Grinding method and grinding medium

Abstract

An improved grinding method for manufacturing microfibrillated cellulose.

1 . A method for preparing microfibrillated cellulose having at least one of increased tensile properties and reduced media wear, the method comprising:
 providing a suspension comprising pulp fibres in a liquid medium, wherein the fibre solids content of the suspension is about 0.3 wt % to about 4 wt %;   microfibrillating the pulp fibres by grinding the suspension in the presence of a grinding medium in one or more wet stirred media mills, wherein:
 the grinding medium comprises about 0.5 mm to about 12 mm particles, 
 the grinding medium has an arithmetic surface roughness from about 0.02 μm to about 2 μm, 
 the media volume concentration of the grinding medium is about 30% to about 65% of the total volume of the charge of the one or more wet stirred media mills, 
 the grinding is performed with an energy input of less than about 6,000 kWh/t, and 
 grinding the suspension results in a worn media content of less than about 20% by dry mass; and 
   recovering the microfibrillated cellulose from the one or more wet stirred media mills.   
     
     
         2 . The method according to  claim 1 , wherein the liquid medium is aqueous or a hydro alcoholic mixture. 
     
     
         3 . (canceled) 
     
     
         4 . The method according to  claim 1 , wherein the pulp fibres are hardwood pulp fibres. 
     
     
         5 - 12 . (canceled) 
     
     
         13 . The method according to  claim 1 , wherein the pulp fibres are softwood pulp fibres. 
     
     
         14 - 19 . (canceled) 
     
     
         20 . The method according to  claim 1 , wherein the pulp fibres are recycled pulp fibres. 
     
     
         21 . The method according to  claim 1 , wherein the pulp fibres are non-wood cellulosic fibres. 
     
     
         22 . (canceled) 
     
     
         23 . The method according to  claim 1 , wherein the pulp fibres are a combination of two or more of hardwood pulp fibres, softwood pulp fibres, recycled pulp fibres, and non-wood cellulosic pulp fibres. 
     
     
         24 . The method according to  claim 1 , wherein the fibre solids content of the suspension is about 0.3 wt. %, about 0.4 wt. %, about 0.5 wt. %, about 0.6 wt. %, about 0.7 wt. %, about 0.8 wt. %, about 0.9 wt. %, about 1 wt. %, about 1.1 wt. %, about 1.2 wt. %, about 1.3 wt. %, about 1.4 wt. %, about 1.5 wt. %, about 1.6 wt. %, about 1.7 wt. %, about 1.8 wt. %, about 1.9 wt. %, about 2 wt. %, about 2.1 wt. %, about 2.2 wt. %, about 2.3 wt. %, about 2.4 wt. %, about 2.5 wt. %, about 2.6 wt. %, about 2.7 wt. %, about 2.8 wt. %, about 2.9 wt. %, about 3 wt. %, about 3.1 wt. %, about 3.2 wt. %, about 3.3 wt. %, about 3.4 wt. %, about 3.5 wt. %, about 3.6 wt. %, about 3.7 wt. %, about 3.8 wt. %, about 3.9 wt. %, or about 4 wt. %. 
     
     
         25 . (canceled) 
     
     
         26 . The method according to  claim 1 , wherein the one or more wet stirred media mills comprises one or more vertical screened grinders, one or more horizontal milling apparatuses, or one or more stirred media detritors. 
     
     
         27 - 28 . (canceled) 
     
     
         29 . The method according to  claim 1 , wherein the one or more wet stirred media mills is two or more wet stirred media mills connected in series, wherein the two or more wet stirred media mills are selected from the group consisting of a screened grinder, a stirred media detritor, a horizontal milling apparatus, and combinations thereof. 
     
     
         30 - 34 . (canceled) 
     
     
         35 . The method according to  claim 1 , wherein the one or more wet stirred media mills is first and second wet stirred media mills, and the first wet stirred media mill includes grinding medium having a particle size greater than a particle size of grinding medium included in the second wet stirred media mill. 
     
     
         36 . The method according to  claim 1 , wherein the one or more wet stirred media mills is first and second wet stirred media mills, and the first wet stirred media mill includes grinding medium having a particle size substantially similar to a particle size of grinding medium included in the second wet stirred media mill. 
     
     
         37 . The method according to  claim 1 , wherein the one or more wet stirred media mills is two or more wet stirred media mills connected in series, and an output of a first of the two or more wet stirred media mills has a fibre breakage factor of 0.2 mm −1 -3 mm −1  as calculated using data measured by a fibre analyzer. 
     
     
         38 . (canceled) 
     
     
         39 . The method according to  claim 1 , wherein the grinding medium comprises about 0.5 mm, about 0.6 mm, about 0.7 mm, about 0.8 mm, about 0.9 mm, about 1 mm, about 1.1 mm, about 1.2 mm, about 1.3 mm, about 1.4 mm, about 1.5 mm, about 1.6 mm, about 1.7 mm, about 1.8 mm, about 1.9 mm, about 2 mm, about 2.1 mm, about 2.2 mm, about 2.3 mm, about 2.4 mm, about 2.5 mm, about 2.6 mm, about 2.7 mm, about 2.8 mm, about 2.9 mm, about 3 mm, about 3.1 mm, about 3.2 mm, about 3.3 mm, about 3.4 mm, about 3.5 mm, about 3.6 mm, about 3.7 mm, about 3.8 mm, about 3.9 mm, about 4 mm, about 4.1 mm, about 4.2 mm, about 4.3 mm, about 4.4 mm, about 4.5 mm, about 4.6 mm, about 4.7 mm, about 4.8 mm, about 4.9 mm, about 5 mm, about 5.1 mm, about 5.2 mm, about 5.3 mm, about 5.4 mm, about 5.5 mm, about 5.6 mm, about 5.7 mm, about 5.8 mm, about 5.9 mm, about 6 mm, about 6.1 mm, about 6.2 mm, about 6.3 mm, about 6.4 mm, about 6.5 mm, about 6.6 mm, about 6.7 mm, about 6.8 mm, about 6.9 mm, about 7 mm, about 7.1 mm, about 7.2 mm, about 7.3 mm, about 7.4 mm, about 7.5 mm, about 7.6 mm, about 7.7 mm, about 7.8 mm, about 7.9 mm, about 8 mm, about 8.1 mm, about 8.2 mm, about 8.3 mm, about 8.4 mm, about 8.5 mm, about 8.6 mm, about 8.7 mm, about 8.8 mm, about 8.9 mm, about 9 mm, about 9.1 mm, about 9.2 mm, about 9.3 mm, about 9.4 mm, about 9.5 mm, about 9.6 mm, about 9.7 mm, about 9.8 mm, about 9.9 mm, about 10 mm, about 10.1 mm, about 10.2 mm, about 10.3 mm, about 10.4 mm, about 10.5 mm, about 10.6 mm, about 10.7 mm, about 10.8 mm, about 10.9 mm, about 11 mm, about 11.1 mm, about 11.2 mm, about 11.3 mm, about 11.4 mm, about 11.5 mm, about 11.6 mm, about 11.7 mm, about 11.8 mm, about 11.9 mm, or about 12 mm particles. 
     
     
         40 - 42 . (canceled) 
     
     
         43 . The method according to  claim 1 , wherein the grinding medium comprises mullite, alumina, silicate, zirconia, glass, steatite, or a combination thereof. 
     
     
         44 - 45 . (canceled) 
     
     
         46 . The method according to  claim 1 , wherein the grinding medium has an arithmetic surface roughness of about 0.02 μm, about 0.03 μm, about 0.04 μm, about 0.05 μm, about 0.06 μm, about 0.07 μm, about 0.08 μm, about 0.09 μm, about 0.1 μm, about 0.2 μm, about 0.3 μm, about 0.4 μm, about 0.5 μm, about 0.6 μm, about 0.7 μm, about 0.8 μm, about 0.9 μm, about 1 μm, about 1.1 μm, about 1.2 μm, about 1.3 μm, about 1.4 μm, about 1.5 μm, about 1.6 μm, about 1.7 μm, about 1.8 μm, about 1.9 μm, or about 2 μm. 
     
     
         47 . (canceled) 
     
     
         48 . The method according to  claim 1 , wherein the grinding medium has a density of about 2 g/cm 3  to about 8 g/cm 3 . 
     
     
         49 . The method according to  claim 1 , wherein the grinding is performed with an energy input of about 500 kWhH/t, about 600 kWhH/t, about 700 kWhH/t, about 800 kWhH/t, about 900 kWhH/t, about 1,000 kWhH/t, about 1,100 kWhH/t, about 1,200 kWhH/t, about 1,300 kWhH/t, about 1,400 kWhH/t, about 1,500 kWhH/t, about 1,600 kWhH/t, about 1,700 kWhH/t, about 1,800 kWhH/t, about 1,900 kWhH/t, about 2,000 k WhH/t, about 2,100 kWhH/t, about 2,200 k WhH/t, about 2,300 kWhH/t, about 2,400 kWhH/t, about 2,500 kWhH/t, about 2,600 kWhH/t, about 2,700 kWhH/t, about 2,800 kWhH/t, about 2,900 kWhH/t, about 3,000 kWhH/t, about 3,100 kWhH/t, about 3,200 kWhH/t, about 3,300 k WhH/t, about 3,400 kWhH/t, about 3,500 kWhH/t, about 3,600 kWhH/t, about 3,700 kWhH/t, about 3,800 kWhH/t, about 3,900 kWhH/t, about 4,000 kWhH/t, about 4,100 kWhH/t, about 4,200 kWhH/t, about 4,300 kWhH/t, about 4,400 kWhH/t, about 4,500 kWhH/t, about 4,600 k WhH/t, about 4,700 kWhH/t, about 4,800 k WhH/t, about 4,900 kWhH/t, about 5,000 kWhH/t, about 5,100 kWhH/t, about 5,200 k WhH/t, about 5,300 kWhH/t, about 5,400 kWhH/t, about 5,500 kWhH/t, about 5,600 kWhH/t, about 5,700 kWhH/t, about 5,800 kWhH/t, about 5,900 kWhH/t, or about 6,000 kWhH/t. 
     
     
         50 . (canceled) 
     
     
         51 . The method according to  claim 1 , wherein the media volume concentration of the grinding medium is about 30%, about 35%, about 40%, about 45%, about 50%, about 55%, about 60%, or about 65% of the total volume of the charge of the one or more wet stirred media mills. 
     
     
         52 . (canceled) 
     
     
         53 . The method according to  claim 1 , wherein the worn media content is about 0.1%, about 0.2%, about 0.3%, about 0.4%, about 0.5%, about 1%, about 2%, about 3%, about 4%, about 5%, about 6%, about 7%, about 8%, about 9%, about 10%, 11%, about 12%, about 13%, about 14%, about 15%, about 16%, about 17%, about 18%, about 19%, or about 20%. 
     
     
         54 - 57 . (canceled)