WO1995035042A1

WO1995035042A1 - Cigarette filter rod elements and cigarettes incorporating such filter rod elements

Info

Publication number: WO1995035042A1
Application number: PCT/GB1994/001306
Authority: WO
Inventors: Tow Pin Liew
Original assignee: Rothmans International Services Limited
Priority date: 1994-06-17
Filing date: 1994-06-17
Publication date: 1995-12-28
Also published as: AU6974794A

Abstract

Disclosed is a filter element (1) for a cigarette, and a cigarette incorporating such a filter element, comprising an axially extending porous barrier tube (2) of micro-fine fibres. The space therebetween is filled with a porous filtering material (5), and there is an adhesive layer in the form of an adhesive tube (4). The element is crimped between its ends to form a crimp (6) impervious to gas flow but offering porous filter surfaces (8).

Description

CIGARETTE FILTER ROD ELEMENTS AND CIGARETTES INCORPORATING SUCH FILTER ROD ELEMENTS

TECHNICAL FIELD OF THE INVENTION This invention relates to cigarette filter rod elements and cigarettes incorporating such elements.

BACKGROUND ART

In the present Applicants' EP-A-No 0 364 253 a cigarette filter rod element is shown having an outer wall which surrounds an axially extending porous barrier tube made from micro-fine fibres to provide a space therebetween which is filled with a porous filtering material. One end of the barrier tube is closed and the tube is located so that at least part of the gas flow passes continuously through its wall. In some of the embodiments described the end of the barrier tube is closed by deforming the tube material, for example by crimping. Again, in some embodiments the barrier tube is carried on a porous support.

DISCLOSURE OF THE INVENTION

It has been found that there are difficulties in crimping the closed end due to the properties of the material and if a porous support is employed the material of the barrier tube and the porous support may be incompatible for self-adhesion with heat and tend not to stick together satisfactorily after crimping under heat and pressure.

Present applicants' PCT/GB93/02613 is intended to overcome or at least alleviate the difficulties referred to above: but a further improvement is provided by the present invention, wherein the end of the barrier tube does not lie, as it does in the examples of that PCT application, at the end of the filter. The present invention provides a cigarette filter comprising an axially extending porous barrier tube enclosing a porous filtering material, said barrier tube being closed by deforming the tube material, the tube being located so that at least part of the gas flow passes continuously through a wall thereof; wherein the inner surface of the tube is provided with an adhesive layer to hold the deformed part together at its closed end, closure of the barrier tube being intermediate the ends of the filter.

In this case there is no need for registration, during the manufacturing process, of the closure with an end of the filter.

The tube may be located so that substantially all the gas flow passes continuously through a wall thereof.

The adhesive layer may conveniently be provided by an adhesive material, for example nitrile rubber, vinyl acetate-acrylic acid, vinyl acetate-ethylene, polyacrylate (carboxylic) polyamides, polyimides, polyhydroxy ether, polyester plus isocyanate or any other suitable adhesive.

It has been found that the material sold under the Trade Mark "WUNDA EB" made by Freudenberg Nonwovens Ltd of Halifax, England, is particularly suitable to provide the adhesive layer.

Preferably the barrier tube is made of micro-fine fibres, a suitable diameter of which is between 0.1 μm and 10 μm. Layers of micro-fine fibres in the barrier tube can have one or more layers of protective fabric made up of coarse fibres and the protective fabric can be porous. Advantageously, these micro-fine fibres and the protective fabric may be composed of organic polymeric materials, for example polypropylene fibres.

The wall thickness of the barrier tube can be between 0.05 mm and 2 mm with a density of between 0.04 and 0.3 gem^"3.

Preferably the barrier tube is carried on a porous support and this can be made as a rod of filter material.

The porous support rod can be made of a filter material which has a low flow resistance and a low filtration efficiency.

In a convenient construction the end of the barrier tube is closed by crimping.

Tip ventilation holes can be provided if desired.

The invention also includes a cigarette filter rod element which comprises an element as set forth above.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be performed in various ways and some embodiments will now be described by way of example and with reference to the accompanying drawings in which: -

Figure 1 is a cross-sectional view of one embodiment of a filter rod element according to the ^* invention; Figure 2 is a cross-sectional view on line II-II of Figure 1;

Figure 3 is a cross-sectional view on line III- III of Figure 1;

Figures 4, 5 and 6 are cross-sectional views of the filter rod element incorporated in a cigarette,

Figures 4 and 5 being on a larger scale than Figure 6 and showing the embodiment at different stages of use.

Figure 7 is a diagram showing a process for manufacturing filter rods according to the invention; and Figure 8 shows an alternative process.

BEST MODE CONTEMPLATED BY THE APPLICANT

As shown in Figures 1, 2 and 3 a filter element 1, embodying the invention, has an outer wall which is an axially extending porous barrier tube 2 made from micro- fine fibres. It is filled with a porous filtering material 5 and has an adhesive layer in the form of an adhesive tube 4. The core rod provided by the barrier tube 2, adhesive tube 1 and filter material 5 is crimped to form a crimp 6 at what will be referred to as the filter end of the tube; this end is however not at an axial end of the filter element and in this embodiment is halfway along the length of the latter.

As will be seen from Figure 3 the crimp 6 is of cruciform shape with legs 7 although other practical shapes can also be used. The centre of the crimp 6 is impervious to gas flow, but inclined transition surfaces 8 lying between the closed crimp 6 and the full diameter of the element.

The barrier tube 2 is made of at least one layer of micro-fine fibres which can be produced by a melt- blown process. The diameter of the micro-fine fibres ranges from between 0.1 μm and 10 μm. The thickness of this layer ranges between 0.05 mm and 2 mm and the density of the layer ranges from between 0.04 and 0.3 gem"³. For easier handling and protection the layer of micro-fine fibres can be supplied with either one or two layers of protective fabric made up of coarse fibres. In the case when two protective fabrics are used, the fine fibre layer is sandwiched between these protective fibres which are porous.

The adhesive tube 4 is located between the barrier tube 2 and the filter material 5 and is made of an adhesive material, preferably a hot melt material. Common adhesive materials such as nitrile rubber, vinyl acetate-acrylic acid, vinyl acetate-ethylene, polyacrylate (carboxylic) polyamides, polyimides, polyhydroxy ether, polyester plus isocyanate, or similar materials are suitable.

The function of the adhesive tube is that it helps to fuse the barrier tube 2 and the material 5 together firmly in the crimp 6 after the crimping process. It will be appreciated that the adhesive tube must be porous to gas flow.

Filter material 5 is any common cigarette filter material such as cellulose acetate tow, polypropylene tow, paper, etc. Material 5 is a filter tow item such as 8Y/14000, 6Y/17000, 8Y/38000 or more preferably 5Y/45000, 6Y/45000, or 8Y/40000 etc., that provides low flow resistance and low filtration efficiency. As illustrated in Figures 4, 5 and 6, the filter element can be incorporated into a cigarette 16 by overwrapping with tipping paper 17 to unite it with a tobacco rod 18 ' "wrapped by conventional cigarette paper 19. The cigarette may be ventilated. As shown, diagrammatically, aperatures 20 are shown in the tipping paper 17. Ventilation can be achieved in any conventional way, includer laser-pierced or electrostatic spark generated apertures which may be so small as to be invisible.

The flow pattern of smoke through the filter rod element or cigarette is shown in Figures 4 and 5. Smoke is shown to flow from left to right, following arrows 21. Figure 4 shows the flow paths of the tobacco smoke during the initial puffing period. Before the smoke passes through the filter, the various filter materials are clean. The smoke being constrained by the tipping paper 17 must flow axially of the filter element, passing through filter material 5 and then through the faces 8 of the crimp i.e. it passes also through the layer 2 and the layer 4. Ventilation air enters at 23 to dilute the smoke.

As smoking proceeds, particulate material builds up on and in the faces 8 as shown at 22, Figure 5, providing flavour enhancement.

In the arrangements described above the adhesive material is shown as a tube but it will be appreciated that it could be provided merely as an adhered layer to the barrier tube 2 and could, for example, be formed by spraying an adhesive material onto the material from which the barrier tube is made. Other ways of providing the layer will be apparent to the man skilled in the art. The filter element may be juxtaposed to a second conventional element in a cigarette. Furthermore, the filter element may be surrounded by further filter material in a conventional polywrap. Figure 7 is a diagram showing a process for manufacturing filter rods embodying the invention and the various features are identified. It will be seen that the filtering material is made from tow indicated by reference numeral 100 and passes through a tow blooming section 101 and a plasticiser applicator 102. It is then forwarded by a transport jet 103 to a garniture (with steam) 104. The formed rod 105 passes into a further garniture (with hot air) 106 where it is joined by the micro-fine fabric and an adhesive web indicated by reference numeral 107. The material 107 is supplied to the garniture 106 and is wrapped around the porous support rod 105. The combined material 108 now passes to a heated crimper 109 where it is crimped under heat and pressure into appropriate lengths. The crimped material 110 passes through to a cutter (not shown) to be cut to length.

In an alternative process, as indicated in Figure 8, the same reference numerals are used to indicate similar parts but in this process the adhesive web is indicated by reference numeral 117 is supplied separately from the micro-fine fabric indicated by reference numeral 118. The adhesive web and micro-fine fabric are combined with the porous support rod 105 in the garniture 106.

In the present embodiments it is not critical to determine any particular relationship between the position of the crimp and the position of cut-off.

Claims

CLAIMS :

1. A cigarette filter element comprising an axially extending porous barrier tube enclosing a porous filtering material, one end of said barrier tube being closed by deforming the tube material, the tube being located so that at least part of the gas flow passes continuously through a wall thereof; wherein the inner surface of the tube is provided with an adhesive layer to hold the deformed part together at its closed end, the closure of the barrier tube being intermediate the ends of the filter.

2. A cigarette filter element according to claim 1 wherein the adhesive layer is provided by an adhesive material selected from nitrile rubber, vinyl acetate- acrylic acid, vinyl acetate-ethylene, a polyacrylate polyamide, a polyimide, polyhydroxy ether, or polyester and isocyanate.

3. A cigarette filter element according to claim 1 or claim 2 wherein the barrier tube is made of micro-fine fibres.

4, A cigarette filter element according to claim 3 wherein the micro-fine fibres have a diameter between 0.1 μm and 10 μm.

5. A cigarette filter element according to claim 4 wherein the micro-fine fibres are composed of an organic polymeric material.

6. A cigarette filter element according to claim 5 * wherein the micro-fine fibres are polypropylene fibres.

7. A cigarette filter element according to any preceding claim wherein the wall thickness of the barrier tube is between 0.05 mm and 2 mm.

8. A cigarette filter element according to any preceding claim wherein the density of the barrier tube wall is between 0.04 and 0.3 gem"³.

9. A cigarette filter element according to claim 4 comprising a plurality of layers of microfine fibres.

10. A cigarette filter element according to any one of the preceding claims wherein the filter material within the barrier tube has a relatively low flow resistance and a relatively low filtration efficiency.

11. A cigarette filter element according to any preceding claim having tip ventilation.

12. A cigarette incorporating a filter element according to any preceding claim.