Polyurethane structural adhesive with high initial strength and detachable property, its preparation method and uses

Abstract

The present invention discloses a polyurethane structural adhesive with high initial strength and detachable property, its preparation method, and its use as a structural adhesive for battery units. The structural adhesive consists of component A and component B with a volume ratio of 1:1. Component A includes 20 parts of polymer polyol, 10 to 20 parts of castor oil-modified polyol, 0.01 to 1 part of coupling agent, 0.1 to 1 part of water, and 20 to 60 parts of carbon dioxide absorbent by weight. Component B includes 1 to 20 parts of isocyanate A and 10 to 40 parts of isocyanate-based prepolymer by weight. After complete curing, the structural adhesive can reach an initial tensile shear strength of more than 4 MPa, meeting the requirement of resisting vibration damage during transportation, and the structural strength drops to a stable value of 0.2 MPa to 0.5 MPa within a short time in the use environment, so that the strength can not only meet the static bonding of battery units but also have a relatively low strength to reduce the disassembly difficulty during maintenance.

Description

Technical Field

[0001] The present invention relates to the technical field of polyurethane structural adhesives, and particularly to a polyurethane structural adhesive with high initial strength and detachable property, and a preparation method and use thereof. Background Art

[0002] Polyurethane has great development space in many fields such as foaming materials, structural adhesives, fibers, and elastomers due to its high wear resistance, low thermal expansion coefficient, and good performance designability. At present, the energy storage battery field has put forward new requirements for polyurethane structural adhesives, that is, not only high strength after complete curing is required to cope with the problem of structural shedding of energy storage batteries caused by bumps during transportation, but also the characteristics of being easy to disassemble the problem battery unit during maintenance. However, it is difficult to achieve the above requirements simultaneously in the formulation design of polyurethane structural adhesives.

[0003] Traditional detachable thermal conductive polyurethane structural adhesives sacrifice the high strength performance after complete curing. Only when the complete curing strength of the polyurethane structural adhesive is about 1 MPa can the static bonding stability of the battery unit be ensured, and the detachable function can be achieved in future maintenance; however, the bonding strength of 1 MPa is not sufficient to withstand the bumps and vibrations during the long-distance transportation of energy storage batteries, and at the same time, the force required for disassembly is higher than the range that can be achieved by human or simple instruments, which is also an important reason why traditional detachable structural adhesives are difficult to be widely used at present.

[0004] Based on this, it is necessary to develop a new idea for preparing polyurethane structural adhesives to meet the requirements of both high bonding strength after complete curing of the structural adhesive and effectively resisting the vibration damage received during the long-distance or ocean transportation of energy storage batteries. Summary of the Invention

[0005] The purpose of the present invention is to provide a polyurethane structural adhesive with high initial strength and detachable property to solve the above technical problems.

[0006] Another purpose of the present invention is to provide a preparation method of the above polyurethane structural adhesive with high initial strength and detachable property.

[0007] Another purpose of the present invention is to provide a use of the above polyurethane structural adhesive with high initial strength and detachable property.

[0008] For this reason, the technical solution of the present invention is as follows:

[0009] A polyurethane structural adhesive with high initial strength and detachable property, which is composed of component A and component B with a volume ratio of 1:1; wherein, component A includes 20 parts of polymer polyol, 10 parts to 20 parts of castor oil-modified polyol, 0.01 part to 0.4 part of coupling agent, 0.1 part to 0.4 part of water and 20 parts to 60 parts of carbon dioxide absorbent by weight; component B includes 1 part to 20 parts of isocyanate A and 10 parts to 40 parts of terminal isocyanate group prepolymer by weight.

[0010] In component A, the polymer polyol can be used alone as polyester polyol, or as a composite of polyester polyol and polyether polyol A, and the weight ratio of polyester polyol to polyether polyol in the composite is ≥1.

[0011] In component A, the polyester polyol, polyether polyol A and castor oil-modified polyol are all polyol compounds with a hydroxyl value of 20mgKOH / g to 400mgKOH / g, a functionality of 2 to 6 and a molecular weight of 100 to 10000, and the three are compounded to provide hydroxyl groups. In practical applications, the polyester polyol can specifically be but not limited to RADIANOL1990 produced by Oriane Company, the polyether polyol A can specifically be but not limited to F3135 produced by Yantai Wanhua Polyurethane Co., Ltd., and the castor oil-modified polyol can specifically be but not limited to refined castor oil produced by Nanjing Xinxu Industry and Trade Co., Ltd.

[0012] According to the conventional configuration method of component A of the polyurethane structural adhesive, component A also includes emulsifier, plasticizer, catalyst, defoamer and filler. As a formulation composition of component A in the polyurethane structural adhesive of the present invention: it is composed of 20 parts of polymer polyol, 10 parts to 20 parts of castor oil-modified polyol, 0.01 part to 0.1 part of emulsifier, 0.01 part to 0.4 part of coupling agent, 1 part to 10 parts of plasticizer A, 0.01 part to 0.1 part of catalyst, 0.1 part to 0.4 part of water, 1 part to 5 parts of defoamer, 20 parts to 60 parts of carbon dioxide absorbent and 100 parts to 200 parts of filler A by weight.

[0013] According to the conventional configuration method of component B of the polyurethane structural adhesive, component B also includes dispersant, plasticizer and filler. As a formulation composition of component B in the polyurethane structural adhesive of the present invention: component B is composed of 1 part to 20 parts of isocyanate A, 10 parts to 40 parts of terminal isocyanate group prepolymer, 0.1 part to 5 parts of dispersant, 5 parts to 1:15 parts of plasticizer B and 100 parts to 200 parts of filler B by weight.

[0014] In component B, the terminal isocyanate group prepolymer is formed by the reaction of isocyanate B and polyether polyol B, and by using an excessive amount of isocyanate B, all the hydroxyl groups in polyether polyol B react with the isocyanate groups.

[0015] Isocyanate A and isocyanate B are each selected from at least one of 2,4-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,6-toluene diisocyanate, 2,4-toluene diisocyanate, 4,4'-diisocyanate dicyclohexylmethane, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, 1,6-hexane diisocyanate, polyphenyl polymethylene polyisocyanate, polycarbodiimide-modified MDI (polycarbodiimide-modified diphenylmethane diisocyanate), and the two use the same or different compounds.

[0016] Polyether polyol B uses a compound with a hydroxyl value of 20 mgKOH / g to 400 mgKOH / g, a functionality of 2 to 6, and a molecular weight of 100 to 10,000. In practical applications, polyether polyol B uses DL2000D produced by Shandong Bluestar Dongda Chemical Co., Ltd.

[0017] Preferably, the defoamer uses a non-silicon defoamer, which is used to remove mechanical bubbles generated after the mixing of component A and component B, and gas components that cannot be completely absorbed by the carbon dioxide absorbent during the curing process; in practical applications, the defoamer can specifically be but is not limited to P-590 produced by Youka Chemical (Shanghai) Co., Ltd.

[0018] Preferably, the emulsifier is used to improve the compatibility of water and polymer polyol in component A, and it specifically uses at least one of sodium dodecyl sulfonate, disodium octadecyl sulfosuccinamate, and disodium 4-(octadecylamino)-4-oxo-2-sulfonato-butyrate, and more preferably sodium dodecyl sulfonate.

[0019] Preferably, the coupling agent is mainly used to improve the adhesion of the polyurethane structural adhesive to the substrate and the aging resistance of the fully cured adhesive layer. It specifically selects a silane coupling agent, and more preferably a silane coupling agent containing an epoxy group. In practical applications, the coupling agent can specifically be but is not limited to γ-(2,3-epoxypropoxy)propyltrimethoxysilane produced by Hubei Jianghan New Materials Co., Ltd.

[0020] Preferably, plasticizer A and plasticizer B are used to adjust the viscosity and density of each component, and the two have the same selection type. Specifically, they use at least one of didecyl phthalate, bis(2-propylheptyl) phthalate, and bisphenol A-bis(diphenyl phosphate), and more preferably didecyl phthalate.

[0021] Preferably, the catalyst is used to adjust the pot life and curing speed after the mixing of the adhesive liquid. It specifically uses an organometallic catalyst. In practical applications, the catalyst can specifically be but is not limited to CUCAT-DG02 produced by Guangzhou Yourun Synthetic Materials Co., Ltd.

[0022] Preferably, the carbon dioxide absorbent is at least one of calcium hydroxide, calcium oxide, and portland cement, more preferably calcium hydroxide. The carbon dioxide absorbent is used to absorb the carbon dioxide generated by the reaction of water and isocyanate, and reacts to form calcium carbonate and water, so as to ensure that there are uniformly distributed water molecules in the cured adhesive layer after the excess isocyanate groups are completely consumed, which is conducive to providing an internal humid and hot aging environment in the external dry and hot aging environment.

[0023] Preferably, the dispersant is a phosphate ester dispersant, which is used to improve the compatibility of the filler in the resin matrix; in actual applications, the dispersant can specifically be, but is not limited to, BYK-W9010 produced by BYK Chemie GmbH.

[0024] Preferably, filler A and filler B are used to adjust the viscosity, density, and thermal conductivity of the adhesive liquid, and the two have the same selection; the two fillers are specifically aluminum hydroxide-based fillers; in actual applications, filler A and filler B can specifically be, but is not limited to, DCN1200U produced by Dongguan Dongchao New Materials Co., Ltd.

[0025] In the specific formulation design process of the A and B components of the polyurethane structural adhesive of the present invention, the technical problems existing in traditional polyurethane structural adhesives are considered, that is: after complete curing and during the aging process, the shear strength basically remains between 1 MPa and 2 MPa. Although it meets the requirements of static bonding of energy storage batteries and detachable under appropriate heating conditions, this shear strength is difficult to resist the bump damage generated by the adhesive layer during long-distance transportation after the initial assembly of the energy storage battery is completed; therefore, the present invention aims to prepare a structural adhesive with a relatively high initial shear strength after complete curing, but during the aging process of the adhesive layer as the battery usage time increases, its shear strength gradually decays to a low stable value that can both meet the requirements of static bonding and detachable requirements.

[0026] Considering the inherent characteristics of the polyurethane structural adhesive, that is, after the structural adhesive is completely cured, the main chain segments in the molecular structure are urethane bonds, and the polymer polyols in its raw materials mostly have ester bonds and ether bonds. These chemical bonds are not easily broken in a thermal aging environment, but are extremely easy to break in a humid and hot aging environment; and the breakage of chemical bonds directly causes the adhesive layer to lose strength due to aging; considering the characteristics of the use environment of the polyurethane structural adhesive, the aging environment inside the battery is mainly thermal aging, and the proportion of humid and hot aging is very small, which results in a very slow aging rate of the polyurethane structural adhesive inside the battery.

[0027] Based on this, in the design of the component composition of the A component of the polyurethane structural adhesive of the present invention, polyester polyol, or a composite of polyester polyol and polyether polyol is adopted, so that it reacts with the isocyanate in the B component, and the purpose of achieving a relatively high initial shear strength after the structural adhesive is completely cured is realized. In some specific embodiments, by limiting the amount of polyester polyol in the A component, or replacing part of the polyester polyol with polyether polyol according to a specified ratio, the initial shear strength of the structural adhesive after complete curing can be adjusted adaptively to meet different initial shear strength requirements.

[0028] A certain amount of deionized water is also added to the A component, so that moisture exists in the completely cured polyurethane adhesive layer. The deionized water exists in the form of water in the completely cured adhesive layer, creating conditions for the formation of a damp-heat aging environment when the cured product is heated. Furthermore, by utilizing the property that polyester polyol is easy to hydrolyze, the aging rate of the polyurethane structural adhesive inside the battery can be accelerated, and the expected result that the shear strength gradually decays during the aging process of the structural adhesive can be achieved. And because water will react with the isocyanate group to generate carbon dioxide, a carbon dioxide absorbent is also added to the A component to make the structural adhesive cure without foaming. In some specific embodiments, a large number of comparative experimental results show that the addition amount of deionized water affects the simulation duration of the damp-heat aging environment. When the amount of deionized water used is too much, the shear strength of the structural adhesive will decay excessively due to the too long simulation time of the damp-heat aging environment and cannot meet the static bonding requirements. On the contrary, when the addition amount of deionized water is too little, the shear strength of the structural adhesive cannot decay to meet the detachable requirements. Therefore, the control of the addition amount of deionized water in the A component, that is, the control of the action duration of the damp-heat aging environment of the adhesive layer. When the moisture inside the adhesive layer is completely consumed during the aging process inside the structural adhesive, the damp-heat aging environment of the adhesive layer disappears and turns into a thermal aging environment, and the decline amplitude of the strength slows down significantly. At this time, the shear strength of the structural adhesive decays to a relatively stable low level value.

[0029] A coupling agent is also added to the A component, which has a hydrolysis competition reaction with the urethane structure in the polyurethane main chain and can snatch water to preferentially undergo hydrolysis reaction, thereby adjusting the starting time that affects the strength decline of the structural adhesive during damp-heat aging to ensure that the polyurethane structural adhesive does not undergo shear strength decay prematurely.

[0030] In the component composition of the B component of the polyurethane structural adhesive of the present invention, isocyanate A is combined with a terminal isocyanate group prepolymer. Based on the differences in the isocyanate group content, viscosity, etc. between the two, by adjusting the ratio of the two, the complex of the two is combined with the polyols having different hydroxyl values in the A component to ensure the relative stability of the R value of the polyurethane structural adhesive. Among them, the R value, also known as the isocyanate index, is specifically the ratio of the total amount of isocyanate groups in isocyanate A and the terminal isocyanate group prepolymer in the B component to the total amount of hydroxyl groups of all polyol compounds in the A component. While modifying the traditional polyurethane structural adhesive, the present invention still maintains an R value similar to that of the conventional polyurethane structural adhesive.

[0031] The preparation method of the A component of the polyurethane structural adhesive with high initial strength and detachable property is as follows: Add polyester polyol, polyether polyol A, castor oil-modified polyol, defoaming agent, plasticizer, filler A and carbon dioxide absorbent into a stirring kettle, and stir and mix evenly under the conditions of vacuum (≤ -0.09 MPa) and 25°C to 60°C. Then add emulsifier, deionized water and coupling agent, and mix evenly under normal pressure and 25°C to 60°C to obtain the A component.

[0032] The preparation method of the B component of the polyurethane structural adhesive with high initial strength and detachable property is as follows: Add polyether polyol B into a stirring kettle, and stir and dehydrate under the conditions of vacuum (≤ -0.09 MPa) and high temperature of 60°C to 120°C. Then, add an excessive amount of isocyanate into the reaction kettle and raise the temperature to 60°C to 120°C for reaction for 2 h to 8 h to make the hydroxyl groups of polyether polyol B all react to obtain a terminal isocyanate group prepolymer; then add isocyanate, dispersant and filler B into the reaction kettle, and stir until evenly mixed again under the conditions of vacuum (≤ -0.09 MPa) and 25°C to 60°C to obtain the B component.

[0033] The use of a polyurethane structural adhesive with high initial strength and detachable property is specifically as a structural adhesive for battery units.

[0034] After testing, after the polyurethane structural adhesive with high initial strength and detachable property is applied and completely cured after mixing, the tensile shear strength tested according to the requirements of GB / T7124 - 2008 is > 4 MPa; after the tensile shear specimen is aged in an environment of 60°C for 1000 h, the tensile shear strength ≤ 2 MPa, which is reduced to the initial shear strength of the traditional polyurethane structural adhesive; after being aged in an environment of 60°C for 5000 h, the tensile shear strength of the structural adhesive is between 0.2 MPa and 0.5 MPa, reaching the shear strength that meets the requirements of static bonding and is convenient for disassembly.

[0035] Compared with traditional polyurethane structural adhesives, the polyurethane structural adhesive with high initial strength and detachable property of the present invention: 1) overcomes the problem of low initial strength after complete curing, enabling the polyurethane structural adhesive to achieve a tensile shear strength of more than 4 MPa after complete curing, meeting the requirement of resisting vibration damage during transportation; 2) during the continuous operation after the energy storage battery is fixed and installed, the heat released during the charge and discharge cycle of the energy storage battery (i.e., the thermal environment temperature ≈ 60 °C) can cause the structural strength of the polyurethane structural adhesive to decline to another stable value (0.2 MPa - 0.5 MPa) under the dual effects of external heat aging and internal moisture erosion in a relatively short time. At this time, the strength can not only meet the static bonding of battery units but also have a relatively low strength to reduce the disassembly difficulty during maintenance. Specific Embodiments

[0036] The following further illustrates the present invention with specific embodiments, but the following embodiments are by no means any limitation to the present invention.

[0037] In the following examples and comparative examples, the polyester polyol uses RADIANOL1990 produced by Orion Corporation, the polyether polyol A uses F3135 produced by Yantai Wanhua Polyurethane Co., Ltd., the castor oil polyol uses refined castor oil produced by Nanjing Xinxu Industry and Trade Co., Ltd., the defoaming agent uses P-590 produced by Youka Chemical (Shanghai) Co., Ltd., the catalyst uses CUCAT-DG02 produced by Guangzhou Yourun Synthetic Materials Co., Ltd., the coupling agent uses γ-(2,3-epoxypropoxy)propyltrimethoxysilane produced by Hubei Jianghan New Materials Co., Ltd., the polyether polyol B uses DL2000D produced by Shandong Bluestar Dongda Chemical Co., Ltd., the isocyanate A uses polyphenyl polymethylene polyisocyanate PM200 (functionality of 2.7) produced by Yantai Wanhua Polyurethane Co., Ltd., the isocyanate B uses polycarbodiimide-modified MDI produced by Yantai Wanhua Polyurethane Co., Ltd., the dispersant uses BYK-W9010 produced by BYK-Chemie GmbH, and the fillers A and B both use DCN1200U produced by Dongguan Dongchao New Materials Co., Ltd. Example 1

[0038] A polyurethane structural adhesive with high initial strength and detachable property, which is composed of component A and component B, and is specifically prepared by the following method:

[0039] Preparation of Component A: Add 10 kg of polyester polyol, 10 kg of polyether polyol A, 10 kg of castor oil polyol, 3 kg of defoamer, 5 kg of didecyl phthalate, 0.02 kg of catalyst, 40 kg of calcium hydroxide, and 120 kg of filler A into the reaction kettle. Control the temperature of the kettle at 25°C - 45°C. After stirring evenly under vacuum conditions, then add 0.02 kg of sodium dodecyl sulfonate, 0.2 kg of deionized water, and 0.1 kg of coupling agent. After stirring evenly under normal pressure, discharge the mixture and fill it into one side tube body of a double-tube hose with a volume ratio of 1:1;

[0040] Preparation of Component B: Add 13.25 kg of polyether polyol B into the reaction kettle. Heat and dehydrate at 105°C under vacuum conditions until the water content ≤ 300 ppm. Add 13.25 kg of isocyanate B and raise the temperature to 80°C for reaction for 2 h. Add 2.75 kg of isocyanate A, 3 kg of dispersant, 11 kg of plasticizer, and 160 kg of filler B into the reaction kettle. Control the temperature of the kettle at 25°C - 45°C. After stirring evenly under vacuum conditions, discharge the mixture and fill it into the other side tube body of a double-tube hose with a volume ratio of 1:1. Example 2

[0041] A polyurethane structural adhesive with high initial strength and detachable property, which is composed of Component A and Component B, and is specifically prepared by the following method:

[0042] Preparation of Component A: Add 15 kg of polyester polyol A, 5 kg of polyether polyol A, 10 kg of castor oil polyol, 3 kg of defoamer, 5 kg of didecyl phthalate, 0.02 kg of catalyst, 40 kg of calcium hydroxide, and 120 kg of filler A into the reaction kettle. Control the temperature of the kettle at 25°C - 45°C. After stirring evenly under vacuum conditions, then add 0.02 kg of sodium dodecyl sulfonate, 0.2 kg of deionized water, and 0.1 kg of coupling agent. After stirring evenly under normal pressure, discharge the mixture and fill it into one side tube body of a double-tube hose with a volume ratio of 1:1;

[0043] Preparation of Component B: Add 11.5 kg of polyether polyol B into the reaction kettle. Heat and dehydrate at 105°C under vacuum conditions until the water content ≤ 300 ppm. Add 11.5 kg of isocyanate B and raise the temperature to 80°C for reaction for 2 h. Add 6.25 kg of isocyanate A, 3 kg of dispersant, 11 kg of plasticizer, and 160 kg of filler B into the reaction kettle. Control the temperature of the kettle at 25°C - 45°C. After stirring evenly under vacuum conditions, discharge the mixture and fill it into the other side tube body of a double-tube hose with a volume ratio of 1:1. Example 3

[0044] A polyurethane structural adhesive with high initial strength and detachable property, which is composed of Component A and Component B, and is specifically prepared by the following method:

[0045] Preparation of Component A: Add 20 kg of polyester polyol A, 10 kg of castor oil polyol, 3 kg of defoamer, 5 kg of dioctyl phthalate, 0.02 kg of catalyst, 40 kg of calcium hydroxide, and 120 kg of filler A into the reaction kettle. Control the temperature of the kettle at 25°C to 45°C. After stirring evenly under vacuum conditions, then add 0.02 kg of sodium dodecyl sulfonate, 0.2 kg of deionized water, and 0.1 kg of coupling agent. After stirring evenly under normal pressure, discharge the mixture and fill it into one side tube body of a double-tube hose with a volume ratio of 1:1;

[0046] Preparation of Component B: Add 10 kg of polyether polyol B into the reaction kettle. Heat and dehydrate at 105°C under vacuum conditions until the water content ≤ 300 ppm. Add 10 kg of isocyanate B and raise the temperature to 80°C for reaction for 2 h. Then add 9.25 kg of isocyanate A, 3 kg of dispersant, 11 kg of plasticizer, and 160 kg of filler B into the reaction kettle. Control the temperature of the kettle at 25°C to 45°C. After stirring evenly under vacuum conditions, discharge the mixture and fill it into the other side tube body of a double-tube hose with a volume ratio of 1:1. Example 4

[0047] A polyurethane structural adhesive is composed of Component A and Component B and is prepared by the following method:

[0048] Preparation of Component A: Add 10 kg of polyester polyol A, 10 kg of polyether polyol A, 10 kg of castor oil polyol, 3 kg of defoamer, 5 kg of dioctyl phthalate, 0.02 kg of catalyst, 40 kg of calcium hydroxide, and 120 kg of filler A into the reaction kettle. Control the temperature of the kettle at 25°C to 45°C. After stirring evenly under vacuum conditions, then add 0.02 kg of sodium dodecyl sulfonate, 0.2 kg of deionized water, and 0.1 kg of coupling agent. After stirring evenly under normal pressure, discharge the mixture and fill it into one side tube body of a double-tube hose with a volume ratio of 1:1;

[0049] Preparation of Component B: Add 11.25 kg of polyether polyol B into the reaction kettle. Heat and dehydrate at 105°C under vacuum conditions until the water content ≤ 300 ppm. Add 11.25 kg of isocyanate B and raise the temperature to 80°C for reaction for 2 h. Then add 6.75 kg of isocyanate A, 3 kg of dispersant, 11 kg of plasticizer, and 160 kg of filler B into the reaction kettle. Control the temperature of the kettle at 25°C to 45°C. After stirring evenly under vacuum conditions, discharge the mixture and fill it into the other side tube body of a double-tube hose with a volume ratio of 1:1. Example 5

[0050] A polyurethane structural adhesive is composed of Component A and Component B and is prepared by the following method:

[0051] Preparation of Component A: Add 10 kg of polyester polyol A, 10 kg of polyether polyol A, 10 kg of castor oil polyol, 3 kg of defoamer, 5 kg of dioctyl phthalate, 0.02 kg of catalyst, 40 kg of calcium hydroxide and 100 kg of filler A into the reaction kettle. Control the temperature of the kettle at 25°C - 45°C. After stirring evenly under vacuum conditions, then add 0.02 kg of sodium dodecyl sulfonate, 0.2 kg of deionized water and 0.1 kg of coupling agent. After stirring evenly under normal pressure, discharge the mixture and fill it into one side tube body of a double-tube rubber hose with a volume ratio of 1:1.

[0052] Preparation of Component B: Add 10 kg of polyether polyol B into the reaction kettle. Heat and dehydrate at 105°C under vacuum conditions until the water content ≤ 300 ppm. Add 10 kg of isocyanate B and raise the temperature to eighty °C and react for 2 h. Add 9.25 kg of isocyanate A, 3 kg of dispersant, 11 kg of plasticizer and 160 kg of filler B into the reaction kettle. Control the temperature of the kettle at 25°C - 45°C. After stirring evenly under vacuum conditions, discharge the mixture and fill it into the other side tube body of a double-tube rubber hose with a volume ratio of 1:1.

[0053] Comparative Example 1

[0054] A polyurethane structural adhesive, which is different from Example 2 only in that: the amount of water used is increased to 0.5 parts.

[0055] Comparative Example 2

[0056] A polyurethane structural adhesive, which is different from Example 2 only in that: the amount of water used is increased to 1 part.

[0057] Comparative Example 3

[0058] A polyurethane structural adhesive, which is different from Example 2 in that: the amount of coupling agent used is increased to 0.5 parts.

[0059] Comparative Example 4

[0060] A polyurethane structural adhesive, which is different from Example 2 in that: the amount of coupling agent used is increased to parts.

[0061] Performance Test:

[0062] Test the thermal conductivity, shear performance and aging performance of the polyurethane structural adhesives of the above examples and comparative examples.

[0063] The thermal conductivity test is carried out according to the method of ISO22007.2 to test the thermal conductivity of the polyurethane structural adhesive after complete curing.

[0064] The shear performance is to prepare a shear specimen according to the method of GB / T7124. The film thickness of the shear specimen is 0.2 mm, and it is cured for 168 h in an environment with an ambient temperature of 23±2°C and an ambient relative humidity of 50%±5%. Then, the shear strength test is carried out in an environment with an ambient temperature of 23±2°C and an ambient relative humidity of 50%±5%.

[0065] The aging performance is tested according to the method of GB / T7124 for the aging performance at 60°C. Specifically, a shear specimen is prepared. The specimen is cured for 168 h in an environment with an ambient temperature of 23±2°C and an ambient relative humidity of 50%±5%RH. Then, it is placed in an oven at a temperature of 60°C for 200, 400, 600, 800, 1000, 2000, 3000, and 5000 h respectively. After taking it out, it is left standing in an environment at a temperature of 25±2°C for 24 h and then the shear strength is tested.

[0066] The specific test results are shown in Table 1 below.

[0067] Table 1:

[0068]

[0069] It can be seen from Table 1 that

[0070] 1) In the thermal conductivity formation test, the thermal conductivity coefficients of the five polyurethane structural adhesives prepared from Example 1 to Example 5 after complete curing are 1.2 W / m·K to 1.4 W / m·K, so as to be approximately the same as that of the traditional polyurethane structural adhesive for batteries, so as to meet the requirement of using the polyurethane structural adhesive to conduct the heat generated by the battery during the use of the battery and avoid damage to the battery due to overheating;

[0071] 2) In the shear strength test, the initial shear strengths of the five polyurethane structural adhesives prepared from Example 1 to Example 5 after complete curing are all >4 MPa, meeting the requirement of resisting vibration damage during transportation; According to the test results analysis of Example 1, Example 2, and Example 3, when the total amount of polymer polyol remains the same and the system R value remains basically the same, by changing the ratio of polyester polyol and polyether polyol in Component A, the initial shear strength after complete curing can be adjusted; Moreover, it can also be seen from these three examples that as the proportion of polyester polyol in the polymer polyol increases, that is, as the content of polyester groups increases, the initial shear strength of the polyurethane structural adhesive after complete curing also gradually increases; Among them, as a modified alternative product of the traditional polyurethane structural adhesive for batteries, the R value in each example is set to 1.00 to 1.40, which is an approximate value of the R value of the traditional polyurethane structural adhesive for batteries;

[0072] According to the results of additional experimental tests, when the dosage of the polyester polyol in Example 2 was adjusted to 5 kg, while the dosage of the polyether polyol was adjusted to 15 kg, and the dosages of other components remained unchanged, the initial shear strength after complete curing decreased significantly, being 3.6 MPa.

[0073] 3) In the aging performance test, for the five polyurethane structural adhesives prepared in Examples 1 to 5, in an aging environment of 60 °C, as the battery usage time increased, their shear strength gradually decayed and finally reached a stable value. The range of this shear strength stable value was 0.2 MPa to 0.45 Mpa, making it easier to disassemble;

[0074] Based on the test result analysis of Examples 1, 2, and 3, when the proportion of the polyester polyol in the polymer polyol gradually increased and even completely replaced the polyether polyol, the decay time of the shear strength (i.e., the aging time period during which the shear strength significantly decayed) gradually became faster. The reason for this analysis was that since the hydrolysis resistance of the polyester structure was lower than that of the polyether structure, the shear strength in an aging environment of 60 °C would decrease earlier; specifically, the shear strength decay of the polyurethane structural adhesive in Example 1 occurred between 400 h and 600 h of aging, the shear strength decay of the polyurethane structural adhesive in Example 2 occurred between 200 h and 400 h of aging, and although the shear strength decay of the polyurethane structural adhesive in Example 3 also occurred between 200 h and 400 h of aging as shown in Table 1, it was inferred from the change in the decay amplitude that it should be closer to a certain moment around 200 h of aging;

[0075] According to Examples 1, 4, and 5, while keeping the polymer polyol ratio the same and the total amount of the three polyols the same, by increasing the proportion of isocyanate A in Component B and slightly increasing the system R value, the start time of the shear strength decay of the structural adhesive gradually advanced, and for the final shear strength value after decay, the reason for the analysis was that the increase in the R value led to an increase in the molar amount of isocyanate groups, that is, there were more excess isocyanate groups that would react with water and generate more substituted ureas. During the damp heat aging resistance process, the hydrolysis resistance of the urea group was much lower than that of the urethane in the main chain segment of the structural adhesive, thus causing the start time of the decay to advance; specifically, the shear strength decay of the polyurethane structural adhesives in Examples 4 and 5 both occurred between 200 h and 400 h of aging, and it could be inferred from the decay amplitude that the start time of the decay of Example 5 was closer to 200 h of aging compared to Example 4;

[0076] In summary, in the formulation of the polyurethane structural adhesive, the compounding ratio of the two complexes in the polymer polyol of component A, and the compounding ratio between the polyol substance in component A and the isocyanate and the terminal isocyanate group prepolymer in combination B comprehensively affect the initial shear strength of the polyurethane structural adhesive and the change trend of the shear strength during the aging process.

[0077] Compared with Example 2, in Comparative Example 1 and Comparative Example 2, the addition amount of deionized water in component A was gradually increased, resulting in too low stable values of the shear strength after attenuation of the polyurethane structural adhesives prepared by the two, <0.1 MPa, which could not meet the static bonding requirements; however, whether in the examples or in the comparative examples, the shear strength of the structural adhesive tended to be stable after aging for 2000 h, indicating that water was continuously consumed during the aging process of the adhesive layer until the water was completely consumed, and then the aging state of the adhesive layer changed from hydrothermal aging to thermal aging and the strength no longer decreased; in addition, according to the results of other experimental tests, when the addition amount of deionized water in component A was too small, the shear strength of the polyurethane structural adhesive was still higher than 0.5 MPa after aging for 5000 h, which not only did not meet the disassembly requirements, but also made it difficult to judge whether the strength decrease was regular and reached a stable value.

[0078] Compared with Example 2, in Comparative Example 3 and Comparative Example 4, the addition amount of the coupling agent in component A was gradually increased, resulting in a significant delay in the starting time of strength attenuation of the polyurethane structural adhesives prepared by the two in the aging test. The reason for the analysis is that the silane coupling agent containing epoxy groups protects the urethane structure due to its hydrophobic effect, and at the same time, since the reaction of small molecule substances with water is faster than that of substances with larger molecular weights, the coupling agent component is more prone to hydrolysis than the urethane structure under heating conditions; as the hydrolysis reaction degree of the coupling agent increases, the content of the coupling agent becomes less and less, and the degree of participation of the remaining water molecules in the hydrolysis reaction of the urethane structure gradually increases, macroscopically manifested as a delay in the starting time of shear strength decrease; specifically, the starting time of shear strength decrease in Comparative Example 3 was delayed to between 600 h and 800 h of aging, while the starting time of shear strength decrease in Comparative Example 4 was delayed to between 1000 h and 2000 h of aging, and it led to that when aging for 5000 h finally, the shear strength was still high, making it difficult to judge whether it attenuated to a stable state and not yet meeting the disassembly requirements.

[0079] In summary, for the polyurethane structural adhesive with high initial strength and disassembly property of the present invention, after mixing and applying the adhesive until it is completely cured, its initial tensile shear strength > 4 MPa; after the tensile shear specimen is aged in an environment of 60 °C for 1000 h, the tensile shear strength ≤ 2 MPa, which is reduced to the initial shear strength of the traditional polyurethane structural adhesive; after aging in an environment of 60 °C for 5000 h, the tensile shear strength of the structural adhesive is between 0.2 MPa and 0.5 MPa, meeting the shear strength requirements for static bonding and being convenient for disassembly.

Claims

1. A polyurethane structural adhesive with high initial strength and detachable property, characterized in that, It is composed of component A and component B with a volume ratio of 1:1; among them, Component A includes 20 parts of polymer polyol, 10 to 20 parts of castor oil-modified polyol, 0.01 to 0.4 part of coupling agent, 0.1 to 0.4 part of water, and 20 to 60 parts of calcium hydroxide by weight; Component B includes 1 to 20 parts of isocyanate A and 10 to 40 parts of terminal isocyanate group prepolymer by weight; The polymer polyol is a polyester polyol or a composite of a polyester polyol and polyether polyol A, and the weight ratio of the polyester polyol to polyether polyol A in the composite is ≥1; The terminal isocyanate group prepolymer is formed by the reaction of isocyanate B and polyether polyol B; The polyester polyol, polyether polyol A, polyether polyol B, and castor oil-modified polyol are all compounds with a hydroxyl value of 20 mgKOH / g to 400 mgKOH / g, a functionality of 2 to 6, and a molecular weight of 100 to 10,000.

2. The polyurethane structural adhesive with high initial strength and detachable according to claim 1, characterized in that, Isocyanate A and isocyanate B are each selected from at least one of 2,4-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,6-toluene diisocyanate, 2,4-toluene diisocyanate, 4,4'-diisocyanate dicyclohexylmethane, 3-isocyanatomethylene-3,5,5-trimethylcyclohexyl isocyanate, 1,6-hexamethylene diisocyanate, polyphenyl polymethylene isocyanate, and polycarbodiimide-modified MDI.

3. The polyurethane structural adhesive with high initial strength and detachable according to claim 1, characterized in that, Component A further includes 0.01 to 0.1 part of emulsifier, 1 to 10 parts of plasticizer A, 0.01 to 0.1 part of catalyst, 1 to 5 parts of defoamer, and 100 to 200 parts of filler A by weight.

4. The polyurethane structural adhesive with high initial strength and being detachable according to claim 3, characterized in that, Component B further includes 0.1 to 5 parts of dispersant, 5 to 15 parts of plasticizer B, and 100 to 200 parts of filler B by weight.

5. The polyurethane structural adhesive with high initial strength and detachable according to claim 3, characterized in that, The coupling agent is a silane coupling agent; the emulsifier is at least one of sodium dodecyl sulfonate, disodium octadecyl succinamide sulfonate, and disodium 4-(octadecylamino)-4-oxo-2-sulfonato-butyrate; the plasticizer A is at least one of dioctyl phthalate, bis(2-propylheptyl) phthalate, and bisphenol A-bis(diphenyl phosphate); the catalyst is an organometallic catalyst; the defoamer is a non-silicon defoamer; the filler A is an aluminum hydroxide filler.

6. The polyurethane structural adhesive with high initial strength and detachable according to claim 4, characterized in that The dispersant is a phosphate ester dispersant; the plasticizer B is at least one of dioctyl phthalate, bis(2-propylheptyl) phthalate, and bisphenol A-bis(diphenyl phosphate); the filler B is an aluminum hydroxide filler.

7. The polyurethane structural adhesive with high initial strength and being detachable according to claim 1, wherein [[ID=IO]]The preparation method of the terminal isocyanate group prepolymer is as follows: Add the dehydrated polyether polyol B and isocyanate B to a stirring kettle, and react at 60°C to 120°C for 2 h to 8 h to obtain the terminal isocyanate group prepolymer.

8. A method for preparing a polyurethane structural adhesive with high initial strength and detachable as described in claim 4, characterized in that the steps Including: Preparation of Component A: Add polyester polyol, polyether polyol, castor oil-modified polyol, defoamer, plasticizer A, catalyst, filler A, and calcium hydroxide into a stirring kettle, and stir at 25°C to 60°C under vacuum until evenly mixed. Then add emulsifier, deionized water, and coupling agent, and continue to stir at 25°C to 60°C under normal pressure until evenly mixed, and discharge the material. Preparation of Component B: Add terminal isocyanate group prepolymer, isocyanate A, plasticizer B, dispersant, and filler B into a stirring kettle, and continue to stir at 25°C to 60°C under vacuum conditions until evenly mixed, and discharge the material.

9. Use of a polyurethane structural adhesive having high initial strength and being detachable as described in any one of claims 1 to 7, characterized in that, As a structural adhesive for battery cells.

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