WO1994014345A1

WO1994014345A1 - Cigarette filter rod elements and cigarettes incorporating such filter rod elements

Info

Publication number: WO1994014345A1
Application number: PCT/GB1993/002613
Authority: WO
Inventors: Tow Pin Liew
Original assignee: Rothmans International Services Limited
Priority date: 1992-12-24
Filing date: 1993-12-21
Publication date: 1994-07-07
Also published as: NO952477D0; ZA939676B; CA2152161A1; AU5708594A; FI953129A0; NO952477L; GB9226940D0; FI953129A

Abstract

Disclosed is a filter element (21) for a cigarette, and a cigarette incorporating such a filter element, comprising an outer wall provided by a plug wrap (4) surrounding an axially extending porous barrier tube (2) of micro-fine fibres. The space therebetween is filled with a porous filtering material (3). A porous support in the form of a rod of filtering material (5) is provided with an adhesive layer in the form of an adhesive tube (1). The core rod, comprising the barrier tube (2), adhesive tube (1), and porous support (5) is crimped to form a crimp (6) impervious for gas flow. 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 another suitable adhesive. The material WUNDAWEBTM is particularly suitable.

Description

CIGARETTE FILTER ROD ELEMENTS AND CIGARETTES INCORPORATING SUCH FILTER ROD ELEMENTS

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

BACKGROUND ART

In the present Applicants' European Patent Application No 89310421.6 (Publication 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 trαpport 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.

The present invention is intended to overcome or at least alleviate the difficulties referred to above.

The present invention provides a cigarette filter rod 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.

Preferably, the barrier tube is surrounded by an outer wall to define a space therebetween which is at least partly filled with a porous filtering material.

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 " UNDAWEB" made by Frudenberg 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 and the filter material surrounding the barrier tube can have a higher flow resistance.

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 a first rod segment formed as an element as set forth above and a second filter rod segment in abutment therewith.

The second filter rod segment may comprise an impervious material or a densely packed filter material with a high resistance to gas flow and a centrally and axially situated core of lower resistance to gas flow.

The invention also includes a cigarette incorporating a filter rod 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;

Figure 4 is a cross-sectional view of another embodiment of a filter rod element according to the invention;

Figure 5 is a cross-sectional view on line V-V of Figure 4;

Figure 6 is a cross-sectional view of another embodiment of the filter rod element according to the invention;

Figure 7 is a cross-sectional view on line VII- VII of Figure 6;

Figure 8 is a cross-sectional view of another embodiment of a filter rod element according to the invention;

Figure 9 is a cross-sectional view on line IX-IX of Figure 8;

Figure 10 is a cross-sectional view of yet another embodiment of a filter rod element according to the invention;

Figure 11 is a cross-sectional view on line XI-XI of Figure 10;

Figure 12 is a cross-sectional view of a still further embodiment of a filter rod element according to the invention;

Figure 13 is the end view of the filter rod element as viewed from filter end 29 as shown in Figure 12;

Figure 14 is the end view of the filter rod element as viewed from filter end 28 as shown in Figure 12;

Figure 15 is a cross-sectional view of the embodiment shown in Figure 1, showing the smoke flow directions inside the filter rod element during the initial smoking period;

Figure 16 is a cross-sectional view of the embodiment as shown in Figure 1, showing the smoke flow directions inside the filter rod element during the later smoking period; Figure 17 is a cross-sectional view of the preferred embodiment of a cigarette according to the present invention;

Figure 18 is a diagram showing a process for manufacturing filter rods according to the invention; and Figure 19 shows an alternative process.

BEST MODE CONTEMPLATED BY THE APPLICANT

As shown in Figures 1, 2 and 3 a filter element 21, according to the invention, comprises an outer wall provided by a plug wrap 4 which surrounds an axially extending porous barrier tube 2 made from micro-fine fibres to provide a space therebetween which is filled with a porous filtering material 3. A porous support in the form of a rod of filtering material 5 is provided with an adhesive layer in the form of an adhesive tube 1. The core rod provided by the barrier tube 2, adhesive tube 1 and porous support 5 is crimped to form a crimp 6 at what will be referred to as the filter end 8 of the element.

As will be seen from Figure 3 the crimp 6 is of cruciform shape although other practical shapes can also be used. The crimp 6 is impervious for gas flow.

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 1 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 materials 3 and 5 are common cigarette filter materials such as cellulose acetate tow, polypropylene tow, paper, etc. Material 5 is the filter tow item such as 8Y/14000, 6Y/17000 etc, that provides low flow resistance and low filtration efficiency. In comparison, material 3 always provides higher flow resistance than the flow resistance from material 5. Both materials 3 and 5 may be processed in the presence of steam. By using a conventional device such as mandrel and steam, material 3 may be moulded so that material 3 does not fill the space 7 where crimp 6 is located. However, the filter is also effective when the spacee 7 is filled, as shown in another embodiment of the present invention illustrated in Figures 4 and 5.

Figures 6 and 7 show another embodiment of a filter rod element according to the present invention. Filter rod element 23 consists of all the parts as shown in Figure 1, except that there are apertures 11 on tubes 1 and 2. The total number of apertures 11 ranges between 1 and 10, preferably 2 . The total opening area of the apertures ranges between 0.1 mm² and 10 mm². The apertures may be located anywhere between locations K and N so that:

M < -. L

where M is the distance of the apertures as measured from the filter end 8, and L is the total length of the filter rod element 23.

Figures 8 and 9 show another embodiment in which the filter rod element 24 is a dual filter rod consisting of a plugwrap 12 and filter rod segments 21 and 25. Filter rod segment 21 is as described in Figure 1. Filter rod segment 25 consists of a plugwrap 4, and filter material 13. Material 13 is common filter material such as cellulose acetate tow, or polypropylene tow, paper, or similar material. Filter element 24 will also be effective if filter rod element 21 is replaced by filter rod component such as filter rod elements 22 or 23. Figures 10 and 11 show yet another embodiment of the filter rod element according to the present invention and in which element 25 is a dual filter rod. It consists of a plugwrap 12 and filter rod segments 21 and 26. Filter rod segment 21 is as described in Figure 1. Filter rod segment 26 consists of a plugwrap 4 and filter materials 15 and 16. Filter materials 15 and 16 are common cigarette filter materials such as cellulose acetate tow, polypropylene tow, paper, etc. Preferably, the material 15 is one that provides a high resistance flow path, and material 16 provides a low resistance flow path. The filter rod element 25 will also be effective if filter rod element 21 is replaced by other elements such as filter rod elements 22 or 23.

Figure 12 shows a still further embodiment of the present invention, being a filter rod element 26 crimped at filter end 28. The filter rod 26 consists of conventional filter material 5, preferably a cellulose acetate tow such as 8Y/38000 tow. Barrier tube 1 acts as the plugwrap of filter rod element 26. Adhesive tube 2 is located between the barrier tube 1 and the filter material 5. Adhesive tube 2 helps to fuse the barrier tube 1 and material 5 together in crimp 6 after the crimping process. Apertures 11 are shown on the barrier tube 1 and adhesive tube 2, but are optional. Filter rod element 26 cart be used to form a filter-tipped cigarette, with crimp 6 preferably placed to abutt the tobacco rod 27.

As shown in Figure 14, the crimp 6 has a cruciform section, but other profiles are possible as previously described.

The flow pattern of smoke through filter rod element according to the invention, without ventilating air, is shown in Figures 15 and 16. Smoke is shown to flow from filter end 8 towards filter end 9. Figure 15 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. There are two paths: paths 31 and 32. Flow path 31 is for smoke that flows through the annulus space passage filled with material 3 and path 32 is for smoke that flows through the core rod material 5. Since material 3 always provides higher flow resistance than that from material 5, the amount of smoke on path 31 is lower or even negligible as compared With the amount of smoke on path 32.

The majority of the smoke flows through the region where the resistance is lowest, i.e. region 40. This smoke has to pass through the micro-fine fabric layer 2 and adhesive layer 1 before reaching material 5

Figure 16 shows the flow paths inside the filter after a number of puffs of cigarette smoke have passed through^" the filter. Region 40 has now collected sufficient "tar" from the smoke on the micro-fine fabric such that the flow resistance in region 40 is greatly increased. Consequently the smoke switches to flow through the cleaner fabric surface away from region 40. Due to flow resistance differences between materials 3 and 5, the amount of smoke flowing in path 31 is again lower or even negligible as compared with the amount of smoke flowing in path 32.

The location B shown in Figures 15 and 16 represents the position of ventilating air flow into filter rod element 21 through ventilation holes on the tipping paper (not shown) and porous plugwrap 4 or through holes formed by a laser.

Figure 17 shows the preferred embodiment of a cigarette according to the present invention. Cigarette 26 consists of a tobacco rod 27, a filter rod element 21 and tipping paper 17 and ventilation holes 18. The cigarette also performs effectively if filter rod element 21 is replaced by other filter rod elements such as element 22, 23, 24 or 25. Filter end 8 is shown preferably in abutment with the tobacco rod. However, the filter is also effective if filter end 9 is in abutment with the tobacco rod' 27. Cigarette 26 performs also effectively, with or without the ventilation holes 18.

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.

Figure 18 is a diagram showing a process for manufacturing filter rods according to the invention and the various features are identified. It will be seen that the porous support, in the form of a rod of 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 a transport jet 111 where it is joined by further tow material taken from a tow bale 112 via a booming section 113 and a plasticiser applicator 114. The wrapped core rod provided by the barrier tube, adhesive layer and porous support, is now wrapped with a plug wrap taken from a reel 115 in a garniture with steam indicated by reference numeral 116.

In an alternative process, as indicated in Figure 19, 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.

Claims

CLAIMS :

1. A cigarette filter 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.

2. A cigarette filter according to claim 1 wherein the barrier tube is surrounded by an outer wall thereby to define a space therebetween which is at least partly filled with a porous filtering material.

3. A cigarette filter according to claim 1 or claim 2 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.

4. A cigarette filter according to any preceding claim wherein the barrier tube is made of micro-fine fibres.

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

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

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

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

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

10. A cigarette filter according to any one of claims 2 to 9 wherein the filter material within the barrier tube has a relatively low flow resistance and a relatively low filtration efficiency, and the filter material surrounding the barrier tube has a relatively higher flow resistance.

11. A cigarette filter according to any preceding claim having tip ventilation holes in the barrier tube.

12. A cigarette filter element comprising a first filter segment according to any preceding claim and a second filter segment in longitudinal abutment therewith.

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