A heat storage material with high low phase change temperature and a preparation method thereof

Abstract

The application discloses a heat storage material with high and low phase change temperatures and a preparation method thereof. Polyethylene glycol diglycidyl ether, an alcohol amine compound and a catalyst are mixed, heated and stirred until a uniform mixture is obtained; the uniform mixture is solidified at 80-100 DEG C, and then solidified at 110-130 DEG C to obtain an epoxy ring-opening polymer; the epoxy ring-opening polymer is dissolved in an organic solvent together with a sugar alcohol phase change material, after complete dissolution, a boronic acid compound is added, stirred and reacted, the solvent is volatilized, and then vacuum drying is carried out to obtain the heat storage material with high and low phase change temperatures; through a reversible polycondensation reaction between hydroxyl groups and boron hydroxyl groups, polyethylene glycol segments are introduced, and the heat storage units of low-temperature and high-temperature phase change are formed by the polyethylene glycol segments and the sugar alcohol phase change material; the interval between the phase change temperature points of the two is wide, the cascade utilization of heat is realized, the requirement for a heat source is reduced, and the risks of volume change and leakage in the process of use of the cascade phase change heat storage material prepared by the physical blending method are overcome.

Description

Technical Field

[0001] This invention belongs to the field of phase change material technology, specifically relating to a thermal storage material with high and low phase change temperatures and its preparation method. Background Technology

[0002] With global population growth and continuous industrialization, energy demand is rapidly increasing. Latent heat storage technology based on phase change materials (PCMs) is a key technology for building renewable energy infrastructure. Traditional PCMs can store and release heat through reversible phase change within a single phase change temperature. Compared to traditional PCMs with only a single phase change temperature, developing cascaded PCMs with multiple phase change temperatures enables the cascaded utilization of heat energy of different grades, thereby improving energy efficiency.

[0003] Chinese patent CN106634856A discloses a two-gradient thermal storage material and its preparation method. The two-gradient thermal storage material is prepared by physical blending of a low-temperature phase change material (methoxyphenol) and a medium-temperature phase change material (pyrogallol), along with a binder, at high temperature. DSC testing showed that the two phase change temperatures of the obtained two-gradient phase change thermal storage material were 54.3℃ and 133.5℃, respectively. However, this preparation process is complex, time-consuming, and energy-intensive, which is not conducive to large-scale production. Furthermore, the two-gradient thermal storage material prepared by the physical mixing method still carries a risk of leakage.

[0004] Chinese patent CN106221676B discloses a phase change thermal storage material with multiple phase change points and its preparation process. The multi-phase change thermal storage material is prepared by combining erythritol, trimethylolethane, and a stabilizer. DSC testing shows that the two phase change temperatures of this thermal storage material are 83℃ and 97℃, respectively. However, the thermal storage material prepared by this method also has a leakage risk.

[0005] Chinese patent CN106675525A discloses a phase change cold storage material with two phase change points and its preparation method. The two-phase change cold storage material is prepared by physically mixing inorganic salts, organic phase change materials, and additives. DSC testing shows that the phase change temperatures of this cold storage material are -10℃ and 13℃, with a total latent heat of phase change of 225 J / g. However, the preparation process is relatively complex, especially considering the potential corrosion of equipment by the inorganic salt phase change material and the risk of leakage during use.

[0006] To address the leakage risks associated with the aforementioned disclosed gradient phase change materials during use, Chinese patent CN117003990A discloses a polyurethane gradient phase change energy storage material and its preparation method. This method introduces the organic phase change material polyethylene glycol and straight-chain thiols into the main chain and side chains of the polymer through a chemical reaction, resulting in two phase change temperature points at 39℃ and 55.1℃. Furthermore, by chemically bonding the phase change material into the polymer structure, the leakage risk of gradient phase change materials is completely eliminated. However, the two phase change temperatures of this polyurethane gradient phase change energy storage material are adjacent, resulting in a narrow range and limiting its practical application. Therefore, further developing multi-phase change point thermal storage materials with a wide phase change temperature range and no leakage risk remains a highly challenging task. Summary of the Invention

[0007] Technical problems to be solved:

[0008] This application addresses the shortcomings of existing technologies and solves the technical problems of narrow phase change temperature range and leakage risk in current gradient phase change energy storage materials. It provides a thermal storage material with both high and low phase change temperatures and its preparation method. The material uses polyethylene glycol segments in polyethylene glycol diglycidyl ether as the low-temperature phase change thermal storage unit and sugar alcohol-based phase change materials as the high-temperature thermal storage unit. First, the melt polymerization reaction of polyethylene glycol diglycidyl ether and an alkanolamine compound is used to obtain an epoxy ring-opening polymer containing three hydroxyl groups in a repeating structural unit and simultaneously possessing low-temperature phase change functionality. Second, a sugar alcohol-based phase change material is introduced. Under the dynamic action of boric acid compounds, a reversible condensation reaction between hydroxyl groups and boron hydroxyl groups is conducted to obtain a thermal storage material with both high and low phase change temperatures triggered by the polyethylene glycol phase change segments and the sugar alcohol-based phase change material.

[0009] Technical solution:

[0010] To achieve the above objectives, this application provides the following technical solution:

[0011] A method for preparing a thermal storage material with high and low two-phase change temperatures specifically includes the following steps:

[0012] Step 1: Take polyethylene glycol diglycidyl ether and an alkanolamine compound in a molar ratio of 1:1. Take a catalyst at 0.1-1% of the total mass of polyethylene glycol diglycidyl ether and alkanolamine compound. Mix polyethylene glycol diglycidyl ether, alkanolamine compound and catalyst, and heat and stir at 60-70°C until a homogeneous mixture is obtained.

[0013] Step 2: Cure the homogeneous mixture obtained in Step 1 at 80-100℃ for 2-6 hours, and then at 110-130℃ for 1-3 hours to obtain the epoxy ring-opening polymer.

[0014] Step 3: Dissolve the epoxy ring-opening polymer obtained in Step 2 and the sugar alcohol phase change material in 50-80 ml of organic solvent. After complete dissolution, add boric acid compound and control the stirring speed at 500-1000 r / min. After reacting for 3-6 h, evaporate the solvent at 30-80 °C and then vacuum dry at 90-110 °C for 12-24 h to obtain a heat storage material with high and low two-phase change temperatures.

[0015] Furthermore, in the first step, the molecular weight of polyethylene glycol diglycidyl ether is 500, 2000 or 6000, and the polyethylene glycol diglycidyl ether is vacuum dehydrated before use. The stirring speed in the first step is 500 r / min.

[0016] Further, in the first step, the alkanolamine compound is ethanolamine, 4-amino-1-butanol or 6-amino-1-hexanol; in the first step, the catalyst is 1,8-diazabicyclo[5.4.0]undec-7-ene, 1,4-diazabicyclo[2.2.2]octane, pyridine or piperidine.

[0017] Furthermore, the repeating structural unit in the second step epoxy ring-opening polymer contains three hydroxyl groups and simultaneously possesses low-temperature phase transition functionality.

[0018] Furthermore, in the third step, the mass ratio of the epoxy ring-opening polymer to the sugar alcohol phase change material is 1:1 to 5.

[0019] Furthermore, in the third step, the sugar alcohol phase change material is one or more of xylitol, D-sorbitol, and erythritol.

[0020] Furthermore, the organic solvent in the third step is one or more of tetrahydrofuran, dichloromethane, N,N-dimethylformamide, and N,N-dimethylacetamide.

[0021] Furthermore, in the third step, the boric acid compound is tetrahydroxydiboronic acid, 1,4-phenyldiboronic acid, or 4,4′-biphenyldiboronic acid.

[0022] Furthermore, in the third step, the amount of boric acid compound used is 5-30% of the total mass of the epoxy ring-opening polymer and the sugar alcohol phase change material.

[0023] This application also discloses thermal storage materials with high and low two-phase change temperatures prepared by any of the above preparation methods.

[0024] Explanation of the principle: This invention uses polyethylene glycol segments in polyethylene glycol diglycidyl ether as low-temperature phase change thermal storage units and sugar alcohol-based phase change materials as high-temperature thermal storage units. The phase change temperature ranges of these two components are relatively wide, and their combined use allows for tiered utilization of heat, reducing the requirements for heat sources and meeting diverse needs. First, polyethylene glycol diglycidyl ether and an alkanolamine compound undergo a melt polymerization reaction under the action of a catalyst to obtain an epoxy ring-opening polymer containing three hydroxyl groups in a repeating structural unit and simultaneously possessing phase change functionality. Then, this epoxy ring-opening polymer is mixed with a sugar alcohol-based phase change material, and under the action of boric acid compounds, a reversible condensation reaction between hydroxyl groups and boron hydroxyl groups yields a thermal storage material with both high and low phase change temperatures. In the thermal storage material described in this invention, polyethylene glycol segments and sugar alcohol-based phase change materials respectively constitute low-temperature and high-temperature phase change thermal storage units, thereby simultaneously achieving the functions of low-temperature and high-temperature phase change thermal storage.

[0025] Beneficial effects:

[0026] This application provides a thermal storage material with high and low two-phase change temperatures and its preparation method, which has the following advantages compared with the prior art:

[0027] 1. This invention utilizes the reversible polycondensation reaction between hydroxyl and boron hydroxyl groups, and simultaneously introduces polyethylene glycol segments and sugar alcohol phase change materials to form low-temperature and high-temperature phase change thermal storage units. The phase change temperature points of the two are widely spaced, and their combined use brings synergistic effects, enabling the cascade utilization of heat, reducing the requirements for heat sources, meeting different needs, and overcoming the risks of volume change and leakage that exist in cascade phase change thermal storage materials prepared by physical blending during use.

[0028] 2. During the melting and crystallization of sugar alcohol phase change materials, the polyethylene glycol segments are in a molten state, which increases the heat transfer rate of sugar alcohol phase change materials and greatly shortens their heat storage and release time;

[0029] 3. Compared with the disclosed technical solutions, the thermal storage material with high and low phase change temperatures prepared by the present invention can not only adjust the low-temperature phase change temperature range (37.2-46.4℃) by adjusting the molecular weight of polyethylene glycol diglycidyl ether, but also adjust the high-temperature phase change temperature range (89.8-119.5℃) by selecting different types of sugar alcohol phase change materials, thus having a wider range of applications in practical use. On the other hand, the total phase change enthalpy value of the thermal storage material with high and low phase change temperatures prepared by the present invention reaches up to 393.0 J / g, which is much higher than the value reported in the existing disclosed technical solutions, and has excellent thermal energy storage capacity.

[0030] 4. The preparation method used in this invention is simple, does not involve high-temperature operation, has low production cost, and is easy to achieve large-scale production. Detailed Implementation

[0031] The technical solution of the present invention will be further described below with reference to specific embodiments. However, it is worth noting that the following embodiments should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made to the present invention by those skilled in the art based on the technical solution of the present invention still fall within the scope of protection of the present invention.

[0032] The phase change value test method of the thermal storage material with high and low phase change temperatures of the present invention is as follows: a differential scanning calorimeter (DSC2500) from TA Instruments, USA, is used. The test temperature range is -20 to 150°C, in a nitrogen atmosphere. The heating and cooling rates are both 10°C / min. The sample test amount is 5 to 10 mg. The first heating eliminates the thermal history of the sample, and the data of the second heating is collected.

[0033] Example 1:

[0034] A method for preparing a thermal storage material with high and low two-phase change temperatures specifically includes the following steps:

[0035] Step 1: Vacuum-dehydrated 1.25g (2.5mmol) of polyethylene glycol diglycidyl ether (M n =500), 0.293g

[0036] (2.5 mmol) 6-amino-1-hexanol and 7.71 mg (0.5 wt.%) 1,8-diazabicyclo[5.4.0]undec-7-ene were mixed and heated and stirred at 70 °C until a homogeneous mixture was obtained; the mixture was then heated to 90 °C and cured for 4 hours, and then heated to 110 °C and cured for 2 hours to obtain an epoxy ring-opening polymer containing three hydroxyl groups in the repeating structural unit.

[0037] Step 2: Dissolve 1.5g of epoxy ring-opening polymer and 3.0g of xylitol obtained in Step 1 in 30ml of tetrahydrofuran. After complete dissolution, add 0.45g of tetrahydroxydiboron and continue stirring for 4h. Pour the mixed solution into a glass dish and place it on a 60℃ hot plate overnight. After the solvent has completely evaporated, place the material in a 100℃ vacuum oven to dry for 12h. Finally, a slightly yellow film is obtained, which is the heat storage material with high and low two-phase change temperatures described in this invention.

[0038] The thermal storage material obtained in this embodiment was tested by DSC. The melting temperature of the polyethylene glycol segment was 37.2℃, the melting enthalpy was 86.5 J / g, the crystallization temperature was 33.4℃, and the crystallization enthalpy was 82.3 J / g. The melting temperature of xylitol was 89.8℃, and the melting enthalpy was 207.8 J / g. Since xylitol cannot crystallize spontaneously and remains in a supercooled liquid state, its crystallization temperature and crystallization enthalpy cannot be determined.

[0039] Example 2

[0040] A method for preparing a thermal storage material with high and low two-phase change temperatures specifically includes the following steps:

[0041] Step 1: Vacuum-dehydrated 5.0g (2.5mmol) polyethylene glycol diglycidyl ether (M n =2000), 0.293g

[0042] (2.5 mmol) 6-amino-1-hexanol and 7.71 mg (0.5 wt.%) 1,8-diazabicyclo[5.4.0]undec-7-ene were mixed and heated and stirred at 70 °C until a homogeneous mixture was obtained; the mixture was then heated to 90 °C and cured for 4 hours, and then heated to 110 °C and cured for 2 hours to obtain the epoxy ring-opening polymer containing three hydroxyl groups in the repeating structural unit of the present invention.

[0043] Step 2: Dissolve 1.5g of epoxy ring-opening polymer and 3.0g of xylitol obtained in Step 1 in 30ml of tetrahydrofuran. After complete dissolution, add 0.45g of tetrahydroxydiboron and continue stirring for 4h. Pour the mixed solution into a glass dish and place it on a 60℃ hot plate overnight. After the solvent has completely evaporated, place the material in a 100℃ vacuum oven to dry for 12h. Finally, a slightly yellow film is obtained, which is the heat storage material with high and low two-phase change temperatures described in this invention.

[0044] The thermal storage material obtained in this embodiment was tested by DSC. The melting temperature of the polyethylene glycol segment was 42.7℃, the melting enthalpy was 106.7 J / g, the crystallization temperature was 36.9℃, and the crystallization enthalpy was 104.5 J / g. The melting temperature of xylitol was 91.1℃, and the melting enthalpy was 204.5 J / g. Since xylitol cannot crystallize spontaneously and remains in a supercooled liquid state, its crystallization temperature and crystallization enthalpy cannot be determined.

[0045] Example 3:

[0046] A method for preparing a thermal storage material with high and low two-phase change temperatures specifically includes the following steps:

[0047] Step 1: Vacuum-dehydrated 15.0g (2.5mmol) of polyethylene glycol diglycidyl ether (M n =6000), 0.293g

[0048] (2.5 mmol) 6-amino-1-hexanol and 7.71 mg (0.5 wt.%) 1,8-diazabicyclo[5.4.0]undec-7-ene were mixed and heated and stirred at 70 °C until a homogeneous mixture was obtained; the mixture was then heated to 90 °C and cured for 4 hours, and then heated to 110 °C and cured for 2 hours to obtain the epoxy ring-opening polymer containing three hydroxyl groups in the repeating structural unit of the present invention.

[0049] Step 2: Dissolve 1.5g of epoxy ring-opening polymer and 3.0g of xylitol obtained in Step 1 in 30ml of tetrahydrofuran. After complete dissolution, add 0.45g of tetrahydroxydiboron and continue stirring for 4h. Pour the mixed solution into a glass dish and place it on a 60℃ hot plate overnight. After the solvent has completely evaporated, place the material in a 100℃ vacuum oven to dry for 12h. Finally, a slightly yellow film is obtained, which is the heat storage material with high and low two-phase change temperatures described in this invention.

[0050] The thermal storage material obtained in this embodiment, as tested by DSC, showed a melting temperature of 46.4°C for the polyethylene glycol segments and a melting enthalpy of 113.5°C.

[0051] The crystallization temperature is 38.2℃ and the enthalpy of crystallization is 105.7 J / g; the melting temperature of xylitol is 88.7℃ and the enthalpy of melting is 208.2 J / g. Since xylitol cannot crystallize spontaneously but remains in a supercooled liquid state, its crystallization temperature and enthalpy of crystallization cannot be determined.

[0052] Example 4:

[0053] A method for preparing a thermal storage material with high and low two-phase change temperatures specifically includes the following steps:

[0054] Step 1: Vacuum-dehydrated 15.0g (2.5mmol) of polyethylene glycol diglycidyl ether (M n =6000), 0.293g (2.5mmol) of 6-amino-1-hexanol and 7.71mg (0.5wt.%) of 1,8-diazabicyclo[5.4.0]undec-7-ene were mixed and heated and stirred at 70°C until a homogeneous mixture was obtained; the temperature was further increased to 90°C and cured for 4 hours, and then increased to 110°C and cured for 2 hours to obtain the epoxy ring-opening polymer containing three hydroxyl groups in the repeating structural unit of the present invention;

[0055] Step 2: Dissolve 1.5g of epoxy ring-opening polymer and 3.0g of D-sorbitol obtained in Step 1 in 30ml of tetrahydrofuran. After complete dissolution, add 0.45g of tetrahydroxydiboron and continue stirring for 4 hours. Pour the mixed solution into a glass dish and place it on a 60℃ hot plate overnight. After the solvent has completely evaporated, place the material in a 100℃ vacuum oven to dry for 12 hours. Finally, a slightly yellow film is obtained, which is the heat storage material with high and low two-phase change temperatures described in this invention.

[0056] The thermal storage material obtained in this embodiment was tested by DSC. The melting temperature of the polyethylene glycol segment was 45.9℃, the melting enthalpy was 113.8 J / g, the crystallization temperature was 37.6℃, and the crystallization enthalpy was 108.2 J / g. The melting temperature of D-sorbitol was 93.5℃, and the melting enthalpy was 164.8 J / g. Since xylitol cannot crystallize spontaneously but remains in a supercooled liquid state, its crystallization temperature and crystallization enthalpy cannot be determined.

[0057] Example 5:

[0058] A method for preparing a thermal storage material with high and low two-phase change temperatures, comprising the following specific steps:

[0059] The first step is to vacuum dehydrate 15.0 g (2.5 mmol) of polyethylene glycol diglycidyl ether (M n =6000), 0.293g (2.5mmol) of 6-amino-1-hexanol and 7.71mg (0.5wt.%) of 1,8-diazabicyclo[5.4.0]undec-7-ene were mixed and heated and stirred at 70°C until a homogeneous mixture was obtained; the temperature was further increased to 90°C and cured for 4 hours, and then increased to 110°C and cured for 2 hours to obtain the epoxy ring-opening polymer containing three hydroxyl groups in the repeating structural unit of the present invention;

[0060] In the second step, 1.5g of epoxy ring-opening polymer and 3.0g of erythritol obtained in the first step are dissolved in 30ml of tetrahydrofuran. After complete dissolution, 0.45g of tetrahydroxydiboron is added and the mixture is stirred for 4 hours. The mixed solution is poured into a glass dish and placed on a hot plate at 60℃ overnight. After the solvent has completely evaporated, the material is dried in a vacuum oven at 100℃ for 12 hours. Finally, a slightly yellow film is obtained, which is the heat storage material with high and low two-phase change temperatures described in this invention.

[0061] The thermal storage material obtained in this embodiment was tested by DSC. The melting temperature of the polyethylene glycol segment was 45.6℃, the melting enthalpy was 113.7 J / g, the crystallization temperature was 36.2℃, and the crystallization enthalpy was 109.3 J / g; the melting temperature of erythritol was 119.5℃, the melting enthalpy was 279.3 J / g, the crystallization temperature was 65.2℃, and the crystallization enthalpy was 202.3 J / g.

[0062] Example 6:

[0063] A method for preparing a thermal storage material with high and low two-phase change temperatures, comprising the following specific steps:

[0064] The first step is to vacuum dehydrate 15.0 g (2.5 mmol) of polyethylene glycol diglycidyl ether (M n =6000), 0.153g (2.5mmol) ethanolamine and 7.71mg (0.5wt.%) 1,8-diazabicyclo[5.4.0]undec-7-ene were mixed and heated and stirred at 70°C until a homogeneous mixture was obtained; the temperature was further increased to 90°C and cured for 4 hours, and then increased to 110°C and cured for 2 hours to obtain the epoxy ring-opening polymer containing three hydroxyl groups in the repeating structural unit of the present invention;

[0065] In the second step, 1.5g of epoxy ring-opening polymer and 3.0g of erythritol obtained in the first step are dissolved in 30ml of tetrahydrofuran. After complete dissolution, 0.45g of tetrahydroxydiboron is added and the mixture is stirred for 4 hours. The mixed solution is poured into a glass dish and placed on a hot plate at 60℃ overnight. After the solvent has completely evaporated, the material is dried in a vacuum oven at 100℃ for 12 hours. Finally, a slightly yellowish film is obtained, which is the heat storage material with high and low two-phase change temperatures described in this invention.

[0066] The thermal storage material obtained in this embodiment was tested by DSC. The melting temperature of the polyethylene glycol segment was 47.2℃, the melting enthalpy was 110.0 J / g, the crystallization temperature was 37.8℃, and the crystallization enthalpy was 106.8 J / g; the melting temperature of erythritol was 117.6℃, the melting enthalpy was 259.8 J / g, the crystallization temperature was 65.8℃, and the crystallization enthalpy was 201.5 J / g.

[0067] Example 7:

[0068] A method for preparing a thermal storage material with high and low two-phase change temperatures, comprising the following specific steps:

[0069] The first step is to vacuum dehydrate 15.0 g (2.5 mmol) of polyethylene glycol diglycidyl ether (M n =6000), 0.223g (2.5mmol) of 4-amino-1-butanol and 7.71mg (0.5wt.%) of 1,8-diazabicyclo[5.4.0]undec-7-ene were mixed and heated and stirred at 70°C until a homogeneous mixture was obtained; the temperature was further increased to 90°C for curing for 4 hours, and then increased to 110°C for curing for 2 hours to obtain the epoxy ring-opening polymer containing three hydroxyl groups in the repeating structural unit of the present invention;

[0070] In the second step, 1.5g of epoxy ring-opening polymer and 3.0g of erythritol obtained in the first step are dissolved in 30ml of tetrahydrofuran. After complete dissolution, 0.45g of tetrahydroxydiboron is added and the mixture is stirred for 4 hours. The mixed solution is poured into a glass dish and placed on a hot plate at 60℃ overnight. After the solvent has completely evaporated, the material is dried in a vacuum oven at 100℃ for 12 hours. Finally, a slightly yellow film is obtained, which is the heat storage material with high and low two-phase change temperatures described in this invention.

[0071] The thermal storage material obtained in this embodiment was tested by DSC. The melting temperature of the polyethylene glycol segment was 44.8℃, the melting enthalpy was 106.9 J / g, the crystallization temperature was 38.5℃, and the crystallization enthalpy was 104.5 J / g; the melting temperature of erythritol was 119.2℃, the melting enthalpy was 263.7 J / g, the crystallization temperature was 66.2℃, and the crystallization enthalpy was 203.7 J / g.

[0072] Example 8:

[0073] A method for preparing a thermal storage material with high and low two-phase change temperatures, comprising the following specific steps:

[0074] The first step is to vacuum dehydrate 15.0 g (2.5 mmol) of polyethylene glycol diglycidyl ether (M n =6000), 0.293g (2.5mmol) of 6-amino-1-hexanol and 7.71mg (0.5wt.%) of 1,8-diazabicyclo[5.4.0]undec-7-ene were mixed and heated and stirred at 70°C until a homogeneous mixture was obtained; the temperature was further increased to 90°C and cured for 4 hours, and then increased to 110°C and cured for 2 hours to obtain the epoxy ring-opening polymer containing three hydroxyl groups in the repeating structural unit of the present invention;

[0075] In the second step, 1.5g of epoxy ring-opening polymer and 3.0g of erythritol obtained in the first step were dissolved in 30ml of tetrahydrofuran. After complete dissolution, 0.45g of 1,4-phenylenediboric acid was added, and stirring was continued for 4 hours. The mixed solution was poured into a glass dish and placed on a hot plate at 60℃ overnight. After the solvent had completely evaporated, the material was placed in a vacuum oven at 100℃ and dried for 12 hours. Finally, a slightly yellow film was obtained, which is the heat storage material with high and low two-phase change temperatures described in this invention.

[0076] The thermal storage material obtained in this embodiment was tested by DSC. The melting temperature of the polyethylene glycol segment was 44.8℃, the melting enthalpy was 110.4 J / g, the crystallization temperature was 37.1℃, and the crystallization enthalpy was 107.3 J / g; the melting temperature of erythritol was 119.5℃, the melting enthalpy was 262.7 J / g, the crystallization temperature was 69.6℃, and the crystallization enthalpy was 207.6 J / g.

[0077] Example 9:

[0078] A method for preparing a thermal storage material with high and low two-phase change temperatures, comprising the following specific steps:

[0079] The first step is to vacuum dehydrate 15.0 g (2.5 mmol) of polyethylene glycol diglycidyl ether (M n =6000), 0.293g (2.5mmol) of 6-amino-1-hexanol and 7.71mg (0.5wt.%) of 1,8-diazabicyclo[5.4.0]undec-7-ene were mixed and heated and stirred at 70°C until a homogeneous mixture was obtained; the temperature was further increased to 90°C and cured for 4 hours, and then increased to 110°C and cured for 2 hours to obtain the epoxy ring-opening polymer containing three hydroxyl groups in the repeating structural unit of the present invention;

[0080] In the second step, 1.5g of epoxy ring-opening polymer and 3.0g of erythritol obtained in the first step were dissolved in 30ml of tetrahydrofuran. After complete dissolution, 0.45g of 4,4′-biphenyl diboronic acid was added, and stirring was continued for 4 hours. The mixed solution was poured into a glass dish and placed on a hot plate at 60℃ overnight. After the solvent had completely evaporated, the material was placed in a vacuum oven at 100℃ and dried for 12 hours. Finally, a slightly yellow film was obtained, which is the heat storage material with high and low two-phase change temperatures described in this invention.

[0081] The thermal storage material obtained in this embodiment was tested by DSC. The melting temperature of the polyethylene glycol segment was 45.5℃, the melting enthalpy was 109.9 J / g, the crystallization temperature was 36.1℃, and the crystallization enthalpy was 108.1 J / g; the melting temperature of erythritol was 118.9℃, the melting enthalpy was 272.1 J / g, the crystallization temperature was 65.6℃, and the crystallization enthalpy was 208.3 J / g.

[0082] Comparative Example 1: A two-gradient phase change thermal storage material disclosed in Chinese Patent CN106634856A.

[0083] Comparative Example 2: Phase change thermal storage material with multiple phase change points disclosed in Chinese Patent CN106221676B.

[0084] Comparative Example 3: A phase change cold storage material with two phase change points disclosed in Chinese Patent CN106675525A.

[0085] Comparative Example 4: A polyurethane gradient phase change energy storage material disclosed in Chinese Patent CN117003990A.

[0086] The performance of the phase change thermal storage materials prepared in Examples 1-9 and Comparative Examples 1-4 is compared in Table 1.

[0087]

[0088]

[0089] Compared with Comparative Examples 1-4, the thermal storage material with high and low phase change temperatures prepared by this invention not only has an adjustable low-temperature phase change temperature range (37.2-46.4℃), but also an adjustable high-temperature phase change temperature range (89.8-119.5℃), thereby expanding the scope of practical applications. Furthermore, the total phase change enthalpy of the thermal storage material with high and low phase change temperatures prepared by this invention reaches a maximum of 393.0 J / g, far exceeding the values ​​reported in existing publicly available technical solutions, and no leakage problems occur even at temperatures above the phase change temperature.

[0090] The foregoing description has fully disclosed the specific embodiments of the present invention. It should be noted that any modifications made to the specific embodiments of the present invention by those skilled in the art do not depart from the scope of the claims. Accordingly, the scope of the claims is not limited to the foregoing specific embodiments.

Claims

1. A method for producing a heat storage material having a high low phase transition temperature, characterized by, The specific steps are as follows: Step 1: polyethylene glycol diglycidyl ether and alcohol amine compound are taken in a molar ratio of 1:1, and a catalyst is taken in an amount of 0.1-1% of the total mass of polyethylene glycol diglycidyl ether and alcohol amine compound; polyethylene glycol diglycidyl ether, alcohol amine compound and catalyst are mixed, and heated and stirred at 60-70 ℃ until a uniform mixture is obtained; the alcohol amine compound in the first step is ethanolamine, 4-amino-1-butanol or 6-amino-1-hexanol; and the catalyst in the first step is 1,8-diazabicyclo[5.4.0]undec-7-ene, 1,4-diazabicyclo[2.2.2]octane, pyridine or piperidine; Step 2: the uniform mixture obtained in Step 1 is solidified at 80-100 ℃ for 2-6 h, and then solidified at 110-130 ℃ for 1-3 h, to obtain an epoxy ring-opening polymer; Step 3: the epoxy ring-opening polymer obtained in Step 2 is dissolved in 50-80 ml of an organic solvent together with a sugar alcohol phase change material, and after complete dissolution, a boronic acid compound is added, the stirring speed is controlled at 500-1000 r / min, and after reaction for 3-6 h, the solvent is volatilized at 30-80 ℃, and then vacuum drying is performed at 90-110 ℃ for 12-24 h, to obtain a heat storage material with high and low phase change temperatures; the boronic acid compound in Step 3 is tetrahydroxydiboron, 1,4-benzenediboronic acid or 4,4'-diphenyldiboronic acid.

2. The method for preparing a thermal storage material with high and low two-phase change temperatures according to claim 1, characterized in that, In Step 1, the molecular weight of polyethylene glycol diglycidyl ether is 500, 2000 or 6000, and the polyethylene glycol diglycidyl ether is vacuum dehydrated before use; and the stirring speed in Step 1 is 500 r / min.

3. The method according to claim 1, wherein the heat storage material having high and low phase transition temperatures is prepared by the following steps. In Step 2, the repeating structural unit in the epoxy ring-opening polymer contains three hydroxyl groups and has a low-temperature phase change function.

4. The method for preparing a thermal storage material with high and low two-phase change temperatures according to claim 1, characterized in that: In Step 3, the mass ratio of the epoxy ring-opening polymer to the sugar alcohol phase change material is 1:1-5.

5. The method according to claim 1, wherein the heat storage material having high and low phase transition temperatures is prepared by the following steps. In Step 3, the sugar alcohol phase change material is one or more of xylitol, D-sorbitol and erythritol.

6. The method for preparing a thermal storage material with high and low two-phase change temperatures according to claim 1, characterized in that: In Step 3, the organic solvent is one or more of tetrahydrofuran, dichloromethane, N,N-dimethylformamide and N,N-dimethylacetamide.

7. The method according to claim 1, wherein the heat storage material having high and low phase transition temperatures is prepared by the following steps. In Step 3, the amount of the boronic acid compound is 5-30% of the total mass of the epoxy ring-opening polymer and the sugar alcohol phase change material.

8. A heat storage material with high and low phase change temperatures prepared by the preparation method of any one of claims 1-7.

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