An active epoxy resin diluent, its preparation method and use

Abstract

The present application relates to epoxy resin diluent, especially to a kind of active epoxy resin diluent and its preparation method and application.The present application first multi-functional epoxy compound and catalyst are added to high-pressure reactor, nitrogen is imported to discharge the air in autoclave, temperature is raised to set temperature and CO2 gas is imported, under certain pressure, reaction is started, after reaction, temperature is reduced, exhaust, filtration is obtained cyclic carbonate compound, i.e.active epoxy resin diluent;The cyclic carbonate compound obtained is mixed with epoxy resin uniformly, then amine curing agent is added, and modified epoxy resin is obtained after curing.The active epoxy diluent prepared in the present application can not only reduce the viscosity of epoxy resin, improve its construction performance, but also improve the comprehensive performance of epoxy resin, play the role of toughening modification.

Description

Technical Field

[0001] This invention relates to epoxy resin diluents, and particularly to an active epoxy resin diluent, its preparation method, and its application. Background Technology

[0002] Epoxy resin, a common thermosetting material, possesses excellent adhesive properties, electrical insulation, chemical resistance, and heat resistance. Furthermore, its low shrinkage after curing has led to its widespread application in construction, automotive, aerospace, and advanced composite matrix applications. However, during application, it has been found that the high viscosity of epoxy resin at room temperature results in poor flowability, making it difficult to meet the requirements of vacuum casting, pultrusion, and winding molding processes during composite material synthesis. When used as an adhesive, it is not conducive to filling the entire bonding cavity during construction, significantly impacting the sealing and bonding effect.

[0003] To address the issue of low viscosity in epoxy resin applications, diluents are typically added during the application process to reduce system viscosity and improve processing performance. Currently, commonly used epoxy resin diluents can be broadly categorized into reactive and inactive types: inactive diluents do not participate in the curing reaction and only reduce viscosity, ultimately existing freely in the system. This not only affects the performance of the epoxy material but also causes environmental pollution due to their volatilization. In contrast, reactive diluents participate in the epoxy resin curing reaction, becoming part of the cross-linked network structure. They can even modify the epoxy resin, ensuring the stability and longevity of the cured product, thus possessing greater practical value.

[0004] CN114874417A discloses a method for preparing and using a high-boiling-point epoxy resin diluent. This diluent is prepared by reacting styrene oxide and its derivatives with alcohols, acids, amines, ethers, and halogenated derivatives containing phenolic hydroxyl groups, followed by purification. When used in epoxy resins, this diluent reduces viscosity and improves the product's performance and gel properties; however, its preparation process is complex, the raw materials used are highly irritating to humans, and the post-processing steps are cumbersome.

[0005] CN113980242A discloses an epoxy resin diluent containing a benzene ring structure and its preparation method. The method involves ring-opening epichlorohydrin with a polyphenol or benzene ring-containing polyether, followed by reaction with a strong alkali, and then aging, separation, neutralization, and purification to obtain the target product. Although the resulting epoxy resin diluent exhibits high reactivity, high adhesive strength, and good compatibility with epoxy resin, its preparation process is lengthy, and the reaction and purification steps are complex.

[0006] CN112940349A describes a combined toughening agent composed of a hydrolyzed aromatic cyclic carbonate and an aliphatic cyclic carbonate. The hydrolyzed aromatic cyclic carbonate is prepared by reacting aromatic epoxy resin with CO2 and distilled water in sequence, while the aliphatic cyclic carbonate is prepared by reacting aliphatic glycidyl ether with CO2. This composition can improve the toughness of epoxy resin to a certain extent.

[0007] Although the above-mentioned diluents or toughening agents can dilute or toughen epoxy resins, their preparation processes are quite complex, some reactions involve toxic substances, and the post-processing is also quite cumbersome, making the preparation process complicated. Summary of the Invention

[0008] While the aforementioned diluents or toughening agents can dilute or toughen epoxy resins, their preparation processes are complex, some reactions involve toxic substances, and post-processing is also cumbersome. The purpose of this invention is to provide a multifunctional cyclic carbonate compound that is simple to prepare and easy to use as an epoxy resin diluent. Because cyclic carbonates can undergo ring-opening reactions with amine compounds to generate urethane and hydroxyl groups, these groups can provide toughness to the cured system and enhance its hydrogen bonding. Furthermore, they can provide intramolecular hydrogen bonds. Therefore, this reactive diluent helps improve the overall performance of epoxy resins while altering their viscosity, exhibiting excellent performance.

[0009] To achieve the above objectives, the present invention employs the following technical solutions:

[0010] A method for preparing an reactive epoxy resin diluent includes the following steps:

[0011] A multifunctional epoxy compound and a catalyst are added to a high-pressure reactor. Nitrogen gas is introduced to purge the air from the reactor. The temperature is raised to a set temperature, and CO2 gas is introduced. The reaction begins under a certain pressure. After the reaction is completed, the temperature is lowered, the gas is exhausted, and the mixture is filtered to obtain a cyclic carbonate compound, which is an active epoxy resin diluent.

[0012] Furthermore, the reaction temperature is 110–170°C, the reaction time is 10–50 h, and the pressure is 0.5–3.0 MPa.

[0013] Furthermore, the multifunctional epoxy compound is any one or more of the following: 1,4-butanediol diglycidyl ether, ethylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, resorcinol diglycidyl ether, 1,4-cyclohexanediol diglycidyl ether, and trifunctional alicyclic epoxy compounds TT386 and trimethylolpropane triglycidyl ether.

[0014] Furthermore, the catalyst is a macroporous resin-supported quaternary ammonium salt amine compound or a carbon nitride catalyst, and the amount of catalyst used is 5% to 15% of the mass of the multifunctional epoxy compound added.

[0015] Furthermore, the macroporous resin-supported quaternary ammonium salt amine compound is any one of tetrabutylammonium bromide, tetramethylammonium iodide, and tetrabutylammonium chloride; the carbon nitride catalyst is prepared by calcination and water washing of urea or melamine precursor.

[0016] The present invention also provides an active epoxy resin diluent prepared by the above preparation method.

[0017] The present invention also provides the application of an active epoxy resin diluent in epoxy resin, wherein the cyclic carbonate compound prepared above is mixed evenly with epoxy resin and then an amine curing agent is added, and after curing, a modified epoxy resin is obtained.

[0018] Furthermore, the curing conditions are: placing at room temperature for 2–6 hours followed by heating at 60–90°C for 1–5 hours.

[0019] Furthermore, the epoxy resin is any one or more of bisphenol A type epoxy resin E-51, bisphenol A type epoxy resin E-54, bisphenol A type epoxy resin E-44, bisphenol F type epoxy resin F-51, bisphenol F type epoxy resin F-44, bisphenol S type epoxy resin, and hydrogenated epoxy resin; the amine curing agent is any one or more of ethylenediamine, propylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, polyethylenepolyamine, isophorone diamine, and polyetheramine.

[0020] Furthermore, the amount of cyclic carbonate is 10% to 40% of the mass of epoxy resin; the amount of amine curing agent is 0.85 to 1.15 times the theoretical amount of curing agent required for the cyclic carbonate and polyfunctional epoxy compound.

[0021] When the active epoxy resin diluent is added to the epoxy resin at a concentration of 40 wt%, the resulting resin has a viscosity of less than 6000 centipoise at room temperature; after curing, the epoxy resin has a tensile strength of up to 80 MPa and a modulus of up to 2256.6 MPa.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] (1) The diluent is simple to prepare and can be prepared in one step. The reaction conditions are mild and the post-treatment can be achieved by filtration. (2) When used as an active diluent, it can effectively reduce the viscosity of epoxy resin and at the same time greatly improve the performance of epoxy resin. Attached Figure Description

[0024] Figure 1The change in epoxy resin viscosity at room temperature with the amount of diluent added;

[0025] Figure 2 The infrared spectrum of the epoxy resin cured product after adding diluent. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0027] Example 1

[0028] (1) 100.0g of 1,4-butanediol diglycidyl ether and 10.0g of supported tetramethylammonium iodide catalyst were added to a high-pressure reactor. Nitrogen gas was introduced to purge the air from the reactor. When the temperature reached 130°C, CO2 gas was introduced to maintain the pressure inside the reactor at 2.0MPa to start the reaction. After 30h of reaction, the temperature was lowered, the gas was vented, and the mixture was filtered to obtain a cyclic carbonate compound.

[0029] (2) Add 18.0g of the above cyclic carbonate compound to 60.0g of epoxy resin E-51, mix evenly at room temperature, add 25.9g of ethylenediamine and stir thoroughly. Then pour the mixture into a PTFE mold and place it at room temperature for 3h, then heat it at 80℃ for 2h to obtain the corresponding epoxy resin.

[0030] Example 2

[0031] (1) 100.0g of polyethylene glycol diglycidyl ether and 5.0g of supported tetrabutylammonium bromide catalyst were added to a high-pressure reactor. Nitrogen gas was introduced to purge the air from the reactor. When the temperature reached 110℃, CO2 gas was introduced to maintain the pressure inside the reactor at 3.0MPa to start the reaction. After 50h of reaction, the temperature was lowered, the gas was vented, and the mixture was filtered to obtain a cyclic carbonate compound.

[0032] (2) Add 6.0g of the above cyclic carbonate compound to 60.0g of epoxy resin E-54, mix evenly at room temperature, add 36.5g of propylenediamine and stir thoroughly. Then pour the mixture into a PTFE mold and place it at room temperature for 6h, then heat it at 90℃ for 1h to obtain the corresponding epoxy resin.

[0033] Example 3

[0034] (1) 100.0g of ethylene glycol diglycidyl ether and 15.0g of urea as precursor carbon nitride catalyst were added to a high-pressure reactor. Nitrogen gas was introduced to purge the air in the high-pressure reactor. When the temperature rose to 140℃, CO2 gas was introduced to maintain the pressure in the reactor at 1.5MPa to start the reaction. After reacting for 10h, the temperature was lowered, the gas was vented, and the mixture was filtered to obtain cyclic carbonate compounds.

[0035] (2) Add 24.0g of the above cyclic carbonate compound to 60.0g of epoxy resin E-44, mix evenly at room temperature, add 56.8g of isophorone diamine and stir thoroughly. Then pour the mixture into a PTFE mold and place it at room temperature for 2h, then heat it at 60℃ for 5h to obtain the corresponding epoxy resin.

[0036] Example 4

[0037] (1) 100.0g of trimethylolpropane triglycidyl ether and 10.0g of supported tetrabutylammonium chloride catalyst were added to a high-pressure reactor. Nitrogen gas was introduced to purge the air from the reactor. When the temperature reached 170°C, CO2 gas was introduced to maintain the pressure inside the reactor at 1.0MPa to start the reaction. After 10 hours of reaction, the temperature was lowered, the gas was vented, and the mixture was filtered to obtain a cyclic carbonate compound.

[0038] (2) Add 12.0g of the above cyclic carbonate compound to 60.0g of epoxy resin E-51, mix evenly at room temperature, add 28.54g of ethylenediamine and stir thoroughly. Then pour the mixture into a PTFE mold and place it at room temperature for 2h, then heat it at 72℃ for 3h to obtain the corresponding epoxy resin.

[0039] Example 5

[0040] (1) 100.0g of polypropylene glycol diglycidyl ether and 7.0g of supported tetrabutylammonium bromide catalyst were added to a high-pressure reactor. Nitrogen gas was introduced to purge the air from the reactor. When the temperature reached 120°C, CO2 gas was introduced to maintain the pressure inside the reactor at 2.5MPa to start the reaction. After 25h of reaction, the temperature was lowered, the gas was vented, and the mixture was filtered to obtain a cyclic carbonate compound.

[0041] (2) Add 9.0g of the above cyclic carbonate compound to 60.0g of epoxy resin F-51, mix evenly at room temperature, add 48.0g of hexamethylenediamine and stir thoroughly. Then pour the mixture into a PTFE mold and place it at room temperature for 5.6h, then heat it at 83℃ for 4.5h to obtain the corresponding epoxy resin.

[0042] Example 6

[0043] (1) 100.0g of neopentyl glycol diglycidyl ether and 18.0g of melamine as precursor carbon nitride catalyst were added to a high-pressure reactor. Nitrogen gas was introduced to purge the air in the high-pressure reactor. When the temperature rose to 136℃, CO2 gas was introduced to maintain the pressure in the reactor at 2.1MPa to start the reaction. After reacting for 30.3h, the temperature was lowered, the gas was vented, and the mixture was filtered to obtain cyclic carbonate compounds.

[0044] 100.0g of 1,4-butanediol diglycidyl ether and 15.0g of supported tetrabutylammonium bromide catalyst were added to a high-pressure reactor. Nitrogen gas was introduced to purge the air from the reactor. When the temperature reached 135.5℃, CO2 gas was introduced to maintain the pressure inside the reactor at 2.0MPa to start the reaction. After reacting for 30.5h, the reactor was cooled, the gas was vented, and the mixture was filtered to obtain a cyclic carbonate compound.

[0045] (2) Add 8.0g of the above neopentyl glycol diglycidyl ether cyclic carbonate and 7.0g of 1,4-butanediol diglycidyl ether cyclic carbonate to 60.0g of epoxy resin F-44. After mixing evenly at room temperature, add 10.4g of ethylenediamine and 12.9g of propylenediamine and stir thoroughly. Then pour the mixture into a PTFE mold and place it at room temperature for 3.2h. Then heat it at 80.3℃ for 2.4h to obtain the corresponding epoxy resin.

[0046] Figure 1 The study investigated the change in epoxy resin viscosity at room temperature with the addition of diluent. The results showed that the addition of cyclic carbonate diluent could effectively reduce the viscosity of epoxy resin at room temperature, which greatly helped improve its construction process. When the addition amount was 40wt%, the viscosity of the resulting resin at room temperature could be lower than 6000 centipoise.

[0047] Figure 2 The image shows the infrared spectrum of the cured epoxy resin after adding a diluent. It can be seen from the image that the cyclic carbonate participated in the reaction with the curing agent amine, acting as an active diluent. After the reaction, the carbonyl group in the cyclic carbonate group of the raw material compound is visible at 1790 cm⁻¹. -1 The stretching vibration peak disappears at 1700 cm⁻¹, corresponding to the peak at 1700 cm⁻¹. -1 The characteristic stretching vibration absorption peak of the carbonyl group of the urethane ester group appeared nearby.

[0048] The epoxy resins obtained in each embodiment were subjected to performance tests after being placed at room temperature for one week. The results of the material performance tests are shown in the table below:

[0049]

[0050] As shown in the table, the addition of this cyclic carbonate reactive diluent can significantly improve the overall performance of epoxy materials, with tensile strength and flexural strength being significantly higher than those of the blank sample. Therefore, this reactive diluent not only regulates the viscosity of the epoxy resin system, but also enhances molecular flexibility by generating tough urethane groups after reacting with amine compounds. Furthermore, the generated hydroxyl groups can enhance the hydrogen bonding of the system, thereby improving the overall performance of the product.

[0051] Contents not described in detail in this specification are prior art known to those skilled in the art. Although illustrative specific embodiments of the invention have been described above to facilitate understanding by those skilled in the art, it should be understood that the invention is not limited to the scope of the specific embodiments. Various modifications are readily apparent to those skilled in the art as long as they fall within the spirit and scope of the invention as defined and determined by the appended claims, and all inventions utilizing the concept of this invention are protected.

Claims

1. A process for the preparation of an active epoxy resin diluent, characterized in that: The method comprises the following steps: The multifunctional epoxy compound and the catalyst are added into a high-pressure reaction kettle, nitrogen is introduced to discharge the air in the kettle, the temperature is raised to a set temperature, CO2 gas is introduced, the reaction is started under a certain pressure, after the reaction is completed, the temperature is lowered, the gas is discharged, and the cyclic carbonate compound, i.e., the active epoxy resin diluent, is obtained by filtration; The reaction temperature is 110-170℃, the reaction time is 10-50h, the pressure is 0.5-3.0MPa, and the multifunctional epoxy compound is trimethylolpropane triglycidyl ether; The catalyst is a macroporous resin loaded quaternary amine salt amine compound, and the catalyst dosage is 5%-15% of the multifunctional epoxy compound addition mass; The macroporous resin loaded quaternary amine salt amine compound is any one of tetrabutylammonium bromide, tetramethylammonium iodide, and tetrabutylammonium chloride.

2. Use of the active diluent for epoxy resins, prepared according to the process of claim 1, for the preparation of epoxy resins, characterized by: The modified epoxy resin is obtained after the cyclic carbonate compound prepared above is mixed with the epoxy resin and then an amine curing agent is added, and the curing condition is that the mixture is placed at room temperature for 2-6h and then heated at 60-90℃ for 1-5h; The epoxy resin is any one or several of bisphenol A type epoxy resin E-51, bisphenol A type epoxy resin E-54, bisphenol A type epoxy resin E-44, bisphenol F type epoxy resin F-51, and bisphenol F type epoxy resin F-44; The amine curing agent is any one or several of ethylenediamine, propylenediamine, hexamethylenediamine, and isophorone diamine.

3. Use of the active diluent of epoxy resins according to claim 2 for the preparation of epoxy resins, characterized by: The cyclic carbonate dosage is 10%-40% of the mass of the epoxy resin, and the amine curing agent dosage is 0.85-1.15 times the theoretical amount of the curing agent required for the cyclic carbonate and the multifunctional epoxy compound.

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