Alternative Fibers and Micro-Fibrillated Cellulose Coated Packaging Papers, and Films and Substrates

This application claims benefit of and priority to U.S. Provisional Patent Application Ser. No. 63/364,613, filed May 12, 2022, the disclosure of which is incorporated herein by reference in its entirety.

The presently disclosed subject matter relates to non-wood biopolymer fibers, e.g., agro-based micro-fibrillated cellulose (A-MFC), and their use in packaging materials, e.g., for food and/or beverage packaging. The non-wood biopolymer fibers can include fibers derived from non-wood wood lignocellulosic feedstocks, including agricultural residues and industrial lignocellulosic waste, and/or which have a high level of primary and/or secondary fines and that have been micro-fibrillated and optionally chemically modified. The fibers can be incorporated into films or coating or composite layers for packaging materials with enhanced tensile strength and stretch, while also having a barrier to oil, grease, water, water vapor, air, and oxygen.

Food packaging plays a significant role in daily life and in the current economy. Food packaging can help to promote a food's value, to reduce food waste, and to reduce food spoilage by preserving food quality during storage, transport, and delivery, as well as through other useful features (Gutta et al., 2013).

According to a recent study, the global packaging market is set to reach over $1 trillion by 2021 (Smithers, 2018). However, growth in the packaging market has also raised concerns about environmental sustainability. Every year, large amounts of packaging materials are used with the intention of “use and throw,” and a large portion of these materials are also made of non-biodegradable and non-renewable materials, such as plastics, glass, and metals. Plastic polymers used in food packaging can have adverse effects on both human health and the environment. These single and short use plastic polymers can be thrown away as solid waste, which can end up in landfills and can ultimately end up in the soil and ocean waterways (MacArthur et al., 2016)(Jambeck et al., 2015).

Consumer demand for sustainability and recent changes in government policies and regulations, such as the initiatives to ban or reduce the use of plastics, especially single-use plastics, has led businesses to consider alternative solutions. Further, the increasing preference from consumers for convenience, small package sizes, and for minimally processed, fresh, and healthy foods has resulted in a desire for highly functional and sustainable food packaging (Tyagi et al., 2022). Thus, there is an interest in sustainable and/or biodegradable packaging in a number of markets, including in the food and beverage industry, to overcome the challenges of functionality, environmental stewardship, and cost, while maintaining an acceptable biodegradation profile.

Accordingly, there is an ongoing need for new sustainable food packaging materials and methods of preparing food packaging materials from sustainable source materials, including biomass materials that are currently considered to be low-value byproducts and/or waste.

The presently disclosed subject matter now will be described more fully hereinafter, in which some, but not all embodiments of the presently disclosed subject matter are described. Indeed, the presently disclosed subject matter can be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements.

In some embodiments, the presently disclosed subject matter provides a packaging material comprising a film or a coating layer comprising agro-based microfibrillated cellulose (A-MFC), wherein said A-MFC comprises a microfibrillated cellulose (MFC) prepared from a pulp from a non-wood lignocellulosic feedstock, wherein the film or coating layer has a weight gain of less than about 5 percent (%) and/or less than about 2.5 grams per square meter (g/m), when contacted with hot oil for 20 minutes, wherein said hot oil has a temperature of about 65 degrees Celsius (° C.).

In some embodiments, the non-wood lignocellulosic feedstock comprises one or more agricultural residue and/or industrial by-product. In some embodiments, the non-wood lignocellulosic feedstock is selected from the group comprising hemp hurds, a mixture of hemp hurds and hemp bast, bagasse, cocoa pod husks, and combinations thereof.

In some embodiments, the A-MFC comprises modified A-MFC, wherein the modified A-MFC comprises MFC derived from a chemically modified pulp. In some embodiments, the modified A-MFC comprises carboxymethylated A-MFC; oxidized A-MFC; carboxymethylated and oxidized MFC; or a combination thereof. In some embodiments, the oxidized A-MFC comprises dialdehyde cellulose.

In some embodiments, the film or coating layer comprises about 5 weight percent (wt %) to about 90 wt % A-MFC, optionally wherein the film or coating layer comprises about 40 wt % A-MFC to about 80 wt % A-MFC. In some embodiments, the film or coating layer further comprises one or more of chitosan, cationic starch, glycerol, triethyl citrate, a polyhydroxyalkanoate (PHA), and alkyl ketene dimer (AKD).

In some embodiments, the A-MFC has a total fines level of about 50% to about 95%. In some embodiments, the A-MFC has an average fiber length of about 0.1 mm to about 0.45 mm.

In some embodiments, the film or coating layer has a thickness of about 1 micrometer to about 200 micrometers, optionally wherein the film or coating layer is a coating layer with a thickness of about 1 micrometer to about 30 micrometers or a film with a thickness of about 10 micrometers to about 200 micrometers, further optionally wherein the film has a thickness of about 20 micrometers to about 140 micrometers. In some embodiments, the film or coating layer has a bulk of about 0.5 cubic centimeters per gram (cm/g) to about 2.0 cm/g.

In some embodiments, the film or coating layer has a weight gain of less than about 2% and/or less than about 1.19 g/m, when contacted with hot oil for 20 minutes, wherein said hot oil has a temperature of about 65 degrees C. In some embodiments, the film or coating layer has a weight gain of less than about 3% and/or less than about 1.8 g/mwhen contacted with room temperature oil for 15 hours.

In some embodiments, the film or coating layer has a water vapor transmission rate (WVTR) of less than 50 grams per square meter millimeter per day (g/m·mm/day), optionally less than 15 g/m·mm/day. In some embodiments, the film or coating layer has a density of about 0.3 grams per cubic centimeter (g/cm) to about 2.1 g/cm. In some embodiments, the film or coating layer has a tensile index of about 30 Newton meter per gram (Nm/g) or more. In some embodiments, the film or coating layer has a stretch of about 1.5% or higher.

In some embodiments, the packaging material is a food or beverage packaging material. In some embodiments, the packaging material further comprises a substrate, wherein said substrate is coated on at least one surface by the film or coating layer comprising A-MFC, optionally wherein the substrate is a flexible substrate. In some embodiments, the substrate comprises paper or another biodegradable and/or sustainable material, optionally wherein the paper comprises or consists of papermaking fibers derived from a waste biomass.

In some embodiments, the presently disclosed subject matter provides a method for preparing a film that has a weight gain of less than about 5 percent (%) and/or less than about 2.5 grams per square meter (g/m), when contacted with hot oil for 20 minutes, wherein said hot oil has a temperature of about 65 degrees Celsius (° C.), the method comprising: (a) preparing a suspension comprising agro-based microfibrillated cellulose (A-MFC), wherein said A-MFC is microfibrillated cellulose (MFC) prepared from a pulp from a non-wood lignocellulosic feedstock; (b) forming a web using from the suspension; and (c) drying the web, thereby providing the film. In some embodiments, the non-wood lignocellulosic feedstock comprises one or more agricultural residue and/or industrial by-product, optionally wherein the non-wood lignocellulosic feedstock comprises hemp hurds, a mixture of hemp hurds and hemp bast, cocoa pod husks, or a combination thereof.

In some embodiments, preparing the suspension comprising A-MFC comprises fibrillating a suspension of pulp from a non-wood lignocellulosic feedstock, wherein said pulp has a primary fines level of more than 10%, optionally wherein the pulp has a primary fines level of about 15% to about 50%. In some embodiments, the pulp is a kraft pulped pulp, an autohydrolyzed pulp, an unbleached pulp, higher yield pulp, or higher lignin containing pulp. In some embodiments, the method further comprises chemically modifying the pulp in an aqueous medium prior to fibrillation. In some embodiments, chemically modifying the pulp comprises carboxymethylating the pulp, oxidizing the pulp, or carboxymethylating and oxidizing the pulp. In some embodiments, the method comprises carboxymethylating the pulp prior to or after fibrillation.

In some embodiments, preparing the suspension comprising A-MFC comprises contacting the A-MFC with a liquid, optionally water, to provide a suspension comprising a total solids content comprising at least about 50 weight percent (wt %) of the A-MFC, optionally to provide a suspension comprising a total solids content comprising about 50 wt % to about 80 wt % A-MFC. In some embodiments, the suspension has a solids content of about 2.0% or higher and/or about 5% or lower. In some embodiments, the suspension comprising A-MFC further comprises one or more of chitosan, cationic starch, glycerol, triethyl citrate, a polyhydroxyalkanoate (PHA), and alkyl ketene dimer (AKD). In some embodiments, preparing the suspension comprises mixing the suspension at a temperature between about room temperature and about 80 degrees Celsius (° C.) for a period of time, optionally for about 30 minutes.

In some embodiments, step (b) comprises casting a web from the suspension. In some embodiments, the method further comprises applying the film to a surface of a substrate, optionally a paper substrate, to provide a film coated substrate. In some embodiments, the method further comprises forming a packaging material from the film or from a film coated substrate.

Accordingly, it is an object of the presently disclosed subject matter to provide packaging materials comprising A-MFC prepared from an agro-based pulp and methods of making the materials. This and other objects are achieved in whole or in part by the presently disclosed subject matter.

An object of the presently disclosed subject matter having been stated above, other objects and advantages of the presently disclosed subject matter will become apparent to those of ordinary skill in the art after a study of the following description of the presently disclosed subject matter and non-limiting Figures.

The presently disclosed subject matter will now be described more fully hereinafter with reference to the accompanying Examples and Figures, in which representative embodiments are shown. The presently disclosed subject matter can, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the embodiments to those skilled in the art.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this presently described subject matter belongs. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety.

Throughout the specification and claims, a given chemical formula or name shall encompass all optical and stereoisomers, as well as racemic mixtures where such isomers and mixtures exist.

While the following terms are believed to be well understood by one of ordinary skill in the art, the following definitions are set forth to facilitate explanation of the presently claimed subject matter.

Following long-standing patent law convention, the terms “a”, “an”, and “the” refer to “one or more” when used herein, including in the claims.

As used herein, the term “about”, when referring to a value or an amount, for example, relative to another measure, is meant to encompass variations of in some embodiments ±20%, in some embodiments ±10%, in some embodiments ±5%, in some embodiments ±1%, and in some embodiments ±0.1% from the specified value or amount, as such variations are appropriate. The term “about” can be applied to all values set forth herein.

As used herein, the term “and/or” when used in the context of a listing of entities, refers to the entities being present singly or in combination. Thus, for example, the phrase “A, B, C, and/or D” includes A, B, C, and D individually, but also includes any and all combinations and sub-combinations of A, B, C, and D.

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

As used herein, the phrase “consisting of” excludes any element, step, or ingredient not specified in the claim. When the phrase “consists of” appears in a clause of the body of a claim, rather than immediately following the preamble, it limits only the element set forth in that clause; other elements are not excluded from the claim as a whole.

As used herein, the phrase “consisting essentially of” limits the scope of a claim to the specified materials or steps, plus those that do not materially affect the basic and novel characteristic(s) of the claimed subject matter.

With respect to the terms “comprising”, “consisting of”, and “consisting essentially of”, where one of these three terms is used herein, the presently disclosed and claimed subject matter can include the use of either of the other two terms.

As used herein, “significance” or “significant” relates to a statistical analysis of the probability that there is a non-random association between two or more entities. To determine whether or not a relationship is “significant” or has “significance”, statistical manipulations of the data can be performed to calculate a probability, expressed in some embodiments as a “p-value”. Those p-values that fall below a user-defined cutoff point are regarded as significant. In some embodiments, a p-value less than or equal to 0.05, in some embodiments less than 0.01, in some embodiments less than 0.005, and in some embodiments less than 0.001, are regarded as significant.

As used herein, ranges can be expressed as from “about” one particular value, and/or to “about” another particular value. It is also understood that there are a number of values disclosed herein, and that each value is also herein disclosed as “about” that particular value in addition to the value itself. For example, if the value “10” is disclosed, then “about 10” is also disclosed. It is also understood that each unit between two particular units are also disclosed. For example, if 10 and 15 are disclosed, then 11, 12, 13, and 14 are also disclosed.

“Paper,” as used herein, refers to a material constructed of dewatered, pressed and dried together cellulosic and/or lignocellulosic fibers in an aqueous medium, primarily water. For example, a paper can comprise a web of cellulosic and/or lignocellulosic fibers having a top side and a bottom side. In some embodiments, the paper is a planar sheet. In some embodiments, the sheet can have a thin (e.g., less than about 5 mm) edge. Alternatively, the paper can be molded to any desirable shape. In some embodiments, the paper can be bendable. In some embodiments, the paper can be unmalleable such that it retains its shape and structure during ordinary usage as a packaging material, such as a food packaging product.

The term “papermaking fibers” as used herein refers to cellulosic and/or lignocellulosic fibers and to fiber mixes comprising cellulosic and/or lignocellulosic fibers. Papermaking fibers include nonwood fibers, such as, but not limited to, cotton, abaca, bamboo, banana, kenaf, grass, flax, straw, jute, hemp, bagasse, milkweed floss, cocoa pod husk and pineapple leaf fibers, and their derivatives and wood fibers such as those obtained from deciduous and coniferous trees, including softwood fibers, such as pines, fir, spruce, cedar, larch, or the like, hardwood fibers, such as eucalyptus, maple, birch, aspen, oak, or the like. In some embodiments, the papermaking fibers are fibers from an agricultural and/or industrial waste biomass, such as hemp hurds, mixes containing hemp hurds and hemp bast fibers, and cocoa pod husks. Papermaking fibers can be liberated from their source material by chemical and/or mechanical pulping processes known in the art, such as, but not limited to, the kraft (sulfate) and sulfite chemical pulping processes, where most of the lignin and hemicellulose components are removed, solvent pulping (ethanol-water, organic acids, SO-ethanol-water, etc.), semi-chemical pulping, enzymatic pulping, chemi-thermomechanical pulping (CTMP), thermomechanical pulping (TMP), hydrothermal pulping, autohydrolysis or hydrothermal pulping, other alkaline (e.g., soda or carbonate) pulping, or any combination of chemical and/or mechanical treatments. Bleaching chemicals such as hydrogen peroxide, oxygen, sodium hydroxide, enzymes, chlorine dioxide, hypochlorite, ozone, peracids, and/or other bleaching agents can be used to whiten the “cellulosic material.” The suitable bleaching techniques can include elemental chlorine free (ECF) or total chlorine free (TCF) bleaching.

The terms “pulping” and “defibration” refer to the process of liberating discrete fibers from a cellulosic or lignocellulosic feedstock.

“Furnishes” and like terminology refers to aqueous compositions including lignocellulosic fibers and optionally additives, such as those typically used in papermaking, including dry strength additives, wet strength resins, and the like. The term “slurry” as used herein refers to an aqueous dispersion of lignocellulosic fibers. In some embodiments, the terms “furnish” and “slurry” can be used interchangeably.

The term “biomass” as used herein refers to a renewable organic material from plants. The term “waste biomass” as used herein refers to biomass materials that are typically underutilized or not utilized and/or considered of low value. Typically, “waste biomass” is a byproduct from an agricultural or industrial process that involves harvesting or otherwise processing a parent biomass material. Thus, for example, waste biomass (or in some embodiments “agro-based”) refer to agricultural residues and byproducts of the processing of other plants.

The term “hemp hurds” as used herein refers to the inner core of the stem of the hemp plant (), comprising relatively short xylem fibers and stem pith. Hemp hurds can be separated from the stem by a process referred to as “retting” or via a decortication process. The term “hemp mix” as used herein refers to a mixture of hemp hurds and material from the outer ring of the hemp stem, which can include longer phloem (or “bast”) fibers.

The term “fines” as used herein refers to the fraction of lignocellulosic particles in a pulp or mixture of lignocellulosic fibers that are able to pass through a 200 mesh screen or a perforated plate with a hole diameter of 76 micrometers (m). The term “primary fines” refers to the fines generated by pulping or by pulping and bleaching a lignocellulosic feed stock. “Total fines” refers to the total amount of primary and “secondary fines”, where “secondary fines” are fines generated by other pulp treatments, e.g., refining and/or chemical modification.

As used herein, the terms “microfibrillated cellulose” or “MFC” refer to cellulosic fibers obtained by fibrillating a cellulose-based pulp. MFC fibers have a high aspect ratio, with average fiber widths in the nanometer range (e.g., between about 5 nm to about 500 nm) and fiber lengths in the micrometer to millimeter range (e.g., between about 0.1 μm to about 1 mm or more). Carboxymethylated microfibrillated cellulose refers to a MFC obtained by fibrillating a carboxymethylated cellulose-based raw material (e.g., pulp). In some embodiments, as described hereinbelow, fibrillation is carried out by mechanical treatment.

Paper is distinct from typical substrates, such as plastics, metals and glass, since cellulose, which is the main component of paper, is relatively reactive under various chemical and thermal processing conditions. It readily absorbs fluids, such as water, grease, and oil. Furthermore, passage of moisture and gaseous materials through paper can be provided by the many air voids and micropores within the fibers. Traditionally, papermakers have relied on extensive refining and surface sizing agents, such as starch, to produce a more closed paper sheet. However, extensive refining can be difficult, particularly with furnishes composed of agro-fibers (i.e., fibers from agricultural feedstocks) due to their high levels of cellulosic fines and the impact of extensive refining on drainage during forming. Even after these treatments, some micropores can remain to provide undesirable fluid and gas flow. According to one aspect of the presently disclosed subject matter, a new generation of flexible food packaging from agro-based fibers is described. In some embodiments, the packaging comprises functional additives and/or chemically modified cellulosic fibers to impart or improve mechanical and/or barrier characteristics.

Cellulose is the most abundant natural polymer on earth. The sustainable development of cellulosic fibers from non-wood biomass has great potential to replace single-use synthetic plastics in packaging and other industrial applications. The valorization of plant-based fibers potentially offers a global platform for developing ecofriendly food packaging and hygiene products. These types of bio-based products are recyclable and can play a significant role in the circular economy. Among the various packaging applications, food packaging holds an important aspect of our daily lives and current economy. As described hereinabove, packaging helps to promote food value, for example, by reducing food waste and chemical contamination by preserving food quality during storage, transport, and delivery, as well as by providing other useful features (Edyta et al., 2015)(Gutta et al., 2013). However, the formability of cellulosic papers is very limited due to its higher degree of deformation and lack of thermoplasticity compared to synthetic polymers, limiting its application (Fengel, 1992). Therefore, to date, extensive utilization of paper-based materials has not been possible in high-quality industrial forming processes and has been limited to simple geometries.

In some embodiments, the presently disclosed subject matter relates to chemical modifications of cellulosic fibers to enhance their usability, e.g., in the preparation of microfibrillated cellulose (MFC) for paper coating, packaging films, and composites development. More particularly, cellulose has three hydroxyl groups on each anhydroglucose unit (AGU) which can be chemically modified in various ways as shown in the Scheme 1, below. The presence of these chemically reactive hydroxyl groups can provide for tailoring of cellulosic fiber functionality through modifications including acid hydrolysis, grafting, and substitution reactions. Among the various chemical modifications, acid hydrolysis can be used to cleave amorphous regions of cellulose fibers in order to synthesize cellulose nanocrystals (CNC) (Ranby et al., 1949)(Elazzouzi-Hafraoui et al., 2008). Other modifications include etherification which can be carried out in alkali-swollen conditions to obtain block-copolymer substituted products, with regioselective homogenous substitution possible in some solvents (Landoll, 1982)(Heinze & Liebert, 2001). The hydroxyl groups of cellulose can be replaced by carboxylates either selectively or non-selectively depending on the types of reagents selected and the type of hydroxyl group involved (i.e., primary or secondary). Introduction of carboxyl groups can lead to further chemical modifications, such as hydrophobizing, crosslinking, and grafting, to bring additional properties into the fibers. Exemplary chemical modifications of fibers include, but are not limited to, carboxymethylation, periodate-oxidation, and (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO)-mediated oxidations.

Carboxymethyl cellulose (CMC) is one of the most used cellulose ethers because of its hypoallergenic and non-toxic nature. It has high viscosity and high surface charge availability which enhances its water absorbency, thickening properties, and film forming abilities. CMC has wide application in ice creams, toothpaste, detergents, fat free products, textiles, etc. CMC can be prepared both homogenously and heterogeneously by changing solvent systems. A homogenous solvent system, for example water, can be used to generate a more sustainable CMC with a low degree of substitution (DS), while a heterogeneous solvent system, such as a 2-propanol-water mixture or a benzene-ethanol-water mixture, or homogenous organic solvents, for example butanol, have been mostly used to prepare CMC with higher DS (Zhao et al., 2003)(Moussa et al., 2019). For softwood fibers, a DS of 1.24 has been achieved with the order of preferred substitution as O6≥O2>O3 and a DS of 2.83 has been achieved by using butanol as a solvent for extensive and longtime treatment of the fig stem cellulosic fibers (Heinze & Pfeiffer, 1999)(Moussa et al., 2019).

CMC can be prepared by reacting cellulose with a carboxymethylating agent, such as chloroacetic acid (i.e., monochloroacetic acid (MCA)). See Scheme 2, below. The preparation of CMC generally involves an alkaline reaction environment to activate cellulose hydroxyl groups and sodium hydroxide (NaOH), or other lye, has typically been used for this purpose. The degree of carboxymethylation and substitution patterns (O2≥O6) can be governed by NaOH concentration and increased with an increased amount of NaOH to a certain extent (Heinze & Pfeiffer, 1999). The DS of carboxymethylation can also be increased by increasing the concentration of chloroacetic acid at a set NaOH concentration. For instance, a maximum DS can be reached at a molar ratio of cellulose: MCA=1:2.05 (Khullar et al., 2005). Reaction conditions of 55° C. and 3 to 4 hours gave maximum DS at a certain chemical concentration regardless of the cellulose sources and solvent systems (Khullar et al., 2005)(Heinze & Pfeiffer, 1999)(Heinze & Koschella, 2005)(Pushpamalar et al., 2006).