JP2012230847A - Insulation wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an insulation wire in which there is no fear of foaming in a crosslinking reaction and deterioration of various physical properties due to a poor appearance in an insulating layer is not caused in the insulation wire including the insulating layer containing crosslinking silicone rubber.SOLUTION: The insulation wire in which a periphery of a conductor is covered with the insulating layer including the crosslinking silicone rubber is constituted in such a way that the insulating layer includes surface preparation magnesium hydroxide where a surface of magnesium hydroxide is surface-prepared by organic polymer surface preparation agent and polytetrafluoroethylene powder.

Description

  The present invention relates to an insulated wire, and more particularly to an insulated wire that is suitably 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 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 when the insulated wire is cross-linked in this way, the insulating layer becomes poor in appearance. Defects in the appearance of insulated wires cause a reduction 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 and polytetrafluoroethylene powder.

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

  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.

  In the insulated wire, the surface-treated magnesium hydroxide preferably has a content of the surface treatment agent with respect to a total amount of the magnesium hydroxide and the surface treatment agent in a range of 0.1 to 10% by mass. .

  The said insulated wire WHEREIN: It is preferable that content of the polytetrafluoroethylene powder in the said insulating layer exists in the range of 0.1-100 mass parts with respect to 100 mass parts of said crosslinked silicone rubber components.

  The insulated wire of the present invention contains surface-treated magnesium hydroxide 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.

  In addition, the insulated wire of the present invention uses a surface-treated magnesium hydroxide whose surface is treated with an organic polymer surface treatment agent as the magnesium hydroxide contained in the insulation layer as a flame retardant. When the composition constituting the insulating layer made of is mixed, the insulated wire is excellent in dispersibility in the crosslinked silicone rubber, and the dispersibility is good, so that 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 is obtained.

  The insulated wire of the present invention can further improve the strength of the insulating layer by containing polytetrafluoroethylene powder in the insulating layer. As a result, the wear resistance can be improved. Moreover, since the polytetrafluoroethylene powder is inactive even when heated, it does not decompose and generate gas or the like, so there is no possibility of causing poor appearance of the electric wire.

  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 as a flame retardant, and a surface-treated magnesium hydroxide whose surface is treated with an organic polymer surface treatment agent. Further, polytetrafluoroethylene (tetrafluoroethylene resin: Polytetrafluoroethylene: Sometimes abbreviated as PTFE).

  The crosslinked silicone rubber of the insulating layer is formed by extruding an insulating layer composition containing at least silicone rubber, a flame retardant, and polytetrafluoroethylene around a conductor to form an insulating wire, and then heating the insulating wire. The silicone rubber is crosslinked by crosslinking treatment.

  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 linear organopolysiloxane as the main raw material (raw rubber) and contains reinforcing filler, filler, dispersion accelerator, and other additives. May be.

  As the surface-treated magnesium hydroxide, magnesium hydroxide that has been surface-treated is used. Magnesium hydroxide before surface treatment is synthesized from seawater by crystal growth method, synthesized by reaction of magnesium chloride and calcium hydroxide, etc., or natural hydroxide obtained by pulverizing naturally produced minerals Magnesium or the like can be used.

  Magnesium hydroxide usually has an average particle size in the range of 0.1 to 20 μm, preferably in the range of 0.2 to 10 μm, and more preferably in the range of 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. The surface-treated magnesium hydroxide surface-treated with the organic polymer surface treatment agent has excellent dispersibility in the crosslinked 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 selected from the group which consists of said resin and those derivatives 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 with respect to magnesium hydroxide is usually in the range of 0.01 to 20% by mass, preferably 0.00 as the content of the surface treatment agent with respect to the total amount of magnesium hydroxide and the surface treatment agent. It exists in the range of 1-10 mass%, More preferably, it exists in the range of 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.

  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 in the range of 0.1 to 100 parts by mass, more preferably in the range of 0.5 to 95 parts by mass. When the content of the surface-treated magnesium hydroxide in the insulating layer is less than 0.1 parts by mass with respect to 100 parts by mass of the crosslinked silicone rubber, the flame retardancy may be deteriorated. May get worse.

  The PTFE powder contained in the insulating layer is not particularly limited. The PTFE powder may be any one produced by a polymerization method such as suspension polymerization or emulsion polymerization, or one pulverized with radiation or electron beam. For example, the following materials are mentioned as commercial products of PTFE powder under the trade name of Seishin Enterprise. “TWF-500 (25 μm)”, “TWF-1000 (10 μm)”, “TWF-2000 (6 μm)”, “TWF-3000 (4 μm)”, “TWF-3000F (3 μm)”. The numerical value in parentheses after the above product name is the average particle diameter.

  By adding PTFE powder to the insulating layer, the slipping property of the insulating layer is improved, and the wear resistance of the insulated wire can be improved. The polytetrafluoroethylene powder is inactive even when heated, and does not decompose and generate gas or the like, so there is no possibility of causing an appearance failure of the electric wire. Moreover, since PTFE powder is self-digesting and hardly burns, there is no possibility of reducing the flame retardancy of the insulating layer.

  The average particle size of the PTFE powder is not particularly limited, but the smaller the average particle size, the better the effect of improving wear resistance. Further, when the average particle size of the PTFE powder increases, the elongation of the insulating layer may decrease. However, when the average particle size is small, the decrease in the elongation of the insulating layer decreases. From this viewpoint, the PTFE powder preferably has an average particle diameter in the range of 3 to 25 μm. Further, the average particle size of the PTFE powder is preferably in the range of 3 to 10 μm.

  The content of PTFE in the insulating layer is usually in the range of 0.05 to 200 parts by weight, preferably in the range of 0.1 to 100 parts by weight, with respect to 100 parts by weight of the crosslinked silicone rubber. Preferably it exists in the range of 0.5-95 mass parts. If the content of PTFE in the insulating layer is less than 0.1 parts by mass with respect to 100 parts by mass of the crosslinked silicone rubber, the effect of improving the wear resistance may not be sufficiently obtained. There is a risk that the cost may decrease, and the cost may become too high.

  In addition to silicone rubber, surface-treated magnesium hydroxide, and PTFE powder, a crosslinking agent can be added to the insulating layer composition. Moreover, you may add other 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. For example, the crosslinking agent is usually preferably added so as to be in the range 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, PTFE powder and cross-linking agent, and extruding the conductor around the conductor to form an insulating layer by insulatingly covering the conductor. It can be obtained by crosslinking the silicone rubber of the insulating layer by means such as heating.

  As a kneading method of the above composition, 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. it can. 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 1-8, Comparative Examples 1-9
Silicone rubbers 1-4 having the component compositions shown in Table 1 and Table 2, PE 5% coated magnesium hydroxide, PTFE 1-2, a crosslinking agent, aluminum hydroxide and the like 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. Then, heat treatment was performed at 200 ° C. for 4 hours to complete the crosslinking, and the insulated wires of Examples 1 to 8 and Comparative Examples 1 to 9 were obtained. The obtained insulated wires were evaluated for cold resistance, appearance, and wear resistance. The results are shown in Tables 1 and 2. The specific composition, test method, evaluation method and the like of each component composition in Tables 1 and 2 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 (polyethylene 5% surface treated magnesium hydroxide: specific composition is as follows)
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)
PTFE1: PTFE powder with an average particle size of 25 μm (manufactured by Seishin Enterprise Co., TFW-500)
PTFE1: PTFE powder with an average particle size of 10 μm (manufactured by Seishin Enterprise Co., TFW-1000)
Aluminum hydroxide: (Showa Denko, Heidilite H42)

[Test method and evaluation of cold resistance]
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.

[Test method and evaluation of the appearance of electric wires]
The appearance of the insulated wire was visually observed, and the case where unevenness and roughness were not seen on the surface of the insulating layer was good, and the case where unevenness and roughness were found on the surface of the product was judged as poor.

[Test method and evaluation of wear resistance of electric wires]
An abrasion resistance test was performed by a 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 the length of 750 mm, 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. Regarding the number of times, 200 times or more was regarded as a pass “◯”, and less than 150 times as a “fail”. About 150 times or more and less than 200 times is not acceptable but is a level that does not cause a problem in actual use, and is marked as Δ. In addition, “◎” is particularly excellent when the number of times is 300 times or more.

  As shown in Table 1, the insulated wires of Examples 1 to 8 all had good cold resistance, appearance, and wear resistance. Moreover, since Examples 4 and 5 have much addition amount of PTFE compared with Examples 1-3, it is supposed that abrasion resistance is especially excellent. In Examples 6 to 8, the average particle size of the PTFE powder is smaller than that in Example 3. Therefore, in Examples 6 to 8, the amount of PTFE added is the same as or less than that in Example 3, but the wear resistance is particularly excellent.

  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 a poor appearance, and the cold resistance was lower than those of Examples 1 to 8. This is because in Comparative Examples 1 to 7, the magnesium hydroxide of the example was changed to aluminum hydroxide, so that the insulating layer foamed during the cross-linking reaction and the physical properties were lowered.

  Moreover, the insulated wires of Comparative Examples 8 and 9 do not contain PTFE powder as compared with the corresponding Examples 1 and 4, respectively. Therefore, Comparative Examples 8-9 had low abrasion resistance compared with Examples 1-4.

[Experimental example]
The relationship between the average particle diameter of the PTFE powder added to the crosslinked silicone rubber and the elongation of the crosslinked silicone rubber was examined. A silicone rubber alone (Experimental Example 1), a composition obtained by adding PTFE powder (Experimental Examples 2 and 3) to silicone rubber, kneaded, extruded into a sheet, and then heated to be crosslinked using a crosslinked silicone rubber sheet. The elongation was measured. In Experimental Example 1, a sheet crosslinked with silicone rubber alone was used. In Experimental Example 2, a sheet obtained by adding 100 parts by mass of PTFE powder having an average particle size of 3.0 μm to 100 parts by mass of silicone rubber and crosslinking the PTFE powder was used. In Experimental Example 3, a sheet obtained by adding 100 parts by mass of PTFE powder having an average particle diameter of 25 μm to 100 parts by mass of silicone rubber and crosslinking the powder was used. Table 3 shows the measurement results. The elongation is measured by creating a JIS No. 4 dumbbell (sample thickness 1 mm), performing a tensile test at a tensile speed of 200 mm / min using a tensile tester, and the elongation when the sample breaks (%). Was measured.

  As shown in Table 3, it was confirmed that the decrease in elongation can be reduced when the average particle size of the PTFE powder is reduced.

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 the insulated wire in which the periphery of the conductor is covered with an insulating layer containing a crosslinked silicone rubber, the insulating layer includes a surface-treated magnesium hydroxide in which the surface of magnesium hydroxide is surface-treated with an organic polymer surface treatment agent, An insulated wire comprising tetrafluoroethylene powder.   The insulated wire according to claim 1, wherein the content of the surface-treated magnesium hydroxide in the insulating layer is in the range of 0.1 to 100 parts by mass with respect to 100 parts by mass of the crosslinked silicone rubber component. .   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 claim 1 or 2, characterized in that:   The surface treated magnesium hydroxide has a content of the surface treatment agent in a range of 0.1 to 10% by mass with respect to a total amount of the magnesium hydroxide and the surface treatment agent. The insulated wire of any one of -3. The content of the polytetrafluoroethylene powder in the insulating layer is in the range of 0.1 to 100 parts by mass with respect to 100 parts by mass of the crosslinked silicone rubber component. The insulated wire according to item 1.