JP2015028899A - Insulated wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an insulated wire which has an insulating layer containing a crosslinked silicone rubber, suppresses deterioration in various physical properties due to poor appearance of the insulating layer caused by foaming during a crosslinking reaction, and is excellent in cold resistance and wear resistance.SOLUTION: In the insulated wire, the periphery of a conductor is coated with an insulating layer containing a crosslinked silicone rubber. The insulating layer contains: a surface-treated magnesium hydroxide obtained by surface-treating magnesium hydroxide with a surface treatment agent comprising an organic polymer; and a barium sulfate powder.

Description

  The present invention relates to an insulated wire, and more particularly to an insulated wire that is suitably used in a vehicle such as an automobile.

  Insulating materials for insulated wires used in vehicles such as automobiles are required to have various characteristics such as mechanical characteristics, flame retardancy, heat resistance, and cold resistance. Conventionally, as this type of insulating material, a material containing halogen such as a compound containing a vinyl chloride resin or a halogen-based flame retardant is often used.

  Since this type of insulating material contains halogen, corrosive gas may be generated when discarded by incineration. Therefore, there is an attempt to use an insulating material that does not contain a halogen from the viewpoint of environmental protection.

  For example, Patent Document 1 describes that a non-halogen insulating material in which aluminum hydroxide is blended with uncrosslinked silicone rubber is used as an insulating material for an insulated wire. Since this non-halogenous insulating material contains uncrosslinked silicone rubber, it is necessary to crosslink the uncrosslinked silicone rubber by heating after coating the outer periphery of the conductor.

Japanese Patent No. 3555101

  However, in the insulating material described in Patent Document 1, the crystal water of aluminum hydroxide is released by heating when the uncrosslinked silicone rubber is cross-linked, and dehydration occurs, and the generated water foams the insulating material. There is. When the insulating material is foamed, the insulating layer becomes defective in appearance, and various physical properties may be deteriorated. In addition, since a rubber material (silicone rubber) is used, there is a problem that the insulating layer is softer and more easily worn than, for example, when vinyl chloride resin is used.

  The problem to be solved by the present invention is an insulated wire having an insulating layer containing a crosslinked silicone rubber, which suppresses deterioration of various physical properties due to poor appearance of the insulating layer caused by foaming at the time of crosslinking, as well as cold resistance and wear resistance. An object of the present invention is to provide an insulated wire that is excellent in performance.

  In order to solve the above problems, an insulated wire according to the present invention is an insulated wire in which the conductor is covered with an insulating layer containing a crosslinked silicone rubber, and the insulating layer is hydroxylated by a surface treatment agent made of an organic polymer. The gist of the present invention is that it contains surface-treated magnesium hydroxide and barium sulfate powder whose surface is treated with magnesium.

  The content of the barium sulfate powder is preferably in the range of 0.1 to 100 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 in the range of 0.1 to 100 parts by mass with respect to 100 parts by mass of the crosslinked silicone rubber. The organic polymer as the surface treatment agent is preferably at least one selected from polyethylene, polypropylene, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, and derivatives thereof. The coating amount of the surface treatment agent on magnesium hydroxide is preferably in the range of 0.1 to 10% by mass as a proportion of the entire surface treatment magnesium hydroxide.

  The insulated wire according to the present invention contains surface-treated magnesium hydroxide and barium sulfate powder in which magnesium hydroxide is surface-treated with a surface treatment agent made of an organic polymer in an insulating layer containing a crosslinked silicone rubber.

  Magnesium hydroxide is not dehydrated like aluminum hydroxide when heated during crosslinking of the 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 fear of dehydration at the temperature of heat crosslinking of silicone rubber, unlike aluminum hydroxide. Therefore, according to the insulated wire according to the present invention, an appearance defect of the insulating layer due to dehydration of magnesium hydroxide does not occur, and a good appearance can be obtained. Thereby, the fall of various physical properties is suppressed.

  Further, since magnesium hydroxide is surface-treated with a surface treatment agent made of an organic polymer, it is excellent in dispersibility of magnesium hydroxide in silicone rubber. Thereby, it is excellent in cold resistance. Thus, when the dispersibility of magnesium hydroxide is good, the load at the time of kneading silicone rubber and magnesium hydroxide becomes small, and the temperature rise at the time of kneading can be suppressed. As a result, it is possible to use a material that is sensitive to temperature rise, and the effect that the width of a material that can be used as an insulated wire is widened can be obtained.

  Further, by using the barium sulfate powder together with magnesium hydroxide, it is possible to suppress a decrease in wear resistance when a rubber material is used for the insulating layer while maintaining flame retardancy.

  At this time, if the content of the barium sulfate powder is within a specific range, it is possible to improve the wear resistance while suppressing a decrease in cold resistance.

  Next, an embodiment of the present invention will be described in detail.

  The insulated wire according to the present invention has a conductor and an insulating layer covering the periphery of the conductor. The insulating layer contains a crosslinked silicone rubber, magnesium hydroxide as a flame retardant, and barium sulfate powder. Magnesium hydroxide is surface-treated with a surface treatment agent made of an organic polymer.

  This insulating layer is formed using the rubber composition for insulating layers containing 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.

  As the uncrosslinked silicone rubber, a millable silicone rubber is preferable. Millable silicone rubber has the advantage that it is easy to mix during kneading and has excellent workability because the crosslinking temperature is relatively high at 180 ° C. or higher and has good stability. On the other hand, since the liquid rubber type silicone rubber has a low crosslinking temperature of about 120 ° C., it is necessary to suppress heat generation at the time of kneading with low stability. Somewhat inferior. Millable silicone rubber is a commercially available rubber compound that contains linear organopolysiloxane as the main raw material (raw rubber) and contains reinforcing filler, filler, dispersion accelerator, and other additives. May be.

  Magnesium hydroxide is synthesized from seawater by crystal growth method, synthetic magnesium hydroxide such as one synthesized by reaction of magnesium chloride and calcium hydroxide, or natural magnesium hydroxide obtained by pulverizing naturally produced minerals. be able to.

Since the surface-treated magnesium hydroxide is surface-treated, secondary aggregation is suppressed even in the case of fine particles, and fine particles may be used. However, from the viewpoint of handleability and availability, its average The particle size is preferably 0.1 μm or more. More preferably, it is 0.2 μm or more, and further preferably 0.5 μm or more. Further, from the viewpoint of being superior in surface smoothness of the insulating layer, the average particle diameter is preferably 20 μm or less. More preferably, it is 10 micrometers or less, More preferably, it is 5 micrometers or less. The average particle diameter of the surface-treated magnesium hydroxide can be obtained as a cumulative weight average value D ₅₀ (or median diameter) using a particle size distribution measuring apparatus such as a laser light diffraction method.

  The organic polymer as the 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, or interpolymers, or 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 as the 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 derivative of unsaturated carboxylic acid include maleic anhydride (MAH), maleic acid monoester, maleic acid diester and the like. Of these, maleic acid and maleic anhydride are preferred. These organic polymer modifiers as the surface treatment agent may be used alone or in combination of two or more.

  Examples of a method for introducing an acid into an organic polymer as a surface treatment agent include a graft method and a direct method. The amount of acid modification is 0.1 to 20% by mass, preferably 0.2 to 10% by mass, and more preferably 0.2 to 5% by mass of the organic polymer as the surface treatment agent.

  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 the composition of an insulating layer, you may knead | mix a surface treating agent simultaneously with materials, such as another rubber raw material.

  The coating amount of surface treatment agent on magnesium hydroxide (addition amount of surface treatment agent) depends on the particle size, but from the viewpoint of easy aggregation of magnesium hydroxide particles, the entire surface treatment magnesium hydroxide It is preferable that it is the range of 0.1-10 mass% as a ratio which occupies.

  The content of the surface-treated magnesium hydroxide is preferably in the range of 0.1 to 100 parts by mass with respect to 100 parts by mass of the crosslinked rubber. More preferably, it is the range of 0.5-95 mass parts. When the content of the surface-treated magnesium hydroxide is 0.1 parts by mass or more, excellent flame retardancy can be secured. Further, when the content of the surface-treated magnesium hydroxide is 100 parts by mass or less, flame retardancy can be improved while suppressing a decrease in cold resistance.

  Barium sulfate powder is effective in improving the strength of an insulating layer containing a crosslinked silicone rubber. Abrasion resistance can be improved by improving the strength of the insulating layer. That is, by blending barium sulfate powder that is less likely to be scraped than crosslinked silicone rubber, the strength of the insulating layer is improved and the wear resistance is enhanced. At this time, it is assumed that the abrasion of the insulating layer occurs when the barium sulfate powder falls off from the insulating layer.

  Further, the barium sulfate powder is effective in improving the gasoline resistance of the insulating layer containing the crosslinked silicone rubber. Silicone rubber swells easily when it comes into contact with gasoline and is inferior in gasoline resistance. However, the use of barium sulfate powder can improve the gasoline resistance. This is presumably because the barium sulfate powder suppresses the penetration of gasoline into the silicone rubber and suppresses the swelling of the silicone rubber by the gasoline.

  It is assumed that the abrasion of the insulating layer is caused by the barium sulfate powder falling off from the insulating layer. From this point of view, it is preferable that the particle diameter of the barium sulfate powder is smaller. This is because the insulating layer is excellent in surface smoothness, and the barium sulfate powder is difficult to drop off from the surface of the insulating layer when subjected to frictional force. Moreover, since the bulk increases as the particle size of the barium sulfate powder becomes smaller, the effect of suppressing the penetration of gasoline into the silicone rubber by the barium sulfate powder in the unit mass is further enhanced. In addition, when the particle size of the barium sulfate powder is smaller, the dispersibility of the barium sulfate powder in the insulating layer can be increased, which is more effective in improving wear resistance and gasoline resistance. Moreover, when the particle size is smaller, the decrease in elongation after thermal degradation of the insulating layer is small, and the heat resistance is also excellent. The average particle diameter of the barium sulfate powder can be measured by an air permeation method.

  Barium sulfate includes barium sulfate (barite powder) and precipitated barium sulfate obtained by pulverizing barite and washing it with iron and washing with water. Precipitated barium sulfate is amorphous, very thin and soft. As barium sulfate powder, either barium sulfate (barite powder) or precipitated barium sulfate can be used.

  The content of the barium sulfate powder is preferably in the range of 0.1 to 100 parts by mass with respect to 100 parts by mass of the crosslinked silicone rubber. More preferably, it exists in the range of 1-95 mass parts, More preferably, it exists in the range of 5-90 mass parts. When the content of the barium sulfate powder is small, the effect of enhancing the wear resistance and gasoline resistance tends to be lowered. In addition, kneading with silicone rubber tends to take time. When the content of the barium sulfate powder is large, the cold resistance tends to decrease due to a decrease in elongation. When the content of the barium sulfate powder is within a specific range, it is possible to improve wear resistance and gasoline resistance while suppressing a decrease in cold resistance.

  The barium sulfate powder is not particularly limited. For example, # 100 (average particle size = 10 μm), # 200 (average particle size = 10 μm), # 300 (average particle size = 10 μm) manufactured by Hakusui Tech Co., Ltd. # 300W (average particle size = 10 μm), 100 (average particle size = 0.5 μm), 300 (average particle size = 0.7 μm), 300R (average particle size = 0.7 μm) manufactured by Sakai Chemical Industry Co., Ltd. Examples thereof include BM-110 (average particle size = 0.5 μm), BM-111 (average particle size = 0.5 μm), and BM-112 (average particle size = 0.5 μm).

  In the rubber composition for the insulating layer, the uncrosslinked silicone rubber can be crosslinked by heating or the like, but may be crosslinked using a crosslinking agent (vulcanizing agent).

  The crosslinking agent can be appropriately selected depending on the type of uncrosslinked rubber, the crosslinking conditions, and the like. Examples of the crosslinking agent include radical generators such as organic peroxides, compounds such as metal soaps, amines, thiols, thiocarbamates, and organic carboxylic acids. As the crosslinking agent, an organic peroxide or the like is preferable from the viewpoint of improving the crosslinking rate.

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

  The amount of the crosslinking agent can be determined as appropriate. It is preferable to mix | blend the compounding quantity of a crosslinking agent in 0.01-10 mass% with respect to the total amount of uncrosslinked rubber | gum and a crosslinking agent, for example.

  The insulating layer may contain various additives in addition to the crosslinked rubber and the specific flame retardant as long as the properties of the insulating layer are not impaired. As such an additive, the common additive used for the insulating layer of an insulated wire can be mentioned. Specifically, other flame retardants, crosslinking agents, fillers, antioxidants, anti-aging agents, pigments and the like can be mentioned.

  The insulated wire according to the present invention can be manufactured, for example, as follows. That is, first, a rubber composition for an insulating layer for forming an insulating layer is prepared. Next, the prepared rubber composition is extruded around the conductor to form a coating layer containing uncrosslinked rubber around the conductor. Next, the uncrosslinked rubber of the coating layer is crosslinked by crosslinking means such as heating. Thereby, the insulated wire by which the circumference | surroundings of the conductor were coat | covered with the insulating layer containing crosslinked rubber can be manufactured. The insulated wire according to the present invention can also be formed by coating a rubber composition for an insulating layer around a conductor to form a coating layer, and crosslinking the uncrosslinked rubber of the coating layer by a crosslinking means such as heating. Can be manufactured.

  The rubber composition for the insulating layer can be prepared by kneading uncrosslinked silicone rubber, magnesium hydroxide, barium sulfate powder, and various additives such as a crosslinking agent blended as necessary. it can. When kneading the components of the rubber composition, for example, a conventional kneader such as a Banbury mixer, a pressure kneader, a kneading extruder, a biaxial kneading extruder, or a roll can be used.

  For extruding the rubber composition for the insulating layer, an electric wire extruding machine or the like used for manufacturing a normal insulated wire can be used. What is used for a normal insulated wire can be utilized for a conductor. For example, a single wire conductor or a stranded wire conductor made of a copper-based material or an aluminum-based material can be used. Moreover, the diameter of a conductor, 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 insulated wire according to the present invention having the above-described configuration contains surface-treated magnesium hydroxide and barium sulfate powder in which magnesium hydroxide is surface-treated with a surface treatment agent made of an organic polymer in an insulating layer containing a crosslinked silicone rubber. doing.

  Magnesium hydroxide is not dehydrated like aluminum hydroxide when heated during crosslinking of the 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 fear of dehydration at the temperature of heat crosslinking of silicone rubber, unlike aluminum hydroxide. Therefore, according to the insulated wire according to the present invention, an appearance defect of the insulating layer due to dehydration of magnesium hydroxide does not occur, and a good appearance can be obtained. Thereby, the fall of various physical properties is suppressed.

  Further, since magnesium hydroxide is surface-treated with a surface treatment agent made of an organic polymer, it is excellent in dispersibility of magnesium hydroxide in silicone rubber. Thereby, it is excellent in cold resistance. Thus, when the dispersibility of magnesium hydroxide is good, the load at the time of kneading silicone rubber and magnesium hydroxide becomes small, and the temperature rise at the time of kneading can be suppressed. As a result, it is possible to use a material that is sensitive to 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, by using the barium sulfate powder together with magnesium hydroxide, it is possible to suppress deterioration in wear resistance and gasoline resistance when a rubber material is used for the insulating layer while maintaining flame retardancy.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention. For example, although the insulated wire of the said aspect was comprised from the single layer insulation layer, you may comprise the insulated wire of this invention from two or more layers of insulation layers.

  The insulated wire according to 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]
A rubber composition for an insulating layer containing uncrosslinked silicone rubber, magnesium hydroxide and barium sulfate powder was prepared by mixing each component so as to have the composition shown in Table 1. Next, an uncrosslinked rubber is extruded by extruding a rubber composition for an insulating layer on the outer periphery of a conductor (cross-sectional area 0.5 mm ² ) of an annealed copper twisted wire obtained by twisting 7 annealed copper wires using an extruder. A coating layer containing was formed. Next, the uncrosslinked rubber was crosslinked by heat-treating the coating layer under conditions of 200 ° C. × 4 hours. Thereby, the insulated wire of Examples 1-7 was obtained.

[Comparative Examples 1-7]
By mixing each component so as to have the composition shown in Table 2, a composition for an insulating layer containing uncrosslinked silicone rubber and aluminum hydroxide was prepared. Subsequently, the insulated wire of Comparative Examples 1-7 was obtained like the Example.

  About the insulated wire of Examples 1-7 and Comparative Examples 1-7, the cold resistance test, the external appearance observation of the wire, the abrasion resistance test, and the gasoline resistance test were performed and evaluated. The results are shown in Tables 1 and 2. In addition, each component composition 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., 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
Barium sulfate powder 1: manufactured by Hakusuitec Co., Ltd., # 300W
Barium sulfate powder 2: BM-112 manufactured by Sakai Chemical Industry Co., Ltd.
Crosslinking agent: manufactured by NOF Corporation, perhexyl D (di-t-hexyl peroxide)
Aluminum hydroxide: Heidilite H42 manufactured by Showa Denko

[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.

[Evaluation of extrusion appearance]
A case where unevenness and roughness were not observed on the surface of the product was evaluated as “good”, and a case where unevenness and roughness were observed on the surface of the product was evaluated as “bad”.

[Abrasion resistance test method]
The test was conducted by the blade reciprocation method in accordance with the automobile technical standard “JASO D618”. That is, the insulated wire of an Example and a comparative example was cut out to 750 mm length, and it was set as the test piece. Then, at a room temperature of 23 ± 5 ° C., the blade is reciprocated at a speed of 50 mm / min with a length of 10 mm or more in the axial direction with respect to the coating material (insulating layer) of the test piece, and the number of reciprocations until contact with the conductor. Was measured. At this time, the load applied to the blade was 7N. About the number of times, the thing of 200 times or more was made into the pass "(circle)", and the thing less than 200 times was made into the disqualified "x". In addition, “◎” is particularly excellent when the number of times is 300 times or more.

[Gasoline resistance test method]
Conforms to Method 2 of ISO 6722 (2011 edition). That is, the manufactured insulated wire was cut to a length of 600 mm to obtain a test piece, immersed in liquid C of ISO1817 at 23 ° C. for 20 hours, and the maximum change rate of the outer diameter of the wire was 15% or less. A sample having a maximum change rate of 10% or less was particularly good “「 ”, and a sample having a maximum change rate exceeding 15% was evaluated as“ poor ”.

  As shown in Table 1, it was confirmed that all of the insulated wires of Examples 1 to 7 had excellent appearance and cold resistance, and excellent wear resistance and gasoline 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. In addition, the cold resistance, wear resistance, and gasoline resistance of the insulated wires of Comparative Examples 1-7 are compared with the cold resistance, wear resistance, and gasoline resistance of the insulated wires of Examples 1-7, respectively. All were lower than the Example.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.

Claims (5)

In an insulated wire whose conductor is covered with an insulating layer containing a crosslinked silicone rubber,
An insulated wire, wherein the insulating layer contains a surface-treated magnesium hydroxide obtained by surface-treating magnesium hydroxide with a surface treatment agent made of an organic polymer and barium sulfate powder.   2. The insulated wire according to claim 1, wherein a content of the barium sulfate powder is in a range of 0.1 to 100 parts by mass with respect to 100 parts by mass of the crosslinked silicone rubber.   The insulated wire according to claim 1 or 2, wherein a content of the surface-treated magnesium hydroxide is in a range of 0.1 to 100 parts by mass with respect to 100 parts by mass of the crosslinked silicone rubber.   The organic polymer as the surface treatment agent is at least one selected from polyethylene, polypropylene, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, and derivatives thereof. Item 4. The insulated wire according to any one of items 1 to 3.   The amount of the surface treatment agent coated on magnesium hydroxide is in the range of 0.1 to 10% by mass as a proportion of the entire surface treated magnesium hydroxide. The insulated wire of Claim 1.