Process for the production of graphite powders of increased bulk density

Abstract

The invention relates to a method for increasing the Scott density of synthetic and/or natural graphite powders of any particle size distribution, preferably of highly-pure graphite, by subjecting the graphite powder to an autogenous surface treatment. The inventive powder is used, in particular, for producing dispersions, coatings with an increased graphite/binder ratio and increased electric and thermal conductivity, gas and liquid-tight coatings on metal substrates, thermoplastic or duroplastic graphite-polymer composites, or for producing metallic, non-ferrous sintering materials.

1 - 15 . (canceled)  
   
   
       16 . A process for increasing the pressed density of a starting graphite powder of any particle size distribution, the starting graphite powder chosen from synthetic graphitic carbon and natural graphitic carbon wherein the starting graphite powder has a high graphite content in the particle, comprising 
 subjecting the starting graphite powder to an autogenous surface treatment in which individual graphite powder particles are allowed to impact with one another at a measured speed so that their surface structure changes while substantially retaining graphite particle shape without a substantial grinding effect occurring and    wherein said autogenous surface treatment is carried out until the pressed density of the starting material has increased by at least about 0.5% to 10%    
   
   
       17 . The process according to  claim 16  wherein the graphite powder is high-purity graphite.  
   
   
       18 . The process according to  claim 16  wherein the graphite powder has a xylene density ranging from 1.80 to 2.27 g/cm 3 , a crystal structure characterized by a c/2 value of 0.3354 to 0.3360, and an L c  value of more than 40nm (L c> 40nm).  
   
   
       19 . The process according to  claim 16  wherein the graphite powder has a particle size of up to 150 μm.  
   
   
       20 . The process according to  claim 19  wherein the graphite powder has a particle size of 1 pm to 50 μm.  
   
   
       21 . The process according to  claim 16  wherein the autogenous surface treatment is carried out until the pressed density of the starting graphite powder has increased by about 1% to 8%.  
   
   
       22 . The process according to  claim 16  wherein the autogenous surface treatment is carried out by fluidizing or dispersing graphite powder particles with sizes of <100 μm in an inert carrier gas with the aid of a carrier gas.  
   
   
       23 . The process according to  claim 16  wherein the autogenous surface treatment is carried out by dispersing graphite powder particles with sizes of <300 μm by means of a rotating mechanical tool.  
   
   
       24 . The process according to  claim 23  wherein the rotating mechanical tool is a turbine.  
   
   
       25 . A process for decreasing the absorption capacity of a starting graphite powder of any particle size distribution, the starting graphite powder chosen from synthetic graphitic carbon and natural graphitic carbon wherein the starting graphite powder has a high graphite content in the particle, comprising 
 subjecting the starting graphite powder to an autogenous surface treatment in which individual graphite powder particles are allowed to impact with one another at a measured speed so that their surface structure changes while substantially retaining graphite particle shape without a substantial grinding effect occurring and    wherein said autogenous surface treatment is carried out until the absorption capacity of the starting material has decreased by at least about 10% to 50%.    
   
   
       26 . The process according to  claim 25  wherein the graphite powder is high-purity graphite.  
   
   
       27 . The process according to  claim 25  wherein the graphite powder has a xylene density ranging from 1.80 to 2.27 g/cm 3 , a crystal structure characterized by a c/2 value of 0.3354 to 0.3360, and an L c  value of more than 40 nm (L c> 40 nm).  
   
   
       28 . The process according to  claim 25  wherein the graphite powder has an average particle size of up to about 150 μm.  
   
   
       29 . The process according to  claim 28  wherein the graphite powder has an average particle size of about 1 μm to 50 μm.  
   
   
       30 . The process according to  claim 25  wherein the autogenous surface treatment is carried out until the absorption capacity of the starting graphite powder has increased by about 20% to 45%.  
   
   
       31 . The process according to  claim 25  wherein the autogenous surface treatment is carried out by fluidizing or dispersing graphite powder particles with sizes of <100 μm in an inert carrier gas with the aid of a carrier gas.  
   
   
       32 . The process according to  claim 25  wherein the autogenous surface treatment is carried out by dispersing graphite powder particles with sizes of <300 μm by means of a rotating mechanical tool.  
   
   
       33 . The process according to  claim 32  wherein the rotating mechanical tool is a turbine.  
   
   
       34 . An apparatus for treating graphite particles comprising 
 a cylindrical chamber comprising a base and a curved face, the cylindrical chamber further comprising 
 a first aperture for graphite particles exiting the cylindrical chamber;  
 a second aperture for graphite particles entering the cylindrical chamber;  
 an internal disk for accelerating the graphite particles, having a diameter less than the inner diameter of the cylindrical chamber wherein the disk further comprises one or more impact pins and a rim;  
   a motor for rotating the internal disk;    a shaft for connecting the motor and the internal disk; and    a tube for circulating graphite particles from the first aperture to the second aperture, further comprising an external input for adding graphite particles to the tube and an external output for removing graphite particles from the tube.    
   
   
       35 . The apparatus of  claim 34  wherein the first aperture is located on the curved face of the cylindrical chamber.  
   
   
       36 . The apparatus of  claim 34  wherein the second aperture located on the base of the cylindrical chamber.  
   
   
       37 . The apparatus of  claim 36  wherein the second aperture is located at about the center of the base of the cylindrical chamber.  
   
   
       38 . The apparatus of  claim 34  wherein the impact pins are mounted flush with the rim of the internal disk and extend towards the center of the internal disk.  
   
   
       39 . The apparatus of  claim 38  wherein the length of the impact pins are less than the radius of the internal disk.  
   
   
       40 . The apparatus of  claim 39  wherein the impact pins are located on a single face of the internal disk.  
   
   
       41 . The apparatus of  claim 40  wherein the impact pins are located on the face of the internal disk nearest to the second aperture.  
   
   
       42 . The apparatus of  claim 41  wherein the internal disk has a periphery of about 0.75m.  
   
   
       43 . The apparatus of  claim 34  wherein the motor rotates the internal disk at about 4800 rpm.  
   
   
       44 . The apparatus of  claim 34  wherein the graphite particles are added to the tube through the external input and removed from the circulation tube through the external output continuously.  
   
   
       45 . A graphite powder subjected to the process of  claim 16  or  25 , having at least one property chosen from increased bulk density, decreased absorption capacity, and increased pressed density.  
   
   
       46 . A graphite material with an average particle size of about 14 micron having 
 a Scott density of about 0.30 g.cm −3 ;    a tamped density of about 0.674 g.cm −3 ;    a dibutyl phthalate (DBP) oil absorption of about 64 g DBP/100 g graphite; and    a pressed density of about 1.957 g.cm −3 .    
   
   
       47 . A graphite material with an average particle size of about 20 micron having 
 a Scott density of about 0.38 g.cm −3 ;    a tamped density of about 0.778 g.cm −3 ;    a dibutyl phthalate (DBP) oil absorption of about 73 g DBP/100 g graphite; and    a pressed density of about 2.051 g.cm −3 .    
   
   
       48 . A graphite material with an average particle size of about 14 micron having 
 a Scott density of about 0.34 g.cm −3 ;    a tamped density of about 0.738 g.cm −3 ;    a dibutyl phthalate (DBP) oil absorption of about 75.0 g DBP/100 g graphite; and    a pressed density of about 2.036 g.cm −3 .    
   
   
       49 . A graphite material with an average particle size of about 15 micron having 
 a Scott density of about 0.36 g.cm −3 ;    a tamped density of about 0.766 g.cm −3 ;    a dibutyl phthalate (DBP) oil absorption of about 81.8 g DBP/100 g graphite; and    a pressed density of about 2.036 g.cm −3 .    
   
   
       50 . A graphite material with an average particle size of about 14 micron having 
 a Scott density of about 0.42 g.cm −3 ;    a tamped density of about 0.862 g.cm −3 ;    a dibutyl phthalate (DBP) oil absorption of about 58.9 g DBP/100 g graphite; and    a pressed density of about 2.064 g.cm −3 .    
   
   
       51 . A graphite material with an average particle size of about 38 micron having 
 a Scott density of about 0.46 g cm −3 ;    a tamped density of about 0.902 g.cm −3 ;    a dibutyl phthalate (DBP) oil absorption of about 54.7 g DBP/100 g graphite; and    a pressed density of about 1.972 g.cm −3 .    
   
   
       52 . A graphite material having a Scott density of about 0.45 g/cm 3  or greater.  
   
   
       53 . A graphite material having a tamped density of about 0.90 g/cm 3  or greater.  
   
   
       54 . A liquid dispersion comprising a detectable amount of at least one graphite material of any one of  claims 46  to  53  and a liquid.  
   
   
       55 . The liquid dispersion of  claim 54 , having an increased solids content.  
   
   
       56 . The liquid dispersion of  claim 55 , wherein the solids content is increased by about 5% to about 30%.  
   
   
       57 . A coating on a metallic substrate, the coating comprising a detectable amount of at least one graphite material of  claim 45  and a polymeric binder.  
   
   
       58 . A negative electrode of a lithium ion battery comprising the coating of  claim 57 .  
   
   
       59 . A lithium ion battery comprising the negative electrode of  claim 58 .  
   
   
       60 . A composite comprising a thermoplastic or thermosetting polymer and a detectable amount of at least one graphite material of  claim 45 .  
   
   
       61 . The composite of  claim 60 , compressed to provide a graphite plate of high electrical conductivity.  
   
   
       62 . An electrolyte fuel cell, comprising the graphite plate of  claim 61  as a bipolar plate.  
   
   
       63 . A metallic sintered material comprising a detectable amount of at least one graphite material of  claim 45  wherein the metallic sintered material is substantially free of iron.