Epoxy adhesive composition

Abstract

The present invention provides an epoxy adhesive composition that is excellent in compatibility and storage stability, has high strength and excellent adhesiveness, is capable of reducing occurrence of warping or peeling when used for bonding different materials, and is also excellent in impact resistance after being cured. Provided is an epoxy adhesive composition including: a modified polyvinyl acetal resin having a constitutional unit with an acid-modified group; and an epoxy resin, the epoxy adhesive composition containing an organic solvent in an amount of 10.0% by weight or less.

Claims

1. An epoxy adhesive composition comprising: a modified polyvinyl acetal resin having a constitutional unit with an acid-modified group; and an epoxy resin, the epoxy adhesive composition containing an organic solvent in an amount of 10.0% by weight or less and an amount of the epoxy resin of 45% by weight to 99.5% by weight, wherein a ratio between the number of the acid-modified groups contained in the modified polyvinyl acetal resin and the number of epoxy groups contained in the epoxy resin is 0.0005 to 0.5.

2. The epoxy adhesive composition according to claim 1, wherein the acid-modified group is a carboxyl group.

3. The epoxy adhesive composition according to claim 1, wherein the modified polyvinyl acetal resin has the constitutional unit with an acid-modified group in a side chain.

4. The epoxy adhesive composition according to claim 1, wherein the amount of the constitutional unit with an acid-modified group in the modified polyvinyl acetal resin is 0.01 to 5.0 mol %.

5. The epoxy adhesive composition according to claim 1, wherein the modified polyvinyl acetal resin has an acetal group content of 60 to 90 mol %.

6. The epoxy adhesive composition according to claim 1, wherein the modified polyvinyl acetal resin is an acetalized product of polyvinyl alcohol having an acid-modified group.

7. The epoxy adhesive composition according to claim 1, wherein the amount of the modified polyvinyl acetal resin is 0.5 to 50% by weight.

8. The epoxy adhesive composition according to claim 1, wherein the amount of the modified polyvinyl acetal resin is 10 to 30% by weight.

Description

DESCRIPTION OF EMBODIMENTS

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

Example 1

(2) An amount of 200 g of polyvinyl alcohol was added to 1,800 g of pure water, and stirred at 90° C. for about two hours to be dissolved. The solution was cooled to 40° C., and to the solution were added 150 g of hydrochloric acid having a concentration of 35% by weight and 75 g of acetaldehyde. The acetalization reaction was carried out to precipitate a reaction product by maintaining the solution temperature at 40° C.

(3) The polyvinyl alcohol used had a degree of polymerization of 400, a degree of saponification of 97.7 mol %, and contained 0.4 mol % of a constitutional unit with a carboxyl group represented by the above formula (1-4)(in the formula (1-4), R.sup.6 represents a single bond, X.sup.6 represents a hydrogen atom, R.sup.7 represents a methylene group, and X.sup.7 represents a hydrogen atom).

(4) Then, the reaction solution was held to maintain the temperature at 40° C. for three hours, thereby completing the reaction. A modified polyvinyl acetal resin powder was obtained through neutralization, washing with water, and drying by normal methods.

(5) The obtained modified polyvinyl acetal resin was dissolved in DMSO-d.sub.6 (dimethylsulfoxide), and analyzed by .sup.13C-NMR (nuclear magnetic resonance spectrum) to confirm the presence of the constitutional unit with a carboxyl group represented by the formula (1-4) (amount: 0.4 mol %). Table 1 shows the acetal group content, the acetyl group content, and the hydroxyl group content measured by .sup.13C-NMR.

(6) An amount of 10 g of the obtained modified polyvinyl acetal resin, 85 g of an epoxy resin, 3 g of dicyandiamide (DICY available from Mitsubishi Chemical Corporation) as a curing agent, and 2 g of an imidazole compound (jERCURE EMI24 available from Mitsubishi Chemical Corporation) as a curing accelerator were blended to prepare an adhesive composition in which the polyvinyl acetal resin and the epoxy resin were mixed at a weight ratio of 10:85.

(7) The epoxy resin used was a bisphenol A-type epoxy resin (jER 828 available from Mitsubishi Chemical Corporation, epoxy equivalent: 190, molecular weight: 370). The obtained adhesive composition was applied to a release-treated polyethylene terephthalate (PET) film to a dry thickness of 20 μm, and dried at 125° C. to prepare a resin sheet.

Examples 2 to 8

(8) Using the modified polyvinyl acetal resin obtained in Example 1, an adhesive composition and a resin sheet were produced as in Example 1, except that the epoxy resin, the curing agent, and the curing accelerator were added as shown in Table 1.

(9) The epoxy resins used are listed below.

(10) (Epoxy Resin)

(11) Bisphenol F-type epoxy resin (jER 807 available from Mitsubishi Chemical Corporation, epoxy equivalent: 170) Neopentyl glycol diglycidyl ether (epoxy equivalent: 138, molecular weight: 216) Polypropylene glycol diglycidyl ether (EX-920 available from Nagase ChemteX Corporation, epoxy equivalent: 176)

Example 9

(12) An amount of 200 g of polyvinyl alcohol was added to 1,800 g of pure water, and stirred at 90° C. for about two hours to be dissolved. The solution was cooled to 40° C., and to the solution were added 150 g of hydrochloric acid having a concentration of 35% by weight and 75 g of acetaldehyde. The acetalization reaction was carried out to precipitate a reaction product by maintaining the solution temperature at 40° C.

(13) The polyvinyl alcohol used had a degree of polymerization of 400, a degree of saponification of 97.7 mol %, and contained 2.0 mol % of a constitutional unit with a carboxyl group represented by the above formula (1-4) (in the formula (1-4), R.sup.6 represents a single bond, X.sup.6 represents a hydrogen atom, R.sup.7 represents a methylene group, and X.sup.7 represents a hydrogen atom).

(14) Then, the reaction solution was held to maintain the temperature at 40° C. for three hours, thereby completing the reaction. A modified polyvinyl acetal resin powder was obtained through neutralization, washing with water, and drying by normal methods.

(15) The obtained modified polyvinyl acetal resin was dissolved in DMSO-d.sub.6 (dimethylsuofoxide), and analyzed by .sup.13C-NMR (nuclear magnetic resonance spectrum) to confirm the presence of the constitutional unit with a carboxyl group represented by the formula (1-4) (amount: 2.0 mol %).

(16) An adhesive composition and a resin sheet were produced as in Example 1, except that the obtained modified polyvinyl acetal resin was used, and that the epoxy resin, the curing agent, and the curing accelerator were added as shown in Table 1.

Example 10

(17) An adhesive composition and a resin sheet were produced as in Example 1, except that the modified polyvinyl acetal resin obtained in Example 9 was used, and that the epoxy resin, the curing agent, and the curing accelerator were added as shown in Table 1.

Example 11

(18) An amount of 200 g of polyvinyl alcohol was added to 1,800 g of pure water, and stirred at 90° C. for about two hours to be dissolved. The solution was cooled to 40° C., and to the solution were added 150 g of hydrochloric acid having a concentration of 35% by weight and 75 g of acetaldehyde. The acetalization reaction was carried out to precipitate a reaction product by maintaining the solution temperature at 40° C.

(19) The polyvinyl alcohol used had a degree of polymerization of 1,000, a degree of saponification of 97.6 mol %, and contained 0.4 mol % of a constitutional unit with a carboxyl group represented by the above formula (1-4) (in the formula (1-4), R.sup.6 represents a single bond, X.sup.6 represents a hydrogen atom, R.sup.7 represents a methylene group, and X.sup.7 represents a hydrogen atom).

(20) Then, the reaction solution was held to maintain the temperature at 40° C. for three hours, thereby completing the reaction. A modified polyvinyl acetal resin powder was obtained through neutralization, washing with water, and drying by normal methods.

(21) The obtained modified polyvinyl acetal resin was dissolved in DMSO-d.sub.6 (dimethylsulfoxide), and analyzed by .sup.13C-NMR (nuclear magnetic resonance spectrum) to confirm the presence of the constitutional unit with a carboxyl group represented by the above formula (1-4) (amount: 0.4 mol %).

(22) An adhesive composition and a resin sheet were produced as in Example 1, except that the obtained modified polyvinyl acetal resin was used, and that the epoxy resin, the curing agent, and the curing accelerator were added as shown in Table 1.

Example 12

(23) An adhesive composition and a resin sheet were produced as in Example 1, except that the modified polyvinyl acetal resin obtained in Example 11 was used, and that the epoxy resin, the curing agent, and the curing accelerator were added as shown in Table 1.

Example 13

(24) An amount of 200 g of polyvinyl alcohol was added to 1,800 g of pure water, and stirred at 90° C. for about two hours to be dissolved. The solution was cooled to 40° C., and to the solution were added 150 g of hydrochloric acid having a concentration of 35% by weight and 75 g of acetaldehyde. The acetalization reaction was carried out to precipitate a reaction product by maintaining the solution temperature at 40° C.

(25) The polyvinyl alcohol used had a degree of polymerization of 1,700, a degree of saponification of 97.7 mol %, and contained 0.4 mol % of a constitutional unit with a carboxyl group represented by the above formula (1-4) (in the formula (1-4), R.sup.6 represents a single bond, X.sup.6 represents a hydrogen atom, R.sup.7 represents a methylene group, and X.sup.7 represents a hydrogen atom).

(26) Then, the reaction solution was held to maintain the temperature at 40° C. for three hours, thereby completing the reaction. A modified polyvinyl acetal resin powder was obtained through neutralization, washing with water, and drying by normal methods.

(27) The obtained modified polyvinyl acetal resin was dissolved in DMSO-d.sub.6 (dimethylsulfoxide), and analyzed by .sup.13C-NMR (nuclear magnetic resonance spectrum) to confirm the presence of a constitutional unit with a carboxyl group represented by the formula (1-4) (amount: 0.4 mol %).

(28) An adhesive composition and a resin sheet were produced as in Example 1, except that the obtained modified polyvinyl acetal resin was used, and that the epoxy resin, the curing agent, and the curing accelerator were added as shown in Table 1.

Example 14

(29) An adhesive composition and a resin sheet were produced as in Example 1, except that the modified polyvinyl acetal resin obtained in Example 13 was used, and that the epoxy resin, the curing agent, and the curing accelerator were added as shown in Table 1.

Examples 15 to 17

(30) Using the modified polyvinyl acetal resin obtained in Example 1, an adhesive composition and a resin sheet were produced as in Example 1, except that the epoxy resin, the curing agent, and the curing accelerator were added as shown in Table 1.

Example 18

(31) An amount of 200 g of polyvinyl alcohol was added to 1,800 g of pure water, and stirred at 90° C. for about two hours to be dissolved. The solution was cooled to 40° C., and to the solution were added 150 g of hydrochloric acid having a concentration of 35% by weight and 75 g of formaldehyde. The acetalization reaction was carried out to precipitate a reaction product by maintaining the solution temperature at 40° C.

(32) The polyvinyl alcohol used was the same as that used in Example 1.

(33) Then, the reaction solution was held to maintain the temperature at 40° C. for three hours, thereby completing the reaction. A modified polyvinyl acetal resin powder was obtained through neutralization, washing with water, and drying by normal methods.

(34) The obtained modified polyvinyl acetal resin was dissolved in DMSO-d.sub.6 (dimethylsulfoxide), and analyzed by .sup.13C-NMR (nuclear magnetic resonance spectrum) to confirm the presence of the constitutional unit with a carboxyl group represented by the above formula (1-4) (amount: 0.4 mol %).

(35) An adhesive composition and a resin sheet were produced as in Example 1, except that the obtained modified polyvinyl acetal resin was used, and that the epoxy resin, the curing agent, and the curing accelerator were added as shown in Table 1.

Example 19

(36) An amount of 200 g of polyvinyl alcohol was added to 1,800 g of pure water, and stirred at 90° C. for about two hours to be dissolved. The solution was cooled to 40° C., and to the solution were added 150 g of hydrochloric acid having a concentration of 35% by weight and 150 g of n-butyraldehyde. The acetalization reaction was carried out to precipitate a reaction product by maintaining the solution temperature at 40° C.

(37) The polyvinyl alcohol used had a degree of polymerization of 400 and a degree of saponification of 97.7 mol %, and contained 0.4 mol % of a constitutional unit with a carboxyl group represented by the above formula (1-4) (in the formula (1-4), R.sup.6 represents a single bond, X.sup.6 represents a hydrogen atom, R.sup.7 represents a vinylene group, and X.sup.7 represents a hydrogen atom).

(38) Then, the reaction solution was held to maintain the temperature at 40° C. for three hours, thereby completing the reaction. A modified polyvinyl acetal resin powder was obtained through neutralization, washing with water, and drying by normal methods.

(39) The obtained modified polyvinyl acetal resin was dissolved in DMSO-d.sub.6 (dimethylsulfoxide), and analyzed by .sup.13C-NMR (nuclear magnetic resonance spectrum) to confirm the presence of a constitutional unit with a carboxyl group represented by the above formula (1-4) (amount: 0.4 mol %).

(40) An adhesive composition and a resin sheet were produced as in Example 1, except that the obtained modified polyvinyl acetal resin was used, and that the epoxy resin, the curing agent, and the curing accelerator were added as shown in Table 1.

Example 20

(41) An amount of 200 g of polyvinyl alcohol was added to 1,800 g of pure water, and stirred at 90° C. for about two hours to be dissolved. The solution was cooled to 40° C., and to the solution were added 150 g of hydrochloric acid having a concentration of 35% by weight and 150 g of n-butyraldehyde. The acetalization reaction was carried out to precipitate a reaction product by maintaining the solution temperature at 40° C.

(42) The polyvinyl alcohol used had a degree of polymerization of 400 and a degree of saponification of 97.7 mol %, and contained 2.0 mol % of a constitutional unit with a carboxyl group represented by the above formula (1-4) (in the formula (1-4), R.sup.6 represents a single bond, X.sup.6 represents a hydrogen atom, R.sup.7 represents a vinylene group, and X.sup.7 represents a hydrogen atom).

(43) Then the reaction solution was held to maintain the temperature at 40° C. for three hours, thereby completing the reaction. A modified polyvinyl acetal resin powder was obtained through neutralization, washing with water, and drying by normal methods.

(44) The obtained modified polyvinyl acetal resin was dissolved in DMSO-d.sub.6 (dimethylsulfoxide), and analyzed by .sup.13C-NMR (nuclear magnetic resonance spectrum) to confirm the presence of the constitutional unit with a carboxyl group represented by the above formula (1-4) (amount: 2.0 mol %).

(45) An adhesive composition and a resin sheet were produced as in Example 1, except that the obtained modified polyvinyl acetal resin was used, and that the epoxy resin, the curing agent, and the curing accelerator were added as shown in Table 1.

Example 21

(46) An amount of 200 g of polyvinyl alcohol was added to 1,800 g of pure water, and stirred at 90° C. for about two hours to be dissolved. The solution was cooled to 40° C., and to the solution were added 150 g of hydrochloric acid having a concentration of 35% by weight and 150 g of n-butyraldehyde. The acetalization reaction was carried out to precipitate a reaction product by maintaining the solution temperature at 40° C.

(47) The polyvinyl alcohol used had a degree of polymerization of 400 and a degree of saponification of 97.7 mol %, and contained 5.0 mol % of a constitutional unit with a carboxyl group represented by the above formula (1-4) (in the formula (1-4), R.sup.6 represents a single bond, X.sup.6 represents a hydrogen atom, R.sup.7 represents a vinylene group, and X.sup.7 represents a hydrogen atom).

(48) Then, the reaction solution was held to maintain the temperature at 40° C. for three hours, thereby completing the reaction. A modified polyvinyl acetal resin powder was obtained through neutralization, washing with water, and drying by normal methods.

(49) The obtained modified polyvinyl acetal resin was dissolved in DMSO-d.sub.6 (dimethylsulfoxide), and analyzed by .sup.13C-NMR (nuclear magnetic resonance spectrum) to confirm the presence of a constitutional unit with a carboxyl group represented by the formula (1-4) (amount: 5.0 mol %).

(50) An adhesive composition and a resin sheet were produced as in Example 1, except that the obtained modified polyvinyl acetal resin was used, and that the epoxy resin, the curing agent, and the curing accelerator were added as shown in Table 1.

Examples 22 and 23

(51) An adhesive composition and a resin sheet were produced as in Example 1, except that the modified polyvinyl acetal resin obtained in Example 19 was used, and that the epoxy resin, the curing agent, and the curing accelerator were added as shown in Table 1.

Example 24

(52) An amount of 200 g of polyvinyl alcohol was added to 1,800 g of pure water, and stirred at 90° C. for about two hours to be dissolved. The solution was cooled to 40° C., and to the solution were added 150 g of hydrochloric acid having a concentration of 35% by weight and 145 g of n-butyraldehyde. The acetalization reaction was carried out to precipitate a reaction product by maintaining the solution temperature at 40° C.

(53) The polyvinyl alcohol used had a degree of polymerization of 1,700 and a degree of saponification of 97.7 mol %, and contained 0.4 mol % of a constitutional unit with a carboxyl group represented by the above formula (1-4) (in the formula (1-4), R.sup.6 represents a single bond, X.sup.6 represents a hydrogen atom, R.sup.7 represents a vinylene group, and X.sup.7 represents a hydrogen atom).

(54) Then, the reaction solution was held to maintain the temperature at 40° C. for three hours, thereby completing the reaction. A modified polyvinyl acetal resin powder was obtained through neutralization, washing with water, and drying by normal methods.

(55) The obtained modified polyvinyl acetal resin was dissolved in DMSO-d.sub.6 (dimethylsulfoxide), and analyzed by .sup.13C-NMR (nuclear magnetic resonance spectrum) to confirm the presence of a constitutional unit with a carboxyl group represented by the above formula (1-4) (amount: 0.4 mol %).

(56) An adhesive composition and a resin sheet were produced as in Example 1, except that the obtained modified polyvinyl acetal resin was used, and that the epoxy resin, the curing agent, and the curing accelerator were added as shown in Table 1.

Example 25

(57) An amount of 200 g of polyvinyl alcohol was added to 1,800 g of pure water, and stirred at 90° C. for about two hours to be dissolved. The solution was cooled to 40° C., and to the solution were added 150 g of hydrochloric acid having a concentration of 35% by weight and 140 g of n-butyraldehyde. The acetalization reaction was carried out to precipitate a reaction product by maintaining the solution temperature at 40° C.

(58) The polyvinyl alcohol used was the same as that used in Example 24.

(59) Then, the reaction solution was held to maintain the temperature at 40° C. for three hours, thereby completing the reaction. A modified polyvinyl acetal resin powder was obtained through neutralization, washing with water, and drying by normal methods.

(60) The obtained modified polyvinyl acetal resin was dissolved in DMSO-d.sub.6 (dimethylsulfoxide), and analyzed by .sup.13C-NMR (nuclear magnetic resonance spectrum) to confirm the presence of a constitutional unit with a carboxyl group represented by the above formula (1-4) (amount: 0.4 mol %).

(61) An adhesive composition and a resin sheet were produced as in Example 1, except that the obtained modified polyvinyl acetal resin was used, and that the epoxy resin, the curing agent, and the curing accelerator were added as shown in Table 1.

Example 26

(62) An amount of 200 g of polyvinyl alcohol was added to 1,800 g of pure water, and stirred at 90° C. for about two hours to be dissolved. The solution was cooled to 40° C., and to the solution were added 150 g of hydrochloric acid having a concentration of 35% by weight and 155 g of n-butyraldehyde. The acetalization reaction was carried out to precipitate a reaction product by maintaining the solution temperature at 40° C.

(63) The polyvinyl alcohol used was the same as that used in Example 1.

(64) Then, the reaction solution was held to maintain the temperature at 40° C. for three hours, thereby completing the reaction. A modified polyvinyl acetal resin powder was obtained through neutralization, washing with water, and drying by normal methods.

(65) The obtained modified polyvinyl acetal resin was dissolved in DMSO-d.sub.6 (dimethylsulfoxide), and analyzed by .sup.13C-NMR (nuclear magnetic resonance spectrum) to confirm the presence of a constitutional unit with a carboxyl group represented by the above formula (1-4) (amount: 0.4 mol %).

(66) An adhesive composition and a resin sheet were produced as in Example 1, except that the obtained modified polyvinyl acetal resin was used, and that the epoxy resin, the curing agent, and the curing accelerator were added as shown in Table 1.

Example 27

(67) An adhesive composition and a resin sheet were produced as in Example 1, except that the modified polyvinyl acetal resin obtained in Example 21 was used, and that the epoxy resin, the curing agent, and the curing accelerator were added as shown in Table 1.

Example 28

(68) Using the polyvinyl acetal resin obtained in Example 1, an adhesive composition and a resin sheet were produced as in Example 1, except that the epoxy resin, the curing agent, and the curing accelerator were added as shown in Table 1.

Example 29

(69) An amount of 200 g of polyvinyl alcohol was added to 1,800 g of pure water, and stirred at 90° C. for about two hours to be dissolved. The solution was cooled to 40° C., and to the solution were added 150 g of hydrochloric acid having a concentration of 35% by weight, 50 g of acetaldehyde, and 50 g of butyraldehyde. The acetalization reaction was carried out to precipitate a reaction product by maintaining the solution temperature at 40° C.

(70) The polyvinyl alcohol used had a degree of polymerization of 800 and a degree of saponification of 97.7 mol %, and contained 2.0 mol % of a constitutional unit with a carboxyl group represented by the above formula (1-4) (in the formula (1-4), R.sup.6 represents a single bond, X.sup.6 represents a hydrogen atom, R.sup.7 represents a methylene group, and X.sup.7 represents a hydrogen atom).

(71) Then, the reaction solution was held to maintain the temperature at 40° C. for three hours, thereby completing the reaction. A modified polyvinyl acetal resin powder was obtained through neutralization, washing with water, and drying by normal methods.

(72) The obtained modified polyvinyl acetal resin was dissolved in DMSO-d.sub.6 (dimethylsulfoxide), and analyzed by .sup.13C-NMR (nuclear magnetic resonance spectrum) to confirm the presence of the constitutional unit with a carboxyl group represented by the formula (1-4) (amount: 2.0 mol %).

(73) An adhesive composition and a resin sheet were produced as in Example 1, except that the obtained modified polyvinyl acetal resin was used, and that the epoxy resin, the curing agent, and the curing accelerator were added as shown in Table 1.

Example 30

(74) An amount of 200 g of polyvinyl alcohol was added to 1,800 g of pure water, and stirred at 90° C. for about two hours to be dissolved. The solution was cooled to 40° C., and to the solution were added 150 g of hydrochloric acid having a concentration of 35% by weight and 75 g of acetaldehyde. The acetalization reaction was carried out to precipitate a reaction product by maintaining the solution temperature at 40° C.

(75) The polyvinyl alcohol used was the same as that used in Example 29.

(76) Then, the reaction solution was held to maintain the temperature at 40° C. for three hours, thereby completing the reaction. A modified polyvinyl acetal resin powder was obtained through neutralization, washing with water, and drying by normal methods.

(77) The obtained modified polyvinyl acetal resin was dissolved in DMSO-d.sub.6 (dimethylsulfoxide), and analyzed by .sup.13C-NMR (nuclear magnetic resonance spectrum) to confirm the presence of the constitutional unit with a carboxyl group represented by the above formula (1-4) (amount: 2.0 mol %).

(78) An adhesive composition and a resin sheet were produced as in Example 1, except that the obtained modified polyvinyl acetal resin was used, and that the epoxy resin, the curing agent, and the curing accelerator were added as shown in Table 1.

Example 31

(79) An amount of 200 g of polyvinyl alcohol was added to 1,800 g of pure water, and stirred at 90° C. for about two hours to be dissolved. The solution was cooled to 40° C., and to the solution were added 150 g of hydrochloric acid having a concentration of 35% by weight and 75 g of acetaldehyde. The acetalization reaction was carried out to precipitate a reaction product by maintaining the solution temperature at 40° C.

(80) The polyvinyl alcohol used had a degree of polymerization of 800 and a degree of saponification of 97.7 mol %, and contained 2.0 mol % of a constitutional unit with a carboxyl group represented by the above formula (1-2) (in the formula (1-2), R.sup.2 represents a single bond, X.sup.2 represents a hydrogen atom, R.sup.3 represents a single bond, and X.sup.3 represents a hydrogen atom).

(81) Then, the reaction solution was held to maintain the temperature at 40° C. for three hours, thereby completing the reaction. A modified polyvinyl acetal resin powder was obtained through neutralization, washing with water, and drying by normal methods.

(82) The obtained modified polyvinyl acetal resin was dissolved in DMSO-d.sub.6 (dimethylsulfoxide), and analyzed by .sup.13C-NMR (nuclear magnetic resonance spectrum) to confirm the presence of a constitutional unit with a carboxyl group represented by the formula (1-2) (amount: 2.0 mol %).

(83) An adhesive composition and a resin sheet were produced as in Example 1, except that the obtained modified polyvinyl acetal resin was used, and that the epoxy resin, the curing agent, and the curing accelerator were added as shown in Table 1.

Example 32

(84) An amount of 200 g of polyvinyl alcohol was dissolved in 1,800 g of pure water, and stirred at 90° C. for about two hours to be dissolved. The solution was cooled to 40° C., and to the solution were added 150 g of hydrochloric acid having a concentration of 35% by weight and 75 g of acetaldehyde. The acetalization reaction was carried out to precipitate a reaction product by maintaining the solution temperature at 40° C.

(85) The polyvinyl alcohol used had a degree of polymerization of 800 and a degree of saponification of 97.7 mol %, and contained 2.0 mol % of a constitutional unit with a carboxyl group represented by the above formula (1-3) (in the formula (1-3), R.sup.4 represents a single bond, X.sup.4 represents a hydrogen atom, R.sup.5 represents a single bond, and X.sup.5 represents a hydrogen atom).

(86) Then, the reaction solution was held to maintain the temperature at 40° C. for three hours, thereby completing the reaction. A modified polyvinyl acetal resin powder was obtained through neutralization, washing with water, and drying by normal methods.

(87) The obtained modified polyvinyl acetal resin was dissolved in DMSO-d.sub.6 (dimethylsulfoxide), and analyzed by .sup.13C-NMR (nuclear magnetic resonance spectrum) to confirm the presence of a constitutional unit with a carboxyl group represented by the formula (1-3) (amount: 2.0 mol %).

(88) An adhesive composition and a resin sheet were produced as in Example 1, except that the obtained modified polyvinyl acetal resin was used, and that the epoxy resin, the curing agent, and the curing accelerator were added as shown in Table 1.

Example 33

(89) An amount of 200 g of polyvinyl alcohol was added to 1,800 g of pure water, and stirred at 90° C. for about two hours. The solution was cooled to 40° C., and to the solution were added 150 g of hydrochloric acid having a concentration of 35% by weight and 75 g of acetaldehyde. The acetalization reaction was carried out to precipitate a reaction product by maintaining the solution temperature at 40° C.

(90) The polyvinyl alcohol used had a degree of polymerization of 800 and a degree of saponification of 97.7 mol %, and contained 2.0 mol % of a constitutional unit with a carboxyl group represented by the above formula (1-1) (in the formula (1-1), R.sup.1 represents a methylene group, X.sup.1 represents a hydrogen atom).

(91) Then, the reaction solution was held to maintain the temperature at 40° C. for three hours, thereby completing the reaction. A modified polyvinyl acetal resin powder was obtained through neutralization, washing with water, and drying by normal methods.

(92) The obtained modified polyvinyl acetal resin was dissolved in DMSO-d.sub.6 (dimethylsulfoxide), and analyzed by .sup.13C-NMR (nuclear magnetic resonance spectrum) to confirm the presence of a constitutional unit with a carboxyl group represented by the formula (1-1) (amount: 2.0 mol %).

(93) An adhesive composition and a resin sheet were produced as in Example 1, except that the obtained modified polyvinyl acetal resin was used, and that the epoxy resin, the curing agent, and the curing accelerator were added as shown in Table 1.

Comparative Example 1

(94) A polyvinyl acetal resin was obtained as in Example 1, except that the polyvinyl alcohol used had a degree of polymerization of 600 and a degree of saponification of 99.5 mol %.

(95) The obtained polyvinyl acetal resin was dissolved in DMSO-d.sub.6 (dimethylsulfoxide), and analyzed by .sup.13C-NMR (nuclear magnetic resonance spectrum). The presence of a constitutional unit with an acid-modified group was not confirmed.

(96) Table 1 shows the acetal group content, the acetyl group content, and the hydroxyl group content measured by .sup.13C-NMR.

(97) An adhesive composition and a resin sheet were produced as in Example 1, except that 30 g of the obtained polyvinyl acetal resin and 70 g of neopentyl glycol diglycidyl ether were blended to prepare an adhesive composition in which the polyvinyl acetal resin and the epoxy resin are mixed at a weight ratio of 30:70.

Comparative Examples 2 to 3

(98) An adhesive composition and a resin sheet were produced as in Example 1, except that the modified polyvinyl acetal resin obtained in Comparative Example 1 was used, and that the epoxy resin, the curing agent, and the curing accelerator were added as shown in Table 1.

Comparative Example 4

(99) A polyvinyl acetal resin was obtained as in Example 1, except that the polyvinyl alcohol used had a degree of polymerization of 400 and a degree of saponification of 97.7 mol %.

(100) The obtained polyvinyl acetal resin was dissolved in DMSO-d.sub.6 (dimethylsulfoxide), and analyzed by .sup.13C-NMR (nuclear magnetic resonance spectrum). The presence of a constitutional unit with an acid-modified group was not confirmed.

(101) Table 1 shows the acetal group content, the acetyl group content, and the hydroxyl group content measured by .sup.13C-NMR.

(102) An adhesive composition and a resin sheet were produced as in Example 1, except that the obtained modified polyvinyl acetal resin was used, and that the epoxy resin, the curing agent, and the curing accelerator were added as shown in Table 1.

(103) <Evaluation>

(104) The adhesive compositions and resin sheets obtained in the examples and comparative examples were evaluated for the followings. Table 2 shows the results.

(105) (1) Gel Fraction

(106) To about 0.1 g (w1) of a sample of the resin sheet was added 40 g of a solvent mixture prepared by mixing toluene and ethanol at a weight ratio of 1:1, and the mixture was stirred for 24 hours so that the sample was dissolved again. Then, solid-liquid separation was performed using a 200-mesh stainless-steel sieve whose mass (w2) was measured in advance. The stainless-steel sieve was taken out and vacuum-dried at 100° C. for one hour, followed by measurement of the mass (w3) thereof. The gel fraction was calculated using the following equation.
Gel fraction (%)={(w3−w2)/w1}×100

(107) The obtained gel fraction was evaluated based on the following criteria.

(108) A higher gel fraction indicates higher curability.

(109) ∘∘ (Excellent): 80% or higher

(110) ∘ (Good): 40% or higher and lower than 80%

(111) Δ (Average): 10% or higher and lower than 40%

(112) x (Poor): Lower than 10%

(113) (2) Storage Stability

(114) An amount of 10 g of the adhesive composition was dissolved in 90 g of a solvent mixture prepared by mixing toluene and ethanol at a weight ratio of 1:1, thereby preparing a sample solution. The viscosity of the obtained sample solution was measured immediately after the preparation of the sample solution and a month later using a B-type viscometer to obtain the change rate of the solution viscosity. The obtained change rate was evaluated based on the following criteria.

(115) ∘∘ (Excellent): Lower than 10%

(116) ∘ (Good): 10% or higher and lower than 20%

(117) Δ (Average): 20% or higher and lower than 30%

(118) x (Poor): 30% or higher

(119) (3) Tensile Modulus of Elasticity, Degree of Elongation, Yield Point Stress

(120) The obtained resin sheet was peeled from the PET film, and the tensile modulus of elasticity (MPa), degree of elongation (%), and yield point stress (MPa) of the peeled sheet were measured at a tensile speed of 20 ram/min by a method in conformity with JIS K 7113 using an autograph (AGS-J available from Shimadzu Corporation).

(121) (4) Shear Adhesive Force

(122) The obtained adhesive composition was applied to various metal bases, and heated at 170° C. for 30 minutes to be cured. The shear adhesive force thereof was measured under the conditions of a temperature of 20° C. and a tensile speed of 5 ram/min by a method in conformity with JIS K 6850.

(123) The metal bases used were an aluminum base, a stainless steel (SUS304) base, and a SPCC steel plate. With a higher shear adhesive force, peeling is less likely to occur even under application of an external force, which indicates that the excellent adhesive force is achieved.

(124) (5) Peel Adhesive Force

(125) The obtained adhesive composition was applied to a SPCC steel plate to bond two SPCC steel plates to each other, and heated at 170° C. for 30 minutes to be cured. The peel adhesive force thereof was measured under the conditions of a peel angle of 180° and a peel rate of 200 mm/min by a method in conformity with JIS K 6854-3.

(126) (6) Impact Resistance

(127) The obtained adhesive composition was poured into a mold and heated at 170° C. for 30 minutes to provide a cured resin article. A Charpy impact test was performed on the obtained cured resin article by a method in conformity with JIS K 7111 using a digital impact tester DG-UB type (available from Toyo Seiki Seisakusho, Ltd.) to measure the Charpy impact value when the cured resin article is broken, thereby evaluating the impact resistance.

(128) (7) Compatibility

(129) In each of the examples and comparative examples, a mixture of a polyvinyl acetal resin and an epoxy resin was prepared without adding a curing agent and a curing accelerator. The haze value of the obtained mixture was measured using a spectrophotometer (U4000 available from Hitachi, Ltd.).

(130) TABLE-US-00001 TABLE 1 Polyvinyl acetal resin Adhesive composition Ratio between Amount of Amount of Acetoacetal Butyral Formal acetoacetal Acetyl Hydroxyl constitutional added group group group group content group group unit with acid- polyvinyl Degree of content content content and butyral content content modified group acetal resin polymerization (mol %) (mol %) (mol %) group content (mol %) (mol %) (mol %) (g) Example 1 400 71.6 — — 10:0 2.3 25.7 0.4 10 Example 2 400 71.6 — — 10:0 2.3 25.7 0.4 10 Example 3 400 71.6 — — 10:0 2.3 25.7 0.4 10 Example 4 400 71.6 — — 10:0 2.3 25.7 0.4 10 Example 5 400 71.6 — — 10:0 2.3 25.7 0.4 10 Example 6 400 71.6 — — 10:0 2.3 25.7 0.4 10 Example 7 400 71.6 — — 10:0 2.3 25.7 0.4 10 Example 8 400 71.6 — — 10:0 2.3 25.7 0.4 10 Example 9 400 70.0 — — 10:0 2.3 25.7 2.0 10 Example 10 400 70.0 — — 10:0 2.3 25.7 2.0 10 Example 11 1000 71.6 — — 10:0 2.3 25.7 0.4 10 Example 12 1000 71.6 — — 10:0 2.3 25.7 0.4 10 Example 13 1700 71.6 — — 10:0 2.3 25.7 0.4 10 Example 14 1700 71.6 — — 10:0 2.3 25.7 0.4 10 Example 15 400 71.6 — — 10:0 2.3 25.7 0.4 20 Example 16 400 71.6 — — 10:0 2.3 25.7 0.4 20 Example 17 400 71.6 — — 10:0 2.3 25.7 0.4 50 Example 18 400 — — 71.6 — 2.3 25.7 0.4 50 Example 19 400 — 71.6 —  0:10 2.3 25.7 0.4 10 Example 20 400 — 70.0 —  0:10 2.3 25.7 2.0 10 Example 21 400 — 67.0 —  0:10 2.3 25.7 5.0 10 Example 22 400 — 71.6 —  0:10 2.3 25.7 0.4 20 Example 23 400 — 71.6 —  0:10 2.3 25.7 0.4 30 Example 24 1700 — 67.5 —  0:10 2.3 29.8 0.4 10 Example 25 1700 — 62.3 —  0:10 2.3 35.0 0.4 10 Example 26 400 — 76.0 —  0:10 2.3 21.3 0.4 10 Example 27 400 — 67.0 —  0:10 2.3 25.7 5.0 50 Example 28 400 71.6 — — 10:0 2.3 25.7 0.4 50 Example 29 800 42.0 28.0 —  6:4 2.3 25.7 2.0 10 Example 30 800 70.0 — — 10:0 2.3 25.7 2.0 10 Example 31 800 70.0 — — 10:0 2.3 25.7 2.0 10 Example 32 800 70.0 — — 10:0 2.3 25.7 2.0 10 Example 33 800 70.0 — — 10:0 2.3 25.7 2.0 10 Comparative 600 79.0 — — 10:0 0.5 20.5 0.0 30 Example 1 Comparative 600 79.0 — — 10:0 0.5 20.5 0.0 10 Example 2 Comparative 600 79.0 — — 10:0 0.5 20.5 0.0 10 Example 3 Comparative 400 58.0 — — 10:0 2.3 39.7 0.0 10 Example 4 Adhesive composition Epoxy resin (g) Curing Neopentyl Polypropylene Curing accelerator Number of Bisphenol Bisphenol glycol glycol agent (g) acid-modified A-type F-type diglycidyl diglycidyl (g) Imidazole groups/number epoxy resin epoxy resin ether ether Dicyandiamide compound of epoxy groups Example 1 85 — — — 3 2 0.00154 Example 2 — 85 — — 3 2 0.00138 Example 3 — — 85 — 3 2 0.00112 Example 4 — — — 85 3 2 0.00143 Example 5 75 — — 10 3 2 0.00153 Example 6 — 75 — 10 3 2 0.00138 Example 7 75 — 10 — 3 2 0.00148 Example 8 — 75 10 — 3 2 0.00134 Example 9 75 — — 10 3 2 0.00764 Example 10 — 75 — 10 3 2 0.00692 Example 11 75 — — 10 3 2 0.00153 Example 12 — 75 — 10 3 2 0.00138 Example 13 75 — — 10 3 2 0.00153 Example 14 — 75 — 10 3 2 0.00138 Example 15 — 55 — 20 3 2 0.00315 Example 16 55 — — 20 3 2 0.00342 Example 17 25 — — 20 3 2 0.01410 Example 18 45 — — — 3 2 0.01460 Example 19 75 — — 10 3 2 0.00153 Example 20 75 — — 10 3 2 0.00764 Example 21 75 — — 10 3 2 0.01910 Example 22 75 — — 10 3 2 0.00305 Example 23 75 — — 10 3 2 0.00458 Example 24 75 — — 10 3 2 0.00153 Example 25 75 — — 10 3 2 0.00153 Example 26 75 — — 10 3 2 0.00153 Example 27 55 — — — 3 2 0.14890 Example 28 75 — — 10 3 2 0.00764 Example 29 75 — — 10 3 2 0.00764 Example 30 75 — — 10 3 2 0.00764 Example 31 75 — — 10 3 2 0.00764 Example 32 75 — — 10 3 2 0.00764 Example 33 75 — — 10 3 2 0.00764 Comparative — — 70 — — — — Example 1 Comparative 75 — — 10 3 2 — Example 2 Comparative — 75 — 10 3 2 — Example 3 Comparative 75 — — 10 3 2 — Example 4

(131) TABLE-US-00002 TABLE 2 Evaluation Composition strength Shear adhesive force Impact Tensile Yield (Mpa) resistance Gel Storage modulus of Degree of point SPCC Peel adhesive Charpy Compatibility fraction stability elasticity elongation stress SUS steel force impact value Haze Evaluation Evaluation (Mpa) (%) (Mpa) Aluminum 304 plate (N/25 mm) (J/m.sup.2) (%) Example 1 ◯ ◯ 900 45 65 20 24.2 31.4 145 1.7 7.5 Example 2 ◯ ◯ 920 50 60 19.6 21.5 27.9 130 1.5 5.0 Example 3 ◯ ◯◯ 700 60 60 2.8 3.4 3.9 80 2.2 0.8 Example 4 ◯ ◯ 720 60 60 2.1 3.2 3.8 75 1.9 2.0 Example 5 ◯◯ ◯ 1200 40 90 18.4 21.6 28.7 230 3.9 0.9 Example 6 ◯◯ ◯ 1350 30 75 16.5 19.6 25.2 210 3.6 1.5 Example 7 ◯◯ ◯ 1300 30 50 17.7 20.2 26.1 225 3.5 1.0 Example 8 ◯◯ ◯ 1450 25 45 15.1 17.7 239 200 3.2 1.5 Example 9 ◯◯ ◯ 950 45 90 23.4 29.2 37.8 245 4.2 0.9 Example 10 ◯◯ ◯ 1000 45 90 22.5 28.1 35.6 225 4 2.7 Example 11 ◯◯ ◯ 850 50 75 23.8 32.4 39.1 240 4.1 1.5 Example 12 ◯◯ ◯ 900 45 75 22.9 30.5 38.2 215 4 4.0 Example 13 ◯ ◯ 750 65 90 26.2 35 42.2 245 4.4 3.5 Example 14 ◯◯ ◯ 1300 30 75 25.6 33.3 41 220 4.2 3.2 Example 15 ◯ ◯◯ 800 75 60 29.8 36.5 47.2 175 4.7 1.5 Example 16 ◯◯ ◯◯ 900 70 62 31.5 37.1 48.8 185 5 3.2 Example 17 ◯ ◯◯ 950 60 60 42.6 48.9 57.2 120 1.2 5.5 Example 18 ◯ ◯◯ 900 55 58 42.6 48.9 57.2 105 1.5 6.2 Example 19 ◯ ◯ 900 48 65 11.5 14.3 20 245 4.2 2.1 Example 20 ◯ ◯ 980 44 68 12.2 15.6 21.5 260 4.7 1.6 Example 21 ◯◯ ◯ 1020 41 70 15.8 19.5 25.7 270 5.4 1.4 Example 22 ◯◯ ◯ 830 52 61 13 16.2 22.2 265 5.1 2.8 Example 23 ◯◯ Δ 750 56 58 14.5 18.1 23.7 260 5.2 3.2 Example 24 ◯◯ Δ 950 47 66 11.8 15 20.4 250 4 2.4 Example 25 ◯◯ Δ 1050 46 67 12.1 15.3 20.9 265 3.8 2.6 Example 26 ◯ ◯ 870 51 63 11.1 13.7 19.9 245 4.4 2.2 Example 27 ◯◯ Δ 1120 38 70 6.2 11.8 16.2 150 2.4 10.5 Example 28 Δ Δ 700 68 55 7.5 12.9 17.3 125 2.2 17.8 Example 29 ◯ Δ 1260 34 56 16.4 21 27 110 2.5 2.8 Example 30 ◯◯ ◯◯ 900 52 65 27.9 35.7 42.5 255 4.8 3.2 Example 31 ◯◯ ◯ 1100 41 68 25.4 33.3 40.1 210 4 3.6 Example 32 ◯◯ Δ 1260 30 87 10.8 19.2 28.7 150 2.1 4.1 Example 33 ◯◯ Δ 1200 28 90 9.5 15.6 26 135 1.8 4.5 Comparative X ◯◯ 500 10 55 1.8 2.7 3.4 70 1.8 6.5 Example 1 Comparative X ◯◯ 1000 5 60 11.5 14.3 20 95 2.1 10.1 Example 2 Comparative X ◯◯ 1200 5 65 9.8 12.8 19.6 90 2 8.5 Example 3 Comparative ◯ X 1500 15 78 14.8 16.2 21.2 100 2.2 14.2 Example 4

INDUSTRIAL APPLICABILITY

(132) The present invention can provide an epoxy adhesive composition that is excellent in compatibility and storage stability, has high strength and excellent adhesiveness, is capable of reducing occurrence of warping or peeling when used for bonding different materials, and is also excellent in impact resistance after being cured.