Polyvinyl acetal resin

Abstract

The present invention provides: a polyvinyl acetal resin that exhibits, even when a solvent in which a large proportion thereof is ethanol is used, little change in viscosity and excellent sheet attack resistance; a slurry for a ceramic green sheet in which said polyvinyl acetal resin is used; a ceramic green sheet; and a multilayer ceramic capacitor. The present invention pertains to a polyvinyl acetal resin which exhibits: a molecular weight distribution difference of not more than 0.5 as calculated from formula (1) by using, in a GPC measurement using a differential refractometer, the weight average molecular weight Mw (THF) and the number average molecular weight Mn (THF) acquired by using THF in a mobile phase and the weight average molecular weight Mw (NMP) and the number average molecular weight Mn (NMP) acquired by using NMP in a mobile phase; and a ratio of 0.29-0.37 for a peak integrated value of a methylene C atom indicated by (a)' in a diad represented by formula (a) with respect to the total of the peak integrated values of the methylene C atoms indicated by (b)' and (c)' in diads represented by formula (b) and formula (c) as acquired by a 13C-nuclear magnetic resonance (NMR) measurement. (1): [Mw (THF) / Mn (THF)]-[Mw (NMP) / Mn (NMP)] Each R indicated in formula (b) and formula (c) independently represents hydrogen or a hydrocarbon group having 1-20 carbon atoms.

Description

Polyvinyl acetal resin

[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.

[0002] In recent years, electronic components mounted in various electronic devices have become increasingly miniaturized and multilayered, resulting in widespread use of multilayer electronic components such as multilayer circuit boards, laminated coils, and multilayer ceramic capacitors. Multilayer ceramic capacitors, among others, are generally manufactured through the following process. First, a plasticizer, dispersant, etc. are added to a solution of a binder resin, such as polyvinyl butyral resin or poly(meth)acrylate resin, dissolved in an organic solvent. Then, ceramic raw material powder is added and 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 SUS plate, using a doctor blade or reverse roll coater. The resulting ceramic green sheets are then heated to remove volatiles such as the solvent, and the sheets are peeled off from the support to obtain ceramic green sheets. Next, multiple sheets of the resulting ceramic green sheets, each coated with a conductive paste for internal electrodes by screen printing, are alternately stacked and heated and pressed together to form a laminate. Thereafter, the laminate is subjected to a process of thermally decomposing and removing binder resin components and the like contained in the laminate, a so-called degreasing process, and then 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. Also, 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 structural units.

[0004] JP 2011-236304 A International Publication No. 2012 / 023517

[0005] Polyvinyl acetal resins are widely used as binders for ceramic slurries for multilayer ceramic capacitors because of their excellent solubility in mixed solvents of ethanol and toluene. However, toluene is subject to environmental restrictions due to its harmful properties, and its higher boiling point than ethanol requires more energy for solvent drying. Therefore, binders that exhibit good solubility in solvents with a high ethanol content are in demand. However, there is also the issue of sheet attack, which occurs when the binder in the dielectric layer leaches into the electrode layer.

[0006] The present invention aims to provide a polyvinyl acetal resin that exhibits little change in viscosity and excellent sheet attack resistance even when a solvent with a high ethanol content is used, as well as a ceramic green sheet slurry, a ceramic green sheet, and a multilayer ceramic capacitor using the polyvinyl acetal resin. In particular, the present invention makes it possible to suppress the solubility of the polyvinyl acetal resin in organic solvents when it is used to prepare a ceramic green sheet, while the polyvinyl acetal resin is sufficiently soluble when it is used to prepare a ceramic green sheet slurry.

[0007] The present disclosure 1 provides a polymer having a molecular weight distribution difference calculated from the following formula (1) using a weight average molecular weight Mw(THF) and a number average molecular weight Mn(THF) obtained by using THF as a mobile phase in GPC measurement with a differential refractive index detector, and a weight average molecular weight Mw(NMP) and a number average molecular weight Mn(NMP) obtained by using NMP as a mobile phase, of 0.5 or less, and １３ The polyvinyl acetal resin has a ratio of the peak integral value of the methylene C atom shown in (a)' of the diad represented by the following formula (a) to the sum of the peak integral values ​​of the methylene C atoms shown in (b)' and (c)' of the diad represented by the following formula (b) and formula (c), as obtained by C-NMR (nuclear magnetic resonance) measurement, of 0.29 to 0.37: [Mw(THF) / Mn(THF)] - [Mw(NMP) / Mn(NMP)] (1) In Formula (b) and Formula (c), R is each independently hydrogen or a hydrocarbon group having 1 to 20 carbon atoms. Disclosure 2 is the polyvinyl acetal resin according to Disclosure 1, having a hydroxyl group content of 20 mol % to 40 mol %. Disclosure 3 is the polyvinyl acetal resin according to Disclosure 1 or 2, having a weight-average molecular weight Mw(THF) of 200,000 to 700,000. Disclosure 4 is the polyvinyl acetal resin according to any one of Disclosures 1 to 3, having a weight-average molecular weight Mw(NMP) of 270,000 or more. Disclosure 5 is a slurry for a ceramic green sheet, containing the polyvinyl acetal resin according to any one of Disclosures 1 to 4, an organic solvent, and a ceramic powder. Disclosure 6 is a ceramic green sheet obtained using the slurry for a ceramic green sheet according to Disclosure 5. Disclosure 7 is a multilayer ceramic capacitor obtained using the ceramic green sheet according to Disclosure 6. The present invention will be described in detail below.

[0008] As a result of extensive investigation, the present inventors have found that the weight average molecular weight and the number average molecular weight measured by changing the solvent satisfy a predetermined relationship, and １３ The present inventors have found that a polyvinyl acetal resin in which the ratio of the peak integral value of the methylene C atom shown in (a)' of the diad represented by the above formula (a) to the sum of the peak integral values ​​of the methylene C atoms shown in (b)' and (c)' of the diads represented by the above formula (b) and formula (c) is within a predetermined range (the ratio of the peak integral value of a diad consisting of two consecutive chains of constitutional units having a hydroxyl group), as measured by C-NMR, exhibits little change in viscosity even when a solvent with a high proportion of ethanol is used, has excellent sheet attack resistance, and can be used to produce a multilayer ceramic capacitor with excellent reliability, thereby 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 difference within this range, viscosity change can be reduced even when a solvent with a high ethanol content is used. The molecular weight distribution difference is preferably 0.48 or less, more preferably 0.45 or less. Furthermore, the molecular weight distribution difference is preferably 0.001 or more, more preferably 0.01 or more. In the present invention, the molecular weight distribution difference serves as an indicator of a low amount of hydrogen bonds. The 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, and 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 this range, the sheet attack resistance of the obtained ceramic green sheet can be maintained. The 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 this range, the sheet attack resistance of the obtained ceramic green sheet can be maintained. The 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 700,000 or less. By setting it within this range, the elongation of the obtained ceramic green sheet can be maintained. The Mw(THF) is more preferably 220,000 or more, more preferably 500,000 or less, and even 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 270,000 or more and 600,000 or less. By setting it within this range, the elongation of the obtained ceramic green sheet can be maintained. The Mw(NMP) is more preferably 275,000 or more, more preferably 400,000 or less, and even more preferably 300,000 or less.

[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 setting it within this range, the strength of the obtained ceramic green sheet can be maintained. The Mw(THF) is more preferably 75,000 or more and 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 setting it within this range, the strength of the obtained ceramic green sheet can be maintained. The Mw(NMP) is more preferably 75,000 or more and more preferably 200,000 or less.

[0016] The molecular weight distribution difference 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 molecular weight distribution difference can be adjusted by changing the aldehyde introduction temperature, number of introductions, introduction intervals, introduction amount ratio, reaction temperature, reaction time, temperature rise time, temperature rise rate, holding (aging) temperature, and holding (aging) time during the acetalization reaction described below, and particularly by changing the aldehyde introduction temperature, number of introductions, introduction intervals, introduction amount ratio, holding (aging) temperature, and holding (aging) time.

[0017] The polyvinyl acetal resin of the present invention is １３ The ratio of the peak integral value of diads consisting of two consecutive hydroxyl group-containing structural units, as measured by C-NMR, is 0.29 or more and 0.37 or less. By setting it in this range, sheet attack resistance can be improved. The ratio of the peak integral value of diads consisting of two consecutive hydroxyl group-containing structural units is preferably 0.30, more preferably 0.31, and more preferably 0.365, and even more preferably 0.36. If it is equal to or greater than the lower limit, hydrogen bonding by hydroxyl groups is improved, and a ceramic green sheet produced using the polyvinyl acetal resin of the present invention can have low solubility in organic solvents, resulting in good sheet attack resistance. If it is equal to or less than the upper limit, the solubility of the polyvinyl acetal resin in organic solvents is not too low, resulting in good handleability, such as in solution preparation.

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

[0019] １３ Obtained by C-NMR (nuclear magnetic resonance) measurement １３In the C-NMR spectrum, the sum of the peak integral values ​​of the methylene C atoms shown in (b)' and (c)' of the diads represented by the following formulas (b) and (c) can be calculated by the sum of these, i.e., [I(b)' + I(c)'], where I(b)' is the peak integral value to which the methylene C atom shown in (b)' of the diad represented by the following formula (b) belongs, and I(c)' is the peak integral value to which the methylene C atom shown in (c)' of the diad represented by the following formula (c) belongs.

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

[0021] １３ Obtained by C-NMR (nuclear magnetic resonance) measurement １３ In the C-NMR spectrum, the peak integral value of the methylene C atom shown in (a)' of the diad represented by the above formula (a) can be determined from the peak integral value [I(a)'] assigned to the methylene C atom shown in (a)' of the diad represented by the above formula (a).

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

[0023] Regarding the polyvinyl acetal resin of the present invention, １３ Obtained by C-NMR (nuclear magnetic resonance) measurement １３ An example of a C-NMR spectrum (partially enlarged) is shown in FIG. １３ The peaks (a)', (b)', and (c)' shown in the C-NMR spectrum are the peaks assigned to the methylene C atoms shown in (a)', (b)', and (c)' of the diads represented by the above formulas (a), (b), and (c), respectively.

[0024] The proportion of the peak integral value of diads each consisting of two consecutive chains of hydroxyl-containing structural units 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 proportion of the peak integral value of diads each consisting of two consecutive chains of hydroxyl-containing structural units can be adjusted by changing the aldehyde introduction temperature, number of introductions, introduction intervals, reaction temperature, reaction time, temperature rise time, temperature rise rate, holding (aging) temperature, and holding (aging) time during the acetalization reaction described below, and particularly by changing the aldehyde introduction 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 dissolved in a 1:1 mixed solvent of ethanol and toluene is measured using a Brookfield viscometer at a solution temperature of 20°C. From the viewpoint of improving tensile strength, the viscosity is more preferably 65 mPa·s or more, and even more preferably 70 mPa·s or more. From the viewpoint of improving the viscosity stability of the ceramic slurry composition, the viscosity is more preferably 300 mPa·s or less, and even more preferably 150 mPa·s or less. As the Brookfield viscometer, for example, a TVB-10 viscometer manufactured by Toki Sangyo Co., Ltd. can be used. Furthermore, the rotor and rotation speed during viscosity measurement are preferably adjusted appropriately depending on the solution viscosity. For example, it is preferable to measure using SPINDLE Nos. 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 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.

[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]

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

[0030] In the above formula (3), R １ 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.

[0031] In the polyvinyl acetal resin of the present invention, the content of the structural unit having an acetal group represented by the above formula (3) (hereinafter also referred to as the "acetal group amount") is preferably 50 mol% in lower limit and 83 mol% in upper limit. When the acetal group amount is 50 mol% or more, the solubility in organic solvents can be improved. When the acetal group amount is 83 mol% or less, the polyvinyl acetal resin can have excellent tensile strength. The acetal group amount is more preferably 52 mol% in lower limit and 81 mol% in upper limit, and even more preferably 55 mol% in lower limit and 80 mol% in upper limit. That is, the acetal group amount is preferably 50 to 83 mol%, more preferably 52 to 81 mol%, and even more preferably 55 to 80 mol%. The acetal group amount may be, for example, １The amount of acetal groups can be measured by H-NMR. Since the acetal groups of the polyvinyl acetal resin are obtained by acetalizing two hydroxyl groups of polyvinyl alcohol, the amount of acetal groups is calculated by counting the two acetalized hydroxyl groups.

[0032] In the polyvinyl acetal resin of the present invention, the content of the structural unit having a hydroxyl group represented by the general formula (4) (hereinafter also referred to as the "hydroxyl group amount") is preferably 20 mol% at the lower limit and 40 mol% at the upper limit. When the hydroxyl group amount is 20 mol% or more, the polyvinyl acetal resin can have high toughness. When the hydroxyl group amount is 40 mol% or less, the solubility in organic solvents can be sufficiently improved. The hydroxyl group amount is more preferably 28 mol% at the lower limit and 35 mol% at the upper limit, and even more preferably 29 mol% at the lower limit and 34 mol% at the upper limit. That is, the hydroxyl group amount is preferably 20 to 40 mol%, more preferably 28 to 35 mol%, and even more preferably 29 to 34 mol%. The hydroxyl group amount may be, for example, １ It can be measured by H-NMR.

[0033] In the polyvinyl acetal resin of the present invention, the content of the structural unit having an acetyl group represented by the general formula (5) (hereinafter also referred to as the "acetyl group amount") is preferably 0.1 mol% at the lower limit and 22.0 mol% at the upper limit. When the acetyl group amount is 0.1 mol% or more, it is possible to suppress the increase in viscosity of the slurry for the ceramic green sheet due to intramolecular and intermolecular hydrogen bonding of hydroxyl groups in the polyvinyl acetal resin. When the acetyl group amount is 22.0 mol% or less, it is possible to improve the handleability of the polyvinyl acetal resin without excessively increasing its flexibility. The acetyl group amount is more preferably 0.5 mol% at the lower limit and 15.0 mol% at the upper limit. That is, the acetyl group amount is preferably 0.1 to 22.0 mol%, and more preferably 0.5 to 15.0 mol%. The acetyl group amount may be, for example, １ It can be measured by H-NMR.

[0034] The polyvinyl acetal resin of the present invention has an average degree of polymerization of preferably 500, more preferably 600, and even more preferably 800, from the viewpoint of maintaining mechanical strength when producing a thin film ceramic green sheet. Furthermore, from the viewpoint of solubility in organic solvents and dissolution viscosity, the average degree of polymerization is preferably 10,000, more preferably 9,000, and even more preferably 8,000. That is, the average degree of polymerization is preferably 500 to 10,000, more preferably 600 to 9,000, and even more preferably 800 to 8,000. 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 be measured in accordance with JIS K 6726.

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

[0036] The polyvinyl alcohol resin can be, 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. The polyvinyl alcohol resin can be fully saponified, but it 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; it can also be a partially saponified polyvinyl alcohol resin. Furthermore, the polyvinyl alcohol resin can also be 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. Examples of the polyvinyl acetate resin include ethylene-vinyl acetate copolymers.

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

[0038] The acetalization is preferably carried out in an aqueous solvent, a mixed solvent of water and a water-compatible organic solvent, or an organic solvent. Examples of the water-compatible organic solvent include alcohol-based organic solvents. 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-based 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 solvents include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methylcyclohexanone, benzophenone, and acetophenone. Examples of the lower paraffin solvents include hexane, pentane, octane, cyclohexane, and decane. Examples of the ether solvents include diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol diethyl ether. Examples of the amide solvents include N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and acetanilide. Examples of the amine solvents 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.

[0039] 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.

[0040] Examples of the aldehyde used in the acetalization include aldehydes having a chain 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 aldehyde used in the acetalization reaction is not particularly limited, and examples 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 these, preferred aldehydes are formaldehyde, acetaldehyde, butylaldehyde, 2-ethylhexylaldehyde, and n-nonylaldehyde, which have excellent acetalization reactivity and can provide a sufficient internal plasticizing effect to the resulting resin, thereby imparting good flexibility. Furthermore, formaldehyde, acetaldehyde, and butylaldehyde are more preferred because they can provide an adhesive composition that is particularly excellent in impact resistance and adhesion to metals.

[0041] 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 from 50 mol % to 95 mol %, more preferably from 55 mol % to 90 mol %, based on 100 mol % of polyvinyl alcohol, because this allows the acetalization reaction to proceed efficiently and makes it easy to remove unreacted aldehyde.

[0042] In the acetalization, the aldehyde is preferably added in multiple portions. The aldehyde is preferably added twice. The ratio of the amount of aldehyde added in the first addition to the total amount of aldehyde is preferably 1% to 50%, more preferably 2% to 40%, and even more preferably 5% to 30% of the total amount. When the aldehyde is added in multiple portions, the temperature during the first addition is preferably 15°C to 60°C, more preferably 20°C to 55°C, and even more preferably 25°C to 50°C. The temperature during the final addition is preferably 10°C to 50°C, more preferably 15°C to 45°C, and even more preferably 20°C to 40°C. Furthermore, the interval between the first and last addition is preferably 5 minutes or more and 180 minutes or less, more preferably 10 minutes or more and 120 minutes or less, and even more preferably 60 minutes or less.

[0043] In the acetalization, it is preferable to add the aldehyde, carry out a reaction at a predetermined temperature (reaction step), and then raise the temperature and maintain the temperature at the predetermined temperature (aging step). The time from the final addition to the start of temperature rise (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 reaction step (reaction temperature) is preferably in the same range as the temperature at the time of the final addition. The temperature rise time from the end of the reaction step to the aging step is preferably 30 minutes or more and 500 minutes or less, more preferably 60 minutes or more and 400 minutes or less, and even more preferably 150 minutes or more and 240 minutes or less. The temperature rise rate from the start of temperature rise to the aging step is preferably 0.1°C / min or more and 2°C / min or less, and more preferably 0.3°C / min or less.

[0044] The retention time in the aging step is preferably 0.5 hours or more and 6 hours or less, more preferably 1 hour or more and 5 hours or less, and even more preferably 4 hours or less. The retention temperature in the aging step is preferably 48° C. or more and 80° C. or less, more preferably 50° C. or more and 78° C. or less, and even more preferably 55° C. or more and 75° C. or less. By setting the retention time and retention temperature as described above, the ratio of the peak integral value of diads consisting of two chains of structural units having a hydroxyl group can be set within a predetermined range.

[0045] The polyvinyl acetal resin of the present invention and a plasticizer can be used to form a resin composition for a ceramic green sheet. The resin composition for a ceramic green sheet may contain other 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.

[0046] 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.

[0047] The resin composition for ceramic green sheets contains a plasticizer. Addition of the plasticizer can significantly improve the mechanical strength and flexibility of the resulting ceramic green sheets. Examples of the plasticizer 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-ethylbutyrate, tetraethylene glycol-di-2-ethylbutyrate, tetraethylene glycol-di-heptanoate, and triethylene glycol-di-heptanoate.

[0048] 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 in lower limit, more preferably 8.5 parts by weight in lower limit, and preferably 18 parts by weight in upper limit, more preferably 13.5 parts by weight in upper limit.

[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 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.

[0051] 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, but if the content is too low, the solubility required for kneading is difficult to exhibit. On the other hand, if the content is too high, the viscosity of the ceramic green sheet slurry 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.

[0052] Examples of the ceramic powder include powders of metal or nonmetal oxides or non-oxides used in ceramic production. These powders may be single compositions, compounds, or mixtures. The constituent elements of the metal oxides or non-oxides, both cations and anions, may be single elements or multiple elements, and may further contain additives added to improve the properties of the oxides or non-oxides. Specific examples include oxides, carbides, nitrides, borides, sulfides, etc. 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, Ni, etc. Specific examples of oxide powders containing multiple metal elements, commonly referred to as double oxides, can be classified based on their crystal structure, such as NaNbO, which has a perovskite structure. ３ , SrZrO ３ , PbZrO ３ , SrTiO ３ , BaZrO ３ , PbTiO ３ , BaTiO ３ Examples of materials that have a spinel structure include MgAl ２ O ４ , ZnAl ２ O ４ , CoAl ２ O ４ , NiAl ２ O ４ , MgFe ２ O ４ Examples of materials with an ilmenite structure include MgTiO ３ , MnTiO ３ , FeTiO ３ As a material having a garnet structure, GdGa ５ O １２ , Y ６ Fe ５ O １２ Among these, the modified polyvinyl acetal resin of the present invention is BaTiO ３ It exhibits high properties compared to ceramic green sheets mixed with powder.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] The ceramic green sheet slurry is applied, followed by heating and drying to obtain a ceramic green sheet. A ceramic electronic component can be manufactured using the ceramic green sheet. For example, a ceramic electronic component can be manufactured by carrying out a step of applying an electrode layer paste to the surface of the ceramic green sheet, and a step of stacking the ceramic green sheets on which the electrode layers have been formed, thermocompression bonding the resulting laminate, and then degreasing and firing the resulting laminate.

[0058] 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.

[0059] 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 one aspect of the present invention.

[0060] The method for producing the ceramic electronic component includes a step of applying an electrode layer paste to the surface of the ceramic green sheet. The electrode layer paste can be obtained by dissolving, for example, a polyvinyl acetal resin, ethyl cellulose, or acrylic resin as a binder resin in an organic solvent and dispersing a conductive powder or the like. These resins may be used alone or in combination. An electrode layer paste containing a polyvinyl acetal resin is preferred because it exhibits excellent adhesion to the ceramic green sheet during the thermocompression bonding step.

[0061] In the method for producing a ceramic electronic component, the ceramic green sheets having electrode layers formed thereon are prepared as described above, and then ceramic green sheets having electrode layers formed thereon that are prepared in the same manner are stacked and thermocompression-bonded 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. Note that the thermocompression-bonding step and the steps of degreasing and firing the laminate are not particularly limited, and conventionally known methods can be used.

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

[0063] Regarding the polyvinyl acetal resin of the present invention, １３ Obtained by C-NMR (nuclear magnetic resonance) measurement １３ FIG. 1 is a partially enlarged view showing an example of a C-NMR spectrum.

[0064] The present invention will be explained 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 300 g of pure water and stirred at 90°C for approximately 2 hours to dissolve the resin. This solution was cooled to 30°C, and 220 g of 35 wt% hydrochloric acid and 30 g of n-butylaldehyde were added thereto (first addition). The solution was then cooled to 20°C, and 30 minutes after the first addition, 130 g of n-butylaldehyde was further added thereto (second addition). The solution was then maintained for 0.5 hours to carry out an acetalization reaction, after which the temperature was increased at a rate of 0.2°C / min (temperature increase time: 150 minutes) and maintained at 55°C for 3 hours (aging step) to complete the reaction. The resulting mixture was neutralized, washed with water, and dried in a conventional manner to obtain a white powder of polyvinyl acetal resin.

[0066] Example 2 3000 g of pure water was added to 300 g of polyvinyl alcohol resin (average degree of polymerization: 1700, degree of saponification: 99.0 mol%), and the mixture was stirred at 90°C for approximately 2 hours to dissolve the resin. This solution was cooled to 30°C, and 220 g of 35 wt% hydrochloric acid and 40 g of n-butylaldehyde were added thereto (first addition). The solution was then cooled to 20°C, and 30 minutes after the first addition, 120 g of n-butylaldehyde was further added thereto (second addition). The mixture was then maintained for 0.5 hours to carry out an acetalization reaction, after which the temperature was increased at a rate of 0.2°C / min (temperature increase time: 150 minutes) and maintained 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 300 g of pure water and stirred at 90°C for approximately 2 hours to dissolve. This solution was cooled to 35°C, and 220 g of hydrochloric acid with a concentration of 35 wt% and 10 g of n-butylaldehyde were added thereto (first addition). The solution was then cooled to 30°C, and 15 minutes after the first addition, 150 g of n-butylaldehyde was further added thereto (second addition). The solution was then maintained for 0.5 hours to carry out an acetalization reaction, and then heated at a temperature increase rate of 0.2°C / min (temperature increase time: 100 minutes) and maintained at 55°C for 3 hours (aging step) to complete the reaction. The solution 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 300 g of pure water and stirred at 90°C for approximately 2 hours to dissolve the resin. This solution was cooled to 30°C, and 220 g of 35 wt% hydrochloric acid and 30 g of n-butylaldehyde were added thereto (first addition). The solution was then cooled to 20°C, and 30 minutes after the first addition, 130 g of n-butylaldehyde was further added thereto (second addition). The solution was then maintained for 0.5 hours to carry out an acetalization reaction, after which the temperature was increased at a rate of 0.2°C / min (temperature increase time: 180 minutes) and maintained at 60°C for 3 hours (aging step) to complete the reaction. The resulting mixture was neutralized, washed with water, and dried in a conventional manner 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 300 g of pure water and stirred at 90°C for approximately 2 hours to dissolve. This solution was cooled to 35°C, and 220 g of hydrochloric acid with a concentration of 35 wt% and 10 g of n-butylaldehyde were added thereto (first addition). The solution was then cooled to 30°C, and 15 minutes after the first addition, 150 g of n-butylaldehyde was further added thereto (second addition). The solution was then maintained for 0.5 hours to carry out an acetalization reaction, and then heated at a temperature increase rate of 0.2°C / min (temperature increase time: 120 minutes) and maintained at 60°C for 3 hours (aging step) to complete the reaction. The solution 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 300 g of pure water and stirred at 90°C for approximately 2 hours to dissolve. This solution was cooled to 45°C, and 220 g of hydrochloric acid with a concentration of 35 wt% and 10 g of n-butylaldehyde were added thereto (first addition). The solution was then cooled to 40°C, and 10 minutes after the first addition, 150 g of n-butylaldehyde was further added thereto (second addition). The solution was then maintained for 0.5 hours to carry out an acetalization reaction, and then heated at a temperature increase rate of 0.2°C / min (temperature increase time: 90 minutes) and maintained at 55°C for 3 hours (aging step) to complete the reaction. The solution 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 300 g of pure water and stirred at 90°C for approximately 2 hours to dissolve. This solution was cooled to 35°C, and 220 g of hydrochloric acid with a concentration of 35 wt% and 10 g of n-butylaldehyde were added thereto (first addition). The solution was then cooled to 30°C, and 15 minutes after the first addition, 150 g of n-butylaldehyde was further added thereto (second addition). The solution was then maintained for 0.5 hours to carry out an acetalization reaction, and then heated at a temperature increase rate of 0.2°C / min (temperature increase time: 200 minutes) and maintained at 70°C for 0.5 hours (aging step) to complete the reaction. The solution was then neutralized, washed with water, and dried by conventional methods to obtain a white powder of polyvinyl acetal resin.

[0072] Example 8 300 g of polyvinyl alcohol resin (average degree of polymerization: 1700, degree of saponification: 99.1 mol%) was added to 300 g of pure water and stirred at 90°C for approximately 2 hours to dissolve the resin. This solution was cooled to 30°C, and 220 g of 35 wt% hydrochloric acid and 30 g of n-butylaldehyde were added thereto (first addition). The solution was then cooled to 20°C, and 30 minutes after the first addition, 120 g of n-butylaldehyde was further added thereto (second addition). The solution was then maintained for 0.5 hours to carry out an acetalization reaction, after which the temperature was increased at a rate of 0.2°C / min (temperature increase time: 150 minutes) and maintained at 50°C for 3 hours (aging step) to complete the reaction. The resulting mixture was neutralized, washed with water, and dried by conventional methods to obtain a white powder of polyvinyl acetal resin.

[0073] Example 9 300 g of polyvinyl alcohol resin (average degree of polymerization: 1700, degree of saponification: 99.0 mol%) was added to 300 g of pure water and stirred at 90°C for approximately 2 hours to dissolve. This solution was cooled to 30°C, and 220 g of 35 wt% hydrochloric acid and 30 g of n-butylaldehyde were added thereto (first addition). The solution was then cooled to 20°C, and 30 minutes after the first addition, 150 g of n-butylaldehyde was further added (second addition). The solution was then maintained for 0.5 hours to carry out an acetalization reaction, after which the temperature was increased at a rate of 0.2°C / min (temperature increase time: 225 minutes) and maintained at 65°C for 3 hours (aging step) to complete the reaction. The solution was then neutralized, washed with water, and dried by conventional methods to obtain a white powder of polyvinyl acetal resin.

[0074] Example 10 300 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 95 mol%) was added to 300 g of pure water and stirred at 90°C for approximately 2 hours to dissolve. This solution was cooled to 30°C, and 220 g of 35 wt% hydrochloric acid and 30 g of n-butylaldehyde were added thereto (first addition). The solution was then cooled to 20°C, and 30 minutes after the first addition, 110 g of n-butylaldehyde was further added thereto (second addition). The mixture was then maintained for 0.5 hours to carry out an acetalization reaction, after which the temperature was increased at a rate of 0.2°C / min (temperature increase time 200 minutes) and maintained 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.

[0075] Example 11 300 g of polyvinyl alcohol resin (average degree of polymerization: 2400, degree of saponification: 99.0 mol%) was added to 300 g of pure water and stirred at 90°C for approximately 2 hours to dissolve the resin. This solution was cooled to 30°C, and 220 g of 35 wt% hydrochloric acid and 30 g of n-butylaldehyde were added thereto (first addition). The solution was then cooled to 20°C, and 30 minutes after the first addition, 130 g of n-butylaldehyde was further added thereto (second addition). The solution was then maintained for 0.5 hours to carry out an acetalization reaction, after which the temperature was increased at a rate of 0.2°C / min (temperature increase time: 165 minutes) and maintained at 55°C for 3 hours (aging step) to complete the reaction. The resulting mixture was neutralized, washed with water, and dried by conventional methods to obtain a white powder of polyvinyl acetal resin.

[0076] Example 12 3000 g of pure water was added to 300 g of polyvinyl alcohol resin (average degree of polymerization: 4000, degree of saponification: 99.0 mol%), and the mixture was stirred at 90°C for approximately 2 hours to dissolve the resin. This solution was cooled to 30°C, and 220 g of hydrochloric acid with a concentration of 35 wt% and 30 g of n-butylaldehyde were added thereto (first addition). The solution was then cooled to 20°C, and 30 minutes after the first addition, 130 g of n-butylaldehyde was further added thereto (second addition). The mixture was then maintained for 0.5 hours to carry out an acetalization reaction, after which the temperature was increased at a rate of 0.2°C / min (temperature increase time: 165 minutes) and maintained at 55°C for 3 hours (aging step) to complete the reaction. The mixture was then neutralized, washed with water, and dried in a conventional manner to obtain a white powder of polyvinyl acetal resin.

[0077] Example 13 3000 g of pure water was added to 300 g of polyvinyl alcohol resin (average degree of polymerization: 4000, degree of saponification: 98.8 mol%), and the mixture was stirred at 90°C for approximately 2 hours to dissolve the resin. This solution was cooled to 30°C, and 220 g of hydrochloric acid with a concentration of 35 wt% and 30 g of n-butylaldehyde were added thereto (first addition). The solution was then cooled to 20°C, and 30 minutes after the first addition, 110 g of n-butylaldehyde and 20 g of acetaldehyde were further added thereto (second addition). The mixture was then maintained for 0.5 hours to carry out an acetalization reaction, and then heated at a temperature increase rate of 0.2°C / min (temperature increase time: 165 minutes) and maintained 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.

[0078] Comparative Example 1 3000 g of pure water was added to 300 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 99.4 mol%), and the mixture was stirred at 90°C for approximately 2 hours to dissolve the resin. This solution was cooled to 20°C, and 220 g of hydrochloric acid with a concentration of 35 wt% and 160 g of n-butyl aldehyde were added to the mixture. The mixture was then maintained for 0.5 hours to carry out an acetalization reaction, and the temperature was increased at a rate of 0.2°C / min (heating time: 120 minutes). The mixture was then maintained 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.

[0079] Comparative Example 2 3000 g of pure water was added to 300 g of polyvinyl alcohol resin (average degree of polymerization: 1700, degree of saponification: 99.4 mol%), and the mixture was stirred at 90°C for approximately 2 hours to dissolve the resin. This solution was cooled to 20°C, and 220 g of hydrochloric acid with a concentration of 35 wt% and 160 g of n-butyl aldehyde were added to the mixture. The mixture was then maintained for 0.5 hours to carry out an acetalization reaction, and the temperature was increased at a rate of 0.2°C / min (heating time: 50 minutes) and maintained 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.

[0080] Comparative Example 3 3000 g of pure water was added to 300 g of polyvinyl alcohol resin (average degree of polymerization: 1700, degree of saponification: 99.1 mol%), and the mixture was stirred at 90°C for approximately 2 hours to dissolve the resin. This solution was cooled to 30°C, and 220 g of 35 wt% hydrochloric acid and 130 g of n-butylaldehyde were added thereto (first addition). The solution was then cooled to 20°C, and 30 minutes after the first addition, 30 g of n-butylaldehyde was further added thereto (second addition). The mixture was then maintained for 0.5 hours to carry out an acetalization reaction, after which the temperature was increased at a rate of 0.2°C / min (temperature increase time: 50 minutes) and the mixture was maintained 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.

[0081] Comparative Example 4 300 g of polyvinyl alcohol resin (average degree of polymerization: 1700, degree of saponification: 99.2 mol%) was added to 300 g of pure water and stirred at 90°C for approximately 2 hours to dissolve. This solution was cooled to 30°C, and 220 g of 35 wt% hydrochloric acid and 130 g of n-butylaldehyde were added thereto (first addition). The solution was then cooled to 20°C, and 30 minutes after the first addition, 30 g of n-butylaldehyde was further added (second addition). The solution was then maintained for 0.5 hours to carry out an acetalization reaction, after which the temperature was increased at a rate of 0.2°C / min (temperature increase time: 200 minutes) and maintained at 60°C for 5 hours (aging step) to complete the reaction. The solution was then neutralized, washed with water, and dried by conventional methods to obtain a white powder of polyvinyl acetal resin.

[0082] Comparative Example 5 300 g of polyvinyl alcohol resin (average degree of polymerization: 1700, degree of saponification: 99.0 mol%) was added to 300 g of pure water and stirred at 90°C for approximately 2 hours to dissolve. This solution was cooled to 30°C, and 220 g of hydrochloric acid with a concentration of 35 wt% and 80 g of n-butylaldehyde were added thereto (first addition). The solution was then cooled to 20°C, and 30 minutes after the first addition, 80 g of n-butylaldehyde was further added (second addition). The solution was then maintained for 0.5 hours to carry out an acetalization reaction, and then heated at a temperature increase rate of 0.2°C / min (temperature increase time: 165 minutes) and maintained 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.

[0083] Comparative Example 6 3000 g of pure water was added to 300 g of polyvinyl alcohol resin (average degree of polymerization: 1700, degree of saponification: 99.0 mol%), and the mixture was stirred at 90°C for approximately 2 hours to dissolve the resin. This solution was cooled to 60°C, and 220 g of hydrochloric acid with a concentration of 35 wt% and 30 g of n-butylaldehyde were added thereto (first addition). The solution was then cooled to 50°C, and 30 minutes after the first addition, 130 g of n-butylaldehyde was further added thereto (second addition). The mixture was then maintained for 0.5 hours to carry out an acetalization reaction, and then heated at a temperature increase rate of 0.2°C / min (temperature increase time: 100 minutes) and maintained at 70°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.

[0084] Comparative Example 7 300 g of polyvinyl alcohol resin (average degree of polymerization: 1700, degree of saponification: 99.5 mol%) was added to 300 g of pure water and stirred at 90°C for approximately 2 hours to dissolve. This solution was cooled to 30°C, and 220 g of hydrochloric acid with a concentration of 35 wt% and 30 g of n-butylaldehyde were added thereto (first addition). The solution was then cooled to 20°C, and 30 minutes after the first addition, 110 g of n-butylaldehyde was further added thereto (second addition). The solution was then maintained for 0.5 hours to carry out an acetalization reaction, and then heated at a temperature increase rate of 0.2°C / min (temperature increase time: 150 minutes) and maintained at 50°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.

[0085] Comparative Example 8 3000 g of pure water was added to 300 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 99.1 mol%), and the mixture was stirred at 90°C for approximately 2 hours to dissolve the resin. This solution was cooled to 30°C, and 220 g of hydrochloric acid with a concentration of 35 wt% and 30 g of n-butylaldehyde were added thereto (first addition). The solution was then cooled to 20°C, and 30 minutes after the first addition, 160 g of n-butylaldehyde was further added thereto (second addition). The mixture was then maintained for 0.5 hours to carry out an acetalization reaction, and then heated at a temperature increase rate of 0.2°C / min (temperature increase time 225 minutes) and maintained at 65°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.

[0086] Comparative Example 9 300 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 76 mol%) was added to 300 g of pure water and stirred at 90°C for approximately 2 hours to dissolve. This solution was cooled to 30°C, and 220 g of hydrochloric acid with a concentration of 35 wt% and 30 g of n-butylaldehyde were added thereto (first addition). The solution was then cooled to 20°C, and 30 minutes after the first addition, 95 g of n-butylaldehyde was further added thereto (second addition). The solution was then maintained for 0.5 hours to carry out an acetalization reaction, and then heated at a temperature increase rate of 0.2°C / min (temperature increase time 200 minutes) and maintained 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.

[0087] Comparative Example 10 300 g of polyvinyl alcohol resin (average degree of polymerization 4000, degree of saponification 99.0 mol%) was added to 300 g of pure water and stirred at 90°C for approximately 2 hours to dissolve. This solution was cooled to 20°C, and 220 g of hydrochloric acid with a concentration of 35 wt% and 160 g of n-butyl aldehyde were added thereto. The mixture was then maintained for 0.5 hours to carry out an acetalization reaction. The temperature was then increased at a rate of 0.2°C / min (heating time: 125 minutes), and the mixture was maintained at 45°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.

[0088] (Evaluation) The polyvinyl acetal resins obtained in the examples and comparative examples were evaluated as follows. The results are shown in Tables 1 and 2.

[0089] (1) Evaluation of Polyvinyl Acetal Resin (1-1) Amount of Acetal Group, Amount of Hydroxyl Group, and Amount of Acetyl Group The obtained polyvinyl acetal resin was measured using an AV400 spectrometer (manufactured by Bruker). １ H-NMR measurement was carried out to calculate the amount of acetal groups, hydroxyl groups, and acetyl groups. ６ The solution was dissolved in water to a concentration of 1.6% by weight to prepare a measurement solution. １ H-NMR measurements were carried out at 80°C.

[0090] (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 wt%, 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 a GPC apparatus HLC-8420 (manufactured by Tosoh Corporation), THF as the mobile phase, a Bryce-type double-pass refractive index detector (manufactured by Tosoh Corporation) as the detector, and a TSKgel Super HZM-H (manufactured by Tosoh Corporation) as the column. The obtained measurement results were calibrated using a molecular weight calibration curve prepared using monodisperse polystyrene standard samples, and the number average molecular weight Mn (THF) and weight average molecular weight Mw (THF) were obtained. 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 apparatus GPC-101 (Shodex Corporation), NMP as the mobile phase, a differential refractive index detector RI-715 (Shodex Corporation) as the detector, and an LF-804 (Shodex Corporation) 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, which was taken as the molecular weight distribution difference.

[0091] (1-3) Proportion of Peak Integration Value of Diads Consisting of Distretched Hydroxyl Group-Containing Structural Units in Polyvinyl Acetal Resin (Proportion of Distretched Hydroxyl Group-Containing Structural Units) The obtained polyvinyl acetal resin was analyzed using an AVANCE 600 spectrometer and a CryoProbe (manufactured by Bruker). １３ By carrying out C-NMR measurement, the ratio of the peak integral value of the triad unit consisting of two consecutive chains of structural units having a hydroxyl group in the polyvinyl acetal resin was measured. The details of the peak integral value measurement are as described above. The obtained polyvinyl acetal resin was dissolved in DMSO-D ６ A relaxation reagent (chromium (III) acetylacetate) was added to prepare a measurement solution.１３ C-NMR measurements were performed at 80°C, power gated. １ Measurements were performed in H decoupling mode.

[0092] (2) Evaluation of polyvinyl acetal resin sheet 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, to obtain a polyvinyl acetal resin composition. The obtained polyvinyl acetal resin 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 produce a polyvinyl acetal resin sheet.

[0093] (2-1) Sheet Attack Resistance Evaluation (Solvent Elution) The obtained polyvinyl acetal resin sheet was cut into a 1.5 cm x 10 cm square and accurately weighed. The test piece was then immersed in 10 ml of dihydroterpineol acetate at 23 ° C. for 1 minute. The test piece was then removed and dried at 150 ° C. for 6 hours to completely dry the solvent. After removing it from the dryer, it was left at room temperature for 1 hour and then weighed. The amount of resin eluted was calculated from the change in weight before and after the test, and the elution rate was calculated from the ratio of the elution amount to the weight of the test piece before the test, and evaluated according to the following criteria. A lower elution rate indicates better sheet attack resistance.

[0094] A: Dissolution rate is 4.1% or less. B: Dissolution rate is more than 4.1% and 4.7% or less. C: Dissolution rate is more than 4.7%.

[0095] (3) Viscosity Change Rate with Change in Ethanol Ratio A 5% by mass solution of a 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 Brookfield viscometer at a solution temperature of 20°C (50% ethanol viscosity). As the Brookfield viscometer, for example, a TVB-10 viscometer manufactured by Toki Sangyo Co., Ltd. can be used. Furthermore, the rotor and rotation speed during viscosity measurement are preferably adjusted appropriately depending on the viscosity of the solution. For example, measurements are preferably performed using SPINDLE Nos. M1 to M4 at a rotation speed in the range of 0.3 to 100 rpm. Furthermore, the viscosity (70% ethanol viscosity) 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" was also measured under the same conditions, and the viscosity change rate of the "70% ethanol viscosity" relative to the "50% ethanol viscosity" [(70% ethanol viscosity / 50% ethanol viscosity) × 100] was calculated. The obtained viscosity change rate was evaluated according to the following criteria.

[0096] A: Viscosity change rate is 104% or less B: Viscosity change rate is more than 104% and less than 110% C: Viscosity change rate is 110% or more

[0097]

[0098]

[0099] According to the present invention, it is possible to provide a polyvinyl acetal resin that exhibits little change in viscosity and excellent sheet attack resistance even when a solvent with a high proportion of ethanol is used, as well as a slurry for a ceramic green sheet, a ceramic green sheet, and a multilayer ceramic capacitor that use the polyvinyl acetal resin.

Claims

1. In GPC measurement 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 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 0.5 or less, and １３ A polyvinyl acetal resin, in which the ratio of the peak integral value of the methylene C atom shown in (a)' of a diad represented by the following formula (a) to the sum of the peak integral values ​​of the methylene C atoms shown in (b)' and (c)' of diads represented by the following formulas (b) and (c), obtained by C-NMR (nuclear magnetic resonance) measurement, is 0.29 or more and 0.37 or less: [Mw(THF) / Mn(THF)] - [Mw(NMP) / Mn(NMP)] (1) In formula (b) and formula (c), R is each independently hydrogen or a hydrocarbon group having 1 to 20 carbon atoms.

2. The polyvinyl acetal resin according to claim 1, wherein the amount of hydroxyl groups is from 20 mol % to 40 mol %.

3. The polyvinyl acetal resin according to claim 1 or 2, having a weight average molecular weight Mw(THF) of 200,000 or more and 700,000 or less.

4. The polyvinyl acetal resin according to any one of claims 1 to 3, having a weight average molecular weight Mw(NMP) of 270,000 or more.

5. A slurry for ceramic green sheets, comprising the polyvinyl acetal resin according to any one of claims 1 to 4, an organic solvent, and ceramic powder.

6. A ceramic green sheet obtained by using the slurry for ceramic green sheet according to claim 5.

7. A multilayer ceramic capacitor obtained by using the ceramic green sheet according to claim 6.

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