A method of processing a thermoplastic film

Abstract

This invention relates to a method of processing a thermoplastic film, the method comprising: (a) providing a length of thermoplastic film with a first outer edge and a second outer edge, wherein the thermoplastic film comprises a polyaryletherketone (PAEK) polymer, wherein a thickness of the film is between about 2 μm and about 250 pm; (b) passing the length of thermoplastic film over an arc of a first film-spreading roller configured to tension the thermoplastic film in a lateral direction; (c) subsequent to (b), measuring a thickness profile of the thermoplastic film by passing the length of thermoplastic film past a thickness measurement device; wherein the first film-spreading roller is substantially cylindrical and substantially linear, and wherein the first film-spreading roller comprises a first tensioning region and a second tensioning region, wherein the first tensioning region and the second tensioning region are each formed from a length of removably adherable tape, and wherein step (b) comprises directing the first outer edge of the thermoplastic film to engage with the first tensioning region and the second outer edge of the thermoplastic film to engage with the second tensioning region.

Description

[0001] A Method of Processing a Thermoplastic Film

[0002] TECHNICAL FIELD

[0003] The present invention relates to a method of processing a thermoplastic film, an apparatus for processing a thermoplastic film, and a thermoplastic film processed according to the method disclosed herein and a thermoplastic film. Further, the present invention relates to the production of ultrathin thermoplastic films, in particular, ultrathin PAEK films.

[0004] BACKGROUND TO THE INVENTION

[0005] Methods for processing thermoplastic films may include a film-spreading step, which helps to prevent and eliminate creases and wrinkles that may develop in the film prior to and during winding. The formation of creases and wrinkles in the film is known to have a negative effect on both the aesthetic properties and the technical performance of the film and is therefore to be avoided.

[0006] Film-spreading apparatus includes items such as “banana” and spreader rollers, which are used in the production of mainstream thermoplastic films (e.g., polyethylene). However, such apparatus has been found to be unsuitable for processing other types of polymers (e.g., PAEK), where its weight can place excessive tension on the film and even result in elastic deformation. Film-spreading apparatus is typically used prior to the film being wound, which helps to prevent and eliminate creases and wrinkles that may be introduced as the film is transferred onto the core.

[0007] An important factor in devising methods of processing thermoplastic films is to provide films of a consistent and repeatable thickness. It is also important that different batches of film are of a consistent thickness. Thermoplastic films have many high-performance uses, for example, in acoustic equipment, where example products include speakers and receivers.

[0008] Accurately measuring the thickness of the thermoplastic film as it is processed is important to ensure that it is of the correct thickness, e.g., for use in acoustic components. Undulations may be observed on the surface of the film as it is processed, and these reduce the reliability of the thickness measurement by distorting the actual thickness values. For example, if undulations are present, the thickness may be measured through a diagonally-oriented part of the film, resulting in a seemingly thicker cross-section. Further the presence of creases and wrinkles present in random positions across the film, mean that the lateral thickness profile cannot be accurately measured. Creases and wrinkles generate noise in the measurement which affects the final thickness profile. Further there is a need to remove creases and wrinkles prior to winding a film on a core. Creases and wrinkles affect the aesthetic appearance of the thermoplastic film when it is wound onto the core. They may also result in yield losses when the film is used, for example, as a lamination or covering.

[0009] There is a need for an accurate way to measure the thickness of a PAEK film. There is a need for a method of producing a PAEK film of uniform thickness. There is a need to reduce undulations in a PAEK film. There is a need to reduce wrinkles and creases in a PAEK film. Further, there is a need to be able to adjust a process for different thicknesses and widths of film. There is a need to reduce or prevent witness marks on a PAEK film. An objective of the present invention is to seek to alleviate the above identified problems.

[0010] SUMMARY OF THE INVENTION

[0011] In a first aspect, there is provided a method of processing a thermoplastic film, the method comprising:

[0012] (a) providing a length of thermoplastic film with a first outer edge and a second outer edge, wherein the thermoplastic film comprises a polyaryletherketone (PAEK) polymer, wherein a thickness of the film is between about 2 pm and about 250 pm;

[0013] (b) passing the length of thermoplastic film over an arc of a first film-spreading roller configured to tension the thermoplastic film in a lateral direction;

[0014] (c) subsequent to (b), measuring a thickness profile of the thermoplastic film by passing the length of thermoplastic film past a thickness measurement device; wherein the first film-spreading roller is substantially cylindrical and substantially linear, and wherein the first film-spreading roller comprises a first tensioning region and a second tensioning region, wherein the first tensioning region and the second tensioning region are each formed from a length of removably adherable tape, and wherein step (b) comprises directing the first outer edge of the thermoplastic film to engage with the first tensioning region and the second outer edge of the thermoplastic film to engage with the second tensioning region.

[0015] In a second aspect, there is provided an apparatus configured measure the thickness of a thermoplastic film, comprising: a first film-spreading roller and a thickness measurement device; wherein the first film-spreading roller is substantially cylindrical and substantially linear, wherein the first film-spreading roller comprises a first tensioning region and a second tensioning region, wherein the first tensioning region and the second tensioning region are each formed from a length of removably adherable tape, wherein the thickness measurement device is configured to measure the thickness of a thermoplastic film after the thermoplastic film has passed over the arc of a first filmspreading device.

[0016] In a third aspect, there is provided a thermoplastic film processed according to the method of the first aspect.

[0017] In a fourth aspect, there is provided a thermoplastic film, wherein the thermoplastic film comprises a layer of thermoplastic film wound onto a core, wherein the thermoplastic film comprises a polyaryletherketone (PAEK) polymer, wherein a thickness of the film is between about 2 pm and about 50 pm; wherein a width of the film is between about 50 cm and about 250 cm and wherein the thermoplastic film is substantially free of undulations.

[0018] BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 shows a partial perspective of an apparatus used to process a thermoplastic film according to aspects of the present disclosure.

[0020] Figure 2 shows a cross-sectional perspective of an apparatus used to process a thermoplastic film according to aspects of the present disclosure.

[0021] Figure 3 shows an example schematic of a system used to process a thermoplastic film according to aspects of the present disclosure.

[0022] Figure 4a shows a thickness scan of a film not processed according to the invention.

[0023] Figure 4b shows a photograph of undulations of a film not processed according to the invention.

[0024] Figure 4c shows a schematic of undulations of a film not processed according to the invention.

[0025] Figure 5a shows a thickness scan of a film processed according to the invention.

[0026] Figure 5b shows a photograph of undulations of a film processed according to the invention.

[0027] Figure 5c shows a schematic of a film substantially free from undulations that has been processed according to the invention DETAILED DESCRIPTION

[0028] In a first aspect, there is provided a method of processing a thermoplastic film, the method comprising:

[0029] (a) providing a length of thermoplastic film with a first outer edge and a second outer edge, wherein the thermoplastic film comprises a polyaryletherketone (PAEK) polymer, wherein a thickness of the film is between about 2 pm and about 250 pm;

[0030] (b) passing the length of thermoplastic film over an arc of a first film-spreading roller configured to tension the thermoplastic film in a lateral direction;

[0031] (c) subsequent to (b), measuring a thickness profile of the thermoplastic film by passing the length of thermoplastic film past a thickness measurement device; wherein the first film-spreading roller is substantially cylindrical and substantially linear, and wherein the first film-spreading roller comprises a first tensioning region and a second tensioning region, wherein the first tensioning region and the second tensioning region are each formed from a length of removably adherable tape, and wherein step (b) comprises directing the first outer edge of the thermoplastic film to engage with the first tensioning region and the second outer edge of the thermoplastic film to engage with the second tensioning region.

[0032] The method described herein substantially removes undulations, creases and wrinkles from the thermoplastic film. Removing the undulations, creases and wrinkles from the thermoplastic film improves the quality of the thermoplastic film. This results in a reliable process where the resulting thermoplastic film is of consistent thickness and substantially free of undulations, creases and wrinkles.

[0033] Further, the film-spreading roller allows a more accurate thickness measurement to be obtained. By removing undulations, creases and wrinkles from the film before measuring its thickness, the accuracy of the thickness profile across its width is improved. The feedback returned to the extrusion die is also improved which, in turn, allows any irregularities identified in the thickness profile of the film to be rectified. Furthermore, the thickness of the film can be adjusted by increase or decreasing the longitudinal tension applied to the length of the thermoplastic film.

[0034] Moreover, processing the thermoplastic film using a film-spreading roller as described herein is less likely to damage the film than using “banana” and spreader rollers, which may introduce excessive tension and cause elastic deformation. PAEK films are particularly sensitive to tension and therefore a banana roller is not suitable for use with such films.

[0035] Consequently, use of the film-spreading roller confers advantageous control of the tension of the film that allows the thickness of the film to be measured accurately.

[0036] An advantage of using a removable adherable tape is that a film-spreading roller can be easily adjusted for films of different widths by adjusting the position of the tape and of different thicknesses by adjusting the thickness of the tape, such as the type of tape or the number of windings of the tape around the circumference of the first film-spreading roller. This provides a cost-effective and easy way of adjusting the roller for different films and allows the operator to tailor the film-spreading roller with ease. This is an advantage over needing to purchase a different roller for each film width and thickness.

[0037] Furthermore, the present invention reduces and preferably prevents any witness marks left on the film as the lateral tension in the film from the film-spreading roller can reduce the amount of longitudinal tension in the film and reduces the impact of the first and second tensioning areas on the film.

[0038] Preferably, a thickness of the film is between about 2 pm and about 100 pm, more preferably between about 2 pm and about 25 pm, more preferably between about 3 pm and about 12 pm, more preferably between about 2 pm and about 10 pm, most preferably between about 2 pm and about 5 pm. It is an advantage of the invention that undulations, wrinkles and creases can be removed from such thin films without using undue tension which could damage a film. Advantageously, films of such a thickness are suitable for use in high-performance acoustic components where it is particularly important that the films are of a known and uniform thickness.

[0039] Preferably, a width of the film is between about 30 cm and about 250 cm, preferably between about 50 cm and about 200 cm, preferably between about 100 cm and about 190 cm, preferably between about 130 cm and about 180 cm. Advantageously, films of such a width can be tensioned effectively by the film-spreading roller. Further advantageously, the positioning of the tape on the roller can be adjusted to tension films of varying widths. Preferably, the first film-spreading roller comprises a diameter in the range of about 2 cm to about 10 cm, preferably about 4 cm to about 8 cm. Film-spreading rollers of this diameter confer advantageous control of the tension of the film that allows the thickness of the film to be measured accurately and helps to substantially remove undulations.

[0040] Preferably, the first film-spreading roller comprises a length in the range of about 10 cm to about 250 cm, preferably about 50 cm to about 210 cm, preferably about 140cm to about 190 cm. Such lengths are suitable for supporting films of the desired width.

[0041] Preferably, the first film-spreading roller comprises metal, preferably steel, preferably stainless steel. Such materials are suitable for the present invention as they reduce the likelihood of the film being locally tensioned and thus distorted when the film passes over the roller.

[0042] Preferably, the removably adherable tape increases a diameter of the first film-spreading roller at each of the first and second tensioning region by about 50 pm to 500 pm, preferably about 100 pm to about 300 pm. An advantage of this is that the increased diameter imposes sufficient tension in the lateral direction. Further advantageously, the film engages with the tape that provides the raised diameter such that an airgap may be formed between the film and the rest of the film-spreading roller, which allows the film to slide over roller thus more easily and undulations in the film to be removed.

[0043] Preferably, the first tensioning region and the second tension region each independently extend about 1 % to about 30% along the length of the first film-spreading roller, preferably about 2% to about 25%, preferably about 3% to about 20%. It is an advantage of the invention that the first and second tensioning regions do not cover the whole width of the roller but instead are arranged so they engage with the first outer edge and the second outer edge of the film.

[0044] Preferably, between about 0.5% and about 15% of the width of the thermoplastic film engages with each of the first and second tensioning regions, preferably between about 2% and about 10%. It is an advantage of the invention that the first and second tensioning regions do not cover the whole width of the film but instead are arranged so they engage with the first outer edge and the second outer edge of the film. This reduces the amount of the film the first and second tensioning reasons come into contact with and thus reduces the area where any witness marks may show.

[0045] Preferably, the coefficient of friction between the thermoplastic film and the removably adherable tape is greater than a coefficient of friction between the thermoplastic film and the first film-spreading roller. An advantage of this is that greater frictional forces between the film and tape creates grip that imposes the tension in the lateral direction. Moreover, because the coefficient of friction between film and roller is reduced, this advantageously allows the film to slide over roller thus more easily and undulations in the film to be removed. The coefficient of friction is preferably calculated according to the formula:

[0046] Frictional force Coefficient of friction = - — -

[0047] Normal force

[0048] Preferably, the first film-spreading roller comprises a third region between the first tensioning region and the second tensioning region, preferably wherein when the first outer edge engages with the first tensioning region and the second outer edge engages with the second tensioning region, wherein there is an airgap between the thermoplastic film and along at least part of the third region, preferably along substantially all of the third region. Without being bound by theory, it is believed that this airgap helps remove any undulations on the film as there is reduced or no force from the roller on the part of the film that is in the third region. This aids the removal of any undulations, wrinkles or creases.

[0049] Preferably, the third region extends about 60% to about 96% along the length of the first film-spreading roller, preferably about 70% to about 90% along the length of the first filmspreading roller. Advantageously, the majority of the film will not come into contact with the first and second tensioning regions. This allows the majority of the film to be laterally tensioned to remove or reduce undulations, creases and wrinkles.

[0050] Preferably undulations in the thermoplastic film are substantially removed, preferably wherein the film is substantially planar, preferably wherein the film does not comprise undulations with a peak of more than about 5 pm, preferably wherein the film does not comprise undulations with a peak of more than about 1 pm, preferably wherein the film does not comprise undulations with a peak of more than about 0.5 pm; and / or wherein the film any undulations have less than about 5% deviation from the average thickness of the film, preferably less than about 3%, preferably less than about 1%, preferably there are substantially no undulations.

[0051] It is an advantage of the invention that any undulations in the thermoplastic film are removes such that the film is substantially planar. This allows consistent and accurate measurement of the thickness of the film. The undulations may be measured by an optical device.

[0052] Preferably, the removably adherable tape comprises an adhesive and a support. This is a suitable way to provide the tape to allow it to be easily applied to and removed from the first film-spreading roller.

[0053] Preferably, “removably adherable” means that the tape can be removed by hand without tearing and / or stretching. This allows the tape to be removed or adjusted easily without damaging the tape.

[0054] Preferably “removably adherable” means the force required to remove the tape is less than the force required to tear the tape.

[0055] Preferably, the peel adhesion of the removably adherable tape is between about 50 g / cm and about 450 g / cm, preferably between about 100 g / cm and about 400 g / cm. Peel adhesion may be measured in accordance with PSTC-101 , Method A. Such peel adhesions allow the removably adherable tape to remain in place while the film is being processed and allow the tape to be removed when needed.

[0056] An advantage of the removably adherable tape is that it allows the tape to be repositioned. This is particularly useful when first applying the tape to the roller to ensure the correct positioning of the tape. The tape is preferably applied by hand. It is an advantage that the tape can be repositioned. Further, it is an advantage that the tape can be removed and replaced as needed.

[0057] Preferably, the removably adherable tape is cleanly removable from the film-spreading roller. Preferably, no tape or adhesive remains on the film-spreading roller after the tape is removed. It is an advantage that the removably adhesive tape can be removed and replaced as needed

[0058] Preferably, the support comprises paper, a polymeric film or a combination of two or more thereof. Such materials allow the tape to be easily applied to and removed from the first film-spreading roller.

[0059] Preferably, the adhesive comprises a pressure sensitive adhesive. Pressure sensitive adhesives are particularly suitable as they can be easily applied to and removed from the first film-spreading roller.

[0060] Preferably, the adhesive comprises a silicone a, polyester, a polyester copolymer, an acrylic based polymer, a polyamide, an alkane polymer, a chlorinated alkane polymer, a polyethylene, a polycarbonate, a polyamide, a polyurethane, a styrene block copolymer, a co-polymer of vinyl chloride and vinyl acetate, a terpolymer of vinyl chloride, vinyl acetate and dicarboxylic acid, polyhydroxyethers, an aliphatic vinyl acetate or a combination of two or more thereof, preferably a silicone or an acrylic based polymer. Such adhesives are suitable to allow application and removal of the tape.

[0061] It will be appreciated that the skilled person can check the suitability of an adhesive by applying the tape comprising a support and adhesive to a roller and assessing the adherence of the tape and the removability of the tape.

[0062] Preferably, the removably adherable tape comprises masking tape. Masking tape is a readily available removably adherable tape and is suitable for use in the present invention.

[0063] Preferably, the width of the removably adherable tape is between about 1 cm and about 5 cm, preferably between about 1 .5 cm and about 4 cm, preferably between about 2 cm and about 3 cm. Such widths are suitable for forming the first and second tensioning regions.

[0064] Preferably, the removably adherable tape has a thickness between about 50 pm and about 250 pm, preferably between about 90 pm and about 200 pm. Such thicknesses are suitable for use as one or more windings around the first film-spreading roller. Preferably, the polyaryletherketone (PAEK) polymer comprises polymers selected from the groups of polyetherketone (PEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyetherketoneetherketoneketone (PEKEKK), polyetherimide (PEI), polyetherdiphenyletherketone (PEDEK), and combinations thereof, preferably a PEEK polymer, a PEEK / PEDEK copolymer, or a combination of two or more thereof. An advantage of using such polymers is that they are particularly well-suited for use in such high-performance acoustic products due to its specific mechanical properties.

[0065] Preferably, the PEEK polymer has a repeat unit of formula I:

[0066] -O-Ph-O-Ph-CO-Ph- wherein Ph represents a phenylene moiety. In this embodiment, all phenylenes are 1 ,3- and I or 1 ,4-substituted to the adjacent ether and / or carbonyl groups.

[0067] Preferably, the PEDEK polymer has a repeat unit of formula II

[0068] -O-Ph-Ph-O-Ph-CO-Ph- wherein Ph represents a phenylene moiety and wherein the repeat units I and II are in the relative molar properties l:ll of from 6555:3545 to 95:5. In this example, all phenylenes are 1 ,3- and I or 1 ,4-substituted to the adjacent ether and / or carbonyl groups.

[0069] Preferably, the removably adherable tape is applied with about one to about two windings around a circumference of the first film-spreading roller. An advantage of using about one to about two windings is that this provides a sufficiently thick layer of tape relative to the thermoplastic film to achieve the tension needed.

[0070] Preferably, the removably adherable tape is applied with at least about two windings around a circumference of the first film-spreading roller, wherein the second winding partially overlaps with the first winding such that a graduated increased in a diameter of the first film-spreading roller at each tensioning region is obtained, preferably wherein the removably adherable tape is applied with at least about two windings to about five windings around the circumference of the first film-spreading roller, wherein at least one subsequent winding partially overlaps with the previous winding such that a graduated increased in a diameter of the first film-spreading roller at each tensioning region is obtained. This is advantageous in two instances: firstly, when the film is being re-wound rather than being extruded for the first time, as the graduated increase helps to avoid leaving a witness mark of the edges of the film. Secondly, where a second film-spreading roller is used, it is advantageous not to leave a witness mark of the edges of the film. This helps to ensure that the film winds onto the core with a constant diameter as well as reducing and preventing the occurrence of other defects such as creases or wrinkles.

[0071] Preferably, the removably adherable tape is wound around a circumference of the first film spreading roller in the same direction as the thermoplastic film goes over the arc of the first film-spreading roller. This means that the trailing edge of the tape is pushed down as the film passes over the film spreading roller. This helps the removably adherable tape to remain on the roller when the roller is in use.

[0072] Preferably, the diameter of the first tensioning region in contact with the thermoplastic film is largest at the first outer edge; and / or wherein the diameter of the second tensioning region in contact with the thermoplastic film is largest at the second outer edge. It is advantageous for the film-spreading roller to have the largest diameter of the first and second tensioning regions closest to the first and second outer edges to taper the film from the largest diameter which helps reduce witness marks.

[0073] It will be understood that the first outer edge and the second outer edge of the film are substantially opposite each other, preferably, wherein the first and second outer edges run substantially perpendicular to the axis of rotation of the first film-spreading roller. The film further comprises a leading edge, preferably wherein the leading edge runs substantially parallel to the axis of rotation of the first film-spreading roller.

[0074] Preferably, the first outer edge and the second outer edge of the thermoplastic film each engages with about the same surface area of each respective tensioning region in step (b). Advantageously, this provides lateral tension by applying a substantially equal but opposite tensioning force at each tensioning region, such that tension is evenly applied across the thermoplastic film and undulations are more effectively removed.

[0075] Preferably, about 0.5 cm to about 5 cm of the width of the thermoplastic film engages with the first tensioning region, preferably about 1 cm to about 4 cm, preferably about 2 cm to about 3 cm, preferably about 2.5 cm; and / or preferably about 0.5 cm to about 5 cm of the width of the thermoplastic film engages with the second tensioning region preferably about 1 cm to about 4 cm. Such amounts balance the need to remove undulations from the film with the need to reduce the amount of film that may be damaged by a witness mark.

[0076] Preferably, the method further comprises subsequent to measuring the thickness profile of the thermoplastic film in step (c), passing the length of thermoplastic film over an arc of a second film-spreading roller configured to tension the thermoplastic film in a lateral direction. Preferably, the second film-spreading roller comprises any of the features of the first film-spreading roller of step (b) as described herein. Advantageously, passing the thermoplastic film over an arc of a second film-spreading roller helps to remove any undulations that remain in the thermoplastic film after it has passed over the first filmspreading roller. Further it is preferable that the first film-spreading roller and the second film-spreading roller are substantially identical.

[0077] Preferably the method further comprises during step (c): (c1) determining an average thickness of the thermoplastic film with the thickness measurement device, and (c2) adjusting a longitudinal tension applied to the length of thermoplastic film in order to effect an adjustment in the thickness of the thermoplastic film, the adjustment in dependence on the average thickness, preferably wherein the measurement device measures a thickness of the thermoplastic film by repeatedly scanning a width of the film to obtain a transverse thickness profile, wherein the average thickness is calculated based on an average of a plurality of transverse thickness profiles, preferably a mean average about 5 to about 15 transverse thickness profiles. Advantageously, monitoring the transverse thickness profile in this way helps to ensure that the thickness of the thermoplastic film is uniform and consistent between batches.

[0078] Preferably, the thickness measurement device is an optical device. An optical device can determine the film thickness by measuring the refractive index of the film. This is particularly suitable for measuring the thickness of PAEK films.

[0079] Preferably, providing a length of thermoplastic film comprises melt extruding a thermoplastic composition comprising the PAEK polymer, optionally where melt extruding comprises extruding the thermoplastic composition through a slot die. Advantageously, this provides an efficient way of producing a thermoplastic film of uniform thickness. Preferably, during step (c), a width of the film is a scanned by the measuring device in (c3) to obtain a transverse thickness profile of a portion of the length of thermoplastic film, and a die used to extrude the thermoplastic composition is adjusted to effect a local adjustment to a portion of the width of the thermoplastic film, the adjustment in dependence on the transverse thickness profile, preferably wherein the transverse thickness profile is obtained based on repeatedly scanning a width of the film to obtain a plurality of initial transverse thickness profiles. Advantageously, monitoring the transverse thickness profile in this way helps to ensure that the thickness of the thermoplastic film is accurate and consistent between batches.

[0080] Preferably, the method comprises subsequent to step (c), trimming the first outer edge and / or the second outer edge from the thermoplastic film. This advantageous removes any witness marks that may have been caused by the first or second tensioning regions. Further, extruded films are typically thicker at the outer edges, therefore the trimming steps improves the consistency of the thickness of the film across the width.

[0081] Preferably, the method further comprising winding the thermoplastic film on to a core. This step can take place after film has passed over the first film-spreading roller, the second film-spreading roller or after the trimming step. The resulting film has reduced undulations, wrinkles and creases, preferably substantially no undulations, wrinkles and creases. Advantageously, winding the thermoplastic film onto a core helps to ensure that it remains substantially free of creases and wrinkles until it is needed.

[0082] Preferably, the method is carried out at about room temperature. An advantage of carrying out the method at about room temperature is that the physical properties of the thermoplastic film at this temperature are known.

[0083] According to a second aspect, there is provided an apparatus configured to measure the thickness of a thermoplastic film, comprising: a first film-spreading roller and a thickness measurement device; wherein the first film-spreading roller is substantially cylindrical and substantially linear, wherein the first film-spreading roller comprises a first tensioning region and a second tensioning region, wherein the first tensioning region and the second tensioning region are each formed from a length of removably adherable tape, wherein the thickness measurement device is configured to measure the thickness of a thermoplastic film after the thermoplastic film has passed over the arc of a first filmspreading device. Such a device is suitable for use in the present invention.

[0084] Preferably, the apparatus further comprises a means for adjusting the thickness of a thermoplastic film. Preferably the means for adjusting the thickness of a thermoplastic film comprises a device to change the longitudinal tension of the film and / or a device to change the extrusion of a thermoplastic melt through a die.

[0085] It will be appreciated that the apparatus will preferably comprise any of the features described herein.

[0086] According to a third aspect, there is provided a thermoplastic film processed according to the method described herein. Such a film has the advantage of being processed to have a consistent thickness as described herein.

[0087] According to a fourth aspect, there is provided a thermoplastic film, wherein the thermoplastic film comprises a layer of thermoplastic film wound onto a core, wherein the thermoplastic film comprises a polyaryletherketone (PAEK) polymer, wherein a thickness of the film is between about 2 pm and about 50 pm; wherein a width of the film is between about 50 cm and about 250 cm and wherein the thermoplastic film is substantially free of undulations.

[0088] Preferably, the width of the film is between about 50 cm and about 190 cm, preferably between about 130 cm and about 180 cm.

[0089] Preferably, the thickness of the film is between about 2 pm and about 25 pm, preferably between about 3 pm and about 12 pm, more preferably between about 2 pm and about 10 pm, most preferably between about 2 pm and about 5 pm.

[0090] Preferably, the percentage deviation from the mean thickness of the film is less than about 5%, preferably less than about 2%, preferably, less than about 1 %, preferably less and about 0.5%, preferably less than about 0.1 %. The percentage deviation may be calculated by measuring the thickness at least 5 points across the width of the film, calculating the mean thickness and the average deviation from the mean thickness and calculating the percentage deviation. It is an advantage of the invention that the films have a consistent thickness, with a reduced percentage deviation than would be otherwise possible if not spreading the film with tape.

[0091] The film has the advantage of having a consistent thickness. It is surprising that such thin and wide films can be wound with substantially no undulations as undulations are particularly problematic for such films. The present invention allows a consistent product to be produced by accurately measuring the thickness of the film. Further, the end product is easier to use as the film on a core is substantially free from undulations.

[0092] It will be appreciated that the thermoplastic film will preferably comprise any of the features described herein.

[0093] Figure 1 shows a partial perspective of an apparatus used to process a thermoplastic film according to aspects of the present disclosure. The thermoplastic film 1 is shown passing over a first film-spreading roller 5. A first tensioning region 3a and a second tensioning region 3b, each formed from a length of removably adherable tape, are shown at either end of the first film-spreading roller 5. The figure shows the overlap of the thermoplastic film 1 with the first tensioning region 3a and the second tensioning region 3b. The width 17 of the thermoplastic film is shown.

[0094] Figure 2 shows a cross-sectional perspective of an apparatus used to process a thermoplastic film according to aspects of the present disclosure. The thermoplastic film 1 is shown passing over a first film-spreading roller 5. A tensioning region 3 formed from a length of removably adherable tape is wound around the film spreading roller 5. A thickness measurement device 7 is shown to measure the thickness of the thermoplastic film 1 after it passes over the film spreading roller 5.

[0095] Figure 3 shows an example schematic of a system used to process a thermoplastic film according to aspects of the present disclosure. The thermoplastic film 1 is shown passing over a first film-spreading roller 5. A tensioning region 3 formed from a length of removably adherable tape is wound around the first film-spreading roller 5. The thickness of the thermoplastic film 1 may be measured using a thickness measurement device 7 after the thermoplastic film 1 has passed over the first film-spreading roller 5. The thermoplastic film 1 then passes over a second film-spreading roller 11 which has a tensioning region 3. The thickness of the thermoplastic film 1 may be measured using a thickness measurement device 9 after the thermoplastic film 1 has passed over the second filmspreading roller 11.

[0096] Examples

[0097] Example 1

[0098] A PAEK film was processed, and the thickness profile was measured. Two processing methods were compared. Figure 4a shows the thickness profile of a film not processed according to the invention. In this case, the film was passed over a film-spreading roller that did not comprise any tensioning regions. As is shown in Figure 4a, there are variations in the five thickness profile scans caused by the undulations in the film. This makes it difficult for the thickness profile to be adjusted as the noise of the undulations results in an inconsistent thickness profile. Further, Figure 4b is a photograph of the film, showing a roller 5 with a film 1 and multiple undulations 15. The undulations 15 are visible in the photograph. The film width in the photograph is shown by arrow 18. It will be appreciated that the actual film is wider as only part of the width of the film and the roller is shown. Figure 4c is a schematic of Figure 4b showing that undulations 15 are visible. It will be appreciated that this is a schematic, and it shows that there are multiple undulations 15 present.

[0099] Figure 5a shows the thickness profile of a film processed according to the invention. In this case, the film was passed over a film-spreading roller that comprises tensioning regions as described herein. Figure 5a shows that the five thickness profile scans are substantially the same showing how the method of the invention has removed the undulations. Further, Figure 5b is a photograph of the film, showing a roller 5 with a film 1 and a first tensioning region 3a. The second tensioning region 3b is not shown. As shown, there are no visible undulations in the film. The film width is shown by arrow 18. It will be appreciated that the actual film is wider as only part of the width of the film and the roller is shown and the second tensioning region is not shown. Figure 5c is a schematic of Figure 5b. This clearly shows that the undulations in the film have been substantially removed and the operator can have confidence in the thickness measurement. This allows adjustments to be made to the thickness of the film by making changes at the extrusion point of the thermoplastic film or by changing the longitudinal tension of the film. This results in a more consistent product as the thickness of the film produced is known and can be adjusted as needed with confidence in the thickness measurement. Tight control of the film thickness and the thickness profile across the film is important for reliably producing a desired film. This has particular utility for acoustic films.

[0100] Within this specification, the term "about" means plus or minus 20%, more preferably plus or minus 10%, even more preferably plus or minus 5%, most preferably plus or minus 2%. Within this specification, the term "substantially" means a deviation of plus or minus 20%, more preferably plus or minus 10%, even more preferably plus or minus 5%, most preferably plus or minus 2%.

[0101] Within this specification, reference to “substantially” includes reference to “completely” and / or “exactly”. That is, where the word substantially is included, it will be appreciated that this also includes reference to the particular sentence without the word substantially.

[0102] It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present invention and without diminishing its attendant advantages. It is therefore intended that such changes and modifications are covered by the appended claims.

[0103] In this disclosure, when the subject of a phase is described as being "configured to" or “arranged to”, followed by a term defining a condition or function, this is used to indicate that the subject of the phrase is in a state in which it has that condition, or is able to perform that function, without the subject being modified or further configured.

[0104] Some implementations may be described using the expressions “one / an embodiment” or “one / an example”, along with their derivatives. These terms mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Moreover, unless otherwise noted the features described above are recognized to be usable together in any combination. Thus, any features discussed separately may be employed in combination with each other unless it is noted that the features are incompatible with each other.

[0105] The foregoing description of example embodiments has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the present disclosure to the precise forms disclosed. Many modifications and variations are possible in light of this disclosure. It is intended that the scope of the present disclosure be limited not by this detailed description, but rather by the claims appended hereto. Future filed applications claiming priority to this application may claim the disclosed subject matter in a different manner and may generally include any set of one or more limitations as variously disclosed or otherwise demonstrated herein.

[0106] Within this specification embodiments have been described in a way which enables a clear and concise specification to be written, but it is intended and will be appreciated that embodiments may be variously combined or separated without parting from the invention. For example, it will be appreciated that all preferred features described herein are applicable to all aspects of the invention described herein and vice versa. For example, all preferred features of the composite apply to all aspects of the invention.

Claims

Claims1 . A method of processing a thermoplastic film, the method comprising:(a) providing a length of thermoplastic film with a first outer edge and a second outer edge, wherein the thermoplastic film comprises a polyaryletherketone (PAEK) polymer, wherein a thickness of the film is between about 2 pm and about 250 pm;(b) passing the length of thermoplastic film over an arc of a first film-spreading roller configured to tension the thermoplastic film in a lateral direction;(c) subsequent to (b), measuring a thickness profile of the thermoplastic film by passing the length of thermoplastic film past a thickness measurement device; wherein the first film-spreading roller is substantially cylindrical and substantially linear, and wherein the first film-spreading roller comprises a first tensioning region and a second tensioning region, wherein the first tensioning region and the second tensioning region are each formed from a length of removably adherable tape, and wherein step (b) comprises directing the first outer edge of the thermoplastic film to engage with the first tensioning region and the second outer edge of the thermoplastic film to engage with the second tensioning region.

2. A method of processing a thermoplastic film according to claim 1 , wherein a thickness of the film is between about 2 pm and about 100 pm, more preferably between about 2 pm and about 25 pm, more preferably between about 3 pm and about 12 pm, more preferably between about 2 pm and about 10 pm, most preferably between about 2 pm and about 5 pm; and / or wherein a width of the film is between about 30 cm and about 250 cm, preferably between about 50 cm and about 190 cm, preferably between about 130 cm and about 180 cm.

3. A method of processing a thermoplastic film according to any preceding claim, wherein the removably adherable tape increases a diameter of the first film-spreading roller at each of the first and second tensioning region by about 50 pm to 500 pm, preferably about 100 pm to about 300 pm.

4. A method of processing a thermoplastic film according to any preceding claim, wherein the first tensioning region and the second tensioning region each independently extend about 1 % to about 30% along the length of the first film-spreading roller, preferably about 2% to about 25%, preferably about 3% to about 20%; and / orwherein the between about 0.5% and about 15% of the width of the thermoplastic film engages with each of the first and second tensioning regions, preferably between about 2% and about 10%.

5. A method of processing a thermoplastic film according to any preceding claim, wherein a coefficient of friction between the thermoplastic film and the removably adherable tape is greater than a coefficient of friction between the thermoplastic film and the first film-spreading roller.

6. A method of processing a thermoplastic film according to any preceding claim, wherein the first film-spreading roller comprises a third region between the first tensioning region and the second tensioning region, preferably wherein when the first outer edge engages with the first tensioning region and the second outer edge engages with the second tensioning region, wherein there is an airgap between the thermoplastic film and along at least part of the third region, preferably along substantially all of the third region.

7. A method of processing a thermoplastic film according to any preceding claim, wherein undulations in the thermoplastic film are substantially removed, preferably wherein the film is substantially planar, preferably wherein the film does not comprise undulations with a peak of more than about 5 pm, preferably wherein the film does not comprise undulations with a peak of more than about 1 pm, preferably wherein the film does not comprise undulations with a peak of more than about 0.5 pm; and / or wherein the film any undulations have less than about 5% deviation from the average thickness of the film, preferably less than about 3%, preferably less than about 1 %, preferably there are substantially no undulations.

8. A method of processing a thermoplastic film according to any preceding claim, wherein the removably adherable tape comprises an adhesive and a support, preferably: i) wherein the support comprises paper, a polymeric film or a combination of two or more thereof; and / or ii) wherein the adhesive comprises a pressure sensitive adhesive, preferably wherein the adhesive comprises a silicone a, polyester, a polyester copolymer,an acrylic based polymer, a polyamide, an alkane polymer, a chlorinated alkane polymer, a polyethylene, a polycarbonate, a polyamide, a polyurethane, a styrene block copolymer, a co-polymer of vinyl chloride and vinyl acetate, a terpolymer of vinyl chloride, vinyl acetate and dicarboxylic acid, polyhydroxyethers, an aliphatic vinyl acetate or a combination of two or more thereof, preferably a silicone or an acrylic based polymer; and / or iii) wherein the removably adherable tape comprises masking tape; and / or iv) wherein the width of the removably adherable tape is between about 1 cm and about 5 cm, preferably between about 1.5 cm and about 4 cm, preferably between about 2 cm and about 3 cm; and / or v) wherein the removably adherable tape has a thickness between about 50 pm and about 250 pm, preferably between about 90 pm and about 200 pm; and / or vi) the peel adhesion of the removably adherable tape is between about 50 g / cm and about 450 g / cm, preferably between about 100 g / cm and about 400 g / cm.

9. A method of processing a thermoplastic film according to any preceding claim, wherein the first film-spreading roller: i) comprises a length in the range of about 10 cm to about 250 cm, preferably about 50 cm to about 210 cm, preferably about 140 cm to about 190 cm; and / or ii) comprises a diameter in the range of about 2 cm to about 10 cm, preferably about 4 cm to about 8 cm; and / or iii) comprises metal or carbon fibre, preferably anodised aluminium or a carbon fibre tube.

10. A method of processing a thermoplastic film according to any preceding claim, wherein the polyaryletherketone (PAEK) polymer comprises polymers selected from the groups of polyetherketone (PEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyetherketoneetherketoneketone (PEKEKK), polyetherimide (PEI), polyetherdiphenyletherketone (PEDEK), and combinations thereof, preferably a PEEK polymer, a PEEK / PEDEK copolymer, or a combination of two or more thereof.11 . A method of processing a thermoplastic film according to any preceding claim, wherein the removably adherable tape is applied with about one to about two windings around a circumference of the first film-spreading roller; and / orwherein the removably adherable tape is wound around a circumference of the first film spreading roller in the same direction as the thermoplastic film goes over the arc of the first film-spreading roller.

12. A method of processing a thermoplastic film according to any preceding claim, wherein the removably adherable tape is applied with at least about two windings around a circumference of the first film-spreading roller, wherein the second winding partially overlaps with the first winding such that a graduated increased in a diameter of the first film-spreading roller at each tensioning region is obtained, preferably wherein the removably adherable tape is applied with at least about two windings to about five windings around the circumference of the first film-spreading roller, wherein at least one subsequent winding partially overlaps with the previous winding such that a graduated increased in a diameter of the first film-spreading roller at each tensioning region is obtained.

13. A method according to any preceding claim, wherein the diameter of the first tensioning region in contact with the thermoplastic film is largest at the first outer edge; and / or wherein the diameter of the second tensioning region in contact with the thermoplastic film is largest at the second outer edge.

14. A method of processing a thermoplastic film according to any preceding claim, wherein the first outer edge and the second outer edge of the thermoplastic film each engages with about the same surface area of each respective tensioning region in step (b); and / or wherein about 0.5 cm to about 5 cm of the width of the thermoplastic film engages with the first tensioning region, preferably about 1 cm to about 4 cm; and / or wherein about 0.5 cm to about 5 cm of the width of the thermoplastic film engages with the second tensioning region preferably about 1 cm to about 4 cm, preferably about 2 cm to about 3 cm, preferably about 2.5cm.

15. A method of processing a thermoplastic film according to any preceding claim, further comprising: subsequent to measuring the thickness profile of the thermoplastic film in step (c), passing the length of thermoplastic film over an arc of a second film-spreading roller configured to tension the thermoplastic film in a lateral direction, preferablywherein the second film-spreading roller comprises any of the features of the first filmspreading roller of step (b) as described in any preceding claim.

16. A method of processing a thermoplastic film according to any preceding claim, further comprising, during step (c): (c1 ) determining an average thickness of the thermoplastic film, and (c2) adjusting a longitudinal tension applied to the length of thermoplastic film in order to effect an adjustment in the thickness of the thermoplastic film, the adjustment in dependence on the average thickness, preferably wherein the measurement device measures a thickness of the thermoplastic film by repeatedly scanning a width of the film to obtain a transverse thickness profile, wherein the average thickness is calculated based on an average of a plurality of transverse thickness profiles, preferably a mean average about 5 to about 15 transverse thickness profiles.

17. A method of processing a thermoplastic film according to any preceding claim, further comprising, during step (c): (c3) scanning, by the measurement device, a width of the film to obtain a transverse thickness profile of a portion of the length of thermoplastic film, and adjusting a die used to extrude the thermoplastic composition to effect a local adjustment to a portion of the width of the thermoplastic film, the adjustment in dependence on the transverse thickness profile, preferably wherein the transverse thickness profile is obtained based on repeatedly scanning a width of the film to obtain a plurality of initial transverse thickness profiles.

18. A method of processing a thermoplastic film according to any preceding claim, wherein providing a length of thermoplastic film comprises melt extruding a thermoplastic composition comprising the PAEK polymer, preferably wherein melt extruding comprises extruding the thermoplastic composition through a slot die.

19. A method of processing a thermoplastic film according to any preceding claim, comprising subsequent to step (c), trimming the first outer edge and / or the second outer edge from the thermoplastic film; and / or further comprising winding the thermoplastic film onto a core.

20. An apparatus configured measure the thickness of a thermoplastic film, comprising: a first film-spreading roller and a thickness measurement device;wherein the first film-spreading roller is substantially cylindrical and substantially linear, wherein the first film-spreading roller comprises a first tensioning region and a second tensioning region, wherein the first tensioning region and the second tensioning region are each formed from a length of removably adherable tape, wherein the thickness measurement device is configured to measure the thickness of a thermoplastic film after the thermoplastic film has passed over the arc of a first filmspreading device.21 . An apparatus according to claim 20, further comprising a means for adjusting the thickness of a thermoplastic film.

22. A thermoplastic film processed according to the method of any of claims 1 to 19.

23. A thermoplastic film, wherein the thermoplastic film comprises a layer of thermoplastic film wound onto a core, wherein the thermoplastic film comprises a polyaryletherketone (PAEK) polymer, wherein a thickness of the film is between about 2 pm and about 50 pm; wherein a width of the film is between about 50 cm and about 250 cm and wherein the thermoplastic film is substantially free of undulations.

24. A thermoplastic film according to claim 22 or claim 23, wherein the width of the film is between about 50 cm and about 190 cm, preferably between about 130 cm and about 180 cm; and / or wherein the thickness of the film is between about 2 pm and about 25 pm, preferably between about 3 pm and about 12 pm, more preferably between about 2 pm and about 10 pm, most preferably between about 2 pm and about 5 pm; and / or wherein the percentage deviation from the mean thickness of the film is less than about 5%, preferably less than about 2%, preferably, less than about 1%, preferably less and about 0.5%, preferably less than about 0.1 %.

25. An apparatus according to claim 20 or claim 21 or a thermoplastic film according to any of claims 22 to 24 further comprising any of the features of claims 1 to 21 .

Images