BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to paper for making filter wrappers or mouth pieces of smoking articles.

[0004] 2. Description of the Background Art

[0005] There is an almost incalculable number of formulas for cigarette papers, filter wrappers and mouth piece papers. These papers are made of cellulose, to which fillers are added. By adding different fillers, the characteristics of the smoking article can be manipulated as desired. For example, by adding the appropriate fillers, a stabile or white band of ashes can be obtained. Other fillers reduce the sidestream smoke. Yet other fillers regulate the smolder characteristics etc.

[0006] A big problem are smoking articles, for example cigarettes, which, when left unsupervised ignite their substrate. There has been, therefore, no lack of attempts to alter the papers used in the manufacture of smoking articles, for example cigarettes, in such a way that the tobacco ember self-extinguishes when the smoker does not take a puff for a certain period of time. See, for example, DE 34 29 260 A, EP 0 262 550 A, U.S. Pat. No. 4,044,778, and also U.S. Pat. No. 5,191,906.

[0007] The cigarette paper disclosed in DE 34 29 260 A has a base wrapper construction containing cellulose fibers, which under normal circumstances does not burn. This base wrapper receives a plurality of zones, which are treated with a burn-promoting additive. In the zones treated with the burn-promoting additive, the tobacco part burns down until it reaches a non-treated paper zone and extinguishes. The zones differ in their BMI (Burn Mode Index) value. For burn-promoting additives, potassium citrate or an alkali metal salt-equivalent is used.

[0008] The cigarette paper described in EP 0 262 550 A also has varying zones, which differ in their combustibility. This cigarette paper has a base wrapper, which contains 30% calcium carbonate as filler and a portion of potassium citrate as a burn-promoting additive. To this base wrapper, encircling bands of a filler-free paper material are attached. The tobacco ember extinguishes when it reaches this filler-free paper zone

[0009] In U.S. Pat. No. 5,191,906, a cigarette paper is described that allegedly makes it possible to slow down the burning of a smoking rod between two puffs. To accomplish this, bands of an additional paper are glued to a paper base wrapper, which contains potassium citrate as a burn-promoting additive. The features of these zones are regulated in such a way, that the tobacco ember is not extinguished but continues to smolder slowly.

[0010] In U.S. Pat. No. 4,044,778, it is suggested to attach bands of alkali silicate, for example water glass (liquid, soluble sodium or potassium silicate) to the cigarette paper.

[0011] GB 528 190 A discloses cigarette papers, the ashes of which are stabilized. Non-combustible fibers are added to the cigarette paper. These fibers are made from glass, asbestos, or clay. According to this disclosure, the clay fibers are produced by extruding a Bentonite-Gel, which is subsequently dried so that the finished clay fibers have the microscopic, chemical, and heat resistant characteristics of mica. The heat resistance of the clay fibers is repeated several times in the patent. Because only burned clay is heat-proof, ceramic fibers of burned clay are added to the cigarette paper.

[0012] From U.S. Pat. No. 4,236,532 a cigarette paper is known that is designed to reduce pollutants in the tobacco smoke. In this invention, the cigarette paper is printed with pigments, which contain bentonite, among other things. Bentonite, however, because of its thixotropic characteristics, is a common additive to all printer colors. It is also known that bentonite absorbs foreign matter. Whether or not the cigarette paper disclosed in this patent reduces or extinguishes the smolder zone is not disclosed.

[0013] U.S. Pat. No. 4,805,644 discloses a cigarette paper that should reduce sidestream smoke. To accomplish this, fillers are added to the paper, which, according to the explicit specification in this patent, must be thermally stabile. This means that these fillers do not have a liquid phase during heating, otherwise they would transform. Furthermore, it is stated in this patent that the paper ashes have a normal appearance. However, the pigments used in the invention as burn inhibitors change the appearance of the ashes, as will be illustrated in the drawings.

[0014] The solutions described in the patents listed above could not, for various reasons, establish any practical importance. Some papers alter the taste, others the appearance, some disrupted the production, etc. There is still an urgent need for filter wrappers or mouth piece papers, which can not be set on fire by the tobacco ember, and at the same time do not produce health problems nor optical or taste problems. The presently used chemicals diammonim phosphate and polyaluminum chloride do not meet these conditions. There are health concerns with diammonium phosphate and polyaluminum chloride produces an acidulous taste when added in a quantity necessary for safe burn inhibition.

[0015] The elements boron and bromine, that is, compounds thereof, the flame-inhibiting characteristics of which are commonly known, can also be eliminated.

[0016] Adding to the burn problem is the fact that the mouth piece papers are printed with a cork-like pattern. The conventionally used printer ink contains iron-3-oxide as dye and nitro-cellulose as a bonding material. Both substances are good burn promoters so that unprinted paper has the desired features, but loses these features again once it is printed.

[0017] Tests with water-emitting fillers like aluminum hydroxide, plaster and satin white, which even contains 37% of crystal water, have also been unsuccessful.

SUMMARY OF THE INVENTION

[0018] It is therefore an object of the present invention to provide a paper for producing filter wrappers and mouth pieces that do not smolder and do not cause health, taste or optical problems, regardless of whether or not it is printed.

[0019] Although, as stated above, the water-emitting minerals were not successful, and although the silicates cited in the conventional art above were not successful, it was found, surprisingly, that the water-emitting silicates do meet the set conditions. They remain neutral, alter neither taste nor optic, are easy to process, and can be obtained everywhere and at a reasonable price.

[0020] Phyllosilicates were found to be particularly suitable, and particularly water-absorbing three-layer silicates, such as smectites.

[0021] Particularly suited among the mineral group of the smectites are montmorillonite, beidellite, hectorite and/or saponite.

[0022] Their ideal composition is as follows:

[0023] Montmorillonit: (Na⁺)_o,8[(Al_3.2Mg_0.8)(OH)₄Si₈O₂₀]^0.8−

[0024] Hektorit: (Na⁺)_o,8[(Mg_5.2Li_0.8)(OH, F)₄Si₈O₂₀]^0.8−

[0025] These contain adsorptively bound water, which they do not lose during the paper manufacturing process, not even while passing through the drying zone of the paper machine; rather, they dispose of the adsorptively bound water only at higher temperatures, but clearly below the temperature of the tobacco ember and at such a speed that the extinguishing effect takes place early enough.

[0026] As the literature on this subject shows, layered silicates have already been added to the cigarette paper to reduce sidestream smoke. Bentonites in particular have been suggested for this purpose. It was found, however, that for meeting the object of this invention, bentonites are not unsuited.

[0027] In a preferred embodiment of this invention, the pigments have a specific surface area according to BET between 5 and 1000 m²/g and/or a pore volume between 0.01 and 1.0 ml/g. Thereby the faster the adsorptively bound water is released, the better the burn-inhibiting effect is.

[0028] Furthermore, it is easily understood that the more water that is adsorptively bound, the better the burn-inhibiting effect is. In particular, those silicates with a water absorption capacity of between 1 and 60% have been found to be of optimal suitability

[0029] As mentioned previously, the layered silicates of this invention only dispose of the adsorptively bound water at temperatures, which are higher than the temperatures in the drying zone of the paper machine. On the other hand, they should dispose of the adsorptively bound water early and quickly enough so that the burn-inhibiting effect takes place on time. Optimal effect in this sense show pigments, which form DTA (Differential Thermal Analysis) peaks for the disposal of adsorptively bound water at a temperature range of between 100 and 200° C.

[0030] The burn-inhibiting features of the pigments of this invention are so good, that the paper can be produced with a relatively high air permeability. Values of 0,5 up to 20 Coresta Units (CU) have no influence on the burn-inhibiting effect. In addition, the mouth piece papers can be perforated electrostatically or by laser without causing production problems as have been found, for example, with paper filled with china (porcelain) clay.

[0031] Depending on the type and the origin of the pigments, they can either be produced synthetically or be of natural origin. Thus, a sufficiently large selection is available.

[0032] Furthermore, the processability of the pigments of this invention is outstanding. They can already be mixed in with the paper mass, before it is put onto the paper machine. In this scenario, the pigments are evenly distributed in the paper.

[0033] The burn-inhibiting effect can also be achieved by distributing the pigments evenly over the paper surface. This can be done either on the paper machine itself or in a special processing step.

[0034] Additionally, it is possible to distribute the pigments of this invention in or on the paper in zones, that is, in bands. These zones can be manufactured in the paper machine. It is not necessary to adhere strips of a second paper.

[0035] Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.