Curable fluorosilicone composition

Abstract

A curable fluorosilicone composition according to the present invention comprises at least (A) an organopolysiloxane that has at least two alkenyl groups and at least one C3-12 fluoroalkyl group in each molecule, (B) an organopolysiloxane that has at least two silicon atom-bonded hydrogen atoms and at least one C3-12 fluoroalkyl group in each molecule, (C) a platinum-group metal-based hydrosilylation reaction catalyst, and (D) a silylated acetylene inhibitor, wherein the content of the platinum-group metal in the (C) component relative to the composition is 0.1-100 ppm in terms of mass, and the molar ratio of the aliphatic unsaturated bonds in the (D) component relative to the platinum-group metal in the (C) component is 100-2,000. The composition exhibits good curing properties and a sufficient pot life at room temperature.

Description

[Technical Field]

[0001] The present invention relates to a curable fluorosilicone composition. [Background technology]

[0002] Curable fluorosilicone compositions that cure via an addition reaction in the presence of a platinum group metal-based hydrosilylation catalyst cure to form silicone cured products that have excellent cold resistance and solvent resistance, and are therefore also used as sealants for electrical and electronic components (see Patent Documents 1 and 2). However, such curable fluorosilicone compositions have a slow cure rate, and one problem is that attempting to achieve a sufficient cure rate results in a significantly shortened pot life at room temperature.

[0003] For this reason, Patent Document 3 proposes a method for controlling the cure initiation time and cure time of a curable fluorosilicone composition by blending a crosslinker mixture containing a fluoroalkyl group-containing alkylhydrogensiloxane.

[0004] Meanwhile, Patent Document 4 discloses that a curable silicone composition containing a platinum group metal-based hydrosilylation catalyst contains 0.001 to 1 part by weight of a silylated acetylenic inhibitor, based on the total weight of the composition. Patent Document 4 discloses that the use of a silylated acetylenic inhibitor reduces yellowing of the resulting cured silicone product, but does not disclose adjusting the molar ratio of aliphatic unsaturated bonds in the silylated acetylenic inhibitor to the platinum group metal in the catalyst in order to ensure the pot life of the composition at room temperature. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 05-070693 [Patent Document 2] Japanese Patent Application Publication No. 07-070444 [Patent Document 3] Japanese Patent Application Publication No. 10-081825 [Patent Document 4] Special Publication No. 2009-523856 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a curable fluorosilicone composition that has good curability and a sufficient pot life at room temperature. [Means for solving the problem]

[0007] The curable fluorosilicone composition of the present invention comprises: (A) 100 parts by mass of an organopolysiloxane having at least two alkenyl groups and at least one fluoroalkyl group having 3 to 12 carbon atoms in one molecule, (B) an organopolysiloxane having, per molecule, at least two silicon-bonded hydrogen atoms and at least one fluoroalkyl group having 3 to 12 carbon atoms, in an amount such that there are 0.1 to 10 moles of silicon-bonded hydrogen atoms in this component per mole of total aliphatic unsaturated bonds in the composition; (C) a platinum group metal-based hydrosilylation catalyst, and (D) Silylated acetylene inhibitors The composition is characterized in that the platinum group metal in component (C) is present in an amount of 0.1 to 100 ppm by mass relative to the composition, and the molar ratio of the aliphatic unsaturated bonds in component (D) to the platinum group metal in component (C) is 10 to 2,000.

[0008] In the above composition, component (A) preferably contains a linear organopolysiloxane having alkenyl groups bonded only to silicon atoms at both ends of the molecular chain.

[0009] In the above composition, component (B) preferably contains an organopolysiloxane having hydrogen atoms bonded exclusively to silicon atoms at the molecular chain terminals, and is particularly preferably a mixture of a linear organopolysiloxane having hydrogen atoms bonded exclusively to silicon atoms at both molecular chain terminals and a branched organopolysiloxane having hydrogen atoms bonded exclusively to silicon atoms at the molecular chain terminals.

[0010] In the above composition, the component (C) is preferably a platinum compound or a platinum complex.

[0011] In the composition, the component (D) is a compound represented by the general formula: [ka] (In the formula, R 1 are the same or different, each a hydrogen atom or a monovalent hydrocarbon group, and R 2 is a linking group or an alkylene group, and R 3 is an alkyl group, an alkenyl group, or an aryl group, a is an integer of 1 to 4, and b is an integer of 0 to 5. Silylated acetylenic inhibitors represented by the general formula: [ka] (In the formula, R 1 , R 3 , a, and b are the same as above, and c is an integer of 4 to 6. Preferably, the inhibitor is a silylated acetylenic inhibitor represented by the formula: [Effects of the Invention]

[0012] The curable fluorosilicone composition of the present invention is characterized by its excellent curability and its sufficient pot life at room temperature. DETAILED DESCRIPTION OF THE INVENTION

[0013] <Terminology> In this specification, the term "aliphatic unsaturated bond" is a general term for an aliphatic carbon-carbon double bond and an aliphatic carbon-carbon triple bond.

[0014] In addition, in this specification, the term "silylated acetylenic inhibitor" refers to an acetylenic inhibitor having a silyl group, such as a reaction product in which a hydroxyl group in an acetylenic alcohol inhibitor is substituted with a siloxy group, as disclosed in U.S. Pat. Nos. 5,449,802 and 5,708,046.

[0015] <Curable fluorosilicone composition> Component (A) is the main component of the composition and is an organopolysiloxane containing, in each molecule, at least two alkenyl groups and at least one fluoroalkyl group having 3 to 12 carbon atoms. Examples of the alkenyl group in component (A) include alkenyl groups having 2 to 12 carbon atoms, such as vinyl, allyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, and decenyl, with vinyl and hexenyl being preferred. Furthermore, examples of the fluoroalkyl group in component (A) include 3,3,3-trifluoropropyl, 4,4,4,3,3-pentafluorobutyl, 5,5,5,4,4,3,3-heptafluoropentyl, 6,6,6,5,5,4,4,3,3-nonafluorohexyl, and 7,7,7,6,6,5,5,4,4,3,3-undecafluoroheptyl groups, with 3,3,3-trifluoropropyl being preferred. Furthermore, examples of groups bonded to silicon atoms in component (A) other than alkenyl groups and fluoroalkyl groups include alkyl groups having 1 to 12 carbon atoms, such as methyl, ethyl, propyl, butyl, pentyl, hexyl, and heptyl; aryl groups having 6 to 12 carbon atoms, such as phenyl, tolyl, and xylyl; and aralkyl groups having 7 to 12 carbon atoms, such as benzyl and phenethyl, with methyl and phenyl being preferred. Furthermore, small amounts of hydroxyl groups or alkoxy groups, such as methoxy and ethoxy groups, may be bonded to silicon atoms in component (A) within the scope of the present invention.

[0016] The molecular structure of component (A) is not limited, and examples include linear, branched, partially branched linear, and resinous structures. Linear and partially branched linear structures are preferred. The viscosity of component (A) at 25°C is also not limited, but is preferably within the range of 100 to 100,000 mPa·s or 500 to 50,000 mPa·s. A viscosity of component (A) above the lower limit of this range improves the mechanical strength of the resulting cured fluorosilicone, while a viscosity below the upper limit of this range improves the handling and packing properties of the composition. The viscosity of component (A) can be measured using a rotational viscometer or rotational rheometer in accordance with JIS K7117-2:1999, "Plastics—Liquid, Emulsion, or Dispersion Resins—Method for Measuring Viscosity at Constant Shear Rate Using a Rotational Viscometer."

[0017] Examples of such component (A) include a dimethylsiloxane-methyl(3,3,3-trifluoropropyl)siloxane copolymer terminated at both molecular chain terminals with dimethylvinylsiloxy groups, a dimethylsiloxane-methylvinylsiloxane-methyl(3,3,3-trifluoropropyl)siloxane copolymer terminated at both molecular chain terminals with dimethylvinylsiloxy groups, a dimethylsiloxane-methylphenylsiloxane-methyl(3,3,3-trifluoropropyl)siloxane copolymer terminated at both molecular chain terminals with dimethylvinylsiloxy groups, a methyl(3,3,3-trifluoropropyl)siloxane-methylvinylsiloxane copolymer terminated at both molecular chain terminals with trimethylsiloxy groups, and a mixture of two or more of these. Preferably, the component (A) contains a linear organopolysiloxane having alkenyl groups bonded only to silicon atoms at both molecular chain terminals.

[0018] Component (B) is the crosslinking agent for the composition, and is an organopolysiloxane containing in each molecule at least two silicon-bonded hydrogen atoms and at least one fluoroalkyl group having 3 to 12 carbon atoms. Examples of the fluoroalkyl group in component (B) include 3,3,3-trifluoropropyl, 4,4,4,3,3-pentafluorobutyl, 5,5,5,4,4,3,3-heptafluoropentyl, 6,6,6,5,5,4,4,3,3-nonafluorohexyl, and 7,7,7,6,6,5,5,4,4,3,3-undecafluoroheptyl, with 3,3,3-trifluoropropyl being preferred. Furthermore, examples of groups bonded to silicon atoms other than hydrogen atoms and fluoroalkyl groups in component (B) include alkyl groups having 1 to 12 carbon atoms, such as methyl groups, ethyl groups, and propyl groups; and aryl groups having 6 to 12 carbon atoms, such as phenyl groups, tolyl groups, and xylyl groups, with methyl groups and phenyl groups being preferred.

[0019] The molecular structure of component (B) is not limited, and examples include linear, branched, partially branched linear, cyclic, and resinous. The viscosity of component (B) is not limited, but preferably has a kinematic viscosity of 1 to 10,000 mm at 25°C. 2 / s range, or 1 to 2,000 mm 2 / s. This is because when the viscosity of component (B) is at or above the lower limit of the above range, the mechanical strength of the resulting fluorosilicone cured product is improved, while when it is at or below the upper limit of the above range, the handling and filling properties of the composition are improved. The viscosity of component (B) can be measured using a viscometer in accordance with JIS K2283:2000 "Crude oil and petroleum products - Test method for kinematic viscosity and calculation method for viscosity index."

[0020] Examples of component (B) include methylhydrogensiloxane-methyl(3,3,3-trifluoropropyl)siloxane copolymers terminated at both molecular chain ends with trimethylsiloxy groups, dimethylsiloxane-methylhydrogensiloxane-methyl(3,3,3-trifluoropropyl)siloxane copolymers terminated at both molecular chain ends with trimethylsiloxy groups, methyl(3,3,3-trifluoropropyl)polysiloxane terminated at both molecular chain ends with dimethylhydrogensiloxy groups, and dimethyl(3,3,3-trifluoropropyl)polysiloxane terminated at both molecular chain ends with dimethylhydrogensiloxy groups. Examples include methylsiloxane-methylhydrogensiloxane-methyl(3,3,3-trifluoropropyl)siloxane copolymers, and mixtures of two or more of these. Preferably, the organopolysiloxane contains an organopolysiloxane having hydrogen atoms bonded only to silicon atoms at the molecular chain terminals. In particular, a mixture of a linear organopolysiloxane having hydrogen atoms bonded only to silicon atoms at both molecular chain terminals and a branched organopolysiloxane having hydrogen atoms bonded only to silicon atoms at the molecular chain terminals is preferred.

[0021] The content of component (B) is an amount that results in 0.1 to 10 moles of silicon-bonded hydrogen atoms in this component per mole of total aliphatic unsaturated bonds in the composition, and preferably an amount that results in 0.1 to 5 moles, 0.5 to 5 moles, or 0.5 to 3 moles. This is because when the content of component (B) is at or above the lower limit of the above range, the composition cures sufficiently, while when it is at or below the upper limit of the above range, the heat resistance of the resulting fluorosilicone cured product is improved.

[0022] Component (C) is a platinum group metal-based hydrosilylation catalyst for accelerating the curing of the composition. Examples of component (C) include platinum group metal catalysts such as platinum, rhodium, ruthenium, iridium, and palladium catalysts, with platinum catalysts being preferred. Examples of platinum catalysts include chloroplatinic acid, chloroplatinic acid hexahydrate, platinum dichloride, alcohol solutions of chloroplatinic acid, olefin complexes of chloroplatinic acid, chloroplatinic acid and alkenylsiloxane complexes, platinum diketone complexes, platinum alkenylsiloxane complexes, and platinum olefin complexes. Platinum alkenylsiloxane complexes are particularly preferred, with platinum and alkenylsiloxane complexes being particularly preferred, including platinum and 1,3-diethynyl-1,1,3,3-tetramethyldisiloxane complexes and platinum and methyl(3,3,3-trifluoropropyl)siloxane oligomer complexes terminated at both molecular chain ends with dimethylvinylsiloxy groups.

[0023] Component (D) is a silylated acetylene inhibitor for adjusting the curing properties of the composition. Examples of component (D) are disclosed in, for example, U.S. Pat. No. 5,449,802 and U.S. Pat. No. 5,708,046, and include, for example, 1-butyn-3-ol, 1-propyn-3-ol, 2-methyl-3-butyn-2-ol, 3-methyl-1-butyn-3-ol, 3-methyl-1-pentyn-3-ol, 3-phenyl-1-butyn-3-ol, 4-ethyl-1-octyn-3-ol, 3,5-diethyl-1-hexyn-3-ol, and 1-ethynyl-1-cyclohexanol in which the hydroxyl groups have been substituted with siloxy groups.

[0024] Examples of such component (D) include compounds represented by the general formula: [ka] Silylated acetylenic inhibitors represented by the general formula: [ka] or a mixture thereof.

[0025] In the formula, R1 are the same or different and each represents a hydrogen atom or a monovalent hydrocarbon group. 1 Examples of the monovalent hydrocarbon group include alkyl groups having 1 to 12 carbon atoms, such as methyl, ethyl, propyl, butyl, pentyl, hexyl, and heptyl; aryl groups having 6 to 12 carbon atoms, such as phenyl, tolyl, and xylyl; and aralkyl groups having 7 to 12 carbon atoms, such as benzyl and phenethyl, with a methyl group being preferred.

[0026] Also, in the formula, R 2 is a linking group or an alkylene group. 2 Examples of the alkylene group in R include alkylene groups having 1 to 12 carbon atoms, such as methylene, ethylene, propylene, butylene, pentylene, hexylene, and heptylene. 2 is preferably a linking group.

[0027] Also, in the formula, R 3 is an alkyl group, an alkenyl group, or an aryl group. 3 Examples of the alkyl group for R include alkyl groups having 1 to 12 carbon atoms, such as methyl, ethyl, propyl, butyl, pentyl, hexyl, and heptyl groups. 3 Examples of the alkenyl group in R include alkenyl groups having 2 to 12 carbon atoms, such as vinyl, allyl, butenyl, pentenyl, hexenyl, and heptenyl. 3 Examples of the aryl group include aryl groups having 6 to 12 carbon atoms, such as a phenyl group, a tolyl group, and a xylyl group.

[0028] In the formula, a is an integer of 1 to 4, and is preferably 3 or 4.

[0029] In the formula, b is an integer of 0 to 5, and is preferably 0.

[0030] In the formula, c is an integer of 4 to 6, and is preferably 5.

[0031] Examples of such component (D) include the following silylated acetylene inhibitors. [ka] [ka] [ka] [ka] [ka] [ka]

[0032] Methods for preparing component (D) are known. For example, as disclosed in U.S. Pat. Nos. 5,449,802 and 5,708,046, a compound represented by the general formula: [ka] and / or acetylenic alcohols represented by the general formula: [ka] and an acetylenic alcohol represented by the general formula: X d SiR 3 (4-d) It can be prepared by a condensation reaction of a chlorosilane represented by the formula: 1 , R 2 , R 3 , b, and c are the same as above. In the above formula, X is a hydrolyzable group, and examples thereof include an alkoxy group such as a methoxy group, an ethoxy group, or a propoxy group; a halogen atom such as a chlorine atom; or an acetoxy group. In the above formula, d is an integer of 1 to 4, and preferably 2 or 3.

[0033] The contents of components (C) and (D) in the composition are such that the platinum group metal in component (C) is 0.1 to 100 ppm by mass and the molar ratio of aliphatic unsaturated bonds in component (D) to the platinum group metal in component (C) is 100 to 2,000, and preferably the platinum group metal in component (C) is 0.1 to 50 ppm by mass and the molar ratio of aliphatic unsaturated bonds in component (D) to the platinum group metal in component (C) is 150 to 1,600. This is because when the content of component (C) is at or above the lower limit of the above range, curing of the composition proceeds sufficiently, whereas when it is below the upper limit of the above range, the resulting fluorosilicone cured product is less likely to be discolored. Furthermore, when the content of component (D) is equal to or greater than the lower limit of the above range, the pot life of the composition at room temperature is sufficient, while when the content is equal to or less than the upper limit of the above range, the curability of the composition is good.

[0034] The composition may also contain a known inhibitor other than component (D) to improve the composition's storage stability and ease of handling. Examples of such inhibitors include acetylene compounds such as 1-ethynylcyclohexane-1-ol, 2-methyl-3-butyn-2-ol, 3,5-dimethyl-1-hexyn-3-ol, and 2-phenyl-3-butyn-2-ol; eneyne compounds such as 3-methyl-3-penten-1-yne and 3,5-dimethyl-3-hexen-1-yne; and triazole compounds such as benzotriazole. The amount of these inhibitors is not limited, but is preferably within the range of 0.001 to 10 parts by mass, or 0.01 to 10 parts by mass, per 100 parts by mass of component (A).

[0035] The composition may optionally contain metal compounds such as copper acetylacetonate and copper phthalocyanine for the purpose of improving the heat resistance, cold resistance, or weather resistance of the resulting cured fluorosilicone. There are no limitations on the amount of such metal compounds added, but it is preferable that the amount of such metal compounds be at most 100 ppm, or at most 50 ppm, by mass, relative to the composition.

[0036] Furthermore, the composition may contain a filler to the extent that it does not impair the object of the present invention. Examples of such fillers include reinforcing fillers such as fumed silica, fused silica, and precipitated silica; extending fillers such as quartz powder, diatomaceous earth, calcium carbonate, and magnesium carbonate; heat-resistant additives such as cerium oxide, cerium hydroxide, and iron oxide; pigments such as red iron oxide, titanium oxide, and carbon black; and flame retardants. [Example]

[0037] The curable fluorosilicone composition of the present invention will be described in more detail with reference to the following examples. The viscosity values ​​given in the examples are measured at 25°C. The pot life of the curable fluorosilicone composition at 25°C was also measured as follows.

[0038] <Ratio of viscosity after 24 hours to initial viscosity> The initial viscosity (mPa·s) of the curable fluorosilicone composition immediately after preparation at 25°C and the viscosity (mPa·s) after standing at 25°C for 24 hours were measured using a rotational rheometer (Anton Paar MCR102 or 302 viscoelasticity measuring device) in accordance with the method specified in JIS K7117-2:1999. This measurement was carried out using a 20 mm diameter, 2° angle cone-plate with a shear rate of 10.0 (S -1 The ratio of the viscosity after 24 hours to the initial viscosity was calculated.

[0039] <Examples 1-4, Comparative Examples 1-8> The following components were mixed uniformly to prepare curable fluorosilicone compositions as shown in Tables 1 to 3. The molar ratio of silicon-bonded hydrogen atoms in component (B) to the total mole of aliphatic unsaturated bonds in this composition was 0.8.

[0040] The following components were used as component (A): (a-1): Methyl(3,3,3-trifluoropropyl)polysiloxane (vinyl group content = approximately 1.08% by mass) terminated at both ends of the molecular chain by dimethylvinylsiloxy groups, with a viscosity of 1,200 mPa·s

[0041] The following components were used as component (B): (b-1): Kinematic viscosity 710mm 2 / s: Dimethylsiloxane-methyl(3,3,3-trifluoropropyl)siloxane copolymer, both ends of which are capped with dimethylhydrogensiloxy groups (silicon-bonded hydrogen atom content = approx. 0.024% by mass) (b-2):Kinematic viscosity 7mm 2 In / s, the formula: CF3C2H4Si[OSi(CH3)2H]3 A branched-chain organopolysiloxane (content of silicon-bonded hydrogen atoms = approximately 0.59% by mass) represented by the formula

[0042] The following components were used as component (C): (c-1): Platinum complex of methyl(3,3,3-trifluoropropyl)siloxane oligomer (degree of polymerization 3) terminated at both ends of the molecular chain with dimethylvinylsiloxy groups (platinum metal content = approximately 5,000 ppm)

[0043] The following components were used as component (D): (d-1):Formula: [ka] A silylated acetylene inhibitor represented by

[0044] In addition, the following components were used for comparison with component (D). (d-2): 1-ethynyl-cyclohexan-1-ol (d-3): 2-methyl-3-butyn-2-ol (d-4): 1,3,5,7-tetravinyl-tetramethylcyclotetrasiloxane

[0045] [Table 1]

[0046] [Table 2]

[0047] [Table 3]

[0048] The curable fluorosilicone compositions of Examples 1-4 were all found to cure rapidly at 150° C., but had sufficient pot life at 25° C. On the other hand, the compositions of Comparative Examples 1 and 3-8 were all found to cure rapidly at 150° C., but had insufficient pot life at 25° C. Furthermore, the composition of Comparative Example 2 contained a relatively large amount of 1,3,5,7-tetravinyl-tetramethylcyclotetrasiloxane, but still had insufficient pot life at 25° C. [Industrial Applicability]

[0049] The curable fluorosilicone composition of the present invention has good curability and a sufficient pot life at room temperature, making it suitable for use as a protective sealing material for ICs and other electrical and electronic components, as well as an impact absorbing material.

Claims

1. (A) 100 parts by mass of an organopolysiloxane having at least two alkenyl groups and at least one fluoroalkyl group having 3 to 12 carbon atoms in each molecule; (B) an organopolysiloxane having, per molecule, at least two silicon-bonded hydrogen atoms and at least one fluoroalkyl group having 3 to 12 carbon atoms, in an amount such that there are 0.1 to 10 moles of silicon-bonded hydrogen atoms in this component per mole of total aliphatic unsaturated bonds in the composition; (C) a platinum group metal-based hydrosilylation catalyst, and (D) Silylated acetylene inhibitors the platinum group metal in component (C) is present in an amount of 0.1 to 100 ppm by mass relative to the composition, and the molar ratio of aliphatic unsaturated bonds in component (D) to the platinum group metal in component (C) is 100 to 2,000; The component (D) is represented by the general formula: 【Chemical 1】 (In the formula, R 1 s are the same or different and are each a hydrogen atom or a monovalent hydrocarbon group; R 2 is a linking group or an alkylene group; R 3 is an alkyl group, an alkenyl group, or an aryl group; a is 3 or 4; and b is an integer from 0 to 5.) The curable fluorosilicone composition comprises a silylated acetylenic inhibitor represented by the formula:

2. 2. The curable fluorosilicone composition according to claim 1, wherein component (A) comprises a linear organopolysiloxane having alkenyl groups bonded exclusively to silicon atoms at both ends of the molecular chain.

3. 2. The curable fluorosilicone composition according to claim 1, wherein component (B) comprises an organopolysiloxane having hydrogen atoms bonded only to silicon atoms at the molecular chain terminals.

4. 2. The curable fluorosilicone composition according to claim 1, wherein component (B) is a mixture of a linear organopolysiloxane having hydrogen atoms bonded exclusively to silicon atoms at both molecular chain terminals, and a branched organopolysiloxane having hydrogen atoms bonded exclusively to silicon atoms at the molecular chain terminals.

5. 2. The curable fluorosilicone composition according to claim 1, wherein component (C) is a platinum compound or a platinum complex.

Images