Preparation method of bio-based epoxy resin anticorrosive paint

Abstract

The invention discloses a preparation method of a bio-based epoxy resin anticorrosive coating, and relates to a preparation method of a bio-based epoxy resin coating. The bio-based epoxy resin anticorrosive paint mainly comprises an anticorrosive filler COFs-AA, bio-based epoxy resin and a curing agent. Wherein the anticorrosive filler COFs-AA is prepared from a two-dimensional covalent organic framework COFs and a bio-based material arachidonic acid (AA) through a covalent condensation reaction; the bio-based epoxy resin is prepared by epoxidizing a bio-based material galangin serving as a raw material through epichlorohydrin, and the curing agent is a common curing agent for epoxy resin. The bio-based epoxy resin anticorrosive paint is compounded by taking biomass as a basic component, and has the characteristics of greenness, environmental protection, no toxicity, good hydrophobicity and good corrosion resistance; the bio-based epoxy resin anticorrosive paint can be applied to the field of corrosion protection of materials such as various metals and woodware.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of anti-corrosion coatings, and in particular to a method for preparing a bio-based epoxy resin anti-corrosion coating. Background Art

[0002] Anti-corrosion coatings are widely used in modern industry, transportation, marine engineering and other fields. The anti-corrosion coatings market is mainly dominated by organic coatings, so organic solvents are also one of the main ingredients in coating formulas. In recent years, the continuous improvement of policies and regulations has begun to control VOC emissions and promoted the development of high-solid coatings, UV light-curing coatings and water-based coatings. With people's high attention to sustainable development, the development of bio-based raw materials for coatings and partial or complete replacement of petrochemical raw materials are becoming a hot topic in the anti-corrosion coatings industry.

[0003] Therefore, the preparation of bio-based coating components and their functional modification methods are crucial to the development of bio-based coatings. Bio-based coatings also face the dispersion and compatibility problems between the multiple phases within the system. For example, the agglomeration and precipitation of fillers lead to obvious defects in the coating, reduced barrier properties, and ultimately reduced protective performance; the incompatibility between the filler and the resin matrix interface leads to phase separation inside the coating, resulting in obvious micropores in the coating, which ultimately leads to a reduction in the protective performance of the coating. Therefore, the development of bio-based protective coatings with excellent performance will be a major demand in the field of corrosion protection. Summary of the invention

[0004] The object of the present invention is to provide a method for preparing a bio-based epoxy resin anti-corrosion coating, wherein the bio-based epoxy resin anti-corrosion coating is mainly composed of an anti-corrosion filler COFs-AA, a bio-based epoxy resin and a curing agent. The bio-based epoxy resin anti-corrosion coating is composited with biomass as the basic component, and has the characteristics of being green, environmentally friendly, non-toxic, having good hydrophobicity and good anti-corrosion performance. The bio-based epoxy resin anti-corrosion coating can be applied to the field of corrosion environment protection of various metals, woodware and other materials.

[0005] The objective of the present invention is achieved through the following technical solutions: A method for preparing a bio-based epoxy resin anti-corrosion coating, the method comprising the following preparation process: firstly, COFs material is prepared according to Schiff base reaction, and then COFs and AA are subjected to condensation reaction to prepare an anti-corrosion functional filler with excellent barrier properties and good compatibility; secondly, galangin is used as a raw material to prepare epoxy resin through epoxidation reaction, which has excellent antioxidant properties and can cooperate with the anti-corrosion filler for anti-corrosion during service; finally, the resin, filler and curing agent are mixed in a certain proportion to prepare a bio-based epoxy resin anti-corrosion coating. The specific scheme is as follows: Step 1. Mix the monomer 1,3,5-trialdehyde phloroglucinol (0.2 mmol), 2,5-dihydroxyterephthaloyl hydrazide (0.3 mmol), solvent (mesitylene / tetrahydrofuran, 4 mL / 4 mL) and catalyst (acetic acid, 0.8 mL, 6M) in a three-necked flask and heat at 120 °C for 72 h to prepare COFs. Subsequently, collect the precipitate in the reactor, wash it with acetone by centrifugation for 3-6 times, and then vacuum dry it at 50 °C to constant weight to obtain COFs.

[0006] Step 2. Dissolve 8 g of arachidonic acid (AA) in 80 mL of dichloromethane solution, then add 2 g of COFs, stir evenly, and drop an appropriate amount of 10 mol / L H2SO4 solution. Stir at 70 °C (speed of 300 r / min) for 4 hours. After the reaction, evaporate the mixture to remove excess solvent, and wash the remaining mixture with deionized water by centrifugation until it is neutral. Finally, dry the solid in vacuum at 50 °C to constant weight to obtain the anti-corrosion filler COFs-AA.

[0007] Step 3. Dissolve 20 g of galangin in 200 g of DMSO, then add 200 g of epichlorohydrin and 2 g of tetrabutylammonium bromide, stir evenly, and put into a three-necked flask. React at 70 °C with condensation reflux stirring (260 r / min) for 3 h. Then, add 40 g of NaOH solution (50%) dropwise to the mixture, stir and react at 60 °C for 2 h to obtain a dark reaction mixture. Rotate the mixture to remove unreacted epichlorohydrin to obtain galangin-based epoxy resin.

[0008] Step 4. Take 10 g of bio-based epoxy resin and add 2.5 g of deionized water to dilute it, then pour it into a ball mill and add an appropriate amount of anti-corrosion filler COFs-AA. Ball mill the mixture to fully disperse the filler, then add 2.5 g of amino curing agent (AQ419), stir with a magnetic stirrer at 1000 r / min to mix evenly, and prepare a bio-based epoxy resin anti-corrosion coating.

[0009] Preferably, the mass ratio of AA to COFs is 4:1; Preferably, the added mass of the 10 mol / L H2SO4 solution as a catalyst is 3% to 7% of the mass of COFs.

[0010] Preferably, the mass ratio of galangin to epichlorohydrin is 1:10; Preferably, during the preparation of the bio-based epoxy resin, NaOH solution is added to make the pH value of the mixed solution 8.

[0011] Preferably, the bio-based material galangin can also be replaced or partially replaced by curcumin. Preferably, the amount of anti-corrosion filler added during the preparation of the bio-based epoxy resin anti-corrosion coating is 0.5% to 3.0% of the resin mass.

[0012] The beneficial effects of the present invention are: 1. This patent uses galangin as the resin raw material, which is green, environmentally friendly, non-toxic and pollution-free. At the same time, galangin has a certain antioxidant ability. After epoxidation, it can be used as a bio-based resin to synergistically prevent corrosion with two-dimensional COFs materials. At the same time, it has excellent aging resistance and good substrate adhesion.

[0013] 2. This patented anti-corrosion functional filler COFs-AA uses two-dimensional COFs as the main material, and successfully introduces arachidonic acid (AA) with a hydrophobic alkyl chain into the bio-based coating through a condensation reaction, thereby reducing the hydrophilicity of COFs and retaining the unique barrier ability of the two-dimensional material. At the same time, compared with inorganic fillers, the filler has better interface compatibility with the resin matrix, thereby maximizing the anti-corrosion ability of the coating.

[0014] 3. This patent uses bio-based materials as the main body to construct coating components, which greatly improves the environmental protection and safety of the coating. It will help promote the research progress of bio-based coatings and provide new ideas for the development of bio-based coatings. DETAILED DESCRIPTION

[0015] The present invention is further described below by specific examples, but the present invention is not limited to the following examples. Within the scope of the present invention or without departing from the content, thought and scope of the present invention, the changes, combinations or substitutions made to the present invention are obvious to those skilled in the art and are included in the scope of the present invention. Example 1

[0016] A bio-based epoxy resin anti-corrosion coating (named A1) includes the following preparation steps: 10 g of bio-based epoxy resin is taken and 2.5 g of deionized water is added thereto for dilution, then the mixture is poured into a ball mill, and 0.1 g of anti-corrosion filler COFs-AA is added. The mixture is ball milled to fully disperse the filler, and then 2.5 g of amino curing agent (AQ419) is added, and the mixture is stirred at 1000 r / min with a magnetic stirrer to be evenly mixed, thereby obtaining a bio-based epoxy resin anti-corrosion coating. Example 2

[0017] A bio-based epoxy resin anti-corrosion coating (named A2) includes the following preparation steps: 10 g of bio-based epoxy resin is taken and 2.5 g of deionized water is added thereto for dilution, then the mixture is poured into a ball mill, and 0.1 g of anti-corrosion filler COFs is added. The mixture is ball milled to fully disperse the filler, and then 2.5 g of amino curing agent (AQ419) is added, and the mixture is stirred at 1000 r / min with a magnetic stirrer to make it uniformly mixed, thereby preparing a bio-based epoxy resin anti-corrosion coating. Example 3

[0018] A bio-based epoxy resin anti-corrosion coating (named A3) includes the following preparation steps: 10 g of bio-based epoxy resin is taken and 2.5 g of deionized water is added thereto for dilution, then the mixture is poured into a ball mill, and 0.1 g of a mixed filler of COFs and AA (0.2 g of COFs and 0.8 g of AA) is added. The mixture is ball milled to fully disperse the filler, and then 2.5 g of an amino curing agent (AQ419) is added, and the mixture is stirred at 1000 r / min with a magnetic stirrer to be uniformly mixed, thereby obtaining a bio-based epoxy resin anti-corrosion coating. Example 4

[0019] A bio-based epoxy resin anti-corrosion coating (A4) comprises the following preparation steps: taking 10 g of a commercially available bio-based epoxy lignin resin and adding 2.5 g of deionized water thereto for dilution, then pouring the resin into a ball mill, adding 0.1 g of an anti-corrosion filler COFs-AA, ball milling the mixture to fully disperse the filler, then adding 2.5 g of an amino curing agent (AQ419), stirring the mixture with a magnetic stirrer at 1000 r / min to uniformly mix the mixture, and preparing the bio-based epoxy resin anti-corrosion coating.

[0020] The bio-based epoxy resin anti-corrosion coatings prepared in the above-mentioned embodiments were sprayed on the surface of a Q235 low-carbon steel substrate. After the coating was cured for one week, its static contact angle, adhesion and neutral salt spray resistance (5.0 wt.% NaCl solution) were tested. The test results are shown in Table 1.

[0021] It can be seen from the test results in Table 1 that the static contact angle of the patented product is the largest, the hydrophobic performance is relatively good, there is no blistering after 240 hours of neutral salt spray test, and the adhesion reaches level 0, showing good barrier and protective performance. For component A2, its static contact angle is only 70°, mainly because the functional filler is only COFs material, which is hydrophilic, making the water resistance of the composite coating worse than that of component A1, resulting in blistering of the coating after 240 hours of neutral salt spray test. For component A3, the anticorrosive filler is a mixture of COFs and AA, which are distributed in the composite coating only through physical blending without chemical bonding. Due to the uneven distribution of the two in the coating and the hydrophilic effect of COFs, the coating has inconsistent local components, resulting in a relatively small static contact angle of the coating, and the barrier and adhesion are also reduced, so obvious blistering occurs after 240 hours of neutral salt spray test. For the A4 component, adding the functional filler (COFs-AA) prepared by this patent to the epoxidized lignin has good protective performance and adhesion, indicating that the functional filler prepared by this patent is not only suitable for the epoxidized galangin matrix of this patent, but also suitable for other resin matrices to a certain extent.

[0022] Table 1 Test results of anticorrosion performance of epoxy composite coating Component name Static contact angle Neutral salt spray resistance Adhesion A1 93° 240 h no foaming Level 0 A2 70° Foaming after 240 h Level 0 A3 64° Obvious bubbling after 240 h Level 1 A4 89° 240 h no foaming Level 0 Test methods Droplet method GB / T 9286-1988 GB / Y 9286-2021 .

Claims

1. A method for preparing a bio-based epoxy resin anti-corrosion coating, characterized in that: The bio-based epoxy resin anti-corrosion coating is composited with an anti-corrosion functional filler, a bio-based epoxy resin and a curing agent, wherein the anti-corrosion functional filler is prepared by condensing a two-dimensional covalent organic framework COFs and a bio-based material arachidonic acid (AA); the bio-based epoxy resin is prepared by epoxidation using a bio-based material galangin as a raw material; the curing agent is a general curing agent; the bio-based anti-corrosion coating includes the following preparation process: Step 1. Preparation of COFs: According to the Schiff base reaction, a solvent, a monomer 1,3,5-trialdehyde pyrogallol, a monomer 2,5-dihydroxyterephthaloyl hydrazide and a catalyst were added to a three-necked flask in sequence, and the mixture was heated at 120 °C for 72 h. The precipitate in the reactor was collected and washed by centrifugation with acetone for 3-6 times, and then vacuum dried at 50 °C to constant weight to obtain COFs. Step 2. Preparation of anti-corrosion functional filler COFs-AA: Dissolve arachidonic acid (AA) in a three-necked flask using dichloromethane solution as solvent, then add COFs, stir evenly and drop the catalyst, stir at 70 °C (speed of 300 r / min) for 4 h, after the reaction, remove excess solvent by rotary evaporation, wash the remaining mixed solution with deionized water by centrifugation until neutral, finally, vacuum dry the solid at 50 °C to constant weight to obtain anti-corrosion filler COFs-AA; Step 3. Preparation of bio-based epoxy resin: Dissolve galangin in a three-necked flask using dimethyl sulfoxide (DMSO) as solvent, then add epichlorohydrin and tetrabutylammonium bromide in sequence, and react at 70 °C with condensation reflux stirring (260 r / min) for 3 h; then, add NaOH solution dropwise to the mixture, and stir and react at 60 °C for 2 h to obtain a dark reaction mixture; the mixture is rotary evaporated to remove unreacted epichlorohydrin to obtain galangin-based epoxy resin; Step 4. Take the bio-based epoxy resin and add deionized water to dilute it, then pour it into a ball mill, add the anti-corrosion filler COFs-AA, ball mill the mixture for 20 min to fully disperse the filler, then add the amino curing agent, stir with a magnetic stirrer to make it evenly mixed, and prepare the bio-based epoxy resin anti-corrosion coating.

2. The method for preparing a bio-based epoxy resin anticorrosive coating according to claim 1, characterized in that: The molar ratio of the monomers 1,3,5-trialdehyde phloroglucinol to 2,5-dihydroxyterephthaloyl hydrazide is 2:

3.

3. The method for preparing a bio-based epoxy resin anticorrosive coating according to claim 1, characterized in that: The solvent is a mixed solution of mesitylene and tetrahydrofuran, wherein the volume ratio of mesitylene to tetrahydrofuran is 1:

1.

4. The method for preparing a bio-based epoxy resin anticorrosive coating according to claim 1, characterized in that: The catalyst is one or more of glacial acetic acid, p-toluenesulfonic acid or piperidine, and the amount of the catalyst is 10% of the volume of the solvent.

5. The method for preparing a bio-based epoxy resin anticorrosive coating according to claim 1, characterized in that: The mass ratio of AA to COFs is 4:

1.

6. The method for preparing a bio-based epoxy resin anticorrosive coating according to claim 1, characterized in that: The catalyst is H2SO4, the concentration of which is 10 mol / L, and the added mass is 3% to 7% of the mass of COFs.

7. The method for preparing a bio-based epoxy resin anticorrosive coating according to claim 1, characterized in that: The mass ratio of galangin to epichlorohydrin is 1:

10.

8. The method for preparing a bio-based epoxy resin anticorrosive coating according to claim 1, characterized in that: After the NaOH solution is added, the pH value of the mixed solution is adjusted to 8.

9. The method for preparing a bio-based epoxy resin anticorrosive coating according to claim 1, characterized in that: The curcumin is a bio-based material, galangin.