DE1169831B - Process for, in particular, the continuous production of mica films - Google Patents

Description

Process for the, in particular, continuous production of mica foils Addition to patent: 1061688 A process is already known for breaking down mica in such a way that foils similar to a paper web can be produced from the finest flakes. As can be seen from the German patent specification 1061688, there are considerable difficulties and differences compared to the actual paper production from fibrous raw material in the analog processing of mica, a platelet-shaped material. For example, in the fibrous paper the fibers are always felted together, which means that even when wet, depending on the type and length of the fiber, an often considerable wet strength is achieved. The paper can therefore be deformed by rolling, pressing or upsetting while it is still wet. It can be B. can also be deformed to crepe paper. This has a significantly higher elasticity and can be so z. B. can be used with advantage to isolate Röbelstäben by z. B. these wrapped with creped paper and treated with resin.

However, mica must be used for numerous electrical insulations or be used as well. Mica splits, as used in the production of mikafolium, a cellulose paper of 30 to 50 g / m2, with one or two layers of split mica is pasted and provided with a binder layer, tend to find application always to split, which is particularly disadvantageous with high-voltage windings. Mica foil does not have these disadvantages, but does not have a sufficiently great elongation and can therefore only be processed or deformed with difficulty. A deformation of the wet Mica foil by mechanical impoverishment methods is not possible because it is at the processing of mica flakes into mica foil does not result in matting. A bonding effect occurs which becomes effective during drying. In the wet State has no strength (wet strength = 0 kg / mm2) and is dry there is a relatively high strength (dry strength = 3 kg / mm2). A shaping the wet mica foil by the known deformation methods is not possible.

The production of mica films by suctioning off a mica suspension on a web of paper or fabric laid over a screen body is in the German Patent 1061688.

It has been found that a mica sheet of high strength and Elongation can be obtained, especially a creped mica sheet, if one is on Creped fiber paper or fabric webs are used instead of normal paper. The mica flakes settle on the web used and adapt to it Wrinkles on. The mica film, for example on the crepe paper, is dried and can be deducted. The peeled off mica film has the same texture like the pad. For example, it is creped when using a creped one Train. Creped paper and fabric webs can be used as a base. The creped mica film obtained according to the invention can either by itself or as well can be further processed together with the paper or fabric backing.

The invention is illustrated by the following exemplary embodiments: Example 1 On a sieve pad of z. B. 300. 1000 mm a web is creped Filter paper placed on top and sealed with the sieve pad by moistening and sucking in tied together. A mica pulp of about 25 g solids poured into the liter. The mica flakes are distributed evenly over the creped paper web and sit on it under negative pressure Paper web at the elevations and depressions given by the creping evenly distributed. The creped paper including the absorbed Mica mass is then lifted off the sieve pad on a drying plate in Fifty to sixty layers placed on top of each other and placed in a drying press at 140 ° C dried within 2 hours. Then the mica tracks now peeled off as a creped film from the base or with it are further processed.

Example 2 A rotating Fourdrinier wire becomes a creped endless wire Paper or fabric web is sucked in and transported along with it. On this track which is under a slight negative pressure, becomes a mica pulp in a steady influx applied from 20 to 30 g solids per liter. As a result of the negative pressure the mica particles are firmly sucked in while maintaining the unevenness of the base. The endless paper or fabric web is attached to the reversal of the Fourdrinier wire lifted off and passed through a drying section until the newly formed creped Mica foil is so dry and firm that it is lifted off the surface and rolled up can be. The strength of the mica film is determined by the speed of rotation of the Fourdrinier set. At low speeds, more is per unit area Mica applied. However, this thicker layer also requires a longer dwell time in the drying section.

The mica films obtained according to the invention, e.g. B. creped Mica paper can be wound directly onto parts to be isolated and z. B. Impregnated under vacuum with casting resin or the like. But you can also use an impregnation and binding agent, such as. B. silicone resin, shellac, epoxy resin, are impregnated, and then wound into molded bodies or placed on top of one another to form sheets and hot hardened under pressure.

Coils made with the creped made according to the invention Mica foil are made, exhibit better adaptability to the wrapping molded body on. Another particular advantage is that during manufacture of laminated bodies using creped mica foil a better connection is obtained from layer to layer than when using smooth paper.

Claims (1)

Claim: Process for, in particular, continuous production of mica foils according to patent 1061688, characterized in that there is a mica suspension on a creped fiber paper or fabric web and then, if necessary after detaching from the base, dries.