High-temperature resistant protective coating containing phosphine oxide polyurethane for converter station or substation fire-fighting pipe network and preparation method and application thereof

Abstract

The application discloses a high-temperature-resistant protective coating containing phosphine oxide polyurethane for a converter station or a substation fire-fighting pipe network and a preparation method and application thereof, and the preparation method comprises the following steps: heating and melting trimethylol phosphine oxide, adding a catalyst and amino siloxane, stirring, adding isocyanate, stirring, adding an intumescent flame-retardant system, stirring, adding a catalyst, stirring, and coating on a base material and solidifying. The preparation method is simple, raw materials are cheap and easy to obtain, and coating preparation does not need a solvent. The film-forming substance of the coating can form an intumescent carbon layer when heated, and the coating has excellent protective performance under high-temperature flame (1200 DEG C). The coating has good adhesion on a steel base material, and the coating is not cracked and peeled off after high-temperature flame combustion. The coating is easy to coat, can realize one-time construction molding of the coating, can be used for high-temperature-resistant protection of a substation or a converter station fire-fighting system pipe, and improves fire-fighting reliability of the fire-fighting pipe network.

Description

Technical Field

[0001] The present invention relates to the technical field of fireproof coatings, and in particular to a phosphine oxide-containing polyurethane high-temperature resistant protective coating for a fire protection pipe network of a converter station or a transformer substation, and a preparation method and application thereof. Background Art

[0002] A typical 1000kV UHV AC transformer contains over 150 tons of transformer oil per phase, and a ±800kV UHV converter transformer contains over 120 tons of oil per phase. Due to the high volume of transformer oil, high operating temperatures, and significant heat generation, a fire can sustain combustion for 10 to 20 hours, and in extreme cases, even explode. In the event of a fire in large oil-containing equipment, the firefighting network, facing fires that can reach temperatures of around 1200°C within tens of seconds, can face challenges. Due to insufficient dry-burn resistance, the firefighting main pipes within the protected area can crack, damaging branches and pipelines. This can lead to a loss of pressure in the network and ultimately lead to firefighting failure. Therefore, research on fire protection and thermal insulation for firefighting system networks in large oil-containing equipment in UHV converter stations and substations is urgently needed.

[0003] Applying fire-retardant coatings to the surface of fire-fighting pipe networks can improve their high-temperature resistance during fires in large oil-containing equipment. Fire-retardant coatings can generally be divided into intumescent and non-intumescent types based on their fire protection mechanism. Intumescent fire-retardant coatings absorb heat and expand under high-temperature conditions, forming a foam insulation layer that blocks heat ingress and provides protection. However, current intumescent fire-retardant coatings can generally only withstand flames of 800°C. Once a fire occurs in a converter transformer, temperatures often reach 1200°C and can last for more than two hours. The sustained high temperatures can damage the fire-fighting system within the converter station, rendering it ineffective and preventing it from being activated and effectively extinguishing the fire.

[0004] Intumescent fire-retardant coatings generally consist of a film-forming substance, an intumescent flame retardant system, pigments, fillers, solvents, and additives. The film-forming substance is the most crucial component of an intumescent fire-retardant coating, determining the overall performance of the coating. Common examples include amino resins, polyester resins, epoxy resins, polyurethane resins, nitro resins, and acrylic resins. Common film-forming substances are generally general-purpose resins, offering advantages such as affordability, availability, and good adhesion. However, these film-forming substances often have a low charring rate, leaving only a small amount of residual char after combustion. Film-forming substances alone cannot achieve fireproofing and heat insulation. Instead, the intumescent flame retardant system is required to form an intumescent carbon layer to achieve these properties. Phosphorus-containing polymers can decompose in the condensed phase to form phosphoric acid and polyphosphate compounds, which promote dehydration and carbonization of the polymer matrix, thereby increasing charring. Consequently, phosphorus-containing polymers often have a high charring rate. However, despite producing a high amount of residual char, most phosphorus-containing polymers fail to form an intumescent carbon layer.

[0005] A method for preparing a phosphine oxide-containing hyperbranched polyurethane is disclosed in the prior art (Synthesis of a phosphine oxide-containing hyperbranched flame retardant and research on flame retardancy and mechanism of typical polymers thereof, Ma Chao, University of Science and Technology of China). The method comprises the following steps: first, THPO and DBTDL are dissolved in anhydrous DMF under a nitrogen atmosphere, and then MDI is added in batches. After the MDI is fed into the reaction mixture, the solution is stirred for 24 hours. The nitrogen is then removed, and the solution is slowly added dropwise to methanol to precipitate. The precipitate is filtered, washed with methanol, and vacuum-dried to obtain a light yellow solid product, i.e., a phosphine oxide-containing hyperbranched polyurethane. The phosphine oxide-containing hyperbranched polyurethane can be used as a carbonizing agent and APP to flame-retard PP, and carbonization can be increased. The increased carbon layer plays a better barrier and protective role. However, the above-mentioned disclosed phosphine oxide-containing hyperbranched polyurethane is a solid product with a hyperbranched structure and is only used as a flame retardant additive for PP. Summary of the Invention

[0006] The technical problem to be solved by the present invention is how to improve the high-temperature protection performance of the coating used for the fire protection pipe network of a converter station or a substation.

[0007] The present invention solves the above technical problems through the following technical means:

[0008] A method for preparing a phosphine oxide-containing polyurethane high-temperature resistant protective coating for a fire protection pipe network in a converter station or a substation comprises the following steps: heating and melting trimethylolphosphine oxide, adding a catalyst and aminosiloxane, stirring evenly, then adding isocyanate, stirring evenly, adding an intumescent flame retardant system, stirring evenly, and then adding a catalyst, stirring evenly, coating the material on a substrate, and curing to obtain the phosphine oxide-containing polyurethane high-temperature resistant protective coating for a fire protection pipe network in a converter station or a substation.

[0009] Preferably, the catalyst is triethylenediamine, dibutyltin dilaurate or a mixture of the two.

[0010] Preferably, the aminosiloxane is one or a mixture of aminopropyltriethoxysilane and aminopropyltrimethoxysilane.

[0011] Preferably, the isocyanate is polymethylene polyphenyl polyisocyanate.

[0012] Preferably, the intumescent flame retardant system comprises an acid source, a carbon source, and a gas source; the acid source is selected from ammonium polyphosphate, melamine polyphosphate, or a mixture of the two.

[0013] Preferably, the carbon source is selected from pentaerythritol, dipentaerythritol or a mixture of the two.

[0014] Preferably, the gas source is selected from melamine, dicyandiamide or a mixture of the two.

[0015] Preferably, the acid source accounts for 20%-80% of the total mass of the intumescent flame-retardant system, the carbon source accounts for 5%-50% of the total mass of the intumescent flame-retardant system, and the gas source accounts for 5%-50% of the total mass of the intumescent flame-retardant system.

[0016] Preferably, the intumescent flame-retardant system further comprises a filler with a mass fraction of ≤25%.

[0017] Preferably, the filler is selected from one or a mixture of both of expandable graphite and metal oxide.

[0018] Preferably, the intumescent flame-retardant system comprises a mixture of ammonium polyphosphate, dipentaerythritol, melamine, expandable graphite, and nano-titanium dioxide.

[0019] Preferably, the molar ratio of isocyanate groups in the isocyanate to hydroxyl groups in the trimethylol phosphate is 0.5:1-1.5:1.

[0020] Preferably, the aminosiloxane accounts for 0.5%-5% of the total mass of the trimethylol phosphate and the isocyanate.

[0021] Preferably, the total added mass of the catalyst is 0.01%-1% of the total mass of the trimethylol phosphate and the isocyanate; and the ratio of the mass of the catalyst added in the front to the mass of the catalyst added in the back is 10:1-0.1:1.

[0022] Preferably, the added amount of the intumescent flame-retardant system is 10%-60% of the total mass of the raw materials of the coating.

[0023] Preferably, the curing temperature is room temperature, and the thickness of the coating after curing is 0.1-10 mm.

[0024] Preferably, the trimethylol phosphate is heated and melted in an oven at 80℃.

[0025] The application further provides a high-temperature-resistant protective coating containing phosphine oxide polyurethane for a converter station or substation fire-fighting pipe network, which is prepared by the preparation method of the high-temperature-resistant protective coating containing phosphine oxide polyurethane for a converter station or substation fire-fighting pipe network.

[0026] The application further provides application of the high-temperature-resistant protective coating containing phosphine oxide polyurethane for a converter station or substation fire-fighting pipe network in a converter station or substation fire-fighting pipe network.

[0027] In the coating forming process of the application, the hydroxyl groups of the trimethylol phosphate, the amino groups of the aminosiloxane, and the isocyanate groups react to form a phosphorus-containing polyurea-polyurethane structure (mainly polyurethane), and then the siloxane groups are hydrolyzed and condensed in the air to form a silicon-silicon structure. The reaction process of the coating is exemplified by aminopropyl triethoxysilane and polymethylene polyphenyl polyisocyanate (PM-200), as shown below:

[0028]

[0029] The advantages of the present invention are:

[0030] (1) The film-forming substance of the coating of the present invention is a cross-linked structure formed in the absence of solvent using trimethylolphosphine oxide, aminosiloxane, and isocyanate as raw materials. The base film-forming substance itself forms an expandable carbon layer when heated. The coating of the present invention has excellent protective properties under high-temperature flames (1200°C) and can be used in fire protection pipe networks in substations or converter stations.

[0031] (2) The coating of the present invention has good adhesion performance on the steel substrate, and the coating does not crack or fall off after flame combustion.

[0032] (3) The present invention adopts a method of adding the catalyst in two steps, which makes it easy to control the viscosity of the material, the coating is easy to apply, and the coating can be formed in one step.

[0033] (4) The preparation method of the coating of the present invention is simple, the raw materials are cheap and easily available, and no solvent is required for the preparation of the coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Graph showing the test results of high temperature protection performance of coatings 1-4 in Example 1 of the present invention and Comparative Examples 1-3;

[0035] Figure 2 This is a photo of carbon residue after testing coating 1 in comparative example 1 of the present invention;

[0036] Figure 3 This is a photo of carbon residue after testing coating 2 in comparative example 2 of the present invention;

[0037] Figure 4 This is a photo of carbon residue after testing coating 3 in comparative example 3 of the present invention;

[0038] Figure 5 This is a photo of carbon residue after testing coating 4 in Example 1 of the present invention. DETAILED DESCRIPTION

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with 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. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0040] Unless otherwise specified, the test materials and reagents used in the following examples can be obtained from commercial sources.

[0041] If no specific techniques or conditions are specified in the examples, they can be carried out according to the techniques or conditions described in the literature in the field or according to the product instructions.

[0042] Example 1

[0043] A method for preparing a high-temperature resistant protective coating made of phosphine oxide-containing polyurethane for fire protection pipe networks in converter stations or substations comprises the following steps: first, heating 28.9g of tris(hydroxymethyl)phosphine oxide to melt in an 80°C oven, then adding 0.084g of dibutyltin dilaurate and 1.45g of aminopropyltriethoxysilane and stirring evenly. Then, adding 84.9g of polymethylene polyphenyl polyisocyanate PM-200, stirring evenly, and standing at room temperature for 0.5 hour. Then, adding a mixture of ammonium polyphosphate (23.5g), dipentaerythritol (9.41g), melamine (9.41g), expandable graphite (4.71g), and nano-titanium dioxide (2.35g), which had been pre-dried in an 80°C oven for 12 hours before the experiment. After addition, stirring evenly and standing at room temperature for 0.5 hour. Then, adding 0.042g of dibutyltin dilaurate to the mixture, stirring, and standing at room temperature for 1 hour. At this point, the material became quite viscous and was manually coated onto a steel plate measuring 300 mm x 300 mm x 2.5 mm. The cured coating thickness was controlled to be 2 mm. This coating was designated as Coating 4 and was tested for its high-temperature performance after 10 days at room temperature.

[0044] Example 2

[0045] A method for preparing a high-temperature resistant protective coating made of phosphine oxide-containing polyurethane for fire protection pipe networks in converter stations or substations comprises the following steps: first, heating 46.4g of trishydroxymethylphosphine oxide in an 80°C oven to melt, then adding 0.084g of dibutyltin dilaurate and 1.45g of aminopropyltriethoxysilane and stirring evenly. Then, adding 67.4g of polymethylene polyphenyl polyisocyanate PM-200, stirring evenly, and standing at room temperature for 0.5 hour. Then, adding a mixture of ammonium polyphosphate (23.5g), dipentaerythritol (9.41g), melamine (9.41g), expandable graphite (4.71g), and nano-titanium dioxide (2.35g), which had been pre-dried in an 80°C oven for 12 hours before the experiment. After addition, stirring evenly, and standing at room temperature for 0.5 hour. Then, adding 0.042g of dibutyltin dilaurate, stirring, and standing at room temperature for 1 hour. The material becomes relatively viscous at this point and is manually coated on a steel plate measuring 300 mm x 300 mm x 2.5 mm, controlling the coating thickness to be 2 mm after curing. The coating is obtained after being left at room temperature for 10 days.

[0046] Example 3

[0047] A method for preparing a high-temperature resistant protective coating made of phosphine oxide-containing polyurethane for fire protection pipe networks in converter stations or substations comprises the following steps: first, heating 21.3g of trishydroxymethylphosphine oxide in an 80°C oven to melt, then adding 0.084g of dibutyltin dilaurate and 1.45g of aminopropyltriethoxysilane and stirring evenly. Then, adding 92.5g of polymethylene polyphenyl polyisocyanate PM-200, stirring evenly, and standing at room temperature for 0.5 hour. Then, adding a mixture of ammonium polyphosphate (23.5g), dipentaerythritol (9.41g), melamine (9.41g), expandable graphite (4.71g), and nano-titanium dioxide (2.35g), which had been pre-dried in an 80°C oven for 12 hours before the experiment. After addition, stirring evenly, and standing at room temperature for 0.5 hour. Then, adding 0.042g of dibutyltin dilaurate, stirring, and standing at room temperature for 1 hour. The material becomes relatively viscous at this point and is manually coated on a steel plate measuring 300 mm x 300 mm x 2.5 mm, controlling the coating thickness to be 2 mm after curing. The coating is obtained after being left at room temperature for 10 days.

[0048] Example 4

[0049] A method for preparing a high-temperature resistant protective coating made of phosphine oxide-containing polyurethane for fire protection pipe networks in converter stations or substations comprises the following steps: first, heating 28.9g of tris(hydroxymethyl)phosphine oxide to melt in an 80°C oven. After melting, 0.084g of dibutyltin dilaurate and 0.569g of aminopropyltriethoxysilane are added and stirred evenly. Then, 84.9g of polymethylene polyphenyl polyisocyanate PM-200 is added, stirred evenly, and allowed to stand at room temperature for 0.5 hour. Then, a mixture of ammonium polyphosphate (23.5g), dipentaerythritol (9.41g), melamine (9.41g), expandable graphite (4.71g), and nano-titanium dioxide (2.35g) is added. This mixture has been pre-dried in an 80°C oven for 12 hours before the experiment. After addition, the mixture is stirred evenly and allowed to stand at room temperature for 0.5 hour. Then, 0.042g of dibutyltin dilaurate is added to the mixture, stirred, and allowed to stand at room temperature for 1 hour. The material becomes relatively viscous at this point and is manually coated on a steel plate measuring 300 mm x 300 mm x 2.5 mm, controlling the coating thickness to be 2 mm after curing. The coating is obtained after being left at room temperature for 10 days.

[0050] Example 5

[0051] A method for preparing a high-temperature resistant protective coating made of phosphine oxide-containing polyurethane for fire protection pipe networks in converter stations or substations comprises the following steps: first, heating 28.9g of trishydroxymethylphosphine oxide in an 80°C oven to melt, then adding 0.084g of dibutyltin dilaurate and 5.69g of aminopropyltriethoxysilane and stirring evenly. Then, adding 84.9g of polymethylene polyphenyl polyisocyanate PM-200, stirring evenly, and standing at room temperature for 0.5 hour. Then, adding a mixture of ammonium polyphosphate (23.5g), dipentaerythritol (9.41g), melamine (9.41g), expandable graphite (4.71g), and nano-titanium dioxide (2.35g), which had been pre-dried in an 80°C oven for 12 hours before the experiment. After addition, stirring evenly and standing at room temperature for 0.5 hour. Then, adding 0.042g of dibutyltin dilaurate, stirring, and standing at room temperature for 1 hour. The material becomes relatively viscous at this point and is manually coated on a steel plate measuring 300 mm x 300 mm x 2.5 mm, controlling the coating thickness to be 2 mm after curing. The coating is obtained after being left at room temperature for 10 days.

[0052] Example 6

[0053] A method for preparing a high-temperature resistant protective coating made of phosphine oxide-containing polyurethane for fire protection pipe networks in converter stations or substations comprises the following steps: first, heating 28.9g of trishydroxymethylphosphine oxide in an 80°C oven to melt, then adding 0.084g of dibutyltin dilaurate and 5.69g of aminopropyltriethoxysilane and stirring evenly. Then, adding 84.9g of polymethylene polyphenyl polyisocyanate PM-200, stirring evenly, and standing at room temperature for 0.5 hour. Then, adding a mixture of ammonium polyphosphate (9.88g), dipentaerythritol (14.36g), melamine (14.36g), expandable graphite (7.19g), and nano-titanium dioxide (3.59g), which had been pre-dried in an 80°C oven for 12 hours before the experiment. After addition, stirring evenly, and standing at room temperature for 0.5 hour. Then, adding 0.042g of dibutyltin dilaurate, stirring, and standing at room temperature for 1 hour. The material becomes relatively viscous at this point and is manually coated on a steel plate measuring 300 mm x 300 mm x 2.5 mm, controlling the coating thickness to be 2 mm after curing. The coating is obtained after being left at room temperature for 10 days.

[0054] Example 7

[0055] A method for preparing a high-temperature resistant protective coating made of phosphine oxide-containing polyurethane for fire protection pipe networks in converter stations or substations comprises the following steps: first, heating 28.9g of trishydroxymethylphosphine oxide in an 80°C oven to melt, then adding 0.084g of dibutyltin dilaurate and 5.69g of aminopropyltriethoxysilane and stirring evenly. Then, adding 84.9g of polymethylene polyphenyl polyisocyanate PM-200, stirring evenly, and standing at room temperature for 0.5 hour. Then, adding a mixture of ammonium polyphosphate (39.5g), dipentaerythritol (3.59g), melamine (3.59g), expandable graphite (1.8g), and nano-titanium dioxide (0.9g), which had been pre-dried in an 80°C oven for 12 hours before the experiment. After addition, stirring evenly, and standing at room temperature for 0.5 hour. Then, adding 0.042g of dibutyltin dilaurate to the mixture, stirring, and standing at room temperature for 1 hour. The material becomes relatively viscous at this point and is manually coated on a steel plate measuring 300 mm x 300 mm x 2.5 mm, controlling the coating thickness to be 2 mm after curing. The coating is obtained after being left at room temperature for 10 days.

[0056] Example 8

[0057] A method for preparing a high-temperature resistant protective coating made of phosphine oxide-containing polyurethane for fire protection pipe networks in converter stations or substations comprises the following steps: first, heating 28.9g of tris(hydroxymethyl)phosphine oxide to melt in an 80°C oven, then adding 0.084g of dibutyltin dilaurate and 1.45g of aminopropyltriethoxysilane and stirring evenly. Then, adding 84.9g of polymethylene polyphenyl polyisocyanate PM-200, stirring evenly, and standing at room temperature for 0.5 hour. Then, adding a mixture of ammonium polyphosphate (23.5g), dipentaerythritol (9.41g), melamine (9.41g), expandable graphite (4.71g), and nano-titanium dioxide (2.35g), which had been pre-dried in an 80°C oven for 12 hours before the experiment. After addition, stirring evenly and standing at room temperature for 0.5 hour. Then, adding 0.042g of dibutyltin dilaurate to the mixture, stirring, and standing at room temperature for 1 hour. The material becomes viscous at this point and is manually coated on a steel plate measuring 300 mm x 300 mm x 2.5 mm, controlling the coating thickness to 0.1 mm after curing. The coating is obtained after standing at room temperature for 10 days.

[0058] Example 9

[0059] A method for preparing a high-temperature resistant protective coating made of phosphine oxide-containing polyurethane for fire protection pipe networks in converter stations or substations comprises the following steps: first, heating 28.9g of tris(hydroxymethyl)phosphine oxide to melt in an 80°C oven, then adding 0.084g of dibutyltin dilaurate and 1.45g of aminopropyltriethoxysilane and stirring evenly. Then, adding 84.9g of polymethylene polyphenyl polyisocyanate PM-200, stirring evenly, and standing at room temperature for 0.5 hour. Then, adding a mixture of ammonium polyphosphate (23.5g), dipentaerythritol (9.41g), melamine (9.41g), expandable graphite (4.71g), and nano-titanium dioxide (2.35g), which had been pre-dried in an 80°C oven for 12 hours before the experiment. After addition, stirring evenly and standing at room temperature for 0.5 hour. Then, adding 0.042g of dibutyltin dilaurate to the mixture, stirring, and standing at room temperature for 1 hour. At this point, the material becomes quite viscous and is manually coated on a steel plate measuring 300 mm x 300 mm x 2.5 mm, controlling the coating thickness to be 10 mm after curing. The coating is obtained after being left at room temperature for 10 days.

[0060] Comparative Example 1

[0061] First, heat 34.4g of tris(hydroxymethyl)phosphine oxide) in an 80°C oven to melt. Once melted, add 0.3g of dibutyltin dilaurate and stir thoroughly. Then, add 100g of polymethylene polyphenyl polyisocyanate PM-200, stir thoroughly, and let stand at room temperature for 2 hours. At this point, the material becomes quite viscous. Hand-coat it onto a 300mm x 300mm x 2.5mm steel plate, controlling the cured coating thickness to 2mm. This coating, designated Coating 1, was then tested for its high-temperature resistance after standing at room temperature for 48 hours.

[0062] Comparative Example 2

[0063] First, 28.9g of tris(hydroxymethyl)phosphine oxide was heated to melt in an 80°C oven. After melting, 0.084g of dibutyltin dilaurate was added and stirred. Then, 84g of polymethylene polyphenyl polyisocyanate PM-200 was added, stirred, and allowed to stand at room temperature for 0.5 hour. A mixture of ammonium polyphosphate (26.9g), dipentaerythritol (10.8g), and melamine (10.8g) was added. This mixture had been pre-dried in an 80°C oven for 12 hours before the experiment. After addition, the mixture was stirred and allowed to stand at room temperature for 0.5 hour. Then, 0.042g of dibutyltin dilaurate was added to the mixture, stirred, and allowed to stand at room temperature for 1 hour. At this point, the material became quite viscous and was manually coated onto a 300mm x 300mm x 2.5mm steel plate. The cured coating thickness was controlled to be 2mm. This coating was designated Coating 2 and tested for its high-temperature protective properties after standing at room temperature for 48 hours.

[0064] Comparative Example 3

[0065] First, 28.9g of tris(hydroxymethyl)phosphine oxide was heated to melt in an 80°C oven. After melting, 0.084g of dibutyltin dilaurate was added and stirred. Then, 84g of polymethylene polyphenyl polyisocyanate PM-200 was added, stirred, and allowed to stand at room temperature for 0.5 hour. A mixture of ammonium polyphosphate (23.0g), dipentaerythritol (9.22g), melamine (9.22g), expandable graphite (4.61g), and nano-titanium dioxide (2.30g) was added. This mixture had been pre-dried in an 80°C oven for 12 hours before the experiment. After addition, the mixture was stirred and allowed to stand at room temperature for 0.5 hour. Then, 0.042g of dibutyltin dilaurate was added to the mixture, stirred, and allowed to stand at room temperature for 1 hour. At this point, the material became quite viscous and was manually coated onto a 300mm x 300mm x 2.5mm steel plate, controlling the coating thickness to 2mm after curing. This coating was designated as coating 3, and its high temperature resistance was tested after being placed at room temperature for 48 hours.

[0066] The high temperature protection performance of the coating was simulated by a large plate combustion device test: a flame spray gun was used to aim at the center of the coated side of the steel plate, and the flame temperature of the coating surface was tested by a thermocouple on the coating surface, and the flame temperature of the coating surface was maintained at about 1200 ° C. The temperature of the center of the back-fired side of the steel plate was tested over time (the blank test is the test result of no coating on the steel plate). The coatings prepared in Example 1 and Comparative Examples 1-3 all had good adhesion on the steel plate, and the adhesion of the coatings tested by ASTM D3359 could reach the highest level. The test results of the high temperature protection performance of coatings 1-4 are shown in Figure 1. Figure 1 shown.

[0067] When uncoated, the backside temperature of the steel plate rapidly increased under the influence of a 1200°C flame and quickly stabilized at approximately 493°C. After application of Coating 1, the backside temperature stabilized at approximately 161°C after one hour. Coating 1, composed solely of tris(hydroxymethyl)phosphine oxide and PM-200, exhibited excellent high-temperature resistance. After application of Coating 2, the backside temperature stabilized at approximately 131°C after one hour. Coating 2 contained an intumescent flame retardant (ammonium polyphosphate, dipentaerythritol, and melamine) compared to Coating 1, indicating that the addition of the intumescent flame retardant improved the coating's high-temperature resistance. After application of Coating 3, the backside temperature stabilized at approximately 118°C after one hour. Coating 3 contained fillers (expandable graphite and nano-titanium dioxide) from the intumescent flame retardant compared to Coating 2, indicating that the addition of fillers improved the coating's high-temperature resistance. After application of Coating 4, the backside temperature stabilized at approximately 108°C after one hour. Compared to Coating 3, Coating 4 incorporates aminopropyltriethoxysilane into the film-forming material, demonstrating that the introduction of silicon improves the coating's high-temperature resistance. It's worth noting that the intumescent flame retardant added to Coatings 2, 3, and 4 is 30% of the total weight of the coating's raw materials, indicating that changes in the intumescent flame retardant formulation or the structure of the film-forming material improve the coating's high-temperature resistance.

[0068] Figure 2-5 Shows the top and side views of the coating after combustion. Figure 2 It can be seen that the film-forming material formed by the polymerization of trimethylolphosphine oxide and PM-200, that is, coating 1, forms an expanded carbon layer when it burns, but the surface of this carbon layer is burned out under the action of the continued flame. After adding the intumescent flame retardant, the intumescent carbon layer formed by the heat of coating 2 can be maintained until the test is completed. Coatings 3 and 4 can also maintain a complete carbon layer, and the degree of expansion of the carbon layer is getting higher and higher. Coatings 1-4 do not crack or fall off after the test is completed (all test time is greater than 1h). In addition, the catalyst is added to coating 1 at one time, and the viscosity of the coating can be controlled. However, once the intumescent flame retardant is added (coatings 2-4), it is difficult to control the viscosity of the material by adding the catalyst at one time. At this time, the method of adding the catalyst in two steps is adopted, which can make the viscosity of the material easy to control, the coating easy to apply, and the coating can be formed in one construction. In general, coating 4 has good adhesion to steel, excellent high temperature protection performance, and is easy to form in one construction.

[0069] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing a high-temperature resistant protective coating of polyurethane containing phosphine oxide for fire protection pipe network of a converter station or substation, characterized by: The following steps are involved: Trimethylolphosphine oxide is heated and melted, a catalyst and aminosiloxane are added, and the mixture is stirred evenly. Then, isocyanate is added, and the mixture is stirred evenly. An intumescent flame retardant system is added, and the mixture is stirred evenly. The catalyst is then added, and the mixture is coated on a substrate after stirring. After curing, the phosphine oxide-containing polyurethane high-temperature resistant protective coating for a fire protection pipe network in a converter station or a substation is obtained.

2. The method for preparing a high-temperature resistant protective coating of polyurethane containing phosphine oxide for fire protection pipe network of a converter station or a substation according to claim 1, characterized in that: The catalyst is one of triethylenediamine and dibutyltin dilaurate or a mixture of the two.

3. The method for preparing a high-temperature resistant protective coating of polyurethane containing phosphine oxide for fire protection pipe network of a converter station or a substation according to claim 1, characterized in that: The aminosiloxane is one of aminopropyltriethoxysilane and aminopropyltrimethoxysilane or a mixture of the two.

4. The method for preparing a high-temperature resistant protective coating of polyurethane containing phosphine oxide for fire protection pipe network of a converter station or a substation according to claim 1, characterized in that: The isocyanate is polymethylene polyphenyl polyisocyanate.

5. The method for preparing a high-temperature resistant protective coating of polyurethane containing phosphine oxide for fire protection pipe network of a converter station or a substation according to claim 1, characterized in that: The intumescent flame retardant system comprises an acid source, a carbon source, and a gas source; the acid source is selected from ammonium polyphosphate, melamine polyphosphate, or a mixture of the two.

6. The method for preparing a high-temperature resistant protective coating of polyurethane containing phosphine oxide for fire protection pipe network of a converter station or a substation according to claim 5, characterized in that: The carbon source is selected from pentaerythritol, dipentaerythritol or a mixture of the two.

7. The method for preparing a high-temperature resistant protective coating of polyurethane containing phosphine oxide for fire protection pipe network of a converter station or a substation according to claim 5, characterized in that: The gas source is selected from melamine, dicyandiamide or a mixture of the two.

8. The method for preparing a high-temperature resistant protective coating of polyurethane containing phosphine oxide for fire protection pipe network of a converter station or a substation according to claim 5, characterized in that: The acid source accounts for 20%-80% of the total mass of the intumescent flame retardant system, the carbon source accounts for 5%-50% of the total mass of the intumescent flame retardant system, and the gas source accounts for 5%-50% of the total mass of the intumescent flame retardant system.

9. The method for preparing a high-temperature resistant protective coating of polyurethane containing phosphine oxide for fire protection pipe network of a converter station or a substation according to claim 5, characterized in that: The intumescent flame retardant system further comprises fillers with a mass fraction of ≤25%.

10. The method for preparing a high-temperature resistant protective coating of polyurethane containing phosphine oxide for fire protection pipe network of a converter station or a substation according to claim 9, characterized in that: The filler is selected from expandable graphite, metal oxide or a mixture of the two.

11. The method for preparing a high-temperature resistant protective coating of polyurethane containing phosphine oxide for fire protection pipe network of a converter station or a substation according to any one of claims 1 to 10, characterized in that: The molar ratio of the isocyanate group contained in the isocyanate to the hydroxyl group of trimethylolphosphine oxide is 0.5:1-1.5:

1.

12. The method for preparing a high-temperature resistant protective coating of polyurethane containing phosphine oxide for fire protection pipe network of a converter station or a substation according to any one of claims 1 to 10, characterized in that: The aminosiloxane accounts for 0.5% to 5% of the total mass of trimethylolphosphine oxide and isocyanate.

13. The method for preparing a high-temperature resistant protective coating of polyurethane containing phosphine oxide for fire protection pipe network of a converter station or a substation according to any one of claims 1 to 10, characterized in that: The total added mass of the catalyst is 0.01%-1% of the total mass of trishydroxymethylphosphine oxide and isocyanate; and the mass ratio of the two added catalysts is 10:1-0.1:

1.

14. The method for preparing a high-temperature resistant protective coating of polyurethane containing phosphine oxide for fire protection pipe network of a converter station or a substation according to any one of claims 1 to 10, characterized in that: The added amount of the expansion flame retardant system is 10%-60% of the total mass of the raw materials of the coating.

15. The method for preparing a high-temperature resistant protective coating of polyurethane containing phosphine oxide for fire protection pipe network of a converter station or a transformer substation according to any one of claims 1 to 10, characterized in that: The curing temperature is room temperature, and the thickness of the coating after curing is 0.1-10 mm.

16. A high-temperature protective coating of polyurethane containing phosphine oxide for fire protection pipe network in converter stations or substations, characterized by: The coating is prepared by the method for preparing a high-temperature resistant protective coating of phosphine oxide-containing polyurethane for a fire protection pipe network of a converter station or a substation according to any one of claims 1 to 15.

17. Use of the phosphine oxide-containing polyurethane high-temperature resistant protective coating for a fire protection pipe network in a converter station or a substation as claimed in claim 16 in the fire protection pipe network in a converter station or a substation.

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