Damp-heat-resistant two-component polyurethane structural adhesive and preparation method thereof

Abstract

The invention discloses a damp-heat-resistant two-component polyurethane structural adhesive, which comprises a component A and a component B in a mass ratio of (1-5): 1, the component A comprises polyether polyol, isocyanate, a reactive plasticizer, a catalyst and an auxiliary agent, and the component B comprises a curing agent, a reactive plasticizer and an auxiliary agent. The reactive plasticizer is at least one kind of grease containing unsaturated double bonds, hydroxyl or epoxy groups. The invention further discloses a preparation method of the damp-heat-resistant two-component polyurethane structural adhesive. The problem that the adhesive property of a two-component polyurethane structural adhesive is degraded due to migration of a plasticizer in a humid and hot environment is solved, and the fatigue property and the adhesive property are considered at the same time.

Description

Technical Field

[0001] The invention relates to the technical field of adhesives, and in particular to a moisture-heat resistant two-component polyurethane structural adhesive and a preparation method thereof. Background Art

[0002] New energy batteries are made up of groups of square cells connected in series. To prevent the risk of leakage during use due to scratches, microcracks in the battery shell, or damage to the insulation layer of the tabs, a leakage protection coating must be sprayed on the battery shell, tabs, and other parts to form an insulating barrier. This can also protect the battery from the effects of harsh environments such as electrolyte corrosion and high and low temperature alternation on the battery cells, thereby ensuring the electrical safety and structural stability of the battery. The square cells of lithium-ion power batteries are often bonded together using a two-component polyurethane structural adhesive. To improve the toughness of the structural adhesive, a large amount of toughening agents, such as phthalates, are generally added to the two-component polyurethane structural adhesive to achieve a balance between toughness and rigidity. However, during use, especially in hot and humid environments, the common small molecule plasticizers in the polyurethane structural adhesive will migrate to the bonding interface between the structural adhesive and the leakage protection coating. The small molecule plasticizers concentrated at the bonding interface will cause the bonding performance to degrade, thereby affecting the safety and service life of the lithium-ion power battery.

[0003] Therefore, it is of great significance to develop a two-component polyurethane structural adhesive that is resistant to moisture, heat and migration. Summary of the Invention

[0004] The purpose of the present invention is to provide a moisture-heat resistant two-component polyurethane structural adhesive, which solves the problem of two-component polyurethane structural adhesives suffering from degradation of bonding performance due to plasticizer migration in a moist and hot environment, while taking into account both fatigue performance (1 million fatigue vibrations at 50% of the maximum stress) and bonding performance.

[0005] The present invention also aims to provide a method for preparing the above-mentioned moisture-heat resistant two-component polyurethane structural adhesive. The preparation method is simple, the process parameters of each step are easy to control, and the method is suitable for industrial large-scale production.

[0006] In order to achieve the above object, the solution of the present invention is: A heat- and moisture-resistant two-component polyurethane structural adhesive comprises component A and component B in a mass ratio of 1 to 5:1, wherein component A comprises a polyether polyol, an isocyanate, a reactive plasticizer, a catalyst, and an additive, and component B comprises a curing agent, a reactive plasticizer, and an additive, wherein the reactive plasticizer is at least one grease containing an unsaturated double bond, a hydroxyl group, or an epoxy group.

[0007] The polyether polyol is at least one of polyoxypropylene diol and polyoxypropylene triol, the number average molecular weight of the polyether polyol is 1000-3000, and the addition amount of the polyether polyol is 45%-55% of the total mass of the A component.

[0008] The isocyanate is at least one of toluene diisocyanate, diphenylmethane diisocyanate and hexamethylene diisocyanate, and the amount of the isocyanate added is 25% to 30% of the total mass of component A.

[0009] The catalyst is dibutyltin dilaurate, and the added amount of the catalyst is 0.1% to 0.5% of the total mass of the A component.

[0010] The auxiliary agent includes at least one of a defoaming agent, a leveling agent and a filler. In the component A, the added amount of the defoaming agent is 0.5% to 1.5% of the total mass of the component A, the added amount of the leveling agent is 0.3% to 1.0% of the total mass of the component A, and the added amount of the filler is 8% to 15% of the total mass of the component A; in the component B, the added amount of the defoaming agent is 1.0% to 5.0% of the total mass of the component B, the added amount of the leveling agent is 0.5% to 2.0% of the total mass of the component B, and the added amount of the filler is 20% to 25% of the total mass of the component B.

[0011] The defoaming agent is an organic silicon defoaming agent, the leveling agent is an acrylic leveling agent, and the filler is at least one of calcium carbonate and talc.

[0012] The reactive plasticizer is at least one of epoxidized soybean oil and hydroxyricinoleic acid ester.

[0013] The amount of the reactive plasticizer added to component A is 5% to 10% of the total mass of component A, and the amount of the reactive plasticizer added to component B is 8% to 15% of the total mass of component B.

[0014] The curing agent includes at least one of an alcohol curing agent and an amine curing agent, the alcohol curing agent is ethylene glycol or propylene glycol, the amine curing agent is ethylenediamine or diethylenetriamine, and the added amount of the curing agent is 55% to 65% of the total mass of the B component.

[0015] A method for preparing a heat- and moisture-resistant two-component polyurethane structural adhesive comprises the following steps: Step 1: Prepare component A: First, add polyether polyol and reactive plasticizer into the reaction kettle, vacuum dehydrate for 2-3 hours at 80-100°C and a vacuum degree of -0.09 MPa to -0.1 MPa, cool to 50-60°C, add isocyanate and catalyst, wherein the molar ratio of polyether polyol to isocyanate is 1:4-6, and react at 60-70°C for 3-4 hours; then add auxiliary agent, stir evenly, vacuum degas for 10-20 minutes at a vacuum degree of -0.09 MPa to -0.1 MPa, and discharge to obtain component A; Step 2: Prepare component B: Then, the curing agent, reactive plasticizer and auxiliary agent are added into the reactor, stirred and mixed at 50-60° C. for 1-2 hours; vacuum degassing is performed for 10-20 minutes under a vacuum degree of -0.09 MPa to -0.1 MPa, and the material is discharged to obtain component B.

[0016] After adopting the above technical solution, the present invention provides a moisture-heat-resistant two-component polyurethane structural adhesive, wherein component A is mainly composed of isocyanate prepolymer, and a reactive plasticizer (such as soybean oil containing hydroxyl or epoxy groups, castor oil ester containing hydroxyl groups and double bonds, etc.) is added to replace common plasticizers such as phthalates, and an appropriate amount of catalyst and auxiliary agent is added. The isocyanate prepolymer provides a basic cross-linking skeleton for bonding, and the reactive plasticizer reacts chemically with isocyanate and other components in the two-component polyurethane structural adhesive by virtue of its own active groups such as epoxy groups, hydroxyl groups and double bonds, and can be firmly bonded to the adhesive skeleton, fundamentally avoiding the migration problem of small molecules of ordinary plasticizers. Component B mainly contains a curing agent, a reactive plasticizer and auxiliary agents. The curing agent reacts with the isocyanate in component A to form a stable polyurethane network.

[0017] This heat-resistant two-component polyurethane structural adhesive shows low attenuation of bonding performance in a double 85 (temperature 85°C, relative humidity 85%), 1000-h accelerated aging test. It also combines good fatigue performance (withstanding 1 million fatigue vibrations at 50% of maximum stress) with excellent bonding performance, solving the problem of reduced bonding performance of ordinary structural adhesives due to plasticizer migration.

[0018] Furthermore, the polyether polyol is at least one of polyoxypropylene diol and polyoxypropylene triol, and the number average molecular weight of the polyether polyol is 1000-3000. The polyether polyol in this molecular weight range can form a suitable crosslinking density with isocyanate to ensure the basic performance of the structural adhesive. DETAILED DESCRIPTION

[0019] In order to further explain the technical solution of the present invention, the present invention is described in detail below through specific embodiments.

[0020] Example 1 A method for preparing a heat- and moisture-resistant two-component polyurethane structural adhesive comprises the following steps: Step 1: Prepare component A: First, 100 g of polyoxypropylene glycol (number average molecular weight 2000) and 10 g of epoxy soybean oil were added to a reactor, dehydrated at 90°C and a vacuum degree of -0.095 MPa for 2.5 hours, cooled to 55°C, and 50 g of toluene diisocyanate and 0.5 g of dibutyltin dilaurate were added. The mixture was reacted at 65°C for 3.5 hours. Then, 2 g of a silicone defoamer, 1 g of an acrylic leveling agent, and 20 g of calcium carbonate were added. The mixture was stirred evenly and vacuum degassed at a vacuum degree of -0.095 MPa for 15 minutes. The mixture was discharged to obtain component A. Step 2: Prepare component B: Then, 30 g of ethylenediamine, 5 g of epoxy soybean oil, 1 g of silicone defoamer, 0.5 g of acrylate leveling agent and 10 g of talc were added to the reactor, stirred and mixed at 55° C. for 1.5 hours, vacuum degassed at a vacuum degree of -0.095 MPa for 15 minutes, and discharged to obtain component B; When using, mix component A and component B evenly in a mass ratio of 3:1.

[0021] Example 2 A method for preparing a heat- and moisture-resistant two-component polyurethane structural adhesive comprises the following steps: Step 1: Prepare component A: First, 120 g of polyoxypropylene triol (number average molecular weight 2500) and 15 g of epoxy soybean oil were added to a reactor, dehydrated at 80°C and a vacuum degree of -0.09 MPa for 3 hours, cooled to 50°C, and 60 g of diphenylmethane diisocyanate and 0.6 g of dibutyltin dilaurate were added. The mixture was reacted at 60°C for 4 hours. Then, 3 g of an organosilicon defoamer, 2 g of an acrylate leveling agent, and 25 g of calcium carbonate were added. The mixture was stirred evenly and vacuum degassed at a vacuum degree of -0.09 MPa for 20 minutes. The mixture was discharged to obtain component A. Step 2: Prepare component B: Then, 40 g of diethylenetriamine, 8 g of epoxy soybean oil, 2 g of silicone defoamer, 1 g of acrylate leveling agent and 15 g of talc were added to the reactor, stirred and mixed at 50° C. for 2 hours, vacuum degassed at a vacuum degree of -0.09 MPa for 20 minutes, and discharged to obtain component B; When using, mix component A and component B evenly in a mass ratio of 5:1.

[0022] Example 3 A method for preparing a heat- and moisture-resistant two-component polyurethane structural adhesive comprises the following steps: Step 1: Prepare component A: First, 80 g of polyoxypropylene glycol (number average molecular weight 1500) and 15 g of hydroxyricinoleate were added to a reactor, dehydrated at 100°C and a vacuum degree of -0.1 MPa for 2 hours, cooled to 60°C, and 40 g of hexamethylene diisocyanate and 0.4 g of dibutyltin dilaurate were added. The mixture was reacted at 70°C for 3 hours. Then, 1 g of a silicone defoamer, 0.5 g of an acrylate leveling agent, and 15 g of calcium carbonate were added. The mixture was stirred evenly and vacuum degassed at a vacuum degree of -0.1 MPa for 10 minutes. The mixture was discharged to obtain component A. Step 2: Prepare component B: Then, 20 g of ethylene glycol, 5 g of hydroxyricinoleate, 0.5 g of silicone defoamer, 0.3 g of acrylate leveling agent, and 8 g of talc were added to the reactor, stirred and mixed at 60° C. for 1 hour, vacuum degassed at a vacuum degree of -0.1 MPa for 10 minutes, and discharged to obtain component B; When using, mix component A and component B evenly in a mass ratio of 1:1.

[0023] Example 4 A method for preparing a heat- and moisture-resistant two-component polyurethane structural adhesive comprises the following steps: Step 1: Prepare component A: First, 90 g of polyoxypropylene triol (number average molecular weight 2200) and 12 g of epoxy soybean oil were added to a reactor and vacuum dehydrated at 85°C and a vacuum degree of -0.092 MPa for 2.2 hours. The temperature was then lowered to 52°C, and 45 g of toluene diisocyanate and 0.5 g of dibutyltin dilaurate were added. The mixture was reacted at 62°C for 3.2 hours. Then, 1.5 g of a silicone defoamer, 1.2 g of an acrylate leveling agent, and 18 g of calcium carbonate were added. The mixture was stirred evenly and vacuum degassed at a vacuum degree of -0.092 MPa for 15 minutes. The mixture was discharged to obtain component A. Step 2: Prepare component B: Then, 25 g of glycerol, 7 g of epoxy soybean oil, 1.2 g of silicone defoamer, 0.8 g of acrylic leveling agent, and 12 g of talc were added to the reactor, stirred and mixed at 52° C. for 1.3 hours, and vacuum degassed at a vacuum degree of -0.092 MPa for 15 minutes, and the material was discharged to obtain component B; When using, mix component A and component B in a mass ratio of 2:1.

[0024] Comparative Example 1 A method for preparing a common two-component polyurethane structural adhesive comprises the following steps: Step 1: Prepare component A: First, 100 g of polyoxypropylene glycol (number average molecular weight 2000) and 10 g of dioctyl phthalate were added to a reactor, dehydrated at 90°C and a vacuum degree of -0.095 MPa for 2.5 hours, cooled to 55°C, and 50 g of toluene diisocyanate and 0.5 g of dibutyltin dilaurate were added. The mixture was reacted at 65°C for 3.5 hours. Then, 2 g of a silicone defoamer, 1 g of an acrylic leveling agent, and 20 g of calcium carbonate were added. The mixture was stirred evenly, and vacuum degassing was carried out at a vacuum degree of -0.095 MPa for 15 minutes. The material was discharged to obtain component A. Step 2: Prepare component B: Then, 30 g of ethylenediamine, 5 g of dioctyl phthalate, 1 g of silicone defoamer, 0.5 g of acrylic leveling agent and 10 g of talc were added to the reactor, stirred and mixed at 55° C. for 1.5 hours, vacuum degassed at a vacuum degree of -0.095 MPa for 15 minutes, and discharged to obtain component B; When using, mix component A and component B evenly in a mass ratio of 3:1.

[0025] Comparative Example 2 A method for preparing a common two-component polyurethane structural adhesive comprises the following steps: Step 1: Prepare component A: First, 120 g of polyoxypropylene triol (number average molecular weight 2500) and 15 g of dibutyl phthalate were added to a reactor, dehydrated at 80°C and a vacuum degree of -0.09 MPa for 3 hours, cooled to 50°C, and 60 g of diphenylmethane diisocyanate and 0.6 g of dibutyltin dilaurate were added. The mixture was reacted at 60°C for 4 hours. Then, 3 g of an organosilicon defoamer, 2 g of an acrylate leveling agent, and 25 g of calcium carbonate were added. The mixture was stirred evenly, and vacuum degassing was performed at a vacuum degree of -0.09 MPa for 20 minutes. The mixture was discharged to obtain component A. Step 2: Prepare component B: Then, 40 g of diethylenetriamine, 8 g of dibutyl phthalate, 2 g of silicone defoamer, 1 g of acrylic leveling agent and 15 g of talc were added to the reactor, stirred and mixed at 50° C. for 2 hours, vacuum degassed at a vacuum degree of -0.09 MPa for 20 minutes, and discharged to obtain component B; When using, mix component A and component B evenly in a mass ratio of 5:1.

[0026] In the above embodiments and comparative examples, polyoxypropylene diol and polyoxypropylene triol were purchased from Sinopec Tianjin Petrochemical Company, toluene diisocyanate and diphenylmethane diisocyanate were purchased from BASF SE, hexamethylene diisocyanate was purchased from Covestro SE, epoxy soybean oil was purchased from Zibo Kailian Chemical Co., Ltd., hydroxyricinoleate was purchased from Shandong Tianxing Biotechnology Co., Ltd., ethylenediamine and diethylenetriamine were purchased from Dow Chemical, ethylene glycol was purchased from Shell, glycerol was purchased from Shanghai Gaoming Chemical Co., Ltd., dibutyltin dilaurate was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., silicone defoamer was purchased from BYK, acrylate leveling agent was purchased from Guangdong Nuoyi Chemical Co., Ltd., and calcium carbonate and talc were purchased from Guangxi Dacheng New Materials Co., Ltd.

[0027] Performance testing: The performance of the two-component polyurethane structural adhesives prepared in Examples 1 to 4 and Comparative Examples 1 to 2 was tested using the following method: 1. Double 85 and 1000h adhesion performance attenuation rate: The test was conducted in accordance with GB / T7124-2008 "Determination of tensile shear strength of adhesives (rigid material to rigid material)", and the initial tensile shear strength and the tensile shear strength after double 85 (temperature 85°C, relative humidity 85%) and 1000h aging were measured respectively. The attenuation rate was calculated as follows: attenuation rate = (initial strength - strength after aging) / initial strength × 100%.

[0028] 2. Fatigue performance: Fatigue vibration test is conducted at 50% of the maximum stress according to GB / T 13936-1992 "Determination of tensile shear strength of bonds between vulcanized rubber and metal". The condition of the structural adhesive is observed after 1 million vibrations.

[0029] 3. Initial bonding strength: Tested in accordance with GB / T7124-2008 "Determination of tensile shear strength of adhesives (rigid material to rigid material)".

[0030] The performance test results are shown in Table 1.

[0031] Table 1 Performance test results of two-component polyurethane structural adhesive

[0032] The test results in Table 1 clearly demonstrate that the structural adhesives prepared using reactive plasticizers in Examples 1-4 exhibit significantly lower adhesive performance degradation in both 85- and 1000-hour accelerated aging tests, at approximately 10%-12%, compared to Comparative Examples 1-2, which employed conventional plasticizers. While the degradation rate for the structural adhesives in Comparative Examples 1-2 was as high as 65%-68%, the structural adhesives prepared in Examples 1-4 remained intact after 1 million fatigue vibration cycles at 50% maximum stress, while cracks appeared in Comparative Examples 1-2. Furthermore, the structural adhesives in Examples 1-4 maintained a relatively good initial bond strength, comparable to that of Comparative Examples 1-2, achieving a good balance between moisture and heat resistance, fatigue resistance, and adhesive performance.

[0033] The above embodiments do not limit the product form and style of the present invention. Any appropriate changes or modifications made by ordinary technicians in the relevant technical field should be deemed to be within the patent scope of the present invention.

Claims

1. A heat-resistant two-component polyurethane structural adhesive comprising component A and component B in a mass ratio of 1 to 5:1, characterized in that: The component A includes polyether polyol, isocyanate, reactive plasticizer, catalyst and auxiliary agent, and the component B includes curing agent, reactive plasticizer and auxiliary agent, wherein the reactive plasticizer is at least one oil containing unsaturated double bonds, hydroxyl groups or epoxy groups.

2. The heat-and-humidity resistant two-component polyurethane structural adhesive according to claim 1, characterized in that: The polyether polyol is at least one of polyoxypropylene diol and polyoxypropylene triol, the number average molecular weight of the polyether polyol is 1000-3000, and the addition amount of the polyether polyol is 45%-55% of the total mass of the A component.

3. The heat-and-humidity resistant two-component polyurethane structural adhesive according to claim 1, characterized in that: The isocyanate is at least one of toluene diisocyanate, diphenylmethane diisocyanate and hexamethylene diisocyanate, and the amount of the isocyanate added is 25% to 30% of the total mass of component A.

4. The heat-and-humidity resistant two-component polyurethane structural adhesive according to claim 1, characterized in that: The catalyst is dibutyltin dilaurate, and the added amount of the catalyst is 0.1% to 0.5% of the total mass of the A component.

5. The heat-and-humidity resistant two-component polyurethane structural adhesive according to claim 1, characterized in that: The auxiliary agent includes at least one of a defoaming agent, a leveling agent and a filler. In the component A, the added amount of the defoaming agent is 0.5% to 1.5% of the total mass of the component A, the added amount of the leveling agent is 0.3% to 1.0% of the total mass of the component A, and the added amount of the filler is 8% to 15% of the total mass of the component A; in the component B, the added amount of the defoaming agent is 1.0% to 5.0% of the total mass of the component B, the added amount of the leveling agent is 0.5% to 2.0% of the total mass of the component B, and the added amount of the filler is 20% to 25% of the total mass of the component B.

6. The heat-and-humidity resistant two-component polyurethane structural adhesive according to claim 5, characterized in that: The defoaming agent is an organic silicon defoaming agent, the leveling agent is an acrylic leveling agent, and the filler is at least one of calcium carbonate and talc.

7. The heat-and-humidity resistant two-component polyurethane structural adhesive according to claim 1, characterized in that: The reactive plasticizer is at least one of epoxidized soybean oil and hydroxyricinoleic acid ester.

8. The heat-and-humidity resistant two-component polyurethane structural adhesive according to claim 1, characterized in that: The amount of the reactive plasticizer added to component A is 5% to 10% of the total mass of component A, and the amount of the reactive plasticizer added to component B is 8% to 15% of the total mass of component B.

9. The heat-and-humidity resistant two-component polyurethane structural adhesive according to claim 1, characterized in that: The curing agent includes at least one of an alcohol curing agent and an amine curing agent, the alcohol curing agent is ethylene glycol or propylene glycol, the amine curing agent is ethylenediamine or diethylenetriamine, and the added amount of the curing agent is 55% to 65% of the total mass of the B component.

10. A method for preparing the heat-and-humidity resistant two-component polyurethane structural adhesive according to claim 1, characterized in that: The following steps are involved: Step 1: Prepare component A: First, add polyether polyol and reactive plasticizer into the reaction kettle, vacuum dehydrate for 2-3 hours at 80-100°C and a vacuum degree of -0.09 MPa to -0.1 MPa, cool to 50-60°C, add isocyanate and catalyst, wherein the molar ratio of polyether polyol to isocyanate is 1:4-6, and react at 60-70°C for 3-4 hours; then add auxiliary agent, stir evenly, vacuum degas for 10-20 minutes at a vacuum degree of -0.09 MPa to -0.1 MPa, and discharge to obtain component A; Step 2: Prepare component B: Then, the curing agent, reactive plasticizer and auxiliary agent are added into the reactor, stirred and mixed at 50-60° C. for 1-2 hours; vacuum degassing is performed for 10-20 minutes under a vacuum degree of -0.09 MPa to -0.1 MPa, and the material is discharged to obtain component B.

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