Small-particle-size liquid amine microcapsule, preparation method thereof and micro-droplet device

Abstract

The invention belongs to the field of microencapsulation, and discloses a small-particle-size liquid amine microcapsule, a preparation method thereof and a micro-droplet device. The method comprises the following steps: firstly, carrying out micro-droplet treatment on liquid amine through ultrasonic spraying to obtain liquid amine micro-droplets, and enabling the liquid amine micro-droplets to fall into a reaction solution to form a primary microcapsule so as to obtain a mixed solution of the primary microcapsule and the reaction solution; then heating the mixture, and continuously stirring or shaking the mixture to obtain a primary microcapsule; and cleaning the primarily prepared microcapsule, and removing a solvent and impurities to obtain the small-particle-size liquid amine microcapsule. According to the invention, liquid amine is subjected to micro-droplet treatment by using ultrasonic spraying, and heat is generated due to vibration during working, so that the viscosity of the liquid amine can be reduced, and microencapsulation of a multi-component liquid amine solution with a relatively wide viscosity range can be completed. The prepared microcapsule is extremely low in impurity content, good in dispersity, stable in quality, small in particle size, thin in capsule wall, uniform, compact and good in thermal stability, and the core material content of the microcapsule can reach 60 wt.%.

Description

Technical Field

[0001] The present invention belongs to the field of microencapsulation, and particularly relates to a small-particle-size liquid amine microcapsule, a preparation method thereof, and a micro-droplet forming device. Background Art

[0002] The microencapsulation technology is a technology for manufacturing microcapsules with protective shell materials and encapsulated different functional core materials. By encapsulating core materials in various forms and converting them into solids, the efficient utilization and stable storage of substances can be achieved. According to the different permeability of the capsule wall, various functions can be exerted: when the capsule wall has good sealing performance, it can be used to store repair fluids, phase change energy storage materials, flame retardants, etc.; while microcapsules with adjustable permeability can be used as sustained-release or controlled-release carriers for the precise release of drugs, antifouling agents, corrosion inhibitors, etc. In recent decades, due to the diversification of the methods for generating small droplets / small particles and the methods for generating shell materials, the microencapsulation technology is mainly divided into three categories: physical method, physical-chemical composite method, and chemical method. Among them, in-situ polymerization and interfacial polymerization are the two most commonly used methods in the chemical method. In actual operation, whether it is "water-in-oil" or "oil-in-water", stable emulsions are formed, and then interfacial deposition is carried out using shell-forming monomers to complete the microcapsule encapsulation.

[0003] Although the microencapsulation technology has shown diverse characteristics, the preparation of high-quality microcapsules for certain substances (such as polyamine liquid amines) still faces challenges. As a curing agent or chain extender widely used in materials such as epoxy resins, polyamines, and nylons, polyamine liquid amines have dual hydrophilic properties and can dissolve in most polar or weakly polar solvents (such as water, benzene, toluene), making it difficult to form stable emulsions in a single solvent. At the same time, its high reactivity makes it easy to react with existing shell-forming monomers, further increasing the difficulty of microencapsulation. In response to the amphiphilicity of polyamine liquid amines and the relatively high viscosity of some liquid amines, researchers in this field have explored several strategies, including microfluidic methods and emulsion methods. The microfluidic method uses a microfluidic chip or a microfluidic device to generate micro-droplets, and can prepare amine microcapsules with stable performance. However, it has low efficiency in the production of amine microcapsules, and the particle size of the microcapsules is usually greater than 100 μm. The emulsion method disperses liquid amines in an immiscible oil-phase solvent (such as n-heptane, cyclohexane), and prepares microcapsules by the interfacial polymerization method of oil-in-water. However, the microcapsules prepared by this method are extremely easy to bond, resulting in poor dispersibility of the microcapsules. Therefore, providing a method for precisely controlling micro-droplets to overcome the technical problems of large viscosity of liquid amines, poor dispersibility of microcapsules, low core material content, many impurities in the preparation process, too large particle size, and low production efficiency in traditional preparation methods has broad application prospects. Summary of the Invention

[0004] In order to overcome the shortcomings and deficiencies of the prior art, the primary object of the present invention is to provide a preparation method for small-particle-size liquid amine microcapsules.

[0005] Another object of the present invention is to provide a liquid amine microcapsule with a small particle size.

[0006] Another object of the present invention is to provide a micro-droplet device, which can well complete the micro-droplet of polyamine liquid, can complete the micro-encapsulation of polyamine liquid solutions with a wide viscosity range, and realize the preparation of liquid amine microcapsules with good comprehensive performance.

[0007] The object of the present invention is achieved by the following technical solutions:

[0008] A method for preparing a liquid amine microcapsule with a small particle size, comprising the following steps:

[0009] First, the liquid amine is subjected to micro-droplet treatment by ultrasonic spraying to obtain liquid amine micro-droplets, and the liquid amine micro-droplets are allowed to fall into the reaction solution to form primary microcapsules, obtaining a mixed solution of primary microcapsules and the reaction solution. Or after replacing the reaction solution of this mixed solution, then the mixed solution is heated for shell growth reaction (the stage of capsule wall growth), and continuously stirred or shaken to obtain preliminary microcapsules; then the preliminary microcapsules are washed, and the solvent and impurities are removed to obtain liquid amine microcapsules with a small particle size.

[0010] Preferably, the temperature of the micro-droplet treatment is 50-60 °C.

[0011] Preferably, the conditions of the micro-droplet treatment are: the ultrasonic power is 70-130 W, and the spraying rate is 1-20 mL / h.

[0012] Preferably, the liquid amine is at least one or any mixture of ethylenediamine condensate, polyetheramine, fatty amine, polypropyleneamine and aromatic amine, and more preferably tetraethylenepentamine (TEPA) amine solution, triethylenetetramine (TETA) amine solution, diethylenetriamine (DETA) amine solution, polyether triamine (JEFFAMINE T403) amine solution.

[0013] Preferably, the viscosity of the liquid amine is 5-80 mPa·s.

[0014] Preferably, the reaction solution is a reaction solution containing shell-forming monomers, including a solute and a solvent, and the solute includes shell-forming monomers, surfactants and catalysts;

[0015] The solvent is a non-polar or weakly polar solvent that cannot dissolve or can only slightly dissolve the liquid amine, and is preferably any one or any mixture of liquid aliphatic hydrocarbons or cycloalkanes with 6-18 carbon atoms, such as cyclohexane, cycloheptane, cyclooctane, cyclodecane, decalin, n-hexadecane;

[0016] The mass-volume ratio g / mL of the solute and the solvent is 0.5-2:35-65.

[0017] The method for preparing the reaction solution is as follows: Add the shell-forming monomer into a solvent containing a surfactant and a catalyst, and continuously stir or shake until a stable solution is formed.

[0018] Preferably, the stirring is mechanical stirring carried out at a speed of 80 - 500 r / min, or magnetic stirring carried out at a speed of 100 - 600 r / min, and the shaking is carried out at a speed of 50 - 200 r / min.

[0019] Preferably, the shell-forming monomer is any one or any combination of 4,4'-dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and toluene diisocyanate;

[0020] The surfactant is Arlacel P135 that can promote the formation of an inverse emulsion;

[0021] The catalyst is any one or any combination of triethylenediamine, 2,4,6-tris(dimethylaminomethyl)phenol, or dibutyltin dilaurate that can promote the reaction between the liquid amine and the shell-forming monomer;

[0022] The weight ratio of the shell-forming monomer, surfactant, and catalyst in the solute is 3 - 12:0.05 - 2:0 - 1.

[0023] Preferably, the heating temperature is 40°C - 60°C, and the time is 3 - 7 hours, more preferably 40°C and the time is 5 hours;

[0024] The cleaning process is as follows: First, add a cleaning agent, which is pure cyclohexane, to the as-prepared microcapsules. After stirring evenly, let it stand until solid precipitation occurs, then remove the supernatant. Repeat adding the cleaning agent to clean it 3 - 6 times. After removing the solvent and impurities therein, a small-particle-size liquid amine microcapsule dispersion is obtained, and the small-particle-size liquid amine microcapsules are stored in cyclohexane.

[0025] A small-particle-size liquid amine microcapsule is prepared by the above method.

[0026] Preferably, the particle size of the liquid amine microcapsules is 30 - 50 μm.

[0027] A micro-droplet forming device includes an ultrasonic generator, an ultrasonic atomizing nozzle, an injection pump, a syringe, a shaker, and a container;

[0028] The ultrasonic atomizing nozzle is internally provided with piezoelectric wafers, and there are at least two piezoelectric wafers, which adopt a sandwich design;

[0029] The piezoelectric wafer material is PZT-4, and the size of the piezoelectric wafer is (15 - 35) mm × (5 - 15) mm × (2 - 8) mm in terms of outer diameter × inner diameter × thickness.

[0030] Preferably, the ultrasonic generator is connected to the ultrasonic atomizing nozzle through a wire. The syringe is placed inside the syringe pump, and the syringe is connected to the liquid inlet of the ultrasonic atomizing nozzle through a catheter.

[0031] The container is placed on a shaker and is placed directly below the ultrasonic atomizing nozzle together to receive the generated micro-droplets.

[0032] Small-sized liquid amine microcapsules can achieve precise release of multi-component liquid amines by controlling their size and permeability. This is of great significance for applications that require long-term and stable performance (such as latent curing agents). Compared with large-sized microcapsules, the small-sized design can significantly shorten or extend the release time of functional substances to meet the requirements in different scenarios. Moreover, through the optimization of the surface and internal structure of small-sized liquid amine microcapsules, the influence of fluidity damage, mechanical damage or environmental factors on the core material can be reduced, thereby improving the physical stability of the overall product. This characteristic is particularly important, especially in scenarios that require long-term storage or transportation, where small-sized microcapsules can better avoid being damaged by force or leaking.

[0033] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0034] (1) The present invention combines an ultrasonic spraying device with an interfacial polymerization technique. Compared with the two methods of forming stable emulsions and then using shell-forming monomers for interfacial deposition to complete microcapsule encapsulation in the most commonly used traditional in-situ polymerization method and interfacial polymerization method, the ultrasonic spraying technique has a high precise control ability during the generation of micro-droplets, and can effectively avoid the problems caused by droplet adhesion or uneven distribution in the traditional encapsulation method. By combining with the interfacial polymerization technique, the efficient preparation of small-sized microcapsules is realized, which not only reduces the production cost but also speeds up the microcapsule preparation process.

[0035] (2) The ultrasonic spray device provided by the present invention is a self-made nozzle. A high-power emission material PZT-4 with a relatively large size (outer diameter × inner diameter × thickness 25 × 10 × 5 mm) is used as the piezoelectric wafer, and a sandwich design is adopted to achieve high-power and high-efficiency energy conversion. Therefore, a large amount of heat is generated during use. By using a high-power ultrasonic atomization nozzle to atomize organic polyamines with a relatively high viscosity, the heat generated during the operation of the ultrasonic atomization nozzle is used to reduce the viscosity of the organic polyamines, realizing the atomization of organic polyamines with a relatively high viscosity, and forming liquid amine micro-droplets with smaller particle sizes and a narrower particle size distribution. Finally, microencapsulation is achieved through an interfacial polymerization reaction to prepare liquid amine microcapsules with smaller particle sizes and a narrower particle size distribution. At the same time, the heat generated by the nozzle is carried away by the continuously flowing organic polyamine liquid, so that the nozzle will not overheat due to heat accumulation, and finally the spraying process is stable and continuous.

[0036] (3) The present invention provides a method for preparing small-sized liquid amine microcapsules based on ultrasonic spraying and the prepared liquid amine microcapsules. The synthesized liquid amine microcapsules have extremely low impurity content, good dispersion, stable quality, small particle size, a thin, uniform and dense capsule wall structure, good thermal stability, and a core material content reaching 60 wt.%. And by adjusting the spraying rate or spraying power, very small liquid amine microcapsules (30 - 50 μm) can be prepared. Through the optimization of the surface and internal structure of the small-sized liquid amine microcapsules, the influence of fluidity damage, mechanical damage or environmental factors on the core material can be reduced, thereby improving the physical stability of the overall product. This is particularly important for scenarios that require long-term storage or transportation. Small-sized liquid amine microcapsules can better avoid being damaged or leaking due to stress.

[0037] (4) Through the optimized design of the nozzle structure and the combined mode of multi-nozzle collaborative work in the present invention, combined with the interfacial polymerization technology, a large number of small-sized liquid amine microcapsules can be synthesized very conveniently. This method can improve the production efficiency of microcapsules while ensuring that the capsule wall structure of the microcapsules is thin, dense and uniform, reduce the production cost of small-sized liquid amine microcapsules, and greatly improve the production efficiency and product quality of small-sized liquid amine microcapsules. Description of the Drawings

[0038] Figure 1 It is a schematic diagram of the micro-droplet device of the present invention;

[0039] Figure 2 It is a schematic diagram of the internal structure of the self-made ultrasonic atomization nozzle of the present invention (a) and a schematic diagram of the heat change during the micro-droplet process (b);

[0040] Figure 3Scanning electron microscope (SEM) image of the liquid amine microcapsules synthesized in Example 1 of the present invention; the core liquid is tetraethylenepentamine (TEPA), and its viscosity at 25 °C is 50 - 60 mPa·s; Figure (a) is the overall dispersion diagram of tetraethylenepentamine (TEPA) microcapsules, and Figure (b) is the diagram of a single microcapsule;

[0041] Figure 4 Scanning electron microscope (SEM) image of the TEPA microcapsules synthesized in Comparative Example 1 of the present invention;

[0042] Figure 5 Scanning electron microscope (SEM) image of the TEPA microcapsules synthesized in Comparative Example 2 of the present invention;

[0043] Figure 6 Scanning electron microscope (SEM) image of the TEPA microcapsules synthesized in Comparative Example 3 of the present invention;

[0044] Figure 7 Scanning electron microscope (SEM) image of the TETA microcapsules synthesized in Example 2 of the present invention; the core liquid is triethylenetetramine (TETA), and its viscosity at 25 °C is 5.6 - 22.5 mPa·s; Figure (a) is the overall dispersion diagram of triethylenetetramine (TETA) microcapsules, and Figure (b) is the diagram of a single microcapsule;

[0045] Figure 8 Scanning electron microscope (SEM) image of the DETA microcapsules synthesized in Example 3 of the present invention. The core liquid is diethylenetriamine (DETA), and its viscosity at 25 °C is 7 - 8 mPa·s; Figure (a) is the overall dispersion diagram of diethylenetriamine (DETA) microcapsules, and Figure (b) is the diagram of a single microcapsule;

[0046] Figure 9 Scanning electron microscope (SEM) image of the JEFFAMINE T403 microcapsules synthesized in Example 4 of the present invention; its viscosity at 25 °C is 72 - 76 mPa·s; Figure (a) is the overall dispersion diagram of JEFFAMINE T403 microcapsules, and Figure (b) is the diagram of a single microcapsule;

[0047] Figure 10For Examples 1, 5, 6, and 7 of the present invention, the optical dispersion diagrams of TEPA microcapsules with relatively high viscosity prepared according to the steps of Example 1 at different spraying rates are shown; wherein Figure (a) is the optical dispersion diagram of TEPA microcapsules prepared at a spraying rate of 1 mL / h in Example 1, Figure (b) is the optical dispersion diagram of TEPA microcapsules prepared at a spraying rate of 5 mL / h in Example 7, Figure (c) is the optical dispersion diagram of TEPA microcapsules prepared at a spraying rate of 10 mL / h in Example 6, and Figure (d) is the optical dispersion diagram of TEPA microcapsules prepared at a spraying rate of 20 mL / h in Example 7;

[0048] Figure 11 For the particle size statistical diagrams of the TEPA microcapsules obtained in Examples 1, 5, 6, and 7 of the present invention, wherein Figure (a) is the particle size statistical diagram of TEPA microcapsules prepared at a spraying rate of 1 mL / h in Example 1, Figure (b) is the particle size statistical diagram of TEPA microcapsules prepared at a spraying rate of 5 mL / h in Example 5, Figure (c) is the particle size statistical diagram of TEPA microcapsules prepared at a spraying rate of 10 mL / h in Example 6, and Figure (d) is the particle size statistical diagram of TEPA microcapsules prepared at a spraying rate of 20 mL / h in Example 7;

[0049] Figure 12 It is the scanning electron microscope (SEM) image of the TEPA microcapsules synthesized in Example 8 of the present invention;

[0050] Figure 13 It is the scanning electron microscope (SEM) image of the TEPA microcapsules synthesized in Example 9 of the present invention;

[0051] Figure 14 It is the scanning electron microscope (SEM) image of the TEPA microcapsules synthesized in Example 10 of the present invention. Detailed implementation manners

[0052] The present invention will be further described in detail below with reference to specific embodiments, but the implementation manners of the present invention are not limited thereto. For process parameters not specifically noted, conventional techniques can be referred to.

[0053] Figure 1 It is a schematic diagram of the micro-droplet forming device of the present invention, which consists of an ultrasonic generator, an ultrasonic atomizing nozzle, an injection pump, a syringe, a shaker, and a glass culture dish containing a reaction solution. The ultrasonic generator transmits signals via a wire connection to the ultrasonic atomizing nozzle, converting electrical energy into mechanical energy. The syringe is placed inside the injection pump and is connected to the liquid inlet of the ultrasonic atomizing nozzle through a catheter. The liquid amine in the injection tube is pushed to the atomizing end face of the ultrasonic atomizing nozzle through the pressure of the injection pump for micro-droplet formation of the liquid amine. The culture dish containing the reaction solution is placed on the shaker and is placed directly below the ultrasonic atomizing nozzle together to receive the generated micro-droplets.

[0054] Figure 2 This is a diagram of the internal structure of the homemade ultrasonic atomizing nozzle of the present invention and a schematic diagram of the heat change during the micro-dropletization process. A sandwich piezoelectric chip is arranged inside the ultrasonic nozzle. The piezoelectric chip is made of an emission-type high-power material PZT-4 and has a size of 25×10×5mm. The larger piezoelectric chip size and sandwich design realize high-power and high-efficiency energy conversion.

[0055] The ultrasonic atomizing nozzle adopts a vertical design, and from top to bottom are the atomizing nozzle assembly and the amplitude transformer. The atomizing nozzle assembly includes a front cover plate, an electrode sheet, a piezoelectric chip and a rear cover, and adopts a coaxial circular stacked structure, and along the axial direction are the front cover plate, the electrode sheet, the piezoelectric chip, the electrode sheet, the piezoelectric chip and the rear cover plate.

[0056] The present invention uses a relatively large power (100W) ultrasonic atomizing nozzle to atomize organic polyamines with relatively large viscosity, and uses the heat generated when the ultrasonic atomizing nozzle is working to reduce the viscosity of the organic polyamines, thereby realizing the atomization of the organic polyamines with relatively large viscosity, and forming liquid amine micro-droplets with relatively small particle size and relatively narrow particle size distribution, and finally realizing microencapsulation through interfacial polymerization reaction, thereby preparing liquid amine microcapsules with relatively small particle size and relatively narrow particle size distribution. At the same time, the organic polyamine liquid continuously flowing through the ultrasonic atomizing nozzle takes away the heat generated by the nozzle, so that the nozzle is not overheated due to heat accumulation, and finally the spraying process is stable and continuous.

[0057] Example 1

[0058] (1) Preparation of tetraethylenepentamine (TEPA) microcapsules

[0059] Step 1: The reaction solution containing the shell monomer is continuously stirred or shaken to form a stable solution: the shell monomer is 4,4'-dicyclohexylmethane diisocyanate (HMDI), and the reaction solution is a mixture of a solvent (decalin) and a solute (Arlacel P135 as an ionic surfactant, HMDI as a shell monomer, and a catalyst triethylenediamine), wherein the weight ratio of HMDI, Arlacel P135, and the catalyst in each solute is 6:1:0.1, and each solute (7.1 g) is matched with 50 mL of decalin solvent. The prepared reaction solution is placed in a room temperature environment and stirred on a shaker or mechanically until a stable solution is formed.

[0060] Step 2: Prepare the prepared pure TEPA amine solution at room temperature using a homemade ultrasonic spray device (attached Figure 1 and 2)Micro-droplet formation is completed at a constant spraying rate (1 mL / h) at a power of 100 W and a frequency of 60 KHz. At a power of 100 W, the temperature of the ultrasonic nozzle is 50 - 60 °C. After the liquid amine is micro-dropletized, it falls into the reaction solution in Step 1. The liquid amine on the surface of the micro-droplets will quickly react with the shell-forming monomer (HMDI) in the reaction solution to form a polyurea thin wall layer to wrap the internal liquid amine, forming a mixed solution of primary microcapsules and the reaction solution.

[0061] Step 3: Take the mixed solution of the primary microcapsules and the reaction solution obtained in Step 2, or after replacing the reaction solution of this mixed solution, heat it to 40 °C, and use a mechanical stirrer to continuously stir the mixture at a speed of 350 r / min. When the mixture of the primary microcapsules containing liquid amine and the reaction solution is heated, the liquid amine will further diffuse through the polyurea thin wall layer already formed by the primary microcapsules and react with the shell-forming monomer (HMDI) in the reaction solution in the thin wall layer or near the outer wall to continue forming polyurea, gradually thickening the capsule wall of the primary microcapsules. After reacting for 5 h, primary microcapsules are obtained.

[0062] Step 4: Wash the primary microcapsules to remove the solvent and impurities therein to obtain finished microcapsules: First, add a cleaning agent to the primary microcapsules. This cleaning agent is pure cyclohexane. After stirring the mixed solution evenly and letting it stand until solid precipitation occurs, remove the supernatant, and repeat adding the cleaning agent to wash it 3 - 6 times. After removing the solvent and impurities therein, store it in clean cyclohexane to obtain a finished microcapsule dispersion.

[0063] Figure 3 This is the scanning electron microscope (SEM) image of the TEPA microcapsules synthesized in this example; Figure (a) is the overall dispersion diagram of tetraethylenepentamine (TEPA) microcapsules, and Figure (b) is the diagram of a single microcapsule. The viscosity of TEPA at 25 °C is 50 - 60 mPa·s. As can be seen from the figure, the liquid amine microcapsules prepared by this method have good dispersibility and dense capsule walls, and their average particle size is 41 ± 8.7 μm. When using an ultrasonic atomizing nozzle with a power as high as 100 W to atomize organic polyamines with relatively high viscosity. Under the action of the heat generated during the operation of the ultrasonic atomizing nozzle, the viscosity of the organic polyamines is reduced, making it easier to achieve their effective atomization. After atomization, liquid amine micro-droplets with small particle sizes and narrow particle size distributions are formed. These micro-droplets are then microencapsulated through an interfacial polymerization reaction to prepare liquid amine microcapsules with the same small particle sizes and narrow particle size distributions. At the same time, the organic polyamine liquid continuously flowing through the ultrasonic atomizing nozzle can take away the heat generated by the nozzle, effectively preventing the nozzle from overheating due to heat accumulation and ensuring the stable and continuous progress of the spraying process.

[0064] Comparative Example 1

[0065] The difference between this comparative example and Example 1 is that the self-made high-power ultrasonic atomizing nozzle (100 W) is replaced with a purchased low-power ultrasonic atomizing nozzle (20 W), and the remaining processes of this comparative example are the same as those of Example 1.

[0066] Traditional ultrasonic atomization technology can only atomize liquids with relatively low viscosities (such as water) to form micro-droplets with relatively small particle sizes. When the liquid to be atomized, such as organic polyamines, has a relatively high viscosity, it cannot be effectively atomized to form micro-droplets with relatively small and uniform particle size distributions. Figure 4 This is the scanning electron microscope (SEM) image of the TEPA microcapsules synthesized in this comparative example. As can be seen from the figure, the TEPA microcapsules synthesized using a low-power ultrasonic atomizing nozzle have large particle sizes and a large particle size distribution. In addition, they also contain a large amount of impurities and agglomerates. The reason for this phenomenon is that the low-power ultrasonic nozzle generates less heat during use. At this time, the temperature of the ultrasonic nozzle is between 25 - 35 °C, and the heating effect on the amine liquid in the flow channel is small. When the amine liquid reaches the atomizing end face through the flow channel, its viscosity is relatively high. When the viscosity of the amine liquid is relatively high, on the one hand, its micro-droplet formation will be more difficult. If the amine liquid on the atomizing end face of the ultrasonic atomizing nozzle cannot be normally atomized, it will directly drip into the reaction solution under the action of gravity, forming impurities and agglomerates; on the other hand, even if normal micro-droplet formation occurs, the particle size and particle size distribution of the micro-droplets are relatively large (72 ± 31.4 μm). In addition, due to the relatively high viscosity and close spacing of the micro-droplets, when they fall into the reaction solution, they are prone to form a structure of continuous microcapsules, resulting in serious agglomeration.

[0067] Comparative Example 2

[0068] The difference between this comparative example and Example 1 is that when using the self-made high-power ultrasonic atomizing nozzle (100 W) to atomize the TEPA amine liquid, the nozzle is cooled, and the cooling method is water cooling or air cooling. At this time, the temperature of the ultrasonic nozzle is between 20 - 30 °C, and the remaining processes of this comparative example are the same as those of Example 1.

[0069] Figure 5 This is the scanning electron microscope (SEM) image of the TEPA microcapsules synthesized in this comparative example. During the operation of the ultrasonic nozzle, it is cooled. Due to the relatively high viscosity of TEPA, cooling the ultrasonic spraying device reduces the heating effect on the atomized liquid, and the viscosity of the atomized liquid is still relatively high, manifested as unstable atomization effect of the ultrasonic spraying device and very poor micro-droplet formation effect on the liquid amine. Specifically, the synthesized microcapsules have large particle sizes (69 ± 34.7 μm) and are prone to adhesion. Therefore, the efficiency of preparing microcapsules with small particle sizes is greatly reduced.

[0070] Comparative Example 3

[0071] The difference between this comparative example and Example 1 is that the power of the self-made ultrasonic atomizing nozzle is adjusted from 100 W to 60 W, and the rest of the process in this comparative example is the same as that in Example 1.

[0072] Figure 6 This is the scanning electron microscope (SEM) image of the TEPA microcapsules synthesized in this comparative example. As can be seen from the figure, the particle size of the TEPA microcapsules synthesized after the power is reduced to 60 W is slightly larger, and the situation of microcapsule clustering is likely to occur. The reason for this phenomenon is that when the power of the nozzle is reduced to 60 W and TEPA with a relatively high viscosity is atomized, the temperature of the ultrasonic nozzle is between 40 - 50 °C at this time. The heat generated by the vibration of the piezoelectric wafer is not sufficient to fully heat the amine liquid in the flow channel. When the amine liquid flows to the atomizing end face of the nozzle, it still has a slightly high viscosity, resulting in a relatively large particle size after its micro-droplet formation. And because the nozzle generates less heat, the micro-droplet formation process on the atomizing surface of the nozzle will also be unstable, resulting in the phenomenon of microcapsule clustering shown in the figure.

[0073] Comparative Example 4

[0074] The difference between this comparative example and Example 1 is that the power of the self-made ultrasonic atomizing nozzle is adjusted from 100 W to 140 W, and the rest of the process in this comparative example is the same as that in Example 1.

[0075] After the ultrasonic power is increased to 140 W, TEPA micro-droplets can be normally sprayed at the initial stage of the micro-droplet formation process. However, due to the too high power, the heat generated by the vibration is much greater than the heat carried away by the amine liquid flowing through the flow channel, resulting in excessive heat accumulation inside the ultrasonic nozzle. When the temperature exceeds 60 °C, the frequency of the ultrasonic generator drops significantly until it is lower than the lowest working frequency of the ultrasonic nozzle, causing the nozzle to finally fail to work properly. The temperature of the ultrasonic nozzle has exceeded 70 °C before it stops working.

[0076] Example 2

[0077] The difference between this example and Example 1 is that the TEPA amine liquid (with a viscosity of 50 - 60 mPa·s at 25 °C) in Step 2 is replaced with a less viscous triethylenetetramine (TETA) amine liquid (with a viscosity of 10 - 25 mPa·s at 25 °C), and the rest of the process in this example is the same as that in Example 1.

[0078] Figure 7 This is the scanning electron microscope (SEM) image of the TETA microcapsules synthesized in this example; Figure (a) is the overall dispersion diagram of the TETA microcapsules, and Figure (b) is the diagram of a single microcapsule. As can be seen from the figure, the TETA microcapsules prepared by this method have good dispersibility and a dense capsule wall, and their average particle size is 38 ± 6.4 μm.

[0079] Example 3

[0080] The difference between this example and Example 1 is that the TEPA amine solution (with a viscosity of 50 - 60 mPa·s at 25°C) in Step 2 is replaced with a diethylenetriamine (DETA) amine solution with a lower viscosity (with a viscosity of 7 - 8 mPa·s at 25°C). The rest of the process in this example is the same as that in Example 1.

[0081] Figure 8 This is the scanning electron microscope (SEM) image of the DETA microcapsules synthesized in this example; Figure (a) is the overall dispersion diagram of the DETA microcapsules, and Figure (b) is the diagram of a single microcapsule. It can be seen from the figure that the DETA microcapsules prepared by this method have good dispersibility and a dense capsule wall, and their average particle size is 31 ± 5.3 μm.

[0082] Example 4

[0083] The difference between this example and Example 1 is that the TEPA amine solution (with a viscosity of 50 - 60 mPa·s at 25°C) in Step 2 is replaced with a polyether triamine (JEFFAMINE T403) amine solution with a higher viscosity (with a viscosity of 72 - 76 mPa·s at 25°C). The rest of the process in this example is the same as that in Example 1.

[0084] Figure 9 This is the scanning electron microscope (SEM) image of the T403 microcapsules synthesized in this example; Figure (a) is the overall dispersion diagram of the T403 microcapsules, and Figure (b) is the diagram of a single microcapsule. It can be seen from the figure that the liquid amine microcapsules prepared by this method have good dispersibility and a dense capsule wall, and their average particle size is 44 ± 10 μm.

[0085] By changing the core material to adjust the viscosity of the atomized liquid amine in the present invention, it can be concluded that the viscosity range of the liquid amine microcapsules that can be prepared by this method is relatively wide, and liquid amines with higher viscosities can be microencapsulated, broadening the scope of the field of liquid amine microencapsulation.

[0086] Example 5

[0087] The difference between this example and Example 1 is that the spraying rate is adjusted from 1 mL / h to 5 mL / h. The rest of the process in this example is the same as that in Example 1.

[0088] Example 6

[0089] The difference between this example and Example 1 is that the spraying rate is adjusted from 1 mL / h to 10 mL / h. The rest of the process in this example is the same as that in Example 1.

[0090] Example 7

[0091] The difference between this example and Example 1 is that the spraying rate is adjusted from 1 mL / h to 20 mL / h. The rest of the process in this example is the same as that in Example 1.

[0092] Comparing the above Examples 1, 5, 6, and 7, Figure 10 (a) is the optical dispersion diagram of TEPA microcapsules prepared in Example 1 at a spraying rate of 1 mL / h, Figure 10 (b) is the optical dispersion diagram of TEPA microcapsules prepared in Example 5 at a spraying rate of 5 mL / h, Figure 10 (c) is the optical dispersion diagram of TEPA microcapsules prepared in Example 6 at a spraying rate of 10 mL / h, Figure 10 (d) is the optical dispersion diagram of TEPA microcapsules prepared in Example 7 at a spraying rate of 20 mL / h. It can be seen from the figure that the TEPA microcapsules prepared at different spraying rates all have good dispersibility and there is no agglomeration phenomenon.

[0093] Figure 11 (a) is the particle size statistical diagram of TEPA microcapsules prepared in Example 1 at a spraying rate of 1 mL / h, Figure 11 (b) is the particle size statistical diagram of TEPA microcapsules prepared in Example 5 at a spraying rate of 5 mL / h, Figure 11 (c) is the particle size statistical diagram of TEPA microcapsules prepared in Example 6 at a spraying rate of 10 mL / h, Figure 11 (d) is the particle size statistical diagram of TEPA microcapsules prepared in Example 7 at a spraying rate of 20 mL / h. It can be seen from the statistical diagram that the average particle sizes of the TEPA microcapsules prepared at different spraying rates are all relatively small (30 - 50 μm). The particle size dispersion indices of Examples 1, 5, 6, and 7 are 0.17, 0.21, 0.30, and 0.37 respectively, indicating that the particle size distributions of the TEPA microcapsules prepared at different spraying rates are narrow. Using this method, TEPA microcapsules with small particle sizes can be obtained, and more small particle size microcapsules can also be obtained at a relatively large injection rate. Comparing the above examples, for the TEPA amine solution with higher viscosity, this method can improve the preparation efficiency of microcapsules without affecting the quality of the microcapsules.

[0094] Comparative Example 5

[0095] The difference between this comparative example and Example 1 is that the reaction temperature in the capsule wall growth stage in step (3) is adjusted from 40 °C to 50 °C, and the rest of the process in this example is the same as that in Example 1. Figure 12 This is the scanning electron microscope (SEM) image of the TEPA microcapsules synthesized in this example. It can be seen from the figure that the surface morphology of the TEPA microcapsules synthesized under this condition is rough, there are more impurities, and there is an agglomeration phenomenon. The reason for this phenomenon is that at a higher temperature in the capsule wall growth stage, the diffusion distance of the core liquid to the outside of the capsule wall will increase, resulting in a rough capsule wall structure and the agglomeration phenomenon of the microcapsules.

[0096] Comparative Example 6

[0097] The difference between this comparative example and Example 1 is that the reaction temperature in the capsule wall growth stage in step (3) is adjusted from 40°C to 60°C, and the remaining processes of this example are the same as those of Example 1.

[0098] Figure 13 This is the scanning electron microscope (SEM) image of the TEPA microcapsules synthesized in this example. As can be seen from the figure, the surface morphology of the TEPA microcapsules synthesized under this condition is rough, with more impurities and agglomeration. The reason for this phenomenon is that in the capsule wall growth stage, the outward diffusion distance of the microcapsule core liquid is farther at this temperature, so the capsule wall morphology is rougher and more prone to agglomeration.

[0099] Example 8

[0100] The difference between this example and Example 1 is that in step 3, two self-made spray nozzles are connected to atomize the polyamine solution at the same time, and the remaining processes of this example are the same as those of Example 1.

[0101] Figure 14 This is the scanning electron microscope (SEM) image of the TEPA microcapsules synthesized in this example. The microcapsules synthesized by this method have good dispersibility and small particle size. It can effectively improve the synthesis efficiency of small particle size microcapsules.

[0102] The above embodiments are the preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A preparation method of small-particle-size liquid amine microcapsules, characterized in that It includes the following steps: Firstly, the liquid amine is subjected to micro-droplet treatment by ultrasonic spraying to obtain liquid amine micro-droplets, and the liquid amine micro-droplets are made to fall into the reaction solution to form primary microcapsules, obtaining a mixed solution of primary microcapsules and the reaction solution; then the mixed solution is heated and continuously stirred or shaken to obtain primary microcapsules; and then the primary microcapsules are washed, and the solvent and impurities are removed to obtain small-sized liquid amine microcapsules.

2. The preparation method of the small-particle-size liquid amine microcapsules according to claim 1, wherein The temperature of the micro-droplet treatment is 50 - 60 °C.

3. The preparation method of the small-particle-size liquid amine microcapsules according to claim 1, wherein The ultrasonic power of the micro-droplet treatment is 70 - 130 W, and the spraying rate is 1 - 20 mL / h.

4. The preparation method of the small-particle-size liquid amine microcapsules according to claim 1, characterized in that, The liquid amine is at least one or any mixture of more than one of ethylenediamine condensate, polyetheramine, fatty amine, polypropyleneamine, and aromatic amine, and the viscosity of the liquid amine is 5 - 80 mPa·s.

5. The preparation method of the small-particle-size liquid amine microcapsules according to any one of claims 1 to 4, characterized in that, The reaction solution is a reaction solution containing shell-forming monomers, including a solute and a solvent; The solute includes shell-forming monomers, surfactants, and catalysts, and the solvent is a non-polar or weakly polar solvent; The mass-volume ratio g / mL of the solute to the solvent is 0.5 - 2:35 - 65.

6. The preparation method of the small-particle-size liquid amine microcapsule according to claim 5, characterized in that, The shell-forming monomer is any one or any combination of more than one of 4,4'-dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and toluene diisocyanate; The surfactant is Arlacel P135; The catalyst is any one or any combination of more than one of triethylenediamine, 2,4,6-tris(dimethylaminomethyl)phenol, or dibutyltin dilaurate; The weight ratio of the shell-forming monomer, surfactant, and catalyst in the solute is 3 - 12:0.05 - 2:0 - 1.

7. The preparation method of the small-particle-size liquid amine microcapsules according to claim 1, characterized in that, The temperature of the heating is 40 °C - 60 °C, and the time is 3 - 7 hours; The cleaning process is as follows: Firstly, a cleaning agent, which is pure cyclohexane, is added to the primary microcapsules. After stirring evenly and standing until the solid precipitates, the supernatant is removed, and the addition of the cleaning agent for cleaning is repeated 3 - 6 times. After removing the solvent and impurities therein, a dispersion of small-sized liquid amine microcapsules is obtained, and the small-sized liquid amine microcapsules are stored in cyclohexane.

8. A small particle size liquid amine microcapsule, characterized in that, Prepared by the method according to any one of claims 1 - 7.

9. The small particle size liquid amine microcapsule according to claim 8, characterized in that, The particle size of the liquid amine microcapsules is 30 - 50 μm.

10. A micro-droplet forming device for the preparation method according to claim 1, characterized in that, It includes an ultrasonic generator, an ultrasonic atomizing nozzle, an injection pump, a syringe, a shaker, and a container; A piezoelectric wafer is arranged inside the ultrasonic atomizing nozzle, and there are at least two piezoelectric wafers, and the material of the piezoelectric wafer is PZT-4.

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