JP2001348481A - Heat-resistant silicone rubber composition and its molded product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-resistant silicone rubber composition which retains practical mechanical properties of a heat cured product even when exposed to high temperatures for a long period of time and gives a heat-curable silicone rubber having excellent resistance to compression set, and a molded product obtained by curing the silicone rubber composition. SOLUTION: The heat-resistant silicone rubber composition comprises (A) 100 pts.wt. silicone rubber composition and (B) 0.01-2.0 pts.wt. polyazo based compound having two or more azo groups, to one side of which a substituted or unsubstituted phenyl group is bonded, in the molecule.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a heat-resistant silicone rubber composition which provides a heat-curable silicone rubber which retains practical mechanical properties even when exposed to high temperatures for a long time and has excellent compression set resistance, and The present invention relates to a molded article obtained by curing the heat-resistant silicone rubber composition.

[0002]

2. Description of the Related Art Silicone rubber products are widely used in various applications because of their inherently superior heat resistance compared to general resins. However, when exposed to a high temperature exceeding 250 ° C. for a long time, the rubber elasticity is high. Degradation occurs. Therefore, in order to be able to withstand such high temperatures, use of a heat resistance improver has been studied.

For example, it has been proposed to mix iron sesquioxide with powdered quartz, fused quartz or a mixture thereof in an addition-reaction-curable silicone rubber (Japanese Patent Publication No. 63-52060). 20-300 parts by weight,
Unless a large amount of powdered quartz, fused quartz, or a mixture of 10 to 200 parts by weight is added, the intended improvement in heat resistance is not exhibited, and the mechanical strength of the cured product is reduced.

Further, a proposal has been made for an elastic roll in which an organic peroxide-curable silicone rubber layer containing iron oxide is provided on the outer peripheral surface of an elastic roll, using iron oxide alone as a heat resistance improving agent (Japanese Patent Publication No. Hei 10-222). However, as in the case of the above proposal, heat resistance was insufficient unless iron oxide was added in an amount as large as 5 to 100 parts by weight.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and retains practical mechanical properties even when a heat-cured product is exposed to a high temperature for a long time, and has excellent compression set resistance. An object of the present invention is to provide a silicone rubber composition that gives a heat-curable silicone rubber, and a molded product obtained by curing the heat-resistant silicone rubber composition.

[0006]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that a specific polyazo compound is added to an organic peroxide-curable or addition-reaction-curable silicone rubber composition. It has been found that the addition of the heat-resistant additive significantly improves the heat resistance and also improves the compression set resistance, and completed the present invention.

That is, the present invention relates to a polyazo compound having (A) 100 parts by weight of a silicone rubber composition and (B) two or more azo groups having one or more substituted or unsubstituted phenyl groups bonded to one side in one molecule. An object of the present invention is to provide a heat-resistant silicone rubber composition containing 0.01 to 2.0 parts by weight and a molded product obtained by curing the composition.

Hereinafter, the present invention will be described in detail. The means for heat-curing the heat-resistant silicone rubber composition of the present invention includes organic peroxide curing or addition reaction curing.

[0009] When the organic peroxide curing type; (A) a silicone rubber composition of the components is not particularly limited as long as it is commonly used, the following general formula _{^{(3), R 6 a SiO}} (4 _{-a) / 2} (3) (R ⁶ in the formula (3) is the same or different and is a substituted or unsubstituted monovalent hydrocarbon group, and a is a positive number of 1.9 to 2.4. ), A material composed mainly of polyorganosiloxane, silica fine powder and organic peroxide.

In the polyorganosiloxane of the above formula (3), R ⁶ is preferably a substituted or unsubstituted monovalent hydrocarbon group having 1 to 12 carbon atoms, specifically, a methyl group,
Ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, 2-ethylhexyl group, heptyl group, octyl group, nonyl group, decyl group, dodecyl group, etc. Alkyl group, cyclopentyl group, cyclohexyl group,
Cycloalkyl group such as cycloheptyl group, vinyl group, allyl group, propenyl group, isopropenyl group, butenyl group, isobutenyl group, hexenyl group, alkenyl group such as cyclohexenyl group,

Aryl groups such as phenyl, tolyl, xylyl, biphenyl and naphthyl; aralkyl such as benzyl, phenylethyl, phenylpropyl and methylbenzyl; and hydrogen in these hydrocarbons A chloromethyl group in which some or all of the atoms are substituted with a halogen atom, a cyano group, etc., a 2-bromoethyl group,
Examples include a halogen-substituted alkyl group such as a 3,3,3-trifluoropropyl group, a 3-chloropropyl group and a cyanoethyl group, and a cyano-substituted alkyl group.

Particularly preferred R ⁶ is a methyl group, a vinyl group,
A phenyl group and a 3,3,3-trifluoropropyl group. Further, it is preferable that 70 mol% or more of all R ⁶ is a methyl group, particularly preferably 90 mol% or more. When the methyl group content is less than 70 mol%, there is a disadvantage that weather resistance and the like are impaired.

In the equation (3), a is 1.9 to 2.4,
It is preferably a positive number of 1.98 to 2.05, and the polyorganosiloxane may be linear or branched, but is usually a linear polydiorganosiloxane. The polyorganosiloxane is prepared by methods known to those skilled in the art.

The polyorganosiloxane comprising the unit of the formula (3) is a low-viscosity liquid or a high-viscosity paste-like substance and has a viscosity at 25 ° C. of 0.1 Pa · s to 50 Pa.
It preferably has a viscosity of 50,000 Pa · s to 100,000 Pa · s. In addition, mixtures of the different polyorganosiloxanes characterized above can also be used.

The type of the silica fine powder is not particularly limited, and those used in conventional silicone rubber compositions can be used. Examples of such silica fine powder include BE
It is essential that the surface area by the T method is at least 50 m ² / g or more, especially 50 to 400 m ² / g of precipitated silica, fumed silica, and calcined silica, and pulverization having an average particle size of 50 μm or less, particularly 0.1 to 20 μm. Quartz, diatomaceous earth and the like are preferably used. These fine silica powders may be used as they are, but may be hydrophobized by treating with an organosiloxane or stearic acid or by etherifying a hydroxyl group to an alkoxy group.

The compounding amount of the silica fine powder is preferably from 1 to 100 parts by weight based on 100 parts by weight of the polyorganosiloxane. If it is less than 1 part, the mechanical strength is weak, and if it exceeds 100 parts, the workability is poor. Become. Preferably it is in the range of 2 to 50 parts by weight.

The organic peroxide for curing the organic peroxide-curable silicone rubber composition is used as a catalyst for accelerating the crosslinking reaction of the polyorganosiloxane. It is used for a product-curable polyorganosiloxane composition.

Examples of suitable organic peroxides include benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, p-methylbenzoyl peroxide, o
-Methylbenzoyl peroxide, 2,4-dicumyl peroxide, 2,5-dimethyl-bis (2,5-t
-Butylperoxy) hexane, di-t-butylperoxide, t-butylperbenzoate and 1,1-bis (t-butylperoxycarboxy) hexane are preferred. It is also possible to use mixtures of different organic peroxides.

The amount of the organic peroxide to be added is a catalytic amount and can be appropriately selected according to the curing rate. Usually, the amount is 0.1 to 100 parts by weight based on 100 parts by weight of the silicone rubber composition of the component (A). The range is 10 parts by weight, preferably 0.4 to 2.0 parts by weight, particularly preferably 0.7 to 1.5 parts by weight.

In the case of the addition reaction-curable type, the silicone rubber composition of the component (A) is not particularly limited as long as it is a commonly used one, and is represented by the following general formula (4): R ⁷ _b SiO _{(4-b ) / 2} (4) (R ⁷ in the formula (4) represents the same or different, substituted or unsubstituted monovalent hydrocarbon group, and the R ⁷ is preferably from 0.01 to 10)
The mole% is an alkenyl group, and b is a positive number from 1.9 to 2.4. An alkenyl group-containing polyorganosiloxane represented by

The following general formula (5): R ⁸ _{c Hd} SiO _{(4-cd) / 2} (5) (R ⁸ in the formula (5) is the same or different, and is a substituted or unsubstituted monovalent hydrocarbon group. And c is 0.7 to 2.1,
d is 0.001-1.0, and b + c is 0.8-3.
0. A) a polyorganohydrogensiloxane liquid at room temperature having at least two hydrogen atoms bonded to silicon atoms in one molecule, a silica fine powder,
A catalyst composed mainly of a hydrosilylation catalyst is used.

In the polyorganosiloxane of the formula (4), R ⁷ is preferably a substituted or unsubstituted monovalent hydrocarbon group having 1 to 12 carbon atoms, specifically, a methyl group, an ethyl group, a propyl group. Isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, 2-ethylhexyl, heptyl, octyl, nonyl, nonyl, decyl, dodecyl and other alkyl groups, cyclopentyl group , Cyclohexyl group, cycloalkyl group such as cycloheptyl group, vinyl group, allyl group, propenyl group, isopropenyl group, butenyl group,
Alkenyl groups such as isobutenyl group, hexenyl group and cyclohexenyl group,

Aryl groups such as phenyl, tolyl, xylyl, biphenyl and naphthyl; aralkyl such as benzyl, phenylethyl, phenylpropyl and methylbenzyl; and hydrogen in these hydrocarbons A chloromethyl group in which some or all of the atoms are substituted with a halogen atom, a cyano group, etc., a 2-bromoethyl group,
Examples include a halogen-substituted alkyl group such as a 3,3,3-trifluoropropyl group, a 3-chloropropyl group and a cyanoethyl group, and a cyano-substituted alkyl group. Particularly preferred R ¹ is a methyl group, a vinyl group, a phenyl group, 3,3,3-
It is a trifluoropropyl group.

In the alkenyl group-containing polyorganosiloxane, 0.01 to 10 mol% of the total R ⁷ is an alkenyl group, preferably 0.02 to 2 mol%, and at least an average of It is necessary to include two alkenyl groups. The alkenyl group may be bonded to either the silicon atom at the terminal of the molecular chain or the silicon atom in the middle of the molecular chain, or may be bonded to both of them. In view of the above, it is preferable that the compound has at least an alkenyl group bonded to silicon atoms at both ends of the molecular chain.

Further, 70 to 99.99 mol% of all R ⁷
Is preferably a methyl group, particularly preferably 90
~ 99.98 mol%. When the methyl group content is less than 70 mol%, there is a disadvantage that weather resistance and the like are impaired.

In the equation (4), a is 1.9 to 2.4;
It is preferably a positive number from 1.98 to 2.05, and the alkenyl group-containing polyorganosiloxane may be linear or branched, but is usually a linear polydiorganosiloxane. It is. The alkenyl group-containing polyorganosiloxane is produced by a method known to those skilled in the art.

The alkenyl group-containing polyorganosiloxane of the formula (4) is a low-viscosity liquid or a high-viscosity paste-like substance.
S to 500,000 Pa · s, a particularly preferred viscosity is 2
It is 1 Pa · s to 100,000 Pa · s at 5 ° C. It is also possible to use mixtures of the different alkenyl-containing polyorganosiloxanes characterized above.

In the polyorganohydrogensiloxane of the formula (5), R ⁸ is the same or different and is a substituted or unsubstituted monovalent hydrocarbon group, specifically the same as those exemplified for R ^6. Is preferably a group having no aliphatic unsaturated bond, and particularly preferably a methyl group, a phenyl group, or a 3,3,3-trifluoropropyl group. b is 0.7 to 2.1, preferably 0.9 to
2, c is 0.001 to 1.0, preferably 0.01 to 1
And b + c is 0.8 to 3.0, preferably 0.9 to 3.0.
2.5.

The polyorganohydrogensiloxane functions as a crosslinking agent, and preferably contains three or more silicon-bonded hydrogen atoms (SiH groups) in one molecule. When using a polyorganohydrogensiloxane having two SiH groups in one molecule,
It is recommended to use alkenyl-containing polyorganosiloxanes having at least three alkenyl groups in one molecule. The SiH group may be located at the terminal of the molecular chain, at the middle of the molecular chain, or at both. The number of silicon atoms in one molecule is 3 to 600, preferably 4 to 200.

Further, the structure of the polyorganohydrogensiloxane may be linear, branched, cyclic or network. The polyorganohydrogensiloxane is prepared by methods known to those skilled in the art. The compounding amount of the polyorganohydrogensiloxane is such that the molar ratio of SiH groups in the polyorganohydrogensiloxane to alkenyl groups bonded to silicon atoms in the alkenyl group-containing polyorganosiloxane is 0.5 to 5.0, preferably 1 to 5.0. It is an amount that becomes 0.0 to 3.0.

As a hydrosilylation catalyst for curing an addition reaction-curable silicone rubber composition, those which are usually used, and metals and compounds thereof include, for example,
Platinum, rhodium, palladium, ruthenium and iridium, preferably platinum, can be used. The metal is optionally fixed to a particulate carrier material (eg, activated carbon, aluminum oxide, silicon oxide). It is preferable to use platinum and a platinum compound as the hydrosilylation catalyst.

Examples of the platinum compound, platinum halides _{(e.g., PtCl 4, H 2 PtCl 4} · 6H 2 O, Na 2
_{PtCl 4 · 4H 2 O, H} 2 PtCl 4 · 6H 2 O and the reaction products of cyclohexane), platinum - olefin complex, a platinum - alcohol complexes, platinum - alcoholate complexes,
Platinum-ether complex, platinum-aldehyde complex, platinum-ketone complex, platinum-vinylsiloxane complex (for example, platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex, bis- (γ- Picoline) -platinum dichloride, trimethylenedipyridine-platinum dichloride,
Dicyclopentadiene-platinum dichloride, cyclooctadiene-platinum dichloride, cyclopentadiene-platinum dichloride).

The hydrosilylation catalyst may be used in a microencapsulated form. In this case, the particulate solid containing the catalyst and insoluble in the polyorganosiloxane may be, for example, a thermoplastic resin (eg, a polyester resin). Or silicone resin). The hydrosilylation catalyst can also be used in the form of an inclusion compound, for example in cyclodextrin. The addition amount of the hydrosilylation catalyst is a catalytic amount. When a platinum catalyst is used, 0.1 to 500 p as a platinum metal in the silicone rubber composition is used.
pm, especially in the range of 10-100 ppm.

The silica fine powder is the same as in the case of organic peroxide curing. The addition reaction-curable silicone rubber composition of the present invention may further contain, as an optional ingredient, an addition reaction control agent such as an acetylene alcohol compound such as ethynylcyclohexanol in addition to the above-mentioned main components as long as the effects of the present invention are not impaired. can do.

The polyazo compound used as the component (B) is a polyazo type in which two or more azo compounds having an azo group, that is, a group having a double bond of two nitrogen atoms (-N = N-) are condensed. It is a compound having a structure and having two or more azo groups in one molecule in which a substituted or unsubstituted phenyl group is bonded to only one side. Preferably, a compound represented by the following general formula (1) or (6) is used.

[0036]

Embedded image (R ¹ and R ² in the formula (1) are the same or different methyl groups or chlorine atoms, and X is a group represented by the following general formula (2).)

[0037]

Embedded image (In formula (2), R ³ represents a methyl group, and R ⁴ and R ⁵ represent the same or different hydrogen atoms or chlorine atoms.)

[0038]

Embedded image

More preferably, of the above two types of polyazo compounds, the former is a compound represented by the general formula (1), and particularly preferred is a compound represented by the above formula (1).
¹ and R ² are methyl groups, and R ^{3 of the} general formula (2)
Is a methyl group, R ⁴ is a hydrogen atom, and R ⁵ is a chlorine atom, the 3,3 ′-((2,5-dimethyl-
1,4-phenylene) bis (imino (1-acetyl-2
-Oxo-2,1-ethanedyl) azo)) bis (4-chloro-N- (5-chloro-2-methylphenyl) -benzamide).

[0040]

Embedded image

The amount of the component (B) is 100
It is 0.01 to 2.0 parts by weight based on parts by weight. 0.0
If the amount is less than 1 part by weight, sufficient improvement in heat resistance cannot be obtained.
Even if the amount exceeds the weight part, no further improvement in heat resistance is exhibited.
The preferred amount of the component (B) is in the range of 0.01 to 1.0 part by weight, and particularly preferably 0.02 to 0.5 part by weight. The polyazo compounds may be used alone or in combination of several kinds.

The heat-resistant silicone rubber composition of the present invention may contain a known heat-resistance improver in addition to the polyazo compound. Examples of the heat resistance improver include iron oxide, titanium oxide, cerium oxide, nickel oxide, cobalt oxide, barium zirconate, and carbon black. When these known heat-resistant improvers and polyazo-based compounds are used in combination, a synergistic effect of improving heat resistance is observed, and the combination of an expensive polyazo-based compound and a relatively inexpensive known heat-resistant improver results in an added amount of the polyazo-based compound. Can be reduced,
High industrial value.

A preferred known heat resistance improver is iron oxide (ferrous oxide, ferric oxide, and a mixture of ferrous oxide and ferric oxide). a ferric oxide mainly composed of -Fe ₂ O _3. The iron oxide is preferably in the form of a fine powder having a particle diameter of 50 μm or less. Further, the compounding amount of iron oxide is preferably 0.1 to 5.0 parts by weight based on 100 parts by weight of the component (A). If the amount is less than 0.1 part by weight, the effect of the addition is not obtained, and if it exceeds 5.0 parts by weight, the tensile strength decreases. Particularly preferred are 0.2-2.
The range is 0 parts by weight.

The organic peroxide-curable silicone rubber composition and the addition-reaction-curable silicone rubber composition of the present invention may contain, in addition to the above components, a free silicone oil, for example, a linear dimethylpolysiloxane or a hydroxyl group-containing silicone oil. Dimethylpolysiloxane and linear methylphenylpolysiloxane can be added, and various additives such as a flame retardant and a plasticizer may be added according to the purpose. The amount of these optional components added is within a range that does not impair the effects of the present invention.

The silicone rubber composition of the present invention can be molded by mixing a polyazo compound or a curing agent with a planetary mixer, a kneading roll machine, a closed mixer (kneader or the like), or the like. The molding method can be freely selected depending on the viscosity of the mixture, and any method such as injection molding, compression molding, injection molding, extrusion molding, and transfer molding may be employed. The curing condition of the silicone rubber composition of the present invention is generally a condition of heating at 80 to 200 ° C. for 5 seconds to 3 hours.

The molded article of the organic peroxide-curable or addition-reaction-curable silicone rubber composition of the present invention thus formed retains practical mechanical properties even when exposed to high temperatures for a long time. In addition, since it has the property of having excellent compression set resistance, its industrial value is extremely high.

The molded article of the composition of the present invention can be used for various rolls such as OA rolls and PPC rolls, for electric wires such as high-temperature insulating wires and fire-resistant wires, and for wire accessory parts, connector seals, wire seals, oil seals, and the like. It is suitable for use in automotive parts such as cylinder head gaskets, O-rings, spark plug boots, ignition cables, and heat-resistant parts such as heat-resistant hoses. It is suitably used for various sealing materials in the field.

[0048]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be specifically described below with reference to examples, but the present invention is not limited to the examples.

[0049]

Example 1 An organic peroxide-curable silicone rubber composition, Watzer Chemie Gesellsyaft Mituto Vesjullenktel Haftung product "ELASTOSIL (registered trademark)"
R401 / 50S ”100 parts by weight 3,3'-
((2,5-dimethyl-1,4-phenylene) bis (imino (1-acetyl-2-oxo-2,1-ethanedyl) azo)) bis (4-chloro-N- (5-chloro-2
-Methylphenyl) -benzamide) (hereinafter abbreviated as compound A) 0.46 parts by weight and an organic peroxide bis- (4-
0.6 parts of methylbenzoyl) -peroxide were uniformly dispersed by a kneading roll machine, press-cured at 120 ° C. for 10 minutes, and then cured at 200 ° C. for 4 hours in a circulating heating oven to form a sheet having a thickness of about 2 mm. Produced. JI for hardness (type A durometer), tensile test and aging test of cured product
The measurement was performed according to SK6249, and the results are shown in Table 1.

Example 2 Compound A used in Example 1 was added from 0.46 parts by weight to 0.2
A test piece was prepared and tested in the same manner as in Example 1 except that the amount was changed to 3 parts by weight and 0.5 part by weight of ferric oxide was added. Table 1 shows the results.

Comparative Example 1 Example 1 was repeated except that the compound A used in Example 1 was not used.
A test piece was prepared and tested in the same manner as described above. Table 1 shows the results.

Comparative Example 2 Example 2 was repeated except that the compound A used in Example 1 was not used.
A test piece was prepared and tested in the same manner as described above. Table 1 shows the results.

Example 3 Wacker which is an addition-curable silicone rubber composition
Chemie Gesellsyaft Mitts
Haftung product "ELASTOSIL <registered trademark> L
R3003 / 60 ”, 50 parts by weight of the A component containing the platinum catalyst, 50 parts by weight of the B component containing the polyorganohydrogensiloxane, and 0.08 parts by weight of the compound A used in Example 1 were uniformly mixed.
After press-curing at 0 ° C. for 5 minutes, it is cured in a circulating heating oven at 200 ° C. for 4 hours and a sheet having a thickness of about 2 mm and a test piece for measuring compression set (diameter of about 29 mm, thickness of about 1 mm)
2.5 mm). The hardness (type A durometer), tensile test, aging test, and compression set test of the cured product were measured according to JIS K6249, and the results are shown in Table 2.

Example 4 Compound A used in Example 1 was added from 0.08 parts by weight to 0.3 part by weight.
A test piece was prepared and tested in the same manner as in Example 3 except that the amount was changed to parts by weight. Table 2 shows the results.

Example 5 The compound A used in Example 1 was added from 0.08 parts by weight to 0.0
A test piece was prepared and tested in the same manner as in Example 3 except that the amount was changed to 3 parts by weight and 0.26 part by weight of ferric oxide was added. Table 2 shows the results.

Comparative Example 3 Example 3 was repeated except that the compound A used in Example 1 was not used.
A test piece was prepared and tested in the same manner as described above. Table 2 shows the results.

Comparative Example 4 Example 5 except that the compound A used in Example 1 was not used.
A test piece was prepared and tested in the same manner as described above. Table 2 shows the results.

[0058]

[Table 1]

[0059]

[Table 2]

[0060]

The heat-resistant silicone rubber composition of the present invention retains practical mechanical properties even when exposed to high temperatures for a long time,
Since it gives a heat-curable silicone rubber having excellent compression set resistance, it is extremely useful for various uses requiring heat resistance.

Continued on the front page F term (reference) 4F071 AA67 AB18 AC12 AH07 AH16 AH19 BB03 BB05 BB06 4J002 CP031 CP041 CP081 CP091 CP131 CP141 DE117 EK028 EK048 EK058 EQ016 FD066 FD067 FD148

Claims (4)

[Claims] 1. A polyazo compound having 100 or more parts by weight of (A) a silicone rubber composition and (B) a polyazo compound having two or more azo groups having one or more substituted or unsubstituted phenyl groups bonded to one side in one molecule. A heat-resistant silicone rubber composition containing 2.0 parts by weight. 2. The heat-resistant silicone rubber composition according to claim 1, wherein the polyazo compound as the component (B) is a compound represented by the following general formula (1). Embedded image (In the formula (1), R ¹ and R ² are the same or different methyl groups or chlorine atoms, and X is a group represented by the following general formula (2).) (In formula (2), R ³ represents a methyl group, and R ⁴ and R ⁵ represent the same or different hydrogen atoms or chlorine atoms.) 3. The heat-resistant silicone rubber composition according to claim 1, wherein (C) iron oxide is compounded in an amount of 0.1 to 5.0 parts by weight per 100 parts by weight of the component (A). 4. A molded article obtained by curing the heat-resistant silicone rubber composition according to claim 1.