Polyvinyl acetal resin composition, adhesive sheet, and method for producing adhesive sheet

Abstract

The present invention aims to provide a polyvinyl acetal resin composition that is moldable by an extrusion method and capable of exhibiting excellent heat resistance after molding, an adhesive sheet containing the polyvinyl acetal resin composition, and a method for producing the adhesive sheet. The present invention relates to a polyvinyl acetal resin composition including: a polyvinyl acetal; a reactive diluent; and a photopolymerization initiator, the polyvinyl acetal resin composition having a storage modulus G′ at 200° C. before irradiation with light of 8×10.sup.4 Pa or lower and a storage modulus G′ at 200° C. after irradiation with light of 8×10.sup.3 Pa or higher, with the storage modulus G′ at 200° C. after irradiation with light being higher than the storage modulus G′ at 200° C. before irradiation with light.

Claims

1. A polyvinyl acetal resin composition comprising: a polyvinyl acetal; a reactive diluent; and a photopolymerization initiator, the polyvinyl acetal resin composition having a storage modulus G′ at 200° C. before irradiation with light of 1.5×10.sup.2 Pa to 7.0×10.sup.4 Pa and a storage modulus G′ at 200° C. after irradiation with light of 9.1×10.sup.3 Pa to 1.2×10.sup.6 Pa, with the storage modulus G′ at 200° C. after irradiation with light being higher than the storage modulus G′ at 200° C. before irradiation with light.

2. The polyvinyl acetal resin composition according to claim 1, wherein the polyvinyl acetal resin composition has a capillary viscosity at 190° C. before irradiation with light of 7,000 Pa.Math.s or lower.

3. The polyvinyl acetal resin composition according to claim 1, wherein the polyvinyl acetal resin composition has a breaking strength at 85° C. of 0.3 MPa or higher.

4. The polyvinyl acetal resin composition according to claim 1, wherein the polyvinyl acetal is polyvinyl butyral.

5. The polyvinyl acetal resin composition according to claim 1, wherein the reactive diluent is a (meth)acrylic reactive diluent, an epoxy reactive diluent, or a silicone reactive diluent.

6. The polyvinyl acetal resin composition according to claim 1, wherein the amount of the reactive diluent is 0.1 to 30 parts by weight relative to 100 parts by weight of the polyvinyl acetal.

7. The polyvinyl acetal resin composition according to claim 1, further comprising a plasticizer.

8. The polyvinyl acetal resin composition according to claim 7, wherein the amount of the plasticizer is 1 to 30 parts by weight relative to 100 parts by weight of the polyvinyl acetal.

9. The polyvinyl acetal resin composition according to claim 8, wherein the amount of the plasticizer is 1 to 15 parts by weight relative to 100 parts by weight of the polyvinyl acetal.

10. An adhesive sheet comprising: the polyvinyl acetal resin composition according to claim 1.

Description

DESCRIPTION OF EMBODIMENTS

(1) Embodiments of the present invention will be specifically described in the following with reference to, but not limited to, the examples.

(2) <Preparation of Polyvinyl Butyral>

(3) A reactor equipped with a stirrer was charged with 2,700 mL of ion exchange water and 300 g of polyvinyl alcohol having an average degree of polymerization of 1,700 and a degree of saponification of 99.3 mol %, and the contents were heated with stirring to be dissolved, thereby preparing a solution. To the obtained solution was added as a catalyst 35% by weight hydrochloric acid such that the hydrochloric acid concentration was set to 0.2% by weight. The temperature of the mixture was adjusted to 15° C., and 21 g of n-butyraldehyde (n-BA) was added thereto with stirring. Then, 145 g of n-butyraldehyde (n-BA) was further added, so that a polyvinyl butyral resin in the form of white particles was precipitated. Fifteen minutes after the precipitation, 35% by weight hydrochloric acid was added such that the hydrochloric acid concentration was set to 1.8% by weight. The mixture was heated to 50° C. and aged at 50° C. for two hours. After cooling and neutralization of the solution, the polyvinyl butyral resin was washed with water and then dried, thereby preparing polyvinyl butyral 1 (PVB1).

(4) The obtained PVB1 had an average degree of polymerization of 1,700, a hydroxy group content of 31.3 mol %, an acetyl group content of 0.7 mol %, and a degree of butyralization (Bu degree) of 68.0 mol %.

(5) Each obtained polyvinyl butyral is shown in Table 1.

(6) Further, polyvinyl butyral 2 (PVB2) to polyvinyl butyral 5 (PVB5) were prepared by selecting the type of polyvinyl alcohol as a raw material and setting the conditions for butyralization.

(7) TABLE-US-00001 TABLE 1 PVB1 PVB2 PVB3 PVB4 PVB5 Hydroxy group content 31.3 31.3 31.3 31.3 31.3 (mol %) Butyralization degree 68.0 68.0 68.0 68.0 68.0 (mol %) Acetyl group content 0.7 0.7 0.7 0.7 0.7 (mol %) Average degree of 1700 2500 850 650 250 polymerization

Example 1

(8) To 100 parts by weight of PVB1 were added 0.2 parts by weight of trimethylolpropane triacrylate (TMPA) as a reactive diluent and 20 parts by weight of triethyleneglycol-di-2-ethylhexanoate (3GO) as a plasticizer. The mixture was sufficiently stirred, thereby obtaining a mixture composition. The mixture composition was sufficiently mixed with benzophenone (BP) as a photopolymerization initiator in an amount of 0.5 parts by weight relative to 100 parts by weight of the reactive diluent, thereby obtaining a polyvinyl butyral resin composition.

(9) The obtained polyvinyl butyral resin composition was pressed at 120° C. and 10 MPa on the mold release-treated side of a mold release polyethylene terephthalate (PET) film having a thickness of 50 μm to achieve a thickness of 800 μm, and further cooled at 20° C. and 10 MPa while being pressurized with a press machine. Thus, an evaluation sample with a mold release PET film attached to each surface was obtained.

(10) The obtained evaluation sample was irradiated with light having a wavelength of 365 nm at a dose of 4,000 mJ/cm.sup.2 using an ultra-high pressure mercury lamp.

(11) The storage moduli G′ at 200° C. of the evaluation sample before and after irradiation with light were measured using a dynamic viscoelastometer (DVA-200 available from IT Measurement Co., Ltd.) under the condition that the temperature was lowered from 200° C. to −50° C. at a temperature decreasing rate of 3° C./min and under the conditions of a frequency of 1 Hz and a strain of 1%.

(12) The capillary viscosity at 190° C. of the obtained polyvinyl butyral resin composition was measured by the method A2 specified in JIS K 7199 (1999) using a capillary rheometer (Toyo Seiki Seisaku-Sho, Ltd.). The shear rate was set at 10(1/s).

Examples 2 to 11 and Comparative Examples 1 to 5

(13) Polyvinyl butyral resin compositions were prepared in the same manner as in Example 1 except that their formulations were as shown in Tables 2 and 3. The storage moduli G′ at 200° C. before and after irradiation with light and the capillary viscosity at 190° C. were measured. In Tables 2 and 3, the number of parts of the photopolymerization initiator is a value relative to 100 parts by weight of the reactive diluent.

(14) (Evaluation)

(15) The polyvinyl butyral resin compositions obtained in the examples and comparative examples were evaluated by the following methods.

(16) Tables 2 and 3 show the results.

(17) (1) Evaluation of Extrusion Moldability

(18) A T-die was attached to a small extruder (Labo Plasto Mill, Toyo Seiki Seisaku-Sho, Ltd.). The obtained polyvinyl butyral resin composition was extruded into a film at an extrusion temperature of 80° C. to 190° C. and a die outlet temperature of 190° C., whereby the extrusion moldability was evaluated. The rating “o (Good)” was given when the composition was formed into a film, and the rating “x (Poor)” was given when the composition was difficult to form into a film.

(19) (2) Evaluation of Adhesiveness

(20) The obtained polyvinyl butyral resin composition was applied to the mold release-treated surface of a mold release polyethylene terephthalate (PET) film having a thickness of 50 μm to a thickness of 800 μm. On the obtained polyvinyl butyral resin composition layer was placed another mold release PET film in such a manner that the mold release-treated surface thereof was in contact with the polyvinyl butyral resin composition layer, thereby preparing a laminate. The resulting sheet was left to stand at 23° C. for five days to give an evaluation sample having a mold release PET film attached to each surface.

(21) The evaluation sample was cut to a size of 5 mm×100 mm and attached to glass. A plasma-treated polyethylene terephthalate (PET) film (25 mm×100 mm) was attached thereto, followed by vacuum lamination at 25° C. and then pressure bonding with heat in an autoclave at 75° C. and 0.5 MPa for 30 minutes. A laminate was thus prepared. The obtained laminate was subjected to 180° peel test at 300 ram/min in conformity with JIS K 6854:1994. The case where the peel strength was 5 N/25 mm or more was rated “o (Good)” and the case where the peel strength was less than 5 N/25 mm was rated “x (Poor)”.

(22) (3) Measurement of Breaking Strength

(23) The obtained polyvinyl butyral resin composition was applied to the mold release-treated surface of a mold release polyethylene terephthalate (PET) film with a thickness of 50 μm to a thickness of 0.2 mm. On the obtained polyvinyl butyral resin composition layer was placed another mold release PET film in such a manner that the mold release-treated surface thereof was in contact with the polyvinyl butyral resin composition layer, thereby preparing a laminate. The resulting sheet was left to stand at 23° C. for five days to give an evaluation sample having a mold release PET film attached to each surface.

(24) The obtained evaluation sample was irradiated with light having a wavelength of 365 nm at a dose of 5,000 mJ/cm.sup.2 using an ultra-high pressure mercury lamp.

(25) The evaluation sample was cut after irradiation with light to give a specimen (10 mm wide×about 100 mm long×about 0.2 mm thick).

(26) The breaking strength of each obtained specimen was measured in conformity with JIS K 7161:2014. Specifically, the specimen was held between chucks at an initial inter-chuck distance of 10 mm and put in a thermostatic bath at 85° C. After the temperature stabilized, the breaking strength was measured by pulling the specimen using a TENSILON RTC (Orientec Co., Ltd.) at a pulling speed of 50 mm/min.

(27) (4) Evaluation of Heat Resistance

(28) The obtained polyvinyl butyral resin composition was applied to the mold release-treated surface of a mold release polyethylene terephthalate (PET) film having a thickness of 50 μm to a thickness of 0.2 mm. On the obtained polyvinyl butyral resin composition layer was placed another mold release PET film in such a manner that the mold release-treated surface thereof was in contact with the polyvinyl butyral resin composition layer, thereby preparing a laminate. The resulting sheet was left to stand at 23° C. for five days to give an evaluation sample having a mold release PET film attached to each surface.

(29) A glass plate (100 mm×70 mm×2 mm thick) was bonded to a SUS plate (100 mm×70 mm×1 mm thick) with the evaluation sample interposed therebetween. The evaluation sample was irradiated from the glass plate side with light having a wavelength of 365 nm at a dose of 5,000 mJ/cm.sup.2 using an ultra-high pressure mercury lamp.

(30) Subsequently, the workpiece was hung in an oven at 85° C. with the SUS plate side fixed, and taken out after 24 hours. The misalignment between an edge of the SUS plate and an edge of the glass was visually checked. The rating “3 points” was given when the misalignment was 0.25 mm or less. The rating “2 points” was given when the misalignment was greater than 0.25 mm but not greater than 0.5 mm. The rating “1 point” was given when the misalignment was greater than 0.5 mm but not greater than 1 mm. The rating “0 point” was given when the misalignment was greater than 1 mm.

(31) TABLE-US-00002 TABLE 2 Ex- Ex- Ex- Ex- Ex- Ex- Ex- Ex- Ex- Ex- Ex- ample ample ample ample ample ample ample ample ample ample ample 1 2 3 4 5 6 7 8 9 10 11 Resin Type PVB1 PVB1 PVB1 PVB1 PVB1 PVB2 PVB3 PVB3 PVB4 PVB5 PVB3 Degree of 1700 1700 1700 1700 1700 2500 850 850 650 250 850 polymer- ization Number 100 100 100 100 100 100 100 100 100 100 100 of parts (parts by weight) Reactive Type TMPA TMPA TMPA TMPA TMPA TMPA TMPA TMPA TMPA TMPA TMPA diluent Number 0.2 4 30 30 30 3 8 4 4 15 30 of parts (parts by weight) Photo- Type BP BP BP BP BP BP BP BP BP BP BP polymer- Number 0.5 1 1 1 1 1 0.5 0.5 1 1 1 ization of parts initiator (parts by weight) Plasti- Type 3GO 3GO 3GO 3GO 3GO 3GO 3GO 3GO 3GO 3GO 3GO cizer Number 20 30 20 1 30 30 20 12.5 13 15 1 of parts (parts by weight) Storage Before 2.9 × 1.5 × 9.8 × 3.9 × 5.9 × 7.0 × 1.4 × 2.2 × 4.5 × 1.5 × 2.1 × modulus irradiation 10.sup.4 10.sup.4 10.sup.3 10.sup.4 10.sup.3 10.sup.4 10.sup.3 10.sup.3 10.sup.5 10.sup.5 10.sup.5 G′ with light (Pa) at After 6.1 × 1.3 × 7.9 × 1.2 × 7.7 × 1.8 × 8.9 × 1.1 × 9.3 × 9.1 × 8.5 × 200° C. irradiation 10.sup.4 10.sup.5 10.sup.5 10.sup.6 10.sup.5 10.sup.5 10.sup.4 10.sup.4 10.sup.3 10.sup.3 10.sup.5 with light Breaking 0.79 1.44 2.55 3.21 1.88 0.96 1.17 0.93 0.32 1.94 2.15 strength (MPa) Capillary viscosity 3700 1300 900 1500 650 6000 200 440 220 150 410 at 190° C. (Pa .Math. s) (before irradiation with light) Eval- Extrusion ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ uation mold- ability Adhesive- ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ness Heat 3 points 3 points 3 points 3 points 3 points 3 points 2 points 2 points 1 point 2 points 3 points resistance * Number of parts of photopolymerization initiator is a value relative to 100 parts by weight of reactive diluent

(32) TABLE-US-00003 TABLE 3 Comparative Comparative Comparative Comparative Comparative Example 1 Example 2 Example 3 Example 4 Example 5 Resin Type PVB1 PVB3 PVB3 PVB3 PVB1 Degree of 1700 850 850 850 1700 polymerization Number of parts 100 100 100 100 100 (parts by weight) Reactive Type TMPA — TMPA TMPA TMPA diluent Number of parts 1 — 0.05 35 4 (parts by weight) Photo- Type BP — BP BP BP polymer- Number of parts 1 — 1 1 0.5 ization (parts by weight) initiator Plasticizer Type 3GO 3GO 3GO 3GO 3GO Number of parts 0.5 35 30 0 0 (parts by weight) Storage Before irradiation 1.1 × 10.sup.5 7.2 × 10.sup.2 9.1 × 10.sup.2 8.9 × 10.sup.4 8.5 × 10.sup.4 modulus G′ with light (Pa) at After irradiation 1.3 × 10.sup.5 7.2 × 10.sup.2 9.8 × 10.sup.2 9.5 × 10.sup.5 1.4 × 10.sup.6 200° C. with light Breaking strength (MPa) — 0.07 0.08 — — Capillary viscosity at 190° C. (Pa .Math. s) (before irradiation with light) 15000 120 160 12000 9800 Evaluation Extrusion moldability x ∘ ∘ x x Adhesiveness — ∘ ∘ — — Heat resistance — 0 point 0 point — — * Number of parts of photopolymerization initiator is a value relative to 100 parts by weight of reactive diluent

INDUSTRIAL APPLICABILITY

(33) The present invention provides a polyvinyl acetal resin composition that is moldable by an extrusion method and capable of exhibiting excellent heat resistance after molding. The present invention also provides an adhesive sheet containing the polyvinyl acetal resin composition, and a method for producing the adhesive sheet.