JPH0959392A - Polyolefin-based resin composition and insulated wire and thermally contracting tube using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a resin composition having a specific value of gel fraction, secant modulus and dielectric constant, excellent resistance to heat deformation and flexibility without leakage current and useful for an insulated wire and a thermally contracting tube by crosslinking by irradiation of an electron beam. SOLUTION: This resin composition is crosslinked by irradiation of an electron beam and has >=76%, preferably >=80%, more preferably >=85% gel fraction, <=10kg/mm<2> , especially preferably <=5kg/mm<2> secant modulus, and <=2.4, especially preferably <=2.2 dielectric constant. As a polyolefin-based resin capable of constructing the composition, a resin having substantially linear and elastic properties is preferably used and obtained from, e.g. ethylene or about a 3-20C α-olefin by polymerizing in the presence of a catalyst composition containing a metal-coordinated complex such as metallocene and an activating cocatalyst, and has >=6C long-branched chains in an amount of 0.01-3 pieces, preferably 0.01-1 piece per 1000 pieces of C-atom constituting its main chain.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyolefin resin composition, an insulated wire using the same, and a heat shrinkable tube.

[0002]

2. Description of the Related Art Insulated wires are manufactured by coating a synthetic resin on the surface of a conductor by extrusion molding or the like to form an insulating coating. Further, the insulating coating, in order to improve the heat deformation resistance thereof, in order to prevent the insulation from being deteriorated and deformed when receiving an external force under heating, or to prevent a short circuit of the conductor, After coating the surface of the conductor, it is crosslinked by irradiation with an electron beam.

On the other hand, the heat-shrinkable tube used for coating the electric wire connecting portion is a synthetic resin tube manufactured by extrusion molding or the like, which is irradiated with an electron beam to impart heat-shrinkability (heat-setting property). After the crosslinking treatment, it is expanded by heating in a radial direction, and then rapidly cooled while maintaining this expanded state. The cross-linking treatment also has the purpose of improving the heat-deformation resistance of the tube when it is heat-shrinked to cover the wire connection portion and the like.

Various kinds of synthetic resins can be used as the material for the above-mentioned insulation coating and heat-shrinkable tube. In particular, the insulation coating and heat-shrinkable tube for which oil resistance, chemical resistance, low temperature characteristics, etc. are required. A polyolefin resin is preferably used as the material. Examples of the polyolefin-based resin include low-density polyethylene (LDPE), linear low-density polyethylene (L-LDPE), and ultra-low-density polyethylene (VLDPE), and other than α-olefins to impart flexibility to the resin. Ethylene-propylene-diene copolymer (EPDM), ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-vinyl acetate copolymer (EVA) into which other monomers have been introduced. Copolymers such as) are also preferably used.

[0005]

All of the above-mentioned conventional polyolefin resins are excellent in the above respective characteristics,
Although it is widely used for general-purpose insulated wires and heat-shrinkable tubes, it has a problem that it cannot be used for insulation coatings and heat-shrinkable tubes for applications requiring higher thermal deformation resistance than the general-purpose ones.

It is generally known that when the irradiation dose of an electron beam is increased, the resin has a higher cross-linking density and the heat distortion resistance is improved. Polyolefin resins are no exception to this rule, but many of the above-mentioned conventional polyolefin resins essentially have a low crosslink density corresponding to the electron beam irradiation dose, so the electron beam irradiation dose is increased above the normal level. There is a limit to the effect of improving the heat distortion resistance by doing so, and therefore, such conventional insulation coatings and heat shrinkable tubes made of polyolefin resin cannot be used for applications requiring higher heat distortion resistance.

Further, among conventional polyolefin resins, LDPE, L-LDPE, etc. do not only improve the heat deformation resistance as described above even if the irradiation dose of the electron beam is increased from the normal level, but rather, Since the flexibility decreases, for example, in the case of an insulated wire, wiring work in a narrow place becomes difficult, so the so-called maneuverability of the wire decreases, and in the case of a heat shrink tube, covering work in a narrow place, etc. However, there is a problem in that it is not easy, or the followability to electric wires is deteriorated. This problem also applies to the case where, in the copolymer in which other monomer is introduced to give flexibility to the resin, the one in which the ratio of the other monomer is small is irradiated with a larger amount of electron beam than the normal level. appear.

Further, among the above copolymers, EMA and EE
A, EVA, and the like having a polar group in the molecule have an increased dielectric constant due to the action of the polar group, and therefore, when this is used for an insulation coating or a heat-shrinkable tube, a leakage current is generated. There was a fear. Among the conventional polyolefin resins, those having a polar group in the molecule as described above can be crosslinked at the time of electron beam irradiation by blending a polyfunctional monomer such as triallyl isocyanurate (TAIC) as a crosslinking agent. It is known that the density can be improved, but since the cross-linking agent does not contribute to the decrease in the dielectric constant, the increase in the dielectric constant due to the action of the polar group and the risk of leakage current generation accompanying it remain unsolved. Met. Although the crosslinking density is improved by blending the crosslinking agent as described above, the flexibility of the resin may be significantly reduced accordingly.

Further, the cross-linking agent such as TAIC also contributes to the cross-linking of EPDM, but since the cross-linking density of EPDM itself is inherently low, the effect of improving the heat distortion resistance is obtained even if the cross-linking agent is blended at a normal level. Was still limited. Further, when the cross-linking agent is blended in a larger amount than the usual level, there is a problem that the cross-linking agent is bled. An object of the present invention is to have a high heat distortion resistance that cannot be obtained with conventional polyolefin-based resins, and with excellent flexibility after crosslinking, and a polyolefin-based resin composition that does not cause leakage current, An object of the present invention is to provide an insulated wire and a heat-shrinkable tube that can be used for applications requiring higher heat distortion resistance using the same.

[0010]

The polyolefin resin composition of the present invention for solving the above-mentioned problems is one which is crosslinked by irradiation of electron beam and has a gel fraction of 7
It is characterized in that it is 6% or more, the secant modulus value is 10 kg / mm ² or less, and the dielectric constant is 2.4 or less.

The polyolefin resin composition of the present invention is highly crosslinked so that the gel fraction, which is an index of the crosslink density, is 76% or more.
Residual rate of heat deformation when a load of 500 g is applied at ℃ (percentage of the dimension after heat deformation to the dimension before heat deformation)
Shows a high heat distortion resistance of 45% or more. Further, the polyolefin resin composition maintains a flexible level of 10 kg / mm ² or less in secant modulus, which is an index of flexibility, even in a highly crosslinked state as described above.

Further, since the above-mentioned polyolefin resin composition has a dielectric constant of 2.4 or less, there is no possibility of generating leakage current. Therefore, an insulated wire using the polyolefin resin composition of the present invention as an insulating coating, or a heat-shrinkable tube formed of the polyolefin resin composition of the present invention has both high thermal deformation resistance and flexibility, and Since there is no risk of generation of electric current, it can be suitably used in applications where higher heat distortion resistance is required.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION First, the polyolefin resin composition of the present invention will be described. As described above, the polyolefin resin composition of the present invention is crosslinked by irradiation with an electron beam, and has a gel fraction of 76% or more,
The secant modulus value is limited to 10 kg / mm ² or less, and the dielectric constant is limited to 2.4 or less.

The gel fraction showing the crosslink density of the polyolefin resin composition crosslinked by electron beam irradiation is 76.
If the gel fraction is less than 76%, the crosslinking density of the polyolefin resin composition is not sufficient, and as described above, heating at the time of applying a load of 500 g at 136 ° C. This is because the residual deformation rate is less than 45%, the thermal deformation resistance becomes insufficient, and it becomes easy to deform when an external force is applied under heating.

In consideration of the thermal deformation resistance of the insulation coating and the heat shrinkable tube, the above-mentioned residual rate of heat deformation is preferably 50% or more, especially within the range of 45% or more, and in order to achieve it, Within the above range, the gel fraction of the polyolefin resin composition is preferably 80% or more, and more preferably 85% or more. In addition, the secant modulus value of the polyolefin-based resin composition crosslinked by electron beam irradiation is 10 kg / mm ²
The following is limited to the case where the secant modulus value is 1
When it exceeds 0 kg / mm ² , the flexibility of the insulation coating and the heat-shrinkable tube formed from the polyolefin-based resin composition is reduced, and, for example, in the case of an insulated wire, the maneuverability is reduced, and This is because, in such a case, the covering work in a narrow place is not easy, or the ability to follow the electric wire is deteriorated.

The secant modulus value is, considering further flexibility of the insulating coating and the heat shrinkable tube,
Even within the above range, it is particularly preferably 5 kg / mm ² or less. Further, the dielectric constant of the polyolefin resin composition crosslinked by electron beam irradiation is limited to 2.4 or less, when the dielectric constant exceeds 2.4, the insulating coating formed by the polyolefin resin is formed. This is because leakage current is generated in the heat shrink tube.

The dielectric constant is preferably 2.2 or less in the above range, considering the effect of preventing leakage current. The polyolefin-based resin that can form the polyolefin-based resin composition satisfying the above-mentioned respective properties by crosslinking by irradiation with an electron beam is not limited to this, but is, for example, JP-A-6-306121 and JP-A-7- The elastic and substantially linear polyolefin resin disclosed in Japanese Patent No. 500622 is preferably used.

Such an elastic and substantially linear polyolefin resin is, for example, ethylene or a carbon number of 3 to 2
Approximately 0 kinds of α-olefins are used alone, or two or more kinds of ethylene and α-olefins having about 3 to 20 carbon atoms are used in combination to form a metal coordination complex such as a metallocene and an activating cocatalyst. It is produced by polymerizing in the presence of a catalyst composition containing, and is 0.01 to 3, preferably 0.01 per 1000 carbon atoms constituting the main chain.
˜1, more preferably 0.5 to 1, with a long branched chain having 6 or more carbon atoms.

The above-mentioned polyolefin resin has a processability similar to that of highly branched low density polyethylene (ordinary LDPE), and is a heterogeneous linear polymer obtained by polymerizing ethylene and α-olefin with a Ziegler catalyst (for example, L-LDPE, etc.) and the same strength and toughness,
Moreover, as described above, it has a completely different structure from LDPE, L-LDPE, or VLDPE in which ethylene and α-olefin are polymerized by a Ziegler catalyst, like L-LDPE.

Specific examples of the above-mentioned elastic and substantially linear polyolefin resin are not limited to these, but include, for example, The Dow Chemical Company (USA).
Chemical Co. ) Product name "AFFIN
The TY (affinity) series and the brand name "ENGAGE" series are listed. Both of the above series are copolymers of ethylene and 1-octene, and various grades are provided depending on the difference in the proportion of octene and the like.

Among them, those which are particularly preferably used in the present invention include, for example, the trade name AFFINITY.
PF1140 [octene content 14.5% by weight, melt index (MI) value 1.6, density 0.895], AFF
INITY PL1880 [octene content 12% by weight, melt index (MI) value 1, density 0.902], E
NGAGE CL8001 [octene content 25% by weight, melt index (MI) value 0.5, density 0.86
8], ENGAGE CL8002 [octene content 24% by weight, MI value 1, density 0.870], ENGAGE C
L8003 [octene content 18% by weight, MI value 1, density 0.885] and the like. Since these polyolefin-based resins have a low MI value and excellent workability, it is easy to manufacture insulated wires and heat-shrinkable tubes. Further, since these polyolefin-based resins have a relatively low density, there is an advantage that the insulated electric wire and the heat-shrinkable tube can be lightened.

The above-mentioned elastic and substantially linear polyolefin resin is, as described above, ethylene and α.
-Since it uses olefin as a raw material and has no polar group in the molecule, it has a low dielectric constant of 2.4 or less.
Further, as is clear from the description of the examples described later, the above polyolefin-based resin has an electron beam irradiation dose of 200 kGy or more, which is twice the normal level of 100 kGy, so that the gel fraction is 76%. It is possible to crosslink to such a high crosslink density and to set the heat deformation residual rate at that time to 45% or more. Moreover, the polyolefin resin has a secant modulus value of 10 kg / mm ² or less even in the above highly crosslinked state, and is excellent in flexibility.

Next, the insulated wire of the present invention will be described. The insulated electric wire of the present invention is one in which the surface of the conductor is formed of the above-mentioned polyolefin resin composition of the present invention, or includes the above polyolefin resin composition, and an insulating coating having flame retardancy is formed. Is. Insulating coating containing a polyolefin resin composition and having flame retardancy is a flame-retardant by using the polyolefin resin composition of the present invention as a base polymer and incorporating various conventionally known additives. It refers to an insulating coating with imparted properties.

As the conductor, any of the conventionally known conductor materials such as copper, annealed copper, silver, nickel-plated annealed copper and tin-plated annealed copper can be used. The additives to be added to impart flame retardancy to the insulating coating include, but are not limited to, for example, antioxidants, flame retardants, fillers and the like. The compounding amounts of these additives may be the same as those in the related art.

When these additives are blended, the insulation coating becomes
Although the dielectric constant tends to slightly increase and the flexibility tends to slightly decrease, the dielectric constant is lower and the flexibility is better than in the case where the same composition is used in the conventional polyolefin-based resin. The insulated wire can be manufactured in a conventional manner. That is, the surface of the conductor may be coated by extrusion molding or the like with a molding material containing a polyolefin resin before being irradiated with an electron beam to be crosslinked, and then the polyolefin resin may be crosslinked with an electron beam.

In the insulated wire, the thickness of the insulating coating, the diameter of the conductor, etc. are not particularly limited, and any dimensions may be adapted to the standard of the insulated wire. Since the insulated wire of the present invention has an insulating coating composed of the polyolefin resin composition of the present invention, it has high thermal deformation resistance, is flexible and has good maneuverability, and has a low dielectric constant and leakage current. It has an excellent property that no

Next, the heat shrinkable tube of the present invention will be described. The heat-shrinkable tube of the present invention is made of the polyolefin-based resin composition of the present invention or contains the above-mentioned polyolefin-based resin composition and is imparted with flame retardancy. Here, the heat-shrinkable tube containing the polyolefin-based resin composition and imparted with flame retardancy has the polyolefin-based resin composition of the present invention as the base polymer and is difficult to be mixed with various conventionally known additives. It has been given flammability.

Examples of the additives to be added to the tube to impart flame retardancy include the same additives as those exemplified in the insulated wire. The compounding amounts of these additives may be the same as those in the related art. When these additives are compounded, the heat-shrinkable tube tends to have a slightly increased dielectric constant and a slight decrease in flexibility, but the dielectric constant is lower than that in the case where the same composition was used in the conventional polyolefin resin. Low,
Flexibility is good.

The heat-shrinkable tube can be manufactured in a conventional manner. That is, a molding material containing a polyolefin resin before being irradiated with an electron beam to be cross-linked is molded into a tube by extrusion molding or the like, and then this tube is irradiated with an electron beam to cross-link the polyolefin resin. Next, while heating the tube at a temperature equal to or higher than the melting point of the polyolefin-based resin, the compressed air is blown into the tube to expand the tube to a predetermined diameter, and then rapidly cooled to produce a heat-shrinkable tube. .

The heat-shrinkable tube, which is made of the polyolefin resin composition of the present invention, is flexible, can be easily covered in a narrow space, and has good followability to electric wires. Further, the heat-shrinkable tube has a high crosslink density as described above, and therefore has a high shrinkage stress when heat-shrinked by heating it to a temperature higher than the melting point of the polyolefin-based resin. Even with a high tightening force, it can be adhered.
Moreover, the tube after heat shrinkage has high thermal deformation resistance, low dielectric constant and no leakage current.
It has excellent characteristics.

[0031]

The present invention will be described below with reference to examples and comparative examples. Example 1 Using an extruder (30 mmφ), an outer diameter of 0.81 mm
On the surface of the conductor of φ, ethylene-1-octene copolymer (EO, trade name “ENGAGE CL800
3 ", 18% by weight of octene), thickness 0.4 m
m insulation coating was formed.

Then, an electron beam accelerator is used to irradiate the insulating coating with an electron beam under the condition of an accelerating voltage of 1.5 MV to crosslink, and the irradiation dose of the electron beam is 200 kGy, 300 k.
Three types of insulated wire were manufactured, which are Gy and 400 kGy. Example 2 The same as Example 1 except that an ethylene-1-octene copolymer having an octene content of 12% by weight (EO, trade name “AFFINITY PL1880” described above) was used as the material for the insulating coating. Then, three types of insulated electric wires were manufactured. Example 3 Example 1 was repeated, except that an ethylene-1-octene copolymer having an octene content of 14.5% by weight (EO, trade name “AFFINITY PF1140” described above) was used as the material for the insulating coating. Three types of insulated wires were manufactured in the same manner as in. Comparative Examples 1 to 10 In the same manner as in Example 1 except that the following polyolefin-based resin was used as the material for the insulating coating, each 3
Each type of insulated wire was manufactured.

Comparative Example 1: EEA (ethyl acrylate content 7% by weight) Comparative Example 2: EEA (ethyl acrylate content 18% by weight) Comparative Example 3: EVA (vinyl acetate content 5% by weight) Comparative Example 4: EVA (vinyl acetate content) 18% by weight) Comparative Example 5: EMA (10% by weight of methyl acrylate) Comparative Example 6: EMA (18% by weight of methyl acrylate) Comparative Example 7: LDPE (density 0.918) Comparative Example 8: L-LDPE ( Density 0.92) Comparative Example 9: VLDPE (Density 0.89) Comparative Example 10: EPDM (Ethylene content 70% by weight) Comparative Example 11 90 parts by weight of the same EEA used in Comparative Example 2 as a material for the insulating coating. Is a polyfunctional monomer, TAI
Three kinds of insulated electric wires were manufactured in the same manner as in Example 1 except that the one containing 10 parts by weight of C was used. Comparative Example 12 As a material for the insulating coating, 90 parts by weight of the same EPDM used in Comparative Example 10 was used, and TA as a polyfunctional monomer was used.
Other than using a mixture of 10 parts by weight of IC,
Three types of insulated electric wires were manufactured in the same manner as in Example 1.

The following tests were conducted on the insulated wires produced in the above-mentioned Examples and Comparative Examples to evaluate their characteristics. Gel Fraction Measurement A test piece having a length of 100 mm was prepared by removing the insulating coating from each of the three types of insulated wires produced in Examples and Comparative Examples, and the weight thereof was weighed as the weight before extraction (g). Next, this test piece was immersed in xylene at a liquid temperature of 130 ° C. in an amount of about 50 times the weight before extraction for 24 hours, and then the liquid was filtered to remove the gel content remaining on the filter paper to 80%. Xylene was removed by drying at 24 ° C. for 24 hours. Then, the weight of the gel portion after drying is weighed as the weight after extraction and drying (g), and the weight after extraction and drying (g) and the weight before extraction (g)
From the above, the gel fraction (%) was determined by the following formula, and the crosslink density of the insulating coating was evaluated.

[0035]

[Equation 1]

Dielectric Constant Measurement Among the three types of insulated wires produced in each of the Examples and Comparative Examples, one having an electron beam irradiation dose of 400 kGy
A 5 cm-wide tin foil was wrapped around the outer periphery of the insulating coating. Then, the dielectric constant (ε) between the tin foil and the conductor of the electric wire was measured by using an impedance analyzer (4262A LCR METER manufactured by Yokogawa Hewlett-Packard Co.).
The electrical characteristics of the insulating coating were evaluated by measurement under the conditions of kHz and 500V. Second Modulus Value Measurement Of the three types of insulated electric wires produced in each of the examples and comparative examples, the insulating coating was peeled off from the one having an electron beam irradiation dose of 400 kGy to produce a test piece having a length of 100 mm. Then, the tensile strength at 2% elongation when this test piece was pulled in the longitudinal direction at a pulling speed of 50 mm / min using an Instron tensile tester was measured and multiplied by 50 to obtain a secant modulus value ( kg / mm ² ) was calculated to evaluate the flexibility of the insulating coating. Heat Deformation Test 136 After measuring the outer diameter of each of the three types of insulated wires produced in Examples and Comparative Examples as the outer diameter before heating deformation (mm), 136
Heat at 60 ° C. for 60 minutes. Next, the insulated electric wire immediately after the heating is placed on a flat plate, and a metal rod having a diameter of 9.5 mmφ is laid on the flat plate so as to cross at right angles, and a load of 500 g is applied for 60 minutes.
After pressurizing, the dimension of the insulated wire sandwiched between the metal rod and the flat plate and deformed is the outer diameter (mm) after heat deformation
Was measured. Then, the outer diameter before the heat deformation (mm)
And outer diameter after heating deformation (mm) and outer diameter of conductor (mm)
From the above, the heat deformation residual rate (%) of the insulated wire was obtained by the following formula, and the heat deformation resistance of the insulating coating was evaluated.

[0037]

[Equation 2]

The above results show that the resins before crosslinking used in Examples and Comparative Examples had a heating temperature of 190 ° C. and a load of 2.16 kg.
Melt index value (MI value, g / 10
Min) and the measurement results of the density are shown in Tables 1 to 4.

[0039]

[Table 1]

[0040]

[Table 2]

[0041]

[Table 3]

[0042]

[Table 4]

Of the examples and comparative examples shown in the above tables,
EEA, EVA, E as polyolefin resin
In the insulated wires of Comparative Examples 1, 2, 4 to 6 using MA, the gel fraction does not reach 76% even when the irradiation dose of the electron beam is increased to 400 kGy, and the residual rate of heating deformation is also low. From this, it was found that the heat distortion resistance was insufficient. It was also found that all of the insulated wires of the above-mentioned comparative examples have a high dielectric constant due to the influence of polar groups in the molecule, and there is a high possibility that leakage current will occur. Furthermore, in each of the comparative examples, the proportion of the monomer having a polar group is small E
It was also found that the insulated electric wires of Comparative Examples 1 and 5 using EA and EMA had a secant modulus value of more than 10 kg / mm ² , and the flexibility was insufficient.

EVA as a polyolefin resin
The insulated wire of Comparative Example 3 in which the heating deformation residual rate was 45% when the irradiation dose of the electron beam was increased to 300 kGy
And the gel fraction exceeds 76% when further increasing to 400 kGy, the heat distortion resistance can be sufficiently improved by increasing the irradiation dose of the electron beam,
It was found that the secant modulus value was more than 10 kg / mm ² , the flexibility was insufficient, and the dielectric constant was high, so that the leakage current was likely to occur.

LDPE, L as polyolefin resin
Comparative Example 7 using LDPE, VLDPE and EPDM
All of the insulated wires of Nos. 10 to 10 had a low dielectric constant because they did not have a polar group in the molecule, and there was no fear that leakage current was generated, but in any case, even if the irradiation dose of the electron beam was increased to 400 kGy. Since the gel fraction did not reach 76% and the residual rate of thermal deformation was low, it was found that the thermal deformation resistance was insufficient. In addition, among the comparative examples above, LDPE and LL
The insulated wires of Comparative Examples 7 and 8 using DPE are
The secant modulus value exceeded 10 kg / mm ² , and it was also found that the flexibility was insufficient.

The same EEA as used in Comparative Example 2 was used as the polyolefin resin, and T as the crosslinking agent was used.
The insulated wire of Comparative Example 11 containing AIC had a gel fraction of 76% when the electron beam irradiation dose was 200 kGy.
Since the heat deformation residual rate exceeds 45% when the temperature is further increased to more than 400 kGy, the heat distortion resistance can be sufficiently improved by increasing the irradiation dose of the electron beam, but since the dielectric constant is high, It was found that there is a high possibility that leakage current will occur. In addition, Comparative Example 1 above
Comparing No. 1 with Comparative Example 2 described above, the secant modulus value is remarkably increased as compared with the increase amount of the gel fraction.
It has been found that the flexibility of the IC is significantly reduced by blending it.

The insulated wire of Comparative Example 12 in which the above TAIC was mixed with the same EPDM as used in Comparative Example 10 had no problem in flexibility and dielectric constant, but the irradiation dose of electron beam was increased to 400 kGy. However, the gel fraction did not reach 76%, and the residual rate of thermal deformation was low, indicating that the thermal deformation resistance was insufficient. In contrast,
In each of the insulated wires of Examples 1 to 3, the gel fraction already exceeds 76% at the irradiation dose of the electron beam of 200 kGy and the residual heating deformation rate exceeds 45%. It was confirmed that it has excellent heat distortion resistance. It was also confirmed that the insulated wires of each of the above Examples have a secant modulus value of 10 kg / mm ² or less, and thus have high flexibility and good maneuverability. Further, it was also confirmed that the insulated wires of each of the above-mentioned examples have a low dielectric constant, and therefore there is no possibility of generating leakage current.

[0048]

As described above in detail, according to the present invention, the resin has a high heat distortion resistance which cannot be obtained by the conventional polyolefin resin, has excellent flexibility after crosslinking, and has a leakage current. A polyolefin-based resin composition that is unlikely to be generated, and an insulated wire and a heat-shrinkable tube using the same that can be used in applications requiring higher thermal deformation resistance because of excellent properties described above.

Claims (5)

[Claims] 1. A polyolefin resin composition crosslinked by electron beam irradiation, having a gel fraction of 76% or more,
A polyolefin resin composition having a secant modulus value of 10 kg / mm ² or less and a dielectric constant of 2.4 or less. 2. An insulated wire, wherein an insulating coating made of the polyolefin resin composition according to claim 1 is formed on the surface of the conductor. 3. An insulated wire, characterized in that an insulating coating containing the polyolefin resin composition according to claim 1 and having flame retardancy is formed on the surface of the conductor. 4. A heat-shrinkable tube comprising the polyolefin-based resin composition according to claim 1. 5. A heat-shrinkable tube containing the polyolefin-based resin composition according to claim 1 and imparted with flame retardancy.