Active epoxy resin diluent as well as preparation method and application thereof

Abstract

The invention relates to an epoxy resin diluent, in particular to an active epoxy resin diluent as well as a preparation method and application thereof. The preparation method comprises the following steps: firstly, adding a multifunctional epoxy compound and a catalyst into a high-pressure reaction kettle, introducing nitrogen to exhaust air in the high-pressure reaction kettle, heating to a set temperature, introducing CO2 gas, starting a reaction under a certain pressure, and after the reaction is finished, cooling, exhausting and filtering to obtain a cyclic carbonate compound, namely an active epoxy resin diluent; uniformly mixing the obtained cyclic carbonate compound with epoxy resin, adding an amine curing agent, and curing to obtain the modified epoxy resin. The prepared active epoxy diluent not only can reduce the viscosity of epoxy resin and improve the construction performance of the epoxy resin, but also can improve the comprehensive performance of the epoxy resin and play a role in toughening modification.

Description

[0001] This application is a divisional application of the invention titled "An active epoxy resin diluent and its preparation method and application", with an application date of March 16, 2023 and an application number of 202310256064.7 Technical Field

[0002] The present invention relates to epoxy resin diluents, and particularly to an active epoxy resin diluent and its preparation method and application. Background Art

[0003] As a common thermosetting material, epoxy resin has good adhesive properties, electrical insulation, chemical resistance, and heat resistance. In addition, its shrinkage rate after curing is low, and it has been widely used in fields such as construction, automotive, aerospace, and advanced composite matrix materials. However, in the application process, it is found that due to the relatively high viscosity of epoxy resin at room temperature, its fluidity is poor, making it difficult to meet the requirements of forming processes such as vacuum infusion, pultrusion, and winding during the synthesis of composite materials. When used as an adhesive, it is not conducive to filling the entire bonding cavity during construction, which has a greater impact on the encapsulation and bonding effect.

[0004] In order to improve the problem of low viscosity during the application of epoxy resin, diluents are usually added during the application process to reduce the viscosity of the system and thus improve the process performance. Currently, commonly used epoxy resin diluents can be divided into two categories: active and non-active. Non-active diluents do not participate in the curing reaction when added to the system, only acting to reduce the viscosity and ultimately existing freely in the system. This not only affects the performance of the epoxy material, but also pollutes the environment due to its volatilization. Compared with non-active diluents, active diluents can participate in the curing reaction of epoxy resin, thus becoming a part of the cross-linked network structure, and even can be used to modify epoxy resin, ensuring the stability and long-term effectiveness of the epoxy resin cured product, and having greater practical value.

[0005] CN114874417A discloses a preparation method and use method of an epoxy resin diluent with a relatively high boiling point. This diluent is prepared by reacting styrene oxide and its derivatives with alcohols, acids, amines, ethers, and halogenated substituents containing phenolic hydroxyl groups, and is obtained after purification. When this diluent is used in epoxy resin, while reducing the viscosity, it also has a certain improvement on the performance and gel characteristics of the product; however, its preparation process is complex, the raw materials used are highly irritating to the human body, and the post-treatment steps are cumbersome.

[0006] CN113980242A provides a benzene ring structure-containing epoxy resin diluent and its preparation method. After polyhydric phenols or benzene ring-containing polyethers are ring-opened with epichlorohydrin and then reacted with strong bases, the target product is obtained after aging, liquid separation, neutralization, and purification. Although the obtained epoxy resin diluent has high reaction activity, high bonding strength, and good compatibility with epoxy resin, its preparation process is long, and the reaction and purification steps are complex.

[0007] CN112940349A prepares a combined toughening agent composed of a hydrolyzable aromatic cyclic carbonate and an aliphatic cyclic carbonate. The hydrolyzable aromatic cyclic carbonate is prepared by reacting an aromatic epoxy resin with CO2 and distilled water in sequence, and the aliphatic cyclic carbonate is prepared by reacting an aliphatic glycidyl ether with CO2. This composition can improve the toughness of epoxy resin to a certain extent.

[0008] Although the above diluents or toughening agents can dilute or toughen epoxy resin, their preparation processes are relatively complex. Some reactions involve toxic substances, and the post-treatment processes are also rather cumbersome, with complex preparation processes. Summary of the Invention

[0009] Regarding the problem that although the above diluents or toughening agents can dilute or toughen epoxy resin, their preparation processes are relatively complex, some reactions involve toxic substances, and the post-treatment processes are also rather cumbersome, with complex preparation processes, the purpose of the present invention is to provide a multi-functional cyclic carbonate compound with a simple preparation process and convenient use as an epoxy resin diluent. Since the cyclic carbonate can undergo a ring-opening reaction with an amine compound to generate a carbamate and a hydroxyl group, this group can provide toughness for the curing system and enhance its hydrogen bond interaction. In addition, it can also provide intramolecular hydrogen bonds. Therefore, while changing the viscosity of epoxy resin, this active diluent helps to improve the comprehensive performance of epoxy resin and has excellent use effects.

[0010] To achieve the above purpose, the present invention adopts the following technical solutions:

[0011] A preparation method of an active epoxy resin diluent, comprising the following steps:

[0012] Add a multi-functional epoxy compound and a catalyst into a high-pressure reaction kettle, introduce nitrogen to discharge the air in the kettle, heat up to a set temperature and introduce CO2 gas, start the reaction under a certain pressure, and after the reaction ends, cool down, exhaust gas, and filter to obtain a cyclic carbonate compound, namely the active epoxy resin diluent.

[0013] Further, the reaction temperature is 110 - 170 °C, the reaction time is 10 - 50 h; the pressure is 0.5 - 3.0 MPa.

[0014] Further, the multi-functional epoxy compound is any one or several of 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-cyclohexanedimethanol diglycidyl ether, trifunctional alicyclic epoxy compound TT386, and trimethylolpropane triglycidyl ether.

[0015] Furthermore, the catalyst is a quaternary ammonium salt amine compound supported on macroporous resin or a carbon nitride catalyst, and the dosage of the catalyst is 5% - 15% of the mass of the polyfunctional epoxy compound added.

[0016] Furthermore, the quaternary ammonium salt amine compound supported on macroporous resin is any one of tetrabutylammonium bromide, tetramethylammonium iodide, and tetrabutylammonium chloride; the carbon nitride catalyst is prepared by calcining and washing a urea or melamine precursor.

[0017] The present invention also provides an active epoxy resin diluent prepared by the above preparation method.

[0018] The present invention also provides the application of the active epoxy resin diluent in epoxy resin. After mixing the above-prepared cyclic carbonate compound with epoxy resin evenly, an amine curing agent is added, and a modified epoxy resin is obtained after curing.

[0019] Furthermore, the curing conditions are to place at room temperature for 2 - 6 h and then heat at 60 - 90 °C for 1 - 5 h.

[0020] Furthermore, the epoxy resin is any one or several of bisphenol A epoxy resin E-51, bisphenol A epoxy resin E-54, bisphenol A epoxy resin E-44, bisphenol F epoxy resin F-51, bisphenol F epoxy resin F-44, bisphenol S epoxy resin, and hydrogenated epoxy resin; the amine curing agent is any one or several of ethylenediamine, propylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, polyethylenepolyamine, isophoronediamine, and polyetheramine.

[0021] Furthermore, the dosage of the cyclic carbonate is 10% - 40% of the mass of the epoxy resin; the dosage of the amine curing agent is 0.85 - 1.15 times the theoretical amount of the curing agent required for the cyclic carbonate and the polyfunctional epoxy compound.

[0022] When the active epoxy resin diluent is used in epoxy resin, when the addition amount is 40 wt%, the viscosity of the obtained resin at room temperature can be lower than 6000 centipoises; the tensile strength of the cured epoxy resin can reach 80 MPa, and the modulus can reach 2256.6 MPa.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] (1) The preparation process of the diluent is simple, and it can be prepared only through one-step reaction. The reaction conditions are mild, and the post-treatment can be realized only by filtration; (2) When used as an active diluent, it can effectively reduce the viscosity of epoxy resin and can greatly improve the performance of epoxy resin at the same time. Description of the Drawings

[0025] Figure 1 The viscosity change of epoxy resin at room temperature with the addition amount of diluent;

[0026] Figure 2 The infrared spectrogram of the cured product of epoxy resin after adding diluent. Specific embodiments

[0027] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0028] Example 1

[0029] (1) Add 100.0 g of 1,4-butanediol diglycidyl ether and 10.0 g of the catalyst loaded with tetramethylammonium iodide into a high-pressure reactor, introduce nitrogen to discharge the air in the high-pressure reactor. When the temperature rises to 130 °C, introduce CO2 gas, maintain the pressure in the reactor at 2.0 MPa and start the reaction. After reacting for 30 h, cool down, exhaust gas, and filter to obtain a cyclic carbonate compound;

[0030] (2) Add 18.0 g of the above cyclic carbonate compound into 60.0 g of epoxy resin E-51, mix evenly at room temperature, add 25.9 g of ethylenediamine and stir well. Then pour the mixture into a tetrafluoro mold and place it at room temperature for 3 h, and then heat it at 80 °C for 2 h to obtain the corresponding epoxy resin.

[0031] Example 2

[0032] (1) Add 100.0 g of polyethylene glycol diglycidyl ether and 5.0 g of the catalyst loaded with tetrabutylammonium bromide into a high-pressure reactor, introduce nitrogen to discharge the air in the high-pressure reactor. When the temperature rises to 110 °C, introduce CO2 gas, maintain the pressure in the reactor at 3.0 MPa and start the reaction. After reacting for 50 h, cool down, exhaust gas, and filter to obtain a cyclic carbonate compound;

[0033] (2) Add 6.0 g of the above cyclic carbonate compound into 60.0 g of epoxy resin E-54, mix evenly at room temperature, add 36.5 g of propylenediamine and stir well. Then pour the mixture into a tetrafluoro mold and place it at room temperature for 6 h, and then heat it at 90 °C for 1 h to obtain the corresponding epoxy resin.

[0034] Example 3

[0035] (1) Add 100.0 g of ethylene glycol diglycidyl ether and 15.0 g of urea as a precursor for the carbon nitride catalyst into a high-pressure reactor. Purge the air in the high-pressure reactor with nitrogen. When the temperature rises to 140 °C, introduce CO2 gas and maintain the pressure in the reactor at 1.5 MPa to start the reaction. After reacting for 10 h, cool down, exhaust the gas, and filter to obtain the cyclic carbonate compound;

[0036] (2) Add 24.0 g of the above cyclic carbonate compound into 60.0 g of epoxy resin E-44. After mixing evenly at room temperature, add 56.8 g of isophorone diamine and stir well. Then pour the mixture into a tetrafluoro mold and let it stand at room temperature for 2 h, and then heat it at 60 °C for 5 h to obtain the corresponding epoxy resin.

[0037] Example 4

[0038] (1) Add 100.0 g of trimethylolpropane triglycidyl ether and 10.0 g of a catalyst loaded with tetrabutylammonium chloride into a high-pressure reactor. Purge the air in the high-pressure reactor with nitrogen. When the temperature rises to 170 °C, introduce CO2 gas and maintain the pressure in the reactor at 1.0 MPa to start the reaction. After reacting for 10 h, cool down, exhaust the gas, and filter to obtain the cyclic carbonate compound;

[0039] (2) Add 12.0 g of the above cyclic carbonate compound into 60.0 g of epoxy resin E-51. After mixing evenly at room temperature, add 28.54 g of ethylenediamine and stir well. Then pour the mixture into a tetrafluoro mold and let it stand at room temperature for 2 h, and then heat it at 72 °C for 3 h to obtain the corresponding epoxy resin.

[0040] Example 5

[0041] (1) Add 100.0 g of polypropylene glycol diglycidyl ether and 7.0 g of a catalyst loaded with tetrabutylammonium bromide into a high-pressure reactor. Purge the air in the high-pressure reactor with nitrogen. When the temperature rises to 120 °C, introduce CO2 gas and maintain the pressure in the reactor at 2.5 MPa to start the reaction. After reacting for 25 h, cool down, exhaust the gas, and filter to obtain the cyclic carbonate compound;

[0042] (2) Add 9.0 g of the above cyclic carbonate compound into 60.0 g of epoxy resin F-51. After mixing evenly at room temperature, add 48.0 g of hexamethylenediamine and stir well. Then pour the mixture into a tetrafluoro mold and let it stand at room temperature for 5.6 h, and then heat it at 83 °C for 4.5 h to obtain the corresponding epoxy resin.

[0043] Example 6

[0044] (1) 100.0 g of neopentyl glycol diglycidyl ether and 18.0 g of melamine as the precursor carbon nitride catalyst were added to a high-pressure reactor. Nitrogen was introduced to expel the air in the autoclave. When the temperature rose to 136 °C, CO2 gas was introduced, and the reaction started while maintaining the pressure in the autoclave at 2.1 MPa. After reacting for 30.3 h, the temperature was decreased, the gas was exhausted, and the cyclic carbonate compound was obtained by filtration;

[0045] 100.0 g of 1,4-butanediol diglycidyl ether and 15.0 g of the catalyst supported with tetrabutylammonium bromide were added to a high-pressure reactor. Nitrogen was introduced to expel the air in the autoclave. When the temperature rose to 135.5 °C, CO2 gas was introduced, and the reaction started while maintaining the pressure in the autoclave at 2.0 MPa. After reacting for 30.5 h, the temperature was decreased, the gas was exhausted, and the cyclic carbonate compound was obtained by filtration;

[0046] (2) 8.0 g of the above-mentioned neopentyl glycol diglycidyl ether cyclic carbonate and 7.0 g of 1,4-butanediol diglycidyl ether cyclic carbonate were added to 60.0 g of epoxy resin F-44. After mixing evenly at room temperature, 10.4 g of ethylenediamine and 12.9 g of propylenediamine were added and stirred well. Then the mixture was poured into a tetrafluoro mold and left at room temperature for 3.2 h, and then heated at 80.3 °C for 2.4 h to obtain the corresponding epoxy resin.

[0047] Figure 1 shows the change of the viscosity of the epoxy resin at room temperature with the addition amount of the diluent. The results show that the addition of the cyclic carbonate diluent can effectively reduce the viscosity of the epoxy resin at room temperature, which is of great help to improving its construction process. When the addition amount is 40 wt%, the viscosity of the obtained resin at room temperature can be lower than 6000 centipoise.

[0048] Figure 2 is the infrared spectrum of the cured epoxy resin after adding the diluent. It can be seen from the figure that the cyclic carbonate participated in the reaction with the curing agent amine and is an active diluent. After the reaction, the stretching vibration peak of the carbonyl group in the cyclic carbonate group of the raw material cyclic carbonate compound disappeared at 1790 cm -1 and the characteristic stretching vibration absorption peak of the carbonyl group of the carbamate group appeared near 1700 cm -1 .

[0049] The epoxy resins obtained in each example were placed at room temperature for one week and then subjected to performance tests. The material performance test results are shown in the following table:

[0050]

[0051] As can be seen from the table, the addition of this cyclic carbonate reactive diluent can significantly improve the comprehensive properties of epoxy materials, and its properties such as tensile strength and flexural strength are significantly higher than those of the blank sample. Therefore, this reactive diluent can not only play a role in adjusting the viscosity of the epoxy resin system, but also, after reacting with amine compounds, generate tough urethane groups, enhancing the molecular flexibility, and the generated hydroxyl groups can also enhance the hydrogen bond interaction in the system, thereby improving the comprehensive properties of the product.

[0052] The content not detailedly described in the specification of the present invention belongs to the prior art well-known to those skilled in the art. Although the illustrative specific embodiments of the present invention are described above for the understanding of those skilled in the art of the present technology, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art of the present technology, as long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions and creations using the concept of the present invention are within the scope of protection.

Claims

1. A preparation method of an active epoxy resin diluent, characterized in that: It includes the following steps: Add a polyfunctional epoxy compound and a catalyst into a high-pressure reactor, introduce nitrogen to expel the air in the reactor, heat up to the set temperature, introduce CO2 gas, start the reaction under a certain pressure. After the reaction is completed, cool down, exhaust the gas, and filter to obtain a cyclic carbonate compound, namely an active epoxy resin diluent.

2. The preparation method of an active epoxy resin diluent according to claim 1, characterized in that: The reaction temperature is 110 - 170 °C, and the reaction time is 10 - 50 h; the pressure is 0.5 - 3.0 MPa.

3. The preparation method of an active epoxy resin diluent according to claim 1, wherein: The polyfunctional epoxy compound is any one or several of 1,4-butanediol diglycidyl ether, ethylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, polyethylene glycol diglycidyl ether, and polypropylene glycol diglycidyl ether.

4. The preparation method of an active epoxy resin diluent according to claim 1, characterized in that: The catalyst is a macroporous resin-supported quaternary ammonium salt amine compound or a carbon nitride catalyst, and the dosage of the catalyst is 5% - 15% of the mass of the added polyfunctional epoxy compound.

5. The preparation method of an active epoxy resin diluent according to claim 4, wherein: 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 calcining and washing urea or a melamine precursor.

6. An active epoxy resin diluent prepared by the preparation method of an active epoxy resin diluent according to any one of claims 1 - 5.

7. Use of the active epoxy resin diluent according to claim 6 in epoxy resin, characterized in that: Mix the above-prepared cyclic carbonate compound with an epoxy resin evenly, then add an amine curing agent, and obtain a modified epoxy resin after curing.

8. Use of the active epoxy resin diluent according to claim 7 in epoxy resin, characterized in that: The curing conditions are to place it at room temperature for 2 - 6 h and then heat it at 60 - 90 °C for 1 - 5 h.

9. Use of the active epoxy resin diluent according to claim 7 in epoxy resin, characterized in that: The epoxy resin is any one or several of bisphenol A epoxy resin E-51, bisphenol A epoxy resin E-54, bisphenol A epoxy resin E-44, bisphenol F epoxy resin F-51, bisphenol F epoxy resin F-44, bisphenol S epoxy resin, and hydrogenated epoxy resin; the amine curing agent is any one or several of ethylenediamine, propylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, polyethylenepolyamine, isophoronediamine, and polyetheramine.

10. Use of the active epoxy resin diluent prepared by the preparation method according to claim 7 in epoxy resin, characterized in that: The dosage of the cyclic carbonate is 10% - 40% of the mass of the epoxy resin; the dosage of the amine curing agent is 0.85 - 1.15 times the theoretical amount of the curing agent required for the cyclic carbonate and the polyfunctional epoxy compound.

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