Method and composition for enhancing paints, adhesives, and coatings using charged cellulosic fibrils or other charged cellulosic fibers derived from the nitro-oxidation process as stabilizers, thickeners, and adhesion promoters

Abstract

A coating formulation and an adhesive formulation includes charged cellulosic fibrils, wherein the charged cellulosic fibrils include carboxyl functional groups. The coating formulation can include pigments to define a paint formulation. The charged cellulosic fibrils can include nitro-oxidation-process-derived charged cellulosic fibrils. The charged cellulosic fibrils include nanocellulose (NC), cellulose nanocrystals (CNC), cellulose nanofibrils (CNF), cellulose microfibrils (CMF), or lignin-containing cellulose nanofibers (LCNFs). The charged cellulose fibrils can define a three-dimensional network that breaks down when a shear force is applied. The carboxylate functional groups can interact electrostatically and chemically with a surface of a substrate when applied to the substrate.

Description

Attorney Docket No. 201291.6. PCTMETHOD AND COMPOSITION FOR ENHANCING PAINTS, ADHESIVES, AND COATINGS USING CHARGED CELLULOSIC FIBRILS OR OTHER CHARGED CELLULOSIC FIBERS DERIVED FROM THE NITRO-OXIDATION PROCESS AS STABILIZERS, THICKENERS, AND ADHESION PROMOTERSCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Patent Application No. 63 / 695,486 filed on September 17, 2024. The entire contents of each application are hereby incorporated by reference.BACKGROUND OF THE INVENTION1. Field of the Invention

[0002] The present invention relates to industrial and non-industrial formulations, specifically to the use of various charged cellulosic fibrils, including nanocellulose (NC), cellulose nanocrystals (CNC), cellulose nanofibrils (CNF), cellulose microfibrils (CMF), lignin-containing cellulose nanofibers (LCNFs), derived from a Nitro-Oxidation Process (NOP) or any other suitable process— as stabilizers, thickeners, and adhesion promoters in paints, adhesives, and coatings in both aqueous and non-aqueous media.2. Description of the Related Art

[0003] In both industrial and non-industrial applications, paints, adhesives, and coatings are used to protect surfaces, providing aesthetic appeal, and ensuring product durability.Conventional formulations often rely on synthetic stabilizers, thickeners, and adhesion promoters that may be toxic, non-biodegradable, and environmentally harmful. There is a growing demand for sustainable alternatives that maintain or enhance the performance of these products while reducing their environmental impact.SUMMARY OF THE INVENTION

[0004] To overcome the problems described above, example embodiments of the present invention improve the performance and sustainability of paints, adhesives, and coatings by utilizing various charged cellulosic fibrils or other charged cellulosic fibers as key functional additives, not only enhancing the quality and durability of these products, but also addressingcritical environmental concerns by reducing the reliance on synthetic, non-biodegradable additives.

[0005] Example embodiments of the present invention provide methods and compositions that enhance the performance of paints, adhesives, and coatings by incorporating various types of charged cellulosic fibrils, including NC, CNC, CNF, CMF, LCNF, or other charged cellulosic fibers derived from an NOP or other suitable process, as stabilizers, thickeners, and adhesion promoters. When added to these formulations, these fibrils improve viscosity control, stability, and adhesion to various substrates while also contributing to the environmental sustainability of the final product.

[0006] An example embodiment uses charged cellulosic fibrils with carboxyl (-COOH) functional groups introduced via an NOP or other suitable process to enhance electrostatic interactions between the charged cellulosic fibrils and other components within the formulation, as well as the substrate to which they are applied.

[0007] Charged cellulosic fibrils, including those derived from NC, CNC, CNF, CMF, LCNF, or other charged cellulosic fibers derived from an NOP or other suitable process, possess unique properties such as high surface area, charge density, and the ability to form entangled networks. These properties make these fibrils highly effective in enhancing the rheological properties, stability, and adhesive characteristics of paints, adhesives, and coatings, providing a biodegradable and non-toxic alternative to conventional additives.

[0008] Enhanced formulation to provide stabilization, thickening, and adhesion promotion typically includes the addition of charged cellulose fibrils (e.g., 0.1 wt%-10 wt%).

[0009] As stabilizers, the charged groups and high surface area of charged cellulose fibrils create a robust, three-dimensional network that prevents solid components like pigments and fillers from settling. In such a network, electrostatic repulsion between the similarly charged cellulosic fibrils and filler particles, in combination with the physical hindrance of the network, keeps the particles well-dispersed. This results in excellent "in-can" stability and a longer shelf life.

[0010] As thickeners and rheology modifiers, charged cellulose fibrils provide high viscosity at rest, while offering strong shear-thinning behavior, which is essential for application andhandling. At rest, the fibrous network traps water, resulting in high viscosity. When a shear force is applied (e.g., during brushing or spraying), the network breaks down, and the viscosity decreases, which allows for easy application. Once the shear is removed, the network quickly re-forms, and the viscosity recovers, preventing sagging or dripping.

[0011] As adhesion promoters, the charge on the fibrils facilitates strong interactions with other components or substrates. A negatively charged cellulosic fibril additive can electrostatically attract and bridge positively charged surfaces (e.g., metal substrates) or other particles, acting as an adhesion promoter or retention aid, which can improve the bond strength of adhesives. Additionally, charged cellulosic fibrils can also form hydrogen bonds and electrostatic bonds at the interface between the coating / adhesive and the substrate, increasing the overall strength and durability of the bond.

[0012] NOP-produced nanocellulose (NC), cellulose nanocrystals (CNC), cellulose nanofibrils (CNF), cellulose microfibrils (CMF), and lignin-containing cellulose nanofibers (LCNFs) can be derived from a biomass source from the diverse wood and non-wood group including hard and soft woods, jute, palm trees, sugarcane bagasse, corn, wheat, oats, rice, sorghum, oil palm, bamboo, spinifex, coastal bermudagrass, miscanthus, switchgrass, azolla, seaweeds, flax, hemp, ramie, kenaf stalk fiber, kenaf core, abaca, sisal, pineapple, banana leaf, banana peel, banana fiber, curaua, lotus leaf stalk, roselle, seed hair fiber, cotton fiber, kapok fiber, areca nut fiber, coconut, potato, cabbage, tomato, rubberwood, Indian screw tree, achira fiber, citrus, soybean, soybean straw, spent grain, soy hull, pea hull, grape pomace, fruit pomace, or a combination thereof. The typical degree of oxidation in NOP-produced charged cellulosic fibrils is typically above 1.0 mmol / g by the potentiometric titrator method as demonstrated in Yasmeen S Abdel Aziz, Alan Liu, Shengyu Yu, Benjamin S Hsiao, "Nitro-oxidation process for sustainable production of carboxylated lignin-containing cellulose nanofibers from sugarcane bagasse" Carbohydrate Polymers, 368 (2), 124109 (2025).

[0013] According to an example embodiment of the present invention, a coating formulation includes charged cellulosic fibrils, wherein the charged cellulosic fibrils include carboxyl functional groups.

[0014] The charged cellulosic fibrils can include nitro-oxidation-process-derived charged cellulosic fibrils. The charged cellulosic fibrils can include nanocellulose (NC), cellulose nanocrystals (CNC), cellulose nanofibrils (CNF), cellulose microfibrils (CMF), or lignin-containing cellulose nanofibers (LCNFs). The charged cellulosic fibrils can have a carboxylate (COO-) content greater than about 1.0 mmol / g. The charged cellulosic fibrils can have a cross-sectional dimension between about 2 nm and about 100 nm. The charged cellulosic fibrils can be included in a range of about 0.1 wt%-about 10 wt%. The charged cellulose fibrils can define a three-dimensional network that breaks down when a shear force is applied.

[0015] When a coating including the coating formulation is applied to a substrate, the carboxyl functional groups can interact electrostatically and chemically with a surface of the substrate.

[0016] The coating formulation can further include a pigment to define a paint formulation. The paint formulation can include acrylic paint and an aqueous cha rged-cel I u losic-fi bri I suspension, wherein a weight ratio of the acrylic paint to the aqueous CNF suspension is in a range between about 1:20 to about 1:1.

[0017] According to an example embodiment of the present invention, an adhesive formulation includes charged cellulosic fibrils, wherein the charged cellulosic fibrils include carboxyl functional groups.

[0018] The charged cellulosic fibrils can include nitro-oxidation-process-derived charged cellulosic fibrils. The charged cellulosic fibrils can include nanocellulose (NC), cellulose nanocrystals (CNC), cellulose nanofibrils (CNF), cellulose microfibrils (CMF), or lignin-containing cellulose nanofibers (LCNFs). The charged cellulosic fibrils can have a carboxylate (COO-) content greater than about 1.0 mmol / g. The charged cellulosic fibrils can have a cross-sectional dimension between about 2 nm and about 100 nm. The charged cellulosic fibrils can be included in a range of about 0.1 wt%-about 10 wt%. The charged cellulose fibrils define a three- dimensional network.

[0019] When the adhesive is applied between substrates, the carboxyl functional groups can interact electrostatically and chemically with surfaces of the substrates.

[0020] The above and other features, elements, characteristics, steps, and advantages of the present invention will become more apparent from the following detailed description of example embodiments of the present invention with reference to the attached drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Fig. 1 shows the viscosity of the carboxylated LCNF aqueous suspensions prepared at different reaction times.

[0022] Fig. 2 shows the viscosity of different paints formulations mixed with different concentrations of CNF suspensions.DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS1. Production of Charged Cellulosic Fibrils

[0023] Charged cellulosic fibrils, including NC, CNC, CNF, CMF, LCNF, or other charged cellulosic fibers, can derived from an NOP or other suitable process. In an NOP, cellulose feedstock can be oxidized with nitric acid under controlled conditions, introducing carboxyl (-COOH) groups onto the fibrils. These functional groups enhance the negative charge density of the fibrils, improving their dispersibility in aqueous and solvent-based formulations, as well as their interaction with other components in the formulation. Charged cellulosic fibrils can be produced using any of the NOPs disclosed in U.S. Patent No. 10,894,838 or in PCT Application No. PCT / US2024 / 055838 and PCT Application No. PCT / US2015 / 060261. The entire contents of U.S. Patent No. 10,894,838, PCT Application No. PCT / US2024 / 055838, and PCT Application No. PCT / US2015 / 060261 are hereby incorporated by reference. Alternatively, the charged cellulosic fibrils can be made by any other suitable process. Example embodiments of the present invention are applicable across multiple industries, including automotive, construction, consumer goods, and packaging, where enhanced performance and environmental sustainability are key considerations.

[0024] The charged cellulosic fibrils can have a range of dimensions. For example, NC and CNC typically exhibit lengths from about 100 nm to about several micrometers and diameters of about 5 nm-about 20 nm, within manufacturing and / or measurement tolerances, while CNF and CMF can be longer, with diameters in the range of about 2 nm-about 100 nm, withinmanufacturing and / or measurement tolerances, depending on the specific production parameters. For example, the charged cellulosic fibrils can have a cross-sectional dimension between about 2 nm and about 100 nm, within manufacturing and / or measurement tolerances.

[0025] Charged cellulosic fibrils can include carboxyl (-COOH) functional groups introduced via an NOP or other suitable process to enhance electrostatic interactions between the charged cellulosic fibrils and other components within the formulation, as well as the substrate to which they are applied. The charged cellulosic fibrils can have a carboxylate (COO-) content greater than about 1.0 mmol / g, within manufacturing and / or measurement tolerances.

[0026] Depending on the reaction conditions in the NOP, lignin-containing cellulose nanofibers (LCNFs) can be produced, which synergistically integrate the favorable properties of both cellulose and lignin. LCNFs are similar to CNFs with high surface areas and long aspect ratios capable of forming entangled networks, while the lignin component can enhance hydrophobicity, thermal stability, and ultraviolet (UV) resistance. Additionally, carboxylated LCNFs also incorporate carboxyl groups on lignin, enabling high defibrillation efficiency, fiber dispersibility, and the ability to interact with a wide range of matrix materials. These features allow LCNFs to be used in diverse applications, such as coatings, packaging, barrier films, and reinforced polymer composites.2. Formulation Compositions

[0027] The example embodiments of the present invention can be applied to a wide range of coating formulations, including components such as epoxy, polyurethane, acrylics, alkyds, silicates, nanoparticles, fluoropolymers, silanes, nano-silica, etc. in protective, decorative, and functional coatings. Some coating formulations include pigments and are considered paint formulations. Charged cellulosic fibrils, e.g., NC, CNC, CNF, LCNF, or other charged cellulosic fibers, can be incorporated as stabilizers, thickeners, and adhesion promoters, enhancing the performance of the coating and providing a smooth, uniform finish. The charged cellulosic fibrils can be typically added at concentrations ranging from about 0.1 wt% to about 10 wt% or ranging from about 0.1 wt% to about 5 wt%, within manufacturing and / or measurement tolerances, depending on the desired adhesive properties and the substrate. The chargedcellulosic fibrils also contribute to the environmental sustainability of the coating by reducing the need for synthetic additives.

[0028] Paint formulations, including components such as resin, acrylics, alkyds, epoxies, polyurethanes, pigments (e.g., titanium dioxide and iron oxides), etc., provide a pigmented aqueous suspension that provides color on a surface when dried or cured. Paint formulations are a type of coating formulation that includes pigments. In paints formulation, the charged cellulosic fibrils can be included as thickeners, stabilizers, and / or adhesion promoters, typically at concentrations ranging from about 0.1 wt% to about 10 wt% or ranging from about 0.1 wt% to about 5 wt%, within manufacturing and / or measurement tolerances. The selected type of charged cellulosic fibril (e.g., NC, CNC, CNF, LCNF, or other charged cellulosic fiber) depends on the desired viscosity, stability, and adhesion characteristics. These charged cellulosic fibrils help to control the viscosity of the paint, preventing settling of pigments and improving the uniformity of the applied coating. The charged cellulosic fibril can also enhance the adhesion of the paint to various substrates, reducing the need for additional adhesion promoters.

[0029] Adhesive formulations, including components such as polyacrylic acid salts, phosphate esters, polycarboxylates, polyurethane thickeners, fumed silica, clays, etc., provide bonding between two surfaces through adhesion and / or cohesion. In adhesive formulations, charged cellulosic fibrils, e.g., NC, CNC, CNF, LCNF, or other charged cellulosic fibers, are used to enhance adhesive strength and reduce reliance on synthetic polymers. The charged cellulosic fibrils can be added at concentrations ranging from about 0.1 wt% to about 10 wt% or ranging from about 0.1% to about 5% by weight, within manufacturing and / or measurement tolerances, depending on the desired adhesive properties and the substrate. The carboxyl groups on the charged cellulosic fibrils interact with the substrate, improving bond strength and durability.3. Mechanisms of Action

[0030] The charged cellulosic fibrils can define or form a three-dimensional network within the formulation, increasing its viscosity and preventing the settling of solid components such as pigments and fillers. This three-dimensional network structure can improve the uniformity of the applied product, ensuring consistent coverage and performance.

[0031] The carboxyl groups on the charged cellulosic fibrils interact electrostatically and chemically with a surface of the substrate, improving the adhesion of the paint, adhesive, or coating to the surface. This results in a stronger, more durable bond that is less prone to peeling or delamination.

[0032] The high aspect ratio of the charged cellulosic fibrils can contribute to the ability of the charged cellulosic fibrils to modify the flow properties of the formulation, providing improved control over the application process. This can be particularly beneficial in applications requiring precise application or where sagging and dripping must be minimized.4. Applications

[0033] In automotive paints and coatings, charged cellulosic fibrils, such as NC, CNC, CNF, LCNF, or other charged cellulosic fibers, can enhance the stability and adhesion of the formulation, resulting in a more durable and aesthetically pleasing finish. The use of these fibrils also reduces the environmental impact of automotive coatings by replacing non- biodegradable thickeners and stabilizers.

[0034] Charged cellulosic fibrils, such as NC, CNC, CNF, LCNF, or other charged cellulosic fibers, can be used in adhesives and coatings for construction materials, improving bond strength and durability, while reducing the reliance on synthetic polymers. This is particularly valuable in applications such as tile adhesives, sealants, and protective coatings for concrete and metal surfaces.

[0035] In consumer goods, such as packaging materials and household products, charged cellulosic fibrils, such as NC, CNC, CNF, LCNF, or other charged cellulosic fibers, can contribute to the development of sustainable and high-performance paints, adhesives, and coatings. The use of charged cellulosic fibrils reduces the environmental footprint of these products while maintaining or improving their performance.5. Advantages

[0036] The use of various types of charged cellulosic fibrils can provide significant improvements in the stability, viscosity control, and adhesion of paints, adhesives, and coatings, resulting in enhanced performance and durability. Charged cellulosic fibrils, such as NC, CNC, CNF, CMF, LCNF, or other charged cellulosic fibers, can provide sustainable,biodegradable alternatives to conventional synthetic additives, reducing the environmental impact of the final product.

[0037] The example embodiments of the present invention can reduce the need for additional chemical additives, simplifying the formulation process and improving the safety of the final product. The use of these charged cellulosic fibrils can improve the application properties of paints, adhesives, and coatings, providing better control over the application process and resulting in a higher-quality finish.6. Example Embodiments:6.1 NOP Prepared Lignin Containing Cellulose Fibers (LCNF) from Sugarcane Bagasse

[0038] Carboxylated LCNFs were prepared by NOP treatment of raw sugarcane bagasse (SCB) sample according to the NOP procedures disclosed in U.S. Patent No. 10,894,838.Following the NOP procedures, the effluent was separated, where the treated fibrous residues (termed lignin containing cellulose nanofibers (LCNF)) were thoroughly rinsed with deionized water until a pH of ~3 was achieved. The yield percentage of LCNFs was measured based on the initial weight of untreated SCB as follows:100 (1) where Wf is the weight of the obtained LCNFs (g), and Wo is the initial weight of untreated SCB used (g).

[0039] The lignin content was measured using a UV-Vis spectrophotometer (GENESYS 10S, Thermo Fisher Scientific, NY, USA) at the wavelength of 280 nm. The lignin content was calculated as follows:100 (2) where C is the lignin content (%) of the biomass sample, Abs is the UV absorbance, V is the total volume of the solution (L), n is the dilution factor, E (L g-1cm-1) is the absorptivity of lignin at appropriate wavelength, m (g) is the dry mass of the sample, and £ is the light path length (= 1 cm).

[0040] Potentiometric titration was carried out using a potentiometric titrator (HI 902, HANNA Instrument, Rl, USA) to quantitatively determine the carboxylate group (COO ) contentof the carboxylated LCNF sample. The degree of oxidation (DO) of LCNF was calculated using Equation (3)where 41 / represents the volume of NaOH solution consumed by the oxidized cellulose fibers (L), CNOOH is the NaOH concentration (M), and m is the mass of the cellulose fibers used in the titration (g). The colloidal stability of the oxidized LCNFs was measured at 25°C using a zeta potential analyzer (Zetasizer Nano ZS, Malvern Panalytical, UK). In this measurement, a0.05 wt% LCNF suspension was vortexed for 10 min before the analysis. All measurements were conducted in triplicate at a pH of ~7.Table 1: The chosen NOP reaction conditions for the preparation of carboxylated LCNFs fromSCB.Table 2: The yield (based on untreated SCB feedstock), lignin content, carboxylate content, zeta potential, and crystallinity index (Crl) of carboxylated LCNFs produced under different NOP reaction conditions.

[0041] Table 1 summarizes the chosen NOP reaction conditions for the preparation of carboxylated LCNFs from raw SCB. The reaction times in the NOP procedures are varied under the same reaction conditions. Table 2 summarizes the yield, lignin content, carboxylate content, zeta potential, and crystallinity index (Crl) of the carboxylated LCNFs produced under the different reaction conditions. The zeta potential analysis was conducted to examine the dispersibility and colloidal stability of the LCNF suspensions in reactions nos. R1-R4. All samples exhibited negative zeta potential values (< about -30 mV) across the different reaction times, indicating the high colloidal stability of the suspensions and a reduced tendency for nanofiber aggregation. This stability can be attributed to strong electrostatic repulsion generated by negatively charged carboxylate groups on both lignin and cellulose surfaces. This study indicates that the lignin component was also effectively oxidized under varying NOP reaction conditions.

[0042] Rheological properties of the carboxylated LCNF suspensions at a concentration of 0.1 wt% were investigated using a Discovery Hybrid Rheometer (HR-3, TA Instruments, DE, USA) with a parallel plate (diameter = 40 mm) geometry. The operation gap of the plates was set to 1050 pm. All the measurements were conducted at 25°C with a 2 min stabilization period to minimize the solvent evaporation effect. The flow sweep tests were performed in a shear rate range of 0.01 s“1- 100.0 s“1with 10 points per decade.

[0043] Fig. 1 shows the shear viscosity of LCNF suspensions in water produced by NOP treatment at varying reaction times in reactions nos. R1-R4. All samples exhibited pronounced shear-thinning behavior, due to the breakdown of the cellulose nanofibrous network under high shear rates. While the viscosity profiles were generally comparable across different reaction times, the observed trend followed the order of 5 h (reaction no. R3) ~ 7 h (reaction no. R2) > 9 h (reaction no. Rl) > 3 h (reaction no. R4). The lower viscosity of the sample with a 3-h reaction of reaction no. R4 can be attributed to a reduced carboxylate content (0.91 ± 0.01mmol / g), increased fiber width (8.48 ± 1.71 nm), and higher lignin content (9.03 ± 0.36%), which collectively limit fibrillation efficiency and reduce aspect ratio. Although the sample with the 9-h reaction time in reaction no. R1 had the highest carboxylate content (1.56 ± 0.02 mmol / g) and the finest fiber width (6.48 ± 1.90 nm), its viscosity was slightly lower than that of the sample with the 7-h reaction time in reaction no. R2 and the sample with the 5-h reaction time in reaction no. R3. This may be due to some degree of fiber degradation at longer reaction times, which reduces the aspect ratio and the resulting viscosity. The results in Fig. 1 show that the rheological and surface properties of NOP produced CNC, CNF and LCNF can be fine-tuned by the NOP conditions, where their aqueous suspensions all exhibit shear thinning behavior.6.2 NOP-CNF-Paint Mix Design

[0044] Paint-CNF mixtures were formulated by weight at a 1:1 ratio of a typical commercially available aqueous acrylic paint to an aqueous CNF suspension of desired concentration, with the control sample involves the mixing of deionized water only. The weight ratio can be in a range between about 1:20 to about 1:1, within manufacturing and / or measurement tolerances. The CNFs were prepared by NOP treatment of untreated jute fibers according to the NOP procedures disclosed in U.S. Patent No. 10,894,838. The resulting CNFs have a carboxylate content about 1.8 mmol / g, within manufacturing and / or measurement tolerances, and an average cross-sectional dimension between about 3 nm-about 4 nm, within manufacturing and / or measurement tolerances. Components were mixed at room temperature in polypropylene vials and stirred on a magnetic stir plate for 1 h to ensure homogeneity. After formulation, samples were kept capped to minimize evaporation. Immediately before viscosity measurements, each sample was gently shaken (to re-suspend pigments and the CNFs), and then the rheological behavior of the samples was performed using Discovery Hybrid Rheometer (HR-10) with 40-mm parallel plate and a parallel plate geometry. The operation gap was set to 1050.0 pm. All the measurements were conducted at 25°C, with 1-mins stabilization period to minimize the solvent evaporation. The flow sweep tests were performed with a shear rate of 0.01 s“1-200.0 s“1with 10 points per decade. To evaluate CNF's effect on viscosity, stability, and pigment suspension, a suspension was prepared with 1:1 paint-water (control) and paint-CNF mixtures (0 wt%-0.25 wt% of CNF suspension with paint:CNF suspension = 1:1).

[0045] Fig. 2 illustrates the viscosity of different paints formulations mixed with different concentrations of CNF suspensions. All viscosity-shear rate curves show monotonic thickening at low shear while preserving shear-thinning. At 1 s“1, viscosity increased from ~0.05 Pa-s (control) to ~0.17 Pa-s (0.05 wt%), ~0.53 Pa-s (0.10 wt%), ~1.7 Pa-s (0.20 wt%), and ~2.17 Pa-s (0.25 wt%); at 0.01 s“1, values reached ~55.9 and ~75.6 Pa-s for 0.20 and 0.25 wt%, respectively, indicating strong low-shear body conducive to improved stability and pigment suspension. At the shear rate of 100 s“1, the 0.25 wt% sample thinned to ~0.12 Pa-s, maintaining high-shear processability for spray / roll application. The families of curves remain ordered and nearly parallel across shear rate, implying that CNF chiefly increases network strength (viscosity magnitude) without altering the underlying shear-thinning mechanism.

[0046] The addition of a small fraction of CNF can substantially or drastically increase the viscosity of the final mixture. For example, at the shear rate at 0.01 s1, the addition of 0.125 wt% CNF (in the mixture of Paint + 0.25 wt% CNF (1:1)) increases the viscosity of the mixture by almost 100 times over the mixture without CNF. Furthermore, the addition of CNF is found to enhance the shear thinning behavior. The shear thinning characteristics make coati ngs / adhesives easy to apply but stable once applied. Additionally, the addition of CNF can prevent sagging or dripping, improve surface coverage (thus better surface adhesion and fewer defects) and controlled thickness, facilitate spraying and printing processes.

[0047] It should be understood that the foregoing description is only illustrative of the present invention. Various alternatives and modifications can be devised by those skilled in the art without departing from the present invention. Accordingly, the present invention is intended to embrace all such alternatives, modifications, and variances that fall within the scope of the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A coating formulation comprising charged cellulosic fibrils, wherein the charged cellulosic fibrils include carboxyl functional groups.

2. The coating formulation of claim 1, wherein the charged cellulosic fibrils include nitrooxidation-process-derived charged cellulosic fibrils.

3. The coating formulation of claim 1 or 2, wherein the charged cellulosic fibrils include nanocellulose (NC), cellulose nanocrystals (CNC), cellulose nanofibrils (CNF), cellulose microfibrils (CMF), or lignin-containing cellulose nanofibers (LCNFs).

4. The coating formulation of one of claims 1-3, wherein the charged cellulosic fibrils have a carboxylate (COO-) content greater than about 1.0 mmol / g.

5. The coating formulation of one of claims 1-4, wherein the charged cellulosic fibrils have a cross-sectional dimension between about 2 nm and about 100 nm.

6. The coating formulation of one of claims 1-5, wherein the charged cellulosic fibrils are included in a range of about 0.1 wt%-about 10 wt%.

7. The coating formulation of one of claims 1-6, wherein the charged cellulose fibrils define a three-dimensional network that breaks down when a shear force is applied.

8. The coating formulation of one of claims 1-7, wherein, when a coating including the coating formulation is applied to a substrate, the carboxyl functional groups interact electrostatically and chemically with a surface of the substrate.

9. The coating formulation of one of claims 1-8, further comprising a pigment to define a paint formulation.

10. The coating formulation of claim 9, wherein the paint formulation includes acrylic paint and an aqueous charged-cel lulosic-fibri I suspension, wherein a weight ratio of the acrylic paint to the aqueous CNF suspension is in a range between about 1:20 to about 1:1.

11. An adhesive formulation comprising charged cellulosic fibrils, wherein the charged cellulosic fibrils include carboxyl functional groups.

12. The adhesive formulation of claim 11, wherein the charged cellulosic fibrils include nitro-oxidation-process-derived charged cellulosic fibrils.

13. The adhesive formulation of claim 11 or 12, wherein the charged cellulosic fibrils include nanocellulose (NC), cellulose nanocrystals (CNC), cellulose nanofibrils (CNF), cellulose microfibrils (CMF), or lignin-containing cellulose nanofibers (LCNFs).

14. The adhesive formulation of one of claims 11-13, wherein the charged cellulosic fibrils have a carboxylate (COO-) content greater than about 1.0 mmol / g.

15. The adhesive formulation of one of claims 11-14, wherein the charged cellulosic fibrils have a cross-sectional dimension between about 2 nm and about 100 nm.

16. The adhesive formulation of one of claims 11-15, wherein the charged cellulosic fibrils are included in a range of about 0.1 wt%-about 10 wt%.

17. The adhesive formulation of one of claims 11-16, wherein the charged cellulose fibrils define a three-dimensional network.

18. The adhesive formulation of one of claims 11-17, wherein, when the adhesive is applied between substrates, the carboxyl functional groups interact electrostatically and chemically with surfaces of the substrates.

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