Wrappers with transparent areas, methods for making wrappers with transparent areas, and packages including such wrappers

Abstract

A wrapper having a transparent region, the wrapper and the region being made from one cellulose layer, the transparent region comprising a coating layer material applied to the wrapper, the coating layer material comprising an oily compound such as paraffin or vegetable oil.

Description

[Technical field]

[0001] The present invention relates to a wrapper. The present invention further relates to a cellulosic package comprising the wrapper, and to a method for producing the wrapper. [Background technology]

[0002] The pouch-like packaging provided with a window and further comprising paper finds particular application for bread, baked goods, vegetables, meat, and fruit. The window is generally transparent, for the purpose of allowing customers and store personnel to view the packaged object within the pouch-like packaging. The window is typically formed by a strip glued to both sides of the paper, and is made from a plastic material such as polypropylene (PP) or polyethylene terephthalate (PET), or optionally another polyester.

[0003] Methods for producing such packaging and the resulting packaging are known from EP 1 894 714 B1 and EP 3 095 723 A1. However, such packaging with a window is difficult to manufacture in practice. A roll of paper and a roll of plastic window material are therefore typically required for this purpose. These rolls are unwound and an adhesive material is applied to the paper and / or the window material. The window material is glued to the paper using the adhesive material. This manufacturing process is difficult to control, since the window material tends to come loose during placement of the window material. To avoid this problem, the manufacturing workers responsible during the manufacturing process need to be highly skilled. This dependency on highly skilled personnel is undesirable. Furthermore, the realized mutual connections are of suboptimal quality. The window therefore tends to be torn off from the paper, which is undesirable in packaging use. Furthermore, plastic windows are expensive compared to paper. The resulting packaging is therefore also expensive. In addition, from an ecological perspective with a view to sustainability, the resulting packaging may be difficult or impossible to recycle.

[0004] WO2020170226 describes a composite package made from different recyclable materials. The composite package described in WO2020170226 is an assembled package constructed from different materials, in particular a recyclable base material and a recyclable window material that is partially transparent and attached to the first recyclable base material to form a window in the composite package. The manufacturing process of the composite package in WO2020170226 is difficult to control because the window material tends to loosen during placement of the window material. Summary of the Invention

[0005] It is therefore an object of the present invention to provide a wrapping paper which can be produced more cheaply in a simple manner. It is a further object of the present invention to provide a method for producing such a wrapping paper and to provide a package comprising the wrapping paper.

[0006] The present invention provides for this purpose a wrapping paper with a transparent area, the wrapping paper and the transparent area being made from one cellulose layer, the transparent area comprising a coating layer material applied to the wrapping paper. The coating layer material comprises an oily compound, such as paraffin or vegetable oil. In this way, a wrapping paper is provided that is at least partially translucent or transparent. Thus, customers and store personnel can see the packaged object in the package made of the wrapping paper. In this way, the use of plastic materials is avoided. Such wrapping paper is more sustainable, cheaper and easier to manufacture.

[0007] The transparent regions preferably extend at least partially in the longitudinal direction of the cellulose layer.

[0008] The transparent region preferably extends at least partially across the width of the cellulosic layer.

[0009] The transparent region is preferably in the form of a strip and extends across the cellulose layer, although it will be apparent to one skilled in the art that the transparent region can take different forms.

[0010] The transparent areas preferably have an opacity, measured according to ISO 2471, between 1% and 35%, more preferably between 3% and 25%, and most preferably between 3% and 15%.

[0011] The applied coating layer material preferably has a density of at least 1 g / m 2 More preferably, the surface density is 2.5 to 6 g / m 2 It should be noted that the predetermined amount of coating layer material can be selected depending on the characteristics of the cellulose layer, such as the type of cellulose layer. For example, in the case of a bleached cellulose layer, also called white paper, the coating layer has a surface density of about 8 g / m 2 or, by way of further example, in the case of brown paper, about 10 g / m 2 Further tests have shown that the applied coating layer material is between 2.5 and 15 g / m 2 Such a predetermined amount of coating layer material, or surface density of the applied coating layer material, is selected such that the cellulose layer onto which the coating layer material is applied is saturated.

[0012] The cellulose layer is preferably 18 g / m 2 It has a higher surface density, the cellulose layer preferably has a density of up to 50 g / m 2 , more preferably up to 35 g / m 2 Such a cellulose layer has a surface density of 0.01 to 0.05 mm. Such a cellulose layer is relatively light in weight, which has the advantage that the wrapper is easily transportable and less expensive. Such a cellulose layer can also be more uniformly impregnated with the coating layer material. The advantageous effect is due to the lower fiber density of a cellulose layer having such a surface density or specific gravity.

[0013] Preferably, at least the first side surface of the cellulose layer has a surface roughness according to ISO 8791 / 2 (also called Bendtsen roughness method) of less than 220 ml / min, preferably less than 100 ml / min, more preferably less than 80 ml / min, most preferably less than 40 ml / min. It is noted that the cellulose layer can have such a surface roughness on both the first side and the second side. The surface roughness may be different on the first side and the second side. The cellulose layer may further have a substantially uniform surface roughness on the first and second sides. Such a surface roughness corresponds to the smoothness of the paper. The inventors have surprisingly found that smoother paper has a tendency to be more transparent with less coating layer material. It is speculated that this effect is achieved because the cellulose fibers are aligned relatively similarly in the smooth paper, which allows the coating layer material to penetrate and impregnate the cellulose layer more uniformly.

[0014] The coating layer material preferably substantially completely coats the transparent area, in other words the entire surface of the transparent area preferably comprises the coating layer material, however it is possible that the transparent area comprises parts that do not comprise the coating layer material.

[0015] The cellulose layer is preferably a bleached cellulose layer.

[0016] The cellulose layer preferably comprises a mixture of long and short fibers and comprises at least 40% long fibers, more preferably at least 50% long fibers, more preferably at least 70% long fibers. Such a cellulose layer has the advantage that it is tear-resistant. The subsequently realized packaging is therefore stronger compared to, for example, glassine paper. Such a cellulose layer further has the advantage that it can be produced in a conventional manner. The cost of a cellulose layer having such a fiber composition can be produced considerably cheaper compared to glassine paper. Furthermore, the production of such a cellulose layer is simpler, faster and more sustainable. According to one example, the cellulose layer can even comprise almost 100% long fibers. Such a cellulose layer is obtained by adding only long fibers during the production of the cellulose layer. In other words, no short fibers are added.

[0017] The coating layer material in the transparent region is preferably applied to the wrapper at a first temperature within a first temperature range and cured stepwise at a second temperature within a second temperature range so as to form a transparent region. Here, the first temperature is higher than the second temperature. The advantage of the present invention is based on the insight that in known manufacturing processes, the coating layer material is immediately and instantaneously cooled, typically at a low temperature such as 5°C, for example with a cooling roller. Thus, the coating layer material on the cellulose layer cures very quickly. This allows for rapid further processing of the wrapper. Thus, in known processes, the coating layer material does not always have time to further penetrate the cellulose layer, and as a result cures into a structure with a cloudy or opaque result due to the sudden temperature drop. The inventors have surprisingly found that the stepwise curing makes the areas penetrated by the coating layer material transparent (also called vitreous), thus forming a transparent region. The stepwise curing of the coating layer material allows the oily material to cure and form a path through the cellulose layer that is transparent to light. In this way, the coating layer material appears to cure into a substantially vitreous structure. In this way, the transparency of the transparent areas is greatly improved.

[0018] The coating layer material in the transparent area is preferably exposed to the second temperature for at least 0.1 seconds, preferably for between 0.5 and 7 seconds, preferably for at least 7 seconds, where the second temperature can vary within a second temperature range.

[0019] The transparent region is formed by applying a quantity of coating layer material to the location of the region at a first temperature, preferably within a first temperature range; The transparent region can be obtained by gradually curing the applied amount of coating layer material at a second temperature within a second temperature range to form a transparent region. The advantage of the present invention is based on the insight that in known manufacturing processes, the coating layer material is immediately cooled, typically at a low temperature such as 5°C, for example using a cooling roller, in order to rapidly cure the coating layer material onto the cellulose layer. This allows for rapid further processing of the wrapper. Thus, in known processes, the coating layer material does not always have time to penetrate the cellulose layer and, as a result, cures into a structure with a cloudy or opaque result due to the sudden temperature drop. The inventors have surprisingly found that the gradually curing makes the regions penetrated by the coating layer material transparent, thus forming a transparent region. The gradually curing of the coating layer material allows the oily material to cure and form a path through the cellulose layer that is transparent to light. It is assumed that the coating layer material thus cures into a substantially glassy structure. In this way, the transparency of the transparent region is improved.

[0020] The cellulose layer having the amount of coating layer material is preferably exposed to the second temperature range for at least 0.1 seconds, preferably for a period of 0.5 to 7 seconds, preferably for at least 7 seconds.

[0021] The second temperature range is preferably between 30°C and 120°C, preferably between 40°C and 110°C, more preferably between 50°C and 100°C. Such a temperature range increases the viscosity of the applied coating layer material, thereby allowing the coating layer material to penetrate the cellulose layer better. The second temperature range is optional. It should therefore be noted that if the first temperature range is sufficiently warm, for example about 150°C, the second temperature range will have only limited or no effect.

[0022] The application of a predetermined amount of coating layer material preferably comprises the steps of: - providing an endless moving surface; - picking up a quantity of coating layer material in an endless moving surface; - contacting the endless moving surface with a first side of the cellulose layer.

[0023] The second temperature range may preferably be provided by residual heat resulting from application of the coating layer material.

[0024] The first temperature range is preferably between 70°C and 180°C, preferably between 80°C and 150°C, more preferably between 100°C and 120°C.

[0025] The advantages of the wrapping paper apply mutatis mutandis to cellulosic packaging and methods of manufacture thereof.

[0026] According to a second aspect, the present invention provides a cellulosic packaging comprising the wrapper described above. The region preferably forms a window in the cellulosic packaging.

[0027] According to a third aspect, the present invention provides a method of making a wrapper having a transparent area, the method comprising: - providing a cellulose layer having a first and a second side; applying a quantity of coating layer material at the location of the region, the coating layer material having a first temperature within a first temperature range; - stepwise curing the applied amount of coating layer material at a second temperature within a second temperature range to form a transparent area.

[0028] The second temperature range is preferably between 30°C and 120°C, preferably between 40°C and 110°C, more preferably between 50°C and 100°C.

[0029] The application of a predetermined amount of coating layer material preferably comprises the steps of: - providing an endless moving surface; - picking up a quantity of coating layer material in an endless moving surface; - contacting the endless moving surface with a first side of the cellulose layer.

[0030] The second temperature range may preferably be provided by residual heat obtained during application of a given amount of coating layer material.

[0031] The first temperature range is preferably between 70°C and 180°C, preferably between 80°C and 150°C, more preferably between 100°C and 120°C.

[0032] The transparent area is preferably arranged to extend at least partially on the cellulose layer, viewed in the longitudinal direction of the cellulose layer.

[0033] The transparent region is preferably arranged to extend at least partially over the cellulose layer in the width direction of the cellulose layer.

[0034] The transparent area is preferably applied in the form of a strip.

[0035] According to ISO 2471, the opacity of the transparent areas is preferably between 1% and 35%, more preferably between 3% and 25%, most preferably between 5% and 15%.

[0036] The predetermined amount of coating layer material is preferably at least 1 g / m 2and more preferably 2.5 to 6 g / m 2 corresponds to a surface density between

[0037] The cellulose layer having the amount of coating layer material is preferably exposed to the second temperature range for at least 0.1 seconds, preferably for a period of 0.5 to 7 seconds, preferably for at least 7 seconds.

[0038] The cellulose layer is preferably 18 g / m 2 It has a higher specific gravity, the cellulose layer preferably has a density of up to 50 g / m 2 , more preferably up to 35 g / m 2 It has a specific gravity of

[0039] The surface on at least the first side of the cellulose layer preferably has a surface roughness of less than 220 ml / min, more preferably less than 100 ml / min, even more preferably less than 80 ml / min, and most preferably less than 40 ml / min. The surface roughness is determined here according to ISO 8791-2 and is also known as Bendtsen roughness. In this way, the coating layer material can penetrate the cellulose layer more uniformly.

[0040] The coating layer material preferably substantially completely coats the transparent areas.

[0041] The cellulose layer is preferably a bleached cellulose layer.

[0042] The cellulosic layer preferably comprises a mixture of long and short fibres, with at least 40% long fibres, more preferably at least 50% long fibres, preferably at least 70% long fibres. [Brief description of the drawings]

[0043] The above and other advantageous features and objects of the present invention will become more apparent and the invention will be better understood by reference to the following detailed description when read in conjunction with the accompanying drawings and tables. [Figure 1] A, B, C, D, E, F, G, and H each show a top view of a wrapper having a transparent area according to an example embodiment. [Figure 2A] 1 illustrates a method of making a wrapper having transparent areas based on a cross-sectional view of a cellulose layer. [Figure 2B] 1 illustrates a method of making a wrapper having transparent areas based on a cross-sectional view of a cellulose layer. [Figure 2C] 1 illustrates a method of making a wrapper having transparent areas based on a cross-sectional view of a cellulose layer. [Figure 2D] 1 illustrates a method of making a wrapper having transparent areas based on a cross-sectional view of a cellulose layer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0044] The invention will now be further explained on the basis of exemplary embodiments shown in the drawings, in which identical or similar elements are designated with the same reference numbers.

[0045] 1A, 1B, 1C, 1D, 1E, 1F, 1G, and 1H show an exemplary embodiment of a wrapper 100 having a transparent region 110. In Figures 1A, 1B, 1C, 1D, 1E, 1F, 1G, and 1H, a coordinate system X, Y is shown, where the indicated axis X indicates the width direction of the wrapper and the indicated axis Y indicates the length direction of the wrapper.

[0046] In the figures, the wrapper 100 is rectangular. Such a form is typically obtained during the manufacture of the wrapper 100. More specifically, the wrapper 100 is manufactured from a roll of paper, also called a cellulose layer. However, it will be clear to a person skilled in the art that the wrapper 100 can take different forms. During the manufacture of the wrapper 100, the cellulose layer is typically supplied in bulk, more specifically in the form of a roll, including the cellulose layer in a rolled-up form. After unwinding from the roll, the cellulose layer forms a strip. The strip has a width, for example, corresponding to the width shown in Figures 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H, and is guided through a processing device, which will be further described below and is configured in particular to process the strip of cellulose layer and cut it into the wrapper 100 shown in Figures 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H. However, it will be clear to a person skilled in the art that the wrapper 100 can take different forms. Thus, in contrast to the straight lines shown in the figures, the edges of the wrapper 100 can be formed such that one or more protrusions and / or one or more depressions are formed. Edges are understood to mean edges that are substantially transverse to the longitudinal direction of the cellulose layer. The transverse edges can also be cut out or preformed with one or more protrusions and / or one or more depressions. The protrusions and / or depressions can serve to attach the wrapper 100 to a corresponding wrapper, for example to form a pouch-like package. Cutting (also called chopping) of strips of cellulose layers is known per se to the person skilled in the art and therefore will not be described for the sake of a brief description.

[0047] The wrapper 100 has a transparent region 110, more specifically, the wrapper 100 having the transparent region 110 is shown. The wrapper 100 and the transparent region 110 are manufactured from one cellulose layer. In other words, the wrapper is manufactured from one piece of cellulose layer. The transparent region 110, also called window, is therefore manufactured from the same cellulose layer as the opaque region of the wrapper 100. This is in stark contrast to known wrappers provided with a plastic window material, such as polypropylene (PP), or polyethylene terephthalate (PET), or optionally another polyester. The known wrappers combine two different material types, i.e. a cellulose layer and a plastic layer, or a first cellulose layer and a second cellulose layer, to achieve a windowed wrapper, with the resulting disadvantages mentioned in the previous sentence. The known wrappers therefore consist of at least two different and separate materials, typically combined by gluing.

[0048] The transparent area 110 comprises a coating layer material applied to the wrapper 100. The coating layer material preferably comprises an oily compound, preferably paraffin. The oily compound permeates the cellulose layer, as shown in FIG. 2C, and allows light to pass through the cellulose layer at the location of the area where the coating layer material is applied. The places where the permeated coating layer material allows the passage of light through the wrapper are called transparent areas 110. In the context of this application, transparency or translucency is defined as the degree to which it is possible to see through a material, i.e. the cellulose layer. This property depends, among other things, on the degree to which the cellulose layer allows light to pass through. The cellulose layer without the coating layer material absorbs or reflects light. Transparency falls under the broader term "transmission". In physics, transmission is understood to mean the permeability of a medium to waves, such as light, sound waves, or electromagnetic waves, the medium in this case being the cellulose layer. In the context of this application, transmittance refers to the portion of the incident radiant or luminous flux that is transmitted through a transparent area. Opacity, which is the inverse of transmittance, is additionally used. According to ISO 2471, the opacity of the transparent area is preferably between 1% and 35%, more preferably between 3% and 25%, most preferably between 5% and 15%. In this way, an at least partially translucent or transparent wrapping paper 100 is provided. Thus, customers and store personnel can see the packaged object in the package formed from the wrapping paper. In this way, the use of plastic materials is avoided. Such wrapping paper is more sustainable, cheaper and easier to manufacture. Alternatively or additionally, the coating layer material can contain vegetable oil. Wrapping paper with a transparent area 110 containing only vegetable oil is furthermore recyclable and / or compostable. A further advantage of the transparent area, formed by applying an oily compound and saturating the cellulose layer with it, is based on the insight that a plastic window is not strong enough and / or under the weight of the product in the wrapping material may result in unpredictable stretching and / or tearing of the plastic, resulting in the product falling out of the wrapping material. A further problem with the use of plastic windows is that the connection line between the plastic and the paper is typically a weak area that is prone to tearing.The packaging material 100, which is formed from a single layer of cellulose, almost completely eliminates these problems.

[0049] 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H show that the transparent regions 110 preferably extend at least partially onto the cellulose layer. Although not shown, the transparent regions 110 can also extend over the entire surface of the cellulose layer. In this way, the entire wrapper 100 is transparent. The transparent regions 110 preferably extend in the form of strips.

[0050] According to the preferred embodiment of FIG. 1A, the transparent area 110 extends in the longitudinal direction Y of the cellulose layer. In FIG. 1A, the transparent area 110 extends from one edge to the opposite edge. In this way, the transparent area 110 forms a transparent strip in the cellulose layer as seen in its longitudinal direction. If the wrapper is used, for example, as a pouch, this allows visibility into the pouch throughout the entire longitudinal direction of the wrapper 100. Shown in each of FIGS. 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H is a representation of an item P, packaged in the wrapper 100. The visibility of the product indicates the transparency of the transparent area 110 and the opacity of the opaque areas.

[0051] In FIG. 1A, the transparent area 110 is located in the center of the cellulose layer. In this way, two non-transparent areas 120 are located on either side of the transparent area 110. The non-transparent zones 120, also called opaque zones 120, can be parts of the cellulose layer where no coating layer material or only a small amount of coating layer material is applied. Such untreated parts of the cellulose layer are opaque. The opaque areas have a higher moisture permeability than the transparent areas. By varying the area ratio of the transparent and opaque areas, the moisture permeability can be further controlled. This reduces the risk that products packaged in the wrapper will develop mold, for example against plastic packaging. The untreated parts of the cellulose layer further allow the wrapper to adhere optimally to itself or to another material.

[0052] In comparison to FIG. 1A, FIG. 1B illustrates that the transparent areas 110 may be disposed on the periphery of the wrapper 100, for example on the transverse edges of the wrapper 100.

[0053] FIG. 1C shows that the transparent regions 110 may also extend in the width direction X of the cellulose layer. The transparent regions 110 in FIG. 1C are therefore wider than the transparent regions 110 shown in FIGS. 1A and 1B. The packaged article P is thus more clearly visible. In this embodiment, the opaque regions in FIG. 1C have a smaller surface area than the opaque regions in FIGS. 1A and 1B. In this way, the wrapper 100 in FIG. 1C has a lower moisture permeability than the wrapper 100 shown in FIGS. 1A and 1B.

[0054] FIG. 1D shows a wrapper 100 having a transparent region 110 extending from a first transverse edge to a second transverse edge opposite the first transverse edge in the width direction X of the cellulose layer. The transparent region 110 in FIG. 1D is therefore smaller in the longitudinal direction Y than the transparent region shown in FIGS. 1A, 1B, and 1C. In this way, the transparent region forms a transparent strip in the width direction of the cellulose layer. As in FIGS. 1A, 1B, and 1C, two non-transparent regions are located on either side of the transparent region. It will be apparent that the formed transverse strip can also be formed to be located adjacent to the edge of the cellulose layer.

[0055] 1E, 1F and 1G show a packaging material with a plurality of transparent regions 110. Thus, FIG. 1E shows that, for example, two or more transparent regions 110 can take the form of transverse strips. The transparent regions 110 are located at a distance from each other when viewed in the longitudinal direction of the cellulose layer. FIG. 1G shows that, for example, two or more transparent regions 110 can take the form of longitudinal strips. These transparent regions 110 are also located at a distance from each other when viewed in the longitudinal direction of the cellulose layer. FIG. 1F shows an example where multiple transparent regions coincide. The example shown in FIG. 1F comprises a first transparent region forming a transverse strip and a second transparent region forming a longitudinal strip. Based on FIG. 1F, it will be clear that multiple transparent regions can overlap and together form one transparent region. The transparent regions are described above as substantially rectangular with substantially straight edges. However, the transparent regions can also have edges that are at least partially curved and / or bent. Thus, the transparent area can also have a round shape, such as a circle or an oval. The transparent area can also be a combination of shapes or have a shape other than a geometric shape, such as a human-shaped silhouette. It will be clear to one skilled in the art that the transparent area can have any shape and can be adapted based on, for example, the shape of a logo, a packaged object or a food product, etc.

[0056] The wrapper 110 can be manufactured by providing a cellulosic layer with a first side and a second side. A method of manufacturing the cellulosic layer is described with reference to Figures 2A, 2B, 2C, and 2D.

[0057] 2A, 2B, 2C, and 2D show a cross-section of a cellulose layer 130 as described in relation to 1A, 1B, 1C, 1D, 1E, 1F, 1G, and 1H. The method includes providing a cellulose layer 130 having a first side 131 and a second side 132. As shown in FIG. 2A, the cellulose layer 130 is initially opaque. Thus, a product P located beneath the cellulose layer 130 is not visible or discernible, or only to a limited extent. The cellulose layer 130 is preferably made of 18 g / m 2 The cellulose layer 130 preferably has a specific gravity of up to 50 g / m 2 , more preferably up to 35 g / m 2 Such a cellulose layer has a specific gravity of 0.1 to 0.2 mm. Such a cellulose layer is relatively light in weight, which has the advantage that the wrapper is easily transportable and less expensive. Such a cellulose layer 130 can also be more easily permeable by the coating layer material 140. In other words, such a cellulose layer can be advantageously saturated by the applied coating layer material 140. The advantageous effect is believed to be due to the lower fiber density of a cellulose layer having such a specific gravity.

[0058] The surface on at least the first side 131 of the cellulose layer 130 preferably has a surface roughness of less than 220 ml / min, preferably less than 100 ml / min, more preferably less than 80 ml / min, and most preferably less than 40 ml / min. The surface roughness is determined here according to ISO 8791-2 and is also known as the Bendtsen roughness. In this way, the coating layer material applied to this first side can penetrate the cellulose layer 130 more uniformly.

[0059] The cellulose layer 130 is preferably a bleached cellulose layer, such as white paper, in which case optimal transparency results are obtained, although it should be noted that white paper is not essential, as tests have shown that nearly the same transparency can be achieved with brown paper.

[0060] The cellulose layer 130 further preferably comprises a mixture of long and short fibers, with at least 40% long fibers, more preferably at least 50% long fibers, preferably at least 70% long fibers. Such a cellulose layer has the advantage that it is tear resistant. The subsequently realized packaging is therefore stronger compared to, for example, glassine paper. Such a cellulose layer further has the advantage that it can be manufactured in a conventional manner. The cost of a cellulose layer with such a fiber composition can be manufactured considerably cheaper compared to glassine paper. Furthermore, the manufacture of such a cellulose layer is simpler, faster and more sustainable.

[0061] As shown in FIG. 2B, a quantity of coating layer material 140 having a first temperature is applied to the first side at the location of the region. The coating layer material is preferably brought to the first temperature immediately before its application. The first temperature is in a first temperature range. The first temperature may vary between the limits of the first temperature range. The first temperature range is preferably between 150° C. and 180° C., more preferably between 80° C. and 150° C., and most preferably between 100° C. and 120° C. Such a temperature range improves the viscosity of the applied coating layer material 140. In this way, the coating layer material becomes more viscous, i.e. more fluid or liquid, whereby the coating layer material can penetrate the cellulose layer 130 in an improved manner and saturate the cellulose layer 130 in an efficient manner. A temperature range between 100° C. and 120° C. realizes the further advantage that the coating layer material cannot burn. The viscosity of the coating layer material 140 is preferably between 5 mPa / s and 500 mPa / s, measured at a temperature of 100° C. The viscosity of the coating layer material 140 is more preferably between 5 mPa / s and 250 mPa / s, measured at a temperature of 100° C. It is noted that the cellulose layer may be heated before the coating layer material is applied. This allows the coating layer material to penetrate further into the cellulose layer in an improved manner.

[0062] The penetration of the coating layer material 140 is illustrated by the circles shown in the cellulose layer 130. The coating layer material 140 penetrates between the fibers of the cellulose layer, preferably up to (close to) the second side 132. In this way, a substantially continuous flow of the coating layer material through the cellulose layer 130 is formed. It is preferable to select a predetermined amount of coating layer material that is sufficiently large to substantially ensure transparency. Thus, the predetermined amount of coating layer material is preferably at least 1 g / m 2 and more preferably 2.5 to 6 g / m 2 In this way, the coating layer material saturates the cellulose layer and the desired transparency is substantially guaranteed. The predetermined amount of coating layer material is more preferably a maximum of 12 g / m 2 It should be noted that the predetermined amount of coating layer material may be selected taking into consideration the type of cellulose layer. For bleached cellulose layers, also called white paper, the amount is, for example, 6 to 8 g / m 2 or, by way of further example, in the case of brown paper, 8 to 10 g / m 2 According to a further exemplary embodiment, a coating weight of 1 to 15 g / m 2 Alternatively, the coating layer material may be applied in a quantity of 0.1 to 0.5% by weight. The amount of coating layer material selected in this way saturates the cellulose layer. It should be noted that if the coating layer material is applied on both the first and second sides, the transparency is further improved. The amount of coating layer material may be different on the first and second sides, but it is preferred that the collective surface density of the coating layer material on the first and second sides corresponds to the above-mentioned value. By applying the coating layer material on both sides, it is almost guaranteed that the coating layer material penetrates the cellulose layer and that the coating layer material saturates the cellulose layer. The inventors have surprisingly found that if the coating layer material is applied on both sides of the cellulose layer, the transparency is further improved.

[0063] FIG. 2C shows that the coating layer material 140 has penetrated the cellulose layer 130. It will be clear that a part of the coating layer material 140 may protrude from the cellulose layer 130. In other words, a certain amount of the coating layer material 140 may still be present on the surface of the cellulose layer 130. Particularly in the advantageous situation where the cellulose layer is completely saturated with the coating layer material 140, a residue or excess of the coating layer material 140 may remain on the cellulose layer surface. The applied amount of coating layer material is then cured stepwise at a second temperature. The second temperature is in a second temperature range. The second temperature may vary between the limits of the second temperature range. The stepwise curing causes the areas penetrated by the coating layer material to become transparent, thus forming the transparent area 110. The stepwise curing of the coating layer material allows the oily material to harden, thus forming a transparent path for light through the cellulose layer 130, as shown in FIG. 2D. It should be noted that the stepwise curing is significantly different from existing manufacturing processes in which the coating layer material is immediately cooled, typically at a very low temperature such as about 5°C, using a cooling roller to harden the coating layer material on the cellulose layer. In known processes, the coating layer material does not have time to penetrate the cellulose layer and thus hardens into a structure with an opaque result due to the sudden temperature drop. The first and second temperature ranges are higher than the melting point of the coating layer material. For example, if the coating layer material has a melting point of 50°C, such as paraffin, it is hardened stepwise at 50°C or higher. The stepwise curing is preferably performed in a second temperature range between 30°C and 120°C, preferably between 40°C and 110°C, more preferably between 50°C and 100°C. It will be clear to one skilled in the art that further specific preferred limits of the second temperature range depend on the coating layer material used. The stepwise curing can also include heating the cellulose layer having the coating layer material applied thereto. Thus, the coating layer material may already be initially cured, for example using a hot air blowing device, as will be further explained, before the coating layer material and the cellulose layer are exposed to the second temperature range.The cellulose layer with the amount of coating layer material is more preferably exposed to the second temperature range for at least 0.1 seconds, preferably 0.5 to 5 seconds, preferably at least 7 seconds. It is assumed that the coating layer material is thus hardened to a substantially glassy structure. Experiments have shown that transparency is thus improved.

[0064] The stepwise hardening can be performed in a different way, for example using a heating device 150, which heats the cellulose layer in a second temperature range. Alternatively or additionally, the second temperature range can be provided by residual heat, obtained by application of a predetermined amount of coating layer material. The heating device 150 can be a hot air device, which blows air at a temperature within the second temperature range onto the cellulose layer with the applied coating layer material. The heated air reheats the coating layer material, so that the coating layer material can spread further through the cellulose layer to saturate the cellulose layer. Such a preferred embodiment can be realized in a simple manner. The heating device 150 can be provided at a distance of, for example, about 0.1 to 7 meters from the application of the coating layer material. This allows the coating layer material to be at least partially hardened in a short time and then melted again. Surprisingly, it has been found that the final transparency of the transparent area is further improved in this way. Alternatively or in combination, one or more heating rollers can be provided, which heat the cellulose layer with the coating layer material to reach the second temperature range. It is further possible to further improve the penetration of the coating layer material by exposing the paper to increased pressure, for example by using a heated pressure roller. As mentioned above, the cellulose layer can be optionally heated both before and after the application of the coating layer material. Even more surprisingly, tests have shown that the coating layer material hardens stepwise even when the cooling roller is disabled, for example by preventing cooling fluid from flowing through it or by removing it. In known devices, such a cooling roller is placed downstream, typically in the immediate vicinity of the position where the coating layer material is applied, so that the coating layer material hardens immediately, resulting in the above-mentioned opaque appearance. By disabling the cooling roller, the stepwise hardening is realized in a very simple manner. In such a preferred embodiment, if the coating layer material is applied on both sides of the cellulose layer, the transparency of the transparent area is further improved.

[0065] The wrapper 100 with transparent regions is highly advantageous as a cellulose packaging material for food products such as bread, baked goods, vegetables, fruits, cheese, or meat, or for non-food products. The wrapper 100 can be converted or formed into, for example, a cellulose bag. The wrapper can also function as a sheet of paper, for example in a butcher shop, or can be supplied in rolls. The wrapper with transparent regions further allows for easy gluing of the wrapper, for example to form a bag closed on itself. Yet another advantage is that the wrapper is rather cheap compared to glassine paper. This advantage is based on the insight that glassine is manufactured using a supercalender. Such a manufacturing process requires a lot of energy, which significantly increases the cost of glassine paper compared to the wrapper 100. Glassine is also prone to tearing, since the fibers are very finely ground. EXAMPLES

[0066] The above-mentioned advantages are demonstrated in the non-limiting exemplary embodiments described below.

[0067] Example 1 Example 1 describes a known method and apparatus for dramatically increasing the moisture permeability of a paper bread bag.

[0068] Flexpack Smooth from STARKRAFT weighs approximately 35g / m 2 According to a first example, STARKRAFT Flexpack Smooth was waxed on one side of the cellulose layer 130, i.e., the first side 131 or the second side 132, or on both sides of the cellulose layer 130, i.e., both the first side 131 and the second side 132, with a specific gravity of 0.01 g / m2 by a HOLWEG-WEBER® RS26 paper bag making machine equipped with a HOLWEG-WEBER® CTH1 waxing unit. 2The paper is coated with a coating layer material 140 of paraffin, having different weights per unit area, in units of 120° C. The paraffin bath of the HOLWEG-WEBER® RS26 paper bag making machine has a temperature of 120° C. The cellulose layer is driven through the HOLWEG-WEBER® RS26 paper bag making machine with a production speed of about 110 m / min. According to a first exemplary embodiment, the cooling rollers of the HOLWEG-WEBER® RS26 paper bag making machine have a temperature of about 6-7° C. The moisture permeability of the paper is typically increased in this way. According to known methods, the paper is then further finished, for example for use as a bread bag by the consumer.

[0069] Exemplary embodiments Continuing from Example 1, further treatment of the cellulose layer 130, e.g., Flexpack Smooth from STARKRAFT, with the coating layer material 140 allows the cellulose layer 130 to be locally made transparent. In other words, it is possible to further create transparent areas 110 within the cellulose layer 130.

[0070] A sample is taken once the cellulose layer 130, also referred to as "paper" in the further description of the exemplary embodiment, has a coating layer 140. In the exemplary embodiment, a paraffin layer or paraffin coating is applied as the coating layer 140. The sample is briefly exposed to high temperatures, for example by holding the paper on a hot plate at 140° C. for a short time, for example about 1 minute. This makes the paper transparent locally, i.e. at the location of the area exposed to the hot plate. It is assumed that the exposure to a very high temperature causes the applied paraffin layer to melt again and penetrate the pores of the paper in an improved manner. The paraffin penetrating the pores of the paper is mainly driven by the capillary action of the paper fiber structure. When the refractive index of paraffin, which is typically about 1.48, and that of paper or cellulose, which is typically about 1.52, are approximately the same, the paper becomes locally transparent.

[0071] The transparency or opacity of the treated paper can be measured with a PCE-RM 100 Reflectance Meter. It will be clear to the skilled artisan that alternative so-called reflectance meters can be used. Reflectance meters typically use a measurement scale of 0-100%, where 0% is completely transparent and 100% is completely opaque. The lower the measurement, the better the transparency. Such measurements can be used in combination with or as an alternative to the ISO 2471 measurements mentioned above.

[0072] In a first exemplary embodiment (exemplary embodiment 1), the paper is coated with TopScreen® Biowax based Barrier Coating ED9 from Solenis® at 12 g / m 2 The paraffin is of the palm oil type. The measured transparency varies from 16 to 19%.

[0073] In a second exemplary embodiment (Exemplary embodiment 2), the paper is coated with TopScreen® Biowax based Barrier Coating ED9 from Solenis® at 8.5 g / m on the first side. 2 and 4.5g / m on the second side 2 In this case, the transparency varies from 16 to 19%.

[0074] In the third exemplary embodiment (exemplary embodiment 3), the paper is 8.5 g / m on the first side, similar to exemplary embodiment 2. 2 and 4.5g / m on the second side 2 However, when coated on both sides with Proquiwax® 56-58, a hydrogenated and refined petroleum-based paraffin from Proquinat, the transparency is greater than 20%.

[0075] The paper is in the fourth exemplary embodiment (exemplary embodiment 4) a TopScreen® Biowax based Barrier Coating ED9 from Solenis®, 4.5 g / m per side. 2If coated on both sides, the transparency varies from 13 to 17%.

[0076] In the fifth exemplary embodiment (exemplary embodiment 5), the paper is 4.5 g / m 2 However, when coated on both sides with Proquiwax® 56-58, a hydrogenated and refined petroleum-based paraffin from Proquinat, the transparency varies between 15-19%.

[0077] Comparing exemplary embodiments 2 and 4 with exemplary embodiments 3 and 5, it can be seen that the type and amount of paraffin applied, in combination with the type of paper, can determine the degree of transparency.

[0078] Additionally, it is noted that time also plays a role in creating transparent regions in an advantageous manner. For example, it was found that one hour after manufacture, the transparency of exemplary embodiments 1, 2, and 4 decreased by an average of 1%. After 24 hours of manufacture, the decrease in transparency is about 2%, and after about 100 days, the decrease can be 4-14%. It is speculated that paraffin continues to crystallize during the relevant time. Crystallization leads to more light scattering due to crystal edges, resulting in decreased transparency.

[0079] In the first comparative experiment (Comparative Experiment 1), Cristal® Flexible & Transparent Paper from Ahlstrom-Munksjo® is used. A very dense and transparent glassine paper is obtained by supercalendering, as described in the introductory part of the present application. Without additional coatings, this glassine paper has a transparency of 17%. Comparing the glassine paper with the exemplary embodiments 1-5, it is clear that the exemplary embodiments 1-5 have at least the same transparency as this expensive and labor-intensive glassine paper, which is due to the simple and inexpensive method described above. Furthermore, the paper according to the exemplary embodiments 1-5 is at least partially moisture and grease resistant, in contrast to the glassine paper, which is only grease resistant.

[0080] The glassine paper was from Solenis®, 3.5 g / m 2 In the second comparative experiment (Comparative Experiment 2), in which the glassine paper is coated on both sides with TopScreen® Biowax-based Barrier Coating ED9, the transparency improves to 13-15%. In the third comparative experiment (Comparative Experiment 3), one side of the glassine paper is coated with 9 g / m 2 When coated with , the transparency increases to about 15%, thus an improved transparency over the previous 17%.

[0081] Comparison of Comparative Experiment 1 with Comparative Experiments 2 and 3, and comparison of Exemplary Embodiment 2 with Exemplary Embodiments 1 and 3, shows that a minimum amount of paraffin is required to achieve improved transparency. However, it is further shown that a higher coating amount does not guarantee improved transparency. As already mentioned above, very dense and smooth papers, such as Cristal® Flexible & Transparent Paper, require less paraffin than Flexpack Smooth Paper.

[0082] In a sixth exemplary embodiment (exemplary embodiment 6), the paper according to exemplary embodiment 4 is held less than 5 cm above a hot plate at about 140° C., removed, and allowed to cool slowly. Note that the transparency is further improved to 12%, showing that gradual cooling, or gradual heating, can result in improved transparency.

[0083] Based on the above description, a person skilled in the art will understand that the present invention can be embodied in different ways and based on different principles. The present invention is not limited to the above-mentioned embodiments. The above-mentioned embodiments and drawings are purely illustrative and merely serve to deepen the understanding of the present invention. Therefore, the present invention is not limited to the embodiments described herein, but is defined in the claims.

Claims

1. A wrapping paper (100) having a transparent region (110), wherein the wrapping paper (100) and the transparent region (110) are made from a single cellulose layer, and the transparent region (110) comprises a coating layer material applied to the wrapping paper (100), the coating layer material comprising an oily compound such as paraffin or vegetable oil.

2. 2. The wrapping paper (100) of claim 1, wherein the transparent region (110) extends at least partially in the longitudinal direction (Y) of the cellulose layer.

3. The wrapping paper (100) according to any one of claims 1 to 2, wherein the transparent region (110) extends at least partially in the width direction (X) of the cellulose layer.

4. 10. The wrapper (100) of claim 1, wherein the transparent region (110) extends on the cellulose layer in the form of a strip.

5. 2. The wrapping paper (100) of claim 1, wherein the transparent region (110) has an opacity according to ISO 2471 between 1% and 35%, more preferably between 3% and 25%, and most preferably between 5% and 15%.

6. The applied coating layer material has a mass of at least 1 g / m ２ surface density of 2.5 and 6 g / m ２ The wrapping paper (100) of claim 1, having a surface density between

7. The cellulose layer has a thickness of 18 g / m ２ It has a higher surface density, the cellulose layer preferably having a density of up to 50 g / m ２ , more preferably at most 35 g / m ２ The wrapping paper (100) of claim 1, having a surface density of

8. 2. The wrapping paper (100) of claim 1, wherein the surface of at least the first side of the cellulose layer has a surface roughness of less than 220 ml / min, preferably less than 100 ml / min, more preferably less than 80 ml / min, and most preferably less than 40 ml / min.

9. The wrapper (100) of claim 1, wherein the coating layer material substantially completely coats the transparent region (110).

10. The wrapper (100) of claim 1, wherein the cellulose layer is a bleached cellulose layer.

11. 2. The wrapping paper (100) of claim 1, wherein the cellulosic layer comprises a mixture of long and short fibers, and comprises at least 40% long fibers, preferably at least 50% long fibers, more preferably at least 70% long fibers.

12. 10. The wrapping paper (100) of claim 1, wherein the coating layer material in the transparent region (110) is applied to the wrapping paper (100) at a first temperature within a first temperature range and cured in stages at a second temperature within a second temperature range to form the transparent region (110).

13. 13. The wrapper (100) of claim 12, wherein the coating layer material in the transparent region (110) is exposed to the second temperature for a period of at least 0.1 seconds, preferably between 0.5 and 7 seconds, preferably at least 7 seconds.

14. 14. The wrapping paper (100) according to any one of claims 12 to 13, wherein the second temperature range is between 30°C and 120°C, preferably between 40°C and 110°C, more preferably between 50°C and 100°C.

15. 13. The wrapper (100) of claim 12, wherein the first temperature range is between 150°C and 180°C, preferably between 80°C and 150°C, more preferably between 100°C and 120°C.

16. A cellulose packaging comprising the wrapper (100) of claim 1, wherein the transparent area forms a window within the cellulose packaging.

17. A method for manufacturing a wrapper (100) having a transparent area (110), said method comprising: - providing a cellulose layer having a first side and a second side; - applying a predetermined amount of coating layer material to the location of the area at a first temperature within a first temperature range, said coating layer material comprising an oily compound such as paraffin or vegetable oil; - curing the applied amount of coating layer material stepwise at a second temperature within a second temperature range to form said transparent area (110); A method comprising:

18. 18. The method of claim 17, wherein the second temperature range is between 30°C and 120°C, preferably between 40°C and 110°C, more preferably between 50°C and 100°C.

19. 19. The method according to any one of claims 17 to 18, wherein the first temperature range is between 70°C and 180°C, preferably between 80°C and 150°C, more preferably between 100°C and 120°C.

20. 18. The method of claim 17, wherein the cellulose layer with the amount of coating layer material is exposed to the second temperature range for a period of at least 0.1 seconds, preferably between 0.5 and 7 seconds, preferably at least 7 seconds.

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