Lightweight Separating Base Paper

Abstract

The invention relates to a separating base paper, having a mass per unit area of at least 25 g/m.sup.2 and at most 40 g/m.sup.2 and a density of at least 0.90 g/cm.sup.3 and at most 1.15 g/cm.sup.3. The separating base paper comprises at least 50 wt % of long-fiber pulp and is coated on at least one side with at least two coatings. The first coating is located between a paper surface and the second coating. The second coating is a topmost coating and comprises a water-soluble film-forming polymer, nanofibrillated cellulose, microfibrillated cellulose or nanocrystalline cellulose. The Cobb-Unger (120 s) value of the surface having said first and second coatings is at least 0.01 g/m.sup.2 and at most 0.90 g/m.sup.2.

Claims

1. Smoking article comprising a smokable material, which is capable of generating an aerosol upon combustion or heating, wherein the smokable material is wrapped with a paper serving as a wrapping material, said paper having a basis weight of at least 25 g/m.sup.2 and at most 40 g/m.sup.2, and is coated with a density of a at least 0.90 g/cm.sup.3 and at most 1.15 g/cm.sup.3, wherein the release base paper comprises at least 50% by weight softwood pulp and is coated on at least one side with at least two coatings, wherein the first coating is located between the paper surface and the second coating, wherein the second coating is the topmost coating and comprises a water-soluble film-forming polymer, nano-fibrillated cellulose, micro-fibrillated cellulose or nano-crystalline cellulose, and wherein the Cobb Unger (120 s) value for the surface with said first and second coating is at least 0.01 g/m.sup.2 and at most 0.90 g/m.sup.2.

2. Smoking article according to claim 1, wherein the basis weight of the paper is at least 30 g/m.sup.2 and/or at most 38 g/m.sup.2.

3. Smoking article according to claim 1, wherein the density of the paper is at least 0.95 g/cm.sup.3 and at most 1.10 g/cm.sup.3.

4. Smoking article according to claim 1, wherein the paper comprises at least 70% by weight softwood pulp.

5. Smoking article according to claim 1, wherein the air permeance of the paper, measured in accordance with the Gurley method defined in ISO 5636-5:2013, is at least 4000 s.

6. (canceled)

7. (canceled)

8. Smoking article according to claim 1, wherein the paper contains at most 40% by weight hardwood pulp.

9. Smoking article according to claim 1, wherein the paper contains at most 15% by weight filler materials.

10. Smoking article according to claim 1, wherein the first coating comprises a coating material which is selected from the group consisting of water-soluble film-forming polymers; nano-fibrillated cellulose; micro-fibrillated cellulose; nano-crystalline cellulose and mixtures thereof; and the second coating comprises a water-soluble film-forming polymer, nano-fibrillated cellulose, micro-fibrillated cellulose or nano-crystalline cellulose.

11. Smoking article according to claim 1, in which the amount of the first coating is at least 0.1 g/m.sup.2 and at most 4.0 g/m.sup.2.

12. (canceled)

13. Smoking article according to claim 1, in which the amount of the second coating is at least 0.5 g/m.sup.2 and at most 5.0 g/m.sup.2.

14. Smoking article according to claim 1, in which the second coating comprises pigment particles, wherein the pigment particle has a flaky shape, and wherein the pigment particle is selected from the group consisting of kaolin, talcum, magnesium silicates, aluminum silicates and mixtures thereof.

15. Smoking article according to claim 1, in which the film-forming polymer of the second coating is selected from the group consisting of polyvinyl alcohol, carboxy methyl cellulose, hydroxy methyl cellulose, starch, starch derivatives, latex and mixtures thereof.

16. (canceled)

17. Smoking article according to claim 1, in which the Cobb Unger (120 s) value for the coated side of the paper is at least 0.01 g/m.sup.2 and at most 0.90 g/m.sup.2.

18. Smoking article according to claim 1, wherein the paper has a transparency in accordance with DIN 53147:1993-01 of at least 55% and at most 80%.

19-24. (canceled)

25. Process for manufacturing a paper for wrapping the smokable material of a smoking article according to claim 1, with the following steps: preparing a pulp-containing suspension, which comprises softwood pulp, applying the pulp-containing suspension to a wire of a paper machine in order to form a base paper, calendering the base paper to adjust the density of the base paper, coating the base paper with a first coating, drying the first coating, applying a second coating, which is a topmost coating, either directly or indirectly with one or more further layers in between, to the first coating, wherein the second coating comprises a water-soluble film-forming polymer, nano-fibrillated cellulose, micro-fibrillated cellulose or nano-crystalline cellulose, and drying the second coating, wherein the proportion of softwood pulp in the pulp-containing suspension is selected such that the finished paper comprises at least 50% by weight softwood pulp, the amount of pulp-containing suspension that is applied to the wire of the paper machine is selected such that the finished paper has a basis weight of at least 25 g/m.sup.2 and at most 40 g/m.sup.2, and the step of calendering is carried out such that the finished paper has a density of at least 0.90 g/cm.sup.3 and at most 1.15 g/cm.sup.3, and wherein the first and the second coating are selected such that the Cobb Unger (120 s) value for the surface with said first and second coating on the finished release base paper is at least 0.01 g/m.sup.2 and at most 0.90 g/m.sup.2.

26. Process according to claim 25, wherein the amount of pulp-containing suspension that is applied to the wire of the paper machine is selected such that the finished paper has a basis weight of at least 30 g/m.sup.2 and/or at most 38 g/m.sup.2.

27. Process according to claim 25, wherein the step of calendering is carried out such that the density is at least 0.95 g/cm.sup.3 and at most 1.10 g/cm.sup.3.

28. Process according to claim 25, in which the base paper in the calendering process is compressed between a plurality of pairs of rolls, wherein each pair of rolls forms a nip through which the base paper is guided.

29. Process according to claim 25, wherein the proportion of softwood pulp in the pulp-containing suspension is selected such that the finished paper comprises at least 70% by weight softwood pulp.

30. Process according to claim 25, in which the finished paper has an air permeance, measured in accordance with the method defined ISO 5636-5:2013 according to Gurley, of at least 4000 s.

31. Process according to claim 25, in which the step of manufacturing the pulp-containing suspension contains a step in which the softwood pulp is refined to a degree of refining of at least 50° SR and at most 80° SR.

32. Process according to claim 25, in which the first coating comprises a coating material that is selected from the group consisting of water-soluble film-forming polymer; nano-fibrillated cellulose, micro-fibrillated cellulose; nano-crystalline cellulose and mixtures thereof; and the second coating comprises a water-soluble film-forming polymer, nano-fibrillated cellulose, micro-fibrillated cellulose or nano-crystalline cellulose.

33. Process according to claim 32, in which the first coating is applied by means of a first coating composition which comprises water and said coating material, wherein the amount of the dried first coating composition which remains after drying on the paper is at least 0.1 g/m.sup.2 and at most 4.0 g/m.sup.2.

34. (canceled)

35. Process according to claim 25, wherein the second coating comprises a water-soluble, film-forming polymer, nano-fibrillated cellulose, micro-fibrillated cellulose or nano-crystalline cellulose and is applied in form of a second coating composition which comprises water and said film-forming polymer, the nano-fibrillated cellulose, micro-fibrillated cellulose or nano-crystalline cellulose.

36. Process according to claim 25, in which the second coating composition comprises pigment particles, wherein the pigment particles have a flaky shape, and wherein the pigment particles are selected from the group consisting of kaolin, talcum, magnesium silicates, aluminum silicates, calcium carbonate and mixtures thereof, wherein the pigment particles make up at least 1% by weight, and at most 30% by weight, with respect to the weight of the second coating composition.

37. Process according to claim 25, in which the film-forming polymer of the second composition is selected from the group consisting of polyvinyl alcohol, carboxy methyl cellulose, hydroxy methyl cellulose, starch, starch derivatives, latex and mixtures thereof.

38-39. (canceled)

40. Process according to claim 25, in which the paper machine is a Fourdrinier paper machine and/or in which a calendering device is integrated into the paper machine, so that the calendering can be carried out during production of the base paper and/or in which the first and/or the second coating composition is applied in a size press, in a film press, by blade coating or a curtain coating process.

41. Smoking article according to claim 1, wherein the smokable material is heated but not burnt during intended use.

42. Smoking article according to claim 9, wherein the paper contains less than 2% by weight filler materials.

43. Smoking article according to claim to, wherein said water-soluble film-forming polymers are formed by starch, starch derivatives, cellulose derivatives or latex.

44. Smoking article according to claim 1, in which the Cobb Unger (120 s) value for the coated side of the paper is at least 0.1 g/m.sup.2 and at most 0.70 g/m.sup.2.

45. Process according to claim 32, wherein said water-soluble film-forming polymers are formed by starch, starch derivatives, cellulose derivatives or latex.

46. The process according to claim 35, wherein the water-soluble film-forming polymer, the nano-fibrillated cellulose, micro-fibrillated cellulose or nano-crystalline cellulose makes up at least 5% by weight and at most 25% by weight with respect to the weight of the second coating composition, and/or wherein the amount of the dried second coating composition which remains after drying on the paper is at least 0.5 g/m.sup.2 and at most 5.0 g/m.sup.2.

Description

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0051] A release base paper according to the invention was produced from a mixture of 80% by weight softwood pulp from spruce and pine and 20% by weight hardwood pulp from birch. The softwood pulp was refined to a degree of refining of 67° SR, measured in accordance with ISO 5267-1:1999. No filler materials were used.

[0052] The release base paper web was formed on a conventional Fourdrinier paper machine from a water-based suspension containing the mixture of refined softwood pulp and hardwood pulp and calendered in the paper machine using a calender integrated into the paper machine.

[0053] The release base paper web was then coated on the full surface with a first coating composition containing water and 15% by weight starch with respect to the weight of the first coating composition, and then dried to obtain the first coating. This step was carried out in a film press.

[0054] The entire surface of the release base paper was then coated with a second coating composition, which was applied to the first coating, consisting of 8% by weight polyvinyl alcohol, 15% by weight kaolin particles, a small amount of cross-linker and water, wherein the percentages refer to the weight of the coating composition. The second coating composition was applied in a blade coater and dried to obtain the second coating and therefore also the finished release base paper according to the invention.

[0055] The basis weight of the release base paper was measured in accordance with ISO 536:2012 and a value of 36.0 g/m.sup.2 was found. The density of the release base paper was calculated from the basis weight and the thickness, measured in accordance with ISO 534:2011, and determined to be 0.99 g/cm.sup.3. The Cobb Unger (120 s) value was determined in accordance with TAPPI T462 cm-16 and a value 0.3 g/m2 was obtained. The transparency of the release base paper was measured in accordance with DIN 53147:1993-01 and a value of 67.0% was obtained.

[0056] The air permeance according to the Gurley method was measured as defined in ISO 5636-5:2013 and a value of 100000 s was determined by extrapolation.

[0057] Tensile strength, tear strength and other mechanical parameters of the release base paper were also checked and found to be well suited for further processing of the release base paper.

[0058] The release base paper was coated with silicone without any problems and it was found that the siliconized release base paper is highly suitable as a carrier material for self-adhesive labels.

[0059] Thus, the release base paper according to the invention combines a low basis weight with at least equal, if not superior, properties compared with a conventional release base paper and thus contributes substantially to a reduction in waste caused by the use of such papers.

[0060] The release base paper according to the invention was also used to wrap the smokable material of a commercially available heat-not-burn product. After the smoking article had been consumed, there were clearly fewer stains on the release base paper than on a conventional cigarette paper after consumption of a smoking article of the same brand wrapped in this conventional cigarette paper.