BRPI0909656B1 - PROCESS FOR PRODUCTION OF MICROCAPSULES - Google Patents

Description

Descriptive Report of the Invention Patent for "MICROCAPLE PRODUCTION PROCESS".

The present invention relates to a novel process for producing microcapsules and to microcapsules produced by the process. It also refers to a process for the use of microcapsules.

Microcapsules are small capsules that comprise a wall surrounding an encapsulated material, usually a liquid. They may be used to protect encapsulated material from the external environment, for example from air or light degradation (especially ultraviolet radiation). They may also be used to isolate hazardous materials within microcapsules to make handling or use of these materials safer. Microcapsules are known to be used for agrochemicals, especially insecticides such as lambda-cyhalothrin, to protect them from degradation by UV light and to provide controlled release following application.

Certain known microcapsules are produced by interfacial polymerization. In such a process, a solution is first formed of a first monomer, such as polyisocyanate, in water-insoluble liquid to be encapsulated. The solution may also contain a biologically active ingredient. This solution is then dispersed in water together with surfactants to form an emulsion. A second monomer, such as a polyamine, is added to water and it reacts with the first monomer on the emulsion droplet surface to produce a crosslinked polymer, in this example a polyurea, which forms a microcapsule wall around the droplets. First and second known monomers also include polyisocyanate and polyol, in the production of a polyurethane wall, polyfunctional acid halide and polyamine, to produce a polyamine wall, and polyfunctional acid halide and polyol to produce a polyester wall.

There are disadvantages of these types of microcapsules. The protection provided to UV light content by walls of polymeric capsules of this known type is poor. In addition, the surfactant used to form the emulsion may be problematic in the further handling of microcapsule dispersion as it may cause foaming.

In a known approach, photoprotectors form part or all of the microcapsule wall material and thus provide capsule protection, thereby protecting any photosensitive active ingredient that is present within the capsules. For example, CA2133779 shows that lignosulfonates and the like can be used in combination with a protein, such as a high bloom gelatin (unit of measure for gelatin viscosity), to form a capsule wall that improves the resistance of agriculturally active substances. such as pesticides, against degradation by ultraviolet light. The capsule wall formed by the interaction of these components is durable and has an ultraviolet shield as an integral part of its structure.

[006] Moy describes in EP539142A1 the use of colloidal inorganic particles, especially those of silica and zirconium dioxide, to produce microcapsules by coacervation or by interfacial polymerization methods. The process involves the formation of the so-called Pickering emulsions and the thermoset microcapsule wall contains the inorganic particles. Moy does not consider the use of surface modified particles or the use of crosslinkers to form the capsule wall.

Copending International Patent Application PCT / GB2007 / 003374 relates to light-shielding particles that are chemically bonded to the microcapsule wall, but does not consider the microcapsule walls themselves formed of light-shielding particles.

The present invention provides an aqueous dispersion of crosslinked particulate inorganic wall microcapsules in aqueous medium. In a further feature, these microcapsules may be further modified by the addition to the aqueous medium of a material which further reacts with any remaining crosslinker. For example, when the crosslinker is a polyisocyanate, a polyamine such as diethylenetriamine may be added. This addition causes more crosslinking and polymer formation in the particulate inorganic wall of the microcapsule and can be used to modify the durability of the capsules or the permeability of the capsule walls to provide, for example, a longer release period under given conditions. conditions.

Brief Description of the Figures: The invention will be better understood with reference to the detailed description when considered in conjunction with non-limiting examples and accompanying figures.

Figure 1 is a light microscopic image of the clay dispersion of Example 1.

Figure 2 is a light microscopic image of the Pickering emulsion of Example 2.

Figure 2a is a light microscopic image showing that the emulsion droplets collapse on drying on a glass slide.

Figure 2b is a light microscopy image showing the effect of adding 5 wt% Synperonic® NP8 to a Pickering emulsion.

Figure 3 is a light microscopic image of the microcapsules of Example 3.

Figure 3a shows a stable dispersion of the microcapsule of Figure 3.

Figure 3b shows the microcapsules of Figure 3 after the addition of Synperonic® NP8.

Figure 4 is a scanning electron microscopy image of the capsules of Example 4.

Figure 5 is a light microscopic image of the capsules of Example 5.

Figure 5a is a light microscopic image showing a stable microcapsule dispersion (Example 5) drying on a microscopic glass slide in air.

Figure 5b is a light microscopic image showing an unbroken capsule dispersion (Example 5) following the addition of Synperonic® NP8.

Figure 6a is a light microscopic image of Example 6a.

[0022] Figure 6b is a scanning electron microscopy image of Example 6b.

[0023] Figure 6c is a scanning electron microscopy image of Example 6c.

Figure 6d is a light microscopic image of Example 6d.

Figure 6e shows release curves for formulations prepared according to Examples 6a to 6d.

[0026] Figure 7 is a scanning electron microscopy image of Example 11a.

Figure 8 is a scanning electron microscopy image of Example 11b.

Figure 9 shows the results of a comparative study of capsules prepared according to Examples 11a and 11b.

Figure 10 shows the release rate of dimethyl phthalate [DMP] in water from capsules prepared according to Example 12.

Figure 11 is a light microscopic image of capsules prepared according to Example 13 in their original dispersion.

Figure 12 is a light microscopic image of capsules prepared according to Example 13 formed from a drydown.

[0032] The present invention relates to a novel process for producing microcapsules which does not require surfactant and which provides relatively high level of protection against ultraviolet protection for the contents; The present invention involves the use of surface modified inorganic particulate material to form microcapsule walls, wherein a crosslinker is used to react with a reactive functional group on the modified surface material such that each microcapsule wall is a crosslinked wall. The present invention also allows surfactants to be used in the same formulation as a Pickering emulsion system. Pickering emulsions are often destabilized by surfactants, but in the present invention cross-linking of interfacial particles prevents this from occurring, and surfactants can be safely added to the system once interfacial cross-linking has occurred. Accordingly, adjuvants may suitably be included in microcapsule compositions of the present invention.

Microcapsules of the present invention are suitable for controlled release applications (e.g., controlled release of an active ingredient from the microcapsule core). The controlled release rate may be adjusted by the present invention.

Another feature of the present invention is that crosslinked systems can be easily modified by the addition of an extra crosslinked molecule (e.g., a water dispersible isocyanate or polyfunctional crosslinker such as diethylenetriamine [DETA]) to the outer phase ( dispersion so that the release rate of any active ingredient from the capsule core can be changed to give the desired release rate profile. The opportunity to use extra crosslinked molecules means that it is possible to strengthen an existing layer in a single layer capsule or to form multilayer capsules.

The microcapsules of the present invention may be produced by a process comprising: i) forming a solution of a crosslinker in liquid; ii) forming a slurry of an inorganic surface-modified particulate material in aqueous medium; iii) dispersing the solution from step i) into the slurry of step ii) to form a Pickering emulsion and causing or allowing the crosslinker to react with the surface modified inorganic particulate material to form a crosslinked microcapsule wall.

Steps i) and ii) may be conducted in any order.

A slurry is a suspension of a solid in a liquid; In this invention, the slurry formed in step ii) is a suspension of surface-modified inorganic particles capable of cross-linking in aqueous medium. It has been found possible to disperse the solution of step i) into slurry of step ii) without the additional use of surfactants. This is because particles of surface modified inorganic material tend to accumulate at the interface between the solution droplets and the continuous aqueous phase and reduce the corresponding surface energy. The effect is known as a "Pickering Emulsion". The use of this combination of a Pickering Emulsion with a crosslinkable inorganic particulate material and a crosslinker allows for a particularly simplified process.

The liquid used in step i) contains the material to be encapsulated. In one embodiment, the liquid contains an active ingredient that will be encapsulated, optionally together with a solvent, particularly if, at room temperature, the active ingredient is solid or high viscosity. Therefore, when present, the active ingredient may be the liquid, part of the liquid, dissolved in the liquid, dispersed in the liquid or a solid complex of an agrochemical with a molecular complex forming agent and dispersed in the liquid. The liquid is suitable and substantially insoluble in water, more suitably, has water solubility at 20 Ό of less than 10g / l and most suitably less than 5g / l. The liquid must dissolve the crosslinker to form a solution.

Any active ingredient encapsulated within the microcapsule core is suitably less than 10 wt.% Water soluble and more suitably less than 1 wt.% Water soluble, most suitably less than 0.1 wt.% Soluble in water. Water.

A wide variety of active materials (active ingredients) may be encapsulated including paints, flavorings, cosmetics, perfumes, sunscreens, fragrances, adhesives, sealers, phase change materials, biocides, petroleum chemicals (including corrosion and scale inhibitors), flame retardants, food additives (including vitamins, ingredients, probiotics and antioxidants), active agents that may be included in detergent, fabric softeners and other household products (such as bleach, enzymes and surfactants), active agents that can be included in fabrics (such as insect repellents, antimicrobial agents, skin softeners and medically active compounds), active agents that can be included in coatings (such as fire retardants, flame retardants). , antiformation of scabs, antibacterials, biocides, scratch and abrasion resistant compounds) and biologic compounds active ingredients (such as pharmaceuticals and agrochemicals). Suitably, the active material is an agrochemical such as a herbicide, fungicide or insecticide. Many such agrochemicals are known and are described in The Pesticide Manual, 14th edition, published by the British Crop Protection Council in 2006. The invention is also suitable for encapsulating a solid complex of an agrochemical with molecular complex forming agent including, for example, a complex of 1-MCP and α-cyclodextrin. The invention is most useful for agrochemicals that are subject to degradation when exposed to sunlight, in particular pyrethroid insecticides such as deltamethrin, tralomethrin, cyfluthrin, alfamethrin, zeta-cypermethrin, fenvalerate, sphenvalerate, acrinatrine, alethrin, bifenthrin, bioalethrin, bioalethrin, cycloprotrin, beta-cyfluthrin, cyhalothrin, beta-cypermethrin, cyphenothrin, empentrin, etofenprox, fenpropathrin, flucitrinate, tau-fluvalinate, phenothrin, pralethrin, tefluthrin, te-trametrine, and lambda-cyrothrin-cydaprine

Suitably, the microcapsules of the present invention may be used in wall partitions or plasterboard in buildings, and may be used to improve cement compositions and processes for the manufacture of cement-based materials.

Suitably the active ingredient is a pharmaceutical compound or an agrochemical; more appropriately, it is an agrochemical.

Suitably, the agrochemical is a fungicide, insecticide, herbicide or growth regulator, used to control or combat pests such as fungi, insects and weeds, or to control the growth of useful plants. The agrochemical can also be used in non-agricultural situations [eg for public health purposes and professional products such as termites, mosquito nets and wall partitions].

More suitable applications include, but are not limited to: Sustained or controlled release uses, eg, pharmaceutical, eg acid-resistant capsules (oral administration after low pH in the stomach), protection of labile assets, release of pseudo-zero order through the capsule wall and Ostwald degradation-resistant emulsion formulations (ostwalm-ripe-ning) \ cosmetics, perfumes, for example, reducing top-note evaporation or sustained release and minimizing excessive odors; capsules having cellulose affinity and fastened to a textile surface during washing; flavors, for example, light stabilized to prevent oxidation; self-healing coating, for example, capsule rupture to release a damage repairing resin; carbonless copy paper; new food with double flavor and texture, for example capsule that dissolves in the mouth and releases a new flavor; pressure sensitive adhesives; sealers; nutrition (eg increased bioavailability of complex molecules and protection of sensitive molecules such as vitamins, probiotics and other food additives); photosensitive or thermally sensitive toner inks; textile coatings, for example, to improve permeability properties; antifouling coatings, surface protective coatings, for example, to improve scratch and abrasion resistance; and building materials, for example, partitions, plasterboard and cement. Examples of capsules that are dried include, for example, various mineral mixtures to form a ceramic after calcination; low density fillers for polymers or inks; insulating materials; low density proppants, e.g. light reinforcing particles, e.g. wood fiber composites; recyclable, for example, low density pigments allowing for easy float separation; and energy buffers, for example, use in voids present in spheres to provide an energy-absorbing "crash barrier". Capsules of the present invention may be of new size or shape, for example: making capsules in plate or rod form; and use of resulting metal particles in conductive capsules, or having a metallic nature, for example, plasmon absorbance.

A solution suitable for use in step i) may be made by shaking a liquid and a crosslinker together. Thermal and mechanical stirring can be used to aid or accelerate crosslinker dissolution. Similar techniques may be used to mix or dissolve an active ingredient with any optionally included solvent.

Examples of particulate inorganic materials are oxy-compounds [i.e. oxygen-based compounds] of at least one of calcium, magnesium, aluminum and silicon (or derivatives thereof) such as silica, silicates, marble, clays and talc. Particulate inorganic materials may be natural or synthesized in reactors. The inorganic particulate material may be a mineral chosen from, among others, kaolin, bentonite, alumina, limestone, bauxite, plaster, magnesium carbonate, calcium carbonate (whether grounded or precipitated), perlite, dolomite, diatomite, huntite, magnesite, boehmite, pali-gorsquite, mica, vermiculite, hydrotalcite, hectorite, haloisite, gibbsite, kaolinite, montmorillonite, illite, attapulgite, laponite and sepiolite; suitably, it can be chosen from kaolin, bentonite, alumina, limestone, bauxite, plaster, magnesium carbonate, calcium carbonate (whether grounded or precipitated), perlite, dolomite, diatomite, huntite, magnesite, boehmite, sepiolite, paligorsquite, mica, vermiculite, illite, hydrotalcite, hectorite, haloisite and gibbsite. Other suitable clays (e.g. aluminosilicates) include those comprising the kaolinite, montmorillonite and illite clay mineral groups. Other specific examples are attapulgite, laponite and sepiolite.

In one feature of the invention, the inorganic particulate material is kaolin clay. Kaolin clay is also referred to as china clay or hydrated kaolin, and is predominantly mineral kaolinite (Al2 Si205 (OH) 4), a hydrated aluminum silicate (or aluminosilicate).

The inorganic particulate material suitably has particle size distribution, wherein the median diameter (d50) is less than or equal to 10 µm as measured by determining the sedimentation rates of the dispersed particulate matter under suspension testing. standard diluted aqueous solution employing a SEDIGRAPH®, for example SEDIGRAPH® 5100, obtained from Micromeritics Corporation, USA. Suitably, the inorganic particulate material has d50 of less than or equal to 5 µm. More suitably, the inorganic particulate material has d50 less than or equal to 2 µm. Even more suitably, the particulate inorganic material has d50 of less than or equal to 1 µm. In increased suitability, the particulate inorganic material has d50 of less than or equal to 0.9; 0.8; 0.7; 0.6; 0.5; 0.4 or 0.3 μτη. In other characteristics, the inorganic particulate material has a dso of less than or equal to 0,2 μπι, for example less than or equal to 0,15 μτη or less than or equal to 0,12 μνη or less than or equal to 0,1 / um.

In one aspect, at least about 90% of the particles of inorganic particulate matter by weight are less than about 2 μτη, for example, approximately at least 95% or 98% are less than about 2 μτη. Suitably at least about 90% of the particles by weight are less than about 1 μνη, for example at least about 95% or 98% are less than about 1 μνη. More suitably, at least about 75% of the particles by weight are less than about 0.25 μιτι, for example at least about 80% or 82% are less than about 0.25 μηι. In another aspect, the inorganic particulate material has particle size distribution of (i) at least about 90% of the particles by weight are less than about 2 μιτι, for example at least about 95% or 98%; (ii) at least 90% of the particles by weight are less than about 1 μηι for example at least about 95% or 98%; and (iii) at least 75% of the particles by weight are less than about 0.25 μηι, for example at least about 80% or 82%; and the particulate inorganic material of such particle size distributions may also have d50 values at the lower limit of the distribution, for example at least about 98% of the particulate inorganic material by weight is less than about 2 μιη, at least about 98% is less than approximately 1 μηι, at least approximately 82% are less than approximately 0.25 μιτι, and the d50 value of particulate inorganic material is less than or equal to 0.12 μιτι.

For finer particulate inorganic materials (eg d50 less than or equal to 2 μιη) the material may be derived by classification including methods such as gravity sedimentation or elutriation, use of any type of hydrocyclone equipment. or, for example, solid bowl settling centrifuge, or disc nozzle centrifuge. The classified particulate inorganic material may be dehydrated in one of the ways known in the art, for example filtration (including filter press), centrifugation or evaporation. The classified and dehydrated material can then be thermally dried (e.g. by spray drying).

[0052] Modified surface means that the surface of the inorganic particle has been (chemically) modified to have crosslinkable, functional reactive groups. The surface of the particles may be modified with modifying agents selected from a wide variety of chemicals having the general structure X-Y-Z, wherein X is a particle surface affinity chemical moiety; Z is a chemical (reactive) moiety with the desired functionality; and Y is a chemical moiety that binds X to Z. The term "high affinity" refers to chemical moieties that are either chemically bonded or are strongly adsorbed physically to the surface of the particle; suitably, they are chemically bonded.

X may be, for example, an alkoxy silane group such as triethoxysilane or trimetroxysilane, which is particularly useful when the particles contain silanoic groups (SiOH) on their surface. X may also be, for example, an acid group (such as a carboxylic group or an acrylic acid group) which is particularly useful when the particles contain basic groups on their surfaces.

Y may be a chemical group that binds X to Z, for example, a polyamide, a polyester or an alkylene chain; more suitably, it is an alkylene chain; and even more suitably, it is a C 2.e alkylene chain, such as ethylene or propylene.

Reactive groups Z may be selected from any groups, preferably different from Y, which may be used to react with a crosslinker to crosslink the modified surface inorganic particulate material. Examples of Z are epoxy groups, carboxylic groups, unsaturated groups such as acrylic or vinyl groups and suitably amino groups.

Suitable examples of surface modification depend on clay reactions with aminosilanes, such as aminopropyl trimethoxysilane. Silane groups react with clay to result in free amino groups attached to the clay surface. There is an extensive range of silanes capable of modifying surfaces with functionality suitable for use in a range of polymer systems.

Reactive groups Z react with a crosslinker to form a capsule wall. Crosslinkers are compounds containing at least two reactive groups that will react with the reactive groups on the modified surface particles. Examples of crosslinkers that can be used to react with amino groups on a clay particle are polyisocyanates. Polyisocyanates provide a well-known class of crosslinkers and include diisocyanates (such as toluene diisocyanate, hexamethylene diisocyanate and isophorone diisocyanate); isocyanates with on average more than two isocyanate groups (such as polymethylene polyphenylene isocyanate); and many others, including diisocyanate prepolymers, such as their trimethylol propane reactive products, and other single polyols, sold as Bayer Desmodur® resins.

Examples of crosslinkers that may be used to react with epoxy groups; with carboxylic groups; or with unsaturated groups such as acrylic or vinyl groups will be familiar to those skilled in the art.

In one embodiment, the clay is reacted with a suitable modifying agent in the range 0.1 to 30% of the modifying molecule based on the weight of the clay (suitably in the range 0.1 to 20%, and more suitably is from 0.1% to 10% by weight).

The aqueous medium suitable for use in step ii) is composed mainly of water, for example by weight is more than 80% water; and adequately more than 90% water. Optionally, the aqueous medium is also composed of additional water miscible solvents, antifreeze or surfactants, although as mentioned above, these are not required. It has been found that surfactants can interfere with the formation of a Pickering emulsion, so it is preferable not to include surfactants at this stage.

A slurry suitable for use in step ii) may be made by shaking the particulate inorganic material in the aqueous medium using a mechanical stirrer (e.g., a rotor / stator, Ystral® or Ultra Turrax®) or by ultrasonic agitation. Suitably, the slurry is stirred until the solution is added thereto, and the dispersion step is carried out.

In step iii), the solution may be dispersed in the slurry by conventional means such as ultrasonic dispersers or suitably high speed mechanical dispersers such as rotor / stator mixer, Ystral® or Ultra Turrax®. The dispersion process is conducted for a period between 30 seconds and 20 minutes.

Dispersion step iii) results in a dispersion of the solution in the slurry which is stabilized as Pickering emulsion by surface modified inorganic particulate material. This emulsion is composed of solution droplets that are surrounded and stabilized by the particles of the inorganic material. The crosslinker in the solution reacts with the reactive functional groups on the particulate inorganic material to form a crosslinked microcapsule wall. This reaction can be performed simply by allowing dispersion to take place at room temperature. Alternatively, the dispersion may be heated. The optimal amount of time and temperature can be established by routine experimentation. Typically, when the inorganic particulate material is surface modified to contain amino groups on its surface and the crosslinker is a polyisocyanate, stirring the dispersion at 15 to 25 ° C for one hour is sufficient to complete the reaction.

The weight ratio of inorganic particle to solution phase will be between 1: 0.1 to 1:40; suitably between 1: 1 to 1:20.

The crosslinker may be used at a rate of from 0.1 to 30% w / w of the oil phase, more suitably from 0.5 to 20% and most suitably from 1 to 10%.

The reaction may be controlled by pH, temperature, electrolyte addition or catalyst use.

The process results in a dispersion of microcapsules in aqueous medium. These microcapsules may be further modified by the addition to the aqueous medium of a material which will further react with any remaining crosslinkers. For example, when a crosslinker is a polyisocyanate, a polyamine such as diethylenetriamine may be added. This addition causes even more crosslinking and polymer formation on the microcapsule wall and can be used to modify the durability of the capsules or the permeability of the capsule walls to result, for example, in a longer release period under certain conditions.

The microcapsules may be isolated by drying, for example spray drying, to form a powder, or may be used as the dispersion in the aqueous medium. When isolated, the microcapsules may be used dry or may be redispersed in water prior to use.

The microcapsules produced according to this process are new. According to the present invention there is provided a microcapsule comprising an encapsulated material surrounded by a wall, characterized in that the wall is composed of an inorganic particulate material whose surface has been modified and crosslinked.

The invention is illustrated by the following Examples. The particulate inorganic material used in the Examples is tabular ultra-fine kaolin (so-called “block,” flat or plate-shaped), with a d50 of 0.12 μιτι and particle size distribution with at least 98% of the smallest particles by weight. than 1 / vm and at least 82% less than 0,25 μνη.

In these Examples, D [4,3] is the average volumetric diameter of the relevant particles, capsules or droplets as obtained by laser light scattering from a diluted Malvern Mastersízer® 2000 sample.

Example 1 This Example illustrates the preparation of a surface modified clay dispersion. Clay particles (U.S. tabular ultrafine kaolin from Irmerys) had their surfaces modified by the addition of 1.6% by weight of aminopropyltriethoxysilane. The modified surface particles were then added to the water and dispersed with an Ultrasonic Probe (Sonic and Materials, Vibra Cell®, with hereinafter referred to as the Ultrasonic Probe), operated under the following conditions: 50% duty cycle; Yield Control 4; for 6 minutes. The composition is provided in Table 1.

Table 1 Result: Clay dispersion size: D [4.3] = 4.4 μη \.

Figure 1 is a light microscopic image of the clay dispersion of Example 1 Example 2 This Example illustrates the preparation of a simple Pickering emulsion.

Initially, Solvesso® 200ND (Exxon aromatic oil) was dispersed dropwise within the continuous phase of a modified kaolin dispersion prepared according to Example 1 under high shear mixing with Ystral® high shear mixer (type X1020) with a double-ended T10 head (hereinafter referred to as a Ystral® high shear mixer), operated at approximately 5000 rpm. The concentrations of the ingredients used are given in Table 2.

Subsequent high shear mixing by the Ystral® high shear mixer operated at approximately 20,000 rpm for 2 minutes produced an oil pickering emulsion in water [O / A], Table 2 Result: Emulsion Droplet Size: D [4.3] = 13 pm.

Figure 2 is a light microscopic image of the Pickering emulsion of Example 2, Figure 2a is a light microscopic image showing that the emulsion droplets collapse on drying on a glass slide, the emulsion broke.

Figure 2b shows that the addition of 5 wt% Synpe-ronic® NP8 to a Pickering emulsion causes the emulsion to break after 4 days as shown by light microscopy.

Example 3 This Example illustrates the preparation of a one-layer capsule suspension.

A 5% w / w solution of Suprasec® 5025 (polymethylene potmethylene cream; PM PI) was prepared in Solvesso® 200ND. Meanwhile, extra water was added to a surface-modified kaolin dispersion prepared according to Example 1, and then, to this dispersion, a solution of Solvesso® 200ND and Suprasec® 5025 drops was added dropwise with Ystral high shear mixer. ® operated at approximately 5000 rpm. The concentrations of these ingredients used are given in Table 3.

Subsequently, an oil-in-water [O / W] emulsion was prepared by high shear mixing with the Ystral® high shear mixer at approximately 20,000 rpm for 2 minutes, which then developed into a microcapsule system at the same time. as a crosslinking reaction occurred.

Table 3 Result: Microcapsule size: D [4,3] = 20 μηη.

Figure 3 is a light microscopic image of the microcapsules of Example 3. After aging for at least one day, the microcapsules did not collapse upon drying on a glass slide [see Light Microscopy Image, Figure 3a, which shows a stable microcapsule dispersion], demonstrating that the wall had increased mechanical strength compared to the simple emulsion of Example 2. Addition of 5% w / w of Synperonic® NP8 caused the emulsion not to break after a period of one hour. week [see light microscopy image, figure 3b, made after addition of Syn-peronic® NP8 and showing unbroken capsule dispersion], demonstrating that crosslinking anchored the modified surface clay at the interface such that it did not has been displaced by tensoactivity. Pickering emulsions are generally incompatible with tensoactives (as shown in figure 2b); Cross-linking the particles allows them to be used with surfactants.

Example 4 This Example illustrates the preparation of a two-layer capsule suspension. Bayhydur® 3100 [hexamethylene diisocyanate-based polyisocyanate based on a polyether chain for water dispersibility (from Bayer)] was dispersed in water by stirring and then the resulting Bayhydur® 3100 solution was added dropwise. to a single layer suspension of capsules prepared according to Example 3, with the mixture coming from a Ystral® high shear mixer at approximately 5000 rpm throughout the dropwise addition.

The resulting capsule suspension was then mixed with the Ystral® high shear mixer at approximately 20,000 rpm for 2 minutes. The composition is provided in Table 4.

Table 4 Result: The capsules remained intact during dry down and scanning electron microscopy examination, see Figure 4, demonstrating that they exhibited good mechanical strength. THE

Bayhydur® 3100 can be seen as spheres attached to the outside of the capsule walls. The capsules were strong enough to survive high shear mixtures at 20,000 rpm for 2 minutes with a Ystral® high shear mixer, Example 5 This Example illustrates the preparation of a single-layer capsule suspension with diethylenetramine; is similar to Example 3, but in this there is a second crosslinker.

A 25% w / w solution of diethylenetramine (DETA) was prepared in water and then this aqueous DETA solution was added dropwise to a single layer capsule suspension prepared according to Example 3, with mixing from a Ystral® high shear mixer at approximately 5000 rpm. This capsule suspension was then mixed by Ystral® high shear mixer at approximately 20,000 rpm for 2 minutes. The composition is provided in Table 5.

Table 5 Result: Capsule size: D [4,3] = 21 μτη.

Figure 5 is a light microscopic image of the capsules of Example 5.

The capsules remained intact during both dry-down on a microscopic glass slide and drying and scanning electron microscopy examination, demonstrating good mechanical strength. The fact that there was no collapse in the capsule under scanning electron microscopy conditions demonstrates that the presence of a second crosslinker increased the mechanical strength of the capsules compared to those of Example 3. The capsules were strong enough to survive the high-shear mixture. -Reading at 20000 rpm for two minutes with Ystral® high-shear mixer, [0092] Figure 5a is a light microscopic image showing a stable microcapsule dispersion (Example 5) drying on a microscopic glass slide in air .

Figure 5b is a light microscopic image showing an unbroken capsule dispersion (Example 5) after the addition of Synperonic® NP8.

Example 6 This Example compares the release rate of non-crosslinked and crosslinked Pickering emulsions compared to a polymer stabilized emulsion.

Example 6a This Example illustrates the preparation of a simple Pickering emulsion.

A 50 wt% solution of dimethyl phthalate in Solvesso® 200ND was dispersed dropwise into a surface-modified kaolin dispersion prepared according to Example 1 under high shear mixing with Ystral® high shear mixer in approximately 5000 rpm for the entire dropwise addition, and an O / W emulsion was then prepared by high shear mixing with Ystral® high shear mixer at approximately 20,000 rpm for 2 minutes. The composition is provided in Table 6a. Table 6a Result: Droplet size: D [4,3] = 43 μντ \.

Figure 6a is a light microscopic image of Example 6a.

Example 6b This Example illustrates the preparation of a diethylenetriamine single-layer capsule suspension containing dimethyl phthalate prepared by an ultrasonic process.

A 10% w / w solution of Suprasec® 5025, 45% w / w of dimethyl phthalate and 45% w / w of Solvesso® 200ND was dispersed dropwise onto a surface modified kaolin dispersion. prepared according to Example 1 under stirring with an Ultrasonic Probe; and then an O / W emulsion was prepared by high shear mixing with a Uithrasonic Probe for 2 minutes under the following conditions: 50% Duty Cycle, Yield Control 4. At this emulsion 25% w / w 4% of a diethylenetriamine solution were added in admixture with the Uitrassonic Probe. The complete composition is provided in Table 6b.

Table 6b Result: Capsule size: D [4.3] = 146 pm. (This size is too large, the reason being that, as seen in Figure 6b, the capsules stick together). Figure 6b is a Scanning Electron Microscopy image of Example 6b.

Example 6c This Example illustrates the preparation of a diethylenetriamine one-layer capsule suspension containing di-methyl phthalate prepared with the Ystral® (or Ultra Turrax®) high shear process of Example 2.

A 10% w / w solution of Suprasec® 5025, 45% w / w of dimethyl phthalate and 45% w / w of Solvesso® 200ND was dispersed dropwise onto a surface modified kaolin dispersion. prepared according to Example 1 under high shear mixing with Ystral® high shear mixer at approximately 5000 rpm; and an O / W emulsion was then prepared by high shear mixing with Ystral® high shear mixer at approximately 20,000 rpm for 2 minutes. A 25% w / w solution of diethylenetriamine was then added to the emulsion under mixing with Ystral® high shear mixer at approximately 5000 rpm, and an O / A emulsion was then prepared by high shear mixing with high shear mixer. Ystral® at approximately 20,000 rpm for 2 minutes. The complete composition is identical to that provided in Table 6b; the difference between Example 6b and Example 6c is in the preparation processes; ultrasonic and Ystral processes, respectively.

Result: Capsule size: D [4,3] = 33 pm.

[00102] Figure 6c is a scanning electron microscopy image of Example 6c.

Example 6d This Example illustrates the preparation of a Mowi-ol® 4-88 emulsion.

A 50 wt% solution of dimethyl phthalate in Solvesso® 200ND was dispersed dropwise in a solution of Mowiol® 4-88 {88% hydrolyzed poly (vinyl acetate), molecular weight about 28,000 Daltons. ) under high shear mixing with Ystral® high shear mixer. An O / W emulsion was then prepared by high shear mixing with Ystral® high shear mixer, the speed of which was adjusted to produce a droplet size of approximately 20 pm. The complete composition is provided in Table 6d.

Table 6d Result: Capsule size: D [4.3] = 17 pm.

[00105] Figure 6d is a light microscopic image of Example 6d.

Example 6e This example provides release rate data for formulations prepared according to Examples 6a to 6d.

Approximately 1 to 1.5g of each of the four formulations described in Examples 6a - 6d was diluted by factor of 10 in water. Each of these solutions was placed in dialysis tubes and sealed. Each dialysis tube was placed in about 100 ml of water, and then left on rollers at controlled room temperature [temperature of 20 (+/- 2) ° C]. At intervals thereafter, the ultraviolet absorbance of the aqueous phase was measured at 276 nm with the Perkin Elmer® ultraviolet spectrophotometer. This process allowed the release of dimethyl phthalate [DMP] in water to be followed over time. The release curves shown below in Figure 6e show that rapid release was seen for dimethyl phthalate from the stabilized PVA emulsion (Example 6d) and the unreacted clay stabilized emulsion (Example 6a). The release rate was greatly reduced when the clay reacted with Suprasec® 5025 (Example 6b) or diethylenetriamine (Example 6c).

Example 7 This Example illustrates the preparation of a pre-dispersed modified surface clay suspension. 30 g of surface-modified clay particles (as described in Example 1) were deglomerated (with J&K mill) for 30 seconds before adding equivalent weight of water. The slurry was then diluted with water to the desired concentration of 50 wt% for use in the following Examples.

Example 8 Examples 8, 9 and 10 illustrate the preparation of a single-layer capsule suspension containing a pesticide, lamba-cyhalothrin dissolved in Solvesso 200ND, prepared with the Ystral® high shear process. A solution of Suprasec® 5025, Lamba Cyhalothrin and Solvesso® 200ND was drop-dispersed in a surface-modified kaolin dispersion prepared according to Example 7 under high shear mixing with Ystral® High Shear Mixer in approximately 5000 rpm; and an O / W emulsion was then prepared by mixing high shear with the Ystral® high shear mixer at approximately 2000 rpm for 2 minutes. A 25% w / w solution of diethylenetriamine was then added to the emulsion in admixture with the Ystral® high shear mixer at approximately 5000 rpm, and an O / W emulsion was then prepared by high shear mixing. with the Ystral® high shear mixer at approximately 20,000 rpm for 2 minutes. This emulsion formed a single layer capsule dispersion. The complete composition is provided in Table 7.

Example 9 Example 9 is an example of a produced capsule containing both crosslinked clay particle and an extra polyurea bonding layer. The capsule was prepared with the emulsion of Example 8 and its treatment with diethylene triamine (crosslinker) in the amounts provided in Table 8, and mixed under low shear to homogenize the product.

Example 10 Example 10 is an example of a produced capsule containing a crosslinked clay particle and an extra polyurethane bonding layer. The capsule was prepared with the emulsion of Example 8 and its treatment with glycerol (crosslinker) and DABCO (catalyst) in the amounts provided in Table 9 and mixing under low shear to homogenize the product.

Table 9 DABCO is (+ -) - (E) -1- (2,6,6-trimethyl-2-cyclohexen-1-yl) -2-buten-1-one.

Examples 8, 9 and 10 immediately provided fluid dispersions that did not change upon standing overnight. Further cross-linking was performed by heating the samples at 50 ° C for 2 hours, but the physical characteristics of the products did not change.

To test the compatibility of these products with other added components, an isopa-raffinic oil-in-water emulsion (Isopar® M) was prepared. Isopar M was dispersed dropwise in 5% w / w of a solution of Gohsenol® GL05 (88% hydrolyzed poly (vinyl acetate)) under high shear mixing with Ystral® high shear mixer. An O / W emulsion was then prepared by high shear mixing with Ystral® high shear mixer, whose speed was adjusted to yield approximately 10 pm droplet size. The complete composition is provided in Table 10.

Equal sample volumes from each of Examples 8, 9 and 10 were then independently mixed with equal volume of the Isopar M emulsion. All samples remained fluid both immediately and after standing for 24 hours, demonstrating the compatibility of products of the invention with an added oil-in-water emulsion.

Example 11 This example illustrates data on the observed enhancement in lamba-cyhalothrin photostability when retained within Pickering capsules.

Example 11a This Example illustrates the preparation of a diethylenetriamine single-layer capsule suspension containing lycia cyrothrin prepared with the Ystral® high shear process. A 10% w / w solution of Suprasec® 5025, 47.5% w / w lamba cyhalothrin and 47.5% w / w Solvesso® 200ND was dispersed dropwise onto a modified surface kaolin dispersion. prepared according to Example 7 under high shear mixing with Ystral® high shear mixer at approximately 5000 rpm; and an O / W emulsion was then prepared by mixing high shear with the Ystral® high shear mixer at approximately 20,000 rpm for 2 minutes. This emulsion formed a dispersion containing single layer capsules. A 25% w / w solution of diethylenetriamine (DETA) was prepared in water, and then this aqueous DETA solution was added dropwise to the suspension containing single layer capsules mixed with the Ystral® high shear mixer in approximately 5000 rpm. This capsule-containing suspension was then mixed by the Ystral® high shear mixer at approximately 20,000 rpm for 2 minutes. The composition is provided in Table 11.

Table 11 Result: Size: D [4.3] = 31.7 Mm.

[00117] Figure 7 is a Scanning Electron Microscopy image of Example 11a.

Example 11b This Example illustrates the preparation of a diethylenotriamine single layer capsule suspension containing lamba-cyhalothrin prepared by the Ultrasonic process. A solution of Sol-vesso® 200N D was dispersed dropwise into a surface modified kaolin dispersion prepared according to Example 7 under agitation with an Ultrasonic Probe; and then an O / W emulsion was then prepared by high shear mixing with the Ultrasonic Probe for 2 minutes under the following conditions: 50% Duty Cycle, Yield Control 4. This emulsion formed a dispersion. containing single layer capsules. To this capsule suspension 25% w / w diethylethylenetriamine solution was added in admixture with the Ultrasonic Probe. The composition is provided below in Table 12.

Table 12 Figure 8 is a Scanning Electron Microscopy image of Example 11b, Result: Capsule size: D [4.3] = 171 pm (this is large due to the aggregation of the capsules in the instrument , the electron micrograph shows that the capsule size is smaller).

Capsules according to Examples 11a and 11b were individually evaluated against commercially available capsules [Karate Zeon®] in a comparative study to determine the extent of protection afforded by each capsule to lambda-cyhalothrin against ultraviolet photodegradation.

For each type of capsule, microcapsule samples were spread on glass slides and exposed to a xenon lamp (simulating sunlight) for up to three days. Using standard techniques, microcapsules were analyzed to determine the amount of lamba-cyhalothrin present in the formulations at the beginning of exposure to ultraviolet light and the amount remaining at various time periods during the three-day exposure.

The results are shown in Figure 9. The capsules of the present invention clearly provide better ultraviolet protection to lambda-cyhalothine than the standard commercial product. Example 12 This Example illustrates the preparation of a diethylenetriamine single-layer capsule suspension containing dimethyl phthalate (which is an example of volatile organic molecule) prepared with the Ystral® high shear process. A 10% w / w solution of Suprasec® 5025, 47.5% w / w of dimethyl phthalate and 47.5% w / w of Solvesso® 200ND was dispersed dropwise onto a surface kaolin dispersion. modified, prepared according to Example 7, under high shear mixing with Ystral® high shear mixer, at approximately 5000 rpm; and an O / W emulsion was then prepared by mixing high shear with the Ystral® high shear mixer at approximately 20,000 rpm for 2 minutes. This emulsion formed a dispersion containing single layer capsules. The composition is provided in Table 13.

25% w / w of a diethylenetriamine solution (DETA) was prepared in water and then varying amounts of this solution were added dropwise to the suspension containing single-layer capsules mixed with the high shear mixer. Ystral® at approximately 5000 rpm to provide a concentration range (0 - 1.3 wt%) in the final dispersions. Each capsule suspension was then mixed by the high shear mixer at approximately 20,000 rpm for 2 minutes. The complete composition is provided in Table 14.

Approximately 1 to 1.5 g of each of these capsule formulations was diluted by a factor of 10 in water. Each of these dilutions was placed in dialysis tubes and sealed. Each dialysis tube was placed in approximately 100 ml of water and then left on temperature controlled room rollers [temperature of 20 (+/- 2) ° C]; At appropriate intervals, the aqueous-phase UV absorbance was measured at 276 nm with Perkin El-mer® UV spectrophotometer. This process allowed the release of dimethyl phthalate [DMP] in water to be followed over time; See Figure 10 which shows that increasing the DETA loading decreases the DMP release rate of the capsules, demonstrating that the release rate is rapidly controlled by the DETA loading used in the formulation.

Example 13 This example illustrates the preparation of a diethylenotriamine single layer capsule suspension containing mefe-noxam prepared with the Ystral® high shear process. Capsule dispersion has been shown to exhibit good redispersion properties after drying to dry pellet. 5% w / w of a Suprasec® 5025 solution, 47.5% w / w of mefenoxam and 47.5% w / w of Solvesso® 200ND was dispersed into a surface-modified kaolin dispersion, prepared according to Example 7, under high shear mixing with Ystral® high shear mixer, at approximately 5000 rpm; and an O / W emulsion was then prepared by mixing high shear with the Ystral® high shear mixer at approximately 20,000 rpm for 2 minutes. This emulsion formed a dispersion containing single layer capsules. 25% w / w of a diethylenetriamine solution (DETA) was prepared in water and then this aqueous DETA solution was added dropwise to the suspension containing single layer capsules mixed with the Ystral® high shear mixer, at approximately 5000 rpm. This capsule suspension was then mixed by the Ystral® high shear mixer at approximately 20,000 rpm for 2 minutes. The complete composition is provided in Table 15.

Result: Capsule Size: D [4.3] = 13.7 pm This formulation provided capsules that remained stable on drying, and the capsules in the aqueous dispersion remained for a period of 9 months at room temperature. A sample of this dispersion was left to dry down on a plastic tray in a hood for 3 days, after which it was found to rapidly redisperse in water with gentle agitation. Figure 11 shows the capsules in their original dispersion and Figure 12 shows them in the dispersion formed from redispersion after drying (dry down). The capsules appeared to have lost some of the more volatile Solvesso® 200ND by evaporation, but the capsules remained essentially intact and exhibited easy redispersion.

Claims (18)

Process for the production of microcapsules, characterized in that it comprises: i) forming a solution of a crosslinker in liquid; ii) forming a slurry of an inorganic surface-modified particulate material in aqueous medium; and iii) dispersing the solution from step 1) into the slurry of step ii) and causing or allowing the crosslinker to react with the surface modified particulate inorganic material to form a microcapsule comprising a microcapsule particulate inorganic crosslinked wall , wherein the surface modified inorganic particulate material is clay that has had the surface modified with aminosilane. Process according to Claim 1, characterized in that the liquid is insoluble in water. Process according to Claim 2, characterized in that the liquid has a water solubility at 20 ° C of less than 10 g / l. Process according to Claim 1, 2 or 3, characterized in that the liquid comprises an active material, which is an agrochemical. Process according to Claim 4, characterized in that the active material is an insecticide. Process according to Claim 5, characterized in that the insecticide is a pyrethroid. Process according to Claim 6, characterized in that the pyrethroid is lamba-cyhalothrin. Process according to any one of claims 1 to 7, characterized in that the particulate inorganic material comprises an oxide compound of at least one of calcium, magnesium, aluminum and silicone; or a derivative of this compound. Process according to any one of claims 1 to 8, characterized in that the particulate inorganic material has a median diameter (d50) of 10 µm or less. Process according to any one of claims 1 to 8, characterized in that the particulate inorganic material has a particle size distribution, wherein at least 90% of the particles by weight are less than 2 pm. A process according to any one of claims 1 to 8, characterized in that the particulate inorganic material has a particle size distribution, wherein at least 90% of the particles by weight are less than 2 pm, at least 90% of the particles by weight are less than 1 pm and at least 75% of the particles by weight are less than 0.25 pm. Process according to any one of claims 1 to 11, characterized in that the aminosilane with which the particle surface of the particulate inorganic material has been modified has a chemical structure X --- Y — Z, wherein X is a chemical affinity with high affinity for the surface of the particle; Z is an amino group; and Y is a chemical portion that joins X and Z together. Process according to Claim 12, characterized in that X is an alkoxy silane group. Process according to Claim 12 or 13, characterized in that Y is a C 2-6 alkylene chain. Process according to any one of claims 1 to 14, characterized in that the crosslinker is a polyisocyanate. Process according to any one of Claims 1 to 15, characterized in that the cross-linked wall of the microcapsule is modified by the addition of an extra cross-linking molecule. Process according to any one of claims 1 to 16, characterized in that the particulate inorganic material is natural. Process according to any one of Claims 1 to 16, characterized in that the particulate inorganic material is synthetic.