WO2005002719A1 - Method for preparing microcapsule by miniemulsion polymerization - Google Patents
Method for preparing microcapsule by miniemulsion polymerization Download PDFInfo
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- WO2005002719A1 WO2005002719A1 PCT/KR2004/001644 KR2004001644W WO2005002719A1 WO 2005002719 A1 WO2005002719 A1 WO 2005002719A1 KR 2004001644 W KR2004001644 W KR 2004001644W WO 2005002719 A1 WO2005002719 A1 WO 2005002719A1
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- B01J13/00—Colloid chemistry, e.g. the production of colloidal materials or their solutions, not otherwise provided for; Making microcapsules or microballoons
- B01J13/02—Making microcapsules or microballoons
- B01J13/06—Making microcapsules or microballoons by phase separation
- B01J13/14—Polymerisation; cross-linking
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- the present invention relates to a method for preparing microcapsules by miniemulsion polymerization, and more particularly to a method for preparing microcapsules, which includes mixing a monomer, an emulsifier, an ultrahydrophobe, a hydrophobic material, an initiator, preferably an oil-soluble initiator, and deionized water, optionally a hydrophilic comonomer and/or a crosslinking agent used as an auxiliary monomer, to prepare a miniemulsion and polymerizing the miniemulsion.
- the method may further include adding a secondary initiator during the miniemulsion polymerization to allow the miniemulsion polymerization to further proceed.
- the crosslinking agent may be added during the miniemulsion polymerization.
- the present invention also relates to microcapsules prepared by the method.
- Microcapsules have been implicitly defined as particles ranging from several tens nanometers to several tens microns which contain a core material composed of a liquid or solid molecule surrounded by a shell made of mainly a polymer material, relative to nanocapsules having a particle size of several hundreds nanometers or less.
- the core material may be selected from drugs, perfumes, catalysts, dyes, and uniform liquid solutions containing the forgoing components.
- These microcapsules and nanocapsules have various application fields. Coacervation, interfacial polymerization, and in-si tu polymerization are representative methods known for preparation of microcapsules. When needed, their supplemented or modified methods can be used.
- microcapsule preparation method using a polymer post-treatment [Chem . Soc . Rev. , 29, 295, 2000].
- a water-insoluble polymer, an organic solvent, and a core material are mixed and sufficiently stirred to obtain a uniform solution, followed by removal of the organic solvent.
- Examples of patent documents using this method include U.S. Patent No. 4,384,975 and U.K. Patent No. 1,394,780.
- Solvent removal by vacuum distillation is disclosed in U.S. Patent No. 4,384,975 and solvent removal by evaporation is disclosed in U.K. Patent No. 1,394,780.
- U.S. Patent No. 3,891,570 discloses a method for preparing microcapsules by heating a water- soluble dispersion or removal of a polymer solvent under vacuum and U.S. Patent No. 3,737,337 discloses a method for preparing microcapsules by extracting an organic solvent with water. Preparation of microcapsules by removal of an organic solvent is also disclosed in Polym. Eng. Sci . , 1990, 30, 915.
- Microcapsules can also be prepared by a suspension- crosslinking method [Polym. Eng. Sci., 1989, 29, 1746]. According to this method, a polymer is dissolved in a solvent and stirred mechanically to obtain suspension particles, followed by polymer crosslinking. Then, produced microcapsules are recovered.
- this method has disadvantages in that appropriate compatibility between the solvent and the polymer is required and the microcapsules may not have a core-shell structure.
- coacervation is a method of forming a permeable polymer coacervate which adjusts the concentration of a core material in response to change in exterior environment under a specific condition [Polym . Eng. Sci . , 1990, 30, 905].
- a third solvent is. added to a polymer solution, particles which are different in the content of the third solvent between inside and outside of the particles in a specific condition can be obtained. Based on this principle, various substances can be encapsulated in these particles under an appropriate condition.
- An exemplary method is a self-assembly approach. This method is to prepare double-layered, spherical particles from a diluted aqueous solution of an amphiphilic lipid molecule. If the double-layered particles have polymerizable functional groups, microcapsules are produced by polymerization. Even though studies about this method have been continued since 1970, since this method is affected by many process parameters such as synthesis of an amphiphilic block compound and a temperature, there have been very few successful instances [Langmuir, 2000, 16, 1035].
- a self-assembly approach using dendrimer is also known [J “ . Am . Chem . Soc , 1995, 117, 4417].
- An amphiphilic dendrimer tends to form spherical particles by self- assembly at a predetermined temperature and concentration according to its type. Due to a low core density and a high surface density, a dendrimer can form nanocapsules. In this regard, encapsulation of a core material by the dendrimer can produce microcapsules.
- dendrimer shells of the microcapsules thus produced are not held by a covalent bond, a shell function can be easily lost by change in exterior environment. Furthermore, there are disadvantages in that dendrimer synthesis is difficult and dendrimer-based microcapsules are produced only in a specific condition.
- a hyperbranched polymer technique [Angew. Chem . Intl . Ed. , 1991, .30, 1178]
- a reverse-phase amphiphilic dendrimer technique [Angew. Chem . Intl . Ed . , 1999, 38, 3552 ⁇ ] and the like have been reported, but have similar disadvantages. There is reported a method for preparing hollow microcapsules -using a template.
- an amphiphilic polyisoprene-polyacrylic acid block copolymer is self- assembled in an aqueous solution, followed by shell crosslinking by condensation between an amine with two reactive groups and a polyacrylic acid and removal of a polyisoprene core by oxidation with ozone, to prepare hollow nanocapsules.
- the preparation method is complicated and can be applied to only an amphiphilic molecule.
- Another method for preparing nanocapsules is an emulsion-diffusion technique disclosed in Drug. Dev. Re . , 2002, 57, 18.
- a polymer is dissolved in a solvent to obtain a polymer solution. Then, the polymer solution is added to a solvent-saturated aqueous solution and vigorously stirred in the presence of an emulsifier to perform emulsification. After the emulsification is terminated, addition of a large amount of an aqueous solution induces transfer of the solvent into an aqueous solution phase by chemical equilibrium, thereby producing hollow nanocapsules.
- a solvent capable of solubilizing most polymers, preparation of a high concentration polymer solution and control of a particle size are difficult, and a preparation process is complicated. Adv. Colloid . Interface .
- Science, 2002, 99, 181 discloses a method for encapsulating a hydrocarbon using a non-solvent for a polymer.
- a low molecular weight polymer latex is used as seed particles.
- the latex particles are swelled by small quantity of isooctane and then polymerization is performed, spontaneous phase separation occurs with increase of a polymer concentration.
- isooctane is encapsulated.
- this method can be applied to only a reaction system in which initial latex particles can be swelled to some degree and phase separation by increase of a polymer concentration is possible .
- microcapsules by miniemulsion polymerization after mixing large amounts of polystyrene (PS) or polymethylmethacrylate (PMMA) and hexadecane which is an ultrahydrophobe [Langmuir, 17, 908, 2001] .
- PS polystyrene
- PMMA polymethylmethacrylate
- ultrahydrophobe ultrahydrophobe
- miniemulsion polymerization due to polymerization except miniemulsion polymerization, like homogeneous nucleation, polymer particles per se (secondary particles) may be produced as byproducts, in addition to microcapsules.
- Prog. Polym . Sci . 2002, 27 689 discloses miniemulsion polymerization for latex preparation, like typical emulsion polymerization.
- a liquid monomer is dispersed in water with a homogenizer having strong pulverizability, such as an ultrasonic homogenizer, a Microfluidizer, and Manton-Gaulin homogenizer, to produce particles which are several tens to
- the concentration of the third component increases in small particles due to escape of a main component from the small particles, but it decreases in large particles due to inclusion of the main component into the large particles. Due to such a concentration difference in the third component, chemical potential difference in the monomer particles is generated, thereby creating an osmotic pressure.
- the Ostwald ripening effect is prevented by the osmotic pressure thus created.
- the Ostwald Ripening effect is a phenomenon that occurs because small particles are superior to large ones in terms of the solubility of a dispersed compound in a continuous phase.
- particle morphology by phase separation between different polymers can be predicted by using the differences of the interfacial tension between each polymer and a continuous phase [J. Coll . Inter. Sci . , 1970, 33, 6783].
- Particle morphology in an equilibrium state can be predicted by comparing dispersion coefficients calculated based on the interfacial tensions.
- a phase separation by a solubility difference between a hydrophobic material and a product polymer occurs in an accurate, rapid, easy, and spontaneous manner due to low viscosity of the hydrophobic material . Since the hydrophobic material, which is added in the form of a liquid phase, is dissolved in monomer particles but not in a polymer, it can be used as a solvent in the microcapsule preparation method according to the present invention.
- a method for preparing microcapsules comprising the steps of: (a) mixing a monomer, an emulsifier, an ultrahydrophobe, a hydrophobic material, an initiator, deionized water, optionally a hydrophilic comonomer and/or a crosslinking agent used as an auxiliary monomer, to prepare a miniemulsion; (b) polymerizing the miniemulsion to prepare the microcapsules; and (c) optionally, adding a secondary initiator during the miniemulsion polymerization to allow the miniemulsion polymerization to further proceed.
- the crosslinking agent may be added during step (a) or (b) .
- the emulsifier may be used in an amount of 0.01 to 5.0 parts by weight, the ultrahydrophobe in an amount of 0.1 to 10 parts by weight, the hydrophobic material in an amount of 10 to 300 parts by weight, the crosslinking agent in an amount of 0.0 to 10 parts by weight, the initiator in an amount of 0.01 to 3 parts by weight, the hydrophilic comonomer in an amount of 0.01 to 10 parts by weight, and the secondary initiator in an amount of 0.01 to 1 part by weight, based on 100 parts by weight of the monomer.
- the miniemulsion polymerization may be performed at a temperature from 25 to 160 ° C, and preferably from 40 to 90 ° C. Time required for the polymerization may vary according to the types of used monomers and a polymerization rate. However, the polymerization may be performed for 3 to 24 hours, preferably 4 to 10 hours, and more preferably 4 to 8 hours.
- the initiator that can be used to initiate the- polymerization may be one or more selected from the group consisting of peroxides, persulfates, azo compounds, and redox compounds.
- the initiator may be inorganic or organic peroxides such as hydrogen peroxide (H 2 0 2 ) , di-tert-butyl peroxide, cumene hydroperoxide, dicyclohexyl percarbonate, tert-butyl hydroperoxide, and p-menthane hydroperoxide; azo compounds such as azobisisobutyronitrile; persulfates such as ammonium persulfate, sodium persulfate, and potassium persulfate; potassium perphosphate; sodium perborate; or redox compounds .
- an oil-soluble initiator may be used as the initiator of the present invention.
- the oil -soluble initiator serves to prevent formation of secondary particles free of cores, thereby ensuring uniformly sized and shaped microcapsules.
- secondary particles refer to hydrophobic material-free particles prepared by monomer polymerization in an aqueous phase and spontaneous particle formation, unlike latex particles prepared by polymerization of hydrophobic material-containing monomer particles obtained by ho ogenization. Since these secondary particles may deteriorate the characteristics of a final product due to the absence of a hydrophobic material, it is necessary to prevent formation of the secondary particles.
- the oil- soluble initiator is present only within monomer particles. Therefore, polymerization of a monomer that may be present in an aqueous phase can be prevented, thereby preventing formation of secondary particles.
- the oil-soluble initiator is advantageously a material having 0.5 g/kg or less, and preferably 0.02 g/kg or less of solubility in 25 ° C water.
- the oil-soluble initiator may be one or more selected from peroxides, azo compounds, and redox compounds, but is not limited thereto.
- the initiator may be used in an amount of 0.01 to 3 parts by weight, based on 100 parts by weight of the monomer. If the content of the initiator is less than 0.01 parts by weight, a polymerization rate may decrease.
- Microcapsules prepared according to the method of the present invention contain a core material surrounded by a polymer shell.
- the core material exists as a separate phase such as a liquid phase or a solid phase.
- the hydrophobic material is used as the core material .
- the hydrophobic material is not limited to a material having solubility lower than the polymer and may be selected from most organic materials having compatibility with a monomer.
- examples of the hydrophobic material include C 4 -C 2 o aliphatic or aromatic hydrocarbons and their isomers such as hexane, heptane, cyclohexane, octane, nonane, decane, benzene, toluene, and xylene; C ⁇ 0 -C 2 o aliphatic or aromatic alcohols; C ⁇ 0 -C 2 o aliphatic or aromatic esters; C ⁇ 0 -C 2 o aliphatic or aromatic ethers; silicone oils, natural and synthetic oils, but are not limited thereto.
- the hydrophobic material may also be an ultrahydrophobe as will be described later.
- the hydrophobic material is used in an amount of 10 to 300 parts by weight, based on 100 parts by weight of the monomer. If the content of the hydrophobic material is less than 10 parts by weight, very small cores that cannot function as cores of microcapsules may be formed. On the other hand, if it exceeds 300 parts by weight, the ratio of a polymer shell to a core may be low, which makes it difficult to maintain particle shapes.
- the ultrahydrophobe serves to stabilize monomer particles.
- the ultrahydrophobe stabilizes miniemulsion particles composed of the monomer (s) and the hydrophobic material using an osmotic pressure. Finally, the polymerization occurs without a material exchange between the miniemulsion particles. As the polymerization proceeds, a phase separation occurs between a polymer and the hydrophobic material, thereby producing microcapsules .
- the ultrahydrophobe may be a material having 5Xl0 5 g/kg or less, and preferably 5XlO ⁇ 6 g/kg or less of solubility in 25 ° C water.
- the ultrahydrophobe may be one or more selected from the group consisting of C 12 ⁇ C 20 aliphatic hydrocarbons, C ⁇ 2 ⁇ C 2 o aliphatic alcohols, C ⁇ 2 ⁇ C 2 o alkyl acrylates, C 12 ⁇ C 2 o alkyl mercaptans, organic dyes, fluorinated alkanes, silicone oil compounds, natural oils, synthetic oils, oligomers with a molecular weight of 1,000 to 500,000, and polymers with a molecular weight of 1,000 to 500,000.
- Illustrate- examples of the ultrahydrophobe include, but are not limited to, hexadecane, heptadecane, octadecane, cetyl alcohol, isopropyl laurate, isopropyl palmitate, hexyl laurate, isopropyl myristate, myristyl myristate, cetyl myristate, 2-octyldecyl myristate, isopropyl palmitate, 2-ethylhexyl palmitate, butyl stearate, decyl oleate, 2-octyldodecyl oleate, polypropylene glycol monooleate, neopentyl glycol 2-ethylhexanoate, polyol ester oil, isostearate, triglyceride, coco fatty acid triglyceride, almond oil, apricot kernel oil, avocado oil, theobroma oil,
- the ultrahydrophobe may be used alone or in combination. More preferably, the ultrahydrophobe is hexadecane or cetyl alcohol . Preferably, the ultrahydrophobe is used in an amount of 0.1 to 10 parts by weight, based on 100 parts by weight of the monomer. If the content of the ultrahydrophobe is less than 0.1 parts by weight, a stable miniemulsion may not be obtained. On the other hand, if it exceeds 10 parts by weight, the ultrahydrophobe may act as an impurity after the polymerization. The ultrahydrophobe may also be encapsulated. - However, when the ultrahydrophobe is used in a small amount, it is incorporated in each polymer chain.
- Microcapsules prepared according to the method of the present invention are composed of a polymer shell encapsulating the hydrophobic material used as a core material.
- the polymer shell is derived from the following monomer selected according to the type of the hydrophobic material to be encapsulated.
- the polarity of a polymer and the interfacial tension between the polymer and water can vary according to the type of the monomer. There are reported many polymers derived from free-radically polymerizable monomers.
- the monomer forming the polymer shell is a free- radically polymerizable ethylenically unsaturated monomer. It is preferable to select the monomer so that the interfacial tension between a product polymer and water is smaller than that between a core material and water.
- the monomer may be one or more selected from the group consisting of methacrylate derivatives, acrylate derivatives, acrylic acid derivatives, methacrylonitriles, ethylenes, butadienes, isoprenes, styrenes, styrene derivatives, acrylonitrile derivatives, vinylester derivatives, and halogenated vinyl derivatives, and mercaptan derivatives.
- Examples, of the monomer include, but are not limited to, styrene, ⁇ -methyl styrene, p-nitro styrene, ethylvinylbenzene, vinylnaphthalene, methyl methacrylate, ethyl acrylate, hydroxyethyl methacrylate, n-butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, n- hexyl acrylate, n-hexyl methacrylate, ethylhexyl acrylate, ethylhexyl methacrylate, n-octyl acrylate, n-octyl methacrylate, decyl acrylate, decyl methacrylate, dodecyl acrylate, dodecyl methacrylate, stearyl acrylate, stearyl methacrylate, cyclohexy
- the crosslinking agent used as an auxiliary monomer in the microcapsule preparation method of the present invention serves to adjust the strength of a polymer shell and diffusion of a core material.
- the use and content of the crosslinking agent are determined by a desired strength of the polymer shells of the microcapsules and a desired diffusion rate of the core material .
- the crosslinking agent is a monomer that can be copolymerized with the monomer forming the polymer shell and has two or more unsaturated bonds .
- the crosslinking agent may be one or more selected from the group consisting of allyl methacrylate, ethylene glycol dimethacrylate, ethylene glycol diacrylate, butanediol diacrylate, butanediol dimethacrylate, neopentyl glycol dimethacrylate, hexanediol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetramethacrylate, and divinylbenzene .
- the crosslinking agent may be used in an amount of 0 to 10 parts by weight, and preferably 0.1 to 10 parts by weight, based on 100 parts by weight of the monomer. If the content of the crosslinking agent exceeds 10 parts by weight, large amounts of floating materials may be generated due to phase instability.
- the crosslinking agent may be added at the time of the miniemulsion preparation. However, in view of the use of a final product, the crosslinking agent may be added during the miniemulsion polymerization.
- the crosslinking agent may be added at a time or continuously. When a miniemulsion has a particle size as small as 500 nm or less, microcapsules can be created regardless of the addition time of the crosslinking agent.
- the addition of the crosslinking agent at the time of the miniemulsion preparation may form a network structure between chains of a polymer prior to phase separation between the polymer and the hydrophobic material.
- microcapsules may have a multi-pore structure in which several small pores are present. ' That is, when the sizes of miniemulsion particles are too large to form a core-shell structure, the addition of the crosslinking agent during the miniemulsion polymerization can form single-core microcapsules.
- the crosslinking agent may be added when a monomer to polymer conversion is 20 to 90%, and preferably 40 to 80%.
- the secondary initiator may be added during the miniemulsion polymerization to prevent lowering of the monomer to polymer conversion that may be caused when the oil-soluble initiator is used.
- the secondary initiator may be added when a monomer to polymer conversion is 50 to 95%, and more preferably 65 to 90%.
- the secondary initiator may be one or more selected from the group consisting of peroxides, persulfates, azo compounds, and redox compounds.
- the secondary initiator may be potassium perphosphate; sodium perborate; persulfates such as ammonium persulfate, sodium persulfate, and potassium persulfate; inorganic or organic peroxides such as H 2 0 2 , di-tert-butyl peroxide, cumene hydroperoxide, dicyclohexyl percarbonate, tert-butyl hydroperoxide, and p-menthane hydroperoxide; azo compounds such as azobisisobutyronitrile; or redox compounds, but is not limited thereto. These compounds mentioned as the secondary initiator may be used alone or in combination.
- the secondary initiator is used in an amount of 0.01 to 1 part by weight, based on 100 parts by weight of the monomer. If the content of the secondary initiator is less than 0.01 parts by weight, a polymerization rate may be decreased. On the other hand, if it exceeds 1 part by weight, the secondary initiator_may act as an impurity after the polymerization.
- the use of the secondary initiator in the method of the present invention can increase the yield of uniformly sized and shaped microcapsules without using a separate subsequent process.
- the hydrophilic comonomer is used to increase the hydrophilicity of a polymer produced by copolymerization with the monomer so that the hydrophobic material used as a core material is stably encapsulated by a polymer shell .
- the hydrophilic comonomer there may be used a compound copolymerizable with the monomer, preferably a compound compatible with the monomer.
- the hydrophilic comonomer serves to impart hydrophilicity to a polymer during phase separation between the hydrophobic material and the polymer.
- the polymer is easily phase- separated from the ultrahydrophobe and the hydrophobic material, thereby forming an interface with a dispersion medium such as water, so that the polymer constitutes an outer shell and the hydrophobic material constitutes an inner core.
- the hydrophilic comonomer is optionally used and its use and content are determined by the type of the monomer and the hydrophilic material.
- the hydrophilic comonomer may be an unsaturated carboxylic acid such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, fumaric acid, and maleic acid; or an unsaturated polycarboxylic acid alkyl ester having at least one carboxyl group such as itaconic acid monoethyl ester, fumaric acid monobutyl ester, and maleic acid monobutyl ester.
- these compounds mentioned as the hydrophilic comonomer may be used alone or in combination.
- the hydrophilic comonomer is used in an amount of 0.01 to 10 parts by weight, based on 100 parts by weight of the monomer.
- hydrophilicity may not be imparted to a polymer shell, which makes it impossible to form a stable core-shell structure.
- it exceeds 10 parts by weight a large amount of the monomer may be dissolved in an aqueous phase and then polymerized, thereby increasing generation of secondary particles.
- an emulsifier, deionized water, and other additives that can be commonly used in microcapsule preparation can be used in an appropriate amount without departing from the spirit and scope of the present invention.
- the emulsifier as used herein may be one or more selected from the group consisting of a non-ionic emulsifier, a cationic emulsifier, an anionic emulsifier, and an amphiphilic emulsifier.
- the emulsifier may be one or more selected from the group consisting of an anionic emulsifier such as sulfonates, carboxylic acids, succinates, sulfur succinates, and metal • salts thereof, for example alkylbenzenesulfonic acid, sodium alkylbenzenesulfonate, alkylsulfonic acid, sodium alkylsulfonate, sodium polyoxyethylenenonylphenylether sulfonate, sodium stearate, sodium dodecyl sulfate, sodium lauryl sulfate, sodium dodecyl succinate, and abietic acid; a cationic emulsifier such as higher amine halogenides, quaternary ammonium salts, and alkylpyridinium salts; a non-ionic emulsifier such as polyvinylalcohol and polyoxyethylenenonylphenylether; and an amphiphilic emulsifier, but is
- the emulsifier is used in an amount of 0.01 to 5.0 parts by weight, based on 100 parts by weight of the monomer. If the content of the emulsifier is less than 0.01 parts by weight, a stable miniemulsion may not be obtained. On the other hand, if it exceeds 5.0 parts by weight, emulsion particles may be decreased, thereby creating secondary particles. However, the content of- the emulsifier used must be determined by particle characteristics, such as particle size, of microcapsules.
- miniemulsion preparation there may be used a homogenizer generating a high energy, such as an ultrasonic generator, a Microfluidizer, or a Manton-Gaulin homogenizer, to prepare small miniemulsion particles.
- a homogenizer generating a high energy
- an ultrasonic generator such as an ultrasonic generator, a Microfluidizer, or a Manton-Gaulin homogenizer
- an emulsion may be prepared using a mechanical stirrer such as Turrax (Ika Laboratory T25 Basic) .
- a method for preparing microcapsules comprising the steps of: (a) mixing a monomer, an emulsifier, an ultrahydrophobe, a hydrophobic material, an initiator, and deionized water, to prepare a miniemulsion; and (b) polymerizing the miniemulsion to prepare the microcapsules .
- a method for preparing microcapsules comprising the steps of: (a) mixing a monomer, an emulsifier, an ultrahydrophobe, a hydrophobic material, a crosslinking agent, an initiator, and deionized water, to prepare a miniemulsion; and (b) polymerizing the miniemulsion to prepare the microcapsules .
- a method for preparing microcapsules comprising the steps of: (a) mixing a monomer, an emulsifier, an ultrahydrophobe, a hydrophobic material, a hydrophilic comonomer, an initiator, and deionized water, to prepare a miniemulsion; and (b) adding a crosslinking agent during polymerizing the miniemulsion to prepare the microcapsules.
- a method for preparing microcapsules comprising the steps of: (a) mixing a monomer, an emulsifier, an ultrahydrophobe, a hydrophobic material, a hydrophilic comonomer, a crosslinking agent, an oil-soluble initiator, and deionized water, to prepare a miniemulsion; and (b) polymerizing the miniemulsion to prepare the microcapsules .
- a method for preparing microcapsules comprising the steps of: (a) mixing a monomer, an emulsifier, an ultrahydrophobe, a hydrophobic material, a hydrophilic comonomer, a crosslinking agent, an oil-soluble initiator, and deionized water, to prepare a miniemulsion; (b) polymerizing the miniemulsion; and (c) adding a secondary initiator during the polymerization.
- Microcapsules prepared by the method of the present invention are in the form of latex with a particle size of 100 to 2,500 nm and a shell thickness of 10 to 1,000 nm.
- the volume of a liquid or solid core material encapsulated by the shell may be 10 to 80%, based on the total particle volume .
- FIGS. 1 through 3 are transmission electron microscopic (TEM) images of polymers prepared in Examples 1 through 3, respectively;
- FIGS. 4 through 6 are TEM images of polymers prepared in Examples 7 through 9, respectively;
- FIGS. 7 and 8 are TEM images of polymers prepared in Examples 10 and 11.
- TEM transmission electron microscopic
- Examples 1 through 3 All components were mixed according to composition ratios presented in Table 1 below and added to a Microfluidizer which is a homogenizer to obtain miniemulsion particles.
- the miniemulsion particles thus obtained were heated in a polymerization reactor at 65 ° C under a nitrogen atmosphere for 5 hours in a batch process to give latexes. Properties of the latexes thus obtained were analyzed and the analysis results are presented in Table 1 below.
- Latexes - were prepared in the same manner as in
- Example 1 according to composition ratios presented in Table 1 below and a property analysis for the latexes was performed. The analysis results are presented in Table 1 below. Table 1 : Latex compositions and properties
- Examples 4 through 9 Preparation of microcapsules by addition of crosslinking agent during miniemulsion polymerization
- All components except a crosslinking agent were mixed according to composition ratios presented in Table 2 below and added to a Microfluidizer which is a homogenizer to obtain miniemulsion particles.
- the miniemulsion particles thus obtained were heated in a polymerization reactor at 90°C under a nitrogen atmosphere in a batch process. At this time, the crosslinking agent was added and the resultant solution was incubated for 10 hours to give latexes. Properties of the latexes thus obtained were analyzed and the analysis results are presented in Table 2 below.
- a miniemulsion having a large particle size of more than 1 j_an can create microcapsules with a non-uniform shell and a poorly distributed core during the polymerization.
- This problem can be solved by addition of a hydrophilic comonomer that serves to decreases an interfacial tension between a polymer and water, thereby forming a core-shell structure.
- Examples 10 through 12 Preparation of microcapsules using hydrophilic comonomer and oil-soluble initiator [Examples 10 through 12] All components were mixed according to composition ratios presented in Table 3 below and added to a homogenizer to obtain a miniemulsion. The miniemulsion thus obtained were heated in a polymerization reactor at 90°C under a nitrogen atmosphere for 10 hours in a batch process to give latexes. Properties of the latexes thus obtained were analyzed and the analysis results are presented in Table 3 below.
- Latex was prepared in the same manner as in Example 10 except that a water-soluble initiator was used instead of an oil-soluble initiator and then centrifuged. The centrifugation result is presented in Table 3 below.
- Examples 13 through 15 Preparation of microcapsules using secondary initiator [Examples 13 through 15] All components except a secondary initiator were mixed according to composition ratios presented in Table 4 below and added to a Microfluidizer which is a homogenizer to obtain a miniemulsion. The miniemulsion thus obtained were heated in a polymerization reactor at 90°C under a nitrogen atmosphere for 10 hours in a batch process. The secondary initiator was added during the polymerization and the resultant solution was incubated for 2 hours to give latexes.
- Table 4 Latex compositions and properties
- the latexes of Examples 13 through 15 were prepared by mixing a hydrophobic material, a monomer, a crosslinking agent, a hydrophilic comonomer, an ultrahydrophobe, an emulsifier, and deionized water, to obtain a miniemulsion, and adding a secondary initiator during polymerizing the miniemulsion in the presence of an oil-soluble initiator.
- the total conversion of monomer to polymer was about 100%. This means that after microcapsule preparation, few monomers remained on the polymer. Therefore, ⁇ a separate subsequent process for removing a residual monomer is not required.
- microcapsules of the present invention miniemulsion particles prepared at an early stage of the method are stabilized by an osmotic pressure generated by an ultrahydrophobe. Therefore, a hydrophobic material which is soluble in monomer particles but not in a polymer, can be encapsulated which makes it possible to produce spherical microcapsules. Furthermore, since a core material encapsulated in the microcapsules of the present invention is not particularly limited, the microcapsules can be used in various fields. That is, various functional substances such as a pharmacological substance and a pigment substance can be used as a core material.
- an easily removable lower molecular material can also be used as a core material, thereby producing hollow microcapsules.
- Addition of a crosslinking agent during polymerization can prevent formation of secondary particles, thereby producing uniformly sized and shaped microcapsules.
- addition of a secondary initiator during polymerization can produce uniformly sized and shaped microcapsules in high yield without a separate subsequent process .
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Application Number | Priority Date | Filing Date | Title |
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US10/563,523 US20060281834A1 (en) | 2003-07-03 | 2004-07-03 | Method for preparing microcapsule by miniemulsion polymerization |
EP04774070A EP1654056A4 (en) | 2003-07-03 | 2004-07-03 | Method for preparing microcapsule by miniemulsion polymerization |
CNA2004800190161A CN1816389A (en) | 2003-07-03 | 2004-07-03 | Method for preparing microcapsule by miniemulsion polymerization |
JP2006518540A JP2007528286A (en) | 2003-07-03 | 2004-07-03 | Method for producing microcapsules through miniemulsion polymerization |
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KR1020030055845A KR100694329B1 (en) | 2003-08-12 | 2003-08-12 | Method for Preparing a Microcapsule Containing Oil Inside |
KR10-2003-0055845 | 2003-08-12 | ||
KR10-2003-0077920A KR100508967B1 (en) | 2003-11-05 | 2003-11-05 | Method for Preparing a Microcapsule with Uniform Size and Morphology |
KR10-2003-0077920 | 2003-11-05 | ||
KR1020040003651A KR100543658B1 (en) | 2004-01-19 | 2004-01-19 | Method for Preparing Microcapsule Having Uniform Size and Morphology with the High Conversion Rate |
KR10-2004-0003651 | 2004-01-19 |
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WO2005002719A1 true WO2005002719A1 (en) | 2005-01-13 |
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PCT/KR2004/001644 WO2005002719A1 (en) | 2003-07-03 | 2004-07-03 | Method for preparing microcapsule by miniemulsion polymerization |
Country Status (5)
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US (1) | US20060281834A1 (en) |
EP (1) | EP1654056A4 (en) |
JP (1) | JP2007528286A (en) |
CN (1) | CN1816389A (en) |
WO (1) | WO2005002719A1 (en) |
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EP1773937A1 (en) * | 2004-12-08 | 2007-04-18 | LG Chem, Ltd. | Processing aid for pvc and method for manufacturing the same |
EP1773937A4 (en) * | 2004-12-08 | 2009-01-14 | Lg Chemical Ltd | Processing aid for pvc and method for manufacturing the same |
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WO2018172434A3 (en) * | 2017-03-21 | 2018-12-27 | Capsum | Method for producing capsules comprising at least one water-soluble or hydrophilic substance, and resulting capsules |
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US11234911B2 (en) | 2017-03-21 | 2022-02-01 | Capsum | Method for producing capsules comprising at least one volatile compound, and resulting capsules |
CN110475607B (en) * | 2017-03-21 | 2022-06-10 | 卡莉西亚公司 | Method for preparing capsules containing at least one water-soluble or hydrophilic substance and capsules obtained by said method |
US11540979B2 (en) | 2017-03-21 | 2023-01-03 | Capsum | Method for producing capsules comprising at least one water-soluble or hydrophilic substance, and resulting capsules |
WO2024023598A1 (en) | 2022-07-25 | 2024-02-01 | S H Kelkar And Company Limited | Microcapsules and encapsulation thereof |
Also Published As
Publication number | Publication date |
---|---|
EP1654056A1 (en) | 2006-05-10 |
JP2007528286A (en) | 2007-10-11 |
EP1654056A4 (en) | 2007-08-08 |
CN1816389A (en) | 2006-08-09 |
US20060281834A1 (en) | 2006-12-14 |
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