JPH09245526A - Heat resistant insulation composition and wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat resistant insulation composition which simultaneously has both superior mechanical strength and superior heat resistance exceeding 200 deg.C, and provide a wire which is equipped with the composition as a coat layer. SOLUTION: A heat resistant insulation composition is formed by mixing tetrafluoroethylene micro powder of two parts by weight or more and less than ten parts by weight into a copolymer mainly composed of ethylene and tetrafluoroethylene of 100 parts by weight, and crosslinking. Or, the same is formed by crosslinking the copolymer mainly composed of the ethylene and the tetrafluoroethylene of 80 percentage by weight or more and less than 98 percentage by weight, and a fluoropolymer mixture made of vinylidene fluoride fluoro-rubber of two percentage by weight or more and less than 20 percentage by weight. Or, the same is formed by mixing the tetrafluoroethylene micro powder of two parts by weight or more and less than ten parts by weight into the copolymer mainly composed of the ethylene and the tetrafluoroethylene of 80 parts by weight or more and less than 98 percentage by weight and 100 parts by weight of the fluoropolymer mixture made of the vinylidene fluoride fluoro-rubber of two percentage by weight or more and less than 20 percentage by weight, and crosslinking. A wire is equipped with a coat layer made of the heat resistant insulation composition.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a heat-resistant insulating composition having both excellent mechanical strength and excellent heat resistance of over 200 ° C., and a coating layer made of this composition. The present invention relates to an electric wire that is preferably used in automobiles, aircraft, thermal equipment and the like.

[0002]

2. Description of the Related Art Conventionally, an ethylene-tetrafluoroethylene binary copolymer capable of being crosslinked by radiation such as an electron beam has been used as an insulating material for electric wiring used in applications where heat resistance is particularly required. Although a crosslinked product of (ETFE) has been used, various studies have been made to improve the properties of the ETFE crosslinked product accordingly. For example, in JP-A-59-100141, JP-A-7-14431, JP-A-7-14667, etc., rubber having excellent heat resistance (for example, fluororubber) is mixed with ETFE,
A method for improving the heat resistance of the ETFE crosslinked body by crosslinking is disclosed.

[0003]

However, in the heat resistance improving technique as described above, the mechanical strength, which is the most excellent feature of ETFE, is largely sacrificed, and 200 ° C. is maintained without impairing the mechanical strength. It has been difficult to obtain excellent heat resistance exceeding the above.

The present invention has been made on the basis of the above points, and an object thereof is to provide a heat-resistant insulating composition having both excellent mechanical strength and excellent heat resistance exceeding 200 ° C. An object of the present invention is to provide an electric wire having a coating layer made of this composition.

[0005]

To achieve the above object, the heat-resistant insulating composition according to claim 1 of the present invention is a copolymer 10 mainly composed of ethylene and tetrafluoroethylene.
It is a composition obtained by mixing 2 parts by weight or more and 10 parts by weight or less of tetrafluoroethylene micropowder with respect to 0 part by weight and crosslinking the mixture.

The heat-resistant insulating composition according to claim 2 of the present invention comprises a copolymer mainly composed of ethylene and tetrafluoroethylene in an amount of 80% by weight or more and 98% by weight or less, and a vinylidene fluoride-based fluororubber of 2% by weight or more 20% by weight or more. It is a composition obtained by cross-linking a fluoropolymer mixture of not more than wt%.

The heat-resistant insulating composition according to claim 3 of the present invention comprises a copolymer mainly composed of ethylene and tetrafluoroethylene in an amount of 80% by weight or more and 98% by weight or less and a vinylidene fluoride-based fluororubber of 2% by weight or more 20% by weight or more. It is a composition obtained by mixing 2 parts by weight or more and 10 parts by weight or less of tetrafluoroethylene micropowder with 100 parts by weight of a fluoropolymer mixture containing 1% by weight or less and crosslinking the mixture.

An electric wire according to a fourth aspect of the present invention is provided with a coating layer made of the above heat resistant insulating composition.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Known copolymers mainly composed of ethylene and tetrafluoroethylene include binary copolymers having various polymerization ratios and multipolymers copolymerized with other fluorine-containing monomers. It is. In the present invention, in order to improve the heat resistance of the obtained composition, preferably,
A copolymer having a fluorine content of 55% by weight or more and 70% by weight or less, more preferably 60% by weight or more and 70% by weight or less is used. If the fluorine content is less than 55% by weight, the desired sufficient heat resistance cannot be obtained, and if it exceeds 70% by weight, the mechanical strength of the obtained composition is remarkably reduced. .

Tetrafluoroethylene micropowder is mainly used to improve the heat resistance of the resulting composition,
As a secondary purpose, it is used to improve mechanical strength (in particular, abrasion resistance). In claim 1, 100 parts by weight of a copolymer mainly composed of ethylene and tetrafluoroethylene is added. On the other hand, 2 parts by weight or more and 10 parts by weight or less are mixed. Further, in claim 3, 2 parts by weight or more and 10 parts by weight or more per 100 parts by weight of a fluoropolymer mixture comprising a copolymer mainly composed of ethylene and tetrafluoroethylene and a vinylidene fluoride-based fluororubber described later. Mixed below. If it is less than 2 parts by weight, the effect of improving heat resistance will not be exhibited, and if it exceeds 10 parts by weight, the mechanical strength (especially elongation) and the extrudability of the obtained composition will be deteriorated.

Examples of the tetrafluoroethylene micropowder include fine particles of low molecular weight polytetrafluoroethylene. Although various particle sizes are known,
In the present invention, preferably, the average particle diameter is 50 μm
Hereinafter, more preferably, fine particles of low molecular weight polytetrafluoroethylene having a size of 0.1 μm or more and 20 μm or less are used. Those having an average particle size of more than 50 μm do not uniformly disperse in a copolymer or fluoropolymer mixture mainly composed of ethylene and tetrafluoroethylene, and the kneading work becomes extremely difficult. Average particle size is 0.1 μm or more 2
If it is 0 μm or less, it is uniformly dispersed in a copolymer or fluoropolymer mixture mainly composed of ethylene and tetrafluoroethylene to facilitate the kneading work, and the mechanical strength of the resulting composition is remarkably improved. Therefore, it is particularly preferable.

The vinylidene fluoride-based fluororubber is used to reduce the deformation of the resulting composition at high temperatures. In claim 2 or 3, 2% by weight of the total fluoropolymer mixture is used. It is mixed so as to be 20% by weight or less. If it is less than 2% by weight, the effect of reducing the deformation at high temperature is not sufficiently exhibited, and if it is 20% by weight.
If it exceeds, the mechanical strength (particularly, abrasion resistance) of the obtained composition will decrease.

As the vinylidene fluoride type fluororubber,
Vinylidene fluoride-propylene hexafluoride binary copolymer,
Vinylidene fluoride-tetrafluoroethylene-propylene hexafluoride terpolymer and the like are known. Any material may be used as long as it reduces the deformation at high temperature, but in the present invention, the main purpose is to improve the heat resistance of the resulting composition, and therefore, the fluorine content is preferably 60% by weight. % Or more, and more preferably 65% by weight or more. With a vinylidene fluoride-based fluororubber having a fluorine content of less than 60% by weight, the desired sufficient heat resistance cannot be obtained.

In the present invention, in addition to the above components,
Various conventionally known additives such as a crosslinking assistant, a filler, and a pigment can be appropriately compounded as necessary.

Taking the case of crosslinking by electron beam irradiation as an example, the crosslinking aid is used to obtain a desired crosslinking density with a smaller irradiation dose. For example, triallyl isocyanurate and triary. Allyl ethers such as lucyanurate, diallyl phthalate, trimethallyl cyanurate, triallyl phthalate, tri (meth) acrylic isocyanurate, tri (meth) acrylic cyanurate, tetramethylolpropane tetra (meth) acrylate, maltose penta (meth) (Meth) acrylic esters such as acrylate, N, N '-(4,4'-
Diimides such as (diphenylmethane) bismaleimide; In addition to these, allyl ether,
There are many known ones in which the molecular structure of the portion other than the (meth) acrylic ester or imide group is devised. The blending amount is not particularly limited because it varies depending on the structure of the crosslinking aid, but when a typical triallyl isocyanurate is used, it is preferably in the range of 0.1 to 4 parts by weight. If the amount is less than 0.1 part by weight, the effect of the crosslinking aid will not be exhibited, and if it exceeds 4 parts by weight, foaming tends to occur during processing.

As the other additives such as fillers and pigments, those which do not cause decomposition or foaming at a processing temperature of 200 ° C. to 400 ° C. are appropriately used.

The above-mentioned constituent materials are melt-kneaded by a known melt-kneader such as an internal mixer, a uniaxial kneader or a biaxial kneader to produce a composition. At this time, each constituent material may be mixed at once, but for example, tetrafluoroethylene micropowder and vinylidene fluoride fluororubber are first mixed and pelletized, and then ethylene and tetrafluoroethylene are the main constituents. Multi-stage mixing may be performed, such as mixing with pellets of the copolymer.

By cross-linking the obtained composition,
The heat resistant insulating composition of the present invention is completed. The crosslinking method is not particularly limited, but radiation crosslinking is preferred. Here, radiation means X-rays, γ-rays, electron beams, proton rays, deuteron rays, α rays,
The term β ray or the like is used, but an electron beam or γ ray is preferably used.
Furthermore, it is preferable to use an electron beam that facilitates radiation control.

[0019]

EXAMPLES Examples of the present invention will be described below together with comparative examples. Details of each compounding material used in this example are as shown in Table 3.

The compounding materials shown in Tables 1 and 2 were sufficiently kneaded with a twin-screw kneader, and the obtained composition was pelletized, and then fed to a 30 mmφ extruder with L / D = 24 to form a cylinder. Under the temperature conditions of 260 ° C. and head 280 ° C., 19 pieces of tin-plated annealed copper wires having a wire diameter of 0.18 mm were twisted together and extrusion-coated with a thickness of 0.25 mm on the circumference of a conductor having an outer diameter of 0.9 mm. After that, pressurization voltage 800kv, irradiation dose 10
Irradiate with an electron beam under the condition of 0 kGy and finish outer diameter 1.4 mm
A cross-linked electric wire was manufactured.

A total of 15 types of crosslinked electric wires (Examples 1 to 10 and Comparative Examples 1 to 5) thus obtained were used as samples, and mechanical strength (tensile strength and elongation, abrasion resistance) was measured. ), Heat resistance 1 (residual tensile strength and residual elongation), and extrudability. Table 1 shows the results
And also shown in Table 2.

The evaluation method is as follows. Mechanical strength Tensile strength and elongation were measured in accordance with JIS C 3005 (1986). Heat resistant 200 ° C tetrafluoroethylene-hexafluoropropylene copolymer (FEP)
The tensile strength is 20 MPa or more and the elongation is 20
0% or more was regarded as a pass line. Wear resistance is JASO
The minimum abrasion resistance was measured according to the blade reciprocation method (load amount 510 g) of the abrasion resistance test of D608-92. Assuming that the edge was touched during wiring, 150 times or more was taken as a pass line.

Heat resistance 1 After being left for 96 hours in a constant temperature bath maintained at 250 ° C., it was taken out, and according to JIS C 3005 (1986),
The residual tensile strength and residual elongation were measured. Based on the standard values of the fluororesin mixture described in Appended Table 1, Appendix 14 "Tensile Strength and Elongation Test" of the Electrical Appliance and Material Control Law Technical Standard, the residual tensile strength ratio is 80% or more and the residual elongation ratio is 80%. % Or more was regarded as a pass line.

Extrusion processability The external appearance of each sample was visually confirmed, and those having irregularities on the surface were indicated as "poor".

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

[Table 3]

As is clear from Tables 1 and 2, the crosslinked electric wires (Examples 1 to 10) provided with the composition according to the present invention as the coating layer were all mechanical strength: tensile strength 20 MPa. Above, elongation 200% or more, abrasion resistance 150
Times or more, heat resistance: tensile strength residual rate 80% or more, elongation residual rate 8
It has passed the pass line of 0% or more, and has a high level of mechanical strength and heat resistance. No abnormalities were observed in the extrusion processability.

On the other hand, Comparative Example 1 (ETF containing no tetrafluoroethylene micropowder)
E crosslinked product) is inferior in heat resistance (tensile strength residual ratio),
On the other hand, in Comparative Example 2 in which the tetrafluoroethylene micropowder is mixed but the weight ratio exceeds the upper limit value (10 parts by weight or less) of the preferred range of the present invention, the mechanical strength (elongation) and the extrudability are excellent. Inferior

Comparative Example 3 is an example in which a vinylidene fluoride fluororubber (vinylidene fluoride-6-fluorinated propylene-4 fluoride ethylene terpolymer) is mixed in place of the tetrafluoroethylene micropowder. However, the weight ratio is the upper limit of the preferred range of the present invention (20% by weight).
The mechanical strength (wear resistance) is inferior. Comparative Examples 4 and 5 are examples of a mixture of tetrafluoroethylene micropowder and vinylidene fluoride-based fluororubber (vinylidene fluoride-6-fluorinated propylene-4 fluoride ethylene terpolymer). Since the weight ratio of the tetrafluoroethylene micropowder exceeds the upper limit value (10 parts by weight or less) of the preferred range of the present invention, mechanical strength (elongation) and extrusion processability are poor.

Comparative Example 6 is an example in which the type (particle size) of the tetrafluoroethylene micropowder in Example 1 was changed, but the average particle size was below the upper limit (50 μm or less) of the preferred range of the present invention. Since it exceeds the limit, tetrafluoroethylene micropowder is a copolymer mainly composed of ethylene and tetrafluoroethylene (ETFE)
An electric wire could not be manufactured because it was not uniformly dispersed in the inside and the kneading work became extremely difficult.

Further, in this example, in order to clarify the effect of the present invention, the crosslinked electric wires of Example 1, Example 2, Example 3, Example 8, Example 9 and Comparative Example 1 were used as samples. The heat resistance 2 (the number of days when the residual withstand voltage is less than 50%) was evaluated. Further, the heat-deformability (heat-deformation rate) was evaluated using the crosslinked electric wires of Example 4, Example 5, Example 6, Comparative Example 1, and Comparative Example 3 as samples. The results are shown in Tables 1 and 2.

The evaluation method is as follows. Heat resistance 2 Peel off the insulator (coating layer) of about 10 mm on both ends of the sample cut to a length of about 200 mm, twist the conductors into each other, leave this in a constant temperature bath kept at 250 ° C, and then take it out. A withstand voltage test (measurement of dielectric breakdown voltage) was performed. Then, the number of days when the residual withstand voltage was less than 50% was measured. The dielectric breakdown voltage is increased by immersing the insulator (coating layer) in water, applying an AC voltage having a waveform close to a sine wave of 60 Hz between the conductor and the ground, and increasing the speed at 500 v / sec. The voltage when the (layer) broke was measured.
4 based on the actual value of the conventional crosslinked product (ETFE crosslinked product)
More than one day was taken as the passing line.

According to UL 1581 heat deformability , test temperature 250 ° C., test load 5
The heating deformation rate was measured under the condition of 00 g. Based on the actual value of the conventional crosslinked product (ETFE crosslinked product), 40% or less was set as the acceptance line.

As is clear from Tables 1 and 2, regarding the heat resistance, all the crosslinked electric wires (Examples 1, 2, 3, 8, 9) provided with the composition according to the present invention as the coating layer were used. , It has passed the passing line that the remaining withstand voltage is less than 50% in 4 days or more. Regarding the heat deformability, all of the crosslinked electric wires (Example 4, Example 5 and Example 6) provided with the composition according to the present invention as a coating layer had a heat deformation rate of 40% or less in a pass line. Has cleared.

On the other hand, in Comparative Example 1 in which tetrafluoroethylene micropowder and vinylidene fluoride fluororubber (vinylidene fluoride-6-propylene propylene-4 fluoride ethylene terpolymer) were not mixed at all. Inferior in heat resistance and heat deformability. Incidentally, Comparative Example 3
Vinylidene fluoride fluororubber (vinylidene fluoride-6
Since it is mixed with fluorinated propylene-4 fluorinated ethylene terpolymer), it is excellent in heat deformability, but its weight ratio is the upper limit (20% by weight) of the preferred range of the present invention.
As described above, the mechanical strength (wear resistance) is inferior.

[0037]

As described in detail above, the composition of the present invention comprises:
It has both excellent mechanical strength and excellent heat resistance exceeding 200 ° C. Therefore, it is suitable as a coating material for electric wires used in, for example, automobiles, aircrafts, and thermal equipment.

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Claims (4)

[Claims] 1. A heat-resistant insulating composition obtained by mixing 2 parts by weight or more and 10 parts by weight or less of tetrafluoroethylene micropowder with 100 parts by weight of a copolymer composed mainly of ethylene and tetrafluoroethylene and crosslinking the mixture. . 2. A fluoropolymer mixture comprising 80% by weight or more and 98% by weight or less of a copolymer mainly composed of ethylene and tetrafluoroethylene and 2% by weight or more and 20% by weight or less of vinylidene fluoride fluororubber is crosslinked. Heat resistant insulating composition. 3. 100 parts by weight of a fluoropolymer mixture comprising 80% by weight or more and 98% by weight or less of a copolymer mainly composed of ethylene and tetrafluoroethylene and 2% by weight or more and 20% by weight or less of vinylidene fluoride fluororubber. On the other hand, a heat-resistant insulating composition obtained by mixing 2 parts by weight or more and 10 parts by weight or less of tetrafluoroethylene micropowder and crosslinking the mixture. 4. An electric wire provided with a coating layer made of the heat-resistant insulating composition according to claim 1, claim 2, or claim 3.