CN116037018A - Phase-change microcapsule carrier particles for spray freeze drying process and preparation method thereof - Google Patents
Phase-change microcapsule carrier particles for spray freeze drying process and preparation method thereof Download PDFInfo
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- CN116037018A CN116037018A CN202310121147.5A CN202310121147A CN116037018A CN 116037018 A CN116037018 A CN 116037018A CN 202310121147 A CN202310121147 A CN 202310121147A CN 116037018 A CN116037018 A CN 116037018A
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- OZAIFHULBGXAKX-UHFFFAOYSA-N 2-(2-cyanopropan-2-yldiazenyl)-2-methylpropanenitrile Chemical group N#CC(C)(C)N=NC(C)(C)C#N OZAIFHULBGXAKX-UHFFFAOYSA-N 0.000 claims description 22
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- 229910001870 ammonium persulfate Inorganic materials 0.000 claims description 5
- DBMJMQXJHONAFJ-UHFFFAOYSA-M Sodium laurylsulphate Chemical compound [Na+].CCCCCCCCCCCCOS([O-])(=O)=O DBMJMQXJHONAFJ-UHFFFAOYSA-M 0.000 claims description 4
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
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- 206010057040 Temperature intolerance Diseases 0.000 description 1
- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical compound CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 description 1
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- WSFSSNUMVMOOMR-NJFSPNSNSA-N methanone Chemical compound O=[14CH2] WSFSSNUMVMOOMR-NJFSPNSNSA-N 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J13/00—Colloid chemistry, e.g. the production of colloidal materials or their solutions, not otherwise provided for; Making microcapsules or microballoons
- B01J13/02—Making microcapsules or microballoons
- B01J13/04—Making microcapsules or microballoons by physical processes, e.g. drying, spraying
- B01J13/043—Drying and spraying
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J13/00—Colloid chemistry, e.g. the production of colloidal materials or their solutions, not otherwise provided for; Making microcapsules or microballoons
- B01J13/02—Making microcapsules or microballoons
- B01J13/06—Making microcapsules or microballoons by phase separation
- B01J13/14—Polymerisation; cross-linking
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K5/00—Heat-transfer, heat-exchange or heat-storage materials, e.g. refrigerants; Materials for the production of heat or cold by chemical reactions other than by combustion
- C09K5/02—Materials undergoing a change of physical state when used
- C09K5/06—Materials undergoing a change of physical state when used the change of state being from liquid to solid or vice versa
- C09K5/063—Materials absorbing or liberating heat during crystallisation; Heat storage materials
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/14—Thermal energy storage
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Dispersion Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Combustion & Propulsion (AREA)
- Thermal Sciences (AREA)
- Materials Engineering (AREA)
- Manufacturing Of Micro-Capsules (AREA)
Abstract
The invention relates to a phase-change microcapsule carrier particle for a spray freeze drying process, which is formed by granulating a plurality of phase-change microcapsules, wherein each phase-change microcapsule comprises a phase-change core material and a wall material wrapping the phase-change core material, the wall material is a resin wall material, the particle size of each phase-change microcapsule is 10-20 um, and the phase-change temperature is the secondary drying temperature of spray freeze drying; the particle size of the phase-change microcapsule carrier particles is 4mm-5mm. According to the preparation method of the phase-change microcapsule carrier particles, a high molecular wall material is mixed with an initiator to obtain a wall material prepolymer suspension, the wall material prepolymer suspension is mixed with a phase-change material to obtain an oil phase system, the oil phase system is mixed with deionized water mixed with a dispersing agent and subjected to suspension polymerization reaction to obtain phase-change microcapsule carrier particles, and the phase-change microcapsule carrier particles are prepared through granulation. The phase change microcapsule carrier particle core material is not easy to leak, the coating rate is high and can reach 90%, the latent heat value is high, the mechanical property is good, the stability is good, and a solid foundation is provided for being applied to a spray freeze drying device.
Description
Technical Field
The invention belongs to the technical field of cold and hot phase change energy storage microcapsule preparation, and particularly relates to phase change microcapsule carrier particles for a spray freeze drying process and a preparation method thereof.
Background
The microcapsule technology is a technology of wrapping solid, gas or liquid by using a film-forming material to form a tiny container isolated from the external environment, wherein a substance wrapped in the microcapsule is called a core material, a substance used for wrapping the core material is called a wall material, and the particle size of the microcapsule is generally in the range of 1-1000 um. Phase change energy storage materials refer to materials that provide latent heat through a transformation of the state of the material itself, and the temperature does not change during the process. By microcapsule technology, a phase change material can be used as a core material to be coated, and the phase change material absorbs or releases a large amount of latent heat to achieve the purpose of storing energy, and the obtained substance is called Phase Change Microcapsule (PCM).
Spray freeze drying is a novel and advanced particle preparation technology, and is commonly used for preparing high value-added foods and powder products with heat sensitivity and biological activity. The powder prepared by the spray freeze drying technology has fluffy powdery or granular particles with porous surfaces and interiors, and spherical particles obtained by drying frozen materials under reduced pressure have excellent fluidity and can well retain the biological activity of products. However, the current spray freeze drying technology is not mature enough and has a plurality of problems. The spray freeze drying process mainly comprises three steps (figure 1), namely, atomizing, and atomizing the solution to be dried into fine mist drops by utilizing atomizers of different types according to the product needs; secondly, freezing, namely rapidly cooling and freezing the fog drops through low-temperature gas or liquid to form frozen particles; finally, unnecessary solvent and the like are removed by sublimation to form a dry powder. Because the spray freeze drying technology needs to keep high vacuum and low temperature environment all the time in the drying process, the problems of limited heat transfer and mass transfer driving force of materials, influence on drying efficiency, long drying time, high energy consumption, high cost and the like of spray freeze drying are caused.
Therefore, the method for utilizing the phase-change microcapsule as inert carrier particles is proposed on the basis of spray freeze drying aiming at the purposes of reducing the energy consumption and improving the drying rate of a spray freeze drying device, namely, after the materials are frozen into ice particles, the frozen ice particles are uniformly sprayed on the surfaces of the precooled phase-change microcapsule carrier particles, and then the phase-change microcapsule carrier particles with the ice particles coated on the surfaces are put into a freeze dryer for freeze drying, so that the materials can obtain heat through a heating plate, and meanwhile, the heat transfer can be carried out through the phase-change microcapsule attached to the surfaces of the materials, the contact surface area of the materials is greatly increased, powder products are prepared through the processes of freezing, vacuum drying, stripping and the like, and the problem of low heat transfer and mass transfer efficiency in the spray freeze drying process can be better solved through the method of introducing the phase-change microcapsule carrier particles, and the drying performance of spray freeze drying equipment is effectively improved. Therefore, there is a need to develop a phase change microcapsule carrier particle and a preparation method suitable for spray freeze drying.
The patent CN114870760A proposes a preparation method of inorganic shell material phase-change microcapsules, which is to add an inorganic shell material precursor solution into a phase-change system for hydrolysis condensation reaction to obtain the inorganic shell material phase-change microcapsules, wherein the core material is one or more of paraffin phase-change materials, fatty acid phase-change materials, inorganic salt phase-change materials and polyalcohol phase-change materials, and the inorganic shell material precursor comprises one or more of a silicon-containing precursor and a titanium-containing precursor. Although the method can successfully encapsulate the phase-change material into the inorganic shell material, the tetraethyl orthosilicate is used as the shell material, the mechanical property of the microcapsule wall material is poor, the porosity of the wall material is large, and the problems of leakage of the core material, damage to spray freeze drying equipment, low coating rate, short service life and the like are caused.
Patent CN114307889a proposes a phase-change microcapsule with photochromic function coated by double-layer wall material and its preparation method. Under the precondition of ensuring the full function of the microcapsule core material, the patent provides excellent mechanical property and heat resistance, and the silicon dioxide wall material on the surface overcomes the defect of lower compactness of the wall material in the polyurea-polyurethane copolymer, thereby further enhancing the stability of the microcapsule. However, various chemical reactions are involved in the preparation process, and the polyurea resin may have unreacted monomers such as formaldehyde, which is not suitable for use in spray freeze drying equipment.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, and provides the phase-change microcapsule carrier particles which are used for a spray freeze drying process, take a phase-change material as a core material, take an organic polymer material as a wall material, adopt a suspension polymerization technology to realize efficient encapsulation of the phase-change material, obtain the phase-change microcapsule carrier particles with a core-shell structure, wherein the phase-change material is completely encapsulated, have good mechanical properties and thermal stability, have high encapsulation rate, and meet the use requirement of serving as inert carrier particles in spray freeze drying.
Another object of the present invention is to provide a method for preparing the phase-change microcapsule carrier particles.
The invention aims at the technical purposes and is realized by the following technical scheme:
a phase change microcapsule carrier particle for use in a spray freeze drying process, characterized by: the phase-change microcapsule carrier particles are formed by granulating a plurality of phase-change microcapsules, the phase-change microcapsules comprise a phase-change core material and wall materials for wrapping the phase-change core material, the wall materials are resin wall materials, the particle size of the phase-change microcapsules is 10-20 um, and the phase-change temperature is the spray freeze drying secondary drying temperature; the particle size of the phase-change microcapsule carrier particles is 4mm-5mm.
The wall material is methyl methacrylate, polyurethane or melamine resin.
The core material is paraffin wax, and the paraffin wax is n-octadecane, n-eicosane or n-docosane.
Moreover, the phase-change microcapsule has a fixed core-shell ratio of 1:1 or 3:4 or 4:3.
Furthermore, the phase transition temperature is 35-45 ℃.
A method of preparing phase change microcapsule carrier particles for use in a spray freeze drying process comprising the steps of:
step 1): adding dispersant polyvinyl alcohol into deionized water, and mixing to obtain a first mixed solution with the weight percent of 0.5-1.0;
step 2): heating the first mixed solution to 85-90 ℃, keeping the stirring speed at 200-300rpm, stirring until the solution is clear, and standing aside to cool to 50 ℃ for standby;
Step 3): mixing resin wall materials and an initiator which can be used for free radical type polyaddition reaction, and slightly oscillating until the solution is clear and white granular substances cannot be observed by naked eyes to obtain a prepolymer suspension;
step 4): the core material of the organic phase change material is melted by heating in water bath and then is dripped into the prepolymer suspension, the core material solution and the prepolymer suspension can be observed to be divided into an upper layer and a lower layer, and at the moment, the mixed solution is stirred to form uniform oil phase mixed solution;
step 5): adding the uniform oil phase mixture obtained in the step 4) into the solution obtained in the step two, heating to 70-80 ℃, adding into a digital display high-speed homogenizing and dispersing machine for emulsification, setting the rotating speed of the homogenizing and dispersing machine to 5000-6000rpm, and the emulsification time to 15-20min, thus obtaining emulsion after emulsification;
step 6): maintaining the temperature of the emulsion obtained in the step 5) at 70-80 ℃, putting the emulsion into a constant-temperature magnetic stirrer, and stirring at 200-300rpm for at least 5-6h;
step 7): the emulsion obtained in the step 6) is phase-change microcapsule emulsion with the coating rate of 80% -90%; filtering, washing and drying the cooled product to obtain phase-change microcapsules;
Step 8): and molding the phase-change microcapsule into phase-change microcapsule carrier particles with the diameter of 4-5mm through a plastic mold.
And the initiator is azodiisobutyronitrile or ammonium persulfate or lauroyl peroxide.
In step 1), after the polyvinyl alcohol is completely dissolved in deionized water, sodium dodecyl sulfate as a dispersant is added to the aqueous solution of polyvinyl alcohol to be thoroughly mixed.
And in the step 8), the prepared phase-change microcapsule and the adhesive are mixed and then injected into a spherical molding die with the diameter of 4-5mm, the weight ratio of the microcapsule to the adhesive is 5-7:2, the microcapsule and the adhesive are heated at 30 ℃ for curing, and finally the phase-change microcapsule carrier particles are obtained after demoulding treatment.
The adhesive is epoxy resin and aromatic ammonia, and the weight ratio of the epoxy resin to the aromatic ammonia is 1:2-3
Compared with the prior art, the invention has the following outstanding effects:
1. the phase-change microcapsule carrier particles with the complete core-shell structure have good thermal stability, do not contain substances harmful to human health, and can be used as inert particles in a spray freeze drying device with reliability; polymethyl methacrylate (PMMA) is formed by suspension polymerization of Methyl Methacrylate (MMA) and is used as a shell, the shell has good mechanical properties, under the condition of external force impact, the shell comprises the process that microcapsule particles are rubbed with each other in the process of microcapsule preparation and the small ice crystals sprayed out after spraying treatment of materials to be dried are sprayed onto microcapsule carrier particles, the integrity and elasticity of the capsule body can be effectively maintained, the capsule core materials are protected from being damaged, the phase-change microcapsule is microsphere, the phase-change enthalpy value of the phase-change microcapsule is up to 179J/g, the thermal conductivity of the phase-change microcapsule can be up to 1.45W/m.K, and the phase-change enthalpy value of the phase-change microcapsule after 100 times of cold-heat cycles is at least 160J/g.
2. The phase-change microcapsule carrier particles with the complete core-shell structure have the complete core-shell structure, and achieve the aim of improving the drying efficiency of a spray freeze drying device by serving as inert particles in the spray freeze drying device; the drying material not only can obtain heat from the heating plate in the drying chamber, but also can obtain heat from the interior of the microcapsule through the phase change of the phase change microcapsule, namely, the phase change latent heat of the microcapsule carrier particles is utilized through the phase change of the microcapsule carrier particles in the spray freeze drying stage, when the temperature of the heating plate reaches the set temperature (the phase change temperature of the phase change microcapsule at the same time), the temperature in the cavity is lower than the phase change temperature of the microcapsule along with the absorption of the heat by the material, the microcapsule is changed from the liquid state to the solid state, a large amount of latent heat is released, the heat is provided for the microcapsule, and the process is repeated repeatedly in the whole drying process. Therefore, the heating plate not only provides heat for the drying material through heat transfer, but also provides heat for the drying material through a great amount of latent heat release due to the change of the phase state of the phase change microcapsule, and the drying efficiency of the material can be effectively improved through combination of the two modes. The normally inert particles provide heat to the dry material only by heat transfer; meanwhile, as the phase-change microcapsule is attached to the surface of the material, the heated surface area of the material is greatly increased.
3. According to the phase change microcapsule carrier particles with the complete core-shell structure, aiming at the characteristics of inert particles required in the spray freeze drying process, the high-molecular organic shell material with high mechanical strength and the phase change material paraffin with high phase change latent heat are adopted, and the phase change material paraffin is encapsulated in a microencapsulated mode through the high-molecular organic shell material, so that the phase change microcapsule carrier particles can be well applied to the spray freeze drying process and used as the inert particles, and the drying efficiency of spray freeze drying equipment is improved.
Drawings
FIG. 1a is an emulsion dispersion diagram of the phase change microcapsules prepared in example 1;
FIG. 1b is a SEM micrograph (700 times) of the phase change microcapsules prepared in example 1 after drying;
FIG. 1c is a SEM micrograph (2000 times) of the phase change microcapsules prepared in example 1 after drying;
FIG. 1d is a SEM micrograph (1000 times) of a partially broken phase change microcapsule prepared according to example 1;
FIG. 1e shows the phase change microcapsules of example 2 with significant dishing and debris adhesion;
FIG. 1f shows that the phase change microcapsules prepared in example 3 have significantly reduced microcapsule adhesion debris;
FIG. 2 is a thermogravimetric graph of the phase change microcapsule prepared in example 1, wherein the abscissa is temperature and the ordinate is mass percent;
FIG. 3 is a phase change latent heat diagram obtained by preparing phase change microcapsules in example 1;
FIG. 4a is a plot of spray-freeze dried material mass versus time without phase change microcapsule carrier particles added;
FIG. 4b is a graph showing the mass of spray-freeze-dried material with the addition of phase-change microcapsule carrier particles over time
Fig. 5 is a graph showing drying rate curves in two modes of spray freeze drying without the addition of phase change microcapsule carrier particles and spray freeze drying with the addition of phase change microcapsule carrier particles.
Detailed Description
The invention is further illustrated by the following examples, which are intended to be illustrative only and not limiting in any way.
Example 1
The phase-change microcapsule carrier particles are formed by granulating a plurality of phase-change microcapsules, the phase-change microcapsules comprise a phase-change core material and a wall material wrapping the phase-change core material, the wall material is methyl methacrylate, the core material is n-octadecane, the particle size of the phase-change microcapsules is 15um, the phase-change temperature of the core material is 40 ℃, and the phase-change microcapsule carrier particles are consistent with the secondary drying temperature of spray freeze drying; the particle size of the phase-change microcapsule carrier particle is 5mm. The core-shell ratio of the phase-change microcapsule in the embodiment is 1:1.
The preparation method of the phase-change microcapsule carrier particle for the spray freeze drying process comprises the following steps:
step 1): adding dispersant polyvinyl alcohol into deionized water, mixing to obtain a first mixed solution with the weight percent of 1 percent, wherein the specific steps are as follows: taking a beaker of 300ml, weighing 120ml of deionized water by using a measuring cylinder, adding the deionized water into the beaker, placing the beaker on one side, weighing 1.20g of dispersing agent polyvinyl alcohol by using an electronic balance, adding the weighed dispersing agent into the pre-measured deionized water, standing for 30 minutes, placing the beaker into an electromagnetic stirrer (the water bath temperature is set to 90 ℃), continuously stirring for 30 minutes until the solution is clear, and completely dissolving the polyvinyl alcohol into the deionized water to obtain a first mixed solution polyvinyl alcohol aqueous solution with the concentration of 1.0wt% for standby as an aqueous phase.
Step 2): heating the first mixed solution to 85-90 ℃, keeping the stirring speed at 200-300rpm, stirring until the solution is clear, and standing aside to cool to 50 ℃ for standby;
step 3): mixing wall methyl methacrylate and an initiator which can be used as a free radical type polyaddition reaction, and slightly oscillating until the solution is clear and white granular substances cannot be observed by naked eyes to obtain a prepolymer suspension, wherein the preparation method comprises the following specific steps of: weighing 15g of Methyl Methacrylate (MMA) in a 50mL beaker by using a liquid transfer device, placing the solution on one side for standby, weighing 0.45g of Azobisisobutyronitrile (AIBN) by using weighing paper as an initiator of polyaddition reaction, adding the azobisisobutyronitrile into the weighed methyl methacrylate for dissolution, and stopping the reaction when the solution is colorless and transparent, namely, the azobisisobutyronitrile is fully dissolved, so as to obtain methyl methacrylate prepolymer suspension;
Step 4): the organic phase change material is melted by heating in water bath and then is dripped into the prepolymer suspension, the core material solution and the prepolymer suspension can be observed to be divided into an upper layer and a lower layer, at the moment, the mixed solution is stirred to form a uniform oil phase, and the specific steps are as follows: weighing 15g of n-octadecane paraffin by using weighing paper, placing the weighing paper into a beaker, standing for later use on one side, heating a water bath kettle to 50 ℃, placing the weighed paraffin into the water bath kettle at 50 ℃, heating and melting the paraffin, controlling the water bath temperature to 50 ℃, slowly dripping the methyl methacrylate prepolymer suspension into the core emulsion by using a dropping funnel, and mixing and stirring the methyl methacrylate prepolymer suspension and the paraffin to form a uniform oil phase;
step 5): adding the mixed solution obtained in the step 4) into the solution obtained in the step 2), heating the system to 70-80 ℃, and adding the system into a digital display high-speed homogenizing and dispersing machine for emulsification, wherein the rotating speed of the homogenizing and dispersing machine is set to 5000-6000rpm, the emulsification time is 15min, and the emulsion is obtained after the emulsification is completed; in this example, the temperature of the aqueous phase prepared in step 2) was controlled between 45-50deg.C, and the prepared oil phase was added to an aqueous phase formed by 120ml deionized water and 1.20g surfactant polyvinyl alcohol (PVA) while stirring at 6000rpm for 15min to form a stable oil-in-water solution emulsion.
Step 6): maintaining the temperature of the emulsion obtained in the step 5) at 70-80 ℃, putting the emulsion into a constant-temperature magnetic stirrer, and stirring at 200-300rpm for 5h; in this example, the solution was rapidly poured into a three-necked flask and reacted under continuous stirring in a constant temperature magnetic stirrer at 70℃and 230rpm for 5 hours.
Step 7): and (3) performing filtration, collection, washing and drying in a vacuum drying oven to obtain the phase-change microcapsule of white powder, wherein the coating rate of the phase-change microcapsule of the emulsion obtained in the step (6) after cooling is 90%.
Step 8): the phase-change microcapsule is molded into phase-change microcapsule carrier particles with the diameter of 5mm through a plastic mold, in the embodiment, the prepared phase-change microcapsule is mixed with an adhesive and then injected into a spherical molding mold with the diameter of 5mm, the weight ratio of the microcapsule to the adhesive is 6:2, and the adhesive adopts epoxy resin and aromatic ammonia, and the weight ratio is 1:2.5; and (3) heating at 30 ℃ for curing, and finally demoulding to obtain the phase-change microcapsule carrier particles.
The spray freeze drying process of the present invention is accomplished in existing spray freeze drying systems having a secondary heating stage.
Example 2
The phase-change microcapsule carrier particles are formed by granulating a plurality of phase-change microcapsules, the phase-change microcapsules comprise a phase-change core material and a wall material wrapping the phase-change core material, the wall material is polyurethane, the core material is n-eicosane paraffin, the particle size of the phase-change microcapsules is 10um, and the phase-change temperature is 40 ℃; the particle size of the phase-change microcapsule carrier particle is 4mm. The core-shell ratio of the phase-change microcapsule in the embodiment is 4:3.
The preparation method of the phase-change microcapsule carrier particle for the spray freeze drying process comprises the following steps:
step 1): adding dispersant polyvinyl alcohol into deionized water, mixing to obtain a first mixed solution with the weight percent of 0.5, wherein the specific steps are as follows: taking a beaker of 300ml, weighing 120ml of deionized water by using a measuring cylinder, adding the deionized water into the beaker, placing the beaker on one side, weighing 0.6g of dispersing agent polyvinyl alcohol by using an electronic balance by using another weighing paper, adding the weighed dispersing agent into the pre-measured deionized water, standing for 30 minutes, placing the beaker into an electromagnetic stirrer (the water bath temperature is set to 90 ℃), continuously stirring for 30 minutes until the solution is clear, and completely dissolving the polyvinyl alcohol into the deionized water to obtain a first mixed solution polyvinyl alcohol aqueous solution with the concentration of 0.5wt% for standby as an aqueous phase.
Step 2): heating the first mixed solution to 85-90 ℃, keeping the stirring speed at 200-300rpm, stirring until the solution is clear, and standing aside to cool to 50 ℃ for standby;
step 3): wall materialPolyurethaneAnd an initiator which can be used as free radical polyaddition reaction, and slightly oscillating until the solution is clear and white granular substances cannot be observed by naked eyes, thus obtaining a prepolymer suspension, which comprises the following specific steps: weighing 15g of polyurethane in a 50mL beaker by using a liquid transfer device, placing the polyurethane in one side for later use, weighing 0.45g of ammonium persulfate by using weighing paper as an initiator of addition polymerization, adding the ammonium persulfate into the weighed polyurethane for dissolution, and stopping the reaction when the solution is colorless and transparent, namely fully dissolving the ammonium persulfate to obtain polyurethane prepolymer suspension;
step 4): the organic phase change material is melted by heating in water bath and then is dripped into the prepolymer suspension, the core material solution and the prepolymer suspension can be observed to be divided into an upper layer and a lower layer, at the moment, the mixed solution is stirred to form a uniform oil phase, and the specific steps are as follows: weighing 20g of n-eicosane by using weighing paper, placing the weighing paper in a beaker, standing for later use on one side, heating a water bath kettle to 50 ℃, placing the weighed paraffin into the water bath kettle at 50 ℃, heating and melting, controlling the water bath temperature to 50 ℃, slowly dripping the polyurethane prepolymer into the core emulsion by using a dropping funnel, and mixing and stirring the polyurethane prepolymer and the paraffin to form a uniform oil phase.
Step 5): adding the mixed solution obtained in the step 4) into the solution obtained in the step 2), heating the system to 70-80 ℃, and adding the system into a digital display high-speed homogenizing and dispersing machine for emulsification, wherein the rotating speed of the homogenizing and dispersing machine is set to 5000-6000rpm, the emulsification time is 15min, and the emulsion is obtained after the emulsification is completed; in this example, the temperature of the aqueous phase prepared in step 2) was controlled between 45-50 ℃, and the prepared oil phase was added to the aqueous phase obtained in step 1) while stirring at 6000rpm for 15min to form a stable oil-in-water solution emulsion.
Step 6): maintaining the temperature of the emulsion obtained in the step 5) at 70-80 ℃, putting the emulsion into a constant-temperature magnetic stirrer, and stirring at 200-300rpm for 5-7h; in this example, the solution was rapidly poured into a three-necked flask and reacted under continuous stirring in a constant temperature magnetic stirrer at 70℃and 230rpm for 5 hours.
Step 7): cooling the emulsion obtained in the step 6), and then filtering, collecting, washing, drying and drying the emulsion to obtain a phase-change microcapsule, wherein the coating rate of the phase-change microcapsule is 80%; in this embodiment, the emulsion obtained in step 6) is filtered, collected, washed and dried, and finally, dried in a vacuum drying oven to obtain white powder, thereby completing the preparation of the phase-change microcapsule.
Step 8): the phase-change microcapsule is molded into phase-change microcapsule carrier particles with the diameter of 4mm through a plastic mold, in the embodiment, the prepared phase-change microcapsule is mixed with an adhesive and then injected into a spherical molding mold with the diameter of 4mm, the weight ratio of the microcapsule to the adhesive is 5:2, the adhesive adopts epoxy resin and aromatic ammonia, the weight ratio of the adhesive is 1:2, the mixture is injected into the spherical molding mold with the diameter of 4mm, the mixture is heated and cured at 30 ℃, and finally the demolding treatment is carried out, so that the phase-change microcapsule carrier particles are obtained.
Example 3
The phase-change microcapsule carrier particles are formed by granulating a plurality of phase-change microcapsules, the phase-change microcapsules comprise a phase-change core material and a wall material wrapping the phase-change core material, the wall material is melamine resin, the core material is n-docosane paraffin, the particle size of the phase-change microcapsules is 20um, and the phase-change temperature is 40 ℃; the particle size of the phase-change microcapsule carrier particle is 4.5mm. The core-shell ratio of the phase-change microcapsule in the embodiment is 3:4.
The preparation method of the phase-change microcapsule carrier particle for the spray freeze drying process comprises the following steps:
Step 1): adding dispersant polyvinyl alcohol into deionized water, mixing to obtain a first mixed solution with the weight percent of 0.8, wherein the specific steps are as follows: taking a beaker of 300ml, weighing 120ml of deionized water by using a measuring cylinder, adding the deionized water into the beaker, placing the beaker on one side, weighing 0.96g of dispersing agent polyvinyl alcohol by using an electronic balance by using another weighing paper, adding the weighed dispersing agent into the pre-measured deionized water, standing for 30 minutes, placing the beaker into an electromagnetic stirrer (the water bath temperature is set to 90 ℃), continuously stirring for 30 minutes until the solution is clear, and completely dissolving the polyvinyl alcohol into the deionized water to obtain a first mixed solution polyvinyl alcohol aqueous solution with the concentration of 0.8wt% for standby as an aqueous phase.
Step 2): heating the first mixed solution to 85-90 ℃, keeping the stirring speed at 200-300rpm, stirring until the solution is clear, and standing aside to cool to 50 ℃ for standby;
step 3): mixing wall melamine resin and initiator capable of being used as free radical addition polymerization, and slightly oscillating until the solution is clear and white granular matters cannot be observed by naked eyes to obtain prepolymer suspension, wherein the preparation method comprises the following specific steps: weighing 20g of melamine resin in a 50mL beaker by using a liquid transfer device, putting the melamine resin in one side for standby, weighing 0.6g of lauroyl peroxide (AIBN) by using weighing paper as an initiator of addition polymerization, adding lauroyl peroxide into the weighed melamine resin for dissolution, and stopping the reaction when the solution is colorless and transparent, namely fully dissolving the lauroyl peroxide to obtain melamine resin prepolymer suspension;
Step 4): the organic phase change material is melted by heating in water bath and then is dripped into the prepolymer suspension, the core material solution and the prepolymer suspension can be observed to be divided into an upper layer and a lower layer, at the moment, the mixed solution is stirred to form a uniform oil phase, and the specific steps are as follows: weighing 15g of paraffin wax by using weighing paper, placing the paraffin wax in a beaker, standing for later use on one side, heating a water bath kettle to 50 ℃, placing the weighed paraffin wax in the water bath kettle at 50 ℃, heating and melting the paraffin wax, controlling the water bath temperature to 50 ℃, slowly dripping melamine resin prepolymer suspension into core emulsion by using a dropping funnel, and mixing and stirring the melamine resin prepolymer suspension and the paraffin wax to form a uniform oil phase;
step 5): adding the mixed solution obtained in the step 4) into the solution obtained in the step 2), heating the system to 80 ℃, and adding the system into a digital display high-speed homogenizing and dispersing machine for emulsification, wherein the rotating speed of the homogenizing and dispersing machine is set to 5000-6000rpm, the emulsifying time is 15min, and the emulsion is obtained after the emulsification is completed; in this example, the temperature of the aqueous phase prepared in step 2) was controlled between 45-50 ℃, and the prepared oil phase was added to the aqueous phase obtained in step 1) while stirring at 6000rpm for 15min to form a stable oil-in-water solution emulsion.
Step 6): maintaining the temperature of the emulsion obtained in the step 5) at 70-80 ℃, putting the emulsion into a constant-temperature magnetic stirrer, and stirring at 200-300rpm for 5-7h; in this example, the solution was rapidly poured into a three-necked flask and reacted under continuous stirring in a constant temperature magnetic stirrer at 75℃and 230rpm for 5 hours.
Step 7): cooling the emulsion obtained in the step 6), and then filtering, collecting, washing, drying and drying the emulsion to obtain a phase-change microcapsule, wherein the coating rate of the phase-change microcapsule is 85%; in this embodiment, the emulsion obtained in step 6) is filtered, collected, washed and dried, and finally, dried in a vacuum drying oven to obtain white powder, thereby completing the preparation of the phase-change microcapsule.
Step 8): the phase-change microcapsule is molded into phase-change microcapsule carrier particles with the diameter of 4.5mm through a plastic mold, in the embodiment, the prepared phase-change microcapsule is mixed with an adhesive and then injected into a spherical molding mold with the diameter of 4.5mm, the weight ratio of the microcapsule to the adhesive is 7:2, the weight ratio of the adhesive is epoxy resin and aromatic ammonia is 1:3, the curing is carried out through heating at 30 ℃, and finally the demolding treatment is carried out, so that the phase-change microcapsule carrier particles are obtained.
Example 4
The phase-change microcapsule carrier particles are formed by granulating a plurality of phase-change microcapsules, the phase-change microcapsules comprise a phase-change core material and a wall material wrapping the phase-change core material, the wall material is methyl methacrylate, the core material is n-octadecane paraffin, the particle size of the phase-change microcapsules is 15um, and the phase-change temperature is 40 ℃; the particle size of the phase-change microcapsule carrier particle is 5mm. The core-shell ratio of the phase-change microcapsule in the embodiment is 1:1.
The preparation method of the phase-change microcapsule carrier particle for the spray freeze drying process comprises the following steps:
step 1): adding dispersant polyvinyl alcohol into deionized water, mixing to obtain a first mixed solution with the weight percent of 1.0 percent, wherein the specific steps are as follows: taking a beaker of 300ml, weighing 120ml of deionized water by using a measuring cylinder, adding the deionized water into the beaker, placing the beaker on one side, weighing 1.20g of dispersing agent polyvinyl alcohol by using an electronic balance for another weighing paper, weighing 0.6g of sodium dodecyl sulfate, adding the weighed dispersing agent into the pre-measured deionized water, standing for 30 minutes, placing the beaker into an electromagnetic stirrer (the water bath temperature is set to 90 ℃), continuously stirring for 30 minutes until the solution is clear, completely dissolving the polyvinyl alcohol into the deionized water, and then adding 0.6g of sodium dodecyl sulfate into the polyvinyl alcohol aqueous solution for full mixing to obtain a first mixed solution polyvinyl alcohol aqueous solution for standby as an aqueous phase.
Step 2): heating the first mixed solution to 85-90 ℃, keeping the stirring speed at 200-300rpm, stirring until the solution is clear, and standing aside to cool to 50 ℃ for standby;
step 3): mixing wall methyl methacrylate and an initiator which can be used as a free radical type polyaddition reaction, and slightly oscillating until the solution is clear and white granular substances cannot be observed by naked eyes to obtain a prepolymer suspension, wherein the preparation method comprises the following specific steps of: weighing 15g of Methyl Methacrylate (MMA) in a 50mL beaker by using a liquid transfer device, placing the solution on one side for standby, weighing 0.45g of Azobisisobutyronitrile (AIBN) by using weighing paper as an initiator of polyaddition reaction, adding the azobisisobutyronitrile into the weighed methyl methacrylate for dissolution, and stopping the reaction when the solution is colorless and transparent, namely, the azobisisobutyronitrile is fully dissolved, so as to obtain methyl methacrylate prepolymer suspension;
step 4): the organic phase change material is melted by heating in water bath and then is dripped into the prepolymer suspension, the core material solution and the prepolymer suspension can be observed to be divided into an upper layer and a lower layer, at the moment, the mixed solution is stirred to form a uniform oil phase, and the specific steps are as follows: weighing 15g of n-octadecane by using weighing paper, placing the weighed n-octadecane in a beaker, standing for later use on one side, heating a water bath kettle to 50 ℃, placing the weighed paraffin in the water bath kettle at 50 ℃, heating and melting, controlling the water bath temperature to 50 ℃, slowly dripping the methyl methacrylate prepolymer suspension into the core emulsion by using a dropping funnel, and mixing and stirring the methyl methacrylate prepolymer suspension and the paraffin to form a uniform oil phase;
Step 5): adding the mixed solution obtained in the step 4) into the solution obtained in the step 2), heating the system to 70-80 ℃, and adding the system into a digital display high-speed homogenizing and dispersing machine for emulsification, wherein the rotating speed of the homogenizing and dispersing machine is set to 5000-6000rpm, the emulsification time is 15min, and the emulsion is obtained after the emulsification is completed; in this example, the temperature of the aqueous phase prepared in step 2) was controlled between 45-50deg.C, and the prepared oil phase was added to an aqueous phase formed by 120ml deionized water and 1.20g surfactant polyvinyl alcohol (PVA) while stirring at 6000rpm for 15min to form a stable oil-in-water solution emulsion.
Step 6): maintaining the temperature of the emulsion obtained in the step 5) at 70-80 ℃, putting the emulsion into a constant-temperature magnetic stirrer, and stirring at 200-300rpm for 5-7h; in this example, the solution was rapidly poured into a three-necked flask and reacted under continuous stirring in a constant temperature magnetic stirrer at 70℃and 230rpm for 5 hours.
Step 7): and (3) performing filtration, collection, washing, drying and drying on the emulsion phase-change microcapsule obtained in the step (6) until the coating rate is 80% -90%, so as to obtain the phase-change microcapsule.
Step 8): the phase-change microcapsule is molded into phase-change microcapsule carrier particles with the diameter of 5mm through a plastic mold, in the embodiment, the phase-change microcapsule is molded into phase-change microcapsule carrier particles with the diameter of 5mm through the plastic mold, in the embodiment, the prepared phase-change microcapsule is mixed with an adhesive and then injected into a spherical molding mold with the diameter of 5mm, the weight ratio of the microcapsule to the adhesive is 6:2, and the weight ratio of the adhesive is 1:2.5; and (3) heating at 30 ℃ for curing, and finally demoulding to obtain the phase-change microcapsule carrier particles.
The difference between this example and example 1 is only that sodium dodecyl sulfonate is additionally added to the water as an emulsifier, ensuring that the emulsion formed does not agglomerate.
Example 5:
phase-change microcapsule carrier particles for spray freeze-drying process with a core-shell ratio of 1:1 and a first mixed solution of 0.5wt% aqueous polyvinyl alcohol, otherwise as in example 1.
Example 6:
phase-change microcapsule carrier particles for spray freeze-drying process with a core-shell ratio of 1:1 and a first mixed solution of 0.75wt% aqueous polyvinyl alcohol, otherwise as in example 1.
Example 7:
phase-change microcapsule carrier particles for spray freeze-drying process with a core-shell ratio of 1:1 and a first mixed solution of 1.25wt% aqueous polyvinyl alcohol, otherwise as in example 1.
Example 8:
phase-change microcapsule carrier particles for spray freeze-drying process, core-shell ratio of 1:1, first mixed solution of 1.5wt% polyvinyl alcohol aqueous solution, and the other is the same as in example 1.
Test analysis:
1. as shown in fig. 1, fig. 1a is an emulsion dispersion diagram of the phase-change microcapsule prepared in example 1; FIG. 1b is a SEM micrograph (700 times) of the phase change microcapsules prepared in example 1 after drying; FIG. 1c is a SEM micrograph (2000 times) of the phase change microcapsules prepared in example 1 after drying; FIG. 1d is a SEM micrograph of partially broken phase change microcapsules prepared in example 1; from fig. 1a, it can be seen that the phase-change microcapsule is full sphere when not dried, and from fig. 1b and fig. 1c, it can be seen that obvious wrinkles appear on the surface of the phase-change microcapsule after drying treatment, which is caused by shrinkage of the polymer shell, and is a reserved expansion space generated inside the microcapsule in the microencapsulation process, and from fig. 1d, it can be seen that the phase-change microcapsule is partially broken, and this in fig. 1 also well illustrates that the microcapsule prepared in example 1 has a core-shell structure. Example 1 phase change microcapsules prepared at a core-shell ratio of 1:1 had a small amount of dishing and adhering debris.
When the core-shell ratio is 4:3 in example 2, the prepared phase-change microcapsule has obvious pits and adhesion scraps as shown in fig. 1 e.
Example 3 when the core-shell ratio was 3:4, the phase change microcapsules were prepared with significantly reduced microcapsule attachment debris as shown in figure 1 f.
Experiments prove that spherical phase-change microcapsules cannot be prepared when the core-shell ratio is too large; when phase-change microcapsules are prepared by adopting different core-shell ratios, a small amount of paraffin is mixed with the wall material, and the wall material remains so as to adhere to the surface of the microcapsules, which is the reason for causing the surface of the microcapsules to be sunken and the chips to adhere to the surface of the microcapsules; when the paraffin dosage is increased, the proportion of the paraffin to the wall material can ensure that the wall material can well wrap the paraffin, so that the chipping and sinking conditions are better improved. The small change of the core-shell ratio can greatly influence the wrapping effect of the phase-change microcapsule, and the proper core-shell ratio is the key for preparing the phase-change microcapsule with better performance.
In example 1, methyl methacrylate is selected and polymerized into polymethyl methacrylate polymer material by utilizing azodiisobutyronitrile to serve as a wall material of the phase-change microcapsule, so that the mechanical properties of the phase-change microcapsule are improved, and compared with those of examples 2 and 3, the mechanical properties of the phase-change microcapsule are better. It can be seen from fig. 1b that although most of the phase-change microcapsules are extruded with each other, only few capsules are broken, which indicates that the synthesized polymethyl methacrylate polymer material has good film forming property, high mechanical strength and good elasticity and toughness, thereby promoting the microcapsules to form agglomerates rather than fracture during the post-treatment process.
2. As shown in fig. 2, a thermogravimetric plot of the phase change microcapsules of example 1 is shown, wherein the abscissa is temperature and the ordinate is mass percent.
3. As shown in FIG. 3, which is a phase change latent heat map obtained by preparing phase change microcapsules in example 1, it can be seen that the microcapsules can store a maximum heat of 179J/g and can provide a heat of about 160J/g when paraffin in the microcapsules is phase-changed.
4. Mass change test of spray freeze drying: FIG. 4a is a graph showing the mass change of spray-freeze-dried material without phase change microcapsule carrier particles added; fig. 4b is a mass change curve of spray freeze-dried material added with phase change microcapsule carrier particles, and the data show that the drying time is shortened from 15h to 10h after the phase change microcapsule carrier particles are added, and the drying efficiency is improved by 33%.
When the phase-change microcapsule carrier particles are used as inert particles in a spray freeze drying device, the effect of improving the drying efficiency of the spray freeze drying device is verified, the influence of the phase-change microcapsule carrier particles on spray freeze drying time is researched, and compared with spray freeze drying experiments without the phase-change microcapsule carrier particles, in order to ensure the accuracy of experimental results, the average value is taken three times for each group of experiments, and the result shows that the spray freeze drying time is obviously shortened after the phase-change microcapsule carrier particles are added.
The phase change microcapsule carrier particle not only shortens the drying time by influencing the drying rate of moisture in the material in the primary drying stage, but also after the sublimation stage in the secondary drying stage is finished, frozen ice crystals in the material, namely free water, are completely sublimated, but also water in the material is not only free water but also a small part of bound water, and the water is not frozen and mainly adheres to the inner walls of the pore structure of the material, and extra heat is needed for removing the water to remove the force among molecules, so that the bottom heating plate is used for providing heat in the secondary drying stage, the material not only draws heat from the heating plate, but also has higher phase change latent heat due to the phase change of the phase change microcapsule carrier particle, and can additionally provide part of heat to the dried material, thereby further shortening the drying time.
5. Drying rate test of spray freeze drying: fig. 5 is a graph showing drying rate curves in two modes of spray freeze drying without the addition of phase change microcapsule carrier particles and spray freeze drying with the addition of phase change microcapsule carrier particles.
According to the different dry basis water contents of the materials, a drying rate curve of the materials changing along with the dry basis water contents can be obtained. From the figure, it can be seen that the addition of inert particles can significantly increase the drying rate with the same moisture content on a dry basis. It was found from the observation that the spray freeze drying experiment with the addition of 5mm phase change microcapsule carrier particles had a maximum drying rate of 0.082 g/g.min, whereas the spray freeze drying experiment without the addition of phase change microcapsule carrier particles had a maximum drying rate of only 0.063 g/g.min. Thus, the addition of phase-change microcapsule carrier particles in spray freeze drying is advantageous in that the drying rate of spray freeze drying can be increased, and the drying time can be further shortened.
In the spray freeze drying experiment, the drying rate curve of the material can be obtained according to the different dry basis water contents of the material. The drying rate profile can be divided into an accelerated drying stage, a uniform drying stage and a reduced drying stage throughout the freeze drying stage. In the initial stage of drying, the sublimation of the moisture in the material begins from the outside, and as the drying proceeds, the drying surface gradually moves from the surface layer to the inside, and after most of ice crystals in the material are removed by sublimation, the drying layer left in the material assumes a loose and porous structure. Meanwhile, the drying layer is much thinner than the freezing layer in the initial stage of drying, and the water content of the material is rapidly reduced due to ice crystal sublimation, so that the drying rate is remarkably improved. Along with the continuous movement of the drying interface towards the inside of the material, the drying layer is gradually thickened, the corresponding freezing layer is thinned, the freeze drying rate of the material also reaches a constant speed stage, and in the constant speed drying stage, the thickness of the material drying layer is equivalent to that of the freezing layer. Over time, the drying layer of the material product becomes thicker gradually, so that the heat and mass transfer resistance of the material is increased, and the drying efficiency is reduced. And when the material is carried out to the end of the constant speed stage, the ice crystals in the material are removed in a sublimation mode. The material enters a deceleration stage, the material drying layer is further thickened, the freezing layer becomes thinner, and the heat transfer resistance become larger. Resulting in a rapid decrease in the sublimation rate, i.e., drying rate, of the material, so the drying rate is extremely slow during this process. The experimental data after the phase-change microcapsule carrier particles are added are compared, so that the addition of the inert phase-change microcapsule carrier particles is beneficial to improving the drying rate of spray freeze drying in the spray freeze drying process, and the drying time can be further shortened.
6. Dispersant dosage test: in the experiments of examples 1, 5, 6, 7 and 8, when the amount of the polyvinyl alcohol is 0.5%, 0.75% and 1%, the small particles and wall material fragments attached to the surfaces of the microcapsules tend to decrease with the increase of the amount of the dispersing agent, so that spherical microcapsule particles can be prepared, because the paraffin core material cannot be completely emulsified into the dispersed small particles by a small amount of the dispersing agent during the emulsification and dispersion; when the content of the dispersing agent is 1.25% and 1.5%, that is, more than 1%, a mixture of flaky paraffin and methyl methacrylate is formed, and the paraffin cannot be well coated, which is probably due to the fact that the concentration of the dispersing agent is too high, the emulsifying and dispersing properties of the dispersing agent cannot be well exerted, and meanwhile, when the dispersing agent is excessive, the dispersed and emulsified system cannot be well kept stable, so that a flaky mixture of core paraffin and methyl methacrylate is formed. The amount of 1% of the dispersant polyvinyl alcohol is most suitable.
7. Stability test: the phase change material is coated by the wall material, so that the whole phase change process of the phase change material is completed in a sealed micro space, the phase change material cannot be damaged or leaked, the phase change process of the phase change core material paraffin is reversible, the phase change material can be repeatedly used, meanwhile, the differential thermogravimetric analyzer is used for respectively performing thermogravimetric analysis on the paraffin and the phase change microcapsule, the phase change microcapsule coated by the polymethyl methacrylate shell material has a complete decomposition temperature of about 570 ℃ relative to the paraffin, and compared with the complete decomposition temperature of 230 ℃, the phase change microcapsule has good thermal stability.
8. According to the invention, paraffin is used as the phase-change material, and the temperature of the secondary heating section of the spray freeze drying device is 40 ℃, so that the selected phase-change material needs to be subjected to phase change at the temperature of about 40 ℃, and the phase-change latent heat released by the material can be maximally utilized to provide heat for the dried material.
Although the embodiments of the present invention and the accompanying drawings have been disclosed for illustrative purposes, those skilled in the art will appreciate that various substitutions, changes and modifications are possible without departing from the spirit and scope of the invention and the appended claims, and thus the scope of the invention is not limited to the embodiments and the disclosure of the drawings.
Claims (10)
1. A phase change microcapsule carrier particle for use in a spray freeze drying process, characterized by: the phase-change microcapsule carrier particles are formed by granulating a plurality of phase-change microcapsules, the phase-change microcapsules comprise a phase-change core material and wall materials for wrapping the phase-change core material, the wall materials are resin wall materials, the particle size of the phase-change microcapsules is 10-20 um, and the phase-change temperature is the spray freeze drying secondary drying temperature; the particle size of the phase-change microcapsule carrier particles is 4mm-5mm.
2. The phase change microcapsule carrier particle for use in a spray freeze drying process of claim 1, wherein: the wall material is methyl methacrylate or polyurethane or melamine resin.
3. The phase change microcapsule carrier particle for use in a spray freeze drying process of claim 1, wherein: the core material is paraffin, and the paraffin is n-octadecane, n-eicosane or n-docosane.
4. The phase change microcapsule carrier particle for use in a spray freeze drying process of claim 1, wherein: the phase-change microcapsule has a fixed core-shell ratio of 1:1, 3:4 or 4:3.
5. The phase change microcapsule carrier particle for use in a spray freeze drying process of claim 1, wherein: the phase transition temperature is 35-45 ℃.
6. A method for preparing phase-change microcapsule carrier particles for a spray freeze drying process, which is characterized by comprising the following steps: the method comprises the following steps:
step 1): adding dispersant polyvinyl alcohol into deionized water, and mixing to obtain a first mixed solution with the weight percent of 0.5-1.0;
step 2): heating the first mixed solution to 85-90 ℃, keeping the stirring speed at 200-300rpm, stirring until the solution is clear, and standing aside to cool to 50 ℃ for standby;
step 3): mixing resin wall materials and an initiator which can be used for free radical type polyaddition reaction, and slightly oscillating until the solution is clear and white granular substances cannot be observed by naked eyes to obtain a prepolymer suspension;
Step 4): the core material of the organic phase change material is melted by heating in water bath and then is dripped into the prepolymer suspension, the core material solution and the prepolymer suspension can be observed to be divided into an upper layer and a lower layer, and at the moment, the mixed solution is stirred to form uniform oil phase mixed solution;
step 5): adding the uniform oil phase mixture obtained in the step 4) into the solution obtained in the step two, heating to 70-80 ℃, adding into a digital display high-speed homogenizing and dispersing machine for emulsification, setting the rotating speed of the homogenizing and dispersing machine to 5000-6000rpm, and the emulsification time to 15-20min, thus obtaining emulsion after emulsification;
step 6): maintaining the temperature of the emulsion obtained in the step 5) at 70-80 ℃, putting the emulsion into a constant-temperature magnetic stirrer, and stirring at 200-300rpm for at least 5-6h;
step 7): the emulsion obtained in the step 6) is phase-change microcapsule emulsion with the coating rate of 80% -90%; filtering, washing and drying the cooled product to obtain phase-change microcapsules;
step 8): and molding the phase-change microcapsule into phase-change microcapsule carrier particles with the diameter of 4-5mm through a plastic mold.
7. The method of preparing phase-change microcapsule carrier particles for use in a spray-freeze drying process of claim 6, wherein: the initiator is azobisisobutyronitrile or ammonium persulfate or lauroyl peroxide.
8. The method of preparing phase-change microcapsule carrier particles for use in a spray-freeze drying process of claim 6, wherein: in the step 1), after the polyvinyl alcohol is completely dissolved in the deionized water, the dispersing agent sodium dodecyl sulfate is added into the polyvinyl alcohol aqueous solution for complete mixing.
9. The method of preparing phase-change microcapsule carrier particles for use in a spray-freeze drying process of claim 6, wherein: in the step 8), the prepared phase-change microcapsule and an adhesive are mixed and then injected into a spherical molding die with the diameter of 4-5mm, the weight ratio of the microcapsule to the adhesive is 5-7:2, the microcapsule and the adhesive are heated at 30 ℃ for curing, and finally the phase-change microcapsule carrier particles are obtained after demoulding treatment.
10. The method of preparing phase change microcapsule carrier particles for use in a spray freeze drying process of claim 9, wherein: the adhesive is epoxy resin and aromatic ammonia, and the weight ratio of the epoxy resin to the aromatic ammonia is 1:2-3.
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