Title of Invention

POROUS CARBON MATERIALS AND SMOKING ARTICLES AND SMOKE FILTERS THEREFOR INCORPORATING SUCH MATERIALS

Abstract

A porous carbon material suitable for incorporation in smoke filters for cigarettes has a BET surface area of at least 800 m2/g and a pore structure that includes mesopores and micropores. The pore volume (as measured by nitrogen absorption) is at least 0.9 cm2/g and from 15 to 65% of the pore volume is in mesopores. The pore structure of the material provides a bulk density generally less than 0.5 g/cc. The material may be produced by carbonizing and activating organic resins and may be in the form of beads for ease of handling.

Full Text

Porous carbon materials and smoking articles and smoke filters therefor incorporating such materials used by those skilled in the art, pores in an adsorbent material are called 'Micropores" if their pore size is less than 2nm ( International patent publication WO 01/19904 discloses a process for producing monolithic porous carbon by carbonising an organic resin produced by polymerisation of a system such as resorcinol/formaldehyde, divmylbenzene/styrene vinylidne chloride or vinylidne chloride/divinylbenzrae, in the presence of a surfectant. Porous carbon materials may also be produced by agglomeration of fine carbon particles with binders. For example, US Patent specification No US-3351071 discloses a process for According to one aspect the present invention there is provided a porous carbon material having a BET surface area of at least 800 m2/g, a density of not more than 0.5 g/cc, a pore structure that includes mesopores and micropores, and a pore volume (as measured by nitrogen adsorption) of at least 0.9 cm2/g- The porous carbon materials of the invention preferably have a bulk density less than 0.5 g/cc. Typical upper values for the range of densities of the carbon materials of the present invention are 0.45 g/cc, 0.40 g/cc, and 0.35 g/cc. Preferably, the bulk density of the carbon materials of the invention is in the range 0.5 to 0.2 g/cc. The carbon materials of the invention may also be characterised by their pore structure rather than density. According to this aspect of the invention, there is provided a porous carbon material having a BET surface area of at least 800 m /g, a pore structure that includes mesopores and micropores, and a pore volume (as measured by nitrogen adsorption) of at least 0.9 cm2/g, from 15 to 65% of which is in mesopores. The preferred porous carbon materials of the invention may be also be characterised by a pore structure wherein the pore volume (as measured by nitrogen adsorption) is at least 1.0 cm2/g, but less than 20% of the pore volume is in pores of from 2-10 nm. Usually less than 15%, and often less than 10% of the combined pore volume is in pores of from 2-1 Onm. The density and pore structure of porous carbon material are closely related. Generally, we have found that in samples of carbon materials of the invention, the higher the combined volume of micro-, meso- and macropores, the lower the density, because pores increase the volume of a given mass of material without increasing its weight. Furthermore, as the density decreases, so the proportion of macro- and mesopores to micropores increases. That is to say, in general, the lower the density of the carbon material of the invention, the higher the proportion of the pore volume in mesopores and macropores compared with the pore volume in micropores. However the correlation between density and pore volume, as determined by nitrogen adsorption, is not precise. Hence, some carbon materials of the invention having the pore structure defined in either of the two preceding paragraphs may have densities greater than 0.5 g/cc, for example densities of up to 0.52, 0,55, 0.60 or 0,65 g/cc. Conversely, some carbon materials of the invention may have densities less than 0.5 g/cc and a pores structure in which less than 15% (e.g. 12%, 10% or 5%) of the combined mesopore and micropore volume is in mesopores. The lack of complete correlation between density and micro- and mesopore structure arises because the technique of nitrogen adsorption used to estimate pore size distribution is not capable of detecting pore sizes greater than about 50 nm. The total pore volume of a material estimated by nitrogen adsorption techniques therefore corresponds to the combined pore volumes of micropores and mesopores. The macropore volume of a material is not revealed by this technique. Thus, where the carbon materials of the invention have a low density and a relatively low proportion of mesopores, as detected by nitrogen adsorption, the low density is attributable to a relatively high pore volume m the macropore range immediately neighbouring mesopore range, i.e. in the range 50nm to 500nm. Whilst pore volumes in the macropore range can be estimated by mercury porosimetry, the results obtained using this technique do not match those obtained using nitrogen adsorption. Hence it is difficult to estimate precisely the pore volume of a material across the full range of pore sizes from 2-500 nm. The invention also includes a smoking article comprising smoking material and a porous carbon material according to the invention. The BET surface area of the preferred porous carbon materials of the invention is at least 800 m2/g, preferably at least 900 m2/g, and desnably at least 1000 m2/g. Typical values for BET surface area of carbon materials of the invention are about 1000, 1100, 1150, 1200, 1250 and 1300 m2/g. Porous carbon materials with BET surface areas of up to 1250 m2/g, e.g. 1000-1250 m2/g, are most preferred. The porous carbon materials of the invention preferably have a pore volume (as estimated by nitrogen adsorption) of at least 0.95 g/cc, and desirably at least 1 g/cc. Carbon materials with pore volumes of at least l.lcc/g are particularly useful as an adsorbent for tobacco smoke. Typical values for the pore volumes of the carbon materials of the invention are 1.15 cc/g, 1.2 cc/g, L25 cc/g and 1.3 cc/g. Usually, the combmed pore volume will be in the range 1.1 to 2.0 cc/g. Carbon materials according to the invention with pore volumes significantly higher than 2.1 cc/g, for example 2.2 or 2.3 cc/g are low in density and are therefore less easy to handle in cigarette production equipment. Such carbon materials are less favourable for use in cigarettes or smoke filters for that reason. In the preferred carbon materials of the present invention, at least 30% but desirably no more than 65% of the pore volume (as estimated by nitrogen adsorption) is in mesopores. Typical minimum values for the volume of mesopores as a percentage of the combined micropore and mesopore volumes of the carbon materials of the invention are 35%, 40% or 45%. Typical maximum values for such volumes are 65%, 60% and 55%. Preferably the mesopore volume of the carbon materials of the mvention is in the range 35-55% of the combined mesopore and micropore volume. The porous carbon materials of the invention may be obtained from any source. However, porous carbon materials of the invention that are formed from carbonised organic resm are preferred to porous carbon materials obtained from other sources, e.g. coconut charcoal. Examples of suitable resins include hydroxyl-substituted aromatic resins such as those derived from phenol, bis-phenol A, aminophenols or resorcinol, and non-phenolic resins such as those derived from styrene and vinyl pyrolidone or from styrene and divinyl benzene. Hydroxy-substituted aromatic resins are preferred, especially those derived from phenols. The preferred carbon materials of the invention are obtained by condensing a nucleophilic component with an electrophilic cross-linking agent in the presence of a pore former, as described in WO-A- 02/12380 (incorporated herein by reference). The invention specifically includes a process for producing a porous carbon material comprismg the steps of condensing a nucleophilic component with an electrophilic cross linking agent in the presence of a pore former to form a resin, carbonising the resin and activating the resulting carbon material. The reaction to form the resm may be carried out m the presence of a catalyst A solvent may also be used, but preferably the pore former also acts as solvent The nucleophilic component may be, for example, a phenolic resm, such as a novolak resin, or another resin based upon copolymers of phenolic compounds, such as m-ammo-phenol, diphenols such as resorcinol, hydroqunione, or amines such as aniline, melamine or urea with aldehydes such as formaldehyde, furfural or salicylaldhyde. The cross linking agent may be, for example, formaldehyde, furfural or hexamelhylenetetramine. The pore former may be, for example, a The porous carbon material may be a monolithic structure, adapted for use in a filter for a smoking article. For example the material may be formed mto a cylindrical filter element Materials that are substantially free of dust create fewer handling and contamination problems in the manufacture of smoking articles and smoke filters. The porous carbon material of the invention is therefore also preferably substantially free of particles smaller than 10 microns. Desirably it is also substantially free from particles analler than 20 microns, and most advantageously it is free from particles smaller than 30 microns. In order that the invention may be better understood, preferred embodiments thereof will now be described, by way of example only - in which reference will be made to the following Figures: In each case, the resulting viscous solution was poured as a stream with stirring into 2 to 4 times its volume of a preheated (115-120° C) mineral oil containing 0.5% by volume of a Table 5 gives further details of the pore size distribution of Examples 2, 3, 4, 7, 8, 9,12 and 13, and of comparative examples A and C. empty cavity 4mm in length, and a sample with a cavity containing 60mg of coconut charcoal. Table 6 summarises the analytical results for 1,3-butadiene and hydrogen cyanide (HCN). In order to compare the performances conveniently with respect to coconut charcoal, the results for each sample were normalised with respect to the results for the coconut charcoal. The normalised data is plotted in Figures 5 and 6, which are scatter charts plotting the percentage reduction in 13-butadiene and HCN, normalised with respect to the coconut charcoal of comparative example A, against the total combined volume of meso- and micropores, and the % micropore volume respectively. ethylene glycol as pore fonner, without any additional cross-linking agent The resulting polymer was washed, carbonised and then activated in carbon dioxide to achieve 40% bum-off. analytes tested, and that the comparative examples performed worse than coconut shell caibon m relation to all four of the analytes. Figure 7 is a similar view to Figure 6 of a smoking article with an alternative smoke filter according to the invention. In the drawings, which are not to scale, similar features are given like reference numerals. Referring to the drawings, Figures 7 and 8 illustrate smoking articles in the form of cigarettes having a rod 1 of tobacco encased in a wrapper 2 attached to a smoke filter 3 by means of a tipping paper 4. For clarity, the tipping paper 4 is shown spaced from the wrapper 2, but in fact they will lie in close contact. In Figure 7, the smoke filter 3 comprises two cylindrical filter elements 3a and 36. The first filter element 3a at the mouth end of the filter is 15mm in length, composed of cellulose acetate tow impregnated with 7% by weight of triacetin plasticiser having a 25mm water gauge pressure drop over its length. The second filter element 3b, positioned adjacent the rod 1 is 12 mm in length, has a 90 mm water gauge pressure drop over its lengh, and comprises 80mg cellulose acetate tow impregnated with 4% by weight of triacetin and has 30mg of an activated porous carbon material according to the invention distributed evenly throughout its volume in a "Dalmatian" style. the cigarette shown in Figure 8 is similar to that of Figure 7 except that the smoke filter 3 has three coaxial, cylindrical filter elements 3a, 3b and 3c. The first filter element 3a at the mouth end of the cigarette is 10mm in length, and composed of cellulose acetate tow impregnated with 7% by weight of triacetin plasticiser- The second filter element 3b, positioned adjacent the first filter element 3a is a cavity 7mm in length containing 100 mg of an activated porous carbon material according to the invention. The third filter element 3c adjacent the second filter element 3b is 10 mm in length and comprises cellulose acetate tow impregnated with 7% by weight of triacetin. A ring of ventilation holes 5 is formed m the tipping paper 4 in a radial plane A-A which deliver air into the second filter element 36 about 3 mm downstream of the junction with the third filter element 3c when smoke is inhaled through the cigarette. In summary, the Examples provide a porous carbon material suitable for incorporation in smoke filters for cigarettes that has a BET surface area of at least 800 m /g and a pore structure that mcludes mesopores and micropores. The pore volume (as measured by nitrogen adsorption) is at least 0.9 cmVg and from 15 to 65% of the pore volume is in mesopores. The pore structure of the material provides a bulk density generally less than 0.5 g/cc. The material may be produced by carbonising and activating orgatuc resins and' may be m the form of beads for ease of handlmg. Various modifications and variations of the described aspects of the invention will be apparent to those skilled in the art without de parting from the scope and spirit of the invention. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described modes of carrying out the invention which are obvious to those skilled in the relevant fields are intended to be within the scope of the following claims. CLAIMS 1. A porous carbon material having a BET surface area of at least 800 m2/g, a density of not more than 0.5 g/cc, a pore structure that includes mesopores and micropores, and a pore volume (as measured by nitrogen adsorption) of at least 0.9 cm2/g. 2. A porous carbon material having a BET surface area of at least 800 m2/g, a pore structure that includes mesopores and micropores, and a pore volume (as measured by nitrogen adsorption) of at least 0.9 cm2/g, from 15 to 65% of which is in mesopores. 3. A material according to Claim 2 wherein the pore volume (as measured by nitrogen adsorption) is at least 1.0 cm3/g and from 30 to 65% of the pore volume is in mesopores. 4. A material according to Claim 2 or Claim 3, wherein less than 20% of the pore volume is in pores having diameters in the range 2-10 nm. 5. A material according to any one of Claims 2 to 4 having a bulk density of not more than 0.5 g/cc. 6. A material according to any one of Claims 1 to 5 having a BET surface area of from 1000 to 1250 m2/g. 7. A material according to any one of Claims 1 to 6 wherein the pore volume m micropores and mesopores is from 1.1 to 2 cm /g. 8. A material according to any one of Claims 1 to 7 wherein from 35 to 55% of the pore volume is in mesopores. 9. A material according to any one of Claims 1 to 8 in particulate form. 10. A material according to any one of Claims 1 to 9 in the form of microbeads. 11. A material according to Claim 9 or Claim 10 having a mean particle size of from 50 to 1000 microns. 12. A material according to any one of Claims 9 to 11 having a D90/D10 particle size distribution of at least 10. 13. A material according to any one of Claims 9 to 12 that is substantially free of particles smaller than 10 microns. 14. A material according to anyone of Claims 1 to 13 composed of a carbonised organic resin. 15. A material according to Claim 14 wherein the organic resin contains nitrogen. 16. A material according to Claim 14 or Claim 154 wherein the resin is produced by condensing a nucleophilic component with an electrophilic cross linking agent in the presence of a pore former. 17. A material according to Claim 16 wherein the nucleophilic component or the cross-linking agent is an organic nitrogen compound. 18. A material according to Claim 16 or Claim 17 whereuin the nucleophilic component comprises a novolak resin. 19. A material according to any one of Claims 16 to 18 where in the crosslmkmg agent comprises hexamethylene tetramine. 20. A material according to any one Claims 16 to 19 wherein the pore former comprises ethylene glycol. 21. A smoking article comprising smoking material and a material according to any one of Claims 1 to 20. 22. A smoking article according to claim 21 comprising a rod of smoking material and a filter, and the porous carbon material is incorporated in the filter. 23. A smoke filter for a smoking article comprising a material according to anyone of claims 1 to 20. 24. A process for producing a material according to any one of Claims 1 tol5 comprising the steps of condsasing a nucleophilic component widi an electrophilic cross linking agent in the presence of a pore former to form a resin, carbonising the resin and activating the resulting carbon material 25. A process according to Claim 24 wherein the nucleophilic component or the cross- linking agent is an organic nitrogen compound. 26. A process according to Claim 24 Claim 25 wherein the nucleophilic component comprises a novolak resin. 27. A process accordmg to any one of Claims 24 to 26 where in the crosslinking agent comprises hexamethylene tetramine. 28. A process according to any one of Claims 24 to 27 where in the pore former is ethylene glycol

Documents:

4253-2007-FORM 3.pdf

4253-2007-Petition 137 for Form 3.pdf

4253-2007-Petiton 137-POR.pdf

4811-CHENP-2007 AMENDED CLAIMS 27-06-2014.pdf

4811-CHENP-2007 AMENDED PAGES OF SPECIFICATION 27-06-2014.pdf

4811-CHENP-2007 CORRESPONDENCE OTHERS 17-09-2014.pdf

4811-CHENP-2007 CORRESPONDENCE OTHERS 06-11-2013.pdf

4811-CHENP-2007 CORRESPONDENCE OTHERS 07-10-2014.pdf

4811-CHENP-2007 EXAMINATION REPORT REPLY RECEIVED 27-06-2014.pdf

4811-CHENP-2007 FORM-1 07-10-2014.pdf

4811-CHENP-2007 OTHERS 27-06-2014.pdf

4811-CHENP-2007 POWER OF ATTORNEY 27-06-2014.pdf

4811-chenp-2007-abstract.pdf

4811-chenp-2007-claims.pdf

4811-chenp-2007-correspondnece-others.pdf

4811-chenp-2007-description(complete).pdf

4811-chenp-2007-drawings.pdf

4811-chenp-2007-form 1.pdf

4811-chenp-2007-form 3.pdf

4811-chenp-2007-form 5.pdf

4811-chenp-2007-pct.pdf