IMPROVED TUBULAR ELEMENTS FOR SMOKING ARTICLES

Abstract

There is provided a tubular element for use in the manufacture of a filter of a smoking article, the tubular element comprising a first and a second layer wound of substantially continuous strips of a cellulose-fibre-based web material. The strips have predetermined thickness (T) and width (W). The web material is coated on a first surface with an activatable polymer and the first surface of the web material in the first layer faces the first surface of the web material in the second layer. An external diameter of the tubular element is substantially uniform over a given length.

Claims

1. A tubular element for use in the manufacture of a filter of a smoking article, the tubular element comprising a first and a second layer wound of substantially continuous strips of a cellulose-fibre-based web material, the strips having predetermined thickness (T) and width (W), wherein the web material is coated on a first surface with an activatable polymer and the first surface of the web material in the first layer faces the first surface of the web material in the second layer, and wherein an external diameter of the tubular element is substantially uniform over a given length.

2. A tubular element according to claim 1 wherein the first and the second layer of substantially continuous strips are spirally wound.

3. A tubular element according to claim 1 wherein the first and the second layer of substantially continuous strips are parallel wound.

4. A tubular element according to claim 1, wherein the thickness (T) of the web material is at least about 50 micrometers.

5. A tubular element according to claim 1, wherein the thickness (T) of the web material is less than about 300 micrometers.

6. A tubular element according to claim 1, wherein the width (W) of the strips of web material is at least about 2.5 millimeters.

7. A tubular element according to claim 1, wherein the external diameter of the tubular element is less than about 8 millimeters.

8. A tubular element according to claim 1, wherein the activatable polymer is a heat-activatable polymer.

9. A tubular element according to claim 1, wherein the activatable polymer is a thermoplastic selected from the group consisting of polyethylene (PE), low density polyethylene (LDPE), polyethylene terephthalate (PET).

10. Method of forming a tubular element for use in the manufacture of a filter of a smoking article, the method comprising: providing a first and a second substantially continuous strip of a cellulose-fibre-based web material having predetermined thickness (T) and width (W), the web material being coated with an activatable polymer on a first surface; winding the first and the second strip in an overlapping manner about a cylindrical mandrel element to form a substantially continuous tube on the mandrel, such that the coated surface of the first strip faces the coated surface of the second strip; wherein winding the strips about the mandrel element comprises introducing the overlapping strips into a clearance between the mandrel element and a sleeve element coaxial with and surrounding the mandrel element, the sleeve element having an internal diameter (D) corresponding substantially to the external diameter of the tubular element; and moving the overlapping strips under pressure along the mandrel element, such that the overlapping strips are forced against the sleeve element; and activating the activatable polymer to form a seal between the first and the second strip of web material.

11. Method according to claim 10, wherein the activatable polymer is a heat-activatable polymer and activating the activatable polymer comprises supplying heat to the overlapping strips as they are advanced along the mandrel element.

12. Method according to claim 10, wherein the activatable polymer is a heat-activatable polymer, the method further comprising providing an ultrasonic vibrating die as the sleeve element, and activating the activatable polymer comprises powering the ultrasonic vibrating die.

13. Method according to claim 10, wherein the internal diameter (D) of the sleeve element is less than about 8 mm.

14. Method according to claim 10, wherein the internal diameter (D) of the sleeve element is at least about 4 mm.

15. Method according to claim 10, comprising winding at least one further strip of cellulose-fibre-based web material coated with an activatable polymer on a first surface about the cylindrical mandrel element and the first and the second strips to form a substantially continuous tube on the mandrel, wherein the first surface of the at least one further strip faces the second surface of the second strip.

16. Method according to claim 1, wherein the internal diameter (D) of the sleeve element is less than about 8 mm.

17. Method according to claim 1, wherein the internal diameter (D) of the sleeve element is at least about 4 mm.

18. Method according to claim 1, comprising winding at least one further strip of cellulose-fibre-based web material coated with an activatable polymer on a first surface about the cylindrical mandrel element and the first and the second strips to form a substantially continuous tube on the mandrel, wherein the first surface of the at least one further strip faces the second surface of the second strip.

Description

[0041] The invention will be further described, by way of example only, with reference to the drawings of the accompanying Figures, wherein:

[0042] FIG. 1 illustrates a schematic side view of a tubular element according to the present invention;

[0043] FIG. 2 shows a schematic transverse cross section of the tubular element of FIG. 1;

[0044] FIG. 3 schematically shows a method of forming a tubular element for use in the manufacture of a filter of a smoking article in accordance with the present invention;

[0045] FIG. 4 is a schematic perspective view of a length of a strip of web material for forming a tubular element in accordance with the present invention being wound into a cylindrical arrangement;

[0046] FIG. 5 is another side view of a tubular element in accordance with the present invention; and

[0047] FIG. 6 is a flow-chart illustrating the steps of a method of forming a tubular element for use in the manufacture of a filter of a smoking article in accordance with the present invention.

[0048] A first and a second substantially continuous strips 100, 102 of a cellulose-fibre-based web material (for example, paper) having a thickness (T) of about 200 micrometers and a width (W) of about 5 millimeters are shown in FIG. 3. The strips 100, 102 are coated on a first surface with a thin layer of polyethylene. The polyethylene coating the strips 100, 102 is cured, such that it does not stick to a non-tacky substrate and is heat-activatable.

[0049] As illustrated in FIG. 3, the strips 100, 102 are wound in an overlapping manner about a cylindrical mandrel element 104 to form a substantially continuous tube 106 on the mandrel. The LDPE-coated surface of the first strip 100 faces the LDPE-coated surface of the second strip 102. As they are wound about the mandrel element 104, the overlapping strips 100, 102 are introduced into a clearance 108 defined between the mandrel element 104 and a sleeve element 110 coaxial with and surrounding the mandrel element 104. The sleeve element 110 has an internal diameter D of about 8 millimeters. The overlapping strips 100, 102 are moved under pressure along the mandrel element 104, such that the strips 100, 102 are forced against the sleeve element 110. This may be achieved by supplying a flow of pressurised air from the surface of the mandrel element 104 into the tubular element being formed, so as to broaden the gap between the mandrel element 104 and the overlapping strips 100, 102 of web material. This is illustrated in FIG. 3 by means of arrow directed substantially radially.

[0050] Simultaneously, the LDPE coating the strips 100, 102 is activated by supplying heat at the sleeve element 110, so as to form a seal between the first and the second strip 100, 102 of web material. The substantially continuous tube 106 may be cut into tubular segments at a location downstream of the sleeve element 110.

[0051] In a typical process, as illustrated by the flow-chart of FIG. 6, the method may further include a step 200 of unwinding the strips from respective reels and a step 202 of aligning the strips in preparation for the winding/wrapping process 204 described above. The winding/wrapping process 204 and the step 206 of advancing the tubular element being formed along the mandrel element are carried out while heat is supplied (step 208) to the activatable adhesive. This is followed by a step 210 of cooling and by a step 212 of cutting the continuous tubular element formed into tubular segments having a predetermined length.

[0052] Table 1 below lists some preferred combinations of width (W) of the strips, external diameter (D), pitch (P) and helix angle (?) for tubular elements of the present invention

TABLE-US-00001 Average external diameter 7.45 7.00 5.16 of tubular element [mm] Width of second strip [mm] 15.0 15.0 10.0 Width of first strip [mm] 14.75 14.69 9.76 Helix Angle [degrees] 46.1 42.1 46.2

COMPARATIVE EXAMPLE

[0053] A tubular element (Example A) was manufactured as described above from strips of a cellulose-fibre-based web coated with polyethylene as the activatable polymer.

[0054] The external diameter of the tubular element was measured according to the procedure set out above with a laser micrometer LS-7030M supplied by Keyence. The micrometer has a measuring range of 0.3 to 30 millimeters, with an accuracy of +/?2 micrometers.

[0055] Commercially available tubular elements (Examples B1 and B2) from two independent sources were also tested. Examples B1 and B2 were manufactured using the cellulose-fibre-based web and poly(vinyl acetate) as a wet glue.

[0056] The results of the measurements of the external diameter of the tubular elements can be found in the following Table 2.

TABLE-US-00002 Maximum Minimum Arithmetic mean external external external diameter diameter diameter Deviation Sample [millimetres] [millimetres] [millimetres] (+/?) A 6.640 6.663 6.615 0.024 B1 7.472 7.512 7.415 0.048 B2 7.480 7.640 7.456 0.092