A method for in-situ synthesis of microcapsules by enzyme catalysis and its application in anticorrosive coatings

Abstract

The application belongs to the field of material preparation, and particularly relates to a method for in-situ synthesis of microcapsules by enzyme catalysis and application thereof in anticorrosive coatings. The method specifically comprises the following steps: firstly, preparing a cellulose nanocrystal dispersion liquid and an emulsion of flaxseed oil containing cembrene; ultrasonic dispersing the emulsion, and then performing magnetic stirring to obtain a Pickering emulsion; adding hydrogen peroxide and horseradish peroxidase solution into the Pickering emulsion, and stirring and reacting; and performing freeze-drying on the emulsion after the reaction is completed to obtain cellulose nanocrystal microcapsules. The application uses an enzyme catalysis method to prepare microcapsules with an anticorrosive function, and the synthesized microcapsules do not contain harmful substances such as formaldehyde and are environmentally friendly. The synthesized microcapsules have good stability, can be easily dispersed in an aqueous solution, can be used as a carrier of healing reagents for water-based anticorrosive coatings, and have a simple preparation method, controllable size and suitability for large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of materials preparation, specifically relating to a method for in-situ synthesis of microcapsules using enzyme catalysis and its application in anti-corrosion coatings. Background Technology

[0002] Microcapsules are tiny containers with a core-shell structure, measuring in the micrometer or nanometer range. A solid or liquid forms the core, while an organic polymer (such as various synthetic resins) forms the shell, protecting the material within the core from deterioration to some extent. When stimulated externally, the capsule releases the stored material to achieve its intended function.

[0003] Microencapsulation technology typically involves emulsifying and dispersing an oil-phase healing agent in an aqueous solution, then polymerizing the monomers adsorbed at the oil-water interface through in-situ polymerization to form an insoluble polymer. The oil-phase healing agent is then encapsulated within the polymer to form functional microcapsules. Commonly used interfacial polymers include urea-formaldehyde resin and formaldehyde-urea-melamine resin. These resins exhibit good thermal stability, impermeability, and flexibility; however, their synthesis involves the use of large amounts of formaldehyde, posing health risks to production workers and undoubtedly increasing occupational health protection costs. The release of residual formaldehyde during coating service also has adverse effects on personnel and the environment. Therefore, developing an environmentally friendly microcapsule for use in anti-corrosion coatings has become an urgent problem to be solved. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention provides a method for in-situ synthesis of microcapsules using enzyme catalysis.

[0005] The present invention also provides an application of the microcapsules synthesized using the above method in anti-corrosion coatings.

[0006] The technical solution adopted by the present invention to achieve the above objectives is as follows:

[0007] This invention provides a method for in-situ synthesis of microcapsules using enzyme catalysis, comprising the following steps:

[0008] (1) Disperse cellulose nanocrystals in water to obtain a cellulose nanocrystal dispersion, and then add flaxseed oil containing coniferyl alcohol to the dispersion to obtain an emulsion;

[0009] (2) The above emulsion was ultrasonically dispersed and then magnetically stirred to obtain Pickering emulsion;

[0010] (3) Add hydrogen peroxide and horseradish catalase solution to Pickering emulsion and stir to react;

[0011] (4) After the reaction is completed, the emulsion is freeze-dried to obtain cellulose nanocrystal microcapsules.

[0012] Furthermore, in step (1), the concentration of the cellulose nanocrystal dispersion is 3 mg / mL; and each 20 mL of flaxseed oil contains 0.5 g of coniferyl alcohol.

[0013] Preferably, the diameter of the cellulose nanocrystals is 5-20 nm and the length is 50-500 nm.

[0014] Furthermore, in step (2), the conditions for ultrasound are 20kHz, 500W output power, and 5min ultrasound time; the rotation speed of the magnetic stirrer is 300-500RPM, and the stirring time is 1h.

[0015] Furthermore, in step (3), the volume ratio of hydrogen peroxide to flaxseed oil is 1:20; the volume ratio of hydrogen peroxide to horseradish catalase solution is 1:0.5; and the reaction is carried out by stirring at room temperature for 12-16 hours.

[0016] Furthermore, the concentration of the hydrogen peroxide is 30%; the concentration of the horseradish catalase solution is 5 mg / mL.

[0017] The present invention also provides an application of cellulose nanocrystal microcapsules prepared by the above preparation method in anti-corrosion coatings.

[0018] Furthermore, the anti-corrosion coating comprises two components, A and B; the mass ratio of component A to component B in the anti-corrosion coating is 5:2.

[0019] Preferably, component A comprises the following raw materials in parts by weight: 100 parts of waterborne epoxy resin, 1 part of defoamer, 0.5 parts of surface wetting agent, and 10 parts of microcapsules; component B comprises the following raw materials in parts by weight: 30 parts of waterborne epoxy resin curing agent, 10 parts of anti-corrosion filler, and 4 parts of anti-flash rust agent.

[0020] Furthermore, the waterborne epoxy resin is WEP804, with an epoxy equivalent of 520-560 g / eq and a solid content of 53%; the defoamer is BYK-022; the surface wetting agent is BYK-3455; the waterborne epoxy resin curing agent is WH-5, with an active hydrogen equivalent of 150-170 g / eq; the anti-corrosion filler is polyaniline-modified halloysite nanotubes; and the flash rust inhibitor is a 10% sodium nitrite aqueous solution.

[0021] The cellulose nanocrystals used in this invention are cellulose nanocrystals with a length of 50-500 nm and a diameter of 5-20 nm, prepared by sulfuric acid hydrolysis. This invention employs an enzyme-catalyzed in-situ synthesis method to prepare environmentally friendly microcapsules, replacing traditional polymer microcapsules. These microcapsules use a synthetic lignin / nanocellulose crystal composite material as the shell polymer and linseed oil with anti-corrosion properties as the core. These microcapsules can be used in water-based epoxy anti-corrosion coatings to enhance the barrier properties of epoxy anti-corrosion coatings, imparting a certain degree of corrosion inhibition and self-healing ability to the coating when damaged by external forces.

[0022] The method for preparing cellulose nanocrystals used in this invention is as follows:

[0023] (1) Add 100g of cellulose powder to 1L of H2SO4 (65wt%) solution while stirring;

[0024] (2) Heat the above solution to 45°C and maintain for 3 hours;

[0025] (3) After the reaction is complete, add 4L of water to dilute the reaction solution, centrifuge the resulting suspension, discard the supernatant, wash the sediment with water, centrifuge again, and repeat the sedimentation process 5 times.

[0026] (4) The sediment was placed in a dialysis bag and dialyzed in deionized water for 3 days, with the water changed 3 times during the period. After the dialysis was completed, the sediment was freeze-dried to obtain cellulose nanocrystals.

[0027] The beneficial effects of this invention are as follows:

[0028] (1) The present invention uses an enzyme catalysis method to prepare microcapsules with antiseptic function. The synthesized microcapsules do not contain harmful substances such as formaldehyde and are environmentally friendly.

[0029] (2) The microcapsules synthesized in this invention have good stability and are easy to disperse in aqueous solution. They can be used as carriers for healing agents in water-based anti-corrosion coatings. The preparation method is simple, the size is controllable, and it is suitable for large-scale production. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of microcapsule synthesis.

[0031] Figure 2 This is a scanning electron microscope image of the microcapsules synthesized in Example 1.

[0032] Figure 3 Salt water corrosion test for anti-corrosion coatings; wherein, (a) salt water corrosion test for example 100 hours; (b) salt water test for example 200 hours; (c) salt water test for comparative example 100 hours; (d) salt water test for comparative example 200 hours. Detailed Implementation

[0033] The technical solution of the present invention will be further explained and described below through specific embodiments.

[0034] A schematic diagram of the synthesis of cellulose nanocrystalline microcapsules according to the present invention is shown below. Figure 1 As shown.

[0035] Example 1: Preparation of microcapsules

[0036] (1) Disperse 0.3g of cellulose nanocrystals in 100mL of water, and then add 20mL of flaxseed oil containing 0.5g of coniferyl alcohol to the above dispersion; (2) Disperse the above emulsion using an ultrasonic disperser at 20kHz and 500W output power for five minutes, and then stir magnetically for 1 hour (300-500RPM) to obtain a Pickering emulsion with an average diameter of about 20 micrometers, using cellulose nanocrystals as stabilizers and flaxseed oil containing coniferyl alcohol as the dispersed oil phase.

[0037] (3) Add 1 mL of hydrogen peroxide (30%) and 0.5 mL of horseradish catalase solution (5 mg / mL) to the above Pickering emulsion and stir overnight at room temperature; under the action of enzymes, coniferol adsorbed on the surface of cellulose nanocrystals polymerizes into artificial lignin, which stabilizes the microcapsules while improving their hydrophobicity.

[0038] (4) The emulsion after the above reaction is completed can be freeze-dried (temperature below -20°C, pressure 2-10Pa) to obtain the desired microcapsules.

[0039] Scanning electron microscope image of the prepared microcapsules is shown below. Figure 2 As shown.

[0040] Example 2: Application of microcapsules in water-based epoxy-based anticorrosive coatings.

[0041] This coating comprises two components, A and B. Component A contains a water-based epoxy emulsion, microcapsules, defoamer, and surface wetting agent. Component B contains a water-based epoxy curing agent, anti-corrosion filler, and anti-flash rust agent. The anti-corrosion coating is obtained by mixing components A and B at a mass ratio of 5:2.

[0042] Component A comprises the following raw materials in parts by weight: 100 parts waterborne epoxy resin, 1 part defoamer, 0.5 parts surface wetting agent, and 10 parts microcapsules.

[0043] Component B comprises the following raw materials in parts by weight: 30 parts water-based epoxy resin curing agent, 10 parts anti-corrosion filler, and 4 parts flash rust inhibitor.

[0044] The waterborne epoxy resin is WEP804, with an epoxy equivalent of 520-560 g / eq and a solid content of 53%; the defoamer is BYK-022; the surface wetting agent is BYK-3455; the epoxy resin curing agent is WH-5, with an active hydrogen equivalent of 150-170 g / eq; the anti-corrosion filler is polyaniline-modified halloysite nanotubes; and the anti-flash rust agent is a 10% sodium nitrite aqueous solution.

[0045] The preparation method of polyaniline-modified halloysite nanotubes is as follows:

[0046] (1) Disperse 20 g halloysite nanotubes in 1 L of 1M hydrochloric acid aqueous solution, sonicate for 10 minutes and then stir magnetically. Add 0.5 L of 1M hydrochloric acid solution containing 40 g aniline to the above solution, continue to stir magnetically for 1 hour, and then stir in an ice water bath for 1 hour.

[0047] (2) Dissolve 98 g of ammonium persulfate in 0.25 L of hydrochloric acid solution, and then slowly add it dropwise to the dispersion prepared in step (1) over a period of 0.5 hours, while maintaining a low temperature. After the addition is complete, the reaction is stirred in an ice-water bath for 2 hours and then brought to room temperature. After 12 hours of reaction, the reaction is centrifuged, washed with 10% sodium hydroxide aqueous solution to remove excess hydrochloric acid, and finally washed with deionized water. The product is then vacuum dried in an oven at 40°C to obtain polyaniline-modified halloysite nanotubes.

[0048] The specific preparation method is as follows: (1) 10 parts by weight of the synthesized microcapsules, 1 part by weight of the defoamer BYK-022 and 0.5 parts by weight of the surface wetting agent BYK-3455 are added to 100 parts by weight of WEP804 and mixed thoroughly to obtain water-based anti-corrosion coating component A.

[0049] (2) Add 10 parts by weight of polyaniline-modified halloysite nanotubes and 4 parts by weight of 10% sodium nitrite aqueous solution to 30 parts by weight of WH-5 and mix thoroughly to obtain water-based anti-corrosion coating component B.

[0050] (3) After thoroughly mixing 5 parts by weight of component A and 2 parts by weight of component B, apply the mixture to Q235 steel plate.

[0051] Comparative Example 1

[0052] Compared with Example 2, Component A includes the following raw materials in parts by weight: 100 parts of waterborne epoxy resin, 1 part of defoamer, and 0.5 parts of surface wetting agent; the rest of the formulation is the same as in Example 2; the preparation method is the same as in Example 2.

[0053] Effect Example

[0054] (a) Saltwater corrosion test: The anti-corrosion coatings obtained in Example 2 and Comparative Example 1 were applied to a 50*100*5mm Q235 clean steel plate with a dry film thickness of 100~120 μm. After curing at room temperature for 7 days, the coating was scratched down to the substrate with a carving tool with a scratch width of 0.3 mm. After standing for 24 h, it was immersed in a 3.5% NaCl aqueous solution. The test results are shown in Table 1.

[0055] Table 1. Results of salt water corrosion tests in the examples and comparative examples

[0056]

[0057] Salt corrosion test results are as follows Figure 3 As shown in the figure, the anti-corrosion coating with the microcapsules prepared in this invention has strong corrosion resistance, and there is no obvious rust at the marked area.

Claims

1. A method for in-situ synthesis of microcapsules using enzyme catalysis, characterized in that, Includes the following steps: (1) Disperse cellulose nanocrystals in water to obtain a cellulose nanocrystal dispersion, and then add flaxseed oil containing coniferyl alcohol to the dispersion to obtain an emulsion; (2) The above emulsion was ultrasonically dispersed and then magnetically stirred to obtain Pickering emulsion; (3) Add hydrogen peroxide and horseradish catalase solution to Pickering emulsion and stir to react; (4) After the reaction is completed, the emulsion is freeze-dried to obtain cellulose nanocrystal microcapsules; In step (3), the volume ratio of hydrogen peroxide to flaxseed oil is 1:20; the volume ratio of hydrogen peroxide to horseradish catalase solution is 1:0.5; and the reaction is carried out by stirring at room temperature for 12-16 hours.

2. The method according to claim 1, characterized in that, In step (1), the concentration of the cellulose nanocrystal dispersion is 3 mg / mL; each 20 mL of the flaxseed oil contains 0.5 g of coniferyl alcohol.

3. The method according to claim 2, characterized in that, The cellulose nanocrystals have a diameter of 5-20 nm and a length of 50-500 nm.

4. The method according to any one of claims 1-3, characterized in that, In step (2), the ultrasonic conditions are 20kHz, 500W output power, and the ultrasonic time is 5min; the magnetic stirring speed is 300-500RPM, and the stirring time is 1h.

5. The method according to claim 1, characterized in that, The concentration of the hydrogen peroxide is 30%; the concentration of the horseradish catalase solution is 5 mg / mL.

6. The application of cellulose nanocrystal microcapsules prepared by the method according to any one of claims 1-5 in anti-corrosion coatings.

7. The application according to claim 6, characterized in that, The anti-corrosion coating comprises component A and component B; the mass ratio of component A to component B in the anti-corrosion coating is 5:

2.

8. The application according to claim 7, characterized in that, Component A comprises the following raw materials in parts by weight: 100 parts of waterborne epoxy resin, 1 part of defoamer, 0.5 parts of surface wetting agent, and 10 parts of microcapsules; Component B comprises the following raw materials in parts by weight: 30 parts of waterborne epoxy resin curing agent, 10 parts of anti-corrosion filler, and 4 parts of anti-flash rust agent.

9. The application according to claim 8, characterized in that, The waterborne epoxy resin is WEP804, with an epoxy equivalent of 520-560 g / eq and a solid content of 53%; the defoamer is BYK-022; the surface wetting agent is BYK-3455; the waterborne epoxy resin curing agent is WH-5, with an active hydrogen equivalent of 150-170 g / eq; the anti-corrosion filler is polyaniline-modified halloysite nanotubes; and the flash rust inhibitor is a 10% sodium nitrite aqueous solution.

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