Epoxy hardener for marine heavy-duty coating and preparation method of epoxy hardener

Abstract

The invention relates to an epoxy curing agent for a marine heavy anti-corrosion coating and a preparation method of the epoxy curing agent. The epoxy curing agent comprises the following components: 4-10 parts of an aminophenol curing agent, 0-10 parts of aliphatic polyamine, 15-40 parts of m-xylylenediamine, 5-8 parts of bisphenol A, 10-30 parts of bisphenol F epoxy resin, 15-40 parts of polyfunctional polyether amine and 10-20 parts of a mixed solvent. The epoxy curing agent can be matched with various epoxy resin coatings for use through addition modification, and the prepared coating has hardness and flexibility, is excellent in wear resistance, acid and alkali resistance and corrosion resistance, and can meet the application requirements of epoxy marine heavy-duty anticorrosive coatings.

Description

TECHNICAL FIELD

[0001] The present application relates to an epoxy resin curing agent and a preparation method thereof, in particular to an epoxy curing agent for marine heavy-duty anticorrosive coating and a preparation method thereof. BACKGROUND

[0002] The marine environment is a harsh corrosive environment, and the requirements for marine engineering anticorrosive coatings are relatively high. In particular, the average corrosion rate of marine engineering equipment and facilities in the tidal zone / splash zone is 3-10 times higher than that of other engineering equipment and facilities. For marine engineering equipment and facilities, in addition to the demand for corrosion resistance, higher film thickness, better wear resistance and impact resistance are required. According to the NORSOK M-501:2022 standard and the ISO 12944-9 standard, the performance requirements are as follows: 1. The corrosion propagation of the zinc-rich area at the scribe line is ≤3 mm, and the corrosion propagation of the non-zinc-rich area is ≤8 mm after a cyclic aging test of ≥4200 h; 2. The cathodic disbonding resistance is ≥4200 h, and the corrosion propagation at the scribe line is ≤20 mm; 3. The 1000-micron impact resistance is ≥5.6 joules; 4. The seawater immersion resistance is ≥4200 h, the paint film is intact, and the corrosion propagation at the scribe line is ≤6 mm.

[0003] In anticorrosive coatings, the use of main resins and curing agents is the most critical. For the main resin formula, the prior art CN104774527B reports a preparation method of an epoxy glass flake coating for marine tidal / splash zones, which meets the requirements of the old NORSOK M-501:2012 standard, but has no impact resistance data. According to experience, low-molecular epoxy resins, bisphenol F epoxy resins, alicyclic amines, and modified phenolic amines have good corrosion resistance, but thick coating impact resistance is generally poor, and weather resistance is poor. CN106047065B reports a solvent-free epoxy glass flake coating for marine splash zone steel structures and a preparation method thereof. Although the hydrogenated bisphenol A type epoxy resin is replaced to improve the weather resistance, the resin molecular weight is low, and the thick coating impact resistance is still not improved. CN120041056A discloses a solvent-free epoxy heavy-duty anticorrosive coating, a preparation method and application thereof. Although the main paint and curing agent are toughened and modified, the salt spray resistance is only 1000 hours, and it is mainly applied to petrochemical corrosion prevention, which is not suitable for marine heavy-duty corrosion prevention.

[0004] Regarding curing agents, CN104774527B discloses a composite curing agent of phenolic amine and aliphatic amine. Although aliphatic amines offer some flexibility, experience suggests they are insufficient to meet the requirements for high film thickness and impact resistance. CN106995527B discloses a composite epoxy curing agent and its preparation method for heavy-duty anti-corrosion coatings, using a mixture of aromatic amines and phenolic amines. While this improves salt spray resistance, such curing agents generally offer only moderate impact resistance at high film thickness, and the modification and synthesis process is time-consuming. CN114163615B and CN120041056A disclose only high flexibility, but their anti-corrosion performance is only average, making it difficult to meet the application requirements of heavy-duty anti-corrosion coatings in marine engineering. Summary of the Invention

[0005] The first technical problem to be solved by this invention is to provide an epoxy curing agent with high flexibility, impact resistance, high hardness, wear resistance, and high corrosion resistance, which can be used in marine heavy-duty anti-corrosion coatings, and can be matched with different epoxy resin coatings to meet the needs of heavy-duty anti-corrosion coatings in different marine environments.

[0006] The second technical problem to be solved by the present invention is to provide a mild and simple preparation method for the epoxy curing agent.

[0007] The technical solution adopted by this invention to solve its first technical problem is an epoxy curing agent for marine heavy-duty anti-corrosion coatings, wherein, by weight, its raw material components include: 4-10 parts of aminophenol curing agent, 0-10 parts of aliphatic polyamine, 15-40 parts of m-phenylenediamine, 5-8 parts of bisphenol A (also known as 2,2-bis(p-hydroxyphenyl)propane, CAS#:80-05-7), 10-30 parts of bisphenol F epoxy resin, 15-40 parts of polyfunctional polyetheramine, and 10-20 parts of mixed solvent.

[0008] Preferably, the aminophenolic curing agent is 2,4,6-tris(dimethylaminomethyl)phenol or bis[(dimethylamino)-methyl]phenol; Preferably, the aliphatic polyamine is one or more of diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, and hexaethyleneheptamine.

[0009] Preferably, the epoxy equivalent of the bisphenol F epoxy resin is 164-172 eq / kg.

[0010] Preferably, the multifunctional polyetheramine is a difunctional or trifunctional polyetheramine.

[0011] Preferably, the mixed solvent is a mixture of benzyl alcohol, xylene, and butanol, and the mass ratio of benzyl alcohol, xylene, and butanol is 3-5:2:1.

[0012] The technical solution adopted by the present invention to solve its second technical problem is a method for preparing the epoxy curing agent for marine heavy-duty anti-corrosion coatings, which includes the following steps: 1) Add aminophenol curing agent, aliphatic polyamine, m-phenylenediamine, bisphenol A and mixed solvent to the reactor, and start stirring; 2) Heat to 70-100℃, then add bisphenol F epoxy resin in batches, maintaining the temperature inside the bottle at 90-110℃. After the bisphenol F epoxy resin is added, continue to maintain the temperature at 95-105℃ for 2-4 hours. 3) After the reaction is complete, cool down to 40-60℃, add multifunctional polyetheramine, and keep warm for 1-2 hours to obtain the product.

[0013] In this invention, the addition of bisphenol F epoxy resin in batches in step 2) is to prevent explosive gelation. Those skilled in the art can adjust the number of batches according to the actual situation. For example, it can be added in 2, 3 or 4 times.

[0014] The curing agent of this invention can be combined with various epoxy resin coatings to meet the application needs of different scenarios in marine engineering environments, such as epoxy zinc-rich coatings and epoxy thick-film coatings used in atmospheric areas, and epoxy glass flake coatings for splash zones, water level fluctuation zones, and underwater zones. The epoxy resin coating of the epoxy zinc-rich coating, epoxy thick-film coating, or epoxy glass flake coating is used as component A, and the epoxy curing agent used in this invention for heavy-duty anti-corrosion coatings in marine engineering is used as component B. More specifically, component A and component B are uniformly mixed at a reaction ratio of 1:0.7~0.9, filtered through a 40-120 mesh filter, and then directly applied to the treated substrate.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The epoxy curing agent of the present invention has a simple preparation method. The epoxy curing agent obtained by prepolymerization modification of epoxy resin with various functional amine groups has good compatibility with the main epoxy resin. At the same time, it has the corrosion resistance of m-phenylenediamine and the toughness of polyetheramine with high functionality. It has high strength, high hardness, wear resistance and media resistance, which can meet the application requirements of epoxy marine heavy-duty anti-corrosion coatings.

[0016] 2. The epoxy curing agent of this invention has good compatibility with various epoxy resin coatings and has multiple properties such as salt spray resistance, chemical resistance, and flexibility, which can meet the application needs of different marine engineering heavy corrosion protection scenarios.

[0017] 3. The epoxy curing agent of this invention, when used with epoxy resin coating, exhibits excellent workability, fast drying, long adaptability, and is environmentally friendly with low VOCs. It also has excellent anti-sagging properties, and the paint film does not crack or shrink after a single thick coating application, with minimal impact on performance. It is particularly suitable for heavy-duty marine engineering anti-corrosion applications where thick coatings and high performance requirements are required. Detailed Implementation

[0018] The present invention will now be described in detail through specific embodiments.

[0019] Unless otherwise specified, the raw materials involved in the embodiments of this invention are all commercially available products.

[0020] Example 1 This embodiment describes a method for preparing an epoxy curing agent for marine heavy-duty anti-corrosion coatings, comprising the following steps: 1) Add 4 parts of 2,4,6-tris(dimethylaminomethyl)phenol, 2 parts of pentaethylenehexamine, 20 parts of m-phenylenediamine, 6 parts of bisphenol A and 15 parts of mixed solvent (benzyl alcohol: xylene: butanol = 4:2:1) to the reaction flask and start stirring; 2) Heat to 80℃, then add 24 parts of bisphenol F epoxy resin (ARALDITE GY285, epoxy equivalent of 164-172eq / kg) in 3 batches every half hour, and maintain the temperature inside the bottle at 100℃. After the bisphenol F epoxy resin is added, continue to maintain the temperature at 100℃ for 3 hours. 3) After the reaction is complete, cool down to 50°C, add 35 parts of multifunctional polyetheramine (Jeffamine T 403), keep warm for 1.5 hours, and discharge to obtain epoxy curing agent 1.

[0021] An epoxy glass flake coating is composed of component A and component B. Component A comprises the following raw materials by weight percentage: 15% bisphenol A epoxy resin (E51:E20=4:1), 34% modified hydrogenated epoxy resin (Shanghai Huayi Resin Co., Ltd., 642 modified hydrogenated epoxy resin), 7% liquid petroleum resin, 1.8% polyamide wax powder, 0.2% dispersant, 0.5% defoamer, 1.5% silane coupling agent, 8% modified glass flakes, 27% functional filler (quartz sand:feldspar powder:bauxite=2:2:1), and 5% composite environmentally friendly solvent (xylene:butanol=2:1). Component B is the epoxy curing agent 1 prepared in this embodiment.

[0022] The preparation method of component A is as follows: Bisphenol A epoxy resin, modified hydrogenated epoxy resin, and liquid petroleum resin were added to a reactor. While stirring at 500-1000 rpm, a rheology modifier was added. The temperature was raised to 55-70℃ and held for 15-30 minutes to fully activate the rheology modifier. The temperature was then lowered to room temperature, and a dispersant, defoamer, and functional filler were added sequentially. The speed was increased to 1000-1500 rpm for high-speed dispersion until the fineness was less than 50 μm. The speed was then reduced to 500-1000 rpm, and while stirring, a silane coupling agent and modified glass flakes were added. The viscosity was adjusted with a composite environmentally friendly solvent, and dispersion was continued for 15 minutes until uniform. After passing inspection, the mixture was filtered and packaged to obtain component A.

[0023] Preparation and application: Mix component A and component B evenly at a mass ratio of 100:15, filter through a 40-120 mesh filter, and then apply directly to the treated substrate.

[0024] Example 2 This embodiment describes a method for preparing an epoxy curing agent for marine heavy-duty anti-corrosion coatings, comprising the following steps: 1) Add 4 parts of bis[(dimethylamino)-methyl]phenol, 1 part of diethylenetriamine, 40 parts of m-phenylenediamine, 8 parts of bisphenol A and 20 parts of mixed solvent (benzyl alcohol: xylene: butanol = 5:2:1) to the reaction flask and start stirring; 2) Heat to 70°C, then add 10 parts of bisphenol F epoxy resin in 3 batches every half hour, maintaining the temperature inside the bottle at 110°C. After the bisphenol F epoxy resin is added, continue to maintain the temperature at 110°C for 4 hours. 3) After the reaction is complete, cool down to 40°C, add 20 parts of difunctional polyetheramine, keep warm for 2 hours, and discharge to obtain epoxy curing agent 2.

[0025] An epoxy glass flake coating is composed of component A and component B, wherein component A is SHG53-820 epoxy glass flake paint (Xiangjiang Coatings Technology Co., Ltd.), and component B is epoxy curing agent 2.

[0026] Preparation and application: Mix component A and component B evenly at a mass ratio of 100:16, filter through a 40-120 mesh filter, and apply directly to the treated substrate.

[0027] Example 3 This embodiment describes a method for preparing an epoxy curing agent for marine heavy-duty anti-corrosion coatings, comprising the following steps: 1) Add 10 parts of bis[(dimethylamino)-methyl]phenol, 10 parts of triethylenetetramine, 15 parts of m-phenylenediamine, 5 parts of bisphenol A and 10 parts of mixed solvent (benzyl alcohol: xylene: butanol = 3:2:1) to the reaction flask and start stirring; 2) Heat to 70°C, then add 15 parts of bisphenol F epoxy resin in 3 batches every half hour, maintaining the temperature inside the bottle at 110°C. After the bisphenol F epoxy resin is added, continue to maintain the temperature at 110°C for 2 hours. 3) After the reaction is complete, cool down to 40°C, add 40 parts of difunctional polyetheramine, keep warm for 1 hour, and discharge to obtain epoxy curing agent 3.

[0028] An epoxy zinc-rich coating is composed of component A and component B, wherein component A is XZH-700 epoxy zinc-rich primer (Xiangjiang Coatings Technology Co., Ltd.) and component B is epoxy curing agent 3.

[0029] Preparation and application: Mix component A and component B evenly at a mass ratio of 100:5, filter through a 40-120 mesh filter, and then apply directly to the treated substrate.

[0030] Example 4 This embodiment describes a method for preparing an epoxy curing agent for marine heavy-duty anti-corrosion coatings, comprising the following steps: 1) Add 6 parts of 2,4,6-tris(dimethylaminomethyl)phenol, 8 parts of polyhexanediamine, 30 parts of m-phenylenediamine, 8 parts of bisphenol A and 20 parts of mixed solvent (benzyl alcohol: xylene: butanol = 4:2:1) to the reaction flask and start stirring; 2) Heat to 80℃, then add 30 parts of bisphenol F epoxy resin in 3 batches every half hour, maintain the temperature inside the bottle at 100℃, and after the bisphenol F epoxy resin is added, continue to maintain the temperature at 100℃ for 4 hours. 3) After the reaction is complete, cool down to 50°C, add 15 parts of trifunctional polyetheramine, keep warm for 1.5 hours, and discharge to obtain epoxy curing agent 4.

[0031] An epoxy thick coating is composed of component A and component B, wherein component A is XZH-900 epoxy thick paste micaceous iron oxide intermediate paint (Xiangjiang Coatings Technology Co., Ltd.), and component B is epoxy curing agent 4.

[0032] Preparation and application: Mix component A and component B evenly at a mass ratio of 100:12.5, filter through a 40-120 mesh filter, and then apply directly to the treated substrate.

[0033] Comparative Example 1 The difference from Example 1 is that 2,4,6-tris(dimethylaminomethyl)phenol and m-phenylenediamine were not added. After cyclic aging tests, severe corrosion and poor adhesion resulted in non-compliance.

[0034] Comparative Example 2 The difference from Example 1 is that no multifunctional polyetheramine is added, resulting in a brittle paint film with poor impact resistance.

[0035] Comparative Example 3 The difference from Example 1 is that: using 200# standard polyamide curing agent as component B, the paint film dries more slowly, has poor acid resistance, and is severely corroded after cyclic aging test, with the adhesion value decreasing by more than 50%.

[0036] Comparative Example 4 The difference from Example 1 is that a phenolic amine curing agent (such as Naxo PLR 718C) is used as component B, resulting in a more brittle paint film with poor impact resistance.

[0037] Comparative Example 5 The difference from Example 2 is that a modified phenolic amine curing agent (such as Wansheng WSCM-1206) is used as component B, which results in slower drying, poor resistance to cyclic aging, and poor cathodic disbondment.

[0038] Comparative Example 6 The difference from Example 3 is that a modified polyamide curing agent (such as Wansheng WSCM-4115E) was used as component B, and blistering was observed around the scribing line after the cyclic aging test.

[0039] Comparative Example 7 The difference from Example 4 is that a modified polyamide curing agent (such as Wansheng WSCM-4115E) is used as component B, which has poor compatibility, especially after cyclic aging test, the interlayer adhesion is poor.

[0040] Note: Commercially available hardeners are based solely on test results after being used with the current base paint. According to NORSOK M-501:2022 standard, the curing agents prepared in Examples 1 and 2, and the curing agents in Comparative Examples 1 to 4, were used with epoxy glass flake coating products, and their performance was tested according to CSDS no. 7A coating system. The results are shown in Table 1. The curing agents prepared in Examples 3 and 4 were used with epoxy zinc-rich coatings and epoxy thick-film micaceous iron oxide coatings, respectively, and their performance was tested according to CSDS no. 1B coating system. The results were compared with those of Comparative Examples 6 and 7, and are shown in Table 2.

[0041] Table 1. Performance test results of the coating systems of Examples 1-2 and Comparative Examples 1-5 on CSDS no. 7A.

[0042] Table 2. Performance test results of the coating systems of Examples 3-4 and Comparative Examples 6-7 on CSDS no. 1B.

[0043] The performance test results in Table 1 show that, when the curing agent of this invention is used in conjunction with component A of the epoxy glass flake coating, the coating film exhibits excellent chemical resistance, cyclic aging resistance, cathodic peel resistance, and seawater immersion resistance. It also possesses impact resistance even after a 1000-micron thick dry film thickness, meeting the performance requirements of NORSOK M-501:2022 CSDS no. 7A coating system. The performance test results in Table 2 show that, when the curing agent of this invention is used in conjunction with component A of the epoxy zinc-rich coating and component A of the epoxy thick-film micaceous iron oxide intermediate paint, and combined with the weather-resistant polyurethane topcoat to form the CSDS no. 1B coating system, it exhibits excellent cyclic aging performance and adhesion, meeting the performance requirements of NORSOK M-501:2022 CSDS no. 1B coating system. The above performance test results demonstrate that the present invention, by scientifically modifying different amines and resins according to a preferred ratio and then matching them with component A of different types of epoxy resin coatings, produces a paint film with excellent chemical resistance, cyclic aging resistance, cathodic disbondment resistance, and seawater immersion resistance. It also exhibits impact resistance even after a 1000-micron thick dry film, meeting the latest standard requirements of NORSOK M-501:2022 and ISO 12944-9. Examples 1-4 of this invention can be used with various epoxy resin coatings, producing a paint film with excellent adhesion, hardness, abrasion resistance, and impact resistance. It also features fast drying time, resistance to cyclic aging, seawater immersion, and cathodic disbondment, meeting the performance requirements of NORSOK M-501:2022 (7th Edition) "Surface Treatment and Protective Coatings".

[0044] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. An epoxy curing agent for marine heavy-duty anti-corrosion coatings, characterized in that, By weight, it includes the following components: 4-10 parts of aminophenol curing agent, 0-10 parts of aliphatic polyamine, 15-40 parts of m-phenylenediamine, 5-8 parts of bisphenol A, 10-30 parts of bisphenol F epoxy resin, 15-40 parts of polyfunctional polyetheramine, and 10-20 parts of mixed solvent.

2. The epoxy curing agent according to claim 1, characterized in that, The aminophenol curing agent is 2,4,6-tris(dimethylaminomethyl)phenol or bis[(dimethylamino)-methyl]phenol.

3. The epoxy curing agent according to claim 1, characterized in that, The aliphatic polyamine is one or more of diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, and hexaethyleneheptamine.

4. The epoxy curing agent according to claim 1, characterized in that, The epoxy equivalent of the bisphenol F epoxy resin is 164-172 eq / kg.

5. The epoxy curing agent according to claim 1, characterized in that, The multifunctional polyetheramine is a difunctional or trifunctional polyetheramine.

6. The epoxy curing agent according to claim 1, characterized in that, The mixed solvent is a mixture of benzyl alcohol, xylene, and butanol, and the mass ratio of benzyl alcohol, xylene, and butanol is 3-5:2:

1.

7. A method for preparing an epoxy curing agent as described in any one of claims 1-6, characterized in that, Includes the following steps: 1) Add aminophenol curing agent, aliphatic polyamine, m-phenylenediamine, bisphenol A and mixed solvent to the reactor, and start stirring; 2) Heat to 70-100℃, then add bisphenol F epoxy resin in batches, maintaining the temperature inside the bottle at 90-110℃. After the bisphenol F epoxy resin is added, continue to maintain the temperature at 95-105℃ for 2-4 hours. 3) After the reaction is complete, cool down to 40-60℃, add multifunctional polyetheramine, and keep warm for 1-2 hours to obtain the product.

8. An epoxy coating for heavy-duty corrosion protection in marine engineering, characterized in that, It is composed of component A and component B, wherein component A is any one of the primer of epoxy zinc-rich coating, primer of epoxy thick film coating or primer of epoxy glass flake coating, and component B is the epoxy curing agent according to any one of claims 1-6.

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