Polyvinyl acetal resin

Abstract

The present invention provides a polyvinyl acetal resin capable of producing ceramic green sheets with high mechanical strength, electrical properties, and excellent resistance to sheet attack, as well as a slurry for ceramic green sheets, a ceramic green sheet, and a multilayer ceramic capacitor using the polyvinyl acetal resin. [Solution] A polyvinyl acetal resin having a total Cr and Fe content of 10 μg / kg or more and 400 μg / kg or less.

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] On the other hand, in recent years, with the increasing multi-functionality and miniaturization of electronic devices, there has been a demand for multilayer ceramic capacitors to be both high-capacity and small-sized, and further thinning of ceramic green sheets is also required. However, when the polyvinyl acetal resin described in Patent Documents 1 and 2 is used in the manufacture of multilayer ceramic capacitors, there is a problem in that the electrical characteristics of the multilayer ceramic capacitor deteriorate due to defects and impurities in the dielectric layer. Furthermore, the resulting ceramic green sheets may have insufficient strength, leading to problems such as tearing due to insufficient strength when peeling them off the release sheet, resulting in a reduced yield. 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] An object of the present invention is to provide a polyvinyl acetal resin capable of obtaining a ceramic green sheet having high mechanical strength, excellent electrical properties, and excellent sheet attack resistance, a slurry for a ceramic green sheet using the polyvinyl acetal resin, a ceramic green sheet, and a multilayer ceramic capacitor.

Means for Solving the Problems

[0007] The present disclosure 1 is a polyvinyl acetal resin in which the total content of Cr and Fe is 10 μg / kg or more and 400 μg / kg or less. The present disclosure 2 is the polyvinyl acetal resin according to the present disclosure 1, in which the content of Cr is 5 μg / kg or more and 100 μg / kg or less, and the content of Fe is 5 μg / kg or more and 300 μg / kg or less. The present disclosure 3 is the polyvinyl acetal resin according to the present disclosure 1 or 2, further containing Mg, and the content of Mg is 0 μg / kg or more and 400 μg / kg or less. The present disclosure 4 is in the IR absorption spectrum measured by an infrared spectrophotometer, when the minimum transmittance of the peak within the range of wave numbers 3050 to 3750 cm -1 is taken as X (%), among the wave numbers indicating the transmittance a (%) satisfying [100 - (100 - X) / 2], when the wave number on the low wave number side is A and the wave number on the high wave number side is B, the polyvinyl acetal resin according to any one of the present disclosures 1 to 3, which has a hydroxyl group amount conversion wave number width obtained by the formula (1) of 8.31 or more using the hydroxyl group amount measured by 1 1H-NMR. Hydroxyl group amount conversion wave number width (cm -1 / mol%) = [(B - A) / hydroxyl group amount] (1) The present disclosure 5 is the polyvinyl acetal resin according to any one of the present disclosures 1 to 4, in which the hydroxyl group amount conversion wave number width obtained by the formula (1) is 8.45 or more. The present disclosure 6 is the polyvinyl acetal resin according to any one of the present disclosures 1 to 5, in which the acetal group amount is 50 mol% or more and 83 mol% or less. The present disclosure 7 is the polyvinyl acetal resin according to any one of the present disclosures 1 to 6, having a hydroxyl group content of 18 mol% or more and 40 mol% or less. The present disclosure 8 is a slurry for a ceramic green sheet, containing the polyvinyl acetal resin according to any one of the present disclosures 1 to 7, an organic solvent, and ceramic powder. The present disclosure 9 is a ceramic green sheet obtained by using the slurry for a ceramic green sheet according to the present disclosure 8. The present disclosure 10 is a multilayer ceramic capacitor obtained by using the ceramic green sheet according to the present disclosure 9. The present invention will be described in detail below.

[0008] As a result of intensive studies, the inventors of the present invention have found that a polyvinyl acetal resin having a total content of Cr and Fe within a predetermined range can produce a ceramic green sheet having high mechanical strength, electrical properties, and excellent sheet attack resistance, and have thus completed the present invention.

[0009] The polyvinyl acetal resin of the present invention has a total content of Cr and Fe of 10 μg / kg or more and 400 μg / kg or less. By having the total content of Cr and Fe within the above range, a ceramic green sheet having high mechanical strength, electrical properties, and excellent sheet attack resistance can be obtained. The total content of Cr and Fe is preferably 20 μg / kg or more, more preferably 30 μg / kg or more, and even more preferably 40 μg / kg or more. Also, the total content of Cr and Fe is preferably 300 μg / kg or less, more preferably 150 μg / kg or less, and even more preferably 90 μg / kg or less. Note that the total content of Cr and Fe means the content with respect to the entire polyvinyl acetal resin. Further, the polyvinyl acetal resin of the present invention contains at least one selected from the group consisting of Cr and Fe. The total Cr and Fe content can be calculated, for example, by microwave decomposing a resin sample in a mixed acid solution such as nitric acid and hydrogen peroxide, measuring the Cr and Fe content in the polyvinyl acetal resin using inductively coupled plasma mass spectrometry (ICP-MS), and then calculating the total amount. Note that "μg / kg" refers to the total weight of Cr and Fe per 1 kg of polyvinyl acetal resin. Examples of ICP-MS measuring instruments that can be used include the "ICPMS-2040" manufactured by Tsu Seisakusho and the "Agilent7900" manufactured by Agilent Technologies.

[0010] The Cr content is preferably 5 μg / kg or more and 100 μg / kg or less, more preferably 7 μg / kg or more and 50 μg / kg or less, and even more preferably 9 μg / kg or more and 30 μg / kg or less. Furthermore, the Fe content is preferably 5 μg / kg or more and 300 μg / kg or less, more preferably 10 μg / kg or more and 150 μg / kg or less, and even more preferably 30 μg / kg or more and 110 μg / kg or less. By keeping the dimensions within the above range, it is possible to obtain a ceramic green sheet with high mechanical strength, electrical properties, and excellent resistance to sheet attacks.

[0011] The polyvinyl acetal resin of the present invention further contains Mg, preferably with an Mg content of 0 μg / kg to 400 μg / kg, and more preferably 10 μg / kg to 200 μg / kg. By keeping the Mg content within the above range, a ceramic green sheet with high mechanical strength, electrical properties, and excellent sheet attack resistance can be obtained. The Mg content mentioned above can be measured in the same way as the Cr and Fe content.

[0012] The respective content of Cr, Fe, and Mg, and the total content of Cr and Fe in the polyvinyl acetal resin of the present invention can be adjusted, for example, by adjusting the Cr, Fe, and Mg contained in the raw material polyvinyl alcohol resin, by adjusting the conditions of the acetalization reaction, by adding substances containing Cr, Fe, and Mg after production, or by performing a washing process or adjusting the washing conditions. In particular, by adjusting the conditions of the acetalization reaction, or by performing a washing process or adjusting the washing conditions when producing the polyvinyl acetal resin, the respective content of Cr, Fe, and Mg, and the total content of Cr and Fe can be effectively brought within the above range.

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

[0014] The polyvinyl acetal resin of the present invention is the same as A, B and 1Using the amounts of hydroxyl groups and acetyl groups measured by 1H-NMR, it is preferable that the wavenumber width in terms of the amount of hydroxyl group acetyl groups obtained by the following formula (2) is 6.5 to 18.0. Wavenumber width in terms of the amount of hydroxyl group acetyl groups (cm -1 / mol% / mol%) = [(B - A) / amount of hydroxyl groups / amount of acetyl groups] (2)

[0015] By setting it within the above range, a ceramic green sheet with high mechanical strength can be obtained. A more preferable lower limit of the wavenumber width in terms of the amount of hydroxyl group acetyl groups is 10.5, an even more preferable lower limit is 11.0, a more preferable upper limit is 16.0, and an even more preferable upper limit is 14.0.

[0016] In the analysis of the polyvinyl acetal resin by the above infrared spectrophotometer, a spectrum derived from the stretching vibration of the C-H bond possessed by the polyvinyl acetal resin appears around 2980 cm -1 For the above peak analysis, first, the film thickness of the measurement sample is adjusted so that the minimum transmittance of the peak derived from the stretching vibration of this C-H bond becomes 20 to 25% when connecting 2500 cm -1 and 3050 cm -1 to form a baseline. Further, for the data corrected so that the transmittances at both ends of the peak become 100% by subtracting the baseline from the peak that appears within the range of the above wavenumbers 3100 to 3700 cm -1 it is carried out.

[0017] The above wavenumber width in terms of the amount of hydroxyl groups and the wavenumber width in terms of the amount of hydroxyl group acetyl groups 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 groups, amount of hydroxyl groups, amount of acetyl groups, etc. of the polyvinyl acetal resin. In particular, the above wavewidth can be adjusted by changing the aldehyde input temperature, number of inputs, input interval, heating time, reaction temperature, reaction time, holding (aging) temperature, and holding (aging) time during the acetalization reaction described later. In particular, it can be adjusted by changing the heating rate, holding (aging) temperature, and holding (aging) time.

[0018] Figure 1 shows an example of the IR absorption spectrum of the polyvinyl acetal resin of the present invention, measured using an infrared spectrophotometer at 20°C. In Figure 1, the vertical axis represents transmittance and the horizontal axis represents wavenumber. In the IR absorption spectrum shown in Figure 1, the minimum transmittance X is 65.7%. Furthermore, the transmittance a (%) that satisfies [100-(100-X) / 2] is 82.85%, and the wavenumber A on the low wavenumber side is 3297 cm⁻¹. -1 The high-frequency wavenumber B is 3557 cm. -1 That is the case. In the above case, if the amount of hydroxyl groups is 30 mol%, the wavenumber width converted to the amount of hydroxyl groups [(BA) / amount of hydroxyl groups] is 8.67 cm. -1 This will be calculated as %) / mol%. The above wave frequency A corresponds to 3250 cm². -1 The above is preferable, 3270cm -1 The above is preferable. 3350cm -1 The following is preferable: 3330cm -1 The following are preferable. The above wave frequency B is 3530 cm. -1 The above is preferable, 3550cm -1 The above is preferable. 3600cm -1 The following is preferable: 3580cm -1 The following are preferable. The above transmittance a is preferably 80% or more, and preferably 85% or less.

[0019] 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).

[0020] [ka]

[0021] In equation (3) above, R 1 represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.

[0022] In the above equation (3), R 1 When the alkyl group has 1 to 20 carbon atoms, examples of the alkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl, iso-butyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, 2-ethylhexyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, and octadecyl groups. Among these, methyl and n-propyl groups are preferred.

[0023] 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 preferred lower limit of 55 mol%, an even more preferred lower limit of 58 mol%, a more preferred upper limit of 80 mol%, and an even more preferred upper limit of 78 mol%. In other words, the above acetal group content is preferably 50 to 83 mol%, more preferably 55 to 80 mol%, and even more preferably 58 to 78 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.

[0024] In the polyvinyl acetal resin of the present invention, R in formula (3) above 1 When the acetacetal group has a methyl group, the preferred lower limit of the content of the constituent unit relative to the total polyvinyl acetal resin (hereinafter also referred to as "acetacetal group amount") is 1 mol%, and the preferred upper limit is 83 mol%. The above acetacetal group amount has a more preferred lower limit of 5 mol%, a more preferred upper limit of 55 mol%, an even more preferred lower limit of 10 mol%, and an even more preferred upper limit of 50 mol%. Furthermore, in the polyvinyl acetal resin of the present invention, R in formula (3) above 1 When the butyral group has an n-propyl group, the preferred lower limit of the content of the constituent unit relative to the total polyvinyl acetal resin (hereinafter also referred to as the "butyral group amount") is 50 mol%, and the preferred upper limit is 83 mol%. The above butyral group amount has a more preferred lower limit of 55 mol%, a more preferred upper limit of 80 mol%, an even more preferred lower limit of 61 mol%, and an even more preferred upper limit of 77 mol%. In the polyvinyl acetal resin of the present invention, R in formula (3) above 1 When the compound has both a methyl group and an n-propyl group, the ratio of the acetal group amount to the butyral group amount [also called the acetal group amount / butyral group amount, or aceto / butyl ratio] is preferably 0.01 or more and 830 or less, and more preferably 0.06 or more and 2 or less.

[0025] In the polyvinyl acetal resin of the present invention, the preferred lower limit of the content of constituent units having a hydroxyl group represented by the above general formula (4) (hereinafter also referred to as "hydroxyl group content") is 18 mol%, and the preferred upper limit is 40 mol%. When the amount of hydroxyl groups is 18 mol% or more, a highly tough polyvinyl acetal resin can be obtained. When the amount of hydroxyl groups is 40 mol% or less, the solubility in organic solvents can be sufficiently improved. The above hydroxyl group content has a more preferable lower limit of 22 mol%, an even more preferable lower limit of 25 mol%, a more preferable upper limit of 38 mol%, and an even more preferable upper limit of 35 mol%. In other words, the above hydroxyl group content is preferably 18 to 40 mol%, more preferably 22 to 38 mol%, and even more preferably 25 to 35 mol%. By using the above-mentioned amount of hydroxyl groups, the wavenumber width converted to the amount of hydroxyl groups and the wavenumber width converted to the amount of hydroxyl groups and acetyl groups can be set to a predetermined range. The amount of hydroxyl groups mentioned above is, for example, 1 It can be measured by 1H-NMR.

[0026] In the polyvinyl acetal resin of the present invention, the preferred lower limit of the content of the constituent unit having an acetyl group represented by the above general formula (5) (hereinafter also referred to as "acetyl group content") is 0.1 mol%, and the preferred upper limit is 22.0 mol%. When the amount of acetyl groups is 0.1 mol% or more, it is possible to suppress the increase in viscosity of the slurry composition for ceramic green sheets due to intramolecular and intermolecular hydrogen bonding of hydroxyl groups in the polyvinyl acetal resin. When the amount of acetyl groups is 22.0 mol% or less, it is possible to improve handling properties without increasing the flexibility of the polyvinyl acetal resin too much. The above acetyl group content has a more preferred lower limit of 0.5 mol%, an even more preferred lower limit of 0.8 mol%, a more preferred upper limit of 15.0 mol%, and an even more preferred upper limit of 12.0 mol%. In other words, the above acetyl group content is preferably 0.1 to 22.0 mol%, more preferably 0.5 to 15.0 mol%, and even more preferably 0.8 to 12.0 mol%. By using the above amount of acetyl groups, the hydroxyl group-acetyl group-equivalent wavenumber width can be set to a predetermined range. The above amount of acetyl groups is, for example, 1 It can be measured by 1H-NMR.

[0027] The polyvinyl acetal resin of the present invention, when used to produce thin-film ceramic green sheets, has a preferred lower limit of 500, a more preferred lower limit of 600, an even more preferred lower limit of 700, and a particularly preferred lower limit of 1000, from the viewpoint of maintaining mechanical strength. Furthermore, from the viewpoint of solubility in organic solvents and dissolution viscosity, it has a preferred upper limit of 10,000, a more preferred upper limit of 5,000, an even more preferred upper limit of 3,500, and a particularly preferred upper limit of 2,000. In other words, the above average degree of polymerization is preferably 500 to 10,000, more preferably 600 to 5,000, even more preferably 700 to 3,500, and particularly preferred 1,000 to 2,000. 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.

[0028] The polyvinyl acetal resin of the present invention can typically be produced by acetalizing a polyvinyl alcohol resin.

[0029] 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.

[0030] 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 99.5 mol%, and even more preferably 78 mol% to 99.4 mol%. That is, the degree of saponification is preferably 76 to 99.5 mol%, and more preferably 78 to 99.4 mol%.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] The amount of aldehyde added can be appropriately set according to the amount of acetal groups in the target polyvinyl acetal resin. In particular, if the amount is preferably 50 mol% to 95 mol%, more preferably 55 mol% to 90 mol%, relative to 100 mol% of polyvinyl alcohol, the acetalization reaction will proceed efficiently and unreacted aldehydes will be easier to remove.

[0035] The aldehyde introduction temperature is preferably 10°C or higher and 55°C or lower, and more preferably 15°C or higher and 30°C or lower.

[0036] In the above acetalization process, it is preferable to add the aldehyde at a predetermined temperature, carry out the reaction for a predetermined time (reaction step), and then maintain the temperature at a predetermined temperature (aging step). The time from the addition of the aldehyde to the start of heating (heating start time or reaction time) is preferably 150 minutes or more and 360 minutes or less, and more preferably 180 minutes or more and 300 minutes or less. By setting the above heating start time, the hydroxyl group amount equivalent wavenumber width and the hydroxyl group amount equivalent wavenumber width can be set to a predetermined range. Furthermore, the heating time is preferably 330 minutes or more and 520 minutes or less, and more preferably 340 minutes or more and 500 minutes or less.

[0037] Furthermore, if the temperature at the time of aldehyde addition (introduction) is below 35°C, it is preferable to change the heating rate from the temperature at the time of the last aldehyde addition to 35°C (heating rate 1) and the heating rate from 35°C to the holding temperature for the maturation process (heating rate 2) to increase the temperature. The heating rate 1 is preferably 0.02°C / min or more and 0.06°C / min or less. By setting the heating rate 1 within the above range, the hydroxyl group amount-based wavenumber width and the hydroxyl group amount-acetyl group amount-based wavenumber width can be set within a predetermined range. The above heating rate 2 is preferably 0.10°C / min or more and 0.30°C / min or less. By setting the above heating rate 2 within the above range, the hydroxyl group amount-based wavenumber width and the hydroxyl group amount-acetyl group amount-based wavenumber width can be set within a predetermined range.

[0038] The holding time in the above maturation process is preferably 1 hour or more and 5 hours or less, and more preferably 2.5 hours or more and 3 hours or less. The holding temperature in the above maturation process is preferably 40°C or higher and 75°C or lower, more preferably 50°C or higher and 70°C or lower, and even more preferably 55°C or higher and 65°C or lower. By setting the above-mentioned holding time and holding temperature, the above-mentioned wavenumber width converted to hydroxyl group amount and wavenumber width converted to hydroxyl group amount and acetyl group amount can be set to a predetermined range.

[0039] When producing the polyvinyl acetal resin of the present invention, it is preferable to add a substance containing Cr, Fe, and Mg. This allows the individual content of Cr, Fe, and Mg, and the total content of Cr and Fe in the polyvinyl acetal resin of the present invention to be kept within a predetermined range. Examples of substances containing Cr, Fe, and Mg include oxides, hydroxides, chlorides, and hydrates of Cr, Fe, and Mg. For example, it is preferable to use iron(III) chloride hexahydrate, chromium(III) chloride hexahydrate, magnesium chloride hexahydrate, etc. The step of adding the substances containing Cr, Fe, and Mg may be performed either during the acetalization process or before the acetalization reaction.

[0040] In the above manufacturing method, it is preferable to perform a washing step after acetalization. The above washing step is preferably carried out by washing with water, and it is particularly preferable to use ultrapure water. Furthermore, it is preferable to perform the above cleaning step after the neutralization step. The number of cleaning steps may be one or two or more.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] The content of the organic solvent in the above-mentioned slurry for ceramic green sheets is determined by the type of polyvinyl acetal resin used, etc., and is not particularly limited. However, if the amount is too small, it will be difficult to achieve the solubility necessary for mixing. On the other hand, if the amount is too large, the viscosity of the slurry composition for ceramic green sheets may become too low, resulting in poor handling when producing ceramic green sheets. For this reason, the content of the organic solvent is preferably 20% by weight or more and 80% by weight or less.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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]

[0058] According to the present invention, it is possible to provide a polyvinyl acetal resin that can produce a ceramic green sheet with high mechanical strength, electrical properties, and excellent resistance to sheet attack, as well as a slurry for ceramic green sheets using the polyvinyl acetal resin, a ceramic green sheet, and a multilayer ceramic capacitor. [Brief explanation of the drawing]

[0059] [Figure 1] This figure shows an example of an IR absorption spectrum of the polyvinyl acetal resin of the present invention, measured using an infrared spectrophotometer at 20°C. [Modes for carrying out the invention]

[0060] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0061] (Example 1) 200 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 98.0 mol%) was mixed with 2100 g of ultrapure water, 1110 mg of iron(III) chloride hexahydrate, 490 mg of chromium(III) chloride hexahydrate, and 464 mg of magnesium chloride hexahydrate, and stirred at 90°C for approximately 2 hours to dissolve. This solution was cooled to 20°C, and 135 g of 35% by weight hydrochloric acid and 110 g of n-butyraldehyde were added to it. Subsequently, after 200 minutes, the temperature was increased to 35°C at a heating rate [heating rate 1] of 0.6°C / min, and from 35°C, the temperature was increased at a heating rate [heating rate 2] of 0.6°C / min (heating time 33 minutes). The temperature was then maintained at 40°C for 3 hours to carry out the acetalization reaction. Neutralization, washing with ultrapure water, and drying were performed by conventional methods to obtain a white powder of polyvinyl acetal resin.

[0062] (Preparation of polyvinyl acetal resin sheets) 10.0 parts by weight of the obtained polyvinyl acetal resin, 1.5 parts by weight of a plasticizer (Sekisui Chemical Co., Ltd., G260), and 50 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.

[0063] (Preparation of ceramic green sheets) (Preparation of inorganic powder dispersion) One part by weight of polyvinyl acetal resin (BL-1, manufactured by Sekisui Chemical Co., Ltd.) was added to a mixed solvent of 20 parts by weight of toluene and 20 parts by weight of ethanol, and dissolved by stirring. Next, 100 parts by weight of barium titanate powder (BT01, manufactured by Sakai Chemical Industry Co., Ltd.) was added to the resulting solution, and the mixture was stirred for 180 minutes using a bead mill (Ready Mill, manufactured by AIMEX Co., Ltd.) to prepare an inorganic powder dispersion. (Preparation of resin solution) Eight parts by weight of the obtained polyvinyl acetal resin and 2.1 parts by weight of a plasticizer (G260, manufactured by Sekisui Chemical Co., Ltd.) were added to a mixed solvent of 45 parts by weight of ethanol and 45 parts by weight of toluene, and the mixture was stirred and dissolved to prepare a resin solution. (Preparation of slurry for ceramic green sheets) A resin solution was added to the obtained inorganic powder dispersion and stirred in a bead mill for 90 minutes to obtain a slurry composition for ceramic green sheets. (Preparation of ceramic green sheets) The obtained slurry composition for ceramic green sheets 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 ceramic green sheet A. Similarly, the obtained slurry composition for ceramic green sheets was coated onto a PET film that had been released using a coater to a thickness of 1.2 μm after drying, and then heated and dried to produce ceramic green sheet B.

[0064] (Example 2) 200 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 98.0 mol%) was mixed with 2100 g of ultrapure water, 570 mg of iron(III) chloride hexahydrate, 50 mg of chromium(III) chloride hexahydrate, and 380 mg of magnesium chloride hexahydrate, and stirred at 90°C for approximately 2 hours to dissolve. This solution was cooled to 20°C, and 135 g of 35% by weight hydrochloric acid and 110 g of n-butyraldehyde were added to it. Subsequently, after 200 minutes, the temperature was increased to 35°C at a heating rate [heating rate 1] of 0.6°C / min, and from 35°C, the temperature was increased at a heating rate [heating rate 2] of 0.6°C / min (heating time 33 minutes). The temperature was then maintained at 40°C for 3 hours to carry out the acetalization reaction. Neutralization, washing with ultrapure water, and drying were performed by conventional methods to obtain a white powder of polyvinyl acetal resin. Furthermore, polyvinyl acetal resin sheets and ceramic green sheets were prepared in the same manner as in Example 1.

[0065] (Example 3) 200 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 99.2 mol%) was mixed with 2100 g of ultrapure water, 520 mg of iron(III) chloride hexahydrate, 55 mg of chromium(III) chloride hexahydrate, and 480 mg of magnesium chloride hexahydrate, and stirred at 90°C for about 2 hours to dissolve. This solution was cooled to 20°C, and 135 g of 35% by weight hydrochloric acid and 110 g of n-butyraldehyde were added to it. Subsequently, after 180 minutes, the temperature was increased to 35°C at a heating rate [heating rate 1] of 0.06°C / min, and then from 35°C, the temperature was increased at a heating rate [heating rate 2] of 0.22°C / min (heating time 340 minutes). The reaction was completed by holding at 55°C for 2.5 hours, followed by neutralization by conventional methods, washing with ultrapure water, and drying to obtain a white powder of polyvinyl acetal resin. Note that the heating time is the time from the start of heating until the holding temperature is reached. Furthermore, polyvinyl acetal resin sheets and ceramic green sheets were prepared in the same manner as in Example 1.

[0066] (Example 4) 200 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 99.2 mol%) was mixed with 2100 g of ultrapure water, 1350 mg of iron(III) chloride hexahydrate, 460 mg of chromium(III) chloride hexahydrate, and 5500 mg of magnesium chloride hexahydrate, and stirred at 90°C for about 2 hours until dissolved. This solution was cooled to 20°C, and 135 g of 35% by weight hydrochloric acid and 113 g of n-butyraldehyde were added to it. Subsequently, after 180 minutes, the temperature was increased to 35°C at a heating rate [heating rate 1] of 0.06°C / min, and from 35°C, the temperature was increased at a heating rate [heating rate 2] of 0.22°C / min (heating time 340 minutes). The reaction was completed by holding at 55°C for 3 hours, followed by neutralization by conventional methods, washing with ultrapure water, and drying to obtain a white powder of polyvinyl acetal resin. Furthermore, polyvinyl acetal resin sheets and ceramic green sheets were prepared in the same manner as in Example 1.

[0067] (Example 5) 200 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 99.2 mol%) was mixed with 2100 g of ultrapure water, 1400 mg of iron(III) chloride hexahydrate, 430 mg of chromium(III) chloride hexahydrate, and 410 mg of magnesium chloride hexahydrate, and stirred at 90°C for approximately 2 hours until dissolved. This solution was cooled to 20°C, and 135 g of 35% by weight hydrochloric acid and 113 g of n-butyraldehyde were added to it. Subsequently, after 180 minutes, the temperature was increased to 35°C at a heating rate [heating rate 1] of 0.06°C / min, and from 35°C, the temperature was increased at a heating rate [heating rate 2] of 0.22°C / min (heating time 340 minutes). The reaction was completed by holding at 55°C for 3 hours, followed by neutralization by conventional methods, washing with ultrapure water, and drying to obtain a white powder of polyvinyl acetal resin. Furthermore, polyvinyl acetal resin sheets and ceramic green sheets were prepared in the same manner as in Example 1.

[0068] (Example 6) 200 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 99.2 mol%) was mixed with 2100 g of ultrapure water, 220 mg of iron(III) chloride hexahydrate, 60 mg of chromium(III) chloride hexahydrate, and 260 mg of magnesium chloride hexahydrate, and stirred at 90°C for about 2 hours until dissolved. This solution was cooled to 20°C, and 135 g of 35% by weight hydrochloric acid and 114 g of n-butyraldehyde were added to it. Subsequently, after 180 minutes, the temperature was increased to 35°C at a heating rate [heating rate 1] of 0.06°C / min, and from 35°C, the temperature was increased at a heating rate [heating rate 2] of 0.22°C / min (heating time 363 minutes). The reaction was then completed by holding at 60°C for 3 hours. Neutralization, washing with ultrapure water, and drying were performed by conventional methods to obtain a white powder of polyvinyl acetal resin. Furthermore, polyvinyl acetal resin sheets and ceramic green sheets were prepared in the same manner as in Example 1.

[0069] (Example 7) 200 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 99.2 mol%) was mixed with 2100 g of ultrapure water, 540 mg of iron(III) chloride hexahydrate, 80 mg of chromium(III) chloride hexahydrate, and 450 mg of magnesium chloride hexahydrate, and stirred at 90°C for approximately 2 hours to dissolve. This solution was cooled to 20°C, and 135 g of 35% by weight hydrochloric acid and 114 g of n-butyraldehyde were added to it. Subsequently, after 180 minutes, the temperature was increased to 35°C at a heating rate [heating rate 1] of 0.04°C / min, and from 35°C, the temperature was increased at a heating rate [heating rate 2] of 0.22°C / min (heating time 466 minutes). The reaction was completed by holding at 55°C for 3 hours, followed by neutralization by conventional methods, washing with ultrapure water, and drying to obtain a white powder of polyvinyl acetal resin. Furthermore, polyvinyl acetal resin sheets and ceramic green sheets were prepared in the same manner as in Example 1.

[0070] (Example 8) 200 g of polyvinyl alcohol resin (average degree of polymerization 800, degree of saponification 98.0 mol%) was mixed with 2100 g of ultrapure water, 210 mg of iron(III) chloride hexahydrate, 50 mg of chromium(III) chloride hexahydrate, and 140 mg of magnesium chloride hexahydrate, and stirred at 90°C for approximately 2 hours to dissolve. This solution was cooled to 20°C, and 135 g of 35% by weight hydrochloric acid and 100 g of n-butyraldehyde were added to it. Subsequently, after 180 minutes, the temperature was increased to 35°C at a heating rate [heating rate 1] of 0.06°C / min, and from 35°C, the temperature was increased at a heating rate [heating rate 2] of 0.22°C / min (heating time 363 minutes). The reaction was then completed by holding at 60°C for 3 hours. Neutralization, washing with ultrapure water, and drying were performed by conventional methods to obtain a white powder of polyvinyl acetal resin. Furthermore, polyvinyl acetal resin sheets and ceramic green sheets were prepared in the same manner as in Example 1.

[0071] (Example 9) 200 g of ultra-polyvinyl alcohol resin (average degree of polymerization 4000, degree of saponification 99.0 mol%) was mixed with 3100 g of pure water, 210 mg of iron(III) chloride hexahydrate, 50 mg of chromium(III) chloride hexahydrate, and 140 mg of magnesium chloride hexahydrate, and stirred at 90°C for about 2 hours until dissolved. This solution was cooled to 20°C, and 135 g of 35% by weight hydrochloric acid, 12 g of acetaldehyde, and 94 g of n-butyraldehyde were added to it. Subsequently, after 180 minutes, the temperature was increased to 35°C at a heating rate [heating rate 1] of 0.04°C / min, and from 35°C, the temperature was increased at a heating rate [heating rate 2] of 0.22°C / min (heating time 466 minutes). The reaction was completed by holding at 55°C for 3 hours, followed by neutralization by conventional methods, washing with ultrapure water, and drying to obtain a white powder of polyvinyl acetal resin. Furthermore, polyvinyl acetal resin sheets and ceramic green sheets were prepared in the same manner as in Example 1.

[0072] (Comparative Example 1) 200 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 98.0 mol%) was mixed with 2100 g of ultrapure water, 1800 mg of iron(III) chloride hexahydrate, 570 mg of chromium(III) chloride hexahydrate, and 410 mg of magnesium chloride hexahydrate. The mixture was stirred at 90°C for approximately 2 hours to dissolve the substances. This solution was cooled to 40°C, and 135 g of 35% by weight hydrochloric acid and 110 g of n-butyraldehyde were added to it. Subsequently, the acetalization reaction was carried out by holding the mixture at 40°C for 3 hours. The mixture was then neutralized by a conventional method, washed with ultrapure water, and dried to obtain a white powder of polyvinyl acetal resin. Furthermore, polyvinyl acetal resin sheets and ceramic green sheets were prepared in the same manner as in Example 1.

[0073] (Comparative Example 2) 200 g of polyvinyl alcohol resin (average degree of polymerization 1700, degree of saponification 98.0 mol%) was mixed with 2100 g of ultrapure water, 1480 mg of iron(III) chloride hexahydrate, 1260 mg of chromium(III) chloride hexahydrate, and 760 mg of magnesium chloride hexahydrate. The mixture was stirred at 90°C for approximately 2 hours to dissolve the substances. This solution was cooled to 40°C, and 135 g of 35% by weight hydrochloric acid and 110 g of n-butyraldehyde were added to it. Subsequently, the acetalization reaction was carried out by holding the mixture at 40°C for 3 hours. The mixture was then neutralized by a conventional method, washed with ultrapure water, and dried to obtain a white powder of polyvinyl acetal resin. Furthermore, polyvinyl acetal resin sheets and ceramic green sheets were prepared in the same manner as in Example 1.

[0074] (Comparative Example 3) 200 g of polyvinyl alcohol resin (average degree of polymerization 800, degree of saponification 98.0 mol%) was mixed with 2100 g of ultrapure water and stirred at 90°C for approximately 2 hours until dissolved. This solution was cooled to 40°C, and 135 g of 35 wt% hydrochloric acid and 110 g of n-butyraldehyde were added to it. Subsequently, the acetalization reaction was carried out by holding the mixture at 40°C for 3 hours. The mixture was then neutralized by a conventional method, washed with ultrapure water, and dried to obtain a white powder of polyvinyl acetal resin. Furthermore, polyvinyl acetal resin sheets and ceramic green sheets were prepared in the same manner as in Example 1.

[0075] (evaluation) The polyvinyl acetal resin and ceramic green sheets obtained in the examples and comparative examples were evaluated as follows. The results are shown in Table 1.

[0076] (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.

[0077] (1-2) IR absorption spectrum The obtained polyvinyl acetal resin was dissolved in a 1:1 weight-ratio ethanol-toluene mixed solution, and then coated onto a PET film, resulting in a 2980 cm² vibration derived from the stretching vibration of the CH bond. -1 The film thickness of the measurement sample was adjusted so that the minimum transmittance of the peak appearing in the vicinity was 20%, and a polyvinyl acetal resin sheet was obtained. The IR absorption spectrum of the obtained polyvinyl acetal resin sheet was measured at 20°C using an infrared spectrophotometer (HORIBA FT-720). The measurement results were obtained for wavenumbers 3050~3750 cm⁻¹. -1 A baseline was drawn for the peaks that appeared within the specified range, and peak analysis was performed on the data corrected so that the transmittance at both ends of the peaks was 100%, to measure the minimum transmittance X, transmittance a, and peak wavenumbers A and B. Subsequently, 1 Using the amount of hydroxyl groups determined by H-NMR measurement, the wavewidth (cm) converted to the amount of hydroxyl groups was calculated. -1 The formula / mol%) was calculated as [(BA) / hydroxyl group amount]. Also, 1 Using the amount of acetyl groups determined from 1H-NMR measurements, the hydroxyl group-acetyl group-reduced wavenumber width = [(BA) / hydroxyl group amount / acetyl groups] was calculated.

[0078] (1-3) Elemental analysis by ICP-MS The obtained polyvinyl acetal resin was subjected to a mixed acid solution consisting of nitric acid and hydrogen peroxide, and a decomposed liquid sample was obtained by microwave decomposition. The Fe, Cr, and Mg content of this sample were measured using an ICP mass spectrometer (Agilent Technologies, Agilent 7900). The total Fe and Cr content was also calculated.

[0079] (2) Evaluation of ceramic green sheets

[0080] (2-1) Sheet attack resistance The obtained ceramic green sheet A was cut into 5cm x 5cm squares. Then, 70 μL of dihydroterpineol acetate at 23°C was dropped onto the test piece, and the time of dropping was set to 0. After that, the ceramic green sheet was visually observed, and the time until wrinkles formed on the ceramic green sheet was measured and judged according to the evaluation criteria below. Note that a longer time until wrinkles form indicates superior sheet attack resistance.

[0081] AA: 100 seconds or more A: 80 seconds or more but less than 100 seconds B: 55 seconds or more, less than 80 seconds C: Less than 55 seconds

[0082] (2-2) Stress and strain at fracture point The obtained ceramic green sheet A was cut into 5cm x 1cm pieces to serve as test specimens. A tensile testing machine (Shimadzu Corporation, AUTOGRAPH AGS-J) was used to pull the sheet at a tensile speed of 500% / min, and the breaking tensile strength (kg / cm²) was measured at a temperature of 20°C. 2 The stress σ (MPa) - strain ε (%) was measured. From the obtained values, a stress σ (MPa) - strain ε (%) curve was obtained. Note that 500% / min means a speed at which the specimen is moved a distance five times the distance between the chucks per minute. The fracture stress and fracture strain were determined from the obtained stress-strain curve and judged according to the evaluation criteria below. (Stress at fracture point) AA:35MPa or more A: 30 MPa or higher, less than 35 MPa B: 26 MPa or higher, less than 30 MPa C: Less than 26 MPa (Fracture point strain) AA: 22% or higher A: 20% or more, less than 22% B: 17% or more, less than 20% C: Less than 17%

[0083] (2-3) Electrical characteristics A sheet composite was obtained by applying a paste consisting of nickel powder, ethyl cellulose, and dihydroterpineol acetate to the ceramic green sheet B prepared above, so that the thickness after drying was 1 μm, and then heating and drying it. Two of the obtained sheet composites were stacked on the ceramic green sheet A, and then another ceramic green sheet A was stacked on top of that, and a laminate was obtained by uniaxial pressure molding. Furthermore, after firing the laminate, external electrodes were formed at the ends to obtain a multilayer capacitor. A DC voltage was applied to 10 capacitor samples, and the average value of the voltage at which dielectric breakdown occurs (Break Down Voltage, BDV) was calculated and used as the measured value. The obtained BDV measured values ​​were evaluated according to the following criteria. AA:215V or more A: Less than 215V, 200V or more B: Less than 200V, 160V or more C: Less than 160V

[0084] [Table 1] [Industrial applicability]

[0085] According to the present invention, it is possible to provide a polyvinyl acetal resin that can produce a ceramic green sheet with high mechanical strength, electrical properties, and excellent resistance to sheet attack, as well as a slurry for ceramic green sheets using the polyvinyl acetal resin, a ceramic green sheet, and a multilayer ceramic capacitor.

Claims

1. The total content of Cr and Fe is 10 μg / kg or more and 400 μg / kg or less. The Cr content is 5 μg / kg or more and 100 μg / kg or less, and the Fe content is 5 μg / kg or more and 300 μg / kg or less. Furthermore, it contains Mg, with an Mg content of 10 μg / kg or more and 400 μg / kg or less. Polyvinyl acetal resin.

2. In the IR absorption spectrum measured by an infrared spectrophotometer, wavenumbers 3050–3750 cm⁻¹ －１ When the minimum peak transmittance within the range is X (%), and among the wavenumbers that show a transmittance a (%) that satisfies [100 - (100 - X) / 2], if the wavenumber on the lower wavenumber side is A and the wavenumber on the higher wavenumber side is B, then A, B and １ The polyvinyl acetal resin according to claim 1, wherein the hydroxyl group amount equivalent wavenumber width calculated by formula (1), using the amount of hydroxyl groups measured by H-NMR, is 8.31 or greater. Hydroxyl group-based wavewidth (cm) －１ / mol%) = [(B - A) / amount of hydroxyl groups] (1)

3. The polyvinyl acetal resin according to claim 2, wherein the hydroxyl group equivalent wavenumber width calculated by formula (1) is 8.45 or greater.

4. The polyvinyl acetal resin according to claim 1 or 2, wherein the acetal group content is 50 mol% or more and 83 mol% or less.

5. The polyvinyl acetal resin according to claim 1 or 2, wherein the amount of hydroxyl groups is 18 mol% or more and 40 mol% or less.

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

7. A ceramic green sheet made using the ceramic green sheet slurry described in claim 6.

8. A multilayer ceramic capacitor obtained using the ceramic green sheet described in claim 7.

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