Polyurethane coated fertilizers

Abstract

The present invention relates to polyurethane coated fertilizers, uses and production methods thereof.

Description

[0001] POLYURETHANE COATED FERTILIZERS

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to polyurethane coated fertilizers, uses and production methods thereof.

[0004] BACKGROUND

[0005] Fertilizers are important materials of synthetic or natural origin used to supply essential nutrients in growing media. Farmers apply these fertilizers in a variety of ways such as in the form of pellets or a liquid composition. Moreover, fertilizers can be classified based on whether they provide a single nutrient such as nitrogen (N), phosphorus (P), or potassium (K) or provide multiple nutrients. To avoid the immediate release of the nutrients in the environment, they are typically encapsulated in a synthetic or plastic material. However, while essential to the global food system and agriculture, the use of fertilizer also has some important environmental consequences. Accordingly, a need exists for alternative encapsulation material that provides more sustainable fertilizer compositions that are more efficient and reduce potential pollution.

[0006] SUMMARY OF THE INVENTION

[0007] A first overview of various aspects of the technology of the present disclosure is given hereinbelow, after which specific embodiments will be described in more detail. This overview is meant to aid the reader in understanding the technological concepts more quickly, but it is not meant to identify the most important or essential features thereof, nor is it meant to limit the scope of the present disclosure, which is limited only by the claims.

[0008] A first aspect of the invention relates to a coated fertilizer composition comprising fertilizer particles coated with at least one polymer coating layer, wherein the polymer coating layer comprises an isocyanate and a modified polyol, and wherein the modified polyol comprises a polyacetal.

[0009] In particular, the coated fertilizer composition as disclosed herein, wherein said polymer coating layer essentially consists of a polyurethane composition comprising polyacetal, polyols and isocyanates.

[0010] In a particular embodiment, the coated fertilizer composition as disclosed herein, wherein said polymer coating layer comprises between 1.0 and 35.0 wt% of polyacetal, between 15.0 and 44.0 wt% of polyols and between 31.0 and 74.0 wt% of isocyanates, preferably between 1.0 and 25.0 wt% of polyacetal, between 25.0 and 44.0 wt% of polyols and between 31.0 and 74.0 wt% of isocyanates, preferably between 5.0 and 20 wt% of polyacetal, between 37.5 and 52.5 wt% of polyols and between 42.5 and 57.5 wt% of isocyanates, more preferably between 7.5 and 12.5 wt% polyacetal, between 35.0 and 45.0 wt% of polyols and between 47.5 and 52.5 wt% of isocyanates. In a particular embodiment, the coated fertilizer composition as disclosed herein, wherein the isocyanate comprises any one of hexamethylene diisocyanate (HDI), isophorone diisocyanate ( I PD I), toluene diisocyanate (TDI) or methylene diphenyl diisocyanate (MDI), including any isomeric, oligomeric, monomeric, or polymeric forms thereof, preferably MDI, including any isomeric, oligomeric, monomeric, or polymeric forms thereof.

[0011] In a particular embodiment, the coated fertilizer composition as disclosed herein, wherein said modified polyol further comprises an aromatic polyester polyol, a polyether polyol, an acrylic polyol and / or a phenolic resin polyol.

[0012] In a particular embodiment, the coated fertilizer composition as disclosed herein, wherein said fertilizer particles comprise macronutrients chosen from urea, nitrogen, potassium, phosphorus, sulphur or combinations thereof.

[0013] In a particular embodiment, the coated fertilizer composition as disclosed herein, wherein said fertilizer particles comprise micronutrients chosen from magnesium (Mg), iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), boron (B), molybdenum (Mo), chlorine (Cl), cobalt (Co), nickel (Ni), selenium (Se), vanadium (V), silicon (Si) or combinations thereof.

[0014] In a particular embodiment, the coated fertilizer composition as disclosed herein, wherein said fertilizer particles are characterized by having an average diameter between about 0.5 and about 10.0 mm, preferably between about 1.0 and about 5.0 mm. In a particular embodiment, the coated fertilizer composition as disclosed herein, wherein said polyacetal is a polycycloacetal.

[0015] In a particular embodiment, the coated fertilizer composition as disclosed herein, wherein said at least one polymer coating layer provides controlled release properties with a release of between 40.0 % and 90.0 % nutrient in 40 hours, preferably between 60.0 % and 90.0 % nutrient in 30 hours, more preferably between 75.0 % and 90.0 % nutrient in 20 hours under boiling water conditions; with % based on the total nutrient content comprised in the coated fertilizer composition; and preferably measured according to according to EN13266:2001.ln a particular embodiment, the coated fertilizer composition as disclosed herein, wherein the at least one polymer coating layer has a bench stability of at least 2 months, preferably at least 4 months, more preferably at least 8 months, and more preferably at least 16 months.

[0016] In a particular embodiment, the coated fertilizer composition as disclosed herein, wherein the at least one polymer coating layer comprises an amount between about 1.0 and 20.0 wt%, preferably between about 2.5 and 10.0 wt%, and most preferably between about 5.0 and 10.0 wt%, based on the total weight of the coated fertilizer composition.

[0017] In another aspect, the present invention relates to a process for preparing a coated fertilizer composition as disclosed herein, wherein the process comprises the steps of: a. contacting a polyacetal with a polyol to obtain a modified polyol; b. contacting a particulate fertilizer with a mixture comprising the modified polyol and an isocyanate to obtain a coated particulate fertilizer; and c. curing of the coated particulate fertilizer to obtain the coated fertilizer with at least one polymer coating layer.

[0018] In a particular embodiment, the process for preparing a coated fertilizer composition as disclosed herein, wherein curing of the coated particulate fertilizer involves the addition of a catalyst, and preferably wherein said catalyst is an amine, a metal, or a mixture thereof.

[0019] In a particular embodiment, the process for preparing a coated fertilizer composition as disclosed herein, wherein the particulate fertilizer is preheated to at least 45.0 °C, preferably at least 55.0 °C, and more preferably at least 65.0 °C; and preferably wherein 1 to 15 coating cycles are carried out by repeating step a) to c) of the process as disclosed herein.

[0020] DETAILED DESCRIPTION

[0021] In the following detailed description, the technology underlying the present disclosure will be described by means of different aspects thereof. It will be readily understood that the aspects of the present disclosure, as generally described herein, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and make part of this disclosure. This description is meant to aid the reader in understanding the technological concepts more easily, but it is not meant to limit the scope of the present disclosure, which is limited only by the claims.

[0022] As used herein, the singular forms "a", "an", and "the" include both singular and plural referents unless the context clearly dictates otherwise.

[0023] The terms "comprising", "comprises" and "comprised of" as used herein are synonymous with "including", "includes", "containing", or "contains", and are inclusive or open-ended and do not exclude additional, non-recited members, elements or method steps. The terms also encompass "constituted of", "consists in", "consisting of", and "consists of", and also the terms "consisting essentially of", "consisting essentially in" and "consists essentially of", which enjoy well-established meanings in patent terminology.

[0024] The recitation of numerical ranges by endpoints includes all integer numbers and, where appropriate, fractions subsumed within the respective ranges, as well as the recited endpoints. This applies to numerical ranges irrespective of whether they are introduced by the expression "from... to..." or the expression "between... and..." or another expression. Any numerical range recited herein is intended to include all sub-ranges subsumed therein.

[0025] The terms "about" or "approximately" as used herein when referring to a measurable value such as a parameter, an amount, a temporal duration, and the like, are meant to encompass variations of and from the specified value, such as variations of + / -10% or less, preferably + / -5% or less, more preferably + / -1% or less, and still more preferably + / -0.1% or less of and from the specified value, insofar such variations are appropriate to perform in the disclosed invention. It is to be understood that the value to which the modifier "about" or "approximately" refers is itself also specifically, and preferably, disclosed.

[0026] Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order, unless specified. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein. Whereas the terms "one or more" or "at least one", such as one or more members or at least one member of a group of members, is clear per se, by means of further exemplification, the term encompasses inter alia a reference to any one of said members, or to any two or more of said members, such as, e.g., any >3, >4, >5, >6 or >7 etc. of said members, and up to all said members. In another example, "one or more" or "at least one" may refer to 1, 2, 3, 4, 5, 6, 7 or more.

[0027] As used herein, the term "and / or" when used in a list of two or more items, means that any one of the listed items can be employed by itself or any combination of two or more of the listed items can be employed. For example, if a list is described as comprising group A, B, and / or C, the list can comprise A alone, B alone, C alone, A and B in combination, A and C in combination, B and C in combination, or A, B, and C in combination.

[0028] As used throughout the present disclosure, the terms "wt%" or "weight %" or "% VJ / VJ" or "% by weight" are used interchangeably and refer to the weight concentration of a constituent, i.e. the weight of a constituent divided by the total weight of all constituents.

[0029] The discussion of the background to the invention herein is included to explain the context of the invention. This is not to be taken as an admission that any of the material referred to was published, known, or part of the common general knowledge in any country as of the priority date of any of the claims.

[0030] Unless otherwise defined, all terms used in disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, term definitions are included to better appreciate the teaching of the invention. When specific terms are defined in connection with a particular aspect of the invention or a particular embodiment of the invention, such connotation or meaning is meant to apply throughout this specification, i.e., also in the context of other aspects or embodiments of the invention, unless otherwise defined. In the following passages, different aspects or embodiments of the invention are defined in more detail. Each aspect or embodiment so defined may be combined with any other aspect(s) or embodiment(s) unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.

[0031] Reference throughout this specification to "one embodiment", "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to a person skilled in the art from this disclosure, in one or more embodiments. Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the appended claims, any of the claimed embodiments can be used in any combination.

[0032] Similarly, it should be appreciated that in the description of illustrative embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects.

[0033] In one or more aspects, the present invention relates to coated fertilizer compositions; in particular comprising a polymer coating layer wherein the polymer coating layer comprises an isocyanate, and a modified polyol. For the purposes of the present invention, coating a fertilizer involves protecting a granule or particle which contains nutrients with a polymeric barrier coating. The polymeric barrier coating comprises at least one polymeric coating layer.

[0034] The modified polyol as disclosed herein comprises a polyacetal, which provides the polymer coating layer with at least improved (bio)degradability. As a result, it was surprisingly found by the inventors that incorporation of polyacetals into the polymer coating layer aids in degrading said barrier coating, which is in contrast to existing polymeric coatings used in the state of the art. Moreover, despite the improved degradability, polymer coating layer(s) comprising the polyacetal still offer controlled release of the fertilizer particles. Upon release or exposure of the fertilizer particles to the environment (e.g. soil conditions), active nutrients are supplied which may improve soil fertility. One desirable attribute of the coated fertilizer composition as described herein is that the release of nutrients may occur under a defined period of time such as hours, days, weeks, or months. The desired release rate of the nutrients to the soil may be optimized towards the specific application; i.e. towards wishes, norms and values in the market environment.

[0035] As used throughout the present disclosure, the terms "polymeric materials" or "polymeric" or "material" or "polymer article" are used interchangeably and refer to organic materials consisting of multiple repeating subunits or monomers, typically created via a polymerization process. Polymeric materials are further optimized to become functional plastic materials by so-called compounding steps: often a customized set of additives and fillers is combined with specific processing conditions to result in a functional plastic article. Additives can be colorants, chemical stabilizers such as antioxidants, process stabilizing agents, nucleating agents or lubricants. Fillers can typically be inorganic salts or (micro)crystalline materials. Processing steps generally rely on extrusion equipment, injection moulding, or additive manufacturing methods. Resulting functionalities are optimized towards the specific application; i.e. towards wishes, norms and values in the market environment.

[0036] The term "(bio)degradation" as used herein refers to the process of (biologically) disintegrating materials by microorganisms, such as bacteria, fungi, or other biological means. Accordingly, a "(bio)degradable material" is a material that can be (biologically) disintegrated by microorganisms in a period of time, such as hours, days or weeks. The (bio)degradability of a material may be primarily determined by the presence of specific enzymes produced by the present microbial community that are capable of endo- or exo-cleaving of the polymeric backbones in the respective polymeric material. The biodegradability of a material can thereby be affected by a number of secondary factors that optimize the degradative capabilities by the present microbial community, such as temperature, pH, water and oxygen. Additionally, auxiliary factors may also influence the biodegradation, which can be intrinsic to the material itself such as crystallinity, surface roughness and bioavailability of polymeric chains or their released fragments, or be dependent on environmental conditions impacting the nature of the material such as light intensity and mechanical wear, such as (oceanic) waving or shaking. In some embodiments the degradability is related to the degradability of a polymeric material in an aqueous (marine) environment.

[0037] In a first aspect, the present invention relates to a coated fertilizer composition comprising fertilizer particles coated with at least one polymer coating layer, wherein the polymer coating layer comprises an isocyanate and a modified polyol, wherein the modified polyol comprises a polyacetal. The coated fertilizer as defined herein further has the (end-of-life) advantage that, at least partially, said polymer coating is compostable (i.e. biodegradable) according to European norm EN13432, or is chemically recyclable.

[0038] Without being bound by any theory, the polymers can thus be degraded biologically (i.e. composted) into water and carbon dioxide or chemically recycled into their corresponding monomers. Hence, by including a polyacetal monomer, it has been found that it is possible to provide a coated fertilizer composition that overcomes at least some of the drawbacks of the prior art. Moreover, the coated fertilizer may be water-soluble.

[0039] As regards biodegradation in soils, polymer coating layers which can reach about 90% relative degradation or mineralization within 48 months after a functionality period of 1 to 6 months at 25 °C are desirable. The "functionality period" (FP) as referred to herein is a use period of the coated fertilizer composition wherein slow degradation of the coating layer is preferred to have a more gradual release of nutrients into the environment. After said period, degradation relative to a reference follows an exponential decay. For functionality periods between 1 and 6 months, a desirable target degradation after 12 months is at least about 25 % for a FP of 6 months or at least about 40 % for a FP of 1 month. In practice, accelerated testing (e.g., at 37 °C) can be used as an alternative option to demonstrate degradation or mineralization.

[0040] In a particular embodiment, the fertilizer particles as disclosed herein can be any granular fertilizer comprising macronutrients chosen from urea, nitrogen, potassium, phosphorus, sulphur or combinations thereof. However, the choice of particulate plant nutrient material useful for the present invention is not to be restricted. As will be apparent to one skilled in the art, other nutrients, including primary nutrients, secondary nutrients and micronutrients, can be used to prepare the coated fertilizer compositions in accordance with the present invention.

[0041] In a particular embodiment, the fertilizer particles as disclosed herein may comprise micronutrients chosen from magnesium (Mg), iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), boron (B), molybdenum (Mo), chlorine (Cl), cobalt (Co), nickel (Ni), selenium (Se), vanadium (V), silicon (Si) or combinations thereof.

[0042] Said fertilizer particles are further characterized by having an average diameter between about 0.5 and about 10.0 mm, preferably between about 1.0 and about 5.0 mm; and preferably determined via Dynamic Light Scattering (DLS) according to ISO 22412:2017.

[0043] In some preferred embodiments, the fertilizer particles comprise a major portion of the coated fertilizer composition with average weight values between about 80.0 wt% and 99.0 wt%, more preferably between about 95.0 wt% to 98.5 wt%, and most preferably between about 96.0 wt% to 98.0 wt%, of the coated fertilizer composition. Advantageously, the polymeric or plastic coating layer comprises only a small portion of the coated fertilizer composition which may result in a more ecologically- and economically-friendly fertilizer. Moreover, release of plant nutrients can be more efficiently controlled to have a long lasting supply of active plant nutrients to the soil.

[0044] The at least one polymer coating layer encapsulates the fertilizer particles and may act as a protective barrier layer for any external environment or growing media. The thickness of the at least one polymer coating layer may vary and may be about 10 to 50 micron, preferably about 20 to 50 micron, more preferably about 20 to 30 micron. A thicker polymer coating layer may decrease the bioavailability of the coated fertilizer particles. As a result, disintegration of the polymer coating may take a longer period of time and release of nutrients to the soil is delayed.

[0045] The amount and number of polymer coating layer(s) relative to the fertilizer particles may vary depending on the required release and longevity. To that end, several coating cycles may be carried out to provide 1 to 15 polymer coating layers. In some embodiments, one or more polymer coating layers may comprise compounds other than polyacetal, polyols and isocyanates . For instance, the coated fertilizer composition may comprise one or more polymeric coating layers essentially consisting of a polyurethane composition comprising polyacetal, polyols and isocyanates and one or more polymeric coating layers essentially consisting of a polyurethane composition comprising polyols and isocyanates. An increased number of coating layers may decrease the bioavailability of the coated fertilizer particles. As a result, disintegration of the polymer coating may take a longer period of time and release of nutrients to the soil is delayed. In preferred embodiments, the at least one polymer coating layer comprises an amount between about 1.0 and 20.0 wt%, preferably between about 2.5 and 10.0 wt%, and most preferably between about 5.0 and 10.0 wt%, based on the total weight of the coated fertilizer composition.

[0046] The performance of the coated fertilizer as disclosed herein was measured by the weight percentage of nutrient release, based on the initial weight percentage of coated fertilizer, from the fertilizer particles when contacted with boiling water or soil conditions. More release may probably indicate faster degradation of the polymer coating layer(s). In a boiling water test (according to EN13266:2001) the coated fertilizer exhibits the following release properties: release of between 40.0 wt% and 90.0 wt% nutrient in 40 hours, between 60.0 wt% and 90.0 wt% nutrient in 40 hours, preferably between 75.0 wt% and 90.0 wt% nutrient in 40 hours, between 40.0 wt% and 90.0 wt% nutrient in 30 hours, between 60.0 wt% and 90.0 wt% nutrient in 30 hours, preferably between 75.0 wt% and 90.0 wt% nutrient in 30 hours, between 40.0 wt% and 90.0 wt% nutrient in 20 hours, between 60.0 wt% and 90.0 wt% nutrient in 20 hours, and preferably between 75.0 wt% and 90.0 wt% nutrient in 20 hours. As a result, the release of plant nutrients can be faster or slower depending on the applied conditions. In some embodiments, the polymeric coating layer(s) may be degraded for at least for 80 wt%, based on the total wt% of the 1 to 15 polymeric coating layers, under soil conditions after at least 8 months, after at least 12 months, after at least 24 months; preferably after at least 48 months. In other embodiments, the polymeric coating layer(s) may be degraded for at least 90 wt%, based on the total wt% of the 1 to 15 polymeric coating layers, under soil conditions after at least 8 months, after at least 12 months, after at least 24 months ; preferably after at least 48 months. As a result, the polymeric coating layer(s) can be degraded in the environment within a defined period of time without requiring additives or additional processing steps.

[0047] The polyurethane used to produce the at least one polymer coating layer according to the various embodiments of the present invention is obtained by mixing a composition comprising polyacetal, polyols and isocyanates. In particular, the polymer coating essentially consists of a polyurethane composition comprising polyacetal, polyols and isocyanates.

[0048] The polyacetal as used herein refers to a prepolymer or oligomer containing two or more hydroxyl groups (-OH) and acetal repeating units in the backbone. The hydroxyl functionality makes the polyacetal suitable for reaction with an isocyanate. In the simplest case, acetals are obtained from the condensation reaction of the carbonyl (i.e. aldehyde or ketone) with two hydroxyl groups. In some preferred embodiments, the weight average molecular weight (Mw) of the polyacetal comprises from 200 to 5000 g / mol, 500 to 2500 g / mol, 500 to 1500 g / mol, or 750 to 1000 g / mol. Polyacetal prepolymers or oligomers within Mwrange as discussed herein allow mixing and dissolving of the polyacetal with isocyanates, and optionally a polyol, for polyurethane formation. Shorter polyacetal prepolymers or oligomers provide control over properties such as crystallinity and rigidity, which allows to optimize the rate of polyurethane degradation. The term "polycycloacetal" as used herein refers to a polyacetal comprising at least one cyclic acetal or cyclic ketal functional group in the polymer backbone. In particular embodiments, the polyacetal as disclosed herein is a polycycloacetal. Polycycloacetals as used herein refer to a prepolymer or oligomer containing two or more hydroxyl groups (-OH) and cylcloacetal repeating units in the backbone. The present inventors have found that polycycloacetals can control the rate of biodegradation more efficiently than linear polyacetal alternatives.

[0049] In particular embodiments, the polyacetal comprised in the modified polyol as disclosed herein is a polymer or oligomer resulting from the condensation of an aldehyde or ketone monomer and an alcohol; and preferably wherein the aldehyde or ketone monomer is selected from the group consisting of: glyoxal, methyl-glyoxal, malonic dialdehyde, succinic dialdehyde, glutaraldehyde, 2,3- pentanedione, 2,4-pentanedione, 2,3-hexanedione, 2,4-hexanedione, 2,5-hexanedione, 3,4- hexanedione, 2-methyl malonic dialdehyde, 2-methyl succinic dialdehyde, 2,3-dimethyl succinic dialdehyde, 2,3-cyclopentanedione, 1,3-cyclopentanedione, 2-methyl-l,3-cyclopentanedione, 1,2- cyclohexanedione, 1,3-cyclohexanedione, 1,4-cyclohexanedione, 2-methyl-l,4-cyclohexanedione, phthalaldehyde, isophthalaldehyde, terephthalaldehyde, homophthalaldehyde, l-phenyl-1,2- propanedione, digoxin, glucosone, 3-deoxyglucosone, 4-deoxyglucodiulose, 1,4- dideoxyglucodiulose, dihydroxyacetone, glyceraldehyde, threose, erythrose, lyxose, xylose, arabinose, ribose, talose, idose, galactose, sorbose, gulose, glucose, mannose, allose, altrose, sedoheptulose, and mixtures thereof. Preferably, the alcohol is a monomer selected from the group consisting of: glucosone, 3-deoxyglucosone, 4-deoxyglucodiulose, 1,4-dideoxyglucodiulose, dihydroxyacetone, glyceraldehyde, threose, erythrose, lyxose, xylose, arabinose, ribose, talose, idose, galactose, sorbose, gulose, glucose, mannose, allose, altrose, sedoheptulose, glycerol, D- threitol, pentaerythreitol, ribitol, sorbitol, trimethylolpropane, trimethylolbutane, trimethylolpentane, trimethylolhexane, and mixtures thereof.

[0050] The term "prepolymer" as used herein refers to a system of monomers that have been reacted to intermediate molecular mass or a polymer capable of entering into further polymerization or curing through its reactive groups. Reactive groups may be positioned at the chain-end or side chain. In the context of the present invention, a prepolymer or oligomer contains at least two functional groups capable of interacting with another reactive molecule.

[0051] The polyol as used herein refers to a prepolymer or oligomer containing two or more hydroxyl groups (-OH). The modified polyol in the coated fertilizer composition as disclosed herein comprises a polyol and a polyacetal. Depending on the desired mechanical properties of the polyurethane, polyols with different backbone structures are used. Suitable polyols may encompass polyether polyol, polyester polyol, acrylic polyol and / or phenolic resin polyol.

[0052] In some embodiments, examples of suitable polyether polyol may include polyoxyethylene polyols or polyoxypropylene polyols. Polyoxyethylene polyol or polyoxypropylene polyol herein refers to polyols that are polymerized products of ethylene oxide or propylene oxide. Suitable commercially available polyoxypropylene polyols include, for example, VORANOL and SPECFLEX available from The Dow Chemical Company.

[0053] In some embodiments, examples of suitable polyester polyol may include reaction products of polycarboxylic acids or their anhydrides with polyhydric alcohols. The polycarboxylic acids or their anhydrides may be aliphatic, cycloaliphatic, aromatic and / or heterocyclic. Examples of suitable polycarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, maleic acid, fumaric acid, glutaconic acid, a- hydromuconic acid, p-hydromuconic acid, a-butyl-a-ethyl-glutaric acid, a,p-diethylsuccinic acid, isophthalic acid, terephthalic acid, hemimellitic acid, 1,4-cyclohexane-dicarboxylic acid, or mixtures thereof. Examples of suitable polyhydric alcohols include ethylene glycol, 1,3-propylene glycol, 1,2- propylene glycol, 1,4-butylene glycol, 1,3-butylene glycol, 1,2-butylene glycol, 1,5-pentane diol, 1,4- pentane diol, 1,3-pentane diol, 1,6-hexane diol, 1,8-octane diol, neopentyl glycol, cyclohexane dimethanol, 1,7-heptane diol, glycerol, 1,1,1-trimethylolpropane, 1,1,1-trimethylolethane, hexane- 1,2,6-triol, a-methyl glucoside, pentaerythritol, quinitol, mannitol, sorbitol, sucrose, methyl glycoside, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, dibutylene glycol, or mixtures thereof. In some embodiments, examples of suitable acrylic polyol may include the radical polymerization product of acrylic monomers, such as acrylic or methacrylic acids and esters with hydroxyalkyl acrylates or hydroxyalkyl methacrylates as comonomers. Examples of suitable phenolic resin polyol may include the reaction product of a phenol, an aldehyde and an aliphatic hydroxy compound containing two or more hydroxy groups. Commercially available examples of suitable phenolic resin polyol may include ASKOCOAT 420 from ASKChemicals.

[0054] The isocyanate used to produce the coating according to the various embodiments of the present invention is not to be restricted. Isocyanates contain two or more -NCO groups available for reaction and, as known to one skilled in the art, are widely used in the production of urethane polymers. Suitable isocyanates may encompass any one of hexamethylene diisocyanate (HDI), isophorone diisocyanate ( I PD I), toluene diisocyanate (TDI) or methylene diphenyl diisocyanate (MDI) , including any isomeric, oligomeric, monomeric, or polymeric forms thereof, preferably MDI, including any isomeric, oligomeric, monomeric, or polymeric forms thereof. Isocyanate condensation products can also be used. Isocyanates having isocyanurate, biuret, iminooxadiazine, and / or uretidione structural units are suitable. Some commercially available examples may include DESMODUR from Bayer Corporation, ASKOCOAT 540 from ASKChemicals, and Rubinate M from Huntsman Corporation.

[0055] Additional non-limiting examples of suitable isocyanates include: 1,6-hexamethylene diisocyanate, 1,4-butylene diisocyanate, furfurylidene diisocyanate, 2,4-toluene diisocyanate (TDI), 2,6-toluene diisocyanate (2,6-TDI), 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate (MDI), 4,4'-diphenylpropane diisocyanate, 4,4'-diphenyl-3,3'-dimethyl methane diisocyanate, 1,5- naphthalenediisocyanate, l-methyl-2,4-diisocyanate-5-chlorobenzene,2,4-diisocyanato-s-triazine, l-methyl-2,4-diisocyanato cyclohexane, p-phenylene diisocyanate, m-phenylene diisocyanate, 1,4- naphthalene diisocyanate, dianisidine diisocyanate, bitoluene diisocyanate, 1,4-xylylene diisocyanate, 1,3-xylylene diisocyanate, bis-(4-isocyanatophenyl)methane, bis-(3-methyl-4- isocyanatophenyl)methane, polymethylene polyphenyl polyisocyanates and mixtures thereof. Preferably, the modified polyol and isocyanate are used in amounts such that the ratio of NCO groups in the isocyanate to the hydroxyl groups in the modified polyol composition ranges from about 0.8 to about 3.0, more preferably from about 0.8 to about 2.0, and most preferably from about 0.8 to about 1.5. In some preferred embodiments, the coated fertilizer composition as disclosed herein comprises at least one polymer coating layer comprising between 1.0 and 35.0 wt% of polyacetal, between 15.0 and 44.0 wt% of polyols and between 31.0 and 74.0 wt% of isocyanates, preferably between 5.0 and 35.0 wt% of polyacetal, preferably between 1.0 and 25.0 wt% of polyacetal, between 25.0 and 44.0 wt% of polyols and between 31.0 and 74.0 wt% of isocyanates, preferably between 5.0 and 20 wt% of polyacetal, between 37.5 and 52.5 wt% of polyols and between 42.5 and 57.5 wt% of isocyanates, more preferably between 7.5 and 12.5 wt% polyacetal, between 35.0 and 45.0 wt% of polyols and between 47.5 and 52.5 wt% of isocyanates. In some preferred embodiments, the coated fertilizer composition as disclosed herein comprises at least one polymer coating layer comprising between 0.5 and 20.0 mol% of polyacetal, between 15.0 and 60.0 mol% of polyol and between 20.0 and 84.5 mol% of isocyanate, preferably between 1.0 and 15.0 mol% of polyacetal, between 25.0 and 54.0 mol% of polyol and between 31.0 and 74.0 mol% of isocyanate, preferably between 5.0 and 15.0 mol% of polyacetal, between 30.0 and 54.0 mol% of polyol and between 31.0 and 65.0 mol% of isocyanate, preferably between 5.0 and 12.5 mol% of polyacetal, between 30.0 and 45.0 mol% of polyol and between 31.0 and 52.5 mol% of isocyanate, and most preferably between 7.5 and 12.5 mol% of polyacetal, between 35.0 and 45.0 mol% of polyol and between 47.5 and 52.5 mol% of isocyanate. Substituting part of the polyol in the polyurethane formulation for a polyacetal provides, next to enhanced (bio)degradability, improved flexibility in terms of properties such as thermal and UV resistance, rigidity, and viscosity. A Lower content of polyacetal is desirable to avoid large changes in the original properties of the thermoplastic polyurethane such as abrasion resistance, shear strength, elasticity, and hydrolysis resistance.

[0056] In a further aspect, the present invention relates to a process for preparing a coated fertilizer composition as disclosed herein, wherein the process comprises the steps of: a. contacting a polyacetal with a polyol to obtain a modified polyol; b. contacting a particulate fertilizer with a mixture comprising the modified polyol and an isocyanate to obtain a coated particulate fertilizer; and c. curing of the coated particulate fertilizer to obtain the coated fertilizer with at least one polymer coating.

[0057] An advantage of the process for preparing a coated fertilizer composition is that it is simplified and can be performed on-site. Furthermore, the quantities of reagents and processing parameters provide a coated fertilizer composition with improved control of nutrient release. Depending on the desired longevity of release of nutrients and activity of the fertilizer particles, the process for preparing a coated fertilizer composition as disclosed herein may be repeated to provide 1 to 15 polymer coating layers. In some embodiments, curing of the coated particulate fertilizer was carried out at 25 °C and may optionally include UV light curing to avoid degradation of temperaturesensitive nutrients. In other embodiments, curing of the coated particulate fertilizer was carried out at 40 °C to 150 °C, preferably 60 °C to 150 °C, preferably 80 °C to 150 °C, more preferably 100 °C to 120 °C. The required curing time may comprise 1 minute to 60 minutes, preferably 5 minutes to 45 minutes, preferably 5 minutes to 30 minutes, more preferably 5 minutes to 20 minutes, and most preferably 5 minutes to 10 minutes, per coating cycle. Curing of the polyurethane coating may further comprise the addition of a catalyst. In some preferred embodiments, the catalyst comprises a metal, an amine, or a mixture thereof. The metal may be any metal known in the polyurethane art to catalyze polyurethane formation such as organotin catalysts. Examples of suitable organotin catalysts include stannous octoate, stannous oleate, stannic chloride, dimethyltin dilaurate and dibutyltin dilaurate. The amine may be any amine known in the polyurethane art to catalyze polyurethane formation such as tertiary amines, including alicyclic tertiary amines and aliphatic tertiary amines. Examples of suitable amine catalysts include aliphatic, alicyclic or heterocyclic tertiary amine catalysts such as N,N- dimethylcyclohexylamine, N,N,N',N'-tetramethyl hexamethylene diamine and N,N'-dimethyl-N,N'- diisopropyl hexamethylenediamine, triethylenediamine, N-ethyl or methyl morpholine, N,N- dimethylaminoethyl morpholine, N-butylmorpholine, N,N'-dimethylpiperazine, bis- (dimethylamino-alkyl)-piperazine, and 1,2-dimethylimidazole. Commercially available examples of suitable tertiary amine catalysts may include CATALYST 704 from ASKChemicals. Organotin catalysts are generally used in conjunction with one or more tertiary amine catalysts.

[0058] The catalyst may be supplied to the polyurethane curing mixture in a gaseous, liquid or solid state. In some preferred embodiments, the catalyst is supplied to the polyurethane curing mixture in the gaseous state by using a suitable carrier gas. Examples of suitable carrier gases include dehydrated air and nitrogen. The gas stream takes up the catalyst which is then applied to the polyurethane layer surrounding the fertilizer granules. Surplus catalyst may be removed by means of, for instance, an amine scrubber. The use of a gaseous catalyst may significantly accelerate curing of the polyurethane. When present, the concentration of the additional catalyst may be, based on the total weight of the polyacetal and polyol composition, 0.1 wt% or more, 1.0 wt% or more, or even 1.5 wt% or more.

[0059] The formulation of the present invention may further comprise any one or combination of the following additives: pigments and colorants, flame retardants, antioxidants, surface modifiers, bioretardant agents, odor masks, antioxidants, ultraviolet (UV) stabilizers, antistatic agents and viscosity modifiers. Some non-limiting examples of pigments and dyes include titanium oxide, iron oxide, talc, kaolin, silica, carbon.

[0060] Polyurethane curing according to current invention may comprise preheating of the particulate fertilizer before applying the curing mixture to at least 45.0 °C, preferably at least 55.0 °C, and more preferably at least 65.0 °C. The temperature may vary depending on the macronutrients and / or micronutrients comprised in the fertilizer particles.

[0061] Any suitable heating method or heating energy source may be used for heating or preheating such as a convection oven, heating plates, infrared oven, microwave heating or a combination thereof. Application of the at least one polymer coating layer to the particulate fertilizer may be performed using a batch and / or continuous coater.

[0062] In accordance with these explanations, any embodiment of the invention so defined may be combined with any other embodiment as provided herein unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features or embodiments indicated as being preferred or advantageous.

[0063] While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as follows in the spirit and scope of the appended claims.

[0064] EXAMPLES

[0065] Three modified polyol samples (A, B, and C) were prepared by mixing polyacetal and polyol in a 1:4 weight ratio.

[0066] The polyol as used herein is a commercially available phenolic resin polyol (ASKOCOAT 420) obtained from ASK Chemicals. The isocyanate as used herein is a commercially available methylene diphenyl diisocyanate (MDI) (ASKOCOAT 540) obtained from ASK Chemicals. The tertiary amine catalyst used herein is a commercially available catalyst (CATALYST 704) obtained from ASK Chemicals.

[0067] EXAMPLE 1

[0068] In a first experiment, a coated fertilizer composition as disclosed herein was prepared according to a process as disclosed herein.

[0069] In a suitable container, modified polyol sample A was mixed with isocyanate to obtain a (coating) mixture comprising 10 wt% polyacetal, 40 wt% polyol, and 50 wt% isocyanate. Spray-coating was used to apply the coating mixture to fertilizer particles (comprising 16% Nitrogen, 10% Phosphorus, 17% Potassium, 3% Magnesium oxide, and trace elements) having an average diameter of between 2.0 and 4.0 mm. The coated fertilizer particles were cured under a gas stream of tertiary amine catalyst to obtain a coated fertilizer composition 1 with 9 wt% of polymer coating, with wt% based on the total weight of the composition.

[0070] The same procedure was repeated but with modified polyol B to obtain coated fertilizer composition 2.

[0071] The same procedure was repeated but with modified polyol C to obtain coated fertilizer composition 3. EXAMPLE 2

[0072] In a second experiment, a comparative coated fertilizer composition was prepared comprising a polymer coating without polyacetal.

[0073] In a suitable container, polyol and isocyanate were mixed to obtain a (coating) mixture comprising 50 wt% polyol and 50 wt% isocyanate. Spray-coating was used to apply the coating mixture to fertilizer particles (comprising 16% Nitrogen, 10% Phosphorus, 17% Potassium, 3% Magnesium oxide, and trace elements) having an average diameter of between 2.0 and 4.0 mm. The coated fertilizer particles were cured under a gas stream of tertiary amine catalyst to obtain comparative composition 1 with 9 wt% of polymer coating, with wt% based on the total weight of the composition.

[0074] EXAMPLE 3

[0075] In a third experiment, the biodegradability of the various coated fertilizer compositions of Example 1 and Example 2 as disclosed herein was tested in soil conditions at 37 °C for 90 days, according to ISO 17556:2019.

[0076] The biodegradation percentage for the coated fertilizer compositions 1-3 and the comparative composition 1 are shown in Table 1, which are relative to cellulose (i.e., a highly biodegradable substrate). From the relative biodegradation rates shown in Table 1 it can be observed that the coated fertilizer compositions according to the invention have an improved biodegradability. In particular, after a functionality period (i.e., use period) it has been found that the coated fertilizer compositions as disclosed herein have a higher relative degradation rate, which extrapolates to a good minimum degradation level at a period of 12 months.

[0077] Table 1

[0078] EXAMPLE 4

[0079] In a fourth experiment, the suitability of the various coated fertilizer compositions of Example 1 and

[0080] Example 2 as disclosed herein as a nutrient supply for container plants was tested. For this purpose, plants of Hypericum (Hidcote) from QP-77 multiplates were potted in 2L containers without additional trace element fertilisation with different fertilizers. The substrate used for potting was a standard white peat substrate, which was calcified to a pH value of 4.8 (measured in calcium chloride solution) using 2.5 g / L carbonated lime. All coated fertilizer compositions 1-3 and the comparative composition 1 were dosed at 3.0 g per litre of substrate. The Hypericum were set up in the field in four replicates with 10 specimens per experimental link. The arrangement was randomised in a randomised block design. Overhead irrigation was applied regularly via spray nozzles on a watering trolley.

[0081] The growth of the different plants, related to the release of plant nutrients, was monitored over a period of 6 months by measuring the fresh weight, shoot length, and chlorosis on the older leaves (i.e., copper deficiency) of the plant. The results for the coated fertilizer compositions 1-3 and the comparative composition 1 are shown in Table 2 below. From the different growth experiments it can be observed that the coated fertilizer compositions according to the invention provided a more gradual release of plant nutrients with reduced nutrient deficiency and stimulated shoot growth. Table 2

Claims

CLAIMS1. A coated fertilizer composition comprising fertilizer particles coated with at least one polymer coating layer, wherein the polymer coating layer comprises an isocyanate and a modified polyol, and wherein the modified polyol comprises a polyacetal.

2. The coated fertilizer composition according to claim 1, wherein said polymer coating layer essentially consists of a polyurethane composition comprising polyacetal, polyols and isocyanates.

3. The coated fertilizer composition according to any one of claim 1 or 2, wherein said polymer coating layer comprises between 1.0 and 35.0 wt% of polyacetal, between 15.0 and 44.0 wt% of polyols and between 31.0 and 74.0 wt% of isocyanates, preferably between 1.0 and 25.0 wt% of polyacetal, between 25.0 and 44.0 wt% of polyols and between 31.0 and 74.0 wt% of isocyanates, preferably between 5.0 and 20 wt% of polyacetal, between 37.5 and 52.5 wt% of polyols and between 42.5 and 57.5 wt% of isocyanates, more preferably between 7.5 and 12.5 wt% polyacetal, between 35.0 and 45.0 wt% of polyols and between 47.5 and 52.5 wt% of isocyanates.

4. The coated fertilizer composition according to any one of claims 1 to 3, wherein the isocyanate comprises any one of hexamethylene diisocyanate (HDI), isophorone diisocyanate ( I PD I), toluene diisocyanate (TDI) or methylene diphenyl diisocyanate (MDI), including any isomeric, oligomeric, monomeric, or polymeric forms thereof, preferably MDI, including any isomeric, oligomeric, monomeric, or polymeric forms thereof.

5. The coated fertilizer composition according to any one of claims 1 to 4, wherein said modified polyol further comprises an aromatic polyester polyol, a polyether polyol, an acrylic polyol and / or a phenolic resin polyol.

6. The coated fertilizer composition according to any one of claims 1 to 5, wherein said fertilizer particles comprise macronutrients chosen from urea, nitrogen, potassium, phosphorus, sulphur or combinations thereof.

7. The coated fertilizer composition according to any one of claims 1 to 6, wherein said fertilizer particles comprise micronutrients chosen from magnesium (Mg), iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), boron (B), molybdenum (Mo), chlorine (Cl), cobalt (Co), nickel (Ni), selenium (Se), vanadium (V), silicon (Si) or combinations thereof.

8. The coated fertilizer composition according to any one of claims 1 to 7, wherein said fertilizer particles are characterized by having an average diameter between about 0.5 and about 10.0 mm, preferably between about 1.0 and about 5.0 mm.

9. The coated fertilizer composition according to any one of claims 1 to 8, wherein said polyacetal is polycycloacetal.

10. The coated fertilizer composition according to any one of claims 1 to 9, wherein said at least one polymer coating layer provides controlled release properties with a release of between 40.0 %and 90.0 % nutrient in 40 hours, preferably between 60.0 % and 90.0 % nutrient in 30 hours, more preferably between 75.0 % and 90.0 % nutrient in 20 hours under boiling water conditions; with % based on the total nutrient content comprised in the coated fertilizer composition.

11. The coated fertilizer composition according to any one of claims 1 to 10, wherein the at least one polymer coating layer has a bench stability of at least 2 months, preferably at least 4 months, more preferably at least 8 months, and more preferably at least 16 months.

12. The coated fertilizer composition according to any one of claims 1 to 11, wherein the at least one polymer coating layer comprises an amount between about 1.0 and 20.0 wt%, preferably between about 2.5 and 10.0 wt%, and most preferably between about 5.0 and 10.0 wt%, based on the total weight of the coated fertilizer composition.

13. A process for preparing a coated fertilizer composition according to any one of claims 1 to 12, wherein the process comprises the steps of:• contacting a polyacetal with a polyol to obtain a modified polyol;• contacting a particulate fertilizer with a mixture comprising the modified polyol and an isocyanate to obtain a coated particulate fertilizer; and• curing of the coated particulate fertilizer to obtain the coated fertilizer with at least one polymer coating.

14. The process according to claim 13, wherein curing of the coated particulate fertilizer involves the addition of a catalyst, and preferably wherein said catalyst is an amine, a metal, or a mixture thereof.

15. The process according to any one of claims 13 or 14, wherein the particulate fertilizer is preheated to at least 45.0 °C, preferably at least 55.0 °C, and more preferably at least 65.0 °C; and preferably wherein 1 to 15 coating cycles are carried out by repeating step a) to c) of the process according to any one of claims 13 or 14.

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