Binder for electrical storage device electrode

Abstract

The present invention aims to provide a binder for a power storage device electrode which exhibits thermal energy stability over a wide temperature range covering from a high-temperature condition to a low-temperature condition when used as a binder for a power storage device electrode, and which enables production of a high-capacity storage battery with a small irreversible capacity and low resistance to have excellent output characteristics. The present invention also aims to provide a binder for a power storage device electrode which is excellent in dispersibility of an active material and adhesiveness, which improves the flexibility of an electrode to be obtained, and which has high resistance against electrolytes to enable production of a high-capacity storage battery even when the added amount thereof is small. The present invention further aims to provide a composition for a power storage device electrode, a power storage device electrode, and a power storage device each prepared using the binder for a power storage device electrode. The present invention relates to a binder for a power storage device electrode used for an electrode of a power storage device, the binder including a polyvinyl acetal resin, the polyvinyl acetal resin having a meso/racemo ratio of an acetal ring structure of 10 or higher and a hydroxy group content of 30 to 60 mol %.

Claims

1. A binder for a power storage device electrode used for an electrode of a power storage device, the binder comprising a polyvinyl acetal resin, the polyvinyl acetal resin having a meso/racemo ratio of an acetal ring structure of 10 or higher and a hydroxy group content of 30 to 60 mol %, the polyvinyl acetal resin having a structural unit of formula (2) having a hydroxy group, a structural unit of formula (3) having an acetyl group, a structural unit of formula (4) having an acetal group, and a structural unit of formula (5) having an acetal group including an ionic functional group: ##STR00005## where, in the formula (4), R.sup.2 represents a hydrogen atom or a C1-C20 alkyl group, and in the formula (5), R.sup.3 represents a C1-C20 alkylene group or an aromatic ring, and X represents an ionic functional group.

2. The binder for a power storage device electrode according to claim 1, wherein the polyvinyl acetal resin has a structural unit of formula (1) in an amount of 0.3 mol % or more: ##STR00006## where R.sup.1 represents a hydrogen atom or a C1-C20 alkyl group.

3. The binder for a power storage device electrode according to claim 2, wherein the polyvinyl acetal resin has a structural unit of the formula (1) in an amount of 0.3 to 5 mol %.

4. The binder for a power storage device electrode according to claim 1, comprising a dispersion containing the polyvinyl acetal resin dispersed in an aqueous medium, wherein the polyvinyl acetal resin is in the form of fine particles.

5. The binder for a power storage device electrode according to claim 4, wherein the polyvinyl acetal resin has a volume average particle size of 10 to 500 nm.

6. A composition for a power storage device electrode, comprising the binder for a power storage device electrode according to claim 1 and an active material, the composition containing the polyvinyl acetal resin in an amount of 0.1 to 12 parts by weight relative to 100 parts by weight of the active material.

7. A power storage device electrode comprising the composition for a power storage device electrode according to claim 6.

8. A power storage device comprising a power storage device electrode according to claim 7.

Description

DESCRIPTION OF EMBODIMENTS

(1) The present invention is more specifically described in the following with reference to, but not limited to, examples.

(2) (Preparation of a Dispersion of Polyvinyl Acetal Resin Fine Particles 1)

(3) In a reaction vessel equipped with a thermometer, a stirrer, and a condenser tube, 20 parts by weight of a polyvinyl acetal resin (degree of polymerization: 1,000, degree of butyralization: 64.4 mol %, hydroxy group content: 33.8 mol %, acetyl group content: 1.8 mol %) was dissolved in 80 parts by weight of isopropanol. To the obtained solution were added 1 part by weight of sodium 2-formylbenzene sulfonate and 0.05 parts by weight of 12 M concentrated hydrochloric acid to set the acid concentration of the reaction system to 0.12 M. The reaction thereof was carried out at 70 C. for four hours. Then, 0.5 parts by weight of 12 M concentrated hydrochloric acid was added to set the acid concentration of the reaction system to 0.21 M. The reaction thereof was carried out at 76 C. for four hours, followed by cooling of the reaction solution. Then, a resin was purified by reprecipitation method and finally dried to be collected. The obtained resin was again dissolved in 80 parts by weight of isopropanol, and to the solution was dropwise added 200 parts by weight of water. The solution was stirred under reduced pressure, while the temperature of the solution was maintained at 30 C. The isopropanol and water were thus evaporated. The resulting substance was concentrated to have a solid content of 20% by weight, thereby preparing a dispersion in which polyvinyl acetal resin 1 in the form of fine particles (hereafter, also referred to as polyvinyl acetal resin fine particles 1) was dispersed (amount of polyvinyl acetal resin fine particles 1: 20% by weight).

(4) According to the measurement of the obtained polyvinyl acetal resin by NMR, the degree of butyralization was 63.6 mol %, the hydroxy group content was 32 mol %, the acetyl group content was 1.5 mol %, the ionic functional group content of the polyvinyl acetal resin was 0.2 mmol/g, and the amount of the acetal bond (in the formula (5), R.sup.3 is a benzene ring, X is sodium sulfonate) having an ionic functional group was 2.9 mol %. Further, the acetal ring structure in the obtained polyvinyl acetal resin had a meso/racemo ratio of 13. According to the measurement using a transmission electron microscope, the obtained polyvinyl acetal resin fine particles 1 had a volume average particle size of 100 nm.

(5) (Preparation of a Dispersion of Polyvinyl Acetal Resin Fine Particles 2)

(6) In a reaction vessel equipped with a thermometer, a stirrer, and a condenser tube, 20 parts by weight of a polyvinyl acetal resin (degree of polymerization: 1,000, degree of butyralization: 47.8 mol %, hydroxy group content: 51 mol %, acetyl group content: 1.2 mol %) was dissolved in 80 parts by weight of isopropanol. To the obtained solution were added 1 part by weight of sodium 2-formylbenzene sulfonate and 0.05 parts by weight of 12 M concentrated hydrochloric acid to set the acid concentration of the reaction system to 0.12 M. The reaction thereof was carried out at 70 C. for four hours. Then, 1 part by weight of 12 M concentrated hydrochloric acid was added to set the acid concentration of the reaction system to 0.29 M. The reaction thereof was carried out at 78 C. for four hours, followed by cooling of the reaction solution. Then a resin was purified by reprecipitation method and finally dried to be collected. The obtained resin was again dissolved in 80 parts by weight of isopropanol, and to the solution was dropwise added 200 parts by weight of water. The solution was stirred under reduced pressure, while the temperature of the solution was maintained at 30 C. The isopropanol and water were thus evaporated. The resulting substance was concentrated to have a solid content of 20% by weight, thereby preparing a dispersion in which polyvinyl acetal resin 2 in the form of fine particles (hereafter, also referred to as polyvinyl acetal resin fine particles 2) was dispersed (amount of polyvinyl acetal resin fine particles 2: 20% by weight).

(7) According to the measurement of the obtained polyvinyl acetal resin by NMR, the degree of butyralization was 47.1 mol %, the hydroxy group content was 48.9 mol %, the acetyl group content was 1 mol %, the ionic functional group content of the polyvinyl acetal resin was 0.2 mmol/g, and the amount of the acetal bond (in the formula (5), R.sup.3 is a benzene ring, X is sodium sulfonate) having an ionic functional group was 3 mol %. Further, the acetal ring structure in the obtained polyvinyl acetal resin had a meso/racemo ratio of 17.5. According to the measurement using a transmission electron microscope, the obtained polyvinyl acetal resin fine particles 2 had a volume average particle size of 90 nm.

(8) (Preparation of a Dispersion of Polyvinyl Acetal Resin Fine Particles 3)

(9) In a reaction vessel equipped with a thermometer, a stirrer, and a condenser tube, 20 parts by weight of a polyvinyl acetal resin (degree of polymerization: 1,000, degree of butyralization: 70 mol %, hydroxy group content: 28.2 mol %, acetyl group content: 1.8 mol %) was dissolved in 80 parts by weight of isopropanol. To the obtained solution were added 1 part by weight of sodium 2-formylbenzene sulfonate and 0.05 parts by weight of 12 M concentrated hydrochloric acid to set the acid concentration of the reaction system to 0.12 M. The reaction thereof was carried out at 70 C. for four hours. Then, 0.1 parts by weight of 12 M concentrated hydrochloric acid was added to set the acid concentration of the reaction system to 0.14 M. The reaction thereof was carried out at 72 C. for one hour, followed by cooling of the reaction solution. Then, a resin was purified by reprecipitation method and finally dried to be collected. The obtained resin was again dissolved in 80 parts by weight of isopropanol, and to the solution was dropwise added 200 parts by weight of water. The solution was stirred under reduced pressure, while the temperature of the solution was maintained at 30 C. The isopropanol and water were thus evaporated. The resulting substance was concentrated to have a solid content of 20% by weight, thereby preparing a dispersion in which polyvinyl acetal resin 3 in the form of fine particles (hereafter, also referred to as polyvinyl acetal resin fine particles 3) was dispersed (amount of polyvinyl acetal resin fine particles 3: 20% by weight).

(10) According to the measurement of the obtained polyvinyl acetal resin by NMR, the degree of butyralization was 69.5 mol %, the hydroxy group content was 26.2 mol %, the acetyl group content was 1.5 mol %, the ionic functional group content of the polyvinyl acetal resin was 0.2 mmol/g, and the amount of the acetal bond (in the formula (5), R.sup.3 is a benzene ring, X is sodium sulfonate) having an ionic functional group was 2.8 mol %. Further, the acetal ring structure in the obtained polyvinyl acetal resin had a meso/racemo ratio of 8.9. According to the measurement using a transmission electron microscope, the obtained polyvinyl acetal resin fine particles 3 had a volume average particle size of 110 nm.

(11) (Preparation of a Dispersion of Polyvinyl Acetal Resin Fine Particles 4)

(12) In a reaction vessel equipped with a thermometer, a stirrer, and a condenser tube, 20 parts by weight of a polyvinyl acetal resin (degree of polymerization: 1,000, degree of butyralization: 58.6 mol %, hydroxy group content: 40 mol %, acetyl group content: 1.4 mol %) was dissolved in 80 parts by weight of isopropanol. To the obtained solution were added 1 part by weight of sodium 2-formylbenzene sulfonate and 0.05 parts by weight of 12 M concentrated hydrochloric acid to set the acid concentration of the reaction system to 0.12 M. The reaction thereof was carried out at 70 C. for four hours. Then, 1 part by weight of 12 M concentrated hydrochloric acid was added to set the acid concentration of the reaction system to 0.29 M. The reaction thereof was carried out at 80 C. for seven hours, followed by cooling of the reaction solution. Then, a resin was purified by reprecipitation method and finally dried to be collected. The obtained resin was again dissolved in 80 parts by weight of isopropanol, and to the solution was dropwise added 200 parts by weight of water. The solution was stirred under reduced pressure, while the temperature of the solution was maintained at 30 C. The isopropanol and water were thus evaporated. The resulting substance was concentrated to have a solid content of 20% by weight, thereby preparing a dispersion in which polyvinyl acetal resin 4 in the form of fine particles (hereafter, also referred to as polyvinyl acetal resin fine particles 4) was dispersed (amount of polyvinyl acetal resin fine particles 4: 20% by weight).

(13) According to the measurement of the obtained polyvinyl acetal resin by NMR, the degree of butyralization was 58.3 mol %, the hydroxy group content was 37.6 mol %, the acetyl group content was 1.2 mol %, the ionic functional group content of the polyvinyl acetal resin was 0.2 mmol/g, and the amount of the acetal bond (in the formula (5), R.sup.3 is a benzene ring, X is sodium sulfonate) having an ionic functional group was 2.9 mol %. Further, the acetal ring structure in the obtained polyvinyl acetal resin had a meso/racemo ratio of 26.4. According to the measurement using a transmission electron microscope, the obtained polyvinyl acetal resin fine particles 4 had a volume average particle size of 100 nm.

(14) (Preparation of a Dispersion of Polyvinyl Acetal Resin Fine Particles 5)

(15) In a reaction vessel equipped with a thermometer, a stirrer, and a condenser tube, 20 parts by weight of a polyvinyl acetal resin (degree of polymerization: 1,000, degree of butyralization: 47.8 mol %, hydroxy group content: 51 mol %, acetyl group content: 1.2 mol %) was dissolved in 80 parts by weight of isopropanol. To the obtained solution were added 0.3 parts by weight of sodium 2-formylbenzene sulfonate and 0.05 parts by weight of 12 M concentrated hydrochloric acid to set the acid concentration of the reaction system to 0.12 M. The reaction thereof was carried out at 70 C. for four hours. Then, 1 part by weight of 12 M concentrated hydrochloric acid was added to set the acid concentration of the reaction system to 0.29 M. The reaction thereof was carried out at 78 C. for four hours, followed by cooling of the reaction solution. Then, a resin was purified by reprecipitation method and finally dried to be collected. The obtained resin was again dissolved in 80 parts by weight of isopropanol, and to the solution was dropwise added 200 parts by weight of water. The solution was stirred under reduced pressure, while the temperature of the solution was maintained at 30 C. The isopropanol and water were thus evaporated. The resulting substance was concentrated to have a solid content of 20% by weight, thereby preparing a dispersion in which polyvinyl acetal resin 5 in the form of fine particles (hereafter, also referred to as polyvinyl acetal resin fine particles 5) was dispersed (amount of polyvinyl acetal resin fine particles 5: 20% by weight).

(16) According to the measurement of the obtained polyvinyl acetal resin by NMR, the degree of butyralization was 47.4 mol %, the hydroxy group content was 50.8 mol %, the acetyl group content was 1 mol %, the ionic functional group content of the polyvinyl acetal resin was 0.06 mmol/g, and the amount of the acetal bond (in the formula (5), R.sup.3 is a benzene ring, X is sodium sulfonate) having an ionic functional group was 0.8 mol %. Further, the acetal ring structure in the obtained polyvinyl acetal resin had a meso/racemo ratio of 17.5. According to the measurement using a transmission electron microscope, the obtained polyvinyl acetal resin fine particles 5 had a volume average particle size of 620 nm.

(17) (Preparation of a Dispersion of Polyvinyl Acetal Resin Fine Particles 6)

(18) In a reaction vessel equipped with a thermometer, a stirrer, and a condenser tube, 20 parts by weight of a polyvinyl acetal resin (degree of polymerization: 1,000, degree of butyralization: 47.8 mol %, hydroxy group content: 51 mol %, acetyl group content: 1.2 mol %) was dissolved in 80 parts by weight of isopropanol. To the obtained solution were added 0.4 parts by weight of sodium 2-formylbenzene sulfonate and 0.05 parts by weight of 12 M concentrated hydrochloric acid to set the acid concentration of the reaction system to 0.12 M. The reaction thereof was carried out at 70 C. for four hours. Then, 1 part by weight of 12 M concentrated hydrochloric acid was added to set the acid concentration of the reaction system to 0.29 M. The reaction thereof was carried out at 78 C. for four hours, followed by cooling of the reaction solution. Then, a resin was purified by reprecipitation method and finally dried to be collected. The obtained resin was again dissolved in 80 parts by weight of isopropanol, and to the solution was dropwise added 200 parts by weight of water. The solution was stirred under reduced pressure, while the temperature of the solution was maintained at 30 C. The isopropanol and water were thus evaporated. The resulting substance was concentrated to have a solid content of 20% by weight, thereby preparing a dispersion in which polyvinyl acetal resin 6 in the form of fine particles (hereafter, also referred to as polyvinyl acetal resin fine particles 6) was dispersed (amount of polyvinyl acetal resin fine particles 6: 20% by weight).

(19) According to the measurement of the obtained polyvinyl acetal resin by NMR, the degree of butyralization was 47.1 mol %, the hydroxy group content was 50.7 mol %, the acetyl group content was 1 mol %, the ionic functional group content of the polyvinyl acetal resin was 0.08 mmol/g, and the amount of the acetal bond (in the formula (5), R.sup.3 is a benzene ring, X is sodium sulfonate) having an ionic functional group was 1.2 mol %. Further, the acetal ring structure in the obtained polyvinyl acetal resin had a meso/racemo ratio of 17.5. According to the measurement using a transmission electron microscope, the obtained polyvinyl acetal resin fine particles 6 had a volume average particle size of 450 nm.

(20) (Preparation of a Dispersion of Polyvinyl Acetal Resin Fine Particles 7)

(21) In a reaction vessel equipped with a thermometer, a stirrer, and a condenser tube, 20 parts by weight of a polyvinyl acetal resin (degree of polymerization: 1,000, degree of butyralization: 47.8 mol %, hydroxy group content: 51 mol %, acetyl group content: 1.2 mol %) was dissolved in 80 parts by weight of isopropanol. To the obtained solution were added 6 parts by weight of disodium 4-formylbenzene-1,3-disulfonate and 0.05 parts by weight of 12 M concentrated hydrochloric acid to set the acid concentration of the reaction system to 0.12 M. The reaction thereof was carried out at 70 C. for four hours. Then, 1 part by weight of 12 M concentrated hydrochloric acid was added to set the acid concentration of the reaction system to 0.29 M. The reaction thereof was carried out at 80 C. for five hours, followed by cooling of the reaction solution. Then, a resin was purified by reprecipitation method and finally dried to be collected. The obtained resin was again dissolved in 80 parts by weight of isopropanol, and to the solution was dropwise added 200 parts by weight of water. The solution was stirred under reduced pressure, while the temperature of the solution was maintained at 30 C. The isopropanol and water were thus evaporated. The resulting substance was concentrated to have a solid content of 20% by weight, thereby preparing a dispersion in which polyvinyl acetal resin 7 in the form of fine particles (hereafter, also referred to as polyvinyl acetal resin fine particles 7) was dispersed (amount of polyvinyl acetal resin fine particles 7: 20% by weight).

(22) According to the measurement of the obtained polyvinyl acetal resin by NMR, the degree of butyralization was 47.1 mol %, the hydroxy group content was 37.9 mol %, the acetyl group content was 1 mol %, the ionic functional group content of the polyvinyl acetal resin was 1.8 mmol/g, and the amount of the acetal bond (in the formula (5), R.sup.3 is a benzene ring, X is sodium sulfonate) having an ionic functional group was 14 mol %. Further, the acetal ring structure in the obtained polyvinyl acetal resin had a meso/racemo ratio of 17.5. According to the measurement using a transmission electron microscope, the obtained polyvinyl acetal resin fine particles 7 had a volume average particle size of 9 nm.

(23) (Preparation of a Dispersion of Polyvinyl Acetal Resin Fine Particles 8)

(24) In a reaction vessel equipped with a thermometer, a stirrer, and a condenser tube, 20 parts by weight of a polyvinyl acetal resin (degree of polymerization: 1,000, degree of butyralization: 47.8 mol %, hydroxy group content: 51 mol %, acetyl group content: 1.2 mol %) was dissolved in 80 parts by weight of isopropanol. To the obtained solution were added 0.6 parts by weight of sodium 2-formylbenzene sulfonate and 0.05 parts by weight of 12 M concentrated hydrochloric acid to set the acid concentration of the reaction system to 0.12 M. The reaction thereof was carried out at 70 C. for four hours. Then, 1 part by weight of 12 M concentrated hydrochloric acid was added to set the acid concentration of the reaction system to 0.29 M. The reaction thereof was carried out at 78 C. for four hours, followed by cooling of the reaction solution. Then, a resin was purified by reprecipitation method and finally dried to be collected. The obtained resin was again dissolved in 80 parts by weight of isopropanol, and to the solution was dropwise added 200 parts by weight of water. The solution was stirred under reduced pressure, while the temperature of the solution was maintained at 30 C. The isopropanol and water were thus evaporated. The resulting substance was concentrated to have a solid content of 20% by weight, thereby preparing a dispersion in which polyvinyl acetal resin 8 in the form of fine particles (hereafter, also referred to as polyvinyl acetal resin fine particles 8) was dispersed (amount of polyvinyl acetal resin fine particles 8: 20% by weight).

(25) According to the measurement of the obtained polyvinyl acetal resin by NMR, the degree of butyralization was 47.1 mol %, the hydroxy group content was 50.1 mol %, the acetyl group content was 1 mol %, the ionic functional group content of the polyvinyl acetal resin was 0.1 mmol/g, and the amount of the acetal bond (in the formula (5), R.sup.3 is a benzene ring, X is sodium sulfonate) having an ionic functional group was 1.8 mol %. Further, the acetal ring structure in the obtained polyvinyl acetal resin had a meso/racemo ratio of 17.5. According to the measurement using a transmission electron microscope, the obtained polyvinyl acetal resin fine particles 8 had a volume average particle size of 240 nm.

(26) (Preparation of a Dispersion of Polyvinyl Acetal Resin Fine Particles 9)

(27) In a reaction vessel equipped with a thermometer, a stirrer, and a condenser tube, 20 parts by weight of a polyvinyl acetal resin (degree of polymerization: 1,000, degree of butyralization: 46 mol %, hydroxy group content: 51.9 mol %, acetyl group content: 2.1 mol %) was dissolved in 80 parts by weight of isopropanol. To the obtained solution were added 2 parts by weight of terephthalaldehydic acid and 0.05 parts by weight of 12 M concentrated hydrochloric acid to set the acid concentration of the reaction system to 0.12 M. The reaction thereof was carried out at 70 C. for four hours. Then, 1 part by weight of 12 M concentrated hydrochloric acid was added to set the acid concentration of the reaction system to 0.29 M. The reaction thereof was carried out at 79 C. for four hours, followed by cooling of the reaction solution. Then, a resin was purified by reprecipitation method and finally dried to be collected. The obtained resin was again dissolved in 80 parts by weight of isopropanol, and to the solution was dropwise added 200 parts by weight of water. The solution was stirred under reduced pressure, while the temperature of the solution was maintained at 30 C. The isopropanol and water were thus evaporated. The resulting substance was concentrated to have a solid content of 20% by weight, thereby preparing a dispersion in which polyvinyl acetal resin 9 in the form of fine particles (hereafter, also referred to as polyvinyl acetal resin fine particles 9) was dispersed (amount of polyvinyl acetal resin fine particles 9: 20% by weight).

(28) According to the measurement of the obtained polyvinyl acetal resin by NMR, the degree of butyralization was 45.2 mol %, the hydroxy group content was 42 mol %, the acetyl group content was 1.8 mol %, the ionic functional group content of the polyvinyl acetal resin was 1 mmol/g, and the amount of the acetal bond (in the formula (5), R.sup.3 is a benzene ring, X is a carboxy group) having an ionic functional group was 11 mol %. Further, the acetal ring structure in the obtained polyvinyl acetal resin had a meso/racemo ratio of 15.2. According to the measurement using a transmission electron microscope, the obtained polyvinyl acetal resin fine particles 9 had a volume average particle size of 450 nm.

(29) (Preparation of a Dispersion of Polyvinyl Acetal Resin Fine Particles 10)

(30) In a reaction vessel equipped with a thermometer, a stirrer, and a condenser tube, 20 parts by weight of a polyvinyl acetal resin (degree of polymerization: 1,000, degree of butyralization: 35.5 mol %, hydroxy group content: 63.3 mol %, acetyl group content: 1.2 mol %) was dissolved in 80 parts by weight of isopropanol. To the obtained solution were added 2 parts by weight of sodium 2-formylbenzene sulfonate and 0.05 parts by weight of 12 M concentrated hydrochloric acid to set the acid concentration of the reaction system to 0.12 M. The reaction thereof was carried out at 70 C. for four hours. Then, 1 part by weight of 12 M concentrated hydrochloric acid was added to set the acid concentration of the reaction system to 0.29 M. The reaction thereof was carried out at 73 C. for one hour, followed by cooling of the reaction solution. Then, a resin was purified by reprecipitation method and finally dried to be collected. The obtained resin was again dissolved in 80 parts by weight of isopropanol, and to the solution was dropwise added 200 parts by weight of water. The solution was stirred under reduced pressure, while the temperature of the solution was maintained at 30 C. The isopropanol and water were thus evaporated. The resulting substance was concentrated to have a solid content of 20% by weight, thereby preparing a dispersion in which polyvinyl acetal resin 10 in the form of fine particles (hereafter, also referred to as polyvinyl acetal resin fine particles 10) was dispersed (amount of polyvinyl acetal resin fine particles 10: 20% by weight).

(31) According to the measurement of the obtained polyvinyl acetal resin by NMR, the degree of butyralization was 34 mol %, the hydroxy group content was 62 mol %, the acetyl group content was 1 mol %, the ionic functional group content of the polyvinyl acetal resin was 0.2 mmol/g, and the amount of the acetal bond (in the formula (5), R.sup.3 is a benzene ring, X is sodium sulfonate) having an ionic functional group was 3 mol %. Further, the acetal ring structure in the obtained polyvinyl acetal resin had a meso/racemo ratio of 9.1. According to the measurement using a transmission electron microscope, the obtained polyvinyl acetal resin fine particles 10 had a volume average particle size of 100 nm.

(32) (Preparation of a Dispersion of Polyvinyl Acetal Resin Fine Particles 11)

(33) In a reaction vessel equipped with a thermometer, a stirrer, and a condenser tube, 20 parts by weight of a polyvinyl acetal resin (degree of polymerization: 1,100, degree of butyralization: 70.2 mol %, hydroxy group content: 27.6 mol %, acetyl group content: 2.2 mol %) was dissolved in 80 parts by weight of isopropanol. To the obtained solution were added 2.3 parts by weight of sodium 2-formylbenzene sulfonate and 0.05 parts by weight of 12 M concentrated hydrochloric acid to set the acid concentration of the reaction system to 0.12 M. The reaction thereof was carried out at 70 C. for four hours. Then, 0.3 parts by weight of 12 M concentrated hydrochloric acid was added to set the acid concentration of the reaction system to 0.14 M. The reaction thereof was carried out at 72 C. for one hour, followed by cooling of the reaction solution. Then, a resin was purified by reprecipitation method and finally dried to be collected. The obtained resin was again dissolved in 80 parts by weight of isopropanol, and to the solution was dropwise added 200 parts by weight of water. The solution was stirred under reduced pressure, while the temperature of the solution was maintained at 30 C. The isopropanol and water were thus evaporated. The resulting substance was concentrated to have a solid content of 20% by weight, thereby preparing a dispersion in which polyvinyl acetal resin 11 in the form of fine particles (hereafter, also referred to as polyvinyl acetal resin fine particles 11) was dispersed (amount of polyvinyl acetal resin fine particles 11: 20% by weight).

(34) According to the measurement of the obtained polyvinyl acetal resin by NMR, the degree of butyralization was 68.8 mol %, the hydroxy group content was 25 mol %, the acetyl group content was 2 mol %, the ionic functional group content of the polyvinyl acetal resin was 0.2 mmol/g, and the amount of the acetal bond (in the formula (5), R.sup.3 is a benzene ring, X is sodium sulfonate) having an ionic functional group was 4.2 mol %. Further, the acetal ring structure in the obtained polyvinyl acetal resin had a meso/racemo ratio of 10.4. According to the measurement using a transmission electron microscope, the obtained polyvinyl acetal resin fine particles 11 had a volume average particle size of 90 nm.

(35) (Preparation of a Dispersion of Polyvinyl Acetal Resin Fine Particles 12)

(36) In a reaction vessel equipped with a thermometer, a stirrer, and a condenser tube, 20 parts by weight of a polyvinyl acetal resin (degree of polymerization: 1,100, degree of butyralization: 33.1 mol %, hydroxy group content: 65.6 mol %, acetyl group content: 1.3 mol %) was dissolved in 80 parts by weight of isopropanol. To the obtained solution were added 2 parts by weight of sodium 2-formylbenzene sulfonate and 0.05 parts by weight of 12 M concentrated hydrochloric acid to set the acid concentration of the reaction system to 0.12 M. The reaction thereof was carried out at 70 C. for four hours. Then, 0.6 parts by weight of 12 M concentrated hydrochloric acid was added to set the acid concentration of the reaction system to 0.21 M. The reaction thereof was carried out at 73 C. for one hour, followed by cooling of the reaction solution. Then, a resin was purified by reprecipitation method and finally dried to be collected. The obtained resin was again dissolved in 80 parts by weight of isopropanol, and to the solution was dropwise added 200 parts by weight of water. The solution was stirred under reduced pressure, while the temperature of the solution was maintained at 30 C. The isopropanol and water were thus evaporated. The resulting substance was concentrated to have a solid content of 20% by weight, thereby preparing a dispersion in which polyvinyl acetal resin 12 in the form of fine particles (hereafter, also referred to as polyvinyl acetal resin fine particles 12) was dispersed (amount of polyvinyl acetal resin fine particles 12: 20% by weight).

(37) According to the measurement of the obtained polyvinyl acetal resin by NMR, the degree of butyralization was 32.5 mol %, the hydroxy group content was 65 mol %, the acetyl group content was 0.8 mol %, the ionic functional group content of the polyvinyl acetal resin was 0.2 mmol/g, and the amount of the acetal bond (in the formula (5), R.sup.3 is a benzene ring, X is sodium sulfonate) having an ionic functional group was 1.7 mol %. Further, the acetal ring structure in the obtained polyvinyl acetal resin had a meso/racemo ratio of 11.6. According to the measurement using a transmission electron microscope, the obtained polyvinyl acetal resin fine particles 12 had a volume average particle size of 90 nm.

(38) (Preparation of Polyvinyl Acetal Resin 13)

(39) In a reaction vessel equipped with a thermometer, a stirrer, and a condenser tube, 20 parts by weight of a polyvinyl acetal resin (degree of polymerization: 1,000, degree of butyralization: 47.8 mol %, hydroxy group content: 51 mol %, acetyl group content: 1.2 mol %) was dissolved in 80 parts by weight of isopropanol. To the obtained solution were added 1 part by weight of sodium 2-formylbenzene sulfonate and 0.05 parts by weight of 12 M concentrated hydrochloric acid to set the acid concentration of the reaction system to 0.12 M. The reaction thereof was carried out at 70 C. for four hours. Then, 0.3 parts by weight of 12 M concentrated hydrochloric acid was added to set the acid concentration of the reaction system to 0.17 M. The reaction thereof was carried out at 74 C. for three hours, followed by cooling of the reaction solution. Then, a resin was purified by reprecipitation method and finally dried to prepare polyvinyl acetal resin 13.

(40) According to the measurement of the obtained polyvinyl acetal resin by NMR, the degree of butyralization was 47.1 mol %, the hydroxy group content was 48.9 mol %, the acetyl group content was 1 mol %, the ionic functional group content of the polyvinyl acetal resin was 0.2 mmol/g, the amount of the acetal bond (in the formula (5), R.sup.3 is a benzene ring, X is sodium sulfonate) having an ionic functional group was 3 mol %. Further, the acetal ring structure in the obtained polyvinyl acetal resin had a meso/racemo ratio of 10.3.

(41) (Preparation of Polyvinyl Acetal Resin 14)

(42) In a reaction vessel equipped with a thermometer, a stirrer, and a condenser tube, 20 parts by weight of a polyvinyl acetal resin (degree of polymerization: 1,000, degree of butyralization: 48 mol %, hydroxy group content: 50.7 mol %, acetyl group content: 1.3 mol %) was dissolved in 80 parts by weight of isopropanol. To the obtained solution was added 0.1 parts by weight of 12 M concentrated hydrochloric acid to set the acid concentration of the reaction system to 0.14 M. The reaction thereof was carried out at 73 C. for one hour, followed by cooling of the reaction solution. Then, a resin was purified by reprecipitation method and finally dried to prepare polyvinyl acetal resin 14.

(43) According to the measurement of the obtained polyvinyl acetal resin by NMR, the degree of butyralization was 47.8 mol %, the hydroxy group content was 51 mol %, the acetyl group content was 1.2 mol %, the ionic functional group content of the polyvinyl acetal resin was 0 mmol/g, and the amount of the acetal bond having an ionic functional group was 0 mol %. Further, the acetal ring structure in the obtained polyvinyl acetal resin had a meso/racemo ratio of 9.4.

(44) (Preparation of a Dispersion of Polyvinyl Acetal Resin Fine Particles 15)

(45) In a reaction vessel equipped with a thermometer, a stirrer, and a condenser tube, 20 parts by weight of a polyvinyl acetal resin (degree of polymerization: 1,100, degree of butyralization: 52 mol %, hydroxy group content: 47.8 mol %, acetyl group content: 0.2 mol %) was dissolved in 80 parts by weight of isopropanol. To the obtained solution were added 1 part by weight of sodium 2-formylbenzene sulfonate and 0.05 parts by weight of 12 M concentrated hydrochloric acid to set the acid concentration of the reaction system to 0.12 M. The reaction thereof was carried out at 70 C. for four hours. Then, 0.2 parts by weight of butyraldehyde and 1 part by weight of 12 M concentrated hydrochloric acid were added to set the acid concentration of the reaction system to 0.15 M. The reaction thereof was carried out at 82 C. for six hours, followed by cooling of the reaction solution. Then, a resin was purified by reprecipitation method and finally dried to be collected. The obtained resin was again dissolved in 80 parts by weight of isopropanol, and to the solution was dropwise added 200 parts by weight of water. The solution was stirred under reduced pressure, while the temperature of the solution was maintained at 30 C. The isopropanol and water were thus evaporated. The resulting substance was concentrated to have a solid content of 20% by weight, thereby preparing a dispersion in which polyvinyl acetal resin 15 in the form of fine particles (hereafter, also referred to as polyvinyl acetal resin fine particles 15) was dispersed (amount of polyvinyl acetal resin fine particles 15: 20% by weight).

(46) According to the measurement of the obtained polyvinyl acetal resin by NMR, the amount of the structural unit of the formula (1) (in the formula (1), R.sup.1 is a propyl group) was 0.3 mol %, the degree of butyralization was 51.7 mol %, the hydroxy group content was 45 mol %, the acetyl group content was 0.2 mol %, the ionic functional group content of the polyvinyl acetal resin was 0.2 mmol/g, and the amount of the acetal bond (in the formula (5), R.sup.3 is a benzene ring, X is sodium sulfonate) having an ionic functional group was 2.8 mol %. Further, the acetal ring structure in the obtained polyvinyl acetal resin had a meso/racemo ratio of 12. According to the measurement using a transmission electron microscope, the obtained polyvinyl acetal resin fine particles 15 had a volume average particle size of 90 nm.

(47) (Preparation of a Dispersion of Polyvinyl Acetal Resin Fine Particles 16)

(48) In a reaction vessel equipped with a thermometer, a stirrer, and a condenser tube, 20 parts by weight of a polyvinyl acetal resin (degree of polymerization: 1,100, degree of butyralization: 45.6 mol %, hydroxy group content: 52.1 mol %, acetyl group content: 2.3 mol %) was dissolved in 80 parts by weight of isopropanol. To the obtained solution were added 0.5 parts by weight of sodium 2-formylbenzene sulfonate and 0.05 parts by weight of 12 M concentrated hydrochloric acid to set the acid concentration of the reaction system to 0.12 M. The reaction thereof was carried out at 70 C. for four hours. Then, 3 parts by weight of butyraldehyde and 0.05 parts by weight of 12 M concentrated hydrochloric acid were added to set the acid concentration of the reaction system to 0.12 M. The reaction thereof was carried out at 70 C. for 0.3 hours, followed by cooling of the reaction solution. Then, a resin was purified by reprecipitation method and finally dried to be collected. The obtained resin was again dissolved in 80 parts by weight of isopropanol, and to the solution was dropwise added 200 parts by weight of water. The solution was stirred under reduced pressure, while the temperature of the solution was maintained at 30 C. The isopropanol and water were thus evaporated. The resulting substance was concentrated to have a solid content of 20% by weight, thereby preparing a dispersion in which polyvinyl acetal resin 16 in the form of fine particles (hereafter, also referred to as polyvinyl acetal resin fine particles 16) was dispersed (amount of polyvinyl acetal resin fine particles 16: 20% by weight).

(49) According to the measurement of the obtained polyvinyl acetal resin by NMR, the amount of the structural unit of the formula (1) (in the formula (1), R.sup.1 is a propyl group) was 5 mol %, the degree of butyralization was 46.4 mol %, the hydroxy group content was 45 mol %, the acetyl group content was 2 mol %, the ionic functional group content of the polyvinyl acetal resin was 0.1 mmol/g, and the amount of the acetal bond (in the formula (5), R.sup.3 is a benzene ring, X is sodium sulfonate) having an ionic functional group was 1.6 mol %. Further, the acetal ring structure in the obtained polyvinyl acetal resin had a meso/racemo ratio of 16.7. According to the measurement using a transmission electron microscope, the obtained polyvinyl acetal resin fine particles 16 had a volume average particle size of 300 nm.

(50) (Preparation of a Dispersion of Polyvinyl Acetal Resin Fine Particles 17)

(51) In a reaction vessel equipped with a thermometer, a stirrer, and a condenser tube, 20 parts by weight of a polyvinyl acetal resin (degree of polymerization: 1,100, degree of butyralization: 46.8 mol %, hydroxy group content: 51.8 mol %, acetyl group content: 1.4 mol %) was dissolved in 80 parts by weight of isopropanol. To the obtained solution were added 2 parts by weight of disodium 4-formylbenzene-1,3-disulfonate and 0.05 parts by weight of 12 M concentrated hydrochloric acid to set the acid concentration of the reaction system to 0.12 M. The reaction thereof was carried out at 70 C. for four hours. Then, 1 part by weight of butyraldehyde and 0.5 parts by weight of 12 M concentrated hydrochloric acid were added to set the acid concentration of the reaction system to 0.21 M. The reaction thereof was carried out at 75 C. for four hours, followed by cooling of the reaction solution. Then, a resin was purified by reprecipitation method and finally dried to be collected. The obtained resin was again dissolved in 80 parts by weight of isopropanol, and to the solution was dropwise added 200 parts by weight of water. The solution was stirred under reduced pressure, while the temperature of the solution was maintained at 30 C. The isopropanol and water were thus evaporated. The resulting substance was concentrated to have a solid content of 20% by weight, thereby preparing a dispersion in which polyvinyl acetal resin 17 in the form of fine particles (hereafter, also referred to as polyvinyl acetal resin fine particles 17) was dispersed (amount of polyvinyl acetal resin fine particles 17: 20% by weight).

(52) According to the measurement of the obtained polyvinyl acetal resin by NMR, the amount of the structural unit of the formula (1) (in the formula (1), R.sup.1 is a propyl group) was 2 mol %, the degree of butyralization was 47.4 mol %, the hydroxy group content was 45 mol %, the acetyl group content was 1.1 mol %, the ionic functional group content of the polyvinyl acetal resin was 0.6 mmol/g, and the amount of the acetal bond (in the formula (5), R.sup.3 is a benzene ring, X is sodium sulfonate) having an ionic functional group was 4.5 mol %. Further, the acetal ring structure in the obtained polyvinyl acetal resin had a meso/racemo ratio of 11.5. According to the measurement using a transmission electron microscope, the obtained polyvinyl acetal resin fine particles 17 had a volume average particle size of 30 nm.

(53) (Preparation of a Dispersion of Polyvinyl Acetal Resin Fine Particles 18)

(54) In a reaction vessel equipped with a thermometer, a stirrer, and a condenser tube, 20 parts by weight of a polyvinyl acetal resin (degree of polymerization: 800, degree of butyralization: 52 mol %, hydroxy group content: 47.9 mol %, acetyl group content: 0.1 mol %) was dissolved in 80 parts by weight of isopropanol. To the obtained solution were added 2 parts by weight of terephthalaldehydic acid and 0.05 parts by weight of 12 M concentrated hydrochloric acid to set the acid concentration of the reaction system to 0.12 M. The reaction thereof was carried out at 70 C. for four hours. Then, 0.1 parts by weight of butyraldehyde and 1 part by weight of 12 M concentrated hydrochloric acid were added to set the acid concentration of the reaction system to 0.29 M. The reaction thereof was carried out at 82 C. for seven hours, followed by cooling of the reaction solution. Then, a resin was purified by reprecipitation method and finally dried to be collected. The obtained resin was again dissolved in 80 parts by weight of isopropanol, and to the solution was dropwise added 200 parts by weight of water. The solution was stirred under reduced pressure, while the temperature of the solution was maintained at 30 C. The isopropanol and water were thus evaporated. The resulting substance was concentrated to have a solid content of 20% by weight, thereby preparing a dispersion in which polyvinyl acetal resin 18 in the form of fine particles (hereafter, also referred to as polyvinyl acetal resin fine particles 18) was dispersed (amount of polyvinyl acetal resin fine particles 18: 20% by weight).

(55) According to the measurement of the obtained polyvinyl acetal resin by NMR, the amount of the structural unit of the formula (1) (in the formula (1), R.sup.1 is a propyl group) was 0.2 mol %, the degree of butyralization was 51.7 mol %, the hydroxy group content was 36 mol %, the acetyl group content was 0.1 mol %, the ionic functional group content of the polyvinyl acetal resin was 1 mmol/g, the amount of the acetal bond (in the formula (5), R.sup.3 is a benzene ring, X is a carboxy group) was 12 mol %. Further, the acetal ring structure in the obtained polyvinyl acetal resin had a meso/racemo ratio of 9.4. According to the measurement using a transmission electron microscope, the obtained polyvinyl acetal resin fine particles 18 had a volume average particle size of 450 nm.

(56) (Preparation of a Dispersion of Polyvinyl Acetal Resin Fine Particles 19)

(57) In a reaction vessel equipped with a thermometer, a stirrer, and a condenser tube, 20 parts by weight of a polyvinyl acetal resin (degree of polymerization: 1,700, degree of butyralization: 37 mol %, hydroxy group content: 55 mol %, acetyl group content: 8 mol %) was dissolved in 80 parts by weight of isopropanol. To the obtained solution were added 1 part by weight of sodium 2-formylbenzene sulfonate and 0.05 parts by weight of 12 M concentrated hydrochloric acid to set the acid concentration of the reaction system to 0.12 M. The reaction thereof was carried out at 70 C. for four hours. Then, 3.5 parts by weight of butyraldehyde and 0.05 parts by weight of 12 M concentrated hydrochloric acid were added to set the acid concentration of the reaction system to 0.12 M. The reaction thereof was carried out at 70 C. for 0.3 hours, followed by cooling of the reaction solution. Then, a resin was purified by reprecipitation method and finally dried to be collected. The obtained resin was again dissolved in 80 parts by weight of isopropanol, and to the solution was dropwise added 200 parts by weight of water. The solution was stirred under reduced pressure, while the temperature of the solution was maintained at 30 C. The isopropanol and water were thus evaporated. The resulting substance was concentrated to have a solid content of 20% by weight, thereby preparing a dispersion in which polyvinyl acetal resin 19 in the form of fine particles (hereafter, also referred to as polyvinyl acetal resin fine particles 19) was dispersed (amount of polyvinyl acetal resin fine particles 19: 20% by weight).

(58) According to the measurement of the obtained polyvinyl acetal resin by NMR, the amount of the structural unit of the formula (1) (in the formula (1), R.sup.1 is a propyl group) was 7 mol %, the degree of butyralization was 38 mol %, the hydroxy group content was 45 mol %, the acetyl group content was 7 mol %, the ionic functional group content of the polyvinyl acetal resin was 0.2 mmol/g, and the amount of the acetal bond (in the formula (5), R.sup.3 is a benzene ring and X is sodium sulfonate) having an ionic functional group was 3 mol %. Further, the acetal ring structure in the obtained polyvinyl acetal resin had a meso/racemo ratio of 17. According to the measurement using a transmission electron microscope, the obtained polyvinyl acetal resin fine particles 19 had a volume average particle size of 90 nm.

(59) (Preparation of a Dispersion of Polyvinyl Acetal Resin Fine Particles 20)

(60) In a reaction vessel equipped with a thermometer, a stirrer, and a condenser tube, 20 parts by weight of a polyvinyl acetal resin (degree of polymerization: 1,700, degree of butyralization: 66.6 mol %, hydroxy group content: 31 mol %, acetyl group content: 2.4 mol %) was dissolved in 80 parts by weight of isopropanol. To the obtained solution were added 1 part by weight of sodium 2-formylbenzene sulfonate and 0.05 parts by weight of 12 M concentrated hydrochloric acid to set the acid concentration of the reaction system to 0.12 M. The reaction thereof was carried out at 70 C. for four hours. Then, 0.9 parts by weight of butyraldehyde and 0.5 parts by weight of 12 M concentrated hydrochloric acid were added to set the acid concentration of the reaction system to 0.21 M. The reaction thereof was carried out at 75 C. for four hours, followed by cooling of the reaction solution. Then, a resin was purified by reprecipitation method and finally dried to be collected. The obtained resin was again dissolved in 80 parts by weight of isopropanol, and to the solution was dropwise added 200 parts by weight of water. The solution was stirred under reduced pressure, while the temperature of the solution was maintained at 30 C. The isopropanol and water were thus evaporated. The resulting substance was concentrated to have a solid content of 20% by weight, thereby preparing a dispersion in which polyvinyl acetal resin 20 in the form of fine particles (hereafter, also referred to as polyvinyl acetal resin fine particles 20) was dispersed (amount of polyvinyl acetal resin fine particles 20: 20% by weight).

(61) According to the measurement of the obtained polyvinyl acetal resin by NMR, the amount of the structural unit of the formula (1) (in the formula (1), R.sup.1 is a propyl group) was 2 mol %, the degree of butyralization was 66.8 mol %, the hydroxy group content was 25 mol %, the acetyl group content was 2 mol %, the ionic functional group content of the polyvinyl acetal resin was 0.3 mmol/g, and the amount of the acetal bond (in the formula (5), R.sup.3 is a benzene ring, X is sodium sulfonate) having an ionic functional group was 4.2 mol %. Further, the acetal ring structure in the obtained polyvinyl acetal resin had a meso/racemo ratio of 10.2. According to the measurement using a transmission electron microscope, the obtained polyvinyl acetal resin fine particles 20 had a volume average particle size of 90 nm.

(62) (Preparation of a Dispersion of Polyvinyl Acetal Resin Fine Particles 21)

(63) In a reaction vessel equipped with a thermometer, a stirrer, and a condenser tube, 20 parts by weight of a polyvinyl acetal resin (degree of polymerization: 1,700, degree of butyralization: 30.3 mol %, hydroxy group content: 68.7 mol %, acetyl group content: 1 mol %) was dissolved in 80 parts by weight of isopropanol. To the obtained solution were added 1 part by weight of sodium 2-formylbenzene sulfonate and 0.05 parts by weight of 12 M concentrated hydrochloric acid to set the acid concentration of the reaction system to 0.12 M. The reaction thereof was carried out at 70 C. for four hours. Then, 1.5 parts by weight of butyraldehyde and 0.5 parts by weight of 12 M concentrated hydrochloric acid were added to set the acid concentration of the reaction system to 0.21 M. The reaction thereof was carried out at 75 C. for four hours, followed by cooling of the reaction solution. Then, a resin was purified by reprecipitation method and finally dried to be collected. The obtained resin was again dissolved in 80 parts by weight of isopropanol, and to the solution was dropwise added 200 parts by weight of water. The solution was stirred under reduced pressure, while the temperature of the solution was maintained at 30 C. The isopropanol and water were thus evaporated. The resulting substance was concentrated to have a solid content of 20% by weight, thereby preparing a dispersion in which polyvinyl acetal resin 21 in the form of fine particles (hereafter, also referred to as polyvinyl acetal resin fine particles 21) was dispersed (amount of polyvinyl acetal resin fine particles 21: 20% by weight).

(64) According to the measurement of the obtained polyvinyl acetal resin by NMR, the amount of the structural unit of the formula (1) (in the formula (1), R.sup.1 is a propyl group) was 2 mol %, the degree of butyralization was 30.5 mol %, the hydroxy group content was 65 mol %, the acetyl group content was 0.8 mol %, the ionic functional group content of the polyvinyl acetal resin was 0.1 mmol/g, and the amount of the acetal bond (in the formula (5), R.sup.3 is a benzene ring and X is sodium sulfonate) having an ionic functional group was 1.7 mol %. Further, the acetal ring structure in the obtained polyvinyl acetal resin had a meso/racemo ratio of 12.4. According to the measurement using a transmission electron microscope, the obtained polyvinyl acetal resin fine particles 21 had a volume average particle size of 90 nm.

(65) (Preparation of a Dispersion of Polyvinyl Acetal Resin Fine Particles 22)

(66) In a reaction vessel equipped with a thermometer, a stirrer, and a condenser tube, 20 parts by weight of a polyvinyl acetal resin (degree of polymerization: 1,700, degree of butyralization: 37.2 mol %, hydroxy group content: 61 mol %, acetyl group content: 1.8 mol %) was dissolved in 80 parts by weight of isopropanol. To the obtained solution were added 6 parts by weight of disodium 4-formylbenzene-1,3-disulfonate and 0.05 parts by weight of 12 M concentrated hydrochloric acid to set the acid concentration of the reaction system to 0.12 M. The reaction thereof was carried out at 70 C. for four hours. Then, 1 part by weight of butyraldehyde and 0.5 parts by weight of 12 M concentrated hydrochloric acid were added to set the acid concentration of the reaction system to 0.21 M. The reaction thereof was carried out at 75 C. for four hours, followed by cooling of the reaction solution. Then, a resin was purified by reprecipitation method and finally dried to be collected. The obtained resin was again dissolved in 80 parts by weight of isopropanol, and to the solution was dropwise added 200 parts by weight of water. The solution was stirred under reduced pressure, while the temperature of the solution was maintained at 30 C. The isopropanol and water were thus evaporated. The resulting substance was concentrated to have a solid content of 20% by weight, thereby preparing a dispersion in which polyvinyl acetal resin 22 in the form of fine particles (hereafter, also referred to as polyvinyl acetal resin fine particles 22) was dispersed (amount of polyvinyl acetal resin fine particles 22: 20% by weight).

(67) According to the measurement of the obtained polyvinyl acetal resin by NMR, the amount of the structural unit of the formula (1) (in the formula (1), R.sup.1 is a propyl group) was 2 mol %, the degree of butyralization was 37.5 mol %, the hydroxy group content was 45 mol %, the acetyl group content was 1.5 mol %, the ionic functional group content of the polyvinyl acetal resin was 1.8 mmol/g, and the amount of the acetal bond (in the formula (5), R.sup.3 is a benzene ring and X is sodium sulfonate) having an ionic functional group was 14 mol %. Further, the acetal ring structure in the obtained polyvinyl acetal resin had a meso/racemo ratio of 10.2. According to the measurement using a transmission electron microscope, the obtained polyvinyl acetal resin fine particles 22 had a volume average particle size of 9 nm.

(68) (Preparation of a Dispersion of Polyvinyl Acetal Resin Fine Particles 23)

(69) In a reaction vessel equipped with a thermometer, a stirrer, and a condenser tube, 20 parts by weight of a polyvinyl acetal resin (degree of polymerization: 800, degree of butyralization: 50.5 mol %, hydroxy group content: 47.7 mol %, acetyl group content: 1.8 mol %) was dissolved in 80 parts by weight of isopropanol. To the obtained solution were added 0.25 parts by weight of sodium 2-formylbenzene sulfonate and 0.05 parts by weight of 12 M concentrated hydrochloric acid to set the acid concentration of the reaction system to 0.12 M. The reaction thereof was carried out at 70 C. for four hours. Then, 1 part by weight of butyraldehyde and 0.5 parts by weight of 12 M concentrated hydrochloric acid were added to set the acid concentration of the reaction system to 0.21 M. The reaction thereof was carried out at 75 C. for four hours, followed by cooling of the reaction solution. Then, a resin was purified by reprecipitation method and finally dried to be collected. The obtained resin was again dissolved in 80 parts by weight of isopropanol, and to the solution was dropwise added 200 parts by weight of water. The solution was stirred under reduced pressure, while the temperature of the solution was maintained at 30 C. The isopropanol and water were thus evaporated. The resulting substance was concentrated to have a solid content of 20% by weight, thereby preparing a dispersion in which polyvinyl acetal resin 23 in the form of fine particles (hereafter, also referred to as polyvinyl acetal resin fine particles 23) was dispersed (amount of polyvinyl acetal resin fine particles 23: 20% by weight).

(70) According to the measurement of the obtained polyvinyl acetal resin by NMR, the amount of the structural unit of the formula (1) (in the formula (1), R.sup.1 is a propyl group) was 2 mol %, the degree of butyralization was 50.8 mol %, the hydroxy group content was 45 mol %, the acetyl group content was 1.5 mol %, the ionic functional group content of the polyvinyl acetal resin was 0.05 mmol/g, and the amount of the acetal bond (in the formula (5), R.sup.3 is a benzene ring, X is sodium sulfonate) having an ionic functional group was 0.7 mol %. Further, the acetal ring structure in the obtained polyvinyl acetal resin had a meso/racemo ratio of 16.1. According to the measurement using a transmission electron microscope, the obtained polyvinyl acetal resin fine particles 23 had a volume average particle size of 700 nm.

(71) (Preparation of a Dispersion of Polyvinyl Acetal Resin Fine Particles 24)

(72) In a reaction vessel equipped with a thermometer, a stirrer, and a condenser tube, 20 parts by weight of a polyvinyl acetal resin (degree of polymerization: 1,100, degree of butyralization: 50.1 mol %, hydroxy group content: 47.6 mol %, acetyl group content: 2.3 mol %) was dissolved in 80 parts by weight of isopropanol. To the obtained solution were added 2.6 parts by weight of sodium 2-formylbenzene sulfonate and 0.05 parts by weight of 12 M concentrated hydrochloric acid to set the acid concentration of the reaction system to 0.12 M. The reaction thereof was carried out at 70 C. for four hours. Then, 1 part by weight of butyraldehyde and 1 part by weight of 12 M concentrated hydrochloric acid were added to set the acid concentration of the reaction system to 0.29 M. The reaction thereof was carried out at 86 C. for seven hours, followed by cooling of the reaction solution. Then, a resin was purified by reprecipitation method and finally dried to be collected. The obtained resin was again dissolved in 80 parts by weight of isopropanol, and to the solution was dropwise added 200 parts by weight of water. The solution was stirred under reduced pressure, while the temperature of the solution was maintained at 30 C. The isopropanol and water were thus evaporated. The resulting substance was concentrated to have a solid content of 20% by weight, thereby preparing a dispersion in which polyvinyl acetal resin 24 in the form of fine particles (hereafter, also referred to as polyvinyl acetal resin fine particles 24) was dispersed (amount of polyvinyl acetal resin fine particles 24: 20% by weight).

(73) According to the measurement of the obtained polyvinyl acetal resin by NMR, the amount of the structural unit of the formula (1) (in the formula (1), R.sup.1 is a propyl group) was 0.2 mol %, the degree of butyralization was 48.6 mol %, the hydroxy group content was 47.1 mol %, the acetyl group content was 2 mol %, the ionic functional group content of the polyvinyl acetal resin was 0.17 mmol/g, and the amount of the acetal bond (in the formula (5), R.sup.3 is a benzene ring, X is sodium sulfonate) having an ionic functional group was 2.1 mol %. Further, the acetal ring structure in the obtained polyvinyl acetal resin had a meso/racemo ratio of 15.3. According to the measurement using a transmission electron microscope, the obtained polyvinyl acetal resin fine particles 24 had a volume average particle size of 200 nm.

(74) (Preparation of Polyvinyl Acetal Resin 25)

(75) In a reaction vessel equipped with a thermometer, a stirrer, and a condenser tube, 20 parts by weight of a polyvinyl acetal resin (degree of polymerization: 1,100, degree of butyralization: 52 mol %, hydroxy group content: 47.8 mol %, acetyl group content: 0.2 mol %) was dissolved in 80 parts by weight of isopropanol. To the obtained solution were added 1 part by weight of sodium 2-formylbenzene sulfonate and 0.05 parts by weight of 12 M concentrated hydrochloric acid to set the acid concentration of the reaction system to 0.12 M. The reaction thereof was carried out at 70 C. for four hours. Then, 0.2 parts by weight of butyraldehyde and 1 part by weight of 12 M concentrated hydrochloric acid were added to set the acid concentration of the reaction system to 0.15 M. The reaction thereof was carried out at 82 C. for six hours, followed by cooling of the reaction solution. Then, a resin was purified by reprecipitation method and finally dried to prepare a polyvinyl acetal resin 25.

(76) According to the measurement of the obtained polyvinyl acetal resin by NMR, the amount of the structural unit of the formula (1) (in the formula (1), R.sup.1 is a propyl group) was 0.3 mol %, the degree of butyralization was 51.7 mol %, the hydroxy group content was 45 mol %, the acetyl group content was 0.2 mol %, the ionic functional group content of the polyvinyl acetal resin was 0.2 mmol/g, and the amount of the acetal bond (in the formula (5), R.sup.3 is a benzene ring, X is sodium sulfonate) having an ionic functional group was 2.8 mol %. Further, the acetal ring structure in the obtained polyvinyl acetal resin had a meso/racemo ratio of 11.6.

(77) TABLE-US-00001 TABLE 1 Polyvinyl acetal resin Amount of Degree Hydroxy Acetyl acetal bond Degree of group group having ionic of butylarization content content functional polymerization (mol %) (mol %) (mol %) group (mol %) Polyvinyl acetal resin fine particles 1 1000 63.6 32 1.5 2.9 Polyvinyl acetal resin fine particles 2 1000 47.1 48.9 1 3 Polyvinyl acetal resin flne particles 3 1000 69.5 26.2 1.5 2.8 Polyvinyl acetal resin fine particles 4 1000 58.3 37.6 1.2 2.9 Polyvinyl acetal resin fine particles 5 1000 47.4 50.8 1 0.8 Polyvinyl acetal resin fine particles 6 1000 47.1 50.7 1 1.2 Polyvinyl acetal resin fine particles 7 1000 47.1 37.9 1 14 Polyvinyl acetal resin fine particles 8 1000 47.1 50.1 1 1.8 Polyvinyl acetal resin fine particles 9 1000 45.2 42 1.8 11 Polyvinyl acetal resin fine particles 10 1000 34 62 1 3 Polyvinyl acetal resin fine particles 11 1100 68.8 26 2 4.2 Polyvinyl acetal resin fine particles 12 1100 32.5 65 0.8 1.7 Polyvinyl acetal resin 13 1000 47.1 48.9 1 3 Polyvinyl acetal resin 14 1000 47.8 51 1.2 Polyvinyl acetal resin fine particles 15 1100 51.7 45 0.2 2.8 Polyvinyl acetal resin fine particles 16 1100 46.4 45 2 1.6 Polyvinyl acetal resin fine particles 17 1100 47.4 45 1.1 4.5 Polyvinyl acetal resin fine particles 18 800 51.7 36 0.1 12 Polyvinyl acetal resin fine particles 19 1700 38 45 7 3 Polyvinyl acetal resin fine particles 20 1700 66.8 26 2 4.2 Polyvinyl acetal resin fine particles 21 1700 30.5 65 0.8 1.7 Polyvinyl acetal resin fine particles 22 1700 37.5 45 1.5 14 Polyvinyl acetal resin fine particles 23 800 50.8 45 1.5 0.7 Polyvinyl acetal resin fine particles 24 1100 48.6 47.1 2 2.1 Polyvinyl acetal resin 25 1100 51.7 45 0.2 2.8 Polyvinyl acetal resin Amount of Ionic Volume structural functional average unit of Ionic group Meso/ particle formula (1) functional content racemo size (mol %) group (mmol/g) ratio (nm) Polyvinyl acetal resin fine particles 1 Sulfonate 0.2 13 100 Polyvinyl acetal resin fine particles 2 Sulfonate 0.2 17.5 90 Polyvinyl acetal resin flne particles 3 Sulfonate 0.2 8.9 110 Polyvinyl acetal resin fine particles 4 Sulfonate 0.2 26.4 100 Polyvinyl acetal resin fine particles 5 Sulfonate 0.06 17.5 620 Polyvinyl acetal resin fine particles 6 Sulfonate 0.08 17.5 450 Polyvinyl acetal resin fine particles 7 Sulfonate 1.8 17.5 9 Polyvinyl acetal resin fine particles 8 Sulfonate 0.1 17.5 240 Polyvinyl acetal resin fine particles 9 Carboxylic 1 15.2 450 acid Polyvinyl acetal resin fine particles 10 Sulfonate 0.2 9.1 100 Polyvinyl acetal resin fine particles 11 Sulfonate 0.2 10.4 90 Polyvinyl acetal resin fine particles 12 Sulfonate 0.2 11.6 90 Polyvinyl acetal resin 13 Sulfonate 0.2 10.3 Polyvinyl acetal resin 14 9.4 Polyvinyl acetal resin fine particles 15 0.3 Sulfonate 0.2 12 90 Polyvinyl acetal resin fine particles 16 5 Sulfonate 0.1 16.7 300 Polyvinyl acetal resin fine particles 17 2 Sulfonate 0.6 11.5 30 Polyvinyl acetal resin fine particles 18 0.2 Carboxylic 1 9.4 450 acid Polyvinyl acetal resin fine particles 19 7 Sulfonate 0.2 17 90 Polyvinyl acetal resin fine particles 20 2 Sulfonate 0.3 10.2 90 Polyvinyl acetal resin fine particles 21 2 Sulfonate 0.1 12.4 90 Polyvinyl acetal resin fine particles 22 2 Sulfonate 1.8 10.2 9 Polyvinyl acetal resin fine particles 23 2 Sulfonate 0.05 16.1 700 Polyvinyl acetal resin fine particles 24 0.2 Sulfonate 0.17 15.3 200 Polyvinyl acetal resin 25 0.3 Sulfonate 0.2 11.6

Example 1

(78) (Preparation of a Composition for a Lithium Secondary Battery Positive Electrode)

(79) To 10 parts by weight of the dispersion of polyvinyl acetal resin fine particles 1 obtained as a binder was added 90 parts by weight of water to prepare a 2 wt % polyvinyl acetal resin solution. To 100 parts by weight of this solution were added 50 parts by weight of lithium cobaltate (CELLSEED C-5 available from Nippon Chemical Industrial Co., Ltd.) as a positive-electrode active material, 1 part by weight of acetylene black (DENKA BLACK available from Denki Kagaku Kogyo Kabushiki Kaisha) as a conductive aid, and 1 part by weight of carboxymethyl cellulose (available from Aldrich) as a thickener, thereby preparing a composition for a lithium secondary battery positive electrode.

Examples 2 to 8 and 10 to 19, Comparative Examples 1 to 4 and 6 to 8

(80) A composition for a lithium secondary battery positive electrode was prepared in the same manner as in Example 1, except that a dispersion of polyvinyl acetal resin fine particles shown in one of Tables 2 to 5 was used and the amount or type of the polyvinyl acetal resin fine particles was changed.

Examples 9 and 20, Comparative Example 5

(81) A composition for a lithium secondary battery positive electrode was prepared in the same manner as in Example 1, except that a solution prepared by adding 98 parts by weight of N-methylpyrrolidone to 2 parts by weight of a polyvinyl acetal resin shown in one of Tables 2 to 5, instead of the dispersion of polyvinyl acetal resin fine particles, was used.

Example 21

(82) (Preparation of a Composition for a Lithium Secondary Battery Negative Electrode)

(83) To 10 parts by weight of the dispersion of polyvinyl acetal resin fine particles 1 obtained as a binder was added 90 parts by weight of water to prepare a 2 wt % polyvinyl acetal resin solution. To 100 parts by weight of this solution were added 50 parts by weight of spherical natural graphite (CGB-20 available from Nippon Graphite Industries, Co., Ltd.) as a negative-electrode active material, 1 part by weight of acetylene black (DENKA BLACK available from Denki Kagaku Kogyo Kabushiki Kaisha) as a conductive aid, and 1 part by weight of carboxymethyl cellulose (available from Aldrich) as a thickener, thereby preparing a composition for a lithium secondary battery negative electrode.

Examples 22 to 28 and 30 to 39, Comparative Examples 9 to 12 and 14 to 16

(84) A composition for a lithium secondary battery negative electrode was prepared in the same manner as in Example 21, except that a dispersion of the polyvinyl acetal resin fine particles shown in one of Tables 2 to 5 was used and the amount or type of the polyvinyl acetal resin fine particles was changed.

Examples 29 and 40, Comparative Example 13

(85) A composition for a lithium secondary battery negative electrode was prepared in the same manner as in Example 21, except that a solution prepared by adding 98 parts by weight of N-methylpyrrolidone to 2 parts by weight of a polyvinyl acetal resin shown in one of Tables 2 to 5, instead of the dispersion of polyvinyl acetal resin fine particles, was used.

Example 41

(86) (Preparation of a Composition for a Lithium Secondary Battery Negative Electrode)

(87) To 10 parts by weight of the dispersion of polyvinyl acetal resin fine particles 1 obtained as a binder was added 90 parts by weight of water to prepare a 2 wt % polyvinyl acetal resin solution. To 100 parts by weight of this solution were added 45 parts by weight of spherical natural graphite (CGB-20 available from Nippon Graphite Industries, Co., Ltd.) and 5 parts by weight of silicon (SiO, available from Osaka Titanium Technologies) as negative-electrode active materials, 1 part by weight of acetylene black (DENKA BLACK available from Denki Kagaku Kogyo Kabushiki Kaisha) as a conductive aid, and 1 part by weight of carboxymethyl cellulose (available from Aldrich) as a thickener, thereby preparing a composition for a lithium secondary battery negative electrode.

Examples 42 to 48 and 50 to 59, Comparative Examples 17 to 20 and 22 to 24

(88) A composition for a lithium secondary battery negative electrode was prepared in the same manner as in Example 41, except that a dispersion of polyvinyl acetal resin fine particles shown in one of Tables 2 to 5 was used and the amount or type of the polyvinyl acetal resin fine particles was changed.

Examples 49 and 60, Comparative Example 21

(89) A composition for a lithium secondary battery negative electrode was prepared in the same manner as in Example 41, except that a solution prepared by adding 98 parts by weight of N-methylpyrrolidone to 2 parts by weight of a polyvinyl acetal resin shown in one of Tables 2 to 5, instead of the dispersion of polyvinyl acetal resin fine particles, was used.

(90) <Evaluation>

(91) The following evaluations were performed on the compositions for a lithium secondary battery electrode (for a positive electrode, for a negative electrode) obtained in the examples and comparative examples. Tables 2 to 5 show the results.

(1) Adhesiveness

(92) For the compositions for a lithium secondary battery positive electrode obtained in Examples 1 to 20 and Comparative Examples 1 to 8, the adhesiveness to aluminum foil was checked. For the compositions for a lithium secondary battery negative electrode obtained in Examples 21 to 60 and Comparative Examples 9 to 24, the adhesiveness to copper foil was checked.

(1-1) Adhesiveness to Aluminum Foil

(93) The composition for a lithium secondary battery electrode was applied to aluminum foil (thickness of 15 m) to have a dry thickness of 40 m, and dried to prepare a sample in which a sheet-shaped electrode was formed on aluminum foil.

(94) The sample was cut to a size of 10 cm in length and 5 cm in width, and the obtained test piece was attached to an acrylic plate (thickness of 2 mm) with a double-stick tape in such a manner that the aluminum foil side was in contact with the acrylic plate. To the electrode surface of the test piece was placed a tape (product name: Cellotape () No. 252 (available from Sekisui Chemical Co., Ltd.)(JIS Z1522 standard)) with a width of 18 mm, and then peeled in a 90 direction at a speed of 300 ram/min. The peeling force (N) for the peeling was measured with an autograph (AGS-J available from Shimadzu Corporation).

(1-2) Adhesiveness to Copper Foil

(95) The peeling force was measured in the same manner as in the (1-1) Adhesiveness to aluminum foil, except that the aluminum foil was changed to copper foil (thickness of 15 m).

(2) Dispersibility

(96) An amount of 10 parts by weight of the obtained composition for a lithium secondary battery electrode was mixed and diluted with 90 parts by weight of water, and then stirred in an ultrasonic disperser (US-303 available from SND Co., Ltd.) for 10 minutes. The particle size distribution of the dilution was measured with a laser diffraction particle size distribution analyzer (LA-910 available from Horiba Ltd.) to determine the average dispersion size.

(3) Electrolyte Resistance

(97) (Preparation of a Binder Resin Sheet)

(98) To a release-treated polyethylene terephthalate (PET) film was applied each of the polyvinyl acetal resin dispersions or resin solutions used in the examples and comparative examples to a dry thickness of 50 m, and dried to prepare a binder resin sheet.

(99) The obtained binder resin sheet was cut to a size of 3050 mm to prepare a test piece.

(100) The obtained test piece was dried at 110 C. for two hours, and the obtained film was weighed to determine the weight (a) of the film.

(101) Next, a mixed solution (1:1 in volume) of ethylene carbonate and diethyl carbonate was prepared as an electrolyte, and the obtained film was immersed in the electrolyte at 25 C. for three days. The film was taken out and the electrolyte on the surface was immediately wiped off. The weight of the resulting film was weighed to determine the weight (b).

(102) The film was then immersed in 500 g of pure water for two days to completely remove the electrolyte inside thereof, dried at 110 C. for two hours, and weighed to determine the weight (c).

(103) Based on the weights (a), (b), and (c), the dissolution rate and swelling rate of the binder were calculated using the following equations.
Dissolution rate (%)=[(ac)/a]100.
Swelling rate (%)=(b/c)100.

(104) A higher dissolution rate indicates that the resin is more likely to be dissolved in the electrolyte, and a higher swelling rate indicates that the resin is more likely to swell with the electrolyte.

(4) Flexibility

(105) For the compositions for a lithium secondary battery positive electrode obtained in Examples 1 to 20 and Comparative Examples 1 to 8, the flexibility of an electrode prepared using aluminum foil was evaluated. For the compositions for a lithium secondary battery negative electrode obtained in Examples 21 to 60 and Comparative Examples 9 to 24, the flexibility of an electrode prepared using copper foil was evaluated.

(4-1) Flexibility in the Case of Using Aluminum Foil

(106) To aluminum foil (thickness of 15 m) was applied the composition for a lithium secondary battery electrode to a dry thickness of 40 m, and dried to prepare a test piece in which a sheet-shaped electrode was formed on aluminum foil.

(107) This sample was cut to a size of 50 cm in length and 2 cm in width, and the obtained test piece was wound around a glass stick with a diameter of 2 mm and left for one day. The sample was released and checked for cracks or fractures in the electrode based on the following criteria.

(108) (Excellent): No cracks or fractures were found.

(109) (Good): Slight cracks or fractures were found but peeling of the active material was not at all found.

(110) (Fair): Cracks or fractures were found and partial peeling of the active material was found.

(111) x (Poor): Cracks or fractures were found all around the test piece and peeling of the active material was found in most part.

(4-2) Flexibility in the Case of Using Copper Foil

(112) The flexibility was evaluated in the same manner as in (4-1) Flexibility in the case of using aluminum foil, except that the aluminum foil was changed to copper foil (thickness of 15 m).

(5) Evaluation of Battery Performance

(5-1) Examples 1 to 20, Comparative Examples 1 to 8

(113) (a) Preparation of a Secondary Battery

(114) The composition for a lithium secondary battery positive electrode obtained in each of Examples 1 to 20 and Comparative Examples 1 to 8 was uniformly applied to aluminum foil (thickness of 15 m), dried, and cut to a size of 0.6 mm, thereby preparing a positive electrode. The electrolyte used was a mixed solvent (1:1 in volume) of ethylene carbonate and diethyl carbonate containing LiPF.sub.6 (1M).

(115) The positive electrode was set in a bipolar coin cell (product name: HS Flat cell (available from Hohsen Corp.)) in such a manner that the electrode layer surface faces upward. Next, a porous polypropylene separator (thickness of 25 m) punched out to a diameter of 24 mm was placed thereon, and the electrolyte was poured into the cell to avoid entering of air. Then, a lithium metal plate as a counter electrode was further placed thereon, and a top cover was screwed to the cell for sealing, thereby preparing a secondary battery.

(116) (b) Evaluation of Discharge Capacity and Charge-Discharge Cycle

(117) Using a battery test system TOSCAT-3100 available from Toyo System Co., Ltd, the discharge capacity and the charge-discharge cycle of the obtained secondary battery was evaluated.

(118) The evaluation of the discharge capacity and charge-discharge cycle was performed under the conditions of the voltage range of 2.7 to 4.2 V and the temperature of 25 C., 5 C., and 50 C. for the charge-discharge cycle evaluation and 25 C. for the discharge capacity evaluation. The charge-discharge cycle was evaluated based on the calculation of the ratio of the discharge capacity in the 30th cycle to the initial discharge capacity.

(5-2) Examples 21 to 60, Comparative Examples 9 to 24

(119) The composition for a lithium secondary battery negative electrode obtained in each of Examples 21 to 60 and Comparative Examples 9 to 24 was uniformly applied to copper foil (thickness of 15 m), dried, and cut to a size of 16 mm, thereby preparing a negative electrode.

(120) A sealed-type secondary battery was prepared in the same manner as in (5-1), except that the obtained negative electrode was used. Then, the evaluation of the discharge capacity and charge-discharge cycle was performed. The evaluation of the discharge capacity and charge-discharge cycle was performed under the conditions of the voltage range of 0.03 to 1.5 V and the temperature of 25 C., 5 C., and 50 C. for the charge-discharge cycle evaluation and 25 C. for the discharge capacity evaluation. The charge-discharge cycle was evaluated based on the calculation of the ratio of the discharge capacity in the 30th cycle to the initial discharge capacity.

(121) TABLE-US-00002 TABLE 2 Evaluation Active material Con- (1) (2) (3) Electrolyte resistance (5) Battery performance (parts by weight) ductive Polyvinyl acetal resin Adhesive- Dispersibility Dissolution Swelling Charge- Charge- Charge- Spherical aid Amount ness Average rate rate at 25 C. (4) Discharge discharge discharge discharge Lithium natural Silicon Acetylene (parts by Peeling dispersion size 25 C. in 3 in 3 days Flex- capacity cycle at 25 C. cycle at 5 C. cycle at 50 C. cobaltate graphite (SiO) black Type weight) force (N) (m) days (%) (%) ibility (mAh/g) (%) (%) (%) Example 1 50 1 Polyvinyl acetal resin 2 4.4 7.3 0.4 146 124 89 86 84 fine particles 1 Example 2 50 1 Polyvinyl acetal resin 2 4.3 7.2 0.3 112 155 98 95 93 fine particles 2 Example 3 50 1 Polyvinyl acetal resin 2 4.4 7.3 0.3 130 140 95 92 89 fine particles 4 Example 4 50 1 Polyvinyl acetal resin 2 4.6 7.2 0.4 112 128 90 87 84 fine particles 5 Example 5 50 1 Polyvinyl acetal resin 2 4.7 7.2 0.4 112 135 95 92 89 fine particles 6 Example 6 50 1 Polyvinyl acetal resin 2 4.4 7 0.2 114 125 90 88 84 fine particles 7 Example 7 50 1 Polyvinyl acetal resin 2 4.7 7.1 0.3 112 153 97 94 90 fine particles 8 Example 8 50 1 Polyvinyl acetal resin 2 4.6 7.3 0.2 112 137 88 87 84 fine particles 9 Example 9 50 1 Polyvinyl acetal 2 4.5 7.5 0.3 112 121 88 85 83 resin 13 Example 10 50 1 Polyvinyl acetal resin 2 4.3 7.2 0.3 112 151 97 94 92 fine particles 15 Example 11 50 1 Polyvinyl acetal resin 0.3 2.8 7.1 0.3 112 144 96 93 91 fine particles 15 Example 12 50 1 Polyvinyl acetal resin 6 5.9 7.5 0.3 112 135 95 92 90 fine particles 15 Example 13 50 1 Polyvinyl acetal resin 15 8.2 8.1 0.3 112 120 91 88 86 fine particles 15 Example 14 50 1 Polyvinyl acetal resin 2 4.7 7.1 0.5 119 145 96 93 91 fine particles 16 Example 15 50 1 Polyvinyl acetal resin 2 5.1 6.9 0.4 113 156 99 96 94 fine particles 17 Example 16 50 1 Polyvinyl acetal resin 2 4.1 8 0.9 133 140 95 92 90 fine particles 19 Example 17 50 1 Polyvinyl acetal resin 2 4.6 11 0.3 115 125 90 87 85 fine particles 22 Example 18 50 1 Polyvinyl acetal resin 2 2.1 15 0.6 114 123 89 86 84 fine particles 23 Example 19 50 1 Polyvinyl acetal resin 2 4.1 8 0.8 124 140 95 92 92 fine particles 24 Example 20 50 1 Polyvinyl acetal 2 4.5 7.5 0.3 112 120 90 88 85 resin 25

(122) TABLE-US-00003 TABLE 3 Evaluation Active material Con- (1) (2) (3) Electrolyte resistance (5) Battery performance (parts by weight) ductive Polyvinyl acetal resin Adhesive- Dispersibility Dissolution Swelling Charge- Charge- Charge- Spherical aid Amount ness Average rate rate at 25 C. (4) Discharge discharge discharge discharge Lithium natural Silicon Acetylene (parts by Peeling dispersion size 25 C. in 3 in 3 days Flex- capacity cycle at 25 C. cycle at 5 C. cycle at 50 C. cobaltate graphite (SiO) black Type weight) force (N) (m) days (%) (%) ibility (mAh/g) (%) (%) (%) Example 21 50 1 Polyvinyl acetal resin 2 4.1 4 0.4 146 286 88 87 86 fine particles 1 Example 22 50 1 Polyvinyl acetal resin 2 4 20 0.3 112 360 98 95 94 fine particles 2 Example 23 50 1 Polyvinyl acetal resin 2 4 22 0.3 130 320 95 90 89 fine particles 4 Example 24 50 1 Polyvinyl acetal resin 2 4.6 21 0.4 112 295 89 84 83 fine particles 5 Example 25 50 1 Polyvinyl acetal resin 2 4.2 21 0.4 112 312 95 89 89 fine particles 6 Example 26 50 1 Polyvinyl acetal resin 2 4.6 22 0.2 114 290 89 84 83 fine particles 7 Example 27 50 1 Polyvinyl acetal resin 2 4.3 22 0.3 112 355 97 93 90 fine particles 8 Example 28 50 1 Polyvinyl acetal resin 2 4.3 22 0.2 112 317 87 84 81 fine particles 9 Example 29 50 1 Polyvinyl acetal 2 4.3 24 0.3 112 279 88 84 82 resin 13 Example 30 50 1 Polyvinyl acetal resin 2 4 21 0.3 112 350 97 94 92 fine particles 15 Example 31 50 1 Polyvinyl acetal resin 0.3 2.4 20 0.3 112 335 96 93 91 fine particles 15 Example 32 50 1 Polyvinyl acetal resin 6 5.1 23 0.3 112 315 95 92 90 fine particles 15 Example 33 50 1 Polyvinyl acetal resin 15 7 25 0.3 112 280 92 89 87 fine particles 15 Example 34 50 1 Polyvinyl acetal resin 2 4.2 20 0.5 119 340 96 93 91 fine particles 16 Example 35 50 1 Polyvinyl acetal resin 2 4.7 19 0.4 113 360 99 96 94 fine particles 17 Example 36 50 1 Polyvinyl acetal resin 2 3.6 23 0.9 133 327 95 92 90 fine particles 19 Example 37 50 1 Polyvinyl acetal resin 2 4 29 0.3 115 290 90 87 85 fine particles 22 Example 38 50 1 Polyvinyl acetal resin 2 1.7 35 0.6 114 285 90 87 85 fine particles 23 Example 39 50 1 Polyvinyl acetal resin 2 3.8 26 0.8 124 334 95 92 92 fine particles 24 Example 40 50 1 Polyvinyl acetal 2 4.3 24 0.3 112 280 90 86 84 resin 25

(123) TABLE-US-00004 TABLE 4 Evaluation Active material (1) (2) (3) Electrolyte resistance (5) Battery performance (parts by weight) Conductive Polyvinyl acetal resin Adhesive- Dispersibility Dissolution Swelling Charge- Charge- Charge- Spherical aid Amount ness Average rate rate at 25 C. (4) Discharge discharge discharge discharge Lithium natural Silicon Acetylene (parts by Peeling dispersion size 25 C. in 3 in 3 days Flex- capacity cycle at 25 C. cycle at 5 C. cycle at 50 C. cobaltate graphite (SiO) black Type weight) force (N) (m) days (%) (%) ibility (mAh/g) (%) (%) (%) Example 41 45 5 1 Polyvinyl acetal resin 2 4.3 17.2 0.4 146 491 92 86 83 fine particles 1 Example 42 45 5 1 Polyvinyl acetal resin 2 4.2 15.4 0.3 112 597 98 95 94 fine particles 2 Example 43 45 5 1 Polyvinyl acetal resin 2 4.2 16.9 0.3 130 530 95 90 89 fine particles 4 Example 44 45 5 1 Polyvinyl acetal resin 2 4.5 16.8 0.4 112 520 94 89 82 fine particles 5 Example 45 45 5 1 Polyvinyl acetal resin 2 4.4 16.2 0.4 112 517 95 89 89 fine particles 6 Example 46 45 5 1 Polyvinyl acetal resin 2 4.5 16.6 0.2 114 511 95 90 89 fine particles 7 Example 47 45 5 1 Polyvinyl acetal resin 2 4.5 16.9 0.3 112 588 97 93 90 fine particles 8 Example 48 45 5 1 Polyvinyl acetal resin 2 4.4 16.9 0.2 112 521 94 90 88 fine particles 9 Example 49 45 5 1 Polyvinyl acetal 2 4.5 18.5 0.3 112 462 88 84 82 resin 13 Example 50 45 5 1 Polyvinyl acetal resin 2 4.2 16.2 0.3 112 580 97 94 92 fine particles 15 Example 51 45 5 1 Polyvinyl acetal resin 0.3 2.5 15.4 0.3 112 555 96 93 91 fine particles 15 Example 52 45 5 1 Polyvinyl acetal resin 6 5.4 17.7 0.3 112 522 95 92 90 fine particles 15 Example 53 45 5 1 Polyvinyl acetal resin 15 7.4 19.3 0.3 112 464 92 89 87 fine particles 15 Example 54 45 5 1 Polyvinyl acetal resin 2 4.4 15.4 0.5 119 563 96 93 91 fine particles 16 Example 55 45 5 1 Polyvinyl acetal resin 2 4.9 14.6 0.4 113 597 99 96 94 fine particles 17 Example 56 45 5 1 Polyvinyl acetal resin 2 3.8 17.7 0.9 133 542 95 92 90 fine particles 19 Example 57 45 5 1 Polyvinyl acetal resin 2 4.2 22.3 0.3 115 481 90 87 85 fine particles 22 Example 58 45 5 1 Polyvinyl acetal resin 2 1.8 27.0 0.6 114 472 90 87 85 fine particles 23 Example 59 45 5 1 Polyvinyl acetal resin 2 3.9 17.4 0.8 124 534 94 90 89 fine particles 24 Example 60 45 5 1 Polyvinyl acetal 2 4.1 18.4 0.3 112 492 93 82 81 resin 25

(124) TABLE-US-00005 TABLE 5 Evaluation Active material Con- (1) (2) (3) Electrolyte resistance (5) Battery performance (parts by weight) ductive Polyvinyl acetal resin Adhesive- Dispersibility Dissolution Swelling Charge- Charge- Charge- Spherical aid Amount ness Average rate rate at 25 C. (4) Discharge discharge discharge discharge Lithium natural Silicon Acetylene (parts by Peeling dispersion size 25 C. in 3 in 3 days Flex- capacity cycle at 25 C. cycle at 5 C. cycle at 50 C. cobaltate graphite (SiO) black Type weight) force (N) (m) days (%) (%) ibility (mAh/g) (%) (%) (%) Comparative 50 1 Polyvinyl acetal resin 2 4.3 19 54 174 Not measurable due to binder dissolution Example 1 fine particles 3 Comparative 50 1 Polyvinyl acetal resin 2 3.6 7.8 90 107 Not measurable due to binder dissolution Example 2 fine particles 10 Comparative 50 1 Polyvinyl acetal resin 2 4 12 62 154 Not measurable due to binder dissolution Example 3 fine particles 11 Comparative 50 1 Polyvinyl acetal resin 2 4 11.4 67 106 Not measurable due to binder dissolution Example 4 fine particles 12 Comparative 50 1 Polyvinyl acetal 2 4 13 0.3 112 X 96 75 68 68 Example 5 resin 14 Comparative 50 1 Polyvinyl acetal resin 2 3.8 9 3 165 98 79 72 71 Example 6 fine particles 18 Comparative 50 1 Polyvinyl acetal resin 2 3.6 7.8 90 450 Not measurable due to binder dissolution Example 7 fine particles 20 Comparative 50 1 Polyvinyl acetal resin 2 4.3 19 0.2 107 X 103 80 71 71 Example 8 fine particles 21 Comparative 50 1 Polyvinyl acetal resin 2 3.4 40 54 174 Not measurable due to binder dissolution Example 9 fine particles 3 Comparative 50 1 Polyvinyl acetal resin 2 3 23 90 107 Not measurable due to binder dissolution Example 10 fine particles 10 Comparative 50 1 Polyvinyl acetal resin 2 3.2 26.4 62 154 Not measurable due to binder dissolution Example 11 fine particles 11 Comparative 50 1 Polyvinyl acetal resin 2 3.3 31 67 106 Not measurable due to binder dissolution Example 12 fine particles 12 Comparative 50 1 Polyvinyl acetal 2 3.9 32 0.3 112 X 215 73 67 66 Example 13 resin 14 Comparative 50 1 Polyvinyl acetal resin 2 3.2 25 3 165 225 78 71 71 Example 14 fine particles 18 Comparative 50 1 Polyvinyl acetal resin 2 3 23 90 450 Not measurable due to binder dissolution Example 15 fine particles 20 Comparative 50 1 Polyvinyl acetal resin 2 3.4 40 0.2 107 X 240 78 71 64 Example 16 fine particles 21 Comparative 45 5 1 Polyvinyl acetal resin 2 3.6 30.8 54 174 Not measurable due to binder dissolution Examole 17 fine particles 3 Comparative 45 5 1 Polyvinyl acetal resin 2 3.2 17.7 90 107 Not measurable due to binder dissolution Example 18 fine particles 10 Comparative 45 5 1 Polyvinyl acetal resin 2 3.5 22.2 62 154 Not measurable due to binder dissolution Example 19 fine particles 11 Comparative 45 5 1 Polyvinyl acetal resin 2 3.3 18.1 67 106 Not measurable due to binder dissolution Examnle 20 fine particles 12 Comparative 45 5 1 Polyvinyl acetal 2 4.1 24.6 0.3 112 X 358 70 64 63 Example 21 resin 14 Comparative 45 5 1 Polyvinyl acetal resin 2 3.4 19.3 3 165 370 74 97 67 Example 22 fine particles 18 Comparative 45 5 1 Polyvinyl acetal resin 2 3.5 18.7 90 450 Not measurable due to binder dissolution Example 23 fine particles 20 Comparative 45 5 1 Polyvinyl acetal resin 2 3.5 19.4 0.2 107 340 52 44 41 Example 24 fine particles 21

INDUSTRIAL APPLICABILITY

(125) The present invention can provide a binder for a power storage device electrode which exhibits thermal energy stability over a wide temperature range covering from a high-temperature condition to a low-temperature condition when used as a binder for a power storage device electrode, and which enables production of a high-capacity storage battery with a small irreversible capacity and low resistance to have excellent output characteristics. The present invention can also provide a binder for a power storage device electrode which is excellent in dispersibility of an active material and adhesiveness, which improves the flexibility of an electrode to be obtained, and which has high resistance against electrolytes to enable production of a high-capacity storage battery even when the added amount thereof is small. The present invention can further provide a composition for a power storage device electrode, a power storage device electrode, and a power storage device each prepared using the binder for a power storage device electrode.