US20230295881A1

US20230295881A1 - Molded pulp article and processes of making same

Info

Publication number: US20230295881A1
Application number: US18/123,573
Authority: US
Inventors: Jonathan Phipps; Camery MA; Johannes Kritzinger; Abigail RULE
Original assignee: FiberLean Technologies Ltd
Current assignee: FiberLean Technologies Ltd
Priority date: 2022-03-21
Filing date: 2023-03-20
Publication date: 2023-09-21

Abstract

A three dimensional molded object comprising a mixture of cellulose fibers and microfibrillated cellulose, and optionally one or more inorganic particulate material, wherein the microfibrillated cellulose is present in an amount of about 0.5 wt. % to about 50 wt. % on a dry weight basis of the total dry mass of the mixture of cellulose fibres and microfibrillated cellulose, and optionally one or more inorganic particulate material; wherein the coarsely microfibrillated cellulose comprises less than about 90 wt. % fines and/or less than 75% fines A, and a length-weighted median length Lc(w) of greater than 0.3 mm, as measured by fibre image analyzer, and wherein the microfibrillated cellulose optionally has a fibre steepness of about 20 to about 50, as measured by Malvern Mastersizer.

Description

BACKGROUND

Field of Invention

Three-dimensional molded packaging articles comprising moldable cellulosic pulp and coarsely fibrillated microfibrillated cellulose, and optionally, inorganic particulate material, processes for manufacturing same, and uses for such three-dimensional molded pulp articles.

Background of the Invention

Many 3-dimensional packaging objects, such as egg boxes, food trays and cushion support for electronics and consumer goods, are made by molding cellulose pulp. Moldable pulp articles are currently manufactured in wet pulp molding processes and, alternatively, in dry pulp forming processes. In one respect, the wet molded pulp process is similar to papermaking, since it involves the filtering of a suspension of pulp in water, then pressing and drying it to make the final product. However, instead of filtering the suspension on a continuous, moving flat wire as in papermaking, in wet pulp molding processing a 3-dimensional wire mold is conventionally submerged in a tank of pulp, and vacuum is applied to the inside of the mold to form a filter cake of pulp on its outside and thus form the object. Wet pulp molding is typically used to make complex shapes which cannot be pressed from flat sheets or cellulose blanks or easily made by folding them. Since each object requires an individual mold, it is a batch process by nature.
Packaging inserts are frequently produced from molded pulp. Molded pulp has the advantage of being considered as a sustainable packaging material, since it is produced from biomaterials and can be recycled after use.
Wet molded pulp articles may be formed by immersing a suction mold into a pulp suspension, while suction is applied. The body of pulp is thereby formed with the shape of the desired article by fibre deposition. The suction mold is then withdrawn from the suspension and the suction is generally continued to compact the deposited fibres while exhausting residual liquid. Different drying techniques may be employed, including oven drying, hot pressing, microwave drying and freeze-drying A disadvantage with all wet-forming techniques is the need for drying of the molded product, which is a time and energy consuming step. Through such wet-forming techniques the molded article develops strong inter-fibre bonds which provides strength and rigidity to the molded article.
Wet forming methods of manufacturing a cellulose product having a flat or non-flat product shape by pressure molding are also known in the art. One such method is described in EP3736099A1, which is incorporated herein by reference in its entirety. In this reference, a method of manufacturing a cellulose product is disclosed having a flat or non-flat product shape by a pressure molding apparatus comprising a forming mold, the forming mold having a forming surface defining the product shape. The method comprises the following steps of: arranging a cellulose blank containing less than 45 weight percent water in a forming mold; heating the cellulose blank to a forming temperature in the range of 100° C. to 200° C.; and pressing the cellulose blank by means of a forming mold with a forming pressure acting on the cellulose blank across the forming surface, the forming pressure being in the range of 1 MPa to 100 MPa.
An alternative method of manufacturing 3-D molded pulp articles involves dry forming a cellulose blank in a forming mold comprising a preheated negative non-flexible pressure mold part and a pre-heated positive non-flexible forming mold part, and then heating the cellulose blank to a forming temperature, conventionally in the range of 100° C. to 200° C. and pressing the cellulose blank in the forming mold with a forming pressure of at least 1 MPa. An example of such a process may be found in EP 3882167A1, which is incorporated herein by reference in its entirety.
A system for producing cellulose products by forming cellulose fibers without using wet-forming techniques is also disclosed in WO2021156222, which is incorporated herein by reference in its entirety. Therein, an air-formed cellulose blank structure is inserted into a forming mold. During the forming of the cellulose products the cellulose blank is subjected to a high forming pressure and a high forming temperature. A problem with such forming methods is that when inserting the cellulose blank structure into the forming mold, there is a risk that the cellulose blank structure can break apart leading to deformation of the cellulose products. This is noted to be a common problem with traditional cellulose high pressure forming molds, especially for deep-drawn products, leading to products of low quality. Other problems with traditional forming molds, especially when forming deep-drawn products, are that that cracks, fibre separations, material fractures, or other unwanted structural weakening of the cellulose blank structure can form during the insertion into the forming mold.
WO2021156222 discloses a forming mold system for forming a cellulose product from an air-formed cellulose blank structure, and a method for forming a cellulose product from an air-formed cellulose blank structure in a forming mold system, where the previously mentioned problems are alleged to be avoided. This solution to the problem of cracking, fibre separations and material weakening and separations, is stated to at least partly be achieved by a forming mold system for forming a cellulose product from an air-formed cellulose blank structure, wherein the forming mold system comprises a first mold part and a second mold part, wherein the first mold part and the second mold part are configured for moving in relation to each other in a pressing direction. wherein the second mold part comprises a forming cavity section and an inlet section, wherein the inlet section is arranged in connection to the forming cavity section and configured for facilitating displacement of the cellulose blank structure into a forming cavity of the forming cavity section, wherein the inlet section comprises a transition surface defining an inlet opening, wherein the inlet opening has a tapered configuration towards the forming cavity.
WO2021037946, which is incorporated herein by reference in its entirety, discloses an alternative method of forming cellulose products from air-formed cellulose blank structures in a rotary forming mold system. In the foregoing systems, the air-formed cellulose blank structure has a dry basis weight in the range of 200-3000 g/m², preferably 300-3000 g/m², and more preferably 400-3000 g/m², The air-formed cellulose blank structure with these properties is asserted to be suitable for the forming of three-dimensional cellulose products. The cellulose blank structure is described as a relatively thick and fluffy structure compared to traditional wet-laid paper or tissue structures. The bulky cellulose blank structure is compacted during the forming process, and the cellulose fibres in the three-dimensional cellulose products are strongly bonded to each other with hydrogen bonds, providing a stiff compacted three-dimensional product structure.
WO2021001276, which is incorporated herein by reference in its entirety, discloses a similar method wherein the air-formed cellulose blank structure formed from cellulose fibre wherein an alkyl ketene dimer (AKD) dispersion is applied to the cellulose blank structure, and in a second application step following the first application step, a latex dispersion is applied to the cellulose blank structure with the applied alkyl ketene dimer (AKD) dispersion; then the cellulose blank structure with the applied alkyl ketene dimer (AKD) dispersion and latex dispersion is introduced into a forming mold and heated to a forming temperature in the range of 100° C. to 300° C., and the cellulose product is formed by pressing the heated cellulose blank structure with a forming pressure of at least 1 MPa, preferably 4-20 MPa.
WO2020229608, which is incorporated herein by reference in its entirety, discloses, another method for producing discrete three-dimensional cellulose products from an air-formed cellulose blank structure in a rotary forming mold system. The rotary forming mold system provides an air-formed cellulose blank structure which is transported and fed into a position between a first mold part and a second mold part, and heated to a forming temperature in the range of 100° C. to 300° C.; and thereafter formed into a three-dimensional cellulose by pressing the heated air-formed cellulose blank structure with a forming pressure of at least 1 MPa, preferably 4-20 MPa, between the first mold part and the second mold part, wherein during forming the first mold part is rotating around a first rotational axis and the second mold part is rotated around a second rotational axis).
The foregoing wet and dry moldable pulp forming processes all utilize cellulose fibres and fail to mention the inclusion of microfibrillated cellulose as an additive.
In the context of the foregoing process, microfibrillated cellulose (MFC) or so called cellulose microfibrils (CMF) is defined as a micro-scale cellulose particle fiber or fibril with at least one average or mean dimension less than 1000 nm. MFC comprises partly or totally fibrillated cellulose or lignocellulose fibers. The cellulose fiber is preferably fibrillated to such an extent that the final specific surface area of the formed MFC is from about 1 to about 500 m²/g, such as from 10 to 400 m²/g or more preferably 50-300 m²/g when determined for a solvent exchanged and freeze-dried material with the BET method. The advantage of including microfibrillated cellulose and metal salts is said to be that a combination of metal salts and microfibrillated is said to enhance printing properties, i.e., the combination of MFC and metal salt is asserted to render the surface of the molded object more receptive to printing ink.
An overview of wet forming processes for moldable pulp articles may be found in Didone, Mattia, et al., “Moulded Pulp Manufacturing: Overview and Prospects for the Process Technology, Packaging Technology and Science 92017): 30:231-249 (2017), which is incorporated herein by reference in its entirety.
Production of 3-D molded articles exclusively from cellulose nanofibrils is described in Rol, Fleur et al., “Production of 100% Cellulose Nanofibril Objects Using the Molded Cellulose Process: A Feasibility Study,” Ind. Eng. Chem. Res. (2020), 59, 16, 7670-7679, which is incorporated herein by reference in its entirety.
In the foregoing study, the authors report preparation of 100% CNF, 3D molded objects. The CNF was produced by a twin screw refining process as described using enzymatically hydrolyzed cellulose fibres (with 300 ECU/g cellulase Fiber Care™ from Novozymes). Two types of CNF were used throughout this work: (i) a commercial CNF grade produced by an enzymatic pretreatment and using a homogenizer at 2 wt % solid content and (ii) high-solid-content CNF (20 wt % solid content) produced by enzymatic hydrolysis of cellulose fibers and twin screw extrusion. Both CNF suspensions were then characterized using several techniques. Nanopapers of 60 g/m²were formed by diluting the CNF suspension followed by filtration through a standard sheet former (Rapid Klothen former, ISO 5269-2 standard). The molded nanostructured objects were produced following different steps: (i) formation of the cellulosic mats by filtration or by pressing and (ii) drying. Different drying techniques were employed, including oven drying, hot pressing, microwave drying and freeze-drying. The authors noted that after optimizing the mold porosity, different methods were tried to form the nanocellulosic mats. Because the amount of bound water is much higher in CNF than in a cellulosic fiber suspension, the maximal dry content achieved after pressing was only 30 wt %. This nanocellulosic mat was formed by pressing for 1 min at 4 tons, and this was possible due to the high-solid-content CNF. Indeed, several hours would be required to filter classic CNF at 2 wt % until reaching this solid content due to its gel-like behavior. The authors concluded that none of the drying methods allowed producing 3D transparent objects due to shrinking and failures, especially in the zones between the plane and curved areas of the mold. 2D objects were produced using a combination of drying methods and were said to present interesting properties such as grease barrier properties and good mechanical properties.
Molded pulp has traditionally been associated with objects where appearance and surface properties are not important.
With recent renewed interest in the replacement of conventional plastics with bio-sourced, recyclable and biodegradable materials, the molded pulp industry is seeing significant growth and development. Molded pulp objects can be made with high surface quality and stiffness, so they are beginning to be used in the primary packaging of higher value goods such as electronics and cosmetics.
For most applications (around 85%), recycled fibres are used.
Mineral fillers are not typically used, although molded pulp products may contain significant ash content originating from the recycled pulp being used.
Although wet molded pulp objects are formed on a wire mold immersed in a pulp suspension, variations in the subsequent pressing and drying processes have led to their classification into four main categories by the International Molded Fiber Association (IMFA).
“Thick wall”: manufactured using an open mold and then oven dried. Typical wall thickness ranges from 5 mm to 10 mm. The surface in contact with the mold is relatively smooth, while the other side is very rough. The raw material is typically Kraft paper mixed with recycled paper. Thick wall parts are usually used as support packaging for non-fragile, heavy items (e.g. furniture and vehicle parts.
“Transfer molded” products in this category have thinner walls, ca., 3 mm to 5 mm. They are manufactured using both a forming mold and a transfer or take-off mold. The result is a product with relatively smooth surfaces on both sides and better dimensional accuracy. The wet product is ejected from the transfer mold and dried in a heated oven. The raw material commonly used is recycled newspaper. Typical examples are egg trays and packaging for electronic equipment.
“Thermoformed” (“Thin wall”) is the most recent approach. The initial formed product is captured in heated molds where it is pressed, densified, and dried. No oven curing is needed. This process produces high quality thin-walled items (from 2 mm to 4 mm), with good dimensional accuracy, and smooth, rigid surfaces. The result resembles the appearance of thermoformed plastic items.
“Processed” refers to molded pulp products that require some further or special treatment, for instance additional printing, coatings, or additives.
Recycled fibre is used for most applications, though virgin fibre may sometimes be used in higher quality thermoforming. Refining of the pulp is not common, but possible at some manufacturers. Enhanced properties, such as oil, grease or moisture barrier for food packaging or improved haptics and appearance for consumer goods are of increasing interest.
Molded pulp products are not defined and sold by basis weight (grams/metre²or gsm); only the properties of interest are important.
Use of increasing levels of microfibrillated cellulose (MFC) increases the time required to form an object and build a constant basis weight whilst the mold is immersed in the pulp tank (the forming or molding time). However, the use of MFC leads to enhanced properties which can enable a very significant reduction in the necessary basis weight of the product for a given application. This reduction of basis weight can compensate for the reduced drainage rate so that the forming time is not increased to an unacceptable level. Any increases in forming time may also be compensated by reduced drying time and energy cost resulting from the reduction in the product weight. Indeed, if the rate determining step of the process is the drying rather than the forming, the reduction in basis weight enabled by the use of MFC may even lead to an increase in productivity.
Accordingly, there is a need for moldable pulp compositions with enhanced properties due to the incorporation of coarsely fibrillated MFC in such moldable pulp compositions to confer better mechanical properties to the molded article.

SUMMARY OF THE INVENTION

The addition of coarsely fibrillated MFC to a composition for wet or dry molding pulp allows very substantial reductions in the weight of the formed objects, without compromising their quality or integrity. Specifically, the tensile stiffness of the moldable pulp article may be greatly improved so that a lighter object with the same rigidity can be made. To a first approximation, the rigidity of a simple 3-dimensional molded object such as a tray is dependent upon the tensile stiffness of its walls. Tensile stiffness of a sheet material is defined as the force per unit width required to stretch the sheet by a unit of strain. The tensile stiffness index of a sheet material is defined as the tensile stiffness divided by the mass/unit area (grams/metre²or gsm) of the material. Addition of coarsely fibrillated MFC to a pulp composition increases its tensile stiffness index, so that a sheet with the same tensile stiffness can be made at lower gsm.
Likewise, a molded object of equivalent rigidity can be made at lower weight by the addition of the coarsely fibrillated MFC to the composition. The addition of coarsely fibrillated MFC to the moldable pulp composition also makes the wet pulp more extensible so that, surprisingly, it can be molded around corners in much thinner layers without tearing. Although the use of coarsely fibrillated MFC will reduce the rate of formation of the object in the mold, this is often not the rate determining step and can be offset by the reduction in required weight. A further advantage of addition of coarsely fibrillated MFC to compositions comprising pulp for molding is the large reduction in Bendtsen porosity that it causes in the dry molded article, which will improve the integrity of any barrier coatings subsequently sprayed onto the molded object.
At high levels, the use of coarsely fibrillated MFC can result in excellent oil and grease resistance even without coating. The foregoing problems noted in the art of wet or dry molding cellulose fibres to produce 3-dimensional molded pulp articles are overcome through the addition of coarsely fibrillated microfibrillated cellulose in an amount of about 0.5 wt. % to about 50 wt. % to the pulp composition, which is to be wet or dry molded, based on the total dry weight of the pulp composition. Such coarsely fibrillated microfibrillated cellulose comprises less than about 90 wt. % fines and/or less than 75% fines A and has a length-weighted median length Lc(w) of greater than 0.3 mm, as measured by fibre image analyzer. The coarsely fibrillated microfibrillated cellulose is introduced into the pulp composition, which is to be wet or dry molded. The inventors have surprisingly found that coarsely fibrillated MFC also drains more quickly, and therefore provides a better combination of properties than a finer fibrillated version of MFC. The coarsely fibrillated MFC material gives a better compromise between strength and drainage compared to more fibrillated versions of MFC. The drainage is quite a bit better, but so too is the increase in tensile stiffness. This is illustrated in FIG. 2 , which shows the calculated grammage required for 1000 N/m tensile stiffness for each blend, plotted against the calculated drainage time for that grammage and blend. For blends of up to 50% MFC, the coarser material achieves any given grammage reduction at lower MFC content and significantly lower drainage time.
In accordance with the description, Figures, examples and claims of the present specification, the inventors have invented methods for the manufacture of three dimensional molded objects sheets comprising (or consisting essentially of, or consisting of) cellulose fibres and coarsely fibrillated microfibrillated cellulose and, optionally one or more inorganic particulate material, which have improved mechanical properties and three dimensional molded objects manufactured by such processes and uses of such three dimensional molded objects as packaging containers, blister packs, egg cartons, bottles, containers or food trays. The three dimensional molded objects comprise coarsely fibrillated microfibrillated cellulose in an amount of about 0.5 wt. % to about 50 wt. % on a dry weight basis of the total dry mass of the mixture of cellulose fibres and microfibrillated cellulose, and optionally one or more inorganic particulate material; wherein the coarsely microfibrillated cellulose comprises less than about 90 wt. % fines and/or less than 75% fines A, and a length-weighted median length Lc(w) of greater than 0.3 mm, as measured by fibre image analyzer, and wherein the coarsely fibrillated microfibrillated cellulose optionally has a fibre steepness of about 20 to about 50, as measured by Malvern Mastersizer. In a first aspect of the present invention, the inventors have invented a three dimensional molded object comprising a mixture of cellulose fibers and coarsely fibrillated microfibrillated cellulose, and optionally one or more inorganic particulate material wherein the coarsely microfibrillated cellulose comprises less than about 90 wt. % fines and/or less than 75% fines A, and a length-weighted median length Lc(w) of greater than 0.3 mm, as measured by fibre image analyzer, and wherein the coarsely fibrillated microfibrillated cellulose optionally has a fibre steepness of about 20 to about 50, as measured by Malvern Mastersizer.
In an embodiment of the first aspect of the present invention, the coarsely fibrillated microfibrillated cellulose has a fibre steepness of about 20 to about 50.
In further embodiments of the first aspect of the present invention, the coarsely fibrillated microfibrillated cellulose is present in an amount of about 0.5 wt. % to about 50 wt. %, or 0.5 wt. % to about 25 wt. %, or about 0.5 wt. % to about 20 wt. %, or about 0.5 wt. % to about 15 wt. %, or about 0.5 wt. % to about 10 wt. %, or about 0.5 wt. % to about 5 wt. %.
In additional embodiments of the first aspect of the invention, the coarsely fibrillated microfibrillated cellulose is obtained from a pulp selected from the group consisting of a chemical pulp, a chemithermomechanical pulp, a mechanical pulp, a thermomechanical pulp, a recycled pulp, a paper broke pulp, a papermill waste stream, waste from a papermill, and combinations thereof.
In other embodiments of the first aspect of the invention, the coarsely fibrillated microfibrillated cellulose is obtained from a recycled pulp, a paper broke pulp, a papermill waste stream, waste from a papermill, and combinations thereof.
In other embodiments of the first aspect of the invention, the cellulose fibres are obtained from a recycled pulp, a paper broke pulp, a papermill waste stream, waste from a papermill, and combinations thereof.
In further embodiments of the first aspect of the invention, the cellulose fibres are obtained from a pulp selected from the group consisting of a chemical pulp, a chemithermomechanical pulp, a mechanical pulp, a thermomechanical pulp, a recycled pulp, a paper broke pulp, a papermill waste stream, waste from a papermill, and combinations thereof.
In further embodiments of the first aspect of the invention, both the cellulose fibres and coarsely fibrillated microfibrillated cellulose are obtained from a recycled pulp, a paper broke pulp, a papermill waste stream, waste from a papermill, and combinations thereof.
In additional embodiments of the first aspect of the invention, the molded object comprises one or more inorganic particulate material.
In further embodiments of the first aspect of the invention, wherein the one or more inorganic particulate material is calcium carbonate or kaolin, or mixtures thereof, or comprise a platy mineral, kaolin and/or talc.
In embodiments of the first aspect of the invention, the calcium carbonate is ground calcium carbonate, precipitated calcium carbonate, or mixtures thereof, or the calcium carbonate is precipitated calcium carbonate.
In further embodiments of the first aspect of the invention, the calcium carbonate is ground calcium carbonate, or the ground calcium carbonate is marble, chalk, limestone and mixtures thereof.
In other embodiments of the first aspect of the invention, the inorganic particulate material is ground calcium carbonate and precipitated calcium carbonate.
In additional embodiments of the first aspect of the invention the inorganic particulate material is selected from the group consisting of an alkaline earth metal carbonate or sulphate, a calcium carbonate, a magnesium carbonate, a dolomite, a gypsum, a bentonite, a hydrous kandite clay, a kaolin, a halloysite, a ball clay, an anhydrous (calcined) kandite clay, a metakaolin, a fully calcined kaolin, a talc, a mica, a perlite, a sepiolite, a huntite, a diatomite, a magnesite, a silicate, a diatomaceous earth, a brucite, an aluminum trihydrate, and combinations thereof.
In a second aspect of the invention, there is provided a method for producing a three dimensional molded object comprising cellulose fibers and coarsely fibrillated microfibrillated cellulose, comprising the steps of: providing a mixture comprising cellulose fibres and coarsely fibrillated microfibrillated cellulose, and optionally one or more inorganic particulate material, wherein the mixture comprises coarsely fibrillated microfibrillated cellulose in an amount of about 0.5 wt. % to about 50 wt. % on a dry weight basis of the total dry mass of the mixture of cellulose fibres and coarsely fibrillated microfibrillated cellulose, and optionally one or more inorganic particulate material wherein the coarsely microfibrillated cellulose comprises less than about 90 wt. % fines and/or less than 75% fines A, and a length-weighted median length Lc(w) of greater than 0.3 mm, as measured by fibre image analyser, and wherein the coarsely fibrillated microfibrillated cellulose optionally has a fibre steepness of about 20 to about 50, as measured by Malvern Mastersizer.
In an embodiment of the second aspect of the invention, the coarsely fibrillated microfibrillated cellulose has a fibre steepness of about 20 to about 50 as measured by Malvern Mastersizer.
In further embodiments of the second aspect of the invention, the forming step is a wet forming step or the forming step is a dry forming step.
In a further embodiment of the second aspect of the invention, the method further comprising the steps of: providing a porous mold having a three-dimensional shape comprising a forming portion having an inside and an outside portion; bringing the forming portion into contact with the mixture comprising cellulose fibres and coarsely fibrillated microfibrillated cellulose, and optionally one or more inorganic particulate material; applying a vacuum to the inside portion of the forming section to form a wet layer of cellulose fibres and coarsely fibrillated microfibrillated cellulose, and optionally one or more inorganic particulate material, on the outside portion of the forming section, thereby forming a three-dimensional molded object, wherein the wet layer of cellulose fibres and coarsely fibrillated microfibrillated cellulose and optionally one or more inorganic particulate material is between about 100 to 3,000 gsm (or 200 to 2,000 gsm, or 250 to 1,000 gsm) in dry weight on a dry weight basis of the total dry mass of the mixture of cellulose fibres and coarsely fibrillated microfibrillated cellulose, and optionally one or more inorganic particulate material; transferring the molded object to a drying conveyor and drying the three dimensional molded object; optionally transferring the three-dimensional molded object to a second inverse shaped mold and pressing the three-dimensional molded prior to oven drying.
In embodiments of the second aspect and embodiments of the invention, the cellulose fibres are obtained from virgin pulp, recycled paper or old corrugated cardboard, or a combination thereof.
In additional embodiments of the second aspect and embodiments of the invention, the cellulose fibres are obtained from virgin pulp, or from a recycled pulp, or from an old, corrugated cardboard.
In embodiments of the second aspect and embodiments of the invention, the coarsely fibrillated microfibrillated cellulose is present in an amount of about 0.5 wt. % to about 50 wt. %, or in an amount of about 0.5 wt. % to about 25 wt. %, or in an amount of about 0.5 wt. % to about 20 wt. %, or in an amount of about 0.5 wt. % to about 15 wt. %, or in an amount of about 0.5 wt. % to about 10 wt. %, in an amount of about 0.5 wt. % to about 5 wt. %.
In embodiments of the second aspect and embodiments of the invention, the coarsely fibrillated microfibrillated cellulose is obtained from a pulp selected from the group consisting of a chemical pulp, a chemithermomechanical pulp, a mechanical pulp, a thermomechanical pulp, a recycled pulp, a paper broke pulp, a papermill waste stream, waste from a papermill, and combinations thereof.
In embodiments of the second aspect and embodiments of the invention, the coarsely fibrillated microfibrillated cellulose is obtained from a pulp selected from the group consisting of a recycled pulp, a paper broke pulp, a papermill waste stream, waste from a papermill, and combinations thereof.
In embodiments of the second aspect and embodiments of the invention, the cellulose fibres are obtained from a recycled pulp, a paper broke pulp, a papermill waste stream, waste from a papermill, and combinations thereof, or the cellulose fibres are obtained from a pulp selected from the group consisting of a chemical pulp, a chemithermomechanical pulp, a mechanical pulp, a thermomechanical pulp, a recycled pulp, a paper broke pulp, a papermill waste stream, waste from a papermill, and combinations thereof.
In embodiments of the second aspect and embodiments of the invention, the molded object comprises one or more inorganic particulate material.
In further embodiments of the second aspect of the invention, the one or more inorganic particulate material is calcium carbonate or kaolin, or mixtures thereof, or the one or more inorganic particulate material comprises a platy mineral, kaolin and/or talc.
In other embodiments of the second aspect and embodiments thereof, the calcium carbonate is ground calcium carbonate, precipitated calcium carbonate, or mixtures thereof or the calcium carbonate is precipitated calcium carbonate; or the calcium carbonate is ground calcium carbonate.
In other embodiments of the second aspect and embodiments thereof, the ground calcium carbonate is marble, chalk, limestone, and mixtures thereof.
In further embodiments of the second aspect and embodiments thereof, the inorganic particulate material is ground calcium carbonate and precipitated calcium carbonate.
In additional embodiments of the second aspect and embodiments thereof, the inorganic particulate material is selected from the group consisting of an alkaline earth metal carbonate or sulphate, a calcium carbonate, a magnesium carbonate, a dolomite, a gypsum, a bentonite, a hydrous kandite clay, a kaolin, a halloysite, a ball clay, an anhydrous (calcined) kandite clay, a metakaolin, a fully calcined kaolin, a talc, a mica, a perlite, a sepiolite, a huntite, a diatomite, a magnesite, a silicate, a diatomaceous earth, a brucite, an aluminum trihydrate, and combinations thereof.
In a third aspect of the present invention there is provided a three-dimensional packaging container, blister pack, egg carton, bottle, container or food tray comprising the three-dimensional article according to the first aspect.
In a fourth aspect of the invention there is provided, a three-dimensional packaging container, blister pack, egg carton, bottle, container, or food tray comprising the three-dimensional article produced according to the second aspect.
In a fifth aspect of the invention there is provided a use of a three-dimensional article as a blister pack, egg carton, bottle, container, or food tray obtained by a process according to the first or second aspect.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the principles disclosed herein, and the advantages thereof, reference is made to the following descriptions taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic of the layout of a pilot molding machine, which depicts a standard sequence for thermoforming to make one product at a time. Commercial machines are more compact and contain many molds making products simultaneously but use the same basic steps.

FIG. 2 is a plot of the calculated gsm required to reach 1000 n/m tensile stiffness against calculated drainage time for different MFC/pulp blends.

DETAILED DESCRIPTION OF THE INVENTION

The titles, headings and subheadings provided herein should not be interpreted as limiting the various aspects of the disclosure. Accordingly, the terms defined below are more fully defined by reference to the specification in its entirety. All references cited herein are incorporated by reference in their entirety.
The foregoing has outlined rather broadly the features and technical advantages of the aspects of the inventions of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described herein, which may form the subject of the claims of the invention. It should be appreciated by those skilled in the art that any conception and specific embodiment disclosed herein may be readily utilized as a basis for modifying or designing other means for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent means do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying Figures. It is to be expressly understood, however, that any description, Figures, Examples, etc. is provided for the purpose of illustration and description only and is by no means intended to define the limits the invention.
Unless otherwise defined, scientific and technical terms used herein shall have the meanings that are commonly understood by those of ordinary skill in the art. Further, unless otherwise required by context, singular terms shall include pluralities and plural terms shall include the singular.
The use of the word “a” or “an” when used in conjunction with the term “comprising” may mean “one,” but it is also consistent with the meaning of “one or more,” “at least one,” and “one or more than one.”
The use of the term “or” is used to mean “and/or” unless explicitly indicated to refer to alternatives only if the alternatives are mutually exclusive, although the disclosure supports a definition that refers to only alternatives and “and/or.”
Throughout this application, the term “about” is used to indicate that a value includes the inherent variation of error for the quantifying device, the method being employed to determine the value, or the variation that exists among the study subjects. For example, but not by way of limitation, when the term “about” is utilized, the designated value may vary by plus or minus twelve percent, or eleven percent, or ten percent, or nine percent, or eight percent, or seven percent, or six percent, or five percent, or four percent, or three percent, or two percent, or one percent.
The use of the term “at least one” will be understood to include one as well as any quantity more than one, including but not limited to, 1, 2, 3, 4, 5, 10, 15, 20, 30, 40, 50, 100, etc. The term “at least one” may extend up to 100 or 1000 or more depending on the term to which it is attached. In addition, the quantities of 100/1000 are not to be considered limiting as lower or higher limits may also produce satisfactory results. In addition, the use of the term “at least one of X, Y, and Z” will be understood to include X alone, Y alone, and Z alone, as well as any combination of X, Y, and Z.
As used herein, the term “biodegradable” as used herein refers to compositions that are degradable over time by water and/or enzymes found in nature, without any harmful effect on the environment. The compositions of the present disclosure exhibit properties that meet the requirements of ASTM D6868-11 “Standard Specification for Labeling of End Items that Incorporate Plastics and Polymers as Coatings or Additives” (ASTM International, West Conshohocken, Pa.). Alternatively, the compositions of the present disclosure exhibit properties that meet the requirements of ASTM D6400-04—“Specification for Compostable Plastics” (ASTM International, West Conshohocken, Pa.).
The use of ordinal number terminology (i.e., “first”, “second”, “third”, “fourth”, etc.) is solely for the purpose of differentiating between two or more items and, unless otherwise stated, is not meant to imply any sequence or order or importance to one item over another or any order of addition.
As used herein, the term “coarsely fibrillated microfibrillated cellulose,” means MFC wherein the coarsely microfibrillated cellulose comprises less than about 90 wt. % fines and/or less than 75% fines A, and a length-weighted median length Lc(w) of greater than 0.3, as measured by fibre image analyzer, and wherein the microfibrillated cellulose optionally has a fibre steepness of about 20 to about 50, as measured by Malvern Mastersizer. As used herein, the terms “comprising” (and any form of comprising, such as “comprise”, “comprises”, and “comprised”), “having” (and any form of having, such as “have” and “has”), “including” (and any form of including, such as “includes” and “include”), or “containing” (and any form of containing, such as “contains” and “contain”), are inclusive or open-ended and do not exclude additional, unrecited elements or method steps. Additionally, a term that is used in conjunction with the term “comprising” is also understood to be able to be used in conjunction with the term “consisting of” or “consisting essentially of.”
As used herein, the term “includes” and its grammatical variants are intended to be non-limiting, such that recitation of items in a list is not to the exclusion of other like items that can be substituted or added to the listed items.
The fibrous substrate comprising cellulose (variously referred to herein as “fibrous substrate comprising cellulose,” “cellulose fibers,” “fibrous cellulose feedstock,” “cellulose feedstock” and “cellulose-containing fibers (or fibrous,” etc.) may be derived from virgin or recycled pulp or a papermill broke and/or industrial waste, or a paper streams rich in mineral fillers and cellulosic materials from a papermill.
As used herein, the term “substantially” means that the subsequently described event or circumstance completely occurs or that the subsequently described event or circumstance occurs to a great extent or degree. For example, when associated with a particular event or circumstance, the term “substantially” means that the subsequently described event or circumstance occurs at least 80% of the time, or at least 85% of the time, or at least 90% of the time, or at least 95% of the time.
As used herein, the phrase “integer from X to Y” means any integer that includes the endpoints. For example, the phrase “integer from 1 to 5” means 1, 2, 3, 4, or 5.
Unless otherwise stated, particle size properties referred to herein for the inorganic particulate materials may be measured in a well-known manner by sedimentation of the particulate material in a fully dispersed condition in an aqueous medium using a Sedigraph 5100 machine as supplied by Micromeritics Instruments Corporation, Norcross, Ga., USA (telephone: +1 770 662 3620; website: www.micromeritics.com), referred to herein as a “Micromeritics Sedigraph 5100 unit”. Such a machine provides measurements and a plot of the cumulative percentage by weight of particles having a size, referred to in the art as the ‘equivalent spherical diameter’ (e.s.d), less than given e.s.d values. The mean particle size d50 is the value determined in this way of the particle e.s.d at which there are 50% by weight of the particles which have an equivalent spherical diameter less than that d50 value.
Alternatively, where stated, the particle size properties referred to herein for the inorganic particulate materials are as measured by the well-known conventional method employed in the art of laser light scattering, using a Malvern Mastersizer 3000 or Malvern Insitec, as supplied by Malvern Instruments Ltd (or equivalent laser light scattering device or by other methods which give essentially the same result). In the laser light scattering technique, the size of particles in powders, suspensions and emulsions may be measured using the diffraction of a laser beam, based on an application of Mie theory. Such a machine provides measurements and a plot of the cumulative percentage by volume of particles having a size, referred to in the art as the ‘equivalent spherical diameter’ (e.s.d), less than given e.s.d values. The mean particle size d₅₀is the value determined in this way of the particle e.s.d at which there are 50% by volume of the particles which have an equivalent spherical diameter less than that d50 value.
Unless otherwise stated, particle size properties of the coarsely fibrillated microfibrillated cellulose materials are as measured by the well-known conventional method employed in the art of laser light scattering, using a Malvern Insitec machine as supplied by Malvern Instruments Ltd (or by other methods which give essentially the same result).
Details of the procedure used to characterize the particle size distributions of mixtures of inorganic particle material and microfibrillated cellulose using a Malvern Insitec machine are provided in Example 7.
The microfibrillated cellulose may be derived from any suitable source.
By “microfibrillated cellulose (MFC)” is meant a cellulose composition in which microfibrils of cellulose are liberated or partially liberated as individual species or as smaller aggregates as compared to the fibers of a pre-microfibrillated cellulose. The microfibrillated cellulose may be obtained by microfibrillating cellulose, including but not limited to the processes described herein. Typical cellulose fibers (i.e., pre-microfibrillated pulp or pulp not yet fibrillated) suitable for use in papermaking include larger aggregates of hundreds or thousands of individual cellulose microfibrils. By microfibrillating the cellulose, particular characteristics, and properties, including but not limited to the characteristics and properties described herein, are imparted to the microfibrillated cellulose and the compositions including the microfibrillated cellulose.
Microfibrillated cellulose (MFC), although well-known and described in the art, for purposes of the presently disclosed and/or claimed inventive concept(s), microfibrillated cellulose is defined as cellulose consisting of microfibrils in the form of either isolated cellulose microfibrils and/or microfibril bundles of cellulose, both of which are derived from a cellulose raw material. Thus, microfibrillated cellulose is to be understood to comprise partly or totally fibrillated cellulose or lignocellulose fibers, which may be achieved by a variety of processes known in the art.
As used herein, “microfibrillated cellulose” can be used interchangeably with “microfibrillar cellulose,” “nanofibrillated cellulose,” “nanofibril cellulose,” “nanofibers of cellulose,” “nanoscale fibrillated cellulose,” “microfibrils of cellulose,” and/or simply as “MFC.” Additionally, as used herein, the terms listed above that are interchangeable with “microfibrillated cellulose” may refer to cellulose that has been completely microfibrillated or cellulose that has been substantially microfibrillated but still contains an amount of non-microfibrillated cellulose at levels that do not interfere with the benefits of the microfibrillated cellulose as described and/or claimed herein.
Microfibrillated cellulose (MFC) shall in the context of the patent application mean a nanoscale cellulose particle fiber or fibril with at least one dimension less than 100 nm. MFC comprises partly or totally fibrillated cellulose or lignocellulose fibers. The liberated fibrils have a diameter less than 100 nm, whereas the actual fibril diameter or particle size distribution and/or aspect ratio (length/width) depends on the source and the manufacturing methods.
The smallest fibril is called elementary fibril and has a diameter of approximately 2-4 nm (see e.g. Chinga-Carrasco, G., Cellulose fibres, nanofibrils and microfibrils: The morphological sequence of MFC components from a plant physiology and fibre technology point of view, Nanoscale research letters 2011, 6:417), while it is common that the aggregated form of the elementary fibrils, also defined as microfibril (Fengel, D., Ultrastructural behavior of cell wall polysaccharides, Tappi J., March 1970, Vol 53, No. 3.), is the main product that is obtained when making MFC e.g. by using an extended refining process or pressure-drop disintegration process. Depending on the source and the manufacturing process, the length of the fibrils can vary from around 1 to more than 10 micrometers. A coarse MFC grade might contain a substantial fraction of fibrillated fibers, i.e. protruding fibrils from the tracheid (cellulose fiber), and with a certain amount of fibrils liberated from the tracheid (cellulose fiber).
There are different acronyms for MFC such as cellulose microfibrils, fibrillated cellulose, nanofibrillated cellulose, fibril aggregates, nanoscale cellulose fibrils, cellulose nanofibers, cellulose nanofibrils, cellulose microfibers, cellulose fibrils, microfibrillar cellulose, microfibril aggregates and cellulose microfibril aggregates. MFC can also be characterized by various physical or physical-chemical properties such as large surface area or its ability to form a gel-like material at low solids (1-5 wt %) when dispersed in water. The cellulose fiber is preferably fibrillated to such an extent that the final specific surface area of the formed MFC is from about 1 to about 300 m²/g, such as from 1 to 200 m²/g or more preferably 50-200 m²/g when determined for a freeze-dried material with the BET method.
The nanofibrillar cellulose may contain some hemicelluloses; the amount is dependent on the plant source. Mechanical disintegration of the pre-treated fibers, e.g. hydrolyzed, pre-swelled, or oxidized cellulose raw material is carried out with suitable equipment such as a refiner, grinder, homogenizer, colloider, friction grinder, ultrasound sonicator, fluidizer such as microfluidizer, macrofluidizer or fluidizer-type homogenizer. Depending on the MFC manufacturing method, the product might also contain fines, or nanocrystalline cellulose or e.g. other chemicals present in wood fibers or in papermaking process. The product might also contain various amounts of micron size fiber particles that have not been efficiently fibrillated. MFC is produced from wood cellulose fibers, both from hardwood or softwood fibers. It can also be made from microbial sources, agricultural fibers such as wheat straw pulp, bamboo, bagasse, or other non-wood fiber sources. It is preferably made from pulp including pulp from virgin fiber, e.g. mechanical, chemical and/or thermomechanical pulps. It can also be made from broke or recycled paper.
In one embodiment of the present invention, the microfibrillated cellulose has a Schopper Riegler value (SR. degree) of more than 85 SR. degree, or more than 90 SR. degree, or more than 92 SR. degree. The Schopper-Riegler value can be determined through the standard method defined in EN ISO 526.
The microfibrillated cellulose preferably has a water retention value of at least 200%, more preferably at least 250%, most preferably at least 300%. The addition of certain chemicals may influence the water retention value.
The above-described definition of MFC includes, but is not limited to, the new proposed TAPPI standard W13021 on cellulose nanofibril (CNF) defining a cellulose nanofiber material containing multiple elementary fibrils with both crystalline and amorphous region.
In an embodiment of any of the foregoing aspects and embodiments, the microfibrillated cellulose is obtained from a chemical pulp, or a chemithermomechanical pulp, or a mechanical pulp, or thermomechanical pulp, including, for example, Northern Bleached Softwood Kraft pulp (“NBSK”), Bleached Chemi-Thermo Mechanical Pulp (“BCTMP”), or a recycled pulp, or a paper broke pulp, or a papermill waste stream, or waste from a papermill, or combinations thereof.
In an embodiment of any of the foregoing aspects and embodiments, the pulp source is kraft pulp, or bleached long fibre kraft pulp.
In an embodiment of any of the foregoing aspects and embodiments, the pulp source is softwood pulp selected from spruce, pine, fir, larch and hemlock or mixed softwood pulp.
In an embodiment of any of the foregoing aspects and embodiments, the pulp source is hardwood pulp selected from Eucalyptus, aspen and birch, or mixed hardwood pulps.
In an embodiment of any of the foregoing aspects and embodiments, the pulp source is Eucalyptus pulp, spruce pulp, pine pulp, beech pulp, hemp pulp, acacia cotton pulp, and mixtures thereof.
By “microfibrillating” is meant a process in which microfibrils of cellulose are liberated or partially liberated as individual species or as small aggregates as compared to the fibers of the pre-microfibrillated pulp. Typical cellulose fibers (i.e., pre-microfibrillated pulp) suitable for use in papermaking include larger aggregates of hundreds or thousands of individual cellulose fibrils.
Microfibrillated cellulose comprises cellulose, which is a naturally occurring polymer comprising repeated glucose units. The term “microfibrillated cellulose”, also denoted MFC, as used in this specification, includes microfibrillated/microfibrillar cellulose and nano-fibrillated/nanofibrillar cellulose (NFC), which materials are also called nanocellulose.
There are numerous methods of preparing microfibrillated cellulose that are known in the art.
WO-A-2010/131016 discloses a process for preparing microfibrillated cellulose comprising microfibrillating, e.g., by grinding, a fibrous material comprising cellulose, optionally in the presence of grinding medium and inorganic particulate material. When used as a filler in paper, for example, as a replacement or partial replacement for a conventional mineral filler, the microfibrillated cellulose obtained by said process, optionally in combination with inorganic particulate material improved the burst strength properties of the paper. That is, relative to a paper filled with exclusively mineral filler, paper filled with the microfibrillated cellulose was found to have improved burst strength. In other words, the microfibrillated cellulose filler was found to have paper burst strength enhancing attributes. In one particularly advantageous embodiment of that invention, the fibrous material comprising cellulose was ground in the presence of a grinding medium, optionally in combination with inorganic particulate material, to obtain microfibrillated cellulose having a fibre steepness of from 20 to about 50.
The method described in WO-A-2010/131016 comprises a step of microfibrillating a fibrous substrate comprising cellulose by grinding in the presence of a particulate grinding medium which is to be removed after the completion of grinding. By “microfibrillating” is meant a process in which microfibrils of cellulose are liberated or partially liberated as individual species or as small aggregates as compared to the fibres of the pre-microfibrillated pulp. Typical cellulose fibres (i.e., pre-microfibrillated pulp) suitable for use in papermaking include larger aggregates of hundreds or thousands of individual cellulose fibrils. By microfibrillating the cellulose, particular characteristics and properties, including the characteristics and properties described herein, are imparted to the microfibrillated cellulose and the compositions comprising the microfibrillated cellulose.
The fibrous substrate comprising cellulose (variously referred to herein as “fibrous substrate comprising cellulose,” “cellulose fibres,” “fibrous cellulose feedstock,” “cellulose feedstock” and “cellulose-containing fibres (or fibrous,” etc.) may be derived from recycled pulp or a papermill broke and/or industrial waste, or a paper streams rich in mineral fillers and cellulosic materials from a papermill.
The recycled cellulose pulp may be beaten (for example in a Valley beater) and/or otherwise refined (for example, processing in a conical or plate refiner) to any predetermined freeness, reported in the art as Canadian standard freeness (CSF) in cm³. CSF means a value for the freeness or drainage rate of pulp measured by the rate that a suspension of pulp may be drained, and this test is carried out according to the T 227 cm-09 TAPPI standard. For example, the cellulose pulp may have a Canadian standard freeness of about 10 cm³or greater prior to being microfibrillated. The recycled cellulose pulp may have a CSF of about 700 cm³or less, for example, equal to or less than about 650 cm³, or equal to or less than about 600 cm³, or equal to or less than about 550 cm³, or equal to or less than about 500 cm³, or equal to or less than about 450 cm³, or equal to or less than about 400 cm³, or equal to or less than about 350 cm³, or equal to or less than about 300 cm³, or equal to or less than about 250 cm³, or equal to or less than about 200 cm³, or equal to or less than about 150 cm³, or equal to or less than about 100 cm³, or equal to or less than about 50 cm³. The recycled cellulose pulp may have a CSF of about 20 to about 700. The recycled cellulose pulp may then be dewatered by methods well known in the art, for example, the pulp may be filtered through a screen to obtain a wet sheet comprising at least about 10% solids, for example at least about 15% solids, or at least about 20% solids, or at least about 30% solids, or at least about 40% solids. The recycled pulp may be utilized in an unrefined state without being beaten or dewatered, or otherwise refined.
The fibrous substrate comprising cellulose may be added to a grinding vessel fibrous substrate comprising cellulose in a dry state. For example, a dry paper broke may be added directly to the grinder vessel. The aqueous environment in the grinder vessel will then facilitate the formation of a pulp.
The inorganic particulate material, when present, may, for example, be an alkaline earth metal carbonate or sulphate, such as calcium carbonate, magnesium carbonate, dolomite, gypsum, a hydrous kandite day such as kaolin, halloysite or ball clay, an anhydrous (calcined) kandite clay such as metakaolin or fully calcined kaolin, talc, mica, perlite or diatomaceous earth, or magnesium hydroxide, or aluminium trihydrate, or combinations thereof.
A preferred inorganic particulate material for use in the method is calcium carbonate. Hereafter, the invention may tend to be discussed in terms of calcium carbonate, and in relation to aspects where the calcium carbonate is processed and/or treated. The invention should not be construed as being limited to such embodiments.
The particulate calcium carbonate used in the present invention may be obtained from a natural source by grinding. Ground calcium carbonate (GCC) is typically obtained by crushing and then grinding a mineral source such as chalk, marble, or limestone, which may be followed by a particle size classification step, in order to obtain a product having the desired degree of fineness. Other techniques such as bleaching, flotation and magnetic separation may also be used to obtain a product having the desired degree of fineness and/or color. The particulate solid material may be ground autogenously, i.e. by attrition between the particles of the solid material themselves, or, alternatively, in the presence of a particulate grinding medium comprising particles of a different material from the calcium carbonate to be ground. These processes may be carried out with or without the presence of a dispersant and biocides, which may be added at any stage of the process.
Precipitated calcium carbonate (PCC) may be used as the source of particulate calcium carbonate in the present invention, and may be produced by any of the known methods available in the art. TAPPI Monograph Series No 30, “Paper Coating Pigments”, pages 34-35 describes the three main commercial processes for preparing precipitated calcium carbonate which is suitable for use in preparing products for use in the paper industry, but may also be used in the practice of the present invention. In all three processes, a calcium carbonate feed material, such as limestone, is first calcined to produce quicklime, and the quicklime is then slaked in water to yield calcium hydroxide or milk of lime. In the first process, the milk of lime is directly carbonated with carbon dioxide gas. This process has the advantage that no by-product is formed, and it is relatively easy to control the properties and purity of the calcium carbonate product. In the second process the milk of lime is contacted with soda ash to produce, by double decomposition, a precipitate of calcium carbonate and a solution of sodium hydroxide. The sodium hydroxide may be substantially completely separated from the calcium carbonate if this process is used commercially. In the third main commercial process the milk of lime is first contacted with ammonium chloride to give a calcium chloride solution and ammonia gas. The calcium chloride solution is then contacted with soda ash to produce by double decomposition precipitated calcium carbonate and a solution of sodium chloride. The crystals can be produced in a variety of different shapes and sizes, depending on the specific reaction process that is used. The three main forms of PCC crystals are aragonite, rhombohedral and scalenohedral, all of which are suitable for use in the present invention, including mixtures thereof.
Wet grinding of calcium carbonate involves the formation of an aqueous suspension of the calcium carbonate which may then be ground, optionally in the presence of a suitable dispersing agent. Reference may be made to, for example, EP-A-614948 (the contents of which are incorporated by reference in their entirety) for more information regarding the wet grinding of calcium carbonate.
In some circumstances, minor additions of other minerals may be included, for example, one or more of kaolin, calcined kaolin, wollastonite, bauxite, talc or mica, could also be present.
When the inorganic particulate material of the present invention is obtained from naturally occurring sources, it may be that some mineral impurities will contaminate the ground material. For example, naturally occurring calcium carbonate can be present in association with other minerals. Thus, in some embodiments, the inorganic particulate material includes an amount of impurities. In general, however, the inorganic particulate material used in the invention will contain less than about 5% by weight, preferably less than about 1% by weight, of other mineral impurities. The inorganic particulate material used during the microfibrillating step of the method of the present invention will preferably have a particle size distribution in which at least about 10% by weight of the particles have an equivalent spherical diameter (e.s.d.) of less than 2 μm, for example, at least about 20% by weight, or at least about 30% by weight, or at least about 40% by weight, or at least about 50% by weight, or at least about 60% by weight, or at least about 70% by weight, or at least about 80% by weight, or at least about 90% by weight, or at least about 95% by weight, or about 100% of the particles have an e.s.d of less than 2 μm.
Unless otherwise stated, particle size properties of the microfibrillated cellulose materials are as measured by the well-known conventional method employed in the art of laser light scattering, using a Malvern Insitec L machine as supplied by Malvern Instruments Ltd (or by other methods which give essentially the same result).
Details of the procedure used to characterize the particle size distributions of mixtures of inorganic particle material and microfibrillated cellulose using a Malvern Mastersizer S machine are provided below.
The fibrous substrate comprising cellulose may be microfibrillated in the presence of an inorganic particulate material to obtain microfibrillated cellulose having a d₅₀ranging from about 5 to μm about 500 μm, as measured by laser light scattering. The fibrous substrate comprising cellulose may be microfibrillated in the presence of an inorganic particulate material to obtain microfibrillated cellulose having a d₅₀of equal to or less than about 400 μm, for example equal to or less than about 300 μm, or equal to or less than about 200 μm, or equal to or less than about 150 μm, or equal to or less than about 125 μm, or equal to or less than about 100 μm, or equal to or less than about 90 μm, or equal to or less than about 80 μm, or equal to or less than about 70 μm, or equal to or less than about 60 μm, or equal to or less than about 50 μm, or equal to or less than about 40 μm, or equal to or less than about 30 μm, or equal to or less than about 20 μm, or equal to or less than about 10 μm.
The fibrous substrate comprising cellulose may be microfibrillated in the presence of an inorganic particulate material to obtain microfibrillated cellulose having a modal fibre particle size ranging from about 0.1-500 μm and a modal inorganic particulate material particle size ranging from 0.25-20 μm. The fibrous substrate comprising cellulose may be microfibrillated in the presence of an inorganic particulate material to obtain microfibrillated cellulose having a modal fibre particle size of at least about 0.5 μm, for example at least about 10 μm, or at least about 50 μm, or at least about 100 μm, or at least about 150 μm, or at least about 200 μm, or at least about 300 μm, or at least about 400 μm.
The fibrous substrate comprising cellulose may be microfibrillated in the presence of an inorganic particulate material to obtain microfibrillated cellulose having a fibre steepness equal to or greater than about 10, as measured by Malvern. Fibre steepness i.e., the steepness of the particle size distribution of the fibres) is determined by the following formula:
Steepness=100×(d30/d70)
The microfibrillated cellulose may have a fibre steepness equal to or less than about 100. The microfibrillated cellulose may have a fibre steepness equal to or less than about 75, or equal to or less than about 50, or equal to or less than about 40, or equal to or less than about 30. The microfibrillated cellulose may have a fibre steepness from about 20 to about 50, or from about 25 to about 40, or from about 25 to about 35, or from about 30 to about 40.
The finer mineral peak can be fitted to the measured data points and subtracted mathematically from the distribution to leave the fibre peak, which can be converted to a cumulative distribution. Similarly, the fibre peak can be subtracted mathematically from the original distribution to leave the mineral peak, which can also be converted to a cumulative distribution. Both these cumulative curves may then be used to calculate the mean particle size (d₅₀) and the steepness of the distribution (d₃₀/d₇₀×100). The differential curve may then be used to find the modal particle size for both the mineral and fibre fraction.
Another preferred inorganic particulate material for use is kaolin clay. The invention should not be construed as being limited to such embodiments. Thus, in some embodiments, kaolin is used in an unprocessed form.
Kaolin clay used in this invention may be a processed material derived from a natural source, namely raw natural kaolin clay mineral. The processed kaolin clay may typically contain at least about 50% by weight kaolinite. For example, most commercially processed kaolin clays contain greater than about 75% by weight kaolinite and may contain greater than about 90%, in some cases greater than about 95% by weight of kaolinite.
Kaolin clay used in the present invention may be prepared from the raw natural kaolin clay mineral by one or more other processes which are well known to those skilled in the art, for example by known refining or beneficiation steps.
For example, the clay mineral may be bleached with a reductive bleaching agent, such as sodium hydrosulfite. If sodium hydrosulfite is used, the bleached clay mineral may optionally be dewatered, and optionally washed and again optionally dewatered, after the sodium hydrosulfite bleaching step.
The clay mineral may be treated to remove impurities, e.g. by flocculation, flotation, or magnetic separation techniques well known in the art. Alternatively the clay mineral used in the first aspect of the invention may be untreated in the form of a solid or as an aqueous suspension.
The process for preparing the particulate kaolin clay used in the present invention may also include one or more comminution steps, e.g., grinding or milling. Light comminution of a coarse kaolin is used to give suitable delamination thereof. The comminution may be carried out by use of beads or granules of a plastic (e.g. nylon), sand or ceramic grinding or milling aid. The coarse kaolin may be refined to remove impurities and improve physical properties using well known procedures. The kaolin clay may be treated by a known particle size classification procedure, e.g., screening and centrifuging (or both), to obtain particles having a desired d50 value or particle size distribution.
In a non-limiting example, the term microfibrillated cellulose is used to describe fibrillated cellulose comprising nanoscale cellulose particle fibers or fibrils frequently having at least one dimension less than 100 nm. When liberated from cellulose fibers, fibrils typically have a diameter less than 100 nm. The actual diameter of cellulose fibrils depends on the source and the method of measuring such fibrils as well as the manufacturing methods that are employed.
The particle size distribution and/or aspect ratio (length/width) of the cellulose microfibrils attached to the fibrillated cellulose fiber or as a liberated microfibril depends on the source and the manufacturing methods employed in the microfibrillation process.
In a non-limiting example, the aspect ratio of microfibrils is typically high and the length of individual microfibrils may be more than one micrometer and the diameter may be within a range of about 5 to 60 nm with a number-average diameter typically less than 20 nm. The diameter of microfibril bundles may be larger than 1 micron.
In a non-limiting example, the smallest fibril is conventionally referred to as an elementary fibril, which generally has a diameter of approximately 2-4 nm. It is also common for elementary fibrils to aggregate, which may also be considered as microfibrils.
In a non-limiting example, the microfibrillated cellulose may at least partially comprise nanocellulose. The nanocellulose may comprise mainly nano-sized fibrils having a diameter that is less than 100 nm and a length that may be in the micron-range or lower. The smallest microfibrils are like so-called elementary fibrils, the diameter of which is typically 2 to 4 nm. Of course, the dimensions and structures of microfibrils and microfibril bundles depend on the raw materials used in addition to the methods of producing the microfibrillated cellulose. Nonetheless, it is expected that a person of ordinary skill in the art would understand the meaning of “microfibrillated cellulose” in the context of the presently disclosed and/or claimed inventive concept(s).
Depending on the source of the cellulose fibers and the manufacturing process employed to microfibrillate the cellulose fibers, the length of the fibrils can vary, frequently from about 1 to greater than 10 micrometers.
A coarse MFC grade might contain a substantial fraction of fibrillated fibers, i.e., protruding fibrils from the tracheid (cellulose fiber), and with a certain amount of fibrils liberated from the tracheid (cellulose fiber).
Manufacturing Microfibrillated Cellulose.
In an embodiment, the microfibrillated cellulose may also be prepared from recycled pulp or a papermill broke and/or industrial waste, or a paper streams rich in mineral fillers and cellulosic materials from a papermill.
The fibrous substrate comprising cellulose may be added to a grinding vessel in a dry state. For example, a dry paper broke may be added directly to the grinder vessel. The aqueous environment in the grinder vessel will then facilitate the formation of a pulp.
In certain embodiments, the microfibrillated cellulose has a d₅₀ranging from about 5 μm to about 500 μm, as measured by laser light scattering. In certain embodiments, the microfibrillated cellulose has a d₅₀of equal to or less than about 400 μm, for example equal to or less than about 300 μm, or equal to or less than about 200 μm, or equal to or less than about 150 μm, or equal to or less than about 125 μm, or equal to or less than about 100 μm, or equal to or less than about 90 μm, or equal to or less than about 80 μm, or equal to or less than about 70 μm, or equal to or less than about 60 μm, or equal to or less than about 50 μm, or equal to or less than about 40 μm, or equal to or less than about 30 μm, or equal to or less than about 20 μm, or equal to or less than about 10 μm.
In certain embodiments, the microfibrillated cellulose has a modal fibre particle size ranging from about 0.1-500 μm. In certain embodiments, the microfibrillated cellulose has a modal fibre particle size of at least about 0.5 μm, for example at least about 10 μm, or at least about 50 μm, or at least about 100 μm, or at least about 150 μm, or at least about 200 μm, or at least about 300 μm, or at least about 400 μm.
Additionally, or alternatively, the microfibrillated cellulose may have a fibre steepness equal to or greater than about 10, as measured by Malvern. Fibre steepness (i.e., the steepness of the particle size distribution of the fibers) is determined by the following formula, where “d” expresses the median diameter, as measured by Malvern:
Steepness=100×(d ₃₀ /d ₇₀)
The microfibrillated cellulose may have a fibre steepness equal to or less than about 100. The microfibrillated cellulose may have a fibre steepness equal to or less than about 75, or equal to or less than about 50, or equal to or less than about 40, or equal to or less than about 30. The microfibrillated cellulose may have a fibre steepness from about 20 to about 50, or from about 25 to about 40, or from about 25 to about 35, or from about 30 to about 40.
Inorganic Particulate Material
The inorganic particulate material may, for example, be an alkaline earth metal carbonate or sulphate, such as calcium carbonate, magnesium carbonate, dolomite, gypsum, a hydrous kandite clay such as kaolin, halloysite or ball clay, an anhydrous (calcined) kandite clay such as metakaolin or fully calcined kaolin, talc, mica, huntite, hydromagnesite, ground glass, perlite or diatomaceous earth, or wollastonite, or titanium dioxide, or magnesium hydroxide, or aluminium trihydrate, lime, graphite, or combinations thereof.
In certain embodiments, the inorganic particulate material comprises or is calcium carbonate, magnesium carbonate, dolomite, gypsum, an anhydrous kandite clay, perlite, diatomaceous earth, wollastonite, magnesium hydroxide, or aluminium trihydrate, titanium dioxide or combinations thereof.
In certain embodiments, the inorganic particulate material is selected from the group consisting of the an alkaline earth metal carbonate or sulphate, calcium carbonate, magnesium carbonate, dolomite, gypsum, bentonite, a hydrous kandite clay, kaolin, halloysite or ball clay; an anhydrous (calcined) kandite clay, as metakaolin or fully calcined kaolin, talc, mica, perlite sepiolite, huntite, diatomite, magnesite, silicates, or diatomaceous earth, brucite, aluminum trihydrate, and cols combinations thereof.
In certain embodiments of the aspects of the invention, the inorganic particulate material is selected from the group consisting of the an alkaline earth metal carbonate or sulphate, calcium carbonate, magnesium carbonate, dolomite, gypsum, bentonite, a hydrous kandite clay, kaolin, halloysite or ball clay, an anhydrous (calcined) kandite clay, as metakaolin or fully calcined kaolin talc, mica, perlite sepiolite, huntite, diatomite, magnesite, silicates, or diatomaceous earth, brucite, aluminum trihydrate, and combinations thereof.
An exemplary inorganic particulate material for use in the present invention is calcium carbonate. Hereafter, the invention may tend to be discussed in terms of calcium carbonate, and in relation to aspects where the calcium carbonate is processed and/or treated. The invention should not be construed as being limited to such embodiments.
The particulate calcium carbonate used in the present invention may be obtained from a natural source by grinding. Ground calcium carbonate (GCC) is typically obtained by crushing and then grinding a mineral source such as chalk, marble or limestone, which may be followed by a particle size classification step, in order to obtain a product having the desired degree of fineness. Other techniques such as bleaching, flotation and magnetic separation may also be used to obtain a product having the desired degree of fineness and/or colour. The particulate solid material may be ground autogenously, i.e. by attrition between the particles of the solid material themselves, or, alternatively, in the presence of a particulate grinding medium comprising particles of a different material from the calcium carbonate to be ground. These processes may be carried out with or without the presence of a dispersant and biocides, which may be added at any stage of the process.
Precipitated calcium carbonate (PCC) may be used as the source of particulate calcium carbonate in the present invention, and may be produced by any of the known methods available in the art. TAPPI Monograph Series No 30, “Paper Coating Pigments”, pages 34-35 describes the three main commercial processes for preparing precipitated calcium carbonate which is suitable for use in preparing products for use in the paper industry, but may also be used in the practice of the present invention. In all three processes, a calcium carbonate feed material, such as limestone, is first calcined to produce quicklime, and the quicklime is then slaked in water to yield calcium hydroxide or milk of lime. In the first process, the milk of lime is directly carbonated with carbon dioxide gas. This process has the advantage that no by-product is formed, and it is relatively easy to control the properties and purity of the calcium carbonate product. In the second process the milk of lime is contacted with soda ash to produce, by double decomposition, a precipitate of calcium carbonate and a solution of sodium hydroxide. The sodium hydroxide may be substantially completely separated from the calcium carbonate if this process is used commercially. In the third main commercial process the milk of lime is first contacted with ammonium chloride to give a calcium chloride solution and ammonia gas. The calcium chloride solution is then contacted with soda ash to produce by double decomposition precipitated calcium carbonate and a solution of sodium chloride. The crystals can be produced in a variety of different shapes and sizes, depending on the specific reaction process that is used. The three main forms of PCC crystals are aragonite, rhombohedral and scalenohedral (e.g., calcite), all of which are suitable for use in the present invention, including mixtures thereof.
In certain embodiments of the aspects of the invention, the PCC may be formed during the process of producing microfibrillated cellulose.
Wet grinding of calcium carbonate involves the formation of an aqueous suspension of the calcium carbonate which may then be ground, optionally in the presence of a suitable dispersing agent. Reference may be made to, for example, EP-A-614948 (the contents of which are incorporated by reference in their entirety) for more information regarding the wet grinding of calcium carbonate.
When the inorganic particulate material of the present invention is obtained from naturally occurring sources, it may be that some mineral impurities will contaminate the ground material. For example, naturally occurring calcium carbonate can be present in association with other minerals. Thus, in some embodiments, the inorganic particulate material includes an amount of impurities. In general, however, the inorganic particulate material used in the invention will contain less than about 5% by weight, or less than about 1% by weight, of other mineral impurities.
The inorganic particulate material may have a particle size distribution in which at least about 10% by weight of the particles have an e.s.d of less than 2 μm, for example, at least about 20% by weight, or at least about 30% by weight, or at least about 40% by weight, or at least about 50% by weight, or at least about 60% by weight, or at least about 70% by weight, or at least about 80% by weight, or at least about 90% by weight, or at least about 95% by weight, or about 100% of the particles have an e.s.d of less than 2 μm.
In another embodiment of the aspects of the invention, the inorganic particulate material has a particle size distribution, as measured using a Malvern Insitec or 3000 machine, in which at least about 10% by volume of the particles have an e.s.d of less than 2 μm, for example, at least about 20% by volume, or at least about 30% by volume, or at least about 40% by volume, or at least about 50% by volume, or at least about 60% by volume, or at least about 70% by volume, or at least about 80% by volume, or at least about 90% by volume, or at least about 95% by volume, or about 100% of the particles by volume have an e.s.d of less than 2 μm.
Details of the procedure used to characterize the particle size distributions of mixtures of inorganic particle material and microfibrillated cellulose using a Malvern Insitec or 3000 machine are provided in Example 7.
Methods of Manufacturing Microfibrillated Cellulose and Inorganic Particulate Material
In certain embodiments of the aspects of the invention, the coarsely fibrillated microfibrillated cellulose may be prepared in the presence of or in the absence of the inorganic particulate material.
The microfibrillated cellulose is derived from fibrous substrate comprising cellulose. The fibrous substrate comprising cellulose may be derived from any suitable source, such as wood, grasses (e.g., sugarcane, bamboo) or rags (e.g., textile waste, cotton, hemp or flax). The fibrous substrate comprising cellulose may be in the form of a pulp (i.e., a suspension of cellulose fibers in water), which may be prepared by any suitable chemical or mechanical treatment, or combination thereof. For example, the pulp may be a chemical pulp, or a chemithermomechanical pulp, or a mechanical pulp, or a recycled pulp, or a papermill broke, or a papermill waste stream, or waste from a papermill, or a dissolving pulp, kenaf pulp, market pulp, partially carboxymethylated pulp, abaca pulp, birch pulp, grass pulp, bamboo pulp, palm pulp, peanut shell, or a combination thereof. The cellulose pulp may be beaten (for example, in a Valley beater) and/or otherwise refined (for example, processing in a conical or plate refiner) to any predetermined freeness, reported in the art as Canadian standard freeness (CSF) in cm³. CSF means a value for the freeness or drainage rate of pulp measured by the rate that a suspension of pulp may be drained. For example, the cellulose pulp may have a Canadian standard freeness of about 10 cm³or greater prior to being microfibrillated. The cellulose pulp may have a CSF of about 700 cm³or less, for example, equal to or less than about 650 cm³, or equal to or less than about 600 cm³, or equal to or less than about 550 cm³, or equal to or less than about 500 cm³, or equal to or less than about 450 cm³, or equal to or less than about 400 cm³, or equal to or less than about 350 cm³, or equal to or less than about 300 cm³, or equal to or less than about 250 cm³, or equal to or less than about 200 cm³, or equal to or less than about 150 cm³, or equal to or less than about 100 cm³, or equal to or less than about 50 cm³.
In certain embodiments of the aspects of the invention, the pulp is obtained from a chemical pulp, or a chemithermomechanical pulp, or a mechanical pulp, or thermomechanical pulp, including, for example, Northern Bleached Softwood Kraft pulp (“NB SK”), Bleached hardwood pulp, Bleached Chemi-Thermo Mechanical Pulp (“BCTMP”), or a recycled pulp, or a paper broke pulp, or a papermill waste stream, or waste from a papermill, or combinations thereof.
The cellulose pulp may then be dewatered by methods well known in the art, for example, the pulp may be filtered through a screen in order to obtain a wet sheet comprising at least about 10% solids, for example at least about 15% solids, or at least about 20% solids, or at least about 30% solids, or at least about 40% solids. The pulp may be utilized in an unrefined state, which is to say without being beaten or dewatered, or otherwise refined.
In certain embodiments of the aspects of the invention, the pulp may be beaten in the presence of an inorganic particulate material, such as calcium carbonate.
Co-Grinding Process of Microfibrillated Cellulose and Inorganic Particulate Material
In an embodiment of the aspects of the invention, the present invention is related to modifications, for example, improvements, to the methods and compositions described in WO-A-2010/131016, the entire contents of which are hereby incorporated by reference.
WO-A-2010/131016 discloses a process for preparing microfibrillated cellulose comprising microfibrillating, e.g., by grinding a fibrous material comprising cellulose, optionally in the presence of grinding medium and/or inorganic particulate material. When used as a filler in paper, for example, as a replacement or partial replacement for a conventional mineral filler, the microfibrillated cellulose obtained by said process, optionally in combination with inorganic particulate material, was unexpectedly found to improve the burst strength properties of the paper. That is, relative to a paper filled with exclusively mineral filler, paper filled with the microfibrillated cellulose was found to have improved burst strength. In other words, the microfibrillated cellulose filler was found to have paper burst strength enhancing attributes. In one particularly advantageous embodiment of that invention, the fibrous material comprising cellulose was ground in the presence of a grinding medium, optionally in combination with inorganic particulate material, to obtain microfibrillated cellulose having a fibre steepness of from 20 to about 50.
For preparation of microfibrillated cellulose, the fibrous substrate comprising cellulose may be added to a grinding vessel or homogenizer in a dry state. For example, a dry paper broke may be added directly to a grinder vessel. The aqueous environment in the grinder vessel will then facilitate the formation of a pulp.
The step of microfibrillating may be carried out in any suitable apparatus, including but not limited to a refiner. In one embodiment, the microfibrillating step is conducted in a grinding vessel under wet-grinding conditions. In another embodiment, the microfibrillating step is carried out in a homogenizer. Each of these embodiments is described in greater detail below.
Wet Grinding
The grinding is suitably performed in a conventional manner. The grinding may be an attrition grinding process in the presence of a particulate grinding medium, or may be an autogenous grinding process, i.e., one in the absence of a grinding medium. By grinding medium is meant to be a medium other than the inorganic particulate material which in certain embodiments may be co-ground with the fibrous substrate comprising cellulose.
The particulate grinding medium, when present, may be of a natural or a synthetic material. The grinding medium may, for example, comprise balls, beads or pellets of any hard mineral, ceramic or metallic material. Such materials may include, for example, alumina, zirconia, zirconium silicate, aluminium silicate or the mullite-rich material which is produced by calcining kaolinitic clay at a temperature in the range of from about 1300° C. to about 1800° C. For example, in some embodiments a Carbolite® grinding media is used. Alternatively, particles of natural sand of a suitable particle size may be used.
In other embodiments, hardwood grinding media (e.g., wood flour) may be used.
Generally, the type of and particle size of grinding medium to be selected for use in the invention may be dependent on the properties, such as, e.g., the particle size of, and the chemical composition of, the feed suspension of material to be ground. In some embodiments, the particulate grinding medium comprises particles having an average diameter in the range of from about 0.1 mm to about 6.0 mm, for example, in the range of from about 0.2 mm to about 4.0 mm. The grinding medium (or media) may be present in an amount up to about 70% by volume of the charge. The grinding media may be present in amount of at least about 10% by volume of the charge, for example, at least about 20% by volume of the charge, or at least about 30% by volume of the charge, or at least about 40% by volume of the charge, or at least about 50% by volume of the charge, or at least about 60% by volume of the charge.
The grinding may be carried out in one or more stages. For example, a coarse inorganic particulate material may be ground in the grinder vessel to a predetermined particle size distribution, after which the fibrous material comprising cellulose is added and the grinding continued until the desired level of microfibrillation has been obtained and a coarsely fibrillated microfibrillated cellulose is produced.
The inorganic particulate material may be wet or dry ground in the absence or presence of a grinding medium. This the case of a wet grinding stage, the course inorganic particulate material is ground in an aqueous suspension in the presence of a grinding medium.
In an embodiment of the aspects of the invention, the median particle size (d₅₀) of the inorganic particulate material is reduced during the co-grinding process. For example, the d₅₀of the inorganic particulate material may be reduced by at least about 10% (as measured by a Malvern Insitec or 3000 machine), for example, the d₅₀of the inorganic particulate material may be reduced by at least about 20%, or reduced by at least about 30%, or reduced by at least about 50%, or reduced by at least about 50%, or reduced by at least about 60%, or reduced by at least about 70%, or reduced by at least about 80%, or reduced by at least about 90%. For example, an inorganic particulate material having a d₅₀of 2.5 μm prior to co-grinding and a d₅₀of 1.5 μm post co-grinding will have been subject to a 40% reduction in particle size.
In certain embodiments of the aspects of the invention, the median particle size of the inorganic particulate material is not significantly reduced during the co-grinding process. By ‘not significantly reduced’ is meant that the d₅₀of the inorganic particulate material is reduced by less than about 10%, for example, the d₅₀of the inorganic particulate material is reduced by less than about 5%.
The fibrous substrate comprising cellulose may be microfibrillated, optionally in the presence of an inorganic particulate material, to obtain microfibrillated cellulose having a d₅₀ranging from about 5 to μm about 500 μm, as measured by laser light scattering. The fibrous substrate comprising cellulose may be microfibrillated, optionally in the presence of an inorganic particulate material, to obtain microfibrillated cellulose having a d₅₀of equal to or less than about 400 μm, for example equal to or less than about 300 μm, or equal to or less than about 200 μm, or equal to or less than about 150 μm, or equal to or less than about 125 μm, or equal to or less than about 100 μm, or equal to or less than about 90 μm, or equal to or less than about 80 μm, or equal to or less than about 70 μm, or equal to or less than about 60 μm, or equal to or less than about 50 μm, or equal to or less than about 40 μm, or equal to or less than about 30 μm, or equal to or less than about 20 μm, or equal to or less than about 10 μm.
The fibrous substrate comprising cellulose may be microfibrillated, optionally in the presence of an inorganic particulate material, to obtain microfibrillated cellulose having a modal fibre particle size ranging from about 0.1-500 μm and a modal inorganic particulate material particle size ranging from 0.25-20 μm. The fibrous substrate comprising cellulose may be microfibrillated, optionally in the presence of an inorganic particulate material to obtain microfibrillated cellulose having a modal fibre particle size of at least about 0.5 μm, for example at least about 10 μm, or at least about 50 μm, or at least about 100 μm, or at least about 150 μm, or at least about 200 μm, or at least about 300 μm, or at least about 400 μm.
The fibrous substrate comprising cellulose may be microfibrillated, optionally in the presence of an inorganic particulate material, to obtain microfibrillated cellulose having a fibre steepness, as described above.
The grinding may be performed in a grinding vessel, such as a tumbling mill (e.g., rod, ball and autogenous), a stirred mill (e.g., SAM or Isa Mill), a tower mill, a stirred media detritor (SMD), or a grinding vessel comprising rotating parallel grinding plates between which the feed to be ground is fed.
In an embodiment of the aspects of the invention, the grinding is performed in a screened grinder, such as a stirred media detritor. The screened grinder may comprise one or more screen(s) having a nominal aperture size of at least about 250 μm, for example, the one or more screens may have a nominal aperture size of at least about 300 μm, or at least about 350 μm, or at least about 400 μm, or at least about 450 μm, or at least about 500 μm, or at least about 550 μm, or at least about 600 μm, or at least about 650 μm, or at least about 700 μm, or at least about 750 μm, or at least about 800 μm, or at least about 850 μm, or at or least about 900 μm, or at least about 1000 μm.
The screen sizes noted immediately above are applicable to the tower mill embodiments described above.
As noted above, the grinding may be performed in the presence of a grinding medium. In an embodiment of the aspects of the invention, the grinding medium is a coarse media comprising particles having an average diameter in the range of from about 1 mm to about 6 mm, for example about 2 mm, or about 3 mm, or about 4 mm, or about 5 mm.
In another embodiment of the aspects of the invention, the grinding media has a specific gravity of at least about 2.5, for example, at least about 3, or at least about 3.5, or at least about 4.0, or at least about 4.5, or least about 5.0, or at least about 5.5, or at least about 6.0.
In another embodiment of the aspects of the invention, the grinding media comprises particles having an average diameter in the range of from about 1 mm to about 6 mm and has a specific gravity of at least about 2.5.
In another embodiment of the aspects of the invention, the grinding media comprises particles having an average diameter of about 3 mm and specific gravity of about 2.7.
As described above, the grinding medium (or media) may present in an amount up to about 70% by volume of the charge. The grinding media may be present in amount of at least about 10% by volume of the charge, for example, at least about 20% by volume of the charge, or at least about 30% by volume of the charge, or at least about 40% by volume of the charge, or at least about 50% by volume of the charge, or at least about 60% by volume of the charge.
In an embodiment of the aspects of the invention, the grinding medium is present in amount of about 50% by volume of the charge.
The term ‘charge’ is meant to be the composition which is the feed fed to the grinder vessel. The charge includes of water, grinding media, fibrous substrate comprising cellulose and optional inorganic particulate material, and any other optional additives as described herein.
The use of a relatively coarse and/or dense media has the advantage of improved (i.e., faster) sediment rates and reduced media carry over through the quiescent zone and/or classifier and/or screen(s).
A further advantage in using relatively coarse grinding media is that the mean particle size (d₅₀) of the inorganic particulate material may not be significantly reduced during the grinding process such that the energy imparted to the grinding system is primarily expended in microfibrillating the fibrous substrate comprising cellulose.
A further advantage in using relatively coarse screens is that a relatively coarse or dense grinding media can be used in the microfibrillating step. In addition, the use of relatively coarse screens (i.e., having a nominal aperture of least about 250 μm) allows a relatively high solids product to be processed and removed from the grinder, which allows a relatively high solids feed (comprising fibrous substrate comprising cellulose and inorganic particulate material) to be processed in an economically viable process. As discussed below, it has been found that a feed having high initial solids content is desirable in terms of energy sufficiency. Further, it has also been found that product produced (at a given energy) at lower solids has a coarser particle size distribution.
The grinding may be performed in a cascade of grinding vessels, one or more of which may comprise one or more grinding zones. For example, the fibrous substrate comprising cellulose and the inorganic particulate material may be ground in a cascade of two or more grinding vessels, for example, a cascade of three or more grinding vessels, or a cascade of four or more grinding vessels, or a cascade of five or more grinding vessels, or a cascade of six or more grinding vessels, or a cascade of seven or more grinding vessels, or a cascade of eight or more grinding vessels, or a cascade of nine or more grinding vessels in series, or a cascade comprising up to ten grinding vessels. The cascade of grinding vessels may be operatively linked in series or parallel or a combination of series and parallel. The output from and/or the input to one or more of the grinding vessels in the cascade may be subjected to one or more screening steps and/or one or more classification steps.
The circuit may comprise a combination of one or more grinding vessels and homogenizer.
In an embodiment the grinding is performed in a closed circuit. In another embodiment, the grinding is performed in an open circuit. The grinding may be performed in batch mode. The grinding may be performed in a re-circulating batch mode.
As described above, the grinding circuit may include a pre-grinding step in which coarse inorganic particulate ground in a grinder vessel to a predetermined particle size distribution, after which fibrous material comprising cellulose is combined with the pre-ground inorganic particulate material and the grinding continued in the same or different grinding vessel until the desired level of microfibrillation has been obtained.
As the suspension of material to be ground may be of a relatively high viscosity, a suitable dispersing agent may be added to the suspension prior to grinding. The dispersing agent may be, for example, a water soluble condensed phosphate, polysilicic acid or a salt thereof, or a polyelectrolyte, for example a water soluble salt of a poly(acrylic acid) or of a poly(methacrylic acid) having a number average molecular weight not greater than 80,000. The amount of the dispersing agent used would generally be in the range of from 0.1 to 2.0% by weight, based on the weight of the dry inorganic particulate solid material. The suspension may suitably be ground at a temperature in the range of from 4° C. to 100° C.
Other additives which may be included during the microfibrillation step include: carboxymethyl cellulose, amphoteric carboxymethyl cellulose, oxidising agents, 2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO), TEMPO derivatives, and wood degrading enzymes.
The pH of the suspension of material to be ground may be about 7 or greater than about 7 (i.e., basic), for example, the pH of the suspension may be about 8, or about 9, or about 10, or about 11. The pH of the suspension of material to be ground may be less than about 7 (i.e., acidic), for example, the pH of the suspension may be about 6, or about 5, or about 4, or about 3. The pH of the suspension of material to be ground may be adjusted by addition of an appropriate amount of acid or base. Suitable bases included alkali metal hydroxides, such as, for example, NaOH. Other suitable bases are sodium carbonate and ammonia. Suitable acids included inorganic acids, such as hydrochloric and sulphuric acid, or organic acids. An exemplary acid is orthophosphoric acid.
The amount of inorganic particulate material, when present, and cellulose pulp in the mixture to be co-ground may be varied in order to produce a slurry which is suitable for use as the top ply slurry, or ply slurry, or which may be further modified, e.g., with additional of further inorganic particulate material, to produce a slurry which is suitable for use as the top ply slurry, or ply slurry.

Homogenizing

Microfibrillation of the fibrous substrate comprising cellulose may be effected under wet conditions, optionally, in the presence of the inorganic particulate material, by a method in which the mixture of cellulose pulp and optional inorganic particulate material is pressurized (for example, to a pressure of about 500 bar) and then passed to a zone of lower pressure. The rate at which the mixture is passed to the low pressure zone is sufficiently high and the pressure of the low pressure zone is sufficiently low as to cause microfibrillation of the cellulose fibers. For example, the pressure drop may be effected by forcing the mixture through an annular opening that has a narrow entrance orifice with a much larger exit orifice. The drastic decrease in pressure as the mixture accelerates into a larger volume (i.e., a lower pressure zone) induces cavitation which causes microfibrillation. In an embodiment, microfibrillation of the fibrous substrate comprising cellulose may be effected in a homogenizer under wet conditions, optionally in the presence of the inorganic particulate material. In the homogenizer, the cellulose pulp and optional inorganic particulate material is pressurized (for example, to a pressure of about 500 bar), and forced through a small nozzle or orifice. The mixture may be pressurized to a pressure of from about 100 to about 1000 bar, for example to a pressure of equal to or greater than 300 bar, or equal to or greater than about 500, or equal to or greater than about 200 bar, or equal to or greater than about 700 bar. The homogenization subjects the fibers to high shear forces such that as the pressurized cellulose pulp exits the nozzle or orifice, cavitation causes microfibrillation of the cellulose fibers in the pulp. Additional water may be added to improve flowability of the suspension through the homogenizer. The resulting aqueous suspension comprising microfibrillated cellulose and optional inorganic particulate material may be fed back into the inlet of the homogenizer for multiple passes through the homogenizer. When present, and when the inorganic particulate material is a naturally platy mineral, such as kaolin, homogenization not only facilitates microfibrillation of the cellulose pulp, but may also facilitate delamination of the platy particulate material.
An exemplary homogenizer is a Manton Gaulin (APV) homogenizer.
After the microfibrillation step has been carried out, the aqueous suspension comprising microfibrillated cellulose and optional inorganic particulate material may be screened to remove fibre above a certain size and to remove any grinding medium. For example, the suspension can be subjected to screening using a sieve having a selected nominal aperture size in order to remove fibers which do not pass through the sieve. Nominal aperture size means the nominal central separation of opposite sides of a square aperture or the nominal diameter of a round aperture. The sieve may be a BSS sieve (in accordance with BS 1796) having a nominal aperture size of 150 μm, for example, a nominal aperture size 125 μm, or 106 μm, or 90 μm, or 74 μm, or 63 μm, or 53 μm, 45 μm, or 38 μm. In one embodiment, the aqueous suspension is screened using a BSS sieve having a nominal aperture of 125 μm. The aqueous suspension may then be optionally dewatered.
It will be understood therefore that amount (i.e., % by weight) of microfibrillated cellulose in the aqueous suspension after grinding or homogenizing may be less than the amount of dry fibre in the pulp if the ground or homogenized suspension is treated to remove fibers above a selected size. Thus, the relative amounts of pulp and optional inorganic particulate material fed to the grinder or homogenizer can be adjusted depending on the amount of microfibrillated cellulose that is required in the aqueous suspension after fibers above a selected size are removed.
In certain embodiments of the aspects of the invention, the microfibrillated cellulose may be prepared by a method comprising a step of microfibrillating the fibrous substrate comprising cellulose in an aqueous environment by grinding in the presence of a grinding medium (as described herein), wherein the grinding is carried out in the absence of inorganic particulate material. In certain embodiments, inorganic particulate material may be added after grinding to produce the top ply slurry, or ply slurry.
Microfibrillation in the Absence of Grindable Inorganic Particulate Material
In another aspect, microfibrillation of cellulose fibres may be performed in a process comprising a step of microfibrillating a fibrous substrate comprising cellulose in an aqueous environment by grinding in the presence of a grinding medium which is to be removed after the completion of grinding, wherein the grinding is performed in a tower mill or a screened grinder, including a stirred media detritor, and wherein the grinding is carried out in the absence of grindable inorganic particulate material. A grindable inorganic particulate material is a material which would be ground in the presence of the grinding medium.
The particulate grinding medium may be of a natural or a synthetic material. The grinding medium may, for example, comprise balls, beads or pellets of any hard mineral, ceramic or metallic material. Such materials may include, for example, alumina, zirconia, zirconium silicate, aluminium silicate or the mullite-rich material which is produced by calcining kaolinitic clay at a temperature in the range of from about 1300° C. to about 1800° C. For example, in some embodiments a Carbolite® grinding media is preferred. Alternatively, particles of natural sand of a suitable particle size may be used.
Generally, the type of and particle size of grinding medium to be selected for use in the invention may be dependent on the properties, such as, e.g., the particle size of, and the chemical composition of, the feed suspension of material to be ground. Preferably, the particulate grinding medium comprises particles having an average diameter in the range of from about 0.5 mm to about 6 mm. In one embodiment, the particles have an average diameter of at least about 3 mm. In yet other embodiments, the average diameter range may be 6 mm to 15 mm.
The grinding medium may comprise particles having a specific gravity of at least about 2.5. The grinding medium may comprise particles have a specific gravity of at least about 3, or least about 4, or least about 5, or at least about 6.
The grinding medium (or media) may be present in an amount up to about 70% by volume of the charge. The grinding media may be present in amount of at least about 10% by volume of the charge, for example, at least about 20% by volume of the charge, or at least about 30% by volume of the charge, or at least about 40% by volume of the charge, or at least about 50% by volume of the charge, or at least about 60% by volume of the charge.
The fibrous substrate comprising cellulose may be microfibrillated in the presence of an inorganic particulate material to obtain microfibrillated cellulose having a d₅₀ranging from about 5 μm to about 500 μm, as measured by laser light scattering. The fibrous substrate comprising cellulose may be microfibrillated in the presence of an inorganic particulate material to obtain microfibrillated cellulose having a d₅₀of equal to or less than about 400 μm, for example equal to or less than about 300 μm, or equal to or less than about 200 μm, or equal to or less than about 150 μm, or equal to or less than about 125 μm, or equal to or less than about 100 μm, or equal to or less than about 90 μm, or equal to or less than about 80 μm, or equal to or less than about 70 μm, or equal to or less than about 60 μm, or equal to or less than about 50 μm, or equal to or less than about 40 μm, or equal to or less than about 30 μm, or equal to or less than about 20 μm, or equal to or less than about 10 μm.
The fibrous substrate comprising cellulose may be microfibrillated to obtain microfibrillated cellulose having a modal fibre particle size ranging from about 0.1-500 μm. The fibrous substrate comprising cellulose may be microfibrillated in the presence to obtain microfibrillated cellulose having a modal fibre particle size of at least about 0.5 μm, for example at least about 10 μm, or at least about 50 μm, or at least about 100 μm, or at least about 150 μm, or at least about 200 μm, or at least about 300 μm, or at least about 400 μm.
The fibrous substrate comprising cellulose may be microfibrillated in the presence of an inorganic particulate material to obtain microfibrillated cellulose having a fibre steepness equal to or greater than about 10, as measured by Malvern. Fibre steepness (i.e., the steepness of the particle size distribution of the fibres) is determined by the following formula:
Steepness=100×(d ₃₀ /d ₇₀)
The microfibrillated cellulose may have a fibre steepness equal to or less than about 100. The microfibrillated cellulose may have a fibre steepness equal to or less than about 75, or equal to or less than about 50, or equal to or less than about 40, or equal to or less than about 30. The microfibrillated cellulose may have a fibre steepness from about 20 to about 50, or from about 25 to about 40, or from about 25 to about 35, or from about 30 to about 40.
The particle size distribution may be calculated from Mie theory and gave the output as a differential volume based distribution.
When minerals a three present, the presence of two distinct peaks may be the group interpreted as arising from the mineral (finer peak) and fibre (coarser peak).
The finer mineral peak can be fitted to the measured data points and subtracted mathematically from the distribution to leave the fibre peak, which can be converted to a cumulative distribution. Similarly, the fibre peak can be subtracted mathematically from the original distribution to leave the mineral peak, which x can also be converted to a cumulative distribution. Both these cumulative curves can then be used to calculate the mean particle size (d₅₀) and the steepness of the distribution (d₃₀/d₇₀×100). The differential curve may be used to find the modal particle size for both the mineral and fibre fractions.
When the process does not include grinding a fibrous substrate comprising cellulose in the presence of inorganic particulate material, the particle size distribution of the microfibrillated cellulose may be calculated from Mie theory and the output as a differential volume based distribution.
In one embodiment, the grinding vessel is a tower mill. In another embodiment, the grinding is performed in a screened grinder, preferably a stirred media detritor. The screened grinder may comprise one or more screen(s) having a nominal aperture size of at least about 250 μm, for example, the one or more screens may have a nominal aperture size of at least about 300 μm, or at least about 350 μm, or at least about 400 μm, or at least about 450 μm, or at least about 500 μm, or at least about 550 μm, or at least about 600 μm, or at least about 650 μm, or at least about 700 μm, or at least about 750 μm, or at least about 800 μm, or at least about 850 μm, or at or least about 900 μm, or at least about 1000 μm or at least 1250 μm or 1500 μm. The screen sizes noted immediately above are applicable to use of a tower mill embodiments as well.
As noted above, the grinding is performed in the presence of a grinding medium. In an embodiment, the grinding medium is a coarse media comprising particles having an average diameter in the range of from about 1 mm to about 6 mm, for example about 2 mm, or about 3 mm, or about 4 mm, or about 5 mm.
In another embodiment, the grinding media has a specific gravity of at least about 2.5, for example, at least about 3, or at least about 3.5, or at least about 4.0, or at least about 4.5, or least about 5.0, or at least about 5.5, or at least about 6.0.
As described above, the grinding medium (or media) may be in an amount up to about 70% by volume of the charge. The grinding media may be present in amount of at least about 10% by volume of the charge, for example, at least about 20% by volume of the charge, or at least about 30% by volume of the charge, or at least about 40% by volume of the charge, or at least about 50% by volume of the charge, or at least about 60% by volume of the charge.
In one embodiment, the grinding medium is present in amount of about 50% by volume of the charge. By ‘charge’ is meant the composition which is the feed fed to the grinder vessel. The charge includes water, grinding media, the fibrous substrate comprising cellulose and any other optional additives (other than as described herein). The use of a relatively coarse and/or dense media has the advantage of improved (i.e., faster) sediment rates and reduced media carry over through the quiescent zone and/or classifier and/or screen(s). A further advantage in using relatively coarse screens is that a relatively coarse or dense grinding media can be used in the microfibrillating step. In addition, the use of relatively coarse screens (i.e., having a nominal aperture of least about 250 μm) allows a relatively high solids product to be processed and removed from the grinder, which allows a relatively high solids feed (comprising fibrous substrate comprising cellulose and inorganic particulate material) to be processed in an economically viable process. As discussed below, it has been found that a feed having a high initial solids content is desirable in terms of energy efficiency. Further, it has also been found that product produced (at a given energy) at lower solids has a coarser particle size distribution.
In accordance with one embodiment, the fibrous substrate comprising cellulose is present in the aqueous environment at an initial solids content of at least about 1 wt. %. The fibrous substrate comprising cellulose may be present in the aqueous environment at an initial solids content of at least about 0.25%, or at least about 0.5%, or at least about 1.5%, or at least about 2 wt. %, or for example at least about 3 wt. %, or at least about at least 4 wt. %. Typically, the initial solids content will be no more than about 10 wt. %.
In another embodiment, the grinding is performed in a cascade of grinding vessels, one or more of which may comprise one or more grinding zones. For example, the fibrous substrate comprising cellulose may be ground in a cascade of two or more grinding vessels, for example, a cascade of three or more grinding vessels, or a cascade of four or more grinding vessels, or a cascade of five or more grinding vessels, or a cascade of six or more grinding vessels, or a cascade of seven or more grinding vessels, or a cascade of eight or more grinding vessels, or a cascade of nine or more grinding vessels in series, or a cascade comprising up to ten grinding vessels. The cascade of grinding vessels may be operatively inked in series or parallel or a combination of series and parallel. The output from and/or the input to one or more of the grinding vessels in the cascade may be subjected to one or more screening steps and/or one or more classification steps.
The total energy expended in a microfibrillation process may be apportioned equally across each of the grinding vessels in the cascade. Alternatively, the energy input may vary between some or all of the grinding vessels in the cascade.
A person skilled in the art will understand that the energy expended per vessel may vary between vessels in the cascade depending on the amount of fibrous substrate being microfibrillated in each vessel, and optionally the speed of grind in each vessel, the duration of grind in each vessel and the type of grinding media in each vessel. The grinding conditions may be varied in each vessel in the cascade in order to control the particle size distribution of the microfibrillated cellulose.
In an embodiment the grinding is performed in a closed circuit. In another embodiment, the grinding is performed in an open circuit.
As the suspension of material to be ground may be of a relatively high viscosity, a suitable dispersing agent may preferably be added to the suspension prior to grinding. The dispersing agent may be, for example, a water soluble condensed phosphate, polysilicic add or a salt thereof, or a polyelectrolyte, for example a water soluble salt of a poly(acrylic add) or of a poly(methacrylic add) having a number average molecular weight not greater than 80,000. The amount of the dispersing agent used would generally be in the range of from 0.1 to 2.0% by weight, based on the weight of the dry inorganic particulate solid material. The suspension may suitably be ground at a temperature in the range of from 4° C. to 100° C.
Other additives which may be included during the microfibrillation step include: carboxymethyl cellulose, amphoteric carboxymethyl cellulose, oxidising agents, 2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO), TEMPO derivatives, and wood degrading enzymes.
The pH of the suspension of material to be ground may be about 7 or greater than about 7 (i.e., basic), for example, the pH of the suspension may be about 8, or about 9, or about 10, or about 11. The pH of the suspension of material to be ground may be less than about 7 (i.e., acidic), for example, the pH of the suspension may be about 6, or about 5, or about 4, or about 3. The pH of the suspension of material to be ground may be adjusted by addition of an appropriate amount of acid or base. Suitable bases included alkali metal hydroxides, such as, for example NaOH. Other suitable bases are sodium carbonate and ammonia. Suitable acids included inorganic acids, such as hydrochloric and sulphuric acid, or organic acids. An exemplary acid is orthophosphoric acid.
The total energy input in a typical grinding process to obtain the desired aqueous suspension composition may typically be between about 100 and 1500 kWht⁻¹based on the total dry weight of the inorganic particulate filler. The total energy input may be less than about 1000 kWht⁻¹, for example, less than about 800 kWht⁻¹, less than about 600 kWht⁻¹, less than about 500 kWht⁻¹, less than about 400 kWht⁻¹, less than about 300 kWht⁻¹, or less than about 200 kWht⁻¹.
A cellulose pulp can be microfibrillated at relatively low energy input when it is co-ground in the presence of an inorganic particulate material. The total energy input per tonne of dry fibre in the fibrous substrate comprising cellulose will be less than about 10,000 kWht⁻¹, for example, less than about 9000 kWht⁻¹, or less than about 8000 kWht⁻¹, or less than about 7000 kWht⁻¹, or less than about 6000 kWht⁻¹, or less than about 5000 kWht⁻¹, for example less than about 4000 kWht⁻¹, less than about 3000 kWht⁻¹, less than about 2000 kWht⁻¹, less than about 1500 kWht⁻¹, less than about 1200 kWht⁻¹, less than about 1000 kWht⁻¹, or less than about 800 kWht⁻¹. The total energy input varies depending on the amount of dry fibre in the fibrous substrate being microfibrillated, and optionally the speed of grind and the duration of grind.

Wet Molding Process for 3D Formable Objects Comprising Pulp and Coarsely Fibrillated Microfibrillated Cellulose

There are multiple methods of wet pulp molding known in the art. They generally begin with a porous mold. In the simplest process (often called thick wall molding), the mold is withdrawn from the pulp and coarsely fibrillated microfibrillated cellulose suspension, optionally comprising one or more inorganic particulate material, when a sufficient amount of solids has been deposited, and then ejected from the mold (usually with compressed air) onto a conveyor belt, which then transports the molded pulp and coarsely fibrillated microfibrillated cellulose (and optional inorganic particulate material), into an oven for drying.
In transfer molding, after the object is withdrawn from the mold it is then transferred to a second, inverse shaped mold (which isn't porous but will have some vents in it to apply vacuum or compressed air). The second mold transports the object to the conveyor and then ejects it onto the conveyor for transport into a drying oven.
A third production method is thermoforming. In thermoforming, the object is heated and dried whilst held between the second mold and a third mold (of the same shape as the first, porous, mold but largely solid with vents for escaping steam). Thus in thermoforming there is no conveyor or oven.
Thus, wet molded pulp products are conventionally manufactured by a process employing two principal steps. These steps comprise forming a pulp mixture into a desired shape (commonly by applying a vacuum) and then drying the pulp to remove water.
While the 3-D article is forming, water is typically removed by vacuum until a total solids content of the formed product is in the range of 40% to 55%. The remaining water is then removed in the drying step. Thus, the 3-D molded article typically contains 4% to 8% water following the drying steps, which roughly corresponds to the moisture content of paper under humidity conditions generally applicable for the storage of the paper product.
Tool design for a 3-D molded article is determined by its intended geometry and surface characteristics, for example a smooth surface may be present on either the inner or outer surface. Thus, the mold is designed to produce the intended geometry of the 3-D product and produce the desired finish of the inner and outer surfaces of the 3-D molded pulp article. In a preferred embodiment of a manufacturing set-up for a 3-D molded pulp article comprising coarsely fibrillated microfibrillated cellulose (and optionally inorganic particulate material), the process comprises providing a porous mold having a three-dimensional shape comprising a forming portion having an inside and an outside portion; bringing the forming portion into contact with the aqueous pulp and coarsely fibrillated microfibrillated cellulose suspension and optionally inorganic particulate material); applying a vacuum to the inside portion of the forming section to form a wet layer of cellulose fibres and coarsely fibrillated microfibrillated cellulose on the outside portion of the forming section, thereby forming a three-dimensional molded object.
The aqueous pulp and coarsely fibrillated microfibrillated cellulose suspension comprises coarsely fibrillated microfibrillated cellulose in an amount of about 0.5 wt % to about 50 wt. %.
The total solids content of the aqueous composition comprising pulp and coarsely fibrillated microfibrillated cellulose would typically be in the range of about 0.05 wt. % to about 10 wt. % in the case of wet molded pulp articles.
The layer of pulp present on said forming molds in a thermoforming process may be press dried with a pressure between 0.2-50 bar, preferably 0.5-15 bar, more preferably 1-10 bar. 3-D molded pulp articles may be produced in the range of 100 to 2,000 grams/square metre (“gsm”).
Drying of the pulp present on the forming molds may be achieved by the means of applying elevated temperatures, which typically would be in the range of about 100-350° C., preferably 120-250° C., more preferably between 150-220° C.

Dry Molding Process for 3-D Formable Objects Comprising Pulp and Coarsely Fibrillated Microfibrillated Cellulose

An alternative manufacturing process for producing a 3-D formable molded pulp object is a dry forming process utilizing a cellulose blank. In the present invention the cellulose blank is formed from pulp and coarsely fibrillated microfibrillated cellulose (and optionally inorganic particulate material) and the cellulose blank is transported to a forming mold where it is heated to a forming temperature of about 100° C. to 200° C., where it is pressed with a forming pressure of at least 1 MPa ad a range of from 1 MPa to about 100 MPa depending upon the article to be formed.
A cellulose blank comprising cellulose fibres is made by a process in which cellulose fibres (and optionally inorganic particulate material) are air-laid or air-formed to form the cellulose blank. When forming the cellulose blank in the air-laid or air-formed process, the cellulose fibres are carried and formed to the blank structure by air as carrying medium.
Aqueous binders can be applied to the air-formed blank. This would include applying a coarsely fibrillated MFC suspension in such a manner. The coarsely fibrillated MFC suspension can be applied to the blank in a manner such as an additive, for example, latex or AKD. Thus, the coarsely fibrillated microfibrillated cellulose suspension, as well as AKD and latex suspensions, can be sprayed onto the surfaces of the air-formed blank before it is pressed. The sprayed suspension thus forms coating layers on the object after molding. A coarsely fibrillated MFC suspension could alternatively be sprayed onto the fibres before they are air-laid into the blank. This would help to bond the fibres together, thereby increasing the strength and decreasing the porosity of the pressed object.
This is unlike the wet molding process described above which resembles a paper-making process where water is used as carrying medium for the cellulose fibres when forming the paper structure.
In the air-laid or air-formed process, water and/or other additives, including a suspension of coarsely fibrillated cellulose may be added, for example by spraying the other additives, including coarsely fibrillated MFC to the cellulose-containing pulp fibres in order to change the properties of the cellulose blank, but air is still used as carrying medium in the forming process.
The advantage of the dry forming process is that the 3-D moldable pulp and coarsely fibrillated microfibrillated cellulose (and optionally inorganic particulate material), when heated and pressed results in 3-D objects having good material properties. A higher forming temperature results in an increase in fibril aggregation, water resistance, Young's modulus and the mechanical properties of the final cellulose product. The high pressure increases fibril aggregation thereby imparting improved mechanical properties to the 3-D formed article from cellulose-containing pulp fibres and coarsely fibrillated microfibrillated cellulose. The 2-D cellulose blanks of the process are formed into 3-D shaped articles by the forming process.
In an embodiment of the dry forming process a sizing agent is applied to the cellulose fibres of the pulp and fibrils of the coarsely fibrillated microfibrillated cellulose (and optionally inorganic particulate material) to increase the hydrophobic properties and/or mechanical strength of the cellulose blank. Different types of sizing agents may be used in order to increase the hydrophobic properties and/or mechanical strength of the cellulose product produced from the cellulose blank, which may depend on the type of product produced. As an example, the sizing agents may be fluorochemicals, alkyl ketene dimer (AKD), alkenyl succinic anhydride (ASA), rosin (acidic sizing), wax, lignin and water glass (sodium silicate). The sizing agent or other substances are applied to the cellulose fibres by an application unit, such as a spray nozzle or a similar device.
In an embodiment, the cellulose blank is formed as a continuous cellulose web in the dry forming unit. The continuous cellulose web may then be used in a continuous manufacturing process, where the continuous cellulose web is dry formed from cellulose fibres in the dry forming unit and then transported to the forming mold. In another embodiment, the cellulose web can be intermittently fed to the forming mold.
Three-dimensional objects formed by the dry molding process described above may be hollow bowls, cups and bottles of uniform wall thickness. In various embodiments the 3-D object is not hollow and may have different thicknesses and shapes.
The dry forming process may use cellulose blanks in the form of a rolled web or a stacked sheet. The cellulose fibres and coarsely fibrillated microfibrillated cellulose (and optionally inorganic particulate material) may be compacted or calendared in a compacting unit having calendar rolls, which may be heated in other embodiments of the process.
An alternative method of producing a cellulose blank comprising coarsely fibrillated microfibrillated cellulose (and optionally inorganic particulate material), is to produce a non-woven material, such as described in WO 2017182877, which is incorporated by reference in its entirety. In such method, fibres comprising coarsely fibrillated cellulose (and optionally inorganic particulate material) are prepared by grinding a fibrous substrate comprising cellulose in a grinding vessel in the presence of an inorganic particulate material, wherein the grinding is carried out in an aqueous environment in the presence or in the absence of a grinding medium; wherein the term “grinding medium” means a medium other than the inorganic particulate material and wherein the grinding medium is 0.5 mm or greater in size; and then extruding the microfibrillated cellulose (and optionally inorganic particulate material) through an extruder; attenuating the extruded microfibrillated cellulose (and optionally inorganic particulate material) with an attenuating gas; and (4) collecting the extruded fibres onto a foraminous surface to form a non-woven web. The foraminous surface is a moving screen or wire. The non-woven web is then bonded by hydroentanglement, or through air thermal bonding or the non-woven web is bonded mechanically.

EXAMPLES

Flat sheets of blends of MFC or MFC and inorganic particulate material composite and Kraft pulp were made in a simple vacuum-assisted handsheet former. After formation of the wet sheet, a blotter was applied and the sheet was transferred to a Rapid Kothen drier, and pressed and heated until dry. After conditioning at 23° C. and 50% RH, sheets were tested for grammage, caliper, tensile stiffness and Bendtsen porosity (air permeability). Tensile stiffness was calculated from the gradient of the force/extension curve divided by the width of the specimen, and tensile stiffness index by dividing the tensile stiffness by the grammage. The grammage required to meet an arbitrary target of 1000 N/m tensile stiffness was calculated from the tensile stiffness index for each sample. It is assumed that 3-dimensional walled objects made with equal tensile stiffness will have equal rigidity, and thus an increase in tensile stiffness index will allow a reduction in weight for the objects whilst maintaining rigidity. Bendtsen porosity at this grammage was estimated assuming Darcy's law, which states that the fluid flux for a fixed pressure drop through a material of constant permeability is inversely proportional to its thickness. Therefore the Bendtsen porosity (air flow rate per unit cross sectional area of sample) was estimated by multiplying the measured Bendtsen porosity value in ml/min by the ratio of the measured grammage to the required grammage. Oil resistance was measured using the Kit test (TAPPI T559), which consists of a series of 16 numbered solutions made from mixtures of castor oil, toluene and n-heptane, where solution 1 is pure castor oil and solution 16 is pure heptane. A drop of each solution is placed on the sheet, and after 15 seconds is wiped off. If a stain is observed, the test is considered a failure. The Kit rating of a sample represents the highest solution number which passes the test; if even solution 1 leaves a stain then the Kit rating is zero.
MFC was made by grinding bleached softwood Kraft pulp in a stirred media mill as described in the specification above. Where present, the inorganic particulate material utilized was Intracarb 60 available from Imerys Minerals Limited (Cornwall, UK).

Example 1: Flat Sheets of MFC/Softwood Pulp

Sheets were made using the procedures described above using different combinations of unrefined softwood Kraft pulp and MFC. As the content of MFC increases, there was a substantial increase in the tensile stiffness index of the sheets. From the measured values for each sheet, the grammage required to reach a target tensile stiffness of 1000 N/m was calculated, indicating that the weight of a tray could be reduced by almost 50% using just 17% of MFC. Furthermore, the porosity of such a tray would be reduced by nearly two orders of magnitude. At 50% MFC, weight is reduced by almost ⅔, and the sheet has the highest oil resistance measurable with the standard test. Table 1 shows the properties of the sheets produced.

TABLE 1

Properties of dry sheets made with blends of unrefined, bleached softwood Kraft pulp and MFC % MFC

					Tensile	Tensile			GSM for	Porosity
				Young's	stiffness	strength	Tensile	Porosity/	1000	@ 1000
%		Caliper/	Kit	modulus/	index/	Index/	stiffness/	ml	N/m	N/m
MFC	GSM	microns	rating	GPa	kN m g−1	N m g−1	N m−1	min−1	stiffness	stiffness

0	250	475	0	1.15	2.19	10.38	548	5429	457	2973
0	350	651	0	1.25	2.32	11.54	814	3768	430	3066
10	371	587	0	2.04	3.23	25.68	1197	289	310	346
17	190	291	0	2.83	4.34	37.46	823	72	231	59
17	225	328	0	2.88	4.21	35.03	945	66	238	62
17	283	406	0	2.90	4.17	36.43	1179	55	240	64
25	182	256	4	3.52	4.94	43.85	900	19	203	17
25	240	318	4	3.47	4.60	45.46	1103	15	217	17
50	282	293	16	5.95	6.19	61.51	1745	1	162	2
50	395	383	16	6.08	5.89	66.06	2327	1	170	2
75	256	219	16	8.80	7.52	86.93	1926	0	133	0
75	360	293	16	8.51	6.94	86.33	2497	0	144	0
100	122	109	16	10.02	8.95	83.17	1092	0	112	0
100	247	198	16	10.68	8.56	100.30	2115	0	117	0
100	371	286	16	11.68	9.00	98.90	3340	0	111	0

Example 2. Wet Tensile Properties of Flat Sheets

Measurements were also made of the tensile properties of the sheets after pressing but before drying. After forming, the sheets were couched and then pressed in a sheet press according to TAPPI T205. Solids content was controlled by the number of blotters used in the press (1 or 4), with targets of approximately 30% and 40% solids for the two different options. Wet sheets were weighed and then carefully cut into strips and mounted in a tensiometer for measurement of tensile strength and elongation. For each sheet, the solids content and grammage were determined from the wet and dry weights of the sheet offcuts.
Despite the higher moisture content after pressing of the sheets containing MFC, tensile breaking elongation and strength increase very substantially with MFC content. This increased ductility leads to much improved performance during thermoforming, allowing lighter objects or deeper shapes to be pressed easily without damage. Table 2 and Table 3 show the tensile properties of the wet sheets under the two respective pressing conditions.

TABLE 2

Wet tensile properties of sheets pressed with single blotter.

MFC	Solids	Av. breaking	Av. breaking	Av. tensile strength
content/%	content/%	energy/kJ	elongation/%	Index/N m g−1

0	38.3	14.1	5.64	0.36
25	31.8	62.9	8.19	1.23
30	31.9	76.7	8.91	1.44
35	32.1	93.4	9.52	1.67
40	32.2	104.0	9.28	1.91
45	32.2	125.2	9.31	2.36
50	32.0	133.5	8.06	2.84

TABLE 3

Wet tensile properties of sheets pressed with 4 blotters.

0	45.9	14.2	5.8	0.4
25	43.0	214.9	10.7	3.2
30	42.5	270.5	11.8	3.8
35	40.4	297.3	12.9	3.8
40	39.8	341.9	13.3	4.3
45	38.8	395.7	14.2	4.6
50	39.1	473.8	14.6	5.4
60	36.9	491.1	15.7	5.6

Example 3: Molded Trays of MFC/Softwood Pulp

Molded trays were made on a pilot molding machine at Bangor Biocomposites Centre. Similar mixtures of softwood Kraft pulp and MFC were used to the flat sheets. After forming, the trays were cut up and the properties of the tray walls evaluated in the same way as for the flat sheets. Note that the pressing and drying conditions are very different for the molded trays, but the conclusion are similar; tray weight for a given stiffness can be almost halved with the use of MFC, which would result in a reduction in porosity of several orders of magnitude. All trays were well formed without defects, despite a more than 50% reduction in tray weight at 25% MFC. Table 4.
Table shows the properties of strips cut from the trays.

TABLE 4

Properties of strips cut from trays made with bleached Kraft pulp and MFC

								GSM for	Porosity
				Tensile	Tensile			1000	@ 1000
%				stiffness	strength	Tensile		N/m	N/m
MFC	GSM	Cal	YM	index	Index	stiffness	Porosity	stiffness	stiffness

0	482	613	2.07	2.63	21.17	1267	2755	381	3490
10	376	469	2.77	3.45	37.17	1297	161	290	209
17	188	263	3.46	4.84	50.83	910	12	206	11
17	232	288	3.82	4.74	52.75	1101	11	211	12
17	284	348	4.11	5.04	53.05	1432	15	198	21
25	174	236	3.96	5.37	56.36	934	4	186	4
25	207	286	3.55	4.91	50.62	1016	12	204	12

Example 4: Flat Sheets of Co-Ground MFC/CaCO₃and Pulp

Sheets were made using the procedure described above using different combinations of unrefined softwood Kraft pulp and a composite of 50/50 MFC/CaCO3.
With equal addition of calcium carbonate as MFC, the tensile properties still increase, and the porosity is reduced. Weight reduction for a target object stiffness remains possible, and the introduction of mineral filler decreases the raw material cost of the products. Table 5 shows the sheet properties.

TABLE 5

Properties of sheets made with bleached Kraft pulp and a 50/50 MFC/CaCO₃blend

					Tensile	Tensile			GSM for	Porosity
				Young's	stiffness	strength	Tensile	Porosity/	1000	@ 1000
%	%		Caliper/	modulus/	index/	Index/	stiffness/	ml	N/m	N/m
MFC	CaCO₃	GSM	microns	GPa	kN m g−1	N m g−1	N m−1	min−1	stiffness	stiffness

0	0	250	475	1.15	2.19	10.38	548	5429	457	2973
0	0	350	651	1.25	2.32	11.54	814	3768	430	3066
8.5	8.5	434	683	1.80	2.83	20.93	1230	361	353	444
8.5	8.5	355	576	1.87	3.02	20.70	1074	390	331	419
8.5	8.5	316	496	1.87	2.94	20.72	930	395	340	367
8.5	8.5	265	431	2.01	3.28	21.41	868	509	305	441
12.5	12.5	291	446	2.22	3.40	24.21	989	216	294	213
12.5	12.5	332	496	2.24	3.35	24.83	1111	209	299	232
12.5	12.5	343	520	2.16	3.28	25.13	1124	194	305	218
16.5	16.5	174	262	2.65	4.00	27.16	694	113	250	78
16.5	16.5	250	361	2.56	3.71	28.93	926	88	270	81

Example 5: Molded Trays of Co-Ground MFC/CaCO₃and Pulp

Molded trays were made as described in Example 3, this time using mixtures of unrefined bleached softwood Kraft pulp and a co-ground composite of 50/50 MFC/CaCO₃. Again, trays all formed without defects and were cut into strips for testing after drying. Table 6 shows properties of strips cut from the trays.

TABLE 6

Properties of strips cut from trays made with bleached Kraft pulp and a 50/50 MFC/CaCO₃blend

0	0	551	692	2.69	3.38	27.56	1864	3473	296	6475
0	0	482	613	2.07	2.63	21.17	1267	2755	381	3490
8.5	8.5	468	595	2.41	3.06	30.16	1432	574	327	821
8.5	8.5	299	402	1.97	2.65	32.82	793	484	377	384
12.5	12.5	308	361	3.30	3.87	38.39	1192	48	258	58
12.5	12.5	344	475	1.87	2.59	31.17	890	71	387	63
16.5	16.5	194	276	2.63	3.74	34.76	725	31	268	23
16.5	16.5	260	368	2.07	2.93	30.37	763	37	341	28

Example 6. Flat Sheets of Microfibrillated Cellulose with Different Pulp Types

Microfibrillated cellulose products were made by grinding different pulp types in the manner described in the present specification to achieve varying MFC characteristics and blended with unrefined softwood Kraft pulp as in the above examples.
MFC A was made from a Northern Softwood bleached Kraft pulp (Botnia RMA, Metsa), which is a mixture of approximately 50% pine and 50% spruce. MFC B was made from a Northern hardwood (birch) bleached Kraft pulp (Sodra Gold), and MFC C was made from a bleached Acacia Kraft pulp.
Each product was analyzed using a Valmet Fiber Analyzer as described in the present specification and Examples, giving the results shown in Table 7a.

TABLE 7

(a) Analysis of MFC products with Valmet Fiber Analyzer

				Fiber	Fines	Fines
MFC pulp	Lc(n)	Lc(l)	Lc(w)	width	A	B	Fines	Fibrillation
source	[mm]	[mm]	[mm]	[μm]	[%]	[%]	[%]	[%]

MFC A	0.151	0.23	0.348	19.47	71.63	32.73	89.65	5.32
MFC B	0.121	0.204	0.428	16.53	87.3	66.37	95.12	7.77
MFC C	0.129	0.204	0.363	18.75	81.38	18.49	94.17	3.71

				Fiber	Fines	Fines
MFC	Lc(n)ISO	Lc(l)ISO	Lc(w)ISO	width	A	B	Fines	Fibrillation
Sample	[mm]	[mm]	[mm]	[μm]	[%]	[%]	[%]	[%]

MFC A	0.312	0.356	0.429	19.47	71.63	32.73	89.65	5.32
MFC B	0.329	0.418	0.606	16.53	87.3	66.37	95.12	7.77
MFC C	0.312	0.383	0.503	18.75	81.38	18.49	94.17	3.71

TABLE 7

(b) Malvern particle size and fibre steepness data

Malvern	Malvern	Malvern	Malvern	Malvern	<25	25-150	150-300	>300
d₃₀	d₅₀	d₇₀	d₉₀	steepness	μm	μm	μm	μm

MFC A	84	167	300	599	28	9	37	24	30
MFC B	67	123	190	304	35	13	45	31	10
MFC C	45	87	152	293	29	17	53	21	9

Fines A is a measure of the fine fibres and fragments that are not well fibrillated, and Fines B is a measure of highly fibrillated fragments. Fines A are low aspect ratio fibers and fragments less than 200 μm in length. Fines B are fibrillated fragments greater than 200 μm in length, but less than 10 μm and width. The MFC made from Northern Softwood has longer fibres and an elevated level of Fines B, whilst keeping fibrillation high and the overall level of fines low. This is beneficial because it limits the effect of the MFC on sheet drainage. In contrast, the MFC made from birch in this case is highly fibrillated, yielding a product with high strength potential but which is significantly more detrimental to drainage rate.
Sheets were made from blends of unrefined softwood Kraft and the MFC products shown in Table 7. In addition, the drainage rate of the blends was measured, and the permeability of the wet sheets made from calculated accordingly using Darcy's Law, in order to be able to predict the drainage time for different sheet grammages. The results are reported in Table 8.

TABLE 8

Properties of sheets made from blends of unrefined softwood
pulp and MFC products made from different sources

			tensile	GSM for		drain		Normalised
			stiffness	1000		time for	Porosity/	porosity
MFC/	grammage/	caliper/	index/	N/m	permeability/	target	ml	at target
%	gsm	μm	kN m g−1	stiffness	m Darcy	GSM	min−1	gsm

MFC B

	5	218	360	3.05	328	212	2.12	976	649
	10	237	357	3.21	311	28.5	12	173	132
	20	246	338	3.5	286	8.53	41.4	14.1	12.2
	30	237	279	3.79	264	5.9	56.7	2.53	2.28
	40	208	211	5.32	188	2.03	79.1	0.233	0.259
	50	204	201	7.21	139	1.41	68.7	0.1	0.147
MFC C	5	218	394	2.71	368	288	1.93	2750	1630
	10	211	356	2.89	346	150	2.9	1020	621
	20	212	325	3.56	281	25.9	9.17	126	95.3
	30	208	291	3.93	254	12.9	17.1	22.6	18.5
	40	203	252	4.51	222	4.95	35.5	3	2.74
	50	208	230	4.73	211	3.09	60.4	1	0.986
MFC A	10	371	587	3.23	310	174	2.06	289	346
	17	225	328	4.2	238	69.7	2.38	66	62.3
	25	240	318	4.62	216	21.2	7.18	15	16.6
	50	282	293	6.18	162	2	47.5	1	1.74

Table 8 shows the properties of the sheets made. Note that those made from Northern softwood are selected from Table 1 to be within the 200-250 gsm range or as close as possible. Of note is that the coarser MFC from the Northern softwood develops tensile stiffness index more rapidly at low MFC levels than either of the other products, even though the highest stiffness is achieved with the finer MFC made from birch. The coarser MFC also drains more quickly, and therefore provides a better combination of properties than the finer version. This is illustrated in FIG. 2 , which shows the calculated grammage required for 100 N/m tensile stiffness for each blend, plotted against the calculated drainage time for that grammage and blend. For blends of up to 50% MFC, the coarser material achieves any given grammage reduction at lower MFC content and significantly lower drainage time.

Example 7; Particle Size Distribution as Measured by Malvern Insitec L Light Scattering Device

Ensure that the MFC slurry is homogeneous by shaking the container contents vigorously. If grinding media is present in the sample use an 850 micron screen to remove the grinding media before running the Malvern analysis. If no grinding medium is present pipette the slurry from the sample. Switch the Malver Insitec unit on and start the pump by pressing.
The pump speed on/off button on top of the Malvern unit and set the speed at 2500 rpm and that and that the ultrasonic is off. Ensure that the Malvern Insitec is clean by flushing the unit 2-3 times with clean, room temperature water±5° C. Raise the stirrer to the marked drain position and remove the outlet hose and syphon the solution from the system ensuring that the inlet hose is lifted to drain any trapped solution. Replace water with clean room temperature tap water±5° C. (800 ml to 900 ml). Fully push down the Malvern stirrer and the pump will start automatically. If the water is very turbulent turn the pump off and on again to help settle the water. Lift the outlet hose to remove any trapped air.

Example 8

Molded fibre trays were formed on a Nature Former KPT Lab Unit 3.1 machine. The furnish consisted of 70:30 hardwood (Birch) to softwood (pine/spruce unbleached Kraft), Eucalyptus based FiberLean MFC at varying doses and 1% sizing agent (AKD).
The mould was dipped into the tank containing the furnish and the draining time adjusted depending on the final article weight desired. The chamber vacuum was used at −0.5 bars. The samples were pressed (cold) for 10 seconds with 9500 N and then dried using a hot press at 11,000 N and 240° C. Drying time was adjusted for each trial point since the basis weights varied. The articles were dried until dry/warm to the touch. The pulp was unrefined with a Schopper Riegler of 18.
The trays were conditioned in the paper test lab at 23° C. and 50% RH and then weighed. Trays were then selected from each trial point and cut up to perform testing on. The base of the object was tested for Tear, Porosity, Scott Bond and Tensile. The trays were cut using a scalpel and guillotine.

TABLE 9

Tear Index results for molded objects of
different basis weight and MFC content

Tear Index/mN · m²· g⁻¹

Object	0%	5%	10%	20%	50%
GSM	MFC	MFC	MFC	MFC	MFC

14-18	8.0	9.2	10.2	12.0	14.9
24-27	9.3	11.5	13.5	14.9	16.7
30-34	13.1	12.5	14.6	15.3	15.6

TABLE 10

Bendsten Porosity results for molded objects
of different basis weight and MFC content.

Bendsten Porosity/ml · min⁻¹

Object	0%	5%	10%	20%	50%
GSM	MFC	MFC	MFC	MFC	MFC

14-18	3099	2025	2312	865	535
24-27	940	857	675	376	328
30-34	757	690	491	316	282

TABLE 11

Scott Bond results for molded objects of
different basis weight and MFC content

Scott Bond/J · m⁻²

Object	0%	5%	10%	20%	50%
GSM	MFC	MFC	MFC	MFC	MFC

14-18	122	176	184	283	304
24-27	166	193	215	313	310
30-34	164	180	203	280	329

TABLE 12

Tensile Index results for molded objects
of different basis weight and MFC content

Tensile Index/Nm · g⁻¹

Object	0%	5%	10%	20%	50%
GSM	MFC	MFC	MFC	MFC	MFC

14-18	18	13	13	23	34
24-27	15	17	21	24	22
30-34	13	18	20	22	21

TABLE 13

Malvern Insitec data for the Eucalyptus based MFC added to molded objects

MFC					Fibre	<25	25-150	150-300	>300
Sample	d30	d50	d70	d90	Steepness	μm	μm	μm	μm

Euca based	74	144	274	553	27	9	43	21	27
MFC

TABLE 14

Valmet Fibre Image Analyzer data for the Eucalyptus based MFC added to molded objects

MFC	Lc(n)ISO	Lc(l)ISO	Lc(w)ISO	Fiberwidth	FinesA	FinesB	Fines	Fibrillation
Sample	[mm]	[mm]	[mm]	[μm]	[%]	[%]	[%]	[%]

Euca based	0.486	0.589	0.689	19.93	47.39	12.1	81.68	4.05
MFC

Example 10

A number of attempts were made to form molded fibre objects with MFC content>50% but all failed as the MFC/pulp furnish would not retain on the forming mould. It was therefore not possible to test any molded fibre objects with >50% MFC content.
The foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the present invention. Also, the description of the embodiments of the present invention is intended to be illustrative and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art.
It is to be understood that while the invention has been described in conjunction with the detailed description thereof, the foregoing description is intended to illustrate and not limit the scope of the invention, which is defined by the scope of the appended claims. Other aspects, advantages, and modifications are within the scope of the following claims.
The various embodiments described in this specification can be combined to provide further embodiments. Aspects of the embodiments can be modified, if necessary to employ concepts of the various patents, applications, and publications to provide yet further embodiments.
The disclosures of each patent, patent application, publication, and accession number cited herein are hereby incorporated herein by reference in their entirety.
While the present disclosure has been disclosed with reference to various embodiments, it is apparent that other embodiments and variations of these may be devised by others skilled in the art without departing from the true spirit and scope of the disclosure. The appended claims are intended to be construed to include all such embodiments and equivalent variations. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.
The foregoing written specification is sufficient to enable one skilled in the art to practice the embodiments. The foregoing description and Examples detail certain embodiments and describes the best mode contemplated by the inventors. It will be appreciated, however, that no matter how detailed the foregoing may appear in text, the embodiment may be practiced in many ways and should be construed in accordance with the appended claims and any equivalents thereof.
References discussed in the application are incorporated by reference in their entirety, for their intended purpose, which is clear based upon their context.

Claims

What is claimed is:

1. A three-dimensional molded object comprising a mixture of cellulose fibers and coarsely fibrillated microfibrillated cellulose, and optionally one or more inorganic particulate material, wherein the coarsely fibrillated microfibrillated cellulose is present in an amount of about 0.5 wt. % to about 50 wt. % on a dry weight basis of the total dry mass of the mixture of cellulose fibres and coarsely fibrillated microfibrillated cellulose, and optionally one or more inorganic particulate material; wherein the coarsely microfibrillated cellulose comprises less than about 90 wt. % fines and/or less than 75% fines A, and a length-weighted median length Lc(w) of greater than 0.3 mm, as measured by Valmet Fibre Image Analyzer, and wherein the coarsely fibrillated microfibrillated cellulose optionally has a fibre steepness of about 20 to about 50, as measured by Malvern Mastersizer.

2. The molded object according to claim 1, wherein the coarsely fibrillated microfibrillated cellulose has a fibre steepness of about 20 to about 50.

3. The molded object according to claim 1, wherein the coarsely fibrillated microfibrillated cellulose is present in an amount of about 0.5 wt. % to about 25 wt. %.

4. The molded object according to claim 1, wherein the coarsely fibrillated microfibrillated cellulose is present in an amount of about 0.5 wt. % to about 15 wt. %.

5. The molded object according to claim 1, wherein the coarsely fibrillated microfibrillated cellulose is present in an amount of about 0.5 wt. % to about 10 wt. %.

6. The molded object according to claim 1, wherein the coarsely fibrillated microfibrillated cellulose is present in an amount of about 0.5 wt. % to about 5 wt. %.

7. The molded object according to claim 1, wherein, the coarsely fibrillated microfibrillated cellulose is obtained from a pulp selected from the group consisting of a chemical pulp, a chemithermomechanical pulp, a mechanical pulp, a thermomechanical pulp, a recycled pulp, a paper broke pulp, a papermill waste stream, waste from a papermill, and combinations thereof.

8. The molded object according to claim 1, wherein, the coarsely fibrillated microfibrillated cellulose is obtained from a recycled pulp, a paper broke pulp, a papermill waste stream, waste from a papermill, and combinations thereof.

9. The molded object according to claim 1, wherein, the cellulose fibres are obtained from a recycled pulp, a paper broke pulp, a papermill waste stream, waste from a papermill, and combinations thereof.

10. The molded object according to claim 1, wherein, the cellulose fibres are obtained from a pulp selected from the group consisting of a chemical pulp, a chemithermomechanical pulp, a mechanical pulp, a thermomechanical pulp, a recycled pulp, a paper broke pulp, a papermill waste stream, waste from a papermill, and combinations thereof.

11. The molded object according to claim 1, wherein both the cellulose fibres and microfibrillated cellulose are obtained from a recycled pulp, a paper broke pulp, a papermill waste stream, waste from a papermill, and combinations thereof.

12. The molded object according to claim 1, wherein the molded object comprises one or more inorganic particulate material.

13. The molded object according to claim 1, wherein the one or more inorganic particulate material is calcium carbonate or kaolin, or mixtures thereof.

14. The molded object according to claim 1, wherein the one or more inorganic particulate material comprises a platy mineral, kaolin and/or talc.

15. The molded object according to claim 13, wherein the calcium carbonate is ground calcium carbonate, precipitated calcium carbonate, or mixtures thereof.

16. The molded object according to claim 15, wherein the calcium carbonate is precipitated calcium carbonate.

17. The molded article according to claim 15, where in the calcium carbonate is ground calcium carbonate.

18. The molded object according to claim 17, wherein the ground calcium carbonate is marble, chalk, limestone and mixtures thereof.

19. The molded object according to claim 12, wherein the inorganic particulate material is ground calcium carbonate and precipitated calcium carbonate.

20. The molded object according to claim 12, wherein the inorganic particulate material is selected from the group consisting of an alkaline earth metal carbonate or sulphate, a bentonite, a hydrous kandite clay, a halloysite, a ball clay, an anhydrous (calcined) kandite clay, a metakaolin, a fully calcined kaolin, a talc, a mica, a perlite, a sepiolite, a huntite, a diatomite, a magnesite, a silicate, a diatomaceous earth, a brucite, an aluminum trihydrate, and combinations thereof.

21. A method for producing a three-dimensional molded object comprising cellulose fibers and coarsely fibrillated microfibrillated cellulose, comprising the steps of:

providing a mixture comprising cellulose fibres and coarsely fibrillated microfibrillated cellulose, and optionally one or more inorganic particulate material, wherein the mixture comprises microfibrillated cellulose in an amount of about 0.5 wt. % to about 50 wt. % on a dry weight basis of the total dry mass of the mixture of cellulose fibres and coarsely fibrillated microfibrillated cellulose, and optionally one or more inorganic particulate material; wherein the coarsely microfibrillated cellulose comprises less than about 90 wt. % fines and/or less than 75% fines A, and a length-weighted median length Lc(w) of greater than 0.3 mm, as measured by Valmet Fibre Image Analyzer, and wherein the coarsely fibrillated microfibrillated cellulose optionally has a fibre steepness of about 20 to about 50, as measured by Malvern Mastersizer;

forming a three-dimensional molded object from the mixture; and

drying the three-dimensional molded object.

22. The method according to claim 21, wherein the coarsely fibrillated microfibrillated cellulose has a fibre steepness of about 20 to about 50.

23. The method according to claim 21, wherein the forming step is a wet forming step.

24. The method according to claim 21, wherein the forming step is a dry forming step.

25. The method according to claim 21, further comprising the steps of:

providing a porous mold having a three-dimensional shape comprising a forming portion having an inside and an outside portion;

bringing the forming portion into contact with the mixture comprising cellulose fibres and coarsely fibrillated microfibrillated cellulose, and optionally one or more inorganic particulate material;

applying a vacuum to the inside portion of the forming section to form a wet layer of cellulose fibres and coarsely fibrillated microfibrillated cellulose, and optionally one or more inorganic particulate material, on the outside portion of the forming section, thereby forming a three dimensional molded object, wherein the wet layer of cellulose fibres and coarsely fibrillated microfibrillated cellulose and optionally one or more inorganic particulate material is between about 100 to 5,000 gsm in dry weight on a dry weight basis of the total dry mass of the mixture of cellulose fibres and coarsely fibrillated microfibrillated cellulose, and optionally one or more inorganic particulate material;

transferring the molded object to a drying conveyor and drying the three-dimensional molded object; optionally transferring the three-dimensional molded object to a second inverse shaped mold and pressing the three-dimensional molded prior to oven drying.

26. The method according to claim 21, wherein the cellulose fibres are obtained from virgin pulp, recycled paper or old corrugated cardboard, or a combination thereof.

27. The method according to claim 21, wherein the cellulose fibres are obtained from virgin pulp.

28. The method according to claim 21, wherein the cellulose fibres are obtained from recycled pulp.

29. The method according to claim 28, wherein the recycled pulp is obtained from old, corrugated cardboard.

30. The method according to claim 21, wherein the coarsely fibrillated microfibrillated cellulose is present in an amount of about 0.5 wt. % to about 25 wt. %.

31. The method according to claim 21, wherein the coarsely fibrillated microfibrillated cellulose is present in an amount of about 0.5 wt. % to about 15 wt. %.

32. The method according to claim 21, wherein the coarsely fibrillated microfibrillated cellulose is present in an amount of about 0.5 wt. % to about 10 wt. %.

33. The method according to claim 21, wherein the coarsely fibrillated microfibrillated cellulose is present in an amount of about 0.5 wt. % to about 5 wt. %.

34. The method according to claim 21, wherein, the coarsely fibrillated microfibrillated cellulose is obtained from a pulp selected from the group consisting of a chemical pulp, a chemithermomechanical pulp, a mechanical pulp, a thermomechanical pulp, a recycled pulp, a paper broke pulp, a papermill waste stream, waste from a papermill, and combinations thereof.

35. The method according to claim 21, wherein, the coarsely fibrillated microfibrillated cellulose is obtained from a pulp selected from the group consisting of a recycled pulp, a paper broke pulp, a papermill waste stream, waste from a papermill, and combinations thereof.

36. The method according to claim 21, wherein, the cellulose fibres are obtained from a recycled pulp, a paper broke pulp, a papermill waste stream, waste from a papermill, and combinations thereof.

37. The method according to claim 21, wherein, the cellulose fibres are obtained from a pulp selected from the group consisting of a chemical pulp, a chemithermomechanical pulp, a mechanical pulp, a thermomechanical pulp, a recycled pulp, a paper broke pulp, a papermill waste stream, waste from a papermill, and combinations thereof.

38. The method according to claim 21, wherein both the cellulose fibres and coarsely fibrillated microfibrillated cellulose are obtained from a recycled pulp, a paper broke pulp, a papermill waste stream, waste from a papermill, and combinations thereof.

39. The method according to claim 21, wherein the molded object comprises one or more inorganic particulate material.

40. The method according to claim 39, wherein the one or more inorganic particulate material is calcium carbonate or kaolin, or mixtures thereof.

41. The method according to claim 39, wherein the one or more inorganic particulate material comprises a platy mineral, kaolin and/or talc.

42. The method according to claim 40, wherein the calcium carbonate is ground calcium carbonate, precipitated calcium carbonate, or mixtures thereof.

43. The method according to claim 40, wherein the calcium carbonate is precipitated calcium carbonate.

44. The method according to claim 40, wherein the calcium carbonate is ground calcium carbonate.

45. The method according to claim 44, wherein the ground calcium carbonate is marble, chalk, limestone, and mixtures thereof.

46. The method according to claim 39, wherein the inorganic particulate material is ground calcium carbonate and precipitated calcium carbonate.

47. The method according to claim 39, wherein the inorganic particulate material is selected from the group consisting of an alkaline earth metal carbonate or sulphate, a bentonite, a hydrous kandite clay, a kaolin, a halloysite, a ball clay, an anhydrous calcined kandite clay, a metakaolin, a fully calcined kaolin, a talc, a mica, a perlite, a sepiolite, a huntite, a diatomite, a magnesite, a silicate, a diatomaceous earth, a brucite, an aluminum trihydrate, and combinations thereof.

48. A three-dimensional packaging container, blister pack, egg carton, bottle, container or food tray comprising the three-dimensional article according to claim 1.

49. A three-dimensional packaging container, blister pack, egg carton, bottle, container or food tray obtained by a process according to claim 21.

50. (canceled)