EP3298198B1 - Wrapping paper having transparent regions - Google Patents

Description

FIELD OF THE INVENTION

The invention relates to a wrapping paper for smoking articles. More particularly, it relates to a wrapping paper for smoking articles which has portions of higher transparency and portions of lesser transparency, and a method for producing such a wrapping paper. Furthermore, it relates to a smoking article comprising such a wrapping paper.

BACKGROUND AND PRIOR ART

A typical cigarette consists of a tobacco rod wrapped in a cigarette paper. In many cases, cigarettes are also equipped with a filter, typically cellulose acetate, wrapped in a filter wrap paper and externally wrapped by a tipping paper that is slightly longer than the filter and thus joins the filter to the tobacco rod wrapped by the cigarette paper. Such cigarettes are usually consumed by burning the tobacco and inhaling the resulting smoke from the smoker through the filter.

Alternative smoking articles do not burn the tobacco, but only heat it, releasing an aerosol that is inhaled by the smoker. It is believed that the aerosol of such smoking articles contains less harmful substances than the smoke of conventional cigarettes. Instead of tobacco, other aerosol generating materials can be used. Depending on the design of these smoking articles, such wrappers may also require a wrapping paper which wraps around the tobacco or aerosol generating material or other parts of the smoking article.

In the design of the wrapping paper for smoking articles in addition to the technical requirements and the optical properties of the wrapping paper play a major role. Since the advertising of smoking articles, especially for cigarettes, is limited or largely prohibited in many countries, one way out is to differentiate the smoking article in the perception of the consumer by the design of the smoking article itself. The wrapping paper of a smoking article is an important tool because it forms the majority of the outer surface of the smoking article in conventional smoking articles. Typisehe Characteristics of the wrapping paper that may differentiate the smoking article are whiteness, transparency or opacity, gloss, watermarks, Vergélinien or applied to the wrapping paper, for example, printed patterns such as logos or logos. Likewise, the ash image after consumption of the smoking article may play a role.

An essential feature of the wrapping paper for differentiating a smoking article is its transparency, ie the ability to show light through. Increased transparency means more light falls through the wrapping paper. On smoking articles, the areas of higher transparency on the wrapping paper typically appear darker as the tobacco or aerosol producing material under the wrapping paper shows through.

A typical wrapping paper for smoking articles comprises pulp fibers, for example wood pulp or flax pulp, and one or more fillers, for example calcium carbonate. Envelope papers without fillers are comparatively transparent, while with increasing filler content the transparency decreases. Also by the choice of the filler, the transparency can be influenced. Titanium dioxide, in particular, can greatly reduce transparency as a filler. In conventional production processes for wrapping papers for smoking articles, the transparency of the wrapping paper can be influenced only by the composition of the wrapping paper as a whole, but not in some areas.

For a differentiation of a smoking article, however, it is desirable if the wrapping paper has portions of higher and lower transparency. For this purpose, various methods are available in the prior art, which, however, have disadvantages.

A known from the prior art method is to compress the wrapping paper in partial areas. Due to the smaller thickness and denser paper structure, the wrapping paper becomes more transparent in the compressed portions. In this way, for example, watermarks or the so-called limescale can be produced. Vergé lines are narrow lines along which the wrapping paper is compressed, allowing the smoking article to form darker circumferential or longitudinal lines. Using the same method that is used for the production of Vergélinien, in addition to lines, any pattern can be generated in the wrapping paper.

While the production of watermarks or limescale typically occurs in the production of the wrapping paper on the paper machine, as an alternative method the wrapping paper can be embossed on the paper machine even after manufacture. Again, the wrapping paper is compressed and the optical appearance and the influence on other properties of the wrapping paper, the method is similar to the production of watermarks or Vergélinien.

A technical disadvantage of both methods is that the air permeability of the wrapping paper is considerably reduced by the compression. The air permeability of the wrapping paper allows the ingress of air from the outside through the wrapping paper into the smoking article. As a result, the smoke or aerosol is diluted and the content of potentially harmful substances in the smoke or aerosol decreases. A reduction of the air permeability of the wrapping paper in the compressed areas is therefore generally disadvantageous.

Another disadvantage of the known methods is that compressing reduces the thickness of the wrapping paper in partial areas. The surface of the wrapping paper is therefore rougher and affects the haptic qualities of the wrapping paper.

Finally, the known method has the further technical disadvantage that the tensile strength of the wrapping paper is reduced in the compressed portions. In particular, when the compressed portions extend transversely of the wrapping paper, they create weaknesses in the machine direction that can lead to tearing of the wrapping paper during further processing.

Another method may be to use a full-coverage translucent wrapping paper as a starting point and to print it in sub-areas so that it is less translucent in these areas. For this purpose, however, the order of compositions in these sub-areas is necessary, which contain at least one pigment or a dye and at least one binder.

Dyes are not legally permitted for use on wrapping papers for smoking articles in many cases, so generally only pigments can be used. In both cases, however, a binder is required, which must be applied in a relatively large amount to the wrapping paper in order to fix the pigments or dyes on the wrapping paper. But this binder closes the pore structure of the wrapping paper and thus reduces the air permeability even more than beispielsweisc when embossing the case would be. Thus, the content of carbon monoxide and other pollutants in the smoke increases, which is undesirable.

Thus, there is a need to have a wrapping paper which has increased transparency in some areas but does not change significantly in other properties such as air permeability, thickness and tensile strength.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a wrapping paper for smoking articles which has subregions of higher and lower transparency and whose air permeability, thickness and tensile strength in the subregions of higher and lower transparency are not substantially different from each other or in relation to use on a smoking article at least not worsen appreciably. Although the subregions of increased transparency per se serve to achieve a particular visual appearance, their production represents a technical task that can be solved by technical means and also has the purpose - unlike the prior art - not other technical properties of the wrapping paper or not decisively negative influence.

This object is achieved by a wrapping paper according to claim 1, and by a method for producing such a wrapping paper according to claim 10 and a smoking article comprising this wrapping paper according to claim 15. Advantageous developments are specified in the dependent claims.

The inventors have found that the object can be achieved by a wrapping paper for smoking articles containing pulp fibers and at least one acid-soluble filler, wherein the content of acid-soluble filler is at least 10 wt .-% based on the mass of the wrapping paper as a whole, and wherein the area-related mass fraction of this acid-soluble filler within subregions of the wrapping paper is at least 10% lower than in other subregions of the wrapping paper. This means, for example, that if the amount of acid-soluble filler in subregions is 5 g / m ² , it is at most 4.5 g / m ² in other subregions.

In the case of the wrapping paper according to the invention, the subregions with the filler content which is at least 10% lower form subregions of higher transparency, and the other regions form subregions of lesser transparency. If the areas are sufficiently large that the transparency can be measured reliably according to DIN 53147: 1993-01, then the transparency be at least 20% higher in the subregions of higher transparency than the transparency measured in accordance with DIN 53147: 1993-01 in the subregions of lesser transparency. However, depending on the desired transparency pattern, it may be that the regions of higher transparency and / or the regions of lower transparency are so small or so shaped that they can not be measured with sufficient accuracy according to DIN 53147: 1993-01. In this case, the transparency in the subregions of higher transparency should be so much higher than in the subregions of lesser transparency that, in the event that the wrapping paper is wrapped around a typical tobacco rod, a pattern of lighter and darker portions perceptible to the naked eye is obtained leaves, the darker sections corresponding to the subregions of higher transparency and the lighter sections to the subregions of lesser transparency. A tobacco rod filled with an American Blend tobacco mixture, a diameter between 7 mm and 8 mm and an average filling density between 0.1 g / cm ³ and 0.3 g / cm ³ applies as the assessment of the differences in transparency typical tobacco rod. Since the purpose of the invention is to produce transparent patterns visible to the naked eye, similar to those obtained by embossing in the prior art, this second criterion is a suitable criterion for characterizing the wrapping paper according to the invention in terms of transparency.

The inventors have found that, by treating a wrapping paper of initially homogeneous composition, the acid-soluble filler content in portions of the wrapping paper can be reduced by applying an acid-containing composition to these portions. This composition dissolves the filler in some areas and thus reduces the filler content in these areas and can lead to an increase in transparency. However, in preferred embodiments, there are still further quite positive effects on the wrapping paper, in particular with regard to the tensile strength, the cause of which the inventors could hitherto not identify.

It will be appreciated by those skilled in the art that a reduced filler content may result in greater transparency, but only with respect to the wrapping paper as a whole, ie, over its entire area. The inventors are unaware of any attempts to vary the transparency locally over the filler content to produce visible transparency patterns, let alone appropriate methods by which this could be accomplished efficiently. In addition, the inventors have found that the filler content can be reduced by treatment with an acid in some areas, but this does not always increase the transparency occurs. As explained below, they have surprisingly found that only with specifically selected acids and appropriately selected pH in fact, the reduced filler content is accompanied by a significant increase in transparency. In particular, the effect could not be achieved with the acids immediately obvious to the person skilled in the art.

However, concrete embodiments are shown below in which the desired effect is effectively achieved. Based on this doctrine and the evidence provided here that the effect according to the invention can be achieved with properly selected acids and properly selected pH value, one skilled in the art will be able to systematically try out further embodiments, in particular further acids and pH values determine which are not mentioned in the present disclosure.

Preferably, the portions of higher transparency form a scheduled, i. not random pattern. This pattern may be regularly arranged geometric figures, in particular lines or stripes, logos, watermarks or logos.

Although the starting point of the present invention is to selectively form transparency patterns of higher and lower transparency portions on the wrapping paper, it is found that the treatment proposed for this purpose not only does not deteriorate the properties of the wrapping paper but in some cases can also improve it in terms of tensile strength. In this respect, in some embodiments, the invention also provides to treat the wrapping paper over the entire surface in order to increase its overall transparency and / or to increase the tensile strength.

The pulp fibers mentioned are preferably wood pulp fibers, particularly preferably pulp fibers of long-fiber pulp or short-fiber pulp and mixtures thereof. Preferably, the pulp fibers are partially or wholly formed from pulp fibers of other plants such as flax, hemp, sisal, jute, abacá, cotton, esparto grass or mixtures thereof. In principle, there are no restrictions on the selection of the pulp fibers for the wrapping paper according to the invention, so that the wrapping paper may, for example, also contain pulp fibers of regenerated cellulose such as lyocell fibers, viscose fibers or modal fibers. Of course, legal requirements concerning the ingredients of a wrapping paper for smoking articles must be observed.

The wrapping paper preferably contains at least 50% by weight, more preferably at least 60% by weight, most preferably at least 70% by weight of pulp fibers and preferably at most 90% by weight, particularly preferably at most 80% by weight of pulp fibers. The percentages are based on the total mass of the wrapping paper.

Said acid-soluble filler is preferably an acid-soluble carbonate or bicarbonate, in particular a calcium carbonate, a calcium hydrogencarbonate, a magnesium carbonate or a mixture thereof. Less preferred but useful are lower solubility fillers in acids such as magnesium oxide, magnesium hydroxide or aluminum hydroxide. While titanium dioxide provides high opacity and whiteness of the coating material, it is unsuitable as an acid-soluble filler for the present invention as well as talc and kaolin. Some fillers, such as titanium dioxide, can also give the ashes of the wrapping paper a particular color, and are therefore mostly undesirable.

The effect of the acid on the acid-soluble filler is above all of a chemical nature, so that there are no particular restrictions on the particle size, particle shape and crystal structure of the acid-soluble filler. The mean particle size of the acid-soluble filler may preferably be at least 0.01 .mu.m, more preferably at least 0.1 .mu.m and most preferably at least 0.5 .mu.m and / or preferably at most 10 .mu.m, more preferably at most 5 .mu.m and most preferably at most 3 μm.

The wrapping paper contains, as described above, at least 10% by weight, but preferably at least 15% by weight, more preferably at least 20% by weight and most preferably at least 25% by weight of the acid-soluble filler and preferably at most 50% by weight .-%, more preferably at most 40 wt .-% and most preferably at most 35 wt .-% of the acid-soluble filler. The percentages are based on the total weight of the wrapping paper, with no difference being made in the determination of the filler content between reduced and non-reduced acid soluble filler portions.

The difference in transparency increases as the difference in the content of acid-soluble filler in the respective subregions increases. In the subregions of higher transparency of the wrapping paper, the content of acid-soluble filler is therefore reduced by at least 10% compared to the content in subregions of lesser transparency, as described above. However, it is preferably reduced by at least 15%, more preferably by at least 20% and most preferably by at least 25%. The percentages refer to the filler content as basis weight within the respective subregions. Thus, if the filler content in a subarea of lower transparency is 8 g / m ² and within a subarea of higher transparency 6 g / m ² , then it is a reduction of 25%.

It is possible, but difficult to achieve by the method proposed below, that no acid-soluble filler is contained within the subregions of higher transparency. The content of acid-soluble filler in the subregions of higher transparency is therefore reduced by at most 100%, preferably at most 80%, particularly preferably at most 60% and very particularly preferably at most 50%, compared to the content in the subregions of lower transparency. These percentages also refer to the filler content as area-related mass within the respective subregions.

The proportion of the area of the subregions of higher transparency, that is with a reduced content of acid-soluble filler, on the total area of the wrapping paper can vary. In order to achieve a particularly readily perceivable optical effect, the proportion should preferably be at least 1%, particularly preferably at least 3% and very particularly preferably at least 5%. Likewise, the proportion should preferably be at most 99%, more preferably at most 97%, and most preferably at most 95%.

In a most preferred embodiment, the proportion of the area of the reduced-acid-content filler portions in the total area of the wrapping paper is at least 10% and at most 70%.

In addition to the at least one acid-soluble filler, the wrapping paper may also contain other non-acid soluble fillers. These fillers are preferably oxides, hydroxides or silicates, particularly preferably titanium dioxide, talc, kaolin or mixtures thereof.

The total content of the fillers, ie the acid-soluble and the non-acid-soluble fillers is at least 10 wt .-% and preferably at least 15 wt .-%, more preferably at least 20 wt .-% and most preferably at least 25 wt .-% of the mass of Enveloping paper and preferably at most 50 wt .-%, more preferably at most 40 wt .-% and most preferably at most 35 wt .-% of the mass of the wrapping paper. It is always assumed that the content of acid-soluble filler is at least 10% by weight of the mass of the wrapping paper.

The transparency of the wrapping paper, measured according to DIN 53147: 1993-01, is increased within the sub-ranges with reduced content of acid-soluble filler. As described above, in certain sub-areas, namely the "subregions of higher transparency", it is at least 20% higher than the transparency in other sub-areas ("subregions of lower transparency"). The increase in transparency is preferably at least 25%, more preferably at least 30% and most preferably at least 50%, and preferably at most 300%, more preferably at most 200%, and most preferably at most 100%. The percentages are to be understood relative to the value of transparency within the subregions of lesser transparency. If, for example, the transparency is 30% in a subarea of lesser transparency, a transparency of 45% within the subregions of higher transparency represents an increase of 50%.

The transparency of the subregions can be increased by the partial or total removal of the acid-soluble filler in these subregions, but at least the pulp flutes still remain in these subregions, so that the transparency can not be increased arbitrarily in absolute terms.

The transparency of the wrapping paper within the reduced acid content filler portions, i. in subregions of "higher transparency", measured according to DIN 53147: 1993-01, is therefore preferably at least 20%, particularly preferably at least 40%, very particularly preferably at least 50% and preferably at most 90%, particularly preferably at most 70% and very particularly preferably maximum 60%.

The transparency of the cover paper outside these subareas should be rather low. In the subregions of lesser transparency, it is therefore, measured according to DIN 53147: 1993-01, preferably at most 70%, particularly preferably at most 60%, very particularly preferably at most 50% and preferably at least 0%, particularly preferably at least 10%.

With regard to the transparency within the respective subregions, of course, the above-mentioned relative relationships to one another must be taken into account, in particular that the transparency within the subregions of higher transparency is actually higher than in the subregions of lesser transparency.

For use on smoking articles, the basis weight of the wrapping paper is preferably at least 10 g / m ² , more preferably at least 20 g / m ² and preferably at most 100 g / m ² , more preferably at most 60 g / m ² and most preferably at most 45 g / m ² .

An important property of the wrapping paper for further processing into a smoking article is its tensile strength, which can be measured according to ISO 1924-2: 2008. A particular advantage of the invention results from the fact that the tensile strength of the wrapping paper is higher than in the case of wrapping papers known from the prior art For example, the transparency was changed by compression of partial areas. In particular, it can be seen that the tensile strength can even be increased by the method described below over a wrapping paper with homogeneous filler distribution. The tensile strength of a wrapping paper is strongly influenced by its basis weight. In particular, it is approximately proportional to the basis weight, so that the tensile strength according to ISO 1924-2: 2008, in N / 15mm, can be related to the basis weight measured in accordance with ISO 536: 2012 in g / m ² and thus to a mass-related tensile strength in N · M ² / (15 mm · g) passes.

The mass-related tensile strength, calculated as the quotient of the tensile strength according to ISO 1924-2: 2008 and the basis weight according to ISO 536: 2012, is preferably at least 0.3 N · m ² / (15 mm × g), particularly preferably at least 0.4 N. · M ² / (15 mm · g), very particularly preferably at least 0.5 N · m ² / (15 mm · g) and preferably at most 1.6 N · m ² / (15 mm · g), particularly preferably at most 1.4 N · m ² / (15 mm · g), and most preferably at most 1.2 N · m ² / (15 mm · g).

The thickness of the wrapping paper is important for use on smoking articles. On the one hand, it plays a role in further processability, for example with regard to the ability to absorb adhesives; on the other hand, the thickness of the wrapping paper on the smoking article should be uniform in order to give a homogeneous visual and haptic impression.

The thickness of the wrapping paper, measured according to ISO 534: 2011 on a single layer, is therefore preferably at least 15 μm, particularly preferably at least 20 μm and preferably at most 100 μm and particularly preferably at most 80 μm.

More important than the absolute thickness is that the thickness in the subregions of higher transparency does not differ significantly from the thickness in subregions of lesser transparency. This represents a significant advantage of the wrapping paper according to the invention in comparison to wrapping papers, which are compressed to increase the transparency in partial areas or printed to reduce the transparency in partial areas.

The quotient of the thickness within the subregions of higher transparency and the thickness within the subregions of lower transparency is preferably at least 0.5, particularly preferably at least 0.7, very particularly preferably at least 0.8 and preferably at most 1.8, particularly preferably at most 1 , 6, most preferably at most 1.5.

Both thicknesses can be measured according to ISO 534: 2011 on a single layer. Since the measuring surface of the thickness measurement according to ISO 534: 2011 can be larger than the subregions with higher or lower transparency, alternatively, the measurement can be carried out on an otherwise similar wrapping paper having sufficiently large subregions. Alternatively, to determine the thickness and in particular the quotient of the two thicknesses, it is also possible to use microscopic analyzes of the cross-section of the wrapping paper, for example using a scanning electron microscope.

Another significant feature of the wrapping paper is its air permeability. The air permeability allows air flow through the wrapping paper as a function of the pressure difference between the sides of the wrapping paper. On smoking articles, particularly cigarettes, the smoker creates a pressure differential between the interior of the smoking article and the environment, allowing air to flow through the wrapping paper into the smoking article and thereby dilute the smoke or aerosol present in the smoking article. Thus, the amount of harmful substances in the smoke or aerosol can be reduced.

The air permeability of the wrapping paper, measured according to ISO 2965: 2009, is preferably at least 5 cm ³ / (cm ² · min · kPa), more preferably at least 20 cm ³ / (cm ² · min · kPa) and preferably at most 300 cm ³ / (cm ² · min · kPa), more preferably at most 200 cm ³ / (cm ² · min · kPa), most preferably at most 150 cm ³ / (cm ² · min · kPa).

A particular advantage of the invention over wrapping papers in which the transparency in portions is increased by compression is that the difference in air permeability between the portions where the acid-soluble filler content is reduced and the remaining portions of the wrapping paper is small ,

The quotient of the air permeability in the subregions of higher transparency and the air permeability in the subregions of lower transparency is preferably at least 0.4, particularly preferably at least 0.5, very particularly preferably at least 0.6 and preferably at most 1.6, particularly preferably at most 1 , 4, most preferably at most 1.2.

In comparison, this quotient is typically less than 0.1 or more than 10 for a paper in which the transparency was partially increased by compression or partially reduced by printing.

The air permeabilities of the sections and the wrapping paper can be determined according to ISO 2965: 2009. However, this standard only allows a minimum measuring area of 2 × 15 mm, so that in many practical cases the measuring surface covers both subareas higher and those with lower transparency. For the measurement of the air permeability of the wrapping paper as a whole, this fact should be ignored. For the measurement of the air permeability in the respective partial regions, the measurement can be carried out in the partial regions of an otherwise similar wrapping paper, on which sufficiently large partial regions are provided. Alternatively, the air permeability of the partial regions can also be calculated from at least two measurements of the air permeability, in which the proportion of the regions of higher transparency at the measuring surface is known in each case and differs significantly from measurement to measurement. The basic assumption here is that the total air flow flowing through the measuring surface during the measurement is the sum of the air flow through the subregions with higher transparency and the air flow through the subregions of lower transparency.

In addition to the air permeability and the diffusion capacity of the wrapping paper is important. The diffusion capacity can be determined according to CORESTA Recommended Method No. 77 (April 2014) and describes the gas transport through the wrapping paper according to a concentration difference between the two sides of the wrapping paper. The diffusion capacity of the wrapping paper is important to smoking articles because in the phases during which the smoker does not draw on the smoking article, that is, there is no pressure differential between the interior of the smoking article and the environment, gases, particularly carbon monoxide and carbon dioxide, can diffuse through the wrapping paper and thus reduce the content of these gases in the smoke or aerosol.

The diffusion capacity of the wrapping paper measured according to CORESTA Recommended Method No. 77 (April 2014) is preferably at least 0.05 cm / s, more preferably at least 0.1 cm / s and preferably at most 5 cm / s, more preferably at most 3.5 cm / s. Again, for the measurement of the diffusion capacity, the fact can be ignored that the measuring surface typically covers at the same time portions with higher and lower transparency.

The diffusion capacity of the subregions of higher transparency can, if the size is sufficient, also be determined according to CORESTA Recommended Method no. 77 (April 2014). Alternatively, an otherwise similar wrapping paper, in which these portions are made sufficiently large, can be used for the measurement. Likewise, as a further alternative, as explained above in the measurement of the air permeability, the diffusion capacity of the subregions with higher and lower transparency can be calculated from at least two measurements, if it is known for each measurement which proportion of the measuring surface is attributable to the respective subregions.

The diffusion capacity of the reduced acid content filler portions, i. the subregions of higher transparency is preferably at least 0.01 cm / s, more preferably at least 0.02 cm / s, very particularly preferably at least 0.05 cm / s and preferably at most 3 cm / s, particularly preferably at most 2.5 cm / s, most preferably at most 2 cm / s.

In a preferred embodiment of the wrapping paper according to the invention, the subareas are designed in terms of their geometry and their diffusion capacity so that a smoking article made therefrom, in particular a cigarette, has self-extinguishing properties. This may mean that, tested according to ISO 19-863: 2010, preferably at least 30%, more preferably at least 50%, and most preferably at least 75% of the smoking articles of a sample of, for example, 40 smoking articles are self-extinguished.

In this preferred embodiment, the partial areas may preferably be designed as bands in the transverse direction of the wrapping paper, so that at least one band, more preferably at least two bands, are located in the circumferential direction on the smoking article made therefrom. The width of such a band in the longitudinal direction of the smoking article is preferably at least 4 mm, particularly preferably at least 5 mm and preferably at most 10 mm, particularly preferably at most 8 mm.

In this preferred embodiment, the portions where the acid-soluble filler content is reduced, i. the subregions of higher transparency, a diffusion capacity measured according to CORESTA Recommended Method No. 77 (April 2014) of preferably at least 0.01 cm / s, more preferably at least 0.02 cm / s, very particularly preferably at least 0.05 cm / s and preferably at most 0.5 cm / s, particularly preferably at most 0, 3 cm / s, most preferably at most 0.2 cm / s.

The wrapping paper may, of course, be provided with further functions and features known in the art, as long as they are compatible with the desired effect, namely, portions of high and low transparency on the wrapping paper.

The wrapping paper according to the invention can be prepared by the following process according to the invention.

In a first step, a preliminary wrapping paper is provided which contains pulp fibers and at least one acid soluble filler wherein the content of acid soluble filler is at least 10% by weight based on the weight of the preliminary wrapping paper.

With regard to the pulp fibers, the at least one acid-soluble filler and other fillers or additives contained in the preliminary wrapping paper, the same information as to the type and amount as disclosed above with respect to the finished wrapping paper shall apply.

Preferably, the content of acid-soluble filler and the transparency of this preliminary wrapping paper over its entire surface are homogeneous, as far as the usual manufacturing tolerances allow. Such a temporary wrapping paper can be produced by methods known in the art for papermaking.

A composition comprising at least one acid and water, which acid is a trivalent acid, preferably a trivalent organic acid and most preferably citric acid, and the pH of the composition is at least 0 and less than 2, is applied to this preliminary wrapping paper , preferably about 1.

After application of the composition, the wrapping paper is dried.

The composition may contain other acids, but monovalent or dibasic acids have proven less useful in the practice of the invention so that the proportion of non-trivalent acids in the composition should be low. Preferably, the molar ratio between the total amount of trivalent acids and the total amount of acids should be greater than 0.7, more preferably greater than 0.8, and most preferably greater than 0.9.

The composition may comprise further components which improve the processability of the composition, that is, for example, influence its viscosity or act as a binder. Therefore, the composition preferably also contains at least one binder selected from a group consisting of starch, starch derivatives, modified Starch, cellulose derivatives or a mixture thereof, more preferably modified starch and most preferably maltodextrin.

The content of these further components in the composition is preferably at least 0.1% by weight, particularly preferably at least 0.5% by weight, very particularly preferably at least 2% by weight of the composition and preferably at most 30% by weight, more preferably at most 20% by weight, most preferably at most 10% by weight of the composition.

The order of the composition can take place over the whole area or in subregions of the wrapping paper. If it takes place only in some areas, the proportion of the area of the areas to which the composition has been applied to the total area of the wrapping paper is preferably at least 1%, more preferably at least 3% and most preferably at least 5%. Likewise, the proportion may preferably be at most 99%, more preferably at most 97%, and most preferably at most 95%.

In a most preferred embodiment, the proportion of the area to which the composition has been applied to the total area of the wrapping paper is at least 10% and at most 70%.

The shape of the subregions may represent, for example, lines, patterns, logos or text and is limited only by the possibilities of the order process.

The application of the composition may preferably be effected by a printing process, more preferably by gravure printing, flexographic printing or offset printing or by spraying.

The amount of composition applied, relative to the area to which the composition is applied, is preferably at least 0.5% by weight, more preferably at least 5.0% by weight, of the basis weight of the finished wrapping paper and preferably at most 50% by weight. %, more preferably at most 30 wt .-% of the basis weight of the finished wrapping paper.

After drying, the wrapping paper may preferably be moistened by substantially full area application of water or water vapor to one or both sides of the wrapping paper to reduce or eliminate stress or wrinkles created by application of the composition.

Following this optional step, the wrapping paper can be dried to the equilibrium moisture content of about 3-7% by weight based on the weight of the finished wrapping paper. Thereafter, the wrapping paper may be rolled up or further processing steps may be performed.

A possible such further processing step is the cutting into narrow rolls, so-called bobbins, the width of which is typically oriented around the circumference or an integral multiple of the circumference of the smoking article to be produced therefrom.

Of course, further known from the prior art processing steps can be carried out with the wrapping paper, provided that they are compatible with the desired effect, namely to produce a change in the transparency on the wrapping paper.

From the wrapping paper, a smoking article may be prepared by methods known in the art. Preferably, such a smoking article containing the wrapping paper of the invention will be a cigarette, most preferably a filter cigarette.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention will be explained in more detail below using the example of a preferred embodiment.

First, a temporary wrapping paper for smoking articles having a basis weight of about 25 g / m ² and a filler content of about 30% by weight, ie 7.5 g / m ² , was prepared. As the sole and at the same time acid-soluble filler, a precipitated calcium carbonate was used. The pulp fibers in the preliminary wrapping paper were a mixture of long fibers and short fibers. The nominal air permeability (Z) according to ISO 2965: 2009 of the preliminary wrapping paper was 60 cm ³ / (cm ² · min · kPa), the diffusion capacity (D *) according to CORESTA Recommended Method no. 77 (April 2014) was about 1.4 cm / s. The data on thickness and tensile strength, both absolute and by weight, can be taken from Table 1, in which the data of the preliminary wrapping paper are given as paper 1.

This provisional wrapping paper was printed by means of a laboratory printing device "Printing Proofer 628" from RK Print - Coat Instruments Ltd. various compositions applied.

The compositions are given in the lines to papers 2-19 of Table 1. All compositions contained water. In the composition for paper 2, only 10% by weight of maltodextrin was added to the water in order to be able to observe the effect of the maltodextrin in isolation. For the papers 3-6, hydrochloric acid, ie a monovalent inorganic acid, was used in addition to the maltodextrin, so that the composition had a pH of 4 (paper 3) to 1 (paper 6). For papers 7-10, maltodextrin (10% by weight) and acetic acid, a monovalent organic acid, were used in the composition, also with a pH range of the composition of 4 (paper 7) to about 1 (paper 10). For papers 11-14, maltodextrin (10% by weight) and oxalic acid, a dibasic organic acid, were used in the composition, with a pH range of the composition of 4 (paper 11) to 1 (paper 15). Finally, for the papers 15-19, citric acid, a trivalent organic acid, was used having a pH of the composition of 4 (paper 15) to 1 (papers 18 and 19). 10% by weight maltodextrin was again used in the composition for papers 15-18, but for paper 19 the composition without maltodextrin was prepared in order to observe the effect of the acid alone.

As will be seen below, however, only the compositions for papers 18 and 19 give the desired result and thus wrapping papers according to the invention. Papers 3-17 not according to the invention show that, contrary to the expectations of the person skilled in the art, the desired effect can only be achieved with the trivalent acid at a correspondingly low pH.

After coating the compositions on the temporary wrapping paper, the wrapping paper was dried and tested for proper properties according to ISO 187 at 23 ° C and 50% relative humidity after appropriate conditioning. The areas in which the composition was applied were sufficiently large so that the measured values for the papers 2-19 in terms of basis weight, thickness and tensile strength (absolute and weight-related) in Table 1 relate to areas in which the composition was applied over the entire area , Also for papers 2-19, air permeability (Z), diffusion capacity (D *), filler content and transparency as shown in Table 2 were each determined on samples of the wrapping paper on which the composition was applied over the entire surface.

Of the composition applied, most of the maltodextrin and also some of the reaction products of the acid with the acid-soluble filler remain on the wrapping paper, thus increasing the basis weight. This is off Table 1 shows that, for papers 2-19, the basis weight was increased from the original 25.54 g / m ² for provisional wrapping paper 1 to at least 27.14 g / m ² (paper 6) and up to 31.97 g / m ² (paper 18) shows.

The increase in the basis weight explains that the thickness of the papers 2-19 is also slightly higher than the thickness of the preliminary wrapping paper 1. According to Table 1, the thickness of the preliminary wrapping paper is 41 μm, while that of the papers 2-19 is between 42.80 μm (Paper 16) and 48.11 microns (paper 7) fluctuates.

In comparison, the thickness of a paper in which partial areas were compressed would be considerably lower in these partial areas.

Also, the absolute value of tensile strength, Table 1, for papers 2-17 is slightly increased over preliminary wrapping paper 1. This small increase in tensile strength is largely due to the order of maltodextrin. However, for papers 18 and 19, where a trivalent acid was applied in a composition having a pH of less than 2, a significant increase in tensile strength of 15.71 N / 15 mm for preliminary wrapping paper 1 to 26 is seen, 45 N / 15 mm for paper 18 and 26.03 N / 15 mm for paper 19. This increase in tensile strength is positive for the processability of the wrapping paper to a smoking article and thus represents an advantage of the wrapping papers according to the invention.

Also in the weight-related tensile strength, Table 1, there is only a slight increase over the provisional wrapping paper 1 for Papers 2-17, whereas for papers treated with trivalent 1-pH organic acid 18 and 19, there is a marked increase the weight-related tensile strength of 0.615 N · m ² / (1.5 mm · g) in preliminary wrapping paper 1 to 0.827 N · m ² / (15 mm · g) for paper 18 and 0.839 N · m ² / (15 mm · g ) comes with paper 19. This shows that there is an increase in the tensile strength, which goes beyond the effect of the increase in basis weight in the wrapping papers 18 and 19 according to the invention. Table 1 Applied composition tensile strenght paper maltodextrin acid PH value grammage thickness absolutely N / 15 mm by weight Nm ² / (15 mm.g) No. Wt .-% g / m ² mm 1 none 25.54 41,0 0 15.71 0.615 2 10 none 6.74 27.60 43.2 0 17.95 0,650 3 10 hydrochloric acid 4 27.92 44.11 18.33 0.656 4 10 hydrochloric acid 3 29.39 46.0 0 19.18 0.653 5 10 hydrochloric acid 2 28.26 45.17 18,32 0.648 6 10 hydrochloric acid 1 27.14 44.4 4 16.89 0.622 7 10 acetic acid 4 27.88 48.11 18.33 0.657 8th 10 acetic acid 3 27.58 45.6 7 17.35 0.629 9 10 acetic acid 2 28.54 46.11 19.07 0.668 10 10 acetic acid 1.28 27.86 44.7 8 17.56 0,630 11 10 oxalic acid 4 27.74 44.7 8 17.63 0.636 12 10 oxalic acid 3 28,88 44.7 8 18.63 0,645 13 10 oxalic acid 2 27.89 44.5 6 18.27 0,655 14 10 oxalic acid 1 28,90 44.6 7 19.17 0.663 15 10 citric acid 4 28.54 44.2 0 18.05 0.632 16 10 citric acid 3 27,90 42.8 0 18.15 0,650 17 10 citric acid 2 28.13 44.2 0 19.34 0.688 18 10 citric acid 1 31.97 47.4 0 26.45 0.827 19 0 citric acid 1 31.04 47.4 0 26.03 0.839

The air permeability (Z) was measured according to ISO 2965: 2009 and is given in Table 2 for all wrapping papers. The measurement for the papers treated with a composition 2-19 was carried out in an area in which the composition was applied over the entire surface. As can be seen from Table 2, taking the air permeability of about 60 cm ³ / (cm ² · min · kPa) at the preliminary wrapping paper 1 to about 50 cm ³ / (cm ² · min · kPa) at paper 2 from, the a composition with 10 wt .-% maltodextrin but without acid was applied. The effect of acid on air permeability is generally low, as can be seen in papers 3-19 in Table 2 is always less than 10 cm ³ / (cm ² · min · kPa) except for papers 14 and 18. The air permeability of the wrapping paper as a whole is then also determined by the proportion of the portions of the total area in which the composition was applied.

The diffusion capacity (D *), measured according to CORESTA Recommended Method No. 77 (April 2014), behaves similar to the air permeability (Z). Table 2 shows that there is a decrease of 1.42 cm / s (Preliminary Covering Paper 1) to 1.01 cm / s (Paper 2) when a composition containing only maltodextrin is applied. In papers 3-17, where the composition also contains an acid, there is no further decrease in diffusion capacity to a comparable extent. By contrast, in the case of the wrapping papers 18 and 19 according to the invention, the decrease in the diffusion capacity is once again markedly greater. According to Table 2, paper 18 has a diffusion capacity of 0.24 cm / s and paper 19 has a diffusion capacity of 0.35 cm / s. Such a significant decrease in diffusion capacity can cause a cigarette to quit itself with a wrapping paper 18 or 19 according to the present invention if the portions in which the composition is applied are designed to match their geometry. In particular, at least one at least 6 mm wide band, which runs on the cigarette in the circumferential direction, for the self-extinction of the cigarette already be sufficient.

In Table 2, in the two columns titled "Filler Content", the filler content ("Value") of the wrapping papers 1-19 and the change ("Change") relative to the preliminary wrapping paper 1 are indicated in percent. Similarly, in Table 2, in the two columns titled "Transparency", the transparency ("Value") of the wrapping papers 1-19, and the change ("Change") relative to the preliminary wrapping paper 1 are indicated in percent. The values for the wrapping papers 2-19, to which the respective composition was applied, refer to a wrapping paper to which the composition has been applied over the entire surface.

The content of calcium carbonate in the wrapping papers 1-19 was determined by titration, the transparency was measured according to DIN 53147: 1993-01.

The object of the invention is to produce a higher transparency in subregions of the wrapping paper. The inventive method achieves this by applying a composition with an acid in these subregions. The acid dissolves part of the acid-soluble filler. The fact that a reduced filler content leads to a higher transparency possibly corresponds to the expectation of the person skilled in the art, however, the situation is more complex than the person skilled in the art would suspect. For it can be seen in papers 2-17 that even a decrease in the filler content of more than 12% (paper 14) is not accompanied by a correspondingly high increase in transparency. By applying a composition with maltodextrin, but without acid, paper 2, there is already an increase in transparency by 11.36%, but also in the papers 3-17 the transparency increases despite the acid and the partially low pH. Value of the composition only by about 10% to about 15%. As can be seen in the wrapping papers 18 and 19 according to the invention, only the use of a trivalent acid at a pH of less than 2 causes a significant increase in transparency by more than 60%. This result is surprising in that it was not foreseeable that both the choice of acid and pH play such a large role in enhancing transparency. Furthermore, it is surprising that the filler content and the transparency are not coupled as closely as one skilled in the art would have expected, but that both properties may be of importance independently of one another. Table 2 filler transparency Paper no. Z cm ³ / (cm ² .min.kPa) D * cm / s Value g / m ² Modification % Value % Modification % 1 60.68 1.42 7.5 31.94 2 50.02 1.01 7.5 0.0 35,65 +11.63 3 50.37 0.96 7.3 -3.4 36.78 +15.15 4 44.32 0.96 8.1 +8.4 35.07 +9.79 5 48.26 0.95 8.0 +6.1 35.38 +10.76 6 53.13 0.93 7.4 -1.0 36.16 +13.23 7 49.28 0.97 7.4 -1.0 35.16 +10.10 8th 49.48 0.96 7.6 +1.3 36.43 +14.07 9 48.40 0.97 7.1 -5.7 36.11 +13.07 10 47.46 1.05 7.1 -5.7 35.04 +9.70 11 49.49 0.98 7.6 +1.4 35,79 +12.06 12 46.59 0.96 7.6 +1.4 35.76 +11.97 13 49.24 0.93 7.6 +1.4 36.49 +14.26 14 37.66 0.80 6.5 -12.8 35.22 +10.27 15 48.92 1.01 7.7 +2.1 34.94 +9.41 16 49.31 1.02 7.7 +2.1 35.31 +10.56 17 49.55 1.00 6.8 -8.9 35.40 +10.82 18 38.39 0.24 4.8 -35.6 53.49 +67.48 19 45.17 0.35 4.4 -41.9 54.20 +69.70

1.42 cm / sec (preliminary wrapping paper 1) decreases to 1.01 cm / s (paper 2) when a composition containing only maltodextrin is applied. In papers 3-17, where the composition also contains an acid, there is no further decrease in diffusion capacity to a comparable extent. By contrast, in the case of the wrapping papers 18 and 19 according to the invention, the decrease in the diffusion capacity is once again markedly greater. According to Table 2, paper 18 has a diffusion capacity of 0.24 cm / s and paper 19 has a diffusion capacity of 0.35 cm / s. Such a significant decrease in diffusion capacity can cause a cigarette to quit itself with a wrapping paper 18 or 19 according to the present invention if the portions in which the composition is applied are designed to match their geometry. In particular, at least one at least 6 mm wide band, which runs on the cigarette in the circumferential direction, for the self-extinction of the cigarette already be sufficient.

In Table 2, in the two columns titled "Filler Content", the filler content ("Value") of the wrapping papers 1-19 and the change ("Change") relative to the preliminary wrapping paper 1 are indicated in percent. Similarly, in Table 2, in the two columns titled "Transparency", the transparency ("Value") of the wrapping papers 1-19, and the change ("Change") relative to the preliminary wrapping paper 1 are indicated in percent. The values for the wrapping papers 2-19, to which the respective composition was applied, refer to a wrapping paper to which the composition has been applied over the entire surface.

The content of calcium carbonate in the wrapping papers 1-19 was determined by titration, the transparency was measured according to DIN 53147: 1993-01.

The object of the invention is to produce a higher transparency in subregions of the wrapping paper. The inventive method achieves this by applying a composition with an acid in these subregions. The acid dissolves part of the acid-soluble filler. The fact that a reduced filler content leads to a higher transparency may correspond to the expectations of the person skilled in the art, but the situation is more complex than would be expected by the person skilled in the art. For it can be seen in papers 2-17 that even a decrease in the filler content of more than 12% (paper 14) is not accompanied by a correspondingly high increase in transparency. By order of a composition with maltodextrin, but without acid, paper 2, it comes on the other hand Transparency increases by as much as 11.36%, but also in papers 3-17, transparency increases by only about 10% to about 15% despite the acid and partially low pH of the composition. As can be seen in the wrapping papers 18 and 19 according to the invention, only the use of a trivalent acid at a pH of less than 2 causes a significant increase in transparency by more than 60%. This result is surprising in that it was not foreseeable that both the choice of acid and pH play such a large role in enhancing transparency. Furthermore, it is surprising that the filler content and the transparency are not coupled as closely as one skilled in the art would have expected, but that both properties may be of importance independently of one another. Table 2 filler transparency Paper no. Z cm ³ / (cm ² .min.kPa) D * cm / s Value g / m ² Modification % Value % Modification % 1 60.68 1.42 7.5 31.94 2 50.02 1.01 7.5 0.0 35,65 +11.63 3 50.37 0.96 7.3 -3.4 36.78 +15.15 4 44.32 0.96 8.1 +8.4 35.07 +9.79 5 48.26 0.95 8.0 +6.1 35.38 +10.76 6 53.13 0.93 7.4 -1.0 36.16 +13.23 7 49.28 0.97 7.4 -1.0 35.16 +10.10 8th 49.48 0.96 7.6 +1.3 36.43 +14.07 9 48.40 0.97 7.1 -5.7 36.11 +13.07 10 47.46 1.05 7.1 -5.7 35.04 +9.70 11 49.49 0.98 7.6 +1.4 35,79 +12.06 12 46.59 0.96 7.6 +1.4 35.76 +11.97 13 49.24 0.93 7.6 +1.4 36.49 +14.26 14 37.66 0.80 6.5 -12.8 35.22 +10.27 15 48.92 1.01 7.7 +2.1 34.94 +9.41 16 49.31 1.02 7.7 +2.1 35.31 +10.56 17 49.55 1.00 6.8 -8.9 35.40 +10.82 18 38.39 0.24 4.8 -35.6 53.49 +67.48 19 45.17 0.35 4.4 -41.9 54.20 +69.70

Claims (15)

1. Wrapping paper for smoking articles, which contains pulp fibers and at least one acid-soluble filler material, wherein the content of acid-soluble filler material is at least 10% by weight with respect to the total mass of the wrapping paper, wherein the wrapping paper has regions of lower transparency and regions of higher transparency, wherein the fraction of the mass per unit area of said acid-soluble filler material is at least 10% lower in the regions of higher transparency than in the regions of lower transparency, and wherein for the transparency in the regions of higher transparency, at least one of the following criteria is met:

   - the transparency measured in accordance with DIN 53147:1993-01 in the regions of higher transparency is at least 20% higher than the transparency measured in accordance with DIN 5314:1993-01 in the regions of lower transparency, or

   - the transparency in the regions of higher transparency is so much higher than in the regions of lower transparency that, when the wrapping paper is wrapped around a tobacco rod with an American Blend tobacco blend, a diameter of 7 mm to 8 mm and a filling density of 0.1 g/cm³ to 0.3 g/cm³, a pattern of lighter and darker sections is obtained which is perceptible to the naked eye, wherein the darker sections correspond to the regions of higher transparency and the lighter sections correspond to the regions of lower transparency.
2. Wrapping paper according to claim 1, in which the regions of higher transparency form a regular, non-random pattern of transparency, in particular regularly arranged geometrical shapes, in particular lines, stripes, text, water marks or logos.
3. Wrapping paper according to claims 1 or 2, in which the pulp fibers are formed by wood pulp fibers, in particular pulp fibers from long-fiber pulp, short-fiber pulp or mixtures thereof, or in which the pulp fibers are at least partially formed by flax, hemp, sisal, jute, abacá, cotton, esparto grass or mixtures thereof, and/or which contains at least 50% by weight, preferably at least 60% by weight, particularly preferably at least 70% by weight and at most 90% by weight, preferably at most 80% by weight of pulp fibers, each with respect to the total mass of the wrapping paper, and/or in which the acid-soluble filler material is formed by an acid-soluble carbonate or hydrogen carbonate, in particular by a calcium carbonate, a calcium hydrogen carbonate, a magnesium carbonate or a mixture thereof.
4. Wrapping paper according to one of the preceding claims, in which the mean particle size of the acid-soluble filler material is at least 0.01 µm, preferably at least 0.1 µm and particularly preferably at least 0.5 µm and/or at most 10 µm, preferably at most 5 µm and particularly preferably at most 3 µm, and/or in which the wrapping paper contains at least 15% by weight, preferably at least 20% by weight and particularly preferably at least 25% by weight of the acid-soluble filler material and/or at most 50% by weight, preferably at most 40% by weight and particularly preferably at most 35% by weight of the acid-soluble filler material, each with respect to the total mass of the wrapping paper, and/or in which the content of acid-soluble filler material in a region of higher transparency with respect to the content in a region of lower transparency is reduced by at least 15%, preferably by at least 20% and particularly preferably by at least 25%, each with respect to the filler content as the mass per unit area within the respective region and/or in which the content of acid-soluble filler material in a region of higher transparency with respect to the content in a region of lower transparency is reduced by at most 100%, preferably by at most 80%, particularly preferably by at most 60% and in particular by at most 50%, each with respect to the filler content as the mass per unit area within the respective region.
5. Wrapping paper according to one of the preceding claims, in which the fraction of the area of the regions of higher transparency on the entire area of the wrapping paper is at least 1%, preferably at least 3% and particularly preferably at least 5%, and at most 99%, preferably at most 97% and particularly preferably at most 95%, wherein the fraction is in particular between 10% and 70%, and/or in addition to said at least one acid-soluble filler material, contains at least one non-acid-soluble filler material, preferably a non-acid-soluble oxide, hydroxide or silicate, in particular titanium dioxide, talcum, kaolin or mixtures thereof, in which preferably the total content of acid-soluble and non-acid-soluble filler materials is at least 10% by weight, preferably at least 15% by weight, particularly preferably at least 20% by weight and in particular at least 25% by weight of the mass of the wrapping paper, and at most 50% by weight, preferably at most 40% by weight and particularly preferably at most 35% by weight of the mass of the wrapping paper.
6. Wrapping paper according to one of the preceding claims, in which the transparency in accordance with DIN 53147:1993-01 of the wrapping paper within regions of higher transparency exceeds the transparency in regions of lower transparency by at least 25%, preferably by at least 30% and particularly preferably by at least 50% and/or by at most 300%, preferably by at most 200% and particularly preferably by at most 100%, and/or in which the transparency in accordance with DIN 53147:1993-01 within the regions of higher transparency is at least 20%, preferably at least 40% and particularly preferably at least 50% and/or at most 90%, preferably at most 70% and particularly preferably at most 60%, and/or in which the transparency in accordance with DIN 53147:1993-01 in the regions of lower transparency is at most 70%, preferably at most 60%, particularly preferably at most 50%, and at least 0%, preferably at least 10%.
7. Wrapping paper according to one of the preceding claims with a basis weight of at least 10 g/m², preferably at least 20 g/m² and at most 100 g/m², preferably at most 60 g/m² and particularly preferably at most 45 g/m², and/or in which the tensile strength with respect to the mass, calculated as the quotient of the tensile strength in accordance with ISO 1924-2:2007 and the basis weight in accordance with ISO 536:2012, is at least 0.3 N·m²/(15 mm·g), preferably at least 0.4 N·m²/(15 mm·g), particularly preferably at least 0.5 N·m²/(15 mm·g) and/or at most 1.6 N·m²/(15 mm·g), preferably at most 1.4 N·m²/(15 mm·g) and particularly preferably at most 1.2 N·m²/(15 mm·g) and/or in which the thickness in accordance with ISO 534:2001 of a single layer is at least 15 µm, preferably at least 20 µm and/or at most 100 µm, preferably at most 80 µm, and/or in which the quotient of the thickness in the regions of higher transparency and the thickness in the regions of lower transparency is at least 0.5, preferably at least 0.7 and particularly preferably at least 0.8 and/or at most 1.8, preferably at most 1.6 and particularly preferably at most 1.5.
8. Wrapping paper according to one of the preceding claims, of which the air permeability is at least 5 cm³/(cm²·min·kPa), preferably at least 20 cm³/(cm²·min·kPa) and/or at most 300 cm³/(cm²·min·kPa), preferably at most 200 cm³/(cm²·min·kPa) and particularly preferably at most 150 cm³/(cm²·min·kPa), and/or in which the quotient of the air permeability in the regions of higher transparency and the air permeability in the regions of lower transparency is at least 0.4, preferably at least 0.5, particularly preferably at least 0.6 and/or at most 1.6, preferably at most 1.4 and particularly preferably at most 1.2.
9. Wrapping paper according to one of the preceding claims, of which the diffusion capacity for CO₂ is at least 0.05 cm/s, preferably at least 0.1 cm/s and/or at most 5 cm/s and preferably at most 3.5 cm/s, and/or in which the CO₂ diffusion capacity in the regions of higher transparency is at least 0.01 cm/s, preferably at least 0.02 cm/s, particularly preferably at least 0.05 cm/s and/or at most 3 cm/s, preferably at most 2.5 cm/s and particularly preferably at most 2 cm/s.
10. Process for the production of a wrapping paper for smoking articles, comprising the following steps:

    - providing a preliminary wrapping paper which contains pulp fibers and at least one acid-soluble filler material, wherein the acid-soluble filler material content is at least 10% by weight with respect to the mass of the preliminary wrapping paper,

    - applying to the preliminary wrapping paper a composition which contains water and a trivalent acid, and wherein the pH is at least 0 and less than 2, and

    - drying the wrapping paper.
11. Process according to claim 10, in which the molar ratio of the total amount of trivalent acids and the total amount of all acids in the composition is greater than 0.7, preferably greater than 0.8 and particularly preferably greater than 0.9.
12. Process according to claim 10 or 11, in which the composition contains at least one binder selected from the group consisting of starch, starch derivatives, modified starch, cellulose derivatives or a mixture thereof, in particular maltodextrin, in which preferably the content of the binder in the composition is at least 0.1% by weight, preferably at least 0.5% by weight and particularly preferably 2% by weight and/or at most 30% by weight, preferably at most 20% by weight and particularly preferably at most 10% by weight of the composition, and/or in which the application of the composition is to the entire surface, or in which the application of the composition is to regions of the wrapping paper, which account for at least 1%, preferably at least 3% and particularly preferably at least 5% and at most 99%, preferably at most 97% and particularly preferably at most 95% of the total area of the preliminary wrapping paper, wherein the fraction is most particularly preferably between 10% and 70% of the total area of the preliminary wrapping paper.
13. Process according to one of claims 10 to 12, in which the shape of the regions represents lines, patterns, logos or text, and/or in which the composition is applied by a printing process, in particular by roto-gravure printing, flexographic printing or offset printing, or by spraying, and/or in which the amount of applied composition with respect to the area to which the composition is applied is, after drying, at least 0.5% by weight, preferably at least 5.0% by weight and at most 50% by weight, preferably at most 30% by weight of the basis weight of the finished wrapping paper, and/or in which the wrapping paper is moistened after drying by an application of water or water vapor to essentially the entire surface on one or both sides of the wrapping paper, to reduce or eliminate stress and creases caused by the application of the composition, and/or in which the trivalent acid is an organic acid, in particular citric acid.
14. Process according to one of claims 10 to 13, in which a wrapping paper according to one of claims 1 to 9 is produced.
15. Smoking article comprising a tobacco rod or an aerosol-generating material and a wrapping paper according to one of claims 1 to 9, wherein the smoking article preferably is formed by a cigarette, in particular a filter cigarette, and/or in which from a sample of 40 smoking articles, at least 30%, preferably at least 50% and particularly preferably at least 75% self-extinguish in a test in accordance with ISO 12863:2010.