Heat-Resistant Wrapper Paper for Aerosol-Generating Articles

Abstract

The invention concerns a wrapper paper which is suitable for use on aerosol-generating articles and which comprises pulp fibers and a char-former, wherein the pulp fibers make up at least 70% and at most 95% of the mass of the wrapper paper and the char-former is contained in a concentration of at least 5% and at most 20% with respect to the mass of the wrapper paper and is present in a concentration in the wrapper paper such that the quotient r=R.sub.T/R.sub.o of the tensile strength R.sub.o, measured in accordance with ISO 1924-2:2008 under the conditions of ISO 187:1990, and of the tensile strength R.sub.T, measured in accordance with ISO 1924-2:2008 under the conditions of ISO 187:1990 after the wrapper paper has been exposed to a temperature of 230° C. for one minute, is at least 0.20 and at most 0.90.

Claims

1. Aerosol-generating article which comprises a wrapper paper and an aerosol-generating material, wherein the wrapper paper wraps the aerosol-generating material, wherein the wrapper paper comprises pulp fibers and a char-former, wherein the pulp fibers make up at least 70% and at most 95% of the mass of the wrapper paper and the char-former is contained in a concentration of at least 5% and at most 20% with respect to the mass of the wrapper paper and is present in a concentration in the wrapper paper such that the quotient r=R.sub.T/R.sub.o of the tensile strength R.sub.o, measured in accordance with ISO 1924-2:2008 under the conditions of ISO 187:1990, and of the tensile strength R.sub.T, measured in accordance with ISO 1924-2:2008 under the conditions of ISO 187:1990 after the wrapper paper has been exposed to a temperature of 230° C. for one minute, is at least 0.20 and at most 0.90.

2. Aerosol-generating article according to claim 1, in which the proportion of pulp fibers in said wrapping paper is at least 75% and at most 90%, each with respect to the mass of the wrapper paper.

3. (canceled)

4. (canceled)

5. Aerosol-generating article according to claim 1, in which the pulp fibers are sourced from coniferous trees to a proportion of at least 40% and at most 100% with respect to the mass of the pulp fibers.

6. Aerosol-generating article according to claim 1, in which the proportion of char-formers in the wrapper paper makes up at least 9% and at most 16% of the mass of the wrapper paper.

7. Aerosol-generating article according to claim 1, wherein the char-former is, a monoammonium phosphate, a diammonium phosphate, a triammonium phosphate, an ammonium polyphosphate or a mixture thereof, or wherein the char-former is at least partially formed by a guanyl urea phosphate, guanidine phosphate, phosphoric acid, a phosphonate, melamine phosphate, dicyandiamide, boric acid or borax.

8. Aerosol-generating article according to claim 1, wherein the tensile strength R.sub.T of the wrapper paper, after the wrapper paper has been exposed to a temperature of 230° C. for one minute is at least 8 N/15 mm and at most 50 N/15 mm.

9. (canceled)

10. Aerosol-generating article according to claim 1, in which the char-former is at least substantially uniformly distributed over at least 70%, of the surface area of the wrapper paper.

11. Aerosol-generating article according to claim 1, wherein the wrapper paper is combined with a further paper layer, so that the wrapper paper according to the invention faces the aerosol-generating material during the intended use and the further paper layer is disposed on the side facing away from the aerosol-generating material.

12. Aerosol-generating article according to claim wherein the further paper layer comprises pulp fibers and calcium carbonate particles, wherein the calcium carbonate particles make up at least 15% and at most 40% of the mass of the further paper layer.

13. Aerosol-generating article according to claim 1, wherein the wrapper paper further comprises at least one further component which is selected from the group consisting of filler materials, sizing agents, wet strength agents, additives, processing aids, humectants and flavors.

14. Aerosol-generating article according to claim 13, in which the proportion of filler materials is at least 0% and at most 20% each with respect to the mass of the wrapper paper.

15. Aerosol-generating article according to claim 1, wherein the filler material is selected from the group consisting of calcium carbonate, magnesium carbonate, titanium dioxide, magnesium dioxide, magnesium hydroxide, aluminum hydroxide, kaolin, talcum and mixtures thereof.

16. Aerosol-generating article according to claim 1, wherein the wrapper paper contains starch or a starch derivative or is coated with starch or a starch derivative, wherein the proportion of the starch or the starch derivative is at least 2% and at most 10% of the mass of the wrapper paper.

17. Aerosol-generating article according to claim 1, wherein said wrapper paper has a KIT level, determined in accordance with TAPPI T559 cm-12, which is at least 4 and at most 8.

18. Aerosol-generating article according to claim 1, wherein said wrapper paper has a basis weight of at least 15 g/m.sup.2 and at most 80 g/m.sup.2.

19. Aerosol-generating article according to claim 1, wherein said wrapper paper has a thickness of at least 25 μm and at most 100 μm.

20. Aerosol-generating article according to claim 1, wherein said wrapper paper has a tensile strength R.sub.o before a thermal load measured in the machine direction of at least 10 N/15 mm and at most 100 N/15 mm.

21. Aerosol-generating article according to claim 1, wherein the wet strength of said wrapper paper in accordance with ISO 12625-5:2016 in the machine direction is at least 1 N/15 mm and at most to N/15 mm.

22. Aerosol-generating article according to claim 1, wherein said wrapper paper has an air permeability of at least 0 cm.sup.3/(cm.sup.2.Math.min.Math.kPa) and at most 20 cm.sup.3/(cm.sup.2.Math.min.Math.kPa).

23. Aerosol-generating article according to claim 1, wherein said wrapper paper has an opacity of at least 40% and at most 80% and/or a brightness of at least 80% and at most 95%.

24. (canceled)

25. Aerosol-generating article according to claim 1, wherein the proportion of said char-former is higher on one side of the wrapper paper than on the other side and the side with the higher proportion of char-former faces the aerosol-generating material.

26.-39. (canceled)

40. Aerosol-generating article according to claim 1, wherein the tensile strength R.sub.T of the wrapper paper, after the wrapper paper has been exposed to a temperature of 230° C. for one minute is at least to N/15 mm and at most 40 N/15 mm.

Description

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0065] Some preferred embodiments of wrapper papers according to the invention will now be described.

[0066] A wrapper paper P1 according to the invention was manufactured on a fourdrinier paper machine. To this end, pulp fibers were suspended in water (step A) and refined in a refining unit (step B). Then the suspension was applied to a running wire (step C) and de-watered there in order to form a fiber web (step D). The fiber web was pressed (step E) in order to de-water it further and dried by contact with heated drying cylinders (step F). In a size press of the paper machine, the fiber web was impregnated over the entire surface on both sides with a composition comprising water and monoammonium phosphate (step F.1) and the fiber web was then dried by contact with heated drying cylinders. Finally, the fiber web was rolled up (step G) and wrapper paper P1 according to the invention was obtained.

[0067] The amount of pulp fibers was selected so that about 87% of the mass contained in the wrapper paper P1 was pulp fibers. The composition in step F.1 comprised water and monoammonium phosphate and was chosen together with the settings of the size press such that the amount of monoammonium phosphate in the wrapper paper after step G was about 7%. It can be assumed that the distribution of the monoammonium phosphate in the wrapper paper P1 over the thickness was essentially homogeneous.

[0068] A wrapper paper P2 according to the invention was manufactured from the wrapper paper according to the invention P1, by unrolling the reel of wrapper paper P1 and printing a composition comprising water and monoammonium phosphate over the full surface on one side of the wrapper paper in a roto-gravure printing unit (step F.3). Then the wrapper paper was dried by hot-air drying and rolled up again (step G). The composition in step F.3 was chosen together with the settings of the roto-gravure printing unit and in particular with the geometry of the printing cylinder was chosen such that in the finished wrapper paper P2, a total of 12.5% of the mass of the wrapper paper was formed by monoammonium phosphate. An inhomogeneous distribution of the monoammonium phosphate in the wrapper paper was obtained in this manner, so that the content of monoammonium phosphate was higher on the printed side than on the other side.

[0069] In wrapper paper P2, 82% of the mass was formed by pulp fibers.

[0070] A wrapper paper Z1 not according to the invention, comprising 70% pulp fibers and 29% precipitated calcium carbonate, but without char-former was used as comparative example.

[0071] In addition, a wrapper paper Z2 not according to the invention comprising 90% pulp fibers and 10% sodium polyphosphate, (NaPO.sub.3).sub.n as char-former was used as comparative example. To obtain a further wrapper paper P3, the wrapper paper Z1 not according to the invention was glued to the wrapper paper according to the invention P2 to form a two-layered structure in a manner such that the side of the wrapper paper P2 with the higher content of monoammonium phosphate was facing away from the wrapper paper Z1.

[0072] The data for the wrapper papers P1 and P2 according to the invention, the two-layered structure P3 and the comparative examples Z1 and Z2 not according to the invention were determined in accordance with the routine standards.

[0073] For the determination of the tensile strength after thermal load R.sub.T, the wrapper papers P1, P2, P3 and Z1, Z2 were stored in a drying oven heated to 230° C. for one minute. Then they were conditioned in accordance with ISO 187:1990 and the tensile strength was measured in accordance with ISO 1924-2:2008.

[0074] From the initial tensile strength R.sub.o. and the tensile strength R.sub.T after thermal load, the quotient r=R.sub.T/R.sub.o was determined in order to characterize the thermal resistance.

[0075] All data for the wrapper papers P1, P2, P3 and Z1, Z2 can be found in Table 1.

TABLE-US-00001 TABLE 1 P1 P2 P3 Z1 Z2 Basis Weight g/m.sup.2 28.8 31.9 72.2 29 30.3 Thickness μm 46.4 46.4 79.2 45.3 47.3 Tensile N/15 mm 30.4 36.0 65.7 15.2 32.7 Strength R.sub.o Tensile N/15 mm 16.7 12.1 27.2 14.3 6.3 Strength R.sub.T r = R.sub.T/R.sub.o 0.55 0.34 0.41 0.94 0.19 Wet Strength N/15 mm 3.0 3.0 10.1 2.5 3.1 Air cm.sup.3/(cm.sup.2 .Math. <20 <20 <20 60 <20 Permeability min .Math. kPa) Opacity % 44.8 41.8 41.2 Brightness % 87.4 88.6 88.6

[0076] Table 1 shows that for the wrapper papers P1 and P2 according to the invention, as well as for the two-layered structure P3 containing the wrapper paper P2 according to the invention, the thermal load reduces the tensile strength by 34% to 55%. For the comparative example Z1 not according to the invention, which does not contain char-former, the tensile strength is hardly reduced by the thermal load and is still about 94% of the initial tensile strength. For the comparative example Z2 not according to the invention, which contains sodium polyphosphate as char-former, the tensile strength after thermal load is only about 19% of the initial tensile strength and also the absolute value of 6.3 N/15 mm is too low to be able to remove an aerosol-generating article manufactured therefrom from the heating device after use without problems.

[0077] The wrapper papers P1 and P2 according to the invention and the two-layered structure P3 all exhibit an acceptable reduction of the tensile strength. But it is noticeable, in comparison to the wrapper papers P1 and P2 according to the invention, that the higher content of monoammonium phosphate in wrapper paper P2 damages the fibers more and reduces the tensile strength after thermal load more severely.

[0078] In addition to not too strong a reduction of the tensile strength, the flame-retardant effect is also of importance. To test the flame-retardant effect, aerosol-generating articles, which are intended for use in a heating device, were manufactured from the wrapper papers P1/P2 according to the invention, the two-layered structure P3 and the comparative examples Z1 and Z2 not according to the invention. The manufacture of the aerosol-generating articles was without any problems for all wrapper papers. When attempting to light the aerosol-generating article like a cigarette with a lighter, it became immediately clear that the comparative example Z1 not according to the invention had no flame-retardant effect. The aerosol-generating article manufactured therefrom could be lit without problems. Despite the longer action of the flame of the lighter, the aerosol-generating articles with the wrapper papers P1/P2 according to the invention, the two-layered structure P3 and the comparative example Z2 not according to the invention could not be lit such that combustion or a stable smoldering process could be started. It was also not possible to smoke these aerosol-generating articles according to a standardized process. With regards to the flame-retardant effect, the wrapper paper according to the invention P2 proved slightly better than P1, which indicates that an uneven distribution of the char-former over the thickness of the wrapper paper can contribute to an enhancement of the flame-retardant effect.

[0079] The two-layered structure P3 was a laminate of the wrapper paper P2 according to the invention and the comparative example Z1 not according to the invention and after use of the aerosol-generating article manufactured therefrom showed significantly less discoloration than the aerosol-generating articles with P1 and P2. The wrapper paper Z1 thus fulfilled its function of covering the discoloration of wrapper paper P2.

[0080] An influence on the taste of the aerosol-generating articles could not be found.

[0081] The wrapper papers according to the invention are thus very well suited for use in aerosol-generating articles and, along with good biological degradability, have a strength after heating and a flame-retardant effect in a better combination than comparable wrapper papers in the prior art.