CN115491105A - Chitosan-gallic acid synergistically modified water-based rust coating and preparation method thereof - Google Patents

Abstract

The invention discloses a chitosan-gallic acid synergistically modified water-based rusty paint and a preparation method thereof. Dispersing chitosan-gallic acid solution and a dispersing agent in aqueous epoxy emulsion at a high speed to obtain chitosan-gallic acid dispersion slurry; adding the aqueous epoxy emulsion, the chitosan-gallic acid dispersion slurry, the antirust filler, the dispersing agent, the defoaming agent and the anti-settling agent into a stirrer according to a certain mass ratio, and dispersing and grinding at a high speed to obtain a component A of the chitosan-gallic acid aqueous rusty paint; the component B is composed of an amine addition curing agent and a proper amount of water, and the component A and the component B are fully mixed according to a proportion to obtain the coating. The invention utilizes the polyhydroxy structures of chitosan and gallic acid, has good stabilizing and transforming effects on a rust layer, avoids a complex rust removal process, shows good construction performance, has the advantages of safety, environmental protection, quick drying, good adhesive force, excellent corrosion resistance and the like, and has wide application prospect.

Description

Chitosan-gallic acid synergistically modified water-based rust coating and preparation method thereof

technical field

The invention belongs to the field of coatings, and relates to an embroidery coating technology, in particular to a chitosan-gallic acid synergistically modified water-based rust coating and a preparation method thereof.

Background technique

Corrosion is ubiquitous in steel structure equipment. According to statistics, nearly 1/4 of the total output of steel substrates in the world is corroded every year. Paint coating is one of the most efficient and direct methods to protect steel substrates. However, when painting the surface of corroded equipment, the traditional coating process requires first derusting the surface of the corroded equipment to Sa2.5 or above before construction. and time cost, the economic cost of general surface treatment is about 30% to 40% of the total project cost, and the time cost accounts for about 50% of the total painting workload. Serious harm to the environment and construction personnel. Therefore, if the rust coating can be directly constructed on the surface of the corroded steel substrate, it can reduce or save the derusting link, greatly reduce the workload and the cost of painting, and also reduce the health hazards of the rust layer to the construction personnel. Chitosan and gallic acid have a polyhydroxy structure, which can stabilize and transform the rust layer. They have good biocompatibility when used in coatings, and can improve the adhesion, stability and corrosion resistance of the coating. At the same time, compared with solvent-based coatings, water-based rust coatings have the advantages of safety and environmental protection, and have broad application prospects. Using chitosan-gallic acid to synergistically modify water-based rust coatings to prepare corrosion-resistant coatings with excellent performance is of great significance for the reuse of corroded steel substrates and the extension of service life.

Contents of the invention

The purpose of the present invention is to provide a chitosan-gallic acid synergistically modified water-based rust coating and a preparation method thereof, to prepare a safe, environmentally friendly, fast-drying, and good adhesion rust coating, which can effectively reduce the impact of the rust layer on the construction personnel. harm and environmental pollution, and improve the corrosion resistance of water-based rust coatings.

In order to solve the problems of the technologies described above, the technical solution adopted by the present invention is as follows:

The invention provides a chitosan-gallic acid synergistically modified water-based paint with rust, and the paint formula is uniformly mixed by component A and component B according to a certain proportion;

The A component includes the following components and parts by mass:

Component B includes the following components and parts by mass:

10-30 parts of water-based epoxy curing agent

Deionized water 0～30 parts

Preferably, the chitosan-gallic acid dispersion slurry is composed of chitosan with a molecular weight of 500-20000, a gallic acid solution, a dispersant, and an aqueous epoxy emulsion.

Preferably, the water-based epoxy emulsion is any one of the epoxy equivalent 300-800g/eq bisphenol A water-based epoxy resin emulsion, bisphenol F water-based epoxy resin emulsion, and water-based acrylic modified epoxy emulsion one or more combinations.

Preferably, the filler is any one or a combination of talc powder, mica powder, titanium dioxide, zinc phosphate, and aluminum tripolyphosphate.

Preferably, the dispersant is a block polymer copolymer dispersant.

Preferably, the defoamer is a polyether modified silicone defoamer.

Preferably, the anti-settling agent is any one or a combination of fumed silica, organic bentonite, and polyamide wax slurry.

Preferably, the curing agent is a modified amine adduct water-based epoxy curing agent.

The present invention also protects a preparation method of chitosan-gallic acid synergistically modified water-based rust coating, comprising the following steps:

Step (1) Preparation of chitosan-gallic acid dispersion slurry: 3 to 6 parts of gallic acid are made into a wt30% to 60% aqueous solution, and 1 to 3 parts of chitosan with a molecular weight of 500-20000 are added to the solution at the same time , stirred at 25-60°C for 0.5h, then added 0.3-1 part of dispersant, 5-10 parts of water-based epoxy emulsion, and grinded for 1-4 hours with a high-speed disperser to obtain chitosan-gallic acid dispersion slurry;

Step (2) preparation of chitosan-gallic acid synergistically modified water-based rust coating A component: the above-mentioned chitosan-gallic acid dispersion slurry and water-based epoxy emulsion, anti-rust filler, dispersant, defoamer, Anti-sedimentation agent etc. are added into the high-speed disperser according to the mass ratio of the coating formula, wherein the defoamer is added in 3 times, and after grinding and dispersing, component A of chitosan-gallic acid synergistically modified water-based rust coating is obtained;

Step (3) Preparation of component B of chitosan-gallic acid synergistically modified water-based rust coating: mix and dilute 10-30 parts of water-based epoxy curing agent with 0-30 parts of deionized water to obtain chitosan - Gallic acid synergistically modified component B of water-based rust coating;

Step (4) After mixing component A and component B, a chitosan-gallic acid synergistically modified water-based rust coating can be obtained, which can be painted.

Preferably, in step (2), use a high-speed disperser to disperse at high speed and grind until the fineness reaches below 50 μm to obtain component A.

The beneficial effects of the present invention are as follows:

In the chitosan-gallic acid synergistically modified water-based rust coating of the present invention, the adjacent phenolic hydroxyl group of gallic acid can have a good chelation reaction with the rust layer, and quickly transform the fluffy rust layer into a stable dense layer, with rust The coating performance is much better than that of ordinary hydroxyl groups; and the rich amino and hydroxyl polar groups of chitosan can not only optimize the network structure of the resin by self-crosslinking, inhibit the cathodic hydrogen evolution reaction, but also - orbital interaction and adsorption on the anode site on the metal surface, inhibiting the dissolution reaction of the anode metal, that is, inhibiting the generation of new rust, so that the present invention synergistically improves the coating on the base from two aspects of transforming the old rust layer and inhibiting the generation of new rust The protective performance of the material avoids the cumbersome rust removal process, and can be directly coated with rust, which prolongs the service life of the rusty substrate; at the same time, the present invention uses water-based epoxy emulsion as the film-forming substance, and its coating film shows adhesion Excellent, fast drying, outstanding environmental protection and other characteristics.

The present invention uses talc powder, mica powder, zinc phosphate, and aluminum tripolyphosphate as anti-rust pigments and fillers to have good barrier performance and corrosion resistance. The chitosan-gallic acid synergistically modified water-based rust coating of the present invention can Covered on the surface of rusted steel substrates, it can also be used as an anti-corrosion coating on the surface of rust-free steel structures.

Description of drawings

Figure 1 is the SEM image of the unmodified waterborne rust coating.

Figure 2 is the SEM image of chitosan-gallic acid synergistically modified waterborne rust coating.

Figure 3 is a macroscopic view of the rusted steel plate prepared according to the standard "Water-based Primer for Rust Painting".

Figure 4 is a macroscopic view of the neutral salt spray of the unmodified water-based rust coating.

Fig. 5 is a neutral salt spray macroscopic image of chitosan-gallic acid synergistically modified waterborne rust coating.

Fig. 6 is the energy-quist diagram of the electrochemical test of the unmodified coating and the chitosan-gallic acid synergistically modified waterborne rust coating.

Figure 7 is the electrochemical test Bode plot of the unmodified coating and the chitosan-gallic acid synergistically modified waterborne rust coating.

detailed description

The embodiment of a kind of chitosan-gallic acid synergistically modified water-based rust coating and its preparation method proposed by the present invention will be described in further detail below in conjunction with the accompanying drawings and examples. The following examples are only used to illustrate the technical solutions of the present invention more clearly, but not to limit the protection scope of the present invention.

The following is the specific embodiment part.

Example 1

A chitosan-gallic acid synergistically modified water-based rust coating, firstly, 3 parts of gallic acid is made into a 30wt% aqueous solution, and at the same time, 1 part of chitosan with a molecular weight of 500 is added to the solution, stirred at 25°C for 0.5h, and then Add 0.3 parts of dispersant and 10 parts of water-based epoxy emulsion, grind for 1 hour with a high-speed disperser to obtain chitosan-gallic acid dispersion slurry. According to the mass ratio, 20 parts of chitosan-gallic acid dispersion slurry, 30 parts of bisphenol A water-based epoxy resin emulsion, 5 parts of talcum powder, 5 parts of mica powder, 5 parts of zinc phosphate, and 5 parts of aluminum tripolyphosphate were dispersed. 1 part of antifoaming agent, 0.5 part of antifoaming agent, and 2 parts of fumed silicon dioxide, wherein the antifoaming agent is added in 3 times (the same amount is added each time), dispersed at high speed and ground until the fineness reaches below 50 μm, and the chitosan-gallate A component of acid synergistically modified waterborne rust paint. At the same time, 10 parts of amine adduct water-based epoxy curing agent and 10 parts of deionized water were diluted and mixed to obtain component B of chitosan-gallic acid synergistically modified water-based paint with rust. Measure the qualified indicators of component A and component B, and package after passing the test. Mix component A and component B according to the above ratio to obtain a chitosan-gallic acid synergistically modified water-based rust coating that can be painted.

Corresponding performance tests were carried out on chitosan-gallic acid synergistically modified water-based rusty coatings and coating films, and the test results are shown in the table below.

Table 1 Example 1 Chitosan-gallic acid synergistically modified water-based rust coating and film performance evaluation

Example 2

A chitosan-gallic acid synergistically modified water-based rust coating, firstly, 5 parts of gallic acid is made into a 50wt% aqueous solution, and 3 parts of chitosan with a molecular weight of 1000 are added to the solution, and stirred at 40 ° C for 0.5h , and then add 0.5 parts of dispersant and 9 parts of water-based epoxy emulsion, and use a high-speed disperser to grind for 2 hours to obtain chitosan-gallic acid dispersion slurry. According to the mass ratio, 15 parts of chitosan-gallic acid dispersion slurry, 35 parts of bisphenol A water-based epoxy resin emulsion, 10 parts of mica powder, 5 parts of zinc phosphate, 10 parts of aluminum tripolyphosphate, 1 part of dispersant, 0.8 parts of foaming agent, 3 parts of organic bentonite, among which the defoaming agent was added in 3 times, dispersed at high speed and ground to a fineness below 50 μm to obtain component A of chitosan-gallic acid synergistically modified water-based rust coating. At the same time, 15 parts of amine adduct water-based epoxy curing agent and 20 parts of deionized water were diluted and mixed to obtain component B of chitosan-gallic acid synergistically modified water-based paint with rust. Measure the qualified indicators of component A and component B, and package after passing the test. Mix component A and component B according to the above ratio to obtain a chitosan-gallic acid synergistically modified water-based rust coating that can be painted.

Corresponding performance tests were carried out on chitosan-gallic acid synergistically modified water-based rusty coatings and coating films, and the test results are shown in the table below.

Table 2 Example 2 Chitosan-gallic acid synergistically modified water-based rust coating and film performance evaluation

Example 3

A chitosan-gallic acid synergistically modified water-based rust coating, firstly, 6 parts of gallic acid is prepared into a 60wt% aqueous solution, and 2 parts of chitosan with a molecular weight of 10000 are added to the solution, and stirred at 40 ° C for 0.5h , and then add 1 part of dispersant, 15 parts of water-based epoxy emulsion, and use a high-speed disperser to grind for 2.5 hours to obtain chitosan-gallic acid dispersion slurry. According to the mass ratio, 10 parts of chitosan-gallic acid dispersion slurry, 40 parts of bisphenol A water-based epoxy resin emulsion, 10 parts of talcum powder, 10 parts of aluminum tripolyphosphate, 1.5 parts of dispersant, 1 part of defoamer, 1 part of fumed silica and 1 part of organic bentonite, among which the defoamer was added in 3 times, dispersed at high speed and ground until the fineness reached below 50 μm, to obtain component A of chitosan-gallic acid synergistically modified water-based rust coating. At the same time, 20 parts of amine adduct water-based epoxy curing agent and 20 parts of deionized water were diluted and mixed to obtain the B component of chitosan-gallic acid synergistically modified water-based paint with rust. Measure the qualified indicators of component A and component B, and package after passing the test. Mix component A and component B according to the above ratio to obtain a chitosan-gallic acid synergistically modified water-based rust coating that can be painted.

Corresponding performance tests were carried out on chitosan-gallic acid synergistically modified water-based rusty coatings and coating films, and the test results are shown in the table below.

Table 3 Example 3 Chitosan-gallic acid synergistically modified water-based rust coating and film performance evaluation

Example 4

A chitosan-gallic acid synergistically modified water-based rust coating, firstly, 4 parts of gallic acid are prepared into a 40wt% aqueous solution, and 2 parts of chitosan with a molecular weight of 20,000 are added to the solution, and stirred at 50°C for 0.5h , and then add 1.5 parts of dispersant, 10 parts of water-based epoxy emulsion, and use a high-speed disperser to grind for 4 hours to obtain chitosan-gallic acid dispersion slurry. According to the mass ratio, 8 parts of chitosan-gallic acid dispersion slurry, 42 parts of bisphenol A water-based epoxy resin emulsion, 12 parts of mica powder, 12 parts of zinc phosphate, 6 parts of aluminum tripolyphosphate, 2 parts of dispersant, disinfectant 1.5 parts of foaming agent, 4 parts of gas polyamide wax slurry, in which the defoaming agent is added in 3 times, dispersed at high speed and ground until the fineness reaches below 50 μm, and the chitosan-gallic acid synergistically modified water-based rust coating A component is obtained . At the same time, 15 parts of amine adduct water-based epoxy curing agent and 15 parts of deionized water were diluted and mixed to obtain component B of chitosan-gallic acid synergistically modified water-based paint with rust. Measure the qualified indicators of component A and component B, and package after passing the test. Mix component A and component B according to the above ratio to obtain a chitosan-gallic acid synergistically modified water-based rust coating that can be painted.

Corresponding performance tests were carried out on chitosan-gallic acid synergistically modified water-based rusty coatings and coating films, and the test results are shown in the table below.

Table 4 Example 4 Chitosan-gallic acid synergistically modified water-based rust coating and film performance evaluation

From examples 1 to 4, it can be seen that the chitosan-gallic acid synergistically modified water-based rust coating has low VOCs content, no heavy metals, fast drying speed, and can be directly coated on rusty steel substrates and can also be coated on It has the characteristics of stainless steel substrate and other characteristics, and also has the advantages of good adhesion, impact resistance and corrosion resistance. The comparison of the neutral salt spray macroscopic morphology of the unmodified coating and the chitosan-gallic acid synergistically modified waterborne rust coating and the electrochemical test results show that the chitosan-gallic acid synergistic modification The corrosion resistance of the waterborne rust coating is better than that of the unmodified coating. From the SEM images in Figure 2, it can be observed that the fillers in the chitosan-gallic acid synergistically modified water-based rust coating have better compatibility with the base material, and the surface morphology is smoother, which can provide corrosion protection for rusted substrates. Better physical barrier to reduce the occurrence of rust reversion.

The above examples are only used to illustrate embodiments of the present invention, but can not limit the scope of implementation of the present invention, and other technical solutions of the present invention are replaced, combined, modified and simplified without departing from the spirit and scope of the technical solutions of the present invention. All should be covered within the scope of the claims of the present invention.

Claims (10)

1. The chitosan-gallic acid synergistically modified water-based rusty paint is characterized in that a paint formula consists of a component A and a component B, and the components are calculated in parts by mass as follows:

the component A comprises the following components in percentage by weight:

the component B comprises the following components in percentage by weight:

10 to 30 portions of waterborne epoxy curing agent

0 to 30 portions of deionized water

Wherein the molecular weight of the chitosan in the chitosan-gallic acid dispersed slurry is 500-20000.

2. The chitosan-gallic acid synergistically modified aqueous rust paint of claim 1, wherein: the chitosan-gallic acid dispersion slurry is formed by uniformly mixing chitosan with the molecular weight of 500-20000, gallic acid solution, a dispersing agent and aqueous epoxy emulsion.

3. The chitosan-gallic acid synergistically modified aqueous rust coating according to claim 1, wherein: the waterborne epoxy emulsion is any one or a combination of a plurality of bisphenol A waterborne epoxy resin emulsion, bisphenol F waterborne epoxy resin emulsion and waterborne acrylic acid modified epoxy emulsion with the epoxy equivalent of 300-800 g/eq.

4. The chitosan-gallic acid synergistically modified aqueous rust paint of claim 1, wherein: the antirust filler is any one or a combination of talcum powder, mica powder, zinc phosphate and aluminum tripolyphosphate.

5. The chitosan-gallic acid synergistically modified aqueous rust paint of claim 1, wherein: the dispersant is a block polymer copolymer dispersant.

6. The chitosan-gallic acid synergistically modified aqueous rust paint of claim 1, wherein: the defoaming agent is a polyether modified organic silicon defoaming agent.

7. The chitosan-gallic acid synergistically modified aqueous rust paint of claim 1, wherein: the anti-settling agent is any one or a combination of gas-phase silicon dioxide, organic bentonite and polyamide wax slurry.

8. The chitosan-gallic acid synergistically modified aqueous rust coating according to claim 1, wherein: the waterborne epoxy curing agent is a modified amine adduct waterborne epoxy curing agent.

9. The preparation method of the chitosan-gallic acid synergistically modified waterborne rusty paint of any one of claims 1-8, comprising the steps of:

step (1), preparation of chitosan-gallic acid dispersion slurry: preparing 30-60 wt% aqueous solution by 3-6 parts of gallic acid according to the mass part, simultaneously adding 1-3 parts of chitosan with the molecular weight of 500-20000 into the aqueous solution, stirring for 0.5h at 25-60 ℃, then adding 0.3-1 part of dispersing agent and 5-10 parts of aqueous epoxy emulsion, and grinding for 1-4 h by using a high-speed dispersion machine to obtain chitosan-gallic acid dispersed slurry;

step (2), preparation of chitosan-gallic acid synergistically modified water-based rust paint A component: adding the chitosan-gallic acid dispersion slurry, aqueous epoxy emulsion, antirust filler, dispersant, defoaming agent, anti-settling agent and the like into a high-speed dispersion machine according to the mass ratio of the coating formula, wherein the defoaming agent is added for 3 times, and grinding and dispersing to obtain a component A of the chitosan-gallic acid synergistic modified aqueous rusty coating;

step (3), preparation of chitosan-gallic acid synergistically modified water-based rust paint component B: mixing and diluting 10-30 parts of waterborne epoxy curing agent and 0-30 parts of deionized water to obtain a chitosan-gallic acid synergistically modified waterborne rusty paint component B;

and (4) mixing the component A and the component B to obtain the chitosan-gallic acid synergistically modified water-based rust paint, and coating.

10. The preparation method of the chitosan-gallic acid synergistically modified waterborne rusty coating according to claim 9, wherein the preparation method comprises the following steps: in the step (2), a high-speed dispersion machine is used for high-speed dispersion and grinding until the fineness reaches below 50 mu m, and the component A is obtained.

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