EP3706896A1 - Non-aqueous encapsulation - Google Patents

Abstract

A non-aqueous encapsulation process for forming encapsulated hydrophilic materials includes providing an emulsion system that includes a hydrocarbon component including one or more hydrocarbons, a hydrophilic component including at least one selected from one or more amines and one or more alcohols, a partitioning inhibitor component including a hydrochloride salt of a base, the conjugate acid of which base has a pKa from 1 to 15, a viscosity modifier component including a polyisobutylene polymer having a weight average molecular weight from 300 to 600 kilodaltons, and an emulsifier component including one or more hydrophobically-modified clay. The process further includes processing the emulsion system to form at least a continuous phase and an encapsulated dispersed phase, the encapsulated dispersed phase including the hydrophilic component enclosed therewithin and the encapsulated dispersed phase is separated from the continuous phase to form the encapsulated hydrophilic materials.

Description

NON-AQUEOUS ENCAPSULATION

Field

[0001] Embodiments relate to a non-aqueous emulsion system for the encapsulation of materials, a method of using the non-aqueous emulsion system for the encapsulation of materials, and microcapsules formed with the non-aqueous emulsion system for the encapsulation of materials.

Introduction

[0002] The encapsulation of micro-particles is sought, e.g., to protect compounds of interest by sequestration and/or allow for controlled release of reactive or non-reactive micro-particles. For example, encapsulation methods for hydrophilic payloads (materials) such as amines and alcohols are in high demand for many materials, biological, and agriculture applications. For example, amine and/or alcohol microcapsules have generated considerable interest for development of advanced smart materials, such as controlled release. However, several problems exist for hydrophilic encapsulation systems such as high water loading in hydrophilic payloads, complicated encapsulation techniques, and/or poor barrier property. In this regard, encapsulation of amines and alcohols may be difficult to achieve by most conventional encapsulation techniques, such as emulsion-templated interfacial polymerization, microfluidics, amine infiltration into hollow microcapsules, solvent evaporation, and microfluidics, e.g., due to issues with substantial solvent residues, poor barrier properties, and/or non-scalable production such as for industrial applications.

[0003] The use of a non-aqueous system for encapsulation of materials such as amines and alcohols has been proposed, e.g., because it is believed premature release of the pay load may potentially be promoted by aqueous residues. Further, many encapsulation systems may react with water, which may lead to undesired by-products. Also, designing a nonaqueous system (e.g., system free of added water) may reduce the possibility of and/or avoid the need for energy-intensive drying steps.

[0004] Accordingly, a simplified technique is sought to produce microcapsules (i.e., encapsulated materials) with the feature of minimized and/or free of water payloads, high payload loading, and/or good barrier property.

Summary

[0005] Embodiments may be realized by providing a non-aqueous encapsulation process for forming encapsulated hydrophilic materials, the process including providing an emulsion system that includes a hydrocarbon component including one or more hydrocarbons, a hydrophilic component including at least one selected from one or more amines and one or more alcohols, a partitioning inhibitor component including a hydrochloride salt of a base, the conjugate acid of which base has a pKa from 1 to 15, a viscosity modifier component including a polyisobutylene polymer having a weight average molecular weight from 300 to 600 kilodaltons, and an emulsifier component including one or more hydrophobically-modified clay. The process further includes processing the emulsion system to form at least a continuous phase and an encapsulated dispersed phase, the encapsulated dispersed phase including the hydrophilic component enclosed therewithin and the encapsulated dispersed phase is separated from the continuous phase to form the encapsulated hydrophilic materials.

Brief Description of the Drawings

[0006] FIG. 1 illustrates an exemplary process for the non-aqueous encapsulation of hydrophilic materials.

[0007] FIGS. 2A, 2B, 2C, 2D, 3A, and 3B illustrate analysis of partitioning inhibitors.

[0008] FIGS. 4A, 4B, and 4C illustrate analysis of emulsifiers.

[0009] FIGS. 5A and 5B illustrate analysis of viscosity modifiers.

[0010] FIGS. 6A and 6B illustrate analysis of Example 1, prepared using DETA as the hydrophilic component.

[0011] FIG. 7 illustrates analysis of examples prepared using other hydrophilic components.

Detailed Description

[0012] Embodiments relate to a non-aqueous encapsulation of hydrophilic materials, such as amines, alcohols, and other reactive or non-reactive additives that may be used to produce polymeric products (e.g., polyurethane based products). The non-aqueous encapsulation is based on an oil-in-oil emulsion system by control of payload partitioning. Typically, capsule formation requires generation of an emulsion that contains at least one aqueous phase. However, water can be detrimental to many reactive systems.

Embodiments relate to introducing a stable, essentially non-aqueous, oil-in-oil emulsion system based on phase separation between two organic, essentially water-free phases. The emulsion system includes a dispersed phase and a continuous phase. By essentially nonaqueous and water-free it is meant that the water is present in an amount less than 0.5 wt%, based on a total weight of the emulsion system. For example, the water may not be separately added to the emulsion system, but may be present in minor amounts in components used to form the emulsion system.

[0013] Oil-in-oil emulsion system may be well suited for forming microcapsules (also referred to as encapsulated materials) in a non-aqueous environment. For the emulsion system an appropriate solvent pair is desired to drive phase separation into an emulsion. For example, liquid pairs employed in conventional non-aqueous emulsions include the combination of non-polar solvents (e.g. hydrocarbons and polymers) and highly polar solvents (e.g. methanol, formamide, and alcohols). Though, polar organic payloads commonly partition in both phases, potentially interfering with the subsequent

encapsulation chemistry. Accordingly, for emulsion systems for encapsulation of hydrophilic payloads, it is desirable to maintain immiscibility of the payload with the continuous phase and tune the interfacial polymerization kinetics. In such emulsion systems, reactive polar payloads such as amines and alcohols, may tend to partition between both emulsion phases, potentially interfering with the subsequent interfacial polymerization and/or promoting Ostwald ripening (which may significantly reduce emulsion stability).

[0014] Incorporation of an efficient partitioning inhibitor is a proposed route to maintain the active core materials inside emulsion droplets. Further, unfavorable reactant delivery may generate local kinetic turbulence leading to interrupted shell growth and/or yielding low-quality shell materials. Maintaining a viscosity certain level for the continuous phase is proposed as an efficient way to modify the diffusion rates of reactants to diminish undesired kinetic turbulence on the interface.

[0015] Exemplary embodiments relate to non-aqueous emulsion systems that may be referred to as a Pickering emulsion system, by which it is meant an emulsion system that is established by solid particles that absorb onto the interface between two phases. An exemplary diagram of such a Pickering emulsion system is as follows:

[0016] For example, in an emulsion system, if two different immiscible solvents (such as non-aqueous solvents) are mixed, small droplets of one solvent may be formed and dispersed throughout the system creating two different phases. Eventually the droplets may coalesce to decrease the amount of energy in the system. However, if solid particles are added to the mixture, the particles may bind to the surface of the interface between the two phases and reduce the possibility of, minimize, and/or prevent the droplets from coalescing. Further, according to exemplary embodiments, the viscosity of the continuous phase may be adjusted between 1500-4500 cP @ 23 °C (e.g., to minimize kinetic turbulence and/or to reduce coalescence). The result may be an emulsion system with increased stability of the system, e.g., having good storage stability at room temperature in which the two phases are substantially maintained over an extended period of time. Further, the resultant encapsulated materials may exhibit good stability (e.g., substantially maintained within the shell formation) within the continuous phase and/or in another liquid such as a liquid epoxy resin and/or a formulated systems for forming polyurethane polymers. The increased stability (e.g., at room temperature and/or higher temperatures) may be realized as extended pot and/or shelf-life for solutions used in industrial applications.

[0017] In exemplary embodiments, an emulsions systems includes an immiscible hydrocarbon-amine pair of liquids and/or an immiscible hydrocarbon-alcohol pair of liquids. The hydrocarbon component includes one or more hydrocarbons. The amine and/or alcohol form a hydrophilic component that includes at least one selected from one or more amines and one or more alcohols. The hydrocarbon component and the hydrophilic component may be present in a weight ratio from 0.5:2.0 to 2.0:0.5 (e.g., 0.7: 1.5 to 1.5:0.7). The emulsion system further includes the incorporation of a partitioning inhibitor component, a viscosity modifier component, and an emulsifier component. The partitioning inhibitor, viscosity modifier, and/or emulsifier may be a solid at room temperature prior to being added to the emulsion system.

[0018] The hydrocarbon liquid may include one or more hydrocarbons having from 2 to 100 carbon atoms (e.g., from 2 to 50 carbon atoms, from 2 to 25 carbon atoms). The hydrocarbon liquid may include a cyclic hydrocarbon, a linear hydrocarbon, and/or a branched hydrocarbon. In exemplary embodiments of the hydrocarbon liquid include at least one cyclic hydrocarbon and a linear hydrocarbon. The cyclic hydrocarbon and the linear hydrocarbon may be present at a weight ratio of 0.5:2.0 to 2.0:0.5 (e.g., 0.7: 1.5 to 1.5:0.7). [0019] The hydrophilic component liquid may include one or more amines and/or one or more alcohols having a weight average molecular weight from 50 daltons to 30 kilodaltons. For example, the one or more amines may have a weight average molecular weight from 50 daltons to 1000 daltons, 50 daltons to 500 daltons, 50 daltons to 250 daltons, etc. The one or more alcohols may have a weight average molecular weight from 50 daltons to 1000 daltons, 50 daltons to 500 daltons, 50 daltons to 250 daltons, etc.

[0020] The emulsion system further includes the partitioning inhibitor component that includes one or more partitioning inhibitors and the viscosity modifier component that includes one or more viscosity modifiers. The one or more partitioning inhibitors may be in the dispersed phase and the one or more viscosity modifiers may be in the continuous phase.

[0021] The partitioning inhibitor is a hydrochloride salt of a base, the conjugate acid of which base has a pKa from 1 to 15 (e.g., from 5 to 15, from 10 to 15, etc.). For example, the hydrochloride salt may not be one that reacts violently with amines. The partitioning inhibitor component may be present in an amount of at least 10 wt%, at least 31 wt%, at least 40 wt%, at least 50 wt%, at least 60 wt%, at least 65 wt%, etc., relative to a total weight of the hydrophilic component. For example, the amount of the partitioning inhibitor component present in the emulsion system may be from 10 wt% to 100 wt% (e.g., 20 wt% to 100 wt%, 25 wt% to 100 wt%, 25 wt% to 90 wt%, 30 wt% to 100 wt%, 35 wt% to 100 wt%, 40 wt% to 100 wt%, 50 wt% to 100 wt%, 60 wt% to 100 wt%, etc.), relative to a total weight of the hydrophilic component.

[0022] The viscosity modifier is a polyisobutylene having a weight average molecular weight from 300 to 600 kilodaltons (e.g., from 400 to 600 kilodaltons, from 450 to 550 kilodaltons, etc.). In exemplary embodiments, the emulsion system includes the

incorporation of at least guanidinium chloride (GuHCl) as the partitioning inhibitor in the dispersed phase and polyisobutylene (PIB) as the viscosity modifier in the continuous phase. The viscosity modifier may be present in an amount of at least 1 w%, at least 2 wt%, at least 3 wt%, at least 4 wt%, at least 10 wt%, etc., based on a total weight of the hydrocarbon component and the viscosity modifier component. For example, the amount of the viscosity modifier present in the emulsion system may be from 1 wt% to 50 wt% (e.g., 4 wt% to 50 wt%, 1 wt% to 40 wt%, 4 wt% to 40 wt%, 1 wt% to 30 wt%, 4 wt% to 30 wt%, 1 wt% to 20 wt%, 4 wt% to 20 wt%, 1 wt% to 15 wt%, 4 wt% to 15 wt%, 1 wt% to 13 wt%, 4 wt% to 13 wt%, 4 wt% to 12 wt%, 10 wt% to 12 wt%, etc.), relative to a total weight of the hydrocarbon component and the viscosity modifier component. [0023] The combination of a partitioning inhibitor such as GuHCl and PIB as a viscosity modifier may yield a robust emulsion with stable morphology for a few weeks (e.g., for approximately 3 weeks). The partitioning inhibitor such as guanidinium chloride may be integrated into the hydrophilic pay loads to act as a partitioning inhibitor, e.g., to minimize dispersion in the continuous phase. The emulsion droplets may serve as encapsulation templates for interfacial polymerization (e.g., with reference to shell formation) of some of the encapsulated amine and optionally added isocyanate, which may be part of the processing of the emulsion system to form at least a continuous phase and an encapsulated dispersed phase. Physical property optimization using polymer solutes in both dispersed and continuous phases may enhance the emulsion stability and modulate viscosity. An exemplary diagram of such as system is as follows:

Robust Poiyamines-fVj-Hydrocarbons Emuision Stabio Microcapsules

[0024] According to exemplary embodiments, shell wall formation may be

accomplished by interfacial polymerization of isocyanates as cross linkers delivered through the continuous phase and polyamines from the droplet core. For experimental purposes, Diethylenetriamine (DETA) is used as the payload, though embodiments are related to various hydrophilic payloads such as other amines and alcohols. The DETA-loaded microcapsules may be isolated in good yield, exhibiting high thermal and chemical stabilities with extended shelf-lives even when dispersed into a reactive epoxy resin. The polyamine phase may be compatible with a variety of basic and hydrophilic actives.

[0025] The emulsion system further includes the emulsifier suspension component that includes one or more hydrophobically-modified clays and optionally one or more polymer surfactants. The one or more hydrophobically-modified clays may be present in an amount from 1 wt% to 10 wt% (e.g., 1 wt% to 8 wt%, 1 wt% to 5 wt%, 1 wt% to 4 wt%, 1 wt% to 3 wt%, 2 wt% to 3 wt%), based on a total weight of the emulsion system. For example, the one or more hydrophobically-modified clays may be present in an amount from 2.0 to 2.5 wt%, based on a total weight of the emulsion system. [0026] Clay minerals may vary based upon the combination of their constituent layers and cations. By hydrophobically-modified clay it is meant clay that has had its surface chemistry modified (e.g., prior to being added to the emulsion system) through the use of a clay modifying agent (such as a surfactant, silane, or other modifier knowns in the art). In exemplary embodiments, the hydrophobically-modified clay is modified by exchange with a surfactant comprising long chain alkyl groups such as a long chain alkylammonium ion, e.g., mono- or di-Ci2-C22 alkylammonium ion, wherein polar substituents such as hydroxyl or carboxyl are not attached to the long chain alkyl. In exemplary embodiments, the clay is a silicate clay such as a bentonite. In exemplary embdoiments, the hydrophobically- modified clay includes is bis (hydrogenated tallow alkyl)dimethyl salt with bentonite, a 2- ethylhexyl (hydrogenated tallow alkyl) dimethyl salt with bentonite, and/or di(hydrogenated tallow alkyl) methyl with bentonite.

[0027] The hydrophobically-modified clay may improve various physical properties of the shell formation, such as reinforcement, synergistic flame retardance, CLTE, barrier properties, and/or enhance flexural or tensile modulus. Further, as shown in the examples, the hydrophobically-modified clay may offer good dispersion in emulsion systems and/or provide miscibility with the thermoplastic systems.

[0028] Referring to FIG. 1, for a non-aqueous encapsulation process for forming encapsulated hydrophilic materials the emulsion system, first a mixture is formed that includes the hydrocarbon component, hydrophilic component, partitioning inhibitor component, viscosity modifier component, and emulsifier suspension component. The components may be added and mixed in varying order, e.g., first the components for the dispersed phase may be added and mixed, second the components for the continuous phase may be added and mixed, and third the emulsifier may be added and mixed. After the components for the emulsion system are added together to for an emulsion mixture, the mixture is processed.

[0029] Processing includes exposing the mixture to ultra-sonication (e.g., of applying sound energy to agitate particles in the mixture at high wattages such as at least 300 W). Processing further includes adding one or more isocyanates to the emulsion mixture, e.g., after exposing the emulsion mixture to ultra-sonication. The isocyanates may be aromatic or aliphatic isocyanates, such as diisocyanates. By aromatic isocyanate it is meant isocyanates that have an N=C=0 group attached directly to an aromatic group. By aliphatic isocyanate it is meant isocyanates that do not have an N=C=0 group attached directly to an aromatic group. In exemplary embodiments, at least one isocyanate may be an aliphatic isocyanate (such as a sterically hindered aliphatic isocyanate). Exemplary sterically hindered aliphatic isocyanates include 4,4'-methylene dicyclohexyl diisocyanate and tetramethylxylene diisocyanate (TMXDI). The process of the emulsion mixture allows for interfacial polymerization, e.g., to form the shell formation around the dispersed phase. Further, the processing allows for isolation of the dispersed phase from the continuous phase (e.g., separated by the shell formation), so as to form encapsulated hydrophilic materials that are separable from the continuous phase. The isolated encapsulated hydrophilic materials may be separated from the continuous phase and used as encapsulated components in other systems, e.g., as discussed below.

[0030] The emulsion system according to embodiments may be used to perform nonaqueous encapsulation of hydrophobic materials such as amines and alcohols. The emulsion systems may result in amine-loaded microcapsules and/or alcohol-loaded microcapsules that may be separated from the continuous phase and used in other systems, such as epoxy and/or polyurethane systems. When the amine-loaded microcapsules and/or alcohol-loaded microcapsules are used in the other systems, they may function as a delayed release and/or controlled release of the system. For example, the amine and/or alcohol may be released after a certain period of time (such through dissolution of the shell formation) and/or upon the use of mechanical force (such as through use of shear force). Accordingly, this non-aqueous encapsulation system may be used to prepare amine-loaded microcapsules or alcohol-loaded microcapsules, which may exhibit good barrier properties under contact with other resins, such as polyurethane or epoxy resins, for extended periods (such as with no significant viscosity increase).

[0031] In an example, the amine-loaded microcapsules may include one or more amine hardeners for an epoxy system. For example, the amine-loaded microcapsules may include one or more amine hardeners for an epoxy system. Application of shear, heat, or other techniques known in the art for allowing release through the shell formation, may allow for the amine hardener to be released from the shell formation which would subsequently enable the amine hardener to act as a curative for the epoxy system.

[0032] In another example, the amine-loaded microcapsules may include one or more amine catalysts for a polyurethane system. For example, the amine catalyst may be one that is known in the art for use in polyurethane systems (e.g., for use in a formulated polyols system of a polyurethane system). Application of shear, heat, or other techniques known in the art for allowing release through the shell formation, may allow for the amine catalyst to be released from the shell formation which would subsequently enable the amine catalyst to act as a catalyst for the formation of polyurethane polymers. In exemplary embodiments, the shear, heat, or like method for release of the amine catalysts may be performed prior to a formulated polyol system, which includes the amine-loaded microcapsules, being mixed with an isocyanate component to form the polyurethane polymers.

[0033] In another example, the polyol-loaded microcapsules may include one or more polyols for a polyurethane system. For example, the polyol may be one that is known in the art for use in polyurethane systems (e.g., for use in a formulated polyols system of a polyurethane system. Application of shear, heat, or other techniques known in the art, would allow for the polyol to be released from the shell formation which would

subsequently enable the polyol to react with an isocyanate for the formation of polyurethane polymers. In exemplary embodiments, the shear, heat, or like method for release of the polyol may be performed prior to a formulated polyol system, which includes the polyol- loaded microcapsules, being mixed with an isocyanate component to form the polyurethane polymers.

[0034] A potential approach to release the amine and/or alcohol from the encapsulation is to use apply heat to cause the shell formation to degrade resulting in release of the amine/alcohol from the shell formation. In an exemplary application of heat, a composition that includes the encapsulated amine/alcohol is sprayed onto a hot substrate at 100 °C, whereas contact of the shell formation with the hot substrate is believed to degrade the shell and allow for release of the amine/alcohol. Another potential approach to release the amine/alcohol from the encapsulation is to use shear force. In an exemplary application of shear, the composition that includes the encapsulated amine/alcohol is sprayed using a high pressure / high shear spray gun and the shell may be broken during the spray process and/or upon impact with a substrate.

[0035] The epoxy and/or polyurethane materials formed using the amine and/or alcohol- loaded microcapsules and/or polyol-loaded microcapsules may be useful encapsulation techniques for a variety of thermoset systems. The emulsion systems may be used to make coatings, adhesives, and/or sealants. The microcapsules may eliminates the need for two- component systems to make hybrid polyurethane coatings, which simplify the

transportation of chemicals and reduce potential pitfalls during the mixing of the two- component systems. Examples

[0036] All parts and percentages are by weight unless otherwise indicated. All molecular weight values are based on weight average molecular weight unless otherwise indicated. Approximate properties, characters, parameters, etc., are provided below with respect to various working examples, comparative examples, and the materials used in the working and comparative examples.

Materials

[0037] All materials and reagents are obtained from commercial suppliers for direct use unless specified. Diethylenetriamine (DETA), polyethylenimine (PEI, branched, Mw of 25,000), pentaethylenehexamine (PEHA), guanidinium chloride (GuHCl), fluorescein isothiocyanate isomer I, hexadecane, decalin, polyisobutylene (Mw of 500 kilodaltons), 4,4'-diphenylmethane diisocyanate (MDI), polymethylene polyphenyl isocyanate (PMPPI, Mw~340), isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), 4,4'- methylene dicyclohexyl diisocyanate (H12MDI) and tetramethylxylene diisocyanate (TMXDI), are available from Sigma Aldrich. Naphthalene 1,5-diisocyanate is purchased from TCI America. Hydrophobically-modified clay CLOISITE^® 20 nano-platelet is available from BYK Additives & Instruments. Epoxy resin D.E.R. 331 is available from Olin Corporation.

Analysis

[0038] General instrumentation information. Viscosity of microcapsule-epoxy composites is monitored using a Brookfield DV-I PRIME viscometer with a 64# spindle at 0.2 Hz for viscosity lower than 50000 cps and 0.0167 Hz for higher viscosity. TGA tests are performed using a TA instrument Q50. Fluorescence spectra are obtained using a Zeiss Observer Zl Fluorescence Light Microscope with 41025 Piston GFP filter set. The intentional rupture and payload release of microcapsules are achieved using an OMNI GLH homogenizer with a 10 mm X 95 mm saw tooth (Fine) Generator Probe at 167 Hz for 180 seconds. ¾ NMR spectra are obtained using a Varian 500 MHz spectrometer in the VOICE NMR laboratory at the University of Illinois.

[0039] Payload partitioning characterization by GC-MS. A calibration curve of DETA concentration in hydrocarbon solvent is developed. For which the calibration curve, DETA is dissolved in a hydrocarbon solvent (decalin or DH solvent, < 12 mg/mL) by sonication for lOmin. 1 mL DETA-hydrocarbon solution is mixed with 20 dodecane as an internal reference and then is subject to GC-MS (Agilent GC 7820A and Agilent MSD 5977 E). The calibration curve is based on the linear correlation between DETA concentration and the integration ratio of DETA/dodecane as shown below. The calibration curves of GC-MS are based on the linear correlation between DETA concentration and the integration ratio of DETA/dodecane.

8

0.00 0.02 0.04 0.08 0.06 0.00 0.01 0.02 0.03 0.04 0

GC-MS integration Ratio (DETA/Docieeane) GC-R1S integration Ratio (DETA/Dodecane)

Referring to the above, (A) is the calibration curve for decalin and (B) is for the DH solvent.

[0040] To quantitatively determine DETA partitioning concentrations, 2 grams of diethylenetriamine (DETA) are mixed with a specific amount of additives to form a transparent solution, followed by vigorous agitation with 6 grams of hydrocarbon solvent to insure the partitioning equilibrium. After settling for 5 hours, 200 of the hydrocarbon solution phase is diluted with 0.8 mL THF and 20 dodecane as an internal reference for the GC-MS test. DETA is observed at the retention time 4.36 minutes and dodecane at 5.89 minutes.

[0041] Contact angles. A clean glass plate is coated with a thin layer of polystyrene (Mw, ca. 3000-4000), which is melt coated under continuous heating by a heating gun, and the coating layer is formed upon cooling to room temperature. A droplet of 10 DETA- GuHCl solution is transferred to the polystyrene surface by a micropipette and the droplet shape is recorded by a high-resolution camera immediately. The image of the droplet on the polystyrene surface is processed by the Drop Shape Analysis plug-in (LB-ADSA) of Image J (National Institutes of Health of the USA). Water exhibits a contact angle of 86.9 + 1.6 ° on this PS surface, indicating a non-polar and hydrophobic surface of the PS coating layer.

[0042] Ternary Phase Diagram. A ternary phase diagram of GuHCl-DETA-DH is built up based on the weight ratios of the components. A series of samples with different component ratios are precisely weighed on an analytical balance and then subject to vigorous vortex agitation for 1 minute. The samples are then allowed to settle for an immiscibility evaluation. If a clear boundary of the two phases appears within 2 minutes, it is labelled as fast phase separation (Fast PS in FIG. 2D). If it takes more than 2 minutes for the samples to show clear phase separation, it is labelled as slow phase separation (Slow PS in FIG. 2(D)).

[0043] Surface and Interfacial Tensions. Surface and interfacial tensions are both measured through the Pendant Droplet Method. A Nordman Optimum^® precision tip (#14 Gauge with φ = 1.83 mm) combined with a syringe pump is used as a capillary device to generate pendant droplets. Each droplet is 0.2 mL. For the measurement of the surface tension, images of the droplets are recorded by a high-resolution camera after waiting for 1 minute to reach equilibrium states. The measurement of the interfacial tension may take longer time (5 minutes) to reach equilibrium due to the increased viscosity.

[0044] COSMOtherm Simulation. Theoretical validation of the phase separation in oil- in-oil emulsions are enabled using COSMO-RS theory implemented in COSMOtherm X (COSMOlogic GmbH & Co. KG, Leverkusen, Germany). Briefly, COSMO-RS theory computes the chemical potential of a molecule in solution by statistical thermodynamics of electronic structure interactions between different molecules. The screening charge densities are generated from geometry optimized chemical structures using the TZVP basis set with TURBOMOLE.

[0045] Overlap concentration estimation. The overlap concentration of PIB is estimated based on Martin Equation log(n_sp/c) = login] + K_m[r/]c, where n_sp is the specific viscosity, c is the PIB concentration, and Km is a consistence. For which, [η] is obtained from the intercept. Huggins and Kraemer equations may not work for this estimation, as PIB wt% is in the semidilute-concentration regime.

Encapsulation Procedure

[0046] An emulsion system for Working Example 1 is prepared using the following procedure: 1.26 grams of diethylenetriamine (DETA), 0.63 grams of pentaethylene- hexamine (PEHA), 0.30 grams of polyethyleneimine (PEI, branched, Mw -25,000), and 0.81 grams of guanidinium chloride (GuHCl) are fully mixed and used as the dispersed phase (DPPG-4213). Then, 2.64 grams of hexadecane, 2.64 grams of decalin, and 0.72 grams of polyisobutylene (PIB, Mw ~ 500,000) are mixed and used as the continuous phase (DHP-012). Further, 0.09 grams of hydrophobically-modified clay nano-platelets

(CLOISITE^® 20) are dispersed into 1.71 grams DHP-012 and used as an emulsifier suspension. The dispersed phase (DPPG-4213, 3.0 grams), the continuous phase (DHP- 012, 6.0 grams) and the emulsifier suspension (1.8 grams) are mixed in a glass vial and then ultra-sonicated using Sonics VCX 500 Watt sonication with a full-size probe (1.27 cm diameter) at 60 % power for 75 seconds (pause 1 second after each 5 seconds sonication) to generate a non-aqueous Pickering emulsion.

[0047] The emulsion system is then diluted with 30 mL DHP-012 and stirred at 16.7 Hz for 20 min. Then, 0.6 grams of crosslinker tetramethylxylene diisocyanate (TMXDI) is dissolved in 6 mL DHP-012 and added to the emulsion (stirred at 8 Hz) with the addition rate of 0.5 mL/h. After the isocyanate addition is finished, the encapsulation suspension is slowly heated to 50 °C (0.5 °C / min) and stirred for 3 hours. After cooling to room temperature, the capsule suspension is diluted by 150 mL hexane and settled down for 1 hour. The supernatant solution is decanted carefully, and the remaining solids are further washed with 20 mL hexane for five times. The resultant capsules are transferred to a watch glass and air dried in a fume hood. The isolation yield is approximate 70 wt% for Example 1.

[0048] FIG. 1 illustrates an exemplary process of general encapsulation procedures with representative microscope images during each key step: optical images (a)(c), SEM image (e), and corresponding fluorescent images (b)(d)(f) on the same caption regions. (Scale bar: 40 μιη).

Phase separation screening is performed as follows:

[0049] In exemplary embodiments, the polar phase of the emulsion system includes at least from 35 wt% to 50 wt% DETA, from 15 wt% to 35 wt% pentaethylenehexamine (PEHA), from 5 wt% to 20 wt% of branched polyethyleneimine (PEI, Mw ca. 20kDa), and from 15 wt% to 40 wt% GuHCl. With respect to the composition, it is believed PEHA and PEI may serve as crosslinkers in the subsequent interfacial polymerization to enhance barrier performance. Without intending to be bound by this theory, an good composition for an exemplary embodiment of the polar phase is believed to be approximately 43 wt% DETA, 20 wt% pentaethylenehexamine (PEHA), 10 wt% branched polyethyleneimine (PEI, Mw ca. 20kDa), and 27 wt% GuHCl, which in the following discussion is referred to as DPPG-4213 (DETA-PEHA-PEI-GuHCl, 4:2: 1:3 in weight ratios).

[0050] Phase separation of DETA from DH is theoretically evaluated using the Liquid Extraction module in COSMOtherm X.²¹ This module performs iterative partitioning and solubility calculations to give the final concentrations of each compound in both phases. The final DETA concentration from the DH phase is taken as the theoretically predicted partitioning of DETA into the continuous phase. The effects of various inhibitors on the partitioning of DETA are evaluated using the same process. While the experimental and theoretical results did not match exactly on an absolute basis, the theoretical prediction very closely matched the observed experimental trend (FIG. 2B) with a correlation coefficient, R² = 0.75. This theoretical partitioning analysis is useful to assist in the identification of other suitable solvent systems and partitioning inhibitors for additional payloads of interest.

[0051] The viscosity of a continuous phase significantly influences the stability of emulsion droplets. The polymeric hydrocarbon additive PIB (M_w ca. 500kDa) is chosen as a viscosity modifier due to its compatibility and commercial availability. Referring to FIG. 5A, the viscosity, η, of the hydrocarbon phase increases from 3 cP (no PIB) to 4085 cP (12 wt% PIB), and a linear correlation between PIB wt% and log η is observed. The enhanced viscosity leads to improved emulsion stability as visualized by optical microscopy (FIG. 5A). In the exemplary embodiment, a stable emulsion is formed when PIB is more than 4 wt% (η ca. 200 cP) and less PIB leads to rapid coalescence of emulsion droplets. Without intending to be bound by this theory, the PIB content in the continuous phase may be more than 10 wt% (η ca. 2000 cP) to maintain a robust emulsion template for the subsequent interfacial polymerization. PIB is observed in the semidilute regime of the solution with an estimated overlap concentration of 0.5 g-dL ¹ (ca. 0.6 wt%). PIB is found to not have much of an effect on the surface tension of the continuous phase (FIG. 5A, dash line) or the interfacial tension, γ, between the two emulsion phases (FIG. 5A, solid line), suggesting that PIB mainly serves as a viscosity modifier without interfering with the interfacial energy.

[0052] Referring to FIG. 5B, the increased viscosity also extended the shelf-life of the emulsions, from 5 min (4 wt% PIB) to 21 days (12 wt% PIB), maintaining intact emulsion droplets with similar morphologies and sizes. Without intending to be bound by this theory, the enhanced shelf-life may be due in part to the reduced diffusion coefficient of the emulsion droplets. According to Stokes-Einstein equation, the diffusion coefficient is reduced by a factor of 10³ with the addition of PIB from 0 to 12 wt%. Such a viscous solvent enhanced the emulsion stability by slowing down the droplet diffusion rate and diminishing the coalescence of the emulsion.

[0053] Increased viscosity also may have an effect on the transport characteristics and reaction kinetics of the subsequent interfacial polymerization. For example, a steady and non-turbulent reactant delivery to the interface during a continuous dispersion may allow for most interfacial polymerizations to form shell materials with good barrier properties. Stable laminar flow with a low Reynolds number (Re < 200) is believed may be ideal for interface polymerization compared to transitional and turbulent flow (Re > 2000).

Efficiency and kinetics of a dispersion process are determined by both convective methods (stirring, mixing, and dispersion) and diffusion. With a typical stirring rate of 500-1000 rpm for the most commonly used stirring devices, the viscosity range of the continuous phase may be adjusted to be 2000-4000 cP (10-12 wt% PIB) to maintain a predetermined Laminar flow and this viscosity range is also suitable to generate a stable emulsion.

Accordingly, exemplary embodiments include about the optimized continuous phase contained 12 wt% PIB and 88 wt% DH (1 : 1 wt/wt), which was referred as DHP-012 (DH- PIB, 12 wt%).

[0054] Further, polar organic payloads may partition in both phases, potentially interfering with the subsequent encapsulation chemistry. Diethylenetriamine, (DETA) a polyamine, is determined to be miscible with a 1 : 1 (wt:wt) mixture of decalin:hexadecane (DH). In particular, this mixture is determined to have a partition coefficient D_np-p

(nonpolar-polar phases) of 0.044 (see FIG. 2C) with a concentration of 11.3 mg- mL ¹ detected in the continuous phase by GC-MS as discussed above.

Partitioning inhibitor screening is performed as follows:

[0055] Organic acids were first tested as partitioning inhibitors to minimize DETA from dispersing into the hydrocarbon phase. Referring to FIG. 2A, DETA partitioning concentrations in the nonpolar DH phase is shown for various additives and concentrations, in which the control example refers to the use of no partitioning inhibitor. It is found that weak organic acids such as acetic acid (HO Ac) slightly reduced the DETA partitioning. The introduction of ions into the polyamine phase is one approach to replace the acidic additives. However, most commonly used sodium, potassium, and ammonium salts are believed to be mostly insoluble in amines and possible alcohols. For example, ammonium hexafluorophosphate (NH4PF6) and guanidinium chloride (GuHCl) are soluble in DETA. It is further found that strong organic acids such as trifluoroacetic acid (TFA), ethanesulfonic acid (EtSOsH), NH4PF6, and GuHCL at certain concentrations of have a relatively better effect in lowering the concentration of DETA in the continuous phase (FIG. 1A). Further, while 65 wt% TFA (relative to 100 wt% of DETA such that for the weight percent of TFA added is 65% of the total amount of DETA add) essentially inhibited DETA from dispersing into the nonpolar phase, the strong organic acid reacted violently and exothermically with DETA, protonating about 30 mol% of the active amino groups in the payload. Similar to TFA, EtSChH is also found to react violently with amines. Further, compared to NH4PF6, GuHCl is believed to both be relatively more economical and mostly unreactive towards DETA. It is believed that these organic acids would behave in a similar manner with respect to alcohols.

[0056] Referring to FIG. 2C, D_np-_P is reduced from 0.044 to 0 (< 0.010, non-detectable in GC-MS) with the addition of 65 wt% GuHCl (FIG. 2C) indicating efficient inhibition of the DETA partitioning. Referring to FIG. 2D, a ternary phase diagram of GuHCl-DETA- DH is shown in which PS refers to phase separation, which is constructed to get a complete overview of the strong polyamine/hydrocarbon phase separation system.

[0057] The introduction of electrolytes into the amine phase significantly altered the phase separation behavior as revealed experimentally by the measurement of contact angles and the construction of phase diagrams. The hydrophilicity of the polar phase is enhanced by the addition of GuHCl as indicated by an increased contact angle, Θ, on a hydrophobic polystyrene surface (FIG. 2C, upward slope line). For example, when the ratio of GuHCl and DETA (RG-D, wt/wt) is increased from 0 to 0.65, Θ is changed from 48.7° to 71.9°.

[0058] As shown in FIG. 2D, GuHCl reached its solubility limit when RG D > 1 (upper region). For RG D < 1, there is a strong phase separation between the polar (DETA-GuHCl) and the nonpolar (DH) phases. Generally, more GuHCl (RG-D > 0.5) led to faster phase separation (FIG. 2D, middle region). With a reduced GuHCl loading (RG-D < 0.5), the speed of phase separation is reduced and takes more than 2 min (FIG. 2D, lower region). The minimum RG-D to completely inhibit payload partitioning is believed to be approximately 0.6. Through extensive experimentation, and without intended to be bound by this theory, a good composition of the polar phase is believed to be approximately 43 wt% DETA, 20 wt% pentaethylenehexamine (PEHA), 10 wt% branched polyethyleneimine (PEI, Mw ca. 20kDa), and 27 wt% GuHCl and in the following discussion will be referred to as DPPG- 4213 (DETA-PEHA-PEI-GuHCl, 4:2: 1 :3 in weight ratios). PEHA and PEI served as crosslinkers in the subsequent interfacial polymerization to enhance barrier performance.

[0059] FIG. 3A shows GC traces of DETA present in the hydrocarbon phase when mixed with different amounts of GuHCl. With more GuHCl present, less DETA, indicated by the smaller peak area in the peak at 4.34, is present in the hydrocarbon phase. This data is quantified in FIG. 2A. [0060] FIG. 3B shows the NMR peaks of DETA with and without the presence of 65 wt% GuHCl. With the GuHCl present, the peaks shift to higher ppm, indicating higher polarity and interaction of GuHCl with DETA.

Emulsion stabilizers (emulsifiers) screening is performed as follows:

[0061] Polymeric surfactants Brij® 93 (HLB 4), Span® 80 (HLB 4.3), Span® 85 (HLB 1.8) and Tween® 20 (HLB 16.7), are found to be unable to facilitate generation or stabilization of the oil-in-oil emulsions under various agitation methods. In particular, for the examples, none of these formed stable emulsion droplets under various agitation methods including ultra-sonication, homogenization, and high-speed stirring.

[0062] With respect to the examples, hydrophobically functionalized clay (CLOISITE^® 20) as a Pickering particle enables generation of a stable oil-in-oil emulsion, e.g., based on its relatively large size. In particular, hydrophobically functionalized clays are suitable emulsifiers, e.g., based on their high stability and relatively large sizes.

[0063] Referring to FIG. 4A, with the combination of hydrophobically functionalized clays, Span® 85 among the four polymer surfactants, yields stable emulsion droplets with uniform morphologies. In particular, FIG. 4A shows comparison of emulsion stability with the various combinations of a hydrophobically functionalized clay (CLOISITE^® 20) and the polymer surfactant Span® 85. The other three polymer surfactants (Brij® 93, Span® 80 and Tween® 20) are found to unable to stabilize non-aqueous emulsions. As shown in FIG. 4A (with scale bar of 40 μιη) emulsion stability and particle size may be dependent upon the amount of Span® 85. With 3 wt% CLOISITE^® 20, emulsion stability is enhanced with less Span® 85 (Er¾$r!j g^ b-c). With 6 wt% Span® 85, the system fails to stabilize an emulsion without any droplet formed. With a reduced amount of Span® 85, an emulsion with a great morphology is exhibited, yet becomes ruptured during the subsequent interfacial reactions, indicating a liable emulsion was formed.

[0064] Referring to FIG. 4B (with scale bar of 40 μιη), ratios for hydrophobically functionalized clays are also evaluated without using other polymer surfactants. Higher amounts of the hydrophobically functionalized clay produces smaller-sized emulsion droplets with enhanced stability. With the addition of 2 wt% CLOISITE^® 20, a further droplet sizes decrease is not visually observed, and the emulsions are found to be stable enough to survive the subsequent interfacial reactions. Without intending to be bound by this theory, it is believed a good amount of the hydrophobically functionalized clay CLOISITE^® 20, with a view toward adding no more than necessary, is approximately 2.0 wt% to 2.5 wt%, based on a total weight of the total emulsion system. Accordingly, it is found that hydrophobically functionalized clay produced smaller-sized emulsion droplets with enhanced stability. Further, with the addition of 2 wt% or more of CLOISITE^® 20, droplet sizes are maintained around approximately 6 μιη.

Isocyanate screening is performed as follows:

[0065] Aromatic isocyanates usually react faster than aliphatic isocyanates. With respect to the examples; however, most of the commercially available aromatic isocyanates (EsroryR^^ such as naphthalene 1,5-diisocyanate

(NDI), 4,4'-diphenylmethane diisocyanate (MDI) and polymethylene polyphenyl isocyanate (PMPPI) had solubility issues in the continuous phase DHP-012. The only miscible aromatic isocyanate was toluene diisocyanate (TDI), which only produced labile microcapsules. TDI is a highly reactive aromatic isocyanate which contains two NCO groups (1-NCO and 4-NCO) with distinct reactivities. The less sterically-hindered 4-NCO exhibits relatively high reactivity compared to 1-NCO. Once the 4-NCO reacts with an amino group, the resultant urea product with an electron-donating feature further diminishes the reactivity of the 1-NCO leading to a decreased crosslinking efficiency, which further diminishes barrier properties of the shell walls.

[0066] Aliphatic isocyanates have less reactivity compared to aromatic isocyanates and are good candidates for better kinetic control. Most of the commercially available aliphatic isocyanates were miscible with the non-polar phase DHP-012, except for isophorone diisocyanate (IPDI) and HDI-oligomers. Among the three commonly used aliphatic isocyanate, hexamethylene diisocyanate (HDI) produced only unstable microcapsules; 4,4'- methylene dicyclohexyl diisocyanate (H12MDI) and tetramethylxylene diisocyanate (TMXDI) yielded stable microcapsules with good isolation yields. Both H12MDI and TMXDI are sterically hindered aliphatic isocyanates, exhibiting lower reactivity compared to the less-hindered HDI with a primary NCO group. Isocyanates with appropriate reactivity to maintain a moderate polycondensation kinetics are desirable to achieve the barrier properties of microcapsules. Sterically hindered aliphatic isocyanates such as H12MDI and TMXDI are found to be the suitable interfacial crosslinkers.

Evaluation of the process is performed as follows:

[0067] With respect to Example 1 (see Encapsulation Procedure described above), the morphology of the entire encapsulation process is monitored by optical microscopy. The size distribution of initial emulsion droplets is 6.0 ± 1.5 μιη. The robust emulsion droplets maintained their morphologies through the interfacial polymerization. Isolated DETA- loaded microcapsules exhibit an increased size distribution of 10.2 ± 2.6 μιη with slight shape deformation following washing with neat hexanes.

[0068] Thermal stability of the DETA-loaded microcapsules is evaluated by dynamic thermal gravimetric analysis (TGA). The dried microcapsules are heated to 100 °C and held at this temperature for 3 hours to examine their thermal stability. The microcapsules maintained a stable weight at 100 °C with only a slight weight loss attributed to solvent residues with high boiling points, indicating good thermal stability and limited permeability. Then, referring to FIG. 6A upward sloping line, the temperature ramped to 650 °C at a heating rate of 10 °C / min. A sharp weight loss appears around 150 °C, e.g., possibly because of the thermal degradation of the shell formation (see FIG. 6A downward sloping line).

[0069] The DETA-loaded microcapsules also exhibited long-term chemical stability in a liquid epoxy resin. A mixture of the unencapsulated liquid DPPG-4123 and epoxy resin (DER-331) solidifies within 2h at room temperature, exhibiting a viscosity increase over a period of weeks. Referring to FIG. 6B, a normalized viscosity of the DER-331 epoxy resin formulations containing DPPG-4123 (first line) or DPPG-4123 capsules (second line). The jump in viscosity in the red curve at 40 days was following exposing the formulation to homogenization for 120 s at 160 Hz. Without intending to be bound by this theory, it is believed that when the DPPG-4213 -loaded microcapsules are suspended in the epoxy resin, the normalized viscosity of the epoxy resin increased only about four fold over 40 days' storage compared to the 2h curing time between the pure payload and the epoxy resin, indicating the significantly enhanced stability of the DETA-loaded microcapsules in the epoxy resin. This stability is also improved over even the previously-reported water-based DETA capsule system. High shear forces are applied to microcapsule suspensions after storage of the microcapsules in the epoxy for 40 days. The rapid sharp viscosity increase indicates that the amine payloads are still chemically active and that the system is triggered to cure by shear.

[0070] For an exemplary polyurethane system, encapsulated diethyltoluenediamine may be added to a prepolymer prepared using ISONATE™ 50 Ο,Ρ (mixture of 2,4 and 4,4 isomers of MDI) and 95:5 weight ratio blend of VORAPEL™ D3201 Polyol and

VORANOL™ 360 Polyol in the presence of Bismuth/Zinc Neodecanoate Mixture. The resulting prepolymer with the encapsulated diethyltoluenediamine is believed to show 6 months shelf life stability (no significant increase in viscosity) at 40 °C.

[0071] With respect to the above, an efficient polyamine/hydrocarbon based anhydrous emulsion system suitable for the non-aqueous encapsulation of hydrophilic payloads has been demonstrated. Good encapsulation is released by using the emulsion system that includes the partitioning inhibitor such GuHCl and the incorporation of a viscosity modifier such as PIB. Morphology monitoring of the entire encapsulation process may be showcase the high efficiency and feasibility of this nonaqueous encapsulation technique. Further, DETA-loaded microcapsules exhibit thermal stability at temperatures as high as 100 °C and chemical stability in epoxy resins with extended shelf-life up to four weeks. The immiscible polyamine/hydrocarbon solvent pair exemplifies a platform anhydrous emulsion system useful for amine/alcohol encapsulation.

Encapsulation of other hydrophilic materials.

[0072] According to exemplary embodiments, other hydrophilic materials can be encapsulated using the process described herein. Referring to the images in FIG. 7, emulsion systems are prepared according to the Encapsulation Procedure described above, except that DETA is replaced with 1.26 grams l,5-Diazabicyclo[4.3.0]non-5-ene (DBN), tri(ethylene glycol), glycerol, pyridine, 1-methylimidazole, or aniline. All of these formulations formed encapsulated hydrophilic materials, stable for at least 20 hours.

Claims

Claims:

1. A non-aqueous encapsulation process for forming encapsulated hydrophilic materials, the process comprising:

providing an emulsion system that includes:

a hydrocarbon component including one or more hydrocarbons, a hydrophilic component including at least one selected from one or more amines and one or more alcohols,

a partitioning inhibitor component including a hydrochloride salt of a base, the conjugate acid of which base has a pKa from 1 to 15,

a viscosity modifier component including a polyisobutylene polymer having a weight average molecular weight from 300 to 600 kilodaltons, and

an emulsifier component including one or more hydrophobically-modified clay; and

processing the emulsion system to form at least a continuous phase and an encapsulated dispersed phase, the encapsulated dispersed phase including the hydrophilic component enclosed therewithin;

the encapsulated dispersed phase being separated from the continuous phase to form the encapsulated hydrophilic materials.

2. The process as claimed in claim 1, wherein the hydrocarbon component includes at least a cyclic hydrocarbon and a linear hydrocarbon present in a weight ratio from 0.5:2.0 to 2.0:0.5.

3. The process as claimed in claim 1 or claim 2, wherein the hydrocarbon component and the hydrophilic component are present in a weight ratio from 0.5:2.0 to 2.0:0.5.

4. The process as claimed in any one of claims 1 to 3, wherein the partitioning inhibitor component is present in an amount of at least 40 wt%, relative to a total weight of the hydrophilic component.

5. The process as claimed in any one of claims 1 to 4, wherein the viscosity modifier component is present in an amount from at least 1 wt%, based on a total weight of the hydrocarbon component and the viscosity modifier component.

6. The process as claimed in any one of claims 1 to 5, wherein the one or more hydrophobically-modified clays are present in an amount from 1 wt% to 10 wt%, based on a total weight of the emulsion system.

7. The process as claimed in any one of claims 1 to 6, wherein the processing of the emulsion system includes adding one or more sterically hindered aliphatic isocyanates to the emulsion.

8. A process of preparing a curable epoxy composition, the process including providing one or more epoxy resins and the encapsulated hydrophilic materials prepared according to the process as claimed in any one of claims 1 to 7, whereas the hydrophilic component includes the one or more amines.

9. A process of preparing a composition for forming polyurethanes, the process including providing the encapsulated hydrophilic materials prepared according to the process as claimed in any one of claims 1 to 7, whereas the hydrophilic component includes the one or more amines.

10. A process of preparing a composition for forming polyurethanes, the process including providing the encapsulated hydrophilic materials prepared according to the process as claimed in any one of claims 1 to 7, whereas the hydrophilic component includes the one or more alcohols.