METHOD AND APPARATUS FOR MANUFACTURING A CORRUGATED WEB

Abstract

There is disclosed a method of manufacturing a corrugated polymeric material web for an aerosol-generating article. Polymeric material pellets are first heated to form a p polymeric material melt. A polymeric material web is formed from the polymeric material melt, and the polymeric material web is then worked at an elevated temperature to form a corrugated polymeric material web. The corrugated polymeric material web is then wound onto a bobbin. A preferred polymeric material is polylactic acid.

Claims

1. A method of manufacturing a corrugated polymeric material web for an aerosol-generating article, the method comprising the steps of: heating polymeric material pellets to form a polymeric material melt; forming a polymeric material web from the polymeric material melt and working the polymeric material web at an elevated temperature to form a corrugated polymeric material web; and winding the corrugated polymeric material web onto a bobbin.

2. A method according to claim 1, wherein working the polymeric material web comprises passing the polymeric material web between at least two crimping rollers to form the corrugated polymeric material web.

3. A method according to claim 1, wherein the polymeric material melt is first passed between at least two smooth rollers to form the polymeric material web, and wherein the polymeric material web is subsequently passed between at least two crimping rollers while at the elevated temperature.

4. A method according to claim 3, wherein the polymeric material web is passed between multiple sets of crimping rollers.

5. A method according to claim 1, wherein the polymeric material melt is first passed between at least two smooth rollers to form the polymeric material web, and wherein the polymeric material web is subsequently passed over or between shaping members configured to impart corrugations to the polymeric material web while at the elevated temperature.

6. A method according to claim 1, wherein forming a polymeric material web from the polymeric material melt and working the polymeric material web comprises extruding the polymeric material melt through an extrusion die with a corrugated profile so as to form the corrugated polymeric material web.

7. A method according to claim 6, wherein the corrugated polymeric material web is passed over or between shaping members configured to impart further corrugations to the corrugated polymeric material web while at the elevated temperature.

8. A method according to claim 1, wherein the elevated temperature is a temperature higher than a temperature 20 degrees Celsius below the glass transition temperature of the polymeric material, optionally a temperature higher than a temperature 10 degrees Celsius below the glass transition temperature of the polymeric material, optionally a temperature higher than a temperature 5 degrees Celsius below the glass transition temperature of the polymeric material, or optionally a temperature not less than the glass transition temperature of the polymeric material.

9. A method according to claim 1, wherein the corrugated polymeric material web has a zig-zag corrugated profile with pointed peaks and troughs.

10. A method according to claim 1, wherein the corrugated polymeric material web has an undulating corrugated profile with curved peaks and troughs.

11. A method according to claim 1, wherein the polymeric material is polylactic acid.

12. A method according to claim 1, wherein the polymeric material is selected from the group consisting of: polyethylene, polypropylene, polyvinylchloride, polyethylene terephthalate, and cellulose acetate.

13. A method according to claim 1, wherein the polymeric material has a glass transition temperature in a range from 40 degrees Celsius to 85 degrees Celsius, and a melting point in a range from 123 degrees Celsius to 228 degrees Celsius.

14. A bobbin comprising a corrugated polymeric material web formed by the method of claim 1 wound onto a spindle.

15. A method of forming rod-shaped articles, comprising gathering a corrugated polymeric material web into a substantially cylindrical bundle by way of a funnel, wrapping the bundle in a wrapper to form a wrapped bundle, and cutting the wrapped bundle into rod-shaped lengths, characterised in that the corrugated polymeric material web is unwound in a corrugated state from a bobbin prior to gathering.

16. A method according to claim 15, wherein the bobbin of corrugated polymeric material web is made by the method of claim 1.

17. An aerosol-generating article comprising a rod-shaped article made by the method of claim 15.

18. An apparatus for forming a corrugated polymeric material web, comprising: a container to heat polymeric material pellets to form a polymeric material melt; a roller or an extruder to work the polymeric material melt to form a corrugated polymeric material web; and a winder to wind the corrugated polymeric material web onto a bobbin.

19. A rod-making apparatus comprising a funnel to gather a corrugated polymeric material web into a substantially cylindrical bundle, a wrapper to wrap the bundle so as to form a wrapped bundle, and a cutter to cut the wrapped bundle into rod-shaped lengths, characterised in that the corrugated polymeric material web is gathered from a bobbin wound with the corrugated polymeric material web.

Description

[0099] Features described in relation to one aspect of the invention may also be applicable to the other aspects of the invention. The invention will be further described, by way of example only, with reference to the accompanying drawings in which:

[0100] FIG. 1 shows a prior art apparatus for manufacturing a crimped web;

[0101] FIG. 2 shows a first embodiment of the present disclosure;

[0102] FIG. 3 shows a bobbin wound with corrugated polylactic acid web;

[0103] FIG. 4 shows a cross section of a pair of forming rollers of the embodiment of FIG. 2;

[0104] FIG. 5 shows a cross section of an alternative forming roller;

[0105] FIG. 6 shows a cross section of a further alternative forming roller;

[0106] FIG. 7 shows a second embodiment of the present disclosure;

[0107] FIG. 8 shows a third embodiment of the present disclosure;

[0108] FIGS. 9 and 10 show a fourth embodiment of the present disclosure;

[0109] FIG. 11 shows a cross section of a corrugated web with a zig-zag profile; and

[0110] FIG. 12 shows a cross section of a corrugated web with an undulating profile.

[0111] FIG. 1 shows a prior art apparatus 100 for manufacturing a crimped web. The apparatus 100 comprises, among other components, a set of crimping rollers 102 including a first roller and a second roller, each of which is corrugated across its width. The set of crimping rollers 102 is arranged such that the corrugations of the first roller substantially interleave with the corrugations of the second roller. The apparatus 100 also comprises a lateral web cutting mechanism 104, a bobbin 106 of polylactic acid web material 108, a drive and brake mechanism 110, and a tensioning mechanism 112. Control electronics 114 are provided to control the apparatus 100 during operation.

[0112] In use, the drive and brake mechanism 110 feeds the web 108 in a longitudinal direction from the bobbin 106 to the set of crimping rollers 102 via the lateral web cutting mechanism 104, which cuts the web to the required width. The tensioning mechanism 112 ensures that the web 108 is fed to the set of crimping rollers 102 at the desired tension. The crimping rollers 102 force the web 108 between the interleaved corrugations of the first and second rollers to apply a plurality of longitudinally extending crimp corrugations to the web 108. In this manner, the web 108 is deformed by the crimping rollers 102 to form a crimped web 116. The crimped web 116 can then be gathered together and used to form an aerosol-cooling element or an aerosol-forming substrate for an aerosol-generating article, as discussed below. For example, the crimped web 116 can be gathered together by a funnel 118 and fed into a rod-making machine 120 to form a continuous rod which is subsequently cut into a plurality of rod-shaped components, each having a gathered crimped sheet formed from a cut portion of the crimped web. It will be noted that the prior art apparatus 100 occupies a relatively large footprint, and that any interruption of the function of the crimping rollers 102 will result in an immediate stopping of the downstream rod-making machine 120. Moreover, the temperature of the web 108 when it reaches the crimping rollers 102 will be ambient or room temperature, typically around 20 degrees Celsius, which is substantially below the glass transition temperature of polylactic acid. Accordingly, the polylactic acid web 108 will have a tendency to elastically resist the crimping process. This results in a significant tendency to resist deformation, which in turn may result in a substantial resetting force and other stress and contortion in the crimped material.

[0113] FIG. 2 shows, in schematic form, a first embodiment of the present disclosure. A pool 200 of molten polylactic acid pellets is formed by heating the pellets to a temperature of at least the melting point temperature of polylactic acid, which is around 173 to 178 degrees Celsius. This may be done in a heating tank in a manner that is known in the art. Molten polylactic acid is passed between a pair of smooth rollers 201 so as to form a substantially flat polylactic acid web 202, as is also known in the art. The substantially flat polylactic acid web 202, while still at an elevated temperature, then passes between a pair of forming rollers 203. The forming rollers 203 each have substantially parallel circumferential corrugations along their surfaces, and the corrugations of one forming roller 203 preferably interleave with the corrugations of the other forming roller 203. The forming rollers 203 impart a corresponding corrugated profile to the polylactic acid web 202 while it is at the elevated temperature and therefore still soft and relatively malleable so as to form a corrugated polylactic acid web 204. The corrugated polylactic acid web 204 can then pass through a set of tensioning rollers 205. Then, the web cools to a temperature sufficiently below the glass transition temperature of the polylactic acid, thus allowing the corrugations to become set or thermally fixed in the web 204, before the corrugated polylactic acid web 204 is wound onto a bobbin 206. When the bobbin 206 is fully wound with corrugated polylactic acid web 204, the web 204 is cut across its width and the fully-wound bobbin 206 is replaced with an empty bobbin, which can then be wound with more of the corrugated polylactic acid web 204. This process is repeated in order to manufacture bobbins 206 wound with corrugated polylactic acid web 204.

[0114] FIG. 3 shows a bobbin 206 fully wound with corrugated polylactic acid web 204. Such a bobbin 206 is used to feed a rod-making machine directly, thus avoiding the need for an additional web crimping step immediately upstream of the rod-making machine.

[0115] FIG. 4 shows a cross-sectional view of the corrugated forming rollers 203 of the embodiment of FIG. 2. There is shown first and second forming rollers 203, each of which is corrugated across its width 1201 in a corrugation zone 124. In this example, the corrugation zone 124 extends around the entire circumference of each roller and extends along substantially the entire width 1201 of each roller. Alternatively, one or both of the rollers could be corrugated across its width around only a portion of its circumference or along only a portion of its length, or around only a portion of its circumference and along only a portion of its length. The first and second rollers 203 are arranged such that their axes are substantially parallel and such that their corrugations are substantially interleaved. The distance 1202 between the axes of the first and second rollers 203 can be controlled to control the clearance between the corrugations of the first and second rollers 203 and thus the amplitude of the crimp corrugations applied to a polylactic acid web passed between the set of rollers 203.

[0116] FIG. 5 shows a schematic cross-sectional view through a corrugated forming roller 203 with an axis of rotation 230. The circumferential surface of the roller 203 is provided with a zig-zag corrugated profile 220, shown here in exaggerated scale. The zig-zag profile 220 has pointed peaks and troughs.

[0117] FIG. 6 shows a schematic cross-sectional view through an alternative corrugated forming roller 203 with an axis of rotation 230. The circumferential surface of the roller 203 is provided with an undulating corrugated profile 221, shown here in exaggerated scale. The undulating profile 221 has curved peaks and troughs.

[0118] The corrugated profiles 220, 221 may have a substantially constant pitch or constant amplitude, or substantially constant pitch and constant amplitude. Alternatively, the corrugated profiles 220, 221 may have a varying pitch or varying amplitude or varying pitch and varying amplitude. These varying pitch or amplitude, may vary periodically or non-periodically.

[0119] FIG. 7 shows, in schematic form, a second embodiment of the present disclosure. A pool 200 of molten polylactic acid pellets is formed by heating the pellets to a temperature of at least the melting point temperature of polylactic acid, which is around 173 to 178 degrees Celsius. This may be done in a heating tank in a manner that is known in the art. Molten polylactic acid is passed directly between a pair of corrugated rollers 203 of the type discussed in relation to the first embodiment. This results in the direct formation of a corrugated polylactic acid web 204, without the need for a pair of smooth rollers 201.

[0120] FIG. 8 shows, in schematic form, a third embodiment of the present disclosure. A pool 200 of molten polylactic acid pellets is formed by heating the pellets to a temperature of at least the melting point temperature of polylactic acid, which is around 173 to 178 degrees Celsius. This may be done in a heating tank in a manner that is known in the art. Molten polylactic acid is passed directly between a pair of smooth rollers 201 so as to form a substantially flat polylactic acid web 202, as is also known in the art. The substantially flat polylactic acid web 202, while still at an elevated temperature, then passes between a first pair of forming rollers 203. The forming rollers 203 each have substantially parallel circumferential corrugations along their surfaces, and the corrugations of one forming roller 203 preferably interleave with the corrugations of the other forming roller 203. The forming rollers 203 impart a first corresponding corrugated profile to the polylactic acid web 202 while it is at the elevated temperature and therefore still soft and relatively malleable so as to form a corrugated polylactic acid web 204. The soft and malleable corrugated polylactic acid web 204 is then passed between a second pair of forming rollers 210, and then between a third pair of forming rollers 211. The forming rollers 210 have a smaller corrugation pitch than the forming rollers 203, and the forming rollers 211 have a smaller corrugation pitch than the forming rollers 210. In this way, a progressively smaller corrugation pitch pattern is applied to the polylactic acid web 204 as it passes between the second and third pairs of forming rollers 210, 211, as indicated schematically in FIG. 8.

[0121] FIGS. 9 and 10 show, in schematic form, a fourth embodiment of the present disclosure. A pool 200 of molten polylactic acid pellets is formed by heating the pellets to a temperature of at least the melting point temperature of polylactic acid, which is around 173 to 178 degrees Celsius. This may be done in a heating tank in a manner that is known in the art. Molten polylactic acid is then forced through an extrusion tank 220 having an extrusion die 230 with an extrusion orifice 221. The extrusion orifice 221 has a corrugation pattern corresponding to the desired corrugation pattern of an extruded corrugated polylactic acid web 204, as shown in FIG. 10. Although a zig-zag corrugation profile is shown here, other corrugation profiles such as undulating profiles may be implemented.

[0122] FIG. 11 shows a cross section of a corrugated polylactic acid web 204 having a zig-zag profile with pointed peaks and troughs. By appropriate configuration of the corrugations in the forming rollers 203 or the extrusion orifice 221, it is possible to impart desired values to various parameters of the corrugation profile, including the pitch 240, the peak angle 241, the trough angle 242 and the amplitude 243. As mentioned before, while any, some or all of these parameters of pitch 240, peak angle 241, trough angle 242 and the amplitude 243 may be constant, each of the values may also vary periodically or randomly across the width of the material. Such a variation of some or all of these parameters may avoid nesting of troughs within the gathered rod.

[0123] FIG. 12 shows a cross section of a corrugated polylactic acid web 204 having an undulating profile with rounded peaks and troughs. By appropriate configuration of the corrugations in the forming rollers 203 or the extrusion orifice 221, it is possible to impart desired values to various parameters of the corrugation profile, including the pitch 240, the peak curvature 244, the trough curvature 245 and the amplitude 243.

[0124] Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to”, and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0125] Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features or steps (or features and steps) are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

[0126] The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.