JPS5878310A - Sheet-like electric insulator - 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 The present invention relates to a sheet-like electrical insulator used as conductor insulation for oil-immersed insulators such as OF cables or transformers.

With the recent trend toward higher voltages for power transmission, the insulators used in oil-immersed insulators are required to have dielectric properties and dielectric strength superior to those of ordinary kraft paper. In response to this demand, the development of semi-synthetic paper with a composite structure made by mixing or laminating plastic and cellulose paper is currently underway, and it has been recognized that it is quite promising, and some of these papers are being put into practical use.

Olefin-based polymers are mainly used as plastics for these materials due to their electrical properties, workability, cost, etc., and highly crystalline polyethylene (p'g'), polypropylene ( pp)
, poly-4-methylpentene-1 (TPX), etc., but even these highly crystalline olefin polymers have a chemical structure that is different from that of hydrocarbon insulating oils, which are mainly used as insulating oils. Due to their similarity, some degree of swelling due to insulating oil is unavoidable.

In addition, as mentioned above, there are two types of semi-synthetic paper: mixed paper and laminated paper. It is constructed by physical adhesion that entangles molten plastic between paper layers, and adhesives cannot be used because they reduce the dielectric properties, so it is used as the plastic sheet for the laminate. Since the olefin thread polymer is a non-polar polymer, chemical bonding with cellulose paper is not expected, and the adhesive strength of the bonded surface is weak, resulting in easy peeling.

Therefore, when slitting such laminated paper into a tape shape or winding it around a conductor, peeling tends to occur, resulting in poor manufacturing efficiency and the possibility of delamination between the layers if electrical equipment is immersed in oil. If this happens, it will greatly affect the electrical performance ('t').Also, since the sheet-shaped plastic and cellulose paper are bonded together, the plastic may swell due to the insulating oil. However, when used as a cable insulator, the terminal opening (11) may be subjected to high-temperature heat treatment such as lead work, and at this time the plastic layer of the laminated paper is melted (IV) and protrudes from the edge of the tape. Meanwhile, +Frj also occurs.

On the other hand, with mixed paper type semi-synthetic paper, there is no chance of the above-mentioned peeling problem occurring, and it also has a structure in which fine plastic fibers or flakes are dispersed between the paper and valve fibers to prevent swelling due to insulating oil. Therefore, the paper valve acts as a kind of cushion and the swelling is alleviated.
Even when subjected to high-temperature heat treatment of lead-[■・
.

Regarding the form of plastics used for mixed paper, fibrous ones are advantageous in terms of processing costs and dispersion into paper valves, and Borin 1 is advantageous in terms of electrical properties, oil resistance, and easy availability. Copylene + J IiU is specifically mentioned.

A mixed paper of paper pulp and polypropylene fibers can be produced by dispersing suitably cut polypropylene fibers in an aqueous paper pulp solution and drying this into a paper shape using a Fourdrinier or circular wire paper machine. .

Polypropylene fiber-containing paper inhibits strong bonding between cellulose bulb fibers, so in some cases thermal calendering is required to obtain mechanical strength or desired density. Ru.

Polypropylene pulp and fiber-mixed paper are manufactured using the procedure described above, but since polypropylene is a non-polar hydrophobic polymer, when dispersing polypropylene fibers in a paper valve aqueous solution, the dispersibility is poor. Unfortunately, this tendency is particularly noticeable when the mixing ratio of polypropylene fibers is high.3 As a result, polypropylene fibers agglomerate at 79 points in the finished mixed paper, resulting in uneven insulation performance of the mixed paper. In addition to creating weak points, the mechanical strength of IW at this agglomerated area is weak, resulting in the difficulty of tearing from this agglomerated area when cutting the mixed paper into a tape shape. However, this also poses the problem of the polypropylene fiber aggregates melting and fusing to the thermal calendar roll.

The present invention was made for the purpose of maintaining good dispersion of polypropylene fibers in a water bath solution in order to prevent the formation of aggregates of polypropylene fibers in paper mixed with polypropylene fibers as described above.

That is, the present invention is a material made of a mixture of polypropylene treated to have a contact angle of less than 9 ('r) and a cellulose bulb to serve as an air insulator. The paper is treated to have a angle of 90 degrees or less: Because the paper is mixed with cellulose bulb to improve its wettability against water and its dispersibility in aqueous solutions, it prevents the occurrence of agglomerated areas of polypropylene fibers. There is no risk of

In order to improve the wettability of polypropylene fibers, other means such as surfactants can be considered, but since surfactants are not chemically bonded to the polypropylene resin, When using the above-mentioned mixed paper in an oil immersion process, it is likely that it will become an ionic substance and therefore have a negative effect on dielectric properties, so it may be possible to use it in very small amounts, but it is usually not recommended. It can be said.

On the other hand, in the present invention, the wettability of polypropylene fibers is improved only by chemical treatment without using any substances such as surfactants that adversely affect dielectric properties. The paper has little deterioration in dielectric properties when immersed in oil.

The method for improving the Li of the polypropylene used in the present invention is as follows.

(1) Surface oxidation method using chemical treatment: Surface oxidation using chemicals such as sulfuric acid/chromic acid mixture, sodium perchlorate solution, potassium chloride solution, hydrogen peroxide solution, nitric acid solution, etc. (2) Gas phase surface oxidation, Surface oxidation in a gas phase such as a heating atmosphere or an ozone atmosphere (3) Surface layer 1411 with a coupling agent; polypropylene fiber # with a silane coupling agent, peroxide, etc.
Grafting process of coupling agent to surface] 11! (4)
In order to graft a silane coupling agent to polypropylene fibers, method (1) of the above methods involves surface oxidation treatment of polypropylene fibers with four solutions, and then washing the chemical solution thoroughly with deionized water, etc. Although it is necessary to oxidize only the surface layer, it does not have a negative effect on the oxidation properties of paper (19). 111, and visiting the city will have a negative impact on its characteristics.

Method (4) is a method of silane grafting/fiberization of Kobolibu 1'' pyrene, but it has little effect on the dielectric % within the range of practical silane coupling agent formulations. In addition to methods (1) to (4), the use of surfactant 111: agents, etc. may be permitted in some cases as long as it does not adversely affect dielectric properties. The silane bubbling agent used is, for example, one shown by the chemical formula below.

RS=X3 (however, R: vinyl group or hydrocarbon group containing vinyl group, -NH-, -NJ (, -εH group total 11161
For the above-mentioned hydrocarbon groups, X; −1, lH
,-[)c](,,-oC2H5゜-000 (!H3, etc.)) If R in the above chemical formula is a vinyl group or a hydrocarbon group containing an 11-vinyl group, peroxide ( Dibenzoyl barogicide, !-butyl perbenzoate,
It is even more effective to use an appropriate amount of dicumyl peroxide) or the like.

Next, examples of the present invention will be described, Example L Potassium dichromate/water/concentrated sulfuric acid-127q/100 ml
/ In a chromic acid mixture adjusted at a ratio of 150 ml,
Polypropylene fibers having a thickness of 2 denier were treated for a time range of 2 seconds to 20 minutes. 1 polypropylene fiber after treatment
The fibers were washed with water for 5 minutes, and the contact angles of the fibers with water were determined as shown in Table 11.The contact angles were determined by the gradient method by placing polypropylene fibers on a fixed plate.

The polypropylene v&Nl treated with each of the above was cut into 12 pieces of the same length, washed with deionized water, and then dispersed in an aqueous kraft pulp solution. Ratio of polypropylene fiber to pulp
Al.

The above mixed aqueous solution of polypropylene twill fibers and Kranotobulb was mixed with 5097 m2 by the Fourdrinier method.
A small sheet of paper was made, and two sheets of this were pasted together using a hot pressure roll to obtain a bodied n-bi1/n fiber-mixed paper with a density of 078 mm and a female diameter of 125 μm.

The resulting polypropylene fiber? l11. Measurements were taken under the shell of the paper, and the dimensions are shown in Table 1 along with the contact angle.

・Number of blocks (pcs/m2); Number of polypropylene fiber #collection points per 1 mg ・Thickness variation △d (tt): Maximum j9 in l m”
Difference in dielectric loss and dielectric loss tangent - δ (%): Commercial frequency 20KV/mrn
Dielectric dissipation tangent with alkylbenzene-based insulating oil included at 80°C. In the table, contact angles larger than 900° are comparative examples.

01 Table 1 As can be seen from Table 1 above, the contact angle of the polypropylene fibers with water was set to 900 or less, and the dispersion of the polypropylene fibers in the kraft pulp aqueous solution was good. There are no agglomerated areas of polypropylene fibers in the fiber-mixed paper, and the variation in the thickness of the mixed paper due to poor dispersion of polypropylene fibers is greatly reduced. has been done.

Example 2 Polypropylene fibers with a thickness of 2 denier are shown in Table 2.
The polypropylene fibers were treated by various methods shown in the following, so that the contact angle with water was 70'-8 cf'.

Those with a contact angle of more than 90° are untreated comparative examples.

The contact angle was measured in the same manner as in Example 1.

1. Polypropylene fibers J and Il subjected to each of the above treatments.
Cut into 2IIIL lengths, wash with deionized water, and disperse in an aqueous kraft pulp solution.
i By the same method as Example 1, the density is 0.78 P/l/
, obtained a polypropylene fiber mixed paper with a J width of 125μ,
The properties (blowing, overlaying, thickness variation, dielectric loss tangent) were measured using the same method as in Example 1, and the results are shown in Table 2.

(11) Table 2 (Note) A treatment: Chemical liquid treatment B treatment: Gas phase treatment C treatment, silane coupling agent grafting treatment PP: Polypropylene (12) As can be seen from Table 2 above, the resistance of polypropylene fibers to water The dispersibility is improved regardless of the type of processing method, and there is no aggregation of polypropylene fibers in the finished paper mixed with polypropylene fibers, and there is little variation in the thickness of the mixed paper, which is +41t? There is no bad influence in I\ tangent.

Patent applicant: Fujikura Electric Wire Co., Ltd. Agent: Patent Attorney Mamoru Seuchi (13)

Claims (1)

[Claims] A sheet-shaped electrical insulator characterized by a mixture of retaboliglopyrene fibers and cellulose pulp treated so that the contact angle with water is 9 (f or less)