Fly ash-chitosan composite modified intumescent fire-retardant coating and preparation method

Abstract

The application provides a fly ash-chitosan composite modified intumescent fireproof coating and a preparation method, and belongs to the technical field of fireproof coatings.The coating is prepared from the following components: a water-based self-drying acrylic acid emulsion, a fly ash-chitosan composite filler, a ternary fire-retardant system, a wetting dispersant, a defoaming agent, a leveling agent, a film-forming aid and water.The chitosan is dissolved by glacial acetic acid and combined on the surface of fly ash microspheres to form an intumescent fireproof coating material with good dispersibility, high thermal stability and compactness.When a fire occurs, the ternary system rapidly expands, and the fly ash-chitosan composite filler increases the thickness and temperature resistance of the carbon layer, inhibits the damage of the flame to the coating from two aspects of heat conduction and heat transfer, improves the adhesion strength of the coating and the base material, and fully solves the problems of easy burning and easy falling of the intumescent fireproof coating.

Description

Technical Field

[0001] This invention relates to the field of fire-retardant coating technology, specifically to a fly ash-chitosan composite modified intumescent fire-retardant coating and its preparation method. Background Technology

[0002] Fire is a significant factor hindering the rapid development of industrial engineering and the construction industry. In a fire, the ignition source can rapidly spread to the entire steel structure. The strength and stiffness of the steel decrease with rising temperature, potentially leading to structural instability and collapse above 600℃, causing enormous economic losses and casualties. Intumescent fire-retardant coatings for steel structures, as an intumescent, flame-retardant, and decorative fire-resistant material, rapidly expand upon contact with a fire source to form a char layer, providing excellent protection for the substrate. Currently, the widely used ternary flame-retardant system (IFR) is a composition of an acid source (such as ammonium polyphosphate (APP)), a carbon source (such as pentaerythritol (PER)), and a gas source (such as melamine (MEL)). However, this intumescent fire-retardant coating is primarily composed of organic materials, which typically cannot remain stable for extended periods above 800℃ and gradually decompose, losing their protective function. Research indicates that adding inorganic particles can enhance the fire resistance limit and thermal insulation performance. With the increasing awareness of turning waste into treasure and conserving resources, fly ash may find applications in fire-retardant materials. However, the dispersibility and compatibility of fly ash in fire-retardant systems (especially intumescent fire-retardant coatings) are key factors affecting the thermal insulation performance of fire-retardant coatings. Therefore, how to improve the dispersibility and compatibility of fly ash in coatings and enhance the fire-retardant effect of coatings is a technical problem that needs to be solved in this field. Summary of the Invention

[0003] The purpose of this invention is to propose a fly ash-chitosan composite modified intumescent fireproof coating and its preparation method, which fully solves the technical problems of easy burn-through and easy peeling of intumescent fireproof coatings.

[0004] The technical solution of this invention is implemented as follows:

[0005] This invention provides a fly ash-chitosan composite modified intumescent fire-retardant coating, characterized in that it comprises the following components in parts by weight:

[0006] 20-50 parts of water-based self-drying acrylic emulsion;

[0007] 3-20 parts of fly ash-chitosan composite filler;

[0008] 30-50 parts of ternary flame retardant system;

[0009] 1-5 parts of wetting and dispersing agent;

[0010] 1-5 parts of defoamer;

[0011] Leveling agent 1-5 parts;

[0012] 1-10 parts of film-forming aid;

[0013] 1-10 parts water.

[0014] As a further improvement of the present invention, the water-based self-drying acrylic emulsion is a medium-hard water-based acrylic emulsion with a viscosity of 5000-15000.

[0015] As a further improvement of the present invention, the fly ash-chitosan composite filler is prepared by a stirring reaction of fly ash, glacial acetic acid, and chitosan; the specific reaction steps are as follows:

[0016] Prepare a glacial acetic acid solution of a certain concentration using glacial acetic acid, add chitosan, and stir at 2000 r / min for 4-5 h to fully dissolve the chitosan. Then add fly ash to the continuously stirred solution, adjust the stirring speed to 2500 r / min, mix and stir for 2-3 h, centrifuge the mixture, wash it 2-3 times with deionized water, and dry it continuously in an oven at 60℃ for 24 h to obtain the fly ash-chitosan composite filler.

[0017] As a further improvement of the present invention, the ternary flame retardant system is composed of an acid source, a carbon source, and a gas source in a mass ratio of 5-4:3-2:2-1; wherein the preferred acid source filler is any one or more of ammonium polyphosphate, ammonium polyphosphate, and ammonium hydrogen phosphate; the preferred carbon source filler is one or more of pentaerythritol, pentaerythritol, and sucrose; and the preferred gas source is selected from one or more of melamine, urea, and dicyandiamide.

[0018] As a further improvement of the present invention, the wetting and dispersing agent is one or more of BYK111, BYK180, BYK103, and BYK108.

[0019] As a further improvement of the present invention, the defoamer is one or a combination of several of BYK035, BYK037, BYK066N, and BYK085.

[0020] As a further improvement of the present invention, the leveling agent is one or both of BYK-085 and BYK-077.

[0021] As a further improvement of the present invention, the film-forming aid is one or more of propylene glycol, methyl ether, ethylene glycol, ethyl ether, and n-butanol.

[0022] This invention further protects a method for preparing the above-mentioned fly ash-chitosan composite modified intumescent fire-retardant coating, the preparation steps of which are as follows:

[0023] According to the formula weight ratio, add 20-50 parts of water-based self-drying acrylic emulsion, 3-20 parts of fly ash-chitosan composite filler, 30-50 parts of ternary flame retardant system, 1-5 parts of wetting and dispersing agent, 1-5 parts of defoamer, 1-5 parts of leveling agent, 1-10 parts of film-forming aid, and 1-10 parts of water in sequence. Stir and disperse in a high-speed mixer at a speed of 1000-3000 r / min for 3-5 hours; then reduce the speed to 1000 r / min and stir for 30 minutes. Sieve and bottle for later use to obtain fly ash-chitosan composite modified intumescent fireproof coating.

[0024] The principle of this invention is as follows:

[0025] This invention uses water-based self-drying acrylic resin as the base material, reducing VOC emissions at the source, which can be achieved by diluting with an appropriate amount of water. A ternary flame-retardant system is used as the main flame-retardant mechanism; through acidification, gasification, and foaming reactions, the three components can produce an expanded char layer of suitable thickness, providing a certain degree of barrier against flames and heat. Based on this, a fly ash-chitosan composite filler prepared by a mixing and stirring method is added to the fire-retardant coating. This fully utilizes the thermal stability and void-filling ability of fly ash, while the polyhydroxy structure of chitosan allows it to participate in the char formation reaction upon exposure to flames, further increasing the expansion thickness of the expanded layer. The synergistic effect of both provides the substrate with longer-lasting protection, extending the lifeline for personnel escape and fire rescue.

[0026] The advantages and beneficial effects of this invention are as follows:

[0027] (1) The instruments and equipment used in the preparation of the intumescent fireproof coating for steel structures of the present invention are all commonly used equipment in the coating preparation process. The preparation process is simple and easy to implement. The entire production process uses water as a solvent, achieving "zero" VOCs emissions.

[0028] (2) The fly ash-chitosan composite filler prepared in this invention is mainly derived from coal combustion residues and shrimp shells from thermal power plants, thus achieving waste utilization and energy conservation and emission reduction through material selection. Moreover, fly ash has excellent thermal stability and filling capacity, which fully improves the density of the coating and the strength of the expansion layer, and effectively inhibits the penetration of heat and flame.

[0029] (3) Chitosan, a natural polymer derived from the shells of crustaceans, is widely used in biomedicine, food additives, coating materials, and other fields due to its excellent biocompatibility and unique chemical modification function. Based on the readily available characteristics of fly ash and chitosan, this invention prepares a fly ash-chitosan composite filler and introduces it into a water-based intumescent fire-retardant coating system to enhance the fire resistance limit and heat insulation performance of the coating, achieving a flame-retardant effect of "taking from nature and using it for flame retardancy," which has broad application prospects. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a SEM image of the fly ash-chitosan composite filler.

[0032] Figure 2 This is a cross-sectional view of the intumescent fireproof coating modified by fly ash-chitosan composite in Example 1.

[0033] Figure 3 This is a surface view of the intumescent fireproof coating modified by fly ash-chitosan composite in Example 1.

[0034] Figure 4 This is a SEM image of the intumescent layer of the fly ash-chitosan composite modified intumescent fireproof coating in Example 1.

[0035] Figure 5 This is a SEM image of the expanded coating layer in Comparative Example 1.

[0036] Figure 6 This is a SEM image of the expanded coating layer in Comparative Example 2.

[0037] Figure 7 This is a SEM image of the expanded coating layer in Comparative Example 3. Detailed Implementation

[0038] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] Example 1:

[0040] 1) Dissolve 200 mL of 0.3 M glacial acetic acid in 3.45 mL of glacial acetic acid and add it to a beaker. Add 2.0 g of chitosan to the beaker and stir at 2000 r / min for 4 h to ensure the chitosan is fully dissolved. Then add 4.0 g of fly ash to the continuously stirred solution, adjust the stirring speed to 2500 r / min, and mix for 2 h. Centrifuge the mixture and wash it three times with deionized water. Dry it in an oven at 60℃ for 24 h to obtain the fly ash-chitosan composite filler.

[0041] 2) Add 40 parts of water-based self-drying acrylic emulsion, 5 parts of fly ash-chitosan composite filler, 40 parts of ternary flame retardant system, 3 parts of wetting and dispersing agent, 4 parts of defoamer, 2 parts of leveling agent, 3 parts of film-forming aid, and 3 parts of water in sequence according to the formula weight ratio. Stir and disperse in a high-speed mixer at a speed of 3000 r / min for 3 h; then reduce the speed to 1000 r / min and stir for 30 min. Sieve and bottle for later use to obtain fly ash-chitosan composite modified intumescent fireproof coating.

[0042] 3) Using a spray bottle with an 8-10mm nozzle, spray the above-mentioned intumescent fire-retardant coating sample onto a 3mm thick steel plate surface. Each spray thickness is 1-1.5mm. After the coating is surface dry, repeat the coating until the dry film thickness is 3mm. Cure the coated sample for 5 days and then conduct a combustion test.

[0043] Example 2:

[0044] 1) Dissolve 4.60 mL of glacial acetic acid in 200 mL of a 0.4 M glacial acetic acid solution in a beaker. Add 10.0 g of chitosan to the beaker and stir at 2000 r / min for 4 h to ensure the chitosan is fully dissolved. Then add 10.0 g of fly ash to the continuously stirred solution, adjust the stirring speed to 2500 r / min, and mix for 2 h. Centrifuge the mixture, wash it three times with deionized water, and dry it in an oven at 60℃ for 24 h to obtain the fly ash-chitosan composite filler.

[0045] 2) Add 36 parts of water-based self-drying acrylic emulsion, 10 parts of fly ash-chitosan composite filler, 44 parts of ternary flame retardant system, 3 parts of wetting and dispersing agent, 2 parts of defoamer, 1 part of leveling agent, 1 part of film-forming aid, and 3 parts of water in sequence according to the formula weight ratio. Stir and disperse in a high-speed mixer at a speed of 3000 r / min for 3 h; then reduce the speed to 1000 r / min and stir for 30 min. Sieve and bottle for later use to obtain fly ash-chitosan composite modified intumescent fireproof coating.

[0046] 3) Using a spray bottle with an 8-10mm nozzle, spray the above-mentioned intumescent fireproof coating sample onto a 3mm thick steel plate surface. Each spray thickness is 1-1.5mm. After the coating is surface dry, repeat the coating until the dry film thickness is 3mm. Cure the coated sample for 7 days and then conduct a combustion test.

[0047] Example 3:

[0048] 1) Dissolve 200 mL of 0.4 M glacial acetic acid in 4.60 mL of glacial acetic acid in a beaker. Add 20.0 g of chitosan to the beaker and stir at 2000 r / min for 4 h to ensure the chitosan is fully dissolved. Then add 10.0 g of fly ash to the continuously stirred solution, adjust the stirring speed to 2500 r / min, and mix for 2 h. Centrifuge the mixture, wash it three times with deionized water, and dry it in an oven at 60℃ for 24 h to obtain the fly ash-chitosan composite filler.

[0049] 2) Add 36 parts of water-based self-drying acrylic emulsion, 15 parts of fly ash-chitosan composite filler, 36 parts of ternary flame retardant system, 5 parts of wetting and dispersing agent, 2 parts of defoamer, 1 part of leveling agent, 1 part of film-forming aid, and 4 parts of water in sequence according to the formula weight ratio. Stir and disperse in a high-speed mixer at a speed of 3000 r / min for 3 h; then reduce the speed to 1000 r / min and stir for 30 min. Sieve and bottle for later use to obtain fly ash-chitosan composite modified intumescent fireproof coating.

[0050] 3) Using a spray bottle with an 8-10mm nozzle, spray the above-mentioned intumescent fireproof coating sample onto a 3mm thick steel plate surface. Each spray thickness is 1-1.5mm. After the coating is surface dry, repeat the coating until the dry film thickness is 3mm. Cure the coated sample for 4 days and then conduct a combustion test.

[0051] Comparative Example 1:

[0052] This comparative example uses an acrylic emulsion / ternary flame retardant system, and the only difference from Example 1 is that no fly ash-chitosan composite filler is added.

[0053] Comparative Example 2:

[0054] This comparative example uses an acrylic emulsion / ternary flame retardant system / fly ash system, and the only difference from Example 1 is that fly ash is used instead of fly ash-chitosan composite filler.

[0055] Comparative Example 3:

[0056] This comparative example uses an acrylic emulsion / ternary flame retardant system / chitosan system, and the only difference from Example 1 is that chitosan is used instead of fly ash-chitosan composite filler.

[0057] Taking Example 1 as an example, SEM observation was performed on the fly ash-chitosan composite filler of the present invention. Figure 1 It can be seen that chitosan adheres to the surface of fly ash microspheres, effectively improving the compatibility of fly ash and providing a basis for improving the dispersibility and film-forming properties of fly ash in acrylic emulsion. Figure 2 and Figure 3Cross-sectional and surface views of the fly ash-chitosan composite modified intumescent fire-retardant coating can be observed. The coating exhibits excellent temperature resistance (60 minutes fire resistance) and superior expansion performance, with an expansion height of 33.5 mm (expansion ratio of 10.2 times). The surface morphology of the expanded layer is also more intact. To further analyze the flame-retardant and fire-resistant mechanism of the expanded coating, its microstructure was characterized using SEM. Figure 4 As can be seen, the surface of the coating expansion layer has obvious pores and cracks, which creates conditions for effectively blocking heat transfer and suppressing flame erosion.

[0058] Similarly, the coatings of Examples 2 and 3 both exhibited excellent temperature resistance (Example 2: fire resistance 57 minutes; Example 3: fire resistance 61 minutes) and superior expansion performance (Example 2: expansion ratio 9.5 times; Example 3: expansion ratio 10.3 times).

[0059] In comparison, the expanded layers of the acrylic emulsion / ternary flame retardant system (Comparative Example 1), acrylic emulsion / ternary flame retardant system / fly ash (Comparative Example 2), and acrylic emulsion / ternary flame retardant system / chitosan (Comparative Example 3) coatings (as shown in Figure 1) Figure 5 , Figure 6 and Figure 7 All exhibited obvious porosity and large-area cracks. This is mainly attributed to: the acidification and gasification reactions of the ternary flame retardant system in the coating material, which gradually form an expansion layer; chitosan participating in the carbonization reaction of the expansion layer, promoting the increase in expansion ratio; and fly ash with excellent heat resistance filling the pores of the expansion layer as a heat-resistant material in the residual char after combustion, forming a high-quality expanded carbonized layer, which increases the thermal stability and barrier capacity of the expansion layer.

[0060] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A fly ash-chitosan composite modified intumescent fire-retardant coating, characterized in that, It contains the following components in parts by weight: 20-50 parts of water-based self-drying acrylic emulsion; 3-20 parts of fly ash-chitosan composite filler; 30-50 parts of ternary flame retardant system; 1-5 parts of wetting and dispersing agent; 1-5 parts of defoamer; Leveling agent 1-5 parts; 1-10 parts of film-forming aid; 1-10 parts water; The fly ash-chitosan composite filler is prepared by reacting fly ash, glacial acetic acid, and chitosan through stirring; the specific reaction steps are as follows. Prepare a glacial acetic acid solution of a certain concentration, add chitosan, and stir at 2000 r / min for 4-5 h to fully dissolve the chitosan; then add fly ash to the continuously stirred solution, adjust the stirring speed to 2500 r / min, mix and stir for 2-3 h, centrifuge the mixture, wash it 2-3 times with deionized water, and dry it continuously in an oven at 60℃ for 24 h to obtain fly ash-chitosan composite filler; The preparation steps of the fly ash-chitosan composite modified intumescent fire-retardant coating are as follows: According to the formula weight ratio, add 20-50 parts of water-based self-drying acrylic emulsion, 3-20 parts of fly ash-chitosan composite filler, 30-50 parts of ternary flame retardant system, 1-5 parts of wetting and dispersing agent, 1-5 parts of defoamer, 1-5 parts of leveling agent, 1-10 parts of film-forming aid, and 1-10 parts of water in sequence. Stir and disperse in a high-speed mixer at a speed of 1000-3000 r / min for 3-5 hours. Then reduce the speed to 1000 r / min and stir for 30 minutes. Sieve and bottle for later use to obtain fly ash-chitosan composite modified intumescent fireproof coating.

2. The fly ash-chitosan composite modified intumescent fire-retardant coating according to claim 1, characterized in that, The water-based self-drying acrylic emulsion is a medium-hard water-based acrylic emulsion with a viscosity of 5000-15000.

3. The fly ash-chitosan composite modified intumescent fire-retardant coating according to claim 1, characterized in that, The ternary flame retardant system is composed of an acid source, a carbon source, and a gas source in a mass ratio of 5-4:3-2:2-1; wherein the acid source filler is any one or more of ammonium polyphosphate, ammonium polyphosphate, and ammonium hydrogen phosphate; the carbon source filler is one or more of pentaerythritol, pentaerythritol, and sucrose; and the gas source is selected from melamine, urea, and dicyandiamide.

4. The fly ash-chitosan composite modified intumescent fire-retardant coating according to claim 1, characterized in that, The wetting and dispersing agent is one or more of BYK111, BYK180, BYK103, and BYK108.

5. The fly ash-chitosan composite modified intumescent fire-retardant coating according to claim 1, characterized in that, The defoamer is one or a combination of several of BYK035, BYK037, BYK066N, and BYK085.

6. The fly ash-chitosan composite modified intumescent fire-retardant coating according to claim 1, characterized in that, The leveling agent is one or both of BYK-085 and BYK-077.

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