JPH10231427A - Silicone rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silicon rubber composition which can be kept black without reddening even when exposed to a temperature of 200 deg.C or above for a long time and has flame retardancy and heat resistance. SOLUTION: This composition comprises 100 pts.wt. organopolysiloxane represented by the formula: Ra SiO(4-a)/2 (wherein Rs are the same or different (un)substituted 1-10C monovalent hydrocarbon groups; and a is a positive number of 1.90-2.05), 10-100 pts.wt. reinforcing silica having a specific surface area of at least 50m<2> /g, a curing agent in an amount necessary for curing and 0.1-50 pts.wt. magnetite surface-treated with 1-10wt.% alumina or silica-alumina or finely powdered hematite doped with 10-20wt.% manganese.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to black and flame retardant,
The present invention relates to a silicone rubber composition having improved heat resistance and flame retardancy, which is useful for applications requiring heat resistance.

[0002]

2. Description of the Related Art Silicone rubber has excellent heat resistance, weather resistance, durability, releasability, and various electric characteristics. Therefore, it has been conventionally processed into various shapes, and electric / electronic-related parts, OA, It is used in various fields such as equipment parts and building materials. Various coloring agents are added to these silicone rubbers as necessary to impart coloring. Carbon black and black red iron oxide (Fe ₃ O ₄ ) are known as typical coloring agents for giving black color to silicone rubber. Also, various additives are added to impart flame retardancy. As a method of imparting flame retardancy to such a silicone rubber composition, generally, a platinum catalyst is representative as a flame retardant, and a combination of a platinum catalyst and an additive such as carbon black has also been proposed. I have. For example, USP 3,652,4
No. 88 mentions carbon black, and US Pat. No. 3,635,874 mentions titanium oxide as an auxiliary agent. In Japan, a method of adding iron oxide (FeO) _x (Fe ₂ O ₃ ) _y is used in Japanese Patent Publication No. 51-24302, and among them, black red iron oxide (Fe ₃ O ₄ ) is effective.

[0003]

However, when Fe ₃ O ₄ is blended, the color changes from black to red when exposed to a temperature of 200 ° C. or higher, and the mechanical strength and flame retardancy decrease accordingly. There was a disadvantage. As a result of various studies, the present inventors have found that the surface is made from 1 to 10% by weight of alumina or silica-
The use of alumina-treated magnetite and / or pulverulent hematite doped with 10 to 20% by weight of manganese does not turn red even when exposed to a temperature of 200 ° C or more for a long time, especially when a platinum catalyst is combined. It was found that the decrease in flammability and mechanical strength was less.

[0004]

The present invention provides (A) an average compositional formula R _a SiO _{(4-a) / 2} (where R is the same or different and is unsubstituted or substituted monovalent having 1 to 10 carbon atoms). A hydrocarbon group, a is a positive number from 1.90 to 2.05), 100 parts by weight of an organopolysiloxane represented by the formula (B): 10 to 100 parts by weight of a reinforcing silica having a specific surface area of at least 50 m ² / g; ) Curing agent The amount required for curing. (D) Magnetite whose surface has been treated with 1 to 10% by weight of alumina or silica-alumina and / or 10 to 20% by weight of manganese-doped pulverized hematite 0.1 to 50%. A silicone rubber composition comprising parts by weight.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The organopolysiloxane of the component (A) has an average composition formula
R _a SiO _{(4-a) / 2} , wherein R is the same or different and is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 10 carbon atoms, and is an alkyl group, an alkenyl group, an aryl group, And a monovalent group selected from a methyl group, a vinyl group and a phenyl group. The alkenyl group is preferably contained in an amount of 0.01 to 5 mol%, particularly preferably 0.02 to 0.5 mol%. Further, as the substituted hydrocarbon group, an alkyl group, an alkenyl group, a part or all of the hydrogen atoms bonded to carbon atoms of an unsubstituted hydrocarbon group such as an aryl group are substituted with a halogen atom, a cyano group, or the like, for example, Examples thereof include a 3-trifluoropropyl group and a 2-cyanoethyl group, and a 3,3,3-trifluoropropyl group is particularly preferable. Examples of both terminal groups of the molecular chain include a hydroxy group, a trimethylsilyl group, a dimethylvinylsilyl group, and a trivinylsilyl group, but are not particularly limited thereto. In the formula average composition formula, a is 1.90 to 2.05
And is basically linear, but may be partially branched. The organopolysiloxane of the component (A)
In order to obtain sufficient mechanical strength, the degree of polymerization is 3,000 or more, preferably from 3,000 to 10,000, and particularly preferably from 5,0 to 10,000.
It is 100 to 10,000. As the organopolysiloxane (A), two or more organopolysiloxanes having different structures and degrees of polymerization can be used in combination.

The reinforcing silica of the component (B) has a specific surface area of 50 m ² / g or more in order to impart appropriate hardness to the silicone rubber and to improve mechanical strength such as tensile strength. Although it is used, it is particularly preferably 100 to 400 m ² / g. Specifically, as such reinforcing silica,
Fumed silica, calcined silica, precipitated silica and the like are used alone or in combination of two or more. These silicas may be surface-treated with a linear organopolysiloxane, a cyclic organopolysiloxane, hexamethyldisilazane, dichlorodimethylsilane, or the like. The compounding amount of the component (B) is 10 to 100 parts by weight, preferably 20 to 50 parts by weight, based on 100 parts by weight of the organopolysiloxane of the component (A). If the compounding amount is out of this range, the processability of the silicone rubber composition may be deteriorated, or sufficient mechanical strength may not be obtained.

The curing agent (C) cures the composition of the present invention to form a silicone rubber, and generally uses an organic peroxide. When the organopolysiloxane of the component (A) contains two or more alkenyl groups in the molecule, a combination of an organohydrogenpolysiloxane and a platinum-based catalyst can be used as a curing agent. The amount of the curing agent may be an amount sufficient to cure the composition of the present invention as described below. Examples of the organic peroxide usable in the present invention include dicumyl peroxide, di-t-butyl peroxide, t-butylcumyl peroxide, and 2,5-dimethyl-2,5-di (t-butylperoxy). Hexane, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, 2,5-dimethyl-2,5-di (t-butylperoxy) 3,3,5-trimethylcyclohexane, benzoyl peroxide ,
Examples thereof include 2,4-dichlorobenzoyl peroxide and 4-chlorobenzoyl peroxide. The compounding amount of these organic peroxides is 0.1 to 100 parts by weight based on 100 parts by weight of the component (A) as an amount sufficient to cure the composition of the present invention.
It is within the range of 10 parts by weight.

[0008] When the organopolysiloxane of the component (A) contains two or more alkenyl groups in the molecule, the organohydrogenpolysiloxane which can be used as a curing agent is a methylhydrogenpolysiloxane having capped trimethylsiloxy groups at both terminals. Examples thereof include siloxane, a dimethylsiloxane / methylhydrogensiloxane copolymer having both ends terminated with a trimethylsiloxy group, and a dimethylsiloxane / methylhydrogensiloxane copolymer having both ends terminated with a methylhydrogensiloxy group. On the other hand, examples of the platinum catalyst include chloroplatinic acid, an alcohol solution of chloroplatinic acid, and a complex of chloroplatinic acid and divinyltetramethylsiloxane. In general, the compounding amount of the above-mentioned organohydrogenpolysiloxane is such that the ratio of the number of moles of hydrogen atoms bonded to silicon atoms contained in the organohydrogenpolysiloxane to the number of moles of alkenyl groups in the component (A) is ( 0.5: 1) to (20: 1). The amount of the platinum-based catalyst is generally about 0.5 to 1,000 ppm in terms of platinum, based on the weight of the component (A). When a platinum compound is used, it can be shared.

[0009] Component (D) is a characteristic component of the silicone rubber composition of the present invention. 1-10% by weight of alumina or silica - alumina treated magnetite (Fe ₃ O ₄₎ and or 10 to 20% by weight of finely divided hematite manganese doped. Generally, magnetite (Fe ₃ O ₄ ) is 200 ℃
If it exceeds, the surface is oxidized and changes from black to red. Thus, the present inventors have conducted various studies on magnetite and manganese-doped fine powdered hematite (Fe ₂ O ₃ ) whose surface has been treated with alumina or silica-alumina.
This is superior to conventional magnetite in heat resistance, does not turn red in a heat resistance test of a cured product of a silicone rubber composition containing it, and shows excellent flame retardancy when used together with a platinum compound, and after exposure to high temperatures Was found to have little decrease in mechanical strength. Alumina or silica - processing of alumina is 1 to 10% by weight with respect to magnetite (Fe ₃ O _4), without applying to the cured sufficient heat resistance and less than 1 wt.% Rubber, also 10 weight %, It becomes difficult to produce magnetite of component (D) having excellent dispersibility. Commercially available magnetites can be used. Hematite is usually red, but finely powdered hematite doped with 10 to 20% by weight of manganese becomes excellent black. If the manganese doping amount is less than 10% by weight, a sufficient black color is not imparted to the silicone rubber. As these hematites, commercially available ones can be used, and for example, there is a hematite HSB series (trade name, manufactured by Toda Kogyo KK). The component (D) may be treated with an organic compound such as a silane coupling agent or an inorganic compound such as Al or Si to improve fluidity and chemical resistance within a range that does not impair the object of the present invention. It is possible. The component (D) preferably has a particle size of 0.1 to 5.0 μm, more preferably
0.1 to 2.0 μm. Those having a particle size of less than 0.1 μm have a high activity and may be difficult to be blended. In the present invention,
When mixing the component (D) with the organopolysiloxane composition, a kneader such as a kneader, a Banbury mixer, or an open roll may be used. Component (D) is used in an amount of 0.1 to 50 parts by weight, preferably 0.5 to 5 parts by weight, per 100 parts by weight of the organopolysiloxane of component (A). If the amount is less than 0.1 part by weight, the black color will not be sufficient, heat resistance and flame retardancy will be insufficient, and if it exceeds 50 parts by weight, the elasticity of the silicone rubber will deteriorate. Further, two or more kinds of the component (D) may be used in combination.

The platinum compound according to the second aspect of the present invention improves the flame retardancy synergistically with the effect of the component (D), and is in the form of chloroplatinic acid or an alcohol of chloroplatinic acid as described above. Solution and the like. The amount of the platinum compound is 0.0001 to 0.1 part by weight, preferably 0.001 to 0.01 part by weight, based on 100 parts by weight of the silicone rubber composition of the first invention of the present invention in terms of platinum. If the value is less than the lower limit of the limited range, the effect becomes insufficient, and if the value exceeds the upper limit of the limited range, the effect is not changed, and it is not economical.

[0011] The silicone rubber composition of the present invention may contain, in addition to the above-mentioned components (A) to (D), various rubber compounding agents which are appropriately blended with the silicone rubber in amounts which do not impair the object of the present invention. For example, dispersants such as diphenylsilanediol, low-polymerization molecular weight terminal hydroxyl group silicone oil, hexamethyldisilazane, and alkoxysilane, pulverized silica, diatomaceous earth, zinc oxide, titanium oxide, carbon black, barium oxide, and carbonic acid Calcium, magnesium carbonate, zinc carbonate, asbestos, glass wool, fine mica, fused silica powder and the like may be added and blended. Further, if necessary, an antioxidant, an antioxidant, an antistatic agent, a thermal conductivity improver such as boron nitride and aluminum oxide may be added.

The method for producing the silicone rubber composition of the present invention is not particularly limited, but the components (A) and (B) are charged into a kneading device such as a kneader and blended at room temperature. A method in which heat treatment is performed at a temperature for 30 minutes to 5 hours, and then the component (D) is added and kneaded with a roller mill, a Banbury mixer, or the like can be employed. After that, the component (C) may be added and heat-cured by a known method.
The cured silicone rubber obtained in this manner has good flame retardancy and heat resistance, and thus is suitable as a raw material for roll materials, electric wire materials, anode caps, rubber coats, and the like.

[0013]

The present invention is not limited to the following examples. (Example 1) The organopolysiloxane [(CH ₃ ) _{2 of} (A)]
99.85 mol% of SiO units, (CH ₃ ) (CH ₂ = CH)
Mol%, and the molecular chain ends are blocked with (CH ₃ ) ₂ (CH ₂ = CH) SiO ₂ , a methylvinylpolysiloxane raw rubber having a degree of polymerization of 7,000] 100 parts by weight, fume having a specific surface area of 200 m ² / g 25 parts by weight of silica, 1 part by weight of a dimethylpolysiloxane having a hydroxyl group at the molecular chain terminal (degree of polymerization 10) as a dispersant and methylvinylpolysiloxane having a hydroxyl group at both molecular terminal groups (polymerization degree 10)
15, 3 parts by weight of a vinyl group content based on all organic groups) were uniformly mixed in a kneader and heat-treated at 150 ° C. for 2 hours to obtain a base resin. 15 for base resin
3 parts by weight of hematite (particle size 0.5 μm) doped with Mn-doped by weight% was added by two rolls. (Example 2) The same base resin as in Example 1 and the same 15 weight
8 parts by weight of hematite doped with% Mn was added by two rolls.

Comparative Example 1 Commercially available magnetite (Fe ₃ O ₄ , particle size 2.3 μm) was added to the same base resin as in Example 1.
Parts by weight were added. 2,5-bis (t-butylperoxy) was added to each of the above compositions.
After adding 0.5 parts by weight of -2,5-dimethylhexane, press-curing was performed at 170 ° C. for 10 minutes, followed by after-curing at 200 ° C. for 120 minutes to obtain a sheet-like molded product. The mechanical strength, hardness and appearance of each of the obtained sheet-like molded products were examined according to JIS K 6301. After heating at 250 ° C. for 72 hours, changes in mechanical strength, hardness and appearance were examined, and the results are shown in Table 1. Indicated.
In addition, the compounding quantity in a table | surface shows a weight part, and a base resin is based on the preparation method of the said Example 1.

[0015]

[Table 1]

Example 3 Hematite (particle size 0.5 μm) doped with 20% by weight of Mn in the same base resin as in Examples 1 and 2.
Was added by 3 parts by weight. (Comparative Example 2) 5% by weight in the same base resin as in Examples 1 and 2
3 parts by weight of Mn-doped hematite (particle size 0.5 μm) was added. The same treatment as in Examples 1 and 2 and Comparative Example 1 was performed on each of the above compositions to obtain sheet-like molded products. For each of the obtained sheet-like molded products, the same measurement was performed by the same method as described above, and the results are shown in Table 1.

Example 4 The same base resin as in Example 1 was used.
10% by weight Mn-doped hematite (particle size 0.5 μm)
Parts by weight were added. Example 5 The same base resin as in Example 1 was added with 3 parts by weight of hematite (particle size: 10.0 μm) doped with 10% by weight of Mn. Examples 1 to 3 and Comparative Examples 1 to 1 for each of the above compositions
The same treatment as in Example 2 was performed to obtain a sheet-like molded product. For each of the obtained sheet-like molded products, the same measurement was performed by the same method as described above, and the results are shown in Table 1.

(Example 6) 99.85 mol% of (CH ₃ ) ₂ SiO units and (CH ₃ ) (CH
₂ = CH) SiO units 0.15 mol%, and the molecular chain ends are (CH ₂ = C
H) (CH ₃ ) ₂ 100 parts by weight of a methylvinylpolysiloxane raw rubber having a degree of polymerization of about 7,000 blocked with SiO groups, and a specific surface area of 2
25 parts by weight of fumed silica of 00 m ² / g, 1 part by weight of dimethylpolysiloxane having a hydroxyl group at a molecular chain terminal (weight 10) as a dispersant and methylvinylpolysiloxane having a hydroxyl group at both molecular terminals (polymerization) In a kneader, 3 parts by weight of a vinyl group content of 5 mol% based on the total organic groups were uniformly mixed in a kneader and heat-treated at 150 ° C. for 2 hours. Next, a platinum catalyst was added so as to be 0.005% by weight of chloroplatinic acid to obtain a base. Next, 3 parts by weight of magnetite (particle size: 1.0 μm) treated with 3% by weight of alumina were mixed with the base using two rolls.

Example 7, Comparative Example 3 Two parts of a base having the same composition as in Example 5 were mixed with 3 parts by weight of magnetite (particle size: 1.0 μm) treated with 5% by weight of alumina. On the other hand, commercially available magnetite
Comparative Example 3 was obtained by mixing 3 parts by weight of Fe ₃ O ₄ (particle diameter: 2.3 μm). After adding 0.5 parts by weight of 2,5-bis (t-butylperoxy) -2,5-dimethylhexane as a curing agent to each of the compositions of Examples 6 to 7 and Comparative Example 3, 170 ° C. After pre-curing for 10 minutes, 200 ° C x 240
After-curing for minutes, a sheet-like molded product was obtained. The mechanical properties of the obtained molded article and the heat resistance after holding at 250 ° C. for 72 hours were evaluated. The flame retardant seconds of the 0.8 mm thick sheet of this molded product were measured by the method specified in UL94,
Table 2 shows the results.

[0020]

[Table 2]

Example 8 5 parts by weight of a magnetite (particle size: 0.5 μm) treated with 10% by weight alumina was mixed with the same base as used in Examples 6 and 7 above. Comparative Example 4 Five parts by weight of magnetite (particle size: 0.5 μm) treated with 0.01% by weight alumina were mixed with a base having the same composition. Next, molded articles were obtained from the compositions of Example 8 and Comparative Example 4 in the same manner as in Examples 5 to 6, and mechanical properties and heat resistance were measured in the same manner. The results are shown in Table 3.

[0022]

[Table 3]

(Example 9) On the basis of the same composition as above
Magnetite treated with 1.0 wt% alumina (particle size 0.5μ)
m) 3 parts by weight were blended. (Comparative Example 5) 3 parts by weight of magnetite (particle size: 10.0 µm) treated with 1.0% by weight alumina was added. For the compositions of Example 9 and Comparative Example 5, a molded article was obtained in the same manner as described above, and the mechanical properties, heat resistance, and flame retardancy were measured in the same manner.
Table 4 shows the results.

[0024]

[Table 4]

[0025]

The cured product of the silicone rubber composition of the present invention maintains a black color even when exposed to high temperatures and has excellent flame retardancy,
Has heat resistance.

Claims (2)

[Claims] (A) An average composition formula R _a SiO _{(4-a) / 2} (where R is the same or different unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, a is 1.90) 100 parts by weight of an organopolysiloxane represented by the following formula: (B) 10 to 100 parts by weight of a reinforcing silica having a specific surface area of at least 50 m ² / g, (C) a curing agent necessary for curing. (D) a silicone rubber composition comprising: 0.1 to 50 parts by weight of magnetite treated on its surface with 1 to 10% by weight of alumina or silica-alumina and / or 10 to 20% by weight of manganese-doped fine powdered hematite. Stuff. 2. A platinum compound is used in an amount of 0.0001 to 0.1 in terms of platinum based on 100 parts by weight of the organopolysiloxane (A).
The silicone rubber composition according to claim 1, which contains parts by weight.