WO2023078783A1

WO2023078783A1 - Process of encapsulation

Info

Publication number: WO2023078783A1
Application number: PCT/EP2022/080111
Authority: WO
Inventors: Guillaume Wojciech JAUNKY; Marc Eberhardt; Rainer KNIESBURGES; Nina KOSTINA; Martin Möller; Jürgen OMEIS; Volker THYSSEN-WALLNER; Sebastian Weiss; Xiaomin Zhu
Original assignee: Byk-Chemie Gmbh
Priority date: 2021-11-05
Filing date: 2022-10-27
Publication date: 2023-05-11

Abstract

The invention relates to a process of encapsulating a compound having a solubility in water of at most 10 g/l at 20°C, comprising the steps of a) Providing a silicon alkoxide based prepolymer modified with a polyalkylene oxide compound, b) Dissolving the compound having a solubility in water of at most 10 g/l at 20°C in a silicon alkoxide having an average of at least two alkoxide groups per molecule to form a non-aqueous solution of the compound,c) Combining an aqueous liquid with the modified prepolymer provided in step a) and the non-aqueous solution prepared in step b) to form an aqueous dispersion, and d) Stirring the aqueous dispersion formed in step c) to form an aqueous dispersion of capsules.

Description

PROCESS OF ENCAPSULATION

The invention relates to a process of encapsulating a compound, to the capsules obtainable by the process, to the use of the capsules for controlled release, and to a composition comprising the capsules and an organic polymer.

WO 2011/131644 relates to a capsule with a core/shell structure, comprising a core which comprises at least one sparingly-soluble or water-insoluble organic active ingredient. This document is concerned with capsules having improved stability and reduced skin irritation potential. The shell of the capsules comprises nanoparticles of a metal oxide or semimetal oxide, and these nanoparticles are joined together by at least one further metal oxide formed by hydrolysis and subsequent polycondensation of a sol-gel precursor.

WO 2017/016636 relates to a method for the encapsulation of substances in silica-based capsules. The method uses a polyalkoxysiloxane (PAOS), preferentially a polyalkylalkoxysiloxane (R-PAOS), which acts as a silica source and as an emulsifier. Alkenes, alkynes, esters, ethers, ketones, aldehydes, aromatic compounds, and polymers are mentioned as hydrophobic organic liquids which can ben encapsulated by the method.

The processes known from these documents allow for encapsulation of substances without the use of external emulsifiers. External emulsifiers or surfactants in the capsules can detract from the properties of the capsules. In particular, the presence of external surfactants can lead to reduced water resistance in compositions or materials wherein the capsules are incorporated. It is therefore desirable to avoid external surfactants in the capsules or during formation of the capsules.

A drawback of the known processes is that the control of the particle size of the capsules becomes increasingly difficult with increasing viscosity of the ingredient to be encapsulated. The formation of small capsules having a high viscous encapsulated material is not possible with the known processes. Capsules having a large particle size can detract from the properties of compositions or materials wherein the capsules are incorporated. In particular, large capsules impair the optical properties of compositions and materials wherein the capsules are incorporated. In case of coatings or coating compositions, capsules having a particle diameter exceeding the layer thickness of the coating prevent the formation of an even coating surface. It is therefore desirable to prepare capsules have a small particle size.

Hence, there is a need for a process of encapsulation which is suitable for encapsulation of materials of various viscosity and wherein the size of the capsules is independent of the viscosity of the encapsulated material. Preferably, the process should not rely on the use of external surfactants.

The invention provides a process of encapsulating a compound having a solubility in water of at most 10 g/l at 20°C, comprising the steps of a) Providing a silicon alkoxide based prepolymer modified with a polyalkylene oxide compound, b) Dissolving the compound having a solubility in water of at most 10 g/l at 20°C in a silicon alkoxide having an average of at least two alkoxide groups per molecule to form a non-aqueous solution of the compound, c) Combining an aqueous liquid with the modified prepolymer provided in step a) and the non-aqueous solution prepared in step b) to form an aqueous dispersion, and d) Stirring the aqueous dispersion formed in step c) to form an aqueous dispersion of capsules.

The process of the invention is suitable for encapsulation of materials of various viscosity, and the size of the capsules is independent of the viscosity of the encapsulated material. The process does not rely on the use of external surfactants.

As mentioned above, the process relates to encapsulating a compound having a solubility in water of at most 10 g/l at 20°C. The compound to be encapsulated suitably has a solubility in water at 20 °C of less than 8 g/l, preferably less than 5 g/l, and most preferably less than 2 g/l. The compounds to be encapsulated may be monomers, oligomers, or polymers. Suitable compounds to be encapsulated generally comprise carbon and hydrogen. In preferred embodiments, the compounds also comprise silicon, such as silicones or modified silicones. The compound to be encapsulated may be a liquid or a solid. The compound to be encapsulated is generally soluble in in a silicon alkoxide having an average of at least two alkoxide groups per molecule. Typically, the compound to be encapsulated has a solubility in the silicon alkoxide having an average of at least two alkoxide groups per molecule of at least 50 g/l, preferably at least 100 g/l at a temperature of 20 °C. It is also possible to encapsulate a mixture of two or more compounds, provided that the individual compounds meet the above-mentioned solubility parameters.

Examples of compounds to be encapsulated include waxes, e.g. alkanes, esters of alkyl alcohols and alkyl carboxylic acids; alkenes; alkynes; esters; ethers; ketones; aldehydes; aromatic compounds; polymers, e.g. polydialkylsiloxanes or modified versions thereof; vitamins; biocides, oils; perfume oils. In some embodiments, the compounds to be encapsulated are oligomers or polymers suitable as additives in the polymer and paint industry, such as silicone- based surface additives, dispersing agents, or rheology control agents.

In some embodiments, the compounds to be encapsulated further include a wax, in a particular a wax which is solid at a temperature below 30 °C, and which is a liquid at a temperature above 50 °C. Such waxes help to immobilize other encapsulated compounds at ambient temperature in a solid matrix. When heated to a temperature above the melting point of the wax, the encapsulated material liquifies and release of the encapsulated material is accelerated. This may be useful to trigger the release of encapsulated compounds by heat, for example when the capsules of the invention are included in heat-curable coating compositions.

In further embodiments, the compounds to be encapsulated further include a disintegrant. Disintegrants are compounds and materials which expand or release gases on an elevation in temperature to a defined temperature range and thus build up the pressure required within the capsule to disintegrate the shell of the capsule. In order to build up a high pressure, it can be advantageous to use compounds which have a very low boiling point, or which participate in a chemical reaction or decomposition with release of gases in a defined temperature range. Such compounds are known to those skilled in the art. It can be advantageous to select the disintegrant so that the expansion, the chemical reaction, or decomposition thereof with release of gases takes place in the previously defined temperature range. As disintegrants, compounds are suitable which release nitrogen (N₂) or carbon dioxide (CO₂). Other compounds which, under the influence of temperature, in a defined temperature range, release non-toxic gases such as neon, argon, vaporous water, low-molecular-weight hydrocarbons or halogenated hydrocarbons, are also suitable. Specific examples of suitable disintegrants include are sodium hydrogencarbonate, sodium carbonate, potassium carbonate, potassium hydrogencarbonate, azodicarbonamides, hydrazides, such as, for example, p-toluenesulphonyl hydrazide, carbazides, such as, for example, 4,4-oxy-bis(benzosulphohydrazide), and 2,2- toluylenesulphonyl semicarbazide, tetrazoles, such as, for example, 5-phenyltetrazole and/or citric acid derivatives.

As mentioned above, the process is also suitable for encapsulating liquid compounds having a higher viscosity while maintaining control over the capsule size.

In preferred embodiments, the compound to be encapsulated has a viscosity of at least 25 mPas at a temperature of 20 °C, measured at a shear rate of 300 s’¹, preferably at least 50 mPas, and most preferably at least 100 mPas, at least 200 mPas, or at least 300 mPas. Generally, there are no upper limits for the viscosity of the compound to be encapsulated. However, if liquid, the compound to be encapsulated typically has a of at most 100000 mPas at a temperature of 20 °C, measured at a shear rate of 300 s'¹ . The viscosity is suitably determined according to ASTM D4283 - 98(2015).

When mixtures of compounds are used, the mentioned viscosities relate to the individual components of the mixture.

In the first step of the process of the invention, a silicon alkoxide based prepolymer is provided which is modified with a polyalkylene oxide compound.

In one embodiment, the silicon alkoxide based prepolymer is modified with a polyalkylene oxide compound by reaction with a polyalkylene oxide compound comprising at least one hydroxyl group, preferably with a polyalkylene oxide compound having one hydroxyl group.

The silicon alkoxide based prepolymer is a partially condensed product of tetraalkoxysilanes, or mixtures of tetraalkoxysilanes with alkyltrialkoxysilane and/or dialkyldialkyoxysilane. Examples of suitable tetraalkoxysilanes are tetramethoxysilane, tetraethoxysilane, tetrapropxysilane, and tetrabutoxysilane. If so desired, tetraalkoxysillanes having more than one type of alkoxy group can be used, as well as mixtures of different types of tetraalkoxysilanes. Suitable silicon alkoxide prepolymers are available commercially, for example polyethoxysilane with a silica content of 40 % by weight (trade designation Dynasylan® SILBOND® 40 from Evonik), polyethoxysilane with a silica content of 50 % by weight (trade designation Dynasylan® SILBOND® 50 from Evonik), and polymethoxysilane with a silica content of 51 % by weight (trade designation SiSiB® PC5411 from Power Chemical Corporation). Suitable silicon alkoxide prepolymers can also be prepared by know methods, for example as described in the article by Moller et al. in Macromolecules, 2006, 39, pp. 1701-1708. Suitable silicon alkoxide prepolymers generally have a number average molecular weight in the range of 500 to 20000. The number average molecular weight can be determined by gel permeation chromatography in chloroform with evaporative light scattering detector calibrated using polystyrene standards).

Modification of the silicon alkoxide based prepolymer with a polyalkylene oxide compound can be carried out by a condensation reaction of the silicon alkoxide based prepolymer with a compound having at least one hydroxyl group. In this reaction a part of the alkoxide groups of the silicon alkoxide based prepolymer is replaced with a polyalkylene oxide group. The reaction can be catalyzed by suitable catalysts, for example tetraalkoxytitanates.

In a further embodiment, modification of the silicon alkoxide based prepolymer can be carried out by a condensation reaction of the silicon alkoxide based prepolymer with a polyalkylene oxide compound which has at least one alkoxysilane group or at least one silanol group, and a terminal hydrocarbyl group, preferably a lower alkyl group having 1 to 4 carbon atoms. An example of a suitable modification compounds is methoxy(polyethyleneoxy)propyltrimethoxy- silane. The advantage of using a using polyalkylene oxide compound which has at least one alkoxysilane group or at least one silanol group is that the polyalkylene oxide is linked to the silicon alkoxide based prepolymer via a non-hydrolyzable bond.

Generally, from 3 to 30 mol-%, preferably 5 to 20 mol-% of the alkoxide groups of the silicon alkoxide based prepolymer are replaced with polyalkylene oxide groups. Suitable polyalkylene oxide groups are polyethylene oxide groups, polypropylene oxide groups, and polybutylene oxide groups, as well as mixtures thereof. Preferred compounds are polyethylene oxide compounds having one hydroxyl group and a terminal lower alkyl group having 1 to 4 carbon atoms. The polyalkylene oxide compound having at least one hydroxyl group generally have 4 to 30, preferably 5 to 20 alkylene oxide repeating units. Instead of modifying the silicon alkoxide based prepolymer with a polyalkylene oxide compound in a separate step after formation of the silicon alkoxide based prepolymer, it is alternatively possible to include the polyalkylene oxide compound in the preparation process of the silicon alkoxide based prepolymer. This can be accomplished by including a polyalkylene oxide compound having at least one hydroxyl group or at least one alkyoxysilane group or at least one silanol group in the reaction mixture for forming the silicon alkoxide based prepolymer. It is also possible to use silicon alkoxides having one or two polyalkylene oxide groups linked to the silicon atom via a Si-O group.

The silicon alkoxide based prepolymer modified with a polyalkylene oxide compound generally contains polyalkylene oxide in an amount of 5 to 50 % by weight, preferably 20 to 30 % by weight, calculated on the weight of the modified silicon alkoxide based polymer.

In step b) of the process of the invention the compound having a solubility in water of at most 10 g/l at 20°C is dissolved in a silicon alkoxide having an average of at least two alkoxide groups per molecule to form a non-aqueous solution of the compound.

Generally, the compound having a solubility in water of at most 10 g/l at 20°C is dissolved in the silicon alkoxide by suitable mixing processes, for example by stirring at ambient temperature, for example in a temperature range of 15 to 30 °C at atmospheric pressure. If so desired, the process of dissolving can be carried out at a higher or lower temperature. Generally, the amount of the compound having a solubility in water of at most 10 g/l at 20°C is in the range of 5 to 80 % by weight, preferably 10 to 70 % by weight, calculated on the weight of the solution.

It is preferred that the solution prepared in step b) has a low viscosity, for example a viscosity in the range of 0.5 to 200.0 mPas, preferably 0.5 to 100 mPas, and most preferably 0.5 to 50 mPas, measured at a temperature of 20 °C and a shear rate of 300 s’¹.

The use of the solution prepared in step b) reduces the interfacial tension between the aqueous phase of step c) and the encapsulant. It is believed that this facilitates the formation of small capsules. It is furthermore believed that a relatively low viscosity of the solution prepared in step b) facilitates the formation of small capsules. The silicon alkoxide has at least two alkoxide groups. In typical embodiments, the silicon alkoxide has three or four alkoxide groups. The non-alkoxide groups linked to the silicon atom are typically alkyl groups, having 1 to 10 carbon atoms. Optionally, the alkyl groups may be substituted by functional groups, such as epoxide groups or amine groups.

In preferred embodiments, the alkoxide groups are independently selected from C1 to C4 alkoxide groups.

Examples of suitable silicon alkoxides are tetraalkoxysilanes, or mixtures of tetraalkoxysilanes with alkyltrialkoxysilane and/or dialkyldialkyoxysilane. Examples of suitable tetraalkoxysilanes are tetramethoxysilane, tetraethoxysilane, tetrapropxysilane, and tetrabutoxysilane. If so desired, tetraalkoxysillanes having more than one type of alkoxy group can be used, as well as mixtures of different types of tetraalkoxysilanes.

In step c) of the process of the invention an aqueous liquid is combined with the modified prepolymer provided in step a) and the non-aqueous solution prepared in step b) to form an aqueous dispersion.

In typical embodiments, the aqueous liquid comprises water in an amount of 90 % by weight or more. In some embodiments, a pH buffer may be present in the aqueous liquid to maintain a desired pH range. Preferably, the aqueous liquid consists essentially of water, more preferably de-ionized water.

The aqueous liquid is combined with the modified prepolymer provided in step a) and the nonaqueous solution prepared in step b). In typical embodiments, the modified prepolymer provided in step a) and the non-aqueous solution prepared in step b) are added as separate feed streams to the aqueous liquid. They may be added sequentially in any suitable order, or simultaneously. If so desired, it is also possible to mix the modified prepolymer provided in step a) and the nonaqueous solution prepared in step b) prior to addition to the aqueous liquid. In preferred embodiments, the modified prepolymer provided in step a) is added to the aqueous liquid prior to addition of the non-aqueous solution prepared in step b). During or after the addition the aqueous liquid is generally subjected to shear force, for example by stirring, to form an aqueous dispersion. It is particularly preferred add modified prepolymer provided in step a) to the aqueous liquid and to form an emulsion, prior to adding the non-aqueous solution prepared in step b). Generally, the modified prepolymer provided in step a) is added to the aqueous liquid in an amount of 0.10 to 15.00 % by weight, preferably 0.50 to 10.00 % by weight, calculated on the weight of the aqueous liquid. Generally, the amount of the non-aqueous solution prepared in step b) is added to the aqueous liquid in an amount of 0.05 to 15.00 % by weight, calculated on the weight of the aqueous liquid.

In step d) of the process of the invention the aqueous dispersion formed in step c) is stirred to form an aqueous dispersion of capsules.

In step d) of the process the alkoxysilane groups undergo a hydrolysis and condensation reaction to form Si-O-Si bonds.

Generally, step d) is carried out in a temperature range of 20 to 90 °C, preferably 20 to 80 °C, for a period of 0.5 to 36.0 hours, preferably 2.0 to 24 hours.

The pH value of the aqueous phase in step d) suitably is in the range of 7.0 to 13.0, preferably 8.0 to 11 .0. The pH value can be adjusted to the desired level by the addition of acid or base, as is known to the person skilled in the art. If so desired, a buffer may be added to the aqueous phase to maintain the pH value at a desired level.

The capsules obtained by the process of the invention generally have an essentially spherical shape. The capsules preferably have a d50 number average particle size in the range of 50 to 600 nm, preferably 60 to 500 nm, determined by dynamic light scattering. The particle size is suitably determined according to ASTM E3247 - 20.

The silicon alkoxide based prepolymer modified with a polyalkylene oxide compound has selfemulsifying properties in water, presumably due to the presence of polyalkylene oxide groups. Therefore, it is generally not required to include additional surfactants to the aqueous phase in steps c) and d) of the process of the invention. Accordingly, it is preferred that surfactants are absent or substantially absent in step d) of the process.

The expression “essentially absent” means that surfactants are either entirely absent in step d) of the process, or that surfactants are present in such a low amount that the properties of the capsules are not materially changed, compared to capsules that are prepared wherein in step d) surfactants are entirely absent. Generally, surfactants are present in step d) in an amount of 0.0 to 0.3 % by weight, preferably 0.0 to 0.1 % by weight, calculated on the weight of the capsules. Surfactants are compounds that lower the surface tension (or interfacial tension) between two liquids, between a gas and a liquid, or between a liquid and a solid. Surfactants generally have a molecular weight below 500 g/mol. It is to be understood that for the surfactants to be absent the silicon alkoxide based prepolymer modified with a polyalkylene oxide is not considered to be a surfactant.

In the step d) of the process of the invention the capsules are obtained as an aqueous dispersion of capsules. If so desired, the capsules can be separated from the aqueous phase by known separation processes, such as centrifugation, filtration, or evaporation of water, such as spray drying, pervaporation through membranes or freeze drying.

It is also possible to increase the capsule concentration in the aqueous dispersion by removing a part of the water from the aqueous phase, for example by the methods mentioned above.

If so desired, one or more additives for specific purposes may be included in the aqueous dispersion of capsules. Examples of suitable additives include biocides, rheology control agents, and dispersion stabilizers.

Generally, the capsules comprise 30 to 90 % by weight, preferably 40 to 80 % by weight, of the compound having a solubility in water of at most x g/l at 20°C, calculated on the weight of the capsules.

The invention further relates to the capsules obtainable by the process of the invention.

The invention also relates to the use of the capsules obtainable by the process of the invention for controlled release of a compound having a solubility in water of at most 10 g/l at 20°C. Controlled release means that the compound is released from the capsule over a longer period of time, for example during days, weeks, or months.

In a further embodiment, the invention relates to a method of controlled release of a compound having a solubility in water of at most 10 g/l at 20°C, comprising providing the compound in the form of the capsules obtainable by the process of the invention. The invention further relates to a composition comprising the capsules obtainable by the process of the invention in an amount of 0.1 to 20.0 % by weight, calculated on the weight of the composition, and at least one other functional ingredient. Examples of functional ingredients are organic polymers, detergents, and skin moisturizers.

The composition may, for example, be formulated as a coating composition, a molding composition, a home care composition, or a personal care composition.

Said composition preferably contains the capsules of the invention in an amount of from 0.2 to 15.0 % by weight, preferably of from 0.3 to 12.0 % by weight, more preferably of from 0.5 to 10.0 % by weight, based in each case on the total weight of the composition.

The properties of the compositions, in particular of coating compositions, moulding compositions, home care compositions, and personal care compositions are not impaired by the amount of the inventive capsules present therein. The presence or use of these capsules does not have a negative effect e.g. in respect of corrosion protection, gloss preservation, weather resistance and/or mechanical strength of the coatings obtained from these compositions.

In a typical embodiment, the composition is liquid at ambient temperature, for example at a temperature of 20°C. In some embodiments, the organic polymer present in the composition is liquid. In such cases, the composition may be liquid at ambient temperature without the need of a liquid volatile diluent. In other embodiments, it may be required or desirable to render the composition liquid or to achieve a desired viscosity by including a volatile diluent. The volatile diluent may be water or an organic solvent, or mixtures thereof. Hence, the composition may be an aqueous composition or a non-aqueous composition.

In some embodiments, the inventive compositions comprise at least one organic polymer. All customary organic polymers known to the skilled person are suitable as polymer component of the composition of the invention. The organic polymer used in accordance with the invention may have crosslinkable functional groups. Any customary crosslinkable functional group known to the skilled person is contemplated here. More particularly the crosslinkable functional groups are selected from the group consisting of hydroxyl groups, amino groups, carboxylic acid groups, and unsaturated carbon double bonds, isocyanates, polyisocyanates, and epoxides such as ethylene oxides.

The organic polymer is preferably selected from the group consisting of epoxide resins, polyesters, wherein the polyesters may be unsaturated, vinyl ester-based resins, poly(meth)acrylates, polyurethanes, polyureas, polyamides, polystyrenes, polyethers, polycarbonates, polyisocyanates, and melamine formaldehyde resins. These polymers may be homopolymers or copolymers.

The composition of the invention can be provided as a one-component system or as a two- component system.

The composition of the invention preferably comprises the organic polymer in an amount of 3 to 90 % by weight, preferably in an amount of 5 to 80 % by weight, more preferably in an amount of 10 to 75 % by weight, based on the total weight of the composition.

Depending on the desired application, the composition of the invention may comprise one or more customarily employed additives as component. These additives are preferably selected from the group consisting of emulsifiers, flow control assistants, solubilizers, defoaming agents, stabilizing agents, preferably heat stabilizers, process stabilizers, and UV and/or light stabilizers, catalysts, waxes, flexibilizers, flame retardants, reactive diluents, adhesion promoters, organic and/or inorganic nanoparticles having a particle size < 100 nm, process aids, plasticizers, fillers, glass fibers, reinforcing agents, additional wetting agents and dispersants, light stabilizers, ageing inhibitors and mixtures of the aforesaid additives. Said additive content of the composition of the invention may vary very widely depending on intended use. The content, based on the total weight of the composition of the invention, is preferably 0.01 to 10.00 % by weight, more preferably 0.01 to 8.00 % by weight, very preferably 0.01 to 6.00 % by weight, especially preferably 0.01 to 4.00 % by weight, and particularly 0.01 to 2.00 % by weight, calculated on the total weight of the composition. The inventive compositions may be used in pigmented or unpigmented form and may also comprise fillers such as calcium carbonate, aluminum hydroxide, reinforcing fibers such as glass fibers, carbon fibers and aramid fibers.

The compositions of the invention may be applied to a large number of substrates, such as wood, paper, glass, ceramic, plaster, concrete and metal, for example. In a multi-coat process the coatings may also be applied to primers, primer-surfacers or basecoats. Curing of the compositions depends on the particular type of crosslinking and may take place within a wide temperature range from, for example, -10° C to 250° C. When the compositions are moulding compounds, they preferably comprise at least one polymer selected from the group consisting of alkyd resins, polyester resins, epoxy resins, polyurethane resins, unsaturated polyester resins, vinyl ester resins, polyethylene, polypropylene, polyamides, polyethylene terephthlate, PVC, polystyrene, polyacrylonitrile, polybutadiene, polyvinyl chloride or mixtures of these polymers or any copolymers thereof.

Examples

Preparation of PEOS-PEG

PEOS is synthesized according to a protocol (Macromolecules, 2006, 39 (5), pp 1701-1708). The PEOS (50 g) is charged with polyethylene glycol) monomethyl ether (15 g, Mw=350 g-mol- 1) under inert gas in a 500 mL two-neck flask equipped with a magnetic stirrer and distillation bridge. The mixture is heated to 135 °C under intensive stirring. The ethanol produced is continuously distilled off. When no further ethanol passes, the reaction is stopped, and the product is dried for 1 h under high vacuum. A yellow oil is obtained.

Ti(OEt)4 is typically used as a catalyst in the transesterification. Since Ti(OEt)4 is also used in the production of PEOS, no addition of catalyst is necessary here. The ratio of ethoxy moieties replaced by PEG is thereby denoted as a number, e.g. PEOS-PEG-10 = 10% of ethoxy replaced by PEG.

Example 1

0.7 g of PEOS-PEG-10 compound was added to 80 g of distilled water at 25 °C and shaken to obtain a homogenous opaque mixture. 0.7 g of PDMS 2000 (polydimethylsiloxane having a viscosity of 2000 mPas at 25 °C) and 0.7 g of tetraethoxysilane (TEOS) were thoroughly mixed and then added to the water. The mixture was emulsified with an Ultra-Turrax® T25 at 18.000 rpm for 10 min. The dispersion was then transferred to a round-flask and stirred vigorously on a magnetic stirrer at 60 °C for 24 h. After 30 min of the 24 h, the pH was adjusted to 9 with aqueous ammonia. The resulting capsules were centrifuged for 25 min at 11 .000 rpm. The d50 number average particle size (dynamic light scattering, Zetasizer) of the resulting particles was 240 nm.

Example 2

A reaction vessel was charged with 10 L distilled water at ambient conditions. The stirrer was set to 1100 rpm and 150 g PEOS-PEG-10 was added. The stirrer and the rotor were started, and instantly 500 g of a hydroxy-functional polydimethylsiloxane having a viscosity of 80 mPas at 20 °C and 250 g TEOS, which were previously mixed, was added. The speed of the stirrer was kept at 1100 rpm, and the speed of the rotor at 5000 rpm. After 6.5 minutes the rotor was stopped, and the resulting white dispersion was transferred to a reaction vessel. The pH was adjusted to 9 with ammonia and the whole mixture was stirred at 60 °C for 24 hours. A milky white dispersion of capsules in water was obtained. The d50 number average particle size (dynamic light scattering, Zetasizer) of the resulting particles was 350 nm.

Example 3

2.0 g of PEOS-PEG-10 compound was added to 200 g of distilled water at 25 °C and shaken to obtain a homogenous opaque mixture. 2.0 g of a hydroxy-functional polydimethylsiloxane having a viscosity of 80 mPas at 20 °C and 2.0 g of TEOS were thoroughly mixed and then added to the water. The mixture was emulsified with an Ultra-Turrax® T25 at 18.000 rpm for 10 min. The dispersion was then transferred to a round-flask and stirred vigorously on a magnetic stirrer at 70 °C for 24 h. After 30 min of the 24h, the pH was adjusted to 9 with aqueous ammonia. The resulting capsules were centrifuged for 25 min at 11 .000 rpm. The d50 number average particle size (dynamic light scattering, Zetasizer) of the resulting particles was 420 nm.

Example 4

2.0 g of PEOS-PEG-10 compound was added to 200 g of distilled water at 25 °C and shaken to obtain a homogenous opaque mixture. 2.0 g of an aralkyl-modified polymethylalkylsiloxane having a viscosity of 700 mPas at 20 °C and 2.0 g of TEOS were thoroughly mixed and then added to the water. The mixture was emulsified with an Ultra-Turrax® T25 at 18.000 rpm for 10 min. The dispersion was then transferred to a round-flask and stirred vigorously on a magnetic stirrer at 70 °C for 24 h. After 30 min of the 24h, the pH was adjusted to 9 with aqueous ammonia. The resulting capsules were centrifuged for 25 min at 11 .000 rpm. The d50 number average particle size (dynamic light scattering, Zetasizer) of the resulting particles was 450 nm.

Example 5

1 .0 g of PEOS-PEG-10 compound was added to 80 g of distilled water at 25 °C and shaken to obtain a homogenous opaque mixture. 1 .0 g of a hydroxy-functional polydimethylsiloxane having a viscosity of 288 mPas at 20 °C and 1 .0 g of TEOS were thoroughly mixed and then added to the water. The mixture was emulsified with an Ultra-Turrax® T25 at 18.000 rpm for 10 min. The dispersion was then transferred to a round-flask and stirred vigorously on a magnetic stirrer at 60 °C for 24 h. After 30 min of the 24h, the pH was adjusted to 9 with aqueous ammonia. The resulting capsules were centrifuged for 25 min at 11 .000 rpm. The d50 number average particle size (dynamic light scattering, Zetasizer) of the resulting particles was 310 nm.

Example 6

35 g of PEOS-PEG-10 compound was added to 900 g of distilled water at 25 °C and shaken to obtain a homogenous opaque mixture. 30 g of PDMS 2000 (polydimethylsiloxane having a viscosity of 2000 mPas at 25 °C) and 20 g of TEOS were thoroughly mixed and then added to the water. The mixture was emulsified with an IKA Magic Lab at 23.000 rpm for 5 min. The dispersion was then transferred to a round-flask and stirred vigorously on a magnetic stirrer at 60 °C for 24 h. The resulting capsules were centrifuged for 25 min at 11 .000 rpm. The d50 number average particle size (dynamic light scattering, Zetasizer) of the resulting particles was 430 nm.

Example 7

10 g of PEOS-PEG-10 compound was added to 1000 g of distilled water at 25 °C and shaken to obtain a homogenous opaque mixture. 10 g of PDMS 2000 (polydimethylsiloxane having a viscosity of 2000 mPas at 25 °C) and 10 g of TEOS were thoroughly mixed and then added to the water. The mixture was emulsified with an IKA Magic Lab at 23.000 rpm until it reached 60 °C after 4 min. The dispersion was then transferred to a round-flask. After 30 min of the 24h, the pH was adjusted to 9 with aqueous ammonia, afterwards the dispersion was stirred vigorously on a magnetic stirrer at 60 °C for 24 h. The resulting capsules were centrifuged for 25 min at 11 .000 rpm. The d50 number average particle size (dynamic light scattering, Zetasizer) of the resulting particles was 370 nm.

Example 8

10 g of PEOS-PEG-10 compound was added to 1000 g of distilled water at 25 °C and shaken to obtain a homogenous opaque mixture. 10 g of PDMS 100 (polydimethylsiloxane having a viscosity of 100 mPas at 25 °C) and 10 g of TEOS were thoroughly mixed and then added to the water. The mixture was emulsified with an I KA Magic Lab at 23.000 rpm until it reached 60 °C after 4 min. The dispersion was then transferred to a round-flask. After 30 min of the 24h, the pH was adjusted to 9 with aqueous ammonia, afterwards the dispersion was stirred vigorously on a magnetic stirrer at 60 °C for 24 h. The resulting capsules were centrifuged for 25 min at 11 .000 rpm. The d50 number average particle size (dynamic light scattering, Zetasizer) of the resulting particles was 290 nm.

Example 9

0.7 g of Octyl-PEOS-PEG-10 (8% Octyl side chains) compound was added to 200 g of distilled water at 25 °C and shaken to obtain a homogenous opaque mixture. 1 g of PDMS 100 (polydimethylsiloxane having a viscosity of 100 mPas at 25 °C) and 3 g of TEOS were thoroughly mixed and then added to the water. The mixture was emulsified with an Ultra- Turrax® T25 at 18.000 rpm for 10 min. The dispersion was then transferred to a round-flask. After 30 min, the pH was adjusted to 9 with aqueous ammonia, afterwards the dispersion was stirred vigorously on a magnetic stirrer at 60 °C for 24 h. The resulting capsules were centrifuged for 25 min at 11 .000 rpm. The d50 number average particle size (dynamic light scattering, Zetasizer) of the resulting particles was 150 nm.

Example 10

0.2 g of PDMS-PEOS-PEG-10 (5.5% PDMS sidechains, 500 g/mol) compound was added to 200 g of distilled water at 25 °C and shaken to obtain a homogenous opaque mixture. 0.5 g of a polymethylalkylsiloxane having a viscosity of 500 mPas at 20 °C and 0.5 g of TEOS were thoroughly mixed and then added to the water. The mixture was emulsified with an Ultrasonic tip for 10 min in a 1 s on 1s off mode. After 30s of dispersion, 0.25 g of PEOS are added. The dispersion is in total dispersed for 10 min. Thereafter, the dispersion was transferred to a roundflask. After 30 min, the pH was adjusted to 9 with aqueous ammonia, afterwards the dispersion was stirred vigorously on a magnetic stirrer at 60 °C for 24 h. The resulting capsules were centrifuged for 25 min at 11 .000 rpm. The d50 number average particle size (dynamic light scattering, Zetasizer) of the resulting particles was 120 nm.

Example 11

0.2 g of PDMS-PEOS-PEG-10 (5.5% PDMS sidechains, 500 g/mol) compound was added to 200 g of distilled water at 25 °C and shaken to obtain a homogenous opaque mixture. 0.5 g of an aralkyl-modified polymethylalkylsiloxane having a viscosity of 725 mPas at 20 °C and 0.5 g of TEOS were thoroughly mixed and then added to the water. The mixture was emulsified with an Ultrasonic tip for 10 min in a 1 s on 1s off mode. After 30s of dispersion, 0.25 g of PEOS are added. The dispersion is in total dispersed for 10 min. Thereafter, the dispersion was transferred to a round-flask. After 30 min, the pH was adjusted to 9 with aqueous ammonia, afterwards the dispersion was stirred vigorously on a magnetic stirrer at 60 °C for 24 h. The resulting capsules were centrifuged for 25 min at 11 .000 rpm. The d50 number average particle size (dynamic light scattering, Zetasizer) of the resulting particles was 150 nm.

Example 12

0.2 g of PDMS-PEOS-PEG-10 (5.5% PDMS sidechains, 500 g/mol) compound was added to 200 g of distilled water at 25 °C and shaken to obtain a homogenous opaque mixture. 0.5 g of a polyether-modified polymethylalkylsiloxane having a viscosity of 300 mPas at 20 °C and 0.5 g of TEOS were thoroughly mixed and then added to the water. The mixture was emulsified with an Ultrasonic tip for 10 min in a 1 s on 1s off mode. After 30s of dispersion, 0.25 g of PEOS are added. The dispersion is in total dispersed for 10 min. Thereafter, the dispersion was transferred to a round-flask. After 30 min, the pH was adjusted to 9 with aqueous ammonia, afterwards the dispersion was stirred vigorously on a magnetic stirrer at 60 °C for 24 h. The resulting capsules were centrifuged for 25 min at 11 .000 rpm. The d50 number average particle size (dynamic light scattering, Zetasizer) of the resulting particles was 150 nm.

Example 13 0.7 g of PEOS-PEG-10 compound was added to 80 g of distilled water at 25 °C and shaken to obtain a homogenous opaque mixture. 0.46 g of a polydimethylsiloxane having a viscosity of 10000 mPas at 25 °C and 0.93 g of TEOS were thoroughly mixed and then added to the water. The mixture was emulsified with an Ultra-Turrax® T25 at 18.000 rpm for 10 min. The dispersion was then transferred to a round-flask. After 30 min, the pH was adjusted to 9 with aqueous ammonia, afterwards the dispersion was stirred vigorously on a magnetic stirrer at 60 °C for 24 h. The resulting capsules were centrifuged for 25 min at 11.000 rpm. The d50 number average particle size (dynamic light scattering, Zetasizer) of the resulting particles was 300 nm.

Example 14

0.7 g of PEOS-PEG-10 compound was added to 80 g of distilled water at 25 °C and shaken to obtain a homogenous opaque mixture. 0.46 g of a polydimethylsiloxane having a viscosity of 30000 mPas at 25 °C and 0.93 g of TEOS were thoroughly mixed and then added to the water. The mixture was emulsified with an Ultra-Turrax® T25 at 18.000 rpm for 10 min. The dispersion was then transferred to a round-flask. After 30 min, the pH was adjusted to 9 with aqueous ammonia, afterwards the dispersion was stirred vigorously on a magnetic stirrer at 60 °C for 24 h. The resulting capsules were centrifuged for 25 min at 11.000 rpm. The d50 number average particle size (dynamic light scattering, Zetasizer) of the resulting particles was 300nm.

Example 15

Step a)

52 g Tetraethoxysilane was mixed with 32 g acetic anhydride, 27.2 g Dynasylan 4148 ((EO) propyltrimethoxysilane) and 0.25 g titanium trimethylsiloxide under an argon atmosphere in a 250 mL three-neck round-bottom flask equipped with a mechanical stirrer and a dephlagmator connected with a distillation bridge. The mixture was heated to 135 °C in a silicon oil bath under intensive stirring. The resulting ethyl acetate was continuously distilled off. The supply of heat was continued until the distillation of ethyl acetate stopped. Afterwards, the product was cooled to room temperature and dried in a vacuum for 1 h. A yellowish oily liquid was obtained.

According to H-NMR spectroscopy, the product contains 14% PEG and 86% alkoxy functionality, PEG-14-PEOS.

Step b) 0.7 g of PEG-14-PEOS compound was added to 80 g of distilled water at 25 °C and shaken to obtain a homogenous opaque mixture. 0.7 g of PDMS 2000 (polydimethylsiloxane having a viscosity of 2000 mPas at 25 °C) and 0.7 g of TEOS were thoroughly mixed and then added to the water. The mixture was emulsified with an Ultra-Turrax® T25 at 18.000 rpm for 10 min. The dispersion was then transferred to a round-flask and stirred vigorously on a magnetic stirrer at 60 °C for 24 h. After 30 min of the 24 h, the pH was adjusted to 9 with aqueous ammonia. The resulting capsules were centrifuged for 25 min at 11 .000 rpm. The d50 number average particle size (dynamic light scattering, Zetasizer) of the resulting particles was 340 nm.

Comparative Example 1

15.0 g polydimethylsiloxane (PDMS) with a viscosity of 10 cSt was added to water of pH 7 heated to 60 °C. Afterwards, 15.0 g PEGS (synthesized according to a protocol Macromolecules, 2006, 39 (5), pp 1701-1708) was added and the mixture was emulsified with Ultra-Turrax operating at 18000 rpm for 5 minutes at 60 °C. The resulting emulsion was stirred at 60°C for 24 h. The milky dispersion was centrifuged at 11000 rpm. The obtained white solid was rinsed several times with water and then dried. The d50 number average particle size (dynamic light scattering, Zetasizer) of the resulting particles was 1 pm.

Application testing

The following coating formulation was prepared.

Setalux®6100 (position 1) was placed in a polyethylene cup and stirred using a Dispermat® CV ( OOrpm, 3.6m/s with a 7cm diameter, toothed dissolver-disc). Positions 2 - 7 were added in the stated order. Position 8 and 9 were mixed in a separate cup and then added.

After addition of all positions, stirring was continued for 15 minutes at 2000rpm (=7,3 m/s).

The resulting liquid coating formulation was stored overnight at room temperature. On the next day, the respective additive listed in the following table was incorporated in the coating formulation using a Dispermat® CV (3 minutes, 1865 rpm, 3.4m/s with a 3.5 cm diameter, toothed dissolver-disc).

A spiral blade was used to apply a 120pm coating (wet film thickness) on a glass substrate. The film was dried for 20 minutes at room temperature and after that cured at 140°C for 25 minutes.

To determine the COF value (sliding resistance), the coated panels were measured using an Altek 9505AER device. A 1 kg weight was drawn over the coated panels at a speed of 127 mm I min. and the required force was measured. The value obtained was multiplied by a factor of 0.01 to calculate the COF value. A low COF value corresponds accordingly to a low sliding resistance.

The contact angle measurements were carried out under controlled conditions (23°C, 65% relative humidity) using a contact angle measuring device from Kruss (model DSA 100 equipped with a camera) and fully deionized water. The contact angles were evaluated with a corresponding analysis software. Three measurements were performed for each sample. The indicated values are mean values.

The following results were obtained.

*calculated on the amount of encapsulated material

** visual judgement

1 = very good, 4 = very bad It can be clearly seen that the non-encapsulated additive causes bad leveling and craters while the encapsulated version shows no negative effects on the coating. The coating containing the capsules of Example 2 exhibits good leveling, and it is also clear and transparent. Additionally, the water contact-angle compared to the control (no additive) is increased indicating that the encapsulated polysiloxane was released from the capsules and migrated to the surface. This effect is demonstrated by the lower COF-value, too.

Claims

22 Claims

1 . A process of encapsulating a compound having a solubility in water of at most 10 g/l at 20°C, comprising the steps of a) Providing a silicon alkoxide based prepolymer modified with a polyalkylene oxide compound, b) Dissolving the compound having a solubility in water of at most 10 g/l at 20°C in a silicon alkoxide having an average of at least two alkoxide groups per molecule to form a non-aqueous solution of the compound, c) Combining an aqueous liquid with the modified prepolymer provided in step a) and the non-aqueous solution prepared in step b) to form an aqueous dispersion, and d) Stirring the aqueous dispersion formed in step c) to form an aqueous dispersion of capsules.

2. The process of claim 1 , comprising the further step e) of separating the capsules from the aqueous dispersion.

3. The process according to claim 1 or 2, wherein the alkoxide groups are independently selected from C1 to C4 alkoxide groups.

4. The process according to any one of the preceding claims, wherein the polyalkylene oxide compound comprises polymerized units of ethylene oxide.

5. The process according to any one of the preceding claims, wherein the silicon alkoxide based prepolymer modified with a polyalkylene oxide compound is prepared by reacting the silicon alkoxide based prepolymer with a polyalkylene oxide compound comprising one hydroxyl group or with a polyalkylene oxide compound comprising at least one alkoxysilane group.

6. The process according to any one of the preceding claims, wherein the compound having a solubility in water of at most 10 g/l at 20°C has a viscosity of at least 25 mPa s at a temperature of 20 °C, measured at a shear rate of 300 s'¹ according to ASTM D4283 - 98(2015).

7. The process according to any one of the preceding claims, wherein step d) is carried out in a temperature range of 20 to 90 °C for a period of 0.5 to 36.0 hours.

8. The process according to any one of the preceding claims, wherein the pH value of the aqueous phase in step d) is in the range of 7.0 to 13.0 The process according to any one of the preceding claims, wherein the capsules have an d50 number average particles size in the range of 50 to 600 nm, determined according to ASTM E3247 - 20. The process according to any one of the preceding claims, wherein surfactants are substantially absent in step d). The process according to any one of the preceding claims, wherein the capsules comprise 30 to 90 % by weight of the compound having a solubility in water of at most 10 g/l at 20°C, calculated on the weight of the capsules.