A pH-responsive epoxy resin curing agent, its preparation method and application

Abstract

This application relates to the technical field of epoxy resin curing agents. Specifically, it relates to a pH-responsive epoxy resin curing agent, its preparation method and application. To a certain extent, it can solve the problems that epoxy resin and curing agent are stored separately and need to be mixed before filling. Since the reaction between epoxy resin and curing agent generates a networked three-dimensional polymer, this polymer has high viscosity and poor fluidity, and manual assistance is required to make the mixture fill the cracks. The pH-responsive epoxy resin curing agent includes: The curing agent is composed of the following raw materials in parts by weight: 15-40 parts of sulfur carboxylic acid, 15-40 parts of aliphatic polyamine, 2-6 parts of dehydrating agent, 45-60 parts of fluorinated fatty acyl chloride, and 120-160 parts of organic solvent.

Description

Technical Field

[0001] The present application relates to the technical field of epoxy resin curing agents. Specifically, it relates to a pH-responsive epoxy resin curing agent, its preparation method and application. Background Technique

[0002] The excellent physical and mechanical properties, electrical insulation properties, adhesion properties with various materials, and flexibility of the use process of epoxy resin are not possessed by other thermosetting plastics. Therefore, it can be made into coatings, composite materials, casting materials, adhesives, molding materials and injection molding materials, and is widely used in various fields of the national economy. Epoxy resin has excellent adhesion properties to various metal materials (such as aluminum, iron, copper), non-metal materials (such as glass, wood, concrete, etc.), and thermosetting plastics (such as phenolic, amino, unsaturated polyester, etc.), except for poor adhesion to non-polar plastics such as polyolefins. Therefore, it is known as the universal glue. At the same time, epoxy resin adhesives also have low viscosity, can be cured on wet surfaces (or in water) and at low temperatures, so they are often used for concrete repair (mainly for connecting new and old concrete surfaces), exterior wall crack repair, bonding of panels, connection of sewer pipes, floor bonding and building structure reinforcement, etc.

[0003] Cement concrete refers to the general term for engineering composite materials formed by mixing cement, sand, stones, etc. with water. Conventional concrete refers to cement concrete obtained by using cement as a binder, sand and stones as aggregates, and mixing with water (with or without additives and admixtures) in a certain proportion, and then through stirring, molding and curing. It is widely used in civil engineering. Concrete cracks are generated in concrete structures due to the action of internal and external factors, and concrete cracks are the main reasons for the reduction of the bearing capacity, durability and waterproofness of concrete structures.

[0004] In the prior art, epoxy resin is often used to fill concrete cracks. Before filling, the epoxy resin and the curing agent are mixed in proportion, and then the mixture is poured into the cracks. The epoxy resin and the curing agent are stored separately, wasting storage costs, and the two need to be mixed before filling. Since a network three-dimensional polymer is formed after the epoxy resin and the curing agent are mixed and react, the polymer has a high viscosity and poor fluidity, and manual assistance is required to make the mixture fill the cracks. Summary of the Invention

[0005] In order to solve the problems that the epoxy resin and the curing agent are stored separately and need to be mixed before filling, and since a network three-dimensional polymer is formed after the epoxy resin and the curing agent are mixed and react, the polymer has a high viscosity and poor fluidity, and manual assistance is required to make the mixture fill the cracks, the present application provides a pH-responsive epoxy resin curing agent, its preparation method and application.

[0006] The embodiments of the present application are implemented as follows:

[0007] An embodiment of the present application provides a pH-responsive epoxy resin curing agent, which is composed of the following raw materials in parts by weight: 10-20 parts of thiocarboxylic acid, 40-60 parts of aliphatic polyamine, 30-40 parts of fluorinated fatty acyl chloride, 1-3 parts of dehydrating agent, and 60-80 parts of organic solvent.

[0008] In some embodiments, the structural formula of the curing agent is:

[0009]

[0010] where x = 1, 2 or 3; y = 2, 3 or 4.

[0011] In some embodiments, the thiocarboxylic acid is at least one of mercaptoacetic acid, mercaptopropionic acid, 4-mercaptobutyric acid.

[0012] In some embodiments, the aliphatic polyamine is at least one of diethylenetriamine, triethylenetetramine, tetraethylenepentamine.

[0013] In some embodiments, the fluorinated fatty acyl chloride is at least one of trifluoroacetyl chloride, trifluoropropionyl chloride.

[0014] In some embodiments, the dehydrating agent is at least one of concentrated sulfuric acid, phosphorus pentoxide, phosphorus oxychloride, phosphorus pentachloride.

[0015] The present application also provides a preparation method of a pH-responsive epoxy resin curing agent, and the method includes:

[0016] Adding thiocarboxylic acid and aliphatic polyamine into an organic solvent and mixing well to form a mixed solution;

[0017] Adding a dehydrating agent to the mixed solution and reacting under a first preset condition to obtain an intermediate product;

[0018] Adding fluorinated fatty acyl chloride to the intermediate product and reacting under a second preset condition to obtain a target product;

[0019] Removing impurities from the target product to obtain a pH-responsive epoxy resin curing agent.

[0020] In some embodiments, removing impurities from the target product further includes:

[0021] Adding an excessive amount of saturated sodium carbonate solution to the target product, washing the target product, and standing for layering after washing;

[0022] Taking the upper organic phase and performing rotary evaporation on the upper organic phase to obtain the pH-responsive epoxy resin curing agent.

[0023] In some embodiments, the reaction temperature of the first preset condition is 60 - 80 °C, and the reaction time is 6 - 8 h; the reaction temperature of the second preset condition is 60 - 80 °C, and the reaction time is 4 - 6 h.

[0024] The present application also provides an application of a pH-responsive epoxy resin curing agent, and the application of the pH-responsive epoxy resin curing agent includes repairing the gaps in cement concrete after the pH-responsive epoxy resin curing agent reacts with the epoxy resin.

[0025] Advantages of the present application: The pH-responsive epoxy resin curing agent of the present application is a mercapto group-protected mercapto curing agent. Therefore, the curing agent of the present application can be premixed into the epoxy resin without causing the hardening of the epoxy resin. Since the two can be stored in a mixed state, the step of preparing the liquid before filling construction is reduced; further, the pH-responsive epoxy resin curing agent of the present application does not cure after being mixed with the epoxy resin. Therefore, the mixture of the two is in a liquid state and has good fluidity. When the mixture is injected into the crack, it can well fill the entire crack, making the repaired crack more surface-dense and not easily leaking after repair; further, under the alkaline condition of cement concrete, the C-S bond in the curing agent molecule of the pH-responsive epoxy resin curing agent of the present application hydrolyzes to regenerate the mercapto group, and the mercapto group quickly reacts with the epoxy group in the epoxy resin to cure, achieving the purpose of filling the concrete crack. Description of the Drawings

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0027] Figure 1 is the structural formula of the pH-responsive epoxy resin curing agent;

[0028] Figure 2 is the reaction equation for the condensation reaction of mercaptoacetic acid, diethylenetriamine, and concentrated sulfuric acid to form an intermediate product containing a mercapto group;

[0029] Figure 3 is the reaction equation for the substitution reaction of the intermediate product containing a mercapto group and trifluoroacetyl chloride to form the pH-responsive epoxy resin curing agent;

[0030] Figure 4 is the reaction equation for the hydrolysis of the C-S bond of the pH-responsive epoxy resin curing agent to regenerate the mercapto group under the alkaline condition of cement concrete. Detailed Embodiments

[0031] To make the objectives, embodiments, and advantages of the present application clearer, the following will clearly and completely describe the exemplary embodiments of the present application in conjunction with the accompanying drawings in the exemplary embodiments of the present application. Obviously, the described exemplary embodiments are only a part of the embodiments of the present application, rather than all of the embodiments.

[0032] It should be noted that the brief description of the terms in the present application is only for the convenience of understanding the embodiments described next, rather than intending to limit the embodiments of the present application. Unless otherwise specified, these terms should be understood in their ordinary and common meanings.

[0033] The terms "first", "second", "third", etc. in the specification, claims, and the above-mentioned accompanying drawings of the present application are used to distinguish similar or like objects or entities, and do not necessarily mean to limit a specific order or sequence, unless otherwise noted. It should be understood that such terms can be interchanged under appropriate circumstances.

[0034] The terms "comprising" and "having" and any variations thereof are intended to cover but not exclude inclusion. For example, a product or device comprising a series of components does not necessarily have to be limited to all the components clearly listed, but may include other components not clearly listed or inherent to these products or devices.

[0035] The terms "arranged" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, and can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0036] A pH-responsive epoxy resin curing agent of the present application, the curing agent is composed of the following raw materials in parts by weight: 10-20 parts of thiocarboxylic acid, 40-60 parts of aliphatic polyamine, 30-40 parts of fluorinated fatty acyl chloride, 1-3 parts of dehydrating agent, and 60-80 parts of organic solvent.

[0037] In some embodiments, as Figure 1 shown as Figure 1 is the structural formula of the pH-responsive epoxy resin curing agent. In the figure, x = 1, 2, or 3; y = 2, 3, or 4.

[0038] In some embodiments, the thiocarboxylic acid is at least one of mercaptoacetic acid, mercaptopropionic acid, and 4-mercaptobutyric acid.

[0039] In some embodiments, the aliphatic polyamine is at least one of diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

[0040] In some embodiments, the fluorinated fatty acyl chloride is at least one of trichloroacetyl chloride and trifluoropropionyl chloride.

[0041] In some embodiments, the dehydrating agent is at least one of concentrated sulfuric acid, phosphorus pentoxide, phosphorus oxychloride, and phosphorus pentachloride.

[0042] In some embodiments, the organic solvent is toluene or ethylbenzene.

[0043] This application also provides a method for preparing a pH-responsive epoxy resin curing agent, the method comprising:

[0044] Adding a thiocarboxylic acid and an aliphatic polyamine to an organic solvent and mixing well to form a mixed solution;

[0045] Adding a dehydrating agent to the mixed solution and reacting under a first preset condition to obtain an intermediate product;

[0046] Adding a fluorinated fatty acyl chloride to the intermediate product and reacting under a second preset condition to obtain a target product;

[0047] Removing impurities from the target product to obtain a pH-responsive epoxy resin curing agent.

[0048] In some embodiments, the removing impurities from the target product further comprises:

[0049] Adding an excessive amount of saturated sodium carbonate solution to the target product, washing the target product, and allowing it to stand for layering after washing;

[0050] Taking the upper organic phase and performing rotary evaporation on the upper organic phase to obtain the pH-responsive epoxy resin curing agent.

[0051] In some embodiments, the reaction temperature of the first preset condition is 60-80°C, and the reaction time is 6-8 h; the reaction temperature of the second preset condition is 60-80°C, and the reaction time is 4-6 h.

[0052] This application also provides an application of a pH-responsive epoxy resin curing agent, including the application of repairing the cracks of cement concrete after the reaction of the pH-responsive epoxy resin curing agent with an epoxy resin.

[0053] In some embodiments, the pH-responsive epoxy resin curing agent of this application first undergoes a dehydration condensation reaction with a thiocarboxylic acid, an aliphatic polyamine, and a dehydrating agent to generate an intermediate product containing a mercapto group; then the intermediate product and a fluorinated fatty acyl chloride undergo a substitution reaction to generate a pH-responsive epoxy resin curing agent with a protected mercapto group.

[0054] As Figure 2The reaction equation for the condensation reaction of mercaptoacetic acid, diethylenetriamine, and concentrated sulfuric acid to form a mercapto-containing intermediate product; Figure 3 The reaction equation for the substitution reaction of the mercapto-containing intermediate product and trifluoroacetyl chloride to form a pH-responsive epoxy resin curing agent; Figure 4 The reaction equation for the hydrolysis of the C-S bond of the pH-responsive epoxy resin curing agent to regenerate mercapto groups under the alkaline conditions of cement concrete.

[0055] The present invention will be further described below in conjunction with specific embodiments and the accompanying drawings:

[0056] Example 1

[0057] Add 120 g of toluene, 15 g of mercaptoacetic acid, and 15 g of diethylenetriamine to a 250 mL three-necked flask equipped with a reflux condenser, and mix well;

[0058] Continue to add 2 g of concentrated sulfuric acid to the three-necked flask, and heat to 60 °C and react for 6 h;

[0059] Continue to add 45 g of trifluoroacetyl chloride to the three-necked flask, keep the temperature at 60 °C and continue to react for 4 h to obtain the target product;

[0060] Add an excessive amount of saturated sodium carbonate solution to the target product for thorough washing. After washing, let it stand for stratification. After liquid separation, take the upper organic phase, and perform rotary evaporation on the upper organic phase to obtain the pH-responsive epoxy resin curing agent.

[0061] Example 2

[0062] Add 120 g of toluene, 20 g of mercaptopropionic acid, and 40 g of triethylenetetramine to a 250 mL three-necked flask equipped with a reflux condenser, and mix well;

[0063] Continue to add 2 g of concentrated sulfuric acid to the three-necked flask, and heat to 60 °C and react for 6 h;

[0064] Continue to add 45 g of trifluoropropionyl chloride to the three-necked flask, keep the temperature at 60 °C and continue to react for 4 h to obtain the target product;

[0065] Add an excessive amount of saturated sodium carbonate solution to the target product for thorough washing. After washing, let it stand for stratification. After liquid separation, take the upper organic phase, and perform rotary evaporation on the upper organic phase to obtain the pH-responsive epoxy resin curing agent.

[0066] Example 3

[0067] Add 120 g of toluene, 15 g of 4-mercaptobutyric acid, and 15 g of tetraethylenepentamine to a 250 mL three-necked flask equipped with a reflux condenser, and mix well;

[0068] Continue to add 2 g of concentrated sulfuric acid to the three-necked flask and heat it to 60 °C for reaction for 6 h;

[0069] Continue to add 60 g of trifluoropropionyl chloride to the three-necked flask, keep the temperature at 60 °C and continue to react for 4 h to obtain the target product;

[0070] Add an excessive amount of saturated sodium carbonate solution to the target product for thorough washing. After washing, let it stand for layering. After liquid separation, take the upper organic phase and perform rotary evaporation on the upper organic phase to obtain the pH-responsive epoxy resin curing agent.

[0071] Example 4

[0072] Add 160 g of toluene, 30 g of mercaptopropionic acid, and 30 g of triethylenetetramine to a 250 mL three-necked flask equipped with a reflux condenser and mix well;

[0073] Continue to add 2 g of phosphorus pentachloride to the three-necked flask and heat it to 60 °C for reaction for 6 h;

[0074] Continue to add 50 g of trifluoroacetyl chloride to the three-necked flask, keep the temperature at 60 °C and continue to react for 4 h to obtain the target product;

[0075] Add an excessive amount of saturated sodium carbonate solution to the target product for thorough washing. After washing, let it stand for layering. After liquid separation, take the upper organic phase and perform rotary evaporation on the upper organic phase to obtain the pH-responsive epoxy resin curing agent.

[0076] Example 5

[0077] Add 120 g of toluene, 15 g of mercaptoacetic acid, and 15 g of diethylenetriamine to a 250 mL three-necked flask equipped with a reflux condenser and mix well;

[0078] Continue to add 4 g of concentrated sulfuric acid to the three-necked flask and heat it to 70 °C for reaction for 8 h;

[0079] Continue to add 45 g of trifluoroacetyl chloride to the three-necked flask, keep the temperature at 70 °C and continue to react for 5 h to obtain the target product;

[0080] Add an excessive amount of saturated sodium carbonate solution to the target product for thorough washing. After washing, let it stand for layering. After liquid separation, take the upper organic phase and perform rotary evaporation on the upper organic phase to obtain the pH-responsive epoxy resin curing agent.

[0081] Example 6

[0082] Add 120 g of toluene, 40 g of mercaptoacetic acid, and 20 g of diethylenetriamine to a 250 mL three-necked flask equipped with a reflux condenser and mix well;

[0083] Add 6 g of concentrated sulfuric acid and heat it to 80 °C for reaction for 8 h;

[0084] Add 45 g of trifluoroacetyl chloride, and continue the reaction at 70 °C for 6 h to obtain the target product;

[0085] Add an excessive amount of saturated sodium carbonate solution to the target product for thorough washing. After washing, let it stand for liquid separation, and take the upper organic phase after liquid separation. Perform rotary evaporation on the upper organic phase to obtain the pH-responsive epoxy resin curing agent.

[0086] In order to characterize the curing performance of the prepared pH-responsive epoxy resin curing agent, the epoxy resin and the pH-responsive epoxy resin curing agent synthesized in Example 5 were mixed in proportion, and then the curing time of the epoxy resin under different pH conditions was tested at room temperature. The results are shown in Table 1.

[0087] As can be seen from Table 1, when the environment is neutral, the epoxy resin hardly cures. As the pH gradually increases, the curing time required for the epoxy resin becomes shorter and shorter. When the pH is 12, the curing time of the epoxy resin with the pH-responsive epoxy resin curing agent added is 1.1 h.

[0088] Table 1 Curing time of epoxy resin with pH-responsive epoxy resin curing agent added under different pH conditions

[0089] pH Curing time (h) 7 ＞24 8 20 9 10 10 5.8 11 3.2 12 1.1

[0090] The pH-responsive epoxy resin curing agent of the present application is a mercapto-based curing agent with protected mercapto groups. Therefore, the curing agent of the present application can be premixed into the epoxy resin without causing hardening of the epoxy resin. Since the two can be stored mixed, the step of preparing the liquid before filling construction is reduced; further, since the pH-responsive epoxy resin curing agent of the present application does not cure after being mixed with the epoxy resin, the mixture of the two is in a liquid state and has good fluidity. When the mixture is injected into the crack, it can well fill the entire crack, making the repaired crack more surface dense and not easily leaking after repair; further, as a crack repair agent for cement walls, keeping the crack wet during repair, under the alkaline conditions of cement concrete, the C-S bond in the curing agent molecule hydrolyzes to regenerate mercapto groups, and the mercapto groups quickly react with the epoxy groups in the epoxy resin to cure, achieving the purpose of filling the concrete crack.

[0091] For the sake of convenience of explanation, the above description has been made in combination with specific embodiments. However, the above discussion in some embodiments is not intended to be exhaustive or to limit the embodiments to the specific forms disclosed above. According to the above teachings, various modifications and deformations can be obtained. The selection and description of the above embodiments are for better explaining the principles and actual applications, so that those skilled in the art can better use the embodiments and various different deformed embodiments suitable for specific use considerations.

Claims

1. A pH-responsive epoxy resin curing agent, characterized in that, The curing agent is composed of the following raw materials by weight: 15-40 parts of thiocarboxylic acid, 15-40 parts of aliphatic polyamine, 2-6 parts of dehydrating agent, 45-60 parts of fluorinated fatty acyl chloride, and 120-160 parts of organic solvent; The structural formula of the curing agent: ； where x = 1, 2 or 3; y = 2, 3 or 4; The preparation method of the pH-responsive epoxy resin curing agent includes: Adding thiocarboxylic acid and aliphatic polyamine into an organic solvent and mixing well to form a mixed solution; Adding a dehydrating agent to the mixed solution and reacting under a first preset condition to obtain an intermediate product; Adding fluorinated fatty acyl chloride to the intermediate product and reacting under a second preset condition to obtain a target product; Removing impurities from the target product to obtain the pH-responsive epoxy resin curing agent.

2. The pH-responsive epoxy resin curing agent according to claim 1, wherein, The thiocarboxylic acid is at least one of mercaptoacetic acid, mercaptopropionic acid, 4-mercaptobutyric acid.

3. The pH-responsive epoxy resin curing agent according to claim 1, wherein, The aliphatic polyamine is at least one of diethylenetriamine, triethylenetetramine, tetraethylenepentamine.

4. The pH-responsive epoxy resin curing agent according to claim 1, wherein The fluorinated fatty acyl chloride is at least one of trifluoroacetyl chloride, trifluoropropionyl chloride.

5. The pH-responsive epoxy resin curing agent according to claim 1, characterized in that, The dehydrating agent is at least one of concentrated sulfuric acid, phosphorus pentoxide, phosphorus oxychloride, phosphorus pentachloride.

6. The pH-responsive epoxy resin curing agent according to claim 1, wherein Removing impurities from the target product further includes: Adding an excessive amount of saturated sodium carbonate solution to the target product, washing the target product, and standing for liquid separation after washing; Taking the upper organic phase and performing rotary evaporation on the upper organic phase to obtain the pH-responsive epoxy resin curing agent.

7. The pH-responsive epoxy resin curing agent according to claim 1, wherein The reaction temperature of the first preset condition is 60-80°C, and the reaction time is 6-8 h; the reaction temperature of the second preset condition is 60-80°C, and the reaction time is 4-6 h.

8. Application of a pH-responsive epoxy resin curing agent, characterized in that, The application of the pH-responsive epoxy resin curing agent includes repairing the cracks in cement concrete after the pH-responsive epoxy resin curing agent as described in any one of claims 1-5 reacts with epoxy resin.

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