Pleated Filter Material for Smoking Articles

Abstract

A filter material for manufacturing a segment of a smoking article is described. The filter material includes a hydro-entangled nonwoven, which includes fibers. The fibers are selected from the group consisting of pulp fibers, fibers of regenerated cellulose and mixtures thereof. These fibers are contained in the nonwoven in an amount of 50% to 100% of the mass of the hydro-entangled nonwoven. The nonwoven is in the form of a web, has a longitudinal direction in the running direction of the web, a cross direction orthogonal thereto and lying in the plane of the web and a thickness direction orthogonal to longitudinal direction and the cross direction. The nonwoven is shaped to have a wave structure in the plane formed by the cross direction and the thickness direction with a wave height from 50 m to 1000 m and a wave length from 150 m to 5000 m.

Claims

1. A process for manufacturing a segment material for smoking articles comprising the following steps: manufacturing a filter material in a method comprising the following steps A to D, Aproviding a fiber web comprising fibers, selected from the group consisting of pulp fibers, fibers from regenerated cellulose and mixtures thereof, Bhydro-entangling the fiber web by means of a plurality of water jets directed onto the fiber web, Cgenerating a wave structure in the nonwoven by means of a plurality of water jets directed onto the fiber web, and Ddrying the hydro-entangled nonwoven, wherein the proportion of said fibers in the fiber web in step A is selected such that these fibers are together contained in an amount of at least 50% and at most 100% of the mass of the hydro-entangled nonwoven in the dried state from step D, wherein the fiber web provided in step A has a longitudinal direction in the running direction of the fiber web, a cross direction orthogonal thereto lying in the plane of the fiber web and a thickness direction orthogonal to longitudinal direction and cross direction, and the water jets directed onto the fiber web in step C are disposed such that they have a distance from each other in cross direction from center point to center point of the water jets at the location of impact on the fiber web of at least 150 m and at most 5000 m and the pressure of each water jet in step C is at least 2 MPa and at most 70 MPa, and the nonwoven obtained in step D has a wave structure in the plane formed by the cross direction and the thickness direction with a wave height of at least 50 m and at most 1000 m, as well as a wave length of at least 150 m and at most 5000 m and manufacturing a segment from said filter material, wherein the segment is cylindrical with a diameter of at least 3 mm and at most 10 mm.

2. The process as claimed in claim 1, in which the water jets for carrying out step B and/or step C are directed onto both sides of the fiber web.

3. The process as claimed in claim 2, in which the water jets in step C are disposed such that they hit areas that, viewed from the respective side, are to form wave valleys.

4. The process as claimed in claim 1, in which the water jets in step C exit from an opening which has an area of at least 450 m.sup.2 and at most 50000 m.sup.2 and is a circular opening.

5. The process as claimed in claim 1, in which the pressure of the water jets in step C is at least 3 MPa and at most 40 MPa, wherein the pressure for generating the wave structure is selected as a function of the speed of the fiber web in a manner such that for the ratio p/v of the pressure p in MPa to the speed v of the fiber web in m/s, that the following holds: 2.5p/v20.

6. The process as claimed in claim 1, in which the pressure of the water jets in step B is at least 0.5 MPa and at most 60 MPa, wherein the pressure in step B is selected as a function of the speed of the fiber web such that for the ratio p/v of the pressure p in MPa to the speed v of the fiber web in m/s, that the following holds: 2p/v20.

7. The process as claimed in claim 1, in which the wave height after step D is at least 100 m and at most 900 m.

8. The process as claimed in claim 1, in which the wave length after step D is at least 300 m and at most 4000 m.

9. The process as claimed in claim 1, in which the hydro-entangled nonwoven obtained in step D has any or an arbitrary combination of the features that are defined in claim 1 in respect of the hydro-entangled nonwoven as a component of the claimed filter material.

10. The process as claimed in claim 1, in which in a variation A1 of the process, the fiber web in step A is provided by means of a wet-laid process, which comprises the following sub-steps A1.1 to A1.3: A1.1manufacturing an aqueous suspension comprising fibers selected from the group consisting of pulp fibers, fibers from regenerated cellulose and mixtures thereof, in which the amount of fibers is selected such that these fibers are together contained in an amount of at least 50% and at most 100% of the mass of the hydro-entangled nonwoven in the dried state from step D, A1.2applying the suspension from step A1.1 to a running wire, and A1.3de-watering the suspension by means of the running wire in order to form a fiber web, in which the process comprises a further sub-step A1.4: A1.4adjusting the moisture content of the fiber web by drying or moistening.

11. The process as claimed in claim 10, wherein the aqueous suspension in step A1.1 has a solid content of at least 0.005% and at most 3.0.

12. The process as claimed in claim 10, in which the running wire of steps A1.2 and A1.3 is inclined upwards in the running direction of the fiber web from the horizontal by an angle of at least 3 and at most 40.

13. The process as claimed in claim 10, in which in step A1.3, de-watering is supported by generating a pressure difference between the two sides of the running wire, in which the pressure difference is generated by vacuum boxes or suitably shaped vanes.

14. The process as claimed in claim 10, in which the drying in step A1.4 is carried out by heated drying cylinders or by hot air and the moistening is carried out by a spraying bar.

15. The process as claimed in claim 10, in which in a variation A2 of the process, the fiber web in step A is provided by means of an air-laid process, which comprises the following sub-steps A2.1 and A2.2: A2.1manufacturing a fiber web by an air-laid process, wherein the fiber web comprises fibers which are selected from the group consisting of pulp fibers, fibers from regenerated cellulose and mixtures thereof, in which the amount of these fibers is selected in a manner such that these fibers are together contained in an amount of at least 50% and at most 100% of the mass of the hydro-entangled nonwoven in the dried state from step D, and A2.2moistening the fiber web.

16. The process as claimed in claim 10, in which the drying in step D is at least partially carried out by contact with hot air, by infra-red radiation or by microwave radiation, wherein the drying in step D is carried out by through-air drying.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0087] FIG. 1 shows a device with which the process according to the invention for manufacturing the hydro-entangled nonwoven can be carried out.

[0088] FIG. 2 shows, as an example, the determination of wave height and wave length of the wave structure of the nonwoven.

[0089] FIG. 3 shows the cross-sectional area of the nonwoven for a filter material according to the invention.

[0090] FIG. 4 shows the cross-sectional area of a filter material not according to the invention after pleating.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0091] Some preferred embodiments of the filter material and the process for manufacturing the hydro-entangled nonwoven are described below.

[0092] In order to manufacture the hydro-entangled nonwoven that is contained in the filter material according to the invention, the process described below was used, in which the device schematically shown in FIG. 1 has been used.

[0093] An aqueous suspension 1 of pulp fibers and fibers of regenerated cellulose was pumped from a storage tank 2 to a running wire 3, inclined upwards against the horizontal, and de-watered by vacuum boxes 9, so that a fiber web 4 was formed on the wire, the general direction of movement of which is indicated by arrow 10. The fiber web 4 was removed from the wire 3 and transferred to a support wire 5, which was also running. If needed, this transfer can be facilitated by a pick-up roll or by entangling the fiber web with water jets before the transfer. On the support wire 5, water jets 11 from devices 6 disposed in three rows in cross direction relative to the fiber web 4 were directed onto the fiber web 4 in order to entangle the fibers and to consolidate the fiber web 4 to form a nonwoven. In a further step, water jets 12 with a higher pressure were also directed onto the fiber web 4 by means of additional devices 7 in order to generate the aforementioned wave structure. In contrast to the devices 6, the devices 7 were set so that the water jets 12 of both rows, in succession in the longitudinal direction, were as far as possible directed to the same position in cross direction. Thus, the water jets 12 of the second row, viewed in the longitudinal direction, were directed onto the wave valleys generated by the water jets 12 of the first row and thus intensified the wave structure generated by the first row. Optional devices 6a could direct further water jets 11a onto the fiber web, wherein these water jets, as a function of the arrangement and the pressure could serve for both entangling the nonwoven as well as generating or intensifying the wave structure. In contrast to the representation in FIG. 1, the water jets of devices 6a could also be directed onto the fiber web 4 from the same side as the water jets 11 or 12. Then the still moist nonwoven ran through a through-air drier 8 and was dried there.

[0094] To manufacture the hydro-entangled nonwoven, a mixture of 80% by weight pulp fibers and 20% by weight Lyocell fibers was used. The entangling of the fibers was carried out by three rows of water jets 11, which were generated with a pressure of 3 MPa, 5 MPa and 6 MPa with respect to the running direction. The wave structure of the nonwoven was produced by two rows of water jets 12, which were generated with a pressure of 8.5 MPa in both rows. The devices 7 for generating the water jets 12 in both rows were each separated in cross direction by a distance of 2000 m and had a diameter of 100 m. The speed of the fiber web was 50 m/min, which is relatively low. At higher speeds, the pressures of the water jets 11 and 12 have to be correspondingly increased. For the ratio p/v of the pressure p of the water jets for entangling the fiber web in MPa to the speed v of the fiber web in m/s, values of 3/(50/60)=3.6 to 6/(50/60)=7.2 were obtained. To generate the wave structure the ratio p/v of the pressure p of the water jets to the speed of the fiber web in m/s was 8.5/(50/60))=10.2.

[0095] For the nonwoven produced thereby, the basis weight was determined to be 49.6g/m.sup.2 , the thickness in accordance with NWSP 120.6.Ro (15) was 522 m and the density was 95 kg/m.sup.3 . The tensile strength in the longitudinal direction was 8.6 N/15 mm, the elongation at break in cross direction was 31%.

[0096] A sample of the nonwoven was embedded in epoxy resin and, after curing the epoxy resin, the sample was cut with a microtome, so that the cross-sectional plane formed by the cross direction and the thickness direction was visible in an optical microscope. With the optical microscope, an image of the cross section was recorded and the wave structure was measured with respect to wave height and wave length.

[0097] FIG. 2 shows, as an example, the determination of wave height and wave length of the wave structure of the nonwoven. If the nonwoven 20 has a pronounced wave structure on both sides, then the wave height 21 is determined by the distance in the thickness direction 41 between the highest point of the wave crest 23 and the lowest point of the neighboring wave valley 23 on the same side. The wave length 22 is the distance in cross direction 40 between two points of equal phase angle of the wave structure, here, as an example, shown as the distance between two neighboring wave crests 24 and 25. If the nonwoven 30 has a pronounced wave structure on only one side, the wave height 31 is determined in the same way as the distance in the thickness direction 41 between the highest point of the wave crest 34 and the lowest point of the neighboring wave valley 33 on the same side. The wave length 32 is the distance in cross direction 40 between two points of the same phase angle of the wave structure, here, by way of example, shown as the distance between two neighboring wave crests 34 and 35. The wave height or the wave length can be determined as a single value or as mean value of several measurements, for example three.

[0098] FIG. 3 shows the acquired image of the cross-sectional area of the manufactured nonwoven under an optical microscope. A wave structure is clearly discernible and the wave height 41 was determined to be 220 m and the wave length 42 was 2030 m.

[0099] The nonwoven was used as a filter material according to the invention without adding further components and a segment of a smoking article was manufactured therefrom wrapped with a wrapper paper with a basis weight of 78 g/m.sup.2 . The manufacture of the segment was possible without any problems; in particular, pleating could be carried out with substantially reduced pressure. In further experiments, it was found that pleating could also be dispensed with entirely without having to reduce the production speed or without substantially changing the properties of the segment.

[0100] For comparison, FIG. 4 shows a filter material not according to the invention, consisting of a paper made from 100% pulp fibers, that is, not of a hydro-entangled material, after it has been pleated by mechanical pressure between two rolls during manufacture of a segment for a smoking article, but before a segment has been manufactured from it. In addition, a cross-sectional sample was analyzed with an optical microscope and the wave height and wave length were measured using this filter material.

[0101] From FIG. 4, a similar wave structure can be seen and here too, the wave height 51 was determined to be 390 m and the wave length 52 was 2000 m. It can be seen that the wave structure of the filter material according to the invention is similar to that of a filter material not according to the invention after pleating, so that pleating of the filter material according to the invention can be carried out with substantially less pressure or can be dispensed with entirely.

[0102] These experiments show that the filter material according to the invention, in comparison to filter materials known in the prior art, can facilitate or entirely avoid the pleating step during manufacture of a segment for smoking articles and thus simplify the manufacturing process and reduce the susceptibility to error.