Polyester-based two-component solventless polyurethane adhesive, preparation method and application thereof

Abstract

This invention belongs to the field of polyurethane adhesive technology, specifically relating to a polyester-based two-component solvent-free polyurethane adhesive, its preparation method, and its application. The adhesive comprises two parts: component A and component B. Component A consists of polyester polyol 1, a chain extender, and a silane coupling agent. Polyester polyol 1 is prepared from a small-molecule polyol and a small-molecule polyacid, wherein the small-molecule polyacid is a dimer acid and isophthalic acid. Component B consists of polyester polyol 2 and isocyanate. Polyester polyol 2 is prepared from a small-molecule polyol, a dimer acid, and lauric acid. The adhesive of this invention has low viscosity, good ink compatibility, good low-temperature flexibility, and can withstand high-temperature cooking at 121°C. This invention also provides its preparation method and application, suitable for bonding PE, PET, OPP, VMPET, aluminum foil, RCPP, and PA films.

Description

Technical Field

[0001] This invention belongs to the field of polyurethane adhesive technology, specifically relating to a polyester-based two-component solvent-free polyurethane adhesive, its preparation method, and its application. Background Technology

[0002] Two-component solvent-free polyurethane adhesives are gradually replacing solvent-based polyurethane adhesives as the mainstream in the flexible packaging industry due to their advantages such as environmental friendliness, energy saving, safety, and high efficiency. Polyester-based two-component solvent-free polyurethane adhesives have high bonding strength, fast curing speed, and moderate coefficient of friction, but their viscosity is usually high. Furthermore, they exhibit a similarity-to-miscibility phenomenon ("ink dissolution") with polyurethane inks commonly used in flexible packaging due to their similar polarity. This often results in appearance defects caused by the dissolution of the ink layer during the lamination process, specifically manifested as darkening of white or light-colored ink areas, or blurring or fading of lines in colored areas. Polyether-based adhesives typically have lower viscosity, good low-temperature flexibility, and excellent hydrolysis resistance, but their bonding strength is not as good as polyester-based adhesives, and they absorb slip agents from the film, leading to an abnormally high coefficient of friction.

[0003] Chinese patent CN 115678477 A discloses a two-component solvent-free polyurethane laminating adhesive and its preparation method. Through the design of the A and B component formulations, particularly the structural design of different polyester polyols, the resulting B component exhibits high viscosity and good initial tack, meeting the requirements for retorting in aluminum-plastic structures. However, this solvent-free two-component polyurethane laminating adhesive has a viscosity between 30,000 and 120,000 mPa·s at 25°C and between 300 and 1400 mPa·s at 65°C, requiring a coating temperature of approximately 65°C. This high viscosity increases the requirements for adhesive application, necessitating higher application temperatures and affecting the adhesive's working time.

[0004] Chinese patent CN 114736645 A discloses a solvent-free two-component polyurethane laminating adhesive with yellowing resistance, its preparation method and application. The laminating adhesive can meet the requirement of 121℃ boiling resistance. Its high temperature resistance is achieved by using aromatic small molecule diacid as the main small molecule acid. While the adhesive improves the temperature resistance, the viscosity increases. At the same time, the large number of benzene ring structures in the system leads to a decrease in its low temperature resistance and a narrowing of the product's applicability. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a polyester-based two-component solvent-free polyurethane adhesive with low viscosity, good ink compatibility, good low-temperature flexibility, and resistance to high-temperature cooking at 121°C.

[0006] Another object of the present invention is to provide a method for preparing and applying a polyester-based two-component solvent-free polyurethane adhesive.

[0007] The technical solution adopted in this invention is as follows:

[0008] The polyester-type two-component solvent-free polyurethane adhesive comprises component A and component B, wherein the weight ratio of component A to component B is 1:(1.3-1.5).

[0009] Component A is the hydroxyl component, which, by weight, is composed of the following raw materials:

[0010] Polyester polyol 1: 95-97 parts;

[0011] Chain extender: 2-4 parts;

[0012] Silane coupling agent: 0.5-1 part;

[0013] The polyester polyol has a hydroxyl value of 150-200 mg KOH / g and is prepared from small molecule polyols and small molecule polyacids. The small molecule polyols include multi-side group small molecule polyols and other small molecule polyols, with the molar amount of multi-side group small molecule polyols accounting for more than 70% of the total molar amount of small molecule polyols. The multi-side group small molecule polyols are one or more of neopentyl glycol, trimethylpentyl glycol, and 2-ethyl-2-methyl-1,3-propanediol. The other small molecule polyols are one or more of methylpropanediol, 1,2-propanediol, 1,4-butanediol, 1,6-hexanediol, glycerol, and trimethylolpropane. The small molecule polyacids are dimer acids and isophthalic acid, with the molar amount of isophthalic acid accounting for 10-20% of the total molar amount of small molecule polyacids.

[0014] When the proportion of multi-side group small molecule polyols is above 70%, the compatibility of the adhesive with different types of inks will be greatly improved, and ink dissolution will not occur due to insufficient compatibility between the adhesive and the ink. If the proportion of multi-side group small molecule polyols is below 70%, the adhesive is prone to dissolving the ink when using certain inks, such as white inks, resulting in a blurry, unclear, or show-through printed pattern.

[0015] When isophthalic acid is used as an auxiliary means to improve the heat resistance of adhesives, if the amount added is less than 10%, the effect is limited and insufficient to significantly improve the heat resistance of the adhesive; if it is more than 20%, it will cause the viscosity of the adhesive to increase significantly, which is not conducive to the application of the adhesive.

[0016] Component B is an isocyanate component with an -NCO content of 15-18%. By weight, the isocyanate component is composed of the following raw materials:

[0017] Polyester polyol 2: 30-50 parts;

[0018] Isocyanate: 50-70 parts;

[0019] The polyester polyol has a hydroxyl value of 120-150 mg KOH / g and is prepared from small molecule polyols, dimer acids, and lauric acid. The small molecule polyols include difunctional and trifunctional small molecule polyols, with the molar amount of trifunctional small molecule polyols accounting for 3-6% of the total molar amount of small molecule polyols. The molar amount of lauric acid is 10-20% of the total molar amount of dimer acids and lauric acid.

[0020] Trifunctional small molecule polyols are the main means of improving the crosslinking degree of adhesives. If the proportion of trifunctional small molecule alcohols is too low (below 3%), the effect of improving the crosslinking degree will not be obvious, and it will be difficult to improve the initial tack of the adhesive and the crosslinking strength of the adhesive after final curing. If the proportion is too high (>6%), it will lead to a significant increase in the viscosity of the adhesive, which is not conducive to the application of the adhesive.

[0021] Lauric acid has a unique structure and mainly plays a role in reducing the viscosity of the polyester polyol chain. Adding more than 10% will have a significant effect on reducing viscosity. However, if the amount added is too high (above 20%), it will affect the final performance of the adhesive and reduce the bonding strength.

[0022] Difunctional small molecule polyols are one or more of the following: neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, methylpropanediol, 1,2-propanediol, ethylene glycol, and diethylene glycol.

[0023] Trifunctional small molecule polyols are one of trimethylolpropane and glycerol.

[0024] The chain extender is one of diisopropanolamine, triisopropanolamine, and triethanolamine, preferably diisopropanolamine.

[0025] The silane coupling agent is one of γ-glycidoxypropyltrimethoxysilane (KH-560), γ-aminopropyltriethoxysilane (KH-550), and γ-methacryloyloxypropyltrimethoxysilane (KH-570), with γ-glycidoxypropyltrimethoxysilane (KH-560) being preferred.

[0026] The isocyanate is one or both of diphenylmethane diisocyanate and carbodiimide-modified diphenylmethane diisocyanate.

[0027] Preferably, the isocyanate is a mixture of diphenylmethane diisocyanate and carbodiimide-modified diphenylmethane diisocyanate in a mass ratio of (3.4-3.6):1.

[0028] The preparation method of the polyester-based two-component solvent-free polyurethane adhesive of the present invention includes the following steps:

[0029] (1) Preparation method of component A: Small molecule polyacid and small molecule polyol are fed into the reaction vessel, heated to 225-235℃ and reacted for 6-8h. After the hydroxyl value is qualified, the temperature is lowered to 55-65℃, silane coupling agent and chain extender are added, and after stirring evenly, component A is obtained.

[0030] (2) Preparation method of component B: Dimer acid, lauric acid and small molecule polyol are added to the reaction vessel, heated to 225-235℃ and reacted for 6-8h. After the hydroxyl value is qualified, the temperature is lowered to 40-45℃, isocyanate is added, and the temperature is raised to 75-80℃ and reacted for 3-4h. The -NCO content is tested and qualified to obtain component B.

[0031] (3) Preheat components A and B to 35-40℃ respectively, mix them evenly, and then apply the adhesive.

[0032] Preferably, in steps (1) and (2), the heating rate to 230°C is 20°C / h.

[0033] The polyester-based two-component solvent-free polyurethane adhesive described in this invention is used for bonding PE, PET, OPP, VMPET, aluminum foil, RCPP, and PA films.

[0034] The bonding process is cured under the following conditions: 35-50℃ for 24-72 hours. Preferably, the curing temperature is 42.5±2.5℃.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] (1) In this invention, a dimer acid containing long-chain aliphatic alkane segments is selected as the main small molecule acid, supplemented with an appropriate amount of isophthalic acid containing a benzene ring structure to synthesize polyester polyol, and the hydroxyl component of the two-component polyurethane adhesive is constructed mainly from it. The introduction of long-chain aliphatic alkane segments can effectively reduce the viscosity of the system, improve its coating fluidity, and facilitate uniform coating of the adhesive.

[0037] (2) The polyurethane adhesive obtained by this invention contains three structural components in its molecular chain: long-chain aliphatic alkane segments, branched small-molecule polyol segments, and lauric acid segments. This allows the adhesive to possess both good flexibility and a certain degree of steric hindrance, thereby improving the hydrolysis resistance and flexibility of the chain segments and thus enhancing the heat resistance stability of the adhesive. Furthermore, by introducing a small amount of rigid benzene ring structures, the heat resistance of the material is further improved, meeting the requirements for high-temperature applications.

[0038] (3) The molecular chain structure of the polyurethane adhesive prepared by the present invention is significantly different from that of the ink binder. While ensuring the bonding performance, it avoids the "ink dissolution" problem that is easy to occur in traditional polyester polyurethane adhesives, and the material has a wider range of applicability. Detailed Implementation

[0039] The present invention will be further described below with reference to the embodiments, but these embodiments do not limit the implementation of the present invention.

[0040] Unless otherwise specified, the raw materials used in the examples and comparative examples are all commercially available materials, and the process methods used in the examples and comparative examples are all conventional methods in the art.

[0041] The following is a description of some of the raw materials used in the examples and comparative examples:

[0042] Trimethylpentanediol, Guangzhou Yuanda New Materials Co., Ltd.;

[0043] Lauric acid, Nantong Zhonghe Chemical New Materials Co., Ltd.;

[0044] Neopentyl glycol, Wanhua Chemical Group;

[0045] 1,6-Hexanediol, Yuanli Chemical Group Co., Ltd.;

[0046] Diethylene glycol, Lianyungang Petrochemical Co., Ltd.;

[0047] Trimethylolpropane, Chifeng Ruiyang Chemical Co., Ltd.;

[0048] Diphenylmethane diisocyanate (MDI-50), Wanhua Chemical Group;

[0049] Carbodiimide-modified diphenylmethane diisocyanate (CD-C), Covestro Polymers (China) Co., Ltd.;

[0050] Dimeric acid, Linyi Daming Bioenergy Co., Ltd.;

[0051] Adipic acid, Shandong Hualu Hengsheng Group Co., Ltd.;

[0052] isophthalic acid, Beijing Yanshan Jilian Petrochemical Co., Ltd.;

[0053] 2-Ethyl-2-methyl-1,3-propanediol, Shanghai Mairui Biochemical Technology Co., Ltd.

[0054] Example 1

[0055] The preparation method of the polyester-based two-component solvent-free polyurethane adhesive comprises the following specific steps:

[0056] (1) Preparation of component A: 776g dimer acid, 26g isophthalic acid, 216g neopentyl glycol, 72g methyl propylene glycol, and 12g trimethylolpropane were added to a reaction vessel and heated to 230℃ at a heating rate of 20℃ / h for 8h to obtain 1024g of polyester polyol with a hydroxyl value of 150mgKOH / g. The temperature was lowered to 60℃, and 43g diisopropanolamine and 10.4g KH-560 were added and stirred evenly to obtain component A.

[0057] (2) Preparation of component B: 800g dimer acid, 72g lauric acid, 152g neopentyl glycol, 152g methyl propylene glycol and 26.4g trimethylolpropane were added to the reactor and heated to 230℃ at a heating rate of 20℃ / h for 6h to obtain 1104g polyester polyol with a hydroxyl value of 150mgKOH / g. The temperature was lowered to 40℃ and 1328g MDI-50 and 376g CD-C were added. The temperature was slowly raised to 75℃ for 3h to obtain component B with a -NCO content of 15%.

[0058] (3) Component A and Component B are coated with adhesive at a mass ratio of 1:1.5 and various properties are tested.

[0059] Example 2

[0060] The preparation method of the polyester-based two-component solvent-free polyurethane adhesive comprises the following specific steps:

[0061] (1) Preparation of component A: 744g dimer acid, 55g isophthalic acid, 224g neopentyl glycol, 80g trimethylpentyl glycol, 64g 1,6-hexanediol and 13.6g trimethylolpropane were added to a reaction vessel and heated to 225℃ at a heating rate of 20℃ / h for 6h to obtain 1080g polyester polyol with a hydroxyl value of 180mgKOH / g. The temperature was lowered to 65℃ and 22.4g triisopropanolamine and 5.6g KH-570 were added and stirred evenly to obtain component A.

[0062] (2) Preparation of component B: 800g dimer acid, 36g lauric acid, 208g diethylene glycol, 104g methyl propylene glycol and 12.8g trimethylolpropane were added to the reactor and heated to 225℃ at a heating rate of 20℃ / h for 7h to obtain 1080g polyester polyol with a hydroxyl value of 120mgKOH / g. The temperature was lowered to 45℃ and 1608g MDI-50 and 456g CD-C were added. The temperature was slowly raised to 75℃ for 4h to obtain component B with a -NCO content of 18%.

[0063] (3) Component A and Component B are coated with adhesive at a mass ratio of 1:1.4 and various properties are tested.

[0064] Example 3

[0065] The preparation method of the polyester-based two-component solvent-free polyurethane adhesive comprises the following specific steps:

[0066] (1) Preparation of component A: 776g dimer acid, 26g isophthalic acid, 137g neopentyl glycol, 156g 2-ethyl-2-methyl-1,3-propanediol, and 78g 1,6-hexanediol were added to a reaction vessel and heated to 235℃ at a heating rate of 20℃ / h for 7h to obtain 1080g of polyester polyol with a hydroxyl value of 170mgKOH / g. The temperature was lowered to 55℃, and 25.1g triethanolamine and 11.2g KH-550 were added and stirred evenly to obtain component A.

[0067] (2) Preparation of component B: 800g dimer acid, 64g lauric acid, 208g diethylene glycol, 136g neopentyl glycol and 12g glycerol were added to the reaction vessel and heated to 235℃ at a heating rate of 20℃ / h for 8h to obtain 1120g polyester polyol with a hydroxyl value of 130mgKOH / g. The temperature was lowered to 40℃ and 1344g MDI-50 and 392g CD-C were added. The temperature was slowly raised to 80℃ for 3h to obtain component B with a -NCO content of 16%.

[0068] (3) Component A and Component B are coated with adhesive at a mass ratio of 1:1.3 and various properties are tested.

[0069] Comparative Example 1

[0070] The specific steps for preparing the two-component solvent-free polyurethane adhesive are as follows:

[0071] (1) Preparation of component A: 800g adipic acid, 471g neopentyl glycol, 296g methyl propylene glycol and 30g trimethylolpropane were added to a reaction vessel and heated to 230℃ at a heating rate of 20℃ / h for 8h to obtain 1320g polyester polyol with a hydroxyl value of 150mgKOH / g. The temperature was lowered to 60℃ and 55.5g diisopropanolamine and 13.6g KH-560 were added and stirred evenly to obtain component A.

[0072] (2) Component B is the same as component B in Example 1;

[0073] (3) Component A and Component B are coated with adhesive at a mass ratio of 1:1.5 and various properties are tested.

[0074] Comparative Example 2

[0075] The specific steps for preparing the two-component solvent-free polyurethane adhesive are as follows:

[0076] (1) Component A is the same as component A in Example 1;

[0077] (2) Preparation of component B: 800g dimer acid, 160g lauric acid, 155g neopentyl glycol, 155g methyl propylene glycol and 27.3g trimethylolpropane were added to the reactor and heated to 230℃ at a heating rate of 20℃ / h for 7h to obtain 1000g polyester polyol with a hydroxyl value of 150mgKOH / g. After cooling to 40℃, 1200g MDI-50 and 340g CD-C were added and the temperature was slowly raised to 75℃ for 2h to obtain component B with a -NCO content of 15%.

[0078] (3) Component A and Component B are coated with adhesive at a mass ratio of 1:1.5 and various properties are tested.

[0079] Comparative Example 3

[0080] The specific steps for preparing the two-component solvent-free polyurethane adhesive are as follows:

[0081] (1) Preparation of component A: 800g adipic acid, 120g isophthalic acid, 896g diethylene glycol and 40g trimethylolpropane were added to a reaction vessel and heated to 230℃ at a heating rate of 20℃ / h for 6h to obtain 1520g polyester polyol with a hydroxyl value of 150mgKOH / g. The temperature was lowered to 60℃ and 64g diisopropanolamine and 16g KH-560 were added and stirred evenly to obtain component A.

[0082] (2) Preparation of component B: 800g adipic acid, 120g isophthalic acid, 384g neopentyl glycol, 384g methyl propylene glycol and 68g trimethylolpropane were added to the reactor and heated to 230℃ at a heating rate of 20℃ / h for 7h to obtain 1440g polyester polyol with a hydroxyl value of 150mgKOH / g. After cooling to 40℃, 1728g MDI-50 and 408g CD-C were added and the temperature was slowly raised to 75℃ for 2h to obtain component B with a -NCO content of 15%.

[0083] (3) Component A and Component B are coated with adhesive at a mass ratio of 1:1.5 and various properties are tested.

[0084] Comparative Example 4

[0085] The specific steps for preparing the two-component solvent-free polyurethane adhesive are as follows:

[0086] Preparation of Component A: 776g dimer acid, 26g isophthalic acid, 154g neopentyl glycol, 157g diethylene glycol, and 12g trimethylolpropane were added to a reaction vessel and heated to 230℃ at a heating rate of 20℃ / h for 8h to obtain 1024g of polyester polyol with a hydroxyl value of 150mgKOH / g. The temperature was then lowered to 60℃, and 43g diisopropanolamine and 10.4g KH-560 were added and stirred until homogeneous to obtain Component A.

[0087] Preparation of Component B: 800g of dimer acid, 72g of lauric acid, 138g of neopentyl glycol, 138g of methyl propylene glycol, and 42g of trimethylolpropane were added to a reaction vessel and heated to 230℃ at a heating rate of 20℃ / h for 6 hours to obtain 1090g of polyester polyol with a hydroxyl value of 150mgKOH / g. The temperature was then lowered to 40℃, and 1312g of MDI-50 and 372g of CD-C were added. The temperature was slowly raised to 75℃ for 2 hours to obtain Component B with a -NCO content of 15%.

[0088] Comparative Example 5

[0089] The specific steps for preparing the two-component solvent-free polyurethane adhesive are as follows:

[0090] Preparation of Component A: 776g of dimer acid, 99g of isophthalic acid, 253g of neopentyl glycol, 85g of methyl propylene glycol, and 14g of trimethylolpropane were added to a reaction vessel and heated to 230℃ at a heating rate of 20℃ / h for 8h to obtain 1150g of polyester polyol with a hydroxyl value of 150mgKOH / g. The temperature was then lowered to 60℃, and 48g of diisopropanolamine and 11.7g of KH-560 were added and stirred until homogeneous to obtain Component A.

[0091] Component B is the same as the component B used in Example 1.

[0092] Preparation of solvent-free composite film: Preheat components A and B to 40℃, mix them evenly according to the weight ratio, and then apply adhesive. VMPET film and PE film are selected for adhesive application. After adhesive application, cure at 42.5±2.5℃ for 24-72h.

[0093] Ink dissolution test: After mixing components A and B evenly, apply the mixture to a PET substrate printed with white ink. Place the substrate at 40°C for 15 minutes, then gently wipe it with a paper towel and observe the appearance of the substrate.

[0094] Ink-insoluble: After wiping, the ink on the substrate surface does not peel off, darken, or show through; the printed pattern has a clear outline and no blurring.

[0095] Slight ink dissolution: After wiping, the ink surface shows a very slight change in gloss, with no obvious peeling, no blurring at the edges of the printed pattern, and the area of ​​ink showing through is ≤5%;

[0096] Ink dissolution: After wiping, the ink comes off, becomes noticeably darker, or the area of ​​ink showing through is greater than 5%, or the outline of the printed pattern becomes blurred or blurred.

[0097] Peel strength test: The peel strength of the composite film was tested according to GB / T 8808-1988, and the maximum peel strength of each comparative example and embodiment was tested every 24 hours.

[0098] Boiling resistance test: The cured film was boiled at 121°C for 30 minutes, and then the peel strength test was performed.

[0099] Test data are shown in Tables 1-5.

[0100] Table 1. Viscosity data of each component A in Examples 1-3 and Comparative Examples 1-5

[0101]

[0102] In the table above, " / " indicates that it was not tested.

[0103] Table 2 Viscosity data of each component B in Examples 1-3 and Comparative Examples 1-5

[0104]

[0105] In the table above, " / " indicates that it was not tested.

[0106] Table 3. Variation of peel strength with curing time in Examples 1-3 and Comparative Examples 1-5

[0107]

[0108] Table 4 Peel strength test data for Examples 1-3 and Comparative Examples 1-5

[0109]

[0110] Table 5 Ink dissolution tests of Examples 1-3 and Comparative Examples 1-5

[0111]

[0112] Based on the comparison of the data in the table above, the following conclusions can be drawn:

[0113] 1. As can be seen from Example 1 and Comparative Examples 1, 3 and 4, when the proportion of multi-side group small molecule polyols in component A is more than 70%, the polyester-type two-component solvent-free adhesive has good compatibility with ink and does not cause ink dissolution.

[0114] 2. As can be seen from Example 1 and Comparative Example 2, the addition of lauric acid will significantly reduce the viscosity of component B. However, if the amount added is too high, it will have a significant impact on the peel strength. The optimal addition range is 10-20%, which balances viscosity and performance.

[0115] 3. As can be seen from Example 1 and Comparative Example 3, dimer acid has significantly better heat resistance than conventional adipic acid raw materials.

[0116] 4. As can be seen from Example 1 and Comparative Examples 1, 3 and 5, increasing the amount of isophthalic acid added can improve the adhesive's resistance to boiling. However, if the amount added is too high, the viscosity will increase sharply, which is not conducive to construction. Considering both performance and viscosity, 10-20% is selected as the optimal amount of isophthalic acid added.

[0117] 5. As can be seen from Example 1 and Comparative Example 4, increasing the amount of trifunctional small molecule polyol in component B improves the heat resistance, but also significantly increases the viscosity. 3-6% is the optimal addition amount.

[0118] In summary, this invention solves the ink dissolution problem by specially designing the polyester polyol structure; when using a combination of dimer acid and lauric acid, the viscosity can be significantly reduced without affecting the strength; compared with the traditional adipic acid and isophthalic acid system, the dimer acid system adhesive of this invention has better low-temperature fluidity, and thus better low-temperature flexibility.

Claims

1. A polyester-based two-component solvent-free polyurethane adhesive, characterized in that, It includes component A and component B, with a weight ratio of component A to component B of 1:(1.3-1.5). Component A is the hydroxyl component, which, by weight, is composed of the following raw materials: Polyester polyol 1: 95-97 parts; Chain extender: 2-4 parts; Silane coupling agent: 0.5-1 part; The polyester polyol has a hydroxyl value of 150-200 mg KOH / g and is prepared from small molecule polyols and small molecule polyacids. The small molecule polyols include multi-side group small molecule polyols and other small molecule polyols, with the molar amount of multi-side group small molecule polyols accounting for more than 70% of the total molar amount of small molecule polyols. The multi-side group small molecule polyols are one or more of neopentyl glycol, trimethylpentyl glycol, and 2-ethyl-2-methyl-1,3-propanediol. The other small molecule polyols are one or more of methylpropanediol, 1,2-propanediol, 1,4-butanediol, 1,6-hexanediol, glycerol, and trimethylolpropane. The small molecule polyacids are dimer acids and isophthalic acid, with the molar amount of isophthalic acid accounting for 10-20% of the total molar amount of small molecule polyacids. Component B is an isocyanate component with an -NCO content of 15-18%. By weight, the isocyanate component is composed of the following raw materials: Polyester polyol 2: 30-50 parts; Isocyanate: 50-70 parts; The polyester polyol has a hydroxyl value of 120-150 mg KOH / g and is prepared from small molecule polyols, dimer acids, and lauric acid. The small molecule polyols include difunctional and trifunctional small molecule polyols, with the molar amount of trifunctional small molecule polyols accounting for 3-6% of the total molar amount of small molecule polyols. The molar amount of lauric acid is 10-20% of the total molar amount of dimer acids and lauric acid.

2. The polyester-based two-component solvent-free polyurethane adhesive according to claim 1, characterized in that, Difunctional small molecule polyols are one or more of the following: neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, methylpropanediol, 1,2-propanediol, ethylene glycol, and diethylene glycol.

3. The polyester-based two-component solvent-free polyurethane adhesive according to claim 1, characterized in that, Trifunctional small molecule polyols are one of trimethylolpropane and glycerol.

4. The polyester-based two-component solvent-free polyurethane adhesive according to claim 1, characterized in that, The chain extender is one of diisopropanolamine, triisopropanolamine, or triethanolamine.

5. The polyester-based two-component solvent-free polyurethane adhesive according to claim 1, characterized in that, The silane coupling agent is one of γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane.

6. The polyester-based two-component solvent-free polyurethane adhesive according to claim 1, characterized in that, The isocyanate is one or both of diphenylmethane diisocyanate and carbodiimide-modified diphenylmethane diisocyanate.

7. The polyester-based two-component solvent-free polyurethane adhesive according to claim 6, characterized in that, The isocyanate is a mixture of diphenylmethane diisocyanate and carbodiimide-modified diphenylmethane diisocyanate in a mass ratio of (3.4-3.6):

1.

8. A method for preparing a polyester-based two-component solvent-free polyurethane adhesive according to any one of claims 1-7, characterized in that, Includes the following steps: (1) Preparation method of component A: Small molecule polyacid and small molecule polyol are fed into the reaction vessel, heated to 225-235℃ and reacted for 6-8 hours, cooled to 55-65℃, silane coupling agent and chain extender are added, and after stirring evenly, component A is obtained. (2) Preparation method of component B: Dimer acid, lauric acid and small molecule polyol are fed into the reaction vessel, heated to 225-235℃ and reacted for 6-8h, cooled to 40-45℃, isocyanate is added, heated to 75-80℃ and reacted for 3-4h to obtain component B. (3) Preheat components A and B to 35-40℃ respectively, mix them evenly, and then apply the adhesive.

9. The application of a polyester-based two-component solvent-free polyurethane adhesive according to any one of claims 1-7, characterized in that, Used for bonding PE, PET, OPP, VMPET, aluminum foil, RCPP, and PA films.

10. The application of the polyester-based two-component solvent-free polyurethane adhesive according to claim 9, characterized in that, The bonding process is cured under the following conditions: 35-50℃ for 24-72 hours.

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