Method for preparing microcapsules

Abstract

1. A method for preparing microcapsules, comprising the steps of: - preparing an oil phase comprising a polyfunctional ethylenically unsaturated monomer or oligomer, wherein the polyfunctional ethylenically unsaturated monomer or oligomer has a water solubility of less than 2 grams per liter in deionized water at 20°C; - forming an oil-in-water emulsion with the oil phase; and - subjecting the oil-in-water emulsion to conditions suitable for initiating interfacial polymerization at the oil-water interface using a radical initiator having a water solubility of at least 1 gram per liter in deionized water at 20°C.

Description

Technical Field

[0001] The present invention relates to a method for preparing microcapsules, an oil-in-water emulsion containing such microcapsules, and a method for preparing microcapsules by interfacial polymerization in an oil-in-water emulsion.

Background Art

[0002] Microencapsulation is known in many technical fields. In the agrochemical field, microencapsulation can be useful, for example, for ensuring the chemical stability of active ingredients and controlling the release rate of active ingredients to protect workers from exposure to the active ingredients. In the method for preparing microcapsules generally employed in the agrochemical field, an oil-soluble monomer selected from diisocyanates and polyisocyanates is used, and then these are subjected to a reaction with water or a water-soluble diamine and polyamine at the oil-water interface of an oil-water emulsion. Thereby, a polyurea capsule wall is formed. Such encapsulation technology in the formulation of agrochemical active ingredients is well known to those skilled in the art (see, for example, P.J. Mulqueen in “Chemistry and Technology of Agrochemical Formulations”, D.A. Knowles, editor, Kluwer Academic Publishers, 1998, pages 132-147).

Summary of the Invention

Problems to be Solved by the Invention

[0003] Sustainability of agricultural chemical formulations has become a key objective in the field of agricultural chemistry. The goal is to develop products with a low environmental impact. As part of this effort, the biodegradability of microplastics has become an important topic. Polyurea microcapsules, which are used in many agricultural chemical formulations, are not biodegradable and pose an environmental challenge. Therefore, there is a need to provide a novel process for preparing biodegradable microcapsules. The present invention aims to provide a novel process for preparing biodegradable microcapsules in an oil-in-water emulsion. This process makes it possible to prepare biodegradable microcapsules at the oil-water interface of the emulsion. [Means for solving the problem]

[0004] Surprisingly, it was discovered that biodegradable microcapsules can be obtained in oil-in-water emulsions by using radical polymerization under specific conditions. [Modes for carrying out the invention]

[0005] Therefore, in the first embodiment, as Embodiment 1: - A step of preparing an oil phase containing a polyfunctional ethylene unsaturated monomer or oligomer, wherein the aqueous solubility of the polyfunctional ethylene unsaturated monomer or oligomer in deionized water at 20°C is less than 2 grams / liter, preferably less than 1 gram / liter, and more preferably less than 0.1 grams / liter; - A step of forming an oil-in-water emulsion with the oil phase; - A step of subjecting an oil-in-water emulsion to conditions suitable for initiating interfacial polymerization at the oil-water interface, using a radical initiator having a water solubility of at least 1 g / liter, preferably 10 g / liter, and more preferably 20 g / liter in deionized water at 20°C. A process for preparing microcapsules containing [the specified ingredient] is provided.

[0006] The oils used in the "oil phase" of the present invention are generally, but are not particularly limited to, aromatic hydrocarbons derived from benzene and naphthalene derivatives such as toluene, xylene, and other alkylated benzenes; aliphatic hydrocarbons such as hexane, octane, and cyclohexane; oils derived from aliphatic or isoparaffinic systems; and mixtures of aromatic and aliphatic hydrocarbons; halogenated aromatic or aliphatic hydrocarbons; short-chain and long-chain dialkylamides; saturated or unsaturated carboxylic acids; and C1-C1 aromatic and dicarboxylic acids. 12 Esters; C1-C1 of aliphatic and cyclic aliphatic carboxylic acids 12 It consists of one or more unhydrated solvents known to those skilled in the art, such as petroleum distillates including esters. Particularly preferred unhydrated solvents include, but are not limited to, Solvesso® 100 / 200 (a mixture of aromatic hydrocarbons), ethyl acetate hexyl, and toluene.

[0007] Due to potential toxicity issues, there is a desire to minimize the use of petroleum distillates and pure aromatic compounds. Therefore, while it is possible to solubilize the relevant monomers, it is also advantageous to use unhydrated solvents derived from different sources. Thus, the oil preferably contains benzoates, one or more alkylamides (e.g., Jeffsol AG1730), benzyl acetate (e.g., Jeffsol AG1705), acetyl-2-ethylhexyl citrate (e.g., Citrofol AH II), N,N-dimethylcapric acid amide (e.g., Hallcomid M-10), dihydrolevoglucocenone (e.g., cyrene), or rapeseed oil. Benzoates are particularly preferred, especially benzyl benzoate, methyl benzoate, and dipropylene glycol dibenzoate (e.g., Benzoflex 9-88). These solvents exhibit comparable performance with an improved environmental profile.

[0008] As used herein, the term "polyfunctional ethylene unsaturated monomer or oligomer" means a substance having two or more ethylene unsaturated groups at the terminal positions of the molecule. The water solubility of the "polyfunctional ethylene unsaturated monomer or oligomer" is important in the above process. The water solubility must be such that the monomer or oligomer is predominantly distributed in the oil phase of the oil-in-water emulsion.

[0009] It is preferable that at least 50% by weight of the total amount of monomers and / or oligomers is polyfunctional, such as at least 60% by weight, at least 70% by weight, at least 80% by weight, or even 90% by weight. It is particularly preferable that at least 95% by weight of the monomers and / or oligomers is polyfunctional, such as 95-100% by weight, or 96-99% by weight.

[0010] As used herein, the term "radical initiator" means a substance capable of generating radical species that promote radical reactions. Typical examples of radical initiators are molecules having nitrogen-halogen bonds, azo compounds, and organic or inorganic peroxides. For the process according to Embodiment 1 to be successfully implemented, the radical initiator must have sufficiently high water solubility so that it is predominantly distributed in the aqueous phase of the oil-in-water emulsion. Preferably, the radical initiator is not present in the oil phase, or is substantially absent.

[0011] Preferred water solubility for both the "polyfunctional ethylene unsaturated monomer or oligomer" and the "radical initiator" is described in Embodiment 1. The order of the process steps in Embodiment 1 is not essential. Typically, the microcapsules according to the present invention can be prepared by first emulsifying an oil phase, composed of oil and a polyfunctional ethylene unsaturated monomer or oligomer, in an aqueous phase, composed of a suitable surfactant and water. The emulsion can be formed by homogenizing this oil-in-water emulsion at low or high pressure until oil droplets of the desired size are obtained. A water-soluble radical initiator can then be added to the oil-in-water emulsion and predominantly present in the aqueous phase. However, it is also conceivable that the water-soluble radical initiator may already be present in the aqueous phase when emulsifying the oil phase in the aqueous phase.

[0012] The phrase "using a radical initiator to bring an oil-in-water emulsion to conditions suitable for initiating interfacial polymerization at the oil-water interface" means that the conditions of the oil-in-water emulsion must be such that the radical initiator in the aqueous phase generates free radical species, which then react at the oil-water interface with oil-soluble polyfunctional ethylene unsaturated monomers or oligomers in the radical polymerization reaction. Those skilled in the art in the field of polymerization and microencapsulation are well aware of such conditions, for example, by heating the oil-in-water emulsion, irradiating (photodegrading) the oil-in-water emulsion, or by redox reactions using a reducing agent. Preferably, the radical polymerization reaction at the oil-water interface is initiated by reacting the radical initiator with a reducing agent.

[0013] Accordingly, Embodiment 2 provides the process according to Embodiment 1, in which interfacial polymerization at the oil-water interface is initiated by the addition of a water-soluble reducing agent suitable for the decomposition of the radical initiator, and the water solubility of the reducing agent in deionized water at 20°C is at least 1 gram / liter, preferably 10 grams / liter, and more preferably 20 grams / liter. It is important that the reducing agent is water-soluble and therefore reactable with the radical initiator. When the reducing agent is predominantly distributed in the oil phase, it has been surprisingly found that the quality of the resulting capsules is poor, and some oil droplets are not even properly encapsulated. Suitable water-soluble reducing agents in this process include, but are not limited to, ascorbic acid, sodium sulfite, sodium metabisulfite, sodium bisulfite, sodium thiosulfate, sodium formaldehyde sulfoxylate dihydrate, thiourea, and Bruggolite FF7® (2-hydroxy-2-sulfinatoacetate disodium salt). A typical water-soluble reducing agent successfully employed in the process according to the present invention is sodium sulfite.

[0014] Furthermore, a "polyfunctional ethylene unsaturated crosslinking agent" may be present in the oil phase. The term "polyfunctional ethylene unsaturated crosslinking agent" means a substance having two or more ethylene unsaturated groups at the terminal positions of its molecule. Such a crosslinking agent needs to be suitable for polymerization with the polyfunctional ethylene unsaturated monomer or oligomer defined above. The main function of the crosslinking agent is to strengthen the capsule wall at the oil-water interface. Therefore, as Embodiment 3, a process according to Embodiment 1 or 2 is provided, in which a polyfunctional ethylene unsaturated crosslinking agent suitable for polymerization with the polyfunctional ethylene unsaturated monomer or oligomer is present in the oil phase, and the water solubility of the polyfunctional unsaturated crosslinking agent in deionized water at 20°C is less than 2 grams / liter, preferably less than 1 gram / liter, and more preferably less than 0.1 grams / liter. Here again, it is important that the crosslinking agent is oil-soluble, as is the polyfunctional ethylene unsaturated monomer or oligomer.

[0015] As described above, the present invention aims to provide microcapsules with a low environmental impact. As part of this objective, it is preferable that the microcapsules are biodegradable.

[0016] The term "biodegradable" is defined as a compound that passes the OECD Guidelines for the Testing of Chemicals, test number 301 (OECD 301 test). In particular, a compound that is "biodegradable" is defined as a compound that exhibits mineralization, measured as CO2 emissions or O2 consumption over 28 days, of at least 30%, preferably more than 40%, more preferably more than 50%, and most preferably more than 60%, where mineralization is measured in accordance with test methods OECD TG 301 B, C, D, F or OECD TG 310.

[0017] Therefore, Embodiment 4 provides a process relating to any one of Embodiments 1 to 3, wherein the polyfunctional ethylene unsaturated monomer or oligomer and the polyfunctional ethylene unsaturated crosslinking agent have mineralization measured as CO2 emissions or O2 consumption over 28 days, at least 30%, preferably more than 40%, more preferably more than 50%, and most preferably more than 60%, where mineralization is measured in accordance with the OECD TG301 B, C, D, F or OECD TG 310 test methods. Preferably, the polyfunctional ethylene unsaturated monomer or oligomer and the polyfunctional ethylene unsaturated crosslinking agent include a group independently selected from esters, ethers, carbonates, and carboxylic acid anhydrides. These groups have been shown to have suitable biodegradability according to the above tests.

[0018] As previously described, both polyfunctional ethylene unsaturated monomers or oligomers and polyfunctional ethylene unsaturated crosslinkers contain ethylene unsaturated groups at the terminal positions of the molecules. The polyfunctional ethylene unsaturated monomers or oligomers and polyfunctional ethylene unsaturated crosslinkers are preferably independently selected from acrylates, methacrylates, vinyl esters, vinyl ethers, allyl esters, and allyl ethers. Specifically, the polyfunctional ethylene unsaturated monomers or oligomers are selected from acrylate or (meth)acrylate-terminated esters, acrylate or (meth)acrylate-terminated ethers, acrylate or (meth)acrylate-terminated carbonates, and acrylate or (meth)acrylate-terminated anhydrides. More specifically, the polyfunctional ethylene unsaturated monomer or oligomer is selected from polycaprolactone diacrylate, polycaprolactone dimethacrylate, tripropylene glycol triacrylate, poly(ethylene glycol)-b-(propylene glycol)-b-ethylene glycol dimethacrylate, and trimethylolpropane ethoxylate triacrylate.

[0019] Furthermore, in particular, the polyfunctional ethylene unsaturated monomer or oligomer is selected from vinyl ether-terminated esters, vinyl ether-terminated ethers, vinyl ether-terminated carbonates, and vinyl ether-terminated anhydrides. In other embodiments, the polyfunctional ethylene unsaturated monomer or oligomer is selected from vinyl ester-terminated esters, vinyl ester-terminated ethers, vinyl ester-terminated carbonates, and vinyl ester-terminated anhydrides. In further embodiments, the polyfunctional ethylene unsaturated monomer or oligomer is selected from allyl ether-terminated esters, allyl ether-terminated ethers, allyl ether-terminated carbonates, and allyl ether-terminated anhydrides. In further embodiments, the polyfunctional ethylene unsaturated monomer or oligomer is selected from allyl ester-terminated esters, allyl ester-terminated ethers, allyl ester-terminated carbonates, and allyl ester-terminated anhydrides.

[0020] In a preferred embodiment, the polyfunctional ethylenically unsaturated monomer is polycaprolactone dimethacrylate.

[0021] This monomer can be prepared according to the following reaction scheme.

Chemical formula

[0022] Preferably, n is from 1 to 200, such as 2 - 150, 2 - 100, 3 - 50, 4 - 25, 4 - 20, or even 4 - 15. Advantageously, n is 5.

[0023] Preferably, the polyfunctional ethylenically unsaturated cross - linking agent is selected from trimethylolpropane triacrylate, glycerol triacrylate, trimethylolpropane trimethacrylate, and glycerol trimethacrylate.

[0024] As described above, the radical initiator needs to be present in the aqueous phase. Preferably, the radical initiator is selected from peroxides and azo compounds. Thus, as Embodiment 5, a process according to any one of Embodiments 1 - 4 is provided, where the radical initiator is selected from peroxides and azo compounds, and preferably, the radical initiator is ammonium persulfate, 4,4’ - azobis(4 - cyanovaleric acid), potassium persulfate, t - butyl hydroperoxide, or hydrogen peroxide.

[0025] As described above, the process of the present invention is particularly employed in the agrochemical field where the microencapsulation of active ingredients has many important functions.

[0026] Thus, as Embodiment 6, a process according to any one of Embodiments 1 - 6 is provided, where the oil phase further contains an active ingredient selected from fungicides, herbicides, insecticides, bactericides, acaricides, nematicides, and / or plant growth regulators.

[0027] Preferably, the active ingredient is selected from λ-cyhalothrin, S-metrachlor, prosulfocarb, tefluthrin, chromazon, dimethachlor, acetamiprid, and trifluoroline, and more preferably, the active ingredient is selected from λ-cyhalothrin and S-metrachlor.

[0028] Advantageously, the resulting microcapsules exhibit sustained release of the active ingredient they contain.

[0029] Those skilled in the art recognize that it is possible to produce oil phases of various sizes by adjusting the length of the homogenization time of the mixture and / or by adjusting the rate or pressure of the homogenizer. This means that it is possible to produce microcapsules of various sizes by controlling the size of the oil phase. It has been shown that the thickness of the microcapsule wall depends on the amount of polyfunctional ethylene unsaturated monomer or oligomer present in the oil phase. Furthermore, the amount of radical initiator present in the aqueous phase affects the polymerization rate at the oil-water interface. It has been shown that the presence of polyfunctional ethylene unsaturated crosslinking agent in the oil phase affects the robustness of the microcapsule wall. A minimum amount of polyfunctional ethylene unsaturated monomer or oligomer is required in the oil phase for capsule wall formation. It has been shown that capsule wall formation was best when the weight of the polyfunctional ethylene unsaturated monomer or oligomer was 2% to 75% by weight, preferably 5% to 50% by weight, and more preferably 5% to 30% by weight, based on the total weight of the oil phase.

[0030] Therefore, Embodiment 7 provides a process according to any one of Embodiments 1 to 6, where the weight of the polyfunctional ethylene unsaturated monomer or oligomer is 2% to 75% by weight, preferably 5% to 50% by weight, and more preferably 5% to 30% by weight, based on the total weight of the oil phase.

[0031] Those skilled in the art also understand that oil-in-water emulsions can be stabilized using further auxiliary components. For example, microcapsules may tend to aggregate in the emulsion, and therefore, the use of dispersants may be necessary to keep the microcapsules separated. This is also particularly important for the long-term storage of these oil-in-water emulsions. For example, it has been shown that microcapsule emulsions can be redispersed after storage at 40°C and 54°C for two weeks using the sodium salt of naphthalene sulfonic acid condensate (Morwet D-425, Nouryon).

[0032] It has been found that the process according to the present invention is best carried out in the following order. (i) A step of preparing an oil phase, - A polyfunctional ethylene unsaturated monomer or oligomer in the oil phase, wherein the water solubility in deionized water at 20°C is less than 2 grams / liter, preferably less than 1 gram / liter, and more preferably less than 0.1 grams / liter. - Optionally, a polyfunctional ethylene unsaturated crosslinking agent, - Optionally, agricultural chemical active ingredients A step of preparing an oil phase containing - A radical initiator suitable for initiating the polymerization of polyfunctional ethylene unsaturated monomers or oligomers, wherein the water solubility in deionized water at 20°C is at least 1 gram / liter, preferably at least 10 grams / liter, and more preferably at least 20 grams / liter. - Optionally, surfactants A step of preparing an aqueous phase containing (ii) A step of forming an oil-in-water emulsion by mixing the oil phase and the aqueous phase; (iii) A step in which polymerization is initiated at the oil-water interface by adding a reducing agent suitable for decomposing the radical initiator, wherein the reducing agent has a water solubility in deionized water at 20°C of at least 1 gram / liter, preferably 10 grams / liter, and more preferably 20 grams / liter.

[0033] Typical solvents for the oil phase include, but are not limited to, ethyl acetate hexyl, toluene, and heavy aromatic solvents (e.g., Aromatic 200, Solvesso® 200), although any of the above solvents may be used.

[0034] A typical polyfunctional ethylene unsaturated monomer or oligomer is the ester acrylate monomer CN2035 (manufactured by Sartomer), and a typical polyfunctional ethylene unsaturated crosslinking agent is trimethylolpropane triacrylate.

[0035] Typical radical initiators, though not limited to these, include ammonium persulfate, 4,4'-azobis(4-cyanovaleric acid), potassium persulfate, t-butyl hydroperoxide, and hydrogen peroxide. Typical reducing agents, though not limited to these, include ascorbic acid, sodium sulfite, sodium metabisulfite, sodium bisulfite, sodium thiosulfate, sodium formaldehyde sulfoxylate dihydrate, thiourea, and Bruggolite FF7®.

[0036] In a second aspect of the present invention, the present invention relates to an oil-in-water emulsion composition.

[0037] Therefore, as Embodiment 8, (a) an oil phase containing a polyfunctional ethylene unsaturated monomer or oligomer, and (b) an aqueous phase containing a radical initiator suitable for initiating the polymerization of polyfunctional ethylene unsaturated monomers or oligomers. An oil-in-water emulsion is provided, wherein the aqueous solubility of the radical initiator in deionized water at 20°C is at least 1 gram / liter, preferably at least 10 grams / liter, and more preferably at least 20 grams / liter. Furthermore, the water solubility of the polyfunctional ethylene unsaturated monomer or oligomer in deionized water at 20°C is less than 2 grams / liter, preferably less than 1 gram / liter, and more preferably less than 0.1 grams / liter.

[0038] Advantageously, such oil-in-water emulsions contain microcapsules as defined herein. Such microcapsules may be detectable by CryoSEM analysis.

[0039] Embodiment 9 provides an oil-in-water emulsion according to Embodiment 8, wherein the oil phase further comprises a polyfunctional ethylene unsaturated crosslinking agent suitable for polymerization with polyfunctional ethylene unsaturated monomers or oligomers, wherein the water solubility of the polyfunctional unsaturated crosslinking agent in deionized water at 20°C is less than 2 grams / liter, preferably less than 1 gram / liter, and more preferably less than 0.1 grams / liter.

[0040] Embodiment 10 provides an oil-in-water emulsion according to Embodiment 8 or 9, wherein the polyfunctional ethylene unsaturated monomer or oligomer and the polyfunctional ethylene unsaturated crosslinking agent are biodegradable in accordance with the OECD 301 test.

[0041] Embodiment 11 provides an oil-in-water emulsion according to any one of Embodiments 8 to 10, where the polyfunctional ethylene unsaturated monomer or oligomer and the polyfunctional ethylene unsaturated crosslinking agent are independently selected from acrylate, methacrylate, vinyl ester, vinyl ether, allyl ester, and allyl ether. Furthermore, Embodiment 12 provides an oil-in-water emulsion according to any one of Embodiments 8 to 11, where the polyfunctional ethylene unsaturated monomer or oligomer is selected from acrylate or (meth)acrylate-terminated ester, acrylate or (meth)acrylate-terminated ether, acrylate or (meth)acrylate-terminated carbonate, and acrylate or (meth)acrylate-terminated anhydride. Embodiment 13 provides an oil-in-water emulsion according to any one of Embodiments 8 to 12, where the polyfunctional ethylene unsaturated monomer or oligomer is selected from polycaprolactone diacrylate, polycaprolactone dimethacrylate, tripropylene glycol triacrylate, poly(ethylene glycol)-b-(propylene glycol)-b-ethylene glycol dimethacrylate, and trimethylolpropane ethoxylate triacrylate. Embodiment 14 provides an oil-in-water emulsion according to any one of Embodiments 8 to 13, where the polyfunctional ethylene unsaturated monomer or oligomer is selected from vinyl ether-terminated esters, vinyl ether-terminated ethers, vinyl ether-terminated carbonates, and vinyl ether-terminated anhydrides. In other embodiments, the polyfunctional ethylene unsaturated monomer or oligomer is selected from vinyl ester-terminated esters, vinyl ester-terminated ethers, vinyl ester-terminated carbonates, and vinyl ester-terminated anhydrides. In further embodiments, the polyfunctional ethylene unsaturated monomer or oligomer is selected from allyl ether-terminated esters, allyl ether-terminated ethers, allyl ether-terminated carbonates, and allyl ether-terminated anhydrides.

[0042] Preferably, the polyfunctional ethylene unsaturated crosslinking agent is selected from trimethylolpropane triacrylate, glycerol triacrylate, trimethylolpropane trimethacrylate, and glycerol trimethacrylate.

[0043] Embodiment 15 provides an oil-in-water emulsion composition according to any one of Embodiments 8 to 14, where the radical initiator is selected from peroxides and azo compounds; Embodiment 16 provides that the radical initiator in the aqueous phase is ammonium persulfate, 4,4'-azobis(4-cyanovaleric acid), potassium persulfate, t-butyl hydroperoxide, or hydrogen peroxide, more preferably ammonium persulfate or 4,4'-azobis(4-cyanovaleric acid).

[0044] Embodiment 16 provides an oil-in-water emulsion composition according to any one of Embodiments 8 to 16, wherein the oil phase further comprises an active ingredient selected from fungicides, herbicides, insecticides, fungicides, acaricides, nematicides and / or plant growth regulators.

[0045] Embodiment 17 provides an oil-in-water emulsion composition according to any one of Embodiments 8 to 16, in which the active ingredient is selected from λ-cyhalothrin, S-methrachlor, prosulfocarb, tefluthrin, chromazon, dimethachlor, acetamiprid, and trifluoroline.

[0046] Embodiment 18 provides an oil-in-water emulsion composition according to any one of Embodiments 8 to 17, in which the active ingredient is selected from λ-cyhalothrin and S-methrachlor.

[0047] In a further embodiment 19 of the present invention, an oil-in-water emulsion composition according to any one of embodiments 8 to 18 is provided, wherein the weight of the polyfunctional ethylene unsaturated monomer or oligomer is 2% to 75% by weight, preferably 5% to 50% by weight, and more preferably 5% to 30% by weight, based on the total weight of the oil phase.

[0048] Embodiment 20 provides an oil-in-water emulsion composition according to any one of Embodiments 8 to 19, wherein the aqueous phase further comprises a reducing agent suitable for decomposing the radical initiator, and the aqueous solubility of the reducing agent in deionized water at 20°C is at least 1 gram / liter, preferably 10 grams / liter, and more preferably 20 grams / liter. Further Embodiment 21 provides an oil-in-water emulsion composition according to Embodiment 20, wherein the reducing agent is selected from ascorbic acid, sodium sulfite, sodium metabisulfite, sodium bisulfite, sodium thiosulfate, sodium formaldehyde sulfoxylate dihydrate, thiourea, and Bruggolite FF7®.

[0049] As previously described, the oil-in-water emulsion according to the present invention brings about radical polymerization at the oil-water interface. Accordingly, as Embodiment 22, an oil-in-water emulsion composition according to any one of Embodiments 8 to 21 is provided, in which the oil phase and the aqueous phase are separated by a microcapsule wall containing polymerized polyfunctional ethylene unsaturated monomer or oligomer.

[0050] As described above, the oil-in-water emulsion according to the present invention has particular applications in agriculture. Therefore, the present invention also provides agricultural compositions comprising a product obtained from a process according to any one of Embodiments 1 to 7, or an oil-in-water emulsion according to any one of Embodiments 8 to 22. Accordingly, Embodiment 23 provides an agricultural composition comprising a product obtained from a process according to any one of Embodiments 1 to 7. Embodiment 24 provides an agricultural composition comprising an oil-in-water emulsion according to any one of Embodiments 8 to 22. Embodiment 25 provides an agricultural composition according to Embodiment 23 or 24, further comprising one or more auxiliary agents.

[0051] In further embodiments, the use of an oil-in-water emulsion according to any one of embodiments 8 to 22, or an agricultural composition according to any one of embodiments 23 to 25, is provided for the countermeasure, prevention, or control of plant pathogenic diseases in useful plants susceptible to damage by plant pathogens.

[0052] Further embodiments provide the use of an oil-in-water emulsion according to any one of embodiments 8 to 22, or an agricultural composition according to any one of embodiments 23 to 25, for controlling or preventing pests.

[0053] In further embodiments, a method for controlling or preventing pests is provided, comprising the step of applying an oil-in-water emulsion according to any one of embodiments 8 to 22, or an agricultural composition according to any one of embodiments 23 to 25, to the pest or its environment.

[0054] In a further embodiment, a method is provided for countermeasures, prevention, or control of plant pathogenic diseases in useful plants susceptible to damage by plant pathogens, comprising the step of applying an oil-in-water emulsion according to any one of Embodiments 8 to 22, or an agricultural composition according to any one of Embodiments 23 to 25, to the plant pathogen or its environment.

[0055] Unless otherwise specified, proportions are given as a percentage of the total weight, and all embodiments and preferred properties may be combined in any combination. [Examples]

[0056] The present invention is illustrated by the following embodiments, but there is no intention to limit the scope of the invention.

[0057] experiment Materials used:

[0058] [Table 1]

[0059] Equipment used: - T25 Ultra-Turrax (IKA homogenizer) - Malvern Mastersizer 2000: Particle size distribution measurement - Leitz Diaplan microscope equipped with a Leica camera: Images were captured at typical magnifications of 4X, 10X, 25X, and 40X and processed using Leitz software. - Cryo-electron microscopy: Used for freeze-rupture to determine the internal structure. - Genevac(SP)

[0060] experiment: A typical method for synthesizing microcapsules involves adding an oil phase to an aqueous phase, then emulsifying the sample at 14,000-18,000 rpm for 1-3 minutes to prepare an emulsion. Radical polymerization is then initiated, for example, by heating or by adding a reducing agent.

[0061] Experiment Overview: After synthesizing the initial emulsion, the experiment was designed to activate the vinyl bond at the end of the CN2035 acrylate chain to initiate crosslinking, resulting in the formation of a microcapsule shell. Furthermore, the robustness of the shell was enhanced by introducing additional hydrophobic crosslinking agents (such as trimethylolpropane triacrylate). Both redox (i.e., the use of reducing agents) and thermal initiation with radical initiators were investigated to achieve capsule synthesis. Varying the solubility of the initiator from hydrophilic to hydrophobic allowed for variations in the type of polymer synthesized, yielding microcapsules and matrix microparticles, respectively. To demonstrate the advantages of encapsulation, LCY (λ-cyhalothrin) and SMOC (S-methrachlor) were successfully encapsulated using redox initiation at room temperature. Characterization of LCY release demonstrated sustained release from the capsule shell. Microcapsules were prepared using ethyl acetate hexyl as the organic core, followed by removal of water and organic solvents using Genevac®, and then redispersion in water. Subsequently, the redispersed empty capsules were analyzed in a series of experiments to determine their biodegradation profiles.

[0062] Thermal radical initiation by various hydrophobic and hydrophilic initiators: For each experiment, the radical initiator was dissolved in its respective soluble phase. For example, AIBN (azobisisobutyronitrile) was dissolved in the oil phase (Solvesso 200 + CN2035 and TMPTA), and ACVA was dissolved in the aqueous phase. The phase containing the radical initiator was added to the second phase (oil or aqueous phase without the radical initiator), and the suspension was then emulsified and heated overnight at 80°C with stirring. Characterization by mastersizer and optical microscopy (wet and dry) showed that the microcapsules exhibited minimal aggregation and maintained their structure well even after drying. Further characterization of each droplet of AIBN and ACVA-initiated microparticles by CryoSEM analysis confirmed the structures of the matrix microparticles and microcapsules, respectively.

[0063] This means that the solubility of the radical initiator determines the final microparticle structure. For example, when an oil-soluble radical initiator is used, radical polymerization occurs throughout the oil phase, resulting in matrix microparticles. Conversely, when a water-soluble radical initiator is used, radical polymerization and crosslinking occur only at the oil-water interface.

[0064] Redox radical initiation: In all the cases described below, water-soluble radical initiators were used (e.g., ACVA or APS). All capsules were characterized by Mastersizer and optical microscopy (wet and after drying on glass slides). To determine the effect of initiator solubility, the following two systems were investigated:

[0065] 1) Attempts were made to synthesize microcapsules using TMEDA and APS, and TMEDA and ACVA. A fixed amount of APS (or ACVA) was added to the aqueous phase, and TMEDA to the oil phase, and then emulsified using the general conditions detailed above. The emulsion was left to stand overnight at 30°C with stirring, and then a fixed amount of the solution was taken and left on a glass slide for 2 days to dry. After 2 days of drying, the microcapsules appeared to retain some structure, indicating that crosslinking had occurred at a low rate. However, not all oil droplets were successfully encapsulated, and the majority of the obtained microcapsules appeared to have a fragile shell after drying.

[0066] 2) Using the same method as detailed above, microcapsules were prepared by dissolving sodium sulfite and APS in the aqueous phase. These capsules were left to stand overnight with stirring at 30°C (and then at room temperature). A certain amount of the solution was then taken and left on a glass slide for 2 days to dry. The resulting samples showed a high level of encapsulation; the capsules had a clear indentation when wet, confirming encapsulation, and a robust capsule structure was maintained even when broken down upon drying.

[0067] It can be concluded that the solubility of the reducing agent is important for efficient encapsulation. Microcapsules were formed using both systems 1) and 2) described above; however, oxidation-reduction initiation using an oil-soluble reducing agent appeared to yield significantly lower results compared to when a completely water-soluble oxidation-reduction initiation system was applied.

[0068] Encapsulation of λ-cyhalothrin (LCY): Delayed release LCY was dissolved in Solvesso 200 and added to a continuous aqueous phase containing ACVA. The mixture was emulsified using the general conditions outlined above, and then the system was heated to 80°C and left to stand overnight with stirring. The resulting solution flocculated heavily, meaning that no useful microcapsule dispersion was formed.

[0069] Oxidation-reduction initiation can occur at room temperature; therefore, in this experiment, LCY was dissolved in Solvesso 200, added to a continuous aqueous phase, emulsified, APS and sodium sulfite were added, and the mixture was left overnight at room temperature under stirring. The resulting capsule suspension was characterized by Mastersizer and optical microscopy (wet and dry). Optical microscopy analysis showed concave capsules with minimal aggregation when wet, and a robust capsule structure, albeit disintegrated, when dry. Characterization of the LCY content before and after crosslinking confirmed that there was no interaction between LCY and radical shell-forming components, thus confirming the success of LCY encapsulation.

[0070] The release rates of LCY from crosslinked and non-crosslinked microcapsules were analyzed using a currently standard method of monitoring capsule release by extraction into an ethanol and hexane mixture. As expected, the non-crosslinked emulsion did not exhibit sustained release, while the crosslinked capsules showed rapid sustained release comparable to commercially available polyurea LCY microcapsules (Warrior® II).

[0071] Encapsulation of S-methracrol (SMOC): Since SMOC (480 mg / L) has higher water solubility than LCY (0.005 mg / L), the effect of active ingredient solubility on the microencapsulation process was investigated. Furthermore, the capsules required storage stability for two years, and therefore, the stability of SMOC microcapsules was investigated under accelerated storage conditions.

[0072] SMOC was dissolved in Solvesso 200, added to the aqueous phase, emulsified, and then APS and sodium sulfite were added. The resulting microcapsule suspension was stirred overnight at room temperature and then characterized by Mastersizer and optical microscopy (wet and dry). Optical microscopy confirmed successful encapsulation, and microcapsules with minimal aggregation and a concave, distorted shape were observed, with good structural retention even after drying. After crosslinking, a series of dispersants were added to individual samples of the microcapsule suspension, and the samples were then stored at 54°C for 2 weeks and at 40°C for 8 weeks. Microcapsules without surfactant aggregation were severely aggregated during accelerated storage; however, the addition of the surfactant Morwet® D425 successfully stabilized the microcapsule suspension, which could be redispersed after 2 weeks at 54°C and 8 weeks at 40°C. Thus, SMOC was successfully encapsulated and then stabilized by the subsequent addition of dispersants.

[0073] Microcapsule synthesis using ethyl acetate hexyl as an organic core in the oil phase: Microcapsules were prepared by dissolving CN2035 and TMPTA in ethyl acetate hexyl, then emulsifying the mixture, and adding APS and sodium sulfite. The emulsion was left to stand overnight under stirring, and the microcapsules were then characterized by Mastersizer analysis and optical microscopy (wet and dry). Good encapsulation was observed with capsule structures similar to those of Solvesso 200, LCY, and SMOC. After observing successful microencapsulation, the water and organic core were successfully removed using Genevac® (freeze-dryer). The dried capsules were redispersed in water. Thus, microcapsules can be successfully synthesized using ethyl acetate hexyl as the organic core, i.e., as the solvent in the oil phase. Furthermore, it is possible to remove the organic core using a suitable technique to provide empty polymer shells for future biodegradation tests.

[0074] Solvent dissolution test A series of solvents were tested for their ability to dissolve CN2035. Samples were left on an IKA roller at 20 rpm at ambient temperature for 2 days to 1 week. The results are shown in Table 2.

[0075] [Table 2]

[0076] Benzoate capsules Based on the above results, we investigated whether capsules could be formed using a benzoate solvent (in this case, benzyl benzoate).

[0077] 2% by weight of CN2035 polyester acrylate monomer and 3% by weight of TMPTA crosslinking agent were used together with ammonium persulfate and sodium sulfite redox initiator.

[0078] Microcapsules were prepared by dissolving CN2035 (2 wt%) and TMPTA (3 wt%) in benzyl benzoate, then emulsifying the mixture, and adding APS and sodium sulfite at the concentrations detailed in Table 3. Mowiol 4-88 (polyvinyl alcohol) was used as a dispersant. The emulsion was then left to stand overnight under stirring, and the microcapsules were characterized by Mastersizer analysis and optical microscopy (wet and dry).

[0079] The methodology is as described above, and the results are shown in Table 3.

[0080] [Table 3]

[0081] The present invention is defined by the claims.

Claims

1. 1. A method for preparing microcapsules comprising: - preparing an oil phase comprising a polyfunctional ethylenically unsaturated monomer or oligomer, the water solubility of said polyfunctional ethylenically unsaturated monomer or oligomer in deionized water at 20°C being less than 2 grams / liter, preferably less than 1 gram / liter, more preferably less than 0.1 gram / liter; - forming an oil-in-water emulsion with said oil phase; - subjecting said oil-in-water emulsion to suitable conditions for initiating interfacial polymerization at the oil-water interface using a radical initiator having a water solubility of at least 1 gram / liter, preferably 10 gram / liter, more preferably 20 gram / liter in deionized water at 20°C. Including, radical initiator is absent or substantially absent from said oil phase; Preferably, the microcapsules are biodegradable.

2. 2. The method of claim 1, wherein the interfacial polymerization at the oil-water interface is initiated by addition of a water-soluble reducing agent suitable for decomposing the radical initiator, the water solubility of the reducing agent in deionized water at 20° C. being at least 1 gram / liter, preferably 10 gram / liter, more preferably 20 gram / liter.

3. 3. The method according to claim 1 or 2, wherein a polyfunctional ethylenically unsaturated crosslinking agent suitable for polymerization with said polyfunctional ethylenically unsaturated monomer or oligomer is present in said oil phase, and the water solubility of said polyfunctional unsaturated crosslinking agent in deionized water at 20° C. is less than 2 grams / liter, preferably less than 1 gram / liter, more preferably less than 0.1 gram / liter.

4. The polyfunctional ethylenically unsaturated monomer or oligomer and the polyfunctional ethylenically unsaturated crosslinking agent have a CO 2 Amount generated or O 2 4. The method of any one of claims 1 to 3, having mineralization measured as consumption, said mineralization being measured according to test method OECD TG 301 B, C, D, F or OECD TG 310.

5. 5. The method of any one of claims 1 to 4, wherein the multifunctional ethylenically unsaturated monomer or oligomer and / or multifunctional ethylenically unsaturated crosslinker are independently selected from acrylates, methacrylates, vinyl esters, vinyl ethers, allyl esters and allyl ethers.

6. 5. The method according to any one of claims 1 to 4, wherein the polyfunctional ethylenically unsaturated monomer or oligomer is selected from acrylate or (meth)acrylate terminated esters, acrylate or (meth)acrylate terminated ethers, acrylate or (meth)acrylate terminated carbonates, and acrylate or (meth)acrylate terminated anhydrides.

7. 7. The method of claim 6, wherein the multifunctional ethylenically unsaturated monomer or oligomer is selected from polycaprolactone diacrylate, polycaprolactone dimethacrylate, tripropylene glycol triacrylate, poly(ethylene glycol)-b-(propylene glycol)-b-ethylene glycol dimethacrylate, and trimethylolpropane ethoxylate triacrylate.

8. The method according to any one of claims 1 to 7, wherein the radical initiator is selected from peroxides and azo compounds.

9. 9. The method according to any one of claims 1 to 8, wherein the oil phase further comprises an active ingredient selected from a fungicide, a herbicide, an insecticide, a bactericide, a miticide, a nematicide and / or a plant growth regulator.

10. The method according to any one of claims 1 to 7, wherein the active ingredient is selected from lambda cyhalothrin, S-metolachlor, prosulfocarb, tefluthrin, clomazone, dimethachlor, acetamiprid and trifluoroline.

11. 11. The method according to any one of claims 1 to 10, wherein the weight of the polyfunctional ethylenically unsaturated monomer or oligomer is from 2% to 75% by weight, preferably from 5% to 50% by weight, more preferably from 5% to 30% by weight, based on the weight of the total oil phase.

12. (a) an oil phase comprising a polyfunctional ethylenically unsaturated monomer or oligomer, and (b) an aqueous phase containing a radical initiator suitable for initiating the polymerization of said multifunctional ethylenically unsaturated monomers or oligomers; 1. An oil-in-water emulsion comprising: the water solubility of said radical initiator in deionized water at 20° C. is at least 1 gram / liter, preferably at least 10 grams / liter, more preferably at least 20 grams / liter; the water solubility of said polyfunctional ethylenically unsaturated monomer or oligomer in deionized water at 20° C. is less than 2 grams / liter, preferably less than 1 gram / liter, more preferably less than 0.1 gram / liter; and wherein radical initiator is absent or substantially absent from said oil phase.

13. 13. The oil-in-water emulsion composition of claim 12, wherein said oil phase further comprises a multifunctional ethylenically unsaturated crosslinking agent suitable for polymerization with said multifunctional ethylenically unsaturated monomer or oligomer, and wherein the water solubility of said multifunctional unsaturated crosslinking agent in deionized water at 20° C. is less than 2 grams / liter, preferably less than 1 gram / liter, more preferably less than 0.1 gram / liter.

14. 14. The oil-in-water emulsion composition according to claim 12 or 13, wherein the aqueous phase further comprises a water-soluble reducing agent suitable for decomposing the radical initiator, the aqueous solubility of said reducing agent in deionized water at 20° C. being at least 1 gram / liter, preferably 10 gram / liter, more preferably 20 gram / liter.

15. 15. The oil-in-water emulsion composition of claim 14, wherein the reducing agent is selected from ascorbic acid, sodium sulfite, sodium metabisulfite, sodium bisulfite, sodium thiosulfate, sodium formaldehyde sulfoxylate dihydrate, thiourea and 2-hydroxy-2-sulfinatoacetic acid disodium salt.