EP1086470A1

EP1086470A1 - Method for making a micaceous product preferably in the form of a mica ribbon and resulting product

Info

Publication number: EP1086470A1
Application number: EP99928915A
Authority: EP
Inventors: Alain Jacques; No[L Mortier
Original assignee: Compagnie Royale Asturienne des Mines
Current assignee: COGEBI SA
Priority date: 1998-06-17
Filing date: 1999-06-17
Publication date: 2001-03-28
Anticipated expiration: 2019-06-17
Also published as: CN1145977C; DE69905362D1; US6699804B1; JP2002518220A; ATE232644T1; AU4593399A; EP0966001A1; BR9911853A; WO1999066515A1; CN1305632A; DE69905362T2; EP1086470B1

Abstract

The invention concerns a method for making a micaceous product capable of being impregnated preferably in the form of a mica ribbon by combining at least a support and a mica sheet. The invention is characterised in that it consists in: coating the support and the sheet with a solvent-free resin or a mixture of solvent-free resins using several coating rollers brought to a temperature for producing the coat; combining the support with the mica sheet; subjecting them to a pressure and heat treatment.

Description

PROCESS FOR PRODUCING A MICACE PRODUCT PREFERABLY IN THE FORM OF A MICA TAPE AND PRODUCT

GOT

Object of the invention

The present invention relates to the production of a micaceous product preferably in the form of a mica tape comprising a support coated with a solvent-free resin associated with a mica sheet.

More specifically, the present invention relates to a process for producing a mica tape suitable for impregnation subsequent to the production process itself.

The present invention also relates to a new micaceous product.

Technological background underlying the invention

The electrical and possibly thermal insulation of copper elements composing the electric motors such as bars or coils, is carried out by wrapping said parts using micaceous products, more specifically micaceous ribbons. These micaceous ribbons are in the form of a support impregnated with a resin, for example epoxy, associated with a sheet of mica. This mica sheet can be mica paper, possibly reinforced with a small amount of resin, for example epoxy.

Among these ribbons, two large families coexist.

The first family includes the ribbons called "saturated ribbons" or even "prepreg", which are ribbons made from mica paper heavily impregnated with a resin of the Novolac type and having as support a glass fabric. The resin content is usually between 30 and 40% of the total weight of the tape. During manufacture, the epoxy resin is brought to stage B, that is to say that it has already undergone hardening. Then, this type of product can be wrapped on the part to be insulated and will then undergo a heat treatment of the order of 160 to 180 ° C. Document JP-07149928 describes a product in the form of a conventionally produced saturated mica tape. It seems that a solvent-free epoxy resin is then used in the second phase of the production, that is to say after the tape is wrapped on the machine, in order to obtain adequate electrical insulation.

The document EP-A-0735071 describes a solvent-free resin composition optionally intended for the manufacture of a micaceous tape of saturated type, that is to say already completely impregnated and therefore having a relatively high resin content. Document GB-A-2083849 describes a process for producing insulation tapes which consists in impregnating a mica support at room temperature using a solvent-free resin followed by attachment to a support and heating the assembly so as to reduce the viscosity of the resin, which will promote the deep impregnation of the mica paper. This will again give a ribbon of the "prepreg" type and therefore already heavily impregnated. The second family includes the so-called ribbons

"porous", which have a relatively low resin content of the order of 4 and 10% by total weight of the ribbon. These ribbons are suitable for being impregnated later in the process for manufacturing said ribbons and will be subjected, after wrapping, to a "VPI (Vacuum Pressure Impregnation)" treatment, which allows impregnation with a resin usually without solvent, in a second phase. . The "VPI" treatment consists in immersing in the impregnation resin the copper parts wrapped with the porous mica tape, applying the vacuum in order to eliminate any inclusion of air; then the vacuum is cut off and a certain pressure is applied for several hours in order to make the post-impregnation resin penetrate into the mica insulation. The course of the entire post-impregnation process and the temperature of the resin are dictated by the nature of this resin, the thickness of the insulation to be impregnated and the porosity of the mica tape used.

Dry, very flexible and non-adherent tapes are obtained before wrapping, which are distinguished by a truly exceptional absorbency. They are of this made used for high voltage machines (up to 1000 MVA).

To make such ribbons of the second family which are considered suitable for impregnation, we know the technique of "spraying" (also called "spraying") which consists in spreading and impregnating a mica paper with a resin epoxy in solvent medium and then to associate it with a support.

To make ribbons suitable for impregnation, it is also known to use techniques for dusting a solid resin either on a sheet of mica or directly on the support, and then to join the two elements together by an action of pressure and heat. In particular, publication EP-A-0194974 describes a process for the preparation of thin mica ribbons suitable for impregnation and comprising an incorporated accelerator, characterized in that a sheet of fine mica is sprinkled with a varnish in hardener-free powder, then either glue the side of the sheet of fine mica sprinkled with varnish by a pressure or heat action with a glass cloth or a felt serving as a support, or impregnate a glass cloth with a liquid accelerator or of a solution of a liquid or solid accelerator in a solvent with low boiling point and the support thus obtained is bonded by a pressure and heat action with one side of the mica sheet sprinkled with varnish, and then the laminate obtained is impregnated with a liquid accelerator or a solution of a liquid or solid accelerator in a solvent with low boiling point. Another possibility is to impregnate a sheet of mica with a liquid accelerator or a solution of a liquid or solid accelerator in a solvent with low boiling point, then sprinkle with a hardener-free powder varnish on the impregnated mica sheet, and then either impregnate a glass cloth with a liquid accelerator or a solution of a liquid accelerator or solid in a solvent with low boiling point by gluing the support thus obtained by an action of heat and pressure with the side of the sheet of fine mica sprinkled with powder varnish, or by gluing the felt serving as support by a pressure and heat action with the side of the thin mica sheet sprinkled with powder varnish. It is observed however that by using this method, the dusting of a varnish requires the use of a certain amount of it. In particular, the varnish will tend, when it is sprinkled on the support, to pass through the meshes and to be found on both sides of the support.

Aims of the invention

The present invention aims to provide a method of manufacturing micaceous products suitable for impregnation which requires the use of a low level of resin.

The present invention aims to propose a technique which makes it possible to avoid the use of solvents for the preparation of micaceous products suitable for impregnation such as mica ribbons of porous type.

The present invention also aims to allow the production of such ribbons having increased flexibility while having sufficient or even increased adhesion qualities.

In addition, the present invention aims to propose, in the particular case of the realization of coiled ribbons, a process which avoids the problem of sticking between successive turns.

Main characteristic elements of the invention The present invention relates first of all to a process for producing a micaceous product suitable for impregnation, preferably in the form of a mica tape obtained by combining a support. and a mica sheet, characterized in that: - a resin or an adhesive or a mixture of resins without solvent is coated on the support or on the mica sheet using of coating rolls at a temperature for applying the coating, - the support is associated with the mica sheet, and

- They are subjected to a pressure and temperature treatment at a second processing temperature.

By "coating processing temperature", it is necessary to understand the temperature to which the resin mixture without solvent is brought in order to be able to coat the support or the mica sheet. This temperature is usually between 40 and 200 ° C. This means that the resin must be in a non-solid form, that is to say in the more or less viscous or liquid state.

By "a pressure and temperature treatment" is meant a treatment at a temperature between 40 and 200 ° C for a pressure between 0 and 20 bars in order to allow the support to be secured to the mica sheet. Among the possible examples of resin intended for coating, mention may be made of solvent-free epoxy resins, solvent-free silicone adhesives or any other solvent-free resin having a viscosity suitable for the temperatures at which the coating is used.

The support can be either a film or a fabric, or even a felt. The mica sheet is preferably a conventional mica paper produced according to the usual stationery techniques. This mica paper may be a 100% mica paper or optionally a mica paper previously reinforced by means of an impregnation resin, for example epoxy, by a conventional implementation process such as impregnation by coating optionally in a solvent medium. . It is possible to envisage incorporating an accelerator either into the resin used for coating, or during a prior step during the preparation of the mica sheet in the so-called impregnation resin, or even directly on the support or on the mica sheet itself.

In the first embodiments, the accelerator is then directly mixed with the resin.

In general, it is conceivable to use an accelerator in the form of a nitrogenous compound such as an amine or an organometallic compound such as zinc naphthenate, or any other compound having the desired catalytic effect.

A second object of the present invention relates to a micaceous product suitable for impregnation which is preferably in the form of a strip of so-called porous mica and which comprises on the one hand a support impregnated by solvent-free coating of a resin and a sheet of mica, or else a sheet of mica impregnated by solvent-free coating of a resin and the support itself, these two elements being joined together.

It is observed that in the case where the support is a fabric, there will be deposits of resin essentially on the intersections of the threads of the weft with those of the warp. More precisely, traces of resin will be observed only at intersections where the weft thread is superimposed on that of the warp. This makes it possible to obtain, in a particularly advantageous manner, a very precise adjustment of the resin content on the finished ribbon, and the resin content of which is clearly lower than for the products obtained by the processes of the state of the art (spraying or use a solid powder). This also makes it possible to preserve or even increase the flexibility characteristics and to limit the risks of sticking between turns when the ribbon is wound.

Preferably, the fabric will be a woven glass fiber fabric or silk, having a grammage of 20 to 50 g / m ² . The mica sheet, and preferably the mica paper, has a grammage of between 100 and

250 g / m ² .

BRIEF DESCRIPTION OF THE FIGURES FIG. 1 represents a schematic view of the device intended to carry out the coating process according to the present invention. FIG. 2 represents a schematic view of the second step of the process for producing a micaceous ribbon according to the present invention, which consists in securing the support to mica paper. FIG. 3 represents a schematic description of a glass fabric impregnated by the technique described.

Description of several preferred embodiments of the invention

FIG. 1 represents a schematic view of a device intended to carry out the method according to the invention. This device comprises on the one hand a coating station consisting essentially of several successive cylinders, and preferably four cylinders (1, 2, 3 and 4), which allow the coating of a very small amount of resin on the support .

This coating unit is followed by a lamination unit which brings the two elements, that is to say the mica sheet and the support, into contact, and which exerts on the assembly a pressure action and temperature as described in Figure 2. This pressure action is carried out using two cylinders (5 and

6). Preferably, only one of the two cylinders will be heated.

The examples which follow more specifically describe two examples of carrying out the process according to the present invention.

Examples Example 1

A mica tape is produced by hot coating a glass fabric support with a solvent-free resin and the coated support is laminated on a mica paper. For this, the following materials are used: 1) An unmodified epoxy resin based on bisphenol A and epichlorohydrin. It is a solid resin at room temperature and free of solvent. This resin has an epoxy equivalent weight of between 350 and 400 g / equiv. and a viscosity at 90 ° C of the order of

4000 mPa.s.

2

2) A glass fabric of 24 g / m grammage consisting of

26 threads / cm in warp and 15 threads / cm in weft, the thread count being 5.5 tex in warp and weft. 3) Muscovite type mica paper with a grammage of

2 2

160 g / m, previously reinforced with 4 g / m of resin

epoxy added with a metal salt type accelerator. The addition of the epoxy resin and the accelerator to the mica paper being carried out in a conventional manner, that is to say by impregnation in a solvent medium. To make the mica tape we proceed as follows:

A) The epoxy resin is preheated in an oven to 90 ° C.

When the resin has reached the temperature and is sufficiently fluid, the appropriate quantity is poured between the cylinders 1 and 2 of the coating stand described in FIG. 1. The cylinders 1 and 3 of the coating stand have been preheated to 90 ° C and are maintained at this temperature for the duration of the coating. The speeds of rotation and the spacing between the different cylinders of the coating stand are adjusted in order to obtain the transfer of a thin layer of resin from cylinder 2 to cylinder 3 and from cylinder 3 to cylinder 4. B) The glass fabric is unwound and brought into tangential contact with the cylinder 4 of the coating stand as described in FIG. 1. The glass fabric entrains part of the resin located on the cylinder 4. C ) On the other hand, the mica paper is unwound and it is brought into contact at the level of the lamination unit described in FIG. 2 with the coated glass fabric. Cylinder 5 was preheated to 80 ° C. A pressure of 20 bars is applied from cylinder 6 to cylinder 5 so as to secure the mica paper to the support in order to obtain a micaceous ribbon. D) The micaceous ribbon thus obtained is wound up.

With the settings used in the example, we

2 obtains a deposit of the order of 4 to 5 g / m of epoxy resin

on the glass fabric, which is equivalent to a content of the order of 2% by total weight of the ribbon. If the resin previously used in the mica paper is taken into account, a finished ribbon will be obtained having a resin content of between 3.5 and 4% by total weight of the ribbon. If we observe a binocular or microscope sample of coated glass fabric as described above, we observe the presence of resin only at the intersections between the warp threads and the weft threads and more precisely only at the intersection where the weft threads are superimposed on the warp threads, that is to say at an intersection on 2 as described in FIG. 3. We also note that there is no transfer of resin onto the other face of the glass cloth.

The characteristics of a mica tape thus produced (tape A) are shown in Table I and compared to those of a tape manufactured by the conventional technique known as spraying in solvent medium (ribbon B). It is found that the ribbon A manufactured according to the process described above contains a resin content lower than the rate normally necessary for a ribbon B manufactured by the conventional spraying technique in solvent medium. In addition, the tape A has better flexibility, greater porosity and better tensile strength than the tape B. The tape A is also completely dry on the outside of the glass fabric since the resin is located only at the interface between the glass fabric and the mica paper, this characteristic limits the risks of sticking between turns of the wound ribbon.

Example 2 A mica tape is produced by hot coating using the same technique as described in Example 1. For this, the following materials are used:

1) An unmodified epoxy resin based on bisphenol A and epichlorohydrin. It is a liquid resin of high viscosity at room temperature and free of solvent. This resin has an epoxy equivalent weight of between 235 and 265 g / equiv. and a viscosity at

90 ° C of the order of 300 mPa.s.

2) A 23 μm thick polyester film 3) A Muscovite type mica paper with a grammage of

2 2

180 g / m, previously reinforced with 5 g / m of epoxy resin by impregnation in a solvent medium.

To make the mica tape, the procedure is the same as in Example 1, replacing the glass fabric with the polyester film. With the settings used in the example, we

2 obtains a deposit of the order of 4 g / m of epoxy resin on

polyester film. The mica tape thus produced is extremely flexible and the adhesion between the polyester film and the mica paper is very good.

Table I

Claims

1. Method for producing a micaceous product suitable for impregnation, preferably in the form of a mica tape obtained by combining at least one support and a mica sheet, characterized in that:

a coating is carried out of a solvent-free resin or of a mixture of solvent-free resins on the support or on the mica sheet using several coating rollers brought to a processing temperature of the coating,

- we associate the support with the mica sheet, and

- they are subjected to a pressure and temperature treatment.

2. Method according to claim 1, characterized in that a micaceous product is produced whose resin content is between 1 and 10%, and preferably between 4 and 8%, by total weight of the ribbon.

3. Method according to claim 1 or 2, characterized in that the temperature of implementation of the coating is between 40 and 200 ° C.

4. Method according to any one of the preceding claims, characterized in that the pressure and temperature treatment is carried out between

40 and 200 ° C for a pressure between 0 and 20 bars.

5. Method according to any one of the preceding claims, characterized in that one incorporates an impregnation resin, optionally in a solvent medium, in the mica sheet in small quantity, and this prior to the coating step .

6. Method according to any one of the preceding claims, characterized in that the resin intended for coating is a resin having a melting point below the processing temperature.

7. Method according to any one of the preceding claims, characterized in that the resin is a solvent-free resin preferably of silicone or epoxy type and more particularly belonging to the family of DGEBA resins.

8. Method according to any one of the preceding claims, characterized in that an accelerator is incorporated into the coating resin.

9. Method according to any one of the preceding claims, characterized in that an accelerator is incorporated in the mica sheet.

10. Method according to any one of the preceding claims, characterized in that an accelerator is incorporated in the support.

11. Method according to any one of the preceding claims, characterized in that the accelerator is a nitrogenous compound, an organometallic compound.

12. Method according to any one of the preceding claims, characterized in that the support can be a film, a fabric or a felt.

13. Method according to any one of the preceding claims, characterized in that the mica sheet is preferably mica paper previously reinforced by means of an impregnation resin.

14. Method according to any one of the preceding claims, characterized in that the mica sheet is produced from calcined muscovite or not, phlogopite, vermiculite or synthetic mica or a combination thereof.

15. Micaceous product suitable for impregnation, preferably in the form of a mica tape, comprising a support coated with a solvent-free resin associated with a mica sheet.

16. Micaceous product according to claim 15, characterized in that the resin content is between 4 and 10% by total weight of the ribbon.

17. Micaceous product according to claim 15 or 16, characterized in that the support is a fabric on which the resin deposits appear essentially on the threads of the weft at the intersection with the warp threads.