Method for applying register marks to wrapping paper for smoking articles

Abstract

The invention relates to a method for marking a wrapping paper for smoking articles, comprising the following steps: (A) providing a wrapping paper for smoking articles, and (B) producing register marks on the wrapping paper by treating the surface of the wrapping paper with laser radiation having an energy density y in J-m-2, to which the following applies: y=k.Math.x, whereby x is the enthalpy of combustion per volume of the wrapping paper in J.Math.m.sup.−2.Math.μm.sup.−1, and k is at least −8 μm and at most −1 μm.

Claims

1. Method for marking a wrapping paper for smoking articles, comprising the following steps: (A) providing a wrapping paper for smoking articles, wherein the wrapping paper comprises pulp fibers, (B) producing register marks on the wrapping paper by means of at least the following step (B.3) treating the surface of the wrapping paper with laser radiation with an energy density y in J.Math.m.sup.−2, for which y=k.Math.x holds, wherein x is the enthalpy of combustion per volume of the wrapping paper in J.Math.m.sup.−2.Math.μm.sup.−1, wherein k is at least −8 μm and at most −1 μm, wherein either in a step (C), regularly repeating structures are produced on the wrapping paper, so that each structure is located at a fixed distance in the machine direction relative to at least one register mark, or a wrapping paper is provided in step (A) which has regularly repeating structures in the machine direction, and the register marks are produced on the wrapping paper in step (B) such that each register mark is located at a fixed distance in the machine direction relative to at least one structure, wherein at least one section of the register mark has an extension in the machine direction of at least 0.01 mm.

2. Method according to claim 1, for which: −5.0 μm≤k≤4.0 μm holds.

3. Method according to claim 1, wherein the pulp fibers are entirely or partially formed by wood pulp fibers from spruce, pine or larch, or from birch, beech or eucalyptus, or mixtures thereof.

4. Method according to claim 1, wherein the pulp fibers are partially or entirely from flax, hemp, sisal, jute, aback cotton, esparto grass or mixtures thereof, and/or wherein the wrapping paper contains pulp fibers from regenerated cellulose.

5. Method according to claim 1, wherein in step (A), a wrapping paper is provided which contains at least 50% by weight of pulp fibers in relation to the total mass of the wrapping paper.

6. Method according to claim 1, wherein a wrapping paper is provided in step (A) which contains a filler, wherein the filler is an oxide, hydroxide, carbonate, hydrogen carbonate or silicate, or a mixture thereof.

7. Method according to claim 6, wherein the filler is entirely or partially formed by calcium carbonate, magnesium oxide, magnesium hydroxide, aluminum hydroxide, titanium dioxide, talc, kaolin, or mixtures thereof, and/or wherein at least a part of the filler is of a type such that it changes its color irreversibly under the action of laser radiation.

8. Method according to claim 6, wherein a wrapping paper is provided in step (A) which contains filler in an amount of at least 10% by weight and at most 50% by weight, each in relation to the total mass of the wrapping paper.

9. Method according to claim 1, wherein a wrapping paper is provided in step (A) which contains at least one burn additive, selected from the group consisting of citrates, malates, tartrates, acetates, nitrates, succinates, fumarates, gulconates, glycolates, lactates, oxalates, salicylates, α-hydroxy caprylates, phosphates, chlorides and hydrogen carbonates and mixtures thereof.

10. Method according to claim 9, wherein the content of burn additives in the wrapping paper provided in step (A) is at least 0.5% by weight and at most 3.0% by weight, each in relation to the mass of the entire wrapping paper.

11. Method according to claim 1, wherein in step (A), a wrapping paper is provided which comprises burn-retarding substances, selected from the group consisting of sodium chloride, magnesium chloride, calcium chloride, monoammonium phosphate, diammonium phosphate, boric acid and mixtures thereof.

12. Method according to claim 1, wherein a wrapping paper is provided in step (A) which has a basis weight of between 20 g/m.sup.2 and 50 g/m.sup.2.

13. Method according to claim 1, wherein a wrapping paper is provided in step (A) which has a thickness of between 15 μm and 100 μm.

14. Method according to claim 1, wherein the repeating structures are formed by one or more of the following structures: printed, embossed or die-cut features on the wrapping paper, which should appear at a fixed position on the smoking article manufactured from this wrapping paper, water marks, wire marks or verge lines, bands printed on the wrapping paper, which serve for self-extinguishing of a smoking article manufactured therefrom, perforations, which serve for dilution of an aerosol flowing through the smoking article, regular, local changes in the composition of the wrapping paper in the machine direction.

15. Method according to claim 1, wherein said repeating structures are formed before step (A) or in step (A) in a process which comprises one or more of the steps of printing, embossing, perforating, die-cutting, soaking, impregnating, coating or spraying, or combinations thereof.

16. Method according to claim 1, wherein step (B.3) comprises the following sub-steps: (B3.1) selecting the energy density of the laser radiation based on the enthalpy of combustion per volume of the wrapping paper, and (B3.2) marking the wrapping paper by using laser radiation with the energy density selected in step (B3.1), so that regularly repeating register marks are produced on the wrapping paper in the machine direction.

17. Method according to claim 16, wherein the enthalpy of combustion of the wrapping paper is determined by measurement with a calorimeter or wherein the enthalpy of combustion of the wrapping paper is calculated or estimated based on information with respect to the type and amount of the components of the wrapping paper and information with respect to the enthalpy of combustion of the individual components.

18. Method according to claim 1, wherein the laser radiation used in step (B.3) has a wavelength of at least 8 μm and at most 12 μm.

19. Method according to claim 18, wherein the laser radiation used in step (B.3) is produced by a CO.sub.2 laser.

20. Method according to claim 1, wherein in step (B.3), register marks in the shape of continuous or discontinuous lines are formed which extend at least approximately orthogonally to the machine direction.

21. Method according to claim 1, wherein at least one section of the register mark has an extension in the machine direction of at least 0.10 mm, and wherein the extension of the register marks in the machine direction is at most 3.00 mm.

22. Method according to claim 1, wherein the extension of the register marks, which are produced in step (B.3), orthogonally to the machine direction is at least 0.20 mm.

23. Method according to claim 1, wherein the register marks are produced on a wide reel of the wrapping paper, which is subsequently cut into narrower reels, and wherein the register marks are arranged on the wrapping paper such that in a direction viewed orthogonally to the machine direction, there is at least one register mark on each of the narrow reels, wherein the extension of the register marks in the direction orthogonally to the machine direction is at most one third of the width of the narrow reel, and/or wherein the register marks are arranged and the cutting process is controlled such that the register marks are not cut through and thus are not located at the edge of the narrow reels.

24. Method according to claim 1, wherein the register marks are formed on that side of the wrapping paper which is on the outside of a smoking article to be manufactured therefrom.

25. Method according to claim 1, wherein the position of the register marks relative to the structures on the wrapping paper is selected such that the register marks are not visible during normal use of the smoking article manufactured from the wrapping paper.

26. Method according to claim 25, wherein the smoking article is formed by a filter cigarette and wherein the register marks are positioned on the wrapping paper such that they are in an area on the filter cigarette in which the tipping paper overlaps the rod of smokable material and thereby covers the register marks on the wrapping paper.

27. Method according to claim 1, wherein in step (A), the wrapping paper is firstly manufactured on a conventional paper machine and wound up, the wrapping paper is unwound on a separate device, the register marks in step (B) are produced on the wrapping paper, the wrapping paper marked thereby is wound up and then in step (C), on a further device, the structures are applied to the marked wrapping paper.

28. Method according to claim 1, wherein steps (B) and (C) are carried out on the same device, wherein the device comprises a marking unit which carries out step (B), and comprises a device for the application of the structures in accordance with step (C) and wherein the positions of the register marks and the structures to be applied are synchronized with each other by means of a register control using the register marks detected by a sensor.

29. Method according to claim 1, wherein k is at least −6.5 μm and at most −2.5 μm.

30. Method according to claim 1, wherein said step (B) of generating register marks on the wrapping paper further comprises one or both of a step (B.1) of removing material from the wrapping paper and a step (B.2) of mechanical modification of the wrapping paper.

31. Method according to claim 30, wherein for each of the steps (B.1), (B.2) and (B.3) it holds that, if at all, only substances are added to the wrapping paper which are already present in the wrapping paper in step (A) or which are generated during smoking of a smoking article manufactured from the wrapping paper.

32. Method according to claim 30, wherein at least one opening in the wrapping paper is produced in step (B.1) by die-cutting, perforating or cutting.

33. Method according to claim 32, wherein in the case of perforating or cutting, mechanical perforation or cutting tools or a laser are used.

34. Method according to claim 30, wherein in step (B.1), material is removed from the surface of the wrapping paper so that the transparency of the wrapping paper is increased in this area, but no opening is formed.

35. Method according to claim 30, wherein in step (B.1), register marks are produced, in which the outermost borders in the cross direction have a radius of curvature which is at least 0.1 mm.

36. Method according to claim 30, wherein the wrapping paper is embossed or compressed in step (B.2) such that the transparency of the wrapping paper increases locally.

37. Method according to claim 36, wherein embossing or compressing of the wrapping paper comprises exerting mechanical pressure between two rolls provided with a corresponding pattern, which produce a register mark in the wrapping paper.

38. Method according to claim 36, wherein for the formation of the register marks, the wrapping paper is embossed with a line load which is 70 N/mm to 130 N/mm.

39. Method according to claim 36, wherein embossing is carried out at a higher moisture content of the paper of 5% by weight to 10% by weight with respect to the mass of the wrapping paper.

40. Method according to claim 36, wherein the register marks in step (B.2) are formed during the manufacture of the wrapping paper, wherein the not yet completely finished wrapping paper is locally compressed in the press section or on a wire in the paper machine by means of a cylinder provided with a corresponding pattern.

41. Method according to claim 30, wherein the extension of the register marks which are produced in step (B.1) is at least 0.20 mm and at most 3.00 mm.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 shows a wrapping paper, to which structures and register marks have been applied.

(2) FIG. 2 shows a wrapping paper, on which register marks are formed as openings.

(3) FIG. 3 illustrates the manufacture of wrapping paper with a paper machine, and the potential production of marks in the wire section or press section.

(4) FIG. 4 illustrates a process in which the register marks and the structures on a wrapping paper are formed in the same device.

(5) FIG. 5 illustrates a process in which a prepared wrapping paper already has structures and register marks are produced on the wrapping paper such that they are located at a fixed distance in the machine direction relative to the corresponding structures.

(6) FIG. 6 illustrates a similar process to that of FIG. 5, which is suitable when register marks are to be formed independently of the movement of the wrapping paper.

DESCRIPTION OF PREFERRED EMBODIMENTS

(7) The method according to the invention will be explained in more detail below by way of preferred exemplary embodiments.

(8) FIG. 3 shows the manufacture of the wrapping paper 150 according to the invention by means of a paper machine running in the machine direction 151. In accordance with exemplary FIG. 3, the paper machine comprises a section 100 of the head box, a wire section 110, a press section 120, a drying section 130 and a winding section 140. From a head box 101, an aqueous fiber suspension or a fiber/filler suspension flows onto a running wire 111, on which a wrapping paper 150 is formed by de-watering. The wrapping paper 150 then runs through a press section 120 in which pressure is exerted on the wrapping paper 150, typically by using felt-covered roll pairs 121, thereby further de-watering the wrapping paper iso. Then the wrapping paper 150 runs through the drying section 130, in which it is contacted with at least one, but preferably more, heated drying cylinders 131 and the water is removed by evaporation, so that the wrapping paper 150 reaches a moisture content of 3% to 10%. Finally, the wrapping paper 150 is wound up on a reel 141.

(9) In order to produce register marks in accordance with step (B.2), a patterned cylinder 112 can, for example, be provided in the wire section 110 of the paper machine, which exerts pressure on the still moist wrapping paper 150 and thereby displaces material in the wrapping paper 150 and produces a pattern of higher transparency. Alternatively and in order to produce register marks in accordance with step (B.2), a pair of rolls 122 can, for example, be provided in the press section 120, which transfers a pattern on the rolls 122 onto the wrapping paper 150 by mechanical pressure. Preferably, the pair of rolls is the last pair of rolls in the press section in the machine direction.

(10) FIG. 4 shows an exemplary manufacturing process for the wrapping paper according to the invention, in which in step (A) according to the invention, a wrapping paper 200, which does not yet have any structures, is provided on a reel 201 and is running in the machine direction 208. In step (B), register marks are produced on the wrapping paper 200 by means of a marking unit 202. In the embodiment shown, the marking unit 202 is formed by a laser, by means of which laser radiation treats the wrapping paper 200 in a step (B.3). The detection unit 205, for example an optical sensor, detects the register marks produced by the marking unit 202 and acts on a register control such that the structures produced by a device 206 on the wrapping paper 200 are located at a fixed distance from the register marks. In the embodiment shown, the device 206 can, for example, be a printing device, by means of which bands are printed on the wrapping paper 200, which serve for self-extinguishing. The register control can be carried out here by a guide roller 203 which is movable in the direction of the arrow 204, which lengthens or shortens the length of the path between the marking unit 202 and device 206 and thereby positions the register marks and the structures relative to each other. Preferably, the detection unit 205 can also be located behind the device 206, as indicated by dashed lines in FIG. 4, because then the position of the register marks and the structures on the wrapping paper 200 relative to each other can be determined directly and control of the relative position is possible. In a final step, the wrapping paper 200 is wound up on a reel 207.

(11) FIG. 5 shows an exemplary manufacturing process according to the invention, in which the wrapping paper provided in step (A) already has structures on it. The wrapping paper 300 is provided here on a reel 301 and runs in the machine direction 308 firstly through a register control, which, for example by means of a guide roll 303 that is movable in the direction of arrow 304, can lengthen or shorten the length of the paper web between a roll 301 and a marking unit 302 (in the embodiment shown, again a laser), so that the register marks produced by the marking unit 302 are precisely located at a fixed distance relative to the structures present on the wrapping paper 300. A detection unit 305, which can be arranged before or after the marking unit, thereby detects at least the structures and acts on the position of guide roll 303 such that a fixed distance between the register marks and the structures is generated on the wrapping paper 300. Preferably, the detection unit 305 is located after the marking unit 302, because at this position, the register marks as well as the structures can be detected and their position relative to each other can be determined directly and thus controlled. If the detection unit 305 is located before the marking unit 302, the distance between detection unit 305 and marking unit 302 is preferably as small as possible. Finally, the wrapping paper 300 is wound up on a reel 307.

(12) FIG. 6 shows a further exemplary embodiment of the manufacturing process according to the invention. In a step (A), a wrapping paper 400 is provided which already has structures on it, in the form of a reel 401 and runs through the process in the machine direction 408. A detection unit 405, which is located before or after the marking unit 402, detects the structures and directly controls the marking unit 402 (laser), so that the register marks produced by the marking unit 402 are located at a fixed distance relative to the structures on the wrapping paper 400. This exemplary embodiment is then preferably employed when the production of the register marks by the marking unit 402 can be triggered independently of the movement of the wrapping paper. Preferably, this will be possible by marking with a laser in accordance with step (B.3). The detection unit 405 can also preferably be located after the marking unit 402 so that the position of the register marks and structures relative to each other can be determined directly, and thus control of this position is possible. Finally, the wrapping paper 300 is wound up on a reel 407.

(13) In a first step (A) of the method according to the invention, four different wrapping papers with the properties of Table 1 were provided, wherein apart from pulp fibers, precipitated calcium carbonate as filler material and tripotassium citrate or mixtures of trisodium citrate and tripotassium citrate were used as burn additives. The papers were manufactured on a conventional Fourdrinier machine, as is schematically shown in FIG. 3 in a highly simplified manner.

(14) TABLE-US-00001 TABLE 1 Properties of the wrapping papers Basis Weight Thickness Pulp Filler Citrate Paper g/m.sup.2 μm Fibers Content Content P1 30.0 54.0 % 62.2 36.0 1.80 g/m.sup.2 18.66 10.80 0.54 P2 45.0 65.0 % 55.0 45.0 0.00 g/m.sup.2 24.75 20.25 0.00 P3 25.0 43.0 % 67.0 32.0 1.00 g/m.sup.2 16.75 8.00 0.25 P4 26.0 47.0 % 70.0 29.0 1.00 g/m.sup.2 18.20 7.54 0.26

(15) As an example of the process step (B.1), a reel with a width of 106 mm was cut from each wrapping paper and register marks were produced on a die-cutting device. The register marks were circular openings with a diameter of 0.5 mm. Several such openings were located next to each other in the cross direction, wherein the center of the first opening viewed from the edge in the cross direction was at a distance of 13.25 mm from the edge and the center of each further opening was spaced 26.5 mm from the center of the preceding opening, viewed in the cross direction. The reel was then cut into bobbins each with a width of 26.5 mm, as is typical for the manufacture of cigarettes with a diameter of about 8 mm. Thereby, in the cross direction the openings were located in the center of each bobbin. The repeat rate of the openings in the machine direction was adapted to the specific manufacturing process for the cigarettes. In this specific embodiment, filter cigarettes were subsequently manufactured with a tobacco rod with a length of 54 mm. To this end, the tobacco rod was firstly cut into pieces each with a length of 54 mm. The pieces were separated in the longitudinal direction and a double-length cigarette filter was added between each two of these pieces. A double-width tipping paper was glued around the filter and a part of each of the two tobacco rod pieces, so that a double cigarette was produced, connected at the mouth end. In a final step, the double cigarette was cut in the middle. From this manufacturing process, an arrangement of the openings in the machine direction results in which, starting from the center of the first opening in the machine direction, the next center of an opening was at a distance of 5 mm and then starting again from the first opening, the next but one center was at a distance of 108 mm, corresponding to double the length of the tobacco rod on the cigarette.

(16) By means of this arrangement, the openings are located under the tipping paper, and were thus not visible. This also avoids cutting the openings during the manufacture of the cigarettes.

(17) The openings could be reliably detected by means of a light barrier and further processing of the wrapping paper to cigarettes was trouble-free, which shows that the reduction in the tensile strength was sufficiently low.

(18) As an example of the process step (B.2), a continuous line in the cross direction with a width of 0.25 mm was embossed on each of the wrapping papers. Because of the greater thickness of the wrapping paper P2, a greater force of about 115 N/mm could be used than for the papers P1, P3 and P4, for which the line load for embossing was between 90 N/mm and 100 N/mm. For embossing, a higher moisture content of the wrapping paper of 5% by weight to 10% by weight in relation to the mass of the wrapping paper was selected, because then the embossing is more clearly visible and more easily detectable. As an alternative to the line pattern a dot pattern was also embossed at similar line loads.

(19) The embossed register marks, the line pattern as well as the dot pattern, were easily visible with the naked eye on all wrapping papers, so that there was no doubt that they could also be detected by sensors at higher speeds.

(20) An example of the process step (B.3) in the preferred embodiment comprising the steps (B3.1) and (B3.2) is described below.

(21) In order to determine the energy density of the laser radiation, firstly, the enthalpy of combustion of the papers was estimated. For this purpose, the enthalpy of combustion of cellulose and citric acid are known in accordance with Table 2 and for calcium carbonate, Table 2 shows the enthalpy of the reaction CaCO.sub.3.fwdarw.CaO+CO.sub.2.

(22) TABLE-US-00002 TABLE 2 Enthalpies for the determination of the enthalpy of combustion Enthalpy Molar Enthalpy kJ/mol Mass g/mol kJ/g Cellulose −2828 162.14 −17.44 Calcium Carbonate +178 100.08 +1.78 Citric Acid −1972 192.13 −10.26

(23) From these values, the enthalpy of complete combustion of the wrapping paper can be estimated, by multiplying for all components the mass per unit area present in the wrapping paper by the enthalpy per mass and summing, wherein the citrate content of Table 1 has also been converted into the citric acid content. The enthalpy per unit area thus obtained was divided by the thickness. The results are provided in Table 3.

(24) TABLE-US-00003 TABLE 3 Estimated enthalpies of combustion for the wrapping papers Paper Enthalpy of Combustion kJ .Math. m.sup.−2 .Math. μm.sup.−1 P1 (−17.44 × 18.7 + 1.78 × 10.8 − −5.75 10.26 × 0.37)/54 P2 (−17.44 × 24.7 + 1.78 × 20.3 − −6.07 10.26 × 0.0)/65 P3 (−17.44 × 16.7 + 1.78 × 8.0 − −6.48 10.26 × 0.16)/43 P4 (−17.44 × 18.2 + 1.78 × 7.5 − −6.51 10.26 × 0.19)/47

(25) The marking of the papers was carried out with a CO.sub.2 laser with a nominal power of 25 W, emitting a continuous laser beam with a wavelength of 90.2 μm to 10.9 μm. The laser was operated at 70% of its nominal power, that is with 17.5 W.

(26) The marking pattern was a continuous line in the cross direction of the wrapping paper with a width of 0.25 mm, which was produced with different speeds of 1 m/s to 7 m/s on the papers P1, P2, P3 and P4. From these technical data, the theoretical energy densities provided in Table 4 resulted by calculation, dividing the laser power (17.5 W) by the speed and the line width. If a function y=f(x)=k.Math.x is taken as a basis for the relationship between the enthalpy of combustion per unit volume of the wrapping paper x in kJ.Math.m.sup.−2 μm.sup.−1 and the energy density of the laser beam y in kJ.Math.m.sup.−2, then a proportionality factor k can be calculated for each of the wrapping papers P1 to P4 at each of the different speeds. The results fork are also shown in Table 4.

(27) TABLE-US-00004 TABLE 4 Proportionality factor k Energy Proportionality Factor K [μM] Speed Density P1 P2 P3 P4 m/s kJ .Math. m.sup.−2 μm 1 70.0 −12.2 −11.5 −10.8 −10.8 2 35.0 −6.1 −5.8 −5.4 −5.4 3 23.3 −4.1 −3.8 −3.6 −3.6 4 17.5 −3.0 −2.9 −2.7 −2.7 5 14.0 −2.4 −2.3 −2.2 −2.2 6 11.7 −2.0 −1.9 −1.8 −1.8 7 10.0 −1.7 −1.6 −1.5 −1.5

(28) The wrapping papers were examined with respect to their suitability for the manufacture of smoking articles and their influence on the taste of a smoking article.

(29) In all of the experiments, the register mark was sufficiently strong in order to reliably detect the register mark with a simple sensor on the wrapping paper running in the machine direction, however, at marking speeds of 6 m/s and 7 m/s, they were no longer strong enough for the register mark to be reliably detected on a wrapping paper running at high speed in the machine direction. Thus, k should not exceed the value of −1 μm and should preferably be less than −2 μm.

(30) On the other hand, the energy density was still sufficiently low for none of the wrapping papers to be perforated, so that solely based on the result of the marking, the values for k can also be substantially less than −12 μm.

(31) To investigate the influence on taste, several continuous lines in the cross direction were produced close to each other in the form of a 6 mm wide band on the wrapping paper and filter cigarettes were manufactured therefrom. The lines located close to each other thereby formed a 6 mm wide band in the circumferential direction of the cigarette. An investigation was carried out as to whether a perceptible difference in taste would result during smoking, if during a puff on the cigarette, the glowing cone moved from the untreated wrapping paper into the area of the band. For all of the smoking articles with wrapping papers that were manufactured at a speed of 1 m/s, that is values for k of about −11 μm, a negative influence on the taste was perceptible, while the other smoking articles were unaffected.

(32) Thus, this means that a value for k should preferably not fall below −8 μm, preferably it should not fall below −7 μm and particularly preferably it should not fall below −6.5 μm. For reasons of detectability of the register marks, the value for k should preferably not be greater than −1 μm, particularly preferably not greater than −2 μm, highly particularly preferably not greater than −2.5 μm. The best results regarding visibility of the register mark and taste of the smoking article resulted for marking speeds of 2 m/s to 3 m/s, that is, a value for k of −5.0 μm to −4.0 μm.

(33) Of course, the inclusion of further paper parameters, such as air permeability, transparency or brightness can further fine-tune the function y=f(x).

(34) On a printing machine with corresponding sensors and register control, a logo was printed on the wrapping paper, to confirm that it is possible to produce structures on the wrapping paper which are positioned at a fixed distance in the machine direction to the register register marks, as is provided in step (C) of the method according to the invention. As expected, this was possible without any problems, because the wrapping papers were not substantially changed in their mechanical properties, in particular in their tensile strength, by marking with the laser.