Film machine and method for producing a film track and use of a film material melting roller device

Description

[0001] The invention relates to a film plant for producing a film web, in particular a cast film or calender plant, with a machine direction along which the film web is transported through the film plant, with a roller device processing a film material melt comprising at least one work roll, with tempering devices for thermally treating the film web and with a stretching device for stretching the film web.

[0002] The invention further relates to a method for producing, in particular for casting or smoothing rolling, a film web, in which a film material melt is fed to a roller device processing the film material melt in question, having at least one film production roller, and this film material melt is formed into the film web by means of the at least one film production roller, and in which the film web is subsequently fed to different tempering devices and at least one stretching device.

[0003] The invention also relates to a use of a roller device for processing foil material melt.

[0004] In particular, generic film systems for producing a film web are known from the state of the art, specifically as cast film systems or as calender systems.

[0005] The US-American patent application US 2 586 820 A discloses a method for producing a film web, in which a film material melt is fed to a roller device processing the film material melt in question, having at least one film production roller, and this film material melt is formed into the film web by means of the at least one film production roller, and in which the film web is subsequently fed to different and at least one stretching device, wherein the stretching temperature required for a stretching process that can be carried out on the stretching device is generated entirely or at least to 50%, preferably at least to 80% or more, by means of the roller device processing a film material melt.

[0006] US Patent Application Nos. US 2017 246 786 A1 and US 2010 090 364 A1 disclose methods for producing a structured, microporous, breathable film. A polyolefin melt containing an inorganic filler and a pigment is extruded and cast onto the surface of a chill roll, and the quenched film is stretched to form the structured, microporous, and breathable film.

[0007] German patent application DE 10 2005 027 085 describes a process for the thermal treatment of a thermoplastic film web to be stretched monoaxially or biaxially, whereby energy consumption and equipment requirements are reduced through the use of selectively transformed infrared radiation. The selectively transformed infrared radiation emits wavelengths that can be adapted to the absorption capacity of the film web to be stretched, e.g., from polyamide, polypropylene, or polyester. The selectively transformed infrared radiation is achieved by coating the outer surface of the emitter of a medium-wave radiator, for example, with a ceramic layer as a functional ceramic.The international patent application WO 2015 / 175593 A1 discloses a film system for producing a film web, with a machine direction along which the film web is transported through the film system, with a roller device for processing a film material melt, comprising at least one film production roller, with tempering devices for thermally treating the film web and with a stretching device for stretching the film web, wherein the stretching device is arranged behind the at least one film production roller in the machine direction, bypassing a critical cooling section, wherein a distance and / or a transfer section between the at least one film production roller and an input roller of the stretching device is less than 1000 mm and wherein the stretching device comprises at least one temperature-controlled stretching roller.The invention is based on the object of further developing generic film systems for producing a film web, but also related methods, in order to achieve improved film properties.

[0008] The object of the invention is achieved according to a first aspect by a film plant for producing a film web with a machine direction along which the film web is transported through the film plant, with a roller device processing a film material melt comprising at least one film production roller or a film production gap, with tempering devices for thermally treating the film web and with a stretching device for stretching the film web, wherein the film plant is characterized in that the stretching device is arranged behind the at least one film production roller in the machine direction, bypassing a critical cooling section.

[0009] Because the stretching device is arranged behind the at least one film production roller and / or accordingly also the film production gap in the machine direction, bypassing a critical cooling section, it is possible to stretch the film web at the temperature still inherent in it with regard to the film material melt at a time at which the film web has not yet cooled down to below a critical stretching temperature.

[0010] This allows the film properties to be significantly improved. In particular, mechanical properties in the longitudinal direction of the film can be significantly improved.

[0011] In addition, the entire film line can be operated particularly efficiently in terms of energy; for the simple reason that energetically unfavorable cooling of the film web or film material after removal from the film production roller or film production gap and feeding to the stretching device is avoided or at least significantly reduced, thus making additional reheating of the film web or film material to, or preferably into, the required stretching temperature unnecessary.

[0012] On the other hand, the present film line is extremely compact, as additional energy-intensive heating devices are not required, as the film web does not cool down below a critical stretching temperature on a section between the roller device processing the film material melt and the stretching device.

[0013] First of all, it should be noted that in the context of this patent application, indefinite articles and indefinite numerical expressions such as "one...", "two...", etc., should generally be understood as "at least one...", "at least two...", etc., unless it is clear from the context or the specific text of a particular passage that only "exactly one...", "exactly two...", etc., are meant.

[0014] At this point, it should also be noted that, in the context of this patent application, the term "in particular" should always be understood as introducing an optional, preferred feature. The term should not be understood as "and indeed" or "namely."

[0015] Furthermore, the term "film line" describes a system by which a wide variety of films can be produced from a film material melt, such as a molten granulate or the like. The film material melt is preferably in the form of a plastic melt.

[0016] In particular, the invention relates to cast film systems or calender systems by means of which a film material melt can be rolled into a film web and thus also into a desired film.

[0017] In this respect, with regard to the present film system, the film material melt is preferably applied in the form of a melt plume onto a casting roll by means of a suitable melt nozzle or, alternatively, is introduced into a roll gap between two smoothing rolls, so that a corresponding film web is produced from the film material melt with the aid of the casting roll or the smoothing rolls.

[0018] For the purposes of the invention, the term "film production roll" describes both such casting rolls and smoothing rolls. Accordingly, the "film production nip" described here is considered to be a corresponding roll nip on a smoothing system, with the film production nip then being formed by film production rolls.

[0019] In this respect, features which are explained with reference to a film-producing roller also apply to a film-producing gap in the context of the present invention, even if this does not need to be explicitly described at corresponding points in order to avoid repetition.

[0020] Since such cast film systems or polishing stack systems are already well known from the state of the art, further functional principles will not be discussed here.

[0021] The term "rolling device for processing foil material melt" essentially refers to the aforementioned devices, which are characterized either by at least one casting roll or at least two smoothing rolls, which create a roll gap between them, whereby such a rolling device can be constructed in different ways.

[0022] For example, the present film material melt processing roller device can be assigned an extrusion unit with a corresponding melt nozzle, by means of which the film material melt can be provided to the respective film production roller.

[0023] The term "film production roller" includes casting rollers or alternatively smoothing rollers, depending on which system is used to produce the film web in question.

[0024] The term "film web" in the sense of the invention describes a wide variety of films which are designed as flat films, whereby the present invention relates to areas of application of, for example, CPP films, barrier films, hygiene films, cast PET films, protective films, films made of PS or PP, mineral-filled films or the like, to show only a few possible applications by way of example.

[0025] The term "tempering devices" in the sense of the present invention describes all devices which act thermally on the film web in addition to the roller device which processes the film material melt and the stretching device, which can come into direct thermal or physical contact with the film web, in particular by means of tempering rollers.

[0026] Such tempering devices can in the present case comprise devices which, in particular with appropriately configured tempering rollers, can introduce heat into the film web or can also remove heat from the film web or can maintain a heat level on the film web.

[0027] In the context of the present invention, the term "critical stretching temperature" describes a temperature on or in the film web or the film material, whereby the critical stretching temperature can be in a temperature range between 70 °C and approximately 180 °C, depending on which film material is used or which film web is produced.

[0028] For the purposes of the present invention, the term "critical cooling section" refers to a section between the roll device processing the film material melt and the stretching device, along which the film web is transported in the machine direction through the film line. The critical cooling section is designed such that the thermal energy inherent in the film web does not critically approach or drop below a critical stretching temperature before the film web is transferred to the stretching device, particularly from the film production roll.

[0029] In the present case, it was recognized that the film plant can be significantly further developed with regard to its energy efficiency if the stretching temperature required for a stretching process that can be carried out on the stretching device can be generated entirely or at least to 50%, preferably at least to 80% or more, by means of the roller device processing a film material melt.

[0030] This advantageously prevents the film temperature from falling below the stretching temperature after the film web leaves the roller device processing the film material melt and before reaching the stretching device, so that the film web does not have to be additionally heated or hardly needs to be heated additionally for a stretching process in between.

[0031] In order to avoid a critical cooling section between the roller device processing the film material melt and the stretching device, a transfer section or intermediate section between the roller device processing the film material melt and the stretching device can be designed in various ways.

[0032] For example, infrared heaters or the like can be arranged on such a transfer section in order to avoid critical cooling of the film web after removal from the film production roller in the sense of the invention, which would, however, again have an adverse effect on the energy balance of the present film system.

[0033] However, it is particularly advantageous if the roller device processing the film material melt and the stretching device are arranged so closely to one another that the transfer section between them is significantly shortened, so that a critical cooling section cannot even occur.

[0034] Thus, it is advantageous if a distance between the at least one film-producing roller or the film-producing gap and an input roller of the stretching device is less than 1000 mm or less than 800 mm, preferably less than 500 mm or less.

[0035] Preferably, this distance or transfer distance should not be less than 200 mm or 250 mm.

[0036] In this respect, it is expedient in this context if a distance and / or a transfer distance between the at least one film production roller and an input roller of the stretching device is more than 200 mm or more than 250 mm, preferably more than 450 mm.

[0037] Such a compact design makes it possible to simply avoid a critical cooling section within the meaning of the invention, thereby significantly improving the energy balance of the film system compared to the prior art. In particular, this allows the film properties to be improved, as already mentioned above.

[0038] In other words, the stretching device is arranged so close to the roller device processing the film material melt that the film web produced is preferably stretched directly with the heat still inherent in it from the casting process or smoothing process, i.e., so to speak, from the first heat of the film web.

[0039] In other words, this means that the stretching temperature of the film for stretching on the stretching device ideally originates entirely from the heat of the casting-rolling or smoothing-rolling process, allowing the present film line to be operated extremely energy-efficiently. Even if only 10% of the stretching temperature originates from the heat of the casting-rolling or smoothing-rolling process, the film line can still be operated more efficiently than in the prior art, in accordance with the invention.

[0040] A significant energy improvement can already be achieved if more than 80% of the required stretching temperature is generated by the roll device processing the film material melt, i.e. comes from the heat of the casting-rolling process or the smoothing-rolling process.

[0041] In this respect, it is advantageous if the film system is characterized by a transfer section between the at least one film production roller or the film production gap, and an input roller of the stretching device, wherein the transfer section is less than 1000 mm or 800 mm, preferably less than 500 mm or less, but preferably more than 250 mm.

[0042] While the distance between the roller device processing the film material melt and the stretching device preferably describes the actual distance between the two aforementioned components of the film system, i.e. the air line, the transfer line can also be straight, but in contrast, also curved between the roller device processing the film material melt and the stretching device.

[0043] The distance or the transfer distance can be selected depending on the type of roller device used to process the film material melt, the film material or plastic material, the thickness of the film web or similar, and the resulting cooling or cooling rate on the film web.

[0044] For example, for thicker film webs, a distance or transfer distance of 1000 mm can be selected, while for thinner film webs or for film materials that require a higher stretching temperature, a shorter distance or transfer distance appears to be necessary, for example 500 mm or less.

[0045] A preferred embodiment provides, for example, that the stretching device is arranged in the machine direction behind the film-producing roller in such a way that the film web leaving the film-producing roller can be transferred directly to the stretching device. By positioning the stretching device directly behind the roller device processing the film melt, it can be ensured that the film web is transferred directly to the stretching device with the least possible heat loss from the roller device processing the film melt, in particular from the film-producing roller and thus possibly also from the film-producing gap, so that additional heating or reheating of the film web before the actual stretching process can be avoided.

[0046] In the context of the present invention, the term "directly" describes that the stretching device is placed or arranged behind the roller device processing a film material melt without the interposition of another technical device, such as an additional tempering device, such as a tempering roller, or another roller, be it a deflection roller, a guide roller, a drive roller or the like.

[0047] Depending on the design and application of the respective film system or the film to be produced, it is advantageous if the stretching device comprises a film web removal roller, by means of which the film web can be removed from the film production roller. This ensures that the film web can be removed directly from the film production roller by a component of the stretching device, thereby significantly reducing the distance or transfer path between the film production roller and the stretching device. With this design variant, critical cooling of the film web can be almost completely eliminated due to the essentially negligible distance or transfer path.

[0048] Should such a direct film transfer between the roller device processing the film melt and the stretching device not be possible or not seem practical, for example due to increased quality requirements for the film web to be produced, it is alternatively advantageous if the stretching device is arranged downstream of the film production roller in the machine direction such that the film web leaving the film production roller can first be transferred to a pre-tempering device and then to the stretching device. Using such a pre-tempering device, a more uniform temperature control of the film web or a more uniform temperature distribution across the film web can be achieved, which can significantly improve the quality of the stretching process and thus the overall quality of the film web.

[0049] In this respect, such a pre-tempering device is preferably provided for equalizing a temperature within or on the film web, preferably between the stretching device or an input roller of the stretching device and the roller device processing the film material melt or its at least one film production roller and / or film production gap.

[0050] In this context, it is advantageous if the pre-tempering device comprises at least one film pre-tempering roller, by means of which the film web can be pre-tempered to a temperature above 70 °C, preferably between 90 °C and 120 °C. The temperatures proposed here allow the film web to be tempered such that the temperature of the film web lies within a required stretching temperature.

[0051] If such a pre-tempering device is provided, it is possible, for example, for the stretching device to operate without temperable rollers.

[0052] Cumulatively or alternatively, it is further advantageous if the stretching device comprises at least one temperature-controlled stretching roller.

[0053] On the one hand, this allows the required stretching temperature on the film web to be adjusted even more optimally.

[0054] On the other hand, the film web can be heated directly by the stretching device or the temperature already inherent in the film web can be maintained in a simple design, even if an additional pre-tempering device is to be dispensed with, for example for reasons of space.

[0055] It is particularly advantageous if the film web can be stretched by means of the stretching device between 0.5% and 5%, or more than 5%, in any case in the machine direction, preferably by 50% or more, often up to 1000%.

[0056] It is understood that the present stretching device can be designed in a variety of ways in order to stretch or extend the film web in the sense of the present invention in the desired or suitable manner in the machine direction and / or transversely to the machine direction, as a stretching process is often also called.

[0057] For example, if the stretching device includes a flatness package, the film web can easily be stretched between 0.5% and 5%.

[0058] If the stretching device cumulatively or alternatively includes an MDO device, the film web can also be stretched by more than 5% without any problem.

[0059] An "MDO" device stands for "Machine Direction Orientation", i.e. for the orientation of plastic molecules in the machine direction, i.e. the transport direction of the film material or the film web through the film system in question.

[0060] Since such flatness packages or "MDO" devices are already well known from the state of the art, their further structure or functionality will not be discussed further here.

[0061] The object of the invention is further achieved according to a second aspect by a method for producing, in particular for casting rolling or smoothing rolling, a film web, in which a film material melt is fed to a roller device processing the film material melt in question, having at least one film production roller and / or a film production gap, and this film material melt is formed into the film web by means of the at least one film production roller and / or the film production gap, and in which the film web is subsequently fed to different temperature control devices and at least one stretching device, wherein the method is characterized in that the stretching temperature required for a stretching process that can be carried out on the stretching device is generated entirely or at least to 50%, preferably at least to 80% or more, by means of the roller device processing a film material melt.

[0062] If the stretching temperature required at the stretching device originates exclusively or at least partly from the heat of the roller device processing the film material melt, additional heating of the film web before the stretching device can be omitted or at least greatly reduced, whereby the existing film plant can be operated more efficiently.

[0063] Flat films in particular are nowadays mainly produced using the casting or calendering process.

[0064] Films produced in this way have mechanical properties which are essentially influenced by the processing of the raw materials used and by the raw materials themselves.

[0065] By stretching the films or film webs, improved mechanical properties or better optical properties can be achieved.

[0066] To date, this stretching has primarily been done inline, by reheating a cooled film web and then stretching it in a one- or two-stage stretching process. This is followed by annealing and cooling.

[0067] A disadvantage of this state-of-the-art technology, however, is that the stretching process only takes place after repeated heating of a previously cooled film web. Therefore, such previously known processes are energetically pointless or ineffective.

[0068] In addition, the film web already has a significantly higher crystalline content once it has cooled, making it more difficult or even impossible for the plastic molecules of the film material to reorient within the film web. In particular, mechanical properties in the longitudinal direction of the film can be significantly improved.

[0069] Advantageously, in the processes proposed here, heat energy is neither unnecessarily extracted from the film web nor additionally added, so that the production of films or film webs can be carried out much more effectively.

[0070] The object of the invention is also achieved according to a third aspect by a method for producing, in particular for casting rolling or smoothing rolling, a film web, in which a film material melt is fed to a roller device processing the film material melt in question, having at least one film production roller and / or a film production gap, and this film material melt is formed into the film web by means of the at least one film production roller and / or the film production gap, and in which the film web is subsequently fed to different tempering devices and at least one stretching device, wherein the method is characterized in that the film web is stretched exclusively with the aid of the heat from the film material melt.

[0071] Advantageously, the film web is stretched on the stretching device using the aforementioned process from the first heat, i.e., essentially the heat of the film material melt, so that this process can also be carried out particularly efficiently. Additional heat sources, such as a heatable film production roller, a heatable stretching roller, or the like, are preferably dispensed with. In particular, mechanical properties in the longitudinal direction of the film can be significantly improved.

[0072] Optionally, it is advantageous if the film web is additionally stretched using heat from the roll device processing the film material melt and the stretching device, in addition to the heat from the film material melt. This allows the film web to be additionally thermally treated with very little additional energy consumption, both before and / or during stretching.

[0073] According to a fourth aspect, the object of the invention is also achieved by a method for producing, in particular for casting or smoothing a film web, in which a film material melt is fed to a roller device processing the film material melt in question, having at least one film production roller and / or a film production gap, and this film material melt is formed into the film web by means of the at least one film production roller and / or the film production gap, and in which the film web is subsequently fed to different tempering devices and at least one stretching device, this method being characterized in that the film web, after leaving the at least one film production roller and / or the film production gap, is stretched by means of a stretching device, bypassing further tempering devices.

[0074] Advantageously, the heat from the film melt can be used directly for the subsequent stretching process, eliminating the need for additional temperature control equipment upstream of the stretching device. This allows the film line used for the process to be particularly compact. In particular, mechanical properties in the longitudinal direction of the film can be significantly improved.

[0075] In this respect, it is advantageous if the film web is first stretched after leaving the at least one film production roller and / or the film production gap, and only then is it fed to further tempering devices for thermally treating the film web.

[0076] In other words, this means that the film web is stretched without any critical intermediate cooling due to a critical cooling section.

[0077] For example, it is advantageous for this purpose if the stretching device is arranged between the at least one film production roller and / or the film production gap, and one of the tempering devices, wherein the stretching device also comprises a film web removal roller which is arranged directly downstream of the film production roller.

[0078] In this respect, it is expedient if the stretching device is arranged in the machine direction between the at least one film production roller and / or the film production gap, and a tempering device and / or a cooling device of the film system.

[0079] In the context of the invention, the term "tempering device" describes a heating device which serves to remove residual stress in the film web and which is carried out, for example, under tensile stress (advance).

[0080] Preferably, the temperature is controlled to just below the actual melting temperature of the film web or film material.

[0081] It is also advantageous if the advance is adjustable on the tempering device.

[0082] In the sense of the invention, the term "cooling device" describes a device by means of which the film web can be cooled preferably to almost ambient temperature.

[0083] This makes it possible to freeze the orientation of plastic molecules in the film web or in the film material.

[0084] This cooling device may comprise cooling rollers by means of which an advance can be adjusted.

[0085] The term "overfeed" describes a process in which a roller and / or a pair of rollers can be operated at different speeds compared to another roller or another pair of rollers, either temporarily or permanently, which results in the film material being stretched or drawn along the film web.

[0086] According to a fifth aspect of the invention, the present object is also achieved by a method for producing, in particular for casting or smoothing rolling, a film web, in which a film material melt is fed to a roller device processing film material melt with at least one film production roller and / or a film production gap, and this film material melt is formed into the film web by means of at least one film production roller and / or the film production gap, and in which the film web is subsequently fed to different tempering devices and at least one stretching device, wherein the method is characterized in that the film web is fed to a pre-tempering device after leaving the at least one film production roller and / or the film production gap, and is then transferred from the pre-tempering device directly to a stretching device,by means of which the film web is stretched.,

[0087] Advantageously, any different temperature ranges that may be present in the film web can be equalized by means of the pre-tempering device, so that ideally there are no or only negligible different temperature ranges with different temperature levels on the film web.

[0088] In all proposed processes, energy efficiency is a particular focus, as it avoids excessive cooling of the film web in the machine direction after the film material melt has been processed by the roller device, as has been the case so far in the state of the art.

[0089] Rather, the film material web is essentially immediately stretched with the thermal energy still inherent in it from the film material melt, whereby additional heating processes can preferably be completely avoided.

[0090] In this respect, it is advantageous if the film web is always kept above a critical stretching temperature, in particular at least above a temperature of 50 °C or, better still, 80 °C, after being removed from the film production roller.

[0091] This makes it possible to carry out a very high-quality stretching process solely due to the inherent heat from the film material melt. In particular, mechanical properties in the longitudinal direction of the film can be significantly improved.

[0092] If necessary, the film web is conveniently brought to the desired stretching temperature by means of the pre-tempering device, whereby the pre-tempering is often between 90 °C and 110 °C.

[0093] It is understood that the present pre-tempering device can be designed in a variety of ways. For example, the pre-tempering device comprises at least one pre-tempering roller, preferably two pre-tempering rollers.

[0094] Ideally, both pre-tempering rollers can be driven individually so that the pre-tempering device can also be operated with an adjustable lead.

[0095] The film material can be cooled directly below its recrystallization temperature, or alternatively the film web temperature can be kept above this recrystallization temperature.

[0096] Cumulatively or alternatively, it is advantageous if the film web is tempered by means of at least one stretching roller of the stretching device after leaving the at least one film production roller.

[0097] Additional tempering can thus be carried out directly by means of the stretching device, wherein it is also conceivable that the function of the pre-tempering device can be at least partially taken over by means of the at least one stretching roller, preferably by means of several tempered stretching rollers, of the stretching device.

[0098] In any case, it is advantageous if the stretching device is arranged in the machine direction immediately behind a preheating device of the tempering devices and immediately before another tempering device.

[0099] In this case, a special embodiment variant can provide that the stretching device is arranged in the machine direction immediately behind the preheating device of the tempering device in front of further tempering devices, wherein the further tempering devices comprise a tempering device and a cooling device, and wherein the stretching device is arranged in the machine direction immediately before the tempering device.

[0100] Furthermore, it is particularly advantageous if the roller device processing the film material melt comprises at least one casting roller or at least two smoothing rollers forming a roller gap with one another.

[0101] Furthermore, it is advantageous if the film web is tempered at least once after leaving the casting roll, namely heated, immediately thereafter stretched and then tempered differently at least once more, preferably more than once.

[0102] According to a further aspect of the invention, the object is also achieved by a method for producing, in particular for casting or smoothing a film web, in which a film material melt is fed to a roller device processing the film material melt in question, having at least one film production roller, and this film material melt is formed into the film web by means of the at least one film production roller, and in which the film web is subsequently fed to different tempering devices and at least one stretching device, wherein the film web is stretched after leaving the at least one film production roller before the film web is fed to a tempering device of the tempering devices and / or a cooling device of the tempering devices.

[0103] In this method, the film web is specifically stretched by means of the stretching device after leaving the at least one film production roller, and only then is the film web fed to the tempering unit for removing residual stresses in the film web or to the cooling device for cooling the film.

[0104] In this respect, the film web passes from a casting roll or smoothing rolls to the stretching device before the film web is fed to the cooling device.

[0105] In this case, the cooling device may comprise at least four cooling rollers.

[0106] According to the invention, the film web is stretched at a significantly earlier stage than in previously known inline stretching units.

[0107] In this respect, the existing processes can be operated in a more energy-efficient manner.

[0108] Stretch values ​​that can be achieved are usually between 100% and 800%.

[0109] However, a so-called ironing operation can also be set on the stretching device, in which the film web is only pulled by 1% to 5% in order to remove flatness errors from the film, as already mentioned at the beginning.

[0110] According to the invention, the stretching takes place essentially by utilizing the "first heat".

[0111] In other words, this means that immediately after the actual film web production on the casting roll or between the calender rolls, the film web is stretched.

[0112] To even out the temperature on the film web, two additional heating rollers (pre-tempering rollers) can be installed downstream of the roller unit that processes the film material melt. This is immediately followed by the actual stretching unit, which can be a single- or two-stage unit. This is followed by annealing rollers of the tempering unit and chill rollers of the cooling unit.

[0113] According to a sixth aspect of the invention, the object is achieved by using a roller device that processes film material melt for heating a film web to stretching temperature for a stretching process on a film line that produces film web, which stretches immediately after the roller device that processes the film material melt.

[0114] While the film web inevitably passes through a presumably required stretching temperature range during its production by the roller device processing the film material melt, the film web usually cools to ambient temperature after leaving the roller device processing the film material melt, or at least well below a designated stretching temperature. Therefore, the roller device processing the film material melt has not yet been used to heat the film web for a subsequent stretching process.

[0115] However, this allows a film system in the sense of the invention to be operated much more efficiently in terms of energy.

[0116] Previously, such a roller device for processing film material melt was used for cooling the film material melt during the formation of a film web. However, it has been advantageously recognized that, with a corresponding design of a film system, this roller device for processing film material melt is also directly suitable as a thermal precursor for a stretching device of the film system, in order to provide the stretching temperature required for the stretching device on the film web.

[0117] It is understood that features of the solutions described above or in the claims may also be combined if necessary in order to be able to implement the advantages and effects that can be achieved in this case in a cumulative manner.

[0118] In addition, further features, effects and advantages of the present invention are explained with reference to the attached drawing and the following description, in which a film system is shown and described as an example.

[0119] The drawing shows the only figure schematically shows a model view of a film plant for producing a film web with a stretching device arranged behind a roller device processing a film material melt, bypassing a critical cooling section in the machine direction.

[0120] The film system 1 shown in Figure 1 is used to produce films 2, which are designed here as a flat film (not separately numbered) by way of example.

[0121] Such film systems 1 can be designed in a variety of ways, for example as a cast film system 3, as shown schematically in the illustration according to the single figure, as a calender system (not shown) or the like.

[0122] The cast film plant 3 shown differs in the sense of the invention from a polishing stack plant (not shown) essentially by a casting roll 4, which is placed on the input side or at the input 5 of the film plant 1, in contrast to polishing rolls (not shown) forming a roll gap (not shown) of a polishing stack plant.

[0123] In any case, the film plant 1 shown in the single figure is a cast film plant 3 with a casting roll 4, upstream of which is an extruder device 6 for producing a film material melt 7, wherein the extruder device 6 is shown by way of example only with regard to a wide spray nozzle 8, by means of which the film material melt 7 is applied in the form of a film material melt plume 9 onto the roll surface 10 of the casting roll 4.

[0124] By means of the casting roller 4, the film material melt strip 9 is formed into a film web 11.

[0125] The casting roller 4 is a chrome-plated steel roller (not numbered again) with a diameter of 1000 mm, which can be heated to at least 120 °C at the roller surface 10 at a temperature difference of + / - 1 °C. The casting roller 4 rotates with a rotation direction 15 around its casting roller axis 16. The film web 11 can be guided around the casting roller 4 with a wrap angle of at least 220 °.

[0126] With the aid of the casting roller 4, the film material melt 7 is cooled to below a recrystallization temperature of the film material melt 7 or is kept in a range of this recrystallization temperature of the film material melt 7, wherein the recrystallization temperature depends on the respective plastic film material to be processed.

[0127] In any case, the film system 1 with the casting roll 4 already described above comprises a roll device 18 for processing film material melt 7 with at least one film production roll 19, namely the casting roll 4 in this exemplary embodiment.

[0128] Furthermore, the film system 1 also comprises both a stretching device 20 and tempering devices 22, 23 and 24 for thermally treating the film web 11, wherein the film web 11 is transported in a meandering manner in the machine direction 26 through the film system 1 by the roller device 18 processing the film material melt 7, here in particular in the form of the casting roller 4.

[0129] In the embodiment shown in the single figure, the first tempering device 22 is a pre-tempering device 28, which is arranged directly downstream of the casting roll 4 and thus the roll device 18 processing the film material melt 7 in the machine direction 26. The pre-tempering device 28 has two corresponding pre-tempering rolls 29 and 30, both of which are designed as chrome-plated steel rolls with a diameter of 310 mm. The two pre-tempering rolls 29 and 30 can be tempered such that temperatures of 90 °C to 110 °C can be set on their respective roll surfaces (no longer explicitly numbered). The two pre-tempering rolls 29 and 30 are also characterized by a wrap angle of at least 160 °. Furthermore, they can be driven individually, whereby an advance on the pre-tempering device 28 can be adjusted.

[0130] The first tempering device 22 or the pre-tempering device 28 essentially serves to uniformly temper the film web 11 to the stretching temperature, wherein the stretching temperature is preferably above the respective recrystallization temperature of the film material melt 7.

[0131] In this embodiment, the second tempering device 23 is designed as a tempering device 32, which comprises two tempering rollers 33 and 34, each of which is a chrome-plated steel roller with a diameter of 310 mm. The tempering rollers 33 and 34 are arranged relative to one another in such a way that they each provide a wrap angle of 220° for the film web 11. An overfeed can also be adjusted on the tempering device 32.

[0132] By means of the tempering device 32, the film web 11 or the film material is tempered briefly below the melting temperature of the film material in order to thereby remove residual stresses in the film 2 or the film web 11 by introducing a tensile stress into the film web 11.

[0133] For this purpose, the first tempering roller 33 and the second tempering roller 34 can be heated such that they can be operated with surface temperatures of approximately 100 °C to 110 °C.

[0134] The temperature rollers 33 and 34 are often also referred to as annealing rollers.

[0135] Furthermore, the film system 1 according to the embodiment shown comprises, with regard to the third tempering device 24, a cooling device 36 which, viewed in the machine direction 26, is arranged immediately downstream of the tempering device 32, wherein the film web 11 is cooled to almost ambient temperature only at this point in time by means of the cooling device 36, whereby the orientation of the film material molecules is finally "frozen" only at the cooling device.

[0136] In this embodiment, the cooling device 36 comprises two cooling rollers 37 and 38, which in turn are designed as chrome-plated steel rollers, each with a diameter of 310 mm.

[0137] The two cooling rollers 37 and 38 can be tempered in such a way that a maximum surface temperature of 100 °C can be provided on their respective roller surfaces.

[0138] The cooling rollers 37 and 38 are arranged relative to one another in such a way that they each ensure a wrap angle of at least 220° for the film web 11.

[0139] In addition, the stretching device 20 has, at least in this embodiment, two stretching roller groups 40 and 41. Each of the stretching roller groups 40 and 41 consists of a first stretching roller contact roller pair 42 and 43, respectively, and one auxiliary roller 44 and 45, respectively.

[0140] The first stretching roller-contact roller pair 42 comprises a rubberized stretching roller 46 and a contact roller 47 corresponding thereto.

[0141] Accordingly, the second stretching roller-contact roller pair 43 also has a rubberized stretching roller 48 and a contact roller 49 corresponding thereto.

[0142] While the first and second stretching rollers 46 and 48 each comprise a rubberized steel roller with a diameter of 210 mm, the first and second contact rollers 47 and 49 each consist of a chrome-plated steel roller with a diameter of 210 mm.

[0143] At least one of the two stretching rollers 46 and 48 can be tempered, preferably in such a way that a surface temperature of approximately 120 °C can be set on the respective stretching roller 46 and 48.

[0144] Furthermore, the individual stretching roller contact roller pairs 42 and 43 are driven individually, so that a stretching factor or an overfeed can preferably be continuously adjusted on the stretching device 20.

[0145] By means of the stretching device 20, the film 2 or the film web 11 can be stretched or extended in a ratio of 1:4.

[0146] Furthermore, the stretching device 20 has a stretching gap length 50, which is preferably adjustable.

[0147] It is advantageous if the stretching gap length 50 is designed to be as small as possible so that the stretching device 20 is as compact as possible and in particular the risk is reduced that the film web 11 cools down unfavorably within the stretching device 20 or between the two stretching roller contact roller pairs 42 and 43 of the stretching device 20.

[0148] The two auxiliary rollers 44 and 45 have a significantly smaller diameter than the stretching rollers 46 and 48 respectively and the contact rollers 47 and 49 respectively, but are also each formed by a chrome-plated steel roller.

[0149] Advantageously, the film plant 1 in the embodiment shown in the single figure is configured such that the stretching device 20 is arranged behind the at least one film production roller 19 or the casting roller 4, bypassing a critical cooling section 53 in the machine direction 26.

[0150] The critical cooling section 53 is shown and drawn only symbolically according to the illustration in the single figure in order to schematically illustrate its position within the present film system 1.

[0151] In this embodiment, it corresponds to a transfer section 54 along which the film web 11 is guided between the melting roller 4 and an input roller 58 of the stretching device 20.

[0152] In a very simple case (not shown here), the input roller 58 can also represent a film web removal roller 60, by means of which the film web 11 can be removed from the melting roller 4.

[0153] In other words, this means that the stretching device 20 is arranged relative to the roller device 18 processing the film material melt 7 or its film production roller 19 or in particular the present casting roller 4 in such a way that the risk of unintentional critical cooling of the film web 11 on the transfer section 54 can ideally be excluded after the film web 11 has left the roller device 18 processing the film material melt 7 and reached the stretching device 20 or the input roller 58 of the stretching device 20.

[0154] The term "critical cooling section" in the sense of the present invention describes a section (transfer section 54) running essentially in the machine direction 26, which the film web 11 travels from the film production roller 19 to the input roller 58 of the stretching device 20, wherein this section can run in a straight line or, as shown in this embodiment according to the single figure, can be designed with multiple curves.

[0155] The term "critical cooling section" in the sense of the invention further describes a section along which the film web 11 can cool down in the prior art to below a stretching temperature of the respective film web material or the respective film web 11, wherein the respective stretching temperature also depends on the respective film material used.

[0156] The critical cooling section 53 or the transfer section 54 begins with the detachment of the film web 11 from the film production roller 19 or the casting roller 4 of the roller device 18 processing the film material melt 7.

[0157] The critical cooling section 53 or the transfer section 54 accordingly ends with the contact of the film web 11 with the stretching device 20 or in particular with the input roller 58 of the stretching device 20.

[0158] According to a very simple embodiment of the present invention or of the film system 1, a critical cooling section 53 within the meaning of the present invention can be avoided if the input roller of the stretching device simultaneously represents a film web removal roller 60, by means of which the film web 11 can be directly removed from the film production roller 19. However, this is not the case in the exemplary embodiment of the film system 1 shown in the single figure, since the pre-tempering device 28 is still located between the stretching device 20 and the roller device 18 processing the film material melt 7. If such a pre-tempering device 28 were to be omitted in an alternatively designed film system 1, the previously described input roller 58 of the stretching device 20 would take over the role of the film web removal roller 60.

[0159] However, in order to avoid the risk of a cooling section 53 being formed on the film system 1 which is critical in the sense of the invention, the stretching device 20 is arranged relative to the roller device 18 processing the film material melt 7 in such a way that the distance 62, in particular between the film production roller 19 or casting roller 4 and the input roller 58 (film web removal roller 60) of the stretching device 20 is less than 1000 mm or less than 800 mm, preferably less than 500 mm or 100 mm.

[0160] In order to ensure that the pre-tempering device 28 still has space between the casting roller 4 and the input roller 58, the distance 62 in the embodiment according to the single figure is less than 1000 mm but more than 800 mm.

[0161] According to the embodiment shown in the single figure, the critical cooling of the film web 11 during the transfer from the roller device 18 processing the material melt 7 to the stretching device 20 is prevented by the pre-tempering device 28 arranged therebetween.

[0162] In other words, this means that a critical cooling section 53 within the meaning of the invention exists neither between the pre-tempering device 28 and the roller device 18 processing the film material melt 7 nor between the pre-tempering device 28 and the stretching device 20.

[0163] In this respect, the film system 1 according to the embodiment of the single figure is designed such that the stretching device 20 is arranged in the machine direction 26 behind the film production roller 19 or casting roller 4 in such a way that the film web 11 leaving the film production roller 19 or casting roller 4 is transferred to the pre-tempering device 28 and then to the stretching device 20.

[0164] The advantage of the stretching device 20 being arranged behind the at least one film production roller 19 in the machine direction 26, bypassing a critical cooling section 53, is that the film web 11 is stretched exclusively with the aid of the heat from the film material melt 7.

[0165] In this respect, the stretching temperature required for a stretching process that can be carried out on the stretching device 20 is generated entirely or at least to 80% by means of the roller device 18 processing a film material melt 7.

[0166] In other words, this means that, in the sense of the invention, stretching is carried out exclusively with the aid of the heat inherent in the film material or the film web 11.

[0167] This advantageously prevents the film material of the film web 11 from cooling below a still reasonable stretching temperature.

[0168] It is understood that the heat from the roller device 18 processing the film material melt and the stretching device 20, which may additionally have a thermal effect on the film material or the film web 11, is negligible.

[0169] Depending on the film material from which the film 2 or the film web 11 to be produced is to be produced or the type of film 2 or film web 11 is involved, it is advantageous if the film web 11 is fed to a pre-tempering device 28 after leaving the at least one film production roller 19 and is then transferred from the pre-tempering device 28 directly to the stretching device 20, as is shown in the single figure.

[0170] However, by means of the pre-tempering device 28, it is very possible to even out the temperature or heat within the film web 11 as much as possible, whereby the stretching or drawing quality of the immediately subsequent stretching process can be increased even further.

[0171] At this point, it should be explicitly pointed out that features of the solutions described above or in the claims and / or the single figure can also be combined if necessary in order to be able to implement or achieve the explained features, effects and advantages accordingly in a cumulative manner.

[0172] It is understood that the exemplary embodiment explained above is merely a first embodiment of a film system according to the invention. Therefore, the embodiment of the invention is not limited to this exemplary embodiment.

[0173] List of reference symbols used 1 Film system 2 Films 3 Cast film system 4 Casting roll 5 Inlet 6 Extruder device 7 Film material melt or plastic melt 8 Wide injection nozzle 9 Film material melt plume 10 Roll surface 11 Film web 15 Direction of rotation 16 Casting roll axis 18 Roll device 19 Film production roll 20 Stretching device 22 First tempering device 23 Second tempering device 24 Third tempering device 26 Machine direction 28 Pre-tempering device 29 First pre-tempering rolls 30 Second pre-tempering roll 32 Tempering device 33 First tempering roll 34 Second tempering roll 36 Cooling device 37 First cooling roll 38 Second cooling roll 40 First stretching roll group 41 Second stretching roll group 42First stretching roller-contact roller pair 43Second stretching roller-contact roller pair 44First auxiliary roller 45Second auxiliary roller 46First stretching roller 47First contact rollers 48Second stretching roller 49Second contact rollers 50Stretching gap length 53Cooling section 54Transfer section 58Input roller 60Film web take-off roller 62Gap

Claims

1. A film plant (1) for producing a film web, in particular a cast film plant or smoothing calender plant (3), having a machine direction (26) along which the film web (11) is conveyed through the film plant (1), having a roller device (18) which processes a film material melt (7), comprising at least one film-producing roller (19), having temperature control devices (22, 24) for thermally treating the film web (11) and having a stretching device (20) for stretching the film web (11), wherein the stretching device (20) is arranged downstream of the at least one film-producing roller (19) in the machine direction (26), circumventing a critical cooling section (53), wherein a distance (62) and / or a transfer section (54) between the at least one film-producing roller (19) and an input roller (58) of the stretching device (20) is less than 1000 mm or less than 800 mm, preferably 500 mm or less and more than 200 mm or more than 250 mm, preferably more than 450 mm, wherein the stretching device (20) is arranged downstream of the film-producing roller (19) in the machine direction (26) in such a way that the film web (11) leaving the film-producing roller (19) can initially be transferred to a pre-temperature control device (22, 28) and subsequently to the stretching device (20) and the stretching device (20) comprises at least one stretching roller which can be tempered, wherein characterised in that the pre-temperature control device (22, 28) comprises at least one film pre-temperature control roller, by means of which the film web (11) can be pre-tempered at a temperature above 70°C, preferably between 90°C and 120°C.

2. A method for operating a film plant (1) according to Claim 1, characterised in that the stretching temperature required for a stretching process which can be carried out at the stretching device (20) is produced at least by 50%, preferably at least by 80% or more, by means of the roller device (18) which processes a film material melt (7).