A polymer-based processable energy storage material and its preparation method

Abstract

The present invention discloses a novel polymer-based processable energy storage material, which comprises the following components by weight: 85-90 parts of PEG, 5-10 parts of PBT, 1.5-3 parts of 1,3,5-benzenetricarboxylic acid, 2-3.5 parts of adipic acid, and 0.001-0.005 parts of catalyst. The present invention also discloses the preparation method thereof. The present invention uses PBT as the main encapsulation material, and 1,3,5-benzenetricarboxylic acid and adipic acid as the auxiliary encapsulation materials. Based on transesterification and esterification reactions, PEG is chemically encapsulated. The prepared novel polymer-based processable phase change energy storage material is a typical solid-solid phase change material, and there will be no solid-liquid transformation and PEG leakage during use. Moreover, no organic solvents are required during the preparation process, and no toxic or harmful substances are generated, which is very environmentally friendly and in line with the country's green development strategy.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy storage, and particularly relates to a novel polymer-based processable energy storage material and a preparation method thereof. Background Art

[0002] Phase change materials (PCMs) refer to a class of materials that undergo phase changes within a certain temperature range. Since phase changes are often accompanied by the absorption and release of a large amount of heat, PCMs can be used in the energy storage field to achieve the recovery and utilization of renewable energy. Compared with molten salt phase change materials, polyethylene glycol (PEG) has a more suitable phase change temperature; compared with polyols, it has a higher latent heat of phase change; compared with other PCMs, PEG also exhibits good physical and chemical stability and low cost before and after phase change. However, during the phase change process of PEG, it is easy to leak when changing from solid to liquid. Therefore, encapsulation is usually required.

[0003] Chinese Patent CN202210712181.5 discloses a method for preparing a composite phase change material by using saccharides to assist in establishing a three-dimensional network of carbon-based materials to prepare a carbon-based aerogel and then adding PEG modified by nanoparticles. Chinese Patent CN202210820416.2 discloses a highly thermally conductive flexible phase change composite material prepared by using highly elastic thermoplastic polyurethane as an encapsulation carrier, PEG with a high heat of fusion as a phase change energy storage molecule, and boron nitride nanosheets as a thermal conductivity enhancing filler. Chinese Patent CN202210230824.2 discloses a method for pre-polymerizing and chain-extending a phase change energy storage material PEG with isophorone diisocyanate and 1,4-butanediol in an anhydrous and oxygen-free heating environment, and then drying the obtained material after the reaction to prepare a polyurethane-based solid-solid phase change material. Chinese Patent CN202011351511.X discloses a degradable phase change energy storage elastomer prepared by using terephthalic acid, adipic acid, 1,4-butanediol, PEG, organic phosphate ester, and an esterification catalyst as raw materials through an esterification reaction and a polycondensation reaction in an inert gas atmosphere.

[0004] As can be seen from the above prior art, physical encapsulation of polyethylene glycol will undergo phase separation during use, resulting in the problem of PEG leakage in the long-term use of the material. In chemical encapsulation, the preparation of PEG-based phase change materials by introducing isocyanates for chain extension requires the use of organic solvents to dissolve PEG and isocyanates for the chain extension reaction, which will cause serious environmental pollution. By replacing part of the raw materials during the production of polybutylene terephthalate (PBT), replacing a part of 1,4-butanediol with PEG to prepare a linear phase change energy storage material, while maintaining the shape stability of the phase change material, the enthalpy value of the phase change material is much lower than that of PEG, and the production process is complex, which is not conducive to application and promotion. Summary of the Invention

[0005] To solve the deficiencies in the prior art, the present invention provides a novel polymer-based processable phase change energy storage material and its preparation method.

[0006] To achieve the object of the present invention, the technical solution adopted by the present invention is:

[0007] A novel polymer-based processable phase change energy storage material is made of the following components by weight: 85-90 parts of PEG, 5-10 parts of PBT, 1.5-3 parts of 1,3,5-benzenetricarboxylic acid, 2-3.5 parts of adipic acid, and 0.001-0.005 parts of catalyst.

[0008] Among them, the PEG is one or several of PEG-200, 400, 600, 800, 1000, 1500, 2000, 3000, 4000, 6000, 8000, 10000, 20000.

[0009] The present invention also includes the preparation method of the novel polymer-based processable phase change energy storage material, which includes the following steps:

[0010] Add a certain proportion of PBT, adipic acid, 1,3,5-benzenetricarboxylic acid, PEG, and catalyst to the reaction kettle, heat and melt under the protection of inert gas to obtain a molten blend. Continuously raise the temperature and turn on the vacuum system of the reaction kettle. Under high temperature and high vacuum conditions, start the esterification and transesterification reactions to prepare a novel polymer-based processable phase change energy storage material.

[0011] Among them, the melting temperature is 180-250 °C, the esterification and transesterification reaction temperature is 220-280 °C, the reaction time is 1-2 h; the vacuum degree of the polymerization reaction kettle is 100-1000 Pa.

[0012] Among them, the catalyst is at least one of germanium oxide, antimony glycolate, antimony trioxide, tetrabutyl titanate, and antimony acetate;

[0013] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0014] 1) The present invention uses PBT as the main encapsulation material, and 1,3,5-benzenetricarboxylic acid and adipic acid as auxiliary encapsulation materials. Based on transesterification and esterification reactions, PEG is chemically encapsulated. The prepared novel polymer-based processable phase change energy storage material is a typical solid-solid phase change material, and solid-liquid transformation will not occur during use, and the situation of PEG leakage will not occur. And no organic solvents are required during the preparation process, and no toxic and harmful substances are produced, which is very green and environmentally friendly and conforms to the country's green development strategy.

[0015] 2) In the present invention, the main encapsulant PBT undergoes a transesterification reaction with PEG, and at the same time, the auxiliary encapsulants 1,3,5-benzenetricarboxylic acid and adipic acid undergo an esterification reaction with PEG, and finally a block copolymer containing a crosslinked network structure is produced. Since PBT, which is easy to crystallize and has a high crystallinity, is used as the main encapsulation material, the amount of the auxiliary encapsulant 1,3,5-benzenetricarboxylic acid used in the present invention is low, and the chemical crosslinking points in the crosslinked network structure of the prepared energy storage material are few, thus ensuring its thermoplastic processability.

[0016] 3) The addition of the encapsulants 1,3,5-benzenetricarboxylic acid and adipic acid in the present invention reduces the usage amount of the main encapsulant PBT. This not only facilitates the preparation of energy storage materials with a high PEG content, but also ensures that PEG leakage does not occur during the phase change process of the energy storage material, and can also well maintain the shape of the material during the phase change process. Therefore, the present invention obtains a phase change energy storage material with a high phase change enthalpy value and good stability.

[0017] 3) The esterification reaction and transesterification reaction conditions in the present invention are the same and can be carried out simultaneously, greatly reducing the production time of the phase change energy storage material, from the original reaction time of up to more than 4 hours (specific properties such as the melting point and molecular chain length of the raw materials) to 1-2 hours. The present invention uses a one-pot method to synthesize the phase change energy storage material, and the preparation process is very simple, which is very suitable for industrial production. Description of the drawings

[0018] Figure 1 is the DSC crystallization curve of Examples 1-5.

[0019] Figure 2 is the DSC melting curve of Examples 1-5.

[0020] Figure 3 is the DSC crystallization curve of Comparative Examples 1-2.

[0021] Figure 4It is the melting curve of DSC for Comparative Examples 1-2.

[0022] Figure 5 It is the photo of the sample before and after heating at 70 °C for 1 hour in Example 5.

[0023] Figure 6 It is the digital photo of the sample before and after heating at 70 °C for 1 hour in Comparative Example 2. Detailed implementation manners

[0024] The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention, and cannot be used to limit the protection scope of this application.

[0025] Example 1

[0026] 10 parts of PBT, 3.5 parts of adipic acid, 1.5 parts of 1,3,5-benzenetricarboxylic acid, 85 parts of PEG-6000, and 0.001 part of antimony trioxide were added to a reaction kettle, and heated to 180 °C under the protection of an inert gas to obtain a molten blend. And continuously heated to 220 °C and the vacuum system of the reaction kettle was turned on. Under the condition of a vacuum degree of 500 Pa, the esterification and transesterification reactions were started for 2 h to prepare a novel polymer-based processable phase change energy storage material.

[0027] Example 2

[0028] 5 parts of PBT, 3.5 parts of adipic acid, 1.5 parts of 1,3,5-benzenetricarboxylic acid, 90 parts of PEG-6000, and 0.002 part of ethylene glycol antimonate were added to a reaction kettle, and heated to 230 °C under the protection of an inert gas to obtain a molten blend. And continuously heated to 260 °C and the vacuum system of the reaction kettle was turned on. Under the condition of a vacuum degree of 100 Pa, the esterification and transesterification reactions were started for 2 h to prepare a novel polymer-based processable phase change energy storage material.

[0029] Example 3

[0030] 5 parts of PBT, 3 parts of adipic acid, 2 parts of 1,3,5-benzenetricarboxylic acid, 90 parts of PEG-6000, and 0.003 part of tetrabutyl titanate were added to a reaction kettle, and heated to 250 °C under the protection of an inert gas to obtain a molten blend. And continuously heated to 270 °C and the vacuum system of the reaction kettle was turned on. Under the condition of a vacuum degree of 300 Pa, the esterification and transesterification reactions were started for 2 h to prepare a novel polymer-based processable phase change energy storage material.

[0031] Example 4

[0032] 5 parts of PBT, 2.5 parts of adipic acid, 2.5 parts of 1,3,5-benzenetricarboxylic acid, 90 parts of PEG-6000, and 0.004 parts of antimony acetate were added to a reaction kettle and heated to 230 °C under the protection of an inert gas to obtain a melt blend. Then, the temperature was continuously raised to 270 °C and the vacuum system of the reaction kettle was turned on. Under a vacuum of 600 Pa, the esterification and transesterification reactions were started for 2 h to prepare a novel polymer-based processable phase change energy storage material.

[0033] Example 5

[0034] 5 parts of PBT, 2 parts of adipic acid, 3 parts of 1,3,5-benzenetricarboxylic acid, 90 parts of PEG-6000, and 0.005 parts of n-butyl acid phosphate were added to a reaction kettle and heated to 250 °C under the protection of an inert gas to obtain a melt blend. Then, the temperature was continuously raised to 280 °C and the vacuum system of the reaction kettle was turned on. Under a vacuum of 1000 Pa, the esterification and transesterification reactions were started for 2 h to prepare a novel polymer-based processable phase change energy storage material.

[0035] Comparative Example 1

[0036] (1) Install a mechanical stirrer in an oil bath and weigh 90 parts of PEG6000 into a three-necked flask. After vacuum drying at 110 °C for 3 h, the temperature was lowered to 82 °C and nitrogen was introduced.

[0037] (2) Take a small glass bottle, weigh 0.0208 parts of the catalyst dibutyltin dilaurate DBDTL, weigh 21.4455 parts of IPDI (10% in excess), draw 36 ml of anhydrous N,N-dimethylformamide DMF as a solvent, mix them in the glass bottle, and then inject the mixed solution into the three-necked flask with a syringe. The reactants in the three-necked flask were mechanically stirred at 82 °C under a nitrogen atmosphere for 2.5 h.

[0038] (3) Weigh 3.9506 parts of BDO into a small glass bottle, draw 45 ml of N,N-dimethylformamide DMF as a solvent, mix them in the small glass bottle, and then inject the mixed solution in the small glass bottle into the three-necked flask with a syringe. The reactants in the three-necked flask were mechanically stirred and reacted for 2 h under a nitrogen atmosphere.

[0039] (4) Pour it into deionized water for washing and sedimentation. After soaking for 12 h, the phase change material obtained in the three-necked flask was poured into a polytetrafluoroethylene petri dish and naturally air-dried in a fume hood for 96 h to obtain a polyurethane-based solid-solid phase change material PU2000 prepared with PEG6000.

[0040] Comparative Example 2

[0041] (1) Esterification reaction

[0042] First, weigh 5 parts in total of terephthalic acid, adipic acid and 1,4-butanediol according to a molar ratio of 1:2:3, as well as 90 parts of PEG-6000 as the matrix raw materials, and 5 parts of ethyl 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate and 0.002 parts of the catalyst antimony acetate into the reaction kettle; heat to 160°C for melting under the protection of inert gas, and carry out the esterification reaction under normal pressure. The esterification reaction temperature is 170°C and the reaction time is 2 h.

[0043] (2) Polycondensation reaction

[0044] After the esterification reaction in step (1) is completed, turn on the vacuum system of the reaction kettle, and start the polycondensation reaction of the esterification product under high temperature and high vacuum conditions to prepare a degradable phase change elastomer; control the vacuum degree in the reaction kettle to be lower than 100 Pa, the polycondensation reaction temperature is 245°C, and the polycondensation reaction time is 2 h. After the viscosity of the material in the reaction kettle no longer increases, end the reaction.

[0045] 1. DSC thermal property test

[0046] Use differential scanning calorimetry to characterize the phase change characteristics of pure PEG and the sample. First, place 3-7 mg of the dried sample in an aluminum crucible for sample preparation, and then put the test sample into a differential scanning calorimeter for testing. Test conditions: Under an N2 atmosphere, first heat the sample from room temperature to 140°C at a heating rate of 10°C / min and hold it at 140°C for 5 min to eliminate the thermal history. Then cool the sample to 0°C at a cooling rate of 10°C / min and keep it warm for 2 minutes, and finally heat it to 100°C again at a heating rate of 10°C / min to collect the phase change data of the sample.

[0047] 2. Shape stability test

[0048] Use a vacuum drying oven and a digital camera to characterize the shape stability performance of the sample. First, use a micro-injection molding machine to make the granular sample into a long strip-shaped sample with a length of 10.0 cm, and then place it in a vacuum drying oven at 70°C for 1 h to observe the sample, and use a digital camera to record the shape change of the sample strip.

[0049] Table 1 Phase change performance of the new polymer-based processable phase change energy storage material

[0050]

[0051] From Figures 1-4, it can be seen that when the content of polyethylene glycol is constant, there is no obvious difference in the melting temperature and crystallization temperature of the material. As can be seen from Table 1, the pre-enthalpy value of the novel PEG-based processable phase change energy storage materials prepared in Examples 1-5 is proportional to the proportion of polyethylene glycol, and the higher the polyethylene glycol content, the greater the pre-enthalpy value. It can be clearly seen from Examples 1-5 that the reaction time for preparing the novel PEG-based processable phase change energy storage material of the present invention is only 2 h, which is much less than that of Comparative Example 1 and Comparative Example 2. Moreover, the preparation process uses a one-pot method to synthesize the phase change energy storage material, and the preparation process is very simple, which is very suitable for industrial production.

[0052] As can be seen from Table 1, for the phase change energy storage material prepared in Comparative Example 2, when the PEG content is the same, there is no obvious difference in the enthalpy value of the phase change material prepared and the enthalpy value of the novel PEG-based processable phase change energy storage material prepared by the present invention. However, from Figures 5-6 it can be seen that when the novel polymer-based processable phase change energy storage material prepared by the present invention is placed in a forced-air oven at 70 °C for 1 h, the shape of the sample strip hardly changes. When the sample strip of the phase change energy storage material prepared in Comparative Example 2 is placed in a forced-air oven at 70 °C for 1 h, the shape of the sample strip changes significantly. The phase change energy storage material prepared by the present invention can well maintain the shape of the material during the phase change process even when the content of PEG is very high. Therefore, the phase change energy storage material obtained by the present invention has a high phase change enthalpy value and good stability.

[0053] From Table 1 and Figure 5 it can be seen that the addition of the loading agents 1,3,5-benzenetricarboxylic acid and adipic acid in the present invention reduces the usage amount of the main encapsulating agent PBT. This not only facilitates the preparation of energy storage materials with a high PEG content, but also ensures that no PEG leakage occurs during the phase change process of the energy storage material, and can also well maintain the shape of the material during the phase change process. Therefore, the phase change energy storage material obtained by the present invention has a high phase change enthalpy value and good stability. Moreover, the preparation method of the phase change material of the present invention is simple, no organic solvents are required during the preparation process, and no toxic and harmful substances are generated, which is very green and environmentally friendly and conforms to the national green development strategy.

[0054] The applicant of the present invention has made a detailed description and illustration of the embodiments of the present invention in combination with the accompanying drawings of the specification. However, those skilled in the art should understand that the above embodiments are only the preferred implementation schemes of the present invention, and the detailed description is only to help readers better understand the spirit of the present invention, rather than a limitation on the protection scope of the present invention. On the contrary, any improvement or modification based on the spirit of the present invention should fall within the protection scope of the present invention.

Claims

1. A polymer-based processable phase change energy storage material, characterized in that, It consists of the following components by weight parts: 90 parts of PEG, 5 parts of PBT, 1.5 - 3 parts of 1,3,5-benzenetricarboxylic acid, 2 - 3.5 parts of adipic acid, and 0.001 - 0.005 parts of catalyst.

2. The polymer-based processable phase change energy storage material according to claim 1, wherein: The PEG is one or several of PEG-200, 400, 600, 800, 1000, 1500, 2000, 3000, 4000, 6000, 8000, 10000, 20000.

3. A polymer-based processable phase change energy storage material according to claim 1, characterized in that: The catalyst is at least one of germanium oxide, antimony glycolate, antimony trioxide, n-butyl titanate, and antimony acetate.

4. A preparation method of the polymer-based processable phase change energy storage material according to any one of claims 1 to 3, characterized in that: It includes the following steps: Step 1) According to the component ratio in Claim 1, add PBT, adipic acid, 1,3,5-benzenetricarboxylic acid, PEG, and catalyst into the reaction kettle, and heat under the protection of inert gas to obtain a molten blend. Step 2) Continuously raise the temperature and turn on the vacuum system of the reaction kettle. Under the state of high temperature and high vacuum, start the esterification and transesterification reactions. The temperature of the esterification and transesterification reactions is 220 - 280 °C, and the reaction time is 1 - 2 h; a polymer-based processable phase change energy storage material is prepared.

5. The preparation method of the polymer-based processable phase change energy storage material according to claim 4, wherein: The melting temperature is 180 - 250 °C.

6. The preparation method of the polymer-based processable phase change energy storage material according to claim 4, wherein: The vacuum degree of the polymerization reaction kettle is 100 - 1000 Pa.

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