JP7152220B2 - Silicone gel composition and cured silicone gel - Google Patents

Description

TECHNICAL FIELD The present invention relates to a silicone gel composition and a cured silicone gel.

The silicone gel composition contains an organohydrogenpolysiloxane having a silicon-bonded hydrogen atom (SiH), an organopolysiloxane having an alkenyl group such as a silicon-bonded vinyl group, and a platinum-based catalyst, It is an addition reaction-curing organopolysiloxane composition that yields a cured product through the addition reaction of SiH to alkenyl groups.

The silicone gel cured product obtained by heating and curing this silicone gel composition (hereinafter also simply referred to as "silicone gel") has heat resistance, weather resistance, oil resistance, cold resistance, electrical insulation, etc. Excellent, low modulus and low stress. The low elastic modulus and low stress characteristic of the cured silicone gel are characteristics not found in other elastomer products. This cured silicone gel is used to protect in-vehicle electronic parts and household electronic parts. Due to demands for reliability and the like, silicone gel materials for such applications are increasingly required to reduce bleeding.

In general, when silicone rubber and silicone gel are compared, silicone rubber is a hard elastomer and silicone gel is a soft elastomer, and silicone rubber bleeds less after curing. Therefore, it is possible to reduce bleeding by applying silicone rubber as a protective material for electronic parts, but in that case, the damage to the wires and the like in the electronic parts increases, and cracks occur in the silicone rubber. It has drawbacks such as ease of use.

In addition, in order to impart properties such as heat resistance to the cured silicone gel, it has been proposed to add various additives to the composition (see, for example, Patent Documents 1 and 2). Since the active ingredient for is dispersed in oil before use, there is a problem that the amount of bleeding increases in proportion to the amount added.

JP 2008-291148 A JP 2015-7203 A

The present invention was made to solve such problems, and provides a silicone gel composition that provides a silicone gel cured product that suppresses bleeding during long-term use, and a silicone gel cured product obtained therefrom. intended to

The silicone gel composition of the present invention is
(A) 100 parts by mass of an alkenyl group-containing organopolysiloxane having two or more alkenyl groups bonded to a silicon atom at the molecular chain end in one molecule and having a viscosity of 10 to 100,000 mPa s at 23°C;
(B1) A polysiloxane having hydrogen atoms bonded to silicon atoms, wherein the hydrogen atoms are bonded only to the silicon atoms at the ends of the molecular chain, the first organohydrogenpolysiloxane having the hydrogen atoms in (A) an amount of 0.05 to 0.8 per silicon-bonded alkenyl group in the alkenyl group-containing organopolysiloxane;
(B2) a monofunctional siloxane unit represented by the formula: R ¹ ₃ SiO _1/2 (wherein each R ¹ is independently a hydrogen atom or a substituted or unsubstituted alkyl group); :R ² HSiO _2/2 (wherein R ² is a substituted or unsubstituted alkyl group), and a first bifunctional siloxane unit represented by the formula: R ² ₂ SiO _2/2 ( In the formula, R ² is as described above.) Each contains a second bifunctional siloxane unit represented by The second organohydrogenpolysiloxane having a content of 10% or more and 65% or less, the hydrogen atoms of which are 0.05 per alkenyl group bonded to the silicon atom of the alkenyl group-containing organopolysiloxane (A). and (C) an effective amount of a platinum-based catalyst.
The silicone gel composition of the present invention preferably has a mass reduction rate of 10% by mass or less due to isopropanol extraction of the cured product. (However, the rate of mass loss due to isopropanol extraction is the ratio of the amount of mass loss after immersing 1 g of the cured product in 40 g of isopropanol and allowing it to stand at room temperature for 7 days to the mass of the cured product before immersion.)

In the silicone gel composition of the present invention, the alkenyl group-containing organopolysiloxane, component (A), is preferably linear and has alkenyl groups bonded to silicon atoms at both ends of the molecular chain.

The silicone gel composition of the present invention preferably has a penetration of 10 to 200 as measured according to ASTM D1403.

The silicone gel cured product of the present invention is obtained by heating and curing the silicone gel composition.

In this specification, "alkenyl group bonded to a silicon atom" may be simply referred to as "alkenyl group". Also, "a hydrogen atom bonded to a silicon atom" may be simply referred to as a "hydrogen atom" or "SiH".

According to the present invention, it is possible to obtain a silicone gel composition that suppresses bleeding during long-term use and provides a silicone gel cured product that is suitable for long-term use. In addition, such a silicone gel composition suppresses bleeding during long-term use, making it possible to obtain a cured silicone gel that is suitable for long-term use.

Hereinafter, embodiments of the present invention will be described in detail.

[Silicone gel composition]
The silicone gel composition of the present invention contains the above components (A), (B1), (B2) and (C) as essential components.
In the present invention, the cured silicone gel is a cured product containing organopolysiloxane as a main component and having a low crosslink density, and having a penetration of 10 to 200, preferably 10, as measured according to ASTM D1403. ~100. This is different from a silicone rubber cured product having rubber-like elasticity, and has a lower hardness (that is, softer), lower elasticity, and lower stress than the silicone rubber cured product.

The silicone gel composition of the present invention preferably has a mass reduction rate of 10% by mass or less due to isopropanol extraction of the cured product. The mass reduction rate due to isopropanol extraction is obtained by immersing 1 g of the cured product in 40 g of isopropanol and leaving it at room temperature (23 ° C.) for 7 days to measure the mass decrease of the cured product. is calculated as a ratio to the mass of

Each component will be described in detail below. In this specification, unless otherwise specified, viscosity is a value at 23°C.

<(A) Alkenyl Group-Containing Organopolysiloxane>
The alkenyl group-containing organopolysiloxane, component (A) of the present invention, has two or more alkenyl groups bonded to silicon atoms at the ends of the molecular chains in one molecule, and is the main ingredient (base polymer) of the silicone gel composition. ).

Component (A) may have two or more alkenyl groups bonded to silicon atoms at the ends of the molecular chain, and may have other alkenyl groups bonded to silicon atoms other than the terminals. However, it is preferred that all alkenyl groups of component (A) are bonded to terminal silicon atoms. The number of alkenyl groups per molecule of component (A) is preferably 2-20, more preferably 2-10, still more preferably 2-5.

The alkenyl group of component (A) includes those having 2 to 6 carbon atoms, preferably 2 to 4 carbon atoms, more preferably 2 to 3 carbon atoms. Specific examples include vinyl group, allyl group, propenyl group, isopropenyl group, butenyl group, isobutenyl group and the like. A vinyl group is preferred. The two or more alkenyl groups that component (A) has in one molecule may be the same or different.

The number of moles of alkenyl groups in the component (A) organopolysiloxane is preferably 0.00001 to 0.2, more preferably 0.0001 to 0.2, based on the number of moles of silicon atoms (alkenyl group/silicon atom molar ratio). It is a number between 0005 and 0.1. When the alkenyl group/silicon atom molar ratio in the organopolysiloxane (A) is from 0.0001 to 0.2, it is easy to obtain a low-elasticity, low-stress silicone gel cured product.

In the alkenyl group-containing organopolysiloxane of component (A), the silicon-bonded hydrocarbon groups other than alkenyl groups are unsubstituted or substituted monovalent hydrocarbon groups containing no aliphatic unsaturated bonds. is preferred, and usually has 1 to 10 carbon atoms, preferably 1 to 6 carbon atoms. Specific examples thereof include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, hexyl, cyclohexyl, octyl, and decyl; phenyl; , an aryl group such as a tolyl group; an aralkyl group such as a benzyl group and a phenylethyl group; 3,3-trifluoropropyl group and the like. A methyl group, a phenyl group or a 3,3,3-trifluoropropyl group is preferable, and a methyl group is particularly preferable, because of excellent heat resistance durability. When (A) alkenyl group-containing organopolysiloxane has two or more hydrocarbon groups other than alkenyl groups in one molecule, they may be the same or different.

(A) The alkenyl group-containing organopolysiloxane may be linear and has the formula: RSiO _3/2 (R is an unsubstituted or substituted monovalent hydrocarbon containing no aliphatic unsaturation and a branched trifunctional siloxane unit represented by the above-described trifunctional siloxane unit represented by a group, which can be exemplified by a hydrocarbon group other than the alkenyl group, or a tetrafunctional siloxane unit represented by the formula: SiO _4/2 may be
(A) When the alkenyl group-containing organopolysiloxane is branched, two or more alkenyl groups are bonded to two or more ends, respectively. (A) When the alkenyl group-containing organopolysiloxane is linear, two or more alkenyl groups are attached to both ends of the molecular chain.

(A) The alkenyl group-containing organopolysiloxane is preferably substantially linear in terms of heat resistance and durability. In the present invention, the organopolysiloxane "substantially linear" means that the total amount of trifunctional siloxane units and tetrafunctional siloxane units with respect to the total amount of all siloxane units is the molar fraction is 5% or less.

(A) The alkenyl group-containing organopolysiloxane has a viscosity of 10 to 100,000 mPa·s, preferably 100 to 10,000 mPa·s. When the viscosity of (A) the alkenyl group-containing organopolysiloxane is within the above range, it is possible to obtain a cured product that is excellent in workability, low elastic modulus, and low stress. The viscosity can be measured using a rotational viscometer.
The component (A) of the present invention may be used singly or in combination of two or more.

<(B1) First organohydrogenpolysiloxane>
Component (B1) is an organohydrogenpolysiloxane having hydrogen atoms bonded to silicon atoms, and has a structure in which the hydrogen atoms are bonded only to the silicon atoms at the ends of the molecular chain. (B1) The first organohydrogenpolysiloxane preferably has two or more hydrogen atoms in one molecule. The component (B1) reacts with the component (A) together with the component (B2), which will be described later, and acts as a cross-linking agent.

In component (B1), the number of hydrogen atoms bonded to silicon atoms at the ends of the molecular chains is preferably 2 to 10, more preferably 2.

(B1) The first organohydrogenpolysiloxane may be branched or linear. (B1) When the first organohydrogenpolysiloxane is branched, two or more hydrogen atoms present in one molecule are bonded to any one of three or more molecular terminal silicon atoms. (B1) When the first organohydrogenpolysiloxane is linear, two hydrogen atoms are bonded to silicon atoms at both ends of the molecule, one at a time. The first organohydrogenpolysiloxane as the component (B1) is preferably substantially linear in terms of heat resistance and durability.

(B1) The first organohydrogenpolysiloxane has silicon-bonded hydrocarbon groups in addition to silicon-bonded hydrogen atoms. (B1) The hydrocarbon group possessed by the first organohydrogenpolysiloxane is preferably an unsubstituted or substituted monovalent hydrocarbon group containing no aliphatic unsaturated bonds, and usually has 1 carbon atom. ~10, preferably 1-6. Specific examples include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyl, and decyl groups. Aryl groups such as phenyl, tolyl, xylyl and naphthyl groups; Aralkyl groups such as benzyl, phenylethyl and phenylpropyl; , 3,3,3-trifluoropropyl groups substituted with halogen atoms such as bromine and fluorine. An alkyl group, an aryl group, and a 3,3,3-trifluoropropyl group are preferable, since a silicone gel cured product having excellent heat resistance durability, low elastic modulus, and low stress can be easily obtained. More preferred are a methyl group, a phenyl group and a 3,3,3-trifluoropropyl group, with a methyl group being particularly preferred.

(B1) The number of silicon atoms in one molecule of the first organohydrogenpolysiloxane (that is, the degree of polymerization) is usually 5 to 500 because gel properties cannot be obtained if it is too large. The number of silicon atoms is preferably 5 to 100, more preferably 10 to 80, because the handling workability of the composition and the properties of the resulting cured product (low elastic modulus, low stress) are good. .
(B1) The first organohydrogenpolysiloxane may be used alone or in combination of two or more.

In the silicone gel composition of the present invention, the amount of component (B1) to be blended is such that the number of hydrogen atoms possessed by component (B1) is from 0.05 to 0.05 per alkenyl group of the alkenyl group-containing organopolysiloxane (A). The amount is 8, preferably 0.1 to 0.7. When the number of hydrogen atoms from the component (B1) is less than 0.05 per alkenyl group in the alkenyl group-containing organopolysiloxane (A), the cured product loses flexibility and has a low elastic modulus and low stress. characteristics cannot be obtained. On the other hand, if it is more than 0.8, it is necessary to reduce the blending amount of component (B2), which will be described later, in order to obtain the desired penetration, and a sufficiently crosslinked gel-like elastic body cannot be obtained.

<(B2) Second organohydrogenpolysiloxane>
Component (B2) comprises a monofunctional siloxane unit represented by the formula: R ¹ ₃ SiO _1/2 (R ¹ is a hydrogen atom or a substituted or unsubstituted alkyl group) and a formula: R ² HSiO A first bifunctional siloxane unit represented by _2/2 (R ² is a substituted or unsubstituted alkyl group) and a formula: R ² ₂ SiO _2/2 (R ² is as described above) ), and the molar ratio of the first bifunctional siloxane units to the total bifunctional siloxane units is 10% or more and 65% or less. Polysiloxane. The component (B2) reacts with the component (A) together with the component (B1) to act as a cross-linking agent.

The component (B2) is a trifunctional siloxane represented by R ² SiO _3/2 (R ² is as defined above) in addition to the monofunctional siloxane unit and the bifunctional siloxane unit described above. Units and/or tetrafunctional siloxane units represented by SiO _4/2 can be included, but the proportion of trifunctional or higher siloxane units is 5 mol% or less of the total units, and substantially linear is preferably

The second organohydrogenpolysiloxane as component (B2) has the unit formula: [R ¹ ₃ SiO _1/2 ][R ² HSiO _2/2 ] _n [R ² ₂ SiO _2/2 ] _m [R ¹ ₃ SiO _1/2 ].
In this unit formula, each R ¹ independently represents a hydrogen atom or a substituted or unsubstituted alkyl group. The number of carbon atoms in the unsubstituted alkyl group is generally 1-10, preferably 1-6. Specific examples include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyl, and decyl groups. etc. Examples of substituted alkyl groups include 3,3,3-trifluoropropyl groups in which some or all of the hydrogen atoms in the above alkyl groups are substituted with halogen atoms such as chlorine, bromine and fluorine.

R ¹ is preferably a hydrogen atom or an unsubstituted alkyl group, since it is easy to obtain a silicone gel cured product with excellent heat resistance durability, low elastic modulus and low stress. A methyl group is particularly preferred. That is, it is particularly preferred that component (B2) is an organohydrogenpolysiloxane having a structure in which no hydrogen atoms are bonded to silicon atoms at the ends of the molecular chain, and all hydrogen atoms are bonded to silicon atoms in the middle of the molecular chain. .

In the above unit formula, ^R2 is a substituted or unsubstituted alkyl group. Substituted or unsubstituted alkyl groups include the same groups as described for R ¹ above. R ² is preferably an unsubstituted alkyl group, especially a methyl group.

In the unit formula, the molar ratio of the first bifunctional siloxane unit having a hydrogen atom to the entire bifunctional siloxane unit, that is, the value of n/(n+m) is 10% or more and 65% or less (0.1 to 0.65). If the molar ratio (n/(n+m)) is less than 10%, the action as a cross-linking agent becomes insufficient, making it difficult to obtain a cured product. Also, even if the molar ratio (n/(n+m)) exceeds 65%, the action as a cross-linking agent becomes insufficient, and as a result, unreacted components remain and bleeding tends to occur.

In addition, the number of silicon atoms in one molecule of the second organohydrogenpolysiloxane (B2) (that is, the degree of polymerization) is usually 5 to 500 because gel properties cannot be obtained if it is too large. be. The number of silicon atoms is preferably 5 to 100, more preferably 10 to 80, because the handling workability of the composition and the properties of the resulting cured product (low elastic modulus, low stress) are good. .

More specifically, the component (B2) is a monofunctional siloxane unit represented by the formula: (CH ₃ ) ₃ SiO _1/2 (hereinafter referred to as M unit) and/or the formula: (CH ₃ ) A monofunctional siloxane unit represented by ₂ HSiO _1/2 (hereinafter referred to as M ^H unit) and a bifunctional siloxane unit represented by the formula: (CH ₃ )HSiO _2/2 (hereinafter referred to as D ^H units) and bifunctional siloxane units represented by the formula: (CH ₃ ) ₂ SiO _2/2 (hereinafter referred to as D units) are preferred. In particular, copolymers composed of M units, ^DH units and D units are preferred.
(B2) The second organohydrogenpolysiloxane may be used alone or in combination of two or more.

In the silicone gel composition of the present invention, the amount of component (B2) to be blended is 0 per alkenyl group in which the hydrogen atoms of component (B2) are bonded to the silicon atoms of the alkenyl group-containing organopolysiloxane (A). 0.05 to 1.0, preferably 0.1 to 0.8.

If the number of hydrogen atoms in component (B2) is less than 0.05 per alkenyl group in component (A), a cured product cannot be obtained. On the other hand, if the number is more than 1.0, a cured gel product having a low elastic modulus, a low stress, and a desired penetration cannot be obtained.

<(C) platinum-based catalyst>
Component (C) is a catalyst that accelerates the addition reaction (hydrosilylation reaction) between the alkenyl group of component (A) and the hydrogen atoms of components (B1) and (B2). Component (C) is a platinum-based catalyst (platinum or platinum-based compound), and known catalysts can be used. Specific examples thereof include platinum black, chloroplatinic acid, alcohol-modified products of chloroplatinic acid, complexes of chloroplatinic acid with olefins, aldehydes, vinyl group-containing siloxanes, acetylene alcohols, and the like.

The amount of component (C) to be blended may be an effective amount, and can be appropriately increased or decreased depending on the desired curing rate. Generally, the amount is 0.1 to 1000 ppm in terms of the mass of platinum atoms with respect to the total amount of the components (A), (B1) and (B2). More preferably, it is in the range of 1 to 300 ppm. If the amount of the platinum-based catalyst (C) is less than 0.1 ppm by mass, the curability is remarkably lowered.

<Other optional ingredients>
In addition to the components (A), (B1), (B2) and (C), the silicone gel composition of the present invention may contain optional components within a range that does not impair the object of the present invention. can. Examples of the optional components include reaction inhibitors, inorganic fillers, organopolysiloxanes containing no silicon-bonded hydrogen atoms and alkenyl groups, heat resistance imparting agents, flame retardant agents, thixotropy imparting agents, and pigments. , dyes, and the like.

The reaction inhibitor is a component for inhibiting the reaction of the composition. -ethynyl-cyclohexanol, 3,5-dimethyl-1-hexyn-3-ol, triallyl isocyanurate, vinyl group-containing cyclic siloxane tetramer, and the like.

Examples of inorganic fillers include fumed silica, crystalline silica, precipitated silica, hollow fillers, silsesquioxane, fumed titanium dioxide, aluminum oxide, magnesium oxide, zinc oxide, iron oxide, aluminum hydroxide, and magnesium carbonate. inorganic fillers such as , calcium carbonate, zinc carbonate, layered mica, carbon black, diatomaceous earth, and glass fibers; Examples include fillers whose surface is hydrophobized with a silicon compound. In addition, silicone rubber powder, silicone resin powder, etc. may be blended. In order to maintain the flexibility of the cured silicone gel, it is preferable that the amount of inorganic filler is small, and it is more preferable that the inorganic filler is not contained.

The viscosity of the silicone gel composition of the present invention is preferably in the range of 100 to 3000 mPa·s as measured by a rotational viscometer at 23° C., because it is easy to fill electronic parts and the like and to be easily defoamed. A more preferable range is 200 to 2000 mPa·s.

The silicone gel composition of the present invention comprises components (A), (B1), (B2) and (C) (including optional ingredients when optional ingredients are added) in a conventional manner. It can be prepared by mixing accordingly. At that time, the components to be mixed may be divided into two or more parts and mixed as necessary. For example, it is possible to separate and mix a part consisting of a part of the component (A) and the component (C) and a part consisting of the remainder of the component (A) and the components (B1) and (B2). .

After that, the composition of the present invention is cured at room temperature or under temperature conditions depending on the application to obtain a cured silicone gel. The curing temperature is, for example, 20 to 200° C., and the curing time is, for example, 0.5 to 24 hours.
The silicone gel composition of the present invention is suitable for sealing or filling electrical and electronic parts.

[Silicone gel cured product]
The cured product (cured silicone gel product) of the silicone gel composition of the present invention preferably has a weight loss rate of 10% by mass or less due to extraction with isopropanol. This mass reduction rate corresponds to the amount of isopropanol extracted from the cured product. is improved.

In addition, this mass reduction rate is a value calculated as follows. That is, first, the silicone gel composition is cured under the conditions described above. Then, 1 g of the obtained cured product is immersed in 40 g of isopropanol and allowed to stand at normal temperature for 7 days, after which the cured product is removed from the isopropanol and weighed. The mass reduction amount is obtained from the measured mass, and the ratio of the mass reduction amount to the mass of the cured product before immersion is calculated as the mass reduction rate. That is, when the weight of the cured product before immersion is W ₁ and the weight after immersion is W ₂ , the weight reduction rate (%) due to isopropanol extraction is calculated by the following formula.
Mass reduction rate (%) = 100 (1-W ₂ /W ₁ )

The cured silicone gel of the present invention preferably has a penetration of 10 to 200, more preferably 10 to 100, and more preferably 30 to 90, as measured according to ASTM D1403. is more preferred. If the penetration is less than 10, the silicone gel composition may not be able to withstand the stress that occurs when it cures, resulting in partial rupture of the electronic circuit or the formation of cracks inside the cured product. On the other hand, if the penetration exceeds 200, the cured product does not have sufficient shape retention, and the filled and cured silicone gel may flow out of the circuit.

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited to these Examples.
In the following description, "parts" means "mass parts". M units, ^MH units, D units and ^DH units are as described above.

Synthesis Example 1 (Synthesis of methylhydrogenpolysiloxane (B2-1))
A 500 ml separable flask equipped with a thermometer, a reflux tube and a glass tube for nitrogen purging was charged with 158.2 g of methylhydrogenpolysiloxane represented by the unit formula: MD ^H ₅₆ M and hexamethyl represented by the unit formula: MM. 10.2 g of disiloxane, 129.2 g of octamethylcyclotetrasiloxane represented by the unit formula: D4, and 2.5 g of activated clay are added, heated at 75° C. for ₄ hours with stirring under a nitrogen atmosphere, and equilibrated. reacted.
Next, the reaction solution was suction-filtered through a filter paper using a filter aid to remove the activated clay to obtain a colorless and transparent methylhydrogenpolysiloxane (B2-1).

It can be seen from the amounts of the starting materials charged that the obtained methylhydrogenpolysiloxane (B2-1) was represented by the unit formula: MD ^H ₂₃ D ₁₆ M. In this methylhydrogenpolysiloxane (B2-1), the molar ratio of bifunctional siloxane units ( ^DH units) having hydrogen atoms to the total number of moles of bifunctional siloxane units ( ^DH units + D units) (hereinafter referred to as , n/(n+m)) is 59% (0.59=23/(23+16)). In addition, the SiH group content ratio obtained from the above formula was 8.4 mmol/g.

Synthesis Example 2 (Synthesis of methylhydrogenpolysiloxane (B2-2))
A 500 ml separable flask equipped with a thermometer, a reflux tube and a glass tube for nitrogen purging was charged with 50.5 g of methylhydrogenpolysiloxane represented by the unit formula: MD ^H ₅₆ M, 4.8 g of hexamethyldisiloxane, and octamethyldisiloxane. 241.8 g of methylcyclotetrasiloxane and 3.1 g of activated clay were added and heated at 75° C. for 4 hours under a nitrogen atmosphere with stirring to carry out an equilibration reaction.
Next, the reaction solution was suction-filtered through a filter paper using a filter aid to remove the activated clay to obtain a colorless and transparent methylhydrogenpolysiloxane (B2-2).

It can be seen from the amounts of the starting materials charged that the obtained methylhydrogenpolysiloxane (B2-2) was represented by the unit formula: MD ^H ₁₈ D ₇₅ M. n/(n+m) in this methylhydrogenpolysiloxane (B2-2) is 19% (0.19=18/(18+75)). Moreover, the content ratio of SiH groups obtained from the above formula was 2.7 mmol/g.

Synthesis Example 3 (Synthesis of methylhydrogenpolysiloxane (B2-3))
A 500 ml separable flask equipped with a thermometer, a reflux tube and a glass tube for nitrogen purging was charged with 10.7 g of tetramethylhydrogendisiloxane represented by the unit formula: M ^H M ^H and 248.0 g of octamethylcyclotetrasiloxane. , 38.3 g of hexamethylcyclotetrahydrogensiloxane represented by the unit formula: D ^H ₄ , and 3.0 g of activated clay are added and heated with stirring at 75 ° C. for 4 hours in a nitrogen atmosphere to perform an equilibration reaction. rice field.
Next, the reaction solution was suction-filtered through a filter paper using a filter aid to remove the activated clay to obtain a colorless and transparent methylhydrogenpolysiloxane (B2-3).

It can be seen from the charged amounts of the starting materials that the resulting _{methylhydrogenpolysiloxane (} ^B2-3 ) was represented by the unit ^formula : ^MHDH8D42MH . n/(n+m) in this methylhydrogenpolysiloxane (B2-3) is 16% (0.16=8/(8+42)). In addition, the SiH group content ratio obtained from the above formula was 2.1 mmol/g.

Synthesis Example 4 (Synthesis of methylhydrogenpolysiloxane (B2-4))
A 500 ml separable flask equipped with a thermometer, a reflux tube and a glass tube for nitrogen purging was charged with 173.4 g of methylhydrogenpolysiloxane represented by the unit formula: MD ^H ₅₆ M, 9.9 g of hexamethyldisiloxane, octa 114.2 g of methylcyclotetrasiloxane and 2.8 g of activated clay were added and heated at 75° C. for 4 hours under a nitrogen atmosphere with stirring to carry out an equilibration reaction.
Next, the reaction solution was suction-filtered through a filter paper using a filter aid to remove the activated clay to obtain a colorless and transparent methylhydrogenpolysiloxane (B2-4).

The obtained methylhydrogenpolysiloxane (B2-4) was found to be represented by the average unit formula: MD ^H ₂₅ D ₁₄ M, based on the amounts of the starting materials charged. n/(n+m) in this methylhydrogenpolysiloxane (B2-4) is 64% (0.64=25/(25+14)). Moreover, the content ratio of SiH groups obtained from the above formula was 9.3 mmol/g.

Synthesis Example 5 (Synthesis of methylhydrogenpolysiloxane (B2-5))
A 500 ml separable flask equipped with a thermometer, a reflux tube and a glass tube for nitrogen purging was charged with 178.2 g of methylhydrogenpolysiloxane represented by the unit formula: MD ^H ₅₆ M, 9.3 g of hexamethyldisiloxane, octa 109.5 g of methylcyclotetrasiloxane and 3.0 g of activated clay were added and heated at 75° C. for 4 hours under a nitrogen atmosphere with stirring to carry out an equilibration reaction.
Then, the reaction solution was suction-filtered through a filter paper using a filter aid to remove the activated clay to obtain a colorless and transparent methylhydrogenpolysiloxane (B2-5).

It can be seen from the amounts of the starting materials charged that the obtained methylhydrogenpolysiloxane (B2-5) was represented by the unit formula: MD ^H ₂₆ D ₁₃ M. n/(n+m) in this methylhydrogenpolysiloxane (B2-5) is 67% (0.67=26/(26+13)). Moreover, the content ratio of SiH groups obtained from the above formula was 9.7 mmol/g.

Synthesis Example 6 (Synthesis of methylhydrogenpolysiloxane (B2-6))
287.0 g of methyldichlorosilane and 13.0 g of trimethylchlorosilane were placed in a 500 ml separable flask equipped with a thermometer, a reflux tube, a dropping funnel, and a glass tube for nitrogen purging, and water was slowly added dropwise to remove the chlorosilanes. hydrolyzed.
Next, after the reaction solution was neutralized, it was suction-filtered through a filter paper using a filter aid to obtain a colorless and transparent methylhydrogenpolysiloxane (B2-6).

It can be seen from the amounts of the starting materials charged that the obtained methylhydrogenpolysiloxane (B2-6) was represented by the unit formula: MD ^H _56M . n/(n+m) in this methylhydrogenpolysiloxane (B2-6) is 100% (1.00=56/(56+0)). Moreover, the content ratio of SiH groups obtained from the above formula was 15.9 mmol/g.

Synthesis Example 7 (Synthesis of methylhydrogenpolysiloxane (B1))
A 500 ml separable flask equipped with a thermometer, a reflux tube and a nitrogen purge glass tube was charged with 24.7 g of tetramethylhydrogendisiloxane represented by the unit formula: M ^H M ^H , 272.3 g of octamethylcyclotetrasiloxane, and 3.0 g of activated clay were put into the flask and heated at 75° C. for 4 hours under a nitrogen atmosphere with stirring to carry out an equilibration reaction.
Next, the reaction solution was suction-filtered through a filter paper using a filter aid to remove the activated clay to obtain a colorless and transparent methylhydrogenpolysiloxane (B1).

It can be seen from the amounts of the starting materials charged that the obtained methylhydrogenpolysiloxane (B1) was represented by the average unit formula: M ^H D ₂₀ M ^H. The content of SiH groups in this dimethylhydrogensilyl group-blocked dimethylpolysiloxane (B1) at both ends was 1.2 mmol/g.

Example 1
(A-1) 70 parts of a dimethylvinylsiloxy-group-blocked dimethylpolysiloxane having a viscosity of 350 mPa s at both ends; (B1) 7.0 parts of dimethylpolysiloxane end-blocked with dimethylhydrogensilyl groups obtained in Synthesis Example 7, 0.32 parts of methylhydrogenpolysiloxane (B2-1) obtained in Synthesis Example 1, 0.004 parts of a platinum complex solution with 1,3-divinyl-1,1,3,3-tetramethyldisiloxane as a ligand (platinum atom content: 2% by mass), and 1-ethynyl-1-cyclo A silicone gel composition was prepared by uniformly mixing 0.014 parts of hexanol.

In the resulting composition, the content of vinyl groups bonded to silicon atoms was 14.06 mmol/g. In addition, the number of silicon-bonded hydrogen atoms per one silicon-bonded vinyl group (hereinafter referred to as the H/Vi ratio) is (B1) from dimethylhydrogensilyl group-blocked dimethylpolysiloxane The hydrogen atom is 0.56, the hydrogen atom from the methylhydrogenpolysiloxane (B2-1) obtained in Synthesis Example 1 is 0.18, and the hydrogen atom from (B1) and (B2-1) The sum with the hydrogen atoms from was 0.74.

Examples 2 to 4, Comparative Examples 1 and 2
Instead of the methylhydrogenpolysiloxane (B2-1) obtained in Synthesis Example 1, the methylhydrogenpolysiloxanes (B2-2) to (B2-6) obtained in Synthesis Examples 2 to 6 were used, respectively. . These were blended in the proportions shown in Table 1 and mixed in the same manner as in Example 1 to prepare a silicone gel composition.

Table 1 shows the content of vinyl groups bonded to silicon atoms in these compositions. Also, the H / Vi ratio for the hydrogen atoms from the methylhydrogenpolysiloxanes (B2-2) to (B2-6) obtained in Synthesis Examples 2 to 6, and the hydrogen atoms from these (B2) components and ( The H/Vi ratios for the sum with the hydrogen atoms from B1) are shown in Table 1.

Examples 5-7
Each component shown in Table 1 was blended in the ratio shown in the same table and mixed in the same manner as in Example 1 to prepare a silicone gel composition.
In these compositions, the content of vinyl groups bonded to silicon atoms, the H/Vi ratio for hydrogen atoms from the methylhydrogenpolysiloxane (B2-1) obtained in Synthesis Example 1, and (B2-1 The H/Vi ratios for the sum of hydrogen atoms from ) and from (B1) are shown in Table 1, respectively.

Next, the silicone gel compositions obtained in Examples 1-7 and Comparative Examples 1-2 were cured by heating at 80° C. for 60 minutes. The penetration of the cured product was measured according to ASTM D1403.
In addition, for the silicone gel cured products obtained from the compositions of Examples 1 to 7 and Comparative Examples 1 and 2, the amount of mass loss due to isopropanol extraction was measured by the following method, and the mass loss rate was calculated. The results are shown in Table 1 together with the viscosity of the silicone gel composition and the penetration of the cured product.

(mass reduction rate)
1 g of the compositions of Examples 1 to 7 and Comparative Examples 1 and 2 were placed in a 50 ml glass bottle and cured. After standing to cool, a glass bottle was filled with 40 g of isopropanol and left at 23° C. for 7 days for isopropanol extraction. After removing the isopropanol and drying the cured product at 150° C. for 1 hour, the mass was measured. The mass reduction amount was obtained from the initial mass of the cured product and the mass after isopropanol extraction, and the mass reduction rate was calculated.

From Table 1 above, the following can be understood. That is, the silicone gel compositions of Examples 1 to 7, which are obtained by blending the components (A), (B1), (B2) and (C) defined in the present invention in a predetermined composition, are cured products. It can be seen that the mass reduction rate due to isopropanol extraction is suppressed to 10% by mass or less. Since the isopropanol-extracted component becomes a source of contamination for bleeding from the cured product, it can be seen that the silicone gel compositions of Examples 1 to 7 of the present invention can suppress bleeding from the cured product even during long-term use. .

On the other hand, the silicone gel compositions of Comparative Examples 1 and 2, which contain methylhydrogenpolysiloxane with n/(n+m) exceeding 65% as component (B2), have a mass reduction rate of the cured product due to isopropanol extraction. exceeds 10% by mass. Therefore, it can be seen that the silicone gel compositions of Comparative Examples 1 and 2 tend to bleed from the cured product during long-term use.

According to the silicone gel composition of the present invention, it is possible to obtain a silicone gel cured product that is excellent in heat resistance and durability and that is suitable for long-term use by suppressing bleeding during long-term use. . This silicone gel cured product can be suitably used as a protective material for in-vehicle electronic parts, household electronic parts, and the like.

Claims (5)

(A) 100 parts by mass of alkenyl group-containing dimethylpolysiloxane having two or more alkenyl groups bonded to silicon atoms at the ends of the molecular chains in one molecule and having a viscosity of 10 to 100,000 mPa s at 23°C;
(B1) A polysiloxane having hydrogen atoms bonded to silicon atoms, wherein the hydrogen atoms are bonded only to the silicon atoms at the ends of the molecular chain, the first organohydrogenpolysiloxane having the hydrogen atoms in (A) an amount of 0.05 to 0.8 per silicon-bonded alkenyl group in the alkenyl group-containing dimethylpolysiloxane;
(B2) a monofunctional siloxane unit represented by the formula: R ¹ ₃ SiO _1/2 (wherein each R ¹ is independently a hydrogen atom or a substituted or unsubstituted alkyl group); :R ² HSiO _2/2 (wherein R ² is a substituted or unsubstituted alkyl group), and a first bifunctional siloxane unit represented by the formula: R ² ₂ SiO _2/2 ( In the formula, R ² is as described above.) Each contains a second bifunctional siloxane unit represented by The second organohydrogenpolysiloxane having a content of 16 % or more and 65% or less is added, and the hydrogen atom of the component is 0.05 per alkenyl group bonded to the silicon atom of the alkenyl group-containing dimethylpolysiloxane (A). and (C) an effective amount of a platinum-based catalyst. 2. The silicone gel composition according to claim 1, wherein the weight reduction rate of the cured product of the silicone gel composition due to extraction with isopropanol is 8.5 % by weight or less. (However, the rate of mass loss due to isopropanol extraction is the ratio of the amount of mass loss after immersing 1 g of the cured product in 40 g of isopropanol and allowing it to stand at room temperature for 7 days to the mass of the cured product before immersion.) 3. The silicone gel composition according to claim 1, wherein the alkenyl group-containing dimethylpolysiloxane , component (A), is linear and has alkenyl groups bonded to silicon atoms at both ends of the molecular chain. The silicone gel composition according to any one of claims 1 to 3, wherein a cured product of said silicone gel composition has a penetration of 10 to 200 as measured according to ASTM D1403. A cured silicone gel obtained by heating and curing the silicone gel composition according to any one of claims 1 to 4.