POLYVINYL ACETAL RESIN

Abstract

The present invention provides a polyvinyl acetal resin which leaves less fine undissolved matter when dissolved in an organic solvent and thus can improve productivity particularly when used as a binder for a ceramic green sheet, and which can also provide a ceramic green sheet having excellent toughness and enables production of a highly reliable multilayer ceramic capacitor. Provided is a polyvinyl acetal resin having: a wavenumber A (cm.sup.−1) of a peak within a range of 3,100 to 3,700 cm.sup.−1 in an IR absorption spectrum measured using an infrared spectrophotometer; and a hydroxy group content (mol %), the wavenumber A of the peak and the hydroxy group content satisfying relations of the following formulas (1) and (2):

[(3,470−A)/Hydroxy group content]≤5.5  (1)

(3,470−A)≤185  (2)

wherein A is a wavenumber which is lower than 3,470 cm.sup.−1 and at which a transmittance a (%) satisfying [100−(100−X)/2] is exhibited, where X (%) is a minimum transmittance of the peak within the wavenumber range of 3,100 to 3,700 cm.sup.−1.

Claims

1. A polyvinyl acetal resin having: a wavenumber A (cm.sup.−1) of a peak within a range of 3,100 to 3,700 cm.sup.−1 in an IR absorption spectrum measured using an infrared spectrophotometer, and a hydroxy group content (mol %), the wavenumber A of the peak and the hydroxy group content satisfying relations of the following formulas (1) and (2):
[(3,470−A)/Hydroxy group content]≤5.5  (1)
(3,470−A)≤185  (2) wherein A is a wavenumber which is lower than 3,470 cm.sup.−1 and at which a transmittance a (%) satisfying [100−(100−X)/2] is exhibited, where X (%) is a minimum transmittance of the peak within the wavenumber range of 3,100 to 3,700 cm.sup.−1.

2. The polyvinyl acetal resin according to claim 1, wherein the hydroxy group content is 18 to 40 mol %.

3. The polyvinyl acetal resin according to claim 1, wherein the polyvinyl acetal resin has a wavenumber B (cm.sup.−1) of the peak within the wavenumber range of 3,100 to 3,700 cm.sup.−1 in the IR absorption spectrum measured using the infrared spectrophotometer, the wavenumber A of the peak and the wavenumber B of the peak satisfy a relation of the following formula (3):
(3,470−A)/(B−3,470)≤3.0  (3) wherein B is a wavenumber which is higher than 3,470 cm.sup.−1 and at which the transmittance a (%) satisfying [100−(100−X)/2] is exhibited, where X (%) is the minimum transmittance of the peak within the wavenumber range of 3,100 to 3,700 cm.sup.−1.

4. The polyvinyl acetal resin according to claim 1, wherein a solution of the polyvinyl acetal resin at a concentration of 0.2% by weight in a 1:1 weight ratio mixture solution of ethanol and toluene has a percentage of particles having a diameter of 0.5 to 1.0 μm of 4.42×10.sup.−8% by volume or lower relative to 100% by volume of the resin solution when a particle size distribution of the resin solution is determined using a particle counter.

5. The polyvinyl acetal resin according to claim 1, wherein the polyvinyl acetal resin is for a ceramic green sheet.

6. The polyvinyl acetal resin according to claim 2, wherein the polyvinyl acetal resin has a wavenumber B (cm.sup.−1) of the peak within the wavenumber range of 3,100 to 3,700 cm.sup.−1 in the IR absorption spectrum measured using the infrared spectrophotometer, the wavenumber A of the peak and the wavenumber B of the peak satisfy a relation of the following formula (3):
(3,470−A)/(B−3,470)≤3.0  (3) wherein B is a wavenumber which is higher than 3,470 cm.sup.−1 and at which the transmittance a (%) satisfying [100−(100−X)/2] is exhibited, where X (%) is the minimum transmittance of the peak within the wavenumber range of 3,100 to 3,700 cm.sup.−1.

7. The polyvinyl acetal resin according to claim 2, wherein a solution of the polyvinyl acetal resin at a concentration of 0.2% by weight in a 1:1 weight ratio mixture solution of ethanol and toluene has a percentage of particles having a diameter of 0.5 to 1.0 μm of 4.42×10.sup.−8% by volume or lower relative to 100% by volume of the resin solution when a particle size distribution of the resin solution is determined using a particle counter.

8. The polyvinyl acetal resin according to claim 3, wherein a solution of the polyvinyl acetal resin at a concentration of 0.2% by weight in a 1:1 weight ratio mixture solution of ethanol and toluene has a percentage of particles having a diameter of 0.5 to 1.0 μm of 4.42×10.sup.−8% by volume or lower relative to 100% by volume of the resin solution when a particle size distribution of the resin solution is determined using a particle counter.

9. The polyvinyl acetal resin according to claim 6, wherein a solution of the polyvinyl acetal resin at a concentration of 0.2% by weight in a 1:1 weight ratio mixture solution of ethanol and toluene has a percentage of particles having a diameter of 0.5 to 1.0 μm of 4.42×10.sup.−8% by volume or lower relative to 100% by volume of the resin solution when a particle size distribution of the resin solution is determined using a particle counter.

10. The polyvinyl acetal resin according to claim 2, wherein the polyvinyl acetal resin is for a ceramic green sheet.

11. The polyvinyl acetal resin according to claim 3, wherein the polyvinyl acetal resin is for a ceramic green sheet.

12. The polyvinyl acetal resin according to claim 4, wherein the polyvinyl acetal resin is for a ceramic green sheet.

13. The polyvinyl acetal resin according to claim 6, wherein the polyvinyl acetal resin is for a ceramic green sheet.

14. The polyvinyl acetal resin according to claim 7, wherein the polyvinyl acetal resin is for a ceramic green sheet.

15. The polyvinyl acetal resin according to claim 8, wherein the polyvinyl acetal resin is for a ceramic green sheet.

16. The polyvinyl acetal resin according to claim 9, wherein the polyvinyl acetal resin is for a ceramic green sheet.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0132] FIG. 1 is an exemplary IR absorption spectrum of the polyvinyl acetal resin of the present invention obtained by IR absorption spectrometry.

[0133] FIG. 2 is an exemplary IR absorption spectrum of the polyvinyl acetal resin of the present invention obtained by IR absorption spectrometry.

[0134] FIG. 3 is a schematic view of a DSC curve.

DESCRIPTION OF EMBODIMENTS

[0135] The present invention is more specifically described in the following with reference to, but not limited to, examples.

Example 1

[0136] Pure water (3,000 g) was added co 300 g of a polyvinyl alcohol resin (average degree of polymerization 1,700, degree of saponification 98 mol %, crystallinity 35%). They were stirred at 90° C. for two hours for dissolution. This solution was cooled to 40° C. To the solution were added 200 g of hydrochloric acid having a concentration of 35% by weight and 160 g of n-butyraldehyde, whereby acetalization reaction was performed and a reaction product was precipitated. The amount of n-butyraldehyde added was 68 mol % relative to 100 mol % of the polyvinyl alcohol resin. The mixture was then held at 40° C. for three hours to complete the reaction. Neutralization, washing with water, and drying were performed by conventional methods, whereby white powder of a polyvinyl acetal resin was obtained.

[0137] The crystallinity of the polyvinyl alcohol resin was measured by the following method.

[0138] Specifically, the polyvinyl alcohol resin was subjected to differential scanning calorimetry using a thermal analyzer (produced by Hitachi High-Tech Science Corporation, DSC6200R) under the following conditions. The heat of fusion in the second heating was measured to measure the crystallinity.

<Measurement Conditions>

[0139] 0° C. (holding for five minutes).fwdarw.(first heating at heating rate of 10° C./min).fwdarw.270° C..fwdarw.(cooling at cooling rate of 10° C./min).fwdarw.0° C. (holding for five minutes).fwdarw.(second heating at heating rate of 10° C./min).fwdarw.270° C.

[0140] The heat of fusion was calculated from the area of a peak appearing between 100° C. and 270° C. in the second heating. The area of the peak was, as shown in FIG. 3, determined as the area of the region surrounded by the straight line connecting the points A and B and the DSC curve. The point A was the point at which a straight line drawn along the linear approximation portion of the DSC curve from 170° C. toward the higher temperature side leaves the DSC curve. The point B was the point on the DSC curve that shows the end-of-melt temperature. The crystallinity was calculated assuming that the heat of fusion of a polyvinyl alcohol resin having a crystallinity of 100% was 156 J/g.

Example 2

[0141] Pure water (3,100 g) was added to 300 g of a polyvinyl alcohol resin (average degree of polymerization 1,900, degree of saponification 84 mol %, crystallinity 12%). They were stirred at 90° C. for about two hours for dissolution. This solution was cooled to 40° C. To the solution were added 200 g of hydrochloric acid having a concentration of 35% by weight and 130 g of n-butyraldehyde, whereby acetalization reaction was performed and a reaction product was precipitated. The amount of n-butyraldehyde added was 61 mol % relative to 100 mol % of the polyvinyl alcohol resin. The mixture was then held at 40° C. for three hours to complete the reaction. Neutralization, washing with water, and drying were performed by conventional methods, whereby white powder of a polyvinyl acetal resin was obtained.

Example 3

[0142] Pure water (3,100 g) was added to 300 g of a polyvinyl alcohol resin (average degree of polymerization 3,000, degree of saponification 98.2 mol %, crystallinity 26%). They were stirred at 90° C. for about two hours for dissolution. This solution was cooled to 40° C. To the solution were added 200 g of hydrochloric acid having a concentration of 354 by weight and 170 g of n-butyraldehyde, whereby acetalization reaction was performed and a reaction product was precipitated. The amount of n-butyraldehyde added was 73 mol % relative to 100 mol % of the polyvinyl alcohol resin. The mixture was then held at 40° C. for three hours to complete the reaction. Neutralization, washing with water, and drying were performed by conventional methods, whereby white powder of a polyvinyl acetal resin was obtained.

Example 4

[0143] Pure water (3,100 g) was added to 300 g of a polyvinyl alcohol resin (average degree of polymerization 800, degree of saponification 98.4 mol %, crystallinity 29%). They were stirred at 90° C. for about two hours for dissolution. This solution was cooled to 40° C. To the solution were added 200 g of hydrochloric acid having a concentration of 35% by weight and 150 g of n-butyraldehyde, whereby acetalization reaction was performed and a reaction product was precipitated. The amount of n-butyraldehyde added was 64 mol % relative to 100 mol % of the polyvinyl alcohol resin. The mixture was then held at 40° C. for three hours to complete the reaction. Neutralization, washing with water, and drying were performed by conventional methods, whereby white powder of a polyvinyl acetal resin was obtained.

Example 5

[0144] Pure water (3,100 g) was added to 300 g of a polyvinyl alcohol resin (average degree of polymerization 1,700, degree of saponification 99.2 mole, crystallinity 37%). They were stirred at 90° C. for about two hours for dissolution. This solution was cooled to 40° C. To the solution were added 200 g of hydrochloric acid having a concentration of 35% by weight and 160 g of n-butyraldehyde, whereby acetalization reaction was performed and a reaction product was precipitated. The amount of n-butyraldehyde added was 68 mold relative to 100 mol % of the polyvinyl alcohol resin. The mixture was then held at 40° C. for three hours to complete the reaction. Neutralization, washing with water, and drying were performed by conventional methods, whereby white powder of a polyvinyl acetal resin was obtained.

Example 6

[0145] Pure water (3,100 g) was added to 300 g of a polyvinyl alcohol resin (average degree of polymerization 1,700, degree of saponification 99.1 mol %, crystallinity 37%). They were stirred at 90° C. for about two hours for dissolution. This solution was cooled to 40° C. To the solution were added 200 g of hydrochloric acid having a concentration of 35% by weight and 160 g of n-butyraldehyde, whereby acetalization reaction was performed and a reaction product was precipitated. The amount of n-butyraldehyde added was 68 mol % relative to 100 mol % of the polyvinyl alcohol resin. The mixture was then held at 40° C. for three hours to complete the reaction. Neutralization, washing with water, and drying were performed by conventional methods, whereby white powder of a polyvinyl acetal resin was obtained.

Example 7

[0146] Pure water (3,100 g) was added to 300 g of a polyvinyl alcohol resin (average degree of polymerization 1,700, degree of saponification 98.3 mol %, crystallinity 33%). They were stirred at 90° C. for about two hours for dissolution. This solution was cooled to 40° C. To the solution were added 200 g of hydrochloric acid having a concentration of 35% by weight and 155 g of n-butyraldehyde, whereby acetalization reaction was performed and a reaction product was precipitated. The amount of n-butyraldehyde added was 66 mol % relative to 100 mol % of the polyvinyl alcohol resin. The mixture was then held at 40° C. for three hours to complete the reaction. Neutralization, washing with water, and drying were performed by conventional methods, whereby white powder of a polyvinyl acetal resin was obtained.

Example 8

[0147] Pure water (3,100 g) was added to 300 g of a polyvinyl alcohol resin (average degree of polymerization 1,900, degree of saponification 89 mol %, crystallinity 13%). They were stirred at 90° C. for about two hours for dissolution. This solution was cooled to 40° C. To the solution were added 200 g of hydrochloric acid having a concentration of 35% by weight and 145 g of n-butyraldehyde, whereby acetalization reaction was performed and a reaction product was precipitated. The amount of n-butyraldehyde added was 67 mol % relative to 100 mol % of the polyvinyl alcohol resin. The mixture was then held at 40° C. for three hours to complete the reaction. Neutralization, washing with water, and drying were performed by conventional methods, whereby white powder of a polyvinyl acetal resin was obtained.

Example 9

[0148] Pure water (3,100 g) was added to 300 g of a polyvinyl alcohol resin (average degree of polymerization 3,000, degree of saponification 88 mol %, crystallinity 13%). They were stirred at 90° C. for about two hours for dissolution. This solution was cooled to 40° C. To the solution were added 200 g of hydrochloric acid having a concentration of 35% by weight and 165 g of n-butyraldehyde, whereby acetalization reaction was performed and a reaction product was precipitated. The amount of n-butyraldehyde added was 76 mol % relative to 100 mol % of the polyvinyl alcohol resin. The mixture was then held at 40° C. for three hours to complete the reaction. Neutralization, washing with water, and drying were performed by conventional methods, whereby white powder of a polyvinyl acetal resin was obtained.

Comparative Example 1

[0149] Pure water (3,000 g) was added to 300 g of a polyvinyl alcohol resin (average degree of polymerization 1,700, degree of saponification 99.5 mol %, crystallinity 40%). They were stirred at 90° C. for about two hours for dissolution. This solution was cooled to 40° C. To the solution were added 200 g of hydrochloric acid having a concentration of 35% by weight and 160 g of n-butyraldehyde, whereby acetalization reaction was performed and a reaction product was precipitated. The amount of n-butyraldehyde added was 68 mol % relative to 100 mol % of the polyvinyl alcohol resin. The mixture was then held at 40° C. for three hours to complete the reaction. Neutralization, washing with water, and drying were performed by conventional methods, whereby white powder of a polyvinyl acetal resin was obtained.

Comparative Example 2

[0150] Pure water (3,100 g) was added to 300 g of a polyvinyl alcohol resin (average degree of polymerization 1,900, degree of saponification 80 mol %, crystallinity 13%). They were stirred at 90° C. for about two hours for dissolution. This solution was cooled to 40° C. To the solution were added 200 g of hydrochloric acid having a concentration of 35% by weight and 100 g of n-butyraldehyde, whereby acetalization reaction was performed and a reaction product was precipitated. The amount of n-butyraldehyde added was 50 mol % relative to 100 mol % of the polyvinyl alcohol resin. The mixture was then held at 40° C. for three hours to complete the reaction. Neutralization, washing with water, and drying were performed by conventional methods, whereby white powder of a polyvinyl acetal resin was obtained.

Comparative Example 3

[0151] Pure water (3,100 g) was added to 150 g of a polyvinyl alcohol resin (average degree of polymerization 8,100, degree of saponification 98 mol %, crystallinity 36%). They were stirred at 90° C. for about two hours for dissolution. This solution was cooled to 40° C. To the solution were added 200 g of hydrochloric acid having a concentration of 354 by weight and 80 g of n-butyraldehyde, whereby acetalization reaction was performed and a reaction product was precipitated. The amount of n-butyraldehyde added was 66 mol % relative to 100 mol % of the polyvinyl alcohol resin. The mixture was then held at 40° C. for three hours to complete the reaction. Neutralization, washing with water, and drying were performed by conventional methods, whereby white powder of a polyvinyl acetal resin was obtained.

Comparative Example 4

[0152] Pure water (3,100 g) was added to 300 g of a polyvinyl alcohol resin (average degree of polymerization 800, degree of saponification 99.5 mol %, crystallinity 38%). They were stirred at 90° C. for about two hours for dissolution. This solution was cooled to 40° C. To the solution were added 200 q of hydrochloric acid having a concentration of 35% by weight and 135 g of n-butyraldehyde, whereby acetalization reaction was performed and a reaction product was precipitated. The amount of n-butyraldehyde added was 56 mol % relative to 100 mol % of the polyvinyl alcohol resin. The mixture was then held at 40° C. for three hours to complete the reaction. Neutralization, washing with water, and drying were performed by conventional methods, whereby white powder of a polyvinyl acetal resin was obtained.

Comparative Example 5

[0153] Pure water (3,100 g) was added to 300 g of a polyvinyl alcohol resin (average degree of polymerization 1,700, degree of saponification 99.1 mol %, crystallinity 39%). They were stirred at 90° C. for about two hours for dissolution. This solution was cooled to 40° C. To the solution were added 200 g of hydrochloric acid having a concentration of 35% by weight and 160 g of n-butyraldehyde, whereby acetalization reaction was performed and a reaction product was precipitated. The amount of n-butyraldehyde added was 68 mol % relative to 100 mol % of the polyvinyl alcohol resin. The mixture was then held at 40° C. for three hours to complete the reaction. Neutralization, washing with water, and drying were performed by conventional methods, whereby white powder of a polyvinyl acetal resin was obtained.

Comparative Example 6

[0154] Pure water (3,100 g) was added to 300 g of a polyvinyl alcohol resin (average degree of polymerization 250, degree of saponification 98.5 mol %, crystallinity 28%). They were stirred at 90° C. for about two hours for dissolution. This solution was cooled to 40° C. To the solution were added 200 g of hydrochloric acid having a concentration of 351 by weight and 150 g of n-butyraldehyde, whereby acetalization reaction was performed and a reaction product was precipitated. The amount of n-butyraldehyde added was 64 mol % relative to 100 mol % of the polyvinyl alcohol resin. The mixture was then held at 40° C. for three hours to complete the reaction. Neutralization, washing with water, and drying were performed by conventional methods, whereby white powder of a polyvinyl acetal resin was obtained.

Comparative Example 7

[0155] Pure water (3,100 g) was added co 300 g of a polyvinyl alcohol resin (average degree of polymerization 1,700, degree of saponification 99 mol %, crystallinity 35%). They were stirred at 90° C. for about two hours for dissolution. This solution was cooled to 40° C. To the solution were added 200 g of hydrochloric acid having a concentration of 351 by weight and 160 g of n-butyraldehyde, whereby acetalization reaction was performed and a reaction product was precipitated. The amount of n-butyraldehyde added was 68 mol % relative to 100 mol % of the polyvinyl alcohol resin. The mixture was then held at 10° C. for three hours to complete the reaction. Neutralization, washing with water, and drying were performed by conventional methods, whereby white powder of a polyvinyl acetal resin was obtained.

Comparative Example 8

[0156] Pure water (3,100 g) was added to 300 g of a polyvinyl alcohol resin (average degree of polymerization 1,700, degree of saponification 99 mol %, crystallinity 35%). They were stirred at 90° C. for about two hours for dissolution. This solution was cooled to 40° C. To the solution were added 200 g of hydrochloric acid having a concentration of 35% by weight and 160 g of n-butyraldehyde, whereby acetalization reaction was performed and a reaction product was precipitated. The amount of n-butyraldehyde added was 68 mol % relative to 100 mol % of the polyvinyl alcohol resin. The mixture was then held at 40° C. for 0.5 hours to complete the reaction. Neutralization, washing with water, and drying were performed by conventional methods, whereby white powder of a polyvinyl acetal resin was obtained.

(Evaluation)

[0157] The polyvinyl acetal resins obtained in the examples and the comparative examples were evaluated as follows. Tables 1 to 3 show the results.

(1) Evaluation of Polyvinyl Acetal Resin

(1-1) Acetal Group Content, Hydroxy Group Content, and Acetyl Group Content

[0158] The obtained polyvinyl acetal resin was dissolved in DMSO-DF at a concentration of 10% by weight. The solution was subjected to .sup.13C-NMR to measure the acetal group content, hydroxy group content, and acetyl group content.

(1-2) IR Absorption Spectrum

[0159] The obtained polyvinyl acetal resin was dissolved in a 1:1 weight ratio mixture solution of ethanol and toluene. The solution was then applied to a PET film. The thickness of the measurement sample was adjusted such that the peak appearing near 2,980 cm.sup.−1 derived from the stretching vibrations of the C—H bond would have a minimum transmittance of 22%. A polyvinyl acetal resin sheet was thus obtained. An IR absorption spectrum was measured for the obtained polyvinyl acetal resin sheet at 20° C. using an infrared spectrophotometer (produced by HORIBA, FT-720). In the measurement results, a baseline was drawn for the peak appearing within the wavenumber range of 3,100 to 3,700 cm.sup.−1, and correction was performed to adjust the transmittance of both ends of the peak to 100%. The corrected data was subjected to peak analysis to measure the minimum transmittance X, the transmittance a, and the wavenumbers A, B and C of the peak.

(1-3) Number and Percentage (8 by Volume) of Particles Having a Diameter of 0.5 to 1.0 μm

[0160] The obtained polyvinyl acetal resin was dissolved to 0.2% by weight in a 1:1 weight ratio mixture solution of ethanol and toluene. The particle size distribution of the obtained solution (10 ml) was measured using a particle counter (produced by Rion Co., Ltd., KS-42C) to measure the number of particles having a diameter of 0.5 to 1.0 μm per 10 ml. The volume of the particles having a diameter of 0.5 to 1.0 μm was calculated assuming that they were true spheres having a diameter of 0.75 μm. Based on the obtained measurement results, the percentage (i by volume) of the particles having a diameter of 0.5 to 1.0 μm was calculated.

(2) Evaluation of Resin Sheet

[0161] The obtained polyvinyl acetal resin (10 parts by weight) was added to 90 parts by weight of a solvent mixture of ethanol and toluene (weight ratio 1:1), and dissolved by stirring. Thus, a composition for a resin sheet was obtained.

[0162] The obtained composition for a resin sheet was applied to a release-treated PET film to a dried thickness of 20 μm using a coater. The composition was heated and dried, whereby a measurement sample (resin sheet) was prepared.

(2-1) Modulus of Elasticity

[0163] The tensile modulus of elasticity (MPa) of the obtained measurement sample was measured in conformity with JIB R 7113 using a tensile tester (produced by Shimadzu Corporation, AUTOGRAPH AGS-J) at a tensile speed of 20 mm/min.

(2-2) Stress at the Upper Yield Point, Stress at Break, and Strain at Break

[0164] The obtained measurement sample was formed into a specimen in the shape of Type 1 dumbbell (in conformity with JIS K 6771). The specimen was stretched using a tensile tester (produced by Shimadzu Corporation, AUTOGRAPH AGS-J) at a tensile speed of 500%/min to measure the tensile strength at break (kg/cm.sup.2) at a measurement temperature of 20° C. From the obtained values, a stress a (MPa)-strain ε (%) curve was determined. The 500%/min means the speed at which the specimen was moved such that the chuck distance of the specimen reaches five times its initial value in one minute. From the obtained stress-strain curve, the stress at the upper yield point, the stress at break, and the strain at break were determined.

(2-3) Breaking after Separation

[0165] The obtained measurement sample was separated from the PET film. The state of the sample was visually observed to evaluate the releasability in accordance with the following criteria. [0166] o (Good): The resin sheet was cleanly separated from the PET film, and no cut or peeling was observed on the separated sheet. [0167] Δ (Fair): The resin sheet was cleanly separated from the PET film, and small cuts were observed in only a small part of the separated sheet. [0168] × (Poor) The resin sheet was not separated from the PET film, or cuts and/or peeling were/was observed in most of the separated sheet.

(3) Evaluation of Ceramic Green Sheet

(Preparation of Inorganic Dispersion)

[0169] One part by weight of a polyvinyl acetal resin (produced by Sekisui Chemical Co., Ltd., BL-1) was added to a solvent mixture of 20 parts by weight of toluene and 20 parts by weight of ethanol, and they were stirred for dissolution. Subsequently, to the obtained solution was added 100 parts by weight of barium titanate powder (produced by Sakai Chemical Industry Co., Ltd., BT01), followed by stirring in a bead mill (produced by AMEX Co., Ltd., Ready Hill) for 180 minutes, whereby an inorganic dispersion was prepared.

(Preparation of Resin Solution)

[0170] The obtained polyvinyl acetal resin (8 parts by weight) and 2 parts by weight of DOP were added to a solvent mixture of 45 parts by weight of ethanol and 45 parts by weight of toluene, and they were stirred for dissolution. Thus, a resin solution was prepared.

(Preparation of Ceramic Green Sheet)

[0171] The resin solution was added to the obtained inorganic dispersion, and they were stirred for 90 minutes in a bead mill, whereby a composition for a ceramic green sheet was obtained.

[0172] The obtained composition for a ceramic green sheet was applied to a release-treated PET film to a dried thickness of 20 μm using a coater. The composition was heated and dried, whereby a ceramic green sheet was prepared.

(3-1) Number of Defects Having a Cross Sectional Area of 1 μm.SUP.2 .or Greater

[0173] Ten 14,000-μm.sup.2 fields of view were randomly selected on a surface of the obtained ceramic green sheet. The average number of defects per field of view was counted using a 3D laser scanning microscope (produced by Keyence Corporation, “VK-X100”).

[0174] The defect herein refers to a reduced valley having a cross sectional area of 1 μm.sup.2 or greater at an areal material ratio of 80%.

(3-2) Arithmetic Mean Height (Sa) and Maximum Height (Sz)

[0175] The arithmetic mean height Sa of the obtained ceramic green sheet was evaluated in conformity with ISO25178 using a surface roughness tester (produced by Ryoka Systems Inc., “VertScan 2.0”).

TABLE-US-00001 TABLE 1 Polyvinyl acetal resin Acetal Acetyl Hydroxy Minimum Average group group group transmittance Transmittance Wave- Wave- Wave- degree of content content content X a number A number B number C polymerization (mol %) (mol %) (mol %) (%) (%) (cm.sup.−1) (cm.sup.−1) (cm.sup.−1) Example 1 1,700 6 .5 2.0 31.5 64.9 82.45 3315 3556 3468 Example 2 1,900 47.0 16.0 37.0 60.1 80.05 3340 3560 3482 Example 3 3,000 70.2 1.8 28.0 66.2 83.10 3327 3556 3468 Example 4 800 62.0 1. 36.4 61.0 80.50 3295 3555 3470 Example 5 1,700 66.8 0.8 32.4 62.8 81.40 3290 3559 3468 Example 6 1,700 67.1 0.9 32.0 63.0 81.50 3300 3580 3466 Example 7 1,700 64.3 1.7 34.0 62.0 81.00 3310 3560 3468 Example 8 1,900 53.0 11.0 36.0 61.3 80. 5 3342 3560 3480 Example 9 3,000 59.0 12.0 29.0 65.9 82.95 33 2 3562 3482 Comparative Example 1 1,700 67.5 0. 32.0 63.2 81. 0 3290 3557 34 8 Comparative Example 2 1,900 35.0 20.0 45.0 56.0 78.00 3280 3550 347 Comparative Example 3 8,100 64.5 1.0 34.5 61.6 80.80 3280 3558 3470 Comparative Example 4 800 54.5 0.5 45.0 56.0 78.00 3255 3546 346 Comparative Example 5 1,700 67.1 0.9 32.0 63.2 81.60 3292 3557 346 Comparative Example 6 2 0 60.5 1.5 38.0 59.5 79.75 3283 3555 3468 Comparative Example 7 1,700 62.0 1.0 37.0 61.8 80.90 3280 3556 3468 Comparative Example 8 1,700 62.0 1.0 37.0 61.3 80. 5 3270 3559 3468 indicates data missing or illegible when filed

TABLE-US-00002 TABLE 2 Polyvinyl acetal resin (3740 − A)/ (3470 − A)/ (C − A)/ (B − 3470)/ (B − 3470)/ Hydroxy Acetal Acetal Hydroxy Acetal [3470 − group group group group group A]/ content content content content content 3470 − A C − A B − C [B − (C − A)/ (cm.sup.−1/ (cm.sup.−1/ (cm.sup.−1/ (cm.sup.−1/ (cm.sup.−1/ (cm.sup.−1) (cm.sup.−1) (cm.sup.−1) 3470] (B − C) mol %) mol %) mol %) mol %) mol %) Example 1 155 153 90 1.76 1.70 4. 2 2.33 2.30 2.79 1.32 Example 2 130 142 78 1.44 1.82 3.51 2.77 3.02 2.43 1.91 Example 3 143 141 88 1. 1.80 5.11 2.04 2.01 3.07 1.23 Example 4 175 175 85 2.08 2.06 4.81 2.82 2.82 2.34 1.37 Example 5 180 178 91 2.02 1.96 5.5 2. 9 2. 6 2.75 1.33 Example 6 170 166 94 1.89 1.77 5.31 2.53 2.47 2.81 1.34 Example 7 160 168 92 1.78 1.72 4.71 2.49 2.48 2.65 1.40 Example 8 128 138 80 1.42 1.73 3.56 2.42 2. 0 2.50 1. 0 Example 9 108 120 80 1.17 1.50 3.72 1.83 2.03 3.17 1.56 Comparative Example 1 180 178 89 2.07 2.00 3 2. 2. 4 2.72 1.29 Comparative Example 2 190 198 72 2.38 2.75 4.22 5.43 5.66 1.78 2.29 Comparative Example 3 190 190 2.16 2.16 .51 2.95 2. 2.55 1.36 Comparative Example 4 215 213 78 2.83 2.73 4.78 3.94 3.91 1.89 1.3 Comparative Example 5 178 176 89 2.05 1.9 5.5 2.65 2.82 3.72 1.30 Comparative Example 6 187 185 87 2.20 2.13 4.92 3.09 3.06 2.24 1.40 Comparative Example 7 190 188 88 2.21 2.14 5.14 3.0 3.03 2.32 1.39 Comparative Example 8 200 198 91 2.2 2.18 5.41 3.23 3.19 2.41 1.44 indicates data missing or illegible when filed

TABLE-US-00003 TABLE 3 Polyvinyl acetal resin Percentage Number of particles of having particles particle having size of Resin sheet Ceramic  sheet particle 0.5 to Stress at Maximum size of 1.0 μm upper  at Strain Breaking Number height height 0.5 to (10 % yield break at after of 1.0 μm by volume)  of #Z,899 (MPa) point (MPa) (MPa) break (%) (μm) (μm) Example 1 12 3 2.79 840 45 75 340 ∘ 585 0.073 3.457 Example 2 212 0.47 748 33 5 350 ∘ 285 0.0 2 2.622 Example 3 34 0.77 97 4 8 3 0 ∘ 2 3 0.0 1 2.633 Example 4 2 7 0.89 740 47 0 240 ∘ 2 1 0.055 2.649 Example 5 191 4.23 855 4 7 330 ∘ 722 0.07 3.501 Example 6 1951 4.31 858 4 78 3 0 ∘ 778 0.082 3.6 9 Example 7 9 1.98 850 4 80 3 0 ∘ 373 0.070 3.337 Example 8 0. 7 0 3 70 370 ∘ 297 0.055 2.608 Example 9 94 0. 80 39 67 3 0 ∘ 254 0.052 2. 78 Comparative Example 1 3325 7.3 790 43 6 3 0 ∘ 1022 0.0 4.301 Comparative Example 2 5 6 11.6 5 0 20 55 0 x 2235 0.084 .233 Comparative Example 3 3 55 8.07 00 53 4 02 Δ 1569 0.101 4.428 Comparative Example 4 7842 17.3 7 0 40 48 x 2 98 0.161 5 Comparative Example 5 3273 7.23 7 0 43 6 80 ∘ 1017 0.0 5 4. 4 Comparative Example 6 2245 4.9 5 0 31 42 1 0 x 955 0.090 4. 00 Comparative Example 7 3703 8.1 770 44 58 40 Δ 1135 0.103 4.450 Comparative Example 8 4115 .0 75 4 58 220 Δ 1243 0.10 5.30 indicates data missing or illegible when filed

INDUSTRIAL APPLICABILITY

[0176] The present invention can provide a polyvinyl acetal resin which leaves less fine undissolved matter when dissolved in an organic solvent and thus can improve productivity particularly when used as a binder for a ceramic green sheet, and which can also provide a ceramic green sheet having excellent toughness and enables production of a highly reliable multilayer ceramic capacitor.