JPH0655899B2 - Silicone rubber composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a silicone rubber composition which has excellent self-adhesiveness and can be suitably used as a protective coating agent or adhesive for electronic / electrical parts and the like.

2. Description of the Related Art Conventionally, a silicone rubber composition of the type in which vinyl polysiloxane and hydrogen polysiloxane are heat-cured by hydrosilation in the presence of a platinum catalyst has been known. The rubber composition is used as a protective coating agent for electronic / electrical components, an adhesive for adhering electronic / electrical components to a substrate, etc. by utilizing its self-adhesiveness.

However, it cannot be said that the conventional silicone rubber composition of this type has sufficiently high adhesiveness to various substrates, and lacks adhesiveness to various substrates such as metals, ceramics and plastics.

Therefore, the silicone rubber composition contains an epoxy group or an alkoxy group-containing hydrogen polysiloxane,
An alkoxysilane compound or a hydrolysis product thereof,
(Japanese Patent Publication No. 53-13508, Japanese Patent Publication No. 57-5836) and the like have been added to improve the adhesiveness to various substrates.

However, the adhesiveness of the above silicone rubber composition is greatly affected by the temperature at the time of curing, and even if such an adhesion aid is added, it is necessary to treat at a temperature of at least 100 to 120 ° C. in order to achieve good adhesion to the substrate. Therefore, it is difficult to obtain sufficient adhesiveness especially at a low temperature of 100 ° C. or less and at an expensive temperature. Therefore, when these silicone rubber compositions are used as adhesives for electronic / electrical components and cured at low temperature, moisture and impurities penetrate through the non-bonding gap between various components and the silicone rubber composition, causing corrosion and insulation of the components. There is a problem such as unfishing.

In recent years, there has been an increasing demand for low-temperature adhesion as a new application or as part of energy rationalization. Therefore, development of a silicone rubber composition that exhibits excellent adhesion even at low-temperature curing is desired.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a silicone rubber composition having excellent self-adhesiveness capable of adhering well to various substrates even when cured under low temperature conditions.

Means and Actions for Solving the Problem As a result of intensive studies to achieve the above object, the present inventors have found that (I) the following general formula (2) (However, in the formula, R ² is the same or different unsubstituted or substituted monovalent hydrocarbon group having no aliphatic unsaturated bond, l is a positive integer, and m is 0 or a positive integer.) And at least two CH ₂ ═CH— in one molecule.
A vinyl group-containing diorganopolysiloxane having a Si bond and (II) a hydrogen atom directly bonded to a silicon atom in the organohydrogenpolysiloxane with respect to one vinyl group in the diorganopolysiloxane of the component (I). The following average composition formula (3) H _a ▲ R ³ _b ▼ SiO _{(4-ab) / 2} (3) (wherein, R ³ is the same kind containing no aliphatic unsaturated bond) Or a heterogeneous unsubstituted or substituted monovalent hydrocarbon group, 0 <
a <2, 1 ≦ b ≦ 2 and 2 ≦ a + b ≦ 3. ), And the total amount of the organohydrogenpolysiloxane having at least two hydrogen atoms directly bonded to one silicon atom in one molecule and (III) the component (I) and the component (II). In a silicone rubber composition containing a catalytic amount of platinum or a platinum compound as platinum, 0.01 to 0.01% based on the total amount of (IV) component (I) and component (II)
5% by weight of the following general formula (1) (Wherein R ¹ is the same or different unsubstituted or substituted monovalent hydrocarbon group containing no aliphatic unsaturated bond, and n is 0 or a positive integer). 0.1 to 0.1 based on the total amount of the ester siloxane compound containing no carbon bond and the component (V) component (I) and component (II).
5% by weight of the following general formula (4) (However, in the formula, R ⁴ is The divalent organic group) the same or different selected from epoxy-containing monovalent organic group, R ⁵ is an unsubstituted or substituted monovalent hydrocarbon group hydrogen atom or a same or different 1 to 6 carbon atoms, 0 < c
≦ 1, 1 ≦ d <3, 1.5 ≦ c + d ≦ 3. ), At least one epoxy group bonded to a silicon atom through a carbon atom directly bonded to the silicon atom in one molecule.
Addition of individual epoxy group-containing polysiloxane compounds provides self-adhesiveness that allows good adhesion to various base materials such as metals, ceramics and plastics even when cured at a low temperature of 100 ° C or less for a relatively short time. It has been found that an excellent silicone rubber composition can be obtained. Therefore, the inventors have found that the silicone rubber composition can be widely used as a protective coating agent and an adhesive for electronic / electrical parts, etc.

Therefore, the present invention provides a silicone rubber composition containing the above-mentioned components (I) to (III), in which a silicon-carbon bond-free ester siloxane compound represented by the above formula (1) is added to a silicon atom in one molecule. There is provided a silicone rubber composition characterized by being blended with an epoxy group-containing polysiloxane compound having at least one epoxy group bonded to a silicon atom via a carbon atom directly bonded.

Hereinafter, the present invention will be described in more detail.

The component (I) constituting the silicone rubber composition of the present invention comprises at least two CH ₂ ═CH—Si≡ in one molecule.
A vinyl group-containing diorganopolysiloxane having a bond. In this vinyl group-containing diorganopolysiloxane, vinyl groups are present at both ends of the molecule and in the middle of the molecule even if they are present only at both ends of the molecule. In particular, the following formula (2) (In the formula, R ² is the same or different unsubstituted or substituted monovalent hydrocarbon group containing no aliphatic unsaturated bond,
Is 0 or a positive integer, and m is 0 or a positive integer. The vinyl group-containing diorganopolysiloxane represented by

Here, the substituted R ² in the formula (2) is the same or different unsubstituted or substituted C ¹ to C ¹ containing no aliphatic unsaturated bond.
0, particularly preferably 1 to 6 monovalent hydrocarbon groups,
For example, lower alkyl groups such as methyl group, ethyl group, propyl group, butyl group, phenyl group, tolyl group, xylyl group,
Aryl groups such as benzyl groups, cycloalkyl groups such as cyclohexyl groups, or chloromethyl groups, cyanoethyl groups, 3,3,3-tri groups in which some or all of the hydrogen atoms of these groups are substituted with halogen atoms, cyano groups, etc. Examples thereof include fluoropropyl group. In addition, l is 0 or a positive integer, m
Is 0 or a positive integer, preferably 0 <l + m ≦ 1000
0, more preferably 0 <l + m ≦ 2000, 0 ≦ m /
It is a number such that (l + m) ≦ 0.2.

Furthermore, the diorganopolysiloxane of formula (2) has a temperature of 25 ° C.
The viscosity at 10 to 1,000,000 centistokes is preferred.

Next, the component (II) is an organohydrogenpolysiloxane containing hydrogen atoms directly bonded to at least two silicon atoms in one molecule and represented by the following formula (3): (In the formula, R ³ is the same or different unsubstituted or substituted monovalent hydrocarbon group containing no aliphatic unsaturated bond,
<A <2, 1 ≦ b ≦ 2 and 1 <a + b ≦ 3. ) Organohydrogenpolysiloxane containing hydrogen atoms directly bonded to at least two silicon atoms in one molecule can be preferably used.

Here, R ³ in the above formula (3) is an unsubstituted or substituted C 1-10 containing no aliphatic unsaturated bond, particularly 1-7.
Preferably, it is a monovalent hydrocarbon group such as a lower alkyl group such as a methyl group, an aryl group such as a phenyl group, and the like as those described for R ² . Also, a and b are 0 <a <2, 1 ≦ b ≦ 2 and 1 <a + b ≦
3 is a number, preferably 0.3 ≦ a ≦ 1 and 2 ≦
It is a number such that a + b ≦ 2.7.

Such an organohydrogenpolysiloxane is
Usually, R ³ SiHCl ₂ , R ³ ₃ SiCl, R ³ ₂ SiCl ₂ ,
It can be obtained by hydrolyzing chlorosilane such as R ³ ₂ SiHCl, or by equilibrating the siloxane obtained by hydrolyzing in this way, and specific examples include compounds represented by the following formula. You can

The amount of the organohydrogenpolysiloxane of the component (II) is not particularly limited, but one vinyl group in the diorganopolysiloxane of the component (I) is equivalent to silicon in the organohydrogenpolysiloxane. It is preferable to mix them in such a ratio that the number of hydrogen atoms directly bonded to the atoms becomes 2 to 4.

Furthermore, the platinum or platinum compound of the component (III) is a silicon-bonded vinyl group in the vinyl group-containing organopolysiloxane of the component (I) and a silicon-bonded hydrogen atom in the organohydrogenpolysiloxane of the component (II). It is a catalyst for carrying out an addition reaction with, and the one usually used in this kind of silicone rubber composition can be used.

As the platinum or platinum compound, specifically, simple platinum,
H ₂ PtCl ₆ · nH ₂ O, NaHPtCl ₆ · nH ₂ O, KH
PtCl ₆ · nH ₂ O, Na ₂ PtCl ₆ · nH ₂ O, K ₂ PtC
l ₆ · nH ₂ O, PtCl ₄ · nH ₂ O, PtCl ₂ , Na ₂ Pt
Examples include Cl ₄ .nH ₂ O and H ₂ PtCl ₄ .nH ₂ O. Further, complexes of these platinum compounds with hydrocarbon, alcohol or vinyl group-containing cyclic siloxane can also be used.

The amount of platinum or the platinum compound added may be a catalytic amount, and for example, the amount of platinum is 0.1 to 100 relative to the total amount of the organopolysiloxanes of the components (I) and (II).
It can be ppm.

In the present invention, the addition reaction type silicone rubber composition containing the above-mentioned components (I) to (III) is added to the component (IV).
An ester siloxane compound represented by the formula (1) is blended as a component, and an epoxy group-containing polysiloxane compound is blended as a component (V). By blending the ester siloxane compound and the epoxy group-containing polysiloxane compound, a composition is obtained. The adhesiveness of the product is improved and the object of the present invention can be achieved.

Here, the silicon of the formula (1) used as the component (IV) is
In the ester siloxane compound having no carbon bond, the substituent R ¹ is the same or different, unsubstituted or substituted, monovalent hydrocarbon group having 1 to 10 carbon atoms, particularly 1 to 7 carbon atoms, which does not contain an aliphatic unsaturated bond. Examples thereof include those similar to R ² in the formula (2), and examples thereof include lower alkyl groups such as methyl group, ethyl group and propyl group, aryl groups such as phenyl group, and the like. Of these, a lower alkyl group is particularly preferable. Further, n is 0 or a positive integer, preferably 1 to 20, particularly 1 to 6.
That is, if n in the compound of the formula (1) is 0 or more, the effect is sufficient to achieve the object of the present invention, but n is 1 to 6 from the viewpoint of compatibility with the base oil. It is preferable.

The ester siloxane compound of formula (1) is synthesized, for example, by adding an appropriate amount of water to a trialkoxysilane compound such as trimethoxysilane, triethoxysilane, and tripropoxysilane and hydrolyzing it in the presence of an acid catalyst. can do. Furthermore, in this case, the molecular weight (value of n) of the obtained compound of formula (1) can be adjusted by adjusting the addition amount to water at the time of hydrolysis.

Further, as the ester siloxane compound of the formula (1), a hydrolyzate of a trialkoxysilane compound can be used in the same manner. It is not suitable to use trialkoxysilane as the (IV) component because it has a higher volatility than the ester siloxane compound of the formula (1) and cannot significantly improve the adhesiveness of the composition. .

Next, the epoxy group-containing polysiloxane compound of the component (V) has at least one epoxy group bonded to a silicon atom through a carbon atom directly bonded to the silicon atom in one molecule, and particularly the following general Formula (4) [However, R ⁴ is (X is The same or different epoxy group-containing monovalent organic group R ⁵ selected from C ¹ to C 6 divalent organic groups) is a hydrogen atom or the same or different monovalent hydrocarbon group similar to R ² and R ^3. , Preferably having 1 to 10 carbon atoms, 0 <c ≦ 1, 1 ≦ d <
3, 1.5 ≦ c + d ≦ 3, preferably 1.8 ≦ c + d ≦
It is 2.2. ] The polysiloxane represented by the following can be preferably used. Examples of such a polysiloxane include a cyclic or chain polysiloxane to which one or more cyclic or acyclic epoxy groups are added, and specifically, a compound represented by the following formula.

The amounts of the above-mentioned components (IV) and (V) are not particularly limited, but the total amount of the vinyl group-containing organopolysiloxane of the component (I) and the organohydrogenpolysiloxane of the component (II) is not limited. On the other hand, the content of the ester silosan compound as the component (IV) is preferably 0.01 to 5% (weight%, the same applies below), particularly 0.1 to 1%, and the epoxy group of the component (V) is The content of the contained organopolysiloxane is preferably 0.1 to 5%, more preferably 0.2 to 2%. In this case, the compounding ratio of the ester silosan compound and the epoxy group-containing organopolysiloxane is not particularly limited and can be appropriately adjusted.

To the silicone rubber composition of the present invention, in addition to the above-mentioned components (I) to (V), a reinforcing or non-reinforcing inorganic filler or the like can be added as another component, if necessary. Examples of the volatile inorganic filler include fumed silica, fumed titanium dioxide and the like, and the non-reinforcing inorganic filler may be those usually used in silicone rubber compositions of this type, such as finely divided quartz, Examples include calcium carbonate, calcium silicate, titanium dioxide, ferric oxide and carbon black. It should be noted that these inorganic fillers do not have to be added to the composition at all, and the amount thereof can be set in the range of 0 to 200 parts based on the total amount of the components of the composition excluding these inorganic fillers.

The silicone rubber composition of the present invention can be divided into two liquids as in the case of a normal silicone rubber composition, and the two liquids can be mixed and cured, but a small amount of a curing inhibitor (for example, acetylene alcohol, etc.) can be used. ) Or the like may be added to use as one liquid.

In this case, in order to prepare each of the above components as a second liquid, the first liquid is blended with the vinyl group-containing organopolysiloxane of the first component and the platinum or platinum compound of the third component, and the second liquid is used. It is preferable to blend the organohydrogenpolysiloxane of the component (II), and the ester siloxane compound of the component (IV) and the epoxy group-containing organopolysiloxane of the component (V) are either the first liquid or the second liquid. May be blended with each other, or may be blended in separate liquids.

The silicone rubber composition of the present invention cures under the same conditions as an ordinary silicone rubber composition, but in particular, the composition of the present invention is 1
Low temperature below 00 ° C, especially 80 to 90 ° C and 0.5 to 2
Good adhesiveness even when cured in a short period of time, so it is suitable as a protective coating agent for various substrates of electrical components and an adhesive that bonds electronic and electrical components to substrates by curing at low temperatures. Can be used for.

EFFECTS OF THE INVENTION As described above, the silicone rubber composition of the present invention can adhere well to various substrates even when cured at a low temperature for a relatively short period of time, and causes corrosion and insulation to parts formed of the cured product. Since it rarely causes defects, it can be widely used as a protective coating agent or adhesive for electronic and electric parts. Furthermore, the composition of the present invention can be used for parts having low heat resistance, can be applied to new uses, and can reduce the cost in terms of energy.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Example 1, Comparative Examples 1 to 4] Dimethylpolysiloxane (400 centistokes) 1 containing two methylvinylsiloxane units in one molecule 1
00 parts, 5.0 parts of methyl hydrogen polysiloxane containing 1.0 mol / 100 g of ≡SiH bond, 0.05 part of octyl alcohol modified solution of chloroplatinic acid (platinum content 2% by weight), fine powdered quartz 30 Part, hydrolyzate of trimethoxysilane (the following formula separated by distillation by adding 0.5 mol of water to 1 mol of trimethoxysilane to hydrolyze in the presence of an acid catalyst) A mixture of the compounds represented by
1.5 parts of the epoxy group-containing siloxane represented by the above formula (5) (1 mol of 1,3,5,7-tetramethylcyclotetrasiloxane partially added with 1 mol of allyl glycidyl ether) was added, After stirring well,
5 cm (length) x 2 cm (width) x 2 mm on the 5 types of substrates shown in Table 1
It was applied in a sheet shape (thickness) and heated at 80 ° C. for 2 hours to be cured to obtain a test piece (Example 1).

A qualitative adhesion test was performed on these test pieces by the following method.

Adhesion test When the cured product was destroyed using a micro spatula and peeled off from the substrate, the ratio between the cohesive failure portion and the peeled portion was observed to determine the adhesiveness.

Criteria: Good adhesion (cohesive failure rate of 80% or more) Fair: Partial adhesion (cohesive failure rate of 80 to 20% or more) X: No adhesion (cohesive failure rate of 20% or less) With the same composition and method, those containing no epoxy group-containing siloxane (Comparative Example 1), those containing no trimethoxysilane hydrolyzate (Comparative Example 2), and those containing epoxy group-containing siloxane and trimethoxysilane hydrolyzate were used. Not containing both (Comparative Example 3), trimethoxysilane 0.
A test piece containing 15 parts (Comparative Example 4) was prepared,
An adhesion test was performed.

The results are shown in Table 1.

From the results shown in Table 1, it was confirmed that the organopolysiloxane composition of the present invention (Example 1) had excellent adhesiveness to aluminum, stainless steel, nickel, silicon wafer and glass. On the other hand, compositions containing neither hydrolyzate of trimethoxysilane nor epoxy group-containing siloxane (Comparative Examples 1 to 3)
Has poor adhesion to the above-mentioned metal substrate, and when trimethoxysilane is blended in place of the hydrolyzate of trimethoxysilane (Comparative Example 4) even if it contains epoxy group-containing siloxane (Comparative Example 4), It was found that the adhesiveness of the was low.

[Example 2, Comparative Examples 5 to 7] Dimethylpolysiloxane containing two methylvinylsiloxane units in one molecule (5000 centistokes)
50 parts, 50 parts of a copolymer having a SiO ₂ unit: trimethylsiloxy unit: dimethylvinylsiloxy unit in a molar ratio of 1: 1: 0.15, 1.2 mol / 10 ≡SiH bond.
5. Methyl hydrogen phophorisiloxane containing 0 g.
0 part, 0.05 part of octyl alcohol solution of chloroplatinic acid (platinum content 2% by weight), 0.05 part of siloxane modified product of acetylene alcohol, and 100 parts of the above-mentioned dimethylpolysiloxane were added to the same trilayer as in Example 1. Methoxysilane, 0.35 part of the hydrolyzate, and 2.0 parts of the epoxy group-containing siloxane represented by the above formula (6) were mixed and stirred well, and then 5 cm (length) on 9 kinds of substrates shown in Table 2. × 2cm (side) ×
It was applied to a sheet of 2 mm (thickness) and cured by heating at 100 ° C. for 1 hour to obtain test pieces (Example 2), and the adhesion of these test pieces was examined.

In addition, by the same composition and method as in Example 2, those containing no epoxy group-containing siloxane (Comparative Example 5), those containing no hydrolyzate of trimethoxysilane (Comparative Example 6), epoxy group-containing siloxane and trimethoxy An adhesive test was carried out by preparing a test piece containing no silane hydrolyzate (Comparative Example 7).

The results are shown in Table 2.

From the results shown in Table 2, the organopolysiloxane composition of the present invention (Example 2) does not contain any one or both of the hydrolyzate of trimethoxysilane and the epoxy group-containing siloxane (Comparative Examples 5 to 5). It was confirmed that the adhesiveness to metal substrates such as aluminum, stainless steel, nickel, silicon wafer and glass, and further to plastic substrates such as polyester, polyimide, glass epoxy and phenol was superior to that of 7).

Claims (1)

[Claims] (1) The following general formula (2) (However, in the formula, R ² is the same or different unsubstituted or substituted monovalent hydrocarbon group having no aliphatic unsaturated bond, l is a positive integer, and m is 0 or a positive integer.) And at least two CH ₂ ═CH— in one molecule.
A vinyl group-containing diorganopolysiloxane having a Si bond and (II) a hydrogen atom directly bonded to a silicon atom in the organohydrogenpolysiloxane with respect to one vinyl group in the diorganopolysiloxane of the component (I). The following average compositional formula (3) H _a ▲ R ³ _b ▼ SiO _{(4-ab) / 2} (3) (wherein R ³ is the same kind containing no aliphatic unsaturated bond) Or a heterogeneous unsubstituted or substituted monovalent hydrocarbon group, 0 <
a <2, 1 ≦ b ≦ 2 and 2 ≦ a + b ≦ 3. ), And the total amount of the organohydrogenpolysiloxane having at least two hydrogen atoms directly bonded to one silicon atom in one molecule and (III) the component (I) and the component (II). In a silicone rubber composition containing a catalytic amount of platinum or a platinum compound as platinum, 0.01 to 0.01% based on the total amount of (IV) component (I) and component (II)
5% by weight of the following general formula (1) (Wherein R ¹ is the same or different unsubstituted or substituted monovalent hydrocarbon group having no aliphatic unsaturated bond, and n is 0 or a positive integer). 0.1 to 0.1 based on the total amount of the ester siloxane compound not containing a bond and the (V) component (I) and component (II).
5% by weight of the following general formula (4) (However, in the formula, R ⁴ is The same or different epoxy group-containing monovalent organic group selected from C1 to C6 divalent organic group), R ⁵ is a hydrogen atom or the same or different unsubstituted or substituted monovalent hydrocarbon group, 0 < c
≦ 1, 1 ≦ d <3, 1.5 ≦ c + d ≦ 3. ), At least one epoxy group bonded to a silicon atom through a carbon atom directly bonded to the silicon atom in one molecule.
A silicone rubber composition comprising an epoxy group-containing polysiloxane compound having an individual compound.