microcapsules

Abstract

The present invention relates to microcapsules comprising a shell and an internal phase, the shell encapsulating the internal phase, the internal phase comprising a thermotropic polymer and a liquid medium. The present invention also provides a method for producing the microcapsules, and an article of manufacture comprising the microcapsules of the present invention, particularly a coating for glass coating applications.

Description

[Technical Field]

[0001] The present invention relates to microcapsules comprising thermotropic polymers and methods for making same. The present invention also provides products comprising the microcapsules of the present invention, including coatings for polish applications. [Background technology]

[0002] Overheating prevention in buildings is still primarily achieved through traditional mechanical shading. The global average annual energy consumption for cooling buildings already nearly exceeds the energy consumption for heating them. The increasing use of glass facades in architecture, including the use of organic glass, is accelerating this trend. While the excellent insulating properties of modern glass facades prevent buildings from cooling down in winter, they have the opposite effect on energy efficiency during warmer months. This results in increased electricity demand for cooling. To avoid increased heat stress in cities, an optimized energy balance is required. Therefore, buildings must be designed to achieve passive cooling rather than equipped with electrical air conditioning systems.

[0003] From this perspective, the use of thermotropic polymers has been investigated. Thermotropic polymers exhibit temperature-dependent changes in transmittance, for example for visible and / or infrared light. In particular, they have the property of switching from a relatively transparent state to a highly light-scattering state as the temperature rises. Such materials can contribute to reducing the energy demand of buildings. In winter, solar heat reduces the heating energy demand. In summer, a large portion of solar radiation is reflected, reducing cooling and ventilation costs.

[0004] Nakamura et al., Ind. Eng. Chem. Res. 2019, 58, 16, 6424-6428, disclose the fabrication of smart windows using thermoresponsive polymers pNIPAM (poly(N-isopropylacrylamide)) and HPC (hydroxypropyl cellulose). At low temperatures, the windows transmit almost all light, but at high temperatures, they reflect some light, thereby reducing solar heat gain and helping to regulate the internal temperature of the structure in which the smart glass is installed.

[0005] The smart window by Nakamura et al. takes the form of a hydrogel layer sandwiched between two glass plates, a structure essential because the thermoresponsive polymer loses its temperature response when it dries.

[0006] However, sandwiching a heat-sensitive polymer between two panes of glass is not always practical, at least due to size, cost, and flexibility factors. Furthermore, if one pane of glass is damaged, the entire window structure must be replaced to fix the problem.

[0007] Furthermore, WO 2013 / 152923 discloses the use of thermotropic particles for doping polymer matrices. The doped polymer matrices according to the present invention are used as sunscreens, for example in the form of paints, coatings, resins, thermosetting resins, or thermoplastic resins. The particles comprise a polymer core that is a thermotropic material and anchor groups extending from the core. These particles are prepared using a water-in-oil emulsion, followed by polymerization of the oil phase to form the particles.

[0008] There is a need in the art for more flexible and versatile uses of thermotropic materials than the products disclosed in the prior art, particularly in sun protection and glass coating applications. Summary of the Invention

[0009] The present invention provides microcapsules comprising a shell and an internal phase, said shell encapsulating said internal phase, said internal phase comprising a thermotropic polymer and a liquid medium.

[0010] The present invention also provides a plurality of microcapsules of the present invention.

[0011] The present invention also provides a method of making a microcapsule or a plurality of microcapsules, the method comprising forming a shell to encapsulate an internal phase comprising a thermotropic polymer and a liquid medium.

[0012] The present invention also provides a method for producing the microcapsules of the present invention, wherein the shell is formed from gelatin, a water-soluble anionic polymer and a crosslinker, the method comprising the steps of: a) preparing a dispersion or emulsion of the internal phase of the microcapsules; b) preparing a continuous phase comprising gelatin, a water-soluble anionic polymer, a base, and water; c) mixing the dispersion and emulsion with a continuous phase; d) adjusting the pH of the product of step c) to less than about 6, thereby forming aggregates; e) cooling the product of step d); f) cross-linking the gelatin in the product of step e) with a cross-linking agent.

[0013] The present invention also provides a method for producing the microcapsules of the present invention, wherein the shell is formed from an ultraviolet curable resin, the method comprising the steps of: a) mixing the components of the internal phase of the microcapsules to prepare the internal phase; b) preparing a mesophase by mixing at least one compound containing at least one carbon-carbon double bond, a radical-based photoinitiator, and optionally an antifoaming agent; c) preparing an external phase by mixing a stabilizer with water; d) flowing the internal phase through the first injection tube and the intermediate phase through the second injection tube, and combining the internal and intermediate phases in the intermediate tube to form a combined stream; e) flowing the external phase into a third injection tube and combining the external phase into the combined stream; f) flowing the product of step e) through an outer tube and exposing the product of step e) to ultraviolet light;

[0014] In the description and claims of this specification, the words "comprise" and "contain" and variations of these words, such as "comprising" and "comprises," mean "including but not limited to" and do not exclude other components, elements or steps. Also, unless the context clearly indicates otherwise, the singular includes the plural, and in particular, where the indefinite article is used, the reference is understood to include the plural as well as the singular unless the context clearly indicates otherwise.

[0015] Preferred features of each aspect of the invention may be the same as those described in connection with any of the other aspects. Within the scope of this application, it is expressly intended that the various aspects, embodiments, examples and alternatives described in the preceding paragraphs, claims and / or the following embodiments and drawings, in particular their individual features, may be employed independently or in any combination. That is, the features of all embodiments and / or any embodiment may be combined in any way and / or combination, provided that the features are not mutually inconsistent.

[0016] As used herein, the term "substituted" refers to a compound that is substituted with any of the following: -F, -Cl, -Br, -I, -OH, -NO, -CN, -SO, -COH, -NH, -C(O)H, unsubstituted C(O)H, -C ... 1-10 Alkyl, unsubstituted C 2-10 Alkenyl or alkynyl, unsubstituted C 5-12 It means substituted with one or more groups selected from aryl (optionally wherein one or more ring carbon atoms are replaced by a heteroatom selected from S, N, or O), and combinations thereof.

[0017] One or more embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 shows a microfluidic device for producing microcapsules of the present invention where the shell is formed from a UV-curable resin. [Figure 2] Figure 2(I) shows the change in transmittance as a function of temperature for a coating of the present invention, and Figure 2(II) shows images of microcapsules of the present invention at 26°C and 32°C at 1x (a, b) and 4x (c, d) magnification. DETAILED DESCRIPTION OF THE INVENTION

[0019] An embodiment of the present invention relates to a microcapsule comprising a shell and an internal phase, the shell encapsulating the internal phase, the internal phase comprising a thermotropic polymer, a liquid medium, and optionally one or more additives.

[0020] (microcapsules) The microcapsules contain a liquid medium, which may be a polar liquid medium or a non-polar liquid medium.

[0021] The liquid medium may be a polar liquid medium, the polarity of which may be determined, for example, by the dielectric constant.

[0022] Suitably, a polar liquid medium as defined in the present invention may be a liquid medium having a dielectric constant at 20°C greater than about 10, or optionally greater than about 15, or preferably greater than about 20.

[0023] Optionally, the polar liquid medium may comprise water and / or an alcohol.

[0024] The polar liquid medium may comprise a single polar solvent or a mixture of two or more polar solvents, which may include water and / or alcohol.

[0025] The alcohol is preferably C 1-10 The alcohol may be an alcohol. It is understood that the alcohol may be substituted with one or more -OH groups. In other words, the alcohol may have a single -OH group, two -OH groups (diol), three -OH groups (triol), four -OH groups (tetraol), or five or more -OH groups (polyol). Representative alcohols include methanol, ethanol, propan-1-ol, propan-2-ol, 1,2-ethanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, propane-1,2,3-triol, butane-1,2,3,4-tetraol, and pentane-1,2,3,4-pental. Preferred alcohols include methanol, ethanol, 1,2-ethanediol, 1,3-propanediol, 1,5-pentanediol, and propane-1,2,3-triol.

[0026] It will be understood that when the polar liquid medium consists of a mixture of two or more polar solvents, the polar liquid medium may consist of a mixture of two or more different polar solvents from the same class (i.e., two or more different alcohols), or may consist of a mixture of two or more polar solvents from different classes (i.e., an alcohol and water).

[0027] Optionally, the polar liquid medium comprises water.

[0028] Optionally, the polar liquid medium comprises water and at least one alcohol. For example, the polar liquid medium may comprise water and at least one alcohol selected from methanol, ethanol, 1,2-ethanediol, 1,3-propanediol, 1,5-pentanediol, propane-1,2,3-triol, and combinations thereof. Exemplary combinations include water and 1,3-propanediol and water and propane-1,2,3-triol.

[0029] The polar liquid medium may be understood to consist essentially of or consist of water and / or alcohol.

[0030] When the polar liquid medium contains water, the water is preferably present in an amount of at least about 5 wt %, more preferably at least about 15 wt %, and even more preferably at least about 30 wt % of the polar liquid medium. For example, the water may be present in an amount of about 5% to about 95%, such as about 20% to about 80%, or for example, about 30% to about 70% of the polar liquid medium.

[0031] When the polar liquid medium comprises an alcohol, the alcohol is preferably present in an amount of at least about 5 wt %, more preferably at least about 15 wt %, and even more preferably at least about 30 wt % of the polar liquid medium, for example, the alcohol may be present in an amount of from about 5% to about 95%, such as from about 20% to about 80%, for example, from about 30% to about 70% of the polar liquid medium.

[0032] The liquid medium may be a non-polar liquid medium. The non-polarity of a liquid medium can be determined by its dielectric constant. For example, a non-polar liquid medium as defined in the present invention may be a liquid medium having a dielectric constant of less than about 10 at 20°C.

[0033] The non-polar liquid medium may comprise an oil such as a silicone oil, a mineral oil, or a vegetable oil such as soybean oil, sunflower oil, or coconut oil.

[0034] The liquid medium is suitably present in an amount of at least about 5 wt% of the internal phase, such as at least about 20 wt% of the internal phase, for example at least about 50 wt% of the internal phase, such as at least about 70 wt% of the internal phase, for example at least about 85 wt% of the internal phase.

[0035] The thermotropic polymer used in the present invention may suitably be a polymer or polymer mixture whose transmittance to visible light and / or infrared light can change depending on temperature.

[0036] Suitably, the thermotropic polymer has a different refractive index than the liquid medium, is homogeneously mixed with the liquid medium below the phase change temperature, and phase separates above the phase change temperature to form domains comprising a substantial proportion (e.g., at least about 40 wt %, e.g., at least about 60 wt %) of either the thermotropic polymer or the liquid medium.

[0037] Advantageously, below the phase change temperature, the difference in refractive index between the thermotropic polymer and the liquid medium has little or no effect, allowing a large proportion (e.g., at least about 80%, e.g., at least about 90%, e.g., at least about 95%) of the visible and infrared light to pass through the internal phase of the microcapsule. Above the phase change temperature, the difference in refractive index between the thermotropic polymer domains and the liquid medium region can scatter some of the visible and infrared light. This reduces the transmittance of the internal phase compared to below the phase change temperature.

[0038] By "a portion of visible and infrared light" is meant that at least about 5%, for example at least about 10%, for example at least about 20%, for example at least about 30% of the visible and infrared light is scattered. In other words, the transmittance of visible and infrared light by the internal phase at or above the phase change temperature is reduced by about 5%, for example at least about 10%, for example at least about 20%, for example at least about 30% compared to the transmittance of the internal phase below the phase change temperature.

[0039] The term "visible and infrared light" refers to radiation with wavelengths from about 0.4 μm to about 1 mm.

[0040] It may be appreciated that the thermotropic polymer domain and the liquid medium domain have refractive indices that differ by at least about 1%, such as at least about 7%, such as at least about 20%.

[0041] "Thermotropic and Thermochromic Polymer Based Materials for Adaptive Solar Control" (Solar Control. Materials 2010; 3 (12): 5143-5168) provides an overview of the development of some embodiments of thermotropic materials and is incorporated herein by reference.

[0042] For example, the thermotropic polymer may be a hydroxypropyl cellulose (HPC) polymer or a polyacrylamide polymer.

[0043] The polyacrylamide polymer may be obtained from the radical polymerization of at least one acrylamide monomer having the structure (I) below: JPEG2026507321000001.jpg32158R1 is H or optionally substituted C 1-10 may be alkyl, preferably H or methyl; R2 is an optionally substituted C 1-10 It may be alkyl, preferably methyl, ethyl, n-propyl or isopropyl, more preferably n-propyl or isopropyl.

[0044] Preferably, R1 is H or methyl, and R2 may be n-propyl or isopropyl.

[0045] Representative polyacrylamide polymers include: Contains JPEG2026507321000002.jpg92158.

[0046] In other words, the representative polyacrylamide polymer may be poly(Nn-propylacrylamide) (NNPAM), poly(N-isopropylacrylamide) (NIPAM), or poly(N-isopropylmethylacrylamide) (NMPAM).

[0047] It will be appreciated that mixtures of acrylamide monomers can be used to obtain polyacrylamide polymers, and it will also be appreciated that thermotropic polymers can be made from mixtures of different monomers such as acrylamide, acrylates, methacrylates, vinyl acetate, and combinations thereof.

[0048] The thermotropic polymer may be a block copolymer comprising at least one block of a polyacrylamide polymer as defined above and at least one block of a further polymer, which may suitably be selected from polyethylene glycol (PEG) and polyacrylic acid.

[0049] The thermotropic polymer may be HPC. HPC can be produced by reacting activated cellulose with ethylene oxide. For example, HPC has the following structure (II): JPEG2026507321000003.jpg49155 Each R3 is H or JPEG2026507321000004.jpg27156, where m is an integer greater than or equal to 1; R4 is JPEG2026507321000005.jpg30156, R5 is JPEG2026507321000006.jpg30156, n is an integer of about 200 to about 8,000.

[0050] Suitably, the HPC has a degree of substitution (DS) value and a molar substitution (MS) value, where DS is the number of R groups of formula (IIa) per repeat unit, up to a maximum of 3, and MS is the average value of m per repeat unit of the polymer. Optionally, DS is at least 1, for example at least 2.

[0051] Optionally, MS is at least about 2, such as at least about 2.5, such as at least about 3. Optionally, MS is less than about 6, such as less than about 5.5, such as less than about 5. It can be understood that MS can be from about 2 to about 6, such as from about 2.5 to about 5.5, such as from about 3 to about 5.

[0052] A representative HPC is manufactured by Ashland under the trade name Klucel® E-Industrial.

[0053] The thermotropic polymer may be a linear polymer or a microgel. When the thermotropic polymer is a microgel, it may be formed by chemical crosslinking of the thermotropic polymer by polymerization or by self-crosslinking of a linear thermotropic polymer. Suitable methods include those described in Soft Matter, Fussell et al., 2019, 15, 8578-8588, which is incorporated herein by reference.

[0054] When the thermotropic polymer is linear, it may preferably have a molecular weight of about 40,000 Da to about 1,200,000 Da.When the thermotropic polymer is linear HPC, it may preferably have a molecular weight of about 60,000 Da to about 100,000 Da, for example, about 70,000 to about 90,000 Da.

[0055] When the thermotropic polymer is a microgel, it preferably has a maximum diameter of about 30 nm to about 2 μm. The maximum diameter of the microgel can be measured using dynamic light scattering, and water can be used as the solvent. The measurement temperature can be about 25° C.

[0056] The thermotropic polymer may be present in an amount of about 0.1 wt% to about 30 wt%, preferably about 0.5 wt% to about 15 wt% of the internal phase. If the thermotropic polymer is HPC, it may be present in an amount of about 3 wt% to about 15 wt% of the internal phase. If the thermotropic polymer is polyacrylamide, it may be present in an amount of about 0.5 wt% to about 10 wt% of the internal phase.

[0057] The internal phase may optionally include one or more additives.

[0058] One or more additives may be advantageously used to aid in the production of the microcapsules of the present invention.

[0059] The one or more additives may be selected from salts, sugars, surfactants, acids, non-thermotropic polymers, and combinations thereof.

[0060] Optionally, the internal phase may contain a salt. Examples of salts that may be used in the present invention include NaCl, LiCl, KCl, KCN, MgCl, Mg(NO), KNO, NaCO, LiCO, KPO, [(CH)NCHCHOH]Cl, (NH)SO, and combinations thereof. Preferably, the salt comprises NaCl.

[0061] The salt may be present in an amount of about 0.01 wt% to about 36 wt%, preferably about 0.5 wt% to about 15 wt%, of the internal phase. The amount of salt may vary depending on the nature of the thermotropic polymer. For example, when the thermotropic polymer is polyacrylamide, the salt may be present in an amount of about 0.01 wt% to about 12 wt%, preferably about 0.5 wt% to about 10 wt% of the internal phase. When the thermotropic polymer is hydroxypropyl cellulose (HPC), the salt may be present in an amount of about 0.1 wt% to about 18 wt%, preferably about 0.5 wt% to about 15 wt% of the internal phase.

[0062] The sugar may be a monosaccharide, disaccharide, or polysaccharide. Examples of sugars include glucose, fructose, galactose, sucrose, lactose, maltose, and cellulose. Preferably, the sugar is sucrose.

[0063] When present, the sugar may comprise at least about 0.5 wt %, such as at least about 1 wt %, of the internal phase.

[0064] The organic acid may contain at least one -COH group. 1-10 It may also be an organic acid. Exemplary organic acids include acetic acid and maleic acid.

[0065] When present, the organic acid may comprise at least about 0.5 wt %, such as at least about 1 wt %, of the internal phase.

[0066] The surfactant may be a poloxamer surfactant. Preferably, the poloxamer surfactant has a molecular weight of about 2,000 Da to about 10,000 Da, for example, about 4,000 Da to about 8,000 Da.

[0067] When present, the surfactant comprises at least about 0.01 wt% of the internal phase, such as from about 0.01 wt% to about 15 wt%, for example from about 0.05 wt% to about 10 wt%.

[0068] The non-thermotropic polymer may be polyvinyl acetate (PVA) or polyethylene glycol (PEG). PVA may have a molecular weight of about 10,000 Da to about 150,000 Da, for example, about 20,000 Da to about 100,000 Da. PEG may have a molecular weight of about 200 Da to about 400,000 Da, for example, about 500 Da to about 400,000 Da, or about 10,000 Da to about 300,000 Da, for example, about 15,000 Da to about 150,000 Da.

[0069] When present, the non-thermotropic polymer may comprise from about 0.1 wt % to about 20 wt %, such as from about 0.5 wt % to about 12 wt %, of the internal phase.

[0070] The shell may be formed from a material that forms a barrier around the encapsulated internal phase to substantially prevent the internal phase from leaking out of the microcapsule.

[0071] By "substantially prevent" is meant that the weight of the microcapsules can be reduced by less than about 40 wt%, e.g., less than about 25 wt%, after about 24 hours of exposure to air at room temperature (25°C, 50% relative humidity). Preferably, the phase transition is visible under a microscope at up to about 4x magnification after the microcapsules are exposed to air at room temperature for about 24 hours.

[0072] The shell may be formed by a complex aggregation of gelatin, a water-soluble anionic polymer and a crosslinking agent, or by an ultraviolet curable resin.

[0073] When the shell is formed from gelatin, a water-soluble anionic polymer and a cross-linking agent, the cross-linking agent may be a compound capable of irreversibly cross-linking polypeptide chains present within the gelatin.

[0074] For example, the crosslinker may be a compound having at least two reactive groups such as an aldehyde group (-C(O)H), a carboxyl group (-COH), or a vinyl group (-CH=CH), or the crosslinker may be a photoactivated free radical crosslinker including, for example, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, or it may be an optionally substituted benzophenone.

[0075] For example, the crosslinker may have at least two aldehyde groups and 2 to 10 carbon atoms, whether substituted or unsubstituted. 2-10 is a divalent aldehyde.

[0076] Representative cross-linking agents include glutaraldehyde, tannic acid, and formaldehyde.

[0077] The gelatin may be porcine, bovine, or fish gelatin. Preferably, porcine or bovine gelatin has a melting point of about 30°C to about 45°C, for example, about 35°C to about 40°C. Fish gelatin may have a melting point of about 5°C to about 30°C, for example, about 23°C to about 27°C.

[0078] Representative water-soluble anionic polymers include gum arabic, sodium alginate, pectin, and gum acacia. Preferably, the water-soluble anionic polymer comprises gum arabic.

[0079] When the shell is formed from gelatin, a water-soluble anionic polymer, and a crosslinker, and the liquid medium is a polar liquid medium, the internal phase further comprises an oil. Preferably, the oil comprises a silicone oil, and more preferably, the oil consists essentially of or consists of a silicone oil. However, the oil may be C 8-20 It can be understood that the liquid medium may include a hydrocarbon oil such as a hydrocarbon oil of the formula: When the liquid medium is a non-polar liquid medium, the oil is optional.

[0080] The silicone oil preferably has a molecular weight of about 1,000 Da to about 30,000 Da, more preferably about 5,000 Da to about 10,000 Da.

[0081] The refractive index (RI) of the oil preferably substantially matches the refractive index of the liquid medium. By "substantially matched," the RI of the oil may preferably be within about 10%, more preferably within about 8%, more preferably within about 5%, and more preferably within about 1% of the RI of the liquid medium.

[0082] It can be seen that when the shell is formed from gelatin, a water-soluble anionic polymer and a cross-linking agent, it provides an additional advantage to the present invention because the shell is biodegradable, making it a more environmentally friendly product compared to microcapsules with non-biodegradable shells.

[0083] When the shell is formed from a UV-curable resin, any UV-curable resin can be used. The UV-curable resin can include at least one compound containing at least one carbon-carbon double bond and a radical photoinitiator.

[0084] The at least one compound containing at least one carbon-carbon double bond may optionally contain at least one acrylate group. The at least one compound containing at least one carbon-carbon double bond may be a monomer, an oligomer, a resin, or a mixture thereof.

[0085] For example, the at least one compound may be an epoxy acrylate, a urethane acrylate, an acrylated silicone urethane or polyester, or an acrylated polyether.

[0086] Representative compounds containing at least one carbon-carbon double bond include bisphenol A epoxy diacrylate, soybean oil epoxidized acrylate, tripropylene glycol diacrylate, methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, isodecyl acrylate, ethyl cyanoacrylate, 1,6-hexanediol diacrylate, 1,4-butanediol diacrylate, neopentyl glycol diacrylate, diethylene glycol diacrylate, polyethylene glycol diacrylate, glyceryl propoxy triacrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylate, and dipentaerythritol (monohydroxy)pentaacrylate.

[0087] The at least one compound containing at least one carbon-carbon double bond may contain at least one methacrylate group. Representative compounds containing at least one carbon-carbon double bond containing at least one methacrylate group include bisphenol A epoxy dimethacrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, hydroxyethyl methacrylate, isodecyl methacrylate, lauryl methacrylate, lauryl tetradecyl methacrylate, 1,6-hexanediol dimethacrylate, 1,4-butanediol dimethacrylate, neopentyl glycol dimethacrylate, ethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, and trimethylpropane trimethacrylate.

[0088] The at least one compound containing at least one carbon-carbon double bond may be triallyl cyanurate or trimethylolpropane triallyl ether.

[0089] The radical photoinitiator may be a Norrish Type I, Type II, or polymeric photoinitiator. Representative radical photoinitiators include azobisisobutyronitrile (AIBN), 1,1'-azobis(cyclohexanecarbonitrile) (ACHN), 2-hydroxy-2-methyl-1-phenylpropanone (Omnirad 1173), 2,2-dimethoxy-2-phenylacetophenone (BDK), 1-hydroxycyclohexyl phenyl ketone (Omnirad 184), 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methylpropanone (Omnirad 2959), benzophenone, 4-methylbenzophenone (4MBZ), methylbenzoylformate (MBF), methyl-o-benzoylbenzoate (OMBB), and the diester of carboxymethoxybenzophenone and polytetramethylene glycol (Omnipol BP).

[0090] The shell may optionally contain an antifoaming agent. Optionally, the antifoaming agent may be a siloxane. For example, the siloxane may be octamethylcyclotetrasiloxane or decamethylcyclopentasiloxane. The antifoaming agent may be Agitan 760 from Munzing Chemie.

[0091] When present, the antifoaming agent may be present in an amount of from about 0.01 wt% to about 2 wt%, such as from about 0.05 wt% to about 1 wt% of the shell.

[0092] The weight ratio of the shell to the internal phase may be from about 75:25 to about 5:95, for example from about 50:50 to about 10:90.

[0093] The microcapsules may have a maximum diameter of about 200 nm to about 1 mm, for example, about 200 nm to 200 μm, preferably about 10 to 150 μm, more preferably about 50 to 100 μm.

[0094] The phase change temperature of the internal phase may be about −20° C. to about 80° C., for example, about 5° C. to about 50° C. The opacity of the internal phase below the phase change temperature is less than the opacity of the internal phase above the phase change temperature.

[0095] It can be seen that as opacity increases, visible and infrared (IR) transmission decreases, and conversely, as opacity decreases, visible and IR transmission increases.

[0096] The phase change temperature of the internal phase may be a single temperature or a narrow temperature range, for example, a particular temperature ±2° C., for example ±1° C., for example ±0.5° C. It may also be understood that the phase change temperature of the internal phase may be a wide temperature range, for example, a range of about 45° C., for example, a range of about 35° C., for example, a range of about 25° C., for example, a range of about 15° C., for example, a range of about 5° C.

[0097] The present invention also provides a plurality of microcapsules. The plurality of microcapsules do not all need to have the same maximum diameter. Therefore, the plurality of microcapsules may each have a maximum diameter within the range of about 200 nm to about 1 mm, for example, 200 nm to about 200 μm, preferably about 10 μm to about 150 μm, and more preferably about 50 μm to about 100 μm.

[0098] The refractive index (RI) can be measured using a refractometer analogue Brix 0-80.

[0099] (Enclosure method) The present invention also provides methods for preparing the subject microcapsules. A variety of methods can be used.

[0100] The present invention provides a method of making a microcapsule or a plurality of microcapsules, the method comprising forming a shell to encapsulate an internal phase comprising a thermotropic polymer and a liquid medium.

[0101] Suitably, the method may comprise forming the internal phase by dispersing a thermotropic polymer in a liquid medium to form an internal dispersion or emulsion.

[0102] The method can include forming a shell from gelatin and a cross-linking agent.

[0103] For example, the method can include the following steps: dispersing an internal phase in a continuous phase comprising gelatin, a water-soluble anionic polymer, a base (such as NaOH), and water to form a dispersion or emulsion in the continuous phase, wherein the pH of the continuous phase is preferably at least about 8, more preferably at least about 9; adjusting the pH of the dispersion or emulsion in the continuous phase to less than about 6, preferably less than about 5, to form aggregates; cooling the aggregates, preferably to a temperature of about 5°C to about 20°C, more preferably about 8°C to about 18°C; and crosslinking the gelatin in the cooled aggregates with a crosslinking agent.

[0104] Optionally, the method may include homogenizing the dispersion or emulsion in the continuous phase, for example by sonication or stirring.

[0105] Dispersing the internal phase in the continuous phase may include passing the internal phase through a membrane into the continuous phase.

[0106] When the shell is formed from gelatin and a cross-linking agent, the microcapsules can be produced by complex aggregation.

[0107] Accordingly, the present invention provides a method for producing the microcapsules of the present invention, wherein the shell is formed from gelatin, a water-soluble anionic polymer and a crosslinker, the method comprising the steps of: a) preparing a dispersion or emulsion of the internal phase of the microcapsules; b) preparing a continuous phase comprising gelatin, a water-soluble anionic polymer, a base, and water; c) mixing the dispersion or emulsion with a continuous phase; d) adjusting the pH of the product of step c) to less than about 6 to form aggregates; e) cooling the product of step d); f) cross-linking the gelatin in the product of step e) with a cross-linking agent.

[0108] Water-soluble anionic polymers form aggregates with gelatin. Representative water-soluble anionic polymers include gum arabic, sodium alginate, pectin, and gum acacia.

[0109] The base may comprise NaOH. Preferably, the pH of the continuous phase in step b) is at least about 8, more preferably at least about 9.

[0110] Step d) can be accomplished by adding an acid to the product of step c). The acid can be a C 2 O 4 O 5 O 6 ... 1-10 Organic acids are preferred. Examples of organic acids include acetic acid and maleic acid.

[0111] In step d), the pH of the resulting mixture may be adjusted to preferably at least about less than 5.

[0112] In step e), the cooling step is preferably carried out to a temperature of about 5°C to about 20°C, more preferably about 8°C to about 18°C.

[0113] In the crosslinking step (e.g., step f), crosslinking is achieved by mixing a crosslinker with the cooled aggregate (i.e., the product of step e). After the crosslinker is mixed, the resulting mixture is allowed to stand for at least 2 hours, e.g., at least 4 hours, e.g., at least 8 hours, e.g., at least 12 hours, to allow substantially all of the crosslinker to react. By "substantially all of the crosslinker," it is meant that at least about 90%, preferably at least about 95%, and more preferably at least about 98% of the initial concentration of crosslinker has reacted.

[0114] The size of the droplets in the dispersion or emulsion affects the size of the microcapsules produced by the above method, and the size of the droplets can be controlled in several different ways.

[0115] For example, the emulsion or dispersion can be produced by membrane emulsification or dispersion.

[0116] Alternatively, or in addition to film emulsification or dispersion, the above method may optionally include the step of homogenizing the product of step c) before carrying out step d).

[0117] Ultrasonic treatment may optionally be performed on the product of step a) and / or after the homogenization step (if performed), which may help remove entrapped air.

[0118] The method can include forming the shell by curing a UV curable resin.

[0119] For example, the method may include dispersing an internal phase in a UV-curable intermediate phase to form a first dispersion or emulsion; dispersing the first dispersion or emulsion in an external phase to form a second dispersion or emulsion; and curing the intermediate phase to form the shell.

[0120] The method can include forming a mesophase by combining at least one compound containing at least one carbon-carbon double bond, a radical-based photoinitiator, and optionally, an antifoaming agent.

[0121] The method can include forming an external phase by combining a stabilizing agent and water.

[0122] The step of curing the interphase may include exposing the interphase to ultraviolet light.

[0123] The step of dispersing the first emulsion in the external phase may include combining a stream of the first emulsion and a stream of the external phase.

[0124] For example, the method may include flowing an internal phase through a first injection tube, flowing an intermediate phase through a second injection tube, combining the internal and intermediate phases in the intermediate tube to form the first dispersion or emulsion, flowing an external phase through a third injection tube, combining the external phase with the first dispersion to form a second dispersion or emulsion, flowing the second dispersion or emulsion between outlets, and exposing it to ultraviolet light.

[0125] The step of dispersing the first emulsion within the external phase may include passing the first emulsion through a membrane into the external phase.

[0126] When the shell is formed from a UV-curable resin, the microcapsules can be produced by microfluidic methods.

[0127] Accordingly, the present invention provides a method for producing the microcapsules of the present invention, wherein the shell is formed from an ultraviolet curable resin, the method comprising the steps of: a) mixing the components of the internal phase of the microcapsules to form the internal phase; b) mixing at least one compound containing at least one carbon-carbon double bond, a radical photoinitiator, and optionally an antifoaming agent to form a mesophase; c) mixing the stabilizer with water to form an external phase; d) flowing the internal phase through the first injection tube and the intermediate phase through the second injection tube, and combining the internal and intermediate phases in the intermediate tube to form a combined stream; e) flowing the external phase into a third injection tube and combining the external phase with the combined stream; f) flowing the product of step e) through an outlet tube and exposing the product of step e) to ultraviolet light.

[0128] Preferably, the internal phase is supplied from the first syringe to the first injection tube. Preferably, the step of flowing the internal phase through the first injection tube can be carried out at a flow rate of about 5 to 50 μl / min.

[0129] Preferably, the intermediate phase is supplied from a second syringe to the second injection tube. Preferably, the step of flowing the intermediate phase through the second injection tube can be carried out at a flow rate of about 5 to 100 μl / min.

[0130] Preferably, the external phase is supplied from a third syringe to a third injection tube. Preferably, the step of flowing the external phase through the third injection tube can be carried out at a flow rate of about 0.5 to 5 ml / min.

[0131] The stabilizer can be any agent that is water-soluble and increases the viscosity of the water. Preferably, the addition of the stabilizer can increase the viscosity by at least about 1 cSt. For example, the stabilizer can be polyvinyl acetate (PVA) or hydroxyethyl cellulose (HEC). The stabilizer can be present in a range of about 0.1 wt% to about 20 wt% of the external phase.

[0132] The step of exposing to UV light (eg, exposing the product of step e) to UV light) may be carried out for at least 5 minutes, such as at least 15 minutes.

[0133] The ultraviolet light has a wavelength of about 100 to 400 nm. Preferably, the ultraviolet light is UVB (i.e., a wavelength of about 280 to 315 nm).

[0134] In all of the above methods, the resulting microcapsules may be collected by centrifugation. Optionally, the centrifuged microcapsules may be washed with deionized water, filtered and / or dried.

[0135] (application) The microcapsules of the present invention may be used in glass coating applications or other applications where thermal regulation is beneficial or desirable.

[0136] For example, a plurality of microcapsules of the present invention may be applied to any exterior surface of a structure, which may be a greenhouse, a polytunnel, a building (such as a residential, commercial, industrial building, or a combination thereof), a vehicle (such as a car, bus, truck, rail car, aircraft, or ship), or a solar panel.

[0137] The surface may be a roof or a wall or glass, for example a sheet of glass.

[0138] The surface may be part of an existing structure. Alternatively, a plurality of microcapsules of the present invention may be applied to the surface before the surface is added to the structure.

[0139] The term "glass" includes silicate glass and polycarbonate glass, and also includes architectural glass, marine glass, and automotive glass. When the surface is glass, the microcapsules of the present invention can be applied to the interior surface of the glass, or the microcapsules can be included within the glass, such as in an interlayer.

[0140] A plurality of microcapsules of the present invention may be applied as part of a coating.

[0141] Thus, the present invention provides a coating comprising a plurality of microcapsules of the present invention. The durability of the plurality of microcapsules is advantageous in that the coating can be applied in a variety of ways. For example, it can be appreciated that the coating can be applied to the surface of glass or polytunnels. As mentioned above, it can be applied to the surface when the glass is part of an existing structure or before the surface is added to the structure.

[0142] The coating may be a paint, such as a water-based paint, a solvent-based paint, or an oil-based paint. When the coating is a paint, the microcapsules of the present invention may be physically mixed with the components of the paint during the manufacture of the paint or prior to application of the paint.

[0143] The coating may be a film, such as a plastic film. The plastic film may include polyethylene terephthalate (PET), polyether polyurethane, ethylene tetrafluoroethylene (ETFE), polyacrylate, polyester, and combinations thereof. Optionally, the film has a % visible light transmittance of at least about 60%, e.g., at least about 70%, e.g., at least about 80%, measured according to ASTM D1003, when tested at or below the phase change temperature of the microcapsules of the present invention.

[0144] When the coating is a film, the microcapsules of the present invention may be added to the film before, during, or after the production of the film. For example, when the film is a plastic film, the film may be produced by extrusion, and the microcapsules of the present invention may be added to the plastic film before, during, or after the extrusion of the plastic film.

[0145] It can be appreciated that when a plurality of microcapsules of the present invention are added before or during manufacture, the microcapsules become at least partially embedded in the film.

[0146] When the microcapsules of the present invention are added after the film is made, the microcapsules may be applied to the surface of the film using, for example, an adhesive.

[0147] The coating may be applied as a spray coating, for example, the spray coating may be applied using a pressurized liquid stream.

[0148] The coating may be a solar panel coating. The microcapsules of the present invention may be included in a self-cleaning solar panel coating.

[0149] Alternatively, a plurality of microcapsules of the present invention can be added to a glass interlayer, which can include polyvinyl butyral (PVB), ethylene vinyl acetate (EVA), ionoplasts, and combinations thereof.

[0150] Preferably, the coating or intermediate layer comprises at least about 0.2 wt % of the microcapsules of the present invention, for example in the range of about 0.2 wt % to about 50 wt % based on the total weight of the coating or intermediate layer.

[0151] The microcapsules of the present invention, as well as the surfaces, glasses, interlayers and / or coatings of the present invention, can be used for sun protection, and the microcapsules of the present invention, as well as the surfaces, glasses, interlayers and / or coatings of the present invention, can be used for passive cooling. [Example]

[0152] Example 1 - Preparation of microcapsules containing a shell formed from a UV-curable resin (material) Klucel E-Industrial HPC (Ashland), 1,3-propanediol (PDO) (Grandtrade), NaCl (Sigma-Aldrich), polyvinyl alcohol (PVA) (hydrolysis degree 87-90%, average molecular weight 30,000-70,000) (Sigma-Aldrich), Miramer PU2560 (50 wt%, Miwon), tripropylene glycol diacrylate - TPGDA (19.2 wt%, Qualipoli), isodecyl acrylate - IDA (19.2 wt%, Qualipoli), methyl benzoyl formate - MBF (5 wt%, IGM), 2-hydroxy-2-methyl-1-phenylpropanone - Omnirad 1173 (5 wt%, IGM), Agitan 760 (0.2 wt%, Munzing), female-male Luer connector (1 / 16 inch, Amazon), silicone tubing with an inner diameter of 1.5 mm (Amazon), needles (Amazon, Somerset). All chemicals were used without further purification.

[0153] (microfluidic device) FIG. 1 shows a microfluidic device (100) that can be used to produce the microcapsules of the present invention.

[0154] The microfluidic device (100) was constructed using readily available materials, including polypropylene male (102, 105) and female Luer fittings, cross junctions (109), Tee links (110), stainless steel dispensing needles (103, 104, 107), and silicone tubing (e.g., 106, 108). The needle gauges used for the internal phase were a 25-gauge, 1.5-inch needle (107) for the Tee junction, and a 25-gauge, 1 / 2-inch needle (104) and a 20-gauge, 1 / 2-inch needle (103) for the cross junction. The middle phase was introduced from a syringe via a female Luer into the silicone tubing (106) connected to the Tee junction (110). The external phase was introduced from a syringe via a 15-gauge, 1.5-inch dispensing needle into the silicone tubing (108), which branched into two silicone tubings at the Tee junction and connected to the cross junction (109) of the microfluidic device.

[0155] The device was washed with DI water and primed with the external phase before use.

[0156] (Microcapsule formation method) Internal phase: 7 wt% NaCl, 27 wt% PDO, and 66 wt% HPC solution of 20 wt% HPC dissolved in water was stirred for 12 hours using a magnetic stirrer.

[0157] Interphase: Miramer PU2560 (50 wt%), tripropylene glycol diacrylate-TPGDA (19.2 wt%), isodecyl acrylate-IDA (19.2 wt% Qualipoli), methyl benzoyl formate-MBF (5 wt%), 2-hydroxy-2-methyl-1-phenylpropanone-Omnirad1173 (5 wt%), and Agitan760 (0.2 wt%) were mixed.

[0158] External phase: A 10% PVA solution was prepared by adding boiling deionized (DI) water to PVA powder and stirring.

[0159] Each phase was added to the first, second, and third syringes, respectively, and connected to the microfluidic device. The flow rates used were: internal phase (35 μl / min), intermediate phase (20 μl / min), and external phase (1.5 ml / min).

[0160] The outlet tube (101) was passed through a UV lamp with a wavelength of 302 nm, and then cured under a UV-LED lamp (365 nm + 405 nm) for 15 minutes.

[0161] The resulting microcapsules were centrifuged, washed with deionized water, filtered and dried.

[0162] Example 2 - Preparation of microcapsules with a shell formed from gelatin and a crosslinker (material) Silicone oil (100 cP) (PMX200, Dow Corning), 1,3-propanediol PDO (40 wt% aqueous solution) (Guntrade), pNIPAM (2.4 wt% aqueous solution), Dowsil 5525C surfactant (Dow Corning), porcine gelatin (Weishardt, 280 bloom, 20 mesh), gum arabic (Nexira, Instagum AA, food grade / Halaal / Kosher), acetic acid (20 wt% aqueous solution, Sigma-Aldrich), glutaraldehyde (50 wt% aqueous solution, Sigma-Aldrich).

[0163] (Microencapsulation method) Emulsion phase: Prepared by heating a solution of 2% by weight of Dowsil 5525C surfactant in silicone oil (100 cP) to 30°C with stirring.

[0164] The emulsion phase was prepared by adding 40% 1,3-PDO dropwise to 6.4 g of 60% pNIPAM aqueous solution over 1 min while homogenizing 9.6 g of silicone oil solution in an Ultraturrax T25 homogenizer at 10,000 rpm, followed by further homogenization for 2 min.

[0165] The resulting emulsion phase was sonicated in an ultrasonic bath for 3 minutes for degassing and then loaded into a syringe connected to an LDC-1 dispersion cell (Micropore Technologies) equipped with a stir bar and dispersion membrane.

[0166] Continuous phase: 350 mL of deionized water was heated to 45°C with stirring. Gum arabic (1.43 wt%) was added, followed by porcine gelatin (1.43 wt%). Once a homogeneous solution was formed, 4 M NaOH was added dropwise until a pH of 9 was reached. 100 mL of the resulting continuous phase was added to an LDC cell. The stir bar was turned on.

[0167] The LDC stirred cell rapidly became turbid as the emulsion phase was added. No membrane blockage occurred. Once the addition of 10 mL of the emulsion phase was complete, the resulting product was transferred to a beaker containing the remainder of the continuous phase. The beaker was kept at 40°C and stirred at low speed (100-150 RPM) with an overhead stirrer.

[0168] Acetic acid was added dropwise until the solution pH reached 4.7. The solution became more turbid due to the formation of aggregated particles caused by the pH change. The solution was then cooled to 20°C. At this point, the capsule walls had formed, so the solution was further cooled to 15°C and cross-linked with 1.5 g of glutaraldehyde (50%).

[0169] Example 3 - Preparation and analysis of coatings containing microcapsules of the present invention An aqueous coating was prepared from a mixture of acrylic copolymer dispersion (EPS 564, 64 wt%), polyurethane dispersion (Tego Variplus DS50, 30 wt%), defoamer (Tego Foamex 24, 0.1 wt%), wetting and dispersing agents (Dyno Add F-608, 0.5 wt% and Valida S231C, 3.5 wt%), rheology modifier (Tafigel PUR48, 0.3 wt%), and water (2 wt%). 20 wt% of the microcapsules prepared in Example 1 were added to the prepared coating and gently stirred.

[0170] The coatings were applied to 10 × 10 cm glass substrates by flood coating method and allowed to dry for 2 h in ambient environment (approximately 25 °C, 30% relative humidity) before measuring the opacity at different temperatures.

[0171] The opacity of the coatings was measured using a light box equipped with a luxmeter externally heated by an infrared lamp, which measured the transmittance of the coating at different temperatures and recorded the temperature at which a decrease in transmittance occurred.

[0172] The results of the transmittance tests are shown in Figure 2(I). The graph shows that the transmittance of the coating decreases from about 95% at 26°C to about 68% at 32°C.

[0173] Example 4 - Analysis of microcapsules produced in Example 1 The microcapsules produced in Example 1 were visually analyzed at 26° C. and 32° C. The results are shown in Figure 2(II).

[0174] Images a and b are images of microcapsules at 1x magnification. Image a shows the microcapsules at 26°C, and image b shows the microcapsules at 32°C. Simple visual inspection confirms that the opacity of the microcapsules increases from 26°C to 32°C.

[0175] Images c and d are images of microcapsules magnified 4 times. Image c shows the microcapsules at 26°C, and image d shows the microcapsules at 32°C. Simple visual inspection confirms that the opacity of the microcapsules increases from 26°C to 32°C.

[0176] Example 5 - Preparation of microcapsules with shells formed from UV-curable resin (material) Klucel E-Industrial HPC (Ashland), 1,3-propanediol (PDO) (Fisher Scientific), NaCl (Sigma-Aldrich), polyvinyl alcohol (PVA) (87-90% hydrolyzed, average molecular weight 30,000-70,000) (Sigma-Aldrich), glycerol (Fisher Scientific), soybean oil, epoxidized acrylate (ESBOA) (IGM), poly(ethylene glycol) diacrylate (PEGDA) (average molecular weight 200) (IGM), methyl benzoyl formate (MBF) (Sigma-Aldrich).

[0177] (Microencapsulation method) Internal phase: 20 wt% HPC solution (7 wt% NaCl, 27 wt% PDO, 66 wt% HPC) dissolved in water was stirred with a magnetic stirrer for 12 h.

[0178] Intermediate phase: 47.5 wt% ESBOA, 47.5 wt% PEGDA, and 5 wt% MBF were stirred with a magnetic stirrer to form a homogeneous mixture.

[0179] Emulsion phase: To emulsify the internal and external phases, the internal phase was added through an 18-gauge needle at a rate of approximately 5 ml / min under stirring at 2500 rpm.

[0180] The resulting emulsion phase was loaded into a syringe connected to an LDC-1 dispersion cell (Micropore Technologies) equipped with a stirrer and dispersion membrane.

[0181] Continuous phase: 35 wt% deionized water, 20 wt% 10 wt% PVA aqueous solution, 7 wt% NaCl, and 38 wt% glycerol were mixed with an overhead stirrer until a homogeneous solution was formed. 70 mL of the resulting continuous phase was added to an LDC-1 cell and the stirrer was turned on.

[0182] The LDC stirred cell rapidly became cloudy upon addition of the emulsion phase. No membrane blockage occurred. After adding 30 mL of the emulsion phase, the product was transferred to a beaker and cured under a UV-LED lamp (365 nm + 405 nm) for 30 minutes.

[0183] The resulting microcapsules were centrifuged, washed with deionized water, filtered and dried.

Claims

1. A microcapsule comprising a shell and an internal phase, the shell encapsulates the internal phase; The internal phase comprises a thermotropic polymer and a liquid medium.

2. 2. The microcapsule of claim 1, wherein the liquid medium is a polar liquid medium, optionally the polar liquid medium comprises water and / or alcohol.

3. 3. The microcapsule of claim 2, wherein the polar liquid medium comprises water, and preferably the water is present in an amount of at least about 5 wt %, more preferably at least about 15 wt %, more preferably at least about 30 wt % of the polar liquid medium.

4. 4. The microcapsule of claim 2 or 3, wherein the polar liquid medium comprises an alcohol, and preferably the alcohol is present in an amount of at least about 5 wt %, more preferably at least about 15 wt %, more preferably at least about 30 wt % of the polar liquid medium.

5. 5. The microcapsule according to claim 1, wherein the thermotropic polymer is a hydroxypropyl cellulose (HPC) polymer or a polyacrylamide polymer.

6. The polyacrylamide polymer is obtained by radical polymerization of an acrylamide monomer having the structure of the following chemical formula (I): In formula (I), R １ is H or optionally substituted C １－１０ alkyl, preferably H or methyl; R ２ is an optionally substituted C １－１０ 6. Microcapsules according to claim 5, wherein the alkyl is preferably methyl, ethyl, n-propyl or isopropyl, more preferably n-propyl or isopropyl.

7. R １ is H or methyl, and R ２ The microcapsules according to claim 6, wherein is n-propyl or isopropyl.

8. The microcapsules according to any one of claims 5 to 7, wherein the polyacrylamide polymer is poly(N-n-propylacrylamide) (NNPAM), poly(N-isopropylacrylamide) (NIPAM), or poly(N-isopropylmethylacrylamide) (NMPAM).

9. The hydroxypropyl cellulose polymer has the structure of formula (II): R ３ is H or and m is an integer of 1 or greater; R ４ teeth, and R ５ teeth, and n is an integer from about 200 to about 8000; Optionally, the HPC has a degree of substitution (DS) value and a mole substitution (MS) value, wherein the DS is a maximum of 3 moles of R of formula (IIa) per repeat unit. ３ 6. The microcapsule of claim 5, wherein DS is the number of m groups, MS is the average value of m per repeat unit of the polymer, and optionally DS is at least 1, such as at least 2, and / or optionally MS is from about 2 to about 6, such as from about 2.5 to about 5.5, such as from about 3 to about 5.

10. 10. The microcapsule of claim 1, wherein the thermotropic polymer is present in an amount of from about 0.1 wt % to about 30 wt %, preferably from about 0.5 wt % to about 15 wt % of the internal phase.

11. The microcapsule according to any one of claims 1 to 10, wherein the thermotropic polymer is a microgel.

12. 12. Microcapsules according to any of the preceding claims, wherein the internal phase has a phase change temperature comprised between about -20°C and about 80°C, preferably between about 5°C and about 50°C.

13. 13. The microcapsule of any one of claims 1 to 12, wherein the internal phase comprises one or more additives, preferably the one or more additives comprise salts, sugars, surfactants, non-thermotropic polymers and combinations thereof.

14. The one or more additives include a salt, preferably the salt is NaCl, LiCl, KCl, KCN, MgCl ２ , Mg(NO ３ ) ２ , KNO ３ , Na ２ CO ３ , Li ２ CO ３ , K. ３ P.O. ４ , [(CH ３ ) ３ NCH ２ CH ２ OH]Cl, (NH ４ ) ２ SO ４ and combinations thereof, more preferably the salt comprises NaCl.

15. 15. The microcapsule of claim 14, wherein the salt is present in an amount of from about 0.01 wt% to about 36 wt%, preferably from about 0.5 wt% to about 15 wt% of the internal phase.

16. 16. The microcapsule according to claim 1, wherein the shell is formed by a complex aggregation action of gelatin, a water-soluble anionic polymer and a crosslinking agent, or by an ultraviolet-curable resin.

17. 17. The microcapsules of claim 16, wherein the gelatin is porcine, bovine or fish gelatin, the porcine or bovine gelatin preferably having a melting point of about 30°C to about 45°C, more preferably about 35°C to about 40°C, and the fish gelatin preferably having a melting point of about 5°C to about 30°C, more preferably about 23°C to about 27°C.

18. The crosslinking agent contains an aldehyde group (—C(O)H), an acid group (—CO ２ H), vinyl group (-CH=CH ２ 18. Microcapsules according to claim 16 or 17, wherein the crosslinker is a compound having at least two reactive groups such as 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, or the crosslinker is a photoactivated free radical crosslinker, including for example 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, or the crosslinker is an optionally substituted benzophenone derivative.

19. 19. A microcapsule according to any one of claims 16 to 18, wherein the liquid medium is a polar liquid medium and the internal phase comprises an oil, preferably a silicone oil, and wherein the oil preferably has a refractive index (RI) within about 10%, more preferably within about 8%, more preferably within about 5%, more preferably within about 3% of the refractive index of the polar liquid medium.

20. 17. The microcapsule of claim 16, wherein the ultraviolet curable resin comprises at least one compound containing at least one carbon-carbon double bond and a radical photoinitiator.

21. 21. The microcapsule of claim 20, wherein the at least one compound containing at least one carbon-carbon double bond comprises at least one acrylate group or at least one methacrylate group, and preferably the at least one monomer type is an epoxy acrylate, an acrylated urethane, an acrylated silicone, or an acrylated polyether.

22. The microcapsules according to any one of claims 1 to 21, wherein the diameter of the widest part of the microcapsules is from about 200 nm to about 1 mm, for example from about 200 nm to about 200 μm, preferably from about 10 μm to 150 μm, more preferably from about 50 μm to about 100 μm.

23. A plurality of microcapsules according to any one of claims 1 to 22, The plurality of microcapsules each have a maximum diameter of about 200 nm to about 1 mm, for example, about 200 nm to about 200 μm, preferably about 10 μm to 150 μm, more preferably about 50 μm to about 100 μm.

24. A method for producing a microcapsule according to any one of claims 1 to 22 or a plurality of microcapsules according to claim 23, comprising: forming a shell to encapsulate an internal phase comprising said thermotropic polymer and said liquid medium.

25. 25. The method of claim 24, comprising forming an internal phase by dispersing the thermotropic polymer in the liquid medium to form a dispersion or emulsion.

26. 26. The method of claim 24 or 25, comprising forming the shell from gelatin and a cross-linking agent.

27. 27. The method of claim 26, comprising the steps of: a. dispersing the internal phase in a continuous phase comprising gelatin, a water soluble anionic polymer, a base (such as NaOH), and water to form a dispersion or emulsion in the continuous phase, preferably wherein the pH of the continuous phase is at least about 8, more preferably at least about 9; b. adjusting the pH of the dispersion or emulsion in the continuous phase to less than about 6, preferably less than about 5, to form aggregates; c. cooling the agglomerate to a temperature preferably of from about 5°C to about 20°C, more preferably from about 8°C to about 18°C; d) Crosslinking the gelatin in the cooled aggregate with the crosslinking agent.

28. 28. The method of claim 27, comprising the step of homogenizing the dispersion or emulsion in the continuous phase, optionally by sonication or stirring.

29. 29. The method of claim 27 or 28, wherein the step of dispersing the internal phase in the continuous phase comprises passing the internal phase through a membrane into the continuous phase.

30. 30. The method of any one of claims 26 to 29, wherein the microcapsule or microcapsules are produced by complex aggregation.

31. A method for producing a microcapsule according to any one of claims 1 to 22 or a plurality of microcapsules according to claim 23, comprising: forming the shell from gelatin and a cross-linking agent; A method comprising the steps of: a. preparing a dispersion or emulsion of the internal phase; b. dispersing said internal phase in a continuous phase comprising gelatin, a water soluble anionic polymer, a base, and water to form a dispersion or emulsion in said continuous phase, preferably wherein the pH of said continuous phase is at least about 8, more preferably at least about 9; c. mixing the dispersion or emulsion with the continuous phase; d. adjusting the pH of the product of step c to less than about 6, preferably less than about 5, to form aggregates; e. cooling the product of step d. above to a temperature of preferably from about 5°C to about 20°C, more preferably from about 8°C to about 18°C; f) Cross-linking the gelatin in the product of step e with said cross-linking agent.

32. 32. The method of claim 31 , wherein the emulsion or dispersion is produced by membrane emulsification or dispersion, and / or the method further comprises the step of homogenizing the product of step c before performing step d.

33. 26. The method of claim 24 or 25, comprising forming the shell by curing an ultraviolet curable resin.

34. 34. The method of claim 33, comprising the steps of: a. dispersing the inner phase in a UV-curable middle phase to form a first dispersion or emulsion; b. dispersing the first dispersion or emulsion in an external phase to form a second dispersion or emulsion; c) curing the interphase to form a shell.

35. 35. The method of claim 34, comprising forming the mesophase by combining at least one compound containing at least one carbon-carbon double bond, a radical photoinitiator, and optionally an antifoaming agent.

36. 36. The method of claim 34 or 35, comprising forming the external phase by mixing the stabilizing agent with water.

37. The method of any of claims 34 to 36, wherein curing the interphase comprises exposing the interphase to ultraviolet light.

38. 38. The method of any one of claims 34 to 37, wherein dispersing the first emulsion in the external phase comprises combining a stream of the first emulsion with a stream of the external phase.

39. 39. The method of any of claims 34 to 38, comprising flowing the internal phase through a first injection tube, flowing the intermediate phase through a second injection tube, combining the internal and intermediate phases in the intermediate tube to form the first dispersion or emulsion, flowing the external phase through a third injection tube, combining the external phase with the first dispersion to form the second dispersion or emulsion, flowing the second dispersion or emulsion through an exit tube, and exposing to ultraviolet light.

40. 40. The method of any of claims 34 to 39, wherein the step of dispersing the first emulsion in the external phase comprises passing the first emulsion through a membrane into the external phase.

41. A method for producing a microcapsule according to any one of claims 1 to 22 or a plurality of microcapsules according to claim 23, comprising: the shell is formed from an ultraviolet curable resin, A method comprising the steps of: a. mixing the components of the internal phase to form the internal phase; b. mixing the at least one compound containing at least one carbon-carbon double bond with the radical photoinitiator and, optionally, an antifoaming agent to form a mesophase; c. mixing a stabilizer with water to form an external phase; d. flowing the internal phase through a first injection tube and the intermediate phase through a second injection tube, combining the internal and intermediate phases within the intermediate tube to form a combined stream; e. passing the external phase through a third injection conduit and combining the external phase with the combined stream; f) Flowing the product of step e through an outlet tube and exposing said product of step e to ultraviolet light.

42. 24. A coating comprising a plurality of microcapsules according to claim 23, Preferably, the coating is a paint or a film.

43. 24. An outer surface of a structure comprising a plurality of microcapsules according to claim 23, Preferably, the surface is a roof or a wall or glass, and / or the structure is an exterior surface selected from the group consisting of a greenhouse, a polytunnel, a building (such as a residential, commercial building, industrial building or a combination thereof), a vehicle (such as a car, bus, truck, rail vehicle, aircraft, ship, etc.), or a solar panel.

44. 24. A glass comprising a plurality of microcapsules according to claim 23, Optionally, the plurality of microcapsules is applied to an outer or inner surface of the glass, or the plurality of microcapsules is applied to an interlayer.

45. 45. Use of a plurality of microcapsules according to claim 23, a coating according to claim 42, an exterior surface according to claim 43, or glass according to claim 44 as a sun protection product.

46. 45. Use of a plurality of microcapsules according to claim 23, a coating according to claim 42, an exterior surface according to claim 43, or a glass according to claim 44 as a passively cooled product.

Images