A capsule with dual temperature indication function and its preparation method

Abstract

This invention discloses a capsule with dual temperature indication function and its preparation method. The capsule can achieve cold storage and temperature warning in both freezing (-25~-15℃) and low-temperature refrigeration (2~8℃). Specifically, it consists of a first and a second reversible thermochromic microcapsule and a framework material forming the core and outer core, respectively, and is encapsulated by a calcium alginate shell. The first reversible thermochromic microcapsule uses a compound of tetradecane-dodecyl alcohol eutectic mixture and a temperature-sensitive material as the core material and high-transparency melamine resin as the wall material; the second reversible thermochromic microcapsule uses a compound of dodecane-nonyl alcohol eutectic mixture and a temperature-sensitive material as the core material and high-transparency melamine resin as the wall material. This invention broadens the selection range of phase change materials that can be used with temperature-sensitive materials, achieves more flexible color-changing temperature selection, enables continuous capsule production, and optimizes the capsule's morphology, particle size, and color-changing performance.

Description

Technical Field

[0001] This invention belongs to the field of phase change cold storage technology, specifically relating to a capsule with dual temperature indication function and its preparation method. Background Technology

[0002] With the rapid development of the food, fresh produce, and medical industries, cold chain logistics has become an important part of modern life and industry. However, diesel engines often cause significant energy waste during cold chain transportation. As of 2021, China had 340,000 refrigerated transport vehicles. Furthermore, issues such as refrigerant leakage, limited capacity, low efficiency, and pollution also restrict the application of refrigerants in transportation. To address this problem, phase change energy storage technology has emerged, which can significantly reduce environmental impact and achieve latent heat storage and temperature regulation at near-constant temperatures. Microencapsulation technology is the most widely used, as it can increase heat transfer area, improve thermal conductivity, reduce supercooling, and prevent leakage during application.

[0003] Thermal damage and freezing damage are two major causes of transported goods failure. Incorporating trace amounts of thermosensitive materials into phase change materials (PCMs) to achieve temperature indication through color changes can effectively prevent these problems. However, this method is not suitable for microcapsules with alkanes as the core material because the solubility of thermochromic materials in alkanes is too low, making temperature indication impossible. To address this issue, patent CN 114369448 A, entitled "An External Immobilization Method for Preparing Reversible Thermochromic Microcapsules," describes a method that separately encapsulates alkane (PCM) as the phase change energy storage material with a reversible thermochromic layer. This invention employs a eutectic alkane-alcohol composite system, where alkane is the primary energy storage material and alcohol serves as the solvent for the thermochromic material. This allows for integrated encapsulation of the alkane and thermochromic material, and the eutectic mixture results in a lower melting point, improving the cold storage quality of the reversible thermochromic energy storage capsule and expanding its application in cryogenic fields.

[0004] Furthermore, research on capsules with dual temperature indication capabilities, which could change color at different temperatures to provide more information and functionality, is limited.

[0005] Patent CN 115888572 A, entitled "A Microcapsule with Multi-Color Gamut Indication and Temperature Regulation Function," comprises a core of reversible thermochromic material, phase change material, and water-soluble dye, and an outer layer covering the core. Patent CN 114656948 A, entitled "A Color-Matching Thermochromic Microcapsule and its Preparation Method," comprises a core containing reversible thermochromic material and an outer layer covering the core. The core includes a thermochromic material and a solvent-based dye complex compounded with it, while the outer layer includes an inner temperature-regulating shell and an outer transparent coating shell. These existing reversible thermochromic capsules achieve color gamut expansion by adding dyes, but only indicate a single temperature zone, failing to meet the dual-temperature zone warning needs of pharmaceuticals, food, and biological products under different storage environments (frozen (-25~-15℃) and refrigerated (2~8℃)). Summary of the Invention

[0006] The technical problem to be solved by this invention is to address the shortcomings of the prior art by providing a capsule with dual temperature indication function and its preparation method. The resulting capsule consists of two reversible thermochromic microcapsules and a framework material forming the core and outer core, respectively, and is encapsulated by a calcium alginate shell. The core material of the two reversible thermochromic microcapsules is a composite of different alkane-fatty alcohol eutectic mixtures and a temperature-sensitive material, while the wall material is a highly transparent melamine resin. Due to the addition of fatty alcohols, the alkane-fatty alcohol eutectic mixture, as an energy storage material, solves the problem of temperature-sensitive materials... The incompatibility between the material and nonpolar alkane compounds broadens the selection range of phase change materials that can be used with temperature-sensitive materials, enabling more flexible selection of color-changing temperatures. Furthermore, this invention utilizes microfluidic technology to achieve continuous production of capsules, and optimizes the morphology, particle size, and color-changing properties of capsules by controlling the composition of the core and outer core, the ratio of the two phases during production, and the temperature of the wall material polymerization reaction. This meets the requirements for cold storage and temperature indication in pharmaceuticals, food, and biological products under frozen (-25~-15℃) and low-temperature refrigeration (2~8℃) environments.

[0007] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing a capsule with dual temperature indication function, comprising:

[0009] Step 1: Prepare a reversible thermochromic cold storage microcapsule with a core material of a tetradecane-dodecyl alcohol eutectic mixture and a thermosensitive material, and a wall material of a highly transparent melamine resin, as the first reversible thermochromic microcapsule;

[0010] Step 2: Prepare a reversible thermochromic cold storage microcapsule with a compound of dodecane-nonanol eutectic mixture and thermosensitive material as the core material and high-transparency melamine resin as the wall material, as the second reversible thermochromic microcapsule;

[0011] Step 3: The first and second reversible thermochromic microcapsules and the framework material are used to form the core and outer core respectively, and then encapsulated with calcium alginate shell to obtain millimeter-sized large capsules with dual temperature storage and temperature warning functions of freezing and low temperature refrigeration.

[0012] To optimize the above technical solution, the specific measures also include:

[0013] The preparation process of the first reversible thermochromic microcapsule in step 1 above includes:

[0014] Weigh tetradecane and dodecanol, and mix them by ultrasonic oscillation to form a tetradecane-dodecanol eutectic mixture;

[0015] A reversible thermochromic compound was obtained by dissolving a leucocyanide and a color developer in a tetradecane-dodecyl alcohol eutectic mixture.

[0016] A white emulsion is formed by emulsifying a reversible thermochromic compound, a composite emulsifier, and distilled water through high-speed shearing.

[0017] Melamine, formaldehyde and distilled water are mixed and stirred to react, the pH is adjusted and stirring is continued until the solution is clear to obtain melamine resin prepolymer;

[0018] The white emulsion was mixed with melamine resin prepolymer and the pH was adjusted. At the same time, the mixture was mechanically stirred under water bath conditions.

[0019] The mixed solution was filtered, washed, and dried to obtain the first reversible thermochromic microcapsule.

[0020] The mass ratio of tetradecane to dodecanol mentioned above is between 3:1 and 9:1, and the resulting tetradecane-dodecanol eutectic mixture has a phase transition temperature range of 2 to 8°C.

[0021] The mass ratio of the dodecanol, color developer, and leucocyanide mentioned above is 50:3:1 to 100:3:1. The dissolution temperature of the leucocyanide and color developer in the alkane-alcohol eutectic mixture is 70 to 120°C. The leucocyanide is selected from one of 6-dimethylamino-3,3-bis(4-dimethylaminophenyl)phthalide, 2-phenylamino-3-methyl-6-diethylfluorane, or 2-phenylamino-3-methyl-6-dibutylaminofluorane. The color developer is selected from one of bisphenol A, gallic acid, or phenolphthalein.

[0022] The mass ratio of the reversible thermochromic compound, the composite emulsifier and distilled water is 10:1:80 ~ 10:3:80, wherein the composite emulsifier is a mixture of SMA and gelatin, and the mass ratio of SMA:gelatin is 3:1~8:1.

[0023] The emulsification speed for high-speed shear emulsification is 5000~10000 r / min, and the emulsification time is 5~15 min;

[0024] The mass ratio of melamine, formaldehyde and distilled water is 4:8:100~1:3:40. The reaction conditions for mixing and stirring are 80~85℃ and pH=8~9. The alkaline reagent used to adjust the pH value is one of triethanolamine solution, sodium hydroxide solution or sodium carbonate solution.

[0025] The mass ratio of the white emulsion to the melamine resin prepolymer is 1:1 to 5:3, and the reaction conditions are 65℃ to 80℃, pH=4 to 6, and the reaction time is 2h.

[0026] Step 2 above describes the preparation process of the second reversible thermochromic microcapsule, which includes:

[0027] Weigh dodecane and nonanol, and mix them by ultrasonic oscillation to form a dodecane-nonanol eutectic mixture;

[0028] A reversible thermochromic compound was obtained by dissolving a leucocyanide and a color developer in a dodecane-nonanol eutectic mixture.

[0029] A white emulsion is formed by emulsifying a reversible thermochromic compound, a composite emulsifier, and distilled water through high-speed shearing.

[0030] Melamine, formaldehyde and distilled water are mixed and stirred to react, the pH is adjusted and stirring is continued until the solution is clear to obtain melamine resin prepolymer;

[0031] The white emulsion was mixed with melamine resin prepolymer and the pH was adjusted. At the same time, the mixture was mechanically stirred under water bath conditions.

[0032] The mixed solution was filtered, washed, and dried to obtain the first reversible thermochromic microcapsule.

[0033] The mass ratio of dodecane and nonanol mentioned above is between 3:2 and 4:1, and the resulting dodecane-nonanol eutectic mixture has a phase transition temperature range of -25 to -15°C.

[0034] The mass ratio of nonanol, color developer, and leucocyanide mentioned above is 50:3:1 to 100:3:1, and the dissolution temperature is 70 to 120°C. The leucocyanide is selected from one of 6-dimethylamino-3,3-bis(4-dimethylaminophenyl)phthalide, 2-phenylamino-3-methyl-6-diethylfluorane, or 2-phenylamino-3-methyl-6-dibutylaminofluorane, and is different from the leucocyanide used in step 1. The color developer is selected from one of bisphenol A, gallic acid, or phenolphthalein.

[0035] The preparation process of the millimeter-sized large capsule with dual-temperature cold storage and temperature alarm functions, as described in step 3 above, includes:

[0036] The first reversible thermochromic microcapsule and the second reversible thermochromic microcapsule were respectively mixed with sodium alginate, glycerol, polyvinyl alcohol and distilled water by mechanical stirring to obtain the first suspension and the second suspension.

[0037] Dissolve CaCl2 in distilled water to obtain a CaCl2 solution;

[0038] A first suspension is delivered into the side inlet of a T-tube using a syringe pump at a flow rate of Q1, and a second suspension is delivered into the vertical inlet of the T-tube using another syringe pump at a flow rate of Q2. The two suspensions form a composite droplet structure at the outlet of the T-tube, in which the second suspension is wrapped around the first suspension. The droplet is then dropped into a CaCl2 solution, where sodium ions in the sodium alginate on the surface of the droplet are replaced by calcium ions, forming a dense wall material. The solution is then filtered and dried to obtain a millimeter-sized large capsule with dual-temperature cold storage and temperature warning functions, including both freezing and low-temperature refrigeration.

[0039] The mass ratio of the first reversible thermochromic microcapsule to sodium alginate, glycerol, polyvinyl alcohol and distilled water is 1:4:1:1:50~1:9:1:1:100, the reaction temperature is 80℃ and the reaction time is 1h.

[0040] The mass ratio of distilled water to CaCl2 is 50:9 to 50:3.

[0041] The T-tube microfluidic device consists of an inlet vertical tube, an outlet vertical tube, a side tube, and a T-connector. The inner diameter of the inlet and outlet vertical tubes is 3 mm, and the inner diameter of the side tube is 1 mm.

[0042] The inlet riser is inserted through the upper inlet of the tee connector, the side riser is inserted through the side inlet of the tee connector to the center of the riser, and the outlet riser is inserted through the lower outlet of the tee connector. All connections are sealed and bonded with sealant.

[0043] The flow rate Q1 is 300~700 uL / min, and the flow rate Q2 is 800~2000 uL / min.

[0044] A capsule with dual temperature indication function, wherein the capsule comprises a core and an outer core consisting of a first and a second reversible thermochromic microcapsule and a framework material, respectively, and is encapsulated by a calcium alginate shell; wherein the first reversible thermochromic microcapsule uses a compound of tetradecane-dodecyl alcohol eutectic mixture and temperature-sensitive material as the core material and high-transparency melamine resin as the wall material; the second reversible thermochromic microcapsule uses a compound of dodecane-nonyl alcohol eutectic mixture and temperature-sensitive material as the core material and high-transparency melamine resin as the wall material.

[0045] The present invention has the following beneficial effects:

[0046] (1) This invention prepares two types of reversible thermochromic microcapsules using cocrystalline alkane-alcohols (dodecyl alcohol-tetradecane and nonanol-dodecane) as the core material, melamine resin as the wall material, and SMA and gelatin as composite emulsifiers. The phase transition temperatures of the two microcapsules are 2~8℃ and -25~-15℃, respectively, with a high encapsulation rate of up to 75%, and the encapsulation effect is good. This invention utilizes cocrystalline alkane-alcohols as phase transition materials, overcoming the limitation of relatively fixed phase transition temperatures of single alkanes or alcohols, and broadening the application range of organic alkane phase transition materials at different temperatures. The microcapsules also have the dual functions of indicating and regulating temperature.

[0047] (2) The millimeter-sized large capsule of the present invention has dual-temperature cold storage and temperature warning functions of freezing and low-temperature refrigeration. It can perform latent heat storage and temperature indication at two temperature points. It is prepared by a T-tube microfluidic device. The side tube and the inlet vertical tube of the T-tube respectively introduce suspension 1 and suspension 2, which are prepared by mixing microcapsules, sodium alginate, glycerol and polyvinyl alcohol aqueous solution. Finally, a composite liquid is dropped into CaC l2 In the solution, after filtration and drying, capsules are formed. These capsules exhibit distinct color changes and regular shapes at different temperatures. Furthermore, the composition of suspensions 1 and 2, the flow rates of peristaltic pumps 1 and 2 (injection pump 1 and injection pump 2), and the temperature of the wall material polymerization reaction can be adjusted to control the capsule morphology, particle size, and color-changing properties. This can meet the temperature control and indication needs of pharmaceuticals, food, and biological products under different environments such as freezing (-25~-15℃) and refrigeration (2~8℃). Attached Figure Description

[0048] Figure 1 This is a microfluidic flowchart of the present invention;

[0049] Figure 2 This is a color-changing effect diagram of the capsule of the present invention;

[0050] Figure 3 This is a macroscopic dimension diagram of the capsule of the present invention. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0052] Although the steps in this invention are arranged by reference numerals, this is not intended to limit the order of the steps. Unless the order of the steps is explicitly stated or the execution of a step requires other steps as a basis, the relative order of the steps can be adjusted. It is understood that the term "and / or" as used herein refers to and covers any and all possible combinations of one or more of the associated listed items.

[0053] A large capsule with dual temperature indication function and its preparation method include the following three typical steps:

[0054] Step 1: Prepare reversible thermochromic cold-storage microcapsules with a core material of a tetradecane-dodecyl alcohol eutectic mixture and a thermosensitive material, and a wall material of highly transparent melamine resin. These are the first reversible thermochromic microcapsules. Figure 1 Microcapsules 1;

[0055] Preparation of tetradecane-dodecyl alcohol eutectic reversible thermochromic cold storage microcapsules:

[0056] Weigh tetradecane and dodecanol, and mix them by ultrasonic oscillation to form an alkane-alcohol eutectic mixture;

[0057] A reversible thermochromic compound was obtained by dissolving a leucocyanide and a color-developing agent in an alkane-ol eutectic mixture.

[0058] A white emulsion is formed by emulsifying a reversible thermochromic compound, a composite emulsifier, and distilled water through high-speed shearing.

[0059] Melamine, formaldehyde and distilled water are mixed and stirred to react, the pH is adjusted and stirring is continued until the solution is clear to obtain melamine resin prepolymer;

[0060] The above white emulsion was mixed with melamine resin prepolymer and reacted. The pH was adjusted, and the mixture was mechanically stirred under water bath conditions.

[0061] The mixed solution was filtered, washed, and dried to obtain the first reversible thermochromic microcapsule.

[0062] Step 2: Prepare reversible thermochromic cold-storage microcapsules with a core material of a dodecane-nonanol eutectic mixture and a thermosensitive material, and a wall material of highly transparent melamine resin. These will serve as the second reversible thermochromic microcapsules. Figure 1 Microcapsules 2;

[0063] Preparation of reversible thermochromic cold-storing microcapsules of dodecane-nonanol eutectic:

[0064] The preparation process in this step is the same as in step 1, except that tetradecane and dodecanol in step 1 are replaced with dodecanane and nonanol, respectively, and different leucocyanidins are used. The final product obtained is a second reversible thermochromic microcapsule.

[0065] Step 3: The first and second reversible thermochromic microcapsules and the framework material are used to form the core and outer core respectively, and then encapsulated with calcium alginate shell to obtain millimeter-sized large capsules with dual temperature storage and temperature warning functions of freezing and low temperature refrigeration.

[0066] Preparation of millimeter-sized large capsules with dual-temperature cold storage and temperature alarm functions, including freezing and low-temperature refrigeration:

[0067] The first reversible thermochromic microcapsule and the second reversible thermochromic microcapsule (microcapsule 1 and microcapsule 2) obtained in steps 1 and 2 are reacted with sodium alginate, glycerol, polyvinyl alcohol and distilled water by mechanical stirring to obtain the first suspension and the second suspension, namely suspension 1 and suspension 2.

[0068] Dissolve CaCl2 in distilled water to obtain a CaCl2 solution;

[0069] Using syringe pump 1 at a flow rate of Q1, the first suspension is delivered into the side inlet of the T-tube, and using syringe pump 2 at a flow rate of Q2, the second suspension is delivered into the vertical inlet of the T-tube. The two form a composite droplet structure at the outlet of the T-tube, in which the second suspension is wrapped around the outer layer of the first suspension. This is then dropped into a CaCl2 solution, where sodium ions in the sodium alginate on the surface of the droplets are replaced by calcium ions, forming a dense wall material. After filtration and drying, a millimeter-sized large capsule with dual-temperature cold storage and temperature warning functions, including freezing and low-temperature refrigeration, is obtained.

[0070] In specific implementation, in step 1, the mass ratio of tetradecane and dodecanol in the eutectic mixture is between 3:1 and 9:1, with a phase transition temperature range of 2 to 8°C.

[0071] The mass ratio of dodecanol, color developer, and leucocyanide in the reversible thermochromic compound is 50:3:1 to 100:3:1. The dissolution temperature of the leucocyanide and color developer in the alkane-alcohol eutectic mixture is 70 to 120°C. The leucocyanide is selected from one of 6-dimethylamino-3,3-bis(4-dimethylaminophenyl)phthalide, 2-phenylamino-3-methyl-6-diethylfluorane, or 2-phenylamino-3-methyl-6-dibutylaminofluorane. The color developer is selected from one of bisphenol A, gallic acid, or phenolphthalein.

[0072] The mass ratio of the reversible thermochromic compound, the composite emulsifier and distilled water is 10:1:80 ~ 10:3:80, wherein the composite emulsifier is a mixture of SMA and gelatin, and the mass ratio of SMA:gelatin is 3:1~8:1.

[0073] The emulsification speed for high-speed shear emulsification is 5000~10000 r / min, and the emulsification time is 5~15 min.

[0074] The mass ratio of melamine, formaldehyde, and distilled water is 4:8:100~1:3:40. The reaction conditions for mixing and stirring are 80~85℃ and pH=8~9. The alkaline reagent used to adjust the pH value is one of triethanolamine solution, sodium hydroxide solution, or sodium carbonate solution.

[0075] The mass ratio of white emulsion to melamine resin prepolymer in the microcapsule reaction solution is 1:1 to 5:3. The reaction conditions are 65℃ to 80℃, pH=4 to 6, and the reaction time is 2h.

[0076] In specific implementation, in step 2, the mass ratio of dodecane and nonanol in the eutectic mixture is between 3:2 and 4:1, with a phase transition temperature range of -25 to -15°C.

[0077] The mass ratio of nonanol, color developer, and leucocyanide in the reversible thermochromic compound is 50:3:1 to 100:3:1, and the dissolution temperature is 70 to 120°C. The leucocyanide is selected from 6-dimethylamino-3,3-bis(4-dimethylaminophenyl)phthalide, 2-phenylamino-3-methyl-6-diethylfluorane, or 2-phenylamino-3-methyl-6-dibutylaminofluorane, while ensuring that it is different from that in step 1. The color developer is selected from bisphenol A, gallic acid, or phenolphthalein.

[0078] In specific implementation, in step 3, the mass ratio of the first reversible thermochromic microcapsule to sodium alginate, glycerol, polyvinyl alcohol and distilled water is 1:4:1:1:50~1:9:1:1:100, the reaction temperature is 80℃, and the reaction time is 1h.

[0079] The mass ratio of distilled water to CaCl2 in a CaCl2 solution is 50:9 to 50:3.

[0080] The T-tube microfluidic device consists of an inlet vertical tube, an outlet vertical tube, a side tube, and a T-connector. The inner diameter of the inlet and outlet vertical tubes is 3 mm, and the inner diameter of the side tube is 1 mm.

[0081] The inlet riser is inserted through the upper inlet of the tee connector, the side riser is inserted through the side inlet of the tee connector to the center of the riser, and the outlet riser is inserted through the lower outlet of the tee connector. All connections are sealed with sealant.

[0082] Suspension 1 is delivered into the side pipe via injection pump 1 at a flow rate Q1 of 300~700 uL / min; suspension 2 is delivered into the inlet vertical pipe via injection pump 2 at a flow rate Q2 of 800~2000 uL / min, forming a composite droplet structure at the end of the outlet vertical pipe where suspension 2 is wrapped around suspension 1.

[0083] This invention yields a millimeter-sized large capsule with dual temperature indication function based on the aforementioned method. This capsule can achieve both cold storage and temperature warning functions in both freezing (-25~-15℃) and low-temperature refrigeration (2~8℃). The capsule consists of two reversible thermochromic microcapsules forming the core and outer core, respectively, and is encapsulated by a calcium alginate shell. The core material of the two reversible thermochromic microcapsules is a composite of different alkane-fatty alcohol eutectic mixtures and a thermosensitive material, while the wall material is a highly transparent melamine resin. Due to the addition of fatty alcohols, the alkane-fatty alcohol eutectic mixture, as an energy storage material, solves the incompatibility problem between the thermosensitive material and non-polar alkane compounds, broadening the selection range of phase change materials that can be used with the thermosensitive material and enabling more flexible selection of the color-changing temperature. Furthermore, this invention utilizes microfluidic technology to achieve continuous production of the capsule and optimizes the morphology, particle size, and color-changing performance of the capsule by controlling the composition of the core and outer core, the ratio of the two phases during production, and the temperature of the wall material polymerization reaction.

[0084] The present invention will be further described in detail below through specific embodiments.

[0085] Example 1:

[0086] (1) Preparation of reversible thermochromic cold storage microcapsules of tetradecane-dodecyl alcohol eutectic: Weigh 9g of tetradecane and 3g of dodecyl alcohol and mix them. Vibrate them with 100Hz ultrasound for 10min to form a eutectic alkane-alcohol system. Weigh an appropriate amount of 0.06g of 6-dimethylamino-3,3-bis(4-dimethylaminophenyl)phthalide and 0.18g of bisphenol A. Grind them thoroughly with a grinding pestle to refine the particles and dissolve them into the alkane-alcohol eutectic system to form a color-changing compound. Add 1.0g of tetradecane-dodecyl alcohol to the color-changing compound. SMA, 0.2g gelatin and 120g distilled water were emulsified using a high-speed homogenizer at 7000r / min to form a uniformly dispersed oil-in-water emulsion. 6g melamine, 12g formaldehyde aqueous solution and 100g distilled water were mixed and stirred. 10wt% triethanolamine was added to adjust the pH of the mixture to 8.5, and stirring was continued until transparent to obtain melamine resin prepolymer. The prepolymer was added dropwise to the oil-in-water emulsion while mechanically stirring at 360r / min. After the melamine resin was completely added, the pH was adjusted to 5.5 using 10wt% glacial acetic acid, and stirring was continued for 2.5h. Finally, the mixture was filtered, washed and dried for 16h to obtain microcapsules 1.

[0087] (2) Preparation of reversible thermochromic cold storage microcapsules of dodecane-nonanol eutectic: replace tetradecane and dodecyl alcohol in step 1 with dodecane and nonanol respectively, and use 2-phenylamino-3-methyl-6-diethylfluorane as leucocyanide to prepare microcapsules 2 in the same steps;

[0088] (3) Preparation of millimeter-sized large capsules with dual temperature indication function: Microcapsules 1 and 2 in step 1 (2) were mixed with sodium alginate, glycerol, polyvinyl alcohol and distilled water in a ratio of 1:4:1:1:50, and suspension 1 and suspension 2 were obtained by ultrasonic vibration at 100 Hz and 60 ℃; 10 g CaCl2 was dissolved in 100 g distilled water to obtain CaCl2 solution; injection pump 1 delivered suspension 1 into the side tube of T-tube at a rate of 1000 uL / min, and injection pump 2 delivered suspension 2 into the inlet vertical tube of T-tube at a rate of 2000 uL / min, and finally the collected liquid was dripped into CaCl2 solution; finally, the mixture was filtered, washed and dried to obtain millimeter-sized large capsules with dual temperature indication function.

[0089] Example 2:

[0090] (1) Preparation of reversible thermochromic cold storage microcapsules of tetradecane-dodecyl alcohol eutectic: Weigh 9g tetradecane and 3g dodecyl alcohol and mix them. Vibrate them with 100Hz ultrasound for 10min to form a eutectic alkane-alcohol system. Weigh an appropriate amount of 0.06g 6-dimethylamino-3,3-bis(4-dimethylaminophenyl)phthalide and 0.18g bisphenol A. Grind them thoroughly with a grinding pestle to refine the particles and dissolve them into the alkane-alcohol eutectic system to form a color-changing compound. Add 1.0g SMA and 0.2g SMA to the color-changing compound. Gelatin and 120g of distilled water were emulsified using a high-speed homogenizer at 7000r / min to form a uniformly dispersed oil-in-water emulsion. 6g of melamine, 12g of formaldehyde aqueous solution, and 100g of distilled water were mixed and stirred. 10wt% triethanolamine was added to adjust the pH of the mixture to 8.5, and stirring was continued until transparent to obtain a melamine resin prepolymer. The prepolymer was added dropwise to the oil-in-water emulsion while mechanically stirring at 360r / min. After the melamine resin was completely added, the pH was adjusted to 5.5 with 10wt% glacial acetic acid, and stirring was continued for 2.5h. Finally, the mixture was filtered, washed, and dried for 16h to obtain microcapsules 1.

[0091] (2) Preparation of reversible thermochromic cold storage microcapsules of dodecane-nonanol eutectic: replace tetradecane and dodecyl alcohol in step 1 with dodecane and nonanol respectively, and use 2-phenylamino-3-methyl-6-diethylfluorane as leucocyanide to prepare microcapsules 2 in the same steps;

[0092] (3) Preparation of millimeter-sized large capsules with dual temperature indication function: Microcapsules 1 and 2 in step 1 (2) were mixed with sodium alginate, glycerol, polyvinyl alcohol and distilled water in a ratio of 1:8:2:2:100, and suspensions 1 and 2 were obtained by ultrasonic vibration at 100 Hz and 60 ℃; 10 g CaCl2 was dissolved in 100 g distilled water to obtain CaCl2 solution; injection pump 1 delivered suspension 1 into the side tube of T-tube at a rate of 1000 uL / min, and injection pump 2 delivered suspension 2 into the inlet vertical tube of T-tube at a rate of 2000 uL / min, and finally the collected liquid was dripped into CaCl2 solution; finally, the mixture was filtered, washed and dried to obtain millimeter-sized large capsules with dual temperature indication function.

[0093] Example 3:

[0094] (1) Preparation of reversible thermochromic cold storage microcapsules of tetradecane-dodecyl alcohol eutectic: Weigh 9g tetradecane and 3g dodecyl alcohol and mix them. Vibrate them with 100Hz ultrasound for 10min to form a eutectic alkane-alcohol system. Weigh an appropriate amount of 0.06g 6-dimethylamino-3,3-bis(4-dimethylaminophenyl)phthalide and 0.18g bisphenol A. Grind them thoroughly with a grinding pestle to refine the particles and dissolve them into the alkane-alcohol eutectic system to form a color-changing compound. Add 1.0g SMA and 0.2g SMA to the color-changing compound. Gelatin and 120g of distilled water were emulsified using a high-speed homogenizer at 7000r / min to form a uniformly dispersed oil-in-water emulsion. 6g of melamine, 12g of formaldehyde aqueous solution, and 100g of distilled water were mixed and stirred. 10wt% triethanolamine was added to adjust the pH of the mixture to 8.5, and stirring was continued until transparent to obtain a melamine resin prepolymer. The prepolymer was added dropwise to the oil-in-water emulsion while mechanically stirring at 360r / min. After the melamine resin was completely added, the pH was adjusted to 5.5 with 10wt% glacial acetic acid, and stirring was continued for 2.5h. Finally, the mixture was filtered, washed, and dried for 16h to obtain microcapsules 1.

[0095] (2) Preparation of reversible thermochromic cold storage microcapsules of dodecane-nonanol eutectic: replace tetradecane and dodecyl alcohol in step 1 with dodecane and nonanol respectively, and use 2-phenylamino-3-methyl-6-diethylfluorane as leucocyanide to prepare microcapsules 2 in the same steps;

[0096] (3) Preparation of millimeter-sized large capsules with dual temperature indication function: Microcapsules 1 and 2 in step 1 (2) were mixed with sodium alginate, glycerol, polyvinyl alcohol and distilled water in a ratio of 1:8:2:2:100, and suspensions 1 and 2 were obtained by ultrasonic vibration at 100 Hz and 60 ℃; 10 g CaCl2 was dissolved in 100 g distilled water to obtain CaCl2 solution; injection pump 1 delivered suspension 1 into the side tube of T-tube at a rate of 400 uL / min, and injection pump 2 delivered suspension 2 into the inlet vertical tube of T-tube at a rate of 800 uL / min. The liquid that was finally collected was dripped into CaCl2 solution; finally, the mixture was filtered, washed and dried to obtain millimeter-sized large capsules with dual temperature indication function.

[0097] Example 4:

[0098] (1) Preparation of reversible thermochromic cold storage microcapsules of tetradecane-dodecyl alcohol eutectic: Weigh 9g tetradecane and 3g dodecyl alcohol and mix them. Vibrate them with 100Hz ultrasound for 10min to form a eutectic alkane-alcohol system. Weigh an appropriate amount of 0.06g 6-dimethylamino-3,3-bis(4-dimethylaminophenyl)phthalide and 0.18g bisphenol A. Grind them thoroughly with a grinding pestle to refine the particles and dissolve them into the alkane-alcohol eutectic system to form a color-changing compound. Add 1.0g SMA and 0.2g SMA to the color-changing compound. Gelatin and 120g of distilled water were emulsified using a high-speed homogenizer at 7000r / min to form a uniformly dispersed oil-in-water emulsion. 6g of melamine, 12g of formaldehyde aqueous solution, and 100g of distilled water were mixed and stirred. 10wt% triethanolamine was added to adjust the pH of the mixture to 8.5, and stirring was continued until transparent to obtain a melamine resin prepolymer. The prepolymer was added dropwise to the oil-in-water emulsion while mechanically stirring at 360r / min. After the melamine resin was completely added, the pH was adjusted to 5.5 with 10wt% glacial acetic acid, and stirring was continued for 2.5h. Finally, the mixture was filtered, washed, and dried for 16h to obtain microcapsules 1.

[0099] (2) Preparation of reversible thermochromic cold storage microcapsules of dodecane-nonanol eutectic: replace tetradecane and dodecyl alcohol in step 1 with dodecane and nonanol respectively, and use 2-phenylamino-3-methyl-6-dibutylaminofluorane as leucocyanide to prepare microcapsules 2 in the same steps.

[0100] (3) Preparation of millimeter-sized large capsules with dual temperature indication function: Microcapsules 1 and 2 in step 1 (2) were mixed with sodium alginate, glycerol, polyvinyl alcohol and distilled water in a ratio of 1:8:2:2:100, and suspensions 1 and 2 were obtained by ultrasonic vibration at 100 Hz and 60 ℃; 10 g CaCl2 was dissolved in 100 g distilled water to obtain CaCl2 solution; injection pump 1 delivered suspension 1 into the side tube of T-tube at a rate of 400 uL / min, and injection pump 2 delivered suspension 2 into the inlet vertical tube of T-tube at a rate of 800 uL / min. The liquid that was finally collected was dripped into CaCl2 solution; finally, the mixture was filtered, washed and dried to obtain millimeter-sized large capsules with dual temperature indication function.

[0101] In the embodiments of the present invention, the capsule color-changing effect and macroscopic dimensions are as follows: Figures 2-3 As shown.

[0102] ;

[0103] Table 1 shows the morphology and particle size of the capsules in Examples 1-3. Reducing the ratio of microcapsules to sodium alginate aqueous solution resulted in a more regular capsule morphology compared to before; proportionally reducing the flow rate Q1 of syringe pump 1 and the flow rate Q2 of syringe pump 2 allowed the capsule particle size to be controlled between 5.5 mm and 2.5 mm.

[0104] ;

[0105] Table 2 shows the color contrast of Examples 3-4 and after 80 cycles. In the color contrast, L represents the lightness (+) and darkness (-) of the example, a represents the redness (+) and greenness (-) of the example, and b represents the yellowness (+) and blueness (-) of the example. In Example 3, the da* value is 15.09 in the first stage of chromaticity, indicating a significant red-green change; and after 80 cycles, the da* value is 14.70, indicating good durability of the color change. In Example 3, the db* value is -23.91 in the second stage of chromaticity, indicating a significant yellow-blue change; and after 80 cycles, the da* value is -23.81, indicating good durability of the color change. In Example 4, the da* value is 14.83 in the first stage of chromaticity, indicating a significant red-green change; and after 80 cycles, the da* value is 14.63, indicating good durability of the color change. In Example 4, during the second stage of chromaticity, the dL* value was -33.56, indicating a significant change in lightness and darkness; and after 80 cycles, the da* value was -32.56, indicating that the color change had good durability.

[0106] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0107] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for producing a capsule having a dual temperature indicating function, characterized in that, The application relates to a reversible thermochromic microcapsule with a dual-temperature cold storage and temperature warning function. The reversible thermochromic microcapsule comprises the following steps: Step 1: preparing a reversible thermochromic microcapsule with a tetradecane-dodecanol eutectic mixture and a temperature-sensitive material as core materials and a melamine resin with high transparency as wall materials as the first reversible thermochromic microcapsule; Step 2: preparing a reversible thermochromic microcapsule with a dodecane-nonanol eutectic mixture and a temperature-sensitive material as core materials and a melamine resin with high transparency as wall materials as the second reversible thermochromic microcapsule; The preparation process of the second reversible thermochromic microcapsule comprises the following steps: dodecane and nonanol are weighed and mixed through ultrasonic oscillation to form a dodecane-nonanol eutectic mixture; a leuco agent and a chromogenic agent are dissolved in the dodecane-nonanol eutectic mixture to obtain a reversible thermochromic compound; the reversible thermochromic compound, a composite emulsifier and distilled water are subjected to high-speed shearing emulsification to form a white emulsion; melamine, formaldehyde and distilled water are mixed and stirred to react, the pH value is adjusted, and stirring is continued until the solution is transparent to obtain a melamine resin prepolymer; the white emulsion and the melamine resin prepolymer are mixed and reacted, the pH value is adjusted, and mechanical stirring is conducted on the mixed solution under the condition of a water bath; the mixed solution is filtered, washed and dried to obtain the second reversible thermochromic microcapsule; 2. The method of claim 1, wherein the capsule having a dual temperature indicating function is prepared by the steps of: The preparation process of the first reversible thermochromic microcapsule comprises the following steps: tetradecane and dodecanol are weighed and mixed through ultrasonic oscillation to form a tetradecane-dodecanol eutectic mixture; a leuco agent and a chromogenic agent are dissolved in the tetradecane-dodecanol eutectic mixture to obtain a reversible thermochromic compound; the reversible thermochromic compound, a composite emulsifier and distilled water are subjected to high-speed shearing emulsification to form a white emulsion; melamine, formaldehyde and distilled water are mixed and stirred to react, the pH value is adjusted, and stirring is continued until the solution is transparent to obtain a melamine resin prepolymer; the white emulsion and the melamine resin prepolymer are mixed and reacted, the pH value is adjusted, and mechanical stirring is conducted on the mixed solution under the condition of a water bath; the mixed solution is filtered, washed and dried to obtain the first reversible thermochromic microcapsule.

3. A method of producing a capsule having a dual temperature indicating function according to claim 2, characterized in that, The mass ratio of the tetradecane and the dodecanol is between 3:1 and 9:1, and the tetradecane-dodecanol eutectic mixture formed has a phase change temperature range of 2-8 DEG C.

4. The method of claim 2, wherein the capsule having a dual temperature indicating function is prepared by the steps of: The mass ratio of the dodecanol, the chromogenic agent and the leuco agent is 50:3:1-100:3:1, the dissolving temperature of the leuco agent and the chromogenic agent in the alkane-alcohol eutectic mixture is 70-120 DEG C, the leuco agent is selected from one of 6-dimethylamino-3,3-bis(4-dimethylaminophenyl) phthalide, 2-anilino-3-methyl-6-diethylfluorophenyl and 2-anilino-3-methyl-6-dibutylaminofluorophenyl, and the chromogenic agent is selected from one of bisphenol A, gallic acid and phenolphthalein. The mass ratio of the reversible thermochromic complex, the composite emulsifier and distilled water is 10:1:80~10:3:80, wherein the composite emulsifier is a mixture of SMA and gelatin, and the mass ratio of SMA to gelatin is 3:1~8:1; The emulsification rotation speed of high-speed shearing emulsification is 5000~10000r / min, and the emulsification time is 5~15min; The mass ratio of the melamine, formaldehyde and distilled water is 4:8:100~1:3:40, the reaction conditions of mixed stirring reaction are 80~85℃, and pH=8~9, and the alkaline reagent used for adjusting the pH value is one of triethanolamine solution, sodium hydroxide solution or sodium carbonate solution; The mass ratio of the white emulsion and melamine resin prepolymer is 1:1~5:3, the reaction conditions are 65℃~80℃, pH=4~6, and the reaction time is 2h.

5. The method of claim 1, wherein the capsule having a dual temperature indicating function is prepared by the steps of: The mass ratio of the dodecane and nonanol is between 3:2~4:1, and the dodecane-nonanol eutectic mixture formed has a phase transition temperature range of-25~-15℃.

6. The method of claim 1, wherein the capsule having a dual temperature indicating function is prepared by the steps of: The mass ratio of the nonanol, the developer and the leuco dye is 50:3:1~100:3:1, and the dissolution temperature is 70~120℃, wherein the leuco dye is one of 6-dimethylamino-3,3-bis(4-dimethylaminophenyl) phthalide, 2-anilino-3-methyl-6-diethylfluorophore and 2-anilino-3-methyl-6-dibutylamino fluorophore, and is different from the leuco dye used in step 1, and the developer is one of bisphenol A, gallic acid or phenolphthalein.

7. The method of claim 1, wherein the capsule having a dual temperature indicating function is prepared by the steps of: (a) preparing a first capsule having a first temperature indicating function; (b) preparing a second capsule having a second temperature indicating function; and (c) combining the first and second capsules. The preparation process of the millimeter-level large capsule with the functions of freezing and low-temperature refrigeration dual-temperature cold storage and temperature warning in step 3 comprises: The first reversible thermochromic microcapsule and the second reversible thermochromic microcapsule are respectively mixed with sodium alginate, glycerol, polyvinyl alcohol and distilled water by mechanical stirring to obtain a first suspension and a second suspension; CaCl2 is dissolved in distilled water to obtain a CaCl2 solution; An injection pump is used to deliver the first suspension into the side pipe inlet of the T-shaped pipe at a flow rate of Q1, and another injection pump is used to deliver the second suspension into the vertical pipe inlet of the T-shaped pipe at a flow rate of Q2, and the two form a composite droplet structure in which the second suspension is wrapped outside the first suspension at the outlet of the T-shaped pipe, and then the composite droplet structure is dripped into the CaCl2 solution, the sodium ions in the sodium alginate on the surface of the droplet are replaced by calcium ions to form a dense wall material, and then the composite droplet structure is filtered and dried to obtain the millimeter-level large capsule with the functions of freezing and low-temperature refrigeration dual-temperature cold storage and temperature warning.

8. A method of producing a capsule having a dual temperature indicating function according to claim 7, characterized in that, The mass ratio of the first reversible thermochromic microcapsule, sodium alginate, glycerol, polyvinyl alcohol and distilled water is 1:4:1:1:50~1:9:1:1:100, the reaction temperature is 80℃, and the reaction time is 1h; The mass ratio of the distilled water and CaCl2 is 50:9~50:3; The T-shaped microfluidic device is composed of an inlet vertical pipe, an outlet vertical pipe, a side pipe and a three-way connector, wherein the inner diameters of the inlet and outlet vertical pipes are 3mm, and the inner diameter of the side pipe is 1mm. The inlet vertical pipe is inserted by the upper inlet of the tee connector, the side pipe is inserted into the center of the vertical pipe by the side inlet of the tee connector, the outlet vertical pipe is inserted by the lower outlet of the tee connector, and the sealing adhesive is used for sealing and bonding at each connection position. The flow rate Q1 is 300-700 uL / min, and the flow rate Q2 is 800-2000 uL / min.

9. Capsule having a dual temperature indicating function, obtained according to the method of any one of claims 1-8, characterized in that, The capsule is composed of a first and a second reversible thermochromic microcapsule and a skeleton material, respectively forming an inner core and an outer core, and is encapsulated by a calcium alginate shell; wherein the first reversible thermochromic microcapsule is a compound of a tetradecane-dodecanol eutectic mixture and a temperature-sensitive material as the core material, and a high-transparency melamine resin as the wall material; the second reversible thermochromic microcapsule is a compound of a dodecane-nonanol eutectic mixture and a temperature-sensitive material as the core material, and a high-transparency melamine resin as the wall material.

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