Synthesis method and application of amine-modified anhydride

Abstract

The application discloses a synthesis method and application of an amine modified anhydride, and the synthesis method comprises the following steps: mixing cyclohexylaminopropylamine with anhydrous ethanol, stirring until uniform at 50-70 DEG C, and then cooling to 0-10 DEG C; slowly dropping methyltetrahydrophthalic anhydride under the ice-salt cooling condition at 0-10 DEG C, and controlling the dropping time to be 30-90 minutes; after the dropping is completed, incubating at room temperature for 20-40 minutes; increasing the temperature to 55-65 DEG C, and continuing to incubate for 20-40 minutes; removing the solvent anhydrous ethanol through reduced pressure distillation to obtain the amine modified anhydride curing agent; the amine modified anhydride curing agent is obtained through the controllable dropping reaction of cyclohexylaminopropylamine and methyltetrahydrophthalic anhydride under the ice-salt cooling condition at 0-10 DEG C, the flexible amine structure is introduced, the violent heat release is inhibited, the internal stress during curing is effectively reduced, the epoxy coating is dense and crack-free, and the comprehensive reliability and environmental durability of the insulating coating of a power battery package shell are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of organic polymer preparation technology, specifically to a method for synthesizing amine-modified acid anhydrides and its application. Background Technology

[0002] With the rapid development of the new energy vehicle industry, the safety and reliability of power batteries, as core components, are receiving increasing attention. The battery pack casing must not only have mechanical protection functions, but also provide long-term stable electrical insulation and environmental tolerance performance to resist harsh service environments such as electrolyte vapor penetration, salt spray corrosion, and high and low temperature cycling.

[0003] Currently, epoxy resin coatings are commonly used for surface insulation protection of power battery pack casings. Among them, acid anhydride curing agents are widely used due to their low volatility, high heat resistance, and good electrical properties. However, traditional unmodified methyltetrahydrophthalic anhydride has a strong molecular structure and high internal stress after curing, which makes the epoxy coating prone to microcracks and insufficient density, resulting in substandard adhesion. Therefore, research has attempted to modify acid anhydrides by introducing amine compounds to reduce internal stress. However, existing methods often involve direct mixing and reaction at room temperature or under heating conditions, which makes it difficult to control the intense exothermic reaction, leading to increased side reactions, poor batch stability of products, and often sacrificing heat resistance or electrical properties. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for synthesizing and applying amine-modified anhydrides, which has the advantages of mild and controllable synthesis process, low internal stress of cured coating and excellent adhesion, thereby improving the safety of power batteries.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A method for synthesizing amine-modified acid anhydrides, characterized by comprising the following steps: S1: Mix cyclohexylaminopropylamine with anhydrous ethanol, stir at 50-70°C until homogeneous, and then cool to 0-10°C; S2: Under ice-salt cooling conditions of 0-10℃, slowly add methyltetrahydrophthalic anhydride dropwise, controlling the dropwise addition time to be 30-90 minutes; S3: After the addition is complete, keep the reaction at room temperature for 20-40 minutes; S4: Heat to 55-65℃ and continue the reaction for 20-40 minutes. S5: Remove the solvent anhydrous ethanol by vacuum distillation to obtain the amine-modified acid anhydride curing agent; The molar amounts of cyclohexylaminopropylamine, methyltetrahydrophthalic anhydride, and anhydrous ethanol were 0.2 mol, 1 mol, and 3 mol, respectively.

[0006] Preferably, in step S2, in addition to methyltetrahydrophthalic anhydride, a second amine compound and a second acid anhydride are also added dropwise for co-modification. The amount of the second amine compound is 0.3–0.4 mol, and the amount of the second acid anhydride is 1 mol. The second amine compound is selected from m-phenylenediamine, isophorone diamine, or hexamethylene diamine, and the second acid anhydride is selected from methylhexahydrophthalic anhydride or methylnadic anhydride.

[0007] Preferably, the second amine compound is 0.3 mol of m-phenylenediamine and the second acid anhydride is 1 mol of methylhexahydrophthalic anhydride.

[0008] Preferably, the second amine compound is 0.4 mol of isophorone diamine and the second anhydride is 1 mol of methylnadic anhydride.

[0009] Preferably, the second amine compound is 0.3 mol of hexamethylenediamine and the second acid anhydride is 1 mol of methylhexahydrophthalic anhydride.

[0010] One use of amine-modified anhydride is to mix the amine-modified anhydride curing agent prepared above with bisphenol A type epoxy resin at a mass ratio of (60~85):100 to prepare an epoxy coating composition.

[0011] The epoxy coating composition also includes one or more additives selected from flame retardants, leveling agents, defoamers, and fillers.

[0012] The above-mentioned epoxy coating composition is sprayed onto the power battery pack casing and cured at 100℃~120℃ for 2~3 hours to form a coating with a dry film thickness of about 90~120μm.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. By controlling the dropwise addition reaction of cyclohexylaminopropylamine and methyltetrahydrophthalic anhydride under ice-salt cooling conditions of 0-10℃, a flexible amine structure is introduced and violent exothermic reaction is suppressed, which effectively reduces the internal stress of curing and thus obtains a dense and crack-free epoxy coating. Compared with the existing technology, this significantly improves the overall reliability and environmental durability of the insulating coating of the power battery pack shell. Attached Figure Description

[0014] Figure 1 This is an overall flowchart of Embodiment 1 of the present invention; Figure 2 This is an overall flowchart of Embodiment 2 of the present invention; Figure 3 This is an overall flowchart of Embodiment 3 of the present invention; Figure 4 This is the overall flowchart of Embodiment 4 of the present invention. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] The following embodiments are used to illustrate the present invention, but should not be used to limit the scope of protection of the present invention. The conditions in the embodiments can be further adjusted according to specific conditions, and simple improvements to the method of the present invention under the premise of the concept of the present invention are all within the scope of protection claimed by the present invention.

[0017] Example 1 In a 500 mL three-necked flask equipped with a stirrer, thermometer and dropping funnel, add 0.2 mol of cyclohexylaminopropylamine and 3 mol of anhydrous ethanol, heat to 60 °C, stir until completely dissolved to form a homogeneous solution, and then place the reaction system in an ice-salt bath to cool to 5 °C. At 5℃, 1 mol of methyltetrahydrophthalic anhydride was slowly added dropwise through a dropping funnel over a time of 60 minutes. The reaction temperature was maintained at ≤10℃ during the addition. After the addition was complete, the ice bath was removed, and the mixture was stirred and kept warm at 25℃ for 30 minutes. Then, the temperature was raised to 60℃ and kept warm for 30 minutes. Finally, the ethanol was removed by vacuum distillation at 80℃ and -0.095MPa to obtain a pale yellow, transparent, viscous liquid, which is the modified methyltetrahydrophthalic anhydride curing agent. The curing agent was mixed with bisphenol A type epoxy resin E-51 at a mass ratio of 80:100 to prepare an epoxy coating. The coating was sprayed onto a sandblasted aluminum alloy plate and cured at 100°C for 3 hours to form a coating with a dry film thickness of about 100μm.

[0018] Example 2 In a 500 mL three-necked flask equipped with a stirrer, thermometer and dropping funnel, add 0.2 mol of cyclohexylaminopropylamine and 3 mol of anhydrous ethanol, heat to 60 °C, stir until completely dissolved to form a homogeneous solution, and then place the reaction system in an ice-salt bath to cool to 5 °C. At 5℃, 0.3 mol of m-phenylenediamine, 1 mol of methylhexahydrophthalic anhydride, and 1 mol of methyltetrahydrophthalic anhydride were slowly added dropwise through a dropping funnel over a period of 70 minutes. The reaction temperature was maintained at ≤10℃ during the addition. After the addition was complete, the ice bath was removed, and the mixture was stirred and kept warm at room temperature (25℃) for 30 minutes. Then, the temperature was raised to 60℃ and kept warm for 30 minutes. Finally, the ethanol was removed by vacuum distillation at 80℃ and -0.095 MPa to obtain a pale yellow, transparent, viscous liquid, which is the modified m-phenylenediamine curing agent. The curing agent was mixed with bisphenol A type epoxy resin E-51 at a mass ratio of 75:100 to prepare an epoxy coating. The coating was sprayed onto a sandblasted aluminum alloy plate and cured at 110°C for 2.5 hours to form a coating with a dry film thickness of about 90μm.

[0019] Example 3 In a 500 mL three-necked flask equipped with a stirrer, thermometer and dropping funnel, add 0.2 mol of cyclohexylaminopropylamine and 3 mol of anhydrous ethanol, heat to 60 °C, stir until completely dissolved to form a homogeneous solution, and then place the reaction system in an ice-salt bath to cool to 5 °C. At 5℃, 0.4 mol of isophorone diamine, 1 mol of methylnadic anhydride, and 1 mol of methyltetrahydrophthalic anhydride were slowly added dropwise through a dropping funnel over a time of 80 minutes. The reaction temperature was maintained at ≤10℃ during the addition. After the addition was complete, the ice bath was removed, and the mixture was stirred and kept warm at 25℃ for 30 minutes. Then, the temperature was raised to 60℃ and kept warm for 30 minutes. Finally, the ethanol was removed by vacuum distillation at 80℃ and -0.095 MPa to obtain a pale yellow, transparent, viscous liquid, which is the modified isophorone diamine curing agent. The curing agent was mixed with bisphenol A type epoxy resin E-51 at a mass ratio of 80:100 to prepare an epoxy coating. The coating was sprayed onto a sandblasted aluminum alloy plate and cured at 120°C for 2 hours to form a coating with a dry film thickness of about 120μm.

[0020] Example 4 In a 500 mL three-necked flask equipped with a stirrer, thermometer and dropping funnel, add 0.2 mol of cyclohexylaminopropylamine and 3 mol of anhydrous ethanol, heat to 60 °C, stir until completely dissolved to form a homogeneous solution, and then place the reaction system in an ice-salt bath to cool to 5 °C. At 5℃, 0.3 mol of hexamethylenediamine, 1 mol of methylhexahydrophthalic anhydride, and 1 mol of methyltetrahydrophthalic anhydride were slowly added dropwise through a dropping funnel over a time of 65 minutes. The reaction temperature was maintained at ≤10℃ during the addition. After the addition was complete, the ice bath was removed, and the mixture was stirred and kept warm at room temperature (25℃) for 30 minutes. Then, the temperature was raised to 60℃ and the reaction was kept warm for 30 minutes. Finally, the ethanol was removed by vacuum distillation at 80℃ and -0.095 MPa to obtain a pale yellow, transparent, viscous liquid, which is the modified hexamethylenediamine curing agent. The curing agent was mixed with bisphenol A type epoxy resin E-51 at a mass ratio of 70:100 to prepare an epoxy coating. The coating was sprayed onto a sandblasted aluminum alloy plate and cured at 100°C for 3 hours to form a coating with a dry film thickness of about 110 μm.

[0021] Comparative Example 1 (Unmodified MTHPA) Commercially available methyltetrahydrophthalic anhydride (unmodified) was used as a curing agent. The curing agent was mixed with bisphenol A type epoxy resin E-51 at a mass ratio of 80:100 to prepare an epoxy coating. The coating was sprayed onto a sandblasted aluminum alloy plate and cured at 100°C for 3 hours to form a coating with a dry film thickness of about 100μm. Explanation of the above coating test methods Adhesion at 25℃: according to GB / T 9286 cross-cut test for varnishes and paints; Shear strength: GB / T 7124 Determination of tensile shear strength of adhesives; Pull-out strength: GB / T 5210 Paint and varnish adhesion test by pull-out method; Water resistance: GB / T 1733 Test method for water resistance of paint film; Resistance to neutral salt spray: Corrosion test under artificial atmosphere according to GB / T 10125; High temperature and high humidity aging: temperature 85℃, humidity 85%, 1000h; Temperature shock resistance: -40℃ to 85℃ (2h / cycle, switching within 5 minutes), 500 cycles; Electrolyte resistance: Soaked in 1 mol / L LiPF6 for 7 days, dissolves in EC:DMC (1:1, v / v). Performance test table of Examples 1-4 and Comparative Example 1: As shown in the table above, under the same testing standards and environmental conditions, the epoxy coating prepared by the amine-modified anhydride curing agent of the present invention is significantly superior to the unmodified traditional anhydride system in key indicators such as adhesion, water resistance, shear strength, pull-out strength, resistance to neutral salt spray, high temperature and high humidity aging, resistance to temperature shock and electrolyte resistance.

[0022] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0023] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for synthesizing amine-modified acid anhydrides, characterized in that, Includes the following steps: S1: Mix cyclohexylaminopropylamine with anhydrous ethanol, stir at 50-70°C until homogeneous, and then cool to 0-10°C; S2: Under ice-salt cooling conditions of 0-10℃, slowly add methyltetrahydrophthalic anhydride dropwise, controlling the dropwise addition time to be 30-90 minutes; S3: After the addition is complete, keep the reaction at room temperature for 20-40 minutes; S4: Heat to 55-65℃ and continue the reaction for 20-40 minutes. S5: Remove the solvent anhydrous ethanol by vacuum distillation at 80℃ and -0.095MPa to obtain the amine-modified anhydride curing agent; The molar amounts of cyclohexylaminopropylamine, methyltetrahydrophthalic anhydride, and anhydrous ethanol were 0.2 mol, 1 mol, and 3 mol, respectively.

2. An amine-modified acid anhydride curing agent, characterized in that, It is prepared by the synthesis method described in claim 1.

3. An epoxy coating composition, characterized in that, The mixture comprises the amine-modified anhydride curing agent as described in claim 2 and bisphenol A type epoxy resin, wherein the curing agent and bisphenol A type epoxy resin are mixed at a mass ratio of (60~85):

100.

4. The epoxy coating composition according to claim 3, characterized in that, The epoxy coating composition also includes one or more additives selected from flame retardants, leveling agents, defoamers, and fillers.

5. A method of using an epoxy coating composition, comprising the epoxy coating composition of claim 3, characterized in that, The battery pack casing is made of sandblasted aluminum alloy or stainless steel plate, and an epoxy coating composition is sprayed onto it to form a coating.

6. The method of using the epoxy coating composition according to claim 5, characterized in that, The coating is cured at 100℃~120℃ for 2~3 hours to form a dry film with a thickness of 90~120μm.

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