DE2409178A1 - PROCESS FOR MANUFACTURING TUBES FROM POLYTETRAFLUORAETHYLENE OF VERY LOW PERMEABILITY AND TUBES MANUFACTURED BY THIS PROCESS - Google Patents

Description

2409173

Steiger Engineering AG, Mainaustrasse 8, 0H-8QQ8 Zurich

Method, son for manufacturing tubes made of ethylene Polytetrafluorine- very small permeability and tubes produced by this method.

The present invention relates to a new process for the production of polytetrafluoroethylene (P ¹ J) FE) pipes of great mechanical strength, low permeability and good physical properties under changing conditions of use and at their ends . connecting edges or connecting flanges can be easily produced by deforming

There are connecting edges in F _o rm known of flanges which have the shape of an annular disc, which are connected to the outer periphery of the pipe end, ■ wherein, in this way a continuous connection of tubes of P ¹ JIE ¹ E into the interior of metal pipes is achieved whose approaches are connected to each other by bolts, flanges or similar fasteners »

The present invention also relates to pipes produced by such a method _o one knows that the PTFE is a synthetic material which is produced in the form of a white powder · To objects made of PTFE to obtain, it is first necessary that To agglomerate powder under pressure. After such a blank has been produced, the powder agglomerated in this way must then be added. a so-called "sintering temperature" are baked, which in practice is generally above 350 ° G. In the course of this thermal treatment, which is referred to as a baking or sintering process, the PTFE material goes through a gel formation process and after subsequent cooling one receives one

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Object which essentially has the shape of the blank obtained by pressing, _o

A method for digging pipes is already known made of PTFE, with the aid of the method described above, a cylindrical block made of PTFE after the baking and The cooling process is rolled out so that a PTFE tape is obtained by mechanical means, which is in the sintered or baked State and has a relatively high rigidityTo produce a tube, the tape is wound on a mandrel, with the turns of the ribbon overlapping ", Man. then carries out heating to a temperature which is higher than the gel-forming temperature, whereby a pressing pressure is applied exerts on the spiral tape, so that a weld takes place in the overlap zones «This method only achieves Unsatisfactory results, because it has been found in practice that the pipes obtained in this way have too great a permeability have, and that the Yerschweißung between the various turns is not sufficiently tight and resistant is·

It is also known to manufacture pipes from PTFE by a process called the "granulate extrusion process". Powder, which is pressed under compression through the nozzle by means of a piston that performs a reciprocating movement.In the zone behind the compression zone, the PTFE powder is heated by means of a heating device to a temperature above the gel is forming temperature. Beyond this heating zone is a zone where the PTFE is cooled after it has passed through the Gelbildungsvorgang, so as to obtain at the outlet of the nozzle a PTFS tube in ^tt-baked "condition, wherein the tube discontinuous in a Movement is promoted from the nozzle,

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what results from the function of the reciprocating piston ', which causes compression of the PTFE powder at the inlet of the nozzle ·

This method results in pipes with a substantially greater permeability than that according to the one described below Invention to be produced · Also allows extrusion the granulate does not allow the production of very large diameter pipes with small wall thicknesses »

The known state of the art also includes a process which is referred to as the "paste extrusion process" To carry out this procedure, the FTFE powder is mixed in with it a lubricant to produce a compact preform which is drawn in a drawing press, in order to obtain a tubular preform which is then placed on the ■ Gel temperature is brought to enable baking or sintering of the PTFE tube ·

This process results in pipes whose permeability is still quite good is pronounced · In addition, it is difficult to attach connecting flanges to these pipes that have a sufficient Quality · It should be noted that in fact the connecting flanges, which are at the ends of the pipes are attached in a conventional manner, tend to form radial cracks in operation, which a replacement of the Make pipe required

It is known that connecting flanges are attached to the ends of pipes made of plastic material in such a way that a conical shape is formed at the end of the pipe in the direction of the pipe axis. 'Is pressed, which has been heated to a temperature sufficient to make the wall areas at the end of the tube funnel-shaped pushing back · By possibly using several formsu of successively increasing conicity works and

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Finally, works with a flat shape in the form of a flat plate with a mandrel engaging into the interior of the tube, for the final shaping of the flange, the result of the described hot deformation process of the plastic material is a flange that has the shape of an annular disc that is perpendicular to the tube axis extending the tube end surrounds · This V _e rfahi? s is likewise in the manufacture of connecting flanges with PTFE tubes application, which are prepared according to the methods described above.

It has also been proposed to use hollow bodies or coatings Manufacture in P'DFE by placing on a mandrel, or other to. A tape made of raw PTFE is wound around the covering bodies which was produced, for example, by extrusion and calendering, with the edges of the various turns of the wound tape overlap · After heating, the edges of the windings are welded, causing the The continuity of the PTFE coating is ensured

The present invention is based on the surprising finding that if you have a tube made of raw PTFE through. Rolling up a tape around a cylindrical core and then subjecting it to the gel formation temperature, exceptionally good properties of the pipe can be achieved, in particular a very low permeability and the possibility of producing particularly good quality end flanges. The values of the pipe are very good if the pipe is produced by winding a considerable number of turns on top of each other, whereby the tape should have a small thickness dimension in such a case and is produced by the so-called ^tt paste * · extrusion process "with subsequent calendering ·

It has been found 'that the properties of the manufactured Pipes are very different depending on where you put the pipe

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-produced by means of a tape, the thickness of which corresponds essentially to the thickness of the pipe itself, or whether you have a small number, ζ "Β. or whether one according to the invention produces a tape mis raw PTFE of very small thickness and the pipe through Aufwickeöh a large number of layers (for example, several times a ten layer) forms two or three winding layers, a very thin band. In the latter case, the PTFE pipes obtained are of very high quality in terms of low permeability, mechanical properties and the possibility of forming flanges which are of the same good quality as the pipe.

In particular, flange attachments can be attached to pipes produced by known methods, which can also withstand stresses characterized by the absence of similar cracks

In this way, even with strongly changing conditions, one obtains Turning conditions have excellent mechanical values, which is particularly advantageous when passing through the pipeline a pressurized liquid is passed through, which is alternately hot and cold, or once in Elüssx— gem or in a vaporous state. The same applies to changes in the pressure within the pipeline. The present Invention has a new process for the production of PTFE tubes as an object, to which at least one.End a flange can be pressed on by deformation, whereby one a tape made of raw PTFE is wound on a mandrel. The inventive The method is characterized in that about 10 to 100 layers of a PTFE tape, which is produced by calendering and has a thickness of round, is wound on the mandrel 5 to 20 hundredths of a mm, so that the PTFE tape rolled up in this way is heated on the mandrel to a temperature, those above the gel temperature, but below about 380 ° to 400 ° G, this temperature being maintained over a period of time which is sufficient to cause the gel formation of the PTFE

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cause, and that one then cools the tube and the mandrel and that finally the mandrel is withdrawn from the inside of the tube

In order to provide an extension at at least one end of the pipe produced in this way (after the PfES pipe has been inserted into the interior of a metal pipe to protect it), the wall of the pipe is widened at this end by means of several upsetting tools which have previously been brought to a temperature of approx
to shape.

approximately 250 to 350 ° G were heated in order to attach the flange

According to a feature of the invention, the ΡΤϊΈ-band by means of of the "paste extrusion process", to which a considerable amount of rolling follows during the calendering » This technique starts with a mixture of one fine freshly made PTFE powder from which approx Contains $ 20 lubricant and compresses this mixture to to obtain a preform, which is passed through an Elach nozzle Extrusion press is pushed out to get a flat band.

Such a PTS ¹ E tape has a density between 1.7 and 18 after extrusion.

The band is then calendered between two calender rolls by., whereby an elongation of the tape around five to twenty times the original length without any significant change the bandwidth is carried out »

The lubricant is then removed using a hot solvent, ζ .B ₀ ! Erichliräthylen; the calendered and degreased PTFE tape has a density of 1.5 to 1.8, preferably 1.65.

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According to the invention, one preferably starts from an extruded tape which has a thickness of 0.57 to 1.7 mm and that after. Completion of the calendering has a Dxcke 5-20 hundredth of a mm _o The best results are obtained when calendered to the mandrel wound tapes whose thickness mm are 5-10 hundredths _o

The number of coiled layers depends on the desired thickness of the PTFE tube. In any case, the number of Layers greater than 10 and preferably a multiple of 10, eg "Bo 30 or 40," can also be used, if desired the number of layers can be greater without damaging the properties of the pipe in any way

The winding up of the windings on the cathedral takes place in such a way that the The axis of the tape forms an angle between ° and 90 ° with the pipe axis · The successive layers of windings become preferably wound in the opposite direction of rotation, so that the inclinations of the successive turns with respect to are opposite to the pipe axis.

The winding of the PTFE tape can be done in such a way that the individual turns overlap more or less or in such a way that the individual turns abut with their edges, but it is also possible to use the turns with free spacings ζτλ. · wrap The fact that the turns overlap ^ are separated from each other with their edges lie gene or from each other, the belt is very dependent on the width of a hand, and the winding operation on the other hand from _o

You can also wind several turns at the same time by unrolling several adjacent strips at the same time It is also possible to make a pipe by the different layers are wrapped at different angles of inclination to the pipe axis, so that the angles of inclination are

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successive layers are different o

Taking into account the T _a tsache that the PTFE tape of very small thickness and the number of layers is large, is obtained after sintering or baking a homogeneous mass _o

In a preferred embodiment of the invention, it is possible to manufacture tubes whose wall, in particular the inner wall, is antistatic (antistatic) by winding a first inner wall-forming layer onto the mandrel by means of a PTFE tape in which an antistatic material is wound , _o for example graphite, is incorporated in the form of a powder feindispergier- th · the graphite content may preferably be between 2 and $ 25 "the winding of the upper layers is then followed by a band having no graphite intercalation _o

Instead of forming an inner layer by means of a graphite-containing one FfFE tape, it is also possible for one execution rungsVariante to form the first layer in that several strips are wound helically, their turns run alternately, with one of the alternating tapes made of PTFE with embedded graphite for the purpose of forming the inner surface of the pipe and the connecting flanges, while the andece tape has no antistatic properties

According to another preferred embodiment of the invention, one can form a heat pipe by one or more electrical conductors ₉ z _o B _o chrome-nickel wires, intercalates into the interior of the multilayer coil whose electrical resistance allows the heating of the tube "The Iigitsrär -seam, which is embedded in the turns, can either be wound helically onto an intermediate layer of the pipe (after which it is then covered by the subsequently wound layer) or the arrangement of the wires in long! = -

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in the tudinal direction along the generatrix of the cylinder surface, which is defined by the respective intermediate winding layer is.

According to another W _e of the invention, which is intended iterbildung to increase the mechanical properties of the pipe within wide limits in order to achieve a high resistance to compression or rupture of the pipe in particular, is an intermediate layer of the belt, a metallic wire of high . Modulus of elasticity, for example a steel spring wire, wound up, the helical winding being carried out in such a way that a free space remains between the turns of the wire, so that the subsequent winding layer adheres to the intermediate layer on which the wire is wound during the baking process, so is that the D AHT _r a certain extent embedded between two layers.

In a variant of this embodiment, instead of winding the wire, a number of circular wire rings can be drawn next to one another on an intermediate layer straight lines running along the generatrix of a cylinder with a high modulus of elasticity can be combined designed to replace or a film of a cylindrically rolled metal strip to be used, which _w in the Z is slid isehenschicht before it is covered by the following winding layer.

According to another development of the invention, it is possible, in particular, if the mechanical properties are essential

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should be improved, especially if the ϊ / resistance to compression or collapse under vacuum conditions need to be especially increased to wrap an outer layer of one or more PTFE tapes that have a certain amount of Number of substantially annular ribs forming one below the other run at a certain distance, each rib being covered by an overlay of layers of the rolled up tape is formed o

A first embodiment of such annular ribs, which is formed by rolling up the tape, can thereby be achieved be that several turns are often enough wound on the same place on top of each other, while the adjacent Rib is wound up in the same way by means of another tape o In another embodiment of the method the rib can run along a helical line or along several alternating helical lines, each bond consists of a superposition of helically wound tapes, which are always wound along the same helix.

One can advantageously, if so desired, the gap fill in between the ribs using a plastic filler material and optionally the cylindrical body thus obtained by winding one or more layers of a PTFE- Cover the tape to obtain an outer wall made of a continuous coating of PTFE. The baking of the cylindrical tubular body, who supports the ribs, anchors them in the most perfect way with the various layers that connect the tube, so that a pipe with great resistance to compressive forces is obtained. Such a pipe can be as it is or in a metallic pipe can be used »

According to a preferred embodiment. of the invention is the cooling of the pipe after sintering in the range from 380 _e B

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up to 400 ° G up to around 280 ° G at a speed of 10 ° to 100 ° G per hour, preferably at 20 ° 0 per hour instead of. The cooling below 250 ° 0 can then with great- be carried out at a higher speed.

The formation of a flange at the end of the PTFE tube according to the invention takes place in such a way that two recoil shapes are used, the first of which has a conicity of 60 ° and the second has the shape of a plate. These two molds are previously heated to a temperature between 250 ° and 35 °° G. Each of these shapes preferably has a cylindrical mandrel in its axis, which engages into the interior of the tube and prevents the walls of the tube from being weakened when the flange is upset _{or the like}

The present invention also relates to a PTFE tube produced by the method according to the invention, which has a particularly low permeability and at the same time has greater mechanical strength under changing operating conditions and is possibly provided with a connection flange at at least one of its ends Permeability and resistance to cracking under stresses have values similar to those of the pipe itself, _etc.

For a better V _e of the invention rständnis is this in the following several embodiments basis described in the nachstehenrden figures ·

Fig. 1 schematically illustrates the different phases of the method of manufacturing the PTFE tape according to the invention?

Fig. 2 shows schematically the winding of the tape a tubular mandrel, with side by side- » other turns overlap · »

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Fig. 3 shows a winding process on a tubular A mandrel in which the successive coils collide with their edges

• Fig. 4 illustrates schematically the winding of a tape on a cylindrical mandrel, in which the adjacent Windings run at a distance from each other ;

Fig. 5> 6 and 7 illustrate schematically axial section on an enlarged scale sections of the winding layers, as achieved in accordance with the methods explained in Figs _o 2, 3 and 4 x;

. 8 and 9 show schematically the formation of end flanges on the pipes according to the invention

10 and 11 show two exemplary embodiments of pipe reinforcements for increasing the resistance Negative pressure,,

In Fig. 1, the various production phases of the PTFE raw tape according to the invention are shown. The preform 1 made by eating a mixture of fine PTFE powder and is obtained with a lubricant, is introduced into the chamber of an extruder 2, where a piston 3 the PTFE pushes through a slotted nozzle, resulting in formation of a flat band 4- leads.

The strip 4 is then rolled out between the two cylinders 5 and 6 in order to obtain a strip 7 of smaller thickness. The rolling or calendering takes place practically without changing the width of the strip, while the elongation of the strip is five to twenty times the initial length before the calendering process, _{or the like}

The belt 7 is then introduced into a container 8, the Z ₀ B ₀ is filled with trichlorethylene to the lubricant to be sawn

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side, which is used for extrusion and calendering In this way, the strip 9 is obtained, which is then further processed in the manner according to the invention

Fig. 2 illustrates how the winding of the tape 9 on a cylindrical mandrel under overlap of the adjacent. Windings can be carried out _o In the present case, one notices that the windings overlap by about half their width, so that when a row of windings has been completed, a total of two layers of tape are applied to the mandrel 10.

In Fig. 3 it is shown how one according to another. variant According to the invention, the tape 11 is wound onto a cylindrical mandrel 10 by applying turns 10a, 10b, 10c, 10d which meet with their edges, with one winding step each corresponds to the width of the tape.

Figo 4 shows how to make it possible, a tape 12 on a cylindrical. Wind up mandrel 10 by placing nan between each Turn 12a, 12b, 12c, 12d, 12e leaves a gap 13, which corresponds to the width of the band 12.

Only the first winding layer is illustrated in FIGS. 2 to 4. It goes without saying that the number of PTFE layers that are necessary according to the invention is approximately between 10 and 100.

It is also possible to combine the aforementioned types of winding, i.e. some layers with overlap, others with spaces between the turns and still other layers to be wound with turns that meet at the edges «.

In Fig. 5 is a schematic partial section of the cylindrical Hollow mandrel 10 illustrates, on which the layers 9a. " 9b, 9c, 9d, 9e, etc. are wound, which, as you can see, partially overlap.

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Above the first layer of turns there are more consecutive ones Layers wound, which in the present case are wound from layer to layer with turns alternating to the mandrel axis are until the boundary line 14 is reached which of the desired Thickness of the tube, which is then subjected to the gel formation process.

6 illustrates schematically in section and on an enlarged scale Scale of a tube obtained according to the winding process described in FIG. 3. The neighboring ones can be seen in FIG Windings 11a, 11b, 11c and 11d as well as the overlying layer, which consists of the windings 11 * a, 11 * b, 11 * c and 11 * d consistsο If the inner wall of the Sohres is antistatic want to make, one only uses a PTFE tape with graphite intercalation for the turns 11a, 11b, 11c, 11d. that the butt lines between the turns of the first and second Layers are offset from each other · Wrap a sufficient number of layers in this way until the desired Thickness of the EEFE tape cover is achieved by the Limit position 14 of Fig. 6 is indicated.

Figure 7 corresponds to Figures 5 and 6, but with the winding of the tape is carried out as illustrated in FIG. 4 is, doh, with turns whose distance from each other is the Width of the band is.

From FIG. 7 the turns 12a, 12b or 12c can be seen, which form the first layer, while the turns 12 ^f a, 12 * b, 12 * c the second layer and the turns 12 ^lt a, 12 ^ll b, 12 ^lt c form the third layer. The tape with which the turns 12a, 12b, 12c etc. are wound can possibly be provided with embedded graphite »

The successive layers consist of edges with tig touching turns, the turns of the tape

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due to the fact that the spaces between two turns of one winding row equal to the width of the tape of the other winding row sir ". ©

If the pipes are to be heated, _{a conductive wire with a sufficiently high electrical resistance can advantageously be inserted between two layers Z 0} B ₀ between the 10 _o and 11th layers, which is wound onto the 10th layer in a helical manner, for example. before it is covered by the 11th layer. In another variant, the wire can be applied in the longitudinal direction of the 10 _o layer before it is covered by the winding up of the 11th layer.

In FIG. 10, a tube is illustrated before the baking or sintering process, with the mandrel for the sake of simplicity is not illustrated in the drawing. It can be seen that the pipe consists of a large number of layers, of each of which is formed from adjacent turns 23 of the raw PTFE tape o On the turns 23 of the last layer One winds up a rib 24, which has the shape of a circular Has ring on the peripheral surface of the tube. Every rib 24 is made by making a band of raw PTFE is used, which is identical to the tape which was used for winding the turns 23 and which is helical are wound up one above the other on the tubular bodyo With the reference number 25 are the spirally superimposed Turns illustrated in section which as a whole form the circular rib 24 ·

For example, with an outer diameter of the pipe of 200 mm, very good stiffening and excellent stiffening are achieved Resistance to compression of the tube by wrapping the ribs 24 with a tape 15 mm wide and the turns 25 winds over each other over a height of 15 cm, whereby

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two adjacent ribs 24 at a distance of the major order of 300 mm separated from each other Fig. 11 illustrated embodiment variant instead of separate ribs 24 is a continuous helical one Rib is provided, which has the slope of the turn 23, for example. It can be seen that the continuous rib 26, which is obtained in this way is obtained by helically winding a ribbon with the turns on the same helix are superimposed. The width of the ribbons that make up the rib 26 and the height of the rib depend on the degree of strength sought.

If so desired, one can use the spaces between result in two successive ribs 24 or between the turns of the continuous rib 26, fill with a filler material. For this, a material is suitable, for example, that is granular, powdery or fibrous and which is between the Ribs is filled until a cylindrical body results, the diameter of which corresponds to the diameter of the ribs 24 or 26. Further layers of PTFE tape can then be wound onto the tube body obtained in this way, in order to create a continuous one to obtain superficial skin made of PTFE material, after the subsequent baking or sintering process has been completed.

FIGS. 8 and 9 show how a connecting flange is produced at the end of a tube according to the invention. FIG. 8 shows a PTFE tube as it looks after the baking or sintering process described above and after the D _o rn 10 has been taken out. This tube is inserted into the interior of a steel tube 16, which serves as a protective tube. The steel tube has; a flange 17, which serves to connect the pipe end to another flanged pipe end, itfobei the yarbiii-dung is done by bolts that go through openings 18 of the Klaiisciisö 17 »

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The flange is intended to be attached to the end 15a of the PTFE tube 15 used to ensure the continuity of the PTFE tube. To form this flange, the expansion tool 19 is used, which is heated to a temperature of 250 ° G to 350 ° G was heated and then stretched into the end of the tube, as illustrated in Figo 8 iso

The expanding tool 19 has a cylindrical section 20, the diameter of which corresponds to the inner diameter of the tube 15 and a subsequent conical section 21, which for this purpose serves, a first expansion of the pipe end 15 & the PTFE pipe to effect. The conicity of the section 21 is about 60 ° with respect to its axis

It is clear that if the expansion tool 19 is moved in the direction of the arrows illustrated in FIG. 8, a conical deformation occurs of the end 15a of the tube 15 takes place in Fig. 9 is then illustrated how after finishing the conical. deformation of the end 15a of the flange is finally formed, by using a tool 19a in the same temperature range which instead of the conical sub-area a having cylindrical portion 22, the diameter of which is greater than the diameter of the coaxial cylindrical portion 20 causes the final pressing of the already conically deformed end region 15a of the pipe against the flange 17 ", as indicated by dash-dotted lines, which indicate the position of the workpiece 19 ^ · in its end position illustrate·

Thanks to the properties of the pipe according to the invention, it is possible to carry out this operation without difficulty and to obtain connecting flanges which have a large mechanical Have strength and a low permeability, which are in the order of magnitude of the corresponding property sizes of the pipe 1 "5 lie.

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The following are several exemplary embodiments of the invention given.

example 1

Is used which is obtained by coagulation of a dispersion having a mean grain size of 500 i 75 microns, a fresh PTFE powder. This powder is mixed with an oil, which consists of hydrocarbons and which serves as a lubricant. 18 percent by weight of lubricant and 82 percent by weight of powder are used here

A blank is then produced by applying pressure

of 15 kg / cm on the mixture of the powder with the lubricant exercises. This preform, which has the shape of a cylinder 18 cm long and 6 cm in diameter, is placed in an extruder press introduced, which forms a band 1 mm thick © This Tape has a density of 1.72 «,

The tape prepared in this way is left between at room temperature two driven calender rolls of a calendering mill run, resulting in a strip of about 7.5 hundredths of a mm * »

This tape is then in contact with hot trichlorethylene several times brought. The tape obtained after this treatment has a thickness of 1.65 and is then made into desired widths «

The 28 mm wide tape is wound onto a mandrel with a diameter of 4-9 * 5 mm in one winding step of 7 mm, which corresponds to an overlap of adjacent spirals of around $ 75. You get in this way with each pass an overlay of four layers of tape. Then you apply nine more layers, which is 56 times the tape thickness, that is 2.7 mm corresponds to

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After completing the winding process, bring the mandrel and that wrapped PTFE tape in an oven at a temperature of 365 ° C is kept · This ... temperature is left during Act for 90 minutes, after which a controlled cooling of to 30 ° G per hour in the temperature range from 365 to down carried out to 285 ° C.

Below a temperature of 285 °, the cooling can then take place more quickly, e.g. in the open air. After this treatment can the Bo2? n be pulled out, possibly before a slight warming of the PTFE tube takes place in order to thereby to obtain a certain expansion of the same for easier removal of the dome.

After the FJEFE tube has been inserted inside a protective steel tube, the end of the PTFE tube on which the flange is to be attached is pulled slightly out of the steel tube, and one proceeds to the formation of the flange like this is shown in Figo 8 and 9 illustrates by first conical ¥ _e tool con tro 21 with a conicity of about 60 and then a flat die is used 22nd in this manner, one a flange forth whose diameter liegte at 85 mm

The density of the PTFE tube obtained in this way is 2.16

In a variant of this embodiment can carry out the winding of the tape PffiE in various ways, for example, _e as shown in FIGS · J or 4, or according to a combination of these types of winding. It is essential that there is a sufficient number of layers and that the turns of the tape are distributed as evenly as possible «>

In the following, other embodiments according to the invention are described by basically as in the execution

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Example 1 proceeds, but works with wandering characteristics, as illustrated in the list below.

Example Example Example 1 game 2 game 3 game 4-

Thickness of the tape
after dividing up
in mm. 0.075 0.050 0.09 0.13 Density of the kalan
third band 1.65 1.7 1.65 1.60 Width of the tape
in mm 28 4-0 20th 28 Winding step in mm
per full turn 7th 20th 20th 56

Number of times wound on the mandrel

land layers 36 70 4-0 30

Thickness of the 'PTFE tube in mm in front of the Sintering

Diameter of the mandrel in mm

Baking or sintering temperature in G

Cooling speed in the range of 365 - 285 ° 0 ( ⁰ G per hour)

Thickness of the tube after the baking or sintering process in mm

Density of the Pi ¹ FE material after the baking process

Diameter of the flange in mm

Molding temperature at or Formation of the flange in ο C

Permeability in cm3 / cm χ cm2 χ see x atm

2.7 3.5 3.6 3.9 4-9.5 201 152 4-33 365 365 365 365 30th 70 10 50 2 2.7 2.6 3 2.161 2.153 2.170 2.160 85
ρ 255 205 500 350 350 350 350 1.20
ΙΟ "" ⁹ χ 1.35 χ
10-9 1.05 χ
10 "" ⁹ 1.30 χ
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As can be seen from the foregoing, the invention allows the achievement of a PTFE tube, which with a Flange is provided, the pipe and the flange having an extremely low permeability and good mechanical strength. has performance values. The connecting flange shows no old- signs, cracks or weak spots, even after a relatively long period of use.

It goes without saying that the above-described statements examples do not limit the invention and that all changes appearing desirable can be made, without departing from the scope of the invention.

In particular, it is clear that the formation of the flange can take place without the PTFE tubes entering the interior of a steel tube are used, which only serves as a support. Indeed, it is possible to request the flange of the PTFE tube. if this is in any suitable mounting device. device is clamped.

It should also be noted that the invention is not limited to the production of straight tubes, but also is applicable to curved tubes or connecting pieces if you can use a structure as a mandrel that can either be destroyed or disassembled when you has completed the sintering process of the PTFE _o

Expectations

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40-9835 / 0842

Claims (17)

A method for producing pipes from polytetrafluoroethylene (PTI ¹ E), which can be provided with a flange at at least one of their ends, wherein a strip of raw PTS ¹ E is wound around a mandrel, characterized that about 10 to 100 layers of a tape produced by means of a paste extrusion process and subsequent considerable reduction in thickness by means of calendering, the thickness of which about 5 to 20 hundredths of a mm are wrapped around the mandrel, that the PTi ¹ E tape unwound on the mandrel is heated to a temperature , which is above the gel formation temperature but below about 380 ° to 400 ° C and is kept at this temperature long enough to bring about the gelation of the PTFE that the tube and the mandrel are then cooled and finally the im The mandrel located inside the tube is pulled out © 2) Method according to claim 1 _f, characterized in that the PTFE tape undergoes an elongation by five to 20 times during calendering. 3) Method according to claims 1 and 2, characterized in that the tape is wound at an angle to the mandrel axis which is between approximately 4-5 ° to 90 ° _β 4), method according to one of claims 1 to 3 »characterized in that that the PTFE tape is wound up in such a way that the windings partially overlap. 5) Method according to one of claims 1 to 3 »germinated thereby—" - 23 - 409835/0842 indicates that the tape is wound onto the mandrel so that the edges of adjacent turns collide, _o 6) Method according to one of claims 1 to 3 »characterized in that that the tape is wound onto the mandrel so that there are gaps between the successive Y / indungen remain. 7) Method according to one of claims 1 to 6, characterized in that that after the baking process, the tube is cooled down in the temperature range from 580 ° to 400 ° C to about 285 ° G at a cooling rate that is about 10 to 100 ° G per hour, preferably about 20 ° C per hour. 8) Method according to one of claims 1 to 7 »marked thereby— ' indicates that the layer of the tape in contact with the mandrel is made of a material which is antistatic Material, e.g. graphite, is embedded. 9) Method according to one of claims 1 to 8, characterized in that an electrical one on a layer of the tape. Conductor is applied, which is wrapped over by the subsequent layer of tape. 10) Method according to one of claims 1 to 9 »characterized in that that mechanical reinforcement elements on a Intermediate layer before they are wrapped over by the next layer of PTFE tape 11). Method according to claim 10, characterized in that the Reinforcement elements are made from straight, circular or helical wires. the". ~ 24 ~ 409835/0842 - 2'Ί- - 12) Method according to one of claims 1 to 11, characterized in that that on the layer of the outer band there is a Kungsrippen are wound, which in an axial .uw stood run apart. 13) Method according to claim 12, characterized in that da3 an annular reinforcing rib is thereby formed, that the tape in the form of superimposed windings · "· in the area the rib to be formed is wrapped on top of each other 14-) procedure according to. Claim 12, characterized in that a helical rib is formed by the Tape is wound several times on top of one another along the same helical line o 15) A method for forming a flange on a tube produced according to one of the methods according to claims 1 to 14, characterized in that - optionally after insertion of the PTFE tube into the interior of a Metallrohr.es a flange is formed on at least one of the tube ends is by the wall of the end area is deformed with the help of tools, which are heated ^{to a temperature between 250 0} and 35Ο ^{0 G.} 16) tube made of PTFE of very low permeability, characterized in that the tube is made according to one of the methods defined in claims 1 to 15 _o 17) Tube according to claim 16, characterized in that it is provided at least at one of its ends with a flange which shows no cracks under load and whose mechanical properties and permeability are identical to those of the tube _o £ 09835/0842 ar Blank page