Process for surface activation and/or devulcanization of sulfur-vulcanized rubber particles

Abstract

Process for surface activation and/or devulcanization of sulfur-vulcanized rubber particles. In order to break the sulfur bridges and to reduce the sulfur, the rubber particles are treated in a biotechnological manner in a medium with mesophilic anaerobic and/or optionally anaerobic and/or microaerophilic bacteria and/or with one or more enzyme systems of such bacteria. The thus-treated activated rubber particles show improved vulcanization properties in comparison with non-treated rubber particles, and permit the production of better quality articles.

1 . A process for treating sulfur-vulcanized rubber particles, comprising:
 treating one or more sulfur-vulcanized rubber particles at temperatures below 50° Celsius in a medium comprising bacteria selected from one or more of:
 a mesophilic bacteria capable of existing without oxygen, 
 (ii) a mesophilic bacteria capable of existing with or without oxygen, or 
 (iii) a mesophilic microaerophilic bacteria; 
   wherein the treating breaks one or more sulfur bridges and reduces an oxidation state of the sulfur.   
   
   
       2 . The process as recited in  claim 1 , wherein the medium is a suspension including water, nutrients, a carbon source, and the bacteria. 
   
   
       3 . The process as recited in  claim 1 , wherein the concentration of rubber particles in the medium is maintained below 35 wt %. 
   
   
       4 . The process as recited in  claim 1 , further comprising carrying out the treating under anaerobic or microaerophilic conditions. 
   
   
       5 . The process as recited in  claim 1 , wherein the treating is carried out at temperatures between about 20° Celsius and about 45° Celsius. 
   
   
       6 . The process as recited in  claim 1 , wherein the treating is carried out at a pH value between about 5 to about 9. 
   
   
       7 . The process as recited in  claim 1 , wherein the one or more sulfur-vulcanized rubber particles are treated in the medium for a period of between about 4 days and about 8 days. 
   
   
       8 . The process as recited in  claim 1 , wherein the bacteria is selected from at least one strain of  Desulfuromonas thiophila, Desulfuromonas palmitatis, Sulfurospirillum deleyianum , or  Desulfuromonas acetoxidans  bacteria. 
   
   
       9 . The process as recited in  claim 1 , further comprising intermixing the medium with an agitator. 
   
   
       10 . The process as recited in  claim 1 , wherein the treating is substantially restricted to the rubber particle surface and/or layers close to the surface that have a thickness of up to 300 nm, in order to substantially avoid altering the material properties of the main mass of the rubber particle. 
   
   
       11 . A process for treating sulfur-vulcanized rubber particles, comprising:
 treating one or more sulfur-vulcanized rubber particles at temperatures below 50° Celsius in a medium comprising enzymes produced from bacteria selected from one or more of:
 (i) a mesophilic bacteria capable of existing without oxygen, 
 (ii) a mesophilic bacteria capable of existing with or without oxygen, or 
 (iii) a mesophilic microaerophilic bacteria; 
   wherein the treating breaks one or more sulfur bridges and reduces an oxidation state of the sulfur.   
   
   
       12 . The process as recited in  claim 11 , wherein medium includes enzymes isolated from the bacteria, and the medium is substantially devoid of the bacteria. 
   
   
       13 . The process as recited in  claim 11 , wherein the medium includes the bacteria and enzymes produced form the bacteria in situ. 
   
   
       14 . The process as recited in  claim 11 , wherein the concentration of rubber particles in the medium is maintained below 35 wt %. 
   
   
       15 . The process as recited in  claim 11 , further comprising carrying out the treating under anaerobic or microaerophilic conditions. 
   
   
       16 . The process as recited in  claim 11 , wherein the treating is carried out at temperatures between about 20° Celsius and about 45° Celsius. 
   
   
       17 . The process as recited in  claim 16 , wherein the treating is carried out at temperatures between about 33° Celsius and about 37° Celsius. 
   
   
       18 . The process as recited in  claim 11 , wherein the treating is carried out at a pH value between about 5 to about 9. 
   
   
       19 . The process as recited in  claim 11 , wherein the bacteria is selected from at least one strain of  Desulfuromonas thiophila, Desulfuromonas palmitatis, Sulfurospirillum deleyianum , or  Desulfuromonas acetoxidans  bacteria. 
   
   
       20 . The process as recited in  claim 11 , wherein the rubber particles comprise any one or more of powdered rubber or rubber granulate, wherein the particle size of the powder or granulate is from about 0.1 mm to about 0.6 mm.