Polyurethane adhesive and preparation method thereof

Abstract

The invention belongs to the technical field of polyurethane adhesives, and particularly relates to a polyurethane adhesive and a preparation method thereof. The polyurethane adhesive prepared from the first polyether polyol with specific molecular weight and hydroxyl value, the second polyether polyol with specific molecular weight and hydroxyl value, the aliphatic isocyanate, the anti-aging aid and the metal catalyst according to a specific ratio has a long-term anti-yellowing effect, and can keep the color of a field bright for a long time; the long-term yellowing-resistant adhesive can resist outdoor aging conditions for a long time, is stable for a long time under the action of outdoor high temperature and ultraviolet rays, does not cause threshing, breaks through the problems that aliphatic glue cannot be applied to exposed surfaces for a long time and is easy to degrade, provides a stable product capable of meeting actual market use requirements, and makes up for the blank that no stable long-term yellowing-resistant adhesive exists in the market.

Description

Technical Field

[0001] This invention belongs to the technical field of polyurethane adhesives, specifically relating to a polyurethane adhesive and its preparation method. Background Technology

[0002] With economic development and the improvement of people's living standards, the construction of various public facilities has been gradually improved, which has also set off a wave of national fitness enthusiasm. In the field of sports facilities, synthetic running tracks and various fitness trails are widely used. They can not only provide good cushioning for athletes and reduce the risk of injury, but their uniquely designed patterns also play a good decorative and aesthetic role, providing a better sports experience.

[0003] Currently, polyurethane adhesives are commonly used in the market to bond plastic granules for sports fields. Outdoor fields are exposed for a long time, and ordinary polyurethane adhesives are prone to yellowing, causing the entire field to change color and look old. Later, yellowing-resistant polyurethane adhesive products were developed, but two problems have occurred in practical applications: they still yellow within a week and cannot resist yellowing for a long time; long-term yellowing-resistant products are not suitable for outdoor exposed surfaces, and the adhesive degrades after about a year of use, causing large-scale granule detachment and failure of the field.

[0004] The prior art discloses a yellowing-resistant polyurethane adhesive, which adds rutile titanium dioxide to the system to act as a UV absorber, but does not change the aromatic isocyanate structure of the system, so the effect is limited and cannot achieve long-term yellowing resistance.

[0005] To address this, existing technology discloses a solvent-free, yellowing-resistant polyurethane adhesive based on aliphatic isocyanates. A novel polyetheramine compound is synthesized to increase the reaction rate between the aliphatic isocyanate and the polyether, accelerating curing. Since aliphatic isocyanates lack unsaturated bonds, they do not produce color-changing groups under ultraviolet light, achieving long-term resistance to yellowing. However, this solvent-free, yellowing-resistant polyurethane adhesive is sensitive to outdoor light and heat. Under external light and heat, the polyether segments are easily damaged, causing overall material degradation. This results in poor long-term aging resistance and can lead to adhesive liquefaction, causing large-scale granulation failure on the application site. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to overcome the defect of poor long-term aging resistance in the prior art, thereby providing a polyurethane adhesive and its preparation method.

[0007] Therefore, this application provides a polyurethane adhesive, which is prepared using raw materials comprising the following parts by weight:

[0008] First polyether polyol, 55-70 parts; the number average molecular weight of the first polyether polyol is 1000-8000; the hydroxyl value is 20-120 mg KOH / g; and the functionality is 2-3.

[0009] The second polyether polyol, 3-10 parts; the number average molecular weight of the second polyether polyol is 200-1000, the hydroxyl value is 200-800 mg KOH / g, and the functionality is 3-4.

[0010] 20-33 parts of aliphatic isocyanate;

[0011] Anti-aging additives: 0.5–3 parts;

[0012] 0.1 to 1.5 parts of metal catalyst.

[0013] Furthermore, the first polyether polyol is selected from one or more of polytetrahydrofuran ether diol and hydroxyl-terminated polyether polyols;

[0014] Furthermore, the first polyether polyol is polymerized from one or more monomers selected from propylene oxide, ethylene oxide, tetrahydrofuran, ethylene glycol, and castor oil.

[0015] Furthermore, the second polyether polyol is selected from one or more of polyether triol and polyether tetraol;

[0016] Preferably, the polyether triol is polyoxypropylene triol, and the polyether tetraol is polyoxypropylene tetraol.

[0017] Furthermore, the aliphatic isocyanate is selected from one or more of isophorone diisocyanate, 4,4-diisocyanate dicyclohexylmethane, and HDI trimer.

[0018] Furthermore, the anti-aging additive is selected from one or more of hindered amine light stabilizers, benzotriazole light stabilizers, hindered phenolic antioxidants, and aromatic secondary amine antioxidants;

[0019] Optionally, the hindered amine light stabilizer is selected from bis(1,2,2,6,6-pentamethylpiperidinol) sebacate;

[0020] Optionally, the benzotriazole light stabilizer is selected from one or more of 2-(5-chloro-2-benzotriazolyl)-6-tert-butyl-4-methylphenol, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 3-[3-(2-H-benzotriazol-2-yl)-4-hydroxy-5-tert-butylphenyl]-propionic acid-polyethylene glycol ester, and 2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol;

[0021] Optionally, the hindered phenolic antioxidant is selected from one or more of the following: isooctyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, n-octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

[0022] Optionally, the aromatic secondary amine antioxidant is selected from N-(ethoxycarbonylphenyl)-N'-methyl-N'-phenylformamidinium.

[0023] Furthermore, the metal catalyst is selected from one or more of organotin compounds, zinc-bismuth composite catalysts, bismuth neodecanoate, bismuth isooctanoate, zinc neodecanoate, zinc isooctanoate, and bismorpholine diethyl ether;

[0024] The organotin compounds include one or more of dibutyltin dilaurate and di(dodecylthio)dibutyltin.

[0025] This application also provides a method for preparing any of the polyurethane adhesives described above, comprising the following steps:

[0026] S1: Under inert atmosphere, the first polyether polyol, the second polyether polyol, the aliphatic isocyanate and a portion of the metal catalyst are mixed and polymerized to obtain an intermediate.

[0027] S2: Mix the intermediate obtained in step S1 with the anti-aging additive and the remaining metal catalyst to obtain a polyurethane adhesive; or,

[0028] Includes the following steps:

[0029] S1: Under inert atmosphere conditions, the first polyether polyol, the second polyether polyol, the metal catalyst, and the aliphatic isocyanate are mixed and polymerized to obtain an intermediate.

[0030] S2: Mix the intermediate obtained in step S1 with the anti-aging additive to obtain a polyurethane adhesive.

[0031] In the former preparation method, the metal catalyst is added in stages, the system reaction is mild, the temperature is controlled stably, the viscosity of the obtained product is further reduced, which is more conducive to on-site construction and has better site operability.

[0032] Furthermore, the polymerization reaction is carried out at a temperature of 70°C to 90°C for 2 to 3 hours; and / or, in step S2, the mixing temperature is below 68°C.

[0033] Furthermore, when the aliphatic isocyanate includes both an aliphatic isocyanate and another aliphatic isocyanate, isophorone diisocyanate is added before the polymerization reaction to carry out the polymerization reaction, and after the reaction is completed, another aliphatic isocyanate is added to continue the reaction.

[0034] The technical solution of this invention has the following advantages:

[0035] 1. The polyurethane adhesive provided by the present invention is prepared from raw materials comprising the following parts by weight: a first polyether polyol, 55-70 parts; the number average molecular weight of the first polyether polyol is 1000-8000; the hydroxyl value is 20-120 mg KOH / g; and the functionality is 2-3; a second polyether polyol, 3-10 parts; the number average molecular weight of the second polyether polyol is 200-1000; and the hydroxyl value is 200-800 mg KOH / g. The polyurethane adhesive prepared by this invention using a specific ratio of a first polyether polyol with a specific molecular weight and hydroxyl value, a second polyether polyol with a specific molecular weight and hydroxyl value, aliphatic isocyanate, anti-aging additive, and metal catalyst not only has long-term resistance to yellowing and can maintain the bright color of the site for a long time, but also can resist outdoor aging conditions for a long time. It is stable under outdoor high temperature and ultraviolet radiation without particle shedding. It overcomes the problem that aliphatic adhesives cannot be used on exposed surfaces for a long time and are easy to degrade. It provides a stable product that can meet the actual market demand and fills the gap in the market for stable long-term yellowing resistant adhesives. The polyurethane adhesive of this invention has excellent physical and mechanical properties and resistance to yellowing and degradation. When used in the field of outdoor adhesives, it can effectively avoid yellowing, discoloration and powdering caused by light exposure, and overcome the technical difficulty of chain liquefaction failure of traditional aliphatic yellowing resistant adhesives under outdoor high temperature and ultraviolet radiation.

[0036] This invention employs aliphatic isocyanate as the backbone to ensure long-term resistance to yellowing. The use of a first and second polyether polyol ensures relatively low viscosity and temperature stability, resulting in good system compatibility. By adding a specific proportion of the second polyether polyol, which has a higher molecular weight compared to chain extenders, the molecular chain flexibility is improved, increasing the system's crosslinking degree. This avoids the problem of decreased system strength caused by using small-molecule chain extenders such as trimethylolpropane. Furthermore, after the high-hydroxyl-value second polyether polyol reacts with the aliphatic isocyanate to form polyurethane, isocyanate can be further grafted onto it under the action of a metal catalyst. The addition of ester groups further enhances the degree of crosslinking and molecular weight, resulting in a roughly doubling of the system viscosity. Because it is a fully polyether system, this moderate increase in viscosity does not lead to a sharp increase in viscosity at low temperatures or crystallization issues. The first polyether polyol exhibits liquefaction during water aging, while the adhesive of this invention undergoes surface hardening and pulverization as its ultimate aging degradation method. This prevents adhesive migration, which is beneficial for protecting the underlying layer. Furthermore, the viscosity of the adhesive in this invention is approximately twice that of ordinary adhesives, resulting in less penetration. After mixing and spreading the particles, the adhesive largely adheres to the particle surface, increasing the thickness of the adhesive film on the particle surface, extending the particle exposure time, preventing particle pulverization, and further enhancing aging resistance.

[0037] 2. The polyurethane adhesive provided by this invention has both the long-term aging resistance of aliphatic products and the environmental adaptability comparable to aromatic products, overcoming the technical difficulty of the current market lacking stable, long-term aging-resistant, and non-yellowing adhesives.

[0038] 3. The preparation method of polyurethane adhesive provided by the present invention is simple and convenient to operate, suitable for industrial production. The viscosity of ordinary adhesives is generally within 3000 mp.s. After being mixed with granules and laid, they will show obvious seepage, resulting in a thinner top layer adhesive film, weakening the protective effect on the granules and making the site prone to pulverization. The present invention achieves secondary crosslinking by using metal catalysts and aliphatic isocyanates to increase viscosity, increase the thickness of the adhesive film on the surface of the granules, and reduce the risk of site pulverization. Detailed Implementation

[0039] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0040] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0041] The abbreviations, sources, and names of the raw materials involved in this invention are summarized below:

[0042] First polyether polyol, brand name: 3135: a polyether triol with a number average molecular weight of 6000-6500, a hydroxyl value of 34mgKOH / g, and a functionality of 3, purchased from Wanhua Chemical Co., Ltd.

[0043] The first polyether polyol, brand name: 2020: number average molecular weight of 2000 polyether diol, hydroxyl value of 56 mg KOH / g, functionality of 2, purchased from Wanhua Chemical Co., Ltd.

[0044] The first polyether polyol, brand name: 2010: number average molecular weight of 1000 polyether diol, hydroxyl value of 112 mg KOH / g, functionality of 2, purchased from Wanhua Chemical Co., Ltd.

[0045] The second polyether polyol, brand name: 2303: a polyether triol with a number average molecular weight of 300, a hydroxyl value of 561 mg KOH / g, and a functionality of 3, was purchased from Wanhua Chemical Co., Ltd.

[0046] The second polyether polyol, brand name: 2304: a polyether triol with a number average molecular weight of 400, a hydroxyl value of 421 mg KOH / g, and a functionality of 3, was purchased from Wanhua Chemical Co., Ltd.

[0047] The second polyether polyol, brand name: 2307: a polyether triol with a number average molecular weight of 700, a hydroxyl value of 240 mg KOH / g, and a functionality of 3, was purchased from Wanhua Chemical Co., Ltd.

[0048] The second polyether polyol, brand name: 405E: a polyether tetraol with a number average molecular weight of 500, a hydroxyl value of 449 mg KOH / g, and a functionality of 4, was purchased from Wanhua Chemical Co., Ltd.

[0049] Aliphatic isocyanates: IPDI: Isophorone diisocyanate, purchased from Wanhua Chemical Co., Ltd.;

[0050] Aliphatic isocyanate: HMDI: 4,4-diisocyanate dicyclohexylmethane, purchased from Wanhua Chemical Co., Ltd.;

[0051] Aliphatic isocyanate: HT-600: HDI trimer, purchased from Wanhua Chemical Co., Ltd.;

[0052] 1135: Liquid hindered phenolic antioxidant, isooctyl 3,5-di-tert-butyl-4-hydroxyphenylpropionate, purchased from Shanghai Xiuyuan Chemical Co., Ltd.

[0053] 1076: Hindered phenolic antioxidant, β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl ester, purchased from Xinxing Chemical Co., Ltd.

[0054] UV-1: An aromatic secondary amine antioxidant, N-(p-ethoxycarbonylphenyl)-N'-methyl-N'-phenylmethylammonium, purchased from Lianlong New Materials Co., Ltd.

[0055] UV-P: Benzotriazole light stabilizer, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, purchased from Lianlong New Materials Co., Ltd.

[0056] UV-292: Hindered amine light stabilizer, bis(1,2,2,6,6-pentamethylpiperidinol) sebacate, purchased from Lianlong New Materials Co., Ltd.

[0057] PC-03S: Metal catalyst, zinc-bismuth composite catalyst, purchased from Shanghai Zhengui Technology Co., Ltd.

[0058] T-12: Metal catalyst, dibutyltin dilaurate, purchased from Shanghai Minchen Chemical.

[0059] Example 1

[0060] This embodiment provides a polyurethane adhesive, the raw materials of which are shown in the table below:

[0061]

[0062] The preparation method is as follows:

[0063] According to the amount of each raw material in the table, the first polyether polyol and the second polyether polyol after dehydration were put into the reactor and heated to 50°C; then aliphatic isocyanate and 0.1g of metal catalyst were added and reacted at 70°C for 3 hours. The temperature was lowered to 65°C and anti-aging additives were added and dispersed for 10 minutes. Then 0.15g of metal catalyst was added and dispersed for 20 minutes before discharging; polyurethane adhesive was obtained.

[0064] Example 2

[0065] This embodiment provides a polyurethane adhesive, the raw materials of which are shown in the table below:

[0066]

[0067] The preparation method is as follows:

[0068] According to the amount of each raw material in the table, the first polyether polyol and the second polyether polyol after dehydration were added to the reactor and heated to 50°C; then aliphatic isocyanate and 0.2g of metal catalyst were added and reacted at 70°C for 3 hours. The temperature was lowered to 65°C and anti-aging additives were added and dispersed for 10 minutes. Then, 0.2g of metal catalyst was added and dispersed for 20 minutes before discharging; polyurethane adhesive was obtained.

[0069] Example 3

[0070] This embodiment provides a polyurethane adhesive, the raw materials of which are shown in the table below:

[0071]

[0072] The preparation method is as follows:

[0073] According to the amount of each raw material in the table, the first polyether polyol and the second polyether polyol after dehydration were added to the reactor and heated to 65°C; then aliphatic isocyanate and 0.3g of metal catalyst were added and reacted at 75°C for 2.5h. The temperature was lowered to 67°C and anti-aging additives were added and dispersed for 10min. Then 0.4g of metal catalyst was added and dispersed for 15min before discharging; polyurethane adhesive was obtained.

[0074] Example 4

[0075] This embodiment provides a polyurethane adhesive, the raw materials of which are shown in the table below:

[0076]

[0077] The preparation method is as follows:

[0078] According to the amount of each raw material in the table, the first polyether polyol and the second polyether polyol after dehydration were added into the reactor and heated to 65°C; then aliphatic isocyanate and 0.3g of metal catalyst were added and reacted at 85°C for 2 hours. The temperature was lowered to 67°C and anti-aging additives were added and dispersed for 20 minutes. After adding 0.3g of metal catalyst and dispersing for 20 minutes, the product was discharged; polyurethane adhesive was obtained.

[0079] Example 5

[0080] This embodiment provides a polyurethane adhesive, the raw materials of which are shown in the table below:

[0081]

[0082] The preparation method is as follows:

[0083] According to the amount of each raw material in the table, the first polyether polyol and the second polyether polyol after dehydration were added to the reactor and heated to 60°C. Then IPDI and 0.05g of metal catalyst were added and reacted at 88°C for 2 hours. HMDI was then added and the reaction continued for 1.5 hours. The temperature was lowered to 65°C and anti-aging additives were added. The mixture was dispersed for 15 minutes and then 0.05g of metal catalyst was added and dispersed for 20 minutes before being discharged. Polyurethane adhesive was obtained.

[0084] Example 6

[0085] This embodiment provides a polyurethane adhesive, the raw materials of which are shown in the table below:

[0086]

[0087] The preparation method is as follows:

[0088] According to the amount of each raw material in the table, the first polyether polyol and the second polyether polyol after dehydration were added to the reactor and heated to 60°C; then IPDI and 0.05g of metal catalyst were added and reacted at 83°C for 2.5h; then HT-600 was added and the reaction continued for 0.5h; the temperature was lowered to 67°C and anti-aging additives were added and dispersed for 15min; then 0.05g of metal catalyst was added and dispersed for 20min before discharging; polyurethane adhesive was obtained.

[0089] Example 7

[0090] This embodiment provides a polyurethane adhesive with the same raw material types and amounts as in Example 4. The only difference is the method of adding the metal catalyst. In this embodiment, the catalyst is added all at once during the reaction process. Specifically, the first polyether polyol, the second polyether polyol, and the metal catalyst after dehydration are added to the reactor and heated to 65°C. Then, aliphatic isocyanate is added and reacted at 85°C for 2 hours. The temperature is then lowered to 67°C, an anti-aging additive is added, and the mixture is dispersed for 20 minutes before being discharged. The polyurethane adhesive is thus obtained.

[0091] Comparative Example 1

[0092] It is basically the same as Example 1, except that no second polyether polyol was added during the preparation process.

[0093] Comparative Example 2

[0094] It is basically the same as Example 2, except that the same amount of trifunctional chain extender TMP (trimethylolpropane) is used instead of the second polyether polyol used in Example 2.

[0095] Comparative Example 3

[0096] It is basically the same as Example 3, except that no metal catalyst was added during the preparation process.

[0097] Comparative Example 4

[0098] It is basically the same as Example 5, except that the same amount of difunctional alcohol DEG (diethylene glycol) is used instead of the second polyether polyol used in Example 5.

[0099] Comparative Example 5

[0100] This is basically the same as Example 5, except that the amount of some raw materials used is different. The raw materials are shown in the table below:

[0101]

[0102] The preparation method is the same as in Example 5.

[0103] Comparative Example 6

[0104] This is basically the same as Example 5, except that the amount of some raw materials used is different. The raw materials are shown in the table below:

[0105]

[0106]

[0107] The preparation method is the same as in Example 5.

[0108] Test case

[0109] 1. Viscosity

[0110] The viscosity of the polyurethane adhesives prepared in each example and comparative example at 25°C was tested according to standard GB / T 12009.3-2009.

[0111] 2. Tensile strength and elongation at break

[0112] The polyurethane adhesives prepared in each embodiment and comparative example were stretched onto a glass plate coated with a release agent. After the adhesive cured, the film was removed to obtain a film with a thickness of 1000 μm. The tensile strength and elongation at break of each group of films were tested according to standard GB / T528-2009 at a stretching speed of 500 mm / min.

[0113] 3. Sample aging test

[0114] The polyurethane adhesives prepared in each embodiment and comparative example were stretched into a film on a glass plate with a film thickness of 1000 μm. After curing, the film was removed after one week to obtain a sample 1 with a thickness of 1 mm. The polyurethane adhesive was mixed with EPDM (ethylene propylene diene monomer) granules with a glue content of 15% at a mass ratio of 1:6 and compacted. After one week, the film was removed to obtain a sample 2 with a thickness of 1 cm.

[0115] According to the laboratory light source exposure test method, part 3 of GB / T 16442.3-2014, test method A for type 1A lamps of fluorescent ultraviolet lamps, the samples 1 and 2 obtained by each group of polyurethane adhesives were tested under exposure cycle 1, with a total test duration of 1000h.

[0116] During the test, the appearance of sample 1 was observed every 1 hour. If it changed from solid to liquid, it indicated that degradation had occurred. The longest time without degradation was recorded as the degradation resistance time. If no change in state occurred during the test (1000 hours), the degradation resistance time of the sample was recorded as >1000 hours, and the state after the aging test was recorded as normal.

[0117] During the test, check sample 2. If the EPDM particles on sample 2 fall off completely when gently rubbed with a finger, record the time when the EPDM particles fall off as the sample granulation time. Test for 1000 hours. If it does not occur, record the sample granulation time as >1000 hours.

[0118] Table 1 Test results for each embodiment

[0119]

[0120] Table 2 Test results of each comparative example

[0121] Material properties Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Viscosity / mpa.s 1987 2523 2147 2319 15323 3560 Tensile strength / MPa 19.7 6.7 18.5 22.8 13.6 16.2 Elongation at break / % 215.1 43.3 227.4 236.4 85.6 218 Degradation resistance time / h 73 431 556 138 >1000 336 Sample 1 after aging test liquefaction liquefaction liquefaction liquefaction normal liquefaction Sample threshing time / h 187 552 731 370 >1000 471

[0122] The polyurethane adhesives prepared in the various embodiments of the present invention have excellent physical properties. Because the pure aliphatic isocyanate system itself has no aging chromogenic groups, it solves the problem of poor aging resistance and short service life of ADI (aliphatic diisocyanate) polyurethane adhesives on the market while ensuring permanent resistance to yellowing. As a result, the samples of this type of polyurethane adhesive have not failed after more than 1000 hours and have not granulated after more than 1000 hours.

[0123] In Comparative Example 1, the second polyether polyol in the system lacks multifunctionality and high hydroxyl value, which cannot provide a sufficiently strong cross-linking structure, has low resistance to ultraviolet light and heat, and fails to liquefy as a whole, thus failing to guarantee the normal use time of the site.

[0124] Comparative Example 2 replaced the high-functionality, high-hydroxyl-value second polyether polyol with low-molecular-weight trimethylolpropane. The cross-linking structure was not concentrated, resulting in poor physical properties. Furthermore, it could not undergo secondary cross-linking under the action of a metal catalyst, thus limiting the improvement in aging resistance.

[0125] Comparative Example 3 did not use a metal catalyst, so the system could not be further cross-linked, the overall viscosity of the system was low, and the improvement in aging resistance was limited.

[0126] Comparative Example 4 used a common difunctional alcohol DEG as the second polyether polyol with high hydroxyl value and multifunctionality. The viscosity increased slightly, but it could not be cross-linked again under the action of a catalyst, and the aging resistance could not be significantly improved.

[0127] In Comparative Example 5, an excessive amount of a second polyether polyol with high hydroxyl value and multifunctionality was added, which further deepened the cross-linking of the system. Although this could improve the aging resistance, it also led to an increase in the overall viscosity of the system, making dispersion difficult in actual use and unfavorable for site construction.

[0128] Compared with Example 7, Example 4 has a catalyst addition method of staged addition, the system reaction is mild, the temperature is controlled stably, the viscosity of the obtained product is further reduced, which is more conducive to on-site construction and has better site operability.

[0129] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A polyurethane adhesive, characterized in that, The polyurethane adhesive is prepared using raw materials comprising the following parts by weight: First polyether polyol, 55-70 parts; the number average molecular weight of the first polyether polyol is 1000-8000; the hydroxyl value is 20-120 mg KOH / g; and the functionality is 2-3. The second polyether polyol, 3-10 parts; the number average molecular weight of the second polyether polyol is 200-1000, the hydroxyl value is 200-800 mg KOH / g, and the functionality is 3-4. 20-33 parts of aliphatic isocyanate; Anti-aging additives: 0.5–3 parts; 0.1 to 1.5 parts of metal catalyst.

2. The polyurethane adhesive according to claim 1, characterized in that, The first polyether polyol is selected from one or more of polytetrahydrofuran ether diol and hydroxyl-terminated polyether polyols.

3. The polyurethane adhesive according to claim 2, characterized in that, The first polyether polyol is polymerized from one or more monomers selected from propylene oxide, ethylene oxide, tetrahydrofuran, ethylene glycol, and castor oil.

4. The polyurethane adhesive according to any one of claims 1-3, characterized in that, The second polyether polyol is selected from one or more of polyether triol and polyether tetraol; Preferably, the polyether triol is polyoxypropylene triol, and the polyether tetraol is polyoxypropylene tetraol.

5. The polyurethane adhesive according to any one of claims 1-4, characterized in that, The aliphatic isocyanate is selected from one or more of isophorone diisocyanate, 4,4-diisocyanate dicyclohexylmethane, and HDI trimer.

6. The polyurethane adhesive according to any one of claims 1-5, characterized in that, The anti-aging additive is selected from one or more of hindered amine light stabilizers, benzotriazole light stabilizers, hindered phenolic antioxidants, and aromatic secondary amine antioxidants; Optionally, the hindered amine light stabilizer is selected from bis(1,2,2,6,6-pentamethylpiperidinol) sebacate; Optionally, the benzotriazole light stabilizer is selected from one or more of 2-(5-chloro-2-benzotriazolyl)-6-tert-butyl-4-methylphenol, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 3-[3-(2-H-benzotriazol-2-yl)-4-hydroxy-5-tert-butylphenyl]-propionic acid-polyethylene glycol ester, and 2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol; Optionally, the hindered phenolic antioxidant is selected from one or more of the following: isooctyl 3,5-di-tert-butyl-4-hydroxyphenylpropionate, octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]. Optionally, the aromatic secondary amine antioxidant is selected from N-(ethoxycarbonylphenyl)-N'-methyl-N'-phenylformamidinium.

7. The polyurethane adhesive according to any one of claims 1-6, characterized in that, The metal catalyst is selected from one or more of organotin, zinc-bismuth composite catalyst, bismuth neodecanoate, bismuth isooctanoate, zinc neodecanoate, zinc isooctanoate, and bismorpholine diethyl ether; The organotin compounds include one or more of dibutyltin dilaurate and di(dodecylthio)dibutyltin.

8. A method for preparing the polyurethane adhesive according to any one of claims 1-7, characterized in that, Includes the following steps: S1: Under inert atmosphere, the first polyether polyol, the second polyether polyol, the aliphatic isocyanate and a portion of the metal catalyst are mixed and polymerized to obtain an intermediate. S2: Mix the intermediate obtained in step S1 with the anti-aging additive and the remaining metal catalyst to obtain a polyurethane adhesive; or, Includes the following steps: S1: Under inert atmosphere conditions, the first polyether polyol, the second polyether polyol, the metal catalyst, and the aliphatic isocyanate are mixed and polymerized to obtain an intermediate. S2: Mix the intermediate obtained in step S1 with the anti-aging additive to obtain a polyurethane adhesive.

9. The method for preparing the polyurethane adhesive according to claim 8, characterized in that, The polymerization reaction is carried out at a temperature of 70°C to 90°C for 2 to 3 hours; and / or, in step S2, the mixing temperature is below 68°C.

10. The method for preparing the polyurethane adhesive according to claim 8, characterized in that, When an aliphatic isocyanate includes both an aliphatic isocyanate and another aliphatic isocyanate, isophorone diisocyanate is added before the polymerization reaction to carry out the polymerization reaction. After the reaction is completed, another aliphatic isocyanate is added to continue the reaction.

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