JP5533351B2 - Insulated wire - Google Patents

Description

  The present invention relates to an insulated wire, and more particularly, to an insulated wire having flame resistance and excellent heat resistance.

  Various properties such as mechanical properties, flame retardancy, heat resistance, and cold resistance are required for members and insulating materials used in automobiles, electrical / electronic devices, and the like. Conventionally, as these insulating materials, a polyvinyl chloride compound or a compound containing a halogen-based flame retardant containing a bromine atom or a chlorine atom in a molecule has been mainly used.

  When such an insulating material is discarded by incineration, a large amount of corrosive gas may be generated. Therefore, as described in Patent Document 1, a non-halogen flame retardant material that does not generate corrosive gas has been proposed.

Japanese Patent No. 3555101

  Patent Document 1 discloses an insulated wire having, as an insulating layer, a fireproof layer made of a crosslinked silicone rubber in which aluminum hydroxide powder and mica powder are blended. In other words, the insulated wire of Patent Document 1 uses silicone rubber as a non-halogen flame retardant material and adds an aluminum hydroxide as a flame retardant to constitute an insulating layer. Insulated wires are formed by, for example, extruding and covering an insulating layer, and then heating to crosslink the silicone rubber to form an insulating layer made of the crosslinked silicone rubber. By using cross-linked silicone rubber for the insulating layer, an insulated wire excellent in heat resistance can be obtained.

  However, when the crosslinking reaction is performed to crosslink the silicone rubber, there is a problem that the water of crystallization of aluminum hydroxide contained in the insulating layer is released to cause dehydration and the insulating layer is foamed. When the insulating layer foams during the cross-linking of the insulated wires in this way, the insulating layer becomes defective in appearance and causes a decrease in various physical properties.

  The problem to be solved by the present invention is to solve the above problems, and in an insulated wire having an insulating layer containing a crosslinked silicone rubber having excellent heat resistance, there is no risk of foaming during the crosslinking reaction. Another object of the present invention is to provide an insulated wire that does not cause deterioration of various physical properties due to poor appearance of the insulating layer.

  In order to solve the above-mentioned problems, the insulated wire of the present invention is an insulated wire in which the conductor is covered with an insulating layer containing a crosslinked silicone rubber. The insulating layer has an organic polymer surface treatment on the surface of magnesium hydroxide. The gist is to contain surface-treated magnesium hydroxide surface-treated with an agent.

  In the insulated wire, the content of the surface-treated magnesium hydroxide in the insulating layer is 0.1 to 100 parts by mass with respect to 100 parts by mass of the crosslinked silicone rubber component, or the organic polymer surface treatment The agent contains at least one selected from the group consisting of polyethylene, polypropylene, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, and derivatives thereof; For magnesium, the content of the surface treatment agent relative to the total amount of the magnesium hydroxide and the surface treatment agent is 0.1 to 10% by mass, or the crosslinked silicone rubber is a millable silicone rubber. preferable.

  The insulated wire of this invention contains the magnesium hydroxide surface-treated with the organic polymer surface treating agent as a flame retardant in the insulating layer. Magnesium hydroxide is not dehydrated like aluminum hydroxide when heated to the extent of a crosslinking reaction of silicone rubber. That is, the temperature at which magnesium hydroxide is dehydrated is higher than the temperature at which aluminum hydroxide is dehydrated, and there is no risk of dehydration at the temperature of the thermal crosslinking of the silicone rubber, unlike aluminum hydroxide. In the insulated wire according to the present invention, an appearance defect due to dehydration does not occur in the insulating layer, and a good appearance is obtained. Therefore, in an insulated wire, for example, various physical properties are not lowered due to appearance defects such as a reduction in wear resistance.

  Further, the present invention provides a silicone rubber having a surface-treated magnesium hydroxide surface-treated with an organic polymer surface treatment agent when mixing a composition constituting an insulating layer comprising a silicone rubber and a flame retardant. Since the dispersibility is excellent and the dispersibility is good, an insulated wire excellent in cold resistance and the like can be obtained.

  Furthermore, since the dispersibility of the flame retardant is good in the present invention, when mixing the composition of the insulating layer, the load is small when mixing with a mixer or the like, and the temperature rise can be suppressed. Therefore, it is possible to use a material that is sensitive to a temperature rise, and the effect that the width of a material that can be used as an insulated wire is widened can be obtained.

  Hereinafter, embodiments of the present invention will be described in detail. The insulated wire of this invention has a conductor and the insulating layer which coat | covers the circumference | surroundings of this conductor. The insulating layer contains a crosslinked silicone rubber and surface-treated magnesium hydroxide whose surface is treated with an organic polymer surface treatment agent as a flame retardant.

  The content of the surface-treated magnesium hydroxide in the insulating layer is usually in the range of 0.05 to 200 parts by mass with respect to 100 parts by mass of the crosslinked silicone rubber. The content of the surface-treated magnesium hydroxide is preferably 0.1 to 100 parts by mass, more preferably 0.5 to 95 parts by mass. If the content of the surface-treated magnesium hydroxide in the insulating layer is less than 0.1 parts by mass, the flame retardancy may be deteriorated, and if it exceeds 100 parts by mass, the heat resistance may be deteriorated.

  Insulating layer cross-linked silicone rubber is obtained by extruding an insulating layer composition containing at least silicone rubber and a flame retardant around a conductor to form an insulating wire, and then cross-linking the silicone rubber by means such as heating the insulating wire. It has been cross-linked by processing.

  The silicone rubber used in the insulating layer composition is an uncrosslinked silicone rubber. The uncrosslinked silicone rubber may be either a millable type (heat-crosslinked type) that becomes an elastic body by kneading a cross-linking agent and then heat-crosslinked, or a liquid rubber type that is liquid before cross-linking. The liquid rubber type silicone rubber includes a room temperature crosslinking type (RTV) capable of crosslinking near room temperature and a low temperature crosslinking type (LTV) capable of crosslinking when heated near 100 ° C. after mixing.

  The silicone rubber used in the insulating layer composition is preferably a millable silicone rubber. This is because the liquid rubber type silicone rubber has a low cross-linking temperature of about 120 ° C., so it is necessary to suppress heat generation during kneading with low stability, and there is a concern that the temperature management and the like may become troublesome. . On the other hand, the millable silicone rubber has an advantage that the cross-linking temperature is relatively high at 180 ° C. or higher and the stability is good, so that it is easy to mix during kneading and has excellent workability. Millable silicone rubber is a commercially available rubber compound that contains straight-chain organopolysiloxane as the main raw material (raw rubber) and contains reinforcing filler, bulking filler, dispersion accelerator, and other additives. May be.

  The magnesium hydroxide before the surface treatment used for the surface-treated magnesium hydroxide is synthesized from seawater by a crystal growth method, synthesized by reaction of magnesium chloride and calcium hydroxide, or the like, or naturally Natural magnesium hydroxide or the like obtained by pulverizing the produced mineral can be used.

  Magnesium hydroxide usually has an average particle size of 0.1 to 20 μm, preferably 0.2 to 10 μm, more preferably 0.5 to 5 μm. If the average particle size of magnesium hydroxide is less than 0.1 μm, secondary aggregation is likely to occur, and the mechanical properties of the composition may be reduced. Moreover, when the average particle diameter of magnesium hydroxide exceeds 20 micrometers, when using as an insulating layer of an insulated wire, there exists a possibility that the external appearance of the obtained electric wire may become defective.

  As the surface treating agent for the surface treated magnesium hydroxide, an organic polymer surface treating agent is used. Surface-treated magnesium hydroxide surface-treated with an organic polymer surface treating agent has excellent dispersibility in silicone rubber.

  The organic polymer surface treatment agent is preferably a hydrocarbon resin such as a paraffin resin or an olefin resin. Specific examples of the hydrocarbon resin include homopolymers of α-olefins such as 1-heptene, 1-octene, 1-nonene and 1-decene, mutual copolymers, mixtures thereof, polypropylene (PP ), Polyethylene (PE), ethylene-ethyl acrylate copolymer (EEA), ethylene-vinyl acetate copolymer (EVA), and derivatives thereof. The surface treating agent should just contain 1 or more types of the said resin at least.

  Examples of the polyethylene include low density polyethylene, ultra-low density polyethylene, linear low density polyethylene, high density polyethylene, and metallocene polymerized polyethylene. Examples of the polypropylene include an atactic structure, a syndiotactic structure, a metallocene polymerized polypropylene, a homopolymer, and a copolymerized polypropylene.

  The addition amount of the surface treatment agent in the surface-treated magnesium hydroxide is usually 0.001 to 20% by mass, preferably 0.1 to 10% by mass, with respect to the total amount of magnesium hydroxide and the surface treatment agent. More preferably, it is 0.2-8 mass%. When the addition amount of the surface treatment agent is small, the dispersibility of the composition of the insulating layer to which the surface-treated magnesium hydroxide is added is improved, and the effect of improving cold resistance and productivity tends to be lowered. If the amount of the surface treatment agent added is too large, the dispersibility of the composition of the insulating layer does not change so much, and there is little influence on the effect of improving cold resistance, productivity, etc., but the cost may increase. .

  The surface treatment agent may be modified with a modifying agent. Examples of the modification of the surface treatment agent include acid modification by introducing a carboxyl group (acid) using an unsaturated carboxylic acid or a derivative thereof as a modifying agent. When the surface treatment agent is acid-modified, the surface of the magnesium hydroxide and the surface treatment agent become easy to conform. Specific examples of the modifier include maleic acid and fumaric acid as the unsaturated carboxylic acid, and examples of derivatives thereof include maleic anhydride (MAH), maleic acid monoester, maleic acid diester and the like. Of these, maleic acid and maleic anhydride are preferred. These modifiers may be used alone or in combination of two or more.

  Examples of the modification method for introducing an acid into the surface treatment agent include graft polymerization and a direct method. Moreover, as a modified | denatured amount, as a usage-amount of a modifier, it is about 0.1-20 mass% normally with respect to a polymer, Preferably it is 0.2-10 mass%, More preferably, it is 0.2-5. % By mass. When the amount of modification is small, the effect of increasing the affinity between magnesium hydroxide and the surface treatment agent tends to be small, and when the amount of modification is large, the surface treatment agent may self-polymerize, and the effect of increasing the affinity with magnesium hydroxide Tends to be small.

  The surface treatment method for treating the surface of magnesium hydroxide with a surface treatment agent is not particularly limited, and various treatment methods can be used. As a surface treatment method of magnesium hydroxide, for example, a surface treatment is performed by mixing a surface treatment agent afterwards with magnesium hydroxide synthesized in advance to a predetermined particle diameter, or a surface treatment agent at the same time when magnesium hydroxide is synthesized. And a method of performing surface treatment by adding.

  The surface treatment method for magnesium hydroxide may be a wet method using a solvent or a dry treatment method using no solvent. Solvents used for wet processing of the flame retardant include aliphatic hydrocarbons such as pentane, hexane, and heptane, and aromatic hydrocarbons such as benzene, toluene, and xylene. Further, the surface treatment of magnesium hydroxide is carried out by adding a surface treatment agent to untreated magnesium hydroxide and base resin at the time of preparing the flame retardant resin composition, and simultaneously kneading the composition. A method of performing processing may be used.

  In addition to silicone rubber and surface-treated magnesium hydroxide, a crosslinking agent can be added to the insulating layer composition. Moreover, you may add various additives etc. to the insulating layer composition in the range which does not impair the characteristic of an insulating layer. Examples of such additives include general pigments, fillers, antioxidants, anti-aging agents and the like that are used as wire covering materials.

  The cross-linking agent is not particularly limited as long as it can cross-link silicone rubber. When millable silicone rubber is used as the silicone rubber, for example, a radical generator such as an organic peroxide can be used. Specific examples of the organic peroxide include dihexyl peroxide, dicumyl peroxide, t-butyl cumyl peroxide, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane, and the like. And peroxyketals such as n-butyl 4,4-di (t-butyl peroxide) valerate.

  The type of the crosslinking agent can be appropriately selected according to the type of silicone rubber to be used, the crosslinking conditions, and the like. Moreover, the compounding quantity of a crosslinking agent can also be determined suitably similarly to the above. In general, the crosslinking agent is preferably added in an amount of 0.01 to 10% by mass with respect to the total amount of the silicone rubber and the crosslinking agent.

  Hereinafter, the manufacturing method of the insulated wire of this invention is demonstrated. Insulated wires are prepared by kneading the composition constituting the insulating layer such as silicone rubber, flame retardant and cross-linking agent, and extruding the conductor around the conductor to insulate the conductor to form an insulating layer, It is obtained by crosslinking the silicone rubber of the insulating layer by means.

  As the kneading method, for example, a Banbury mixer, a pressure kneader, a kneading extruder, a biaxial kneading extruder, a method of melting and kneading with a normal kneader such as a roll, and the like can be used. The kneading is preferably performed at about 50 to 60 ° C. by water cooling or the like.

  In order to extrude the insulating layer around the conductor, a wire extrusion molding machine or the like used for manufacturing a normal insulated wire can be used. The conductor used for an insulated wire can utilize what is used for a normal insulated wire. Moreover, the diameter of the conductor of an insulated wire, the thickness of an insulating layer, etc. are not specifically limited, According to the use etc. of an insulated wire, it can determine suitably. The insulating layer used may be a single layer or may be composed of two or more layers.

  The insulated wire of the present invention can be used for insulated wires used in automobiles, electronic / electrical equipment. It is particularly suitable as an insulated wire for applications that require high heat resistance and flame resistance. For example, in an insulated electric wire for automobiles, such high heat resistance is required for high voltage and large current applications such as a power cable connecting an engine and a battery of a hybrid vehicle or an electric vehicle.

Examples of the present invention and comparative examples are shown below.
Examples 1-7
Silicone rubbers 1-4 having the composition shown in Table 1, PE5% coated magnesium hydroxide, and a crosslinking agent were mixed at room temperature using a Banbury mixer. Thereafter, using an extrusion molding machine, an insulating layer was formed by extruding and coating the outer periphery of an annealed copper strand wire (cross-sectional area 0.5 mm ² ) of seven annealed copper wires in a thickness of 0.2 mm. Thereafter, heat treatment was performed at 200 ° C. for 4 hours to complete the crosslinking, and the insulated wires of Examples 1 to 7 were obtained. The appearance of the obtained insulated wire was observed and evaluated. Moreover, the cold resistance test of the insulated wire was performed and evaluated. The results are also shown in Table 1. The specific composition of each component composition in Table 1 and the cold resistance test method are as follows.

[Ingredients in Tables 1 and 2]
Silicone rubber 1: manufactured by Shin-Etsu Chemical Co., Ltd., 931 (composition: dimethylsiloxane)
Silicone rubber 2: manufactured by Shin-Etsu Chemical Co., Ltd., 541 (composition: dimethylsiloxane)
Silicone rubber 3: manufactured by Toshiba Corporation, 2267 (composition: dimethylsiloxane)
Silicone rubber 4: manufactured by Toshiba Corporation, 2277 (composition: dimethylsiloxane)
PE 5% coated magnesium hydroxide Magnesium hydroxide: crystal growth method, average particle size 1.0 μm
Surface treatment agent: Polyethylene (Mitsui Chemicals, 800P)
Use amount of surface treatment agent: 5% by mass of the total amount of polyethylene and magnesium hydroxide
Crosslinking agent: manufactured by NOF Corporation, perhexyl D (di-t-hexyl peroxide)

[Cold resistance test method]
This was performed in accordance with JIS C3055. That is, the produced insulated wire was cut into a length of 38 mm to obtain a test piece. The test piece was mounted on a cold resistance tester, cooled to a predetermined temperature, hit with a hitting tool, and the state after hitting the test piece was observed. Using five test pieces, the temperature at which all five test pieces were broken was defined as the cold resistant temperature.

Comparative Examples 1-7
As shown in Table 2, an insulated wire was obtained in the same manner as in the example except that the PE 5% coated magnesium hydroxide of the example was changed to aluminum hydroxide (Hidelite H42, manufactured by Showa Denko KK) as a flame retardant. It was. About the obtained insulated wire, the external appearance and cold resistance were evaluated similarly to the Example. The results are also shown in Table 2.

  As shown in Table 1, the insulated wires of Examples 1 to 7 all had good appearance and cold resistance. On the other hand, as shown in Table 2, the insulated wires of Comparative Examples 1 to 7 were foamed on the surface of the insulating layer and had poor appearance. Moreover, the cold resistance of Comparative Examples 1-7 was lower than that of the Examples, as compared with the cold resistance of the corresponding Examples 1-7. This is because, in the comparative example, the magnesium hydroxide of the example was changed to aluminum hydroxide, so that the insulating layer foamed during the crosslinking reaction and the physical properties were lowered.

Claims (4)

In the insulated wire in which the periphery of the conductor is coated with an insulating layer containing a crosslinked silicone rubber, the insulating layer is a surface-treated water whose surface is treated by coating the surface of magnesium hydroxide with an organic polymer surface treating agent. Contains magnesium oxide ,
The organic polymer surface treatment agent contains at least one selected from the group consisting of polyethylene, polypropylene, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, and derivatives thereof. Characterized insulated wire.   The insulated wire according to claim 1, wherein the content of the surface-treated magnesium hydroxide in the insulating layer is 0.1 to 100 parts by mass with respect to 100 parts by mass of the crosslinked silicone rubber component. The surface treatment of magnesium hydroxide, the content of the surface treatment agent to the total amount of the magnesium hydroxide and the surface treatment agent is, in claim 1 or 2, characterized in that from 0.1 to 10 wt% Insulated wire as described. The insulated wire according to any one of claims 1 to 3 , wherein the crosslinked silicone rubber is a millable silicone rubber.