EP2551407A1 - Oil-resistant filter wrapping paper - Google Patents

Abstract

The filter wrapper paper for a smoking article, is claimed, where the filter wrapper paper: has a content of long-fiber pulp of 40 wt.% relative to the pure fiber mass of the paper, and a filler content of less than 6 wt.%, relative to the total mass of the paper; and is impregnated with a material that is provided for forming an aqueous solution or an aqueous suspension. The filter wrapper paper has a basis weight of 20-25 g/m 2>without impregnation, and/or the finished filter wrapper paper has a basis weight of 205-390 g/m 2>. The filter wrapper paper for a smoking article, is claimed, where the filter wrapper paper: has a content of long-fiber pulp of 40 wt.% relative to the pure fiber mass of the paper, and a filler content of less than 6 wt.% relative to the total mass of the paper; and is impregnated with a material that is provided for forming an aqueous solution or an aqueous suspension. The filter wrapper paper has a basis weight of 20-25 g/m 2>without impregnation, and/or the finished filter wrapper paper has a basis weight of 205-390 g/m 2>. The contribution of the material of the impregnation to the basis weight of the finished filter paper is 1.3-2 g/m 2>. An average fiber length of the unmilled long fiber pulp is >= 2 mm. The filter wrapper paper is printed or sprayed on other material layer, which is applied on a side facing filter plug. The contribution of the other material layer to the basis weight of the finished wrapper paper in a treated area is 2-4 g/m 2>. The material of the other material layer is adapted to form an aqueous solution or suspension. The filter wrapper paper is configured to bond the filter plugs and/or a tipping paper without using the adhesive after humidification. Independent claims are included for: (1) a method for producing a filter wrapper paper for a smoking article; and (2) a smoking article.

Description

Field of the invention

The present invention is in the field of papermaking for smoking articles. More particularly, it relates to a filter wrapper paper for a smoking article, a method of making the same, and a smoking article using such filter wrapper paper.

Background and related art

A commercial filter cigarette consists of a cylindrical, round or oval tobacco rod wrapped in a cigarette paper, a similarly shaped filter plug surrounded by a filter wrap paper, and a tipping paper usually coated with the entire filter wrap paper and a portion of the tobacco rod Cigarette paper is bonded, and so connects the filter plug with the tobacco rod.

The filter plug itself can be made of various materials, often cellulose acetate fibers, sometimes used in combination with activated carbon particles. The filter wrapper enveloping the filter plug is typically bonded in one or more narrow balanar regions to the surface of the filter plug, which typically extends along a direction parallel to the axis of symmetry of the filter plug. Likewise, the filter wrapper paper is usually adhered to itself along a narrow seam to prevent bursting of the filter plug. For this purpose, a variety of different adhesives is used in the prior art, but often polyvinyl acetate or hot melt adhesives are used.

Typical filter wrap papers in the range of relatively low and medium air permeabilities consist of wood pulp using a mixture of long or short fibers depending on the desired properties of the paper. Further, these papers typically contain mineral fillers, such as calcium carbonate, kaolin, talc, titanium dioxide or other mineral fillers, and mixtures thereof. Additionally or alternatively For example, other additives may be provided to achieve specific properties, such as wet strength agents.

The production of such filter wrapper paper is done on paper machines, for example, on fourdrinier machines.

The pulp fibers used for papermaking are usually distinguished into long and short fibers, with long fibers typically being pulp fibers of softwoods, such as spruce or pine, with a length of more than 2 mm, while the short fibers of hardwoods, such as birch, Beech or eucalyptus are derived and typically have a length of less than 2 mm, often about 1 mm.

In a first step of paper production, the pulp is suspended in water and then ground in a milling unit, a so-called refiner. It is common for short and long fibers to be ground separately. The intensity with which the pulp was ground is determined by measuring the degree of grinding, for example according to ISO 5267 (Pulps: Determination of drainability - Part 1: Schopper-Riegler method). The result of this measurement is given in degrees according to Schopper-Riegler (° SR). Typically, long fiber pulp is ground for use in filter wrap papers to a freeness of 50-70 ° SR.

Short fiber pulp is usually ground much less strongly and reaches a freeness of 15 ° SR to 40 ° SR. The grinding of short fiber pulps can be completely eliminated.

After the addition of fillers, such as calcium carbonate, kaolin, talc, titanium dioxide or other mineral fillers or mixtures thereof, the fiber-filler suspension from the headbox of the paper machine flows to the wire and can be dewatered there by various means, for example by gravity or Vacuum. Thereafter, the wet fiber network can pass through the press section where it is dried by mechanical pressure against a dry felt. Finally, the fiber network can still pass through the dryer section where it is dried by contact with cylinders, for example steam heated ones. Then the finished paper can be rolled up. It can be performed even more processing steps in the paper machine be, for example, a sizing in a glue or film press, the application of watermarks, an embossing, etc.

The finished filter wrapper paper is then usually in the form of a roll, with a width corresponding to the width of the paper machine. This role is then usually cut into narrower roles, so-called bobbins, the width of which depends on the circumference of the filter plug and the desired width of the seam. A typical bobbin is about 5000 to 6000 m long and 25 to 27 mm wide. Considerable deviations in length and width of the reel are possible to adapt to the wide range of commercial cigarette filters. It is also common that the width of a reel is about an integer multiple of the width needed to make a filter plug since filter making machines can make several, typically two, filter strands in parallel at a time.

In some filter cigarettes, one or more capsules which can be destroyed by mechanical pressure are introduced into the filter plugs. These capsules contain a liquid, usually an oil, with flavorings, such as menthol. The smoker thus has the option of destroying this capsule (s) by pressure on the filter plug, for example with the fingers, and thus releasing the aroma substances. The released flavors then aromatize the smoke flowing through the filter plug and exiting from the mouth end of the cigarette so that the smoker can perceive the flavors. Thus, the smoker can control the taste of the cigarette by destroying the capsules. Such a filter cigarette is for example in US 2008/142028 described.

However, the liquid emanating from the destroyed capsules has a tendency to penetrate through the filter wrapping paper as well as through the tipping paper, so that stains are visible on the outside of the cigarette. These stains are noticeable to the smoker and affect the visual appearance of the cigarette.

Such stains can be prevented by providing the filter wrapper with some barrier to oil. The ability of a paper to form a barrier to oil, hereafter also referred to as "oil resistance", can be determined using a Tappi T559 cm-02 "Grease Resistance Test for Paper and Paperboard" test, which is customary in the paper and paper industry , In this test, drops of 12 different test fluids sorted in ascending order of wettability are applied to the paper applied, and it is determined which of the liquids penetrates to the other side of the paper. The result of the test is the so-called KIT level, which describes in which of the test fluid the breakdown to the other side of the paper has occurred for the first time. It is therefore described by a number between 1 and 12, with higher values corresponding to a higher oil barrier effect. In the event that a breakdown already occurs at the first test fluid, the result is indicated as "<1". For filter wrapper paper in the above application, a KIT level of about 5 has been found to be sufficient to prevent staining on the cigarette.

One way to give the paper such a barrier function against oil or "oil resistance" is to coat the filter paper with fluorinated hydrocarbons, which give the paper oil-repellent properties. For example, such fluorinated hydrocarbons are commonly used in paper food packaging, but are not approved for use in cigarettes in many countries. In addition, the coating may complicate the bonding of the filter wrapper paper.

In addition to fluorinated hydrocarbons, it has also been proposed to use specially modified starch products, specifically octenylsuccinate-substituted starches, for impregnating paper for food packaging, cf. WO 2008/100688 , However, these starches have the disadvantage that they must be applied in a relatively large amount to the paper in order to achieve the desired effect. A sufficient effect could only be achieved from order quantities of more than about 80 kg of this starch product per tonne of paper.

Applying the proposed method to a filter paper, this ratio would correspond to an order of typically significantly more than 2 g / m ² . As a result, not only the material costs, but also the energy required for drying would be increased unfavorably.

Also in CA 2467601 is the order of starch products to achieve oil resistance described. There it is proposed to use a composition consisting of a modified starch, an agent for increasing the mechanical flexibility, such as glycol, and a means for adjusting the rheological behavior. Although this may improve the mechanical flexibility of the coating, it also requires, according to this patent, an order of more than 75 kg of this composition per Ton of paper to ensure adequate oil resistance. Therefore, the material used and the associated costs for material and energy for drying the paper are comparatively high here as well. The effect could only be demonstrated for papers with a basis weight of more than 37 g / m ² , which corresponds to an order of at least 2.78 g / m ² . However, it is by no means obvious that the effect described in this patent can be easily transferred to filter wrapping papers with a much lower basis weight. Moreover, in some countries the use of glycols in papers for the cigarette is not allowed.

In filter wrap papers, which are generally much lighter and thinner than food packaging papers, higher order quantities of starch products are required from the outset in relation to the pulp, since the papers offer less resistance to the oil by itself because of their low basis weight and small thickness, and because due to the low basis weight of the order per weight unit of the filter wrapper paper takes place on a comparatively much larger area.

The order of large quantities of starch products, however, brings with it additional costs as well as other disadvantages. For example, papers heavily coated with starch tend to form dust, which increases the number of cleaning cycles on processing machines and reduces their productivity.

Zusamtnenfassung of the invention

The invention has for its object to provide a filter wrapper available, which can be produced at low cost and yet has sufficient resistance to oil and has favorable mechanical properties for further processing.

This object is achieved by a filter wrapper according to claim 1 and a method for its production according to claim 11. Advantageous developments are specified in the dependent claims.

1. (i) Der Mahlgrad des Langfaserzellstoffs beträgt zwischen 80 °SR und 100 °SR, vorzugsweise zwischen 85 °SR und 95 °SR, nach ISO 5267, Schopper-Riegler-Verfahren,
2. (ii) das Filterhüllpapier hat einen Füllstoffgehalt van < 10 Gew.-%, vorzugsweise < 8 Gew.-% und besonders vorzugsweise < 6 Gew.-%, bezogen auf die Gesamtmasse des Papiers und
3. (iii) das Filterhüllpapier ist mit einem Material imprägniert, das geeignet ist, eine wässrige Zusammensetzung, insbesondere eine wässrige Lösung oder Suspension zu bilden.

The filter paper according to the invention contains a proportion of long-fiber pulps of at least 30 wt .-%, preferably at least 40 wt .-% based on the pure amount of fiber of the paper. Furthermore, the filter wrapper paper is characterized by the combination of the following three features:

1. (i) The freeness of the long-fiber pulp is between 80 ° SR and 100 ° SR, preferably between 85 ° SR and 95 ° SR, according to ISO 5267, Schopper-Riegler method,
2. (ii) the filter wrapper paper has a filler content of van <10% by weight, preferably <8% by weight and particularly preferably <6% by weight, based on the total weight of the paper and
3. (iii) the filter wrapper paper is impregnated with a material suitable for forming an aqueous composition, in particular an aqueous solution or suspension.

The inventors have found that the combination of these features produces a filter wrapper having a Tappi T559 cm-02 KIT level of at least 4, typically even 5 or more. This is true even if the filter paper as the starting material, that is still without impregnation, a very low basis weight of 15-35 g / m ² .

This is a surprising and unpredictable result from the point of view of the inventors, which is obviously due to a synergistic effect between the three features (i) to (iii). Because no two of the above features (i) to (iii) in combination indicate this positive effect, as shown in more detail below by means of comparative examples. The investigations of the inventors rather indicate that this special technical effect is only achieved by the combination of these three special features.

As mentioned above, the filter paper according to the invention allows a sufficient oil resistance at comparatively low basis weights of 15 to 35 g / m ² , based on the starting material without impregnation. Preference is given to papers whose basis weight before impregnation is 20-30 g / m ² , particularly preferably 20-25 g / m ² . Such filter paper may have an average air permeability according to ISO 2965 of less than 12,000 cm ³ / (cm ² min kPa), preferably less than 8,000 cm ³ / (cm ² min kPa). The effect according to the invention can also be achieved with filter papers having a higher basis weight. However, with filter papers above 35 g / m ^{2, it is} also possible in other conventional ways to produce sufficient oil resistance, unlike in the preferred range here, for which the prior art to the knowledge of the inventors does not yet provide a truly satisfactory solution provides.

The impregnation and an optional further application of material described below increase the basis weight of the finished filter wrapper paper. Preferred ranges for the finished filter wrapper paper are 15.5-24.0 glm ² , preferably 20.5-39.0 g / m ² and particularly preferably 20.5-34.0 g / m ² .

The appropriate amount of application of the impregnating material may be determined experimentally to give the desired oil resistance. Preferably, however, the contribution of the material for impregnation to the basis weight of the finished filter paper is 0.5-3.0 g / m ² , preferably 1.0-2.5 g / m ² , and more preferably 1.3-2.0 g / m ² .

As mentioned above, the filter wrapper paper of the invention is impregnated with a material suitable for forming an aqueous composition, in particular an aqueous solution or suspension. This aqueous solution or suspension may then be used in the impregnation to introduce the material into the paper while the water component evaporates or vaporizes after impregnation. As an advantageous material for the impregnation starch or a starch derivative has been found, preferably a hydrolyzed starch, in particular maltodextrin.

However, the invention is not limited to these materials. Instead, one or more of the following substances may be used for the impregnation material: gelatin, shellac, collodium, gum arabic, agar-agar, tragacanth, locust bean gum, guar gum, carboxymethyl starch, alginic acid and its salts, especially sodium, potassium and potassium salts Calcium alginates, or a cellulose derivative, especially methyl cellulose or carboxymethyl cellulose and their sodium, potassium, calcium or magnesium compounds.

As described above, a special feature of the filter paper according to the invention is that the proportion of fillers is chosen to be relatively low. Nevertheless, fillers, albeit in a relatively smaller proportion, may be present, which are preferably mineral fillers, in particular calcium carbonate, kaolin, talc, titanium dioxide or a mixture of two or more of these fillers.

Although the above-described impregnation of the paper - in combination with the specially high freeness of the long fiber pulp and the comparatively small proportion of fillers - can achieve a sufficient increase in oil resistance for most applications, the oil resistance can be further increased if necessary by: a further layer of material is applied, in particular printed or sprayed on. This additional material layer can basically be applied to each of the two sides of the filter wrapper paper. Preferably, however, it is applied at least on the side facing the filter plug in use. In contrast to the impregnation in which the material is introduced into the paper, the optional further application of material is essentially limited to the surface of the already impregnated paper, and is therefore also referred to herein as a "coating".

Preferably, the contribution of the further material layer to the basis weight of the finished filter wrapper paper in the treated area is 1.0-6.0 g / m ² , preferably 2.0-4.0 g / m ² . The restriction "in the treated area" indicates that the entire surface of the filter wrap paper does not necessarily need to be coated with the other material. This is the case in particular in the applications described in more detail below, in which the further material coating primarily serves to provide a self-adhesive effect.

The material of the further material layer is also preferably suitable for forming an aqueous composition, in particular an aqueous solution or suspension. Oxidized starch has proved to be particularly advantageous. However, all of the materials mentioned above in connection with the impregnation come into consideration.

The material of the impregnation and / or the material of the further material layer is preferably suitable, after its moistening, to bond the filter wrapping paper to itself, a filter plug and / or a tipping paper without further adhesive. As below is explained in more detail with reference to exemplary embodiments, the impregnation and the optional further coating not only serves to increase the oil resistance, but they give the filter wrapper paper as a particular further advantage a self-adhesive effect. For this purpose, the material of the impregnation or the further coating must only be wetted and thus dissolved, whereupon it can be glued to another section of the filter wrap paper, the filter plug or a Tippingpapier. This self-adhesive effect can be generated by the impregnation itself, but is reinforced by the further material coating. If the impregnation alone is sufficient to produce the oil resistance, the application of the further material, ie the coating, can be limited to those selected areas serving as splices when the filter wrap paper is adhered to itself, the filter plug or a tipping paper.

In the production method of the filter wrapper paper of the present invention, a precursor paper having the above features (i) and (ii) is first prepared. Thereafter, the precursor paper is impregnated with a suitable material in an aqueous composition, in particular an aqueous solution or suspension. This impregnation can take place, for example, in the size press of a paper machine. Alternatively, the impregnation can be carried out by two-sided application of the aqueous composition in a film press of a paper machine or by two-sided roller application.

After impregnation and drying, the filter wrapper paper can optionally be optionally coated with additional material. As a coating method, the gravure printing method is preferred. Further suitable application methods are flexographic printing, spraying or application by means of a film press or a roller. Characteristic here is that the material is applied to the surface and not, as in the impregnation example in the size press, is introduced into the paper structure.

Description of the preferred embodiments

It has been found that by a special treatment of the fibers, by a suitable choice of the paper composition and by impregnation of the paper with an aqueous composition, a surprising synergistic effect is achieved, which allows all of them before simultaneously meet the requirements described. These are illustrated by the following examples.

EXAMPLES 1-8: Lack of Oil Resistance of Conventional and Modified Filter Wrapping Papers and Achievement of Oil Resistance by the Invention

Several filter wrap papers were produced having a basis weight of about 23 g / m ² , comprising about 60% long fiber pulp and about 40% short fiber pulp, both percentages based on the pure pulp, and a 0-10% variable filler content, based on total pulp , The filler used was precipitated calcium carbonate (PCC).

In addition to the filler content, the freeness of the long-fiber pulp was also varied. In Table 1, "normal" refers to a long fiber pulp with a typical freeness of 50 to 70 ° SR, while in the variants with a highly ground long fiber pulp ("intensive"), the long fiber pulp in a double disc refiner was ground to a 93 ° SR freeness. Impregnation of the papers, if carried out, was carried out in the size press of the paper machine with a 10-15% aqueous suspension of a short-chain hydrolysed starch (maltodextrin Eliane MD2 from Avebe, obtainable for example from Brenntag CEE GmbH), so that in the paper structure after drying The paper remained about 1-2 g of this thickness per square meter of paper, which is hereinafter also referred to as "order quantity", although this is strictly speaking not an "order" in terms of a coating, but an impregnation. Unless otherwise specified, all percentages are by weight.

To prepare the starch suspension 150 kg of this starch product were stirred in 800 liters of tap water at room temperature with a conventional stirrer and filled after about 5-15 minutes of stirring to 1000 kg with tap water.

The amount of starch added in the paper by the impregnation was determined as the difference in basis weight determined before and after the impregnation according to ISO 536.

All papers were tested for oil resistance according to Tappi T559 cm-02 with 9 tests on each paper. The range of values obtained and all other results of these experiments are summarized in Table 1. Table 1: Oil resistance of conventional, modified and coated filter wrap papers Filterhüllpapier impregnation oil resistance No. Long fiber pulp grinding Filler content [%] Starch suspension [%] Order quantity [g / m ² ] KIT-Level 1 normal 10 None 0 <1 2 Intensive 10 None 0 <1 3 normal 0 None 0 1 4 Intensive 0 None 0 1-2 5 normal 10 12 1.5 <1 6 Intensive 10 12 1.5 <1 7 normal 0 12 1.5 1-2 8th Intensive 0 10 1.2 5-6

Example 1 describes a conventional filter wrapper paper, showing that conventional filter wrapper papers do not have sufficient oil resistance.

In Example 2, the long fiber pulp was ground intensively, resulting in a denser paper structure. Nevertheless, no improvement in oil resistance could be achieved.

In Example 3, no filler was used. This measure also leads to a denser paper structure, but also does not improve oil resistance.

Example 4 shows that even the combination of highly ground long-fiber pulp and the absence of filler does not achieve a sufficient improvement in oil resistance.

Examples 5-7 show the same papers as in Examples 1-3, but with an additional impregnation by the starch suspension. Although the amount of the order of starch is about the same amount as in WO 2008/100688 or CA 2467601 is proposed and thus at least a small improvement in oil resistance would have been expected, this can not be confirmed experimentally.

It can therefore be concluded from Examples 1-7 that the low basis weight and the small thickness of filter wrap papers are a particular difficulty in achieving oil resistance, which can not be overcome in an obvious manner by methods known in the art.

• durch Verwendung von hoch ausgemahlenem Langfaserzellstoff,
• durch Reduktion des Füllstoffgehalts und
• durch Imprägnierung mit einer Stärkesuspension

ein Synergieeffekt erzielt werden kann, der sich nicht bloß aus der einfachen Überlagerung einzelner Beiträge dieser Maßnahmen ergibt. Denn die Messungen zeigen für das Papier aus Beispiel 8 einen KIT-Level von 5-6, während für keines der Beispiele 1-7, in denen bis zu zwei der beschriebenen Maßnahmen ebenfalls zur Anwendung kamen, ein KIT-Level von mehr als 2 erreicht wurde. Ein KIT-Level von 5-6 hingegen stellt schon eine ausreichende Ölbeständigkeit dar.Surprisingly, however, the inventors have found that by a combination of all of these measures, ie

• by using highly milled long-fiber pulp,
• by reducing the filler content and
• by impregnation with a starch suspension

a synergy effect can be achieved which does not merely result from the simple superimposition of individual contributions of these measures. For the measurements show a KIT level of 5-6 for the paper of Example 8, while for none of Examples 1-7, in which up to two of the measures described were also used, a KIT level of more than 2 achieved has been. A KIT level of 5-6, however, already represents a sufficient oil resistance.

It should also be noted that in Example 8, a KIT level of 5-6 can already be achieved by impregnation with only 1.2 g of starch per square meter of paper, whereas impregnation with 1.5 g of starch per square meter of paper in Examples 5-7 does not causes significant improvement.

EXAMPLES 9-20: Applicability of the invention in the area of typical filter wrap papers

The following examples show that the observed synergy effect does not depend strongly on the paper properties, but can be used in the entire spectrum of typical filter wrap papers. Table 2: Oil resistance of coated filter wrap papers paper impregnation oil resistance No. Basis weight [g / m ² ] Long fiber [%] Filler content [%] Order quantity [g / m ² ] KIT-Level 9 20 55 2 1.2 4-5 10 25 55 2 1.3 5-6 11 30 55 2 1.4 8-9 12 25 30 2 1.2 4-5 13 25 45 2 1.3 6-7 14 25 70 2 1.4 6-8 15 25 55 4 1.3 6-7 16 25 55 6 1.3 6-7 17 25 55 8th 1.2 4-6 18 25 55 2 1.5 5-7 19 25 55 2 1.7 6-8 20 25 55 2 2.0 8-9

From Examples 9-11, it can be seen that an increasing basis weight is favorable for oil resistance, and therefore with increasing basis weight either a higher KIT level is achieved for the same application amount in the impregnation, or the same KIT level with low application rate in the impregnation can hold. The method can be carried out with similar results for filter wrap papers having a basis weight from about 15 g / m ² to about 35 g / m ² . But it will preferably select the basis weight in the range of 20 g / m ² to 30 g / m ² due to these examples, and particularly preferably in the range of 20 glm ² to 25 g / m ^2. The basis weight here refers to the weight per unit area of the filter wrap paper before impregnation, which is also referred to below as "initial basis weight". Even over a starting basis weight of 35 g / m ² , the described effect is achieved, however, other known methods for achieving oil resistance can be used for such papers.

In Examples 12-14, the content of highly ground long fiber pulp is varied at constant fiber weight. As expected, increasing oil resistance is seen to increase the content of long fiber pulp since the highly ground long fiber pulp contributes to a denser paper structure. In order to achieve sufficient oil resistance, the content of long-fiber pulp, based on the total fiber mass of the paper, should be at least 30%, preferably at least 40%. There is basically nothing against using up to 100% long-fiber pulp. However, the benefits in oil resistance at very high levels of long fiber pulp no longer increase to the same extent like at low levels. Since long-fiber pulp is usually more expensive than short-fiber pulp and the grinding is associated with energy costs, resulting in an ideal for each application proportion of long-fiber pulp, inter alia, for economic reasons.

With regard to the grinding of the long-fiber pulp, an effect occurs from a freeness of about 80 ° SR, but is preferably the range of 85 ° SR to 95 ° SR. As the tensile strength of the paper decreases with increasing grinding, the long-fiber pulp will not be ground arbitrarily intensively. An upper limit for the freeness of the long-fiber pulp is set at 100 ° SR.

Finally, in Examples 15-17, the filler content (here precipitated calcium carbonate) in the filter wrap paper is varied. Increasing content of calcium carbonate or similar fillers loosens the paper structure and degrades the oil resistance, thus closing the calcium carbonate content as in Example 6 is, in any case less than 10% but preferably less than 8% and more preferably less than 6% will choose. It is also possible to completely dispense with filler. On the one hand, since calcium carbonate is less expensive than pulp, but on the other hand, with higher filler content, it may be necessary to use more starch in the impregnation in order to achieve sufficient oil resistance, the concrete choice of filler content - within the limits defined here - not least for economic reasons.

Finally, as shown in Examples 10 and 18-20, the amount of starch applied to the paper in the impregnation can be varied. Increasing the application amount shows increasing oil resistance, but just as with the content of long-fiber pulp, the improvement in oil resistance does not increase to the same extent at higher application rates as at low levels. Application quantities of 0.5 g / m ² to 3 g / m ^{2 have} proved to be suitable, preferably those of between 1.0 g / m ² and 2.5 g / m ² , more preferably between 1.3 g / m ² and 2.0 g / m ² .

In addition to the impregnation by means of a suspension of a short-chain, hydrolyzed starch shown here by way of example, the invention can also be achieved by impregnation with other water-based compositions, such as, for example, solutions or suspensions. As an alternative to the short-chain hydrolyzed starch, for example, gelatin, Shellac, collodium, gum arabic, agar-agar, tragacanth, locust bean gum, guar gum, also proposed starch and starch derivatives, such as carboxymethyl starch, or alginic acid and its salts, in particular sodium, potassium, and calcium alginates, and cellulose derivatives, such as methyl cellulose or carboxymethyl cellulose and their sodium, potassium, calcium or magnesium compounds. Mixtures containing one or more of these substances may also be used. In the concrete selection of the substance or mixture of substances, in addition to the processability, the legal provisions must also be taken into account.

Since the ability to improve the oil resistance by impregnation with ever greater amounts of starch is technically limited, it is proposed in a further development of the invention to additionally apply a further aqueous composition to the surface of the paper after the impregnation. The aqueous composition may contain a starch or a starch derivative, which may also be the same as that used for impregnation. In many cases, however, one will choose another substance or a mixture of substances which can be used better in the selected application process, for example because of the requirements for the rheological behavior.

A comparable effect can also be achieved, for example, with gelatin, shellac, collodium, gum arabic, agar-agar, tragacanth, locust bean gum, guar gum, also with starch and starch derivatives, such as carboxymethyl starch, or with alginic acid and its salts, in particular sodium, potassium , and calcium alginates, as well as with cellulose derivatives, such as methylcellulose or carboxymethylcellulose and their sodium, potassium, calcium or magnesium compounds.

There are no restrictions on the type of order procedure. Conventional printing methods such as gravure printing or flexographic printing can be used, but it is also possible to spray on the composition, as can one-sided application using a film press or a roller. It is characteristic, however, that the material is applied to the surface and not, as in the impregnation, for example, in a size press, introduced into the paper structure. For conceptual distinction from the above "impregnation" this provided in addition to impregnation material application is referred to as "coating". This term is to be understood broadly and is merely intended to express bring that the additional material for the most part applied to the already impregnated paper instead of being introduced into the paper structure.

In the following examples, some of the already impregnated papers from Examples 9-20 were additionally additionally printed over the entire surface with an approximately 20% aqueous composition, specifically an aqueous suspension of an oxidized starch (Perfectamyl A5760 from Avebe), in a customary gravure printing process (ie "coated). In addition, 3 g of the oxidized starch per square meter of printed area of the paper were applied. Table 3: Oil resistance of printed and impregnated filter wrap papers Example no. Impregnated paper such as Example No. KIT level Before printing After printing 21 9 4-5 6-8 22 10 5-6 8-9 23 12 4-5 6-8 24 17 4-6 7-9

From Examples 21-24, it can be seen that by printing, in general, a further increase in oil resistance by 2-3 points can be achieved, with the measurement of oil resistance being made on the printed side. In the application on the cigarette, it is then recommended, but not essential, that the printed side faces the filter plug.

The amount of solids of the aqueous composition applied in the intaglio printing process in addition to the above-mentioned impregnation brings about detectable effects in the range from 1.0 to 6.0 g / m ² printed area, but the range from 2.0 to 4.0 g / l is preferred. m ² printed area. The stated application amounts refer to the dried paper, ie after the water of the applied aqueous composition has evaporated or evaporated. It is also to be expected with other application methods that with an applied amount of 1.0-6.0 g / m ² and preferably 2.0-4.0 g / m ² an effect which is at least approximately comparable to the gravure printing method can be achieved the oil resistance obviously depends more on the order quantity than on the type of application method.

Example 25: Bonding of the filter wrapping papers

Both the impregnation alone and in combination with the additional application to the surface ("coating") make it possible to obtain a filter wrapping paper which can be bonded to itself or to the filter plug without the need for further adhesives. Instead, it is sufficient to first apply a small amount of water to the surface of the paper in a partial area or over the entire area. There are no special requirements for the water, it may preferably be usual power water, also deionized water is possible. The temperature of the water is also not particularly relevant for the bonding, it will preferably be in a range of 15 ° C to 60 ° C.

Thereafter, the surface wetted with water with the surface to be bonded under slight mechanical pressure to bring into contact and a short time, preferably at elevated temperature, for example, about 60 ° C to dry. Preference is given in this case to temperatures which allow rapid drying, preferably above 40 ° C., particularly preferably above 50 ° C. However, the temperature should not be so high that thermal decomposition of the paper occurs, which is why it is below 105 ° C, preferably below 90 ° C.

Of particular importance in the production of cigarette filters is that the bond reaches a certain minimum strength very quickly, so that the filter does not burst in the further processing steps or the filter paper dissolves from the filter. The bonding takes place in such a way that the adhesive seam is approximately 2 mm wide and lies in the machine direction of the filter paper. Where the filter wrapping paper is glued to itself, the bonding between the top and the wire side of the filter wrap paper takes place.

To mimic this process in the laboratory, each of the papers of Examples 10, 11, 14 and 22 was tested for adhesiveness. In addition to the paper from Example 10 and its printed variant from Example 22, which correspond to an approximately average filter paper, the papers from Examples 11 and 14 were chosen because they higher because of the higher basis weight or because of the higher proportion of long fiber pulp Have tensile strength.

For the test, first two strips of paper 15 mm wide in the machine direction and sufficiently long in the transverse direction for a tensile strength measurement according to ISO 1924-2 were prepared. Water was applied to the top of the first strip with a brush along a straight line about 2 mm wide in the machine direction of the paper, ie parallel to the short side of the strip. Thereafter, the paper strip was brought into contact with the screen side of the second strip such that a 15 mm wide but now longer, straight strip resulted from the bonding of the two strips. The splice was loaded with a flat metal body heated to a temperature of about 60 ° C by manual pressure for about 1 second. Immediately thereafter, the glued paper strip was subjected to a tensile test in accordance with ISO 1924-2. The paper strip is clamped at both ends and stretched until it breaks. In the experiments it was observed whether the tear occurred at the tack or at another location of the paper strip. Four strips were tested per paper.

It turns out that except for the paper of Example 11, three or more of the four strips tested did not tear at the splice. Therefore, the strength of the bond is already higher than the tensile strength of the paper itself at this time, and it is therefore considered that the strength of the bond is sufficient for the machine processing. This was not the case with Example 11, as the paper was not torn at the glue site just once in four trials. However, because of the higher tensile strength of this paper, it can also be assumed in this case that the bond strength for the machine production of filters from this paper is sufficient.

If sufficient oil resistance of the paper has already been achieved by impregnating the paper, but the bond strength is insufficient for machine processing, it is proposed that the composition intended for application to the surface or "coating" should not be applied over the whole area but only in some areas , These sections can have any shape per se, but will depend on the shape of the surface to be bonded. These subregions are preferably designed in their shape, as it previously corresponds to the areas of the filter wrapper paper provided with adhesive in the filter production.

The composition is typically and preferably applied in partial regions on the side of the paper facing the filter plug. But it is also conceivable, these sections provided on the other side of the paper or on both sides of the paper, for example, if additional bonding of the filter wrapper paper with the tipping paper is to be achieved in a later step of cigarette production.

The features described above may be of importance in any combination.

Claims (15)

Filter wrapper paper for a smoking article,
which has a content of long-fiber pulp of at least 30% by weight, preferably at least 40% by weight, based on the pure pulp of the paper, characterized in that the freeness of the long fiber pulp according to ISO 5267, Schopper-Riegler method is between 80 ° SR and 100 ° SR, preferably between 85 ° SR and 95 ° SR, the filter wrapper paper has a filler content of less than 10% by weight, preferably less than 8% by weight and more preferably less than 6% by weight, based on the total weight of the paper, - The filter wrapper paper is impregnated with a material which is suitable to form an aqueous composition, in particular an aqueous solution or suspension, and the oil resistance of the filter paper has a Tappi T559 cm-02 KIT level of at least 4, preferably of at least 5. Filter wrapping paper according to claim 1, which without impregnation has a basis weight of 15-35 g / m ² , preferably 20-30 g / m ² and particularly preferably 20-25 g / m ² , and / or
the finished filter paper has a basis weight of 15.5-44.0 g / m ² , preferably 20.5-39.0 g / m ² and particularly preferably 20.5-34.0 g / m ² . The filter wrap paper of claim 1 or 2, wherein the contribution of the impregnation material to the basis weight of the finished filter paper is 0.5-3.0 g / m ² , preferably 1.0-2.5 g / m ^2, and most preferably 1.3 -2.0 g / m ² . A filter wrapper paper according to any one of the preceding claims, wherein the impregnation material comprises starch or a starch derivative, preferably hydrolyzed starch and most preferably maltodextrin, or
in which the material of impregnation comprises one or more of the following substances: gelatin, shellac, collodium, gum arabic, agar-agar, tragacanth, locust bean gum, guar gum, carboxymethyl starch, alginic acid and its salts, in particular sodium, potassium and calcium alginates, or a cellulose derivative, especially methyl cellulose or carboxymethyl cellulose and its sodium, potassium, calcium or magnesium compounds. A filter wrapper paper according to any one of the preceding claims, wherein the average fiber length of the unmilled long fiber pulp is 2 mm or more. Filter wrapping paper according to one of the preceding claims, wherein the filler is at least partially formed by a mineral filler, in particular calcium carbonate, kaolin, talc, titanium dioxide or a mixture of two or more of these fillers. Filter wrapping paper according to one of the preceding claims, on which a further material layer is applied, in particular printed or sprayed on, wherein the further material layer is preferably applied at least on the side which faces the filter plug in use. The filter wrapper paper of claim 7, wherein the contribution of the further material layer to the basis weight of the finished filter wrapper paper in the treated area is 1.0-6.0 g / m ² , preferably 2.0-4.0 g / m ² . Filter wrapping paper according to claim 7 or 8, in which the material of the further material layer is suitable for forming an aqueous composition, in particular an aqueous solution or suspension,
wherein the material preferably comprises oxidized starch or one or more of the materials of claim 4. Filter wrapping paper according to one of the preceding claims, wherein the material of the impregnation and / or the material of the further material layer is suitable, after the moistening of the filter wrap paper without further adhesive to stick to itself, a filter plug and / or Tippingpapier. Method for producing a filter paper, comprising the following steps: Grinding of a long-fiber pulp to a grinding degree according to ISO 5267, Schopper-Riegler method, between 80 ° SR and 100 ° SR, preferably between 85 ° SR and 95 ° SR, Preparing a precursor paper, - The proportion of ground long-fiber pulp is at least 30 wt .-%, preferably at least 40 wt .-% based on the pure fiber mass, and - Has a filler content of <10 wt .-%, preferably <8 wt .-% and particularly preferably <6 wt .-%, based on the total mass of the precursor paper, and - Impregnating the precursor paper with an aqueous composition, in particular an aqueous solution or suspension. A method according to claim 11, wherein the impregnation is carried out in a size press of a paper machine, in a film press of a paper machine or by double-sided roller application. A method according to claim 11 or 12, wherein after impregnation a further layer of material is applied to at least a portion of the filter wrapper paper in the form of an aqueous composition, preferably in a gravure printing process,
the further layer of material preferably being applied in selected areas which may serve as splices when the filter wrapping paper is adhered to itself, a filter plug or a tipping paper,
wherein the aqueous composition for the impregnation and / or the aqueous composition for the further application of material preferably has a solids content of 5-20 wt .-%, preferably 10-15 wt .-%. Method according to one of claims 11 to 13, wherein the precursor paper has a basis weight of 15-35 g / m ² , preferably 20-30 g / m ² and particularly preferably 20-25 g / m ² , and / or
in which the material of the impregnation comprises one or more of the substances mentioned in claim 4, and / or
in which the aqueous composition for the further application of material comprises, as a solid component, oxidized starch or one or more of the materials of claim 4. A smoking article comprising a filter plug surrounded by a filter wrapper paper according to any one of claims 1 to 10,
wherein the filter plug includes one or more mechanical pressure breakable capsules filled with a flavorant-containing liquid.