JPS61185816A - Insulating material for oil-filled cable - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an insulating material for oil-immersed cables, which is formed by laminating electrically insulating paper and two-wheeled or uniaxially oriented polypropylene film through an adhesive layer. It is.

[Prior art and its disadvantages] As an insulating material for oil-immersed cables, insulating paper is known in which fiber paper and unstretched polypropylene extruded with a biaxially oriented polypropylene film are bonded together using an adhesive (for example, Special Publication No. 54-10712, etc.). However, since this adhesive uses a melt extruded directly from an extruder, the adhesive is non-oriented, and its thickness cannot be made thinner than 15 μm.As a result, the paper ratio is low. Not only does the dielectric constant and tan δ increase as the temperature increases, but when the insulating paper is immersed in electrical insulating oil, the insulating paper swells with oil, and when used for oil-immersed cables, it becomes difficult to wrap the insulating layer and draw it. This can cause insulation defects. Furthermore, when the fiber paper and polypropylene film are laminated together, excessive linear pressure is applied, which compresses the porous paper, giving the appearance that the thickness of the top paper has decreased. When insulating paper is immersed in electrical insulating oil, the insulating paper swells with the oil, causing electrical defects similar to those described above. In addition, since the propylene homopolymer is extruded as an adhesive, the crystallization rate during the cooling process from the molten state is very fast. Therefore, when adhering during the cooling process, crystallization occurs before a sufficient anchoring effect can be expected. As this progresses, it is not possible to maintain a strong adhesive force of 1q, and as a result, when used as a cable, the adhesive may peel off due to mechanical bending, resulting in electrical defects. .

[Object of the present invention] The present invention is directed to the above-mentioned conventional swelling of an insulating material due to oil immersion.
The purpose is to eliminate the problems associated with deterioration of nδ, decrease in interlayer adhesion, etc., and its purpose is to minimize the degree of swelling during oil immersion, and to
, nδ, etc., and has strong adhesive strength between layers, and is highly economical.

[Structure of the present invention] The present invention comprises a -axially or biaxially oriented polypropylene film (A), a polyolefin layer (B) having a melting point of 100 to 150'C, and an electrically insulating paper (C> is C/B/A/B/ In an electrically insulating material that is integrated into five layers in an arrangement of C, the film (A) and/or the polyolefin layer (B) contain imino-type and/or amine-type nitrogen atoms in the surface layer up to 100 mm from the surface. This invention relates to an insulating material for oil-immersed cables, which has at least 3 atoms per 100 atoms, and the film (A) has a surface embossed to a roughness in the range of 10 to 100 μm.

In the present invention, the intrinsic viscosity [η] of the uniaxially or biaxially oriented polypropylene film (A> is 1.2 to 2.8 dl
/c+, preferably 1.3 to 2.2 dl/(7). The value of [η] is less than 1.2, preferably 1.
If it is less than 3, the film will be brittle and prone to cracking, making it undesirable as an electrical insulating material. In addition, when the value of [η] exceeds 2.8, preferably exceeds 2.2, the degree of swelling by oil is hardly improved compared to conventional polypropylene, and the swelling value is large, that is, the degree of swelling is 3. % or more, which is not preferable. In addition, other components may be copolymerized with the polypropylene, but the melting point is 155°
It is desirable to maintain the temperature above C, preferably above 160'C.

In the case of the film of the present invention (A>), the isotactic degree is 93% or more, preferably 96% or more, more preferably 9
When it is 8% or more, the degree of swelling due to oil is small, which is preferable. The polypropylene also contains antistatic agents, slip agents,
It is important not to contain additives such as heat stabilizers, antiblocking agents, lubricants, and viscosity modifiers.

The thickness of the film (A) is preferably in the range of 10 to 1000 μm for handling purposes, and more preferably 50% or more of the thickness of the insulating material of the present invention.

When the film (△) has -axis orientation, the higher the degree of molecular orientation, the smaller the swelling value in oil, which is preferable, and the in-plane birefringence value is 0.
．． A range of 0.028-0.040 is preferred. Also,
In the case of biaxial orientation, the birefringence value is preferably in the range of 0-0.020.

The polyolefin layer (B) used as an adhesive between layers is
A propylene copolymer containing 50 mol% or more of propylene, such as a binary or tertiary copolymer (random,
(graft, block) are typical examples, but the invention is not necessarily limited to these. As the polyolefin used in the present invention, ethylene/propylene (ethylene content: 1 to 10 mol%) random copolymer and ethylene/propylene (ethylene content: 110 to 50 mol%) block copolymer are particularly preferred.The melting point of the polyolefin is 100%. ~1
50'C1 preferably should be 110-145°C. This melting point is less than 100°0'', preferably 11
This is because if it is less than 0'C, the electrical tan δ becomes large and the degree of swelling U during oil immersion becomes large, resulting in electrical defects and cannot be used as an insulating material for oil immersed cables. Moreover, when the melting point exceeds 150°C, preferably 145°C, the adhesiveness between the electrically insulating paper (C) and the film (A> is poor, and it peels off during oil immersion, making it less economical. This is necessary because lamination cannot be performed at high speed.The intrinsic viscosity [η] of the polyolefin is 0.4 to 235, preferably 0.6 to 1.8, more preferably 0.7 to 1.4 (
A low viscosity of d I/g is preferable because it suppresses swelling during oil immersion and improves the adhesive strength between layers.

In addition, imino-type and/or amine-type nitrogen atoms are added to the surface layer of the polyolefin layer (B) and/or film (A) up to 100 carbon atoms.
There must be 3 or more, preferably 7 or more.

When the number of nitrogen atoms is less than 3, preferably less than 7, the temperature at which the bonding between the insulating paper (C) and the film (A) starts is high, and the laminating pressure required for bonding is also high, resulting in poor lamination economy. Not only does the resulting laminate become prone to curling and wrinkles due to heat deformation, resulting in various drawbacks for electrical insulation laminates, but when immersed in oil, it becomes difficult to use. Insulating paper (
The interlayer adhesion between C) and film (A) decreases, leading to the occurrence of freezing and wrinkles, and the electrical properties, particularly the withstand voltage, are significantly decreased. Note that the upper limit of the number of nitrogen atoms is not particularly limited, but from the viewpoint of adhesiveness, it is preferably 30 or less, and more preferably 25 or less.

In addition, the wetting tension of the surface of the polyolefin layer (B) is 4
5 dyn/cm or more, preferably 5 Q dyn/c
It is preferable for the present invention that it is at least m.

Furthermore, the thickness of the polyolefin layer (B) is 0.5 to 8.
It is desirable to have a diameter of .mu.m, preferably in the range of 0.8 to 3.0 .mu.m. When the thickness of the layer (B) is less than 0.5 μm, preferably less than 0.8 μm, the insulating paper (C) and the film (A
), and conversely, when the thickness of the layer is 8μ
If it exceeds m, preferably exceeds 3 μm, the electric tan δ becomes large, and the degree of swelling in oil immersion becomes large, which is not preferable.

Moreover, rather than the polyolefin layer (B) being non-oriented,
It is preferable that the molecular chains are oriented in terms of swelling properties with insulating oil, mechanical properties, and electrical properties. The degree of orientation is
The arithmetic average value (N
It is preferable that the value obtained by subtracting the refractive index Nzd in the thickness direction from the in-plane average refractive index, which is md+Ntd)/2, is 0.005 or more.

In the present invention, the film (A) has a polyolefin layer (B).
) Electrical insulating paper (hereinafter referred to as paper) (C) is a natural fiber whose main component is cellulose as specified in JIS C2301-2308, or a natural fiber such as cellulose. Either mixed paper made of fibers and plastic fibrils or synthetic paper made only of plastic fibrils may be used.
Particularly suitable for the present invention is natural fiber paper whose main component is cellulose.

The value of the maximum surface roughness Rmax of electrically insulating paper (C) is 5 to
25μm apparent density is 0.6-1.2g10f.

Thicknesses in the range of 15 to 150 μm are preferred because they have excellent electrical properties and flowability. In the case of the present invention, it is preferable that the insulating paper (C) be paper whose surface has been smoothed by calendering or the like, since it has a high charging voltage and interlayer adhesive strength.

The insulating material for oil-immersed cables of the present invention has the above (A>, (B)
) and (C) are arranged in the order of C/B/A/B/C, which has a five-layer integrated structure.

Moreover, the surface of at least the film (A>) of the insulating material for oil-immersed cables of the present invention is embossed to have a roughness in the range of 10 to 100 μ in terms of RmaX value.

[Manufacturing method] Next, a method for manufacturing an insulating material according to the present invention will be described.

The method for producing the raw material for biaxially oriented polypropylene film used in the present invention is not particularly limited, but to give a preferred example, a titanium tetrachloride catalyst supported on various known magnesium chloride, an interwoven aluminum compound, and an ester-based Using a catalyst system consisting of a third component such as a compound, propylene is polymerized by a bulk polymerization method using propylene itself as a solvent, and then a low stereoregular polypropylene soluble in propylene is produced using a low boiling point hydrocarbon such as propylene. Obtained by removing.

[nl method: 10 to 40% ethylene is added to the polypropylene polymer raw material (A>) and polyolefin as an adhesive polymer.
The block copolymerized ethylene/propylene block copolymer (B) is copolymerized in a sheet extruder, and B
A three-layer, single-layer melt consisting of /A/B is discharged from a nozzle and cast onto a cooling drum. After preheating this sheet by external heating, it is stretched or rolled 4 to 12 times in the longitudinal direction at 80 to 150'C, and further stretched 6 to 12 times in the width direction at 120 to 170'C, if necessary. , followed by heat treatment at 100 to 170°C for 2 to 10 seconds, followed by a mixed gas of carbon dioxide p and nitrogen gas q (volume ratio D/q is 1/9).
9 to 10/90) to obtain a three-layer laminated biaxially stretched or uniaxially stretched polypropylene film.

The total thickness of the thus obtained three-layer single-layer polypropylene film was 40 to 250 μm, and the surface of the ethylene-propylene block copolymer layer had nitrogen and oxygen incorporated therein, and was also roughened. , the thickness thereof is preferably 0.5 to 8 μm. The reason for roughening the surface is to improve slipperiness and anti-blocking properties. Electrical insulating paper was superimposed on both surfaces of this three-layer monolaminated film, and then extruded for a short time at a linear pressure of 0.01 to 1 t/cm between embossing rolls heated to 150 to 220'C. An integrated laminated embossed insulating material consisting of laminated film/insulating paper is obtained.

[nl method] Another manufacturing method is to coat insulating paper with a polyolefin, such as an ethylene-propylene random copolymer, as an adhesive by hot-melt coating.
It is coated uniformly to a thickness of 5 to 8 μm and subjected to corona discharge treatment under nitrogen gas. A single layer of biaxially oriented or uniaxially oriented polypropylene film is wrapped between the two coated insulating papers, and the insulating paper/biaxially oriented polypropylene film is pressed between embossing rolls in the same manner as above. An integrated laminated insulating material consisting of propylene film/insulating paper is obtained.

[After embossing a uniaxially or biaxially oriented polypropylene film consisting of a three-layer laminate using the NL Method 1 method to a thickness of about 5 to 100 μm, electrically insulating paper is placed on both surfaces of the film, and carbon dioxide gas and nitrogen are mixed. After corona discharge treatment under gas and pressing between hot press rolls heated to 150-220°C, a 3-layer laminated film with insulating paper 77' boss was formed.
A laminated and integrated insulating material made of insulating paper is obtained.

In the case of the insulating material of the present invention, production by [Method I] is particularly preferred in that the polyolefin layer as the adhesive polymer has orientation.

Further, when embossing electrically insulating paper, there is a risk that the structure of the paper will be destroyed. Therefore, in the present invention, it is preferable to apply embossing as lightly as possible or to process only a film.

[Effects of the present invention] The insulating material of the present invention includes electrically insulating paper (C) and film (
A) is integrally laminated with a specific polyolefin (B) as an adhesive layer, and since the film (A> has a specific embossed structure, the following effects can be achieved. .

(1) Swelling due to oil is extremely small.

(2) Excellent oil circulation.

(3) Both dielectric constant and dielectric loss tangent are small, and dielectric breakdown voltage is extremely high.

(4) The mechanical properties of the insulating material are excellent.

(5) Since there are few dissolving valves in oil, the degree of contamination of oil is extremely small.

(6) The manufacturing cost is low and it is highly economical.

Therefore, the insulating material for oil-immersed cables of the present invention is extremely useful as an insulating layer for oil-immersed cables.

Next, the measurement methods used in the present invention are summarized below.

(1) Cut the film of the isotactic index (II) sample into a size of approximately 10 m square, place it in a Soxhlet extractor, and add boiling methyl alcohol to
Extract time. The extracted sample is vacuum dried at 60°C for 6 hours. A sample of weight W (mq>) is taken from this, put into the Soxhlet extractor again, and extracted with boiling 11!N-hebutane for 6 hours.Then, this sample is taken out, thoroughly washed with acetone, and then extracted with 60' After vacuum drying at C for 6 hours, the weight is measured.

If the weight is W'(mQ>), the isotactic index (II) is determined by the following formula.

II (%) = 100xW' /W (2) Birefringence Using Atsube's refractometer, measure the refractive index in the longitudinal direction (NV) and the refractive index in the width direction (Nx) of the film, and calculate the difference between NY and Nx. The absolute value of is the birefringence of the film. In addition,
The light source during the measurement is sodium D line, and the mounting liquid is methyl salicylate.

(3) Swelling degree due to electrical insulating oil: Cut out a 100 square sample and heat it in a constant temperature bath at 120℃ for 2 hours.
After drying for 0 hours, the thickness is immediately measured and defined as D (μm).

This sample was immersed in dodecylbenzene oil at 100℃ for 2 hours.
After leaving it for 4 hours, take it out and immediately measure the thickness of the sample.
Let this be D' (μm).

The degree of swelling is determined by the following formula.

Swelling degree (%)=100 After washing thoroughly with water, leave it at room temperature of 20°C for 1 day. Using this sample as a sample, the peel strength of the adhesive between the paper and the film was measured according to the method of T-peel test for flexible materials between flexible materials as described in JIS K 6854-1973, and this was taken as the adhesive strength.

(5) The method for measuring weight average molecular weight MW and number average molecular weight Mn is as follows.

Equipment Nigel permeation chromatography GPC-1 column
: 5hodex A 80M Solvent: O-dichlorobenzene (added with 0.1% ionol) Speed: 1 ml/min Temperature: 135°C Sample concentration: 0.1 (wt/vol)% filtration and 0.1 μm baking Injection amount: 0.4 ml Detector: Differential refractive index detector Molecular composition: Polystyrene standard (6) Intrinsic viscosity [η] Measured in tetralin at 135° C. according to ASTM D1601.

(7) Dielectric breakdown voltage [BDV] Measured according to ASTM D149. Atmosphere 20℃
.

(8) Dielectric loss [tanδ] Frequency 50H2° 100 according to ASTM D150
Measurement is performed at ℃ using an insulated paper measuring electrode MED-C type (manufactured by Nissin Electric Co., Ltd.).

(9) Melting point [Tm The melting point is the equilibrium temperature associated with the melting point of the crystal determined by a scanning calorimeter (DSC) and is called the endothermic peak.If there are two or more endothermic peak temperatures, the highest endothermic peak temperature A temperature with a high temperature is used, but if the temperature is almost the same, the average temperature of these numbers is used.The DSC measurement conditions are a sample weight of 5 mg, a temperature increase rate of 20'C/min, and a nitrogen flow.

60) Surface roughness [RmaX] Measured according to JIS B 0601-1976. Note that the cutoff value is 0.25m+.

(11) The imino type or/and amino type nitrogen atom is directly bonded to the carbon of the holybropyrene polymer chain,
The amount is measured using the ESCA method.

The ESCA method referred to in the present invention is an abbreviation for soft X-ray excitation photoelectron spectroscopy, and the type of elements near the surface of the sample is determined from the spectrum of photoelectrons ejected from atoms in the sample compound by soft X-ray irradiation. and a method for analyzing chemical bonding states.

In the ESCA method, the ability of photoelectrons to pass through hydrocarbon-based polymeric substances is small, and ESCA measurement of such polymeric substances has the characteristic that relatively strong information can be obtained from the surface, especially within 100 layers of the surface. .

The amino-type and/or imino-type nitrogen referred to in the present invention refers to the bonded nitrogen identified by the ESCA method. (hereinafter simply referred to as amino type or/and imino type nitrogen) having a peak in the range of binding energy from 397°0 to 402°58V (however, the main peak of C1. in polypropylene is 285.OeV) The ESCA spectrometer ES-20 manufactured by Kokusai Electric Co., Ltd.
Using type 0, the N spectrum and c15 spectrum of the treated surface of the treated film were measured, and the integrated intensity of the peak corresponding to the bond energy of amine type or I and imino type nitrogen in the NIS spectrum, and the C1, spectrum of the NIS spectrum were measured. The ratio of integrated intensities was calculated.

The number ratio N/C of amino type and/or imino type nitrogen and carbon atoms in the present invention is calculated based on the above-mentioned integrated intensity ratio.

[Example 1] Ethylene-propylene copolymer (intrinsic viscosity [η] 0.7 dl/g, melting point 129°C) obtained by randomly copolymerizing 6 mol% ethylene was supplied to a hot melt coater, and the mixture was heated at 200° C. under a nitrogen blanket. After heating to 'C, pressurize and slit gap 0.
．． Extruded from a 4 mm nozzle, 30 μm thick electrically insulating kraft paper (specific gravity 0°90Q/ffl, surface roughness Rmax
= 18 μm> was hot-melt coated on one side to a thickness of 3 μm, and corona discharge treated one barley was rolled up under a nitrogen stream.

Approximately 1' of up to 100 carbon atoms from the treated film surface
The number of nitrogen atoms per OO was 4.

On the other hand, the intrinsic viscosity is 1.85 dl/g, the weight average molecular weight is M
Ratio of W to number average intermolecular Mn MW/M n =4.0,
Polypropylene with an isotactic index (II) of 98% is melted at 250°C, this melt is extruded into a sheet from a die, and cast onto a casting drum cooled to 50'C by a conventional method, and solidified by cooling. I let it happen.

After heating the cooled assimilated sheet to 146°C, it was stretched 5 times in the longitudinal direction, then fed into a stenter heated to 160°C, stretched 10 times in the width direction, and further stretched to 165°C.
A biaxially oriented polypropylene film with a thickness of 90 μm was produced by heat treatment at °C for 4 seconds while allowing 5% relaxation in the width direction.

[η] of the film thus obtained was 1.80 dl/
g, Mw/Mn is 3.9, II is 98%, and birefringence is 0.
016, and the entire film was embossed using an embossing roll heated to 125°C to give an apparent film thickness of 140 μm.

Next, the ethylene-propylene copolymer surface coated on the insulating paper was overlapped with both sides of the biaxially oriented embossed evolipropylene film, and then heated to 180°C.
The material was fed between chrome-plated rolls having an outer diameter of 250 mm and heated to 250 mm, and pressed for 0.1 seconds at a linear pressure of 30 oh/cm to obtain an integrated insulating material made of insulating paper and having a thickness of 20 μm.

The thickness fraction of the thus obtained biaxially oriented polypropylene film of insulation + Δ material was 57%.

Subsequently, the insulating material was immersed in dodecylbenzene oil and its physical properties were measured.

Swelling rate: 1% or less Dielectric constant: 2.5 (20°C), 2.5 (100'C)
) tan δ: 0.04% (20°C), 0.05% (1
00'C) Adhesive Crab 400g/cm As described above, the insulating material of the present invention not only has excellent electrical properties but also excellent adhesive strength and swelling resistance, making it an excellent insulating material for oil-immersed cables. It can be seen that this shows the characteristics.

[Example 2] As the polypropylene, [η] = 2.0, an ethylene-propylene block copolymer made by copolymerizing chips with an index of 98% (1,1>=98%) and 20 mol% block of ethylene. ([η]=1.4, melting peak temperature by DSC is 121℃, 145℃1160℃
However, the melting point is 132°C as the average of the former two)
were introduced into separate nozzles, and a three-layer laminate sheet consisting of block copolymer layer/polypropylene layer/copolymer layer was extruded from the nozzles. This sheet was brought into close contact with a cooling drum maintained at 45°C using air pressure, cooled and solidified, then heated in a hot air oven heated to 145°C, stretched 5 times in the longitudinal direction, and immediately heated to 15°C. It was cooled by adhering it to a cooling roll. This sheet is fed into a tenter set of stenters heated to 160°C, stretched 10 times in the width direction,
Next, it was heat-treated for 2 seconds while allowing 7% relaxation in the width direction, and subjected to corona discharge treatment under a mixed gas of charcoal gas/nitrogen gas = 2/98 to obtain a three-layer laminated polypropylene film with a thickness of 90 μm. Here, the difference between the in-plane average refractive index and the refractive index in the thickness direction of the block copolymer layer must be 0.012, and the thickness of each layer is 2 μm, and the thickness of the polypropylene layer is 86 μm. there were. The block copolymer layer contained 8 nitrogen atoms per 100 carbon atoms from the surface layer. Although this three-layer laminated polypropylene film does not contain any additives such as slipping agents or anti-blocking agents, it exhibits excellent slipperiness with a coefficient of friction of 0.6 due to the use of a specific polymer. Ta. On both sides of this three-layer laminated polypropylene film, electrically insulating kraft paper (specific gravity 0
．． 92/a+f, surface roughness Rmax = 15 μm), and pressed with a heated embossing roll at 200 °C for 0.1 seconds at a linear pressure of 200 kq/Cm to form an integral laminate. A 210 μm embossed electrically insulating material was obtained. The thickness fraction of the biaxially oriented polypropylene film was 61%.

The properties of the thus obtained insulating material in dodecylbenzene at 20'C are as follows: Dielectric constant: 2.5 tan δ: 0.04 (%) Swelling rate: 1 (%) Breakdown voltage: 60 ( KV/mm) interlayer adhesive crab 3
80 (q/cm) Oil flowability: Good Longitudinal breaking strength: 29 (lq/15mm width) Longitudinal breaking elongation: 120 (%) As described above, it is an excellent insulating material for oil-immersed ultra-high voltage cables. It can be seen that it is used as a characteristic.

[Comparative Example 1] The electrically insulating kraft paper used in Example 2 and the biaxially oriented polypropylene film with a thickness of 60 μm produced in the same manner as in Example 1 were mixed with the ethylene/propylene random copolymer used in Example 1. A 140 μm thick insulating material consisting of paper/random copolymer/film/random copolymer/paper was made by melt extrusion laminating at 260'C between paper and film using polymer as an adhesive. Obtained. Here, the thickness of each random copolymer layer was 15 μm, and the thickness fraction of the biaxially oriented polypropylene film was 42%. Subsequently, the insulating material was embossed using an embossing roll in the same manner as in Example 2 to obtain an electrically insulating material with a thickness of 210 μm. Various physical properties are shown in Table 1.

[Comparative Example 2] The same procedure as in Example 1 was carried out except that the corona discharge treatment under the mixed gas used in Example 2 was not performed.

Various physical properties of the thus obtained embossed insulating material were measured in the same manner as in Example 2, and the results are summarized in Table 1.

As is clear from Table 1, the structure of the insulating material is the same as in Example 2, but the dielectric constant, tan
Not only is δ large, but the degree of swelling is also large, making it unsuitable as an oil-immersed cable material. It can also be seen that it cannot be used as an oil-immersed cable material unless a specific surface treatment is applied.

Table 1 [Example 3 and Comparative Example 3] As Example 3 and Comparative Example 3 of the cable structure shown in FIG. 1 with the specifications of Table 2 shown below, Example 2 and Comparative Example 2
We manufactured an electric cable using this insulating material and investigated its properties.

In FIG. 1, 1 is a six-part conductor made of copper, 2 is an oil passage, 3 is a single layer of conductive binder formed by winding stainless steel tape and carbon paper together, 4 is an oil-immersed insulating layer, 5 is a metal shielding layer formed by winding metallized paper and aluminum tape together; 6 is a core binder layer formed by winding, for example, copper wire woven cloth tape; 7 is a lead-covered sheath; and 8 is a vinyl chloride-covered sheath. be.

Table 3 shows the characteristics obtained for each cable.

According to the results in Tables 2 and 3, compared to the OF cable using the insulating material of Comparative Example 1, the OF cable using the insulating material of the present invention can achieve lower capacitance and higher breakdown stress. I know that there is.

In other words, it can be seen that electrical insulation characteristics better than that of the conventional one can be achieved with an insulating layer that is thinner than that of the conventional one.

Table 2 Table 3

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of a cable using the insulating material of the present invention. DESCRIPTION OF SYMBOLS 1... Conductor, 2... Oil passage, 3... One layer of conductor binder, 4... Oil-immersed insulation layer, 5... Metal shielding layer, 6...
...Core binder single layer, 7...Lead-coated sheath, 8...
PVC sheath. Patent applicant Toshi Co., Ltd. Company No. 1m Procedural amendment Manabu Shiga Director General of the Patent Office 1, Indication of the case Patent Application No. 24333 of 1985 2, Name of the invention Insulating material for oil-immersed cables 3, Make amendments Patent applicant 4, date of amendment order voluntarily 5, number of inventions not increased by amendment 6, “Detailed description of the invention” column 7 of the specification to be amended, content of amendment (1) Specification, page 19, line 10, "Nitrogen," is amended to "Nitrogen," (2) Insert the following sentence between lines 7 and 8 on page 20. [Surface wetting tension] According to JIS K 6768 Wetting test method for polyethylene and polypropylene films. (3) Same page 22, lines 4-5, "20 μm thick made of insulating paper" is changed to "200 μm thick made of biaxially oriented polypropylene film and insulating paper"
and correct it.

Claims (1)

[Claims] Uniaxially or biaxially oriented polypropylene film (A),
An electrically insulating material in which a polyolefin layer (B) with a melting point of 100 to 150°C and an electrically insulating paper (C) are laminated into five layers in a C/B/A/B/C arrangement, and the film (A) and/or Or the polyolefin layer (B) is 100% from the surface.
The film (A) has 3 or more imino-type or/and amino-type nitrogen atoms per 100 carbon atoms in the surface layer up to Å, and the surface of the film (A) is embossed to a roughness in the range of 10 to 100 μm. An insulating material for oil-immersed cables.