JPH09245521A - Resin composition and power cable for dc use - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress accumulation of a space charge in an insulator and prevent decreasing of an insulation characteristic or the like, by containing zeolite fine powder in an insulating or semiconductive resin composition with polyolefin serving as a base polymer. SOLUTION: In a power cable for DC use successively provided with an internal semiconductive layer 2, an insulating layer 3, an external semiconductive layer 4, a metal shield layer 5, and a sheath 6 on a conductor 1, the layers 2, 4 are constituted by a semiconductive resin composition, and the layer 3 is constituted by an insulating resin composition. Here, the insulating or semiconductive resin composition contains zeolite fine powder with polyolefin serving as a base polymer. A space charge source in the layer 2 is adsorbed by zeolite, magnesium silicate aluminate, etc., and a transfer of the space charge source from the layers 2, 4 to the layer 3 is also prevented, so as to suppress accumulation of the space charge in the layer 3, a DC electric breakdown characteristic can be improved. In this way, reliability can be improved without decreasing an insulation characteristic and electric characteristic.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin composition useful as an insulating material or a semiconductive material for a DC power cable or a device having a DC insulating portion, and a DC power cable using the same.

[0002]

2. Description of the Related Art Conventionally, in equipment having an AC power transmission power cable and an AC insulating portion, an insulator made of a polyolefin such as cross-linked polyethylene has a high and stable dielectric strength and water resistance. Resistance, chemical resistance,
It is widely used because of its excellent solvent resistance.

For this reason, in recent years, it has been considered to use a polyolefin insulated cable or device having such excellent features for direct current.

However, in this case, there are problems peculiar to direct current insulation to be solved, and above all, the problem of space charge formed in the insulator by the application of direct current voltage is caused by the direct current of such a polyolefin insulated cable or equipment. This is a major obstacle to expanding applications.

That is, for example, in the conventional polyolefin insulated cable, when a DC voltage is applied, electronic homopolar charges (homo-charges) are formed near the conductor electrode side and the shield electrode side, which are around the electrodes. However, if a lightning impulse voltage of the opposite polarity to the direct current enters or the polarity of the direct current voltage is reversed, the electric field at the interface between the conductor electrode and the insulator rises and the breakdown voltage drops significantly. Invite. In addition, it is unavoidable that impurities such as cross-linking residues, which are compounded to prevent long-term chemical deterioration and impurities such as polymerization catalyst residues, are mixed in the insulator. Is polarized, a space charge is formed. This space charge is called a hetero-charge, and as a result of being attracted to electrodes of opposite signs by electrostatic attraction, the electric field near the electrodes is increased and dielectric breakdown easily occurs.

Therefore, an inorganic filler such as carbon black or magnesium oxide is added, an organic acid such as maleic acid is added or grafted, and further,
Various measures have been proposed to suppress the formation and accumulation of space charges, such as adding polar monomers such as vinyl acetate.

However, carbon black is intended to enhance the conductivity and promote the disappearance of charges.
This causes deterioration of insulation resistance and insulation characteristics. Further, although magnesium oxide can trap anions such as halogen and sulfuric acid, it reionizes with a small amount of water to form a large amount of hetero charges. Furthermore, if an electric charge is to be adsorbed by an organic acid or the like, the higher-order structure is disturbed due to a large amount of polar groups, and the insulation characteristics, particularly the impulse breakdown voltage, are greatly reduced. Moreover, these are all
The effect of suppressing the formation of space charge under the high temperature where the cable is used is small, and the reliability in practical use is lacking.

[0008]

As described above, in recent years, in order to apply a polyolefin-insulated cable or device for direct current, a cable or a cable for suppressing the formation and accumulation of space charge due to the application of direct current voltage, which is a problem in this case, or Equipment is being developed. However, in reality, the effect of suppressing the formation and accumulation of space charges, especially the effect of suppressing the charge at high temperature is insufficient, and other electric characteristics are deteriorated. .

The present invention has been made in consideration of such conventional circumstances, and it is possible to sufficiently suppress the formation and accumulation of space charge in an insulator in a polyolefin insulated cable or a device even at high temperature, and It is an object of the present invention to provide a resin composition and a DC power cable using the same, which enables a highly reliable DC power cable or a device that does not deteriorate the insulation characteristics and electrical characteristics of the above.

[0010]

The first invention of the present application is an insulative or semi-conductive resin composition comprising a polyolefin as a base polymer, characterized by containing fine zeolite powder. It is a thing.

A second invention of the present application is an insulating or semiconductive resin composition comprising a polyolefin as a base polymer, which is characterized in that it contains magnesium aluminate silicate fine powder. is there.

A third invention of the present application is an insulating or semi-conductive resin composition containing polyolefin as a base polymer, which is characterized by containing a Li-Al-Mg type inorganic compound. Is.

Further, a fourth invention of the present application is a direct-current power cable characterized in that the insulating layer and / or the semiconductive layer is composed of the above resin composition.

In the resin compositions of the first to third inventions, the zeolite fine powder, the magnesium aluminate silicate fine powder, or the Li-Al-Mg-based inorganic compound contained in the resin composition contains impurities causing a heterocharge. Because of the trapping, the DC breakdown characteristic is improved. Moreover, since this effect does not decrease even at high temperatures, it also has excellent DC breakdown characteristics at high temperatures. Moreover, since it does not lower the insulation resistance or disturb the higher-order structure of the polyolefin, other insulating properties and electrical properties are not significantly deteriorated.

Further, in the DC power cable of the third invention, since the insulating layer and / or the semiconductive layer is constituted by the resin composition having such characteristics, the formation of space charge in the insulating layer is formed. Suppresses accumulation, has stable DC breakdown characteristics even at high temperatures, and other insulation characteristics,
It also has excellent electrical characteristics.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The resin composition of the present invention will be described below.

The resin composition of the present invention is (A) an insulating or semi-conductive resin composition containing a polyolefin as a base polymer, wherein (B) fine zeolite powder and (C) fine magnesium aluminate silicate. Powder, or (D) Li-A
It contains an l-Mg type inorganic compound.

The polyolefin in the insulating or semiconductive resin composition containing the above-mentioned polyolefin (A) as a base polymer is an ultra low density polyethylene (VL).
DPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), medium density polyethylene,
High density polyethylene (HDPE), metallocene-catalyzed polyethylene, polypropylene, polybutene-1, polymethylpentene-1, ethylene copolymers such as ethylene vinyl acetate copolymer, ethylene propylene rubber, ethylene ethyl acrylate copolymer, etc. These may be used alone or in combination of two or more. In the present invention, among others, a polyolefin synthesized by a single-site catalyst such as metallocene, which has excellent electric characteristics and has very little catalyst residue that causes a heterocharge, for example, ethylene or propylene, is used. It is desirable to use those homopolymerized by the same catalyst, or those copolymerized with ethylene or propylene as a copolymer with propylene, butene, pentene, hexene, octene and the like. Examples of such products include Engage C manufactured by Dow Chemical Company.
L8001, Engage CL8002, Affinity FM1570,
Affinity HF 1030 (both are trade names).

The zeolite as the component (B) is a crystalline aluminosilicate having a unique three-dimensional network structure, and various natural and synthetic zeolites such as faujasite, mordenite, chabazite and A-type zeolite are known. ing. In the present invention, at least one kind can be appropriately selected and used from such conventionally known ones.

The component (C), magnesium aluminate silicate, has a porous amorphous structure, and particularly in the case where the above polyolefin is crosslinked with an organic peroxide, its crosslinking residue is well adsorbed. Therefore, it is preferable.
That is, the space charge sources inside the insulator are various as described above, and the decomposition residue of the cross-linking agent (organic peroxide) is one of them, but magnesium aluminate silicate is not limited to acid and alkali. Since it also exhibits excellent adsorption ability to organic impurities such as decomposition residues of the cross-linking agent, it can well adsorb various space charge sources inside the insulator and prevent the formation of hetero charges. Further, in the semi-conductive layer, the conductivity-imparting agent and impurities that migrate to the insulator and become the space charge source are adsorbed,
Prevent the formation of heterocharges in the insulator.

The adsorbing effect of such zeolite or magnesium aluminate silicate does not change even at high temperature, and it lowers the insulation resistance of the insulator like carbon black, or like magnesium oxide. It does not ionize itself to serve as a charge generation source, and moreover, unlike an organic acid or the like, it hardly disturbs the higher-order structure of the polyolefin and lowers the electrical characteristics. Therefore, it is possible to suppress the formation of space charge and improve and stabilize the dielectric breakdown voltage without deteriorating the insulating property and the electrical property.

The component (D), the Li-Al-Mg type inorganic compound, is a porous inorganic powder that is generally used as a stabilizer for vinyl chloride, such as Li ₂ CO ₃ .xMgO.yAl ₂ 0.
₃ · nH ₂ O and the like are exemplified. This Li-Al-Mg-based inorganic compound has an excellent ability to adsorb acids and alkalis, and like the zeolite of (B) above, adsorbs space charge sources inside these insulators well and prevents the formation of heterocharges. To do.
In addition, in the semiconductive layer, the space charge source that migrates to the insulator is adsorbed to prevent the formation of hetero charge in the insulator. In addition, this adsorption effect does not change even at high temperatures, and it lowers the insulation resistance of insulators such as carbon black, and disturbs the higher-order structure of polyolefins such as organic acids to lower the electrical properties. There is little to do.
Therefore, it is possible to suppress the formation of space charges and to improve and stabilize the dielectric breakdown voltage without significantly deteriorating the insulating property and the electrical property.

Incidentally, these (B) component zeolites,
The blending amount of component (C), magnesium aluminate silicate, or component (D), Li-Al-Mg-based inorganic compound, is preferably in the range of 0.1 to 20% by weight based on the polyolefin.
This is because if it is less than 20% by weight, the adsorption of the space charge generation source becomes insufficient, and if it exceeds 20% by weight, the electric characteristics may be adversely affected. A more desirable range is 1 to 3% by weight based on the polyolefin.

The resin composition of the present invention may contain, if necessary, a crosslinking agent, a crosslinking aid, an antioxidant and other additives as long as they are within the range usually used. . Further, the conductivity-imparting agent to be added in order to impart semiconductivity, those conventionally used in general,
It may be blended within the range usually used. Many of these additives are sources of space charge, but the above zeolite, magnesium aluminosilicate, or Li
The formation of space charge is suppressed by the action of the -Al-Mg-based inorganic compound. Further, another adsorbent may be used in combination as long as the effect of the present invention is not impaired.

Next, an example of a DC power cable using the resin composition of the present invention as described above will be described.

That is, FIG. 1 shows an example of a DC power cable according to the present invention. In FIG.
Indicates a conductor, and on this conductor 1, an internal semiconductive layer 2,
The insulating layer 3, the outer semiconductive layer 4, the metal shielding layer 5, and the sheath 6 are provided in this order. The inner semiconductive layer 2 and the outer semiconductive layer 4 are made of the semiconductive resin composition according to the present invention as described above, and the insulating layer 3 is made of the insulating resin composition.

In such a DC power cable, the space charge source in the insulating layer 2 is adsorbed by zeolite, magnesium aluminate silicate, or a Li-Al-Mg type inorganic compound, and the inner semiconductive layer 2 is used. Since the space charge source is prevented from migrating from the outer semiconductive layer 4 to the insulating layer 3, the formation and accumulation of space charges in the insulating layer 2 due to the application of a DC voltage is suppressed, and a good DC breakdown characteristic is obtained. Have.
Moreover, since the effects of zeolite and the like do not decrease even at high temperatures, the DC breakdown characteristics during practical use are also good.
Further, since zeolite or the like does not increase the insulation resistance or disturb the higher-order structure of the polymer, it does not significantly deteriorate other insulating properties and electrical properties.

In this example, both the semiconductive layer and the insulating layer are made of the resin composition according to the present invention. However, one of the semiconductive layer and the insulating layer is made of the resin composition according to the present invention. It may be configured. However, in terms of effects, it is desirable that at least the insulating layer be composed of the resin composition according to the present invention.

[0029]

The present invention will be described in more detail with reference to the following examples.

Examples 1 to 10 Insulating compositions having various compositions shown in Table 1 were obtained, and by using the insulating compositions, a DC power cable was manufactured. The physical properties of the three magnesium aluminate silicates used are shown in Table 2.

That is, a copper conductor having a diameter of 2 mm was coated with the semiconductive composition, the insulating composition, and the semiconductive composition in this order by three-layer coextrusion, and heat-crosslinked by a conventional method to give 0.5. mm semi-conductive inner layer, 2 mm thick insulating layer,
A 0.5 mm thick outer semiconductive layer was formed, and a metal shielding layer and a 1 mm thick sheath made of extruded soft vinyl chloride resin were sequentially provided on the outer side of the outer semiconductive layer. For the formation of the inner semiconductive layer and the outer semiconductive layer, a semiconductive composition prepared by mixing 38% by weight of conductive carbon with an ethylene / vinyl acetate copolymer was used.

Next, the long-term DC breakdown voltage at room temperature and 90 ° C. was examined for the obtained power cables of the respective examples. The voltage was applied by applying a DC voltage of -100 kV for 1 hour, and then stepping up to breakdown at a step of 10 kV / 1 hour, and the number of samples was 3 samples each. The results are shown in the lower column of Table 2.

Further, in Table 2, for comparison, an example in which carbon black is blended (Comparative Example 1), an example in which magnesium oxide is blended and an organic acid copolymerized polyethylene is used as a polyolefin (Comparative Example 2) 3) is also shown.

[0034]

[Table 1]

[Table 2] As is clear from Table 1, the cable according to the present invention is
Not only at room temperature but also at 90 ° C, which is a practical temperature range, the DC breakdown characteristics were improved over a long period of time, which improves the reliability during use.

Example 11 100 parts by weight of metallocene-polymerized polyethylene (density 0.917, MI3.4, Affinity FM1570 manufactured by Dow Chemical Co.) is represented by the general formula Li ₂ CO ₃ .xMgO.yAl ₂ 0 ₃ .nH ₂ O. Li-Al-Mg inorganic powder (BET specific surface area 31.99m ² / g,
3 parts by weight of Fuji Chemical Industry Co., Ltd. (trade name LMA) was mixed, and the resulting composition was subjected to PEA method (pulse electrostatic stress method).
The space charge distribution characteristics were investigated by. Measurement about the composition
A sample sheet extruded into a sheet with a thickness of 1 mm was applied with DC voltage at room temperature. The results are shown in the graph of FIG. For comparison, the space charge distribution characteristics of the metallocene-polymerized polyethylene not blended with the Li-Al-Mg-based inorganic powder are also shown in the graph of FIG. 2 (b).

As is clear from these graphs, Li
In the case where the -Al-Mg-based inorganic powder is blended, the formation and accumulation of space charges are greatly suppressed.

Subsequently, a DC power cable was manufactured in the same manner as in Example 1 using the above composition. That is, on a copper conductor having a diameter of 2 mm, a semiconductive composition, Li-Al-
A composition containing Mg-based inorganic powder and a semiconductive composition are sequentially coated by three-layer coextrusion to form a 0.5 mm thick inner semiconductive layer, a 2 mm thick insulating layer, and a 0.5 mm thick outer semiconductive layer. Then, a metal shielding layer and a 1 mm-thick sheath made of extruded soft vinyl chloride resin were sequentially provided on the outer side. The long-term DC breakdown voltage of the obtained power cable at room temperature and 90 ° C. was measured in the same manner as in Example 1. As a result, 370 kV at room temperature and 340 kV at 90 ° C., both of which were good results. .

Example 12 Affinity of metallocene polymerized polyethylene FM1570 100
38 parts by weight of acetylene carbon as conductive carbon black, and 5 parts by weight of magnesium aluminometasilicate (trade name Neusilin UFL2 manufactured by Fuji Chemical Industry Co., Ltd.) were added to and mixed with the parts by weight to obtain a semiconductive composition, and its characteristics Was evaluated. The evaluation was performed by extruding the obtained semiconductive composition into a sheet with a thickness of about 1 mm to form a sheet, and stacking this on an insulating sheet with a thickness of about 0.5 mm made of ordinary crosslinked polyethylene prepared in advance and integrally heating it. After fusing, the space charge distribution characteristics (90 ° C.) of the insulating sheet were examined by the PEA method.

The results are shown in the graph of FIG. Also,
For comparison, the graph of FIG. 3 (b) shows the space charge distribution characteristics similarly examined for the semiconductive composition not containing magnesium aluminometasilicate.

As is clear from these graphs, in the example, the sheet interface is included even at high temperature.
The formation and accumulation of space charges are greatly suppressed.

Although not described in detail, the space charge is similarly obtained in an example in which Li-Al-Mg type inorganic powder (trade name LMA manufactured by Fuji Chemical Industry Co., Ltd.) is used instead of magnesium aluminometasilicate. It was confirmed by the experiment that the formation and accumulation of P.

[0042]

As is clear from the above examples, according to the resin composition of the present invention, formation and accumulation of space charges due to direct current application in the insulating layer are sufficiently suppressed even at high temperature, and It is possible to form an insulating layer or a semi-conductive layer that has good other characteristics required for the insulating layer, and therefore, the DC power cable of the present invention using this has stable dielectric breakdown characteristics, In addition, other insulation characteristics and electric characteristics are also excellent and highly reliable.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a DC power cable of the present invention.

2A is a space charge distribution characteristic measured for an example of a resin composition of the present invention, and FIG. 2B is a space charge distribution characteristic of a comparative example.

FIG. 3A is a space charge distribution characteristic measured with respect to another example of the resin composition of the present invention, and FIG. 3B is a space charge distribution characteristic of a comparative example.

[Explanation of symbols]

1 ... Conductor 2 ... Inner semiconducting layer 3 ... Insulating layer 4 ... Outer semiconducting layer 5 ... Metal shielding layer 6 ... Sheath Applicant Showa Cable Denki Co., Ltd. Attorney Attorney Suichi Saichi

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hajime Tanimoto 2-1-1 Oda Sakae, Kawasaki-ku, Kawasaki City, Kanagawa Prefecture, Showa Electric Wire & Cable Co., Ltd. No. 1-1 No. 1 Showa Electric Cable Co., Ltd.

Claims (7)

[Claims] 1. An insulating or semi-conductive resin composition containing polyolefin as a base polymer, wherein the resin composition contains fine zeolite powder. 2. An insulating or semi-conductive resin composition comprising a polyolefin as a base polymer, the resin composition comprising fine magnesium aluminate silicate powder. 3. The resin composition according to claim 2, wherein the magnesium aluminate silicate has (a) an oil absorption of 2.0 ml / g.
A resin composition satisfying at least one of the above and (b) a specific surface area of 120 m ² / g or more. 4. An insulating or semiconductive resin composition comprising a polyolefin as a base polymer, which comprises Li-Al-Mg.
A resin composition containing an inorganic compound. 5. The resin composition according to claim 4, wherein Li
-Al-Mg-based inorganic _{compound, Li 2 CO 3 · xMgO ·} yAl 2 0 3 ·
A resin composition comprising nH ₂ O. 6. The resin composition according to claim 1, wherein the polyolefin is a polyolefin synthesized by a single site catalyst. 7. A DC power cable, wherein the insulating layer and / or the semiconductive layer is formed of the resin composition according to any one of claims 1 to 6.