Phase change energy storage materials and their preparation methods, energy storage laminates

Abstract

This invention provides a phase change energy storage material and its preparation method, as well as an energy storage laminate, belonging to the field of polymer materials technology. The phase change energy storage material comprises a block polymer and a carboxymethyl cellulose-copper crosslinked composite. The block polymer has the structure shown in formula (I): Formula (I); x is 40~60, y is 90~105, and n is 130~150. The block copolymer formed by polyethylene glycol and polyethylene terephthalate of this invention is a solid-solid phase change material with energy storage properties. The copper ions in the carboxymethyl cellulose-copper crosslinked composite form dynamic metal coordination bonds with the carboxyl groups on cellulose. The composite formed by these two components can support structural stability at the phase change temperature, providing relatively rapid self-healing and reprocessing capabilities, which is beneficial for subsequent applications in the hot and cold pressing processes of card manufacturing lamination.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a phase change energy storage material and its preparation method, as well as an energy storage laminate. Background Technology

[0002] Bank cards have a multi-layered structure, typically laminated into a single unit using a laminator to create the card body. The lamination process involves hot pressing and cold pressing, with hot pressing at temperatures above 100°C. During lamination, multiple metal plates are usually used to form the laminated structure, with the multi-layered film structure of the bank card placed between the metal plates. Heated metal plates (heat sources) are located at the top and bottom of the laminated structure to provide heating and pressure.

[0003] Because the outer metal plate is closer to the heat source, its temperature rises faster, while the inner metal plate heats up relatively slowly, resulting in a large temperature difference between the inner and outer metal plates. This leads to uneven lamination and a potential risk of deformation of the card.

[0004] Therefore, it is necessary to find a material that can reduce the temperature difference between the inner and outer metal plates in order to improve the lamination effect. Summary of the Invention

[0005] In view of this, in order to at least partially solve the aforementioned technical problems, the present invention provides a phase change energy storage material and its preparation method, as well as an energy storage laminate.

[0006] According to one aspect of the present invention, a phase change energy storage material is provided, comprising: a block polymer and a carboxymethyl cellulose-copper crosslinked composite; the block polymer has a structure as shown in formula (I); x is 40~60, y is 90~105, and n is 130~150.

[0007] Formula (I).

[0008] According to another aspect of the present invention, a method for preparing a phase change energy storage material is provided. The method includes: dissolving a block polymer in a solvent to form a block polymer dispersion; adding the block polymer dispersion to a copper salt solution of carboxymethyl cellulose to carry out a crosslinking reaction, thereby obtaining a compound of the block polymer and the carboxymethyl cellulose-copper crosslinked composite, and thus obtaining a phase change energy storage material; the carboxymethyl cellulose has the structure shown in formula (II):

[0009] Formula (II), where m ranges from 240 to 260; the solvent includes a mixture of water and ethanol.

[0010] According to another aspect of the present invention, an energy storage laminate is provided, comprising a plurality of parallel metal plates, with a through-cavity between adjacent metal plates, and the aforementioned phase change energy storage material is filled in the through-cavity.

[0011] According to embodiments of the present invention, the phase change energy storage material utilizes polyethylene terephthalate (PET) segments in the block copolymer to provide rigid support and mechanical strength, suppressing the possibility of the phase change energy storage material changing from a solid to a liquid state. Polyethylene glycol (PEG) segments, as the phase change host, absorb and release latent heat through crystallization / melting processes, contributing to improved heat storage capacity. A network structure is formed by cross-linking between carboxymethyl cellulose and copper ions. Copper ions, as a highly thermally conductive material, significantly improve the overall thermal conductivity of the phase change energy storage material. The carboxymethyl cellulose-copper cross-linked composite provides support, promotes uniform dispersion of the block copolymer, avoids phase separation, and ensures the stability of heat storage and heat release processes. Attached Figure Description

[0012] The above and other objects, features and advantages of the present invention will become clearer from the following description of embodiments of the invention with reference to the accompanying drawings.

[0013] Figure 1 A flowchart illustrating the preparation method of phase change energy storage material according to an embodiment of the present invention is shown;

[0014] Figure 2 A schematic diagram of the structure of an energy storage laminate according to an embodiment of the present invention is shown;

[0015] Figure 3 The NMR spectrum of the block polymer of Example 1 of the present invention is shown. Detailed Implementation

[0016] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the invention. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the invention for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0017] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "comprising" as used herein indicates the presence of features, steps, or operations, but does not exclude the presence or addition of one or more other features.

[0018] When using expressions such as "at least one of A, B or C", they should generally be interpreted in accordance with the meaning that is commonly understood by those skilled in the art (e.g., "a system having at least one of A, B or C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B, and C, etc.).

[0019] A bank card typically consists of five layers, from top to bottom: an adhesive film (which can be understood as a thin film material with adhesive), a printed substrate, a plastic material containing the integrated circuit chip (IC chip), also called a smart card (Inlay), another printed substrate, and the adhesive film. Bank cards are usually produced by laminating them together in a heat press and then processing them using a card-making process.

[0020] In related technologies, laminators used for hot pressing typically employ eleven layers of metal plates as laminators. Heat sources are located at the top and bottom of the laminator for heating and pressurization, facilitating the hot pressing process. Due to the multi-layered structure and the presence of contact and interfacial thermal resistance between layers, the middle metal plates require a relatively longer time to reach the appropriate hot pressing temperature. While heat transfer allows the middle layer to reach a suitable hot pressing temperature (e.g., between 110 and 150°C), the outer metal plates, being closer to the heat source, experience a rapid temperature rise within a short time. This results in a significant temperature difference between the inner and outer heat-conducting materials, potentially leading to lamination deformation in the hot-pressed material.

[0021] In realizing the concept of this invention, it was discovered that the polyethylene glycol segments in the block copolymer provide a high latent heat of phase change, while the rigidity of the polyethylene terephthalate segments increases the phase change temperature. The synergistic effect of these two segments allows the block copolymer to form a solid-solid phase change material with energy storage properties. Strong hydrogen bonds form between carboxymethyl cellulose and the polyethylene glycol segments, and coordination bonds are formed between the carboxyl groups on the carboxymethyl cellulose and copper ions, further supporting the structural stability of the phase change energy storage material at the phase change temperature. This provides rapid self-healing and reprocessing performance while maintaining good energy storage performance and thermal conductivity.

[0022] Specifically, according to one embodiment of the present invention, a phase change energy storage material is provided, comprising: a block polymer and a carboxymethyl cellulose-copper crosslinked composite; the block polymer has a structure as shown in formula (I):

[0023] Equation (I); x is 40~60, y is 90~105, and n is 130~150.

[0024] It is understandable that the block polymer is a polyethylene glycol (PEG) and polyethylene terephthalate (PET-b-PEG) block copolymer, where the PEG-b-PEG block copolymer includes PEG segments and PEG segments. PEG in the PEG segments is a long-chain polymer, possessing both water and organic solubility, and exhibiting a high latent heat of phase transition. However, its phase transition temperature is relatively low, and the flexible structure of its molecular chains results in phase transitions primarily involving inter-solid-liquid states, making it difficult to withstand repeated use under pressure. PEG in the PEG segments, containing benzene rings, possesses greater rigidity, which helps to increase the phase transition temperature of the block copolymer. In the block copolymer formed by the two, the PET segment acts as a relatively rigid supporting part, and the PEG segment provides the latent heat of phase change. The two work together to make the block polymer form a solid-solid phase change material with energy storage properties. That is, at the phase change temperature, the block polymer changes from solid to solid.

[0025] Carboxymethyl cellulose (CMC) is an abundant natural polymer and renewable raw material with good water solubility, film-forming properties, and transparency. The CMC-copper crosslinked complex is based on the metal coordination bonds formed between the carboxyl groups on CMC and copper ions, and the strong hydrogen bonding between CMC and PEG in the CMC-copper crosslinked complex helps to support the structural stability of the block polymer and the CMC-copper crosslinked complex compound at the phase transition temperature.

[0026] According to embodiments of the present invention, a material with energy storage function is formed by providing a rigid skeleton (i.e., PET segments) and flexible energy storage units (i.e., PEG segments) based on block copolymers. This material tends to transition from solid to solid at the phase change temperature and can be repeatedly used at the phase change temperature (e.g., between 110 and 150°C) and under pressure. Furthermore, based on the compounding with carboxymethyl cellulose-copper crosslinked composite, there is a strong hydrogen bond between CMC and PEG, which further consolidates the structural stability at the phase change temperature. It can be used as a phase change energy storage material and can be repeatedly used at its phase change temperature. It can also provide good self-healing and reprocessing performance. In particular, when introduced into a hot press, it can replace the intermediate layer material between metal plates or replace the outer laminated metal plate. This helps to reduce metal plate damage and poor lamination caused by the rapid temperature rise of the outer metal plate through heat energy storage, and can also reduce the temperature difference between the inner and outer metal plates and improve the uniformity of lamination.

[0027] It should be noted that the ester groups in the PET segments can also interact with the carboxymethyl cellulose-copper crosslinked complex, improving the compatibility of the block polymer and the carboxymethyl cellulose-copper crosslinked complex.

[0028] In this embodiment, in formula (I), x is 40~60, y is 90~105, and n is 130~150. This setting can ensure that a sufficient number of PET segments provide good structural support, and also provide enough PEG segments to provide high latent heat of phase change, thereby providing high heat storage capacity.

[0029] Alternatively, x can be, for example, 40, 45, 50, 55, or 60.

[0030] Alternatively, y can be, for example, 90, 95, 100, or 105.

[0031] Alternatively, n can be, for example, 130, 135, 140, 145, or 150.

[0032] In some embodiments of the present invention, it was found during the use of lamination that, based on the good solid-solid phase change heat storage effect of the compound, simply replacing the outer lamination metal plate of the laminate, that is, the laminate closest to the heat source, can greatly improve the unevenness in the lamination process, thereby improving card production efficiency while saving costs.

[0033] In some embodiments of the present invention, the phase change energy storage material further includes a dispersant and a thermally conductive agent. The dispersant helps improve the compatibility between the polar carboxymethyl cellulose-copper crosslinked composite and the non-polar PET segments, reducing phase separation. The thermally conductive agent can further enhance the thermal conductivity of the aforementioned phase change energy storage material, thereby forming a phase change energy storage material that balances thermal conductivity and heat storage and can adapt to dynamic environmental changes (e.g., environments that are repeatedly heated to the phase change temperature and then cooled).

[0034] Optionally, the dispersant includes at least one of sodium dodecyl sulfate, dodecyl acetic acid, and polyoxyethylene lauryl ether. The aforementioned dispersants have good dispersing effects and reduce interfacial tension.

[0035] Preferably, the dispersant is sodium dodecyl sulfate (SDS). SDS has both hydrophilic and lipophilic ends, which helps to anchor the polar carboxymethyl cellulose-copper crosslinked complex and the non-polar PET segments, reducing interfacial tension, preventing phase separation, and thus improving interfacial heat transfer efficiency.

[0036] Optionally, the thermal conductive agent includes at least one of graphene, graphene oxide, boron nitride, and aluminum nitride. The aforementioned thermal conductive agents have high thermal conductivity, and their addition helps to improve the thermal conductivity of the phase change energy storage material. Further, the thermal conductive agent is preferably graphene oxide (sheet-like), thus utilizing the spatial effect of graphene oxide to bridge the gaps in the carboxymethyl cellulose-copper crosslinked composite network structure, further enhancing the thermal conductivity.

[0037] In some embodiments of the present invention, the phase change energy storage material is in the form of a casting liquid. It is understood that in the field of hot pressing, preparing the phase change energy storage material in the form of a casting liquid allows it to be injected into the cavity between multiple metal plates via methods such as pouring, avoiding accumulation and agglomeration of the phase change energy storage material and improving the uniformity and consistency of thermal conductivity. Furthermore, when using the phase change energy storage material as the outer metal plate of a laminator, a uniform thin film can be formed through methods such as scraping, spin coating, or spraying, thereby replacing the outermost metal plate closest to the heat source in a conventional hot press. This maintains good heat conduction while reducing the temperature difference between the inner and outer metal plates, improving the uniformity of the lamination process.

[0038] In some embodiments of the present invention, the phase change energy storage material has a phase change temperature of 110~120℃, a latent heat of phase change of 100~130J / g, and a thermal conductivity of 3~4W / (m·K). This configuration allows it to be adapted to the hot pressing process of a laminator, matching the phase change temperature with the hot pressing temperature, providing higher latent heat of phase change and thermal conductivity, improving the uniformity of temperature transfer during lamination, and increasing production efficiency.

[0039] According to another embodiment of the present invention, a method for preparing a phase change energy storage material as described above is provided. Figure 1 A flowchart illustrating the preparation method of phase change energy storage material according to an embodiment of the present invention is shown, as follows: Figure 1 As shown, the preparation method includes steps S101 to S102.

[0040] In step S101, the block polymer is dissolved in a solvent to form a block polymer dispersion.

[0041] In step S102, the block polymer dispersion is added to the copper salt solution of carboxymethyl cellulose to carry out a crosslinking reaction, thereby obtaining a compound of block polymer and carboxymethyl cellulose-copper crosslinked complex, and then obtaining a phase change energy storage material.

[0042] According to embodiments of the present invention, the block polymer is fully dissolved in a solvent to avoid agglomeration. Then, it is further mixed with a copper salt solution of carboxymethyl cellulose. This helps to promote the interaction between copper ions and ester groups of PET segments while ensuring the formation of coordination bonds between the carboxyl groups of CMC and copper ions, thus forming a complex of the two. This allows the PEG segments, which are prone to forming a molten state, to be bound within the cross-linked network, preventing the phase change energy storage material from turning into a liquid state at the phase change temperature. This makes it better suited for use in the laminator field.

[0043] In this embodiment, carboxymethyl cellulose has the structure shown in formula (II):

[0044] In formula (II), the value of m ranges from 240 to 260. This setting ensures that the formed copper salt solution of carboxymethyl cellulose has a certain fluidity, which can better bind the PEG segments in the crosslinked network, while also taking into account the structural strength of the phase change energy storage material. If m is too small, the carboxymethyl cellulose molecular chains will be too short, resulting in a low density of crosslinking sites and the formation of a crosslinked network that is prone to collapse; if m is too large, there will be too much molecular entanglement, hindering the copper ion coordination reaction.

[0045] Alternatively, m can be, for example, 240, 245, 250, 255 or 260.

[0046] Furthermore, the solvent includes a mixture of water and ethanol. It is understood that the addition of ethanol enhances the solubility of the hydrophobic PET segments and reduces aggregation. Meanwhile, the aqueous phase maintains the extension of the hydrophilic PEG segments, ensuring the activity of the phase transition portion. Additionally, the addition of ethanol helps reduce the surface tension of the mixture.

[0047] Preferably, the volume ratio of water to ethanol is 1:1. This setting enhances the solubility of hydrophobic PET segments while ensuring the full extension of PEG segments.

[0048] Optionally, copper salts can be listed as copper chloride. The present invention does not particularly limit the type of copper salt, as long as it can provide copper ions and does not have a negative impact on the crosslinking reaction.

[0049] In some embodiments of the present invention, the mass ratio of the block polymer to the solvent is 1:(9~11). This setting ensures the complete dissolution of the block polymer.

[0050] Optionally, the mass ratio of the block polymer to the solvent can be, for example, 1:9, 1:10 or 1:11, preferably 1:10.

[0051] In some embodiments of the present invention, the preparation process of the copper salt solution of carboxymethyl cellulose is as follows: carboxymethyl cellulose and copper salt are added to water to form a copper salt solution of carboxymethyl cellulose.

[0052] It is understandable that in the process of forming the copper salt solution of carboxymethyl cellulose, the mass ratio of carboxymethyl cellulose to water is 1:20, and the mass ratio of copper salt to water is 1:50. This setting ensures that carboxymethyl cellulose and copper ions form a suitable cross-linking network.

[0053] In some embodiments of the present invention, a dispersant and a thermal conductive agent are also added in step S102. As previously described, the dispersant helps improve the compatibility between the polar carboxymethyl cellulose-copper crosslinked composite and the nonpolar PET segments; the thermal conductive agent enhances thermal conductivity.

[0054] It is understandable that the types of dispersants and thermal conductive agents are the same as those mentioned above, and will not be repeated here.

[0055] In some embodiments of the present invention, the dispersant is sodium dodecyl sulfate (SDS), and the mass ratio of SDS to carboxymethyl cellulose is 1:(7~9), for example, it can be 1:7, 1:8, 1:9, etc., preferably 1:8.

[0056] In some embodiments of the present invention, the thermal conductive agent is graphene oxide (GO), and the mass ratio of GO to carboxymethyl cellulose is 1:(4~6), for example, it can be 1:4, 1:5, 1:6, etc., preferably 1:5.

[0057] In some embodiments of the present invention, the mass ratio of block polymer to CMC is 1:(1.5~2.5), for example, it can be 1:1.5, 1:2, 1:2.5, etc., preferably 1:2.

[0058] More preferably, the mass ratio of block polymer, CMC and copper ions is 1:2:0.2.

[0059] In some embodiments of the present invention, the crosslinking reaction temperature is 25-37°C, and the reaction time is 24-48 hours. Setting the crosslinking reaction temperature in this way helps to form a uniform and stable crosslinked network. If the crosslinking temperature is too high, the coordination process becomes overly active, leading to an uneven crosslinked network structure; if the temperature is too low, the crosslinking rate is too slow, making it difficult to improve production efficiency. Controlling the reaction time within the aforementioned range helps to achieve a gradient crosslinked network. For example, copper ions can preferentially form primary crosslinking sites before the carboxyl groups in CMC, and then further interact with the ester groups in PET and / or the ether bonds in PEG, further refining the pore size of the crosslinked network. This avoids PEG leakage at the phase change temperature and helps maintain the integrity and self-healing properties of the phase change energy storage material during subsequent hot pressing in a laminator.

[0060] Optionally, the temperature of the crosslinking reaction can be, for example, 25°C, 27°C, 30°C, 33°C, 35°C, or 37°C, or a range consisting of any two of the above values.

[0061] Optionally, the crosslinking reaction time can be, for example, 24h, 28h, 32h, 36h, 40h, 44h, or 48h, or a range consisting of any two of the above values.

[0062] In one specific embodiment, the preparation process of the phase change energy storage material can be as follows: A block polymer is dissolved in a 1:1 volume ratio of water to ethanol and dispersed using ultrasound to form a block polymer dispersion. A small amount of copper chloride is dissolved in deionized water, and CMC is added for ultrasonic dispersion. During the dispersion process, small amounts of SDS and GO are gradually added. After thorough mixing, the block polymer dispersion and the CMC-copper crosslinked composite dispersion are mixed and stirred continuously at room temperature for 24-48 hours to obtain the phase change energy storage material.

[0063] As mentioned above, the phase change energy storage material is in the form of a casting liquid.

[0064] In some embodiments of the present invention, prior to step S101, the preparation method further includes: acetylation of hydroxyl-terminated polyethylene terephthalate with acetic anhydride to obtain acetylated polyethylene terephthalate; mixing the acetylated polyethylene terephthalate with polyethylene glycol and subjecting it to transesterification and polycondensation under the action of a Lewis acid catalyst and a nucleophile to obtain a block polymer. This converts the terminal hydroxyl groups of PET to acetoxy groups, preventing premature reaction between the hydroxyl groups and polyethylene glycol during subsequent polycondensation. The addition of the Lewis acid catalyst and nucleophile helps to synergistically improve the polycondensation effect. In the block polymer prepared in this way, the PET segments form a continuous backbone, which helps to encapsulate the PEG segments and reduces the possibility of subsequent leakage of molten PEG.

[0065] In some embodiments of the present invention, the Lewis acid catalyst can be tetrabutyl titanate, and the nucleophile can be triphenyl phosphate. This configuration helps to promote transesterification and polycondensation reactions.

[0066] In some embodiments of the present invention, the temperature of the acetylation reaction is 70~90°C, for example, 70°C, 80°C or 90°C, preferably 80°C.

[0067] In some embodiments of the present invention, the reaction time is 0.5 to 1.5 hours, for example, 0.5 hours, 1 hour or 1.5 hours, preferably 1 hour.

[0068] In some embodiments of the present invention, the molar ratio of acetylated polyethylene terephthalate to polyethylene glycol is (2~4):(1~3), for example, it can be 2:1, 3:1, 3:2, 4:1, 4:3, etc., preferably 3:2. Adjusting the acetylated polyethylene terephthalate to an excess in this manner helps to fully form a through-type rigid backbone, while the PEG segments are confined within the rigid backbone, reducing leakage of flexible segments at the phase transition temperature and improving the self-healing properties of the block polymer.

[0069] It should be noted that the polyethylene glycol of the present invention needs to be dried before use to avoid the negative impact of water introduction on the reaction process.

[0070] Furthermore, the polyethylene glycol was dried under vacuum at 100°C for 24 hours until the moisture content was <0.01%.

[0071] In some embodiments of the present invention, the conditions for the transesterification and polycondensation reactions are as follows: Under a nitrogen atmosphere, the reaction is first carried out at a temperature of 205-215°C, for example, 205°C, 210°C, or 215°C, preferably 210°C, for 0.5-1.5 hours, for example, 0.5 hours, 1 hour, or 1.5 hours, preferably 1 hour. Thus, the transesterification reaction is mainly completed during the atmospheric pressure reaction stage. The vacuum is then evacuated to 0.5-1 kPa, and the temperature is raised to 215-225°C, for example, 215°C, 220°C, or 225°C, preferably 220°C, for 2-4 hours, for example, 2 hours, 3 hours, or 4 hours, preferably 3 hours. Then, nitrogen is introduced to release the vacuum, followed by cooling to obtain a pale yellow block polymer solid. Thus, under vacuum reaction conditions, the polycondensation reaction is promoted.

[0072] In some embodiments of the present invention, the mass ratio of tetrabutyl titanate to the total mass of the reaction system (which can be understood as the sum of the masses of acetylated polyethylene terephthalate, polyethylene glycol, Lewis acid catalyst and nucleophile) can be 1:2000.

[0073] In some embodiments of the present invention, the ratio of the mass of triphenyl phosphate to the total mass of the reaction system (which can be understood as the sum of the masses of acetylated polyethylene terephthalate, polyethylene glycol, Lewis acid catalyst and nucleophile) can be 1:3000.

[0074] In one specific embodiment, polyethylene terephthalate with hydroxyl-terminated groups is mixed with acetic anhydride to modify the hydroxyl groups. The mixture is reacted at 80°C for 1 hour to obtain acetylated polyethylene terephthalate. The acetylated polyethylene terephthalate is then mixed uniformly with polyethylene glycol, and triphenyl phosphate and tetrabutyl titanate are added. Under a nitrogen atmosphere, the mixture is slowly heated to 210°C and reacted for 1 hour. The reaction is then gradually evacuated to a vacuum level below 0.5 kPa and heated to 220°C, continuing the reaction for 3 hours. The reaction is terminated when the intrinsic viscosity of the system is ≥0.5 dL / g. Nitrogen gas is introduced to release the vacuum, and the mixture is discharged while hot. After cooling, a pale yellow solid is obtained, which is the block polymer.

[0075] In some embodiments of the present invention, hydroxyl-terminated polyethylene terephthalate (PET) is prepared by the following steps: terephthalic acid and ethylene glycol undergo a polycondensation reaction under a nitrogen atmosphere in the presence of a Lewis acid catalyst to obtain hydroxyl-terminated PET. It is understood that the Lewis acid catalyst used here can be tetrabutyl titanate. Forming hydroxyl-terminated PET helps to improve the acetylation conversion rate and the polymerization efficiency of the block polymer during subsequent acetylation. The nitrogen atmosphere helps to remove volatile byproducts and promotes the continued progress of the reaction.

[0076] In some embodiments of the present invention, the molar ratio of terephthalic acid to ethylene glycol is 1:(1.5~2.5), for example, it can be 1:1.5, 1:2 or 1:2.5, preferably 1:2. This setting can ensure the complete reaction of carboxyl groups while promoting the smooth progress of polycondensation reaction, resulting in a high conversion rate of terminal hydroxyl groups, thereby promoting the subsequent acetylation conversion rate.

[0077] In some embodiments of the present invention, the temperature of the polycondensation reaction is 230~250°C, for example, 230°C, 240°C or 250°C, preferably 240°C. The reaction time is 1.5~2.5h, for example, 1.5h, 2h or 2.5h, preferably 2h. This setting helps to promote the smooth progress of the polycondensation reaction.

[0078] In some embodiments of the present invention, the molar ratio of terephthalic acid to acetic anhydride is (5~7):1, for example, it can be 5:1, 6:1 or 7:1, preferably 6:1.

[0079] In one specific embodiment, under a nitrogen atmosphere, terephthalic acid, ethylene glycol, and tetrabutyl titanate are added to a flask and mixed evenly. The mixture is reacted at 240°C for 2 hours, and the resulting water is discharged to prepare polyethylene terephthalate with hydroxyl end groups.

[0080] In some embodiments of the present invention, phase change energy storage materials that combine heat storage, heat release and thermal conductivity can be prepared by the following process.

[0081] 1. Condensation polymerization

[0082] In a nitrogen atmosphere, terephthalic acid and ethylene glycol undergo a polycondensation reaction in the presence of a Lewis acid catalyst to prepare polyethylene terephthalate with hydroxyl end groups.

[0083] 2. Acetylation reaction

[0084] Hydroxyl-terminated polyethylene terephthalate (PET) is acetylated with acetic anhydride to obtain acetylated PET. Preparing hydroxyl-terminated PET beforehand helps improve the conversion rate of the acetylation reaction.

[0085] 3. Transesterification and polycondensation reactions

[0086] Acetylated polyethylene terephthalate was mixed with polyethylene glycol and subjected to transesterification and polycondensation reactions in the presence of Lewis acid catalysts and nucleophiles to obtain a block polymer.

[0087] 4. Cross-linking reaction

[0088] A block polymer dispersion was added to a copper salt solution of carboxymethyl cellulose for a crosslinking reaction, yielding a compound of block polymer and carboxymethyl cellulose-copper crosslinked composite, thus obtaining a phase change energy storage material. The crosslinking reaction helps confine the polyethylene glycol segments with latent heat of phase change in the block polymer within the crosslinked network. This reduces the likelihood of the segments transitioning to a liquid state at the phase change temperature during hot pressing in a laminator, thereby improving the self-healing and reprocessing properties of the phase change energy storage material.

[0089] According to another aspect of the present invention, an energy storage laminate is provided, comprising a plurality of parallel metal plates, with a through-cavity between adjacent metal plates, the through-cavity being filled with the aforementioned phase change energy storage material.

[0090] According to embodiments of the present invention, stainless steel plates can be used as the metal plates; the present invention does not impose any particular limitation on this, only requiring good thermal conductivity. The infusion of the phase change energy storage material (casting solution) ensures its flow within adjacent metal plates, which helps to reduce the temperature difference between the outer and inner metal plates through its heat storage, improving the energy storage effect, thereby enhancing the heat transfer effect during the lamination process, improving the uniformity of temperature transfer during lamination, and increasing the production stability during the lamination process, ultimately improving production efficiency.

[0091] Furthermore, the stainless steel sheet can be, for example, a composite high-chromium-nickel austenitic stainless steel sheet. A composite high-chromium-nickel austenitic stainless steel sheet can be understood as a layered functional material formed by combining high-chromium-nickel austenitic stainless steel with other materials, such as carbon steel or low-alloy steel. The working surface can be high-chromium-nickel austenitic stainless steel, possessing properties such as corrosion resistance and high-temperature resistance. The base layer can be carbon steel or low-alloy steel, which helps provide mechanical strength and reduce costs.

[0092] It is understandable that multiple metal plates can be, for example, as follows: Figure 2 The two metal plates shown are opposite each other.

[0093] In some embodiments of the present invention Figure 2A schematic diagram of the structure of an energy storage laminate according to an embodiment of the present invention is shown. Figure 2 As shown, the metal plate is rectangular, with a length of 300-350 mm and a width of 200-250 mm. The through-cavity is divided into multiple grids, creating a three-dimensional structure that helps ensure the compressive strength of the energy storage laminate. Sealable openings are located on the grid walls along the width of the through-cavity. These sealable openings can be triangular, rhomboid, rectangular, or square, but are preferably triangular to facilitate the flow of the phase change energy storage material. It is understood that the phase change energy storage material is injected into the through-cavity through the sealable openings. After injection, the sealable openings can be sealed with high-temperature resistant tape.

[0094] Optionally, the length of the metal plate can be 300mm, 320mm, 340mm or 350mm, preferably 320mm; the width of the metal plate can be 200mm, 220mm, 240mm or 250mm, preferably 220mm.

[0095] Optionally, the size of the grid can be (5~6) mm × (4~5) mm, preferably 5.3 mm × 4.95 mm, and the wall thickness of the cut grid can be 0.5 mm.

[0096] Optionally, the sealable opening can be a triangle with a height of 0.5 mm and a base of 1 mm.

[0097] According to another aspect of the present invention, a method for preparing an energy storage laminate is provided, comprising: injecting a phase change energy storage material into a through-hole cavity of a laminate mold through a sealable opening to obtain a laminate mold filled with the phase change energy storage material; curing the phase change energy storage material by vacuum drying; and sealing the sealable opening with high-temperature resistant tape to obtain an energy storage laminate.

[0098] According to an embodiment of the present invention, an energy storage laminate with phase change energy storage material is prepared through the above process, which ensures the stability and uniformity of heat transfer, reduces the temperature difference between the inner and outer metal plates, and improves the lamination effect.

[0099] In some embodiments of the present invention, the vacuum drying conditions are: a drying temperature of 30~37°C and a drying time of 24~48 hours. This configuration helps to fully solidify the phase change energy storage material, thereby providing better heat storage and heat release effects.

[0100] The present invention will be further illustrated below through embodiments and their results. In the following detailed description, numerous specific details are set forth for ease of explanation to provide a comprehensive understanding of the embodiments of the present invention. However, it will be apparent that one or more embodiments may be practiced without these specific details. Moreover, the details in the following embodiments can be arbitrarily combined to form other feasible embodiments without conflict.

[0101] It should be noted that the specific embodiments described below are merely illustrative examples, and the scope of protection of the present invention is not limited thereto. The raw materials used in the following embodiments are commercially available or prepared by recognized processing methods.

[0102] Example 1

[0103] Preparation process of solid-solid block polymer (PET-b-PEG) with energy cycling function:

[0104] First, during the feeding stage, terephthalic acid (60 mmol, 9.96 g) and ethylene glycol (120 mmol, 7.44 g) were added to a four-necked flask and mixed thoroughly. Then, tetrabutyl titanate (0.05 wt%, 0.008 g) was added as a catalyst. After thorough mixing, the mixture was heated to 240 °C under nitrogen protection and reacted for 2 hours. During the reaction, water (theoretical amount: 60 mmol × 2 = 120 mmol, 2.16 g) was continuously discharged. When the amount of water discharged reached 90% of the theoretical amount, esterification was complete, yielding oligomeric polyethylene terephthalate (PET-OH) with hydroxyl-terminated ends.

[0105] To protect the end groups, acetic anhydride (10 mmol, 1.02 g) was added, and an acetylation reaction was carried out at 80 °C for 1 h to convert the terminal -OH group to -OCOCH3, preventing premature reaction with polyethylene glycol in subsequent steps.

[0106] The purchased polyethylene glycol (40 mmol, 240 g) with a molecular weight of 6000 was vacuum dried at 100°C for 24 h to remove moisture.

[0107] Acetylated polyethylene terephthalate (PET-OCOCH3) (60 mmol) and polyethylene glycol (PEG) (40 mmol) were first added to the reactor for premixing, followed by the addition of tetrabutyl titanate (0.03 wt%, 0.07 g). Under nitrogen protection, the temperature was raised to 220 °C and reacted for 1 h to initially couple the end groups of PEG with those of PET. The pressure was gradually reduced to <0.5 kPa, and the reaction continued for 3 h to promote chain growth. When the melt viscosity increased significantly (increased stirring resistance), heating was stopped, the vacuum was released by purging with nitrogen, and the product was discharged to obtain PET-b-PEG (182.6 g, yield 72%), the specific structural formula of which is as follows:

[0108] .

[0109] The structure of the prepared PET-b-PEG was confirmed: The prepared PET-b-PEG was dried in a vacuum oven at 37℃ for 48 h to obtain the dried block polymer solid. 10 mg of the block polymer solid was dissolved in 0.6 mL of deuterated chloroform (CDCl3). After complete dissolution, it was transferred to an NMR tube for NMR testing. Figure 3 The 1H NMR spectrum of the block polymer of Example 1 of the present invention is shown. Figure 3 It can be seen that there is an aromatic ring with PET chain segment at 7.8 ppm and a methylene group with PEG at 3.7 ppm. Further determination of its molecular structure and actual block ratio, x=48, y=96, n=136.

[0110] The phase transition temperature of the block copolymer was tested, and the melting point was tested using a precision micro melting point tester. At about 95°C, part of the polymer melted, which is called the PEG leakage process. Therefore, it is necessary to prepare a stable solid-solid phase change energy storage material.

[0111] Preparation process of phase change energy storage materials

[0112] Dissolve PET-b-PEG at 10wt% (10g) in a mixed solvent (100g) of water and ethanol at a volume ratio of 1:1, and disperse using ultrasound for at least 30 minutes.

[0113] 2g of copper chloride was dissolved in 100g of deionized water to a concentration of 2wt%, and 5wt% of water (5g of carboxymethyl cellulose) was added for ultrasonic dispersion for at least 30min. During the dispersion process, 0.63g of sodium dodecyl sulfate and 1g of graphene oxide were gradually added and thoroughly mixed. The two dispersions were then mixed in a volume ratio of 1:1 and stirred continuously. The cross-linking reaction was carried out at 25℃ for 48h to obtain the phase change energy storage material casting solution.

[0114] The performance of the prepared phase change energy storage material was tested. The phase change energy storage material casting solution was dried in a vacuum oven at 37℃ for 48 hours to obtain the dried phase change energy storage material. 20 mg of the dried phase change energy storage material was placed in an aluminum box and compacted, with an empty aluminum box used as a control. The temperature was increased to 300℃ from an initial temperature of 20℃ at a rate of 10℃ / min, with nitrogen as a protective gas. The phase change temperature of the dried phase change energy storage material was found to be 110–120℃, and the latent heat of phase change was 100–130 J / g.

[0115] The dried phase change energy storage material was hot-pressed into sheets at 120℃ (pressure of 10MPa, held for 5 minutes) to avoid air bubbles, ultimately pressing into circular sheets with a diameter of approximately 30mm and a thickness of 2mm. These sheets were then annealed at 80℃ for 2 hours to eliminate internal stress. After calibrating and zeroing the thermal conductivity meter, the discs were tested at temperatures of 20℃ and 70℃, respectively. The tests were repeated three times, yielding thermal conductivity values ​​of 3~4 W / (m·K) for each sheet.

[0116] Preparation process of energy storage laminate

[0117] The obtained phase change energy storage material casting liquid was injected into the laminate mold through a sealable opening and dried in a vacuum oven at 37°C for 24-48 hours to obtain an energy storage laminate with energy recycling function. The sealable opening was sealed with high-temperature resistant tape.

[0118] Application Example 1

[0119] The first layer of the 11-layer laminate is an energy storage laminate.

[0120] Comparative Application Example 1

[0121] The first layer of the 11-layer laminate is made of ordinary steel plate, which has a tight internal structure.

[0122] The hot-pressing performance was tested corresponding to Application Example 1 and Comparative Application Example 1. During the lamination process at 130℃, the temperature difference between layers 1-2 and 5-6 was calculated after 5 minutes of measurement using a probe thermometer. The temperature difference in Application Example 1 was 15.1℃, while the temperature difference in Comparative Application Example 1 was 31.2℃. The comparison between Application Example 1 and Comparative Application Example 1 shows that the energy storage phase change material plays a protective role in the energy transfer process of lamination. Furthermore, during the use of Application Example 1, the intercalated phase change energy storage material remains solid and can be recycled.

[0123] When the 11-layer laminate from Application Example 1 was used in the card manufacturing process, it was found that the resulting card body was more regular, had a higher lamination effect, and significantly improved lamination efficiency.

[0124] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A phase change energy storage material, characterized in that, The phase change energy storage material includes: Combinations of block polymers and carboxymethyl cellulose-copper crosslinked complexes; The block polymer has the structure shown in formula (I): Formula (I); Where x is 40~60, y is 90~105, and n is 130~150; The carboxymethyl cellulose-copper crosslinked complex was prepared by the following method: The block polymer is dissolved in a solvent to form a block polymer dispersion; The block polymer dispersion was added to a copper salt solution of carboxymethyl cellulose to carry out a crosslinking reaction, thereby obtaining a compound of block polymer and carboxymethyl cellulose-copper crosslinking complex.

2. The phase change energy storage material according to claim 1, characterized in that, The phase change energy storage material also includes: a dispersant and a thermally conductive agent; The dispersant includes at least one of sodium dodecyl sulfate, dodecyl acetic acid, and polyoxyethylene lauryl ether; the thermal conductive agent includes at least one of graphene, graphene oxide, boron nitride, and aluminum nitride.

3. The phase change energy storage material according to claim 2, characterized in that, The phase change energy storage material is in the form of a casting liquid.

4. A method for preparing a phase change energy storage material as described in any one of claims 1 to 3, characterized in that, The preparation method includes: The block polymer is dissolved in a solvent to form a block polymer dispersion; The block polymer dispersion is added to a copper salt solution of carboxymethyl cellulose to carry out a crosslinking reaction, thereby obtaining a compound of block polymer and carboxymethyl cellulose-copper crosslinked complex, and then obtaining the phase change energy storage material. The carboxymethyl cellulose has the structure shown in formula (II): In equation (II), the value of m ranges from 240 to 260; The solvent includes a mixture of water and ethanol.

5. The preparation method according to claim 4, characterized in that, When the block polymer is added to a copper salt solution of carboxymethyl cellulose, a dispersant and a thermal conductive agent are also added. Wherein, the mass ratio of the dispersant to the carboxymethyl cellulose is 1:(7~9); the mass ratio of the thermal conductive agent to the carboxymethyl cellulose is 1:(4~6); the mass ratio of the block polymer to the carboxymethyl cellulose is 1:(1.5~2.5); and / or; The crosslinking reaction is carried out at a temperature of 25-37°C for 24-48 hours.

6. The preparation method according to claim 4, characterized in that, Before dissolving the block polymer in a solvent to form a block polymer dispersion, the preparation method further includes: Polyethylene terephthalate with hydroxyl-terminated groups was acetylated with acetic anhydride to obtain acetylated polyethylene terephthalate. The block polymer was obtained by mixing acetylated polyethylene terephthalate with polyethylene glycol and carrying out transesterification and polycondensation reactions in the presence of a Lewis acid catalyst and a nucleophile.

7. The preparation method according to claim 6, characterized in that, The Lewis acid catalyst is tetrabutyl titanate, and the nucleophile is triphenyl phosphate; The acetylation reaction is carried out at a temperature of 70~90℃ for a reaction time of 0.5~1.5h. The molar ratio of the acetylated polyethylene terephthalate to the polyethylene glycol is (2~4):(1~3). The conditions for the transesterification and polycondensation reactions are as follows: Under a nitrogen atmosphere, the reaction is first carried out at a temperature of 205~215℃ for 0.5~1.5h, then evacuated to 0.5~1kPa, and then heated to 215~225℃ for 2~4h.

8. The preparation method according to claim 6, characterized in that, The polyethylene terephthalate with hydroxyl end groups is prepared by the following steps: In a nitrogen atmosphere, terephthalic acid and ethylene glycol are subjected to a polycondensation reaction in the presence of a Lewis acid catalyst to prepare polyethylene terephthalate with hydroxyl end groups. Wherein, the molar ratio of terephthalic acid to ethylene glycol is 1:(1.5~2.5). The polycondensation reaction is carried out at a temperature of 230~250℃ for 1.5~2.5h.

9. An energy storage laminate, characterized in that, It includes multiple metal plates arranged in parallel, with a through-cavity between adjacent metal plates, and the through-cavity is filled with the phase change energy storage material according to any one of claims 1 to 3.

10. The energy storage laminate according to claim 9, characterized in that, The metal plate is rectangular, with a length of 300-350 mm and a width of 200-250 mm. The through-type inner cavity is divided into multiple grids, and the grid walls in the width direction of the through-type inner cavity have sealable openings.

Images