DE4007201A1 - Polarisable electrode for electric double layer capacitor - made by performing mixt. of carbon powder, fluorine contg. polymer and liq. lubricant into sheet and redn. thickness - Google Patents

Abstract

A polarisable electrode for an electric double-layer capacitor is prepd. by performing a kneaded mixt. of ine carbon powder, fluorine-contg. polymer and liq. lubricant into a layer, removing the liq. lubricant from the laminar preform, and passing the preform between heated rollers to form a laminar material of predetermined thickness.

Description

The invention relates to a method for producing a polarizable electrode for an electrical double Layer capacitor according to the generic terms of the subsidiary Neten claims 1, 3, 6, 8 and 11.

In the following, an electrical double-layer capacitor will be described in more detail with reference to FIGS . 4 and 5.

According to the Fig. 5 includes an electric double-layer capacitor 1, in general, a plurality of z. B. six capacitor cells 2 , which are coaxially stacked or arranged one above the other and are located within a cup-shaped housing 3 .

Each capacitor cell 2 has the shape of a circular plate, as shown in FIG. 4, and contains two polarizable electrodes 4 a and 4 b , a separator 5 , ei ne annular seal 6 and two current collectors 7 a and 7 b , the thermal are connected (bonded) to upper and lower surfaces of the seal 6 , respectively.

More specifically, the polarizable electrodes 4 a and 4 b contain solid carbon-containing packages or densifications, the electrodes 4 a and 4 b being insulated from one another, specifically by the electrically insulating separator 5 . The separator 5 consists, for example, of a polyolefin microporous film or of a non-woven structure or of a nonwoven fabric or of paper and preferably has a projecting part along its peripheral edge. This projecting part encompasses the second polarizable electrode 4 b , in order to prevent the polarizable electrodes 4 a and 4 b from being short-circuited via their respective edge regions. The polarizable electrodes 4 a and 4 b and the separator 5 are firmly connected to each other, namely by adhesive 8 , which are in partial areas between the interfaces of the respective elements. These polarizable electrodes 4 a and 4 b and the separator 5 are impregnated with an electrolytic solution, for example with an aqueous solution containing 50% by weight of sulfuric acid.

The seal 6 consists of a substrate 9 , which is made of a vulcanized ethylene-propylene rubber (EPR rubber) and which is integral on both surfaces, for. B. is provided with polyethylene layers 10 a and 10 b low density. The current collectors 7 a and 7 b consist of polyethylene len films, the z. B. have been made conductive by carbon material such as carbon black or the like. These current collectors 7 a and 7 b serve as electrical conductors for the polarizable electrodes 4 a and 4 b and as an airtight seal for the polarizable electrodes 4 a and 4 b and the separator 5 within the seal 6 .

A required number of e.g. B. six capacitor cells 2 with the aforementioned construction are arranged one above the other or stacked, depending on the nominal voltage, as shown in FIG. 5. An electrically isolating and thermally contractible tube 11 encloses the stacked capacitor cells 2 in order to integrate or hold them together. A cell device 12 obtained by such integration is held in the housing 3 under pressure.

Resiliently conductive plates 13 a and 13 b made of highly conductive resin or rubber are in the housing 3 and in contact with the upper and lower surfaces of the device 12 . A connection device 14 is arranged on the upper elastic, conductive plate 13 a . At this circuit device 14 contains two connections 15 a and 15 b , which are made of metal plates and which are connected to one another via an insulating plate 16 . At the circuit 15 a is electrically connected to the upper surface of the cell device 12 via the elastic, conductive plate 13 a . In contrast, the terminal 15 b , which is in contact with the upper edge of the housing 3, is electrically connected to the lower surface of the cell device 12 via the housing 3 and the elastic, conductive plate 13 b . As can be seen on the basis of the structure of the electrical connections, the elastic conductive plates 13 a and 13 b serve the contact resistances between the upper surface of the cell device 12 and the terminal 15 a and between the lower surface of the cell device 12 and the bottom surface of the housing 3 each to reduce in this way to stabilize the electrical connection.

A sealing resin member 17 is used to cover the opening area of the housing 3rd This sealing resin member 17 forms an airtight seal for the case 3 to make the electric double layer capacitor 1 washable. Another thermally contractible tube 18 covers the outer peripheral surface of the housing 3 to isolate it.

In order to reduce the size of the above-mentioned electrical double-layer capacitor 1 , in particular in the vertical direction, that is to say to reduce the height H in FIG. 5, it is necessary to reduce the thickness of the capacitor cells 2 which form the cell device 12 . The Kon capacitor cells 2 can be effectively reduced in thickness by the fact that the polarizable electrodes 4 a and 4 b are formed as thin layers or plates.

In general, layered polarizable elec troden produced in that a rubber-like, vis kose mixture (admixture) of polytetrafluoroethylene (PTFE) resin and a liquid lubricant rolled out to maintain the layers. The river sige lubricant z. B. from water, alcohol, glycol, etc. exist.

Are the panels or layers described in the above Reduced in thickness, they stick over overlapping layers, however, because of the extension due to the plastic elasticity of the case mixture and the adherence of the liquid lubricant, so that they are practically unmanageable. The minimal The thickness of such a layer was therefore 0.6 mm borders.

To solve the above problem, it can be thought first to produce a plate-like preform, the egg ne has a certain thickness, and then a liquid  Remove lubricant from the preform. Subsequently the preform could then be rolled out into a thin film. However, this method also does not allow one Make film with a thickness less than 0.6 mm because there may be cracks, breaks, etc.

For this reason, a method for removing a liquid lubricant from a layered preform as well as for the subsequent uniaxial or multiaxial drawing hen the preform as proposed in the disclosed yes panicky patent publication No. 1 07 011/1988 is.

With the help of this method it is possible to To produce plates with a thickness that is less than 0.6 mm is. However, the method is not suitable for ind strial application, especially after the roll an additional drawing step can be carried out must, which also takes a relatively long time.

The invention has for its object a method for Production of a polarizable electrode for an elec trical double layer capacitor to create one Reduction in the thickness of the polarizable electrode for the purpose Reduction of the vertical size of the electric double Layer capacitor allows and a high at the same time Yield or productivity allowed.

Solutions to the task at hand are the defining ones Parts of the independent claims 1, 3, 6, 8 and 11 can be seen. Advantageous embodiments of the invention are specified in the subordinate claims ben.

In accordance with the invention, in a first Step (starting step) a kneaded substance made of fine  Carbon powder, a fluorine-containing polymer resin and preformed into a layer of a liquid lubricant. This step is always carried out.

According to a first aspect of the invention, the start follows took the next steps: 1-a) Removing the liquid lubricant from the preform and 1-b) Deforming this layered preform into one Layer of predetermined thickness using heated Rolls or rolls.

According to a second aspect of the invention Started the following further steps: 2-a) Setting the proportion of liquid lubricant in the preform to 10 to 47% by weight, 2-b) Deform this layered preform into one Layer of predetermined thickness using rollers or rollers and 2-c) removing the liquid lubricant from the preform or shift.

In accordance with a third aspect of the invention step 2-b) is carried out according to the aforementioned second Aspect replaced by the following step: 3-b) Deforming the preform to form a layer with a predetermined thickness is carried out with the help of heated rollers or rollers.

In accordance with a fourth aspect of the invention After the start step the following steps are carried out: 4-a) Stacking or stacking a plurality  of layered preforms in their respective final areas and connecting them into a continuous, long preform by rolling or rolling, 4-b) Remove the liquid lubricant from the long one Preform and 4-c) Deform this preform into a layer with prep of proper thickness using heated rollers.

In accordance with a fifth aspect of the invention Steps 4-b) and 4-c) are in the aforementioned fourth aspect replaced by the following steps: 5-b) Adjust the amount of liquid lubricant in the preform to 10 to 47% by weight, 5-c) Deform the long preform into one layer thickness with the help of rollers or rollers and 5-d) Remove the liquid lubricant from the preform or long shift.

In a sixth aspect of the present invention step 5-c) in the aforementioned fifth aspect replaced the following step: 6-c) deforming the preform into a layer with predetermined thickness using heated rollers.

According to a seventh aspect of the present invention, who the following steps after the start step leads: 7-a) Setting the amount of liquid lubricant in the preform to 20 to 47% by weight, 7-b) Placing a plurality on top of one another of layered preforms in their respective final areas and connecting them into a continuous, long preform by rolling or rolling,  7-c) Deform this long preform into one layer thickness with the help of rollers or rollers and 7-d) removing the liquid lubricant from the preform or shift.

According to an eighth aspect of the invention, the step 7-c) in the aforementioned seventh aspect by the follow replaced the step: 8-c) Deform the long preform into one layer of a certain thickness with the help of heated rolls or rollers.

In the invention having the aforementioned aspects the fine carbon powder is at least activated by activated carbon or soot.

The fluorine-containing polymer resin can e.g. B. made be made of polytetrafluoroethylene (PTFE), an ethylene Tetrafluoroethylene copolymer, a chlorotrifluoroethylene Ethylene copolymer, a vinylidene fluoride copolymer, a Tetrafluoroethylene-perchloroalkyl vinyl ether copolymer or the like.

The liquid lubricant can e.g. B. water, alcohol, pro pylene glycol, ethylene glycol, glycerin, white oil or the like Chen be or contain.

The mixing ratios between the aforementioned fei NEN carbon powder, the fluorine-containing polymer resin and the liquid lubricant are chosen so that the ge kneaded substance 100 parts by weight of fine carbon powder contains, 0.5 to 30 parts by weight of the fluorine-containing Polymer resin and 95 to 150 parts by weight of liquid lubricant material. These values are only to be considered as examples ten.  

The "heated rolls" in accordance with the first, third, fourth, sixth and eighth aspects of the present the invention are heated to a temperature which in a temperature range of 40 to 350 ° C, vorweiwei se in a temperature range from 90 to 120 ° C.

The invention is described below with reference to the Drawing described in more detail. Show it:

Fig. 1 shows a rolling step which reaches at a preform for application to,

Fig. 2 is a graph showing a relationship Zvi a specific volume and the tempera ture rule of polytetrafluoroethylene,

Fig. 3 is a graph for explaining the relationship between an extension and the tem perature of drawn polytetrafluoroethylene,

Fig. 4 shows a cross section through a capacitor cell in an electrical double-layer capacitor, and

Fig. 5 is a cross-sectional view of an electric double layer capacitor having a plurality of condensate sator cell of FIG. 4.

The present invention is proposed in view of this suggest that it is more optimal for industrial purposes To reduce the thickness of a preform, of which a liquid Lubricant has been eliminated, reducing the thickness Decoration is not done by pulling, but by rolling should. This allows the creation steps to be verified simple and necessary to reduce the thickness Shorten the time.  

The inventors have examined the mechanism for reducing the thickness of a preform by rolling in more detail and have come to the following result: As shown in FIG. 1, a preform 21 is guided into a rolled layer 23 by means of two rollers 22 (pair of rollers). According to FIG. 1, a compression shear force acts within the shaded surface layers 24 as a result of the curling. The surface layers 24 must be quickly deformed and extended if the preform 21 passes through the two rollers 22 . It should be remembered that cracks or breaks occur when the percentage of surface layers 24 is increased, based on the total rolled layer 23 , that is, when the thickness of the rolled layer 23 decreases, since the preform 21 cannot be deformed. The minimum thickness of the layer 23 , which is obtained by rolling, is thus limited to 0.6 mm.

As shown in Fig. 2, polytetrafluoroethylene (PTFE) has room temperature transition points at about 20 ° C and about 30 ° C at which its specific volume changes. This is explained by a reversible change in the crystal structure at room temperature. An elongation or elongation of PTFE increases abruptly, as shown in FIG. 3, when it is heated to a temperature which is above the room temperature transition points.

It can thus be considered to heat PTFE to a temperature above the room temperature transition points in order to facilitate its deformation, so that the surface layers 24 , which are subjected to the shear force during rolling of the compression, can expand or deform.

From this point of view, a preform was created with the help of heated rolls processed, the temperature of the Rol  len was above room temperature. It was therefore possible Lich a plate or a layer in a simple way and quickly manufacture with a thickness that was smaller than 0.6 mm. Platelets or layers with such a small With the help of the conventional method, thicknesses could not be generated.

Although the above considerations regarding room temperature ratur transition points were made with a view to PTFE, they also apply to the other materia mentioned above lien, for example for polymer resin with contained therein Fluorine.

In accordance with another aspect of the invention it was found that a thin layer by rolling can also be obtained without heating the rollers, and by adjusting the proportion of liquid lubricant or lubricant in the preform at any stage the rolling step. Is the preform in a so-called semi-dried state transferred to the proportion of the rivers sigen lubricant in the preform so that it to be within a range of 10 to 47% by weight comes, there is no pro in further handling problem because the remaining liquid lubricant is soft effect. The layer can then be in its thickness can be reduced because the surface layers that the Are subjected to compression shear as a result of the plasticizer effect caused by the liquid lubricant can easily deform.

The preform to be rolled out, the liquid lubricant still contains up to a portion that still has a handling is not prevented in this case by semi-drying of a compact (compact), which is sufficient Has amount of the liquid lubricant. It is impossible Lich, such a layer of a kneaded substance  manufacture that was originally only a small part of contained liquid lubricant, due to the ver poorer rollability.

The preform is semi-dried in the manner previously mentioned net, so before going to the endbe with other preforms are put together and together with them is rolled to form a continuous, long preform hold the proportion of liquid lubricant in the preform preferably set so that it is within a loading is from 20 to 47 wt .-%.

In accordance with the invention it is possible to use a Layer or a plate for a polarizable electric de from 0.20 to 0.25 mm thickness in a simple manner len within a relatively short time. Plat Chen or layers with such a small thickness can be with the help of a conventional rolling process put. The vertical size of an electric double Layer capacitor can thus be used in the polarizable manufactured in the manner described above Electrodes are significantly reduced.

example 1

120 parts by weight of propylene glycol, which is used as a liquid lubricant 100 parts by weight of activated carbon are used added fabric powder, which is obtained by pulverizing acti fourth carbon fibers using a 200 mesh screen will hold. The carbon fibers are made of polyacrylonitrile produced. With the help of a spiral mixer, these Ma materials mixed together. Then 5 parts by weight aqueous PTFE dispersion ("Polyfluon D-1" from Daikin Indu stries, Ltd.) added, the mixture kneaded is a rubber-like, viscous mixture or Beimi maintenance.  

This viscous mixture or admixture is made using Rolls processed so that a layered preform with with a thickness of 1 mm.

Then the liquid lubricant is reduced in thickness by rollers that are heated to 90 ° C to 120 ° C to produce a layer with a thickness of 0.25 mm. The rolling process is effective in a temperature range of 40 ° C to 350 ° C, however, the optimal temperature range is between 90 ° C and 120 ° C, with regard to egg facilitated rolling / deformation process, on a special more workability and with a view to better Water repellency.

The layer was made at a rate of 2 m / min.

Reference example 1

The preform according to Example 1 was pulled reduced in thickness to a layer with a thickness of Obtain 0.25 mm. The rate at which the layer was made was limited to 0.5 m / min. That rate is very much smaller than that in example 1.

Example 2

(Sketch) In comparison to example 1, a semi-dry Nete preform used to reduce thickness in space to allow temperature.

A layered preform with a thickness of 1 mm prepared in a manner similar to Example 1.

Then the proportion of liquid lubricant in the Preform set to 10 to 47 wt .-%, with Hil Fe of a hot air dryer at a temperature of 90 ° C.  

This preform becomes thicker by rolling at room temperature temperature reduced to a layer with a thickness of 0.25 mm to obtain. Then the liquid lubricant completely removed from the layer so that the layer as polarizable electrode can be used. To this There is no further change in the thickness of the layer at this time.

It is thus possible to apply a thin layer without a heated roller len because the surfaces of the layer, the exposed to compression shear, easily as a result the softening properties of the remaining lubricant can deform material.

Example 3

(Sketch) In comparison to example 2 the thickness is with Help heated rollers reduce the layer strength to improve and further reduce the thickness.

A layered preform with 10 to 47 wt .-% of liquid The lubricant is used in a similar manner as in Example 2 produced.

This preform is made with the help of roles that are based on a tem temperature between 90 ° C and 120 ° C are heated, so out rolls that finally a layer with a thickness of 0.20 mm is obtained. Then the liquid Lubricant completely removed from the layer so it can be used as a polarizable electrode. To there is no further change in thickness at this time the layer.

In Examples 1 and 2, fine cracks remain before the Thickness reduction has been observed even after Obtain roles so that the appropriate areas easily can break. In contrast, in example 3 these disappear  Cracks so that there are absolutely no breaks after rolling there are more. The minimum thickness, on the other hand, became limited to 0.25 mm in Examples 1 and 2 while it was possible according to Example 3, a simple Obtain layer with a thickness of 0.20 mm.

In accordance with Examples 1 to 3, in contrast to reference example 1, in which one layer like a preform is drawn, thin layers through a Produce the rolling process quickly and easily.

Example 4 (Sketch) Extension of example 1

In accordance with Examples 1 to 3, each Preform reduced in thickness so that the length of a he holding layer can be at most about 4 m. It is therefore not possible to be continuous or subtle to get broken, long layer. Example 4 judges focusing on making a continuous, long Layer.

A layer-like preform with a thickness of 1 mm is in prepared in a similar manner as in Example 1.

A plurality of such preforms are made on each of them End areas plugged together and rolled together other connected to an uninterrupted or continuous to form a long preform. The stacked ones Parts or areas of the preforms can be easily deformed by the softening effect of a liquid lubricant or lubricant that is in the preforms. In this way it becomes a verb  of the preforms.

Then the liquid lubricant from the long pre removed by hot air drying at a Temperature of 200 ° C.

The long preform is then rolled into it Reduced thickness, with the help of rollers on egg ner temperature in the range between 90 ° C and 120 ° C, around a continuous layer with a thickness of 0.25 mm to build.

Example 5 (Sketch) Extension of example 2

A continuously long layered preform is used in prepared in a similar manner as in Example 4.

Then the proportion of liquid lubricant in the long preform set to 10 to 47 wt .-%, namely by hot air drying at a temperature of 90 ° C.

This preform is then rolled up in thickness Room temperature reduced to finally a continuous uninterrupted layer with a thickness of 0.25 mm to obtain.

After that, the liquid lubricant is completely removed from the Layer removed so this layer as polarizable Electrode can be used. Is done at this time no further change in thickness of the layer.  

Example 6 (Sketch) Extension of example 3

A continuously long layered preform with 10 to 47% by weight of liquid lubricant is used in a similar manner prepared as in Example 5.

Then the preform is reduced in thickness by rolling adorned, the rollers at a temperature in the loading between 90 ° C and 120 ° C. In this way a layer with a thickness of 0.20 mm is obtained. On finally the liquid lubricant is completely eliminated removed the layer so that this layer as polarizable re electrode can be used. Is done at this time no further change in the thickness of the layer.

In Examples 4 and 5, fine cracks remain before the Thickness reduction has been observed even after Get rolling so that the corresponding parts can easily break. In example 6, however, disappear the cracks so that even after rolling there is absolutely no breakage there is a risk.

Example 7

(Sketch) A semi-dried preform is extended and reduced in thickness at room temperature.

First, a layer-like preform with 20 to 47 % By weight of liquid lubricant.

A plurality of such preforms are made at their end parts or end areas placed on top of each other and by rolling with connected to one another in a continuous or uneven manner to get broken long preform. The put together  or superimposed preforms can be softening effect of the liquid lubricant connect, the proportion of which is 20 to 47 wt .-%.

The long preform mentioned above is at room temperature reduced in thickness by curling, so that finally receive a continuous or uninterrupted shift whose thickness is 0.25 mm.

Then the liquid lubricant is completely out removed from the layer so that this layer is polarized bare electrode can be used. At that time he there is no further change in thickness of the layer.

Example 8

(Sketch) A semi-dried preform is extended and reduced in thickness by heated rollers.

A continuously long layered preform with 20 to 47% by weight of liquid lubricant is used in a similar manner prepared as in Example 7.

This preform is then made with the help of rolls in its thickness reduced, with the rollers at a temperature in the range between 90 and 120 ° C. The layer will look so far rolled until it has a thickness of 0.20 mm.

Then the liquid lubricant is completely out removed from the layer, so the layer as polarizable Electrode can be used. Is done at this time no further change in thickness of the layer.

In example 7 there are fine cracks that precede the thickness reduction tion have been observed, even after rolling hold so that the corresponding areas break easily  can. In Example 8, however, these disappear ge cracks completely, so that after the rolling process none There is a risk of breakage due to cracks.

Table 1 below shows results of the previous ones mentioned Examples 1 to 8 and Reference Example 1.

Table 1

As can be seen in Table 1, layers with a Thickness from 0.20 to 0.25 mm for a polarizable electrical de manufactured in a simple manner and in a short time those who would otherwise not be in the usual rolling process let form.

Circular plates are punched out of the layers obtained according to Examples 1 to 8 and the reference example 1 in order to obtain polarizable electrodes 4 a and 4 b , which are shown in FIG. 4. These polarizable electrodes 4 a and 4 b are used to form the capacitor cells 2 , which are integrated into electrical double-layer capacitors 1 , as shown in FIG. 5. The following Ta table 2 shows measurement results with regard to the product heights and the capacities of such electrical double-layer capacitors 1 . To determine the capacitances given in Table 2, the samples were charged with constant currents of 2 mA. The times were measured between an increase in the voltage at the terminals of the capacitors from 2 V to 4 V.

Table 2

Claims (13)

1. A method for producing a polarizable electrode for an electrical double-layer capacitor, characterized by the following steps:

• Preforming a kneaded substance from fine carbon powder, a fluorine-containing polymer resin and a liquid lubricant into a layer ( 21 ),
• - Removing the liquid lubricant from the layered preform and
• - Deforming this layer-like preform into a layer ( 23 ) with a predetermined thickness using heated rollers ( 22, 22 ).

2. The method according to claim 1, characterized in that the rollers ( 22, 22 ) during the deformation of the layer-like preform in the layer ( 23 ) are heated to a temperature with a predetermined thickness which is in the range from 90 ° C to 120 ° C . 3. A method for producing a polarizable electrode for an electrical double-layer capacitor, characterized by the following steps:

• - Preforming a kneaded substance from fine carbon powder, a fluorine-containing polymer resin and a liquid lubricant into a layer ( 21 ),
• Adjusting the proportion of liquid lubricant in the layered preform to 10 to 47% by weight,
• - Deforming this layer-like preform into a layer ( 23 ) with a predetermined thickness using rollers ( 22 , 22 ) and
• - Removing the liquid lubricant from the preform or layer ( 23 ).

4. The method according to claim 3, characterized in that in the step for deforming the preform for the purpose of setting a predetermined thickness with the help of the rollers ( 22 , 22 ) ge heated rollers are used. 5. The method according to claim 4, characterized in that the rollers are heated to a temperature that is in the range from 90 ° C to 120 ° C. 6. A process for producing a polarizable electrode for an electrical double-layer capacitor, characterized by the following steps:

• - Preforming a kneaded substance from fine carbon powder, a fluorine-containing polymer resin and egg nem liquid lubricant in a layer ( 21 ),
• - placing a plurality of the layer-like preforms in their respective end regions and connecting them into a continuous, long preform by rolling or rolling,
• - Removing the liquid lubricant from the long pre and
• - Deform this preform into a layer ( 23 ) with a predetermined thickness using heated rollers ( 22 , 22 ).

7. The method according to claim 6, characterized in that that in the step of deforming the preform into one layer of a predetermined thickness using heated rollers these rolls are heated to a temperature that is in the Range is from 90 ° C to 120 ° C. 8. A method for producing a polarizable electrode for an electrical double-layer capacitor, characterized by the following steps:

• - Preforming a kneaded substance from fine carbon powder, a fluorine-containing polymer resin and egg nem liquid lubricant in a layer ( 21 ),
• - placing a plurality of the layer-like preforms in their respective end regions and connecting them into a continuous, long preform by rolling or rolling,
• Adjusting the proportion of liquid lubricant in the long preform to 10 to 47% by weight,
• - Deforming this long preform into a layer ( 23 ) of a certain thickness with the help of rollers ( 22 , 22 ) and
• - Removing the liquid lubricant from the preform or layer ( 23 ).

9. The method according to claim 8, characterized in that in the step of deforming the long preform into the Layer with a predetermined thickness using the rollers this Rolls are heated. 10. The method according to claim 9, characterized in that the rollers to a temperature in the range between 90 ° C. and heated to 120 ° C. 11. A method for producing a polarizable electrode for an electrical double-layer capacitor, characterized by the following steps:

• - Preforming a kneaded substance from fine carbon powder, a fluorine-containing polymer resin and egg nem liquid lubricant in a layer ( 21 ),
• Adjusting the proportion of liquid lubricant in the layered preform to 20 to 47% by weight,
• - placing a plurality of the layer-like preforms in their respective end regions and connecting them to form a continuous, long preform by rolling or rolling,
• - Deforming this long preform into a layer ( 23 ) of a certain thickness with the help of rollers ( 22 , 22 ) and
• - Removing the liquid lubricant from the preform or layer ( 23 ).

12. The method according to claim 11, characterized in that in the step of deforming the long preform into the layer ( 23 ) of predetermined thickness with the help of the rollers ( 22 , 22 ) these rollers are heated. 13. The method according to claim 12, characterized in that the rollers ( 22 , 22 ) are heated to a temperature in the range from 90 ° C to 120 ° C.