Controlled release fertiliser

Abstract

Multilayered controlled release fertiliser particles comprising at least a polyurethane layer obtained from a polyester polyol composition with a molecular weight between 3000 and about 4000 g / mol, and less than about 10 wt% of a multifunctional isocyanate compound based on the total weight of the polyester composition. Methods for making the same and their use.

Description

[0001] 1 EU-51180

[0002] CONTROLLED RELEASE FERTILISER

[0003] Cross Reference to Related Applications

[0004]

[0001] This application claims priority to U.S. Provisional Patent Application Serial Number 63 / 772,863 filed March 17, 2025. The noted application is incorporated herein by reference.

[0005] Background to the disclosure

[0006]

[0002] 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.

[0007]

[0003] Current methods to control the release of fertiliser have focused on encapsulated particles. These encapsulated particles typically include one or more polymer layers, preferably a polyurethane, with or without other added functional materials disposed about a core particle. The thickness and integrity of the polymer layers limits the dissolution rate of the core particle into the soil. The limited dissolution has been done so that the growing plants are neither adversely deprived of nutrients nor exposed to an oversupply of nutrients. An oversupply of nutrients can result in toxicity to the plants or nutrient waste from leaching or other atmospheric losses. The resulting improvement in FUE (fertilizer use efficiency) can reduce the rate and the frequency of nutrient application lowering the overall cost of fertilizer application.

[0008]

[0004] In recent years the art has focused on ways to deliver controlled amounts of plant nutrients to the soil or other growing media through either specially prepared coatings or coating methods or a combination of both. Despite these advances in the art, there is still room for improvement. Specifically, it would be desirable to have a controlled release fertilizer and process for production thereof which would allow for the ready customization of the release rate profile of a given particulate plant nutrient. It would also be desirable to be able to achieve a desirable release rate profile for a given particulate plant nutrient with a coating that ultimately biodegrades in the soil.

[0009]

[0005] Presently commercialized and disclosed fertilizer coatings are materials made with non-degradable polymers which, because of the low rate of degradation, ultimately create a buildup of microplastics in the soil. The EU has recently banned the use of plastic coated CRFs due to the concern of microplastic contamination. Accordingly, there remains a need to develop an2 EU-51180

[0010] improved encapsulated particle that simultaneously provides a desired release profile and one that degrades after the nutrients are released.

[0011] Description of Figures

[0012] Figure 1 shows the release rate over aliphatic semicrystalline polymers.

[0013] Figure 2 shows the effect of the CO2 / COO index on release rate.

[0014] Figure 3 shows the enzymatic degradation of polymer coatings

[0015] Figure 4 shows the effect of Isocyanate index on nutrient release kinetics.

[0016] Figure 5 shows the time taken for release of nutrient against the isocyanate index.

[0017] Figure 6 shows the effect of Molecular Weight on nutrient release.

[0018] Figure 7 shows the time taken for nutrient release against the molecular weight of the polyurethane coating.

[0019] Figure 8 shows the effect of crystallinity on release rate.

[0020] Figure 9 shows the release rate of optimised polymer coatings.

[0021] Figure 10 shows the drop and abrasion results from optimised polymer coatings.

[0022] Figure 11 shows the comparison of release rates for aliphatic and aromatic-aliphatic polyesters

[0023] Object of the Disclosure

[0024]

[0006] It is therefore an object of the present disclosure to provide a fertilizer coating that is fully biodegradable whilst providing a desired release profile.

[0025] Detailed Disclosure

[0026]

[0007] The present disclosure will be described with respect to particular aspects and embodiments.

[0027]

[0008] 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.

[0028]

[0009] Throughout this specification, reference to "one embodiment" or "an embodiment" are made. Such references indicate that a particular feature, described in relation to the embodiment3 EU-51180

[0029] 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.

[0030]

[0010] 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 disclosure.

[0031] [Oil] 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.

[0032]

[0012] 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-.

[0033]

[0013] 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.

[0034]

[0014] 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.

[0035]

[0015] 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 contain 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 no4 EU-51180

[0036] 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.

[0037]

[0016] When used herein the term “multifunctional” is used to describe a compound with two or more functional groups. For example, a multifunctional isocyanate is a compound comprising two or more isocyanate groups.

[0038]

[0017] When used herein, the term “isocyanate index” is the ratio of used isocyanate to theoretical amounts of isocyanate required.

[0039]

[0018] 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. In preferred embodiments it is determined by ASTM D4274 method for determining hydroxyl value which details a procedure to measure the hydroxyl groups in polyols by reacting them with acetic anhydride in pyridine, followed by hydrolysis and titration with a standardized sodium hydroxide solution to determine the hydroxyl number; essentially, it measures the amount of hydroxyl groups present in a sample by converting them to esters and then titrating the excess reagent. The molecular weight is then calculated using the nominal functionality of the polyol.

[0040]

[0019] When used herein, the term semicrystalline refers to a material with both crystalline and amorphous regions. A crystalline polymer has polymer chains that are folded and stacking in a regular order; where, as an amorphous polymer has polymer chains that are entangled and have no long-range order.

[0041]

[0020] In one aspect the disclosure provides, a multilayered controlled release fertiliser particle comprising:

[0042] i. A nutrient granule;

[0043] ii. At least one polyurethane layer; and

[0044] iii. At least one wax layer;

[0045] wherein the at least one polyurethane layer comprises a polyurethane obtained from a polyester composition comprising a semicrystalline polyester polyol with a number average molecular weight between about 3000 and about 4000 g / mol, and a multifunctional isocyanate compound, wherein the multifunctional isocyanate compound is present at less than about 10 wt% based on the total weight of the polyester composition.

[0046]

[0021] The inventors have surprisingly found that a multilayered control release fertiliser particle such as that described above can release nutrients over a desired period of time and5 EU-51180

[0047] when the particle’s useful life is over, the material will biodegrade leaving little to no residue in the soil.

[0048]

[0022] Without wishing to be bound by theory, by controlling the molecular weight of the polyester polyol used to make the polyurethane, it is possible to provide a coating with sufficient crystallinity to improve and control the release properties of a polyurethane coating. Furthermore, by limiting the amount of multifunctional isocyanate in the polyurethane composition it is possible to provide a coating which has good biodegradation properties.

[0049]

[0023] In one embodiment, melting point of the polyester is below that of the nutrient granule. For example, in some embodiments, the polyester will melt between about 60 °C and about 80 °C and the nutrient granule is a urea granule which melts at around 130 °C. By ensuring that the polyester melting point is below that of the nutrient granule it is possible to ensure that the nutrient granule does not melt during processing.

[0050]

[0024] In some embodiments, the polyester has a CH2 / COO ratio of 5 or more, preferably 6 or more and 8 or less. The Applicant has surprisingly found that using polyesters with a lower CH2 / COO ratio leads to an unacceptable release profile of the nutrient granule due to the high polarity of the polyol; whereas, higher CH2 / COO ratios can decrease the degradation rate of the resultant polyurethane below what is desired.

[0051]

[0025] In some embodiments, the multifunctional isocyanate compound has an isocyanate index of between about 130 to about 160. The Applicants have found that multilayer controlled release particles prepared with polyurethane coatings from isocyanate compounds it lower isocyanate indexes have poor release properties. As the isocyanate index increases the release properties improve and then plateau. Polyurethanes prepared from multifunctional isocyanate compounds with higher isocyanate indexes have poor biodegradation properties.

[0052]

[0026] In some embodiments, the multifunctional isocyanate compound is present at less than about 9 wt%, less than about 8 wt%, less than about 7wt%, less than about 6 wt% based on the total weight of the polyester composition.

[0053]

[0027] In some embodiments, the multifunctional isocyanate compound is an aromatic isocyanate. Aromatic isocyanates result in polyurethanes with better release characteristics.

[0054]

[0028] In some embodiments, the multifunctional isocyanate is an aliphatic isocyanate. Aliphatic isocyanates have good biodegradation characteristics.

[0055]

[0029] Examples of multifunctional aliphatic or aromatic isocyanate compounds include, but are not limited to, ethylene diisocyanate; 1,4-tetram ethylene diisocyanate; 1,6-hexamethylene diisocyanate; 1,12-dodecane diisocyanate; cyclobutane-l,3-diisocyanate; cyclohexane- 1,3-and -1,4-diisocyanate, and mixtures of these isomers; isophorone diisocyanate; 2,4- and 2,6-6 EU-51180

[0056] hexahydrotoluene diisocyanate and mixtures of these isomers; dicyclohexylmethane-4,4'-diisocyanate (hydrogenated MDI or HMDI); 1,3- and 1,4-phenylene diisocyanate; 2,4- and 2,6-toluene diisocyanate and mixtures of these isomers (TDI); diphenylmethane-2,4'- and / or -4,4'-diisocyanate (MDI); naphthylene-l,5-diisocyanate; triphenylmethane-4,4',4"-triisocyanate; polyphenyl-polymethylene-polyisocyanates of the type which may be obtained by condensing aniline with formaldehyde, followed by phosgenation (polymeric MDI); norbomane diisocyanates; m- and p-isocyanatophenyl sulfonylisocyanates; perchlorinated aryl polyisocyanates; modified polyfunctional isocyanates containing carbodiimide groups, urethane groups, allophonate groups, isocyanurate groups, urea groups, or biuret groups; polyfunctional isocyanates obtained by telomerization reactions; polyfunctional isocyanates containing ester groups; and polyfunctional isocyanates containing polymeric fatty acid groups. Those skilled in the art will recognize that it is also possible to use mixtures of the polyfunctional isocyanates described above, preferably using mixture of polymeric MDI, mixture of MDI isomers and mixture of TDI.

[0057]

[0030] In some embodiments, the controlled release fertiliser particle has multiple alternating polyurethane and wax layers.

[0058]

[0031] In some embodiments, the wax is biodegradable. For example, the wax may be a mineral oil, a paraffin wax or a natural wax. Preferably, the wax should have a similar melting point to the processing temperature of the at least one polyurethane layer. A biodegradable substance is one which is capable of being decomposed by bacteria or other living organisms and thereby avoiding pollution.

[0059]

[0032] In some embodiments, the nutrient granule comprises the elements nitrogen, phosphorous or potassium, or any combination of these materials. Preferably, the elements of nitrogen, phosphorous or potassium are biologically available.

[0060]

[0033] Examples of a suitable semicrystalline polyester polyol include both aliphatic and aromatic polyesters. Polyester polyols for use in the present disclosure include, but are not limited to, those produced by reacting a dicarboxylic acid with an excess of a diol, for example, adipic acid with ethylene glycol or butanediol, or reaction of a lactone with an excess of a diol such as caprolactone with propylene glycol. A combination of aliphatic and aromatic acids may be used as long as the ratio of the two still give a semicrystalline material with the appropriate melting point and suitable viscosity. In addition, polyester polyols for use in the present disclosure may also include: linear or lightly branched aliphatic (mainly adipates) polyols with terminal hydroxyl group; low molecular weight aromatic polyesters; polycaprolactones; polycarbonate polyol. Those linear or lightly branched aliphatic(mainly adipates) polyols with7 EU-51180

[0061] terminal hydroxyl group are produced by reacting a dicarboxyl acids with an excess of diols, triols and their mixture; those dicarboxyl acids include, but are not limited to, for example, adipic acid, AGS mixed acid; those diols, triols include, but are not limited to, for example, ethylene glycol, di ethylene glycol, propylene glycol, dipropylene glycol, 1,4-butane diol, 1,6-hexane diol, glycerol, trimethylolpropane and pentaerythritol. Those low molecular weight aromatic polyesters include products derived from the process residues of dimethyl terephthalate (DMT) production, commonly referred to as DMT still bottoms, products derived from the glycolysis of recycled poly(ethyleneterephthalate) (PET) bottles or magnetic tape with subsequent re-esterification with di-acids or reaction with alkylene oxides, and products derived by the directed esterification of phthalic anhydride. Polycaprolactones are produced by the ring opening of caprolactones in the presence of an initiator and catalyst. The initiator includes ethylene glycol, di ethylene glycol, propylene glycol, dipropylene glycol, 1,4-butane diol, 1,6-hexane diol, glycerol, trimethylolpropane and pentaerythritol. Polycarbonate polyols are derived from carbonic acid that can be produced through the polycondensation of diols with phosgene, although transesterification of diols, commonly hexane diol, with a carbonic acid ester, such as diphenylcarbonate.

[0062]

[0034] Biorenewable polyols suitable for use in the present disclosure include castor oil, sunflower oil, palm kernel oil, palm oil, canola oil, rapeseed oil, soybean oil, com oil, peanut oil, olive oil, algae oil, and mixtures thereof.

[0063]

[0035] Another aspect provides a method for preparing a multilayered controlled release fertiliser particle, said method comprising:

[0064] a. Providing a nutrient granule;

[0065] b. Providing a mixing apparatus;

[0066] c. Heating said mixing apparatus to a predetermined temperature

[0067] d. Placing said nutrient granule into the mixing apparatus;

[0068] e. Optionally injecting a wax composition into the mixer and mixing for a predetermined amount of time; and either step f) or g)

[0069] f. Injecting a polyester composition comprising a semicrystalline polyester polyol with a molecular weight between about 3000 and about 4000 g / mol, followed by injecting less than about 10 wt% of a multifunctional isocyanate compound based on the total weight of the polyester composition into the mixing apparatus and mixing for a predetermined amount of time; or

[0070] g. Injecting less than about 10 wt% of a multifunctional isocyanate compound based on the total weight of the polyester composition followed by Injecting a polyester composition8 EU-51180

[0071] comprising a semicrystalline polyester polyol with a molecular weight between about 3000 and about 4000 g / mol into the mixing apparatus and mixing for a predetermined amount of time; h. Optionally injecting a wax composition comprising a wax into the mixer and mixing for a predetermined amount of time;

[0072] i. Optionally repeating steps e), f) or g), and h);

[0073] j . Removing resultant particle from mixer;

[0074] Wherein the predetermined temperature is a temperature above the melting point of the polyester polyol, above the melting point of the wax in the wax composition and below the melting point of the nutrient granule and wherein the resulting controlled release fertiliser particle comprises at least one wax layer.

[0075]

[0036] The mixing apparatus may be any apparatus capable of mixing the granules.

[0076]

[0037] In some embodiments, the polyester polyol, the multifunctional isocyanate and the wax are as described above in relation to the first aspect of the disclosure.

[0077]

[0038] In some embodiments, a catalyst is added to the mixer to facilitate the formation of a polyurethane layer. Any organometallic or amine catalyst useful for promoting the hydroxyl / isocyanate reaction may be used.

[0078]

[0039] In some embodiments, the predetermined temperature is from about 120 °F to about 200 °F, preferably from about 140 °F to about 175 °F.

[0079]

[0040] In some embodiments, the method is performed at atmospheric pressure.

[0080]

[0041] In an aspect there is provided a controlled release fertiliser particle produced by the method described above wherein said controlled release fertiliser particle comprises a nutrient granule coated at least one polyurethane layer (sometimes referred to herein as a polymer film) and preferably at least one wax layer.

[0081]

[0042] In an embodiment, greater than 50% of the organic carbon in the coating system comprising the polymer film and the wax converts to CO2 within 48 months, preferably greater than 80% of the coating system, more preferably greater than 90% of the coating system.

[0082]

[0043] In an embodiment, the polymer film has no eco-toxic effects. An eco-toxic compound is one which is harmful to the environment, plants, or animals. It can also refer to substances which are hazardous to the environment.

[0083]

[0044] In an aspect there is provided use of a polyester composition comprising a semicrystalline polyester polyol with a molecular weight between about 3000 and about 4000 g / mol, and less than about 10 wt% of a multifunctional isocyanate compound based on the total weight of the polyester composition for use in coating a nutrient granule.9 EU-51180

[0084]

[0045] In some embodiments of the above-described use, the polyester polyol and multifunctional isocyanate are as described above.

[0085] Examples

[0086]

[0046] More details and advantages will become obvious from the following examples. The materials shown in Table 1 were used:

[0087] Name Formal name CH2 / COO diacid diol Manufacturer BDAA p(butylene adipate) 4 Adipic acid 1,4- Chanda BDO PCL Polycaprolactone 5 NA NA Chanda HDAA p(hexamethylene 5 Adipic acid 1,6- Chanda adipate) HDO

[0088] BDSA p(butylene sebacate) 6 S eb acid acid 1,4- Chanda- BDO HATC HDSA p(hexamethylene 7 S eb acid acid 1,6- DIC sebacate) HDO

[0089] BDDA p(butylene 7 Dodecanedioc 1,4- Chanda dodecanedioate) acid BDO

[0090] HDDA p(hexamethylene 8 Dodecanedioc 1,6- Stepan dodecanedioate) acid HDO

[0091] ODDA p(octamethylene 9 Dodecanedioc 1,8- HATC dodecanedioate) acid ODO

[0092]

[0093] Table 1

[0094]

[0047] The following protocols and methods were used in the examples.

[0095]

[0048] Controlled release fertilizer particles were made using the following method:

[0096] 1. A known amount of uncoated urea was loaded into the mixing pan and the mixing rotor was lowered into the pan.

[0097] 2. The desired amount of polyol, isocyanate, and wax were weighed out.

[0098] 3. The mixing bowl is heated using the attached hot air gun to match desired processing temperature. Typically, a mixing temperature of 160°F is used (for higher melting polyester10 EU-51180

[0099] polyols this may be increased to a maximum of 180°F). The heater is set to medium heat to avoid heating the urea too rapidly and overshooting the required temperature.

[0100] 4. While heating the urea, the particles are constantly mixed to achieve uniform heating. Likewise, when the chemicals are introduced the particles are constantly being mixed to insure uniform distribution of the chemicals.

[0101] 5. Once substrate and mixing pan have reached processing temperature the heating gun is turned off. Typically, a pan speed of 30Hz is used and a rotor speed of 30Hz.

[0102] 6. Polyol was injected into the mixer and allowed to mix for 30 seconds.

[0103] 7. Isocyanate was injected into the mixer and allowed to mix for 60 seconds.

[0104] 8. Wax was injected into mixer and allowed to mix for 30 seconds

[0105] 9. Steps 6-8 were repeated as many times as necessary to reach the desired coating weight / number of layers.

[0106] 10. Upon completion of the desired process time the contents of the mixer were discharged into a large cooling tray.

[0107] 11. The coated particles were agitated every 5 minutes to stop particles from conglomerating due to the wax cooling and solidifying.

[0108] Reactivity parameters

[0109]

[0048] Add required weights of the fully formulated Polyol component (B-component), including any optional additives such as catalyst and dye, necessary to achieve 300 g into a small cup. The chemical components and apparatus are initially all at 180°F. The B-component is first weighed into the mixing container, followed by A-component, at the appropriate weight ratio of the components. Immediately and simultaneously start a timer and start mixing the compounds. Continue mixing for 20 seconds or until the material solidifies if it is less than 20 seconds.

[0110]

[0049] To check for the reaction time, periodically lightly touch a stainless-steel spatula (or alternately a wood tongue depressor) to the surface of the material. When the spatula hits a hard, or cured, spot on the surface of the material that is considered the reaction time. The system needs to be formulated such that the full curing takes place within 35 s to 55 s.

[0111] Release

[0112]

[0050] Nutrient solutions, prepared by dissolving a variety of known concentrations of nutrient in distilled water, are prepared. The refractive index of the known concentrations is measured with a refractometer so that a calibration curve of refractive index vs concentration may be11 EU-51180

[0113] constructed. Then, 10 g of CRF is accurately weighed into a small jar and 90 g of water is added. The sample is gently swirled and allowed to rest until the required measurement time. Before each new measurement the sample is gently swirled to ensure uniformity. A small sample of the solution is placed on the refractometer and the measurement recorded. Comparison to the calibration curve gives the nutrient concentration in the solution. The percentage of nutrient released from the CRF can then be calculated.

[0114] Drop Test

[0115] Testing Device Description:

[0116]

[0051] The drop test device consists of 3” (inner diameter) PVC pipe that is mounted vertically and a metal can that is positioned at the bottom of the PVC pipe. The metal can have diameter of 14.5” and height of 24”. The bottom end of the PVC pipe is positioned 20” above the bottom of the metal can. The top of the PVC pipe is located 19.5’ above the bottom of the metal can.

[0117] Testing procedure:

[0118] 1. Weigh 200 g of CRF and place it in a cup.

[0119] 2. The whole amount of the CRF is then poured into the opening of the 3” PVC pipe from the top.

[0120] 3. The tested sample is retrieved from the metal can.

[0121] Abrasion Test

[0122] Testing Device Description:

[0123]

[0052] A portable paint shaker (Blair TORNADO II Model 51000) is used for the CRF abrasion test.

[0124] Testing procedure:

[0125] 1. Weigh 500 g of CRF and pour it gently into a one-gallon paint (tin) can.

[0126] 2. Secure the tin can on the fixture of the paint shaker.

[0127] 3. Set the dial at 2.

[0128] 4. Close the metal cage.

[0129] 5. Turn on the power switch and start the timer.

[0130] 6. Turn off the power after 30 seconds.

[0131] 7. Remove samples from the tin can.12 EU-51180

[0132] Enzymatic degradation

[0133]

[0053] This method is designed to qualitatively analyze the degradation of polymeric samples as a surrogate to environmental degradation process. Degradation is determined by measuring the changes in the weight of samples during the degradation process.

[0134] Buffer preparation

[0135]

[0054] To prepare 500 mL of lOOmM PBS buffer solution at pH 7.4, mix the following solutions:

[0136] 1. Solution A: 100 mM sodium sulphate dibasic dihydrate (405 mL)

[0137] 2. Solution B: 100 mM sodium sulphate monobasic monohydrate (95 mL)

[0138] Sample preparation

[0139] 1. Place and fix peal-ply paper onto the tempered glass.

[0140] 2. Place the system on the hot press to heat up.

[0141] 3. Mix the isocyanate with pre heated PO and catalyst.

[0142] 4. Pour the mixture onto the heated glass and use the draw down method to prepare a film with pre-defined thickness (#40 = 1mm).

[0143] 5. Leave the system on hot press (190 F) for at least 30 mins to ensure full crosslinking.

[0144] 6. Take the system out and let it cool down at room temperature.

[0145] 7. Punch disks through the film.

[0146] Experimental procedure

[0147] 1. Prepare the enzyme solution using PBS buffer containing 10% v / v cutinase Novozyme 52130 15 kLU / mL and 10% Lapolase from A- Oryzae Novozyme 100 kLU / mL.

[0148] 2. Add lOmL of the solution to 2oz jars.

[0149] 3. Drop the sample in j ar (one sample per j ar).

[0150] 4. Place the jars on the reciprocal shaker. Rotate at 90 RPM. In case higher temperatures needed, place the shaker inside an oven.

[0151] 5. After designated time-frames, take samples out, wash them with water and air dry them.

[0152] 6. Weigh samples and record the results.

[0153] 7. Refresh the enzyme solution and continue the experiment until more than 50% in weight loss is achieved. For polyesters, repeat the steps each day. For polyurethanes, repeat every 3 days.

[0154] Example 113 EU-51180

[0155]

[0055] Each of the following polyester polyols were individually used to prepare polyurethane coatings (MDI / polyol index: 105) and the release rates were tested over time: 1,4 BDO (BD) and Adipic acid (AA) (BDAA from Chandra), Caprolactone, 1,6 Hexane diol (HD) and AA (PCL from Chandra), BD and Sebacic acid (SA) (BDSA from Chandra-HATC), BD and dodecanedioic acid (DA)(BDDA from Chandra), HD and SA (HDSA from DIC), and Octane diol and DA (ODDA from HATC). The results are shown in Figure 1. The release rate (%) on the y axis versus the time in days (x axis) for various different types of polymers. These results demonstrate that semicrystalline polymers prepared with aliphatic polyesters have excellent release properties.

[0156] Example 2

[0157]

[0056] The results in figure 2 show the effect of CO2 / COO index (x-axis) on release properties in days (y-axis). Urea was coated by 3 layers of polymer and 2 layers of wax at the total coating weight of 2.5% (MDI / polyol index: 105).

[0158]

[0057] These results show that increasing the CO2 / COO index reduces the release rate.

[0159]

[0058] In order to evaluate the relative degradation rates of different polyester, an enzymatic degradation method was used. This method uses specific naturally-occurring enzymes, derived from different microorganisms, to degrade ester and urethane bonds and serves as a surrogate method to help develop the desired formulation in terms of biodegradation. Figure 3 shows the normalised weight loss (y-axis) against time (days) for the different polyurethanes. These results show that it takes 2 days for PCL to lose 50% of its weight. Whereas, BDSA takes roughly 16 days. The time required for degradation goes exponentially higher as the CH2 / COO index increases. Thus, according to Fig. 3, it is best to keep CH2 / COO index between 4-8, more preferably, at or below 7.

[0160] Example 3

[0161]

[0059] To investigate the effect of isocyanate content, the release rate of a MDEpolyol polyurethane with different isocyanate indexes was tested. The results are shown in Figures 4 and 5. Figure 4 shows the release rate (%) on the y-axis against the time in days (x-axis) for different isocyanate indexes. Figure 5 shows the time in days (y -axis) for polymers of different isocyanate index (x-axis) to reach different release rates. These results show that it is preferable to use isocyanates with an isocyanate index above 130 and below 155. This optimization extremely enhances the release properties opening windows for a more economical system while keeping or even improving the biodegradability.14 EU-51180

[0162] Example 4

[0163]

[0060] The effect of the polyester’s molecular weight (MW) on the performance of coating system from different angles was investigated. Polyesters with MW higher than 5000 Da tend to have higher melt viscosity which makes them hard to process. In order to overcome high viscosity, one may suggest increasing the operation temperature. However, urea or any other fertilizer can be heated up to only a certain point it will melt. In case of urea, it starts to melt down at temperatures above 185F, and disrupt the coating process. Thus, we chose the 175F as the operation temperature at which, polyester must be flowable and its viscosity should be less that 2000cp. Moreover, MWs higher than 5000 Da will require less cross linker which make it hard to achieve effective mixing and low crosslinking density results in faster release of the nutrient which is not favourable.

[0164]

[0061] Low MW polyesters require higher amount of crosslinker (higher OH value), which naturally helps solving the above mentioned issues. However, polymer chains must be larger than a threshold to be able to form crystals large enough to enhance barrier properties. Effective crystal formation should not be confused with the degree of crystallinity. Moreover, the isocyanate content is preferably below 10%, which will dictate the lower MW limited to 2000 Da. Thus, we investigated the effect of MW of the release properties to find the optimum range. HD AA with MW 2-5 kDa was investigated, as depicted in Figures 6 and 7 the results clearly demonstrates the preferred MW range to be between 3-4 kDa. Figure 6 shows the release rate (y axis) against time in days (x-axis) for different MW polymers. Figure 7 shows the time (y-axis) in days for different MW polymers (x-axis) to achieve 20%, 50%, and 80% release.

[0165] Example 5

[0166]

[0062] To investigate the effect of crystallinity on nutrient release, the urea granule was coated with an aliphatic polyester polyol with little-to-zero degree of crystallinity. Thus, BHAS, a random linear polyester from AA, SA, BD, and HD, with MW=5000 was synthesized. This product has a CH2 / COO=5, similar to HDAA. The release profile of this coating is compared with HDAA (equal CH2 / COO and MW). The results are shown in Figure 8 which shows the release rate (5) on the y-axis versus time in days on the x axis. These demonstrate that the semicrystalline polymer has better controlled release.

[0167] Example 615 EU-51180

[0168]

[0063] After optimising the factors discussed above, 5 optimised formulations were prepared and their release profile is shown in Figure 9. The release % is shown on the y axis plotted against time (in days) on the x-axis. Release profile of BDDA (7), HDSA (7), and BDSA (6) found not dramatically different as they were able to provide a 90-day release rate. Lastly, HDAA exhibits the least favorable release rate as it has low CH2 / COO index of 5 and no further optimization can improve its performance.

[0169]

[0064] These optimised coated fertilisers were then subjected to drop and abrasion tests. The results of which are shown in Figure lOa-f. These tests are used to simulate the handling and distribution of the CRF when applied in the field. While there is a decrease in the release performance, the results demonstrate that the coating has enough integrity to provide acceptable release profiles without significant catastrophic release that would result from fractured coatings or coatings separated from the nutrient particle.

[0170] Example 7

[0171]

[0065] The properties of aliphatic and aromatic-aliphatic semicrystalline polyesters was investigated. Aromatic aliphatic used herein is comprised of BD, SA, and Terephthalic acid (TA). Diacid monomer ratio SA:TAis equal to 7:3, thus called 30% aromatic. Since its structure is somewhat similar to BDSA, their release performance was compared. As expected, Aromatic aliphatic polyester urethane yields slower release kinetics confirming that improved release properties due are to the hydrophobicity and different crystallization behaviour. The results are shown in Figure 11 as the % released on the y-axis against the time in days on the x-axis.

Claims

16 EU-51180What is claimed:

1. A multilayered controlled release fertiliser particle comprising:a. A nutrient granule;b. At least one polyurethane layer;c. At least one wax layer;wherein the at least one polyurethane layer comprises a polyurethane obtained from a polyester composition comprising a semicrystalline polyester polyol with a molecular weight between about 3000 and about 4000 g / mol, and less than about 10 wt% of a multifunctional isocyanate compound based on the total weight of the polyester composition.

2. The multilayered controlled release fertiliser particle of claim 1, wherein a melting point of the polyester is below that of the nutrient granule.

3. The multilayered controlled release fertiliser particle of claim 1 or claim 2, wherein the polyester has a CH2 / COO ratio of 5 or more, preferably 6 or more and 8 or less.

4. The multilayered controlled release fertiliser particle of any preceding claim, wherein the multifunctional isocyanate compound has an isocyanate index of about 130 to about 160.

5. The multilayered controlled release fertiliser particle of any preceding claim, wherein the multifunctional isocyanate compound is an aromatic isocyanate.

6. The multilayered controlled release fertiliser particle of any preceding claim, wherein the controlled release fertiliser particle has multiple alternating polyurethane and wax layers.

7. The multilayered controlled release fertiliser particle of any preceding claim, wherein the at least one wax layer comprises a biodegradable wax, preferably wherein the biodegradable wax is a mineral oil, a paraffin wax, or a natural wax.

8. The multilayered controlled release fertiliser particle of any preceding claim, wherein the nutrient granule contains the elements nitrogen, phosphorous or potassium, or any combination of these materials.

9. The multilayered controlled release fertiliser particle of any preceding claim, wherein the at least one polyurethane layer is less than 10 wt%, preferably less than 6 wt%, more preferably less than 4 wt% of the total weight of the controlled release fertiliser particle.

10. A method for preparing a multilayered controlled release fertiliser particle, said method comprising:a. Providing a nutrient granule;b. Providing a mixing apparatus;c. Heating said mixing apparatus to a predetermined temperatured. Placing said nutrient granule into the mixing apparatus;17 EU-51180e. Optionally injecting composition comprising a wax into the mixer and mixing for a predetermined amount of time; and either step f) or g)f. Injecting a polyester composition comprising a semicrystalline polyester polyol with a molecular weight between about 3000 and about 4000 g / mol, followed by injecting less than about 10 wt% of a multifunctional isocyanate compound based on the total weight of the polyester composition into the mixing apparatus and mixing for a predetermined amount of time; org. Injecting less than about 10 wt% of a multifunctional isocyanate compound based on the total weight of the polyester composition followed by injecting a polyester composition comprising a semicrystalline polyester polyol with a molecular weight between about 3000 and about 4000 g / mol into the mixing apparatus and mixing for a predetermined amount of time;h. Optionally injecting a wax composition into the mixer and mixing for a predetermined amount of time;i. Optionally repeating steps e), f) or g), and h);j . Removing resultant particle from mixer;Wherein the predetermined temperature is a temperature above the melting point of the polyester polyol, above the melting point of the wax in the wax composition and below the melting point of the nutrient granule and optionally wherein the resulting controlled release fertiliser particle comprises at least one wax layer.

11. The method of claim 10, wherein the polyester has a CH2 / COO ratio of 5 or more, preferably 6 or more and 8 or less.

12. The method of claim 10 or claim 11, wherein the multifunctional isocyanate compound has an isocyanate index of about 130 to about 160.

13. The method of any one of claims 10 to 12, wherein the multifunctional isocyanate compound is an aromatic isocyanate.

14. The method of any one of claims 10 to 13, wherein the wax in the wax composition is biodegradable, preferably wherein the wax in the wax composition is a mineral oil, a paraffin wax, or a natural wax.

15. The method of any one of claims 10 to 14, wherein the nutrient granule contains the elements nitrogen, phosphorous or potassium, or any combination of these materials.

16. A multilayered controlled release fertiliser particle produced by the method of any one of claims 10 to 15, wherein said controlled release fertiliser particle comprises a nutrient granule coated with at least one polyurethane layer and at least one wax layer.18 EU-5118017. The multilayered controlled release fertiliser particle of claim 16, wherein greater than 50% of the organic carbon in the coating system converts to CO2 within 48 months, preferably greater than 80% of the coating system, more preferably greater than 90% of the coating system.

18. The multilayered controlled release fertiliser particle of claim 16 or claim 17, wherein the at least one polyurethane layer has no eco toxic effects.

19. Use of a polyester composition in the manufacture of a controlled release fertiliser particle, said composition comprising a semicrystalline polyester polyol with a molecular weight between about 3000 and about 4000 g / mol, and less than about 10 wt% of a multifunctional isocyanate compound based on the total weight of the polyester composition.

20. Use according to claim 19, wherein the polyester has a CH2 / COO ratio of 5 or more, preferably 6 or more and 8 or less.

21. Use according to claim 19 or claim 20, wherein the multifunctional isocyanate compound has an isocyanate index of about 130 to about 160.

22. Use according to any one of claims 19 to 21, wherein the multifunctional isocyanate compound is an aromatic isocyanate.

23. Use according to any one of claims 19 to 22, wherein the wax is biodegradable, preferably wherein the wax is a mineral oil, a paraffin wax, or a natural wax.

24. Use according to any one of claims 19 to 23, wherein the nutrient granule contains the elements nitrogen, phosphorous or potassium, or any combination of these materials.

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