CN115888575A - Method for synthesizing microcapsule in situ by enzyme catalysis and application of microcapsule in anticorrosive paint - Google Patents

Abstract

The invention belongs to the field of material preparation, and particularly relates to a method for synthesizing microcapsules in situ by enzyme catalysis and application of the microcapsules in anticorrosive paint. The method specifically comprises the following steps: firstly, preparing cellulose nanocrystal dispersion liquid and linseed oil emulsion containing coniferyl alcohol; ultrasonically dispersing the emulsion, and then carrying out magnetic stirring to obtain a Pickering emulsion; adding hydrogen peroxide and horseradish catalase solution into the pickering emulsion, and stirring for reaction; and (4) freeze-drying the emulsion after the reaction is finished to obtain the cellulose nanocrystal microcapsule. The invention uses the enzyme catalysis method to prepare the microcapsule with the antiseptic function, and the synthesized microcapsule does not contain harmful substances such as formaldehyde and the like and is environment-friendly. The microcapsule synthesized by the invention has good stability, is easy to disperse in aqueous solution, can be used as a carrier of a healing reagent for water-based anticorrosive paint, has simple preparation method and controllable size, and is suitable for large-scale production.

Description

Method for synthesizing microcapsule in situ by enzyme catalysis and application of microcapsule in anticorrosive paint

Technical Field

The invention belongs to the field of material preparation, and particularly relates to a method for synthesizing microcapsules in situ by enzyme catalysis and application of the microcapsules in an anticorrosive coating.

Background

Microcapsules refer to tiny containers having a core-shell structure, with dimensions on the micrometer or nanometer scale, among others. Solid or liquid is used as a core layer, and organic polymers (such as various synthetic resins) are used as shell layers, so that the materials in the core are protected to a certain extent from being deteriorated. When subjected to an external stimulus, the capsule releases the material stored inside to perform a certain function.

The microcapsule preparation technology is to emulsify and disperse the oil phase healing agent in the water solution, and to polymerize the monomer adsorbed on the oil-water interface by the in-situ polymerization method to form the insoluble high polymer. The oil phase healing agent is wrapped in the high polymer to form a functional microcapsule. The commonly used interfacial polymers are urea-formaldehyde resins, formaldehyde-urea-melamine resins, and the like. The resins have good thermal stability, permeability resistance and flexibility, but the resins can use a large amount of formaldehyde in the synthesis process, so that the health of production operators is affected, and the occupational health protection cost is increased undoubtedly. The release of residual formaldehyde during the service of the coating can also have adverse effects on personnel and the environment. Therefore, the development of an environment-friendly microcapsule applied to an anticorrosive coating is a problem to be solved.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a method for synthesizing microcapsules in situ by enzyme catalysis.

The invention also provides an application of the microcapsule synthesized by the method in anticorrosive paint.

The technical scheme adopted by the invention for realizing the purpose is as follows:

the invention provides a method for synthesizing microcapsules in situ by enzyme catalysis, which comprises the following steps:

(1) Dispersing cellulose nanocrystals in water to obtain a cellulose nanocrystal dispersion, and then adding linseed oil containing coniferyl alcohol into the dispersion to obtain an emulsion;

(2) Ultrasonically dispersing the emulsion, and then carrying out magnetic stirring to obtain a Pickering emulsion;

(3) Adding hydrogen peroxide and horseradish catalase solution into the pickering emulsion, and stirring for reaction;

(4) And (4) freeze-drying the emulsion after the reaction is finished to obtain the cellulose nanocrystal microcapsule.

Further, in the step (1), the concentration of the cellulose nanocrystal dispersion liquid is 3mg/mL; the linseed oil contains 0.5g of coniferyl alcohol per 20 mL.

Preferably, the cellulose nanocrystals have a diameter of 5 to 20nm and a length of 50 to 500nm.

Further, in the step (2), the ultrasonic condition is 20kHz,500W output power, and the ultrasonic time is 5min; the rotating speed of the magnetic stirring is 300-500RPM, and the stirring time is 1h.

Further, in the step (3), the volume ratio of the hydrogen peroxide to the linseed oil is 1; the volume ratio of the hydrogen peroxide to the horseradish catalase solution is 1; the reaction is stirred at room temperature for 12-16h.

Further, the concentration of the hydrogen peroxide is 30%; the concentration of the horseradish catalase solution is 5mg/mL.

The invention also provides an application of the cellulose nanocrystal microcapsule prepared by the preparation method in anticorrosive paint.

Further, the anticorrosive paint comprises two components A and B; the mass ratio of the component A to the component B in the anticorrosive paint is 5:2.

preferably, the component A comprises the following raw materials in parts by weight: 100 parts of water-based epoxy resin, 1 part of defoaming agent, 0.5 part of surface wetting agent and 10 parts of microcapsule; the component B comprises the following raw materials in parts by weight: 30 parts of a water-based epoxy resin curing agent, 10 parts of an anticorrosive filler and 4 parts of an anti-flash rust agent.

Further, the waterborne epoxy resin is WEP804, the epoxy equivalent is 520-560 g/eq, and the solid content is 53%; the defoaming agent is BYK-022; the surface wetting agent is BYK-3455, the waterborne epoxy resin curing agent is WH-5, and the equivalent of active hydrogen is 150-170 g/eq; the anticorrosive filler is a halloysite nanotube modified by polyaniline; the flash rust inhibitor is 10% sodium nitrite aqueous solution.

The cellulose nanocrystalline used by the invention is prepared by a sulfuric acid hydrolysis method, and the cellulose nanocrystalline has the length of 50-500nm and the diameter of 5-20 nm. The invention uses the enzyme catalysis in-situ synthesis environment-friendly microcapsule preparation method to replace the traditional polymer microcapsule. The microcapsule takes the artificial lignin/nano cellulose crystal composite material as a shell polymer and takes linseed oil with an antiseptic function as an inner core. The microcapsule can be used in a water-based epoxy anticorrosive coating, improves the barrier property of the epoxy anticorrosive coating, and endows a coating with certain corrosion inhibition and self-repairing capability when the coating is damaged by external force.

The preparation method of the cellulose nanocrystal used by the invention comprises the following steps:

(1) 100g of cellulose powder was added to the 1L of H2SO4 (65 wt%) solution with stirring;

(2) Heating the solution to 45 ℃ and keeping the temperature for 3 hours;

(3) After the reaction is finished, adding 4L of water to dilute the reaction solution, centrifuging the obtained suspension, discarding the supernatant, washing the sediment with water, and performing centrifugal separation, wherein the sediment is repeatedly subjected to water treatment for 5 times;

(4) And putting the sediment into a dialysis bag, putting the dialysis bag into deionized water for dialysis for 3 days, changing water for 3 times, and freeze-drying the sediment after dialysis to obtain the cellulose nanocrystal.

The invention has the beneficial effects that:

(1) The invention uses the enzyme catalysis method to prepare the microcapsule with the antiseptic function, and the synthesized microcapsule does not contain harmful substances such as formaldehyde and the like, thereby being environment-friendly.

(2) The microcapsule synthesized by the invention has good stability, is easy to disperse in aqueous solution, can be used as a carrier of a healing reagent for water-based anticorrosive paint, has simple preparation method and controllable size, and is suitable for large-scale production.

Drawings

FIG. 1 is a schematic diagram of microcapsule synthesis.

Fig. 2 is a scanning electron micrograph of the microcapsule synthesized in example 1.

FIG. 3 is a brine corrosion test of an anticorrosion coating; wherein, (a) the brine corrosion test of the examples was conducted for 100 hours; (b) example brine experiment 200 hours; (c) comparative brine test for 100 hours; (d) comparative example brine test for 200 hours.

Detailed Description

The technical solution of the present invention is further explained and illustrated by the following specific examples.

The synthetic schematic diagram of the cellulose nanocrystalline microcapsule prepared by the invention is shown in figure 1.

EXAMPLE 1 preparation of microcapsules

(1) Dispersing 0.3g of cellulose nanocrystals in 100mL of water, followed by adding 20mL of linseed oil containing 0.5g of coniferyl alcohol to the above dispersion; (2) Dispersing the emulsion by using an ultrasonic disperser, outputting power at 20kHz and 500W, ultrasonically stirring for five minutes by using a magnetic force for 1 hour (300-500 RPM) to obtain a Pickering emulsion (Pickering emulsion) with the average diameter of about 20 micrometers, wherein the Pickering emulsion takes cellulose nanocrystals as a stabilizer and takes linseed oil containing coniferyl alcohol as a dispersed oil phase;

(3) Adding 1mL of hydrogen peroxide (30%) and 0.5mL of horseradish catalase solution (5 mg/mL) into the pickering emulsion, and stirring at room temperature overnight; under the action of enzyme, coniferyl alcohol adsorbed on the surface of the cellulose nanocrystal is polymerized into artificial lignin, so that the hydrophobicity of the microcapsule is improved while the microcapsule is stabilized;

(4) The emulsion after the reaction is frozen and dried (the temperature is below 20 ℃ below zero and the pressure is 2 to 10 Pa) to obtain the required microcapsules.

The scanning electron micrograph of the prepared microcapsule is shown in fig. 2.

Example 2 application of microcapsules in aqueous epoxy based anticorrosive coatings.

The coating comprises two components A and B. Wherein the component A comprises aqueous epoxy emulsion, microcapsule, defoaming agent and surface wetting agent. The component B comprises a water-based epoxy curing agent, an anticorrosive filler and an anti-flash rust agent. Mixing the component A and the component B according to the mass ratio of 5:2 mixing to obtain the anticorrosive paint.

The component A comprises the following raw materials in parts by weight: 100 parts of water-based epoxy resin, 1 part of defoaming agent, 0.5 part of surface wetting agent and 10 parts of microcapsule.

The component B comprises the following raw materials in parts by weight: 30 parts of a water-based epoxy resin curing agent, 10 parts of an anticorrosive filler and 4 parts of an anti-flash rust agent.

Wherein the waterborne epoxy resin is WEP804, the epoxy equivalent is 520-560 g/eq, and the solid content is 53%; the defoaming agent is BYK-022, the surface wetting agent is BYK-3455, the epoxy resin curing agent is WH-5, and the equivalent weight of active hydrogen is 150-170 g/eq; the anticorrosive filler is a polyaniline-modified halloysite nanotube; the flash rust inhibitor is 10% sodium nitrite water solution.

The preparation method of the polyaniline modified halloysite nanotube comprises the following steps:

(1) Dispersing 20 g of halloysite nanotubes in 1L of 1M hydrochloric acid aqueous solution, performing ultrasonic treatment for 10 minutes, performing magnetic stirring, adding 0.5L of 1M hydrochloric acid solution containing 40 g of aniline into the solution, performing magnetic stirring for 1 hour, and then stirring in an ice-water bath for 1 hour;

(2) 98 g of ammonium persulfate was dissolved in 0.25L of a hydrochloric acid solution, and then slowly dropped in the dispersion prepared in step (1) for 0.5 hour, while maintaining a low temperature. After the dropwise addition, the reaction is continued to be stirred in an ice-water bath for 2 hours and then is recovered to the room temperature, after the reaction is carried out for 12 hours, the reaction is centrifuged, 10% sodium hydroxide aqueous solution is washed to remove excessive hydrochloric acid, finally, the reaction product is washed by deionized water, and the product is dried in a vacuum oven at 40 ℃ to obtain the polyaniline modified halloysite nanotube.

The preparation method comprises the following steps: (1) 10 parts by weight of the microcapsule obtained by synthesis, 1 part by weight of defoaming agent BYK-022 and 0.5 part by weight of surface wetting agent BYK-3455 are added into 100 parts by weight of WEP804, and the mixture is fully mixed to obtain the component A of the water-based anticorrosive paint.

(2) Adding 10 parts by weight of polyaniline-modified halloysite nanotubes and 4 parts by weight of 10% sodium nitrite aqueous solution into 30 parts by weight of WH-5, and fully mixing to obtain the component B of the water-based anticorrosive paint.

(3) After 5 parts by weight of the A component and 2 parts by weight of the B component were thoroughly mixed, they were coated on a Q235 steel plate.

Comparative example 1

Compared with the embodiment 2, the component A comprises the following raw materials in parts by weight: 100 parts of waterborne epoxy resin, 1 part of defoamer and 0.5 part of surface wetting agent; the rest of the formulation is the same as example 2; the preparation method is the same as example 2.

Effects of the embodiment

Brine corrosion test: the anticorrosive paint obtained in example 2 and comparative example 1 was coated on a 50 × 100 × 5mm q235 clean steel plate with a dry film thickness of 100 to 120 μm, cured at room temperature for 7 days, then the coating was scribed with an engraving knife to break the coating to a substrate with a scribe width of 0.3 mm, and after standing for 24 hours, the substrate was immersed in a 3.5% NaCl aqueous solution, and the test results are shown in table 1.

TABLE 1 brine Corrosion test results for examples and comparative examples

The results of the brine corrosion test are shown in FIG. 3: as can be seen from the figure, the anticorrosive paint added with the microcapsule prepared by the invention has strong corrosion resistance, and no obvious corrosion at the marked line.

Claims (10)

1. A method for synthesizing microcapsules in situ by enzyme catalysis is characterized by comprising the following steps:

(1) Dispersing cellulose nanocrystals in water to obtain a cellulose nanocrystal dispersion, and then adding linseed oil containing coniferyl alcohol into the dispersion to obtain an emulsion;

(2) Ultrasonically dispersing the emulsion, and then carrying out magnetic stirring to obtain a Pickering emulsion;

(3) Adding hydrogen peroxide and horseradish catalase solution into pickering emulsion, and stirring for reaction;

(4) And (4) freeze-drying the emulsion after the reaction is finished to obtain the cellulose nanocrystal microcapsule.

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

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

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

5. The method according to claim 1 or 2, wherein in step (3), the volume ratio of the hydrogen peroxide to the linseed oil is 1; the volume ratio of the hydrogen peroxide to the horseradish catalase solution is 1; the reaction is stirred at room temperature for 12-16h.

6. The method according to claim 5, wherein the concentration of the hydrogen peroxide is 30%; the concentration of the horseradish catalase solution is 5mg/mL.

7. Use of cellulose nanocrystal microcapsules prepared by the method according to any one of claims 1 to 6 in an anticorrosive coating.

8. The use according to claim 7, wherein the anticorrosive coating comprises two components A, B; the mass ratio of the component A to the component B in the anticorrosive paint is 5:2.

9. the use of claim 8, wherein the component A comprises the following raw materials in parts by weight: 100 parts of water-based epoxy resin, 1 part of defoamer, 0.5 part of surface wetting agent and 10 parts of microcapsule; the component B comprises the following raw materials in parts by weight: 30 parts of waterborne epoxy resin curing agent, 10 parts of anticorrosive filler and 4 parts of flash rust inhibitor.

10. The use according to claim 9, wherein the aqueous epoxy resin is WEP804, the epoxy equivalent is 520-560 g/eq, the solid content is 53%; the defoaming agent is BYK-022; the surface wetting agent is BYK-3455, the waterborne epoxy resin curing agent is WH-5, and the equivalent of active hydrogen is 150-170 g/eq; the anticorrosive filler is a halloysite nanotube modified by polyaniline; the flash rust inhibitor is 10% sodium nitrite aqueous solution.

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