EP3830337A1

EP3830337A1 - Lightweight separating base paper

Info

Publication number: EP3830337A1
Application number: EP19725943.5A
Authority: EP
Inventors: Tuomas TURTOLA
Original assignee: Delfortgroup AG
Current assignee: Delfortgroup AG
Priority date: 2018-07-27
Filing date: 2019-05-14
Publication date: 2021-06-09
Also published as: DE102018118271A1; WO2020020503A1; CN112384657A; JP2021531033A; US20210274831A1; JP7291776B2; CN112384657B

Abstract

The invention relates to a separating base paper, having a mass per unit area of at least 25 g/m² and at most 40 g/m² and a density of at least 0.90 g/cm³ and at most 1.15 g/cm³. The separating base paper comprises at least 50 wt% of long-fiber pulp and is coated on at least one side with at least two coatings. The first coating is located between a paper surface and the second coating. The second coating is a topmost coating and comprises a water-soluble film-forming polymer, nanofibrillated cellulose, microfibrillated cellulose or nanocrystalline cellulose. The Cobb-Unger (120 s) value of the surface having said first and second coatings is at least 0.01 g/m² and at most 0.90 g/m².

Description

LIGHT RELEASE BASE PAPER

FIELD OF THE INVENTION

The invention relates to a release paper with a low basis weight but otherwise equivalent or better technical properties compared to a conventional release paper, in particular with regard to the resistance to the absorption of silicone. In particular, the invention relates to a release paper with a low basis weight and a special two-layer coating and the use of the release paper for siliconization.

BACKGROUND AND PRIOR ART

A release paper is a paper that is intended to be coated with silicone. If it is coated with silicone, it can be used as a backing paper for self-adhesive labels, as baking paper or in other applications that require the release properties that can be achieved with a silicone coating.

Certain technical requirements are important for release paper. The silicon kon, which is applied later, is usually applied in amounts of only lg / m ² to 2 g / m ² over the entire surface of the release base paper. Although this amount is very small, it is necessary for the silicone to cover 100% of the surface of the release paper, otherwise labels, for example, cannot be completely removed from the siliconized release paper. Therefore, the penetration of the silicone in the release paper plays an important role and it should be as small as possible. The ability of a release base paper to allow only a small amount of silicone to penetrate but at the same time to produce a closed coating is called the absorption resistance.

The release paper is said to have high transparency. In many applications, the self-adhesive labels are removed from the siliconized release paper by machines that detect the presence of a label using optical sensors through the release paper. The detection can only work reliably if the release paper is sufficiently transparent.

Finally, the self-adhesive label material is first applied to the entire surface of the siliconized release paper and then the self-adhesive label material is typically punched into individual labels in the desired shape and Cut size. When punching, of course, only the self-adhesive label material should be cut, but not the release paper. This requires a certain density and compressibility of the release paper.

Furthermore, there are additional technical requirements such as good tensile strength, good tear strength, suitable energy absorption capacity and a thickness, all of which influence the productivity of the processing machines of such release paper.

Conventional release papers have a basis weight of about 50 g / m ² to about 60 g / m ^{2 to} meet all technical requirements. The siliconized release paper must be disposed of after use, for example after the self-adhesive labels have been removed. Siliconized release base papers are difficult to recycle due to the silicone coating, so there is an interest in reducing the amount of waste generated by such siliconized release base papers. It has proven difficult to reduce the basis weight of release paper and thus the amount of waste that is generated, because the technical requirements described above can then only be met inadequately. For this reason, lightweight release papers have so far not achieved any commercial importance.

There is therefore an interest in having a lightweight release paper which is at least equivalent in terms of its technical performance compared to heavier conventional release papers from the prior art.

SUMMARY OF THE INVENTION

The invention has for its object to provide a release paper that has a low basis weight but still meets the technical requirements that are expected from a release paper, such as good absorption resistance against silicone and easy processing. This object is achieved by a release base paper according to claim 1 and a method for its production according to claim 25. Advantageous further developments are specified in the dependent claims. Further aspects of the invention relate to a self-adhesive label which uses a release paper according to the invention, a baking paper which is based on the release paper of the present invention, a use of the release paper according to the invention for wrapping a smokable material, a smoking article obtained in this way and the use of the release base paper according to the invention as packaging paper. The inventor has found that this goal can be achieved by a release paper that has a basis weight of at least 25 g / m ² and at most 40 g / m ² and a density of at least 0.9 g / cm ³ and at most 1.15 g / cm ³ , wherein the release paper comprises at least 50% by weight of long-fiber pulp and is provided on at least one side with at least two coatings, the first coating being between the paper surface and the second coating and the second coating is the top coating and comprises a water-soluble film-forming polymer, nanofibrillated cellulose, microfibrillated cellulose or nanocrystalline cellulose, and wherein the Cobb Unger (120 s) value of the coated surface is at least 0.01 g / m ² and at most 0.90 g / m ² .

The separating base paper according to the invention has a basis weight of at least 25 g / m ² , preferably at least 30 g / m ² and at most 40 g / m ² , preferably at most 38 g / m ² . The basis weight can be determined in accordance with ISO 536: 2012 and describes the basis weight of the finished release paper, including the at least two coatings, but without the silicone coating. The reduction in the basis weight results in a significant reduction in waste by about 50%, but without further measures a simple reduction in the basis weight does not lead to a release paper with satisfactory technical properties.

The inventor has therefore found that the release paper of the invention has a density of at least 0.90 g / cm ³ , preferably at least 0.95 g / cm ³ , particularly preferably at least 0.99 g / cm ³ and at most 1.15 g / cm ³ , preferably at most 1.10 g / cm ³ , particularly preferably at most 1.07 g / cm ³ and very particularly preferably at most 1.05 g / cm ³ . The density of the release paper is related to compressibility. After the release paper has been coated with silicone and the label material has been applied, the label material is cut, typically by punching. It is particularly important when punching that only the label material but not the siliconized release paper is cut, and therefore the siliconized release paper has to give in to the pressure of the punch by a defined distance. In general, density and compressibility are closely related, so that conventional release papers require a density of approximately 1.17 g / cm ^{3 in} order to achieve the desired compressibility. However, the release base paper according to the invention has a low basis weight and therefore a small thickness and therefore inherently yields less than the conventional release base paper. The density of the release base paper according to the invention can therefore be lower than that of conventional release base papers. The density of the release base paper is generally set in a calendering process, the paper being compressed between several pairs of rollers and each pair of rollers forming a nip. Since the release base paper according to the invention does not require such a high density, fewer roll gaps are required compared to conventional release base papers, which means a saving in energy and production expenditure. However, a lower density leads to a more porous paper structure and it can therefore deteriorate the absorption resistance against silicone. The inventor has determined that this disadvantage can be overcome by the coatings mentioned, as will be explained further below using exemplary embodiments.

The reduction in the basis weight can lead to a reduction in the tensile strength, so that the release base paper tears off more often in further processing steps. The inventor has found that a particularly good tensile strength can be achieved if the release base paper comprises at least 50% by weight of long fiber pulp, preferably at least 60% by weight and particularly preferably at least 70% by weight.

The air permeability of the release paper is related to the porosity of the release paper and therefore influences the absorption of the silicone. In general, higher porosity and higher air permeability mean that the release paper absorbs more silicone. Therefore, the air permeability should be as low as possible. Air permeability can be measured using the Gurley method defined in ISO 5636-5: 2013. The time is measured until a certain volume of air has flowed through a defined area of the paper under defined pressure conditions. The measurement time can be very long for papers with a very low air permeability, i.e. very high values according to Gurley. In this case, it is common to stop the measurement after some time and then to determine the time by extrapolation, which would be necessary for the defined air volume to flow through the paper.

The air permeability of the Gurley separating base paper according to the invention is preferably at least 40,000 s, particularly preferably at least 60,000 s and very particularly preferably at least 70,000 s. This is significantly higher than the Gurley air permeability of conventional release paper, which typically has a Gurley air permeability of less than 30,000 s. The release paper according to the invention therefore has the further advantage that less silicone is required for a full-surface coating.

The release base paper according to the invention comprises long fiber pulp. Long fiber pulp is preferably obtained from conifers such as spruce, pine and fir. In preferred out In the embodiment, at least 70% by weight, preferably at least 85% by weight, of the long fiber cellulose mentioned is obtained from conifers. Other preferred sources of long fiber pulp can be plants such as flax, hemp, sisal, jute or abaca. Mixtures of long fiber pulps from different origins can also be used. The long fiber pulp provides the release paper with a particularly good tensile strength.

The long fiber pulp is ground for the production of the release paper according to the invention. Milling is an energy-intensive mechanical treatment which has the task of exposing the fibrils of the cellulose fibers, but which also shortens the fibers to a certain extent. Intensive grinding increases the tensile strength of the paper and reduces the porosity. The effect of grinding on the pulp can be determined in accordance with ISO 5267-1: 1999 and is given as the Schopper-Riegler (° SR) grinding degree. Conventional release papers require very intensive grinding to achieve a high density, which requires a large amount of energy. The separating base paper according to the invention, however, requires a significantly lower grinding intensity, so that the ground long fiber pulp has a degree of grinding of preferably at least 50 ° SR, particularly preferably at least 60 ° SR and preferably at most 80 ° SR, particularly preferably at most 70 ° SR. A less intensive grinding has additional positive effects on the tear strength of the release paper. The inventor has found that the special coating of the release paper according to the invention helps to overcome the disadvantages of lower tensile strength and higher porosity, which result from the less intensive grinding. Therefore, the production of the release paper according to the invention requires less energy, because on the one hand less long fiber pulp has to be ground per paper surface because of the low basis weight and on the other hand the intensity of the grinding can be reduced by the special coating.

The release paper can contain short fiber pulp, which is preferably obtained from deciduous trees such as beech, birch or eucalyptus. Another preferred source of short fiber pulp can be grasses such as esparto grass. Mixtures of short fiber pulp from different origins can also be used. Short fiber pulp gives the release liner a larger volume and can reduce tensile strength, neither of which is desirable for the intended application. However, short fiber pulp is generally cheaper than long fiber pulp and therefore the release paper can contain a portion of short fiber pulp.

The separating base paper according to the invention preferably comprises at most 40% by weight of short fiber pulp and particularly preferably at most 30% by weight of short fiber pulp. The release paper can contain fillers, such as calcium carbonate, titanium dioxide, kaolin, aluminum hydroxide, magnesium silicates, aluminum silicates, talc or mixtures thereof. However, fillers in release paper have certain disadvantages because they can increase the porosity and air permeability of the release paper and can reduce tensile strength and transparency. The release base paper according to the invention therefore preferably contains at most 15% by weight of fillers, particularly preferably at most 10% by weight and very particularly preferably less than 2% by weight of fillers. In this context, fillers have to be distinguished from pigments, which can be contained in coatings of the release paper according to the invention. In this context, fillers only refer to substances that are added to the paper pulp during paper production and not substances that are applied to the surface of the paper in the form of a coating.

The release base paper may further contain sizing agents or other additives and process aids which the person skilled in the art can select based on his experience.

The release paper of the invention is coated and comprises at least two coatings. These coatings significantly improve the absorption resistance to silicone and ensure that the advantages of the invention can also be achieved in combination with the low basis weight and the low density.

The task of the first coating is to seal the surface of the release paper and prepare it for the application of the second coating. The second coating then produces a smooth, chemically homogeneous surface that is particularly well suited for coating with silicone. By coating twice, less air permeability and higher smoothness can be achieved with less coating material than could be achieved with a single coating. This also saves on coating material, which is an advantage of the invention. This positive effect can also be achieved and demonstrated on the release paper if the coating materials of the first and the second coating are the same.

The first coating comprises a coating material which consists of the group consisting of water-soluble film-forming polymers, such as starch, starch derivatives, cellulose derivatives or latex; nanofibrillated cellulose; nanocrystalline cellulose; microfibrillated cellulose and mixtures thereof is selected and the second coating comprises a water-soluble film-forming polymer, nanofibrillated cellulose, microfibrillated cellulose or nanocrystalline cellulose. The release base paper according to the invention can comprise more than two coatings, provided that said first coating is between the paper surface and said second coating and said second coating forms the uppermost coating of the release base paper. Additional coatings can therefore be located between the paper surface and said first coating or between said first coating and said second coating. Additional coatings can be used to achieve further special effects, but the release paper according to the invention preferably comprises exactly two coatings.

The first coating is preferably applied by means of a first coating composition comprising water and the said coating material. After the first coating composition has been applied to the paper, the paper is dried and the amount of the dried first coating composition which remains on the release base paper according to the invention, that is to say the amount of the first coating, is preferably at least 0.1 g / m ² , particularly preferably at least 0.4 g / m ² and preferably at most 4.0 g / m ² and particularly preferably at most 2.5 g / m ² .

The first coating composition comprises water and said coating material. The coating material preferably makes up at least 5.0% by weight, particularly preferably at least 10.0% by weight and preferably at most 25.0% by weight, particularly preferably at most 20.0% by weight, the Percentages relate to the weight of the first coating composition.

The coating material in the first coating and in the first coating composition is preferably a starch or a starch derivative and is particularly preferably selected from the group consisting of potato starch, corn starch, tapioca starch, wheat starch, derivatives of these starches, and mixtures thereof.

The first coating composition can furthermore contain additives, viscosity influencing agents or other components which the person skilled in the art can select from experience in terms of type and amount in order to obtain a coating composition which is suitable for use in the application device.

The second coating comprises a water-soluble, film-forming polymer, nanofibrillated cellulose, microfibrillated cellulose or nanocrystalline cellulose and is applied in the form of a second coating composition which comprises water and the said film-forming polymer, nanofibrillated cellulose, microfibrillated cellulose or nanocrystalline cellulose. After the application of the second coating composition, the paper is dried and the amount of the dried second coating composition, that which remains on the release base paper according to the invention, ie the amount of the second coating, is preferably at least 0.5 g / m ² , particularly preferably at least 1.5 g / m ² and preferably at most 5.0 g / m ² , particularly preferably at most 3.0 g / m ² . The second coating composition comprises water and a water-soluble film-forming polymer, nanofibrillated cellulose, microfibrillated cellulose or nanocrystalline cellulose. The water-soluble film-forming polymer, the nanofibrillated cellulose, the microfibrillated cellulose or the nanocrystalline cellulose preferably make up at least 5% by weight, particularly preferably at least 8% by weight and preferably at most 25% by weight and particularly preferably at most 15 % By weight, the percentages relating to the weight of the second coating composition.

The second coating or the second coating composition preferably comprise pigment particles, and particularly preferably the pigment particles have a plate-like shape.

The pigment particles are preferably selected from the group consisting of kaolin, talc, magnesium silicates, aluminum silicates, calcium carbonate and mixtures thereof. Pigment particles with a platelet-like shape, in particular platelet-like calcium carbonate, kaolin or talc, are particularly preferred.

The pigment particles, regardless of whether they have a platelet-like shape, preferably make up at least 1% by weight, particularly preferably at least 10% by weight and preferably at most 30% by weight and particularly preferably at most 20% by weight, where the percentages relate to the weight of the second coating composition.

The second coating composition may further include viscosity modifiers, crosslinking agents, or other components that one of ordinary skill in the art can choose from experience based on type and amount to obtain a coating composition suitable for use in the applicator ,

The water-soluble, film-forming polymer of the second coating or coating composition can preferably be selected from the group consisting of polyvinyl alcohol, carboxymethyl cellulose, hydroxymethyl cellulose, starch, starch derivatives, latex and mixtures thereof. In a particularly preferred embodiment, the second coating or coating composition comprises modified nanofibrillated cellulose, modified microcrystalline cellulose, modified nanocrystalline cellulose, modified polyvinyl alcohol or modified carboxymethyl cellulose, this coating tion materials have been modified so that they have vinyl groups that can react with the silicone and thus promote or improve the adhesion of the silicone to the release paper. Such modified polyvinyl alcohol, modified carboxymethyl cellulose, modified nanofibrillated cellulose, modified microcrystalline cellulose or modified nanocrystalline cellulose can be obtained, for example, from processes in which some hydroxyl groups of the coating materials react with organic molecules which have a vinyl group, so that after the reaction the vinyl group is available for a further reaction with the silicone and improves the adhesion of the silicone on the surface of the release paper. The reaction with the organic molecule can take place before or after the application of the second coating composition. Such coating materials and processes for their production are described, for example, in European Patents EP 2300544 or EP 2539505.

In a particularly preferred embodiment, the coating materials of the first and second coating are different, the coating material of the first coating being selected from the group consisting of starch, starch derivatives and cellulose derivatives and the coating material of the second coating being selected from the group consisting of latex, Polyvinyl alcohol, nanofibrillated cellulose, microfibrillated cellulose nanocrystalline cellulose, with vinyl groups modified polyvinyl alcohol, with vinyl groups modified carboxymethyl cellulose, with vinyl groups modified nanofibrillated cellulose, with vinyl groups modified microfibrillated cellulose and with vinyl groups modified nanocrystalline cellulose. “Modified with vinyl groups” means that some of the hydroxyl groups in the coating materials mentioned have reacted with an organic molecule that has a vinyl group. The reaction with the organic molecule can take place before or after the application of the second coating composition. This vinyl group is then available for reaction with the silicone and improves the adhesion of the silicone to the surface of the release base paper. Methods for producing coating materials modified in this way are described, for example, in EP2300544 or EP 2539505.

The inventor has found that the two coatings serve to seal the paper structure and produce a smooth, chemically uniform surface that is particularly suitable for being coated with silicone. In particular, the inventor found that in combination with a low basis weight and a low density, the coatings improve the absorption resistance against silicone, so that the light-weight separating base paper is suitable for a large number of applications. The absorption resistance to silicone, that is, the ability of the paper to prevent the silicon from penetrating into the paper structure and to enable a homogeneous silicone coating can be assessed by measuring the Cobb Unger (120 s) according to the test described in TAPPI T462 cm-16. In this test, a certain area of the paper is exposed to a certain amount of oil, typically castor oil, for a certain time, typically 120 seconds, and after the oil is removed, the weight gain of the paper per unit area is determined and is the Cobb Unger (120 seconds) value the side that was exposed to the oil. The inventor has stated that a low Cobb Unger (120 s) value is related to a good absorption resistance against silicone.

The Cobb Unger (120 s) value of the coated side of the release paper according to the invention is therefore at least 0.01 g / m ² , preferably at least 0.10 g / m ² , particularly preferably at least 0.15 g / m ² and at most 0 , 90 g / m ² , preferably at most 0.70 g / m ² , particularly preferably at most 0.60 g / m ² and very particularly preferably at most 0.50 g / m ² . The coated side of the release base paper according to the invention is the side which is intended to be coated with silicone, that is to say the side to which the first and second coating have been applied. This value is better than that of conventional release papers with a much higher basis weight, which typically achieve a Cobb Unger (120 s) value on the coated side of approximately 1.0 g / m ² . The Cobb Unger (120 s) value can be adjusted by selecting suitable coating materials for the first and second coatings and by the amount of the first and second coating compositions that are applied to the release paper. In general, a higher order quantity will result in a lower Cobb Unger (120 s) value.

The transparency of the release paper is also important. The transparency can be measured according to DIN 53147: 1993-01 and is given as a percentage from 0% to 100%, where 0% means completely opaque and 100% completely transparent. High transparency is useful because the presence of a Labels are often detected through the separation base paper by means of optical sensors. If the transparency is too low, this detection method is unreliable or cannot be carried out at normal production speeds. In general, a transparency of at least 45% is sufficient and most conventional release papers achieve a transparency of around 50%. In contrast, the release paper of the invention achieves a significantly higher transparency of preferably at least 55%, particularly preferably at least 60% and preferably at most 80%, particularly preferably at most 75%. This high level of transparency is achieved by the low basis weight, the absence of fillers and by suitable treatment of the release paper, such as calendering and coating. A high level of transparency means that less expensive and less powerful optical sensors have to be used to detect the labels, or that the pro Production speed can be increased, which is an additional advantage of the release paper according to the invention.

The separating base paper according to the invention can be produced by means of processes known from the prior art, it being possible to use a conventional paper machine, in particular a Fourdrinier paper machine, calendering and coating devices. The calendering device is preferably integrated in the paper machine, so that the calendering can be carried out during paper production. The first and second coating compositions can be applied by means of conventional application methods, for example in a size press, a film press, by knife coating or by a curtain coating method.

The release paper according to the invention can be used for siliconization and then used as a backing material for self-adhesive labels or as baking paper.

The inventor has also found other surprising applications for the release paper of the invention.

The release paper of the invention can be used on smoking articles. Smoking articles comprise a smokable material which is capable of producing an aerosol, by combustion, as in conventional cigarettes, or merely by heating, as in so-called heated tobacco products or heat-not-burn products. The smokable material is typically formed into a cylindrical strand and covered by a wrapping material, for example a cigarette paper. Depending on the climatic conditions, certain substances such as oils, humectants or water can pass from the smokable material into the wrapping material when the smoking article is stored or used. These substances then create undesirable stains on the wrapping material. This is particularly true of smoking articles which only heat up and do not burn the smokable material because the smokable material in these smoking articles typically contains a comparatively high amount of humectants, such as glycerol or propylene glycol. The inventor has found that the use of the release base paper according to the invention as a wrapping material for smoking articles can considerably reduce the number and area of the stains which form during storage and use.

The release paper of the invention can therefore be used to encase the smokable material of a smoking article, preferably the smokable material of a smoking article, which only heats up the smokable material but does not burn it. The invention therefore also includes a smoking article comprising a smokable material which is encased in the release paper, the smoking article preferably being a smoking article which heats up but does not burn the smokable material.

The inventor has also found another surprising application in the field of packaging papers. The smoothness and transparency of the release paper according to the invention make it particularly suitable for wrapping articles such as shirts, shoes or handbags in it. The separating base paper according to the invention envelops and protects the article, which is then packed in an overpack, usually made of cardboard. The transparency allows the article to be better recognized through the release paper according to the invention and is therefore particularly suitable for luxury articles. The smoothness of the release base paper according to the invention allows the packaging process to be automated better than is the case with conventional papers from the prior art for this application.

The invention therefore also includes the use of the release base paper according to the invention as packaging paper.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A release base paper according to the invention was produced from a mixture of 80% by weight long fiber pulp made of spruce and pine and 20% by weight short fiber pulp made of birch. The long fiber pulp was ground to a freeness of 67 ° SR, measured according to ISO 5267-1: 1999. No fillers were used.

The separating base paper web was formed in a conventional Fourdrinier paper machine from a water-based suspension containing the mixture of ground long fiber pulp and short fiber pulp and calendered in the paper machine using a calender integrated in the paper machine.

The release base paper was then coated over the entire surface with a first coating composition containing 15% by weight starch based on the weight of the coating composition and water and then dried to obtain the first coating. This step was carried out in a film press.

The release base paper was then coated over the entire area with a second coating composition, which was applied to the first coating, consisting of 8% by weight of polyvinyl alcohol, 15% by weight of kaolin particles, a small amount of crosslinking agent and water, the percentages based on the weight of the coating composition. The second coating composition was applied in a knife coater and dried in order to obtain the second coating and thus also the finished release paper of the invention.

The basis weight of the release paper was measured according to ISO 536: 2012 and a value of 36.0 g / m ² was obtained. The density of the release paper was calculated from the basis weight and the thickness, measured according to ISO 534: 2011, and determined to be 0.99 g / cm ³ . The Cobb Unger (120 s) value was determined according to TAPPI T462 cm-16 and a value of 0.3 g / m ² was obtained. The transparency of the release paper was measured according to DIN 53147: 1993-01 and a value of 67.0% was obtained.

The Gurley air permeability was measured according to the method defined in ISO 5636-5: 2013 and determined by extrapolation with a value of 100000 s.

The tensile strength, tear strength and other mechanical parameters of the release paper were also tested and found to be well suited for further processing of the release paper.

The release paper was coated with silicone without any problems and it was found that the siliconized release paper is particularly well suited as a backing material for self-adhesive labels.

The release base paper according to the invention therefore combines a low basis weight with at least equivalent, if not better, properties compared to a conventional release base paper and therefore contributes significantly to a reduction in waste through the use of such papers.

The release liner paper of the present invention was also used to encase the smokable material of a commercially available heat-not-burn product. After consuming this smoking article, significantly fewer stains were found on the release paper than on conventional cigarette paper after consuming a smoking article of the same brand with this conventional cigarette paper.

Claims

EXPECTATIONS

1. release paper, with a basis weight of at least 25 g / m ² and at most 40 g / m ² , and a density of at least 0.90 g / cm ³ and at most 1.15 g / cm ³ , the release paper at least 50 wt % Long fiber pulp and is coated on at least one side with at least two coatings,

the first coating being between a paper surface and the second coating,

the second coating being an uppermost coating and comprising a water-soluble film-forming polymer, nanofibrillated cellulose, microfibrilated cellulose or nanocrystalline cellulose,

and wherein the Cobb Unger (120 s) value of the surface with said first and second coating is at least 0.01 g / m ² and at most 0.90 g / m ² .

2. release paper according to claim 1, wherein the basis weight is at least 30 g / m ² and / or at most 38 g / m ² .

3. release paper according to claim 1 or 2, wherein the density at least 0.95 g / cm ³ , preferably at least 0.99 g / cm ³ and / or at most 1.10 g / cm ³ , preferably at most 1.07 g / cm ³ and particularly preferably at most 1.05 g / cm ³ .

4. release paper according to any one of the preceding claims, wherein the release paper comprises at least 60 wt .-%, preferably at least 70 wt .-% long fiber pulp.

5. release paper according to one of the preceding claims, the air permeability, measured according to the Gurley method defined in ISO 5636-5: 2013, is at least 40,000 s, preferably at least 60,000 s and particularly preferably at least 70,000 s.

6. release paper according to any one of the preceding claims, in which at least 70 wt .-%, preferably at least 85 wt .-% of the long fiber pulp is obtained from conifers.

7. release paper according to any one of the preceding claims, wherein said long fiber pulp is ground to a freeness of at least 50 ° SR, preferably at least 60 ° SR and / or at most 80 ° SR, preferably at most 70 ° SR.

8. release paper according to any one of the preceding claims, which contains at most 40 wt .-% short fiber pulp, preferably at most 30 wt .-% short fiber pulp.

9. release paper according to any one of the preceding claims, which contains at most 15 wt .-% fillers, preferably at most 10 wt .-% and particularly preferably less than 2 wt .-% fillers.

10. Release base paper according to one of the preceding claims, wherein the first coating comprises a coating material which consists of the group consisting of water-soluble film-forming polymers, in particular starch, starch derivatives, cellulose derivatives or latex; nanofibrillated cellulose; microfibrillated cellulose; nanocrystalline cellulose and mixtures thereof is selected; and the second coating comprises a water-soluble film-forming polymer, nanofibrillated cellulose, microfibrillated cellulose or nanocrystalline cellulose.

11. Release paper according to one of the preceding claims, in which the amount of the first coating is at least 0.1 g / m ² , preferably at least 0.4 g / m ² and / or at most 4.0 g / m ² , preferably at most 2, 5 g / m ² .

12. Release paper according to one of the preceding claims, in which the coating material in the first coating is formed by a starch or a starch derivative, preferably selected from the group consisting of potato starch, corn starch, tapioca starch, wheat starch, derivatives of these starches, and mixtures thereof.

13. Release paper according to one of the preceding claims, in which the amount of the second coating is at least 0.5 g / m ² , preferably at least 1.5 g / m ² and / or at most 5.0 g / m ² , preferably at most 3, Is 0 g / m ² .

14. Release paper according to one of the preceding claims, wherein the second coating comprises pigment particles, the pigment particles preferably having a platelet-like shape, and wherein the pigment particles are preferably selected from the group consisting of kaolin, talc, magnesium silicates, aluminum silicates, calcium carbonate and mixtures thereof ,

15. release paper according to any one of the preceding claims, wherein the film-forming polymer of the second coating from the group consisting of polyvinyl alcohol, Carboxymethyl cellulose, hydroxymethyl cellulose, starch, starch derivatives, latex and mixtures thereof are selected.

16. Release paper according to one of the preceding claims, in which the second coating comprises modified nanofibrillated cellulose, modified microfibrillated cellulose, modified nanocrystalline cellulose, modified polyvinyl alcohol or modified carboxymethyl cellulose, these coating materials being modified so that they have vinyl groups which react with the silicone can to promote the adhesion of the silicone on the release paper.

17. Release base paper according to one of the preceding claims, in which the Cobb Unger (120 s) value of the coated side is at least 0.01 g / m ² , preferably at least 0.10 g / m ² , particularly preferably at least 0.15 g / m ² and / or at most 0.90 g / m ² , preferably at most 0.70 g / m ² , particularly preferably at most 0.60 g / m ² and very particularly preferably at most 0.50 g / m ² .

18. Release paper according to one of the preceding claims, which has a transparency according to DIN 53147: 1993-01 of at least 55%, preferably at least 60% and / or at most 80%, preferably at most 75%.

19. Backing material for self-adhesive labels, comprising a release paper according to one of the preceding claims, which is siliconized on the side of the second coating.

20. Self-adhesive label, which is glued to a carrier material according to claim 19.

21. baking paper comprising a release base paper according to any one of claims 1 to 18, which is siliconized on the side of the second coating.

22. Use of a release base paper according to any one of claims 1 to 18 for wrapping a smokable material which is capable of producing an aerosol by combustion or heating.

23. A smoking article comprising a smokable material capable of producing an aerosol by combustion or heating, the smokable material being coated with a release liner paper according to any one of claims 1 to 18, which smokable material in the intended use of the smoking article is preferably heated, but not burned.

24. Use of a release paper according to one of claims 1 to 18 as packaging paper.

25. A method for producing a release paper, comprising the following steps:

Preparing a pulp-containing suspension comprising long-fiber pulp,

Applying the pulp-containing suspension to a sieve of a paper machine to produce a base paper,

Calendering the base paper to adjust the density of the base paper,

Coating the base paper with a first coating,

Drying the first coating,

Applying a second coating, which is an uppermost coating, either directly or indirectly with one or more further layers in between, to the first coating, the second coating being a water-soluble film-forming

Polymer, nanofibrillated cellulose, microfibrillated cellulose or nanocrystalline

Includes cellulose, and

Drying the second coating,

in which

the proportion of long-fiber pulp in the cellulose-containing suspension is selected such that the finished release base paper comprises at least 50% by weight of long-fiber cellulose, the amount of the cellulose-containing suspension which is applied to the sieve of the paper machine is selected such that the finished release base paper has a weight per unit area at least 25 g / m ² and at most 40 g / m ² , and the calendering step is carried out so that the finished release paper has a density of at least 0.90 g / cm ³ and at most 1.15 g / cm ³ ,

and wherein the first and the second coating are selected such that the Cobb Unger (120 s) value of the surface with said first and second coating in the finished release paper is at least 0.01 g / m ² and at most 0.90 g / m ² ,

26. The method according to claim 25, wherein the amount of pulp-containing suspension that is applied to the wire of the paper machine is selected so that the finished release paper has a basis weight of at least 30 g / m ² and / or at most 38 g / m ² .

27. The method according to claim 25 or 26, wherein the calendering step is carried out such that the density is at least 0.95 g / cm ³ , preferably at least 0.99 g / cm ³ and / or at most 1.10 g / cm ³ , preferably at most 1.07 g / cm ³ and particularly preferably at most 1.05 g / cm ³ .

28. The method according to any one of claims 25 to 27, in which the base paper is compressed in the calendering process between a plurality of pairs of rollers, each pair of rollers forming a nip through which the base paper is passed.

29. The method according to any one of claims 25 to 28, wherein the proportion of long fiber pulp in the pulp-containing suspension is selected so that the finished release paper comprises at least 60 wt .-%, preferably at least 70 wt .-% long fiber pulp.

30. The method according to any one of claims 25 to 29, wherein the finished release paper has an air permeability, measured by the Gurley method defined in ISO 5636-5: 2013, of at least 40,000 s, preferably at least 60,000 s and particularly preferably at least 70,000 s ,

31. The method according to any one of claims 25 to 30, wherein the step of producing the pulp-containing suspension includes a step in which the long fiber pulp to a freeness of at least 50 ° SR, preferably at least 60 ° SR and at most 80 ° SR, preferably at most 70 ° SR is ground.

32. The method according to any one of claims 25 to 31, wherein the first coating comprises a coating material which consists of the group consisting of water-soluble film-forming polymers, in particular starch, starch derivatives, cellulose derivatives or latex; nanofibrillated cellulose; microfibrillated cellulose; nanocrystalline cellulose and mixtures thereof is selected; and the second coating comprises a water-soluble film-forming polymer, nanofibrillated cellulose, microfibrillated cellulose or nanocrystalline cellulose.

33. The method of claim 32, wherein the first coating is applied using a first coating composition comprising water and said coating material, the amount of dried first coating composition remaining on the release base paper after drying, preferably at least 0.1 g / m ² , particularly preferably at least 0.4 g / m ² and / or preferably at most 4.0 g / m ² , particularly preferably at most 2.5 g / m ² .

34. The method according to any one of claims 32 or 33, wherein the coating material in the first coating is formed by a starch or a starch derivative, preferably selected from the group consisting of potato starch, corn starch, tapioca starch, wheat starch, derivatives of these starches, and mixtures thereof ,

35. The method according to any one of claims 25 to 34, wherein the second coating comprises a water-soluble, film-forming polymer, nanofibrillated cellulose, microfibrillated cellulose or nanocrystalline cellulose and is applied in the form of a second coating composition, the water and said film-forming polymer, the nanofibrillated cellulose , microfibrillated cellulose or nanocrystalline cellulose,

the water-soluble film-forming polymer, the nanofibrillated cellulose, microfibrillated cellulose or nanocrystalline cellulose preferably at least 5% by weight, particularly preferably at least 8% by weight and / or preferably at most 25% by weight and particularly preferably at most 15% by weight , based on the weight of the second coating composition, and / or

wherein the amount of the dried second coating composition which remains on the release base paper after drying, preferably at least 0.5 g / m ² , particularly preferably at least 1.5 g / m ² and / or preferably at most 5.0 g / m ² , is particularly preferably at most 3.0 g / m ² .

36. The method according to any one of claims 25 to 35, wherein the second coating composition comprises pigment particles, wherein the pigment particles preferably have a platelet-shaped shape, and wherein the pigment particles are preferably selected from the group consisting of kaolin, talc, magnesium silicates, aluminum silicates, calcium carbonate and Mixtures thereof, the pigment particles preferably making up at least 1% by weight, particularly preferably at least 10% by weight and / or preferably at most 30% by weight, particularly preferably at most 20% by weight, based on the weight of the second coating composition.

37. The method according to any one of claims 25 to 36, wherein the film-forming polymer of the second coating is selected from the group consisting of polyvinyl alcohol, carboxymethyl cellulose, hydroxymethyl cellulose, starch, starch derivatives, latex and mixtures thereof.

38. The method according to any one of claims 25 to 37, wherein the second coating composition comprises modified nanofibrillated cellulose, modified microfibrillated cellulose, modified nanocrystalline cellulose, modified polyvinyl alcohol or modified carboxymethyl cellulose, these coating materials being modified so that they have vinyl groups which are compatible with the Silicones can react to promote the adhesion of the silicone to the release paper.

39. The method according to any one of claims 25 to 38, wherein the finished release paper is a release paper according to any one of claims 1 to 18.

40. The method according to any one of claims 25 to 39, in which the paper machine is a Fourdrinier paper machine, and / or in which a calendering device is integrated in the paper machine, so that the calendering can be carried out during the production of the base paper and / or in which the first and / or the second coating composition is applied in a size press, in a film press, by knife coating or a curtain coating process.