CS231720B1 - Fibrous material for the production of laminated insulators and the method of its production - Google Patents

Abstract

The invention relates to materials for the production of insulation for rotating or non-rotating electrical machines, for which insulation made on the basis of asbestos or mica paper is mainly used. The invention solves a completely new material base, while eliminating the problems that exist with currently used materials. The essence of the invention is a fibrous material made of glass microfibers, which may optionally contain up to 50% by weight of pulp fibers. The essence of the production method lies in the process of preparing the fibrous components and mixing them using a suitable process. The material is then produced using a conventional process on a paper machine. The subject of the invention can be used in the production of the material using a paper production method.

Description

BACKGROUND OF THE INVENTION The present invention relates to fibrous material for the production of laminated insulators which are used for insulating both rotating and non-rotating electrical machines, such as insulation of grooves, pole coils, phase outlets and the like.

For these purposes, the use of insulators made on the basis of mica paper or asbestos paper, as well as materials based on macromolecular foil, or their combinations, is widespread. The suitability of use of the various types of insulators depends, on the one hand, on the thermal class for which the insulator is to be suitable, and in particular on the particular product in which it is to be applied.

Mica paper, as a material for the production of layered insulators, has only a limited use, because of its lack of strength and resistance to removal, causing difficulties in inserting the insulator into the grooves. In addition, the creep of the material is detected at higher pressures, for example in the manufacture of pole coil insulations.

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Asbestos paper is, from the above mentioned points of view, a much more suitable raw material. However, it has other disadvantages for which its use is also limited. Asbestos as a raw material contains »metal particles that cannot be completely removed during production. These particles cause serious defects in finished products - insulators, eg inter-turn shorts. Getting asbestos as a raw material is becoming increasingly difficult. As asbestos dust has been found to have an extremely high carcenogenicity, asbestos mining is limited and asbestos paper production has been banned in some countries. In addition to the above-mentioned reasons, the production of asbestos paper is also a major technical problem, since it can only be realized on specially adapted machinery,

The above drawbacks eliminate the use of a material according to the invention which can be produced by a conventional process on a conventional paper machine. The present invention provides a fibrous material comprising 50 to 99% by weight of glass microfibers with an average fiber diameter of up to 4 microns. Further, the material comprises 1 to 50% by weight of pulp and may further comprise 1 to 10% by weight of epoxy resin based on the weight of the fibers.

The principle of the process for the production of said material is that glass microfibers having an average microfiber diameter of up to 4 microns are converted into an aqueous suspension in which the pH is adjusted to 3.0 to 3.5 by a suitable process. The fiber content of the suspension must not exceed 1% by weight in order to achieve complete disintegration. Only then is it mixed with the pre-ground pulp fibers and homogenized the mixture. It is also possible to add 1 to 10% by weight of epoxy resin, which is prepared in advance by a suitable process so that it can be mixed into the aqueous suspension. It is then precipitated onto the fibers by the addition of aluminum sulfate. The production of the material is then carried out in a conventional paper machine.

The advantage of this material is first of all its high homogeneity, low thickness, good strength and, according to the needs of further processing technology, also controllable absorbency, decisive for receiving the required amount of impregnants. The purity of the raw materials used also ensures its good electroinsulating properties. By the appropriate ratio of the individual components of the material, its properties can be varied according to the purpose of its use.

In the following, embodiments of the invention are illustrated in the examples.

He did

The unbleached kraft pulp is ground to 40-45 ° SR at a density of about 5%. An amount of glass microfibers having a mean fiber diameter of 2.5 microns is added to a dutch water-impregnated water having a pH pre-adjusted to a value of 3.0 to 3.5 such that its mass content does not exceed 1% by weight. After perfect loosening, the two fiber components are mixed in a weight ratio of 1: 9, followed by homogenization of the mixture, for example, by passing through an unloaded high-speed refiner.

The resulting homogeneous fiber mixture is processed on a paper machine to a 75 g / m @ 2 material which is used to produce laminated insulators instead of asbestos paper hitherto used.

Example 2

The fibrous raw materials were prepared as in Example 1 except that microfibers having a mean fiber diameter of 4.0 microns were used. They are mixed so that the resulting mixture contains 65% by weight of glass microfibers and 35% by weight of pulp. An epoxy resin solution is prepared so that it can be mixed into the aqueous fiber suspension. Thereafter, an amount of epoxy resin is mixed into the suspension so that its content in the suspension is 6% by weight, based on the weight of the cloths, and the mixture is homogenized. The epoxy resin is then precipitated onto the fibers by the addition of aluminum sulphate and a 0.2 mm thick material is produced on a paper machine.

Claims (4)

SUBJECT OF THE INVENTION A fibrous material for the production of layered insulators, characterized in that it comprises 50 to 99% by weight of glass microfibers with a maximum mean diameter of the fibers up to 4 micrometers and 1 to 50% by weight of pulp fibers. 2. The fibrous material of claim 1, further comprising epoxy resin precipitated on the fibers in an amount of 1 to 10% by weight based on the weight of the socks. 3. A method according to claim 1, characterized in that the glass microfibers are separately transferred to an aqueous suspension in which the pH has been previously adjusted to a value of 3.0 to 3.5 and the content of the slugs in the suspension does not exceed 1% by weight. after complete disintegration, the fibers are mixed with pre-ground pulp and homogenized. 4. A method according to claim 3, characterized in that an epoxy resin is introduced into the aqueous suspension of the fibrous mixture and, after mixing into the fibrous suspension, it is precipitated onto the fibers by addition of aluminum sulphate.