A phase change microcapsule and a preparation method thereof

Abstract

The present invention discloses a phase change microcapsule and a preparation method thereof. Among them, the preparation method of the phase change microcapsule of the present invention includes the following steps: (1) uniformly mixing a molten phase change material, an aromatic polyaldehyde, a neutral surfactant and a mixed solvent, and performing high-speed shearing treatment to obtain a phase change microemulsion; (2) heating and refluxing the phase change microemulsion obtained in step (1) under the protection of an inert gas, while dropping an aqueous solution of polyetheramine, and then adding an acidic liquid to adjust the pH value of the mixed material to 4.5-5.5, and continuing the reflux heating reaction to obtain a solid-liquid mixture; (3) the solid-liquid mixture obtained in step (2) is cooled to room temperature, the solvent is removed by rotary evaporation, then extracted with ethyl acetate, and then rotary evaporated and recrystallized with an alcohol solvent to obtain a phase change microcapsule. The phase change microcapsule obtained by the preparation method provided by the present invention has strong mechanical strength and wear resistance, and also has good phase change heat storage and temperature control performance. The preparation process is environmentally friendly and the operation is simple.

Description

Technical Field

[0001] The present invention belongs to the technical field of phase change energy storage materials, and particularly relates to a phase change microcapsule and a preparation method thereof. Background Art

[0002] Phase change energy storage materials are functional materials that can absorb, store, and release a large amount of heat energy. So far, phase change energy storage materials have been widely used in technical fields such as industrial waste heat recovery, building temperature regulation, solar heat storage, advanced functional textiles, food and serum protein preservation. Microcapsule phase change energy storage materials, also known as phase change microcapsules (MEPCM), are a typical encapsulation and use method of phase change energy storage materials. Their characteristic lies in having a core-shell structure, and the shell material can effectively prevent the leakage of the core material during the melting process. At the same time, the core-shell structure of the phase change microcapsule also provides a larger specific surface area for the heat transfer process, which can improve the defect of low thermal conductivity of organic phase change materials (such as paraffin, stearic acid, fatty alcohol).

[0003] CN103936953A discloses a synthesis method of a phase change energy storage material polybutylene glycol ammonia aldehyde condensation cross-linked copolymer. By combining the aldol condensation reaction and the ammonia aldehyde condensation reaction, using polybutylene glycol as the phase change functional material, amine compounds and aldehyde compounds as cross-linking agents, a chemical reaction occurs in an aqueous medium under controlled temperature and acidity. The alcohol hydroxyl group, amino group, and carbonyl group undergo a co-condensation reaction to form new chemical bonds. After removing water, a cross-linked copolymer is synthesized. The synthesized cross-linked copolymer prevents the free movement of polybutylene glycol molecular chains and has the characteristics of being insoluble and infusible, becoming a solid-solid phase change material. However, in this method, the aldol condensation reaction and the ammonia aldehyde condensation reaction are completed synchronously, which is likely to cause interference, that is, the reaction of polybutylene glycol is not sufficient, resulting in low quality and phase change latent heat value of the solid-solid phase change material. In addition, the solid-solid phase change material formed by this method is not encapsulated in a core-shell structure, and its durability is limited.

[0004] CN1732043A discloses a method for microencapsulating a phase change alkane compound. Using polypropylene glycol with an average molecular weight exceeding 400 as a surface tension improver to assist in the emulsification of the alkane compound, and also using polyisocyanate soluble in the phase change material to promote the deposition of melamine, partially hydroxymethylated melamine, and melamine-formaldehyde pre-condensate on the hydrophobic oil droplets. The shell material component of the microcapsules prepared by this method is composed of melamine and melamine-formaldehyde pre-condensate, and both melamine and formaldehyde have strong pollution, posing environmental hazards in textiles. Summary of the Invention

[0005] To overcome the deficiencies of the prior art, the present invention provides a phase change microcapsule and a preparation method thereof. The phase change microcapsule obtained by the preparation method provided by the present invention has strong mechanical strength and wear resistance, and also has good phase change heat storage and temperature control performance. The preparation process is environmentally friendly and simple to operate.

[0006] The first aspect of the present invention provides a preparation method of a phase change microcapsule, comprising the following steps:

[0007] (1) Mix the molten phase change material, aromatic polyaldehyde, neutral surfactant and mixed solvent evenly, and perform high-speed shearing treatment to obtain a phase change microemulsion;

[0008] (2) Heat and reflux the phase change microemulsion obtained in step (1) under the protection of inert gas, while dropping an aqueous solution of polyetheramine, and then add an acidic liquid to adjust the pH value of the mixed material to 4.5 - 5.5, and continue reflux heating reaction to obtain a solid-liquid mixture;

[0009] (3) For the solid-liquid mixture obtained in step (2), after cooling to room temperature, rotary evaporate the solvent, then extract with ethyl acetate, and then rotary evaporate and recrystallize with an alcohol solvent to obtain the phase change microcapsule.

[0010] Further, in step (1), the phase change material is selected from one or more of normal paraffins, paraffins, and stearic acid esters with a phase change temperature of 18°C - 35°C, preferably paraffin.

[0011] Further, in step (1), the aromatic polyaldehyde is selected from one or more of benzene-1,3,5-tricarbaldehyde, isophthalaldehyde, and naphthalene-2,3-dicarbaldehyde, preferably benzene-1,3,5-tricarbaldehyde.

[0012] Further, in step (1), the neutral surfactant is selected from one or more of Span 60, Span 80, Tween 60, and Tween 80, preferably Span 80 and Tween 80, and the mass ratio of Span 80 to Tween 80 is 1:(0.35 - 2.5), preferably 1:(0.7 - 1.5).

[0013] Further, in step (1), the mixed solvent is selected from organic solvents and water, preferably one or more of ethanol aqueous solution, methanol aqueous solution, and acetone aqueous solution, and the mass ratio of the organic solvent to deionized water is 1:(5 - 12), preferably 1:(7 - 10).

[0014] Further, in step (1), the mass ratio of the phase change material, aromatic polyaldehyde, neutral surfactant, and mixed solvent is 1:(0.05 - 0.35):(0.005 - 0.05):(25 - 70), preferably 1:(0.08 - 0.2):(0.007 - 0.015):(35 - 50).

[0015] Further, in step (1), for the high-speed shearing treatment, the reaction temperature is 40°C to 75°C, preferably 50°C to 60°C. The shearing reaction time is 5 min to 30 min, preferably 10 min to 20 min; the rotation speed of the high-speed shearing is 6000 rpm to 13000 rpm, preferably 8000 rpm to 10000 rpm.

[0016] Further, in step (2), the phase change microemulsion obtained in step (1) is heated and refluxed under the protection of an inert gas. The inert gas is selected from any one of nitrogen, helium, and argon. The gas flow rate is 75 mL / min to 275 mL / min relative to each liter of the phase change microemulsion, preferably 100 mL / min to 150 mL / min. The heating temperature in the heating and reflux reaction is 40°C to 80°C, preferably 45°C to 55°C. The reflux reaction time in the heating and reflux reaction is 15 min to 45 min, preferably 20 min to 30 min.

[0017] Further, in step (2), the acidic liquid is selected from one or more of inorganic acids, organic acids, and acidic ionic liquids, preferably acidic ionic liquids, and more preferably [C3SO3HMim]HSO4 type acidic ionic liquids. The mass concentration of the acidic liquid is 5% to 15%, preferably 8% to 10%. The heating temperature for the continued reflux heating is 40°C to 80°C, preferably 45°C to 55°C. The reaction time for the continued reflux heating is 0.5 h to 3 h, preferably 1.5 h to 2.5 h.

[0018] Further, in step (2), the polyetheramine is selected from one or more of bifunctional and trifunctional polyetheramines with an average molecular weight of 200 to 600, preferably trifunctional polyetheramine (such as T-403).

[0019] Further, in step (2), the mass concentration of the polyetheramine aqueous solution is 5% to 10%, preferably 6.5% to 8.5%.

[0020] The dropping rate of the polyetheramine aqueous solution is 5 g / min to 40 g / min relative to each liter of the phase change microemulsion, preferably 20 g / min to 25 g / min.

[0021] Further, in step (2), the mass ratio of the polyetheramine to the aromatic polyaldehyde in step (1) is 1:(0.1 to 1.2), preferably 1:(0.3 to 0.7).

[0022] Further, in step (3), the rotary evaporation temperature is 100°C to 150°C, the rotary evaporation speed is 60 rpm to 100 rpm, and the rotary evaporation time is 20 min to 30 min.

[0023] Further, in step (3), after extraction with ethyl acetate, the temperature for the second rotary evaporation is 85°C to 150°C, preferably 95°C to 110°C. The rotary evaporation speed is 60 rpm to 120 rpm, preferably 80 rpm to 100 rpm. The rotary evaporation time is 10 min to 50 min, preferably 25 min to 35 min.

[0024] Further, in step (3), the alcohol solvent is selected from one or more of anhydrous methanol, anhydrous ethanol, and anhydrous isopropanol, preferably anhydrous methanol.

[0025] Further, in step (3), the temperature for recrystallization is 35°C to 75°C, preferably 40°C to 55°C.

[0026] The second aspect of the present invention provides a phase change microcapsule obtained by the above preparation method.

[0027] Further, the average particle size of the phase change microcapsule is 1 μm to 5 μm, the latent heat of fusion value is 94 J / g to 112 J / g, the coating rate is 60% to 70%, and the thermal conductivity is 0.32 W·m -1 ·k -1 ~0.43 W·m -1 ·K -1 , the compressive strength is 0.75 MPa to 1.06 MPa, and the fluidization wear rate is 2% to 6%.

[0028] The third aspect of the present invention provides a phase change microcapsule obtained by the above preparation method for use in technical fields such as solar energy heat storage and temperature regulation, building insulation, and functional heat fluids.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] (1) In the present invention, aromatic polyaldehydes are used as one of the components of the phase change microcapsule shell material. Due to the coexistence of an aromatic ring structure and aldehyde functional groups, they have amphiphilic properties in both oil and water, that is, they can be used as components of surfactants and closely combine with the molten phase change material droplets during the preparation of phase change microemulsions. Then, through the aldehyde-amine condensation reaction, the molten phase change material droplets are tightly coated to generate phase change microcapsules with good physical and chemical properties and mechanical strength. The [C3SO3HMim]HSO4 type acidic ionic liquid is selected as the catalyst for the aldehyde-amine condensation reaction. The sulfonic acid group therein is hydrophilic, while the imidazole group is soluble in the organic phase, enabling this type of ionic liquid to participate in the reaction well and providing the required acidity for the reaction system to effectively complete the condensation reaction.

[0031] (2) For the phase change microcapsules prepared in the present invention, their shell material structure has an aromatic ring structure and ether bond groups, and they have good compatibility properties in both oily and aqueous solution systems.

[0032] (3) The preparation method of the present invention is simple, highly controllable, the reaction process is safe and environmentally friendly, and it is suitable for industrial batch production of phase change microcapsule materials. Description of the Drawings

[0033] Figure 1 is the differential scanning calorimetry curve (DSC) of paraffin and the phase change microcapsules prepared in Example 1;

[0034] Figure 2 is the scanning electron microscope photograph (SEM) of the phase change microcapsules prepared in Example 1. Detailed Embodiments

[0035] The preparation method and effects of the phase change microcapsules of the present invention will be further described below through examples. The examples are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to the following examples.

[0036] In the following examples, the experimental methods, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, are all purchased from conventional biochemical reagent stores.

[0037] In the present invention, a Hitachi S-4700 type field emission scanning electron microscope (SEM) made in Japan is used to observe the morphology and particle size of the phase change microcapsules.

[0038] In the present invention, a differential scanning calorimeter (DSC) is used to test the latent heat of phase change value during the melting process of the phase change microcapsules, and the instrument model is DSC-60 Plus of Shimadzu Corporation, Japan.

[0039] In the present invention, under a nitrogen atmosphere, the temperature test range is -70°C to 70°C, the heating rate is 10°C / min, and the sample weight is approximately 3.5 mg.

[0040] In the present invention, a fluidized bed wear device is used to test the wear rate of the phase change microcapsules. The phase change microcapsules are added into the fluidized bed equipment through the upper feeding port of the fluidized bed. Air flows through the air distribution plate from the bottom through the gas delivery pipe and enters the fluidized bed device, and the phase change microcapsules are subjected to fluidized wear testing under the action of the air flow.

[0041] In the present invention, a DRL-III-P type thermal conductivity tester of Xiangyi Instrument Co., Ltd. is used to measure the thermal conductivity of the phase change microcapsule samples. A YL-C10K pressure testing machine of Guangdong Yuelian Instrument Co., Ltd. is used to measure the compressive strength of the phase change microcapsule samples. The calculation formula for the coating rate of the phase change microcapsules is as follows:

[0042] Coating rate / % = (latent heat of fusion value of microcapsules / latent heat of fusion value of phase change material) × 100%.

[0043] Example 1

[0044] Take 5 g of paraffin with a melting phase change temperature of 24°C, 0.5 g of mellitic aldehyde, 0.025 g of Span 80, 0.025 g of Tween 80, and 200 g of an ethanol aqueous solution and mix them. Among them, the mass ratio of ethanol to deionized water is 1:8. Under the conditions of 55°C and 9000 rpm, carry out high-speed shear reaction for 15 min to obtain a phase change microemulsion. Pour the phase change microemulsion into a flask, and under the protection of high-purity nitrogen with a flow rate of 25 mL / min, heat and reflux at 50°C for 25 min, and at the same time, dropwise add 17 g of an aqueous solution of polyetheramine at a rate of 4.5 g / min. The mass concentration of the aqueous solution of polyetheramine is 7%. After the dropping is completed, adjust the pH value of the system to 5 with a [C3SO3HMim]HSO4 type acidic ionic liquid with a mass concentration of 9%, and continue to heat and reflux at 50°C for 2 h to obtain a solid-liquid mixture. Cool to room temperature, rotary evaporate at 120°C and 80 rpm for 25 min, extract the residue with ethyl acetate, and then rotary evaporate at 105°C and 90 rpm for 30 min to obtain a crude product, and carry out recrystallization reaction with anhydrous methanol at 50°C, and filter while it is hot to obtain the phase change microcapsules.

[0045] Example 2

[0046] Take 5 g of paraffin wax with a melting-phase transition temperature of 24 °C, 0.4 g of trimesic aldehyde, 0.0175 g of Span 80, 0.0175 g of Tween 80, and 175 g of an ethanol aqueous solution and mix them. Among them, the mass ratio of ethanol to deionized water is 1:7. Under the conditions of 50 °C and 8000 rpm, carry out high-speed shearing reaction for 10 min to obtain a phase-change microemulsion. Pour the phase-change microemulsion into a flask, and under the protection of high-purity nitrogen with a flow rate of 20 mL / min, carry out heating reflux reaction at 45 °C for 20 min. At the same time, dropwise add 17 g of an aqueous solution of polyetheramine at a rate of 4 g / min. The mass concentration of the aqueous solution of polyetheramine is 7%. After the dropping is completed, adjust the pH value of the system to 4.5 with an acidic ionic liquid of [C3SO3HMim]HSO4 type with a mass concentration of 8%, and continue the heating reflux reaction at 45 °C for 1.5 h to obtain a solid-liquid mixture. Cool to room temperature, carry out rotary evaporation at 100 °C and 60 rpm for 20 min, extract the residue with ethyl acetate, and then carry out rotary evaporation at 95 °C and 80 rpm for 25 min to obtain a crude product. Carry out recrystallization reaction with anhydrous methanol at 40 °C, and filter while it is hot to obtain phase-change microcapsules.

[0047] Example 3

[0048] Take 5 g of paraffin wax with a melting-phase transition temperature of 24 °C, 1 g of trimesic aldehyde, 0.0375 g of Span 80, 0.0375 g of Tween 80, and 250 g of an ethanol aqueous solution and mix them. Among them, the mass ratio of ethanol to deionized water is 1:8. Under the conditions of 60 °C and 10000 rpm, carry out high-speed shearing reaction for 20 min to obtain a phase-change microemulsion. Pour the phase-change microemulsion into a flask, and under the protection of high-purity nitrogen with a flow rate of 30 mL / min, carry out heating reflux reaction at 55 °C for 30 min. At the same time, dropwise add 17 g of an aqueous solution of polyetheramine at a rate of 5 g / min. The mass concentration of the aqueous solution of polyetheramine is 7%. After the dropping is completed, adjust the pH value of the system to 5.5 with an acidic ionic liquid of [C3SO3HMim]HSO4 type with a mass concentration of 10%, and continue the heating reflux reaction at 55 °C for 2.5 h to obtain a solid-liquid mixture. Cool to room temperature, carry out rotary evaporation at 150 °C and 100 rpm for 30 min, extract the residue with ethyl acetate, and then carry out rotary evaporation at 110 °C and 100 rpm for 35 min to obtain a crude product. Carry out recrystallization reaction with anhydrous methanol at 55 °C, and filter while it is hot to obtain phase-change microcapsules.

[0049] Example 4

[0050] Same as Example 1, except that n-octadecane is used instead of paraffin wax, and other reaction conditions and material compositions remain unchanged, to obtain phase-change microcapsules.

[0051] Example 5

[0052] Same as Example 1, except that vinyl stearate is used instead of paraffin wax, and other reaction conditions and material compositions remain unchanged, to obtain phase change microcapsules.

[0053] Example 6

[0054] Same as Example 1, except that isophthalaldehyde is used instead of benzene-1,3,5-tricarbaldehyde, and other reaction conditions and material compositions remain unchanged, to obtain phase change microcapsules.

[0055] Example 7

[0056] Same as Example 1, except that 2,3-naphthalenedicarbaldehyde is used instead of benzene-1,3,5-tricarbaldehyde, and other reaction conditions and material compositions remain unchanged, to obtain phase change microcapsules.

[0057] Example 8

[0058] Same as Example 1, except that a combination of equal amounts and equal proportions of Span 60 and Tween 60 is used instead of the combination of Span 80 and Tween 80, and other reaction conditions and material compositions remain unchanged, to obtain phase change microcapsules.

[0059] Example 9

[0060] Same as Example 1, except that an equal amount of Span 80 is used instead of the combination of Span 80 and Tween 80, and other reaction conditions and material compositions remain unchanged, to obtain phase change microcapsules.

[0061] Example 10

[0062] Same as Example 1, except that the mass of Span 80 is increased to 0.029 g and the mass of Tween 80 is reduced to 0.021 g, and other reaction conditions and material compositions remain unchanged, to obtain phase change microcapsules.

[0063] Example 11

[0064] Same as Example 1, except that the mass of Span 80 is reduced to 0.02 g and the mass of Tween 80 is increased to 0.03 g, and other reaction conditions and material compositions remain unchanged, to obtain phase change microcapsules.

[0065] Example 12

[0066] Same as Example 1, except that the mass ratio of ethanol to deionized water is reduced to 1:7, and other reaction conditions and material compositions remain unchanged, to obtain phase change microcapsules.

[0067] Example 13

[0068] Same as Example 1, except that the mass ratio of ethanol to deionized water is increased to 1:10, and other reaction conditions and material compositions remain unchanged, to obtain phase change microcapsules.

[0069] Example 14

[0070] Same as Example 1, except that during the high-speed shearing reaction process, the reaction temperature was increased to 75 °C, the reaction time was shortened to 5 min, and the reaction rotation speed was increased to 13,000 rpm. Other reaction conditions and material compositions remained unchanged, and phase change microcapsules were obtained.

[0071] Example 15

[0072] Same as Example 1, except that high-purity helium was used instead of high-purity nitrogen, and the gas flow rate was reduced to 15 mL / min. Other reaction conditions and material compositions remained unchanged, and phase change microcapsules were obtained.

[0073] Example 16

[0074] Same as Example 1, except that the initial reflux reaction temperature was increased to 80 °C and the time was reduced to 15 min. Other reaction conditions and material compositions remained unchanged, and phase change microcapsules were obtained.

[0075] Example 17

[0076] Same as Example 1, except that bifunctional polyetheramine D-230 was used instead of trifunctional T-403. Other reaction conditions and material compositions remained unchanged, and phase change microcapsules were obtained.

[0077] Example 18

[0078] Same as Example 1, except that an aqueous solution of 14.1 g of polyetheramine was added dropwise at a rate of 4.5 g / min, and the mass concentration of the aqueous polyetheramine solution was 8.5%. Other reaction conditions and material compositions remained unchanged, and phase change microcapsules were obtained.

[0079] Example 19

[0080] Same as Example 1, except that the mass of the aqueous polyetheramine solution was reduced to 10.2 g. Other reaction conditions and material compositions remained unchanged, and phase change microcapsules were obtained.

[0081] Example 20

[0082] Same as Example 1, except that hydrochloric acid with the same concentration was used instead of the [C3SO3HMim]HSO4 type acidic ionic liquid. Other reaction conditions and material compositions remained unchanged, and phase change microcapsules were obtained.

[0083] Example 21

[0084] Same as Example 1, except that tartaric acid with the same concentration was used instead of the [C3SO3HMim]HSO4 type acidic ionic liquid. Other reaction conditions and material compositions remained unchanged, and phase change microcapsules were obtained.

[0085] Example 22

[0086] Same as Example 1, except that the temperature of the continuous reflux reaction was reduced to 40 °C and the time was extended to 3 h, while other reaction conditions and material compositions remained unchanged, obtaining phase change microcapsules.

[0087] Example 23

[0088] Same as Example 1, except that the temperature of the rotary evaporation was increased to 150 °C, the rotation speed was reduced to 60 rpm, and the time was shortened to 10 min, while other reaction conditions and material compositions remained unchanged, obtaining phase change microcapsules.

[0089] Example 24

[0090] Same as Example 1, except that absolute ethanol was used instead of absolute methanol, while other reaction conditions and material compositions remained unchanged, obtaining phase change microcapsules.

[0091] Example 25

[0092] Same as Example 1, except that absolute isopropanol was used instead of absolute methanol, while other reaction conditions and material compositions remained unchanged, obtaining phase change microcapsules.

[0093] Example 26

[0094] Same as Example 1, except that the crystallization temperature was increased to 75 °C, while other reaction conditions and material compositions remained unchanged, obtaining phase change microcapsules.

[0095] Comparative Example 1

[0096] Same as Example 1, except that in the preparation process of the phase change microemulsion, Span 80 and Tween 80 were omitted, while other reaction conditions and material compositions remained unchanged, obtaining phase change microcapsules.

[0097] Comparative Example 2

[0098] Same as Example 1, except that glutaraldehyde was used instead of mellitic aldehyde, while other reaction conditions and material compositions remained unchanged, obtaining phase change microcapsules.

[0099] Comparative Example 3

[0100] Same as Example 1, except that the monofunctional polyetheramine M-60 was used instead of the trifunctional polyetheramine T-403, while other reaction conditions and material compositions remained unchanged, obtaining phase change microcapsules.

[0101] Comparative Example 4

[0102] Same as Example 1, except that the monofunctional polyetheramine M-1000 was used instead of the trifunctional polyetheramine T-403, while other reaction conditions and material compositions remained unchanged, obtaining phase change microcapsules.

[0103] Comparative Example 5

[0104] Same as Example 1, except that the pH value of the system was reduced to 2, and other reaction conditions and material compositions remained unchanged, obtaining phase change microcapsules.

[0105] Comparative Example 6

[0106] Same as Example 1, except that during the addition of the polyetheramine aqueous solution, instead of adding dropwise, the prepared polyetheramine aqueous solution was directly poured into the phase change microemulsion for reaction, and other reaction conditions and material compositions remained unchanged, obtaining phase change microcapsules.

[0107] Comparative Example 7

[0108] According to the method described in CN103936953A, 50 g of polybutylene glycol 2000, 10 g of acetaldehyde solution, and 5 g of butanediamine were added to 130 g of water, and slowly stirred until completely dissolved. The temperature was 50 °C, and acetic acid was added dropwise to adjust the pH value to 5, and the reaction was carried out for 180 min. Then, the obtained precursor mixed solution of polybutylene glycol 2000-acetaldehyde-butanediamine condensation cross-linked copolymer was placed in an incubator at 100 °C until the water was completely removed, obtaining a polybutylene glycol 2000-acetaldehyde-butanediamine condensation cross-linked copolymer product.

[0109] Comparative Example 8

[0110] According to the method described in CN1732043A, 2.5 g of sodium poly(styrene-alt-maleic acid) was added to 57.5 g of water, and then the pH value of the system was adjusted to 5. 30 g of octadecane was melted at 33 °C, and then, 0.15 g of polypropylene glycol (average molecular weight 2000) and 0.1 g of toluene diisocyanate were added in sequence, fully mixed and stored in a thermostat. Then, the prepared core composition was added to the aqueous solution of the protective colloid, and strongly stirred at 2000 rpm for 10-15 min, then the stirring speed was reduced to 400-600 rpm, and the melamine-formaldehyde precondensate solution was gradually added, and stirring was continued for 10 min, and the pH value was adjusted to 5.6. The temperature was raised and the reaction was continued for 2 h, 0.4 g of ethylenethiourea was added and the reaction was continued for 1 h, and the pH value of the solution was adjusted to 7.5. It was cooled to room temperature under gentle stirring to obtain a microcapsule emulsion.

[0111] Test Example 1

[0112] The physical and chemical properties of the phase change microcapsules in Examples 1-26 and Comparative Examples 1-8 were measured, and the specific results are shown in Table 1.

[0113] Table 1 Properties of the phase change microcapsules prepared in Examples and Comparative Examples

[0114] Sample Average particle size / μm <![CDATA[Latent heat of fusion value / J·g -1 > <![CDATA[Latent heat of fusion value / J·g after 20 consecutive cycles -1 > Coating rate / % <![CDATA[Thermal conductivity / W·m -1 ·K -1 > Compressive strength / MPa Fluidization wear rate / % Paraffin wax — 157.3 — — 0.13 — — Example 1 2.0 110.1 108.6 70.0 0.43 1.06 2.0 Example 2 1.0 99.0 96.4 63.0 0.36 0.89 2.9 Example 3 5.0 102.8 99.7 65.4 0.39 0.97 3.5 Example 4 2.5 102.2 98.9 65.0 0.38 0.95 3.7 Example 5 3.0 100.0 97.5 63.6 0.37 0.91 4.3 Example 6 4.0 98.7 95.0 62.8 0.34 0.81 4.9 Example 7 4.5 95.9 92.3 61.0 0.34 0.82 5.0 Example 8 4.0 99.8 95.2 63.5 0.33 0.79 4.5 Example 9 5.0 95.7 92.1 60.9 0.33 0.75 4.3 Example 10 2.5 103.8 100.0 66.0 0.37 0.88 4.0 Example 11 3.0 102.5 98.9 65.2 0.36 0.83 3.8 Example 12 3.0 105.8 102.0 67.3 0.40 0.98 3.7 Example 13 1.5 102.5 98.6 65.2 0.38 0.92 4.0 Example 14 2.5 106.8 104.2 67.9 0.40 0.92 3.3 Example 15 3.0 100.6 97.0 64.0 0.35 0.79 3.9 Example 16 4.5 99.4 96.1 63.2 0.34 0.77 4.2 Example 17 5.0 97.5 93.4 62.0 0.35 0.78 4.8 Example 18 3.0 95.9 92.3 61.0 0.38 0.80 5.3 Example 19 2.0 106.9 102.3 68.0 0.41 0.99 3.9 Example 20 2.3 105.8 101.2 67.3 0.39 0.97 3.7 Example 21 3.0 105.2 102.0 66.9 0.38 0.95 3.9 Example 22 3.2 102.2 98.7 65.0 0.37 0.90 4.1 Example 23 3.0 103.3 100.0 65.7 0.36 0.88 4.5 Example 24 3.3 100.5 96.0 64.0 0.37 0.85 4.3 Example 25 4.0 97.7 92.9 62.0 0.36 0.79 5.0 Example 26 4.5 95.0 91.8 61.0 0.36 0.75 6.0 Comparative Example 1 10.6 71.7 60.9 45.6 0.26 0.58 15.0 Comparative Example 2 20.0 60.8 51.0 38.7 0.24 0.50 23.6 Comparative Example 3 0.3 52.8 40.1 33.6 0.21 0.46 37.9 Comparative Example 4 12.0 54.7 42.0 35.0 0.21 0.46 26.5 Comparative Example 5 15.0 63.2 50.9 40.2 0.23 0.50 24.8 Comparative Example 6 25.0 55.0 42.3 35.0 0.24 0.43 30.0 Comparative Example 7 35.0 86.7 78.5 — 0.19 0.42 19.8 Comparative Example 8 8.5 89.0 76.0 50.0 0.27 0.60 20.6

[0115] From Table 1, Figure 1 - Figure 2It can be seen that the phase change microcapsules prepared by the present invention have good physical and chemical properties and regular microscopic morphology. Since the shell material is formed by the aldehyde-amine condensation reaction, the phase change core material is firmly encapsulated therein and is not easily leaked (i.e., has good recycling performance), and has better mechanical strength compared with other phase change microcapsules. The latent heat of fusion value of the sample in Example 1 is 110.1 J / g. After continuous use for 20 cycles, its latent heat of fusion value remains at 108.6 J / g, which is higher than the latent heat of fusion value of the sample in the comparative example. That is, the phase change microcapsules prepared by the present invention have good phase change heat storage and temperature control performance.

Claims

1. A preparation method of phase change microcapsules, comprising the following steps: (1) Mix the molten phase change material, aromatic polyaldehyde, neutral surfactant and mixed solvent evenly, and perform high-speed shearing treatment to obtain a phase change microemulsion; (2) Heat and reflux the phase change microemulsion obtained in step (1) under the protection of inert gas, while dropping an aqueous solution of polyetheramine, and then add an acidic liquid to adjust the pH value of the mixed material to 4.5 - 5.5, and continue the reflux heating reaction to obtain a solid-liquid mixture; (3) For the solid-liquid mixture obtained in step (2), after cooling to room temperature, rotary evaporate the solvent, then extract with ethyl acetate, and then rotary evaporate and recrystallize with an alcohol solvent to obtain phase change microcapsules; In step (1), the aromatic polyaldehyde is selected from one or more of mellitic aldehyde, isophthalaldehyde and 2,3-naphthalenedialdehyde; In step (2), the polyetheramine is selected from one or more of bifunctional and trifunctional polyetheramines with an average molecular weight of 200 - 600; 2. The method according to claim 1, characterized in that, In step (1), the phase change material is selected from one or more of normal alkanes, paraffins, and stearic acid esters with a phase change temperature of 18°C - 35°C; the aromatic polyaldehyde is selected from mellitic aldehyde; the neutral surfactant is selected from one or more of Span 60, Span 80, Tween 60 and Tween 80; 3. The method according to claim 1, characterized in that In step (1), the phase change material is selected from paraffin; the neutral surfactant is selected from Span 80 and Tween 80, and the mass ratio of Span 80 to Tween 80 is 1:(0.35 - 2.5); 4. The method according to claim 1, characterized in that, In step (1), the mixed solvent is selected from organic solvents and water; in the aqueous solution of the organic solvent, the mass ratio of the organic solvent to deionized water is 1:(5 - 12); 5. The method according to claim 1, characterized in that, In step (1), the mixed solvent is selected from one or more of ethanol aqueous solution, methanol aqueous solution, and acetone aqueous solution; in the aqueous solution of the organic solvent, the mass ratio of the organic solvent to deionized water is 1:(7 - 10); 6. The method according to claim 1, wherein In step (1), the mass ratio of the phase change material, aromatic polyaldehyde, neutral surfactant and mixed solvent is 1:(0.05 - 0.35):(0.005 - 0.05):(25 - 70); 7. The method according to claim 1, characterized in that In step (1), the mass ratio of the phase change material, aromatic polyaldehyde, neutral surfactant and mixed solvent is 1:(0.08 - 0.2):(0.007 - 0.015):(35 - 50); 8. The method according to claim 1, wherein In step (1), for the high-speed shearing treatment, the reaction temperature is 40°C - 75°C; the shearing reaction time is 5 min - 30 min; the rotation speed of the high-speed shearing is 6000 rpm - 13000 rpm.

9. The method according to claim 1, characterized in that In step (2), the phase change microemulsion obtained in step (1) is heated under reflux with an inert gas protection. The inert gas is selected from any one of nitrogen, helium, and argon. The gas flow rate is 75 mL / min to 275 mL / min per liter of the phase change microemulsion; the heating temperature in the heating reflux reaction is 40°C to 80°C; the reflux reaction time in the heating reflux reaction is 15 min to 45 min.

10. The method according to claim 1, wherein In step (2), the phase change microemulsion obtained in step (1) is heated under reflux with an inert gas protection. The inert gas has a gas flow rate of 100 mL / min to 150 mL / min per liter of the phase change microemulsion.

11. The method according to claim 1, characterized in that, In step (2), the acidic liquid is selected from one or more of inorganic acids, organic acids, and acidic ionic liquids; the mass concentration of the acidic liquid is 5% to 15%; the heating temperature for the continued reflux heating is 40°C to 80°C; the reaction time for the continued reflux heating is 0.5 h to 3 h.

12. The method according to claim 1, wherein In step (2), the acidic liquid is selected from acidic ionic liquids.

13. The method according to claim 1, characterized in that, In step (2), the acidic liquid is selected from [C3SO3HMim]HSO4 type acidic ionic liquids.

14. The method according to claim 1, wherein In step (2), the polyetheramine is selected from trifunctional polyetheramines; the mass concentration of the polyetheramine aqueous solution is 5% to 10%; the dropping rate of the polyetheramine aqueous solution is 5 g / min to 40 g / min per liter of the phase change microemulsion.

15. The method according to claim 1, wherein In step (2), the mass ratio of the polyetheramine to the aromatic polyaldehyde in step (1) is 1:(0.1 - 1.2).

16. The method according to claim 1, wherein In step (2), the mass ratio of the polyetheramine to the aromatic polyaldehyde in step (1) is 1:(0.3 - 0.7).

17. The method according to claim 1, characterized in that, In step (3), the rotary evaporation temperature is 100°C to 150°C, the rotary evaporation speed is 60 rpm to 100 rpm, and the rotary evaporation time is 20 min to 30 min; after extraction with ethyl acetate, the rotary evaporation temperature is 85°C to 150°C again; the rotary evaporation speed is 60 rpm to 120 rpm; the rotary evaporation time is 10 min to 50 min.

18. The method according to claim 1, characterized in that, In step (3), the alcohol solvent is selected from one or more of anhydrous methanol, anhydrous ethanol, and anhydrous isopropanol.

19. The method according to claim 1, characterized in that In step (3), the alcohol solvent is selected from anhydrous methanol.

20. The method according to claim 1, wherein In step (3), the recrystallization temperature is 35°C to 75°C.

21. The method according to claim 1, wherein In step (3), the recrystallization temperature is 40°C to 55°C.

22. A phase change microcapsule obtained by the preparation method according to any one of claims 1 - 21.

23. The phase change microcapsule according to claim 22, wherein, The average particle size of the phase change microcapsules is 1 μm to 5 μm, the latent heat of fusion value is 94 J / g to 112 J / g, the coating rate is 60% to 70%, the thermal conductivity is 0.32 W·m -1 ·k -1 ~0.43 W·m -1 ·K -1 , the compressive strength is 0.75 MPa to 1.06 MPa, and the fluidization wear rate is 2% to 6%.

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