Lignin dispersion for seed coating

Abstract

Lignin dispersions may include an aqueous external phase; and an internal phase containing one or more water-insoluble lignins at a percent by weight (wt%) of the internal phase ranging from 30 wt% to 95 wt%; and one or more dispersing agents ranging from 5 wt% to 70 wt%. Methods may include preparing a lignin dispersion including dispersing a composition into an aqueous external phase, the composition containing one or more water-insoluble lignins at a percent by weight (wt%) of the internal phase ranging from 30 wt% to 95 wt%; and one or more dispersing agents ranging from 5 wt% to 70 wt%.

Description

[0001] LIGNIN DISPERSION FOR SEED COATING

[0002] FIELD

[0003] Embodiments relate to the use of a lignin dispersion as a bio-based additive in seed coating formulation to reduce dust and attrition and improve flowability, and methods of using same.

[0004] BACKGROUND

[0005] Seeds used for growing crops often include coatings disposed on an exterior surface of the seed. The coatings may serve to adhere agriculturally active components (e.g., fertilizers, pesticides, antibacterial agent, plant growth regulator) to the surface of the seed and / or impart a variety of beneficial properties (e.g., protection of seeds from bacteria / insect / injury, promoting plant growth, gas or water permeability etc.). During manufacturing, transportation and planting of the seed, the coating is exposed to a variety of conditions such as mechanical forces and moisture that may negatively affect the integrity of the coating and / or its adherence to the seed. The coating’s resistance to flaking and chipping due to mechanical forces is quantified as its “attrition rate” with smaller values representing less loss of the coating. Generally, an attrition rate of greater than 8% is considered failing. The coating should also have a low coefficient of friction surface such that the coated seeds do not clump and bind to one another during handling.

[0006] Seed coating to apply active ingredients such as pesticides, biologies, or nutrients to the surface of seeds often involves the help of additives such as wetting agents, dispersants, and film forming agents (FFA). FFA in the formulation serves to bind all ingredients into a continuous film, while also improving dust control, wet and dry flowability, water resistance, and other properties. Conventional FFAs included polyacrylic latex as the dominant industrial chemistry, while other solutions having included celluloses and polymer systems such as polyolefin or polyurethane dispersions, polyvinyl alcohols, and polyvinyl acetates. However, concerns regarding environmental and health safety of microplastic materials has placed conventional treatments under increasing scrutiny from regulatory bodies.

[0007] Summary

[0008] In an aspect, embodiments disclosed herein are directed to lignin dispersions that may include an aqueous external phase; and an internal phase containing one or more water-insoluble lignins at a percent by weight (wt%) of the internal phase ranging from 30 wt% to 95 wt%; and one or more dispersing agents ranging from 5 wt% to 70 wt%.

[0009] In another aspect, embodiments disclosed herein may be directed to methods of preparing a lignin dispersion including dispersing a composition into an aqueous external phase, the composition containing one or more water-insoluble lignins at a percent by weight (wt%) of the internal phase ranging from 30 wt% to 95 wt%; and one or more dispersing agents ranging from 5 wt% to 70 wt%.

[0010] Detailed Description

[0011] Embodiments relate to lignin dispersions and methods of application as a bio-based filmforming additive (FFA) in seed coating formulations to improve overall handling, including reducing dust and coating attrition, modifying flowability, and increasing storage stability compared to conventional FFAs that may be sources of microplastics. Methods may include the formulation and production of lignin dispersions using a melt dispersion method to produce a (sub)micronized emulsion in the absence of added base. Methods may also include the application of lignin dispersions as FFAs in various seed coatings.

[0012] As used herein, the term “average particle size” refers to the median particle size or diameter of a distribution of particles. Particle size d50 and d90 is measured by laser diffraction using a COULTER™ LS-230 or LS-320 particle size analyzer (Beckman Coulter Corporation, Fullerton, CA) with the particle (sample) refractive index set to 1.5 and is reported as the d50 particle size or volume mean diameter (Vmean) or as d90 particle size.

[0013] FFAs disclosed herein may be used for seed coating and similar agricultural applications, as an alternative or partial replacement for conventional FFAs. When applied to seeds, FFA may reduce dust generation and attrition of active ingredients that can present handling and health hazards. For example, FFA compositions may minimize dust during handling in seed coating process, bagging, transportation, planting, and the like. FFA composition may also enhance flowability, which allows coated seeds to flow easily through handling equipment such as hoppers, tubing, meters, and the like.

[0014] FFA compositions disclosed herein may have the advantages of sustainability and being microplastics free. In some cases, FFA compositions may meet the microplastic-free derogations set by EU REACH proposed restriction (Annex XVII), which restricts use of standard solutions such as acrylic latex. While other solutions such as polyvinyl alcohol may remain viable in view of regulation, the performance of such solutions is often insufficient, particularly viscosity for solutions having higher concentrations (e.g., >10%). In contrast, FFA compositions and lignin dispersions disclosed herein may exhibit viscosities below 3000 cP at 25 °C at normal solid content levels (30-60 wt%), which allows for easier handling and pumping at standard pressures.

[0015] FFA compositions disclosed herein may include a lignin dispersion containing a water insoluble lignin emulsified in an aqueous solution with one or more dispersants and optional additives. Optional additives may include performance modifiers such as plasticizers, thickeners, fillers cosolvents and the like. FFA compositions may be water-based seed coating formulations that are applied to a seed or other suitable substrate. In some cases, films generated by compositions disclosed herein may be applied without additional organic solvents or heating.

[0016] FFA compositions may incorporate an aqueous lignin dispersion in which a waterinsoluble lignin and dispersing agent form an internal phase within an external phase containing an aqueous fluid or solvent system. The term "aqueous fluid" refers to water, and aqueous mixtures of salts and other minor soluble components that do not change the primary characteristics of the external phase. The term “lignin” refers to a polymer or oligomer composed of the lignin monomers p-coumaryl alcohol, coniferyl alcohol, sinapyl alcohol, and related organics. The molecular weight of lignin may vary widely, such as from about 500 to about 50,000 g / mol, and be derived from various plants and biomass residues including hardwoods and softwoods, straw, bagasse, corn stover, and the like. Lignin extraction methods may include solvent pulping, sulfite pulping, soda pulping, alkali pulping, semi-mechanical pulping, steam explosion, enzymatic pulping processes, recovery from distillation bottoms of a process fermenting lignocellulosic biomass-derived sugars, and the like.

[0017] Water-insoluble lignin is derived from the insoluble fractions obtained from lignin production, and is contrasted with water-soluble lignins, sulfonated derivatives, and the like. Water-insoluble lignin may be produced in various processes, including as a byproduct of paper production, such as Kraft pulping processes soda pulping processes, dissolving pulp processes (i.e., from the chip prehydrolysis step prior to pulping), enzymatic processes, steam explosion processes, and the like. Suitable examples of water-insoluble lignin include hydrophobic unmodified lignins, resins, and powders, such as kraft lignin (e.g., H-form), organosolv lignin, milled wood lignin, and any other types of hydrophobic lignin that are not readily soluble in aqueous fluids. Commercially available water-insoluble lignin includes Biochoice™ lignin from Domtar, which is a pine kraft lignin precipitated from black liquor of bleachable-grade pulp.

[0018] Lignin dispersions may be formulated with a water-insoluble lignin at a percent by weight (wt%) ranging from 15 wt% to 80 wt%, 20 wt% to 75 wt%, or 45 wt% to 50 wt%. Water-insoluble lignins may be in the form of a resin having a percent solids (wt%) ranging from 15 wt% to 60 wt%, or 20 wt% to 60 wt%. Lignin dispersions may include an aqueous fluid at a percent by weight (wt%) from 50 wt% to 80 wt%.

[0019] Lignin dispersions disclosed herein may be prepared by using one or more dispersants to facilitate emulsification of the water-insoluble lignin in an aqueous external phase. In some cases, the dispersant may include a water-soluble dispersant. Suitable dispersants may include polyvinyl alcohols (PVOH), polyalkylene oxides, polyalkylene oxide copolymers such as ethylene oxide / propylene oxide (EO / PO) copolymers or EO / BO copolymers, functionalized polyalkylene oxides, alcohol ethoxylates, fatty alcohols, fatty acids, salts of fatty acids, polysaccharides, modified polysaccharides such as cellulose ethers, polyacrylate copolymers (e.g., branched or non-branched), heterocyclic polymers, polynaphthalene sulfonate, copolymers containing the above listed polymer blocks or segments, mixtures thereof, and the like.

[0020] Lignin dispersions may include one or more dispersants at a percent by weight (wt%) ranging from 15 wt% to 80 wt%, 20 wt% to 75 wt%, or 45 wt% to 50 wt%. The weight ratio of water-insoluble lignin to dispersant in the lignin dispersion may range from 1 :9 to 19:1, or 1:1 to 9:1.

[0021] FFA compositions may include one or more plasticizers. Example of plasticizers include ethylene glycol, di- and triethylene glycol, glycerin, propylene glycol, benzylic acids such as homovanillic acid, glycol ethers, polyglycols, sucrose, maltose, maltodextrins, and sugar alcohols such as sorbitol, urea, sodium lactate, amino acids, citric acid esters, and the like. Plasticizers maybe in the form of a resin or suspension containing plasticizer solids at a percent by weight (wt%) of the resin or suspension ranging from 5 wt% to 60 wt%, or 20 to 60 wt%.

[0022] FFA compositions may contain one or more plasticizers at a percent by weight (wt%) of the composition ranging from 5 wt% to 65 wt%, 5 wt% to 50 wt%, or 10 wt% to 50 wt%.

[0023] FFA compositions may include one or more optional additives to optimize the processing, such as thickeners, fillers, cosolvents, and the like. For example, the seed coating composition may comprise an antifreezing agent, a thickener, an antifoaming agent, a pigment, an antiseptic agent, a pH modifier, a coalescent agent, a stabilizer, an active ingredient and / or combinations thereof. Exemplary antifreezing agents include a dihydric alcohol such as ethylene glycol or propylene glycol. The seed coating composition may comprise an antifreezing agent in an amount from 0.5 wt% to 30 wt% based on the total weight of the seed coating composition. Exemplary thickeners include polysaccharides such as xanthan gum, rhamsan gum, locust bean gum, carrageenan or welan gum; a synthetic polymer such as sodium polyacrylate; a semisynthetic polysaccharide such as carboxy methyl cellulose; a mineral fine powder such as aluminum magnesium silicate, smectite, bentonite, hectorite or fumed silica, or alumina sol. The seed coating composition may comprise from 1.0 wt% to 50.0 wt% of an active ingredient based on a total weight of the seed coating composition. Examples of active ingredients include pesticides (e.g., thiamethoxam, abamectin, fenobucarb, isoprocarb, chlorfluazuron, chlorpyrifos, fipronil, clothianidin, spinetoram, spinosad, dinotefuran, methoxyfenozide, ethofenprox, ethiprole, acephate, benfuracarb, monocrotophos, silafluofen, imidacloprid, etc.), fertilizers and / or combinations thereof. Exemplary coalescent agents include dipropylene glycol monobutyl ether, [(butoxymethylethoxy )methylethoxy]propan- 1 -ol, 2,2,4-Trimethyl-l,3-Pentanediol

[0024] Monoisobutyrate; Isobutyric acid, ester with 2,2,4- trimethyl- 1,3 -pentanediol, 2,2,4-Trimethyl- 1,3 -pentanediol monoisobutyrate, other coalescing agents and / or combinations thereof.

[0025] Lignin dispersions may be generated using a mechanical process to melt emulsify lignin at elevated temperature as an internal phase having micron and submicron sized particles into an aqueous external phase. Melt emulsification processes may include processing in batch, semibatch, or continuous modes, lignin dispersion may be prepared with the assistance of one or multiple dispersing agents, and optionally one or more plasticizers. Examples of batch equipment includes mixed pressure vessels equipped with a Cowles™ blade impeller, helicone mixers, and planetary mixers. Continuous processes may include rotor stator mixers and melt kneading devices such as extruders.

[0026] Lignin dispersion may be made by extrusion in which lignin and dispersant are processed through an extruder (e.g., twin-screw or single-screw extruder) melted at a suitable temperature (e.g., 180 °C).

[0027] At various stages in a batch or continuous process, aqueous solvents may be added to dilute the lignin dispersion to the target solids content. Lignin dispersions disclosed herein may have a solids content as a percent by weight (wt%) of the dispersion of 60 wt% or less, such as in a range of 5 wt% to 60 wt%.

[0028] Lignin dispersion may have a viscosity of 6000 cP or less, such as ranging from 500 cP to 6000 cP. The viscosity of the polyester dispersion is measured using a Brookfield RV viscometer at 50 rpm using the appropriate spindle for the given viscosity (for example RV3)

[0029] Lignin dispersion disclosed herein may have an average particle size measured by volume (Vmean) ranging from 20 nm to 3 pm, or 20 nm to 1 pm. In some cases, lignin dispersion disclosed herein may have an average particle size in any of the above ranges and a d90 of 3 pm or less, or 2.5 pm or less.

[0030] Prior to application to seeds or other substrate, the lignin dispersion can be premixed with a flowable concentrate active (e.g., pesticide, agricultural additive) formulation or post-added into a flowable concentrate active formulation before seed coating. In some cases, the lignin dispersion may be combined with an active formulation and optional aqueous solvent to generate a coating composition that may then be applied to seeds or other substrate to form a coated seed or substrate. Coating compositions may include a lignin dispersion at a percent by weight (wt%) of the composition of 10 wt% or less, such as in a range of 0.5 wt% to 50 wt%, or 0.5 wt% to 40 wt%; and actives ranging from 1 wt% to 80 wt% actives, or 5 to 60 wt% actives.

[0031] Coating compositions may be applied to a variety of seeds, pesticides, and / or agricultural actives. Seeds and substrates for coating are not particularly limited, and include seed for cereals (e.g., wheat, oats, rice, corn (maize), barley, sorghum, rye, millet), fruits, vegetables, legumes, or other types of seeds. Forming the coated seed may first start with a step of forming a film using a coating composition. The coating composition may be directly applied to the seeds (e.g., sprayed on) and / or the seeds may be mixed into the coating composition and then removed. After the coating composition has been applied to the seeds, the coating composition is dried to form a seed coating.

[0032] In some cases, coating compositions may improve the coating properties in non- agricultural contexts, such as use with water-based paint, ink, adhesive, paper-coating compositions, , concrete, or asphalt.

[0033] While formulation components and properties have been disclosed individually, it is envisioned that component elements may be included, excluded, or combined in any manner or subcombination utilizing any of the above concentration ranges and nested subranges therein. Further, that the recited formulation properties may be similarly achieved through various combinations of the recited components within the recited ranges.

[0034] Examples

[0035] The following examples are provided to illustrate the embodiments of the invention, but are not intended to limit the scope thereof. Table 1 provides the materials used in the following examples.

[0036] Preparation of lignin dispersion

[0037] In this example, inventive and comparative FFA are prepared and applied

[0038] Lignin dispersions used in the examples and shown in Table 4, were prepared by a batch method using a helicone mixer. An intermeshing helical mixer bowl was charged with 42 g lignin, 18 g of Poval 18-88 and 31 g DI water. The mixer bowl was loaded into the mixer, and was then sealed and pressurized to 65 psi with nitrogen. The heater was increased to 170 °C, and reached an internal temperature of 157 °C after 60 minutes. The mixer was then operated for 30 minutes. Following the initial mixing, an 85 ml dilution of water was added at 1.5 ml / min. When the dilution addition was complete the mixing was stopped, and the bowl heater was turned off. When temperature dropped below 100 °C, pressure was released and the material recovered.

[0039] Particle Size Testing of lignin dispersions

[0040] Particle size of the dispersions was measured by laser diffraction using a COULTER™ LS-230 or LS-320 particle size analyzer (Beckman Coulter Corporation, Fullerton, CA) with the particle (sample) refractive index set to 1.5 and is reported as the d50 particle size or volume mean diameter of the lignin particles.

[0041] FFA preparation and application

[0042] In this example, com seeds were coated with inventive and comparative FFA compositions and tested for attrition and flowability. In addition to the lignin dispersions provided in Table 2, further comparative examples of conventional FFAs and water-soluble lignin derivatives in Tables 3 and 4 were tested.

[0043] Application of the coating to com seeds was done using a KMC Coating pan. The coating speed was set at 65 rpm, with application over 5 minutes. All coatings were applied at room temperature (72 °F). The detailed steps of coating are as described below:

[0044] 1. Com seeds are first measured into a single batch (either 1000g or 1300g).

[0045] 2. The coating formulation which is already prepared is then measured to be about 2% of the mass of the uncoated seeds (20g or 26g). The coating solution is then pulled into a 50 mL syringe.

[0046] 3. Initially the uncoated seeds are loaded into the pan while it is off and not turning.

[0047] 4. The pan rotational speed is set at 65 rpm.

[0048] 5. The coating formulation is then slowly added to the seeds while the pan is rotating.

[0049] 6. Once the formulation is added, the seeds continue to rotate for 5 minutes until there is a uniform layer of formulation on all the seeds.

[0050] 7. After coating is completed, the coated corn seeds are then placed into storage jars and set at room temperature for 2 days to let the coating dry completely.

[0051] The weight gain to the seed after coating is 1.4 to 2. 1 wt% of the dry seed weight for tested samples, with minimal loss of coating material to the wall of the KMC coater.

[0052] The seed coating formulation includes a commercial Imidacloprid pesticide concentrate (Gaucho 600, 600 g imidacloprid per liter; Bayer Crop Science AG, Mohnheim, Germany). The formulation was diluted to 80 wt% by DI water (blank), or 5% binder + water (experimental). All components were mixed sufficiently and stored for at least 24 hours before application to seed.

[0053] Com seeds were first treated with a commercial flowable concentrate formulation with or without 5 wt% of different film forming agents in the formulation. Seed coatings all provided good initial coverage except for CE-PVOH, which was attributed to the high viscosity of the solution creating difficulty in spray application. All lignin dispersions (LD) and lignin sulfonates (LS) provided as good coverage as the blank sample (CE-Blank) and the sample using commercial acrylic latex as film former (CE- Acrylic).

[0054] Attrition testing

[0055] Following application, seeds coated with FFA compositions were then tested for dust generation / attrition testing, carried out using a ball mill. The details of the material, container, and conditions are presented in Table 6.

[0056] The dust measurement process was executed as follows:

[0057] 1. Measure 650g of material, which is approximately 13 grams of coating material and 637g of corn seeds.

[0058] 2. Screen the pre-existing fines from the coating process using mesh #12 (1.7mm) screen and Rotap sieve shaker for 1 minute without tapping enabled. 3. Separate the fines from the coating material, record the mass of the sample after the first sieve: mi.

[0059] 4. Load the coated seed into the grinding chamber.

[0060] 5. Place the loaded grinding chamber onto the roller of the ball mill shown in Figure 1.

[0061] 6. Run the ball mill at 65 rpm for 5 minutes.

[0062] 7. Unloaded all particles on a stack of screen (#12).

[0063] 8. Shake the screens for 1 minute using Rotap shaker and record the mass retained,

[0064] The total dust attrition is calculated according to the equation (1).

[0065] %total dust = (rm - m / mi (1)

[0066] Following coating, seed samples then underwent dust attrition testing. After attrition, seed appearance was visually rated and compared (Table 7 and Table 8). Without any film forming agent, the coating of the blank example became thin and crumbled after attrition. The addition of commercial acrylic latex (CE-Acrylic) did not improve the attrition. Even worse failure was observed for CE-PVOH, where com seed skin was exposed for many seeds. The coated seeds with lignin dispersions showed more integrated coating after attrition test with minimal surface lost and minimal crumbled particles on the surface. Lignin sulfonates (LS) samples exhibited similar performance to CE-PVOH.

[0067] For quantitative comparison, dust was separated from the seeds by sieving, and weight loss and weight loss percentage of the coating were recorded. Surprisingly, neither acrylic latex nor PVOH provided sufficient protection to the coated seed in terms of attrition and dust. The weight loss by percentage of CE-acrylic and CE-PVOH were higher than the blank sample CE-Blank. For the inventive lignin dispersion example 1E-LD1, the coating loss after attrition is 3 times lower comparing to the blank sample. Without being bound by any theory, it is believed that the aromatic lignin may be interacting with pesticide particles through hydrogen bonding and pi- pi interaction, creating higher cohesion with the film at the surface and in bulk and reducing attrition and dust generation.

[0068] The particle size of the lignin dispersion may also play a factor, potentially by reducing total lignin particle concentration and pesticide binding capacity. For example, CE-LD2 (Vmean - 1 pm and D90 of >3 pm) underperformed when compared to IE-LD2 (Vmean = 360 nm).

[0069] To understand whether the dispersion form of lignin is necessary or not, we picked two water soluble lignin derivatives (lignin sulfonate) and added them to our test (LS 1 and LS2). The results showed very obviously that they failed to provide protection to the coating film, evidenced by high dust loss and poor seed coverage after attrition.

[0070] Flowability testing

[0071] Flowability was measured using a custom hopper having a valve positioned at its outlet in combination with a high-speed camera to record the discharge of coated seeds. The outlet of the hopper had a diameter of 4.2 cm, where the inner diameter of the vertical section of the hopper is 8.9 cm and height of the vertical part is 14.6 cm. The angle of conical portions between the outlet and the vertical portions of the hopper were 14.47 degrees. The flowability tests were done at room temperature (22 °C). During the filling process, the valve of the hopper remained securely closed. All flowability experiments were conducted with batches containing 750 grams of material, encompassing both seeds and their respective coatings. Once the valve was secured in the closed position, the high-speed camera commenced its recording process. Simultaneously, the valve is promptly opened, allowing seeds to flow freely until complete discharge is achieved. Following the conclusion of the discharge, the image recording process is temporarily paused. The total discharged time required for the granules to completely exit the hopper was calculated with an accuracy of up to 0.001 seconds. Consequently, a determine of the average mass flow rate associated with each specific coating can be calculated with Equation (2).

[0072] Mass flow rate = m / t Equation (2) where m is the total mass of the seeds and t is the time used from beginning to conclusion of the discharge.

[0073] Flowability results for tested samples is shown in Table 9. The IE-LD1 sample significantly improved the flowability of the coated seed comparing with CE-Blank and CE- Acrylic.

[0074] While the foregoing is directed to exemplary embodiments, other and further embodiments may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

Claims1. A lignin dispersion comprising: an aqueous external phase; and an internal phase comprising: one or more water-insoluble lignins at a percent by weight (wt%) of the internal phase ranging from 30 wt% to 95 wt%; and one or more dispersing agents ranging from 5 wt% to 70 wt%.

2. The lignin dispersion of claim 1, wherein the one or more water- insoluble lignins are selected from kraft lignin, organosolv lignin, or milled wood lignin.

3. The lignin dispersion of claim 1 , wherein the one or more dispersing agent is selected from the group consisting of polyvinyl alcohol, fatty alcohol ethoxylates, ethylene oxide / propylene oxide block copolymers, salts of fatty acids, polyacrylate copolymers, and modified polysaccharides.

4. The lignin dispersion of claim 1 , wherein the internal phase comprises particles having a volume mean diameter ranging from 20 nm to 1 pm.

5. The lignin dispersion of claim 1, wherein the solids content as a percent by weight (wt%) is 60 wt% or less.

6. The lignin dispersion of claim 1 , further comprising a plasticizer at a percent by weight (wt%) ranging from 5 wt% to 50 wt%.

7. The lignin dispersion of claim 1, wherein the viscosity of the lignin dispersion is 6000 cP or less.

8. A coating composition, comprising: a lignin dispersion at a percent by weight (wt%) of 0.5 wt% to 40 wt% and comprising: one or more water-insoluble lignins at a percent by weight (wt%) of the lignin dispersion ranging from 30 wt% to 95 wt%; and one or more dispersing agents ranging from 5 wt% to 70 wt%; and one or more actives at 5 wt% to 60 wt%.

9. A coated seed coated with the composition of claim 8.

10. A method of preparing a lignin dispersion comprising: dispersing a composition into an aqueous external phase, the composition comprising one or more water-insoluble lignins at a percent by weight (wt%) of the internal phase ranging from 30 wt% to 95 wt%; and one or more dispersing agents ranging from 5 wt% to 70 wt%.

11. The method of claim 10, wherein dispersing comprises a continuous method.

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