Epoxy resin latent curing accelerator and preparation method thereof

Abstract

The invention discloses an epoxy resin latent curing accelerator and a preparation method thereof. The latent curing accelerator has a structure as shown in a formula (I). The latent curing accelerator keeps chemical inertness at normal temperature, prolongs the storage life of epoxy resin, and avoids the phenomenon of viscosity increase or advanced curing in the storage process. When the temperature is raised to a set temperature, the latent curing accelerator is activated to quickly promote the curing reaction of the epoxy resin, and the curing speed and temperature can be adjusted by adjusting the dosage of the catalyst. # imgabs0 #

Description

Technical Field

[0001] The invention relates to the field of epoxy materials, in particular to an epoxy resin latent curing accelerator and a preparation method thereof. Background Art

[0002] Epoxy resin is one of the most widely used thermosetting polymers, accounting for about 70% of the global thermosetting resin market, and is widely used in aerospace, electronics and electrical, automotive manufacturing, construction, composite materials and coatings. This is due to its excellent mechanical properties, chemical stability, electrical insulation and its highly cross-linked structure. However, most current epoxy resin formulations require that each component be stored separately before use and that they be prepared and used immediately when used, which brings many inconveniences to industrial production. In large-scale industrial production, this requirement not only increases operational complexity and reduces production efficiency, but also increases the risk of material waste.

[0003] In order to simplify the production process and reduce the number of operating steps, achieving single-component storage and use of epoxy resin has become an important goal of the industry. The single-component formula enables the epoxy resin to be stored stably for a long time at room temperature and to be cured by heating when needed. However, existing single-component formulas usually rely on latent curing agents, which have problems such as poor storage stability, easy viscosity increase and premature curing of the glue. In addition, these formulas usually require higher curing temperatures (usually about 150°C), which is not conducive to rapid production, increases the complexity and cost of the process, and significantly increases energy consumption.

[0004] To address this problem, the introduction of latent catalysts provides an effective solution for achieving single-component epoxy resins. Latent catalysts can maintain catalyst inertness at room temperature or lower temperatures, preventing premature curing of epoxy resins, thereby achieving long-term storage of epoxy resins. After being activated by heating, the catalyst is quickly released, prompting the epoxy resin to cure quickly. This not only meets the storage requirements of epoxy resins, but also ensures the mechanical properties and chemical stability of the cured material.

[0005] Therefore, developing a latent curing accelerator that can provide long-term storage stability for the epoxy resin system before activation and effectively promote rapid curing after activation has become the key to solving the existing technical problems. Summary of the invention

[0006] The present invention aims to solve one of the technical problems in the related art at least to a certain extent. The present invention discloses a latent curing catalyst for epoxy resin, which aims to improve the storage stability of epoxy resin and reduce its curing temperature. The latent curing accelerator maintains chemical inertness at room temperature, prolongs the shelf life of epoxy resin, and avoids the phenomenon of viscosity increase or premature curing during storage. When the temperature is raised to the set temperature, the latent curing accelerator is activated, and the curing reaction of epoxy resin is rapidly promoted. The curing speed and temperature can be adjusted by adjusting the amount of catalyst. The present invention simplifies the production process, reduces energy consumption, and is particularly suitable for industrial application scenarios that require efficient production and storage. The latent curing accelerator is suitable for a variety of epoxy systems, including: epoxy-acid system, epoxy-thiol system, epoxy-anhydride system. In addition, the latent curing accelerator is also suitable for other base-catalyzed curing systems, including: polyurethane, acrylate-thiol system, cyanate resin, polycarbonate, etc.

[0007] In one aspect of the present invention, the present invention provides a latent curing accelerator. According to an embodiment of the present invention, the latent curing accelerator has a structure as shown in formula (I):

[0008]

[0009] The latent curing accelerator remains chemically inert at room temperature, prolongs the shelf life of the epoxy resin, and avoids the phenomenon of increased viscosity or premature curing during storage. When the temperature is raised to the set temperature, the latent curing accelerator is activated and rapidly promotes the curing reaction of the epoxy resin. The curing speed and temperature can be adjusted by adjusting the amount of catalyst. The latent curing accelerator is suitable for a variety of epoxy systems, including: epoxy-acid system, epoxy-thiol system, epoxy-anhydride system. In addition, the latent curing accelerator is also suitable for other base-catalyzed curing systems, including: polyurethane, acrylate-thiol system, cyanate resin, polycarbonate, etc.

[0010] In another aspect of the present invention, the present invention also provides a method for preparing a latent curing accelerator. According to an embodiment of the present invention, the method comprises:

[0011] Cyanoacetic acid is reacted with 1,5,7-triazabicyclo[4.4.0]decene-5-ene to obtain a latent curing accelerator having a structure as shown in formula (I),

[0012]

[0013] According to an embodiment of the present invention, the method may further include at least one of the following additional technical features:

[0014] According to an embodiment of the present invention, the molar ratio of the cyanoacetic acid to the 1,5,7-triazabicyclo[4.4.0]decene-5-ene is (1-1.2):1.

[0015] According to an embodiment of the present invention, the cyanoacetic acid is pre-dissolved in methanol.

[0016] According to an embodiment of the present invention, the usage ratio of the cyanoacetic acid to the methanol is 0.893 g:30 mL.

[0017] According to an embodiment of the present invention, the 1,5,7-triazabicyclo[4.4.0]decene-5-ene is pre-dissolved in 10% methanol.

[0018] According to an embodiment of the present invention, the usage ratio of the 1,5,7-triazabicyclo[4.4.0]decene-5-ene to the methanol is 1.392 g:90 mL.

[0019] According to an embodiment of the present invention, the reaction time is 24 hours.

[0020] According to an embodiment of the present invention, the reaction temperature is room temperature.

[0021] In another aspect of the present invention, the present invention also provides a method for preparing an epoxy cured product. According to an embodiment of the present invention, the method comprises:

[0022] Bisphenol A diglycidyl ether, anhydride curing agent and the aforementioned latent curing accelerator or the latent curing accelerator prepared according to the aforementioned method are mixed and cured to obtain an epoxy cured product.

[0023] According to an embodiment of the present invention, the method may further include at least one of the following additional technical features:

[0024] According to an embodiment of the present invention, the molar ratio of bisphenol A diglycidyl ether to the acid anhydride curing agent is 0.5:(1-0.5), such as 0.5:1 or 1:1.

[0025] According to an embodiment of the present invention, the latent curing accelerator is (0.25-1)% of the total mass of the bisphenol A diglycidyl ether and the anhydride curing agent, for example, 0.25%, 0.5%, 0.75% or 1%.

[0026] According to an embodiment of the present invention, the acid anhydride curing agent is methyltetrahydrophthalic anhydride.

[0027] According to an embodiment of the present invention, the mixing process is performed at room temperature.

[0028] According to an embodiment of the present invention, the mixing process is performed by stirring uniformly in a vortex.

[0029] According to an embodiment of the present invention, the curing process is performed in a vacuum drying oven.

[0030] According to an embodiment of the present invention, the curing process is performed in a polytetrafluoroethylene mold.

[0031] According to an embodiment of the present invention, the curing treatment is performed at 80° C. for 4 hours, then at 120° C. for 4 hours, and finally at 150° C. for 4 hours. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0033] Figure 1 Synthesis route of latent curing accelerator LA-TBD;

[0034] Figure 2 H NMR spectrum of latent curing accelerator LA-TBD;

[0035] Figure 3 Viscosity changes of the formulation containing latent curing accelerator LA-TBD and curing accelerator BDMA at different room temperature storage times. DETAILED DESCRIPTION

[0036] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0037] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0038] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0039] Example 1. Preparation of latent curing accelerator LA-TBD

[0040] Synthesis route such as Figure 1 shown.

[0041] Cyanoacetic acid (10.5mmol, 0.893g) was dissolved in 30mL of methanol to obtain a cyanoacetic acid solution. Then, 1,5,7-triazabicyclo[4.4.0]decene-5-ene (TBD, 10.0mmol, 1.392g) was dissolved in 90mL of 10% methanol to obtain a TBD solution. Subsequently, the TBD solution was added dropwise to the cyanoacetic acid solution under vigorous stirring. After stirring at room temperature for 24 hours, methanol was removed on a rotary evaporator and precipitation of white powder was observed. The obtained powder was dispersed in ether to remove unreacted cyanoacetic acid, filtered to obtain a solid, and repeated three times. Vacuum drying obtained a latent curing accelerator LA-TBD.

[0042] Depend on Figure 2 Shown 1 It can be seen from the H-NMR spectrum that the target latent curing accelerator LA-TBD was obtained in this example.

[0043] Example 2: Rheological test of catalyst latency

[0044] Preparation of epoxy: Mix bisphenol A diglycidyl ether (epoxy equivalent: 182-192g / equivalent, epoxy equivalent: 0.0535, 10.00g), methyltetrahydrophthalic anhydride (anhydride curing agent, anhydride equivalent: 0.0535, 8.89g), latent curing accelerator LA-TBD (0.0472g, determined based on 0.25% of the total mass of epoxy and anhydride) or commercial curing accelerator N,N-dimethylbenzylamine (BDMA, 0.0472g, determined based on 0.25% of the total mass of epoxy and anhydride), and stir evenly in a vortex at room temperature. Pour the mixture into a polytetrafluoroethylene mold (4cm×4cm×0.5cm) and cure it in a vacuum drying oven. The curing process is 80℃4h+120℃4h+150℃4h. The cured sample is taken out of the mold to obtain an epoxy cured product.

[0045] Rheological test: The viscosity of the two glass-like polymer formulations in Example 2 was analyzed using a rheometer (placed at room temperature for different days, shear rate 1s-1). The results are as follows: Figure 3 As shown. For the commercial curing accelerator BDMA system, the viscosity increases rapidly with the number of days, indicating that the epoxy and anhydride undergo partial polymerization reaction, resulting in an increase in the viscosity of the system, indicating that the BDMA catalyst is not latent. The viscosity of the latent curing accelerator LA-TBD system remains at a low level, indicating that the catalyst remains inert when left at room temperature for a long time, effectively avoiding the occurrence of curing reaction, indicating that LD-TBD has good latency, which provides the possibility for one-pot storage of epoxy resin.

[0046] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0047] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A latent curing accelerator, characterized in that: Having a structure as shown in formula (I):

2. A method for preparing a latent curing accelerator, characterized in that: include: Cyanoacetic acid is reacted with 1,5,7-triazabicyclo[4.4.0]decene-5-ene to obtain a latent curing accelerator having a structure as shown in formula (I), 3. The method according to claim 2, characterized in that The molar ratio of the cyanoacetic acid to the 1,5,7-triazabicyclo[4.4.0]decene-5-ene is (1-1.2):

1.

4. The method according to claim 2, characterized in that: The cyanoacetic acid is pre-dissolved in methanol; Optionally, the usage ratio of the cyanoacetic acid to the methanol is 0.893 g:30 mL.

5. The method according to claim 2, characterized in that: The 1,5,7-triazabicyclo[4.4.0]decene-5-ene is pre-dissolved in 10% methanol; Optionally, the usage ratio of the 1,5,7-triazabicyclo[4.4.0]decene-5-ene to the methanol is 1.392 g:90 mL.

6. The method according to claim 2, characterized in that The reaction time is 24 hours; Optionally, the temperature of the reaction is room temperature.

7. A method for preparing an epoxy cured product, characterized in that: include: Bisphenol A diglycidyl ether, anhydride curing agent and the latent curing accelerator according to claim 1 or the latent curing accelerator prepared by the method according to any one of claims 2 to 6 are mixed and cured to obtain an epoxy cured product.

8. The method according to claim 7, characterized in that The molar ratio of bisphenol A diglycidyl ether to anhydride curing agent is 0.5:(1-0.5); Optionally, the latent curing accelerator is (0.25-1)% of the total mass of the bisphenol A diglycidyl ether and the anhydride curing agent; Optionally, the anhydride curing agent is methyltetrahydrophthalic anhydride.

9. The method according to claim 7, characterized in that: The mixing process is carried out at room temperature; Optionally, the mixing process is carried out by stirring uniformly in a vortex.

10. The method according to claim 7, characterized in that The curing process is carried out in a vacuum drying oven; Optionally, the curing process is carried out in a polytetrafluoroethylene mold; Optionally, the curing treatment is performed at 80° C. for 4 hours, then at 120° C. for 4 hours, and finally at 150° C. for 4 hours.

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