System and method for dehydrating and drying nanocellulose

Abstract

The present invention allows for the production of nanocellulose in a dry form, enabling its incorporation into a variety of end-use applications. Some variations provide a nanocellulose slurry dewatering system that includes a nanocellulose slurry supply subsystem, a pre-concentration unit (e.g., a centrifuge) for removing at least a portion of the water from the nanocellulose slurry, an inlet for a dispersing / desiccant, a twin-screw extruder in flow communication with the nanocellulose slurry supply subsystem, the twin-screw extruder configured to thoroughly mix the nanocellulose slurry and the dispersing / desiccant, shear the nanocellulose slurry, and have one or more extruder vents for removing water from the nanocellulose slurry, and an extruder outlet for recovering the nanocellulose dispersion concentrate. A milling device may be used to produce a fine powder of the nanocellulose dispersion concentrate. Methods for producing and using dewatered or dried nanocellulose are also described.

Description

Technical Field

[0001] Priority Data This international patent application claims priority to U.S. Provisional Patent Application No. 62 / 795,277, filed on January 22, 2019, which is incorporated herein by reference in its entirety.

[0002] Field The present invention generally relates to systems and methods for dehydrating and drying nanocellulose for incorporation into polymers and other systems.

Background Art

[0003] Background Nanocellulose has attracted attention as a nanostructured material. Since nanocellulose is obtained from cellulose, a natural resource that is the most abundant polymer on earth, it is characterized by biodegradability and environmental sustainability. Furthermore, nanocellulose offers great technical potential to improve the mechanical strength and other properties of composites, regardless of its social and environmental sustainability. Nanocellulose is composed of parallel linear polysaccharide molecules. Nanocellulose has attractive physicochemical properties such as extremely high rigidity and strength, along with its abundance and sustainability.

[0004] Nanocellulose has been developed for use in a variety of applications such as polymer reinforcements, antibacterial films, biodegradable food packaging, printing paper, pigments and inks, paper and board packaging, barrier films, adhesives, biocomposites, wound healing, pharmaceuticals and drug delivery, textiles, water-soluble polymers, construction materials, recyclable interior and structural components for the transportation industry, rheology modifiers, low-calorie food additives, cosmetic thickeners, binders for pharmaceutical tablets, bioactive paper, pickering stabilizers for emulsions and particle-stabilized foams, paint formulations, films for optical switching, and detergents.

[0005] However, significant technical challenges remain associated with the widespread use of nanocellulose. In particular, it is very difficult to remove water from a nanocellulose suspension while maintaining nanoscale dimensions. In most cases, due to its hydrophilicity and tendency to aggregate during drying, nanocellulose particles are processed as an aqueous suspension. There is an industrial need to develop robust dispersion and drying processes that can maintain nanoscale dimensions for materials applications that require a dry form. Also, a drier form of nanocellulose reduces the high transportation costs of dilute aqueous suspensions and increases the number of end uses where there is a limit to the amount of water that can be added to the product.

[0006] In both the case of cellulose nanocrystals and cellulose nanofibrils (or microfibrils), non-aqueous polymers and other systems typically require a dry form of nanocellulose for incorporation, so the dispersibility of nanocellulose in these systems remains a problem. Nanocellulose has a tendency to irreversibly self-bond during drying, resulting in large aggregates of nanocellulose. Large aggregates often interfere with, or even destroy, the benefits of the intended properties for the polymer composites or other systems into which the nanocellulose particles are introduced. For example, nanocellulose particles well-dispersed in a polymer can bring about a significant enhancement of mechanical strength. However, when nanocellulose aggregates, there may be no enhancement of mechanical strength or even a deterioration, for example large aggregates can result in stress concentrators that can cause premature failure of polymer components.

[0007] Regarding the improvement of the dispersion of nanocellulose in non-aqueous products, various drying approaches have been attempted. These approaches typically require extreme means that can prove difficult to scale up to commercial quantities and are thus uneconomical. In general, these methods are based on the freeze-drying of nanocellulose, which is an established laboratory method for preventing irreversible interparticle binding of nanocellulose. Freeze-drying is not economical or scalable for the commercial production of nanocellulose.

[0008] For virtually all non-aqueous applications in which nanocellulose is used, the improvement of its dispersion, and thus the usefulness and benefits of these applications, is a major obstacle to the realization of nanocellulose. Therefore, it has become important to improve the dispersion of nanocellulose using an economical method that enables high dispersion of nanocellulose in polymers and other systems. Economical methods typically require a dry composition containing nanocellulose. The dry form of nanocellulose is particularly important in the field of thermoplastic resin processing such as extrusion and injection molding where a heat melting process is induced. In the heat melting process with non-polar thermoplastic resins, water is disadvantageous for satisfactory processing.

[0009] Dehydrating or concentrating a nanocellulose slurry for more efficient transport or use in applications where water is restricted is inherently difficult because these materials have a high water retention capacity and high viscosity at low concentrations. For aqueous applications, end users require a nanocellulose "concentrate" that has the highest possible solid content and can be rapidly redispersed using standard low-energy mixing devices. Depending on the application, nanocellulose may need to be redispersed in water such that its uniquely designed nanoscale properties are retained. Summary of the Invention Problems to be Solved by the Invention

[0010] In view of the above needs in the art, there is a strong need for an improved system and method for dehydrating and drying nanocellulose for polymer composites and other systems other than polymers.

Means for Solving the Problems

[0011] Overview Some variations of the present invention A nanocellulose slurry supply subsystem, wherein the nanocellulose slurry contains nanocellulose and water, a nanocellulose slurry supply subsystem; An inlet for a dispersant / drying agent; A twin-screw extruder in fluid communication with the nanocellulose slurry supply subsystem, configured to thoroughly mix the nanocellulose slurry and the dispersant / drying agent, and having one or more extruder vents for removing at least a portion (e.g., all) of the water from the nanocellulose slurry, a twin-screw extruder; (i) Nanocellulose, (ii) a dispersant / drying agent, and (iii) an extruder outlet for recovering a nanocellulose dispersion concentrate containing residual water (if present); An optional grinding device configured to produce a powder containing the nanocellulose dispersion concentrate; A nanocellulose slurry dehydration system is provided.

[0012] In some embodiments, for example, when processing a dilute slurry, the nanocellulose slurry supply subsystem is configured to have an internal rotating agitator and / or a wiping blade for mixing the nanocellulose slurry.

[0013] In some embodiments, the nanocellulose slurry dehydration system includes a nanocellulose slurry pre-concentration unit configured to remove at least a portion of the water from the nanocellulose slurry prior to water removal in the extruder. For example, the nanocellulose slurry pre-concentration unit can be a centrifuge or a filtration device.

[0014] In some embodiments, the nanocellulose slurry dehydration system includes a mixing unit configured to mix the nanocellulose slurry with a dispersant / drying agent.

[0015] In some embodiments, the inlet for the dispersant / drying agent is an inlet to the nanocellulose slurry supply subsystem. In other embodiments, the inlet for the dispersant / drying agent is a direct inlet to the twin screw extruder. Also, both an inlet to the nanocellulose slurry supply subsystem and an inlet to the twin screw extruder may be present for the dispersant / drying agent. The dispersant / drying agent can be combined with the nanocellulose slurry before addition to the pre-concentration unit or after the nanocellulose slurry has been pre-concentrated in the pre-concentration unit (if present). Preferably, the nanocellulose slurry and the dispersant / drying agent are mixed, for example, by a stirred mixing tank or an in-line mixer, before adding the mixture to the nanocellulose slurry supply subsystem.

[0016] The twin screw extruder can be a co-rotating twin screw extruder, a counter-rotating twin screw extruder, or another type of twin screw extruder.

[0017] If an optional grinding device is present, the grinding device can be selected, for example, from a hammer mill, a ball mill, a jet mill, an impact crusher, a pulverizer, a cage mill, a grinder, or an extruder.

[0018] Some variations do not necessarily use a dispersant / drying agent. In some of these variations, the nanocellulose slurry dehydration system is a nanocellulose slurry supply subsystem, wherein the nanocellulose slurry contains nanocellulose and water, A twin-screw extruder in fluid communication with a nanocellulose slurry supply subsystem, the twin-screw extruder being configured to shear the nanocellulose slurry and having one or more extruder vents configured to remove at least a portion of the water from the nanocellulose slurry, An optional grinding device configured to produce a powder containing the nanocellulose slurry, An extruder outlet for recovering the dehydrated nanocellulose and the like.

[0019] Some variations are, A nanocellulose slurry supply subsystem, wherein the nanocellulose slurry contains nanocellulose and water, An inlet for a dispersant / drying agent, A twin-rotor mixer in communication with the nanocellulose slurry supply subsystem, the twin-rotor mixer being configured to thoroughly mix the nanocellulose slurry and the dispersant / drying agent and having one or more mixer vents configured to remove at least a portion of the water from the nanocellulose slurry, An optional grinding device configured to produce a powder containing the nanocellulose dispersion concentrate and the like, to provide a nanocellulose slurry dehydration system.

[0020] In some embodiments, the nanocellulose slurry dehydration system includes a mixing unit configured to mix the nanocellulose slurry with a dispersant / drying agent.

[0021] In some embodiments, the inlet for the dispersant / drying agent is an inlet to the nanocellulose slurry supply subsystem. In some embodiments, the inlet for the dispersant / drying agent is an inlet to the twin-rotor mixer.

[0022] In some embodiments, the nanocellulose slurry dehydration system includes a nanocellulose slurry pre-concentration unit configured to remove at least a portion of water from the nanocellulose slurry before water removal in a twin rotor mixer. The nanocellulose slurry pre-concentration unit can be, for example, a centrifuge or a filtration device.

[0023] In some embodiments, the inlet for the dispersant / drying agent is the inlet to the nanocellulose slurry pre-concentration unit.

[0024] The twin rotor mixer can be a co-rotating twin rotor mixer or a counter-rotating twin rotor mixer.

[0025] The present invention also provides a method for dehydrating and optionally drying a nanocellulose slurry, the method comprising: (a) providing a nanocellulose slurry comprising nanocellulose and water; (b) providing a dispersant / drying agent selected to be compatible with the nanocellulose; (c) thoroughly mixing the nanocellulose slurry and the dispersant / drying agent in a twin screw system (e.g., a twin screw extruder or a twin rotor mixer); (d) removing at least a portion of water from the nanocellulose slurry through one or more system vents in the twin screw system to produce a nanocellulose dispersion concentrate; (e) optionally, grinding the nanocellulose dispersion concentrate to produce a powder that may or may not have residual moisture; (f) recovering the nanocellulose dispersion concentrate in a solid or liquid form and including.

[0026] In some embodiments, the nanocellulose slurry is pre-concentrated in a nanocellulose slurry pre-concentration step to remove at least a portion of the water from the nanocellulose slurry before step (c). The nanocellulose slurry pre-concentration step can be, for example, centrifugation and / or filtration. If the pre-concentration step is carried out, the dispersion / drying agent is combined with the nanocellulose slurry either before or after pre-concentration.

[0027] The dispersion / drying agent can be selected from the group consisting of, for example, waxes, polyolefins, olefin-maleic anhydride copolymers, olefin-acrylic acid copolymers, polyols, fatty acids, fatty alcohols, polyol-glyceride esters, polydimethylsiloxanes, polydimethylsiloxane-alkyl esters, polyacrylamides, starches, cellulose derivatives, microparticles, and combinations or reaction products thereof.

[0028] In some embodiments, the dispersion / drying agent is added to the nanocellulose slurry before step (c). The dispersion / drying agent can be added directly to the twin screw system, for example through an additive inlet port. Preferably, the nanocellulose slurry and the dispersion / drying agent are mixed, for example by a stirred mixing tank or an in-line mixer, before adding the mixture to the twin screw system. In certain embodiments, the nanocellulose slurry supply subsystem is configured to stir the nanocellulose slurry and the dispersion / drying agent.

[0029] The twin screw system can be a co-rotating twin screw extruder, a counter-rotating twin screw extruder, or another type of twin screw extruder that typically operates continuously. The twin screw system can also be a twin rotor mixer that operates in batch or semi-batch mode.

[0030] The twin-screw system can be operated, for example, at an average system temperature of about 120 °C to about 300 °C. The twin-screw system is preferably operated at a maximum system temperature that is lower than the thermal decomposition onset temperature of the nanocellulose and preferably lower than the thermal decomposition onset temperature of the dispersant / drying agent.

[0031] In some embodiments, the twin-screw system is a twin-screw extruder containing a plurality of extruder zones, and the zone temperature of each of the extruder zones is independently controlled. In certain embodiments, the zone temperature increases along the length of the twin-screw extruder.

[0032] The twin-screw system can be heated by a heat transfer medium selected from the group consisting of steam, hot oil, electric heating elements, and combinations thereof. The twin-screw system can be cooled by a heat transfer medium selected from the group consisting of cooling water, air, oil, and combinations thereof. The heating and cooling configurations can be designed based on the desired temperature profile, throughput, materials present, shear rate, screw or rotor design, and other parameters along the length of the twin-screw system.

[0033] The twin-screw system can be operated, for example, at an average nanocellulose residence time of about 30 seconds to about 30 minutes. In a batch twin-rotor mixer, the residence time is the batch time.

[0034] In some embodiments, at least one of the system vents is operated under vacuum. If step (d) utilizes a plurality of system vents, each of the system vents may be operated under vacuum, or not all of the system vents need to be operated under vacuum.

[0035] In the nanocellulose dispersion concentrate produced in step (d), the nanocellulose can be present, for example, at a concentration of about 10 wt% to about 90 wt%. The dispersion / drying agent can be present in the nanocellulose dispersion concentrate at a concentration of, for example, about 5 wt% to about 65 wt%. In some embodiments, the weight ratio of nanocellulose to dispersion / drying agent in the nanocellulose dispersion concentrate is selected from about 0.5 to about 2.

[0036] The nanocellulose can include cellulose nanocrystals, cellulose nanofibers, microfibrillated cellulose, or combinations thereof. In some embodiments, the nanocellulose includes lignin-containing nanocellulose. In certain embodiments, the nanocellulose includes lignin-coated nanocellulose.

[0037] Some methods do not necessarily use a dispersion / drying agent. In some of these methods, the method for dehydrating and optionally drying the nanocellulose slurry is (a) providing a nanocellulose slurry comprising nanocellulose and water; (b) optionally pre-concentrating the nanocellulose slurry, for example, by centrifugation or filtration; (c) shearing the nanocellulose slurry in a twin-screw system and removing at least a portion of the water from the nanocellulose slurry through one or more system vents to produce dehydrated nanocellulose; (d) optionally, pulverizing the nanocellulose dispersion concentrate to produce a powder; (e) recovering the dehydrated nanocellulose in solid or liquid form and includes.

[0038] In the dehydrated nanocellulose recovered in step (d), the nanocellulose can be present, for example, at a concentration of about 10 wt% to about 25 wt%.

Brief Description of the Drawings

[0039] Brief Description of the Drawings

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[0040] Detailed description of some embodiments This description enables those skilled in the art to make and use the invention and describes some embodiments, adaptations, variations, alternatives, and uses of the invention. These and other embodiments, features, and advantages of the invention will become more apparent to those skilled in the art when considered in reference to the following detailed description of the invention together with any accompanying drawings.

[0041] As used in this specification and the claims, unless the context clearly dictates otherwise, the singular forms "a", "an", and "the" include plural referents. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. All numbers and ranges of compositions based on percentages are, unless otherwise indicated, weight percentages. All ranges of numbers or conditions are meant to include any specific value within the range, rounded to any appropriate decimal place.

[0042] Unless otherwise stated, all numbers representing parameters, reaction conditions, concentrations of components, etc., used in this specification and the claims should be understood to be modified in all cases by the term "about". Accordingly, unless the contrary is indicated, the numerical parameters set forth in the following specification and claims are approximations that may vary depending at least upon the particular analytical technique employed.

[0043] The term "comprising", which is synonymous with "including", "containing", or "characterized by", is inclusive or open-ended and does not exclude additional, unrecited elements or method steps. "Comprising" is a term of art used in claim terminology and means that the named claim elements are essential, but that other claim elements may be added and still form a construct within the scope of that claim.

[0044] As used herein, the phrase "consisting of" excludes any element, step, or ingredient not specified in the claim. When the phrase "consisting of" (or a variant thereof) appears in a clause of the claim body rather than immediately following the preamble, it limits only the elements recited in that clause; other elements are not excluded from the claim as a whole. As used herein, the phrase "consisting essentially of" limits the scope of a claim to the specified elements or method steps, in addition to those that do not materially affect the basic and novel characteristics of the claimed subject matter.

[0045] With respect to the terms "comprising," "consisting of," and "consisting essentially of," when one of these three terms is used herein, the disclosure and the claimed subject matter may include the use of either of the other two terms. Thus, in some embodiments where not otherwise expressly stated, any example of "comprising" can be replaced by "consisting of" or by "consisting essentially of."

[0046] In some embodiments, the present invention is based on dehydrating and drying an aqueous nanocellulose slurry using a twin-screw system (e.g., a twin-screw extruder) configured to allow the release of water vapor. In some embodiments, the present invention is also based on selecting and incorporating a dispersion / drying agent for the nanocellulose, where the dispersion / drying agent is added to the nanocellulose slurry to be dehydrated in the twin-screw system. A twin-screw system having one or more system vents has been found to function surprisingly well in combination with the dispersion / drying agent to dehydrate the nanocellulose slurry. When water is removed from the system vents, the dispersion / drying agent prevents the nanocellulose from aggregating and irreversibly self-bonding.

[0047] As explained in the background, in many cases, composite products desirably incorporate discrete nanocellulose particles and prevent the binding (aggregation) of those particles during manufacture or use. When produced from cellulose-based biomass or by bacterial synthesis, nanocellulose is typically available as an aqueous dispersion. In dilute aqueous dispersions, the nanocellulose particles remain non-aggregated or reversibly aggregate. In most polymer-based cases, for example, the aqueous dispersion itself cannot be introduced into the polymer matrix and the water must first be removed. Even in aqueous solution-based cases, additive products containing as little water as possible are preferred in order to minimize the product delivery costs and the amount of water introduced into the end-use product system along with the additives. In general, introducing excess water into the product system with the additives is not tolerable, and thus the product must be dehydrated or dried beyond normal levels.

[0048] The present invention represents a breakthrough enabling the production of nanocellulose in a dried or dehydrated (concentrated) form that can be incorporated into non-polymer matrices including a wide range of plastics, elastomers, and adhesives, as well as electronic inks, sealants, and other non-aqueous applications. The present invention also provides a method for concentrating nanocellulose for transport and storage purposes for dispersion in an aqueous solution-based system.

[0049] As used herein, the "dispersant / drying agent" is a chemical substance or combination of chemical substances that functions to prevent irreversible aggregation of nanocellulose during drying or dehydration. The dispersant / drying agent disclosed herein is selected to hold individual nanocellulose particles by preventing bonding between nanocellulose particles while the aqueous dispersion is being dried or dehydrated (removal of water). Without an effective dispersant / drying agent, irreversible bonding between nanocellulose particles was observed through heat drying to a solid slurry of about 20 wt%. The dispersant / drying agent also holds individual nanocellulose particles while the nanocellulose is incorporated into the composite product and effectively and readily releases the individual nanocellulose particles during compounding of the composite product so that the effectiveness of the nanocellulose is maximized. The dispersant / drying agent can be selected to sufficiently interact with the surface of the nanocellulose and / or be uniformly distributed between nanocellulose particles to reduce or prevent self-bonding of the nanocellulose during drying or dehydration, thereby reducing or preventing aggregation of the nanocellulose.

[0050] In this patent application, "dehydration" means the removal of liquid water from the nanocellulose slurry. "Drying" generally refers to a relatively high degree of dehydration below that which includes removing all water from the nanocellulose using thermal energy.

[0051] As used herein, "nanocellulose dispersion concentrate" refers to a composition containing at least nanocellulose and a dispersant / drying agent. "Dehydrated nanocellulose", "dried nanocellulose", "dehydrated nanocellulose slurry", etc. refer to compositions containing nanocellulose and optionally a dispersant / drying agent.

[0052] Exemplary embodiments of the present invention will now be described. These embodiments are not intended to limit the scope of the present invention as claimed. The order of steps (or unit operations of the system) may be changed in any logical order, some steps or units may be omitted, and / or other steps or units may be added. References herein to a first step, a second step, etc. are for illustrative purposes only in describing some embodiments. Also, the location of steps or units may differ at one or more sites. Also, references to "embodiments" are all non-limiting, and it should be understood that they are also alternatives with respect to any other disclosed embodiments unless the context clearly indicates otherwise. In the drawings, dashed lines indicate optional unit operations or streams.

[0053] Some variations of the present invention are a nanocellulose slurry supply subsystem, wherein the nanocellulose slurry contains nanocellulose and water, the nanocellulose slurry supply subsystem; an inlet for a dispersant / drying agent; a twin-screw extruder in fluid communication with the nanocellulose slurry supply subsystem, configured to thoroughly mix the nanocellulose slurry and the dispersant / drying agent and having one or more extruder vents configured to remove at least a portion of the water from the nanocellulose slurry; an extruder outlet for recovering a nanocellulose dispersion concentrate containing nanocellulose and the dispersant / drying agent; an optional grinding device configured to produce a powder containing the nanocellulose dispersion concentrate to provide a nanocellulose slurry dehydration system including.

[0054] In some embodiments, for example, when processing a dilute slurry (e.g., solids of about 8 wt% or less), the nanocellulose slurry supply subsystem is configured to have an internal rotating agitator and / or a wiping blade to mix the nanocellulose slurry before the slurry is supplied to the twin-screw extruder. A control valve can be used to meter the rate of addition of the nanocellulose slurry from the supply subsystem to the twin-screw extruder.

[0055] In some embodiments, the nanocellulose slurry dehydration system includes a nanocellulose slurry pre-concentration unit configured to remove at least a portion of the water from the nanocellulose slurry before water removal in the extruder. Pre-concentration of the slurry is advantageous for reducing the overall volume supplied to the twin-screw extruder and results in a higher throughput based on nanocellulose. The nanocellulose slurry pre-concentration unit can reduce the overall energy cost by using mechanical separation of water rather than thermal separation (evaporation of water). Mechanical separation means that separation is achieved using mechanical forces such as centrifugal or centripetal forces, or physical forces such as pressure that causes permeation of water through a filtration medium or membrane.

[0056] For example, the nanocellulose slurry pre-concentration unit can be a centrifuge or a filtration device. An exemplary centrifuge is a decanter centrifuge that uses high-speed rotation with centrifugal force to separate nanocellulose, which has a higher density than water, from the water that is continuously removed (decanted). An exemplary filtration device is a pressure filter that uses high-pressure air (or another inert gas) to produce a mat of nanocellulose and a water-rich filtrate. Filtration devices include filter presses, belt presses, and the like.

[0057] When the nanocellulose slurry is pre-concentrated by a pre-concentration unit to provide nanocellulose containing more than about 15 wt% solids, the nanocellulose feed subsystem can essentially consist of a traditional hopper feed system. Hoppers are well known for feeding wet solids to an extruder. If the wet solid is not a free-flowing material, the hopper can have a rotating agitator and / or a wiping blade to prevent bridging of the feed material, or can be designed to involve vibration of the hopper.

[0058] In some embodiments, the inlet for the dispersant / dryer is an inlet to the nanocellulose slurry feed subsystem, which may be the same inlet as the feed stream of the nanocellulose slurry or a separate inlet as shown in FIG. 1. In certain embodiments, the nanocellulose slurry and the dispersant / dryer are combined prior to feeding to the feed subsystem, for example after the production of the nanocellulose slurry, or are also integrated with the production of the nanocellulose. In other embodiments, the inlet for the dispersant / dryer is an inlet directly to a twin-screw extruder, for example through a feed port (see, e.g., FIG. 1) or a side port. Also, both the inlet to the nanocellulose slurry feed subsystem and the inlet to the twin-screw extruder may be present for the dispersant / dryer.

[0059] As intended herein, a "twin-screw system" is a machine that preferably utilizes at least two solid screws or rotors that rotate (radially) with a small gap between the screws or rotors to impart a significant shear force to the material being processed. In the case of the present invention where the material is a nanocellulose slurry, the high shear and preferably the small gap result in the formation of a thin layer of material with a large surface area exposed for evaporation of water. The high shear force enables thorough mixing of the nanocellulose slurry and the dispersant / dryer. Also, depending on the dispersant / dryer used, as water is released, the thorough mixing provided by the twin-screw or rotor results in tumbling and fragmentation of the particles, and thus the drying of the particles is relatively uniform.

[0060] The twin-screw system can be a continuous system, a semi-continuous system, a semi-batch system, or a batch system. When the twin-screw system is a continuous or semi-continuous twin-screw extruder, the material is continuously conveyed axially through the system from the feed subsystem to the extruder outlet for a certain period of time. When the twin-screw system is a batch or semi-batch twin-rotor mixer, the material is first added to the system, then the system is usually closed except for vents or steam removal, and then it undergoes thorough mixing by the high shear force generated by two radially rotating rotors with preferably small gaps between the rotors. After a certain period of time (batch time), the system is opened and the processed material is recovered. In a semi-batch system, the system can be operated for a certain period of time, and the material can be added to the system periodically or removed from the system (for example, water release can be intermittent, or dehydrated nanocellulose can be periodically recovered from the valve). In the case of batch or semi-batch, the feed subsystem can be the container itself that can be initially loaded, and the system outlet can also be the container itself after batch operation. For examples of semi-batch twin-rotor mixers, refer to Examples 1-8 in this specification, and for examples of continuous twin-screw extruders, refer to Examples 9-11.

[0061] When the twin-screw system is a twin-screw extruder, the solid screw is usually manufactured from metal or metal alloy, such as stainless steel, optionally using a ceramic coating such as chromium carbide. The screw can be manufactured as a single piece or segmented and assembled on the shaft. The screws can be arranged parallel to each other, or the screw axes may not be parallel to each other but rather in a conical arrangement that converges along the length of the extruder.

[0062] The twin-screw extruder can be a co-rotating twin-screw extruder, a counter-rotating twin-screw extruder, or another type of twin-screw extruder (e.g., a gear pump extruder). When the two screws are designed to rotate in the same radial direction (co-rotate), the twin-screw is a co-rotating screw. When the two screws are designed to rotate in opposite radial directions, the twin-screw is a counter-rotating screw. The flights of the screws can be designed such that the two screws mesh with each other (meshing screws) or do not fully mesh with each other (non-meshing screws). The screws form the outer wall around the screw and are thereby contained within one or more barrels that contain the material being processed.

[0063] In the case of a continuous system, the counter-rotating twin-screw extruder has beneficial material feeding and conveying characteristics. Also, the residence time and material temperature control within the counter-rotating twin-screw extruder are relatively uniform. However, air entrapment, high pressure generation, and low maximum screw speed can be disadvantageous. The advantages of the co-rotating twin-screw extruder are that the screws wipe each other clean (self-wiping), and high screw speeds and high outputs can be achieved along with good mixing. The co-rotating twin-screw extruder may also be desirable for reducing wear of the screws and barrels.

[0064] In the case of a continuous system, the screws may be designed to incorporate different screw elements along the screw length. Such screw elements can include, but are not limited to, flight elements, mixing elements, and zoning elements. The flight elements pass the material over the barrel ports, through the mixer, and out of the extruder through the die. The mixing elements facilitate the mixing of the various components being processed. The zoning elements separate two operations. Some elements may be multifunctional.

[0065] In the case of a continuous system, the mixing efficiency of a twin-screw extruder can be increased by incorporating a number of mixing elements along the screw. These and other elements can be fitted onto a central shaft to construct a screw section. Preferably, the length, number, and configuration of the elements can be easily changed. The elements can take various configurations such as reverse screw flights, kneading disks, pins, rotors, slotted blades, blister rings, etc. The mixing elements can be designed to impart extensional mixing and planar shear to the material being processed to facilitate distributive mixing. The mixing elements can be designed to effect stream splitting and recombination to facilitate distributive mixing.

[0066] In the case of a continuous system, the screw outer diameter, screw inner diameter, and channel depth are important twin-screw extruder design parameters as they determine the available free volume and torque (and thus the radial shear force). As the channel depth increases, the screw inner diameter decreases, resulting in a lower achievable shaft torque.

[0067] Generally speaking, the screw design will be tailored to a particular application (e.g., type of nanocellulose, dispersant / drying agent, desired degree of dehydration, throughput, etc.). Those skilled in the art of twin-screw extrusion will be able to customize the screw design using known principles and calculations.

[0068] This specification incorporates by reference Goff et al., The Dynisco Extrusion Processors Handbook, 2nd edition, 2000, for its teachings on the principles and design parameters of twin screw extruders. This specification also incorporates by reference Martin, “Twin Screw Extruders as Continuous Mixers for Thermal Processing: a Technical and Historical Perspective”, AAPS PharmSciTech, Vol. 17, No. 1, February 2016, for its teachings on the various design and operating principles of twin screw extruders.

[0069] Extruders using three or more screws are included within the scope of the twin screw extruders in this specification. In a three-screw extruder, all three screws may rotate in the same direction, or two screws may rotate in the same direction and one screw may rotate in the opposite direction with respect to the radial direction of the other screw.

[0070] A gear pump extruder is a simple twin screw extruder that moves material by the action of two meshing gears, which are essentially relatively short length screws or rotors. The gears are typically manufactured from metal or metal alloys, such as stainless steel, optionally with a ceramic coating such as chromium carbide. When designed such that the two gears rotate in the same radial direction (co-rotate), the gear pump extruder is a co-rotating gear pump extruder. When designed such that the two gears rotate in opposite radial directions, the gear pump extruder is a counter-rotating gear pump extruder. The flights of the gears may be designed such that the two gears mesh with each other or do not fully mesh with each other.

[0071] In some embodiments, the twin-screw system is a gear pump extruder that operates in a batch rather than a continuous mode. The meshing gears can be designed to rotate co-rotatingly or counter-rotatingly, and the flights of the gears can be designed such that the two gears mesh with each other or do not mesh completely with each other. The gear pump extruder is first loaded with the nanocellulose slurry and optionally a dispersion-drying agent. The batch gear pump is operated for a certain period of time (batch time) to allow thorough high-shear mixing and the release of water vapor from the vents.

[0072] In some embodiments, the twin-screw system is a batch or semi-batch twin-rotor mixer. The twin-rotor mixer is configured to have two rotors that may or may not be meshed. The two rotors rotate (radially) and impart a significant shear force to the material being processed. The high shear force allows thorough mixing of the nanocellulose slurry and the dispersion / drying agent. The rotors are typically manufactured from metal or metal alloy, such as stainless steel, optionally with a ceramic coating such as chromium carbide. The two rotors can be designed to rotate in the same radial direction (co-rotating) or in opposite radial directions (counter-rotating). Examples 1-8 herein utilize a semi-batch twin-rotor mixer. In principle, such twin-rotor mixers can be scaled up to commercial scale.

[0073] A twin rotor mixer contains a cavity (or mixing chamber) with rotor blades, where the blades pump the material in opposite directions and thoroughly mix it. The rotors of the twin rotor mixer can be designed such that the number, shape, and angle of the blades are optimized for a particular application. The rotors generally have two or four flights, although other numbers of flights are possible. The rotors of the twin rotor mixer can be selected from, for example, tangential rotors, roller rotors, delta rotors, cam rotors, sigma rotors, Banbury rotors, or other industrially available rotors. In some embodiments of the twin rotor mixer, the two rotors rotate relative to each other at slightly different speeds. Each rotor has blades that extend along the length of the rotor in a generally spiral form. Each rotor may be centrally removed to allow for cooling or heating by the passage of water or a suitable heating agent. An example of a commercial scale two-wing rotor is the well-known Banbury design.

[0074] In the case of batch or semi-batch systems, the mixing efficiency of the twin rotor mixer can be increased by incorporating a number of mixing elements into the rotors. The rotor elements can take various forms. The rotor mixing elements can be designed to impart elongational mixing and planar shear to the material being processed to promote dispersive mixing. The rotor mixing elements can be designed to effect stream splitting and recombination to promote distributive mixing. Generally speaking, the rotor design will be adapted to a particular application (e.g., type of nanocellulose, dispersing / drying agent, desired degree of dehydration, throughput, etc.). One skilled in the art of twin rotor mixers will be able to customize the rotor design using known principles and calculations.

[0075] The twin screw system can be designed to operate at an average system temperature of, for example, about 120°C to about 300°C. The twin screw system is preferably designed to operate at a maximum system temperature that is lower than the thermal decomposition onset temperature of the dehydrated or dried nanocellulose and preferably lower than the thermal decomposition onset temperature of the dispersant / drying agent. In some embodiments, when the twin screw system is a twin screw extruder, there are a plurality of extruder zones, where the zone temperature of each of the extruder zones can be independently controlled, for example, by a control panel or a computer interface. When the twin screw system is a batch or semi-batch twin rotor mixer, the mixer can be operated at a desired temperature or a temperature that varies with time, as desired.

[0076] The twin screw system can be heated by a heat transfer medium selected from the group consisting of steam, hot oil, electric heating elements, and combinations thereof. The twin screw system can be cooled by a heat transfer medium selected from the group consisting of cooling water, air, oil, and combinations thereof. In the case of a twin screw extruder, the heating and cooling configuration can be designed based on the desired temperature profile, throughput, materials present, shear rate, screw design, and other parameters along the length of the twin screw extruder.

[0077] In some embodiments, the twin screw system is electrically heated using resistance coils, bands, or cuffs strapped or bolted around the barrel or mixer bowl. Depending on requirements such as start-up by thermocouple, current is passed through the resistance wire inside the coil. The resistance generates heat, and the barrel or mixer bowl temperature, as well as the internal system temperature, is increased by heat transfer. In the case of a twin screw extruder, the resistance set value required to achieve the desired temperature can depend on the screw rotation speed, pressure within the system, and throughput.

[0078] In some embodiments, the twin-screw extruder is configured to have steam heating for one or more barrels. Depending on requirements such as start-up by thermocouple, steam is introduced to the barrel surface for indirect heating (i.e., steam is not directly introduced into the extruder), whereby the barrel temperature and the internal temperature of the extruder are increased by heat transfer. In the case of a twin-screw extruder, the steam pressure and flow rate to achieve the desired temperature may depend on the screw rotation speed, the pressure within the system, and the throughput.

[0079] In some embodiments, the twin-screw extruder is provided with an air-cooling system for reducing the temperature when excessive heating occurs (e.g., when the electric heating exceeds the set point or when the shear heating becomes excessive). An exemplary air-cooling system consists of a fan that circulates air around the barrel as required.

[0080] In some embodiments, the twin-screw extruder is provided with a liquid-cooling system such as a closed-loop heat exchanger that uses cooling water contained within a sealed coil surrounding the barrel. When the set-point temperature is exceeded, the steam from this cooling water is cooled by the water flow so that the cooling water vapor condenses and absorbs additional heat.

[0081] The twin-screw system is preferably configured to have one or more system vents for removing at least a portion of the water from the nanocellulose slurry. A "vent" is a port, adjustable valve, pressure relief valve, pressure relief disk, permeable membrane, or other device that allows water vapor to be released from the system. The vent may be normally open or normally closed; for example, the vent can be designed to open only when sufficient outward vapor pressure exists or as required. In the case of a twin-screw extruder, the vent may also be referred to as an extruder vent. In the case of a twin-rotor mixer, the vent may also be referred to as a mixer vent.

[0082] In some embodiments of the twin screw extruder, the extruder vent is incorporated into the barrel. In these or other embodiments, the extruder vent can be configured within a vent ring or other vent element between axially separated barrels. In the case of a gear pump extruder, the extruder vent can be incorporated, for example, into a gear box, a case seal, or an intake port.

[0083] Generally, the system vent allows volatile substances such as water vapor, and entrained air to be removed from the system. In the present invention, dehydration or drying of the nanocellulose slurry means that at least water is removed. Other components can sometimes be unintentionally removed through the system vent (e.g., entrainment of small amounts of solids). In some embodiments, the system vent allows for the removal not only of some water, but also of components derived from the nanocellulose manufacturing process, such as acids, sugar degradation compounds, or lignin-derived compounds.

[0084] The number of system vents can vary, for example, according to the overall length of the twin screw extruder or the total volume of the twin rotor mixer, and can be, for example, 1, 2, 3, 4, 5, or more. The placement of the extruder vents can vary along the length of the twin screw extruder. For example, if there is a temperature profile that increases along the length of the extruder, the extruder vents can be placed near the end of the extruder where water evaporation is faster or thermodynamically more favorable.

[0085] The system vent may allow the vapor to escape to the atmosphere, or may be adapted in a flow line such that, for example, the vapor is captured and potentially reused for other purposes or analyzed for composition. The flow line may communicate with a vacuum system such that the vent is under vacuum. When multiple vents are utilized, each of the vents may be the same size or different sizes, i.e., one vent may have a larger opening area (for more vapor release) than another vent.

[0086] In some embodiments, at least one of the system vents operates under vacuum. When multiple system vents are utilized, each of the system vents may operate under vacuum, or not all of the system vents need to operate under vacuum. The vacuum pressure can be from about 0.01 bar to about 0.99 bar (absolute pressure), for example, about 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.95 bar. When multiple system vents are present, they can operate at the same pressure or different pressures. As an example, when three system vents are present (implied in FIG. 1), the three vents can all be connected to a common vacuum system operating at an absolute pressure of 0.1 bar, i.e., a gauge pressure of -0.9 bar. Or, for example, one vent can be at atmospheric pressure (1 bar), while two system vents can be at a pressure of 0.5 bar.

[0087] The twin-screw extruder outlet is typically configured to have an extruder die. The extruder die is an assembly located at the end of the extruder and contains an orifice for discharging the dehydrated nanocellulose. The extruder die is a block of metal or metal alloy and may be of the same material as the screw and / or barrel. In certain embodiments, the extruder vent is configured as part of the extruder die at or near the extruder outlet. It should also be noted that an additional amount of water vapor can be released when the extruder outlet is opened to the atmosphere.

[0088] In addition to the number and size of the extruder vents and the vacuum level, other parameters can also determine the water removal efficiency from a twin-screw extruder. For example, a longer residence time, especially within the zone having the extruder vents, is helpful as it increases the time for water masses to be transported to the vents. The screw design can be optimized such that one or more screw elements enhance the flushing and removal of water from the extruder vents. A higher surface area of the mixture from high shear rates can be helpful by reducing the limitations of mass transport by diffusion and / or convection. Of course, the temperature and pressure within the extruder or an extruder zone can determine whether water exists in the liquid state or in the vapor state at thermodynamic equilibrium. A true equilibrium may or may not exist.

[0089] A person skilled in chemical engineering can perform experiments using a twin-screw system, varying the number and size of the vents, the vacuum pressure, the screw or rotor design, and the process conditions within the system to determine the number of vents required to achieve the desired degree of dehydration or drying. Alternatively or additionally, a person skilled in chemical engineering can simulate a twin-screw system, varying the number of vents, the vacuum pressure, and the process conditions to calculate or estimate the number of vents required to achieve the desired degree of dehydration or drying. For example, it can be assumed that each vent can be modeled as one equilibrium flash stage where vapor is completely released and there is no solid uptake. In practice, due to the high surface area (thin film) in a twin-screw system, more than two equilibrium flashes can occur at each vent.

[0090] If an optional grinding device is present, the grinding device can be directly connected to the outlet of the system (e.g., the extruder outlet) such that the outlet of the system is essentially the inlet of the grinding device. Alternatively, the nanocellulose dispersion concentrate can be collected from the outlet and then introduced into the grinding device potentially at a later time and / or at a different location. The grinding device can be selected from, for example, a hammer mill, ball mill, jet mill, impact crusher, pulverizer, cage mill, grinder, or extruder. The grinding device can be operated to reduce the particle size of the nanocellulose dispersion concentrate to an average size range of, for example, from about 10 microns to about 1 millimeter, for example, to about 25, 50, 100, 200, 300, 400, 500, 600, 700, 800, 900, or 950 microns.

[0091] Some variations of the present invention do not necessarily use a dispersing / drying agent. In some of these variations, the nanocellulose slurry dehydration system comprises a nanocellulose slurry feed subsystem comprising a nanocellulose slurry containing nanocellulose and water, a twin screw system in communication with the nanocellulose slurry feed subsystem, the twin screw extruder being configured to shear the nanocellulose slurry and having one or more system vents configured to remove at least a portion of the water from the nanocellulose slurry, an optional grinding device configured to produce a powder containing the nanocellulose slurry, an outlet for recovering the dehydrated nanocellulose and comprising.

[0092] As described above, the present invention provides both a system and a method. The exemplary schematic diagram of FIG. 1 illustrates both a system (system elements, e.g., a twin-screw extruder, are shown) and a method (method steps, e.g., conveyance through a twin-screw extruder, are shown). In FIG. 1, the dispersant / dryer is optional but preferred. A mixing unit for mixing the nanocellulose slurry with the dispersant / dryer is optional. Also, a centrifuge or a filtration unit for pre-concentrating the nanocellulose slurry is optional. In some preferred embodiments, a dispersant / dryer is used and a centrifuge or a filtration unit is included. The particle grinder is optional.

[0093] FIG. 2 provides an exemplary flowchart showing some methods of the present invention. The method for dehydrating or drying the nanocellulose slurry can be continuous, semi-continuous, or batchwise.

[0094] The present invention provides a method for dehydrating and optionally drying a nanocellulose slurry, the method comprising: (a) providing a nanocellulose slurry comprising nanocellulose and water; (b) providing a dispersant / dryer selected to be compatible with the nanocellulose, preferably selected to be compatible with the end use; (c) thoroughly mixing the nanocellulose slurry and the dispersant / dryer in a twin-screw system (e.g., a twin-screw extruder or a twin-rotor mixer); (d) removing at least a portion of the water from the nanocellulose slurry through one or more system vents in the twin-screw system to produce a nanocellulose dispersion concentrate; (e) optionally, grinding the nanocellulose dispersion concentrate to produce a powder which may or may not have residual moisture; (f) recovering the nanocellulose dispersion concentrate in solid or liquid form and comprising.

[0095] In some embodiments, the nanocellulose slurry is pre-concentrated in a nanocellulose slurry pre-concentration step to remove at least a portion of the water from the nanocellulose slurry before step (c). The nanocellulose slurry pre-concentration step can be, for example, centrifugation and / or filtration.

[0096] The dispersion / drying agent can be selected from the group consisting of, for example, waxes, polyolefins, olefin-maleic anhydride copolymers, olefin-acrylic acid copolymers, polyols, fatty acids, fatty alcohols, polyol-glyceride esters, polydimethylsiloxanes, polydimethylsiloxane-alkyl esters, polyacrylamides, starches, cellulose derivatives, microparticles, and combinations or reaction products thereof. Further discussion of various dispersion / drying agents can be found later herein.

[0097] In some embodiments, the dispersion / drying agent is added to the nanocellulose slurry before step (c). In these or other embodiments, the dispersion / drying agent can be added directly to the twin screw system, for example, through an additive inlet port. Preferably, the nanocellulose slurry and the dispersion / drying agent are mixed in a mixing unit, such as a stirred mixing tank or an in-line mixer (see FIG. 1), before adding the mixture to the twin screw system. In certain embodiments, the nanocellulose slurry supply subsystem is configured to stir the nanocellulose slurry and the dispersion / drying agent.

[0098] The twin screw system can be a twin screw extruder, such as a co-rotating twin screw extruder, a counter-rotating twin screw extruder, or another type of twin screw extruder (e.g., a gear pump extruder). Some of the design and operating principles of twin screw extruders were discussed above.

[0099] The twin screw system temperature is preferably monitored and controlled. The system temperature refers to the temperature of the materials inside the system, not the temperature of the outer barrel or the mixer bowl, although the barrel or mixer bowl temperature may be measured and correlated with the system temperature. If the twin screw extruder contains multiple extruder zones, the zone temperature of each extruder zone is preferably monitored and controlled independently. The control of temperature can utilize programmable control logic executed by a computer using well-known techniques.

[0100] The twin screw system can be operated at an average system temperature of, for example, about 120 °C to about 250 °C. The average system temperature may be calculated as the average of all measured temperatures, or may be estimated based on temperature measurements and other parameters (e.g., the amount of water released, the solid concentration at the outlet, etc.). In a continuous twin screw extruder, the zone temperature, i.e., the temperature at different spatial points, can be measured. In a batch or semi-batch twin rotor mixer, the temperature at different times can be measured, and the system may be at a constant temperature or a temperature that changes over time. In the case of a twin screw extruder, since the local temperature profile around the screws and between the screws is usually complex, even in a given extruder zone, the measured temperature represents the average within that zone. In various embodiments, the average extruder temperature is about, at least about, or up to about 120 °C, 125 °C, 130 °C, 135 °C, 140 °C, 145 °C, 150 °C, 160 °C, 170 °C, 180 °C, 190 °C, 200 °C, 210 °C, 220 °C, 230 °C, 240 °C, or 250 °C.

[0101] The twin-screw system can be operated at a maximum extruder temperature of, for example, from about 150°C to about 300°C. In various embodiments, the maximum system temperature is about, or at most about 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, 290°C, or 300°C. The twin-screw system is preferably operated at a maximum system temperature lower than the thermal decomposition onset temperature of nanocellulose (defined below).

[0102] In certain continuous embodiments, the zone temperature increases along the length of the twin-screw extruder. In other certain embodiments, the zone temperature decreases along the length of the twin-screw extruder. It is also possible to have a non-monotonic temperature profile along the extruder.

[0103] The twin-screw system can be heated by a heat transfer medium selected from the group consisting of steam, hot oil, electric heating elements, and combinations thereof. The twin-screw system can be cooled by a heat transfer medium selected from the group consisting of cooling water, air, oil, and combinations thereof. The heating and cooling configurations can be designed based on the desired temperature profile, throughput, materials present, shear rate, screw or rotor design, and other parameters.

[0104] The continuous twin-screw extruder can be operated at a wide range of shear rates, including axial and radial shear rates. Without limiting the scope of the present invention in any way, the twin-screw extruder can have an average axial shear rate of about 10 s -1 to about 200 s -1 , for example, about, or at least about 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, or 190 s -1 Without limiting the scope of the present invention in any way, the twin-screw extruder can have an average axial shear rate of about 100 s -1 to about 10000 s -1 (10 3 / s), e.g., about, or at least about 110, 125, 150, 200, 300, 400, 500, 1000, 2000, 3000, 4000, or 5000 s -1 can be operated at an average radial shear rate of. Generally, the radial shear rate is significantly higher than the axial shear rate. It should be noted that especially in the case of radial shear, the local shear rate may be substantially higher than the average shear rate.

[0105] Batch or semi-batch twin rotor mixers can be operated at a wide range of shear rates. Without limiting the scope of the present invention in any way, the twin rotor mixer can be from about 10 s -1 to about 10000 s -1 , e.g., about, or at least about 25, 50, 100, 125, 150, 200, 300, 400, 500, 1000, 2000, 3000, 4000, or 5000 s -1 and can be operated at an average radial shear rate of.

[0106] The twin screw system can be operated at an average nanocellulose residence time of, for example, about 30 seconds to about 120 minutes. In various embodiments, the average nanocellulose residence time is about, at least about, or at most about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, or 100 minutes. When the twin screw system is a batch system, the residence time is the batch time (e.g., in Example 1, the residence time is 90 minutes).

[0107] Since the multiphase system has a separate residence time distribution for different phases and at least a portion of the water exits the twin screw extruder, the residence time of the water will generally vary. In various embodiments, the average residence time of the water is about, at least about, or at most about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 minutes.

[0108] The residence time distribution of the material within the twin screw extruder will depend on whether the extruder is fully filled or starve-fed. A fully filled extruder means that during operation, the material is present throughout the entire internal volume, excluding entrapped air. In a starve-fed extruder, there are internal regions of the extruder that are void of material (nanocellulose or water) during operation. The more the screw gaps are filled, the narrower the nanocellulose residence time distribution becomes. Conversely, the more starved the screw is, the broader the nanocellulose residence time distribution becomes. A starved screw can provide a more axially well-mixed flow pattern compared to a fully filled plug flow. Axial mixing may be desirable for water removal because the local residence time and mass transfer of water in the axial mixing zone with an extruder vent are greater.

[0109] In some embodiments, at least one of the system vents is operated under vacuum. If step (d) utilizes multiple system vents, each of the system vents may be operated under vacuum or not all of the system vents need to be operated under vacuum.

[0110] In the nanocellulose dispersion concentrate produced in step (d), the nanocellulose can be present at a concentration of, for example, from about 10 wt% to about 90 wt%.

[0111] The starting nanocellulose slurry itself can have various nanocellulose concentrations, for example, from about 1 wt% to about 10 wt%, for example, about, or at least about, or up to about 2, 3, 4, 5, 6, 7, 8, or 9 wt% of nanocellulose. If a pre-concentration step (e.g., centrifugation) is used, the nanocellulose slurry fed to the twin screw system can have a wide range of nanocellulose concentrations, for example, from about 10 wt% to about 40 wt%, for example, about, or at least about, or up to about 5, 10, 15, 20, or 25 wt% of nanocellulose.

[0112] In various embodiments of the present invention, the nanocellulose dispersion concentrate can have a nanocellulose concentration of about, or at least about 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 wt% (including all intermediate ranges) on a dry weight basis. In certain embodiments where the nanocellulose slurry is substantially dehydrated or dried, the nanocellulose dispersion concentrate can have a nanocellulose concentration of about, or at least about 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 99, 99.5, 99.9, or 100 wt% (including all intermediate ranges) on a dry weight basis. The remainder of the nanocellulose dispersion concentrate that is not nanocellulose can be water, a dispersion / drying agent, and potentially other additives.

[0113] In various embodiments, the degree of water removal from the nanocellulose slurry by a twin screw system, calculated as the amount of water removed from the nanocellulose slurry divided by all the water present in the material fed to the extruder, can vary from about 10% to 100%. The degree of water removal can be about, or at least about 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 99% (including all intermediate ranges).

[0114] In various embodiments using a preliminary concentration step, the degree of water removal from the nanocellulose slurry, calculated as the water removed from the nanocellulose slurry divided by all of the water present in the material fed to the twin screw system, can vary from about 25% to 100% for the overall system (mechanical separation in the preliminary concentration unit and thermal separation in the twin screw system). The degree of water removal can be about, or at least about, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 99%, or 100% (including all intermediate ranges). In these embodiments, the water removed in the preliminary concentration step can be, for example, from about 10% to about 90% of all of the water removed from the system.

[0115] The dispersing / drying agent can be present in the nanocellulose dispersion concentrate at a concentration of, for example, from about 5 wt% to about 65 wt%. In some embodiments, the weight ratio of nanocellulose to dispersing / drying agent in the nanocellulose dispersion concentrate is selected from about 0.5 to about 2.

[0116] The nanocellulose can include cellulose nanocrystals, cellulose nanofibrils, microfibrillated cellulose, or combinations thereof. In some embodiments, the nanocellulose includes lignin-containing nanocellulose. In certain embodiments, the nanocellulose includes lignin-coated nanocellulose.

[0117] Some methods do not necessarily use a dispersing / drying agent. In some of these methods, the method for dehydrating the nanocellulose slurry is (a) providing a nanocellulose slurry comprising nanocellulose and water; and (b) optionally, pre-concentrating the nanocellulose slurry, for example, by centrifugation or filtration. (c) In a twin screw system, shearing the nanocellulose slurry and removing at least a portion of water from the nanocellulose slurry through one or more system vents to produce dehydrated nanocellulose; (d) Optionally, pulverizing the nanocellulose dispersion concentrate to produce a powder; (e) Recovering the dehydrated nanocellulose in solid or liquid form and comprising.

[0118] If no dispersant / drying agent is used, it may be appropriate not to dehydrate too significantly to avoid irreversible aggregation of the nanocellulose. In the dehydrated nanocellulose recovered in step (d) above, the nanocellulose may be present, for example, at a concentration of about 10 wt% to about 25 wt%. In various embodiments of dehydrating nanocellulose without using a dispersant / drying agent, the dehydrated nanocellulose may have a nanocellulose concentration of about, or at least about 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 wt% (including all intermediate ranges) on a dry weight basis.

[0119] As a rule of thumb, without limitation, the nanocellulose slurry can be dehydrated until the nanocellulose reaches about 10 - 25 wt% before irreversible aggregation begins to become significant, depending on the drying temperature profile. Despite this rule of thumb, the use of a twin screw extruder (even when no dispersant / drying agent is used) provides benefits resulting from the particularly thorough mixing that occurs within the twin screw extruder. For example, the degree of nanocellulose aggregation or the reversibility of the aggregation can be improved when a twin screw system is used for dehydration or drying compared to other devices, regardless of the dispersant / drying agent (if present). However, particularly when significantly dehydrating the nanocellulose slurry (e.g., completely drying it), it is preferred to use a dispersant / drying agent in the present invention.

[0120] In various embodiments of dehydrating or drying nanocellulose without using a dispersing / drying agent, the degree of water removal from the nanocellulose slurry by a twin-screw extruder can vary from about 10% to 100%. The degree of water removal can be about, or at least about, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 99% (including all intermediate ranges).

[0121] In various embodiments that use a pre-concentration step but do not use a dispersing / drying agent, the degree of water removal from the nanocellulose slurry by the entire system (mechanical separation in the pre-concentration unit and thermal separation in the twin-screw system), calculated as the amount of water removed from the nanocellulose slurry divided by all the water present in the material fed to the extruder, can vary from about 25% to 100%. The degree of water removal can be about, or at least about, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 99% (including all intermediate ranges). In these embodiments, the water removed from the pre-concentration step can be, for example, about 10% to about 90% of all the water removed from the system.

[0122] Some variations are (a) about 5 wt% to about 90 wt% of nanocellulose, and (b) about 5 wt% to about 95 wt% of a dispersing / drying agent selected to be compatible with the nanocellulose and are used in the production of a nanocellulose dispersion concentrate containing wherein the dispersing / drying agent is selected from the group consisting of waxes, polyolefins, olefin-maleic anhydride copolymers, olefin-acrylic acid copolymers, polyols, fatty acids, fatty alcohols, polyol-glyceride esters, polydimethylsiloxanes, polydimethylsiloxane-alkyl esters, polyacrylamides, starches, cellulose derivatives, microparticles, and combinations or reaction products thereof. Moreover, the nanocellulose dispersion concentrate is in solid or liquid form.

[0123] In some embodiments, the nanocellulose is present at a concentration of about 10 wt% to about 90 wt%, and the dispersant / drying agent is present at a concentration of about 5 wt% to about 65 wt%. In various embodiments, the nanocellulose is present at a concentration of about, at least about, or up to about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, or 90 wt% (including all intermediate ranges). In these or other embodiments, the dispersant / drying agent is present at a concentration of about, at least about, or up to about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, or 95 wt% (including all intermediate ranges).

[0124] In some embodiments, the total of the nanocellulose and the dispersant / drying agent is about, at least about, or up to about 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 99, or 100 wt%. The nanocellulose dispersion concentrate may consist essentially of nanocellulose and the dispersant / drying agent, i.e., no other functional components may be present.

[0125] In some embodiments, the weight ratio of nanocellulose to the dispersant / drying agent is selected from about 0.5 to about 2. In various embodiments, the weight ratio of nanocellulose to the dispersant / drying agent is about, at least about, or up to about 0.1, 0.2, 0.5, 0.75, 0.9, 1, 1.1, 1.25, 1.5, 1.8, 2, 3, 4, 5, 6, 7, 8, 9, or 10 (including all intermediate ranges).

[0126] The nanocellulose dispersion concentrate may be completely dry or may contain water at a concentration of about 0.1 wt% to about 90 wt%. In various embodiments, the nanocellulose dispersion concentrate contains about, or up to about 0.1, 0.2, 0.3, 0.4, 0.5, 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, or 70 wt% water (including all intermediate ranges).

[0127] The nanocellulose dispersion concentrate may further include a liquid solvent such as a polar liquid solvent selected from the group consisting of water, C1-C8 alcohols, C2-C8 polyols, and combinations thereof. Additionally or alternatively, a nonpolar liquid solvent such as an aromatic hydrocarbon, for example, toluene, xylene, or a lignin derivative may be present.

[0128] In some embodiments, the nanocellulose dispersion concentrate further includes an elastomer such as natural rubber or synthetic rubber. The concentration of the elastomer in the nanocellulose dispersion concentrate can be from about 0.1 wt% to about 80 wt%, for example, about 0.2, 0.3, 0.4, 0.5, 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, or 75 wt%.

[0129] In addition to nanocellulose, water, a dispersant / drying agent, and a solvent, the nanocellulose dispersion concentrate may contain additives or other components. For example, the additives can include compatibilizers, plasticizers, antioxidants, colorants, flame retardants, nucleating agents, viscosity modifiers, density modifiers, pest control agents, herbicides, bactericidal disinfectants, virus inactivators, etc. Such additives may be added to the nanocellulose dispersion concentrate after manufacture or may be introduced into the process upstream of the twin-screw extruder, for example, in a nanocellulose slurry supply subsystem.

[0130] A nanocellulose dispersion concentrate is a composition containing nanocellulose that is preferably redispersible in a target matrix (e.g., a polymer). The redispersibility of the nanocellulose dispersion concentrate can be tested or indicated in other systems that are not necessarily polymers, such as water, propanol, or other liquids or solids.

[0131] In certain embodiments, the nanocellulose dispersion concentrate or dehydrated nanocellulose is redispersed in an aqueous solution. In a typical example of such an embodiment, water is removed from the starting nanocellulose slurry (to avoid transporting the weight of water) for transporting the nanocellulose, and different water is added back at the place of use. Preferably, the nanocellulose is easily dispersible in water to form a nanocellulose slurry without the need for homogenization or other mechanical refining (other than standard industrial mixing). For example, the nanocellulose dispersion concentrate powder can be very easily separated into individual nanoparticles in water by tank stirring, for example, within 30 minutes.

[0132] The nanocellulose dispersion concentrate or dehydrated nanocellulose can be recovered from a twin-screw extruder and optionally packaged. The packaging can be, for example, a small container, tube, vial, jar, bag, supersack, or bucket. In certain embodiments, the nanocellulose dispersion concentrate is stored in a powder form such as a dry powder. In some embodiments, the nanocellulose dispersion concentrate is part of a kit that includes the nanocellulose dispersion concentrate packaged with instructions for use tailored to a specific composite system.

[0133] When used in preferred embodiments, the dispersant / drying agent is selected based on its compatibility with the selected nanocellulose and preferably also with the end-use product. In some embodiments, the dispersant / drying agent contains chemical components and / or functional groups capable of hydrogen bonding with polar groups present in the nanocellulose. Nanocellulose polar groups include at least -OH and to some extent -O-. When functionalized nanocellulose is utilized, other polar groups may be present. In other embodiments, the dispersant / drying agent does not necessarily have to be capable of hydrogen bonding with polar groups present in the nanocellulose. In these or other embodiments, the dispersant / drying agent contains components that serve as particle spacers. Particle spacers not only physically distribute the nanocellulose particles but also do not repel the nanocellulose phase. Repelling the nanocellulose is important because it leads to self-association and aggregation of the nanocellulose, resulting in irreversible bonding during drying. Rather, the particle spacers within the dispersant / drying agent prevent the nanocellulose from associating in this way, thereby reducing or preventing irreversible aggregation.

[0134] The dispersant / drying agent may also be selected based on economy (cost or availability), the ability to produce it as a by-product on-site, or its environmental sustainability. In some embodiments, the dispersant / drying agent is bio-based, biodegradable, and / or compostable.

[0135] In some embodiments, the dispersant / drying agent is a functionalized polyalkylene wax functionalized to be compatible with nanocellulose and optionally nanocellulose-polymer composite products. As used herein, a "functionalized" hydrogen-containing compound is one in which at least one hydrogen atom has been replaced by a functional group. Without limitation, -H can be replaced by -OH, -COOH, =O, or other oxygen-containing functional groups. In certain embodiments, for example, -H can be replaced by a non-oxygen-containing functional group such as a metal, halogen, nitrogen, sulfur, or a group containing these components.

[0136] The functionalized polyalkylene wax can be a functionalized polyethylene wax, a functionalized polypropylene wax, a functionalized polybutylene wax, or a combination thereof. In certain embodiments, the dispersant / drier is a low molecular weight oligomer or polymer of ethylene or functionalized ethylene. When functionalized ethylene is utilized, each repeating unit can have an average of about 0.1 to about 4.0 hydrogen atoms substituted by other functional groups. The number average degree of polymerization of ethylene or functionalized ethylene can be from 2 to 1000, such as from 5 to 500. In various embodiments, the number average degree of polymerization of ethylene or functionalized ethylene is at least, or at most, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 25, 50, 75, 100, 150, 200, 300, 400, 500, 600, 700, 800, 900, or 1000 (including all intermediate ranges).

[0137] In some embodiments, the dispersant / drier is a copolymer of (a) one or more C2-C4 olefins and (b) maleic anhydride. The C2 olefin is ethylene, the C3 olefin is propylene, and the C4 olefin is 1-butene, 2-butene, isobutene, butadiene, or a combination thereof. The C2-C4 olefins can be functionalized olefins such as functionalized ethylene. Maleic anhydride is an organic compound having the formula C2H2(CO)2O and is the acid anhydride of maleic acid. For the purposes herein, a polymer of maleic acid or a salt thereof is also considered to be a polymer of maleic anhydride. For example, maleic anhydride can be produced from 5-hydroxymethylfurfural, which itself can be derived from biomass (glucose dehydration). Also, the C2-C4 olefins can be produced from biomass, for example, by dehydration of alcohols produced by fermentation of sugars.

[0138] The copolymer of C2-C4 olefin and maleic anhydride can be a block copolymer, an alternating copolymer, a random copolymer, or a combination thereof. When the olefin is ethylene, for example, the copolymer can be poly(ethylene-alt-maleic anhydride) and / or poly(ethylene-graft-maleic anhydride). A graft copolymer is a type of copolymer in which one or more blocks of a homopolymer are grafted onto the main chain as branches, meaning it is a branched copolymer in which one or more side chains of a homopolymer are attached to the backbone of the main chain. Thus, poly(ethylene-graft-maleic anhydride) can also be considered a polymer of functionalized ethylene in which ethylene is functionalized by maleic acid or maleic anhydride. This type of copolymer can also be called maleated polyethylene.

[0139] In some embodiments, the dispersant / drying agent is a copolymer of (a) one or more C2-C4 olefins and (b) acrylic acid. The C2 olefin is ethylene, the C3 olefin is propylene, and the C4 olefin is 1-butene, 2-butene, isobutene, butadiene, or a combination thereof. The C2-C4 olefin can be a functionalized olefin such as functionalized ethylene. Acrylic acid is an organic compound having the formula CH2=CHCOOH. For the purposes herein, a polymer of acrylic acid or its salt is also considered to be a polymer of acrylic anhydride.

[0140] The copolymer of C2-C4 olefin and acrylic acid can be a block copolymer, an alternating copolymer, a random copolymer, or a combination thereof. Usually, acrylic acid polymerizes across its double bond, similar to ethylene polymerization (e.g., free radical copolymerization), resulting in a graft copolymer or a copolymer that can be considered a polymer of functionalized ethylene in which ethylene is functionalized by acrylic acid.

[0141] In some embodiments, the dispersant / drying agent comprises a polyol selected from ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, glycerol, butylene glycol, polybutylene glycol, butanediol, or combinations thereof. In some embodiments, the polyol is esterified by a fatty acid such as stearic acid.

[0142] In certain embodiments, the dispersant / drying agent is glycerol, or comprises glycerol, or is dissolved in glycerol as a solvent. Glycerol has a high boiling point (about 290 °C) and three hydroxyl groups (one OH group per C atom). When the nanocellulose is dried, glycerol can enter between the nanocellulose particles by forming hydrogen bonds, thereby preventing the formation of H bonds and resulting aggregation that could otherwise occur between the nanocellulose particles. The high boiling point of glycerol is beneficial for use in dry powders. The powder can be dispersed in a hydrophobic polymer matrix such as polylactic acid (PLA). Glycerol between the nanocellulose particles may function as a plasticizer when the PLA is extrusion processed, or the glycerol may be removed by vacuum during processing, or a combination thereof.

[0143] The dispersant / drying agent can be a polar molecule having a vapor pressure of less than 1.0 bar at 100 °C and optionally a vapor pressure of greater than 0.001 bar, greater than 0.01 bar, or greater than 0.1 bar at 180 °C. A relatively high vapor pressure at high temperature can be beneficial, for example, when it is desirable to remove the dispersant / drying agent during the formulation of the final polymer. The polar additive can be a polyol, such as ethylene glycol, glycerol, butanediol, etc. In some embodiments, the polar additive contains at least 0.5 OH groups per carbon atom, such as at least 1.0 OH group per carbon atom. The OH groups prevent irreversible bonding between the nanoparticles during drying. The polar additive can be organic or inorganic.

[0144] In some embodiments, the dispersant / dryer contains a fatty acid. A fatty acid is a carboxylic acid having a long aliphatic chain that is saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of 4 to 28 even-numbered carbon atoms. The fatty acids herein can be selected, for example, from caprylic acid, capric acid, lauric acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, or combinations thereof. Fatty acids that are unsaturated and / or branched may be used.

[0145] In some embodiments, the dispersant / dryer contains a fatty alcohol. A fatty alcohol is a long-chain alcohol that is a straight-chain primary alcohol having a carbon atom range of 4 to 26. Exemplary fatty alcohols include lauryl alcohol (dodecanol), stearyl alcohol, and oleyl alcohol. The fatty alcohol may be an oily liquid (for a smaller number of carbon atoms) or a waxy solid. Fatty alcohols typically have an even number of carbon atoms and a single alcohol group (-OH) bonded to the terminal carbon. Some are unsaturated and some are branched. Unsaturated and / or branched fatty alcohols may be used. Fatty alcohols having an odd number of carbon atoms may be used. Ethylene can be oligomerized, and the oligomer can undergo hydroformylation to yield an odd aldehyde, which can subsequently be hydrogenated. For example, from 1-decene, C 11 alcohol is produced by hydroformylation.

[0146] In some embodiments, the dispersant / dryer contains a siloxane-based additive. The siloxane-based additive can include a siloxane or polysiloxane material having one or more functional groups selected from the group consisting of methyl, C2-C 24 alkyl, epoxide, hydroxy, amino, carboxyl, acrylate, and combinations thereof. An exemplary siloxane-based additive is polydimethylsiloxane.

[0147] Siloxane-based additives preferably provide a hydrophobic portion and a hydrophilic portion. Typically, the hydrophobic and hydrophilic portions are at opposite ends of the molecule or polymer chain. The siloxane-based additives preferably exist as an emulsion in water. In certain embodiments, the dispersion / drying agent comprises an alkyl ester polydimethylsiloxane emulsion. While drying the nanocellulose with the emulsion, the nanocellulose surrounds the oil phase droplets during drying, and when the water is removed, the nanocellulose is drawn into the oil phase. In certain embodiments, the siloxane-based additive functions as an aid to prevent hydrogen bonding during drying.

[0148] In some embodiments, the dispersion / drying agent comprises starch, such as cationic starch, amphoteric starch, thermoplastic starch, or combinations thereof.

[0149] Cationic starch is positively charged, which may be desirable when the nanocellulose particles have a slightly negative surface charge. Exemplary cationic starches include quaternary ammonium cationic starch and quaternary amino cationic starch.

[0150] Amphoteric starch is a modified starch containing both positively and negatively charged substituents. Exemplary amphoteric starches contain a quaternary ammonium cationic group and a phosphate group as an anionic group.

[0151] Thermoplastic starch is starch plasticized by a relatively low level (e.g., 15 - 30 wt%) of molecules that can hydrogen bond to the hydroxyl groups of the starch. The starch plasticizer can be water, a polyol (e.g., glycerol), pentaerythritol, a sugar alcohol (e.g., sorbitol), poly(oxyethylene), poly(oxypropylene), a nonionic surfactant, an anionic surfactant, or combinations thereof.

[0152] In some embodiments, the dispersant / dryer contains fine particles. The fine particles can be selected from, but are not limited to, clay, nanoclay, talc, wollastonite, calcium carbonate (e.g., precipitated calcium carbonate), silica, mica, kaolin, nickel, glass fiber, bentonite, biotite, illite, kaolin, vermiculite, zeolite, carbon fiber, carbon nanotube, graphene, or combinations thereof. In some embodiments, the fine particles preferably have a surface charge that is positively charged. Known surface treatments such as treatment with an acidic solution at low pH can be used to provide a surface charge on the fine particles. Other surface treatments for the fine particles may be performed, such as silylation to improve interfacial adhesion.

[0153] In certain embodiments, the dispersant / dryer contains at least one fatty acid and at least one fine particle. The fatty acid and the fine particle may be present in a non-reactive form or may be reacted with each other in the dispersant / dryer. In these embodiments, the dispersant / dryer can include, for example, (a) a fatty acid selected from caprylic acid, capric acid, lauric acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, or combinations thereof, and (b) clay, nanoclay, talc, wollastonite, calcium carbonate, silica, mica, kaolin, limonite, glass fiber, bentonite, biotite, illite, kaolin, vermiculite, zeolite, or combinations thereof. Exemplary dispersants / dryers having both a fatty acid and a fine particle include talc and stearic acid. Another exemplary dispersant / dryer having both a fatty acid and a fine particle includes calcium carbonate and stearic acid.

[0154] In various embodiments, the dispersant / dryer contains an ionomer in association with a metal cation such as calcium or zinc to form a neutral salt. In various embodiments, the dispersant / dryer contains, in association with an anion, a positively charged component (e.g., surface-charged fine particles or cationic starch) to form a neutral salt.

[0155] If present, the dispersing / drying agent must be selected based on the properties of the nanocellulose to be dispersed and dried. In particular, the hydrophilicity of the nanocellulose can at least in part determine the appropriate dispersing / drying agent. When selecting an appropriate dispersing / drying agent, composition, particle size, melting point, and other factors can also be considered.

[0156] A hydrophilic molecule or part of a molecule is one in which the interaction with water and other polar substances is more thermodynamically favorable than the interaction with oil or other hydrophobic solvents. Hydrophilic molecules are usually charge-polarized and can form hydrogen bonds. On the other hand, hydrophobic molecules are not attracted to water or other polar molecules. Nanocellulose is usually very hydrophilic, but it can also be otherwise. In some embodiments, for example, lignin-containing nanocellulose is relatively hydrophobic. Since lignin itself is not purely hydrophobic, there is usually still some hydrophilicity in lignin-containing nanocellulose.

[0157] In a preferred embodiment, the hydrophilicity of the dispersing / drying agent (or part of the dispersing / drying agent) is selected to match or be similar to the hydrophilicity of the nanocellulose, and thus they are phase-bound and the dispersing / drying agent separates the regions of the nanocellulose.

[0158] In some embodiments, the hydrophilicity of the dispersing / drying agent is selected based at least in part on the hydrophilicity of the polymer or other matrix materials in the final composite, i.e., the final specification product. The dispersing / drying agent can be designed, for example, to have both hydrophilic and hydrophobic components at the two ends of the molecule. In such embodiments, for example, the hydrophilic end adheres to the nanocellulose surface, while the hydrophobic end is captured on the hydrophobic polymer during compounding.

[0159] In some embodiments, the dispersant / drying agent is selected based on its melting point. In these embodiments, the dispersant / drying agent at least partially melts during the drying of the nanocellulose dispersion concentrate. When the dried nanocellulose dispersion concentrate is cooled, the dispersant / drying agent returns to a solid phase in which the nanocellulose is uniformly dispersed. As an example, polyethylene wax (including functionalized modifications) has a melting point in the range of approximately 100 to 150 °C. At least a part of the twin screw system must be operated at a temperature above the melting point of the selected dispersant / drying agent.

[0160] In addition to enhancing the dispersion of the nanocellulose, the dispersant / drying agent may have other functions. For example, in some embodiments, the dispersant / drying agent may function as a compatibilizer (between the matrix material and the nanocellulose), a plasticizer, a density modifier, a viscosity modifier, or a toughness modifier. The dispersant / drying agent may also provide auxiliary properties to the final material, such as color or texture.

[0161] In some variations, the technical scheme provides the following steps (see also the flowchart of FIG. 2). First, a nanocellulose slurry is provided. Second, a dispersant / drying agent is selected based on the selected nanocellulose material such that the dispersant / drying agent is compatible with the nanocellulose and preferably the final composite material. Third, optionally, the nanocellulose slurry is pre-concentrated using a centrifuge or a filtration device. Fourth, a nanocellulose dispersion concentrate is produced by combining the dispersant / drying agent, the nanocellulose, and optionally other components and transporting the materials through a twin-screw system with the release of water from one or more system vents. Fifth, optionally, the nanocellulose dispersion concentrate is ground to produce a dry powder (e.g., less than 10 wt% water). Sixth, optionally, in a final application, the nanocellulose dispersion concentrate can be used to produce a composition product containing, for example, a matrix material such as nanocellulose and a polymer. The nanocellulose can also improve some properties of the matrix material (e.g., mechanical strength, viscosity, etc.) or provide a renewable content to the material.

[0162] Some variations provide a method for producing a nanocellulose dispersion concentrate, the method comprising providing a nanocellulose slurry comprising nanocellulose and water, and selecting a dispersant / drying agent compatible with the nanocellulose, the dispersant / drying agent being selected from the group consisting of wax, polyolefin, olefin-maleic anhydride copolymer, olefin-acrylic acid copolymer, polyol, fatty acid, fatty alcohol, polyol-glyceride ester, polydimethylsiloxane, polydimethylsiloxane-alkyl ester, polyacrylamide, starch, cellulose derivative, fine particles, and combinations or reaction products thereof, and optionally, pre-concentrating the nanocellulose slurry to remove a first portion of the water, and Using a twin-screw system, mixing the nanocellulose slurry and the dispersing / drying agent, and removing at least a second portion of water (or, if the pre-concentration step is omitted, the first portion) to produce a nanocellulose dispersion concentrate; Optionally, pulverizing the nanocellulose dispersion concentrate to produce a powder; Recovering the nanocellulose dispersion concentrate in solid or liquid form and including.

[0163] The water in the nanocellulose slurry can be at least partially replaced by another polar solvent. Usually, nanocellulose is produced in an aqueous solution, but this is not strictly essential. Biomass fractionation procedures for producing nanocellulose use polar solvents such as glycerol or ethanol instead of or in addition to water in principle. Thus, although most of the present disclosure refers to water as the main or only polar solvent in the starting nanocellulose slurry, it will be understood that one or more polar solvents other than water can be utilized.

[0164] In some variations, the method for producing a nanocellulose dispersion concentrate is providing a nanocellulose slurry comprising nanocellulose and water; selecting a dispersing / drying agent adapted to the nanocellulose, the dispersing / drying agent being selected from the group consisting of waxes, polyolefins, olefin-maleic anhydride copolymers, olefin-acrylic acid copolymers, polyols, fatty acids, fatty alcohols, polyol-glyceride esters, polydimethylsiloxanes, polydimethylsiloxane-alkyl esters, polyacrylamides, starches, cellulose derivatives, microparticles, and combinations or reaction products thereof; mixing the nanocellulose slurry and the dispersing / drying agent to produce a mixture; pre-concentrating the mixture using mechanical separation and / or pre-concentrating the nanocellulose slurry prior to mixing with the dispersing / drying agent; Using a twin-screw system, removing at least a portion of water to produce a nanocellulose dispersion concentrate; Optionally, grinding the nanocellulose dispersion concentrate to produce a powder; Recovering the nanocellulose dispersion concentrate in a solid or liquid form; and including.

[0165] All methods disclosed herein can be carried out batchwise, continuously, or semi-continuously. Feedthrough can vary widely, including laboratory scale, pilot scale, semi-works scale, and commercial scale.

[0166] In various embodiments, the nanocellulose dispersion concentrate can contain water at a moisture concentration of about, or up to about 70 wt%, 60 wt%, 50 wt%, 45 wt%, 40 wt%, 35 wt%, 30 wt%, 25 wt%, 20 wt%, 15 wt%, 10 wt%, 9 wt%, 8 wt%, 7 wt%, 6 wt%, 5 wt%, 4 wt%, 3 wt%, 2.5 wt%, 2 wt%, 1.5 wt%, 1 wt%, 0.9 wt%, 0.8 wt%, 0.7 wt%, 0.6 wt%, 0.5 wt%, 0.4 wt%, 0.3 wt%, 0.2 wt%, 0.1 wt%, 0.05 wt%, 0.01 wt%, or 0 wt% (including any intermediate range), such as water at about 0.5 - 1.5 wt% or about 0.1 - 7 wt%.

[0167] Nanocellulose can be characterized by unbound moisture and bound moisture. This ratio generally differs for lignin-containing nanocellulose compared to non-lignin-containing nanocellulose when all other factors are the same. Thus, the apparatus configuration and operating parameters can be adapted to the ratio of unbound moisture to bound moisture in the system feed. In some embodiments, a pre-concentration step (e.g., by filtration or centrifugation) targets the removal of unbound water, and the twin-screw system can remove bound water by the combined use of high shear force and thermal energy.

[0168] The present invention is applicable to various types of nanocellulose materials. Nanocellulose can be produced by breaking down biomass into submicron cellulose nanofibers or nanocrystals using chemical means, mechanical means, or a combination of chemical and mechanical means. Other methods for producing nanocellulose, such as bacterial nanocellulose and nanocellulose derived from tunicates, are also available.

[0169] Generally, the production of nanocellulose occurs in two main stages. The first stage is the purification of biomass to remove most of the non-cellulose components in the biomass, such as lignin, hemicellulose, extractives, and inorganic contaminants. This stage is usually carried out by conventional pulping and bleaching. For the production of cellulose nanofibers, the second stage usually involves mechanical refining of the purified biomass fibers, with or without chemical or enzymatic treatment to reduce the amount of mechanical energy required. In the case of cellulose nanocrystals, the second stage usually involves acid hydrolysis of the purified fibers followed by high-shear mechanical treatment.

[0170] Nanocellulose can be obtained by fractionating lignocellulosic biomass in the presence of an acid catalyst, a solvent for lignin, and water to produce a cellulose-rich solid, and then mechanically treating the cellulose-rich solid to produce nanocellulose or its precursor. In some embodiments, the solvent for lignin is an aliphatic alcohol (e.g., ethanol), and the acid catalyst is a sulfur-containing compound selected from the group consisting of sulfur dioxide, sulfurous acid, sulfur trioxide, sulfuric acid, elemental sulfur, sulfonic acid, lignosulfonic acid, and combinations thereof.

[0171] Nanocellulose can be obtained from the AVAP® lignocellulosic biomass fractionation process. It has been found that very high crystallinity can be generated and maintained during the formation of nanofibers or nanocrystals without the need for enzymes or a separate acid treatment step to hydrolyze amorphous cellulose. The high crystallinity can lead to mechanically strong fibers or good physical strengthening properties, which are advantageous for, for example, composites, reinforced polymers, and high-strength spun fibers and textiles.

[0172] In some embodiments, the nanocellulose comprises hydrophobic nanocellulose. In these or other embodiments, the nanocellulose comprises hydrophilic nanocellulose. In certain embodiments, the nanocellulose comprises lignin-containing cellulose nanocrystals (e.g., lignin-coated cellulose nanocrystals) and / or lignin-containing cellulose nanofibers (e.g., lignin-coated cellulose nanofibers).

[0173] In some embodiments, the nanocellulose material is at least partially hydrophobic by at least a portion of the lignin adhering to the surface of the cellulose-rich solid (nanocellulose precursor). In these or other embodiments, the nanocellulose material is at least partially hydrophobic by at least a portion of the lignin adhering to the surface of the nanocellulose material after mechanical refining.

[0174] In some embodiments, the acid is SO2 at a concentration of about 5 wt% to about 30 wt%. In some embodiments, the fractionation temperature is about 130 °C to about 180 °C. In some embodiments, the fractionation time is about 15 minutes to about 4 hours. The process can be controlled such that a portion of the solubilized lignin intentionally returns and adheres to the surface of the cellulose-rich solid, thereby making the cellulose-rich solid at least partially hydrophobic.

[0175] Process conditions that facilitate the adhesion of lignin to the fiber can be used, such as extended time and / or temperature, or a reduced concentration of the lignin solvent. Alternatively or additionally, one or more washing steps may be performed to attach at least a portion of the lignin solubilized during the first fractionation. One approach is to wash with water rather than a solution of water and solvent. Since lignin does not normally dissolve in water, it will begin to precipitate. Optionally, other conditions such as pH and temperature may be varied during fractionation, washing, or other steps to optimize the amount of lignin adhering to the surface. Optionally, a method for producing a hydrophobic nanocellulose material may further include chemically modifying the lignin to increase the hydrophobicity of the nanocellulose material.

[0176] Alternatively or additionally, nanocellulose can be obtained by fractionating lignocellulosic biomass in the presence of steam or hot water, optionally using a fractionation catalyst (e.g., acetic acid), to obtain a cellulose-rich solid, and then producing nanocellulose by mechanical refining of the cellulose-rich solid. These steps can be collectively referred to as a hydrothermal-mechanical treatment. The reaction solution for fractionation can consist essentially of steam or hot water. Note that "steam or hot water" refers to water in one or more phases determined by thermodynamics at a given temperature and pressure. The temperature of the fractionation can be from about 120°C to about 220°C, such as from about 150 to 200°C. The water can be in the form of steam, superheated steam, supersaturated steam, or pressurized liquid water. In some embodiments, the fractionation step is carried out with a residence time of from about 1 minute to about 60 minutes, such as about 2, 2.5, 3, 3.5, 4, 5, 7.5, 10, 12.5, 15, 20, 25, 30, 35, 40, 45, 50, or 55 minutes.

[0177] In embodiments using hydrothermal-mechanical treatment, the cellulose-rich solids typically contain a significant concentration of lignin. Thus, these embodiments can be beneficial when hydrophobic nanocellulose is desired. Hydrothermal-mechanical treatment can produce nanocellulose that can be called nanolignocellulose due to its high lignin content. Nanolignocellulose can contain, on a completely dry, ash-free, and acetyl-free basis, from about 35 wt% to about 80 wt% cellulose nanofibrils, cellulose microfibrils, or a combination thereof, from about 15 wt% to about 45 wt% lignin, and from about 5 wt% to about 20 wt% hemicellulose. Of the lignin present, some can coat the nanocellulose particles, while the remainder of the lignin is within the nanocellulose particles.

[0178] Nanocellulose is preferably obtained from lignocellulosic biomass. As used herein, "lignocellulosic biomass" means any material containing cellulose and lignin. Lignocellulosic biomass can also contain hemicellulose. A mixture of one or more types of biomass can be used. In some embodiments, the biomass feedstock includes both a lignocellulosic component (e.g., those described above) in addition to a sucrose-containing component (e.g., sugarcane or energy cane) and / or a starch component (e.g., corn, wheat, rice, etc.). Various moisture levels can be associated with the starting biomass. The biomass feedstock need not be dry, although it can be. Generally, the biomass is in the form of microparticles or chips, although the particle size of the starting biomass is not critical.

[0179] Biomass raw materials for producing nanocellulose can be selected from hardwood, softwood, forest residues, eucalyptus, industrial waste, pulp and paper waste, consumer waste, or combinations thereof. In some embodiments, agricultural residues including lignocellulosic biomass associated with edible crops, annuals, energy crops, or other annually renewable raw materials are utilized. Exemplary agricultural residues include, but are not limited to, corn stover, corn fiber, wheat straw, sugarcane bagasse, sugarcane straw, rice straw, oat straw, barley straw, miscanthus, energy cane straw / residue, or combinations thereof.

[0180] Other nanocellulose sources include bacterial nanocellulose, nanocellulose derived from tunicates, pulp treatment with sulfuric acid, pulp treatment with 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO), or pulp treatment with cellulase enzymes. In some embodiments, the nanocellulose used herein is not bacterial nanocellulose, not derived from tunicates, not obtained from sulfuric acid hydrolysis, not obtained from TEMPO, and / or not obtained by enzymatic hydrolysis of lignocellulosic biomass or cellulose.

[0181] As intended herein, "nanocellulose" is broadly defined to include various cellulose-based materials including, but not limited to, microfibrillated cellulose, nanofibrillated cellulose, microcrystalline cellulose, nanocrystalline cellulose, and microparticulated or fibrillated dissolved pulp. In certain embodiments, nanocellulose includes particles having at least one length dimension (e.g., diameter) on the nanometer scale. In some embodiments, nanocellulose has particles with all average dimensions greater than 1 micron, such as in the case of certain microfibrillated cellulose.

[0182] "Nanofibrillated cellulose" or equivalently "cellulose nanofibril" means cellulose fibers or regions containing particles or fibers of nanometer size, or particles or fibers of both micron size and nanometer size. "Nanocrystalline cellulose" or equivalently "cellulose nanocrystal" means cellulose particles, regions, or crystals containing domains of nanometer size, or domains of both micron size and nanometer size. "Micron size" includes 1 μm to 100 μm, and "nanometer size" includes 0.01 nm to 1000 nm (1 μm). In any of these materials, larger domains (including long fibers) may also be present.

[0183] The specific size and shape of the nanocellulose can range from the nanometer scale to the micron scale in terms of width and / or length. Cellulose nanofibers typically have a width dimension of 5 to 20 nm and a length dimension of 500 to 5000 nm and contain both amorphous and crystalline domains of cellulose. Cellulose nanocrystals typically have a width of 3 to 8 nm and a length of 100 to 500 nm and are mainly crystalline. Although these ranges and dimensions are typical, the present invention encompasses all nanocellulose materials regardless of particle shape or particle size.

[0184] Some embodiments use a blend of nanocellulose crystals and fibrils. The blend of nanocellulose crystals and fibrils can contain 1% to 99% nanocellulose crystals and 99% to 1% nanocellulose fibrils, respectively. In various embodiments, the blend of nanocellulose crystals and fibrils contains 2%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 98% (all weight percentages) of nanocellulose crystals, with the remainder of the nanocellulose being nanocellulose fibrils.

[0185] Some embodiments use a blend of cellulose nanofibrils and microfibrils. The blend of cellulose nanofibrils and cellulose microfibrils can contain from 1% to 99% cellulose nanofibrils and from 99% to 1% cellulose microfibrils, respectively. In various embodiments, the blend of cellulose nanofibrils and microfibrils contains 2%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 98% (all weight percentages) of cellulose nanofibrils, with the remainder being cellulose microfibrils.

[0186] Since nanocellulose fibrils are much larger than nanocellulose crystals, one characteristic of the nanocellulose blend is the wide range of particle sizes present. The width of the nanocellulose crystals can vary, for example, from about 2 nanometers to about 10 nanometers, or from about 3 nanometers to about 6 nanometers. The length of the nanocellulose crystals can vary, for example, from about 50 nanometers to about 500 nanometers, or from about 100 nanometers to about 350 nanometers. The width of the nanocellulose fibrils can vary, for example, from about 5 nanometers to about 100 nanometers, or from about 10 nanometers to about 50 nanometers. The length of the nanocellulose fibrils can vary, for example, from about 200 nanometers to about 10 microns, or from about 400 nanometers to about 3 microns. The average nanocellulose particle width in the blend can vary from about 3 nanometers to about 50 nanometers, for example, from about 5 nanometers to about 30 nanometers. The average nanocellulose particle length in the blend can vary from about 50 nanometers to about 5 microns, for example, from about 100 nanometers to about 2 microns.

[0187] In some variations, the nanocellulose is (a) providing a lignocellulosic biomass feedstock; and (b) fractionating the feedstock in the presence of an acid, a solvent for lignin, and water to produce a cellulose-rich solid and a liquid containing hemicellulose and lignin. (c) Mechanically treating the cellulose-rich solid to form cellulose fibrils and / or cellulose crystals, thereby producing a nanocellulose material having a crystallinity of at least 60% (i.e., cellulose crystallinity); (d) Recovering the nanocellulose material; obtained from a process comprising.

[0188] In some embodiments, the acid is selected from the group consisting of sulfur dioxide, sulfurous acid, sulfur trioxide, sulfuric acid, lignosulfonic acid, and combinations thereof. In certain embodiments, the acid is sulfur dioxide.

[0189] In some embodiments, during step (c), the cellulose-rich solid is treated with a total mechanical energy of less than about 5000 kilowatt-hours per ton of cellulose-rich solid, such as less than about 4000, 3000, 2000, or 1000 kilowatt-hours per ton of cellulose-rich solid. The energy consumption can be measured with any other suitable device. An ammeter that measures the current drawn by the motor driving the mechanical treatment device is one way to obtain an estimate of the total mechanical energy.

[0190] The mechanical treatment in step (c) can use one or more known techniques such as, for example, grinding, crushing, beating, ultrasonic treatment, or any other means, but is by no means limited to these, to form or release nanofibrils and / or nanocrystals in cellulose. In essence, any type of mill, or device for physically separating fibers, can be utilized. Such mills are well known in the industry and include, but are not limited to, valley beaters, single disk refiners, double disk refiners, conical refiners including both wide and narrow angles, cylindrical refiners, homogenizers, microfluidizers, and other similar grinding or crushing devices. See, for example, Smook, Handbook for Pulp&Paper Technologists, Tappi Press, 1992; and Hubbe et al., “Cellulose Nanocomposites: A Review,” BioResources 3(3), pages 929 - 980 (2008).

[0191] The degree of mechanical treatment can be monitored by any of several means during the process. Certain optical instruments can provide continuous data regarding fiber length distribution and % fines, both of which can be used to define the end point of the mechanical treatment step. Time, temperature, and pressure can vary during the mechanical treatment. For example, in some embodiments, ultrasonic treatment at ambient temperature and pressure for about 5 minutes to 2 hours can be utilized.

[0192] In some embodiments, a portion of the cellulose - rich solid is converted to nanofibrils, while the remainder of the cellulose - rich solid is not fibrillated. In various embodiments, about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 99%, or substantially all of the cellulose - rich solid is fibrillated into nanofibrils.

[0193] In some embodiments, some of the nanofibrils are converted to nanocrystals, while the rest of the nanofibrils are not converted to nanocrystals. In various embodiments, about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 99%, or substantially all of the nanofibrils are converted to nanocrystals. During drying, a small amount of nanocrystals can also aggregate and form nanofibrils.

[0194] After mechanical treatment, the nanocellulose material can be classified by particle size. A portion of the material can undergo another process, such as enzymatic hydrolysis to yield glucose. Such materials may have, for example, good crystallinity but may not have the desired particle size or degree of polymerization.

[0195] Step (c) can further include treating the cellulose-rich solid with one or more enzymes or one or more acids. When an acid is used, the acid can be selected from the group consisting of sulfur dioxide, sulfurous acid, lignosulfonic acid, acetic acid, formic acid, and combinations thereof. Acids related to hemicellulose, such as acetic acid or uronic acid, can be used alone or in combination with other acids. Step (c) can also include treating the cellulose-rich solid with heat. In some embodiments, step (c) does not use any enzymes or acids.

[0196] In step (c), when an acid is used, the acid can be a strong acid such as sulfuric acid, nitric acid, or phosphoric acid. Weaker acids can be used at more severe temperatures and / or times. Instead of, or potentially in sequential configuration before or after acid hydrolysis, enzymes that hydrolyze cellulose (i.e., cellulase) and possibly hemicellulose (i.e., having hemicellulase activity) can be used in step (c).

[0197] In some embodiments, the method includes enzymatically treating the cellulose-rich solid to hydrolyze the amorphous cellulose. In other embodiments, or sequentially before or after the enzymatic treatment, the method may include acid treating the cellulose-rich solid to hydrolyze the amorphous cellulose.

[0198] In some embodiments, the method further includes enzymatically treating the nanocrystalline cellulose. In other embodiments, or sequentially before or after the enzymatic treatment, the method further includes acid treating the nanocrystalline cellulose.

[0199] Optionally, the enzymatic treatment can be used before the mechanical treatment or perhaps simultaneously with the mechanical treatment. However, in a preferred embodiment, the enzymatic treatment is not necessary to hydrolyze the amorphous cellulose or to weaken the structure of the fiber wall prior to the isolation of the nanofibers.

[0200] After the mechanical treatment, the nanocellulose can be recovered. The separation of cellulose nanofibrils and / or nanocrystals can be achieved using an apparatus capable of degrading the ultrastructure of the cell wall while preserving the integrity of the nanofibrils. For example, a homogenizer can be used. In some embodiments, cellulose aggregate fibrils having component fibrils in the range of 1 to 100 nm in width are recovered, where the fibrils are not completely separated from each other.

[0201] The method may further include bleaching the cellulose-rich solid before step (c) and / or as part of step (c). Alternatively or additionally, the method may further include bleaching the nanocellulose material during and / or after step (c). Any known bleaching technique or sequence including enzymatic bleaching can be used.

[0202] Optionally, the method further includes hydrolyzing the amorphous cellulose to glucose in step (b) and / or step (c), recovering the glucose, and fermenting the glucose to a fermentation product. Optionally, the method further includes recovering, fermenting, or further processing the hemicellulose sugars derived from hemicellulose. Optionally, the method further includes recovering, combusting, or further processing the lignin.

[0203] The nanocellulose material may comprise nanofibrillated cellulose or may consist essentially of nanofibrillated cellulose. The nanocellulose material may comprise nanocrystalline cellulose or may consist essentially of nanocrystalline cellulose. In some embodiments, the nanocellulose material may comprise nanofibrillated cellulose and nanocrystalline cellulose or may consist essentially of nanofibrillated cellulose and nanocrystalline cellulose.

[0204] In some embodiments, the crystallinity of the cellulose-rich solid (i.e., the nanocellulose precursor material) is at least 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86% or more. In these or other embodiments, the crystallinity of the nanocellulose material is at least 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86% or more. The crystallinity can be measured using any known technique. For example, X-ray diffraction and solid 13 C nuclear magnetic resonance can be utilized.

[0205] In some embodiments, the nanocellulose material is characterized by an average degree of polymerization of from about 100 to about 3000, such as about 125, 150, 175, 200, 225, 250, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 2000, 2500, or 2600. For example, the nanocellulose material may be characterized by an average degree of polymerization of from about 300 to about 700, or from about 150 to about 250. When the nanocellulose material is in the form of nanocrystals, it may have a degree of polymerization of less than 100, such as about 75, 50, 25, or less than 10. A portion of the material may have a degree of polymerization exceeding 3000, 4000, or 5000.

[0206] In some embodiments, the nanocellulose material is characterized by a degree of polymerization distribution having a single peak. In other embodiments, the nanocellulose material is characterized by a degree of polymerization distribution having two peaks, such as one peak centered in the range of 150 - 250 and another peak centered in the range of 300 - 700.

[0207] In some embodiments, the nanocellulose material is characterized by an average length - to - width aspect ratio of the particles of from about 10 to about 1000, such as about 15, 20, 25, 35, 50, 75, 100, 150, 200, 250, 300, 400, or 500. Nanofibrils are generally associated with a higher aspect ratio than nanocrystals. The nanocrystals can have, for example, a length range of about 100 nm to 500 nm and a diameter of about 4 nm, which results in an aspect ratio of 25 - 125. The nanofibrils can have a length of about 2000 nm and a diameter range of 5 - 50 nm, which results in an aspect ratio of 40 - 400. In some embodiments, the aspect ratio is less than 50, less than 45, less than 40, less than 35, less than 30, less than 25, less than 20, less than 15, or less than 10.

[0208] In some embodiments, the nanocellulose contains less than 0.05 wt% sulfur, e.g., about 0.02 wt% or less sulfur, and may also contain undetectable sulfur. In some embodiments, the nanocellulose does not contain sulfate half - ester groups bound to the surface of the nanocellulose particles because these groups can reduce the thermal stability of the nanocellulose.

[0209] The "onset temperature of thermal decomposition" of a material is defined by thermogravimetric analysis of the material. Thermogravimetric analysis, also known as TGA, is a technique in which the mass of a substance is monitored as a function of temperature or time when the sample is subjected to a controlled temperature program in a controlled atmosphere. For thermogravimetric analysis, a PerkinElmer STA6000 Simultaneous Thermal Analyzer (London, UK) can be utilized. The abscissa (x - axis) is temperature and the ordinate (y - axis) is weight percent (%). A decrease in the TGA thermocurve indicates that weight loss has occurred. From the TGA thermocurve, an extrapolated onset temperature indicating the temperature at which weight loss begins can be calculated. The extrapolated onset temperature is a reproducible temperature calculation and is defined to be used by ASTM and ISO for TGA. The extrapolated onset temperature is the intersection of the tangent at the maximum slope point at the leading edge of the peak and the extrapolated baseline. This technique can be applied to nanocellulose or the dispersant / drying agent.

[0210] For the purposes of this specification, to determine the onset temperature of thermal decomposition of nanocellulose, using a PerkinElmer STA6000 Simultaneous Thermal Analyzer, under a nitrogen atmosphere at a flow rate of 40 mL / min, the sample is heated from 50 °C to 600 °C at a heating rate of 10 °C / min. The mass is measured as a function of temperature. Mass loss other than water loss indicates thermal decomposition of the material. The extrapolated onset temperature from the TGA graph is the estimated onset temperature of thermal decomposition of the nanocellulose or the dispersant / drying agent.

[0211] In some preferred embodiments, for example, in the case of BioPlus® cellulose nanocrystals or nanofibrils produced from a fraction using an acid catalyst, a lignin solvent, and water, the nanocellulose is characterized by a thermal decomposition onset temperature of about, or at least about, 300 °C, 310 °C, 320 °C, or 330 °C. In other embodiments, the nanocellulose is characterized by a thermal decomposition onset temperature of about 220 °C to about 300 °C, for example, about 225 °C in the case of cellulose nanofibrils produced from TEMPO or about 285 °C in the case of cellulose nanocrystals produced from sulfuric acid.

[0212] Optionally, the nanocellulose itself is functionalized with one or more surface functional groups to yield a nanocellulose derivative. Such functionalization can be carried out, for example, to improve compatibility with a matrix polymer or to impart special properties to the nanocellulose. Since nanocellulose has a large surface area and a high concentration of surface hydroxyl groups, targeted surface modification can introduce substantially any desired surface functionality.

[0213] For example, the nanocellulose derivative can be selected from the group consisting of nanocellulose esters, nanocellulose ethers, nanocellulose ether esters, alkylated nanocellulose compounds, crosslinked nanocellulose compounds, acid-functionalized nanocellulose compounds, base-functionalized nanocellulose compounds, and combinations thereof. Functionalization or derivatization of various types of nanocellulose can be used, for example, functionalization with polymers, chemical surface modification, functionalization with nanoparticles (i.e., in addition to nanocellulose, other nanoparticles), modification with inorganic substances or surfactants, or biochemical modification.

[0214] Dehydrated nanocellulose can be used in a wide range of end - uses. In many embodiments, the nanocellulose is incorporated into a matrix material to form a nanocellulose - containing composite material. Various apparatuses such as a single - screw extruder, a twin - screw extruder, an injection - molding line, a compression - molding line, a kneader, a calender, a rotor - stator dispersing mill, a high - shear mixer, a stirred tank, or an in - line mixer (not limited thereto) can be used to compound the nanocellulose to produce the composite material.

[0215] The matrix material can be a matrix polymer. For example, the matrix polymer can be selected from the group consisting of polyolefins, polyols, polyesters, polyamides, polylactic acid, polystyrene, polycarbonates, polyacrylates, polystyrene, styrenic rubbers, natural rubber, synthetic rubbers, polyurethanes, polyureas, poly(amide - enamine), polyanhydrides, polyhydroxyalkanoates, poly(alkenedicarboxylates), silicones, thermoplastic resin elastomers, thermoplastic polyurethane (TPU), synthetic rubbers, natural rubber, carbonaceous polymers, and combinations or copolymers thereof.

[0216] Alternatively or additionally, the matrix material may be a material other than a polymer, such as paper, paperboard, fibers and wood composites (e.g., particle board and molded pulp products), emulsions, hydrogels, carbon, organic solids, inorganic solids, oils, organic liquids, inorganic liquids, cement - based materials (e.g., concrete or cement), minerals, ceramics, metals, metal alloys, glass, and materials selected from the group consisting of combinations thereof. The non - polymer matrix material may be, for example, an adhesive matrix, a battery electrode matrix, a bioink matrix, or an electronic ink matrix.

[0217] In some embodiments, the matrix material comprises a polymer selected from polyester, polyolefin, polyamide, polystyrene, styrene rubber, natural rubber, synthetic rubber, polyurethane, polyurea, poly(amide-eneamine), polyanhydride, polyacrylate, polyhydroxyalkanoate, poly(alkenedicarboxylate), silicone, thermoplastic resin elastomer, thermoplastic polyurethane (TPU), synthetic rubber, natural rubber, or a combination or copolymer thereof. Some polymer blends include polylactic acid, polyhydroxyalkanoate, aliphatic-aromatic copolyesters, both polylactic acid and aliphatic-aromatic copolyesters, polyethylene and / or polypropylene.

[0218] In various embodiments, the polymer is selected from the group consisting of polyethylene, polypropylene, polybutene, polyisobutylene, polybutadiene, polyisoprene, poly(ethylene-co-acrylic acid), poly(lactic acid) (or polylactic acid), poly(glycolic acid) (or polyglycolide), poly(hydroxybutyrate), poly(butylene adipate-co-terephthalate), poly(butylene succinate), poly(hydroxybutyrate-co-hydroxyvalerate), poly(ethylene terephthalate), polyvinyl alcohol, polystyrene, poly(butyl acrylate), poly(tert-butyl acrylate-co-ethyl acrylate-co-methacrylic acid), poly(ethyl acrylate), poly(2-ethylhexyl acrylate), poly(methyl acrylate), polyacrylonitrile, poly(acrylonitrile-co-methyl acrylate), poly(styrene-co-maleic anhydride), poly(methyl methacrylate), poly(alkyl methacrylate), polyvinylcyclohexane, poly(bisphenol A carbonate), poly(propylene carbonate), poly(1,4-butylene adipate), poly(1,4-butylene succinate), poly(1,4-butylene terephthalate), poly(ethylene succinate), poly(vinyl acetate), poly(propylene glycol), poly(tetrahydrofuran), poly(ethyl vinyl ether), polydimethylsiloxane, nylon (aliphatic polyamide), and combinations or copolymers thereof. A carbonaceous polymer may also be incorporated into the composite. Examples of carbonaceous polymers include polyacenaphthylene, graphite, graphene, carbon fiber, and lignin.

[0219] The polymers that can be included in the composite product can be, for example, hydrophobic, partially hydrophobic, or lipophilic. Hydrophilic polymers can be modified to be at least partially hydrophobic using a suitable coating or combination of components (e.g., an interpenetrating network of polymers).

[0220] The polymer or copolymer can be produced by polymerizing one or more monomers selected from the group consisting of acrylic, amide, carbon, carbonate, diene, ester, ether, fluorocarbon, imide, olefin, organic acid (such as lactic acid, glycolic acid, succinic acid, hydroxypropionic acid, etc.), styrene, siloxane, vinyl acetal, vinyl chloride and vinylidene, vinyl ester, vinyl ether, vinyl ketone, vinyl pyridine, vinyl pyrrolidone, and combinations thereof.

[0221] The polymer in the composite can include a thermoplastic polymer, a thermosetting polymer, or a combination thereof. Thermosetting polymers include, but are not limited to, polyurethanes, polyesters, polyureas, polyisoprenes (including natural rubber or synthetic rubber), phenol-formaldehyde resins, polyepoxides, polyimides, polycyanurates, polyfurans, silicones, and combinations or copolymers thereof.

[0222] In some embodiments, the matrix polymer is particularly an elastomer. Exemplary elastomers include natural rubber (such as natural latex unvulcanized rubber) and synthetic rubber. Natural rubber is mainly poly-cis-isoprene. Synthetic rubbers are made from various petroleum-based monomers. The most common synthetic rubber is styrene-butadiene rubber (SBR) obtained from the copolymerization of styrene and 1,3-butadiene. Other synthetic rubbers are prepared from isoprene (2-methyl-1,3-butadiene, which gives polyisoprene), chloroprene (2-chloro-1,3-butadiene), and isobutylene (methylpropene) with a small proportion of isoprene for crosslinking (butyl rubber is produced).

[0223] In some embodiments, the matrix polymer is bio-based, biodegradable, and / or compostable. In these or other embodiments, the carrier polymer is bio-based, biodegradable, and / or compostable. In some embodiments, the matrix polymer or the carrier polymer is a biodegradable polymer, such as any polymer described in Vroman and Tighzert, “Biodegradable Polymers,” Materials 2009, 2, 307-344, which is incorporated herein by reference, or includes these. In some embodiments, for example, 13 As measurable by 13C analysis, the nanocellulose-containing composite product has a renewable carbon content of at least 50%, 60%, 70%, 80%, 90%, 95%, or 100%.

[0224] One or more additives can be included in the composite material, where the additives can be selected from the group consisting of compatibilizers, plasticizers, antioxidants, colorants, flame retardants, nucleating agents, viscosity modifiers, density modifiers, and combinations thereof. Exemplary additives include, but are by no means limited to, clay, nanoclay, talc, wollastonite, calcium carbonate, silica, mica, kaolin, nickel, glass fiber, carbon, cellulose fiber, aramid fiber, polyimide fiber, jute fiber, polyethylene fiber, polyethylene terephthalate fiber, polyamide fiber, and combinations thereof. In some embodiments, carbonaceous additives such as carbon fiber, carbon nanotube, graphene, lignin-derived carbon, or lignin are used.

[0225] Many types of composite products are possible, including films, coatings, packaging, appliances, fibers, fabrics, clothing, durable consumer goods, non-woven fabrics, etc. The composite product can be in the form of, for example, pellets, extruded parts, injection molded parts, blow molded parts, spun fibers, laminated sheets, films, foams, containers, bags, engineering parts, 3D printing substrates, 3D printed parts, or combinations thereof.

[0226] The nanocellulose-containing composite can be 3D printed. Three-dimensional (3D) printing or additive manufacturing is a process in which an object is created in its three-dimensional form using a special printer. The printer receives instructions from a design file created on a computer with the assistance of a 3D modeling program. The file or digital blueprint of the object to be printed is then sliced into 2D displays and sent to the printer. Layers of material are formed according to the information contained in the file; the layers continue to be added until the complete object is printed. The process of 3D printing requires much more time and involves a significant investment in equipment compared to 2D printing, but provides a wide range of advantages such as the ability to print virtually any geometric structure in principle.

[0227] In some of the composite products provided herein, the product in which nanocellulose is dispersed has a higher tensile modulus of elasticity compared to the polymer alone or to a composite that is identical except for not containing a dispersing / drying agent and / or not using a twin-screw system for dehydration or drying.

[0228] In some of the composite products provided herein, the product in which nanocellulose is dispersed has a higher tensile modulus of elasticity compared to the polymer alone or to a composite that is identical except for not containing a dispersing / drying agent and / or not using a twin-screw system for dehydration or drying.

[0229] In some of the composite products provided herein, the product in which nanocellulose is dispersed has a higher compressive modulus of elasticity compared to the polymer alone or to a composite that is identical except for not containing a dispersing / drying agent and / or not using a twin-screw system for dehydration or drying.

[0230] In some of the composite products provided herein, the product in which nanocellulose is dispersed has a higher toughness compared to the polymer alone or to a composite that is identical except for not containing a dispersing / drying agent and / or not using a twin-screw system for dehydration or drying.

[0231] In some composite products provided herein, products in which nanocellulose is dispersed have better moisture barrier and / or oxygen barrier properties compared to the polymer alone or to composites that are identical except that they do not contain a dispersion / drying agent and / or do not use twin-screw system dehydration or drying.

[0232] Due to the inherent properties of the nanocellulose particles and as a result of the twin-screw system dehydration or drying and the dispersion / drying agent, such that the nanocellulose particles are well dispersed in the composite, the tensile modulus, compressive modulus, toughness, and other properties of the composite product are improved.

[0233] The degree of dispersion of the nanocellulose in the final composite can be measured or qualitatively evaluated. The degree of dispersion is inversely proportional to the degree of aggregation. In the case of a complete homogeneous dispersion, there is no particle aggregation. The present invention does not require a complete dispersion such that all single nanoparticles are isolated from all other nanoparticles.

[0234] The nanocellulose dispersion can be measured or qualitatively evaluated using techniques such as, for example, scanning electron microscopy, transmission electron microscopy, interference microscopy, confocal laser scanning microscopy, optical microscopy, small-angle X-ray scattering, atomic force microscopy, dynamic light scattering, nanotomography, or thermogravimetric analysis. Figures 3-10 (see Examples 1-8, respectively) are optical micrographs demonstrating good dispersion (no aggregation), in contrast to Figures 11 and 12, which are optical micrographs showing insufficient dispersion (significant particle aggregation).

[0235] The nanocellulose dispersion can also be measured or qualitatively evaluated using a calibration technique in which a validated polymer having a known nanocellulose dispersion is tested for relevant properties. Next, the test sample is measured for the same properties, which is correlated to the degree of nanocellulose dispersion using a given graph, equation, or lookup table.

[0236] In a composite product, when present, the dispersing / drying agent can be present in the same phase as the nanocellulose, in the same phase as the matrix material, and / or in a separate phase. The dispersing / drying agent may be disposed between the nanocellulose particles and the matrix material. In some embodiments, the dispersing / drying agent surrounds the nanocellulose particles.

[0237] In some embodiments, the nanocellulose-containing composite product is configured as a catalyst, a catalyst substrate, or a co-catalyst. In some embodiments, the nanocellulose-containing composite product is configured to electrochemically transmit or store current or voltage.

[0238] In some embodiments, the nanocellulose-containing composite product is incorporated into a filter, a membrane, or other separation device.

[0239] In some embodiments, the nanocellulose-containing composite product is incorporated as an additive into a coating, a paint, or an adhesive. In some embodiments, the nanocellulose-containing composite product is a cement additive.

[0240] The nanocellulose-containing composite product can include any of the disclosed compositions. A number of composite products are possible. For example, the composite product can be selected from the group consisting of a structural object, a foam, an aerogel, a carbon composite, a film, a coating, a coating precursor, a current or voltage carrier, a filter, a membrane, a catalyst, a catalyst substrate, a coating or coating additive, a paint or paint additive, an adhesive or adhesive additive, an ink or ink additive, a cement additive, a paper coating or paper additive, a thickener, a rheology modifier, an additive for drilling fluids, and combinations or derivatives thereof.

[0241] The nanocellulose-containing composite products provided herein are suitable as coating materials as they are expected to have high oxygen barrier and affinity to wood fibers for uses in food packaging and printing papers. Alternatively or additionally, the nanocellulose-containing composite products can be incorporated into products, for example, to improve barrier properties or to improve nucleation.

[0242] The nanocellulose-containing composite products provided herein are suitable as additives for improving the durability of paints and protect paints and varnishes from abrasion caused by ultraviolet radiation.

[0243] The nanocellulose-containing composite products provided herein are suitable as thickeners in food and cosmetic products. Nanocellulose can be used as a thixotropic, biodegradable, dimensionally stable thickener (stable against temperature and salt addition). The nanocellulose-polymer composite products provided herein are suitable as Pickering stabilizers for emulsions and particle-stabilized foams. The large surface area of nanocellulose, combined with its biodegradability, makes nanocellulose an attractive material for very porous and mechanically stable aerogels.

[0244] In other embodiments, the nanocellulose dispersion concentrate is incorporated into structural objects, foams, aerogels, carbon composites, films, coatings, coating precursors, current or voltage carriers, filters, membranes, catalysts, catalyst substrates, coating additives, paint additives, adhesive additives, cement additives, paper coatings, thickeners, rheology modifiers, additives for drilling fluids, and combinations or derivatives thereof.

[0245] Other uses suitable for the present invention include high-strength spun fibers and textiles, advanced composites, barrier films, paints, lacquers, adhesives, switchable optical elements, pharmaceuticals, drug delivery systems, bone replacements, dental restorations, papers, packaging, building products, additives for food and cosmetics, and hydrogels.

[0246] Aerospace and transportation composites can benefit from the disclosed nanocellulose dispersion concentrate. Automotive applications include nanocellulose composites containing polypropylene, polyamide (e.g., nylon), or polyester (e.g., PBT).

[0247] The nanocellulose dispersion concentrate provided herein is suitable as a strength enhancing additive for renewable and biodegradable composites. The dispersant / dryer can function as a binder between two organic phases for improving fracture toughness and preventing crack formation for applications in packaging, construction materials, appliances, and renewable fibers.

[0248] The nanocellulose dispersion concentrate provided herein is suitable as a transparent and dimensionally stable strength enhancing additive for applications in flexible displays, flexible circuits, printable electronics, and flexible solar panels.

[0249] The nanocellulose dispersion concentrate provided herein is suitable for composites and cement additives that enable crack reduction and increases in toughness and strength. Foamed porous nanocellulose-concrete hybrid materials enable crack reduction and lightweight structures with increased strength.

[0250] Strength enhancement by nanocellulose increases both the bonding area and bonding strength for applications in high-strength, bulky, high filler content papers and boards with enhanced moisture and oxygen barrier properties. The pulp and paper industry can particularly benefit from the nanocellulose dispersion concentrate provided herein.

[0251] In some embodiments, the nanocellulose dispersion concentrate is incorporated as a thickener or rheology modifier. For example, the nanocellulose dispersion concentrate can be an additive in drilling or fracturing fluids such as (but not limited to) oil recovery fluids and / or gas recovery fluids.

[0252] The nanocellulose dispersion concentrate can generally be useful in any system that can benefit from the incorporation of the nanocellulose dispersion concentrate. As discussed herein, the systems include, but are not limited to, polymers, oligomers, paper, paperboard, fiber and wood composites, emulsions, hydrogels, carbon, organic solids, inorganic solids, oils, organic liquids, inorganic liquids, cementitious materials (e.g., concrete or cement), minerals, ceramics, metals, metal alloys, glass, or combinations thereof. The non-polymer matrix material can be, for example, an adhesive matrix, a battery electrode matrix, a bioink matrix, or an electronic ink matrix.

Examples

[0253] Examples Example 1: Preparation of Nanocellulose Dispersion Concentrate and Nanocellulose-Polypropylene Composite The lignin-coated nanofibrils are obtained by fractionating lignocellulosic biomass (softwood chips) in the presence of an acid catalyst (sulfur dioxide), a solvent for lignin (ethanol), and water to produce a cellulose-rich solid, and then mechanically treating the cellulose-rich solid to produce lignin-coated nanofibrils. The lignin-coated nanofibrils are present in an aqueous suspension containing about 3 wt% solids. The aqueous suspension is sometimes referred to as a nanocellulose slurry.

[0254] The dispersant / dryer is selected to be a copolymer of ethylene and maleic anhydride based on lignin-coated nanofibrils and a selected matrix polymer (polypropylene). A specific dispersant / dryer is Honeywell A-C® 573A wax (Honeywell Performance Materials and Technologies, Morris Plains, New Jersey, USA), which is an ethylene maleic anhydride copolymer in powder form. Honeywell A-C® 573A wax is a low molecular weight copolymer of maleic anhydride and propylene or ethylene. Functionalization of nonpolar propylene or ethylene with maleic anhydride provides a copolymer having both nonpolar and polar characteristics. According to Honeywell, maleic anhydride provides polarity without polymer degradation.

[0255] The starting nanocellulose dispersion slurry is produced by combining, under mechanical agitation, an aqueous suspension of 2,917 grams of lignin-coated nanofibrils with 88 grams of the above-mentioned dispersion / drying agent to yield the starting slurry. The starting nanocellulose dispersion slurry initially contains approximately 3 wt% nanocellulose (lignin-coated nanofibrils) and approximately 94 wt% water. The starting slurry is dried by a semi-batch process under heat and shear using a laboratory-scale twin-screw system consisting of a Brabender PL200 Plasti-Corder torque rheometer equipped with a Haake Rheomix 3000 mixer, mixing at a mixing blade speed of 100 revolutions per minute (RPM) and a temperature of 120 °C. As water evaporates and the volume within the mixer bowl decreases, slurry is continuously added to the twin-screw system. The process continues for approximately 90 minutes until all of the slurry is fed and all of the moisture has evaporated from the material, at which point the dried concentrate is recovered from the twin-screw system. The processing time and the amount of water that needs to be removed during drying can be significantly reduced, for example, by pre-concentrating the slurry by centrifugation. During the heat mixing, water is evaporated from the nanocellulose slurry contained within the extruder. When water is removed in the shear mixing, aggregation and self-bonding of the nanocellulose are prevented and the wax phase serves as a spacer between the nanocellulose particles.

[0256] When essentially all of the water has been removed from the starting nanocellulose dispersion slurry, a nanocellulose dispersion concentrate containing approximately 50 wt% nanocellulose (lignin-coated nanofibrils) and approximately 50 wt% dispersion / drying agent results. It is preferred to remove all of the water, although it is possible for some residual moisture to remain in the nanocellulose dispersion concentrate. It will also be recognized that other nanocellulose concentrations can be used for the nanocellulose dispersion concentrate.

[0257] The nanocellulose dispersion concentrate obtained above is then ground into a powder in a Bel-Art micro mill. The resulting powder is then dispersed in polypropylene as follows. 4 parts by weight of the nanocellulose dispersion concentrate (meaning 2 parts of nanocellulose and 2 parts of dispersant / drying agent) and 96 parts by weight of a polypropylene random copolymer (ExxonMobil, Houston, Texas, USA) are combined and mixed in a Brabender torque rheometer. The rheometer is operated for 11 minutes at a speed of 40 RPM and a temperature of 150 °C. The resulting nanocellulose-polymer composite is shown in the optical micrograph (magnification 100x) of Figure 3, showing 2 wt% nanocellulose (lignin-coated nanofibrils) uniformly dispersed in polypropylene.

[0258] Example 2: Preparation of Nanocellulose Dispersion Concentrate and Nanocellulose-Polypropylene Composite Lignin-coated nanofibrils are obtained by fractionating lignocellulosic biomass (softwood chips) in the presence of an acid catalyst (sulfur dioxide), a solvent for lignin (ethanol), and water to produce a cellulose-rich solid, and then mechanically treating the cellulose-rich solid to produce lignin-coated nanofibrils. The lignin-coated nanofibrils are present in an aqueous suspension (slurry) containing about 3 wt% solids.

[0259] The dispersant / drying agent is selected to be a copolymer of ethylene and acrylic acid based on the lignin-coated nanofibrils and the selected matrix polymer (polypropylene). A specific dispersant / drying agent is Honeywell AClyn® 295A wax (Honeywell Performance Materials and Technologies, Morris Plains, New Jersey, USA), which is a zinc ionomer of an ethylene acrylic acid copolymer in powder form neutralized to 98% with zinc (corrosion protection).

[0260] The starting nanocellulose dispersion slurry is produced by combining, under mechanical stirring, an aqueous suspension of 2,917 grams of lignin-coated nanofibrils with 88 grams of the above-mentioned dispersion / drying agent. The starting nanocellulose dispersion slurry initially contains approximately 3 wt% nanocellulose (lignin-coated nanofibrils) and approximately 94 wt% water. The starting slurry is dried by a semi-batch process under heat and shear using a laboratory-scale twin-screw system consisting of a Brabender PL200 Plasti-Corder torque rheometer equipped with a Haake Rheomix 3000 mixer, mixing at a mixing blade speed of 100 RPM and a temperature of 120 °C. As water evaporates and the volume within the mixer bowl decreases, slurry is continuously added to the twin-screw system. The process is continued for approximately 90 minutes until all of the slurry is fed and all of the moisture has evaporated from the material, at which point the dried concentrate is recovered from the twin-screw system. The processing time and the amount of water that needs to be removed during drying can be significantly reduced, for example, by pre-concentrating the slurry by centrifugation. During the heat mixing, water is evaporated from the nanocellulose slurry contained within the extruder. When water is removed in the shear mixing, aggregation and self-bonding of the nanocellulose are prevented and the wax phase serves as a spacer between the nanocellulose particles.

[0261] When essentially all of the water has been removed from the starting nanocellulose dispersion slurry, a nanocellulose dispersion concentrate is obtained that contains approximately 50 wt% nanocellulose (lignin-coated nanofibrils) and approximately 50 wt% dispersion / drying agent. It is preferred to remove all of the water, although it is also possible for some residual moisture to remain in the nanocellulose dispersion concentrate. It will also be recognized that other nanocellulose concentrations can be used for the nanocellulose dispersion concentrate.

[0262] The nanocellulose dispersion concentrate obtained above is then ground into a powder in a Bel-Art micromill. The resulting powder is then dispersed in polypropylene as follows. 4 parts by weight of the nanocellulose dispersion concentrate and 96 parts by weight of polypropylene random copolymer (ExxonMobil, Houston, Texas, USA) are combined and mixed in a Brabender torque rheometer. The rheometer is operated for 11 minutes at a speed of 40 RPM and a temperature of 150 °C. The resulting nanocellulose-polymer composite is shown in the optical micrograph (magnification 100x) of Figure 4, showing 2 wt% nanocellulose (lignin-coated nanofibrils) uniformly dispersed in polypropylene.

[0263] Example 3: Preparation of Nanocellulose Dispersion Concentrate and Nanocellulose-Polypropylene Composite Lignin-coated nanofibrils are obtained by fractionating lignocellulosic biomass (softwood chips) in the presence of an acid catalyst (sulfur dioxide), a solvent for lignin (ethanol), and water to produce a cellulose-rich solid, and then mechanically treating the cellulose-rich solid to produce lignin-coated nanofibrils. The lignin-coated nanofibrils are present in an aqueous suspension (slurry) containing about 3 wt% solids.

[0264] The dispersant / dryer is selected to be a copolymer of ethylene and acrylic acid based on the lignin-coated nanofibrils and the selected matrix polymer (polypropylene). A specific dispersant / dryer is Honeywell AClyn® 201A wax (Honeywell Performance Materials and Technologies, Morris Plains, New Jersey, USA), which is a calcium ionomer of an ethylene acrylic acid copolymer in powder form neutralized 47% with calcium.

[0265] The starting nanocellulose dispersion slurry is produced by combining, under mechanical agitation, an aqueous suspension of 2,917 grams of lignin-coated nanofibrils with 88 grams of the above-mentioned dispersion / drying agent. The starting nanocellulose dispersion slurry initially contains approximately 3 wt% nanocellulose (lignin-coated nanofibrils) and approximately 94 wt% water. The starting slurry is dried by a semi-batch process under heat and shear using a laboratory-scale twin-screw system consisting of a Brabender PL200 Plasti-Corder torque rheometer equipped with a Haake Rheomix 3000 mixer, mixing at a mixing blade speed of 100 RPM and a temperature of 120 °C. As water evaporates and the volume in the mixer bowl decreases, slurry is continuously added to the twin-screw system. The process is continued for approximately 90 minutes until all of the slurry is fed and all of the moisture has evaporated from the material, at which point the dry concentrate is recovered from the twin-screw system. The processing time, and the amount of water that needs to be removed during drying, can be significantly reduced, for example, by pre-concentrating the slurry by centrifugation. During the heat mixing, water is evaporated from the nanocellulose slurry. When water is removed in the shear mixing, aggregation and self-bonding of the nanocellulose are prevented, and the wax phase serves as a spacer between the nanocellulose particles.

[0266] When essentially all of the water has been removed from the starting nanocellulose dispersion slurry, a nanocellulose dispersion concentrate is obtained that contains approximately 50 wt% nanocellulose (lignin-coated nanofibrils) and approximately 50 wt% dispersion / drying agent. It is preferred to remove all of the water, although it is also possible for some residual moisture to remain in the nanocellulose dispersion concentrate. It will also be recognized that other nanocellulose concentrations can be used for the nanocellulose dispersion concentrate.

[0267] The nanocellulose dispersion concentrate obtained above is then ground into a powder in a Bel-Art micro mill. The resulting powder is then dispersed in polypropylene as follows. 4 parts by weight of the nanocellulose dispersion concentrate and 96 parts by weight of a polypropylene random copolymer (ExxonMobil, Houston, Texas, USA) are combined and mixed in a Brabender torque rheometer. The rheometer is operated for 11 minutes at a speed of 40 RPM and a temperature of 150 °C. The resulting nanocellulose-polymer composite is shown in the optical micrograph (magnification 100x) of Figure 5, showing 2 wt% nanocellulose (lignin-coated nanofibrils) uniformly dispersed in polypropylene.

[0268] Example 4: Preparation of Nanocellulose Dispersion Concentrate and Nanocellulose-Polypropylene Composite Lignin-coated nanofibrils are obtained by fractionating lignocellulosic biomass (softwood chips) in the presence of an acid catalyst (sulfur dioxide), a solvent for lignin (ethanol), and water to produce a cellulose-rich solid, and then mechanically treating the cellulose-rich solid to produce lignin-coated nanofibrils. The lignin-coated nanofibrils are present in an aqueous suspension (slurry) containing approximately 3 wt% solids.

[0269] The dispersant / dryer is selected to be a copolymer of ethylene and acrylic acid based on the lignin-coated nanofibrils and the selected matrix polymer (polypropylene). A specific dispersant / dryer is Honeywell A-C® 540A wax (Honeywell Performance Materials and Technologies, Morris Plains, New Jersey, USA), which is an ethylene acrylic acid copolymer in powder form. Honeywell A-C® 540A wax contains 5 wt% acrylic acid.

[0270] The starting nanocellulose dispersion slurry is produced by combining, under mechanical agitation, an aqueous suspension of 2,917 grams of lignin-coated nanofibrils with 88 grams of the above-mentioned dispersion / drying agent. The starting nanocellulose dispersion slurry initially contains approximately 3 wt% nanocellulose (lignin-coated nanofibrils) and approximately 94 wt% water. The starting slurry is dried by a semi-batch process under heat and shear using a laboratory-scale twin-screw system consisting of a Brabender PL200 Plasti-Corder torque rheometer equipped with a Haake Rheomix 3000 mixer, mixing at a mixing blade speed of 100 RPM and a temperature of 120 °C. As water evaporates and the volume within the mixer bowl decreases, slurry is continuously added to the twin-screw system. The process is continued for approximately 90 minutes until all of the slurry has been fed and all of the moisture has evaporated from the material, at which point the dried concentrate is recovered from the twin-screw system. The processing time, and the amount of water that needs to be removed during drying, can be significantly reduced, for example, by pre-concentrating the slurry by centrifugation. During the heat mixing, water is evaporated from the nanocellulose slurry. As water is removed in the shear mixing, aggregation and self-bonding of the nanocellulose are prevented, and the wax phase serves as a spacer between the nanocellulose particles.

[0271] When essentially all of the water has been removed from the starting nanocellulose dispersion slurry, a nanocellulose dispersion concentrate is obtained that contains approximately 50 wt% nanocellulose (lignin-coated nanofibrils) and approximately 50 wt% dispersion / drying agent. It is preferred to remove all of the water, although it is possible for some residual moisture to remain in the nanocellulose dispersion concentrate. It will also be recognized that other nanocellulose concentrations can be used for the nanocellulose dispersion concentrate.

[0272] The nanocellulose dispersion concentrate obtained above is then ground into a powder in a Bel-Art micromill. The resulting powder is then dispersed in polypropylene as follows. 4 parts by weight of the nanocellulose dispersion concentrate and 96 parts by weight of polypropylene random copolymer (ExxonMobil, Houston, Texas, USA) are combined and mixed in a Brabender torque rheometer. The rheometer is operated for 11 minutes at a speed of 40 RPM and a temperature of 150 °C. The resulting nanocellulose-polymer composite is shown in the optical micrograph (magnification 100x) of Figure 6, showing 2 wt% nanocellulose (lignin-coated nanofibrils) uniformly dispersed in polypropylene.

[0273] Example 5: Preparation of Nanocellulose Dispersion Concentrate and Nanocellulose-Polypropylene Composite Lignin-coated nanofibrils are obtained by fractionating lignocellulosic biomass (softwood chips) in the presence of an acid catalyst (sulfur dioxide), a solvent for lignin (ethanol), and water to produce a cellulose-rich solid, and then mechanically treating the cellulose-rich solid to produce lignin-coated nanofibrils. The lignin-coated nanofibrils are present in an aqueous suspension (slurry) containing approximately 3 wt% solids.

[0274] The dispersant / dryer is selected to be a copolymer of ethylene and acrylic acid based on the lignin-coated nanofibrils and the selected matrix polymer (polypropylene). A specific dispersant / dryer is Honeywell A-C® 580 wax (Honeywell Performance Materials and Technologies, Morris Plains, New Jersey, USA), which is an ethylene acrylic acid copolymer in pellet form. Honeywell A-C® 580 wax contains 10 wt% acrylic acid and has an acid value of 75.

[0275] The starting nanocellulose dispersion slurry is produced by combining, under mechanical stirring, an aqueous suspension of 2,917 grams of lignin-coated nanofibrils with 88 grams of the above-mentioned dispersing / drying agent. The starting nanocellulose dispersion slurry initially contains approximately 3 wt% nanocellulose (lignin-coated nanofibrils) and approximately 94 wt% water. The starting slurry is dried by a semi-batch process under heat and shear using a laboratory-scale twin-screw system consisting of a Brabender PL200 Plasti-Corder torque rheometer equipped with a Haake Rheomix 3000 mixer with a mixing blade speed of 100 RPM and a temperature of 120 °C. As water evaporates and the volume in the mixer bowl decreases, slurry is continuously added to the twin-screw system. The process is continued for approximately 90 minutes until all of the slurry is fed and all of the moisture has evaporated from the material, at which point the dried concentrate is recovered from the twin-screw system. The processing time and the amount of water that needs to be removed during drying can be significantly reduced, for example, by pre-concentrating the slurry by centrifugation. During the heat mixing, water is evaporated from the nanocellulose slurry. When water is removed in the shear mixing, aggregation and self-bonding of the nanocellulose are prevented and the wax phase serves as a spacer between the nanocellulose particles.

[0276] When essentially all of the water has been removed from the starting nanocellulose dispersion slurry, a nanocellulose dispersion concentrate containing approximately 50 wt% nanocellulose (lignin-coated nanofibrils) and approximately 50 wt% dispersing / drying agent results. Although it is preferred to remove all of the water, it is also possible for some residual moisture to remain in the nanocellulose dispersion concentrate. It will also be recognized that other nanocellulose concentrations can be used for the nanocellulose dispersion concentrate.

[0277] The nanocellulose dispersion concentrate obtained above is then ground into a powder in a Bel-Art micro mill. The resulting powder is then dispersed in polypropylene as follows. 4 parts by weight of the nanocellulose dispersion concentrate and 96 parts by weight of polypropylene random copolymer (ExxonMobil, Houston, Texas, USA) are combined and mixed in a Brabender torque rheometer. The rheometer is operated for 11 minutes at a speed of 40 RPM and a temperature of 150 °C. The resulting nanocellulose-polymer composite is shown in the optical micrograph (magnification 100x) of Figure 7, showing 2 wt% nanocellulose (lignin-coated nanofibrils) uniformly dispersed in polypropylene.

[0278] Example 6: Preparation of Nanocellulose Dispersion Concentrate and Nanocellulose-Polylactic Acid Composite Lignin-coated nanocrystals are obtained by fractionating lignocellulosic biomass (hardwood chips) in the presence of an acid catalyst (sulfur dioxide), a solvent for lignin (ethanol), and water to produce a cellulose-rich solid, and then mechanically treating the cellulose-rich solid to produce lignin-coated nanocrystals. The lignin-coated nanocrystals are present in an aqueous suspension (slurry) containing about 6 wt% solids.

[0279] The dispersant / dryer is selected to be a copolymer of ethylene and acrylic acid based on the lignin-coated nanocrystals and the selected matrix polymer (polylactic acid). A specific dispersant / dryer is Honeywell A-C® 540A wax (Honeywell Performance Materials and Technologies, Morris Plains, New Jersey, USA), which is an ethylene acrylic acid copolymer in powder form. Honeywell A-C® 540A wax contains 5 wt% acrylic acid.

[0280] The starting nanocellulose dispersion slurry is produced by combining an aqueous suspension of 1,458 grams of lignin-coated nanocrystals with 88 grams of the above-mentioned dispersion / drying agent under mechanical stirring. The starting nanocellulose dispersion slurry initially contains approximately 6 wt% nanocellulose (lignin-coated nanocrystals) and approximately 89 wt% water. The starting slurry is dried by a semi-batch process under heat and shear using a laboratory-scale twin-screw system consisting of a Brabender PL200 Plasti-Corder torque rheometer equipped with a Haake Rheomix 3000 mixer that mixes at a mixing blade speed of 100 RPM and a temperature of 120 °C. As water evaporates and the volume in the mixer bowl decreases, slurry is continuously added to the twin-screw system. The process is continued for approximately 90 minutes until all of the slurry is fed and all of the moisture has evaporated from the material, at which point the dried concentrate is recovered from the twin-screw system. The processing time and the amount of water that needs to be removed during drying can be significantly reduced, for example, by pre-concentrating the slurry by centrifugation. During the heat mixing, water is evaporated from the nanocellulose slurry. When water is removed in the shear mixing, aggregation and self-bonding of the nanocellulose are prevented, and the wax phase serves as a spacer between the nanocellulose particles.

[0281] When essentially all of the water has been removed from the starting nanocellulose dispersion slurry, a nanocellulose dispersion concentrate containing approximately 50 wt% nanocellulose (lignin-coated nanocrystals) and approximately 50 wt% dispersion / drying agent results. It is preferred to remove all of the water, although it is possible for some residual moisture to remain in the nanocellulose dispersion concentrate. It will also be recognized that other nanocellulose concentrations can be used for the nanocellulose dispersion concentrate.

[0282] The nanocellulose dispersion concentrate obtained above is then ground into a powder in a Bel-Art micro mill. The resulting powder is then dispersed in polylactic acid as follows. 1 part by weight of the nanocellulose dispersion concentrate and 99 parts by weight of polylactic acid (INGEO® PLA 4043D, NatureWorks LLC, Minnetonka, Minnesota, USA) are combined and mixed in a Brabender torque rheometer. The rheometer is operated for 11 minutes at a speed of 40 RPM and a temperature of 140 °C. The resulting nanocellulose-polymer composite is shown in the optical micrograph (magnification 100x) of Figure 8, showing 0.5 wt% nanocellulose (lignin-coated nanocrystals) uniformly dispersed in polylactic acid.

[0283] Example 7: Preparation of Nanocellulose Dispersion Concentrate and Nanocellulose-Polylactic Acid Composite Lignin-coated nanocrystals are obtained by fractionating lignocellulosic biomass (hardwood chips) in the presence of an acid catalyst (sulfur dioxide), a solvent for lignin (ethanol), and water to produce a cellulose-rich solid, and then mechanically treating the cellulose-rich solid to produce lignin-coated nanocrystals. The lignin-coated nanocrystals are present in an aqueous suspension (slurry) containing about 6 wt% solids.

[0284] The dispersant / dryer is selected to be a copolymer of ethylene and acrylic acid based on the lignin-coated nanofibers and the selected matrix polymer (polylactic acid). A specific dispersant / dryer is Honeywell A-C® 580 wax (Honeywell Performance Materials and Technologies, Morris Plains, New Jersey, USA), which is an ethylene acrylic acid copolymer in pellet form. Honeywell A-C® 580 wax contains 10 wt% acrylic acid and has an acid value of 75.

[0285] The starting nanocellulose dispersion slurry is produced by combining, under mechanical stirring, an aqueous suspension of 1,458 grams of lignin-coated nanocrystals with 88 grams of the above-mentioned dispersion / drying agent. The starting nanocellulose dispersion slurry initially contains approximately 6 wt% nanocellulose (lignin-coated nanocrystals) and approximately 89 wt% water. The starting slurry is dried by a semi-batch process under heat and shear using a laboratory-scale twin-screw system consisting of a Brabender PL200 Plasti-Corder torque rheometer equipped with a Haake Rheomix 3000 mixer, mixing at a mixing blade speed of 100 RPM and a temperature of 120 °C. As water evaporates and the volume in the mixer bowl decreases, slurry is continuously added to the twin-screw system. The process continues for about 90 minutes until all of the slurry is fed and all of the moisture has evaporated from the material, at which point the dried concentrate is recovered from the twin-screw system. The processing time and the amount of water that needs to be removed during drying can be significantly reduced, for example, by pre-concentrating the slurry by centrifugation. During the heat mixing, water is evaporated from the nanocellulose slurry. When water is removed in the shear mixing, aggregation and self-bonding of the nanocellulose are prevented, and the wax phase serves as a spacer between the nanocellulose particles.

[0286] When essentially all of the water has been removed from the starting nanocellulose dispersion slurry, a nanocellulose dispersion concentrate containing approximately 50 wt% nanocellulose (lignin-coated nanocrystals) and approximately 50 wt% dispersion / drying agent results. It is preferred to remove all of the water, although it is also possible for some residual moisture to remain in the nanocellulose dispersion concentrate. It will also be recognized that other nanocellulose concentrations can be used for the nanocellulose dispersion concentrate.

[0287] The nanocellulose dispersion concentrate obtained above is then ground into a powder in a Bel-Art micromill. The resulting powder is then dispersed in polylactic acid as follows. 1 part by weight of the nanocellulose dispersion concentrate and 99 parts by weight of polylactic acid (INGEO® PLA 4043D, NatureWorks LLC, Minnetonka, Minnesota, USA) are combined and mixed in a Brabender torque rheometer. The rheometer is operated at a speed of 40 RPM and a temperature of 140 °C for 11 minutes. The resulting nanocellulose-polymer composite is shown in the optical micrograph (magnification 100x) of Figure 9, showing 0.5 wt% nanocellulose (lignin-coated nanocrystals) uniformly dispersed in polylactic acid.

[0288] Example 8: Preparation of a nanocellulose dispersion concentrate for non-aqueous chemical systems Lignin-coated nanocellulose fibrils are obtained by fractionating lignocellulosic biomass (softwood chips) in the presence of an acid catalyst (sulfur dioxide), a solvent for lignin (ethanol), and water to produce a cellulose-rich solid, and then mechanically treating the cellulose-rich solid to produce lignin-coated nanocrystals. The lignin-coated nanocrystals are present in an aqueous suspension (slurry) containing about 3 wt% solids.

[0289] The dispersant / drying agent is selected to be an ammonium stearate emulsion which is the ammonium salt of stearic acid. Stearic acid is an 18-carbon chain fatty acid with the chemical formula C 17 H 35 CO2H and is selected for its bifunctionality having a polar head group capable of reacting with the nanocellulose and lignin hydroxyl groups and a non-polar chain imparting solubility in organic solvents.

[0290] The starting nanocellulose dispersion slurry is produced by mixing 3889 grams of an aqueous suspension of lignin-coated nanofibrils with 58 grams of an ammonia stearate dispersant / drying agent in the form of an aqueous emulsion. The starting nanocellulose dispersion slurry initially contains approximately 3 wt% nanocellulose (lignin-coated nanofibrils) and approximately 96 wt% water. The starting slurry is dried by a semi-batch process under heat and shear using a laboratory-scale twin-screw system consisting of a Brabender PL200 Plasti-Corder torque rheometer equipped with a Haake Rheomix 3000 mixer with a mixing blade speed of 100 RPM and a temperature of 120 °C for 90 minutes. As water evaporates and the volume in the mixer bowl decreases, slurry is continuously added to the twin-screw system. The process continues for approximately 90 minutes until all of the slurry is fed and all of the moisture has evaporated from the material, at which point the dried concentrate is recovered from the twin-screw system. The processing time and the amount of water that needs to be removed during drying can be significantly reduced, for example, by pre-concentrating the slurry by centrifugation. During heat mixing, water is evaporated from the nanocellulose slurry. When water is removed in shear mixing, aggregation and self-bonding of the nanocellulose are prevented and stearic acid (or stearate) serves as a spacer between the nanocellulose particles.

[0291] When essentially all of the water has been removed from the starting nanocellulose dispersion slurry, a nanocellulose dispersion concentrate is obtained that contains approximately 67 wt% nanocellulose (lignin-coated nanofibrils) and approximately 33 wt% dispersant / drying agent. It is preferred to remove all of the water, although it is possible for some residual moisture to remain in the nanocellulose dispersion concentrate. It will also be recognized that other nanocellulose concentrations can be used for the nanocellulose dispersion concentrate.

[0292] The nanocellulose dispersion concentrate obtained above is then ground in a hammer mill and dispersed in a common plasticizer, diisononyl phthalate (DINP), as follows. About 2 parts by weight of the nanocellulose dispersion concentrate and 98 parts by weight of DINP are combined in a vortex mixer for 4 minutes under ambient conditions. The resulting stable thixotropic nanocellulose non-aqueous dispersion is shown in the optical micrograph (magnification 400x) of FIG. 10, showing about 1.3 wt% nanocellulose (lignin-coated nanofibrils) uniformly dispersed in DINP.

[0293] Comparative Example A: Oven drying instead of twin screw system for dehydration / drying of nanocellulose Lignin-coated nanocellulose fibrils are obtained by fractionating lignocellulosic biomass (softwood chips) in the presence of an acid catalyst (sulfur dioxide), a solvent for lignin (ethanol), and water to produce a cellulose-rich solid, and then mechanically treating the cellulose-rich solid to produce lignin-coated nanocrystals. The lignin-coated nanocrystals are present in an aqueous suspension (slurry) containing about 3 wt% solids.

[0294] The dispersing / drying agent is selected to be an ammonium stearate emulsion which is an ammonium salt of stearic acid. Stearic acid is an 18-carbon chain fatty acid having the chemical formula C 17 H 35 CO2H and is selected for its bifunctionality having a polar head group capable of reacting with nanocellulose and lignin hydroxyl groups and a non-polar chain imparting solubility in organic solvents.

[0295] The starting nanocellulose dispersion slurry is produced by mixing 3889 grams of an aqueous suspension of lignin-coated nanofibrils with 58 grams of an ammonium stearate dispersing / drying agent in the form of an aqueous emulsion. The starting nanocellulose dispersion slurry initially contains about 3 wt% nanocellulose (lignin-coated nanofibrils) and about 96 wt% water.

[0296] The starting nanocellulose dispersion slurry is oven-dried to evaporate water from the slurry. When essentially all of the water has been removed, a nanocellulose dispersion concentrate containing approximately 67 wt% nanocellulose (lignin-coated nanofibrils) and approximately 33 wt% dispersant / drying agent is obtained as a result.

[0297] The resulting nanocellulose dispersion concentrate is then milled in a hammer mill and dispersed in a common plasticizer, diisononyl phthalate (DINP), as follows. Approximately 2 parts by weight of the nanocellulose dispersion concentrate and 98 parts by weight of DINP are combined in a vortex mixer for 4 minutes at ambient conditions. The resulting non-aqueous dispersion of nanocellulose is shown in the optical micrograph (magnification 400x) of Figure 11, showing large aggregates that are not dispersed in DINP. This poor result is in contrast to the good dispersion observed in Figure 10 from Example 8 that utilized a twin-screw system instead of a heat oven for drying.

[0298] Comparative Example B: High-intensity mixing instead of a twin-screw system for dehydration / drying of nanocellulose Lignin-coated nanofibrils are obtained by fractionating lignocellulosic biomass (softwood chips) in the presence of an acid catalyst (sulfur dioxide), a solvent for lignin (ethanol), and water to produce a cellulose-rich solid, followed by mechanical treatment of the cellulose-rich solid to produce lignin-coated nanofibrils. The lignin-coated nanofibrils are present in an aqueous suspension (starting slurry) containing approximately 6 wt% solids.

[0299] The dispersant / dryer is selected to be a copolymer of ethylene and acrylic acid, based on lignin-coated nanocrystals and a selected matrix polymer (polylactic acid). A specific dispersant / dryer is Honeywell A-C® 540A wax (Honeywell Performance Materials and Technologies, Morris Plains, New Jersey, USA), which is an ethylene acrylic acid copolymer in powder form. Honeywell A-C® 540A wax contains 5 wt% acrylic acid.

[0300] The starting slurry is dried by a semi-batch process under heat and shear using an FM10L Henschel® mixer operating at 3800 RPM with a heating jacket and vents for steam release. The dispersant / dryer melts and coats the sides of the heated vessel and does not mix with the nanocellulose. There is intense steam generation. During drying, it is observed that the dispersant / dryer separates to the sides due to incompatibility with water. This bad result is in contrast to Example 1 which utilizes a twin-screw extruder instead of a high-intensity mixer without screws for drying. In a twin-screw extruder, the wax phase and water are forced together and cannot separate from each other except that the vapor phase of water escapes through the vents.

[0301] Comparative Example C: Oven drying without using a dispersant / dryer for nanocellulose dehydration / drying The lignin-coated nanofibrils are obtained by fractionating lignocellulosic biomass (softwood chips) in the presence of an acid catalyst (sulfur dioxide), a solvent for lignin (ethanol), and water to produce a cellulose-rich solid, and then mechanically treating the cellulose-rich solid to produce lignin-coated nanofibrils. The lignin-coated nanofibrils are present in an aqueous suspension (starting slurry) containing about 6 wt% solids.

[0302] The starting nanocellulose dispersion slurry is oven-dried to evaporate water from the slurry. Figure 12 is an exemplary optical micrograph (magnification 100x) showing insufficient nanocellulose dispersion (significant particle aggregation) of 2 wt% nanocellulose (lignin-coated nanofibrils) in diisononyl phthalate, where the nanocellulose is dried without using a dispersion / drying agent and using oven drying instead of a twin-screw system.

[0303] Example 9: Dehydration of Nanocellulose Using a Pilot-Scale Twin-Screw Extruder Lignin-coated nanofibrils are obtained by fractionating lignocellulosic biomass (softwood chips) in the presence of an acid catalyst (sulfur dioxide), a solvent for lignin (ethanol), and water to produce a cellulose-rich solid, and then mechanically treating the cellulose-rich solid to produce lignin-coated nanofibrils. The lignin-coated nanofibrils are present in an aqueous suspension (starting slurry) containing approximately 6.3 wt% nanocellulose solids.

[0304] A pilot-scale twin-screw extruder equipped with co-rotating screws each having an outer diameter (D) of 36 mm and a screw length (L = 40D) of 1.44 m is designed. The feed tank to the twin-screw extruder is configured to have internal wiping blades for a controlled supply of the nanocellulose slurry to the screws. The twin-screw extruder has eight heating zones (barrels) and one extruder vent in the seventh barrel close to the extruder outlet die. The extruder vent is operated at a pressure of 1 bar rather than under vacuum so that the release of water vapor can be observed. Each heating zone barrel is configured to have an electric heater and jacket inlets and outlets for a heat transfer medium (e.g., steam, oil, or cooling water). In this example, electric heaters are used to reach the setpoint temperature of each zone and steam or cooling water is not used.

[0305] The nanocellulose slurry is fed to a twin-screw extruder at a feed rate of 10 pounds per hour (about 4.5 kg per hour). The twin-screw extruder screw speed is 330 RPM. The material passes through the twin-screw extruder once, and the estimated residence time is less than 1 minute. Release of water vapor is observed.

[0306] Two temperature profiles, labeled profile 9(a) and 9(b) in Table 1 below, are tested in this Example 9. In Table 1, T x is the measured temperature of zone x (x = 1 to 8) recorded from the control panel.

[0307]

Table 1

[0308] As observed from Table 1, temperature profile 9(a) results in a dehydrated nanocellulose material that is 23 wt% nanocellulose, which is a wet powder. The average temperature of profile 9(a) is about 118 °C. Temperature profile 9(b) results in a dehydrated nanocellulose material that is 61 wt% nanocellulose, which is a free-flowing powder. The average temperature of profile 9(b) is about 137 °C. It is expected that an even higher degree of dehydration can be achieved when the extruder vent is operated under vacuum.

[0309] Example 10: Dehydration of Nanocellulose Using a Pilot-Scale Twin-Screw Extruder Lignin-coated nanofibrils are obtained by fractionating lignocellulosic biomass (softwood chips) in the presence of an acid catalyst (sulfur dioxide), a solvent for lignin (ethanol), and water to produce a cellulose-rich solid, and then mechanically treating the cellulose-rich solid to produce lignin-coated nanofibrils. The lignin-coated nanofibrils are present in an aqueous suspension (starting slurry) containing about 8.9 wt% nanocellulose solids.

[0310] A pilot-scale twin-screw extruder equipped with co-rotating screws having an outer diameter (D) of 36 mm each and a screw length (L = 40D) of 1.44 m is designed. The supply tank to the twin-screw extruder is configured to have an internal wiping blade for the controlled supply of the nanocellulose slurry to the screws. The twin-screw extruder has eight heating zones (barrels) and has one extruder vent in the seventh barrel close to the extruder outlet die. The extruder vent is operated at a pressure of 1 bar rather than under vacuum so that the release of water vapor can be observed. Each heating zone barrel is configured to have an electric heater and a jacket inlet and a jacket outlet for a heat transfer medium (e.g., steam, oil, or cooling water). In this example, electric heaters are used to reach the setpoint temperature of each zone, and steam or cooling water is not used.

[0311] The nanocellulose slurry is fed to the twin-screw extruder at a feed rate of 10 pounds per hour (about 4.5 kg / h) during a 20-minute test. The twin-screw extruder screw speed is 300 RPM. The material passes through the twin-screw extruder once, and the estimated residence time is less than 1 minute. The release of water vapor is observed.

[0312] Two temperature profiles, labeled Profile 10(a) and 10(b) in Table 2 below, are tested in this Example 10. In Table 2, T x is the measured temperature of zone x (x = 1 to 8) recorded from the control panel.

[0313]

Table 2

[0314] As observed from Table 2, temperature profile 10(a) results in a dehydrated nanocellulose material that is 31.4 wt% nanocellulose, which is a wet powder. The average temperature of profile 10(a) is about 123 °C. Temperature profile 10(b) results in a dehydrated nanocellulose material that is 36.1 wt% nanocellulose, which is a wet powder. The average temperature of profile 10(b) is about 136 °C.

[0315] Example 11: Dehydration of nanocellulose using a twin-screw extruder on a commercial scale Lignin-coated nanofibrils are obtained by fractionating lignocellulosic biomass (softwood chips) in the presence of an acid catalyst (sulfur dioxide), a solvent for lignin (ethanol), and water to produce a cellulose-rich solid, and then mechanically treating the cellulose-rich solid to produce lignin-coated nanofibrils. Lignin-coated nanofibrils are present in an aqueous suspension (starting slurry) containing about 7.6 wt% nanocellulose solids.

[0316] A twin-screw extruder equipped with co-rotating screws each having an outer diameter (D) of 65 mm and a screw length (L = 69D) of 4.5 m is designed. Nanocellulose is poured directly from a bucket into the mouth of the twin-screw extruder. The twin-screw extruder has eight heating zones (barrels) and one extruder vent in the seventh barrel near the extruder exit die. The extruder vent is operated at a pressure of 1 bar rather than under vacuum so that the release of water vapor can be observed. Each heating zone barrel is configured to have an electric heater and jacket inlets and outlets for a heat transfer medium (e.g., steam, oil, or cooling water). In this example, an electric heater is used for each zone and steam or cooling water is not used.

[0317] The nanocellulose slurry is fed into a twin-screw extruder operating at a screw speed of about 300 RPM. By collecting the material after one pass and feeding the material back into the twin-screw extruder, the material is passed through the twin-screw extruder six times. It is observed that each pass results in a drier material than the previous pass. The release of water vapor is observed during each pass.

[0318] Table 3 below shows the measured temperatures of each zone during the last pass. In Table 3, T x is the measured temperature of zone x (x = 1 to 8) recorded from the control panel. The average measured temperature is about 132 °C.

[0319]

Table 3

[0320] As observed from Table 3, this experiment yields a dehydrated nanocellulose material that is 96 wt% nanocellulose, which is a free-flowing dry powder.

[0321] It is expected that this degree of dehydration can be achieved in fewer passes if the extruder vent is operated under vacuum and / or the twin-screw extruder is operated at a higher zone temperature. Also, if the starting slurry is pre-concentrated to about 15 - 25 wt% solids (for example) by centrifugation or the like, the amount of water removed from the twin-screw extruder will be reduced and the number of passes required to achieve the desired degree of dehydration will be reduced.

[0322] Examples 9 - 11 demonstrate that the twin - screw extrusion dehydration of nanocellulose is unexpectedly effective, robust, and easily adjustable for a wide range of moisture contents in the extruder product stream. The thorough mixing provided by the twin - screws results in particle tumbling and fragmentation, and thus the particle drying is relatively uniform. In these tests, it is shown that the twin - screw extruder can be configured to produce fine powders of nanocellulose that are solids in excess of 95 wt%. The fine powder products are easy to handle and transport, avoiding the problems associated with handling visco - elastic nanocellulose materials with significant water content.

[0323] In this detailed description, multiple embodiments and non - limiting examples of the invention are referred to with respect to ways in which the invention can be understood and practiced. Other embodiments that do not provide all of the features and advantages recited herein may be utilized without departing from the spirit and scope of the invention. The invention encompasses routine experimentation and optimization of the methods and systems described herein. Such modifications and variations are considered to be within the scope of the invention as defined by the claims.

[0324] All publications, patents, and patent applications cited herein are hereby incorporated by reference in their entirety as if each individual publication, patent, or patent application were specifically and individually recited herein.

[0325] If the above - described methods and steps indicate particular events occurring in a particular order, one of ordinary skill in the art will recognize that the ordering of the particular steps may be modified and that such modifications are in accordance with variations of the invention. Further, some of the steps may be implemented not only sequentially but, where possible, in parallel processes simultaneously.

[0326] Accordingly, there are variations of the present invention, and this patent is intended to cover those variations as well, provided they are within the spirit of the present disclosure or are equivalent to the present invention as found in the claims. The present invention is to be limited only by the claims.

Claims

1. A nanocellulose slurry supply subsystem, wherein the nanocellulose slurry contains nanocellulose and water, the nanocellulose slurry supply subsystem, An inlet for a dispersion / drying agent, A twin-screw extruder in fluid communication with the nanocellulose slurry supply subsystem, configured to mix the nanocellulose slurry and the dispersion / drying agent, and having one or more extruder vents configured to remove at least a portion of the water from the nanocellulose slurry, a twin-screw extruder, An extruder outlet for recovering a nanocellulose dispersion concentrate containing the nanocellulose and the dispersion / drying agent, A nanocellulose slurry dehydration system comprising:

2. The nanocellulose slurry dehydration system according to claim 1, wherein the nanocellulose slurry supply subsystem is configured to have an internal rotating stirrer and / or a wiping blade for mixing the nanocellulose slurry.

3. The nanocellulose slurry dehydration system according to claim 1, wherein the nanocellulose slurry dehydration system includes a mixing unit configured to mix the nanocellulose slurry with the dispersion / drying agent.

4. The nanocellulose slurry dehydration system according to claim 1, wherein the nanocellulose slurry dehydration system includes a nanocellulose slurry preliminary concentration unit configured to remove at least a portion of the water from the nanocellulose slurry before removal of the water in the extruder.

5. The nanocellulose slurry dehydration system according to claim 4, wherein the nanocellulose slurry preliminary concentration unit is a centrifuge.

6. The nanocellulose slurry dehydration system according to claim 4, wherein the nanocellulose slurry preliminary concentration unit is a filtration device.

7. The nanocellulose slurry dehydration system according to claim 4, wherein the inlet for the dispersion / drying agent is an inlet to the nanocellulose slurry preliminary concentration unit.

8. The nanocellulose slurry dehydration system according to claim 1, wherein the twin-screw extruder is a co-rotating twin-screw extruder.

9. The nanocellulose slurry dehydration system according to claim 1, wherein the twin-screw extruder is a counter-rotating twin-screw extruder.

10. The nanocellulose slurry dehydration system according to claim 1, further comprising a pulverizing device.

11. A nanocellulose slurry supply subsystem, wherein the nanocellulose slurry contains nanocellulose and water, An inlet for a dispersant / drying agent, A twin rotor mixer in communication with the nanocellulose slurry supply subsystem, configured to mix the nanocellulose slurry and the dispersant / drying agent, and configured to have one or more mixer vents for removing at least a portion of the water from the nanocellulose slurry, An extruder outlet for recovering a nanocellulose dispersion concentrate containing the nanocellulose and the dispersant / drying agent, A nanocellulose slurry dehydration system comprising.

12. The nanocellulose slurry dehydration system according to claim 11, wherein the inlet for the dispersant / drying agent is an inlet to the nanocellulose slurry supply subsystem.

13. The nanocellulose slurry dehydration system according to claim 11, wherein the nanocellulose slurry dehydration system includes a mixing unit configured to mix the nanocellulose slurry with the dispersant / drying agent.

14. The nanocellulose slurry dehydration system according to claim 11, wherein the nanocellulose slurry dehydration system includes a nanocellulose slurry pre-concentration unit configured to remove at least a portion of the water from the nanocellulose slurry before removal of water in the twin rotor mixer.

15. The nanocellulose slurry dehydration system according to claim 14, wherein the nanocellulose slurry pre-concentration unit is a centrifuge.

16. The nanocellulose slurry dehydration system according to claim 14, wherein the nanocellulose slurry pre-concentration unit is a filtration device.

17. The nanocellulose slurry dehydration system according to claim 14, wherein the inlet for the dispersant / drying agent is an inlet to the nanocellulose slurry pre-concentration unit.

18. The nanocellulose slurry dehydration system according to claim 11, wherein the twin rotor mixer is a co-rotating twin rotor mixer.

19. The nanocellulose slurry dehydration system according to claim 11, wherein the twin rotor mixer is a reverse rotation twin rotor mixer.

20. The nanocellulose slurry dehydration system according to claim 11, further comprising a pulverizing device.

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