Flame-retardant adhesive and preparation method thereof

Abstract

The invention relates to the field of adhesives, and discloses a flame-retardant adhesive and a preparation method thereof. The flame-retardant adhesive is prepared from the following raw materials in percentage by weight: 50-60% of polyurethane acrylate, 12-18% of a diluent, 10-15% of a flexibilizer, 6-10% of a flame retardant, 5-8% of a photoinitiator and 1-3% of an antioxidant, the flame retardant is prepared by modifying an inorganic flame retardant, a phosphazene flame retardant and a coating agent, the inorganic flame retardant is aluminum hydroxide and / or magnesium hydroxide, and the phosphazene flame retardant is poly (diphenyl oxyphosphazene) and / or hexaphenoxy cyclotriphosphazene. The preparation method comprises the following steps: mixing the raw materials and carrying out vacuum defoamation. The flame-retardant adhesive prepared by the invention has relatively good flame retardance and thermal bonding stability, is applied to bonding of new energy battery modules, and is not easy to have the problems of degumming and separation in corner areas after being used in a high-temperature environment for a long time.

Description

Technical Field

[0001] This application relates to the field of adhesives, and more specifically, to a flame-retardant adhesive and a method for preparing the same. Background Technology

[0002] During the assembly process of new energy battery modules, flame-retardant adhesive is used to fill the gaps between the battery modules to form a flame-retardant isolation layer. This layer not only provides good flame retardancy but also has good thermal conductivity, preventing the battery modules from catching fire due to overheating or external fire sources.

[0003] Commonly used flame-retardant adhesives are generally polyurethane or acrylate systems, achieving good flame-retardant properties by adding flame retardants to the system. Traditional flame retardants are generally halogen-containing flame-retardant powders, which can achieve good flame-retardant effects with very small amounts, but these types of flame retardants are less environmentally friendly. There are also some more environmentally friendly flame retardants, such as magnesium hydroxide, aluminum hydroxide, and zinc borate. These flame retardants require larger amounts to achieve good flame-retardant effects, but the addition of large amounts of flame retardants reduces the toughness and adhesion of the flame-retardant adhesive.

[0004] When used in the bonding of new energy battery modules, the new energy batteries are used in a long-term high-temperature environment, and the corners are prone to separation, which reduces the application of flame retardant adhesive in new energy batteries. Summary of the Invention

[0005] To address the issue of unstable adhesion at edges and corners in conventional flame-retardant adhesives used in new energy batteries under long-term high-temperature environments, this application provides a flame-retardant adhesive and its preparation method.

[0006] In a first aspect, this application provides a flame-retardant adhesive, which adopts the following technical solution: A flame-retardant adhesive is prepared from the following raw materials by weight percentage: 50-60% polyurethane acrylate Diluent 12-18% 10-15% Flexing agent Flame retardant 6-10% Photoinitiator 5-8% Antioxidant 1-3%; The flame retardant is prepared by modifying an inorganic flame retardant, a phosphazene flame retardant, and a coating agent; the inorganic flame retardant is aluminum hydroxide and / or magnesium hydroxide, and the phosphazene flame retardant is polydiphenyloxyphosphazene and / or hexaphenoxycyclotriphosphazene.

[0007] By adopting the above technical solution, the flame-retardant adhesive of this application is a UV flame-retardant adhesive system. The polyurethane acrylate, diluent, and flexibility agent in the flame-retardant adhesive work together to form a system with excellent adhesion and flexibility. The flame retardant is a composite modified inorganic flame retardant, phosphazene flame retardant, and coating agent. The coating agent can form a uniform coating layer on the surface of the inorganic flame retardant and phosphazene flame retardant. This coating layer entangles with the flexible segments of the polyurethane acrylate, effectively avoiding brittle fracture caused by stress concentration, and significantly improving the thermal bonding stability and flexibility of the flame-retardant adhesive. Furthermore, the flame retardant forms a continuous network in the matrix, enhancing the overall mechanical properties and flame-retardant effect of the flame-retardant adhesive. The synergistic effect of the photoinitiator and antioxidant improves the performance stability of the flame-retardant adhesive under long-term high-temperature environments, exhibiting excellent comprehensive performance in the bonding application of new energy battery modules. Under long-term high-temperature environments, delamination and separation are less likely to occur in the corner areas.

[0008] Preferably, the weight ratio of the inorganic flame retardant, the phosphazene flame retardant, and the coating agent is (1-2):(2-3):(0.2-0.4).

[0009] By adopting the above technical solution, the inorganic flame retardant, phosphazene flame retardant, and coating agent are compounded in a specific weight ratio, forming a good synergistic effect. This allows the flame-retardant adhesive to maintain excellent flame retardancy while also having better thermal bonding stability and high-temperature resistance, effectively preventing delamination and separation of new energy battery modules during long-term high-temperature use.

[0010] Preferably, the coating agent is composed of a light-curing silicone resin and a polyether-modified heptamethyltrisiloxane in a weight ratio of (1.2-1.8):1.

[0011] By employing the above technical solution, the epoxy groups contained in the photocurable silicone resin can adsorb onto the surface of the flame retardant during dispersion, thereby significantly improving the bonding force between the flame retardant and the matrix. The flexible segments provided by the polyether-modified heptamethyltrisiloxane are interwoven and dispersed with the photocurable silicone resin, further enhancing the coating stability of inorganic flame retardants and phosphazene flame retardants. The resulting flame retardant, dispersed in the system, can further interweave and disperse with the system, improving the flame retardancy and adhesive stability of the prepared flame-retardant adhesive.

[0012] Preferably, the flame retardant is prepared by the following steps: A1. Add the light-curable silicone resin to the polyether-modified heptamethyltrisiloxane and disperse it evenly to obtain the coating agent; A2. Add the inorganic flame retardant and phosphazene flame retardant to the coating agent prepared in step A1, heat and knead to disperse, and obtain the flame retardant.

[0013] By employing the above technical solution, a coating agent is prepared by mixing and dispersing photocurable silicone resin with polyether-modified heptamethyltrisiloxane. This coating agent can uniformly coat the surfaces of inorganic flame retardants and phosphazene flame retardants, forming a stable coating layer. During the kneading process, the inorganic flame retardants and phosphazene flame retardants are fully dispersed, and the resulting flame retardant exhibits good system uniformity and dispersion stability.

[0014] Preferably, the kneading temperature in step A2 is 60-80℃, and the kneading time is 30-60 minutes.

[0015] By adopting the above technical solutions and controlling the optimal kneading temperature and kneading time, it is helpful to promote the full coating between the components of the flame retardant and improve the full dispersion and coating of the coating agent on the surface of the inorganic flame retardant and phosphazene flame retardant.

[0016] Preferably, the diluent is composed of methyl acrylate, lauryl acrylate and glycidyl methacrylate in a weight ratio of 1:(2-3):(0.5-1).

[0017] By adopting the above technical solution, methyl acrylate, lauryl acrylate and glycidyl methacrylate have a good synergistic effect and can further react with polyurethane acrylate, flexibility agent and flame retardant. While improving the flowability of flame retardant adhesive, it can also give flame retardant adhesive excellent flexibility and adhesion. Preferably, the flexibility agent is composed of 1,2-epoxy-4-vinylcyclohexane and ethoxylated trimethylolpropane triacrylate in a weight ratio of 1:(1.8-2.6).

[0018] By adopting the above technical solution, 1,2-epoxy-4-vinylcyclohexane and ethoxylated trimethylolpropane triacrylate can be used as flexibility agents to further crosslink with the system, improve the cohesiveness and flexibility of the flame retardant adhesive, and enable the flame retardant adhesive to maintain excellent adhesion in the corner areas during long-term high-temperature use, avoiding the problems of delamination and separation.

[0019] Preferably, the photoinitiator is one or a combination of 1-hydroxycyclohexylphenyl ketone, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, and 2-hydroxy-2-methyl-1-phenyl-1-propanone.

[0020] By adopting the above technical solutions, the curing efficiency of flame retardant adhesive under light conditions can be effectively promoted, and the strength and bonding performance of the cured adhesive can be improved.

[0021] Secondly, this application provides a method for preparing a flame-retardant adhesive, which adopts the following technical solution: A method for preparing a flame-retardant adhesive includes the following steps: mixing and dispersing polyurethane acrylate, diluent, flexibility agent, flame retardant, photoinitiator and antioxidant, and degassing under vacuum to obtain the flame-retardant adhesive.

[0022] By adopting the above technical solution, the preparation method of flame retardant adhesive can effectively ensure that the components are fully mixed to form a uniform and stable system.

[0023] Preferably, the mixing and dispersion temperature is 40-50℃ and the time is 1-2h.

[0024] By adopting the above technical solution and controlling the optimal mixing and dispersion temperature and time, it is possible to effectively promote the uniform dispersion of each raw material, avoid component decomposition or performance degradation due to excessively high temperature, and prevent uneven dispersion caused by excessively low temperature.

[0025] In summary, this application includes at least one of the following beneficial technical effects: 1. The flame-retardant adhesive of this application is a UV flame-retardant system. It is prepared by rationally proportioning polyurethane acrylate, diluent, flexible agent, flame retardant, photoinitiator and antioxidant, and by combining inorganic flame retardant with phosphazene flame retardant and modifying it with a coating agent. The resulting flame-retardant adhesive has high flame-retardant performance while improving environmental protection. It solves the problem of poor environmental protection or performance degradation caused by large addition of traditional flame retardants. The resulting flame-retardant adhesive is used in the bonding of new energy battery modules. It can maintain good adhesion in long-term high-temperature environment, and the corner areas are not easy to separate or crack.

[0026] 2. The coating agent is composed of light-cured silicone resin and polyether-modified heptamethyltrisiloxane, which can work synergistically with inorganic flame retardants and phosphazene flame retardants to improve the dispersion uniformity of flame retardants in the system and enhance the bonding stability and high-temperature resistance of the flame-retardant adhesive.

[0027] 3. The flexibility agent is composed of 1,2-epoxy-4-vinylcyclohexane and ethoxylated trimethylolpropane triacrylate, which can further crosslink with the system, significantly improving the cohesion and flexibility of the flame retardant adhesive. This allows the flame retardant adhesive to effectively resist stress changes under long-term high-temperature use conditions, preventing delamination and separation in the corner areas, thereby enhancing the thermal bonding stability of the flame retardant adhesive. Detailed Implementation

[0028] The present application will be further described in detail below with reference to the embodiments.

[0029] The following are some of the sources and specifications of the raw materials used in this application. The raw materials used in the preparation examples and embodiments of this application can all be obtained commercially, including but not limited to the following models and manufacturers of raw materials. Raw materials with equivalent performance can also be used: 1. Polyurethane acrylate: EBECRIL 8413; 2. Aluminum hydroxide: 50-100nm; 3. Magnesium hydroxide: 50-100 nm; 4. Polydiphenyloxyphosphazene: CAS No. 28212-48-8, content 99%; 5. Hexaphenoxycyclotriphosphazene: CAS No. 1184-10-7, content 99%; 6. Light-cured silicone resin: Kemick, light-cured silicone resin, 99% content, viscosity 10000cps.

[0030] 7. Polyether-modified heptamethyltrisiloxane: Huaxiang, CAS No. 27306-78-1, content 99%.

[0031] Example of flame retardant preparation Preparation Example 1 Preparation Example 1 discloses a flame retardant, which is prepared by the following steps: A1. Disperse 0.12 kg of light-curable silicone resin in 0.08 kg of vinyltrimethoxysilane until uniformly dispersed to obtain a coating agent; A2. Add the inorganic flame retardant and phosphazene flame retardant to the coating agent prepared in step A1, heat and knead to disperse, kneading temperature is 60-80℃, kneading time is 30-60min to obtain the flame retardant.

[0032] Preparation Examples 2-3 The difference between Preparation Example 2-3 and Preparation Example 1 lies in the amount of raw materials used and the preparation conditions, as detailed in Table 1 below.

[0033] Table 1. Parameters for Preparation Examples 1-3 Preparation Example 4 Preparation Example 4 differs from Preparation Example 1 in that the coating agent is composed of a light-curing silicone resin and a polyether-modified heptamethyltrisiloxane in a weight ratio of 1.2:1, and is otherwise the same as Preparation Example 1.

[0034] Preparation Example 5 The difference between Preparation Example 5 and Preparation Example 1 is that the coating agent is composed of a light-curing silicone resin and a polyether-modified heptamethyltrisiloxane in a weight ratio of 1.8:1, while the rest is the same as Preparation Example 1.

[0035] Preparation of Comparative Example 1 The difference between Comparative Example 1 and Preparation Example 1 is that the phosphazene flame retardant was replaced with an equal amount of ammonium polyphosphate, CAS No. 68333-79-9, with a content of 99%. Otherwise, they are the same as Preparation Example 1. Example

[0036] Example 1 Example 1 discloses a flame-retardant adhesive, which is prepared by the following steps: The process includes the following steps: 5 kg of polyurethane acrylate, 1.8 kg of diluent (composed of methyl acrylate, lauryl acrylate and glycidyl methacrylate in a weight ratio of 1:2:0.5), 1.5 kg of ethoxylated trimethylolpropane triacrylate as a flexibility agent, 0.8 kg of the flame retardant prepared in Preparation Example 1, 0.6 kg of 1-hydroxycyclohexylphenyl ketone as a photoinitiator, and 0.3 kg of antioxidant (composed of antioxidant 1010 and antioxidant 168 in a weight ratio of 2:1) are mixed and dispersed at 40°C for 2 hours. After uniform mixing, the mixture is degassed under vacuum to obtain the flame retardant adhesive.

[0037] Example 2-3 The difference between Examples 2-3 and Example 1 lies in the amount of raw materials used and the preparation conditions, as detailed in Table 2 below.

[0038] Table 2 Parameter table for Examples 1-3 Example 4 The difference between Example 4 and Example 1 is that the flame retardant is derived from Preparation Example 4, while the rest is the same as Example 1.

[0039] Example 5 The difference between Example 5 and Example 1 is that the flame retardant is derived from Preparation Example 5, while the rest is the same as Example 1.

[0040] Example 6 The difference between Example 6 and Example 5 is that the flexibility agent is composed of 1,2-epoxy-4-vinylcyclohexane and ethoxylated trimethylolpropane triacrylate in a weight ratio of 1:1.8, while the rest is the same as in Example 5.

[0041] Example 7 The difference between Example 7 and Example 5 is that the flexibility agent is composed of 1,2-epoxy-4-vinylcyclohexane and ethoxylated trimethylolpropane triacrylate in a weight ratio of 1:2.6, while the rest is the same as in Example 5.

[0042] Comparative Example Comparative Example 1 The difference between Comparative Example 1 and Example 4 is that the flame retardant was derived from the preparation of Comparative Example 1, while the rest is the same as Example 1.

[0043] Comparative Example 2 The difference between Comparative Example 2 and Example 6 is that the flexibility agent was replaced with an equal amount of polyurethane acrylate, while the rest was the same as Example 6.

[0044] Performance testing 1. Adhesion test Referring to the test method in GB / T 2792-2014, using a stainless steel plate as the bonding test plate, the flame retardant adhesive was applied at a concentration of 30 g / m². 2 The coating was applied to a stainless steel test plate, then cured under an LED UV lamp with a wavelength of 395nm for 30s, and placed at 25℃ for 2h. The peel strength (unit: N / 25mm) was tested at a peel angle of 90° and recorded as the initial peel strength. The test results were recorded.

[0045] 2. High temperature resistance test Using a stainless steel plate as the bonding test board, the flame retardant adhesive was applied at a rate of 30 g / m². 2 The coating was applied to a stainless steel test plate, then cured for 30 seconds under an LED UV lamp with a wavelength of 395nm, and placed at 25℃ for 2 hours. The plate was then placed in a constant temperature and humidity chamber at 85℃ and 85% for 72 hours. After drying and returning to room temperature, the peel strength (unit: N / 25mm) was tested at a peel angle of 90° according to the test method in GB / T 2792-2014. This was recorded as the heat-resistant peel strength, and the test results were recorded.

[0046] 3. Adhesion stability test: Flame retardant adhesive at 30g / m 2 After the coating was applied to the stainless steel test plate, it was cured for 30 seconds under an LED UV lamp with a wavelength of 395nm, placed at 25℃ for 2 hours, and then placed in a constant temperature and humidity chamber at 85℃ and 85% for 10 days. The test results were recorded and observed for any bubbles, curling, or separation in the corner areas.

[0047] 4. Flame retardancy test: Flame retardant adhesive was applied to the surface of the release film and cured under an LED ultraviolet lamp with a wavelength of 395nm to form a test strip. The limiting oxygen index (unit: %) of the test strip was tested according to the test method in GB / T 2406.2-2009, and the test results were recorded.

[0048] The following are the performance test data of the flame retardant adhesives prepared in Examples 1-7 and Comparative Examples 1-2, as detailed in Table 3 below.

[0049] Table 3. Data on flame retardant adhesives from Examples 1-7 and Comparative Examples 1-2 Combining Examples 1-5 and Comparative Example 1, it can be concluded that the flame-retardant adhesive prepared using the flame retardant of this application has good flame retardancy, as well as good adhesion and temperature resistance. Compared with Example 1, Examples 4-5 further optimized the type of coating agent, resulting in improved adhesion stability of the flame-retardant adhesive. No edge curling occurred after damp heat testing, and the adhesion stability in corner areas was good, with a significantly improved limiting oxygen index. In contrast, Comparative Example 1 used ammonium polyphosphate as a flame retardant. After temperature resistance testing, the resulting flame-retardant adhesive showed reduced peel strength and slight bubbling issues, and the limiting oxygen index also decreased. This may be because the coating agent of this application has a better coating effect on the flame retardant used in this application, but a poorer coating effect on ammonium polyphosphate, resulting in lower dispersion uniformity of ammonium polyphosphate in the system, thus reducing both adhesion stability and flame retardancy.

[0050] Based on Examples 6-7 and Comparative Example 2, it can be concluded that by further optimizing the composition of the flexible agent of this application, it can achieve a better synergistic effect with polyurethane acrylate and flame retardant, further improving the bonding stability of the prepared flame retardant adhesive, while also slightly improving the flame retardancy of the flame retardant adhesive. This may be because the addition of the flexible agent further improves the dispersion uniformity of the flame retardant in the system.

[0051] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A flame-retardant adhesive, characterized in that, It is made from the following raw materials by weight percentage: Polyurethane acrylate 50-60% Diluent 12-18% 10-15% flexibility agent Flame retardant 6-10% Photoinitiator 5-8% Antioxidant 1-3%; The flame retardant is prepared by modifying an inorganic flame retardant, a phosphazene flame retardant and a coating agent. The inorganic flame retardant is aluminum hydroxide and / or magnesium hydroxide, and the phosphazene flame retardant is polydiphenyloxyphosphazene and / or hexaphenoxycyclotriphosphazene.

2. The flame-retardant adhesive according to claim 1, characterized in that, The weight ratio of the inorganic flame retardant, the phosphazene flame retardant, and the coating agent is (1-2):(2-3):(0.2-0.4).

3. The flame-retardant adhesive according to claim 1, characterized in that, The coating agent is composed of a light-curing silicone resin and a polyether-modified heptamethyltrisiloxane in a weight ratio of (1.2-1.8):

1.

4. The flame-retardant adhesive according to claim 3, characterized in that, The flame retardant is prepared by the following steps: A1. Add the light-curable silicone resin to the polyether-modified heptamethyltrisiloxane and disperse it evenly to obtain the coating agent; A2. Add the inorganic flame retardant and phosphazene flame retardant to the coating agent prepared in step A1, heat and knead to disperse, and obtain the flame retardant.

5. The flame-retardant adhesive according to claim 4, characterized in that, The kneading temperature in step A2 is 60-80℃, and the kneading time is 30-60 minutes.

6. The flame-retardant adhesive according to claim 1, characterized in that, The diluent is composed of methyl acrylate, lauryl acrylate and glycidyl methacrylate in a weight ratio of 1:(2-3):(0.5-1).

7. The flame-retardant adhesive according to claim 1, characterized in that, The flexibility agent is composed of 1,2-epoxy-4-vinylcyclohexane and ethoxylated trimethylolpropane triacrylate in a weight ratio of 1:(1.8-2.6).

8. The flame-retardant adhesive according to claim 1, characterized in that, The photoinitiator is one or a combination of 1-hydroxycyclohexylphenyl ketone, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, and 2-hydroxy-2-methyl-1-phenyl-1-propanone.

9. A method for preparing a flame-retardant adhesive as described in any one of claims 1-8, characterized in that: The process includes the following steps: mixing and dispersing polyurethane acrylate, diluent, flexibility agent, flame retardant, photoinitiator and antioxidant, and then degassing under vacuum to obtain a flame retardant adhesive.

10. The method for preparing the flame-retardant adhesive according to claim 9, characterized in that, The mixing and dispersion temperature is 40-50℃, and the time is 1-2 hours.

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