An antibacterial epoxy resin and a synthesis method and application thereof

Abstract

The application provides an antibacterial epoxy resin and a synthesis method and application thereof. The synthesis method comprises the following steps: step (1), condensation reaction of excess di-primary amine and salicylaldehyde in the presence of a first solvent, after reaction for a first preset time, the obtained reaction product is dried to obtain a mixture containing di-primary amine, mono-Schiff base product and bis-Schiff base product; step (2), polycondensation reaction of the primary amine in the mixture and the epoxy group in bisphenol A type epoxy resin in the presence of a second solvent, after reaction for a second preset time, the obtained product is dried to obtain the antibacterial epoxy resin. The synthesis method provided by the application makes the excess di-primary amine and salicylaldehyde undergo insufficient reaction, a large number of Schiff base groups are generated, and part of the primary amine groups are reserved to undergo polycondensation reaction with the epoxy group in bisphenol A type epoxy resin, and the obtained antibacterial epoxy resin has good antibacterial property, flexibility and weather resistance.

Description

Technical Field

[0001] This invention belongs to the field of epoxy resin preparation technology, specifically relating to an antibacterial epoxy resin, its synthesis method, and its application. Background Technology

[0002] Epoxy resin (EP) is an important thermosetting material widely used in coatings, food, medical, and composite materials, and has extensive applications in the national economy. However, bisphenol A (BPA) type epoxy resin coatings have poor weather resistance and lack antibacterial properties, making them unsuitable for outdoor and decorative coatings. Therefore, it is necessary to improve the weather resistance and antibacterial properties of BPA type epoxy resin coatings to broaden their application range. Summary of the Invention

[0003] The purpose of this invention is to provide a method for synthesizing a branched antibacterial epoxy resin containing a large number of Schiff base groups. The synthesized antibacterial epoxy resin has good antibacterial properties, flexibility and weather resistance, so as to solve the technical problems of poor weather resistance and poor antibacterial properties of existing bisphenol A type epoxy resin coatings.

[0004] To achieve the above objectives, the present invention provides a method for synthesizing an antibacterial epoxy resin, the method comprising the following steps:

[0005] Step (1): In the presence of a first solvent, excess diamine and salicylaldehyde undergo a condensation reaction. After a first preset reaction time, the resulting reaction product is dried to obtain a mixture containing diamine, a mono-Schiff base product, and a bis-Schiff base product. The diamine is an aliphatic diamine, and the molar ratio of the diamine to salicylaldehyde is 1:(1.4-1.8). The first preset time is 12-48 h.

[0006] Step (2): In the presence of a second solvent, the primary amine in the mixture undergoes a polycondensation reaction with the epoxy groups in the bisphenol A epoxy resin. After a second preset reaction time, the resulting reaction product is dried to obtain the antibacterial epoxy resin. The molar ratio of the primary amine in the mixture to the epoxy groups in the bisphenol A epoxy resin is 1:(1.4-2.8), and the second preset time is 12-48h.

[0007] In one specific embodiment, in step (1), the molar ratio of the diamine to salicylaldehyde is 1:(1.5-1.6).

[0008] In one specific embodiment, in step (2), the molar ratio of the primary amine in the mixture to the epoxy group in the bisphenol A type epoxy resin is 1:(1.9~2.2).

[0009] In one specific embodiment, the first solvent and the second solvent are one or more of toluene, xylene, and benzene.

[0010] In one specific embodiment, the primary amine is selected from methylcyclohexanediamine, m-phenylenediamine, isophoronediamine, and 4,4'-diaminodicyclohexylmethane.

[0011] In one specific embodiment, the bisphenol A type epoxy resin is selected from bisphenol A type epoxy resin E51, bisphenol A type epoxy resin E44, and bisphenol A type epoxy resin E55.

[0012] In one specific embodiment, the reaction temperature of the condensation reaction in step (1) is 50 to 200°C, and the reaction temperature of the polycondensation reaction in step (2) is 20 to 120°C.

[0013] The present invention also provides an antibacterial epoxy resin, which is synthesized using the synthesis method described above.

[0014] The present invention also provides an application of the antibacterial epoxy resin described above in the preparation of coatings and adhesives.

[0015] The beneficial effects of the present invention include at least the following:

[0016] The synthesis method provided by this invention involves an incomplete reaction between an excess of primary amine and salicylaldehyde, which generates a large number of Schiff base groups while retaining some of the primary amine groups to undergo a polycondensation reaction with the epoxy groups of bisphenol A type epoxy resin. The resulting antibacterial epoxy resin contains a large number of Schiff base groups, thus exhibiting good antibacterial properties, flexibility, and weather resistance.

[0017] Second, this invention controls the gel point of the polycondensation reaction by controlling the amount of diamine raw material within a suitable range. On the one hand, it avoids excessive diamine from causing gelation and affecting the performance of the antibacterial epoxy resin; on the other hand, it avoids insufficient diamine raw material from affecting the degree of branching, so that the synthesized antibacterial epoxy resin containing a large number of Schiff base groups has good antibacterial properties, flexibility and weather resistance. Attached Figure Description

[0018] Figure 1 The 1H NMR spectrum of the antibacterial epoxy resin prepared in Example 1;

[0019] Figure 2 The antibacterial diagram of S. aurues for the antibacterial epoxy resin prepared in Example 1;

[0020] Figure 3 Antibacterial diagram of S. aurues for the target product prepared in Comparative Example 5. Detailed Implementation

[0021] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. However, the present invention may be implemented in many different ways as limited and covered by the claims.

[0022] This invention provides a method for synthesizing an antibacterial epoxy resin, the method comprising the following steps:

[0023] Step 1: In the presence of a first solvent, excess diamine and salicylaldehyde undergo a condensation reaction. After a first preset reaction time, the resulting reaction product is neutralized with alkali, separated by precipitation, and dried to obtain a mixture containing diamine, a single Schiff base product, and a double Schiff base product. The diamine is an aliphatic diamine, and the molar ratio of the diamine to salicylaldehyde is 1:(1.4-1.8). The first preset time is 12-48 hours.

[0024] Preferably, the first solvent is one or a mixture of toluene, xylene, and benzene.

[0025] Preferably, the primary amine is selected from methylcyclohexanediamine, m-phenylenediamine, isophoronediamine, and 4,4'-diaminodicyclohexylmethane.

[0026] Preferably, the molar ratio of the primary amine to salicylaldehyde is 1:(1.5-1.6), and more preferably, the molar ratio of the primary amine to salicylaldehyde is 1:1.5.

[0027] Preferably, the reaction temperature of the condensation reaction is 50–200°C.

[0028] Step one is as follows:

[0029] Add the primary diamine, salicylaldehyde and the first solvent, stir at 50-200°C for 12-48 hours, and then remove the first solvent by rotary evaporation at 55-65°C to obtain a mixture containing the primary diamine, a mono-Schiff base product and a bis-Schiff base product.

[0030] Step 2: In the presence of a second solvent, the primary amine in the mixture undergoes a polycondensation reaction with the epoxy groups in the bisphenol A type epoxy resin. After a second preset reaction time, the resulting reaction product is dried to obtain the antibacterial epoxy resin. The molar ratio of the primary amine in the mixture to the epoxy groups in the bisphenol A type epoxy resin is 1:(1.4-2.8), and the second preset time is 12-48 hours.

[0031] Preferably, the second solvent is one or a mixture of toluene, xylene, and benzene.

[0032] Preferably, the molar ratio of the primary amine to the epoxy groups in the bisphenol A type epoxy resin in the mixture is 1:

[0033] (1.9~2.2), more preferably, the molar ratio of the primary amine to the epoxy group in the bisphenol A type epoxy resin in the mixture is 1:2.

[0034] Preferably, the bisphenol A type epoxy resin is selected from bisphenol A type epoxy resin E51, bisphenol A type epoxy resin E44, and bisphenol A type epoxy resin E55.

[0035] Preferably, the reaction temperature of the polycondensation reaction is 20–120°C.

[0036] Step two is as follows:

[0037] The mixture, bisphenol A type epoxy resin, and second solvent are mixed, and the mixture is polymerized with bisphenol A type epoxy resin at 20-120°C for 12-48 hours. After the polymerization reaction, the resulting product is dried by rotary evaporation at 55-65°C to remove the second solvent, thereby obtaining a branched antibacterial epoxy resin containing a large number of Schiff base groups.

[0038] This invention utilizes the incomplete reaction between the primary amine and salicylaldehyde in the raw materials to generate a large number of Schiff base groups while retaining some of the primary amine groups to undergo a polycondensation reaction with the epoxy groups of the bisphenol A type epoxy resin. This process, by retaining a portion of the primary amine raw material for branching reaction with the bisphenol A type epoxy resin, enhances the flexibility of the antibacterial epoxy resin. Simultaneously, the presence of a large number of Schiff base groups gives the antibacterial epoxy resin superior weather resistance. However, it is necessary to carefully control the amount of primary amine added within a suitable range to avoid gelation and insufficient branching, so that the antibacterial epoxy resin simultaneously possesses good antibacterial properties, flexibility, and weather resistance.

[0039] The present invention also provides an antibacterial epoxy resin, which is synthesized using the synthesis method described above.

[0040] The present invention also provides an application of the antibacterial epoxy resin described above in the preparation of coatings and adhesives.

[0041] Example 1

[0042] Step 1: Add 10g of raw material 4,4'-diaminodicyclohexylmethane (molecular weight 210), 8.71g of salicylaldehyde and 100mL of toluene. After stirring at 120℃ for 24 hours, remove the toluene by rotary evaporation at 65℃ to obtain a mixture containing a primary amine raw material, a single Schiff base product and a double Schiff base product (containing 0.024mol of primary amine), wherein the molar ratio of primary amine to salicylaldehyde is 1:1.5.

[0043] Step 2: Add 9.32g of bisphenol A type epoxy resin E51 and 50mL of benzene to the rotary evaporated flask and polymerize at 70℃ for 24 hours. After drying by rotary evaporation at 55℃, a branched antibacterial epoxy resin containing a large number of Schiff base groups is obtained. The molar ratio of the primary amine in the mixture to the epoxy group in the bisphenol A type epoxy resin is 1:2.

[0044] The 1H NMR spectrum of the antibacterial epoxy resin prepared in Example 1 is shown below. Figure 1 As shown, the antibacterial properties of S. aurues are illustrated below. Figure 2 As shown, from Figure 1 It can be seen that there is no peak belonging to the epoxy group at 2.61, indicating that the epoxy group reacted completely at the ratio of Example 1; from Figure 2 It can be seen that the antibacterial epoxy resin prepared in Example 1 has an antibacterial rate of 95.7% against S. aurues.

[0045] The performance test results of the antibacterial epoxy resin prepared in Example 1 are shown in Table 1:

[0046] Table 1. Performance test results of the antibacterial epoxy resin synthesized in Example 1.

[0047]

[0048]

[0049] Example 2

[0050] Similar to Example 1, except that in step 1, 10 g of 4,4'-diaminodicyclohexylmethane and 6.97 g of salicylaldehyde were added, corresponding to a molar ratio of 1:1.2 between the primary amine and salicylaldehyde. The primary amine in the mixture in step 1 was 0.038 mol. Correspondingly, in step 2, 14.9 g of bisphenol A epoxy resin E51 were added, and the molar ratio of the primary amine to the epoxy group in step 2 was 1:2.

[0051] Example 3

[0052] Similar to Example 1, except that in step 1, 10 g of 4,4'-diaminodicyclohexylmethane and 10.45 g of salicylaldehyde were added, corresponding to a molar ratio of 1:1.8 between the primary amine and salicylaldehyde. The primary amine in the mixture in step 1 was 0.0095 mol. Correspondingly, in step 2, 3.73 g of bisphenol A epoxy resin E51 was added, and the molar ratio of the primary amine to the epoxy group in step 2 was 1:2.

[0053] Example 4

[0054] Similar to Example 1, except that the mass of bisphenol A type epoxy resin E51 added in step 2 is 6.53 grams, and the corresponding molar ratio of primary amine to epoxy group is 1:1.4.

[0055] Example 5

[0056] Similar to Example 1, except that the mass of bisphenol A type epoxy resin E51 added in step 2 is 13.05 grams, and the corresponding molar ratio of primary amine to epoxy group is 1:2.8.

[0057] Comparative Example 1

[0058] Similar to Example 1, except that in step 1, 10 g of 4,4'-diaminodicyclohexylmethane and 5.81 g of salicylaldehyde were added, with a corresponding molar ratio of 1:1 between the primary amine and salicylaldehyde. The primary amine in the mixture in step 1 was 0.048 mol. Correspondingly, in step 2, 18.64 g of bisphenol A epoxy resin E51 were added, with a molar ratio of 1:2 between the primary amine and epoxy groups.

[0059] Comparative Example 2

[0060] Similar to Example 1, except that in step 1, 10 g of 4,4'-diaminodicyclohexylmethane and 11.62 g of salicylaldehyde were added, with a corresponding molar ratio of 1:2 between the primary amine and salicylaldehyde. The primary amine in the mixture in step 1 was 0.002 mol. Correspondingly, in step 2, 0.78 g of bisphenol A epoxy resin E51 was added, with a molar ratio of 1:2 between the primary amine and epoxy groups.

[0061] Comparative Example 3

[0062] Similar to Example 1, except that the mass of bisphenol A type epoxy resin E51 added in step 2 is 4.67 grams, and the corresponding molar ratio of primary amine to epoxy group is 1:1.

[0063] Comparative Example 4

[0064] Similar to Example 1, except that the mass of bisphenol A type epoxy resin E51 added in step 2 is 13.99 grams, and the corresponding molar ratio of primary amine to epoxy group is 1:3.

[0065] Performance testing

[0066] The antibacterial epoxy resins prepared in Examples 1 to 5 and the antibacterial epoxy resins prepared in Comparative Examples 1 to 4 were subjected to performance tests according to the following methods. The performance test results are shown in Table 2.

[0067] Specifically, the performance testing method is as follows:

[0068] Paint film hardness test: Prepare the paint film according to the sample requirements of GB1727-92. Use a set of 6B-B, HB, and H-6H pencils for the experiment. Use a pencil sharpener to remove the wood from the pencils, exposing a 5-6mm columnar lead core (do not damage the lead core). Sand the lead core at a 90° angle with 400-grit sandpaper to obtain a smooth end with a sharp edge. Fix the prepared pencil on a pencil holder, with the working end of the lead approximately 25mm from the holder. Place the paint film sample to be tested on the sample, lowering the pencil lead onto the sample. Rotate the handwheel to move the paint film sample approximately 5mm towards the scratch direction, and observe whether the paint film surface is scratched. Replace the pencil and repeat the operation.

[0069] Drop hammer impact strength test: After drying, the paint film samples with different proportions of curing accelerator are placed face up on an iron drill and fixed. The hammer is lifted using the hammer fixing screw, and the hook on the hammer is caught by the automatic controller. Press the control pin, and the hammer will fall freely onto the punch. Remove the sample and observe the paint film with a 4x magnifying glass for cracks, wrinkles, and peeling. Repeat the experiment by changing the drop hammer height.

[0070] Bending test: Open the bending test plate, insert the template into the cylindrical shaft, with one end of the template pressing against the stop bar. Then, smoothly close the hinge plate over 1-2 seconds to bend the template to the endpoint. Inspect the template bent around the cylinder and observe the changes in the paint film. Repeat the operation by changing the diameter of the cylinder.

[0071] Table 2 shows the antibacterial rate and performance test results of the antibacterial epoxy resins synthesized in Examples 1 to 5 and Comparative Examples 1 to 4.

[0072]

[0073]

[0074] The reactions in Examples 1-5 and Comparative Examples 1-4 were all carried out at the same temperature and reaction time. The main difference was the molar ratio of the primary amine to salicylaldehyde or the molar ratio of the primary amine to the epoxy groups of the diepoxy resin in the mixture. Comparing the test results of the examples and comparative examples, it can be found that the appropriate molar ratio of the primary amine to salicylaldehyde and the molar ratio of the primary amine to the epoxy groups of the diepoxy resin in the mixture have a significant impact on the antibacterial effect of the epoxy resin. Comparing the test results of Example 1 with Comparative Examples 1 and 2, it can be seen from Comparative Example 1 that when the molar ratio of the primary amine to salicylaldehyde is lower than a certain value, the antibacterial performance is greatly reduced, and gelation also occurs, increasing the degree of crosslinking of the epoxy resin, making it harder but worse in terms of bending performance. From Comparative Example 2, it can be seen that when the molar ratio of the primary amine to salicylaldehyde is higher than a certain value, the primary amine in the system decreases, affecting the degree of branching in the next reaction, resulting in a significant decrease in both hardness and strength, and poor antibacterial performance. Comparing the test results of Example 1 with those of Comparative Examples 3 and 4, it can be seen from Comparative Example 3 that a low molar ratio of the primary amine to the epoxy groups of the diepoxy resin in the mixture leads to reduced hardness and strength, and poor antibacterial properties. Comparative Example 4 shows that a high molar ratio of the primary amine to the epoxy groups of the diepoxy resin in the mixture results in a higher degree of crosslinking, increased hardness, but poorer bending performance and unsatisfactory antibacterial properties. Examples 1, 2, and 3 show that as the molar ratio of the primary amine to salicylaldehyde gradually increases, the antibacterial properties first increase and then decrease, while the hardness and strength gradually decrease, and the bending performance gradually improves. Examples 1, 4, and 5 show that as the molar ratio of the primary amine to the epoxy groups of the diepoxy resin in the mixture gradually increases, the antibacterial properties first increase and then decrease, while the hardness and strength continuously increase, but the bending performance gradually decreases.

[0075] Examples 6 to 8:

[0076] Examples 6 through 8 all employ the synthesis method of Example 1, differing only in the use of different primary amine raw materials and the addition of different masses of salicylaldehyde in step 1 and different masses of bisphenol epoxy resin in step 2, to ensure the same molar ratio of primary amine to salicylaldehyde and the same molar ratio of primary amine to cyclic group. Specifically, Example 6 uses 10g of isophorone diamine as the primary amine raw material, with a molar ratio of primary amine to salicylaldehyde of 1:1.5. The mixture obtained in step 1 contains 0.029mol of primary amine, and the molar ratio of primary amine to cyclic group is... The molar ratio of oxygen groups is 1:2; the primary amine raw material used in Example 7 is 10g of m-phenylenediamine, the molar ratio of primary amine to salicylaldehyde is 1:1.5, the mixture obtained in step 1 contains 0.037mol of primary amine, and the molar ratio of primary amine to epoxy group is 1:2; the primary amine raw material used in Example 8 is 10g of methylcyclohexanediamine, the molar ratio of primary amine to salicylaldehyde is 1:1.5, the mixture obtained in step 1 contains 0.039mol of primary amine, and the molar ratio of primary amine to epoxy group is 1:2.

[0077] The antibacterial epoxy resins prepared in Examples 6-8 and their performance test results are shown in Table 3.

[0078] Table 3. Antibacterial rate and performance test results of different diamine raw materials

[0079] Example 1 95.7 4H 50 2mm Example 6 93.4 4H 50 2mm Example 7 90.6 4H 50 2mm Example 8 92.7 4H 50 2mm

[0080] As can be seen from Table 3, different primary diamine raw materials only affect the antibacterial rate, and the performance test results are completely the same, indicating that isophorone diamine, m-phenylenediamine and m-phenylenediamine can all be used as primary diamine raw materials.

[0081] Examples 9 to 11

[0082] Example 9

[0083] Similar to Example 1, the difference lies in the reaction conditions of the condensation reaction in step 1 and the polycondensation reaction in step 2. In Example 9, the condensation reaction is the reaction of the primary amine with salicylaldehyde at 50°C for 48 hours, and the polycondensation reaction is the reaction of the primary amine with bisphenol epoxy resin at 20°C for 48 hours.

[0084] Example 10

[0085] Similar to Example 1, the difference lies in the reaction conditions of the condensation reaction in step 1 and the polycondensation reaction in step 2. In Example 10, the condensation reaction is the reaction of the primary amine with salicylaldehyde at 200°C for 12 hours, and the polycondensation reaction is the reaction of the primary amine with bisphenol epoxy resin at 120°C for 12 hours.

[0086] Example 11

[0087] Similar to Example 1, the difference lies in the reaction conditions of the condensation reaction in step 1 and the polycondensation reaction in step 2. In Example 11, the condensation reaction is the reaction of the primary amine with salicylaldehyde at 100°C for 24 hours, and the polycondensation reaction is the reaction of the primary amine with bisphenol epoxy resin at 90°C for 24 hours.

[0088] The antibacterial rate and performance test results of the antibacterial epoxy resins synthesized in Examples 9-10 are shown in Table 4.

[0089] Table 4. Antibacterial rate and performance test results of antibacterial epoxy resins synthesized under different reaction conditions.

[0090] Example 1 95.7 4H 50 2mm Example 9 69.4 2H 40 1mm Example 10 85.7 4H 50 2mm Example 11 91.2 4H 50 2mm

[0091] As can be seen from Table 4, if the reaction temperature is too low and the reaction degree is insufficient, it will lead to a significant decrease in the antibacterial rate and a reduction in performance.

[0092] Examples 12-13

[0093] Example 12

[0094] Similar to Example 1, the main difference is that the solvent used in step 1 is different. In Example 12, the solvent used in step 1 is xylene, and the rotary evaporation temperature is 85°C.

[0095] Example 13

[0096] Similar to Example 1, the main difference is that the solvent used in step 1 is different. In Example 13, the solvent used in step 1 is benzene, and the rotary evaporation temperature is 45°C.

[0097] The antibacterial rate and performance test results of the antibacterial epoxy resins synthesized in Examples 12-13 are shown in Table 5.

[0098] Table 5. Antibacterial rate and performance test results of antibacterial epoxy resins synthesized under different reaction solvents.

[0099] Example 1 95.7 4H 50 2mm Example 12 89.7 4H 50 2mm Example 13 88.4 4H 50 2mm

[0100] As can be seen from Table 5, different solvents have an impact on the antibacterial rate, but the performance test results are completely the same.

[0101] Comparative Example 5

[0102] A comparative sample was prepared using a method disclosed in existing technology CN115651167A (application number 202211325168.0) for preparing a biodegradable and recyclable epoxy cured product. Specifically, 39.2 g of bisphenol A glycidyl ether, 12.2 g of salicylaldehyde, and a trace amount of imidazole were added to a beaker equipped with a magnetic stirrer and reacted at 120°C for 6 h to obtain an aldehyde-containing epoxy derivative. 4.5 g of ethylenediamine was added to the aldehyde-containing epoxy derivative, stirred until fully mixed, and cured at 120°C for 6 h to obtain a brown transparent solid target product. The antibacterial spectrum of this target product in *S. aurues* is shown below. Figure 3 As shown, Figure 2 and Figure 3 By comparison, it can be seen that the antibacterial rate of the antibacterial epoxy resin prepared in Example 1 of the present invention is much higher than that of the target product.

[0103] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions and substitutions can be made without departing from the inventive concept, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for synthesizing an antibacterial epoxy resin, characterized in that, The synthesis method includes the following steps: Step (1): In the presence of a first solvent, excess diamine and salicylaldehyde undergo a condensation reaction. After a first preset reaction time, the resulting reaction product is dried to obtain a mixture containing diamine, a mono-Schiff base product, and a bis-Schiff base product. The diamine is 4,4'-diaminodicyclohexylmethane, the molar ratio of diamine to salicylaldehyde is 1:(1.5~1.6), the first preset time is 12~48h, and the reaction temperature of the condensation reaction is 50~200℃. Step (2): In the presence of a second solvent, the primary amine in the mixture undergoes a polycondensation reaction with the epoxy groups in the bisphenol A epoxy resin. After a second preset reaction time, the resulting reaction product is dried to obtain the antibacterial epoxy resin. The molar ratio of the primary amine in the mixture to the epoxy groups in the bisphenol A epoxy resin is 1:(1.9~2.2), the second preset time is 12~48h, and the reaction temperature of the polycondensation reaction is 20~120℃. The first solvent and the second solvent are one or more of toluene, xylene, and benzene.

2. The method for synthesizing the antibacterial epoxy resin according to claim 1, characterized in that, The bisphenol A type epoxy resin is selected from bisphenol A type epoxy resin E51, bisphenol A type epoxy resin E44, and bisphenol A type epoxy resin E55.

3. An antibacterial epoxy resin, characterized in that, The antibacterial epoxy resin is synthesized using the synthesis method described in claim 1 or 2.

4. The application of the antibacterial epoxy resin according to claim 3 in the preparation of coatings and adhesives.

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