Cryotropic hydrogels and their use as filters

Abstract

There is provided a particle-filter comprising at least one hydrogel formed in aqueous solution at a temperature below 0° C. The filter can arrest particulates of smoke by physisorption on the solid surface of the gel or by chemisorption if the gel is suitably functionalized. The effectiveness of filter in arresting the solid particles and the pressure drop can be controlled by varying the porosity and the pore size distribution of the filter which in turn can be modulated by varying the monomer to water and monomer to cross-linker ratio in the pre-polymer solution. The filter is able to reduce the particle content of the smoke. There is further provided a cigarette comprising at least one particle-filter according as well as a method for the filtration of smoke.

1 . A particle-filter comprising at least one hydrogel formed in aqueous solution at a temperature below 0° C. 
     
     
         2 . The particle-filter according to  claim 1 , wherein said particle-filter is a cigarette filter. 
     
     
         3 . The particle-filter according to  claim 1 , wherein said hydrogel is insoluble in water. 
     
     
         4 . The particle-filter according to  claim 1 , wherein said hydrogel comprises water. 
     
     
         5 . The particle-filter according to  claim 1 , wherein said hydrogel is hydrophilic. 
     
     
         6 . The particle-filter according to  claim 1 , wherein said hydrogel is supermacroporous. 
     
     
         7 . The particle-filter according to  claim 1 , wherein said hydrogel comprises at least one material selected from the group consisting of poly-acrylamide, agarose, and alginate. 
     
     
         8 . The particle-filter according to  claim 1 , wherein said hydrogel is formed at a temperature below −10° C. 
     
     
         9 . The particle-filter according to  claim 1 , wherein said hydrogel is formed without using any organic solvents. 
     
     
         10 . A cigarette comprising at least one particle-filter according to  claim 1 . 
     
     
         11 . A method for the filtration of smoke comprising the steps:
 providing at least one filter comprising a macroporous hydrogel formed in aqueous solution at a temperature below 0° C., and   filtering the smoke through the filter.   
     
     
         12 . The method according to  claim 11  , wherein said at least one filter is recycled. 
     
     
         13 . The method according to  claim 11 , wherein said at least one filter is washed with water. 
     
     
         14 . The method according to  claim 11 , wherein particulate matter in the smoke is reduced. 
     
     
         15 . The method according to  claim 14 , wherein the amount of particulate matter is reduced by more than 99 wt %. 
     
     
         16 . The method according to  claim 11 , wherein the amount of at least one substance in the smoke is reduced, wherein the substance is at least one substance selected from the group consisting of methane, acetylene, ethane, propene, chloromethane, propane, ethanol, acetaldehyde, butene, ethanol, acetonitrile, acrolein, acetone, acrylonitrile, isoprene, pentadiene, 2-butanone, hexane, benzene, dimethylfuran, pyridine, toluene, benzopyrine, napthalene, N-nitrosamine, chloro-biphenyls, phenols, 2-pentanone, 3-buten-2-one, 3-pentanone, ethylbenzene, isobutyronitrile, isoprene, o-xylene, propionaldehyde, propionitrile, m-/p-xylene, styrene and toluene. 
     
     
         17 . The method according to  claim 16 , wherein the amount of the at least one substance in the smoke is reduced by more than 95 wt %.