Amino-siloxane-modified self-emulsifying waterborne epoxy curing agent and its synthesis

Abstract

The invention discloses a kind of amino-type siloxane-modified self-emulsifying waterborne epoxy curing agent and its synthesis;Comprise the following steps:Organic silicon monomer and polyamine are placed in a container, after material is heated to 60~80 ℃, polyether alcohol diglycidyl ether is added dropwise at a uniform speed, keeps temperature unchanged and continues to react 2.0~4.0h;Continue to maintain 60~80 ℃, continue to react 2.0~4.0h after adding epoxy resin solution dropwise at a uniform speed;After being heated to 80 ℃, 3-glycidyl ether oxypropyl trimethoxy silane is added dropwise at a uniform speed, continues to react 2.0~3.0h;It is cooled to 40~60 ℃, deionized water is added dropwise, high-speed stirring 20~40min, prepares the curing agent with solid content of 50~60%.The curing agent of the present invention has low VOC characteristics, safety and environmental protection;The corresponding paint film has good comprehensive properties, especially excellent water resistance, weather resistance and impact resistance.

Description

Technical Field

[0001] The present invention belongs to the technical field of waterborne epoxy curing agents, and particularly relates to an amino-siloxane-modified self-emulsifying waterborne epoxy curing agent and a synthesis method thereof. Background Art

[0002] Waterborne epoxy curing agents are a crucial component of waterborne epoxy systems, and their composition and structure directly influence the physical and chemical properties of the coating. Waterborne epoxy curing agents can be categorized as ionic or non-ionic, depending on the type of groups introduced during the synthesis process. Ionic curing agents utilize organic acids in the final adduct to neutralize a portion of the primary or secondary amines to form salts, creating a waterborne epoxy system. The organic acid added during the salt formation process can react with the metal substrate, thereby reducing the corrosion resistance of the coating. The common "epoxy-polyamine" ionic curing agent synthesis process involves reacting a low-molecular-weight liquid epoxy with polyethylene polyamine to produce an amine-terminated epoxy resin, which is then capped and salted to obtain the product. However, the direct combination of low-molecular-weight epoxy resins and polyamines can lead to high curing agent concentrations at the interface of the epoxy emulsion particles during curing, resulting in an overly rapid crosslinking reaction. Furthermore, the restricted mobility of the polyamine chains hinders diffusion and mass transfer of the polyamine segments, leading to uneven and incomplete curing. Therefore, it is particularly important to increase the molecular weight of the polyamine to enhance its molecular mobility before introducing the epoxy resin. Furthermore, nonionic curing agents, by introducing nonionic hydrophilic segments into the curing agent, render it water-based, avoiding the drawbacks of ionic curing agents often associated with the addition of organic acids, while also enhancing other properties of the curing agent and the cured film. Therefore, nonionic water-based epoxy curing agents are currently a key research and development focus in the field of water-based coatings. However, the introduction of nonionic hydrophilic segments into the curing agent poses challenges to the water resistance and impact resistance of the coating film.

[0003] Silicone-containing resins refer to polymers and prepolymers containing silicon-carbon (Si-C) and silicon-oxygen (Si-O-Si) bonds. When used in modified coatings, they not only impart excellent film flexibility but also enhance the film-forming properties of the silicone resin. Since the bond energy of a silicon-oxygen bond is 460 kJ / mol, far greater than the 332 kJ / mol of a carbon-carbon single bond, the resulting film exhibits excellent impact resistance. Furthermore, the low surface tension and energy of the silicon-oxygen bond impart a degree of hydrophobicity, theoretically improving the water resistance of the coating. Physical mixing of silica sol with water-based coatings can improve film impact resistance, but the dehydration and polycondensation process of the silica sol system exhibits high cohesion, rapid reaction times, and susceptibility to cracking. Chemical grafting can be used to modify the resin by directly reacting organosiloxanes as modifying groups or silicone monomers containing reactive double bonds with the monomers of the synthetic resin base under suitable conditions. This introduces siloxy groups while avoiding the overly rapid reaction of the silica sol system. Some researchers have introduced epoxy phenyl silicone oil into the curing agent molecular chain by epoxy ring opening to improve the water resistance of the paint film. However, there are the following problems: (1) Excessive introduction of epoxy groups can easily lead to poor weather resistance of the paint film; (2) The presence of phenyl groups in the modifier can theoretically make the paint film brittle and affect the impact resistance; (3) Epoxy phenyl silicone oil does not contain amino groups with curing effect, and the resulting curing agent has low curing efficiency. In addition, conventional silicon modification is mostly used in coating systems, while research on water-based epoxy curing agents has rarely been reported. Summary of the Invention

[0004] The present invention aims to address the problem of reduced water resistance and impact resistance of coatings caused by non-ionic curing agents, and to provide an aminosiloxane-modified self-emulsifying waterborne epoxy curing agent and a method for synthesizing the same. The present invention avoids direct contact between epoxy resin and polyamine in the conventional "epoxy-polyamine addition method" and uses a chemical grafting method to introduce aminosiloxane-based organosilicon monomers such as 1,3-bis(3-aminopropyl)tetramethyldisiloxane, aminopropyl di-terminated polydimethylsiloxane, and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane into the curing agent backbone. Polyether diglycidyl ether is used to increase the molecular weight of the polyamine, which is then reacted with epoxy resin and capped with 3-glycidyloxypropyltrimethoxysilane to prepare an aminosiloxane-modified self-emulsifying epoxy curing agent. The curing agent is then used to cure waterborne epoxy coatings.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a silicon-containing waterborne epoxy curing agent and a preparation method thereof, the method comprising the following steps:

[0007] S1) placing an organosilicon monomer and a polyamine in a container, and after the material temperature is raised to 60-80° C., adding polyether alcohol diglycidyl ether dropwise at a uniform rate over 1.0-2.0 h. After the addition is complete, maintaining the temperature constant and continuing the reaction for 2.0-4.0 h;

[0008] S2) keeping the material at 60-80°C, adding the epoxy resin solution dropwise within 1.0h (at a constant rate), and after the addition is complete, keeping the temperature constant and continuing the reaction for 2.0-4.0h;

[0009] S3) After the temperature is raised to 80° C., 3-glycidoxypropyltrimethoxysilane is added dropwise at a uniform rate over 1.0 h, and the reaction is continued for 2.0 to 3.0 h;

[0010] S4) cooling to 40-60° C., adding deionized water dropwise, and stirring at high speed (stirring speed of 100-800 rpm, stirring time of 20-40 min) to prepare a self-emulsifying waterborne epoxy curing agent with a solid content of 50-60%.

[0011] As an embodiment of the present invention, the organosilicon monomer is selected from any one or more of 1,3-bis(3-aminopropyl)tetramethyldisiloxane, aminopropyl di-terminated polydimethylsiloxane and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane.

[0012] As an embodiment of the present invention, the polyamine is selected from any one or more of ethylenediamine, diethylenetriamine, triethylenetetramine and tetraethylenepentamine.

[0013] As an embodiment of the present invention, the polyether alcohol diglycidyl ether is selected from any one or more of polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether and polybutylene glycol diglycidyl ether.

[0014] As an embodiment of the present invention, the relative molecular weight of the polyether alcohol diglycidyl ether is 350-580.

[0015] In one embodiment of the present invention, the molar ratio of the organosilicon monomer, polyamine, and polyether alcohol diglycidyl ether is (0.2-1.0):(2.0-1.0):1.0. If the amount of organosilicon monomer added is too much, the reaction between the organosilicon monomer and the polyether alcohol diglycidyl ether will be incomplete, resulting in the presence of the organosilicon monomer in the product.

[0016] As an embodiment of the present invention, the epoxy resin is selected from any one or more of E51, E44, and E20.

[0017] As an embodiment of the present invention, the mass fraction of the epoxy resin in the epoxy resin solution is 70 to 95%.

[0018] As an embodiment of the present invention, the solvent in the epoxy resin solution is propylene glycol methyl ether.

[0019] As one embodiment of the present invention, the molar ratio of the epoxy resin to the polyether alcohol diglycidyl ether is (0.4-0.6):1.0.

[0020] As an embodiment of the present invention, the molar ratio of the 3-glycidyloxypropyltrimethoxysilane to the polyether alcohol diglycidyl ether is (0.4-0.5):1.0.

[0021] The present invention also provides the use of the self-emulsifying waterborne epoxy curing agent prepared by the above method in curing waterborne epoxy coatings. The obtained paint film has good water resistance and impact resistance.

[0022] The principle behind this invention is to use aminosiloxane-based organosilicon monomers to transition a portion of the polyamine, and to increase the molecular weight of the polyamine using polyether diglycidyl ether. This avoids the direct reaction between the epoxy resin and the polyamine used in the conventional "epoxy-polyamine addition method." This step enhances the molecular mobility of the polyamine during the curing process, accelerating the diffusion and mass transfer of the polyamine chain segments, thus overcoming the limitations of conventional curing agents, which often result in uneven and incomplete curing. Furthermore, the organosilicon monomers contain a portion of amine groups, which can be used for both chain extension reactions during curing agent synthesis and as amino groups during curing, thereby improving curing efficiency.

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

[0024] 1) The raw materials are traditional chemical raw materials with abundant sources;

[0025] 2) The synthesis method is simple, without high temperature and high pressure, and without the addition of catalysts;

[0026] 3) The curing agent is low in VOC, safe and environmentally friendly;

[0027] 4) The corresponding paint film has excellent water resistance, weather resistance and impact resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The following will further illustrate the concept, specific structure and technical effects of the present invention with reference to the accompanying drawings to fully understand the purpose, features and effects of the present invention:

[0029] Figure 1 is the infrared spectrum of the curing agent synthesized in Example 1;

[0030] Figure 2 The left paint film is the original paint film, and the right paint film is the paint film after being immersed in deionized water for 240 hours. DETAILED DESCRIPTION

[0031] The present invention will be described in detail below with reference to the examples. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that those skilled in the art may make several adjustments and improvements without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0032] Example 1

[0033] (1) 0.08 mol (11.69 g) of triethylenetetramine (TETA) and 0.03 mol of 1,3-bis(3-aminopropyl)tetramethyldisiloxane were added to a four-necked flask. After the temperature of the material was raised to 65°C, 0.05 mol (19.00 g) of polypropylene glycol diglycidyl ether (PPGDGE) was added dropwise at a constant rate within 1.0 h. After the addition was complete, the reaction was kept warm for 3.0 h.

[0034] (2) Keeping the material at 65° C., add 0.025 mol of epoxy resin E51 solution (containing 20% propylene glycol methyl ether) dropwise at a constant rate within 1.0 h. After the addition is complete, keep the temperature and react for 3.0 h.

[0035] (3) After the temperature is raised to 80°C, 0.025 mol of 3-glycidoxypropyltrimethoxysilane is added dropwise at a uniform rate within 1.0 h, and the reaction is continued for 3.0 h.

[0036] (4) Cooling to 25°C, adding deionized water dropwise, and stirring at high speed for 20 minutes to obtain a silicon-containing water-based epoxy resin curing agent.

[0037] The synthesized water-based silicon-containing curing agent was characterized by infrared spectroscopy. Figure 1 The infrared spectrum of the curing agent shows a strong and broad polyether characteristic peak absorption peak (1090cm -1 ), and the characteristic peak of epoxy group (918cm -1 ) basically disappeared, indicating that the polyether segment and epoxy resin segment were successfully introduced into the molecular structure of the curing agent; at 800 cm -1 The absorption peaks on the left and right are the symmetrical stretching vibration absorption peaks of the Si-O-Si bond, indicating that the organosilicon monomer has been successfully introduced.

[0038] At room temperature, a commercially available water-based epoxy coating (Guangzhou Zhujiang Chemical Coatings Co., Ltd., TV Tower brand, component A) and a synthetic water-based epoxy curing agent (component B) were mixed in appropriate proportions, with component A and B ratios of 1:1, 2:1, 3:1, 4:1, and 5:1. Steel plates were sanded, and varnish was applied to tinplate using a wire rod. The coatings were left at room temperature for seven days to form films with dry film thicknesses of approximately 30 μm and 50 μm. The coatings were then tested for adhesion, impact resistance, and water resistance according to the national standard HG / T 4759-2014. Figure 2 The paint films corresponding to the curing agent synthesized in this example are shown. The left film is the original paint film, and the right film is the paint film after immersion in deionized water for 240 hours. Test results show that the paint film of this example meets the Level 1 cross-cut test, the 40cm impact resistance test, and the 240h water resistance test, demonstrating excellent adhesion, impact resistance, and water resistance.

[0039] Example 2

[0040] (1) 0.08 mol (11.69 g) of triethylenetetramine (TETA) and 0.03 mol of 1,3-bis(3-aminopropyl)tetramethyldisiloxane were added to a four-necked flask. After the temperature of the material was raised to 65°C, 0.05 mol (19.00 g) of polypropylene glycol diglycidyl ether (PPGDGE) was added dropwise at a constant rate within 1.0 h. After the addition was complete, the reaction was kept warm for 3.0 h.

[0041] (2) Maintaining the material temperature at 65° C., add 0.030 mol of epoxy resin E51 solution (containing 20% propylene glycol methyl ether) dropwise at a constant rate over 1.0 h. After the addition is complete, keep the temperature and react for 3.0 h.

[0042] (3) After the temperature is raised to 80°C, 0.025 mol of 3-glycidoxypropyltrimethoxysilane is added dropwise at a uniform rate within 1.0 h, and the reaction is continued for 3.0 h.

[0043] (4) Cooling to 25°C, adding deionized water dropwise, and stirring at high speed for 20 minutes to obtain a silicon-containing water-based epoxy resin curing agent.

[0044] The waterborne epoxy coating (Component A) and the synthesized waterborne epoxy curing agent (Component B) consistent with Example 1 were mixed in proportion. The steel plate was sandpapered, and a varnish was applied to the tinplate using a wire rod. The coating was cured at room temperature to obtain a film with a dry film thickness of approximately 30 μm and 50 μm. The film was cured for 7 days. The adhesion, impact resistance, and water resistance of the coating were tested according to the national standard HG / T 4759-2014. The test results showed that the paint film of this example met the level 1 cross-hatch test, the 40 cm impact resistance test, and the 240 h water resistance test, and therefore had excellent adhesion, impact resistance, and water resistance.

[0045] Example 3

[0046] (1) 0.08 mol (11.69 g) of triethylenetetramine (TETA) and 0.04 mol of 1,3-bis(3-aminopropyl)tetramethyldisiloxane were added to a four-necked flask. After the temperature of the material was raised to 65°C, 0.05 mol (19.00 g) of polypropylene glycol diglycidyl ether (PPGDGE) was added dropwise at a constant rate within 1.0 h. After the addition was complete, the reaction was kept warm for 3.0 h.

[0047] (2) Maintaining the material temperature at 65° C., add 0.030 mol of epoxy resin E51 solution (containing 20% propylene glycol methyl ether) dropwise at a constant rate over 1.0 h. After the addition is complete, keep the temperature and react for 3.0 h.

[0048] (3) After the temperature is raised to 80°C, 0.025 mol of 3-glycidoxypropyltrimethoxysilane is added dropwise at a uniform rate within 1.0 h, and the reaction is continued for 3.0 h.

[0049] (4) Cooling to 25°C, adding deionized water dropwise, and stirring at high speed for 20 minutes to obtain a silicon-containing water-based epoxy resin curing agent.

[0050] The waterborne epoxy coating (Component A) and the synthesized waterborne epoxy curing agent (Component B) consistent with Example 1 were mixed in proportion. The steel plate was sandpapered, and a varnish was applied to the tinplate using a wire rod. The coating was cured at room temperature to obtain a film with a dry film thickness of approximately 30 μm and 50 μm. The film was cured for 7 days. The adhesion, impact resistance, and water resistance of the coating were tested according to the national standard HG / T 4759-2014. The test results showed that the paint film of this example met the level 1 cross-hatch test, the 40 cm impact resistance test, and the 240 h water resistance test, and therefore had excellent adhesion, impact resistance, and water resistance.

[0051] Example 4

[0052] (1)(1) Add 0.08 mol (11.69 g) of triethylenetetramine (TETA) and 0.03 mol of aminopropyl dicapped polydimethylsiloxane into a four-necked flask. After the material is heated to 65°C, 0.05 mol (19.00 g) of polypropylene glycol diglycidyl ether (PPGDGE) is added dropwise at a uniform rate within 1.0 h. After the addition is complete, the mixture is kept warm for 3.0 h.

[0053] (2) Maintaining the material temperature at 65° C., add 0.030 mol of epoxy resin E51 solution (containing 20% propylene glycol methyl ether) dropwise at a constant rate over 1.0 h. After the addition is complete, keep the temperature and react for 3.0 h.

[0054] (3) After the temperature is raised to 80°C, 0.025 mol of 3-glycidoxypropyltrimethoxysilane is added dropwise at a uniform rate within 1.0 h, and the reaction is continued for 3.0 h.

[0055] (4) Cooling to 25°C, adding deionized water dropwise, and stirring at high speed for 20 minutes to obtain a silicon-containing water-based epoxy resin curing agent.

[0056] The waterborne epoxy coating (Component A) and the synthesized waterborne epoxy curing agent (Component B) consistent with Example 1 were mixed in proportion. The steel plate was sandpapered, and a varnish was applied to the tinplate using a wire rod. The coating was cured at room temperature to obtain a film with a dry film thickness of approximately 30 μm and 50 μm. The film was cured for 7 days. The adhesion, impact resistance, and water resistance of the coating were tested according to the national standard HG / T 4759-2014. The test results showed that the paint film of this example met the level 1 cross-hatch test, the 40 cm impact resistance test, and the 240 h water resistance test, and therefore had excellent adhesion, impact resistance, and water resistance.

[0057] Example 5

[0058] (1) 0.08 mol (11.69 g) of triethylenetetramine (TETA) and 0.01 mol of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane were added to a four-necked flask. After the temperature of the material was raised to 65°C, 0.05 mol (19.00 g) of polypropylene glycol diglycidyl ether (PPGDGE) was added dropwise at a uniform rate within 1.0 h. After the addition was complete, the reaction was kept warm for 3.0 h.

[0059] (2) Maintaining the material temperature at 65° C., add 0.030 mol of epoxy resin E51 solution (containing 20% propylene glycol methyl ether) dropwise at a constant rate over 1.0 h. After the addition is complete, keep the temperature and react for 3.0 h.

[0060] (3) After the temperature is raised to 80°C, 0.025 mol of 3-glycidoxypropyltrimethoxysilane is added dropwise at a uniform rate within 1.0 h, and the reaction is continued for 3.0 h.

[0061] (4) Cooling to 25°C, adding deionized water dropwise, and stirring at high speed for 20 minutes to obtain a silicon-containing water-based epoxy resin curing agent.

[0062] The waterborne epoxy coating (Component A) and the synthesized waterborne epoxy curing agent (Component B) consistent with Example 1 were mixed in proportion. The steel plate was sandpapered, and a varnish was applied to the tinplate using a wire rod. The coating was cured at room temperature to obtain a film with a dry film thickness of approximately 30 μm and 50 μm. The film was cured for 7 days. The adhesion, impact resistance, and water resistance of the coating were tested according to the national standard HG / T 4759-2014. The test results showed that the paint film of this example met the level 1 cross-hatch test, the 40 cm impact resistance test, and the 240 h water resistance test, and therefore had excellent adhesion, impact resistance, and water resistance.

[0063] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for synthesizing an amino-based siloxane-modified self-emulsifying waterborne epoxy curing agent, characterized in that: The method comprises the following steps: S1) placing an organosilicon monomer and a polyamine in a container, and after the material temperature is raised to 60-80° C., adding polyether alcohol diglycidyl ether dropwise over 1.0-2.0 hours, and after the addition is complete, maintaining the temperature constant and continuing the reaction for 2.0-4.0 hours; the organosilicon monomer is selected from any one or more of 1,3-bis(3-aminopropyl)tetramethyldisiloxane, aminopropyl di-terminated polydimethylsiloxane, and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane; S2) maintaining the material at 60-80°C, adding epoxy resin solution dropwise within 1.0h, and after the addition is complete, maintaining the temperature constant and continuing the reaction for 2.0-4.0h; S3) After the temperature is raised to 80° C., 3-glycidoxypropyltrimethoxysilane is added dropwise within 1.0 h, and the reaction is continued for 2.0 to 3.0 h; S4) cooling to 40-60° C., adding deionized water dropwise, and stirring at high speed to prepare a self-emulsifying waterborne epoxy curing agent with a solid content of 50-60%.

2. The method for synthesizing a self-emulsifying waterborne epoxy curing agent according to claim 1, wherein: The polyamine is selected from any one or more of ethylenediamine, diethylenetriamine, triethylenetetramine and tetraethylenepentamine.

3. The method for synthesizing a self-emulsifying waterborne epoxy curing agent according to claim 1, wherein: The polyether alcohol diglycidyl ether is selected from any one or more of polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether and polybutylene glycol diglycidyl ether; and the relative molecular weight of the polyether alcohol diglycidyl ether is 350-580.

4. The method for synthesizing a self-emulsifying waterborne epoxy curing agent according to claim 1, wherein: The molar ratio of the organic silicon monomer, the polyamine and the polyether alcohol diglycidyl ether is 0.2-1.0:2.0-1.0:1.

0.

5. The method for synthesizing the self-emulsifying waterborne epoxy curing agent according to claim 1, wherein: The epoxy resin is selected from any one or more of E51, E44, and E20.

6. The method for synthesizing the self-emulsifying waterborne epoxy curing agent according to claim 1, wherein: The mass fraction of the epoxy resin in the epoxy resin solution is 70-95%; the solvent is propylene glycol methyl ether.

7. The method for synthesizing the self-emulsifying waterborne epoxy curing agent according to claim 1, wherein: The molar ratio of the epoxy resin to the polyether alcohol diglycidyl ether is 0.4-0.6:1.

0.

8. The method for synthesizing the self-emulsifying waterborne epoxy curing agent according to claim 1, wherein: The molar ratio of the 3-glycidyloxypropyltrimethoxysilane to the polyether alcohol diglycidyl ether is 0.4-0.5:1.

0.

9. Use of the self-emulsifying waterborne epoxy curing agent prepared by the method according to any one of claims 1 to 8 in curing waterborne epoxy coatings.

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