JPH0210528B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing an insulated wire useful as a heat-resistant flexible wire. Fluorine-containing elastomer copolymers, especially copolymers of propylene and tetrafluoroethylene, have excellent heat resistance, oil resistance, and chemical resistance, as well as excellent electrical insulation properties, and are expected to be used as insulation materials for electric wires. It is also an expensive material. A method for obtaining heat-resistant flexible electric wire using a propylene-tetrafluoroethylene copolymer is as follows:
It is common to coat the outer periphery of a stranded wire conductor with a propylene/tetrafluoroethylene copolymer containing peroxide as a crosslinking agent, and then react with heat to form a crosslinked insulator. However, in this case, volatile components generated by the decomposition of peroxide cause foaming and cracks in the crosslinked insulator. To prevent this, heating must be carried out using a pressurized medium, such as steam or nitrogen gas, but the pressure causes the insulation to sink into the spaces between the strands of the stranded conductor. If the insulator sinks into between the strands, the insulation thickness becomes non-uniform, and it becomes difficult to peel the insulator from the conductor during terminal treatment. In order to prevent this sinking, the present inventors have considered interposing a paper separator between the stranded wire conductor and the insulator, but in this case, when the wire is wound around its own diameter at room temperature, It was found that when heated to a temperature of 1000, cracks occur in the insulator, resulting in poor insulation, making it unusable for heat-resistant applications. The present inventors have conducted extensive research to solve the above problems and provide an insulated wire useful as a heat-resistant flexible wire. As a result, the copolymer of propylene, tetrafluoroethylene, and glycidyl vinyl ether It is possible to use amines such as tertiary amines and aromatic polyamines as crosslinking agents, which do not generate decomposition and volatile components, which eliminates the need to apply pressure during the crosslinking reaction and prevents the insulator from sinking into the stranded conductor. It was discovered that the . The present invention is based on the above knowledge, and even when a coating layer is provided directly on a stranded conductor, it is possible to prevent the coating layer from sinking into between the conductor strands during thermal crosslinking, and to improve heat resistance. The object of the present invention is to provide a method for manufacturing an insulated wire that does not require the use of a paper separator, which is an obstacle to the realization of the method. That is, the present invention involves directly coating the outer periphery of a stranded wire conductor with a composition containing a copolymer of propylene, tetrafluoroethylene, and glycidyl vinyl ether, and then thermally crosslinking the composition at or near atmospheric pressure. This is a characteristic feature. In the present invention, the molar ratio of propylene/tetrafluoroethylene is 5/95 to 70/
30, preferably from the range of 10/90 to 55/45, from the viewpoint of heat resistance, extrusion molding, etc. Glycidyl vinyl ether is 0.1 to 10 mol%,
Preferably, the content is 2 to 5 mol %; if the content is too small, the crosslinking reaction will be insufficient, and if the content is too large, the heat resistance properties will be impaired. In addition to the main components of propylene, tetrafluoroethylene, and glycidyl vinyl ether,
Components copolymerizable with these, such as ethylene, isobutylene, vinyl fluoride, vinylidene fluoride,
Hexafluorinated propylene, fluorovinyl ether,
Alkyl vinyl ether, chlorotrifluoroethylene, etc. may be copolymerized, and the content thereof is preferably selected from a range of 15 mol% or less. Examples of crosslinking agents added to promote the crosslinking component of such copolymers include amines, such as tertiary amines or their salts, tertiary amines or their salts and one or more -OH groups in the molecule. Combinations with hydroxy compounds containing aromatic polyamines or salts thereof can be preferably employed. Tertiary amines include hexyl benzoate, benzyldimethylamine, α-methylbenzyldimethylamine, dimethylaminomethylphenol, tris(dimethylaminomethyl)phenol, diethylaminopropylamine, N-aminoethylpiperazine, and ethylmethylimidazole. , triethylenediamine, N,N'-bis(alkyl)piperazine, 4,4'-trimethylenedipyridine, 2,3-bis(2-pyridyl)-5,6
-dihydropyrazine, N-ethylmorpholine,
Examples include 1,8-diaza-bicyclo(5,4,0)undecene-7 and salts thereof. Hydroxy compounds used in combination with tertiary amines include octanol, cyclohexanol, phenol, ethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol, hydroquinone, catechol, resorcinol, 2,2'-bis(4-hydroxy phenyl) propane (bisphenol A),
1,3,5-trihydroxybenzene, dihydroxynaphthalene, 4,4'-dihydroxydiphenyl, 4,4'-dihydroxystilbene, 2,2'-
Bis-4-(hydroxyphenyl)butane (bisphenol B), 2,4-dihydroxybenzophenone, 2,4-dihydroxybenzoic acid, 4,4'-
Examples include dihydroxydiphenyl sulfone, 2-methylresorcinol, trimethylolallyloxyphenol, and tolyl(4-hydroxyphenyl)methane. Examples of aromatic polyamines include xylylene diamine, metaphenylene diamine, diaminodiphenylmethane, and diaminodiphenyl sulfone. As the crosslinking method, a crosslinking method by heating is employed, but an important point in the present invention is that unlike the case where peroxide is used as a crosslinking agent, pressurization is not required. Thermal crosslinking is carried out under atmospheric pressure or near atmospheric pressure.
That is, it is carried out under such pressure that the insulator does not sink into the gaps between the strands of the stranded conductor. Heating methods include heating using gases such as air, nitrogen gas, and sulfur hexafluoride gas, heating using molten salts such as sodium nitrite, calcium nitrite, and mixtures thereof, hot air, and fluidized immersion heating. Various methods can be employed, such as , high frequency heating. In the present invention, in addition to copolymers and crosslinking agents, fluororesins such as polyvinylidene fluoride, vinylidene fluoride-hexafluoropropene copolymers, carbon black such as MT carbon, silicic acid, etc. White fillers such as magnesium and calcium carbonate may be added, and other substances such as dispersants, processing aids, and stabilizers such as metal oxides may also be added. Various components including the copolymer are uniformly mixed using a Banbury mixer, rolls, etc., and then introduced into an extruder as a crosslinkable composition. The Mooney viscosity ML ₁₊₄ (100°C) of such a composition is 10
~100, especially 20~60, moldability,
This is preferable from the viewpoint of the surface condition of the insulator. Examples of the present invention will be described below along with comparative examples. Example 100 parts by weight of a copolymer having a number average molecular weight of 50,000, a propylene/tetrafluoroethylene molar ratio of 45/55, and a glycidyl vinyl ether content of 2 mol%, 1 part by weight of hexylamine benzoate, thermal carbon (filled Add 40 parts by weight of sodium stearate (lubricant) and 1 part by weight of sodium stearate (lubricant) and knead for 15 minutes with a 150 mm diameter rubber roll set at a temperature of 50 to 60°C to obtain a Mooney viscosity of ML ₁₊₄ (100°C). 40 compositions were obtained. Next, head: 80℃, cylinder 1: 80
Cylinder 2: Using a 40 m/m extruder (L/D = 22) set at 60°C, a conductor with an outer diameter of 1.6 mm (tin-plated copper stranded wire) was coated (coating thickness 0.6
mm), and then kept in a nitrogen atmosphere at 200°C maintained at atmospheric pressure for 3 minutes to obtain an insulated wire. Comparative Example 1 In Example 1, 1 part by weight of 1,3-bis-(t-butylperoxyisopropyl)benzene was added as a crosslinking agent, and the mixture was maintained in steam at 13 atmospheres for 3 minutes to effect crosslinking. Comparative Example 2 In Comparative Example 1, a paper separator was wound around the outer periphery of the conductor, and a composition was coated thereon for crosslinking. The test results for the three types of electric wires thus obtained are shown in the table below. The occurrence of cracks was determined by wrapping the electric wire around a brass rod of the same diameter at room temperature and placing it in a constant temperature oven at 200°C, and observing the surface condition after 3 hours. Also. After the wire was thermally degraded in a constant temperature bath at 200°C for 10 days, it was wrapped around a brass rod of its own diameter and its surface condition was observed.

[Table] As is clear from the above description, according to the present invention, even when a coating layer is provided directly on a stranded conductor, the coating layer does not sink into between the conductor strands during thermal crosslinking. . Therefore, there is no need to interpose a paper separator between the stranded wire conductor and the coating layer, and heat resistance can be improved.

Claims (1)

[Claims] 1. A composition containing a copolymer of propylene, tetrafluoroethylene, and glycidyl vinyl ether, to which an amine is added as a crosslinking agent, is directly coated on the outer periphery of a stranded wire conductor, and then exposed to atmospheric pressure. or a method for producing an insulated wire, characterized by carrying out thermal crosslinking under a pressure close to this. 2. Claim 1, characterized in that the molar ratio of propylene/tetrafluoroethylene in the copolymer is 5/95 to 70/30, and glycidyl vinyl ether is contained in an amount of 0.1 to 10 mol%.
2. Method for manufacturing an insulated wire as described in . 3. The method for producing an insulated wire according to claim 1 or 2, wherein the crosslinking is carried out in the presence of a tertiary amine or a salt thereof. 4. The method for producing an insulated wire according to claim 1 or 2, wherein the crosslinking is carried out in the presence of an aromatic polyamine or a salt thereof.