JPH11323053A - Fluororesin composition, insulating tube, heat shrinkable tube and insulating electric wire all using the composition, and their production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fluororesin composition excellent in insulating property, heat resistance and esp. excellent in oil resistance to lubricating oil containing an amino-type additive and capable of forming an insulated tube and an insulated electric wire both having high flexibility, and to provide an insulated tube and an insulated electric wire both using the composition and to provide a method for producing the tube and the electric wire. SOLUTION: This fluororesin composition contains (A) a copoly(tetrafluoroethylene/propylene)-based fluororubber and (B) a crystalline polymer obtained by copolymerizing 30-50 mol.% vinylidene fluoride, 30-50 mol.% tetrafluoroethylene and 10-30 mol.% hexafluoropropylene in a weight ratio (A:B) of (90:10)-(50:50). This heat shrinkable tube is produced by extrusion molding of the above fluororesin composition into a tube, by crosslinking the tube through ionizing radiation and by expanding the tube with heat in the radial direction, followed by refrigeration. This insulated electric wire is produced by covering a conductor with the above fluororesin composition and by crosslinking it through ionizing radiation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluororesin composition excellent in flexibility, heat resistance and oil resistance suitable for automobile harnesses and the like, and insulated tubes, heat-shrinkable tubes, insulated wires and the like using the same. And a method for producing the same.

[0002]

2. Description of the Related Art Insulating compositions such as insulated wires used for harnesses and the like in engine rooms of automobiles, and insulating tubes used for bundling of insulated wires and insulating protection at connection portions, are required to have a high rating of 200 ° C or higher. Heat resistance and oil resistance to various lubricating oils such as engine oil and automatic transmission fluid are required,
Excellent flexibility is also required from the viewpoint of maneuverability of the harness.

Conventionally, various insulating materials have been studied to satisfy such demands. Among them, vinylidene fluoride-based fluororubber and tetrafluoroethylene-
If a propylene-based fluororubber is used, a tube excellent in heat resistance, oil resistance and flexibility as well as excellent in insulation can be obtained. For this reason, the use amount of fluororubber has increased in recent years.

[0004] Further, the fluoro rubber is coated with a conductor to a predetermined thickness by an extruder or the like, and then irradiated with an ionizing radiation such as an accelerated electron beam, or a vulcanizing agent such as a peroxide is blended in advance. Crosslinking by a method such as steam vulcanization can also be used as an insulated wire.

On the other hand, the heat-shrinkable tube is formed, for example, by extruding polyethylene or the like into a tube, cross-linking the tube by irradiating an accelerated electron beam, and then feeding compressed air into the tube under heating conditions. It is manufactured by a method of expanding in the radial direction, cooling immediately, and fixing the expanded shape.

However, since fluororubber is an amorphous polymer, even if a heat-shrinkable tube is to be manufactured by the same method as described above, that is, even if a cross-linked tubular molded product is expanded by the same method, The expanded shape cannot be maintained, and soon contracts to the original shape.

[0007]

Therefore, generally, a heat-shrinkable tube is manufactured using a fluororubber blended with a polymer having crystallinity.

Examples of the crystalline polymer include polyvinylidene fluoride (PVDF), ethylene-tetrafluoroethylene copolymer (E / TFE), and ethylene-tetrafluoroethylene-fluoroolefin copolymer. JP-A-63-283929, JP-A-2-283432 and JP-A-2-2834.
No. 33 discloses a heat-shrinkable tube using a material obtained by blending the above-mentioned crystalline polymer with tetrafluoroethylene-propylene-based fluororubber.

On the other hand, with the recent improvement in the performance of automobiles, studies have also been made on improving the performance of lubricating oils. For example, the use of automatic transmission fluids and the like blended with amine-based additives has been particularly increasing in recent years. ing.

However, a fluororubber heat-shrinkable tube using polyvinylidene fluoride (PVDF) as a crystalline polymer has a problem in that the oil resistance of the heat-shrinkable tube is reduced due to poor resistance to amine-based additives.

On the other hand, a fluororubber heat-shrinkable tube using an ethylene-tetrafluoroethylene copolymer (E / TFE) or an ethylene-tetrafluoroethylene-fluoroolefin copolymer as a crystalline polymer has an amine-based additive. There is no problem that the oil resistance is reduced even with a lubricating oil blended with an agent.

However, since the crystalline melting point of the copolymer is as high as 220 to 270 ° C., the heat shrinkage is required to be 220 to 250 ° C. in the case of the above-mentioned publication and 300 ° C. in some cases.
There is a drawback in that a very high temperature is required and workability of heat shrinkage is poor.

Therefore, an object of the present invention is to provide insulation, heat resistance,
And a fluororesin composition which is excellent in oil resistance to lubricating oil containing especially an amine-based additive and can obtain highly flexible insulated tubes and insulated wires, and insulated tubes, insulated wires and the production thereof using the same. Is to provide a method and.

Another object of the present invention is to perform heat shrinkage work at a low temperature, which is excellent in insulation, heat resistance, and especially oil resistance to a lubricating oil containing an amine-based additive. And a method for manufacturing the same.

[0015]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, a tetrafluoroethylene-propylene copolymer-based fluororubber (A) has been obtained.
A crystalline polymer (B) obtained by copolymerizing 30 to 50 mol% of vinylidene fluoride, 30 to 50 mol% of tetrafluoroethylene, and 10 to 30 mol% of hexafluoropropylene was used in a weight ratio A: B = 90: A fluororesin composition characterized in that it is contained in a ratio of 10 to 50:50,
The new fact that it has excellent insulation properties, heat resistance and oil resistance to lubricating oils containing amine-based additives, as well as a highly flexible insulating tube and excellent workability during heat shrinkage. As a result, the present invention has been completed.

According to the fluororesin composition of the present invention,
In applications where not only high insulation and heat resistance are required, but also excellent oil resistance to lubricating oils containing amine-based additives and high flexibility are required, insulation coating on insulated wires, insulation It can be suitably used as an insulating tube or the like used for bundling and protecting insulation at a connection part.
Further, since the crystal melting point is low, the heat shrinkage temperature can be lowered, and the workability of the heat shrink tube becomes excellent. Therefore, the fluororesin composition of the present invention is also suitable for heat shrinkable tubes.

[0017] The insulating tube and the heat-shrinkable tube of the present invention are characterized by comprising a crosslinked product of the fluororesin composition of the present invention.

In the method for producing a heat-shrinkable tube of the present invention, the fluororesin composition of the present invention is extruded into a tube, irradiated with ionizing radiation, crosslinked, expanded radially under heating, and then expanded. It is characterized by cooling and fixing the shape. According to the method for manufacturing such a heat-shrinkable tube,
Since the heat shrinking operation can be performed at a low temperature, the workability of the heat shrinkage is improved, and the heat shrinkable tube can be manufactured efficiently.

The insulated wire of the present invention is characterized in that a covering layer made of a crosslinked body of the fluororesin composition of the present invention is provided on a conductor.

The method for producing an insulated wire of the present invention is characterized in that a conductor is coated with the fluororesin composition of the present invention, and the conductor is crosslinked by irradiation with ionizing radiation. According to the method for manufacturing an insulated wire, the insulated wire can be efficiently manufactured.

[0021]

First, the fluororesin composition of the present invention will be described in detail.

The tetrafluoroethylene (T) in the tetrafluoroethylene-propylene copolymer fluororubber (hereinafter referred to as "fluororubber (A)") used in the present invention.
Copolymerization ratio of EF) and propylene (P) (TEF: P)
Is not particularly limited, but in a molar ratio of 90:10 to 40: 6
It is preferably 0.

As a commercially available product, for example, trade name “Afras 150” (trade name, manufactured by Nippon Synthetic Rubber Co., Ltd.)
F: P) = 55: 45].
00 "(TFE / P / fluoromonomer copolymer).

Generally, tetrafluoroethylene-propylene copolymer-based fluororubber is inferior to vinylidene fluoride-based fluororubber, so-called FKM, in properties such as mechanical strength in a low-temperature range (so-called low-temperature properties). On the other hand, a product obtained by copolymerizing a tetrafluoroethylene-propylene copolymer with another fluorine-based monomer as a third component to improve low-temperature properties is also commercially available, but in this case, a lubricant blended with an amine-based additive is used. There arises a problem that oil resistance to oil is reduced. Therefore, in the fluororesin composition of the present invention, for the purpose of improving low-temperature properties, within the range not impairing the oil resistance of the fluororesin composition, a fluororubber copolymerized with the third component may be used. Good.

The copolymer of 30 to 50 mol% of vinylidene fluoride (VF), 30 to 50 mol% of tetrafluoroethylene (TFE) and 10 to 30 mol% of hexafluoropropylene (HFP) used in the present invention. Examples of the crystalline polymer (hereinafter referred to as “crystalline polymer (B)”) include, for example, a product name “TH” manufactured by Sumitomo 3M Limited.
V200 "[crystal melting point 124 ° C (scanning differential thermal analysis (D
SC)), heat of fusion -5.4 J / g].

This crystalline polymer (B) [VF / TFE
/ HFP] has the same structure as that of FMK. However, since the copolymerization ratio of tetrafluoroethylene (TFE) is higher than that of FMK, the polymer is not amorphous but has crystallinity unlike FMK.

In the measurement of the crystalline polymer (B) by DSC, an endothermic peak accompanying the crystal melting was observed at about 100 to 130 ° C., and the heat of fusion was about -5 to −20 J / g.
It is. The presence of the crystal component can be confirmed by this measurement, but such a crystal component is used in the production of a heat-shrinkable tube.
It is responsible for fixing the expanded shape.

[0028] Vinylidene fluoride (VF), tetrafluoroethylene (TFE) and hexafluoropropylene (H
Regarding the crystalline polymer copolymerized with FP), the copolymerization composition ratio is different. For example, a copolymer obtained by copolymerizing about 20 mol% of VF, about 60 mol% of TFE, and about 20 mol% of HFP [THV500G (trade name, manufactured by Sumitomo 3M Limited) (crystal melting point: 168 ° C, DSC: -10.9 J /
g)], a copolymer of about 70 mol% of VF, about 20 mol% of TFE, and about 10 mol% of HFP [trade name "Kyner 9300" (manufactured by Mitsubishi Chemical Corporation, DSC measurement) Melting point 91.2 ° C, heat of fusion -0.9 J / g)]
Are also commercially available.

However, using a material obtained by mixing the former crystalline polymer (the content of VF is less than 30 mol% and the content of TFE exceeds 50 mol%) with fluororubber (A) In the case of producing a tubular molded product, crosslinking by irradiation with ionizing radiation such as an accelerated electron beam does not proceed well. For example, when heat aging in a 260 ° C. gear oven for 96 hours, the original shape cannot be maintained. Problems arise. In addition, when an insulating tube or the like is produced by molding a fluororesin composition into a tube shape, there is also a problem that the appearance of the molded product is deteriorated due to low extrusion processability.

Conversely, the latter crystalline polymer (the content of VF exceeds 50 mol% and the content of TFE is 30
Mol%) and a material obtained by mixing a fluororubber (A) and a tube-shaped molded product, the cross-linking by irradiation with ionizing radiation proceeds without any problem.
There is a problem that oil resistance to lubricating oil containing an amine-based additive is significantly reduced.

On the other hand, if the content of hexafluoropropylene (HFP) in the crystalline polymer (B) is less than 10 mol%, the flexibility may be reduced. vice versa,
If the content of HFP exceeds 30 mol%, the heat aging resistance may decrease.

Accordingly, the copolymerization ratio of each component of the crystalline polymer (B) in the present invention is determined by the ratio of vinylidene fluoride (V
F) in an amount of 30 to 50 mol%, tetrafluoroethylene (T
FE) is set in the range of 30 to 50 mol% and hexafluoropropylene (HFP) is set in the range of 10 to 30 mol%.

The mixing ratio of the fluororubber (A) and the crystalline polymer (B) in the fluororesin composition of the present invention can be set at any ratio.

However, when the fluororesin composition of the present invention is used for a heat-shrinkable tube, it is preferable that the ratio of the crystalline polymer (B) is higher from the viewpoint of enhancing the stability of the expanded shape. Conversely, from the viewpoint of increasing the flexibility of the tube, it is preferable that the ratio of the crystalline polymer (B) is low.

Therefore, the ratio A: B of the fluororubber (A) to the crystalline polymer (B) in the fluororesin composition of the present invention is determined by the draw-down ratio D at the time of heat-shrinkable tube molding described later.
A: B = 90: 10-5 by weight ratio in consideration of DR and the occurrence of melt fracture during the production of insulated wires.
It is set in the range of 0:50. The ratio A: B is more preferably 80:20 to 70:30 in this range.

The fluororesin composition of the present invention comprises a vulcanization accelerator, an acid acceptor, a stabilizer, a lubricant, a colorant, a flame retardant, a foaming agent,
Conventionally known various compounding agents such as reinforcing agents, if necessary,
Further, it can be arbitrarily compounded within a range that does not impair the properties of the fluororesin composition of the present invention.

Next, the heat-shrinkable tube of the present invention and the method of manufacturing the same will be described in detail.

The heat-shrinkable tube of the present invention comprises a crosslinked product of the above-mentioned fluororesin composition of the present invention. The fluororesin composition is formed into a tube and crosslinked by irradiation of ionizing radiation or the like. Obtained by:

Fluororubber (A) and crystalline polymer (B)
Can be performed using a conventionally known mixing apparatus such as an open roll mixer, a Banbury mixer, a pressure kneader, and a Henschel mixer. The temperature at which the two are mixed is 1 point below the melting point of the crystalline polymer (B).
The temperature may be set to a high temperature of 0 ° C. or higher, preferably 50 ° C. or higher. The fluororesin composition of the present invention, which is a mixture of both, from the viewpoint of workability when molding a heat-shrinkable tube,
For example, it is preferable to form a pellet using a conventionally known pelletizing apparatus such as a feeder ruder.

Next, the obtained pellets are put into a hopper of a conventionally known plastic extruder or the like, melt-molded into a tube, and then crosslinked by a method such as irradiation with ionizing radiation. As the ionizing radiation, an accelerating electron beam or the like can be used. The crosslinked tube thus obtained is expanded in the radial direction by using a method such as blowing compressed air into the tube under heating, and the expanded shape is immediately cooled and solidified by a method such as water cooling. A shrink tube can be obtained.

Fluororubber (A) and crystalline polymer (B)
With respect to the molding of a tube using a tubing die using a fluororesin composition containing a mixture of the above, there is a problem that the appearance of the extruded tube depends on the mixing ratio of the fluororubber (A) and the crystalline polymer (B). is there. For example, when the weight ratio A: B of the fluororubber (A) to the crystalline polymer (B) is in the range of 10:90 to 50:50, the following formula:

[0042]

(Equation 1) Under the extrusion conditions having a low drawdown ratio (DDR), a tube having a relatively good appearance can be obtained. However, when A: B exceeds 50:50 and the ratio of A increases, a tube with good appearance cannot be obtained unless the value of the withdrawal rate DDR is increased.
This tendency becomes more remarkable as the extrusion linear speed is increased from the viewpoint of increasing productivity.

On the other hand, when the heat-shrinkable tube is manufactured by extruding the tube while setting the draw-down ratio DDR to a large value, not only the tube shrinks not only in the radial direction but also in the longitudinal direction of the tube when the heat-shrinkable tube shrinks. To become
Not preferred. In general, it is preferable that the shrinkage ratio in the longitudinal direction of the heat-shrinkable tube is within 5%.

In consideration of this point, in the heat-shrinkable tube of the present invention, the weight ratio of A: B in the fluororesin composition is adjusted so that a tube having a good appearance can be produced even under extrusion conditions with a low draw-down ratio DDR. Is 10: 90-5
It is set in the range of 0:50. The above range is preferably 20:80 to 30:70, as described above.

Next, the insulated wire of the present invention and the method of manufacturing the same will be described in detail.

The insulated wire of the present invention comprises a conductor provided with a coating layer comprising a crosslinked body of the above-mentioned fluororesin composition of the present invention. It is obtained by crosslinking by irradiation with sexual radiation or the like.

Fluororubber (A) and crystalline polymer (B)
The mixing method and the temperature during mixing are set in the same manner as in the above-described heat-shrinkable tube.

In the production of an insulated wire, the fluororesin composition of the present invention is put into a conventionally known hopper such as a plastic extruder and melted, and then the composition is extruded onto a conductor and coated, and then ionized. Crosslinking may be performed by a method such as irradiation with radiation. As the ionizing radiation, an accelerating electron beam or the like can be used as described above.

Fluororubber (A) and crystalline polymer (B)
With respect to the production of a coating layer by an extruder using a fluororesin composition containing a mixture of the above, a problem that the appearance of the coating layer depends on the mixing ratio of the fluororubber (A) and the crystalline polymer (B). There is. That is, even in the case of manufacturing an insulated wire, the same tendency as in the manufacturing of the heat-shrinkable tube described above is observed.

For example, when the weight ratio A: B of the fluororubber (A) to the crystalline polymer (B) is increased, the oil resistance to lubricating oil containing an amine-based additive is improved as the B is increased. In the production of electric wires, the condition of DDR = 1, in which the diameter of the die is equal to the diameter of the insulating coating, is usually employed. Therefore, when the ratio of the crystalline polymer (B) is increased, melt fracture is likely to occur.

Therefore, also in the insulated wire of the present invention, the weight ratio of A: B in the fluororesin is set in the range of 10:90 to 50:50 so that a coating layer having good appearance can be produced. Note that the above range is 20:
The ratio is preferably from 80 to 30:70.

[0052]

The present invention will be described below with reference to examples and comparative examples.

[Production of heat-shrinkable tube] Examples 1 to 3 (Production of tube) The copolymerization ratio (TFE: P) of tetrafluoroethylene (TFE) and propylene (P) as the fluororubber (A) was 55: The copolymerization ratio (VDF: vinylidene fluoride (VDF), tetrafluoroethylene (TFE) and hexafluoropropylene (VDF: TFE: HFP) is about 40:40:20
"THV200G" (described above), which is a (molar ratio), was used. Then, both were mixed at a weight ratio A: B shown in Table 1 to prepare a fluororesin composition.

With respect to 100 parts by weight of the fluororesin composition, 10 parts by weight of calcium carbonate and 1 part by weight of trimethylolpropane trimethacrylate were blended, and the mixture was charged into a pressure kneader and mixed. And pelletized.

The pellets thus obtained are put into a 50 mmφ single screw extruder, and the draw-down rate (DDR) is set to the following conditions under the conditions of an extrusion linear speed of 50 m / min and a mold temperature of 260 ° C. Extrusion molding, inner diameter 10mm
A tube (extruded tube) having a φ of 0.5 mm in wall thickness was obtained.・ Condition 1: Die inner diameter 20mmφ, point outer diameter 12m
mφ, DDR12 ・ Condition 2: Die inner diameter 28mmφ, point outer diameter 12m
mφ, DDR30 Molding under condition 2 was performed only when melt fracture occurred due to molding under condition 1.

Next, an accelerating voltage of 2M was applied to the extrusion tube.
An electron beam of eV was irradiated at 100 kGy to crosslink.

(Preparation of heat-shrinkable tube) One end of the cross-linked tube obtained by the above-mentioned electron beam irradiation was closed, and the tube was connected to the compressed air pipe at the other end.
After inserting into an aluminum pipe with a diameter of 1 mm and a diameter of 1 mm,
Preheat for a minute.

After preheating, the compressed air was sent into the tube to expand the tube until the cross-linked tube stuck to the inner wall of the aluminum pipe. Then, the expanded tube was immediately taken out of the constant temperature bath together with the aluminum pipe, cooled with water, and expanded. Was fixed to obtain an expansion tube.

(Evaluation of Extrudability and Heat Shrinkability) Appearance of Tube The appearance of the extruded tube was visually observed and evaluated according to the following criteria. ：: No melt fracture and good appearance. Δ: Melt fracture was slightly generated, and the appearance was insufficient. X: Melt fracture was remarkably generated and the appearance was extremely insufficient.

Shrinkage rate in the longitudinal direction of the tube The above-mentioned expansion tube is cut into a sample of about 30 cm to obtain a sample, and two mark lines (distance between the mark lines: 20 cm) are arranged in the circumferential direction of the sample.
Was filled in. Next, the sample was placed on an aluminum pipe having an outer diameter of 12 mm, and was placed in a thermostat at a heat shrink temperature described below for 3 minutes to be thermally shrunk around the aluminum pipe, and the distance between the marked lines after the heat shrink was measured. The distance between the marked lines indicates the shrinkage in the radial direction of the tube. Those with a shrinkage of 5% or less were evaluated as ○, and those with more than 5% were evaluated as x.

Heat shrink temperature The above expansion tube is cut into a length of about 10 cm to obtain a sample,
100 ° C, 120 ° C, 150 ° C, 180 ° C, 200 ° C
And into a thermostat set at 250 ° C. for 3 minutes, respectively, and it was examined whether or not it shrinks to the diameter before expansion, and the heat shrinkage temperature was determined. For example, when the sample did not shrink in a thermostat at 100 ° C. but shrank in a thermostat at 120 ° C., the shrinkage temperature was determined to be 120 ° C.

(Flexibility) The flexibility of the tube was evaluated by measuring the secant modulus value (value obtained by multiplying the 2% modulus by 50) of the above-mentioned inflation tube.

Secant modulus value (kg / mm ² )
Indicates that the smaller the value, the higher the flexibility of the tube. In the present invention, the secant modulus value is 10
kg / mm ² or less, especially 5k
g / mm ² or less.

(Initial Characteristics) The crosslinked tube before expansion with compressed air was subjected to a tensile tester (tension speed 200 mm /
Min), the tensile strength (kg / mm ² ) and elongation (%) were measured.

The larger the tensile strength (kg / mm ² ) and the elongation (%), the better. In the present invention, the tensile strength is required to be 1.0 kg / mm ² , and the elongation is required to be 100% or more.
It is preferable that m ² and elongation be 200% or more.

(Oil resistance) A crosslinked tube having a DDR of 12 at the time of extrusion (before expansion) was placed at 150 ° C. on an automatic fluid for automobiles (trade name “SWS3305” manufactured by Esso Oil Co., Ltd.) containing an amine-based additive. For 500 hours, and the rate of weight change was determined.

The smaller the rate of change in weight, the better the oil resistance to the lubricating oil blended with the amine additive. The oil resistance was evaluated as ○ when the weight change rate was 10% or less, and as × when the weight change rate exceeded 10%.

(Heat Aging Resistance) A crosslinked tube having a DDR of 12 at the time of extrusion (before expansion) was heat aged for 96 hours in a gear oven, and the tensile strength and elongation were measured in the same manner as in the above “initial properties”. did. Next, the measured value was divided by the value in the above “initial properties” to calculate the tensile strength and elongation retention (%) to evaluate the heat aging resistance.

In the present invention, the retention of tensile strength is 50.
% Or more, and the retention of elongation is required to be 50% or more. In particular, it is preferable that the retention of tensile strength is 70% or more and the retention of elongation is 65% or more.

The evaluation of the initial properties, oil resistance and heat aging resistance in Example 3 was performed only for the crosslinked tube having a DDR of 12 at the time of extrusion.

Comparative Example 1 Preparation of a tube and preparation of a heat-shrinkable tube were performed in the same manner as in Example 1 except that fluororubber (A) (the above-mentioned “Afras 150”) was used alone as the fluororesin composition. And went.

Comparative Example 2 As a fluororesin composition, a fluororubber (A) [the above-mentioned “Afras 150”] and a crystalline polymer (B) [the above-mentioned “THV200G”] were A: B = 30: A tube was prepared and a heat-shrinkable tube was prepared in the same manner as in Example 1 except that a mixture at a weight ratio of 70 was used.

Comparative Example 3 Example 1 was repeated except that the crystalline polymer (B) (the above-mentioned “THV200G”) was used alone as the fluororesin composition.
In the same manner as in the above, a tube and a heat-shrinkable tube were prepared.

Comparative Example 4 "Afras 150" (described above) was used as the fluororubber (A), and polyvinylidene fluoride (melting point: 145 ° C., trade name “Kyner 2800” manufactured by Mitsubishi Chemical Corporation) was used as the crystalline polymer (B). ") Was used.

Next, Example 2 was repeated except that a mixture of the two at a weight ratio of A: B = 70: 30 was used as a fluororesin.
In the same manner as in the above, a tube and a heat-shrinkable tube were prepared.

Comparative Example 5 "Afras 150" (described above) was used as the fluororubber (A), and an ethylene-tetrafluoroethylene copolymer (melting point: 224 ° C., manufactured by Daikin Industries, Ltd.) was used as the crystalline polymer (B). Trade name "NEOFLON EP610"].

Next, Example 2 was repeated except that a mixture of the two at a weight ratio of A: B = 70: 30 was used as a fluororesin.
In the same manner as in the above, a tube and a heat-shrinkable tube were prepared.

Comparative Example 6 "Afras 150" (described above) was used as the fluororubber (A), and vinylidene fluoride (VDF), tetrafluoroethylene (TFE) and hexafluoropropylene (HFP) were used as the crystalline polymer (B). Is about 2
Copolymer having a ratio of 0:60:20 [Sumitomo 3M Co., Ltd.
“THV500G”, melting point 168 ° C.].

Next, Example 2 was repeated except that a mixture of the two at a weight ratio of A: B = 70: 30 was used as a fluororesin.
In the same manner as in the above, a tube and a heat-shrinkable tube were prepared.

Comparative Example 7 "Afras 150" (described above) was used as the fluororubber (A), and vinylidene fluoride (VDF), tetrafluoroethylene (TFE), and hexafluoropropylene (HFP) were used as the crystalline polymer (B). Is about 7
A copolymer having a ratio of 0:20:10 [Kina 9300, trade name, manufactured by Mitsubishi Chemical Corporation, melting point: 91.2 ° C] was used.

Next, Example 2 was repeated except that a mixture of the two at a weight ratio of A: B = 70: 30 was used as the fluororesin.
In the same manner as in the above, a tube and a heat-shrinkable tube were prepared.

The characteristics of Comparative Examples 1 to 7 were evaluated in the same manner as in Examples 1 to 3.

The mixing ratios of the fluororubber (A) and the crystalline polymer (B) in Examples 1 to 3 and Comparative Examples 1 to 7 are shown in Tables 1 and 2, and the measurement and evaluation results of each of the above properties are shown in Tables 1 and 2. Shown in 3 and 4.

[0084]

[Table 1]

[0085]

[Table 2]

[0086]

[Table 3]

[0087]

[Table 4] As is clear from Tables 1 to 4, in Examples 1 and 2,
An extruded tube having a good appearance was obtained under the condition of DDR = 12, and shrinking at a relatively low temperature of 120 ° C. was possible. In Example 3, although melt fracture was slightly generated under the extrusion conditions of DDR = 12, an extruded tube having a good appearance was obtained under the conditions of DDR = 30, and the extrusion temperature was relatively low at 120 ° C. in any case. Shrinking work was possible.

In Examples 1 to 3, the shrinkage in the longitudinal direction, the secant modulus and the rate of change in weight during the heat shrinkage were small, the tensile strength and the elongation of the heat shrinkable tube were large, and 260 ° C. × There was little change in physical properties after 96 hours. That is, in Examples 1 to 3, good results were obtained in all of the heat shrinkage, flexibility, initial properties, oil resistance, and heat aging resistance.

On the other hand, in Comparative Example 1 in which only the fluororubber (A) was used as the fluororesin composition, DDR = 1
Although a tube with excellent appearance was obtained under the conditions of 2, the tube self-shrinked during the water cooling process of the expansion process,
It could not be a heat-shrinkable tube.

Fluororubber (A) and crystalline polymer (B)
In Comparative Example 2 having a weight ratio of 70:30 (weight ratio), melt fracture was remarkable under the extrusion conditions of DDR = 12, and a tube having a good appearance could not be obtained. On the other hand, under the extrusion conditions of DDR = 30, although there was some melt fracture, a tube having a relatively good appearance was obtained, and the heat shrinkage temperature was relatively low at 120 ° C. However, the shrinkage in the longitudinal direction upon heat shrinkage was large, and was insufficient for practical use.

In Comparative Example 3 in which the crystalline polymer (B) was used alone as the fluororesin composition, an extruded tube having a good appearance was obtained under the extrusion conditions of DDR = 12, and the heat shrinkage temperature of the heat shrinkable tube was 120. At a relatively low temperature of ° C., the shrinkage in the longitudinal direction was small, and the initial physical properties were good. However, it was inferior in flexibility and practically insufficient. In Comparative Example 4 using polyvinylidene fluoride as the crystalline polymer (B), a tube having a good appearance could be obtained under the extrusion conditions of DDR = 12, and the initial properties of the heat-shrinkable tube were good. The shrinkage temperature is as high as 180 ° C,
Flexibility, oil resistance and heat aging resistance were poor.

In Comparative Example 5 using an ethylene-tetrafluoroethylene copolymer as the crystalline polymer (B),
To obtain a tube with good appearance, set the extrusion conditions to DDR = 3.
It was necessary to set it to 0, and although a heat-shrinkable tube could be obtained under these conditions, the heat-shrinkage temperature was extremely high at 250 ° C.

As the crystalline polymer (B), vinylidene fluoride (VDF) and tetrafluoroethylene (TFE)
Comparative Example 6 using a copolymer having a low copolymerization ratio of VDF and a high copolymerization ratio of TFE, which is a copolymer of styrene and hexafluoropropylene (HFP), has a DDR = 12
Under the extrusion conditions, a tube having a good appearance was obtained, and the initial properties of the heat-shrinkable tube were good, but the secant modulus was large and the flexibility was poor. In addition, since the heat aging resistance was low and the shape change was large, the tensile test after immersion in lubricating oil could not be measured.

Comparative Example 7 using, as the crystalline polymer (B), a copolymer of VDF, TFE and HFP having a high copolymerization ratio of VDF and a low copolymerization ratio of TFE, contrary to Comparative Example 6. , A tube having a good appearance is obtained under the extrusion conditions of DDR = 12, and the heat shrinkage temperature of the heat shrinkable tube is 120 ° C.
At a relatively low temperature, the shrinkage in the longitudinal direction during heat shrinkage was small, the secant modulus was small, and the flexibility was excellent. However, the rate of weight change after lubricating oil immersion was extremely high, and the oil resistance was very poor.

[Production of Insulated Wire] Example 4 As a conductor of an insulated wire, one obtained by twisting 19 tin-plated soft copper wires having an element wire diameter of 0.127 mm (outer diameter 0.64 mm) was used.

The fluororesin composition used in Examples was 50
into a single-screw extruder having a mold diameter of 260 mm so that the thickness of the insulating coating layer on the conductor is 0.38 mm.
Extrusion coating was performed at a temperature of 30 ° C. and a linear speed of 30 m / min.

Next, the coating layer thus obtained was irradiated with an electron beam at an acceleration voltage of 2 MeV at 15 kGy to crosslink.

With respect to the coating layer of the obtained insulated wire, the tensile strength, elongation and secant modulus were measured in the same manner as in the evaluation of the flexibility and initial properties in Example 1, and as shown in Table 3, It was found that the resin had high flexibility and excellent tensile strength and elongation.

Further, after the conductor was pulled out from the insulated wire and only the coating layer was formed, the oil resistance and the heat aging resistance were evaluated in the same manner as in Example 1. As shown in Table 3, the weight change rate was as shown in Table 3. , And high retention of tensile strength and elongation, and excellent oil resistance and heat aging resistance.

[0100]

As described in detail above, according to the present invention,
Manufacture of heat-shrinkable tubing that not only excels in flexibility, oil resistance, and heat resistance but also has excellent shrinkage workability and a small shrinkage rate in the longitudinal direction, and insulated wires that have high flexibility and excellent heat resistance and oil resistance. Thus, a heat-shrinkable tube suitable for protecting an insulated wire used for a harness for an automobile and a binding portion and a connection portion of the harness can be obtained. Therefore, the present invention has very high utility value in fields such as the automobile industry.

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Claims (7)

[Claims] 1. A tetrafluoroethylene-propylene copolymer fluororubber (A), comprising 30 to 50 mol% of vinylidene fluoride, 30 to 50 mol% of tetrafluoroethylene and 10 to 30 mol% of hexafluoropropylene. The weight ratio of the copolymerized crystalline polymer (B) and A: B =
A fluororesin composition, which is contained at a ratio of 90:10 to 50:50. 2. The fluororesin composition according to claim 1, wherein the weight ratio A: B is 80:20 to 70:30. 3. An insulating tube comprising a crosslinked product of the fluororesin composition according to claim 1 or 2. 4. A heat-shrinkable tube comprising a crosslinked product of the fluororesin composition according to claim 1. 5. The fluororesin composition according to claim 1 or 2 is extruded into a tube, crosslinked by irradiation with ionizing radiation, expanded radially under heating, and then cooled to form a shape. A method for producing a heat-shrinkable tube, characterized by fixing. 6. An insulated wire comprising a conductor and a coating layer comprising a crosslinked body of the fluororesin composition according to claim 1 provided on the conductor. 7. A method for producing an insulated wire, comprising coating a fluororesin composition according to claim 1 on a conductor and irradiating with ionizing radiation to crosslink the conductor.