Method for preparing microcapsule powder and microcapsule powder using same

Abstract

The present invention relates to: a method for preparing microcapsule powder including a styrene-based shell material and a nematic liquid crystal as a core material; and microcapsule powder prepared thereby. A styrene-based shell is formed by combining solution polymerization and emulsion dispersion processes, a silane-based material (vinyl silane, epoxy silane, etc.) is added to enhance chemical resistance and heat resistance of the shell, and finally the product is converted into a powder form. The present invention significantly improves chemical and physical stability of a shell, increases compatibility with various adhesives and coating systems, and simplifies a production process to achieve a high production yield. Accordingly, the microcapsule powder of the present invention provides excellent durability and performance compared to existing technologies in various application fields, such as displays, smart windows, and functional coatings.

Description

Method for manufacturing microcapsule powder and microcapsule powder using the same

[0001] The present invention relates to a method for manufacturing microcapsule powder and microcapsule powder using the same, and more specifically, to a method for manufacturing microcapsule powder comprising a styrene-based shell and a nematic liquid crystal as a core, and microcapsule powder using the same.

[0002]

[0003] Across various industries, microcapsule technology plays a crucial role in diverse fields such as coatings, drug delivery, and chemical material protection. Microcapsules form shell structures to protect core materials and exhibit desired properties, and this technology is becoming increasingly sophisticated. In particular, microcapsules utilizing nematic liquid crystals as core materials are attracting attention as important materials in high-tech industries, such as displays and window coatings, as they can provide smart functions like light transmittance control.

[0004] Currently, various methods are used to manufacture microcapsules. A representative method widely utilized involves encapsulating a core using shell materials such as gelatin, PMMA (Polymethyl Methacrylate), and PLA (Polylactic Acid). These technologies fundamentally perform coating processes by mixing with water-based adhesives or curing via heat or UV. Additionally, nematic liquid crystals have been mixed with prepolymers and formed into droplets, which have been applied to various products.

[0005] However, conventional technology has the following limitations. First, gelatin and PMMA-based capsules used as shell materials have low durability against high-temperature environments or chemical stresses such as organic solvents, making them prone to breakage. Second, the method of mixing prepolymers containing nematic liquid crystals is limited to large-scale industrial applications due to the complex manufacturing process and low production yield. Third, shells manufactured using conventional methods have limited compatibility with various adhesives and coating systems, making them usable only in specific application fields.

[0006]

[0007] In order to solve the problems of the conventional technology described above, we intend to overcome the limitations of existing shell materials by manufacturing microcapsules containing a nematic liquid crystal as a core using a styrene-based shell material, thereby significantly improving chemical resistance and heat resistance, increasing compatibility with various adhesives and coating processes, and strengthening the durability of the shell by adding a silane-based material.

[0008] In addition, the present invention aims to provide a microcapsule powder that operates stably even in organic solvents and high-temperature environments while maintaining high productivity through a simple process.

[0009] The technical problems that the invention aims to solve are not limited to those mentioned above, and other unmentioned technical problems will be clearly understood by those skilled in the art to which the invention belongs from the description below.

[0010]

[0011] To achieve the above objectives, a method for manufacturing microcapsule powder according to one embodiment of the present invention comprises: an aqueous solution preparation step of preparing an aqueous solution mixed with water and a surfactant by stirring; an emulsion preparation step of preparing an emulsion solution mixed with styrene, divinylbenzene, and n-hexadecane by stirring; an emulsion formation step of mixing the aqueous solution and the emulsion solution, adding silica and glycerol, and stirring with an emulsion disperser to form an emulsion; a microcapsule formation step of adding azobisisobutyronitrile (AIBN) and a silane-based substance to the formed emulsion in a heating mantle and stirring to form a microcapsule composed of a styrene-based shell and a nematic liquid crystal as a core; and a powder conversion step of washing and drying the microcapsule with a centrifuge to convert it into a powder form.

[0012] In addition, a method for manufacturing microcapsule powder according to one embodiment of the present invention is characterized in that the aqueous solution preparation step is stirred at 75°C for 2 hours, the emulsion preparation step is stirred at 65°C for 10 minutes, the microcapsule formation step is stirred at 5 hours, and the washing and drying step is washed three times with a centrifuge.

[0013] In addition, a method for manufacturing microcapsule powder according to one embodiment of the present invention is characterized in that the surfactant is sodium dodecyl sulfate (SDS).

[0014] In addition, a method for manufacturing microcapsule powder according to one embodiment of the present invention is characterized in that the silane-based material is at least one of amino silane (3-aminopropyltriethoxysilane) or epoxy silane (3-glycidoxypropyltrimethoxysilane).

[0015] Meanwhile, a microcapsule powder according to one embodiment of the present invention provides a microcapsule powder manufactured by any one of the microcapsule powder manufacturing methods described above.

[0016] In addition, a microcapsule powder according to one embodiment of the present invention is characterized by being composed of a styrene-based shell and a nematic liquid crystal as a core.

[0017]

[0018] By means of the solution to the above problem, the method for manufacturing microcapsule powder and the microcapsule powder using the same according to the present invention overcome the limitations of chemical resistance and heat resistance of shell materials composed of existing gelatin, PMMA, PLA, etc., and have the effect of operating stably even in chemical stress environments such as high temperatures and organic solvents.

[0019] In addition, chemical resistance was enhanced by using styrene and divinylbenzene as shell materials and adding silane-based materials (amino silane (3-aminopropyltriethoxysilane), epoxy silane (3-glycidoxypropyltrimethoxysilane, etc.)), and heat resistance was significantly improved by using reinforcing materials such as silica and glycerol.

[0020] In addition, by combining solution polymerization and emulsion dispersion processes, the complex manufacturing process was simplified and high production yields were achieved, and the creation of powder-form microcapsules enhanced compatibility with various adhesives and coating systems.

[0021] Furthermore, the present invention can be utilized in various industrial fields such as displays, smart windows, and functional coatings, and provides superior performance and application possibilities compared to existing technologies.

[0022]

[0023] FIG. 1 is a block diagram of a method for manufacturing microcapsule powder according to one embodiment of the present invention.

[0024] Figure 2 is a photograph of a microcapsule in an aqueous solution state before washing according to one embodiment of the present invention.

[0025] Figure 3 is a photograph of a microcapsule in a dried state after washing in an aqueous solution state according to one embodiment of the present invention.

[0026] Figure 4 is a photograph showing an emulsion dispersion according to one embodiment of the present invention.

[0027] Figure 5 is a photograph of a microcapsule in an aqueous solution according to one embodiment of the present invention.

[0028] Figure 6 is a photograph of microcapsule powder after drying according to one embodiment of the present invention.

[0029] Figure 7 is a photograph of the finished microcapsule powder according to one embodiment of the present invention.

[0030] Figure 8 is a photograph taken before applying a temperature of 130°C to test liquid crystal operation after dispersing the finished microcapsule powder according to one embodiment of the present invention in water.

[0031] Figure 9 is a photograph taken after applying a temperature of 130°C to test liquid crystal operation after dispersing the finished microcapsule powder according to one embodiment of the present invention in water.

[0032]

[0033] Specific embodiments of the present invention will be described in detail below with reference to the drawings. However, the concept of the present invention is not limited to the presented embodiments. Those skilled in the art who understand the concept of the present invention may easily propose other inventions that are inferior or other embodiments included within the scope of the concept of the present invention by adding, changing, or deleting other components within the same scope of the concept, and such are also to be considered to be included within the scope of the concept of the present invention.

[0034]

[0035] The present invention relates to a method for manufacturing microcapsule powder and microcapsule powder using the same.

[0036] FIG. 1 is a block diagram of a method for manufacturing microcapsule powder according to one embodiment of the present invention.

[0037] A method for manufacturing microcapsule powder according to one embodiment of the present invention comprises: an aqueous solution preparation step of preparing an aqueous solution mixed with water and a surfactant by stirring; an emulsion preparation step of preparing an emulsion solution mixed with styrene, divinylbenzene, and n-hexadecane by stirring; an emulsion formation step of mixing the aqueous solution and the emulsion solution, adding silica and glycerol, and stirring with an emulsion disperser to form an emulsion; a microcapsule formation step of adding azobisisobutyronitrile (AIBN) and a silane-based substance to the formed emulsion in a heating mantle and stirring to form a microcapsule composed of a styrene-based shell and a nematic liquid crystal as a core; and a powder conversion step of washing and drying the microcapsule with a centrifuge to convert it into a powder form.

[0038] In the aqueous solution preparation step (100), an aqueous solution mixed with water and a surfactant is stirred. The surfactant helps to emulsify and stabilize non-polar monomers (such as styrene).

[0039] The emulsion preparation step (200) involves mixing and stirring styrene, divinylbenzene (DVB), and n-hexadecane. Styrene and DVB act as shell-forming agents, and n-hexadecane acts as an emulsifier to increase stability.

[0040] The emulsion formation step (300) involves mixing an aqueous solution and an emulsion, adding silica and glycerol, and stirring with an emulsion disperser to produce an emulsion. This is a process of homogeneously dispersing the monomers required for shell formation. It is a step of forming micelles while determining the size of the microcapsules.

[0041] Silica and glycerol are added to increase heat resistance; silica provides high heat resistance, while glycerol increases the elasticity and stability of the shell. This step prevents the shell from breaking in high-temperature environments and improves reliability in specific applications such as smart windows.

[0042] If the heat resistance of the microcapsule powder is not improved, the shell does not break in an aqueous solution because the surfactant (sodium nodecyl sulfate) protects the outside of the shell, but a problem arises where the shell breaks during low-temperature drying. If a large amount of divinylbenzene (DVB) is added to thicken the shell to prevent breakage, there is a problem of a large amount of impurities being generated during the polymerization reaction. To solve this problem, silica and glycerol are added to increase heat resistance.

[0043]

[0044] The microcapsule formation step (400) involves adding azobisisobutyronitrile (AIBN), which is used as an initiator in a heating mantle, and a silane-based material that enhances chemical resistance to the formed emulsion and stirring to form microcapsules consisting of a styrene-based shell and a nematic liquid crystal as a core. The shell is formed through a polymerization reaction, and durability against organic solvents and chemical stress is improved.

[0045]

[0046] Figure 2 is a photograph of a microcapsule in an aqueous solution state before washing according to one embodiment of the present invention.

[0047] Figure 3 is a photograph of a microcapsule in a dried state after washing in an aqueous solution state according to one embodiment of the present invention.

[0048] The powder conversion step (700) converts the generated microcapsules into a powder form by washing and drying them with a centrifuge.

[0049] Before washing, the microcapsules are distributed within an aqueous solution, while after washing, they exist in a powder state. The reason for washing is to increase the purity of the capsules by removing surfactants, solvent residues, and unreacted substances remaining on the surface.

[0050]

[0051] In addition, a method for manufacturing microcapsule powder according to one embodiment of the present invention is characterized in that the aqueous solution preparation step is stirred at 75°C for 2 hours, the emulsion preparation step is stirred at 65°C for 10 minutes, the microcapsule formation step is stirred for 5 hours, and the washing and drying step is washed three times with a centrifuge.

[0052] The stirring time and temperature conditions of each process have a significant impact on the polymerization reaction and emulsion stability. In particular, stirring for 5 hours in a heating mantle ensures the uniformity and durability of shell formation.

[0053] The reason for stirring at 500 rpm at 75°C during the aqueous solution preparation stage is to achieve viscosity for SDS dissolution and micelle formation, and to ensure a uniform distribution. If the temperature is lower than 75°C, SDS is not evenly dispersed, and if the temperature is higher, bubbles are generated and the SDS interfacial tension decreases.

[0054] If the temperature is below 75°C during the aqueous solution preparation stage, the dissolution and activation of the surfactant may be incomplete, making it difficult to stably emulsify the monomer (such as styrene). Additionally, the stability of the emulsion may be reduced, leading to the formation of uneven capsule sizes during the shell formation process. This results in a wider size distribution of the powder, which can adversely affect the optical performance of specific applications, such as smart windows.

[0055] If the temperature exceeds 75°C, the surfactant may thermally decompose or excessive bubbles may form due to the high temperature, and the viscosity of the emulsion solution may change, negatively affecting stable shell formation. This may lead to a decrease in the physical stability of the shell and a reduction in production yield.

[0056] In addition, if the duration is less than 2 hours, the surfactant is not sufficiently dissolved, so it cannot function effectively, and non-polar substances such as styrene are not uniformly dispersed in the aqueous solution, which may reduce emulsion stability. This can lead to non-uniform capsule size during the shell formation process, resulting in reduced durability and performance.

[0057] If the duration exceeds 2 hours, the surfactant may be excessively dispersed, the surfactant effect may be reduced due to excessive interaction with water molecules, and the dispersion efficiency may be lowered during the emulsion formation stage due to high viscosity issues. This may lead to reduced stability of the emulsion and a decrease in the uniformity of the shell structure.

[0058]

[0059] If the emulsion preparation stage takes less than 2 hours, uniform mixing of styrene and divinylbenzene is not achieved, and the free radical initiator (AIBN) is not sufficiently dispersed, which may reduce the efficiency of the polymerization reaction. This increases the likelihood of incomplete formation of the shell structure or damage to some capsules.

[0060] If the duration exceeds 2 hours, excessive stirring may initiate premature polymerization reactions between monomers, and excessive aggregation of polymers may increase the viscosity of the emulsion, negatively affecting subsequent processes. This leads to a decrease in shell homogeneity and may cause clogging during the production process.

[0061]

[0062] If the temperature is below 65°C during the emulsion formation stage, the surfactant (SDS) is not sufficiently activated, so the monomers (styrene, divinylbenzene) are not stably dispersed, which may result in the formation of large and non-uniform emulsion particles. Additionally, if the surface tension of the monomers is not sufficiently lowered, the emulsion may separate or undergo phase separation over time, and the capsule thickness and size may be formed non-uniformly.

[0063] If the temperature exceeds 65°C, monomers (styrene, divinylbenzene) may undergo premature polymerization reactions during the emulsion stage, which can lead to a non-uniform capsule structure. If stirred at excessive temperatures, the surfactant may thermally decompose or its function may be weakened, which can cause the viscosity of the emulsion to increase excessively.

[0064] In addition, if the time is less than 10 minutes, the aqueous solution and the emulsion solution are not sufficiently mixed, resulting in reduced stability of the emulsion and uneven dispersion of monomers during shell formation, which leads to unevenness in capsule size and thickness. This can cause problems such as reduced product quality and reduced functionality (e.g., optical performance).

[0065] If the duration exceeds 10 minutes, excessive emulsification may cause the emulsified particles to become excessively small or some particles to aggregate, potentially inducing an unbalanced polymerization reaction during the shell formation stage. This may lead to problems such as reduced shell strength and decreased chemical resistance.

[0066]

[0067] If the time taken during the microcapsule formation stage is less than 5 hours, the polymerization reaction is not completed, which may result in insufficient physical strength and chemical stability of the shell, and some capsules may break or the core material (nematic liquid crystal) may leak out. This can significantly reduce the chemical and heat resistance of the capsules, thereby limiting their potential applications.

[0068] If the time exceeds 5 hours, excessive polymerization may cause the shell thickness to increase inefficiently or cracks to occur, and changes in the surface properties of the capsule may lead to reduced adhesion during the subsequent addition of silane-based materials. This may result in reduced capsule production efficiency and excessive energy consumption.

[0069]

[0070] If the capsule is washed less than three times with a centrifuge during the washing and drying steps, there is a high possibility that the surfactant, monomer (styrene, divinylbenzene), and other reaction by-products used will remain on the capsule surface, which reduces the chemical and heat resistance of the capsule and may cause chemical reactions or side effects in the application product.

[0071] Excessive washing exceeding three times applies mechanical stress to the surface of microcapsules, increasing the likelihood of the shell cracking or breaking, and causing problems such as an inefficiently prolonged production process and increased production costs. Additionally, reactivity with silane-based materials and other reinforcing coating materials may decrease.

[0072]

[0073] Therefore, stirring at 75°C for 2 hours, emulsion preparation for 2 hours, emulsification at 65°C for 10 minutes, capsule formation for 5 hours, and washing three times with a centrifuge are optimized conditions for ensuring chemical and physical stability in each process and creating a uniform shell and core structure. In terms of reproducibility and cost-effectiveness, microcapsules manufactured under critical conditions possess uniform size, high chemical and heat resistance, and guarantee efficiency in mass production processes. Furthermore, by preventing problems that may occur when conditions fall below or exceed critical conditions, it ensures the quality required for high-performance smart window and functional coating applications.

[0074]

[0075] In addition, a method for manufacturing microcapsule powder according to one embodiment of the present invention is characterized in that the surfactant is sodium dodecyl sulfate (SDS).

[0076] Sodium dodecyl sulfate (SDS) can be used as a surfactant. SDS is a substance that promotes the emulsification of monomers and helps form a stable emulsion. SDS helps non-polar substances, such as styrene, to be stably dispersed in an aqueous solution. This increases polymerization efficiency during the shell formation stage and directly affects the size and uniformity of the resulting capsules.

[0077]

[0078] In addition, a method for manufacturing microcapsule powder according to one embodiment of the present invention is characterized in that the silane-based material is at least one of amino silane (3-aminopropyltriethoxysilane) or epoxy silane (3-glycidoxypropyltrimethoxysilane).

[0079] Silane-based materials improve chemical resistance by strengthening the chemical bonds of the shell.

[0080] In order to use in organic solvents, amino silane (3-aminopropyl)triethoxysilane or epoxy silane (3-glycidoxypropyl)trimethoxysilane, etc., can be added for shell reinforcement and surface modification to form strong bonds on the surface, thereby increasing the durability and stability of the capsule.

[0081] Amino silanes (3-aminopropyltriethoxysilanes) form strong chemical bonds with amino groups, which enhance durability against physical / chemical stress and increase stability, especially in environments requiring heat and moisture resistance.

[0082] Epoxy silane (3-glycidoxypropyltrimethoxysilane) has epoxy functional groups that provide high chemical stability and enhance chemical resistance, and can maintain physical stability even in solvents such as methyl ethyl ketone and high-temperature environments.

[0083] In addition, the silane-based material may further include at least one selected from the group consisting of vinyl silane, methoxy silane, and ethoxy silane.

[0084] Vinyl silane promotes bonding between polymers and inorganic materials, while methoxy / ethoxy silane improves the water and heat resistance of the shell. Through the use of various silane-based materials, the performance of the shell can be adjusted according to the application.

[0085]

[0086] Meanwhile, a microcapsule powder according to one embodiment of the present invention provides a microcapsule powder manufactured by any one of the microcapsule powder manufacturing methods described above.

[0087] In addition, a microcapsule powder according to one embodiment of the present invention is characterized by being composed of a styrene-based shell and a nematic liquid crystal as a core.

[0088] A microcapsule according to one embodiment of the present invention uses a styrene-based shell, has enhanced chemical resistance and heat resistance, and includes a nematic liquid crystal as a core material to exhibit optical properties. This is clearly differentiated from existing gelatin and PMMA-based capsules.

[0089]

[0090] In the following, an experiment on a method for manufacturing microcapsule powder according to one embodiment of the present invention is performed, and the experimental results are explained in detail using examples.

[0091]

[0092] [Example 1] Preparation of microcapsule powder (excluding shell reinforcement step)

[0093] Preparation of aqueous solution: 2 g of the surfactant Sodium Dodecyl Sulfate (SDS) was added to 100 g of water, heated to 75°C, and mixed with a stirrer for 2 hours to prepare a homogeneous aqueous solution.

[0094] Preparation of emulsion solution: 50 g of styrene, 5 g of divinylbenzene (DVB), and 10 g of n-hexadecane were mixed and stirred with a stirrer for 2 hours to prepare an emulsion solution.

[0095] Emulsion formation: The prepared aqueous solution and emulsion solution were mixed in a ratio of 4:1, and then stirred with an emulsion disperser at 65°C for 10 minutes to form an emulsion.

[0096] Microcapsule formation: The emulsion was placed in a heating mantle, 0.5 g of azobisisobutyronitrile (AIBN) was added, and the mixture was stirred for 5 hours to form microcapsules containing a styrene-based shell and a nematic liquid crystal as a core.

[0097] Powder conversion: Microcapsules were washed three times repeatedly with a centrifuge to remove residual impurities, and then dried in a dryer at 60°C for 12 hours to be converted into a powder form.

[0098]

[0099] [Example 2] Enhanced Chemical Resistance

[0100] Shell reinforcement: Prepared in the same manner as in Example 1, but with the addition of a silane-based material (Vinyl Silane 1 g) during the microcapsule formation step to reinforce the chemical resistance of the shell.

[0101]

[0102] [Example 3] Enhanced heat resistance

[0103] Coating: Prepared in the same manner as in Example 2, but with 2 g of silica and 2 g of glycerol added during the emulsion formation step to further enhance heat resistance.

[0104]

[0105] [Experimental Example 1] Chemical Resistance Test

[0106] 1 g of each of the microcapsules prepared in Examples 1 and 2 was placed in methyl ethyl ketone (MEK) solvent and stirred for 24 hours.

[0107] After stirring, the capsule's breakage and solvent resistance were checked.

[0108] Example 1, which did not include a shell reinforcement step to enhance chemical resistance, had cracks in part of the shell, while Example 2, which included a shell reinforcement step to enhance chemical resistance, maintained complete chemical resistance without damage to the shell.

[0109]

[0110] [Experimental Example 2] Heat Resistance Test

[0111] The structural stability of the shell of the microcapsules prepared in Examples 2 and 3 was confirmed after heating them in a 200°C environment for 2 hours.

[0112] Example 2, which did not contain silica and glycerol for heat resistance enhancement, showed deformation in part of the shell, while Example 3, which contained silica and glycerol, maintained the structural stability of the shell.

[0113]

[0114] [Experimental Example 3] Capsule Uniformity and Size Analysis

[0115] The microcapsules of Example 1 and Example 3 were measured using an optical microscope and a laser particle size analyzer to analyze the capsule size and uniformity.

[0116] In Example 1, the capsule size distribution was 5 to 20 μm, and in Example 3, the capsule size distribution was narrowed to 5 to 15 μm, and the thickness of the shell was reinforced. Through this, it was confirmed that the chemical resistance and heat resistance of the microcapsules in Example 3, which had silane-based materials and silica added, were significantly improved. Therefore, the method for manufacturing microcapsule powder according to one embodiment of the present invention provides uniform and highly durable microcapsules, and has been proven to have superior production efficiency and quality compared to conventional manufacturing methods.

[0117]

[0118] As such, those skilled in the art to which the present invention pertains will understand that the technical configuration of the present invention described above can be implemented in other specific forms without altering the technical concept or essential features of the present invention.

[0119] Therefore, the embodiments described above should be understood as illustrative in all respects and not limiting, and the scope of the invention is defined by the claims set forth below rather than by the detailed description above, and all modifications or variations derived from the meaning and scope of the claims and equivalent concepts thereof should be interpreted as being included within the scope of the invention.

[0120]

[0121] The present invention can be utilized in various industrial fields, such as displays, smart windows, and functional coatings.

Claims

1. Aqueous solution preparation step of preparing an aqueous solution mixed with water and surfactant by stirring; An emulsion preparation step of preparing an emulsion solution by stirring a mixture of styrene, divinylbenzene, and n-hexadecane; An emulsion formation step comprising mixing the above aqueous solution and the above emulsion solution, adding silica and glycerol, and stirring with an emulsion disperser to form an emulsion; A microcapsule formation step of adding azobisisobutyronitrile (AIBN) and a silane-based material to the above-formed emulsion in a heating mantle and stirring to form a microcapsule comprising a styrene-based shell and a nematic liquid crystal core; and A powder conversion step comprising washing and drying the above microcapsules with a centrifuge to convert them into a powder form; Method for manufacturing microcapsule powder.

2. In Paragraph 1, The above aqueous solution preparation step involves stirring at 75°C for 2 hours, and The above emulsion preparation step involves stirring for 2 hours, and The above emulsion formation step involves stirring at 65°C for 10 minutes, and The above microcapsule formation step involves stirring for 5 hours, and The above washing and drying steps are characterized by washing three times with a centrifuge. Method for manufacturing microcapsule powder.

3. In Paragraph 2, The above surfactant is characterized as being sodium dodecyl sulfate (SDS, Sodium Dodecyl Sulfate), Method for manufacturing microcapsule powder.

4. In Paragraph 2, The above silane-based material is, Characterized as being at least one of an amino silane (3-aminopropyltriethoxysilane) or an epoxy silane (3-glycidoxypropyltrimethoxysilane), Method for manufacturing microcapsule powder.

5. Microcapsule powder manufactured by a method for manufacturing microcapsule powder according to at least one of claims 1 to 4.

6. In Paragraph 5, The above microcapsule powder is, Characterized by comprising a styrene-based shell and a nematic liquid crystal as a core, Microcapsule powder.

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