JP3477145B2 - Crosslinkable ethylene resin composition and electric wire / cable coated with the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crosslinkable ethylene resin composition excellent in moisture absorption suppressing property, an electric wire / cable coated with the same, and a method for producing the same, more specifically, as an outdoor distribution line. A crosslinkable ethylene-based resin composition in which generation of eye drops is reduced / suppressed at the time of coating an electric wire used as an insulating layer and / or a sheath layer of the crosslinked polyethylene electric wire used, and a crosslinked polyethylene electric wire obtained by coating the same on a conductor or The present invention relates to a cable and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, electric wires and cables (in the present invention,
It may be simply referred to as an electric wire / cable or an electric wire. )
A vinyl chloride resin composition has been generally used as a resin material such as a coating material, but in recent years, there is a movement to substitute a resin having a smaller environmental load, and actually, an ethylene-based resin having excellent electrical characteristics is used. Resin compositions have been developed. In addition, as an outdoor distribution line, a conductor is coated with an insulating layer,
This has a structure that doubles as an outer shell layer 6,000-33,0
An electric wire for transmitting 00V, and a conductor for transmitting a voltage higher than this, are composed of multiple layers such as an inner semiconductive layer, an insulating layer, an outer semiconductive layer, and a sheath layer, and the sheath layer is an outer shell. There are electric wires that have a layered structure. The outer shell layer and the sheath layer (hereinafter, also simply referred to as the outer shell layer) may contain up to about 3.0% by weight in order to impart weather (light) resistance, particularly ultraviolet resistance. Carbon black is blended, and a crosslinkable ethylene resin composition is used in order to enhance weather resistance (light) resistance and mechanical strength.

However, the crosslinkable ethylene-based resin composition for the outer shell layer is generally compounded and prepared in an ethylene polymerization factory, and the product molded into pellets is sent to an electric wire manufacturing factory to be extruded and coated on a conductor, Crosslinked by heating,
It is processed into electric wires, for example, pellets transported to hot and humid areas or stored for a long time, for example, exported from Japan to Asian countries and usually covered with electric wires.
When extruding and coating the pellets that have passed 5 to 30 days, the formation of so-called eyes and eyes is noticed around the die nipple at the time of processing, and the surface of the outer shell layer has dents and irregularities. (In the present invention, the surface spots, irregularities, bumps, etc. may be collectively referred to simply as surface roughness. In the present invention, a state without surface roughness may be referred to as surface smoothness. There was.)
These adversely affect the quality of electric wires and have been a problem.

[0004]

The object of the present invention is to maintain the ultraviolet resistance, electrical performance, mechanical properties, etc. of the crosslinkable ethylene resin composition for the outer shell layer obtained by the prior art, Furthermore, even if it is stored under high humidity conditions, or if it takes time to store and transport it, it has high stability within 30 days from the time of production, and compared to conventional products, it causes less eyesore during extrusion molding of wire production. It is an object of the present invention to provide a crosslinkable ethylene resin composition capable of producing a high-quality electric wire having little practical value and no surface roughness, a crosslinked polyethylene electric wire or cable formed by coating the same, and a method for producing the same.

[0005]

Means for Solving the Problems As a result of intensive studies conducted by the present inventors in order to solve the above-mentioned problems, the occurrence of surface roughening and surface roughness has a correlation with the amount of moisture absorbed by a crosslinkable ethylene resin composition. Further, it was found that the moisture absorption amount of the crosslinkable ethylene-based resin composition is due to the hygroscopicity of carbon black in which most of the moisture is absorbed, and the produced crosslinkable ethylene-based resin composition is , For example, it is transported in an inner bag made of a flexible container made of polyethylene and an outer box made of cardboard, but if this is replaced with a moisture-proof bag such as an aluminum vapor-deposited inner bag or an aluminum inner bag, the amount of moisture absorbed can be controlled. The increase in cost due to the cost cannot be ignored, and in the case of transportation in moisture-proof containers, additional costs are required to recover the containers, and transportation to customers who do not reach this capacity Further in view of the lack of practicality without cost increase is avoided, thereby completing the present invention.

That is, according to the first aspect of the present invention,
A cross-linkable ethylene resin composition comprising 100 parts by weight of an ethylene resin, 0.3 to 3.0 parts by weight of low hygroscopic carbon black and 0.5 to 4.0 parts by weight of a cross-linking agent. 100 mm pellets granulated from the composition
After drying under Hg pressure at 50 ° C for 6 hours, the moisture content (W) at the specified moisture content (W) when exposed to a relative humidity of 79% and a temperature of 23 ° C for 30 days in a thermo-hygrostat (unit: weight basis) Is satisfied by the following formula (1),
A crosslinkable ethylene-based resin composition is provided. W ≦ 500 …… (1)

According to the second aspect of the present invention, the low hygroscopic carbon black is a low hygroscopic furnace black having an average particle diameter of 10 to 30 nm, and the high pressure low density ethylene containing 40% by weight of the low hygroscopic carbon black. The pellets granulated from the homopolymer composition were heated at 80 ° C. under a pressure of 100 mmHg for 6 minutes.
After drying for an hour, in a thermo-hygrostat, the specified moisture absorption amount (W ') (unit: ppm by weight) when exposed to the conditions of a relative humidity of 79% and a temperature of 23 ° C for 30 days is as follows: 2)
The crosslinkable ethylene resin composition according to the first aspect of the present invention is provided. W'≤5000 (2)

Further, according to the third aspect of the present invention, the low hygroscopic carbon black is made of a hydrocarbon oil having a low sulfur content as a raw material and has an average particle diameter of 10 to 30.
The second aspect of the present invention, which is obtained by adjusting the thickness to nm and thoroughly washing the surface of impurities including potassium, calcium, sulfur and the like with pure water.
The crosslinkable ethylene resin composition according to the invention is provided.

Further, according to a fourth invention of the present invention, the crosslinkable ethylene resin composition according to any one of the first to third inventions of the present invention is extrusion-coated with a die. A method of making a crosslinked polyethylene wire or cable is provided.

Furthermore, according to a fifth aspect of the present invention, there is provided a cross-linked polyethylene electric wire or cable produced by the manufacturing method according to the fourth aspect of the present invention.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. First, each constituent component used in the present invention will be described in detail.

1. Ethylene Resin As the ethylene resin used as the base resin in the present invention, a high pressure method low density ethylene homopolymer, a high density ethylene homopolymer, a medium density ethylene homopolymer, a linear low density ethylene-α- Examples thereof include an olefin copolymer and a linear ultra-low density ethylene-α-olefin copolymer. These ethylene-based resins can be prepared by using respective known polymerization methods.As the polymerization catalyst, in the case of the high pressure method, organic peroxides, azo compounds, radical generating catalysts such as oxygen and other heavy catalysts are used. When legal,
Examples include Phillips type catalysts, Ziegler type catalysts, standard type catalysts and metallocene type catalysts.

The α-olefin copolymerized with ethylene includes propylene, butene-1, hexene-1,4-
Methyl pentene-1, octene-1, decene-1, dodecene-1 etc. are illustrated. The ethylene-based resins may be used alone or in combination of two or more (for example, including two or more high-pressure method low-density ethylene homopolymers) and have a melt mass flow rate of 0.005 to 10 g / 10. Minutes,
The density is preferably 0.916 to 0.928 g / cm ³ , and more preferably, a high-pressure method low-density ethylene homopolymer excellent in electrical characteristics can be preferably used.

2. Carbon Black Carbon black used in the present invention is 30% of the crosslinkable ethylene resin composition of the present invention to be described later in which the carbon black is blended.
Normal moisture absorption (W) after daily exposure is 500ppm
It is essential that the carbon black is a so-called low hygroscopic carbon black having a characteristic of not more than (weight unit), preferably not more than 450 ppm, more preferably not more than 400 ppm.

In the present invention, any of acetylene black, thermal black and furnace black can be used as long as they are carbon blacks having a low hygroscopicity, but they are resistant to ultraviolet rays and weather (light). Furnace black is preferred. Further, in order to ensure low hygroscopicity, it has excellent dispersibility and has a particle size of 10 to 3
Furnace black of about 0 nm, preferably 15 to 20 nm, and more preferably about 18 nm is good. The low hygroscopic furnace black is prepared from oil having a low sulfur content as a raw material, and the particle size of the furnace black is adjusted as described above, and impurities including potassium, calcium and sulfur on the surface thereof are thoroughly washed with pure water. Can be obtained.

A preferred low hygroscopic carbon black in the present invention is BLACK PEARL from Cabot Corporation.
S 6100 (registered trademark, hereinafter BLACK PEARL
It may be abbreviated as S. ) Available as. This carbon black has low hygroscopicity, is suitable for the crosslinkable ethylene-based resin composition of the present invention, and that the crosslinkable ethylene-based resin composition using the same shows good results, the experiments described below. Confirmed by the results. That is, BLACK PEARLS (average particle diameter 18 nm) from Cabot, which is a preferred low hygroscopic carbon black in the present invention, VULCAN 9A32 (average particle diameter 15 nm) from Cabot, which is a conventional furnace black, and Mitsubishi Chemical. No. In order to know the degree of hygroscopicity such as 650B (average particle size 16 nm), a high-pressure low-density ethylene homopolymer composition containing 40% by weight of these carbon blacks (in the present invention, simply HP-LDP
It may be abbreviated as E composition. When the pellets granulated from () are dried at 80 ° C. under a pressure of 100 mmHg for 6 hours, and then exposed in a constant temperature and humidity chamber at a relative humidity of 79% and a temperature of 23 ° C. for any number of days (hereinafter, , It may be simply described as exposure time (days) or exposure days.)
The moisture content of the specified moisture content was measured for each number of exposure days. The results are shown in Table 1 and FIG. 1, which illustrates Table 1. In the present invention, the specified moisture absorption amount when the number of exposure days is 30 days is particularly important and is described as a numerical value having a critical meaning in the claims. Therefore, the specified moisture absorption amount defined in claim 1 is particularly important. Is attached to (W), and (W ') is attached to the specified moisture absorption amount defined in claim 2 so as to differentiate from the specified moisture absorption amount for the number of exposure days other than 30 days. Therefore, when simply described as the specified moisture absorption amount, the number of exposure days is, for example, 1, 3, 7, 10, 20, 3
There are specified moisture absorption amounts for 0, 40, 50, and 60 days (in the case of Table 1), which are collectively referred to.

[0017]

[Table 1]

From Table 1, BLACK POT of Cabot Corporation
The specified moisture absorption after exposure to EARLS for 20 days is:
At 3,840 ppm, almost saturation was reached, and then the number of exposure days increased to 6 with a slight increase with the increase in exposure days.
It was found to be 4,160 ppm on day 0. on the other hand,
The conventional moisture absorption moisture content of Cabot's VULCAN9A32 after 20 days of exposure was 7,010 ppm, and then increased considerably as the number of days of exposure increased, which was as high as 8,490 ppm after 60 days of exposure. It turns out that the value is reached. In addition, the conventional product made by Mitsubishi Chemical N
O. The specified moisture absorption by 20 days exposure of 650B is
At 7,500 ppm, it increased further with the increase in the number of exposure days.
It was found to reach an even higher value of 0 ppm. From the above, it was found that BLACK PEARLS manufactured by Cabot Co., Ltd. has a remarkably low specified moisture absorption amount as compared with the conventional product, and has a characteristic of reaching a saturated equilibrium after 20 days of exposure.

Next, a crosslinkable ethylene resin composition was prepared using the above-mentioned carbon black, granulated, and the specified moisture absorption amount was measured. The specified moisture absorption amount of each resin composition was the same as that of carbon black. It was confirmed as follows that it depends on the type and blending amount. HP-having a melt mass flow rate of 3.0 g / 10 minutes and a density of 0.922 g / cm ³ .
LDPE, 4,4'-thiobis (3
-Methyl-6-t-butylphenol) and dicumyl peroxide as a cross-linking agent were used to prepare a cross-linkable ethylene-based resin composition having the composition shown in Table 2 and granulated. , As shown in Table 2 and FIG.
The specified moisture absorption amount (W) when resin composition 1 using 0.65 parts by weight of BLACK PEARLS of Cabot Corporation is exposed for 30 days is a low level of 330 ppm, while the conventional product VULCAN 9A manufactured by Cabot Corporation.
When the resin composition 2 containing 0.65 parts by weight of 32 is exposed for 30 days, the specified moisture absorption amount (W) is 650 ppm.
It is a high level and 0.9% of the same carbon black.
When the resin composition 3 used in parts by weight was exposed for 30 days, the specified moisture absorption amount (W) was 770 ppm, which was a higher level, and a significant difference was observed between the two.

[0020]

[Table 2]

Next, with respect to the resin compositions 1 and 2 shown in Table 2 having different specified moisture absorption amounts, 13 with a Labo Plastomill.
Kneading at 0 ° C, rotation speed 50 rpm for 60 minutes and extruding for 6 hours,
The eyes and eyes attached to the mold were measured. The results show that, as shown in Table 3, the occurrence of eyelashes correlates with the normal moisture absorption amount of the resin composition, and when the normal moisture absorption amount of the resin composition defined and used in the present invention is 500 ppm or less, it is based on the eyelashes described below. C and above, which was a level of practical value. According to the above three-stage experiment, the cross-linkable ethylene resin composition using the low hygroscopic carbon black is
It has been confirmed that it has a moisture absorption suppressing property, and therefore, even if it is stored under high humidity conditions, it causes less eye bleeding, that is, it has an excellent eye swelling suppressing property.

[0022]

[Table 3]

The amount of carbon black compounded is 0.3 to 3.0 parts by weight, based on 100 parts by weight of the ethylene resin.
It is preferably 0.4 to 2.5 parts by weight, more preferably 0.5 to 1.2 parts by weight. If this amount is less than 0.3 parts by weight, effective weather resistance (light) cannot be obtained, while 3.
If it exceeds 0 parts by weight, the insulation performance is deteriorated and the mechanical properties are deteriorated, which is not desirable.

3. Crosslinking Agent As the crosslinking agent used in the present invention, organic peroxides, peresters, and azo compounds are used, and specifically, 1,1-bis-t-butylperoxycyclohexane and 2,2-bis -T-butylperoxybutane, dicumyl peroxide, 2,5-dimethyl-2,5-di-t
-Butylperoxyhexane, t-butylcumyl peroxide, 2,5-dimethyl-2,5-di-t-butylperoxyhexyne-3, α, α'-bis-t-butylperoxydipropylbenzene , Di-t-butyl peroxide, diisopropylbenzene hydroperoxide and the like. Dicumyl peroxide is particularly preferable. The amount of the cross-linking agent to be added is 0.5 to 4.0, preferably 1.0 to 4.0, based on 100 parts by weight of the ethylene resin.
2.5 parts by weight. If the blending amount is less than 0.5 parts by weight, effective crosslinking cannot be obtained, while if it exceeds 4.0 parts by weight, gel or the like is generated, and the uniformity of electrical properties begins to deteriorate,
In addition, the surface is roughened, which is not preferable.

4. Additives, etc. Various additives may be further added to the crosslinkable ethylene resin composition of the present invention. As various additives, stabilizers, antioxidants, ultraviolet absorbers, light stabilizers, antistatic agents, lubricants, fillers, dispersants, colorants, copper damage inhibitors, antifoam agents, nucleating agents, etc. Can be mentioned. The crosslinkable ethylene resin composition of the present invention preferably contains an antioxidant, an ultraviolet absorber and / or a light stabilizer.

Examples of the antioxidants include phenolic antioxidants, phosphorus antioxidants, amine antioxidants, sulfur antioxidants, etc., which may be used alone or in combination of two or more. It may be added, and the blending amount is about 0.001 to 5 parts by weight based on 100 parts by weight of the ethylene resin.

Examples of the ultraviolet absorbers and light stabilizers include 2-hydroxybenzophenone type, 2- (2-hydroxyphenyl) benzotriazole type, salicylic acid type, phthalic acid type ultraviolet absorbers and hindered amine type light stabilizers. They may be used alone or in combination of two or more, and the compounding amount thereof is about 0.05 to 1 part by weight based on 100 parts by weight of the ethylene resin.

5. Crosslinkable ethylene-based resin composition The crosslinkable ethylene-based resin composition of the present invention is a predetermined amount of the above-mentioned component ethylene-based resin, carbon black and a cross-linking agent, and if necessary, an appropriate amount of the above additives and the like is blended, It can be prepared by a general method, for example, a kneader, a Banbury mixer, a continuous mixer or an extruder, which is uniformly melt-kneaded at a temperature not higher than the decomposition temperature of the crosslinking agent at 110 to 130 ° C. The preparation may be carried out, for example, by preparing a masterbatch with the above-mentioned ethylene resin and carbon black, and using this to prepare it in two steps. The crosslinking agent may be prepared by heating pellets prepared in advance and heating the pellets. You may mix by the method of impregnating a crosslinking agent.

The crosslinkable ethylene resin composition of the present invention, which is usually in the form of pellets, produced as described above,
Since it has low hygroscopicity, if it is within 30 days after manufacturing,
Even when stored in a place where the humidity is as high as about 79%, the specified moisture absorption amount (W) is 500 ppm or less, and the generation level is low and the pass level is low. Since the water content of the crosslinkable ethylene resin composition of the present invention immediately after the production of the pellets is usually 100 ppm (weight unit) or less, it can be directly stored in, for example, a polyethylene flexible container and stored / transported. . If the water content of the pellets immediately after production significantly exceeds 100 ppm,
Of course, it is preferable to dry the pellets by a conventional method and then put them in a container or the like. Further, the crosslinked polyethylene electric wire of the present invention is excellent in surface smoothness without surface roughness, and the crosslinkable ethylene resin composition prepared as described above is melted by heating,
It is extruded and coated as an outer shell layer on the core wire of the electric wire or on the outer semiconductive layer, and this is coated, for example, in a cross-linked tube at 200 to 450 ° C.
It is produced by heat-crosslinking with.

[0030]

The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited to these examples. The physical property values used in the present specification and the evaluated physical property values evaluated in Examples and the like are based on the measurement methods summarized below.

[Measuring method]

1. Melt mass flow rate Crosslinking agent-free pellets of an ethylene-based resin composition were tested according to JIS K 6760, and a load of 2.1 was applied.
The measurement was performed at 6 kg and a measurement temperature of 190 ° C.

2. The pellets of the ethylene resin composition in which the density crosslinking agent was not blended were measured in accordance with JIS K6760.

3. Regarding the pellets of the ethylene resin composition containing no carbon black content cross-linking agent, JCS (Japan Cable Maker's)
Association Standard: carried out in compliance with the Japanese electric wire Industrial Standard) 375, it was measured content of carbon black (% by weight).

4. The pellets of the ethylene resin composition containing no carbon black dispersion cross-linking agent were prepared according to JCS 375, and the size and number of non-dispersed particles per unit area were measured with an optical microscope.
Grades 7.5 and below were accepted.

5. Specified Moisture Absorption Moisture Content (5-1) Specified Moisture Absorption Water Content of Ethylene Resin Composition Pellets granulated from the crosslinkable ethylene resin composition are dried at 50 ° C. for 6 hours under a pressure of 100 mmHg, and then weighed. , Relative humidity 79%, temperature 23 in a constant temperature and humidity chamber
The sample was exposed to an atmosphere of ° C for a specified number of days, and after the specified number of days, it was weighed again and the weight increase was defined as a specified moisture absorption amount, and expressed in ppm (weight basis). (5-2) Normal moisture content of high-pressure low-density ethylene homopolymer composition containing 40% by weight of low hygroscopic carbon black High-pressure low-density ethylene homopolymer composition containing 40% by weight of low hygroscopic carbon black The pellets granulated from the above were dried under a pressure of 100 mmHg at 80 ° C. for 6 hours, then weighed, and in a thermo-hygrostat, relative humidity 79%, temperature 23
The sample was exposed to an atmosphere of ° C for a specified number of days, and after the specified number of days, it was weighed again and the weight increase was defined as a specified moisture absorption amount, and expressed in ppm (weight basis).

6. Tensile Properties (Tensile Strength, Elongation) It was measured according to JIS K 6760. The sheet thickness of the evaluation sample was 1 mm, and the measurement was performed using a No. 3 dumbbell at a pulling speed of 500 mm / min.

7. Heat Aging Residual Rate It was performed in accordance with JIS K 6760. Tensile strength and elongation were measured on the sample after heating at 150 ° C. for 168 hours, and the results were compared with those before the test.

8. The dielectric constant was measured according to JIS K 6760. A score of 2.4 or less was passed.

9. Dielectric loss tangent was performed according to JIS K 6760. 1000 x 1
Less than 0 ^-6 it was passed. 10. Volume resistivity

Measured in accordance with JIS K 6723,
A pass of 1 × 10 ¹⁶ Ωcm or more was determined.

11. The gel fraction was measured according to JIS C 3005, and the content was expressed as the insoluble residue after the sample was placed in xylene and left at 110 ° C. for 24 hours. 75% or more was passed.

12. Hot creep IEC (International Electro)
Technical Commission: International Electrical Commission) 60502. A load of 0.2 MPa was applied to the sample prepared by compression molding, and the elongation rate after 15 minutes at 200 ° C. was 175% or less, which was regarded as acceptable.

13. The shrinkage of the sample after hot creep measurement was measured according to Hot Set IEC 60502. Passing 15% or less.

14. Thermal deformation rate: Performed in accordance with JIS K 6723, and apply a load of 10 kg to a 3 mm thick sheet prepared by compression molding to 120 ° C.
After 30 minutes, the rate of change in thickness was measured. 40% or less was passed.

15. Weather resistance (light) resistance test Using a weather odometer (manufactured by Suga Test Instruments Co., Ltd.) under the conditions of a carbon arc light source, a temperature of 60 ° C. and a relative humidity of 60%, 209. According to the method described in the weather resistance of crosslinked polyethylene, the glass filter was exposed under the condition that the glass filter was removed. This is outdoor exposure 4
It is a 0 times accelerated test condition. Irradiation time 500 hours, 10
00 hours, 2000 hours, 3000 hours and 5000 hours
It was measured by the residual ratio of tensile strength and elongation of a 1.0 mm thick sheet sample prepared by compression molding after a lapse of time. The residual rate of tensile strength of 40% or more after 5000 hours and the residual rate of elongation of 20% or more were passed.

16. Pellets granulated from the crosslinkable ethylene-based resin composition used in the eye-specific moisture absorption moisture test were dried at 50 ° C. for 6 hours at a pressure of 100 mmHg, then a relative humidity of 79% and a temperature of 23.
The pellets stored at 30 ° C. for 30 days were kneaded with a Labo Plastomill at 130 ° C. and a rotation speed of 50 rpm for 60 minutes, extruded from a circular die having a diameter of 3 mm for 6 hours, and the eye area attached to the die nipple was measured. The evaluation was performed according to the following criteria, and A, B and C were regarded as passed. Evaluation Criteria A for Eyes: Occurrence of eyes is not observed. B: Eyes are recognized up to 1 mm in the entire hole of the die nipple. C: Eyes are recognized up to 2 mm in the entire hole of the die nipple. D: Eyes and eyes are recognized up to 3 mm in the entire hole of the die nipple. E: Eyes were observed in the entire hole portion of the die nipple exceeding 3 mm, and a drop in the eye from the die nipple was also observed.

Example 1 HP-LDPE (manufactured by Nippon Unicar, NUC-9025,
Melt mass flow rate 3.2 g / 10 minutes, density 0.9
22 g / cm ³ ) 100 parts by weight and carbon black (manufactured by Cabot, BLACK PEARLS 610)
No. 0, furnace black, average particle diameter 18 nm, HP-LDPE composition containing 40% by weight thereof has a specified moisture absorption amount (W ′) of 4000 ppm. ) 0.5 parts by weight and antioxidant 4,4'-thiobis (3-methyl-6-
0.2 part by weight of (t-butylphenol) was placed in a Banbury mixer, and the mixture was kneaded at 120 ° C. for 10 minutes and then granulated to obtain pellets. With respect to the obtained pellets, melt mass flow rate, density, carbon black content and carbon black dispersion were measured. The results are shown in Table 4.

[0049]

[Table 4]

As is apparent from the results, the pellets showed good processability and carbon black dispersion.
The pellets heated to 40 ° C. and the above HP-LDPE
1.6 parts by weight of dicumyl peroxide as a crosslinking agent based on 100 parts by weight was placed in a closed container and mixed for 24 hours while maintaining 40 ° C. to impregnate the crosslinking agent. The pellets obtained have a specified moisture absorption (W) of 330 pp after 30 days of exposure.
m was the crosslinkable ethylene resin composition of the present invention. The results of evaluation of the obtained crosslinkable ethylene-based resin composition of the present invention by the above method are shown in Table 4. It has good mechanical properties, electrical properties, crosslinking properties, and a weather (light) resistance test. But he had excellent results. In addition, the evaluation result of B was also shown in the eye and eye test, and the eye and eye had excellent inhibitory properties and excellent storage stability. This resin composition having a specified moisture absorption (W) of 330 ppm after 30 days of exposure was extrusion-coated with a thickness of 1.5 mm on a core wire of aluminum (cross-sectional area 60 mm ² ), and a butt size of 0.
An electric wire of practical value having no surface roughness where 5 mm or more was not observed was obtained.

Examples 2 to 4 Pellets were prepared in the same manner as in Example 1 with the formulations shown in the compositions of Examples 2, 3 and 4 in Table 4, and evaluated in the same manner. The HP-LDPE used in Example 2 is NUC-9024 manufactured by Nippon Unicar Co., Ltd., and melt mass flow rate is 2.
It was 0 g / 10 minutes and the density was 0.922 g / cm ³ . Three
Specified moisture absorption (W) of 0 day exposure is 340pp each
The crosslinkable ethylene-based resin composition of the present invention having m, 350 ppm and 370 ppm shows the same excellent processability, electrical characteristics, and storage stability as in Example 1, and the evaluation for the eye is B or C, It was excellent in weather resistance (light) and was excellent in storage stability and had practical value.

Comparative Examples 1 and 2 Example 1 having the composition shown in the compositions of Comparative Examples 1 and 2 in Table 4 was used.
Pellets were prepared in the same manner as above and evaluated in the same manner. In Comparative Example 1, VULCAN 9A32 manufactured by Cabot
(The specified moisture absorption water content (W ') of 30-day exposure of an HP-LDPE composition containing 40% by weight thereof is 8120 ppm). 650B
(The prescribed moisture absorption (W ') of 30 days exposure is the same as above.)
It is 470 ppm. ) Furnace black was used. The evaluation results are shown in Table 4. The obtained ethylene-based resin composition had good dispersibility of carbon black and was excellent in electrical characteristics and weather (light) resistance, but after 30 days exposure The specified moisture absorption amount (W) is 650 ppm,
It became 770 ppm and was evaluated as D in the eye and eye evaluation test using these, and was inferior in storage stability. The prescribed moisture absorption amount (W) of 30 days exposure obtained in Comparative Example 2 was 6
When the core wire was coated with 50 ppm of the crosslinkable ethylene-based resin composition in the same manner as in the example, the particle size was 0.5 m.
The number of m or more was 3.1 per 5 m of electric wire length. The obtained electric wire had an appearance in which the surface was rough to the touch.

[0053]

As described above in detail, according to the present invention, the ethylene resin and the specific specified moisture absorption amount (W ') are used.
Since it provides a crosslinkable ethylene-based resin composition having a specific moisture absorption (W) under a specific condition, which is composed of carbon black and a crosslinking agent having It has a low load, has the same workability, mechanical properties, electrical properties, and weather (light) resistance as conventional products, and is excellent in storage stability even when stored under high humidity conditions, making it easier to see when covering wires. Provided is a cross-linked polyethylene electric wire having high surface smoothness and high practical value, which does not cause the surface of the electric wire coating to become rough.

[0054]

[Brief description of drawings]

[0055]

FIG. 1 is a diagram showing the relationship between the number of days of exposure of a high-pressure low-density ethylene homopolymer composition containing 40% by weight of various carbon blacks and a specified moisture absorption amount.

FIG. 2 is a graph showing the relationship between the number of days of exposure of various crosslinkable ethylene resin compositions and the specified moisture absorption amount.

Continuation of front page (56) References JP-A-61-283659 (JP, A) JP-A-2000-290437 (JP, A) JP-A-8-169991 (JP, A) JP-A-2000-21243 (JP, A) ) JP-A-7-288046 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C08L 23/00-23/36 C08K 3/00-13/08 H01B 3/44

Claims (5)

(57) [Claims] 1. A crosslinkable ethylene resin composition comprising 100 parts by weight of an ethylene resin, 0.3 to 3.0 parts by weight of a low hygroscopic carbon black and 0.5 to 4.0 parts by weight of a crosslinking agent. In the product, pellets granulated from the resin composition were dried under a pressure of 100 mmHg at 50 ° C. for 6 hours, and then exposed to a relative humidity of 79% and a temperature of 23 ° C. for 30 days in a thermo-hygrostat. Moisture absorption moisture content (W)
(Unit: ppm on a weight basis) satisfies the following formula (1), a crosslinkable ethylene-based resin composition. W ≦ 500 …… (1) 2. A low hygroscopic carbon black is a low hygroscopic furnace black having an average particle size of 10 to 30 nm, and is pelletized from a high-pressure low-density ethylene homopolymer composition containing 40% by weight of the same. Was dried at 80 ° C. for 6 hours under a pressure of 100 mmHg, and then in a thermo-hygrostat,
Specified moisture content (W ') when exposed to conditions of relative humidity 79% and temperature 23 ° C for 30 days (unit: pp on weight basis)
The crosslinkable ethylene resin composition according to claim 1, wherein m) satisfies the following formula (2). W'≤5000 (2) 3. The low hygroscopic carbon black is prepared from a hydrocarbon oil having a low sulfur content as a raw material, and its average particle size is adjusted to 10 to 30 nm, and impurities including potassium, calcium, sulfur and the like on the surface thereof are contained. The crosslinkable ethylene resin composition according to claim 2, which is obtained by sufficient washing with pure water. 4. A method for producing a crosslinked polyethylene electric wire or cable, which comprises extruding and coating the crosslinkable ethylene resin composition according to any one of claims 1 to 3 through a die. 5. A cross-linked polyethylene electric wire or cable manufactured by the manufacturing method according to claim 4.