JPH06340813A - Curing-bondable silicone composition - Google Patents

Abstract

PURPOSE:To obtain the title composition which, even when containing a large amount of an inorganic filler, has flowability suited for casting and can be effectively inhibited from suffering filler sedimentation. CONSTITUTION:The title composition comprises an alkenyl-containing organopolysiloxane having a viscosity at 25 deg.C of 10-1,000cSt; an alkenyl- containing organopolysiloxane having a viscosity at 25 deg.C of 1,500-100,000 cSt; an organohydrogenpolysiloxane; a platinum-group metal catalyst; an organosilicon compound having in each molecule a functional group undergoing an addition reaction for curing and a functional group contributive to adherence; an inorganic filler having an average particle diameter of 1-50mum; and finely powdery silica having a BET specific surface area of 50m<2>/g or larger.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organopolysiloxane composition which is rich in fluidity, has less sedimentation and separation of filler components, and is capable of curing and adhering well to various substrates.

[0002]

2. Description of the Related Art A low viscosity and curable silicone composition used for potting and the like is a crystalline silica having a relatively high purity because of its strength, reduction of thermal expansion coefficient and the like.
It contains a relatively large amount of inorganic fillers such as alumina. However, with the recent miniaturization of electric and electronic parts, it is necessary to cast into small parts, so that a curable silicone composition having a particularly low viscosity is required.

[0003]

By the way, in a composition in which a large amount of a filler is mixed with a low-viscosity silicone oil, there arises a problem that the filler precipitates or separates from the silicone oil during storage thereof. Further, in the case where an adhesiveness-imparting agent is blended in order to improve the adhesiveness to various base materials, the viscosity when the filler is blended is remarkable and the fluidity of the composition is impaired. There is.

Therefore, the object of the present invention is to effectively prevent the separation or sedimentation of the silicone oil and the filler even during long-term storage, and to have an appropriate fluidity, and to cast a particularly small part. Another object of the present invention is to provide a curable silicone composition having good adhesion to various substrates.

[0005]

According to the present invention, (A)
25 ° C having at least one alkenyl group in one molecule
Organopolysiloxane (A1) having a viscosity of 10 to 1,000 cSt and an organopolysiloxane (A2) having a viscosity of 1,500 to 100,000 cSt at 25 ° C. having at least one alkenyl group in one molecule, (B) one molecule Organohydrogenpolysiloxane having at least two hydrogen atoms bonded to silicon atoms therein, (C) platinum group metal-based catalyst, (D) addition-curable functional group and adhesive functional group in one molecule A curable adhesive organopolysiloxane composition containing an organosilicon compound having (E) an inorganic filler having an average particle size of 1 to 50 μm, and (F) a fine powder silica having a BET specific surface area of 50 m ² / g or more. Will be provided.

[0006]

An important feature of the present invention is that two kinds of silicone oils having different viscosities are used in combination as the alkenyl group-containing organopolysiloxane as the base component, and finely divided silica is blended separately from the inorganic filler. Therefore, as shown in the examples described later,
It is possible to effectively suppress the increase in viscosity due to the use of the filler and the adhesion-imparting agent, and to avoid the sedimentation and separation of the filler.

[0007]

Preferred Embodiment of the Invention

(A) Alkenyl Group-Containing Organopolysiloxane In the curable composition of the present invention, the component (A) is a base component, and one having at least one alkenyl group in its molecule is used. This alkenyl group undergoes an addition reaction with the hydrogen atom bonded to the silicon atom of the component (B) described below to form a rubber-elastic cured product.

According to the present invention, the alkenyl group organopolysiloxane has a viscosity at 25 ° C. of 10 to 10.
Those in the range of 1,000cSt (A1) and 1,500 to 100,000c
Two kinds of those in the range of St (A2) are used in combination, and as described above, the increase in viscosity and the sedimentation and separation of the filler are suppressed.

Examples of these organopolysiloxanes are those used as the base component of a usual addition-curable silicone rubber composition, except that they have different viscosities (different polymerization degrees). For example, the following average composition formula (1): R _a SiO _{(4-a) / 2} (1) In the formula, R may be the same or different, and at least one is an alkenyl group. A group selected from an unsubstituted or substituted monovalent hydrocarbon group, a hydroxyl group, and an alkoxy group, provided that a is a number of 1.9 to 2.4. Is commonly used. Among the groups R in the above formula, the monovalent hydrocarbon group is methyl, ethyl,
Alkyl groups such as propyl, alkenyl groups such as vinyl, propenyl, butenyl, cycloalkyl groups such as cyclohexyl, aryl groups such as phenyl, tolyl, xylyl, aralkyl groups such as benzyl and phenylethyl, and hydrogen atoms of these groups. Examples thereof include a group partially or wholly substituted with a halogen atom, a cyano group, etc., such as a 3,3,3-trifluoropropyl group.

The substituent R bonded to the silicon atom may be any of the monovalent hydrocarbon groups exemplified above, a hydroxyl group and an alkoxy group, provided that at least one of them is an alkenyl group. However, a vinyl group is preferable as the alkenyl group, and a methyl group and a phenyl group are preferable as the other groups.

The alkenyl group-containing organopolysiloxane may be linear or RSi.
_It may have a branched shape containing _3/2 units or SiO _4/4 units.

These organopolysiloxanes are produced by known methods and are obtained, for example, by an equilibration reaction between an organocyclopolysiloxane and a hexaorganodisiloxane in the presence of an alkali or acid catalyst.

In the present invention, the low-viscosity organopolysiloxane (A1) and the high-viscosity organopolysiloxane (A1) are used.
Generally speaking, 2) is used in an amount ratio of (A1) / (A2) = 10/90 to 90/10, especially 50/50 to 90/10 on a weight basis. When the amount of the low-viscosity organopolysiloxane (A1) used is less than the above range, the viscosity of the composition becomes too high, and casting into a mold having a small volume becomes extremely difficult. When the amount of siloxane (A2) used is less than the above range, it tends to be difficult to prevent the filler from separating and settling.

In the present invention, if necessary, in addition to the low viscosity organopolysiloxane (A1) and the high viscosity organopolysiloxane (A2), a nonfunctional silicone oil can be used as a part of the base component. However, it is desirable to avoid the use of a large amount of non-functional silicone oil because it causes the oil to seep out from the cured product.

(B) Organohydrogenpolysiloxane The organohydrogenpolysiloxane used as the component (B) has at least two silicon-bonded hydrogen atoms in its molecule. This component is a cross-linking agent, and as described briefly above, Si in the molecule is
A rubber elastic cured product is formed by an addition reaction between the H group and the alkenyl group in the base component (A).

As the organohydrogenpolysiloxane, those used as a cross-linking agent for conventionally known addition-curable silicone rubber compositions can be used.
The molecular structure is not particularly limited, and various structures such as a chain structure, a ring structure, and a branched structure can be used. Examples of the substituent other than the hydrogen atom in the organohydrogenpolysiloxane molecule include the same groups as those exemplified for the substituent R in the organopolysiloxane of the component (A). This organohydrogenpolysiloxane is, for example, octamethylcyclotetrasiloxane and / or tetramethylcyclotetrasiloxane,
Hexamethyldisiloxane or 1, which can be a terminal group
1-dihydro-2,2,3,3-tetramethyldisiloxane unit-containing compound in the presence of a catalyst such as sulfuric acid, trifluoromethanesulfonic acid, methanesulfonic acid -10 ~ +40 ℃
It is easily obtained by equilibration at moderate temperature.

In the component (B), the amount of hydrogen atoms bonded to the silicon atom is the total of the amount of hydrogen atoms bonded to the silicon atom in the component (D), which will be described later, and the alkenyl group contained in the composition. 0.4 to 5.0 equivalents, especially 0.8 to 2.0 per piece
It is used in a ratio so as to be equivalent. If this amount is less than 0.4 equivalent, the crosslinking density tends to be too low, and the heat resistance of the cured silicone rubber tends to decrease. Also,
If the amount is more than 5.0 equivalents, a problem of foaming due to a dehydrogenation reaction may occur, or the heat resistance of the cured product tends to decrease.

(C) Platinum group metal catalyst The component (C) is a catalyst for promoting the addition curing reaction (hydrosilation) between the above components (A) and (B). There are platinum-based, palladium-based, and rhodium-based ones, but in general, platinum-based ones are preferably used from the viewpoint of cost and the like. Specific examples thereof include platinum black, chloroplatinic acid, alcohol-modified chloroplatinic acid, and complexes of chloroplatinic acid with olefins, aldehydes, vinylsiloxanes, acetylene alcohols, and the like.

The blending amount of the component (C) can be appropriately determined according to the desired curing rate, but it is generally 0.1 to 2,000 ppm, particularly, in terms of platinum group metal per composition, particularly , 1 to 200 ppm.

(D) Organosilicon Compound The component (D) in the curable silicone composition of the present invention is an adhesiveness-imparting agent for causing the composition of the present invention to function as an adhesive, and is added as a functional group. It is necessary to have both a curable functional group and an adhesive functional group. Here, the addition-curable functional group is a SiH group or an alkenyl group,
A vinyl group is preferable as the alkenyl group. Further, the adhesive functional group is selected from an alkoxysilyl group, an epoxy group, an acid anhydride group, peroxysilyl and the like, but in the present invention, an alkoxysilyl group and an epoxy group are preferable.

In the present invention, the organosilicon compound is not limited to this, but for example,
1,5-dihydrogen-1,3,5,7-tetramethyl-3-trimethoxysilylethyl-7-glycidylpropyltetrasiloxane, bis (trimethoxysilylpropyl) allyl isocyanate, 1,5-dihydrogen -1,3,5,7-Tetramethyl-3-trimethoxysilylethyl-7- (γ-methacryloxypropyltetrasiloxane, 3,5,7-trihydrogen-
1,3,5,7-tetramethyl-1-glycidylpropyltetrasiloxane, 3,5,7-trihydrogen-1,3,5,7-tetramethyl-1-trimethoxysilylethyltetrasiloxane and the like can be mentioned. To be

The component (D) is generally 0.1 to 30 parts by weight, especially 0.5 per 100 parts by weight of the component (A).
Used in amounts of up to 10 parts by weight. If it is used in an amount of more than 30 parts by weight, mechanical properties such as strength of the cured product may be impaired, and if it is less than 0.1 part by weight, adhesiveness will not be exhibited.

(E) Inorganic Filler The inorganic filler of the component (E) has an average particle size in the range of 1 to 50 μm, and improves the mechanical properties of the cured product, the electrical properties, and the thermal expansion coefficient. It is used for the purpose of reduction.
Specific examples of such an inorganic filler include those normally used as fillers for silicone rubber, such as silica,
Alumina, aluminum hydroxide, titanium oxide, red iron oxide, calcium carbonate, magnesium carbonate, high thermal conductivity magnesium carbonate (trade name: Pyrokisma) and the like can be mentioned, but silica and alumina are generally preferable in view of particle size, purity and the like. .

The inorganic filler having an average particle size of 1 to 50 μm is 10 to 500 parts by weight per 100 parts by weight of the component (A).
It is commonly used, especially in amounts of 50 to 300 parts by weight. If it is used in an amount of more than 500 parts by weight, the workability of the composition may be deteriorated, and the mechanical properties of the cured product may be deteriorated. Also, if less than 10 parts by weight, thermal conductivity,
The coefficient of thermal expansion tends to decrease.

(F) Fine-powder silica The fine-powder silica of component (F) acts as an anti-settling agent for the inorganic filler of component (E). This fine powder silica is B
It is different from silica used as the inorganic filler of the component (E) in that the ET specific surface area is 50 m ² / g or more. When silica having a BET specific surface area lower than 50 m ² / g is used, it becomes difficult to effectively suppress the sedimentation and separation of the inorganic filler.

Examples of such fine powder silica include, as hydrophilic silica, Aerosil 130, 200, 300 (manufactured by Nippon Aerosil Co., Ltd., Degussa Co.), Cabosil MS-5, MS-7 (Cab
ot), Rheorosil QS-102, 103 (Tokuyama Soda), Nips
il LP (manufactured by Nippon Silica) can be used, and as the hydrophobic silica, Aerosil R-812, R-812S, R-972, R-9
74 (manufactured by Degussa), Rheorosil MT-10 (manufactured by Tokuyama Soda Co., Ltd.), Nipsil SS series (manufactured by Nippon Silica) and the like. In particular, in the present invention, wet-type precipitated silica (for example, Nipsil LP) is preferable among them, and silica subjected to hydrophobic treatment (for example, Nipsil S
(S series) is most preferable because it prevents the sedimentation of the filler while maintaining the fluidity.

When it is desired to control the fluidity, dry type calcined silica can be used in combination with wet precipitable silica. In this case, the component (D) and dry silica are allowed to coexist. It is desirable to avoid storing the composition in the state, and it is preferable to store the component (D) and the dry silica in the form of a separate pack and mix them at the time of use. This is because the coexistence of both tends to increase the thixotropic properties of the composition and impair the fluidity.

The fine silica powder is preferably added in an amount of 0.1 to 20 parts by weight, particularly 1 to 10 parts by weight. If it is used in an amount of more than 20 parts by weight, the viscosity of the composition increases, workability tends to deteriorate, and casting tends to be difficult. Also 0.
If the amount is less than 1 part by weight, it becomes difficult to prevent the inorganic filler of component (E) from settling and separating.

Other Components In addition to the above-mentioned essential components (A) to (F), various additives known per se may be added to the curable composition of the present invention as appropriate according to the purpose. You can For example, when it is necessary to adjust the curing time, as a control agent, vinyl group-containing organopolysiloxane such as vinylcyclotetrasiloxane, triallyl isocyanurate, alkyl maleate, acetylene alcohol and its silane, siloxane modification Compound, hydroperoxide, tetramethylethylenediamine, benzotriazole and the like can be blended. A silane coupling agent having an adhesive functional group such as an alkoxysilyl group, an epoxy group, an acid anhydride group, or a peroxysilyl group can be added as an adhesion reinforcing agent.

Further, inorganic pigments such as cobalt blue, colorants such as organic dyes, heat resistance or flame retardance improvers such as cerium hydroxide, cerium oxide, zinc carbonate, manganese carbonate, red iron oxide and titanium oxide, carbon black, etc. It is also possible to add a heat resistance additive, a flame retardant improver, a conductivity imparting agent, and the like.

Curable Composition The curable composition of the present invention is obtained by uniformly mixing the above-mentioned components. This composition can be stored as a one-pack type, and the organohydrogenpolysiloxane (B) which is a crosslinking agent and the platinum group metal-based catalyst (C) which is a curing catalyst are separately packaged. It is also possible to store them as a two-liquid mixed type divided so that they can be mixed at the time of use.

The curable composition of the present invention thus obtained is preferably used as a potting material or a sealing material having adhesiveness.

[0033]

EXAMPLES In the following examples, the viscosity is a value measured at 25 ° C. and is a value measured according to the method specified in JIS K-7117. Further, "part" means "part by weight".

Example 1 70 parts of dimethylsiloxane with both ends sealed with vinyl groups (viscosity: 600 cSt) 30 parts Dimethylsiloxane with both ends sealed with vinyl groups (viscosity: 10,000 cSt) 30 parts Grinding with an average particle size of 15 μm Silica 150 parts 3 parts of wet hydrophobic precipitable silica (BET specific surface area: 150 m ² / g) treated with dimethylpolysiloxane was mixed for 30 minutes at room temperature and −700 mmHg. 1,5-dihydrogen-1,3,5,7-tetramethyl was added to this mixture.
-3-Trimethoxysilylethyl-7-glycidylpropyl tetrasiloxane 1 part, bis (trimethoxysilylpropyl) allyl isocyanurate 1 part, Surfynol 61 (acetylene alcohol manufactured by Air Products)
0.1 part, and the following formula:

[Chemical 1] Hydrogen methyl polysiloxane combined in 5
Parts were added and mixed for 10 minutes at room temperature and -700 mmHg. Finally, add 50ppm (platinum equivalent) of isopropanol complex of chloroplatinic acid containing 2% of platinum atom,
Mixing was performed for 10 minutes under the condition of -700 mmHg to obtain a curable composition.

Example 2 The same as Example 1 except that the same amount of Nipsil LP (BET specific surface area: 200 m ² / g) manufactured by Nippon Silica Industry Co., Ltd. was used instead of the wet hydrophobic precipitable silica. Then, a curable composition was prepared.

Example 3 The same as Example 1 except that the same amount of Aerosil R-972 (BET specific surface area: 110 m ² / g) manufactured by Nippon Aerosil Co., Ltd. was used instead of the wet hydrophobic precipitable silica. A curable composition was prepared in the same manner.

Example 4 A curable composition was prepared in the same manner as in Example 3 except that the first-stage mixing was carried out at 170 ° C. and -700 mmHg for 2 hours, and the following mixing was carried out after cooling. did.

Example 5 Dimethylsiloxane with both ends sealed with vinyl groups (viscosity: 600 cSt) 70 parts Dimethylsiloxane with both ends sealed with vinyl groups (viscosity: 10,000 cSt) 30 parts Grinding with an average particle size of 15 μm Silica 150 parts 3 parts of wet hydrophobic precipitable silica (BET specific surface area: 150 m ² / g) treated with dimethylpolysiloxane was mixed for 30 minutes at room temperature and −700 mmHg. Then, 50 ppm of an isopropanol complex of chloroplatinic acid containing 2% of platinum atoms (converted to platinum) was added and mixed at room temperature and -700 mmHg for 10 minutes to prepare an A package.

Dimethylsiloxane having both ends sealed with a vinyl group (viscosity: 600 cSt) 70 parts Dimethylsiloxane having both ends sealed with a vinyl group (viscosity: 10,000 cSt) 30 parts Pulverized silica having an average particle size of 15 μm 150 parts Dimethylpolysiloxane treated wet type hydrophobic precipitable silica was mixed for 30 minutes at room temperature and -700mmHg, then 1,5-dihydrogen-1,3,5,7-tetramethyl- 3
-Trimethoxysilylethyl-7-glycidylpropyltetrasiloxane 1 part, bis (trimethoxysilylpropyl) allyl isocyanurate 1 part, Surfynol
61 parts (manufactured by Air Products Co., Ltd.) was added, and further, 5 parts of hydrogenmethylpolysiloxane used in Example 1 was added, and at room temperature and -700 mmHg.
The B package was prepared by mixing for 10 minutes.

Example 6 Instead of the wet type hydrophobic precipitating silica of the A package of Example 5, the same amount of Aerosil R-972 (BE manufactured by Nippon Aerosil Co., Ltd. was used.
A and B packages were prepared in the same manner as in Example 1 except that T specific surface area: 110 m ² / g) was used.

Comparative Example 1 1,5-hydrogen-1,3,5,7-tetramethyl-3-trimethoxysilylethyl-7-glycidylpropyltetrasiloxane and bis (trimethoxysilylpropyl) allyl isocyanurate were added. A curable composition was prepared in the same manner as in Example 1 except that it was not used.

Comparative Example 2 A curable composition was prepared in the same manner as in Example 1 except that the wet type hydrophobic precipitated silica treated with dimethylpolysiloxane was not added.

Comparative Example 3 A curable composition was prepared in the same manner as in Example 1 except that the amount of dimethylsiloxane having a viscosity of 600 cst was 100 parts and the dimethylsiloxane having a viscosity of 10,000 cSt was not used.

Comparative Example 4 The amount of dimethylsiloxane having a viscosity of 10,000 cSt was changed to 10
A curable composition was prepared in the same manner as in Example 1 except that 0 part was used and dimethylsiloxane having a viscosity of 600 cSt was not used.

Experimental Example The curable compositions or packages obtained in the above Examples and Comparative Examples were measured for viscosity, thixotropy and adhesiveness. Each composition or package was centrifuged at 2500 rpm / 1hr using a centrifuge, and the presence or absence of sedimentation of the packing material and liquid separation was observed. The results are shown in Table 1.

[0046]

[Table 1] Sedimentation liquid separation Viscosity / P thixotropy * Adhesion ** Example 1 ○ ○ 300 1.2 ○ Example 2 ○ ○ 320 1.4 ○ Example 3 ○ ○ 640 3.2 ○ Example 4 ○ ○ 350 1.5 ○ Implementation Example 5 A package ○ ○ 290 1.2 − B package ○ ○ 300 1.3 − After mixing − − 300 1.2 ○ Example 6 A package ○ ○ 310 1.2 − B package ○ ○ 300 1.3 − After mixing − − 510 2.3 ○ Comparative example 1 △ △ 270 1.1 × Comparative Example 2 × × 290 1.1 ○ Comparative Example 3 × × 250 1.2 ○ Comparative Example 4 ○ ○ 1540 1.2 ○

* Thixo coefficient = η (4 rpm) / η (20 rpm) ** Adhesion was evaluated as follows. The composition (after mixing A and B packages in equal amounts in Examples 5 and 6) was placed on a PBT test panel manufactured by Nippon Test Panel Industry, and this was left in an atmosphere at 120 ° C. for 10 minutes. After allowing this to cool, the cured product on the test panel is scraped off with a metal spatula, and when the cured product remains on the test panel surface, adhesive ant (○), nothing remains on the surface,
The case where the PBT was exposed was designated as having no adhesiveness (x).

[0048]

INDUSTRIAL APPLICABILITY The curable composition of the present invention has fluidity (viscosity) suitable for casting, even though it contains a large amount of inorganic filler, and its sedimentation is effective. It is suppressed. It also has good adhesiveness to various substrates.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masaya Arakawa No. 1 Hitomi, Osamu Matsuida-cho, Usui-gun, Gunma 10 Shin-Etsu Chemical Co., Ltd. Silicone Electronic Materials Research Laboratory

Claims (1)

[Claims] 1. An organopolysiloxane (A1) having (A) at least one alkenyl group in one molecule and having a viscosity at 25 ° C. of 10 to 1,000 cSt, and 25 ° C. having at least one alkenyl group in one molecule. Viscosity of 1,500 to 100,
Organopolysiloxane (A2) having 000 cSt, (B) Organohydrogenpolysiloxane having at least two hydrogen atoms bonded to silicon atoms in one molecule, (C) platinum group metal-based catalyst, (D) addition curing Organosilicon compound having an organic functional group and an adhesive functional group in one molecule, (E) an inorganic filler having an average particle size of 1 to 50 μm, (F) a BET specific surface area of 50 m ² / g or more A cured adhesive organopolysiloxane composition containing finely divided silica.