JP3080121B2 - Electrical wire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric wire excellent in stress crack resistance and bending life.

[0002]

2. Description of the Related Art Conventionally, electric wires coated with a fluoropolymer have been known, for example, a copolymer of tetrafluoroethylene and hexafluoropropylene (hereinafter referred to as FEP) or tetrafluoroethylene and perfluoroethylene. Copolymers with fluoroalkyl vinyl ether (hereinafter referred to as PFA) have excellent heat resistance, electrical insulation, dielectric properties, and chemical resistance, and are used for various electrical insulation materials and wire coating materials. Has been used as

[0003]

The wire covering material is required to be free from cracks and breaks due to bending, in addition to the various physical properties described above. FEP and PFA above
Has heat resistance, insulation properties, dielectric properties and chemical resistance, but it is liable to crack due to repeated bending, and furthermore, to stress cracking resistance and bending life such as cutting. It has the disadvantage of being inferior.

[0004] In order to improve the stress crack resistance and the bending life, a method of increasing the molecular weight is conceivable. However, when the molecular weight is increased, the melt viscosity is increased, which causes a problem that the moldability is reduced, and the electric wire has a problem. It is not preferable from the viewpoint of the productivity of the coating material. Therefore, there has been a demand for a method of improving stress crack resistance and bending life without lowering moldability.

[0005]

The present inventors have intensively studied to solve the above-mentioned problems. As a result, they have found that a copolymer of tetrafluoroethylene and a specific fluorine-containing vinyl ether exhibits excellent stress crack resistance and bending life, and have completed the present invention and have proposed the present invention.

That is, in the present invention, the monomer unit based on tetrafluoroethylene is 97 mol% to 80 mol%, and the following general formula (I) CF ₂ ＣＦCFOCH ₂ (CF ₂ ) nX (I) (where X is Is a halogen atom or a hydrogen atom, and n is an integer of 1 or more.) The copolymer is coated with a fluorine-containing copolymer containing 3 to 20 mol% of a monomer unit based on a fluorine-containing vinyl ether represented by the following formula: It is an electric wire.

In the present invention, a fluorine-containing copolymer containing, as a coating material, a monomer unit based on tetrafluoroethylene and a monomer unit based on a specific fluorine-containing vinyl ether represented by the above formula (I) Is important in order to obtain an electric wire having excellent stress crack resistance and bending life.

In the fluorine-containing vinyl ether represented by the general formula (I), n may be an integer of 1 or more, but from 1 to 12 and further from 1 to 10 from the viewpoint of easy availability of raw materials. It is desirable. X is generally a hydrogen atom or a halogen atom, and chlorine, fluorine, or bromine is used, and hydrogen or fluorine is desirable from the viewpoint of chemical and thermal stability.

Specific examples of the fluorine-containing vinyl ether represented by the general formula (I) used in the present invention are as follows: CF ₂ ＯCFOCH ₂ CF ₃ , CF ₂ ＯCFOCH ₂ CF ₂ CF ₃ , CF ₂ ＣＦCFOCH _{2 CF 2 CF 2 H, CF} 2 = CFOCH 2 (CF 2) 2 CF 3, CF 2 = CFOCH 2 (CF 2) 3 CF 3, CF 2 = CFOCH 2 (CF 2) 4 CF 3, CF 2 = CFOCH _{2 (CF 2) 5 CF 3} , CF 2 = CFOCH 2 (CF 2) 6 CF 3, CF 2 = CFOCH 2 (CF 2) 7 CF 3, CF 2 = CFOCH 2 CF 2 Cl, CF 2 = CFOCH 2 CF _{2 Br, CF 2 = CFOCH 2} CF 2 CF 2 Cl, CF 2 = CFOCH 2 CF 2 CF 2 H, CF 2 = CFOCH 2 (CF 2) 2 CF 2 Cl, CF 2 = CFOCH 2 (CF 2) 2 CF ₂ H, C _{2 = CFOCH 2 (CF 2)} 3 CF 2 Cl, a _{CF 2 = CFOCH 2 (CF 2} ) 3 CF 2 H or the like.

The proportion of each monomer unit based on tetrafluoroethylene and the fluorine-containing vinyl ether represented by the general formula (I) is from 97 mol% to 80 mol% of the monomer unit based on tetrafluoroethylene; The monomer unit based on the fluorine-containing vinyl ether represented by the general formula (I) must be 3 to 20 mol%. When the monomer unit of the fluorinated vinyl ether represented by the general formula (I) is less than 3 mol%, especially when it is less than 1 mol%, the molecular weight is reduced to obtain a sufficiently low melt viscosity for molding. It is necessary to lower the value, which is not preferable because the stress crack resistance decreases accordingly.
Further, when the monomer unit of the fluorinated vinyl ether is more than 20 mol%, even if high stress crack resistance is obtained, physical properties such as heat resistance are deteriorated, which is not preferable.

In order to obtain an electric wire covering material having sufficient stress crack resistance and melt viscosity, the monomer unit based on tetrafluoroethylene is 97 mol% to 80 mol%, and is represented by the general formula (I). It is necessary that the monomer unit based on the fluorinated vinyl ether is 3 mol% to 20 mol%.

The fluorine-containing copolymer 3 used in the present invention
The melt viscosity at 72 ° C. is generally 1 × 10 ³ to 1 × 1.
0 is a ⁶ poise. For good moldability, the melt viscosity is preferably 3 × 10 ^{3 to} 3 × 10 ⁵ poise.

The method for producing the copolymer of the present invention is not particularly limited, and known methods can be employed.
The method disclosed in Japanese Patent No. 6808 can be cited.

The electric wire obtained by the present invention is excellent in chemical resistance, heat resistance, and fatigue resistance, and has good electric characteristics, especially low dielectric constant and low dielectric loss.
It can be suitably used for a computer that requires high reliability, a cable that transmits a high-frequency signal under a very severe environment, and the like.

A known method such as a method of coating with an electric wire coating extruder is used without any particular limitation. Although the thickness of the wire coating is not particularly limited,
Generally, it is preferable that it is 0.01 to 2 mm. Powders such as glass filler and silica may be added as additives in order to increase mechanical strength.

The copolymer used in the present invention is useful because it can be converted into a perfluoropolymer having excellent thermal stability by fluorination.

[0017]

The electric wire of the present invention is more resistant to stress cracking and MIT bending life than the case where a currently used fluororesin, for example, an electric wire covering material such as FEP and PFA is used. Excellent in FEP
In PFA and PFA, it is necessary to lower the molecular weight in order to obtain a melt viscosity that enables high-speed molding.
The stress crack resistance decreases. However, since the electric wire covering material used in the present invention contains the monomer unit of fluorine-containing vinyl ether, the moldable melt viscosity can be maintained. Therefore, the electric wire of the present invention exhibits excellent stress crack resistance and MIT bending life.

[0018]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. In addition, the measurement of the physical property in the following Examples was based on the following.

1. Measurement of tensile rupture strength Preparation of test sample in accordance with JIS K-7113 Fluorine-containing copolymer and resin for comparison are melted at a temperature of 350 ° C., and rapidly cooled with water under a pressure of 120 kg / cm ² to obtain 1 mm. Thick sheets were prepared and test pieces required for the above test method were prepared.

2. Measurement of Specific Melt Viscosity A Koka type flow tester was used.

Using a die having a diameter of 1 mm and a length of 10 mm, the measurement was performed at a temperature of 372 ° C. under a load of 13.14 kg.

3. Measurement of MIT bending life The bending life was measured using a standard bending durability tester described in ASTM D-2176-63T. The measurement was performed using a film having a thickness of about 0.20 to 0.23 mm obtained by quenching with water under a pressure of 120 kg / cm ² . A test piece having a length of 120 mm and a width of 15 mm was attached to an MIT bending tester, and a load of 1.25 kg was applied. Using an MIT bending tester, the film is bent right and left at an angle of 135 ° at a speed of about 175 cycles / minute. The number of cycles to failure is recorded on the counter of this machine. Each sample was measured three times, and the average value was adopted as the MIT bending life of the sample.

4. Crack test The coated electric wire was cut into a length of 120 mm, wound 10 times around a mandrain having a diameter of 1.4 mm and 3.0 mm, respectively, heated at 250 ° C. for 10 hours in an electric furnace, and taken out.
It was left to cool in air for 60 minutes. After unwinding, it was wound again in the direction opposite to the previous winding direction, heated in an electric furnace at 250 ° C. for 10 hours, taken out, and allowed to cool in air. The winding was unwound and the presence or absence of cracks on the outer surface of the covered electric wire was observed.

Example 1 1.9 kg of 1,1,2-trichlorotrifluoroethane which had been purified by distillation was put into a 3 l stainless steel reactor equipped with a stirrer, and the inside thereof was degassed. Thereafter, tetrafluoroethylene was introduced into the reactor to attain atmospheric pressure, and 0.94 g of methanol and 2,2,3,3,3-
Pentafluoropropyl trifluorovinyl ether 6
1.26 g was added, and then the rotation speed of the stirring motor was set to 800 rpm, tetrafluoroethylene was introduced, the pressure in the reactor was set to 7 kg / cm ² -G, and the introduction valve for tetrafluoroethylene was closed. Here, while keeping the inside of the reactor at 22 ° C., 3.15 g of a 1,1,2-trichlorotrifluoroethane solution (5% by weight) of bis (heptafluorobutyryl) peroxide was introduced to initiate polymerization. During the polymerization, the polymerization temperature was 22 ° C. The pressure inside the reactor is 5k
g / cm ² -G, the pressure inside the reactor was released, and the reactor was connected to a vacuum pump via a cooling trap, and the pressure was reduced while stirring to remove low boiling components such as solvent and unreacted monomer. Collected in trap. After the distillation, the reactor was disassembled, and the copolymer was taken out and dried at 150 ° C. for 12 hours to obtain 135 g of the copolymer.

This copolymer is formed into a film at 330 ° C.
When R was measured, it was found that monomer units derived from 2,2,3,3,3-pentafluoropropyltrifluorovinyl ether were contained in the 7.2 mol% copolymer. The specific melt viscosity measured at 372 ° C. was 4.5 × 10 ⁴ poise, and the tensile strength at break was 456 kg / cm ² . The MIT bending life was 744,840 times.

Example 2 3.0 kg of perfluorocyclohexyldimethylamine purified by distillation was put into a stainless steel 3 L reactor having a stirrer, and the inside was degassed. Thereafter, a gas mixture with tetrafluoroethylene having a concentration of 3.1 mol% of 2,2,3,3,3-pentafluorotrifluorovinyl ether prepared in advance was introduced into the reactor to obtain atmospheric pressure,
1.84 g of methanol was put into the reactor, and then the number of revolutions of the stirring motor was set to 800, and the above-mentioned monomer mixed gas was introduced to 6 kg / cm ² -G. Here, while maintaining the inside of the reactor at 22 ° C., bis (heptafluorobutyryl)
5.25 g of a 1,1,2-trichlorotrifluoroethane solution of peroxide (5 wt%) was introduced to initiate polymerization.
During the polymerization, the polymerization temperature was kept at 22 ° C., and the pressure was kept at 6 kg / cm ² -G by introducing the above monomer mixture gas. 80 minutes after the start of the reaction, when the introduction amount of the monomer mixed gas reached 170 g, the pressure in the reactor was released. Then, the reactor was connected to a vacuum pump via a cooling trap, and the pressure was reduced while stirring. Low boiling components such as reaction monomers were collected in the trap. After the distillation, the reactor was disassembled, and the copolymer was taken out and vacuum-dried at 150 ° C. for 12 hours to obtain 175 g of the copolymer. When this copolymer was formed into a film at 330 ° C. and the IR was measured, 2,2,3,
It was found that the monomer units derived from 3,3-pentafluoropropyl trifluorovinyl ether were contained in the 3.1 mol% copolymer. The specific melt viscosity measured at 372 ° C. is 4.0 × 10 ⁴ poise and the tensile strength at break is 4
It was 30 kg / cm ² . The MIT bending life is 2
It was 25,480 times.

Examples 3 to 6 The same procedure as in Example 1 was carried out except that the charged amounts of fluorine-containing vinyl ether, fluorine-containing vinyl ether and methanol were changed. Specific melt viscosity and MIT of Examples 3 to 6
The measurement results of the bending life were as shown in Table 1.

[0028]

[Table 1]

Comparative Examples 1 to 4 Polymerization was carried out in the same manner as in Example 1 except that the charged amounts of fluorine-containing vinyl ether, fluorine-containing vinyl ether and methanol were changed. A polymer out of the range was produced, and the specific melt viscosity and the MIT bending life were measured in the same manner as in the examples. Further, the specific melt viscosity and the MIT bending life of the commercially available PFA resins (A) and (B) were measured in the same manner, and the results are also shown in Table 1.

Example 7 The copolymers obtained in the above Examples and Comparative Examples were melted and formed into pellets having a diameter of 3.0 mm and a length of 3.0 mm.
Under the following conditions, an electric wire (diameter 0.7m)
m) with a thickness of 0.15 mm and a crack test
The results are shown in Table 2.

Wire extruder The withdrawal ratio was determined by the following equation.

[0032]

(Equation 1)

Where D _d = inner diameter of opening die (mm) D _g = outer diameter of chip (mm) D _CW = outer diameter of covered electric wire (mm) D _W = outer diameter of core wire (mm)

[0034]

[Table 2]

Continuation of the front page (56) References JP-A-2-276808 (JP, A) JP-A-2-28206 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01B 3 / 44 C08F 214/26

Claims (1)

(57) [Claims] 1. A monomer unit based on tetrafluoroethylene is 97 mol% to 80 mol%, and has the following general formula: CF ₂ ＣＦCFOCH ₂ (CF ₂ ) nX (where X is a halogen atom or a hydrogen atom; Is an integer of 1 or more.) An electric wire coated with a fluorinated copolymer containing 3 to 20 mol% of a monomer unit based on a fluorinated vinyl ether represented by the following formula: