JPH05151846A - Manufacture of foamed-insulation layer clad electric wire - Google Patents

Abstract

PURPOSE:To manufacture a small-thickness and fine-diameter foamed insulation layer clad electric wire which has an insulation layer having a high foam rate and an excellent outer appearance, and is suitable as a signal transmission electric wire in term of the performance such as a signal transmission speed, etc. CONSTITUTION:A thermally meltable fluorine resin is supplied to an extruder, and is melted. Then, a liquid foaming agent is injected into the molten material. Then, the molten fluorine resin and the foaming agent are kneaded together, and the foaming agent is uniformly dispersed into the resin. Thereafter, the resulting fluorine resin is extruded and coated onto a conductor, and this resin is foamed to thereby form a foamed-insulation layer clad electric wire. A fluorine-based foaming agent having as a main component at least one kind of fluorocarbon having a molecular weight of approximately 338 to 488 is used as the foaming agent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a foam insulated wire which can be applied to an insulated wire or a coaxial cable.

[0002]

2. Description of the Related Art A foam insulated wire having a foamed fluororesin as an insulating layer is used as a plenum coaxial cable or an electric wire for signal transmission in electronic equipment or the like. Fluororesin has excellent properties such as flame retardancy, heat resistance, electrical characteristics, mechanical characteristics, and chemical resistance, and since the dielectric constant decreases when it is further foamed, the signal propagation delay speed in the above insulated wire is reduced. It is known that the signal transmission speed is shortened and the signal transmission speed is improved.

In recent years, foamed insulated electric wires using fluororesin have been required to further reduce the variation in signal transmission time or to further increase the signal transmission speed as the signal processing capacity increases. Therefore, in such an insulated wire, it is necessary to increase the foaming rate of the fluororesin foam insulation layer and reduce its variation to stabilize the outer diameter. Further, when it is used for internal wiring of a computer or the like, further thinning of the insulating layer and reduction in diameter of the electric wire are required in accordance with downsizing and large capacity of equipment.

Conventionally, for manufacturing the foam insulated wire as described above, for example, chlorofluorocarbon (CCl ₃ F, CCl ₂ F, CC
A method of introducing a fluorine-based foaming agent such as 1 ₂ F-CClF ₂ , CClF ₂ -CF ₃ ) or hydrochlorofluorocarbon (CHClF ₂ ) and extruding and coating it on a conductor, and then foaming is adopted.

However, since these fluorine-based blowing agents contain chlorine which causes destruction of the ozone layer, their use is environmentally problematic.

When a foamed insulated electric wire is manufactured using the above-mentioned fluorine-based foaming agent, the foaming rate is limited to about 60 to 65% (volume ratio) in a system in which the thickness of the insulating layer is 0.5 mm or more. Is. Further, in the insulated wire, the fluctuation range of the foaming rate and the fluctuation range of the outer diameter are large, and as a result, the variations of the signal propagation delay time (τ) and the characteristic impedance (Z ₀ ) are ± 0.1 (ns / ns), respectively. m) and ± 10 (Ω), which are large.

On the other hand, as a technique for producing a foamed insulated wire for further reducing the thickness of the insulating layer and increasing the foaming rate, Japanese Patent Laid-Open No. 3-97746 discloses a melt flow rate of 10 g /
10 min. The following tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) 1 cc
On the other hand, disclosed is a method of injecting a halogenated carbon or a halogenated hydrocarbon having a boiling point of 0 ° C. or more at a ratio of 0.01 to 1 cc as a foaming agent, extrusion-coating the same on a conductor, and then performing foaming. Has been done. According to this method, it is possible to obtain a foamed insulated wire having a high foaming rate and a thin wall thickness, in which the foaming insulating layer has a foaming rate of 70% or more and a thickness of 0.5 mm or less.

However, according to this method, for example, the conductor diameter and the outer diameter after forming the foam insulating layer are both 0.2 m.
When producing a small-diameter and thin-walled foam insulated wire having a diameter of m or less and 0.6 mm or less, in the extrusion step of the resin (PFA), due to its flow characteristics, that is, the level of the melt flow rate, The pressure in the die section of the extruder rises excessively. Therefore, in the foamed insulated wire produced, appearance failure such as loss of smoothness of the insulating layer surface,
Also, there are drawbacks such as disconnection.

Further, in the above method, as the foaming agent, specifically, a methane derivative having a molecular weight in the range of 66.1 to 287.2 and containing fluorine, chlorine and bromine in the structure,
Halogenated carbon and halogenated hydrocarbons such as ethane derivatives, ethylene derivatives and cyclic compounds have been used.
In one example, trichlorotrifluoroethane (CFC 113) is used as a blowing agent to melt P in the extruder.
Used by pumping into FA. However, a blowing agent such as trichlorotrifluoroethane is environmentally problematic in that it contains chlorine and the like as described above, and in particular, when it is injected into a fluororesin such as PFA which is in a hot melt state at 300 ° C. or higher, Since it decomposes in the extruder, it may cause the resin to burn.

Fluorine resins such as PFA are known to show an excellent appearance during molding only in a limited shearing region. Therefore, in the above method, when the die diameter of the extruder is reduced in order to manufacture a thin-walled, foam-insulated electric wire having a small diameter, the linear velocity and the discharge amount of the resin must be reduced. It is also necessary to reduce the amount of foaming agent injected into the resin. For example, melt flow rate 10 g / 10 min. PF having the following flow characteristics
To A, monochloro difluoromethane as the blowing agent (CHClF _2: Freon 22) was pumped, foamed outer diameter after forming the insulating layer is thin as or less 0.75 mm, the thin foam insulated with this When manufacturing an electric wire, in order to secure sufficient adhesion between the conductor and the foam insulating layer, the injection amount of the foaming agent is about 0.005 ml / min. Must be set to: However, since the injection amount of this foaming agent is near the lower limit value set by the discharge capacity of a precision pump that is generally used for pump injection, delicate control becomes extremely difficult, and an insulated wire with an excellent appearance cannot be obtained. ..

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and its main purpose is to have an insulating layer having a high foaming ratio and an excellent appearance, and to improve performance such as signal transmission speed. The object of the present invention is to provide a method capable of producing a thin insulated foam wire having a small diameter, which is suitable as an electric wire for signal transmission.

[0012] Another object of the present invention is to provide a method for producing the foamed insulated electric wire, which has a small influence on the environment and facilitates quantitative control of the foaming agent when forming the insulating layer. That is.

[0013]

Means and Actions for Solving the Problems In the method for producing a foam insulated wire of the present invention, a step of introducing a foaming agent into a molten fluororesin and uniformly dispersing the foaming agent in the molten fluororesin And a step of extruding and coating a molten fluororesin in which the foaming agent is dispersed on a conductor to foam, wherein the foaming agent contains at least one fluorocarbon having a molecular weight of about 338 to 488 as a main component. Is a fluorine-based foaming agent.

The method for producing the foam insulated wire of the present invention will be described in detail below.

In the method of the present invention, a blowing agent is introduced into a molten fluororesin by using a precision pump or the like, and then the fluororesin is kneaded at a general molding temperature (about 300 to 400 ° C.). The foaming agent is uniformly dispersed in the molten fluororesin. Next, the surface of the conductor is extrusion-coated with a molten fluororesin in which such a foaming agent is dispersed. Further, the fluororesin in a molten state is foamed on the conductor under predetermined conditions and cooled to form a foam insulated wire.

The method for producing a foam insulated wire as described above can be carried out by an extruder which is generally used for producing a resin-coated electric wire.

The method of the present invention is most characterized in that a fluorine-based foaming agent containing at least one fluorocarbon having a molecular weight of about 338 to 488 as a main component is used as the foaming agent.

The fluorine-based foaming agent has a molecular weight about 4 to 5 times that of conventional foaming agents such as monochlorodifluoromethane (CHClF ₂ ). Therefore, the diffusion rate of the foaming agent in the molten fluororesin is slower than that of the conventional foaming agent, and the bubbles that grow when the molten fluororesin foams on the conductor surface become large. Therefore, according to the method of the present invention, in the formed foam insulated wire, the foaming rate of the insulating layer is increased, the characteristics such as the signal propagation delay time are stabilized, and the signal transmission speed is improved.

Further, the fluorine-based blowing agent has excellent controllability of the injection amount to the molten fluororesin due to the molecular weight range of its main component, and has a high foaming rate and an excellent appearance. The foamed insulated electric wire having the foamed insulating layer is easily formed.

Generally, in forming a foam, the injection amount v of the foaming agent into the foam material can be approximated by the following equation.

V = n · Mw / ρ n: number of moles of foaming agent required to obtain a certain foaming ratio Mw: molecular weight of foaming agent, ρ: specific gravity of foaming agent According to this formula, the ratio of molecular weight to specific gravity It is estimated that the larger the value of Mw / ρ, the more the injection amount v of the foaming agent can be increased.

Here, Mw / ρ of monochlorodifluoromethane which is a conventional foaming agent is about 73, whereas Mw / ρ of fluorocarbon which is the main component of the foaming agent used in the present invention is equal to its molecular weight. Due to about 190-280
Is. Therefore, in the present invention, when forming a thin fluororesin foam insulating layer having a high foaming rate, the injection amount of the foaming agent can be set to be larger than that in the conventional case. Thus, according to the method of the present invention, in particular, it becomes easy to quantitatively control the injection of the foaming agent into the resin by the precision pump, and further, sufficient adhesion between the conductor and the foam insulating layer and an excellent appearance are obtained. Is secured. For example, in the case of manufacturing a thin, small-diameter foam insulated wire having an outer diameter of 0.75 mm or less after the foam insulating layer is formed, a fluorocarbon having a molecular weight of about 338 to 488 is contained as a main component according to the method of the present invention. If a fluorine-based foaming agent is used, the injection amount of the foaming agent is
It can be set to about 3 to 4 times that of monochlorodifluoromethane, and its control becomes extremely easy.

On the other hand, the foaming agent has a molecular weight of about 3
When a fluorocarbon or fluorohydrocarbon of less than 38 is used, the injection amount of the foaming agent into the molten resin has to be set to a small amount, which makes it difficult to perform delicate quantitative control in injection using a precision pump. Further, when the injection amount of the foaming agent is small, the diffusion rate in the molten resin becomes excessively high, and the foaming agent cannot be retained in the layer, especially when a thin insulating layer is to be formed on the conductor. Therefore,
It becomes difficult to reduce the thickness of the foam insulating layer. When a fluorocarbon or fluorohydrocarbon having a molecular weight of more than about 488 is used as the foaming agent, the diffusion rate in the molten resin becomes excessively slow and the foaming rate of the foamed insulation layer cannot be increased.

In the fluorine-based blowing agent used in the method of the present invention, the fluorocarbon having a molecular weight of about 338 to 488 is preferably a compound represented by the following general formula (1).

C _x F _y (1) where x = 6, 7, 8, 9 and y = 2x + 2 are satisfied.

Specific examples of the fluorocarbon (1) include C ₆ F ₁₄ (molecular weight 338) and C ₇ F ₁₆ (molecular weight 3).
88), C ₈ F ₁₈ (molecular weight 438), C ₉ F ₂₀ (molecular weight 488) and the like.

These foaming agents containing fluorocarbon as a main component are generally liquid at room temperature and pressure.
The blowing agent is very stable thermally and chemically,
Does not decompose at the molding temperature (melting temperature) of fluororesin,
It also does not react with fluororesin. Therefore, the fluororesin in the molten state is kneaded in a stable state and uniformly dispersed. For example, when a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) as described below is used as the fluororesin and the above foaming agent is injected in the molten state at 300 ° C. or higher, it decomposes in the extruder. Without causing problems such as burning of the resin.

Furthermore, since the fluorine-based blowing agent contains fluorocarbon as a main component, it does not contain chlorine or bromine in all the components, the influence on the ozone layer is reduced, and it is environmentally friendly.

Fluorine-based blowing agents used in the present invention include
In addition to the above-mentioned main component (fluorocarbon), for example, C
Molecular weight, such as ₅ F ₁₂ (molecular weight 288) is from 338 to 48
Fluorocarbons outside the range of 8, C ₉ F ₁₆ H
Fluorohydrocarbons such as ₄ (molecular weight 416), organic compounds containing oxygen in the structure such as the following compounds, and the like may be contained.

[0030]

[Chemical 1] On the other hand, in the method of the present invention, the fluororesin in a molten state is a fluororesin that can be heat-melted, which is melted in an extruder or the like. Examples of the heat-meltable fluororesin include, for example, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer, ethylene-tetrafluoroethylene copolymer, tetrafluoroethylene. -Hexafluoropropene-perfluorovinyl ether copolymer (for example, about 80 to 95% by weight of tetrafluoroethylene, about 5% of hexafluoropropene)
.About.20% by weight, and a perfluorovinyl ether about 0.2 to 6% by weight).

In the method of the present invention, of these fluororesins, those having specific flow characteristics can be preferably used. That is, for PFA, tetrafluoroethylene-hexafluoropropylene copolymer, and tetrafluoroethylene-hexafluoropropene-perfluorovinyl ether copolymer, temperature 372 ° C., load 5
Melt flow rate in kgf is 10g / 10mi
n. Larger ones are preferred, and for ethylene-tetrafluoroethylene copolymers, a temperature of 297 ° C,
Melt flow rate at a load of 5 kgf is 5 g / 10
min. The above is preferable. The fluororesin having such fluidity has a higher fluidity in a heat-melted state. Therefore, if a thin and thin foam insulated wire having an outer diameter of 1.0 mm or less after the foam insulating layer is formed is manufactured by using these fluororesins, it is possible to improve the efficiency of the extruder in the resin melt extrusion step. The pressure in the die part does not rise excessively, and an insulated wire having an excellent appearance can be obtained.

In the fluororesin having these flow characteristics,
PFA is more preferred. Especially, temperature 372 ℃, load 5k
Melt flow rate at gf is 20g / 10mi
n. It has been confirmed that the use of the above PFA improves the shear region where a good appearance can be obtained.

In the method of the present invention, the fluororesin having the above-mentioned flow characteristics may be used in the form of a mixture of two or more kinds. As a specific example, a temperature of 372 ° C. and a load of 5 kgf
Melt flow rate at 10 g / 10 min. Mention may be made of a mixture of about 60-98% by weight of a larger tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer and about 40-2% by weight of a tetrafluoroethylene-hexafluoropropylene copolymer having a similar melt flow rate.

Further, it is also possible to use two or more kinds of fluororesins made of the same compound and having different melt flow rates from each other.

Further, in the method of the present invention, a foam nucleating agent such as boron nitride may be appropriately added to the fluororesin.

[0036]

EXAMPLES The present invention will be described in more detail below with reference to examples. It should be noted that these examples are described for the purpose of facilitating the understanding of the present invention, and do not limit the present invention.

Example 1 As a fluororesin, PFA340J (tetrafluoroethylene-perfluoroalkylvinylether copolymer (PFA), temperature 372 ° C., melt flow rate under load of 5 kgf, 14 g / 10 min., Manufactured by Mitsui DuPont Fluorochemicals, foaming As a nucleating agent, boron nitride (0.5% by weight) was supplied to the extruder to heat-melt the resin, and in this state, Fluorinert FC- was used as a foaming agent.
75 (main component: C ₈ F ₁₈ (linear molecule, molecular weight 43
8), boiling point: 102 ° C., manufactured by Sumitomo 3M Ltd.). This was kneaded in an extruder to disperse a foaming agent, and a fluororesin in a molten state was extrusion-coated on a conductor having a diameter of 0.4 mmφ. Next, the molten fluororesin was foamed on the conductor under predetermined conditions to form a coaxial insulated wire having an outer diameter of 1.6 mmφ and a foaming ratio central value of 60%.

Example 2 As a fluororesin, Tefzel 200 (ethylene-tetrafluoroethylene copolymer, temperature 297 ° C., load 5 kg)
f melt flow rate 8 g / 10 min. , Mitsui DuPont Fluorochemical Co., Ltd., compounded with 0.5% by weight of boron nitride as a foam nucleating agent), but with the same method and conditions as in Example 1 and having an outer diameter of 1.6 m.
A coaxial insulated wire having mφ and a foaming center value of 60% was formed.

Example 3 As a fluororesin, SP100 (tetrafluoroethylene-hexafluoropropene-perfluorovinylether copolymer, temperature 372 ° C., melt flow rate at load 5 kgf, 25 g / 10 min., Manufactured by Daikin Industries, Ltd., foam nucleating agent As boron nitride 0.5% by weight
Except that the compounding) is used, the outer diameter is 1.6 mmφ and the foaming rate central value is 60% by the same method and conditions as in Example 1.
The insulated wire for coaxial was formed.

Example 4 As a fluororesin, FEP110J (tetrafluoroethylene-hexafluoropropylene copolymer, temperature 37
Melt flow rate 16g at 2 ℃ and load 5kgf
/ 10 min. , Manufactured by Mitsui DuPont Fluorochemical Co., Ltd., containing 0.5% by weight of boron nitride as a foam nucleating agent)
A coaxial insulated wire was formed by the same method and conditions as in Example 1, except that was used.

Comparative Example 1 Freon 22 (main component: CHClF) was used as a foaming agent.
_A coaxial insulated wire was formed by the same method and conditions as in Example 4 except that ₂ (molecular weight 86.5, manufactured by Asahi Glass Co., Ltd.) was used.

Each of the insulated wires manufactured in Examples 1 to 4 and Comparative Example 1 was evaluated for characteristics as a signal transmission wire. That is, on each insulated wire,
A horizontal winding shield having a wire diameter of 0.05 mm was applied, and the surface thereof was further covered with a PVC jacket. Then, each sample 20 about 1m from each insulated wire (about 100m)
Randomly picked up a book, and according to the usual method, characteristic impedance (Z ₀ ) and signal propagation delay time (τ) of these samples
Was measured and the variation in the value was obtained. The results are shown in Table 1.

[0043]

[Table 1] As is clear from the results of Table 1, according to the method of the present invention, a fluorinated blowing agent containing at least one fluorocarbon having a molecular weight in the range of about 338 to 488 as a main component is used as the blowing agent. When a thick foam insulated wire is formed, variations in the signal propagation delay time (τ) and characteristic impedance (Z ₀ ) of the obtained wire are smaller than in the conventional method using hydrochlorofluorocarbon as a foaming agent. Therefore, it is possible to stabilize the characteristics of the signal transmission wire.

Example 5 TE9773 (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer: P
FA, containing 1% by weight of boron nitride, manufactured by Mitsui DuPont Fluorochemical Co., Ltd.) was supplied to the extruder, and the resin was melted, and Fluorinert FC-77 was used as a foaming agent.
(Main component: C ₈ F ₁₈ (straight chain molecule, molecular weight 438), boiling point: 97 ° C., manufactured by Sumitomo 3M Ltd.) at a pressure of about 50 kgf
/ Cm ² . This was kneaded in an extruder to disperse the foaming agent in the system, and the molten fluororesin was extrusion-coated on the conductor. Next, the molten fluororesin was foamed on the conductor under predetermined conditions to form a foam insulated wire.

Example 6 Fluorinert FC-75 (main component: C ₈ F) as a foaming agent
Example 5 except that ₁₈ (linear molecule, molecular weight 438), boiling point: 102 ° C., manufactured by Sumitomo 3M Limited was used.
A foam insulated wire was formed by the same method and conditions.

Comparative Example 2 A foam insulated wire was prepared in the same manner as in Example 5 except that Freon 22 (main component: CHClF ₂ (molecular weight 86.5), manufactured by Asahi Glass Co., Ltd.) was used as a foaming agent. Formed.

With respect to the foamed insulated electric wires produced in Examples 5 and 6 and Comparative Example 2, the foaming rate (%) of the insulating layer and the signal propagation delay time (ns / ns) of the insulating layer were measured according to a conventional method.
m) was measured. The results are shown in Table 2.

[0048]

[Table 2] In addition, a foamed insulated wire was manufactured by the same method and conditions as in Example 5, using a foaming agent containing a linear fluorocarbon having a carbon number of 10 or more (molecular weight of 538 or more) as a main component as a foaming agent. The foaming rate in the insulating layer was not improved. It is considered that this is because the number of bubbles was small when the cross-sectional state of the foamed insulating layer in the foamed insulated wire was observed, and thus the growth of bubbles was delayed.

From the above results, according to the method of the present invention, as the foaming agent, the foaming agent formed by using the fluorine-based foaming agent containing at least one fluorocarbon having a molecular weight in the range of about 338 to 488 as the main component. It is clear that the foaming rate in the insulating layer of the insulated wire is improved, and that the signal propagation delay speed is reduced and the signal transmission speed is improved accordingly.

Example 7 As a heat-meltable fluororesin, PFA340J (PF
A, containing 1% by weight of boron nitride, temperature 372 ° C.,
Melt flow rate at a load of 5 kgf 14 g / 10
min. , Manufactured by Mitsui DuPont Fluorochemicals Co., Ltd.) was supplied to the extruder, and Fluorinert FC-77 as a foaming agent was injected from the middle of the extruder cylinder using a precision pump while the resin was molten. This was kneaded in an extruder to disperse the foaming agent, and the fluororesin in a molten state was extrusion-coated on the conductor. Next, the molten fluororesin was foamed on the conductor under predetermined conditions to form a foam insulated wire.

Example 8 As a fluororesin, TE9777 (PFA, containing 1% by weight of boron nitride, temperature 372 ° C., melt flow rate at load 5 kgf, 30 g / 10 min., Manufactured by Mitsui DuPont Fluorochemical Co., Ltd.) was used. ,
A foam insulated wire was formed by the same method and conditions as in Example 7.

Example 9 As a fluororesin, a mixed resin of 20 parts by weight of PFA340J and 80 parts by weight of TE9777 (temperature: 372 ° C.,
Melt flow rate at a load of 5 kgf 20 g / 10
min. ) Was used to form a foam insulated wire in the same method and conditions as in Example 7.

The appearance of the foamed insulated electric wires produced in Examples 7, 8 and 9 was observed, and the foaming rate (%) of the insulating layer and the adhesion between the conductor and the insulating layer were measured according to a conventional method. .. The results are shown in Table 3.

[0054]

[Table 3] Comparative Example 3 Freon 113 (main component: CCl ₂ FC) was used as a foaming agent.
An attempt was made to form a foam insulated wire by the same method and conditions as in Example 7 except that ClF ₂ (molecular weight: 187.4), specific gravity: 1.565, manufactured by Asahi Glass Co., Ltd. was used. Occurred, and the insulated wire could not be completed (see Table 4).

Comparative Example 4 The same method and conditions as in Example 7 except that Freon 22 (main component: CHClF ₂ (molecular weight 86.5), specific gravity 1.194, manufactured by Asahi Glass Co., Ltd.) was used as a foaming agent. To form a foam insulated wire. However, the adhesiveness between the fluororesin and the conductor was extremely poor, and the resin could not be foamed (see Table 4).

Comparative Example 5 Fluorinert FC-40 (main component: C ₁₂ F) was used as a foaming agent.
_A foam insulated wire was formed by the same method and conditions as in Example 7, except that ₂₆ (linear molecule, molecular weight 638), specific gravity 1.87, manufactured by Sumitomo 3M Limited was used.

The foamed insulated wire produced in Comparative Example 5 was observed for its appearance, and the foaming rate (%) of the insulating layer and the adhesion between the conductor and the insulating layer were measured by a conventional method.
The results are shown in Table 4.

[0058]

[Table 4] As is clear from the results of Tables 3 and 4, as a foaming agent, a fluorine-containing foaming agent containing at least one fluorocarbon having a molecular weight in the range of about 338 to 488 as a main component, was further used as a fluororesin at a temperature of 372 ° C., and a load. 5 kg
f has a melt flow rate of 10 g / 10 min.
According to the method of the present invention using PFA of more than 10%, it is possible to form a foam-insulated electric wire having an insulating layer having a high foaming rate and a more excellent appearance. In particular, Examples 7 to 9
Then, the quantitative control at the time of injecting the fluorine-based foaming agent was extremely easy.

[0059]

As described in detail above, according to the present invention,
It is possible to manufacture a foamed insulated electric wire having a high foaming rate and an insulating layer having an excellent appearance and having a thin wall and a small diameter, which is suitable as an electric wire for signal transmission and has performance such as signal transmission speed.

Further, in the method of the present invention, since the main component of the foaming agent used is fluorocarbon containing no chlorine, bromine, etc., the influence on the environment is reduced. Further, since the main component (fluorocarbon) of this foaming agent is in a specific molecular weight range, it becomes easy to quantitatively control the foaming agent when forming the insulating layer.

Claims (7)

[Claims] 1. A step of introducing a foaming agent into a molten fluororesin to uniformly disperse the foaming agent in the molten fluororesin, and the molten fluororesin having the foaming agent dispersed on a conductor. A method for producing a foam insulated wire, comprising the steps of extrusion coating and foaming, wherein the foaming agent is at least one kind of molecular weight of about 338 to 48.
8. A method for producing a foam insulated wire, which is a fluorine-based foaming agent containing the fluorocarbon of 8 as a main component. 2. The method for producing a foam insulated wire according to claim 1, wherein the fluorocarbon having a molecular weight of about 338 to 488 is a compound represented by the following general formula (1). C _x F _y (1) However, in the formula, x = 6, 7, 8, 9 and y = 2x + 2 are satisfied. 3. The fluororesin is a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer,
Tetrafluoroethylene-hexafluoropropylene copolymer, ethylene-tetrafluoroethylene copolymer,
The method for producing a foam insulated wire according to claim 1 or 2, which is at least one selected from the group consisting of and a tetrafluoroethylene-hexafluoropropene-perfluorovinyl ether copolymer. 4. The fluororesin comprises 372 ° C. and a load of 5 k.
Melt flow rate at gf is 10 g / 10 mi
n. The method for producing a foam insulated wire according to claim 1 or 2, which is a larger tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer. 5. The fluororesin comprises 372 ° C. and a load of 5 k.
Melt flow rate at gf is 10 g / 10 mi
n. The method for producing a foam insulated wire according to claim 1 or 2, which is a larger tetrafluoroethylene-hexafluoropropylene copolymer. 6. The fluororesin comprises 297 ° C. and a load of 5 k.
Melt flow rate at gf 5 g / 10 min. The method for producing a foam insulated wire according to claim 1, which is the above ethylene-tetrafluoroethylene copolymer. 7. The fluororesin comprises 372 ° C. and a load of 5 k.
Melt flow rate at gf is 10 g / 10 mi
n. The method for producing a foam insulated wire according to claim 1 or 2, which is a larger tetrafluoroethylene-hexafluoropropene-perfluorovinyl ether copolymer.