DE1704979A1 - Process for the production of an electrical conductor insulated with plastic foam - Google Patents

Description

Dipl-Ing. RWeickmann, Dr. Ing. A ^ e'ickmAnn ^ Ϊ> ιΑΉν & .Ή. Weickmann Dipl.-Phys. Dr. K. Fincke Patent Attorneys 170aQ7Q

8 MUNICH 27, MÖHXSTR.ASSE 22, CALL NUMBER 483921/22

5715/1966
Dr.K / B

Sumitomo Electric Corporation, Osaka-Gity, Japan Method of making one with plastic foam

insulated electrical conductor -

The present invention "relates to a method and to one Device for the production of electrical conductors which are insulated by a foamed crystalline polymer, whereby a viscous solution of a crystalline polymer is drawn over the conductor, then the coated conductor for crystallization of the crystalline polymer is cooled from the drawn-up solution and off to evaporate the solvent the drawn-up solution is dried, then heated, so that closed cells in the coating. fresh melting of the crystalline polymer and the evaporation of the remaining solvent by the heating are formed. The procedures previously used for this purpose passed in that a polyolefin, such as polyethylene, was dissolved in an organic solvent, this solution on the

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Conductor was drawn up 'and the coated conductor was then cooled so that crystals of the polyolefin "were formed, and then, after drying until the weight of the solvent was about 50 percent of its original weight, by electric, to about 350 to 40CW to melt the polyolefin and at the same time to evaporate the residual solvent in the interstices between the crystallized polyolefin particles, closed cells being formed in the coating due to its pressure and the pressure of the air present in the interstices.

In research to improve electrical conductors and in efforts to produce finer closed ones Cells in the coating were found to be that previously used Method has the following disadvantages:

1.) In a system in which the solution of the polyolefin between the reserve tanks and the coating tank by means of a pump or pressure, as detailed below described, is circulated, a part of the crystalline polymer in the line of the circulation system always remains in solution and if the operation during a is continued for a long period of time, the remaining crystalline polymer can increase by oxidation Temperatures (100 - 135 ° C) decompose, resulting in pinholes

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Oäer damage to the coating leads. So that a ■ The quality of the coating will deteriorate. Except- that part of the solution is not removed when the inside of the circulatory system is cleaned and solidifies and the solidified polymer is found in the solution again during operation and results in pin-ocher and others Damage.

- i

2.) When the coated conductor is cooled and, after solution coating, dried so that 50 to 60? Ί of solvent remain in the coating and it is heated in this state, it was found that the remaining solvent does not evaporate uniformly in the coating of the coated conductor, so that eccentricity and voids in which coating and other defects in the electrical conductor are caused

In order to reduce the disadvantages listed above, According to the present invention, a device for pressing the solution and a measuring gear pump for adjusting the Outflow rate of the solution used when drawing up the solution, so that the total from the reservoir through the pressure increasing device EU-led solution can be drawn up over the conductor through the measuring gear pump, whereby the the first-mentioned disadvantage is reduced. It was also fixed etellt that the uniformity of the longitudinal direction in the

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Coated ladder hereby far superior to that one as it was obtained in the previous process represents that if spherical polyolefin particles are melted after the solvent in the coating is practical completely removed, it becomes possible for those present in the interstices around the spherical polyolefin particles To isolate gases, air and solvent vapor and thereby obtain a coating that has closed cells. When applied this method has been found to make it very easy to obtain a uniformly foamed conductor of high Produce quality and at the same time improve the production efficiency, since there is no evaporation of large amounts of solvent takes place. The manufacturing process and the device used are described in detail below.

According to Pig. 1 is the conductor fed from a peeling stand 1 is passed through the voltage regulator 2, through which the voltage of the conductor is precisely regulated. The ladder steps on it into the conductor preheater 3, hereinafter referred to simply as the Yoreheater.

Like from Pig. 2, the preheater is constructed so that the conductor goes through a pipe 31 which is kept warm and that heated air 32 in this tube 31 for heating the

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Conductor is blown in "

The advantage of the application of heated air is that defr heat transfer coefficient of air flowing is about ten times as large as that of stationary air, so that ■ ',' it is possible to reduce the heating temperature and Erhitzungs "period or, in other words, to reduce the heat capacity for heating and the length of the tube.

If, as in FIG. 3, an electric heater 33 is used inside the tube 31 to keep it warm, the conductor I is heated by the heat radiation from the wall of the electric heater 33 in addition to being heated by the hot air. ; heated, the hot air is not cooled in this Lall in the tube off I, so that the heating temperature and heating time can be further reduced. . j

The preheated conductor is then passed through the extrusion head 4, where a viscous solution of a crystalline polymer, such as polyethylene, polypropylene and the like over the preheated Head is raised. The following is the extrusion head 4 described in detail.

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Am crystalline polymer such as polyethylene, polypropylene and the like is heated and together with a solvent such as xylene, toluene and the like in a dissolving tank 41 stirred so that a solution results. This solution is fed from the dissolving tank 41 to a reservoir 42 and stored there. This solution is first conveyed to the measuring gear pump 44 by a pressure device 43. By the measuring gear pump, the solution is squeezed out to the extrusion head 4 at a constant flow rate and via the Ladder raised »

If the solution is very viscous and not very liquid, it cannot simply be fed to the measuring gear pump 44-. this represents the reason why the printer 4'3'applied to apply pressure to the solution as it is delivered to the metering gear pump 44. If the solution the measuring gear pump is completely supplied, the measuring gear pump Squeeze out a constant amount of the solution, which is independent of the number of revolutions of the gearbox is determined by the pressure applied to the solution. With regard to the printing device 43 used for this purpose it is sufficient that the pressure applied to the solution is sufficient to feed the solution to the measuring gear pump. Therefore no very great accuracy with regard to the pressure necessary.

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A rotating deck device!

for example a gear pump, a screw pump and the « same or a compressed gas can be used * As shown in Pig, 4, it is possible with a pressure device to effect the feeding of the viscous solution to some measuring gear pumps 44 through a common pipe. On the other hand is a measuring gear pump is necessary for each individual extrusion

head 4th m

A · feature of the present invention is that the Solution is not being circulated. The solution of a crystalline Polymer is only pressed in one direction when used, so that the total amount is within a certain Period is squeezed out. Therefore, no part of the solution is exposed to a high temperature for a long period of time and consequently there is the possibility of damage to a crystalline polymer in the present novel coating process very substantially reduced. Furthermore, the inside of the tube can be easily cleaned when in use is interrupted.

So far it has been constant practice that the solution in a cycle € H * £ was led. As a result, there were some parts of the solution, which exposed to high temperatures for long periods of time was. It becomes ζ · Β. assumed that half of the solution is in the Reservoir is squeezed out and the rest to the reservoir

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is returned. Then (i / 2) ^{n of} the initial volume remain uncompressed after η passes in this operation. Theoretically, such a part remains in the system indefinitely. In this case, at least a portion of this remaining part is damaged because it is exposed to a high temperature for a long period of time and it becomes at least a gel which, when pressed, is the cause of Hadelholes becomes.

A metering gear pump is used to perform a squeeze in one direction without recirculation applied to to avoid such bad parts and to stabilize the outflow speed when squeezing out. The head over which the solution has been drawn up, goes through a trough of warm water (5), which is effective in stopping the vibration of the coated * To prevent the conductor and to accelerate the cloudiness of the coating, then runs through a water removal inlet. direction 6, in which air is blown in, and

7th
enters a drying device / when hot air is blown onto the coated conductor. and also for the stabilization of the turbidity time, which is necessary for the appearance of the debris closure, is

The method of accelerating the haze phenomenon by means of a trough of warm water 5 and a drying » device 7, in which hot air is blown, stops The procedure already proposed represents "The procedure has further advantages in that it changes depending on the season". The time it takes for the coated conductor to be wound up by a first guide roller after coating is, brings to a minimum and that is thereby prevented that the unpleasant and harmful vapor of the solvent enters the work area. By blowing air onto the coated conductor in the drying device 7 in a controlled manner Set by controlled temperature and humidity, this is cooled and the solvent is removed from the coating in such Removed to the extent that the coating is not damaged and / or is deformed when the coated conductor passed around the reel 8 after the conductor has passed the reel 8, I occurs

it enters a collecting device 9 for removing the solvent · j * from the coating. A reel 8 is in front of the collecting device. ; device 9 provided for the purpose that the linear speed ■

■■■■■■ ■■ i

of the conductor running through the extrusion head 4 is constant

will hold "j

■■ '■ "■'" )

As already stated, the solution with constant Aus * becomes: Flow velocity squeezed out. An increment of the linear velocity the through the extrusion head 4 Lauföndett.Leitera j

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would therefore result in a change in the thickness of the coating «,

Balls the reel 8 after, the collecting device 9 is provided would be, the linear speed of the going through the extrusion head 4 conductor would be significantly by changing the Elongation of the conductor caused by the tension imparted to it in the collector itself if this tension in itself is only low, since the distance between the extrusion head and the reel would be very long> even if it could be kept constant

The collecting device 9 may be of the dancer roller type shown in FIG. 5, the length of the collected coated conductor being determined by the distance between the roller shafts 93 and 94 and the number of revolutions. The rollers 91 and 92 are rotatably mounted on the roller shafts 94 and 94 with ball bearings. The roller shafts 93 and 94 are arranged vertically. The lower roller shaft 94 is fixed, while the upper roller shaft 93 is movable up and down. To make the work of arranging the conductor around the pulleys easy, the upper pulley shaft 93 can be lowered closer to the lower shaft. If the device is in normal operation, the upper roller shaft is pulled by means of a torsion motor 95 in order to obtain the desired collection length of the coated conductor.

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The voltage applied to the conductor at this point will be determined by the rotation of the engine. It is therefore possible to give the conductor a desired tension by applying the voltage supplied to the motor is regulated. shaft 93 is movable. However, both the upper and lower shafts can be driven to reduce the tension or some of the rollers can be driven on one shaft or on both bells »

In the case of an electric wire insulated by a foam plastic, the conductor is usually of a small diameter between Q ₁ 32 and 0.4-mm * Br is therefore prone to breakage or stretching, so that it is necessary to prevent the tension from becoming firm Value exceeds »On the other hand, however, it is necessary that a voltage exceeding a certain fixed value is given to it during operation without interference and for other reasons. As a result, the range of allowable tension is narrow and a change in tension must be kept to a minimum. In the collector 9 the pods receive the turning force through the coated conductor and the greater the number of turns, the greater the tension the coated conductor receives _e. In this connection, the rotation of the roller shafts is an effective means of suppressing the increase in tension or increasing the tension

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reduce · The rollers are mounted on the roller shafts with ball bearings in between, the friction between them transmitting the rotating force from the shafts to the rollers. The appropriate number of revolutions of the shaft is equal to, or vice around $ 10> greater than the number of revolutions of the rollers corresponding to the linear speed of the conductor ,, However, even when the number of revolutions is smaller than the number of revolutions of the rollers these are effective in reducing the increase in tension.

According to test results, if the number of revolutions of the shafts is made 10 # larger than that of the rollers, a tension of 500 g at the inlet of the collector is reduced to a tension of 450 g at the outlet of the device, i.e. there is a voltage drop of 50 g.

In the illustration of FIG. 5, only the lower roller shaft is shown shown as rotatable. However, it is possible to rotate both the upper and lower roller shafts.

The ■ required collection period, i.e. the collection length, is further abbreviated when in the collecting device 9 warm air with a temperature above room temperature, for example 50 to 80 ^ C to accelerate evaporation of the solvent remaining in the coating is blown.

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The speed of the reel 8, which is in front of the collecting device is, and that of the receiving device 13 as last stage must be synchronized. However, it is very difficult to fully synchronize the recording speedi% these facilities because of inaccuracies in the manufacture of the shafts., and for other reasons to reach. Even if the difference in the recording speeds of the two devices is very small, this slight difference gradually accumulates and becomes great during operation for a long period of time. Because of this, they are immediately in front of the receiving device 13 traveling rollers are provided so that the difference in take-up speeds between the reel 8 and the take-up device 13 is reduced. However, it is possible to adjust the recording speeds of the two recording devices without using such traveling rollers by determining the Position of the movable roller shaft of the collecting device 9 to regulate and thus reduce the cost of the equipment.

It is preferred to place the traveling rollers directly in front of the receiving device 13, since this makes it possible to reduce the linear velocity of the through the foaming device running overdone to make Deiters constant. However, since the range of heating time required for foaming has a relatively large width, it is completely permissible to reduce the recording speed of the recording device 13 by Use of the upper movable rollers of the collecting device 9 to regulate as traveling rollers »

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With regard to this collecting device 9, the working ability is obtained at the time when the conductor is passed around the rollers is greatly improved if the roller shaft is made cantilevered, as in Pig. 6 shown.

The collecting device 9, which has been scanned above, is of vertical arrangement with the roller shafts mounted vertically. A collecting device from the horizontal Type is also possible.

It is also possible to use the drying device listed above 7 and the collecting device 9 as shown in Fig. 7. This is particularly advantageous when doing this a horizontal type collecting and drying device is used for handling a ladder.

The coated conductor, its solvent in its coating was removed while it was in the collection device, enters the foaming device. As such A foaming device can be a known electric oven can be used, but it is beneficial to use a liquid

trough
schäumungsäawwdi: 10, for example with glycerine, to be used * which is far superior to an electric oven in terms of heating efficiency and temperature control.

* rog The overdone leader who dlch this ShäiimungsiteEait 10

has been carried out, is rinsed and cooled in the RLn--

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guideline 11, in which he was first treated with warm water of 4 (K! or rinsed over it in one or more stages and then in one stage with cold water at room temperature or lower or is rinsed and cooled in several stages.

This step serves the GrIyceridln or other heating fluids, which adhere to the surface of the foamed insulated conductor, rinse, Ealls hot water is used, m is hereby greatly reduces the length of Spültroges because it has a much greater washing effectiveness than cold water .

The rinsed and cooled foamed insulated conductor is received by the receiving device 13 after it, if necessary has gone through instruments 12 to the; measure electrical properties of the conductor.

. ' WHEEL OR1G1N ^AL

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Claims (1)

Claims 1.) / Method of producing a with foamed plastic insulated-electrical! conductor by pulling up a viscous Solution of a crystalline polymer over a conductor, [drying the thereby obtained coated conductor and then Heating of the coated conductor to foam its coating, characterized in that the solution is pressurized in a container, the required amount thereof to an extrusion head by means of a metering gear pump conveyed and the solution is drawn up over the conductor in the extrusion head. 2.) Device for the production of electrical conductors insulated with foamed plastic, characterized by a device (43) j in which the viscous solution of a crystalline polymer stored in a container (42) is pressurized, a metering gear pump (44) _; which supplies the required amount of the pressurized solution to the extrusion head (4), an extrusion head (4) in which the solution is drawn up over the conductor introduced there, a drying device (7) in which the coated conductor is dried, and means (10) for foaming the coating of the coated conductor. ³⁶² BATHROOM ORIGINAL 5.) Device for the production of electrical conductors insulated with foamed plastic, characterized by a device (43) for pressurizing a viscous solution of a crystalline polymer stored in a container (42), a measuring gear pump (44) for! , ■ required amount of this solution in an extrusion head (4) and for drawing up this solution over the conductor, a device (5) for cooling the be * with the drawn up solution. (7) covered ladder with warm water, a facility / for Drying of the cooled coated conductor by hot ■ * ■ - ■ ' air flow, a collecting device (9) for practically complete Removal of the solvent from the coating of the coated conductor, one between the drying device (8) (7) and the collecting device (9) lying reel / and a Foaming device (10) for foaming the Coating the coated conductor by heating. 209811/1362