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-51176

[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-51176

[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-51176

[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 (amidation) 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, also referred to as a dicarboxylic ester, is any compound containing two carboxylic acid an ester groups.

[0021]

[0015] 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 Averages and Molecular Weight Distribution of Polystyrene by High Performance Size-Exclusion Chromatography .

[0022]

[0016] 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:

[0023] i. providing a polycondensation polymer, sometimes referred to herein as a polyester or polyamide, at least two monomers selected from structure (I), (II), or (III) (comprising at least two monomers selected from structures (I), (II), or (III);4 EU-51176

[0024] providing a compound with at least two nucleophilic groups; and in. reacting the polycondensation polymer and the compound with at least two nucleophiles to form a polymeric coating;

[0025] wherein said polycondensation polymer has a number average Mw between about 500 and about 12000

[0026]

[0027]

[0017] wherein R1 and R2 are independently selected from H and CH3;

[0028] Xi and X2 are independently selected from O, NH, and N-.

[0029]

[0018] 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 act as Michael acceptors. Advantageously, the use of the structures (I-III), in which the unsaturated moiety bears 2 electron-withdrawing groups, allows faster reaction times with Michael donors compared to mono-activated moieties (e.g. acrylates, methacrylates).

[0030]

[0019] 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.

[0031]

[0020] 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.

[0032]

[0021] 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:5 EU-51176

[0033] i. a polycondensation polymer (sometimes referred to herein as a polyester or a polyamide) with at least two structures (I), (II), and (IIII) described above;

[0034] ii. a compound with at least two nucleophilic groups;

[0035] wherein said polycondensation polymer has a number average Mw between about 500 and about 12000.

[0036]

[0022] The nucleophilic group of the compound with at least two nucleophilic groups is any nucleophilic group that can react with an a,P-unsaturated ester or amide group to form a covalent bond. In some embodiments, examples of the nucleophilic group include amine groups or thiol groups. The compound with at least two nucleophilic groups may contain at least one amine group, at least one thiol group or a combination thereof.

[0037]

[0023] In some embodiments, the molar ratio of the C=O-Xi and C=O-X2 groups to the nucleophilic functional groups is between about 0.5:1 to about 8:1. Preferably between about 0.5:1 to about 4:1. By controlling the ratio of the reactive groups it is possible to control the cross linking density of the resultant polymer and the hydrophilicity which in turn impacts the release characteristics.

[0038]

[0024] In some embodiments, the reaction between the polycondensation polymer and the compound with at least two nucleophilic groups is a Michael addition. The 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. falkylamines, 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.

[0039]

[0025] In some embodiments, the catalyst is present in an amount between about 0.01 wt% and about 1 wt%.

[0040]

[0026] The compound of structure (I), (II), or (III) may be a polyester with at least two a, [3-unsaturated ester groups or a polyamide. In some embodiments, the unsaturated polyester is the product of at least one unsaturated acid and at least one diol, preferably wherein the at least one unsaturated diacid or cyclic anhydride and is selected from the group consisting of itaconic acid, maleic acid, citraconic acid, mesaconic acid, or fumaric acid and at least one diol,6 EU-51176

[0041] preferably wherein the diol is selected from the group consisting of 1,3-propanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,10-decanediol, 1,12-dodecanediol.

[0042]

[0027] 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.

[0043]

[0028] 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.

[0044]

[0029] In some embodiments, the biodegradable polymer film has some or all of the following properties:

[0045] 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.

[0046] iii. No eco toxic effects, that is, it has limited or no impact on a population of animals, plants, or microbes in the environment.

[0047]

[0030] In an aspect, there is provided fertiliser granule comprising:

[0048] i. a nutrient granule; and

[0049] ii. at least one layer of biodegradable polymer film as described above, wherein the polymer film substantially coats said urea granule.

[0050]

[0031] 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 of 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.

[0051]

[0032] In some embodiments, the nutrient comprises urea.

[0052]

[0033] 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.

[0053]

[0034] 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.7 EU-51176

[0054]

[0035] 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.

[0055]

[0036] In some embodiments, the fertiliser granule is stable for 12 months between 4°C and 50°C.

[0056]

[0037] 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.

[0057]

[0038] 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

[0058]

[0039] More details and advantages will become obvious from the following examples.

[0059] Methods

[0060]

[0040] The following methods were used:

[0061]

[0041] ASTM D5296 Standard Test Method for Molecular Weight Averages and Molecular Weight Distribution of Polystyrene by High Performance Size-Exclusion Chromatography was used to determine the molecular weight of any samples.

[0062]

[0042] Method to plot a curve of the relationship between released mass fraction urea and time for coated spherical urea particles

[0063]

[0043] Step 1: the input parameters

[0064]

[0044] 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%).

[0065]

[0045] The diffusivity (D) of urea through the thin film determined according to the method for urea diffusivity using a Franz Diffusion Cell.

[0066]

[0046] Step 2: the mathematical model

[0067]

[0047] 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.

[0068]

[0048] 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 water8 EU-51176

[0069] transport were assumed fast and were not simulated. The outer boundary was treated as a single large water volume.

[0070]

[0049] 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.

[0071]

[0050] Contact angle measurement

[0072]

[0051] Contact angle was measured using an optical goniometer. The goniometer software to automatically detect the droplet contour and calculate the contact angle. The average of the lift and right contact angles represents the final contact angle. Three measurements at different points on the polymer surface were made.

[0073]

[0052] Method for Urea diffusivity using a Franz Diffusion Cell

[0074]

[0053] Equipment

[0075]

[0054] 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.

[0076]

[0055] 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:

[0077] J=D-(Cd-Cr) / d where:

[0078] • J is the flux (mol / cm2 / s),

[0079] • D is the diffusion coefficient (cm2 / s),

[0080] • Cd and Cr are the concentrations in the donor and receptor phases (mol / cm3),

[0081] • d is the thickness of the polymer film (cm).

[0082]

[0056] Biodegradability indication via accelerated hydrolysis

[0083]

[0057] The hydrolysis (assumed to be the rate determining step in biodegradation) of films of unsaturated polyesters cured with thiols was quantified by gravimetric mass loss tests. Pieces of films prepared with comparable thickness in the range 200-250 microns have been dried until constant weight in a vacuum oven (P = 0.2 mbar, T = 40°C), weighed to record the initial mass and immersed in a 2.5 wt% water / KOH solution. For a more accurate determination,9 EU-51176

[0084] small pieces of the same coating have been hydrolyzed in separate bottles. At regular intervals, a piece of film was extracted from the KOH / water solution, the surface was wiped to remove the excess water and dried until constant weight in a vacuum oven (P = 0.2 mbar, T = 40°C). Once dry, the mass of the film was measured on an analytical balance and the percentage of mass loss was reported according to the following equation: mass loss = 100 - (mass post hydrolysis / mass dry *100).

[0085]

[0058] Cross link density

[0086]

[0059] Theoretical crosslink density calculation

[0087] System dry weight

[0060] Mcgei (average mol weight between crosslinks) = - — - - — ■ - — -

[0088]

[0089] Thiols

[0090]

[0061] Where:

[0091] • fn = functionality of Michael Acceptor or Thiol

[0092] • System dry weight = total grams of Michael Acceptor and Thiol employed

[0093] • Moles reacting = moles of reactive components (Michael Acceptor or Thiol)

[0094]

[0062] Assumptions

[0095] • No side reactions occurring

[0096] • Exact desired stoichiometric ratio

[0097] • Full conversion (check via FT-IR)

[0098]

[0063] Synthesis of unsaturated polyesters (UPEs) for CRF coatings

[0099]

[0064] The following chemicals were used:

[0100] • Titanium tetrabutoxide (catalyst) - CAS 5593-70-4: 0.008 wt.%

[0101] • Zinc acetate (catalyst) - CAS 557-34-6: 0.1 wt.%

[0102] • Paratoluensulfonic acid - CAS 104-15-4: 0.1 wt.%

[0103] • 4-methoxyphenol (radical inhibitor) - CAS 150-76-5: 0.5 wt.%

[0104] • Niax 15-CS (color stabilizer): 0.25 wt.%

[0105] • Maleic anhydride (MA)

[0106] • Dimethyl fumarate (DF)

[0107] • Diethylenglycol (DEG)

[0108] • Triethylenglycol (TEG)

[0109] • Dodecandioic Acid (DA)

[0110] • 3 -methyl- 1,3 -propanediol (MP)

[0111] • 3-methyl-l,5-pentanediol (MPD)

[0112] • 1,12-dodecandiol (12DD)10 EU-51176

[0113] • 1,10-decanediol ( 1 ODD)

[0114] • 1,3-propanediol (13PD)

[0115] • 1,6-hexanediol (16HD)

[0116]

[0065] Polyesters were synthesised using the chemicals below.

[0117]

[0118]

[0066] Polyester Synthesis Procedure

[0119]

[0067] 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 (methanol) generated by the condensation (transesterification) reaction. A thermocouple was placed at the beginning of the condenser to monitor vapors’ temperature. The whole setup was additionally insulated with glass wool. The system was kept dry by slowly flowing nitrogen to avoid hydrolysis and oxidation side reactions.

[0120]

[0068] All the chemicals, 4-methoxyphenol and Niax 15-CS were weighed and added in the flask (catalyst was added at a later stage). The temperature was initially set to 80°C to have the anhydrides react with diols minimizing their sublimation, and gradually increased to 180°C (10°C steps) when water (methanol) condensation stopped. Finally, the catalyst was added to complete the reaction, and the expected water (methanol) was condensed. Reaction time can be different, it was therefore monitored by regularly inspecting the condensation of water (methanol) and by monitoring the decrease of the acid value (hydroxyl value in case of polycondensation). The composition and number average Mw of the obtained polyester was confirmed by13C-NMR, GPC and hydroxyl value (when applicable).

[0121]

[0069] Preparing a biodegradable polymer coating via Thiol-Michael addition combining a Michael Donor and Michael Acceptor

[0122]

[0070] Polymer coatings were prepared as described below.

[0123]

[0071] Chemicals

[0124] • DBN (l,5-Diazabicyclo[4.3.0]non-5-ene) - CAS 3001-72-711 EU-51176

[0125] • DBU TA V (blocked)

[0126] • Glycol di(3 -mercaptopropionate) CAS 22504-50-3 (Thiol 1)

[0127] • Thiocure 341 (Thiol 2)

[0128] • Trimethylolpropane tris(3-mercaptopropionate) - CAS 33007-83-9 (Thiol 3)

[0129] • Chloroform

[0130]

[0131]

[0072] Procedure

[0132]

[0073] Solvent-based film formation was employed to prepare defect-free thin films for diffusion measurements. Approximately 2.5 grams of Michael Acceptor are weighed in a glass jar and dissolved with 50 ml of Chloroform. In a separate jar, the calculated amount of thiol curing agent (molar ratio C=C bond : Thiol group = 1 : 1) was weighed and dissolved with 15 mol of Chloroform. DBN catalyst (0.5 wt.% on total thiol and Michael Acceptor weight) was then added to the solution of Michael acceptor. The solution containing the thiol curing agent was eventually poured into the solution containing the Michael Acceptor under magnetic stirring. The resulting mixture was poured into a PTFE petri dish and the solvent was allowed to slowly evaporate overnight in order to obtain a defect-free solvent-free thin film. The solvent-free thin films were prepared for accelerated hydrolysis tests, contact angle measurement and urea diffusivity measurement.

[0133]

[0074] The results are shown below.12 EU-51176

[0134]

[0135]

[0075] 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

13 EU-51176What is claimed:

1. A method for preparing a biodegradable polymer coating for use as a semipermeable barrier on a fertiliser granule, said method comprising:i. providing a polycondensation polymer comprising at least two monomers independently selected from structures (I), (II), and (III);wherein Ri and R2 are independently selected from H and CH3; andXi and X2 are independently selected from O, NH, and N;ii. providing a compound with at least two nucleophilic groups; andiii. reacting the polycondensation polymer and the compound with at least two nucleophilic groups to form a biodegradable polymer coating;wherein said polycondensation 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:i) a polycondensation polymer comprising at least two monomers independently selected from structures (I), (II), and (III);14 EU-51176wherein Ri and R2 are independently selected from H and CH3; andXi and X2 are independently selected from O, NH, and Nii) a compound with at least two nucleophilic groups;wherein said polycondensation polymer has a number average Mw between about 500 and about 12000.

4. The method of claim 1 or claim 2, or the composition of claim 3, wherein at least one of the nucleophilic groups in the compound with at least two nucleophilic groups is an amine or a thiol.

5. The method or composition of any preceding claim, wherein the molar ratio of the C=O-Xi and C=O-X2 groups to the nucleophilic functional groups is between about 0.5:1 to about 8:1, preferably 0.5:1 to about 4:1.

6. 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 triethylamine, l,8-Diazabicyclo[5.4.0]undec-7-ene, 1,5-Diazabicyclo[4.3.0]non-5-ene, di-isopropyl-ethylamine), n-alkylamines, dimethylaminopyridine, imidazoles, 3,4-dimethylpyrazole phosphate, and trialkylphosphines.

7. The method or composition of claim 6, wherein the catalyst is present in an amount between about 0.1 wt% and about 1 wt%.15 EU-511768. The method or composition of any preceding claim, wherein the polycondensation polymer is the product of at least one unsaturated acid and at least one diol, preferably wherein the at least one unsaturated acid or cyclic anhydride and is selected from the group consisting of itaconic acid, maleic acid, citraconic acid, mesaconic acid, or fumaric acid and at least one diol, preferably wherein the diol is selected from the group consisting of 1,3-propanediol, 3-methyl-l,5-pentanediol, 1,6-hexanediol, 1,10-decanediol, 1,12-dodecanediol.

9. The method of any preceding claim, 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 any one of claims 3 to 8, wherein the composition has a viscosity less than or equal to 10000 cps, preferably less than or equal to 1000 cps.

10. A biodegradable polymer film made by the method of, or use of the composition, of any one of the preceding claims.

11. The biodegradable polymer film of claim 10, 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.

12. The biodegradable polymer film of claim 10 or claim 11, wherein 90% of the organic carbon in the polymer film converts to CO2 within 48 months.

13. The biodegradable polymer film of claim 10 or claim 11, wherein the polymer film has no eco toxic effects.

14. A fertiliser granule comprising:a. a nutrient granuleb. at least one layer of biodegradable polymer film according to any one of claims 10 to 13, wherein the polymer film substantially coats said urea granule.

15. The fertiliser granule of claim 14, wherein the fertiliser granule further comprises at least one layer of wax.

16. The fertiliser granule of claim 14 or claim 15, wherein 90% of the organic carbon in the fertiliser granule converts to CO2 within 48 months.16 EU-5117617. The fertiliser granule of any one of claims 14 to 16, wherein 80% of the nutrient is released within 14 days of application.

18. The fertiliser granule of any one of claims 14 to 17, wherein the fertiliser granule is stable for 12 months at between 4°C and 50°C.

19. The fertiliser granule of any one of claims 14 to 18, wherein less than 15% of the nutrient is released in 24 hours.

20. The fertiliser granule of any one of claims 14 to 19, wherein the fertiliser has a linear release profile over at least 30 days.

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