Surface-modified activated carbon in smoking articles

Abstract

A surface-modified activated carbon is provided to reduce the amount of free fine carbon particles among the activated carbon. By surface-modifying the activated carbon with a layer, the activated carbon can have increased mechanical strength and the fine carbon particles among the activated carbon can be fastened to the layer. Therefore, the layer allows for the level of free fine carbon particles among the activated carbon to be reduced. Surface-modified activated carbon can be used in smoking articles so as to allow for adsorption by the activated carbon with reduced free fine carbon particles in the smoking article and the smoke produced.

1 . A cigarette, comprising: 
 a tobacco rod including tobacco and a filter, wherein said filter includes a surface-modified activated carbon comprising: 
 activated carbon;  
 fine carbon particles on a surface of the activated carbon; and  
 a layer on a surface of the activated carbon, wherein the layer comprises a hydrocarbon compound, an additional layer of carbon or a polymer on the activated carbon, wherein if the layer is a polymer, the polymer is about 9-20 wt % of the surface-modified activated carbon total weight.  
   
   
   
       2 . The cigarette of  claim 1 , wherein the hydrocarbon compound comprises a non-polar, weakly polar hydrocarbon compound, wax, chained or branched paraffin or a polymeric hydrocarbon, wherein the additional layer of carbon comprises a non-activated carbon which at least partially fills pores in the surface-modified activated carbon, or wherein the polymer is present in an amount of 10-18 wt % or 11-17 wt % of the surface-modified activated carbon total weight.  
   
   
       3 . The cigarette of  claim 1 , wherein the layer comprises an additional layer of carbon, wherein the layer of carbon has a different density than the activated carbon and modifies the pore size distribution of the activated carbon.  
   
   
       4 . The cigarette of  claim 1 , wherein the layer comprises an additional layer of carbon, wherein the additional layer of carbon has a higher density than the activated carbon.  
   
   
       5 . The cigarette of  claim 1 , wherein the layer comprises a polymer, wherein the polymer comprises a non-toxic, biodegradable and/or permeable polymer.  
   
   
       6 . The cigarette of  claim 1 , wherein the layer comprises a polymer, wherein the polymer comprises polypropylene, polyethylene, silicone polymer, poly(ethylene oxide), poly(ethylene glycol), poly(acrylic acid), poly(vinyl acetate), poly(vinyl alcohol), pectin, alginate, starch or block poly(ethylene oxide)-poly(propylene oxide)copolymers or their derivatives.  
   
   
       7 . The cigarette of  claim 1 , wherein the activated carbon comprises granules, spheres, monoliths, beads, powders or fibers of activated carbon.  
   
   
       8 . The cigarette of  claim 1 , wherein the layer entraps the fine carbon particles within the bulk of the layer, fastens the fine carbon particles to surfaces of the layer or the activated carbon, or increases the mechanical strength of the surface-modified activated carbon to a mechanical strength greater than the activated carbon without the layer.  
   
   
       9 . The cigarette of  claim 1 , wherein the layer has a thickness sufficient to at least partially cover the activated carbon and the fine carbon particles.  
   
   
       10 . The cigarette of  claim 1 , wherein the layer is effective for adsorbing a targeted gas phase constituent when the cigarette is smoked.  
   
   
       11 . The cigarette of  claim 1 , wherein the layer is electrically charged to attach the fine carbon particles on a surface of the layer with a force greater than a force of a smoke stream formed when the cigarette is smoked.  
   
   
       12 . The cigarette of  claim 1 , wherein the surface-modified activated carbon is located in a cavity of the filter.  
   
   
       13 . The cigarette of  claim 1 , wherein the fine carbon particles are less than 10 microns in diameter.  
   
   
       14 . A cigarette filter, comprising: 
 a filter with a cavity, wherein said cavity includes a surface-modified activated carbon therein comprising: 
 activated carbon;  
 fine carbon particles on a surface of the activated carbon; and  
 a layer on a surface of the activated carbon, wherein the layer comprises a hydrocarbon compound, an additional layer of carbon or a polymer, wherein if the layer is a polymer, the polymer is about 9-20 wt % of the surface-modified activated carbon total weight.  
   
   
   
       15 . The cigarette filter of  claim 14 , wherein the hydrocarbon compound comprises a non-polar or weak polar hydrocarbon compound, wax, chained or branched paraffin, or a polymeric hydrocarbon, wherein the additional layer of carbon comprises a non-activated carbon which at least partially fills pores in the surface-modified activated carbon, or wherein the polymer is present in an amount of 10-18 wt % or 11-17 wt % of the surface-modified activated carbon total weight.  
   
   
       16 . The cigarette filter of  claim 14 , wherein the layer comprises an additional layer of carbon, wherein the additional layer of carbon has a higher density than the activated carbon and modifies the pore size distribution of the activated carbon.  
   
   
       17 . The cigarette filter of  claim 14 , wherein the layer comprises a polymer, wherein the polymer comprises a non-toxic, biodegradable and/or permeable polymer.  
   
   
       18 . The cigarette filter of  claim 14 , wherein the layer comprises a polymer, wherein the polymer comprises polypropylene, polyethylene, silicone polymer, poly(ethylene oxide), poly(ethylene glycol), poly(acrylic acid), poly(vinyl acetate), poly(vinyl alcohol), pectin, alginate, starch or block poly(ethylene oxide)-poly(propylene oxide)copolymers or their derivatives.  
   
   
       19 . The cigarette filter of  claim 14 , wherein the activated carbon comprises granules, spheres, monoliths, beads, powders or fibers of activated carbon.  
   
   
       20 . The cigarette filter of  claim 14 , wherein the layer entraps the fine carbon particles within the bulk of the layer, fastens the fine carbon particles to surfaces of the layer or the activated carbon, or increases the mechanical strength of the surface-modified activated carbon to a mechanical strength greater than the activated carbon without the layer.  
   
   
       21 . The cigarette filter of  claim 14 , wherein the layer has a thickness sufficient to at least partially cover the activated carbon and the fine carbon particles.  
   
   
       22 . A method of manufacturing a cigarette, comprising: 
 forming surface-modified activated carbon by: 
 providing activated carbon having fine carbon particles on surfaces thereof; and  
 forming a layer on surfaces of the activated carbon, wherein the layer comprises hydrocarbon compound, carbon or polymer on the activated carbon, wherein if the layer is polymer, the polymer is about 9-20 wt % of the surface-modified activated carbon total weight;  
   incorporating the surface-modified activated carbon into a cigarette filter; and    attaching the cigarette filter to a tobacco rod to form a cigarette.    
   
   
       23 . The method of  claim 22 , wherein the forming a layer on surfaces of the activated carbon comprises: 
 melting or dissolving a layer compound in a solvent or solvent mixture to form a liquid solution;    suspending activated carbon in the liquid solution to impregnate the layer compound into the activated carbon; and    removing the solvent or solvent mixture.    
   
   
       24 . The method of  claim 23 , wherein the melting or dissolving the layer compound in a solvent or solvent mixture comprises: 
 mixing or dissolving petroleum pitch, coal tar pitch, pine tar pitch or a synthetic aromatic polymer in a solvent or solvent mixture.    
   
   
       25 . The method of  claim 23 , wherein the melting or dissolving the layer compound in a solvent or solvent mixture comprises: 
 mixing or dissolving an aromatic compound in 1-methyl-2-pyrrolidinone (NMP), quinoline, trichlorobenzene, toluene, xylene or a mixture thereof.    
   
   
       26 . The method of  claim 23 , wherein the melting or dissolving a layer compound in a solvent or solvent mixture comprises: 
 mixing or dissolving a low-volatility, non-polar or weak-polar organic compound or organic compound mixture with a boiling point above about 150° C. at about one atmosphere with low vapor pressure at ambient conditions in a solvent or solvent mixture.    
   
   
       27 . The method of  claim 23 , wherein the melting or dissolving the layer compound in a solvent or solvent mixture comprises: 
 mixing or dissolving wax, chained or branched paraffin, a polymeric hydrocarbon, or a mixture thereof in a solvent or solvent mixture.    
   
   
       28 . The method of  claim 23 , wherein the melting or dissolving a layer compound in a solvent or solvent mixture comprises: 
 mixing or dissolving a non-toxic and biodegradable and/or permeable polymer in a solvent or solvent mixture.    
   
   
       29 . The method of  claim 23 , wherein the melting or dissolving a layer compound in a solvent or solvent mixture comprises: 
 mixing or dissolving polypropylene, polyethylene, silicone polymer, poly(ethylene oxide), poly(ethylene glycol), poly(acrylic acid), poly(vinyl acetate), poly(vinyl alcohol), pectin, alginate, starch, poly(ethylene oxide)-poly(propylene oxide)copolymer or their derivatives in a solvent or a solvent mixture.    
   
   
       30 . The method of  claim 23 , wherein the melting or dissolving a layer compound in a solvent or solvent mixture comprises: 
 mixing or dissolving a polymer compound in water, alcohol, hexane or a mixture thereof.    
   
   
       31 . The method of  claim 23 , wherein the suspending activated carbon in the liquid solution to impregnate the layer compound into the activated carbon comprises: 
 suspending activated carbon granules, spheres, monoliths, beads, powders or fibers in the liquid solution to impregnate the layer compound into the activated carbon granules, spheres, monoliths, beads, powders or fibers.    
   
   
       32 . The method of  claim 23 , wherein the suspending activated carbon in the liquid solution to impregnate the layer compound into the activated carbon comprises: 
 suspending activated carbon and fine carbon particles in the liquid solution to impregnate the layer compound into the activated carbon, wherein the layer compound entraps the fine carbon particles within the layer compound.    
   
   
       33 . The method of  claim 23 , wherein the suspending activated carbon in the liquid solution to impregnate the layer compound into the activated carbon, comprises suspending activated carbon and fine carbon particles with a diameter of less than 10 microns in the liquid solution to impregnate the layer compound into the activated carbon and fasten the fine carbon particles on surfaces of the activated carbon.  
   
   
       34 . The method of  claim 23 , wherein the forming of the layer step further comprises: 
 carbonizing the layer compound by heating the layer compound after removing the solvent or solvent mixture, wherein the carbonizing of the layer compound forms a carbon layer with a density different from the activated carbon.    
   
   
       35 . The method of  claim 34 , wherein the carbonizing of the layer compound by heating the layer compound comprises heating the layer compound in an environment with a temperature between about 300° C. and 1000° C.  
   
   
       36 . The method of  claim 23 , wherein the suspending activated carbon in the liquid solution to impregnate the layer compound into the activated carbon comprises wetness-incipient impregnation of the layer compound into the activated carbon, rinsing the layer compound through an activated carbon bed, or soaking activated carbon in the layer compound.  
   
   
       37 . A method of treating mainstream tobacco smoke, comprising: 
 drawing smoke from the smoking article, wherein the smoke passes through a filter containing surface-modified activated carbon comprising: 
 activated carbon; and  
 a layer on an internal surface and an external surface of the activated carbon, wherein the layer comprises a hydrocarbon compound, an additional layer of carbon or a polymer on the activated carbon, wherein if the layer is a polymer, the polymer is about 9-20 wt % of the surface-modified activated carbon total weight.  
   
   
   
       38 . The method of  claim 37 , wherein the layer is adapted to reduce free fine carbon particles in the smoking article that are drawn when smoke passes though the filter containing surface-modified activated carbon.