Grinding method and grinding medium

Abstract

A method for manufacturing microfibrillated cellulose, a particulate grinding medium suitable for use in said method, a material which wears rough, and a method for making said particulate grinding medium.

1 - 44 . (canceled) 
     
     
         45 . A method for making a particulate ceramic grinding medium comprising mullite, zirconia (ZrO 2 ), zirconium silicate or alumina (Al 2 O 3 ) and mixtures thereof having (i) a surface roughness of at least about 0.5 μm, or (ii) a mean coefficient of friction of at least about 0.10, or both (i) and (ii), wherein the particulate ceramic grinding medium has a specific gravity of at least 3.5, said method comprising:
 a. obtaining, providing or making a composition comprising raw materials comprising at least one of mullite, zirconia, zirconium silicate or alumina (Al 2 O 3 ); 
 b. mixing the composition comprising raw materials, forming a mixture; 
 c. combining the mixture with binder, forming a bound mixture; 
 d. granulating the bound mixture by mixing the bound mixture composition over a period of time during which the mixing speed is reduced; 
 e. optionally drying the granulated composition; 
 f. optionally shaping the granulated composition; 
 g. optionally sizing the granulated composition; and 
 h. sintering the granulated composition, optionally wherein steps b) to d) are performed in a mixer equipped with an impeller, wherein the impeller speed during step b) is greater than the impeller speed during steps c) and d), and wherein the impeller speed during step c) is equal to or greater than the impellor speed during step d). 
 
     
     
         46 . The method according to  claim 45 , wherein the sintering temperature is from about 1400° C. to about 1500° C. 
     
     
         47 . The method according to  claim 45 , wherein the sintering temperature is from about 1425° C. to about 1475° C. 
     
     
         48 . The method according to  claim 45 , wherein the sintering temperature is from about 1440° C. to about 1460° C. 
     
     
         49 . The method according to  claim 45 , wherein the dwell time is of from about 2 hours to about 6 hours. 
     
     
         50 . The method according to  claim 45 , wherein the dwell time is of from 3 hours to about 5 hours. 
     
     
         51 . The method according to  claim 45 , wherein the dwell time is of from about 3.5 hours to about 4.5 hours. 
     
     
         52 . The method according to  claim 45 , wherein the composition comprising raw materials comprises at least 90 wt. % alumina. 
     
     
         53 . The method according to  claim 45 , wherein the composition comprising raw materials comprises at least 95 wt. % alumina. 
     
     
         54 . The method according to  claim 45 , wherein the composition comprising raw materials comprises at least 99 wt. % alumina. 
     
     
         55 . The method according to  claim 45 , wherein the composition comprising raw materials comprises at least 99.5 wt. % alumina. 
     
     
         56 . The method according to  claim 45 , wherein the composition comprising raw materials comprises at least 99.9 wt. % alumina. 
     
     
         57 . The method according to  claim 45 , wherein the composition comprising raw materials comprises substantially 100 wt. % alumina. 
     
     
         58 . The method according to  claim 45 , wherein the sintering temperature is from about 1500° C. to about 1700° C. 
     
     
         59 . The method according to  claim 45 , wherein the sintering temperature is from about 1550° C. to about 1650° C. 
     
     
         60 . The method according to  claim 45 , wherein the sintering temperature is from about 1575° C. to about 1700° C.