JPH06179819A - Solvent-resistant silicone gel composition - Google Patents

Abstract

PURPOSE:To enable the formation of a silicone gel which stably retains the properties including softness even when exposed to a solvent. CONSTITUTION:The silicone gel composition comprises an organopolysiloxane derived from a product of the ring-opening polymerization of the cyclic trimer of methyl-3,3,3-trifluoropropylsiloxane with the aid of a pentacoordinate silicon complex catalyst and containing 0.1-2 alkenyl groups per molecule on the average, an organohydrogenpolysiloxane containing 2 or more Si-bonded hydrogen atoms per molecule on the average, and a catalyst for additional reaction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solvent-resistant silicone gel composition, and more particularly to a silicone gel composition having a small extraction loss due to a solvent.

[0002]

2. Description of the Related Art Silicone gel has excellent electrical insulation properties, stabilization of electrical properties and flexibility,
It is used for potting and sealing electronic parts, especially as a covering material for control circuit elements such as power transistors, ICs and capacitors, and protects these from thermal and mechanical damage. However, in order to sufficiently cope with the recent electronicization of automobiles, it is desired to develop a silicone gel which has not only the above properties but also solvent resistance to hydrocarbon fluids and gasoline.

[0003]

The organopolysiloxane having a 3,3,3-trifluoropropyl group, which has been conventionally recommended as solvent resistance, is a methyl-3,3,3-trifluoropropylsiloxane cyclic trisiloxane. The monomer is produced by ring-opening polymerization using an equilibrium catalyst such as an alkali metal hydroxide or an acid catalyst (see, for example, US Pat. No. 4,029,629).
However, the silicone gel formed using such an organopolysiloxane has a problem that when placed in a solvent environment, the flexibility becomes unsatisfactory and the original properties of the gel are lost. Therefore, an object of the present invention is to provide a silicone gel composition having excellent solvent resistance.

[0004]

According to the present invention, (A)
Methyl-3,3,3-trifluoropropyl siloxane cyclic trimer contains 0.1 to 2 alkenyl groups on average in one molecule derived from the ring-opening polymerization product of pentacoordinated silicon catalyst. Solvent-resistant silicone containing organopolysiloxane, (B) organohydrogenpolysiloxane containing an average of two or more hydrogen atoms bonded to silicon atoms in one molecule, and (C) catalyst for addition reaction A gel composition is provided.

[0005]

The important feature in the present invention is methyl-3,3,3-
This is because an alkenyl group-containing organopolysiloxane derived from a ring-opening polymerization product of trifluoropropylsiloxane cyclic trimer with a pentacoordinated silicon catalyst is used as a base component. It is possible to form a silicone gel having excellent solvent resistance. In the present invention, the reason why the silicone gel excellent in solvent resistance can be formed by using the organopolysiloxane obtained by such a specific production method is as follows. Is estimated. That is, as described above, methyl-3,3,
Organopolysiloxane obtained by ring-opening polymerization by equilibration of 3-trifluoropropylsiloxane cyclic trimer itself has excellent solvent resistance, but in this method, methyl-3,3,3- A large amount of trifluoropropylsiloxane cyclic tetramer and pentamer (F ₄ , F ₅ ) are produced as by-products, which cannot be distilled off under reduced pressure. Therefore, since the silicone gel using the organopolysiloxane thus prepared contains a large amount of F ₄ and F ₅ which do not participate in the crosslinking reaction, when placed in a solvent environment, F ₄ and F ₅
Are extracted with a solvent. As a result, it seems that the flexibility becomes unsatisfactory and the original properties of the gel are lost.

However, the methyl-3, used in the present invention,
In the ring-opening polymerization product of 3,3-trifluoropropylsiloxane cyclic trimer with a pentacoordinated silicon catalyst, F ₄ and F ₅ as described above are scarcely produced as a by-product. In the alkenyl group-containing organopolysiloxane described above, the content of F ₄ and F ₅ is 6% by weight or less. Therefore, in the composition of the present invention containing an organopolysiloxane obtained by using such a ring-opening polymerization product as a base component, the gel formed from the composition contains F ₄ and F ₅ which are solvent extraction components. It is considered that the compound exhibits good solvent resistance in relation to the fact that it is hardly contained.

(A) Alkenyl group-containing organopolysiloxane
Xan In the present invention, the alkenyl group-containing organopolysiloxane used as the base component is the ring-opening of methyl-3,3,3-trifluoropropylsiloxane cyclic trimer with a pentacoordinated silicon catalyst, as described above. Derived from polymerization products.

Methyl-3,3,3- using a five-coordinate silicon catalyst
The ring-opening polymerization of the trifluoropropylsiloxane cyclic trimer can be carried out by a method known per se. For example, as disclosed in JP-A-45-1070, water, organosiloxane, terminal silanol can be used. It can be carried out by reacting an organopolysiloxane, an organosilanol or the like with a methyl-3,3,3-trifluoropropylsiloxane cyclic trimer in the presence of a pentacoordinated silicon catalyst. In this case, in order to suppress the by-products of F ₄ and F ₅ to 6% by weight or less, the reaction temperature condition is preferably 40 ° C. or less. Further, in order to prevent crystallization of methyl-3,3,3-trifluoropropylsiloxane cyclic trimer having a melting point of 35 ° C, it is desirable to carry out the reaction using the minimum necessary solvent. The solvent is not particularly limited as long as it can dissolve the methyl-3,3,3-trifluoropropylsiloxane cyclic trimer, but acetonitrile is most preferable from the viewpoint that the formed polymer can also be dissolved.

As the pentacoordinated silicon catalyst, various ones can be used, but the following are particularly preferable in the present invention.

[0010]

[Chemical 1]

In the above formula, M ⁺ is BzMe ₃ N ⁺ , Bu
₄ N ⁺ , Me ₄ N ⁺ , Li ⁺ , Na ⁺ or K ⁺ (Me is a methyl group, Bu is a butyl group and Bz is a benzyl group, the same applies hereinafter), R is a phenyl group, a methyl group,
It is a cyclohexyl group or a 3,3,3-trifluoropropyl group. Such pentacoordinated silicon catalysts are generally 10-100
Used in an amount of 0 ppm.

According to the present invention, the organopolysiloxane to be used as the base component can be obtained by silylating the molecular end of the polymerization product obtained above with a silylating agent containing an alkenyl group. The alkenyl group introduced into the molecule here has 2 carbon atoms.
Those in the range of to 8 are preferable, and specific examples thereof include a vinyl group, an allyl group, a 1-butenyl group, and a 1-hexenyl group. It is necessary that these alkenyl groups are introduced at an average ratio of 0.1 to 2, preferably 0.5 to 1.8 in one molecule of the organopolysiloxane. If the number of alkenyl groups is less than 0.1, the number of organopolysiloxane molecules that do not participate in the cross-linking reaction increases, which causes problems such as a decrease in cross-linking density.
When the number of alkenyl groups is more than 2, the resulting gel hardened product becomes too hard to function as a gel.

Examples of such an alkenyl group-introduced organopolysiloxane include those represented by the following formulas. In the present invention, these may be used alone or in combination of two or more kinds. You can

[0014]

[Chemical 2]

[0015]

[Chemical 3]

25 ° C. of these organopolysiloxanes
Viscosity at 50-100,000 cP, especially 300-5,000 cP
It is preferable that it is within the range. The silylation using the alkenyl group-containing silylating agent, which is carried out to obtain the above-mentioned organopolysiloxane, may be carried out by using a silylating agent such as an alkenyldiorganohalogenated silane having an alkenyl group to be introduced into the molecule. It is easily carried out by reacting with the above-mentioned polymerization product in the presence of an acid or an alkali. The amount of the silylating agent used is set according to the average number of alkenyl groups introduced into the molecule. In the alkenyl group-containing organopolysiloxane thus obtained, the content of F ₄ and F ₅ is suppressed to 6% by weight or less.

(B) Organohydrogen polysiloxy
San organohydrogenpolysiloxane of the component (B) used in the present invention, (A) reacts with the alkenyl groups in component is intended to form a gel-like material, one molecule of hydrogen atoms bonded to the silicon atom It is necessary to have two or more on average. This organohydrogenpolysiloxane is such that the amount of hydrogen atoms bonded to silicon atoms in the molecule is 0.3 to 2.0 mol, relative to 1 mol of alkenyl groups bonded to silicon atoms in component (A). Is preferred. If the amount of hydrogen atoms bonded to silicon atoms is too small or too large, the resulting gel tends to have unsatisfactory heat resistance. Such a hydrogen atom may be bonded to any silicon atom at the molecular end or in the molecular chain. The siloxane skeleton may be linear or branched.
Further, it is preferable that the component (A) and the component (B) organohydrogenpolysiloxane are compatible with each other. Therefore, the higher the fluorine content of the (A) component, the (B)
As the component organohydrogenpolysiloxane, it is preferable to use one having a high fluorine content.

An example of the organohydrogenpolysiloxane preferably used in the present invention is shown below.

[0019]

[Chemical 4]

[0020]

[Chemical 5]

In the present invention, these organohydrogenpolysiloxanes may be used alone or in admixture of two or more.

(C) Addition Reaction Catalyst The addition reaction catalyst of component (C) is used to accelerate the curing by the addition reaction between the alkenyl group of component (A) and the SiH group in component (B). And is known per se. Examples of such an addition reaction catalyst include chloroplatinic acid, an alcohol-modified solution of chloroplatinic acid, a coordination compound of chloroplatinic acid and an olefin or vinylsiloxane, tetrakis (triphenylphosphine) palladium, chlorotris (triphenyl). Phosphine) rhodium and the like are exemplified, but platinum-based ones are particularly preferable. Such a catalyst is usually used in an amount of 0.1 to 1000 p in terms of metal based on the total amount of the components (A) and (B).
It is blended in the proportion of pm.

Other Compounding Agents In addition to the components (A) to (C) described above, various known compounds can be added to the organopolysiloxane composition of the present invention. For example, fumed silica, silica aerosil, precipitated silica, ground silica,
Mechanical strength and the like can be adjusted by adding an inorganic filler such as diatomaceous earth, iron oxide, alumina, zinc oxide, titanium oxide, calcium carbonate, magnesium carbonate, zinc carbonate and carbon black. Of course, a hollow inorganic filler, a hollow organic filler, an organosilicone resin, a rubbery spherical filler, or the like can be added. It is also possible to control the curing reaction by adding a reaction control agent such as a polymethylvinylsiloxane cyclic compound, an acetylene compound or an organic phosphorus compound. The amount of these compounding agents used is optional as long as the properties of the resulting cured product are not impaired.

Organopolysiloxane Composition The organopolysiloxane composition of the present invention is prepared by uniformly mixing the above-mentioned components. This composition forms a gel cured product having excellent solvent resistance when heated to a temperature of 40 to 150 ° C., for example. The gel cured product stably retains characteristics such as flexibility even when placed in a solvent environment.

[0025]

EXAMPLES In the following examples, "parts" means "parts by weight", and viscosities are measured values at 25 ° C. Example 1 Methyl-3,3,3-trifluoropropylsiloxane cyclic trimer (195 g, water 1.1 g, acetonitrile 80 g) was stirred at 10 ° C. and stirred to give the following formula: [C ₆ H ₅ Si (O ₂ C ₆ H ₄ ) ₂ ] ^-・ C ₆ H ₅ CH
Polymerization was carried out by adding 0.02 g of a pentacoordinated silicon catalyst represented by ₂ (CH ₃ ) ₃ N ⁺ and polymerizing for 5 hours, and then adding 20 g of vinyldimethylchlorosilane. By performing silylation and then distilling off the solvent by heating under reduced pressure, the viscosity
1,500 cP of organopolysiloxane A was obtained (average number of alkenyl groups in the molecule was 2).

(Me) ₃ SiO _0.5 unit 16.7 mol%, CF ₃ C ₂ H per 100 parts of the above organopolysiloxane A
₄ (Me) SiO unit 50 mol% and H (Me) SiO
Methylhydrogenpolysiloxane consisting of 33.3 mol% unit 11 parts Ethynylhexanol 0.1 part was added and mixed homogeneously, and then the vinylsiloxane complex of chloroplatinic acid was added to the mixture so that the amount of platinum was 5 ppm. Was added and mixed uniformly to prepare an organopolysiloxane composition. This composition is 150 ℃ × 1
After heat curing for a period of time, a transparent gel was obtained. The gel-like material was subjected to a penetration test and a gasoline immersion test. The results are shown in Table 1.

Example 2 Methyl-3,3,3-trifluoropropylsiloxane cyclic trimer (135 g), trimethylsilanol (2.6 g), water (0.06 g) and acetonitrile (40 g) were stirred at 10 ° C. and the following formula: _{C 6 H 5 Si (O 2} C 6 H 4) 2 ] ^- · C ₆ H ₅ CH
0.003 g of a pentacoordinated silicon catalyst represented by ₂ (CH ₃ ) ₃ N ⁺ was added and polymerized for 5 hours, and then vinyldimethylchlorosilane 3.9 g [CH ₂ ═CH (Me) ₂ Si] ₂ NH 6.5 g was added to carry out silylation of the molecular end of the polymer, then the solvent was distilled off under reduced pressure with heating, and the resulting salt was filtered to give an organopolysiloxane having a viscosity of 2,500 cP. B was obtained (average number of alkenyl groups in the molecule is 1.1
Individual).

Organopolysiloxane B 10 obtained
An organopolysiloxane composition was prepared in the same manner as in Example 1, except that 0 part of the methylhydrogenpolysiloxane used in Example 1 was used in 7 parts.
This composition was heat-cured at 150 ° C. for 1 hour to obtain a transparent gel-like material. The gel-like material was subjected to a penetration test and a gasoline immersion test. The results are shown in Table 1.

Comparative Example 1 Methyl-3,3,3-trifluoropropylsiloxane cyclic trimer 187.2 g [CH ₂ ═CH (Me) ₂ Si] ₂ O 6.1 g [(Me) ₃ Si] ₂ O 4.37 g was mixed and further equilibration catalyst CF ₃ SO ₃ H 0.1 g was added, and the equilibration reaction was carried out at room temperature for 8 hours. After the reaction was completed, 1 g of sodium bicarbonate was added for neutralization, and the product was filtered to remove neutralized salt and excess sodium bicarbonate.
The product was stripped to obtain polyorganosiloxane C having a viscosity of 500 cP.

Organopolysiloxane C 10 obtained
An organopolysiloxane composition was prepared in the same manner as in Example 1, except that 15 parts of the methyl hydrogen polysiloxane used in Example 1 was used as 0 part. This composition was heat-cured at 150 ° C. for 1 hour to obtain a transparent gel-like material. The gel-like material was subjected to a penetration test and a gasoline immersion test. The results are shown in Table 1.

Incidentally, the gasoline immersion test was conducted on a cured sample.
It was carried out by immersing 10 g in 200 ml of gasoline at 25 ° C. and measuring the rate of weight loss due to gasoline extraction. The penetration was performed according to JIS K2220 1/4 cone.

[0032]

[Table 1]

[0033]

EFFECTS OF THE INVENTION According to the present invention, it is possible to form a silicone gel in which properties such as flexibility are stably maintained even when placed in a solvent environment.

 ─────────────────────────────────────────────────── ─── 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 alkenyl group is averaged in one molecule derived from a ring-opening polymerization product of (A) methyl-3,3,3-trifluoropropylsiloxane cyclic trimer with a pentacoordinated silicon catalyst. 0.1 to 2 contained organopolysiloxane, (B) an organohydrogenpolysiloxane containing an average of two or more hydrogen atoms bonded to silicon atoms in one molecule, and (C) an addition reaction catalyst. A solvent-resistant composition for silicone gel, which is characterized by containing.