CN117836484A

CN117836484A - Movable dispersion system and method for resuspension of dried microfibrillated cellulose

Info

Publication number: CN117836484A
Application number: CN202280057534.0A
Authority: CN
Inventors: P·塔罕丹; M·温德班克; D·R·斯库斯
Original assignee: Fibrin Technology Co ltd
Current assignee: Fibrin Technology Co ltd
Priority date: 2021-09-08
Filing date: 2022-09-07
Publication date: 2024-04-05
Also published as: CA3228405A1; AU2022342781A1; KR20240051941A; WO2023037167A1; CA3228404A1; WO2023037161A1

Abstract

An associated method for redispersing a substantially dry or partially dry and optionally powdered composition comprising microfibrillated cellulose and optionally one or more inorganic particulate materials in a liquid medium to form a transportable system (1) of liquid composition and producing a substantially homogeneous redispersed suspension of microfibrillated cellulose and optionally one or more inorganic particulate materials; wherein the microfibrillated cellulose has a tensile index comparable to that of a comparable never-dried suspension of microfibrillated cellulose and optionally one or more inorganic particulate materials.

Description

Movable dispersion system and method for resuspension of dried microfibrillated cellulose

Technical Field

The present invention relates generally to transportable equipment systems and associated methods for redispersing a previously substantially dry or partially dry and optionally powdered composition comprising microfibrillated cellulose and optionally one or more inorganic particulate materials.

Background

Transportable equipment systems of the type described herein require reduced energy input to redisperse a previously substantially dry or partially dry and optionally powdered composition comprising microfibrillated cellulose and optionally one or more inorganic particulate materials into a substantially uniform suspension for end use applications. The described transportable equipment system minimizes or avoids agglomeration and/or keratinization typically associated with redispersion of microfibrillated cellulose. The arming system and associated method also restore optimal tensile properties, including tensile strength and tensile index, of the redispersed microfibrillated cellulose in various end use applications of such redispersion compositions utilizing the microfibrillated cellulose and optionally one or more inorganic particulate material compositions. The described arming system also addresses the need for a transportable mobile arming system that can be installed at a remote end user location.

The present invention also relates generally to a method of improving the redispersibility of a dried and powdered composition comprising microfibrillated cellulose and optionally one or more inorganic particulate materials. The described method comprises preparing a slurry comprising a composition of previously substantially dried or partially dried and optionally powdered fibrillated cellulose and optionally one or more inorganic particulate materials, wherein the slurry of microfibrillated cellulose and one or more inorganic particulate materials can be redispersed in a single pass (single pass) with reduced energy input required to redisperse the microfibrillated cellulose and optionally one or more inorganic particulate material compositions. The described methods minimize or eliminate agglomeration and/or keratinization of microfibrillated cellulose upon redispersion. The described method also restores the tensile properties, including tensile strength and tensile index properties, of the redispersed microfibrillated cellulose.

Microfibrillated cellulose and inorganic particulate materials such as alkaline earth metal carbonates (e.g., calcium carbonate) or kaolin are widely used in a variety of applications. These applications include the production of compositions containing microfibrillated cellulose and inorganic particulate material. For example, according to U.S. patent nos. 8,231,764, 9,127,405 and 10,100,464, which are incorporated herein by reference in their entirety, these compositions can be used as fillers in papermaking and/or paper coating. In paper and coated paper products, such fillers are typically added to replace a portion of the paper and/or other more expensive components of the coated paper product. Fillers may also be added in order to modify the physical, mechanical and/or optical requirements of the paper and/or coated paper products in the manner described, for example, in U.S. patent No. 10,253,457, which is incorporated herein by reference in its entirety. Obviously, the greater the amount of filler that can be included, the greater the potential for cost savings. However, the amount of filler added and the associated cost savings must be balanced against the physical, mechanical and optical requirements of the final or coated paper product. Thus, there remains a need to develop improved fillers for paper and paper coating that can be used at high loading levels without negatively affecting the physical, mechanical and/or optical requirements of such paper and/or coated paper products. There is also a need to develop processes for economically preparing such fillers.

In recent years, microfibrillated cellulose and compositions comprising microfibrillated cellulose and one or more inorganic particulate materials have been demonstrated to have a variety of useful properties, including enhancing the mechanical, physical and/or optical properties of a variety of end use products such as paper, paperboard, polymeric articles, coatings, and the like.

Microfibrillated cellulose compositions, typically prepared in aqueous form, are often dried for transportation in order to reduce the total weight of the composition and the associated transportation costs. The end user will then typically redisperse the microfibrillated cellulose prior to use in the intended end use application. An exemplary process for dewatering and drying a composition comprising microfibrillated cellulose and one or more inorganic particulate materials is described in U.S. patent No. 11,001,644, which is incorporated herein in its entirety. However, after drying and redispersion, some or all of the advantageous properties of the microfibrillated cellulose may be reduced or lost due to reasons including agglomeration and/or keratinization of the microfibrillated cellulose. Accordingly, there is a continuing need to improve the properties of microfibrillated cellulose after drying and redispersion.

Disclosure of Invention

The present invention seeks to solve the following problems: the dehydrated and optionally powdered substantially dry or partially dry composition comprising microfibrillated cellulose and optionally one or more inorganic particulate matter compositions is redispersed in a dispersion, optionally in the presence of additives other than inorganic particulate material and/or in the presence of a combination of inorganic particulate materials, while avoiding the well known agglomeration and/or keratinization problems. The combination of additives and/or inorganic particulate materials may, for example, enhance the mechanical and/or physical properties of the redispersed microfibrillated cellulose. The invention also relates to a composition comprising the redispersed microfibrillated cellulose and to the use of the redispersed microfibrillated cellulose in an article, product or composition.

The present invention seeks to provide paper and/or coated paper products with alternative and/or improved fillers that can be incorporated into the paper and/or coated paper products at relatively high loading levels while maintaining or even improving the physical, mechanical and/or optical properties of the paper and/or coated paper products.

The present invention also seeks to provide an economical method and corresponding portable manufacturing system for redispersing a composition comprising microfibrillated cellulose and optionally one or more inorganic particulate materials, to prepare such fillers comprising this ingredient for various end use applications, as described more fully herein. Such portable systems allow for the construction of systems for redispersing substantially dry or partially dry compositions comprising microfibrillated cellulose and optionally one or more inorganic particulate materials at locations near end use manufacturing sites (e.g., paper making and/or paper coating sites).

A solution to this problem is a transportable system for redispersing a previously substantially dry or partially dry and optionally powdered composition comprising microfibrillated cellulose and one or more inorganic particulate materials, and an associated method for redispersing a previously substantially dry or partially dry and optionally powdered composition comprising microfibrillated cellulose and optionally one or more inorganic particulate materials, as described in detail in the present specification.

A transportable redispersion system of the type described comprises: a mixing apparatus comprising a shear head impeller to partially deagglomerate microfibrillated cellulose and optionally one or more inorganic particulate materials to form a flowable slurry (i.e., a liquid suspension); the first stage high shear rotor-stator device (e.g.,a mill, colloid mill, ultra-fine grinding apparatus, or refiner), wherein the flowable slurry of microfibrillated cellulose and optionally one or more inorganic particulate materials is subjected to further high shear mixing to form a substantially uniform suspension of microfibrillated cellulose and optionally one or more inorganic particulate materials; optionally, a hydrocyclone for separating a substantially homogeneous suspension of microfibrillated cellulose and optionally one or more inorganic particulate materials into a sheared fine particle stream and an under-sheared coarse particle stream, the hydrocyclone comprising a recirculation loop for returning the under-sheared coarse particle stream to the mixing device for further moderate shear mixing and flowing the fine particle stream to a second stage high shear device (e.g., a rotor-rotor device, a second high shear rotor-stator device, a colloid mill, an ultra-fine grinding device or a refiner) for subjecting the substantially homogeneous suspension to additional high shear processing to produce microfibrillated cellulose and optionally one or more of A uniform redispersed suspension of a plurality of inorganic particulate materials; wherein the tensile properties of the microfibrillated cellulose are comparable to those of a comparable never-dried suspension of microfibrillated cellulose and optionally one or more inorganic particulate materials; and collecting the redispersed suspension of microfibrillated cellulose and optionally one or more inorganic particulate materials in a suitable containment vessel for further end use applications.

The rotor-rotor high shear apparatus comprises a counter-rotating ring for subjecting the fine particle stream to a high shear process to produce a substantially uniform or homogeneous redispersed suspension of microfibrillated cellulose and optionally one or more inorganic particulate materials, wherein the tensile properties of the microfibrillated cellulose are comparable to the tensile strength of a comparable never-dried suspension of microfibrillated cellulose and one or more inorganic particulate materials. The system includes a suitable containment vessel to collect a redispersed suspension of microfibrillated cellulose and one or more inorganic particulate materials in the suitable containment vessel for further end use applications.

The associated method comprises redispersing a previously substantially dry or partially dry and optionally powdered composition comprising microfibrillated cellulose and optionally one or more inorganic particulate materials. The method includes the following examples and steps.

A process for redispersing a substantially dry or partially dry and optionally powdered composition comprising microfibrillated cellulose and optionally one or more inorganic particulate materials, the process comprising the steps of:

(a) Providing a quantity of dispersion to a mixing tank through a first inlet; wherein the mixing tank comprises a medium shear mixing device comprising a shear head impeller, and wherein the mixing tank further comprises an outlet and a first pump attached to the outlet;

(b) Providing a sufficient amount of a substantially dry or partially dry and optionally powdered composition comprising microfibrillated cellulose and optionally one or more inorganic particulate materials to the mixing tank through the first inlet to produce a liquid slurry having a solids content of about 0.5wt% to about 5wt% fiber solids;

(c) Mixing the liquid slurry under moderate shear conditions via the mixing apparatus to partially depolymerize the liquid slurry to form a flowable slurry;

(d) Pumping the flowable slurry via the pump attached to the first outlet of the mixing tank to an inlet of a first stage high shear rotor-stator device, the first stage high shear rotor-stator device further comprising an outlet and a pump attached to the outlet; wherein the inlet of the first stage high shear rotor-stator device is in communication with the outlet of the mixing tank; wherein the flowable slurry is subjected to high shear mixing to form a substantially uniform suspension;

(e) Pumping the substantially uniform suspension from the outlet of the first stage high shear rotor-stator device to an inlet of a second stage high shear device selected from the group consisting of a rotor-rotor device, a second high shear rotor-stator device, a colloid mill, an ultra-fine grinding device, or a refiner, wherein the rotor-rotor device comprises counter-rotating rings for subjecting the substantially uniform suspension to additional high shear processing to produce a uniform redispersed suspension of microfibrillated cellulose and optionally one or more inorganic particulate materials; wherein the tensile index of the microfibrillated cellulose is comparable to the tensile index of a comparable never-dried suspension of microfibrillated cellulose and optionally one or more inorganic particulate materials; and

(h) The redispersed suspension of microfibrillated cellulose and optionally one or more inorganic particulate materials is collected in a suitable holding vessel for further end use applications.

In embodiments, the substantially dry or partially dry microfibrillated cellulose may be powdered prior to mixing with the dispersion in the mixing tank.

In further embodiments, the microfibrillated cellulose composition may comprise one or more inorganic particulate materials. In embodiments of the invention, one or more of the optional components may form part of the process.

In another embodiment of the foregoing aspect of the invention, the method further comprises: a hydrocyclone after the rotor-stator apparatus, wherein the hydrocyclone comprises an inlet, a first hydrocyclone outlet and a second hydrocyclone outlet; wherein the hydrocyclone separates the substantially homogeneous suspension into (i) a sheared fine particle stream, preferably having an FLT index greater than 25% of the target value and a Malvern d less than 160 μm ₅₀ And (ii) a coarse particle stream under-sheared, preferably Malvern d having a smaller than sheared fine particle stream ₅₀ At least 20% greater Malvern d ₅₀ The method comprises the steps of carrying out a first treatment on the surface of the Pumping the under-sheared coarse particle stream from the first hydrocyclone outlet to the second inlet of the mixing apparatus to permit recirculation of the under-sheared coarse particle stream and remixing with the flowable slurry in the mixing tank; passing the fine particle stream from the second hydrocyclone outlet to an inlet of a second stage high shear device selected from the group consisting of a rotor-rotor device, a second high shear rotor-stator device, a colloid mill, an ultra fine grinding device, or a refiner, wherein the rotor-rotor device comprises a counter-rotating ring for subjecting the substantially uniform suspension to additional high shear processing.

In another embodiment of the foregoing aspects and embodiments of the invention, the microfibrillated cellulose composition further comprises one or more inorganic particulate materials.

In another aspect of the present invention, there is provided a process for redispersing a substantially dry or partially dry and optionally powdered composition comprising microfibrillated cellulose and optionally one or more inorganic particulate materials, the process comprising the steps of:

(a) Flowing a liquid medium comprising microfibrillated cellulose and optionally one or more inorganic particulate materials obtained from substantially dry or partially dry microfibrillated cellulose and optionally one or more inorganic particulate materials to a medium shear mixing device comprising a shear head impeller to form a liquid slurry comprising fibrillated cellulose and optionally one or more inorganic particulate materials;

(b) Flowing the liquid slurry to a first stage high shear rotor-stator apparatus, wherein the liquid slurry is subjected to high shear mixing to form a substantially uniform suspension;

(c) Flowing the substantially uniform suspension to a second stage high shear device selected from a rotor-rotor device, a second stage high shear rotor-stator device, a colloid mill, an ultra-fine grinding device, or a refiner, wherein the rotor-rotor device comprises counter-rotating rings for subjecting the substantially uniform suspension to high shear processing to produce a uniform redispersed suspension of microfibrillated cellulose and optionally one or more inorganic particulate materials; wherein the tensile properties of the microfibrillated cellulose are comparable to those of a comparable never-dried suspension of microfibrillated cellulose and optionally one or more inorganic particulate materials; and

(d) The redispersed suspension of microfibrillated cellulose and optionally one or more inorganic particulate materials is collected in a suitable holding vessel for further end use applications.

Another embodiment of the foregoing aspect and embodiments of the invention further comprises the following steps. The method of the foregoing aspect of the invention, wherein a substantially uniform suspension is flowed to a hydrocyclone, wherein the substantially uniform suspension is separated into an undershot coarse particle stream and a sheared fine particle stream, wherein the undershot coarse particle stream is recycled to the medium shear mixing device and the sheared fine particle stream is flowed to the second high shear rotor-stator device, a colloid mill, an ultra-fine grinding device, or a refiner.

In yet another embodiment of the foregoing aspects and embodiments of the invention, the composition of microfibrillated cellulose further comprises one or more inorganic particulate materials.

In another aspect of the invention, there is provided a transportable system for redispersing a substantially dry or partially dry and optionally powdered composition comprising microfibrillated cellulose and optionally one or more inorganic particulate materials in a liquid medium to form a liquid composition, the transportable system comprising:

A mixing tank (20) comprising a mixer-a device (21) comprising a shear head impeller (22); wherein the mixing tank (20) comprises a first mixing tank inlet (24) for receiving a liquid slurry of microfibrillated cellulose and optionally one or more inorganic particulate materials and a mixing tank outlet (26) comprising a pump (27); a first stage high shear rotor-stator device (30) comprising a rotor-stator inlet (31) and a rotor-stator outlet (32) connected to the mixing tank outlet (26); a second stage high shear device selected from the group consisting of a rotor-rotor device,A mill, colloid mill, ultra-fine grinding apparatus or refiner; wherein the second stage high shear device comprises a second stage high shear inlet (52) connected to the first stage high shear rotor-stator outlet and an outlet (53); and a reservoir (60) comprising a reservoir inlet (61) connected to the rotor-rotor outlet (53).

In another embodiment of the foregoing aspect of the invention, the system further comprises a hydrocyclone (40) comprising a hydrocyclone inlet (41), a first hydrocyclone outlet (42) and a second hydrocyclone outlet (43); wherein the hydrocyclone inlet (41) is connected to the rotor-stator outlet (32) of the rotor-stator apparatus; wherein the hydrocyclone separates the slurry of microfibrillated cellulose and optionally one or more inorganic particulate materials into a sheared fine particle stream and an under sheared coarse particle stream, wherein the first hydrocyclone outlet (42) is connected to the second inlet (25) of the mixing tank (20) for returning the under sheared coarse particle stream to the mixing tank (20); wherein the fine particle stream flows through a second hydrocyclone outlet (43) to a second stage high shear inlet (52).

In a further embodiment of the foregoing aspects and embodiments of the invention, the substantially dry or partially dry and optionally powdered composition comprising microfibrillated cellulose further comprises one or more inorganic particulate materials.

In further embodiments of the foregoing method and system aspects of the invention, the substantially dry or partially dry composition comprising microfibrillated cellulose and optionally one or more inorganic particulate materials is powdered.

In further embodiments of the foregoing method and system aspects of the invention, the method is a continuous process, a semi-continuous process, or a batch process.

In further embodiments of the foregoing method and system aspects of the invention, the dispersion is water.

In further embodiments of the foregoing method and system aspects of the invention, the liquid composition of microfibrillated cellulose is about 0.5wt% to about 5wt% fibrous solids, or about 0.5wt% to about 2.5wt% fibrous solids, or about 0.75wt% fibrous solids, about 1wt% fibrous solids, about 1.25wt% fibrous solids, about 1.5wt% fibrous solids, about 1.75wt% fibrous solids, about 2wt% fibrous solids, about 2.5wt% fibrous solids, about 3wt% fibrous solids, about 4wt% fibrous solids, or about 5wt% fibrous solids. The foregoing examples relate to compositions comprising microfibrillated cellulose and alternative compositions comprising microfibrillated cellulose and one or more inorganic particulate materials.

In further embodiments of the foregoing method and system aspects of the invention, the microfibrillated cellulose may be prepared from chemical pulp, or chemi-thermo-mechanical pulp, or recycled pulp, or broke pulp, or paper mill waste streams, or waste from paper mills, or a combination thereof.

In further embodiments of the foregoing method and system aspects of the invention, the one or more inorganic particulate materials include alkaline earth metal carbonates or sulfates, hydrous kaolinite group clays, anhydrous (calcined) kaolinite group clays, talc, mica, perlite or diatomaceous earth or combinations thereof; or may include calcium carbonate, magnesium carbonate, dolomite, gypsum, kaolin, halloysite, ball clay, metakaolin, fully calcined kaolin, or a combination thereof.

In other embodiments of the foregoing method and system aspects of the invention, the one or more inorganic particulate materials comprise calcium carbonate.

In other embodiments of the foregoing method and system aspects of the invention, the one or more inorganic particulate materials comprise kaolin.

In still other embodiments of the foregoing method and system aspects of the invention, the one or more inorganic particulate materials include kaolin and calcium carbonate.

In still other embodiments of the foregoing method and system aspects of the invention, the calcium carbonate is precipitated calcium carbonate, ground calcium carbonate, or a combination thereof; or calcium carbonate includes calcite, aragonite or vaterite structures; or in the form of scalenohedral or rhombohedral crystals.

In other embodiments of the foregoing method and system aspects of the invention, the kaolin is ultraplaty kaolin (hyperplaty kaolin).

In other embodiments of the foregoing method and system aspects of the invention, the inorganic particulate material (e.g., calcium carbonate and/or kaolin clay) may include at least about 50wt% calcium carbonate, respectively, having an equivalent spherical diameter of less than about 2 μm; or at least about 50wt% of the calcium carbonate has an equivalent spherical diameter of less than about 2 μm.

In still other embodiments of the foregoing method and system aspects of the invention, the end use includes methods of making paper or coated paper, paint, coating, building material, ceiling tile, composite material, or barrier coating.

In still other embodiments of the foregoing method and system aspects of the invention, the first stage high shear rotor-stator device is selected from the group consisting ofA mill, colloid mill, ultra-fine grinding equipment, or refiner.

In further embodiments of the foregoing method and system aspects of the invention, the second stage high shear rotor-stator device is selected from the group consisting of a rotor-rotor device, A mill, colloid mill, ultra-fine grinding equipment, or refiner.

Drawings

FIG. 1 is a schematic diagram of a transportable equipment device and process flow diagram for redispersing microfibrillated cellulose and optionally one or more inorganic particulate materials and optionally additives. The schematic shown in fig. 1A does not include a feed hopper. The schematic shown in fig. 1B includes a feed hopper.

Fig. 2 is a schematic diagram of a transportable equipment device and process flow diagram for redispersing microfibrillated cellulose and optionally one or more inorganic particulate materials and optionally additives, wherein the process or system further comprises a hydrocyclone device. The schematic shown in fig. 2A does not include a feed hopper. The schematic shown in fig. 2B includes a feed hopper.

Fig. 3 is a graph of cumulative particle size distribution via a vibrating screen technique.

Fig. 4 is example 4: a graph of tensile strength (FLT) results of control test 1. The operating conditions were 3.5% total solids, 50 pulp percent (POP), 12m ³ Flow per h, BVG Shear-Master at 100% speed, cowles blade mixer at 100% speed.

FIG. 5 is example 5 refined using 12 "Sprout: a graph of tensile strength (FLT) results of control test 2. The operating conditions were an intensity of 0.1J/m, MFC 20kWh/DMT per Cheng Jingte energy input, 1320RPM, cutting edge length of 1.111 km/rev. The total solids was 9% and POP was 50%.

FIG. 6 is a use ofExample 6 of SM 180: a graph of tensile strength (FLT) results of control test 3. The operating condition is 5400RPM, a 0.1mm clearance setting, and the reduction tool is W3F.S.GL. The total solids was 9% and POP was 50%.

FIG. 7 is a use ofExample 7 of CD 650: a graph of tensile strength (FLT) results of control test 4. The operating conditions are: 55kg/min, 2000RPM, and total solids were varied as indicated by the legend. A standard 6-ring counter-rotating design developed by Megatrex was used.

FIG. 8 is a schematic diagram of a preferred embodiment of the present inventionA plot of tensile strength (FLT) for continuous operation of a CD650 rotor-rotor high shear device. The operating conditions were 2000RPM, 55kg/min and 9.7% total solids (average measured). From the feed vessel the slurry is passedWaterfall-like falls into the buffer tank. For the second pass, the contents of the buffer vessel are transferred into the feed vessel and the process is repeated.

FIG. 9A is a diagram depicting the use of a 6-ring, and FIG. 9B depicts the useAn 8-ring embodiment of counter-rotating rotor-rotor ring.

FIG. 10 is in useUse of +.>The tensile strength (FLT) results obtained for FLT results for the loop design (first pass). The operating conditions were 55kg/min, 2000RPM and 9.7% total solids (average measured). POP is 50%.

FIG. 11 is in useIn the case of a batch mixer prewetting>A graph of tensile strength (FLT) results for the ring design (first and second strokes). The results are shown against the cumulative energy input (total).

Fig. 12 is a graph of tensile strength (FLT) results for two different solids concentrations for the inventive system and process (single pass).

Fig. 13 is a graph depicting how the selected vortex finder to casing (spot) ratio affects D50 at 4 bar pressure and 1.7% total solids on a 1 "hydrocyclone.

Fig. 14 is a graph depicting how selected vortex finder to sleeve ratios affect the <300 μm fraction at 4 bar pressure and 1.7% total solids on a 1 "hydrocyclone.

Fig. 15 is a graph depicting how the selected vortex finder to sleeve ratio affects fibrillation (with constant finesse B (constant fines B)) at 4 bar pressure and 1.7% total solids on a 1 "hydrocyclone, as measured by Valmet fiber analyzer.

Fig. 16 is a graph depicting how the selected vortex finder to sleeve ratio affects total solids at 4 bar pressure and 1.7% total solids on a 1 "hydrocyclone.

Fig. 17 is a graph depicting how vortex finder to sleeve ratio affects total solids percentage at 2 bar pressure and 9% total solids on a 2 "hydrocyclone.

Fig. 18 is a graph depicting how vortex finder to sleeve ratio affects Malvern D50 at 2 bar pressure and 9% total solids on a 2 "hydrocyclone.

Detailed Description

Certain definitions

The headings (title), sub-headings (head) and sub-headings provided herein are not to be construed as limiting aspects of the disclosure. Accordingly, by referring to the specification as a whole, the terms defined below may be more fully defined. All references cited herein are incorporated by reference in their entirety.

Unless otherwise defined, scientific and technical terms used herein will have the meanings commonly understood by one of ordinary skill in the art. Furthermore, unless the context requires otherwise, singular terms shall include the plural and plural terms shall include the singular.

In this application, unless otherwise stated, the use of "or" means "and/or". In the context of multiple dependent claims, the use of "or" means that more than one of the preceding independent or dependent claims is referred to in an alternative manner only. The use of the word "a/an" when used in conjunction with the term "comprising" may mean "one" but it also corresponds to the meaning of "one" or more "," at least one "and" one "or more". The term "or" is used to mean "and/or" unless explicitly indicated to refer to alternatives only when alternatives are mutually exclusive, but the disclosure supports definitions of alternatives and "and/or".

Throughout this application, the term "about" is used to indicate that the value includes the quantitative means, inherent error variations of the method used to determine the value, or variations that exist between subjects. For example, and without limitation, when the term "about" is used, the specified 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 amount of more than one, including but not limited to 1, 2, 3, 4, 5, 10, 15, 20, 30, 40, 50, 100, etc. The terms "at least one" or "one or more" may extend to 100 or 1000 or more, depending on the terminology to which it is attached. Furthermore, the number of 100/1000 should not be considered limiting, as lower or higher limits may also yield satisfactory results. Furthermore, the use of the term "at least one of X, Y and Z" will be understood to include any combination of X alone, Y alone, and Z alone, and X, Y and Z. Ordinal terms (i.e., "first," "second," "third," "fourth," etc.) are used merely for the purpose of distinguishing between two or more items and are not intended to imply any order or sequence or importance of one item relative to another or any order of addition unless otherwise indicated.

As used herein, the terms "comprises," comprising, "" and any form of comprising, such as "comprises," "including," and "containing," are inclusive or open-ended, and do not exclude additional, unrecited elements or method steps. In addition, the term "comprising" is also understood to be able to be used in conjunction with the term "consisting of … …" or "consisting essentially of … …".

"deagglomerate", "deagglomeration" and the like means the process of breaking up agglomerates.

By "substantially dry" or "dry" is meant that the water content of an aqueous composition comprising microfibrillated cellulose and optionally one or more inorganic particulate materials is reduced by at least about 95% by weight water.

By "partially dried" or "partially dried" is meant that the water content of the aqueous composition comprising microfibrillated cellulose is reduced by an amount of less than 95% by weight. In certain embodiments, "partially dried" or "partially dried" means that the water content of the aqueous composition comprising microfibrillated cellulose is reduced by at least 50 wt%, such as at least 75 wt%, or at least 90 wt%. In embodiments, the aqueous suspension is treated to remove at least a portion or substantially all of the water to form a partially dried or substantially dried product. For example, at least about 10% by volume of the water in the aqueous suspension may be removed from the aqueous suspension, e.g., at least about 20%, or at least about 30%, or at least about 40%, or at least about 50%, or at least about 60%, or at least about 70%, or at least about 80%, or at least about 90%, or at least about 95%, or at least 100% by volume of the water in the aqueous suspension is removed. Any suitable technique may be used to remove the water from the aqueous suspension including, for example, by gravity or vacuum assisted drainage with or without compression, or by evaporation, or by filtration, or by a combination of these techniques. The partially dried or substantially dried composition will comprise microfibrillated cellulose and optionally one or more inorganic particulate materials and any other optional additives that may have been added to the aqueous suspension prior to drying. The partially dried or substantially dried product may be stored or packaged for sale. As described herein, the partially dried or substantially dried product may optionally be rehydrated and incorporated into papermaking compositions and other paper products.

The skilled person knows various methods for preparing a partially dried or substantially dried composition comprising microfibrillated cellulose and optionally one or more inorganic particulate materials. Methods disclosed in the prior art and incorporated herein by reference in their entirety are disclosed, for example, in U.S. patent nos. 10,435,482 and 11,001,644.

The process of us patent No. 10,435,482 is described as a method of improving the physical and/or mechanical properties of a redispersed dried or partially dried microfibrillated cellulose, the method comprising: (a) providing an aqueous composition of microfibrillated cellulose; (b) Dehydrating the aqueous composition to produce a dehydrated microfibrillated cellulose composition by one or more of: i. dewatering by a belt press, ii. high pressure automated belt press, iii. centrifugation, iv. tube press, v. screw press, and vi. rotary press; (c) Drying the dewatered microfibrillated cellulose composition by one or more of the following to produce a dried or partially dried microfibrillated cellulose composition: i. fluidized bed dryer, microwave and/or radio frequency dryer, iii hot air sweep mill or dryer, cell mill or multi-rotor cell mill, and iv freeze drying; and (d) redispersing the dried or at least partially dried microfibrillated cellulose in a liquid medium; wherein the tensile index and/or viscosity of the microfibrillated cellulose is at least 50% of the tensile index and/or viscosity of the aqueous composition of microfibrillated cellulose before drying at comparable concentrations and fiber steepness of 20 to 50.

The process of us patent No. 11,001,644 is described as a method of improving the physical and/or mechanical properties of a redispersed dried or partially dried microfibrillated cellulose, the method comprising: (a) Providing an aqueous composition of microfibrillated cellulose, wherein the microfibrillated cellulose is obtained from a recycled pulp, or from a paper mill broke, or from a paper mill waste stream, or from a powder from a paper mill; (b) Dehydrating the aqueous composition to produce a dehydrated microfibrillated cellulose composition by one or more of: dewatering by belt press, high pressure automated belt press, iii. centrifuge, tube press, screw press and rotary press; (c) Drying the dewatered microfibrillated cellulose composition by one or more of the following to produce a dried or partially dried microfibrillated cellulose composition: i. fluidized bed dryer, microwave and/or radio frequency dryer, hot air sweep mill or dryer, cell mill or multi-rotor cell mill, and freeze drying; and (d) redispersing the dried or at least partially dried microfibrillated cellulose in a liquid medium; wherein the tensile index and/or viscosity of the microfibrillated cellulose is at least 50% of the tensile index and/or viscosity of the aqueous composition of microfibrillated cellulose before drying at comparable concentrations and fiber steepness of 20 to 50. An alternative process for redispersing partially or substantially dry microfibrillated cellulose is disclosed in U.S. patent publication No. 20200263358A1, which is incorporated herein by reference in its entirety.

In U.S. patent publication No. 20200263358, a process for redispersing a dehydrated, partially dried or substantially dried microfibrillated cellulose is provided, the process comprising the steps of: (a) Adding a quantity of a suitable dispersion to a tank having at least a first inlet and a second inlet and an outlet, wherein the tank further comprises a mixer and a pump attached to the outlet; (b) Adding a sufficient amount of dehydrated, partially dried or substantially dried microfibrillated cellulose to the tank through the first inlet to produce a microfibrillated cellulose liquid composition with a desired solids concentration of 0.5% to 5% fiber solids; (c) Mixing the dispersion and the dewatered, partially dried or substantially dried microfibrillated cellulose in a tank with a mixer to partially depolymerize and redisperse the microfibrillated cellulose to form a flowable slurry; (d) Pumping the flowable slurry with a pump to an inlet of a flow cell, wherein the flow cell comprises a recirculation loop and one or more ultrasonic probes in series and at least a first outlet and a second outlet, wherein the second outlet of the flow cell is connected to the second inlet of the tank, thereby providing a continuous recirculation loop to continuously apply ultrasonic energy to the slurry for a desired period of time and/or total energy, wherein the flow cell comprises an adjustable valve at the second outlet to create a backpressure of the recirculating slurry, further wherein the liquid composition comprising microfibrillated cellulose of step (c) is continuously recirculated through the recirculation loop at an operating pressure of 0 to 4 bar and at a temperature of 20 ℃ to 50 ℃; (e) Applying an ultrasonic energy input of 200 to 10,000kwh/t continuously to the slurry by means of an ultrasonic probe at a frequency ranging from 19 to 100kHz with an amplitude of up to 60%, up to 100% or up to 200% for 1 to 120 minutes up to the physical limit of the ultrasonic meter used; (f) A redispersed suspension comprising microfibrillated cellulose with enhanced tensile strength and/or viscosity properties is collected from the first outlet of the flow cell in a suitable holding vessel.

The terms "redisperse", "redispersing" and "redispersing" refer to suspending dry and optionally powdered microfibrillated cellulose and optionally one or more inorganic particulate materials in an aqueous medium to achieve comparable tensile index characteristics as before drying occurs. This is characterized by a "tensile index" or "FLT index".

As used herein, the "FLT index" is a tensile strength measurement made according to the procedure of example 1.

The FLT index is a tensile test aimed at assessing the quality of microfibrillated cellulose and redispersed microfibrillated cellulose. The pulp percentage (Percentage of Pulp, POP) of the test material was adjusted to 20% by adding any inorganic particles used in the production of the microfibrillated cellulose/inorganic material composite (in the case of microfibrillated cellulose without inorganic particles, 60wt% <2 μm GCC calcium carbonate was used). A 220gsm sheet was formed from this material using a custom-made Buchner filter apparatus. The resulting sheet was processed and its tensile index was measured using an industry standard tensile tester.

As used herein, the term "include" and grammatical variants thereof are intended to be non-limiting such that recitation of items in a list is not to the exclusion of other like items that may be substituted for or added to the listed items.

As used herein, "mechanical properties" of a partially or substantially dry MFC composition include one or more of the following: tensile strength, tensile elongation, tensile index, breaking strength, tear index, scott Bond, energy to break, and elongation to break.

As used herein, the terms "powderized", "powderized" and "comminution" mean mechanically comminuting the MFC cake to a powder having a cumulative particle size distribution measured using a shaker in which screens are stacked in descending order of particle size fraction, as shown in fig. 3.

By linearly interpolating the raw data, the following features of the curve can be used, as shown in table 1 below.

TABLE 1

As used herein, a mixer with a shear head impeller applies "moderate shear" to a substantially dry or partially dry and optionally powdered composition comprising microfibrillated cellulose or microfibrillated cellulose and one or more inorganic particulate material compositions. Examples of moderate shear mixers that can be used in the present invention are Cowles blades (radial flow impellers) inside the containment vessel, where the diameter is less than 0.5 (i.e., D/T) between impeller (D) and tank (T), for example <0.5 A tip speed of less than 20m/s is encountered. Other exemplary mixers include various propeller mixers, twin and triaxial mixers (e.g., ross mixers), dispersers with blade mixers, and,Mixers, myers mixers, PVC mixers, and other similar general purpose mixers as known to the skilled person.

As used herein, a rotor-stator mixer is, for example, one that applies a relatively high shear rateMixers (Siefer-Trigonal machines) or more generally colloid mills or refiners, depending on the desired shear level and physical limitations of design compared to a shear head mixer that applies moderate shear. Another device comprises a device consisting of German->Hagen of (R)&Funke Co., ltd>A rotor-stator mixer.

As used herein, a "rotor-rotor mixer" produces high and concentrated shear for high viscosity slurries, as compared to conventional mixers. The rotor-rotor mixer has two counter-rotating mixing elements (rotors) capable of applying high shear forces. Due to the geometry of the mixer, the liquid slurry is forced through the high shear zone formed by the rotor. An exemplary rotor-rotor mixer is manufactured by Finland Is supplied by Megatrex Oy>A mixer. Alternative devices include an ultra-fine friction mill (available from Masuko Sangyo Co., ltd., japan)>)。/>An example of a mixer is a rotor-rotor debonder, model G30, 500mm diameter, 6 rotor peripherals, applied at a rotational speed of 1500rpm (counter rotating rotor). The preferred gap width is less than 10mm and preferably less than 5mm. So-called rotor-rotor debonder, in which a series of frequent repetitions of the dispersion is caused by the blades of several rotors rotating in opposite directionsIs a function of (a) and (b).A debonder is an example of such a debonder. Adjacent rotors rotated in opposite directions at 1500 rpm.

As used herein, "under-sheared coarse particle stream" includes the ratio overflow/fine particle stream d ₅₀ (μm) particle size at least 20% larger.

Fibrous substrate comprising cellulose

The cellulose-containing fibrous substrate (variously referred to herein as "cellulose-containing fibrous substrate", "cellulose fibers", "fibrous cellulosic feedstock", "cellulosic feedstock", and "cellulose-containing fibers (or fibers)", etc.) may be derived from virgin pulp or recycled pulp.

As used herein, the term "substantially" means that the event or circumstance described subsequently occurs entirely or to a substantial extent. For example, when related to a particular event or circumstance, the term "substantially" means that the event or circumstance described subsequently 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. In the context of a "substantially homogeneous suspension", a suspension is understood to have minimal agglomerates.

As used herein, "viscosity" is measured according to the procedure of example 2.

Unless otherwise indicated, the particle size characteristics referred to herein for inorganic particulate materials are measured by sedimentation of the particulate material in a fully dispersed state in an aqueous medium, as measured in a well known manner, using a Sedigraph 5100 machine supplied by Micromeritics Instruments Corporation, norcross, ga., USA (telephone: +1 770 6623620; web site: www.micromeritics.com), referred to herein as "Micromeritics Sedigraph 5100 units". Such a machine provides a measured value and cumulative weight percent curve for particles having a size less than a given e.s.d. value, which is known in the art as the "equivalent spherical diameter" (e.s.d.). Average particle size d ₅₀ Is the value of the particle e.s.d measured in this way, at which50% by weight of the particles have a particle size less than d ₅₀ Equivalent sphere diameter of the values.

Alternatively, in the context of the description, the particle size characteristics referred to herein for inorganic particulate materials are measured by well-known conventional methods employed in the art of laser scattering, using Malvern Mastersizer S machine supplied by Malvern Instruments Ltd (or by other methods that give substantially the same results). In laser scattering techniques, the particle size in powders, suspensions and emulsions can be measured using diffraction of a laser beam based on the application of Mies theory. Such a machine provides a measured value and cumulative volume percent curve for particles having a size less than a given e.s.d. value, which is known in the art as the "equivalent spherical diameter" (e.s.d.). Average particle size d ₅₀ Is the value of the particle e.s.d measured in this way, at which 50% by volume of the particles have a value smaller than d ₅₀ Equivalent sphere diameter of the values.

As used herein, the phrase "an integer from X to Y" is meant to include any integer of endpoints. For example, the phrase "an integer from 1 to 5" means 1, 2, 3, 4, or 5.

Microfibrillated cellulose

Although microfibrillated cellulose ("MFC") is well known and described in the art, for the purpose of one or more of the presently disclosed and/or claimed inventive concepts, microfibrillated cellulose is defined as cellulose consisting of isolated cellulose microfibrils and/or microfibrils in the form of cellulose microfibril bundles, both of which are derived from cellulosic raw materials. Microfibrillated cellulose is thus understood to include partially or fully fibrillated cellulose or lignocellulose fibers, which can be achieved by various methods known in the art.

As used herein, "microfibrillated cellulose (microfibrillated cellulose)" may be used interchangeably with "microfibrillated cellulose (microfibrillar cellulose)", "nanofibrillated cellulose", "nanocellulose", "nanofibrillated cellulose" and/or simply "MFC". In addition, as used herein, the terms listed above interchangeably with "microfibrillated cellulose" may refer to cellulose that has been fully microfibrillated or cellulose that has been substantially microfibrillated but still contains an amount of non-microfibrillated cellulose that does not interfere with the benefits of microfibrillated cellulose as described and/or claimed herein.

"microfibrillating" means a process in which microfibrils of cellulose are released or partially released as individual substances or as small aggregates, as compared to the fibers of a pre-fibrillated pulp. Typical cellulosic fibers suitable for use in papermaking (i.e., pre-fibrillated pulp) include large aggregates of hundreds or thousands of individual cellulosic fibers.

Microfibrillated cellulose comprises cellulose, which is a naturally occurring polymer comprising repeating glucose units. The term "microfibrillated cellulose" as used in this specification is also denoted MFC, including microfibrillated/microfibrillated cellulose and nanofibrillated/nanofibrillated cellulose (NFC), these materials are also referred to as nanocellulose.

Microfibrillated cellulose is prepared by stripping off the outer layers of cellulose fibers, which may have been exposed by mechanical shearing, with or without prior enzymatic or chemical treatments. There are many methods known in the art for preparing microfibrillated cellulose.

In a non-limiting example, the term microfibrillated cellulose is used to describe fibrillated cellulose comprising nano-sized cellulose particle fibers or fibrils typically having at least one dimension less than 100 nm. When released from cellulose fibers, fibrils generally have a diameter of less than 100 nm. The actual diameter of the cellulose fibrils depends on the source and the method of manufacture.

The particle size distribution and/or aspect ratio (length/width) of the cellulose microfibrils attached to fibrillated cellulose fibres or as released microfibrils (microfibrils) depends on the source and the manufacturing method used in the microfibrillation process.

In a non-limiting example, the aspect ratio of the microfibers is generally high, and individual microfibers may be greater than 1 micron in length and may range in diameter from about 5 to 60nm, with number average diameters generally less than 20nm. The microfiber bundles may be greater than 1 micron in diameter, but are typically less than 1 micron in diameter.

In a non-limiting example, the smallest fibrils are conventionally referred to as primary fibrils, which typically have a diameter of about 2 to 4nm. Basic fibril aggregation is also common, which can also be considered as microfibers.

In a non-limiting example, the microfibrillated cellulose may at least partially comprise nanocellulose. Nanocellulose may mainly comprise nano-sized fibrils having a diameter of less than 100nm and a length that may be in the micrometer range or less. The smallest microfibrils resemble so-called elemental fibrils, which are typically 2 to 4nm in diameter. Of course, the size and structure of the microfibers and microfiber bundles depend on the raw materials used, in addition to the method of producing microfibrillated cellulose. Nonetheless, those of ordinary skill in the art will understand the meaning of "microfibrillated cellulose" in the context of one or more of the presently disclosed and/or claimed inventive concepts.

The length of the fibrils may vary, typically from about 1 to greater than 10 microns, depending on the source of the cellulose fibers and the manufacturing process used to microfibrillate the cellulose fibers.

The coarse MFC grade may contain a large amount of fibrillated fibers, i.e. fibrils protruding from the tracheids (cellulose fibers), and a certain amount of fibrils released from the tracheids (cellulose fibers).

In certain embodiments, the microfibrillated cellulose has a d in the range of about 5 μm to about 500 μm ₅₀ As measured by laser light scattering. In certain embodiments, the microfibrillated cellulose has a d of equal to or less than about 400 μm, such as equal to or less than about 300 μm, or equal to or less than about 200 μm, or equal to or less than about 150 μm, or equal to or less than about 125 μm, or equal to or less than about 100 μm, or equal to or less than about 90 μm, or equal to or less than about 80 μm, or equal to or less than about 70 μm, or equal to or less than about 60 μm, or equal to or less than about 50 μm, or equal to or less than about 40 μm, or equal to or less than about 30 μm, or equal to or less than about 20 μm, or equal to or less than about 10 μm ₅₀ 。

In certain embodiments, the microfibrillated cellulose has a modal fiber particle size in the range of about 0.1 to 500 μm.

In certain embodiments, the microfibrillated cellulose has a modal fiber particle size of at least about 0.5 μm, e.g., at least about 10 μm, or at least about 50 μm, or at least about 100 μm, or at least about 150 μm, or at least about 200 μm, or at least about 300 μm, or at least about 400 μm.

In one embodiment, microfibrillated cellulose may also be prepared from recycled pulp or paper mill broke and/or industrial waste, or a paper stream (paper stream) from a paper mill rich in mineral fillers and cellulose materials.

The microfibrillated cellulose may be treated, for example, before dewatering and/or drying. For example, one or more additives (e.g., salts, sugars, glycols, urea, glycols, carboxymethyl cellulose, guar gum, or combinations thereof, as specified below) may be added to the microfibrillated cellulose, as specified below. For example, one or more oligomers (e.g., with or without the additives specified above) may be added to the microfibrillated cellulose. The additives may be, for example, suspended in a low dielectric solvent prior to dewatering and/or drying, the microfibrillated cellulose may be, for example, in an emulsion, for example, an oil/water emulsion, prior to dewatering and/or drying, the microfibrillated cellulose may be, for example, in a masterbatch composition, for example, a polymer masterbatch composition and/or a high solids masterbatch composition, prior to dewatering and/or drying, the microfibrillated cellulose may be, for example, a high solids composition (for example, a solids content of equal to or greater than about 60wt%, or equal to or greater than about 70wt%, or equal to or greater than about 80wt%, or equal to or greater than about 90wt%, or equal to or greater than about 95wt%, or equal to or greater than about 98wt%, or equal to or greater than about 99wt%, but any combination of the microfibrillated cellulose may alternatively be applied to any one or more of the microfibrillated cellulose after dewatering and drying.

The fibrous substrate comprising cellulose may be added to the milling vessel in a dry state. For example, the dried broke may be added directly to the mill vessel. The aqueous environment in the mill vessel will promote pulp formation.

Various methods of producing microfibrillated cellulose ("MFC") are known in the art. Certain methods and compositions comprising microfibrillated cellulose produced by the milling procedure are described in WO 2010/131016. Husband, j.c., svinding, p., skuse, d.r., motsi, t., likitalo, m., coles, a., fiberLean Technologies ltd.,2015, "Paper filler composition," PCT international application No. WO 2010/131016. Paper products comprising such microfibrillated cellulose have shown excellent paper properties such as paper break strength and tensile strength. The method described in WO 2010/131016 is also capable of economically producing microfibrillated cellulose.

WO 2007/091942 A1 describes a method in which a chemical pulp is first refined, then treated with one or more wood degrading enzymes and finally homogenized to produce MFC as the final product. The consistency of the pulp is taught to be preferably 0.4 to 10%. The advantage is said to be that clogging in the high pressure fluidizer or homogenizer is avoided.

WO 2010/131016 describes a milling procedure for producing microfibrillated cellulose with or without inorganic particulate material. This milling procedure is described below. In one embodiment of the method set forth in WO 2010/131016, the contents of which are incorporated herein by reference in their entirety, the method utilizes mechanical disintegration of cellulose fibers to cost-effectively and mass-produce microfibrillated cellulose ("MFC") without requiring cellulose pretreatment. One embodiment of the method uses a stirred media crumb mill milling technique that disintegrates the fiber into MFC by stirring the milled media beads. In this process, minerals such as calcium carbonate or kaolin are added as grinding aids, greatly reducing the energy required. Husband, j.c., svinding, p., skuse, d.r., motsi, t., likitalo, m., coles, a., fiberLean Technologies ltd.,2015, "Paper filler composition," U.S. patent No. 9127405B2.

Preparation of an aqueous suspension of microfibrillated cellulose and inorganic particulate material

In certain embodiments, the composition comprising microfibrillated cellulose may be obtained by a process comprising microfibrillating a fibrous substrate comprising cellulose in the presence of a grinding medium. The process is advantageously carried out in an aqueous environment.

When grinding media is present, it may be a natural or synthetic material. The grinding media may, for example, comprise spheres, beads or pills of any hard mineral, ceramic or metallic material. Such materials may include, for example, alumina, zirconia, zirconium silicate, aluminum silicate, or mullite-rich materials produced by calcining kaolinite clay at a temperature in the range of about 1300 ℃ to about 1800 ℃. For example, in some embodiments, the first and second substrates,grinding media are preferred. Alternatively, natural sand particles having a suitable particle size may be used.

Grinding may be performed in one or more stages. For example, the coarse inorganic particulate material may be milled in a milling vessel to a predetermined particle size distribution, after which cellulosic containing fibrous material is added and milling continued until the desired level of microfibrillation is obtained. The coarse inorganic particulate material used in accordance with the first aspect of the present invention may initially have a particle size distribution wherein less than about 20% by weight of the particles have an equivalent spherical diameter (e.s.d) of less than 2 μm, 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 μm. In another embodiment, the coarse inorganic particulate material used in accordance with the first aspect of the present invention may initially have a particle size distribution (as measured using a Malvern instrument or equivalent apparatus) wherein less than about 20% by volume of the particles have an e.s.d. of less than 2 μm, 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 μm. In another embodiment, the cellulose-containing fibrous material may be milled in the presence of a milling medium and in the absence of inorganic particulate matter, as described below.

The coarse inorganic particulate material may be wet or dry milled with or without the presence of a milling medium. In the case of the wet milling stage, the coarse inorganic particulate material is preferably milled in an aqueous suspension in the presence of a milling medium. In such suspensions, 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 from about 30% to about 75% by weight of the suspension. As described above, the coarse inorganic particulate material may be milled to a particle size distribution such that at least about 10 wt% of the particles have an e.s.d. of less than 2 μm, for example, at least about 20 wt%, or at least about 30 wt%, or at least about 40 wt%, or at least about 50 wt%, or at least about 60 wt%, or at least about 70 wt%, or at least about 80 wt%, or at least about 90 wt%, or at least about 95 wt%, or about 100 wt% of the particles have an e.s.d. of less than 2 μm, after which the cellulose pulp is added, and the two components are co-milled to microfibrillate the fibers of the cellulose pulp. In another embodiment, the coarse inorganic particulate material is milled to a particle size distribution (as measured using a Malvern instec device (or equivalent device)) such that at least about 10% by volume of the particles have an e.s.d. of less than 2 μm, 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 μm, after which the cellulose pulp is added, and the two components are co-milled to microfibrillate the fibers of the cellulose pulp.

In general, the type and particle size of the grinding media to be selected for use in the present invention may depend on characteristics such as, for example, the particle size and chemical composition of the feed suspension of the material to be ground. Preferably, the particulate grinding media comprises particles having an average diameter in the range of about 0.1mm to about 6.0mm and more preferably in the range of about 0.2mm to about 4.0 mm. The grinding medium (or media) may be present in an amount up to about 70% by volume of the charge. The grinding media may be present in an amount of at least about 10% by volume of the charge, such as 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.

Unless otherwise indicated, the particle size characteristics of the microfibrillated cellulose material were measured by well known conventional methods employed in the art of laser scattering using the Malvern instec device (or equivalent device) supplied by Malvern Instruments Ltd (or by other methods that give substantially the same results).

The fibrous substrate comprising cellulose may be in the form of pulp (i.e., a suspension of cellulose fibers in water) which may be prepared by any suitable chemical or mechanical treatment or combination thereof.

Details of procedures for characterizing the particle size distribution of a mixture of inorganic particulate material and microfibrillated cellulose using a Malvern instec apparatus (or equivalent apparatus) are provided below.

The fibrous substrate comprising cellulose may be microfibrillated in the presence of inorganic particulate material to obtain a fiber having a d in the range of about 5 μm to about 500 μm ₅₀ As measured by laser light scattering. The fibrous substrate comprising cellulose may be microfibrillated in the presence of inorganic particulate material to obtain a fibrous substrate having the following d ₅₀ Is a microfibrillated cellulose of (a): equal to or less than about 400 μm, such as equal to or less than about 300 μm, or equal to or less than about 200 μm, or equal to or less than about 150 μm, or equal to or less than about 125 μm, or equal to or less than about 100 μm, or equal to or less than about 90 μm, or equal to or less than about 80 μm, or equal to or less than about 70 μm, or equal to or less than about 60 μm, or equal to or less than about 50 μm, or equal to or less than about 40 μm, or equal to or less than about 30 μm, or equal to or less than about 20 μm, or equal to or less than about 10 μm.

The fibrous substrate comprising cellulose may be microfibrillated in the presence of inorganic particulate material to obtain microfibrillated cellulose having a modal fiber particle size in the range of about 0.1 μm to 500 μm and a modal inorganic particulate material particle size in the range of 0.25 μm to 20 μm. The fibrous substrate comprising cellulose may be microfibrillated in the presence of inorganic particulate material to obtain microfibrillated cellulose having the following modal fiber particle size: at least about 0.5 μm, such as at least about 10 μm, or at least about 50 μm, or at least about 100 μm, or at least about 150 μm, or at least about 200 μm, or at least about 300 μm, or at least about 400 μm.

The fibrous substrate comprising cellulose may be microfibrillated in the presence of inorganic particulate material to obtain microfibrillated cellulose having a fiber steepness equal to or greater than about 10, as measured by Malvern. The fiber steepness (i.e., steepness of the fiber particle size distribution) is determined by the following formula:

steepness=100× (d ₃₀ /d ₇₀ )

Microfibrillated cellulose may have a fiber steepness equal to or less than about 100. The microfibrillated cellulose may have a fiber steepness of 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 fiber steepness of about 20 to about 50, or about 25 to about 40, or about 25 to about 35, or about 30 to about 40.

Finer mineral peaks can be fitted to the measured data points and subtracted mathematically from the distribution to leave fiber peaks, which can be converted to cumulative distributions. Similarly, the fiber peaks can be mathematically subtracted from the original distribution to leave the mineral peaks, and the mineral peaks can also be converted to cumulative distributions. These two cumulative curves can then be used to calculate the average particle size (d ₅₀ ) And steepness of distribution (d ₃₀ /d ₇₀ X 100). The differential curve can then be used to find the modal particle size of both the mineral and fiber fractions.

Inorganic particulate material

When present, the inorganic particulate material may be, for example, an alkaline earth metal carbonate or sulfate such as calcium carbonate, magnesium carbonate, dolomite, gypsum, an hydrous kaolinite group clay such as kaolin, halloysite or ball clay, an anhydrous (calcined) kaolinite group clay such as metakaolin or fully calcined kaolin, talc, mica, perlite or diatomaceous earth, or magnesium hydroxide, or aluminum trihydrate or combinations thereof.

A preferred inorganic particulate material for use in the process is calcium carbonate. Hereinafter, the present invention may be intended to be discussed in terms of calcium carbonate and aspects related to aspects of calcium carbonate being processed and/or treated. The invention should not be construed as being limited to such embodiments.

The particulate calcium carbonate used in the present invention may be obtained from natural sources by grinding. Ground Calcium Carbonate (GCC) is generally obtained by crushing and then grinding mineral sources such as chalk, marble or limestone, which may be followed by a size classification step to obtain a product having the desired fineness. Other techniques such as bleaching, flotation and magnetic separation may also be used to obtain products having the desired fineness and/or color. The particulate solid material may be milled spontaneously, i.e. by friction between the particles of the solid material themselves, or alternatively, in the presence of a particulate milling medium comprising particles of a different material from the calcium carbonate to be milled. These processes may be performed with or without the presence of dispersants and biocides, which may be added at any stage of the process.

Precipitated Calcium Carbonate (PCC) may be used as a source of particulate calcium carbonate in the present invention and may be produced by any method known in the art. TAPPI Monograph Series No 30, "Paper Coating Pigments", pages 34-35 describe three main commercial processes for preparing precipitated calcium carbonate suitable for use in the preparation of products for the paper industry, but which can also be used in the practice of the present invention. In all three processes, a calcium carbonate feed (such as limestone) is first calcined to produce quicklime, which is then slaked in water to produce calcium hydroxide or milk of lime. In the first process, milk of lime is directly carbonated with carbon dioxide gas. The advantage of this process is that no by-products are formed and the properties and purity of the calcium carbonate product are relatively easy to control. In the second process, milk of lime is contacted with soda to produce calcium carbonate precipitate and sodium hydroxide solution by metathesis. If the process is used commercially, the sodium hydroxide may be substantially completely separated from the calcium carbonate. In the third main commercial process, milk of lime is first contacted with ammonium chloride to obtain a calcium chloride solution and ammonia gas. The calcium chloride solution is then contacted with soda ash to produce calcium carbonate precipitate and sodium chloride solution by metathesis. The crystals may be produced in a variety of different shapes and sizes depending on the particular reaction process used. Three major forms of PCC crystals are aragonite, rhombohedral and scalenohedral, all of which are suitable for use in the present invention, including mixtures thereof.

Wet milling of calcium carbonate involves forming an aqueous suspension of calcium carbonate, which may then optionally be milled in the presence of a suitable dispersant. Reference may be made to, for example, EP 614948 (the contents of which are incorporated by reference in their entirety) for more information about wet grinding of calcium carbonate.

In some cases, other minerals may be included in small additions, for example, one or more of kaolin, calcined kaolin, wollastonite, bauxite, talc, bentonite, or mica may also be present.

When the inorganic particulate material of the present invention is obtained from a naturally occurring source, some mineral impurities may contaminate the abrasive material. For example, naturally occurring calcium carbonate may be present with other minerals. Thus, in some embodiments, the inorganic particulate material includes a certain amount of impurities. Generally, however, the inorganic particulate material used in the present invention will contain less than about 5 wt.%, preferably less than about 1 wt.% of other mineral impurities.

The inorganic particulate material used during the microfibrillation step of the process of the present invention preferably has a particle size distribution wherein at least about 10 wt% of the particles have an e.s.d. of less than 2 μm, for example, at least about 20 wt%, or at least about 30 wt%, or at least about 40 wt%, or at least about 50 wt%, or at least about 60 wt%, or at least about 70 wt%, or at least about 80 wt%, or at least about 90 wt%, or at least about 95 wt%, or about 100 wt% of the particles have an e.s.d. of less than 2 μm.

Unless otherwise indicated, the particle size characteristics mentioned herein for inorganic particulate materials are those described using the compositions described by Micromeritics Instruments Corporation, norcross, ga., USA (telephone: +1 770 6623620; web site: www.mic)Com), as measured by sedimentation of the particulate material in a fully dispersed state in an aqueous medium in a well known manner, is referred to herein as "Micromeritics Sedigraph 5100 units". Such a machine provides a measured value and cumulative weight percent curve for particles having a size less than a given e.s.d. value, which is known in the art as the "equivalent spherical diameter" (e.s.d.). Average particle size d ₅₀ Is the value of the particle e.s.d measured in this way, at which 50% by weight of the particles have a value less than d ₅₀ Equivalent sphere diameter of the values.

Alternatively, in the context of the description, the particle size characteristics referred to herein for inorganic particulate materials are measured by well-known conventional methods employed in the art of laser scattering, using a Malvern instec device (or equivalent device) supplied by Malvern Instruments Ltd (or by other methods that give substantially the same results). In laser scattering techniques, the particle size in powders, suspensions and emulsions can be measured using diffraction of a laser beam based on the application of Mies theory. Such a machine provides a measured value and cumulative volume percent curve for particles having a size less than a given e.s.d. value, which is known in the art as the "equivalent spherical diameter" (e.s.d.). Average particle size d ₅₀ Is the value of the particle e.s.d measured in this way, at which 50% by volume of the particles have a value smaller than d ₅₀ Equivalent sphere diameter of the values.

Unless otherwise indicated, the particle size characteristics of the microfibrillated cellulose material were measured by well known conventional methods employed in the art of laser light scattering using the Malvern Insitec L machine supplied by Malvern Instruments Ltd (or by other methods that give substantially the same results).

Details of the procedure for characterizing the particle size distribution of a mixture of inorganic particulate material and microfibrillated cellulose using a Malvern Mastersizer S machine are provided below.

Another inorganic particulate material that is preferably used is kaolin clay. Hereafter, this portion of the specification may be intended to discuss kaolin as well as aspects related to aspects of kaolin being processed and/or treated. The invention should not be construed as being limited to such embodiments. Thus, in some embodiments, the kaolin is used in raw form.

The kaolin clay used in the present invention may be a processed material derived from a natural source, i.e., virgin natural kaolin clay minerals. The processed kaolin clay may generally contain at least about 50% by weight of kaolinite. For example, most commercially processed kaolin clays contain greater than about 75% by weight kaolinite, and may contain greater than about 90% by weight, in some cases greater than about 95% by weight kaolinite.

The kaolin clay used in the present invention may be prepared from the original natural kaolin clay mineral by one or more other processes well known to those skilled in the art, such as by known refining or beneficiation steps.

For example, clay minerals may be bleached with a reducing bleaching agent such as sodium dithionite. If sodium dithionite is used, the bleached clay mineral may optionally be dewatered, optionally washed and optionally dewatered again after the sodium dithionite bleaching step.

The clay minerals may be treated to remove impurities, for example, by flocculation, flotation, or magnetic separation techniques well known in the art. Alternatively, the clay mineral used in the first aspect of the invention may be untreated in solid form or as an aqueous suspension.

The process for preparing the particulate kaolin clay used in the present invention may also include one or more comminution steps, such as grinding or milling. Coarse kaolin is suitably delaminated by light comminution. Comminution may be carried out by using beads or granules of plastics (e.g. nylon), sand or ceramic grinding or milling aids. The crude kaolin may be refined using well known procedures to remove impurities and improve physical properties. The kaolin clay may be treated by known particle size classification procedures such as sieving and centrifugation (or both) to obtain a clay having the desired d ₅₀ Particles of value or particle size distribution.

Fibrous substrate comprising cellulose

Comprising celluloseThe fibrous substrate may be derived from any suitable source, such as wood, grass (e.g., sugarcane, bamboo) or rag (e.g., textile waste, cotton, hemp, or flax). The fibrous substrate comprising cellulose may be in the form of pulp (i.e., a suspension of cellulose fibers in water) which may be prepared by any suitable chemical or mechanical treatment or combination thereof. For example, the pulp may be chemical pulp, or chemimechanical pulp, or mechanical pulp, or recycled pulp, or paper mill broke, or paper mill reject stream, or reject from a paper mill, or a combination thereof. The cellulose pulp may be beaten (e.g., in a Valley beater) and/or otherwise refined (e.g., processed in a cone or plate refiner) to any predetermined freeness, reported in the art as Canadian Standard Freeness (CSF) in cm ³ . CSF means a value of pulp freeness or drainage rate measured by the rate at which the pulp suspension can be drained. For example, the cellulose pulp may have about 10cm before being microfibrillated ³ Or higher Canadian standard freeness. The cellulose pulp may have the following CSF: about 700cm ³ Or lower, e.g., equal to or less than about 650cm ³ Or equal to or less than about 600cm ³ Or equal to or less than about 550cm ³ Or equal to or less than about 500cm ³ Or equal to or less than about 450cm ³ Or equal to or less than about 400cm ³ Or equal to or less than about 350cm ³ Or equal to or less than about 300cm ³ Or equal to or less than about 250cm ³ Or equal to or less than about 200cm ³ Or equal to or less than about 150cm ³ Or equal to or less than about 100cm ³ Or equal to or less than about 50cm ³ . The cellulose pulp may then be dewatered by methods well known in the art, for example, the pulp may be filtered through a screen 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. The pulp may be utilized in an unrefined state, that is, without being pulped or dewatered or otherwise refined.

The cellulose pulp may be pulped (e.g., at VaIn a lley beater) and/or otherwise refined (e.g., processed in a cone or plate refiner) to any predetermined freeness, reported in the art as Canadian Standard Freeness (CSF) in cm ³ . CSF means a value of pulp freeness or drainage rate measured by the rate at which the pulp suspension can be drained, and this test is performed according to the T227 cm-09TAPPI standard. For example, the cellulose pulp may have about 10cm before being microfibrillated ³ Or higher Canadian standard freeness. The cellulose pulp may have the following CSF: about 700cm ³ Or lower, e.g., equal to or less than about 650cm ³ Or equal to or less than about 600cm ³ Or equal to or less than about 550cm ³ Or equal to or less than about 500cm ³ Or equal to or less than about 450cm ³ Or equal to or less than about 400cm ³ Or equal to or less than about 350cm ³ Or equal to or less than about 300cm ³ Or equal to or less than about 250cm ³ Or equal to or less than about 200cm ³ Or equal to or less than about 150cm ³ Or equal to or less than about 100cm ³ Or equal to or less than about 50cm 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 to obtain a wet sheet comprising at least about 10% solids, such as at least about 15% solids, or at least about 20% solids, or at least about 30% solids, or at least about 40% solids. The pulp may be utilized in an unrefined state, that is, without being pulped or dewatered or otherwise refined.

Microfibrillated cellulose may be produced by any method that reduces the particle size of the polysaccharide, as known to one of ordinary skill in the art. However, a method for reducing particle size while maintaining a high aspect ratio of the polysaccharide is preferred. In particular, the at least one microfibrillated cellulose may be produced by a process selected from the group consisting of: grinding; performing ultrasonic treatment; homogenizing; a collision mixer; heat; steam explosion; a boost-decompression cycle; a freeze-thaw cycle; striking; grinding (such as a disc grinder); pumping; mixing; ultrasonic waves; microwave explosion; and/or milling. Various combinations of these methods may also be used, such as homogenization after milling. In one embodiment, the at least one microfibrillated cellulose is formed by subjecting one or more cellulose-containing raw materials to a sufficient amount of shear in an aqueous suspension such that a portion of the crystalline regions of cellulose fibers in the one or more cellulose-containing raw materials are fibrillated.

Microfibrillation of fibrous substrates comprising cellulose can be obtained in wet conditions in the presence of inorganic particulate material by the following method: wherein the mixture of cellulose pulp and inorganic particulate material is pressurized (e.g., to a pressure of about 500 bar) and then passed through a low pressure zone. The rate of passage of the mixture through the low pressure zone is sufficiently high and the pressure in the low pressure zone is sufficiently low to cause microfibrillation of the cellulose fibers. For example, the pressure drop may be obtained by forcing the mixture through an annular opening having a narrow inlet aperture and a much wider outlet aperture. As the mixture accelerates into a larger volume (i.e., low pressure zone), a sharp drop in pressure causes cavitation, resulting in microfibrillation. In embodiments, microfibrillation of fibrous substrates comprising cellulose may be obtained in a homogenizer under wet conditions in the presence of inorganic particulate material. In the homogenizer, the cellulose pulp-inorganic particulate material mixture is pressurized (e.g., to a pressure of about 500 bar) and forced through small nozzles or orifices. The mixture may be pressurized to a pressure of about 100 to about 1000 bar, for example to a pressure of 300 bar or greater, or about 500 bar or greater, or about 200 bar or greater, or about 700 bar or greater. The homogenization subjects the fibers to high shear forces such that cavitation causes microfibrillation of the cellulose fibers in the pulp as the pressurized cellulose pulp exits the nozzle or orifice. Additional water may be added to improve the flow of the suspension through the homogenizer. The resulting aqueous suspension comprising microfibrillated cellulose and inorganic particulate material may be returned to the inlet of the homogenizer to make multiple passes through the homogenizer. In a preferred embodiment, the inorganic particulate material is a natural platy mineral such as kaolin. Thus, the homogenization is advantageous not only for microfibrillation of the cellulose pulp, but also for delamination of the plate-like particulate material.

The microfibrillated cellulose may be in the form of at least one of a dispersion (e.g., gel or gel-like form), a diluted dispersion and/or a suspension.

Microfibrillated cellulose prepared without adding inorganic particulate material

In a preferred embodiment, microfibrillated cellulose is prepared according to a process comprising the steps of: microfibrillating a fibrous substrate comprising cellulose in an aqueous environment by milling in the presence of a milling medium, which is removed after milling is completed, wherein milling is performed in a tower mill or a screen mill, and wherein milling is performed in the absence of a millable inorganic particulate material.

A stirred media mill consists of a rotating impeller that imparts kinetic energy to small grinding media beads that grind material via a combination of shear, compression and impact forces. A variety of milling apparatuses can be used to produce MFC by the methods disclosed herein, including, for example, tower mills, screen mills, or stirred media chippers.

The abradable inorganic particulate material is a material that will be abraded in the presence of an abrasive medium.

The particulate grinding media may be a natural or synthetic material. The grinding media may, for example, comprise spheres, beads or pills of any hard mineral, ceramic or metallic material. Such materials may include, for example, alumina, zirconia, zirconium silicate, aluminum silicate, or mullite-rich materials produced by calcining kaolinite clay at a temperature in the range of about 1300 ℃ to about 1800 ℃. For example, in some embodiments, the first and second substrates, Grinding media are preferred. Alternatively, natural sand particles having a suitable particle size may be used.

In general, the type and particle size of the grinding media to be selected for use in the present invention may depend on the characteristics, such as, for example, the particle size and chemical composition of the feed suspension of the material to be ground. Preferably, the particulate grinding media comprises particles having an average diameter in the range of about 0.5mm to about 6 mm. In one embodiment, the particles have an average diameter of at least about 3 mm.

The grinding media may comprise particles having a specific gravity of at least about 2.5. The grinding media may comprise particles having a specific gravity of at least about 3, or at least about 4, or at least about 5, or at least about 6.

The grinding medium (or media) may be present in an amount up to about 70% by volume of the charge. The grinding media may be present in an amount of at least about 10% by volume of the charge, such as 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 can be microfibrillated to obtain microfibrillated cellulose having a d-infinity as measured by laser light scattering ranging from about 5 μm to about 500 μm.

The fibrous substrate comprising cellulose may be microfibrillated to obtain a fibrous substrate having the following d ₅₀ Is a microfibrillated cellulose of (a): equal to or less than about 400 μm, such as equal to or less than about 300 μm, or equal to or less than about 200 μm, or equal to or less than about 150 μm, or equal to or less than about 125 μm, or equal to or less than about 100 μm, or equal to or less than about 90 μm, or equal to or less than about 80 μm, or equal to or less than about 70 μm, or equal to or less than about 60 μm, or equal to or less than about 50 μm, or equal to or less than about 40 μm, or equal to or less than about 30 μm, or equal to or less than about 20 μm, or equal to or less than about 10 μm.

The fibrous substrate comprising cellulose may be microfibrillated to obtain microfibrillated cellulose having a modal fiber particle size in the range of about 0.1 μm to 500 μm. The fibrous substrate comprising cellulose may be microfibrillated in the presence of inorganic particulate material to obtain microfibrillated cellulose having the following modal fiber particle size: at least about 0.5 μm, such as at least about 10 μm, or at least about 50 μm, or at least about 100 μm, or at least about 150 μm, or at least about 200 μm, or at least about 300 μm, or at least about 400 μm.

The fibrous substrate comprising cellulose may be microfibrillated to obtain microfibrillated cellulose having a fiber steepness as measured by Malvern of equal to or greater than about 10. The fiber steepness (i.e., steepness of the fiber particle size distribution) is determined by the following formula:

Steepness=100× (d ₃₀ /d ₇₀ )

The microfibrillated cellulose may have a fiber steepness equal to or less than about 100. The microfibrillated cellulose may have a fiber steepness of 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 fiber steepness of about 20 to about 50, or about 25 to about 40, or about 25 to about 35, or about 30 to about 40. In embodiments, the preferred steepness range is about 20 to about 50.

In one embodiment, the milling vessel is a tower mill. The tower mill may include a stationary zone above one or more grinding zones. The quiescent zone is the zone located toward the top of the interior of the tower mill in which little or no grinding occurs and which contains microfibrillated cellulose and inorganic particulate material. The quiescent zone is the region in which grinding media particles settle into one or more grinding zones of the tower mill.

The tower mill may include a classifier above one or more grinding zones. In an embodiment, the classifier is mounted on top and positioned adjacent to the quiescent zone. The classifier may be a hydrocyclone.

The tower mill may include a screen above one or more grinding zones. In embodiments, the screen is positioned adjacent to the quiescent zone and/or classifier. The screen may be sized to separate the grinding media from the aqueous suspension of the product comprising microfibrillated cellulose and enhance settling of the grinding media.

In another embodiment, microfibrillated cellulose may be prepared in a stirred media crumb machine. A stirred media mill consists of a rotating impeller that imparts kinetic energy to small grinding media beads that grind material by a combination of shear, compression and impact forces. A variety of milling apparatuses can be used to produce MFC by the methods disclosed herein, including, for example, tower mills, screen mills, or stirred media chippers.

In embodiments, the milling is performed under plug flow conditions. Under plug flow conditions, the flow through the column is such that mixing of the abrasive material through the column is limited. 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. Thus, in practice, the grinding zone in a tower mill may be considered to include one or more grinding zones having a characteristic viscosity. Those skilled in the art will appreciate that there is no apparent boundary between adjacent grinding zones in terms of viscosity.

In one embodiment, water is added to the mill near the top of a stationary zone or classifier or screen above the one or more milling zones to reduce the viscosity of the aqueous suspension comprising microfibrillated cellulose in these zones in the mill. It has been found that by diluting the product microfibrillated cellulose at this point in the mill, the prevention of carrying of the grinding media to the rest area and/or classifier and/or screen is improved. In addition, limited mixing through the column allows for treatment at the lower portion of the column at higher solids and dilution at the top, with limited reflux of dilution water to the lower portion of the column into one or more grinding zones. Any suitable amount of water effective to dilute the viscosity of the aqueous suspension of the product comprising microfibrillated cellulose may be added. The water may be added continuously during the milling process, or periodically, or aperiodically.

In another embodiment, water may be added to the one or more grinding zones via one or more water injection points located along the length of the tower mill, or each water injection point may be located at a position corresponding to the one or more grinding zones. Advantageously, the ability to add water at various points along the tower allows for further adjustment of the grinding conditions at any or all locations along the mill.

The tower mill may include a vertical impeller shaft equipped with a series of impeller rotor disks throughout its length. The action of the impeller rotor disk creates a series of discrete grinding zones throughout the mill.

In another embodiment, the milling is performed in a screening mill (preferably a stirred media chipper). The screening mill may include one or more screens having a nominal pore size of at least about 250 μm, for example, the one or more screens may have a nominal pore size of at least about 300 μm, or at least about 350 μm, or at least about 400 μm, or at least about 450 μm, or at least about 500 μm, or at least about 550 μm, or at least about 600 μm, or at least about 650 μm, or at least about 700 μm, or at least about 750 μm, or at least about 800 μm, or at least about 850 μm, or at least about 900 μm, or at least about 1000 μm.

The screen sizes just mentioned above are applicable to the tower mill embodiments described above.

As described above, the grinding is performed in the presence of a grinding medium. In one embodiment, the grinding media is a coarse media comprising particles having an average diameter in the range of about 1mm to about 6mm, such as about 2mm, or about 3mm, or about 4mm, or about 5 mm.

In another embodiment, the grinding media has a specific gravity of at least about 2.5, such as at least about 3, or at least about 3.5, or at least about 4.0, or at least about 4.5, or at least about 5.0, or at least about 5.5, or at least about 6.0.

As noted above, the amount of grinding medium (or media) may be up to about 70% by volume of the charge. The grinding media may be present in an amount of at least about 10% by volume of the charge, such as 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.

In one embodiment, the grinding media is present in an amount of about 50% by volume of the charge.

By "charge" is meant a composition that is added as a feed to the mill vessel. The charge comprises water, grinding media, fibrous substrate comprising cellulose, and any other optional additives (except as described herein).

The use of relatively coarse and/or dense media has the advantage of increasing (i.e., faster) deposition rates and reducing media carryover through the quiescent zone and/or classifier and/or screen.

Another advantage of using a relatively coarse screen is that a relatively coarse or dense grinding medium may be used in the microfibrillation step. Furthermore, the use of a relatively coarse screen (i.e., having a nominal pore size of at least about 250 μm) allows the relatively high solids content product to be treated and removed from the mill, which allows the relatively high solids content feed (including fibrous substrates comprising cellulose and inorganic particulate material) to be treated in an economically viable manner. As discussed below, it has been found that a feed with a high initial solids content is desirable in terms of energy sufficiency. Furthermore, it was found that the product produced at a lower solids content (at a given energy) had a coarser particle size distribution.

According to one embodiment, the fibrous substrate comprising cellulose is present in an aqueous environment at an initial solids content of at least about 1% by weight. The fibrous substrate comprising cellulose may be present in the aqueous environment at an initial solids content of at least about 2wt%, for example at least about 3wt% or at least about 4 wt%. Typically, the initial solids content will not exceed about 10wt%.

In another embodiment, milling is performed in a cascade of milling vessels, one or more of which may include one or more milling zones. For example, a fibrous substrate comprising cellulose may be milled in a cascade of two or more milling vessels, such as a cascade of three or more milling vessels, or a cascade of four or more milling vessels, or a cascade of five or more milling vessels, or a cascade of six or more milling vessels, or a cascade of seven or more milling vessels, or a cascade of eight or more milling vessels, or a cascade of nine or more milling vessels in series, or a cascade of up to ten milling vessels. The cascade of milling vessels may be operably connected in series or parallel or a combination of series and parallel. The output and/or input of one or more milling vessels in the cascade may be subjected to one or more screening steps and/or one or more classification steps.

The total energy consumed in the microfibrillation process may be equally distributed in each grinding vessel in the cascade. Alternatively, the energy input may vary between some or all of the milling vessels in the cascade.

Those skilled in the art will appreciate that the energy consumed by each vessel may vary from vessel to vessel in the cascade, depending on the amount of fibrous substrate being microfibrillated in each vessel, and optionally the grinding speed in each vessel, the duration of grinding in each vessel, and the type of grinding media in each vessel. The milling conditions may be changed in each vessel of the cascade so as to control the particle size distribution of the microfibrillated cellulose.

In one embodiment, the milling is performed in a closed circuit. In another embodiment, milling is performed in an open circuit.

Since the suspension of the material to be ground may have a relatively high viscosity, it may be preferable to add a suitable dispersant to the suspension prior to grinding. The dispersant may be, for example, a water-soluble condensed phosphate, polysilicic acid or a salt thereof, or a water-soluble salt of a polyelectrolyte such as poly (acrylic acid) or poly (methacrylic acid) having a number average molecular weight of no more than 80,000. The amount of dispersant used will typically be in the range of 0.1 to 2.0 wt% based on the dry weight of the inorganic particulate solid material. The suspension may suitably be milled at a temperature in the range 4 ℃ to 100 ℃.

Other additives that may be included during the microfibrillation step include: carboxymethyl cellulose, amphoteric carboxymethyl cellulose, oxidizing agents, 2, 6-tetramethylpiperidin-1-oxyl (TEMPO), TEMPO derivatives and wood degrading enzymes.

The pH of the suspension of the material to be abraded may be about 7 or greater (i.e., alkaline), 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 the material to be abraded 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 the material to be ground can be adjusted by adding an appropriate amount of acid or base. Suitable bases include alkali metal hydroxides such as, for example, naOH. Other suitable bases are sodium carbonate and ammonia. Suitable acids include mineral acids such as hydrochloric acid and sulfuric acid, or organic acids. An exemplary acid is orthophosphoric acid.

Based on the total dry weight of the inorganic particulate filler, in a typical milling process to obtain the desired aqueous suspensionThe total energy input of the float composition may typically be between about 100 and 1500kwh t ^-1 Between them. The total energy input may be less than about 1000kWht ^-1 For example less than about 800kWht ^-1 Less than about 600kWht ^-1 Less than about 500kWht ^-1 Less than about 400kWht ^-1 Less than about 300kWht ^-1 Or less than about 200kWht ^-1 . Thus, the inventors have surprisingly found that when co-grinding cellulose pulp in the presence of inorganic particulate material, the cellulose pulp can be microfibrillated at relatively low energy input. It will be apparent that the total energy input per ton of dry fibers in the cellulosic containing fibrous substrate will be less than about 10,000kwht ^-1 For example less than about 9000kWht ^-1 Or less than about 8000kWht ^-1 Or less than about 7000kWht ^-1 Or less than about 6000kWht ^-1 Or less than about 5000kWht ^-1 For example less than about 4000kWht ^-1 Less than about 3000kWht ^-1 Less than about 2000kWht ^-1 Less than about 1500kWht ^-1 Less than about 1200kWht ^-1 Less than about 1000kWht ^-1 Or less than about 800kWhf ^-1 . The total energy input varies depending on the amount of dry fibers in the fibrous substrate being microfibrillated and the optional grinding speed and grinding duration.

Mechanical properties of microfibrillated cellulose

The redispersed microfibrillated cellulose has mechanical and/or physical properties that are relatively close to those of the microfibrillated cellulose prior to drying or at least partial drying.

The mechanical property may be any determinable mechanical property associated with microfibrillated cellulose. For example, the mechanical property may be a strength property, such as a tensile index. The tensile index may be measured using a tensile tester. Any suitable method and apparatus may be used provided that it is controlled to compare the tensile index of the microfibrillated cellulose before drying and after redispersion. For example, the comparison should be made at the same concentration of microfibrillated cellulose and any other additives or inorganic particulate material that may be present. The tensile index may be expressed in any suitable unit, such as, for example, nm/g or kNm/kg.

The physical property may be any determinable physical property associated with microfibrillated cellulose. For example, the physical property may be viscosity. The viscosity can be measured using a viscometer. Any suitable method and apparatus may be used provided that it is controlled to compare the viscosity of the microfibrillated cellulose before drying and after redispersion. For example, the comparison should be made at the same concentration of microfibrillated cellulose and any other additives or inorganic particulate material that may be present. In certain embodiments, the viscosity is a Brookfield viscosity in mPas.

In certain embodiments, substantially fully or partially dried microfibrillated cellulose is prepared according to the procedure of U.S. patent No. 10,001,644, which is incorporated herein by reference in its entirety.

In certain embodiments, the tensile index and/or viscosity of the redispersed microfibrillated cellulose is at least about 25% of the tensile index and/or viscosity of the aqueous composition of the microfibrillated cellulose prior to drying, e.g., at least about 30%, or at least about 35%, or at least about 40%, or at least about 45%, or at least about 50%, or at least about 55%, or at least about 60%, or at least about 65%, or at least about 70%, or at least about 75%, or at least about 80% of the tensile index and/or viscosity of the microfibrillated cellulose prior to drying.

In certain embodiments, the viscosity of the redispersed microfibrillated cellulose is at least about 25% of the viscosity of the aqueous composition of the microfibrillated cellulose prior to drying, e.g., at least about 30%, or at least about 35%, or at least about 40%, or at least about 45%, or at least about 50%, or at least about 55%, or at least about 60%, or at least about 65%, or at least about 70%, or at least about 75%, or at least about 80% of the viscosity of the microfibrillated cellulose prior to drying.

Radial flow impeller

Radial flow impellers are capable of producing moderate to high shear mixing of suspended solids in a solvent (e.g., water). Such radial flow impellers are exemplified by Cowles blades, wherein tip speeds of less than 20m/s are utilized, wherein the impeller (D) to tank (T) diameter is less than 0.5, i.e. D/T <0.5.

Rotor-stator mixer

The rotor-stator imparts a higher shear rate than the radial impeller when mixing suspended solids in a solvent (e.g., water). Rotor-stator devices, e.g. byThe mixer is exemplified. Rotor-stator mixers typically have>Tip speeds of 20m/s and in situ adjustable rotor-stator gap widths of 0.1mm, 0.2mm, 0.3mm, etc., depending on the desired shear level and physical constraints of the design.

A hydrocyclone.

Hydrocyclones are devices for separating or classifying particles in a liquid suspension based on their ratio of centripetal force to fluid resistance. Generally, a hydrocyclone includes a base end and a vertex end and a separation chamber between the base end and the vertex end, the separation chamber having an elongate shape. At least one inlet for feeding the cellulose-containing suspension to be cleaned is arranged at the base end, at least one downflow outlet is arranged at the apex end, and at least one overflow outlet is arranged at the base end. In the present apparatus, the inlet, which is fed tangentially to the separation chamber, is divided into an accept portion and a reject portion. The accept portion is sent forward in the system for downstream processing. The reject fraction from the hydrocyclone underflow stage is returned to the rotor-stator mixer for further processing. The suspension is injected into the hydrocyclone in such a way as to generate a vortex. Depending on the relative densities of the phases, centrifugal acceleration causes the dispersed phase to move away from or toward the central core of the vortex. Hydrocyclones or cyclones for separating particles from a liquid mixture by using centripetal force are known. By injecting the liquid mixture into the vessel and rotating therein, the heavy or large particles move outwards towards the wall of the vessel due to centripetal forces and spiral downwards to the bottom of the vessel. The light components move towards the centre of the vessel and can be discharged via the outlet. This ratio is higher for coarse particles and lower for fine particles.

The vortex finder to sleeve ratio versus Malvern D is presented in FIGS. 13, 14, 15 and 16, respectively ₅₀ 、>300 μm fraction, percent fibrillation, and total solids. The trickle and feed streams are very similar to each other in terms of particle size distribution. The downflow stream is a more concentrated stream (i.e., more than 1.5 times the total solids concentration of the coarser overflow as depicted in FIG. 6 (overflow D ₅₀ More than 1.5 times).

Examples

Example 1: redispersion of microfibrillated cellulose: FLT index (tensile index) test

By using what is calledIs used to achieve laboratory scale dispersion of microfibrillated cellulose and inorganic particulate material composite cake material into a slurry. These steps are performed to thoroughly disperse the pressed cake into a uniform slurry so that it can be used for handsheet evaluation or quality control characterization.

An empty, clean balance pot (poise pot) was placed on the balance and the tare was measured. The FiberLean cake material was weighed into a balance tank. Based on mass in the tank, water was used to dilute to 2% fiber solids (about 4% total solids for 50% mfc cake). Soaking for 1 hour. At the position ofMix for 1 minute at full power. The total solids content was re-measured.

Is in accordance with ISO9001.

Laboratory procedure for making sheets and measuring their strength on custom-made filtration devices with pure microfibrillated cellulose or a composite sample of microfibrillated cellulose and inorganic particulate material.

Tensile index test: microfibrillated cellulose FiberLean product at 20% pulp percent (POP) and above. Microfibrillated cellulose and inorganic particulate material composite was adjusted to 20% POP by adding filler. By dilution on a filter apparatusThe microfibrillated cellulose and inorganic particulate material slurry is dewatered, then pressed and treated with RapidThe dryer dried to make a sheet of approximately 220 gsm. The tests that need to be performed on the sheet are gsm and tensile strength.

A method for microfibrillating a composite of cellulose and inorganic particulate material. The% solids and POP of the samples were recorded (see procedure alone). If the POP% is greater than 20%, the same type of mineral as in the microfibrillated cellulose and inorganic particulate material composite product is added to bring it to 20% (see separate procedure for microfibrillated cellulose and inorganic particulate material composite handsheet). If POP% is between 18% and 20%, it will be necessary to apply correction factors to the result. About 4.4g dry weight of sample (44 g for 10% solids sample) was taken and diluted with water to 400mls to obtain about 1.1% total solids (0.22% fiber solids), which would result in a 220gsm sheet on a 15.9cm diameter exposed screen of the apparatus. Stirring was sufficient to ensure good dispersion. 1ml of a 0.2wt% polydadmac solution was added to the diluted sample and stirred well. If the drainage is very slow, this can be increased to 5ml. The top section is removed from the filter unit and the filter paper is placed on top of the screen. The filter paper is wetted with the wash bottle and any bubbles that form are pushed to the edge of the paper. Ensure that the drain valve at the bottom of the unit is closed and then the vibration is turned on to adhere the filter paper to the screen, ensuring that it sits flush without wrinkles. The top section is placed back and clamped in place, then the vacuum is turned off and the drain valve is opened to release the vacuum and drain. The drain valve is closed and then the sample is poured into the top section above the end of a spatula or the like to ensure uniform distribution. The sample was prevented from being poured directly onto the filter paper. The sample was allowed to stand for a few seconds, then the vacuum was turned on and the sample was filtered. This should take about 2 minutes. Wait 1 minute, then turn off the vacuum supply and open the drain valve to release the vacuum and remove the water from the unit. The top section of the unit is loosened and removed. The filter paper and the filtered sample were carefully removed together. The sample and filter paper were placed in Rapid And the carrier plate. Will Rapid->A sheet-like cover was placed over the sample. The sample and the lid are placed into Rapid +.>Drying in a dryer and at-0.9 bar or-26.5 inches Hg pressure for 7 minutes would require an extended time in the dryer unit if the vacuum pressure was low. The dried samples were separated from the filter paper and lid and treated at 23 ℃ +/-2 ℃ and 50% rh +/-5% for a minimum of 20 minutes.

The sheet (4 d.p.) was weighed to determine its gsm. The samples were cut into 15mm wide strips using a cutter. A minimum of 5 strips is required. The force required to break each strip with a tensile tester was measured in newtons. The tensile index of each sample was calculated using the Excel spreadsheet provided, as in section 6.

Calculate in m ² (A) Sheet area in units = 0.0001x pi x (diameter in cm) ² 4 (0.0199 for a 15.9cm diameter sheet). Sheet gsm = sheet mass in grams/a. Mass of slurry required = 100x 220x a/TS (TS = total solids%). Microfibrillated cellulose and inorganic particulate material composite tensile index kN m kg ^-1 (T)＝1000x F _m /(W x gsm), where F _m Maximum tension (N). W = bar width (15 mm of standard), gsm = gsm of sample. The average tensile index and standard deviation of the 5 measurements in each case were recorded. If POP% is less than 20%, it should be based on T _{Correction of} ＝T/[1-7.6*(0.2-POP％)]The tensile index was corrected.

Equipment inspection and calibration. The calibration and procedure followed those in the following standards: paper test-T220 sp-96.

Example 2: and (5) measuring viscosity. Brookfield viscosity testing was performed on a 1.0% fiber solids microfibrillated cellulose and inorganic particulate material composite sample using a blade Spindle (Vane Spindle). The composite sample of microfibrillated cellulose and inorganic particulate material based on kaolin and calcium carbonate can be measured in the following manner.

A viscometer: brookfield YR-1 or R.V. or similar instruments comprising a blade spindle.

A method for microfibrillating a composite of cellulose and inorganic particulate material. By vigorously shaking the container and contents, it is ensured that the slurry is uniform. At least 100ml was dug out using a palette knife and transferred to polystyrene cans. Stirring thoroughly with spatula (or spindle). The speed of the viscometer is set to the desired speed (10 rpm) and turned on. The spindle was rotated for 30 seconds. The viscometer readings, speed and blade count are noted and recorded.

Viscosity measurements were made at 1.0% fiber solids content. The slurry was thoroughly mixed by vigorously shaking the container and contents. A representative portion (about 100 g) of the microfibrillated cellulose and inorganic particulate material composite slurry was transferred to a tar coated polystyrene tank. The weight of the slurry was weighed and recorded. The water addition required to achieve a fiber solids content of 1.0% was calculated. Deionized water was added to give the required volume of solids for the specified test. The viscosity of the microfibrillated cellulose and inorganic particulate material composite is expressed in millipascal-seconds (mpa.s) and calculated according to the chart provided according to the manufacturer's instructions. The standard deviation of the test paste with a viscosity of 500mpa.s was 5.

The fiber solids content was calculated.

FS＝TS x POP/10

Where FS =% fiber solids. TS = total solids%. POP = product pulp%.

And (5) dilution calculation. The water volume required to give a dilution of D mass% is calculated as follows:

where V = required water volume

I = initial fiber solids wt%

R = desired fiber solids wt%

W = weight of slurry content in the tank.

Dilution calculation-Total solids concentration

The weight of minerals required to give a dilution of D mass% is calculated as follows:

M＝(I–R)x W/R

where M = required mineral weight

I = initial total solids wt%

R = wt% of total solids desired

W = weight of fibrilean slurry contents in the tank.

Minerals are the product used in the composite slurry content of cellulosic fibers and inorganic particulate material. (calcium carbonate or kaolin).

The total solids% is obtained after drying the microfibrillated cellulose and inorganic particulate material composite slurry at 80 to 100 ℃.

The product pulp (POP)% was obtained after combustion of the "total solids" sample at 450 ℃ (kaolin at 950 ℃).

In the following comparative examples and examples, all experiments used a dry powdered mixture of ground calcium carbonate (60% <2 μm) and bleached softwood kraft pulp. The total consistency is nominally 75 wt% and the pulp consistency of the dried product is 50 wt%.

A dry powdered mixture of heavy calcium carbonate (60% <2 μm) and bleached softwood kraft pulp was mixed with water using different commercial equipment under optimal conditions as specified by its manufacturer. The combination of equipment was developed to achieve a process of substantially uniform suspension.

Analysis of the redispersed microfibrillated cellulose composition included: tensile (FLT) strength, as described in example 1; and apparent viscosity using a Brookfield blade spindle viscometer, as described in example 2. The particle size distribution was measured by light scattering on Malvern Insitec L as described in example 3.

Particle size analyzer: malvern Insitec L

A method for microfibrillating a composite of cellulose and inorganic particulate material.

By vigorously shaking the container and contents, it is ensured that the slurry is uniform.

The Malvern Insite unit was opened and the water in the recirculation beaker was replaced with clean room temperature.+ -. 5 ℃ tap water (800 ml to 900 ml). The recirculation pump was started and the pump speed was ensured to be set at 2500RPM.

The Malvern "RTSIzer" software program on the computer desktop was opened and background measurements were made on tap water.

After notification of the effective background measurement, granularity data collection is performed via a "new granularity history" icon.

The slurry was added to the recirculation beaker using a pipette until a transfer between 40% and 60% was reached.

The instrument was allowed to continue for an additional 1 minute measurement at 40% to 60% of delivery.

The mean value of the particle size history data over a 1 minute time period was calculated using the "Malvern RTSizer" software function and the mean particle size distribution parameters were recorded.

After data collection, the system was cleaned with tap water and deionized water to remove any residue on the window test cell.

Example 4: control test 1.

The dry powdered mixture was redispersed using a system consisting of two Cowles blade (saw tooth impeller) mixers in series with a high shear rotor-stator inline mixer. The control system is shown in fig. 2 below.

The standard conditions for operating the equipment were 100% speed of 3.5% total solids (for 50% POP) and BVG shear-master. The flow is kept at 12m ³ /h to maximize residence time in the tank.

As seen in fig. 4, the slurry failed the primary test parameters (tensile strength and apparent viscosity) even after 2400kWh/DMT MFC specific energy input and 18 passes through the system.

Example 5: control test 2.

A pilot scale 12"sprout refiner was used to evaluate redispersion of the dry powdered mixture. This is commonly used in the paper industry for pulp refining. The powder was mixed with water in a Denver pulper and then recycled around a 12"sprout refiner and holding tank. The best conditions were a strength of 0.1J/m, MFC per Cheng Jingte energy input of 20kWh/DMT, 1320RPM speed and disk design to give a cutting edge length of 1.111 km/rev. The total solids concentration was 9%. Pulp percentage (POP) was 50%.

The results are shown in fig. 5. The main mass parameters (tensile index and apparent viscosity) recovered after 15 strokes and a MFC total specific energy input of 2840 kWh/DMT. Unfortunately, this limits the process to batch operation (batch operation) and the high energy consumption makes it economically unfeasible.

Example 6: control test 3.

UsingSM180 evaluates redispersion of the dry powdered mixture. This is commonly used in the asphalt industry to uniformly mix additives into the mixture and also as a slurry fluffer. The slurry was mixed in a small vessel using a hand-held mixer, and the mixed slurry was contained in a holding tank. Holding tank and->SM180 is in a recirculating connection. According to a series of experiments, -w3f.s.gl reduction tool (reverse cut groove pattern), 5400RPM, gap setting of 0.1mm and total solids concentration of 9%, the selected conditions were determined to be optimal. POP is 50%.

The results are shown in fig. 6. The main mass parameters (tensile strength and viscosity) recovered after 18 strokes and MFC total specific energy input of 1808 kWh/DMT. Unfortunately, this also limits it to batch operations, which are costly to both capital and operating.

Example 7: control test 4.

Using Megatrex OyTo evaluate the redispersion of the dry powdered mixture. This is commonly used in the paper industry to redisperse broke (waste from paper machinesMaterial) and also for disintegrating coarse mineral matter. Selecting the optimal conditions: a rotational speed of 2000RPM and a flow rate of 55 kg/min. A standard 6-ring design was used. The counter rotation of each segment produces a very high shear rate. Throughput is limited by the high motor power requirements that create such shear rates in the fluid.

The results are shown in fig. 7. The main mass parameters (tensile strength and apparent viscosity) were higher than the targets in run 3 after MFC total specific energy input of 1000kWh/DMT using 9% total solids. After trip 2, they appear to be close to the target of MFC total specific energy input at 9% total solids with 700 kWh/DMT.

However, as shown in fig. 8, in continuous operation, both passes are not sufficient to completely redisperse the product to the same quality parameters of the never-dried slurry. The system seems not to be viable with energy consumption and corresponding quality parameters.Is a high capital cost equipment with significantly large power consumption requirements per pass at a fixed throughput.

Example 8: control test 5.

Will be discussed after the project team discussion with Megatrex Reverse rotation ring upgrades. The existing 6-ring design (shown in fig. 9A on the left) was redesigned to include more rods to maximize contact with the fiber/mineral particles in the slurry, and two more rings to extend the shearing effect between the rings (as shown in fig. 9B on the right).

The dry powdered mixture was also pre-wetted in a mixing tank with a medium shear head impeller to simulate the effect of using a Cowles blade mixer. FLT results improved much, as seen in fig. 10 below, but were still insufficient. The two passes add significantly to the capital and operating costs of the process, as seen in fig. 11.

Example 9: test examples of the present invention.

Depicted in the flow chartThe system is intended to be improved by feeding partially wetted and suspended fibers into a high shear counter-rotating chamberIs not limited to the above-described embodiments. />The SM180 and Cowles blade mixer act as a low cost prewetting device, while the hydrocyclone improves the efficiency of the prewetting stage by separating the unwetted components from the flow stream. The fibre-mineral component that has been wetted and disintegrated proceeds to +.>In the high shear zone, as shown in fig. 12.

The system of example 9: the test sheet demonstrates a process of redispersing dry powdered MFC using a combination of equipment that results in lower capital and operating costs than when used alone. The properties are comparable in terms of tensile strength and apparent viscosity, as shown in table 2 below.

TABLE 2

The system of example 9: trial 1 combines low capital equipment and relatively high capital equipment in order to maximize the efficiency of redispersing the powdered mixture while minimizing the overall cost. Wetting stageThe closed-loop operation of SM180 is allowed to be +.>The slurry was previously subjected to low energy, high throughput, cost effective processing. In single pass operation, the reduction ofIs used for (1)Power consumption requirements and throughput limitations that result in very high shear rates. Thus, combining the equipment together provides an overall cost-effective treatment of dry powdered MFC to produce a slurry at the customer site that has the same tensile strength characteristics as never-dried slurry.

All references cited in this application are incorporated herein by reference in their entirety.

All patents, patent applications, and publications cited herein are hereby incorporated by reference in their entirety. The disclosures of these publications are hereby incorporated by reference in their entirety into this application. The disclosures of each patent, patent application, publication, and accession number cited herein are hereby incorporated by reference in their entirety.

It is to be understood that while the invention has been described in conjunction with the specific embodiments thereof, the foregoing description is intended to illustrate and not limit the scope of the invention, which is defined by the scope of the appended claims. Other aspects, advantages, and modifications are within the scope of the following claims.

The foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the present invention. The present disclosure may be readily applied to other types of methods. Furthermore, the description of the embodiments of the invention is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art.

The various embodiments described in this specification can be combined to provide further embodiments. Aspects of the embodiments can be modified, if necessary, to employ concepts of the various patents, applications and publications to provide yet other embodiments.

Although the present disclosure has been disclosed with reference to various embodiments, other embodiments and variations of those embodiments can be devised by others skilled in the art without departing from the true spirit and scope of the disclosure. It is intended that the following claims be interpreted to embrace all such embodiments and equivalent variations. The foregoing written description is considered to be sufficient to enable one skilled in the art to practice the embodiments.

The foregoing description and examples detail certain embodiments and describe the best mode contemplated by the inventors. It should be understood, however, that the embodiments may be practiced in various ways, regardless of the degree of detail in the foregoing description, and should be interpreted in accordance with the claims appended hereto and any equivalents thereof.

Claims

1. A process for redispersing a substantially dry or partially dry and optionally powdered composition comprising microfibrillated cellulose and optionally one or more inorganic particulate materials, the process comprising the steps of:

2. The method of claim 1, further comprising: a hydrocyclone subsequent to the rotor-stator apparatus, wherein the hydrocyclone comprises an inlet, a first hydrocyclone outlet and a second hydrocyclone outlet; wherein the hydrocyclone separates the substantially uniform suspension into (i) a sheared fine particle stream and (ii) an under-sheared coarse particle stream; pumping the undershot coarse particle stream from the first hydrocyclone outlet to the second inlet of the mixing apparatus to permit recirculation of the undershot coarse particle stream and remixing with the flowable slurry in the mixing tank; flowing the fine particle stream from the second outlet of the hydrocyclone to an inlet of the second stage high shear device selected from a rotor-rotor device, a second high shear rotor-stator device, a colloid mill, an ultra fine grinding device, or a refiner, wherein the rotor-rotor device comprises a counter-rotating ring for subjecting the substantially uniform suspension to additional high shear processing.

3. The method of claim 1 or claim 2, wherein the composition of microfibrillated cellulose further comprises one or more inorganic particulate materials.

4. The method of claim 1 or claim 2, wherein the substantially dry or partially dry composition comprising microfibrillated cellulose and optionally one or more inorganic particulate materials is powdered.

5. A method according to claim 3, wherein the substantially dry or partially dry composition comprising microfibrillated cellulose and one or more inorganic particulate materials is powdered.

6. The method of claim 1 or claim 2, wherein the method is a continuous process, a semi-continuous process, or a batch process.

7. The method of claim 3, wherein the method is a continuous process, a semi-continuous process, or a batch process.

8. The method of claim 1 or claim 2, wherein the dispersion is water.

9. A method according to claim 3, wherein the dispersion is water.

10. The method of claim 1 or claim 2, wherein the liquid composition of microfibrillated cellulose is about 0.5wt% to about 2.5wt% fiber solids.

11. The method of claim 3, wherein the liquid composition of microfibrillated cellulose is about 0.5wt% to about 2.5wt% fiber solids.

12. The method of claim 1 or claim 2, wherein the liquid composition of microfibrillated cellulose is about 0.75wt% fiber solids.

13. The method of claim 3, wherein the liquid composition of microfibrillated cellulose is about 0.75wt% fiber solids.

14. The method of claim 1 or claim 2, wherein the liquid composition of microfibrillated cellulose is about 1wt% fiber solids.

15. The method of claim 3, wherein the liquid composition of microfibrillated cellulose is about 1wt% fiber solids.

16. The method of claim 1 or claim 2, wherein the liquid composition of microfibrillated cellulose is about 1.25wt% fiber solids.

17. The method of claim 3, wherein the liquid composition of microfibrillated cellulose is about 1.25wt% fiber solids.

18. The method of claim 1 or claim 2, wherein the liquid composition of microfibrillated cellulose is about 1.5wt% fiber solids.

19. The method of claim 3, wherein the liquid composition of microfibrillated cellulose is about 1.5wt% fiber solids.

20. The method of claim 1 or claim 2, wherein the liquid composition of microfibrillated cellulose is about 1.75wt% fiber solids.

21. The method of claim 3, wherein the liquid composition of microfibrillated cellulose is about 1.75wt% fiber solids.

22. The method of claim 1 or claim 2, wherein the liquid composition of microfibrillated cellulose is about 2wt% fiber solids.

23. The method of claim 3, wherein the liquid composition of microfibrillated cellulose is about 2wt% fiber solids.

24. The method of claim 1 or claim 2, wherein the liquid composition of microfibrillated cellulose is about 2.5wt% fiber solids.

25. The method of claim 3, wherein the liquid composition of microfibrillated cellulose is about 2.5wt% fiber solids.

26. The method of claim 1 or claim 2, wherein the liquid composition of microfibrillated cellulose is about 3wt% fiber solids.

27. The method of claim 3, wherein the liquid composition of microfibrillated cellulose is about 3wt% fiber solids.

28. The method of claim 1 or claim 2, wherein the liquid composition of microfibrillated cellulose is about 4wt% fiber solids.

29. The method of claim 3, wherein the liquid composition of microfibrillated cellulose is about 4wt% fiber solids.

30. The method of claim 1 or claim 2, wherein the liquid composition of microfibrillated cellulose is about 5wt% fiber solids.

31. The method of claim 3, wherein the liquid composition of microfibrillated cellulose is about 5wt% fiber solids.

32. The method of claim 1 or claim 2, wherein the microfibrillated cellulose can be prepared with chemical pulp, or chemi-thermo-mechanical pulp, or recycled pulp, or broke pulp, or paper mill waste streams, or waste from paper mills, or a combination thereof.

33. The method of claim 3, wherein the microfibrillated cellulose can be prepared with chemical pulp, or chemi-thermo-mechanical pulp, or recycled pulp, or broke pulp, or paper mill waste streams, or waste from paper mills, or a combination thereof.

34. The method of claim 3, wherein the one or more inorganic particulate materials comprise alkaline earth metal carbonates or sulfates, hydrous kaolinite group clays, anhydrous (calcined) kaolinite group clays, talc, mica, perlite, or diatomaceous earth, or combinations thereof.

35. The method of claim 3, wherein the one or more inorganic particulate materials can comprise calcium carbonate, magnesium carbonate, dolomite, bentonite, gypsum, kaolin, halloysite, ball clay, metakaolin, fully calcined kaolin, or a combination thereof.

36. A method according to claim 3, wherein the one or more inorganic particulate materials comprise calcium carbonate.

37. A method according to claim 3, wherein the one or more inorganic particulate materials comprise kaolin.

38. A method according to claim 3, wherein the one or more inorganic particulate materials comprise kaolin and calcium carbonate.

39. The method of claim 36, wherein the calcium carbonate is precipitated calcium carbonate, ground calcium carbonate, or a combination thereof.

40. The method of claim 36, wherein the calcium carbonate comprises a calcite, aragonite or vaterite structure.

41. The method of claim 36, wherein the calcium carbonate is in the form of scalenohedral or rhombohedral crystals.

42. The method according to claim 37, wherein the kaolin is ultraplaty kaolin.

43. The method of claim 36, wherein at least about 50wt% of the calcium carbonate has an equivalent spherical diameter of less than about 2 μιη.

44. The method of claim 37, wherein at least about 50wt% of the kaolin has an equivalent spherical diameter of less than about 2 μm.

45. The method of claim 36, wherein the ground calcium carbonate is limestone or marble.

46. A method according to any one of claims 1 to 3, wherein the end use comprises a method of making paper or coated paper, paint, coating, building material, ceiling tile, composite material or barrier coating.

47. A method according to claim 1 or claim 2, wherein the first stage high shear rotor-stator device is selected from the group consisting ofA mill, colloid mill, ultra-fine grinding equipment, or refiner.

48. A method according to claim 3, wherein the first stage high shear rotor-stator device is selected from the group consisting ofA mill, colloid mill, ultra-fine grinding equipment, or refiner.

49. The method of claim 1 or claim 2, wherein the second stage high shear rotor-stator device is selected from the group consisting of a rotor-rotor device,A mill, colloid mill, ultra-fine grinding equipment, or refiner.

50. A method according to claim 3, wherein the second stage high shear rotor-stator device is selected from the group consisting of a rotor-rotor device, A mill, colloid mill, ultra-fine grinding equipment, or refiner.

51. A transportable system (1) for redispersing a substantially dry or partially dry and optionally powdered composition comprising microfibrillated cellulose and optionally one or more inorganic particulate materials in a liquid medium to form a liquid composition, comprising:

a mixing tank (20) comprising a mixing device (21) comprising a shear head impeller (22); wherein the mixing tank (20) comprises a first mixing tank inlet (24) for receiving a liquid slurry of microfibrillated cellulose and optionally one or more inorganic particulate materials and a mixing tank outlet (26) comprising a pump (27); a first stage high shear rotor-stator device (30) comprising a rotor-stator inlet (31) and a rotor-stator outlet (32) connected to the mixing tank outlet (26); a second stage high shear device (50) selected from the group consisting of a rotor-rotor device,A mill, colloid mill, ultra-fine grinding apparatus or refiner; wherein the second stage high shear device (50) comprises a rotor-stator connected to the first stage high shear deviceAn outlet second stage shear inlet (52) and an outlet (53); and a reservoir (60) comprising a reservoir inlet (61) connected to the rotor-rotor outlet (53).

52. The system of claim 51, further comprising a hydrocyclone (40) comprising a hydrocyclone inlet (41), a first hydrocyclone outlet (42) and a second hydrocyclone outlet (43); wherein the hydrocyclone inlet (41) is connected to the rotor-stator outlet (32) of the rotor-stator apparatus; wherein the hydrocyclone separates the slurry of microfibrillated cellulose and optionally one or more inorganic particulate materials into a sheared fine particle stream and an under sheared coarse particle stream, wherein the first hydrocyclone outlet (42) is connected to the second inlet (25) of the mixing tank (20) for returning the under sheared coarse particle stream to the mixing tank (20); wherein the fine particle stream flows through the second hydrocyclone outlet (43) to the second stage high shear inlet (52).

53. The system of claim 51 or claim 52, wherein the substantially dry or partially dry and optionally powdered composition comprising microfibrillated cellulose further comprises one or more inorganic particulate materials.

54. The system of claim 51 or claim 52, wherein the substantially dry or partially dry and optionally powdered composition comprising microfibrillated cellulose further comprises one or more inorganic particulate materials, powdered.

55. The system of claim 53, wherein the substantially dry or partially dry and optionally powdered composition comprising microfibrillated cellulose further comprises one or more inorganic particulate materials, powdered.

56. The system of claim 51 or claim 52, wherein the liquid medium is water.

57. The system of claim 53, wherein the liquid medium is water.

58. The system of claim 51 or claim 52, wherein the liquid composition of microfibrillated cellulose is about 0.5wt% to about 5wt% fiber solids.

59. The system of claim 53, wherein the liquid composition of microfibrillated cellulose is about 0.5wt% to about 5wt% fiber solids.

60. The system of claim 50 or claim 52, wherein the liquid composition is about 0.75wt% fiber solids.

61. The system of claim 53, wherein the liquid composition is about 0.75% fiber solids by weight.

62. The system of claim 51 or claim 52, wherein the liquid composition is about 1wt% fiber solids.

63. The system of claim 53, wherein the liquid composition is about 1% fiber solids by weight.

64. The system of claim 51 or 52, wherein the liquid composition is about 1.25wt% fiber solids.

65. The system of claim 53, wherein the liquid composition is about 1.25wt% fiber solids.

66. The system of claim 51 or claim 52, wherein the liquid composition is about 1.5wt% fiber solids.

67. The system of claim 53, wherein the liquid composition is about 1.5% fiber solids by weight.

68. The system of claim 51 or claim 52, wherein the liquid composition is about 1.75wt% fiber solids.

69. The system of claim 53, wherein the liquid composition is about 1.75wt% fiber solids.

70. The system of claim 51 or claim 52, wherein the liquid composition is about 2wt% fiber solids.

71. The system of claim 53, wherein the liquid composition is about 2% fiber solids by weight.

72. The system of claim 51 or claim 52, wherein the liquid composition is about 2.5wt% fiber solids.

73. The system of claim 53, wherein the liquid composition is about 2.5wt% fiber solids.

74. The system of claim 51 or claim 52, wherein the liquid composition is about 3wt% fiber solids.

75. The system of claim 53, wherein the liquid composition is about 3% fiber solids by weight.

76. The system of claim 51 or claim 52, wherein the liquid composition is about 4wt% fiber solids.

77. The system of claim 53, wherein the liquid composition is about 4wt% fiber solids.

78. The system of claim 51 or claim 52, wherein the liquid composition is about 5wt% fiber solids.

79. The system of claim 53, wherein the liquid composition is about 5% fiber solids by weight.

80. The system of claim 51 or claim 52, wherein the microfibrillated cellulose can be prepared with chemical pulp, or chemimechanical pulp, or mechanical pulp, or recycled pulp, or broke pulp, or paper mill waste streams, or waste from paper mills, or a combination thereof.

81. The system of claim 53, wherein the microfibrillated cellulose can be prepared with chemical pulp, or chemi-thermo-mechanical pulp, or recycled pulp, or broke pulp, or paper mill waste streams, or waste from paper mills, or a combination thereof.

82. The system of claim 53, wherein the one or more inorganic particulate materials comprise an alkaline earth carbonate or sulfate, an hydrous kaolinite group clay, an anhydrous (calcined) kaolinite group clay, talc, mica, perlite, or diatomaceous earth, or a combination thereof.

83. The system of claim 53, wherein the one or more inorganic particulate materials can comprise calcium carbonate, magnesium carbonate, dolomite, gypsum, kaolin, halloysite, ball clay, metakaolin, fully calcined kaolin, or a combination thereof.

84. The system of claim 53, wherein the one or more inorganic particulate materials can comprise calcium carbonate.

85. The system of claim 53, wherein the one or more inorganic particulate materials can comprise kaolin.

86. The system of claim 53, wherein the one or more inorganic particulate materials can comprise kaolin and calcium carbonate.

87. The system of claim 84, wherein the calcium carbonate is precipitated calcium carbonate, ground calcium carbonate, or a combination thereof.

88. The system of claim 84, wherein the calcium carbonate comprises a calcite, aragonite or vaterite structure.

89. The system of claim 84, wherein the calcium carbonate is in the form of scalenohedral or rhombohedral crystals.

90. The system of claim 85, wherein the kaolin is ultraplaty kaolin.

91. The system of claim 84, wherein at least about 50wt% of the calcium carbonate has an equivalent spherical diameter of less than about 2 μm.

92. The system of claim 85, wherein at least about 50wt% of the kaolin has an equivalent spherical diameter of less than about 2 μm.

93. The system of claim 87, wherein the ground calcium carbonate is limestone or marble.

94. The system of claim 51 or claim 52, wherein the first stage high shear rotor-stator device is selected from the group consisting ofA mill, colloid mill, ultra-fine grinding equipment, or refiner.

95. The method according to claim 53A system wherein the first stage high shear rotor-stator device is selected from the group consisting ofA mill, colloid mill, ultra-fine grinding equipment, or refiner.

96. The system of claim 51 or claim 52, wherein the second stage high shear rotor-stator device is selected from the group consisting of a rotor-rotor device,A mill, colloid mill, ultra-fine grinding equipment, or refiner.

97. The method of claim 53, wherein said second stage high shear rotor-stator device is selected from the group consisting of a rotor-rotor device,A mill, colloid mill, ultra-fine grinding equipment, or refiner.

98. A process for redispersing a substantially dry or partially dry and optionally powdered composition comprising microfibrillated cellulose and optionally one or more inorganic particulate materials, the process comprising the steps of:

99. The method of claim 98, wherein the substantially uniform suspension flows to a hydrocyclone, wherein the substantially uniform suspension is split into an under-sheared coarse particle stream and a sheared fine particle stream, wherein the under-sheared coarse particle stream is recycled to the medium shear mixing device and the sheared fine particle stream flows to the second high shear rotor-stator device, a colloid mill, an ultra-fine grinding device, or a refiner.

100. The method of claim 98 or claim 99, wherein the composition of microfibrillated cellulose further comprises one or more inorganic particulate materials.

101. The method of claim 98 or 99, wherein the substantially dry or partially dry and optionally powdered composition comprising microfibrillated cellulose and optionally one or more inorganic particulate materials is powdered.

102. The method of claim 99, wherein the substantially dry or partially dry composition comprising microfibrillated cellulose and one or more inorganic particulate materials is powdered.

103. The method of claim 98 or claim 99, wherein the method is a continuous process, a semi-continuous process, or a batch process.

104. The method of claim 100, wherein the method is a continuous process, a semi-continuous process, or a batch process.

105. The method of claim 98 or claim 99, wherein the dispersion is water.

106. The method of claim 100, wherein the dispersion is water.

107. The method of claim 98 or claim 99, wherein the liquid composition of microfibrillated cellulose is about 0.5wt% to about 2.5wt% fiber solids.

108. The method of claim 100, wherein the liquid composition of microfibrillated cellulose is about 0.5wt% to about 2.5wt% fiber solids.

109. The method of claim 98 or claim 99, wherein the liquid composition is about 0.75wt% fiber solids.

110. The method of claim 100, wherein the liquid composition is about 0.75wt% fiber solids.

111. The method of claim 98 or 99, wherein the liquid composition is about 1wt% fiber solids.

112. The method of claim 100, wherein the liquid composition is about 1wt% fiber solids.

113. The method of claim 98 or claim 99, wherein the liquid composition is about 1.25wt% fiber solids.

114. The method of claim 99, wherein the liquid composition is about 1.25wt% fiber solids.

115. The method of claim 98 or claim 99, wherein the liquid composition is about 1.5wt% fiber solids.

116. The method of claim 100, wherein the liquid composition is about 1.5wt% fiber solids.

117. The method of claim 98 or claim 99, wherein the liquid composition is about 1.75wt% fiber solids.

118. The method of claim 100, wherein the liquid composition is about 1.75wt% fiber solids.

119. The method of claim 98 or claim 99, wherein the liquid composition is about 2wt% fiber solids.

120. The method of claim 100, wherein the liquid composition is about 2wt% fiber solids.

121. The method of claim 98 or claim 99, wherein the liquid composition is about 2.5wt% fiber solids.

122. The method of claim 100, wherein the liquid composition is about 2.5wt% fiber solids.

123. The method of claim 98 or claim 99, wherein the liquid composition is about 3wt% fiber solids.

124. The method of claim 100, wherein the liquid composition is about 3wt% fiber solids.

125. The method of claim 98 or claim 99, wherein the liquid composition is about 4wt% fiber solids.

126. The method of claim 100, wherein the liquid composition is about 4wt% fiber solids.

127. The method of claim 98 or claim 99, wherein the liquid composition is about 5wt% fiber solids.

128. The method of claim 100, wherein the liquid composition is about 5wt% fiber solids.

129. The method of claim 98 or claim 99, wherein the microfibrillated cellulose can be prepared with chemical pulp, or chemi-thermo-mechanical pulp, or recycled pulp, or broke pulp, or paper mill waste streams, or waste from paper mills, or a combination thereof.

130. The method of claim 100, wherein the microfibrillated cellulose can be prepared with chemical pulp, or chemi-thermo-mechanical pulp, or recycled pulp, or broke pulp, or paper mill waste streams, or waste from paper mills, or a combination thereof.

131. The method of claim 100, wherein the one or more inorganic particulate materials comprise alkaline earth metal carbonates or sulfates, hydrous kaolinite group clays, anhydrous (calcined) kaolinite group clays, talc, mica, perlite, or diatomaceous earth, or combinations thereof.

132. The method of claim 100, wherein the one or more inorganic particulate materials can comprise calcium carbonate, magnesium carbonate, dolomite, gypsum, kaolin, halloysite, ball clay, metakaolin, fully calcined kaolin, or a combination thereof.

133. The method of claim 98, wherein the one or more inorganic particulate materials comprise calcium carbonate.

134. The method of claim 100, wherein the one or more inorganic particulate materials comprise kaolin.

135. The method of claim 100, wherein the one or more inorganic particulate materials can comprise kaolin and calcium carbonate.

136. The method of claim 133, wherein the calcium carbonate is precipitated calcium carbonate, ground calcium carbonate, or a combination thereof.

137. The method of claim 133, wherein the calcium carbonate comprises a calcite, aragonite or vaterite structure.

138. The method of claim 133, wherein the calcium carbonate is in the form of scalenohedral or rhombohedral crystals.

139. The method according to claim 134, wherein the kaolin is ultraplaty kaolin.

140. The method of claim 133, wherein at least about 50wt% of the calcium carbonate has an equivalent spherical diameter of less than about 2 μιη.

141. The method of claim 134, wherein at least about 50wt% of the kaolin has an equivalent spherical diameter of less than about 2 μm.

142. The method of claim 133, wherein the ground calcium carbonate is limestone or marble.

143. The method of claim 98 or claim 99, wherein the end use comprises a method of making paper or coated paper, paint, coating, building material, ceiling tile, composite material, or barrier coating.

144. The method of claim 100, wherein the end use comprises a method of making paper or coated paper, paint, coating, building material, ceiling tile, composite material, or barrier coating.

145. The method of claim 98 or claim 99, wherein the first stage high shear rotor-stator device is selected from the group consisting of A mill, colloid mill, ultra-fine grinding equipment, or refiner.

146. The method of claim 100, wherein said first stage high shear rotor-stator device is selected from the group consisting ofA mill, colloid mill, ultra-fine grinding equipment, or refiner.

147. The method of claim 98 or claim 99, wherein the second stage high shear rotor-stator device is selected from the group consisting of a rotor-rotor device,A mill, colloid mill, ultra-fine grinding equipment, or refiner.

148. The method of claim 100, wherein the second-stage high shear rotor-statorThe sub-devices are selected from the group consisting of rotor-rotor devices,A mill, colloid mill, ultra-fine grinding equipment, or refiner.