Polyurea-based water-based intumescent fire retardant coating for steel structure and preparation method thereof

Abstract

The invention relates to the field of coatings, in particular to a polyurea-based water-based intumescent fire retardant coating for a steel structure and a preparation method thereof. The water-based flame-retardant coating comprises the following components in parts by weight: 15-30 parts of water-based polyurea, 20-30 parts of ammonium polyphosphate, 8-10 parts of melamine, 8-10 parts of pentaerythritol, 1-6 parts of a synergist, 8-20 parts of titanium dioxide, 1-4 parts of anhydrous calcium sulfate whisker, 1-3 parts of an auxiliary agent and a proper amount of water, self-made water-based polyurea is used as a base material, ammonium polyphosphate, melamine and pentaerythritol are used as an intumescent flame-retardant system, the proportion and the total addition amount of the three are set, a synergist is added, a B-P-C-N quaternary intumescent system is further formed, inorganic high-temperature-resistant pigment rutile type titanium dioxide is used as an auxiliary material, and the flame-retardant performance of the flame-retardant coating is improved. And the anhydrous calcium sulfate whisker is added as a reinforcing filler, an expanded carbon layer formed when meeting fire is moderate in expansion rate, the carbon layer is more compact and can effectively cope with the impact of hot air flow, and the molecular structure contains ureido and a chemically bonded hydrophilic chain and does not have small molecule migration, so that the water resistance is good.

Description

Technical Field

[0001] This invention relates to the field of coatings, and more particularly to a polyurea-based water-based intumescent fire-retardant coating for steel structures and its preparation method. Background Technology

[0002] In recent years, with the widespread application of steel structure buildings in the domestic market, their fire resistance has become a crucial issue of great concern. While steel structure buildings possess advantages such as high strength, light weight, strong resistance to deformation, rapid construction, and recyclability, their poor fire resistance is an unavoidable problem. In a fire, bare steel can reduce its load-bearing capacity by 40%-45% within 10 minutes, causing the building to collapse. Therefore, applying fire-retardant coatings to the surface of steel structures is a common method for fire protection.

[0003] Currently, with increasingly stringent environmental protection requirements and the implementation of new VOC emission standards, such as GB38597-2020 "Technical Requirements for Coatings with Low Volatile Organic Compound Content" and GB30981.2-2025 "Limits of Hazardous Substances in Coatings," water-based intumescent fire-retardant coatings for steel structures are being used more and more frequently. However, most water-based intumescent fire-retardant coatings for steel structures on the market use film-forming substances such as acrylic emulsions, tert-vinyl acetate emulsions, and vinyl acetate-acrylic emulsions. After exposure to fire, the cohesive strength of the char layer is poor, and under the impact of hot air currents, it is easy to peel off from the surface of the steel structure, leading to failure of fire protection. Moreover, the water resistance of the coating is not very good.

[0004] Therefore, there is an urgent need for a fireproof coating that can effectively withstand the impact of thermal flow and has good water resistance. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a polyurea-based water-based intumescent fire-retardant coating for steel structures and its preparation method.

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

[0007] The first aspect of the present invention is to provide a polyurea-based waterborne intumescent fireproof coating for steel structures, comprising, by weight, 15-30 parts of waterborne polyurea, 20-30 parts of ammonium polyphosphate, 8-10 parts of melamine, 8-10 parts of pentaerythritol, 1-6 parts of synergist, 8-20 parts of titanium dioxide, 1-4 parts of anhydrous calcium sulfate whiskers, 1-3 parts of additives, and an appropriate amount of water.

[0008] Preferably, each part of the aqueous polyurea comprises, by weight, 60-65 parts of polypropylene glycol, 30-35 parts of polyethylene glycol, 40-50 parts of isophorone diisocyanate, 20-30 parts of water-soluble amino-terminated polyether, 20-30 parts of acetone, and 120-130 parts of deionized water.

[0009] More preferably, the water-soluble amino-terminated polyether has a relative molecular mass of 2000-2500 and a functionality of 2.

[0010] Preferably, the synergist is a mixture of zinc borate and boron phosphate modified with a silane coupling agent.

[0011] More preferably, the mass ratio of zinc borate to boron phosphate is (4:1) to (8:1).

[0012] Preferably, the additives include at least one of the following: dispersant, pH adjuster, defoamer, and thickener.

[0013] The second aspect of the present invention is to provide a method for preparing the above-mentioned polyurea-based water-based intumescent fireproof coating for steel structures, comprising the following steps: weighing a portion of the additives and mixing them with deionized water, dispersing them at a speed of 500 r / min, adding a synergist and titanium dioxide, dispersing and grinding them at 1500 r / min until the fineness is qualified, then adding melamine, pentaerythritol, ammonium polyphosphate, and anhydrous calcium sulfate whiskers, dispersing them at 1000 r / min, and finally adding water-based polyurea and the remaining additives, stirring at 500 r / min until uniform, thereby obtaining the polyurea-based water-based intumescent fireproof coating for steel structures.

[0014] Preferably, the preparation steps of the aqueous polyurea include:

[0015] S1. Polypropylene glycol and polyethylene glycol are added to a dry reaction vessel, and after vacuum dehydration, isophorone diisocyanate is slowly added under an inert atmosphere while stirring at 500 r / min to prepare a prepolymer.

[0016] S2. Cool the prepolymer to 40°C, stir at 1500 r / min and slowly add acetone, then disperse for 40 min to obtain the prepolymer emulsion.

[0017] S3. Dissolve the water-soluble amino-terminated polyether in water at 5°C and stir at 500 r / min to disperse it evenly to obtain a water-soluble amino-terminated polyether aqueous solution.

[0018] S4. The prepolymer emulsion is slowly added dropwise to a water-soluble amino-terminated polyether aqueous solution. After the addition is complete, the mixture is stirred, distilled, adjusted for solid content, and filtered in sequence to obtain the waterborne polyurea.

[0019] More preferably, in step S1, the temperature of the vacuum dehydration treatment is 120°C, and the reaction time is 3 hours.

[0020] More preferably, in step S4, the stirring speed is 2500 r / min, the time is 1-2 h, and the temperature is less than 25°C; the distillation temperature is 40°C.

[0021] The present invention adopts the above technical solution and has the following technical effects compared with the prior art:

[0022] This invention uses a self-made waterborne polyurea as the base material, and ammonium polyphosphate, melamine, and pentaerythritol as the intumescent flame retardant system. The proportions and total addition amounts of these three components are set, and a synergist is added to further form a quaternary intumescent system of BPCN. This is supplemented with inorganic high-temperature resistant pigment rutile titanium dioxide, and anhydrous calcium sulfate whiskers are added as reinforcing fillers. The resulting intumescent char layer upon exposure to fire has a moderate expansion ratio and is more dense, effectively resisting the impact of hot air currents. Furthermore, the presence of urea groups in the molecular structure, chemically bonded hydrophilic chains, and absence of small molecule migration contribute to its good water resistance. In this invention, titanium dioxide acts as an active substance participating in the series of chemical reactions of ammonium polyphosphate. The resulting titanium pyrophosphate strengthens and supports the skeleton of the intumescent char layer. The synergist is a mixture of zinc borate and boron phosphate, which can form gradient protection at different temperature stages, strengthening the char layer and promoting its ceramic transformation. Anhydrous calcium sulfate whiskers, as reinforcing fillers, result in a higher cohesive strength and a denser intumescent char layer formed upon exposure to fire. Detailed Implementation

[0023] 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.

[0024] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0025] The present invention will be further described below with reference to specific embodiments, but these are not intended to limit the scope of the invention.

[0026] Example

[0027] This embodiment provides a method for preparing a polyurea-based water-based intumescent fire-retardant coating for steel structures, the steps of which include:

[0028] Deionized water and some additives were added to a high-speed disperser and dispersed at 500 rpm. Then, 4 parts of synergist (zinc borate and boron phosphate modified with silane coupling agent, mass ratio 5:1) and 10 parts of rutile titanium dioxide were added and dispersed and ground at 1500 rpm until the fineness met the requirements. Next, 8 parts of melamine, 8 parts of pentaerythritol, 24 parts of ammonium polyphosphate (using a high degree of polymerization type II product that has been coated and modified), and 2 parts of anhydrous calcium sulfate whiskers were added and dispersed at 1000 rpm. Finally, 20 parts of aqueous polyurea and the remaining additives were added and stirred evenly at 500 rpm. All the above powders are ultrafine raw materials with a fineness ≥500 mesh.

[0029] The preparation steps of the waterborne polyurea include: adding 60 parts of polypropylene glycol and 32 parts of polyethylene glycol to a dry reaction vessel, vacuum dehydrating at 120°C, and determining the moisture content to be <0.05%; lowering the temperature to 80°C, stirring at 500 r / min under nitrogen protection, slowly adding 43 parts of isophorone diisocyanate, and maintaining the temperature for 3 h to obtain a prepolymer; cooling the obtained prepolymer to 40°C, and slowly and uniformly adding 20 parts of acetone under stirring at 1500 r / min to disperse the prepolymer. A prepolymer emulsion was prepared in 40 min. 30 parts of water-soluble amino-terminated polyether were dissolved in water at 5℃ under stirring at 500 r / min and stirred until evenly dispersed. Under stirring at 2500 r / min, the prepolymer emulsion was slowly added dropwise to the aqueous solution of water-soluble amino-terminated polyether at a temperature <25℃. After the addition was complete, stirring was continued for 1.5 h. Finally, the mixture was distilled at 40℃ and deionized water was added to adjust the solid content to 40% and the pH to 7.0-7.5. The mixture was then filtered to obtain waterborne polyurea.

[0030] Detection Examples

[0031] The performance of the polyurea-based waterborne intumescent fireproof coating for steel structures prepared in the examples and commercially available coatings were tested. The furnace temperature of the test furnace conformed to the heating curve of GB / T 9978. The fire resistance limit was calculated based on the time it took for the back temperature of Q235 steel plate to reach 580℃. The results are shown in Table 1.

[0032] Table 1

[0033]

[0034] The water resistance of the polyurea-based water-based intumescent fire-retardant coating for steel structures prepared in the examples was tested according to the GB14907-2018 standard "Fire-retardant Coatings for Steel Structures". The results are shown in Table 2.

[0035] Table 2

[0036]

[0037] As can be seen from the data in the two tables above, the polyurea-based water-based intumescent fireproof coating for steel structures developed in this invention has excellent fireproof and heat insulation effects and a longer fire resistance limit even with a thin coating thickness. Furthermore, the water resistance test results, when tested according to the national standard GB14907-2018 "Fireproof Coatings for Steel Structures", are significantly better than the standard requirements.

[0038] The above description is merely a preferred embodiment of the present invention and does not limit the implementation and protection scope of the present invention. Those skilled in the art should realize that any equivalent substitutions and obvious changes made based on the content of this specification should be included within the protection scope of the present invention.

Claims

1. A polyurea-based water-based intumescent fire-retardant coating for steel structures, characterized in that, By weight, the components include: 15-30 parts of waterborne polyurea, 20-30 parts of ammonium polyphosphate, 8-10 parts of melamine, 8-10 parts of pentaerythritol, 1-6 parts of synergist, 8-20 parts of titanium dioxide, 1-4 parts of anhydrous calcium sulfate whiskers, 1-3 parts of additives, and an appropriate amount of water.

2. The polyurea-based water-based intumescent fire-retardant coating for steel structures according to claim 1, characterized in that, Each part of the aqueous polyurea comprises, by weight, 60-65 parts of polypropylene glycol, 30-35 parts of polyethylene glycol, 40-50 parts of isophorone diisocyanate, 20-30 parts of water-soluble amino-terminated polyether, 20-30 parts of acetone, and 120-130 parts of deionized water.

3. The polyurea-based water-based intumescent fire-retardant coating for steel structures according to claim 2, characterized in that, The water-soluble amino-terminated polyether has a relative molecular mass of 2000-2500 and a functionality of 2.

4. The polyurea-based water-based intumescent fire-retardant coating for steel structures according to claim 1, characterized in that, The synergist is a mixture of zinc borate and boron phosphate modified with a silane coupling agent.

5. The polyurea-based water-based intumescent fire-retardant coating for steel structures according to claim 4, characterized in that, The mass ratio of zinc borate to boron phosphate is (4:1) to (8:1).

6. The polyurea-based waterborne intumescent fire-retardant coating for steel structures according to claim 1, characterized in that, The additives include at least one of the following: dispersant, pH adjuster, defoamer, and thickener.

7. A method for preparing a polyurea-based waterborne intumescent fire-retardant coating for steel structures as described in any one of claims 1-6, characterized in that, The steps include: Weigh out a portion of the additives and mix them with deionized water. Disperse the mixture at 500 r / min. Add the synergist and titanium dioxide, and disperse and grind at 1500 r / min until the fineness is qualified. Then add melamine, pentaerythritol, ammonium polyphosphate, and anhydrous calcium sulfate whiskers, and disperse at 1000 r / min. Finally, add waterborne polyurea and the remaining additives, and stir evenly at 500 r / min to obtain the polyurea-based waterborne intumescent fireproof coating for steel structures.

8. The preparation method according to claim 7, characterized in that, The preparation steps of the aqueous polyurea include: S1. Polypropylene glycol and polyethylene glycol are added to a dry reaction vessel, and after vacuum dehydration, isophorone diisocyanate is slowly added under an inert atmosphere while stirring at 500 r / min to prepare a prepolymer. S2. Cool the prepolymer to 40°C, stir at 1500 r / min and slowly add acetone, then disperse for 40 min to obtain the prepolymer emulsion. S3. Dissolve the water-soluble amino-terminated polyether in water at 5°C and stir at 500 r / min to disperse it evenly to obtain a water-soluble amino-terminated polyether aqueous solution. S4. The prepolymer emulsion is slowly added dropwise to a water-soluble amino-terminated polyether aqueous solution. After the addition is complete, the mixture is stirred, distilled, adjusted for solid content, and filtered in sequence to obtain the waterborne polyurea.

9. The preparation method according to claim 8, characterized in that, In step S1, the temperature of the vacuum dehydration treatment is 120°C; the reaction time is 3 hours.

10. The preparation method according to claim 8, characterized in that, In step S4, the stirring speed is 2500 r / min, the time is 1-2 h, and the temperature is less than 25℃; the distillation temperature is 40℃.

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