JPS6366010B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to insulating paper, particularly insulating paper for power cables, and a method for producing the same.

Ultra-high voltage OF (Oil) for the purpose of large-capacity power transmission
Synthetic fibers, synthetic resin films, or laminates of these films and insulating papers such as kraft paper have recently been used as insulating materials with low loss, ie, low dielectric loss, used in cables.

However, the synthetic resin film has a drawback that it has low oil resistance against the insulating oil flowing inside the cable, increases oil flow resistance due to swelling, and is prone to buckling and wrinkles when the cable is bent.
On the other hand, when a synthetic resin film and insulating paper are used in combination, the increase in oil flow resistance due to swelling is alleviated to some extent, but problems remain with oil flow in the radial direction and the polarity effect on impulse voltage is large. There are drawbacks.

An object of the present invention is to provide an insulating paper with excellent electrical and mechanical properties and good workability.

The present invention is based on natural fibers and synthetic resin powder (powder).
An insulating paper made of a mixture of The first layer and the second layer are both insulating paper made from a mixture of natural fibers and synthetic resin powder. Both facing portions are provided with insulating paper containing a larger amount of synthetic resin powder than the other portions.

The above insulating paper may be manufactured as follows.

For example, kraft pulp is prepared as a natural fiber. After beating this kraft pulp, synthetic resin powder is added to it and a normal papermaking process is carried out. The machine used for this paper making is preferably an ordinary Fourdrinier paper machine. The preferred synthetic resin is polypropylene, but other materials such as tetrafluoroethylene, polyethylene, and polycarbonate may also be used.

The made sheet is preferably calendered to increase density and
Thickness reduction and surface smoothing are achieved, and mechanical strength is increased by applying heated pressure rolls. In addition, in a mixed solution of beaten pulp and synthetic resin powder, the synthetic resin powder is present in a larger amount above the natural fibers of the pulp due to the influence of density and hydrophobicity. As shown in FIG. 1, the insulating paper 10, which is a product obtained by paper making using a net-type paper machine, has a portion 11 near its top surface which has a higher amount of synthetic resin powder (shown by dots) than other portions 12. There will be more.

In the present invention, as shown in FIG. 2, two sheets of insulating paper 10 are prepared and laminated with the parts 11 containing a large amount of synthetic resin powder facing each other. 50-200
Insulating paper formed by heating and pressing at a pressure of Kg/cm ² is more preferably used.

The insulating paper stacked one on top of the other and heated and pressurized in this way has a greater mechanical strength than when two sheets of insulating paper are used. Furthermore, since this insulating paper has many entangled natural fibers on both sides, it can be handled like kraft paper when winding it around a cable conductor, and has excellent workability.

Furthermore, by stacking two sheets, the non-uniformity of the dispersion of the synthetic resin powder is compensated for, and the uniformity of the distribution is greatly improved.

The insulating paper according to the second aspect of the present invention is made of a mixture of natural fibers and synthetic resin powder, and as shown in FIG. and an inner layer 32 containing a large amount of resin powder. The method for manufacturing this insulating paper consists of sequentially and continuously weaving together first, second and third layers each consisting of natural fibers and synthetic resin powder, and the first and third layers are The second layer is characterized by having a low content of synthetic resin powder, and the second layer having a high content of synthetic resin powder. FIG. 4 is a diagram illustrating an example of manufacturing the three-layer insulating paper of the present invention by arranging three circular mesh paper machines in series. In FIG. 4, 41, 42, and 43 indicate first, second, and third circular mesh paper machines arranged in series, respectively. In the first circular mesh paper machine 41, the cylindrical mesh 44 contacts the pulp water 45 that does not contain synthetic resin powder and rotates in the direction of the arrow, so that the natural fibers with a low content of synthetic resin powder are mixed into the mesh. 44 to form the first layer. In the second circular mesh paper machine 42, the cylindrical mesh 46 contacts the pulp water 47 with a high content of synthetic resin powder and rotates in the direction of the arrow, so that the natural fibers with a high content of synthetic resin powder are transferred to the mesh. 46 to form a second layer. In the third circular mesh paper machine 43, the cylindrical mesh 48 contacts the pulp water 49 with a low content of synthetic resin powder and rotates in the direction of the arrow, so that the natural fibers with a low content of synthetic resin powder are 48 to form a third layer. 50 indicates an endless belt moving in the direction of arrow 51. The first, second and third layers made as described above by the first, second and third circular mesh paper machines 41, 42 and 43 are sequentially and continuously applied to the endless belt 50 from below. After being kneaded by contact, it is separated from the endless belt 50 and the desired three-layer structure insulating paper 5 is produced.
2 is formed, which further advances in the direction of arrow 53 and is subjected to calendering (not shown).

According to the third aspect of the present invention, as shown in FIG. 5, fiber paper 62 is formed by forming natural fibers on both upper and lower surfaces of mixed paper 61 formed by forming paper from a mixture of natural fibers and synthetic resin powder, 62 is provided, and this three-layer structure is heated and pressed, for example, by passing it through a pair of heating rolls, and is fused together to provide an insulating paper.

According to the fourth aspect of the present invention, as shown in FIG. 6, fiber paper 64 made by making natural fibers on one side of mixed paper 63 made by making paper from a mixture of natural fibers and synthetic resin powder is heated. The mixed paper 63 includes a part with a high content of synthetic resin powder and a part with a low content of synthetic resin powder, and the part with a large content of synthetic resin powder is fused into a fiber paper 64 by applying pressure. Provided is an insulating paper that is directly bonded and is characterized in that the portion containing less synthetic resin powder is exposed to the outside air.

In addition, in the mixed paper shown in FIGS. 5 and 6, the dots mean synthetic resin powder.

As the fiber papers 62 and 64, kraft paper with a thickness of several μm to 15 μm is preferably used.

The preferred average particle diameter of the synthetic resin powder used in the present invention is several μm to 50 μm. The amount of synthetic resin powder in the insulating paper of the present invention is preferably about 40-60% by weight.

The insulating paper of the present invention has the following advantages.

Since it is mixed with synthetic resin, it has low loss.

Since synthetic resin powder is mixed with natural fibers, the oil flow resistance in the radial direction in power cables is smaller than insulating paper made by laminating synthetic resin film onto paper.

Swelling of synthetic resins by oil is reduced by the presence of natural fibers.

In one embodiment of the invention, both sides of the insulating paper have a greater amount of natural fibers than synthetic resin or are substantially composed of natural fibers, so that the surface is similar to kraft paper and can be easily wrapped around a conductor. is as good as kraft paper.

In one embodiment of the invention, at least 3
Since the layered insulating paper can be made in one step, manufacturing is extremely simple.

As described above, the insulating paper of the present invention is preferably used as an insulating paper for power cables, but is not limited thereto, and can also be used as other electrical insulating materials.

[Brief explanation of drawings]

FIG. 1 is a sectional view for explaining the insulating paper of the present invention, and FIGS. 2, 3, 5, and 6.
Each figure is a sectional view of an embodiment of the insulating paper of the present invention, and FIG. 4 is an explanatory diagram showing a method for manufacturing the insulating paper of FIG. 3. 11, 32... Part with a lot of synthetic resin powder,
12, 31... Part with less synthetic resin powder,
41, 42, 43... Circular paper machine, 52... 3-layer structure insulating paper, 61, 63... Mixed paper making, 62, 6
4...Fiber paper.

Claims (1)

[Claims] 1. Formed by laminating a first layer and a second layer and heating and pressurizing them, both the first layer and the second layer are made of a mixture of natural fibers and synthetic resin powder. An insulating paper made by papermaking, in which the facing portions of the first layer and the second layer both contain a larger amount of synthetic resin powder than the other portions. 2. The insulating paper according to claim 1, wherein the synthetic resin is polypropylene. 3. Insulating paper made by pressurizing and heating paper made from a mixture of natural fibers and synthetic resin powder,
An insulating paper comprising an outer layer containing a small amount of synthetic resin powder and an inner layer containing a large amount of synthetic resin powder. 4. The insulating paper according to claim 3, wherein the synthetic resin is polypropylene. 5. Fiber paper made by making natural fibers on one side of mixed paper made from a mixture of natural fibers and synthetic resin powder is fused together by pressure heating,
The mixed paper includes a part with a high content of synthetic resin powder and a part with a low content of synthetic resin powder, and the part with a high content of synthetic resin powder is joined to the fiber paper, An insulating paper characterized by a small portion being exposed to the outside air. 6. The insulating paper according to claim 5, wherein the synthetic resin is polypropylene. 7. The insulating paper according to claim 5, wherein the fiber paper is kraft paper. 8. Insulating paper made of mixed paper made of a mixture of natural fibers and synthetic resin powder, and fibrous paper made of natural fibers on both sides of the paper, which are fused together by pressure heating. 9. The insulating paper according to claim 8, wherein the synthetic resin is polypropylene. 10. The insulating paper according to claim 8, wherein the fiber paper is kraft paper. 11 Each of the first, second and third layers each consisting of natural fibers and synthetic resin powder, the first and third layers have a low content of synthetic resin powder, and the second layer has a low content of synthetic resin powder. 1. A method for producing insulating paper, which contains a large amount of insulating paper and is characterized by sequentially and continuously combining a first layer, a second layer, and a third layer.