JP2022173524A - polyvinyl acetal resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyvinyl acetal resin that has less fine undissolved matter when dissolved in an organic solvent, can improve productivity when used particularly as a binder for ceramic green sheets, can obtain ceramic green sheets excellent in toughness, and can produce a multilayer ceramic capacitor excellent in reliability.

SOLUTION: A polyvinyl acetal resin in which the number of undissolved matters measured by the following method is 300 or smaller. <Measurement method> After a polyvinyl acetal resin is charged to a 150 ml ethanol-toluene mixed solution at a weight ratio of 1:1 in a flak such that the solution viscosity at 20°C measured by a rotary viscometer becomes 20 mPa s and shaken, and left to stand for 30 minutes at 20°C, further left to stand for 30 minutes in an upside down state, and then the number of undissolved matters adhering to a bottom surface is measured.

SELECTED DRAWING: None

COPYRIGHT: (C)2023,JPO&INPIT

Description

The present invention produces a ceramic green sheet that has less fine undissolved matter when dissolved in an organic solvent, can improve productivity particularly when used as a binder for a ceramic green sheet, and has excellent toughness. The present invention relates to a polyvinyl acetal resin that can be obtained and can be used to manufacture a highly reliable laminated ceramic capacitor.

2. Description of the Related Art In recent years, electronic components mounted on various electronic devices have been miniaturized and laminated, and multilayer electronic components such as multilayer circuit boards, laminated coils, and laminated ceramic capacitors are widely used.
Among them, multilayer ceramic capacitors are generally manufactured through the following steps.
First, add a plasticizer, a dispersant, etc. to a solution of a binder resin such as polyvinyl butyral resin or poly(meth)acrylic acid ester resin dissolved in an organic solvent, then add ceramic raw material powder and mix in a bead mill, ball mill, etc. Uniform mixing is performed by a device to obtain a ceramic slurry composition having a constant viscosity after defoaming. This slurry composition is cast onto a release-treated polyethylene terephthalate film or a support surface such as a SUS plate using a doctor blade, reverse roll coater, etc., and heated to remove volatile matter such as a solvent. After removing it, it is peeled off from the support to obtain a ceramic green sheet.
Next, on the obtained ceramic green sheets, a plurality of sheets to which a conductive paste to be an internal electrode is applied by screen printing are alternately stacked and heat-pressed to form a laminate. After that, a process of thermally decomposing and removing binder resin components and the like contained in the laminate, a so-called degreasing process, is performed, and external electrodes are sintered on the end faces of the ceramic sintered body obtained by firing. A capacitor is obtained.

Polyvinyl acetal resins used for producing ceramic green sheets are generally used as solutions dissolved in organic solvents such as methyl ethyl ketone, toluene, alcohol and mixtures thereof. However, conventional polyvinyl acetal resins leave a small amount of undissolved matter when dissolved in an organic solvent. If such undissolved matter is present, voids are likely to remain in the degreasing and firing steps when used in a multilayer ceramic capacitor, or the dispersibility of ceramic powder, etc., is reduced, resulting in poor product quality. Electrical properties were degraded.
Therefore, when polyvinyl acetal resin is used for ceramic green sheets, it is necessary to remove undissolved substances by blending organic and inorganic compounds, etc., dissolving them in an organic solvent, and performing a filtering process. there were.

On the other hand, in Patent Document 1, a polyvinyl acetal resin solution dissolved in a 1:1 mixed solvent of methyl ethyl ketone and/or toluene and ethanol to form a 5% by weight solution was filtered through a filter with an opening of 5 μm at a filtration temperature of A polyvinyl acetal resin has been proposed that has a rate of decrease in filtration flow rate of less than 10% when filtered under conditions of 25° C. and a filtration pressure of 10 mmHg. In addition, by using such a polyvinyl acetal resin, when it is dissolved in an organic solvent, the amount of undissolved matter is small, and the filtration time can be shortened, thereby improving productivity.

JP 2005-325342 A

On the other hand, in recent years, as electronic devices have become more multi-functional and smaller, multilayer ceramic capacitors are required to have larger capacity and smaller sizes. In order to meet such demands, it is necessary to sufficiently remove finer undissolved matter. The undissolved matter cannot be removed, and it is necessary to remove the undissolved matter by filtration or the like, resulting in a problem of reduced productivity.

The present invention produces a ceramic green sheet that has less fine undissolved matter when dissolved in an organic solvent, can improve productivity particularly when used as a binder for a ceramic green sheet, and has excellent toughness. It is an object of the present invention to provide a polyvinyl acetal resin which can be obtained and which can be used to manufacture a highly reliable laminated ceramic capacitor.

The present invention is a polyvinyl acetal resin having 300 or less undissolved particles as measured by the following method.
<Measurement method>
Polyvinyl acetal resin was added to 150 ml of an ethanol/toluene mixed solution with a weight ratio of 1:1 in a flask so that the solution viscosity at 20° C. measured with a rotary viscometer was 20 mPa·s, and the mixture was shaken. After allowing to stand at 20° C. for 30 minutes, turning it upside down and allowing it to stand still for 30 minutes, the number of undissolved substances adhering to the bottom surface is counted.

As a result of intensive studies, the present inventors have found that a polyvinyl acetal resin having 300 or less undissolved substances measured by a predetermined measuring method has few undissolved substances when dissolved in an organic solvent, and the filtration time is can be shortened to improve productivity. In addition, it was found that by using such a polyvinyl acetal resin as a binder resin for ceramic green sheets, it is possible to produce a highly reliable laminated ceramic capacitor in which defects hardly occur in the ceramic green sheets. I came to complete it.

The polyvinyl acetal resin of the present invention has 300 or less undissolved particles measured by the above method.
Specifically, 150 ml of an ethanol/toluene mixed solution with a weight ratio of 1:1 is put into an Erlenmeyer flask with a capacity of 300 ml. Furthermore, polyvinyl acetal resin is added so that the solution viscosity at 20°C becomes 20 mPa·s, shaken with the mouth of the Erlenmeyer flask facing upward, and allowed to stand at 20°C for 30 minutes. After that, the flask is turned upside down and left still for 30 minutes with the mouth of the Erlenmeyer flask facing downward, and the number of undissolved substances adhering to the bottom surface of the flask is counted. At this time, the concentration of the polyvinyl acetal resin is previously confirmed to be 20 mPa·s. A rotational viscometer can be used as the viscometer.
The Erlenmeyer flask made of borosilicate glass can be used. In addition, it is preferable to use a bottom surface with an inner diameter of 87 mm, a total height of 148 mm, and an inner diameter of 31 mm, or with an equivalent shape and an equivalent material. As the flask, for example, Erlenmeyer flask 010530-30071A manufactured by Shibata Kagaku Co., Ltd. can be used.
Shaking conditions are preferably, for example, a reciprocating shaking method, a shaking speed of 250 rpm, and an amplitude of 40 mm for 3 hours.
As the shaker, for example, a shaker (“SR-2DW” manufactured by TAITEC) can be used.
The number of undissolved matter is counted visually within a radius of 40 mm from the center of the bottom of the flask. The size of the undissolved matter to be counted should be 0.1 to 2.0 mm in maximum diameter.
When the number of undissolved matter is 300 or less, the productivity can be improved when used as a binder for ceramic green sheets. Moreover, a ceramic green sheet having excellent toughness can be obtained, and a multilayer ceramic capacitor having excellent reliability can be produced.
The upper limit of the number of undissolved substances is preferably 250, more preferably 200. The preferable lower limit of the number of undissolved substances is 0, and the smaller the number, the better.
In addition, undissolved matter having a large particle size causes a significant deterioration in the performance of the ceramic green sheet. It is preferable that the number of objects is zero.

The number of undissolved substances can be determined by appropriately setting the acetalization reaction conditions such as the degree of crystallinity and saponification of the raw material polyvinyl alcohol resin, the reaction time and reaction temperature, and the amount of acetal groups and hydroxyl groups of the polyvinyl acetal resin. can be adjusted.

The polyvinyl acetal resin of the present invention was dissolved in a mixed solution of ethanol and toluene at a weight ratio of 1:1 to a concentration of 0.2% by weight, and the particle size distribution of the polyvinyl acetal resin solution was measured using a particle counter. In this case, the ratio of particles with a diameter of 0.5 to 1.0 μm is preferably 4.42×10 ⁻⁸ volume % or less with respect to 100 volume % of the resin solution. The volume of particles is determined by measuring the number of particles with a diameter of 0.5 to 1.0 μm using a particle counter, and assuming that the particles with a diameter of 0.5 to 1.0 μm are true spheres with a diameter of 0.75 μm. is calculated, and the proportion (% by volume) of particles with a diameter of 0.5 to 1.0 μm is calculated based on the number and volume of the particles.
When the above ratio is 4.42 × 10 ^-8 vol% or less, in addition to being able to shorten the filtration time, the uniformity of the slurry is improved, a smoother green sheet can be produced, and sheet defects such as cracks is less likely to occur, so dielectric breakdown is less likely to occur. That is, there is an advantage that the reliability of the laminated ceramic capacitor is improved.
More preferably, the ratio is 3.31×10 ⁻⁸ volume % or less. The lower limit of the above ratio is not particularly limited, and the lower the better, preferably 0% by volume.
As the particle counter, for example, "KS-42C" manufactured by Rion Co., Ltd. can be used.

The volume ratio of the particles having a diameter of 0.5 to 1.0 μm can be determined by appropriately adjusting, for example, the crystallinity of the raw material polyvinyl alcohol resin, the degree of saponification, the conditions of the acetalization reaction, the amount of acetal groups of the polyvinyl acetal resin, the amount of hydroxyl groups, and the like. You can adjust it by setting

The polyvinyl acetal resin of the present invention preferably has a lower limit of 300, more preferably 600, from the viewpoint that mechanical strength can be maintained when producing a thin ceramic green sheet. , the upper limit is preferably 8,000, more preferably 7,000 from the viewpoint of the melt viscosity.
In addition, the said average degree of polymerization can be measured based on JISK6726.

The polyvinyl acetal resin of the present invention includes 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 an acetyl group represented by the following formula (3). It is preferable to have a structural unit having

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

In the above formula (1), when R ¹ is an alkyl group having 1 to 20 carbon atoms, examples of the alkyl group include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, iso -butyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, 2-ethylhexyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group , pentadecyl group, octadecyl group and the like. Among them, a methyl group and an n-propyl group are preferred.

In the polyvinyl acetal resin of the present invention, the content of the structural unit having an acetal group represented by the above formula (1) (hereinafter also referred to as "acetal group content") preferably has a lower limit of 45 mol% and a preferred upper limit of 80 mol. %.
When the acetal group content is 45 mol % or more, the solubility in organic solvents can be improved. When the acetal group content is 80 mol % or less, a polyvinyl acetal resin having excellent toughness can be obtained.
The more preferable lower limit of the acetal group content is 47 mol%, the more preferable lower limit is 49 mol%, the more preferable upper limit is 78 mol%, and the more preferable upper limit is 76 mol%.
The amount of acetal groups can be measured, for example, by NMR.
Regarding the method of 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, a method of counting the two acetalized hydroxyl groups is used. adopt.

In the polyvinyl acetal resin of the present invention, the content of the structural unit having a hydroxyl group represented by the general formula (2) (hereinafter also referred to as "hydroxyl group content") preferably has a lower limit of 18 mol% and a preferred upper limit of 50 mol%. is.
When the amount of hydroxyl groups is 18 mol % or more, a polyvinyl acetal resin having excellent toughness can be obtained. When the amount of hydroxyl groups is 50 mol % or less, the solubility in organic solvents can be sufficiently improved.
The hydroxyl group content has a more preferable lower limit of 20 mol%, a more preferable lower limit of 22 mol%, a more preferable upper limit of 40 mol%, a still more preferable upper limit of 39 mol%, and a still more preferable upper limit of 38 mol%.
The amount of hydroxyl groups can be measured, for example, by NMR.

In the polyvinyl acetal resin of the present invention, the preferred lower limit of the content of the structural unit having an acetyl group represented by the general formula (3) (hereinafter also referred to as "acetyl group content") is 0.5 mol%, and the preferred upper limit is is 20 mol %.
When the amount of acetyl groups is 0.5 mol % or more, it is possible to suppress an increase in the viscosity of the ceramic green sheet composition due to intramolecular and intermolecular hydrogen bonding of hydroxyl groups in the polyvinyl acetal resin. When the acetyl group content is 20 mol % or less, the flexibility of the polyvinyl acetal resin is not excessively increased, and the handleability can be improved.
A more preferable lower limit of the acetyl group content is 1.0 mol %, and a more preferable upper limit thereof is 16 mol %.
The amount of acetyl groups can be measured, for example, by NMR.

In the polyvinyl acetal resin of the present invention, the weight average molecular weight (Mw) preferably has a lower limit of 40,000, a more preferred lower limit of 70,000, a preferred upper limit of 1,400,000, and a more preferred upper limit of 1,200,000. .
In the polyvinyl acetal resin of the present invention, the number average molecular weight (Mn) preferably has a lower limit of 15,000, a more preferred lower limit of 40,000, a preferred upper limit of 500,000, and a more preferred upper limit of 400,000.
In the polyvinyl acetal resin of the present invention, the ratio (Mw/Mn) of weight average molecular weight (Mw) to number average molecular weight (Mn) preferably has a lower limit of 2.0, a more preferred lower limit of 2.2, and a preferred upper limit of 4.0. 0, and a more preferable upper limit is 3.7.
The above Mw and Mn can be measured, for example, by gel permeation chromatography (GPC) using an appropriate standard (eg, polystyrene standard). Columns used for measuring Mw and Mn include, for example, TSKgel SuperHZM-H.

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

As the polyvinyl alcohol resin, conventionally known polyvinyl alcohol resins such as resins produced by saponifying polyvinyl acetate-based resins with alkali, acid, aqueous ammonia, or the like can be used.
The above polyvinyl alcohol resin may be completely saponified, but it is not necessary to be completely saponified if at least one unit having two consecutive hydroxyl groups with respect to the meso- and racemo-positions is present in at least one of the main chains. , partially saponified polyvinyl alcohol resin. Further, as the polyvinyl alcohol resin, copolymers of vinyl alcohol and monomers copolymerizable with vinyl alcohol, such as ethylene-vinyl alcohol copolymer resins and partially saponified ethylene-vinyl alcohol copolymer resins, can also be used. can.
Examples of the polyvinyl acetate-based resin include ethylene-vinyl acetate copolymers.

The upper limit of the crystallinity of the polyvinyl alcohol resin is preferably 37% or less, more preferably 36% or less, and even more preferably 33% or less. Although the lower limit is not particularly limited, it is preferably 3% or more.
By using the polyvinyl alcohol resin, the number of undissolved substances measured by the above method can be set within a predetermined range.
The degree of crystallinity can be measured by differential scanning calorimetry (DSC) as described in Examples below.

The polyvinyl alcohol resin preferably has a saponification degree of 70 mol % or more and 99.4 mol % or less, more preferably 78 mol % or more and 98 mol % or less.
By using the polyvinyl alcohol resin, the number of undissolved substances measured by the above method can be set within a predetermined range.

A known method can be used for the acetalization, and it is preferably carried out in a water solvent, in a mixed solvent of water and an organic solvent having compatibility with water, or in 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, tert-butanol and the like.
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 solvents include hexane, pentane, octane, cyclohexane, and decane.
Examples of the ether solvent include diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol diethyl ether and the like.
Examples of the amide solvent include N,N-dimethylformamide, N,N-dimethyltesetamide, N-methylpyrrolidone, acetanilide and the like.
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 can be used alone, or two or more solvents can be used in combination. Among these, ethanol, n-propanol, isopropanol, and tetrahydrofuran are particularly preferred from the viewpoints of solubility in resins and ease of purification.

The acetalization is preferably carried out in the presence of an acid catalyst.
The acid catalyst is not particularly limited, and includes mineral acids such as sulfuric acid, hydrochloric acid, nitric acid and phosphoric acid, carboxylic acids such as formic acid, acetic acid and propionic acid, methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid and paratoluenesulfone. sulfonic acids such as acids. These acid catalysts may be used alone or in combination of two or more compounds. Among them, hydrochloric acid, nitric acid and sulfuric acid are preferred, and hydrochloric acid is particularly preferred.

In the method for producing a polyvinyl acetal resin of the present invention, it is preferable to start acetalization after stirring the polyvinyl alcohol resin at a temperature of 90° C. or higher for 2 hours or longer.
By setting the stirring time to 2 hours or longer, the polyvinyl alcohol resin can be sufficiently dissolved, the degree of acetalization can be sufficiently increased, and the generation of undissolved matter can be suppressed.

Aldehydes used in the acetalization include aldehydes having a chain aliphatic group, a cycloaliphatic group or an aromatic group having 1 to 10 carbon atoms. Conventionally known aldehydes can be used as these aldehydes. The aldehyde used in the acetalization reaction is not particularly limited, and examples 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, amylaldehyde and the like.
The aromatic aldehydes include benzaldehyde, cinnamaldehyde, 2-methylbenzaldehyde, 3-methylbenzaldehyde, 4-methylbenzaldehyde, p-hydroxybenzaldehyde, m-hydroxybenzaldehyde, phenylacetaldehyde, β-phenylpropionaldehyde and the like.
These aldehydes may be used individually by 1 type, and may use 2 or more types together. Among the aldehydes, formaldehyde, acetaldehyde, butyraldehyde, 2-ethylhexylaldehyde, 2-ethylhexylaldehyde, etc., which are excellent in acetalization reactivity, bring about a sufficient internal plasticizing effect on the resin to be produced, and as a result impart good flexibility. n-nonylaldehyde is preferred. More preferred are formaldehyde, acetaldehyde, and butyraldehyde, since an adhesive composition having particularly excellent impact resistance and adhesiveness to metal can be obtained.

The amount of the aldehyde to be added can be appropriately set according to the amount of acetal groups in the desired polyvinyl acetal resin. In particular, with respect to 100 mol% of polyvinyl alcohol, when it is 55 mol% or more and 95 mol% or less, preferably 60 mol% or more and 90 mol% or less, the acetalization reaction is efficiently performed, and unreacted aldehyde is easily removed. Therefore, it is preferable.

A composition for ceramic green sheets can be produced by mixing the polyvinyl acetal resin of the present invention and an organic solvent.

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. Also included are alcohols such as methanol, ethanol, isopropanol and butanol, and aromatic hydrocarbons such as toluene and xylene. Furthermore, methyl propionate, ethyl propionate, butyl propionate, methyl butanoate, ethyl butanoate, butyl butanoate, methyl pentanoate, ethyl pentanoate, butyl pentanoate, methyl hexanoate, ethyl hexanoate, butyl hexanoate, Examples include esters such as 2-ethylhexyl acetate and 2-ethylhexyl butyrate. Also included are methyl cellosolve, ethyl cellosolve, butyl cellosolve, terpineol, dihydroterpineol, butyl cellosolve acetate, butyl carbitol acetate, terpineol acetate, dihydroterpineol acetate and the like. In particular, alcohols, ketones, aromatic hydrocarbons, and mixed solvents thereof are preferred from the standpoint of coatability and drying properties. Among them, a mixed solvent of ethanol and toluene and a mixed solvent of methyl ethyl ketone and toluene are more preferable.

The content of the organic solvent in the ceramic green sheet slurry composition is set according to the type of polyvinyl acetal resin used and is not particularly limited. It is difficult to exhibit the solubility necessary for On the other hand, when the amount is too large, the viscosity of the slurry composition for ceramic green sheets becomes too low, which may deteriorate the handleability 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.

The ceramic green sheet composition may contain a plasticizer. By adding a plasticizer, the mechanical strength and flexibility of the resulting ceramic green sheet can be greatly improved.
Examples of the plasticizer include phthalate diesters such as dioctyl phthalate (DOP) and dibutyl phthalate (DBP), adipic acid diesters such as dioctyl adipate, triethylene glycol-di-2-ethylhexanoate, tetraethylene glycol- Di-2-ethylhexanoate, triethylene glycol-di-2-ethylbutyrate, tetraethylene glycol-di-2-ethylbutyrate, tetraethylene glycol-di-heptanoate, triethylene glycol-di-heptanoate, etc. Alkylene glycol diesters and the like can be mentioned.

In the ceramic green sheet composition, the content of the plasticizer has a preferable lower limit of 7 parts by weight, a more preferable lower limit of 8.5 parts by weight, and a preferable upper limit of 18 parts by weight, more preferably 18 parts by weight, per 100 parts by weight of the polyvinyl acetal resin. The upper limit is 13.5 parts by weight.

The ceramic green sheet composition may contain a polyvinyl acetal resin other than the polyvinyl acetal resin of the present invention, or other resins such as acrylic resin and ethyl cellulose, as long as the effects of the present invention are not impaired. In such a case, the content of the polyvinyl acetal resin of the present invention with respect to the total binder resin is preferably 50% by weight or more.

Ceramic powders, dispersants, antioxidants, UV absorbers, surfactants, fillers, and the like may be added to the ceramic green sheet composition as needed. A small amount of other resin such as urethane resin may be added.

The ceramic powders include metal or non-metal oxide or non-oxide powders used in the manufacture of ceramics. In addition, the composition of these powders may be a single composition or a compound state, which may be used singly or in combination. The constituent elements of the metal oxide or non-oxide may be composed of a single element or a plurality of elements together with cations or anions. may contain. Specifically, 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 and other oxides, carbides, nitrides, borides and sulfides.
Further, when specific oxide powders containing a plurality of metal elements, which are usually called double oxides, are classified from the crystal structure, those having a perovskite structure are NaNbO ₃ , SrZrO ₃ , PbZrO ₃ , SrTiO ₃ , BaZrO ₃ , PbTiO ₃ , BaTiO ₃ and the like. Materials having a spinel structure include MgAl ₂ O ₄ , ZnAl ₂ O ₄ , CoAl ₂ O ₄ , NiAl ₂ O 4 and MgFe ₂ O ₄ . Materials having an ilmenite structure include MgTiO ₃ , MnTiO ₃ and FeTiO ₃ . GdGa ₅ O ₁₂ , Y ₆ Fe ₅ O ₁₂ and the like can be mentioned as those having a garnet structure. Among these, the modified polyvinyl acetal resin of the present application exhibits high properties for ceramic green sheets mixed with BaTiO ₃ powder.

The average particle size of the ceramic powder is not particularly limited, but is preferably 0.5 μm or less for producing a thin layer ceramic green sheet (thickness of 5 μm or less).

The method for producing the ceramic green sheet composition is not particularly limited. The method of mixing using various mixers, etc. are mentioned.

After applying the composition for ceramic green sheets, the resin sheet is obtained by heating and drying.

The method for applying the ceramic green sheet composition is not particularly limited, and examples thereof include methods such as a roll coater, a die coater, and a curtain coater. In addition, a conventionally well-known method can be used about another specific method.

A resin sheet containing ceramic powder can be used as a ceramic green sheet.
A ceramic electronic component can be manufactured using the ceramic green sheet. For example, a step of applying an electrode layer paste to the surface of a ceramic green sheet, and a step of degreasing and firing a laminated body obtained by laminating ceramic green sheets having electrode layers formed thereon and performing thermocompression bonding, Ceramic electronic components can be manufactured.

The ceramic electronic component is not particularly limited, and examples thereof include laminated ceramic capacitors, laminated ceramic inductors, capacitors, piezoelectric actuators, laminated varistors, laminated thermistors, EMI filters, aluminum nitride multilayer substrates, and alumina multilayer substrates. Such a laminated ceramic capacitor is also one aspect of the present invention.

In the method for manufacturing the ceramic electronic component, the step of applying the electrode layer paste to the surface of the ceramic green sheet is performed.
The electrode layer paste can be obtained, for example, by dissolving polyvinyl acetal resin, ethyl cellulose, acrylic resin, or the like as a binder resin in an organic solvent, and dispersing conductive powder or the like. These resins may be used alone or in combination of two or more. An electrode layer paste containing a polyvinyl acetal resin is preferable because it exhibits excellent adhesiveness to the ceramic green sheet in the thermocompression bonding process.

In the method for manufacturing the ceramic electronic component, after the ceramic green sheets having the electrode layers formed thereon are produced, the ceramic green sheets having the electrode layers formed in the same manner are laminated and heat-press-bonded. By degreasing and firing the laminate, a laminated ceramic electronic component in which problems such as sheet attack and cracks are resolved can be obtained.
The thermocompression bonding step and the step of degreasing and baking the laminate are not particularly limited, and conventionally known methods can be used.

According to the present invention, when dissolved in an organic solvent, the amount of fine undissolved matter is small, productivity can be improved particularly when used as a binder for ceramic green sheets, and ceramic green excellent in toughness A polyvinyl acetal resin can be obtained from which a sheet can be obtained and a laminated ceramic capacitor with excellent reliability can be produced.

It is a schematic diagram of a DSC curve.

EXAMPLES The present invention will be described in more detail with reference to Examples below, but the present invention is not limited to these Examples.

(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 mol %, degree of crystallinity: 35%), and the mixture was stirred at 90° C. for 2 hours to dissolve. This solution was cooled to 40° C., and 200 g of hydrochloric acid having a concentration of 35% by weight and 160 g of n-butyraldehyde were added to carry out an acetalization reaction to precipitate a reaction product. Thereafter, the mixture was held at 40° C. for 3 hours to complete the reaction, and then neutralized, washed with water and dried in a conventional manner to obtain a white powder of polyvinyl acetal resin.
In addition, the crystallinity degree of polyvinyl alcohol resin was measured by the following method.
Specifically, the polyvinyl alcohol resin was subjected to differential scanning calorimetry using a thermal analyzer (DSC6200R, manufactured by Hitachi High-Tech Science Co., Ltd.) under the following measurement conditions to measure the heat of fusion during the second temperature rise. Crystallinity was measured.
<Measurement conditions>
0°C (hold for 5 minutes) → (heating rate 10°C/min for the first time) → 270°C → (cooling at cooling rate 10°C/min) → 0°C (holding for 5 minutes) → (heating rate Second temperature rise at 10°C/min) → 270°C
The heat of fusion was calculated from the peak area appearing between 100°C and 270°C in the second heating. The area of the peak was defined as the area surrounded by the straight line connecting points A and B and the DSC curve as shown in FIG. Here, point A is the point where the DSC curve is separated from the straight line drawn along the straight-line approximation portion of the DSC curve from 170° C. to the high temperature side. Point B is a point on the DSC curve that indicates the final melting temperature. The degree of crystallinity was calculated assuming that the heat of fusion of a polyvinyl alcohol resin with a degree of crystallinity of 100% was 156 J/g.

(Example 2)
3100 g of pure water was added to 300 g of polyvinyl alcohol resin (average degree of polymerization: 1,900, degree of saponification: 84 mol %, degree of crystallinity: 12%), and the resin was dissolved by stirring at 90° C. for about 2 hours. This solution was cooled to 40° C., and 200 g of hydrochloric acid having a concentration of 35% by weight and 140 g of n-butyraldehyde were added to carry out an acetalization reaction to precipitate a reaction product. Thereafter, the mixture was held at 40° C. for 3 hours to complete the reaction, and then neutralized, washed with water and dried in a conventional manner to obtain a white powder of polyvinyl acetal resin.

(Example 3)
3100 g of pure water was added to 300 g of polyvinyl alcohol resin (average degree of polymerization: 3,000, degree of saponification: 98.2 mol %, degree of crystallinity: 26%), and the mixture was stirred at 90° C. for about 2 hours to dissolve. This solution was cooled to 40° C., and 200 g of hydrochloric acid having a concentration of 35% by weight and 160 g of n-butyraldehyde were added to carry out an acetalization reaction to precipitate a reaction product. Thereafter, the mixture was held at 40° C. for 3 hours to complete the reaction, and then neutralized, washed with water and dried in a conventional manner to obtain a white powder of polyvinyl acetal resin.

(Example 4)
3100 g of pure water was added to 300 g of polyvinyl alcohol resin (average degree of polymerization: 800, degree of saponification: 98.4 mol %, degree of crystallinity: 29%), and the mixture was dissolved by stirring at 90° C. for about 2 hours. This solution was cooled to 40° C., and 200 g of hydrochloric acid having a concentration of 35% by weight and 160 g of n-butyraldehyde were added to carry out an acetalization reaction to precipitate a reaction product. Thereafter, the mixture was held at 40° C. for 3 hours to complete the reaction, and then neutralized, washed with water and dried in a conventional manner to obtain a white powder of polyvinyl acetal resin.

(Example 5)
3100 g of pure water was added to 200 g of polyvinyl alcohol resin (average degree of polymerization: 4,000, degree of saponification: 99.2 mol %, degree of crystallinity: 34%), and the resin was dissolved by stirring at 90° C. for about 2 hours. This solution was cooled to 40° C., and 200 g of hydrochloric acid having a concentration of 35% by weight and 105 g of n-butyraldehyde were added to carry out an acetalization reaction to precipitate a reaction product. Thereafter, the mixture was held at 40° C. for 3 hours to complete the reaction, and then neutralized, washed with water and dried in a conventional manner to obtain a white powder of polyvinyl acetal resin.

(Example 6)
3100 g of pure water was added to 200 g of polyvinyl alcohol resin (average degree of polymerization: 4,500, degree of saponification: 88 mol %, degree of crystallinity: 13%), and the mixture was stirred at 90° C. for about 2 hours to dissolve. This solution was cooled to 40° C., and 200 g of hydrochloric acid having a concentration of 35% by weight and 150 g of n-butyraldehyde were added to carry out an acetalization reaction to precipitate a reaction product. Thereafter, the mixture was held at 40° C. for 3 hours to complete the reaction, and then neutralized, washed with water and dried in a conventional manner to obtain a white powder of polyvinyl acetal resin.

(Example 7)
3100 g of pure water was added to 300 g of polyvinyl alcohol resin (average degree of polymerization: 1,900, degree of saponification: 94 mol %, degree of crystallinity: 18%), and the resin was dissolved by stirring at 90° C. for about 2 hours. This solution was cooled to 40° C., and 200 g of hydrochloric acid having a concentration of 35% by weight and 145 g of n-butyraldehyde were added to carry out an acetalization reaction to precipitate a reaction product. Thereafter, the mixture was held at 40° C. for 3 hours to complete the reaction, and then neutralized, washed with water and dried in a conventional manner to obtain a white powder of polyvinyl acetal resin.

(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: 99.5 mol %, degree of crystallinity: 40%), and the resin was dissolved by stirring at 90° C. for about 2 hours. This solution was cooled to 40° C., and 200 g of hydrochloric acid having a concentration of 35% by weight and 160 g of n-butyraldehyde were added to carry out an acetalization reaction to precipitate a reaction product. Thereafter, the mixture was held at 40° C. for 3 hours to complete the reaction, and then neutralized, washed with water and dried in a conventional manner to obtain a white powder of polyvinyl acetal resin.

(Comparative example 2)
3100 g of pure water was added to 300 g of polyvinyl alcohol resin (average degree of polymerization: 1,900, degree of saponification: 80 mol %, degree of crystallinity: 13%), and the mixture was dissolved by stirring at 90° C. for about 2 hours. This solution was cooled to 40° C., and 200 g of hydrochloric acid having a concentration of 35% by weight and 100 g of n-butyraldehyde were added to carry out an acetalization reaction to precipitate a reaction product. Thereafter, the mixture was held at 40° C. for 3 hours to complete the reaction, and then neutralized, washed with water and dried in a conventional manner to obtain a white powder of polyvinyl acetal resin.

(Comparative Example 3)
3100 g of pure water was added to 150 g of polyvinyl alcohol resin (average degree of polymerization: 8,100, degree of saponification: 98 mol %, degree of crystallinity: 36%), and the mixture was stirred at 90° C. for about 2 hours to dissolve. This solution was cooled to 40° C., and 200 g of hydrochloric acid having a concentration of 35% by weight and 100 g of n-butyraldehyde were added to carry out an acetalization reaction to precipitate a reaction product. Thereafter, the mixture was held at 40° C. for 3 hours to complete the reaction, and then neutralized, washed with water and dried in a conventional manner to obtain a white powder of polyvinyl acetal resin.

(Comparative Example 4)
3100 g of pure water was added to 300 g of polyvinyl alcohol resin (average degree of polymerization: 800, degree of saponification: 99.5 mol %, degree of crystallinity: 38%), and the mixture was dissolved by stirring at 90° C. for about 2 hours. This solution was cooled to 40° C., and 200 g of hydrochloric acid having a concentration of 35% by weight and 130 g of n-butyraldehyde were added to carry out an acetalization reaction to precipitate a reaction product. Thereafter, the mixture was held at 40° C. for 3 hours to complete the reaction, and then neutralized, washed with water and dried in a conventional manner to obtain a white powder of polyvinyl acetal resin.

(Comparative Example 5)
3100 g of pure water was added to 300 g of polyvinyl alcohol resin (average degree of polymerization: 1,700, degree of saponification: 99.3 mol %, degree of crystallinity: 30%), and the mixture was stirred at 90° C. for about 2 hours to dissolve. This solution was cooled to 40° C., and 200 g of hydrochloric acid having a concentration of 35% by weight and 160 g of n-butyraldehyde were added to carry out an acetalization reaction to precipitate a reaction product. Thereafter, the mixture was held at 40° C. for 3 hours to complete the reaction, and then neutralized, washed with water and dried in a conventional manner to obtain a white powder of polyvinyl acetal resin.

(Comparative Example 6)
3100 g of pure water was added to 300 g of polyvinyl alcohol resin (average degree of polymerization: 3,300, degree of saponification: 99.5 mol %, degree of crystallinity: 37%), and the mixture was stirred at 90° C. for about 2 hours to dissolve. This solution was cooled to 40° C., and 200 g of hydrochloric acid having a concentration of 35% by weight and 160 g of n-butyraldehyde were added to carry out an acetalization reaction to precipitate a reaction product. Thereafter, the mixture was held at 40° C. for 3 hours to complete the reaction, and then neutralized, washed with water and dried in a conventional manner to obtain a white powder of polyvinyl acetal resin.

(Comparative Example 7)
3100 g of pure water was added to 300 g of polyvinyl alcohol resin (average degree of polymerization: 1,700, degree of saponification: 98 mol %, degree of crystallinity: 35%), and the mixture was stirred at 90° C. for about 2 hours to dissolve. This solution was cooled to 40° C., and 200 g of hydrochloric acid having a concentration of 35% by weight and 160 g of n-butyraldehyde were added to carry out an acetalization reaction to precipitate a reaction product. Thereafter, the mixture was held at 10° C. for 3 hours to complete the reaction, and then neutralized, washed with water and dried in a conventional manner to obtain a white powder of polyvinyl acetal resin.

(Comparative Example 8)
3100 g of pure water was added to 300 g of polyvinyl alcohol resin (average degree of polymerization: 1,700, degree of saponification: 98 mol %, degree of crystallinity: 35%), and the mixture was stirred at 90° C. for about 2 hours to dissolve. This solution was cooled to 40° C., and 200 g of hydrochloric acid having a concentration of 35% by weight and 160 g of n-butyraldehyde were added to carry out an acetalization reaction to precipitate a reaction product. Thereafter, the mixture was held at 40° C. for 0.5 hours to complete the reaction, and then neutralized, washed with water and dried in a conventional manner to obtain a white powder of polyvinyl acetal resin.

(evaluation)
The polyvinyl acetal resins obtained in Examples 1-7 and Comparative Examples 1-8 were evaluated as follows. The results are shown in Tables 1 and 2.

(1) Evaluation of polyvinyl acetal resin (1-1) Content ratio of acetal group content, hydroxyl group content, acetyl group content, and content of structural units having a hydroxyl group with a chain length of 1 ₆ at a concentration of 10% by weight, and the amounts of acetal group, hydroxyl group and acetyl group were measured using ¹³ C-NMR.

(1-2) number average molecular weight (Mn), weight average molecular weight (Mw), Mw/Mn
The obtained polyvinyl acetal resin was dissolved in tetrahydrofuran at a concentration of 0.2% by weight, and measured with a GPC device HLC-8220 (manufactured by Tosoh Corporation). Number average molecular weight (Mn), weight average molecular weight (Mw), and Mw/Mn were calculated using the molecular weight calibration curve. As a column, a column TSKgel SuperHZM-H (manufactured by Tosoh Corporation) was used.

(1-3) Number of undissolved substances Ethanol/toluene mixed at a weight ratio of 1:1 in a 300 ml Erlenmeyer flask (“010530-30071A” manufactured by Shibata Kagaku Co., Ltd., borosilicate glass, bottom inner diameter 87 mm, total height 148 mm, inner diameter 31 mm) 150 ml of the solution was added, and the obtained polyvinyl acetal resin was added so that the viscosity of the solution at 20° C. was 20 mPa·s. At this time, the concentration of the polyvinyl acetal resin was previously confirmed to be 20 mPa·s. As the viscometer, a rotary viscometer (TVB-10 viscometer manufactured by Toki Sangyo Co., Ltd.) was used. SPINDLE NO. Measurement was performed for 30 seconds at a rotation speed of 60 rpm using M1. Using a shaker (SR-2DW manufactured by TAITEC), the conical flask was shaken for 3 hours by a reciprocating shaking method at a shaking speed of 250 rpm and an amplitude of 40 mm with the mouth facing upward. After shaking, the conical flask was allowed to stand at 20°C for 30 minutes with the mouth facing up. After that, the Erlenmeyer flask was turned upside down and left for 30 minutes with the mouth of the Erlenmeyer flask facing down. The number of undissolved objects of ~2 mm was visually counted.
In addition, the presence or absence of undissolved matter with a maximum diameter exceeding 2 mm was confirmed.

(1-4) Number of particles with a diameter of 0.5 to 1.0 μm and proportion (% by volume)
The obtained polyvinyl acetal resin was dissolved in an ethanol/toluene mixed solution having a weight ratio of 1:1 so as to have a concentration of 0.2% by weight. The particle size distribution of 10 ml of the resulting solution was measured using a particle counter (KS-42C manufactured by Rion) to determine the number of particles with a diameter of 0.5 to 1.0 μm per 10 ml. Particles with a diameter of 0.5 to 1.0 μm are assumed to be true spheres with a diameter of 0.75 μm, and the volume of the particles is calculated. (% by volume) was calculated.

(2) Evaluation of resin sheet 10 parts by weight of the obtained polyvinyl acetal resin was added to 90 parts by weight of a mixed solvent of ethanol/toluene (weight ratio 1:1) and dissolved with stirring to obtain a composition for a resin sheet.
A measurement sample (resin sheet) is prepared by applying the obtained resin sheet composition on a release-treated PET film using a coater so that the thickness after drying becomes 20 μm, followed by heating and drying. did.

(2-1) Elasticity The tensile elasticity of the obtained measurement sample was measured according to JIS K 7113 using a tensile tester (AUTOGRAPH AGS-J manufactured by Shimadzu Corporation) at a tensile speed of 20 mm/min. Modulus (MPa) measurements were made.

(2-2) Upper yield point stress, breaking point stress, breaking point strain The measurement sample obtained is a dumbbell No. 1 (JIS K 6771 compliant) shape test piece, and a tensile tester (manufactured by Shimadzu Corporation, AUTOGRAPH AGS -J) was used to pull at a tensile speed of 500%/min, and the tensile strength at break (kg/cm ² ) was measured at a measurement temperature of 20°C. A stress σ (MPa)-strain ε (%) curve was obtained from the obtained values. Note that 500%/min means the speed at which the test piece is moved five times the chuck-to-chuck distance in one minute. The obtained stress-strain curve was used to determine the upper yield point stress, breaking point stress and breaking point strain.

(2-3) Breakage after Detachment The obtained measurement sample was detached from the PET film, the state was visually observed, and detachability was evaluated according to the following criteria.
◯: The resin sheet could be peeled cleanly from the PET film, and no breakage or peeling was observed on the peeled sheet.
Δ: The resin sheet could be peeled cleanly from the PET film, and small cuts were observed in a small portion of the peeled sheet.
x: The resin sheet could not be peeled off from the PET film, or most of the peeled sheet was observed to be cut or peeled off.

(3) Evaluation of ceramic green sheet (preparation of inorganic dispersion)
1 part by weight of polyvinyl acetal resin (manufactured by Sekisui Chemical Co., Ltd., BL-1) was added to a mixed solvent of 20 parts by weight of toluene and 20 parts by weight of ethanol, and stirred and dissolved. Next, 100 parts by weight of barium titanate powder (BT01, manufactured by Sakai Chemical Industry Co., Ltd.) is added to the obtained solution and stirred for 180 minutes in a bead mill (Ready Mill, manufactured by Aimex) to obtain an inorganic dispersion. made.

(Preparation of resin solution)
A resin solution was prepared by adding 8 parts by weight of the obtained polyvinyl acetal resin and 2 parts by weight of DOP to a mixed solvent of 45 parts by weight of ethanol and 45 parts by weight of toluene and dissolving the mixture with stirring.

(Preparation of ceramic green sheet)
A composition for ceramic green sheets was obtained by adding a resin solution to the resulting inorganic dispersion and stirring the mixture in a bead mill for 90 minutes.
The resulting ceramic green sheet composition was applied onto a release-treated PET film using a coater so that the thickness after drying was 20 μm, and then dried by heating to produce a ceramic green sheet.

(3-1) Number of defects with a cross-sectional area of 1 μm ² or more On the surface of the obtained ceramic green sheet, a field of view of 14,000 μm ² was randomly selected at 10 locations, and a shape analysis laser microscope (Keyence “VK-X100” ”) was used to count the average number of defects with a cross-sectional area of 1 μm ² or more per field of view.
The defect was defined as a portion having a cross-sectional area of 1 μm ² or more in the protruding trough when the load area ratio was 80%.

(3-2) Arithmetic mean height (Sa), maximum height (Sz)
The arithmetic mean height Sa of the obtained ceramic green sheet was evaluated in accordance with ISO25178 using a three-dimensional surface roughness meter (“VertScan 2.0” manufactured by Ryoka Systems Co., Ltd.).

According to the present invention, when dissolved in an organic solvent, the amount of fine undissolved matter is small, productivity can be improved particularly when used as a binder for ceramic green sheets, and ceramic green excellent in toughness A polyvinyl acetal resin can be obtained from which a sheet can be obtained and a laminated ceramic capacitor with excellent reliability can be produced.

Claims (4)

A polyvinyl acetal resin having 300 or less undissolved particles as measured by the method described below.
<Measurement method>
Polyvinyl acetal resin was added to 150 ml of an ethanol/toluene mixed solution with a weight ratio of 1:1 in a flask so that the solution viscosity at 20° C. measured with a rotary viscometer was 20 mPa·s, and the mixture was shaken. After allowing to stand at 20° C. for 30 minutes, turning it upside down and allowing it to stand still for 30 minutes, the number of undissolved substances adhering to the bottom surface is counted. When the particle size distribution of a polyvinyl acetal resin solution dissolved to a concentration of 0.2% by weight in an ethanol/toluene mixed solution with a weight ratio of 1:1 was measured using a particle counter, the diameter was 0.5 to 0.5%. 2. The polyvinyl acetal resin according to claim 1, wherein the proportion of particles having a diameter of 1.0 μm is 4.42×10 ⁻⁸ vol % or less with respect to 100 vol % of the resin solution. 3. The polyvinyl acetal resin according to claim 1, wherein the amount of hydroxyl groups is 18-40 mol %. The polyvinyl acetal resin according to any one of claims 1 to 3, which is for ceramic green sheets.

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