EP0471581A1

EP0471581A1 - Smoking article

Info

Publication number: EP0471581A1
Application number: EP91307543A
Authority: EP
Inventors: Martin Graham Duke
Original assignee: Rothmans International Services Ltd; Rothmans International Tobacco Ltd
Current assignee: Rothmans International Services Ltd
Priority date: 1990-08-17
Filing date: 1991-08-15
Publication date: 1992-02-19
Anticipated expiration: 2011-08-15
Also published as: EP0471581B1; IE912890A1; DE69115383D1; NZ239440A; CA2049364C; MY112865A; GR3018910T3; GB9018131D0; DE69115383T2; JP3012714B2; CA2049364A1; ES2082930T3; ZA916492B; IE74219B1; JPH04229166A; AU8253691A; AU653163B2; DK0471581T3

Abstract

A smoking article comprising a rod of smokable material (1) and a downstream filter unit (5) which includes granular material (6) containing adsorbed compounds that will generate an aerosol when hot gases are passed through it and means for providing a flow of gases from the ignited tip of the smokable granular material which is hot enough to activate said granular material.

Description

This invention relates to a smoking article which produces smoke and/or an aerosol that resembles tobacco smoke.
It is well known that tobacco smoke consists of thousands of chemicals which are the result of pyrolysis and incomplete combustion of tobacco. Many smoking articles have been proposed that will reduce the amounts of these compounds whilst still maintaining an acceptable smoking article or product.
According to the present invention, a smoking article comprises a rod of smokable material and a downstream filter unit which includes granular material containing adsorbed compounds that will generate an aerosol when hot gases are passed through it and means for producing a flow of gases from the ignited tip of the smokable material which is hot enough to activate said granular material.
Preferably the rod of smoking material is provided with a passage having impervious walls extending longitudinally therethrough to the filter unit.
When the tobacco rod is lit, hot gases from the burning coal travel preferentially along the passage to the filter end. These hot gases pass through the granular material, thus releasing adsorbed components and forming an aerosol. The quantity of hot gases transmitted along the passage is a function of its size, the density of the smokeable material surrounding it and the permeability of any outer wrapper. The passage may have a diameter in the range of 0.5 to 5.0 mm but preferably is in the range of 1.0 to 5.00 mm. Temperatures measured at the end of the passage can reach up to 550°C, thus providing sufficient heat to release components from granular material. The longitudinal passage can have a wall made from combustible material such as paper or reconstituted tobacco sheet and should be substantially impervious.
The granules in the tip element can be provided as a granular element adjacent the end of the said passage, and thus can be backed by a conventional filter element.
Granular materials such as alumina, magnesium silicate, zeolites, ceramics, activated carbon or other porous materials impregnated with selected components or compounds (e.g. nicotine, glycerol, tobacco flavours, tobacco extracts) are contained in a cavity adjacent to the end of a tobacco rod containing the longitudinal passage, and can be loose packed or in sintered form. Thus adsorbed components are desorbed when the hot gas mixture from the passage passes through the granular element of the filter unit.
The desorbed components form an aerosol which preferably then pass through a low efficiency filter which can be made from cellulose acetate, polypropylene, paper or other similar filter material.
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 :
Figures 1 to 5 are longitudinal cross-sectional views through five different embodiments of smoking articles according to the invention.
The smoking article shown in Figure 1 comprises a cylindrical tobacco rod 1 made from conventionally processed and cut tobacco at a filling density of 150 to 300 mg cm³ wrapped in a cigarette paper 2 of porosity in the range of 4 to 150 CORESTA units but preferably 20 to 80 CORESTA units. A longitudinal passage 3 extends the length of the tobacco rod with the wall of the passage 4 being substantially impervious to air and made of cigarette paper or reconstituted tobacco sheet. When the end of the smoking article is lit, smoke travels preferentially along the tobacco rod 1 whilst the hot gases travel along the passage 3 to a filter unit 5. Hot air/gas mixtures pass through a granular element 6 and desorb the components from granules 7. These components form an aerosol and pass through an end filter 8 into the mouth of the smoker. This filter should preferably be of very low retention so that maximum transfer is achieved from the granules to the smoker's mouth and can be made as a conventional filter from cellulose acetate, polypropylene, paper or other similar filter material.
In the arrangement described above the granular material can be magnesium silicate, for example Sepiolite in granular form of for example 15 - 30 mesh, but in order to ease manufacture the granules could be sintered into a rod which is then cut to appropriate size, and between 50 - 200 mg. of granules can be contained in each filter unit.
Typically, the overall length of the smoking article is in the range of 50 to 120 mm with an overall diameter of 5 mm to 8 mm, for example 7.8 mm.
If desired the granular material can be treated with nicotine and glycerol in the range of 0.5 % to 20 % w/w and 0 % to 40 % w/w respectively which will give rise to the release of nicotine when in use.
In the embodiment shown in Figure 2 the same reference numerals are used to indicate similar parts to that shown in Figure 1 but this embodiment includes an additional filtration element 9. This filter element which is located between the tobacco and the granular bed 6 is made of high efficiency material such as ultra-fine fibres of polypropylene or other polyolefin material and removes most of the smoke components that travel along the tobacco rod 1 preferentially.
In this embodiment the quantity of smoke formed by combustion of tobacco that reaches the smoker's mouth is substantially reduced.
In the third embodiment, shown in Figure 3, a cavity 10 is located between the filter element 9 and the granular element 6. This allows the hot gas mixture to pass through a larger area of the granular element and helps to prevent the end 11 of the passage 3 becoming blocked with any ash that may come down the passage.
Figure 4 shows a fourth embodiment of the present invention in which similar reference numerals are used to indicate similar parts as in Figure 1. In this construction the passage 3 extending axially throughout the length of the tobacco rod 1 is placed at the periphery thereof.
In order to retain heat within the area of the granules 7 a fifth embodiment of the present invention is shown in Figure 5 and which includes a thermal insulation section 12 made of for, example, ceramic or other thermal insulating fibres. This prevents excessive heat loss to the surroundings at the same time keeping the outside of the smoking article cool enough to hold. If desired the thermal insulation material 12 can also be arranged to act as a filter to remove the smoke which travels along the tobacco rod. The materials can be fine fibre and web materials.
It is an object of the present invention to deliver an aerosol to the smoker with significantly reduced quantities of pyrolysis and combustion products from the tobacco. To achieve this, components and flavours are adsorbed onto granular materials in the filter element. When the cigarette is lit, air drawn through the central tube is heated by the burning coal and it is this hot air that "activates" the granular material by releasing components and flavours. These vapours condense and form an aerosol which then passes through the filter section. Use of the impervious tube ensures that there is no diffusion of the hot gas from the tube to the tobacco rod or of smoke into the tube.
An additional feature of these designs is the flow characteristics of the hot air and smoke when a puff is taken on the cigarette. These flow characteristics have been modelled using a simple resistor network which indicates that smoke travels preferentially along the tobacco column whilst the hot air travels along the tube. It is for this reason that the additional filter element 9 is shown in Figures 2 and 3 . It is the intention that the element is highly efficient, thus significantly reducing the quantity of smoke particles formed by the burning tobacco section which pass to the smoker. Gases passing through this route will be of low temperature and will not desborb components from the granular material.
In the present invention it is the hot air/gases passing along the tube that provides the activating effect on the granules. It has been shown that tobacco smoke itself at ambient temperature has no effect whatsoever on the granular material, as would be the case in Figures 2 and 3.

Claims

A smoking article comprising a rod of smokable material and a downstream filter unit which includes granular material containing adsorbed compounds that will generate an aerosol when hot gases are passed through it and means for providing a flow of gases from the ignited tip of the smokable material which is hot enough to activate said granular material.
A smoking article as claimed in claim 1 in which the rod of smoking material is provided with a passage having impervious walls extending longitudinally therethrough to the filter unit.
A smoking article as claimed in claim 2 in which the granules in said tip element are provided as a granular element adjacent the end of the said passage.
A smoking article as claimed in claim 3 in which said granular element is backed by a conventional filter element.
A smoking article as claimed in claim 3 or claim 4 in which a filtration element is provided between the smokable material and the granular element.
A smoking article as claimed in claim 5 in which the filtration element is made from high efficiency material.
A smoking article as-claimed in claim 6 in which the high efficiency material is ultra-fine fibres of polypropylene or polyolefin material.
A smoking article as claimed in claims 4 to 7 in which the conventional filter element is made from a very low retention material.
A smoking article as claimed in claims 3 to 8 in which the granular element is surrounded by a thermal insulation section.
A smoking article as claimed in claims 2 to 8 in which said passage is substantially centrally co-axial with said tobacco rod.
A smoking article as claimed in claims 2 to 8 in which said passage is located co-axially and at one side of said rod.
A smoking article as claimed in claims 1 to 11 in which the granular material is alumina, magnesium silicate, zeolites, ceramics, activated carbon or other porous materials impregnated with selected components or compounds.
A smoking article as claimed in claim 12 in which the selected components or compounds are nicotine, glycerol, tobacco flavours or tobacco extracts.