Radiation-curable silicone composition

Abstract

To provide a radiation-curable silicone composition which provides a cured product whose odor is decreased, particularly is odorless, and has excellent curability and releasing properties. A radiation-curable silicone composition including the following components (A) and (B): (A) an epoxy group-containing cation-polymerizable organopolysiloxane which is represented by the following average composition formula (1): R.sup.1.sub.aR.sup.2.sub.bSiO.sub.(4-a-b)/2 (1) and (B) an iodonium salt having a cation moiety represented by the following general formula (2) in an effective amount to cure said component (A), [(R.sup.3)—I—(R.sup.3)].sup.+ (2) wherein R.sup.3 is, independently of each other, a substituted or unsubstituted monovalent aromatic hydrocarbon group having 15 to 26 carbon atoms, wherein said component (A) may be accompanied by any other compounds volatilizing during heating at 105 degrees C. for 3 hours, a content of said compounds is at most 2.0 mass %, based on a total amount of component (A) and said compound.

Claims

1. A radiation-curable silicone composition comprising the following components (A) and (B): (A) an epoxy group-containing cation-polymerizable organopolysiloxane which is represented by the following average composition formula (1):
R.sup.1.sub.aR.sup.2.sub.bSiO.sub.(4-a-b)/2  (1) wherein R.sup.1 is, independently of each other, an epoxy group-containing monovalent organic group, R.sup.2 is, independently of each other, a substituted or unsubstituted monovalent hydrocarbon group having 1 to 10 carbon atoms, a>0, b>0 and a total of a and b is in a range of larger than 0 and at most 3, and (B) an iodonium salt having a cation moiety represented by the following general formula (2) in an effective amount to cure said component (A),
[(R.sup.3)—I—(R.sup.3)].sup.+  (2) wherein R.sup.3 is, independently of each other, a substituted or unsubstituted monovalent aromatic hydrocarbon group having 15 to 26 carbon atoms, wherein said component (A) is accompanied by other compounds that volatilize during heating at 105 degrees C. for 3 hours, and a content of said compounds is at most 2.0 mass %, based on a total amount of component (A) and said compounds, and the compounds volatilizing during heating at 105 degrees C. for 3 hours comprise at least an epoxy group-containing low molecular weight organopolysiloxane having a degree of polymerization of 8 or lower.

2. The radiation-curable silicone composition according to claim 1, wherein the compounds volatilizing during heating at 105 degrees C. for 3 hours further comprise a starting alkenyl group-containing epoxy compound used in the preparation of the cation-polymerizable organopolysiloxane.

3. The radiation-curable silicone composition according to claim 1, wherein the content of the compounds volatilizing during heating at 105 degrees C. for 3 hours, based on a total amount of component (A) and said compounds is 1.8 mass % or less.

4. The radiation-curable silicone composition according to claim 3, wherein the content of the compounds volatilizing during heating at 105 degrees C. for 3 hours, based on a total amount of component (A) and said compounds is 1.5 mass % or less.

5. The radiation-curable silicone composition according to claim 1, wherein a part of hydrogen atoms bonded to carbon atoms of the aromatic hydrocarbon group, R.sup.3, in the formula (2) is substituted with a linear or branched alkyl group having 9 to 20 carbon atoms.

6. The radiation-curable silicone composition according to claim 1, wherein component (B) has an anion moiety selected from the group consisting of SbF.sub.6.sup.−, [B(C.sub.6F.sub.5).sub.4].sup.−, [B(C.sub.6H.sub.4CF.sub.3).sub.4].sup.−, [(C.sub.6F.sub.5).sub.2BF.sub.2].sup.−, [C.sub.6F.sub.5BF.sub.3].sup.−, [B(C.sub.6H.sub.3F.sub.2).sub.4].sup.−, [(CF.sub.3CF.sub.2).sub.3PF.sub.3].sup.−, [(CF.sub.3CF.sub.2CF.sub.2).sub.3PF.sub.3].sup.−, [((CF.sub.3).sub.2CF).sub.3PF.sub.3].sup.−, [((CF.sub.3).sub.2CF).sub.2PF.sub.4].sup.−, [((CF.sub.3).sub.2CFCF.sub.2).sub.3PF.sub.3].sup.− and [((CF.sub.3).sub.2CFCF.sub.2).sub.2PF.sub.4].sup.−.

7. The radiation-curable silicone composition according to claim 1, wherein component (A) is at least one selected from organopolysiloxane (A1) represented by the following average formula (3), organopolysiloxane (A2) represented by the following average formula (4) and organopolysiloxane (A3) represented by the following average formula (5): ##STR00011## wherein R.sup.1 and R.sup.2 are as defined above, c is, independently of each other, a positive number of 2 or larger, d is, independently of each other, 0 or a positive number, and e is a positive number of 2 or larger.

8. The radiation-curable silicone composition according to claim 1, wherein component (A) comprises the following components (A4) and (A5) in a weight ratio of 0.1 to 1.5: (A4) an organopolysiloxane represented by the following average formula (6):
(R.sup.2.sub.3SiO.sub.1/2).sub.f(SiO.sub.4/2).sub.g(XO—SiO.sub.3/2).sub.h  (6) wherein R.sup.2 is as defined above, X is, independently of each other, a hydrogen atom or a group represented by the following formula (7), (8) or (9), f, g, and h are positive numbers satisfying the equation, f/(g+h)=0.5 to 2, ##STR00012## wherein R.sup.1 and R.sup.2 are as defined above, i, z, m, n and o are, independently of each other, 0 or a positive number, p is a positive number of 1 or larger, provided that a total of i and z is 1 to 50, a total of m and n is 1 to 50, a total of o and p is 2 to 7, and k and x are, independently of each other, 0, 1, 2 or 3, provided that a total of i and k is 1 or larger and a total of n and x is 1 or larger, (A5) an organopolysiloxane represented by the following average formula (10) or (11): ##STR00013## wherein R.sup.1 and R.sup.2 are as defined above, r, s, and t are, independently of each other, 0 or a positive number, u is a positive number of 1 or larger, provided that a total of r and s is 3 to 55, a total oft and u is 3 to 8, and q is 0, 1, 2 or 3, provided that s and q is not zero at the same time.

9. An article having a substrate, wherein substrate has on its surface a cured product obtained by curing the radiation-curable silicone composition according to claim 1, so that the surface has a releasing property.

Description

BEST MODE OF THE INVENTION

(1) The present invention will be described below in detail.

(2) (A) Epoxy Group-Containing Cation-Polymerizable Organopolysiloxane

(3) The epoxy group-containing cation-polymerizable organopolysiloxane may be prepared, for instance, by a hydrosilylation of a hydrogen organopolysiloxane and an alkenyl group-containing epoxy compound in the presence of a metal catalyst, as described in Japanese Patent Nos. 3384268 and 3993533. In the hydrosilylation, a solvent and volatile compounds are removed by vacuum distillation under heating. However, the unreacted starting alkenyl group-containing epoxy compound, and a compound formed by a reaction of a low molecular weight siloxane present in the starting hydrogenorganopolysiloxane with the alkenyl group-containing epoxy compound tend to remain in the cation-polymerizable organopolysiloxane obtained. Such compounds, i.e. volatile low molecular weight compounds, would be a cause of odor in the cation-polymerizable organopolysiloxane.

(4) The present invention is characterized in that an amount of compounds volatilizing during heating at 105 degrees C. for 3 hours, by which component (A) is accompanied, is at most 2.0 mass %, preferably at most 1.8 mass %, more preferably at most 1.5 mass %, based on a total amount of said compounds and component W. The amount of the compounds volatilizing during heating at 105 degrees C. for 3 hours is near to the amount of odor components contained in the cation-polymerizable organopolysiloxane. Therefore, odor of a cured product is decreased by lowering the amount of the compounds volatilizing during heating at 105 degrees C. for 3 hours to the aforesaid range. Examples of the compounds volatilizing during heating at 105 degrees C. for 3 hours include a low molecular weight organopolysiloxane having an epoxy group. The low molecular weight organopolysiloxane here has a degree of polymerization is 8 or lower, particularly 7 or lower, and may be a linear, branched or cyclic. Further, the staring alkenyl group-containing epoxy compound is also an example. There is no lower limit for the amount of the volatile compounds. A smaller amount gives a less odor product. If the amount of the volatile compounds is larger than the upper limit, the volatile compounds cause much odor and an odorless product cannot be obtained.

(5) The amount of the compounds volatilizing during heating at 105 degrees C. for 3 hours, by which the epoxy group-containing cation-polymerizable organopolysiloxane is accompanied, is determined with an air-blowing thermostat oven. Specifically, 2 grams of the epoxy group-containing cation-polymerizable organopolysiloxane (hereinafter referred to as “sample”) is put into a 50-milliliter beaker and then, the beaker is left in an air-blowing thermostat oven which is set at 105 degrees C. After 3 hours, the beaker is took out, cooled in a desiccator and, then, weighed to record a decreased amount of the sample. A mass of the components which volatilized during heating is calculated as a percentage, based on the mass of the sample in the beaker before heating. The air-blowing thermostat oven used in the present invention is DN-610H, ex Yamato Scientific Co., Ltd. The rate of air is 12.3 m.sup.3/min, the internal volume of the thermostat oven is 223 liters, the internal dimensions is 620×600×600 mm, and there are two exits having an inner diameter of 30 mm in the back. The 50-milliliter beaker has a product code 010020-5051A, ex Sibata Scientific Technology Ltd. (HARIO CO., LTD.), with an outer diameter of 46 mm and a height of 61 mm. When the epoxy group-containing cation-polymerizable organopolysiloxane is left in the air-blowing thermostat oven, volatile low molecular weight compounds volatilize, which have a boiling point of higher than 105 degrees C., for instance a compound having a boiling point of 200 degrees C.

(6) Component (A) is an epoxy group-containing cation-polymerizable organopolysiloxane represented by the following average composition formula (1):
R.sup.1.sub.aR.sup.2.sub.bSiO.sub.(4-a-b)/2  (1)
wherein R.sup.1 is, independently of each other, an epoxy group-containing monovalent organic group, R.sup.2 is, independently of each other, a substituted or unsubstituted monovalent hydrocarbon group having 1 to 10 carbon atoms, a is larger than 0, b is larger than 0 and a total of a and b is larger than 0 and at most 3. Component (A) is accompanied by components volatilizing during heating at 105 degrees C. for 3 hours. A content of the compounds is at most 2.0 mass %, preferably at most 1.8 mass %, more preferably at most 1.5 mass %, based on a total amount of the compounds and component (A).

(7) In the average composition formula (1), R.sup.1 is, independently of each other, an epoxy group-containing monovalent organic group. Examples of the epoxy group-containing monovalent organic group include a glycidoxyalkyl group, an epoxycyclohexylalkyl group, and an oxiranyl alkyl group, which have 3 to 20 carbon atoms, preferably 3 to 16 carbon atoms, more preferably 4 to 10 carbon atoms. In particular, the groups represented by the following formulas are preferable.

(8) ##STR00001##

(9) In the average composition formula (1), R.sup.2 is, independently of each other, an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms. Examples of R.sup.2 include alkyl groups such as a methyl group, an ethyl group, a propyl group, a butyl group, cyclo alkyl groups such as a cyclohexyl group, aryl groups such as a phenyl group and a tolyl group, and those groups where a part or the whole of their hydrogen atoms are replaced with a hydroxy group, a cyano group or a halogen atom(s), such as a hydroxypropyl group, a cyanoethyl group, a 1-chloropropyl group, and a 3,3,3-trifluoropropyl group. Among these, alkyl groups and aryl groups are preferable in view of the releasing property of the cured product. Further, 80 mole % or more of a total mole of R.sup.2 groups is preferably a methyl group.

(10) In the average composition formula (1), a is larger than 0, b is larger than 0 and a total of a and b is larger than 0 and at most 3. The structure of the organopolysiloxane represented by the aforesaid average composition formula (1) is not limited to any particular one and may be a linear, branched, cyclic or three-dimensional by crosslinked structure. In particular, a linear or branched structure is preferable. The organopolysiloxane may be one kind or a combination of two or more kinds of such. Component (A) has an average epoxy equivalent of 600 to 2,500 g/mol and a viscosity of 5 to 1,000,000 mPa.Math.s. Further preferably, the average epoxy equivalent is 650 to 2,300 g/mol and a viscosity is 10 to 100,000 mPa.Math.s. The viscosity is determined with a rotational viscometer at 25 degrees C.

(11) If the average epoxy equivalent is smaller than the aforesaid lower limit, the cured product obtained from the composition may have a release with strong force. Further, the content of the epoxy group is large, so that odor of the epoxy group tends to be strong. If the average epoxy equivalent is larger than the aforesaid upper limit, the odor of the epoxy group is weak, but the curability tends to significantly worsen because of the smaller amount of epoxy group. If the viscosity of component (A) is smaller than the aforesaid lower limit, it may be difficult to apply the composition without a solvent. If the viscosity is larger than the aforesaid upper limit, the viscosity of the composition is too high and it may be difficult to handle the composition.

(12) Preferably, component (A) is at least one selected from organopolysiloxanes (A1) to (A3), represented by the following average formula (3), (4) or (5), respectively.

(13) Epoxy group-containing cation-polymerizable organopolysiloxane (A1):

(14) ##STR00002##

(15) Epoxy group-containing cation-polymerizable organopolysiloxane (A2):

(16) ##STR00003##

(17) Epoxy group-containing cation-polymerizable organopolysiloxane (A3):

(18) ##STR00004##

(19) In the average formulas (3) to (5), R.sup.1 and R.sup.2 are as defined above. c is, independently of each other, a positive number of 2 or larger, d is, independently of each other, 0 or a positive number, and e is a positive number of 2 or larger. Component (A) may be one of or a mixture of two or more of the organopolysiloxanes (A1) to (A3). The upper limits of c, d and e are not limited to any particular ones. c, d and e are preferably such that the average epoxy equivalent of the organopolysiloxanes (A1) to (A3) is 600 to 2,500 g/mol and a viscosity of the organopolysiloxanes (A1) to (A3) is 5 to 1,000,000 mPa.Math.s. Further preferred is that the average epoxy equivalent is 650 to 2,300 g/mol and the viscosity is 10 to 100,000 mPa.Math.s. The viscosity of the organopolysiloxane is determined with a rotational viscometer at 25 degrees C. When component (A) is a mixture of two or more of the organopolysiloxanes (A1) to (A3), the aforesaid average epoxy equivalent is an average one of the mixture and the aforesaid viscosity is the viscosity of the mixture.

(20) If the average epoxy equivalent is smaller than the aforesaid lower limit, the cured product obtained from the composition may have a release with strong force. Further, the content of the epoxy group is larger, so that odor of the epoxy group tends to be strong. If the average epoxy equivalent is larger than the aforesaid upper limit, the odor of the epoxy group is weak, but the curability tends to significantly worsen because of the smaller amount of epoxy group. If the viscosity is smaller than the aforesaid lower limit, it may be difficult to apply the composition without a solvent. If the viscosity is larger than the aforesaid upper limit, the viscosity of the composition is too high and it may be difficult to handle the composition.

(21) The composition (A) may comprise component (A4) represented by the following average formula (6) and component (A5) represented by the following average formula (10) or (11). A weight ratio of component (A4) to component (A5) is 0.1 to 1.5, preferably 0.3 to 1.2. A mixture of components (A4) and (A5) may work as a release adjusting agent, in particular an additive for a release with strong force.

(22) Epoxy Group-Containing Cation-Polymerizable Organopolysiloxane (A4):
(R.sup.2.sub.3SiO.sub.1/2).sub.f(SiO.sub.4/2).sub.g(XO−SiO.sub.3/2).sub.h  (6)

(23) Epoxy group-containing cation-polymerizable organopolysiloxane (A5):

(24) ##STR00005##

(25) In the average formula (6), R.sup.2 is as defined above. f, g, and h are positive numbers satisfying the equation f/(g+h)=0.5 to 2, preferably f/(g+h)=0.6 to 1.3. If the value of f/(g+h) is smaller than the aforesaid lower limit, the viscosity of a mixture of components (A4) and (A5) increases and it is difficult to use. If the value of f/(g+h) is larger than the aforesaid upper limit, the effect of attaining a release with strong force is small, which is not preferable.

(26) In the average formula (6), X is, independently of each other, a hydrogen atom or a group represented by the following formula (7), (8) or (9). Preferred is that at least one of X is any one of the following formulas (7), (8) and (9), in particular, the formula (7).

(27) ##STR00006##

(28) In the aforesaid formulas (7) to (9), R.sup.1 and R.sup.2 are as defined above, i, z, m, n and o are, independently of each other, 0 or a positive number, p is a positive number of 1 or larger, provided that a total of i and z is 1 to 50, a total of m and n is 1 to 50, and a total of o and p is 2 to 7, and k and x are, independently of each other, 0, 1, 2 or 3, provided that a total of i and k is 1 or larger and a total of n and x is 1 or larger. Preferably, k and x are, independently of each other, 0 or 1, a total of i and k is 2 or larger, a total of n and x is 2 or larger, p is 2 or larger, a total of i and z is 1 to 40, a total of m and n is 1 to 40, a total of o and p is 2 to 6. If the total of i and k, the total of n and x, or p is smaller than 1, the amount of the epoxy group is smaller and, therefore, the curability of the composition is poor. If the total of i and z, or the total of m and n is smaller than the aforesaid lower limit, it is difficult to synthesize such organopolysiloxane. If the total of i and z, or the total of m and n is larger than the aforesaid upper limit, the viscosity of the mixture becomes too high and it is difficult to handle it.

(29) In the average formulas (10) and (11), R.sup.1 and R.sup.2 are as defined above, r, s, and t are, independently of each other, 0 or a positive number, u is a positive number of 1 or larger, provided that a total of r and s is 3 to 55, a total of t and u is 3 to 8, q is 0, 1, 2 or 3, provided that s and q are not zero at the same time. Preferably, q is 0 or 1, a total of r and s is 3 to 40, and a total of t and u is 3 to 7, provided that s and q are not zero at the same time. If the total of r and s is larger than the aforesaid upper limit, the viscosity of the mixture of components (A4) and (A5) is too high and it is difficult to handle.

(30) In the mixture of the cation-polymerizable organopolysiloxane (A4) and (A5), an average epoxy equivalent of the organopolysiloxanes is preferably 600 to 2, 500 g/mol and a viscosity of the mixture is preferably 5 to 1,000,000 mPa.Math.s. Further preferably, the average epoxy equivalent of the mixture is 650 to 2,300 g/mol and the viscosity of the mixture is 10 to 100,000 mPa.Math.s. The viscosity is determined with a rotational viscometer at 25 degrees C.

(31) If the average epoxy equivalent is smaller than the aforesaid lower limit, the cured product obtained from the composition may have a release with strong force. Further, the content of the epoxy group is large, so that odor of the epoxy group tends to be strong. If the average epoxy equivalent is larger than the aforesaid upper limit, the odor of the epoxy group is weak, but the curability tends to significantly worsen because of the smaller amount of epoxy group. If the viscosity of mixture is smaller than the aforesaid lower limit, it may be difficult to apply the composition without a solvent. If the viscosity is larger than the aforesaid upper limit, the viscosity of the composition is too high and it may be difficult to handle the composition.

(32) In a case where component (A) comprises at least one of components (A1) to (A3) as a base polymer and further comprises a mixture of components (A4) and (A5) as a release adjusting agent, the silicone composition provides a cured product having a release with strong force. That is, the cured product needs a large force to be peeled from an adhesive and, thus, has a large release resistance. When the amount of the mixture of components (A4) and (A5) is larger, the force needed for releasing is larger. In a case where component (A) does not comprise the mixture of components (A4) and (A5), the silicone composition provides a cured product having a release with less force. That is, the cured product can be peeled from an adhesive with a smaller force and, thus, the release resistance is small. Such cured products can be used in release paper. The present silicone composition may provide cured products which have various releasing properties of from a release with strong force to release with less force, by adjusting the amount of the mixture of components (A4) and (A5). When the silicone composition comprises the mixture of components (A4) and (A5) as a release adjusting agent, the amount of the mixture is not particularly limited and is preferably 10 to 90 mass %, more preferably 25 to 75 mass %, further preferably 40 to 60 mass %, based on the total mass of component (A). Further, component (A) may be composed only of a mixture of components (A4) and (A5).

(33) The present silicone composition may comprise a mixture of the following component (C) which is an organopolysiloxane having no epoxy group and the aforesaid component (A5) or a mixture of the aforesaid components (A4) and (A5) and the component (C) as a release adjusting agent, in place of the aforesaid mixture of components (A4) and (A5).

(34) The component (C) is an organopolysiloxane having no epoxy group, represented by the following average formula (6′).
(R.sup.2.sub.3SiO.sub.1/2).sub.f′(SiO.sub.4/2).sub.g′(X′O—SiO.sub.3/2).sub.h′  (6′)
In the average formula (6′), R.sup.2 is as defined above. X′ is, independently of each other, a hydrogen atom or a group represented by the following formula (7′), (8′) or (9′). f′, g′, and h′ are positive numbers satisfying the equation f′/(g′+h′)=0.5 to 2, preferably f′/(g′+h′)=0.6 to 1.3. If the value of f′/(g′+h′) is smaller than the aforesaid lower limit, the viscosity of the mixture is larger and it is difficult to use. If the value of f′/(g′+h′) is larger than the aforesaid upper limit, the effect of giving a release with strong force is smaller, which is not preferable. In the formula (6′), X′ is preferably a hydrogen atom.

(35) ##STR00007##
In the formula (7′) to (9′), R.sup.2 are as defined above, z′ is a positive number of 1 to 50, m′ is a positive number of 1 to 50, and o′ is a positive number of 2 to 7.

(36) In a case where the release adjusting agent is a mixture of component (C) and component (A5), a weight ratio of component (C) to component (A5) is 0.1 to 1.5, preferably 0.3 to 1.2. The total amount of components (C) and (A5) is 1 to 100 parts by mass, preferably 10 to 90 parts by mass, more preferably 25 to 75 parts by mass, further preferably 40 to 60 parts by mass, relative to a total 100 parts by mass of components (A) and (C).

(37) In a case where the release adjusting agent is a mixture of components (A4) and (A5) and component (C), a weight ratio of components (A4) and (C) to component (A5) is 0.1 to 1.5, preferably 0.3 to 1.2. The total amount of components (A4), (C) and (A5) is 1 to 100 parts by mass, preferably 10 to 90 parts by mass, more preferably 25 to 75 parts by mass, further preferably 40 to 60 parts by mass, relative to a total 100 parts by mass of components (A) and (C). The ratio of component (A4) to component (C) is not limited to any particular one.

(38) A method for making the content of the aforesaid volatile compounds, mass %, to the upper limit or less in the epoxy group containing cation-polymerizable organopolysiloxane is not limited to any particular one. For instance, stripping may be used. The stripping conditions may be selected according to the conventional manners so as to making a content, mass %, of the volatile compounds in the organopolysiloxane to less than the upper limit.

(39) (B) Photoacid Generator

(40) Component (B) is an iodonium salt having a cation moiety represented by the following general formula (2). The ionium salt is a photoacid generator and works as a catalyst for curing component (A) with a radiation. Component (B) is characterized in that R.sup.3 in the following general formula (2) is a substituted or unsubstituted, monovalent aromatic hydrocarbon atom having 15 to 26 carbon atoms.
[(R.sup.3)—I—(R.sup.3)].sup.+  (2)

(41) In the formula (2), R.sup.3 is, independently of each other, a substituted or unsubstituted monovalent aromatic hydrocarbon atom having 15 to 26 carbon atoms, preferably 16 to 24 carbon atoms. Examples of R.sup.3 include aromatic hydrocarbon groups such as a nonylphenyl group, a decylphenyl group, an undecylphenyl group, a dodecylphenyl group, a tridecylphenyl group, a tetradecylphenyl group and a pentadecylphenyl group, and those groups where a part or the whole of their hydrogen atoms bonded to carbon atoms are replaced with a hydroxy group, a cyano group or a halogen atom(s), such as a hydroxypropylphenyl group, a cyanoethylphenyl group, a 1-chloropropylphenyl group, and a 3,3,3-trifluoropropylphenyl group. In particular, a part or the whole of hydrogen atoms bonded to carbon atoms of the aromatic hydrogen group may be preferably replaced with a linear or branched alkyl group having 9 to 20 carbon atoms. For instance, preferred are a decylphenyl group, an undecylphenyl group, a tridecylphenyl group, a tetradecylphenyl group and a pentadecylphenyl group.

(42) If the number of the carbon atoms of R.sup.3 is smaller than the aforesaid lower limit, an alkylbenzen iodide and an alkylbenzen, which generate in decomposition of the photoacid generator, volatilize easily and, therefore, odor tends to cause from a cured product obtained by curing the silicone composition. If the number of carbon atoms of R.sup.3 is larger than the upper limit, no further increased effect of decreasing odor is attained.

(43) Regarding the catalyst activity of the photoacid generator, if the number of carbon atoms of R.sup.3 is smaller than the lower limit, the activation by radiation absorption is lower, so that the curability of the composition decreases. If the number of carbon atoms of R.sup.3 is larger than the upper limit, no further increased activation by radiation absorption is attained.

(44) Sulfonium salts are known as a photoacid generator. However, a sulfur atom is liberated from the sulfonium salts in decomposition. Therefore, a cured product obtained has odor of the sulfur atom, so that sulfonium salts is not suitable in the present invention.

(45) As mentioned above, component (B) is characterized in that the iodonium salt has the aforesaid cation moiety. An anion moiety may have any moiety as long as the iodonium salt having its moiety works as a photoacid generator. In view of the curability and solubility in the cation-polymerizable organopolysiloxane, preferred are selected from the group consisting of SbF.sub.6.sup.−, [B(C.sub.6F.sub.5).sub.4].sup.+, [B(C.sub.6H.sub.4CF.sub.3).sub.4].sup.−, [(C.sub.6F.sub.5).sub.2BF.sub.2].sup.−, [C.sub.6F.sub.5BF.sub.3].sup.−, [B(C.sub.6H.sub.3F.sub.2).sub.4].sup.−, [(CF.sub.3CF.sub.2).sub.3PF.sub.3].sup.−, [(CF.sub.3CF.sub.2CF.sub.2).sub.3PF.sub.3].sup.−, [((CF.sub.3).sub.2CF).sub.3PF.sub.3].sup.−, [((CF.sub.3).sub.2CF).sub.2PF.sub.4].sup.−, [((CF.sub.3).sub.2CFCF.sub.2).sub.3PF.sub.3].sup.− and [((CF.sub.3).sub.2CFCF.sub.2).sub.2PF.sub.4].sup.−.

(46) Examples of component (B) include bis(alkyl phenyl) iodonium hexafluoroantimonate, bis(alkyl phenyl) iodonium tetrakis(pentafluorophenyl) borate and bis(alkyl phenyl) iodonium tris(pentafluoroethyl)trifluorophosphate. The alkyl group is preferably a linear or branched alkyl group having 9 to 20 carbon atoms, more preferably 9 to 15 carbon atoms. They may be used alone or a combination of two or more of them. Component (B) may be solved in a solvent such as isopropyl alcohol.

(47) The amount of component (B) may be an effective amount to work as a photoacid generator. That is, the amount may be enough to cure component (A) with radiation and is not limited particularly. In particular, the amount is preferably 0.05 to 20 parts by mass, more preferably 0.1 to 10 parts by mass, relative to a total 100 parts by mass of component (A) and any other compound volatilizing during heating at 105 degrees C. for 3 hours.

(48) The present silicone composition is applied on various substrates, then cured with radiation to form a cured film having a release property so as to provide a releasing property on a surface of the substrate. Thus, release paper and release films are prepared. The substrate is not limited to any particular one and the present composition is used to various general purpose substances. Examples of the substrate include glassine paper, clay coated paper, fine paper, polyethylene laminated paper, plastic film, and transparent resins such as polycarbonate. In particular, the present composition is applied on polyethylene films, polypropylene films and polyester films which are to be processed into individual packaging films for sanitary supplies such as sanitary napkin and disposable diapers.

(49) A method for applying the present silicone composition on the substrate is not particularly limited. For instance, any known manners such as roll coating, gravure coating, wire doctor coating, air-knife coating and dipping coating may be used. The amount applied may be decided depending on a purpose of use. For instance, the amount applied may be 0.01 to 3.0 g/m.sup.2. The coating is easily cured with radiation.

(50) The present silicone composition is prepared by mixing the aforesaid components (A) and (B). The silicone composition may further comprise optional materials other than components (A) and (B). Examples of the optional materials include additives such as fillers, antistatic agents, flame retarders, defoaming agents, fluidity modifiers, light stabilizers, solvents, non-reactive resins and radical-curable compounds. The amount of optional components may be according to conventional manners and selected so that the effects of the present invention are not obstructed.

(51) The present silicone composition is cured by irradiation of a radiation energy ray. Any radiation energy ray which has an energy enough to induce decomposition of the photoacid generator (B) may be used. Preferred are such emitted by a high-pressure or ultra-high-pressure mercury lamp, a metal halide lamp, a xenon lamp, a carbon ark lamp, a fluorescent, a semiconductor or solid-state laser, an argon laser, He—Cd laser, KrF excimer laser, ArF excimer laser and F2 laser. Preferred is an energy ray in a range of from ultraviolet to visible light of approximate 100 to 800 nm. In particular, a radiation source having a strong light intensity in a region of 200 and 400 nm is preferable. Alternatively, a radiation having a high energy such as an electron ray and an X-ray may be used. A time for irradiation of the radiation energy may be usually 0.1 to 10 seconds at room temperature. When transmittance of the energy ray is low or the coating obtained from the silicone composition is thick, the irradiation time may be longer than the aforesaid time. If needed, after the irradiation with the energy ray, the silicone composition may be heated at room temperature to 150 degrees C. for a few seconds to a few hours to after cure.

(52) An energy of 5 to 500 mJ/cm.sup.2 of a radiation a wavelength of 254 nm is effective, preferably 10 to 450 mJ/cm.sup.2, further preferably 15 to 400 mJ/cm.sup.2. If the amount of energy is smaller than the aforesaid lower limit, the silicone composition is not cured sufficiently. If the amount of the energy is larger than the aforesaid upper limit, no further increased curability is confirmed.

EXAMPLES

(53) The present invention will be explained in detail by reference to the Examples and the Comparative Examples, but shall not be limited thereto. In the following descriptions, the viscosity was determined with a rotational viscometer at 25 degrees C., and “Me” is an abbreviation for a methyl group and “Ep” is an abbreviation for an epoxy group-containing organic group represented by the following formula:

(54) ##STR00008##
[Determination of a Content of Volatile Compounds]

(55) In the following Examples and Comparative Examples, a content of a compound volatilizing during heating at 105 degrees C. for 3 hours, hereinafter referred to as “a content of volatile compound”, by which an epoxy group-containing cation-polymerizable organopolysiloxane prepared is accompanied, was determined according to the following methods.

(56) In a 50-milliliter beaker, were put 2 grams of an epoxy group-containing cation-polymerizable organopolysiloxane, (hereinafter referred to as a sample) and, then, the beaker was left in an air-blowing thermostat oven, ex Yamato Scientific Co., Ltd., which was set at 105 degrees C. After 3 hours, the beaker was took out and cooled in a desiccator and, then, weighed to record a decreased amount of the sample. A mass percentage of the components which volatilized during the heating was calculated, based on the mass of the sample in the beaker before the heating.

(57) The air-blowing thermostat oven was DN-610H, ex Yamato Scientific Co., Ltd. The rate of air was 12.3 m.sup.3/min, the internal volume of the thermostat oven was 223 liters, the internal dimensions 620×600×600 mm, and the inner diameter of the exits was 30 mm×2. The 50-milliliter beaker had a product code 010020-5051A, ex Sibata Scientific Technology Ltd. (HARIO CO., LTD.), with the outer diameter was 46 mm and the height was 61 mm.

Example 1

(58) 100 Parts by mass of component (A) and 2.0 parts by mass of a solution of component (B) were homogeneously mixed to obtain silicone composition 1. Component (A) was a mixture (a-1) of epoxy group-containing cation-polymerizable organopolysiloxanes each represented by the following average formulas (a-a) and (a-b), wherein an average epoxy equivalent of the mixture was 1100 g/mol, a content of volatile compounds was 1.2 mass %, and a viscosity at 25 degrees C. was 150 mPa.Math.s.

(59) ##STR00009##
The solution of component (B) comprises 50 mass % of bis[4-n-alkyl (C10-13) phenyl]iodonium hexafluoroantimonate in 50 mass % of isopropyl alcohol, hereinafter referred to as photoacid generator b-1.

Example 2

(60) The procedures of Example 1 were repeated to obtain silicone composition 2, except that a 50 mass % solution of bis[4-n-alkyl (C10-13) phenyl]iodonium tetrakis(pentafluorophenyl)borate in isopropyl alcohol, hereinafter referred to as photoacid generator b-2, was used instead of the photoacid generator b-1.

Example 3

(61) The procedures of Example 1 were repeated to obtain silicone composition 3, except that a 50 mass % solution of bis[4-n-alkyl (C10-13) phenyl]iodonium tris(pentafluoroethyl)trifluorophosphate in isopropyl alcohol, hereinafter referred to as photoacid generator b-3, was used instead of the photoacid generator b-1.

Example 4

(62) The procedures of Example 1 were repeated to obtain silicone composition 4, except that a mixture of 50 parts by mass of the aforesaid mixture (a-1) and 50 parts by mass of mixture (a-2) of an epoxy group-containing cation-polymerizable organopolysiloxane (A4) represented by the following formula (12) and an epoxy group-containing cation-polymerizable organopolysiloxane (A5) represented by the following formula (14) was used instead of the aforesaid component (A) in Example 1.

(63) In the mixture (a-2), the weight ratio of component (A-4) to component (A5) was 1.0, an average epoxy equivalent was 800 g/mol, a content of volatile compounds was 1.6 mass %, a viscosity at 25 degrees C. was 350 mPa.Math.s.
(Me.sub.3SiO.sub.1/2).sub.f(SiO.sub.4/2).sub.g(XO—SiO.sub.3/2).sub.h  (12)
wherein f/(g+h) was 0.7 and X was a group represented by the following formula (13).
—SiMe.sub.2O-(Me.sub.2SiO).sub.8—SiEpMe.sub.2  (13)
EpMe.sub.2SiO-(Me.sub.2SiO).sub.8—SiEpMe.sub.2  (14)

Example 5

(64) The procedures of Example 4 were repeated to obtain silicone composition 5, except that a 50 mass % solution of bis[4-n-alkyl (C10-13) phenyl]iodonium tetrakis(pentafluorophenyl)borate in isopropyl alcohol, hereinafter referred to as photoacid generator b-2, was used instead of the photoacid generator b-1.

Example 6

(65) The procedures of Example 4 were repeated to obtain silicone composition 6, except that a 50 mass % solution of bis[4-n-alkyl (C10-13) phenyl]iodonium tris(pentafluoroethyl)trifluorophosphate in isopropyl alcohol, hereinafter referred to as photoacid generator b-3, was used instead of the photoacid generator b-1.

Comparative Example 1

(66) The procedures of Example 1 were repeated to obtain silicone composition 7, except that 100 parts by mass of mixture (y−1) of an epoxy group-containing cation-polymerizable organopolysiloxane represented by the following formula (a-a) and an epoxy group-containing cation-polymerizable organopolysiloxane represented by the following formula (a-c) was used instead of the aforesaid component (A) in Example 1. In the mixture (y−1), an average epoxy equivalent was 1100 g/mol, a content of volatile compounds was 2.5 mass %, a viscosity at 25 degrees C. was 140 mPa.Math.s.

(67) ##STR00010##

Comparative Example 2

(68) The procedures of Comparative Example 1 were repeated to obtain silicone composition 8, except that a 50 mass % solution of bis[4-n-alkyl (C10-13) phenyl]iodonium tetrakis(pentafluorophenyl)borate in isopropyl alcohol, hereinafter referred to as photoacid generator b-2, was used instead of the photoacid generator b-1.

Comparative Example 3

(69) The procedures of Comparative Example 1 were repeated to obtain silicone composition 9, except that a 50 mass % solution of bis[4-n-alkyl (C10-13) phenyl]iodonium tris(pentafluoroethyl)trifluorophosphate in isopropyl alcohol, hereinafter referred to as photoacid generator b-3, was used instead of the photoacid generator b-1.

Comparative Example 4

(70) The procedures of Comparative Example 1 were repeated to obtain silicone composition 10, except that a mixture of 50 parts by mass of the aforesaid mixture (y−1) and 50 parts by mass of mixture (y-2) of an epoxy group-containing cation-polymerizable organopolysiloxane (A4′) represented by the following formula (15) and an epoxy group-containing cation-polymerizable organopolysiloxane (A5′) represented by the following formula (17) was used instead of aforesaid component (A) used in Comparative Example 1.

(71) In the mixture (y-2), the weight ratio of component (A4′) to component (A5′) was 1.0, an average epoxy equivalent was 750 g/mol, a content of volatile compounds was 3.0 mass %, a viscosity at 25 degrees C. was 320 mPa.Math.s. The structures of the cation-polymerizable organopolysiloxanes (A4′) and (A5′) were same as the structures of the cation-polymerizable organopolysiloxanes (A4) and (A5) used in Example 4. However, the cation-polymerizable organopolysiloxanes (A4′) and (A5′) included a larger amount of epoxy group-containing siloxanes which had low molecular weight weight and was volatile and, therefore, the average epoxy equivalent of mixture (y-2) was smaller than that of mixture (a-2).
(Me.sub.3SiO.sub.1/2).sub.f(SiO.sub.4/2).sub.g(XO—SiO.sub.3/2).sub.h  (15)
wherein f/(g+h) was 0.7 and X was the group represented by the following formula (16).
—SiMe.sub.2O-(Me.sub.2SiO).sub.8—SiEpMe.sub.2  (16)
EpMe.sub.2SiO-(Me.sub.2SiO).sub.8—SiEpMe.sub.2  (17)

Comparative Example 5

(72) The procedures of Example 1 were repeated to obtain silicone composition 11, except that a 50 mass % solution of 4-(isopropyl)-phenyl(p-tolyl) iodonium hexafluoroantimonate in isopropyl alcohol, hereinafter referred to as photoacid generator z-1, was used instead of the photoacid generator b-1.

Comparative Example 6

(73) The procedures of Example 1 were repeated to obtain silicone composition 12, except that a 50 mass % solution of 4-(isopropyl)-phenyl(p-tolyl) iodonium tetrakis(pentafluorophenyl) borate in isopropyl alcohol, hereinafter referred to as photoacid generator z-1, was used instead of the photoacid generator b-1.

Comparative Example 7

(74) The procedures of Example 1 were repeated to obtain silicone composition 13, except that a 50 mass % solution of 4-(isopropyl)-phenyl(p-tolyl) iodonium tris(pentafluoroethyl)trifluorophosphate in isopropyl alcohol, hereinafter referred to as photoacid generator z-3, was used instead of the photoacid generator b-1.

(75) Cured products obtained from the silicone composition prepared in the Examples and the Comparative Examples were evaluated in the following manners.

(76) [Curability]

(77) The silicon composition was applied on polyethylene laminated high-quality paper by roll coating in an amount of approximately 0.8 g/m.sup.2. The silicone composition was irradiated by ultraviolet rays of 15 mJ/cm.sup.2 with two high-pressure mercury-vapor lamps of 80 W/cm to be cured, so that a cured film was formed. When the whole of the composition cured, the composition was evaluated as “A”. When a part of the composition did not cure, the composition was evaluated as “B”. When the whole of the composition did not cure, the composition was evaluated as “C”. The results are as shown in Table 1.

(78) [Force Needed for Releasing]

(79) A force needed for releasing a cured film obtained from the silicone composition was determined in the following manner.

(80) The silicone composition was applied on polyethylene laminated paper in an amount of approximately 0.8 g/m.sup.2 to form a coating. The coating was irradiated by ultraviolet rays of 75 mJ/cm.sup.2 with two high-pressure mercury-vapor lamps of 80 W/cm to form, a cured film. An acryl adhesive tape, TESA7475 (trade name), having a width of 25 mm was attached on the surface of the cured film and, then, the adhesive tape was pressed with one cycle of going and returning of a 2 kg roller to prepare a test sample. The test sample was aged at 70 degrees C. for 20 to 24 hours with a load of 70 g/cm.sup.2 being applied. Then, the adhesive tape was peeled at an angle of 180° and a rate of 0.3 m/min with a tensile testing machine to determine a power, in N/25 mm, needed for peeling the adhesive tape from the cured film. The results are as shown in Table 1.

(81) [Evaluation of Odor]

(82) The odor of the cured film obtained in the aforesaid test for release was evaluated by twenty panelists and given scores according to the following criteria. The twenty scores were averaged. The results are as shown in Table 1.

(83) 4: Not smell

(84) 3: Slightly smell

(85) 2: Smell

(86) 1: Strongly smell

(87) TABLE-US-00001 TABLE 1 Example Example Example Example Example Example 1 2 3 4 5 6 Component, Organopoly a-1 Volatile 100 100 100 50 50 50 part by siloxane compound: mass 1.2 mass % a-2 Volatile 50 50 50 compound: 1.6 mass % Photoacid b-1 R.sup.3: C16 to C18 2 2 generator b-2 R.sup.3: C16 to C18 2 2 b-3 R.sup.3: C16 to C18 2 2 Property Curability A A A A A A Force needed N/25 mm 0.15 0.13 0.14 0.83 0.79 0.81 for peeling Evaluation of odor 4 4 4 4 4 4

(88) TABLE-US-00002 TABLE 2 Com. Com. Com. Com. Com. Com. Com. Exam. Exam. Exam. Exam. Exam. Exam. Exam. 1 2 3 4 5 6 7 Component, Organopoly a-1 Volatile 100 100 100 part by siloxane compound: mass 1.2 mass % y-1 Volatile 100 100 100 50 compound: 2.5 mass % y-2 Volatile 50 compound: 3.0 mass % Photoacid b-1 R.sup.3: C16 to C18 2 2 generator b-2 R.sup.3: C16 to C18 2 b-3 R.sup.3: C16 to C18 2 z-1 R.sup.3: C9 and C7 2 z-2 R.sup.3: C9 and C7 2 z-3 R.sup.3: C9 and C7 2 Property Curability A A A A B B B Force needed N/25 mm 0.17 0.15 0.18 0.87 0.16 0.14 0.15 for peeling Evaluation of odor 3 3 3 2 3 3 3

INDUSTRIAL APPLICABILITY

(89) The present radiation-curable silicone composition provides a cured silicone product whose odor is decreased, particularly is odorless, and has excellent curability and releasing properties. Further, the present radiation-curable silicone composition provides cured products having various releasing properties such as a release with strong force and a release with less force. That is, it is possible to control a releasing force of the cured product. Accordingly, the present silicone composition is usable to produce articles with a releasing property.