RADIATION-CURABLE ORGANOPOLYSILOXANE COMPOSITION AND A RELEASE SHEET

Abstract

A radiation-curable organopolysiloxane composition comprising the components (A), (B) and (C): (A) organopolysiloxane represented by the formula (1), wherein at least one of R.sup.1 is a (meth)acryloyl group-containing organic group, a is an integer of 2 or more, a, b, c and d satisfy an equation, 2≤a+b+c+d≤1,000, and a ratio of the total number of the hydroxyl group and the hydroxyl group-containing organic group to the total number of the (meth)acryloyl group-containing organic group, the hydroxyl group and the hydroxyl group-containing organic group is 0.4 or less; (B) compound having two or more acrylic groups in one molecule in an amount of 0.1 to 50 parts by mass, relative to 100 parts by mass of component (A); and (C) radical polymerization initiator in an amount of 0.1 to 15 parts by mass, relative to 100 parts by mass of component (A).

Claims

1. A radiation-curable organopolysiloxane composition comprising the following components (A), (B) and (C): (A) organopolysiloxane represented by the following formula (1): ##STR00018##  wherein R.sup.1 is, independently of each other, a substituted or unsubstituted, monovalent hydrocarbon group having 1 to 10 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, a hydroxyl group, a hydroxyl group-containing organic group, or a (meth)acryloyl group-containing organic group, with at least one of R.sup.1 being a (meth)acryloyl group-containing organic group, a is an integer of 2 or more, b is an integer of 0 or more, c is an integer of 0 or more, d is an integer of 0 or more, a, b, c and d satisfy an equation, 2≤a+b+c+d≤1,000, and a ratio of the total number of the hydroxyl group and the hydroxyl group-containing organic group to the total number of the (meth)acryloyl group-containing organic group, the hydroxyl group and the hydroxyl group-containing organic group is 0.4 or less; (B) compound having two or more acrylic groups in one molecule in an amount of 0.1 to 50 parts by mass, relative to 100 parts by mass of component (A); and (C) radical polymerization initiator in an amount of 0.1 to 15 parts by mass, relative to 100 parts by mass of component (A).

2. The radiation-curable organopolysiloxane composition according to claim 1, wherein component (B) is an organosilane having three or more acrylic groups in one molecule or a hydrolytic condensation product thereof.

3. The radiation-curable organopolysiloxane composition according to claim 1, wherein component (B) is a hydrocarbon compound having three or more acrylic groups in one molecule and may have a hetero atom.

4. The radiation-curable organopolysiloxane composition according to claim 1, wherein at least one of R.sup.1 in the formula (1) is a hydroxyl group or a hydroxyl group-containing organic group and a ratio of the total number of the hydroxyl group and the hydroxyl group-containing organic group to the total number of the (meth)acryloyl group-containing organic group, the hydroxyl group and the hydroxyl group-containing organic group is 0.001 to 0.3.

5. The radiation-curable organopolysiloxane composition according to claim 1, wherein a ratio of the total number of the hydroxyl group and the hydroxyl group-containing organic group to the total number of the (meth)acryloyl group-containing organic group, the hydroxyl group and the hydroxyl group-containing organic group is less than 0.001 and may be zero.

6. The radiation-curable organopolysiloxane composition according to claim 1, comprising no organopolysiloxane which is represented by the formula (1) and has a ratio of the total number of the hydroxyl group and the hydroxyl group-containing organic group to the total number of the (meth)acryloyl group-containing organic group, the hydroxyl group and the hydroxyl group-containing organic group being more than 0.4.

7. A cured product obtained by curing the radiation-curable organopolysiloxane composition according to claim 1.

8. A release sheet comprising a substrate and a layer of the cured product according to claim 7, wherein the layer of the cured product is laminated on at least one surface of the substrate.

9. The radiation-curable organopolysiloxane composition according to claim 2, wherein at least one of R.sup.1 in the formula (1) is a hydroxyl group or a hydroxyl group-containing organic group and a ratio of the total number of the hydroxyl group and the hydroxyl group-containing organic group to the total number of the (meth)acryloyl group-containing organic group, the hydroxyl group and the hydroxyl group-containing organic group is 0.001 to 0.3.

10. The radiation-curable organopolysiloxane composition according to claim 3, wherein at least one of R.sup.1 in the formula (1) is a hydroxyl group or a hydroxyl group-containing organic group and a ratio of the total number of the hydroxyl group and the hydroxyl group-containing organic group to the total number of the (meth)acryloyl group-containing organic group, the hydroxyl group and the hydroxyl group-containing organic group is 0.001 to 0.3.

11. The radiation-curable organopolysiloxane composition according to claim 2, wherein a ratio of the total number of the hydroxyl group and the hydroxyl group-containing organic group to the total number of the (meth)acryloyl group-containing organic group, the hydroxyl group and the hydroxyl group-containing organic group is less than 0.001 and may be zero.

12. The radiation-curable organopolysiloxane composition according to claim 3, wherein a ratio of the total number of the hydroxyl group and the hydroxyl group-containing organic group to the total number of the (meth)acryloyl group-containing organic group, the hydroxyl group and the hydroxyl group-containing organic group is less than 0.001 and may be zero.

13. The radiation-curable organopolysiloxane composition according to claim 2, comprising no organopolysiloxane which is represented by the formula (1) and has a ratio of the total number of the hydroxyl group and the hydroxyl group-containing organic group to the total number of the (meth)acryloyl group-containing organic group, the hydroxyl group and the hydroxyl group-containing organic group being more than 0.4.

14. The radiation-curable organopolysiloxane composition according to claim 3, comprising no organopolysiloxane which is represented by the formula (1) and has a ratio of the total number of the hydroxyl group and the hydroxyl group-containing organic group to the total number of the (meth)acryloyl group-containing organic group, the hydroxyl group and the hydroxyl group-containing organic group being more than 0.4.

15. The radiation-curable organopolysiloxane composition according to claim 4, comprising no organopolysiloxane which is represented by the formula (1) and has a ratio of the total number of the hydroxyl group and the hydroxyl group-containing organic group to the total number of the (meth)acryloyl group-containing organic group, the hydroxyl group and the hydroxyl group-containing organic group being more than 0.4.

16. The radiation-curable organopolysiloxane composition according to claim 5, comprising no organopolysiloxane which is represented by the formula (1) and has a ratio of the total number of the hydroxyl group and the hydroxyl group-containing organic group to the total number of the (meth)acryloyl group-containing organic group, the hydroxyl group and the hydroxyl group-containing organic group being more than 0.4.

17. A cured product obtained by curing the radiation-curable organopolysiloxane composition according to claim 2.

18. A cured product obtained by curing the radiation-curable organopolysiloxane composition according to claim 3.

19. A cured product obtained by curing the radiation-curable organopolysiloxane composition according to claim 4.

20. A cured product obtained by curing the radiation-curable organopolysiloxane composition according to claim 5.

Description

EXAMPLES

[0057] The present invention will be explained below in further detail with reference to a series of the Examples and the Comparative Examples, though the present invention is no way limited by these Examples.

[0058] The evaluation results in the following table were determined by the following test methods. The viscosity is determined at 25° C. by a BM type rotational viscometer. In the structural formula, Me represents a methyl group and AO represents an acryloyloxy group.

[0059] In the Examples, the structure of the (meth)acryloyl group-containing organopolysiloxane was analyzed by .sup.1H-NMR and .sup.29Si-NMR. A ratio of the number of the hydroxyl group-containing organic group to the total number of the (meth)acryloyl group-containing organic group and the hydroxyl group-containing organic group bonded to a silicon atom (the ratio will hereinafter be referred to as “hydroxyl group ratio” in the following Examples and Comparative Examples) was calculated as follows.

[0060] For example, in Synthesis Example 3, the numbers of the hydroxyl group-containing organic group and the (meth)acryloyl group-containing organic group determined by the .sup.1H-NMR and .sup.29Si-NMR analyses were 0.1 and 1.9, respectively. Therefore, a ratio of the hydroxyl group-containing organic group to the total number of the (meth)acryloyl group-containing organic group and the hydroxyl group-containing organic group is 0.1/(0.1+1.9)=0.05.

Synthesis Example 1

[0061] In a 300-mL three-necked flask equipped with a stirrer and a thermometer, were placed 4.4 g of 1,1,1,3,5,5,5-heptamethyl-3-[(trimethylsilyl)oxy]pentanetrisiloxane, 182.3 g of octamethylcyclotetrasiloxane, 42.3 g of an organopolysiloxane represented by the following formula (8), 0.15 g of 2,6-di-tert-butyl-4-methylphenol, and 0.005 g of N,N′-diphenyl-p-phenylenediamine and stirred at room temperature for 5 minutes. Then, 2.7 g of methanesulfonic acid was added to the mixture and the resulting mixture was heated and stirred at 90° C. for 8 hours. The reaction mixture was cooled to room temperature, to which 7.05 g of sodium bicarbonate was then added and the resulting mixture was heated and stirred at 105° C. for 2 hours. After the reaction mixture was filtered under a pressure, the filtrate was subjected to a distillation under a reduced pressure of 20 mmHg at 115° C. for 6 hours to obtain an acryloyl group-containing organopolysiloxane represented by the following average composition formula (A-1). The viscosity at 25° C. was 400 mPa-s. The hydroxyl group ratio in the acryloyl group-containing organopolysiloxane was less than 0.001.

##STR00010##

[0062] In the aforesaid and following formulas, Me is a methyl group and AO— is an acryloyloxy group. The bonding order of the siloxane units in the parentheses is not limited to the aforesaid one.

Synthesis Example 2

[0063] In a 300-mL three-necked flask equipped with a stirrer and a thermometer, were placed 7.4 g of 1,1,1,3,5,5,5-heptamethyl-3-[(trimethylsilyl)oxy]pentanetrisiloxane, 200.7 g of octamethylcyclotetrasiloxane, 24.8 g of the organopolysiloxane represented by the aforesaid formula (8), 0.12 g of 2,6-di-tert-butyl-4-methylphenol, and 0.005 g of N,N′-diphenyl-p-phenylenediamine and stirred at room temperature for 5 minutes. Then, 2.7 g of methanesulfonic acid was added to the mixture and the resulting mixture was heated and stirred at 90° C. for 8 hours. The reaction mixture was cooled to room temperature, to which 7.05 g of sodium bicarbonate was then added and the resulting mixture was heated and stirred at 105° C. for 2 hours. After the reaction mixture was filtered under a pressure, the filtrate was subjected to a distillation under a reduced pressure of 20 mmHg at 115° C. for 6 hours to obtain an acryloyl group-containing organopolysiloxane represented by the following average composition formula (A-2). The viscosity at 25° C. was 180 mPa-s. The hydroxyl group ratio in the acryloyl group-containing organopolysiloxane was less than 0.001.

##STR00011##

Synthesis Example 3

[0064] In a 300-mL three-necked flask equipped with a stirrer, a thermometer, and a Dean-Stark apparatus, were placed 79.70 g of an organopolysiloxane represented by the following formula (9) and having a viscosity at 25° C. of 35 mPa-s, 34.32 g of ethyl acrylate, 4.179 g of zirconium acetyl acetonate, 0.58 g of diethylhydroxyamine, 0.059 g of 2,6-di-tert-butyl-4-methylphenol, and 92.81 g of toluene. The resulting mixture was heated and stirred at 85° C. for 24 hours while removing a byproduct ethanol generated during the reaction. After the reaction mixture was filtered, the filtrate was subjected to a distillation under a reduced pressure of 20 mmHg at 85° C. for 2 hours to obtain an acryloyl group-containing organopolysiloxane represented by the following average composition formula (A-3). The viscosity at 25° C. was 18 mPa-s. The hydroxyl group ratio in the aforesaid acryloyl group-containing organopolysiloxane was 0.05.

##STR00012##

Synthesis Example 4

[0065] In a 300-mL three-necked flask equipped with a stirrer, a thermometer, and a Dean-Stark apparatus, were placed 110.74 g of an organopolysiloxane represented by the following formula (10) and having a viscosity at 25° C. of 500 mPa-s, 72.40 g of ethyl acrylate, 5.88 g of zirconium acetylacetonate, 0.82 g of diethylhydroxyamine, 0.097 g of 2,6-di-tert-butyl-4-methylphenol, and 18.31 g of toluene. The resulting mixture was heated and stirred at 85° C. for 24 hours while removing a byproduct ethanol generated during the reaction. After the reaction mixture was filtered, the filtrate was subjected to a distillation under a reduced pressure of 20 mmHg at 85° C. for 2 hours to obtain an acryloyl group-containing organopolysiloxane represented by the following average composition formula (A-4). The viscosity at 25° C. was 200 mPa-s. The hydroxyl group ratio in the aforesaid acryloyl group-containing organopolysiloxane was 0.10.

##STR00013##

Synthesis Example 5

[0066] The procedures of Synthesis Example 4 were repeated, except that 132.34 g of the organopolysiloxane represented by the aforesaid formula (10), 86.53 g of ethyl acrylate, 0.70 g of zirconium acetylacetonate, and 0.10 g of diethylhydroxyamine were used; 0.328 g of 2-tert-butyl-4-methyl-6-(2-hydroxy-3-tert-butyl-5-methylbenzyl)phenyl acrylate was used instead of 2,6-di-tert-butyl-4-methylphenol; and toluene was not used, whereby an acryloyl group-containing organopolysiloxane represented by the following average composition formula (A-5) was obtained. The resulting product had a viscosity at 25° C. of 220 mPa-s. The hydroxyl group ratio in the aforesaid acryloyl group-containing organopolysiloxane was 0.20.

##STR00014##

Comparative Synthesis Example 1

[0067] The procedures of Synthesis Example 4 were repeated, except that 70.76 g of the organopolysiloxane represented by the aforesaid formula (10) and 45.70 g of ethyl acrylate were used and 1.45 g of paratoluenesulfonic acid monohydrate and 0.060 g of 2,6-d-tert-butyl-4-methylphenol were used instead of zirconium acetylacetonate and diethylhydroxyamine, and 94.80 g of toluene were used, whereby an acryloyl group-containing organopolysiloxane represented by the following average composition formula (D-1) was obtained. The resulting product had a viscosity at 25° C. of 26 mPa.Math.s. The hydroxyl group ratio in the aforesaid acryloyl group-containing organopolysiloxane was 0.45.

##STR00015##

Comparative Synthesis Example 2

[0068] In a 300-mL separable flask equipped with a stirrer, a thermometer, a dropping funnel, and a reflux condenser, were placed 80.86 g of an epoxy-modified organopolysiloxane represented by the following formula (11), 0.95 g of 1,4-diazabicyclo[2.2.2]octane, 0.059 of 2,6-di-tert-butyl-4-methylphenol, and 95.40 of toluene and heated to 50° C. When the temperature reached 50° C., a mixture of 36.55 g of acrylic acid and 6.40 g of acrylic anhydride was added dropwise from the dropping funnel. After completion of the dropwise addition, the temperature was elevated and the reaction mixture was heated and stirred at 90 to 100° C. for 40 hours. The reaction mixture was subjected to a distillation under a reduced pressure of 20 mmHg at 120° C. for 3 hours and then filtered to obtain an acryloyl group-containing organopolysiloxane represented by the following average composition formula (D-2). The viscosity at 25° C. was 600 mPa.Math.s. The hydroxyl group ratio in the aforesaid acryloyl group-containing organopolysiloxane was 0.50.

##STR00016##

[0069] The components used in the Examples and the Comparative Examples will be described below.

(B) Polyfunctional Acrylate

[0070] (B-1) Trimethylolpropane triacrylate (ex Shin-Nakamura Chemical Co., Ltd.)

[0071] (B-2) Ditrimethylolpropane tetraacrylate (ex Shin-Nakamura Chemical Co., Ltd.)

[0072] (B-3) Pentafunctional acrylsilane compound represented by the following formula (ex Shin-Etsu Chemical Co., Ltd.)

##STR00017##

(C) Radical Polymerization Initiator

[0073] (C-1) 2-Hydroxy-2-methyl-1-phenyl-propan-1-one

Example 1

[0074] 100 Parts by mass of the (meth)acryloyl group-containing organopolysiloxane (A-1) obtained in Synthesis Example 1, 10 parts by mass of trimethylolpropane triacrylate (B-1) as component (B), and 5.0 parts by mass of 2-hydroxy-2-methyl-1-phenyl-propan-1-one (C-1) as the radical polymerization initiator (C) were uniformly mixed to obtain a radiation-curable organopolysiloxane composition.

Examples 2 to 10 and Comparative Examples 1 to 10

[0075] In Examples 2 to 10 and Comparative Examples 1 to 10, the components having the compositions shown in the following Table 1 were uniformly mixed as in Example 1 to obtain the radiation-curable organopolysiloxane compositions.

[0076] Releasability of release sheets formed from the radiation-curable organopolysiloxane compositions obtained in Examples 1 to 10 and Comparative Examples 1 to 10 were evaluated in accordance with the following methods.

[Determination of a Release Force of a Release Sheet]

[0077] The radiation-curable organopolysiloxane composition was applied by a roll on a PET film having a thickness of 38-μm at a coating weight of about 1.0 g/m.sup.2 and exposed to ultraviolet rays at a dose of 100 mJ/cm.sup.2 by two 80 W/cm high-pressure mercury lamps having an oxygen concentration set at 150 ppm to form a release sheet having a cured film. The release sheet thus formed was stored at 25° C. for 20 hours. Then, an acrylic adhesive tape TESA7475 (trade name) having a width of 25 mm was put on the surface of the cured film and pressure-bonded by moving a 2-Kg roller back and force once to prepare a test sample for evaluating a release force.

[0078] The test sample was aged at 70° C. for 20 to 24 hours while applying a load of 70 g/cm.sup.2 thereto. Then, a force, N/25 mm, required for pulling and peeling the acrylic adhesive tape from the release sheet was determined at an angle of 180° and a release rate of 0.3 m/min by a tensile tester. The results are shown in Table 1.

[Residual Adhesion of Adhesive Tape]

[0079] The test sample for evaluating a release force was prepared according to the aforesaid manner. The test sample was aged at 70° C. for 20 to 24 hours while applying a load of 70 g/cm.sup.2 thereto. Then, the acrylic adhesive tape was peeled off from the release sheet at an angle of 180° and a release rate of 0.3 m/min by a tensile tester. The resulting acrylic adhesive tape was put on a SUS plate. They were pressure-bonded by moving a 2-Kg roller back and force once and left to stand at 25° C. for 30 minutes. Then, a force (Y) required for releasing the adhesive tape from the SUS plate was determined. For comparison, a force (Z) required for releasing an acrylic adhesive tape TESA7475, which had not been bonded to the release sheet, from a SUS plate was determined. A residual adhesion was obtained by dividing Y by Z. The results are shown in Table 1.

[Adhesion Test of the Release Sheet]

[0080] The release sheet was prepared according to the aforesaid manner. The release sheet thus obtained was stored in a wet and heat dryer of 60° C. and 90% RH for 7 days. Then, the cured film was rubbed 10 times with a finger to check adhesion to the substrate. The cured film which was not cloudy and was not peeled off was evaluated as A. The cured film which was slightly cloudy and slightly peeled off was evaluated as B. The cured film which was peeled off from the substrate was evaluated as C. The results are shown in Table 1.

TABLE-US-00001 TABLE 1 Composition, part by mass (Meth)acryl group-containing Radical Result organopolysiloxane Polyfunctional polymerization Release Hydroxyl A-1 A-2 A-3 A-4 A-5 D-1 D-2 acrylate initiator force, Residual group ratio <0.001 <0.001 0.05 0.10 0.20 0.45 0.50 B-1 B-2 B-3 C-1 N/25 mm) adhesion, % Adhesion Example 1 100 10 5 0.15 9 A Example 2 100 10 5 0.15 99 A Example 3 100 10 5 0.16 99 A Example 4 90 10 10 5 0.11 96 A Example 5 100 10 5 0.43 98 A Example 6 20 80 10 5 0.14 97 A Example 7 100 10 5 0.45 99 A Example 8 20 80 10 5 0.15 97 A Example 9 100 10 5 0.42 99 A Example 10 20 80 10 5 0.14 96 A Com. Ex. 1 100 5 0.11 98 C Com. Ex. 2 100 5 0.41 99 B Com. Ex. 3 100 5 0.44 97 B Com. Ex. 4 100 5 0.43 98 B Com. Ex. 5 100 5 0.57 92 B Com. Ex. 6 100 10 5 0.6 94 B Com. Ex. 7 20 80 10 5 0.17 90 C Com. Ex. 8 100 5 1.5 98 B Com. Ex. 9 100 10 5 1.53 99 B Com. Ex. 20 80 10 5 0.12 97 C 10

[0081] As seen in Table 1, the release sheet obtained from the composition comprising the organopolysiloxane having the large amount of a hydroxyl group is inferior in light releasability, has poor adhesion to a substrate after stored under wet and heat conditions and, accordingly, is inferior in storage stability. In contrast, the release sheet having the cured product layer obtained from the radiation-curable organopolysiloxane composition of the present invention is released from the adhesive layer with a small force and is therefore excellent in easy releasability. In addition, the release sheet has high adhesion to a substrate and has long-term stability without showing reduced adhesion even after a storage under wet and heat conditions.

INDUSTRIAL APPLICABILITY

[0082] A cured product obtained from the radiation-curable organopolysiloxane composition of the present invention is released from an adhesive layer with a small force and, therefore, has easy releasability, high adhesion to a substrate and excellent storage stability. Therefore, the present radiation-curable organopolysiloxane composition is useful as a composition for a release sheet such as a release paper or a release film for various adhesive substances.