EP0002224B1 - Process for manufacturing insulated binding wires by extrusion of thermoplasts and thermoplasts for carrying out this process - Google Patents

Description

The present invention relates to a method for producing insulated winding wires by extrusion of partially crystalline thermoplastic polycondensates and thermoplastics which are particularly suitable for carrying out the method.

Enamel-insulated winding wires, so-called "enamelled wires", are precisely characterized in the German standard DIN 46435 from April 1977. They are used on a large scale in electrical engineering, transformer construction and electronics.

The conductor metal, preferably copper or aluminum, is insulated with a thin, but mechanically and thermally extremely resistant synthetic resin lacquer layer.

Such enamelled wires are produced on wire enamelling machines by repeatedly applying an enamelled wire, i.e. in principle, the solution of an organic synthetic resin in a solvent, on the metal wire.

In order to achieve a smooth, bubble-free and solvent-free lacquer film, the number of lacquer coats must be increased as much as possible and the layer thickness of the individual coats kept thin.

In general, 6-10 individual orders are placed, the required layer thicknesses are very dependent on the diameter. For simple (1 L) insulated copper round wires with a diameter of 1 mm, an insulation layer of 15-34 _{fL is} provided according to DIN 46435, for example.

The baking process that follows each coat of paint causes the solvents to evaporate and the paint film to harden. The solvent vapors are removed from the baking chamber by a fan. The baking temperature for this process is between 300 and 550 ° C and depends on the lacquer base, the wire diameter, the chamber length and the take-off speed.

Paint solutions according to the prior art contain solids contents in the range from approx. 20 to approx. 40%, i.e. the proportion of solvents to be evaporated is 60-80%. When the solids content is increased, processing solutions are disadvantageous because the coating solutions are too viscous.

Because of their great solvent power, their high boiling range, which promotes the flow and not least because of their value for money, the isomeric cresol and xylenol mixtures obtained from tar or lignite tar mixed with aromatic hydrocarbons are used as solvents for the common wire enamels, with some special wire enamels also N -Methylpyrolidon and Dimethylformamid used.

The state of Tecknik outlined above in the manufacture of enamelled insulated winding wires must obviously be described as unsatisfactory.

The application of a large number of very thin individual orders requires a high level of technical effort and must have a negative impact on the economy of the process.

The complete removal of the solvents from the reaction space, which is absolutely necessary to achieve optimal enamelled wire properties, is only possible with high energy consumption.

The hardening process running parallel to this - with most wire enamels a crosslinking taking place with elimination of volatile condensation products - also requires large amounts of energy due to the need to achieve economically acceptable take-off speeds.

Despite this considerable effort, the take-off speeds which can be achieved on conventional machines - for example with 1 mm copper wires 25 m / min. - are comparatively low.

• Maximale Arbeitsplatzkonzentration (MAK-Wert) 1t. deutsch. Kommission zur Prüfung gesundheitsschädlicher Arbeitsstoffe, 1977: 5 ppm bzw. 22 mg/m³.

The following data for the preferred cresols and xylenols:

• Maximum workplace concentration (MAK value) 1t. German. Commission for the Testing of Harmful Working Materials, 1977: 5 ppm or 22 mg / m ³ .

German Ordinance on Hazardous Working Materials from 8.9.1975: Class I b, i.e. toxic and can be identified with a skull, even when mixed with other solvents, down to a cresol or xylenol content of 1%.

Technical instructions for keeping the air clean (TA-Luft) from 28.8.74: Class I, ie the max. allowed emission of cresols or xylenols is only 20 mg / m ³ exhaust air.

To comply with official regulations, i.e. To avoid health risks, complex safety precautions are necessary.

In the enamelled wire machines corresponding to the conventional art, the solvent vapors are removed from the baking chamber by a fan, as mentioned. The installation of combustion catalytic converters, through which a large part of the solvent vapors arising from the stoving chamber is destroyed, leads to a considerable financial burden and thus to an increase in the price of the end product.

In order to overcome the difficulties resulting from the use of solvents, the proposal has already been made to use aqueous systems.

Both the use of Drahtlach dispersions (DE-A-2351078) and that of in Water-soluble wire enamel resin materials (DE-A-1720321 and DE-A-2605790), however, involve the problem of extremely energy-intensive evaporation of large amounts of water, the complete removal of which is absolutely necessary in order to obtain functional enameled wire insulation.

In addition, the environmental problems outlined above are compounded by the known need, in aqueous systems, to modify them with varying amounts of organic auxiliaries, such as high-boiling solvents which act as leveling agents, dispersing agents and, if appropriate, thickening agents and, above all, at most are mitigated by organic amines which impart solubility in water.

Also known is a process for the insulation of electrical conductors with resin melts, especially curable polyesterimides (DE-A-2135157 and DE-A-2401027).

The processing of melts of such reactive resins at the temperatures under discussion is problematic with regard to their shelf life.

The removal speeds that can be achieved by this process are also in no way higher, preferably even considerably lower than that of conventional lacquers.

It has been the applicant has already proposed a process for the production of so-called enamel-insulated winding wires by extrusion of thermoplastics, which is characterized by the use of partially crystalline thermoplastic polycondensates with crystallite melting points above 170 ° C., preferably above 250 ° C. (see, for example, DE-A- 26 38 763).

• 1. Da die nach diesem Verfahren zur Anwendung kommenden teilkristallinen Thermoplasten keinerlei Lösemittel oder sonstige toxische Substanzen enthalten, entfallen die aufwendigen Verbrennungsvorrichtungen und sonstigen zur Vermeidung von Gesundheitsgefährung erforderlichen Maßnahmen.
  Dieses Verfahren ist also eindeutig unweltfreundlicher als die bisher angewendeten Verfahren. Die infolge des Wegfalls von Lösemittelverdampfung ein tretende Energieeinsparung trägt außerdem entscheidend zur Verbesserung der Wirtschaftlichkeit des Verfahrens bei.
• 2. Die laut DIN 46435 vorgesehene Isolierschicht kann in einem Arbeitsgang aufgebracht werden. Vorteilhafterweise gilt dies auch für doppelt (2 L)-isolierte Drähte, bei denen nach DIN 46435 für Kupferrunddrähte von 1 mm Durchmesser beispielsweise eine Isolierschicht von 3O­47 µ vorgesehen ist.
  Das Verfahren ist also diesbezüglich gegenüber den bisher angewandten Verfahren (6-10 Durchzuge) eindeutig bevorzugt.
• 3. Da verfahrensgemäß Thermoplaste zum Einsatz kommen, entfällt die bei den bisher angewandten Verfahren notwendige Härtungsreaktion, was wiederum eine beträchtliche Energieeinsparung zur Folge hat.
• 4. Als Konsequenz aus allen vorgenannten Punkten ergibt sich eine eindeutige und entscheidende Erhöhung der Abzugsgeschwindigkeit und damit der Wirtschaftlichkeit bei der Beschichtung von Leiterdrähten.
  Bei 1 mm Kupferrunddrähten sind beispielsweise Geschwindigkeiten bis zu 500 m/min durchaus praktikabel, gegenüber dem herkömmlichen Verfahren läßt sich also die Geschwindigkeit problemlos um den Faktor 20 erhöhen.

This method makes a decisive contribution to overcoming the disadvantages which clearly burden the known prior art:

• 1. Since the semi-crystalline thermoplastics used in accordance with this process contain no solvents or other toxic substances, the elaborate combustion devices and other measures necessary to avoid health risks are eliminated.
  This process is therefore clearly more environmentally friendly than the processes previously used. The energy saving that occurs as a result of the elimination of solvent evaporation also makes a decisive contribution to improving the economy of the process.
• 2. The insulating layer provided in accordance with DIN 46435 can be applied in one operation. This advantageously also applies to double (2 L) insulated wires, in which, according to DIN 46435, for example, an insulating layer of 3047 μ is provided for round copper wires of 1 mm diameter.
  In this regard, the method is clearly preferred over the previously used methods (6-10 swipes).
• 3. Since thermoplastics are used in accordance with the method, the hardening reaction required in the previously used methods is eliminated, which in turn results in considerable energy savings.
• 4. As a consequence of all of the above, there is a clear and decisive increase in the take-off speed and thus the economy in the coating of conductor wires.
  With 1 mm round copper wires, for example, speeds of up to 500 m / min are quite practicable, so the speed can easily be increased by a factor of 20 compared to the conventional method.

Before filing the above-mentioned DE-A-26 38 763, the use of aliphatic and araliphatic polyamides as insulation material for electrical conductors was known, namely coating from solution, from the melt or with films or tapes of such polyamides. However, coatings made from the polyamides mentioned have also been sprayed and shrunk onto the electrical conductor in the form of tubes, the layer thickness being regulated exclusively by the rate of removal (see US Pat. Nos. 2,348,536 and 2,308,638) ).

In the examples of the abovementioned application, the extrusion conditions for polyethylene terephthalate, 6,6-polyamide and polyphenylene sulfide and the properties of the corresponding winding wires are described.

• Terephthalsäure und Hexamethylendiamin (1, 6),
• Terephthalsäure und Äthylendiamin,
• Terephthalsäure und Nonamethyleridiamin (1, 9),
• Terephthalsäure und Decamethylendiamin (1, 10),
• Adipinsäure und p-Phenylendiamin.

In addition, the text also refers to the basic suitability of araliphatic polyamides from aromatic dicarboxylic acids or their functional derivatives and unbranched aliphatic diprimeric diamines or corresponding aliphatic dicarboxylic acids and aromatic diamines, for example to polyamides

• Terephthalic acid and hexamethylenediamine (1, 6),
• Terephthalic acid and ethylenediamine,
• Terephthalic acid and nonamethyleridiamine (1, 9),
• Terephthalic acid and decamethylenediamine (1, 10),
• Adipic acid and p-phenylenediamine.

Such polyamides have the high melting points desired for the intended application, but the range between the melting point and the decomposition point is too narrow. In most cases, decomposition takes place even during the melting process, ie the polymers mentioned cannot be melted without decomposition. It is obvious that in such cases a Processing by "thermal forming" impossible or the processing latitude is too tight.

It is already proposed in the abovementioned application to loosen the crystalline structure in the case of very high-melting thermoplastics and thus to lower the melting point by cocondensation with monomers of a different structure.

For example, in the case of very high-melting or non-decomposing araliphatic polyamides, part of the unbranched aliphatic diprimeric diamines can be replaced by linear aliphatic diamines with side groups, e.g. part of the hexamethylenediamine (1.6) is replaced by trimethylhexamethylenediamine, or part of the aromatic is replaced by aliphatic dicarboxylic acids.

The present invention was based on the requirement to develop special polycondensates for the extrusion process with which the disadvantages described above can be avoided.

It was found, and this was not suggested by the prior art, nor was it foreseen in any way, that the process for producing insulated winding wires by extrusion of partially crystalline thermoplastic polycondensates leads to particularly favorable results when araliphatic polyamides with crystalline melting points of at least 280 ° and viscosity numbers of at least 0.5 from terephthalic acid or its functional derivatives capable of amide formation, hexamethylenediamine and isophoronediamine in a molar ratio of dicarboxylic acid to total diamine of 1: 1 to 1: 1.1 with isophoronediamine contents of at least 5 mol%, based on the total mol of diamine, are used .

• t₇ = Auslaufzeit der Polymerlösung in sec.
• _1]0 = Auslaufzeit des Lösemittels in sec.
• c = Konzentration der Polymerlösung in g/100 ml

The viscosity number (also known under the expression reduced viscosity, referred to in the Anglo-Saxon literature as "viscosity number" or "reduced specific viscosity") is defined by the following relationship:

• t ₇ = run-out time of the polymer solution in sec.
• _{1] 0} = solvent drain time in sec.
• c = concentration of the polymer solution in g / 100 ml

The synthesis of such polyamides, to which no protection claim is made, is based on generally known technologies for the production of polyamides.

In order to obtain higher molecular weight products, it is necessary to maintain a dicarboxylic acid: diamine molar ratio of 1: 1 as precisely as possible. To produce the polyamides used according to the invention, 100 moles of diamine, i.e. 100 moles of terephthalic acid. the sum of hexamethylenediamine and isophoronediamine-required.

In principle, any molar ratio of hexamethylene diamine to isophorone diamine is possible. However, since the melting point decreases with increasing isophoronediamine content - (the pure polyamide made of terephthalic acid and isophoronediamine has a melting point of 270-280 ° C) - a limitation of the isophoronediamine content is required for winding wires for which high softening temperatures (according to DIN 46453) are required values that are as low as possible, but still guarantee a flawless processing range, are advisable. For example, enamelled wires made from the polyamide described in Example 1 with 12 mol% isophoronediamine, based on the total amount of diamine, with a melting point of 340-350 ° C. have softening temperatures (according to DIN 46453, also called "thermal pressure") from 265-275 ° C, a value which, according to DIN 46416, part 4, justifies an assignment to type W 155 (temperature index 155). Such a product can still be processed well on the extruder, since noticeable decomposition only begins at 385 ° C.

However, if the isophoronediamine content is increased to 20 mol% based on the total amount of diamine, the melting point of the polyamide already drops to 310-320 ° C. Such a polyamide can also be used with advantage, but the enamelled wires produced with it have a lower temperature index.

The question of limiting the isophoronediamine content cannot therefore be answered in general. The isophorone diamine content should only be limited to a max. 15 mol% remain limited.

A polyamide made with 8 mol% isophoronediamine has a melting point of 365-370 ° C. Noticeable decomposition begins at 380 ° C, so the product can still be processed. As the isophoronediamine content continues to decrease, the range between the melting point and the decomposition point becomes narrower and the difficulties become greater.

In order to keep the degree of decomposition as low as possible during the melting process, a short residence time of the resin melt in the extruder is required. However, polyamides with isophoronediamine contents of less than 5 mol% - based on the total amount of diamine - can no longer be processed sensibly even when all technological possibilities have been exhausted.

It should also be mentioned that there are currently no special test regulations for the new winding wires insulated in the extrusion process. The test is therefore carried out in accordance with DIN 46453 for paint-insulated Winding wires, especially since the winding wires insulated in the extrusion process are used for the same areas of application as the former.

example

A fine-grained polyamide composed of terephthalic acid, hexamethylene diamine (1) and isophoronediamine (2) in a molar ratio of (1) to (2) of 88:12 and in a molar ratio of terephthalic acid to total diamine of 1: 1, with a reduced viscosity (η _red ) of 0. 8 and a melting range of 340-350 ° C. was introduced into the filler neck of an extruder described in detail in DT-OS 2728883.

The extruder temperatures from the inlet to the die were 290 ° C / 310 ° C / 325 ° C / 350 ° C / 360 ° C.

These temperatures affect the various heating zones in the extruder screw with graduated heating output. This slowly brings the thermoplastic material to the final temperature.

Soft-annealed copper wire with a diameter of 0.6 mm was used, which first passed through a preheating section and, after passing through the coating zone in the extruder head, through a wiper nozzle that regulates the layer thickness.

After passing through a cooling section, the coated wire was wound up, the take-off speed was 210 m / min.

The total layer thickness applied was 60 µ and thus corresponded to grade ^- 2 according to DIN 46435 from April 1977.

. Properties of the winding wire

Unless otherwise noted, all values according to DIN 46453, Part 1, from April 1977.

Claims (2)

1. A process for the preparation of insulated electric wires through the extrusion of partially crystalline thermoplastic polycondensates, involving the use of araliphatic polyamides with melting points of at least 280°C and viscosity numbers of at least 0,5, consisting of terephthalic acid or a functional derivative thereof, hexamethylenediamine and isophoronediamine, wherein said acid component and said amine component are in a ratio of 1:1 to 1:1,1, and said isophoronediamine comprises at least 5 mol% of the total amine component.

2. Partially crystalline thermoplastic araliphatic polyamides used for the process of claim 1 comprising terephthalic acid or a functional derivative thereof, hexamethylenediamine and isophoronediamine, wherein said acid component and said amine component are in a ratio of 1:1 to 1:1,1, and said isophoronediamine comprises at least 5 mol% of the total amine component, said polyamides having melting points of at least 280°C and viscosity numbers of at least 0,5.