Bi-component polyurethane structural adhesive as well as preparation method and application thereof

Abstract

The invention belongs to the field of polyurethane adhesives, and particularly relates to a two-component polyurethane structural adhesive as well as a preparation method and application thereof. The bi-component polyurethane structural adhesive contains a composition A and a component B, the component A contains polyol, a molecular sieve, a first filler, a first plasticizer, a first thixotropic agent and a first auxiliary agent; the polyol contains polyether polyol, alicyclic polyester polyol, aromatic polyester polyol, alicyclic modified castor oil polyol and aromatic modified castor oil polyol at the same time; and the component B contains isocyanate, an NCO-terminated polyurethane prepolymer, a water removal agent, a second filler, a second plasticizer, a second thixotropic agent and a second auxiliary agent. The bi-component polyurethane structural adhesive provided by the invention has both low-temperature low modulus and high-temperature high modulus.

Description

Technical Field

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

[0002] In recent years, the new energy vehicle industry has developed rapidly, with long driving range and fast charging becoming major research directions for automakers. Reducing vehicle weight remains a key solution for improving driving range, and the reduction in the overall weight of the battery pack in new energy vehicles has a clear impact on the overall vehicle weight. Suppliers of two-component polyurethane thermally conductive structural adhesives for new energy vehicle battery packs need to actively cooperate with customers to reduce the overall weight of the battery pack while maintaining the required adhesive material performance. In the early stages of the new energy vehicle industry, the density of the polyurethane structural adhesive used in battery packs was approximately 1.3~1.4 g / cm³. 3 To reduce the density of two-component polyurethane structural adhesives, the applicant has developed a low-density two-component polyurethane structural adhesive. This low-density two-component polyurethane structural adhesive reduces the density of the adhesive to 0.75 g / cm³ while maintaining good mechanical and aging properties. 3 With these improvements, the overall weight of the battery pack can be reduced by approximately 3-4 kg. However, with the increase in battery pack energy density and the iteration of fast charging technology, the internal temperature of the battery pack will also increase during charging, discharging, and use (potentially rising from the current 60°C to 80°C). The increased temperature will lead to a decrease in the modulus and strength of the two-component polyurethane structural adhesive, which will pose risks such as delamination and battery pack slippage in the moving vehicle. This is mainly because complex road conditions will cause the battery pack to be subjected to forces in the vertical vibration and forward and backward slippage directions. The mainstream two-component polyurethane structural adhesives on the market experience a sharp drop in DMA modulus from 500-700 MPa at room temperature to 10-30 MPa at high temperatures (usually 60°C). This leads to a significant decrease in the mechanical properties (bulk strength, interfacial shear strength, and T-peel strength) of the two-component polyurethane structural adhesives. Specifically, the bulk strength decreases from over 12 MPa at room temperature to around 2 MPa, the interfacial shear strength decreases from over 10 MPa at room temperature to approximately 1.5-2.0 MPa, and the T-peel strength decreases from over 3-4 N / mm at room temperature to below 1 N / mm.

[0003] Meanwhile, for the two-component polyurethane thermally conductive structural adhesive in the battery pack of new energy vehicles, it is necessary to ensure low temperature and low modulus in order to guarantee the workability time. This is mainly because if the modulus is too high at low temperature, it will cause the adhesive to become brittle and reduce its impact resistance. When the car is driving in an extremely cold environment, it is affected by the combined effects of vertical vibration and front and rear forces, which can easily cause the adhesive to crack.

[0004] Therefore, it is very difficult to obtain both low modulus at low temperatures and high modulus at high temperatures (high modulus at high temperatures means that the modulus decreases slightly at high temperatures, but still maintains a relatively high modulus value after the decrease). If the low density is further restricted, the overall formulation design becomes extremely difficult, and a variety of different problems need to be overcome. Summary of the Invention

[0005] The primary objective of this invention is to overcome the deficiency of low high-temperature modulus in existing two-component polyurethane structural adhesives, and to provide a two-component polyurethane structural adhesive that combines low low-temperature modulus with high high-temperature modulus.

[0006] A second objective of this invention is to provide a method for preparing the aforementioned two-component polyurethane structural adhesive.

[0007] A third objective of this invention is to provide the application of the above-mentioned two-component polyurethane structural adhesive in the bonding of new energy vehicle battery packs.

[0008] As mentioned above, existing two-component polyurethane structural adhesives exhibit a decrease in modulus as temperatures rise. To mitigate this decrease at high temperatures, common practices include introducing rigid structures such as benzene rings, increasing the hardness content of the polyurethane, and enhancing functionality to improve heat resistance. However, these methods introduce new problems, primarily: Firstly, the low-temperature modulus also increases dramatically, often leading to brittleness and reduced impact resistance at low temperatures. Secondly, increased modulus results in decreased elongation at break, especially in low-density structural adhesives where hollow glass microspheres are introduced as fillers to reduce adhesive density. Compared to solid fillers, hollow glass microspheres are more prone to breakage during use, causing defects and having a greater impact on elongation at break. Thirdly, increasing the modulus through these methods increases the adhesive's cohesive strength, weakens its wettability to the substrate, reduces adhesion, and significantly decreases interfacial shear properties and T-peel strength. Therefore, to solve the problem of performance degradation at high temperatures, it is necessary not only to consider the modulus at high temperatures, but also to comprehensively consider the impact of increasing the modulus on the low-temperature modulus, impact resistance, elongation at break, interfacial shear properties and T-peel strength of the two-component polyurethane structural adhesive, so as to achieve low modulus at low temperatures and high modulus at high temperatures.

[0009] The key to this invention lies in the synergistic use of polyether polyols, alicyclic polyester polyols, aromatic polyester polyols, alicyclic modified castor oil polyols, and aromatic modified castor oil polyols as the polyol components of a polyurethane structural adhesive. The introduction of the aromatic and alicyclic rigid structures provides excellent heat resistance and adhesion to the substrate. This approach maintains excellent heat resistance while avoiding the problem of a sharp increase in modulus at low temperatures compared to using a benzene ring structure alone. Furthermore, the introduction of an appropriate amount of plasticizer combined with long-chain polyester polyols reduces the low-temperature modulus. Simultaneously, the use of alicyclic resins to replace part of the plasticizer further reduces the low-temperature modulus while maintaining high performance at both room and high temperatures. In summary, this invention, through the synergistic effect of polyether polyols, alicyclic polyester polyols, aromatic polyester polyols, alicyclic modified castor oil polyols, and aromatic modified castor oil polyols, endows a two-component polyurethane structural adhesive with excellent adhesion, low low-temperature modulus (toughness), and high high-temperature modulus (high-temperature resistance), providing a safer and more reliable solution for downstream automotive customers and consumers.

[0010] The two-component polyurethane structural adhesive provided by this invention contains component A and component B; component A contains polyol, molecular sieve, first filler, first plasticizer, first thixotropic agent, and first auxiliary agent; the polyol contains polyether polyol, polyester polyol, and castor oil polyol in a mass ratio of 1:(0.25~7):(0.25~7), the polyester polyol contains alicyclic polyester polyol and aromatic polyester polyol in a mass ratio of (0.2~5):1, and the castor oil polyol contains alicyclic modified castor oil polyol and aromatic modified castor oil polyol in a mass ratio of (0.2~5):1; component B contains isocyanate, NCO-terminated polyurethane prepolymer, dehydrating agent, second filler, second plasticizer, second thixotropic agent, and second auxiliary agent.

[0011] The preparation method of the two-component polyurethane structural adhesive provided by the present invention includes the following steps: mixing each component in component A evenly to obtain component A; mixing each component in component B evenly to obtain component B.

[0012] The two-component polyurethane structural adhesive provided by this invention possesses both low modulus at low temperatures and high modulus at high temperatures. Specifically, at 60°C, the DMA modulus increases from the original 10-30 MPa to 100-120 MPa, while the DMA modulus at room temperature and -40°C remains at a relatively low level, increasing from approximately 500-700 MPa to approximately 700-900 MPa and from approximately 800-1000 MPa to approximately 1200-1500 MPa, respectively. The bulk strength and elongation at break remain at a relatively high level, at approximately 10-12 MPa and 45-75%, respectively. The interfacial shear strength (2 mm adhesive thickness) can reach over 10 MPa, and at high temperature (60°C), the interfacial shear strength increases from the original 1.5-2 MPa to approximately 3-4 MPa. The T-peel strength at 60°C increases from below 1.0 N / mm to above 2.5 N / mm. Detailed Implementation

[0013] The two-component polyurethane structural adhesive provided by this invention contains component A and component B. Preferably, the mass ratio of component A to component B is such that the molar ratio of the total hydroxyl content in the polyol to the total isocyanate content in the isocyanate and NCO-terminated polyurethane prepolymer is 1:(0.8~1.4). Specifically, the molar ratio of the total hydroxyl content in the polyol to the total isocyanate content in the isocyanate and NCO-terminated polyurethane prepolymer can be 1:(0.8~1.4), such as 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, etc.

[0014] The key to this invention lies in the synergistic combination of polyether polyol, alicyclic polyester polyol, aromatic polyester polyol, alicyclic modified castor oil polyol, and aromatic modified castor oil polyol as the polyol component of the polyurethane structural adhesive. This results in the polyurethane structural adhesive having a low modulus (excellent impact resistance) at low temperatures and a high modulus (excellent heat resistance) at high temperatures. The reasons for this are speculated to be as follows: On the one hand, aromatic polyester polyols have a benzene ring structure in their main chain, resulting in extremely rigid molecular chains and high cohesive energy. This significantly increases the glass transition temperature (Tg) of polyurethane, and the conjugation effect of the benzene ring can disperse thermal stress, enhance the material's resistance to heat oxidation, and allow the adhesive to maintain its solid properties at high temperatures, reducing the modulus drop. Alicyclic polyester polyols have a cyclic structure in their main chain, resulting in strong molecular rigidity and highly polar ester bonds. This allows them to form a dense cross-linked structure with isocyanates, improving material rigidity and reducing the modulus drop caused by thermal motion at high temperatures. Aromatic modified castor oil polyols form local cross-linking points by embedding rigid aromatic groups into the flexible segments of castor oil, enhancing resistance to deformation at high temperatures. On the other hand, alicyclic and aromatic polyester polyols provide rigid cross-linking points, while modified castor oil polyols and polyether polyols... Hydroxyl groups participate in the reaction, forming localized chemical crosslinks. This multi-level crosslinking structure can improve the elastic modulus at high temperatures. The regular arrangement of alicyclic molecular chains can reduce molecular chain slippage at high temperatures and maintain modulus stability. Polyether polyols have low cohesive energy, and their molecular chains are easy to rotate, maintaining fluidity at low temperatures and reducing the overall modulus. Castor oil's main chain contains long carbon chains and hydroxyl groups, and its molecular chains are highly flexible. The introduction of aromatic and alicyclic rings in castor oil can regulate the flexibility of the molecular chains, avoiding excessive rigidity that leads to low-temperature brittleness. Furthermore, the synergistic effect of polyether polyols, alicyclic polyester polyols, aromatic polyester polyols, alicyclic modified castor oil polyols, and aromatic modified castor oil polyols can form a clear microphase separation structure and optimize the crosslinking network. This allows the flexible soft segments to play a dominant role at low temperatures, reducing the modulus, while the rigid hard segments play a dominant role at high temperatures, increasing the modulus.

[0015] In the aforementioned two-component polyurethane structural adhesive, component A contains a polyol, a molecular sieve, a first filler, a first plasticizer, a first thixotropic agent, and a first auxiliary agent. The polyol contains polyether polyol, polyester polyol, and castor oil polyol, wherein the mass ratio of the polyester polyol, castor oil polyol, and polyether polyol is (0.25~7):(0.25~7):1. Specifically, the mass ratio of the polyester polyol to the polyether polyol can be 0.25:1, 0.5:1, 0.8:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, etc. The mass ratio of castor oil polyol to polyether polyol can be 0.25:1, 0.5:1, 0.8:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, etc. The polyester polyol contains both alicyclic and aromatic polyester polyols, wherein the mass ratio of the alicyclic and aromatic polyester polyols is (0.2~5):1, such as 0.2:1, 0.5:1, 0.8:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, etc. The castor oil polyol contains both alicyclic modified castor oil polyol and aromatic modified castor oil polyol, wherein the mass ratio of the alicyclic modified castor oil polyol to the aromatic modified castor oil polyol is (0.2~5):1, such as 0.2:1, 0.5:1, 0.8:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, etc.

[0016] In a preferred embodiment, based on the total weight of component A, the content of the polyether polyol is 10-40%, such as 10%, 15%, 20%, 25%, 30%, 35%, 40%, etc.; the content of the polyester polyol is 10-70%, such as 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, etc.; the content of the castor oil polyol is 10-70%, such as 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, etc.; and the content of the molecular sieve is 1-10%, such as 1%, 2%. The contents of the first filler are 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc.; the contents of the first filler are 10-50%, such as 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc.; the contents of the first plasticizer are 1-20%, such as 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc.; the contents of the first thixotropic agent are 1-5%, such as 1%, 2%, 3%, 4%, 5%, etc.; the contents of the first auxiliary agent are 0.1-5%, such as 1%, 2%, 3%, 4%, 5%, etc.

[0017] In the aforementioned two-component polyurethane structural adhesive, component B contains isocyanate, NCO-terminated polyurethane prepolymer, dehydrating agent, second filler, second plasticizer, second thixotropic agent, and second auxiliary agent. In a preferred embodiment, based on the total weight of component B, the isocyanate content is 1-15%, such as 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, etc.; the NCO-terminated polyurethane prepolymer content is 30-85%, such as 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, etc.; the dehydrating agent content is 0.1-1.5%, such as 0.1%, 0.2%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, etc. The content of the second filler is 10-50%, such as 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc.; the content of the second plasticizer is 1-20%, such as 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc.; the content of the second thixotropic agent is 1-5%, such as 1%, 2%, 3%, 4%, 5%, etc.; the content of the second auxiliary agent is 0.1-5%, such as 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, etc.

[0018] In the above-mentioned two-component polyurethane structural adhesive, the polyether polyol can be selected from at least one of polyethylene oxide polyol, polypropylene oxide polyol, polytetrahydrofuran diol, and bisphenol A modified polyether polyol. The number-average molecular weight of the polyethylene oxide polyol can be 100-6000, such as 100, 500, 1000, 2000, 3000, 4000, 5000, 6000, etc.; and the functionality can be 2-4, such as 2, 3, or 4. The number-average molecular weight of the polypropylene oxide diol can be 100-6000, such as 100, 500, 1000, 2000, 3000, 4000, 5000, 6000, etc.; and the functionality can be 2-4, such as 2, 3, or 4. Specifically, the polypropylene oxide diol can be polypropylene oxide diol and / or polypropylene oxide triol. The polytetrahydrofuran diol is particularly preferably a polytetrahydrofuran diol with a number average molecular weight of 100-4000. The bisphenol A modified polyether polyol is particularly preferably a bisphenol A modified polyether polyol with a number average molecular weight of 100-6000 and a functionality of 2-3.

[0019] In the above-mentioned two-component polyurethane structural adhesive, the number average molecular weight of the alicyclic polyester polyol and the aromatic polyester polyol is preferably 500-6000, such as 500, 800, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000, 5500, 6000, etc. The functionality of the alicyclic polyester polyol and the aromatic polyester polyol is preferably 2-4, such as 2, 3, or 4.

[0020] In the above-mentioned two-component polyurethane structural adhesive, the alicyclic polyester polyol is the esterification product of a polyacid I and a polyol I, wherein the polyacid I and / or polyol I contain an alicyclic structure. Examples of polyacid I include at least one of 1,4-cyclohexanedicarboxylic acid, hexahydrophthalic anhydride, and hydrogenated bisphenol A. Examples of polyol I include 1,4-cyclohexanediethanol and / or 1,6-hydroxymethylcyclohexane.

[0021] In the above-mentioned two-component polyurethane structural adhesive, the aromatic polyester polyol is an esterification reaction product of polyacid II and polyol II, wherein the polyacid II and / or polyol II contain an aromatic structure. Examples of polyacid II include at least one selected from phthalic anhydride, terephthalic acid, and isophthalic acid. Examples of polyol II include at least one selected from diethylene glycol, ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 2-methylpropanediol, trimethylolpropane, and glycerol.

[0022] In the aforementioned two-component polyurethane structural adhesive, the polyester polyol may further contain at least one of adipic acid-based polyester polyol, dimer acid polyester polyol, polycaprolactone polyester polyol, and polycarbonate polyester polyol. The total proportion of alicyclic and aromatic polyester polyols in the polyester polyol is preferably 60-100%, such as 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 98%, 100%, etc.

[0023] In the above-mentioned two-component polyurethane structural adhesive, the number average molecular weight of the alicyclic modified castor oil polyol and the aromatic modified castor oil polyol is preferably independently 400-5000, such as 400, 500, 800, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000, etc. The functionality of the alicyclic modified castor oil polyol and the aromatic modified castor oil polyol is preferably independently 2-4, such as 2, 3, or 4.

[0024] In the aforementioned two-component polyurethane structural adhesive, the castor oil polyol preferably further contains polyether-modified castor oil polyol and / or epoxy-modified castor oil polyol. The total proportion of alicyclic-modified castor oil polyol and aromatic-modified castor oil polyol in the castor oil polyol is preferably 60-100%, such as 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 98%, 100%, etc.

[0025] In the aforementioned two-component polyurethane structural adhesive, the isocyanate can be any existing organic compound having at least two isocyanate groups. Specific examples include, but are not limited to: toluene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (4,4'-MDI), a mixture of diphenylmethane-2,2'-diisocyanate and diphenylmethane-2,4'-diisocyanate, a mixture of 4,4'-diphenylmethane diisocyanate, diphenylmethane-2,2'-diisocyanate and diphenylmethane-2,4'-diisocyanate, a mixture of 4,4'-diphenylmethane diisocyanate and diphenylmethane-2,2'-diisocyanate or diphenylmethane-2,4'-diisocyanic acid, liquefied MDI (carbamate-modified MDI, carbodiimide-modified MDI), polymethylene polyphenyl polyisocyanate (PAPI), 4,4'-bicyclo[] Hexylmethane diisocyanate (HMDI), hexamethylene diisocyanate (HDI), naphthalene diisocyanate (NDI), terephthalic diisocyanate (PPDI), 1,4-cyclohexane diisocyanate (CHDI), phenylenediamine diisocyanate (XDI), cyclohexane diisocyanate (HXDI), trimethyl-1,6-hexamethylene diisocyanate (TMHDI), tetramethyl-methylenediisocyanate (TMXDI), norbornane diisocyanate (NBDI), dimethylbiphenyl diisocyanate (TODI), methylcyclohexyl diisocyanate (HTDI), dimethyl diphenylmethane diisocyanate (DMMDI), lysine diisocyanate, isophorone diisocyanate, TDI dimer, TDI trimer, HDI trimer, HDI dimer, HDI biuret, and IPDI trimer.

[0026] In the above-mentioned two-component polyurethane structural adhesive, the isocyanate content in the NCO-terminated polyurethane prepolymer is preferably 8-20%, such as 8%, 10%, 12%, 14%, 16%, 18%, 20%, etc. The NCO-terminated polyurethane prepolymer is obtained by esterification of polyisocyanates with polyol compounds. The polyisocyanates mentioned include, for example, toluene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (4,4'-MDI), a mixture of diphenylmethane-2,2'-diisocyanate and diphenylmethane-2,4'-diisocyanate, 4,4'-diphenylmethane diisocyanate, a mixture of diphenylmethane-2,2'-diisocyanate and diphenylmethane-2,4'-diisocyanate, a mixture of 4,4'-diphenylmethane diisocyanate and diphenylmethane-2,2'-diisocyanate or diphenylmethane-2,4'-diisocyanic acid, liquefied MDI (carbamate-modified MDI, carbodiimide-modified MDI), polymethylene polyphenyl polyisocyanate (PAPI), 4,4'-dicyclohexylmethane diisocyanate (HMDI), hexamethylene diisocyanate, etc. The polyisocyanate is selected from at least one of the following: HDI, NDI, PPDI, CHDI, XDI, HXDI, TDI, TDI, 1,4-cyclohexane diisocyanate, CHDI, XDI, HXDI, TDI, TMHDI, TMXDI, NBDI, TODI, TODI, DMMDI, LYSDI, TDI, TDI trimer, HDI trimer, HDI dimer, HDI biuret, and IPDI trimer. The polyol compound may include at least one of the following: polyester polyol, polyether polyol, and castor oil polyol. In one specific embodiment, the esterification reaction includes dehydrating a polyol compound to a water content below 300 ppm, then adding a polyisocyanate to the dehydrated polyol compound at a temperature controlled at 40°C to 55°C, and reacting under esterification conditions. After the reaction is complete, an NCO-terminated polyurethane prepolymer is obtained. Preferably, the dehydration conditions include a temperature of 110°C to 110°C and a time of 30 min to 90 min.

[0027] In the aforementioned two-component polyurethane structural adhesive, the first filler and the second filler can be the same or different, and each can be independently selected from at least one of the following: micronized powder, aluminum hydroxide, magnesium hydroxide, aluminum oxide, magnesium oxide, zinc oxide, calcium carbonate, talc, boron nitride, aluminum nitride, graphene, diamond, quartz powder, molybdenum disulfide, mica powder, titanium dioxide, silica, bentonite, hollow glass microspheres, and carbon black. The first filler and the second filler are preferably both hollow glass microspheres. In this case, the resulting two-component polyurethane structural adhesive not only has low modulus at low temperatures and high modulus at high temperatures, but also has a relatively low density.

[0028] In the above-mentioned two-component polyurethane structural adhesive, the first plasticizer and the second plasticizer may be the same or different, and may be independently selected from one of phthalates, aliphatic diacidates, benzoic acid glycol esters, hydrophobic petroleum plasticizers and phosphate plasticizers.

[0029] In the above-mentioned two-component polyurethane structural adhesive, the first thixotropic agent and the second thixotropic agent can be the same or different, and preferably both are fumed silica.

[0030] In the above-mentioned two-component polyurethane structural adhesive, the first additive and the second additive may be the same or different, and each may be independently selected from at least one of color paste, defoamer, dehydrating agent, rheology modifier, leveling agent, silane coupling agent, wetting and dispersing agent, adhesion promoter and catalyst.

[0031] In the aforementioned two-component polyurethane structural adhesives, the terms "Ⅰ" and "Ⅱ", "first" and "second" are merely used to distinguish similar compounds appearing in different positions for ease of description, and have no other special meaning.

[0032] The preparation method of the two-component polyurethane structural adhesive provided by the present invention includes the following steps: mixing each component in component A evenly to obtain component A; mixing each component in component B evenly to obtain component B.

[0033] In a preferred embodiment, the method for uniformly mixing the components in component A includes mixing polyester polyol, polyether polyol, castor oil polyol, first plasticizer and first auxiliary agent for 20 min to 40 min, then adding molecular sieve, first filler and first thixotropic agent and continuing to mix for 40 min to 80 min, and then removing the vacuum to obtain component A.

[0034] In a preferred embodiment, the method for uniformly mixing the components in component B includes mixing isocyanate, NCO-terminated polyurethane prepolymer, dehydrating agent, second filler, second plasticizer, second thixotropic agent and second auxiliary agent for 60 min to 90 min and then removing the vacuum to obtain component B.

[0035] This invention provides the application of the above-mentioned two-component polyurethane structural adhesive in the bonding of new energy vehicle battery packs.

[0036] The present invention will be described in detail below through embodiments.

[0037] In the following examples and comparative examples, the molecular sieve was purchased from Luoyang Jianlong Micro-Nano New Materials Co., Ltd., with the grade JLH-03-B; the hollow glass microspheres were purchased from Zhengzhou Shenglete Hollow Microsphere New Materials Co., Ltd., with the grade HL-40; the calcium carbonate was purchased from Jiangxi Guangyuan Chemical Co., Ltd., with the grade CC-1500; the additive was an antifoaming agent purchased from BYK Company, with the grade BYK-A 535; and the fumed silica was purchased from CABOT Company, with the grade TS-720.

[0038] Example 1 The two-component polyurethane structural adhesive provided in this embodiment consists of component A and component B. Component A and component B are prepared according to the following methods: Component A was obtained by mixing 10% polyether polyol (polypropylene glycol, number average molecular weight 1000, purchased from Jiangsu Zhongshan Chemical Co., Ltd., brand name N-210), 10% polyester polyol, 60% castor oil polyol, 6% plasticizer (phthalate), and 2% additives for 20 min. Then, 1% molecular sieve, 10% filler (hollow glass microspheres), and 1% fumed silica were added and the mixture was continued for 80 min before devastation. The polyester polyol was composed of alicyclic polyester polyol (purchased from Lexin Chemical (Shanghai) Co., Ltd., brand name 81R) and aromatic polyester polyol (purchased from Shanghai BenyoCoat New Materials Co., Ltd., brand name BenyoCoat BP 40) in a mass ratio of 0.2:1. The castor oil polyol is composed of alicyclic modified castor oil polyol (purchased from Lexin Chemical (Shanghai) Co., Ltd., brand name 1000-170-1) and aromatic modified castor oil polyol (purchased from Ito Oil Co., Ltd., brand name H368) in a mass ratio of 5:1.

[0039] Component B is obtained by mixing 1% isocyanate (toluene diisocyanate (TDI)), 85% NCO-terminated polyurethane prepolymer (purchased from Huntsman, brand name Suprasec 9272, isocyanate content 8%), 0.5% dehydrating agent, 10% filler (hollow glass microspheres), 2% plasticizer (phthalate), 1% fumed silica, and 0.5% additives for 60 min and then removing the vacuum.

[0040] The ratio of component A to component B is preferably 1:0.8, where the total molar ratio of the hydroxyl content in the polyol to the total isocyanate content in the isocyanate and NCO-terminated polyurethane prepolymer.

[0041] Example 2 The two-component polyurethane structural adhesive provided in this embodiment consists of component A and component B. Component A and component B are prepared according to the following methods: Component A was obtained by mixing 40% polyether polyol (polytetrahydrofuran diol, number average molecular weight 1000, purchased from Basf, brand name m-PolyTHF 10P), 20% polyester polyol, 20% castor oil polyol, 5% plasticizer (phthalate), and 2% additives for 40 min. Then, 1% molecular sieve, 10% filler (hollow glass microspheres), and 3% fumed silica were added, and the mixture was further mixed for 40 min before removing the vacuum. The polyester polyol consisted of an alicyclic polyester polyol (purchased from Lexin Chemical (Shanghai) Co., Ltd., brand name 81R) and an aromatic polyester polyol (purchased from Shanghai BenyoCoat New Materials Co., Ltd., brand name BenyoCoat BP 40) in a mass ratio of 5:1. The castor oil polyol is composed of alicyclic modified castor oil polyol (purchased from Lexin Chemical (Shanghai) Co., Ltd., brand name 1000-170-1) and aromatic modified castor oil polyol (purchased from Ito Oil Co., Ltd., brand name H368) in a mass ratio of 0.2:1.

[0042] Component B is obtained by mixing 15% isocyanate (isophorone diisocyanate), 57% NCO-terminated polyurethane prepolymer (purchased from Huntsman, brand name Suprasec 2644, isocyanate content 20%), 1% dehydrating agent, 20% filler (hollow glass microspheres), 5% plasticizer (phthalate), 1% fumed silica and 1% additives for 90 min and then removing the vacuum.

[0043] The ratio of component A to component B is preferably 1:1.4, where the total molar ratio of hydroxyl content in the polyol to the total isocyanate content in the isocyanate and NCO-terminated polyurethane prepolymer.

[0044] Example 3 The two-component polyurethane structural adhesive provided in this embodiment consists of component A and component B. Component A and component B are prepared according to the following methods: Component A was obtained by mixing 10% polyether polyol (bisphenol A modified polyether polyol, number average molecular weight 400, purchased from Arkema, brand name DIANOL 330HP), 50% polyester polyol, 10% castor oil polyol, 10% plasticizer (phthalate), and 1% additives for 30 min. Then, 5% molecular sieve, 10% filler (hollow glass microspheres), and 4% fumed silica were added, and the mixture was further mixed for 60 min before devastation. The polyester polyol consisted of alicyclic polyester polyol (purchased from Lexin Chemical (Shanghai) Co., Ltd., brand name 81R) and aromatic polyester polyol (purchased from Shanghai Benyo Coat New Materials Co., Ltd., brand name BenyoCoat BP 40) in a mass ratio of 2.5:1. The castor oil polyol is composed of alicyclic modified castor oil polyol (purchased from Lexin Chemical (Shanghai) Co., Ltd., brand name 1000-170-1) and aromatic modified castor oil polyol (purchased from Ito Oil Co., Ltd., brand name H368) in a mass ratio of 2.5:1.

[0045] Component B is obtained by mixing 10% isocyanate (4,4'-diphenylmethane diisocyanate), 62% NCO-terminated polyurethane prepolymer (purchased from Huntsman, brand name Suprasec 7139, isocyanate content 12%), 1% dehydrating agent, 20% filler (hollow glass microspheres), 5% plasticizer (phthalate), 1% fumed silica, and 1% additives for 75 min and then removing the vacuum.

[0046] The ratio of component A to component B is preferably 1:1.1, where the total molar ratio of the hydroxyl content in the polyol to the total isocyanate content in the isocyanate and NCO-terminated polyurethane prepolymer.

[0047] Example 4 A two-component polyurethane structural adhesive was prepared according to the method of Example 1, except that the hollow glass microspheres were replaced with the same amount of calcium carbonate by weight, and the other conditions were the same as in Example 1, to obtain the two-component polyurethane structural adhesive.

[0048] Comparative Example 1 A two-component polyurethane structural adhesive was prepared according to the method of Example 1, except that the alicyclic polyester polyol was replaced with an aromatic polyester polyol of the same weight, and the other conditions were the same as in Example 1, to obtain the two-component polyurethane structural adhesive.

[0049] Comparative Example 2 A two-component polyurethane structural adhesive was prepared according to the method of Example 1, except that the aromatic polyester polyol was replaced with an alicyclic polyester polyol of the same weight, and the other conditions were the same as in Example 1, to obtain the two-component polyurethane structural adhesive.

[0050] Comparative Example 3 A two-component polyurethane structural adhesive was prepared according to the method of Example 1, except that the alicyclic modified castor oil polyol was replaced with the same amount of aromatic modified castor oil polyol, and the other conditions were the same as in Example 1, to obtain the two-component polyurethane structural adhesive.

[0051] Comparative Example 4 A two-component polyurethane structural adhesive was prepared according to the method of Example 1, except that the aromatic modified castor oil polyol was replaced by the same amount of alicyclic modified castor oil polyol, and the other conditions were the same as in Example 1, to obtain the two-component polyurethane structural adhesive.

[0052] Comparative Example 5 A two-component polyurethane structural adhesive was prepared according to the method of Example 1, in which the aromatic modified castor oil polyol and the alicyclic modified castor oil polyol were replaced by the same parts by weight of conventional castor oil polyol (purchased from Shanghai Hongyuan Chemical Co., Ltd., brand name: refined castor oil), and the other conditions were the same as in Example 1, to obtain the two-component polyurethane structural adhesive.

[0053] Test case The performance of the above embodiments and comparative examples was tested according to the following method, and the results are shown in Table 1.

[0054] (1) Low-temperature (-40℃) modulus: After uniformly mixing components A and B of the two-component polyurethane structural adhesives obtained in the above examples and comparative examples, the mixture was cured at 25℃ and 50%RH for 7 days. The cured product was then made into a sample. The sample size was 50mm*7mm*0.3mm. The low-temperature modulus was tested using a thin film stretching method. The test frequency was 1Hz, and the heating rate was 2℃ / min. The temperature was increased from -40℃ to 90℃ to obtain the DMA curve. The modulus at -40℃ was marked, which is the low-temperature modulus.

[0055] (2) Modulus at room temperature (25℃): After uniformly mixing components A and B of the two-component polyurethane structural adhesives obtained in the above examples and comparative examples, the mixture was cured for 7 days at 25℃ and 50%RH. The cured product was then made into a sample. The sample size was 50mm*7mm*0.3mm. The modulus at room temperature was tested by thin film stretching. At a test frequency of 1Hz and a heating rate of 2℃ / min, the temperature was increased from -40℃ to 90℃ to obtain the DMA curve. The modulus at 25℃ was marked, which is the modulus at room temperature.

[0056] (3) High-temperature (60℃) modulus: After uniformly mixing components A and B of the two-component polyurethane structural adhesives obtained in the above examples and comparative examples, the mixture was cured for 7 days at 25℃ and 50%RH. The cured product was then made into a sample. The sample size was 50mm*7mm*0.3mm. The high-temperature modulus was tested by thin film stretching. At a test frequency of 1Hz and a heating rate of 2℃ / min, the temperature was increased from -40℃ to 90℃ to obtain the DMA curve. The modulus at 60℃ was marked, which is the high-temperature modulus.

[0057] (4) Density: After uniformly mixing components A and B of the two-component polyurethane structural adhesives obtained in the above examples and comparative examples, the mixture was cured for 7 days at a temperature of 25°C and a humidity of 50%RH. A small piece of the cured sample was weighed in air and recorded as m1. The small sample was placed into a density cup (filled as much as possible). Impregnation liquid was poured into the density cup containing the sample until the liquid level was flush with the overflow hole (ensuring that air bubbles in the gaps between the sample pieces were eliminated; slight vibration or vacuuming could be used). The lid was closed, the outer wall was wiped dry, and the total weight of "sample + liquid + cup" was weighed and recorded as m2. The sample and liquid were poured out, and the density cup was cleaned and dried. The impregnation liquid was refilled, and the mass of "liquid + cup" was weighed and recorded as m3. The density was calculated using the formula... The density of the sample was calculated.

[0058] (5) Integrity and elongation at break: The two-component polyurethane structural adhesive obtained in the above examples and comparative examples is made into a 2 mm test sample sheet. After curing at room temperature for 7 days, the integrity and elongation at break are tested according to the methods of GB / T528-2009 & ASTM D412. At a test temperature of 25℃±2℃, the test sample is stretched to break at a test speed of 50 mm / min. The tensile stress at this time is recorded and the integrity and elongation at break are calculated.

[0059] (6) Shear strength: The two-component polyurethane structural adhesive obtained in the above examples and comparative examples was coated on 3003 aluminum sheets. The 3003 aluminum sheets were overlapped and pressed together to make test samples. The bonding area was 25.0mm×12.5mm, and the thickness of the adhesive layer was 0.2mm. The test samples were cured. Then, the fully cured samples were pulled apart in opposite directions using a universal testing machine at room temperature. The measured force value was recorded as strength (MPa). The results of the shear strength of the sample are shown in Table 1.

[0060] (7) Shear strength at 60℃: The two-component polyurethane structural adhesive obtained in the above examples and comparative examples were coated on 3003 aluminum sheets. The 3003 aluminum sheets were overlapped and pressed together to make test samples. The bonding area was 25.0mm×12.5mm, and the thickness of the adhesive layer was 0.2mm. The test samples were cured. Then, the fully cured samples were kept at 60℃ for 30min. At 60℃, the two sheets were pulled apart in opposite directions using a universal testing machine. The measured force value was recorded as strength (MPa). The results of the shear strength of the prepared samples at 60℃ are shown in Table 1.

[0061] (8) Peel strength: The test was conducted according to the method in standard GB 2791-1995. The flexible material sample was 200mm*25mm in size and 3mm thick. The two-component polyurethane structural adhesive obtained in the examples and comparative examples was applied to the entire width of the flexible material substrate. The application length was 150mm and the application thickness was 1mm. The flexible material adhesive and the substrate were bonded together and cured at a temperature of 25±2℃ and a humidity of 50±10%RH to obtain the flexible test specimen. The unbonded part of the flexible test specimen was symmetrically clamped in the upper and lower clamps. The clamping parts should not slip. The testing machine was started and the clamps were separated at a speed of 100mm / min. The peel length of the flexible test specimen should be at least 125mm. The peel load curve was recorded and plotted. The average peel strength was calculated by dividing the average force within the length of 25~125mm by the bonding width.

[0062] (9) T-peel strength at 60℃: The test was conducted according to the method in standard GB 2791-1995. The size of the flexible material sample was 200mm*25mm and the thickness was 3mm. The two-component polyurethane structural adhesive obtained in the examples and comparative examples was applied to the entire width of the flexible material bonded part. The application length was 150mm and the application thickness was 1mm. The flexible material bonded part and the bonded part were bonded together and cured under the conditions of temperature of 25±2℃ and humidity of 50±10%RH to obtain the flexible test piece. After the cured sample is placed at 60℃ for 30 minutes, the unbonded part of the flexible test piece is symmetrically clamped in the upper and lower clamps at 60℃. The clamping part should not slip. Start the testing machine and separate the clamps at a speed of 100 mm / min. The peel length of the flexible test piece should be at least 125 mm. Record and plot the peel load curve. Divide the average force within the length of 25~125 mm by the bond width to calculate the average T peel strength at 60℃.

[0063] (10) Drop ball impact performance: The two-component polyurethane structural adhesive obtained in the examples and comparative examples was applied at room temperature using a dispensing machine. A rectangular adhesive frame of 25mm*25mm (the size of the center line of the adhesive line) was applied to the ink glass with an adhesive thickness of 0.15mm and an adhesive width of 3mm. Then, another 3003 aluminum substrate was bonded to the ink glass. After the bonding was completed, the sample was cured in an environment of 25℃ and 50%RH for 7 days. Then, the bonded sample was repeatedly dropped from a height of 100mm using a drop ball tester with a weight of 100g until the bonded substrate was separated by the impact. The number of impacts displayed by the instrument was recorded.

[0064] Table 1

[0065] As can be seen from the results in Table 1, the DMA modulus of the two-component polyurethane structural adhesive provided by this invention increases from 10-30 MPa to 100-120 MPa at 60°C, while the DMA modulus at room temperature and -40°C remains at a low level. The DMA modulus at room temperature increases from approximately 500-700 MPa to approximately 700-900 MPa, and the DMA modulus at -40°C increases from approximately 800-1000 MPa to approximately 1200-1500 MPa. The bulk strength and elongation at break remain at a high level, at approximately 10-12 MPa and 45-75%, respectively. The interfacial shear strength (2 mm adhesive thickness) can reach over 10 MPa, and the interfacial shear strength at high temperature (60°C) increases from approximately 1.5-2 MPa to approximately 3-4 MPa. The T-peel strength at 60°C increases from below 1.0 N / mm to above 2.5 N / mm. In other words, the two-component polyurethane structural adhesive provided by this invention has both low modulus at low temperatures and high modulus at high temperatures, as well as high high-temperature shear strength and T-peel strength. It has excellent comprehensive performance and broad application prospects.

[0066] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A two-component polyurethane structural adhesive characterized in that, The two-component polyurethane structural adhesive comprises A component and B component; the A component comprises polyhydric alcohol, molecular sieve, first filler, first plasticizer, first thixotropic agent and first auxiliary agent; the polyhydric alcohol comprises polyether polyol, polyester polyol and castor oil polyol with a mass ratio of 1:(0.25-7):(0.25-7); the polyester polyol comprises alicyclic polyester polyol and aromatic polyester polyol with a mass ratio of (0.2-5):1; the castor oil polyol comprises alicyclic modified castor oil polyol and aromatic modified castor oil polyol with a mass ratio of (0.2-5):1; the B component comprises isocyanate, NCO-terminated polyurethane prepolymer, water removing agent, second filler, second plasticizer, second thixotropic agent and second auxiliary agent.

2. The two-component polyurethane structural adhesive according to claim 1, characterized in that, The content of the polyether polyol is 10-40% based on the total weight of the A component; the content of the polyester polyol is 10-70% based on the total weight of the A component; the content of the castor oil polyol is 10-70% based on the total weight of the A component; the content of the molecular sieve is 1-10% based on the total weight of the A component; the content of the first filler is 10-50% based on the total weight of the A component; the content of the first plasticizer is 1-20% based on the total weight of the A component; the content of the first thixotropic agent is 1-5% based on the total weight of the A component; the content of the first auxiliary agent is 0.1-5% based on the total weight of the A component; The content of the isocyanate is 1-15% based on the total weight of the B component; the content of the NCO-terminated polyurethane prepolymer is 30-85% based on the total weight of the B component; the content of the water removing agent is 0.1-1.5% based on the total weight of the B component; the content of the second filler is 10-50% based on the total weight of the B component; the content of the second plasticizer is 1-20% based on the total weight of the B component; the content of the second thixotropic agent is 1-5% based on the total weight of the B component; the content of the second auxiliary agent is 0.1-5% based on the total weight of the B component.

3. The two-component polyurethane structural adhesive according to claim 1, characterized in that, The molar ratio of the total content of hydroxyl groups in the polyhydric alcohol to the total content of isocyanate groups in the isocyanate and the NCO-terminated polyurethane prepolymer is 1:(0.8-1.4).

4. The two-component polyurethane structural adhesive according to claim 1, wherein The polyether polyol is selected from at least one of polyoxyethylene polyol, polyoxypropylene polyol, polytetrahydrofuran diol and bisphenol A modified polyether polyol; Preferably, the polyoxyethylene polyol has a number average molecular weight of 100-6000 and a functionality of 2-4. Preferably, the polyoxypropylene polyol has a number average molecular weight of 100-6000 and a functionality of 2-4. Preferably, the polytetrahydrofuran diol has a number average molecular weight of 100-4000. Preferably, the bisphenol A modified polyether polyol has a number average molecular weight of 100-6000 and a functionality of 2-3.

5. The two-component polyurethane structural adhesive according to claim 1, wherein The number average molecular weight of the alicyclic polyester polyol and the aromatic polyester polyol is independently 500-6000, and the functionality is independently 2-4. Preferably, the alicyclic polyester polyol is an esterification product of a polybasic acid I and a polyol I, the polybasic acid I and / or the polyol I containing an alicyclic structure; preferably, the polybasic acid I is at least one selected from 1,4-cyclohexane dicarboxylic acid, hexahydrophthalic anhydride and hydrogenated bisphenol A; preferably, the polyol I is 1,4-cyclohexane dimethanol and / or 1,6-hydroxymethyl cyclohexane; Preferably, the aromatic polyester polyol is an esterification product of a polybasic acid II and a polyol II, the polybasic acid II and / or the polyol II containing an aromatic structure; preferably, the polybasic acid II is at least one selected from phthalic anhydride, terephthalic acid and isophthalic acid; preferably, the polyol II is at least one selected from diethylene glycol, ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 2-methylpropanediol, trimethylolpropane and glycerol; Preferably, the polyester polyol further contains at least one of adipic acid polyester polyol, dimer acid polyester polyol, polycaprolactone polyester polyol and polycarbonate polyester polyol; Preferably, the total proportion of the alicyclic polyester polyol and the aromatic polyester polyol in the polyester polyol is 60% to 100%.

6. The two-component polyurethane structural adhesive according to claim 1, wherein The number average molecular weight of the alicyclic modified castor oil polyol and the aromatic modified castor oil polyol is independently 400 to 5000, and the functionality is independently 2 to 4; Preferably, the castor oil polyol further contains a polyether modified castor oil polyol and / or an epoxy modified castor oil polyol; Preferably, the total proportion of the alicyclic modified castor oil polyol and the aromatic modified castor oil polyol in the castor oil polyol is 60% to 100%.

7. The two-component polyurethane structural adhesive according to any one of claims 1 to 6, characterized in that, The isocyanate is at least one selected from toluene diisocyanate, a mixture of 4,4'-diphenylmethane diisocyanate, diphenylmethane-2,2'-diisocyanate and diphenylmethane-2,4'-diisocyanate, a mixture of 4,4'-diphenylmethane diisocyanate, diphenylmethane-2,2'-diisocyanate and diphenylmethane-2,4'-diisocyanate, a mixture of 4,4'-diphenylmethane diisocyanate and diphenylmethane-2,2'-diisocyanate and / or diphenylmethane-2,4'-diisocyanate, liquefied MDI, 4,4'-dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, naphthalene diisocyanate, p-phenylene diisocyanate, 1,4-cyclohexane diisocyanate, xylylene diisocyanate, cyclohexane dimethylene diisocyanate, trimethyl-1,6-hexamethylene diisocyanate, tetramethyl-m-xylylene diisocyanate, norbornane diisocyanate, dimethyl diphenylmethane diisocyanate, methylcyclohexyl diisocyanate, dimethyl diphenylmethane diisocyanate, lysine diisocyanate, isophorone diisocyanate, TDI dimer, TDI trimer, HDI trimer, HDI dimer, HDI biuret and IPDI trimer; Preferably, the content of isocyanate groups in the NCO-terminated polyurethane prepolymer is 8% to 20%. Preferably, the NCO-terminated polyurethane prepolymer is obtained by esterification of a polyisocyanate and a polyol compound; Preferably, the esterification is performed by dehydrating the polyol compound to a water content of 300 ppm or less, controlling the temperature of the dehydrated polyol compound to 40°C to 55°C, adding the polyisocyanate, and reacting under esterification conditions, to obtain the NCO-terminated polyurethane prepolymer.

8. The method for preparing the two-component polyurethane structural adhesive according to any one of claims 1-7, characterized in that, The method comprises the following steps: mixing the components in the A component to obtain the A component; and mixing the components in the B component to obtain the B component.

9. The method of claim 8, wherein the two-component polyurethane structural adhesive is prepared by mixing the polyol component and the isocyanate component at a weight ratio of 1:1 to 1:2.

5. The method of mixing the components in the A component comprises mixing the polyester polyol, the polyether polyol, the castor oil polyol, the first plasticizer, and the first additive for 20 min to 40 min, then adding the molecular sieve, the first filler, and the first thixotropic agent, and continuing to mix for 40 min to 80 min, and then vacuumizing to obtain the A component. The method of mixing the components in the B component comprises mixing the isocyanate, the NCO-terminated polyurethane prepolymer, the water-removing agent, the second filler, the second plasticizer, the second thixotropic agent, and the second additive for 60 min to 90 min, and then vacuumizing to obtain the B component.

10. Application of the two-component polyurethane structural adhesive according to any one of claims 1 to 7 to bonding of a new energy automobile battery pack.

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