TWI764098B - High thermal conductivity and low resistance phase change material microcapsule and its preparation and application - Google Patents

Abstract

A high thermal conductivity and low resistance phase change material microcapsule and its preparation and application, which uses the copolymer of acrylic monomer and vinylsilane as the microcapsule shell and sodium dodecyl sulfate as the stabilizer to make the size of the microcapsule uniform and miniaturized, and the nano-inorganic powder with high thermal conductivity and low resistance is introduced into the shell, so that the surface area of the microcapsule is increased and the heat conduction is carried out quickly, effectively adjusting the temperature of phase change material, moreover, the prepared microcapsule with high thermal conductivity and low resistance phase change material have antistatic effect after adding non-conductor materials, such a microcapsule can be used in building materials, polymer composites, heat dissipation or energy storage materials for electronic optoelectronic products.

Description

High thermal conductivity and low resistance phase change material microcapsule and its preparation method and application

The invention relates to the technical field of microencapsulation of a phase change material, in particular to a microcapsule of a phase change material with high thermal conductivity and low resistance, and a preparation method and application thereof.

Recently, due to the improvement of economy and quality of life, the demand for environment-friendly energy has greatly increased, so the development of materials for thermal energy storage and effective utilization of thermal energy has attracted much attention. Phase change materials are suitable materials because they can regulate heat and thermal comfort. This latent heat storage material has a higher heat storage density than traditional materials. Among them, solid-liquid phase change materials have been widely developed, but their leakage problems during the phase change process limit their applications. Therefore, encapsulating the phase change material by microcapsules can avoid its leakage and adverse reaction with surrounding and environmental substances. However, because the shell layer of the general microcapsule is a polymer material, the thermal conductivity is poor and the resistance is high, and it is easy to generate static electricity, resulting in the ineffectiveness of the phase change material microcapsule.

In order to improve the above-mentioned problems, the Republic of China Invention Patent No. I535486 discloses a preparation method of a phase-change microcapsule with a thermally conductive shell, which is improved on the polymer structure of the microcapsule shell, using the original acrylic sheet. A method of copolymerizing the body (eg: methyl methacrylate, Methyl methacrylate, MMA) with a silane compound (eg: triethoxyvinylsilane, Triethoxyvinylsilane), Furthermore, thermal conductive materials (such as boron nitride) can be introduced into the shell material, and polyvinyl alcohol (PVA) is used as a stabilizer, and phase change microcapsules with high thermal conductivity are successfully prepared.

It is worth noting that the high thermal conductivity microcapsules of the aforementioned patents have high electrical resistance, and if they are added to non-conductive materials (such as polymer materials), there is a danger of static electricity accumulation. Therefore, the present invention considers that it is necessary to provide a high thermal conductivity and low resistance phase change material microcapsule and its preparation method and application to improve the above problems.

In order to overcome the above-mentioned technical problems, the purpose of the present invention is to provide microcapsules of phase-change materials with high thermal conductivity and low resistance and their preparation method and application. In addition, sodium dodecyl sulfate (SDS) is used as a stabilizer to make the size of the microcapsules uniform and miniaturized, and nano-inorganic powders with high thermal conductivity and low resistance are introduced into the shell layer, so that the microcapsules are The surface area of the material is increased, and it can conduct heat quickly, so as to effectively exert the temperature regulation effect of the phase change material. In addition, the high thermal conductivity and low resistance phase change material microcapsules prepared by the method of the present invention have antistatic effect after adding non-conductive materials (such as polymer materials). In conclusion, the high thermal conductivity and low resistance phase change material microcapsules prepared by the method of the present invention can be respectively applied in building materials, polymer composite materials, temperature regulating fabrics and heat dissipation or energy storage materials of electronic and optoelectronic products.

The reason is that, in order to achieve the above purpose, the present invention provides a method for preparing microcapsules of phase change materials with high thermal conductivity and low resistance. The oil bath is heated and stirred to carry out the prepolymerization reaction to form the first solution; (B) provide a phase change material; (C) adding the stabilizer sodium dodecyl sulfate aqueous solution to the phase change material, and raising the temperature to exceed the melting point of the phase change material to perform a liquefaction action, and stirring evenly to form a second solution; (D) the second solution The solution is added to the first solution and stirred evenly; (E) ethylene glycol dimethacrylate and nano-inorganic powder with high thermal conductivity and low resistance are added, and then an initiator is added, and the microcapsule polymerization is completed by heating in a stirring oil bath Coating; (F) ice bath, centrifugation, filtration, and drying of the lower layer of microcapsules to obtain thermally conductive shell phase change material microcapsules.

In the preparation method of the phase change material microcapsule of the present invention, the nano-inorganic powder system with high thermal conductivity and low resistance is selected from one or a combination of two or more of graphite, graphene or carbon tube.

In the preparation method of the phase change material microcapsules of the present invention, the heating temperature of the oil bath in step (A) ranges from 50°C to 120°C.

In the preparation method of the phase change material microcapsules of the present invention, the temperature range of the temperature increase in step (C) is 30°C to 80°C.

In the preparation method of the phase change material microcapsules of the present invention, the oil bath heating temperature in step (E) ranges from 50°C to 120°C.

In the preparation method of the phase change material microcapsules of the present invention, the acrylic monomer system is selected from methyl acrylate, methyl methacrylate, or hydroxyethyl methacrylate.

In the preparation method of the phase change material microcapsules of the present invention, the silane compound is selected from trimethoxyvinylsilane or triethoxyvinyl silane.

In the preparation method of the phase change material microcapsules of the present invention, the starting agent is benzyl peroxide.

In the preparation method of the phase change material microcapsules of the present invention, the phase change material is an organic phase change material, and the organic phase change material is selected from the group consisting of higher aliphatic hydrocarbons, higher fatty acids, higher fatty acid esters, salts of higher fatty acids, and higher aliphatic alcohols , aromatic hydrocarbons, aromatic ketones, aromatic amides, or a group consisting of a mixture of two or more of them.

In the preparation method of the phase change material microcapsule of the present invention, the equivalent ratio of the acrylic monomer and the silane compound is 5:1.

In the preparation method of the phase change material microcapsule of the present invention, the phase change material microcapsule is a core-shell material, wherein the core material is an organic phase change material, and the shell material is a copolymer of a silane compound and an acrylic monomer.

In the preparation method of the phase change material microcapsule of the present invention, the addition ratio of the phase change material is 20wt%-60wt% of the whole microcapsule.

In the preparation method of the phase change material microcapsule of the present invention, the addition ratio of the high thermal conductivity and low resistance nano-inorganic powder accounts for 10wt% to 40wt% of the whole microcapsule.

In the preparation method of the phase change material microcapsules of the present invention, the machine used for the stirring is a magnetic stirrer, a motor stirrer or a homogenizer.

The present invention further provides a phase change material microcapsule with high thermal conductivity and low resistance.

The present invention further provides the application of a phase change material microcapsule with high thermal conductivity and low resistance. A temperature-adjusting composite material is formed in the material, the thermal conductivity of the temperature-adjusting composite material is 0.4-0.6 W/mK, and the resistance of the temperature-adjusting composite material is 2×10 ⁵ -2×10 ⁶ Ω/sq.

The high thermal conductivity and low resistance phase change material microcapsules of the present invention obtained by the above-mentioned preparation method can be added to building or polymer composite materials to adjust the temperature and reduce the amount of air conditioners; they can also be added to textile materials to adjust the temperature of fabrics to improve the comfort of use. Reduce the amount of air conditioners; or as a heat dissipation or energy storage material for electronic optoelectronic products. In addition, in recent years, due to extreme climate and power shortage, the market for energy-saving related products has grown year by year. The phase change material microcapsules have a constant temperature effect, can prevent phase change leakage, and have the functions of energy-saving heat storage and safe use. High market acceptance is expected. Furthermore, the phase change material microcapsules of the present invention have the characteristics of high thermal conductivity and low resistance, and the high thermal conductivity can accelerate the transfer of heat energy, and the low resistance can solve the problem of static electricity accumulation in the material, and indeed achieve the antistatic effect.

Regarding the techniques, means and other effects adopted by the present invention to achieve the above-mentioned objects, a preferred feasible embodiment is given and described in detail with the drawings as follows.

A~F: The steps of making microcapsules of phase change materials with high thermal conductivity and low resistance

10: Box body

20: Blackout Barrier

30: Temperature sensing device

40: Light source

FIG. 1 is a schematic flow chart of a method for preparing microcapsules of phase-change materials with high thermal conductivity and low resistance according to the present invention.

Figure 2 is an enlarged structural view of the microcapsules prepared with PVA as a stabilizer.

Figure 3 is an enlarged structural view of the microcapsules prepared with SDS as a stabilizer.

FIG. 4 is a schematic diagram of a device for conducting a phase transition temperature test on a high-density polyethylene box or a microcapsule/high-density polyethylene box according to the present invention.

In order to facilitate the understanding of the present invention, the following description is given in conjunction with the embodiments.

Some embodiments of the features and advantages of the present invention are set forth in detail in the following description. It should be understood that the present invention can have various changes in different aspects without departing from the scope of the present invention, and the descriptions and drawings therein are essentially used for illustration rather than limitation this invention.

The manufacturing method of the high thermal conductivity and low resistance phase change material microcapsules of the present invention firstly modifies the acrylic monomer, then adds the nano thermal conductive material to bond it to the modified acrylic monomer, and finally prepares the phase change of the thermally conductive shell layer Materials Microcapsules, described below:

1. Modification of acrylic monomer:

Using vinylsilane (VS) and acrylic monomer (AM) as reactive monomers, the copolymer (VS-AM copolymer) is polymerized through peroxide initiation reaction without the use of organic solvents. ), the reaction formula is as follows (1). The silane compound is trimethoxyvinylsilane or triethoxyvinylsilane. The acrylic monomer is methyl acrylate, methyl methacrylate, or hydroxyethyl methacrylate.

2. Add nano thermal conductive material to bond it to the modified acrylic monomer:

In the organic material, adding a nano-inorganic powder with high thermal conductivity properties, the nano-inorganic powder system is selected from one or a combination of two or more of graphite, graphene or carbon tube, which can effectively improve the thermal conductivity of the organic material. , and prepared into a high thermal conductivity composite material. The silane compound-acrylic copolymer (VS-MMA copolymer) and the nano thermal conductive material synthesized in the present invention can form the compound of the following formula (2) It can effectively improve the compatibility between the inorganic powder with high thermal conductivity and the organic substrate. The preferred addition ratio of the nano-inorganic powder with high thermal conductivity is 10wt%~40wt% of the whole microcapsule .

3. Preparation of thermal conductive shell phase change material microcapsules:

The thermally conductive shell phase change material microcapsule is based on the phase change material as the core and the copolymerized polymer as the shell. The mixture of acrylic monomer and silane compound after adding a small amount of initiator is stirred under oil bath heating to carry out prepolymerization to form a first solution. The phase change material is added to an aqueous solution of sodium dodecyl sulfate (SDS), and the temperature is raised beyond the melting point of the phase change material to perform a liquefaction action to form a second solution. The first solution and the second solution are mixed, and ethylene glycol dimethacrylate and a thermally conductive material are added, and after stirring, a thermally conductive shell phase change material microcapsule solution is formed. Then, after ice bathing, centrifugation and filtration, the microcapsules of the lower layer are taken out and dried to obtain the microcapsules of the thermally conductive shell phase change material.

Wherein, the phase change material described in the present invention is an organic phase change material; the organic phase change material is mainly higher aliphatic hydrocarbons, higher fatty acids, higher fatty acid esters, salts of higher fatty acids, higher aliphatic alcohols, aromatic hydrocarbons, aromatic ketones, The group consisting of aromatic amides and mixtures thereof, but not limited to the above organic phase change material, the phase change material is preferably added in a ratio of 20wt% to 60wt% of the entire microcapsule.

Higher aliphatic hydrocarbons are usually aliphatic hydrocarbons containing more than 6 carbon atoms, preferably 6-36 carbon atoms; higher aliphatic alcohols are usually aliphatic hydrocarbons containing more than 6 carbon atoms, preferably 6-36 carbon atoms.

As shown in Figure 1, the specific implementation steps of the method for preparing the high thermal conductivity and low resistance phase change material microcapsules of the present invention are shown, and the steps of the method of the present invention include:

(A) Copolymerize the acrylic monomer and the silane compound, add an initiator, heat and stir in an oil bath to carry out a prepolymerization reaction to form a first solution. In the embodiment of the present invention, the heating temperature range of the oil bath in step (A) is preferably 50°C to 120°C; the acrylic monomer system is selected from methyl acrylate, methyl methacrylate, or hydroxy methacrylate. Ethyl ester; the silane compound is selected from trimethoxyvinylsilane or triethoxyvinyl silane; the initiator is benzyl peroxide. Wherein, the equivalent ratio of the acrylic monomer and the silane compound is 5:1.

(B) Provides a phase change material. In the embodiment of the present invention, the phase change material is an organic phase change material, and the organic phase change material is selected from higher aliphatic hydrocarbons, higher fatty acids, higher fatty acid esters, salts of higher fatty acids, higher aliphatic alcohols, aromatic hydrocarbons, A group consisting of one of aromatic ketones and aromatic amides or a mixture of two or more of them. Wherein, the addition ratio of the phase change material accounts for 20wt% to 60wt% of the whole microcapsule.

(C) adding the stabilizer sodium dodecyl sulfate aqueous solution to the phase change material, and heating up to exceed the melting point of the phase change material, to carry out liquefaction action, and stirring uniformly to form the second solution; In the embodiment of the present invention, The temperature range of the temperature increase in step (C) is preferably 30°C to 80°C.

(D) this second solution is added to this first solution, and stir;

(E) adding ethylene glycol dimethacrylate and nano-inorganic powder with high thermal conductivity and low resistance, then adding an initiator, and heating in a stirred oil bath to complete the polymerization and coating of microcapsules; in the embodiment of the present invention, the The nano-inorganic powder system with high thermal conductivity and low resistance is selected from one or two of graphite, graphene or carbon tube. a combination of more than one. In the embodiment of the present invention, the heating temperature range of the oil bath in step (E) is preferably 50°C to 120°C; the starting agent is benzyl peroxide. Wherein, the addition ratio of the high thermal conductivity and low resistance nano-inorganic powder accounts for 10wt% to 40wt% of the whole microcapsule.

(F) After ice bath, centrifugation and filtration, the microcapsules of the lower layer are taken out and dried to obtain the microcapsules of the phase change material of the thermally conductive shell layer.

In the embodiment of the present invention, the stirring mentioned in the steps of the preparation method is preferably performed by a machine, and the machine can be selected from a magnetic stirrer, a motor stirrer or a homogenizer, but is not limited thereto.

The following provides method of the present invention embodiment one to embodiment four:

Example 1:

Example 1 is to add methyl methacrylate to benzyl peroxide and polymerize it into a prepolymer solution under the heating of an oil bath. In addition, paraffin (organic phase change material) in a weight ratio of 1:1 with methyl methacrylate was added to an aqueous solution of sodium dodecyl sulfate (SDS), and the temperature was raised above the melting point of the paraffin, and stirred evenly. Pour in the prepolymer solution and stir well. Add ethylene glycol dimethacrylate and heat in an oil bath to stir well. After ice bath, centrifugation, filtration procedures, and drying of the upper microcapsules, phase change microcapsules were obtained. The thermal conductivity of the microcapsules was measured to be 0.1996 W/mk. Resistance is >10 ¹⁶ Ω/sq.

Embodiment 2:

In the second embodiment, methyl methacrylate and the silane compound trimethoxyvinylsilane were mixed in an equivalent ratio of 5:1 under heating in an oil bath at 60°C. Add benzyl peroxide and polymerize into a prepolymer solution under heating in an oil bath. In addition, paraffin wax (organic phase change material) in a weight ratio of 3:1 with methyl methacrylate was added to the sodium dodecyl sulfate aqueous solution, and the temperature was raised to exceed the melting point of the paraffin wax, and stirred evenly. Pour in the prepolymer solution and stir well. Add ethylene glycol dimethacrylate, and stir evenly under heating in an oil bath. Ice bath, centrifugation, filtration, and drying of the upper microcapsules to obtain phase change microcapsules. The thermal conductivity of the microcapsules was measured to be 0.1985 W/mk. Resistance is >10 ¹⁶ Ω/sq.

Embodiment three:

In the third embodiment, methyl methacrylate and the silane compound triethoxyvinylsilane were mixed at an equivalent ratio of 5:1 under heating in an oil bath at 60°C. Add benzyl peroxide and polymerize into a prepolymer solution under heating in an oil bath. In addition, paraffin (organic phase change material) in a weight ratio of 1:1 with methyl methacrylate was added to the sodium dodecyl sulfate aqueous solution, and the temperature was raised to exceed the melting point of the paraffin, and stirred evenly. Pour in the prepolymer solution and stir well. Add ethylene glycol dimethacrylate and nano-graphite, place it under heating in an oil bath and stir evenly, wherein the ratio of nano-graphite to methyl methacrylate is 1:2 by weight. Ice bath, centrifugation, filtration, and drying of the microcapsules in the lower layer to obtain the microcapsules of the phase change material with high thermal conductivity and low resistance of the present invention. The thermal conductivity of the microcapsules was measured to be 1.136 W/mk. The resistance was 1.831×10 ³ Ω/sq.

Embodiment 4:

In the fourth example, methyl methacrylate and the silane compound triethoxyvinylsilane were mixed at an equivalent ratio of 5:1 under heating in an oil bath at 60°C. Add benzyl peroxide and polymerize into a prepolymer solution under heating in an oil bath. In addition, paraffin wax (organic phase change material) in a weight ratio of 3:1 with methyl methacrylate was added to the sodium dodecyl sulfate aqueous solution, and the temperature was raised to exceed the melting point of the paraffin wax, and stirred evenly. Pour in the prepolymer solution and stir well. Add ethylene glycol dimethacrylate and nano-graphite, place it under heating in an oil bath and stir evenly, wherein the ratio of nano-graphite to methyl methacrylate is 1:2 by weight. Ice bath, centrifugation, filtration, and drying of the microcapsules in the lower layer to obtain the microcapsules of the phase change material with high thermal conductivity and low resistance of the present invention. The thermal conductivity of the microcapsules was measured to be 1.144 W/mk. The resistance was 1.712×10 ³ Ω/sq.

Thereby, the microcapsules of the phase change material with high thermal conductivity and low resistance prepared by the above-mentioned preparation method of the present invention, as shown in FIG. 3 , have a size of less than 200 nanometers, and have good uniformity. The size of the capsules, which are stabilizers, is as large as 2 microns as shown in Figure 2 and is less uniform. The high thermal conductivity and low resistance phase change material microcapsules of the present invention can be used to form a temperature-adjusting composite material by adding it into a polymer material. ×10 ¹⁵ Ω/sq is reduced to 2.17×10 ⁵ Ω/sq of the temperature-adjusting composite material, so that the antistatic function is indeed formed. In addition, as shown in FIG. 4 , a schematic diagram of a device for conducting a phase transition temperature test after the conventional high-density polyethylene and the microcapsules/high-density polyethylene of the present invention are respectively made into boxes 10 is shown. After the body or the microcapsule/HDPE box is respectively disposed inside the light-shielding barrier 20 and connected to the temperature sensing device 30, the light source 40 is illuminated from top to bottom to measure the phase transition temperature change. With reference to the temperature analysis data in Table 1, it can be found that the surface and inner temperatures of the microcapsule/HDPE box are 39.6°C and 36.5°C after 3 hours of illumination, compared with 45.8°C and 40.5°C for the HDPE box. ℃, significantly decreased by 4~6℃. And the temperature of the microcapsule/HDPE box was almost maintained at 36.5°C after 1 hour of illumination, confirming that the addition of phase change material microcapsules indeed has the property of adjusting the temperature and reducing the indoor temperature.

A~F: The steps of making microcapsules of phase change materials with high thermal conductivity and low resistance

Claims (8)

A method for preparing microcapsules of phase-change materials with high thermal conductivity and low resistance. The steps of the method include: (A) copolymerizing acrylic monomer and silane compound, adding an initiator, heating and stirring in an oil bath to carry out a prepolymerization reaction, A first solution is formed; wherein, the acrylic monomer system is selected from methyl acrylate, methyl methacrylate, or hydroxyethyl methacrylate, and the silane compound is selected from trimethoxyvinylsilane or trimethoxyvinylsilane Ethoxyvinyl silane (triethoxyvinyl silane); the equivalent ratio of the acrylic monomer to the silane compound is 5:1; the initiator is benzyl peroxide; (B) provides a phase change material; wherein , the phase change material is an organic phase change material, and the organic phase change material is selected from higher aliphatic hydrocarbons, higher fatty acids, higher fatty acid esters, salts of higher fatty acids, higher aliphatic alcohols, aromatic hydrocarbons, aromatic ketones, aromatic amides (C) adding a stabilizer sodium lauryl sulfate aqueous solution to the phase change material, and heating up to exceed the melting point of the phase change material to perform liquefaction, and stir evenly to form a second solution; (D) add the second solution to the first solution, and stir evenly; (E) add ethylene glycol dimethacrylate and nano-inorganic powder with high thermal conductivity and low resistance , and then add the initiator, and complete the microcapsule polymerization coating with stirring oil bath heating; wherein, the nano-inorganic powder system with high thermal conductivity and low resistance is selected from one or more of graphite, graphene or carbon tube. combination; (F) through ice bath, centrifugation, filtration, and drying the lower layer of microcapsules to obtain thermally conductive shell phase change material microcapsules; wherein, the phase change material microcapsules are a core-shell material, and the core material is Organic phase change material, the shell material is a copolymer of silane compound and acrylic monomer; the addition ratio of the phase change material is 20wt%~60wt% of the whole microcapsule, the high thermal conductivity and low resistance nano-inorganic The addition ratio of powder is 10wt%~40wt% of the whole microcapsule, and the thermal conductivity of the microcapsule is greater than 1.1W/mk, and the resistance of the microcapsule is lower than 2×10 ³ Ω/sq. According to the method for preparing microcapsules of phase change material with high thermal conductivity and low resistance as described in item 1 of the patent application scope, wherein, the heating temperature of the oil bath in step (A) ranges from 50°C to 120°C. According to the method for preparing microcapsules of phase change material with high thermal conductivity and low resistance as described in item 1 of the patent application scope, wherein, the temperature range of the temperature increase in step (C) is 30°C to 80°C. According to the method for preparing microcapsules of phase change material with high thermal conductivity and low resistance as described in item 1 of the patent application scope, wherein, the heating temperature of the oil bath in step (E) ranges from 50°C to 120°C. The method for producing microcapsules of phase-change materials with high thermal conductivity and low resistance as described in item 1 of the scope of the patent application, wherein the machine used for the stirring is a magnetic stirrer, a motor stirrer or a homogenizer. A phase-change material microcapsule with high thermal conductivity and low resistance, which is prepared by the method for producing a microcapsule of a phase-change material with high thermal conductivity and low resistance as described in any one of items 1 to 5 of the patent application scope, and the size of the microcapsule is smaller than is equal to 200 nanometers. A phase-change material microcapsule with high thermal conductivity and low resistance, which is prepared by the method for producing a microcapsule of a phase-change material with high thermal conductivity and low resistance as described in any one of items 1 to 5 of the patent application scope, and the nanocapsule of the microcapsule has a nanocapsule. The rice inorganic powder system is selected from nano-graphite; the thermal conductivity of the microcapsules is greater than 1.1 W/mk, and the electrical resistance of the microcapsules is lower than 2×10 ³ Ω/sq. A kind of application of phase change material microcapsules with high thermal conductivity and low resistance, which is made by the method for preparing microcapsules of phase change materials with high thermal conductivity and low resistance as described in any one of items 1 to 5 of the patent application scope, wherein the microcapsules ^Capsules are used to add in polymer materials to form temperature ^- adjusting composite materials. sq.

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