Adhesive, method for producing the same and use thereof

Abstract

The application discloses an adhesive, a preparation method and application thereof. The adhesive comprises a main agent and a curing agent. The main agent comprises polyester polyol. Raw materials for preparing the polyester polyol comprise aromatic dibasic acid, aliphatic dibasic acid, aliphatic dihydric alcohol, trifunctional epoxy resin, a catalyst and an antioxidant. The curing agent comprises polyisocyanate. Thus, the adhesive with excellent impact deep performance, high bonding strength, excellent boiling water resistance and excellent heat resistance can be obtained.

Description

Technical Field

[0001] This invention belongs to the field of batteries, specifically relating to an adhesive, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries are widely used in the 3C (computer, communication, and consumer electronics) and home appliance industries. Aluminum-plastic film, as a crucial material for encapsulating soft-pack batteries, plays a vital role in protecting the battery's contents. The aluminum-plastic film generally consists of three layers from the outside in: a protective layer, a barrier layer, and a heat-sealing layer. Currently, solvent-based adhesives are mostly used to bond the various layers of the aluminum-plastic film together. In later applications, the sheet-like aluminum-plastic film is deepened and heat-sealed to obtain a casing with a certain internal volume. However, current adhesives still have many problems.

[0003] Therefore, current adhesives still need improvement. Summary of the Invention

[0004] This invention is based on the inventor's discovery of the following problems:

[0005] The inventors discovered that during the deep-cutting process, aluminum-plastic film breaks due to insufficient adhesive bonding strength, breakage, or insufficient elongation. During the heat-sealing process after deep-cutting, the heat-sealing layer and the barrier layer in the aluminum-plastic film may also delaminate due to poor high-temperature adhesion of the adhesive. In addition, in a humid and hot environment, the adhesive will hydrolyze, resulting in adhesive bonding failure.

[0006] The present invention aims to at least alleviate or resolve at least one of the aforementioned problems to some extent.

[0007] In a first aspect, the present invention provides an adhesive. According to an embodiment of the invention, the adhesive comprises a main agent and a curing agent. The main agent comprises a polyester polyol, and the raw materials for preparing the polyester polyol include aromatic diacids, aliphatic diacids, aliphatic diols, trifunctional epoxy resins, catalysts, and antioxidants. The curing agent comprises polyisocyanate. Thus, by adding aromatic diacids, aliphatic diacids, aliphatic diols, trifunctional epoxy resins, catalysts, and antioxidants to the raw materials for preparing the polyester polyol, the trifunctional epoxy resin can increase the crosslinking degree of the polyester polyol and reduce the contact between ester bonds and water, thereby improving the adhesive strength and hydrolysis resistance of the adhesive. The isocyanate groups in the curing agent undergo a crosslinking reaction with the hydroxyl groups in the main agent polyester polyol to form a highly crosslinked network structure containing aliphatic long carbon chains and aromatic rings, thereby improving the flexibility and heat resistance of the adhesive, which is beneficial for achieving deeper drawing depths in the aluminum-plastic film during the deep-drawing process.

[0008] According to embodiments of the present invention, the raw materials for preparing the polyester polyol include: 40-45 parts by weight of an aromatic diacid; 14-16 parts by weight of an aliphatic diacid; 40-45 parts by weight of an aliphatic diol; 0.1-0.3 parts by weight of a trifunctional epoxy resin; 0.015-0.025 parts by weight of a catalyst; and 0.05-0.15 parts by weight of an antioxidant. Thus, an adhesive with excellent deep-draw resistance, high bonding strength, excellent hydrolysis resistance, and excellent heat resistance can be obtained.

[0009] According to embodiments of the present invention, the trifunctional epoxy resin includes o-cresylaldehyde epoxy resins. This improves the crosslinking degree of the polyester polyol and reduces the contact between the ester bonds and water.

[0010] According to embodiments of the present invention, the aromatic dicarboxylic acid includes at least one of isophthalic acid, phthalic acid, and terephthalic acid. This enhances the flexibility of the polyester polyol molecular structure, thereby improving the adhesive's bonding performance and high-temperature resistance, and ultimately ensuring that the aluminum-plastic film using this adhesive exhibits good water resistance and deep-drawing performance.

[0011] According to embodiments of the present invention, the aliphatic diol comprises C2-C6 aliphatic diols, wherein the C2-C6 aliphatic diols include at least one of straight-chain aliphatic diols and branched aliphatic diols. Preferably, the straight-chain aliphatic diols include at least one of ethylene glycol, 1,3-propanediol, 1,4-butanediol, and 1,6-hexanediol, and the branched aliphatic diols include at least one of 3-methyl-1,5-pentanediol, 2-methyl-1,3-propanediol, and neopentanediol. This enhances the flexibility of the polyester polyol molecular structure.

[0012] According to embodiments of the present invention, the aliphatic dicarboxylic acid includes C6-C10 aliphatic dicarboxylic acids, preferably, the aliphatic dicarboxylic acid includes at least one of adipic acid, azelaic acid, and sebacic acid. This enhances the flexibility of the polyester polyol molecular structure, thereby improving the heat resistance and hardness of the adhesive, which is beneficial for the adhesion between the protective layer or heat-sealing layer and the aluminum foil layer in the aluminum-plastic film, thus improving the performance of the aluminum-plastic film.

[0013] According to embodiments of the present invention, the catalyst comprises at least one of antimony acetate, antimony oxide, zinc oxalate, and tetrabutyl titanate. Thus, the catalyst can further increase the degree of polymerization of the polyester polyol, obtaining a polyester polyol that meets the application requirements (e.g., reaching a certain molecular weight or hydroxyl value).

[0014] According to an embodiment of the present invention, the antioxidant includes at least one of antioxidant 1010, antioxidant 168, and butylphenol.

[0015] According to embodiments of the present invention, the molecular weight of the polyester polyol is 30,000-50,000. This results in a polyester polyol with high cohesive strength, thereby improving the toughness and heat resistance of the adhesive.

[0016] According to embodiments of the present invention, the hydroxyl value of the polyester polyol is 15 (mgKOH / g)-30 (mgKOH / g). Therefore, a polyester polyol with a high degree of crosslinking can be obtained, thereby improving the bonding strength of the adhesive.

[0017] According to an embodiment of the present invention, the alkyd molar ratio of the polyester polyol is (1.15-1.35):1. This results in an adhesive with excellent deep-dip resistance, high bond strength, excellent hydrolysis resistance, and excellent heat resistance.

[0018] According to embodiments of the present invention, the total equivalent [NCO] / ([OH]+[COOH]) of the isocyanate groups in the polyisocyanate and the hydroxyl and carboxyl groups in the polyester polyol is 15-25. This allows for sufficient cross-linking of the active functional groups in the main agent and curing agent, improving the flexibility and heat resistance of the adhesive.

[0019] In a second aspect of the invention, a method for preparing an adhesive is provided. According to an embodiment of the invention, the method comprises: (1) heating an aromatic diacid, an aliphatic diacid, and an aliphatic diol under a protective atmosphere to perform an esterification reaction; (2) simultaneously with heating, mixing the material obtained from the esterification reaction with a catalyst and an antioxidant to perform a first polycondensation reaction, and then evacuating the vacuum; (3) mixing the material obtained in step (2) with a trifunctional epoxy resin under a protective atmosphere to perform a second polycondensation reaction to obtain a polyester polyol; and (4) mixing the polyester polyol, a polyisocyanate, and a solvent to obtain the adhesive. Thus, this method can yield an adhesive with excellent impact resistance, high bonding strength, excellent hydrolysis resistance, and excellent heat resistance.

[0020] According to an embodiment of the present invention, in step (1), the temperature of the esterification reaction is 210°C-230°C. This improves the reaction efficiency of the esterification reaction.

[0021] According to an embodiment of the present invention, in step (2), the temperature of the first polycondensation reaction is 240°C-260°C. This improves the reaction efficiency of the first polycondensation reaction.

[0022] In a third aspect, the present invention provides an aluminum-plastic film comprising the aforementioned adhesive or an adhesive prepared by the aforementioned method. Thus, the aluminum-plastic film possesses all the features and advantages of the aforementioned adhesive, which will not be elaborated further here.

[0023] In a fourth aspect, the present invention provides a secondary battery comprising the aforementioned aluminum-plastic film, thereby possessing all the features and advantages of the aforementioned aluminum-plastic film, which will not be repeated here. Attached Figure Description

[0024] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0025] Figure 1 This is a process flow diagram for preparing an adhesive according to an embodiment of the present invention. Detailed Implementation

[0026] The embodiments of this application are described in detail below, and are only used to explain this application, and should not be construed as limiting this application.

[0027] In a first aspect, the present invention provides an adhesive comprising a main agent and a curing agent, wherein the main agent comprises a polyester polyol, and the raw materials for preparing the polyester polyol include aromatic diacids, aliphatic diacids, aliphatic diols, trifunctional epoxy resins, catalysts, and antioxidants; the curing agent comprises polyisocyanate. Thus, an adhesive with excellent deep-dip resistance, high bond strength, excellent water resistance, and excellent heat resistance can be obtained.

[0028] To facilitate understanding, the principle behind the aforementioned beneficial effects of the adhesive in this application will be explained below:

[0029] The inventors discovered that in the process of preparing polyester polyols, by mixing aromatic diacids, aliphatic diacids, aliphatic diols, trifunctional epoxy resins, catalysts, and antioxidants, the trifunctional epoxy resins can increase the molecular arrangement space of the polyester polyols, thereby increasing the crosslinking density of the polyester polyols and reducing the contact between ester bonds and water, thus improving the adhesive strength and hydrolysis resistance of the adhesive.

[0030] Furthermore, the inventors discovered that because the polyester polyol contains aromatic rings, it can improve the heat resistance of the adhesive. In addition, the isocyanate groups in the curing agent undergo a cross-linking reaction with the hydroxyl groups in the main polyester polyol to form an adhesive with a highly cross-linked network structure containing aliphatic long carbon chains and aromatic rings. This adhesive has excellent heat resistance and flexibility. The aluminum-plastic film prepared from the aforementioned adhesive can achieve a deeper drawing depth during the deep-drawing process. Therefore, the adhesive of this invention has excellent deep-drawing resistance, high bonding strength, excellent water resistance, and excellent heat resistance.

[0031] According to some embodiments of the present invention, the raw materials for preparing polyester polyols are not particularly limited. For example, the raw materials for preparing polyester polyols include 40-45 parts by weight of aromatic dicarboxylic acid; 14-16 parts by weight of aliphatic dicarboxylic acid; 40-45 parts by weight of aliphatic diol; 0.1-0.3 parts by weight of trifunctional epoxy resin; 0.015-0.025 parts by weight of catalyst; and 0.05-0.15 parts by weight of antioxidant. Specifically, when the weight percentage of trifunctional epoxy resin is less than 0.1%, the content of trifunctional epoxy resin in the polyester polyol raw material is too low, and it does not play a significant role in improving the crosslinking degree of the polyester polyol. When the weight percentage of trifunctional epoxy resin is greater than 0.3%, the content of trifunctional epoxy resin in the polyester polyol raw material is too high, which will cause excessive crosslinking of the polyester polyol, resulting in a higher viscosity of the system, thereby reducing the toughness of the adhesive and thus reducing the depth-of-dip performance of the aluminum-plastic film. If there is too much aromatic dicarboxylic acid, it will lead to excessive crosslinking of the polyester polyol. Polyester polyols contain free acid radicals, which reduces the adhesive's depth-of-draw and hydrolysis resistance. Excessive aliphatic diacids reduce the adhesive's high-temperature resistance. Excessive aliphatic diols reduce the adhesive's bond strength. Excessive catalysts result in excessively high viscosity of the obtained polyester polyol, causing the coating solution to become cloudy during application, which is detrimental to the adhesion between the protective layer or heat-sealing layer and the aluminum foil layer. Excessive antioxidants lead to excessively high polymerization of the obtained polyester polyol, further reducing the adhesive's bond strength. Therefore, by controlling the amount of each raw material in the polyester polyol, a polyester polyol with hydroxyl value and molecular weight that meet the requirements for subsequent use can be obtained.

[0032] According to some embodiments of the present invention, the type of trifunctional epoxy resin is not particularly limited. For example, trifunctional epoxy resins include o-cresphenolic epoxy resins. When the trifunctional epoxy resin is an o-cresphenolic epoxy resin, it can not only improve the crosslinking degree of the polyester polyol, thereby improving the adhesive strength, but also the added functional epoxy resin will not introduce side reactions, that is, it will not have an adverse effect on the adhesive strength.

[0033] According to some embodiments of the present invention, the type of aliphatic dicarboxylic acid is not particularly limited. For example, the aliphatic dicarboxylic acid may include C6-C10 aliphatic dicarboxylic acids. Preferably, the aliphatic dicarboxylic acid may include at least one of adipic acid, azelaic acid, and sebacic acid. When the aliphatic dicarboxylic acid includes at least one of the aforementioned C6-C10 aliphatic dicarboxylic acids, the aliphatic dicarboxylic acid is introduced during the preparation of the polyester polyol. Through the linear long carbon chain in the aliphatic dicarboxylic acid, the flexibility of the polyester polyol molecular structure is enhanced, thereby improving the heat resistance and hardness of the adhesive. This is beneficial to the adhesion between the protective layer or heat-sealing layer and the aluminum foil layer in the aluminum-plastic film, and improves the performance of the aluminum-plastic film.

[0034] According to some embodiments of the present invention, the type of aromatic dicarboxylic acid is not particularly limited. For example, the aromatic dicarboxylic acid may include at least one of isophthalic acid, phthalic acid, and terephthalic acid. Preferably, the aromatic dicarboxylic acid may be isophthalic acid and terephthalic acid, or isophthalic acid alone may be used. When the aromatic dicarboxylic acid includes at least one of isophthalic acid, phthalic acid, and terephthalic acid, introducing the aromatic dicarboxylic acid during the preparation of the polyester polyol can enhance the flexibility of the polyester polyol molecular structure, thereby improving the adhesive properties and high-temperature resistance of the adhesive, and thus ensuring that the aluminum-plastic film using the adhesive has good water resistance and deep-drawing performance.

[0035] According to some embodiments of the present invention, when the aromatic dicarboxylic acid includes isophthalic acid and terephthalic acid, the molar ratio of terephthalic acid to isophthalic acid is 1:(5-10). Preferably, the molar ratio of terephthalic acid to isophthalic acid is 1:(6-9). When the molar ratio of terephthalic acid to isophthalic acid is greater than 1:5, due to the low activity of terephthalic acid, its excessive content will cause incomplete polymerization reaction, resulting in the product containing a certain amount of unreacted terephthalic acid and free acid radical ions, which has a significant impact on the cohesive strength and hydrolysis resistance of the polyester polyol. When the content ratio of terephthalic acid to isophthalic acid is less than 1:10, the incomplete structural reaction and the reduction in the overall crystallinity of the structure will lead to the strength of the adhesive layer. At the same time, the free acid radical ions in the product will cause the hydrolysis of the product to be aggravated, thereby significantly reducing the depth of drawing and hydrolysis performance. When the molar ratio of terephthalic acid to isophthalic acid is within the aforementioned range, the polyester polyol with better properties is obtained.

[0036] According to some embodiments of the present invention, the type of aliphatic diol is not particularly limited. For example, the aliphatic diol may include C2-C6 aliphatic diols. Specifically, the C2-C6 aliphatic diols include at least one of straight-chain aliphatic diols and branched aliphatic diols. Preferably, the straight-chain aliphatic diols include at least one of ethylene glycol, 1,3-propanediol, 1,4-butanediol, and 1,6-hexanediol, and the branched aliphatic diols include at least one of 3-methyl-1,5-pentanediol, 2-methyl-1,3-propanediol, and neopentanediol. Therefore, when the aliphatic diol includes the aforementioned C2-C6 aliphatic diols, the obtained polyester polyol has good heat resistance and flexibility. When the number of carbon atoms in the aliphatic diol is greater than 6, the heat resistance of the polyester polyol prepared thereby becomes relatively poor, and delamination may occur during the heat sealing process of aluminum-plastic film. Furthermore, when the branched aliphatic diol is 3-methyl-1,5-pentanediol, the methyl groups on the branches of 3-methyl-1,5-pentanediol can regulate the interaction forces between polyester polyol molecular chains, making the polyester polyol molecular chains easier to move under external force, thereby enhancing the flexibility of the polyester polyol molecular structure and thus improving the flexibility of the adhesive.

[0037] According to some embodiments of the present invention, the type of catalyst is not particularly limited; for example, the catalyst may include at least one of antimony acetate, antimony oxide, zinc oxalate, and tetrabutyl titanate. Thus, the aforementioned catalyst can increase the reaction rate for the preparation of polyester polyols.

[0038] According to some embodiments of the present invention, the type of antioxidant is not particularly limited. For example, the antioxidant may include at least one of antioxidant 1010, antioxidant 168, and butylphenol. Thus, the aforementioned antioxidants can effectively improve the antioxidant properties of polyester polyols.

[0039] According to some embodiments of the present invention, the adhesive further includes a solvent intended to fully dissolve the polyester polyol or curing agent. Specifically, the solvent may include at least one of ethyl acetate, butyl acetate, acetone, and butanone.

[0040] According to some embodiments of the present invention, in order to ensure good performance of the adhesive, the molecular weight of the polyester polyol is 30,000-50,000. When the molecular weight of the polyester polyol is less than 30,000, the cohesive force of the polyester polyol is reduced due to its low molecular weight, resulting in a relatively poor high-temperature resistance of the adhesive. Consequently, the high-temperature resistance of the aluminum-plastic film obtained also deteriorates, affecting the adhesion strength between the protective layer or heat-sealing layer and the aluminum foil layer during the heat-sealing process. When the molecular weight of the polyester polyol is greater than 50,000, the viscosity of the polyester polyol is too high, and the adhesive obtained from this polyester polyol is prone to cloudiness during coating, which is not conducive to the adhesion between the protective layer or heat-sealing layer and the aluminum foil layer. Therefore, when the molecular weight of the polyester polyol is within the aforementioned range, the obtained polyester polyol has better high-temperature resistance and adhesion strength, thereby giving the adhesive better high-temperature resistance and adhesion strength.

[0041] According to some embodiments of the present invention, the hydroxyl value of the polyester polyol is not particularly limited. For example, the hydroxyl value of the polyester polyol can be between 15 (mgKOH / g) and 30 (mgKOH / g). When the hydroxyl value of the polyester polyol is less than 15 (mgKOH / g), the crosslinking density of the polyester polyol is insufficient, thereby reducing the heat resistance of the adhesive. When the hydroxyl value of the polyester polyol is greater than 30 (mgKOH / g), the polyester polyol is over-crosslinked, thereby reducing the toughness of the adhesive and thus reducing the depth-of-drilling resistance of the aluminum-plastic film. Therefore, when the hydroxyl value of the polyester polyol is within the aforementioned range, the degree of crosslinking of the polyester polyol is moderate, thereby improving the adhesive performance of the adhesive.

[0042] According to some embodiments of the present invention, the acid-alcohol ratio of the polyester polyol is not particularly limited. For example, the acid-alcohol ratio of the polyester polyol can be (1.15-1.35):1, preferably 1.25:1. Specifically, when the acid-alcohol ratio of the polyester polyol is within the aforementioned range, the high-temperature resistance of the adhesive can be improved. When the acid-alcohol ratio is less than 1.15:1, the content of diol in the main agent is too high, and the alcohol is easily converted into gas during heating, resulting in a decrease in the alcohol content and an increase in the relative acid content in the system. This leads to an excessively high acid value in the system, causing the adhesive to have poor hydrolysis resistance. As a result, the aluminum-plastic film obtained is prone to delamination during boiling. When the acid-alcohol ratio is greater than 1.35:1, the content of dicarboxylic acid in the main agent is too high, resulting in an excessively high acid value in the system, which in turn causes the adhesive to have poor hydrolysis resistance. As a result, the aluminum-plastic film obtained is prone to delamination during boiling.

[0043] According to some embodiments of the present invention, the total equivalent [NCO] / ([OH]+[COOH]) of the isocyanate groups in the curing agent polyisocyanate and the hydroxyl and carboxyl groups in the polyester polyol is 15-25. This allows for sufficient cross-linking of the active functional groups in the main agent and the curing agent, further improving the cohesive strength and heat resistance of the adhesive.

[0044] In a second aspect, the present invention provides a method for preparing an adhesive. According to some embodiments of the present invention, the method includes:

[0045] S100: Mix aromatic dicarboxylic acid, aliphatic dicarboxylic acid, and aliphatic diol and heat.

[0046] According to some embodiments of the present invention, in this step, aromatic diacids, aliphatic diacids, and aliphatic diols are added to a reactor, and a protective gas is introduced into the reactor to 150 kPa to purge the air from the reactor. The reactor is then heated to the esterification reaction temperature at a heating rate of 20°C / h-50°C / h to carry out the esterification reaction. Specifically, aromatic diacids, aliphatic diacids, and aliphatic diols are added to the reactor. To prevent air from participating in the reaction, a protective gas can be introduced into the reactor. It should be noted that the order in which the protective gas is introduced is not particularly limited, and the protective gas can also be introduced before the feed. According to some other embodiments of the present invention, the protective gas can be selected from at least one of nitrogen and inert gases. Thus, aromatic diacids, aliphatic diacids, and aliphatic diols are mixed to undergo an esterification reaction to form esters with different carbon chain lengths and multiple functionalities.

[0047] According to some embodiments of the present invention, the temperature of the esterification reaction is not particularly limited; for example, the temperature of the esterification reaction can be 210°C-230°C, thereby allowing the aromatic diacids, aliphatic diacids, and aliphatic diols in the reactor to undergo a complete esterification reaction. According to some other embodiments of the present invention, in order to make the reaction proceed more rapidly and thoroughly, stirring can be started when the temperature rises to 100°C-130°C to ensure thorough mixing and contact of the reactants, thereby improving the reaction efficiency.

[0048] According to some embodiments of the present invention, the reaction time of the esterification reaction is not particularly limited. For example, the reaction time of the esterification reaction can be 3h-5h, thereby promoting a more complete esterification reaction.

[0049] S200: The material obtained from the esterification reaction is mixed with the catalyst and antioxidant.

[0050] According to some embodiments of the present invention, in this step, a catalyst and an antioxidant are added to the reactor, and the pressure is slowly reduced to raise the reactor temperature to the temperature of the first polycondensation reaction. A vacuum is then applied to carry out the first polycondensation reaction. Specifically, after the esterification reaction is completed and a certain amount of water is distilled off, a catalyst and an antioxidant are added to the reactor, and the pressure is slowly reduced to heat the reactor to the reaction temperature of the first polycondensation reaction. The vacuum pump is then turned on to carry out the first polycondensation reaction. Thus, the catalyst is used to increase the rate of the first polycondensation reaction, thereby forming a disordered polyester polyol with a multidimensional network structure.

[0051] According to some embodiments of the present invention, the reaction temperature of the first polycondensation reaction can be 240-260°C, thereby allowing the substances in the reactor to undergo the first polycondensation reaction more fully. When the reaction temperature of the first polycondensation reaction is less than 240°C, the acid value of the polyester polyol will be too high, which will affect the water boiling performance of the adhesive. When the reaction temperature of the first polycondensation reaction is greater than 260°C, the molecular weight of the obtained polyester polyol is large, the system becomes viscous, and the reaction is difficult to proceed.

[0052] According to some embodiments of the present invention, the vacuum degree of the reactor after evacuation can be 30Pa-300Pa. Therefore, when the vacuum degree is 30Pa-300Pa, the pressure is close to weightlessness, which can improve the reaction controllability of the polyester polyol preparation process and obtain a uniform molecular weight distribution of the polyester polyol. When the vacuum degree is greater than 300Pa, the vacuum degree is too high, which will accelerate the reaction rate of polyester polyol preparation, and thus lead to an uneven molecular weight distribution of polyester polyol. When the vacuum degree is less than 30Pa, the vacuum degree is too low, and air will enter the reactor, which will lead to side reactions in the reactor to generate byproducts such as acetaldehyde, affecting the purity and properties of the final product.

[0053] According to some embodiments of the present invention, the first polycondensation reaction can be carried out for 2-4 hours. Therefore, when the first polycondensation reaction is carried out for 2-4 hours, the reaction can proceed more completely.

[0054] S300: Mix the material obtained in step S200 with trifunctional epoxy resin.

[0055] According to some specific embodiments of the present invention, in this step, a protective gas is continued to be introduced, and a trifunctional epoxy resin is added to the material obtained in step S200. A vacuum is then drawn to carry out the second polycondensation reaction. Specifically, a protective gas is introduced into the reactor, and a trifunctional epoxy resin is added. Then, a vacuum pump is turned on, and a vacuum is drawn to 30 Pa-300 Pa to carry out the second polycondensation reaction. The reaction temperature of the second polycondensation reaction is the same as that of the first polycondensation reaction. Thus, by adding the trifunctional epoxy resin during the second polycondensation reaction, the trifunctional epoxy resin can increase the molecular arrangement space of the polyester polyol, thereby increasing the crosslinking density of the polyester polyol and reducing the contact between ester bonds and water, thereby improving the adhesive strength and hydrolysis resistance of the adhesive.

[0056] According to one embodiment of the present invention, the timing of adding trifunctional epoxy resin can be determined by referring to the torque of the stirring paddle during the reaction. Since the first polycondensation reaction is a process in which small molecules gradually become large molecules, the solution viscosity gradually increases, and the stirring paddle speed gradually decreases. When the first torque of the stirring paddle is 25 NM-40 NM, nitrogen gas is introduced into the reactor, and trifunctional epoxy resin is added. When the second torque of the stirring paddle is 45 NM-60 NM, the reaction ends, and polyester polyol is obtained. The present invention obtains an adhesive product with stable application performance by controlling the order of material addition, that is, adding specific materials at different reaction temperature stages, and controlling the torque to control the degree of reaction.

[0057] According to some embodiments of the present invention, the second polymerization reaction can be carried out for 0.2 h to 0.5 h. Therefore, when the second polycondensation reaction takes 0.2 h to 0.5 h, the reaction can proceed more completely.

[0058] It should be noted that aliphatic diols, byproducts, binary oligomers, and impurities that did not participate in the polycondensation reaction can be pumped into the cold hydrazine under high vacuum conditions, and other macromolecular substances can then serve as components of the polyester polyol; while aliphatic diacids and aromatic diacids can be determined to have reacted completely by detecting the acid value after the reaction is finished.

[0059] S400: A mixture of polyester polyol, polyisocyanate, and solvent.

[0060] According to some embodiments of the present invention, in this step, the polyisocyanate is diluted in a solvent, stirred evenly, and then the prepared polyester polyol is added and stirred evenly to obtain an adhesive.

[0061] Therefore, this method can be used to obtain adhesives with excellent impact resistance, high bonding strength, excellent hydrolysis resistance, and excellent heat resistance.

[0062] It should be noted that the features and advantages described above for the adhesive also apply to the method for preparing the adhesive, and will not be repeated here.

[0063] In a third aspect, the present invention provides an aluminum-plastic film comprising the aforementioned adhesive or an adhesive prepared by the aforementioned method, thereby possessing all the features and advantages of the aforementioned adhesive, which will not be repeated here.

[0064] In a fourth aspect, the present invention provides a secondary battery comprising the aforementioned aluminum-plastic film, thereby possessing all the features and advantages of the aforementioned aluminum-plastic film, which will not be repeated here.

[0065] The embodiments of the present invention are described in detail below. These embodiments are exemplary and are only used to explain the present invention, and should not be construed as limiting the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0066] Example 1

[0067] Esterification reaction: 6.97g of terephthalic acid, 62.75g of isophthalic acid, 26.28g of adipic acid, 13.41g of ethylene glycol, 34.04g of 1,6-hexanediol, and 28.99g of 3-methyl-1,5-pentanediol were added to the reaction vessel. Nitrogen gas was slowly introduced into the reaction vessel to 150kPa, and the pressure was slowly released to remove the air from the reaction vessel. Stirring was started at 130℃, and the temperature was raised to 220℃ to carry out the esterification reaction. The reaction time of the esterification reaction was 4.5h.

[0068] First polycondensation reaction: After distilling off a specific amount of water, add 0.04g of antimony acetate and 0.17g of antioxidant 1010, continue heating to 250℃, turn on the vacuum pump, and slowly pressurize to 200Pa to carry out the polycondensation reaction. The reaction time of the first polycondensation reaction is 4h.

[0069] Second polycondensation reaction: When the first torque of the reactor reaches 35 NM, nitrogen gas is introduced and 0.42 g of o-cresol epoxy resin ECON6650 is added. Then, the vacuum pump is turned on and the pressure is slowly reduced to 30 Pa-300 Pa to continue the second polycondensation reaction. The reaction time of the second polycondensation reaction is 0.3 h. When the second torque of the reactor reaches 60 NM, the reaction ends and polyester polyol is obtained.

[0070] Adhesive preparation: The polyester polyol solution with a solid content of 50% was prepared by adjusting the polyester polyol with ethyl acetate, and the polyester polyol solution with a solid content of 50% was mixed with a curing agent polyisocyanate solution with a solid content of 75% to prepare an adhesive, wherein the ratio of isocyanate groups in the curing agent to hydroxyl groups in the polyester polyol was 20:1.

[0071] Preparation of aluminum-plastic film: An adhesive is applied to the surface of aluminum foil with a thickness of 6μm. After drying, it is thermally laminated with a nylon layer. The heat-sealing layer is a composite of a polypropylene film and a nylon layer. Then, it is cured at a temperature of 80℃ for 4 days to obtain the aluminum-plastic film.

[0072] Example 2

[0073] The first polycondensation reaction, the second polycondensation reaction, the adhesive preparation, and the aluminum-plastic film preparation in this embodiment are the same as in Example 1. The difference is the esterification reaction: 6.97g of terephthalic acid, 62.75g of terephthalic acid, 33.85g of azelaic acid, 13.41g of ethylene glycol, 34.04g of 1,6-hexanediol, and 28.99g of 3-methyl-1,5-pentanediol are added to the reaction vessel. Nitrogen gas is slowly introduced into the reaction vessel to 150kPa, and the pressure is slowly released to remove the air from the reaction vessel. Stirring is started at 130°C, and the temperature is raised to 220°C to carry out the esterification reaction. The reaction time of the esterification reaction is 4.5h.

[0074] Example 3

[0075] The first polycondensation reaction, the second polycondensation reaction, the adhesive preparation, and the aluminum-plastic film preparation in this embodiment are the same as in Example 1. The difference is the esterification reaction: 6.97g of terephthalic acid, 62.75g of terephthalic acid, 36.45g of sebacic acid, 13.41g of ethylene glycol, 34.04g of 1,6-hexanediol, and 28.99g of 3-methyl-1,5-pentanediol are added to the reaction vessel. Nitrogen gas is slowly introduced into the reaction vessel to 150kPa, and the pressure is slowly released to remove the air from the reaction vessel. Stirring is started at 130°C, and the temperature is raised to 220°C to carry out the esterification reaction. The reaction time of the esterification reaction is 4.5h.

[0076] Example 4

[0077] The esterification reaction, the first polycondensation reaction, and the preparation of the aluminum-plastic film in this embodiment are the same as in Example 1. The difference is the second polycondensation reaction: when the first torque of the reactor is 25 NM, nitrogen gas is introduced and 0.175 g of o-cresphenolic epoxy resin ECON6650 is added. Then, the vacuum pump is turned on and the pressure is slowly reduced to 30 Pa-300 Pa to continue the second polycondensation reaction. The reaction time of the second polycondensation reaction is 0.3 h. When the second torque of the reactor is 60 NM, the reaction ends and polyester polyol is obtained.

[0078] Adhesive preparation: The polyester polyol solution with a solid content of 50% is prepared by adjusting the polyester polyol with ethyl acetate, and the polyester polyol solution with a solid content of 50% is mixed with a curing agent polyisocyanate solution with a solid content of 75% to prepare an adhesive, wherein the ratio of isocyanate groups in the curing agent to hydroxyl groups in the polyester polyol is 15:1.

[0079] Example 5

[0080] The esterification reaction, the first polycondensation reaction, and the preparation of the aluminum-plastic film in this embodiment are the same as in Example 1. The difference is the second polycondensation reaction: when the first torque of the reactor is 40 NM, nitrogen gas is introduced and 0.53 g of o-cresyl epoxy resin ECON6650 is added. Then, the vacuum pump is turned on and the pressure is slowly reduced to 30 Pa-300 Pa to continue the second polycondensation reaction. The reaction time of the second polycondensation reaction is 0.3 h. When the second torque of the reactor is 55 NM, the reaction ends and polyester polyol is obtained.

[0081] Adhesive preparation: The polyester polyol solution with a solid content of 50% was prepared by adjusting the polyester polyol with ethyl acetate, and the polyester polyol solution with a solid content of 50% was mixed with a curing agent polyisocyanate solution with a solid content of 75% to prepare an adhesive, wherein the ratio of isocyanate groups in the curing agent to hydroxyl groups in the polyester polyol was 25:1.

[0082] Example 6

[0083] The esterification reaction, the first polycondensation reaction, and the preparation of the aluminum-plastic film in this embodiment are the same as in Example 1. The difference is the second polycondensation reaction: when the first torque of the reactor is 35 NM, nitrogen gas is introduced and 0.35 g of o-cresyl epoxy resin ECON6650 is added. Then, the vacuum pump is turned on and the pressure is slowly reduced to 30 Pa-300 Pa to continue the second polycondensation reaction. The reaction time of the second polycondensation reaction is 0.3 h. When the second torque of the reactor is 45 NM, the reaction ends and polyester polyol is obtained.

[0084] Adhesive preparation: The polyester polyol solution with a solid content of 50% was prepared by adjusting the polyester polyol with ethyl acetate, and the polyester polyol solution with a solid content of 50% was mixed with a curing agent polyisocyanate solution with a solid content of 75% to prepare an adhesive, wherein the ratio of isocyanate groups in the curing agent to hydroxyl groups in the polyester polyol was 20:1.

[0085] Example 7

[0086] The first polycondensation reaction, the second polycondensation reaction, the adhesive preparation, and the aluminum-plastic film preparation in this embodiment are the same as in Example 1. The difference is the esterification reaction: 6.97g of terephthalic acid, 62.75g of terephthalic acid, 36.45g of sebacic acid, 26.81g of ethylene glycol, and 47.34g of 1,6-hexanediol are added to the reactor. Nitrogen gas is slowly introduced into the reactor to 150kPa, and the pressure is slowly released to remove the air from the reactor. Stirring is started at 130°C, and the temperature is raised to 220°C to carry out the esterification reaction. The reaction time of the esterification reaction is 4.5h.

[0087] Comparative Example 1

[0088] The first polycondensation reaction, the second polycondensation reaction, the preparation of the adhesive, and the preparation of the aluminum-plastic film in this comparative example are the same as in Example 1. The difference is the esterification reaction: 13.95g of terephthalic acid, 55.77g of terephthalic acid, 26.28g of adipic acid, 13.41g of ethylene glycol, 34.04g of 1,6-hexanediol, and 28.99g of 3-methyl-1,5-pentanediol are added to the reaction vessel. Nitrogen gas is slowly introduced into the reaction vessel to 150kPa, and the pressure is slowly released to remove the air from the reaction vessel. Stirring is started at 130°C, and the temperature is raised to 220°C to carry out the esterification reaction. The reaction time of the esterification reaction is 4.5h.

[0089] Comparative Example 2

[0090] The first polycondensation reaction, the second polycondensation reaction, the preparation of the adhesive, and the preparation of the aluminum-plastic film in this comparative example are the same as in Example 1. The difference is the esterification reaction: 6.97 g of terephthalic acid, 62.75 g of terephthalic acid, 21.25 g of 1,4-butanediol, 13.41 g of ethylene glycol, 34.04 g of 1,6-hexanediol, and 28.99 g of 3-methyl-1,5-pentanediol are added to the reaction vessel. Nitrogen gas is slowly introduced into the reaction vessel to 150 kPa, and the pressure is slowly released to remove the air from the reaction vessel. Stirring is started at 130°C, and the temperature is raised to 220°C to carry out the esterification reaction. The reaction time of the esterification reaction is 4.5 h.

[0091] Comparative Example 3

[0092] The esterification reaction, first polycondensation reaction, adhesive preparation, and aluminum-plastic film preparation in this comparative example are the same as in Example 1. The difference is that no o-cresol epoxy resin is added in this comparative example. After the first polycondensation reaction is completed, the vacuum pump is turned on and the pressure is slowly reduced to 30Pa-300Pa to allow the reactor to continue the reaction for 0.3 hours. When the second torque of the reactor reaches 45 NM, the reaction ends and polyester polyol is obtained.

[0093] Comparative Example 4

[0094] The esterification reaction, the first polycondensation reaction, and the preparation of the aluminum-plastic film in this comparative example are the same as in Example 1. The difference is the second polycondensation reaction: when the first torque of the reactor is 15 NM, nitrogen gas is introduced and 1 g of o-cresyl epoxy resin ECON6650 is added. Then, the vacuum pump is turned on and the pressure is slowly reduced to 30 Pa-300 Pa to continue the second polycondensation reaction. The reaction time of the second polycondensation reaction is 0.3 h. When the second torque of the reactor is 70 NM, the reaction ends and polyester polyol is obtained.

[0095] Adhesive preparation: The polyester polyol solution with a solid content of 50% was prepared by adjusting the polyester polyol with ethyl acetate, and the polyester polyol solution with a solid content of 50% was mixed with a curing agent polyisocyanate solution with a solid content of 75% to prepare an adhesive, wherein the ratio of isocyanate groups in the curing agent to hydroxyl groups in the polyester polyol was 30:1.

[0096] The key parameters of the polyester polyols obtained in Examples 1-7 and Comparative Examples 1-4 are shown in Table 1.

[0097] Table 1

[0098]

[0099]

[0100] The aluminum-plastic films obtained in Examples 1-7 and Comparative Examples 1-4 were tested as follows, and the results are shown in Table 2.

[0101] (1) Peel strength test: Referring to the standard GB-T2791-1995 Adhesives T Peel Strength Test Method Flexible Materials to Flexible Materials, the aluminum-plastic film sample was cut into a strip shape of 15mm×15cm. The unbonded ends of the nylon layer and aluminum foil layer were symmetrically clamped on the upper and lower clamps of the universal testing machine. The clamping parts should not slip to ensure that the applied tensile force is evenly distributed across the width of the sample. The testing machine was started, and the upper and lower clamps separated the sample at a rate of 100±10mm / min. The peel length should be at least 125mm. The evaluation index is as follows:

[0102] √: 7N / 15mm or higher (excellent in practical use)

[0103] O: 5N / 15mm or more, but less than 7N / 15mm (practical area)

[0104] Less than 5N / 15mm

[0105] (2) Drawing performance test: A double-cavity drawing die was used, with a die punch size of 50×60mm, a cavity spacing of 1mm, a corner radius of 2mm, and a cavity depth of 7mm. The evaluation criteria for any delamination, whitening, or other abnormalities at the edges of the outer film after drawing are as follows:

[0106] √: 7mm or larger (excellent in practical use)

[0107] O: 2mm or more, but less than 6mm (practical area)

[0108] Less than 2mm

[0109] (3) Water resistance: The aluminum-plastic film sample after deep-cutting was placed in a constant temperature water bath and placed at 100℃ for 5 hours. The outer film was observed for abnormal phenomena such as delamination, blistering, and white marks at the edges and corners. The evaluation indicators are as follows:

[0110] √: No abnormalities such as layering, bubbling, or white marks (excellent in practical use)

[0111] Abnormal phenomena such as layering, bubbling, and white marks may occur.

[0112] (4) Peel strength test after boiling: Place the deep-cut aluminum-plastic film sample in a constant temperature water bath and place it at 100℃ for 5 hours. Cut the aluminum-plastic film sample into a strip shape of 15mm×15cm. The unbonded ends of the nylon layer and aluminum foil layer are symmetrically clamped on the upper and lower clamps of the universal testing machine. The clamping parts should not slip to ensure that the applied tensile force is evenly distributed on the width of the sample. Start the testing machine and separate the sample at a rate of 100±10mm / min. The peel length should be at least 125mm. The evaluation index is as follows:

[0113] √: 5N / 15mm or higher (excellent in practical use)

[0114] O: 5N / 15mm or more, but less than 3N / 15mm (practical area)

[0115] Less than 3N / 15mm

[0116] (5) Extreme drawing depth performance test: A single-cavity drawing die is used, with a die punch size of 20×30mm and a cavity depth of 10-13mm. After drawing, check whether there are any abnormal phenomena such as delamination or whitening at the edges and corners of the outer film. The number of products tested is 50. The pass rate is considered qualified if it meets or exceeds 95%. If it does not meet the standard, the cavity depth is reduced until it meets or exceeds 95% to be considered qualified.

[0117] Table 2

[0118]

[0119] As shown in the table above, adding an appropriate amount of trifunctional epoxy resin to further promote the polycondensation reaction during the preparation of polyester polyols improves the molecular arrangement space, which can meet the requirements for hydroxyl value and molecular weight in practical applications. Furthermore, the trifunctional epoxy resin can increase the crosslinking density of the polyester polyol and reduce the contact between ester bonds and water, thereby reducing the hydrolysis of the adhesive and obtaining an adhesive with excellent hydrolysis resistance and impact resistance. Additionally, by controlling the torque during the reaction process, the extent of the reaction can be controlled, thus obtaining an adhesive product with stable application performance.

[0120] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0121] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0122] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. An adhesive, characterized in that, include: Main agent and curing agent, The main agent includes polyester polyol; The curing agent includes polyisocyanate; The raw materials for preparing the polyester polyol include: 40-45 parts by weight of aromatic dicarboxylic acid; 14-16 parts by weight of aliphatic dicarboxylic acid; 40-45 parts by weight of aliphatic diols; 0.1-0.3 parts by weight of trifunctional epoxy resin; 0.015 to 0.025 parts by weight of catalyst; 0.05-0.15 parts by weight of antioxidant; The molecular weight of the polyester polyol is 30,000-50,000; The hydroxyl value of the polyester polyol is 15 mgKOH / g-30 mgKOH / g; The aromatic dicarboxylic acid is isophthalic acid and terephthalic acid; The molar ratio of terephthalic acid and isophthalic acid is 1:(6-9); The aliphatic dicarboxylic acid is a C6-C10 aliphatic dicarboxylic acid; The trifunctional epoxy resin is an o-cresol formaldehyde epoxy resin. A method for preparing the adhesive includes: (1) Under a protective atmosphere, aromatic dicarboxylic acid, aliphatic dicarboxylic acid and aliphatic diol are mixed and heated to carry out esterification reaction; (2) Accompanied by heating, the material obtained from the esterification reaction is mixed with the catalyst and antioxidant to carry out the first polycondensation reaction, and a vacuum is drawn; (3) The material obtained in step (2) is mixed with trifunctional epoxy resin under a protective atmosphere to carry out a second polycondensation reaction in order to obtain polyester polyol; (4) The polyester polyol, polyisocyanate and solvent are mixed to obtain the adhesive.

2. The adhesive according to claim 1, characterized in that, The aliphatic diols include C2-C6 aliphatic diols, and the C2-C6 aliphatic diols include at least one of straight-chain aliphatic diols and branched aliphatic diols. Optionally, the catalyst comprises at least one of antimony acetate, antimony oxide, zinc oxalate, and tetrabutyl titanate; Optionally, the antioxidant includes at least one of antioxidant 1010, antioxidant 168, and butylphenol.

3. The adhesive according to claim 2, characterized in that, The straight-chain aliphatic diols include at least one of ethylene glycol, 1,3-propanediol, 1,4-butanediol, and 1,6-hexanediol, and the branched aliphatic diols include at least one of 3-methyl-1,5-pentanediol, 2-methyl-1,3-propanediol, and neopentanediol.

4. The adhesive according to claim 1, characterized in that, The aliphatic dicarboxylic acid includes at least one of adipic acid, azelaic acid, and sebacic acid.

5. The adhesive according to any one of claims 1-4, characterized in that, The alkyd molar ratio of the polyester polyol is (1.15-1.35):

1.

6. The adhesive according to any one of claims 1-4, characterized in that, The total equivalent [NCO] / ([OH]+[COOH]) of the isocyanate groups in the polyisocyanate and the hydroxyl and carboxyl groups in the polyester polyol is 15-25.

7. A method for preparing the adhesive according to any one of claims 1-6, characterized in that, include: (1) Under a protective atmosphere, aromatic dicarboxylic acid, aliphatic dicarboxylic acid and aliphatic diol are mixed and heated to carry out esterification reaction; (2) Accompanied by heating, the material obtained from the esterification reaction is mixed with the catalyst and antioxidant to carry out the first polycondensation reaction, and a vacuum is drawn; (3) The material obtained in step (2) is mixed with trifunctional epoxy resin under a protective atmosphere to carry out a second polycondensation reaction in order to obtain polyester polyol; (4) The polyester polyol, polyisocyanate and solvent are mixed to obtain the adhesive.

8. The method according to claim 7, characterized in that, In step (1), the temperature of the esterification reaction is 210℃-230℃; In step (2), the temperature of the first polycondensation reaction is 240℃-260℃.

9. An aluminum-plastic film, characterized in that, The aluminum-plastic film comprises the adhesive according to any one of claims 1-6 or the adhesive obtained by the method according to claim 7 or 8.

10. A secondary battery, characterized in that, Includes the aluminum-plastic film as described in claim 9.

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