Compositions and methods for producing microfibrillated cellulose with increased tensile properties

Abstract

Methods for preparing aqueous suspensions comprising microfibrillated cellulose, and optionally inorganic particulate material, with increased tensile properties, and methods for selecting a fibrous substrate comprising cellulose for preparation of microfibrillated cellulose having increased tensile properties.

What is claimed is: 
     
         1 .- 73 . (canceled) 
     
     
         74 . A method for preparing an aqueous suspension comprising microfibrillated cellulose with increased tensile properties and further comprising inorganic particulate material, the method comprising the steps of:
 (i) providing a multiplicity of fibrous substrates comprising cellulose;   (ii) determining the zero-span tensile index in Nm/g and hemicellulose content of the fibrous substrates comprising cellulose;   (iii) predicting the MFC tensile index in Nm/g from the product of the hemicellulose content and fibre zero-span tensile index of the fibrous substrates comprising cellulose;   (iv) selecting the fibrous substrates comprising cellulose having a desired MFC tensile index; and   (v) microfibrillating the fibrous substrates comprising cellulose in an aqueous environment by grinding in the presence of a grinding medium, wherein the grinding is carried out in the presence or the absence of grindable inorganic particulate material.   
     
     
         75 . The method according to  claim 74 , wherein the grinding is carried out in the presence of grindable inorganic particulate material. 
     
     
         76 . The method according to  claim 74 , wherein the grinding is carried out in the absence of grindable inorganic particulate material. 
     
     
         77 . The method according to  claim 74 , wherein the predicted MFC tensile index is calculated using the equation T= 2 ZH+σ 0 , wherein Z represents the zero-span tensile index of the fibre in Nm/g, H represents the hemicellulose content (mass fraction), B2 is a proportionality coefficient, and σ 0  is a constant. 
     
     
         78 . The method according to  claim 74 , wherein the grinding medium is removed at the completion of grinding. 
     
     
         79 . The method according to  claim 74 , wherein the MFC has a fibre steepness of from about 20 to about 50. 
     
     
         80 . The method according to  claim 74 , wherein the grinding medium is present in an amount of at least about 10% by volume of the aqueous environment. 
     
     
         81 . The method according to  claim 75 , wherein the fibrous substrate to the inorganic particulate material are in a ratio of about 99.5:0.5 to about 0.5:99.5. 
     
     
         82 . The method according to  claim 74 , wherein the grinding is performed in a tower mill. 
     
     
         83 . The method according to  claim 74 , wherein the grinding is performed in a screened grinder. 
     
     
         84 . The method according to  claim 74 , wherein the screened grinder is a stirred media detritor. 
     
     
         85 . The method according to  claim 84 , wherein the screened grinder comprises one or more screens having a nominal aperture size of at least about 250 μm. cm  86 . The method according to  claim 74 , wherein the grinding is performed in a cascade of grinding vessels. 
     
     
         87 . The method according to  claim 74 , wherein the fibrous substrate comprising cellulose has a Canadian Standard freeness equal to or less than 450 cm 3 . 
     
     
         88 . The method according to  claim 74 , wherein the fibrous substrate comprising cellulose has a Canadian Standard freeness equal to or greater than 450 cm 3 . 
     
     
         89 . The method according to  claim 74 , wherein the grinding medium comprises particles having an average diameter in ranging from about 0.5 mm to about 6 mm. 
     
     
         90 . The method of  claim 74 , wherein the fibrous substrate comprising cellulose is present in the aqueous environment at an initial solids content of at least about 5 wt. %. 
     
     
         91 . The method according to  claim 74 , wherein the fibrous substrate comprising cellulose is present in the aqueous environment at an initial solids content of less than about 5 wt. %. 
     
     
         92 . The method according to  claim 74 , wherein the total amount of energy used in the method is less than about 2,500 kWh per tonne of dry fibre in the fibrous substrate comprising cellulose. 
     
     
         93 . The method according to  claim 74 , wherein the total amount of energy used in the method is less than about 2,000 kWh per tonne of dry fibre in the fibrous substrate comprising cellulose. 
     
     
         94 . The method according to  claim 74 , wherein the fibrous substrate comprising cellulose is selected from the group consisting of Nordic Pine, Black Spruce, Radiata Pine, Southern Pine, Enzyme-Treated Nordic Pine, Douglas Fir, Dissolving Pulp, Birch #1, Birch #2, Eucalyptus, Acacia, Mixed European Hardwood, Mixed Thai Hardwood, Tissue Dust, Cotton, Jeans, Abaca, Sisal, Bagasse, Kenaf, Miscanthus, Sorghum, Giant Reed and Flax. 
     
     
         95 . The method according to  claim 74 , wherein the product of hemicellulose mass fraction and fibre zero-span tensile index is about 15 to about 25 Nm/g. 
     
     
         96 . The method according to  claim 74 , wherein the product of hemicellulose mass fraction and fibre zero-span tensile index is greater than 15 Nm/g. 
     
     
         97 . The method according to  claim 74 , wherein the product of hemicellulose mass fraction and fibre zero-span tensile index is greater than 20 Nm/g. 
     
     
         98 . The method according to  claim 74 , wherein the product of hemicellulose mass fraction and fibre zero-span tensile index is greater than 25 Nm/g. 
     
     
         99 . The method according to  claim 74 , wherein the product of hemicellulose mass fraction and fibre zero-span tensile index is greater than 30 Nm/g. 
     
     
         100 . The method according to  claim 74 , wherein the product of hemicellulose mass fraction and fibre zero-span tensile index is greater than 35 Nm/g. 
     
     
         101 . The method according to  claim 74 , wherein the WC fibre length is about 0.1 to 0.25 mm. 
     
     
         102 . The method according to  claim 74 , wherein the WC fibre length is greater than 0.25 mm. 
     
     
         103 . The method according to  claim 75 , wherein the inorganic particulate material is an alkaline earth metal carbonate or sulphate. 
     
     
         104 . The method according to  claim 75 , wherein the inorganic particulate material is calcium carbonate. 
     
     
         105 . The method according to  claim 104 , wherein the calcium carbonate is ground calcium carbonate. 
     
     
         106 . The method according to  claim 104 , wherein the calcium carbonate is precipitated calcium carbonate. 
     
     
         107 . The method according to  claim 75 , wherein the inorganic particulate material is selected from the group consisting of an alkaline earth metal carbonate or sulphate, a hydrous kandite clay and an anhydrous (calcined) kandite clay or combinations thereof. 
     
     
         108 . The method according to  claim 75 , wherein the inorganic particulate material is selected from the group consisting of calcium carbonate, magnesium carbonate, dolomite, gypsum, kaolin, halloysite or ball clay, metakaolin, fully calcined kaolin, talc, mica, perlite, diatomaceous earth, magnesium hydroxide, and aluminium trihydrate, or combinations thereof. 
     
     
         109 . The method according to  claim 75 , wherein the inorganic particulate material has a particle size distribution in which at least about 10% by weight of the particles have an e.s.d of less than 2 μm. 
     
     
         110 . The method according to  claim 75 , wherein the inorganic particulate material has a particle size distribution in which at least about 20% by weight of the particles have an e.s.d of less than 2 μm. 
     
     
         111 . A method for selecting a fibrous substrate comprising cellulose for preparation of microfibrillated cellulose having increased tensile properties, the method comprising the steps of:
 (i) providing a multiplicity of fibrous substrates comprising cellulose;   (ii) determining the zero-span tensile index in Nm/g and hemicellulose content of the fibrous substrates comprising cellulose;   (iii) predicting the MFC tensile index in Nm/g from the product of the hemicellulose content and fibre zero-span tensile index of the fibrous substrates comprising cellulose; and   (iv) selecting the fibrous substrates comprising cellulose having a desired MFC tensile index.   
     
     
         112 . The method according to  claim 111 , wherein the predicted MFC tensile index is calculated using the equation T=B 2 AH+σ 0 , wherein Z represents the zero-span tensile index of the fibre in Nm/g, H represents the hemicellulose content (mass fraction), B2 is a proportionality coefficient, and σ 0  is a constant. 
     
     
         113 . The method according to  claim 111 , wherein the MFC has a fibre steepness of from about 20 to about 50. 
     
     
         114 . The method according to  claim 111 , wherein the fibrous substrate comprising cellulose has a Canadian Standard freeness equal to or less than 450 cm 3 . 
     
     
         115 . The method according to  claim 111 , wherein the fibrous substrate comprising cellulose has a Canadian Standard freeness equal to or greater than 450 cm 3 . 
     
     
         116 . The method according to  claim 111 , wherein the fibrous substrate comprising cellulose is selected from the group consisting of Nordic Pine, Black Spruce, Radiata Pine, Southern Pine, Enzyme-Treated Nordic Pine, Douglas Fir, Dissolving Pulp, Birch #1, Birch #2, Eucalyptus, Acacia, Mixed European Hardwood, Mixed Thai Hardwood, Tissue Dust, Cotton, Jeans, Abaca, Sisal, Bagasse, Kenaf, Miscanthus, Sorghum, Giant Reed and Flax. 
     
     
         117 . The method according to  claim 111 , wherein the product of hemicellulose mass fraction and fibre zero-span tensile index is about 15 to about 25 Nm/g. 
     
     
         118 . The method according to  claim 111 , wherein the product of hemicellulose mass fraction and fibre zero-span tensile index is greater than 5 Nm/g. 
     
     
         119 . The method according to  claim 111 , wherein the product of hemicellulose mass fraction and fibre zero-span tensile index is greater than 10 Nm/g. 
     
     
         120 . The method according to  claim 111 , wherein the product of hemicellulose mass fraction and fibre zero-span tensile index is greater than 15 Nm/g. 
     
     
         121 . The method according to  claim 111 , wherein the product of hemicellulose mass fraction and fibre zero-span tensile index is greater than 20 Nm/g. 
     
     
         122 . The method according to  claim 111 , wherein the product of hemicellulose mass fraction and fibre zero-span tensile index is greater than 25 Nm/g. 
     
     
         123 . The method according to  claim 111 , wherein the product of hemicellulose mass fraction and fibre zero-span tensile index is greater than 30 Nm/g. 
     
     
         124 . The method according to  claim 111 , wherein the product of hemicellulose mass fraction and fibre zero-span tensile index is greater than 35 Nm/g. 
     
     
         125 . The method according to  claim 111 , wherein the product of hemicellulose mass fraction and fibre zero-span tensile index is greater than 40 Nm/g. 
     
     
         126 . The method according to  claim 111 , wherein the product of hemicellulose mass fraction and fibre zero-span tensile index is greater than 50 Nm/g. 
     
     
         127 . The method according to  claim 111 , wherein the hemicellulose mass fraction of the fibrous substrate comprising cellulose is between about 10% and about 25%. 
     
     
         128 . The method according to  claim 111 , wherein the hemicellulose mass fraction of the fibrous substrate comprising cellulose is 25% or more. 
     
     
         129 . The method according to  claim 111 , wherein the MFC fibre length is about 0.1 to 0.25 mm. 
     
     
         130 . The method according to  claim 111 , wherein the MFC fibre length is greater than 0.25 mm. 
     
     
         131 . The method according to  claim 111 , wherein the fibrous substrate comprising cellulose has a d 50  ranging from about 5 μm to about 500 μm, as measured by laser light scattering. 
     
     
         132 . The method according to  claim 111 , wherein the fibrous substrate comprising cellulose has a d 50  equal to or less than about 300 μm, as measured by laser light scattering. 
     
     
         133 . The method according to  claim 111 , wherein the fibrous substrate comprising cellulose has a d 50  equal to or less than about 200 μm, as measured by laser light scattering.