Method and device for producing a microfibrillated cellulose film

Abstract

A method for manufacturing an MFC film from a microfibrillated cellulose (MFC) dispersion includes subjecting a wet MFC film on a support to at least one drying step to form a dry MFC film (F’), measuring at least one parameter indicative of the dry solid content of the wet MFC film (F) and / or the dry MFC film (F’) at at least two data points spaced apart laterally over at least the width of the MFC film (F, F’), and varying at least one drying condition of the at least one drying step over the width of the wet MFC film (F, F’) according to the parameter. Also disclosed are a device for manufacturing an MFC film, the use of such a device, and an MFC film.

Description

Technical Field

[0001] The present invention relates to microfibrillated cellulose, MFC, methods and devices for producing films. The present invention particularly relates to a method for providing a high-quality MFC film. The present disclosure further relates to a device for producing such an MFC film and the use of such a device for producing an MFC film. The present disclosure also relates to an MFC film produced according to this method.

Background Art

[0002] In the context of the present application, microfibrillated cellulose ("MFC") is taken to have cellulose particles, fibers or fibrils with a width or diameter of 20 nm to 1000 nm.

[0003] There are various methods for producing MFC, such as single or multiple pass refining, pre-hydrolysis, followed by refining or high-shear defibrillation or fibril liberation. To achieve both energy efficiency and sustainability in the production of MFC, usually one or more pretreatment steps are required. Thus, the cellulose fibers of the pulp used in the production of MFC can be natural or, for example, pretreated enzymatically or chemically to reduce the amount of hemicellulose or lignin. The cellulose fibers can be chemically modified prior to fibrillation, in which case the cellulose molecules contain functional groups other than (or more than) those found in the original cellulose. Such groups include, inter alia, carboxymethyl (CM), aldehyde and / or carboxyl groups (cellulose obtained by N-oxyl-mediated oxidation, such as "TEMPO"), or quaternary ammonium (cationic cellulose). After being modified or oxidized by one of the above methods, the fibers are easily defibrillated by MFC.

[0004] MFC can be manufactured from hardwood and / or softwood wood cellulose fibers. MFC can also be made from microbial sources, agricultural fibers such as straw pulp, bamboo, bagasse, or other non-wood fiber sources. For example, it can be manufactured from pulp containing virgin fibers such as mechanical pulp, chemical pulp, and / or thermomechanical pulp. It can also be made from waste paper, recycled paper, and other packaging materials.

[0005] Current research indicates that MFC may be a suitable material for packaging and packaging coatings due to its barrier properties. Therefore, MFC has the potential to replace or complement currently used barrier films and layers, including polymer and metal films and coatings.

[0006] The formation of MFC films can be achieved by solvent casting a viscous or gel-like fluid material onto a support such as a continuous conveyor belt, followed by dehydration / drying (e.g., evaporation) of the solvent.

[0007] The term "solvent casting" refers to a known method by which a film is produced by applying a wet film containing film-forming components dispersed in a medium that is essentially removed by, for example, dehydration and / or evaporation. The film-forming components are either dispersed in the dispersion medium or dissolved in a solvent, hence the name "solvent casting".

[0008] In the following, the term "MFC dispersion" is used to refer to a dispersion / suspension or solution containing MFC and a dispersion medium (usually water). The MFC dispersion becomes viscous.

[0009] The use of MFC films in packaging applications involves certain challenges due to the brittleness of the MFC films. The elasticity and ductility of the MFC films are related to the moisture present within the MFC films, and when the MFC films become too dry, they become brittle. Drying and the associated brittleness can potentially have a local impact on the MFC films, particularly on the edge regions of the films. In the casting process, the side edges of the MFC films tend to dry faster than the central portion of the films, resulting in a difference in the moisture content and ductility in the machine cross-direction (CD), and accordingly, the edges can become brittle. Due to the brittleness, particularly in the edge regions, the MFC films can tend to break easily during the conversion process. The problem is not necessarily limited to the narrow and slow speeds seen in laboratory and pilot-scale manufacturing processes as well as the use of the films, but becomes even more significant when operating film production on wider machines and / or on a large scale and at higher speeds.

[0010] Known approaches use plasticizers and humectants such as sugar alcohols (e.g., sorbitol) or polyethylene glycol to make the MFC films more ductile. However, such hygroscopic additives and the water they bind to the film can potentially interfere with the binding of the microfibrils, increase the strain value at break, and decrease the tensile strength. The use of such additives improves the overall level of ductility of the film, but problems regarding changes in the moisture content of the film in the machine cross-direction and brittle edges can still remain as the film is still too brittle.

[0011] A further problem relates to the manufacture of MFC films by casting techniques when impact drying from the top of the film, infrared (IR) drying, or other thermal drying is used to dry the film on a non-porous casting support. The casting support needs to be slightly wider in the machine transverse direction than the wet MFC film deposited thereon. However, due to the heat flux applied from above, the temperature of the casting support edges without the wet MFC layer thereon increases, so that the side edge portions of the film are exposed to additional heat. This additional heat at the edges of the casting support causes the MFC film to dry faster at the edges. Since the MFC film is very thin, it is easily over-dried.

[0012] Furthermore, if the MFC film can have a non-uniform moisture profile within the CD, the peeling behavior or adhesion of the dry or semi-wet MFC film to the casting support changes and becomes unpredictable or has greater variability. Since the edges of the film dry faster than the center, the edges tend to lose adhesion to the casting support quickly. This can also cause the edges of the MFC film to deform or be damaged, or the web to break during MFC film manufacture.

[0013] Therefore, it is necessary to dry the wet MFC film on the support and to improve the properties of the MFC film. SUMMARY OF THE INVENTION

[0014] The object is to provide a method and system for improving the quality of MFC films while minimizing or even reducing the manufacturing cost, preferably while reducing the manufacturing cost. A specific object is to address problems related to non-uniform film properties such as barrier properties, local brittleness, and / or running properties in film manufacture and conversion.

[0015] The present invention is defined by the appended independent claims, and embodiments are described in the appended dependent claims, the following description and the appended drawings.

[0016] According to a first aspect, a method for manufacturing a microfibrillated cellulose (MFC) film from an MFC dispersion is provided. The method comprises providing an MFC dispersion comprising a dispersion medium and a film-forming component comprising about 50 to 100% by weight of MFC, applying a layer of the MFC dispersion to a support to form a wet MFC film, subjecting the wet MFC film on the support to at least one drying step to form a dry MFC film, measuring at least one parameter indicative of the dry solid content in the wet MFC film and / or the dry MFC film at at least two data points spaced transversely across at least the width of the MFC film, and varying at least one drying condition of at least one of the at least one drying step across the width of the wet MFC film in response to the parameter.

[0017] The content of the dispersion medium in the MFC dispersion may be at least 75% by weight, preferably more than 80% by weight, more than 85% by weight, more than 90% by weight or more than 95% by weight. The film-forming component comprises MFC, consists of MFC, or is essentially composed of MFC, and optionally may be accompanied by one or more water-soluble polymers that can function as co-additives and / or co-film-forming agents. Thus, the MFC dispersion contains a dispersion medium and a film-forming component, and the film-forming component contains 50 to 100% by weight of MFC (i.e., based on the total dry weight of the film-forming component). For example, in addition to MFC, the film-forming component can contain a water-soluble polymer that can form a film and / or improve the bonding between cellulose fibers. Typical examples of such polymers include natural gums or polysaccharides or their derivatives, such as carboxymethylated cellulose (CMC), starch, or polyvinyl alcohol (PVOH) or their analogs. The film-forming component can also contain further additives such as one or more property-modifying additives and / or fillers. Non-limiting examples of such additives / chemicals include softeners and plasticizers such as glycols, sugar alcohols such as sorbitol, polysaccharides such as sorbitol and glucose, film-forming agents such as PVOH, carboxymethylated cellulose or methylcellulose, fillers, pigments, retention chemicals and dispersants or other polyelectrolytes, latexes, cross-linking agents, optical dyes, fluorescent whitening agents, defoaming chemicals, salts, pH-adjusting chemicals, surfactants, biocides and / or optical chemicals. The film-forming component can contain other natural fiber materials in addition to MFC.

[0018] The dispersion medium can contain water and optionally one or more solvents.

[0019] The layer of the MFC dispersion can be applied to a substrate by a casting technique.

[0020] The support may be a non-porous support, in particular a continuous non-porous support such as a metal belt, in particular a steel belt, a polymer belt, or a polymer-coated belt. The metal belt can be coated, for example, with a ceramic material.

[0021] The parameter indicating the dry solid content may be, as non-limiting examples, a temperature at which the temperature generally rises as the dry solid content increases, or a material composition that can be determined by various spectroscopic methods.

[0022] Data points can be spaced at least in the machine cross direction (CD), which is usually the direction perpendicular to the machine direction (MD) in which the MFC film moves during drying. For example, the data points can be spaced only within the CD or spaced in both the CD and the MD.

[0023] By changing the drying conditions based on the measured dry solid content, i.e., at least one measured parameter indicating the dry solid content of the MFC dispersion or MFC film during production, it is possible to dry the film substantially uniformly, in particular to ensure or at least facilitate that the film does not dry excessively at the edges. Therefore, since the distribution of moisture and some additives in the dried MFC film can be improved, problems such as local brittleness are reduced. By the method defined above, the dispersion medium content of the dried MFC film can be controlled to a desired value with high precision, which facilitates the handling of the resulting dried film, for example, peeling from the support, subsequent packaging, and handling.

[0024] Furthermore, the content of the dispersion medium and the additives following the dispersion medium may affect the barrier properties of the finished film, etc. For example, a region with a low dry solid content due to locally fast drying can be identified as a region where soluble additives may be present at a higher concentration.

[0025] The dry film can be considered as a material formed in a thin continuous sheet shape. Depending on its composition, purpose, and properties, the dry film can also be considered as a thin paper or web, or even a membrane.

[0026] In an actual embodiment, a number of data points are provided, by which it becomes possible to derive a detailed profile of the dry solid content of the film.

[0027] The measurement step may be performed after at least a part of the at least one drying step.

[0028] Therefore, the measurement can be performed after one or more drying steps, such as after the entire drying process, or it can also be performed between drying steps.

[0029] The method further includes at least one dehydration step before the at least one drying step, and the measurement step can be performed after at least a part of the at least one dehydration step and before the at least one drying step.

[0030] Therefore, the measurement can be performed after one or more dehydration steps, such as after the entire dehydration process, before the drying step, or between sub-steps of the dehydration process. Alternatively or additionally, at least one drying step may form a pre-drying step that is performed before the dehydration step. As yet another option, the measurement can also be performed after separating the dry MFC film from the support. In such a case, the measurement can be performed on the upper surface and / or the back surface of the dry MFC film.

[0031] The method further includes a pre-drying step that is performed before the dehydration step, and the measurement step is performed after the pre-drying step and before the dehydration step.

[0032] At least one of the data points may indicate the dry solid content at a position on the side edge portion of the MFC film.

[0033] The side edge portion can be defined as a region extending by a distance of 50 mm, preferably 30 mm or 10 mm, from the outermost edge (side edge) of the MFC film in a direction perpendicular to the longitudinal direction (parallel to the manufacturing direction MD) of the MFC film.

[0034] At least one of the data points may indicate the dry solid content in a portion spaced laterally from the side edge portion of the MFC film.

[0035] The concept of changing the drying conditions may include selectively changing the drying effect across the width direction.

[0036] For example, changing the drying effect may include reducing the drying effect at at least one side edge portion of the wet MFC film.

[0037] In particular, changing the drying effect may include restricting the drying width to be narrower than the MFC film width.

[0038] For example, changing the drying effect may include restricting the impingement width of the drying gas and / or radiation (microwave, infrared (IR)) to be narrower than the MFC film width.

[0039] The drying gas may be air or another type of gas suitable for the purpose.

[0040] As another example, changing the drying effect may include guiding the drying gas away from at least one side edge portion of the MFC film. As another example, changing the drying effect may include extracting the drying gas from at least one side edge portion of the MFC film.

[0041] As another example, varying the drying effect may include, for example, masking the side edge portion of the MFC film from the drying gas and / or radiation.

[0042] As another example, varying the drying effect may include sealing the surface of the support laterally outside the side edge portion of the MFC film to prevent the drying gas and / or radiation from reaching the support.

[0043] Accordingly, the heating of the support is reduced, and the drying effect at the edge portion of the film is reduced.

[0044] Furthermore, it is also possible to vary the drying effect by controlling the temperature profile of the support, for example, by controlling the heating and / or cooling of the support from below.

[0045] As another example, varying the drying effect may include selectively controlling the duty cycle, combustion gas pressure, and / or intensity of the radiation source for performing the drying.

[0046] As another example, varying the drying conditions may include selectively injecting at least one of a cooling medium and a dispersion medium onto the wet MFC film.

[0047] As a non-limiting example, water can be used as the cooling medium and / or dispersion medium.

[0048] As another example, varying the drying conditions may include laterally cooling at least one support edge portion outside the wet MFC film by applying a cooling medium.

[0049] Varying the drying conditions may include applying the cooling medium to the side edge portion of the MFC film and / or applying the dispersion medium to the side edge portion of the MFC film.

[0050] The method further includes separating the dried MFC film from the support and winding the separated MFC film onto a reel.

[0051] Thus, the MFC film remains on the support throughout the drying process (and the dehydration process if there is one).

[0052] In the method, the provided MFC dispersion may have a dry solids content of about 2.5 to 25 wt%, preferably about 2.5 to 15 wt%, or 2.5 to 10 wt%, or about 2.5 to 8 wt%.

[0053] Regardless of the dry solids content, the viscosity of the MFC dispersion can exceed about 4 Pa·s at a shear rate of 20 s -1 . The viscosity can be measured for the dispersion at a temperature of about 20 to 80 °C, preferably about 20 to 60 °C. A preferred method for measuring the viscosity is to use a rheometer with a bob-cup geometry, such as an Anton Paar MCR 302 dynamic rotational rheometer.

[0054] In the method, the average film thickness of the dried MFC film may be about 5 to 60 μm, preferably 10 to 50 μm, 15 to 45 μm or 20 to 40 μm. The average film thickness can be defined as the average thickness across the entire width of the film.

[0055] In the method, the film weight of the dried MFC film is about 4 to 80 g / m 2 , preferably 8 to 67 g / m 2 , 12 to 60 g / m 2 , 16 to 53 g / m 2 or 20 to 45 g / m 2 and may be.

[0056] In the method, the content of the dispersion medium in the dried MFC film may be about 0.1 to 20 wt%, preferably 1 to 15 wt% or 2 to 14 wt%.

[0057] In this method, the film-forming component content of the dry MFC film (F’) may be at least 80 to 99.9% by weight, preferably 85 to 99% by weight or 86 to 98% by weight.

[0058] In this method, the film-forming component can contain at least 60% by weight of MFC, preferably at least 70% by weight of MFC, or at least 80% by weight of MFC.

[0059] In this method, the film width of the dry MFC film may be about 0.3 to 4 m, preferably 0.5 to 4 m, 1 to 4 m or 2 to 4 m.

[0060] This method may further include measuring at least one parameter indicating the dry solid content in the wet MFC film and / or the dry MFC film at at least two data points spaced apart from each other in the thickness direction of the MFC film.

[0061] Measurement data indicating the dry solid content at various points spaced apart in the thickness direction can be saved and used to track the quality of the MFC film and / or grade the produced MFC film.

[0062] Such data can be used to evaluate the drying performance and serve as a basis for steps to vary the drying conditions across the width of the wet MFC film.

[0063] According to a second aspect, there is provided a device for producing a microfibrillated cellulose (MFC) film from a microfibrillated cellulose (MFC) dispersion. The device includes a support guiding device configured to guide a continuous support, a casting device configured to apply the MFC dispersion as a wet MFC film onto the support, a drying device configured to remove the dispersion medium from the wet MFC film to form a dry MFC film, at least one measuring device configured to provide data at at least two data points spaced laterally across at least the width of the MFC film indicative of the dry solid content of the wet MFC film and / or the dry MFC film, and a controller configured to receive the data and control the drying device based on the data to vary the drying conditions across the width of the wet MFC film.

[0064] The device can be configured to perform the method disclosed above.

[0065] The support guide can be configured to guide a support having a width of at least about 0.3 - 4 m, preferably 0.5 - 4 m, 1 - 4 m, or 2 - 4 m.

[0066] The support can be a continuous non-porous support such as a non-porous support, particularly a metal belt, particularly a steel belt, a polymer belt, or a polymer-coated belt. The metal belt can be coated with, for example, a ceramic material.

[0067] The device can further include a dehydration device upstream of the drying device, and the measuring device is disposed downstream of at least a part of the dehydration device and upstream of the drying device.

[0068] Thus, the measurement can be performed after one or more dehydration steps, such as after the entire dehydration process, before the drying step, or between sub-steps of the dehydration process.

[0069] It is understood that the measuring device may include a first measuring device with at least a part of the drying device arranged downstream, and a second measuring device with at least a part of the dehydrating device arranged downstream.

[0070] The device may further include a preliminary drying device upstream of the dehydrating device, and the measuring device is arranged downstream of at least a part of the preliminary drying device and upstream of the dehydrating device.

[0071] Therefore, an additional measuring device or a part of the measuring device can be arranged downstream of at least a part of the preliminary drying device.

[0072] According to a third aspect, a dried MFC film having a dispersion medium content of about 0.1 to 20 wt%, preferably 1 to 15 wt%, or 2 to 14 wt%, a dry solid content of about 2.5 to 25 wt%, preferably 2.5 to 15 wt% or 2.5 to 10 wt% or about 2.5 to 8 wt%, and a viscosity exceeding about 4 Pa·s at a shear rate of 20 s -1 is provided for forming from an MFC dispersion as described above.

[0073] According to a fourth aspect, a microfibrillated cellulose (MFC) film having a longitudinal direction parallel to the film manufacturing direction and a width direction perpendicular to the longitudinal direction is provided. The MFC film has a film-forming component content of at least 80 to 99.9 wt%, preferably 85 to 99 wt% or 86 to 98 wt%. The film-forming component contains at least 50 wt% of MFC. The width of the MFC film is about 0.3 to 4 m, preferably 0.5 to 4 m, 1 to 4 m or 2 to 4 m. The MFC film has a dispersion medium content of about 0.1 to 20 wt%, preferably 1 to 15 wt% or 2 to 14 wt%. The dispersion medium content of the MFC film has a standard deviation of less than 1% by weight along the width direction, and the moisture content is analyzed per 1 cm of the MFC film width.

[0074] In the MFC film, the film-forming component can contain at least 60% by weight of MFC, preferably at least 70% by weight of MFC, or at least 80% by weight of MFC.

[0075] The average film thickness can be about 5 - 60 μm, preferably about 10 - 50 μm, about 15 - 45 μm or about 20 - 40 μm.

[0076] The film weight is about 4 - 80 g / m 2 preferably about 8 - 67 g / m 2 about 12 - 60 g / m 2 about 16 - 53 g / m 2 or about 20 - 45 g / m 2 and may be.

Brief Description of the Drawings

[0077]

Fig. 1a

Fig. 1b

Fig. 2

Fig. 3a

Fig. 3b

Fig. 3c

Fig. 4

Fig. 5

Fig. 6

Fig. 7

Fig. 8

Fig. 9

Fig. 10

Fig. 11

Embodiments for Carrying Out the Invention

[0078] Referring to FIG. 1a, a top view of the film forming device 1 is schematically shown. FIG. 1b schematically shows a side view of the film forming device 1.

[0079] In the present disclosure, the film forming device 1 is described with reference to a film forming device 1 for forming a non-laminated film, i.e., a "self-supporting film", i.e., a film not laminated to any base material. Therefore, as shown in FIGS. 1a-1b, the completed film F' is peeled off from the support 10 and wound onto the reel 4.

[0080] The support 10 from which the dried film F' is peeled off is in a non-porous form and can preferably be provided in the form of an endless belt, such as a metal belt, such as a steel belt, or a polymer belt or a polymer-coated belt. The metal belt can be coated, for example, by a ceramic coating. The support 10 is preferably non-porous in order to provide a smooth film surface. In particular, the support can be polished until it has a mirror finish. In the illustrated embodiment, the support 10 is an endless support that runs on a support guide in the form of a pair of pulleys 11, 12.

[0081] The MFC supply unit 2 is provided to supply the MFC dispersion to the casting device 16, and the casting device 16 is configured to deposit the MFC dispersion as a thin wet film F with a uniform thickness. The support 10 that supports the wet film F passes through a dryer 13 that may include one or more drying devices 131 and 132. When there are two or more drying devices 131 and 132, the drying devices may be the same as each other, or may be different, for example, in terms of length. Further, the drying devices 131 and 132 may be individually controlled to provide different drying parameters.

[0082] Optionally, a dehydrating device 133 such as a dehydrating device including a press can be provided upstream of the drying devices 131 and 132. Such a dehydrating device 133 is known per se.

[0083] For example, dehydration may be performed by applying a press fabric that directly contacts the wet MFC film and passing the wet MFC film disposed between the press fabric and the support through a pressing device. Alternatively, dehydration can be performed by applying a porous wire or membrane that directly contacts the wet MFC film and passing the wet MFC film disposed between the porous wire or membrane and the support through a vacuum dehydrating device, and the porous wire or membrane covers one or more vacuum cavities that remove the dispersion medium from the wet MFC film.

[0084] Furthermore, optionally, a pre-drying device 134 can be provided upstream of the dehydrating device 133.

[0085] In other embodiments, the drying devices 131 and 132 and, if present, the pre-drying device 134 can use the same or different drying techniques, for example, each can be selected according to the non-limiting options mentioned herein.

[0086] One or more measuring devices 14a, 14b, 14c, 14d, 14e are provided inside or outside the dryer 13 for measuring at least one parameter indicating the dry solid content in the wet MFC film F and / or the dry MFC film F'. For example, the measuring device 14a may be provided between a pair of drying devices 131, 132 inside the dryer 13. As another example, the measuring device 14b may be provided downstream of the drying devices 131, 132 inside the dryer 13. As yet another example, the measuring device 14c may be provided downstream and outside the dryer 13. For example, a cooling device (not shown) can be provided between the dryer 13 and the measuring device 14c.

[0087] It is understood that it is also possible to provide one, two, three, four or all of the measuring devices 14a, 14b, 14c, 14d, 14e shown above.

[0088] When a dehydrating device 133 is provided upstream of the drying devices 131, 132, the measuring device 14d can be provided downstream of the dehydrating device 133 and upstream of the drying devices 131, 132. In some embodiments, the measuring device or a sub - part thereof can be provided downstream of a part of the dehydrating device 133, for example, between sub - steps of the dehydrating device 133, or between dehydrating devices when a plurality of dehydrating devices are provided.

[0089] It is also possible to provide the measuring device 14e upstream of the dehydrating device 133.

[0090] A controller 3 can be provided to control at least the dryer 13 and the measuring devices 14a, 14b, 14c, 14d, 14e. Optionally, the controller can also control further functions or all functions of the film forming device 1. The controller can control the dehydrating device 133, if present, and the pre - drying device 134, if present.

[0091] FIG. 2 is a schematic cross - sectional view taken along line A - A of FIG. 1a and shows a first embodiment of a drying device that can be arranged inside the dryer 13.

[0092] Drying and pre-drying can be carried out by evaporation, impact drying with hot gas or hot air, infrared (IR) drying, microwave, near-infrared drying, UV drying, radiation drying, heat heating, heating of the support by steam or electricity, or other methods or combinations of methods well known in the art.

[0093] It is understood that all of the drying techniques described herein are controllable across the entire width of the support 10 and, optionally, also along the length of the film. For example, the technique of heating the support 10 from below can also be easily divided into zones as needed.

[0094] The drying device shown in FIG. 2 is a controllable convection drying device that selectively supplies dried, preferably warm or hot gas, such as air, towards the wet film F.

[0095] In the drying device shown in FIG. 2, three individually controllable convection zones 1311a, 1311b, 1311c are provided. It is understood that the number of convection zones 1311a, 1311b, 1311c can be selected according to the width of the film and the support, and the required resolution.

[0096] For each of the convection zones 1311a, 1311b, 1311c, the gas flow rate and / or gas flow direction and / or gas temperature and / or gas composition (e.g., moisture content) can be individually controlled by the controller 3 by controlling the respective blowers, the respective nozzles, the respective heaters and / or the respective gas mixers. Alternatively, or in addition, the supply of gas to each of the convection zones 1311a, 1311b, 1311c can be controlled by valves (not shown).

[0097] Therefore, during operation, the drying effects of the respective zones 1311a, 1311b, and 1311c are individually controlled by the controller 3. For example, by applying a lower gas flow rate and / or a lower temperature and / or a higher moisture content to the zones 1311a and 1311c near the side edges of the film F, the drying effect at the side edge portion of the film F can be reduced.

[0098] In the embodiment of FIG. 2, it is possible to make the collision width of the drying gas narrower than the collision width of the MFC films F and F'. For example, the collision width may be 30 to 70 mm, preferably 40 to 60 mm or about 50 mm, which is narrower than the width of the MFC films F and F'.

[0099] FIG. 3a is a schematic cross-sectional view taken along line A-A of FIG. 1a, showing a first version of a second embodiment of the drying device that can be disposed inside the dryer 13.

[0100] The drying device shown in FIG. 3a has a single convection zone 1311, which can be operated in the same manner as one of the convection zones described with reference to FIG. 2, and the gas flow rate and / or the gas flow direction and / or the gas temperature and / or the gas composition (such as moisture content) can be controlled by the controller 3.

[0101] FIG. 3a is provided with at least one discharge port 1312a, 1312b, which can be moved in the horizontal and / or vertical directions, optionally controlled by the controller 3, and can be arranged in a desired horizontal direction with respect to the film F. The discharge ports 1312a, 1312b are connected to an extraction device such as a fan that can be controlled by the controller 3, and the extraction speed can be controlled by the controller 3.

[0102] Therefore, during operation, the drying air and / or the hot air are extracted from the region of the side edge portion, and by preventing the interaction with the wet film F, the drying effect at the side edge portion of the film F is reduced, and thus, the drying effect at the side edge portion of the film F is reduced.

[0103] Figure 3b schematically shows a second version of a second embodiment of the drying device. The inlets to the exhaust ports 1312a, 1312b are arranged laterally inside the ends of the MFC films F, F', preventing the drying gas from reaching the ends of the MFC films.

[0104] Figure 3c schematically shows a third version of a second embodiment of the drying device. The convection zone 1311 is configured to provide a greater drying gas flow at its lateral central portion, for example, by reducing the gas flow resistance at the central portion of the convection zone 1311 compared to the edge portions of the convection zone 1311. This embodiment can be combined with the embodiments of FIGS. 3a and / or 3b.

[0105] Figure 4 is a schematic cross-sectional view along line A-A of FIG. 1a, showing a third embodiment of the drying device that can be arranged inside the dryer 13.

[0106] The drying device shown in FIG. 4 has a single convection zone 1311, which can be operated in the same manner as the convection zones described with reference to FIGS. 3a - 3c.

[0107] FIG. 4 is provided with at least one shield 1313a, 1313b, which are movable laterally and can be arbitrarily controlled by the controller 3, whereby the shields 1313a, 1313b can be arranged at a desired lateral position with respect to the film F.

[0108] Therefore, during operation, the incoming high-temperature and / or drying gas is diverted from the side edge portions, so there is a possibility that the drying effect at the side edge portions of the film F will decrease.

[0109] Figure 5 is a schematic cross-sectional view along line A-A of FIG. 1a, showing a fourth embodiment of the drying device that can be arranged inside the dryer 13.

[0110] The drying device shown in Fig. 5 has a single convection zone 1311, which can be operated in the same manner as the convection zones described with reference to Figs. 3a - 3c.

[0111] Fig. 5 is provided with at least one seal arrangement 1314a, 1314b, which can seal against the support 10 just outside the film F, so that the gas flow from the convection zone 1311 does not impinge on the support 10.

[0112] Therefore, during operation, it prevents the high - temperature gas from reaching the support 10, which is a metal support and has a higher thermal coefficient than the film F, reduces the heating of the support outside the lateral sides of the film F, and thus also reduces the drying effect at the side edge portions of the film F.

[0113] Fig. 6 is a schematic cross - sectional view along line A - A of Fig. 1a, showing a fifth embodiment of the drying device that can be arranged inside the dryer 13.

[0114] The drying device shown in Fig. 6 is a controllable radiation drying device for selectively irradiating the wet film F with radiation, such as infrared (IR) radiation.

[0115] In the drying device shown in Fig. 6, three individually controllable radiation zones 1315a, 1315b, 1315c are provided. It is understood that the number of irradiation zones 1315a, 1315b, 1315c can be selected according to the width of the film F and the support 10 and the required resolution.

[0116] For each radiation zone 1315a, 1315b, 1315c, the radiation intensity and / or radiation duty cycle can be individually controlled by the controller 3, for example, by controlling each radiation source and / or by controlling a radiation filter or valve.

[0117] Therefore, during operation, the drying effects in each radiation zone 1315a, 1315b, 1315c are individually controlled by the controller 3. For example, in order to reduce the drying effect at the side edge portion of the film F, it is also possible to irradiate the irradiation zones 1315a, 1315c near the side edge portion of the film.

[0118] FIG. 7 is a schematic cross-sectional view taken along line A-A of FIG. 1a, and shows a sixth embodiment of a drying device that can be disposed inside the dryer 13.

[0119] The drying device shown in FIG. 7 has a single radiation zone 1315, which can be operated in the same manner as one of the radiation zones described with reference to FIG. 6.

[0120] FIG. 7 is provided with at least one shield 1316a, 1316b, which are movable in the lateral direction and are optionally controllable by the controller 3, and the shields 1316a, 1316b can be arranged in a desired lateral direction with respect to the film F. The shield may be completely opaque to radiation. Alternatively, the shield may be variable, for example, controllable by the controller 3, and may be transmissive to radiation or partially transmissive to radiation.

[0121] The shields 1316a, 1316b can be operated to mask only the support 10 or both the support 10 and the side edge portions of the film F in order to reduce the heating of the support 10.

[0122] Therefore, during operation, since the incident radiation is shielded from the support 10 and also optionally from the side edge portions, the drying effect at the side edge portions of the film F is reduced, and the drying effect at the side edge portions of the film may be reduced.

[0123] FIG. 8 is a schematic cross-sectional view taken along line A-A of FIG. 1a, and shows a seventh embodiment of a drying device that can be disposed inside the dryer 13.

[0124] The drying device shown in FIG. 8 has a single radiation zone 1315, which can be operated in the same manner as one of the radiation zones described with reference to FIG. 6.

[0125] FIG. 8 is provided with at least one injector 1317a, 1317b for a dispersion medium and / or a coolant. The injectors 1317a, 1317b are controllable by the controller 3 and selectively apply the dispersion medium and / or the coolant to the film F and / or the support 10 immediately outside the film to increase the moisture level in the film and / or cool the film F and / or the support 10.

[0126] Therefore, during operation, as the moisture level of the film F is selectively increased and / or as the support 10 and optionally the side edge portions are also cooled, the drying effect at the side edge portions of the film F is reduced, and there is a possibility that the drying effect at the side edge portions of the film F is reduced.

[0127] FIG. 9 is a schematic cross-sectional view taken along line B-B of FIG. 1a and shows a first embodiment of a measuring device 14a that can be arranged inside or outside the dryer 13.

[0128] In the measuring device 14a shown in FIG. 9, a measuring sensor is connected to the controller 3 and is formed as a 1D sensor (line sensor) having a plurality of sensor zones 141a, 141b, 141c, 141d, each of which can generate sensor data regarding a portion limited in the lateral direction of the film F and optionally a portion limited in the lateral direction of the support 10. The number of sensor zones 141a, 141b, 141c, 141d can be arbitrarily selected according to the required resolution.

[0129] Various sensing techniques can be utilized.

[0130] For example, the measurement sensor may be a temperature sensor, and each sensor zone 141a, 141b, 141c, 141d provides corresponding portions of the film F and optionally the temperature data of the support 10, and the moisture level of each film portion can be derived based on the temperature of that film portion.

[0131] As a further example, the sensor uses infrared (IR) spectroscopy or Raman spectroscopy to provide data corresponding to the composition of the film F, whereby the composition of the material can be derived based on the resulting spectral data. Accordingly, a 2D map of the dispersion medium content of the wet or dry MFC films F, F' can be created.

[0132] Using spectroscopy such as Raman spectroscopy or near-infrared (NIR) spectroscopy, it is possible to measure not only the dry solid content at a point on the surface of the wet or dry MFC film, but also the dry solid content at various points along the thickness direction of the wet or dry MFC films F, F'.

[0133] Accordingly, substantially, a 3D map of the dispersion medium content of the wet or dry MFC films F, F' can be created.

[0134] The sensor operates continuously or at regular intervals to derive the temperature or composition profile of the films F, F', and this can be used as an input to the controller 3 to determine how the dryer 13 operates.

[0135] FIG. 10 is a schematic cross-sectional view taken along line B-B of FIG. 1a and shows a second embodiment of a measuring device that can be arranged inside or outside the dryer 13.

[0136] In the measurement arrangement shown in FIG. 10, the measurement sensor 1422 is connected to the controller 3 and may be formed as a point sensor that can be scanned across the films F, F' and optionally also across the support 10. The scan can be achieved by moving the measurement sensor along the guide 1421 and / or by using a beam guide.

[0137] The sensor can use any of the sensing techniques described with reference to FIG. 9.

[0138] Similar to the arrangement described with reference to FIG. 9, the sensor 1422 operates continuously or at regular intervals to derive the temperature or composition profile of the films F, F', and this can be used as an input to the controller 3 to determine how the dryer 13 operates.

[0139] FIG. 11 is a schematic cross-sectional view taken along line B-B of FIG. 1a and shows a third embodiment of a measuring device that can be arranged inside or outside the dryer 13.

[0140] In the measurement arrangement shown in FIG. 11, a camera 1423, for example, a 2D sensor such as a hyperspectral camera or an infrared (IR) camera, can be arranged such that the field of view covers the width of the films F, F' and optionally also the width of the support 10.

[0141] Thus, the camera 1423 can use any of the sensing techniques described with reference to FIG. 9.

[0142] Similar to the device described with reference to FIG. 9, the camera 1423 can be operated continuously or at regular intervals to derive the temperature or composition profile of the film F, and this profile can be used as an input to the controller 3 for determining how the dryer 13 operates.

[0143] At least one measurement arrangement disclosed with respect to any one of FIGS. 9 to 11 can be applied at any position along the support 10 on which the measurement arrangements 14a, 14b, 14c, 14d, 14e are shown.

[0144] The wet MFC film F can be formed from an MFC dispersion having a dry solids content of about 2.5 to 4 wt%, about 4 to 6 wt%, about 6 to 8 wt%, about 8 to 10 wt%, about 10 to 12 wt%, about 12 to 14 wt%, about 14 to 16 wt%, about 16 to 18 wt%, about 18 to 20 wt%, about 20 to 22 wt% or about 22 to 25 wt%, which is regarded as a high dry solids content MFC. Preferably, the dry solids content may be greater than 3 wt% or greater than 4 wt%.

[0145] The dry film thickness F' can be measured, as non-limiting examples, by white light interferometry, laser profilometry, or optically, by cutting the sample with a line in the machine transverse direction (whether cast in resin or not) and taking a microscopic image in the thickness direction of the cut cross-section (e.g., scanning electron microscopy or other applicable methods).

[0146] The average dry film thickness F' may be on the order of 5 to 60 μm, 15 to 20 μm, preferably 20 to 60 μm, 10 to 50 μm, 30 to 50 μm, 15 to 45 μm, or 20 to 40 μm.

[0147] A specific dry film F' thickness may be 5 to 10 μm, 10 to 15 μm, 15 to 20 μm, 20 to 25 μm, 25 to 30 μm, 30 to 35 μm, 35 to 40 μm, 40 to 45 μm, 45 to 50 μm, 50 to 55 μm or 55 to 60 μm.

[0148] The basis weight of the dry film F' is 4 to 80 g / m 2 preferably 8 to 67 g / m 2 , 12 to 60 g / m 2 , 16 to 53 g / m 2 or 20 to 45 g / m 2 and is.

[0149] The basis weight of the specific dry film F’ is 4 to 10 g / m 2 , 10 to 20 g / m 2 , 20 to 30 g / m 2 , 30 to 40 g / m 2 , 40 to 50 g / m 2 , 50 to 60 g / m 2 , 60 to 70 g / m 2 or 70 to 80 g / m 2 and may be such.

[0150] The content of the dispersion medium in the dry film F’ may be about 0.1 to 20% by weight, preferably 1 to 15% by weight, or about 2 to 14% by weight.

[0151] The content of the specific dispersion medium in the dry film F’ may be 0.1 to 1% by weight, 1 to 2% by weight, 2 to 3% by weight, 3 to 4% by weight, 4 to 5% by weight, 5 to 6% by weight, 6 to 7% by weight, 7 to 8% by weight, 8 to 9% by weight, 9 to 10% by weight, 10 to 11% by weight, 11 to 12% by weight, 12 to 13% by weight, 13 to 14% by weight or 14 to 15% by weight.

[0152] The content of the film-forming components in the dry film F’ may be 80 to 99.9% by weight, preferably 85 to 99% by weight, or 86 to 98% by weight, and the balance is the dispersion medium and / or one or more additives.

[0153] In particular, the film-forming components may have an MFC content of 50 to 60% by weight, 60 to 70% by weight, 70 to 80% by weight, 80 to 90% by weight, 90 to 95% by weight or 95 to 99% by weight.

[0154] The width of the dry film F’ may be about 0.3 to 4 m, preferably 0.5 to 4 m, 1 to 4 m, or 2 to 4 m.

[0155] The width of the specific films F, F' may be 0.3 - 0.5 m, 0.5 - 1 m, 1 - 1.5 m, 1.5 - 2 m, 2 - 2.5 m, 2.5 - 3 m, 3 - 3.5 m, or 3.5 - 4 m. The width of the corresponding support 10 is at least the same as the width of the film, and in some cases is about 10 - 20 cm wider than the width of the film.

[0156] By using the method of the present disclosure, a dried MFC film F' having a uniform composition with respect to the dispersion medium can be produced. By measuring the content of the dispersion medium at a plurality of points across the width of the dried MFC film F', for example, at 1 cm intervals across the width of the dried MFC film F', it is possible to derive the average content of the dispersion medium and the standard deviation of the content. According to the method disclosed herein, it is possible to achieve a standard deviation of 1 wt% or less across the width of the MFC film F' having a width exceeding the width of laboratory-scale equipment.

[0157] It is also possible to affect the dry solid content of the films F, F' by measures implemented in the casting device 16.

[0158] For example, the nozzle of the casting device 16 can be adjusted to change the thickness of the wet MFC dispersion layer applied to the support 10, for example, increasing the thickness of the portion where the MFC films F, F' dry faster.

[0159] It is also possible to change the temperature of the nozzle, and as a result, the temperature of the wet MFC films F, F' applied to the support 10 varies across the width of the support 10.

[0160] It is also possible to locally cool or heat the support 10 at the casting device 16 or immediately downstream thereof.

Claims

1. A method for producing an MFC film from a microfibrillated cellulose (MFC) dispersion, To provide an MFC dispersion liquid comprising a dispersion medium and a film-forming component containing approximately 50 to 100% by weight of MFCs, Applying a layer of MFC dispersion to a support to form a wet MFC film (F), The wet MFC film on the support is subjected to at least one drying step to form a dried MFC film (F'), At least one parameter indicating the dry solids content in the wet MFC film (F) and / or dry MFC film (F') is measured at at least two data points spaced laterally across at least the width of the MFC films (F, F'), Depending on the parameters, at least one of the drying conditions in the at least one drying step is varied over the width of the wet MFC film (F, F'). A method that includes this.

2. The method according to claim 1, wherein the measurement step is performed after at least a portion of the at least one drying step.

3. The method according to claim 1, further comprising at least one dehydration step prior to the at least one drying step, wherein the measurement step is performed after at least a portion of the at least one dehydration step and before the at least one drying step.

4. The method according to claim 1, wherein at least one data point indicates the dry solids content at a position on the side edge portion of the MFC film (F, F').

5. The method according to claim 1, wherein at least one data point indicates the dry solids content in a portion of the MFC film (F, F') spaced laterally from the side edges.

6. The method according to claim 1, wherein changing the drying conditions includes selectively changing the drying effect over the width direction.

7. The method according to claim 6, wherein changing the drying effect includes reducing the drying effect at at least one side edge portion of the wet MFC film.

8. The method according to claim 6, wherein changing the drying effect includes limiting the collision width of the drying gas and / or radiation to be narrower than the width of the MFC film (F, F').

9. The method according to claim 5, wherein changing the drying effect includes guiding the drying gas away from at least one side edge portion of the MFC film (F, F').

10. The method according to claim 5, wherein changing the drying effect includes extracting a drying gas from at least one side edge portion of the MFC film (F, F').

11. The method according to claim 6, wherein changing the drying effect includes masking the side edges of the MFC film (F, F').

12. The method according to claim 6, wherein changing the drying effect includes sealing the lateral support surface on the outer side edge portion of the MFC film (F, F').

13. The method according to claim 6, wherein changing the drying effect includes selectively controlling the duty cycle, combustion gas pressure, and / or the intensity of the radiation source for providing the drying.

14. The method according to claim 1, wherein changing the drying conditions includes selectively injecting at least one of the cooling medium and the dispersion medium onto a wet MFC film (F, F').

15. The MFC dispersion has a dry solids content of approximately 2.5 to 25% by weight, preferably approximately 2.5 to 15% by weight, 2.5 to 10% by weight, or approximately 2.5 to 8% by weight, and optionally a shear rate of 20 s. －１ The method according to claim 1, wherein the viscosity is greater than approximately 4 Pa·s.

16. The method according to claim 1, wherein the average film thickness of the dried MFC film (F') is about 5 to 60 μm, preferably 10 to 50 μm, 15 to 45 μm, or 20 to 40 μm.

17. The film weight of dry MFC film (F') is approximately 4-80 g / m². ２ Preferably 8 to 67 g / m ２ , 12-60 g / m ２ 16-53 g / m ２ Or 20-45 g / m ２ The method according to claim 1.

18. The method according to claim 1, wherein the dispersion medium content of the dried MFC film (F') is about 0.1 to 20% by weight, preferably 1 to 15% by weight, or 2 to 14% by weight.

19. The method according to claim 1, wherein the film-forming component content of the dried MFC film (F') is at least 80 to 99.9% by weight.

20. The method according to claim 19, wherein the film-forming component comprises at least 60% by weight of MFC, at least 70% by weight of MFC, or at least 80% by weight of MFC.

21. The method according to claim 1, wherein the film width of the dried MFC film (F') is approximately 0.3 to 4 m, preferably 0.5 to 4 m, 1 to 4 m, or 2 to 4 m.

22. A device for producing an MFC film from a microfibrillated cellulose (MFC) dispersion, Support guide devices (11, 12) configured to guide a continuous support (10), A casting device (16) configured to apply an MFC dispersion onto a support (10) as a wet MFC(F) film, A drying apparatus (13, 131, 132, 134) is configured to remove the dispersion medium from a wet MFC film (F) to form a dry MFC film (F'), Data indicating the dry solids content in a wet MFC film (F) and / or a dry MFC film (F'), comprising at least one measuring device (14a, 14b, 14c, 14d, 14e) configured to provide data at at least two data points spaced laterally across at least the width of the MFC film (F, F'), A controller (3) is configured to receive the aforementioned data and control the drying devices (13, 131, 132, 134) based on the aforementioned data to change the drying conditions across the width of the wet MFC film (F). A device that includes this.

23. A dry MFC film (F') having a dispersion medium content of approximately 0.1 to 20% by weight, preferably 1 to 15% by weight, or 2 to 14% by weight, is subjected to a dry solids content of approximately 2.5 to 25% by weight, preferably 2.5 to 15% by weight, or 2.5 to 10% by weight, or approximately 2.5 to 8% by weight, and a shear speed of 20 s. －１ Use of the device according to claim 22 for forming from an MFC dispersion having a viscosity of more than approximately 4 Pa·s.

24. A microfibrillated cellulose (MFC) film (F') having a longitudinal direction parallel to the manufacturing direction of the film and a width direction perpendicular to the longitudinal direction, The MFC film has a film-forming component content of at least 80 to 99.9% by weight. The film-forming component contains at least 50% by weight of MFC, The MFC film has a width of approximately 0.3 to 4 m, preferably 0.5 to 4 m, 1 to 4 m, or 2 to 4 m. The MFC film has a dispersion medium content of about 0.1 to 20% by weight, preferably 1 to 15% by weight, or 2 to 14% by weight. The dispersion medium content of the MFC film (F') has a standard deviation of less than 1% by weight along the width direction, and the moisture content is analyzed every 1 cm of the width of the MFC film (F'). MFC film.

Images