WO2020096454A1

WO2020096454A1 - Controlled-release device in agriculture

Info

Publication number: WO2020096454A1
Application number: PCT/NL2019/050727
Authority: WO
Inventors: Jan Willem BLANKESTIJN; Geraldus Gerardus Johannes Schennink; Hendrikus Antonius HAGENAARS; Thijs Rodenburg; Joost Rodenburg
Original assignee: 4Grow Fun B.V.; Stichting Kennis Exploitatie Rb
Priority date: 2018-11-06
Filing date: 2019-11-06
Publication date: 2020-05-14
Also published as: EP3877354A1; NL2021946B1

Abstract

The invention is directed to a controlled-release device for horticulture such as a plant pot, rod, stick, tablet, coating or the like, said device comprising a biodegradable composition comprising a bioactive component and a biodegradable matrix, wherein the biodegradable matrix comprises a natural polymer (e.g. a polymeric carbohydrate) and a biopolyester. The invention is further directed to a method for preparing the biodegradable controlled-release device by: a) providing a masterbatch comprising the biopolyester and the bioactive component and compounding said masterbatch; followed by b) blending the compounded masterbatch with a biodegradable compound comprising the polymeric carbohydrate to provide a dry blend and processing said dry blend to provide the device.

Description

Title: Controlled-release device in agriculture

The invention is in the field of agriculture such as horticulture. In particular, the invention is directed to a controlled-release device for controlled-release of a bioactive component to plants.

In the field of agriculture and in particular horticulture, controlled-release fertilizers (CRFs) are known to release nutrients gradually into the soil. These conventional CRFs are typically granulates that are embedded in the soil in which the plant is planted, after which nutrient are gradually released. Most CRFs are based on the principle of poor water-solubility such that the nutrients are not dispersed to rapidly into the soil. An example of a CRF is isobutylidenediurea (IBDU), which is a urea-derivate having low-solubility properties in water. A drawback of the poor water-solubility approach for CRFs is that for every nutrient or every desired release profile, a dedicated derivate of the nutrient has to be developed. In addition, the control over the release profile is limited. As for instance described in Du et al. Journal of Polymers and the Environment 14 (2006) 223-230, attempts have been made to address these drawbacks by CRFs with semi-permeable coatings ( e.g . polyolefin-coated CRFs). However, control of the release profile has proven to be difficult and the coatings based on for instance polyolefins are generally not biodegradable such that these coatings remain as plastic waste in the soil. Moreover, this approach is limited in the possible bioactive components that can be provided to the plant, as the components must be able to sufficiently cross the semi- permeable coating.

In EP0763510, a system for controlled release of one or more agrochemicals is disclosed. It is disclosed that a very low amount of starch (1 wt%) can be present as a spread improver. In US2014/083148, a foamed material having a plurality of pores includes a starch, a biodegradable polyester and a plasticizer and a nutrient is disclosed. In W096/18591 and DE 102005121221 a controlled release matrix- type fertilizer and super-absorber as respectively disclosed.

In addition to the above-mentioned drawbacks drawback of conventional approaches is the absence of a good control over the

shapeability of e.g. the CRF products, which is generally limited to

granulation and the absence of a good control over the release profile.

The object of the present invention is to provide a device that overcomes one or more of the above-mentioned drawbacks. Accordingly, the present invention is directed to a controlled-release device for controlled- release of a bioactive component to plants, said device comprising a biodegradable composition (herein also referred to as the composition) comprising the bioactive component and a biodegradable matrix that is based on a biopolyester, preferably in combination with a natural polymer, more preferably in combination with a polymeric carbohydrate.

The term‘natural polymer’ as used herein refers to polymers that occur in nature and includes polymeric carbohydrates (i.e. polysaccharides) and proteins (see also John and Thomas, Natural Polymers Volume 1:

Composites (2012) RSC Green Chemistry No.16). Examples of proteins that can be suitably applied in the present invention are prolamin and

prolamine-like proteins such as glutelin, in particular wheat gluten.

Generally, it is preferred that the biodegradable composition comprises a homogeneous mixture (e.g. homogeneous dispersed or

homogeneous mixed on molecular level) of the bioactive component and a biodegradable matrix, which matrix comprises a biopolyester, preferably in combination the polymeric carbohydrate, as it was found that this approach allows good control over the release profile and a flexible variation of bioactive components that can be released. Without wishing to be bound by theory, it is beheved that the actually degradation of the matrix is the primary cause of release of the bioactive component. Accordingly, by tuning the degradation properties of the matrix, the release profile can be tuned. Figures 1, 2 and 3 are photographs of devices in accordance with the present invention.

Figure 4 shows curves of the release profile of devices in accordance with the present invention.

The bioactive component may be any type of component that is typically used in horticulture. Suitable examples thereof include nutrients (which include fertilizers such as cut flower fertilizers), repellants (e.g. citronella and various etheric oils), attractants (e.g. pheromones), fragrances, dyes, pesticides, herbicides, algae and the hke. The present invention is particularly suitable for the release of nutrients selected from the group consisting of macronutrients and micronutrients. Nutrients herein included natural, biological and non-natural (chemical) nutrients. Suitable examples include manure and compost. In addition, the term bioactive component herein include in particular cut flower fertilizers that i.a. include carbohydrates, acidity stabilizers (buffering agent), anti bacterial and anti-fungal components and the like, for instance available under the tradename Chrysal™. In particular, nutrients selected from the group consisting of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), sulfur (S), magnesium (Mg), iron (Fe), boron (B), chlorine (Cl), manganese (Mn), zinc (Zn), copper (Cu), Molybdenum (Mo), nickel (Ni) and combinations thereof are preferred. Most preferred are embodiments wherein the bioactive component comprises nitrogen (N), phosphorus (P) and potassium (K). Specific examples thereof include ammonium (NH ), nitrates (NO3), phosphates (PO4) and potassium ions (K).

The present invention enables good control over the release time of the bioactive compound (i.e. the time over which the bioactive compound is essentially fully released). With respect to the present invention, essentially full release may be considered to have been achieved if no substantial further release is observed. Essentially full release of the bioactive compound can be achieved from 1 day to 1 year, depending on the intended application of the product. The present inventors found that the release time can be influenced by the composition of the biodegradable matrix material, e.g. by the content of the natural polymer and in particular of the polymeric carbohydrate. This is particularly the case if the bioactive compound has a hydrophilic character.

The natural polymer, preferably the polymeric carbohydrate is typically present in an amount of up to 60%, preferably 2 to 50%, more preferably 4 to 40% based on the total weight of the biodegradable

composition. Higher amount generally lead to shorter release times.

In one embodiment, essentially full release of the bioactive compound is achieved in a typical time period of about 2 to 12 months, in particular of about 4 to 8 months such as about 6 months with an

essentially linear release profile. This release time is particularly applicable to plants put or growing in soil. For plants that are put in water {e.g. flowers in vases), the preferred release time is however generally much shorter, as the life-time of these plants is also much shorter, e.g. several weeks.

Accordingly, in another embodiment, essentially full release of the bioactive compound is typically to take place in a time period of about 1 day to 1 month, preferably 7 days to 2 weeks.

The present invention advantageously enables a relatively high loading of the bioactive component in the biodegradable composition and the device, without this being detrimental to an effective release profile.

Typically, the bioactive component may be present in an amount more than 10%, preferably more than 15%, more preferably about 20%, based on the total weight of the composition. Generally, if the bioactive component is present in an amount of more than 50%, the structural integrity of the device, stability and there with an effective control of the release profile, is compromised. However, this may depend on the nature and properties of the biodegradable matrix. As such, the bioactive component may preferably be present in an amount less than 60%, preferably less than 50% or 40%. It may be appreciated however, that for certain bioactive components ( e.g . pesticides) a high concentration is not particularly favorable. Accordingly, the bioactive component may also be present in lower amounts, e.g. in amounts of 1% to 5%, or more based on the total weight of the composition.

The polymeric carbohydrate includes linear and branched polysaccharides and oligosaccharides (both native and physically and chemically modified carbohydrates are possible). Polysaccharides are preferred. In a particular embodiment, the polymeric carbohydrate is selected from the group consisting of starch, cellulose and hemicellulose. Starch is particularly preferred, especially thermoplastic starch. Other thermoplastic polymeric carbohydrate or mixtures thereof may therefore also be very suitable for the present invention. The combination of the polymeric carbohydrate and the biopolyester further provide good

processability such as shapeability of the composition and the device.

Particular good results are obtained by a combination of the polymeric carbohydrate comprising starch and the biopolyester comprising a vinyl ester polymer as disclosed in WO 2011/053131, which is incorporated herein in its entirety. It was found however, that the one or more plasticizer(s) for the vinyl ester polymer as defined in WO 2011/053131 is not required for the present invention and may therefore be absent. Particularly suitable polymeric carbohydrate and biopolyester materials include Solanyl™ and Optinyl™ products respectively, both commercially available from

Rodenburg Biopolymers, the Netherlands.

The starch is preferably thermoplastic starch, which can be obtained by destructurizing or plasticizing starch, as is described in WO 2011/053131. In general, this involves applying shear forces under elevated temperatures, optionally in the presence of water. The starch may not necessarily be fully plasticized or destructurized for it to be considered thermoplastic starch. As such, thermoplastic starch as meant herein may still include 5%, preferably less than 2% crystalline starch, based on the weight of the total amount of starch. Suitable examples of raw material for thermoplastic starch include natural starch from vegetable sources such as potato, wheat, corn, tapioca, rice, and peas (including starch from

genetically modified starch -producing plants); and chemically or physically modified starch (oxidized, esterified, etherified, enzymatically treated starch and the like). Other natural starchy materials that contain a high

proportion of starch are suited as well.

Other examples of a suitable starchy materials include flour such as wheat flour (about 68-73% starch based on dry matter) or pretreated wheat flour, i.e. after removal of fibers (about 80-85% starch based on dry matter). In WO 2010/133560, which is incorporated herein in its entirety, suitable compositions including the polymeric carbohydrate comprising flour is disclosed. Flours typically contain, besides starch, protein-containing fractions which may accordingly also be present in the biodegradable matrix.

For facile processability, the biodegradable matrix, and preferably the composition as well, is thermoplastic, meaning that the matrix and the composition (if also being thermoplastic) can be processed in thermoplastic melt-processes without being damaged due to disintegration, degradation, delamination and the like.

As described herein-above, in order to provide the biodegradable composition and the device with the desirable material properties, such as processability and release profile, the device comprises a combination of the polymeric carbohydrate and the biopolyester in the biodegradable matrix. The term‘bio’ in the biopolyester refers herein to the biodegradable nature of the polymer. The term biodegradation herein means degradation typically catalyzed by biological activity leading to mineralisation (i.e. conversion of constituents in naturally occurring compounds, preferably gasses, water and inorganic constituents and/or biomass), not limited to within a certain timeframe. Preferably, the biodegradability is according to the industrial ί norm EN 13432. Preferably, the term‘bio’ also refers to the preferred renewable and sustainable origin of the building blocks of the polymer. The biopolyester preferably comprises a thermoplastic biopolyester. Particular good results are obtained by using polylactic acid (PLA). However, the biopolyester may in general be selected from the group consisting of polylactic acid (PLA), polycaprolacton (PCL), polyhydroxyalkanoates (PHA) such as polyhydroxy butyrate (PHB), polyalkylene succinates or

polyalkylene adipates of C2 to C6 alkylenes such as polybutylene succinate (PBS), polybutylene adipate, poly(butylene adipate-co-terephthalate (PBAT) and combination thereof. PLA herein includes homopolymers of L-lactic acid, of D-lactic acid, or of racemic mixture of L-lactic acid and D-lactic acid, as well as copolymers with for instance hydroxy butyrate, caprolacton and/or glyoxyhc acid. The fraction of the comonomer units in these copolymers is preferably less than 50 mol%, more preferably less than 10 mol%.

The biopolyester is preferably present in an amount in the range of 5 to 99%, preferably 5 to 80%, more preferably 10 to 70%, most preferably 20 to 60%, based on the total weight of the composition.

It was found that a suitable weight ratio of the polymeric carbohydrate to biopolyester in the composition, without being detrimental to the properties of the composition, is in the range of 1:25 to 15:1, preferably 1: 15 to 5: 1, most preferably 1:10 to 1: 1. Typically the amount of biopolyester in the biodegradable matrix is higher than the amount of polymeric carbohydrate. The more preferred weight ratio show improve material properties such as desirable degradation profiles and

processability.

Not every polymeric carbohydrate and biopolyester may inherently be compatible with each other. For instance, the may be immiscible or result in a poor morphology of the blend. See for instance, Jozef Bicerano, A Practical Guide to Polymeric Compatibilizers for Polymer Blends, Composites and Laminates", Polymer Additives and Colors, 2005, 1- 26. Accordingly, in some embodiments it may be advantageous that the biodegradable matrix further comprises a compatibilizer. The compatibilizer may for instance be one or more of random copolymers, block or graft copolymers, nonreactive polymers containing polar groups, reactive functional polymers. Specific examples of suitable polymers are

compatibilizers include those based on vinyl esters, (meth)acrylic esters, vinyl aromatics, olefins, 1,3-dienes, vinyl halides, and the like. Vinyl ester polymer are particularly preferred in this respect. The vinyl ester polymer is preferably selected from the group consisting of vinyl ester homo, co- and/or terpolymers. Suitable vinyl esters are vinyl esters of straight- chain or branched carboxylic acids having 1 to 15 carbon atoms. Particular examples of such polymers are polymers based on vinylacetate, vinyl propionate, vinyl butyrate, vinyl 2-ethylhexanoate, vinyl laurate, 1 -methyl vinyl acetate, vinyl pivalate and vinyl esters of alpha-branched monocarboxyhc acids having 9 to 11 carbon atoms. Vinyl acetate polymers are particularly preferred, including copolymers of vinylacetate/ ethylene, vinylacetate/

ethylene/vinyllaurate, vinylacetate/ ethylene/vinyl ester of versatic acid or combinations thereof. The vinyl ester homo, co- and/or terpolymers may be stabilized by a protective colloid/emulsifier system for instance based on polyvinyl alcohol or a surfactant. Further details can be found in

US6576698, which content is herein incorporated by reference. These stabilizers (and the amounts thereof) are considered incorporated in the term vinyl ester homo-, co- of terpolymer. In certain embodiments, it may be preferable to provide a mixture of the biopolyester and the compatibilizer. A specific example thereof is the blend of vinyl ester and polylactic acid polymer as for instance commercially available under the tradename

Optinyl™ FI3341 from Rodenburg Biopolymers.

The biodegradable matrix may further comprise plasticizers and/or lubricants to improve the processability of the composition into the device. Suitable plasticizers for the polymeric carbohydrate, in particular for starch in this respect, include polyol, such as a polyol selected from the group consisting of a polyol, more preferably a polyol selected from the group consisting of diethylene glycol, glycol, glycerol, sorbitol and the like. Glycerol is a particularly preferred plasticizer. These types of plasticizers may assist in destructurizing or plasticizing the polymeric carbohydrate, in particular biobased matrices comprising starch. Lubricants that may be added include oils, both natural as synthetic, although natural, vegetable oils sue as palm oil, peanut oil and sunflower oil may be preferred. Stearates of zinc, calcium and magnesium may also be suitable used as lubricant. In general, the amount of lubricant is less than 5%, based on the weight of the polymeric carbohydrate.

A particular advantage of the biodegradable composition in accordance with the present invention, is that is it enables shaping of the device in various shapes and objects. Particular examples of preferred shapes and objects include plant pots, rods, sticks, tablets, labels, tags and coatings. A plant pot in accordance with the present invention may for instance entirely of partially comprise the composition as a coating on the inside. This may for instance be obtained by 2K injection molding processes. Another possibihty, although not preferred, may be that the biodegradable composition is comprised in the device together with a different material that is not part of the biodegradable composition.

In a preferred embodiment, the device consists entirely of the biodegradable composition. For instance, in case of a plant pot, the plant may be potted in the plant pot consisting of the composition, which pot is placed in a non-biodegradable pot or place in the earths soil. Alternatively, the device according to this embodiment may be a stick or rod, having a length of about 10 to 60 cm and/or a diameter of about 2 to 10 mm, preferably 3 to 7 mm. The degradation profile (and concomitantly the release profile) be further be influenced by providing the device with a specific surface, such as protrusions, waffle-shapes surfaces, holes, indentations, notches and the like.

The composition of the present invention has several preferred mechanical properties such as E-modulus, stress-max, elongation at break (as measured according to ISO 527-1) for it to be effectively applicable in horticulture, in particular as a rod or stick that can be placed into the soil of the plant ( vide infra). Accordingly, the E-modulus is preferably more than 0.1 GPa, more preferably more than 0.15 GPa. The stress-max is preferably more than 15 MPa, more preferably more than 20 MPa. The elongation at break is preferably more than 10%, preferably more than 15%, more preferably more than 20%.

The composition as such has a preferred melt -flow index (MFI, as measured according to ISO 1133;) in order for it to be suitable for processing it into the device. In general, the higher the MFI, the more easily a mold can be filled ( vide infra). Preferably the MFI of the composition is more than 5 g/10 min, more preferably more than 20 g/10 min, most preferably more than 25 g/10 min.

Another aspect of the present invention is a method for the preparation of the biodegradable controlled-release device. Typically, the device can be prepared by the steps of:

a) providing a masterbatch comprising the biopolyester and the bioactive component and compounding said masterbatch, followed by;

b) blending the compounded masterbatch with a biodegradable compound, preferably comprising the polymeric carbohydrate, to provide a dry blend and processing said dry blend to provide the device.

In step b), the biodegradable compound may be any biodegradable compound. For example, the biodegradable compound may comprise the biopolyester (in addition to the one added in step a), the polymeric carbohydrate or a combination thereof. It preferably comprises up to 60% polymeric carbohydrate, based on the total weight of the dry blend. It may be appreciated that steps a) and b) each, independently, may comprise sub-steps. Accordingly, providing the dry blend and

processing this into the device may comprise two different sub-steps, which each may or may not be carried out on a separate apparatus.

Production of the masterbatch can be carried out in a

conventional apparatus, for instance in a screw extruder such as a co rotating twin screw extruder, including an arrangement at the die adapted for pelletization of the extrusion product. The compounded masterbatch can be mixed with the biodegradable compound to form the dry blend, which may be processed in thermoplastic melt-processing, for example.

Conventional melt -processes such as thermoforming, molding, extrusion or combinations thereof are generally all possible. The dry blend is particularly suitable for injection molding.

In a further aspect, the invention is directed to the application of the device in plant agriculture. With agriculture herein is meant in particular the field of cultivation and growing of plants. This comprises crop cultivation, which includes cereals, legumes, forage, fruits and vegetables cultivation and horticulture, which includes cultivation of ornamental plants and flowers. Accordingly, the invention is also directed to a method for providing a bioactive component to a plant via a substrate such as soil or water in which the plant is embedded. This method may be carried out in the field of agriculture, and particular in horticulture. The method comprises contacting ( e.g . by sticking the device into) the substrate with one or more biodegradable controlled-release devices. The substrate can absorb the bioactive component after it is released from the device (believed to occur through degradation of the device), after which the roots or stem of the plant can absorb the bioactive component from the substrate. The device may serve more than only providing the bioactive component. For instance, it may also serve to provide structural support to the plant, e.g. as a supporting stick positioned next to the plant. For instance, orchids (also referred to as orchidaceae) are typically grown besides a stick to which the plant is bound. At the end of the flowering period, the orchid (or any other plant for that matter) may be disposed off, after which the stick preferably degrades. As such, the device of the present invention may also suitably replace conventional support stick for plants that are based on bamboo or other materials. It may be appreciated that advantageously, the device of the present invention may thus also provide nutrients or other favorable bioactive components. A supporting stick of about 20 to about 60 cm, having a diameter of about 3 to 10 mm is thus a specific example of an embodiment according to the present invention

Unless specifically indicated otherwise, all amounts expressed herein in percentages refer to weight-percentages relative to the total weight of the biodegradable composition of the invention. All weights herein are expressed based on dry matter.

As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The term "and/or" includes any and all combinations of one or more of the associated listed items. It will be understood that the terms "comprises" and/or "comprising" specify the presence of stated features but do not preclude the presence or addition of one or more other features.

For the purpose of clarity and a concise description features are described herein as part of the same or separate embodiments, however, it will be appreciated that the scope of the invention may include

embodiments having combinations of all or some of the features described.

The invention is illustrated by the following non-limiting examples. Example 1

Step a):

An NPK fertilizer masterbatch was produced based on an

Optinyl™ FI3341 carrier material (supplier Rodenburg Biopolymer B.V., Oosterhout, The Netherlands) and pelletized NPK artificial fertilizer from Triferto B.V., Doetinchem, The Netherlands (containing 12% N, 10% P and 18% K). Both components were dried before compounding (Optinyl FI3341: 16 hours at 45 °C in a desiccant dryer; fertilizer: 16 hours at 55 °C in a vacuum drier). After drying each component, a mixture of 60 parts of the Optinyl™ FI3341 carrier material and 40 parts of the NPK artificial fertilizer was extruded on a Berstorff ZE 25 CE * 40 D into a homogeneous strand with a temperature profile of

20/80/180/180//180/180/180/175/170/170/155 °C and 300 rpm. After cooling the strand with help of a water bath, the strand was pelletized into cylindrical shaped pellets. After extrusion the cylindrical shaped pellets were dried for 16 hours at 45 °C in a desiccant dryer

Step b):

A device (length 16 cm; weight 2.5 gram) was produced with help of an Arburg 520M - Alrounder 2000 - 675 injection molding machine equipped with a 60 parts cavity. Material composition was based on a dry blend of 40% Solanyl™ C1201 (supplier Rodenburg Biopolymer B.V., Oosterhout, The Netherlands) and 60% of the masterbatch as prepared in step a). Processing temperatures were injection cylinder:

130/145/160/165/170/175/180 °C and mold: 25-30 °C.

The sticks as depicted in Figures 1 and 2 were obtained, of which 24% by weight is NPK fertilizer.

The mechanical properties were determined to be as indicated in

Table 1. Table 1

¹ MFI measurements were conducted according to ISO 1133 using a Zwick MFLOW MFI measuring apparatus with a 9.55 mm diameter barrel. The utilised die was 8.000 x 2.095 mm and weights were standard. The barrel is filled prior to the experiment with 5-6 grams of material and the material is melted during 4 minutes. Temperature and weight were chosen according to the specification of the material (in this case 170 °C and 2.16 kg).

²Mechanical properties (tensile) were measured using a Zwick Z010 all-round line lOkN mechanical testing machine according to ISO 527-

1 Samples were prepared according to ISO 527-2. E-Modulus test speed: 1 nim/min; Test speed: 10 mm/min

Example 2

A dry blend is prepared as described in Example 1, which is melt- processed by extrusion to provide rods as depicted in Figure 3.

Example 3

The release profile of the sticks prepared according to Example 1 has been determined by placing 12.5 grams of the sticks (i.e. six sticks) into 1.1 L peat soil of the type Irish coarse mixed with 10 to 15% perlite under storage conditions 20-21 °C and 80-85 % relative humidity

The results are depicted in Figure 4. A release of the fertilizer in about 6 months was determined. It is noted that the ammonium (NH i) likely evaporated, resulting in the decreased cumulative release. Example 4

Step a): compounding

A batch containing 11% of Chrysal™ Professional 7 (supplier Agrifirm, Apeldoorn, The Netherlands) was produced based on a Solanyl C1201™ carrier material (supplier Rodenburg Biopolymer B.V., Oosterhout,

The Netherlands). Production was performed on a Berstorff ZE 42 * 40 D Blue Power twin screw extruder equipped with a LPU Gala underwater pelletiser. Setpoint of the temperature profile of the extruder is

20/80/120/125/150/150/120/120 °C; die temperature is 150 °C and screw speed 200 rpm. After production of the pellets, moisture content of these pellets was equilibrated on 2%.

Step b): injection moulding

Tensile bars from both formulation C1201 + 11% Chrysal™ and reference formulation C1201 (length 7.5 cm; weight 1.35 gram; designed according to ISO 527-2 1BA) were produced with help of an DEMAG Ergotech NC IV 25- 80 compact injection molding machine equipped with a 2 parts cavity.

Processing temperatures were injection cylinder: 45/130/150/162/170 °C and mold: 30 °C.

Step c): analysis

The mechanical properties after conditioning the samples for 1 week at 20 °C and 50% relative humidity (RH) were determined to be as indicated in Table 2. Table 2

²Mechanical properties (tensile) were measured using a Zwick

Z010 all-round line lOkN mechanical testing machine according to ISO 527- 1 Samples were prepared according to ISO 527-2. E-Modulus test speed: 1 mm/min; Test speed: 10 mm /min

Example 5

The release profiles of the tensile bars prepared according to Example 4 step b have been determined by placing 8 grams of bars (i.e. six bars) into 300 ml demineralized water in closed testing trays at 23 °C. The amount of soluble carbohydrates was subsequently determined according to the following procedure: 1 ml sample is taken from the test trays on 4 different moments: 1, 2, 7 and 14 days after starting the test. 200 mΐ sample solution and 800 mΐ 2.5 % (w/w) phenol are added to a 20 ml test tube. 2.5 ml concentrated sulfuric acid is added to the test tubes and mixed well using a Vortex mixer. After cooling, the samples are analyzed at 490 nm with the UV-vis. With help of a calibration line the amount of soluble carbohydrates can be calculated. For full release a maximum concentration of 150 pg/ml of soluble carbohydrates needs to be analysed. Table 3

A full release of the Chrysal™ additive in about 2-3 days was found.

Claims

1. Controlled-release device such as a plant pot, rod, stick, tablet, coating or the like, for use in agriculture, said device comprising a biodegradable composition comprising a bioactive component and a biodegradable matrix, wherein the biodegradable matrix comprises a biopolyester and preferably additionally a natural polymer, more preferably a polymeric carbohydrate.

2. Controlled-release device according to claim 1, wherein the bioactive component is present in an amount of more than 10%, preferably more than 15%, more preferably more than 20%, based on the total weight of the biodegradable composition.

3. Controlled-release device according to any of the previous claims, wherein the bioactive component comprises nutrients, repellants, attractants, fragrances, dyes, pesticides, herbicides, algae and/or the like, preferably nutrients selected from the group consisting of macronutrients and micronutrients, more preferably from the group consisting of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), sulfur (S), magnesium (Mg), iron (Fe), boron (B), chlorine (Cl), manganese (Mn), zinc (Zn), copper (Cu), Molybdenum (Mo), nickel (Ni) and combinations thereof, most preferably wherein the bioactive component comprises nitrogen (N), phosphorus (P) and potassium (K).

4. Controlled-release device according to any of the previous claims, wherein the polymeric carbohydrate comprises starch, cellulose,

hemicellulose or flour preferably thermoplastic starch.

5. Controlled-release device according to any of the previous claims, wherein the natural polymer, preferably the polymeric carbohydrate is present in an amount in the range of up to 60%, preferably 2 to 50%, more preferably 4 to 40% based on the total weight of the biodegradable composition.

6. Controlled-release device according to any of the previous claims, wherein the biopolyester comprises a thermoplastic biopolyester, preferably selected from the group consisting of polylactic acid (PLA), polycaprolacton (PCL), polyhydroxyalkanoates (PHA) such as polyhydroxy butyrate (PHB), polyalkylene succinates or polyalkylene adipates of C2 to C6 alkylenes such as polybutylene succinate (PBS), polybutylene adipate, poly(butylene adipate-co-terephthalate (PBAT) and combination thereof, most preferably PLA.

7. Controlled-release device according to any of the previous claims, wherein the biopolyester is present in an amount in the range of 5 to 99%, preferably 10 to 70%, more preferably 20 to 60%, most preferably 30 to 55% based on the total weight of the biodegradable composition.

8. Controlled-release device according to any of the previous claims, wherein the biodegradable matrix further comprises a compatibilizer, preferably a vinyl ester, (meth)acrylic esters, vinyl aromatics, olefins, 1,3- dienes, vinyl halides, or the like, more preferably a vinyl ester polymer, most preferably a vinyl ester homo, co- and/or terpolymers.

9. Controlled-release device according to the previous claim, wherein the compatibilizer is present in an amount of 0 to 30%, preferably about 15- 27%, based on the total weight of the biodegradable composition.

10. Method for providing a bioactive component to a plant via a substrate such as soil in which the plant is embedded, said method comprising contacting the substrate with one or more biodegradable controlled-release devices in accordance with any of the previous claims.

11. Method for preparing the controlled-release device according to any of claims 1-9, said method comprising the steps of:

a) providing a masterbatch comprising the biopolyester the bioactive component, and optionally the compatibilizer, and compounding said masterbatch;

b) blending the compounded masterbatch with a biodegradable compound, preferably comprising the polymeric carbohydrate to provide a dry blend and processing said dry blend to provide the device.

12. Method according to claim 11, wherein the polymeric

carbohydrate is present in an amount of up to 60% in the biodegradable compound preferably 2 to 50%, more preferably 4 to 40%, based on the total weight of the dry blend.

13. Method according to any of claims 11-12, wherein processing of the dry blend in step b) comprises thermoplastic melt-processing, preferably thermoforming, molding, extrusion or a combination thereof, more preferably injection molding.

14. Kit comprising a plurality of controlled-release device according to any of claims 1-9.

15. Agriculture product, preferably a horticulture product such as a potted plant, said product comprising the controlled-release device according to any of claims 1-9.