Epoxy Resin Curing Agent and Its Preparation Method

Abstract

This invention relates to an epoxy resin curing agent and its preparation method. The preparation method includes: adding a certain amount of epoxy resin and a certain amount of a first mixed solvent to a reaction flask at room temperature, stirring evenly, then adding a certain amount of dodecyl primary amine to cap the reaction with epoxy, stirring in a water bath at a certain temperature for a period of time to obtain a first mixed solution; then adding 4,4'-diaminodicyclohexylmethane to the first mixed solution, heating to another certain temperature, continuing to stir in a water bath for another period of time, and then naturally cooling to room temperature to obtain a second mixed solution; adding a second mixed solvent to the second mixed solution to achieve a certain solid content, stirring evenly to obtain the epoxy resin curing agent, bottling and sealing it, and storing it in a refrigerator. The epoxy resin curing agent of this invention has good high-temperature resistance and flexibility, and good compatibility with epoxy resin.

Description

[Technical Field]

[0001] This invention relates to the field of chemical materials, particularly to the field of polymer materials, and especially to epoxy resin curing agents and their preparation methods. [Background Technology]

[0002] In the field of chemical materials, acrylic adhesives are widely used in various industries, such as automotive manufacturing, electronics, and construction, due to their excellent water resistance, environmental corrosion resistance, and colorfastness. However, as electronic products continue to develop towards multifunctionality, miniaturization, lightweighting, and / or high performance, acrylic esters are also incorporating certain high-temperature resistant functional groups (such as epoxy functional groups). Epoxy resins (EP), due to their unique molecular structure, possess excellent properties such as high dimensional stability, corrosion resistance, high adhesion, and excellent resistance to various media. They are one of the most widely used resins and are extensively applied across various industries. Epoxy resin is a thermoplastic resin with a linear structure and cannot be used alone. It requires the addition of a curing agent. The resin only becomes usable when it undergoes a cross-linking reaction with the curing agent to form an insoluble or infusible macromolecular polymer with a three-dimensional network structure. Therefore, the structure and properties of the curing agent are crucial to epoxy resin, making the development of various novel curing agents essential for expanding the applications of epoxy resin. Epoxy resin curing agents are diverse, mainly including polyamines, isocyanates, acid anhydrides, imidazoles, and polythiols. Among them, amine curing agents are the most widely used, including aliphatic polyamines, alicyclic polyamines, and low-molecular-weight polyamides. Existing commercial curing agents have many drawbacks, such as high toxicity, low reactivity, poor high-temperature resistance, high brittleness of the cured coating, and significant susceptibility to environmental humidity. Furthermore, most epoxy resin curing agents have poor solubility in epoxy resins, leading to uneven mixing and affecting the performance of the final product. Therefore, developing an epoxy resin curing agent compatible with epoxy resins is a technical problem that needs to be solved in the near future. [Summary of the Invention]

[0003] The technical problem to be solved by the present invention is to avoid the shortcomings of the prior art and provide an epoxy resin curing agent and its preparation method. The epoxy resin curing agent prepared by the present invention has a large number of benzene rings, dodecyl groups, etc. on its chain, so the epoxy resin curing agent has good high temperature resistance and flexibility, and has good compatibility with epoxy resin.

[0004] The technical solution adopted by the present invention to solve the aforementioned technical problem is as follows:

[0005] A method for preparing an epoxy resin curing agent is provided, comprising the following steps:

[0006] Step A: At room temperature, add a certain amount of epoxy resin and a certain amount of the first mixed solvent to the reaction flask, stir evenly, then add a certain amount of dodecyl primary amine, and the reaction is epoxy-terminated. Stir in a water bath at a certain temperature for a period of time to obtain the first mixed solution.

[0007] Step B: Next, 4,4'-diaminodicyclohexylmethane is added to the first mixed solution in step A. After heating to another certain temperature, the mixture is stirred in a water bath for another period of time. Then, it is naturally cooled to room temperature to obtain the second mixed solution.

[0008] Step C: Add the second mixed solvent to the second mixed solution in step B to make its solid content reach a certain value, stir evenly, and you will get the epoxy resin curing agent. After bottling, seal it and put it in the refrigerator for refrigeration.

[0009] In step A, the mass ratio of the epoxy resin to dodecyl primary amine is 1:(0.3-0.4).

[0010] In step A, the temperature in the water bath is 50–100°C.

[0011] In step B, the mass ratio of 4,4'-diaminodicyclohexylmethane to epoxy resin is (0.2-0.4):1.

[0012] In steps A and C, both the first mixed solvent and the second mixed solvent include anhydrous ethanol and ethyl acetate, with the mass ratio of anhydrous ethanol to ethyl acetate being (0.4 to 1):1.

[0013] The temperature in the water bath in step B is 5-10°C higher than the temperature in the water bath in step A.

[0014] In step C, the solid content is 25% to 50%.

[0015] In step A, the dodecyl primary amine can be replaced by laurylamine dipropylenediamine, 1-aminotetradecane, octadecyl primary amine, or hexamethylenediamine.

[0016] The present invention also provides an epoxy resin curing agent. The epoxy resin curing agent obtained by the above preparation method specifically includes epoxy resin, dodecyl primary amine and 4,4'-diaminodicyclohexylmethane.

[0017] Compared with the prior art, the beneficial effects of the epoxy resin curing agent and its preparation method of the present invention are as follows:

[0018] I. The present invention contains a large number of high-temperature resistant monomers or groups in the molecular configuration, which can provide good temperature resistance, such as epoxy resin E51, etc.

[0019] Second, the flexible monomers used in the molecular combination of this invention are amine monomers, which have good flexibility, making the curing agent molecular chains easy to move, thereby giving the curing agent good flexibility; for example, dodecyl primary amine, laurylamine dipropylenediamine, 1-aminotetradecane, octadecyl primary amine or hexamethylenediamine, etc.

[0020] Third, the other end-capping monomer used in the molecular combination of the present invention is an alicyclic amine monomer, which can provide more reaction sites and can also better react with epoxy resin according to the designed molecular chain structure. For example, 4,4'-diaminodicyclohexylmethane can be used.

[0021] IV. In the molecular combination of this invention, the material is a polymer material with a molecular weight in the range of 10,000 to 20,000, which has good compatibility with epoxy resin and can cure epoxy resin at room temperature.

[0022] V. The epoxy resin curing agent of the present invention is first prepared by chain extension of bisphenol A type epoxy resin containing a large number of benzene rings and amine monomers containing flexible groups, with excess epoxy resin, and finally by end capping with alicyclic amine monomers. The preparation process is simple.

[0023] Therefore, the epoxy resin curing agent prepared by this invention has good high temperature resistance and flexibility, and good compatibility with epoxy resin. It can effectively solve the problems of poor high temperature resistance and compatibility between curing agent and epoxy resin, and brittle coating caused by strong molecular chain rigidity. The synthesis method of this epoxy resin curing agent is simple and environmentally friendly, and provides a new idea for the research of subsequent curing agents. [Attached Image Description]

[0024] Figure 1 This is a summary table of the various properties of the new adhesive prepared using the epoxy resin curing agent prepared in Example 1 of this invention.

[0025] Figure 2 This is a summary table of the various properties of the new adhesive prepared using the epoxy resin curing agent prepared in Example 2 of this invention. Detailed Implementation

[0026] The present invention will now be described in further detail with reference to the accompanying drawings.

[0027] A method for preparing an epoxy resin curing agent includes the following steps:

[0028] Step A: Under room temperature conditions (generally 21℃~25℃), add a certain amount of epoxy resin and a certain amount of the first mixed solvent to the reaction flask. After stirring evenly, add a certain amount of dodecylamine. The reaction is epoxy-terminated and stirred in a water bath at a certain temperature (50~100℃, for example, maintaining the temperature at 60℃). Stir and react for a period of time (10~30 hours, for example, 12 hours) to obtain the first mixed solution, which is generally a colorless, transparent, viscous solution. The reaction flask is generally a four-necked flask equipped with a reflux condenser, a constant pressure dropping funnel, a stirring device, and a thermometer. The mass ratio of epoxy resin to dodecylamine is 1:(0.3~0.4). The amount of the first mixed solvent is sufficient to completely dissolve both epoxy resin and dodecylamine; generally, the mass ratio of the first mixed solvent to the total mass of epoxy resin and dodecylamine is (0.7~1):1. The first mixed solvent is mainly a co-solvent. Amines are soluble in alcohols, and epoxy resins are soluble in ethyl acetate. Therefore, ethyl acetate and alcohols can be combined to form a first mixed solvent. For example, the first mixed solvent includes anhydrous ethanol and ethyl acetate. In the early stage of the reaction, anhydrous ethanol is used as a co-solvent, which is very beneficial for the dissolution of amines. In this first mixed solution, the mass ratio of anhydrous ethanol to ethyl acetate is (0.4~1):1. The epoxy resin can be E51 type epoxy resin.

[0029] Step B: Next, 4,4'-diaminodicyclohexylmethane is added to the first mixed solution in Step A. The temperature is raised to another set temperature, which is 5-10°C higher than the temperature in the water bath in Step A. For example, if the temperature in the water bath in Step A is maintained at 60°C, then the temperature in the water bath in Step B is maintained at 65°C-70°C. The mixture is stirred in the water bath for another period of time, which is 10-30 hours, for example, 12 hours. Then it is naturally cooled to room temperature to obtain a second mixed solution, which is an amino-terminated polymer. In this Step B, the mass ratio of 4,4'-diaminodicyclohexylmethane to epoxy resin is (0.2-0.4):1.

[0030] Step C: Add the second mixed solvent to the second mixed solution in step B to achieve a certain solid content, stir evenly, and the epoxy resin curing agent is obtained. After bottling, seal and refrigerate. The purpose of refrigeration is to extend the shelf life of the epoxy resin curing agent. In step C, the solid content is 25% to 50%, for example, 40%. The second mixed solvent is also mainly a co-solvent. Generally, amines are soluble in alcohols, and epoxy resins are soluble in ethyl acetate. Therefore, ethyl acetate and alcohols can be combined to form the second mixed solvent. For example, the second mixed solvent includes anhydrous ethanol and ethyl acetate. In this second mixed solution, the mass ratio of anhydrous ethanol to ethyl acetate is (0.4 to 1): 1.

[0031] The present invention also provides an epoxy resin curing agent obtained by the above preparation method. Specifically, the epoxy resin curing agent of the present invention comprises epoxy resin, dodecylamine, and 4,4'-diaminodicyclohexylmethane. The mass ratio of the epoxy resin, dodecylamine, and 4,4'-diaminodicyclohexylmethane is 1:(0.3-0.4):(0.2-0.4).

[0032] The dodecyl primary amine can be replaced by laurylamine dipropylenediamine, 1-aminotetradecane, octadecyl primary amine, or hexamethylenediamine. Example

[0033] A method for preparing an epoxy resin curing agent includes the following steps:

[0034] Step A: At room temperature, add 90 grams of E51 epoxy resin and 90 grams of a first mixed solvent to the reaction flask. The first mixed solvent is a mixture of anhydrous ethanol and ethyl acetate, wherein anhydrous ethanol accounts for 50% of the total mass of the first mixed solvent, and ethyl acetate accounts for 50% of the total mass of the first mixed solvent. After stirring evenly, add 28 grams of dodecylamine, and end-cap the reaction mixture with epoxy resin. Stir the mixture in a water bath at 60°C for 12 hours to obtain a first mixed solution. This first mixed solution is generally a colorless, transparent, viscous solution. The reaction flask is generally a four-necked flask equipped with a reflux condenser, a constant pressure dropping funnel, a stirring device, and a thermometer.

[0035] Step B: Next, add 32 g of 4,4'-diaminodicyclohexylmethane to the first mixed solution in step A, raise the temperature of the water bath to 65°C, continue stirring in the water bath, stir and react for 12 hours, and then cool naturally to room temperature to obtain the second mixed solution, which is an amino-terminated polymer.

[0036] Step C: Add a second mixed solvent to the second mixed solution from Step B. This second mixed solvent is a mixture of anhydrous ethanol and ethyl acetate, with anhydrous ethanol accounting for 50% of the total mass of the second mixed solvent and ethyl acetate accounting for 50% of the total mass of the second mixed solvent, bringing the solid content to 40%. Stir until homogeneous to obtain the epoxy resin curing agent. After bottling and sealing, store in a refrigerator. GPC analysis shows a polymer with a weight-average molecular weight of approximately 10,000 and a viscosity of 800–900 cps. GPC (gel permeation chromatography) is a liquid chromatography technique mainly used to separate and determine the molecular weight and molecular weight distribution of polymers. cps is a unit of viscosity, short for centipoise second, commonly used to express the viscosity of fluids.

[0037] Experimental results:

[0038] Prepare 8 grams each of homemade epoxy resin adhesive, 0.1 gram, 0.2 gram, and 0.3 gram of epoxy resin curing agent prepared in Example 1, and 0.08 grams of DMP-30, and mix them separately to form new adhesives; Figure 1 As shown, from this Figure 1 It can be seen that: the freshly prepared adhesive is visually "clear", indicating that it is soluble in epoxy resin adhesive; the high temperature resistance at 210℃ is "very good", indicating that the fresh adhesive has strong high temperature resistance; and there is no residue. Therefore, the epoxy resin curing agent prepared in Example 1 has good high temperature resistance and flexibility and is soluble in epoxy resin adhesive. DMP-30 is a catalyst for epoxy resin curing, namely 2,4,6-tris(dimethylaminomethyl)phenol. Example

[0039] A method for preparing an epoxy resin curing agent includes the following steps:

[0040] Step A: At room temperature, add 90 grams of E51 epoxy resin and 90 grams of a first mixed solvent to the reaction flask. The first mixed solvent is a mixture of anhydrous ethanol and ethyl acetate, wherein anhydrous ethanol accounts for 50% of the total mass of the first mixed solvent, and ethyl acetate accounts for 50% of the total mass of the first mixed solvent. After stirring evenly, add 34 grams of dodecylamine, and end-cap the reaction mixture with epoxy resin. Stir the mixture in a water bath at 60°C for 12 hours to obtain a first mixed solution. This first mixed solution is generally a colorless, transparent, viscous solution. The reaction flask is generally a four-necked flask equipped with a reflux condenser, a constant pressure dropping funnel, a stirring device, and a thermometer.

[0041] Step B: Next, add 19 g of 4,4'-diaminodicyclohexylmethane to the first mixed solution in step A, raise the temperature of the water bath to 65°C, continue stirring in the water bath, stir and react for 12 hours, and then cool naturally to room temperature to obtain the second mixed solution, which is an amino-terminated polymer.

[0042] Step C: Add a second mixed solvent to the second mixed solution in step B. The second mixed solvent is a mixture of anhydrous ethanol and ethyl acetate, wherein anhydrous ethanol accounts for 50% of the total mass of the second mixed solvent and ethyl acetate accounts for 50% of the total mass of the second mixed solvent, so that the solid content reaches 40%. Stir evenly to obtain epoxy resin curing agent. After bottling, seal and refrigerate. GPC test shows that the polymer has a weight average molecular weight of about 15,000 and a viscosity of 3,000 to 3,300 cps.

[0043] Experimental results:

[0044] Prepare 8 grams each of homemade epoxy resin adhesive, 0.1 gram, 0.2 gram, and 0.3 gram of curing agent prepared in Example 2, and 0.08 grams of DMP-30, respectively, and mix them to form new adhesives; Figure 2 As shown, from this Figure 2 It can be seen that: the prepared new adhesive is "clear" in appearance, indicating that the new adhesive can dissolve in epoxy resin adhesive; the high temperature resistance at 210℃ is "very good", indicating that the new adhesive has strong high temperature resistance; and there is "no residue" in all cases. Therefore, the curing agent prepared in this Example 2 has good high temperature resistance and flexibility, and can dissolve in epoxy resin adhesive.

[0045] The above-described embodiments are merely preferred embodiments of the present invention, and are described in a relatively specific and detailed manner. However, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements are all within the scope of protection of the present invention. Therefore, all equivalent transformations and modifications made within the scope of the claims of the present invention should be covered by the claims of the present invention.

Claims

1. A method for producing an epoxy resin curing agent, characterized by comprising the steps of: The method comprises the following steps: ​ Step A: a certain amount of epoxy resin and a certain amount of first mixed solvent are added into a reaction bottle at room temperature, and after being stirred uniformly, a certain amount of dodecyl primary amine is added to seal the end of the epoxy, and stirring is carried out in a water bath at a certain temperature, and after a period of stirring reaction, a first mixed solution is obtained; the mass ratio of the epoxy resin to the dodecyl primary amine is 1: (0.3-0.4); the temperature in the water bath is 50-100℃; the epoxy resin is an epoxy resin of type E51; Step B: then, 4, 4'-diamino dicyclohexyl methane is added into the first mixed solution of step A, and after being heated to another certain temperature, stirring is continuously carried out in a water bath, and after another period of stirring reaction, natural cooling to room temperature is carried out, and a second mixed solution is obtained; the temperature in the water bath in step B is 5-10℃ higher than that in the water bath in step A; the mass ratio of 4, 4'-diamino dicyclohexyl methane to epoxy resin is (0.2-0.4): 1; Step C: a second mixed solvent is added into the second mixed solution of step B to make the solid content reach a certain value, and after being stirred uniformly, an epoxy resin curing agent is obtained, which is bottled and sealed and stored in a refrigerator.

2. The method for preparing the epoxy resin curing agent according to claim 1, characterized in that: in steps A and C, the first mixed solvent and the second mixed solvent both comprise anhydrous ethanol and ethyl acetate, and the mass ratio of the anhydrous ethanol to the ethyl acetate is (0.4-1):

1.

3. The method for preparing the epoxy resin curing agent according to claim 1, characterized in that: in step C, the solid content is 25%-50%.

4. The method for preparing the epoxy resin curing agent according to claim 1, characterized in that: in step A, the dodecyl primary amine can be replaced by 1-amino tetradecane or octadecyl primary amine.

5. An epoxy resin curing agent, characterized in that: the epoxy resin curing agent obtained by the method according to any one of claims 1-4.

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