Polyvinyl acetal resin

Abstract

To provide a polyvinyl acetal resin which has less viscosity change even when using a solvent with a high ratio of ethanol and has excellent sheet attack resistance and to provide a ceramic green sheet slurry, a ceramic green shee and a laminated ceramic capacitor using the polyvinyl acetal resin.SOLUTION: There is provided a polyvinyl acetal resin, wherein in GPC measurement using a differential refractive index detector, the molecular weight distribution difference, which is calculated from the specific expression (1) using the weight-average molecular weight Mw (THF) and number-average molecular weight Mn (THF) obtained using THF as the mobile phase and the weight-average molecular weight Mw (NMP) and number-average molecular weight Mn (NMP) obtained using NMP as the mobile phase, is 0.01 or more and 0.45 or less and the ratio of peak integral values for diads of constituent units having hydroxyl groups measured by 13C-NMR measurement is 0.30 or more and 0.36 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to polyvinyl acetal resin, 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] Polyvinyl acetal resin is widely used as a binder in ceramic slurries for multilayer ceramic capacitors, partly due to its good solubility in a mixed solvent of ethanol and toluene. However, toluene is subject to environmental regulations due to its harmful properties, and it also has a higher boiling point than ethanol, requiring more energy for solvent drying. Therefore, there is a need for a binder that exhibits good solubility even in solvents with a high proportion of ethanol. On the other hand, there is also the problem of sheet attack, which occurs when the binder in the dielectric layer dissolves into the electrode layer.

[0006] The present invention aims to provide a polyvinyl acetal resin that exhibits minimal viscosity change and excellent sheet attack resistance even when using a solvent with a high proportion of ethanol, as well as a slurry for ceramic green sheets, a ceramic green sheet, and a multilayer ceramic capacitor using the polyvinyl acetal resin. [Means for solving the problem]

[0007] Disclosure 1 describes a GPC measurement using a differential refractive index detector in which the difference in molecular weight distribution calculated from the following formula (1) using the weight-average molecular weight Mw(THF) and number-average molecular weight Mn(THF) obtained when THF is used as the mobile phase, and the weight-average molecular weight Mw(NMP) and number-average molecular weight Mn(NMP) obtained when NMP is used as the mobile phase, is 0.5 or less, and 13 This is a polyvinyl acetal resin in which the ratio of the peak integral value of the methylene C atom shown in (a)' of the two-bend configuration shown in (b)' and (c)' of the two-bend configuration shown in (b)' and (c)' of the two-bend configuration shown in (a)' below to the sum of the peak integral values ​​of the methylene C atoms shown in (b)' and (c)' of the two-bend configuration shown in (a)' below, obtained by 13C-NMR (nuclear magnetic resonance) measurement, is 0.29 or more and 0.37 or less. [Mw(THF) / Mn(THF)]-[Mw(NMP) / Mn(NMP)] (1) [ka] In formulas (b) and (c), R is independently either hydrogen or a hydrocarbon group having 1 to 20 carbon atoms. Disclosure 2 is the polyvinyl acetal resin according to Disclosure 1, wherein the hydroxyl group content is 28 mol% or more and 35 mol% or less. Disclosure 3 is a polyvinyl acetal resin according to Disclosure 1 or 2, having a weight-average molecular weight Mw(THF) of 200,000 or more and 500,000 or less. Disclosure 4 is a polyvinyl acetal resin according to Disclosure 1 or 2, having a weight-average molecular weight Mw (NMP) of 270,000 or more. Disclosure 5 is a slurry for ceramic green sheets, comprising the polyvinyl acetal resin described in Disclosure 1 or 2, an organic solvent, and ceramic powder. Disclosure 6 is a ceramic green sheet made using the ceramic green sheet slurry described in Disclosure 5. Disclosure 7 is a multilayer ceramic capacitor obtained using the ceramic green sheet described in Disclosure 6. The present invention will be described in detail below.

[0008] As a result of diligent research, the inventors have found that the weight-average molecular weight and number-average molecular weight measured by changing the solvent satisfy a predetermined relationship, and 13 We have discovered that polyvinyl acetal resins in which the ratio of the peak integral value of the methylene C atom shown in (a)' of the double-chain represented by formula (a) to the sum of the peak integral values ​​of the methylene C atoms shown in (b)' and (c)' of the double-chain represented by formula (b) and (c) above, measured by 13C-NMR (the ratio of the peak integral values ​​of the double-chain consisting of two chains of constituent units having hydroxyl groups) is within a predetermined range, exhibit less viscosity change even when using solvents with a high proportion of ethanol, have excellent sheet attack resistance, and enable the production of highly reliable multilayer ceramic capacitors, thus completing the present invention.

[0009] The polyvinyl acetal resin of the present invention has a molecular weight distribution difference of 0.5 or less, calculated from the following formula (1) using the weight-average molecular weight Mw(THF) and number-average molecular weight Mn(THF) obtained using THF as the mobile phase, and the weight-average molecular weight Mw(NMP) and number-average molecular weight Mn(NMP) obtained using NMP as the mobile phase. [Mw(THF) / Mn(THF)]-[Mw(NMP) / Mn(NMP)] (1) By keeping the viscosity within the above range, it is possible to minimize viscosity changes even when using solvents with a high proportion of ethanol. The molecular weight distribution difference is preferably 0.48 or less, and more preferably 0.45 or less. Furthermore, the molecular weight distribution difference is preferably 0.001 or more, and more preferably 0.01 or more. In this invention, the difference in molecular weight distribution serves as an indicator of a low amount of hydrogen bonding. The above molecular weight distribution difference can be calculated by measuring the weight average molecular weight Mw(THF) and the number average molecular weight Mn(THF) by gel permeation chromatography (GPC) measurement using tetrahydrofuran as the mobile phase and a differential refractive index detector as the detector, then measuring the weight average molecular weight Mw(NMP) and the number average molecular weight Mn(NMP) by GPC measurement using N-methylpyrrolidone as the mobile phase and a differential refractive index detector as the detector, and calculating [Mw(THF) / Mn(THF)] - [Mw(NMP) / Mn(NMP)].

[0010] The z-average molecular weight Mz(THF) of the polyvinyl acetal resin of the present invention is preferably 300,000 or more and 2,000,000 or less. By setting it within the above range, the sheet attack resistance of the obtained ceramic green sheet can be maintained. The above Mz(THF) is more preferably 400,000 or more and more preferably 1,200,000 or less.

[0011] The z-average molecular weight Mz(NMP) of the polyvinyl acetal resin of the present invention is preferably 300,000 or more and 1,000,000 or less. By setting it within the above range, the sheet attack resistance of the obtained ceramic green sheet can be maintained. The above Mz(NMP) is more preferably 400,000 or more and more preferably 600,000 or less.

[0012] The weight average molecular weight Mw(THF) of the polyvinyl acetal resin of the present invention is preferably 200,000 or more and 500,000 or less. By setting it within the above range, the elongation of the obtained ceramic green sheet can be maintained. The above Mw(THF) is more preferably 220,000 or more and more preferably 400,000 or less.

[0013] The weight-average molecular weight Mw(NMP) of the polyvinyl acetal resin of the present invention is preferably between 270,000 and 400,000. Maintaining this range allows for the elongation of the resulting ceramic green sheet. More preferably, the Mw(NMP) is 275,000 or higher, and even more preferably 300,000 or lower.

[0014] The number-average molecular weight Mn(THF) of the polyvinyl acetal resin of the present invention is preferably 50,000 or more and 200,000 or less. By keeping it within this range, the strength of the resulting ceramic green sheet can be maintained. The above Mw(THF) is more preferably 75,000 or more, and even more preferably 200,000 or less.

[0015] The number-average molecular weight Mn (NMP) of the polyvinyl acetal resin of the present invention is preferably 50,000 or more and 200,000 or less. By keeping it within this range, the strength of the resulting ceramic green sheet can be maintained. The above Mw (NMP) is more preferably 75,000 or more, and even more preferably 200,000 or less.

[0016] The above molecular weight distribution difference 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 molecular weight distribution difference can be adjusted by changing the aldehyde input temperature, number of inputs, input interval, ratio of input amounts, reaction temperature, reaction time, heating time, heating rate, holding (aging) temperature, and holding (aging) time during the acetalization reaction described later. Specifically, it can be adjusted by changing the aldehyde input temperature, number of inputs, input interval, ratio of input amounts, holding (aging) temperature, and holding (aging) time.

[0017] The polyvinyl acetal resin of the present invention is 13The ratio of the peak integral values ​​of a double chain consisting of two hydroxyl group constituent units, as measured by 13C-NMR, is between 0.29 and 0.37. Maintaining this range improves sheet attack resistance. The ratio of the peak integral values ​​of a double chain consisting of two chains of the above-mentioned hydroxyl group constituent units is preferably 0.30 as the lower limit, more preferably 0.31 as the lower limit, preferably 0.365 as the upper limit, and still more preferably 0.36 as the upper limit. If it is above the lower limit, the hydrogen bonding properties due to the hydroxyl group are improved, and the ceramic green sheet made using the polyvinyl acetal resin of the present invention can have its solubility in organic solvents reduced, resulting in good sheet attack resistance. If it is below the upper limit, the solubility of the polyvinyl acetal resin in organic solvents is not reduced too much, resulting in good handling properties such as solution preparation.

[0018] The ratio of the peak integral values ​​of a double chain, which is a chain consisting of two constituent units having two hydroxyl groups, is This is the ratio of the sum of the peak integral values ​​of methylene C atoms shown in (a)' of the two-branch shown in (b)' and (c)' of the two-branch shown in formula (b) and (c) below to the sum of the peak integral values ​​of methylene C atoms shown in (b)' and (c)' of the two-branch shown in formula (a) below, 13 It can be measured by 13C-NMR.

[0019] 13 Obtained by 13C-NMR (nuclear magnetic resonance) measurements. 13 In the 13C-NMR spectrum, the sum of the peak integral values ​​of the methylene C atoms shown in the double dendrograms (b)' and (c)' represented by the following equations (b) and (c) can be calculated as the sum of [I(b)' + I(c)'], where I(b)' is the peak integral value to which the methylene C atom shown in the double dendrogram (b)' represented by equation (b) belongs, and I(c)' is the peak integral value to which the methylene C atom shown in the double dendrogram (c)' represented by equation (c) belongs.

[0020] [ka] In formula (b) and formula (c), R is, independently of each other, hydrogen or a hydrocarbon group having 1 to 20 carbon atoms.

[0021] 13 obtained by 13C-NMR (nuclear magnetic resonance) measurement 13 In the 13C-NMR spectrum, the peak integration value of the methylene C atom shown by (a)' of the two-link unit represented by the above formula (a) can be determined from the peak integration value [I(a)'] of the peak to which the methylene C atom shown by (a)' of the two-link unit represented by the above formula (a) belongs.

[0022] 13 In the 13C-NMR spectrum, the above I(a)' is the peak integration value in the range of 44.6 to 46.0 ppm, and the above I(b)' + I(c)' is the peak integration value in the range of 42.9 to 44.6 ppm.

[0023] Regarding the polyvinyl acetal resin of the present invention, 13 obtained by 13C-NMR (nuclear magnetic resonance) measurement 13 An example (partial enlarged view) of the 13C-NMR spectrum is shown in FIG. 1. 13 The peaks (a)', (b)' and (c)' shown in the 13C-NMR spectrum respectively indicate the peaks to which the methylene C atoms shown by (a)', (b)' and (c)' of the two-link units represented by the above formulas (a), (b) and (c) belong.

[0024] The ratio of the peak integration value of the two-link unit composed of two chains of the structural unit having the above hydroxyl group can be adjusted, for example, by changing the average degree of polymerization, saponification degree of the raw polyvinyl alcohol resin, and temperature and time conditions of the acetalization reaction, and appropriately setting the amount of acetal group, amount of hydroxyl group, amount of acetyl group, etc. of the polyvinyl acetal resin. In particular, the ratio of the peak integral values ​​of the double chains consisting of two chains of the above-mentioned hydroxyl group-containing constituent units can be adjusted by changing the aldehyde input temperature, number of inputs, input interval, reaction temperature, reaction time, heating time, heating rate, holding (aging) temperature, and holding (aging) time during the acetalization reaction described later. In particular, it can be adjusted by changing the aldehyde input temperature, holding (aging) temperature, and holding (aging) time.

[0025] The polyvinyl acetal resin of the present invention preferably has a solution viscosity of 60 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 65 mPa·s or higher, and even more preferably 70 mPa·s or higher. From the viewpoint of improving the viscosity stability of the ceramic slurry composition, it is more preferably 300 mPa·s or lower, and even more preferably 150 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.

[0026] 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.

[0027] 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).

[0028] [ka]

[0029] In equation (3) above, R 1 represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.

[0030] In equation (3) above, 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.

[0031] 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.

[0032] 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 28 mol%, and the preferred upper limit is 35 mol%. When the amount of hydroxyl groups is 28 mol% or more, a highly tough polyvinyl acetal resin can be obtained. When the amount of hydroxyl groups is 35 mol% or less, the solubility in organic solvents can be sufficiently improved. The above hydroxyl group content has a more preferable lower limit of 29 mol% and a more preferable upper limit of 34 mol%. That is, the above hydroxyl group content is preferably 28 to 35 mol%, and more preferably 29 to 34 mol%. The amount of hydroxyl groups mentioned above is, for example, 1 It can be measured by 1H-NMR.

[0033] 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 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 the 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 mol%. The above amount of acetyl groups is, for example, 1 It can be measured by 1H-NMR.

[0034] When producing thin-film ceramic green sheets, the polyvinyl acetal resin of the present invention 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 9,000 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 9,000. 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.

[0035] The polyvinyl acetal resin of the present invention can typically be produced by acetalizing a polyvinyl alcohol resin.

[0036] 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.

[0037] The polyvinyl alcohol resin described above preferably has a degree of saponification of 75 mol% or more. The degree of saponification is more preferably 76 mol% to 99.4 mol%, and even more preferably 78 mol% to 98 mol%. That is, the degree of saponification is preferably 76 to 99.4 mol%, and more preferably 78 to 98 mol%. By using the above-mentioned polyvinyl alcohol resin, the above-mentioned Mz can be set to a predetermined range.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] In the acetalization process described above, it is preferable to add the aldehyde in multiple stages. It is preferable that the above-mentioned aldehyde is added twice. Furthermore, the ratio of the amount of aldehyde added in the first addition to the total amount of aldehyde added is preferably 1% or more and 50% or less of the total amount for the first addition, and more preferably 2% or more and 40% or less. When the above aldehyde is added in multiple stages, the temperature at the time of the first addition is preferably 15°C or higher and 60°C or lower, and more preferably 25°C or higher and 50°C or lower. Furthermore, the temperature at the time of the final addition is preferably 10°C or higher and 50°C or lower, and more preferably 20°C or higher and 40°C or lower. Furthermore, the interval between the first and last additions is preferably 5 minutes or more and 180 minutes or less, and more preferably 10 minutes or more and 120 minutes or less.

[0043] In the above acetalization process, it is preferable to add the aldehyde, carry out the reaction at a predetermined temperature (reaction step), then raise the temperature and maintain it at the predetermined temperature (aging step). The time from the last addition to the start of heating (reaction time) is preferably 10 minutes or more and 120 minutes or less, and more preferably 20 minutes or more and 90 minutes or less. The temperature in the above reaction step (reaction temperature) is preferably within the same range as the temperature at the time of the last addition. Furthermore, the heating time from the end of the above reaction step to the maturation step is preferably 30 minutes or more and 500 minutes or less, and more preferably 60 minutes or more and 400 minutes or less. Furthermore, the heating rate from the start of the heating process to the maturation process is preferably 0.1°C / min or more and 2°C / min or less.

[0044] The holding time in the above maturation process is preferably 0.5 hours or more and 6 hours or less, and more preferably 1 hour or more and 5 hours or less. The holding temperature in the above maturation process is preferably 50°C or higher and 80°C or lower, and more preferably 55°C or higher and 75°C or lower. By using the above-mentioned holding time and holding temperature, the ratio of the peak integral values ​​of the double chain, which consists of two chains of the above-mentioned hydroxyl group constituent units, can be set to a predetermined range.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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 for ceramic green sheets may become too low, which may impair the handling when manufacturing the 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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]

[0062] According to the present invention, it is possible to provide a polyvinyl acetal resin that exhibits little viscosity change even when a solvent with a high proportion of ethanol is used, and has excellent sheet attack resistance, as well as a slurry for ceramic green sheets, a ceramic green sheet, and a multilayer ceramic capacitor using the polyvinyl acetal resin. [Brief explanation of the drawing]

[0063] [Figure 1] This is a partially enlarged view showing an example of a 13C-NMR spectrum obtained by 13C-NMR (nuclear magnetic resonance) measurement for the polyvinyl acetal resin of the present invention. [Modes for carrying out the invention]

[0064] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0065] (Example 1) 300 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 30°C, and 220 g of 35 wt% hydrochloric acid and 30 g of n-butyraldehyde were added (first addition). The solution was then cooled to 20°C, and 30 minutes after the first addition, an additional 130 g of n-butyraldehyde was added (second addition). Subsequently, the mixture was held for 0.5 hours to carry out the acetalization reaction. After that, the temperature was increased at a rate of 0.2°C / min (heating time 150 minutes), and the mixture was held at 55°C for 3 hours (aging step) to complete the reaction. The mixture was then neutralized, washed with water, and dried by conventional methods to obtain a white powder of polyvinyl acetal resin.

[0066] (Example 2) 300 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 99.0 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 30°C, and 220 g of 35 wt% hydrochloric acid and 40 g of n-butyraldehyde were added (first addition). The solution was then cooled to 20°C, and 30 minutes after the first addition, an additional 120 g of n-butyraldehyde was added (second addition). Subsequently, the mixture was held for 0.5 hours to carry out the acetalization reaction. After that, the temperature was increased at a rate of 0.2°C / min (heating time 150 minutes), and the mixture was held at 55°C for 3 hours (aging step) to complete the reaction. The mixture was then neutralized, washed with water, and dried by conventional methods to obtain a white powder of polyvinyl acetal resin.

[0067] (Example 3) 300 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 35°C, and 220 g of 35 wt% hydrochloric acid and 10 g of n-butyraldehyde were added (first addition). Next, the solution was cooled to 30°C, and 15 minutes after the first addition, another 150 g of n-butyraldehyde was added (second addition). Subsequently, the mixture was held for 0.5 hours to carry out the acetalization reaction. After that, the temperature was increased at a rate of 0.2°C / min (heating time 100 minutes), and the mixture was held at 55°C for 3 hours (aging step) to complete the reaction. The mixture was then neutralized, washed with water, and dried by conventional methods to obtain a white powder of polyvinyl acetal resin.

[0068] (Example 4) 300 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 30°C, and 220 g of 35 wt% hydrochloric acid and 30 g of n-butyraldehyde were added (first addition). The solution was then cooled to 20°C, and 30 minutes after the first addition, an additional 130 g of n-butyraldehyde was added (second addition). Subsequently, the mixture was held for 0.5 hours to carry out the acetalization reaction. After that, the temperature was increased at a rate of 0.2°C / min (heating time 180 minutes), and the mixture was held at 60°C for 3 hours (aging step) to complete the reaction. The mixture was then neutralized, washed with water, and dried by conventional methods to obtain a white powder of polyvinyl acetal resin.

[0069] (Example 5) 300 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 35°C, and 220 g of 35 wt% hydrochloric acid and 10 g of n-butyraldehyde were added (first addition). Next, the solution was cooled to 30°C, and 15 minutes after the first addition, another 150 g of n-butyraldehyde was added (second addition). Subsequently, the mixture was held for 0.5 hours to carry out the acetalization reaction. After that, the temperature was increased at a rate of 0.2°C / min (heating time 120 minutes), and the mixture was held at 60°C for 3 hours (aging step) to complete the reaction. The mixture was then neutralized, washed with water, and dried by conventional methods to obtain a white powder of polyvinyl acetal resin.

[0070] (Example 6) 300 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 45°C, and 220 g of 35 wt% hydrochloric acid and 10 g of n-butyraldehyde were added (first addition). The solution was then cooled to 40°C, and 10 minutes after the first addition, another 150 g of n-butyraldehyde was added (second addition). Subsequently, the mixture was held for 0.5 hours to carry out the acetalization reaction. After that, the temperature was increased at a rate of 0.2°C / min (heating time 90 minutes), and the mixture was held at 55°C for 3 hours (aging step) to complete the reaction. The mixture was then neutralized, washed with water, and dried by conventional methods to obtain a white powder of polyvinyl acetal resin.

[0071] (Example 7) 300 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 35°C, and 220 g of 35 wt% hydrochloric acid and 10 g of n-butyraldehyde were added (first addition). Next, the solution was cooled to 30°C, and 15 minutes after the first addition, another 150 g of n-butyraldehyde was added (second addition). Subsequently, the mixture was held for 0.5 hours to carry out the acetalization reaction. After that, the temperature was increased at a rate of 0.2°C / min (heating time 200 minutes), and the mixture was held at 70°C for 0.5 hours (aging step) to complete the reaction. The mixture was then neutralized, washed with water, and dried by conventional methods to obtain a white powder of polyvinyl acetal resin.

[0072] (Comparative Example 1) 300 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 99.4 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 220 g of 35 wt% hydrochloric acid and 160 g of n-butyraldehyde were added to it. Subsequently, the mixture was held for 0.5 hours to carry out the acetalization reaction. After that, the temperature was increased at a rate of 0.2°C / min (heating time 120 minutes), and the mixture was held at 55°C for 3 hours (aging step) to complete the reaction. The mixture was then neutralized, washed with water, and dried by conventional methods to obtain a white powder of polyvinyl acetal resin.

[0073] (Comparative Example 2) 300 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 99.4 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 220 g of 35 wt% hydrochloric acid and 160 g of n-butyraldehyde were added to it. Subsequently, the mixture was held for 0.5 hours to carry out the acetalization reaction. After that, the temperature was increased at a rate of 0.2°C / min (heating time 50 minutes), and the mixture was held at 30°C for 3 hours (aging step) to complete the 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) 300 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 30°C, and 220 g of 35 wt% hydrochloric acid and 130 g of n-butyraldehyde were added (first addition). The solution was then cooled to 20°C, and 30 minutes after the first addition, an additional 30 g of n-butyraldehyde was added (second addition). Subsequently, the mixture was held for 0.5 hours to carry out the acetalization reaction. After that, the temperature was increased at a rate of 0.2°C / min (heating time 50 minutes), and the mixture was held at 30°C for 3 hours (aging step) to complete the reaction. The mixture was then neutralized, washed with water, and dried by conventional methods to obtain a white powder of polyvinyl acetal resin.

[0075] (Comparative Example 4) 300 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 30°C, and 220 g of 35 wt% hydrochloric acid and 130 g of n-butyraldehyde were added (first addition). The solution was then cooled to 20°C, and 30 minutes after the first addition, an additional 30 g of n-butyraldehyde was added (second addition). Subsequently, the mixture was held for 0.5 hours to carry out the acetalization reaction. After that, the temperature was increased at a rate of 0.2°C / min (heating time 200 minutes), and the mixture was held at 60°C for 5 hours (aging step) to complete the reaction. The mixture was then neutralized, washed with water, and dried by conventional methods 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. The results are shown in Table 1.

[0077] (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.

[0078] (1-2) Measurement of weight-average molecular weight and number-average molecular weight 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 number-average molecular weight Mn(THF) and weight-average molecular weight Mw(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 number-average molecular weight Mn(NMP) and weight-average molecular weight Mw(NMP). From the obtained Mw(THF), Mn(THF), Mw(NMP), and Mn(NMP), [Mw(THF) / Mn(THF)]-[Mw(NMP) / Mn(NMP)] was calculated and used as the molecular weight distribution difference.

[0079] (1-3) Ratio of peak integral values ​​of double chains consisting of two hydroxyl group constituent units in polyvinyl acetal resin (ratio of double chain hydroxyl group constituent units) The obtained polyvinyl acetal resin was analyzed using an AVANCE600 spectrometer and a CryoProbe (manufactured by Bruker). 13 By performing 1C-NMR measurements, the proportion of peak integral values ​​of triple units consisting of two chains of hydroxyl group-containing structural units in polyvinyl acetal resin was measured. Details of the peak integral value measurement are as described above. The obtained polyvinyl acetal resin was dissolved in DMSO-D6 to a concentration of 12% by weight, and a relaxation reagent (chromium(III) acetylacetate) was added to prepare the measurement solution. 13 ¹¹¹¹¹¹¹H decoupling mode was used for ¹

[0080] (2) Evaluation of polyvinyl acetal resin sheets 10.0 parts by weight of the obtained polyvinyl acetal resin and 45 parts by weight of an ethanol / toluene mixed solvent (weight ratio 1:1) were added and stirred to dissolve, thereby obtaining a polyvinyl acetal resin composition. The obtained polyvinyl acetal resin composition 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 polyvinyl acetal resin sheet.

[0081] (2-1) Evaluation of sheet attack resistance (solvent elution) The obtained polyvinyl acetal resin sheet was cut into 1.5 cm x 10 cm squares, and its weight was accurately measured. The test pieces were then immersed in 10 ml of dihydroterpineol acetate at 23°C for 1 minute. Afterward, the test pieces were removed and dried at 150°C for 6 hours to completely dry the solvent. After removing from the dryer, the specimens were left at room temperature for one hour and their weight was measured. The amount of resin leached was calculated from the weight change before and after the test, and the leaching rate was calculated from the ratio of the leached amount to the weight of the specimen before the test, and evaluated according to the following criteria. Note that the value of the leaching rate low This means that it has superior resistance to sheet attacks.

[0082] A: Dissolution rate of 4.1% or less B: Dissolution rate greater than 4.1% and 4.7% or less C: Dissolution rate greater than 4.7%

[0083] (3) Viscosity change rate when ethanol ratio is changed A 5% by mass solution of polyvinyl acetal resin dissolved in a mixed solvent of 50 parts by weight of ethanol and 50 parts by weight of toluene was measured using a Type B viscometer at a solution temperature of 20°C (viscosity of 50% by weight of ethanol). As the 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 during viscosity measurement. 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. Furthermore, the viscosity (70% ethanol viscosity) was measured under the same conditions when the mixture was changed from "50 parts by weight of ethanol and 50 parts by weight of toluene" to "70 parts by weight of ethanol and 30 parts by weight of toluene," and the viscosity change rate [(70% ethanol viscosity / 50% ethanol viscosity) × 100] was calculated relative to the "50% ethanol viscosity." The obtained viscosity change rates were evaluated according to the following criteria.

[0084] A: Viscosity change rate is 104% or less B: Viscosity change rate greater than 104% but less than 110% C: Viscosity change rate is 110% or more

[0085] [Table 1] [Industrial applicability]

[0086] According to the present invention, it is possible to provide a polyvinyl acetal resin that exhibits little viscosity change even when a solvent with a high proportion of ethanol is used, and has excellent sheet attack resistance, as well as a slurry for ceramic green sheets, a ceramic green sheet, and a multilayer ceramic capacitor using the polyvinyl acetal resin.

Claims

1. In GPC measurements using a differential refractive index detector, the difference in molecular weight distribution calculated from the following formula (1) using the weight-average molecular weight Mw(THF) and number-average molecular weight Mn(THF) obtained when THF is used as the mobile phase, and the weight-average molecular weight Mw(NMP) and number-average molecular weight Mn(NMP) obtained when NMP is used as the mobile phase, is 0.01 or more and 0.45 or less, and １３ A polyvinyl acetal resin having a ratio of the peak integral value of the methylene C atom shown in (a)' of the double-branch shown in (b)' and (c)' of the double-branch shown in formula (a) below to the sum of the peak integral values ​​of the methylene C atoms shown in formula (b)' and (c)' below, obtained by 13C-NMR (nuclear magnetic resonance) measurement, which is 0.30 or more and 0.36 or less, and an acetal group content of 50 mol% or more and 83 mol% or less. [Mw(THF) / Mn(THF)]-[Mw(NMP) / Mn(NMP)] (1) 【Chemistry 1】 In formulas (b) and (c), R is independently hydrogen or a hydrocarbon group having 1 to 20 carbon atoms.

2. The polyvinyl acetal resin according to claim 1, wherein the weight-average molecular weight Mw (THF) is 200,000 or more and 500,000 or less.

3. The polyvinyl acetal resin according to claim 1, wherein the weight-average molecular weight Mw (NMP) is 270,000 or more.

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

5. A ceramic green sheet made using the ceramic green sheet slurry described in claim 4.

6. A multilayer ceramic capacitor obtained using the ceramic green sheet described in claim 5.

Images