Patent Description:
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 transparent 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.

A method for making such a packaging and a resulting packaging are known from <CIT> and from <CIT>. 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.

<CIT> describes a composite packaging manufactured from different recyclable materials. The composite packaging described in <CIT> is an assembled packaging constructed from different materials, particularly a recyclable base material and a recyclable window material which is partially transparent 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 <CIT> is difficult to control because the window material has a tendency to come loose during arranging of the window material.

It is therefore an object of the invention to provide a packaging paper which can be manufactured in simple manner and more cheaply. 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.

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, in which:.

The invention will now be further described on the basis of an exemplary embodiment shown in the drawing. The same or similar elements are designated in the drawing with the same reference numeral.

<FIG> show exemplary embodiments of a packaging paper <NUM> with a transparent zone <NUM>. Shown in <FIG> 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.

In the figures the packaging paper <NUM> is rectangular. Such a form is typically obtained during manufacture of the packaging paper <NUM>. More specifically, the packaging paper <NUM> 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 <NUM> can also take different forms. During manufacture of packaging paper <NUM> 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 <FIG> 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 <NUM> shown in <FIG>. It will however be apparent that the packaging paper <NUM> can take a different form. In contrast to the straight line shown in the figures, an end edge of the packaging paper <NUM> 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 <NUM> 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.

Packaging paper <NUM> has a transparent zone <NUM>, more specifically, a packaging paper <NUM> with a transparent zone <NUM> is shown. The packaging paper <NUM> and the transparent zone <NUM> are manufactured from one cellulose layer. In other words, the packaging paper is manufactured from one piece of cellulose layer. The transparent zone <NUM>, also referred to as window, is thus manufactured from the same cellulose layer as a non-transparent zone of the packaging paper <NUM>. 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.

The transparent zone <NUM> comprises a coating layer material applied to the packaging paper <NUM>. The coating layer material preferably comprises an oily compound, preferably a paraffin. The oily compound penetrates the cellulose layer, as shown in <FIG>, and allows light to pass through the cellulose layer at the position of the zone where the coating layer material has been applied. The location where the penetrated coating layer material allows the passage of light through the packaging paper is referred to as the transparent zone <NUM>. 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 coating layer material absorbs or reflects light.

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 transparent zone. The reciprocal value of the transmission, the opacity, is additionally also used. According to ISO <NUM>, an opacity of the transparent zone preferably lies between <NUM>% and <NUM>%, more preferably between <NUM>% and <NUM>%, most preferably between <NUM>% and <NUM>%. A packaging paper <NUM> which is at least partially translucent or transparent is thus provided in this way. Customers and shop staff can thus see what is packaged 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. Alternatively or additionally, the coating layer material can comprise a vegetable oil. A packaging paper with a transparent zone <NUM> comprising only vegetable oil is furthermore recyclable and/or compostable. A further advantage of a transparent zone which is formed by applying the oily compound 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 <NUM> which is formed from one piece of cellulose layer neutralizes these problems almost completely.

<FIG> show that the transparent zone <NUM> extends, preferably, at least partially over the cellulose layer. Although not shown, the transparent zone <NUM> can also extend over the whole surface of the cellulose layer. In this way the whole packaging paper <NUM> is transparent. The transparent zone <NUM> preferably extends in the form of a strip.

According to the preferred embodiment of <FIG>, the transparent zone <NUM> extends in a longitudinal direction Y of the cellulose layer. In <FIG> the transparent zone <NUM> extends from one end edge to the opposite end edge. In this way the transparent zone <NUM> forms a transparent 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 <NUM>. Shown in each of the <FIG> is a representation of an item P packaged in the packaging paper <NUM>. The visibility of the product shows the transparency of the transparent zone <NUM> and the opacity of the non-transparent zone.

In <FIG> the transparent zone <NUM> is arranged centrally on the cellulose layer. In this way two non-transparent zones <NUM> are situated on either side of the transparent zone <NUM>. The non-transparent zones <NUM>, also referred to as opaque zones <NUM>, can be a part of the cellulose layer where no coating layer material is applied, or where only a small quantity of coating layer material is applied. Such an untreated portion of the cellulose layer is non-transparent. The non-transparent zones have a higher moisture permeability than the transparent zone. Changing an area ratio of the transparent zone and a non-transparent 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.

Compared to <FIG> shows that the transparent zone <NUM> can also be positioned at a peripheral edge of the packaging paper <NUM>, for instance a transverse edge of the packaging paper <NUM>.

<FIG> shows that the transparent zone <NUM> can also extend in a width direction X of the cellulose layer. The transparent zone <NUM> in <FIG> thus takes a wider form than the transparent zone <NUM> shown in <FIG>. The packaged item P is more clearly visible in this way. In this embodiment the non-transparent zone in <FIG> has a smaller surface area than the non-transparent zone in <FIG>. In this way the packaging paper <NUM> in <FIG> has a lower moisture permeability than the packaging paper <NUM> shown in <FIG>.

<FIG> shows a packaging paper <NUM> with a transparent zone <NUM> which extends from a first transverse edge to a second transverse edge lying opposite the first transverse edge, as seen in the width direction X of the cellulose layer. The transparent zone <NUM> in <FIG> is thus smaller than the transparent zone shown in <FIG>, as seen in a longitudinal direction Y. In this way the transparent zone forms a transparent strip, as seen in the width direction of the cellulose layer. Similarly to <FIG>, two non-transparent zones are situated on either side of the transparent zone. It will be apparent that the formed transverse strip can also be formed to lie adjacently of an end edge of the cellulose layer.

<FIG> show a packaging material with a plurality of transparent zones <NUM>. <FIG> thus shows that for instance two or more transparent zones <NUM> can take the form of a transverse strip. The transparent zones <NUM> lie at a mutual distance, as seen in a longitudinal direction of the cellulose layer. <FIG> shows that for instance two or more transparent zones <NUM> can take the form of a longitudinal strip. These transparent zones <NUM> also lie at a mutual distance, as seen in a longitudinal direction of the cellulose layer. <FIG> shows an example wherein the plurality of transparent zones coincide. The example shown in <FIG> comprises a first transparent zone which forms a transverse strip and a second transparent zone which forms a longitudinal strip. It will be apparent on the basis of <FIG> that the transparent zones can overlap and together form one transparent zone. The transparent zone is described above as substantially rectangular with substantially straight edges. The transparent zone can however also have at least partially curved and/or bent edges. The transparent zone can thus for instance also take a round form, such as that of a circle or oval. The transparent 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 transparent 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.

Packaging paper <NUM> 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 <FIG>, <FIG>.

<FIG>, <FIG> show a cross-section of a cellulose layer <NUM> as described in relation to 1A, 1B, 1C, 1D, 1E, 1F, <NUM>, <NUM>. The method comprises of providing a cellulose layer <NUM> with a first side <NUM> and a second side <NUM>. As shown in <FIG>, the cellulose layer <NUM> is initially non-transparent. A product P situated below the cellulose layer <NUM> is thus not visible or identifiable, or is so only to limited extent. The cellulose layer <NUM> preferably has a specific weight higher than <NUM>/m<NUM>. The cellulose layer <NUM> further preferably has a specific weight which is at most <NUM>/m<NUM>, more preferably at most <NUM>/m<NUM>. Such a cellulose layer is relatively light-weight, which has the advantage that the packaging paper is easily transportable and is cheaper. Such a cellulose layer <NUM> is furthermore more easily penetrable by the coating layer material <NUM>. In other words, such a cellulose layer can be advantageously saturated by the applied coating layer material <NUM>. It is thought that the advantageous effect thereof is due to the lower fibre density of the cellulose layer with such a specific weight.

It is preferred for a surface on at least the first side <NUM> of the cellulose layer <NUM> to have a surface roughness of less than <NUM>/min, preferably less than <NUM>/min, more preferably less than <NUM>/min, most preferably less than <NUM>/min. The surface roughness is determined here in accordance with ISO <NUM>-<NUM> 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 <NUM> more uniformly.

It is preferred for the cellulose layer <NUM> to be a bleached cellulose layer, for instance a white paper. In this way an optimal transparent result is obtained, although it is noted that a white paper is not essential. This is because tests have shown that almost identical transparencies can be realized with a brown paper.

The cellulose layer <NUM> further preferably comprises a mixture of long fibre and short fibre, with at least <NUM>% long fibres, more preferably at least <NUM>%, preferably at least <NUM>%. 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.

As shown in <FIG>, a predetermined quantity of coating layer material <NUM> with a first temperature is applied to the first side at the position of a zone. The coating layer 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 <NUM> and <NUM>, more preferably between <NUM> and <NUM>, most preferably between <NUM> and <NUM>. Such a temperature range enhances the viscosity of the applied coating layer material <NUM>. In this way the coating layer material becomes more viscous, i.e. more runny or liquid, whereby the coating layer material penetrates the cellulose layer <NUM> in improved manner and is able to saturate the cellulose layer <NUM> in efficient manner. A temperature range between <NUM> and <NUM> realizes the further advantage that the coating layer material cannot burn. The viscosity of the coating layer material <NUM> preferably lies between <NUM> mPa/s and <NUM> mPa/s, measured at a temperature of <NUM>. The viscosity of the coating layer material <NUM> more preferably lies between <NUM> mPa/s and <NUM> mPa/s, measured at a temperature of <NUM>. It is noted that the cellulose layer can also be heated before the coating layer material is applied. This allows the coating layer material to further penetrate the cellulose layer in improved manner.

The penetration of the coating layer material <NUM> is illustrated by the circles shown in cellulose layer <NUM>. The coating layer material <NUM> penetrates between the fibres of the cellulose layer, preferably to (a position close to) the second side <NUM>. In this way a substantially continuous flow of coating layer material through cellulose layer <NUM> is formed. In order to substantially guarantee a transparency it is preferable to opt for a sufficiently large predetermined quantity of coating layer material. The predetermined quantity of coating layer material is thus preferably at least <NUM>/m<NUM>, more preferably a quantity corresponding to a surface density of between <NUM> to <NUM>/m<NUM>. In this way the coating layer material saturates the cellulose layer and a desired transparency is substantially guaranteed. The predetermined quantity of coating layer material is more preferably a maximum of <NUM>/m<NUM>. It is noted that the predetermined quantity of coating layer 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, <NUM> to <NUM>/m<NUM> of coating layer material can for instance be applied, or, according to a further example, <NUM> to <NUM>/m<NUM> can be applied in the case of a brown paper. According to a further exemplary embodiment, <NUM> to <NUM>/m<NUM> of coating layer material can alternatively be applied. Such a chosen predetermined quantity of coating layer material saturates the cellulose layer. It is further noted that the transparency improves further still when the coating layer material is applied to both the first and the second side. The quantity of coating layer material can differ for the first side and the second side, although it is preferred for the collective surface density of the coating layer material on the first and the second side to correspond to the above stated values. Applying the coating layer material to both sides almost certainly guarantees that coating layer material penetrates through the cellulose layer and the coating layer material saturates the cellulose layer. The inventors have surprisingly found that when coating layer material is applied to both sides of the cellulose layer, the transparency is further improved.

<FIG> shows that the coating layer material <NUM> has penetrated through the cellulose layer <NUM>. It will be apparent that a portion of the coating layer material <NUM> may protrude from the cellulose layer <NUM>. In other words, a quantity of coating layer material <NUM> may still be present on the surface of cellulose layer <NUM>. It is possible, especially in advantageous circumstances in which the cellulose layer is wholly saturated by the coating layer material <NUM>, for a residue or excess of coating layer material <NUM> to remain on the cellulose layer surface. The applied predetermined quantity of coating layer material is then gradually hardened at a second temperature. The second temperature lies in a second temperature range. The second temperature can vary between the limits of the second temperature range. Owing to the gradual hardening, the zone where the coating layer material has penetrated becomes transparent and thus forms the transparent zone <NUM>. The gradual hardening of the coating layer material allows the oily material to harden and thus form a path transparent to light through the cellulose layer <NUM>, as shown in <FIG>. It is noted that the gradual hardening differs significantly from existing production processes where a coating layer material is immediately cooled with a cooling roller, typically at a very low temperature, about <NUM>, in order 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 consequently hardens into a structure with an opaque result due to the sudden temperature drop. The first and second temperature range lie above a melting point of the coating layer material. When the melting point of the coating layer material is for instance <NUM>, as is the case for paraffin, the gradual hardening is performed at <NUM> or above. The gradual hardening is preferably performed in the second temperature range which lies between <NUM> and <NUM>, preferably between <NUM> and <NUM>, more preferably between <NUM> and <NUM>. It will be apparent to the skilled person that further specific preferred limits of the second temperature range depend on the coating layer material used. The gradual hardening can also comprise heating of the cellulose layer with applied coating layer material. The coating layer material can thus initially already be hardened before the coating layer material and the cellulose layer are exposed to the second temperature range, for instance with a hot air blowing device, as will be further elucidated. The cellulose layer with the predetermined quantity of coating layer material is further preferably exposed to the second temperature range for a period of at least <NUM> second, preferably between <NUM> and <NUM> seconds, preferably at least <NUM> seconds. It is suspected that the coating layer material hardens into a substantially vitreous structure in this way. Experiments have shown that the transparency is improved in this manner.

The gradual hardening can be performed in different ways, for instance using a heating device <NUM> which heats the cellulose layer at said second temperature range. Alternatively or additionally, the second temperature range can be provided by residual heat obtained by application of the predetermined quantity of coating layer material. The heating device <NUM> can be a hot air device which blows air at a temperature lying in the second temperature range onto the cellulose layer with 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 in order to saturate the cellulose layer. Such a preferred embodiment can be realized in simple manner. The heating device <NUM> can be provided at a distance from the application of the coating layer material, for instance about <NUM> to <NUM> metres. This allows the coating layer material to at least partially harden for a short time and then melt again. Surprisingly, it has been found that the final transparency of the transparent zone is further improved in this way. One or more heating rollers, which heat the cellulose layer with the coating layer material in order to reach the second temperature range, can alternatively or in combination also be provided. It is further possible to further improve the penetration of the coating layer material by exposing the paper to an increased pressure, for instance by making use of heated pressure rollers. As described above, the cellulose layer can optionally be heated both before application of the coating layer material and after application of the coating layer material. Tests have further surprisingly shown that the coating layer material also hardens gradually when a cooling roller is disabled, for instance by preventing coolant from flowing through the cooling roller or by removing the cooling roller. In known devices such a cooling roller is located downstream of a location where the coating layer material is applied, typically in the immediate vicinity thereof so that coating layer material is immediately hardened, resulting in the above stated opaque view. By disabling the cooling roller the gradual hardening is realized in very simple manner. The transparency of the transparent zone is further improved when the coating layer material is applied to both sides of the cellulose layer in such a preferred embodiment.

The packaging paper <NUM> with the transparent 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 <NUM> 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 transparent 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 <NUM>. Glassine is moreover fragile because the fibres have been extremely finely ground.

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

Example <NUM> describes a known method and device for drastically increasing the moisture-permeability of bread bags made of paper.

Flexpack Smooth from STARKRAFT is an exemplary embodiment of a cellulose layer <NUM> with a specific weight of about <NUM>/m<NUM>. According to the first example, the Flexpack Smooth by STARKRAFT is coated on one side, i.e. on the first side <NUM> or on the second side <NUM> of the cellulose layer <NUM>, or on two sides, i.e. on both the first side <NUM> and the second side <NUM> of cellulose layer <NUM>, with a coating layer material <NUM> of paraffin with a different weight per unit area in g/m<NUM> by means of a HOLWEG-WEBER® RS26 paper bag making machine with a HOLWEG-WEBER® CTH1 waxing unit. The paraffin bath of the HOLWEG-WEBER® RS26 paper bag making machine has a temperature of <NUM>. The cellulose layer is driven through the HOLWEG-WEBER® RS26 paper bag making machine at a production speed of about <NUM>/min. According to the first exemplary embodiment, the cooling rollers of the HOLWEG-WEBER® RS26 paper bag making machine have a temperature of about <NUM> to <NUM>. A moisture-permeability of paper is typically increased in this way. According to the known method, the paper is then finished further for use as for instance a bread bag by the consumer.

Continuing on from example <NUM>, a further treatment of the cellulose layer <NUM>, for instance the Flexpack Smooth from STARKRAFT, with coating layer material <NUM> allows the cellulose layer <NUM> to be made transparent locally. In other words, it is possible to further create a transparent zone <NUM> in the cellulose layer <NUM>.

Once cellulose layer <NUM>, also referred to as "the paper" in the further elucidation of the exemplary embodiments, has a coating layer <NUM>, a sample is taken. In the exemplary embodiments a paraffin layer or paraffin coating is applied as coating layer <NUM>. The sample is briefly exposed to a high temperature by holding the paper above a hot plate, for instance of <NUM>, for a brief period of time, for instance for about <NUM> minute. This makes the paper transparent locally, i.e. at the position of the zone which is exposed to the hot plate. It is suspected that, due to the exposure to the very high temperature, the applied paraffin layer melts again and penetrates the pores of the paper in improved manner. The paraffin penetrating the pores of the paper is mainly driven by the capillarity of the paper fibre structure. When a refractive index of paraffin, typically about <NUM>, and paper or cellulose, typically about <NUM>, are roughly the same, the paper becomes transparent locally.

Transparency or opacity of the treated paper can be measured with a PCE-RM <NUM> Reflectance Meter. It will be apparent to the skilled person that alternative so-called reflectometers can be used. Reflectometers typically use a measuring scale from <NUM> to <NUM>%. It is the case here that <NUM>% is fully transparent and <NUM>% fully opaque. The lower the measured value, the better the transparency. Such measurement can be used in combination with or as alternative to the above stated ISO <NUM> measurement.

In a first exemplary embodiment (exemplary embodiment <NUM>), the paper is coated on one side with <NUM>/m<NUM> TopScreen®Biowax-based Barrier Coating ED9 from Solenis®. This paraffin is a palm oil type. The measured transparency varies from <NUM> to <NUM>%.

In a second exemplary embodiment (exemplary embodiment <NUM>) the paper is coated on two sides with <NUM>/m<NUM> on a first side and <NUM>/m<NUM> on a second side with TopScreen®Biowax-based Barrier Coating ED9 from Solenis®. The transparency varies here from <NUM> to <NUM>%.

When the paper is in a third exemplary embodiment (exemplary embodiment <NUM>) coated on two sides with <NUM>/m<NUM> on the first side and <NUM>/m<NUM> on the second side, as in exemplary embodiment <NUM> but with a hydrogenated and refined petroleum-based paraffin, Proquiwax® <NUM>-<NUM> from Proquinat, the transparency is higher than <NUM>%.

When the paper is in a fourth exemplary embodiment (exemplary embodiment <NUM>) coated on two sides with <NUM>/m<NUM> TopScreen®Biowax-based Barrier Coating ED9 from Solenis® on each side, the transparency varies from <NUM> to <NUM>%.

When the paper is in a fifth exemplary embodiment (exemplary embodiment <NUM>) coated on two sides with <NUM>/m<NUM>, as in the fourth exemplary embodiment but with a hydrogenated and refined petroleum-based paraffin, such as Proquiwax® <NUM>-<NUM> from Proquinat, the transparency varies between <NUM> and <NUM>%.

A comparison of exemplary embodiments <NUM> and <NUM> to exemplary embodiments <NUM> and <NUM> shows that the type and quantity of the applied paraffin in combination with the type of paper can determine the degree of transparency.

It is further noted that time also plays a part in creating a transparent zone in advantageous manner. It was for instance found that, one hour after production, the transparency of exemplary embodiments <NUM>, <NUM> and <NUM> will deteriorate by an average of <NUM>%. <NUM> hours after production, the decrease in transparency is about <NUM>% and after about <NUM> days the decrease can be <NUM> to <NUM>%. It is suspected that the paraffin continues to crystallize during the relevant time durations. The crystallization results in more light scattering due to the crystal edges and the transparency decreases as a result.

In a first comparative experiment (comparative experiment <NUM>) Cristal® Flexible & Transparent Paper from Ahlstrom-Munksjö® is used. A very dense and transparent glassine paper has been obtained by supercalandering, as described in the description introduction of this application. Without additional coating, this glassine paper has a transparency of <NUM>%. When glassine paper is compared to the exemplary embodiments <NUM>-<NUM>, it will be apparent that exemplary embodiments <NUM>-<NUM> have at least the same transparency as this expensive and labour-intensive glassine paper, this owing to the above described simple and inexpensive method. The paper according to exemplary embodiments <NUM>-<NUM> is furthermore at least partially moisture and grease-resistant, this in contrast to glassine paper, which is only grease-resistant.

When glassine paper is in a second comparative experiment (comparative experiment <NUM>) coated on two sides with <NUM>/m<NUM> TopScreen®Biowax-based Barrier Coating ED9 from Solenis®, the transparency thereof improves to <NUM> to <NUM>%. When glassine paper is coated on one side with <NUM>/m<NUM> in a third comparative experiment (comparative experiment <NUM>), the transparency thereof increases to about <NUM>%, which is thus an improved transparency relative to the previous <NUM>%.

A comparison of comparative experiment <NUM> to comparative experiments <NUM> and <NUM>, and also of exemplary embodiments <NUM> to exemplary embodiments <NUM> and <NUM>, shows that a minimal quantity of paraffin is needed to achieve an improved transparency. It is further shown that a greater coating quantity however does not guarantee an improved transparency. As already noted above, very dense and smooth paper, such as Cristal® Flexible & Transparent Paper, requires less paraffin than Flexpack Smooth Paper.

Claim 1:
A packaging paper (<NUM>) with a transparent zone (<NUM>), wherein the packaging paper (<NUM>) and the transparent zone (<NUM>) are made from one cellulose layer and wherein the transparent zone (<NUM>) comprises a coating layer material applied to the packaging paper (<NUM>), wherein the coating layer material comprises an oily compound such as a paraffin or vegetable oil.