Patent Application
20100086603
The present invention relates to a method for improving the lifetime of compounds that are prone to photo-degradation by containing the compounds in microcapsules, which have light protecting particles bonded chemically to the capsule walls. In particular, the present invention relates to a microcapsule comprising a biologically active compound inside the microcapsule and light protecting particles which are chemically bonded to the microcapsule wall material; to the use of such a microcapsule; to a process for preparing such a microcapsule; and to surface-modified light protecting particles and their use in such a microcapsule.
Many biologically active agrochemical compounds, commonly termed active ingredients (AIs), are photo-labile and may be degraded within hours or days upon exposure to sunlight, typically between the wavelengths of 200 nm to 800 nm. Degradation due to sunlight is typically termed photo-instability or photo degradation and an AI which is susceptible to such degradation is deemed to be photolabile, photo-unstable, photosensitive or light sensitive.
Photoprotectants may be used to photostabilise intrinsically photosensitive AIs. The term photoprotectant means a compound, or combination of compounds, that reduces the rate or extent of photo-degradation of an AI.
Microencapsulation technology may provide an effective means for photoprotection whereby a photoprotectant shields, or is in very close proximity to, the AI.
The encapsulation of a sunscreen by the cosmetics industry has been described as a means of (a) avoiding direct contact between human skin and potentially irritant chemicals while maintaining the efficacy of the sunscreen; and (b) simplifying the formulation of such chemicals. Therefore the reason for encapsulating sunscreens is different from that of the present invention which protects the contents of microcapsules from photo-degradation.
In one known approach, photoprotectants form part or all of the microcapsule wall materials and thus provide a shield for the capsule, thereby protecting any photosensitive AI that is present within the capsules. For example in CA 2133779 Lebo and Detroit show that lignosulphonates and the like can used in combination with a protein such as a high bloom gelatin to form a capsule wall that improves the resistance of agriculturally active substances, such as pesticides, to UV light degradation. The capsule wall formed by the interaction of these components is durable and has a UV protectant as an integral part of its structure.
In another approach, photoprotectants may be co-encapsulated with the AI. The photoprotectant may be dissolved in the core contents of a microcapsule as disclosed by Marcus in WO 9523506A1 for chlorpyrifos or endosulfan. This approach is also used in the printing and duplicating industry where leuco-dyes are co-encapsulated with photoprotectants
Alternatively the photoprotectant may be dispersed as particulate suspensions in the core contents of microcapsule as disclosed in WO96/33611, where the capsule contains particulate suspensions selected from titanium dioxide, zinc oxide and mixtures thereof.
Moy describes in EP539142A1 the use of colloidal inorganic particles, particularly those of silica and zirconium dioxide, to make microcapsules by coacervation or by interfacial polymerisation methods. The process involves the formation of so called Pickering emulsions and the thermoset microcapsule wall comprises the inorganic particles. Moy does not disclose the use of light protecting particles bonded chemically to the capsule walls.
Stover [Macromolecules, 38(7) 2903-2910] describes the incorporation of functionalised organic microspheres into polyurea microcapsule walls made by interfacial polymerisation but does not suggest the use of light protecting particles bonded chemically to the capsule walls.
Odera teaches in JP 86-242834 861013 that titanium dioxide may be incorporated into the walls of 200-500 μm microcapsules made by coacervating gelatine and gum Arabic on a carotene-rape oil mixture in the presence of a titanium dioxide dispersion in the aqueous phase.
The present invention relies on light protecting particles to provide a photoprotectant system for microcapsule formulations. A light-sensitive compound may be contained within the core of a microcapsule and the light protecting particles are chemically bonded to the microcapsule wall, thereby providing photoprotection to the microcapsule wall, to the contents of the core of the microcapsule or to both the wall and the core contents. Although the present invention is most useful when dealing with biologically light-sensitive compounds, it is also appropriate for biologically light-stable compounds which may require a light-sensitive partner [for example, a light-sensitive adjuvant].
The microcapsules of the present invention may be prepared by interfacial polymerisation.
The light protecting particles may provide photoprotection by a variety of means including light absorbance and light reflectance.
The light protecting particles may be organic or inorganic or may comprise a mixture of inorganic and organic compounds [for example Si particles may be impregnated with an organic photo-protectant as described in JP 02002867A2 900108 Heisei].
Furthermore, the light protecting particles may be surface modified by reactive compounds. The light protecting particles may be used in place of conventional surfactants to make stable oil-in-water (so called Pickering) emulsions, in which case wall formation at the oil-water interface is then carried out using compounds dissolved in the oil phase so that the surface modified inorganic particles form chemical bonds with the wall material.
The biologically active compound is suitably a pharmaceutical compound or an agrochemical; more suitably it is an agrochemical.
Suitably, the agrochemical is a fungicide, insecticide or herbicide, used for controlling or combating pests such as fungi, insects and weeds. The agrochemical may also be used in non-agricultural situations [for example public health and professional product purposes, such as termite barriers, mosquito nets and wall-boards].
More suitably the agrochemical is an insecticide, even more suitably a pyrethroid and most suitably lambda-cyhalothrin.
The microcapsules of the present invention may be further processed [for example, in the preparation of granular formulations].
Therefore, in a first aspect, the present invention provides a microcapsule comprising a biologically active compound inside the microcapsule and light protecting particles which are chemically bonded to the microcapsule wall.
The chemical bonds anchor the light protecting particles to the microcapsule wall irreversibly. Further anchorage may be provided when chemical bonds are formed between adjacent light protecting particles.
Suitably the photoprotectant (light protecting particles) is selected from the group consisting of all-trans-(all-E)-1,1′-(3,7,12,16-tetramethyl-1,3,5,7,9,11,13,15,17-octadecanonaene-1,18-diyl)bis[2,6,6-trimethylcyclohexene; 2-ethylhexyl-p-methoxycinnamate; 1,3-bis-[2′-cyano-3′,3-diphenylacryloyl)oxy]-2,2-bis-{[2-cyano-3′,3′-diphenylacryloyl)oxy]methyl}propane; ethyl 2-cyano-3,3-diphenyl-2-propenoate; 2-ethylhexyl-2-cyano-3,3-diphenylacrylate; 2,3-dihydro-1,3,3-trimethyl-2-[(2-methyl-3H-indol-3-ylidene)ethylidene]-1H-Indole, monohydrochloride; 3,6-diamino-10-methylacridinium chloride+3,6-diaminoacridine; monosodium 1-amino-9,10-dihydro-9,10-dioxo-4-(phenylamino)-2-anthracenesulfonate; 1-amino-2-methyl-9,10-anthracenedione; 1,4-bis[(1-methylethyl)amino]-9,10-anthracenedione; 1,4-bis[(4-methylphenyl)amino]-9,10-anthracenedione; 1-hydroxy-4-[(4-methylphenyl)amino]-9,10-anthracenedione; monosodium 4-hydroxy-3-[(2-hydroxy-1-naphthalenyl)azo]-benzenesulfonate; monosodium 4-[(2-hydroxy-1-naphthalenyl)azo]-3-methyl-benzenesulfonate; 4-[(4-nitrophenyl)azo]-N-phenyl-benzenamine; 4-[[4-(phenylazo)-1-naphthalenyl]azo]-phenol; 3-[ethyl[4-[(4-nitrophenyl)azo]phenyl]amino]-propanenitrile; 4-[(4-nitrophenyl)azo]-benzenamine; monosodium 3-hydroxy-4-[(1-hydroxy-2-naphthalenyl)azo]-7-nitro-1-naphthalenesulfonate; 1-[[2,5-dimethyl-4-[(2-methylphenol)azo]phenyl]azo]-2-naphthalenol; 1-[[4-[(dimethylphenyl)azo]dimethylphenyl]azo]-2-naphthalenol; 1-(ortho-tolylazo)-2-naphthol; tetrasodium 4-amino-5-hydroxy-3,6-bis[[4-[[2-(sulfooxy)ethyl]sulfonyl]phenyl]azo]-2,7-naphthalenedisulfonate; 1-[[4-(phenyl)azo)phenyl]azo]-2-naphthalenol; 1-[[3-methyl-4-[(3-methylphenol)azo]phenyl]azo]-2-naphthalenol; 2,3-dihydro-2,2-dimethyl-6-[[4-(phenylazo)-1-naphthalenyl]azo]-1H-perimidine; 1-(phenylazo)-2-naphthalenol; 1-[[2-methyl-4-[(2-methylphenol)azo]phenyl]azo]-2-naphthalenol; 1,3(2H)-dione, 2-(3-hydroxy-2-quinolinyl)-1H-indene; 2-(1,3-dihydro-3-oxo-2H-indol-2-ylidene)-1,2-dihydro-3H-indole-3-one; disodium 2-(1,3-dihydro-3-oxo-5-sulfo-2H-indol-2-ylidene)-2,3-dihydro-3-oxo-1H-indole-5-sulfonate; mixture of 1-(phenylazo)-2-naphthalenol with 1,4-bis[(1-methylethyl)amino]-9,10-anthracenedione; mixture of 1-(phenylazo)-2-naphthalenol with 1,4-bis[(1-methylethyl)amino]-9,10-anthracenedione and 1-[[2-methyl-4-[(2-methylphenol)azo]phenyl]azo]-2-naphthalenol; benzo[a]phenoxazin-7-ium, 5-amino-9-(diethylamino)-, sulfate; N-[4-[[-(diethylamino)phenyl](2,4-disulfophenyl)methylene]-2,5-cyclohexadien-1-ylidene]-N-ethyl-ethanaminium, inner salt, sodium salt; N-[4-[[4-(dimethylamino)phenyl][4-(phenylamino)-1-napthalenyl]methylene]-2,5-cyclohexadien-1-ylidene]-N-methyl-methanaminium chloride; N-[4-[[4-(dimethylamino)phenyl][4-(ethylamino)-1-napthalenyl]methylene]-2,5-cyclohexadien-1-ylidene]-N-methyl-methanaminium chloride; 4,5,6,7-tetrachloro-3′,6′-dihydroxy-2′,4′,5′,7′-tetraiodospiro[isobenzofuran-1(3H),9′-[9H]xanthen]-3-one disodium salt; 2-(3,4-dihydroxyphenyl)-3,5,7-trihydroxy-4H-1-benzopyran-4-one; N,N′,N″,N′″-tetrakis(4,6-bis(butyl-(N-methyl)-2,2,6,6-tetramethylpiperidin-4-yl)amino)triazin-2-yl)-4,7-diazadecane-1,10-diamine; poly[[6-[(1,1,3,3-tetramethylbutyl)amino]-1,3,5-triazine-2-4-diyl][2,2,6,6-tetramethyl-4-piperidinyl)imino]-1,6-hexanediyl[(2,2,6,6-etramethyl-4-piperidinyl)imino]]); mixture of esters of 2,2,6,6-tetra-methyl-4-piperidinol with higher fatty acids (mainly stearic and palmitic acids); propanedioic acid, [(4-methoxy-phenyl)-methylene]-, bis(1,2,2,6,6-pentamethyl-4-piperidinyl)ester; bis(2,2,6,6-tetramethyl-4-piperidyl) sebaceate; bis(1,2,2,6,6-pentamethyl-4-piperidinyl)ester; polymer of N,N′-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine with 2,4,6-trichloro-1,3,5-triazine reaction products with 3-bromo-1-propene, N-butyl-1-butanamine and N-butyl-2,2,6,6-tetramethyl-4-piperidinamine, oxidised, hydrogenated; 4-methyl-2,6-di-tert-butylphenol; octadecyl-3,5-di-tert-butyl-4-hydroxyhydrocinnamate; 2-tert-butyl-1,4-benzenediol; ′2,2′-dihydroxy-4-methoxybenzophenone; 2-hydroxy-4-methoxybenzophenone; 2-hydroxy-4-n-octyloxybenzophenone; 2-(4-diethylamino-2-hydroxybenzoyl)-benzoic acid, hexyl ester; 2,2′,4,4′-tetrahydroxybenzophenone; ′2(2′-hydroxy-5′-t-octylphenyl) benzotriazole; α-[3-[3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxyphenyl]-1-oxopropyl]-ω-hydroxy-poly(oxy-1,2-ethanediyl); 2-(2′-hydroxy-3′-dodecanyl-5′-methylphenyl)-benzotriazole; 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1phenylethyl)phenol; ′2-(2′-hydroxy-3′-t-butyl-5′-methylphenyl)-5-chlorobenzotriazole; ′2-(2′-hydroxy-3,5-di-t-butylphenyl)-5-chlorobenzotriazole; 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol; 3-(2H-benzotriazol-2-yl)-5-(1,1-di-methylethyl)4-hydroxy-benzenepropanoic acid, C7-9 branched and linear alkyl esters; 2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl]-5-[2-hydroxy-3-(dodecyloxy- and tridecyloxy)propoxy]phenols; zinc oxide; titanium dioxide; mixture of zinc oxide and titanium dioxide; micronised carbon black; 3,5,6-trihydroxybenzoic acid n-propyl ester; sodium iodide; 2,2′-thiobis[4-t-octylphenolato]-beta-butylamine nickel (II); 2-ethyl,2′-ethoxyoxalanilide; 3,9-bis(octadecyloxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane+1,1′,1″-nitrilotris-2-propanol; 3,9-bis[2,4-bis(1-methyl,1-phenylethyl)phenoxy]-2,4,8,10-tetraoxa, 3,9-diphosphaspiro[5.5]undecane; tris(2,4-di-tert-butylphenyl) phosphite; 1,2-dihydroxyanthraquinone; 7-β-D-glucopyranosyl-9,10-dihydro-3,5,6,8-tetrahydroxy-1-methyl-9,10-dioxo-2-anthracenecarboxylic acid; 5-hydroxy-1,4-naphthoquinone; sodium sulfite; distearyl-disulfide; and distearylthiodipropionate.
More suitably, the light protecting particles are selected from zinc oxide; titanium dioxide; and a mixture of zinc oxide and titanium dioxide. Even more suitably the light protecting particles are titanium dioxide particles.
The light protecting particles may be present on the microcapsule wall as a single layer or may be present in a multi-layered system.
In addition to being bonded to the outside surface of the microcapsule wall, the light protecting particles may also be chemically bonded to the inside surface of the microcapsule wall; bonding to the inside surface may be achieved by a preparation process in which the light protecting particles are dispersed in the oil phase prior to emulsification.
In a further aspect, the present invention provides a process for preparing a microcapsule as described above comprising the steps:
Throughout this specification, the following abbreviations are used:
In another aspect, the present invention provides a process for modifying the surface of a light protecting particle by a reactive compound where:
The present invention also provides a surface-modified light protecting particle [suitably titanium dioxide] obtainable by such a process.
For example, a reactive copolymer, such as poly([EMA-s-TMSPMA]-b-[DEAEMA-s-TMSPMA]), is first reacted with light protecting particles, such as titanium dioxide particles, which are subsequently used in place of conventional emulsifiers or colloid stabilisers to disperse an oil droplet which is subsequently incorporated into a capsule wall [that is, the capsule is made via a Pickering emulsion]. By irreversibly binding the particles through chemical bonds, they are not-displaced by subsequent addition of normal surfactants [that is, the particles are colloidally robust].
The reactive compound is designed to enable adjacent surface modified particles to be locked in space by chemically linking the reactive compounds between particles or with microcapsule wall forming materials. This process may be put in to effect by other chemistry.
Those TMSPMA groups that do not react are available for further elaboration as described below. The composition of the reactive compound may be designed such that the surface modified particles are able to form a Pickering emulsion with oil.
The invention is illustrated, but not limited, by the following Examples, in which ‘parts’ are given by weight.
1Purchased from Sigma-Aldrich.
2Prepared according to the literature (Haddleton et al., Macromolecules, 1997, 30, 2190)
A mixture of hexadecane (100 parts), poly(trimethylpropylsilylmethacrylate) (10 parts) and poly(dimethoxysiloxane) (10 parts) was emulsified into water (900 parts) containing surface modified TiO2 particles (23 parts). Capsule wall formation plus embedding of the particles was catalysed by the addition of triethylamine.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0617859.4 | Sep 2006 | GB | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/GB07/03374 | 9/7/2007 | WO | 00 | 11/13/2009 |
