JP5757078B2 - Manufacturing method of molded product and manufacturing method of covered electric wire - Google Patents

Description

The present invention relates to a method for manufacturing a molded product and a method for manufacturing a covered electric wire.

Polytetrafluoroethylene [PTFE] has been used for various applications because of its excellent properties. Along with recent technological advances, information communication equipment, medical equipment, automobile parts, etc. have become smaller, and along with this, electric wires, cables, tubes, filters, etc. that use fluororesin are also becoming increasingly finer and thinner. It has been demanded.

When PTFE is formed into an electric wire, cable, tube, filter, etc., PTFE is used in a form called molding powder, fine powder, or pellet. In conventional manufacturing methods, naphtha and petroleum hydrocarbons such as Isopar E and Isopar G have been used as molding aids for PTFE fine powder paste extrusion, but when molding these molding materials, The limit of the thickness of the obtained molded product exceeds 100 μm, and when trying to mold to a thickness of 100 μm or less, a uniform thickness could not be obtained.

Under such circumstances, Patent Document 1 discloses that a fluorine-based solvent is molded from polytetrafluoroethylene fine powder as a method for producing a fluororesin molded product for facilitating rolling to obtain a thin PTFE film. A method for producing a fluororesin molded product that is used as an auxiliary agent and is produced by paste extrusion molding is described.

Incidentally, in Patent Document 2, as a method for efficiently obtaining a fluororesin sintered body having a desired shape, a fluororesin powder and at least one low-temperature decomposable binder are mixed, and the mixture is injection molded. A method for producing a fluororesin sintered body is described in which a molded body is degreased and then sintered.

Patent Document 3 proposes a fluororesin that does not cause a shortage of coating when coated on a core wire having a diameter of 0.05 to 0.07 mm under certain conditions as a thin wire. However, the fluororesin is limited to resins that can be melt-processed such as a tetrafluoroethylene / hexafluoropropylene copolymer and a tetrafluoroethylene / perfluoro (alkyl vinyl ether) copolymer.

JP 2007-38423 A JP-A-6-262893 International Publication No. 2005/052015 Pamphlet

The molding aid used in Patent Document 1 is a mixture of two types of fluorine-based solvents, C ₆ F ₁₄ and C ₁₂ F ₂₆ , but the fluorine-based solvent is compared with hydrocarbon-based solvents. The surface energy is extremely low.

Patent Document 2 describes that in order to obtain a compound for injection molding, a mixture of a low-temperature decomposable binder and a fluororesin powder is dissolved and mixed in a solvent such as n-paraffin. Evaporates by heating and does not remain at the time of molding.

In view of the above situation, the present invention can make the thickness of a molded article made of polytetrafluoroethylene extremely thin, and the thickness of the coating material made of polytetrafluoroethylene can be made extremely thin. Provided is a method for manufacturing a covered electric wire.

The present invention includes a step of obtaining a molding composition by adding an organic solvent (A) having a surface energy of 16 to 20 mN / m to polytetrafluoroethylene fine powder, and compression molding the molding composition. And a step of obtaining a molded product.

The molded article preferably has a thickness of 100 μm or less.

The present invention also includes a step of obtaining a molding composition by adding an organic solvent (A) having a surface energy of 16 to 20 mN / m to polytetrafluoroethylene fine powder, and the molding composition by a paste extrusion molding method. And a step of forming a covering material by extruding onto the core wire to obtain a covered electric wire composed of the core wire and the covering material.

The covering material preferably has a thickness of 100 μm or less.

In the method for producing a molded article or a covered electric wire of the present invention, it is preferable to add 1 to 60 parts by mass of the organic solvent (A) with respect to 100 parts by mass of the molding composition to be obtained.

The organic solvent (A) is preferably at least one hydrocarbon solvent selected from the group consisting of normal hexane, normal pentane, and dimethylpolysiloxane.

The present invention is described in detail below.

In the method for producing a molded article and a covered electric wire according to the present invention, an organic solvent (A) having a surface energy of 16 to 20 mN / m is added to polytetrafluoroethylene fine powder (hereinafter also referred to as “PTFE fine powder”). Obtaining a composition for use.

Since the molding composition contains the organic solvent (A) and PTFE fine powder, the molded product obtained by the production method of the present invention and the covering material of the covered electric wire are uniform even if the thickness is reduced. Can be molded to a thickness. Moreover, when shaping | molding by the paste extrusion molding method, extrusion pressure can be made small. The organic solvent (A) is used as a so-called molding aid.

The method of adding the organic solvent (A) to the PTFE fine powder is not particularly limited, and examples thereof include a method of putting the PTFE fine powder into a container and then pouring the organic solvent (A) into the container. After adding the organic solvent (A) to the PTFE fine powder, it is also preferable to mix the PTFE fine powder and the organic solvent (A) by stirring or the like.

The organic solvent (A) has a surface energy of 16 to 20 mN / m. The surface energy of the organic solvent (A) is preferably 17 mN / m or more. Moreover, it is preferable that it is 19 mN / m or less.

The surface energy of the organic solvent (A) can be measured by a surface tension measurement method using a Dunui surface tension meter in accordance with JIS K2241.

The organic solvent (A) preferably has a boiling point of 50 ° C. or higher. Moreover, it is also preferable that it exceeds 50 degreeC.

Examples of the organic solvent (A) include hydrocarbon solvents. Among them, the organic solvent (A) is at least one carbonization selected from the group consisting of normal hexane, normal pentane, and dimethylpolysiloxane. A hydrogen solvent is preferred. The above compounds may be used alone or in combination. More preferably, the organic solvent (A) is normal hexane. Moreover, you may mix with the solvent which is not contained in the range whose surface energy is 16-20 mN / m.

In the manufacturing method of the molded article or the covered electric wire of the present invention, it is preferable to add the organic solvent (A) so as to be 1 to 60 parts by mass with respect to 100 parts by mass of the obtained molding composition. More preferably, it is 10-50 mass parts, More preferably, it is 20-40 mass parts.

The PTFE fine powder is made of polytetrafluoroethylene [PTFE]. The PTFE may be a tetrafluoroethylene homopolymer or a non-melt processable fluoropolymer [modified PTFE] obtained by polymerizing tetrafluoroethylene [TFE] and a trace amount of monomer. . Examples of the trace monomer include fluoroolefins such as hexafluoropropylene [HFP] and chlorotrifluoroethylene [CTFE], and fluoro having an alkyl group having 1 to 5 carbon atoms, particularly 1 to 3 carbon atoms. (Alkyl vinyl ether); fluorodioxole; perfluoroalkylethylene; ω-hydroperfluoroolefin and the like. By using the modified PTFE, the extrusion pressure can be reduced as compared with the case where a TFE homopolymer is used.

The modified PTFE preferably contains the trace monomer unit in an amount of 0.01 to 1% by mass with respect to the total of the TFE unit and the trace monomer unit. When there is too little content of the said trace monomer unit, there exists a possibility that the effect by trace monomer addition may not be acquired, and when too large, there exists a possibility that mechanical strength may fall. The more preferable lower limit of the content of the trace monomer unit is 0.03% by mass, and the more preferable upper limit is 0.2% by mass.

The PTFE preferably has a standard specific gravity [SSG] of 2.195 or less from the viewpoint of the mechanical strength of the obtained molded product. The more preferable lower limit of the SSG is 2.14, and the more preferable lower limit is 2.145, and the more preferable upper limit is 2.18 in terms of formability. The SSG is a value measured according to ASTM D 4895.

The PTFE fine powder preferably has an average particle size of 400 to 600 μm, more preferably 420 to 500 μm. If the average particle size is too large, a thin and uniform thickness may not be obtained, and if it is too small, the mechanical strength of the molded product may be deteriorated. In the present specification, the average particle diameter is measured in accordance with ASTM D 1457.

The PTFE fine powder is preferably a PTFE fine powder obtained by emulsion polymerization from the viewpoint that a thin molded product is obtained and molding is easy. That is, the method for producing a molded article of the present invention may include a step of polymerizing TFE by emulsion polymerization to obtain a PTFE fine powder.
The PTFE fine powder can be obtained, for example, by obtaining a PTFE aqueous dispersion by emulsion polymerization, collecting PTFE fine particles from the PTFE aqueous dispersion, aggregating them, and drying. The agglomeration can be performed by adding a coagulant to the PTFE aqueous dispersion and stirring, or by stirring the PTFE aqueous dispersion at a high speed without adding the aggregating agent. As the coagulant, nitric acid, hydrochloric acid, ammonium carbonate, alcohol and the like are preferable, and among them, ammonium carbonate is more preferable. The drying performed after the aggregation is not particularly limited, but is preferably performed at a temperature of 100 to 250 ° C, more preferably 130 to 200 ° C.

The PTFE fine powder preferably has an average primary particle size of 0.02 to 0.5 μm, a more preferable lower limit is 0.1 μm, and a more preferable upper limit is 0.3 μm. If the average primary particle size is too large, a thin and uniform thickness may not be obtained, and if it is too small, the mechanical strength of the molded product may be deteriorated.
In the present specification, the average primary particle size is defined as the following: PTFE aqueous dispersion in which PTFE primary particles obtained by emulsion polymerization are dispersed is prepared in a cell with a solid content concentration of 0.15% by mass, and 550 nm light is applied. The correlation between the transmittance at the time of incidence and the number average primary particle size calculated by measuring the unidirectional diameter with a transmission electron micrograph was collected in a calibration curve, and the obtained calibration curve and each sample were measured. It is a value obtained from the transmittance.

The molding composition contains an organic solvent (A) and PTFE fine powder. That is, the method for producing a molded article or a covered electric wire according to the present invention forms a molding composition containing an organic solvent (A) and PTFE fine powder.
Moreover, it is preferable that the manufacturing method of the molded article of this invention does not include the process of drying the organic solvent (A) before the process of obtaining a molded article after the process of obtaining a molding composition. Similarly, the method for producing a coated electric wire of the present invention preferably does not include a step of drying the organic solvent (A) after the step of obtaining the molding composition and before the step of obtaining the coated electric wire.

The molding composition may further contain a resin other than PTFE. That is, the method for producing a molded article or a covered electric wire according to the present invention may include a step of obtaining a molding composition by adding an organic solvent (A) to a mixture of PTFE fine powder and a resin other than PTFE. Good. Further, before the step of obtaining the molding composition, a step of mixing a PTFE fine powder and a resin other than PTFE to obtain a mixture of the PTFE fine powder and a resin other than PTFE may be included.

The molding composition may be prepared by adding a powder of resin other than PTFE to a dispersion of PTFE, and then obtaining a mixture of PTFE fine powder and powder of resin other than PTFE by coagulation or the like. A dispersion of resin other than PTFE may be added to the dispersion of PTFE, and then a mixture of PTFE fine powder and resin powder other than PTFE may be obtained by coagulation or the like.

Examples of the resin other than PTFE include TFE / HFP copolymer [FEP], TFE / perfluoro (alkyl vinyl ether) [PAVE] copolymer [PFA], ethylene / TFE copolymer [ETFE], and polybilylene. Examples thereof include niden fluoride [PVdF], polychlorotrifluoroethylene [PCTFE], polypropylene, and polyethylene.

As the above PAVE, in terms of thermal stability, perfluoro (methyl vinyl ether) [PMVE], perfluoro (ethyl vinyl ether) [PEVE], perfluoro (propyl vinyl ether) [PPVE], perfluoro (butyl vinyl ether) [ PBVE] is preferable, and PPVE is more preferable. Moreover, it may have one type of the PAVE unit, or may have two or more types.

In the present specification, the PAVE unit is a value obtained by performing infrared spectroscopic analysis in the range of characteristic absorption of 1040 to 890 cm ⁻¹ .

As the resin other than PTFE, a fluororesin that can be melt-processed is preferable in that it improves the heat resistance of the obtained molded product and enables stable use even at a relatively high temperature. As the melt-processable fluororesin, for example, at least one fluororesin selected from the group consisting of FEP, PFA, PVdF, and ETFE is preferable, and in particular, selected from the group consisting of FEP and PFA. At least one fluororesin is preferred. Examples of the PFA include a TFE / PMVE copolymer and a TFE / PPVE copolymer.

When the molding composition contains a resin other than PTFE, the molding composition has a PTFE fine powder of 40 wt% or more and less than 100 wt% with respect to the total mass of the PTFE fine powder and the resin other than PTFE. It is preferable that the resin other than PTFE is more than 0% by weight and 60% by weight or less. If the PTFE fine powder is less than 40% by weight, the resulting molded product may be inferior in heat resistance, chemical resistance, weather resistance, non-adhesiveness, electrical insulation, flame retardancy, and mechanical strength. The molding composition is more preferably 70% by weight or more of PTFE fine powder and 30% by weight or less of resin other than PTFE with respect to the total mass of PTFE fine powder and resin other than PTFE. .

The method for producing a molded article of the present invention includes a step of obtaining a molded article by compression-fibre-molding the molding composition. Compressed fiber molding is molding by compression and fiberization. The compression fiber forming is not particularly limited as long as it is a method of causing fiber formation by applying a compressive stress to the molding composition. For example, a paste extrusion molding method, a calender molding method, or a blade molding method is preferable. .
In the step of obtaining the molded article, the paste extrusion molding method, the calendar molding method, or the blade molding method can be molded without using a closed mold, and the molding composition is molded. Even if the thickness of the molded product obtained in this way is extremely thin, it can be made uniform. The method for producing a molded product of the present invention is preferably a method for obtaining a molded product by molding by a paste extrusion molding method from the viewpoint of obtaining a molded product such as a columnar shape or a tube shape.

In addition to the organic solvent (A) and the PTFE fine powder, the molding composition may contain additives such as an antioxidant, a light stabilizer, a fluorescent brightener, a colorant, a pigment, a dye, and a filler. Good. Examples of the additive include carbon black, graphite, alumina, mica, silicon carbide, boron nitride, titanium oxide, bismuth oxide, bronze, gold, silver, copper, nickel powder, fiber powder, and the like. In addition, polymer fine particles other than the above-described resin and other components may be added as long as the object of the present invention is not impaired.

With the paste extrusion molding method, an extrudate is placed in a cylinder having a cross-sectional shape such as a circle or a square, and is pressurized by a mechanical means such as a ram or a piston from normal pressure (natural pressure), This is a molding method in which a molded product is obtained by extruding from a die smaller than the cylinder cross-sectional area.

When the molding is performed by the paste extrusion molding method, the molding may be performed by heating. The heating temperature is preferably equal to or lower than the boiling point of the organic solvent (A), more preferably 10 ° C. or lower than the boiling point of the organic solvent (A). Specifically, the heating temperature is, for example, 30 to 70 ° C, preferably 30 to 60 ° C, and more preferably 40 to 50 ° C.
Conventionally, in paste extrusion molding, an extrusion aid having a low boiling point has not been used because the extrusion mold is heated to a relatively high temperature so that the resin can be softened and finely and stably extruded during extrusion. Even if the organic solvent (A) has a relatively low boiling point, the transpiration can be suppressed by making the temperature of the extrusion mold relatively low at a low temperature as in the above range.

The paste extrusion molding method is preferably performed at an extrusion pressure of 50 MPa or less. More preferably, it is 30 MPa or less, More preferably, it is 10 MPa or less. Although the minimum of extrusion pressure is not specifically limited, For example, it is 0.1 MPa. In the manufacturing method of the molded article or the covered electric wire of the present invention, it is preferable to mold at a lower extrusion pressure than a normal paste extrusion molding method.

The method for producing a molded article or a covered electric wire according to the present invention is obtained by preforming a composition obtained by adding an organic solvent (A) to PTFE fine powder to obtain a preformed article, and molding the preform by a paste extrusion molding method. It may be performed by doing.

Examples of the molded product obtained by molding by the paste extrusion molding method include a covering material for a covered electric wire, a tube, and the like.

The calendar forming method is a method of forming the molding composition by rolling with a calender roll, and the rolling is usually performed with two or more heated calender rolls. Thereby, it can shape | mold into the film-shaped or sheet-shaped molded object of desired thickness.
The calendar molding method can be performed with a conventionally known apparatus and molding conditions. For example, an apparatus for performing a calendar molding method includes a series type, an L type, an inverted L type, a Z type, and the like.
When the molding is performed by the calendar molding method, the molding may be performed by heating. The heating temperature is preferably equal to or lower than the boiling point of the organic solvent (A), more preferably 10 ° C. or lower than the boiling point of the organic solvent (A). Specifically, the heating temperature is, for example, 30 to 70 ° C, preferably 30 to 60 ° C, and more preferably 40 to 50 ° C.
As a molded product obtained by molding by a calendar molding method, for example, a sheet or a film is preferable. Examples of the sheet or film include a pipe seal tape, an apparel water-repellent breathable sheet, and the like.
That is, the present invention includes a step of obtaining a molding composition by adding an organic solvent (A) having a surface energy of 16 to 20 mN / m to polytetrafluoroethylene fine powder, and the molding composition by a calendar molding method. And a method for producing a sheet or film comprising molding and obtaining a sheet or film.

The blade molding method is a molding method generally referred to as blade molding. For example, a molding composition containing PTFE fine powder and an organic solvent (A) is applied to the surface of a substrate, and the blade and the base are formed. In this method, the molding composition is molded into a sheet by moving the substrate at the bottom of the blade by adjusting the gap with the material.
When molding by the blade molding method, the molding may be performed by heating. The heating temperature is preferably not higher than the boiling point of the organic solvent (A). More preferably, it is less than the boiling point of the organic solvent (A), and more preferably a temperature that is 10 ° C. or more lower than the boiling point of the organic solvent (A). Specifically, the heating temperature is, for example, 30 to 70 ° C, preferably 30 to 60 ° C, and more preferably 40 to 50 ° C. After forming into a sheet shape, the organic solvent (A) is evaporated to obtain a sheet-like molded product.
The blade is a blade-like component such as a doctor blade. The sheet-like molded product may be used after being peeled off from the base material, or may be a covering material that covers the base material.
Examples of the product having a base material and a sheet-like coating material include a printed board. The present invention includes a step of obtaining a molding composition by adding an organic solvent (A) having a surface energy of 16 to 20 mN / m to polytetrafluoroethylene fine powder, and the molding composition as a substrate for a printed circuit board. And a blade forming process to form a coating material for the printed circuit board.

In the method for producing a molded product according to the present invention, after molding, the resulting green molded product may be fired. The firing temperature preferably exceeds the melting point of the PTFE, more preferably 360 to 400 ° C, still more preferably 370 to 390 ° C.

When the molded product obtained by the production method of the present invention is a porous body, the molding composition preferably contains a resin other than PTFE, and the resin other than PTFE is a melt-processable fluororesin. More preferred.
In this case, after molding, the temperature at which the obtained unsintered molded product is fired is equal to or lower than the melting point of the PTFE and higher than the melting point of the resin having the lowest melting point among resins other than the PTFE. It is preferable that it is 280-320 degreeC, and it is still more preferable that it is 300-318 degreeC.

Since the PTFE is not melted by firing, it is soft at low density, and since the resin other than the PTFE is once melted and solidified, the obtained molded product has fine voids and excellent mechanical strength. It can be made into a porous molded body, a low dielectric constant molded body, a low dielectric loss tangent molded body, and the like, and can be particularly suitably used as a covering material for electric wires, cables and filters. This is because the resin other than PTFE is partially dissolved by firing within a specific temperature range, so that the resin other than PTFE enters the gap between the PTFEs and solidifies after cooling, thereby maintaining the cavity. This is probably because the strength can be increased.

The molded product obtained by the method for producing a molded product of the present invention preferably has a thickness of 100 μm or less. More preferably, it is 80 micrometers or less, More preferably, it is 50 micrometers or less. The lower limit of the thickness of the molded product is preferably 5 μm.
The molded product obtained by the production method of the present invention can be molded to a uniform thickness even if it is extremely thin as described above. This invention is also a molded article obtained by the manufacturing method of the said molded article.

Examples of the molded article obtained by the production method of the present invention include coating materials such as electric wires and cables, coating materials for printed boards, tubes, sheets, films such as biaxially stretched films, and the like. Moreover, the woven fabric, unemployed fabric, etc. which shape | mold by performing cylindrical form and a thread form extrusion are mentioned.
The manufacturing method of the present invention can make the thickness of PTFE extremely thin, and is particularly excellent as a manufacturing method of a thin-walled wire covering material, a thin-film tube, or a filter, which is called a thin or thin object.

The thickness is the thickness of the coating material when PTFE is used as a coating material for electric wires or cables, the thickness when used as a tube, the diameter when used as a cylindrical filter, and the thickness when used as a tube-shaped filter. One of them. The thickness can be determined by measuring the diameter of a wire or cable with a micrometer and dividing the measured value by subtracting the core wire diameter by 2. In the case of a tube, crush the tube. It can be obtained by measuring the thickness and dividing the measured value by 2.

Since the molded product obtained by the production method of the present invention can be reduced in thickness, it can be suitably used for tubes such as medical tubes, semiconductor tubes, insulating tubes, and heat exchange tubes. The said tube can be manufactured also by drawing out a core wire from the molded article with a core wire obtained similarly to the manufacturing method of the covered electric wire mentioned later.

When the molded product obtained by the production method of the present invention is a filter, for example, it can have a property of allowing air to pass but not allowing water to pass through, and for filter applications such as oxygen-enriched membranes and gas-liquid separation membranes. It can be used suitably.

As a method of using as a filter, it can be formed into a tube shape to use the filter action by flowing from the inside of the tube to the outside or vice versa, or it can be formed into a rod shape (columnar shape) and inserted into the tube to form a cylinder. For example, use of a filter action by a flow in a direction parallel to the center line can be mentioned.

The molded product obtained by the production method of the present invention is particularly suitable as a coating material for ultrafine electric wires, cables and the like because the thickness of the coating material containing PTFE can be reduced.
In the present invention, an organic solvent (A) having a surface energy of 16 to 20 mN / m is added to polytetrafluoroethylene fine powder to obtain a molding composition, and the molding composition is cored by a paste extrusion molding method. And a step of forming a covering material by extrusion onto a wire to obtain a covered electric wire made of a core wire and a covering material. The present invention is also a coated electric wire obtained by the method for producing a coated electric wire.

In the method for producing a covered electric wire, a preferred embodiment of the step of obtaining a molding composition is the same as the method for producing a molded product described above.

As a method of forming a coating material by extruding a molding composition onto a core wire by a paste extrusion molding method, a method of extruding through a mandrel of an extrusion molding machine through a core wire at the time of extrusion molding, drying as necessary, and further firing, etc. Can be mentioned.
When a copper wire is used as the core wire, a thin-walled coated electric wire is obtained, which is useful as an ultrafine coaxial cable, flat cable, motor coil wire, or transformer coil wire.

The covering material preferably has a thickness of 100 μm or less. More preferably, it is 80 micrometers or less, More preferably, it is 50 micrometers or less. The lower limit of the thickness of the covering material is preferably 5 μm.

Since the manufacturing method of the molded product of the present invention has the above-described configuration, the thickness of the molded product obtained can be extremely reduced when molding PTFE fine powder. Since the manufacturing method of the covered wire of the present invention consists of the above-mentioned composition, the thickness of the covering material of the obtained covered wire can be made very thin.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.
In each example and comparative example, each value was measured by the following method.

(Thickness of coating material)
The diameter of the electric wire was measured with a micrometer, and the value obtained by subtracting the core wire diameter from the measured value was divided by 2.

(Measurement of partial discharge start voltage)
The partial discharge start voltage was measured at a frequency of 100 kHz and a charge amount of 100 pC for the twist piece using a DAC-PD-3 manufactured by Soken Denki Co., Ltd.

Example 1
170 g of n-hexane (24% by weight with respect to the auxiliary powder mixture) was mixed with 500 g of Polyflon PTFE fine powder F-208H manufactured by Daikin Industries, Ltd., and left at 25 ° C. for 8 hours. This auxiliary powder mixture (molding composition) was preformed at 1 MPa using a preforming machine to prepare a preformed product, and this preformed product was inserted into the molding machine.

As the core wire, a 0.7 mm diameter annealed copper wire was used, and the inner diameter of the mold was 0.77 mm, resulting in a ReduceRatio 21800. ReductionRatio is the cross-sectional area ratio between the cylinder and the mold. Cylinder temperature shall be normal temperature (21-27 degreeC), and shall set the die front-end | tip to 40 degreeC which is a temperature 10 degreeC or more lower than the boiling point of extrusion adjuvant (n-hexane). Extrusion is started by setting the core wire to 25 m / min and the ram speed to 1.5 mm / min. A stable extrudate was obtained by setting the diameter immediately after extrusion to 0.77 to 0.80 mm.

The extrudate was passed through a dry cap stern of 30 m at a dry substance stroke of 70 ° C., drying oven 1 at 100 ° C., drying oven 2 at 180 ° C., drying oven 3 at 250 ° C., firing oven 1 at 330 ° C., firing oven 2 A fired product was obtained at 410 ° C., the firing furnace 3 at 410 ° C., and the firing furnace 4 at 380 ° C. The fired product had a diameter of 0.75 mm and a coating thickness on one side of 25 μm. Moreover, the partial discharge start voltage was 630V.

Example 2
Example 1 was repeated except that the inner diameter of the extrusion mold was 0.79 mm. The diameter of the fired product was 0.77 mm, and the coating thickness on one side was 35 μm. The partial discharge start voltage was 800V.

Comparative Example 1
A preform was produced under the same conditions as in Example 1 except that Isopar E, which is a hydrocarbon solvent, was used instead of n-hexane. Similar to Example 1, extrusion molding was performed with ReduceRatio 21800 using 0.7 mm diameter annealed copper wire and the inner diameter of the mold being 0.77 mm. could not.

The manufacturing method of the present invention requires the excellent properties of PTFE, and in fields where fine or thin materials are required, covering materials such as electric wires and cables, covering materials for printed boards, tubes, sheets, biaxial It can be suitably used as a method for producing a film such as a stretched film.

Claims (8)

A step of surface energy obtain molding compositions by the addition of only the organic solvent (A) of 16~20mN / m polytetrafluoroethylene fine powder as an organic solvent,
A step of compression molding the molding composition to obtain a molded product having a thickness of 100 μm or less;
The manufacturing method of the molded article characterized by including this. The method for producing a molded article according to claim 1, wherein the organic solvent (A) is at least one hydrocarbon solvent selected from the group consisting of normal hexane, normal pentane, and dimethylpolysiloxane. The manufacturing method of the molded article of Claim 1 or 2 which adds 1-60 mass parts organic solvent (A) with respect to 100 mass parts of molding compositions obtained. The method of manufacturing a molded product according to claim 1, 2 or 3, wherein the molded product has a thickness of 80 µm or less. A step of surface energy obtain molding compositions by the addition of only the organic solvent (A) of 16~20mN / m polytetrafluoroethylene fine powder as an organic solvent,
Extruding the molding composition onto a core wire by a paste extrusion molding method to form a coating material, and obtaining a coated electric wire comprising a core wire and a coating material having a thickness of 100 μm or less;
The manufacturing method of the covered electric wire characterized by including. The method for producing a coated electric wire according to claim 5, wherein the organic solvent (A) is at least one hydrocarbon solvent selected from the group consisting of normal hexane, normal pentane, and dimethylpolysiloxane. The manufacturing method of the covered electric wire of Claim 5 or 6 which adds 1-60 mass parts organic solvent (A) with respect to 100 mass parts of molding compositions obtained. The method for manufacturing a covered electric wire according to claim 5, 6 or 7, wherein the covering material has a thickness of 80 µm or less.