EP4185748A1 - Compositions de charge comprenant de la cellulose microfibrillée et des composites de matériaux particulaires inorganiques microporeux pour application de papier et de carton présentant des propriétés mécaniques améliorées - Google Patents

Compositions de charge comprenant de la cellulose microfibrillée et des composites de matériaux particulaires inorganiques microporeux pour application de papier et de carton présentant des propriétés mécaniques améliorées

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Publication number
EP4185748A1
EP4185748A1 EP21790548.8A EP21790548A EP4185748A1 EP 4185748 A1 EP4185748 A1 EP 4185748A1 EP 21790548 A EP21790548 A EP 21790548A EP 4185748 A1 EP4185748 A1 EP 4185748A1
Authority
EP
European Patent Office
Prior art keywords
inorganic particulate
particulate material
microporous inorganic
filler composition
microporous
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP21790548.8A
Other languages
German (de)
English (en)
Inventor
David Skuse
Jonathan Phipps
Thomas REEVE-LARSON
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
FiberLean Technologies Ltd
Original Assignee
FiberLean Technologies Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by FiberLean Technologies Ltd filed Critical FiberLean Technologies Ltd
Publication of EP4185748A1 publication Critical patent/EP4185748A1/fr
Pending legal-status Critical Current

Links

Classifications

    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H11/00—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only
    • D21H11/16—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only modified by a particular after-treatment
    • D21H11/18—Highly hydrated, swollen or fibrillatable fibres
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
    • D21C9/001—Modification of pulp properties
    • D21C9/002—Modification of pulp properties by chemical means; preparation of dewatered pulp, e.g. in sheet or bulk form, containing special additives
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H11/00—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
    • D21H17/63—Inorganic compounds
    • D21H17/64—Alkaline compounds
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
    • D21H17/63—Inorganic compounds
    • D21H17/67—Water-insoluble compounds, e.g. fillers, pigments
    • D21H17/675—Oxides, hydroxides or carbonates
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
    • D21H17/63—Inorganic compounds
    • D21H17/67—Water-insoluble compounds, e.g. fillers, pigments
    • D21H17/68—Water-insoluble compounds, e.g. fillers, pigments siliceous, e.g. clays
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
    • D21H17/71—Mixtures of material ; Pulp or paper comprising several different materials not incorporated by special processes
    • D21H17/74—Mixtures of material ; Pulp or paper comprising several different materials not incorporated by special processes of organic and inorganic material
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
    • D21H21/14—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties characterised by function or properties in or on the paper
    • D21H21/18—Reinforcing agents
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
    • D21H21/14—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties characterised by function or properties in or on the paper
    • D21H21/22—Agents rendering paper porous, absorbent or bulky
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
    • D21H21/50—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties characterised by form
    • D21H21/52—Additives of definite length or shape
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H23/00—Processes or apparatus for adding material to the pulp or to the paper
    • D21H23/02—Processes or apparatus for adding material to the pulp or to the paper characterised by the manner in which substances are added
    • D21H23/04—Addition to the pulp; After-treatment of added substances in the pulp
    • D21H23/06—Controlling the addition
    • D21H23/08—Controlling the addition by measuring pulp properties, e.g. zeta potential, pH
    • D21H23/10—Controlling the addition by measuring pulp properties, e.g. zeta potential, pH at least two kinds of compounds being added

Definitions

  • FILLER COMPOSITIONS COMPRISING MICROFIBRILLATED CELLULOSE AND MICROPOROUS INORGANIC PARTICULATE MATERIAL COMPOSITES FOR PAPER AND PAPERBOARD APPLICATIONS WITH IMPROVED MECHANICAL PROPERTIES
  • the present invention relates to methods of manufacturing paper comprising microfibrillated cellulose (“MFC”) and bulky microporous inorganic particulate material with improved mechanical properties through selection of bulky microporous inorganic particulate materials having optimal particle sizes and particle size distributions.
  • MFC microfibrillated cellulose
  • Inorganic particulate material is commonly used in graphic papers to enhance optical and printing properties. Because inorganic particulate material (also referred to herein as “minerals and “filler”) is substantially less expensive than pulp fibres, use of inorganic particulate material also allows the papermaker to save costs. The amount of inorganic particulate material that can be used is limited because of the effect the inorganic particulate material has on the strength properties of paper, both in the wet state during manufacture and after drying.
  • MFC microfibrillated cellulose
  • calcined clays and scalenohedral and aragonite precipitated calcium carbonates consist of aggregates of particles with open porous structures (i.e. , these are examples of microporous inorganic particulate materials).
  • Calcined clays are described in U.S. Patent No. 3,586,523, which is hereby incorporated herein by reference in its entirety.
  • Such calcined kaolin clays are substantially anhydrous, amorphous aluminum silicates which are obtained by calcining a specific type of kaolin clay, for example, hard sedimentary kaolin clay.
  • PCC Precipitated calcium carbonate
  • the PCC is produced in a unique clustered form having a substantial proportion of particles having a prismatic morphology.
  • calcite may have either prismatic, scalenohedral or rhombohedral crystal forms.
  • microporous inorganic particulate materials include chemically aggregated filler materials. Examples of such chemically aggregated fillers may be found in U.S> Patent No. 4,072,537, which is hereby incorporated herein in its entirety.
  • Such microporous inorganic particulate materials comprise a composite silicate material comprising a clay component and a metal silicate component.
  • the clay component is typically kaolin clay or kaolinite and the metal silicate material is typically a water-soluble alkali metal silicate, for example sodium silicate.
  • preferred methods for preparing the composite pigment comprise the steps of, (a) forming an aqueous suspension of a clay pigment, (b) blending into the clay slurry a quantity of a salt such as calcium chloride, (c) metering into the slurry of clay and salt at high shear a quantity of a silicate component such as sodium silicate, and, optionally, (d) adjusting the pH of the slurry with the addition of alum to a pH no lower than pH 4, before (e) filtering and washing the precipitated product to remove any soluble salts.
  • a microporous composite silicate material is either used directly in a papermaking process or dried and used later.
  • Additional microporous inorganic particulate material includes materials such as diatomaceous earth and expanded perlite.
  • microporous inorganic particulate materials consist of particles which contain rigid internal void spaces that persist through paper pressing and drying, and should also remain largely intact after calendering.
  • microporous inorganic particulate materials comprise discrete particles or aggregates of particles with outer dimensions of several microns, which contain void spaces within the volume defined by the outer dimensions which are several times smaller than said outer dimensions.
  • microporous inorganic particulate materials When used in paper, these microporous inorganic particulate materials have a much larger effect, per unit mass of added particulate material, on the spacing of the fibres than solid filler particles. This makes them more detrimental to paper strength, but generates increased light scattering which is beneficial to optical properties.
  • MFC microflbrillated cellulose
  • Certain methods and compositions comprising microflbrillated cellulose are produced by grinding procedures are described in WO-A-2010/131016.
  • MFC produced by the described grinding processes may include the co-grinding of cellulose-containing fibres with inorganic particulate material.
  • MFC may be produced by grinding cellulose fibres in the presence of grinding media other than inorganic particulate material. Paper products comprising such microflbrillated cellulose have been shown to exhibit excellent paper properties, such as paper burst and tensile strength. The methods described in WO-A- 2010/131016 also enable the production of microflbrillated cellulose economically.
  • W02010/131016 describes a grinding procedure for the production of microflbrillated cellulose with or without inorganic particulate material. Such a grinding procedure is described below.
  • the process utilizes mechanical disintegration of cellulose fibres to produce microflbrillated cellulose (“MFC”) cost-effectively and at large scale, without requiring cellulose pre- treatment.
  • MFC microflbrillated cellulose
  • An embodiment of the method uses stirred media detritor grinding technology, which disintegrates fibres into MFC by agitating grinding media beads.
  • a mineral such as calcium carbonate or kaolin is added as a grinding aid, greatly reducing the energy required.
  • the present invention is based on the use of microfibrillated cellulose and microporous inorganic particulate material, which are added to a papermaking furnish to produce paper and paperboard having enhanced mechanical properties that are not substantially degraded or are maintained or even improved when the compositions of MFC and microporous inorganic particulate material are utilized in lieu of MFC and conventional inorganic particulate material alone.
  • the microfibrillated cellulose and microporous inorganic particulate material can be added to a papermaking furnish separately mish or as a filler composition comprising the MFC and the one or more microporous inorganic particulate material.
  • MFC microporous inorganic particulate material
  • inorganic particulate material with a coarser (larger) than conventional particle and agglomerate size
  • MFC microporous inorganic particulate material with a coarser (larger) than conventional particle and agglomerate size
  • the MFC also offsets the typical increase in porosity associated with microporous inorganic particulate materials and the increased content of MFC and microporous inorganic particulate material offsets the loss of light scattering efficiency associated with using a microporous inorganic particulate material with a coarser than optimum particle size.
  • the one or more microporous inorganic particulate material comprises coarse particle size inorganic particulate material and agglomerates of coarse particle size microporous inorganic particulate material having a median particle size (d 50 ) ranging from about 3 ⁇ m to about 50 ⁇ m, such as, for example, from about 5 ⁇ m to about 30 ⁇ m, from about 10 ⁇ m to about 30 ⁇ m, from about 15 ⁇ m to about 25 ⁇ m, from about 20 ⁇ m to about 30 ⁇ m, from about 3 ⁇ m to about 15 ⁇ m, from about 5 ⁇ m to about 15 ⁇ m, from about 5 ⁇ m to about 10 ⁇ m, from about 2 ⁇ m to about 6 ⁇ m, and, particularly preferred between 3 ⁇ m and 6 ⁇ m, as measured by sedimentation methods described herein and as known in the art.
  • d 50 median particle size
  • the term mechanical properties comprises one or more of Tensile Elongation, Tensile Stiffness, Bulk, and Bending Stiffness.
  • the foregoing properties may be measured by methods described herein and as well known in the art of making paper and paperboard.
  • a paper or paperboard filler composition comprising microfibrillated cellulose (MFC) and one or more microporous inorganic particulate material for addition to a papermaking furnish for the manufacture of paper or paperboard, wherein the MFC and the one or more microporous inorganic particulate material impart mechanical properties to the paper or paperboard that are improved compared to paper and paperboard products made from an identical papermaking furnish not containing MFC and the one or more microporous inorganic particulate material.
  • MFC microfibrillated cellulose
  • a paper or paperboard filler composition comprising microfibrillated cellulose (MFC) and one or more microporous inorganic particulate material for use in a method for making a papermaking furnish for the manufacture of paper or paperboard, wherein the MFC and the one or more microporous inorganic particulate material impart mechanical properties to the paper or paperboard that are improved compared to paper and paperboard products made from an identical papermaking furnish not containing MFC and the one or more microporous inorganic particulate material [0027] In another aspect of the present disclosure, there is disclosed a paper or paperboard filler composition comprising microfibrillated cellulose (MFC) and one or more microporous inorganic particulate material for addition to a papermaking furnish for the manufacture of paper or paperboard, wherein the MFC is obtained by a co-grinding process using the same or different microporous inorganic particulate material and/or a conventional non-a
  • the one or more microporous inorganic particulate material comprises (or is selected from the group consisting of) calcined clay, kaolin, kaolinite, amorphous aluminum silicates, Scalenohedral precipitated calcium chloride, aragonite precipitated calcium carbonate, chemically aggregated filler materials, diatomaceous earth, and milled expanded perlite.
  • the one or more microporous inorganic particulate material comprises (or consists essentially of or consists of) calcined clay.
  • the one or more microporous inorganic particulate material comprises (or consists essentially of or consists of) kaolin.
  • the one or more microporous inorganic particulate material comprises (or consists essentially of or consists of) kaolinite.
  • the one or more microporous inorganic particulate material comprises (or consists essentially of or consists of) amorphous aluminum silicates.
  • the one or more microporous inorganic particulate material comprises (or consists essentially of or consists of) Scalenohedral precipitated calcium carbonate.
  • the one or more microporous inorganic particulate material comprises (or consists essentially of or consists of) aragonite precipitated calcium carbonate.
  • the one or more microporous inorganic particulate material comprises (or consists essentially of or consists of) chemically aggregated filler materials.
  • the one or more microporous inorganic particulate material comprises (or consists essentially of or consists of) diatomaceous earth.
  • the one or more microporous inorganic particulate material comprises (or consists essentially of or consists of) milled expanded perlite.
  • the MFC and the one or more microporous inorganic particulate material may be added separately or may be added together as a filler composition to the papermaking furnish.
  • the papermaking furnish comprises one or more pulp selected from softwood pulps.
  • the softwood pulp is selected from (or selected from the group consisting of) spruce, pine, fir, larch and hemlock and mixed softwood pulps.
  • the papermaking furnish comprises one or more pulp selected from (or selected from the group consisting of) hardwood pulps
  • the hardwood pulp is selected from (or selected from the group consisting of) eucalyptus, aspen and birch, and mixed hardwood pulps.
  • the pulp source for the papermaking furnish is selected from (or consists essentially of or consists of) eucalyptus pulp, spruce pulp, pine pulp, beech pulp, hemp pulp, cotton pulp, acacia and mixtures thereof
  • the pulp source for the papermaking furnish is selected from (or consists essentially of or consists of) Nordic Pine, Black Spruce, Radiata Pine, Southern Pine, Enzyme-Treated Nordic Pine, Douglas Fir, Dissolving Pulp, Birch (including Birch #1, Birch #2 set forth herein), Eucalyptus, Acacia, Mixed European Hardwood, Mixed Thai Hardwood, Recycled Paper, Cotton, Abaca, Acacia, Sisal, Bagasse, Kenaf, Miscanthus, Sorghum, Giant
  • the mechanical property is selected from one or more of Tensile Strength, Tensile Elongation, Bulk, Tensile Stiffness, Bending Stiffness, Porosity, Burst, Tear Strength, and Tensile Strength in the ‘Z’ direction.
  • the mechanical property is Tensile Strength.
  • the mechanical property is Tensile Elongation.
  • the mechanical property is Bulk.
  • the mechanical property is Tensile Stiffness.
  • the mechanical property is Bending Stiffness.
  • the mechanical property is Porosity
  • the mechanical property is Burst.
  • the mechanical property is Tear Strength.
  • the mechanical property is Tensile Strength in the ‘Z’ direction.
  • the microfibrillated cellulose has a modal fibre particle size ranging from about 0.1 ⁇ m-500 ⁇ m.
  • microfibrillated cellulose has a modal fibre particle size of at least about 0.5 ⁇ m, at least about 10 ⁇ m, at least about 50 ⁇ m, at least about 100 ⁇ m, at least about 150 ⁇ m, at least about 200 ⁇ m, at least about 300 ⁇ m, or at least about 400 ⁇ m.
  • the one or more microporous inorganic particulate material has a median particle size (d 50 ) ranging from about 3 ⁇ m to about 50 ⁇ m, from about 5 ⁇ m to about 30 ⁇ m, from about 10 ⁇ m to about 30 ⁇ m, from about 15 ⁇ m to about 25 ⁇ m, from about 20 ⁇ m to about 30 ⁇ m, from about 3 ⁇ m to about 15 ⁇ m, from about 5 ⁇ m to about 15 ⁇ m, from about 5 ⁇ m to about 10 ⁇ m, from about 3 ⁇ m to about 6 ⁇ m, or from about 3 to about 5 ⁇ m, as measured by laser light scattering.
  • d 50 median particle size
  • the one or more microporous inorganic particulate material and microfibrillated cellulose composite may be associated with one or more dispersing agents such as those selected from the group comprising (or elected from the group consisting of) homopolymers or copolymers of poly carboxylic acids and/or their salts or derivatives, esters based on, acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid; acryl amide or acrylic esters, methylmethacrylate, or mixtures thereof; alkali polyphosphates, phosphonic-, citric- and tartaric acids and the salts or esters thereof; and mixtures thereof.
  • the one or more microporous inorganic particulate material and microfibrillated cellulose composite is provided in the form of a powder.
  • the one or more microporous inorganic particulate material and microfibrillated cellulose composite is provided in the form of a suspension, or an aqueous suspension and in alternative embodiments the aqueous suspension is a pumpable liquid.
  • the one or more microporous inorganic particulate material comprises a blend of a first and second microporous inorganic particulate material
  • the ratio of the first microporous inorganic particulate material to the second microporous inorganic particulate material may range from about 10:90 to about 90:10 by weight, or from about 20:80 to about 80:20 by weight, or from about 25:75 to about 75:25 by weight, or from about 40:60 to about 60:40 by weight, or from about 50:50 by weight.
  • the binder composition further comprises a binder and in an embodiment may be an inorganic or organic binder.
  • the binder may be an alkali metal silicate, such as sodium silicate or potassium silicate.
  • the binder composition has a weight ratio of microfibrillated cellulose to the one or more microporous inorganic particulate material on a dry weight basis is from 1 :5 to 5: 1, or from 1:3 to 3: 1, or from 1:2 to 2:1, or from 1:1.5 to 1.5 to 1, or from 1:1.
  • the total content of the one or more microporous inorganic particulate material is present in an amount of from 10 wt. % to 95 wt.% on a dry weight basis of the filler composition, or from 15 wt.% to 90 wt.%, or from 20 to 75 wt.%, or from 25 wt.% to 67 wt.%, or from 33 to 50 wt.% on a dry weight basis of the filler composition.
  • a method of making a papermaking furnish comprising microfibrillated cellulose (MFC) and one or more microporous inorganic particulate material, the method comprising the steps of: adding the one or more microporous inorganic particulate material to the papermaking furnish; adding the MFC to the papermaking furnish; wherein the MFC and the one or more microporous inorganic particulate material impart mechanical properties to the paper or paperboard that are improved compared to paper and paperboard products made from an identical papermaking furnish not containing the microfibrillated cellulose and the one or more microporous inorganic particulate material.
  • MFC microfibrillated cellulose
  • a method of making a papermaking furnish comprising microfibrillated cellulose (MFC) and one or more microporous inorganic particulate material comprising the steps of: adding the one or more microporous inorganic particulate material to the papermaking furnish; adding the MFC to the papermaking furnish; wherein the MFC is obtained by a co-grinding process using the same or different microporous inorganic particulate material and/or a conventional non-agglomerated inorganic particulate material and a fibrous substrate comprising cellulose; and wherein the MFC and the one or more microporous inorganic particulate material impart mechanical properties to said paper or paperboard that are improved compared to paper and paperboard products made from an identical papermaking furnish not containing the microfibrillated cellulose and the one or more microporous inorganic particulate material.
  • MFC microfibrillated cellulose
  • a method of making a papermaking furnish comprising microfibrillated cellulose (MFC) and one or more microporous inorganic particulate material, the method comprising the steps of: adding a filler composition comprising MFC and the one or more microporous inorganic particulate material to the papermaking furnish; wherein the MFC and the one or more microporous inorganic particulate material impart mechanical properties to the paper or paperboard that are improved compared to paper and paperboard products made from an identical papermaking furnish not containing the microfibrillated cellulose and the one or more microporous inorganic particulate material.
  • MFC microfibrillated cellulose
  • a papermaking furnish comprising microfibrillated cellulose (MFC) and one or more microporous inorganic particulate material
  • the method comprising the steps of: adding a filler composition comprising MFC and the one or more microporous inorganic particulate material to the papermaking furnish; wherein the MFC is obtained by a co- grinding process using the same or different microporous inorganic particulate material and/or a conventional non-agglomerated inorganic particulate material and a fibrous substrate comprising cellulose; and wherein the MFC and the one or more microporous inorganic particulate material impart mechanical properties to said paper or paperboard that are improved compared to paper and paperboard products made from an identical papermaking furnish not containing the microfibrillated cellulose and the one or more microporous inorganic particulate material.
  • a paper or paperboard made from a papermaking furnish comprising microfibrillated cellulose (MFC) and one or more microporous inorganic particulate material comprising the steps of: adding a filler composition comprising MFC and the one or more microporous inorganic particulate material to the papermaking furnish; wherein the filler composition imparts mechanical properties to said paper or paperboard that are improved compared to paper and paperboard products made from an identical papermaking furnish not containing the MFC and the one or more microporous inorganic particulate material.
  • a method of making a paper or paperboard with improved mechanical properties comprising the steps of: preparing a papermaking furnish for production of paper or paperboard; adding one or more microporous inorganic particulate material to the papermaking furnish; adding microfibrillated cellulose (MFC) to the papermaking furnish; wherein the MFC and the one or more microporous inorganic particulate material are added separately to the papermaking furnish or as a filler composition comprising the MFC and the one or more microporous inorganic particulate material; manufacturing the paper or paperboard from the papermaking furnish by dewatering and drying the papermaking furnish; wherein the MFC and the one or more microporous inorganic particulate materials impart mechanical properties to the paper or paperboard that are improved compared to paper and paperboard products made from an identical papermaking furnish not containing MFC and microporous inorganic particulate material.
  • MFC microfibrillated cellulose
  • a method of making method of making a paper or paperboard from a papermaking furnish comprising microfibrillated cellulose (MFC) and one or more microporous inorganic particulate materials comprising the steps of: adding a filler composition comprising MFC and the one or more microporous inorganic particulate material to the papermaking furnish; wherein the MFC is obtained by a co- grinding process using the same or different microporous inorganic particulate material and/or a conventional non-agglomerated inorganic particulate material and a fibrous substrate comprising cellulose; and wherein the filler composition imparts mechanical properties to said paper or paperboard that are improved compared to paper and paperboard products made from an identical papermaking furnish not containing the MFC and one or microporous inorganic particulate material.
  • the MFC and the one or more microporous inorganic particulate material are added separately to the papermaking furnish or as a
  • a paper or paperboard from a papermaking furnish comprising microfibrillated cellulose (MFC) and one or more microporous inorganic particulate materials
  • the method comprising the steps of: adding the one or more microporous inorganic particulate material to the papermaking furnish; adding MFC to the papermaking furnish; wherein the MFC and the one or more microporous inorganic particulate material imparts mechanical properties to said paper or paperboard that are improved compared to paper and paperboard products made from an identical papermaking furnish not containing the microfibrillated cellulose and the one or more microporous inorganic particulate material.
  • MFC microfibrillated cellulose
  • the MFC and the one or more microporous inorganic particulate material are added separately to the papermaking furnish or as a filler composition comprising the MFC and the one or more microporous inorganic particulate material.
  • a method of making a paper or paperboard from a papermaking furnish comprising microfibrillated cellulose (MFC) and one or more microporous inorganic particulate materials comprising the steps of: adding the one or more microporous inorganic particulate material to the papermaking furnish; adding the MFC to the papermaking furnish; wherein the MFC is obtained by a co-grinding process using the same or different microporous inorganic particulate material and/or a conventional non-agglomerated inorganic particulate material and a fibrous substrate comprising cellulose; and wherein the MFC and the one or more microporous inorganic particulate material imparts mechanical properties to said paper or paperboard
  • a method of making a paper or paperboard with improved mechanical properties comprising the steps of: preparing a papermaking furnish for production of paper or paperboard; preparing a filler composition comprising microfibrillated cellulose (MFC) and one or more microporous inorganic particulate material; adding the filler composition to the papermaking furnish; manufacturing a paper or paperboard from the papermaking furnish by dewatering and drying the papermaking furnish; wherein the filler composition imparts mechanical properties to said paper or paperboard that are improved compared to paper and paperboard products made from an identical papermaking furnish not containing MFC and microporous inorganic particulate material.
  • the MFC and the one or more microporous inorganic particulate material are added separately to the papermaking furnish or as a filler composition comprising the MFC and the one or more microporous inorganic particulate material.
  • a method of making a paper or paperboard with improved mechanical properties comprising the steps of: preparing a papermaking furnish for production of paper or paperboard; preparing a filler composition comprising microfibrillated cellulose (MFC) and one or more microporous inorganic particulate material; adding the filler composition to the papermaking furnish; manufacturing a paper or paperboard from the papermaking furnish by dewatering and drying the papermaking furnish; wherein the MFC is obtained by a co-grinding process using the same or different microporous inorganic particulate material and/or a conventional non- agglomerated inorganic particulate material and a fibrous substrate comprising cellulose; and wherein the filler composition imparts mechanical properties to said paper or paperboard that are improved compared to paper and paperboard products made from an identical papermaking furnish not MFC and the one or more microporous inorganic particulate material.
  • the MFC and the one or more microfibrillated cellulose MFC
  • a method of making a paper or paperboard with improved mechanical properties comprising: preparing a papermaking furnish for production of paper or paperboard; adding one or more microporous inorganic particulate material to the papermaking furnish; adding microfibrillated cellulose
  • MFC to the papermaking furnish
  • manufacturing a paper or paperboard from the papermaking furnish by dewatering and drying the papermaking furnish wherein the MFC and the one or more microporous inorganic particulate materials impart mechanical properties to said paper or paperboard that are improved compared to paper and paperboard products made from an identical papermaking furnish not containing MFC and microporous inorganic particulate material.
  • the MFC and the one or more microporous inorganic particulate material are added separately to the papermaking furnish or as a filler composition comprising the MFC and the one or more microporous inorganic particulate material.
  • a method of making a paper or paperboard with improved mechanical properties comprising: preparing a papermaking furnish for production of paper or paperboard; adding one or more microporous inorganic particulate material to the papermaking furnish; adding microfibrillated cellulose (MFC) to the papermaking furnish; manufacturing a paper or paperboard from the papermaking furnish by dewatering and drying the papermaking furnish; wherein the MFC is obtained by a co-grinding process using the same or different microporous inorganic particulate materials and/or a conventional non-agglomerated inorganic particulate material and a fibrous substrate comprising cellulose; and wherein the MFC and the one or more microporous inorganic particulate materials impart mechanical properties to said paper or paperboard that are improved compared to paper and paperboard products made from an identical papermaking furnish not containing MFC and the one or more microporous inorganic particulate material.
  • MFC microfibrillated cellulose
  • the MFC and the one or more microporous inorganic particulate material are added separately to the papermaking furnish or as a filler composition comprising the MFC and the one or more microporous inorganic particulate material.
  • the one or more microporous inorganic particulate material is selected from the group comprising (or selected from the group consisting of) calcined clay, kaolin, kaolinite, amorphous aluminum silicates, Scalenohedral precipitated calcium chloride, aragonite precipitated calcium carbonate, chemically aggregated filler materials, diatomaceous earth, or milled expanded perlite.
  • the one or more microporous inorganic particulate material comprises or is calcined clay.
  • the one or more microporous inorganic particulate material comprises or is kaolin.
  • the one or more microporous inorganic particulate material comprises or is kaolinite.
  • the one or more microporous inorganic particulate material comprises or is amorphous aluminum silicate.
  • the one or more microporous inorganic particulate material comprises or is Scalenohedral precipitated calcium carbonate.
  • the one or more microporous inorganic particulate material comprises or is aragonite precipitated calcium carbonate.
  • the one or more microporous inorganic particulate material comprises or is chemically aggregated filler materials.
  • the one or more microporous inorganic particulate material comprises or is diatomaceous earth.
  • the one or more microporous inorganic particulate material comprises or is milled expanded perlite.
  • the papermaking furnish comprises one or more pulp selected from softwood pulps.
  • the softwood pulp is selected from (or is selected from the group consisting of) spruce, pine, fir, larch and hemlock or mixed softwood pulps.
  • the papermaking furnish comprises one or more pulp selected from hardwood pulp.
  • the hardwood pulp is selected from (or is selected from the group consisting of) eucalyptus, aspen and birch, or mixed hardwood pulps.
  • the pulp source for the papermaking furnish is selected from (or is selected from the group consisting of) eucalyptus pulp, spruce pulp, pine pulp, beech pulp, hemp pulp, acacia, cotton pulp, and mixtures thereof.
  • the pulp source for the papermaking furnish is selected from (or is selected from the group consisting of) Nordic Pine, Black Spruce, Radiata Pine, Southern Pine, Enzyme-Treated Nordic Pine, Douglas Fir, Dissolving Pulp, (Birch (including Birch #1, Birch #2 set forth herein), Eucalyptus, Acacia, Mixed European Hardwood, Mixed Thai Hardwood, Recycled Paper, Cotton, Abaca, Sisal, Bagasse, Kenaf, Miscanthus, Sorghum, Giant Reed and Flax.
  • the microfibrillated cellulose is prepared by a co-grinding process with one or more non-agglomerated inorganic particulate material utilized in preparation of the microfibrillated cellulose and one or more microporous inorganic particulate material composite.
  • the microfibrillated cellulose has a fibre steepness of about 20 to about 50.
  • the microfibrillated cellulose has a d 50 ranging from about 5 to about 500 ⁇ m, as measured by laser light scattering.
  • the microfibrillated cellulose has a d 50 of equal to or less than about 400 ⁇ m, as measured by laser light scattering.
  • the microfibrillated cellulose has a d 50 of equal to or less than about 200 ⁇ m, as measured by laser light scattering.
  • the microfibrillated cellulose has a d 50 of equal to or less than about 200 ⁇ m, as measured by laser light scattering.
  • the microfibrillated cellulose has a d 50 of equal to or less than about 150 ⁇ m, as measured by laser light scattering.
  • the one or more microporous inorganic particulate material and microfibrillated cellulose composite is provided in the form of a powder.
  • the one or more microporous inorganic particulate material and microfibrillated cellulose composite is provided in the form of a suspension.
  • the suspension may be an aqueous suspension.
  • the aqueous suspension is a pumpable liquid.
  • the one or more microporous inorganic particulate material comprises a blend of a first and second microporous inorganic particulate material, wherein the ratio of the first microporous inorganic particulate material to the second microporous inorganic particulate material may range from about 10:90 to about 90:10 by weight, from about 20:80 to about 80:20 by weight, or from about 25:75 to about 75:25 by weight, or from about 40:60 to about 60:40 by weight, or from about 50:50 by weight.
  • the method further comprises a binder.
  • the binder is an organic or inorganic binder.
  • the binder is an alkali metal silicate, such as sodium silicate or potassium silicate.
  • the weight ratio of microfibrillated cellulose to the one or more microporous inorganic particulate material on a dry weight basis is from 1:5 to 5:1, or 1:3 to 3:1, or 1:2 to 2:1, or 1:1.5 to 1.5 to 1, or about 1: 1.
  • the total content of the one or more microporous inorganic particulate material is present in an amount of from 10 wt-% to 95 wt-% on a dry weight basis of the filler composition, from 15 wt.% to 90 wt.%, or from 20 to 75 wt.%, or from 25 wt.% to 67 wt.%, or from 33 to 50 wt-% on a dry weight basis of the filler composition.
  • particle size properties referred to herein for the inorganic particulate materials are as measured in a well-known manner by sedimentation of the particulate material in a fully dispersed condition in an aqueous medium using a Sedigraph 5100 machine as supplied by Micromeritics Instruments Corporation, Norcross, Ga., USA (telephone: +1 770 662 3620; web-site: www. micromeritics. com), referred to herein as a "Micromeritics Sedigraph 5100 unit".
  • Such a machine provides measurements and a plot of the cumulative percentage by weight of particles having a size, referred to in the art as the 'equivalent spherical diameter' (e.s.d), less than given e.s.d values.
  • the mean particle size d 50 is the value determined in this way of the particle e.s.d at which there are 50% by weight of the particles which have an equivalent spherical diameter less than that d 50 value.
  • the blend of the first and second inorganic particulate materials and the binder solution may be mixed with sufficient agitation to at least substantially uniformly distribute the binder composition (slurry or suspension) among the agglomeration points of contact of the blend of first and second inorganic particulate materials without damaging the structure of the first or second inorganic particulate materials.
  • the contacting is performed in a low-shear mixing apparatus.
  • the mixing may occur at about room temperature (i.e., from about 20° C. to about 23° C ).
  • the mixing may occur at about room temperature (i.e., from about 20° C. to about 50° C.)
  • the mixing may occur at about room temperature (i.e., from about 30° C. to about 45° C.)
  • the mixing may occur at about room temperature (i.e., from about 35° C. to about 45° C.)
  • the contacting may include spraying the blend of first and/or first and second inorganic particulate materials with a binder composition (slurry or suspension).
  • the contacting is intermittent.
  • the contacting is continuous.
  • the binder may be present in a binder composition (slurry or suspension) in an amount less than about 40% by weight, relative to the weight of the binder solution. In some embodiments, the binder may range from about 1% to about 10% by weight.
  • Fig. 1 is a plot of Scott Bond, Bending Stiffness, Tensile Index, Bulk and Light Scattering properties for compositions comprising ground calcium carbonate (GCC) compositions at 20% and 30% levels with and without MFC compared to precipitated calcium carbonate (PCC) compositions at 20% and 30% levels with and without MFC.
  • GCC ground calcium carbonate
  • PCC precipitated calcium carbonate
  • Fig. 2 is a graph of Bending Stiffness in mN.m versus percentage filler proportion comprising PCC (remainder is GCC).
  • Fig. 3 is a graph of Light Scattering Coefficient (F10) in cm 2 g -1 versus percentage filler proportion comprising PCC (remainder is GCC).
  • Fig. 4 is a graph of Tensile Index in N.m/g versus percentage filler proportion comprising PCC (remainder is GCC).
  • Fig. 5 is a graph of Scott Bond in J/m 2 versus percentage filler proportion comprising PCC (remainder is GCC).
  • Fig. 6 is a graph of Tensile Index in N.m/g versus Sheet Filler Content in percentage PCC content.
  • Fig. 7 is a graph of Light Scattering (F10 S) versus Sheet Filler Content in percentage PCC content.
  • Fig. 8 is a graph of Bending Stiffness in mN versus Sheet Filler Content in percentage PCC content.
  • the present invention relates to filler composition comprising MFC and one or more microporous inorganic particulate material composite to be utilized in papermaking furnishes for the production of paper and paperboard with improved mechanical properties compared to paper and paperboard produced without MFC and one or more microporous inorganic particulate material.
  • the designated value may vary by plus or minus twelve percent, or eleven percent, or ten percent, or nine percent, or eight percent, or seven percent, or six percent, or five percent, or four percent, or three percent, or two percent, or one percent.
  • the use of the term "at least one” will be understood to include one as well as any quantity more than one, including but not limited to, 1, 2, 3, 4, 5, 10, 15, 20, 30, 40, 50, 100, etc.
  • the term “at least one” may extend up to 100 or 1000 or more depending on the term to which it is attached.
  • the quantities of 100/1000 are not to be considered limiting as lower or higher limits may also produce satisfactory results.
  • the use of the term "at least one of X, Y, and Z" will be understood to include X alone, Y alone, and Z alone, as well as any combination of X, Y, and Z.
  • one or more microporous inorganic particulate material comprises coarse particle size inorganic particulate material and agglomerates of coarse particle size inorganic particulate material having a median particle size (d 50 ) ranging from about 3 ⁇ m to about 50 ⁇ m, such as, for example, from about 5 ⁇ m to about 30 ⁇ m, from about 10 ⁇ m to about 30 ⁇ m, from about 15 ⁇ m to about 25 ⁇ m, from about 20 ⁇ m to about 30 ⁇ m, from about 3 ⁇ m to about 15 ⁇ m, from about 5 ⁇ m to about 15 ⁇ m, from about 5 ⁇ m to about 10 ⁇ m, from about 2 ⁇ m to about 6 ⁇ m, and, particularly preferred between 3 ⁇ m and 6 ⁇ m, as measured by sedimentation methods described herein and as known in the art.
  • d 50 median particle size
  • the terms “comprising” (and any form of comprising, such as “comprise”, “comprises”, and “comprised”), “having” (and any form of having, such as “have” and “has”), “including” (and any form of including, such as “includes” and “include”), or “containing” (and any form of containing, such as “contains” and “contain”), are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.
  • the fibrous substrate comprising cellulose may be derived from virgin or recycled pulp or a papermill broke and/or industrial waste, or a paper streams rich in mineral fillers and cellulosic materials from a papermill.
  • mechanical properties comprise one or more of the following properties: Tensile Strength, Tensile Elongation, Bulk, Tensile Stiffness, Bending Stiffness,
  • the term “substantially” means that the subsequently described event or circumstance completely occurs or that the subsequently described event or circumstance occurs to a great extent or degree. For example, when associated with a particular event or circumstance, the term “substantially” means that the subsequently described event or circumstance occurs at least 80% of the time, or at least 85% of the time, or at least 90% of the time, or at least 95% of the time.
  • the degradation of tensile strength and/or bending stiffness are not diminished by more than 15%, or more than 10% or more than 5% from the properties of the control.
  • integer from X to Y means any integer that includes the endpoints.
  • integer from 1 to 5" means 1, 2, 3, 4, or 5.
  • microflbrillated cellulose although well-known and described in the art, for purposes of the presently disclosed and/or claimed inventive concept(s), microflbrillated cellulose is defined as cellulose consisting of microfibrils in the form of either isolated cellulose microfibrils and/or microfibril bundles of cellulose, both of which are derived from a cellulose raw material.
  • microflbrillated cellulose is to be understood to comprise partly or totally fibrillated cellulose or lignocellulose fibers, which may be achieved by a variety of processes known in the art.
  • microflbrillated cellulose can be used interchangeably with “microfibrillar cellulose,” “nanofibrillated cellulose,” “nanofibril cellulose,” “nanofibers of cellulose,” “nanoscale fibrillated cellulose,” “microfibrils of cellulose,” and/or simply as
  • microfibrillated cellulose may refer to cellulose that has been completely microfibrillated or cellulose that has been substantially microfibrillated but still contains an amount of non- microfibrillated cellulose at levels that do not interfere with the benefits of the microfibrillated cellulose as described and/or claimed herein
  • microfibrillating is meant a process in which microfibrils of cellulose are liberated or partially liberated as individual species or as small aggregates as compared to the fibres of the pre-microfibrillated pulp.
  • Typical cellulose fibres i. e. , pre-microfibrillated pulp
  • suitable for use in papermaking include larger aggregates of hundreds or thousands of individual cellulose fibrils
  • Microfibrillated cellulose comprises cellulose, which is a naturally occurring polymer comprising repeated glucose units.
  • microfibrillated cellulose also denoted MFC, as used in this specification, includes microfibrillated/microfibrillar cellulose and nano-fibrillated/nanofibrillar cellulose (NFC), which materials are also called nanocellulose.
  • Microfibrillated cellulose is prepared by stripping away the outer layers of cellulose fibers that may have been exposed through mechanical shearing, with or without prior enzymatic or chemical treatment. There are numerous methods of preparing microfibrillated cellulose that are known in the art.
  • microfibrillated cellulose is used to describe fibrillated cellulose comprising nanoscale cellulose particle fibers or fibrils frequently having at least one dimension less than 100 nm. When liberated from cellulose fibres, fibrils typically have a diameter less than 100 nm. The actual diameter of cellulose fibrils depends on the source and the manufacturing methods. [00149] The particle size distribution and/or aspect ratio (length/width) of the cellulose microfibrils attached to the fibrillated cellulose fiber or as a liberated microfibril depends on the source and the manufacturing methods employed in the microfibrillation process.
  • the aspect ratio of microfibrils is typically high and the length of individual microfibrils may be more than one micrometer and the diameter may be within a range of about 5 to 60 nm with a number-average diameter typically less than 20 nm.
  • the diameter of microfibril bundles may be larger than 1 micron, however, it is usually less than one
  • the smallest fibril is conventionally referred to as an elementary fibril, which generally has a diameter of approximately 2-4 nm. It is also common for elementary fibrils to aggregate, which may also be considered as microfibrils.
  • the microfibrillated cellulose may at least partially comprise nanocellulose.
  • the nanocellulose may comprise mainly nano-sized fibrils having a diameter that is less than 100 nm and a length that may be in the micron-range or lower.
  • the smallest microfibrils are similar to the so-called elemental fibrils, the diameter of which is typically 2 to 4 nm.
  • the dimensions and structures of microfibrils and microfibril bundles depend on the raw materials used in addition to the methods of producing the microfibrillated cellulose. Nonetheless, it is expected that a person of ordinary skill in the art would understand the meaning of "microfibrillated cellulose" in the context of the presently disclosed and/or claimed inventive concept(s)
  • a coarse MFC grade might contain a substantial fraction of fibrillated fibers, i.e. protruding fibrils from the tracheid (cellulose fiber), and with a certain amount of fibrils liberated from the tracheid (cellulose fiber).
  • the microfibrillated cellulose may also be prepared from recycled pulp or a papermill broke and/or industrial waste, or a paper streams rich in mineral fillers and cellulosic materials from a papermill.
  • the fibrous substrate comprising cellulose may be added to a grinding vessel fibrous substrate comprising cellulose in a dry state.
  • a dry paper broke may be added directly to the grinder vessel.
  • the aqueous environment in the grinder vessel will then facilitate the formation of a pulp.
  • the present invention is related to modifications, for example, improvements, to the methods and compositions described in WO-A-2010/131016, the entire contents of which are hereby incorporated by reference.
  • WO-A-2010/131016 discloses a process for preparing microfibrillated cellulose comprising microfibrillating, e.g., by grinding, a fibrous material comprising cellulose, optionally in the presence of grinding medium and inorganic particulate material.
  • a fibrous material comprising cellulose
  • inorganic particulate material When used as a filler in paper, for example, as a replacement or partial replacement for a conventional mineral filler, the microfibrillated cellulose obtained by said process, optionally in combination with inorganic particulate material, was unexpectedly found to improve the burst strength properties of the paper. That is, relative to a paper filled with exclusively mineral filler, paper filled with the microfibrillated cellulose was found to have improved burst strength.
  • the microfibrillated cellulose filler was found to have paper burst strength enhancing attributes.
  • the fibrous material comprising cellulose was ground in the presence of a grinding medium, optionally in combination with inorganic particulate material, to obtain microfibrillated cellulose having a fibre steepness of from 20 to about 50.
  • co-grinding (or “co-ground”) composite of microfibrillated cellulose and inorganic particulate material refers to a composite obtained by a “co-grinding microfibrillation process,” wherein a fibrous substrate comprising cellulose is microfibrillated in an aqueous environment in a grinding apparatus in the presence of the at least one inorganic particulate material, and optionally a grinding medium other than the at least one inorganic particulate material (or stated differently by “co-processing” a fibrous substrate comprising cellulose in the presence of the at least one inorganic particulate material in a wet grinding apparatus and optionally in the presence of a grinding medium other than the at least one inorganic particulate material, which is removed after grinding, to produce microfibrillated cellulose). See the description below of an exemplary microfibrillation process and wet-grinding process.
  • additional inorganic particulate material may be added (e.g., by blending or mixing) to reduce the microfibrillated cellulose content of the co-processed microfibrillated cellulose and inorganic particulate material composite.
  • the MFC may be manufactured using a tower mill or a screened grinding mill such as a stirred media detritor.
  • a stirred media mill consists of a rotating impeller that transfers kinetic energy to small grinding media beads, which grind down the charge via a combination of shear, compressive, and impact forces.
  • a variety of grinding apparatus may be used to produce MFC by the disclosed methods herein, including, for example, a tower mill, a screened grinding mill, or a stirred media detritor.
  • the microflbrillating step is conducted in the presence of an inorganic particulate material which acts as a microflbrillating agent.
  • the microflbrillating step is conducted in the presence of an inorganic particulate material and a grinding medium other than the at least one inorganic particulate material, which is removed after grinding.
  • microfibrillated cellulose utilized in the present invention is, however, not limited to a single manufacturing method. Such microfibrillation processes are presented for illustrative purposes.
  • microflbrillating is meant a process in which microfibrils of cellulose are liberated or partially liberated as individual species or as smaller aggregates as compared to the fibres of the pre-microfibrillated cellulose-containing pulp.
  • Typical cellulose fibres i.e., pre-microfibrillated cellulose-containing pulp
  • suitable for use in papermaking include larger aggregates of hundreds or thousands of individual cellulose microfibrils.
  • the step of microfibrillating may be carried out in any suitable apparatus.
  • the microfibrillating step is conducted in a grinding vessel under wet-grinding conditions.
  • the microfibrillating step is carried out in a homogenizer.
  • the grinding may be an attrition grinding process in the presence of a grinding medium, or may be an autogenous grinding process, i.e., one performed in the absence of a grinding medium.
  • grinding medium is meant a medium other than the at least one inorganic particulate material which is co-ground with the fibrous substrate comprising cellulose.
  • the grinding medium when present, may be of a natural or a synthetic material.
  • the grinding medium may, for example, comprise balls, beads or pellets of any hard mineral, ceramic or metallic material.
  • Such materials may include, for example, alumina, zirconia, zirconium silicate, aluminum silicate or the mullite-rich material which is produced by calcining kaolinitic clay at a temperature in the range of from about 1300°C. to about 1800°C.
  • a Carbolite® grinding medium is used.
  • particles of natural sand of a suitable particle size may be used.
  • the type of and particle size of grinding medium to be selected for use in the invention may be dependent on the properties, such as, e.g., the particle size of, and the chemical composition of, the feed suspension of material to be ground.
  • the particulate grinding medium comprises particles having an average diameter in the range of from about 0.1 mm to about 6.0 mm and, more preferably, in the range of from about 0.2 mm to about 4.0 mm.
  • the grinding medium (or media) may be present in an amount up to about
  • the grinding media may be present in amount of at least about 10% by volume of the charge, for example, at least about 20% by volume of the charge, or at least about 30% by volume of the charge, or at least about 40% by volume of the charge, or at least about 50% by volume of the charge, or at least about 60% by volume of the charge.
  • the grinding may be carried out in one or more stages. For example, a coarse inorganic particulate material may be ground in the grinder vessel to a predetermined particle size distribution, after which the fibrous material comprising cellulose is added and the grinding continued until the desired level of microfibrillation has been obtained.
  • the coarse inorganic particulate material used in accordance with an first aspect of this invention initially may have a particle size distribution in which less than about 20% by weight of the particles have an essential spherical diameter (e.s.d) of less than 2 ⁇ m, for example, less than about 15% by weight, or less than about 10% by weight of the particles have an e.s.d. of less than 2 ⁇ m.
  • an essential spherical diameter e.s.d
  • the coarse inorganic particulate material used in accordance with the first aspect of this invention initially may have a particle size distribution, as measured using a Malvern Mastersizer S machine, in which less than about 20% by volume of the particles have an e.s.d of less than 2 ⁇ m, for example, less than about 15% by volume, or less than about 10% by volume of the particles have an e.s.d. of less than 2 ⁇ m.
  • the coarse inorganic particulate material may be wet or dry ground in the absence or presence of a grinding medium.
  • the coarse inorganic particulate material is preferably ground in an aqueous suspension in the presence of a grinding medium.
  • the coarse inorganic particulate material may preferably be present in an amount of from about 5% to about 85% by weight of the suspension; more preferably in an amount of from about 20% to about 80% by weight of the suspension. Most preferably, the coarse inorganic particulate material may be present in an amount of about 30% to about 75% by weight of the suspension.
  • the coarse inorganic particulate material may be ground to a particle size distribution such that at least about 10% by weight of the particles have an e.s.d of less than 2 ⁇ m, for example, at least about 20% by weight, or at least about 30% by weight, or at least about 40% by weight, or at least about 50% by weight, or at least about 60% by weight, or at least about 70% by weight, or at least about 80% by weight, or at least about 90% by weight, or at least about 95% by weight, or about 100% by weight of the particles, have an e.s.d of less than 2 ⁇ m, after which the cellulose pulp is added and the two components are co-ground to microfibrillate the fibres of the cellulose pulp.
  • the coarse inorganic particulate material is ground to a particle size distribution, as measured using a Malvern Mastersizer S machine such that at least about 10% by volume of the particles have an e.s.d of less than 2 ⁇ m, for example, at least about 20% by volume, or at least about 30% by volume or at least about 40% by volume, or at least about 50% by volume, or at least about 60% by volume, or at least about 70% by volume, or at least about 80% by volume, or at least about 90% by volume, or at least about 95% by volume, or about 100% by volume of the particles, have an e.s.d of less than 2 ⁇ m, after which the cellulose pulp is added and the two components are co-ground to microfibrillate the fibres of the cellulose pulp.
  • the mean particle size (d 50 ) of the inorganic particulate material is reduced during the co-grinding process.
  • the d 50 of the inorganic particulate material may be reduced by at least about 10% (as measured by a Malvern Mastersizer S machine), for example, the d 50 of the inorganic particulate material may be reduced by at least about 20%, or reduced by at least about 30%, or reduced by at least about 50%, or reduced by at least about 50%, or reduced by at least about 60%, or reduced by at least about 70%, or reduced by at least about 80%, or reduced by at least about 90%.
  • an inorganic particulate material having a d 50 of 2.5 ⁇ m prior to co-grinding and a d 50 of 1.5 ⁇ m post co- grinding will have been subject to a 40% reduction in particle size.
  • the mean particle size of the inorganic particulate material is not significantly reduced during the co-grinding process.
  • 'not significantly reduced' is meant that the d 50 of the inorganic particulate material is reduced by less than about 10%, for example, the d 50 of the inorganic particulate material is reduced by less than about 5%.
  • the fibrous substrate comprising cellulose may be microfibrillated in the presence of at least one inorganic particulate material to obtain microfibrillated cellulose having a d 50 ranging from about 5 ⁇ m to about 500 ⁇ m, as measured by laser light scattering.
  • the fibrous substrate comprising cellulose may be microfibrillated in the presence of an inorganic particulate material to obtain microfibrillated cellulose having a d 50 of equal to or less than about 400 ⁇ m, for example equal to or less than about 300 ⁇ m, or equal to or less than about 200 ⁇ m or equal to or less than about 150 ⁇ m, or equal to or less than about 125 ⁇ m, or equal to or less than about 100 ⁇ m, or equal to or less than about 90 ⁇ m, or equal to or less than about 80 ⁇ m, or equal to or less than about 70 ⁇ m, or equal to or less than about 60 ⁇ m, or equal to or less than about 50 ⁇ m, or equal to or less than about 40 ⁇ m, or equal to or less than about 30 ⁇ m, or equal to or less than about 20 ⁇ m, or equal to or less than about 10 ⁇ m.
  • a d 50 of equal to or less than about 400 ⁇ m for example equal to or less than about 300 ⁇
  • the fibrous substrate comprising cellulose may be microfibrillated in the presence of an inorganic particulate material to obtain microfibrillated cellulose having a modal fibre particle size ranging from about 0.1-500 ⁇ m and a modal inorganic particulate material particle size ranging from 0.25-20 ⁇ m.
  • the fibrous substrate comprising cellulose may be microfibrillated in the presence of an inorganic particulate material to obtain microfibrillated cellulose having a modal fibre particle size of at least about 0.5 ⁇ m, for example at least about 10 ⁇ m, or at least about 50 ⁇ m, or at least about 100 ⁇ m, or at least about 150 ⁇ m, or at least about 200 ⁇ m, or at least about 300 ⁇ m, or at least about 400 ⁇ m.
  • the fibrous substrate comprising cellulose may be microfibrillated in the presence of an inorganic particulate material to obtain microfibrillated cellulose having a fibre steepness equal to or greater than about 10, as measured by Malvern.
  • Fibre steepness i.e. , the steepness of the particle size distribution of the fibres
  • Steepness 100 X (d 30 /d 70 ).
  • the microfibrillated cellulose may have a fibre steepness equal to or less than about 100.
  • the microfibrillated cellulose may have a fibre steepness equal to or less than about 75, or equal to or less than about 50, or equal to or less than about 40, or equal to or less than about 30.
  • the microfibrillated cellulose may have a fibre steepness from about 20 to about 50, or from about 25 to about 40, or from about 25 to about 35, or from about 30 to about 40.
  • the grinding is suitably performed in a grinding vessel, such as a tumbling mill (e.g., rod, ball and autogenous), a stirred mill (e.g., SAM or IsaMill), a tower mill, a stirred media detritor (SMD), or a grinding vessel comprising rotating parallel grinding plates between which the feed to be ground is fed.
  • a tumbling mill e.g., rod, ball and autogenous
  • a stirred mill e.g., SAM or IsaMill
  • a tower mill e.g., a stirred media detritor (SMD), or a grinding vessel comprising rotating parallel grinding plates between which the feed to be ground is fed.
  • SMD stirred media detritor
  • the grinding vessel is a tower mill.
  • the tower mill may comprise a quiescent zone above one or more grinding zones.
  • a quiescent zone is a region located towards the top of the interior of tower mill in which minimal or no grinding takes place and comprises microfibrillated cellulose and inorganic particulate material.
  • the quiescent zone is a region in which particles of the grinding medium sediment down into the one or more grinding zones of the tower mill.
  • the tower mill may comprise a classifier above one or more grinding zones.
  • the classifier is top mounted and located adjacent to a quiescent zone.
  • the classifier may be a hydrocyclone.
  • the tower mill may comprise a screen above one or more grinding zones.
  • a screen is located adjacent to a quiescent zone and/or a classifier.
  • the screen may be sized to separate grinding media from the product aqueous suspension comprising microfibrillated cellulose and inorganic particulate material and to enhance grinding media sedimentation.
  • the grinding is performed under plug flow conditions.
  • plug flow conditions the flow through the tower is such that there is limited mixing of the grinding materials through the tower. This means that at different points along the length of the tower mill the viscosity of the aqueous environment will vary as the fineness of the microfibrillated cellulose increases.
  • the grinding region in the tower mill can be considered to comprise one or more grinding zones which have a characteristic viscosity. A skilled person in the art will understand that there is no sharp boundary between adjacent grinding zones with respect to viscosity.
  • water is added at the top of the mill proximate to the quiescent zone or the classifier or the screen above one or more grinding zones to reduce the viscosity of the aqueous suspension comprising microfibrillated cellulose and inorganic particulate material at those zones in the mill.
  • the prevention of grinding media carry over to the quiescent zone and/or the classifier and/or the screen is improved.
  • the limited mixing through the tower allows for processing at higher solids lower down the tower and dilute at the top with limited backflow of the dilution water back down the tower into the one or more grinding zones.
  • any suitable amount of water which is effective to dilute the viscosity of the product aqueous suspension comprising microfibrillated cellulose and inorganic particulate material may be added.
  • the water may be added continuously during the grinding process, or at regular intervals, or at irregular intervals.
  • water may be added to one or more grinding zones via one or more water injection points positioned along the length of the tower mill, or each water injection point being located at a position which corresponds to the one or more grinding zones.
  • water injection points positioned along the length of the tower mill, or each water injection point being located at a position which corresponds to the one or more grinding zones.
  • the ability to add water at various points along the tower allows for further adjustment of the grinding conditions at any or all positions along the mill.
  • the tower mill may comprise a vertical impeller shaft equipped with a series of impeller rotor disks throughout its length. The action of the impeller rotor disks creates a series of discrete grinding zones throughout the mill.
  • the grinding is performed in a screened grinder, preferably a stirred media detritor.
  • the screened grinder may comprise one or more screen(s) having a nominal aperture size of at least about 250 ⁇ m, for example, the one or more screens may have a nominal aperture size of at least about 300 ⁇ m, or at least about 350 ⁇ m, or at least about 400 ⁇ m, or at least about 450 ⁇ m, or at least about 500 ⁇ m, or at least about 550 ⁇ m, or at least about 600 ⁇ m, or at least about 650 ⁇ m, or at least about 700 ⁇ m, or at least about 750 ⁇ m, or at least about 800 ⁇ m, or at least about 850 ⁇ m, or at or least about 900 ⁇ m, or at least about 1000 ⁇ m.
  • the grinding may be performed in the presence of a grinding medium.
  • the grinding medium is a coarse media comprising particles having an average diameter in the range of from about 1 mm to about 6 mm, for example about 2 mm, or about 3 mm, or about 4 mm, or about 5 mm.
  • the grinding media has a specific gravity of at least about
  • the grinding media comprises particles having an average diameter in the range of from about 1 mm to about 6 mm and has a specific gravity of at least about 2.5.
  • the grinding medium may present in an amount up to about 70% by volume of the charge.
  • the grinding media may be present in amount of at least about 10% by volume of the charge, for example, at least about 20% by volume of the charge, or at least about 30% by volume of the charge, or at least about 40% by volume of the charge, or at least about 50% by volume of the charge, or at least about 60% by volume of the charge.
  • the grinding medium is present in amount of about 50% by volume of the charge.
  • ' charge' is meant the composition which is the feed fed to the grinder vessel.
  • the charge includes of water, grinding media, fibrous substrate comprising cellulose and inorganic particulate material, and any other optional additives as described herein.
  • the use of a relatively coarse and/or dense media has the advantage of improved (i. e. , faster) sediment rates and reduced media carry over through the quiescent zone and/or classifier and/or screen(s).
  • a further advantage in using relatively coarse grinding media is that the mean particle size (d 50 ) of the inorganic particulate material may not be significantly reduced during the grinding process such that the energy imparted to the grinding system is primarily expended in microfibrillating the fibrous substrate comprising cellulose.
  • a further advantage in using relatively coarse screens is that a relatively coarse or dense grinding media can be used in the microfibrillating step.
  • relatively coarse screens i.e. , having a nominal aperture of least about 250 um
  • a relatively high solids product to be processed and removed from the grinder, which allows a relatively high solids feed (comprising fibrous substrate comprising cellulose and inorganic particulate material) to be processed in an economically viable process.
  • a feed having a high initial solids content is desirable in terms of energy sufficiency.
  • product produced (at a given energy) at lower solids has a coarser particle size distribution.
  • the fibrous substrate comprising cellulose and inorganic particulate material are present in the aqueous environment at an initial solids content of at least about 4 wt.%, of which at least about 2% by weight is fibrous substrate comprising cellulose.
  • the initial solids content may be at least about 10 wt. %, or at least about 20 wt. %, or at least about 30 wt. %, or at least about at least 40 wt. %.
  • At least about 5% by weight of the initial solids content may be fibrous substrate comprising cellulose, for example, at least about 10%, or at least about 15%, or at least about 20% by weight of the initial solids content may be fibrous substrate comprising cellulose.
  • the grinding is performed in a cascade of grinding vessels, one or more of which may comprise one or more grinding zones.
  • the fibrous substrate comprising cellulose and the inorganic particulate material may be ground in a cascade of two or more grinding vessels, for example, a cascade of three or more grinding vessels, or a cascade of four or more grinding vessels, or a cascade of five or more grinding vessels, or a cascade of six or more grinding vessels, or a cascade of seven or more grinding vessels, or a cascade of eight or more grinding vessels, or a cascade of nine or more grinding vessels in series, or a cascade comprising up to ten grinding vessels.
  • the cascade of grinding vessels may be operatively linked in series or parallel or a combination of series and parallel.
  • the output from and/or the input to one or more of the grinding vessels in the cascade may be subjected to one or more screening steps and/or one or more classification steps.
  • the total energy expended in a microfibrillation process may be apportioned equally across each of the grinding vessels in the cascade. Alternatively, the energy input may vary between some or all of the grinding vessels in the cascade.
  • the energy expended per vessel may vary between vessels in the cascade depending on the amount of fibrous substrate being microfibrillated in each vessel, and optionally the speed of grind in each vessel, the duration of grind in each vessel, the type of grinding media in each vessel and the type and amount of inorganic particulate material.
  • the grinding conditions may be varied in each vessel in the cascade in order to control the particle size distribution of both the microfibrillated cellulose and the inorganic particulate material.
  • the grinding media size may be varied between successive vessels in the cascade in order to reduce grinding of the inorganic particulate material and to target grinding of the fibrous substrate comprising cellulose.
  • the grinding is performed in a closed circuit. In another embodiment, the grinding is performed in an open circuit. The grinding may be performed in batch mode. The grinding may be performed in a re-circulating batch mode. In another embodiment, the grinding may be performed in a continuous mode, as described elsewhere in this specification.
  • the grinding circuit may include a pre-grinding step in which coarse inorganic particulate ground in a grinder vessel to a predetermined particle size distribution, after which fibrous material comprising cellulose is combined with the pre- ground inorganic particulate material and the grinding continued in the same or different grinding vessel until the desired level of microfibrillation has been obtained.
  • the suspension of material to be ground may be of a relatively high viscosity
  • a suitable dispersing agent may preferably be added to the suspension prior to grinding.
  • the dispersing agent may be, for example, a water soluble condensed phosphate, polysilicic acid or a salt thereof, or a poly electrolyte, for example a water soluble salt of a poly(acrylic acid) or of a poly(methacrylic acid) having a number average molecular weight not greater than 80,000.
  • the amount of the dispersing agent used would generally be in the range of from 0.1 to 2.0% by weight, based on the weight of the dry inorganic particulate solid material.
  • the suspension may suitably be ground at a temperature in the range of from 4°C. to 100°C.
  • the pH of the suspension of material to be ground may be about 7 or greater than about 7 (i.e., basic), for example, the pH of the suspension may be about 8, or about 9, or about 10, or about 11.
  • the pH of the suspension of material to be ground may be less than about 7 (i.e., acidic), for example, the pH of the suspension may be about 6, or about 5, or about 4, or about 3.
  • the pH of the suspension of material to be ground may be adjusted by addition of an appropriate amount of acid or base.
  • Suitable bases included alkali metal hydroxides, such as, for example NaOH. Other suitable bases are sodium carbonate and ammonia.
  • Suitable acids included inorganic acids, such as hydrochloric and sulphuric acid, or organic acids. An exemplary acid is orthophosphoric acid.
  • the amount of inorganic particulate material and cellulose pulp in the mixture to be co-ground may vary in a ratio of from about 99.5:0.5 to about 0.5:99.5, based on the dry weight of inorganic particulate material and the amount of dry fibre in the pulp, for example, a ratio of from about 99.5:0.5 to about 50:50 based on the dry weight of inorganic particulate material and the amount of dry fibre in the pulp.
  • the ratio of the amount of inorganic particulate material and dry fibre may be from about 99.5:0.5 to about 70:30.
  • the ratio of inorganic particulate material to dry fibre is about 80:20, or for example, about 85:15, or about 90:10, or about 91:9, or about 92:8, or about 93:7, or about 94:6, or about 95:5, or about 96:4, or about 97:3, or about 98:2, or about 99:1.
  • the weight ratio of inorganic particulate material to dry fibre is about 95:5.
  • the weight ratio of inorganic particulate material to dry fibre is about 90:10.
  • the weight ratio of inorganic particulate material to dry fibre is about 85:15.
  • the weight ratio of inorganic particulate material to dry fibre is about 80:20.
  • the total energy input in a typical grinding process to obtain the desired aqueous suspension composition may typically be between about 100 and 1500 kWht -1 based on the total dry weight of the inorganic particulate filler.
  • the total energy input may be less than about 1000 kWht -1 , for example, less than about 800 kWht -1 , less than about 600 kWht -1 , less than about 500 kWht -1 , less than about kWht -1 , less than about 300 kWht -1 , or less than about 200 kWht -1 .
  • the present inventors have surprisingly found that a cellulose pulp can be microfibrillated at relatively low energy input when it is co-ground in the presence of an inorganic particulate material.
  • the total energy input per tonne of dry fibre in the fibrous substrate comprising cellulose will be less than about 10,000 kWht -1 , for example, less than about 9000 kWht -1 , or less than about 8000 kWht -1 , or less than about 7000 kWht -1 , or less than about 6000 kWht -1 , or less than about 5000 kWht -1 , for example less than about 4000 kWht -1 , less than about 3000 kWht -1 , less than about 2000 kWht -1 , less than about 1500 kWht -1 , less than about 1200 kWht -1 , less than about 1000 kWht -1 , or less than about 800 kWht -1 .
  • the total energy input varies depending on the amount of dry fibre in the fibrous substrate being microfibrillated, and optionally the speed of grind and the duration of grind.
  • the grinding media comprises particles having an average diameter of about 3 mm and specific gravity of about 2.7.
  • the MFC is manufactured in accordance with the method described in WO-A-2010/131016, which comprises a step of microfibrillating a fibrous substrate comprising cellulose by grinding in the presence of a particulate grinding medium which is to be removed after the completion of grinding.
  • microfibrillating is meant a process in which microfibrils of cellulose are liberated or partially liberated as individual species or as small aggregates as compared to the fibres of the pre-microfibrillated pulp.
  • Typical cellulose fibres i.e., pre-microfibrillated pulp
  • Typical cellulose fibres suitable for use in papermaking include larger aggregates of hundreds or thousands of individual cellulose fibrils.
  • microfibrillating the cellulose particular characteristics and properties, including the characteristics and properties described herein, are imparted to the MFC and the compositions comprising the MFC.
  • the fibrous substrate comprising cellulose may be derived from recycled pulp or a papermill broke and/or industrial waste, or a paper streams rich in mineral fillers and cellulosic materials from a papermill.
  • the cellulose pulp may be beaten (for example in a Valley beater) and/or otherwise refined (for example, processing in a conical or plate refiner) to any predetermined freeness, reported in the art as Canadian standard freeness (CSF) in cm 3 .
  • CSF means a value for the freeness or drainage rate of pulp measured by the rate that a suspension of pulp may be drained, and this test is carried out according to the T 227 cm-09 TAPPI standard.
  • the cellulose pulp may have a Canadian standard freeness of about 10 cm 3 or greater prior to being microfibrillated.
  • the cellulose pulp may have a CSF of about 700 cm 3 or less, for example, equal to or less than about 650 cm 3 , or equal to or less than about 600 cm 3 , or equal to or less than about 550 cm 3 , or equal to or less than about 500 cm 3 , or equal to or less than about 450 cm 3 , or equal to or less than about 400 cm 3 , or equal to or less than about 350 cm 3 , or equal to or less than about 300 cm 3 , or equal to or less than about 250 cm 3 , or equal to or less than about 200 cm 3 , or equal to or less than about 150 cm 3 , or equal to or less than about 100 cm 3 , or equal to or less than about 50 cm 3 .
  • the cellulose pulp may have a CSF of about 20 to about 700.
  • the cellulose pulp may then be dewatered by methods well known in the art, for example, the pulp may be filtered through a screen in order to obtain a wet sheet comprising at least about 10% solids, for example at least about 15% solids, or at least about 20% solids, or at least about 30% solids, or at least about 40% solids or at least 50% solids.
  • the pulp may be utilized in an unrefined state, that is to say, without being beaten or dewatered, or otherwise refined.
  • the microfibrillated cellulose is prepared in accordance with a method comprising a step ofmicrofibrillating a fibrous substrate comprising cellulose in an aqueous environment by grinding in the presence of a grinding medium which is to be removed after the completion of grinding, wherein the grinding is performed in a tower mill or a screened grinder, and wherein the grinding is carried out in the absence of grindable inorganic particulate material.
  • a grindable inorganic particulate material is a material which would be ground in the presence of the grinding medium.
  • the particulate grinding medium may be of a natural or a synthetic material.
  • the grinding medium may, for example, comprise balls, beads or pellets of any hard mineral, ceramic or metallic material.
  • Such materials may include, for example, alumina, zirconia, zirconium silicate, aluminium silicate or the mullite-rich material which is produced by calcining kaolinitic clay at a temperature in the range of from about 1300°C to about 1800°C.
  • a Carbolite® grinding media is preferred.
  • particles of natural sand of a suitable particle size may be used.
  • the type of and particle size of grinding medium to be selected for use in the invention may be dependent on the properties, such as, e.g., the particle size of, and the chemical composition of, the feed suspension of material to be ground.
  • the particulate grinding medium comprises particles having an average diameter in the range of from about 0.5 mm to about 6 mm. In one embodiment, the particles have an average diameter of at least about 3 mm.
  • the grinding medium may comprise particles having a specific gravity of at least about 2.5.
  • the grinding medium may comprise particles have a specific gravity of at least about 3, or least about 4, or least about 5, or at least about 6.
  • the grinding medium may be present in an amount up to about 70% by volume of the charge.
  • the grinding media may be present in amount of at least about 10% by volume of the charge, for example, at least about 20 % by volume of the charge, or at least about 30% by volume of the charge, or at least about 40 % by volume of the charge, or at least about 50% by volume of the charge, or at least about 60 % by volume of the charge.
  • the fibrous substrate comprising cellulose may be microfibrillated to obtain microfibrillated cellulose having a d 50 ranging from about 5 to ⁇ m about 500 ⁇ m, as measured by laser light scattering.
  • the fibrous substrate comprising cellulose may be microfibrillated to obtain microfibrillated cellulose having a d 50 of equal to or less than about 400 ⁇ m, for example equal to or less than about 300 ⁇ m, or equal to or less than about 200 ⁇ m, or equal to or less than about 150 ⁇ m, or equal to or less than about 125 ⁇ m, or equal to or less than about 100 ⁇ m, or equal to or less than about 90 ⁇ m, or equal to or less than about 80 ⁇ m, or equal to or less than about 70 ⁇ m, or equal to or less than about 60 ⁇ m, or equal to or less than about 50 ⁇ m, or equal to or less than about 40 ⁇ m, or equal to or less than about 30 ⁇ m, or equal to or less less less
  • the fibrous substrate comprising cellulose may be microfibrillated to obtain microfibrillated cellulose having a modal fibre particle size ranging from about 0.1-500 ⁇ m.
  • the fibrous substrate comprising cellulose may be microfibrillated in the presence to obtain microfibrillated cellulose having a modal fibre particle size of at least about 0.5 ⁇ m, for example at least about 10 ⁇ m, or at least about 50 ⁇ m, or at least about 100 ⁇ m, or at least about 150 ⁇ m, or at least about 200 ⁇ m, or at least about 300 ⁇ m, or at least about 400 ⁇ m.
  • the fibrous substrate comprising cellulose may be microfibrillated to obtain microfibrillated cellulose having a fibre steepness equal to or greater than about 10, as measured by Malvern.
  • Fibre steepness i.e., the steepness of the particle size distribution of the fibres
  • the microfibrillated cellulose may have a fibre steepness equal to or less than about 100.
  • Tire microfibrillated cellulose may have a fibre steepness equal to or less than about 75, or equal to or less than about 50, or equal to or less than about 40, or equal to or less than about 30.
  • the microfibrillated cellulose may have a fibre steepness from about 20 to about 50, or from about 25 to about 40, or from about 25 to about 35, or from about 30 to about 40. In an embodiment, a preferred steepness range is about 20 to about 50.
  • the slurry is then added in 1 cm 3 aliquots to water in the sample preparation unit attached to the Mastersizer S (or Mastersizer Insitec or other comparable apparatus) until the optimum level of obscuration is displayed (normally 10 - 15%).
  • the light scattering analysis procedure is then carried out.
  • the instrument range selected was 300RF : 0.05-900, and the beam length set to 2.4 mm.
  • the refractive index for calcium carbonate 1.596
  • the particle size distribution is calculated from Mie theory and gives the output as a differential volume based distribution. The presence of two distinct peaks is interpreted as arising from the mineral (finer peak) and fibre (coarser peak).
  • the finer mineral peak is fitted to the measured data points and subtracted mathematically from the distribution to leave the fibre peak, which is converted to a cumulative distribution.
  • the fibre peak is subtracted mathematically from the original distribution to leave the mineral peak, which is also converted to a cumulative distribution. Both these cumulative curves may then be used to calculate the mean particle size (d5 o) and the steepness of the distribution (d30/d 70 x 100).
  • the differential curve may be used to find the modal particle size for both the mineral and fibre fractions
  • the grinding vessel is a tower mill.
  • the tower mill may comprise a quiescent zone above one or more grinding zones.
  • a quiescent zone is a region located towards the top of the interior of a tower mill in which minimal or no grinding takes place and comprises microfibrillated cellulose and inorganic particulate material.
  • the quiescent zone is a region in which particles of the grinding medium sediment down into the one or more grinding zones of the tower mill.
  • the tower mill may comprise a classifier above one or more grinding zones.
  • the classifier is top mounted and located adjacent to a quiescent zone.
  • the classifier may be a hydrocyclone.
  • the tower mill may comprise a screen above one or more grind zones.
  • a screen is located adjacent to a quiescent zone and/or a classifier.
  • the screen may be sized to separate grinding media from the product aqueous suspension comprising microfibrillated cellulose and to enhance grinding media sedimentation.
  • the grinding is performed under plug flow conditions.
  • plug flow conditions the flow through the tower is such that there is limited mixing of the grinding materials through the tower. This means that at different points along the length of the tower mill the viscosity of the aqueous environment will vary as the fineness of the microfibrillated cellulose increases.
  • the grinding region in the tower mill can be considered to comprise one or more grinding zones which have a characteristic viscosity. A skilled person in the art will understand that there is no sharp boundary between adjacent grinding zones with respect to viscosity.
  • water is added at the top of the mill proximate to the quiescent zone or the classifier or the screen above one or more grinding zones to reduce the viscosity of the aqueous suspension comprising microfibrillated cellulose at those zones in the mill.
  • the limited mixing through the tower allows for processing at higher solids lower down the lower and dilute at the top with limited backfl ow of the dilution water back down the tower into the one or more grinding zones.
  • Any suitable amount of water which is effective to dilute the viscosity' of the product aqueous suspension comprising microfibrillated cellulose may be added.
  • the water may be added continuously during the grinding process, or at regular intervals, or at irregular intervals.
  • water may be added to one or more grinding zones via one or more water injection points positioned along the length of the tower mill, the or each water injection point being located at a position which corresponds to the one or more grinding zones.
  • the ability to add water at various points along the tower allows for further adjustment of the grinding conditions at any or all positions along the mill.
  • the tower mill may comprise a vertical impeller shaft equipped with a series of impeller rotor disks throughout its length. The action of the impeller rotor disks creates a series of discrete grinding zones throughout the mill.
  • the grinding is performed in a screened grinder, preferably a stirred media detritor.
  • the screened grinder may comprise one or more screen(s) having a nominal aperture size of at least about 250 ⁇ m, for example, the one or more screens may have a nominal aperture size of at least about 300 ⁇ m, or at least about 350 ⁇ m, or at least about 400 ⁇ m, or at least about 450 ⁇ m, or at least about 500 ⁇ m, or at least about 550 ⁇ m, or at least about 600 ⁇ m, or at least about 650 ⁇ m, or at least about 700 ⁇ m, or at least about 750 ⁇ m, or at least about 800 ⁇ m, or at least about 850 ⁇ m, or at or least about 900 ⁇ m, or at least about 1000 ⁇ m, or at least about 1 ,250 ⁇ m, or at least about 1,500 ⁇ m.
  • the grinding is performed in the presence of a grinding medium.
  • the grinding medium is a coarse media comprising particles having an average diameter in the range of from about 1 mm to about 6 mm, for example about 2 mm, or about 3 mm, or about 4 mm, or about 5 mm.
  • the grinding media has a specific gravity of at least about
  • the grinding medium may be in an amount up to about 70% by volume of the charge.
  • the grinding media may be present in amount of at least about 10% by volume of the charge, for example, at least about 20 % by volume of the charge, or at least about 30% by volume of the charge, or at least about 40 % by volume of the charge, or at least about 50% by volume of the charge, or at least about 60 % by volume of the charge.
  • the grinding medium is present in amount of about 50% by volume of the charge.
  • 'charge' is meant the composition which is the feed fed to the grinder vessel.
  • the charge includes water, grinding media, the fibrous substrate comprising cellulose and any other optional additives (other than as described herein).
  • the use of a relatively coarse and/or dense media has the advantage of improved (i.e,, faster) sediment rates and reduced media carry over through the quiescent zone and/or classifier and/or screen(s).
  • a further advantage in using relatively coarse screens is that a relatively coarse or dense grinding media can be used in the microfibrillating step.
  • relatively coarse screens i.e., having a nominal aperture of least about 250 urn
  • a relatively high solids product to be processed and removed from the grinder, which allows a relatively high solids feed (comprising fibrous substrate comprising cellulose and inorganic particulate material) to be processed in an economically viable process.
  • a feed having a high initial solids content is desirable in terms of energy sufficiency.
  • product produced (at a given energy) at lower solids has a coarser particle size distribution.
  • the fibrous substrate comprising cellulose is present in the aqueous environment at an initial solids content of at least about 1 wt. %.
  • the fibrous substrate comprising cellulose may be present in the aqueous environment at an initial solids content of at least about 2 wt. %, for example at least about 3 wt. %, or at least about at least 4 wt. %.
  • the initial solids content will be no more than about 10 wt. %.
  • the grinding is performed in a cascade of grinding vessels, one or more of which may comprise one or more grinding zones.
  • the fibrous substrate comprising cellulose may be ground in a cascade of two or more grinding vessels, for example, a cascade of three or more grinding vessels, or a cascade of four or more grinding vessels, or a cascade of five or more grinding vessels, or a cascade of six or more grinding vessels, or a cascade of seven or more grinding vessels, or a cascade of eight or more grinding vessel s, or a cascade of nine or more grinding vessel s in series, or a cascade comprising up to ten grinding vessels.
  • the cascade of grinding vessels may be operatively inked in series or parallel or a combination of series and parallel.
  • the output from and/or the input to one or more of the grinding vessels in the cascade may be subjected to one or more screening steps and/or one or more classification steps.
  • the total energy expended in a microfibrillation process may be apportioned equally across each of the grinding vessels in the cascade. Alternatively, the energy input may vary between some or all of the grinding vessels in the cascade.
  • the energy expended per vessel may vary between vessels in the cascade depending on the amount of fibrous substrate being microfibrillated in each vessel, and optionally the speed of grind in each vessel, the duration of grind in each vessel and the type of grinding media in each vessel.
  • the grinding conditions may be varied in each vessel in the cascade in order to control the particle size distribution of the microfibrillated cellulose.
  • the grinding is performed in a closed circuit. In another embodiment, the grinding is performed in an open circuit.
  • a suitable dispersing agent may preferably be added to the suspension prior to grinding.
  • the dispersing agent may be, for example, a water soluble condensed phosphate, polysilicic acid or a salt thereof, or a poly electrolyte, for example a water soluble salt of a poly(acrylic acid) or of a poly(methacrylic acid) having a number average molecular weight not greater than 80,000.
  • the amount of the dispersing agent used would generally be in the range of from 0.1 to 2.0% by weight, based on the weight of the dry' inorganic particulate solid material.
  • the suspension may suitably be ground at a temperature in the range of from 4°C to 100°C.
  • Other additives which may be included during the microfibrillation step include: carboxy methylcellulose, amphoteric carboxymethylcellulose, oxidising agents, 2, 2,6,6- Tetramethylpiperidine-1-oxyl (TEMPO), TEMPO derivatives, and wood degrading enzymes.
  • the pH of the suspension of material to be ground may be about 7 or greater than about 7 (i.e., basic), for example, the pH of the suspension may be about 8, or about 9, or about 10, or about 11.
  • the pH of the suspension of material to be ground may be less than about 7 (i.e., acidic), for example, the pH of the suspension may be about 6, or about 5, or about 4, or about 3.
  • the pH of the suspension of material to be ground may be adjusted by addition of an appropriate amount of acid or base.
  • Suitable bases included alkali metal hydroxides, such as, for example NaOH. Other suitable bases are sodium carbonate and ammonia.
  • Suitable acids included inorganic acids, such as hydrochloric and sulphuric acid, or organic acids. An exemplary acid is orthophosphoric acid.
  • the total energy input in a typical grinding process to obtain the desired aqueous suspension composition may typically be between about 100 and 1500 kWh 4 based on the total dry weight of the inorganic particulate filler.
  • the total energy input may be less than about 1000 kWht -1 , for example, less than about 800 kWht -1 less than about 600 kWht -1 A less than about 500 kWht -1 , less than about 400 kWht -1 less than about 300 kWht -1 A or less than about 200 kWht -1
  • the present inventors have surprisingly found that a cellulose pulp can be microfibrillated at relatively low energy input when it is co-ground in the presence of an inorganic particulate material.
  • the total energy input per tonne of dry fibre in the fibrous substrate comprising cellulose will be less than about 10,000 kWht -1 , for example, less than about 9000 kWht -1 or less than about 8000 kWht -1 , or less than about
  • the total energy input varies depending on the amount of dry fibre in the fibrous substrate being microfibrillated, and optionally the speed of grind and the duration of grind.
  • MFC may be produced in a continuous or batch mode.
  • MFC is an aqueous suspension mixture of microfibrillated cellulose and inorganic particulate material.
  • MFC is prepared by co-grinding a low solids aqueous suspension of cellulose wood pulp in the presence of inorganic particulate material particles in a wet vertically stirred media mill.
  • the mineral particles act as grinding aids and facilitate the cost-effective fibrillation of pulp fibers to microfibrils in a process analogous to pulp refining.
  • the inorganic particulate material used is a standard paper filler, often calcium carbonate or kaolin. Most processes will use kaolin, ground calcium carbonate or precipitated calcium carbonate. The inorganic particulate material will be in aqueous slurry form.
  • the cellulose used is typically unrefined Kraft or sulphite pulp from a paper mill’s pulp source (>99% cellulose) or recycled pulp from paper and board recycling activities.
  • the pulp is received from the paper mill as an aqueous slurry usually at approximately 4-5 wt.% solids.
  • the water used will be from the mill’s process streams or in some cases council (city) water.
  • the ceramic grinding media are typically 3mm diameter beads made from calcined kaolin. In some cases when recycled pulp is used, the pulp will already contain some inorganic particulate material.
  • the same process is operated batchwise.
  • the ingredients are added at the start of a batch, then the grinders are run for an allocated time such that 1500-5000 kWhr/dry tonne of MFC is applied and then at the end of the batch further water is added and the product is discharged before the process being repeated.
  • the above MFC product which results from the grinding and screening process contains agglomerates which reduce performance and can cause blockages if subjected to very fine screening. These agglomerates may be reduced by the use of a homogeniser.
  • some of the water associated with the MFC product is removed to lower transportation costs. This is achieved by use of dewatering via a belt press and/or drying using a hot air dryer or by other means known in the art.
  • dewatered and dried products are prepared, a biocide is sometimes added to increase shelf life and protect the product from decomposition.
  • the biocide is mixed into the MFC, for example, using a plough shear mixer.
  • the dewatered and partially dried products are usually shipped in bulk bags.
  • the biocides used are DBNPA (2,2-dibromo-3-nitrilopropionamide), and CMIT/ MIT (5-chloro-2-methyl-2H-isothiazol-3-one/2-methyl-2Hi sothiazol-3-one (CMIT/MIT) or for the partially dried product and OIT (2-octyl-2H-isothiazol-3-one).
  • the continuous production process is a pass- through process with cellulose, inorganic particulate material and water being sourced from the mill and returned to the mill after processing.
  • Parameters that may be used to control production are product d 50 , as measured by laser light scattering and either viscosity or tensile properties, for example, the FLT tensile index described elsewhere in this specification.
  • Some types of filler such as calcined clays and scalenohedral and aragonite precipitated calcium carbonates (PCC), consist of aggregates of particles with open porous structures (i.e. , these are examples of microporous inorganic particulate materials).
  • Calcined clays are described in U.S. Patent No. 3,586,523, which is hereby incorporated in by reference in its entirety.
  • Such calcined kaolin clays are substantially anhydrous, amorphous aluminum silicates which are obtained by calcining a specific type of kaolin clay, for example, hard sedimentary kaolin clay.
  • PCC Precipitated calcium carbonate
  • the PCC is produced in a unique clustered form having a substantial proportion of particles having a prismatic morphology.
  • calcite may have either prismatic, scalenohedral or rhombohedral crystal forms.
  • microporous inorganic particulate materials include chemically aggregated filler materials. Examples of such chemically aggregated fillers may be found in U.S. Patent No. 4,072,537, which is incorporated herein in its entirety.
  • Such microporous inorganic particulate materials comprise a composite silicate material comprising a clay component and a metal silicate component.
  • the clay component is typically kaolin clay or kaolinite and the metal silicate material is typically a water soluble alkali metal silicate, for example sodium silicate.
  • preferred method for preparing the composite pigment comprises the steps of, (a) forming an aqueous suspension of a clay pigment, (b) blending into the clay slurry a quantity of a salt such as calcium chloride, (c) metering into the slurry of clay and salt at high shear a quantity of a silicate component such as sodium silicate, and, optionally, (d) adjusting the pH of the slurry with the addition of alum to a pH no lower than pH 4, before (e) filtering and washing the precipitated product to remove any soluble salts.
  • a salt such as calcium chloride
  • a silicate component such as sodium silicate
  • Such microporous composite silicate material is either used directly in a papermaking process or dried and used later. Additional microporous inorganic particulate material include materials such as diatomaceous earth and expanded perlite.
  • microporous inorganic particulate materials comprise discrete particles or aggregates of particles with outer dimensions of several microns, which contain void spaces within the volume defined by the outer dimensions and which are several time smaller than said outer dimensions.
  • microporous inorganic particulate materials When used in paper, these microporous inorganic particulate materials have a much larger effect per unit mass of filler on the spacing of the fibres than solid filler particles. This makes them more detrimental to paper strength, but generates increased light scattering which is beneficial to optical properties.
  • the effective density of the microporous inorganic particulate materials is also lower than that of solid fillers, and the combination of these effects can lead to an increase in sheet bulk and thickness as fibre is substituted for filler.
  • the microporous inorganic particulate material composite has a median particle size (d 50 ) less than about 10 ⁇ m and greater than about 3 ⁇ m, or from about 3 ⁇ m to about 6 ⁇ m.
  • the microporous inorganic particulate material composite, the d 50 of the microporous mineral composites is substantially larger compared to the d50 of an unagglomerated mixture of the same constituents used to form the microporous mineral composites.
  • microporous inorganic particulate material and microfibrillated cellulose composite can be provided in the form of a powder, although they are preferably added in the form of a suspension, such as an aqueous suspension.
  • a suspension such as an aqueous suspension.
  • the solids content of the suspension is not critical as long as it is a pumpable liquid.
  • a Sedigraph 5100 device from the company Micromeritics, USA may be used. The measurement may be performed in an aqueous solution of 0.1 wt-% Na 4 P 2 O 7 . The samples may be dispersed using a high-speed stirrer and ultrasound. For the determination of the volume median particle size for particles having a d 50 ⁇ 500 nm, a Malvern Mastersizer from the company Malvern, UK may be used. The measurement may be performed in an aqueous solution of 0.1 wt% Na 4 P 2 O 7 The samples may be dispersed using a high-speed stirrer and ultrasound.
  • the Sedigraph 5100 provides measurements and a plot of the cumulative percentage by weight of particles having a size, referred to in the art as the “equivalent spherical diameter,” or “esd.”
  • the particle size characteristics of microporous mineral composites may be measured by a Malvern Mastersizer or Microtrac laser particle size distribution analyzer utilizing the suppliers instructions.
  • the ratio of the first inorganic particulate material to the second inorganic particulate material may range from about 10:90 to about 90:10 by weight, for example, from about 20:80 to about 80:20 by weight, about 25:75 to 75:25 by weight, about 40:60 to about 60:40 by weight, or about 50:50 by weight.
  • a binder may be used to facilitate agglomeration of the second microporous inorganic particulate material to the first microporous inorganic particulate material, and/or to the microfibrillated cellulose.
  • the binder may be an alkali silica binder.
  • the binder may include at least one of an inorganic binder or an organic binder.
  • the binder may also improve the adhesion and mechanical strength between components of the microporous mineral composites.
  • the binder may include an inorganic binder, such as an alkali metal silicate.
  • a blend of inorganic particulate materials may be contacted with a binder solution by mixing the binder solution with the blend of inorganic particulate materials.
  • the mixing may include agitation.
  • the blend of the first and second microporous inorganic particulate materials and the binder solution is mixed sufficiently to at least substantially uniformly distribute the binder solution among the agglomeration points of contact of the first and/or first and second inorganic particulate materials.
  • a blend of the first and second microporous inorganic particulate materials and the binder solution may be mixed with sufficient agitation to at least substantially uniformly distribute the binder solution among the agglomeration points of contact of the blend of first and second inorganic particulate materials without damaging the structure of the first or second inorganic particulate materials.
  • the contacting may include low-shear mixing.
  • mixing may occur at about room temperature (i.e., from about 20° C. to about 23° C ). In other embodiments, mixing may occur at a temperature ranging from about 20° C. to about 50° C. In further embodiments, mixing may occur at a temperature ranging from about 30° C. to about 45° C. In still other embodiments, mixing may occur at a temperature of from about 35° C. to about 40° C. [00283] In an embodiment of the foregoing aspects and embodiments of the present disclosure, contacting may include spraying the blend of first and/or first and second microporous inorganic particulate materials with a binder solution.
  • the spraying may be intermittent. In other embodiments, the spraying may be continuous. In further embodiments, spraying includes mixing the blend of the first and second microporous inorganic particulate materials while spraying with a binder solution, for example, to expose different agglomeration points of contacts to the spray. In some embodiments, such mixing may be intermittent. In other embodiments, such mixing may be continuous.
  • the binder may be present in the binder solution in an amount less than about 40% by weight, relative to the weight of the binder solution. In some embodiments, the binder may range from about 1% to about 10% by weight. In further embodiments, the binder may range from about 1% to about 5% by weight.
  • the binder facilitates agglomeration of the second microporous inorganic particulate material to the first microporous inorganic particulate material.
  • the second microporous inorganic particulate material has a smaller diameter than the first microporous inorganic particulate material.
  • the microporous inorganic particulate material and microfibrillated cellulose composite may be associated with dispersing agents such as those selected from the group comprising homopolymers or copolymers of poly carboxylic acids and/or their salts or derivatives such as esters based on, e.g., acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid; e.g. acryl amide or acrylic esters such as methylmethacrylate, or mixtures thereof; alkali polyphosphates, phosphonic-, citric- and tartaric acids and the salts or esters thereof; or mixtures thereof.
  • dispersing agents such as those selected from the group comprising homopolymers or copolymers of poly carboxylic acids and/or their salts or derivatives such as esters based on, e.g., acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid; e.g. acryl amide or acrylic esters such
  • the combination of microfibrillated cellulose and microporous inorganic particulate material can be carried out by adding the microporous inorganic particulate material to the MFC in one or several steps.
  • the combination of microporous inorganic particulate material can be added to the MFC in one or several steps.
  • the microfibrillated cellulose and microporous inorganic particulate material can be added entirely or in portions after the fibrillating step.
  • the weight ratio of MFC to microporous inorganic particulate material on a dry weight basis is from 1:33 to 10:1, more preferably 1:10 to 7:1, even more preferably 1:5 to 5:1, typically 1:3 to 3:1, especially 1:2 to 2:1 and most preferably 1:1.5 to 1.5:1, e.g. 1:1.
  • the total content of microporous inorganic particulate material is present in an amount of from 10 wt-% to 95 wt-%, preferably from 15 wt-% to 90 wt-%, more preferably from 20 to 75 wt-%, even more preferably from 25 wt-% to 67 wt-%, especially from 33 to 50 wt-% on a dry weight basis of the composite material.
  • Precipitated calcium carbonate may be used as the source of particulate calcium carbonate in the present invention, and may be produced by any of the known methods available in the art.
  • TAPPI Monograph Series No 30, 'Paper Coating Pigments", pages 34-35 describes the three main commercial processes for preparing precipitated calcium carbonate which is suitable for use in preparing products for use in the paper industry, but may also be used in the practice of the present invention.
  • a calcium carbonate feed material such as limestone
  • the quicklime is then slaked in water to yield calcium hydroxide or milk of lime.
  • the milk of lime is directly carbonated with carbon dioxide gas.
  • This process has the advantage that no by-product is formed, and it is relatively easy to control the properties and purity of the calcium carbonate product.
  • the milk of lime is contacted with soda ash to produce, by double decomposition, a precipitate of calcium carbonate and a solution of sodium hydroxide.
  • the sodium hydroxide may be substantially completely separated from the calcium carbonate if this process is used commercially.
  • the milk of lime is first contacted with ammonium chloride to give a calcium chloride solution and ammonia gas.
  • the calcium chloride solution is then contacted with soda ash to produce by double decomposition precipitated calcium carbonate and a solution of sodium chloride.
  • the crystals can be produced in a variety of different shapes and sizes, depending on the specific reaction process that is used.
  • the three main forms of PCC crystals are aragonite, rhombohedral and scalenohedral, all of which are suitable for use in the present invention, including mixtures thereof.
  • the PCC may be formed during the process of producing microfibrillated cellulose.
  • wet grinding of calcium carbonate involves the formation of an aqueous suspension of the calcium carbonate which may then be ground, optionally in the presence of a suitable dispersing agent.
  • a suitable dispersing agent for more information regarding the wet grinding of calcium carbonate.
  • other minerals may be included, for example, one or more of kaolin, calcined kaolin, wollastonite, bauxite, talc or mica, could also be present.
  • Example 1 Use of Coarse Scalenohedral PCC and FiberLean MFC for Maintaining Bulk and Stiffness When Increasing the Filler Content.
  • the furnish was prepared from 70% hardwood (Eucalyptus, ex. UPM convinced) and 30% softwood (BOTNIA RMA90 Pine, ex. Metsa) co-refined to 450 CSF (28.5 °S.R.).
  • the study design targeted 80 g/m 2 UWF paper with a starting filler content of 19% arising from GCC (60% ⁇ 2 ⁇ m) addition.
  • the MFC product used was 50% POP MFCslurry comprised of NBSK Botnia RMA90 and GCC mineral (60% ⁇ 2 ⁇ m).
  • a retention aid was added at 0.12% based on dry sheet weight.
  • the retention aid was cationic polyacrylamide (Percol 292NS, ex. BASF).
  • the white water was re-circulated during sheet-forming (in that the white- water from each sheet was used to form the subsequent sheets in the trial point series to ensure retention equilibrium was reached with each formulation). Further details on the sheet forming methodology are shown in the Appendix
  • Example 1 Summary of results when using PCC with MFC to restore Bulk and Stiffness when increasing the filler content.
  • N.B. The furnish (70% Eucalyptus / 30% Pine) represent 100% of the pulp furnish, which was then replaced in the proportions shown by filler and MFC in terms of overall mass per sheet.
  • MFC addition improves mechanical properties, Opacity, Porosity and Roughness. In exchange for these improvements, several possibilities are presented: [00196] Furnish adjustments: Reduced long fibre or increased CTMP contents (adjusting short fibre content proportionately).
  • Thickness (Caliper for Bulk calculations): T411
  • Handsheets were made from a blend of bleached Kraft pulps, comprising 70% hardwood (Eucalyptus, UPM convinced) and 30% softwood (Pine, Metsa Botnia RMA90). These were co-refined in a laboratory Valley beater to a freeness of 450ml CSF (28.5 °S.R.). Each sheet was made to a target substance of 80gsm, with target filler contents of either 20% or 30% by weight.
  • MFC was produced by co-grinding Botnia RMA90 bleached Kraft Pine pulp with a standard filler grade ground calcium carbonate (GCC, Intracarb 60, 60% ⁇ 2 ⁇ m by weight, d50 1.4 ⁇ m, Imerys), at a 50/50 ratio by weight, using a stirred media detritor mill.
  • GCC standard filler grade ground calcium carbonate
  • Table 3 below and Fig. 1 show the relative change in key properties of each composition compared with the reference sheets filled with 20% GCC.
  • Increase of filler content to 30% with GCC causes a significant loss of mechanical properties, which are partially restored by the addition of 3% MFC.
  • Switching from GCC to the coarse PCC at 20% loading causes a significant increase in bulk and stiffness at the expense of tensile index and Scott Bond, and further increase to 30% PCC reduces the latter to below the level of the GCC, whilst also reducing stiffness to below the reference.
  • the addition of 4% MFC restores the stiffness to within 5% of its original value, whilst providing improvements in bulk, Scott Bond and light scattering over the reference.
  • Example 3 Handsheets were made from a blend of 95% bleached Eucalyptus Kraft pulp and 5% bleached chemi-thermomechanical pulp (BCTMP). The Kraft pulp was refined in a laboratory Valley beater to a freeness of 330ml CSF (37.5 °S.R.). Each sheet was made to a target substance of 75gsm, with target filler contents of either 25% or 35% by weight.
  • BCTMP bleached Eucalyptus Kraft pulp
  • BCTMP bleached chemi-thermomechanical pulp
  • MFC was produced by co-grinding bleached Eucalyptus Kraft pulp with a standard filler grade ground calcium carbonate (GCC, Hydrocarb 60, 60% ⁇ 2 ⁇ m by weight, d50 1.4 ⁇ m, Omya), at a 50/50 ratio by weight, using a stirred media detritor mill.
  • GCC Standard filler grade ground calcium carbonate
  • the reference sheet contained 25% GCC.
  • 2% MFC was added, and a blend of GCC (Hydrocarb 60) and scalenohedral PCC (3.1 ⁇ m d50, obtained from a satellite PCC plant at a paper mill) was added to the furnish for each sheet so that its total filler content, including the filler added with the co-ground MFC, would be 35%, and the proportion of PCC filler in the blend would be a fixed value between 0 and 100%.
  • Paper properties of the formed handsheets are shown in 4 below.
  • Handsheets were made from a blend of bleached Kraft pulps, comprising 70% eucalyptus and 30% pine. These were co-refined in a laboratory Valley beater to a freeness of 350ml CSF (36 °S.R.). Each sheet was made to a target substance of 80gsm, with target filler contents ranging between 16% and 35% by weight.

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  • Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
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  • Life Sciences & Earth Sciences (AREA)
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Abstract

L'invention concerne un procédé de fabrication d'une composition de charge comprenant de la cellulose microfibrillée et un ou plusieurs matériaux particulaires inorganiques microporeux et des procédés de fabrication de compositions de fabrication de papier et de produits de papier comprenant de la cellulose microfibrillée et un ou plusieurs matériaux particulaires inorganiques microporeux.
EP21790548.8A 2020-09-11 2021-09-03 Compositions de charge comprenant de la cellulose microfibrillée et des composites de matériaux particulaires inorganiques microporeux pour application de papier et de carton présentant des propriétés mécaniques améliorées Pending EP4185748A1 (fr)

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PCT/IB2021/000613 WO2022053869A1 (fr) 2020-09-11 2021-09-03 Compositions de charge comprenant de la cellulose microfibrillée et des composites de matériaux particulaires inorganiques microporeux pour application de papier et de carton présentant des propriétés mécaniques améliorées

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JP (1) JP2023544488A (fr)
KR (1) KR20230066009A (fr)
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AU (1) AU2021339980A1 (fr)
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Publication number Priority date Publication date Assignee Title
US3586523A (en) 1968-01-15 1971-06-22 Engelhard Min & Chem Calcined kaolin clay pigment
US4072537A (en) 1976-03-19 1978-02-07 Westvaco Corporation Composite silicate pigment
EP0633864A1 (fr) 1992-04-03 1995-01-18 Minerals Technologies, Inc. Particules agglomerees de carbonate de calcium precipite
GB2275876B (en) 1993-03-12 1996-07-17 Ecc Int Ltd Grinding alkaline earth metal pigments
FI20085760L (fi) * 2008-08-04 2010-03-17 Teknillinen Korkeakoulu Muunnettu komposiittituote ja menetelmä sen valmistamiseksi
DK2808440T3 (da) * 2009-03-30 2019-09-30 Fiberlean Tech Ltd Fremgangsmåde til fremstilling af nanofibrillære cellulosesuspensioner
GB0908401D0 (en) 2009-05-15 2009-06-24 Imerys Minerals Ltd Paper filler composition
JP6513037B2 (ja) * 2013-03-15 2019-05-15 ファイバーリーン テクノロジーズ リミテッド マイクロフィブリル化セルロースを処理する方法
EP3362508B1 (fr) * 2015-10-14 2019-06-26 FiberLean Technologies Limited Matériau formable en feuille 3d
CA3059535A1 (fr) * 2017-04-21 2018-10-25 Fiberlean Technologies Limited Cellulose microfibrillee a proprietes ameliorees et ses procedes de fabrication
SE543549C2 (en) * 2018-03-02 2021-03-23 Stora Enso Oyj Method for manufacturing a composition comprising microfibrillated cellulose

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AU2021339980A1 (en) 2023-03-02
WO2022053869A1 (fr) 2022-03-17
JP2023544488A (ja) 2023-10-24
BR112023004460A2 (pt) 2023-05-09
CA3189813A1 (fr) 2022-03-17
CN116157571A (zh) 2023-05-23
KR20230066009A (ko) 2023-05-12

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