WO2007040275A1

WO2007040275A1 - Water-treeing resistant insulating composition and water-treeing resistant electric wire/cable

Info

Publication number: WO2007040275A1
Application number: PCT/JP2006/320090
Authority: WO
Inventors: Yoshinao Murata
Original assignee: J-Power Systems Corporation
Priority date: 2005-10-06
Filing date: 2006-10-06
Publication date: 2007-04-12
Also published as: JP2007103247A

Abstract

A water-treeing resistant insulating composition comprising a polyolefin resin and, dispersed therein, an inorganic filler, wherein the inorganic filler has an average particle diameter of 500 nm or less. Further, there is provided a water-treeing resistant electric wire/cable making use of the same.

Description

Specification

Water-resistant tree insulation composition and water-resistant tree wire 'cable

Technical field

TECHNICAL FIELD [0001] The present invention relates to an insulating composition in which an inorganic filler is dispersed in a polyolefin resin, and an electric wire cable using the insulating composition as a coating material, and in particular, a water-resistant tree that does not deteriorate electrical characteristics. The present invention relates to a water-resistant insulating composition and a water-resistant electrical wire / cable with improved performance.

Background art

[0002] For example, it is known that when an electric wire or cable is used in a humid atmosphere, a water tree is generated in the insulator! When the external force electric field of the insulator is applied while moisture has entered the insulator, the moisture in the insulator moves toward the high electric field (this is called dielectrophoresis). The water tree is generated when moisture that has entered the insulator moves and concentrates on a high electric field portion such as a foreign object, void, or protrusion in the insulator by this dielectrophoresis. When water trees are generated, the insulation performance of electric wires and cables used for a long period of several decades will gradually deteriorate, and measures to suppress water trees are important. Has been debated.

[0003] One of the methods is to suppress the generation of water trees by adding an additive to the insulator, and a method of adding EVA (ethylene acetate butyl copolymer) to a polyolefin resin such as polyethylene is known. (For example, see Patent Documents 1 and 2;).

[0004] Further, a method of adding carbon black to an insulator (see, for example, Patent Document 3) or

During polyolefin榭脂such as polyethylene, a method of incorporating the magnesium Sani匕(MgO) is known (for example, see Patent Document 4.) ₀

Patent Document 1: JP-A-5-89725

Patent Document 2: Japanese Patent Laid-Open No. 2002-289043

Patent Document 3: Japanese Patent Laid-Open No. 10-312717

Patent Document 4: Japanese Patent Laid-Open No. 5-250919

Disclosure of the invention Problems to be solved by the invention

[0005] However, in the methods described in Patent Documents 1 and 2, EVA scattered in polyethylene (PE) is dispersed like a sea-island structure, and water is trapped in the EVA to generate water trees. On the other hand, the addition of EVA leads to a decrease in electrical properties such as volume resistivity. However, the upper limit of the amount of EVA added is limited and satisfactory water-resistant tree resistance cannot be obtained.

[0006] In addition, the method described in Patent Document 3 is a force for combining carbon black as an additive in PE. As the amount of carbon black added increases, aggregates of carbon particles in the insulator. Due to the problem that this agglomerated component affects the insulation performance, the amount of carbon black added was limited, and sufficient water-resistant tree resistance was not obtained.

[0007] Further, Patent Document 4 has made various studies on the amount of MgO added for the purpose of improving the volume resistivity of the insulator. However, MgO increases the volume resistivity of the insulator and increases the insulation resistance. Although the electrical properties such as resistance have been improved, no investigation has been made on the water-resistant tree properties. This is thought to be due to the fact that the average particle diameter of the added MgO is large, and that it is impossible to find an effect that can improve the water-resistant tree resistance.

[0008] Accordingly, an object of the present invention is to provide a water-resistant tree insulating composition and a water-resistant electric wire cable that can improve water-resistant tree properties without deteriorating electrical characteristics.

Means for solving the problem

[0009] In order to achieve the above object, the first invention is an insulating composition in which an inorganic filler is dispersed in a polyolefin resin, wherein the average particle diameter of the inorganic filler is 500 nm or less in diameter. A water-resistant insulating composition is provided.

In order to achieve the above object, a second invention provides a water-resistant electric wire 'cable characterized in that the water-resistant tree-resistant insulating composition is formed as an insulator for insulating a conductor.

The invention's effect

[0011] According to the water-resistant tree insulating composition according to the first invention, the inorganic filler is dispersed in the polyolefin resin by dispersing the nano-sized inorganic filler having an average particle diameter of 500 nm or less in the polyolefin resin. The water absorption effect suppresses the movement of moisture in the insulating composition. Lee can be prevented.

[0012] According to the water-resistant tree-resistant electric wire 'cable according to the second invention, the water-resistant tree-resistant insulating composition that suppresses the movement of moisture in the insulating composition and suppresses the generation of the water tree is formed as an insulator. As a result, the number of water trees generated can be suppressed even when cables are used in a humid atmosphere. Accordingly, it is possible to obtain a water-resistant tree-insulating composition and a water-tree-resistant electric wire and a cape nore that can improve the water-resistant tree properties without deteriorating the electrical characteristics such as dielectric breakdown characteristics and insulation resistance.

Brief Description of Drawings

FIG. 1 is a cross-sectional view showing a configuration of a water-resistant tree cable according to an embodiment of the present invention.

Explanation of symbols

[0014] 1 Water-resistant tree cable

2 conductor

3 Internal semiconductive layer

4 Insulator

5 External semiconductive layer

6 Shielding layer

7 sheath

BEST MODE FOR CARRYING OUT THE INVENTION

[0015] (Configuration of water-resistant tree-resistant cable)

FIG. 1 shows a configuration of a water-resistant tree-resistant cable according to an embodiment of the present invention. The water-resistant cable 1 has a conductor 2 having a substantially circular cross section at the center, and an outer periphery of the conductor 2 has an inner semiconductive layer 3, an insulator 4, an outer semiconductive layer 5, a shielding layer 6, and a sheath. 7 is covered sequentially.

[0016] (Configuration of insulator)

The insulator 4 is made of a water-resistant insulating composition in which a nano-sized inorganic filler having a non-conductive average particle diameter of 500 nm or less is dispersed in a polyolefin resin. [0017] As the polyolefin resin, low density polyethylene (LDPE) can be used. This polyolefin resin may be a high-density polyethylene, medium-density polyethylene, ultra-low-density polyethylene, linear low-density polyethylene, or the like, or a cross-linked product of these, based on LDPE. ! /

[0018] The inorganic filler is dispersed in an amount of 1 part by weight or more based on 100 parts by weight of polyolefin resin. The inorganic filler is magnesium oxide (MgO) having an average particle size of 500 nm or less, and is uniformly dispersed in LDPE so as to obtain high water-resistant tree properties. In addition to MgO, the inorganic filler may be titanium oxide, calcium carbonate, magnesium hydroxide, silica or the like.

[0019] As a method of dispersing the inorganic filler in the polyolefin resin, there is a method using a twin screw extruder, in which the polyolefin resin and the inorganic filler are kneaded. This kneading method is not limited to the above method as long as the average particle diameter of the inorganic filler can be controlled to be 500 nm or less. As another method, for example, there is a method of using a twin screw extruder and a roll machine in combination, and diluting a polyolefin resin material having a high concentration of an inorganic filler added to a low concentration with a roll machine.

[0020] In addition, the inorganic filler is subjected to a surface treatment with vinylsilane and then a powder frame treatment by jet pulverization.

[Effect of the embodiment]

According to the present embodiment, the following effects are obtained.

(Ii) Insulator 4 has a structure in which an inorganic filler having an average particle size of 500 nm or less is dispersed in the polyolefin resin, so that the water content in the polyolefin resin can move due to the water absorption effect of the inorganic filler. The water tree suppression effect of the water-resistant tree-resistant cable 1 can be enhanced without affecting the electrical characteristics such as dielectric breakdown characteristics and insulation resistance.

(Mouth) The insulator 4 in which the nano-sized inorganic filler is uniformly dispersed in the polyolefin resin can obtain a higher water tree resistance. The smaller the particle size of the inorganic filler, the shorter the interparticle distance of the inorganic filler dispersed in the polyolefin resin, and the higher the moisture trapping probability. That is, the smaller the particle size and the shorter the interparticle distance, the higher the water tree deterrent effect of the water resistant cartridge 1 can be. (C) In the case of an inorganic filler having the same particle size, by dispersing 1 part by weight or more with respect to 100 parts by weight of the polyolefin resin, the distance between the particles of the inorganic filler in the polyolefin resin is short. Therefore, the water tree deterrence effect can be enhanced because the moisture trapping probability increases.

(2) The inorganic filler can prevent re-aggregation in the polyolefin resin by performing surface treatment with bursilane and pulverization treatment with jet pulverization, and a more uniform dispersion state can be obtained.

Example 1

Next, Examples 1, 2, and 3 of the present invention will be described.

As a sample, a water-resistant tree cable 1 having the configuration shown in FIG. 1 was produced as follows. As the conductor 2, the cross-sectional area on the outer periphery of the conductor containing copper as a main component of 100 mm ^2, and extruded to a thickness of 0. 7 mm internal semiconductive layer 3. Next, the insulating composition shown in Table 1 is extruded on the outer periphery of the inner semiconductive layer 3 as an insulator 4 to a thickness of 3 mm, and the outer semiconductive layer 5 is formed on the outer periphery of the insulator 4. The water-resistant tree-resistant cable 1 was produced by sequentially extruding the thickness 1 mm, the shielding layer 6 and the sheath 7 so that each thickness would be 3 mm.

[0023] [Table 1]

Table 1 Thread and sample of sample and B T-cho results

* 1: Average particle size 50 0 墮

* 2: Average particle size 1mm

* 3: AC in 500 Hz, 4.5 kV 90 days after B TT

* 4: 9 0. C, value at 80 k VZmm

* 5: AC ® £ Value displayed by electricity (details of examples)

Table 1 shows the case where the average particle diameter of MgO is constant and the amount of applied force is varied. As the insulator 4 in Fig. 1, the average particle diameter is compared to the base polyethylene made of low density polyethylene (LDPE). Water-resistant tree-resistant cable 1 with a water-resistant insulating composition comprising lphr-added nano-sized MgO with a diameter of 50 nm (hereinafter referred to as nano-sized MgO) as in Example 1, and water-resistant tree-resistant cable 1 with 5 phr. The water tree generation was evaluated in the same manner as in Example 2, and the water-resistant tree cable 1 to which lOphr was added in the same manner as Example 3. [0025] (Details of comparative example)

In addition, cable 1 in which insulator 4 was used as LDPE without adding MgO was used as comparative example 1. Further, a cable 1 in which an insulating composition containing 1 Ophr of micro-sized MgO having an average particle diameter of 1 / z m (hereinafter referred to as micro-sized MgO) was used as the insulator 4 was used as Comparative Example 2.

[0026] (Evaluation of water tree generation)

Water tree generation was evaluated as follows. Strip a part of the sheath 7 of the water-resistant tree-resistant cable 1 and place the water-resistant tree-resistant cable 1 in room temperature water so that the outer semiconductive layer 5 is in direct contact with the water and conduct an AC high voltage of 500 Hz, 4.5 kV. Applied between 2 and shielding layer 6. When 90 days had elapsed since the start of the application of electricity, the application of electricity was stopped, and the insulator 4 was sliced into a lmm-thick shape and used as a water tree observation sample. This sliced sample is made into a spiral piece of a predetermined size, 20 of which are stained with a methylene blue aqueous solution, and the size and number of the boutontrie (BTT) generated in the insulator 4 are examined with an optical microscope. did. The number of BTT occurrences is evaluated by the cumulative number of occurrences per volume, and the number of BTT occurrences of 150 μm or less and the number of BTT occurrences of 300 μm or less are counted and evaluated. The results shown in Table 1 were obtained.

[0027] (Evaluation of volume resistivity)

Further, the volume resistivity was evaluated as follows. Measure the volume leakage current flowing between the shielding layer 6 and the ground by applying a DC voltage of 240 kV (80 kVZmm as an electric field) between the conductor 2 and the shielding layer 6 while grounding the shielding layer 6 of the water-resistant cable 1. The volume resistivity was obtained and evaluated. The volume leakage current was measured with the water-resistant tree cable 1 heated to 90 ° C.

[0028] (Evaluation of dielectric breakdown strength)

Furthermore, the dielectric breakdown strength was evaluated as follows. The shielding layer 6 of the water-resistant cable 1 was grounded, 60 kV AC high voltage was applied to the conductor 2, the voltage was increased by 3 kV every 10 minutes from 60 kV, and the voltage at which the water-resistant tree cable 1 breaks down was measured and evaluated. . At this time, the water-resistant triaxial cable temperature was set to room temperature.

[0029] (Evaluation of Examples 1 to 3)

Table 1 shows the following. First of all, nano-sized MgO in insulator 4 that also has LDPE power In Examples 1 to 3 where the additive was added, the number of BTT generated in the insulator 4 was significantly smaller than in Comparative Example 1 where MgO was not added. Furthermore, as in Examples 2 and 3, by increasing the amount of nano-sized MgO added, the number of BTT generated is further reduced. On the other hand, Comparative Example 2 to which microsize MgO was added had a smaller BTT suppression effect than Examples 1 to 3.

[0030] In Examples 1 to 3, the volume resistivity is improved by adding nano-sized MgO, and the strength is further improved by increasing the added amount. The dielectric breakdown strength was the same value or about the same value in each example and each comparative example. In Comparative Example 2, the volume resistivity is improved compared to Comparative Example 1, and the dielectric breakdown strength is lower and worse than Comparative Example 1.

[0031] From the above results, it can be seen that in Examples 1 to 3, BTT suppression effect is obtained by adding nano-sized MgO, and other electrical characteristics are not affected. On the other hand, Comparative Example 2 to which microsize MgO is added cannot provide a sufficient BTT suppression effect, and the dielectric breakdown strength decreases.

[0032] (Examples 4 and 5)

Next, Examples 4 and 5 of the present invention will be described.

In the water-resistant tree cable 1 shown in Fig. 1, the water-resistant tree cable 1 is formed by using a water-resistant tree-resistant insulating composition in which nano-sized MgO with an average particle diameter of 200 nm is added to the LDPE as the insulator 4 with 1 Ophr. This was prepared as Example 4. Similarly, Example 5 was a water-resistant tree-resistant cable 1 to which a water-resistant tree-resistant insulating composition added with lOphr of nano-sized MgO having an average particle diameter of 500 nm was applied. Table 2 shows the results of evaluating the cumulative number of BTT generated for these samples. A comparative example is Comparative Example 2 implemented in Example 1 and shown in Table 1. The evaluation method was the same as in Example 1.

[0033] [Table 2] Sample objects and observation results

* 1: VIEW Exchange in water 500 Hz, 4.5 kV 90 days Observing wheat BTT

* 2: Value at 90 t: 80 kVZmm

* 3: Value on the display by AC Sffi electricity

[0034] Table 2 shows the case where the average particle size is changed while the addition amount of MgO is constant.

[0035] (Evaluation of Examples 4 and 5)

As is clear from Table 2, Examples 4 and 5 have the power to make the average particle diameter of MgO 4 times and 10 times or more that of Examples 1 to 3, and in this case also, insulation is higher than that of Comparative Example 2. BT in body 4

Good results are obtained with significantly fewer T occurrences.

[0036] (Comprehensive evaluation)

From the results in Tables 1 and 2, it can be seen that if the MgO-added amount is the same, the BTT generation suppression effect of the MgO-added additive can be increased as the average particle size of MgO decreases. Divide. It can also be seen that when the average particle diameter of MgO is 500 nm or less, the volume resistivity is improved and the dielectric breakdown strength is not lowered as compared with the case of Comparative Example 1 where no MgO is added. That is, as the particle size of the inorganic filler becomes smaller, the water trapping probability of the inorganic filler dispersed in LDPE improves, and the closer the distance between the particles, the more effective the water tree suppression effect on the water-resistant carpet. Can be increased.

[0037] [Other Embodiments] The present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the invention. For example, a water-resistant tree cable 1 without a sheath 7 V may be an electric wire whose conductor is covered with an insulator.

Industrial applicability

According to the water-resistant tree insulating composition and the water-resistant electric wire cable of the present invention, the inorganic filler having an average particle diameter of 500 nm or less is dispersed in the polyolefin resin. Since the agent suppresses the movement of moisture in the insulating composition due to its water absorption effect, the generation of water trees can be suppressed.

Claims

The scope of the claims

[1] An insulating composition in which an inorganic filler is dispersed in a polyolefin resin,

A water-resistant insulating composition having an average particle diameter of the inorganic filler of 500 nm or less.

[2] The water-resistant insulating composition according to claim 1, wherein the polyolefin resin is crosslinked.

3. The water-resistant insulating composition according to claim 1 or 2, wherein the polyolefin resin is low density polyethylene.

[4] The water-resistant insulating composition according to any one of claims 1 to 3, wherein the inorganic filler has been subjected to a surface treatment and a pulverization treatment.

5. The water-resistant insulating composition according to claim 4, wherein the surface treatment uses vinylsilane as a surface treatment agent.

6. The water-resistant insulating composition according to claim 4 or 5, wherein the pulverization treatment is performed by jet pulverization.

[7] The water-resistant insulating composition according to any one of claims 1 to 6, wherein the inorganic filler is magnesium oxide.

8. The water-resistant insulating composition according to any one of claims 1 to 7, wherein the inorganic filler is dispersed in an amount of 1 part by weight or more with respect to 100 parts by weight of polyolefin resin.

[9] A water-resistant tree wire cable formed by forming the insulating composition according to any one of claims 1 to 8 as an insulator for insulating a conductor.