluation of polyvinyl acetal resin (1-1) Amount of acetal groups, amount of hydroxyl groups, amount of acetyl groups The obtained polyvinyl acetal resin was analyzed using an AV400 spectrometer (manufactured by Bruker). 1 H-NMR measurement was carried out, and the amounts of acetal groups, hydroxyl groups, and acetyl groups were calculated. The obtained polyvinyl acetal resin was dissolved in DMSO-D6 to a concentration of 1.6% by weight to prepare a measurement solution. 1 H-NMR measurements were carried out at 80°C.

[0078] (1-2) Number of peaks in chromatograms measured by GPC-MALS and z-average radius of gyration 5 ml of tetrahydrofuran (THF) was added to 3 mg of the obtained polyvinyl acetal resin, and the mixture was gently stirred at 40° C. After that, the mixture was filtered using a 0.5 μm filter to prepare a sample for GPC-MALS. A gel permeation chromatography system [pump (Shimadzu Corporation, LC-20AD), autosampler (Shimadzu Corporation, SIL-10AXL), column oven (Shimadzu Corporation, CTO-20AC)], a multi-angle light scattering detector (Wyatt Technology, DAWN HELEOS II), and a differential refractive index detector (Wyatt Technology, Optilab T-rEX) were used. The mobile phase was tetrahydrofuran at 1 mL / min, and two PLgel 20 μm MIXED-A columns (7.5 mm x 30 cm, Polymer Laboratories) were used. The column temperature was 40°C, the detector temperature was 25°C, and the sample injection volume was 0.2 mL. Using a data processing system (ASTRA) manufactured by Wyatt Technology, dn / dc was calculated from the RI curve and the measurement results at θ=90°, and the z-average radius of gyration was obtained. In addition, the number of LS intensity peaks was counted for the LS detection peaks observed in the elution time region of 7 to 10 minutes and the elution time region of 10 to 17 minutes from the chromatogram using the following procedure.

[0079] The LS detection peaks are designated P1, P2, Px in order from the shortest elution time, and the LS detection peak value of Px is designated Sx. The maximum LS intensity value at elution times 4.9 to 5.1 minutes is designated LSI. Max and minimum LSI Min In this case, N was calculated using the following formula (6), and then peaks satisfying formula (7) were determined to be LS intensity peaks, and the number of peaks was counted. N=|LSI Max |-|LSI Min | (6) Sx / N≧50 (7) In addition, when calculating the z-average radius of gyration, the P L and the peak P seen on the largest side H In this case, P L The peak intensity of the LS peak is 2 / 3 of the peak value. LX From P H The peak intensity of the LS peak is 2 / 3 of the peak value. HY The z-average radius of gyration was calculated by setting the range as follows:

[0080] (1-3) IR absorption spectrum The obtained polyvinyl acetal resin was dissolved in a 1:1 ethanol / toluene mixed solution by weight, and then coated onto a PET film. -1 The film thickness of the measurement sample was adjusted so that the minimum transmittance of the peak appearing around 20% was 20%, and a polyvinyl acetal resin sheet was obtained. The IR absorption spectrum of the obtained polyvinyl acetal resin sheet was measured using an infrared spectrophotometer (HORIBA, FT-720) at 20°C. The measurement results showed that the IR absorption spectrum was measured at wavenumbers of 3050 to 3750 cm. -1A baseline was drawn for the peaks that appeared within this range, and peak analysis was performed on the data corrected so that the transmittance at both ends of the peak was 100%, and the minimum transmittance X, transmittance a, and peak wavenumbers A and B were measured. 1 Using the amount of hydroxyl groups determined by H-NMR measurement, the hydroxyl group amount converted wavenumber width (cm -1 / mol%) = [(BA) / amount of hydroxyl groups] was calculated. 1 Using the amount of acetyl groups determined by H-NMR measurement, the wave number width of hydroxyl groups converted into the amount of acetyl groups = [(BA) / amount of hydroxyl groups / acetyl groups] was calculated.

[0081] (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. The B-type viscometer used was a TVB-10 viscometer (manufactured by Toki Sangyo Co., Ltd.), and measurements were carried out with the following rotation speeds and rotors: Examples 1 to 9 and Comparative Examples 1 to 4: Rotation speed 30 rpm, SPINDLE No. M1

[0082] (1-5)z average molecular weight [Mz(THF), Mz(NMP)] measurement The resulting polyvinyl acetal resin was dissolved in tetrahydrofuran (THF) at a concentration of 0.2 wt% and passed through a 0.45 μm PTFE filter. The gel was analyzed using a GPC system (HLC-8420, Tosoh Corporation) with a THF mobile phase, a Bryce-type double-pass refractive index detector (Tosoh Corporation), and a TSKgel Super HZM-H column (Tosoh Corporation) at a flow rate of 0.35 mL / min. The results were calibrated using a molecular weight calibration curve prepared using monodisperse polystyrene standards 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 wt%, 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 apparatus, NMP as the mobile phase, a differential refractive index detector RI-715 (Shodex) as the detector, and an LF-804 (Shodex) column. The measurement results were calibrated using a molecular weight calibration curve prepared using monodisperse polystyrene standards to obtain the z-average molecular weight Mz (NMP). From the obtained Mz(THF) and Mz(NMP), "Mz(THF) / Mz(NMP)" was calculated.

[0083] (2) Evaluation of ceramic green sheets (Preparation of inorganic 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 stirred for 180 minutes in a bead mill (Ready Mill, manufactured by Imex Co., Ltd.) to prepare an inorganic dispersion.

[0084] (Preparation of resin solution) 8 parts by weight of the obtained polyvinyl acetal resin and 2 parts by weight of DOP were added to a mixed solvent of 45 parts by weight of ethanol and 45 parts by weight of toluene, and the mixture was stirred and dissolved to prepare a resin solution.

[0085] (Preparation of ceramic green sheets) The resin solution was added to the obtained inorganic dispersion and stirred for 90 minutes in a bead mill to obtain a composition for ceramic green sheets. The obtained ceramic green sheet composition was applied to a release-treated PET film using a coater so that the thickness after drying would be 20 μm, and then heated and dried to prepare a ceramic green sheet.

[0086] (2-1) Seat attack resistance The obtained ceramic green sheet was cut into a 5 cm x 5 cm square. Then, 70 μL of dihydroterpineol acetate at 23°C was dripped onto the test piece, and the dripping time was set to 0. The ceramic green sheet was then visually observed, and the time until wrinkles appeared on the ceramic green sheet was measured and evaluated according to the following evaluation criteria. The longer the time until wrinkles appeared, the better the sheet attack resistance. AA: 100 seconds or more A: 80 seconds or more and less than 100 seconds B: 60 seconds or more but less than 80 seconds C: Less than 60 seconds

[0087] (2-2) Breaking stress and breaking strain The obtained ceramic green sheet was cut into a size of 5 cm x 1 cm to prepare a test piece. The test piece was pulled at a tension speed of 500% / min using a tensile tester (Shimadzu Corporation, AUTOGRAPH AGS-J) at a measurement temperature of 20°C, and the breaking tensile strength (kg / cm 2 ) was measured. A stress σ (MPa)-strain ε (%) curve was calculated from the obtained values. Note that 500% / min means a speed at which the test piece is moved a distance five times the distance between the chucks in one minute. The stress at break and strain at break were calculated from the obtained stress-strain curve and evaluated according to the following evaluation criteria. (stress at break) AA:34MPa or more A: 33 MPa or more and less than 34 MPa B: 30MPa or more and less than 33MPa C: Less than 30 MPa (strain at break) AA: 22% or more A: 21% or more but less than 22% B: 17% or more but less than 21% C: Less than 17%

[0088] [Table 1] [Industrial Applicability]

[0089] According to the present invention, it is possible to provide a polyvinyl acetal resin that can produce a ceramic green sheet having high mechanical strength and excellent sheet attack resistance, and that can produce a highly reliable multilayer ceramic capacitor, as well as a ceramic green sheet slurry, a ceramic green sheet, and a multilayer ceramic capacitor that use the polyvinyl acetal resin.

Claims

1. In the chromatogram measured using GPC-MALS, there is one or more LS intensity peaks in the retention time region of 7 to 10 minutes, and in the IR absorption spectrum measured using an infrared spectrophotometer, there is a peak in the wave number range of 3050 to 3750 cm －１ When the minimum transmittance of the peak within the range is X (%), among the wave numbers showing transmittance a (%) that satisfies [100-(100-X) / 2], the wave number on the low wave number side is A and the wave number on the high wave number side is B, １ A polyvinyl acetal resin having a hydroxyl group amount converted wavenumber width of 8.31 or more, calculated by formula (1) using the amount of hydroxyl groups measured by H-NMR. Hydroxyl group amount equivalent wavenumber width (cm －１ / mol%) = [(B - A) / amount of hydroxyl groups] (1)

2. 2. The polyvinyl acetal resin according to claim 1, which has three or more LS intensity peaks in a retention time region of 7 to 17 minutes in a chromatogram measured using GPC-MALS.

3. The polyvinyl acetal resin according to claim 1 or 2, which has a z-average radius of gyration of 55 nm or more as measured by GPC-MALS.

4. 3. The polyvinyl acetal resin according to claim 1, wherein the hydroxyl group amount converted wavenumber width calculated by the formula (1) is 8.45 or more.

5. The above A, B and １ 3. The polyvinyl acetal resin according to claim 1, wherein the hydroxyl group-acetyl group amount converted wavenumber width calculated by the following formula (2) using the hydroxyl group amount and the acetyl group amount measured by H-NMR is 6.5 to 18.0: Hydroxyl group acetyl group amount converted wave number width (cm －１ / mol% / mol%) = [(B - A) / amount of hydroxyl groups / amount of acetyl groups] (2)

6. 3. The polyvinyl acetal resin according to claim 1, wherein Mz(THF) / Mz(NMP) is 1.2 to 1.93, where Mz(THF) is the z-average molecular weight obtained using THF as a mobile phase and Mz(NMP) is the z-average molecular weight obtained using NMP as a mobile phase in GPC measurement using a differential refractive index detector.

7. 3. The polyvinyl acetal resin according to claim 1, wherein a 5% by mass solution of the polyvinyl acetal resin in a 1:1 mixed solvent of ethanol and toluene has a solution viscosity of 30 mPa s or more and 200 mPa s or less, as measured using a Brookfield viscometer at a solution temperature of 20°C.

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

9. A ceramic green sheet obtained by using the slurry for ceramic green sheet according to claim 8.

10. A multilayer ceramic capacitor obtained by using the ceramic green sheet according to claim 9.

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