Packaging paper with translucent zone, method for manufacturing packaging paper with translucent zone, and packaging comprising such packaging paper

Abstract

The invention relates to a packaging paper. The invention further relates to a cellulose packaging comprising the packaging paper and to a method for manufacturing the packaging paper.

Description

[0001] Packaging paper with translucent zone, method for manufacturing packaging paper with translucent zone, and packaging comprising such packaging paper

[0002] Field of the invention

[0003] The invention relates to a packaging paper. The invention further relates to a cellulose packaging comprising the packaging paper and to a method for manufacturing the packaging paper.

[0004] Background to the invention

[0005] Bag-like packagings which are provided with a window and further comprise paper are applied inter alia for bread, baked goods, vegetables, meat and fruit. The window is generally translucent and has for its object to allow customers and shop staff to see what is packaged in the bag-like packaging. The window is typically formed by a strip which is adhered on both sides to the paper and is manufactured from a plastic material such as polypropylene (PP) or polyethylene terephthalate (PET), or optionally another polyester.

[0006] A method for making such a packaging and a resulting packaging are known from EP1894714B1 and from EP3095723A1. Such packagings with windows are however difficult to manufacture in practice. A roll of paper and a roll of plastic window material are thus typically needed for this purpose. These rolls are unwound and an adhesive material is applied to at least one of the paper and the window material. The window material is adhered to the paper using the adhesive material. This manufacturing process is difficult to control because the window material has a tendency to come loose during arranging of the window material. The production workers responsible during the manufacturing process must be highly skilled in order to obviate this problem. This dependence on highly skilled personnel is undesirable. The realized mutual connection is moreover of sub- optimal quality. The window thus has a tendency to tear away from the paper. This is undesirable in use of the packaging. The plastic window is further expensive compared to the paper. The resulting packaging is therefore also expensive. From an ecological viewpoint with the aim of sustainability, it is additionally the case that the resulting packaging is difficult or impossible to recycle.

[0007] W02020170226 describes a composite packaging manufactured from different recyclable materials. The composite packaging described in W02020170226 is an assembled packaging constructed from different materials, particularly a recyclable base material and a recyclable window material which is partially translucent and which is attached to the first recyclable base material in order to form the window in the composite packaging. The manufacturing process of the composite packaging of W02020170226 is difficult to control because the window material has a tendency to come loose during arranging of the window material.

[0008] W02023073620 describes a solution to the above-defined difficulties, in the form of a packaging material made of a single recyclable cellulose material, in which a translucent zone is obtained by impregnating the material with an oily compound such as a paraffine. The disadvantage of the method described in ‘620 is that the opacity values of the translucent zone are highly dependent on the type of paraffines or waxes used. Over time, the crystallinity of the applied paraffine, and thus the opacity of the translucent zone may change due to external factors, such as moisture, temperature, UV radiation,... Accordingly, it was an object of the present invention to provide a solution to those problems. Hence, the present invention provides packaging materials and methods in which carefully selected impregnating materials are used, which results in improved opacity values of the translucent zone, even after longer storage times.

[0009] Summary of the invention

[0010] It is therefore an object of the invention to provide a packaging paper which can be manufactured in a simple manner and more cheaply, with improved opacity values in the translucent zone. It is a further object of the invention to provide a method for manufacturing such packaging paper and to provide a packaging with the packaging paper.

[0011] In order to be suitably used for making translucent zones in cellulose materials, the impregnating material needs to comply with several requirements. One of the requirements is that the melting temperature of the impregnating material should be sufficiently high such that the impregnating material does not ‘leak out’ of the translucent zone. Higher melting temperatures are typically observed in more crystalline materials. However, the higher the crystallinity of the impregnating material, the less translucent the zone becomes. Therefore, there is a fine balance between melting temperature and crystallinity of the impregnating material in order to obtain the best possible results. The inventors have now found that impregnating materials having particular characteristics, are very beneficial for these applications, in having high melting temperatures, yet showing improved crystallinity, especially when applied to further shock-cooling during the process as described herein below. The melting temperature of the impregnating materials is preferably above 50°C, such as between 60°C and 200°C, in particular between 70°C and 150°C, more in particular between 80°C and 100°C.

[0012] The characteristics of the preferred impregnating materials are:

[0013] - a Differential Scanning Calorimetry value (DSC) of 40 J / g or less at 32°C and below; and

[0014] - a melting temperature of more than 50°C.

[0015] Additionally, the impregnating materials of the invention may comprise a component having at least 10 wt% of functionalized acids, wherein said functionalized acids comprise at least one functional group selected from the list comprising hydroxyl groups, ester groups, ether groups, ketone groups, aldehyde groups, amide groups, and amine groups; in particular at least one hydroxyl group.

[0016] Thus, the invention provides a packaging paper (100) with a translucent zone (110), wherein the packaging paper (100) and the translucent zone (110) are made from one cellulose layer and wherein the translucent zone (110) comprises an impregnating material applied to the packaging paper (100), wherein the impregnating material:

[0017] - has a Differential Scanning Calorimetry value (DSC) of 40 J / g or less at 32°C and below; and

[0018] - has a melting temperature of more than 50°C; and wherein the translucent zone (110) has an opacity which, according to ISO 2471 , is below 16 %.

[0019] More preferably, the impregnating material has a Differential Scanning Calorimetry value (DSC) of 40 J / g or less at 32°C and at 10°C. Particularly, the impregnating material has a Differential Scanning Calorimetry value (DSC) of 35 J / g or less at 32°C and at 10°C. Even more particularly, the impregnating material has a Differential Scanning Calorimetry value (DSC) of 28 J / g at 32°C and 31 J / g or less at 10°C. Therefore, the impregnating material preferably has a Differential Scanning Calorimetry value (DSC) of maximum 40 J / g at a maximum temperature of 32°C; in particular maximum 35 J / g; more in particular maximum 30 J / g; most in particular maximum 28 J / g.

[0020] Very good results are obtained using impregnating materials having a Differential Scanning Calorimetry value (DSC) of 20 J / g or less at 32°C and at 10°C. Additionally, the invention provides a packaging paper with a translucent zone, wherein the packaging paper and the translucent zone are made from one cellulose layer and wherein the translucent zone comprises an impregnating material applied to the packaging paper, wherein the impregnating material comprises (a component having) at least 10 wt% of functionalized acids; in particular wherein said functionalized acids comprise at least one functional group selected from the list comprising hydroxyl groups, ester groups, ether groups, ketone groups, aldehyde groups, amide groups, and amine groups.

[0021] A packaging paper which is at least partially transparent or translucent is provided in this way. Customers and shop staff can thus see what is packaged in a packaging made with the packaging paper. The use of a plastic material is avoided in this way. Such packaging paper is more sustainable, cheaper and simpler to manufacture.

[0022] The impregnating material preferably comprises a component having at least 20 wt% of functionalized acids; in particular at least 30 wt% of functionalized acids; more in particular at least 50 wt% of functionalized acids.

[0023] The functionalized acids are preferably fatty acids comprising one or more functional groups selected from the list comprising: hydroxyl groups, ester groups, ether groups, ketone groups, aldehyde groups, amide groups, and amine groups; in particular the functionalized fatty acids are hydroxylated acids , more in particular hydroxylated fatty acids.

[0024] The functionalized acids are preferably selected from the list comprising: functionalized C14 acids, functionalized C15 acids, functionalized C16 acids, functionalized C17 acids, functionalized C18 acids, functionalized C19 acids, functionalized C20 acids.

[0025] The functionalized acids are more preferably selected from the list comprising: sebacic acid, ricinoleic acid, dimorphecolic acid, densipolic acid, auricolic acid lesquerolic acid, hydroxybenzoic acid and hydroxycarboxylic acid.

[0026] Preferred impregnating materials are castor wax, hydrogenated castor oil, rice bran wax, candelilla wax, shellac wax or combinations and hydrogenated forms thereof, such as hydrogenated rice bran wax, hydrogenated candelilla wax, hydrogenated shellac wax.

[0027] The translucent zone preferably extends at least partially in a longitudinal direction of the cellulose layer. The translucent zone preferably extends at least partially in a width direction of the cellulose layer. The translucent zone preferably extends over the cellulose layer in the form of a strip. It will however be apparent to the skilled person that the translucent zone can take different forms.

[0028] The translucent zone preferably has an opacity, measured according to ISO 2471 , below 16%, in particular between 1 % and 16%, more preferably below 14%; most preferably below 12%.

[0029] The applied impregnating material preferably has a surface density of at least 1 g / m2, more preferably a surface density lying between 2 and 15 g / m2, more preferably between 4 and 10 g / m2, such as between 6 and 8 g / m2. It is noted that a predetermined quantity of impregnating material can be selected depending on properties, such as type, of the cellulose layer. In the case of a bleached cellulose layer, also referred to as white paper, about 6-8 g / m2of impregnating material can thus for instance be applied. Such predetermined quantities of impregnating material or surface densities of the applied impregnating material are chosen such that the cellulose layer to which the impregnating material is applied is saturated. The amount of impregnating material can be determined based on the surface density of the cellulose layer. The pore volume of a paper typically covers between 25 and 30% of the surface area. Therefore, a paper having a surface density of about 50 g / m2would need to be impregnated with an impregnating material weighing a surface density of about 12-15 g / m2in order to substantially fill all of the pores.

[0030] The cellulose layer preferably has a surface density which is higher than 18 g / m2, the cellulose layer preferably having a surface density which is at most 50 g / m2, more preferably at most 35 g / m2. Such a cellulose layer is relatively thin and light-weight, which has the advantage that the packaging paper is easily transportable and is cheaper. Such a cellulose layer can furthermore be penetrated more uniformly by the impregnating material.

[0031] It is preferred for a surface on at least a first side of the cellulose layer to have a surface roughness according to ISO 8791 / 2 (also referred to as Bendtsen Roughness method) 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. It is noted that the cellulose layer can have such a surface roughness on both the first and the second side. The surface roughness can differ on the first and the second side. The cellulose layer can further have a substantially uniform surface roughness on the first and second side. Such surface roughness corresponds with the smoothness of the paper. A smoother paper has a tendency to become more translucent with a smaller quantity of impregnating material. It is suspected that this effect is achieved in that the cellulose fibres in a smooth paper are aligned relatively similarly, causing the impregnating material to penetrate and impregnate the cellulose layer more uniformly. Moreover, smoothening has a tendency to compact the fibers, thereby reducing the pore volume. Accordingly, for smoother paper, lower amounts of impregnating material will typically be required.

[0032] The impregnating material preferably coats the translucent zone substantially wholly. In other words, it is preferred for the whole surface of the translucent zone to comprise impregnating material. It is however also possible for the translucent zone to comprise parts without impregnating material.

[0033] The cellulose layer is preferably a bleached cellulose layer.

[0034] The cellulose layer preferably comprises a mixture of long fibre and short fibre, with at least 40% long fibres, more preferably at least 50% long fibres, more preferably at least 70% long fibres. Such a cellulose layer has the advantage that it is resistant to tearing. The subsequently realized packaging is therefore stronger, for instance compared to a glassine paper. Such a cellulose layer further has the advantage that it can be produced in the usual manner. The price of a cellulose layer with such a fibre composition can be produced considerably more inexpensively compared to glassine paper. The production of such a cellulose layer is moreover simpler, faster and more sustainable. According to one example, the cellulose layer can even comprise almost 100% long fibres. Such a cellulose layer is obtained by adding only long fibres during manufacture of the cellulose layer. In other words, no short fibres are added.

[0035] The impregnating material in the translucent zone is preferably applied to the packaging paper at a first temperature within a first temperature range, and shock-cooled at a second temperature, such that the translucent zone is formed. The first temperature is here substantially higher than the second temperature. Hereby, the impregnating material is cooled immediately and instantaneously with for instance a cooling roller, typically at a low temperature such as below 5°C. The impregnating material of the present invention is thus hardened very quickly, which appeared to be highly beneficial for the opacity of the translucent zone. In this way, the impregnating material appears to harden into a substantially vitreous structure. The transparency of the translucent zone is considerably improved in this way. This additionally allows for rapid further processing of the packaging paper. The first temperature range, at which the impregnating of the impregnating material takes place, typically lies between 50°C and 180°C, preferably between 80°C and 160°C, more preferably between 120°C and 150°C. In particular, the first temperature range is preferably above the melting temperature of the impregnating material. Thus is in the event that the melting temperature of the impregnating material is about 85-90°C, the first temperature range is preferably above 90°C, such as between 100°C and 110°C.

[0036] The second temperature is much lower in order to achieve the shock-cooling effect and is preferably below 10°C, more preferably below 7°C, most preferably below 5°C. This low temperature can for example be achieved by means of a cooling roll positioned after the impregnating device, in order to rapidly harden the impregnating material on the cellulose layer.

[0037] The impregnating material in the translucent zone is preferably exposed to the second temperature for a period of at least 0.1 second, preferably between 0.5 and 7 seconds, preferably at least 7 seconds. The second temperature is for example applied during the whole transfer of the packaging paper through the cooling roller.

[0038] The translucent zone can preferably be obtained by applying at the position of the zone a predetermined quantity of impregnating material at the first temperature which lies within the first temperature range, and subsequent shock-cooling of the applied predetermined quantity of impregnating material at the second temperature, in order to form the translucent zone.

[0039] Application of the predetermined quantity of impregnating material preferably comprises the following steps of: providing a moving endless surface; taking up the predetermined quantity of impregnating material with the moving endless surface; bringing the moving endless surface into contact with the first side of the cellulose layer.

[0040] Advantages of the packaging paper apply mutatis mutandis to a cellulose packaging and to a method for manufacture thereof.

[0041] According to a second aspect, the invention provides a cellulose packaging comprising a packaging paper as described above. The translucent zone preferably forms a window in the cellulose packaging. According to a third aspect, the invention provides a method for manufacturing a packaging paper with a translucent zone, the method comprising of: providing a cellulose layer with a first side and a second side; applying at the position of a zone a predetermined quantity of impregnating material at a first temperature which lies within a first temperature range; shock-cooling the applied predetermined quantity of impregnating material at a second temperature in order to form the translucent zone; wherein the impregnating material

[0042] - has a Differential Scanning Calorimetry value (DSC) of 40 J / g or less at 32°C and below; and

[0043] - has a melting temperature of more than 50°C.

[0044] The impregnating material, may comprise a component having at least 10 wt% of functionalized acids.

[0045] The first temperature range preferably lies between 50°C and 180°C, preferably between 80°C and 160°C, more preferably between 120°C and 150°C. The second temperature is preferably below 10°C, more preferably below 7 °C, most preferably below 5 °C.

[0046] Application of the predetermined quantity of impregnating material preferably comprises the following steps of: providing a moving endless surface; taking up the predetermined quantity of impregnating material with the moving endless surface; bringing the moving endless surface into contact with the first side of the cellulose layer.

[0047] Brief description of the figures

[0048] The above and other advantageous features and objectives of the invention will become more apparent and the invention better understood with reference to the following detailed description when read in combination with the accompanying drawings.

[0049] Figures 1A and 1 B, shows a top view of a packaging paper with a translucent zone according to an exemplary embodiment; figures 2A, 2B, 2C and 2D show a method for manufacturing a packaging paper with a translucent zone on the basis of cross-sectional drawings of a cellulose layer.

[0050] Detailed embodiments

[0051] The invention will now be further described on the basis of an exemplary embodiment shown in the drawings. The same or similar elements are designated in the drawing with the same reference numeral. Figures 1A and 1 B show exemplary embodiments of a packaging paper 100 with a translucent zone 110. Shown in figure 1 A and 1 B is a coordinate system X, Y, wherein the shown axis X designates a width direction of the packaging paper and wherein the shown axis Y designates a longitudinal direction of the packaging paper.

[0052] In the figures, the packaging paper 100 is rectangular. Such a form is typically obtained during manufacture of the packaging paper 100. More specifically, the packaging paper 100 is manufactured from a roll of paper, also referred to as a cellulose layer. It will however be apparent to the skilled person that packaging paper 100 can also take different forms. During manufacture of packaging paper 100 the cellulose layer is typically supplied in bulk, more specifically in the form of a roll comprising the cellulose layer in rolled-up form. After unwinding from the roll, the cellulose layer forms a strip. The strip has a width corresponding for instance to the width shown in figures 1A and 1 B and is guided through a processing device which will be further elucidated, but is configured particularly to treat the strip of cellulose layer and cut it into the packaging paper 100 shown in figures 1A and 1 B. It will however be apparent that the packaging paper 100 can take a different form. In contrast to the straight line shown in the figures, an end edge of the packaging paper 100 can thus be formed such that one or more protrusions and / or one or more recesses are formed. End edge is understood to mean the edge lying substantially transversely of the longitudinal direction of the cellulose layer. A transverse edge can also be cut out or can be preformed with one or more protrusions and / or one or more recesses. The protrusions and / or recesses can serve to attach the packaging paper 100 to a corresponding packaging paper, for instance in order to form a bag-like packaging. The cutting, also referred to as chopping, of the strip of cellulose layer is per se known to the skilled person and will therefore not be elucidated, this in favour of a brief description.

[0053] Packaging paper 100 has a translucent zone 110, more specifically, a packaging paper 100 with a translucent zone 110 is shown. The packaging paper 100 and the translucent zone 110 are manufactured from one cellulose layer. In other words, the packaging paper is manufactured from one piece of cellulose layer. The translucent zone 110, also referred to as window, is thus manufactured from the same cellulose layer as a non-translucent zone of the packaging paper 100. This is in stark contrast to known packaging paper which is provided with plastic window material such as polypropylene (PP) or polyethylene terephthalate (PET), or optionally another polyester. The known packaging paper combines two different material types, i.e. a cellulose layer and a plastic layer, or a first cellulose layer and a second cellulose layer, in order to realize a packaging material which is provided with a window, with the resulting drawbacks stated in the preamble. The known packaging paper thus consists of at least two different, separate materials which are combined, typically by means of glueing.

[0054] The translucent zone 110 comprises an impregnating material applied to the packaging paper 100. The impregnating material has a Differential Scanning Calorimetry value (DSC) of 40 J / g or less at 32°C and below; and a melting temperature of more than 50°C; and may further comprise a component having at least 10 wt% of functionalized acids.

[0055] In particular embodiments, the impregnating material comprises a component having at least 20 wt% of functionalized acids; in particular at least 30 wt% of functionalized acids; more in particular at least 50 wt% of functionalized acids, such as between 10 wt% and 95 wt%, in particular between about 30 wt % and about 85-95 wt%.

[0056] The functionalized acids are preferably acids comprising at least one functional group selected from the list comprising hydroxyl groups, ester groups, ether groups, ketone groups, aldehyde groups, amide groups, and amine groups; in particular at least one hydroxyl group.

[0057] Particularly preferred acids within the context of the invention are hydroxylated fatty acids, hydroxybenzoic acids and / or hydroxycarboxylic acids.

[0058] Hydroxy(lated) fatty acids (HFAs) have hydroxyl functional groups attached to the principal chain. HFAs can be saturated or unsaturated. The principal chain can be branched, and these branches are sometimes quite long. The main positions of attachment of the hydroxyl group to the chain are the a attachment to the C2 site and the p attachment to the C3 site. However, HFAs also exist that have positions of attachment of the hydroxyl group to the chain at other sites, such as the C12 site in ricinoleic acid (main component of castor oil).

[0059] The general formula for:

[0060] - a-HFAs is CH3-(CH2)n-CH(OH)-COOH, and

[0061] - p-HFAs is CH3-(CH2)n-CH(OH)-CH2-COOH

[0062] There are two other HFA homologous series: the co and (co - 1 ). The general formula for co-HFAs is HOCH2-(CH2)n-COOH and the general formula for (co - 1 ) HFAs is CH3-CH(OH)- (CH2)n-COOH. Other substituents, such as branches or double bonds, are often present in HFAs. Examples include 3-hydroxy-13-methyltetradecanoic and 3-hydroxy-15- methylhexadecanoic acids. An example of an unsaturated HFA is ricinoleic acid (systematic name: 12-hydroxy-c / s-9-octadecenoic acid; IUPAC name: (9Z,12F?)-12-hydroxyoctadec-9- enoic acid), which is the main component of castor oil. Two or more hydroxy functions can be present in the principal chain. Examples include 9,10-dihydroxyoctadecanoic acid and ustilic acid (also known as 2,15,16-trihydroxy palmitic acid or 2,15,16-trihydroxy- hexadecanoic acid). Further examples of HFAs are: 15-Hydroxyeicosatetraenoic acid, 12- Hydroxyeicosatetraenoic acid, 9-Hydroxyoctadecadienoic acid 13- Hydroxyoctadecadienoic acid.

[0063] Hydroxybenzoic acids are a class of organic compounds characterized by a benzene ring with one or more hydroxyl (-OH) groups attached. These compounds are derivatives of benzoic acid in which one or more hydrogen atoms on the benzene ring are replaced by hydroxyl groups. The general formula for hydroxybenzoic acids is C6H4(OH)COOH. Common hydroxybenzoic acids are 2-hydroxybenzoic acid (also known as salicylic acid), 3-hydroxybenzoic acid, 4-hydroxybenzoic acid, but also includes hydroxycinnamic acids such as caffeic acid (3,4-dihydroxycinnamic acid), ferulic acid (4-hydroxy-3- methoxycinnamic) acid and p-coumaric acid (4-hydroxycinnamic acid), which is one of the main components of carnauba oil.

[0064] Hydroxycarboxylic acids are organic compounds characterized by the presence of both a hydroxyl (-OH) group and a carboxylic acid (-COOH) group within the same molecule. These compounds are a subgroup of carboxylic acids and exhibit properties of both alcohol and carboxylic acid functional groups. The general structural formula for hydroxycarboxylic acids is R-C(OH)COOH, where R represents an organic substituent. Hydroxycarboxylic acids are found in carnauba oil.

[0065] The functionalized acids of the invention are preferably selected from the list comprising: functionalized C14 acids, functionalized C15 acids, functionalized C16 acids, functionalized C17 acids, functionalized C18 acids, functionalized C19 acids, and functionalized C20 acids.

[0066] The functionalized acids of the present invention are more preferably selected from the list comprising sebacic acid, ricinoleic acid, dimorphecolic acid, densipolic acid, auricolic acid lesquerolic acid, hydroxybenzoic acid and hydroxycarboxylic acid. The impregnating material is preferably provided in the form of a wax or an hydrogenated oil. Waxes are generally composed of esters derived from long chain fatty acids and long chain alcohols. Triglycerides, on the other hand, are composed of three fatty acids esterified to a glycerol molecule. Triglycerides are typically found in high amounts in oils and fats, but less so in waxes. While waxes and triglycerides share some similarities in terms of being esters of fatty acids, they are distinct types of compounds. However, some natural substances, like certain vegetable waxes contain both esters and triglycerides. Accordingly, in a preferred embodiment, the impregnating material comprises triglycerides, in particular triglycerides containing at least 30 wt% of hydroxylated fatty acids.

[0067] One example of such natural substances is castor oil, which is a vegetable oil pressed from castor beans obtained from the castor bean plant scientifically known as Ricinus communis. Castor oil has a unique composition in containing very high levels of ricinoleic acid, i.e. levels of above 80 wt%, such as about 85 - 95 wt% of ricinoleic acid. The average composition of castor oil is as follows:

[0068] Other suitable impregnating materials according to the invention are for example rice bran wax, candelilla wax and shellac wax. Preferred impregnating materials according to the invention are castor oil, rice bran wax and shellac wax, more preferably rice bran wax and shellac wax.

[0069] The main components of rice bran wax are aliphatic acids (wax acids) and higher alcohol esters. The aliphatic acids are for example palmitic acid (C16), behenic acid (C22), lignoceric acid (C24). The higher alcohol esters are mainly ceryl alcohol (C26) and melissyl alcohol (C30). Rice bran wax also contains constituents such as free fatty acids (palmitic acid), squalene and phospholipids. Candelilla wax comprises mainly hydrocarbons (about 50%, chains with 29-33 carbons), esters of higher molecular weight (20-29%), free acids (7-9%), and resins (12-14%, mainly triterpenoid esters).

[0070] Shellac wax is mainly composed of aleurtic acids, jalaric acid, shellolic acid, and other natural waxes.

[0071] Castor wax, rice bran wax, candelilla wax and shellac wax have all been found to be highly suitable for use in the present invention. As shown in the examples part, all of these waxes have a DSC (Differential Scanning Calorimetry) value of 40 or less at 32°C and below.

[0072] The DSC of an impregnating material can be determined by using the following DSC method: between 6 and 10 mg of impregnating material is introduced into an aluminum measuring pan which is then placed in a Mettler Toledo DSC 3+.

[0073] Standard cooling and melting:

[0074] To clear the temperature history of the impregnating materials, they are first cooled from 25 to -50°C at 20°C / min, then reheated from -50 to 120°C at 20°C / min. This procedure is repeated in a second cooling and reheating step.

[0075] Thermal shock test:

[0076] 1. The impregnating material is melted in 5 min by heating at 20°C / min to a temperature of 30°C above its melting point. It is then cooled at 100°C / min to 32°C. This is followed by isothermal recording of crystallization as a function of time at 32°C for at least 24 hr.

[0077] 2. In a second method, the impregnating material is melted by heating at 20°C / min to a temperature of 130°C. It is then cooled at 100°C / min to 10°C. This is followed by isothermal recording of crystallization as a function of time at 10°C for at least 24 hours.

[0078] Preferably, the DSC value is determined using at least thermal shock test 1 with cooling to 32°C.

[0079] Materials showing a DSC value of below 40 in the first (32°C) and second (10°C) shock test are preferred within the context of the invention.

[0080] Many oils and fats are not suitable for the present application in that they typically do not sufficiently harden at room temperature, and therefore result in greasiness of the packing papers to which they are applied. A solution to that problem may reside in hydrogenation of such oils and fats. For example, castor oil may be provided in its hydrogenated form. The hydrogenated form of castor oil, often referred to as hydrogenated castor oil or castor wax, undergoes a process called hydrogenation. Hydrogenation involves the addition of hydrogen to unsaturated fatty acids in the oil, resulting in a more saturated and solid product. This process transforms the liquid castor oil into a waxy substance with different characteristics, such as becoming solid at room temperature and having an increased melting point over natural castor oil.

[0081] Contrary to castor oil, carnauba wax is typically sourced in the form of a wax. Also its composition is rather unique, with high levels of hydroxybenzoic acids, such as hydroxycinnamic acid (typically about 20 wt%) and hydroxycarboxylic acids (typically about 10-15 wt%). Accordingly, carnauba wax contains about 30-45 wt% of hydroxylated acids. Further thereto, carnauba wax contains about 40 wt% of aliphatic esters and about 12 wt% of fatty alcohols. However, carnauba wax has the disadvantage that it does not provide for the desired opacity values when used alone, due to its DSC values not falling within the desired ranges. Only mixtures of carnauba wax with other impregnating materials may provide for the desired properties.

[0082] The impregnating material penetrates the cellulose layer, as shown in figure 2C, and allows light to pass through the cellulose layer at the position of the zone where the impregnating material has been applied. The location where the penetrated impregnating material allows the passage of light through the packaging paper is referred to as the translucent zone 110. In the context of the 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 inter alia on the degree to which the cellulose layer allows light through. The cellulose layer without impregnating material scatters or partially reflects light. By impregnating the material with a impregnating material having a refractive index close to cellulose, the scattering can be reduced such that the impregnated zone of the cellulose layer becomes translucent.

[0083] Transparency falls under the wider 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 the application the transmission describes the portion of the incident radiant flux or luminous flux which penetrates the translucent zone. The reciprocal value of the transmission, the opacity, is additionally also used. According to ISO 2471 , an opacity of the translucent zone preferably lies between 1% and 20%, more preferably below 18% most preferably below 16%, such as about or below 5%, about or below 10%, about or below 15%.

[0084] A packaging paper 100 which is at least partially translucent or transparent is thus provided in this way. Customers and shop staff can thus see what is packed in a packaging formed from the packaging paper. The use of a plastic material is avoided in this way. Such packaging paper is more sustainable, cheaper and simpler to manufacture. A packaging paper with a translucent zone 110 comprising the impregnating materials of the invention is furthermore recyclable and / or compostable.

[0085] A further advantage of a translucent zone which is formed by applying the impregnating material of the invention and saturating the cellulose layer therewith is based on the insight that plastic windows are not strong enough and / or, under the weight of the product in the packaging material, could result in unpredictable stretching and / or tearing of the plastic, with the result that the product may fall out of the packaging material. An additional problem in the use of plastic windows is that the connecting lines between the plastic and the paper are typically weak zones which are susceptible to tearing. The packaging material 100 which is formed from one piece of cellulose layer neutralizes these problems almost completely. Figures 1A and 1 B show that the translucent zone 110 extends, preferably, at least partially over the cellulose layer. Although not shown, the translucent zone 110 can also extend over the whole surface of the cellulose layer. In this way the whole packaging paper 100 is translucent. The translucent zone 110 preferably extends in the form of a strip.

[0086] According to the preferred embodiment of figure 1 A, the translucent zone 110 extends in a longitudinal direction Y of the cellulose layer. In figure 1 A the translucent zone 110 extends from one end edge to the opposite end edge. In this way the translucent zone 110 forms a translucent strip in the cellulose layer, as seen in the longitudinal direction thereof. When this packaging paper is for instance used as bag-like packaging, this makes it possible to see into the bag-like packaging through a whole longitudinal direction of the packaging paper 100. Shown in each of the figures 1A and 1 B is a representation of an item P packaged in the packaging paper 100. The visibility of the product shows the transparency of the translucent zone 110 and the opacity of the non-translucent zone.

[0087] In figure 1A the translucent zone 110 is arranged centrally on the cellulose layer. In this way two non-translucent zones 120 are situated on either side of the translucent zone 110. The nontranslucent zones 120, also referred to as opaque zones 120, can be a part of the cellulose layer where no impregnating material is applied, or where only a small quantity of impregnating material is applied. Such an untreated portion of the cellulose layer is non- translucent. The non-translucent zones have a higher moisture permeability than the translucent zone. Changing an area ratio of the translucent zone and a non-translucent zone furthermore allows the moisture permeability to be controlled. This reduces the risk of products packaged in the packaging paper becoming mouldy, for instance relative to a plastic packaging. The untreated portion of the cellulose layer further allows optimal glueing of the packaging paper to itself or to another material.

[0088] Compared to figure 1A, figure 1 B shows that the translucent zone 110 can also be positioned at a peripheral edge of the packaging paper 100, for instance a transverse edge of the packaging paper 100.

[0089] The translucent zone is described above as substantially rectangular with substantially straight edges. The translucent zone can however also have at least partially curved and / or bent edges. The translucent zone can thus for instance also take a round form, such as that of a circle or oval. The translucent zone can further be a combination of a plurality of shapes or have a shape differing from a geometrical form, for instance the silhouette of a person. It will be apparent to the skilled person that the translucent zone can take any form and can for instance be adapted on the basis of logos, shapes of packaged objects or foods, and so on.

[0090] Packaging paper 110 can be manufactured by providing a cellulose layer with a first side and a second side. The method for manufacturing the cellulose layer will be explained with reference to figures 2 A, 2B, 2C and 2D.

[0091] Figures 2A, 2B, 2C and 2D show a cross-section of a cellulose layer 130 as described in relation to 1A and 1 B. The method comprises of providing a cellulose layer 130 with a first side 131 and a second side 132. As shown in figure 2A, the cellulose layer 130 is initially nontranslucent. A product P situated below the cellulose layer 130 is thus not visible or identifiable, or is so only to limited extent. The cellulose layer 130 preferably has a specific weight higher than 18 g / m2. The cellulose layer 130 further preferably has a specific weight which is at most 50 g / m2, more preferably at most 35 g / m2. Such a cellulose layer is relatively thin and light-weight, which has the advantage that the packaging paper is easily transportable and is cheaper. Such a cellulose layer 130 is furthermore more easily penetrable by the impregnating material 140. In other words, such a cellulose layer can be advantageously saturated by the applied impregnating material 140. Treatments such as smoothing, refining or calendaring will have a tendency to break down the fibers, reduce its average fiber length and reduce the porosity. However less paraffin is typically required to fill the reduced pore volume, and as the pores are smaller, the capillary forces will draw the paraffin more easily.

[0092] It is preferred for a surface on at least the first side 131 of the cellulose layer 130 to have a surface roughness 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. The surface roughness is determined here in accordance with ISO 8791 -2 and is also known as the Bendtsen Roughness. In this way the impregnating material applied to this first side can penetrate the cellulose layer 130 more uniformly.

[0093] It is preferred for the cellulose layer 130 to be a bleached cellulose layer, for instance a white paper. In this way an optimal translucent result is obtained, although it is noted that a white paper is not essential.

[0094] The cellulose layer 130 further preferably comprises a mixture of long fibre and short fibre, with at least 40% long fibres, more preferably at least 50%, preferably at least 70%. Such a cellulose layer has the advantage that it is resistant to tearing. The subsequently realized packaging is therefore stronger, for instance compared to a glassine paper. Such a cellulose layer further has the advantage that it can be produced in usual manner. The price of a cellulose layer with such a fibre composition can be produced considerably more inexpensively compared to glassine paper. The production of such a cellulose layer is moreover simpler, faster and more sustainable.

[0095] As shown in figure 2B, a predetermined quantity of impregnating material 140 with a first temperature is applied to the first side at the position of a zone. The impregnating material is preferably brought to the first temperature just before application thereof. The first temperature lies within a first temperature range. The first temperature can vary between the limits of the first temperature range. The first temperature range preferably lies between 50°C and 180°C, more preferably between 80°C and 150°C, most preferably between 100°C and 120°C. Such a temperature range modifies the viscosity of the applied impregnating material 140. In this way the impregnating material becomes more runny or liquid, whereby the impregnating material penetrates the cellulose layer 130 in improved manner and is able to saturate the cellulose layer 130 in efficient manner. A temperature range between 100°C and 120°C realizes the further advantage that the impregnating material cannot burn. The viscosity of the impregnating material 140 preferably lies between 5 mPa / s and 500 mPa / s, measured at a temperature of 100°C. The viscosity of the impregnating material 140 more preferably lies between 5 mPa / s and 250 mPa / s, measured at a temperature of 100°C. It is noted that the cellulose layer can also be heated before the impregnating material is applied. This allows the impregnating material to further penetrate the cellulose layer in improved manner. In doing so, the temperature of the cellulose layer is preferably higher than the melting temperature of the impregnating material, in this way, the impregnating material will have a longer time available to fill the complete volume of the pores of the cellulose layer.

[0096] The penetration of the impregnating material 140 is illustrated by the circles shown in cellulose layer 130. The impregnating material 140 penetrates between the fibres of the cellulose layer, preferably to (a position close to) the second side 132. In this way a substantially continuous flow of impregnating material through cellulose layer 130 is formed. In order to substantially guarantee a transparency it is preferable to opt for a sufficiently large predetermined quantity of impregnating material to fill the pores of the cellulose layer. Both incomplete filling as well as over-filling of the pores may result in reduced opacity. Depending on the used cellulose layer, one skilled in the art will be able to determine the preferred amount of impregnating material to obtain the best opacity values The predetermined quantity of impregnating material is thus preferably at least 1 g / m2, more preferably a quantity corresponding to a surface density of between 2.5 to 6 g / m2. In this way the impregnating material saturates the cellulose layer and a desired transparency is substantially guaranteed. The predetermined quantity of impregnating material is more preferably a maximum of 12 g / m2. It is noted that the predetermined quantity of impregnating material can be selected taking into consideration the type of cellulose layer. In the case of a bleached cellulose layer, also referred to as white paper, 6 to 8 g / m2of impregnating material can for instance be applied, or, according to a further example, 8 to 10 g / m2can be applied in the case of a brown paper. According to a further exemplary embodiment, 1 to 15 g / m2of impregnating material can alternatively be applied. Such a chosen predetermined quantity of impregnating material saturates the cellulose layer. It is further noted that the transparency improves further still when the impregnating material is applied to both the first and the second side. The quantity of impregnating material can differ for the first side and the second side, although it is preferred for the collective surface density of the impregnating material on the first and the second side to correspond to the above stated values. Applying the impregnating material to both sides almost certainly guarantees that impregnating material penetrates through the cellulose layer and the impregnating material saturates the cellulose layer. The inventors have surprisingly found that when impregnating material is applied to both sides of the cellulose layer, the transparency is further improved.

[0097] Figure 2C shows that the impregnating material 140 has penetrated through the cellulose layer 130. It will be apparent that a portion of the impregnating material 140 may protrude from the cellulose layer 130. In other words, a quantity of impregnating material 140 may still be present on the surface of cellulose layer 130. It is possible, especially in advantageous circumstances in which the cellulose layer is wholly saturated by the impregnating material 140, for a residue or excess of impregnating material 140 to remain on the cellulose layer surface. The applied predetermined quantity of impregnating material is then shock-cooled at a second temperature.

[0098] The second temperature is typically below 32°C, such as below 10°C, preferably below 7 °C, more preferably below 5°C. The second temperature results in a quick hardening of the impregnating material, of which it was surprisingly found herein, that this reduces crystallization of the impregnating material over longer periods of time, thereby providing a more stable, yet sufficiently translucent zone. The hardening of the impregnating material forms a path translucent to light through the cellulose layer 130, as shown in figure 2D. While in existing production processes an impregnating material is also often immediately cooled with a cooling roller, the selected type of impregnating material typically hardens into a structure with an opaque result due to the sudden temperature drop. The inventors have found herein that the impregnating materials of the invention surprisingly do not suffer from this problem. In contrast, fast cooling of the selected materials results in very stable and highly translucent impregnated zones. The cooling roller is located downstream of a location where the impregnating material is applied, typically in the immediate vicinity thereof so that impregnating material is immediately hardened, resulting in the desired translucent zone to form. The transparency of the translucent zone is further improved when the impregnating material is applied to both sides of the cellulose layer in such a preferred embodiment.

[0099] The packaging paper 100 with the translucent zone is highly advantageous as a cellulose packaging material for foods, such as bread, baked goods, vegetables, fruit, cheese or meat, or non-foods. The packaging paper 100 can for instance be processed or formed into a cellulose bag. The packaging paper can also function as a sheet of paper, for instance at a butcher’ s shop, or can be supplied on a roll. The packaging paper with the translucent zone further allows simple glueing of the packaging paper in order to form for instance a per se closed bag. Yet another advantage is that the packaging paper is considerably cheaper compared to glassine. This advantage is based on the insight that glassine is manufactured using a supercalander. Such a production process requires a lot of energy, which raises the cost of glassine considerably compared to the packaging paper 100.

[0100] Glassine is moreover fragile because the fibres have been extremely finely ground.

[0101] EXAMPLES

[0102] The above stated advantages will be demonstrated in the non-limitative exemplary embodiments stated below.

[0103] In the below examples, and in order to make a distinction between the embodiments of the invention and the comparative examples, the abbreviation UV is used for the examples of the invention, whereas the abbreviation VE is used for the comparative examples.

[0104] Materials

[0105] Impregnating materials

[0106] • UV1 : Paraflex Nowax CW 6089 - commercially available from Paramelt. Independent GC / LCMS analyses teach that this is a hydrogenated castor oil. This material has a melting point of 85°C.

[0107] • UV2: Kahlwax 2811 is a Rice Bran wax from Kahl GmbH & Co. KG. This material has a melting point of about 80°C (typical range is 77-86°C).

[0108] • UV3: Kahlwax 2039L is a Candelilla wax from Kahl GmbH & Co. KG. This material has a melting point of about 70°C (typical range is 68-73°C).

[0109] • UV4: Kahlwax 7302L is a Shellac wax from Kahl GmbH & Co. KG. This material has a melting point of about 80°C (typical range is 75-85°C).

[0110] • VE1 : TopScreen Biowax-based Barrier Coating ED9 - palm oil from Solenis. This material has a melting point of 60°C

[0111] • VE2: Sunflower Wax 70 - Sunflower wax from Proquinat. This material has a melting temperature of 73°C

[0112] • VE3: Proquiwax 56-58 - hydrogenated and refined petroleum-based paraffin from Proquinat. This material has a melting point of 58°C

[0113] • VE4: Topscreen™ Bio-based Barrier Coating HM9 - rapeseed kerosene from Solenis. This material has a melting temperature of 70°C

[0114] • VE5: Carnaubax wax T1 - Carnauba wax from Proquinat. This material has a melting point of 85°C Paper Types:

[0115] Flexpack SMOOTH of 32 and 35 g / m2and RELEASE of 30 and 35 g / m2from STARKRAFT, are used. As a reference, CRISTAL Flexible & Transparent Paper from AHLSTROM MUNKSJO of 32 g / m2is used. The latter material was measured frequently and has an average opacity of 17.1%, with a standard deviation of 1 .4%.

[0116] Methods

[0117] Transparency or opacity

[0118] Transparency or opacity of the treated paper is measured with a PCE-RM 100 Reflectance Meter. This device uses a measurement scale from 0 to 100%. Here, 0% is completely transparent and 100% is completely opaque. The lower the measured value, the better the transparency or the lower the opacity.

[0119] Statistics

[0120] To make a sufficiently reliable estimate of the mean of the measurements, at least 5 different measurements are made, in each material direction. An average over all measurements together is also performed.

[0121] The 95% confidence interval for the mean is calculated as

[0122] Wherein x is the calculated average, s is the calculate average deviation, n is the number of measurements, and t.025 is the critical t value for 2.5% probability in the upper and lower tails of the distribution

[0123] Impregnating step

[0124] In a typical impregnating treatment, packaging paper is covered on two sides with impregnating material of different surface weight in g / m2by means of a HOLWEG-WEBER RS26 paper bag production machine with a HOLWEG-WEBER CTH1 paraffinizer. The two- sided covering is achieved by passing the paper through a bath of impregnating material. The relatively long residence time in the bath gives the paper a chance to warm up completely and the impregnating material is given time to penetrate the pores of the paper. After the impregnating bath, the packaging paper is rapidly cooled by means of a cooling roll positioned behind the impregnating bath, thereby obtaining the desired opacity of the packaging paper.

[0125] Typically, the impregnating bath is set at 150°C, the paper runs through the machine at a production speed of 110 m / min and the cooling rollers are set at 6 to 7 °C.

[0126] DSC method:

[0127] Thermal characterization of impregnating materials is done by Differential Scanning Calorimetry (DSC). For this purpose, between 6 and 10 mg of impregnating material is introduced into an aluminum measuring pan which is then placed in a Mettler Toledo DSC 3+.

[0128] Standard cooling and melting:

[0129] To clear the temperature history of the impregnating materials, they are first cooled from 25 to -50°C at 20°C / min, then reheated from -50 to 120°C at 20°C / min. This procedure is repeated in a second cooling and reheating step.

[0130] Thermal shock test:

[0131] 1. The impregnating material is melted in 5 min by heating at 20°C / min to a temperature of 30°C above its melting point. It is then cooled at 100°C / min to 32°C. This is followed by isothermal recording of crystallization as a function of time at 32°C for at least 24 hr.

[0132] 2. In a second method, the impregnating material is melted by heating at 20°C / min to a temperature of 130°C. It is then cooled at 100°C / min to 10°C. This is followed by isothermal recording of crystallization as a function of time at 10°C for at least 24 hours. Results

[0133] Table 1 summarizes the thermal cooling properties of the different impregnating materials. After shock cooling, UV1 to UV4 have a very low residual cooling enthalpy. This indicates that very low crystallization of these impregnating materials occurred. Due to the low crystallization amount after shock cooling, the transparency is expected to be better than for VEI to VE5.

[0134] Table 1 : Cooling properties of various impregnating materials

[0135] Without being bound to theory, it is suspected that this behavior for UV1 is due to the special character and composition of the fatty acids in castor oil. Castor oil consists of 85 to 95% ricinoleic acid. This fatty acid of 18 carbons long has not only an unsaturation at position 9, but also a hydroxy functional group at position 12. Not only does this make this material more polar than other impregnating materials, but also the crystallization behavior can be greatly influenced by this.

[0136] The data further evidence that the impregnating materials having a DSC value at 32°C (and below, i.e. 10°C) of 40 g / J or less, show significantly better (i.e. lower) crystallinity after 24h, compared to impregnating materials, such as palm oil, having higher DSC values. Obviously, the lower the crystallinity, the more transparent the translucent zone will be. Therefore, translucent zones having a very low opacity can be obtained using impregnating materials having a DSC value at 32°C (or below) of 40 g / J or less. Shock cooling can be achieved by using a cooling roller just after the impregnating step. The effect of this cooling roller is demonstrated in Table 2 for UV1 , castor oil, for 2 different paper types of two different gram weights each. Due to the different structure and gram weight, the different papers absorb different gram weights of impregnating material. The date clearly show that the cooling roller in each case lowers the opacity of the paper in both directions of the paper. In each case, the differences are statistically significant at the 95% probability level.

[0137] Table 2: Effect of shock cooling by using cooling roller on opacity for UV1 , hydrogenated castor oil

[0138] In contrast, Table 3 shows the results for VE1 , palm oil. Palm oil crystallizes quickly after shock cooling. That effect is evident in the increase in opacity after shock cooling by using a cooling roller. In that case, the opacity deteriorates even further than when no shock cooling or cooling roller is used. Moreover, it is clear that when no shock cooling is used for VE1 (palm oil), the opacity is not as good as for UV1 (castor oil) without shock cooling. Shock cooling further improves opacity for UV1 . Table 3: Effect of shock cooling by using cooling roller on opacity for VE1 , palm oil

[0139] It was further observed that for UV1 , the opacity also remained stable over a longer period of time, whereas for VE1 it deteriorates faster (data not shown).

Claims

CLAIMS1. A packaging paper (100) with a translucent zone (110), wherein the packaging paper (100) and the translucent zone (110) are made from one cellulose layer and wherein the translucent zone (110) comprises an impregnating material applied to the packaging paper (100), wherein the impregnating material:- has a Differential Scanning Calorimetry value (DSC) of 40 J / g or less at 32°C and below; and- has a melting temperature of more than 50°C; and wherein the translucent zone (110) has an opacity which, according to ISO 2471 , is below 16 %.

2. The packaging paper (100) as defined in claim 1 ; wherein said impregnating material - comprises a component having at least 10 wt% of functionalized acids, wherein said functionalized acids comprise at least one functional group selected from the list comprising hydroxyl groups, ester groups, ether groups, ketone groups, aldehyde groups, amide groups, and amine groups; in particular at least one hydroxyl group.

3. The packaging paper (100) as defined in claim 2, wherein said impregnating material comprises a component having at least 20 wt% of functionalized acids; in particular at least 30 wt% of functionalized acids; more in particular at least 50 wt% of functionalized acids.

4. The packaging paper (100) as defined in claim 3, wherein said functionalized acids are selected from the list comprising: functionalized C14 acids, functionalized C15 acids, functionalized C16 acids, functionalized C17 acids, functionalized C18 acids, functionalized C19 acids, functionalized C20 acids.

5. The packaging paper (100) as defined in claim 2, wherein said functionalized acids, are hydroxylated fatty acids.

6. The packaging paper (100) as defined in claim 2, wherein said functionalized acid is selected from the list comprising sebacic acid, ricinoleic acid, dimorphecolic acid, densipolic acid, auricolic acid lesquerolic acid, hydroxybenzoic acid and hydroxycarboxylic acid.

7. The packaging paper (100) as defined in claim 1 , wherein said impregnating material is castor wax, or hydrogenated castor oil.

8. The packaging paper (100) as defined in claim 1 , wherein said impregnating material is rice bran wax, candelilla wax or shellac wax or a combination thereof.

9. The packaging paper (100) as defined in claim 1 , wherein said impregnating material has a melting point of above 75°C, preferably between 80°C and 100 °C, more preferably between 85°C and 90°C.

10. The packaging paper (100) according to the foregoing claims, wherein the translucent zone (110) extends at least partially in a longitudinal direction (Y) of the cellulose layer.11 . The packaging paper (100) according to any one of the foregoing claims, wherein the translucent zone (110) extends at least partially in a width direction (X) of the cellulose layer.

12. The packaging paper (100) according to any one of the foregoing claims, wherein the translucent zone (110) extends over the cellulose layer in the form of a strip.

13. The packaging paper (100) according to any one of the foregoing claims, wherein the translucent zone (110) has an opacity which, according to ISO 2471 , lies between 1% and 16%, more preferably below 14 %.

14. The packaging paper (100) according to any one of the foregoing claims, wherein the translucent zone (110) has an opacity which, according to ISO 2471 , lies below 12%.

15. The packaging paper (100) according to any one of the foregoing claims, wherein the cellulose layer has a surface density which is higher than 18 g / m2, the cellulose layer preferably having a surface density which is at most 50 g / m2, more preferably at most 35 g / m2.

16. The packaging paper (100) according to any one of the foregoing claims, wherein a surface on at least a 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.

17. The packaging paper (100) according to any one of the foregoing claims, wherein the impregnating material impregnates the translucent zone (110) substantially wholly.

18. The packaging paper (100) according to any one of the foregoing claims, wherein the cellulose layer is a bleached cellulose layer.

19. The packaging paper (100) according to any one of the foregoing claims, wherein the cellulose layer comprises a mixture of long fibres and short fibres, with at least 40% long fibres, preferably at least 50%, more preferably at least 70%.

20. The packaging paper (100) according to any one of the foregoing claims, wherein the impregnating material in the translucent zone (110) is applied to the packaging paper (100) at a first temperature within a first temperature range, and shock-cooled at a second temperature, such that the translucent zone (110) is formed.21 . The packaging paper (100) according to claim 19, wherein the first temperature range lies between 50°C and 180°C, preferably between 80°C and 160°C, more preferably between 120°C and 150°C.

22. The packaging paper (100) according to any one of the foregoing claims 20-21 , wherein the second temperature is below 10°C, preferably below 7 °C, more preferably below 5°C.

23. A cellulose packaging comprising a packaging paper (100) according to any one of the foregoing claims.

24. Use of an impregnating material for providing a packaging paper (100) with a translucent zone, wherein the packaging paper (100) and the translucent zone (110) are made from one cellulose layer, wherein said impregnating material- has a Differential Scanning Calorimetry value (DSC) of 40 J / g or less at 32°C and below; and- has a melting temperature of more than 50°C.

25. Use as defined in claim 24, wherein said impregnating material comprises a component having at least 10 wt% of functionalized acids, wherein said functionalized acids comprise at least one functional group selected from the list comprising hydroxyl groups, ester groups, ether groups, ketone groups, aldehyde groups, amide groups, and amine groups; in particular at least one hydroxyl group.

26. Use as defined in claim 24, wherein said impregnating material comprises a component having at least 20 wt% of functionalized fatty acids; in particular at least 30 wt% of functionalized fatty acids; more in particular at least 50 wt% of functionalized fatty acids.

27. Use as defined in claim 26, wherein said functionalized acids are selected from the list comprising: functionalized C14 acids, functionalized C15 acids, functionalized C16 acids,functionalized C17 acids, functionalized C18 acids, functionalized C19 acids, functionalized C20 acids.

28. Use as defined in claim 27, wherein said functionalized acids, are hydroxylated fatty acids.

29. Use as defined in claim 24, wherein said functionalized acids acid is selected from the list comprising sebacic acid, ricinoleic acid, dimorphecolic acid, densipolic acid, auricolic acid lesquerolic acid, hydroxybenzoic acid and hydroxycarboxylic acid.

30. Use as defined in claim 24, wherein said impregnating material is castor wax or hydrogenated castor oil.

31. Use as defined in claim 24, wherein said impregnating material is rice bran wax, candelilla wax or shellac wax or a combination thereof.

32. The use as defined in claim 24, wherein said impregnating material has a melting point of above 75°C, preferably between 80°C and 100°C, more preferably between 85°C and 90°C.

33. A method for manufacturing a packaging paper (100) with a translucent zone (110) having an opacity which, according to ISO 2471 , is below 16 %, the method comprising:- providing a cellulose layer with a first side and a second side;- applying at the position of a zone a predetermined quantity of impregnating material at a first temperature which lies within a first temperature range, wherein the impregnating material is as defined in any one of claims 1 to 9;- shock-cooling the applied predetermined quantity of impregnating material at a second temperature in order to form the translucent zone (110).

34. The method according to claim 33, wherein the first temperature range lies between 50°C and 180°C, preferably between 80°C and 160°C, more preferably between 120°C and 150°C.

35. The packaging paper (100) according to any one of the foregoing claims 33-34, wherein the second temperature is below 35°C, preferably below 10°C, even more preferably below 7°C.

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