JP2012074171A - Insulated electric wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an insulated electric wire having an insulating layer containing cross-linked silicone rubber with excellent heat resistance in which, even when the crosslinking reaction of rubber in the insulating layer is performed at a high temperature, poor appearance due to foaming is prevented from occurring, and even in an uncrosslinked state, adhesion is hard to occur and excellent handleability is provided.SOLUTION: The insulated electric wire has a conductor of which the periphery is covered with an insulating layer containing cross-lined rubber obtained by mixing the cross-linked silicone rubber and cross-linked acrylic rubber, and is constituted by making the surface-treated magnesium hydroxide obtained by applying surface treatment to magnesium hydroxide contained in the insulating layer using an organic polymer surface treatment agent.

Description

  The present invention relates to an insulated wire, and more particularly relates to an insulated wire having excellent flame resistance and excellent heat resistance, which is preferably used for automobiles, electrical / electronic devices and the like.

  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 such a material, 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.

  Such a material containing a halogen atom may generate a large amount of corrosive gas when discarded by incineration. For this reason, as described in Japanese Patent No. 3555101 (Patent Document 1), a non-halogen flame retardant material that does not cause the generation of corrosive gas has been proposed.

Japanese Patent No. 3555101

  In the non-halogen flame retardant material described in Patent Document 1 above, aluminum hydroxide is added as a flame retardant to silicone rubber. However, the addition of aluminum hydroxide has a problem that, since the dehydration temperature of aluminum hydroxide is low, there is a possibility that the aluminum hydroxide foams due to dehydration during the crosslinking reaction, resulting in poor appearance.

  In addition, in the case of an insulated wire using a crosslinked silicone rubber, the insulating layer composition before crosslinking has an adhesive property peculiar to uncrosslinked silicone rubber, and the composition tends to adhere to a roller or the like, resulting in poor handling properties. there were.

  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, the crosslinking reaction of the rubber in the insulating layer at a high temperature. It is an object of the present invention to provide an insulated wire that does not cause poor appearance due to foaming and does not easily stick even in an uncrosslinked state and has good handling properties.

  In order to solve the above problems, the insulated wire of the present invention is an insulated wire in which the periphery of the conductor is covered with an insulating layer containing a crosslinked rubber obtained by mixing a crosslinked silicone rubber and a crosslinked acrylic rubber, and the insulating layer comprises: The gist is that magnesium hydroxide contains surface-treated magnesium hydroxide that has been surface-treated with an organic polymer surface treatment agent.

  In the insulated wire, the mass ratio of the crosslinked silicone rubber to the crosslinked acrylic rubber is preferably in the range of crosslinked silicone rubber / crosslinked acrylic rubber = 9/1 to 1/9.

  The said insulated wire WHEREIN: It is preferable that content in the said insulating layer of the said surface treatment magnesium hydroxide exists in the range of 0.1-100 mass parts with respect to 100 mass parts of said crosslinked rubber.

  In the insulated wire, the organic polymer surface treatment agent is any one or more selected from the group consisting of polyethylene, polypropylene, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, and derivatives thereof. It is preferable to contain.

  The said insulated wire WHEREIN: The coating amount of the said organic polymer surface treating agent in the said surface treatment magnesium hydroxide is 0.1-10 mass% with respect to the total amount of the said magnesium hydroxide and the said organic polymer surface treating agent. Is preferred.

  The insulated wire of the present invention contains conventional aluminum hydroxide as a flame retardant by containing surface-treated magnesium hydroxide whose surface is treated with an organic polymer surface treatment agent as a flame retardant. Compared to insulated wires with an insulating layer containing silicone rubber, even when a rubber cross-linking reaction is performed in the insulating layer at a high temperature, foaming due to dehydration does not occur in the insulating layer, so there is no appearance defect. Thus, an insulated wire having excellent appearance and flame retardancy can be obtained. In an insulated wire, there is no possibility that various physical properties are deteriorated due to poor appearance.

  That is, magnesium hydroxide has a higher dehydration temperature than the dehydration temperature of aluminum hydroxide. Magnesium hydroxide is not dehydrated like aluminum hydroxide at a temperature about the crosslinking reaction of silicone rubber.

  In addition, the present invention uses a surface-treated magnesium hydroxide surface-treated with an organic polymer surface treatment agent when mixing a composition that constitutes an insulating layer made of rubber and a flame retardant. Insulated wires with excellent cold resistance and the like can be obtained because of their excellent properties and dispersibility.

  Furthermore, since the dispersibility of the flame retardant is good in the present invention, the load when kneading with a mixer or the like is reduced when mixing the composition of the insulating layer, 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.

  Furthermore, the insulated wire of the present invention contains a crosslinked rubber obtained by mixing a crosslinked silicone rubber with a crosslinked acrylic rubber, so that the rubber component is not present as compared with an insulated wire having an insulating layer composed only of a conventional crosslinked silicone rubber. An insulated wire that is difficult to adhere even in a crosslinked state and has good handling properties 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 rubber obtained by mixing a crosslinked silicone rubber and a crosslinked acrylic rubber, and surface-treated magnesium hydroxide obtained by surface-treating magnesium hydroxide with an organic polymer surface treatment agent as a flame retardant.

  The insulating layer is formed by extrusion coating around the conductor using an insulating layer composition containing silicone rubber, acrylic rubber and a flame retardant, and then crosslinking the silicone rubber and the acrylic rubber by a crosslinking means such as heating, thereby crosslinking the silicone. It is formed as a layer containing a crosslinked rubber composed of rubber and crosslinked acrylic rubber. Silicone rubber and acrylic rubber can be crosslinked by heating or the like, but a crosslinking agent (crosslinking agent) or the like may be added to the insulating layer composition as necessary.

  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 acrylic rubber used in the insulating layer composition is an elastic body mainly composed of an acrylate ester, and has excellent heat resistance, flexibility and the like. Acrylic rubber can be crosslinked by heating. By adding acrylic rubber to the insulating layer composition, it is possible to improve the tackiness peculiar to uncrosslinked silicone rubber. That is, by adding acrylic rubber, it is possible to reduce the tackiness after mixing the insulating layer composition and before crosslinking. When the insulating layer composition is mixed and then pelletized, the pellets of the composition do not stick, so that the handling properties are good when taking out the pellets, putting them into an extruder, transporting them with a roller, and the like.

  Examples of the acrylic rubber include those having ethyl acrylate as a main component and copolymerized with other monomers such as butyl acrylate and acrylonitrile and a comonomer for crosslinking. Examples of the comonomer for crosslinking the acrylic rubber include halogen-containing compounds such as 2-chloroethyl vinyl ether, epoxy compounds such as glycidyl acrylate and allyl glycidyl ether, and diene compounds such as ethylidene norbornene.

  The mixing ratio of the crosslinked silicone rubber and the crosslinked acrylic rubber is preferably in the range of crosslinked silicone rubber / crosslinked acrylic rubber = 9/1 to 1/9 by mass ratio. If the amount of cross-linked silicone rubber is too large and falls outside the above range, the effect of improving the tackiness specific to silicone rubber may not be sufficiently exhibited. Further, if the amount of the cross-linked acrylic rubber is too large and falls outside the above range, the heat resistance by the cross-linked silicone rubber may be insufficient.

  The mixing ratio of the crosslinked silicone rubber and the crosslinked acrylic rubber is more preferably in the range of crosslinked silicone rubber / crosslinked acrylic rubber = 85/15 to 15/85 by mass ratio.

  The content of the surface-treated magnesium hydroxide in the insulating layer is preferably in the range of 0.1 to 100 parts by mass with respect to 100 parts by mass of the crosslinked rubber which is the total amount of the crosslinked silicone rubber and the crosslinked acrylic rubber. The content of the surface-treated magnesium hydroxide is 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.

  Since the surface-treated magnesium hydroxide is surface-treated with an organic polymer surface treatment agent, the dispersibility in rubber is excellent. The pre-surface-treated magnesium hydroxide used for surface-treated magnesium hydroxide is synthesized from seawater by a crystal growth method, synthesized by reaction of magnesium chloride and calcium hydroxide, etc., or produced naturally. Natural magnesium hydroxide or the like obtained by pulverizing minerals to be used can be used.

  Magnesium hydroxide before the surface treatment 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.

  The organic polymer surface treatment agent used for the surface treatment of magnesium hydroxide 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.

  The organic polymer surface treatment agent may be modified. As the modifier, an unsaturated carboxylic acid or a derivative thereof can be used. Specific examples of the unsaturated carboxylic acid include maleic acid and fumaric acid. Examples of the unsaturated carboxylic acid derivative include maleic anhydride (MAH), maleic acid monoester, maleic acid diester and the like. Of these, maleic acid, maleic anhydride and the like are preferable. These organic polymer surface treating agents may be used alone or in combination of two or more.

  Examples of the method for introducing an acid into the organic polymer surface treatment agent include a graft method and a direct method. Moreover, as an acid modification amount, it is 0.1-20 mass% of an organic polymer surface treating agent, Preferably it is 0.2-10 mass%, More preferably, it is 0.2-5 mass%.

  The surface treatment method using a surface treatment agent for magnesium hydroxide is not particularly limited. As the surface treatment method of magnesium hydroxide, for example, the surface treatment may be performed on magnesium hydroxide having a predetermined particle diameter, or at the same time as synthesis. Moreover, as a processing method, the wet process using a solvent may be sufficient and the dry process which does not use a solvent may be sufficient. In the wet treatment, examples of suitable solvents include aliphatic solvents such as pentane, hexane, and heptane, and aromatic solvents such as benzene, toluene, and xylene. Moreover, when preparing an insulating layer composition, you may knead | mix a surface treating agent simultaneously with materials, such as another rubber raw material.

  In the surface-treated magnesium hydroxide, the coating amount of the organic polymer surface treatment agent with respect to magnesium hydroxide (addition amount of the surface treatment agent) is 0.1 to 10 mass relative to the total amount of magnesium hydroxide and the organic polymer surface treatment agent. % Is preferable. If the coating amount of the organic polymer surface treatment agent is less than 0.1% by mass, the dispersion may be poor, and if it exceeds 10% by mass, aggregation may occur.

  In the insulating layer composition, a crosslinking agent for crosslinking rubber can be blended. The crosslinking agent can be appropriately selected according to the types of silicone rubber and acrylic rubber, crosslinking conditions, and the like, and is not particularly limited. Examples of the type of the crosslinking agent include radical generators such as organic peroxides, compounds such as metal soaps, amines, thiols, thiocarbamates, and organic carboxylic acids. The crosslinking agent is preferably an organic peroxide-based crosslinking agent such as an organic peroxide from the viewpoint of improving the crosslinking rate.

  Examples of the organic peroxide include dialkyl peroxide, dicumyl peroxide, t-butylcumyl peroxide, and dialkyl such as 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane. And peroxyketals such as peroxide and n-butyl 4,4-di (t-butyl peroxide) valerate.

  In addition to silicone rubber, acrylic rubber, flame retardant, and crosslinking agent, various additives and the like may be added to the insulating layer composition as long as the properties of the insulating layer are not impaired. Examples of such additives include general pigments, fillers, antioxidants, anti-aging agents and the like that are used as wire covering materials.

  Moreover, the compounding quantity of the said crosslinking agent in an insulating layer composition can be determined suitably. 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 acrylic rubber and the crosslinking agent.

  Hereinafter, the manufacturing method of said insulated wire is demonstrated. Insulated wires are kneaded with an insulating layer composition that constitutes an insulating layer such as silicon rubber, acrylic rubber, flame retardant, and crosslinking agent, extruded around the conductor, and after insulatingly covering the conductor to form an insulating layer, It can be obtained by crosslinking the silicone rubber and acrylic rubber of the insulating layer by means such as heating. After kneading the insulating layer composition, it can be pelletized and pelletized once. The pellet may be extruded with an extruder or the like to form an insulating layer.

  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 kneading machine 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 form the insulating layer by extruding the insulating layer composition around the conductor, an electric 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 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, applications requiring such high heat resistance include 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 to 13, Comparative Examples 1 to 7]
Silicone rubber 1-4, acrylic rubber 1-2, PE-coated water mug (surface-treated magnesium hydroxide), aluminum hydroxide, cross-linking agent, etc. having the composition shown in Table 1 and Table 2 at room temperature using a Banbury mixer Mixed. 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. Then, heat treatment was performed at 200 ° C. for 4 hours to complete the crosslinking, and the insulated wires of Examples 1 to 13 and Comparative Examples 1 to 7 were obtained. The obtained insulated wire was evaluated by performing a cold resistance test, a wire appearance test, and a pelletizing test before crosslinking. The results are shown in Tables 1 and 2. In addition, each component of Table 1 and Table 2, a test method, and evaluation are as follows.

[Ingredients in Tables 1 and 2]
・ Silicone rubber 1 [manufactured by Shin-Etsu Chemical Co., Ltd., trade name “931”]
・ Silicone rubber 2 [made by Shin-Etsu Chemical Co., Ltd., trade name “541”]
・ Silicone rubber 3 [trade name “2267” manufactured by Toshiba Corporation]
・ Silicone rubber 4 [product name “2277” manufactured by Toshiba Corporation]
・ Acrylic rubber 1 [Product name "4200", manufactured by Electrochemical Co., Ltd.]
・ Acrylic rubber 2 [manufactured by Nippon Zeon, trade name “Nipol AR14”]
-PE 5% coated water mug [surface treated magnesium hydroxide, surface treatment agent: polyethylene, surface treatment amount: 5% by mass]
・ PE 0.1% coated water mug [Surface treatment magnesium hydroxide, surface treatment agent: polyethylene, surface treatment amount: 0.1 mass%]
・ PE10% coated water mug [surface treated magnesium hydroxide, surface treatment agent: polyethylene, surface treatment amount: 10% by mass]
As the surface-treated magnesium hydroxide, magnesium hydroxide having an average particle diameter of 1.0 μm by a crystal growth method was used. Moreover, the product name "800P" by Mitsui Chemicals, Inc. was used for the surface treatment agent polyethylene. The surface treatment amount is mass% with respect to the total amount of polyethylene and magnesium hydroxide.
・ Aluminum hydroxide [made by Showa Denko Co., Ltd., trade name “Hijilite H42”
・ Crosslinking agent [Nippon Yushi Co., Ltd., trade name “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.

[Wire appearance test method]
The insulation thickness of the electric wire was measured, and when it was between 0.15 and 0.25 mm, it was set as “good”, and other cases were set as “bad”.

[Pelletization test method before cross-linking]
When the composition before cross-linking was cut into a die and then pressed and not bonded, it was determined as “Yes”, and when bonded, it was determined as “No”.

  As shown in Table 1, all of the insulated wires of Examples 1 to 13 have good cold resistance and appearance of the wires. Moreover, the test of pelletization before cross-linking was possible, and the handling property was also good. On the other hand, since the insulated wires of Comparative Examples 1 to 7 used aluminum hydroxide as a flame retardant, the appearance of the wires was poor due to foaming by heating during crosslinking, and the cold resistance was also low. Furthermore, since the insulated wires of Comparative Examples 1 to 7 did not contain cross-linked acrylic rubber, as shown in Table 2, the result of pelletizing before cross-linking was not possible, and the handleability was poor.

Claims (5)

  An insulated wire in which a conductor is covered with an insulating layer containing a crosslinked rubber in which a crosslinked silicone rubber and a crosslinked acrylic rubber are mixed, and the insulating layer is surface-treated with an organic polymer surface treatment agent with magnesium hydroxide. An insulated wire characterized by containing surface-treated magnesium hydroxide.   2. The insulated wire according to claim 1, wherein a mass ratio of the crosslinked silicone rubber and the crosslinked acrylic rubber is in a range of crosslinked silicone rubber / crosslinked acrylic rubber = 9/1 to 1/9.   The insulation according to claim 1 or 2, wherein a content of the surface-treated magnesium hydroxide in the insulating layer is in a range of 0.1 to 100 parts by mass with respect to 100 parts by mass of the crosslinked rubber. Electrical wire.   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. The insulated wire according to any one of claims 1 to 3, characterized in that   The coating amount of the organic polymer surface treatment agent in the surface-treated magnesium hydroxide is 0.1 to 10% by mass based on the total amount of the magnesium hydroxide and the organic polymer surface treatment agent. Item 5. The insulated wire according to any one of Items 1 to 4.