IMPROVED WRAPPING PAPER HAVING A LOW DIFFUSION CAPACITY

Abstract

The invention relates to a wrapping paper for a smoking article, said wrapping paper comprising long-fibre pulp, short-fibre pulp, and inorganic filler, wherein: at least a portion of the long-fibre pulp is ground and the ground long-fibre pulp constitutes at least 15% and at most 70% of the mass of the wrapping paper, at least a portion of the short-fibre pulp is ground and the ground short-fibre pulp constitutes at least 5% and at most 80% of the mass of the wrapping paper, and the ground short-fibre pulp has a freeness value of at least 20? SR and at most 60? SR; the short-fibre pulp as a whole constitutes at least 10% and at most 80% of the mass of the wrapping paper, at least 5% and at most 45% of the mass of the wrapping paper is constituted by one or more inorganic fillers; the mass per unit area of the wrapping paper is at least 15 g/m.sup.2 and at most 45 g/m.sup.2; the diffusion capacity of the wrapping paper is at least 0.05 cm/s and at most 0.5 cm/s; and the standard deviation of the diffusion capacity of the wrapping paper is at most 0.05 cm/s. The invention also relates to an associated manufacturing method and to a smoking article making use of said wrapping paper.

Claims

1. Wrapping paper for a smoking article, which comprises long-fiber pulp, short-fiber pulp, and inorganic filler material, wherein at least a part of the long-fiber pulp is refined and the refined long-fiber pulp makes up at least 15% and at most 70% of the mass of the wrapping paper, wherein at least a part of the short-fiber pulp is refined and the refined short-fiber pulp makes up at least 5% and at most 80% of the mass of the wrapping paper, and the refined short-fiber pulp has a degree of refining of at least 20? SR and at most 60? SR, wherein the short-fiber pulp in total makes up at least 10% and at most 80% of the mass of the wrapping paper, wherein at least 5% and at most 45% of the mass of the wrapping paper is formed by one or more inorganic filler materials, wherein the basis weight of the wrapping paper is at least 15 g/m.sup.2 and at most 45 g/m.sup.2, and wherein the diffusion capacity of the wrapping paper is at least 0.05 cm/s and at most 0.5 cm/s, and wherein the standard deviation for the diffusion capacity of the wrapping paper is at most 0.05 cm/s.

2. Wrapping paper according to claim 1, in which the degree of refining of the refined long-fiber pulp, measured in accordance with ISO 5267-1:1993, is at least 88? SR and at most 94? SR.

3. (canceled)

4. (canceled)

5. Wrapping paper according to claim 1, in which the degree of refining of the refined short-fiber pulp, measured in accordance with ISO 5267-1:1993, is at least 25? SR and at most 50? SR.

6. (canceled)

7. Wrapping paper according to claim 1, in which the proportion of the short-fiber pulp makes up at least 30% and at most 75% of the mass of the wrapping paper.

8. Wrapping paper according to claim 1, in which the inorganic filler material makes up at least 10% and at most 35% of the mass of the wrapping paper.

9. (canceled)

10. (canceled)

11. Wrapping paper according to claim 1, in which the diffusion capacity, measured in accordance with CRM 77, is at least 0.1 cm/s and at most 0.39 cm/s.

12. Wrapping paper according to claim 1, in which the standard deviation for the diffusion capacity is at least 0.005 cm/s and at most 0.03 cm/s, wherein the standard deviation is determined by measurement of the diffusion capacity in accordance with CRM 77 on at least 10 randomly selected positions on the wrapping paper.

13. Wrapping paper according to one claim 1, onto which either no film-forming composition has been applied, or onto which a film-forming composition which contains starch, starch derivatives, cellulose derivatives, alginates or other film-forming polymers is applied to the entire surface.

14. Wrapping paper according to claim 1, the air permeability of which, measured in accordance with ISO 2965:2019 at a pressure difference of 1 kPa, is at least 1 cm.sup.3/(cm.sup.2.Math.min) and at most 25 cm.sup.3/(cm.sup.2.Math.min).

15. (canceled)

16. (canceled)

17. (canceled)

18. Wrapping paper according to claim 1, the thickness of which, measured in accordance with ISO 534:2011, at least 22 ?m and at most 60 ?m.

19. (canceled)

20. (canceled)

21. Smoking article comprising an aerosol-generating material and a wrapping paper according to claim 1, wherein the wrapping paper wraps at least a part of the aerosol-generating material and forms a cylindrical rod.

22. Smoking article according to claim 21, which is formed by a cigarette.

23. Smoking article according to claim 21, in which the aerosol-generating material is only heated but not burned during intended use, wherein the smoking articles is intended to be heated electrically.

24. Process for manufacturing a wrapping paper for smoking articles, which comprises the steps A to E, I and J: Aproviding an aqueous suspension of unrefined long-fiber pulp, Bproviding an aqueous suspension of unrefined short-fiber pulp, Crefining at least a part of the long-fiber pulp in the suspension from step A to a first target value for the degree of refining, Drefining at least a part of the short-fiber pulp in the suspension from step B to a second target value for the degree of refining, Eforming a fiber web from at least the refined long-fiber pulp from step C, the refined short-fiber pulp from step D and inorganic filler material, and optionally unrefined long-fiber pulp and/or unrefined short-fiber pulp, Idrying the fiber web to obtain a wrapping paper, Jremoving the wrapping paper, wherein in step E, the amount of refined long-fiber pulp from step C is selected such that at least 15% and at most 70% of the mass of the wrapping paper in step J is formed by refined long-fiber pulp, wherein in step E, the amount of refined short-fiber pulp from step D is selected such that at least 5% and at most 80% of the mass of the wrapping paper in step J is formed by refined short-fiber pulp, wherein the short-fiber pulp in step D is refined to a degree of refining of at least 20? SR and at most 60? SR, wherein in step E, the total amount of short-fiber pulp is selected such that at least 10% and at most 80% of the mass of the wrapping paper in step J is formed by short-fiber pulp, wherein in step E, the amount of inorganic filler material is selected such that at least 5% and at most 45% of the mass of the wrapping paper in step J is formed by inorganic filler material, and wherein during the formation of the fiber web in step E, the amounts and proportions of refined long-fiber pulp, refined short-fiber pulp, inorganic filler material and optionally unrefined long-fiber pulp and/or unrefined short-fiber pulp are selected such that the wrapping paper of step J has the following properties: a basis weight of at least 15 g/m.sup.2 and at most 45 g/m.sup.2, a diffusion capacity of at least 0.05 cm/s and at most 0.5 cm/s, and a standard deviation for the diffusion capacity of at most 0.05 cm/s.

25. Process according to claim 24, which contains the following steps between the steps E and I: Fdrying the fiber web to obtain a preliminary wrapping paper, Gmeasuring the diffusion capacity of the preliminary wrapping paper from step F, Hchecking whether the absolute difference between the diffusion capacity measured in step G and a target value exceeds a pre-defined threshold and, if this is the case, adapting the manufacturing process by at least one of the following adaptation steps H.1 to H.6: H.1changing the first target value for the degree of refining in step C, H.2changing the second target value for the degree of refining in step D, H.3changing the proportion of unrefined long-fiber pulp when forming the fiber web in step E, H.4changing the proportion of unrefined short-fiber pulp when forming the fiber web in step E, H.5changing the proportion of refined long-fiber pulp when forming the fiber web in step E, H.6changing the proportion of refined short-fiber pulp when forming the fiber web in step E.

26. Process according to claim 25, in which the threshold of step H is at least 0.01 cm/s and at most 0.07 cm/s.

27. Process according to claim 24, in which the amount of the refined long-fiber pulp in step E is selected such that at least 20% and at most 65% of the mass of the wrapping paper is formed by refined long-fiber pulp.

28. Process according to claim 24, in which the first target value for the degree of refining in step C, measured in accordance with ISO 5267-1:1993, is at least 85? SR and at most 95? SR.

29. (canceled)

30. Process according to claim 24, in which the amount of refined short-fiber pulp in step E is selected such that at least 10% and at most 70% of the mass of the wrapping paper in step J is formed by refined short-fiber pulp.

31. Process according to claim 24, in which the second target value for the degree of refining in step D, measured in accordance with ISO 5267-1:1993, is at least 25? SR and at most 50? SR.

32. (canceled)

33. Process according to claim 24, in which the total amount of short-fiber pulp in step E is selected such that at least 30% and at most 75% of the mass of the wrapping paper in step J is formed by short-fiber pulp.

34. (canceled)

35. (canceled)

36. (canceled)

37. Process according to claim 24, in which the wrapping paper from step J has a diffusion capacity, measured in accordance with CRM 77, of at least 0.1 cm/s and at most 0.39 cm/s.

38. Process according to claim 24, in which the standard deviation for the diffusion capacity of the wrapping paper from step J is at least 0.005 cm/s and at most 0.03 cm/s.

39. (canceled)

40. (canceled)

41. Process according to claim 25, in which the diffusion capacity in step G is determined by the mean value of to measurements in accordance with CRM 77 on randomly selected positions.

42. (canceled)

43. Process according to claim 25, wherein in the case in which the diffusion capacity measured in step G is significantly too high, the first target value for the degree of refining in step C is increased, step H.1, or the proportion of the unrefined long-fiber pulp is reduced, step H.3, and at the same time the proportion of the refined long-fiber pulp is increased, step H.5.

44. Process according to claim 43, in which in said case in which the diffusion capacity measured in step G is significantly too high, the proportion of short-fiber pulp is reduced, step H.4 or step H.6, and the proportion of refined long-fiber pulp is increased, step H.5.

45. Process according to claim 25 in which, in the case in which the diffusion capacity measured in step G is only slightly too high, the second target value for the degree of refining in step D is increased, step H.2, or the proportion of unrefined short-fiber pulp is reduced, step H.4, and at the same time the proportion of refined short-fiber pulp is increased, step H.6.

46. Process according to claim 45, in which in said case in which the diffusion capacity measured in step G is only slightly too high, the proportion of unrefined long-fiber pulp is reduced, step H.3, and at the same time the proportion of refined short-fiber pulp is increased, step H.6.

47. Process according to claim 25, in which, in order to reduce the standard deviation for the diffusion capacity, the proportion of refined short-fiber pulp is increased, step H.6, and at the same time the proportion of refined long-fiber pulp is reduced, step H.5.

48. Process according to claim 25, in which in the case in which the absolute difference between the diffusion capacity measured in step G and the target value for the diffusion capacity exceeds the threshold, step H comprises carrying out a combination of two of the steps H.1 to H.6, in which, in the case in which the absolute difference between the diffusion capacity measured in step G and the target value for the diffusion capacity exceeds the threshold, step H comprises at least one of the following combinations of two steps H.3 to H.6, H.3 and H.5, H4 and H.5, H.6 and H.5; H.4 and H.6 or H.3 and H.6.

49. (canceled)

50. Process according to claim 25, in which, in the case in which the absolute difference between the diffusion capacity measured in step G and the target value for the diffusion capacity exceeds the threshold, step H comprises carrying out a combination of three of steps H.1 to H.6, in which, in the case in which the absolute difference between the diffusion capacity measured in step G and the target value for the diffusion capacity exceeds the threshold, step H comprises carrying out at least one of the following combinations of three steps H.1 to H.6, H.3 and H.5, H2, H.3 and H.5; H.1, H.4 and H.5; H.2, H.4 and H.5; H.1, H.6 and H.5; H.1, H.6 and H.5; H.2, H.6 ad H.5; H.1, H.4 and H.6; H.2, H.4 and H.6; H.1, H.3 and H.6; H.2, H.3 and H.6.

51. (canceled)

52. (canceled)

Description

DESCRIPTION OF SOME PREFERRED EMBODIMENTS AND EXAMPLES FOR COMPARISON

[0106] Some preferred embodiments of wrapping papers according to the invention will be described below.

Exemplary Embodiments

[0107] Several wrapping papers according to the invention were manufactured using the process according to the invention. The composition of the wrapping papers is shown in Table 1, wherein LF is the content of refined long-fiber pulp with respect to the mass of the wrapping paper, SF-? is the content of unrefined short-fiber pulp with respect to the mass of the wrapping paper, SF-R is the content of refined short-fiber pulp with respect to the mass of the wrapping paper, FI is the content of inorganic filler material with respect to the mass of the wrapping paper, DR-L is the degree of refining of the refined long-fiber pulp, DR-S is the degree of refining of the refined short-fiber pulp, BW is the basis weight, MW is the mean diffusion capacity and SD is the standard deviation for the diffusion capacity. All wrapping papers according to the invention from Table 1 respectively contained 0.5% to 1.5% citrate as a burn additive, with respect to the mass of the wrapping paper. The entirety of the long-fiber pulp proportion was formed by refined long-fiber pulp.

TABLE-US-00001 TABLE 1 Diffusion Capacity Composition DR-L DR-S BW MW SD LF SF-U SF-R FI ? SR ? SR g/m.sup.2 cm/s cm/s Paper % % % % ISO 5267-1 ISO 536 CRM 77 1 45 18 16 20 92 40 29 0.12 0.013 2 39 24 16 20 94 40 28 0.18 0.017 3 30 33 16 20 93 40 27 0.24 0.016 4 19 44 16 20 92 40 26 0.32 0.017 5 42 20 16 21 92 40 30 0.16 0.020 6 30 29 25 15 93 40 25 0.32 0.019 7 28 31 25 15 94 40 25 0.39 0.024 8 26 32 26 15 94 40 25 0.44 0.049 9 20 55 9 15 93 40 30 0.40 0.043

Comparative Examples

[0108] Several wrapping papers not according to the invention were manufactured; the data are summarized in Table 2, wherein the abbreviations have the same meaning as in Table 1. Also, the wrapping papers not according to the invention A and B respectively contained 0.5% to 1.5% citrate as a burn additive. The wrapping paper C, not according to the invention, did not contain burn additives. The entirety of the long-fiber pulp proportion was formed by refined long-fiber pulp.

TABLE-US-00002 TABLE 2 Diffusion Capacity Composition DR-L DR-S BW MW SD LF SF-U SF-R FI ? SR ? SR g/m.sup.2 cm/s cm/s Paper % % % % ISO 5267-1 ISO 536 CRM 77 A 40 39 0 20 95 48 0.25 0.048 B 40 39 0 20 93 27 0.52 0.063 C 75 0 0 25 92 26 0.23 0.056

[0109] The wrapping papers 1 to 9 according to the invention show that over a specific range regarding basis weight, content of refined long-fiber pulp, refined and unrefined short-fiber pulp and the filler content, a very low standard deviation could be obtained for the diffusion capacity. By intense refining of the entirety of the long-fiber pulp, the diffusion capacity was shifted to a low range and the specific value for the diffusion capacity was primarily adjusted by the mixture of refined and unrefined short-fiber pulp. Due to the natural variability of the raw materials, this ratio had to be individually adjusted for each production batch.

[0110] Compared with the wrapping papers 1 to 7, the wrapping paper 9 according to the invention, with a content of unrefined short-fiber pulp of only 9% of the mass of the wrapping paper, has a significantly higher standard deviation for the diffusion capacity, so that this comes close to the limits of the invention.

[0111] The wrapping paper 8 according to the invention is also almost at the limits of the invention, in particular compared with wrapping paper 7. The essential difference is the diffusion capacity, which for wrapping paper 8 is 0.44 cm/s and is slightly higher than for wrapping paper 7, with 0.39 cm/s. Apparently, at this diffusion capacity, the effect of the refined short-fiber pulp decreases so that the standard deviation for the diffusion capacity can no longer be reduced so efficiently.

[0112] In the wrapping papers 1 to 9 according to the invention, the filler content is selected to be rather low. If the filler content is to be increased, for example to 40% or 45% of the mass of the wrapping paper, then it is beneficial to further increase the degree of refining of the short-fiber pulp and also to increase the proportion of refined short-fiber pulp and to reduce the proportion of unrefined short-fiber pulp.

[0113] The wrapping paper A not according to the invention is very similar to the wrapping paper 5 according to the invention, but has a higher basis weight of 48 g/m.sup.2 and does not contain refined short-fiber pulp. It can be seen that the standard deviation for the diffusion capacity for comparative example A is significantly higher than for the wrapping paper 5, but is in an acceptable range, so that at this high basis weight, refined short-fiber pulp is no longer required.

[0114] For the wrapping paper B not according to the invention, no refined short-fiber pulp was used and despite the otherwise almost identical properties as for wrapping paper 2 according to the invention, it was not possible to reduce the diffusion capacity sufficiently and, furthermore, the standard deviation for the diffusion capacity was more than twice as high.

[0115] Finally, the wrapping paper C not according to the invention shows that a wrapping paper that consists exclusively of refined long-fiber pulp and filler material can indeed achieve a low diffusion capacity, but the standard deviation for the diffusion capacity is too high. This is caused by the proportion of filler material and, as shown by the approximately similar exemplary embodiment 4, can be compensated for by using refined short-fiber pulp.

[0116] It can be seen from the wrapping papers according to the invention and the comparative examples not according to the invention that in fact the combination of several features, in particular the basis weight, the degree of refining of the short-fiber pulp, the mixing ratio between refined and unrefined short-fiber pulp and the filler content in the wrapping paper, is relevant in order to obtain the advantages according to the invention.