Method and apparatus for manufacturing a plastic hose

Abstract

Method for producing a plastic hose, wherein the hose is formed from a plastic material which is extruded from a die in liquid or paste form, wherein a raw material is fed to an extruder and is liquefied and compacted in the extruder and optionally degassed, characterized in that the raw material is rinsed with a fluid before extrusion and the hose (17) is rinsed with a fluid after extrusion to remove impurities, in particular TOC impurities, wherein the hot and low-viscosity hose (17) is rinsed from the outside with a fluid in a melt bath (13) directly after extrusion.

Description

[0001] The invention relates to a method and a device for manufacturing a plastic hose.

[0002] Such hoses are used, for example, for the transport of fluids in semiconductor technology.

[0003] Hoses made of plastic materials are usually manufactured using an extrusion process. In this process, a typically solid raw material is passed through an extruder, liquefied and compacted, then pressed through a die and cooled in a cooling bath.

[0004] Such a procedure is known from US 3 826 122 A and US 6 526 859 B1.

[0005] From DE 695 30 876 T2, a method for producing a hose blank is known, in which a semi-finished hose blank is produced which can then be subjected to further processing steps, such as stretching or drawing. Production is carried out using an extrusion device comprising an extruder and a die body. A PTFA paste is fed into the extrusion device, pre-formed into a strand, and inserted into the extruder. The tubular PTFA strand passing through the extruder is then guided to a die body. The emerging tubular extrudate leaves the extrusion device and is subsequently cut to the desired length. During production, the extrusion device, and thus the hose blank being produced, is kept at a constant temperature.

[0006] It is known to variably control the temperature conditions during such an extrusion process depending on the melting temperature of the polymer precursor used. US Patent 2013 / 0000767 A1 discloses an extrusion process in which the hoses to be produced are vulcanized at an elevated temperature after forming in an extruder and then cooled with a cold fluid.

[0007] Further details of the state of the art can be found in the publications DE 37 12 809 A1, DE 10 2004 059 808 A1, DE 10 2015 106 398 A1, US 6 369 192 B1 and DE 10 2010 040 984 A1.

[0008] Known manufacturing processes have the disadvantage that various impurities, especially those of organic origin, are introduced into the hose material during production. If such contaminated hoses are installed in a system, these impurities, or their volatile and non-volatile components, can be released into the system. This process is called outgassing.

[0009] The presence of the aforementioned impurities is referred to as “TOC” (Total Organic Contamination) and is characterized by a so-called TOC value.

[0010] The released TOC impurities can impair the operation of a plant to such an extent that the efficiency of the affected plant is significantly reduced.

[0011] It is known to expose the finished hoses to a cold or warm airflow to minimize subsequent outgassing. However, this process is not suitable for removing TOC impurities sufficiently. Furthermore, this process is time-consuming and expensive.

[0012] It has been found that conventional hoses arbitrarily exceed or fall below the TOC limits, without any predictable outcome. This leads to considerable effort, as the actual values ​​must be determined and the hoses may only be classified as unsuitable once they are in the user's possession.

[0013] The object of the invention is to create a method for manufacturing plastic hoses with which compliance with TOC limits can be predictably and reliably ensured.

[0014] The problem is solved by the method with the features of claim 1.

[0015] Advantageous further training courses are indicated in the dependent sub-claims.

[0016] Another object of the invention is to create a device for manufacturing a plastic hose with which hoses can be produced that comply with the TOC limits.

[0017] Advantageous further training courses are indicated in the dependent sub-claims.

[0018] The problem is solved with the device having the features of claim 12.

[0019] Another objective of the invention is to create a suitable hose that reliably complies with the TOC limits.

[0020] It was recognized that conventionally manufactured hoses often exhibit excessively high TOC (Total Organic Carbon) levels. TOC fluctuations are unpredictable, and the high levels are frequently only discovered during use, leading to the disposal of heavily contaminated hoses. Furthermore, high TOC levels contaminate the affected system. To prevent this, the inventors realized that the hoses must be thoroughly cleaned beforehand, particularly in several stages.

[0021] In a further development of the invention, each manufacturing step is inspected for TOC impurities in order to eliminate any potential TOC contamination at that stage. For this purpose, the purest possible, uncontaminated raw materials are used. These are subjected to an extrusion process and a purification process at each manufacturing step.

[0022] Suitable raw materials are compounds that can be used as precursors for thermoplastics.

[0023] Thermoplastics are plastics that can be deformed or liquefied within a specific temperature range. This process is reversible, and cooling and reheating can be repeated indefinitely. Once the so-called decomposition temperature is reached, which depends on the material, the material degrades irreversibly.

[0024] The most commonly used thermoplastics are polyolefins such as polyethylene and polypropylene. Other thermoplastics also find industrial applications, such as acrylonitrile butadiene styrene (ABS), polyamides (PA), polylactate (PLA), polymethyl methacrylate (PMMA), polycarbonate (PC), polyethylene terephthalate (PET), polystyrene (PS), polyetheretherketone (PEEK), and polyvinyl chloride (PVC).

[0025] According to the invention, a raw material, preferably packaged under cleanroom conditions and usually in granular form, is fed to an extrusion device.

[0026] A cleanroom is a room in which the concentration of airborne particles is kept very low. Packaging under cleanroom conditions serves to prevent potential contamination. The raw material to be used can be packaged under cleanroom conditions in special packaging, preferably suitable for cleanroom applications. To keep contamination to an absolute minimum, the raw material can be packaged multiple times, for example, double or triple.

[0027] In the extrusion device, the material undergoes at least one cleaning step. A fluid can be used as the cleaning medium. Preferably, several cleaning stages can be provided.

[0028] Suitable fluids can be gaseous or liquid.

[0029] Fluids such as XCDA (Extreme Clean Dry Air), XCHA (Extreme Clean Humid Air), or UPW (Ultra Pure Water) are particularly well-suited. These fluids can be cold or warm.

[0030] The invention thus relates in particular to a method for producing an extruded hose, wherein the hose is formed from a plastic material which is pressed out of a die in liquid or paste form, wherein a raw material is fed to an extruder and is liquefied and compacted in the extruder and optionally degassed, characterized in that the raw material and / or the hose is rinsed with a fluid before and / or after extrusion.

[0031] Another advantageous embodiment provides that the raw material is rinsed with the fluid before being fed into the extruder.

[0032] In a further advantageous embodiment, the hose is flushed with the fluid from the inside and / or outside as it exits the die.

[0033] It is advantageous if the melt pool area is surrounded by a casing to shield it from external contamination.

[0034] Advantageously, the hose is additionally rinsed with the fluid in a cooling bath from the inside and / or outside.

[0035] In another embodiment, the raw material and / or the hose is rinsed with a gaseous fluid.

[0036] It is also advantageous if the fluid is an extremely dry or humid gas.

[0037] Another advantageous embodiment provides that the fluid is air, nitrogen, carbon dioxide, water vapor, reaction gases such as ozone, a noble gas or a mixture of the aforementioned gases.

[0038] Advantageously, the fluid can be a liquid, in particular purified and / or distilled water or another liquid solvent.

[0039] Furthermore, it is advantageous to use a die which has a fluid supply device such that the fluid can be flushed inside the squeezed-out hose.

[0040] Advantageously, the fluid is guided through the raw material against the feed direction of the raw material.

[0041] Another advantageous embodiment provides that the fluid is extracted after passing through the raw material or the hose.

[0042] The invention further relates to a device for carrying out the above-mentioned method, wherein the device is an extrusion device comprising a raw material feed device with a feed opening, wherein the raw material feed device is connected to a first cleaning device, wherein the lower end of the first cleaning device is connected to an extruder inlet, wherein the extruder inlet is arranged on an extruder comprising a screw and an extruder outlet, wherein a die comprising a fluid feed device is arranged on the extruder outlet.

[0043] An advantageous embodiment provides that a melt bath with a second cleaning device is arranged after the die.

[0044] In a further advantageous embodiment, a cooling bath with a third cleaning device is arranged after the melt bath.

[0045] The invention is explained by way of example with the aid of a drawing. The drawing shows: Fig. 1: An extrusion device according to the invention; Fig. 2: A conventional extrusion device.

[0046] A conventional extrusion device 101 ( Fig. 2) is known to comprise a feeding device 102 with a feeding opening 103. The lower end of the feeding device 101 is connected to an extruder. The extruder comprises a screw 104 and an extruder outlet 105. A die 106 is arranged at the extruder outlet 105. A cooling bath 107 and an outlet 108 are arranged downstream of the die 106.

[0047] The raw material is introduced through the feed opening 103 and enters the extruder via the feed device 102. In the extruder, the raw material is liquefied and compacted, and then forced through the die 106. This produces a tube 109, which is then directed into the cooling bath 107. The tube 109 is cooled in the cooling bath 107. The finished product is removed through the outlet 108. Cleaning is typically carried out by rinsing the finished product with air at the end of the manufacturing process.

[0048] An extrusion device 1 according to the invention ( Fig.1) comprises a raw material feeding device 2 with a feeding opening 3. A first cleaning device 4 is arranged at the lower end of the feeding device 2. The first cleaning device 4 can be tubular. The first cleaning device 4 comprises a first fluid inlet 5 and a first fluid outlet 6. The first fluid inlet 5 is arranged at the lower end and the first fluid outlet 6 at the upper end of the first cleaning device 4. The lower end of the first cleaning device 4 is connected to an extruder inlet 7. The extruder inlet 7 is part of an extruder 8, which also comprises a screw 9 and an extruder outlet 10. The screw 9 is arranged axially inside the extruder 8. A die 11 is connected to the extruder outlet 10. The die 11 includes a second fluid inlet 12. Downstream of the die 11 is a melt bath 13. A second cleaning device 14 is provided in the area of ​​the melt bath 13.The melting bath 13 is surrounded by a casing 13a. A cooling bath 15 is arranged downstream of the melting bath 13. The cooling bath 15 includes a third cleaning device 16.

[0049] The extrusion device 1 can, of course, also be located in a cleanroom, so that the outer surface of the blank or the tube 17 is protected from possible external contamination after production. Furthermore, the produced tube 17 can then also be packaged under cleanroom conditions.

[0050] The raw material, preferably packaged multiple times under cleanroom conditions, is fed into the extrusion device 1 through the feed opening 3 of the feeding device 2. From the feeding device 2, it enters the first cleaning unit 4, where it is cleaned with a cleaning medium. This medium can be, for example, a cold or warm XCDA or XCHA fluid. Cleaning is carried out by introducing the appropriate fluid at the lower end of the first cleaning unit 4 through the first fluid inlet 5, where it flows against the feed direction of the raw material. The impurities contained in the raw material are absorbed by the cleaning medium and flushed out through the first fluid outlet 6, which is located at the upper end of the cleaning unit 4.

[0051] The pre-cleaned raw material is fed into the extruder inlet 7 and enters the extruder 8. In the extruder 8, the raw material is liquefied and compacted in the conventional manner and, if necessary, degassed. The liquefied raw material exits the extruder 8 through the extruder outlet 10 and is forced through the die 11, forming a tube 17. During this process, the cleaning medium, in particular XCDA or XCHA, is introduced through the second fluid inlet 12, through the die 11, and into the interior of the tube. The impurities, especially TOC impurities, are absorbed by the cleaning medium and transported out at the end of the tube. In this way, the interior of the tube 17 is cleaned.

[0052] The tube then exits the extruder nozzle in molten state. This area is referred to as the melt pool 13. The outside of the tube 17 is cleaned in a third cleaning step. This third cleaning step takes place in the melt pool 13, where the cleaning medium, a fluid, in particular XCDA, is introduced through the second cleaning device 14. The hot and still very low-viscosity tube 17 is then rinsed from the outside with the cleaning medium. In this way, the contaminants, especially TOC contaminants, are removed from the outside of the tube 17.

[0053] Advantageously, a sheathing 13a or enclosure 13a is provided in the area of ​​the melt bath 13 such that the hose does not come into contact with the outside atmosphere when exiting the extruder nozzle, but is shielded and preferably routed to the cooling bath. The sheathing 13a, which surrounds the area of ​​the melt bath, thus shields the hose 17, which is still in a liquid state, so that no external contaminants can enter the melt.

[0054] The casing 13a can be in a raw or cylindrical shape. It consists of a solid and may have transparent areas.

[0055] Thus, the cleaning step also takes place effectively within the casing, i.e., a closed space; for this purpose, an inlet for the cleaning fluid and an outlet for the cleaning fluid are advantageously provided.

[0056] This results in simultaneous cleaning of the inside and outside, especially in the hot area where TOC contaminants are particularly volatile.

[0057] The fourth cleaning step takes place in the cooling bath 15. The cleaning medium, in particular UPW, is introduced through the third cleaning unit 16, and further contaminants are removed. In this way, a particularly reliable and effective cleaning process can be ensured.

[0058] The invention has the advantage that the impurities, in particular TOC impurities, are reliably removed in several cleaning steps if necessary.

[0059] In the first cleaning step, the raw material is pre-cleaned to reduce the TOC load beforehand.

[0060] Advantageously, a raw material with a particularly high degree of purity can also be used.

[0061] In the second cleaning step, the hose 17 is cleaned internally with a fluid, and in the third cleaning step, it is cleaned externally. These steps take place virtually simultaneously. Furthermore, the still low-viscosity hose 17 is protected from potential external contamination in the area of ​​the melt pool 13 by a sheath 13a.

[0062] Advantageously, in the fourth cleaning step, which takes place in the cooling bath 15, any remaining impurities are largely removed with a fluid.

[0063] Another advantage is that the effects of outgassing can be reduced or even prevented.

[0064] According to the invention, it is advantageous that hoses can be manufactured with a very high degree of purity, so that no additional cleaning is necessary before use, for example in a plant.

[0065] The cleaning method according to the invention has been described using an extrusion process as an example. It is clear to those skilled in the art that the invention can, of course, be used with equal success regardless of the forming process, since the inventive finding of maintaining and cleaning the components and intermediate products is, naturally, independent of the forming process. In this respect, extrusion here stands as a representative example of all suitable forming processes, which could include, for example, blow molding, compression molding, injection molding, and combinations thereof. However, this list is not exhaustive.

Claims

[1] Method for producing a plastic hose, wherein the hose is formed from a plastic material which is extruded from a die in liquid or paste form, wherein a raw material is fed to an extruder and is liquefied and compacted in the extruder and may be degassed, characterized by , that the raw material is rinsed with a fluid before extrusion and the tube (17) is rinsed with a fluid after extrusion to remove impurities, in particular TOC impurities, wherein the hot and low-viscosity tube (17) is rinsed with a fluid from the outside in a melt bath (13) directly after extrusion. [2] Method according to claim 1, characterized by , that the raw material is rinsed with the fluid before being fed into the extruder (8). [3] Method according to any one of the preceding claims, characterized by , that the hose (17) is flushed with the fluid from the inside and / or outside as it exits the die (11). [4] Method according to any one of the preceding claims, characterized by that the hose (17) is additionally rinsed with the fluid from the inside and / or outside in a cooling bath (15). [5] Method according to any one of the preceding claims, characterized by that the raw material and / or the hose is rinsed with a gaseous fluid. [6] Method according to any one of the preceding claims, characterized by that the fluid is an extremely dry or humid gas. [7] Method according to any one of the preceding claims, characterized by that the fluid is air, nitrogen, carbon dioxide, water vapor, reaction gases such as ozone, a noble gas or a mixture of the aforementioned gases. [8] Method according to any one of the preceding claims, characterized by that the fluid is a liquid, in particular purified and / or distilled water or another liquid solvent. [9] Method according to any one of the preceding claims, characterized by , that a die (11) is used which has a fluid supply device (12) such that the fluid can be flushed inside the squeezed-out hose (17). [10] Method according to any one of the preceding claims, characterized by that the fluid is guided through the raw material against the feed direction of the raw material. [11] Method according to any one of the preceding claims, characterized by that the fluid is extracted after passing through the raw material or the hose. [12] Device for carrying out the method according to claim 1, characterized by, that the device is an extrusion device (1) comprising a raw material feed device (2) with a feed opening (3), wherein the feed device (2) is connected to a first cleaning device (4), wherein the lower end of the first cleaning device (4) is connected to an extruder inlet (7), wherein the extruder inlet (7) is arranged on an extruder (8) comprising a screw (9) and an extruder outlet (10), wherein a die (11) comprising a fluid supply device (12) is arranged on the extruder outlet (10). [13] Device according to claim 12, characterized by , that a melt bath (13) with a second cleaning device (14) is arranged after the die (11). [14] Device according to claim 12 or 13, characterized by , that the melt bath area (13) is surrounded by a casing (13a) to shield against external contamination. [15] Device according to claim 12, 13 or 14, characterized by , that after the melting bath (13) a cooling bath (14) with a third cleaning device (16) is arranged.

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