Coated fertilizer, method for preparing the same, and use thereof

Abstract

The present disclosure relates to a controlled-release coated fertilizer product comprising a fertilizer granule core and a coating of an easily biodegradable component and a natural polymer. The coating comprises an inner layer containing lignin and a hydrophobic outer layer. The present disclosure further relates to a method for preparing the coated fertilizer product and the use of the coated fertilizer for controlled release of nutrients in agriculture.

Description

Technical Field

[0001] Field of Disclosure The present disclosure relates to a controlled-release coated fertilizer product comprising a fertilizer granule core and a coating of an easily biodegradable component and a natural polymer. The coating comprises an inner layer containing lignin and a hydrophobic outer layer. In particular, the present disclosure relates to a coated fertilizer product in which the lignin of the inner coating is trapped within a biodegradable biobased polymer. The present disclosure further relates to a method for preparing the coated fertilizer product and the use of the coated fertilizer for controlled release of nutrients in agriculture.

Background Art

[0002] Background of Disclosure The increasing world population has led to an increase in food production. This means that the agricultural sector will use large amounts of fertilizers for food production, further contributing to the emission of harmful gases and eutrophication of water associated with fertilizer use. In addition to the limited availability of arable land, controlled-release fertilizers (CRFs) are used to enhance crop production (by reducing nitrogen losses due to volatilization and leaching) and limit environmental pollution caused by the use of large amounts of fertilizers.

[0003] As the name suggests, CRFs enable controlled release of nutrients to plants and are typically achieved by coating water-soluble fertilizer granules with a (semipermeable, semi-impermeable or water-insoluble) membrane. Several polymers are used as coating materials for fertilizers; however, the cost, biodegradability, and toxicity of these materials are major drawbacks in their use. To overcome these issues, the use of renewable and biobased resources such as natural polymers and biodegradable synthetic polymers has attracted attention. Among these natural polymers, lignin is a major component of plant cells along with cellulose and hemicellulose and is the second most abundant biopolymer after cellulose.

[0004] Today, the two main lignin resources are the paper industry and biorefineries. In Kraft pulp mills, approximately 70 million tons of lignin are produced annually. Most of this lignin is used as fuel for the operation of the mills. The world production of Kraft lignin that is not used as fuel is approximately 100,000 tons, but the production of sulfur-free lignin is less than 5,000 tons. Lignin has attracted attention in the materials field due to its low cost, non-toxicity, diverse functional groups, renewability, and degradability. However, due to the complex nature of its structure, the use of lignin in large-scale applications is limited.

[0005] Despite the continued research and development of processes for producing controlled-release fertilizers, particularly from natural and biodegradable polymers, there is still a need to overcome the challenges associated with the use of bio-based resources in the production of controlled-release fertilizers.

[0006] Brief Description of the Disclosure The object of the present disclosure is to provide a controlled-release coated fertilizer product and a method for preparing a controlled-release coated fertilizer.

[0007] The object of the present disclosure is achieved by products, methods, and uses characterized by what is described in the independent claims. Preferred embodiments of the present disclosure are disclosed in the dependent claims.

[0008] The present disclosure is based on the idea of providing a coated fertilizer product and a method for preparing a coated fertilizer, wherein the coating of the fertilizer comprises an inner layer containing lignin and a hydrophobic outer layer.

[0009] More specifically, the present disclosure is based on the idea of providing a coating consisting only of non-toxic and easily biodegradable components and / or natural polymers. This means that the coating does not contain organic solvents, does not use non-easily biodegradable copolymers containing microplastics, and the lignin itself is not chemically modified.

[0010] The advantages of the products, methods, and uses of the present disclosure are that, since it does not use plastic-type polymers that are not easily biodegradable, after the fertilizer dissolves, no microplastics remain in the soil from the biodegradable coating.

[0011] Furthermore, since no organic solvents are used and the biobased polymers, plasticizers, and any stabilizers and / or thickeners are preferably water-soluble, a further advantage of the products, methods, and uses of the present disclosure is that drying and coating are easier.

[0012] A further advantage of the products, methods, and uses of the present disclosure is that improved release control of the fertilizer product is provided. Preferably, the release control period, release rate (conductivity over time), and weight loss of the release control fertilizer product are improved.

[0013] Brief Description of the Drawings Hereinafter, the present disclosure will be described in more detail with reference to the preferred embodiments with reference to the accompanying drawings.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

[0015] Detailed Description of the Disclosure The present disclosure relates to a coated fertilizer product, the coated fertilizer product comprising a fertilizer granule core and a coating of an easily biodegradable component and / or natural polymer, the coating comprising an inner layer containing lignin and a hydrophobic outer layer.

[0016] The coated fertilizer products of the present disclosure, the coated fertilizers obtained by the disclosed method, are fertilizer products coated for the control of fertilizer release. Typically, the release control period of the coated fertilizer products exceeds 4 days, preferably exceeds 30 days, more preferably exceeds 3 months, and most preferably exceeds 6 months.

[0017] The disclosure also relates to a method of preparing a coated fertilizer, the fertilizer having a coating of readily biodegradable components and / or natural polymers, the method using a coating dispersion comprising lignin, a biobased polymer and a plasticizer for coating the fertilizer granules, providing an inner coating layer, and then obtaining a single-layer coated fertilizer coated with a hydrophobic outer layer. The biobased polymer and the plasticizer are biodegradable. A coated fertilizer is obtained.

[0018] The present disclosure further relates to the use of the coated fertilizer products, or the coated fertilizer products prepared by the method, for the control of nutrient release in agriculture and as a soil conditioner, preferably in turf, crop cultivation, greenhouse cultivation and / or ornamental horticulture. The coated fertilizer products or the coated fertilizers prepared by the method are administered by topdressing the soil or mixing the fertilizer into the soil before sowing.

[0019] As used herein, the term "lignin" refers to lignin derived from any suitable lignin source. The term "chemically unmodified lignin" refers to lignin that has not been chemically modified after extraction. Generally, lignin is classified into three categories: softwood, hardwood, and annual grass. Lignin is a complex polymer, and its chemical structure varies even within the same species. Lignin consists of three phenylpropane units with p-hydroxyphenyl alcohol (H), guaiacyl alcohol (G), and syringyl alcohol (S) as the main precursors (monolignol monomers), and is heterogeneously linked through several types of C-C and C-O bonds. Ether bonds account for 60-70% of the bonds between phenylpropane units, and the most common one is the β-O-4 bond. However, other types of bonds such as α-O-4 bonds or C-C bonds also exist. The latter are mainly 5-5, β-5, or β-β' bonds. Lignin contains many functional groups, some of which are conjugated, so it absorbs ultraviolet light and gives color to wood. Softwoods generally have a higher lignin content than hardwoods. The lignin in softwoods has a higher proportion of guaiacyl alcohol, while most of the lignin in hardwoods is syringyl alcohol. This affects the chemical groups that make up lignin. Therefore, softwoods have more hydroxyl groups and hardwoods have more methoxyl groups.

[0020] In some embodiments of the present disclosure, the lignin is essentially pure lignin. The expression "essentially pure lignin" should be understood to mean at least 70% pure lignin, or at least 90% pure lignin, or at least 95% pure lignin, or at least 98% pure lignin. Essentially pure lignin may contain at most 30%, or at most 10%, or at most 5%, or at most 2% of other components and / or impurities. Examples of such other components can include carbohydrates such as extracts and hemicellulose.

[0021] Typically, lignin contains less than 30 wt%, or less than 10 wt%, or less than 5 wt%, or less than 3 wt%, or less than 2.5 wt%, or less than 2 wt% of carbohydrates. The amount of carbohydrates present in lignin can be measured by high-performance anion-exchange chromatography with pulsed amperometric detection (HPAE-PAD) according to standard SCAN-CM 71.

[0022] The ash content of lignin is typically less than 7.5 wt%, or less than 5 wt%, or less than 3 wt%, or less than 1.5 wt%. The ash content can be measured by the following method. First, measure the dry solid content of the sample in an oven at 105 °C for 3 h. Preheat the ceramic crucible at 700 °C for 1 hour and weigh it after cooling. Weigh out the sample (1.5 g - 2.5 g) into the ceramic crucible. Place the crucible with the lid in a cold oven. Increase the oven temperature: 20 - 200 °C for 30 min => 200 - 600 °C for 60 min => 600 - 700 °C for 60 min. Continue combustion at 700 °C for 60 min without the lid. Cool the crucible in a desiccator, add a few drops of hydrogen peroxide (H2O2, 30%) to the sample, and combust it in the oven at 700 °C for 30 min. If there are still black spots in the ash, repeat the hydrogen peroxide treatment and combustion. Cool the crucible and weigh it. All weight measurements are performed with an accuracy of 0.1 mg after cooling in a desiccator.

[0023] Calculation of Results Ash content % = (100 a x 100) / (b x c) Where a = weight of ash, g b = weight of sample, g c = dry solids of sample, %

[0024] The ash content of the sample refers to the mass remaining in the sample after combustion and annealing and is presented as a percentage of the dry content of the sample.

[0025] In some embodiments of the present disclosure, the lignin is technical lignin. As used herein, the term "technical lignin" refers to lignin obtained from lignin in any biomass by any technical process. In one embodiment, the technical lignin is lignin received from an industrial process.

[0026] The lignin used to prepare the coating dispersion is typically selected from the group consisting of Kraft lignin, steam explosion lignin, biorefinery lignin, supercritical separation lignin, hydrolyzed lignin, flash precipitation lignin, biomass-derived lignin, lignin from an alkaline pulping process, lignin from a soda process, lignin from an organosolv pulping process, lignin from an alkali process, lignin from an enzymatic hydrolysis process, and any combination thereof. In one embodiment, the lignin is wood-based lignin. The lignin can be derived from softwood, hardwood, annual grass, or any combination thereof, and typically, the lignin is not chemically modified after extraction of the lignin.

[0027] As used herein, the term "flash precipitation lignin" should be understood as lignin precipitated from black liquor in a continuous process by using a carbon dioxide-based acidifying agent, preferably carbon dioxide, to lower the pH of the black liquor stream to the precipitation level of lignin under the influence of an overpressure of 200 - 1000 kPa and suddenly releasing the pressure for precipitating the lignin. The method for producing flash precipitation lignin is disclosed in patent application FI20106073. The residence time in the above method is less than 300 s. Flash precipitation lignin particles having a particle size of less than 2 μm form aggregates and can be separated from the black liquor, for example, using filtration. The advantage of flash precipitation lignin is its higher reactivity compared to normal Kraft lignin. Flash precipitation lignin can be purified and / or activated as needed for further processing.

[0028] Lignin may be obtained from an alkaline process. The alkaline process can start by liquefying biomass with strong alkali and then a neutralization process can be carried out. After the alkaline treatment, lignin can be precipitated in the same manner as presented above.

[0029] Lignin may be obtained from steam explosion. Steam explosion is a pulping and extraction technology applicable to wood and other fibrous organic materials.

[0030] As used herein, "biorefinery lignin" is understood to mean lignin that can be recovered from a purification facility or process that converts biomass into fuels, chemicals, and other materials, unless otherwise specified.

[0031] As used herein, "supercritical separation lignin" is understood to mean lignin that can be recovered from biomass using supercritical fluid separation or extraction technology, unless otherwise specified. The supercritical state corresponds to a temperature and pressure above the critical point of a particular substance. In the supercritical state, there is no distinct liquid phase and gas phase. Supercritical water or liquid extraction is a method of decomposing biomass using water or liquid in the supercritical state and converting it into cellulose sugars. The water or liquid functions as a solvent, extracts sugars from cellulose plant materials, and lignin remains as solid particles.

[0032] Lignin may be obtained from a hydrolysis process. Lignin obtained from the hydrolysis process can be recovered from paper pulp or wood chemical processes.

[0033] Lignin may be derived from an organosolv process. Organosolv is a pulping technology that solubilizes lignin and hemicellulose using organic solvents.

[0034] In some embodiments of the present disclosure, the lignin consists of Kraft lignin such as softwood Kraft lignin. In one embodiment, the lignin is softwood Kraft lignin. In some embodiments of the present disclosure, the lignin is a combination of softwood lignin and hardwood lignin, and typically, at most 30 wt%, or at most 25 wt%, or at most 10 wt%, or at most 5 wt% of the lignin is derived from hardwood. In some embodiments of the present disclosure, the lignin consists of EH lignin, and / or the lignin is EH lignin obtained from hardwood.

[0035] As used herein, "Kraft lignin" is understood to be lignin derived from Kraft black liquor, unless otherwise specified. Black liquor is an alkaline aqueous solution of lignin residues, hemicellulose, and inorganic chemicals used in the Kraft pulping process. The black liquor from the pulping process contains components derived from various softwood and hardwood species in various proportions. Lignin can be separated from the black liquor by various techniques such as precipitation and filtration. Lignin typically begins to precipitate at a pH value of less than 11 - 12. Different pH values can be used to precipitate lignin fractions with different properties. These lignin fractions differ from each other in molecular weight distribution (e.g., Mw and Mn), polydispersity, hemicellulose, and extract content. The molar mass of lignin precipitated at a higher pH value is higher than that of lignin precipitated at a lower pH value. Furthermore, the molecular weight distribution of the lignin fraction precipitated at a lower pH value is broader than that of the lignin fraction precipitated at a higher pH value. The precipitated lignin can be purified from inorganic impurities, hemicellulose, and wood extracts using an acid washing step. Further purification can be achieved by filtration.

[0036] As used herein, the term "enzymatic lignin" (EH) should be understood as lignin from the enzymatic hydrolysis process of lignocellulosic biomass. In the enzymatic hydrolysis process, cellulose is hydrolyzed to carbohydrates by enzymes, and the undigested solid residue contains lignin. The lignin can be purified if necessary. EH lignin separated from pure biomass is essentially sulfur-free (sulfur content less than 3%). Preferably, the biomass is pretreated to remove hemicellulose and then the cellulose is hydrolyzed.

[0037] As used herein, the term "dispersion" should be understood as the dispersion formed when lignin is dispersed in water during the preparation of the coating dispersion of the present disclosure.

[0038] In this specification, the term "readily biodegradable" should be understood as a compound that is assumed to be biodegradable, i.e., a compound that degrades rapidly and ultimately (to "mineralization") in the environment. If a compound is considered readily biodegradable, no further investigation is required regarding the potential environmental impact of the chemical substance itself or its transformation products. In other words, compounds that pass the screening tests (e.g., OECD TG 301 B, C, D, F, and 310 with a maximum 60-day duration extension, in accordance with the Annex (Committee for Risk Assessment (RAC), Committee for Socio-economic Analysis (SEAC)) of the Background Document for the Opinion on the Proposal to Limit Intentionally Added Microplastics in December 2020) are considered not to cause serious problems to the metabolic capacity of the aerobic aquatic environment and to be readily decomposed in the actual environment. Furthermore, although some natural polymers such as lignin do not pass all tests of biodegradability criteria, lignin itself is considered to meet the biodegradability criteria because unmodified natural polymers are exempted. Typically, lignin degrades slowly in water and soil (80 - 98 wt%, half-life 1 month - 1 year). For example, Kraft lignin and other "isolated lignins" are also considered natural polymers and are exempted as long as the lignin has not been further chemically modified after being isolated using various extraction processes.

[0039] In this specification, the term "hydrophobic outer layer" should be understood as the outermost layer of a coated fertilizer product having a surface that repels water. The term "hydrophobic" means that the surface repels water and is difficult to wet. Also, generally, hydrophobicity means that the hydrophobic surface is a low-energy surface that repels water. Hydrophobic molecules are usually non-polar, meaning that the atoms constituting the molecule do not generate an electrostatic field. Test methods for detecting the presence of a hydrophobic (non-wetting) film on the surface include visual inspection (appearance), contact angle (static, dip coating on a glass slide), immersion (heating & cooling), temperature & humidity exposure, salt spray / fog for corrosion resistance, refractive index, glass transition temperature (Tg), thermal stability, dielectric strength, dielectric constant, dielectric loss tangent, solder penetration ability, UV exposure, and moisture & insulation resistance (MIR).

[0040] In embodiments of the present disclosure, the coating of the coated fertilizer product and the coating of the coated fertilizer prepared according to the method of the present disclosure are composed of easily biodegradable components and / or natural polymers. This should be understood as not containing microplastics or organic solvents in this specification.

[0041] In this specification, the term "controlled-release fertilizer" should be understood to mean, for example, a granular fertilizer that gradually releases nutrients into the soil during a controlled-release period. Controlled-release fertilizers are also known as slow-release fertilizers.

[0042] In embodiments of the present disclosure, the coating of the coated fertilizer product and the coating of the coated fertilizer prepared according to the method of the present disclosure have an inner layer containing lignin. Typically, this first inner layer further comprises at least one additional biobased polymer that is biodegradable and not lignin, and / or a biodegradable plasticizer. Optionally, the inner layer further comprises one or more substances, such as natural gums, preferably xanthan gum or gellan gum, as stabilizers and / or thickeners. In embodiments of the present disclosure, the biobased polymer typically forms a crosslink around the lignin of the inner layer, and the lignin is trapped or confined within the biobased polymer. Preferably, the biobased polymer, the plasticizer, or both the biobased polymer and the plasticizer are water-soluble.

[0043] In embodiments of the present disclosure, the coating of the coated fertilizer product and the coating of the coated fertilizer prepared according to the method of the present disclosure, in addition to the inner layer, comprise at least one additional layer that is a hydrophobic outer layer, preferably the hydrophobic outer layer is the outermost layer. Typically, the hydrophobic outer layer is an esterified fatty acid, suberin or wax, preferably selected from the group consisting of incombustible oils, suberin or waxes, more preferably the wax is selected from the group consisting of carnauba wax, Biomere (80-130), rice bran wax and candelilla wax, and most preferably the wax is carnauba wax.

[0044] In embodiments of the present disclosure, a coated fertilizer product is provided that includes a fertilizer granule core and a coating. The coating includes an inner layer that includes lignin; at least one additional biobased polymer; and a plasticizer. The coating also includes a hydrophobic outer layer that repels water. The coatings of the present disclosure do not include organic solvents, and the biobased polymers and plasticizers are biodegradable. The lignin is typically not chemically modified, and the outer layer typically includes esterified fatty acids, suberin, and / or waxes. Typically, the biodegradable biobased polymers and / or plasticizers do not include microplastics and are compounds that have passed biodegradability screening tests (e.g., OECD TG 301 B, C, D, F, and 310 with a maximum 60-day extended duration according to the background document of the opinion on Annex XV document proposing restrictions on intentionally added microplastics in December 2020 (Committee for Risk Assessment (RAC), Committee for Socio-economic Analysis (SEAC)) and are natural polymers or natural polymers that have not been chemically modified).

[0045] In a preferred embodiment of the present disclosure, the coating of the coated fertilizer product and the coating of the coated fertilizer prepared according to the method of the present disclosure include at least two different layers, and preferably, the two-layer coating is obtained by a two-layer process according to the method of the present disclosure.

[0046] In embodiments of the present disclosure, the coating of the coated fertilizer product and the coating of the coated fertilizer prepared according to the method of the present disclosure are 1 to 25 wt% of the total weight of the coated fertilizer product, preferably 5 to 20 wt% of the total weight of the coated fertilizer product, more preferably 8 to 16 wt%. The amount of the coating can be between two of the amounts of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, and 25 wt% of the total weight of the coated fertilizer product. The thickness measured by a scanning electron microscope (SEM) is typically in the range of 20 to 225 μm. Since typical fertilizer granules are not perfectly spherical, the thickness varies depending on the shape of a particular granule. Generally, the performance improves as the thickness of the coating increases. Typically, the hydrophobic outer layer forms a smaller (wt%) and / or thinner (μm) portion of the coating.

[0047] In embodiments of the present disclosure, the method for preparing a coated fertilizer comprises a) providing a coating dispersion comprising lignin, at least one additional biobased polymer, and a plasticizer, wherein the lignin is unchemically modified and the biobased polymer and the plasticizer are biodegradable; b) coating the fertilizer granules with the coating dispersion to provide an inner coating layer and obtaining a once-coated fertilizer; c) coating the once-coated fertilizer with an outer layer, and d) obtaining a coated fertilizer, wherein no organic solvent is used during the coating. Typically, the outer layer is hydrophobic.

[0048] In embodiments of the present disclosure, the coating dispersion is prepared from a mixture comprising at least lignin, a biobased polymer, a plasticizer, and water, and the biobased polymer and the plasticizer are biodegradable. Typically, the coating dispersion is prepared by heating a mixture comprising lignin, a biobased polymer, a plasticizer, and water to 70 to 120 °C, or by heating water to 70 to 120 °C and then adding it to a mixture comprising lignin, a biobased polymer, and a plasticizer. The lignin particles of lignin do not dissolve in the mixture but are dispersed. Preferably, the amount of lignin in the coating dispersion is between 5 wt% and 15 wt%, preferably 8 to 10 wt%, the amount of the biobased polymer is between 1 wt% and 10 wt%, preferably 3 to 5 wt%, the amount of the plasticizer in the coating dispersion is between 0.5 wt% and 5 wt%, preferably 0.5 to 2.5 wt%, and the amount of water is between 70 wt% and 93.5 wt%, preferably 77.5 to 86 wt%. Optionally, the mixture further comprises a stabilizer and / or a thickener (natural gum, preferably gellan gum or xanthan gum), and preferably the amount of the stabilizer and / or the thickener is 0.001 to 0.005 wt%, preferably 0.0025 to 0.005 wt%. Typically, the temperature is the boiling point of water, and the temperature depends on the pressure. For example, at 120 °C, the pressure is 2 bar. Preferably, the coating dispersion is prepared by stirring the mixture for 10 minutes to 2 hours, preferably between 10 minutes and 60 minutes, more preferably between 10 minutes and 40 minutes, and most preferably between 15 minutes and 35 minutes, using any conventional mixer or stirrer.

[0049] In embodiments of the present disclosure, the hydrophobic outer layer is typically an esterified fatty acid, suberin, or a wax emulsion, preferably selected from the group consisting of a nonflammable oil, suberin, or a wax emulsion, and more preferably, the wax of the wax emulsion is selected from the group consisting of carnauba wax, Biomere (80 - 130), rice bran wax, and candelilla wax, and most preferably, the wax is carnauba wax.

[0050] In embodiments of the present disclosure, the amount of the coating dispersion sprayed, compared to the fertilizer, is typically from 0.1 to 1 part by weight, preferably from 0.3 to 0.7 part by weight. The amount of the compound sprayed onto the hydrophobic outer layer, preferably the wax emulsion, is typically from 0.05 to 1 part by weight, preferably from 0.1 to 0.25 wt% part by weight.

[0051] In embodiments of the present disclosure, the fertilizer granules are typical commercial products, usually multi-nutrient granular fertilizers in which each granule contains nutrients in the ratios required for a particular application. Typically, the fertilizer is composed of nitrogen, phosphorus, and potassium compounds essential for plant growth.

[0052] In embodiments of the present disclosure, the coating is typically performed by spray coating, preferably by drum, rotary pan or fluidized bed coating, more preferably by fluidized bed coating.

[0053] In embodiments of the present disclosure, the biodegradable biobased polymers used for the coated fertilizer products and the coated fertilizers prepared according to the methods of the present disclosure are typically selected from the group consisting of polyvinyl alcohol (PVOH), polybutylene succinate (PBS), polyhexamethylene succinate (PHS), polyglycolide (PGA), polyhydroxyalkanoate (PHA), polylactide (PLA), polycaprolactone Capa and poly(butylene adipate-co-terephthalate) (PBAT), preferably PVOH.

[0054] In embodiments of the present disclosure, the biodegradable plasticizer used for the coated fertilizer product and the coated fertilizer prepared according to the method of the present disclosure helps to keep the mixture in the form of a dispersion. The biodegradable plasticizer is typically selected from the group consisting of polyethylene glycol (PEG), propylene carbonate, epoxidized cardanol, acetylated castor oil, methyl epoxidized soyate, dibutyl phthalate, and triethyl citrate, and preferably polyethylene glycol 6000 (PEG 6000).

[0055] In embodiments of the present disclosure, the coated fertilizer product and the coated fertilizer prepared according to the method of the present disclosure are controlled-release fertilizer products, and preferably the controlled-release period of the controlled-release fertilizer product is more than 4 days, preferably more than 30 days, more preferably more than 3 months, and most preferably more than 6 months. Typically, the release rate of the controlled-release fertilizer product after 96 hours at 23 °C and 50% relative humidity is less than 8 mS / cm, preferably less than 6 mS / cm, more preferably 4 mS / cm. Typically, the weight loss of the controlled-release fertilizer product after 96 hours is less than 40 wt% of the total dry matter, preferably less than 20 wt%, more preferably less than 18 wt%, and most preferably less than 15 wt%.

Example

[0056] Example 1 Preparation of lignin coating The one-pot method was applied to the preparation of the formulation.

[0057] An appropriate amount of lignin (KL, Kraft lignin powder (80 - 98 wt%), pH 2.5 - 4.5 (10% solution) or EH, enzyme hydrolyzed lignin), PEG6000 (solubility at 20°C = 1.2 g / mL; aerobic biodegradability - exposure time 28d, result: 74, 85% - easily biodegradable. (OECD Test Guideline 301D)), PVOH (Exceval, biodegradable, purity > 94%; solubility = 10 - 99%), xanthan gum and optionally wax (anionic carnauba wax) were mixed in the dry state and then poured into excess water at 100°C with continuous stirring. The weight ratio of lignin:PEG:PVOH was 1:0.25:0.5 (200 g:50 g:100 g). Further, xanthan gum was added at a ratio of 0.025 (EHNM(15), and EHNM + CW) or 0.05 (KLNM_2X(15) and KLNM_2X + CW), and wax was added at a ratio of 0.5 to some of the mixtures (EHNM + CW and KLNM_2X + CW). There was about 100 g of excess water to compensate for evaporation during mixing. Stirring was continued for about 30 minutes to ensure dissolution of soluble compounds and formation of a homogeneous mixture.

[0058] The characteristics of the coating and the coated fertilizer are listed in Table 1.

[0059]

Table 1

[0060] Here, the coatings in Table 1 have the following characteristics: CW_1 = single - layer coating, wax only EHNM(15) = single - layer coating, containing enzyme hydrolyzed lignin KLNM_2X(15) = single - layer coating, containing Kraft lignin EHNM + CW = single - layer coating, containing enzyme hydrolyzed lignin and wax KLNM_2X + CW = single - layer coating, containing Kraft lignin and wax CW_KLNM_2X = Two-layer coating: inner layer KLNM_2X, outer layer wax CW_EHNM(15) = Two-layer coating: inner layer EHNM(15), outer layer wax

[0061] The coating dispersion was fed into a fluidized bed coater (Neuhaus Neotec Laboratory Fluid Bed Center LFB) for coating of fertilizer granules.

[0062] The fertilizer granules used in this example were commercially available multi-nutrient fertilizer granules.

[0063] The two-step coating was achieved by feeding 10 wt% anionic carnauba emulsion (25% solids content; pH = 10; viscosity (23 °C) = 150 mPa·s) into a fluidized bed coater (Neuhaus Neotec Laboratory Fluid Bed Center LFB) for coating of fertilizer granules already coated with a coating dispersion containing lignin (EHNM(15) and KLNM_2x(15)).

[0064] Slow-release behavior in H2O The slow-release behavior of the coating was analyzed by placing 1 g of uncoated fertilizer granules (REF) and different coated fertilizer granules in 100 mL of H2O. The samples were stored in a room conditioned to 23 °C and 50% relative humidity. The water dissolution method was used for the evaluation of release control. The conductivity of the granule-H2O solution was measured according to standard SFS-EN 27888 (1994). The weight loss was calculated over 4 days by removing the liquid, drying the solids at 60 °C for 12 h, and then measuring the weight.

[0065] Figure 1 shows the conductivity as a function of time for selected samples in water over 4 days (96 h). The release rates of the two-stage coating granules (named CW_KLNM_2X and CW_EHNM(15)) were compared with those of the uncoated fertilizer-containing sample (named REF), the single-layer coatings without wax (named EHNM(15) and KLNM_2x(15)), the single-layer coatings with a mixture containing wax (named EHNM+CW and KLNM_2X+CW), the single-layer coating containing only wax (named CW_1), and a commercially available polyethylene fertilizer coating (named Poligen).

[0066] As can be seen from Figure 1, the release rates (conductivity versus time) of the two-stage coatings (CW_KLNM_2X and CW_EHNM(15)) indicate that the release rate of ions from the fertilizer granules is significantly improved compared to the reference sample and any of the single-layer coatings. No significant decrease in the release rate was shown for the single-layer coatings. The release rates of the single-layer coatings using EH or KL lignin (EHNM(15) and KLNM_2x(15)), or the single-layer coatings using a mixture of KL or EH lignin and carnauba wax (EHNM+CW and KLNM_2X+CW) showed only a slight improvement in the release rate compared to the uncoated reference fertilizer (REF). After 24 h, the release rate of the wax-only (CW_1) was also equivalent to that of the other single-layer coated fertilizers. The results obtained with the two-layer coating were equivalent to those of the commercially graded polyethylene fertilizer coating (Poligen).

[0067] Figure 2 shows the remaining relative dry matter of several samples after 4 days (96 h) in water. The weight loss of the coated fertilizers was correlated with the results obtained from the conductivity measurements.

[0068] Ions present in the solution were identified using ICP-MS (Inductively Coupled Plasma Mass Spectroscopy). As can be seen from Table 2, the results from ICP-MS, particularly for potassium and phosphorus, correlate with the results obtained from both conductivity measurements and weight loss measurements.

[0069]

Table 2

[0070] Further tests (not described above) showed that the conductivity of samples having a first layer of wax and a second layer of a coating dispersion containing lignin was equivalent to that of a single-layer coating with wax only.

[0071] Morphology & Thickness Analysis Scanning electron microscopy (SEM) and stereomicroscopy were used for morphology analysis. The thickness of the coating layer was estimated using SEM. Three grains were randomly selected and analyzed for morphology using SEM and stereomicroscopy. A rough estimate of the thickness was made by cutting the grains in half, fixing them to the support, and analyzing them with SEM.

[0072] The thickness of the single-layer coating containing wax varied between 86 μm and 132 μm, and the thickness of the two-layer coating varied between 102 μm and 142 μm.

Claims

1. A coated fertilizer product comprising a fertilizer granule core and a coating, wherein the coating comprises an inner layer and an outer layer containing lignin; a bio-based polymer; and a plasticizer, and the coating is characterized in that it does not contain organic solvents, the bio-based polymer and plasticizer are biodegradable, the lignin is not chemically modified, and the outer layer is hydrophobic.

2. The product according to claim 1, wherein the coated fertilizer product is a release-controlled fertilizer product, and preferably the release-controlled period of the coated fertilizer product is more than 4 days, preferably more than 30 days, more preferably more than 3 months, and most preferably more than 6 months.

3. The product according to claim 1, characterized in that the bio-based polymer forms crosslinks around the lignin in the inner layer.

4. The product according to claim 1, characterized in that the bio-based polymer is water-soluble.

5. The product according to claim 1, characterized in that the plasticizer is water-soluble.

6. The product according to claim 1, characterized in that the outer layer is an esterified fatty acid, suberin, or wax, preferably selected from the group consisting of non-flammable oil, suberin, or wax, more preferably the wax is selected from the group consisting of carnauba wax, rice bran wax, and candelilla wax, and most preferably the wax is carnauba wax.

7. The product according to claim 1, characterized in that the coating is 1 to 25 wt%, preferably 5 to 20 wt%, and more preferably 8 to 16 wt%, of the total weight of the coated fertilizer product.

8. The product according to claim 1, characterized in that the release rate of the release-controlled fertilizer product is less than 8 mS / cm, preferably less than 6 mS / cm, and more preferably less than 4 mS / cm after 96 hours at 23°C and 50% relative humidity.

9. The product according to claim 1, characterized in that the weight loss of the coated fertilizer product is less than 40 wt%, preferably less than 20 wt%, more preferably less than 18 wt%, and most preferably less than 15 wt% of the total dry matter after 96 hours.

10. A method for preparing coated fertilizer, the method is: a) To provide a coating dispersion containing lignin, a bio-based polymer, and a plasticizer, wherein the lignin is not chemically modified, and the bio-based polymer and plasticizer are biodegradable; b) Coating fertilizer granules with a coating dispersion to provide a coating inner layer and obtain a single-layer coated fertilizer; c) Coating a single-layer coated fertilizer with a hydrophobic outer layer, and d) Obtain coated fertilizer, A method characterized by containing and not using organic solvents.

11. The method according to claim 10, characterized in that the coating dispersion is prepared by heating a mixture containing lignin, a bio-based polymer, a plasticizer, and water to 70°C to 120°C, or by heating water to 70°C to 120°C and then adding it to a mixture containing lignin, a bio-based polymer, a plasticizer, and optionally a stabilizer and / or a thickener.

12. The method according to claim 11, characterized in that the mixture is mixed for 10 minutes to 2 hours, preferably between 10 minutes and 60 minutes, more preferably between 10 minutes and 40 minutes, and most preferably between 15 minutes and 35 minutes.

13. The method according to claim 11, characterized in that the lignin content of the coating dispersion is between 5 wt% and 15 wt%, preferably 8 to 10% by weight, the bio-based polymer content is between 1 wt% and 10 wt%, preferably 3 to 5 wt%, the plasticizer content is between 0.5 wt% and 5 wt%, preferably 0.5 wt% to 2.5 wt%, and the water content is between 70 wt% and 93.5 wt%, preferably 77.5 to 86 wt%.

14. The method according to claim 10, characterized in that the coating is a spray coating, preferably a drum, rotary pan, or fluidized bed coating, more preferably a fluidized bed coating.

15. The method according to claim 10, wherein the outer layer is an esterified fatty acid, suberin, or wax emulsion, preferably selected from the group consisting of non-flammable oil, suberin, or wax emulsion, more preferably the wax emulsion wax is selected from the group consisting of carnauba wax, biomeres (80-130), rice bran wax, and candelilla wax, and most preferably the wax is carnauba wax.

16. The product according to claim 1, characterized in that the bio-based polymer is selected from the group consisting of polyvinyl alcohol (PVOH), polybutylene succinate (PBS), polyhexamethylene succinate (PHS), polyglycolide (PGA), polyhydroxyalkanoate (PHA), polylactide (PLA), polycaprolactone Capa, and poly(butylene adipate-co-terephthalate) (PBAT), and is preferably PVOH.

17. The product according to claim 1, characterized in that the plasticizer is selected from the group consisting of polyethylene glycol (PEG), propylene carbonate, epoxidized cardanol, acetylated castor oil, methyl epoxy soyate (soyate), dibutyl phthalate, and triethyl citrate, and preferably polyethylene glycol 6000 (PEG 6000).

18. The product according to claim 1, characterized in that the biodegradable bio-based polymer and / or plasticizer is a compound that has passed the screening tests of OECD TG 301 B, C, D, F and 310 with a maximum duration extension of 60 days, in accordance with the Annex to the Background Document of the Opinion on the December 2020 Annex XV Document Proposing Restrictions on Intentionally Added Microplastics (Committee for Risk Assessment (RAC), Committee for Socio-economic Analysis (SEAC)), and is a natural polymer or an unmodified natural polymer.

19. The method according to claim 10, characterized in that the bio-based polymer is selected from the group consisting of polyvinyl alcohol (PVOH), polybutylene succinate (PBS), polyhexamethylene succinate (PHS), polyglycolide (PGA), polyhydroxyalkanoate (PHA), polylactide (PLA), polycaprolactone Capa, and poly(butylene adipate-co-terephthalate) (PBAT), and is preferably PVOH.

20. The method according to claim 10, characterized in that the plasticizer is selected from the group consisting of polyethylene glycol (PEG), propylene carbonate, epoxidized cardanol, acetylated castor oil, methyl epoxy soyate, dibutyl phthalate, and triethyl citrate, and preferably polyethylene glycol 6000 (PEG 6000).

21. The method according to claim 10, characterized in that the biodegradable bio-based polymer and / or plasticizer is a compound that has passed the screening tests of OECD TG 301 B, C, D, F and 310 with a maximum duration extension of 60 days, in accordance with the Annex to the Background Document of the Opinion on the December 2020 Annex XV Document Proposing Restrictions on Intentionally Added Microplastics (Committee for Risk Assessment (RAC), Committee for Socio-economic Analysis (SEAC)), and is a natural polymer or an unmodified natural polymer.

22. Use of the product of claim 1 or a product prepared by the method of claim 10 for controlling nutrient release in agriculture, preferably in turf, crop cultivation, greenhouse agriculture and / or ornamental horticulture.

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