Polyvinyl acetal resin, slurry for ceramic green sheet, and ceramic green sheet

Abstract

The purpose of the present invention is to provide: a polyvinyl acetal resin from which a ceramic green sheet having a low elution rate to a solvent, excellent thermocompression bonding properties, low incidence of structural defects, and high mechanical strength can be obtained; and a slurry for a ceramic green sheet and a ceramic green sheet which use said polyvinyl acetal resin. The present invention pertains to a polyvinyl acetal resin having a constitutional unit represented by formula (1), wherein: R1 in formula (1) is a C4-C11 hydrocarbon group; the content of the constitutional unit represented by formula (1) is at least 0.01 mol%; the amount of a hydroxyl group is at least 28 mol%; and the viscosity parameter is at most 0.200, as calculated using expression (2) from the viscosity (3 wt% E / T viscosity) of a solution dissolved in 3 wt% in a mixed solvent containing ethanol and toluene at a ratio of 50:50, the weight-average molecular weight (Mw [NMP]) when measured by GPC using NMP as the solvent, the content of the constitutional unit represented by formula (1), and the number of carbon atoms in a hydrocarbon of R1.

Description

Polyvinyl acetal resin, slurry for ceramic green sheet, and ceramic green sheet

[0001] The present invention relates to a polyvinyl acetal resin, a slurry for a ceramic green sheet, and a ceramic green sheet.

[0002] In recent years, electronic components mounted in various electronic devices have become increasingly miniaturized and multilayered, resulting in widespread use of multilayer electronic components such as multilayer circuit boards, laminated coils, and multilayer ceramic capacitors. Multilayer ceramic capacitors, among others, are generally manufactured through the following process. First, a plasticizer, dispersant, etc. are added to a solution of a binder resin, such as polyvinyl butyral resin or poly(meth)acrylate resin, dissolved in an organic solvent. Then, ceramic raw material powder is added and uniformly mixed using a mixing device such as a bead mill or ball mill. After degassing, a ceramic slurry composition with a constant viscosity is obtained. This slurry composition is cast onto a support surface, such as a release-treated polyethylene terephthalate film or SUS plate, using a doctor blade or reverse roll coater. The resulting ceramic green sheets are then heated to remove volatiles such as the solvent, and the sheets are peeled off from the support to obtain ceramic green sheets. Next, multiple sheets of the resulting ceramic green sheets, each coated with a conductive paste for internal electrodes by screen printing, are alternately stacked and heated and pressed together to form a laminate. Thereafter, the laminate is subjected to a process of thermally decomposing and removing binder resin components and the like contained in the laminate, a so-called degreasing process, and then external electrodes are sintered onto the end faces of the ceramic sintered body obtained by firing, to obtain a multilayer ceramic capacitor.

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

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

[0005] On the other hand, in recent years, with the increasing functionality and miniaturization of electronic devices, multilayer ceramic capacitors are required to have higher capacitance and be smaller, and ceramic green sheets are also required to be thinner. However, when the polyvinyl acetal resins described in Patent Documents 1 and 2 are used as binders for ceramic green sheets, there is a problem of poor thermocompression bondability (adhesion) with internal electrodes (conductive layers). Furthermore, attempts to improve thermocompression bondability result in a decrease in strength due to structural defects in the ceramic green sheets, and new elution into solvents occurs when forming conductive layers, making it difficult to achieve both of these goals.

[0006] The present invention aims to provide a polyvinyl acetal resin that has a low elution rate in solvents, excellent thermocompression bondability, and is capable of producing ceramic green sheets with few structural defects and high mechanical strength, as well as a ceramic green sheet slurry and a ceramic green sheet that use the polyvinyl acetal resin.

[0007] The present disclosure 1 has a constitutional unit represented by the following formula (1), and R １ is a hydrocarbon group having 4 to 11 carbon atoms, the content of the structural unit represented by the following formula (1) is 0.01 mol % or more, the amount of hydroxyl groups is 28 mol % or more, and the viscosity of a solution obtained by dissolving the structural unit represented by the formula (1) at 3 wt % in a mixed solvent containing ethanol and toluene at a ratio of 50:50 (3 wt % E / T viscosity), the weight average molecular weight (Mw[NMP]) measured by GPC using NMP as a solvent, the content of the structural unit represented by the formula (1), and R １ and the number of carbon atoms of the hydrocarbon, using the following formula (2), the viscosity parameter of the polyvinyl acetal resin is 0.200 or less. Disclosure 2 is the polyvinyl acetal resin according to Disclosure 1, wherein the content of the structural unit represented by Formula (1) is 70 mol% or less. Disclosure 3 is the polyvinyl acetal resin according to Disclosure 1 or 2, wherein the content of the structural unit represented by Formula (1) is 35 mol% or less. Disclosure 4 is the polyvinyl acetal resin according to any one of Disclosures 1 to 3, wherein the structural unit having an acetal group is only the structural unit represented by Formula (1). Disclosure 5 is the polyvinyl acetal resin according to any one of Disclosures 1 to 4, wherein the hydrocarbon group having 4 to 11 carbon atoms is a linear alkyl group. Disclosure 6 is the polyvinyl acetal resin according to any one of Disclosures 1 to 5, further comprising a structural unit represented by Formula (3). In formula (3), R ２ represents a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms. １ is one kind or two or more kinds, and R ２The polyvinyl acetal resin according to Disclosure 6, wherein the structural units represented by Formula (1) and the structural units represented by Formula (3) are of a single type or two or more types. Disclosure 8 is the polyvinyl acetal resin according to Disclosure 6 or 7, wherein the total content of the structural units represented by Formula (1) and the content of the structural units represented by Formula (3) (total acetal group content) is 50 to 70 mol %. Disclosure 9 is the polyvinyl acetal resin according to any one of Disclosures 1 to 8, wherein the acetyl group content is 8.5 mol % or less. Disclosure 10 is the polyvinyl acetal resin according to any one of Disclosures 1 to 9, wherein the tan δ peak top temperature is 0°C or higher and 80°C or lower in dynamic viscoelasticity measurement at 1 Hz. Disclosure 11 is the polyvinyl acetal resin according to any one of Disclosures 1 to 10, wherein, in a dynamic viscoelastic measurement at 1 Hz, the storage modulus ratio (E'- / E'+) between the storage modulus E'- at a tan δ peak top temperature −5°C and the storage modulus E'+ at a tan δ peak top temperature +5°C is 5 or more and 100 or less. Disclosure 12 is the polyvinyl acetal resin according to any one of Disclosures 1 to 11, wherein Mw[NMP] is 50,000 or more and 1,000,000 or less. Disclosure 13 is a slurry for a ceramic green sheet, containing the polyvinyl acetal resin according to any one of Disclosures 1 to 12, an organic solvent, and a ceramic powder. Disclosure 14 is a ceramic green sheet obtained using the slurry for a ceramic green sheet according to Disclosure 13.

[0008] As a result of extensive investigations, the present inventors have found that a polyvinyl acetal resin in which the content of the structural unit represented by formula (1), the amount of hydroxyl groups, and the viscosity parameter satisfy a predetermined relationship can be used to obtain a ceramic green sheet that has excellent thermocompression bonding properties, a low elution rate into solvents, and high mechanical strength, and have thus completed the present invention.

[0009] The polyvinyl acetal resin of the present invention has a structural unit represented by the following formula (1), and R １ is a hydrocarbon group having 4 to 11 carbon atoms. By having such a hydrocarbon group, excellent thermocompression bondability can be imparted.

[0010]

[0011] The above R １ The lower limit of the number of carbon atoms in R is preferably 5, more preferably 6, and the upper limit is preferably 10, more preferably 9. １ is preferably a single type or two or more types of hydrocarbon groups.

[0012] The hydrocarbon group having from 4 to 11 carbon atoms is preferably an alkyl group having from 4 to 11 carbon atoms. Examples of the alkyl group having from 4 to 11 carbon atoms include a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, and an undecyl group.

[0013] The hydrocarbon group having from 4 to 11 carbon atoms may be a linear alkyl group or a branched alkyl group, but from the viewpoint of thermocompression bondability, a linear alkyl group is preferable. Examples of the linear alkyl group include an n-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, and an n-undecyl group.

[0014] Examples of the branched alkyl group include an isobutyl group, an isopentyl group, a neopentyl group, a 1-methylhexyl group, a 1-methylheptyl group, a 1-methyloctyl group, a 1-methylnonyl group, and a 1-methyldecyl group. Further examples include alkyl groups in which an alkyl group having two or more carbon atoms is substituted on the first carbon atom (e.g., a 1-ethylnonyl group, a 1-propyloctyl group, a 1-butylheptyl group, and a 1-pentylhexyl group). Furthermore, in a branched alkyl group, the branching position is not limited to the first carbon atom, but may be the second or higher carbon atom. For example, alkyl groups in which a methyl group is substituted on the second or higher carbon atom include a 2-methyldecyl group, a 3-methyldecyl group, and a 4-methyldecyl group. Furthermore, alkyl groups in which an alkyl group having two or more carbon atoms is substituted on the second or higher carbon atom include a 2-ethylhexyl group, a 2-ethylheptyl group, and a 2-ethyloctyl group. Furthermore, a 3-ethylnonyl group is also included.

[0015] In the present invention, the hydrocarbon group having 4 to 11 carbon atoms is preferably a linear alkyl group. The alkyl group having 4 to 11 carbon atoms may be composed of two or more alkyl groups including a linear alkyl group and a branched alkyl group, or may be composed of only a linear alkyl group. １ may be an alkyl group derived from a bio-derived aldehyde having from 4 to 11 carbon atoms. Furthermore, in the present invention, it is preferable that the structural unit having an acetal group is only a structural unit represented by formula (1).

[0016] The content of the structural unit represented by the above formula (1) in the polyvinyl acetal resin of the present invention (hereinafter also referred to as the amount of long-chain acetal groups) is 0.01 mol% or more. This allows for excellent thermocompression bonding properties to be imparted. The preferred lower limit of the content of the structural unit represented by the above formula (1) is 1 mol%, more preferably 3 mol%, and the preferred upper limit is 72 mol%, more preferably 70 mol%, even more preferably 60 mol%, and particularly preferably 35 mol%. This allows for even better thermocompression bonding properties to be imparted. The content of the structural unit represented by the above formula (1) is １ H-NMR and １３ Measurement is performed using C-NMR (nuclear magnetic resonance spectrum).

[0017] The polyvinyl acetal resin of the present invention preferably further contains an acetal unit represented by the following formula (3), which is different from the constitutional unit represented by the above formula (1). By containing the acetal unit represented by the following formula (3), viscosity stability can be imparted in addition to excellent thermocompression bondability.

[0018] In formula (3), R ２ represents a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms.

[0019] Examples of the hydrocarbon group having 1 to 3 carbon atoms include a methyl group, an ethyl group, and a propyl group. The hydrocarbon group having 1 to 3 carbon atoms is preferably an alkyl group, and may be linear or branched. In the present invention, the R １is one kind or two or more kinds, and R ２ is preferably a single type or two or more types. １ and the number of carbon atoms in R ２ The difference in the number of carbon atoms between R and R is preferably 2 or more and 8 or less, and more preferably 3 or more and 7 or less. １ , R ２ When either or both of the above components are composed of two or more hydrocarbons, the difference is maximized.

[0020] The content of the acetal unit represented by the formula (3) in the polyvinyl acetal resin of the present invention is preferably 1 mol %, more preferably 10 mol %, and more preferably 70 mol %, and even more preferably 69 mol %. By setting the content of the acetal unit represented by the formula (3) within the above range, solubility in the dielectric layer solvent can be imparted. The content of the acetal unit represented by the formula (3) is １ H-NMR and １３ Measurement is performed using C-NMR (nuclear magnetic resonance spectrum).

[0021] When the polyvinyl acetal resin of the present invention contains acetal units represented by the above formula (1) and acetal units represented by the above formula (3), the ratio between them (content of acetal units represented by formula (1) / content of acetal units represented by formula (3)) is preferably 10 or more and 600 or less. By setting the ratio within the above range, it is possible to achieve both excellent thermocompression bondability and solubility in a dielectric layer solvent.

[0022] The total content of the structural unit represented by the formula (1) and the structural unit represented by the formula (3) in the polyvinyl acetal resin of the present invention (total acetal group content, total amount of all acetal units) preferably has a lower limit of 50 mol% and an upper limit of 72 mol%. By setting the total acetal group content within the above range, both solubility in the dielectric layer solvent and resistance to electrode layer sheet attack can be achieved. A more preferred lower limit of the total acetal group content is 60 mol%, a more preferred upper limit is 70 mol%, and an even more preferred upper limit is 69 mol%. The total acetal group content is １ H-NMR and１３ The content of the structural unit represented by formula (1) relative to the total amount of acetal groups is measured using C-NMR (nuclear magnetic resonance spectroscopy). When the acetal unit represented by formula (1) and the acetal unit represented by formula (3) are contained, the content of the structural unit represented by formula (1) relative to the total amount of acetal groups (content of structural unit represented by formula (1) / total amount of acetal groups) is preferably 0.001, more preferably 0.01, and more preferably 0.95.

[0023] The polyvinyl acetal resin of the present invention has structural units having hydroxyl groups, and the content of the structural units having hydroxyl groups (hydroxyl group amount) is 28 mol% or more. This makes it possible to impart resistance to electrode layer sheet attack. The hydroxyl group amount in the polyvinyl acetal resin of the present invention is preferably 30 mol% or more and 50 mol% or less. By setting it within this range, it is possible to achieve both solubility in the dielectric layer solvent and resistance to electrode layer sheet attack. A more preferred lower limit of the hydroxyl group amount is 31 mol%, and a more preferred upper limit is 40 mol%. The hydroxyl group amount １ H-NMR and １３ Measurement is performed using C-NMR (nuclear magnetic resonance spectrum).

[0024] The polyvinyl acetal resin of the present invention has a structural unit having an acetyl group. The content of the structural unit having an acetyl group (acetyl group amount) in the polyvinyl acetal resin of the present invention is preferably 0.1 mol% at the lower limit and 8.5 mol% at the upper limit. By setting the acetyl group amount to 0.1 mol% or more, it is possible to improve solubility in solvents, and by setting the acetyl group amount to 8.5 mol% or less, it is possible to achieve both viscosity stability and solubility in solvents. The more preferred lower limit of the acetyl group amount is 0.3 mol%, and the more preferred upper limit is 5 mol%. The acetyl group amount １ H-NMR and １３ Measurement is performed using C-NMR (nuclear magnetic resonance spectrum).

[0025] The polyvinyl acetal resin of the present invention may have a structural unit having a carboxylic acid. The content of the structural unit having a carboxylic acid (amount of carboxylic acid modification) in the polyvinyl acetal resin of the present invention is preferably 0.1 mol% at the lower limit and 10 mol% at the upper limit. By setting the amount of carboxylic acid groups to 0.1 mol% or more, the paste viscosity can be increased, and by setting the amount of carboxylic acid modification to 10 mol% or less, the solubility in solvents can be improved. The lower limit of the amount of acetyl groups is more preferably 0.3 mol%, and the upper limit is more preferably 5 mol%. The amount of carboxylic acid modification is １ H-NMR and １３ Measurement is performed using C-NMR (nuclear magnetic resonance spectrum).

[0026] The preferred lower limit of the average polymerization degree of the polyvinyl acetal resin of the present invention is 300, and the preferred upper limit is 5000. When the average polymerization degree is 300 or more, industrial production becomes easy. When the average polymerization degree is 5000 or less, the solution viscosity becomes appropriate, and industrial production becomes possible. A more preferred lower limit of the average polymerization degree is 500, and a more preferred upper limit is 4000, and an even more preferred lower limit is 800, and an even more preferred upper limit is 3000. The average polymerization degree of the polyvinyl acetal resin can be determined from the polyvinyl alcohol used as a raw material.

[0027] The polyvinyl acetal resin of the present invention may be copolymerized with an ethylenically unsaturated monomer, provided that the effects of the present invention are not impaired. The ethylenically unsaturated monomer is not particularly limited, and examples thereof include acrylic acid, methacrylic acid, phthalic acid (anhydride), maleic acid (anhydride), and itaconic acid (anhydride). Other examples include acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, trimethyl-(3-acrylamido-3-dimethylpropyl)-ammonium chloride, acrylamido-2-methylpropanesulfonic acid, and its sodium salt. Further examples include ethyl vinyl ether, butyl vinyl ether, N-vinylpyrrolidone, vinyl chloride, vinyl bromide, vinyl fluoride, vinylidene chloride, vinylidene fluoride, tetrafluoroethylene, sodium vinyl sulfonate, and sodium allyl sulfonate. Alternatively, a terminal-modified polyvinyl alcohol can be used, which is obtained by copolymerizing a vinyl ester monomer such as vinyl acetate with ethylene in the presence of a thiol compound such as thiolacetic acid or mercaptopropionic acid, and then saponifying the copolymer.

[0028] The polyvinyl acetal resin of the present invention has a viscosity of a solution obtained by dissolving the resin at 3% by weight in a mixed solvent containing ethanol and toluene at a ratio of 50:50 (3% by weight E / T viscosity), a weight average molecular weight (Mw[NMP]) measured by GPC using NMP as a solvent, a content of a constitutional unit represented by the following formula (1) (amount of long-chain acetal groups), and R １ The viscosity parameter calculated using the above formula (2) from the carbon number of the hydrocarbon (long-chain carbon number) is 0.200 or less. The viscosity parameter defined by the above formula (2) is a value obtained by subtracting factors that have a significant influence, such as the weight-average molecular weight and the amount of long-chain acetal groups, and therefore it is possible to more accurately express the desired viscosity of the polyvinyl acetal resin (viscosity development) and viscosity stability. Therefore, when the viscosity parameter is 0.200 or less, viscosity development and viscosity stability are obtained, and as a result, a ceramic green sheet with few structural defects and high mechanical strength can be produced. Note that in the constitutional unit represented by the above formula (1), R １When the hydrocarbon group contains two or more hydrocarbon groups having different carbon numbers, the value of "log10 (the content of the structural unit represented by formula (1) × R １ The carbon number of the hydrocarbon group (R) is calculated based on the content of two or more hydrocarbon groups with different carbon numbers. １ R has different carbon numbers １ａ , R １ｂ and R １ｃ If it contains log10([R １ａ Content of × R １ａ number of carbon atoms in hydrocarbons] + [R １ｂ Content of × R １ｂ number of carbon atoms in hydrocarbons] + [R １ｃ Content of × R １ｃ The carbon number of hydrocarbons is calculated as follows:

[0029] The viscosity parameter is preferably 0.190 or less, more preferably 0.180 or less, and is preferably 0.050 or more, more preferably 0.075 or more.

[0030] The viscosity parameters can be adjusted by the "amount of long-chain acetal groups," "number of long-chain carbon atoms," "3 wt. % E / T viscosity," and "Mw[NMP]" of the polyvinyl acetal resin, as well as the method and reaction conditions of the acetalization reaction when producing the polyvinyl acetal resin, the average degree of polymerization of the polyvinyl acetal resin, the amount of hydroxyl groups, the amount of acetal groups, the amount of acetyl groups, the structure of the acetal unit, the amount of long-chain acetal groups, the number of hydrocarbon carbon atoms in the long-chain acetal groups (long-chain carbon number), and the type and content of modifying groups. In particular, the viscosity parameters cannot be adjusted only by the "amount of long-chain acetal groups" and the "long-chain carbon number," and adjustment of the "3 wt. % E / T viscosity" and "Mw[NMP]" is important. Adjustment of the "3 wt. % E / T viscosity" and "Mw[NMP]" can be performed by the methods described herein.

[0031] The polyvinyl acetal resin of the present invention preferably has a viscosity (3 wt % E / T viscosity) of 5 mPa·s or more and 1,000 mPa·s or less when dissolved at 3 wt % in a mixed solvent containing ethanol and toluene in a 50:50 ratio. From the viewpoint of enhancing mechanical strength, the 3 wt % E / T viscosity is more preferably 8 mPa·s or more, even more preferably 10 mPa·s or more, more preferably 900 mPa·s or less, even more preferably 800 mPa·s or less, and particularly preferably 750 mPa·s or less. The 3 wt % E / T viscosity is preferably measured at 20°C using a Brookfield viscometer. As the Brookfield viscometer, for example, a TVB-10 viscometer manufactured by Toki Sangyo Co., Ltd. can be used. Furthermore, the rotor and rotation speed during viscosity measurement are preferably adjusted appropriately depending on the viscosity of the solution. For example, a rotation speed of 0.3 to 100 rpm can be used, using a SPINDLE No. It is preferable to measure using M1 to M4.

[0032] The 3 wt % E / T viscosity can be adjusted by the method and reaction conditions of the acetalization reaction when preparing the polyvinyl acetal resin, the average degree of polymerization of the starting polyvinyl alcohol or polyvinyl acetal resin, the amount of hydroxyl groups, the amount of acetal groups, the amount of acetyl groups, the structure of the acetal unit (the number of carbon atoms in the alkyl group), the amount of long-chain acetal groups, the number of carbon atoms in the hydrocarbon in the long-chain acetal group (the number of long-chain carbon atoms), the type and content of the modifying group, etc. In particular, it can be adjusted by the average degree of polymerization of the starting polyvinyl alcohol or polyvinyl acetal resin, the solution concentration of the starting polyvinyl alcohol in the acetalization reaction, the pressure when dissolving the starting polyvinyl alcohol, and the amount of long-chain acetal groups.

[0033] When the weight average molecular weight of the polyvinyl acetal resin of the present invention is measured by GPC using NMP as a solvent, Mw[NMP] is preferably 50,000 or more, more preferably 100,000 or more, and preferably 1,000,000 or less, more preferably 800,000 or less. This allows the strength of the dielectric layer to be maintained. The Mw[NMP] can be measured by GPC using N-methylpyrrolidone as a mobile phase and solvent and a differential refractive index detector as a detector.

[0034] The Mw[NMP] can be adjusted by the method and reaction conditions of the acetalization reaction when producing the polyvinyl acetal resin, the average degree of polymerization of the starting polyvinyl alcohol or polyvinyl acetal resin, the amount of hydroxyl groups, the amount of acetal groups, the amount of acetyl groups, the structure of the acetal unit (the number of carbon atoms in the alkyl group), the amount of long-chain acetal groups, the number of carbon atoms in the hydrocarbon in the long-chain acetal group (the number of long-chain carbon atoms), the type and content of the modifying group, etc. In particular, it can be adjusted by the average degree of polymerization of the starting polyvinyl alcohol or polyvinyl acetal resin.

[0035] The polyvinyl acetal resin of the present invention preferably has a tan δ peak top temperature of 0°C or higher and 80°C or lower in dynamic viscoelasticity measurement at 1 Hz. By setting the temperature to 0°C or higher, the mechanical strength can be increased, and by setting the temperature to 80°C or lower, the thermocompression bondability can be improved. The lower limit of the tan δ peak top temperature is more preferably 30°C, and the upper limit is more preferably 75°C. The tan δ peak top temperature is the temperature value at the peak top of tan δ when dynamic viscoelasticity is measured using, for example, a DMA (manufactured by IT Measurement Co., Ltd.) under conditions of a temperature range of 30°C to 150°C, a heating rate of 6°C / min, and a frequency of 1 Hz.

[0036] In a dynamic viscoelasticity measurement at 1 Hz, the polyvinyl acetal resin of the present invention preferably has a storage modulus ratio (E'- / E'+) of 5 to 100, where E'- is the storage modulus at tan δ peak top temperature minus 5°C and E'+ is the storage modulus at tan δ peak top temperature plus 5°C. By achieving a ratio within this range, the peelability of the dielectric layer can be maintained. The lower limit of the storage modulus ratio (E'- / E'+) is more preferably 15, and the upper limit is preferably 50. The storage modulus E'- and E'+ are measured values ​​of the storage modulus E'- and E'+ at tan δ peak top temperature minus 5°C and tan δ peak top temperature plus 5°C, respectively, by performing dynamic viscoelasticity measurement using, for example, a DMA (manufactured by IT Measurement Co., Ltd.) at a temperature range of 30°C to 150°C, a heating rate of 6°C / min, and a frequency of 1 Hz, to measure the peak top temperature.

[0037] The tan δ peak top temperature and storage modulus ratio (E'- / E'+) can be adjusted by, for example, appropriately setting the method and reaction conditions of the acetalization reaction when preparing the polyvinyl acetal resin, the average degree of polymerization of the polyvinyl acetal resin, the amount of hydroxyl groups, the amount of acetal groups, the amount of acetyl groups, the structure of the acetal unit (the number of carbon atoms in the alkyl group), the amount of long-chain acetal groups, the number of carbon atoms in the hydrocarbon in the long-chain acetal group (the number of long-chain carbon atoms), the type and content of the modifying group, etc. In particular, they can be adjusted by the content of the structural unit represented by the above formula (1) relative to the total amount of acetal groups.

[0038] Examples of methods for producing the polyvinyl acetal resin include a method of acetalizing polyvinyl alcohol with an aldehyde, and a method of acetalizing polyvinyl alcohol with an aldehyde having 4 or less carbon atoms and / or an aldehyde having from 5 to 12 carbon atoms. In particular, it is preferable to use a method of acetalizing polyvinyl alcohol with an aldehyde having 4 or less carbon atoms and an aldehyde having from 5 to 12 carbon atoms. By using such a production method, the viscosity parameters, 3 wt % E / T viscosity, Mw[NMP], tan δ peak top temperature, and storage modulus ratio (E'- / E'+) can be adjusted.

[0039] In the method of acetalizing the polyvinyl alcohol using an aldehyde having 4 or less carbon atoms and / or an aldehyde having 5 to 12 carbon atoms, for example, aldehydes having different carbon numbers are prepared and then acetalized to introduce acetal units having multiple alkyl groups having different carbon numbers. When producing the polyvinyl acetal resin, acetalization may be carried out in the presence of a dispersant. More specifically, for example, a method of introducing the acetal unit represented by the formula (1) by acetalizing polyvinyl alcohol not having the acetal unit represented by the formula (1) with a specific aldehyde is exemplified.

[0040] The polyvinyl alcohol can be obtained, for example, by saponifying a vinyl ester polymer. Examples of the vinyl ester include vinyl formate, vinyl acetate, vinyl propionate, and vinyl pivalate. Among these, vinyl acetate is preferred from the viewpoint of economy.

[0041] The polyvinyl alcohol resin preferably has a degree of saponification of 85 mol% or more, more preferably 90 mol% or more and 99.9 mol% or less, and even more preferably 95 mol% or more and 99.4 mol% or less. That is, the degree of saponification is preferably 90 to 99.9 mol%, and more preferably 95 to 99.4 mol%.

[0042] In the method of reacting polyvinyl alcohol with an aldehyde having from 5 to 12 carbon atoms, the aldehyde used in the acetalization reaction is not particularly limited, and examples thereof include linear aliphatic aldehydes and branched aliphatic aldehydes having from 5 to 12 carbon atoms. Examples of the aliphatic aldehydes having from 5 to 12 carbon atoms include valeraldehyde, hexylaldehyde, 2-ethylbutyraldehyde, 2-ethylhexylaldehyde, heptylaldehyde (heptaldehyde), octylaldehyde, nonylaldehyde, decylaldehyde, undecylaldehyde, and dodecylaldehyde. These aldehydes may be used alone or in combination of two or more. Examples of the aliphatic aldehydes having 4 or less carbon atoms include formaldehyde, acetaldehyde, propionaldehyde, and butylaldehyde. It is particularly preferable to use a combination of an aldehyde having from 5 to 11 carbon atoms and an aldehyde having not more than 4 carbon atoms. Of these, acetaldehyde, butylaldehyde, hexylaldehyde, heptaldehyde, decylaldehyde, and dodecylaldehyde are preferred as aldehydes.

[0043] When carrying out the acetalization, it is preferable to prepare a polyvinyl alcohol solution by dissolving the raw material polyvinyl alcohol in a solvent such as water. The average degree of polymerization of the polyvinyl alcohol is preferably 300 to 5000, more preferably 500 to 4000, and even more preferably 800 to 3000. The polyvinyl alcohol concentration of the polyvinyl alcohol solution is preferably 1 to 5 wt %. Furthermore, the pressure when dissolving the polyvinyl alcohol in the solvent is preferably 0.1 to 1.0 MPa. By keeping the viscosity within the above ranges, it is possible to adjust the viscosity parameters, 3 wt % E / T viscosity, and Mw[NMP], and in particular, the 3 wt % E / T viscosity and Mw[NMP].

[0044] 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, an amount of the aldehyde added relative to 100 mol% of polyvinyl alcohol of preferably 50 mol% to 120 mol%, more preferably 55 mol% to 110 mol%, is preferred because the acetalization reaction proceeds efficiently and unreacted aldehyde is easily removed. That is, the amount of the aldehyde added is preferably 50 to 120 mol%, more preferably 55 to 110 mol%.

[0045] In the acetalization step, in addition to the linear aliphatic aldehydes and branched aliphatic aldehydes, an aldehyde having a cyclic aliphatic group or an aromatic group may be used in combination. Examples of the aldehyde having an aromatic group include benzaldehyde, cinnamaldehyde, 2-methylbenzaldehyde, 3-methylbenzaldehyde, 4-methylbenzaldehyde, p-hydroxybenzaldehyde, m-hydroxybenzaldehyde, phenylacetaldehyde, and β-phenylpropionaldehyde.

[0046] In the acetalization step, when an aldehyde having from 5 to 12 carbon atoms is contained, a dispersant may or may not be used. Furthermore, in the acetalization step, a method in which the polyvinyl acetal resin is reacted in a precipitated state during the acetalization reaction (precipitation method) is preferably used, compared to a method in which the acetalization reaction is carried out in a dissolved state (dissolution method). Furthermore, when acetalization is carried out using the dispersant, the precipitation method is preferably used.

[0047] Examples of the dispersant include sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol, colloidal silica, polyoxyethylene polyoxypropylene cetyl ether, polyoxyethylene polyoxypropylene lauryl ether, etc. These dispersants may be used alone or in combination of two or more. Among them, sodium dodecylbenzenesulfonate and polyoxyethylene polyoxypropylene cetyl ether are preferred.

[0048] The acetalization reaction is preferably carried out in the presence of an acid catalyst. Examples of the acid catalyst include mineral acids, carboxylic acids, sulfonic acids, etc. Examples of the mineral acids include sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, etc. Examples of the carboxylic acids include formic acid, acetic acid, propionic acid, etc. Examples of the sulfonic acids include paratoluenesulfonic acid, methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, etc. These acid catalysts may be used alone or in combination of two or more. Among these, paratoluenesulfonic acid and hydrochloric acid are preferred.

[0049] The acetalization reaction preferably includes a dissolving step of the raw material polyvinyl alcohol, a cooling step, a reaction step, and an aging step. By performing each of the steps under the following conditions, the viscosity parameters, 3 wt% E / T viscosity, Mw[NMP], tan δ peak top temperature, and storage modulus ratio (E'- / E'+) can be adjusted.

[0050] The solution concentration (charge concentration) of the raw polyvinyl alcohol in the dissolving step of the raw polyvinyl alcohol is preferably 2% by weight or more and 7% by weight or less, and more preferably 3% by weight or more and 6% by weight or less. The temperature (dissolution temperature) in the dissolving step of the raw polyvinyl alcohol is preferably 90°C or more and 100°C or less, and more preferably 92°C or more and 99°C or less. The dissolution time in the dissolving step is preferably 1 hour or more and 5 hours or less, and more preferably 1.5 hours or more and 4.5 hours or less. The pressure in the dissolving step is preferably 0.01 MPa or more and 0.5 MPa or less, and more preferably 0.1 MPa or more and 0.4 MPa or less. By adjusting the polyvinyl alcohol solution concentration and pressure in these dissolving steps and sufficiently dissolving polyvinyl alcohol aggregates and the like, the viscosity of the polyvinyl acetal resin can be controlled, and the viscosity parameters, 3 wt% E / T viscosity, Mw[NMP], tan δ peak top temperature, and storage modulus ratio (E'- / E'+) can be adjusted.

[0051] The acetalization reaction is preferably carried out by a step of lowering the temperature to a predetermined temperature (cooling step). The cooling time in the cooling step is preferably 0.5 hours or more and 5 hours or less, and more preferably 1 hour or more and 3 hours or less. The cooling step may be carried out multiple times. In this case, the cooling time is the total time of each cooling step. The temperature when the acid catalyst is added is preferably 30°C or more and 50°C or less.

[0052] The temperature (reaction temperature) at which the aldehyde is added in the acetalization reaction is preferably 5°C or higher and 50°C or lower, and more preferably 10°C or higher and 40°C or lower.

[0053] The reaction time for the acetalization reaction is preferably 0.25 hours or more and 5 hours or less, and more preferably 0.5 hours or more and 3 hours or less.

[0054] In the above acetalization, it is preferable that after the reaction (reaction step) is carried out at the above temperature for the above time, the temperature is raised and maintained at a predetermined temperature (aging step).

[0055] The retention time in the aging step is preferably 1 hour or more and 8 hours or less, and more preferably 1.5 hours or more and 6 hours or less. The retention temperature in the aging step is preferably 25°C or more and 60°C or less, and more preferably 30°C or more and 50°C or less. The temperature rise time from the end of the reaction step to the aging step is preferably 15 minutes or more and 300 minutes or less, and more preferably 30 minutes or more and 180 minutes or less. The temperature rise rate from the start of the temperature rise to the aging step is preferably 0.2°C / min or more and 3°C / min or less.

[0056] The polyvinyl acetal resin of the present invention and a plasticizer can be used to form a resin composition for a ceramic green sheet. The resin composition for a ceramic green sheet may contain other components such as an antioxidant, a surfactant, an ultraviolet absorber, and an antifoaming agent, as long as the effects of the present invention are not impaired.

[0057] As a method for producing the resin composition for a ceramic green sheet, for example, a plasticizer and other additives that are added as needed can be added to a polyvinyl acetal resin obtained by acetalizing a polyvinyl alcohol resin with an aldehyde, and then mixed to obtain a resin composition for a ceramic green sheet.

[0058] The resin composition for ceramic green sheets contains a plasticizer. Addition of the plasticizer can significantly improve the mechanical strength and flexibility of the resulting ceramic green sheets. Examples of the plasticizer include phthalate diesters such as dioctyl phthalate (DOP) and dibutyl phthalate (DBP), adipic acid diesters such as dioctyl adipate, and alkylene glycol diesters such as triethylene glycol-di-2-ethylhexanoate, tetraethylene glycol-di-2-ethylhexanoate, triethylene glycol-di-2-ethylbutyrate, tetraethylene glycol-di-2-ethylbutyrate, tetraethylene glycol-di-heptanoate, and triethylene glycol-di-heptanoate.

[0059] In the resin composition for a ceramic green sheet, the content of the plasticizer relative to 100 parts by weight of the polyvinyl acetal resin is preferably 7 parts by weight in lower limit, more preferably 8.5 parts by weight in lower limit, and preferably 18 parts by weight in upper limit, more preferably 13.5 parts by weight in upper limit.

[0060] 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.

[0061] 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.

[0062] The content of the organic solvent in the ceramic green sheet slurry is determined depending on the type of polyvinyl acetal resin used and is not particularly limited, but if it is too low, the solubility required for kneading is difficult to exhibit. On the other hand, if it 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.

[0063] Examples of the ceramic powder include powders of metal or nonmetal oxides or non-oxides used in ceramic production. These powders may be single compositions, compounds, or mixtures. The constituent elements of the metal oxides or non-oxides, both cations and anions, may be single elements or multiple elements, and may further contain additives added to improve the properties of the oxides or non-oxides. Specific examples include oxides, carbides, nitrides, borides, sulfides, etc. of Li, K, Mg, B, Al, Si, Cu, Ca, Sr, Ba, Zn, Cd, Ga, In, Y, lanthanides, actinides, Ti, Zr, Hf, Bi, V, Nb, Ta, W, Mn, Fe, Co, Ni, etc. Specific examples of oxide powders containing multiple metal elements, commonly referred to as double oxides, can be classified based on their crystal structure, such as NaNbO, which has a perovskite structure. ３ , SrZrO ３ , PbZrO ３ , SrTiO ３ , BaZrO ３ , PbTiO ３ , BaTiO ３ Examples of materials that have a spinel structure include MgAl ２ O ４ , ZnAl ２ O ４ , CoAl ２ O ４ , NiAl ２ O4, MgFe ２ O ４ Examples of materials with an ilmenite structure include MgTiO ３ , MnTiO３ , FeTiO ３ As a material having a garnet structure, GdGa ５ O １２ , Y ６ Fe ５ O １２ Among these, the modified polyvinyl acetal resin of the present invention is BaTiO ３ It exhibits high properties compared to ceramic green sheets mixed with powder.

[0064] 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.

[0065] The ceramic green sheet slurry may contain other polyvinyl acetal resins other than the polyvinyl acetal resin of the present invention, as well as other resins such as acrylic resins and ethyl cellulose, within the range that does not impair the effects of the present invention. In such cases, the content of the polyvinyl acetal resin of the present invention relative to the total binder resins is preferably 50% by weight or more.

[0066] If necessary, a dispersant, an antioxidant, an ultraviolet absorber, a surfactant, a filler, etc. may be added appropriately to the above-mentioned slurry for the ceramic green sheet, and in some cases, a small amount of other resin such as an acrylic resin or a urethane resin may also be added.

[0067] The method for producing the slurry for the ceramic green sheet is not particularly limited, and examples thereof include a method in which the polyvinyl acetal resin of the present invention, an organic solvent, a ceramic powder, and various additives to be added as needed are mixed using various mixers such as a ball mill, a blender mill, and a three-roll mill.

[0068] The ceramic green sheet slurry is applied, followed by heating and drying to obtain a ceramic green sheet. A ceramic electronic component can be manufactured using the ceramic green sheet. For example, a ceramic electronic component can be manufactured by carrying out a step of applying an electrode layer paste to the surface of the ceramic green sheet, and a step of stacking the ceramic green sheets on which the electrode layers have been formed, thermocompression bonding the resulting laminate, and then degreasing and firing the resulting laminate.

[0069] The method for applying the slurry for the ceramic green sheet is not particularly limited, and examples thereof include methods using a roll coater, a die coater, a curtain coater, etc. As for other specific methods, conventionally known methods can be used.

[0070] 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, and an alumina multilayer substrate.

[0071] The method for producing the ceramic electronic component includes a step of applying an electrode layer paste to the surface of the ceramic green sheet. The electrode layer paste can be obtained by dissolving, for example, a polyvinyl acetal resin, ethyl cellulose, or acrylic resin as a binder resin in an organic solvent and dispersing a conductive powder or the like. These resins may be used alone or in combination. An electrode layer paste containing a polyvinyl acetal resin is preferred because it exhibits excellent adhesion to the ceramic green sheet during the thermocompression bonding step.

[0072] In the method for producing a ceramic electronic component, the ceramic green sheets having electrode layers formed thereon are prepared as described above, and then ceramic green sheets having electrode layers formed thereon that are prepared in the same manner are stacked and thermocompression-bonded to obtain a laminate, which is then degreased and fired, thereby obtaining a multilayer ceramic electronic component that solves problems such as sheet attack and cracking. Note that the thermocompression-bonding step and the steps of degreasing and firing the laminate are not particularly limited, and conventionally known methods can be used.

[0073] According to the present invention, there are provided a polyvinyl acetal resin that has a low elution rate in solvents, excellent thermocompression bonding properties, and is capable of producing ceramic green sheets with few structural defects and high mechanical strength, as well as a ceramic green sheet slurry and a ceramic green sheet using the polyvinyl acetal resin. Note that structural defects include not only mechanical defects but also geometric defects, chemical defects, etc.

[0074] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0075] Example 1 (Preparation of Polyvinyl Acetal Resin) 120 g of polyvinyl alcohol having a saponification degree of 99.0 mol% and an average degree of polymerization of 1700 was added to 3400 g of pure water and stirred at 95°C and 0.2 MPa for 3 hours to obtain a PVA solution (polyvinyl alcohol concentration [charge concentration] 3 wt%). This solution was cooled to 40°C over 0.5 hours, and 220 g of hydrochloric acid with a concentration of 35% by mass was added. The solution was then cooled to 10°C over 1.5 hours, and 30 g of n-butyl aldehyde and 50 g of n-heptaldehyde were added. The liquid temperature was maintained at 10°C for 1 hour to carry out an acetalization reaction, thereby precipitating the reaction product. The temperature was then increased to 35°C at a rate of 0.5°C / min, and the liquid temperature was maintained at 35°C for 3 hours to complete the reaction. The solution was then neutralized, washed with water, and dried in a conventional manner to obtain a powder of polyvinyl acetal resin (long-chain alkyl-modified). The obtained polyvinyl acetal resin was dissolved in CDCl ３ Dissolved in (deuterated chloroform) １ H-NMR and １３Using C-NMR (nuclear magnetic resonance spectroscopy), the content of each acetal unit, including the content of the structural unit represented by formula (1) (amount of long-chain acetal groups), the amount of acetyl groups, and the amount of hydroxyl groups were measured. The total amount of acetal groups (total amount of each acetal unit) was calculated from the measured values. The results are shown in Table 1. The content of each acetal unit was calculated as follows: １３ The acetal unit was determined by C-NMR. １ = (CH ２ ) ５ CH ３ ] and the structural unit represented by the above formula (3) [R ２ = (CH ２ ) ２ CH ３ ] and R １ The carbon number of the hydrocarbon (long chain carbon number) was 6.

[0076] Example 2 A powder of polyvinyl acetal resin (modified with a long chain alkyl) was obtained in the same manner as in Example 1, except that the pressure used for dissolving polyvinyl alcohol was 0.4 MPa.

[0077] Example 3 A powder of polyvinyl acetal resin (long-chain alkyl-modified) was obtained in the same manner as in Example 1, except that the amount of n-butylaldehyde added before the acetalization reaction was 60 g and the amount of n-heptaldehyde added was 20 g.

[0078] Example 4 A powder of polyvinyl acetal resin (long-chain alkyl-modified) was obtained in the same manner as in Example 1, except that the amount of n-heptaldehyde added before the acetalization reaction was 100 g (n-butylaldehyde was not added).

[0079] Example 5 A powder of polyvinyl acetal resin (long-chain alkyl-modified) was obtained in the same manner as in Example 1, except that the aldehyde added before the acetalization reaction was changed to 85 g of n-hexyl aldehyde (n-butyl aldehyde was not added). The acetal unit is a structural unit [R １ = (CH ２ ) ４ CH ３] and the structural unit represented by the above formula (3) [R ２ = (CH ２ ) ２ CH ３ ] and R １ The carbon number of the hydrocarbon (long chain carbon number) was 5.

[0080] Example 6 A powder of polyvinyl acetal resin (long-chain alkyl-modified) was obtained in the same manner as in Example 1, except that the aldehyde added before the acetalization reaction was changed to 30 g of n-butyl aldehyde and 70 g of n-decyl aldehyde. The acetal unit is a structural unit [R １ = (CH ２ ) ８ CH ３ ] and the structural unit represented by the above formula (3) [R ２ = (CH ２ ) ２ CH ３ ] and R １ The carbon number of the hydrocarbon (long chain carbon number) was 9.

[0081] Example 7 A powder of polyvinyl acetal resin (long-chain alkyl-modified) was obtained in the same manner as in Example 1, except that the aldehyde added before the acetalization reaction was changed to 65 g of n-butyl aldehyde and 15 g of n-dodecyl aldehyde. The acetal unit is a structural unit [R １ = (CH ２ ) １０ CH ３ ] and the structural unit represented by the above formula (3) [R ２ = (CH ２ ) ２ CH ３ ] and R １ The number of carbon atoms (long chain carbon number) of the hydrocarbon was 11.

[0082] Example 8 80 g of polyvinyl alcohol having a saponification degree of 99.0 mol% and an average degree of polymerization of 3,300 was added to 3,450 g of pure water and stirred at 95°C and 0.2 MPa for 3 hours to obtain a PVA solution (polyvinyl alcohol concentration [charge concentration] 2 wt%). Thereafter, a powder of polyvinyl acetal resin (long-chain alkyl-modified) was obtained in the same manner as in Example 1, except that the aldehydes added before the acetalization reaction were changed to 20 g of n-butylaldehyde and 33 g of n-heptaldehyde.

[0083] Example 9 160 g of polyvinyl alcohol having a saponification degree of 99.0 mol% and an average degree of polymerization of 600 was added to 3,350 g of pure water and stirred at 95°C and 0.2 MPa for 3 hours to obtain a PVA solution (polyvinyl alcohol concentration [charge concentration] 4 wt%). Thereafter, a powder of polyvinyl acetal resin (long-chain alkyl-modified) was obtained in the same manner as in Example 1, except that the aldehydes added before the acetalization reaction were changed to 40 g of n-butylaldehyde and 67 g of n-heptaldehyde.

[0084] Example 10: 120 g of polyvinyl alcohol having a saponification degree of 99.0 mol% and an average degree of polymerization of 1700 was added to 3350 g of pure water and stirred at 95°C and 0.2 MPa for 3 hours to obtain a PVA solution (polyvinyl alcohol concentration [charge concentration] 3 wt%). Thereafter, a powder of polyvinyl acetal resin (long-chain alkyl-modified) was obtained in the same manner as in Example 1, except that the aldehydes added before the acetalization reaction were 30 g of n-butylaldehyde and 40 g of 3-methylbutanal.

[0085] Example 11 120 g of polyvinyl alcohol having a saponification degree of 99.0 mol% and an average degree of polymerization of 1700 was added to 3350 g of pure water and stirred at 95°C and 0.2 MPa for 3 hours to obtain a PVA solution (polyvinyl alcohol concentration [charge concentration] 3 wt%). Thereafter, a powder of polyvinyl acetal resin (long-chain alkyl-modified) was obtained in the same manner as in Example 1, except that the aldehyde added before the acetalization reaction was changed to 110 g of n-heptaldehyde.

[0086] Comparative Example 1 300 g of polyvinyl alcohol having a saponification degree of 99.0 mol% and an average degree of polymerization of 1700 was added to 2800 g of pure water and stirred at 95°C and 0 MPa for 3 hours to obtain a PVA solution (polyvinyl alcohol concentration [charge concentration] 8 wt%). Thereafter, a powder of polyvinyl acetal resin (long-chain alkyl-modified) was obtained in the same manner as in Example 1, except that the amount of n-heptaldehyde added before the acetalization reaction was 270 g (n-butylaldehyde was not added).

[0087] Comparative Example 2 300 g of polyvinyl alcohol having a saponification degree of 99.0 mol% and an average degree of polymerization of 1700 was added to 2800 g of pure water and stirred at 95°C and 0 MPa for 3 hours to obtain a PVA solution (polyvinyl alcohol concentration [charge concentration] 8 wt %). Thereafter, a powder of polyvinyl acetal resin (long-chain alkyl-modified) was obtained in the same manner as in Example 1, except that the aldehyde added before the acetalization reaction was changed to 230 g of n-hexyl aldehyde (n-butyl aldehyde was not added). The acetal unit is a structural unit [R １ = (CH ２ ) ４ CH ３ ] and the structural unit represented by the above formula (3) [R ２ = (CH ２ ) ２ CH ３ ] and R １ The carbon number of the hydrocarbon (long chain carbon number) was 5.

[0088] Comparative Example 3 300 g of polyvinyl alcohol having a saponification degree of 99.0 mol% and an average degree of polymerization of 1700 was added to 2800 g of pure water and stirred at 95°C and 0 MPa for 3 hours to obtain a PVA solution (polyvinyl alcohol concentration [charge concentration] 8 wt%). Thereafter, a powder of polyvinyl acetal resin (long-chain alkyl-modified) was obtained in the same manner as in Example 1, except that the aldehydes added before the acetalization reaction were 145 g of n-butylaldehyde and 180 g of n-heptaldehyde.

[0089] Comparative Example 4 240 g of polyvinyl alcohol having a saponification degree of 99.0 mol% and an average degree of polymerization of 3,300 was added to 3,300 g of pure water and stirred at 95°C and 0 MPa for 3 hours to obtain a PVA solution (polyvinyl alcohol concentration [charge concentration] 6 wt%). Thereafter, a powder of polyvinyl acetal resin (long-chain alkyl-modified) was obtained in the same manner as in Example 1, except that the aldehydes added before the acetalization reaction were 60 g of n-butylaldehyde and 100 g of n-heptaldehyde.

[0090] Comparative Example 5: 400 g of polyvinyl alcohol having a saponification degree of 99.0 mol% and an average degree of polymerization of 600 was added to 3,100 g of pure water and stirred at 95°C and 0 MPa for 3 hours to obtain a PVA solution (polyvinyl alcohol concentration [charge concentration] 10 wt%). Thereafter, a powder of polyvinyl acetal resin (long-chain alkyl-modified) was obtained in the same manner as in Example 1, except that the aldehydes added before the acetalization reaction were 100 g of n-butylaldehyde and 170 g of n-heptaldehyde.

[0091] Comparative Example 6 300 g of polyvinyl alcohol having a saponification degree of 99.0 mol% and an average degree of polymerization of 1700 was added to 3200 g of pure water and stirred at 95°C and 0 MPa for 3 hours to obtain a PVA solution (polyvinyl alcohol concentration [charge concentration] 8 wt%). Thereafter, a powder of polyvinyl acetal resin (long-chain alkyl-modified) was obtained in the same manner as in Example 1, except that the amount of n-heptaldehyde added before the acetalization reaction was 280 g (n-butylaldehyde was not added).

[0092] Comparative Example 7 120 g of polyvinyl alcohol having a saponification degree of 99.0 mol% and an average degree of polymerization of 1700 was added to 2700 g of pure water and stirred at 95°C and 0 MPa for 3 hours to obtain a PVA solution (polyvinyl alcohol concentration [charge concentration] 3 wt%). Thereafter, a powder of polyvinyl acetal resin (long-chain alkyl-modified) was obtained in the same manner as in Example 1, except that the aldehydes added before the acetalization reaction were 30 g of n-butylaldehyde and 60 g of n-heptaldehyde.

[0093] Comparative Example 8 120 g of polyvinyl alcohol having a saponification degree of 88.0 mol% and an average degree of polymerization of 1700 was added to 2700 g of pure water and stirred at 95°C and 0 MPa for 3 hours to obtain a PVA solution (polyvinyl alcohol concentration [charge concentration] 3 wt%). Thereafter, a powder of polyvinyl acetal resin (long-chain alkyl-modified) was obtained in the same manner as in Example 1, except that the aldehydes added before the acetalization reaction were 30 g of n-butylaldehyde and 50 g of n-heptaldehyde.

[0094] Comparative Example 9 300 g of polyvinyl alcohol having a saponification degree of 99.0 mol% and an average degree of polymerization of 1700 was added to 2800 g of pure water and stirred at 95°C and 0 MPa for 3 hours to obtain a PVA solution (polyvinyl alcohol concentration [charge concentration] 8 wt%). Thereafter, a powder of polyvinyl acetal resin (not long-chain alkyl-modified) was obtained in the same manner as in Example 1, except that the aldehyde added before the acetalization reaction was changed to 150 g of n-butylaldehyde (n-heptaldehyde was not added). The acetal units were butyral units.

[0095] <Evaluation> The obtained polyvinyl acetal resin was evaluated as follows.

[0096] (1-1) Measurement of tan δ Peak Top Temperature and Storage Modulus Ratio (E'- / E'+) The obtained polyvinyl acetal resin was coated onto a release-treated PET film using a coater so that the thickness after drying would be approximately 5 to 20 μm, and then heated and dried at 70°C for 180 minutes to produce a transparent resin sheet. The obtained resin sheet was cut into 0.5 cm x 3.0 cm specimens, and then dynamic viscoelasticity was measured using a DMA (manufactured by IT Measurement Co., Ltd.) under the following conditions. The peak top temperature was measured for the obtained tan δ (loss tangent). In addition, the storage modulus E'- at the peak top temperature -5°C and the storage modulus E'+ at the peak top temperature +5°C were also measured, and the storage modulus ratio (E'- / E'+) was calculated. (Measurement Conditions) Measurement mode: Tensile mode Forced vibration frequency: 1 Hz Temperature range: 30°C to 150°C Heating rate: 6°C / min

[0097] (1-2) Viscosity Measurement The obtained polyvinyl acetal resin was dissolved in a mixed solvent of ethanol and toluene (ethanol:toluene = 50:50) to a concentration of 3 wt %, to prepare a viscosity measurement sample consisting of a 3 wt % ethanol-toluene mixed solution. The viscosity (3 wt % E / T viscosity) of the obtained viscosity measurement sample was measured using a Brookfield viscometer at a solution temperature of 20°C. The Brookfield viscometer used was a TVB-10 viscometer (manufactured by Toki Sangyo Co., Ltd.), and the rotation speed and rotor were as follows: Examples and Comparative Examples: rotation speed 30 rpm, SPINDLE No. M1

[0098] (1-3) Measurement of weight average molecular weight (Mw[NMP]) The obtained polyvinyl acetal resin was dissolved in N-methylpyrrolidone (NMP) at a concentration of 0.2 wt%, passed through a PTFE filter having a pore size of 0.45 μm, and measured at a flow rate of 0.5 mL / min using a GPC apparatus GPC-101 (manufactured by Shodex Corporation), NMP as the mobile phase, a differential refractive index detector RI-715 (manufactured by Shodex Corporation) as the detector, and an LF-804 (manufactured by Shodex Corporation) as the column. The obtained measurement results were calibrated using a molecular weight calibration curve prepared using monodisperse polystyrene standard samples, and the weight average molecular weight Mw[NMP] was obtained.

[0099] (1-4) Calculation of Viscosity Parameter The viscosity parameter was calculated using the following formula (2) from the "amount of long-chain acetal groups" and "number of long-chain carbon atoms" of the obtained polyvinyl acetal resin, and the "3 wt% E / T viscosity" and "Mw[NMP]" obtained above.

[0100]

[0101] (2-1) Evaluation of Thermocompression Bondability The obtained polyvinyl acetal resin was applied to a release-treated PET film using a coater so that the thickness after drying would be approximately 5 to 20 μm, and then heated and dried at 70°C for 180 minutes to produce a transparent resin sheet. The obtained resin sheet was cut into 1.0 cm x 1.0 cm to prepare a test piece, and then the tack force was measured using a tack tester (manufactured by RHESCA) under the following conditions (measurement temperature: 70°C). The obtained peak value was evaluated according to the following criteria. (Measurement conditions) Pressing speed: 1.0 mm / s Pressing load: 400 gf Pressing hold time: 30 s Pulling speed: 1.0 mm / s Measurement temperature: 70°C

[0102] A: Peak value is over 50 gf B: Peak value is over 22 gf, 50 gf or less C: Peak value is 22 gf or less

[0103] (2-2) Evaluation of Sheet Attack Resistance (Solvent Elution) The resin sheet obtained in "(2-1) Evaluation of Thermocompression Bondability" was cut into a 1.5 cm x 10 cm square and accurately weighed. The test piece was then immersed in 10 ml of dihydroterpineol acetate at 23 ° C for 1 minute. The test piece was then removed and dried at 150 ° C for 6 hours to completely dry the solvent. After removing it from the dryer, it was left at room temperature for 1 hour and then weighed. The amount of resin eluted was calculated from the change in weight before and after the test, and the elution rate was calculated from the ratio of the elution amount to the weight of the test piece before the test, and evaluated according to the following criteria. Note that a higher elution rate indicates better sheet attack resistance.

[0104] A: Dissolution rate is 3% or less. B: Dissolution rate is more than 3% and 6% or less. C: Dissolution rate is more than 6%.

[0105] (2-3) Mechanical Strength (Structural Defects) For the ten resin sheets obtained in "(2-1) Evaluation of Thermocompression Bondability", the stress at break was measured in a 30°C environment at a tension speed of 20 mm / min using a tensile tester (AUTOGRAPH AGS-J, manufactured by Shimadzu Corporation) in accordance with JIS K 7113. The standard deviation (standard deviation of stress at break) of the obtained stress at break was determined and evaluated according to the following criteria.

[0106] A: Standard deviation of stress at break is 15 N / mm２ B: Standard deviation of stress at break is 15 N / mm ２ Super, 30N / mm ２ C: Standard deviation of stress at break is 30 N / mm ２ super

[0107] (2-4) Resin Coagulation / Sheet Shrinkage The obtained polyvinyl acetal resin was applied to a release-treated PET film using a coater so that the thickness after drying would be about 10 μm, and then dried for 48 hours at 30° C. to prepare a transparent resin sheet. The appearance of the obtained resin sheet was observed to determine whether or not there was resin coagulation, and the sheet was evaluated according to the following criteria.

[0108] A: No irregularities on the sheet surface B: Irregularities on the sheet surface, no signs of shrinkage at the edges C: Irregularities on the sheet surface, signs of shrinkage at the edges

[0109]

[0110] According to the present invention, it is possible to provide a polyvinyl acetal resin that has a low elution rate in a solvent, excellent thermocompression bondability, and is capable of producing a ceramic green sheet with few structural defects and high mechanical strength, as well as a ceramic green sheet slurry and a ceramic green sheet that use the polyvinyl acetal resin.

Claims

1. A structural unit represented by the following formula (1), wherein R １ is a hydrocarbon group having 4 to 11 carbon atoms, the content of the structural unit represented by the following formula (1) is 0.01 mol % or more and the amount of hydroxyl groups is 28 mol % or more, and the viscosity of a solution obtained by dissolving the structural unit in a 3 wt % mixed solvent containing ethanol and toluene in a ratio of 50:50 (3 wt % E / T viscosity), the weight average molecular weight (Mw[NMP]) measured by GPC using NMP as a solvent, the content of the structural unit represented by the following formula (1), and R １ and the number of carbon atoms of the hydrocarbon, the viscosity parameter calculated by using the following formula (2) is 0.200 or less.

2. The polyvinyl acetal resin according to claim 1, wherein the content of the structural unit represented by formula (1) is 70 mol % or less.

3. The polyvinyl acetal resin according to claim 1 or 2, wherein the content of the structural unit represented by formula (1) is 35 mol % or less.

4. The polyvinyl acetal resin according to any one of claims 1 to 3, wherein the structural unit having an acetal group is only the structural unit represented by formula (1).

5. The polyvinyl acetal resin according to any one of claims 1 to 4, wherein the hydrocarbon group having 4 to 11 carbon atoms is a linear alkyl group.

6. The polyvinyl acetal resin according to any one of claims 1 to 5, further comprising a structural unit represented by formula (3). In formula (3), R ２ represents a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms.

7. R １ is one kind or two or more kinds, and R ２ The polyvinyl acetal resin according to claim 6 , wherein:

8. The polyvinyl acetal resin according to claim 6 or 7, wherein the total content of the structural unit represented by formula (1) and the structural unit represented by formula (3) (total acetal group content) is 50 to 70 mol %.

9. The polyvinyl acetal resin according to any one of claims 1 to 8, wherein the amount of acetyl groups is 8.5 mol % or less.

10. The polyvinyl acetal resin according to any one of claims 1 to 9, which has a peak top temperature of tan δ of 0°C or higher and 80°C or lower in dynamic viscoelasticity measurement at 1 Hz.

11. The polyvinyl acetal resin according to any one of claims 1 to 10, wherein, in dynamic viscoelasticity measurement at 1 Hz, the storage modulus ratio (E'- / E'+) of the storage modulus E'- at a temperature equal to or lower than 5°C (tan δ peak top temperature -5°C) to the storage modulus E'+ at a temperature equal to or higher than 5°C (tan δ peak top temperature +5°C) is 5 or more and 100 or less.

12. The polyvinyl acetal resin according to any one of claims 1 to 11, having Mw[NMP] of 50,000 or more and 1,000,000 or less.

13. A slurry for ceramic green sheets, comprising the polyvinyl acetal resin according to any one of claims 1 to 12, an organic solvent, and ceramic powder.

14. A ceramic green sheet produced by using the slurry for ceramic green sheet according to claim 13.

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