A deep-drawing and high-temperature resistant block structure polyurethane adhesive for lithium ion battery packaging and a preparation method thereof

Abstract

The present application claims a kind of deep-drawing and high-temperature-resistant block structure polyurethane adhesive for lithium ion battery packaging and its preparation method, the adhesive is prepared by uniformly mixing the following components by weight parts: 100 parts branched liquid rubber polyol-polyether-branched liquid rubber polyol polyurethane copolymer;3-5 parts high molecular weight ultraviolet light initiator;20-35 parts isocyanate end-capped high-temperature-resistant hydrolysis polyester polyol.Compared with the solvent-based polyurethane adhesive on the market at present, the adhesive of the present application does not contain organic solvent, has the advantages of non-toxic, safe to use, environment-friendly, etc., and its water resistance, yellowing resistance, deep-drawing resistance, high-temperature resistance and other properties are very outstanding after composite curing with the substrate, especially suitable for the special requirements of lithium ion battery aluminum-plastic composite packaging material.

Description

Technical Field

[0001] This invention relates to a polyurethane adhesive and its preparation method, specifically to a deep-drawing and high-temperature resistant block polyurethane adhesive for lithium-ion battery packaging and its preparation method; belonging to the field of new materials technology. Background Technology

[0002] Polyurethane adhesives are generally composed of two basic units: diisocyanate and polyester diol or polyether diol. The structure of polyurethane is usually described using "soft segments" and "hard segments," with polyester diol or polyether diol segments called soft segments and diisocyanate segments called hard segments. Because the raw materials for the main chain of polyurethane are widely available and diverse, its molecular structure design is quite flexible. Furthermore, the physical cross-linking of the main chain molecules of polyurethane adhesives, consisting of numerous hydrogen bonds, endows traditional polyurethane adhesives with high strength, modulus, adhesive properties, high-temperature resistance, and simple molding processes. Among them, two-component reactive polyurethane dry composite adhesives with excellent flexibility and deep-drawing resistance exhibit superior composite strength for plastic / plastic and plastic / aluminum composite structures, making them particularly suitable for aluminum-plastic composites used in lithium-ion battery packaging.

[0003] Patent application number 202010174304.5 discloses a polyurethane coating adhesive for lithium-ion batteries, mainly composed of a water-soluble anionic polyurethane and a water-soluble cationic polyurethane. The water-soluble anionic polyurethane is composed of diisocyanate, polyethylene polyol, and a salt-forming agent, while the water-soluble cationic polyurethane is composed of diisocyanate, polyetherimide, vegetable oil-modified polyol, and a salt-forming agent. Patent application number 201810524575.1 discloses a reactive polyurethane hot melt adhesive for folding the edges of soft-pack lithium-ion batteries. The raw materials for preparation include polyester polyol, polyether polyol, tackifying resin, thermoplastic elastomer, diisocyanate, catalyst, antioxidant, and stabilizer.

[0004] Lithium-ion battery aluminum-plastic composite packaging materials prepared with polyurethane adhesives not only require deep-drawing resistance but also high-temperature resistance; otherwise, they may become flammable and explosive due to poor safety. For polyurethane adhesives, good flexibility is needed for deep-drawing resistance, while high cross-linking density is required for high-temperature resistance. However, these two requirements are contradictory. Finding a balance between these two is key to developing deep-drawing and high-temperature resistant block-structure polyurethane adhesives. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a deep-drawing and high-temperature resistant block polyurethane adhesive and its preparation method, thereby solving the problem that existing polyurethane adhesives for lithium-ion battery aluminum-plastic composite packaging materials cannot simultaneously achieve both deep-drawing resistance and high-temperature resistance.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A deep-drawing and high-temperature resistant block polyurethane adhesive for lithium-ion battery packaging is prepared by uniformly mixing the following components in parts by weight:

[0008] 100 parts of branched liquid rubber polyol-polyether-branched liquid rubber polyol polyurethane copolymer;

[0009] 3-5 parts of high molecular weight ultraviolet photoinitiator;

[0010] 20–35 parts isocyanate-terminated high-temperature hydrolyzable polyester polyol;

[0011] The branched liquid rubber polyol-polyether-branched liquid rubber polyol polyurethane copolymer is first prepared by obtaining a branched liquid rubber polyol from a liquid rubber diol, and then isocyanate-terminated polyether diol oligomers are prepared by reacting polyisocyanate with polyether diol, and finally the branched liquid rubber polyol-polyether-branched liquid rubber polyol polyurethane copolymer is obtained; the high molecular weight ultraviolet photoinitiator is prepared by modifying a hydroxyl-containing low molecular weight ultraviolet photoinitiator; the isocyanate-terminated high-temperature hydrolyzable polyester polyol is prepared by reacting polyisocyanate with high-temperature hydrolyzable polyester polyol, and the high-temperature hydrolyzable polyester polyol is prepared by esterification and dehydration reaction of aromatic dicarboxylic acid and flexible polyol.

[0012] This invention also discloses a method for preparing a deep-drawing and high-temperature resistant block polyurethane adhesive for lithium-ion battery packaging, as described above, comprising the following steps:

[0013] S1. Preparation of branched liquid rubber polyol:

[0014] Add 100 parts by mass of liquid rubber diol to a reaction vessel, heat to 60-90℃, and then add isocyanate trimer dropwise at a molar ratio of -NCO / -OH of 0.1-0.3 for 1-2 hours. After the isocyanate trimer is completely added, continue to keep the temperature for 1-3 hours to obtain branched liquid rubber polyol.

[0015] S2. Preparation of branched liquid rubber polyol-polyether-branched liquid rubber polyol polyurethane copolymer:

[0016] Add 100 parts by mass of polyisocyanate to the reaction vessel, heat to 60-90℃, and then add polyether diol dropwise at a molar ratio of -NCO / -OH for 1-2 hours. After the polyether diol is completely added, continue to keep the temperature and react for 1-3 hours to obtain isocyanate-terminated polyether diol oligomers.

[0017] Next, slowly add 100% of the remaining isocyanate content of the branched liquid rubber polyol obtained in step S1 above, over 1-2 hours. After the addition is complete, continue the reaction at a constant temperature for 3-5 hours. Cool to obtain the branched liquid rubber polyol-polyether-branched liquid rubber polyol polyurethane copolymer.

[0018] S3. Preparation of high molecular weight ultraviolet photoinitiator:

[0019] Add 100 parts by mass of polyisocyanate to the reaction vessel, heat to 60-90℃, and then add polyether diol dropwise at a molar ratio of -NCO / -OH for 1-2 hours. After the polyether diol is completely added, continue to keep the temperature and react for 1-3 hours to obtain isocyanate-terminated polyether diol oligomers.

[0020] Next, slowly add 100% of the remaining isocyanate material of hydroxyl-containing low molecular weight ultraviolet photoinitiator, continue the reaction at a constant temperature for 3-5 hours, and then cool to obtain a high molecular weight ultraviolet photoinitiator.

[0021] S4. Preparation of high-temperature resistant hydrolyzable polyester polyols:

[0022] Add 100 parts by mass of aromatic dicarboxylic acid and 80-90 parts by mass of flexible polyol to a reaction vessel, heat to 160-190℃, carry out esterification and dehydration reaction for 3-5 hours, then raise the temperature to 210-230℃, carry out vacuum polycondensation reaction for 4-6 hours, and cool to room temperature to obtain high temperature resistant hydrolyzable polyester polyol.

[0023] S5. Preparation of isocyanate-terminated high-temperature hydrolyzable polyester polyols:

[0024] Add 100 parts by mass of polyisocyanate to the reaction vessel, heat to 60-90℃, and then add the high-temperature resistant hydrolyzed polyester polyol prepared in step S4 above dropwise at a molar ratio of -NCO / -OH of 2. Add the dropwise polyol for 1-2 hours, and after the dropwise addition is complete, continue to keep the reaction at the temperature for 3-5 hours. Cool to obtain isocyanate-terminated high-temperature resistant hydrolyzed polyester polyol.

[0025] S6. Preparation of deep-drawing and high-temperature resistant block polyurethane adhesives:

[0026] 100 parts by weight of the branched liquid rubber polyol-polyether-branched liquid rubber polyol polyurethane copolymer obtained in step S2 above, 3-5 parts by weight of the high molecular weight ultraviolet photoinitiator obtained in step S3 above, and 20-35 parts by weight of the isocyanate-terminated high-temperature hydrolyzable polyester polyol obtained in step S5 above are mixed evenly to obtain a deep-drawing and high-temperature resistant block structure polyurethane adhesive.

[0027] Preferably, the aforementioned reaction vessel is a four-necked flask equipped with a stirrer, a thermometer, and a condenser.

[0028] More preferably, the aforementioned liquid rubber diol is one of liquid polybutadiene diol and liquid polyisoprene diol, preferably liquid polybutadiene diol.

[0029] More preferably, the aforementioned isocyanate trimer is one of isophorone diisocyanate trimer and hexamethylene diisocyanate trimer.

[0030] More preferably, the aforementioned polyisocyanate is one of isophorone diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and lysine diisocyanate.

[0031] More preferably, the aforementioned polyether diol is one of polyoxypropylene diol, polyethylene propylene diol, and polytetrahydrofuran diol; the molecular weight of the polyether diol is 4000-6000.

[0032] More preferably, the aforementioned aromatic dicarboxylic acid is a mixture of phthalic acid and isophthalic acid, wherein the mass ratio of phthalic acid to isophthalic acid is 100:50-150.

[0033] More preferably, the aforementioned flexible polyol is one of diethylene glycol, triethylene glycol, tetraethylene glycol, isopentyl glycol, 1,6-hexanediol, and 1,4-cyclohexanediethanol, with 1,4-cyclohexanediethanol being the most preferred.

[0034] More preferably, the aforementioned hydroxyl-containing low molecular weight ultraviolet photoinitiator is one of 2-hydroxy-2-methyl-1-phenyl-1-propanone (photoinitiator 1173), 1-hydroxy-cyclohexyl-phenyl ketone (photoinitiator 184), 1,1'-(methylenedi-4,1-phenylene)bis[2-hydroxy-2-methyl-1-propanone] (photoinitiator 127), and 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylpropanone (photoinitiator 2959).

[0035] The advantages of this invention are:

[0036] (1) Compared with solvent-based polyurethane adhesives currently on the market, the deep-drawing and high-temperature resistant block polyurethane adhesive of the present invention does not contain organic solvents and has the advantages of being non-toxic, safe to use, and environmentally friendly.

[0037] (2) The adhesive of the present invention takes into account the requirements of deep-drawing and high-temperature resistant block polyurethane adhesive for use in aluminum-plastic composite packaging materials for lithium-ion batteries. Through molecular design, a special "high-temperature resistant hydrolyzed polyester-branched liquid rubber polyol-polyether-branched liquid rubber polyol-high-temperature resistant hydrolyzed polyester" block polyurethane chain segment is prepared, which optimizes the water resistance, yellowing resistance, deep-drawing resistance and high-temperature resistance of the polyurethane adhesive.

[0038] (3) In this invention, the higher molecular weight polyether diol can provide high flexibility, and the high-temperature hydrolytic polyester polyol can not only improve the high-temperature hydrolysis resistance of the film, but also improve the adhesion to the substrate. In the material design, the polyether diol and the high-temperature hydrolytic polyester polyol are separated by branched liquid rubber polyol molecules, so that the two form a certain distance to avoid mutual interference and give full play to their respective advantages.

[0039] (4) More importantly, the self-made high molecular weight ultraviolet photoinitiator used in this invention can avoid low molecular weight residues, has good compatibility with block polyurethane segments, and has a synergistic effect. At the same time, it causes the liquid rubber to undergo a cross-linking reaction under ultraviolet light, further improving the high temperature resistance. Thus, the polyurethane adhesive integrates safety, environmental protection, water resistance, yellowing resistance, deep drawing resistance, and high temperature resistance. The peel strength and deep drawing depth are significantly improved compared with the existing technology and comparative example. Attached Figure Description

[0040] Figure 1 This is a picture of a deep-drawing sample (lithium-ion battery packaging) prepared with the adhesive prepared in Example 1 of the present invention, after aging at 120°C for 24 hours.

[0041] Figure 2 This is a picture of a deep-drawing sample (lithium-ion battery packaging) prepared with the adhesive prepared in Comparative Example 1, after aging at 120°C for 24 hours. Detailed Implementation

[0042] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0043] Example 1

[0044] (1) Preparation of branched liquid rubber polyols

[0045] 100 parts by mass of liquid polybutadiene diol were added to a four-necked flask equipped with a stirrer, thermometer and condenser, and heated to 60°C. Then 2.1 parts by mass of hexamethylene diisocyanate trimer were added dropwise over 2 hours. After the addition was complete, the reaction was continued at the temperature for 3 hours to obtain branched liquid rubber polyol.

[0046] (2) Preparation of branched liquid rubber polyol-polyether-branched liquid rubber polyol polyurethane copolymer

[0047] 100 parts by mass of isophorone diisocyanate were added to a four-necked flask equipped with a stirrer, thermometer and condenser. The mixture was heated to 60°C and 900 parts by mass of polyoxypropylene diol with a molecular weight of 4000 were added dropwise over 1 hour. After the addition was completed, the mixture was kept at the temperature for another 3 hours to obtain isocyanate-terminated polyether diol oligomer.

[0048] Next, 900 parts by mass of the branched liquid rubber polyol prepared above were slowly added dropwise over 1 hour. After the addition was complete, the reaction was continued at a constant temperature for 3 hours. After cooling, the branched liquid rubber polyol-polyether-branched liquid rubber polyol polyurethane copolymer was obtained.

[0049] (3) Preparation of high molecular weight ultraviolet photoinitiators

[0050] 100 parts by mass of isophorone diisocyanate were added to a light-proof four-necked flask equipped with a stirrer, thermometer, and condenser. The mixture was heated to 60°C, and 900 parts by mass of polyoxypropylene diol with a molecular weight of 4000 were added dropwise over 1 hour. After the addition was complete, the reaction was continued at the temperature for 3 hours to obtain isocyanate-terminated polyether diol oligomers. Then, 74 parts by mass of 2-hydroxy-2-methyl-1-phenyl-1-propanone were slowly added, and the reaction was continued for 3 hours. After cooling, a high molecular weight ultraviolet photoinitiator was obtained.

[0051] (4) Preparation of high-temperature resistant hydrolyzable polyester polyols

[0052] Add 67 parts by mass of terephthalic acid, 33 parts by mass of isophthalic acid, and 80 parts by mass of 1,4-cyclohexanediethanol to a four-necked flask equipped with a stirrer, thermometer, and condenser. Heat to 160°C and carry out an esterification and dehydration reaction for 5 hours. Then raise the temperature to 210°C and carry out a vacuum polycondensation reaction for 6 hours. Cool to room temperature to obtain a high-temperature resistant hydrolyzable polyester polyol.

[0053] (5) Preparation of isocyanate-terminated high-temperature hydrolyzable polyester polyols

[0054] 100 parts by mass of isophorone diisocyanate were added to a four-necked flask equipped with a stirrer, thermometer and condenser and heated to 60°C. 225 parts by mass of the high-temperature resistant hydrolyzable polyester polyol prepared above were added dropwise over 1 hour. After the addition was completed, the reaction was kept at the temperature for 5 hours. After cooling, the isocyanate-terminated high-temperature resistant hydrolyzable polyester polyol was obtained.

[0055] (6) Preparation of deep-drawing and high-temperature resistant block polyurethane adhesive

[0056] The deep-drawing and high-temperature resistant block structure polyurethane adhesive is prepared by mixing 100 parts by mass of the branched liquid rubber polyol-polyether-branched liquid rubber polyol polyurethane copolymer prepared above, 3 parts by mass of the high molecular weight ultraviolet photoinitiator prepared above, and 20 parts by mass of the isocyanate-terminated high-temperature resistant hydrolyzed polyester polyol prepared above evenly.

[0057] Example 2

[0058] (1) Preparation of branched liquid rubber polyols

[0059] 100 parts by mass of liquid polybutadiene diol were added to a four-necked flask equipped with a stirrer, thermometer and condenser, and heated to 75°C. Then 7 parts by mass of isophorone diisocyanate trimer were added dropwise over 1.5 hours. After the addition was complete, the reaction was continued at the temperature for 2 hours to obtain branched liquid rubber polyol.

[0060] (2) Preparation of branched liquid rubber polyol-polyether-branched liquid rubber polyol polyurethane copolymer

[0061] 100 parts by mass of dicyclohexylmethane diisocyanate were added to a four-necked flask equipped with a stirrer, thermometer and condenser. The mixture was heated to 80°C and 950 parts by mass of polyoxypropylene diol with a molecular weight of 5000 were added dropwise over 1.5 hours. After the addition was completed, the mixture was kept at the temperature for another 2 hours to obtain isocyanate-terminated polyether diol oligomers.

[0062] Next, 760 parts by mass of the branched liquid rubber polyol prepared above were slowly added dropwise over 1.5 hours. After the addition was complete, the reaction was continued at a constant temperature for 4 hours. After cooling, the branched liquid rubber polyol-polyether-branched liquid rubber polyol polyurethane copolymer was obtained.

[0063] (3) Preparation of high molecular weight ultraviolet photoinitiators

[0064] 100 parts by mass of dicyclohexylmethane diisocyanate were added to a light-proof four-necked flask equipped with a stirrer, thermometer and condenser. The mixture was heated to 80°C, and 954 parts by mass of polyoxypropylene diol with a molecular weight of 5000 were added dropwise over 1.5 hours. After the addition was completed, the reaction was continued at the temperature for 3 hours to obtain isocyanate-terminated polyether diol oligomers.

[0065] Next, 78 parts by mass of 1-hydroxy-cyclohexyl-phenyl ketone were slowly added, and the reaction was continued for 4 hours. After cooling, a high molecular weight ultraviolet photoinitiator was obtained.

[0066] (4) Preparation of high-temperature resistant hydrolyzable polyester polyols

[0067] Add 50 parts by mass of terephthalic acid, 50 parts by mass of isophthalic acid, and 85 parts by mass of 1,4-cyclohexanediethanol to a four-necked flask equipped with a stirrer, thermometer, and condenser. Heat to 180°C and carry out an esterification and dehydration reaction for 4 hours. Then raise the temperature to 220°C and carry out a vacuum polycondensation reaction for 5 hours. Cool to room temperature to obtain a high-temperature resistant hydrolyzable polyester polyol.

[0068] (5) Preparation of isocyanate-terminated high-temperature hydrolyzable polyester polyols

[0069] 100 parts by mass of dicyclohexylmethane diisocyanate were added to a four-necked flask equipped with a stirrer, thermometer and condenser. The mixture was heated to 80°C, and 286 parts by mass of the high-temperature hydrolyzable polyester polyol prepared above were added dropwise over 1.5 hours. After the addition was completed, the mixture was kept at the temperature for another 4 hours. The mixture was then cooled to obtain isocyanate-terminated high-temperature hydrolyzable polyester polyol.

[0070] (6) Preparation of deep-drawing and high-temperature resistant block polyurethane adhesive

[0071] The deep-drawing and high-temperature resistant block structure polyurethane adhesive is prepared by mixing 100 parts by weight of the branched liquid rubber polyol-polyether-branched liquid rubber polyol polyurethane copolymer prepared above, 3-5 parts by weight of the high molecular weight ultraviolet photoinitiator prepared above, and 30 parts by weight of the isocyanate-terminated high-temperature resistant hydrolyzed polyester polyol prepared above evenly.

[0072] Example 3

[0073] (1) Preparation of branched liquid rubber polyols

[0074] 100 parts by mass of liquid polybutadiene diol were added to a four-necked flask equipped with a stirrer, thermometer and condenser, and heated to 90°C. Then 6.3 parts by mass of hexamethylene diisocyanate trimer were added dropwise over 1 hour. After the addition was complete, the reaction was continued at the temperature for another hour to obtain branched liquid rubber polyol.

[0075] (2) Preparation of branched liquid rubber polyol-polyether-branched liquid rubber polyol polyurethane copolymer

[0076] 100 parts by mass of hexamethylene diisocyanate were added to a four-necked flask equipped with a stirrer, thermometer and condenser. The mixture was heated to 90°C and 1800 parts by mass of polyoxypropylene diol with a molecular weight of 6000 were added dropwise over 2 hours. After the addition was completed, the reaction was continued at the temperature for 1 hour to obtain isocyanate-terminated polyether diol oligomers.

[0077] Next, 600 parts by mass of the branched liquid rubber polyol prepared above were slowly added dropwise over 2 hours. After the addition was complete, the reaction was continued at a constant temperature for 3 hours. After cooling, the branched liquid rubber polyol-polyether-branched liquid rubber polyol polyurethane copolymer was obtained.

[0078] (3) Preparation of high molecular weight ultraviolet photoinitiators

[0079] 100 parts by mass of hexamethylene diisocyanate were added to a light-proof four-necked flask equipped with a stirrer, thermometer and condenser. The mixture was heated to 90°C and 1786 parts by mass of polyoxypropylene diol with a molecular weight of 6000 were added dropwise over 2 hours. After the addition was completed, the reaction was kept at the temperature for another hour to obtain isocyanate-terminated polyether diol oligomers.

[0080] Next, 100 parts by weight of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone were slowly added, and the reaction was continued for 3 hours. After cooling, a high molecular weight ultraviolet photoinitiator was obtained.

[0081] (4) Preparation of high-temperature resistant hydrolyzable polyester polyols

[0082] Add 40 parts by mass of terephthalic acid, 60 parts by mass of isophthalic acid, and 90 parts by mass of 1,4-cyclohexanediethanol to a four-necked flask equipped with a stirrer, thermometer, and condenser. Heat to 190°C and carry out an esterification and dehydration reaction for 3 hours. Then raise the temperature to 230°C and carry out a vacuum polycondensation reaction for 4 hours. Cool to room temperature to obtain a high-temperature resistant hydrolyzable polyester polyol.

[0083] (5) Preparation of isocyanate-terminated high-temperature hydrolyzable polyester polyols

[0084] 100 parts by mass of hexamethylene diisocyanate were added to a four-necked flask equipped with a stirrer, thermometer and condenser. The mixture was heated to 90°C, and 595 parts by mass of the high-temperature resistant hydrolyzable polyester polyol prepared above were added dropwise over 2 hours. After the addition was completed, the mixture was kept at the temperature for another 3 hours. The mixture was then cooled to obtain isocyanate-terminated high-temperature resistant hydrolyzable polyester polyol.

[0085] (6) Preparation of deep-drawing and high-temperature resistant block polyurethane adhesive

[0086] The deep-drawing and high-temperature resistant block structure polyurethane adhesive is prepared by mixing 100 parts by mass of the branched liquid rubber polyol-polyether-branched liquid rubber polyol polyurethane copolymer prepared above, 5 parts by mass of the high molecular weight ultraviolet photoinitiator prepared above, and 35 parts by mass of the isocyanate-terminated high-temperature resistant hydrolyzed polyester polyol prepared above evenly.

[0087] Comparative Example 1

[0088] (1) Preparation of hydroxyl-terminated polyurethane

[0089] 100 parts by mass of isophorone diisocyanate and 1 part by mass of triphenyl phosphate were added to a four-necked flask equipped with a stirrer, thermometer and condenser. The mixture was heated to 60°C, and 3603 parts by mass of polyoxypropylene diol with a molecular weight of 4000 were added dropwise over 1 hour. After the addition was completed, the reaction was continued at the temperature for 3 hours. The mixture was then cooled to obtain hydroxyl-terminated polyurethane.

[0090] (2) Preparation of isocyanate-terminated polyester polyols

[0091] 100 parts by mass of isophorone diisocyanate were added to a four-necked flask equipped with a stirrer, thermometer and condenser and heated to 60°C. 225 parts by mass of poly(ethylene adipate) with a molecular weight of 1000 were added dropwise over 1 hour. After the addition was completed, the reaction was kept at the temperature for another 5 hours. After cooling, isocyanate-terminated polyester polyol was obtained.

[0092] (3) Preparation of polyurethane adhesives

[0093] The polyurethane adhesive is prepared by mixing 100 parts by weight of the hydroxyl-terminated polyurethane prepared above and 20 parts by weight of the isocyanate-terminated polyester polyol prepared above evenly.

[0094] Comparative Example 2

[0095] (1) Preparation of branched liquid rubber polyols

[0096] 100 parts by mass of liquid rubber diol were added to a four-necked flask equipped with a stirrer, thermometer and condenser, and heated to 60°C. Then 2.1 parts by mass of hexamethylene diisocyanate trimer were added dropwise over 2 hours. After the addition was complete, the reaction was continued at the temperature for 3 hours to obtain branched liquid rubber polyol.

[0097] (2) Preparation of branched liquid rubber polyol-polyether-branched liquid rubber polyol polyurethane copolymer

[0098] 100 parts by mass of isophorone diisocyanate were added to a four-necked flask equipped with a stirrer, thermometer and condenser. The mixture was heated to 60°C and 900 parts by mass of polyoxypropylene diol with a molecular weight of 4000 were added dropwise over 1 hour. After the addition was completed, the mixture was kept at the temperature for another 3 hours to obtain isocyanate-terminated polyether diol oligomer.

[0099] Next, 900 parts by mass of the branched liquid rubber polyol prepared above were slowly added dropwise over 1 hour. After the addition was complete, the reaction was continued at a constant temperature for 3 hours. After cooling, the branched liquid rubber polyol-polyether-branched liquid rubber polyol polyurethane copolymer was obtained.

[0100] (3) Preparation of high-temperature resistant hydrolyzable polyester polyols

[0101] Add 67 parts by mass of terephthalic acid, 33 parts by mass of isophthalic acid, and 80 parts by mass of 1,4-cyclohexanediethanol to a four-necked flask equipped with a stirrer, thermometer, and condenser. Heat to 160°C and carry out an esterification and dehydration reaction for 5 hours. Then raise the temperature to 210°C and carry out a vacuum polycondensation reaction for 6 hours. Cool to room temperature to obtain a high-temperature resistant hydrolyzable polyester polyol.

[0102] (4) Preparation of isocyanate-terminated high-temperature hydrolyzable polyester polyols

[0103] 100 parts by mass of isophorone diisocyanate were added to a four-necked flask equipped with a stirrer, thermometer and condenser and heated to 60°C. 225 parts by mass of the high-temperature resistant hydrolyzable polyester polyol prepared above were added dropwise over 1 hour. After the addition was completed, the reaction was kept at the temperature for 5 hours. After cooling, the isocyanate-terminated high-temperature resistant hydrolyzable polyester polyol was obtained.

[0104] (5) Preparation of polyurethane adhesives

[0105] The polyurethane adhesive of this comparative example is prepared by mixing 100 parts by mass of the branched liquid rubber polyol-polyether-branched liquid rubber polyol polyurethane copolymer prepared above, 3 parts by mass of 2-hydroxy-2-methyl-1-phenyl-1-propanone (1173) ultraviolet initiator, and 20 parts by mass of the isocyanate-terminated high-temperature hydrolyzable polyester polyol prepared above evenly.

[0106] Performance testing

[0107] Preparation of peel strength test samples: Polyurethane adhesive was uniformly coated onto a 200mm×200mm nylon film, which was then stacked with an aluminum foil of the same size. The film was cured at 45±1℃ for 24 hours and subjected to light intensity of 100mW / cm². 2 After being irradiated with 365nm ultraviolet light for 30s, the samples were cut into 200mm×15mm pieces for peel strength testing.

[0108] Preparation of deep-drawing test samples: Polyurethane adhesive was uniformly coated onto a 200mm×200mm nylon film, which was then stacked with an aluminum foil of the same size. The film was cured at 45±1℃ for 24 hours and subjected to light intensity of 100mW / cm². 2 The deep-drawing test sample was obtained after irradiation with 365nm ultraviolet light for 30s.

[0109] 1. Yellowing resistance test

[0110] The polyurethane adhesive was uniformly applied to a polytetrafluoroethylene (PTFE) board and cured at 45±1℃ for 24 hours, followed by exposure to light intensity of 100mW / cm². 2 Irradiate with 365nm ultraviolet light for 30s to obtain a thin film sample with a thickness of 0.1-0.2 mm. Irradiate with a 1KW ultraviolet lamp for 15 minutes and measure according to GB / T1766-2008 standard.

[0111] 2. Peel strength at room temperature

[0112] According to the national standard GB / T 2791-1995, the peel strength was tested at 25±1℃ using a CMT microcomputer-controlled electronic universal tensile testing machine.

[0113] 3. Peel strength after boiling

[0114] The peel strength was tested at 25 ± 1 °C using a CMT microcomputer-controlled electronic universal tensile testing machine in accordance with GB / T 2791-1995.

[0115] 4. High-temperature peel strength

[0116] The peel strength was tested at 100 ± 1 °C using a CMT microcomputer-controlled electronic universal tensile testing machine in accordance with GB / T 2791-1995.

[0117] 5. Peel strength after thermal aging

[0118] The prepared peel strength test samples were thermally aged at 120 ± 1 °C for 120 hours, then placed at 25 ± 1 °C for 24 hours, and the peel strength was tested at 25 ± 1 °C using a CMT microcomputer-controlled electronic universal tensile testing machine in accordance with GB / T 2791-1995.

[0119] 6. Peel strength after damp heat aging

[0120] The prepared peel strength test samples were damp heat aged at a temperature of 85 ± 1 °C and a relative humidity of 85 ± 5% for 120 hours, then placed at 25 ± 1 °C for 24 hours, and the peel strength was tested at 25 ± 1 °C using a CMT microcomputer-controlled electronic universal tensile testing machine in accordance with GB / T 2791-1995.

[0121] 7. Deep drawing depth

[0122] The stamping die was 80 mm * 40 mm, with a maximum depth of 20 mm and an impact pressure of 0.7 MPa. When punching the shell 20 times continuously at a certain depth without any tearing or breakage of the aluminum filling or delamination of the aluminum-plastic film, it indicated that the nylon / aluminum foil adhesive layer passed the test at this punching depth. The maximum qualified impact depth of each sample was recorded as the deep drawing depth.

[0123] The test results of the products of Examples 1-3 and Comparative Examples 1-2 are shown in Table 1 below:

[0124]

[0125] Table 1

[0126] As shown in Table 1, after lamination and curing, the peel strength at room temperature, peel strength at high temperature, peel strength after heat aging, peel strength after damp heat aging, and deep drawing depth of Examples 1-3 are all significantly improved compared to Comparative Examples 1-2. The applicant analyzes that this is because the specific polyurethane segments with the structure of "high-temperature resistant hydrolyzed polyester - branched liquid rubber polyol - polyether - branched liquid rubber polyol - high-temperature resistant hydrolyzed polyester" were prepared by molecular design. Different polyurethane segments with different structures play their respective roles and have a synergistic effect. The high molecular weight ultraviolet photoinitiator can avoid low molecular weight residues and has good compatibility with block polyurethane segments. At the same time, under ultraviolet light, the liquid rubber undergoes a cross-linking reaction, which further improves the high-temperature resistance. The peel strength under all conditions is significantly improved, and the deep drawing depth reaches more than 8.8 mm.

[0127] In addition, to make a more intuitive comparison of product performance, Figure 1 and Figure 2 Images of deep-drawn samples (lithium-ion battery packaging) prepared with the adhesives of Example 1 and Comparative Example 1, after being aged at 120°C for 24 hours following deep drawing, are presented. As can be seen from the images, the deep-drawn sample of Example 1 remains intact, while the deep-drawn sample of Comparative Example 1 exhibits significant wrinkles, bulges, and cracks due to its poor peel strength and aging resistance. This demonstrates that the polyurethane adhesive of the present invention is more suitable for lithium-ion battery packaging, and the product exhibits outstanding deep-drawing resistance and high-temperature resistance.

[0128] In summary, the deep-drawing and high-temperature resistant block polyurethane adhesive produced by this invention has excellent performance, good system compatibility, fast curing speed, high production efficiency, is easy to industrialize, and has a wide range of applications. The entire process does not release toxic solvents, making it a non-toxic and pollution-free environmentally friendly adhesive.

[0129] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any way, and all technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A deep-drawing and high-temperature resistant block polyurethane adhesive for lithium-ion battery packaging, characterized in that, It is prepared by uniformly mixing the following components in the indicated weight proportions: 100 parts of branched liquid rubber polyol-polyether-branched liquid rubber polyol polyurethane copolymer; 3-5 parts of high molecular weight ultraviolet photoinitiator; 20-35 parts isocyanate-capped high-temperature hydrolyzable polyester polyol; The branched liquid rubber polyol-polyether-branched liquid rubber polyol polyurethane copolymer is first prepared by liquid rubber diol to obtain branched liquid rubber polyol, then by polyisocyanate and polyether diol to obtain isocyanate-terminated polyether diol oligomer, and finally the branched liquid rubber polyol-polyether-branched liquid rubber polyol polyurethane copolymer is obtained. The high molecular weight ultraviolet photoinitiator is prepared by modifying a low molecular weight ultraviolet photoinitiator containing hydroxyl groups; The isocyanate-terminated high-temperature hydrolyzable polyester polyol is prepared by reacting polyisocyanate with high-temperature hydrolyzable polyester polyol, and the high-temperature hydrolyzable polyester polyol is prepared by esterification and dehydration reaction of aromatic dicarboxylic acid and flexible polyol.

2. The preparation method of the deep-drawing and high-temperature resistant block polyurethane adhesive for lithium-ion battery packaging as described in claim 1, characterized in that, Includes the following steps: S1. Preparation of branched liquid rubber polyol: Add 100 parts by mass of liquid rubber diol to a reaction vessel, heat to 60-90℃, and then add isocyanate trimer dropwise at a molar ratio of -NCO / -OH of 0.1-0.3 for 1-2 hours. After the isocyanate trimer is completely added, continue to keep the temperature for 1-3 hours to obtain branched liquid rubber polyol. S2. Preparation of branched liquid rubber polyol-polyether-branched liquid rubber polyol polyurethane copolymer: Add 100 parts by mass of polyisocyanate to the reaction vessel, heat to 60-90℃, and then add polyether diol dropwise at a molar ratio of -NCO / -OH for 1-2 hours. After the polyether diol is completely added, continue to keep the temperature and react for 1-3 hours to obtain isocyanate-terminated polyether diol oligomers. Next, slowly add 100% of the remaining isocyanate content of the branched liquid rubber polyol obtained in step S1 above, over 1-2 hours. After the addition is complete, continue the reaction at a constant temperature for 3-5 hours. Cool to obtain the branched liquid rubber polyol-polyether-branched liquid rubber polyol polyurethane copolymer. S3. Preparation of high molecular weight ultraviolet photoinitiator: Add 100 parts by mass of polyisocyanate to the reaction vessel, heat to 60-90℃, and then add polyether diol dropwise at a molar ratio of -NCO / -OH for 1-2 hours. After the polyether diol is completely added, continue to keep the temperature and react for 1-3 hours to obtain isocyanate-terminated polyether diol oligomers. Next, slowly add 100% of the remaining isocyanate content of the low molecular weight hydroxyl-containing UV photoinitiator, continue the reaction at the temperature for 3-5 hours, and then cool to obtain the high molecular weight UV photoinitiator. S4. Preparation of high-temperature resistant hydrolyzable polyester polyols: Add 100 parts by mass of aromatic dicarboxylic acid and 80-90 parts by mass of flexible polyol to a reaction vessel, heat to 160-190℃, carry out esterification and dehydration reaction for 3-5 hours, then raise the temperature to 210-230℃, carry out vacuum polycondensation reaction for 4-6 hours, and cool to room temperature to obtain high temperature resistant hydrolyzable polyester polyol. S5. Preparation of isocyanate-terminated high-temperature hydrolyzable polyester polyols: Add 100 parts by mass of polyisocyanate to the reaction vessel, heat to 60-90℃, and then add the high-temperature resistant hydrolyzed polyester polyol prepared in step S4 above dropwise at a molar ratio of -NCO / -OH of 2. Add the dropwise polyol for 1-2 hours, and after the dropwise addition is complete, continue to keep the reaction at the temperature for 3-5 hours. Cool to obtain isocyanate-terminated high-temperature resistant hydrolyzed polyester polyol. S6. Preparation of deep-drawing and high-temperature resistant block polyurethane adhesives: 100 parts by weight of the branched liquid rubber polyol-polyether-branched liquid rubber polyol polyurethane copolymer obtained in step S2 above, 3-5 parts by weight of the high molecular weight ultraviolet photoinitiator obtained in step S3 above, and 20-35 parts by weight of the isocyanate-terminated high-temperature hydrolyzable polyester polyol obtained in step S5 above are mixed evenly to obtain a deep-drawing and high-temperature resistant block structure polyurethane adhesive.

3. The preparation method of the deep-drawing and high-temperature resistant block structure polyurethane adhesive for lithium-ion battery packaging according to claim 2, characterized in that, The reaction vessel is a four-necked flask equipped with a stirrer, thermometer, and condenser.

4. The preparation method of the deep-drawing and high-temperature resistant block structure polyurethane adhesive for lithium-ion battery packaging according to claim 2, characterized in that, The liquid rubber diol is one of liquid polybutadiene diol and liquid polyisoprene diol.

5. The preparation method of the deep-drawing and high-temperature resistant block polyurethane adhesive for lithium-ion battery packaging according to claim 2, characterized in that, The isocyanate trimer is one of isophorone diisocyanate trimer and hexamethylene diisocyanate trimer.

6. The deep-drawing and high-temperature resistant block polyurethane adhesive according to claim 1, characterized in that, The polyisocyanate is one of isophorone diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and lysine diisocyanate.

7. The deep-drawing and high-temperature resistant block polyurethane adhesive according to claim 1, characterized in that, The polyether diol is one of polypropylene oxide diol, polyethylene oxide propylene diol, and polytetrahydrofuran diol; the molecular weight of the polyether diol is 4000-6000.

8. The deep-drawing and high-temperature resistant block polyurethane adhesive according to claim 1, characterized in that, The aromatic dicarboxylic acid is a mixture of phthalic acid and isophthalic acid, wherein the mass ratio of phthalic acid to isophthalic acid is 100:50-150.

9. The deep-drawing and high-temperature resistant block polyurethane adhesive according to claim 1, characterized in that, The flexible polyol is one of diethylene glycol, triethylene glycol, tetraethylene glycol, isopentyl glycol, 1,6-hexanediol, and 1,4-cyclohexanediol.

10. The deep-drawing and high-temperature resistant block polyurethane adhesive according to claim 1, characterized in that, The hydroxyl-containing low molecular weight ultraviolet photoinitiator is one of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxy-cyclohexyl-phenyl ketone, 1,1'-(methylenedi-4,1-phenylene)bis[2-hydroxy-2-methyl-1-propanone], and 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylpropanone.

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