JPS6043864B2 - New silicone rubber composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses a novel reactive silica-based inorganic filler as an organopolysiloxane rubber (hereinafter referred to as silicone rubber).

), and aims to provide compositions and products that are economical and have excellent processability, mechanical properties, electrical properties, and thermal properties. It is. Silicone rubber has excellent properties such as heat resistance and is applied to a wide range of useful products.

However, in general, the mechanical properties of silicone rubber such as rubber components alone are not sufficient for practical use, such as tensile strength, and in order to obtain a composition with advanced mechanical properties, silicone rubber is generally compatible with silicone rubber. A silica-based inorganic filler with reinforcing properties is used. Conventionally, this type of silica-based inorganic filler has been produced by dry process silica (fumed silica, hereinafter referred to as dry process silica) obtained by thermal decomposition of silicon halide, or by acid decomposition of sodium silicate. The resulting wet process silica (hereinafter referred to as wet process silica) is known. When filled with silicone rubber, dry process silica provides better properties compared to wet process silica, such as relatively advanced mechanical and electrical properties.
Due to its physical and chemical properties, it is difficult to fill silicone rubber, the amount of filling is limited to a relatively low range, and the filled composition exhibits a hardening phenomenon known as creep hardening. ing. Compared to dry process silica, wet process silica is relatively easy to fill into silicone rubber and can be filled at a relatively high concentration, but the processability is affected by the creep hardening phenomenon of the filling composition. are still unsatisfactory in practice; moreover, due to their physical and chemical properties, the mechanical and electrical properties obtained with the filling compositions are not satisfactory. Proposals for improving such silica-based fillers include a method of treating the surface of the silica-based filler with silane, and a well-known dispersant that promotes filling when filling silicone rubber with silica-based filler. For example, octamethylcyclotetrasiloxane,
It is known to add things such as diphenylsilane diol.

However, it is still insufficient to economically obtain a silicone rubber composition containing a silica-based inorganic filler that has excellent processability, mechanical properties, electrical properties, and thermal properties from such conventional techniques. . Therefore, we need a composition that is practical and economical, has excellent processability, allows effective filling of such silica-based inorganic filler at a high concentration, and has excellent mechanical, electrical, and thermal properties. If something can be obtained, its industrial value is extremely large.

The present inventors discovered a method for producing an active filler with novel properties by first reacting an inorganic filler with an organic acid under dehydration conditions (Japanese Patent Publication No. 1239/1983).
(Special Publication No. 51-12, No. 403 of 1973), and furthermore, by forming a coating reaction layer of an appropriate thickness on the surface of the inorganic filler using an unsaturated organic acid or other functional organic acid. By blending a reactive filler with an elastomer into an elastomer and kneading it under heat, an excellent elastomer composition was obtained (Japanese Patent Application Laid-Open No. 109436/1983).

As a result of further studies on active fillers, the present inventors completed a silicone rubber composition that is practical, economical, has excellent processability, and has excellent mechanical, electrical, and thermal properties. I came to the conclusion.

That is, the present invention provides 10 parts by weight of an organopolysiloxane rubber having a repeating unit group (wherein R is an alkyl group, a halogenated alkyl group, a furyl group, or an alkenyl group). The present invention relates to a new heat-curable silicone rubber composition comprising 5 to 15 parts by weight of a reactive silica-based inorganic filler coated with a polymerizable organic acid monomer.

The present invention will be explained in more detail below.

The organopolysiloxane rubber used in the present invention is:
It is an organopolysiloxane having a substantially linear structure having a repeating unit group (wherein R is an alkyl group, a halogenated alkyl group, an aryl group, or an alkenyl group).

In this formula, R is an alkyl group such as a methyl group, ethyl group, propyl group, or butyl group, and a portion of the hydrogen atoms bonded to the carbon atoms of the alkyl group is replaced with a halogen atom such as chlorine or fluorine. Examples include halogenated alkyl groups, aryl groups such as phenyl, tolyl, and naphthyl groups, and alkenyl groups such as vinyl and allyl groups.Generally, dimethylpolysiloxane in which R is a methyl group, and 80 mol% Diorganopolysiloxanes in which the above are methyl groups and the remainder are vinyl groups, phenyl groups, etc. are used, but in the present invention, dimethylpolysiloxane, or methylvinylpolysiloxane into which a small amount of vinyl has been introduced, Alternatively, methylphenylvinyl polysiloxane into which a small amount of phenyl group and vinyl group are introduced is preferable.

Both ends of the molecular chain of the above-mentioned organopolysiloxane consist of a hydroxyl group in addition to the group represented by R. These include, for example, octamethylcyclotetrasiloxane and tetraalkyltetravinylcyclotetrasiloxane, or mixtures of octaphenylcyclotetrasiloxane, tetramethyltetraphenylcyclotetrasiloxane, etc. as required, which are polymerized in the presence of an alkali catalyst. It is something that can be obtained by letting people. The average repeating number n of the above-mentioned repeating unit groups of the organopolysiloxane used in the present invention is generally 1000 or more and 15000J). It may be lower than 35, but preferably 35 to obtain a composition with preferable properties.
00 or more is desirable. As the silica-based inorganic filler which is a raw material for the reactive silica-based inorganic filler used in the present invention, dry process silica and wet process silica, which are commonly known as white carbon, are used.

The average particle diameter of the silica-based inorganic filler that fully exhibits the effects of the present invention is 17T! ．． μ~1μ, preferably 5~
It is in the range of 1007T1,μ.

In addition, its specific surface area is 10 to 1000 in BET comparison area.
dIq, preferably in the range of 50 to 500 rf1Iy. The BET specific surface area referred to here is obtained from a commonly used adsorption method for measuring the specific surface area of powder, and the value used in the description of the present invention is based on the adsorption of nitrogen gas at liquid nitrogen temperature. It means the value of specific surface area measured by BET method. The method for measuring specific surface area is BET
Although there are various methods other than the BET method, the BET method was adopted because it is the most common method and is especially suitable for fine particle powders. Naturally, since the BET method specific surface area is not an absolute value, there is no reason to restrict the present invention. In carrying out the present invention, the particle surface of the silica-based inorganic filler must be activated with a polymerizable organic acid monomer by the method described below.

The polymerizable organic acid monomer used in the present invention is
having a hydrocarbon moiety having one or more ethylenic double bonds and one or more carboxyl groups, 50
Unsaturated carboxylic acids having the following carbon atoms, such as acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, sorpic acid, α-chloroacrylic acid, 2,4-pentadienoic acid, etc. α/β substituted product,
These include unsaturated polyhydric carboxylic acids such as maleic acid, fumaric acid, itaconic acid, citraconic acid, and mesaconic acid, fatty acids with a series of double bonds such as vinyl acetic acid, allyl acetic acid, and their substituted products, and their Li ．． ．． K. ,N
a. ．． Ca. ．． Zn. ．． These are metal salts such as Al, and esters with alkyl groups such as methyl, ethyl, butyl, and substituted alkyl groups such as hydroxyethyl.

In particular, acrylic acid-based unsaturated carboxylic acids such as the above-mentioned acrylic acid, its α and β substituted products, and unsaturated polyhydric carboxylic acids are effective. These may be used alone or as a mixture of two or more. In addition, in the case of a polymerizable organic acid, an acid anhydride may be used as a precursor thereof to perform a conversion reaction into an organic acid. When treating the silica-based inorganic filler with the polymerizable organic acid monomer, the amount of the polymerizable organic acid monomer used is one of the factors that influences the effect of the composition of the present invention. Become. That is, the amount used is 1 part by weight for 100 parts by weight of the silica-based inorganic filler.
From 1 part by weight to 15 parts by weight, preferably from 1 part by weight to 1 part by weight
The amount is in the range of up to 0 parts by weight, more preferably from 2 parts by weight to 6 parts by weight. When the amount of the polymerizable organic acid monomer used is less than the above range, the effect obtained is not so great.

If the amount used exceeds the above range, undesirable phenomena such as a reduction in the reinforcing effect of the resulting reactive silica-based inorganic filler will occur. Several methods have been proposed for manufacturing the reactive silica-based inorganic filler according to the present invention by coating the surface of the silica-based inorganic filler particles with a polymerizable organic acid monomer. What is important is that the particle surface of the silica-based inorganic filler is uniformly and firmly coated with the polymerizable organic acid monomer, and that as many ethylenically unsaturated groups as possible remain. It is necessary to be present.

One of the manufacturing methods is to coat and react the silica-based inorganic filler in powder form with a polymerizable organic acid monomer in various mixers,
This is a way to tighten it.

Various types of mixers include various powder mixers such as general glue pump blenders, tumblers, and ball mills, but a method of high-speed fluid mixing in a high-speed fluid mixer such as a Henschel mixer is particularly preferred. In this case, if the polymerizable organic acid monomer is a liquid, it is preferable to add and mix it directly or to spray it, but if it has a relatively high viscosity, an appropriate amount of a non-aqueous solvent may be used. In the case of a solid, it is preferable to add it as it is and mix it under melting temperature conditions, but it may also be added after being dissolved or suspended in an appropriate amount of a non-aqueous solvent. The temperature for producing the reactive silica-based inorganic filler is appropriately selected depending on the type, combination, and properties of the silica-based inorganic filler, polymerizable organic acid monomer, etc. The temperature is within the range below the decomposition temperature of the polymer, but generally the temperature is preferably in the range of 50 to 200°C.

Further, the time required for the above production is appropriately selected depending on various conditions and purposes, and is usually in the range of 1 minute to 2 hours, but generally in the range of 5 to 3 gin. Further, the above-mentioned production is desirably carried out in the substantial absence of liquid water, and preferably carried out under conditions such that water generated during the reaction is removed from the system (dehydration conditions). Therefore, it is desirable that the silica-based inorganic filler and polymerizable organic acid-based monomer used be dehydrated and dried before use. Furthermore, during the above production, production conditions are appropriately selected to avoid polymerization of the polymerizable organic acid monomer, but a polymerization inhibitor is not added to the polymerizable organic acid monomer. It is desirable to keep it. General polymerization inhibitors such as hydroquinone, methoxyhydroquinone, P-benzoquinone, naphthoquinone, and t-butylcatechol can be used as the polymerization inhibitor, and the amount used is O to 1% relative to the polymerizable organic acid monomer. % by weight, preferably 0.0
It ranges from 2 to 0.5% by weight. Another manufacturing method is to stir and mix a sufficiently dried silica-based inorganic filler and a polymerizable organic acid monomer in a non-aqueous solvent, and then purify it by filtering, washing, and drying. . Solvents that can be used in this production method include benzene, toluene, xylene, hepta,
hexane, tetralin, decalin, chloroform, carbon tetrachloride, methanol, ethanol, propanol, diethyl ether, acetone, methyl ethyl ketone,
Various organic solvents are possible, such as ethyl acetate. The silicone rubber composition of the present invention is obtained by kneading the reactive silica-based inorganic filler thus obtained with organopolysiloxane rubber.

The composition ratio of the silicone rubber composition of the present invention is ! The reactive silica-based inorganic filler is in the range of 5 to 15 parts by weight per 10 parts by weight of the ganopolysiloxane rubber, and the optimum composition ratio is appropriately selected within the above composition range depending on the use of the silicone rubber composition. be done.

Examples of the method for producing the composition of the present invention include a method of kneading organopolysiloxane rubber and a reactive silica-based inorganic filler under normal pressure, increased pressure, or reduced pressure using a general kneading machine. It will be done. As the above kneading machine,
Common kneading machines such as extruders, kneaders, co-kneaders, internal mixers (Panbury mixers), and mixing rolls are used. The kneading temperature is appropriately selected depending on various conditions and purposes such as the properties of the organopolysiloxane rubber used, the type of polymerizable organic acid monomer, the presence or absence of a radical generator, and the function of the kneader, but in general, room temperature to 250°C, more preferably room temperature to 1
A temperature range of 80'C is preferred. The kneading time is appropriately selected depending on the performance of the kneader and the mixing conditions. The silicone rubber composition of the present invention can be cured into a cured composition by a conventionally known method.

The most common method is to mix a radical generator into the composition and harden it by heating or other methods. As a radical generator, 2,5-dimethyl-2.
5-di(t-butylperoxy)hexane, dicumyl peroxide, t-butyl peroxybenzoate, t-butyl peroxyacetate, benzoyl peroxide, lauroyl peroxide, diisopropyl peroxydicarbonate, di-t-butyl peroxide,
Organic peroxides such as parachlorobenzoyl peroxide and 2,4-dichlorobenzoyl peroxide can be used as the most common radical generators, but azo compounds such as azobisisobutyronitrile and inorganic peroxides such as ammonium persulfate can be used as radical generators. Peroxides and the like may also be used. The above radical generators may be used alone or in combination of two or more. The amount of the radical generator used varies depending on the performance of the resulting cured composition, the performance and amount of the organopolysiloxane rubber in the composition, the type of polymerizable organic acid monomer, the type of radical generator, etc. In general, for the diorganopolysiloxane rubber component in the composition,
0. The range is from heel weight% to 5% by weight.

In addition to the above-mentioned components, the composition of the present invention includes conventionally known stabilizers,
Plasticizers, lubricants, pigments, foaming agents, flame retardants, compression set modifiers, fillers, reinforcing agents, etc. may be blended, and dispersants such as diphenylsilanediol and octamethylcyclotetrasiloxane may be blended. Also good.

EXAMPLES The present invention will be specifically explained below using examples and reference examples, but the scope of the present invention is not limited by the following examples and reference examples.

Note that parts used in Examples and Reference Examples indicate parts by weight. Example 1 Wet method white carbon, Tokusil U (average particle size 5 15
~18m. μ, specific surface area 200 to 250 dIy1 1 (4) parts of Tokuyama Soda Co., Ltd. were placed in a Henschel mixer,
While heating to 1200C and stirring, add hydroquinone 5.
A reactive silica-based inorganic filler 1 was obtained by spraying w parts of acrylic acid containing 00 ppm and mixing at normal pressure for 3 minutes.

During mixing, air heated and dried at 110° C. was introduced into the system, and water vapor generated during the reaction was removed from the system in gaseous form. A blending test was conducted on this reactive silica-based inorganic filler under the conditions shown below.

That is, 35 parts of the filler described above is mixed and kneaded in a kneader with 1 (1) part of silicone raw rubber having a degree of polymerization of about 7500, which is composed of 99.8 mol% dimethylsiloxane units and 0.2 mol% methylvinylsiloxane units. I got the compound. This compound was left at room temperature for a day and night, and then, using an open roll, 1 part of dicumyl peroxide (as the component in 20% silicone paste) was mixed and kneaded per 1 part of the silicone raw rubber in the compound, and a sheet-like product was obtained. I took it out as Next, this sheet was cut into a predetermined shape, and press vulcanization was performed using 1601 powder and a pressure of 20k91 cd to obtain a vulcanized sheet with a thickness of 2 mm.
Heat treatment was carried out in a gear type open oven for 1 hour at 180°C. Physical property tests were conducted on the thus obtained cured sheet.
The results shown in the table were obtained. Example 2 Reactive silica was prepared in the same manner as in Example 1, except that w part of ethylene glycol monoacrylate containing 500 ppm of hydroquinone was used for the wet method white carbon used in Example 1, Toksil UlOO part. A system inorganic filler was obtained.

A blending test and a physical property test were conducted in the same manner as in Example 1, except that this reactive silica-based inorganic filler was used instead of the reactive silica-based inorganic filler of Example 1. The results are shown in Table 1. Example 3 The wet method white carbon used in Example 1, Toksil UlOO, was placed in a Henschel mixer and heated at 110°C.
A reactive silica-based inorganic filler was obtained in the same manner as in Example 1, except that part w of maleic anhydride was dissolved in acetone and added while stirring.

Example 1 except that this reactive silica-based inorganic filler was used instead of the reactive silica-based inorganic filler of Example 1.
A blending test and a physical property test were conducted in the same manner as above. The results are shown in Table 1. Example 4 Example except that a dry process white carbon, Aerosil 200 (average particle size: 12 mp1, specific surface area: 200 d19, manufactured by Nippon Aerosil Co., Ltd.) was used instead of the wet process white carbon, Tokusil U, used in Example 1. A reactive silica-based inorganic filler was obtained in the same manner as in Example 1.

Example 1 except that this reactive silica-based inorganic filler was used instead of the reactive silica-based inorganic filler of Example 1.
A blending test and a physical property test were conducted in the same manner as above.

The results are shown in Table 1. Reference Example 1 Instead of the reactive silica-based inorganic filler, the wet method white carbon used in Example 1, Tokusil U and Tokusil U1 (
A blending test and a physical property test were carried out in the same manner as in Example 1, except that 5 parts of diphenylsilanediol were used for 1 part.

The results are shown in Table 1. Reference Example 2 A blending test and a physical property test were carried out in the same manner as in Example 1, except that Toxil U, the wet process white carbon used in Example 1, was used instead of the reactive silica-based inorganic filler. I went.

The results are shown in Table 1. Reference Example 3 Implemented except that 5 parts of diphenylsilanediol was used for 2 (1) parts of Aerosil 2005, the dry method white carbon used in Example 4, and 2 (1) parts of Aerosil instead of the reactive silica-based inorganic filler. A blending test and a physical property test were conducted in the same manner as in Example 1.

The results are shown in Table 1. Reference Example 4 A blending test and a physical property test were conducted in the same manner as in Example 1, except that Aerosil 200, the dry process white carbon used in Example 4, was used instead of the 0-reactive silica-based inorganic filler. Ivy.

The results are shown in Table 4. Examples 5-1 to 3 Same as Example 1, except that the reactive silica-based inorganic filler used in Example 1 was blended at 50 parts and 65 parts per 10 parts of silicone raw rubber. A blending test and a physical property test were conducted in the same manner.

The results are shown in Table 2. Reference Examples 5-1 to 3 Instead of the reactive silica-based inorganic filler, the wet process white carbon used in Example 1, Toksil U, was added at 2 parts per 1 (4) parts of silicone raw rubber, and the marked part and 65 parts. A blending test and a physical property test were conducted in the same manner as in Example 1, except that 5 parts of diphenylsilanediol were blended with respect to 1 part of Toxil U1 (1) part.

The results are shown in Table 2. Example 6 Instead of Toksil U, the wet process white carbon used in Example 1, an average particle size of 20 to 407 TL. The reactive silica-based An inorganic filler was obtained.

A blending test and a physical property test were carried out in the same manner as in Example 1, except that this reactive silica-based inorganic filler was used instead of the reactive silica-based inorganic filler of Example 1. The results are shown in Table 3. Reference Example 6 Tokusil G used in Example 6
A reactive silica-based inorganic filler was obtained in the same manner as in Example 1 except that U-S was used and 200 parts of acrylic acid was used for the Toxyl GU-SlOO part.

Example 1 except that this reactive silica-based inorganic filler was used instead of the reactive silica-based inorganic filler of Example 1.
A blending test and a physical property test were conducted in the same manner as above.

The results are shown in Table 3. Reference Example 7 The reactivity of Example 1 was determined in the same manner as in Example 1 except that 1.75 parts of Toxyl GU-S and diphenylsilanediol used in Example 6 were used instead of the silica-based inorganic filler. A blending test and a physical property test were conducted.

Claims (1)

[Claims] 1 (a) General formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (
In the formula, R is 100 parts by weight of an organopolysiloxane rubber having a repeating unit group of an alkyl group, a halogenated alkyl group, an aryl group, or an alkenyl group. 1. A novel heat-curable silicone rubber composition comprising 5 to 150 parts by weight of a reactive silica-based inorganic filler coated with a polymer.