JP4868272B2 - Heat resistant wire - Google Patents

Description

  The present invention relates to a heat resistant electric wire.

  Fluororesin is excellent in heat resistance, electrical insulation, and stress crack resistance, and is therefore used as a coating material for heat resistant wires. In particular, they are used as wires for wiring of aircraft, semiconductors, automobiles, office automation equipment, and IT equipment that require high reliability.

  At present, an electric wire that has been coated with a conductor with an ethylene / tetrafluoroethylene copolymer (hereinafter also referred to as ETFE) and then cross-linked is used as a heat-resistant electric wire for aircraft (for example, see Non-Patent Document 1). . However, in order to further improve the safety of aircraft, a coating material that is superior in heat resistance to ETFE is required. As candidate materials, a repeating unit (A) based on tetrafluoroethylene (hereinafter referred to as TFE) and perfluoro ( TFE / PPVE copolymer (conventional PFA) comprising a repeating unit (B) based on (propyl vinyl ether) (hereinafter referred to as PPVE) and having a molar ratio (A) / (B) of 99/1 to 98/2 ) However, although the conventional PFA has a higher heat resistance temperature than ETFE, the cut-through resistance is not sufficient. In order to improve the cut-through resistance, the present inventors tried to increase the hardness of the coating material by adding an insulating filler to PFA, but this method improved the cut-through resistance. However, it was found that the stress crack resistance was lowered.

Satokawa Takaomi, Fluorine Resin Handbook, page 498, Nikkan Kogyo Shimbun, 1990

  An object of the present invention is to provide a heat-resistant electric wire having excellent heat resistance and stress crack resistance, excellent cut-through resistance, and excellent reliability.

The present invention contains a repeating unit (A) based on TFE, a repeating unit (B) based on PPVE, and the molar ratio of (A) / (B) is 97.5 / 2.5 to 85/15, The conductor is coated with a coating material containing a fluorine-containing copolymer and an insulating filler having a capacity flow rate at 380 ° C. of 0.1 to 20 mm ³ / sec and an MIT bending life of 3 million times or more. A heat-resistant electric wire is provided.

  The heat-resistant electric wire of the present invention is excellent in heat resistance, excellent in stress crack resistance, excellent in cut-through resistance, and excellent in reliability.

  The fluorine-containing copolymer in the present invention contains a repeating unit (A) based on TFE and a repeating unit (B) based on PPVE, and the molar ratio of (A) / (B) is 97.5 / 2.5 to 85/15. When the repeating unit (B) is less than this range, the fluorine-containing copolymer does not have sufficient stress crack resistance, and when it is large, the heat resistance is not sufficient. (A) / (B) is preferably 97/3 to 90/10, more preferably 96/4 to 92/8.

In addition to the repeating unit (A) and the repeating unit (B), the fluorine-containing copolymer preferably further contains a repeating unit (C) based on another monomer that can be copolymerized with TFE. Specific examples of other monomers include hydrocarbon olefins such as ethylene, vinyl fluoride, vinylidene fluoride, trifluoroethylene, CH ₂ ═CX (CF ₂ ) _n Y (where X and Y are independent of each other). Or a hydrogen atom or a fluorine atom, n is an integer of 2 to 8.) A fluoroolefin having a hydrogen atom in an unsaturated group such as hexafluoropropylene (hereinafter referred to as HFP), chlorotrifluoroethylene (hereinafter referred to as CTFE). ) Fluoroolefins that do not have hydrogen atoms in unsaturated groups (excluding TFE), perfluoro (methyl vinyl ether), perfluoro (ethyl vinyl ether), perfluoro (butyl vinyl ether), etc. , PAVE.) (However, excluding PPVE .), Vinyl esters such as vinyl acetate, alkyl vinyl ether, glycidyl vinyl ether, hydroxybutyl vinyl ether, and vinyl ether such as methyl vinyloxy butyl carbonate.

The other monomer is preferably at least one selected from the group consisting of HFP, CTFE, and PAVE (excluding PPVE). When the repeating unit (C) based on other monomers is contained, the fluorine-containing copolymer is excellent in heat resistance and chemical resistance. The content of the repeating unit (C) is preferably (C) / ((A) + (B) + (C)) in a molar ratio of 0.1 / 100 to 10/100, preferably 0.2 / 100 to 8 / 100 is more preferable.
As the fluorine-containing copolymer, a fluorine-containing copolymer consisting only of the repeating unit (A) and the repeating unit (B) is preferable.

The volume flow rate at 380 ° C. of the fluorinated copolymer in the present invention is 0.1 to 20 mm ³ / sec. The volume flow rate is a measure of the molecular weight, and when the volume flow rate is small, the molecular weight is high and when large, the molecular weight is low. When the capacity flow rate is smaller than this range, the melt moldability is low, and when it is larger than this range, the stress crack resistance of the heat-resistant electric wire is not sufficient. Preferably 0.5 to 15 mm ³ / sec, more preferably from 1 to 10 mm ³ / sec.

  The MIT bending life of the fluorinated copolymer in the present invention is 3 million times or more. Here, the MIT bending life is the number of bendings until the sample breaks in a bending test performed in accordance with ASTM D2176. It shows that it is excellent in stress crack resistance, so that this value is large. When the MIT bending life is shorter than this, the stress crack resistance of the heat-resistant electric wire is low. Preferably it is 4 million times or more, more preferably 5 million times or more.

  There is no restriction | limiting in particular in the manufacturing method of the fluorine-containing copolymer in this invention, The polymerization method using the radical polymerization initiator generally used is used. Polymerization methods include bulk polymerization, solution polymerization using organic solvents such as fluorinated hydrocarbons, chlorinated hydrocarbons, fluorinated chlorinated hydrocarbons, fluorinated alkyl ethers, alcohols and hydrocarbons, aqueous media, and as appropriate. And suspension polymerization using an organic solvent, and emulsion polymerization using an aqueous medium and an emulsifier. In particular, suspension polymerization is preferable. Further, the organic solvent used in the suspension polymerization is preferably one or more selected from the group consisting of fluorinated hydrocarbons, fluorinated chlorohydrocarbons, and fluorinated alkyl ethers.

As the radical polymerization initiator, an initiator having a half-life of 10 hours and a temperature of 0 to 100 ° C. is preferable, and an initiator having a temperature of 20 to 90 ° C. is more preferable. Specific examples include azo compounds such as azobisisobutyronitrile, peroxydicarbonates such as diisopropyl peroxydicarbonate, tert-butyl peroxypivalate, tert-butyl peroxyisobutyrate, and tert-butyl peroxy. Peroxyesters such as acetate, non-fluorinated diacyl peroxides such as isobutyryl peroxide, octanoyl peroxide, benzoyl peroxide, lauroyl peroxide, (Z (CF ₂ ) _p COO) ₂ (where Z is hydrogen Fluorine-containing diacyl peroxide such as an atom, fluorine atom or chlorine atom, and p is an integer of 1 to 10, and inorganic peroxides such as potassium persulfate, sodium persulfate and ammonium persulfate.

As polymerization conditions, the polymerization temperature is preferably 0 to 100 ° C, more preferably 20 to 90 ° C. The polymerization pressure is preferably from 0.1 to 10 MPa, more preferably from 0.5 to 3 MPa. The polymerization time is preferably 1 to 30 hours.
In the present invention, it is also preferable to use a chain transfer agent in order to control the volume flow rate of the fluorine-containing copolymer. Chain transfer agents include alcohols such as methanol and ethanol, chlorofluorohydrocarbons such as 1,3-dichloro-1,1,2,2,3-pentafluoropropane, 1,1-dichloro-1-fluoroethane, Examples thereof include hydrocarbons such as pentane, hexane, and cyclohexane.

The coating material in the present invention contains a fluorine-containing copolymer and an insulating filler. Insulating fillers include inorganic fillers such as mica, silica, talc, alumina, kaolin, calcium sulfate, calcium carbonate, titanium oxide and zinc oxide, glass fibers, whiskers such as potassium titanate and aluminum borate, polyimide Examples include organic fillers such as fibers. The insulating filler is preferably at least one selected from the group consisting of mica, silica, talc, alumina, kaolin, calcium sulfate, calcium carbonate, titanium oxide and zinc oxide.
The content ratio of the insulating filler is preferably 99.9 / 0.1 to 10/90, more preferably 99/1 to 30/70, as the mass ratio of the fluorine-containing copolymer to the insulating filler. And most preferably 90/10 to 40/60.

  The coating material in the present invention is preferably produced by kneading a fluorine-containing copolymer and an insulating filler with an extrusion kneader. As a kneading method, a fluorine-containing copolymer and an insulating filler are premixed with a tumbler, a V mixer, a Henschel mixer or the like and then supplied to a twin-screw extrusion kneader in the same direction or different directions, Alternatively, a method of melt-kneading and pelletizing by supplying from a plurality of hoppers charged with a fluorine-containing copolymer and an insulating filler to a biaxial extrusion kneader in the same direction or different direction without premixing Is preferred. As the kneading screw of the twin-screw extrusion kneader, a screw with a kneading function is preferable. The kneading temperature is preferably not less than the melting point of the fluorinated copolymer and not more than the decomposition temperature. Specifically, 300 to 400 ° C is preferable.

  A well-known technique can be used as a manufacturing method of the heat-resistant electric wire of the present invention. A method of coating a conductor with a melted coating material using an extruder, a method of winding a tape-shaped coating material around a conductor, a dipping conductor in a bath in which a powder of the coating material is flowed, and Examples thereof include a method of forming a coating layer by heating and melting the attached powder. In particular, a method of coating a conductor with a coating material melted using an extruder is preferable.

  As an extruder, a single screw or a twin screw extruder is preferable. As extrusion conditions, a cylinder temperature is 250 to 380 ° C, a crosshead temperature is 300 to 400 ° C, and a die temperature is preferably 320 to 420 ° C.

  The conductor used as the core wire of the heat-resistant electric wire of the present invention is not particularly limited, and various plated wires such as copper, copper alloy, aluminum and aluminum alloy, tin plating, silver plating, nickel plating, stranded wire, superconductor, and semiconductor element. Examples include lead plating wires. The diameter of the conductor and the coating thickness of the coating material can be selected as appropriate. In addition, it is also preferable to coat the outer periphery of the bundled heat-resistant electric wires with the coating material in the present invention.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in detail, this invention is not limited to these. The composition, the capacity flow rate, and the MIT bending life of the fluorinated copolymer were measured by the methods described below.

[Composition of TFE copolymer] According to the description of Asahi Glass Research Report 1990, 40 (1), 75, it was determined by a method of ¹⁹ F-NMR measurement of the fluorinated copolymer in a hot melt state.

[Capacity flow rate] Fluorine-containing copolymer when a fluorine-containing copolymer is extruded into an orifice having a diameter of 2.1 mm and a length of 8 mm under a load of 380 ° C. and 7 kg using a flow tester (manufactured by Shimadzu Corporation) The combined flow rate (mm ³ / sec) was taken as the volume flow rate.

  [MIT Bending Life] A measurement sample was obtained by punching a film having a thickness of 0.220 to 0.236 μm obtained by compression molding of a fluorine-containing copolymer at 340 ° C. into a strip shape having a width of 12.5 mm. In accordance with ASTM D2176, a bending test of the measurement sample was performed using a bending tester MIT-D (manufactured by Toyo Seiki Seisakusho) at a load of 1.25 kg, a bending angle of ± 135 degrees, and room temperature. The number of folds until rupture was defined as the MIT fold life.

  [Stress crack resistance test] A heat-resistant electric wire was wound around its own diameter, and the coating material of the heat-resistant electric wire after being held in an oven at 250 ° C for 2 weeks was visually observed for cracks. Those having no cracks were evaluated as having good stress crack resistance.

  [Cut-through resistance test] A covered electric wire having a core wire diameter of 0.26 mm, a coating thickness of 0.15 mm, and a finished diameter of 0.56 mm was placed on the edge of a mild steel prism, and a load of 2 kg was applied at a temperature of 150 ° C. In addition, when the insulating property was maintained for 1 hour or more, the cut-through resistance was evaluated as good.

[Example 1]
The inside of the polymerization tank equipped with a stirrer with an internal volume of 400 L was evacuated to vacuum, and 204 L of water, 1.82 L of methanol, 41.7 L of CFHClCF ₂ CF ₂ Cl (hereinafter referred to as AK225cb), and 33.9 L of PPVE were added. After charging and raising the temperature in the polymerization tank to 50 ° C., TFE was introduced to 1.21 MPa / G. A 0.12% by mass 225 cb solution of di (perfluorobutyryl) peroxide was charged as a polymerization initiator to initiate the polymerization reaction. Since the pressure decreased as the polymerization progressed, additional TFE was added to keep the pressure constant. During the polymerization, a total of 2.5 L of the initiator solution was continuously charged. When the additional amount of TFE reached 38 kg, the temperature in the polymerization tank was cooled to 25 ° C., and unreacted TFE was purged. The polymerization time was 7 hours. The obtained polymerization solution was allowed to stand, separated into water and a fluorinated copolymer slurry, and the slurry was dried at 150 ° C. for 8 hours, whereby 46.4 kg of the fluorinated copolymer 1 was obtained. Obtained. In the composition of the fluorinated copolymer 1, the molar ratio of the repeating unit based on TFE / the repeating unit based on PPVE was 93.7 / 6.3, and the volume flow rate was 1.23 mm ³ / sec. The MIT bending life was 12 million times.

  Calcium carbonate (NS200 manufactured by Nitto Flour Chemical Co., Ltd.) is used as the hopper of the first feeder of the same-direction twin-screw extrusion kneader in which screws having two kneading parts are set, and fluorine-containing co-polymer is used as the hopper of the second feeder. The coalescence 1 was charged so that the mass ratio of calcium carbonate / fluorinated copolymer 1 was 1/1, and carbonation was performed while sucking with a vacuum pump from the vent section under the conditions of a cylinder temperature of 380 ° C. and a screw rotation speed of 100 rpm. Calcium and the fluorinated copolymer 1 were kneaded, the discharged strand was gradually cooled, and cut into a 3 mm length with a pelletizer to prepare a pellet 1.

  An electric wire was formed using the obtained pellet 1. The extruder was a short shaft, the screw diameter was 40 mm, the screw type was metalling, the screw L / D was 25, and the screw compression ratio was 2.6: 1. The die had an inner diameter of 4.3 mm, a nipple outer diameter of 2.0 mm, and a land length of 20 mm. As the molding conditions, a cylinder C1 temperature of 320 ° C., a C2 temperature of 350 ° C., a C3 temperature of 380 ° C., a crosshead temperature of 390 ° C., a die temperature of 400 ° C., a draw ratio of 59, and a take-up speed of 100 m / min were employed. A tin-plated copper wire was used as the conductor. The obtained heat-resistant electric wire 1 had a core wire diameter of 0.26 mm, a coating thickness of 0.15 mm, and a finished diameter of 0.56 mm. The stress crack resistance of the coating material of the obtained heat-resistant electric wire 1 was good. Cut-through resistance was good.

[Example 2]
Initially, 204 L of water, 2.96 L of methanol, 54.3 L of 225 cb, and 21.3 L of PPVE were charged, and a fluorinated copolymer 2 was produced in the same manner as in Example 1. A total of 1.4 L of the polymerization initiator solution was charged, and the additional amount of TFE added was 43 kg. The polymerization time was 7 hours. 47.3 kg of fluorinated copolymer 2 was obtained. As for the composition of the fluorinated copolymer 2, the molar ratio of the repeating unit based on TFE / the repeating unit based on PPVE was 95.5 / 4.5, and the capacity flow rate was 1.10 mm ³ / sec. The MIT bending life was 7.5 million times. A heat-resistant electric wire 2 was produced in the same manner as in Example 1 using the fluorine-containing copolymer 2 obtained as described above. The stress crack resistance of the coating material of the heat resistant electric wire 2 was good. Cut-through resistance was good.

[Comparative example]
TFE / PPVE copolymer (conventional PFA, Asahi Glass Co., Ltd.) having a molar ratio of repeating unit based on TFE / repeating unit based on PPVE of 98.7 / 1.3 and a capacity flow rate of 1.8 mm ³ / sec. MIT bending life was 600,000 times. A heat-resistant electric wire 3 was produced in the same manner as in Example 1 using the PFA. A stress crack resistance test of the heat resistant electric wire 3 was performed. Innumerable fine cracks occurred in the coating material of the heat-resistant electric wire 3, and the stress crack resistance was poor. Cut-through resistance was good.

The heat-resistant electric wire of the present invention is used for electric wire applications that require heat resistance and reliability, such as aircraft, semiconductors, automobiles, OA equipment, and IT equipment.

Claims (3)

It contains a repeating unit (A) based on tetrafluoroethylene and a repeating unit (B) based on perfluoro (propyl vinyl ether), and the molar ratio (A) / (B) is 97.5 / 2.5 to 90/10 Yes, the conductor is coated with a coating material containing a fluorine-containing copolymer and an insulating filler having a capacity flow rate at 380 ° C. of 0.1 to 20 mm ³ / sec and an MIT bending life of 3 million times or more. A heat-resistant electric wire formed by coating,
The mass ratio of the fluorine-containing copolymer and the insulating filler in the coating material is 99/1 to 30/70,
The filler in the coating material is at least one selected from the group consisting of mica, silica, talc, alumina, kaolin, calcium sulfate, calcium carbonate, titanium oxide and zinc oxide,
The heat-resistant electric wire coated with the coating material is (i) a heat-resistant electric wire having a core wire diameter of 0.26 mm, a coating thickness of 0.15 mm, and a finished diameter of 0.56 mm is wound around its own diameter and held at 250 ° C. for 2 weeks. has a stress cracking resistance that no crack occurs in the coating material of the heat wire after, and the diameter of (ii) core is 0.26 mm, the coating thickness is 0.15 mm, the finished diameter of 0.56mm When a heat-resistant electric wire is placed on the edge of a mild steel prism that is a conductor and a load of 2 kg is applied at 150 ° C., the edge of the mild steel prism that is a conductor passes through the sheath and energizes the core wire for 1 hour or longer. heat wires, characterized in that it has a no insulation cut-through resistance that holds the thing.   The heat-resistant electric wire according to claim 1, wherein a mass ratio of the fluorine-containing copolymer and the insulating filler is 90/10 to 40/60.   The heat-resistant electric wire according to claim 1 or 2, wherein the filler is calcium carbonate.