Method and apparatus for producing a plastics profile

Abstract

A method for producing a plastics profile, wherein the plastics profile is made from a plastics material, which is extruded in liquid or pasty form from a die, wherein the extruded extrudate is shaped into a plastics profile and then calibrated and cooled, wherein, to clean the plastics profile, the open end of the plastics profile is connected to a fluid treatment device, wherein a treated fluid is introduced through the open end into the interior of the plastics profile counter to the extrusion direction and is directed through as far as the die, wherein the fluid that has been directed through is conducted to the outside via a fluid outlet opening and the die.

Description

[0001] Method and device for producing a plastic profile

[0002] The invention relates to a method and a device for producing a plastic profile.

[0003] Such plastic profiles are used, for example, for the transport of fluids in semiconductor technology.

[0004] Plastic profiles, such as hoses made of plastic materials, are typically manufactured using an extrusion process. This process involves passing a typically solid raw material through an extruder, liquefied and compacted, then pressed through a die and cooled in a cooling bath.

[0005] Such a process is known from US 3 826 122 and US 6 526 859 B1.

[0006] DE 695 30 876 T2 discloses a method for producing a hose blank, in which a semi-finished hose blank is produced, which can then be subjected to further processing steps, such as stretching or drawing. Production takes place using an extrusion device comprising an extruder and a die body. A PTFE paste is fed to the extrusion device, preformed into a strand, and introduced into the extruder. The tubular PTFE strand passed through the extruder is then guided to a die body. The emerging tubular extrudate leaves the extrusion device and is then cut to any desired length. During production, the extrusion device and thus the producible hose blank are kept at a constant temperature.

[0007] 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 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.

[0008] From DE 20 2010 018 606 U1, it is known to draw air from the end face of a plastic profile for cooling purposes, so that the air is drawn against the extrusion direction up to the extrusion die and released back into the environment via an air outlet. For this purpose, a pump is used, which is provided on the extrusion die and creates a vacuum against the extrusion direction. In this way, the interior of the plastic profile is cooled after extrusion.

[0009] However, cooling or cleaning using vacuum instead of compressed air, for example, leads to instability in the extrusion process. This can negatively impact quality and production throughput. Furthermore, such a process has disadvantages such as increased costs, limited production throughput, and extended lead times.

[0010] Known manufacturing processes have the disadvantage that various contaminants, particularly those of organic origin, are introduced into the hose material during production. If such contaminated hoses are installed in a system, these contaminants or their volatile and non-volatile components can be released into the system. This process is known as outgassing.

[0011] The presence of these contaminants is referred to as "TOC" (Total Organic Contamination).

[0012] TOC is, in particular, a measure of the concentration of organic substances in a sample. The sample can be a gas or a liquid, for example. The result of the analytical measurement is an indicator of the chemical purity of the medium.

[0013] The analysis of liquid samples can be performed using TOC analyzers. During the analysis, the sample is burned or oxidized, ultimately forming carbon dioxide. The CO2 concentration is then measured using a non-dispersive infrared (NDIR) sensor.

[0014] Gaseous samples can be analyzed using gas chromatography (GC) coupled with a flame ionization detector (GC-FID) or a mass spectrometer (GC-MS). TOC analyses are used in a variety of industries, including pharmaceuticals, environmental research, and the semiconductor industry. In the latter, ultra-high-purity media such as ultra-pure water (UPW), ultra-high-purity nitrogen gas (UHP N2), and ultra-clean dry air (XCDA) are used to minimize the risk of contamination throughout the supply chain and integrated circuit (IC) manufacturing process.

[0015] Materials and components for use in the semiconductor industry are subject to a variety of requirements defined by the trade association Semiconductor Equipment and Materials International (SEMI).

[0016] The industry standard SEMI F57-0314 applies to polymeric materials and components used in ultrapure water (UPW) and liquid chemical distribution systems. The purity specifications defined therein include particulate matter content, surface extractable ionic contaminants, surface extractable metallic contaminants, total organic carbon (TOC), and surface roughness requirements.

[0017] The SEMI F57-0314 standard specifies that polymeric materials and components for use in the semiconductor industry must meet the following total organic carbon (TOC) requirements:

[0018] Static value at 85 + / - 5 °C for 7 days should be < 60 000 pg / m 2 be.

[0019] The industry standard SEMI F-40 is used to prepare polymer materials and components for surface extractable testing. The test method for polymer materials and components for surface extractable TOC testing is specified in ASTM D4779 and / or ASTM D5904.

[0020] Thus, a contaminant is defined as a TOC contaminant if it is an organic compound, in particular a carbon-containing compound, and may also include heterogeneous atoms.

[0021] TOC contamination can impair the operation of a plant to such an extent that its efficiency is significantly reduced. Furthermore, it significantly impairs the quality and purity of the final product.

[0022] Shear stress is one of the main causes of elevated TOC values ​​in extruded plastic profiles. The shear stress (T W) is defined as the ratio of pressure (P) and die diameter (R) to die length (L):

[0023] PR W = 2L

[0024] Since polymer melts are non-Newtonian fluids, there is no linear correlation between shear stress and shear rate. The viscosity of polymer melts depends on the shear rate:

[0025] T = shear stress on the die wall (= PR / 2L)

[0026] P = measured pressure

[0027] R = die diameter

[0028] L = matrix length y w = Shear rate at the die wall

[0029] Q = volumetric output power.

[0030] A fundamental distinction can be made between primary and secondary TOC contaminants. Primary contaminants result from the lack of purity of the raw material. Secondary contaminants are introduced into the product during the manufacturing process from the environment, such as the ambient air.

[0031] The primary TOC contaminants can, for example, be a product of chain scission during extrusion. Chain scission is a process of thermomechanical degradation of a polymer in which the polymer chains are randomly split into several shorter chains under the influence of heat and shear stress. For example, fluoropolymers in particular can release decomposition products when heated as a result of pyrolysis. The release of volatile compounds causes the so-called (fluoro)polymer fever, which is why fluoropolymers should only be processed in a well-ventilated room.

[0032] Such decomposition products can also occur well below the extrusion temperature of the polymers. The decomposition rate increases with increasing temperature.

[0033] Various TOC contaminants are present in the walls and on the surface of PFA pipes, in particular. Until now, it has been virtually impossible to remove them.

[0034] PFAS are organic compounds of various chain lengths in which the hydrogen atoms are replaced by fluorine atoms. Thus, PFAS refers to per- and polyfluorinated organic fluorine compounds, particularly fluoropolymers. In addition, PFAS can also contain chlorine atoms in their structure.

[0035] Breaking the carbon-fluorine bond requires a lot of energy. Therefore, PFA compounds are hardly degradable under normal conditions and therefore very durable. They can remain in the environment for a very long time.

[0036] Because PFAS are only partially bound to the polymer used, the free PFA molecules can be released into the environment. Furthermore, the polymer used can degrade over time, releasing PFAS.

[0037] Some PFAS accumulate in soil, animals, plants and humans and also have harmful effects on health.

[0038] Accordingly, PFA compounds are generally considered to be harmful to the environment.

[0039] PFAS are a global problem due to their longevity and widespread use. They can only be broken down and disposed of through high-temperature treatment.

[0040] Therefore, it is very important to observe the precautionary principle right from the production stage.

[0041] The inventors recognized that, in addition to PFAS, other compounds, especially BTEX contaminants, can also be critical. BTEX is an abbreviation for benzene, toluene, ethylbenzene, and xylene. These are cyclic aromatic hydrocarbons with six to eight carbon atoms.

[0042] BTEX is found in natural gas and petroleum and is used extensively in the production of petroleum products and as solvents. Consequently, this class of pollutants is formed during the production of the base monomers or during the polymerization process.

[0043] Even if the presence of BTEX in PFA granules can be minimized, chain scission still occurs during extrusion. Furthermore, secondary parameters such as compressed air purity or resin quality also require laborious monitoring.

[0044] The extrusion of plastic profiles, especially PFA plastic profiles, is therefore subject to numerous variables and production steps, making them inherently sensitive to quality issues such as TOC contamination in this case.

[0045] The object of the invention is to create a method for producing a plastic profile which allows its use under extremely clean conditions.

[0046] The problem is solved with the features of claim 1.

[0047] Advantageous further training is indicated in the dependent subclaims.

[0048] Maximum cleanliness conditions within the meaning of the invention are conditions under which the concentration of waterborne particles does not exceed 160 pg / m 2 , preferably not more than 130 pm / m 2 , preferably not more than 100 pg / m 2 amounts.

[0049] A further object of the invention is to provide a device for producing a plastic profile with which plastic profiles can be produced which allow their use under extremely clean conditions.

[0050] The problem is solved with the features of claim 18.

[0051] Advantageous developments are characterized in the dependent subclaims. The inventors recognized that it is not necessary to control all variables and production steps to reduce the TOC level in the final product. They recognized that the concept of internal counterflow extrusion (ICE) enables the production of high-purity plastic profiles.

[0052] Several types of organic contaminants can be present in the walls and on the surface of plastic profiles. Even if the presence of primary TOC contaminants in the raw material granules is minimized, chain scission still occurs during extrusion. Furthermore, secondary parameters such as compressed air purity must also be laboriously monitored.

[0053] It was found that the organic TOC compounds in plastic granules, especially in PFA granules, mainly consist of branched alkanes and aromatics, while the TOC impurities in plastic profiles, especially in PFA profiles, mainly consist of perfluorinated organic compounds.

[0054] This implies that there is an additional source of organic contamination in plastic profiles, especially PFA profiles.

[0055] A sample of PFA plastic profiles was tested. The results showed that 84% of the organic contaminants consisted of BTEX.

[0056] The invention is therefore based on the finding that there are two main classes of contaminants that lead to high TOC values. The first are perfluorinated organic compounds, which are released by chain scission during extrusion. The second are BTEX, which are introduced during the production of the granulate.

[0057] For this reason, it is advantageous to clean the granules before extrusion. The granules or raw material are pre-cleaned to reduce PFAS contamination in advance. It is also advantageous to use a raw material with a particularly high degree of purity.

[0058] The granules can be cleaned using a fluid. For this purpose, the granules are rinsed with the fluid before being fed into the extruder. The fluid used can be a liquid. In particular, the fluid can comprise one or more fluids from the following group: ultrapure water (UPW), purified and / or distilled water, or another liquid solvent. Before further use, the granules are dried. Drying is performed using a fluid. The fluid can be gaseous. For example, the fluid used can be extremely clean, dry air.

[0059] The BTEX compounds are released from the molten plastic, particularly PFA, during extrusion. They are then suspended and displaced by the air flow used to shape and calibrate the extrudate. As the plastic profiles and contaminants cool in the calibration vessel, the gaseous contaminants condense and adhere to the inner surface of the plastic profile.

[0060] Existing extrusion processes rely on the use of compressed air to calibrate the radial dimensions of the profiles. Organic contaminants released from the molten plastic, such as PFA, float in this fluid stream, such as air, and are displaced by it. They then condense and adhere to the inner surface of the profiles, such as pipes.

[0061] According to the invention, it was recognized that with internal countercurrent extrusion (ICE), the contaminants released into the fluid or air flow are at least largely, preferably completely, removed from the interior of the profile, for example, a hose, before adhesion can occur. For this purpose, in contrast to conventional processes, the direction of the fluid or air flow is reversed.

[0062] The advantage is that only a few structural changes need to be made to the existing extrusion lines.

[0063] Applying pressurized fluid at the open end of the extrudate rather than at the beginning of the extruder, i.e., at the extrusion die, provides better flow control. This is due to the pressure drop that occurs inside the extrudate. With pressurized fluid, such as compressed air, the pressure drop acts as a buffer against pressure fluctuations. This enables good flow control. It also prevents the melt cone from collapsing.

[0064] The pressure drop is defined by the Darcy-Weisbach equation:

[0065] Ap _ pv) 2

[0066] L ~ ' D 2 D H where Ap = pressure drop L = profile length f D = pipe friction coefficient p = fluid density v = average flow velocity

[0067] D H = hydraulic diameter

[0068] In the case of vacuum, for example, which is conventionally used to clean plastic profiles, the pressure drop fluctuates and acts as a flow restriction that is difficult to control. Meaningful, process-capable pressure flow control is virtually impossible in this case.

[0069] In known methods, pressure is conventionally measured for flow control. However, this is often difficult to achieve, especially with smaller profile diameters. For this reason, the invention measures flow rather than pressure. A measuring device is provided for this purpose, preferably at a fluid outlet opening.

[0070] The invention thus relates to a method for producing a plastic profile, wherein the plastic profile is formed from a plastic material which is pressed out of a die in liquid or pasty form, wherein the pressed-out extrudate is shaped into a plastic profile and then calibrated and cooled, wherein for cleaning the plastic profile the open plastic profile end is connected to a fluid processing device, wherein a processed fluid is introduced through the open end into the interior of the plastic profile against the extrusion direction and is passed through to the die, wherein the passed-through fluid is passed out via a fluid outlet opening on the die.

[0071] An advantageous further development provides that the fluid from the fluid treatment device is introduced into the plastic profile with a predetermined pressure against the extrusion direction.

[0072] An advantageous development provides that the fluid in the fluid treatment device is subjected to one or more treatments from the following group: filtering, purification, ionization. An advantageous development provides that the fluid is a treated gas, in particular treated air.

[0073] An advantageous further development provides that one or more fluids from the group of helium, argon, nitrogen, ozone are used as the fluid.

[0074] An advantageous further development provides for the process to be carried out in a clean room.

[0075] An advantageous further development provides that the open end of the extruded and fluid-cleaned plastic profile is separated from the fluid treatment device and covered with at least one cover unit.

[0076] An advantageous further development provides that the cover unit is a plastic film, in particular a polyester film.

[0077] An advantageous further development provides that the cover unit is a plastic profile cap, in particular a cap made of polyethylene.

[0078] An advantageous further development provides for a flow measurement to be carried out.

[0079] An advantageous further development provides that the pressure is regulated depending on the flow measurement.

[0080] An advantageous further development provides that the pressure is regulated automatically by means of a control device.

[0081] An advantageous further development provides for the use of a device that encloses the plastic profile.

[0082] An advantageous further development provides that the enveloping device is arranged around the hot extrudate, in particular in a high-temperature area.

[0083] An advantageous further development provides that the enveloping device is made of a ceramic material or glass, in particular quartz glass.

[0084] An advantageous development provides that the enclosing device is formed from at least one or more compounds from the following group: nitrides, oxides, carbides. An advantageous development provides that the enclosing device is transparent.

[0085] An advantageous further development provides that a granulate is used for the extrusion, which is rinsed with a fluid before being fed into an extruder.

[0086] An advantageous further development provides that the fluid used is a liquid, in particular the fluid comprises one or more fluids from the following group: ultrapure water, purified and / or distilled water, another liquid solvent.

[0087] An advantageous further development provides that after cleaning the granulate is dried by means of a fluid, in particular the granulate is dried with a gaseous fluid such as, for example, extremely clean dry air.

[0088] An advantageous further development provides that a first filter device is used which is provided in the outlet opening, wherein the first filter device is designed in particular as an activated carbon filter.

[0089] The invention further relates to a device for carrying out the method described above, the device comprising at least one extruder, a screw, and a crosshead, wherein a fluid treatment device is provided which can be connected to an open end of an extruded, calibrated and cooled plastic profile.

[0090] An advantageous further development provides that the fluid treatment device comprises a compression device.

[0091] An advantageous further development provides that the fluid treatment device comprises a filter device.

[0092] An advantageous further development provides that the fluid treatment device comprises a cleaning device.

[0093] An advantageous development provides that the fluid treatment device comprises an ionization device. An advantageous development provides that the fluid treatment device is designed to introduce a fluid through the open end into the interior of the plastic profile against the extrusion device.

[0094] An advantageous further development provides that a fluid outlet opening is provided on the die.

[0095] An advantageous further development provides that a first filter device is provided in the outlet opening, wherein the first filter device is designed in particular as an activated carbon filter.

[0096] An advantageous further development provides that a measuring device for flow measurement is provided in the outlet opening.

[0097] An advantageous further development provides that a pressure control device is arranged downstream of the cleaning device in the fluid flow direction or downstream of the compression device in the fluid flow direction.

[0098] An advantageous further development provides that the control device is designed to convert the data received from the measuring device into control data in order to control the pressure.

[0099] An advantageous further development provides for a device enclosing the plastic profile.

[0100] An advantageous further development provides that the enveloping device is arranged around the hot extrudate, in particular in a high-temperature area.

[0101] An advantageous further development provides that the enveloping device is made of a ceramic material or glass, in particular quartz glass.

[0102] An advantageous further development provides that the enveloping device is formed from at least one or more compounds from the following group: nitrides, oxides, carbides.

[0103] An advantageous further development provides that the enveloping device is designed to be transparent.

[0104] The invention will be explained by way of example with reference to the accompanying drawings, in which: Fig. 1 shows a device for producing hollow plastic profiles, comprising a

[0105] fluid supply device;

[0106] Fig. 2 shows a device for producing hollow plastic profiles comprising a

[0107] measuring device and an enclosing device;

[0108] Fig. 3 an enveloping device;

[0109] Fig. 4 a mass spectrogram of an untreated sample;

[0110] Fig. 5 Mass spectrogram of a treated sample;

[0111] Fig. 6 TOC contaminants in ambient and compressed air;

[0112] Fig. 7 a mass spectrogram of TOC contaminants in ambient air;

[0113] Fig. 8 a mass spectrogram of TOC impurities in the compressed air;

[0114] Fig. 9 Reference spectrogram of propan-2ol.

[0115] The inventors recognized that the location where the plastic profiles are cleaned is of great importance. It has been found that cleaning is most effective between the exit from the extrusion head and the inlet into the cooling tank, i.e., where the plastic profile has the highest temperature. This suspends the contaminants released at high temperatures in a fluid stream, such as air, and then removes them. This prevents the condensation of organic compounds and their adhesion to the inner surface of the profiles.

[0116] For this purpose, a device 1 is provided (Figure 1), which comprises an extruder 2, a raw material feed device 3, a melter 4, and a crosshead 5. A fluid outlet opening 6 is provided on the extruder 2, for example, on the crosshead 5.

[0117] A first filter device 6a can be provided in the outlet opening 6. The first filter device 6a can, in particular, be designed as an activated carbon filter.

[0118] The first filter device 6a serves to collect particles or components of the plastic used that are not to be further processed in the extrusion process. When using a PFA plastic, the first filter device 6a can collect PFA particles and forward them from the system for further disposal. Since PFA compounds are considered environmentally hazardous, the collected PFA particles can be properly disposed of without entering the environment. This enables environmentally friendly process management.

[0119] The collected PFA particles can then be disposed of or otherwise processed at a temperature of, for example, 1240 °C.

[0120] Downstream of the extruder 2, in the extrusion direction 10, a calibration device 7 is arranged to calibrate the still-hot extrudate 8. The calibrated extrudate 8 is then cooled in a cooling device 9, which is arranged downstream of the calibration device 7 in the extrusion direction 10. The thus extruded plastic profile 11 is drawn off in a drawing-off device 12 and coiled by a coiling device 13.

[0121] A fluid supply device 14 is also provided, which can be connected to the device 1, so that the fluid can be introduced into the interior of the profile through the open end 15 of the plastic profile 11. The fluid is introduced against the extrusion direction 10 and passed through to the extruder. A fluid outlet opening 6 is provided on the extruder 2, through which the passed fluid is released into the environment.

[0122] The fluid flow direction 19 is opposite to the extrusion direction 10. The fluid is thus passed through, among other things, the high-temperature region 20, i.e., the region between the outlet from the extrusion head 5 and the inlet into the cooling device 9. The plastic profile has the highest temperature in the high-temperature region 20. This is where most contaminants are released. Since the contaminants are suspended and removed immediately after they are formed, cleaning with the fluid is most effective in this region. This prevents condensation of the organic contaminants and their adhesion to the inner surface of the profiles.

[0123] Furthermore, the fluid supply device 14 comprises at least one compression device 16. The compression device 16 functions as a compressor and compresses the fluid to be used. If air is used as the fluid, for example, the ambient air is compressed in the compression device 16.

[0124] In addition, the fluid supply device 14 can comprise at least one cleaning device 17, in which the fluid to be used is purified of undesirable gases, such as oxygen. The cleaning is performed before introduction into the plastic profile 11. The fluid supply device 14 can also comprise at least one filter device 18. In the filter device 18, the fluid is cleaned of dust, small particles, or other contaminants. The cleaning is performed before introduction into the plastic profile 11.

[0125] In an advantageous embodiment, the fluid supply device 14 may comprise an ionization device in which the fluid to be introduced is ionized.

[0126] Filtered and purified air prevents potential TOC contamination of the inner tube surface, while ionization enables effective removal of any remaining contaminants. Furthermore, it is advantageous to seal the finished tubes immediately after cutting with a film, especially a polyester film, and tube caps.

[0127] The hot extrudate 8 is particularly influenced by pressure and fluid flow velocity, ie flow rate.

[0128] In one embodiment, a measuring device 22 can be provided (Figure 2). The measuring device 22 can be arranged at the fluid outlet opening 6. The measuring device 22 can be designed, for example, as a Pitot tube.

[0129] By applying the Bernoulli principle, the Pitot tube can also serve as a sensor for the flow velocity, i.e. flow:

[0130] V 2 p

[0131] - 1- gz + — = constant

[0132] 2 P where v = internal countercurrent velocity g = gravitational constant z = height difference p = pressure at the location to be measured (e.g. at the crosshead) p = fluid density.

[0133] Measuring the counterflow velocity allows for control of the internal pressure, especially in the area of ​​the hot extrudate 8. If the measured flow rate is too low, the fluid pressure is increased. If, on the other hand, the measured flow rate is too high, the fluid pressure is reduced. This can also be done automatically. Thus, by measuring the flow rate and the resulting pressure regulation, it is ensured that the counterflow through the extrudate is sufficient.

[0134] A control device can be provided to monitor the counterflow. The control device is preferably automated, so that the fluid pressure is automatically adjusted based on the values ​​transmitted by the measuring device 22 in order to maintain the desired flow rate.

[0135] Accordingly, the process is monitored and controlled by means of a flow measurement.

[0136] A pressure control device 23 is provided for pressure regulation. It can be arranged downstream of the cleaning device 17 in the fluid flow direction 19 or downstream of the compression device 16 in the fluid flow direction 19.

[0137] The pressure control device 23 can be designed like a valve.

[0138] Flow monitoring is important because if the internal pressure is too low, the hot extrudate 8 can implode. If the internal pressure is too high, the hot extrudate can explode.

[0139] To prevent this, a sheathing device 21 can be provided around the hot extrudate 8 (Figure 3). It is arranged between the crosshead 5 and the calibration device 7. It can be attached to the crosshead 5 and the calibration device 7 with fastening means 24.

[0140] The enveloping device 21 may have the shape of a cone.

[0141] Furthermore, it can be tubular. In a further embodiment, it can be formed from at least one half-shell. It can also be formed from several segments, which allow for at least partial encasing of the hot extrudate 8.

[0142] The enveloping device 21 can also have any other shape that at least partially or completely envelops the hot extrudate 8. The enveloping device 21 is dimensioned such that it does not come into contact with the hot extrudate 8. Thus, the dimensions of the enveloping device 21 can be flexibly adapted depending on the profile diameter.

[0143] The enclosing device 21 is formed from a material which can withstand at least 350 °C, preferably 390 °C, further preferably 400 °C, further preferably 410 °C, particularly preferably 420 °C.

[0144] In addition, the material is designed to withstand corrosive conditions, particularly those for metals. Corrosive conditions are particularly referred to as the use of corrosive polymers.

[0145] Furthermore, the material must have a low coefficient of friction. Since friction coefficients depend on both contact materials, the coefficient of friction for the enclosing device 21 and the plastic profile should, for example, be no greater than 0.4, preferably no greater than 0.3, and further preferably no greater than 0.2.

[0146] In an advantageous embodiment, the enveloping device 21 is made of a ceramic material.

[0147] The ceramic material may comprise at least one or more compounds from the following group: nitrides, oxides, carbides.

[0148] In a further advantageous embodiment, the enclosing device 21 is made of a transparent material. For example, the transparent material can be a transparent ceramic material.

[0149] A transparent enclosing device 21 has the advantage of enabling better process control. This allows the operator to visually check the dimensions of the melt cone or the hot extrudate 8.

[0150] Cleaning in the high-temperature range 20 is particularly advantageous for several reasons. First, it occurs after the actual extrusion process. This means that any decomposition or contamination from rinsing agents, compounds, solvents, or other variables has already occurred. In this way, all production steps that could contaminate the final product are arranged before the cleaning process. Second, most of the released organic compounds have a boiling point that is far below the temperature of the plastic, for example, PFA, at this point in the extrusion line. Plastics, especially PFA, are therefore very susceptible to thermal decomposition at processing temperatures. Therefore, any contaminants released from the molten plastic, for example, PFA, are in a gaseous state and are easily stirred up by an air stream.

[0151] The effectiveness of fluid cleaning is shown in Figures 4 and 5.

[0152] A comparison mass spectrogram of an unpurified (Figure 4) and a purified (Figure 5) sample is shown in Figures 4 and 5. These are two plastic profiles containing PFA (PFA Chemours 450HP). The respective plastic profiles are cleaned at 210 °C for 60 minutes with extremely clean dry air (XCDA). The pressure of the extremely clean dry air is 0.2 bar and the flow rate is 32 Nl / min.

[0153] The mass spectrogram in Figure 6 shows that the purified sample contains significantly fewer contaminants. Thus, the method according to the invention succeeds in reducing contamination in plastic profiles, especially in PFA-containing plastic profiles, several times over.

[0154] The results show a 98 percent reduction in non-volatile contaminants (TOCnv) and a 90 percent reduction in volatile contaminants (TOCv).

[0155] Compressed air generally contains more contaminants than ambient air. Figure 5 shows that the TOC concentration in compressed air is at least three times higher than in ambient air. Pretreatment of the used air, such as purification, filtering, or ionization, is therefore particularly beneficial.

[0156] Conventional rinsing of the freshly extruded plastic profiles, particularly in the extrusion direction 10, would distribute the TOC contaminants present in the compressed air from the high-temperature zone 20 in which they are formed, inside the plastic profile over the entire length.

[0157] Flushing against the extrusion direction 10, particularly with a purified, filtered, and / or ionized fluid, removes the TOC contaminants at their source. This prevents the TOC contaminants from spreading. To avoid cross-contamination, the extrusion of plastic profiles is carried out in a controlled environment.

[0158] It is advantageous if the extrusion and cleaning of the plastic profiles are carried out in a clean room.

[0159] It was also found that some TOC contamination can arise from cross-contamination. In particular, the use of solvents such as isopropanol or similar can lead to cross-contamination.

[0160] Figure 9 shows a reference spectrogram of isopropan-2-ol. It can be seen that a large portion of the TOC impurities (see Figures 7 and 8) originate from isopropanol.

[0161] It is therefore advantageous if the extruded plastic profiles are sealed at the open end immediately after extrusion. They can be sealed with a plastic film, for example, a polyester film (PET).

[0162] Alternatively, they can be closed with a plastic profile closure device, such as a hose flap.

[0163] It is particularly advantageous if the open end of the extruded plastic profile is closed with both a film and a plastic profile closure device.

[0164] The invention thus makes it possible to remove TOC contamination directly at its source, preventing further spread within the plastic profile.

[0165] A vacuum calibration tank, which is used in conventional rinsing and / or cleaning with vacuum, is not necessary.

[0166] Major structural changes to the existing system are also not necessary.

[0167] The invention also makes it possible to control the quality of the fluid used. If necessary, it can be cleaned, filtered, and / or ionized. Reference symbol Device Extruder Raw material feed device Screw Crosshead Fluid outlet opening a First filter device Calibration device Extrudate Cooling device 0 Extrusion direction 1 Plastic profile 2 Stripping device 3 Coiling device 4 Fluid feed device 5 Open end of the plastic profile 6 Compression device 7 Cleaning device 8 Second filter device 9 Fluid flow direction 0 High temperature area 1 Enveloping device 2 Measuring device 3 Pressure control device 4 Fastening means 5 Ionization device

Claims

AMENDED CLAIMS received by the International Bureau on 29 January 2025 (29.01.2025) 1. A method for producing a plastic profile, wherein the plastic profile is formed from a plastic material which is pressed out of a die in liquid or pasty form, wherein the pressed-out extrudate is shaped into a plastic profile and then calibrated and cooled, characterized in that for cleaning the plastic profile the open plastic profile end is connected to a fluid processing device, wherein a processed fluid is introduced through the open end into the interior of the plastic profile against the extrusion direction (10) and is passed through to the die, wherein the passed-through fluid is passed outwards via a fluid outlet opening (6) on the die, wherein a device (21) enclosing the plastic profile is used, which is arranged between the die and a calibrating device (7).

2. Method according to claim 1, wherein the fluid from the fluid treatment device is introduced into the plastic profile at a predetermined pressure against the extrusion direction (10).

3. The method according to claim 1 or 2, wherein the fluid in the fluid treatment device is subjected to one or more treatments selected from the group consisting of filtering, purifying and ionizing.

4. Method according to one of the preceding claims, wherein the fluid is a treated gas, in particular treated air.

5. Method according to one of the preceding claims, wherein one or more fluids from the group of helium, argon, nitrogen, ozone are used as the fluid. AMENDED SHEET (ARTICLE 19) 6. Method according to one of the preceding claims, wherein the method is carried out in a clean room.

7. A method according to any one of the preceding claims, wherein the open end of the extruded and fluid-cleaned plastic profile is Fluid treatment device is separated and covered with at least one cover unit.

8. The method according to claim 7, wherein the covering unit is a plastic film, in particular a polyester film.

9. The method according to claim 7, wherein the cover unit is a plastic profile cap, in particular a cap made of polyethylene.

10. Method according to one of the preceding claims, wherein a flow measurement is carried out.

11. The method according to claim 10, wherein the pressure is regulated as a function of the flow measurement.

12. A method according to claim 10 or 11, wherein the pressure is automatically regulated by means of a control device.

13. Method according to one of the preceding claims, wherein the enveloping device (21) is arranged around the hot extrudate (8), in particular in a high-temperature region (20).

14. The method according to claim 13, wherein the enclosing device (21) is made of a ceramic material or glass, in particular quartz glass.

15. The method according to claim 13 or 14, wherein the enclosing device (21) is formed from at least one or more compounds from the following group: nitrides, oxides, carbides.

16. Method according to one of claims 13 to 15, wherein the enveloping device (21) is transparent. AMENDED SHEET (ARTICLE 19) 17. A method according to any one of the preceding claims, wherein granules are used for the extrusion which are rinsed with a fluid before being fed into an extruder.

18. The method according to claim 17, wherein the fluid used is a liquid, in particular the fluid comprises one or more fluids from the following group: ultrapure water, purified and / or distilled water, another liquid solvent.

19. The method according to claim 17 or 18, wherein after cleaning the granules are dried by means of a fluid, in particular the granules are dried with a gaseous fluid such as extremely clean dry air.

20. Method according to one of the preceding claims, wherein a first filter device (6a) is used which is provided in the outlet opening (6), wherein the first filter device (6a) is designed in particular as an activated carbon filter.

21. Device for carrying out the method according to one of the preceding claims, wherein the device comprises at least one extruder (2), a screw (4), and a die, characterized in that a fluid processing device is provided which can be connected to an open end of an extruded, calibrated and cooled plastic profile, wherein a fluid passed through can be discharged to the outside via a fluid outlet opening (6) on the die, wherein a device (21) is provided which encloses the plastic profile and is arranged between the die and a calibrating device (7).

22. Apparatus according to claim 21, wherein the fluid processing device comprises a compression device (16).

23. Device according to claim 21 or 22, wherein the fluid treatment device comprises a filter device (18).

24. Device according to one of claims 21 to 23, wherein the fluid treatment device comprises a cleaning device (17). AMENDED SHEET (ARTICLE 19) 25. Device according to one of claims 21 to 24, wherein the fluid conditioning device comprises an ionization device.

26. Apparatus according to any one of claims 21 to 25, wherein the fluid conditioning device is designed to introduce a fluid through the open end into the interior of the plastic profile against the extrusion device.

27. Device according to one of claims 21 to 26, wherein a fluid outlet opening (6) is provided on the die.

28. Device according to claim 27, wherein a first filter device (6a) is provided in the outlet opening (6), wherein the first filter device (6a) is designed in particular as an activated carbon filter.

29. Device according to one of claims 21 to 28, wherein a measuring device (22) for flow measurement is provided in the outlet opening (6).

30. Device according to one of claims 21 to 29, wherein a pressure control device (23) is arranged downstream of the cleaning device (17) in the fluid flow direction (19) or downstream of the compression device (16) in the fluid flow direction (19).

31. Device according to one of claims 21 to 30, wherein a control device for automatic pressure regulation is provided, wherein the control device is designed to convert the data obtained from the measuring device (22) into control data in order to control the pressure.

32. Device according to one of claims 21 to 31, wherein the enveloping device (21) is arranged around the hot extrudate (8), in particular in a high-temperature region (20).

33. Device according to claim 32, wherein the enveloping device (21) is formed from a ceramic material or glass, in particular quartz glass.

34. Device according to claim 32 or 33, wherein the enclosing device (21) is formed from at least one or more compounds from the following group: nitrides, oxides, carbides.

35. Device according to one of claims 32 to 34, wherein the enveloping device (21) is transparent. AMENDED SHEET (ARTICLE 19)

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