Biodegradable controlled release fertilisers

Abstract

Described is a fertiliser granule comprising a nutrient granule and at least one layer of biodegradable polymer film. Also described are methods and compositions for preparing a biodegradable polymer film useful for coating a fertiliser granule.

Description

[0001] 1 EU-51183

[0002] Biodegradable Controlled Release Fertilisers

[0003] Background to the invention

[0004]

[0001] In agriculture, a major challenge associated with the use of urea fertilizers is the significant loss to the environment, leading to environmental pollution and high crop production costs. One potential solution to mitigate fertilizer losses is the implementation of Controlled Release Fertilizers (CRF). These fertilizers consist of nutrient granules coated with materials that have lower water permeability, thus controlling the release of water and nutrients into the soil and making them gradually available to crops.

[0005]

[0002] Numerous types of controlled release fertiliser exist. A common method is to coat the fertiliser granule in a shell that degrades at a specified rate. Examples of shell materials include sulfur and thermoplastics. However, due to recent changes in European legislation, the coating cannot contain conventional plastic coatings which may lead to microplastics in soil.

[0006]

[0003] There is therefore a need to provide a coating for a fertiliser granule that is biodegradable without leaving microplastics in the soil, whilst providing good release characteristics.

[0007] Object of the Invention

[0008]

[0004] It is an object of the disclosure to provide a biodegradable coating for CRF for use in broadacre agriculture, turf, ornamental, and specialty agriculture applications worldwide. The coating must meet the European regulatory definition of biodegradability, which requires that it achieve 90% biodegradability within 48 months and have no (eco)toxicity or toxic degradation products.

[0009] Detailed Description

[0010]

[0005] The present disclosure will be described with respect to particular aspects and embodiments.

[0011]

[0006] It is to be noticed that the term "comprising", used in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It is thus to be interpreted as specifying the presence of the stated features, steps or components as referred to, but does not preclude the presence or addition of one or more other features, steps or components, or groups thereof. Thus, the scope of the expression "a compound comprising components X and Y" should not be limited to compounds consisting only of components X and Y. It means that with respect to the present disclosure, the only relevant components of the compound are X and Y.2 EU-51183

[0012]

[0007] Throughout this specification, reference to "one embodiment" or "an embodiment" are made. Such references indicate that a particular feature, described in relation to the embodiment is included in at least one embodiment of the present disclosure. 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, though they could. Furthermore, the particular features or characteristics may be combined in any suitable manner in one or more embodiments, as would be apparent to one of ordinary skill in the art.

[0013]

[0008] It is to be understood that although preferred embodiments and / or materials have been discussed for providing embodiments according to the present disclosure, various modifications or changes may be made without departing from the scope and spirit of this invention.

[0014]

[0009] The terms “preferred” and “preferably” refer to embodiments that may afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful and is not intended to exclude other embodiments from the scope of the present disclosure.

[0015]

[0010] Where substituent groups are specified by their conventional chemical formula, written from left to right, they equally encompass the chemically identical substituents that would result from writing the structure from right to left, for example, -CH2O- is equivalent to -OCH2-.

[0016]

[0011] The term “optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances where it does not.

[0017]

[0012] Throughout this disclosure, the term “about” is used to indicate that a value includes the inherent variation of error for the quantifying device, mechanism, or method, or the inherent variation that exists among the subject(s) to be measured. For example, but not by way of limitation, when the term “about” is used, the designated value to which it refers may vary by plus or minus ten percent, or nine percent, or eight percent, or seven percent, or six percent, or five percent, or four percent, or three percent, or two percent, or one percent, or one or more fractions therebetween.

[0018]

[0013] The phrases “or combinations thereof’ and “and combinations thereof’ as used herein refers to all permutations and combinations of the listed items preceding the term. For example, “A, B, C, or combinations thereof’ is intended to include at least one of A, B, C, AB, AC, BC, or ABC and, if order is important in a particular context, also BA, CA, CB, CBA, BCA, ACB, BAC, or CAB. Continuing with this example, expressly included are combinations that contain3 EU-51183

[0019] repeats of one or more items or terms such as BB, AAA, CC, AABB, AACC, ABCCCC, CBBAAA, CABBB, and so forth. The skilled artisan will understand that typically there is no limit on the number of items or terms in any combination, unless otherwise apparent from the context. In the same light, the terms “or combinations thereof’ and “and combinations thereof’ when used with the phrases “selected from” or “selected from the group consisting of’ refers to all permutations and combinations of the listed items preceding the phrase.

[0020]

[0014] A polycondensation polymer is a polymer obtained by reacting via polycondensation, transesterification (esterification), or transamidation at least two of the compounds selected among, but not limited to, diols, diamines, hydroxyacids, hydroxyamines, aminoacids, cyclic anhydrides, epoxides, dicarboxylic acids, dicarboxylic acid esters, carbonates. Any of which can be linear, cyclic, branched, aromatic, aliphatic, unsaturated and combination thereof. The monomers must be selected such in order to have at least 90% of them soil-biodegradable according ECHA regulation (ISO 17556:2019 for biodegradability of microplastics in soil). The monomer names are intended to take their normal meaning in the art. For example, a diol is a compound containing two hydroxyl groups (-OH groups), a diamine is a compound containing two amine (-NH2) groups. When used herein, the term hydroxyacid, also known as polycarboxylic acids, has at least two carboxylic groups. Hydroxyamine is a compound comprising an -NH group and an -OH group. When used herein, the term “amino acid” is intended to describe any compound containing both an amino (-NH2) and a carboxylic acid (-COOH) functional group. A cyclic anhydride is any compound is a cyclic compound containing a (RC(O))2O group. An epoxide is any compound containing a cyclic ether with the formula -C2H4O. A dicarboxylic acid is any compound containing two carboxylic acid groups. A dicarboxylic (acid) ester is any compound containing two carboxylic acid groups and an ester group.

[0021]

[0015] A Thiol ended polymer is a polymer obtained by end-capping a hydroxy ended polycondensation polymer with a molecular weight comprised between 500 and 12000 g / mol via Fisher Esterification or general esterification reaction with at least one of the compounds selected among, but not limited to, carboxylic acid containing a thiol functional group, carboxylic acid containing an amine functional group, amino acids, cyclic anhydrides containing a pending thiol or amine group, dicarboxylic acids containing a thiol or amine group.

[0022]

[0016] When used herein the term number average molecular weight refers to the ordinary arithmetic mean or average of the molecular weights of the individual constituents. It is measured according to ASTM D5296 Standard Test Method for Molecular Weight Averages4 EU-51183

[0023] and Molecular Weight Distribution of Polystyrene by High Performance Size-Exclusion Chromatography .

[0024]

[0017] In a first aspect, the invention provides a method for preparing a biodegradable polymer coating for use as a permeable barrier on a fertiliser granule, said method comprising:

[0025] i. providing a thiol ended polymer with the structure Formula (I);

[0026] ii. providing a compound with at least two acrylate or methacrylate groups or polycondensation polymer with at least 2 carbon-carbon double bonds; and iii. reacting the thiol ended polymer and the compound with at least two acrylate or methacrylate groups, or a polycondensation polymer with at least 2 carboncarbon double bonds under conditions effective to form a polymeric coating; wherein said thiol ended polymer has a number average Mw between about 500 and about 12000

[0027]

[0018]

[0028]

[0029] wherein Ri is selected from H and CH3; n = 1 - 6

[0030]

[0019] The Applicant has surprisingly found that a biodegradable polymer prepared by the above method has excellent biodegradable characteristics and good nutrient release profiles. Such a polymer can also be prepared by green click chemistry mechanisms. In this case, the nucleophilic functional groups act as Michael donors and the alpha, beta unsaturated ester groups (acrylate or methacrylate) or polycondensation polymer with at least 2 carbon-carbon double bonds act as Michael acceptors.

[0031]

[0020] In some embodiments, the polycondensation condensation polymer is any polymer formed by the combination of different monomers that is accompanied by the release of water, alcohol or salt. For example, formed by the combination of compounds with at least two functional groups selected from amines, alcohols, carboxylic acids and combinations thereof.

[0032]

[0021] In some embodiments, the polycondensation polymer comprises at least two monomers selected from (A), (B), and (C):5 EU-51183

[0033]

[0034] (C),

[0035] Wherein R1 and R2 are independently selected from H and CH3;

[0036] Xi and X2 are independently selected from O, NH,

[0037]

[0022] In some embodiments, examples of the compound comprising at least two acrylate groups include compounds of the formula (CH2=CHCO2)xR. Where R is an alkyl group with 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 carbons and x is an integer from 1 to 4. In some embodiments, examples of the compound with at least two methacrylate groups include Ethylene Glycol Dimethacrylate (EGDMA) and Polyethylene glycol) dimethacrylate (PEG-DMA). In some embodiments, the compound is Pentaerythritol tetraacrylate (PETA) or Trimethylolpropane triacrylate (TMPTA).

[0038]

[0023] In some embodiments, the reaction in step (iii) is performed at a temperature between about 20 °C and about 132°C, preferably between about 40°C and about 100°C, most preferably between about 60°C and about 80°C, at atmospheric pressure.

[0039]

[0024] When used herein, the term biodegradable means that the polymer is capable of being decomposed by bacteria or other living organisms and thereby avoids pollution.

[0040]

[0025] In an aspect there is provided a composition for use in preparing a biodegradable polymer coating for use as a semipermeable barrier on a fertiliser granule, said composition comprising:

[0041] i. a thiol ended polymer described above;

[0042] ii. a compound with at least two acrylate or methacrylate groups or polycondensation polymer with at least 2 carbon-carbon double bonds;6 EU-51183

[0043] wherein said thiol ended polymer has a number average Mw between about 500 and about 12000.

[0044]

[0026] In some embodiments, the Thiol-Michael addition is performed in the presence of a catalyst which may also be present in the composition. Preferably the catalyst is a Lewis base catalyst. For example, selected from the group consisting of non-nucleophilic bases (e.g. triethylamine, l,8-Diazabicyclo[5.4.0]undec-7-ene, l,5-Diazabicyclo[4.3.0]non-5-ene, di-isopropyl-ethylamine), N-based nucleophiles (e.g. alkylamines, dimethylaminopyridine, imidazoles), phosphorus compounds (e.g. 3,4-dimethylpyrazole phosphate, trialkylphosphines). The inclusion of a catalyst in the reaction mixture increases the rate of reaction between the Michael acceptor and the Michael donor functional groups.

[0045]

[0027] In some embodiments, the catalyst is present in an amount between about 0.01 wt% and about 1 wt%.

[0046]

[0028] In some embodiments, the reaction mixture prior to curing has a viscosity less than or equal to about 10000 cps, preferably below about 1000 cps. If the viscosity is too high, processing of the mixture prior to curing can be difficult.

[0047]

[0029] In an aspect is also provided a biodegradable polymer film suitable for use in coating a fertiliser granule. Said biodegradable film is made by the method described above and / or using the composition described above.

[0048]

[0030] In some embodiments, the biodegradable polymer film has some or all of the following properties:

[0049] i. Capable of full biodegradation in 48 months, for example, wherein 90% of the organic carbon in the polymer film converts to CO2 within 48 months ii. Can be processed into a coating at temperatures between about 20 °C and about 132°C, preferably between about 40°C and about 100°C, most preferably between about 60°C and about 80°C.

[0050] iii. No eco toxic effects, that is, it has limited or no impact on a population of animals, plants, or microbes in the environment.

[0051]

[0031] In an aspect, there is provided fertiliser granule comprising:

[0052] i. a nutrient granule; and

[0053] ii. at least one layer of biodegradable polymer film as described above, wherein the polymer film substantially coats said nutrient granule.

[0054]

[0032] The nutrient granule may contain any type of nutrient necessary to improve plant (including leaf, stem, flower, seed, and fruit growth). Examples of suitable nutrients include nitrogen useful for lead growth and stem growth; phosphorus, useful for the development of7 EU-51183

[0055] roots, flowers, seeds and fruit; potassium useful for strong stem growth, movement of water in plants, and promotion of flowering and fruiting; calcium, magnesium, and sulphur. The nutrient granule may also contain micronutrients such as copper, iron, manganese, molybdenum, zinc, boron, silicon, cobalt and vanadium.

[0056]

[0033] In some embodiments, the nutrient comprises urea.

[0057]

[0034] In some embodiments, the fertiliser granule further comprises at least one layer of wax. Any type of wax may be used. Severally commercially available coating waxes are available. For example, AlphaPlus® which is a mixture C30+ waxes and fruit wax coatings.

[0058]

[0035] In some embodiments, 90% of the organic carbon in the fertiliser granule converts to CO2 within 48 months. That is, the fertiliser granule is biodegradable.

[0059]

[0036] In some embodiments, 80% of the nutrient is released within 14 days of application. For example, if the nutrient granule is a urea granule 80% of the urea is released within 14 days of application.

[0060]

[0037] In some embodiments, the fertiliser granule is stable for 12 months between 4°C and 50°C.

[0061]

[0038] In some embodiments, less than 15% of the nutrient is released in 24 hours. For example, if the nutrient granule is a urea granule less than 15% of the urea is released in 24 hours.

[0062]

[0039] In some embodiments, the nutrient has a linear release profile over at least 30 days. For example, if the nutrient is urea, the urea has a linear release profile over at least 30 days. Examples

[0063]

[0040] More details and advantages will become obvious from the following examples.

[0064] Methods

[0065]

[0041] The following methods were used:

[0066]

[0042] ASTM D5296 Standard Test Method for Molecular Weight Averages and Molecular Weight Distribution of Polystyrene by High Performance Size-Exclusion Chromatography (HPSEC) was used to determine the molecular weight of any samples.

[0067]

[0043] Method to plot a curve of the relationship between released mass fraction urea and time for coated spherical urea particles

[0068]

[0044] Step 1: the input parameters

[0069]

[0045] A chosen spherical pellet size (in this case with a 3mm radius) and a thin film thickness expressed as a mass fraction of the pellet (in this case 3 m%).

[0070]

[0046] The diffusivity (D) of urea through the thin film determined according to the method for urea diffusivity using a Franz Diffusion Cell.8 EU-51183

[0071]

[0047] Step 2: the mathematical model

[0072]

[0048] The mathematical description is that of concentration gradient driven transport (Fickian diffusion) in a symmetric spherical shell geometry, where the dissolved urea molecule transport through a surface is proportional to the concentration gradient, the surface area and the diffusion coefficient D.

[0073]

[0049] At the inner boundary (the pellet - coating interface), water is assumed to have penetrated and to have dissolved its maximum capacity of urea. This saturated solution condition persists until enough urea has been transported outwards and replaced by water such that the remaining urea can be fully dissolved. Initial water permeation and inward water transport were assumed fast and were not simulated. The outer boundary was treated as a single large water volume.

[0074]

[0050] The calculation of the evolution of diffusive fluxes through the discretized shell allows the prediction of the urea release rate over a long time, comparable to the intended coated pellet use. The released urea accumulation was plotted as a mass fraction of the initial pellet mass as a function of time (days). The results are shown in Figure 1. The mass fraction released is shown on the Y-axis against days on the X- axis. The dotted (...) shows D = 30 x 10’15m2 / s, the solid line ( ) shows D= 3 x 10'15m2 / s, and the dashed line ( - ) shows D = 1 x 10'15m2 / s.

[0075]

[0051] Method for Urea diffusivity using a Franz Diffusion Cell

[0076]

[0052] Equipment

[0077]

[0053] Urea diffusivity was measured using a Franz diffusion cell (donor and receptor compartments). A urea solution was used as the donor phase. The polymer film was used to separate the donor and receptor compartments. Samples were taken at pre-determined intervals from the receptor compartment and the urea concentration was measured using HPLC.

[0078]

[0054] Concentration of urea vs. time in the receptor compartment as a function of time was plotted and the diffusion coefficient calculated using Fick’s law:

[0079] J=D-(Cd-Cr) / d where:

[0080] • J is the flux (mol / cm2 / s),

[0081] • D is the diffusion coefficient (cm2 / s),

[0082] • Cd and Cr are the concentrations in the donor and receptor phases (mol / cm3),

[0083] • d is the thickness of the polymer film (cm).

[0084]

[0055] Synthesis of Thiol Ended Polymers for CRF coatings

[0085]

[0056] The following chemicals were used:9 EU-51183

[0086] • Diol: Kuraray P2010 - CAS 39751-34-3

[0087] • p-Toluene-Sulphonic Acid - CAS 104-15-4

[0088] • Carboxylic Acid Thiol Ended: 3-Mercapto Propionic Acid - CAS 107-96-0

[0089]

[0090]

[0057] Thiol Ended Polymer Synthetic Procedure

[0091]

[0058] The reaction was performed in a 4-neck round bottom flask equipped with mechanical stirrer, nitrogen inlet, temperature controller and condenser to distil off the water generated by the condensation (esterification) reaction. A thermocouple was placed at the beginning of the condenser to monitor vapors’ temperature. The system is kept dry by slowly flowing nitrogen to avoid hydrolysis and oxidation side reactions.

[0092]

[0059] All the chemicals, p-Toluene Sulphonic Acid, 3-Mercapto Propionic Acid and Kuraray P2010 have been weighed and added in the flask. The temperature was initially set to 135°C to have a good flowability of the polyol and allow better mixing, avoiding the 3 -MercaptoPropionic acid evaporating from the reaction mixture, and gradually increased to 165°C (10°C steps) to have a good reaction speed. When the reaction starts and till it goes to completion, water was condensed. Reaction goes to completion after 40 h. The composition and number average Mw of the obtained polyester was confirmed by HPSEC.

[0093]

[0060] Preparing a biodegradable polymer coating using a Thiol Ended Polymer

[0061] Polymer coatings were prepared as described below:

[0094]

[0062] Chemicals

[0095] • Polyester 1 as described above.

[0096] • Pentaerythritol tetraacrylate (PETA) - CAS 4986-89-4

[0097] • Trimethylolpropane triacrylate (TMPTA) - CAS 15625-89-5

[0098] • l,5-Diazabicyclo[4.3.0]non-5-ene (DBN) - CAS 3001-72-7

[0099] • Chloroform

[0100]

[0101] 10 EU-51183

[0102]

[0063] Procedure

[0103]

[0064] Solvent-based film formation was employed to prepare defect-free thin films for diffusion measurements. 2.5 grams of Michael Donor are weighed in a glass jar and dissolved with 50 ml of Chloroform. In a separate jar, the calculated amount of Michael Acceptor (molar ratio C=C bond : Thiol group = 1 : 1) was weighed and dissolved with 15 mol of Chloroform. DBN catalyst (0.5 wt.% or lwt% on total thiol and Michael Acceptor weight) was then added to the solution of Michael Acceptor. The solution containing the acrylate curing agent is eventually poured into the solution containing the Michael Donor under magnetic stirring. The resulting mixture is poured into a PTFE petri dish and the solvent was allowed to slowly evaporate overnight to obtain a defect-free solvent-free thin film. The solvent-free thin films were prepared for urea diffusivity measurement.

[0104]

[0065] The urea diffusivity results are shown below.

[0105]

[0106]

[0066] These results show that the coatings prepare according to the present disclosure have superior properties. The figure 1 according to the method to plot a curve of the relationship between released mass fraction urea and time for coated spherical urea particles shows the effect of diffusivity (D [m2 / s]) on the urea release performance. In the graph the behaviour is shown for D = 1 x 10'15m2 / s, 3 x 10'15m2 / s and 30 x 10'15m2 / s.

Claims

11 EU-51183What is claimed:

1. A method for preparing a biodegradable polymer coating for use as a semipermeable barrier on a fertiliser granule, said method comprising:providing a thiol ended polymer of formula (I):wherein Ri is selected from H and CH3; n = 1 - 6ii. providing a compound with at least two acrylate or methacrylate groups, or providing a polycondensation polymer comprising at least 2 unsaturated hydrocarbon groups; andiii. reacting the thiol ended polymer and the compound with at least two acrylate or methacrylate groups, or reacting the thiol ended polymer and the polycondensation polymer with at least 2 carbon-carbon double bonds to form a polymeric coating;wherein said thiol ended polymer has a number average Mw between about 500 and about 12000.

2. The method of claim 1 wherein the reaction is performed at a temperature between about 20°C and about 132°C, preferably between about 40°C and about 100°C, most preferably between about 60°C and about 80°C.

3. A composition for use in preparing a biodegradable polymer coating for use as a semipermeable barrier on a fertiliser granule, said composition comprising:a thiol ended polymer of Formula (I) ;wherein Ri is selected from H and CH3; n = 1 - 612 EU-51183ii. a compound with at least two acrylate or methacrylate groups, or a polycondensation polymer with at least 2 carbon-carbon double bonds; and wherein said thiol ended polymer has a number average Mw between about 500 and about 12000.

4. The method of claim 1 or claim 2, wherein the reaction is formed in the presence of a catalyst, or the composition of claim 3, wherein the composition comprises a catalyst, preferably wherein the catalyst is a Lewis base catalyst, preferably wherein the Lewis base catalyst is a non-nucleophilic base, preferably wherein the catalyst is selected from the group consisting of tri ethyl amine, l,8-Diazabicyclo[5.4.0]undec-7-ene, 1,5-Diazabicyclo[4.3.0]non-5-ene, di-isopropyl-ethylamine), alkylamines, dimethylaminopyridine, imidazoles, 3,4-dimethylpyrazole phosphate, and trialkylphosphines.

5. The method or composition of claim 3 or 4, wherein the catalyst is present in an amount between about 0.1 wt% and about 1 wt%.

6. The method of any one of claims 1, 2, and 4 wherein the polymer produced in step iii) prior to curing has a viscosity less than or equal to 10000 cps, preferably less than or equal to 1000 cps, or the composition of claim 3 or claim 4, wherein the composition has a viscosity less than or equal to 10000 cps, preferably less than or equal to 1000 cps7. A biodegradable polymer film made by the method of, or use of the composition, of any one of the preceding claims.

8. The biodegradable polymer film of claim 7, wherein the polymer film can be processed into a coating at temperatures between about 20 °C and about 132°C, preferably between about 40°C and about 100°C, most preferably between about 60°C and about 80°C.

9. The biodegradable polymer film of claim 7 or claim 8, wherein 90% of the organic carbon in the polymer film converts to CO2 within 48 months.

10. The biodegradable polymer film of claim 7 or claim 8, wherein the polymer film has no eco toxic effects.

11. A fertiliser granule comprising:a. a nutrient granule13 EU-51183b. at least one layer of biodegradable polymer film according to any one of claims 7 to 9, wherein the polymer film substantially coats said nutrient granule.

12. The fertiliser granule of claim 11, wherein the fertiliser granule further comprises at least one layer of wax.

13. The fertiliser granule of claim 11 or claim 12, wherein 90% of the organic carbon in the fertiliser granule converts to CO2 within 48 months.

14. The fertiliser granule of any one of claims 11 to 13, wherein 80% of the nutrient is released within 14 days of application.

15. The fertiliser granule of any one of claims 11 to 14, wherein the fertiliser granule is stable for 12 months at between 4°C and 50°C.

16. The fertiliser granule of any one of claims 11 to 15 wherein less than 15% of the nutrient is released in 24 hours.

17. The fertiliser granule of any one of claims 11 to 16, wherein the fertiliser has a linear release profile over at least 30 days.

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