JP2002309091A - Silicone rubber composition for coating electric wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silicone rubber composition for coating electric wires, not causing adhesion of a silicone rubber coating layer to core wires when and after subjected to the first vulcanization, thermal treatment with varnish or the second vulcanization, nor causing decrease of heat resistance. SOLUTION: This coating silicone rubber composition for coating the electric wires comprises (A) an organopolysiloxane raw rubber which is expressed by the average composition formula of R<1> a SiO(4-a)/2 (R<1> is a monovalent hydrocarbon residue which may be substituted or not substituted; and a is 1.8-2.3) and has at least two silicon atom-bonding alkenyl groups in its molecule in an amount of 100 pts.wt., (B) a reinforcing filler in an amount of 10-100 pts.wt., (C) an oxidized product or a carboxylated product of ethylene polymer or ethylene-propylene copolymer having an acid value of 10-100 (KOH mg/g) in an amount of 0.01-5 pts.wt., and (D) an organic peroxide in an amount of 0.1-5 pts.wt.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicone rubber composition for covering electric wires, and more particularly, when a conductor such as a tin-plated copper wire or a copper wire is coated with silicone rubber and vulcanized, the silicone rubber adheres to the conductor. Alternatively, the present invention relates to a silicone rubber composition for covering electric wires, which does not adhere (hereinafter, referred to as core wire adherence) and has excellent heat resistance.

[0002]

2. Description of the Related Art Silicone rubber is used as an electric wire coating material because of its excellent heat resistance, weather resistance, heat conductivity, flame retardancy, high pressure resistance, extrudability, electrical insulation, etc. Rubber-coated wires are widely used in motor wires, heater wires such as jars, and ignition wires. However, conventionally, in a wire coated with silicone rubber, a silicone rubber coating layer and an electric conductor are used during a primary vulcanization, a heat treatment of silicone varnish for converging a glass braid for reinforcement, or a secondary vulcanization. Core wire adhesion was likely to occur between them. For this reason, there is a problem that it takes a long time since the silicone rubber coating layer is hardly peeled off from the core wire during work such as wiring and connection of electric wires. In particular, the tendency was remarkable at the time of use at a high temperature utilizing the heat resistance characteristic of silicone rubber.

[0003] As a method of improving such a problem,
Conventionally, fatty acids or metal salts of fatty acids have been added to silicone rubber compositions. For example, JP
In the invention described in JP-A-9-129259, metal salts of fatty acids such as zinc stearate and calcium stearate are used, but the improvement effect cannot be said to be sufficient yet, and these additives are used for covering electric wires. There are problems such as a decrease in heat resistance, which is one of the important properties of the composition.

Japanese Patent Application Laid-Open No. H11-140321 proposes the addition of an ester wax, which can provide a sufficient effect of improving the core wire adhesion, and the addition thereof causes a decrease in electric insulation. However, there was a problem in that the heat resistance was reduced.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to overcome the above-mentioned problems and to prevent the silicone rubber coating layer from adhering to the core wire at the time of primary vulcanization, varnish heat treatment, or after secondary vulcanization. An object of the present invention is to provide a silicone rubber composition for coating electric wires, which does not reduce heat resistance.

[0006]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result, it has been found that addition of a specific ethylene polymer or an ethylene-propylene copolymer oxide or carboxy oxide. They have found that they are extremely effective and arrived at the present invention.

[0007] The present invention, (A) the average compositional formula ^{_{R 1 a SiO (4-a}} ) / 2 ( wherein, R ¹ represents a substituted or unsubstituted monovalent hydrocarbon radical, a
Is represented by 1.8 to 2.3), and at least 2
100 parts by weight of organopolysiloxane raw rubber having an alkenyl group bonded to a silicon atom (B) 10 to 100 parts by weight of a reinforcing filler (C) ethylene having an acid value of 10 to 100 (KOH mg / g) A silicone rubber composition for covering electric wires, comprising 0.01 to 5 parts by weight of a polymer or an oxide or carboxy oxide of an ethylene-propylene copolymer (D) 0.1 to 5 parts by weight of an organic peroxide. Things.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The organopolysiloxane raw rubber (A), which is the main component of the silicone rubber composition of the present invention, has at least two alkenyl groups bonded to silicon atoms in one molecule. This organopolysiloxane raw rubber is represented by the above average composition formula, wherein R ¹ is a substituted or unsubstituted monovalent hydrocarbon group, preferably a monovalent hydrocarbon group having 1 to 12 carbon atoms, and a methyl group, an ethyl group Alkyl groups such as propyl, butyl, hexyl and octyl groups; alkenyl groups such as vinyl, allyl and hexenyl groups; aryl groups such as phenyl groups; halogens such as 3,3,3-trifluoropropyl group It is a substituted hydrocarbon group or the like, preferably a methyl group, a vinyl group, a phenyl group or a 3,3,3-trifluoropropyl group. It is preferably contained in an amount of from 0.01 to 0.5 mol%. a is 1.8 to 2.3.

Although the molecular structure of the organopolysiloxane raw rubber (A) in the present invention is linear, it may have a slightly branched siloxane skeleton. The degree of polymerization is not particularly limited, but the degree of polymerization is such that the rubber after curing is in the form of a raw rubber at normal temperature in terms of mechanical strength, that is, the degree of polymerization at 23 ° C. is 3000 cSt or more. It is preferred to use.

The reinforcing filler of the component (B) in the present invention is necessary for increasing the mechanical strength of the silicone rubber, and is a wet silica or a fumed silica generally used conventionally. Commercially available reinforcing fillers that can be used in the present invention include Aerosil 130, 200, 30
0,380 (trade name, manufactured by Nippon Aerosil Co., Ltd.), Nipsil LP (trade name, manufactured by Nippon Silica Industry) and the like. Among these, fumed silica is preferred, and in particular, the particle diameter is 50 μm or less, and the specific surface area is 100 m ² / g or more, and especially 120 to 40 μm.
0 m ² / g fumed silica is preferred. These fillers may be used as they are, or those obtained by surface-treating them with organopolysiloxane, organopolysilazane, chlorosilane, alkoxysilane or the like may be used.

In the present invention, the amount of the component (B) added is
(A) 10 to 100 parts by weight with respect to 100 parts by weight of the component;
Preferably it is 40 to 70 parts by weight. If the amount is less than 10 parts by weight, the reinforcing effect is insufficient and sufficient mechanical strength cannot be obtained. If the amount is more than 100 parts by weight, the extrudability deteriorates. Inefficient in actual work.

The acid value of the component (C) in the present invention is 10 to 10.
An oxide or carboxylic oxide of an ethylene polymer or an ethylene-propylene copolymer, which is 100 (KOH mg / g), is an essential component for imparting excellent core releasability to the composition of the present invention. Such an oxide or carboxy oxide can be obtained by heat treatment of a usual ethylene polymer or ethylene-propylene copolymer in an oxygen atmosphere or by reaction with a carboxylic acid such as maleic acid.

The acid value is 10 to 100 (KOH m
g / g), preferably 15 to 80. If the acid value is less than 10, sufficient core wire releasability cannot be obtained, and if it is more than 100, the workability and stability of the silicone rubber compound may be affected. The density and the molecular weight are not particularly limited, but considering the dispersibility in the silicone rubber compound, the component (C) has a melting point of 180 ° C. or lower, particularly 15 ° C.
Those having a temperature of 0 ° C. or lower are preferred.

Such a component (C) can be obtained as a commercial product, and examples thereof include Mitsui High Wax [trade names of Mitsui Chemicals, Inc .; Mitsui High Wax 4202E, Mitsui High Wax 2203A] and the like. You.

In the present invention, the amount of component (C) added is
(A) 0.01 to 5 parts by weight with respect to 100 parts by weight of the component;
Preferably it is 0.02 to 1 part by weight. 0.0
If the amount is less than 2 parts by weight, sufficient core wire releasability cannot be obtained and 5
When the amount is more than the weight part, heat resistance may be inferior.

In the present invention, the method of adding the component (C) to the silicone rubber compound is not particularly limited,
Using a kneading device such as a kneader or a roll, the components (A) and (B) are kneaded at the same time as the component (C), or the components (A) and (B) are kneaded. It is preferable to mix the component (C) with the mixture. In this case, the kneading temperature is preferably slightly higher than the melting point of the component (C) so that the component (C) is uniformly dispersed in the silicone rubber compound.

The organic peroxide as the component (D) in the present invention is a catalyst which is usually used for accelerating the heat curing of the silicone rubber composition, and includes benzoyl peroxide, monochlorobenzoyl peroxide, 2,4 −
Dichlorobenzoyl peroxide, 2,5-bis (t
-Butylperoxy) -2,5-dimethylhexane, t
-Butyl perbenzoate, dicumyl peroxide,
Examples include p-methylbenzoyl peroxide, o-methylbenzoyl peroxide, and 2,4-dimethylbenzoyl peroxide. Of these, those represented by the above general formula (1), which are suitable for normal pressure hot air vulcanization and are also non-halogen peroxides, are preferable. Among them, considering the vulcanization rate and the stability of the peroxide, , P-methylbenzoyl peroxide is most preferred. In the formula, R ² is an unsubstituted monovalent hydrocarbon group, and is preferably an alkyl group having 1 to 12 carbon atoms such as a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, and a dodecyl group. Is preferred. n is an integer of 1 to 3.

The amount of component (D) to be added is 100% for component (A).
It is in the range of 0.1 to 5 parts by weight based on parts by weight. 0.1
If the amount is less than 5 parts by weight, curing is not sufficiently performed, and if the amount exceeds 5 parts by weight, heat resistance and electrical properties are deteriorated.

The silicone rubber composition for covering electric wires of the present invention can be easily produced by uniformly mixing the above-mentioned components (A) to (D). If necessary, this is usually called a wetter. A low molecular weight organosilicon compound such as diorganopolysiloxane having a hydroxyl group at a terminal, diphenylsilanediol, hexaorganodisilazane, or organoalkoxysilane may be blended. Further, for the purpose of increasing the amount, non-reinforcing inorganic fillers such as diatomaceous earth, quartz powder, siliceous sandstone, clay and the like, and coloring agents such as titanium oxide may be added. The performance can also be improved by adding a known heat resistance improver, a flame retardant imparting agent, a fire resistance imparting agent, or the like as an additive. Further, in addition to the above components (A) to (D), a metal salt of a fatty acid such as zinc oxide or zinc stearate, which is a known core wire adhesion preventive agent, can be used in combination as long as the electrical characteristics are not impaired.

[0020]

Hereinafter, the present invention will be described with reference to Examples.
The present invention is not limited to these. Parts in Examples and Comparative Examples are parts by weight.

(Method of Manufacturing Silicone Rubber-Coated Electric Wire for Test)
Using a φ extruder, the core of a tin-plated soft conductive wire with an outer diameter of 0.6 mm is covered and molded to make an electric wire with an outer diameter of 1.2 mm.
It was vulcanized with hot air at 350 ° C. for 30 seconds under normal pressure to obtain a coated electric wire for testing.

(Evaluation of Core Wire Adhesion) The coated wire prepared by the above-mentioned manufacturing method was left under a predetermined deterioration condition, cooled, and then the silicone rubber coating layer was peeled off using a wire stripper to determine the degree of core wire adhesion. Evaluation was made according to the following criteria. ：: No residual silicone rubber is observed on the core wire. △: Slight residual silicone rubber is observed on the core wire. The initial hardness, tensile strength, and elongation characteristics of the silicone rubber coating layer of the coated electric wire manufactured by the method described in (1) were measured. 96 at 220 ° C
The characteristics of the sample left for a while were also measured, and the rate of change was determined. Examples 1 to 2 99.75 mol% of dimethyl siloxane units and 0.25 mol% of methyl vinyl siloxane units, both ends of which are blocked with a dimethylvinylsilyl group, have a viscosity of 1000
0000 cSt methyl vinyl polysiloxane raw rubber 1
Fumed silica with a specific surface area of 200 m ² / g
Aerosil 200 [trade name of Nippon Aerosil Co., Ltd.] 40
Parts by weight, quartz powder CRYSTALITE VX-S 100 parts by weight,
Polymerization degree of about 10 in which both ends of the molecular chain are blocked with silanol groups
Of dimethylpolysiloxane was uniformly mixed in a kneader and heat-treated at 170 ° C. for 2 hours to obtain a base compound. Next, Mitsui High Wax 405, an oxide of ethylene polymer having a melting point of 115 ° C. and an acid value of 12, was added to 100 parts by weight of the base compound at 130 ° C. for 30 minutes.
0.1E (manufactured by Mitsui Chemicals, Inc.) in an amount of 0.1 part by weight or 0.1 part by weight.
After blending 5 parts by weight and mixing uniformly, cool to room temperature,
Compositions A and B were prepared by mixing 1.5 parts by weight of p-methylbenzoyl peroxide. Table 1 shows the results of measuring the core wire releasability, rubber physical properties, and heat resistance of the silicone rubber-coated electric wire manufactured by the above method using this. Examples 3-4 In place of Mitsui High Wax 4051E used in Example 1, Mitsui High Wax 1105A which is an anhydrous maleic oxide of an ethylene-propylene copolymer having a melting point of 104 ° C and an acid value of 60 [Mitsui Chemicals, Inc. C) and D) were prepared in the same manner as in Compositions A and B, except that 0.1 part by weight or 0.5 part by weight was blended. did. Table 1 shows the results of the measurement by the above method. Comparative Example 1 The same composition as Composition A was prepared except that Mitsui High Wax 4051E used in Examples 1 and 2 was not added or blended, and a silicone rubber-coated electric wire was produced by the above-described method using this composition. (Composition E). Table 1 shows the results of the measurement by the above method. Comparative Example 2 Mitsui High Wax 210MP [manufactured by Mitsui Chemicals, Inc.] 0, which is an ethylene polymer oxide having a melting point of 112 ° C. and an acid value of 1, without using the Mitsui High Wax 4051E used in Example 1, was used. Composition F containing 0.5 parts by weight
Was prepared, and a coated electric wire was produced and evaluated in the same manner as described above. The results are shown in Table 1. Comparative Example 3 0.5 part by weight of Mitsui High Wax 210P [manufactured by Mitsui Chemicals, Inc.] which is an ethylene-propylene copolymer having a melting point of 114 ° C. instead of using Mitsui High Wax 4051E used in Example 1 Was added and blended, and a coated wire was prepared and evaluated in the same manner as described above. The results are shown in Table 1. Comparative Example 4 Mitsui High Wax 200P [made by Mitsui Chemicals, Inc.] which is an ethylene copolymer having a melting point of 122 ° C. instead of using Mitsui High Wax 4051E used in Example 1
A composition H was prepared by adding and blending 0.5 parts by weight, and a coated electric wire was prepared and evaluated in the same manner as described above. The results are shown in Table 1. Comparative Example 5 Composition I was prepared by adding and mixing 0.5 part by weight of zinc stearate instead of the Mitsui High Wax 4051E used in Example 1, and preparing a coated electric wire in the same manner as described above. The results are shown in Table 1. Comparative Example 6 A composition J was prepared without using the Mitsui High Wax 4051E used in Example 1 and instead adding and blending 0.5 part by weight of calcium stearate. A coated wire was prepared and evaluated in the same manner. The results are shown in Table 1. Comparative Example 7 A composition K was prepared by adding and compounding 0.5 parts by weight of Kaohwax 220 (manufactured by Kao Corporation), which is an ester wax, without using Mitsui High Wax 4051E used in Example 1. A coated wire was produced and evaluated in the same manner, and the results were shown in Table 1.

[0023]

[Table 1]

[0024]

When the silicone rubber composition for covering electric wires according to the present invention is used, it does not adhere to the core wire, so that the wiring,
In electrical work such as connection, work can be performed efficiently and heat resistance does not decrease.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // (C08L 83/07 H01B 7/34 B 23:26) F term (Reference) 4J002 BB252 CP141 DJ016 EK047 FD016 FD147 GQ01 5G305 AA02 AB36 AB40 BA12 BA15 CA26 CA47 CB03 CB14 CC02 CD01 CD12 DA12 5G315 CA02 CC08 CD06

Claims (3)

[Claims] (A) An average compositional formula R ¹ _a SiO _{(4-a) / 2} (wherein R ¹ is a substituted or unsubstituted monovalent hydrocarbon group, a
Is represented by 1.8 to 2.3), and at least 2
100 parts by weight of organopolysiloxane raw rubber having an alkenyl group bonded to a silicon atom (B) 10 to 100 parts by weight of a reinforcing filler (C) ethylene having an acid value of 10 to 100 (KOH mg / g) A silicone rubber composition for covering electric wires, comprising 0.01 to 5 parts by weight of a polymer or an oxide or carboxy oxide of an ethylene-propylene copolymer (D) 0.1 to 5 parts by weight of an organic peroxide. object. 2. The silicone rubber composition for covering electric wires according to claim 1, wherein the organic peroxide is represented by the following general formula (1). Embedded image (Wherein, R ² is an unsubstituted monovalent hydrocarbon group, and n is an integer of 1 to 3) 3. The silicone rubber composition according to claim 1, wherein the organic peroxide is p-methylbenzoyl peroxide.