Lightweight wear-resistant fireproof coating containing silicon dioxide aerogel for steel structure

Abstract

The invention discloses a lightweight wear-resistant fireproof coating containing silicon dioxide aerogel for a steel structure, and belongs to the technical field of fireproof coatings. Comprising the following raw materials in parts by weight: 40-80 parts of gypsum, 10-20 parts of modified silicon dioxide aerogel, 5-15 parts of nano silicon nitride, 2-6 parts of a retarder, 15-25 parts of water, 5-10 parts of mullite fibers and 1-3 parts of a defoaming agent. The prepared fireproof coating takes gypsum as a matrix, so that the coating is endowed with good heat insulation performance and fireproof performance; wherein the nano silicon nitride can enhance the wear resistance, heat resistance and mechanical properties of the coating; the silicon dioxide aerogel is added, so that the heat insulation performance of the coating is improved, the coating is lightened, and the aerogel is modified, so that the heat insulation performance is further improved, and the waterproof performance of the aerogel is also enhanced; therefore, the prepared coating is light in weight, wear-resistant, heat-resistant, excellent in fireproof performance, high in mechanical strength and good in durability, and has important application value in the technical field of fireproof coatings.

Description

Technical Field

[0001] The invention belongs to the technical field of fire retardant coatings, and in particular relates to a light-weight, wear-resistant fire retardant coating containing silica aerogel for steel structures. Background Art

[0002] As a form of high-rise building structure, steel structure is widely used in the construction industry for its high strength, light weight, good ductility, earthquake resistance and short construction period. However, due to the non-combustibility of steel structure itself, the fire protection and heat insulation of steel structure was once ignored. According to relevant domestic and foreign data reports and tests and statistics of relevant institutions, the fire resistance of steel structure buildings is worse than that of masonry and reinforced concrete structures. The mechanical strength of steel decreases with the increase of temperature. Under the continuous burning of open flames, the mechanical properties of steel, such as yield point, compressive strength, elastic modulus and load capacity, all decrease rapidly, and the supporting capacity is quickly lost, resulting in the collapse of the building. Therefore, fire retardant coatings are often used to protect steel structures to prevent the steel from rapidly heating up in a fire and reducing its strength, and to avoid the steel structure from losing its supporting capacity and causing the collapse of the building.

[0003] At present, steel structure fire retardant coatings are divided into two categories, organic intumescent and inorganic non-intumescent. Among them, organic intumescent fire retardant coatings are popular because of their good decorative properties; but most organic substances are prone to aging, have poor weather resistance, and can only meet the flame retardant requirements, and the fire resistance still needs to be improved. In addition, the flame retardants contained in organic fire retardant coatings are mostly CNP or CNP-Cl systems, which contain substances such as melamine and chlorinated paraffin. These substances will quickly decompose and generate harmful gases such as NO2, CO and HCl after being exposed to high temperatures. These gases have a suffocating effect. Therefore, environmentally friendly inorganic non-intumescent fire retardant coatings are increasingly sought after.

[0004] Inorganic non-expanding fire retardant coatings are mainly based on gypsum or cement, and have the advantages of low use cost and long ultimate fire resistance time. However, the dry density of non-expanding fire retardant coatings is relatively large, and they are thickly coated (the coating thickness is about 3 cm). The coating has a large deadweight, and it is easy to cause the fire retardant coating to fall off during impact or collision. The coating is required to be lightweight. Moreover, many coatings used for steel structures are outdoors and are prone to scratches, causing the coating to fall off. Therefore, it is urgent to invent a lightweight and wear-resistant fire retardant coating to meet the higher demands in the field of fire retardant coating technology. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects of the prior art and provide a lightweight wear-resistant fire-retardant coating containing silica aerogel for steel structures.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A lightweight wear-resistant fire-retardant coating containing silica aerogel for steel structure is prepared by the following steps:

[0008] A1. Stir gypsum, modified silica aerogel, nano silicon nitride, water and retarder at 1200-1800 rpm for 15-45 min to obtain a mixture;

[0009] A2. The mixture obtained in step A1 is mixed with mullite fiber and a defoaming agent, and mechanically stirred for 1-3 hours to obtain a lightweight, wear-resistant and fire-retardant coating containing silica aerogel for steel structure.

[0010] Furthermore, the raw materials are calculated in parts by weight as follows: 40-80 parts of gypsum, 10-20 parts of modified silica aerogel, 5-15 parts of nano silicon nitride, 2-6 parts of retarder, 15-25 parts of water, 5-10 parts of mullite fiber, and 1-3 parts of defoamer.

[0011] Furthermore, the gypsum is a mixture of hemihydrate gypsum and desulfurized gypsum in a mass ratio of 1:3.

[0012] Furthermore, the retarder is one of sodium polyphosphate, sodium hexametaphosphate, sodium citrate, potassium tartrate and sodium acrylate.

[0013] Furthermore, the defoaming agent is one of polyethylene glycol, polypropylene glycol, and silicone defoaming agent.

[0014] The prepared fireproof coating is based on gypsum, which gives the coating good thermal insulation and fireproof properties, and is low-priced, environmentally friendly and energy-saving. Gypsum contains semi-hydrated gypsum. As a gelling material, the bound water in the gypsum can increase the gelling effect of the coating on the one hand. In addition, when a fire occurs, the bound water can also effectively reduce the surface temperature of the steel structure and delay the impact of the fire on the steel structure. The introduced nano silicon nitride is a ceramic powder with excellent performance, good high-temperature strength, high fracture strength, high hardness, and excellent friction and wear resistance. Using it as one of the raw materials can greatly enhance the wear resistance, heat resistance and mechanical properties of the coating. Adding mullite fiber as a reinforcing fiber can not only further enhance the mechanical strength of the coating, but also enhance the hydrophobicity of the silica aerogel.

[0015] Furthermore, the modified silica aerogel is prepared by the following steps:

[0016] S1. After uniform mixing of tetraethyl orthosilicate, ethanol and deionized water, a precursor solution is obtained. An oxalic acid solution (mass fraction 12%) is added dropwise to the precursor solution to adjust the pH to 3-4, thereby obtaining an intermediate 1.

[0017] S2, mixing the intermediate 1, tin tetrachloride pentahydrate, barium chloride dihydrate and an aqueous solution of hydrogen peroxide (mass fraction 28%), and stirring them thoroughly to obtain the intermediate 2;

[0018] S3, after mixing hexamethylenetetramine and intermediate 2, place in an oven at 80°C for 6 hours to cause gelation reaction, add ethanol solution for aging for 12 hours, and exchange solvents for 1-2 days, in order, ethanol once, n-hexane twice, to obtain intermediate 3;

[0019] S4, immersing the intermediate 3 in hexamethyldisilazane, placing it in a water bath at 50° C. and stirring it for 3 h to perform hydrophobic modification. After the modification is completed, washing the residual hexamethyldisilazane with n-hexane, and drying it in an oven to obtain the intermediate 4;

[0020] S5. Place the intermediate 4 in a tubular furnace, introduce an inert gas, and calcine. After the calcination is completed, wait for the tubular furnace to cool naturally to room temperature to obtain a modified silica aerogel.

[0021] Furthermore, in step S1, the ratio of tetraethyl orthosilicate, ethanol, and deionized water is 10 g: 10 mL: 30 mL.

[0022] Furthermore, in step S2, the ratio of the intermediate 1, tin tetrachloride pentahydrate, barium chloride dihydrate, and aqueous hydrogen peroxide solution is 10 g: 2 g: 2 g: 100 mL.

[0023] Furthermore, in step S3, the ratio of hexamethylenetetramine to intermediate 2 is 7.5 g:10 g.

[0024] Furthermore, in step S4, the ratio of the amount of intermediate 3 to hexamethyldisilazane is 10 g:100 mL.

[0025] Furthermore, in step S5, the inert gas is one of nitrogen and argon; the calcination condition is to increase the temperature to 600-800° C. at a heating rate of 5° C. / min and keep the temperature for 2-4 hours.

[0026] Silica aerogel has a high porosity and a large specific surface area, so it has good thermal insulation properties and is lightweight. By modifying the silica aerogel, introducing Sn and Ba energy heteroatoms, and forming SnO2, BaO, and BaSnO3 nanoparticles through calcination to form an amorphous core-shell structure, the porosity of the silica aerogel can be significantly improved, and the thermal insulation properties of the silica aerogel can be further enhanced. In addition, by modifying the surface of the silica aerogel to give it a certain hydrophobicity, the waterproof properties of the silica aerogel can be improved and the durability can be enhanced.

[0027] Beneficial effects of the present invention:

[0028] 1. The fire-retardant coating prepared by the present invention uses gypsum as a matrix to give the coating good thermal insulation and fire-retardant properties, and is low in price, environmentally friendly and energy-saving;

[0029] 2. Gypsum contains semi-hydrated gypsum, which not only enhances the gelling effect of the coating, but also improves the fire retardant performance of the coating;

[0030] 3. Adding nano silicon nitride can greatly enhance the wear resistance, heat resistance and mechanical properties of the coating;

[0031] 4. Adding mullite fiber can enhance the mechanical strength of the coating and the hydrophobicity of silica aerogel;

[0032] 5. Adding silica aerogel improves the thermal insulation performance of the coating and makes the coating lighter. By modifying the silica aerogel, the thermal insulation performance is further improved, and the waterproof performance and durability of the aerogel are also enhanced.

[0033] Therefore, the coating prepared by the present invention is lightweight and wear-resistant, has excellent heat resistance and fire resistance, high mechanical strength, and good durability, and has important application value in the field of fire retardant coating technology. DETAILED DESCRIPTION

[0034] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] Example 1

[0036] Preparation of modified silica aerogel:

[0037] S1. After 10 g of tetraethyl orthosilicate, 10 mL of ethanol and 30 mL of deionized water were mixed and stirred uniformly to obtain a precursor solution, and oxalic acid solution (mass fraction 12%) was added dropwise to the precursor solution to adjust the pH to 3 to obtain intermediate 1;

[0038] S2, 10 g of intermediate 1, 2 g of tin tetrachloride pentahydrate, 2 g of barium chloride dihydrate and 100 mL of aqueous hydrogen peroxide solution (mass fraction 28%) were mixed and stirred thoroughly to obtain intermediate 2;

[0039] S3, 7.5 g of hexamethylenetetramine was mixed with 10 g of intermediate 2, and placed in an oven at 80°C for 6 h to cause gelation reaction, and then aging was performed with ethanol solution for 12 h, and solvent exchange was performed for 1 day, in order of ethanol once and n-hexane twice, to obtain intermediate 3;

[0040] S4, soaking 10 g of intermediate 3 in 100 mL of hexamethyldisilazane, placing in a 50° C. water bath and stirring for 3 h for hydrophobic modification, after the modification is completed, washing the residual hexamethyldisilazane with n-hexane, and drying in an oven to obtain intermediate 4;

[0041] S5. Place the intermediate 4 in a tubular furnace, introduce nitrogen, and heat to 600°C at a heating rate of 5°C / min. Calcinate for 2h. After the calcination is completed, wait for the tubular furnace to cool naturally to room temperature to obtain modified silica aerogel.

[0042] Example 2

[0043] Preparation of modified silica aerogel:

[0044] S1. Mix 20 g of tetraethyl orthosilicate, 20 mL of ethanol and 60 mL of deionized water and stir to obtain a precursor solution. Add oxalic acid solution (mass fraction 12%) to the precursor solution to adjust the pH to 3 to obtain intermediate 1.

[0045] S2, 20 g of intermediate 1, 4 g of tin tetrachloride pentahydrate, 4 g of barium chloride dihydrate and 200 mL of aqueous hydrogen peroxide solution (mass fraction 28%) were mixed and stirred thoroughly to obtain intermediate 2;

[0046] S3, 15 g of hexamethylenetetramine was mixed with 20 g of intermediate 2, and the mixture was placed in an oven at 80°C for 6 h to cause gelation reaction, and then ethanol solution was added for aging for 12 h, and solvent exchange was performed for 2 days, in order of ethanol once and n-hexane twice, to obtain intermediate 3;

[0047] S4, soaking 20g of intermediate 3 in 200mL of hexamethyldisilazane, placing it in a water bath at 50°C and stirring for 3h to perform hydrophobic modification. After the modification is completed, washing the residual hexamethyldisilazane with n-hexane, and drying in an oven to obtain intermediate 4;

[0048] S5. Place the intermediate 4 in a tubular furnace, introduce argon, and heat to 800°C at a heating rate of 5°C / min. Calcinate for 4 hours. After the calcination is completed, wait for the tubular furnace to cool naturally to room temperature to obtain modified silica aerogel.

[0049] Example 3

[0050] A1, 40g of gypsum (mixed with 10g of hemihydrate gypsum and 30g of desulfurized gypsum), 10g of the modified silica aerogel prepared in Example 1, 5g of nano silicon nitride, 15g of water and 2g of sodium polyphosphate were stirred at 1200 rpm for 15min to obtain a mixture;

[0051] A2. The mixture obtained in step A1 was mixed with 5 g of mullite fiber and 1 g of polyethylene glycol defoamer, and mechanically stirred for 1 hour to obtain a lightweight, wear-resistant and fire-retardant coating containing silica aerogel for steel structure.

[0052] Example 4

[0053] A1, 60g of gypsum (mixed with 15g of hemihydrate gypsum and 45g of desulfurized gypsum), 15g of the modified silica aerogel prepared in Example 2, 10g of nano silicon nitride, 20g of water and 4g of sodium hexametaphosphate were stirred at 1500 rpm for 30min to obtain a mixture;

[0054] A2. The mixture obtained in step A1 was mixed with 8 g of mullite fiber and 2 g of polypropylene glycol defoamer, and mechanically stirred for 2 h to obtain a lightweight, wear-resistant and fire-retardant coating containing silica aerogel for steel structure.

[0055] Example 5

[0056] A1, 80g of gypsum (mixed with 20g of hemihydrate gypsum and 60g of desulfurized gypsum), 20g of the modified silica aerogel prepared in Example 2, 15g of nano silicon nitride, 25g of water and 6g of sodium citrate were stirred at 1800 rpm for 45min to obtain a mixture;

[0057] A2. The mixture obtained in step A1 was mixed with 10 g of mullite fiber and 3 g of polypropylene glycol defoamer, and mechanically stirred for 3 h to obtain a lightweight, wear-resistant and fire-retardant coating containing silica aerogel for steel structure.

[0058] Comparative Example 1

[0059] Ordinary silica aerogel of the same mass was used to replace the modified silica aerogel in Example 5, and the remaining steps were the same as in Example 5 to prepare the coating.

[0060] Comparative Example 2

[0061] Use commercially available gypsum-based fire-retardant coatings.

[0062] The coatings of Examples 3-5 and Comparative Examples 1-2 were made into corresponding shapes according to different test standards and subjected to the following performance tests:

[0063] The impact resistance height is measured using the national standard GB / T 1732-1993 "Determination of impact resistance of paint film";

[0064] The thermal conductivity at 160°C is measured using the national standard GB / T 10295-2008 "Determination of Steady-State Thermal Resistance and Related Properties of Insulating Materials - Heat Flow Meter Method". The lower the thermal conductivity, the better the thermal insulation performance.

[0065] The national standard GB 14907-2018 "Fire retardant coating for steel structures" is used to determine the dry density and fire resistance time;

[0066] The wear resistance is measured using the national standard GB / T 23988-2009 "Falling sand method for determination of wear resistance of coatings";

[0067] The measured results are shown in Table 1:

[0068] Table 1

[0069]

[0070]

[0071] The contact angles of Examples 1-2 and common silica aerogel were measured and characterized using a DY-100 contact angle meter to explore the surface hydrophobic properties of the measured samples;

[0072] The measured results are shown in Table 2:

[0073] Table 2

[0074] Test items Example 1 Example 2 Comparative Example 1 Contact angle / ° 153 154 83

[0075] Therefore, the coating prepared by the present invention is lightweight and wear-resistant, has excellent heat resistance and fire resistance, high mechanical strength, good durability, and the surface hydrophobicity of the modified silica aerogel is good, and has important application value in the field of fire retardant coating technology.

[0076] In the description of the specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0077] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A lightweight wear-resistant fire-retardant coating containing silica aerogel for steel structure, characterized in that: The invention comprises the following raw materials in parts by weight: 40-80 parts of gypsum, 10-20 parts of modified silicon dioxide aerogel, 5-15 parts of nano silicon nitride, 2-6 parts of retarder, 15-25 parts of water, 5-10 parts of mullite fiber and 1-3 parts of defoamer.

2. A lightweight wear-resistant fire-retardant coating containing silica aerogel for steel structure according to claim 1, characterized in that: The modified silica aerogel is prepared by the following steps: S1. After uniform mixing of tetraethyl orthosilicate, ethanol and deionized water, a precursor solution is obtained. An oxalic acid solution (mass fraction 12%) is added dropwise to the precursor solution to adjust the pH to 3-4, thereby obtaining an intermediate 1. S2, mixing the intermediate 1, tin tetrachloride pentahydrate, barium chloride dihydrate and an aqueous solution of hydrogen peroxide (mass fraction 28%), and stirring them thoroughly to obtain the intermediate 2; S3, after mixing hexamethylenetetramine and intermediate 2, place in an oven at 80°C for 6 hours to cause gelation reaction, add ethanol solution for aging for 12 hours, and exchange solvents for 1-2 days, in order, ethanol once, n-hexane twice, to obtain intermediate 3; S4, immersing the intermediate 3 in hexamethyldisilazane, placing it in a water bath at 50° C. and stirring it for 3 h to perform hydrophobic modification. After the modification is completed, washing the residual hexamethyldisilazane with n-hexane, and drying it in an oven to obtain the intermediate 4; S5. Place the intermediate 4 in a tubular furnace, introduce an inert gas, and calcine. After the calcination is completed, wait for the tubular furnace to cool naturally to room temperature to obtain a modified silica aerogel.

3. A lightweight wear-resistant fire-retardant coating containing silica aerogel for steel structure according to claim 2, characterized in that: In step S1, the ratio of ethyl orthosilicate, ethanol and deionized water is 10 g: 10 mL: 30 mL.

4. A lightweight wear-resistant fire-retardant coating containing silica aerogel for steel structure according to claim 2, characterized in that: In step S2, the ratio of the intermediate 1, tin tetrachloride pentahydrate, barium chloride dihydrate, and aqueous hydrogen peroxide solution is 10 g: 2 g: 2 g: 100 mL.

5. The lightweight wear-resistant fire-retardant coating containing silica aerogel for steel structure according to claim 2, characterized in that: In step S3, the ratio of hexamethylenetetramine to intermediate 2 is 7.5 g:10 g.

6. A lightweight wear-resistant fire-retardant coating containing silica aerogel for steel structure according to claim 2, characterized in that: In step S4, the ratio of the amount of intermediate 3 to hexamethyldisilazane is 10 g:100 mL.

7. The lightweight wear-resistant fire-retardant coating containing silica aerogel for steel structure according to claim 2, characterized in that: In step S5, the inert gas is one of nitrogen and argon; the calcination conditions are to increase the temperature to 600-800° C. at a heating rate of 5° C. / min and keep the temperature for 2-4 hours.

8. The lightweight wear-resistant fire-retardant coating containing silica aerogel for steel structure according to claim 1, characterized in that: The gypsum is a mixture of hemihydrate gypsum and desulfurized gypsum in a mass ratio of 1:

3.

9. The lightweight wear-resistant fire-retardant coating containing silica aerogel for steel structure according to claim 1, characterized in that: The retarder is one of sodium polyphosphate, sodium hexametaphosphate, sodium citrate, potassium tartrate and sodium acrylate.

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