Filter Element for Tobacco Articles, the Filter Element Having a Capsule with a Liquid Medium as Its Core Material

Abstract

The present invention relates to a filter element for use in a tobacco article, the filter element having at least one filter body and at least one capsule with a liquid medium as core material, characterized in that the at least one capsule has a water vapor-impermeable shell of a polymeric material which was obtained from a UV-polymerizable precursor material, wherein the UV-polymerizable precursor material is at least one compound with two in each case terminal diacrylate and/or dimethacrylate groups which are linked by a rigid, non-polar, non-crosslinking group.

Claims

1-22. (canceled)

23. A filter element for use in a tobacco article, the filter element having at least one filter body and at least one capsule with a liquid medium as core material: wherein the at least one capsule has a water vapor-impermeable shell of a polymeric material which was obtained from a UV-polymerizable precursor material; wherein the UV-polymerizable precursor material is at least one compound having two in each case terminal diacrylate and/or dimethacrylate groups which are linked by a rigid, non-polar, non-crosslinking group; and wherein the capsules have an average particle size of 0.1 to 10 mm preferably of 1 to 5 mm, and an average wall thickness of 10 m to 2 mm, preferably of 50 m to 200 m.

24. The filter element according to claim 23, wherein the at least one capsule has a WVTR (measured at 23 C. and a relative humidity of 80%) of 0.005 to 50 g/m.sup.2d, preferably of 0.1 to 10 g/m.sup.2d.

25. The filter element according claim 23, wherein the liquid medium of core material is releasable by mechanical loading.

26. The filter element according to claim 23, wherein the rigid group of the UV-polymerizable precursor material comprises or is derived from at least one compound which is selected from the group consisting of: a. aliphatic bicyclic or tricyclic ring diol systems which may be substituted by alkyl groups with 1 to 3 carbon atoms; b. bisphenol A or derivatives thereof in which one or both phenyl residues are substituted by alkyl groups with 1 to 3 carbon atoms; and c. diurethanes which are formed from a branched C.sub.5 to C.sub.10 alkyl diisocyanate or C.sub.5 to C.sub.10 cycloalkyl diisocyanate and monoethylene glycol.

27. The filter element according to claim 23, wherein the UV-polymerizable precursor material is selected from bisphenol A diacrylate, bisphenol A dimethacrylate, tricyclodecanedimethanol diacrylate, tricyclodecanedimethanol dimethacrylate and/or urethane dimethacrylate (UDMA) of the following formula, this generally being an isomer mixture: ##STR00003##

28. The filter element according to claim 23, wherein the UV-polymerizable precursor material has a viscosity of 0.001 to 50 Pa.Math.s, preferably to 0.1 to 10 Pa.Math.s.

29. The filter element according to claim 23, wherein the UV-polymerizable precursor material contains no solvent and no substances which are readily volatile at room temperature and atmospheric pressure.

30. The filter element according to claim 23, wherein the liquid medium is a hydrophilic liquid medium, preferably an aqueous solution or dispersion, particularly preferably water.

31. The filter element according to claim 23, wherein the liquid medium of the core material contains salts, salt hydrates, carbohydrates, proteins, vitamins, amino acids, nucleic acids, lipids, medicines, thickeners, emulsifiers, surfactants, colorants, cell material, aroma substances, fragrances or other active ingredients.

32. The filter element according to claim 23, wherein the capsule has an additional coating on the outside, with the coating preferably being obtained by means of vacuum processes such as sputtering, vapor deposition or plasma processes, or by means of chemical or electrodeposition coating, in order to obtain coated capsules.

33. The filter element according to claim 23, wherein the capsule is embedded in the at least one filter element.

34. The filter element according to claim 23, wherein the capsule is arranged next to the at least one filter body.

35. The filter element according to claim 23, wherein the filter element has more than one filter body, the capsule preferably being arranged between two adjacent filter bodies.

36. The filter element according to claim 23, wherein the filter element has at least one filter body which has one or more hollow recesses in the longitudinal direction.

37. The filter element according to claim 23, wherein the at least one capsule has a compressive strength in the range from 5 N to 25 N.

38. The filter element according to claim 23, wherein the at least one filter body and the at least one capsule are surrounded by a shell material, the shell material being paper or paperboard.

39. A tobacco article containing a tobacco-containing, rod-shaped element and filter element according to claim 23, which is arranged in the axial direction thereto.

40. A method for producing a capsule for use in a filter element of a tobacco article, the capsule having a shell and a liquid medium as core material, the method comprising: co-extruding the core material and a composition which contains a UV-polymerizable precursor material of the shell and a free-radical initiator in such a manner that the UV-polymerizable precursor material surrounds droplets of the core material in order to obtain a co-extruded material, and subsequently passing the co-extruded material through a curing zone which is a region filled with air, another gas, or in particular inert gas, in which polymerization and crosslinking of the precursor material of the shell is brought about by actinic radiation and the residence time of the co-extruded material in said curing zone amounts to 0.02 to 0.2 seconds, wherein the UV-polymerizable precursor material is at least one compound with two in each case terminal diacrylate groups and/or dimethacrylate groups which are linked by a rigid group, and wherein the core material contains an agent for achieving interfacial compatibility between the core material and the shell.

41. The method according to claim 40, wherein the residence time of the co-extruded material in the curing zone amounts to 0.05 to 0.1 seconds.

42. The method according to either of claim 40, wherein the intensity of the actinic radiation is selected such that the residual monomer content of the introduced monomers after curing is 15 wt. % or less, preferably 2 to 10 wt. % and still more preferably 1 to 5 wt. %.

43. The method according claim 40, wherein post-curing induced by actinic radiation is carried out.

44. The method according to claim 40, wherein the interfacially active agent is selected from nonionic surfactants and polyalkylene oxides, in particular polyethylene oxides with a molar mass of 100,000 to 3,000,000 dalton, and combinations thereof.

Description

FIGURES

[0088] FIG. 1 is a schematic diagram showing the technical sequence of a method for producing suitable capsules for the filter element according to the invention.

[0089] FIG. 2 is a schematic diagram showing a filter element according to the invention for use in a tobacco article.

[0090] FIG. 3 shows a first embodiment of a tobacco article according to the invention with a filter element according to the invention.

[0091] FIG. 4 shows a second embodiment of a tobacco article according to the invention with a filter element according to the invention.

[0092] FIG. 5 shows a third embodiment of a tobacco article according to the invention with a filter element according to the invention.

[0093] FIG. 6 shows the results of an investigation of the storage life of the capsules produced by the described method.

EXAMPLES

[0094] Production of a Capsule with a Liquid Medium as Core Material for Use in a Filter Element According to the Invention

[0095] The method according to the invention for producing water (vapor)-impermeable capsules is described in greater detail below, as is the use thereof in a filter element according to the invention or tobacco article.

[0096] The technical sequence of the crosslinking reaction (curing reaction) is shown by way of example in FIG. 1. As has already been mentioned, the capsules are produced by means of an annular nozzle with a preferably concentric inner nozzle. The water- and additive-containing core material to be encapsulated and the composition which contains the precursor material for the encapsulation material and the free-radical initiator are separately conveyed with the assistance of a suitable delivery device (e.g. by means of pumps or by pressurization) from the holding tanks into the nozzle structure. There is no specific limit to the diameter of the outer nozzle; it is typically in the range from approx. 5 mm to 0.1 mm, but may be a further order of magnitude smaller for obtaining still smaller capsules. The diameter of the inner nozzle is appropriately coordinated with the external diameter and is accordingly for example 2:3. Fine adjustment of the wall thicknesses of the capsules is, however, above all also determined by parameters other than those of nozzle geometry, for example by the selected delivery pressures which may favorably be in the range from 0.1 to 5 bar overpressure in comparison with ambient pressure. It is preferred for the holding tank and nozzle to be separately temperature-controllable. In this way, any relatively high viscosity resins as shell material can be adjusted to the desired viscosity range without (as a result of the transient thermal stress) any damage or unwanted side-effects occurring. Given suitable coordination of process parameters (e.g. a temperature in the range from approx. 5 to 50 C. and/or a delivery rate of approx. 10.sup.4 cm.sup.3/min to approx. 10 cm.sup.3/min for the resin and/or the content, depending on the desired size/thickness of the capsules and desired relationship between encapsulated material and wall thickness), it is possible to produce spheres consisting of the shell material with the core material in the interior. The diameter of the spheres is preferably in the range from 0.1 to 10 mm, more preferably 1 to 5 mm. It is principle possible according to the invention to establish a ratio of wall thickness to capsule diameter of 1:100. It is accordingly possible to produce stable capsules of for example 4 mm in diameter with a wall thickness of 40 m.

[0097] The capsules of the core material enveloped with the precursor material composition are preferably not extruded into a liquid but instead, after leaving the nozzle, move generally in free fall towards a curing zone, i.e. are accelerated under the influence of gravitational force. The greater the distance between the nozzle and curing zone, the faster they fall through the curing zone and thus the shorter is the residence time. The distance should be selected such that individual capsules are formed: these usually leave the nozzle in droplet form and require a certain amount of time in order to form the desired (ideally spherical) geometry. The geometry of the device must take this into account because otherwise capsules with an uneven shell thickness are obtained which, in the most unfavorable case, have defects. A distance in the range from 10 to 50 cm has proved to be a favorable compromise. One or more diaphragms (in particular iris diaphragms) may be provided within this falling path in order to protect the nozzle from scattered light from the curing zone.

[0098] The contact time of the contents with the precursor material prior to curing generally amounts overall to only a short time interval (e.g. fractions of a second, in particular 0.1 to 0.5 sec), such that the risk of the contents being contaminated by dissolution of shell constituents is minimized.

[0099] The curing zone is a region of high radiant intensity which can be provided by commercially obtainable radiators such as UV radiators from Hoenle or Fusion. The length of the zone is in principle not defined; it favorably amounts to 15-60 cm. Droplet formation is conventionally vibration-induced with the assistance of a vibration device. A high-voltage electrostatic field between the annular nozzle and a counter-electrode below the collecting tank may be provided to assist droplet breakaway.

[0100] According to the invention, the residence time of the capsules in the curing zone amounts, depending on the length of the curing zone and the nozzle-curing zone distance, to between approx. 0.05 and 0.2 seconds, preferably approx. 0.05 to 0.1 seconds. In particular, a residence time of approx. 0.06 seconds as a typical residence time is obtained at a curing zone length, in particular a radiator length of 15 cm and a nozzle-radiator distance (which preferably amounts to approx. 10-30 cm) of approx. 20 cm. If inhibition by atmospheric oxygen is observed, the radiation field may optionally be flushed with inert gas. In the case of particularly thick shells, the capsules may, if required, also be post-cured to ensure complete curing by locating the collecting vessel in the scattered line zone of the radiator.

[0101] As stated, curing proceeds with the assistance of actinic radiation. Exposure of the contents to high temperatures is largely avoided as a consequence (cold curing).

[0102] If capsule formation proceeds without active droplet shearing, i.e. if the capsule is detached from the nozzle only under the effect of the droplets' weight force, droplet size is primarily determined by the surface and interfacial characteristics of the content and of the capsule material and only to a subordinate extent by nozzle geometry. Capsules typically of a diameter of 0.5 to 5 mm are obtained by addition of substances which reduce surface and interfacial tension (e.g. surfactants). Shearing and thus breakaway of the droplets in order to achieve smaller diameters or to achieve a higher throughput may optionally be assisted by a special nozzle configuration, a directional gas stream, by oscillation (vibration), electrostatic fields or other mechanisms known in specialist circles. In the case of laminar jet breakup, in which droplet formation proceeds with vibration assistance, capsule geometry is directly determined by nozzle dimensions.

[0103] One suitable approach to upscaling is to parallelize the method with the assistance of multiple nozzles.

[0104] The radiation field should be illuminated differently depending whether an individual or parallel mode of operation is used. In the case of an individual or monomodal mode of operation, it is favorable to use an ellipsoidal reflector or the like to focus the radiant intensity into a focal line through which the capsules fall. In the case of a multimodal mode of operation, a parabolic reflector geometry which ensures uniform illumination of the radiation field may be advantageous.

Example of Application 1

[0105] Production of capsules with a diameter of 4 mm based on Sartomer SR 833 S (Arkema) (tricyclodecanedimethanol diacrylate)

[0106] Core material preparation: 0.5 g of PEO (2 million) was dissolved with stirring at 30 C. in 100 ml of demineralized water which had previously been boiled (to remove dissolved oxygen).

[0107] Shell preparation: 0.25 g of Lucirin TPO was stirred into 25 g of SR 833 S and dissolved at 50 C. under an argon atmosphere with shielding from light.

[0108] The two materials were transferred into the corresponding holding tanks for core and shell. Both tanks were adjusted to 25 C.

[0109] The falling path was flooded with argon as inert gas. The UV radiator was set to 60% of maximum power, corresponding to a radiant intensity of 84 W/cm. The frequency of the vibration generator was set to 60 Hz. Delivery pressures were set to 100 mbar (core) and 400 mbar (shell) and extrusion through a concentric nozzle configuration consisting of annular nozzle (with a diameter of 3.1 mm) with a concentric cannula (2.2 mm bore) was begun. Droplet formation was checked stroboscopically. Curing of the capsules as they formed proceeded in free fall and the capsules were collected in a container (beaker). Capsules of a uniform size (4 mm external diameter) and an average shell thickness of approx. 145 m were obtained. The capsules remained in the scattered light from the radiator for approx. 5 minutes and were consequently post-cured.

[0110] Permeation (water (vapor) permeability) was determined gravimetrically on the basis of the weight loss over time of a capsule sample consisting of 20 capsules on storage at 23 C. and 20% rel. humidity. Monitoring of weight loss over a period 2 weeks reveals water vapor permeation of 2.7 g/m.sup.2d for a shell thickness of 150 m.

[0111] A conversion rate of 93% was determined from DSC measurements.

Example of Application 2

[0112] Production of capsules with a diameter of 4 mm based on Sartomer SR 833 S with a reduced wall thickness

[0113] Core material preparation: 0.6 g of TWEEN 80 was dissolved in 100 ml of previously boiled demineralized water.

[0114] Shell preparation: 0.4 g of Irgacure 184 was stirred into 20 g of SR 833 S and dissolved at 50 C. under an argon atmosphere with shielding from light. The two materials were transferred into the holding tanks for core and shell. Both tanks were adjusted to 25 C.

[0115] The falling path was flooded with argon as inert gas. The UV radiator was set to 70% of maximum power, corresponding to a radiant intensity of 98 W/cm. The frequency of the vibration generator was set to 60 Hz. Delivery pressures were set to 50 mbar (core) and 400 mbar (shell) and extrusion through a concentric nozzle configuration consisting of annular nozzle (with diameter of 3.1 mm) with a concentric cannula (2.2 mm bore) was begun. Droplet formation was checked stroboscopically. Curing of the capsules as they formed proceeded in free fall and the capsules were collected in a container (beaker). Capsules of a uniform size (4 mm external diameter) and an average shell thickness of approx. 120 m were obtained. Post-curing in scattered light.

Example of Application 3

[0116] Production of capsules with reduced diameter (2.4 mm) based on shell material consisting of the combination UDMA:TMPTA (trimethylolpropane triacrylate)=3:1 with a shell thickness comparable to Example 2.

[0117] Core material preparation: 0.5 g of PEO (2 million) was dissolved in 100 ml of water.

[0118] Shell preparation: 0.4 g of Lucirin TPO was stirred into 33 g of the UDMA:TMPTA acrylate combination=3:1 and dissolved at 50 C. with shielding from light. The two materials were transferred into the holding tanks for core and shell. The holding tank for the shell material and the nozzle were adjusted to 50 C. and the tank for the core material to 25 C.

[0119] The falling path was flooded with argon as inert gas. The UV radiator was set to 60% of maximum power, corresponding to a radiant intensity of 84 W/cm. The frequency of the vibration generator was to at 90 Hz. Delivery pressures were set to 200 mbar (core) and 4300 mbar (shell) and extrusion through a concentric nozzle configuration consisting of annular nozzle (with a diameter of 1.75 mm) with a concentric cannula (1.1 mm bore) was begun. Droplet formation was checked stroboscopically. Curing of the capsules as they formed proceeded in free fall and the capsules were collected in a container (beaker). Capsules of a uniform size (2.4 mm external diameter) and an average shell thickness of approx. 110 m were obtained.

[0120] Investigation of the Storage Life of the Capsules Produced by the Described Method:

[0121] In the investigation, a known number of capsules were stored in a conditioning cabinet under defined climatic conditions (22 C., 60% rel. humidity). Weight loss over time was determined by regular weighing. The only possible cause for weight loss is the evaporation of water. Evaluation took account of the weight of the capsule shell.

[0122] Conversion of the losses into WVTR revealed a value of 1.06 g/m.sup.2/day.

[0123] The observation period was 42 days.

[0124] It was possible to demonstrate that the capsules according to the invention are distinguished by particularly low water loss. Water loss after 42 days was accordingly less than 10 wt. % based on the original total weight of the filled capsules at the start of the experiment.

Exemplary Embodiments of the Filter Element According to the Invention or the Tobacco Article According to the Invention

[0125] FIG. 2 shows an embodiment of filter element 1 according to the invention. The filter element 1 comprises a filter body 2 and a capsule 3 which is embedded in the filter body 2 and is filled with a liquid medium as core material. The combination of filter body 2 and capsule 3 is surrounded by a shell material 4 which defines the outer edge of the filter element 1.

[0126] FIG. 3 shows a first embodiment of the tobacco article 10 according to the invention, wherein the tobacco article 10 includes the filter element 1 according to the invention of FIG. 2. The tobacco article comprises a tobacco-containing, rod-shaped element 7 which comprises a tobacco-containing material 5 which is surrounded by a shell material 6. The tobacco-containing, rod-shaped element 7 is connected to the filter element 1 by a retaining element 8, wherein the retaining element 8 (known as tipping paper) is manufactured from paper or paper-containing material. The retaining element 8 connects the tobacco-containing, rod-shaped element 7 to a filter element 1, as shown in FIG. 2, and ensures that these two components remain in their spatial arrangement to one another.

[0127] FIG. 4 shows a second embodiment of a tobacco article 10 according to the invention, wherein the tobacco article 10 of FIG. 4 differs from the tobacco article of FIG. 3 merely in the embodiment of the filter element 1 according to the invention. In contrast with the filter element 1 of the tobacco article 10 of FIG. 3, the capsule in the filter element 1 of the tobacco article 10 of FIG. 4 is not embedded in the at least one filter body 2 but is instead arranged is between the two filter bodies 2 and 9.

[0128] FIG. 5 shows a third embodiment of a tobacco article 10 according to the invention, wherein the tobacco article 10 of FIG. 5 differs from the tobacco article of FIG. 4 merely in the embodiment of the filter element 1 according to the invention. In contrast with the filter element 1 of the tobacco article 10 of FIG. 4, the filter body 9 has a hollow recess. The tobacco article 10 according to FIG. 5 thus has a recess at the mouth end of the filter element 1 and is thus a tobacco article 10 with a recess filter.