JP2501502B2 - Flame-retardant silicone rubber composition for wire coating - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a flame-retardant silicone rubber composition, and more specifically, to an electric wire braided with glass cloth or the like, further impregnating the glass cloth portion with acrylic, polyester or silicone varnish. It relates to a flame-retardant silicone rubber composition used.

[0002]

TECHNICAL BACKGROUND OF THE INVENTION AND ITS PROBLEMS Conventionally, silicone compositions which are cured into silicone rubber have been well known, and their excellent properties such as weather resistance, heat resistance and electric insulation are utilized. It is widely used as potting material for electric and electronic parts, coating material, molding material for molding, electric wire material, etc. It is also common to add various additives to the silicone composition to impart characteristics suitable for the application, such as flame retardancy. As a technique for imparting flame retardancy to the silicone rubber composition, a number of reports have hitherto been made, for example, a method of blending a platinum compound as a flame retardant imparting agent (Japanese Patent Publication No. 44-2591). Japanese Patent Publication No. 48-94252
48-20839, 49-356, etc.) and a method of using a platinum compound and a metal oxide in combination (Japanese Patent Laid-Open No. 48-4839).
-96650, 48-96651, 49-67933, 53-110650, 50-97644, 50
-98961, JP52-14654, JP56-5851, JP56-106957, JP57-105455, etc.), and a method of using a platinum compound and carbon black in combination (see JP-A-53-130753 and 54-53164) are known. Further, flame-retardant silicone compositions in which titanium dioxide, zirconium dioxide, zinc oxide and the like are used in combination with platinum compounds are also known (JP-A-62-13453, JP-A-62-882098, JP-A-2).
-115268, 2-115268, etc.). on the other hand,
An electric wire is known in which it is braided with glass cloth or the like, and the glass cloth portion is further impregnated with acrylic, polyester, or silicone varnish. It has been demanded. However, when considering the above conventional flame-retardant silicone composition for coating an electric wire, it may be possible to achieve a desired flame retardancy with a non-braided electric wire, but it can be considered as a state in which air is almost blocked. The braided wire had a large drip property and could not achieve the flame retardancy specified in UL758 and UL62.

[0003]

DISCLOSURE OF THE INVENTION The present invention has been devised in view of the above problems of the prior art, and provides a flame-retardant silicone rubber composition having excellent flame retardancy and drip resistance, which is extremely suitable for coating electric wires. The purpose is to provide.

[0004]

The present inventors have conducted extensive studies to achieve the above object, and as a result, found that it is extremely effective to use rutile type titanium oxide and a platinum compound in combination as a flame retarding agent. The invention was completed. The flame-retardant silicone rubber composition for electric wire coating of the present invention is based on at least (A) a polyorganosiloxane that can be cured into an elastomer, on which (B) a curing agent and (C) rutile titanium dioxide. And (D) a platinum compound.

The base polymer of the polyorganosiloxane of component (A) is a polyorgano group in which at least two of the organic groups bonded to silicon atoms in one molecule are alkenyl groups such as vinyl, propenyl, butenyl and hexenyl. Siloxane is used. Particularly, vinyl groups are often used among the above groups because of easy synthesis and easy availability of raw materials. The organic group other than the alkenyl group bonded to the silicon atom is a monovalent substituted or unsubstituted hydrocarbon group, and is an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, and a dodecyl group. An unsubstituted hydrocarbon group such as an aryl group such as a phenyl group, a β-phenylethyl group, an aralkyl group such as a β-phenylpropyl group, a chloromethyl group, a 3,3,3-trifluoropropyl group, etc. The substituted hydrocarbon group of is exemplified, and in general, a methyl group is often used because it is easy to synthesize.

Among various components used in the basic silicone rubber composition, the polyorganosiloxane base polymer as the component (A) and the curing agent as the component (B) are selected according to the reaction mechanism for obtaining the rubber elastic body. It is selected appropriately. As the reaction mechanism, (1) a crosslinking method with an organic peroxide vulcanizing agent, (2) a method by an addition reaction, etc. are known. Depending on the reaction mechanism, (a) component and (b) component, that is, curing It is well known that the preferred combination with the catalyst or cross-linking agent will be determined. That is, when the crosslinking method (1) is applied, the base polymer of the component (A) usually contains an alkenyl group among organic groups bonded to a silicon atom in one molecule and has a degree of polymerization of Ten
00 or more polydiorganosiloxane is used. Further, as the curing agent for the component (B), benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, dicumyl peroxide, cumyl-t-butyl peroxide, 2,
Various organic peroxide vulcanizing agents such as 5-dimethyl-2,5-di-t-butylperoxyhexane and di-t-butylperoxide are used, and since they give particularly low compression set, dicumyl peroxide is used. , Cumyl-t-butylperoxide, 2,5-dimethyl-2,5-di-t-butylperoxyhexane, di-t-butylperoxide are preferred. In addition, these organic peroxide vulcanizing agents are used as one kind or as a mixture of two or more kinds. The content of the organic peroxide as the component (B) is preferably 0.05 to 15 parts by weight with respect to 100 parts by weight of the base polymer as the component (A). If the blending amount of the organic peroxide is less than 0.05 parts by weight, the vulcanization is not sufficiently performed, and if blending is more than 15 parts by weight, not only there is no particular effect, but also the obtained silicone rubber It may adversely affect the physical properties.

As the base polymer (A) in the case of applying the addition reaction of the above (2), the same base polymer as that in the above (1) is used. Also,
The curing agent of the component (B) is chloroplatinic acid, a platinum olefin complex, a platinum vinyl siloxane complex, as a curing catalyst,
A platinum-based catalyst such as platinum black or platinum triphenylphosphine complex is used, and a polydiorganosiloxane having at least an average of more than 2 hydrogen atoms bonded to silicon atoms in one molecule is used as a crosslinking agent. In the curing agent of the component (B), the amount of the curing catalyst blended is
The amount of platinum atoms in the component (A) is preferably in the range of 1 to 100 ppm. If the compounding amount of the curing catalyst is less than 1 ppm as the amount of platinum atom, curing does not proceed sufficiently, and if it exceeds 100 ppm, no particular improvement in the curing rate can be expected. The amount of the cross-linking agent to be added is preferably such that 0.5 to 4.0 hydrogen atoms bonded to silicon atoms in the cross-linking agent are present with respect to one alkenyl group in the component (A), and more preferably. The quantity is 1.0 to 3.0. When the amount of hydrogen atoms is less than 0.5, curing of the composition does not proceed sufficiently and the hardness of the composition after curing becomes low, and when the amount of hydrogen atoms exceeds 4.0, after curing. The physical properties and heat resistance of the composition are deteriorated.

The organic group of the polyorganosiloxane base polymer of the component (A) used in the above various reaction mechanisms is a monovalent substituted or unsubstituted hydrocarbon group, such as methyl group, ethyl group and propyl group. Group, butyl group,
Hexyl group, alkyl group such as dodecyl group, aryl group such as phenyl group, β-phenylethyl group, unsubstituted hydrocarbon group such as aralkyl group such as β-phenylpropyl group, chloromethyl group, 3 Substituted hydrocarbon groups such as a 3,3,3-trifluoropropyl group are exemplified, and in general, a methyl group is often used because of ease of synthesis.

The rutile titanium dioxide as the component (C) is
It has a pure white crystal structure in appearance, which is generally used as a white coloring pigment. The average particle size is not particularly limited, but is preferably about 0.1 to 10 μm. In addition, the presence or absence of surface treatment and the type and state thereof do not matter. As titanium oxide, those having a rutile structure and those having an anatase structure are generally known, but in the present invention, those having a rutile structure are limitedly used. It is not clear why only the rutile structure exerts a specific effect in the electric wire coating application where flame retardancy and drip resistance as in the present invention are required, but thermal stability in a semi-oxygen blocking state. Presumed to be based on gender differences. That is, the thermal stability of the anatase structure is inferior to that of the rutile structure. As is clear from the fact that the anatase type titanium dioxide is transformed into the rutile structure when heated, it is considered that the rutile structure titanium dioxide can impart more thermal stability. The blending amount of component (C) is
(A) 0.1 to 20 parts by weight is preferable with respect to 100 parts by weight, but if the physical properties are not limited, blending up to about 200 parts by weight is satisfactory.

Examples of the platinum compound as the component (D) include chloroplatinic acid, alcohol-modified chloroplatinic acid, platinum-olefin complex, platinum-ketone complex, platinum-vinylsiloxane complex, alumina or silica. Examples of the carrier include platinum supported on a carrier such as platinum black.
The compounding amount of the platinum compound is 0.1 to 10 in terms of the amount of platinum metal element based on the silicone base polymer of the component (A).
It is in the range of 1000 ppm, preferably in the range of 0.5 to 200 ppm.

The flame-retardant silicone rubber composition for coating an electric wire of the present invention may optionally further contain a filler, a pigment, a heat resistance improver, an adhesion aid and the like. You may use together other polyorganosiloxane in the range which does not impair the effect. Such things include fumed silica,
Precipitated silica, reinforcing fillers such as diatomaceous earth, aluminum oxide, zinc oxide, cerium oxide, mica, clay, zinc carbonate, cerium hydroxide, glass beads, polydimethylsiloxane, alkenyl group-containing polysiloxane, etc. It

[0012]

The silicone rubber composition of the present invention is excellent in flame retardancy and drip resistance, and is extremely suitable for flame retardation of electric wires, especially electric wires braided with glass cloth or the like. Further, it is useful not only for electric wires but also for flame retardant silicone rubber tubes braided with glass cloth or the like.

[0013]

EXAMPLES Examples of the present invention will be described below. In addition, all "parts" in the following sentences shall show "weight part."

Example 1, Comparative Examples 1-2 Polydimethylsiloxane containing 0.21 mol% of methylvinylsiloxane unit (polymerization degree: about 7000) 100 parts of polydimethylsiloxane having a phenyl group (viscosity 20 cSt) 1.5
Part, rutile type titanium dioxide (Taipaque R-820; trade name, manufactured by Ishihara Sangyo Co., Ltd.) 2.0 parts was charged in a kneader, and fumed silica (Aerosil 200; trade name, Nippon Aerosil Co., Ltd.) at a rotation speed of 30 rpm. 40 parts by weight were gradually added and kneaded, and the temperature was further raised to 160 ° C. and kneading was carried out for 2 hours to prepare a silicone rubber compound. Then to this,
Chloroplatinic acid in an amount of 15 ppm as the platinum element amount and 1.5 parts of 2,4-dichlorobenzoyl peroxide as a vulcanizing agent were uniformly mixed to obtain a silicone rubber composition.

The obtained silicone rubber composition was placed on a 1 mmφ copper wire using an extruder (L / D = 10) to have an outer diameter of 2.4 mm (wall thickness).
(0.6 mm), then primary vulcanization at 400 ° C for 1 minute, then hot air vulcanization as secondary vulcanization at 200 ° C for 1 hour, and return to room temperature to insulate silicone rubber. Manufactured an electric wire. After this, a braiding machine was passed through for braiding with glass cloth. The silicone varnish was dipped and hot air vulcanization was performed under the conditions of 200 ° C. and 1 hour. For comparison, a system containing no rutile titanium dioxide (Comparative Example 1) and 2.0 parts of anatase titanium dioxide (Taipaque A-100; trade name, manufactured by Ishihara Sangyo Co., Ltd.) in place of rutile titanium dioxide. A braided electric wire was manufactured in exactly the same manner as in Example 1 using the above system (Comparative Example 2). The three wires were compared in a UL758 vertical burn test. The number of seconds of combustion is the evaluation of flame retardancy, and the combustion of absorbent cotton is the confirmation of drip property.

The results are shown in Table 1.

[0017]

[Table 1]

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Claims (1)

(57) [Claims] 1. A flame-retardant silicone rubber composition for electric wire coating, comprising a polyorganosiloxane capable of curing to an elastomer, and a rutile-type titanium oxide and a platinum compound.