Polyvinyl acetal resin

Abstract

To provide a polyvinyl acetal resin which enables production of a ceramic green sheet that is excellent in sheet attach resistance and tensile strength when being used, especially, as a binder for a ceramic green sheet, and enables manufacture of a laminate ceramic capacitor that prevents lowering of electric characteristics and deterioration in fraction defective, and is excellent in reliability.SOLUTION: There is provided a polyvinyl acetal resin in which when a vinyl alcohol residue is represented by (V) and an acetal residue is represented by (A), a ratio of a peak integral value of a methine C atom of a VVV unit to the total of a peak integral value of a methine C atom of a central V residue of triad units VVV, AVA and AVV, which is obtained by 13C-NMR measurement, is 0.23 or more, and a weight average molecular weight is 230,000 or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polyvinyl acetal resin. [Background technology]

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

[0003] However, when conventional polyvinyl acetal resins are dissolved in organic solvents, trace amounts of undissolved matter are generated. The presence of such undissolved matter can lead to voids remaining during the degreasing and firing processes in the production of multilayer ceramic capacitors, or to poor dispersibility of ceramic powder. As a result, the electrical properties of the resulting products are degraded. For this reason, when polyvinyl acetal resin is used for ceramic green sheets, it is necessary to mix it with organic and inorganic compounds, dissolve it in an organic solvent, and then perform a filtration process to remove any undissolved materials.

[0004] In contrast, Patent Document 1 proposes a polyvinyl acetal resin in which the reduction rate of the filtration flow rate is less than 10% when the polyvinyl acetal resin solution, which is prepared by dissolving it in a 1:1 mixed solvent of methyl ethyl ketone and / or toluene and ethanol to prepare a 5 wt % solution, is filtered using a filter with a mesh size of 5 μm under conditions of a filtration temperature of 25° C. and a filtration pressure of 10 mmHg. Also, Patent Document 2 proposes a polyvinyl acetal resin in which the reduction rate of the filtration flow rate is less than 10% when the polyvinyl acetal resin solution is dissolved in a 1:1 mixed solvent of methyl ethyl ketone and / or toluene and ethanol to prepare a 5 wt % solution. -1 The wavenumber A (cm -1 ), and polyvinyl acetal resins in which the amount of hydroxyl groups (mol %) is controlled within a specific range have been proposed. It is said that by using such a polyvinyl acetal resin, when dissolved in an organic solvent, there is little undissolved matter, and the filtration time can be shortened, thereby improving productivity. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-325342 [Patent Document 2] International Publication No. 2021 / 060499 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when the polyvinyl acetal resin described in Patent Document 1 is used, there is a problem that the sheet attack resistance and tensile strength of the resulting ceramic green sheet are insufficient. Also, when the polyvinyl acetal resin described in Patent Document 2 is used, there is still room for improvement in the sheet attack resistance of the resulting ceramic green sheet. Furthermore, as ceramic green sheets become thinner, insufficient sheet attack resistance and tensile strength can lead to sheet defects, which can cause deterioration in the electrical properties and increase in the defect rate of multilayer ceramic capacitors.

[0007] The present invention aims to provide a polyvinyl acetal resin that, when used as a binder for ceramic green sheets, can provide ceramic green sheets that are excellent in sheet attack resistance and tensile strength, thereby reducing the deterioration of the electrical properties and the increase in the defect rate of multilayer ceramic capacitors and leading to the production of highly reliable multilayer ceramic capacitors. [Means for solving the problem]

[0008] This disclosure (1) 13 The polyvinyl acetal resin has a weight-average molecular weight of 230,000 or more, and the ratio of the peak integral value of the methine C atom shown in (a)' of the triad unit represented by the following formula (a) to the sum of the peak integral values ​​of the methine C atoms shown in (a)', (b)', and (c)' of the triad units represented by the following formulas (a), (b), and (c), as measured by C-NMR (nuclear magnetic resonance), is 0.23 or more.

[0009] [ka] In formula (b) and formula (c), R is each independently hydrogen or a hydrocarbon group having 1 to 20 carbon atoms.

[0010] The present disclosure (2) is the polyvinyl acetal resin according to the present disclosure (1), wherein a 5% by mass solution of the polyvinyl acetal resin in a 1:1 mixed solvent of ethanol and toluene has a solution viscosity of 30 mPa s or more and 600 mPa s or less, as measured using a Brookfield viscometer at a solution temperature of 20°C. The present disclosure (3) is the polyvinyl acetal resin according to the present disclosure (1) or (2), in which the amount of hydroxyl groups is 23 mol % or more and 40 mol % or less. The present disclosure (4) is the polyvinyl acetal resin according to any one of the present disclosures (1) to (3), in which the amount of acetyl groups is 0.1 mol % or more and 5 mol % or less. The present disclosure (5) is the polyvinyl acetal resin according to any one of the present disclosures (1) to (4), which has a molecular weight distribution of 2.75 or less. The present disclosure (6) is the polyvinyl acetal resin according to any one of the present disclosures (1) to (5), which is used for a ceramic green sheet. The present disclosure (7) is a slurry composition for a ceramic green sheet, which contains the polyvinyl acetal resin according to any one of the present disclosures (1) to (6), an organic solvent, and ceramic powder. The present disclosure (8) is a ceramic green sheet obtained by using the slurry composition for a ceramic green sheet according to the present disclosure (7). The present disclosure (9) is a multilayer ceramic capacitor obtained by using the ceramic green sheet according to the present disclosure (8). The present invention will be described in detail below.

[0011] As a result of extensive investigation, the present inventors have found that 13The inventors have found that a ceramic green sheet obtained using a polyvinyl acetal resin in which the ratio of the peak integral of the methine C atom shown in (a)' of the triad unit represented by the above formula (a) to the sum of the peak integrals of the methine C atoms shown in (a)', (b)', and (c)' of the triad units represented by the above formulas (a), (b), and (c), as measured by C-NMR (the ratio of the peak integral of the triad unit consisting of three consecutive hydroxyl group-containing constitutional units), and the weight-average molecular weight satisfy a specific relationship, has excellent sheet attack resistance and tensile strength, leading to the completion of the present invention. Furthermore, when the polyvinyl acetal resin of the present invention is used in a slurry composition for a ceramic green sheet, it is possible to obtain the effect of preventing an increase in the viscosity of the slurry over time and improving productivity.

[0012] The polyvinyl acetal resin of the present invention is 13 The ratio of the peak integral value of a triad unit consisting of three consecutive hydroxyl group-containing structural units measured by C-NMR is 0.23 or more. By setting the ratio within this range, sheet attack resistance can be improved. The ratio of the peak integral value of the triad unit consisting of three consecutive hydroxyl-containing structural units has a preferred lower limit of 0.24, a more preferred lower limit of 0.25, and a preferred upper limit of 0.32, an even more preferred upper limit of 0.30. That is, the ratio of the peak integral value of the triad unit consisting of three consecutive hydroxyl-containing structural units is preferably 0.24 to 0.32, and more preferably 0.25 to 0.30. If the ratio is equal to or greater than the lower limit, the hydrogen bonding strength due to the hydroxyl groups is improved, and the 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 the ratio 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.

[0013] The ratio of the peak integral value of the triad unit consisting of three consecutive hydroxyl group-containing constitutional units is the ratio of the sum of the peak integral values ​​of the methine C atoms shown in (a)' of the triad unit represented by the formula (a) to the sum of the peak integral values ​​of the methine C atoms shown in (a)', (b)', and (c)' of the triad units represented by the formula (a), (b) and (c), 13 It can be measured by C-NMR.

[0014] The sum of the peak integral values ​​of the methine C atoms shown in (a)', (b)', and (c)' of the triad units represented by the above formulas (a), (b), and (c) [I(a)'+I(b)'+I(c)'] is 13 Obtained by C-NMR (nuclear magnetic resonance) measurement 13 In the C-NMR spectrum, the integral value of the peak assigned to the methine C atom at the position (f)' of the triad unit represented by the following formula (f) is I(f)', the integral value of the peak assigned to the methine C atom at the position (g)' of the triad unit represented by the following formula (g) is I(g)', the integral value of the peak assigned to the methine C atom at the position (k)'2 of the triad unit represented by the following formula (k) is I(k)'2, the integral value of the peak assigned to the methine C atom at the position (i)' of the triad unit represented by the following formula (i) is I(i)', the integral value of the peak assigned to the methine C atom at the position (j)' of the triad unit represented by the following formula (j) is I(j)', and the integral value of the peak assigned to the methine C atom at the position (m)' of the triad unit represented by the following formula (m) is I(m)'. The sum of these values ​​can be calculated using the following formula (4). I(a)'+I(b)'+I(c)'=I(f)'+I(g)'+I(k)'2+I(i)'+I(j)'+I(m)' (4)

[0015] [ka] R in formula (i), formula (j) and formula (m) 6 ~R 9are each independently hydrogen or a hydrocarbon group having 1 to 20 carbon atoms.

[0016] The peak integral value [I(a)'] of the methine C atom shown in (a)' of the triad unit represented by the above formula (a) is 13 Obtained by C-NMR (nuclear magnetic resonance) measurement 13 In the C-NMR spectrum, the integral value of the peak assigned to the methine C atom at position (f)' of the triad unit represented by the following formula (f) is I(f)', the integral value of the peak assigned to the methine C atom at position (g)' of the triad unit represented by the following formula (g) is I(g)', and the integral value of the peak assigned to the methine C atom at position (k)'2 of the triad unit represented by the following formula (k) is I(k)'2. The sum of these values ​​can be calculated using the following formula (5): I(a)'=I(f)'+I(g)'+I(k)'2(5)

[0017] The ratio of the peak integral value of the methine C atom shown in (a)' of the triad unit represented by the above formula (a) to the sum of the peak integral values ​​of the methine C atoms shown in (a)', (b)', and (c)' of the triad units represented by the above formulas (a), (b) and (c) can be calculated by the following formula (6): I(a)' / (I(a)'+I(b)'+I(c)')=(I(f)'+I(g)'+I(k)'2) / (I(f)'+I(g)'+I(k)'2+I(i)'+I(j)'+I(m)') (6)

[0018] 13 In the C-NMR spectrum, I(f)' is the peak integral value in the range of 64.0 to 64.8 ppm, and I(g)' is the peak integral value in the range of 65.8 to 66.7 ppm. Furthermore, I(i)' is the peak integral value in the interval from 61.5 to 63.1 ppm, I(j)' is the peak integral value in the interval from 64.8 to 65.8 ppm, and I(m)' is the peak integral value in the interval from 63.1 to 64.0 ppm. The above I(k)'2 is based on the peak in the range of 66.7 to 70.5 ppm, but since it overlaps with peaks of other structures, it can be calculated by subtracting from other peaks. For example, since the peak assigned to the methine C atom at the (e1)' position of the following structural unit (e) also exists in the range of 66.7 to 70.5 ppm, the peak integral value of the above I(k)'2 can be calculated using the following formula (7). Here, I(t) is the peak integral value in the range of 66.7 to 70.5 ppm, I(d1)' is the peak integral value in the range of 98.5 to 101.5 ppm to which the methine C atom of the acetal moiety of the 6-membered acetal ring having a meso configuration at the (d1)' position of the structural unit (d) belongs, and I(e1)' is the peak integral value in the range of 91.5 to 101.5 ppm to which the methine C atom of the acetal moiety of the 6-membered acetal ring having a racemo configuration at the (e1)' position of the structural unit (e) belongs. I(d2)' is the peak integral value in the interval from 71.0 to 74.6 ppm, to which the methine C atom in the main chain of the 6-membered acetal ring having the meso structure at the (d2)' position of the structural unit (d) belongs; I(e2)' is the peak integral value in the interval from 66.7 to 70.5 ppm, to which the methine C atom in the main chain of the 6-membered acetal ring having the racemo structure at the (e2)' position of the structural unit (e). I(k)'2=I(t)-I(d1)'×I(e2)'÷I(d2)' (7)

[0019] [ka] R in formula (d) and formula (e) 4 , R 5 are each independently hydrogen or a hydrocarbon group having 1 to 20 carbon atoms.

[0020] The ratio of the peak integral value of the triad unit consisting of three consecutive hydroxyl group-containing structural units can be adjusted, for example, by appropriately setting the degree of saponification of the raw material polyvinyl alcohol resin, the type of aldehyde, the conditions for the acetalization reaction, and the amounts of acetal groups, hydroxyl groups, and acetyl groups of the polyvinyl acetal resin. Specifically, the aging temperature (holding temperature) for the acetalization reaction is preferably 45° C. or higher, and more preferably 50° C. or higher. By using this reaction temperature, the proportion of the peak integral value of a triad unit consisting of three consecutive sequences of structural units having hydroxyl groups can be increased, making it easier to satisfy the proportion of the peak integral value of a triad unit consisting of three consecutive sequences of structural units having hydroxyl groups specified in the present invention.

[0021] The polyvinyl acetal resin of the present invention preferably has a solution viscosity of 30 mPa s or more and 600 mPa s or less when a 5 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. To improve the tensile strength, the viscosity is preferably 30 mPa·s or more, more preferably 50 mPa·s or more, and particularly preferably 60 mPa·s or more. To improve the viscosity stability of the ceramic slurry composition, the viscosity is preferably 600 mPa·s or less, more preferably 400 mPa·s or less, and particularly preferably 200 mPa·s or less. That is, the viscosity is preferably 30 to 600 mPa·s, more preferably 50 to 400 mPa·s, and particularly preferably 60 to 200 mPa·s. The B-type viscometer may be, for example, a TVB-10 viscometer manufactured by Toki Sangyo Co., Ltd. The rotor and rotation speed during viscosity measurement are preferably adjusted appropriately depending on the viscosity of the solution, and for example, measurements are preferably performed using spindles No. M1 to M4 at a rotation speed in the range of 0.3 to 100 rpm.

[0022] The viscosity can be adjusted by appropriately setting, for example, the degree of saponification and average degree of polymerization of the raw material polyvinyl alcohol resin, the conditions of the acetalization reaction, the amount of acetal groups, the amount of hydroxyl groups, the amount of acetyl groups, the weight-average molecular weight, the number-average molecular weight, the molecular weight distribution, etc. of the polyvinyl acetal resin. Specifically, the aging temperature (retention temperature) in the acetalization reaction is preferably 45° C. or higher, more preferably 50° C. or higher, and is preferably 75° C. or lower, more preferably 72° C. or lower. That is, the retention temperature is preferably 45 to 75° C., more preferably 50 to 72° C. By setting the holding temperature within the above range, it becomes easier to adjust the ratio of the peak integral value of the triplet unit consisting of three consecutive hydroxyl group-containing structural units, and it becomes easier to satisfy the viscosity specified in the present invention.

[0023] The polyvinyl acetal resin of the present invention preferably has a structural unit having an acetal group represented by the following formula (1), a structural unit having a hydroxyl group represented by the following formula (2), and a structural unit having an acetyl group represented by the following formula (3).

[0024] [ka] In the above formula (1), R 1 represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.

[0025] In the above formula (1), R 1 When 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.

[0026] In the polyvinyl acetal resin of the present invention, the content of the structural unit having the acetal group represented by the above formula (1) (hereinafter also referred to as "acetal group amount") is preferably 55 mol % in lower limit and 75 mol % in upper limit. When the amount of acetal groups is 55 mol % or more, the solubility in organic solvents can be improved, and when the amount of acetal groups is 75 mol % or less, the polyvinyl acetal resin can have excellent tensile strength. The lower limit of the acetal group amount is more preferably 57 mol%, even more preferably 60 mol%, and the upper limit is more preferably 73 mol%. That is, the acetal group amount is preferably 55 to 75 mol%, more preferably 57 to 73 mol%, and even more preferably 60 to 73 mol%. The amount of acetal groups is 1 It can be measured by H-NMR. Regarding the method for calculating the amount of acetal groups, since the acetal groups of the polyvinyl acetal resin are obtained by acetalizing two hydroxyl groups of polyvinyl alcohol, the method of counting the two acetalized hydroxyl groups is adopted.

[0027] In the polyvinyl acetal resin of the present invention, the content of the structural unit having a hydroxyl group represented by the above general formula (2) (hereinafter also referred to as "hydroxyl group amount") is preferably 23 mol % in lower limit and 40 mol % in upper limit. When the amount of hydroxyl groups is 23 mol % or more, the polyvinyl acetal resin can have high toughness, and when the amount of hydroxyl groups is 40 mol % or less, the solubility in organic solvents can be sufficiently improved. The lower limit of the hydroxyl group content is more preferably 25 mol%, even more preferably 27 mol%, and particularly preferably 29 mol%, and the upper limit is more preferably 35 mol%, and even more preferably 33 mol%. That is, the hydroxyl group content is preferably 23 to 40 mol%, more preferably 25 to 35 mol%, even more preferably 27 to 33 mol%, and particularly preferably 29 to 33 mol%. The amount of hydroxyl groups is 1 It can be measured by H-NMR.

[0028] In the polyvinyl acetal resin of the present invention, the content of the structural unit having an acetyl group represented by the above general formula (3) (hereinafter also referred to as "acetyl group amount") preferably has a lower limit of 0.1 mol % and an upper limit of 5 mol %. When the acetyl group content is 0.1 mol % or more, the increase in viscosity of the slurry composition for ceramic green sheets due to intramolecular and intermolecular hydrogen bonding of hydroxyl groups in the polyvinyl acetal resin can be suppressed.When the acetyl group content is 5 mol % or less, the flexibility of the polyvinyl acetal resin is not excessively increased, and handling properties can be improved. The acetyl group content is more preferably 0.3 mol% at its lower limit, even more preferably 0.5 mol%, more preferably 4 mol%, even more preferably 3 mol%, and particularly preferably 2 mol% at its upper limit. That is, the acetyl group content is preferably 0.1 to 5 mol%, more preferably 0.3 to 4 mol%, even more preferably 0.5 to 3 mol%, and particularly preferably 0.5 to 2 mol%. The amount of acetyl groups is 1 It can be measured by H-NMR.

[0029] The polyvinyl acetal resin of the present invention has a lower limit of the weight average molecular weight (Mw) of 230000. When the weight average molecular weight is 230000 or more, the tensile strength can be improved. The lower limit of the weight average molecular weight is preferably 270,000, more preferably 290,000, and the upper limit is preferably 700,000, more preferably 450,000. That is, the weight average molecular weight is preferably 270,000 to 700,000, more preferably 290,000 to 450,000. Furthermore, the polyvinyl acetal resin of the present invention has a number average molecular weight (Mn) whose lower limit is preferably 98,000, and whose upper limit is preferably 250,000, and more preferably 160,000. That is, the number average molecular weight is preferably 98,000 to 250,000, and more preferably 98,000 to 160,000.

[0030] The polyvinyl acetal resin of the present invention has a molecular weight distribution, which is the ratio (Mw / Mn) of weight average molecular weight (Mw) to number average molecular weight (Mn), of preferably 2.2 at the lower limit, more preferably 2.3 at the lower limit, and preferably 2.75 at the upper limit, more preferably 2.73 at the upper limit, and even more preferably 2.7 at the upper limit. That is, the Mw / Mn is preferably 2.2 to 2.75, more preferably 2.3 to 2.73, and even more preferably 2.3 to 2.7. The Mw and Mn can be measured, for example, by gel permeation chromatography (GPC) using an appropriate standard (e.g., polystyrene standard). Columns used for measuring the Mw and Mn include, for example, TSKgel SuperHZM-H.

[0031] From the viewpoint of maintaining mechanical strength when producing a thin film ceramic green sheet, the polyvinyl acetal resin of the present invention has an average degree of polymerization of preferably 600, more preferably 800, and even more preferably 1000 as a lower limit, and from the viewpoint of solubility in organic solvents and dissolution viscosity, the average degree of polymerization is preferably 4000, more preferably 3000, and even more preferably 2500. That is, the average degree of polymerization is preferably 600 to 4000, more preferably 800 to 3000, and even more preferably 1000 to 2500. The average degree of polymerization of the polyvinyl acetal resin is the same as that of the raw material polyvinyl alcohol, and can be measured in accordance with JIS K 6726.

[0032] The polyvinyl acetal resin of the present invention can usually be produced by acetalizing a polyvinyl alcohol resin.

[0033] As the polyvinyl alcohol resin, for example, a conventionally known polyvinyl alcohol resin such as a resin produced by saponifying a polyvinyl acetate resin with an alkali, an acid, aqueous ammonia, or the like can be used. The polyvinyl alcohol resin may be fully saponified, but does not need to be fully saponified as long as it has at least one unit having two consecutive hydroxyl groups at the meso and racemo positions at at least one location on the main chain, and may be a partially saponified polyvinyl alcohol resin. Furthermore, as the polyvinyl alcohol resin, a copolymer of vinyl alcohol and a monomer copolymerizable with vinyl alcohol, such as an ethylene-vinyl alcohol copolymer resin or a partially saponified ethylene-vinyl alcohol copolymer resin, may also be used. The polyvinyl acetate resin may be, for example, an ethylene-vinyl acetate copolymer.

[0034] The polyvinyl alcohol resin preferably has a saponification degree of 70 mol % or more and 99.5 mol % or less, and more preferably 95 mol % or more and 99.3 mol % or less, i.e., the saponification degree is preferably 70 to 99.5 mol %, and more preferably 95 to 99.3 mol %. By using the above polyvinyl alcohol resin, the proportion of peak integral values ​​of triad units each consisting of three consecutive hydroxyl group-containing structural units in the polyvinyl acetal resin and the viscosity can be set within a predetermined range.

[0035] The polyvinyl alcohol resin may be a single type or a plurality of types. By using the plurality of types of polyvinyl alcohol resins, it is possible to easily adjust the viscosity within a predetermined range and to prepare a slurry composition for a ceramic green sheet that has excellent viscosity stability over time.

[0036] The acetalization is preferably carried out in a water solvent, a mixed solvent of water and an organic solvent compatible with water, or an organic solvent. As the organic solvent compatible with water, for example, an alcohol-based organic solvent can be used. Examples of the organic solvent include alcohol-based organic solvents, aromatic organic solvents, aliphatic ester-based solvents, ketone-based solvents, lower paraffin-based solvents, ether-based solvents, amide-based solvents, and amine-based solvents. Examples of the alcohol-based organic solvent include methanol, ethanol, n-propanol, isopropanol, n-butanol, and tert-butanol. Examples of the aromatic organic solvent include xylene, toluene, ethylbenzene, and methyl benzoate. Examples of the aliphatic ester solvent include methyl acetate, ethyl acetate, butyl acetate, methyl propionate, ethyl propionate, methyl butyrate, ethyl butyrate, methyl acetoacetate, and ethyl acetoacetate. Examples of the ketone solvent include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methylcyclohexanone, benzophenone, and acetophenone. Examples of the lower paraffin solvent include hexane, pentane, octane, cyclohexane, and decane. Examples of the ether solvent include diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol diethyl ether. Examples of the amide solvent include N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and acetanilide. Examples of the amine solvent include ammonia, trimethylamine, triethylamine, n-butylamine, di-n-butylamine, tri-n-butylamine, aniline, N-methylaniline, N,N-dimethylaniline, and pyridine. These solvents can be used alone or in combination of two or more. Among these, ethanol, n-propanol, isopropanol, and tetrahydrofuran are particularly preferred from the viewpoints of solubility in the resin and ease of purification.

[0037] 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.

[0038] The aldehyde used in the acetalization reaction includes aldehydes having a chain aliphatic group, a cyclic aliphatic group, or an aromatic group having 1 to 10 carbon atoms. Any known aldehyde can be used as this aldehyde. The aldehyde used in the acetalization reaction is not particularly limited, and examples thereof include aliphatic aldehydes and aromatic aldehydes. Examples of the aliphatic aldehyde include formaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, n-valeraldehyde, n-hexylaldehyde, 2-ethylbutyraldehyde, 2-ethylhexylaldehyde, n-heptylaldehyde, n-octylaldehyde, n-nonylaldehyde, n-decylaldehyde, and amylaldehyde. Examples of the aromatic aldehyde include benzaldehyde, cinnamaldehyde, 2-methylbenzaldehyde, 3-methylbenzaldehyde, 4-methylbenzaldehyde, p-hydroxybenzaldehyde, m-hydroxybenzaldehyde, phenylacetaldehyde, and β-phenylpropionaldehyde. These aldehydes may be used alone or in combination of two or more. Among them, formaldehyde, acetaldehyde, butylaldehyde, 2-ethylhexylaldehyde, and n-nonylaldehyde are preferred as aldehydes, as they have excellent acetalization reactivity, bring about a sufficient internal plasticizing effect in the resulting resin, and as a result, can impart good flexibility. Furthermore, formaldehyde, acetaldehyde, and butylaldehyde are more preferred, as they can provide an adhesive composition that is particularly excellent in impact resistance and adhesion to metals.

[0039] The amount of the aldehyde added can be appropriately set 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 55 mol% to 95 mol%, more preferably 60 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. That is, the amount of the aldehyde added is preferably 55 to 95 mol%, more preferably 60 to 90 mol%. The temperature at which the aldehyde is added (aldehyde introduction temperature) is preferably 0° C. or higher, more preferably 10° C. or higher, and preferably 35° C. or lower. That is, the aldehyde introduction temperature is preferably 0 to 35° C., more preferably 10 to 35° C. By setting the aldehyde introduction temperature in the above range, the proportion of peak integral values ​​of triad units each consisting of three consecutive hydroxyl group-containing structural units in the polyvinyl acetal resin and the viscosity can be set within a predetermined range.

[0040] The acetalization reaction is preferably carried out by raising the temperature at a predetermined rate and then maintaining the temperature for a certain period of time. The temperature rise time in the acetalization reaction is preferably 60 minutes or more and 500 minutes or less, and more preferably 120 minutes or more and 400 minutes or less, i.e., the temperature rise time is preferably 60 to 500 minutes, and more preferably 120 to 400 minutes. The temperature rise rate is preferably 0.1° C. / min or more and 2° C. / min or less, that is, the temperature rise rate is preferably 0.1 to 2° C. / min. By increasing the temperature at the above-mentioned temperature increase rate, the proportion of peak integral values ​​of triad units each consisting of three consecutive hydroxyl group-containing structural units in the polyvinyl acetal resin, viscosity, and particle size can be set within a predetermined range.

[0041] The retention time in the acetalization reaction is preferably 0.1 to 7 hours, more preferably 0.5 to 5 hours. That is, the retention time is preferably 0.1 to 7 hours, more preferably 0.5 to 5 hours. By using the retention time, the proportion of peak integral values ​​of triad units each consisting of three consecutive hydroxyl group-containing structural units in the polyvinyl acetal resin and the viscosity can be set within a predetermined range. The holding temperature in the acetalization reaction is preferably 45° C. or higher and 75° C. or lower, more preferably 50° C. or higher and 72° C. or lower, and even more preferably 59° C. or higher and 71° C. or lower. That is, the holding temperature is preferably 45 to 75° C., more preferably 50 to 72° C., and even more preferably 59 to 71° C. By setting the holding temperature in the above ranges, the proportion of peak integral values ​​of triad units each consisting of three consecutive sequences of structural units having a hydroxyl group in the polyvinyl acetal resin and the viscosity can be set within a predetermined range.

[0042] A slurry composition for ceramic green sheets can be prepared by mixing the polyvinyl acetal resin of the present invention with an organic solvent and ceramic powder.

[0043] 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.

[0044] The content of the organic solvent in the ceramic green sheet slurry composition is determined depending on the type of polyvinyl acetal resin used and is not particularly limited. However, if the content is too low, the solubility required for kneading is difficult to exhibit. Also, if the content is too high, the viscosity of the ceramic green sheet slurry composition becomes too low, which can result in poor handling when producing ceramic green sheets. Therefore, the content of the organic solvent is preferably 20% by weight or more and 80% by weight or less. In other words, the content of the organic solvent is preferably 20 to 80% by weight.

[0045] The ceramic powders include metal or nonmetal oxide or non-oxide powders used in ceramic production. These powders may be single compositions, compounds, or mixtures. The constituent elements of the metal oxide or non-oxide, both cations and anions, may be single elements or multiple elements, and may further contain additives to improve the properties of the oxide or non-oxide. Specific examples include oxides, carbides, nitrides, borides, and sulfides of elements such as Li, K, Mg, B, Al, Si, Cu, Ca, Sr, Ba, Zn, Cd, Ga, In, Y, lanthanides, actinides, Ti, Zr, Hf, Bi, V, Nb, Ta, W, Mn, Fe, Co, and Ni. Furthermore, when specific oxide powders containing multiple metal elements, commonly called double oxides, are classified based on their crystal structure, those with a perovskite structure include NaNbO3, SrZrO3, PbZrO3, SrTiO3, BaZrO3, PbTiO3, BaTiO3, etc. Those with a spinel structure include MgAl2O4, ZnAl2O4, CoAl2O4, NiAl2O4, MgFe2O4, etc. Those with an ilmenite structure include MgTiO3, MnTiO3, FeTiO3, etc. Those with a garnet structure include GdGa5O 12 , Y6Fe5O 12 Among these, the modified polyvinyl acetal resin of the present invention exhibits excellent properties when mixed with BaTiO3 powder to form a ceramic green sheet.

[0046] The ceramic green sheet slurry composition may contain a plasticizer. Addition of a plasticizer can significantly improve the mechanical strength and flexibility of the resulting ceramic green sheet. Examples of the plasticizer include phthalic acid diesters such as dioctyl phthalate (DOP) and dibutyl phthalate (DBP), adipic acid diesters such as dioctyl adipate, and alkylene glycol diesters such as triethylene glycol-di-2-ethylhexanoate, tetraethylene glycol-di-2-ethylhexanoate, triethylene glycol-di-2-ethylbutyrate, tetraethylene glycol-di-2-ethylbutyrate, tetraethylene glycol-di-heptanoate, and triethylene glycol-di-heptanoate.

[0047] 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.

[0048] In the slurry composition for ceramic green sheets, the content of the plasticizer relative to 100 parts by weight of the polyvinyl acetal resin is preferably 7 parts by weight at the lower limit, more preferably 8.5 parts by weight at the lower limit, and preferably 40 parts by weight at the upper limit, more preferably 30 parts by weight at the upper limit. That is, the content of the plasticizer is preferably 7 to 40 parts by weight, more preferably 8.5 to 30 parts by weight.

[0049] The slurry composition 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 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.

[0050] The slurry composition for a ceramic green sheet may contain, as needed, a dispersant, an antioxidant, an ultraviolet absorber, a surfactant, a filler, a release agent, etc., and in some cases, a small amount of other resin such as an acrylic resin or a urethane resin may be added.

[0051] The method for producing the above-mentioned slurry composition for ceramic green sheets 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.

[0052] After the slurry composition for ceramic green sheets is applied, the composition is heated and dried to obtain ceramic green sheets. The ceramic green sheets can be used to manufacture ceramic electronic components, for example, by carrying out a step of applying an electrode layer paste to the surfaces of the ceramic green sheets, and a step of stacking the ceramic green sheets on which the electrode layers have been formed, and then heat-pressing and bonding the stacked body, and then degreasing and firing the resulting laminate.

[0053] The method for applying the slurry composition for a 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.

[0054] The ceramic electronic component is not particularly limited, and examples thereof include a multilayer ceramic capacitor, a multilayer ceramic inductor, a capacitor, a piezoelectric actuator, a multilayer varistor, a multilayer thermistor, an EMI filter, an aluminum nitride multilayer substrate, an alumina multilayer substrate, etc. Such a multilayer ceramic capacitor also constitutes part of the present invention.

[0055] The method for producing a ceramic electronic component includes a step of applying a paste for electrode layers to the surfaces of the ceramic green sheets. The electrode layer paste can be obtained by dissolving, for example, polyvinyl acetal resin, ethyl cellulose, acrylic resin, or the like as a binder resin in an organic solvent and dispersing conductive powder, etc. These resins may be used alone or in combination of two or more. An electrode layer paste containing a polyvinyl acetal resin is preferred because it exhibits excellent adhesion to the ceramic green sheet in the thermocompression bonding process.

[0056] In the method for producing a ceramic electronic component, the ceramic green sheets having electrode layers formed thereon are produced as described above, and then ceramic green sheets having electrode layers formed thereon that are produced in the same manner are stacked and heated and pressed together to obtain a laminate, which is then degreased and fired, thereby obtaining a multilayer ceramic electronic component that solves problems such as sheet attack and cracking. The above-mentioned thermocompression bonding step and the steps of degreasing and firing the laminate are not particularly limited, and conventionally known methods can be used. [Effects of the Invention]

[0057] According to the present invention, it is possible to provide a polyvinyl acetal resin that can be used to obtain ceramic green sheets that are excellent in sheet attack resistance and tensile strength, particularly when used as a binder for ceramic green sheets, and that is unlikely to cause a decrease in electrical properties or an increase in the defect rate, and that can be used to produce highly reliable multilayer ceramic capacitors. DETAILED DESCRIPTION OF THE INVENTION

[0058] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0059] Example 1 3000 g of pure water was added to 210 g of polyvinyl alcohol resin (average degree of polymerization 1,750, saponification degree 99.1 mol%) and dissolved by stirring at 90°C for approximately 2 hours. This solution was cooled to 20°C, and 200 g of 35 wt% hydrochloric acid and 115 g of n-butyl aldehyde were added to precipitate a polyvinyl acetal resin. The temperature was then increased at a rate of 0.3°C / min (heating time: 150 minutes) and maintained at 65°C for 3 hours to carry out an acetalization reaction. The reaction was then completed, and the mixture was neutralized, washed with water, and dried by conventional methods to obtain a white powder of polyvinyl acetal resin.

[0060] Example 2 193 g of polyvinyl alcohol resin (average degree of polymerization 1,750, saponification degree 99.1 mol%, first PVA) and 17 g of polyvinyl alcohol resin (average degree of polymerization 800, saponification degree 98.4 mol%, second PVA) were added to 3,000 g of pure water and dissolved by stirring at 90° C. for approximately 2 hours. This solution was cooled to 20° C., and 200 g of 35 wt% hydrochloric acid and 120 g of n-butyl aldehyde were added thereto. The temperature was increased at a rate of 0.3° C. / min (heating time 150 min). The mixture was then maintained at 65° C. for 3 hours to carry out an acetalization reaction. After completion of the reaction, the mixture was neutralized, washed with water, and dried in a conventional manner to obtain a white powder of polyvinyl acetal resin.

[0061] Example 3 3,000 g of pure water was added to 210 g of polyvinyl alcohol resin (average degree of polymerization 1,700, saponification degree 99.0 mol%), and the mixture was stirred at 90°C for approximately 2 hours to dissolve. This solution was cooled to 20°C, and 200 g of 35 wt% hydrochloric acid and 115 g of n-butylaldehyde were added thereto. The temperature was increased at a rate of 0.30°C / min (heating time: 150 minutes). The mixture was maintained at 65°C for 2 hours to carry out an acetalization reaction, after which the reaction was completed. The mixture was neutralized, washed with water, and dried in the usual manner to obtain a white powder of polyvinyl acetal resin.

[0062] (Comparative Example 1) 3000 g of pure water was added to 300 g of polyvinyl alcohol resin (average degree of polymerization 1,700, degree of saponification 98.0 mol%) and dissolved by stirring at 90°C for approximately 2 hours. This solution was cooled to 40°C, and 200 g of hydrochloric acid with a concentration of 35 wt% and 160 g of n-butylaldehyde were added thereto. The mixture was maintained at 40°C for 3 hours to carry out an acetalization reaction, after which the reaction was completed. The mixture was neutralized, washed with water, and dried by a conventional method to obtain a white powder of polyvinyl acetal resin.

[0063] (Comparative Example 2) 3100 g of pure water was added to 300 g of polyvinyl alcohol resin (average degree of polymerization 3,000, degree of saponification 98.5 mol%) and dissolved by stirring at 90°C for approximately 2 hours. This solution was cooled to 40°C, and 200 g of hydrochloric acid with a concentration of 35 wt% and 160 g of n-butylaldehyde were added thereto. The mixture was maintained at 40°C for 3 hours to carry out an acetalization reaction, after which the reaction was completed. The mixture was neutralized, washed with water, and dried by a conventional method to obtain a white powder of polyvinyl acetal resin.

[0064] (Comparative Example 3) 3100 g of pure water was added to 300 g of polyvinyl alcohol resin (average degree of polymerization 800, saponification degree 98.4 mol%) and dissolved by stirring at 90°C for approximately 2 hours. This solution was cooled to 40°C, and 200 g of hydrochloric acid with a concentration of 35 wt% and 150 g of n-butylaldehyde were added thereto. The mixture was maintained at 40°C for 3 hours to carry out an acetalization reaction, after which the reaction was completed. The mixture was neutralized, washed with water, and dried by a conventional method to obtain a white powder of polyvinyl acetal resin.

[0065] Comparative Example 4 3100 g of pure water was added to 300 g of polyvinyl alcohol resin (average degree of polymerization 800, saponification degree 98.4 mol%) and dissolved by stirring at 90°C for approximately 2 hours. This solution was cooled to 20°C, and 200 g of 35 wt% hydrochloric acid and 145 g of n-butylaldehyde were added thereto. The temperature was increased at a rate of 0.25°C / min (heating time: 150 minutes). The mixture was maintained at 58°C for 3 hours to carry out an acetalization reaction, after which the reaction was completed. The mixture was neutralized, washed with water, and dried by conventional methods to obtain a white powder of polyvinyl acetal resin.

[0066] (evaluation) The polyvinyl acetal resins obtained in the examples and comparative examples were evaluated as follows, and the results are shown in Table 1.

[0067] (1) Evaluation of polyvinyl acetal resin (1-1) Amount of acetal groups, amount of hydroxyl groups, amount of acetyl groups The obtained polyvinyl acetal resin was analyzed using an AV400 spectrometer (manufactured by Bruker). 1 H-NMR measurement was carried out, and the amounts of acetal groups, hydroxyl groups, and acetyl groups were calculated. The obtained polyvinyl acetal resin was dissolved in DMSO-D6 to a concentration of 1.6% by weight to prepare a measurement solution. 1 H-NMR measurements were carried out at 80°C.

[0068] (1-2) Proportion of the peak integral value of triad units consisting of three consecutive hydroxyl group-containing structural units in polyvinyl acetal resin (proportion of triad hydroxyl group structural units) The obtained polyvinyl acetal resin was analyzed using an AV400 spectrometer (manufactured by Bruker). 13 The proportion of the peak integral value of the triad unit consisting of three consecutive hydroxyl group-containing structural units in the polyvinyl acetal resin was measured by C-NMR measurement. The details of the peak integral value measurement are as described above. The obtained polyvinyl acetal resin was dissolved in DMSO-D6 to a concentration of 12% by weight to prepare a measurement solution. 13 C-NMR measurements were carried out at 80°C.

[0069] (1-3) Average molecular weight measurement 0.04 g of the obtained polyvinyl acetal resin was added to 20 g of tetrahydrofuran and stirred to dissolve, producing a resin solution. The weight average molecular weight (Mw) and number average molecular weight (Mn) of the resin solution, calculated in terms of polystyrene, were measured by gel permeation chromatography using an LF-804 (manufactured by SHOKO Corporation) column. The Mw / Mn ratio was calculated from the obtained Mw and Mn.

[0070] (1-4) Viscosity measurement The obtained polyvinyl acetal resin was dissolved in a 1:1 ethanol / toluene mixed solution to a concentration of 5% by mass to prepare a sample for viscosity measurement. The viscosity of the obtained sample for viscosity measurement was measured using a B-type viscometer. The B-type viscometer used was a TVB-10 viscometer (manufactured by Toki Sangyo Co., Ltd.), and measurements were carried out with the following rotation speeds and rotors: Examples 1 to 3, Comparative Example 1: Rotational speed 30 rpm, SPINDLE No. M1 Comparative example 2: Rotation speed 30 rpm, SPINDLE No.M2 Comparative Examples 3 and 4: Rotational speed 60 rpm, SPINDLE No. M1

[0071] (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 dissolved with stirring 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 the film was dried by heating to prepare a polyvinyl acetal resin sheet.

[0072] (2-1) Seat attack resistance evaluation 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 evaporate the solvent. After removing from the dryer, the specimen 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 this elution amount to the weight of the specimen before the test, and evaluated according to the following criteria. Note that a higher elution rate indicates better sheet attack resistance.

[0073] AA: Dissolution rate less than 2.0% A: Dissolution rate is 2.0% or more and less than 2.5% B: Dissolution rate is 2.5% or more and less than 3.0% C: Dissolution rate is 3.0% or more

[0074] (3) Evaluation of Slurry Composition for Ceramic Green Sheets [Temporal Viscosity Stability] (Preparation of inorganic powder dispersion) One part by weight of polyvinyl acetal resin (BL-1, manufactured by Sekisui Chemical Co., Ltd.) was added to a mixed solvent of 20 parts by weight of toluene and 20 parts by weight of ethanol and dissolved by stirring. Next, 100 parts by weight of barium titanate powder (BT01, manufactured by Sakai Chemical Industry Co., Ltd.) was added to the resulting solution and stirred for 180 minutes in a bead mill (Ready Mill, manufactured by Imex Co., Ltd.) to prepare an inorganic powder dispersion. (Preparation of resin solution) A resin solution was prepared by adding 8 parts by weight of polyvinyl acetal resin and 2.1 parts by weight of plasticizer (G260 manufactured by Sekisui Chemical Co., Ltd.) to a mixed solvent of 45 parts by weight of ethanol and 45 parts by weight of toluene and stirring to dissolve. (Preparation of slurry for ceramic green sheets) The resin solution was added to the obtained inorganic powder dispersion and stirred for 90 minutes in a bead mill to obtain a slurry composition for ceramic green sheets.

[0075] (3-1) Viscosity stability over time The viscosity of the obtained slurry composition for ceramic green sheet was measured at 20°C and a rotation speed of 1.0 (1 / s) using a rheometer (Discovery HR 10 manufactured by TA Instruments). The viscosity of the slurry composition for ceramic green sheet after leaving it at 23°C for one week was also measured under the same conditions, and the rate of change in viscosity before and after one week was calculated. The obtained rate of change in viscosity was evaluated according to the following criteria.

[0076] AA: Viscosity change rate is 400% or less A: Viscosity change rate is over 400% and 500% or less B: Viscosity change rate is over 500% and 600% or less C: Viscosity change rate exceeds 600%

[0077] (4) Evaluation of ceramic green sheets (Preparation of ceramic green sheets) The obtained slurry was applied to a release-treated PET film using a coater so that the thickness after drying would be 20 μm, and then heated and dried to prepare a ceramic green sheet.

[0078] (4-1) Tensile strength The breaking stress (MPa) of the obtained ceramic green sheets was measured at a tension speed of 20 mm / min in an environment of 23°C using a tensile tester (AUTOGRAPH AGS-J, manufactured by Shimadzu Corporation) in accordance with JIS K 7113. The breaking stress obtained was evaluated according to the following criteria.

[0079] AA: Breaking stress is over 32 MPa A: Breaking stress is over 30 MPa and 32 MPa or less B: Breaking stress is over 25 MPa and 30 MPa or less C: Breaking stress is 25 MPa or less

[0080] [Table 1] [Industrial Applicability]

[0081] According to the present invention, it is possible to provide a polyvinyl acetal resin that can be used to obtain ceramic green sheets that are excellent in sheet attack resistance and tensile strength, particularly when used as a binder for ceramic green sheets, and that is unlikely to cause a decrease in electrical properties or an increase in the defect rate, and that can be used to produce highly reliable multilayer ceramic capacitors.

Claims

1. It is a polyvinyl acetal resin used in ceramic green sheets, １３ a ratio of the peak integral value of the methine C atom shown in (a)' of the triad unit represented by the following formula (a) to the sum of the peak integral values ​​of the methine C atoms shown in (a)', (b)', and (c)' of the triad units represented by the following formulas (a), (b) and (c), as obtained by C-NMR (nuclear magnetic resonance) measurement, of 0.23 or more; the amount of hydroxyl groups is 23 mol% or more and 40 mol% or less, and the amount of acetyl groups is 0.1 mol% or more and 5 mol% or less, The weight average molecular weight is 230,000 or more and the molecular weight distribution is 2.75 or less. Polyvinyl acetal resin. 【Chemistry 1】 In formula (b) and formula (c), R is each independently hydrogen or a hydrocarbon group having 1 to 20 carbon atoms.

2. 2. The polyvinyl acetal resin according to claim 1, wherein a 5 mass% solution of the polyvinyl acetal resin in a 1:1 mixed solvent of ethanol and toluene has a solution viscosity of 30 mPa s or more and 600 mPa s or less, as measured using a Brookfield viscometer at a solution temperature of 20°C.

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

4. A ceramic green sheet obtained by using the slurry composition for a ceramic green sheet according to claim 3.

5. A multilayer ceramic capacitor obtained by using the ceramic green sheet according to claim 4.

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