A kind of ablation-resistant glass steel pipeline and its preparation method

Abstract

The application provides an ablation-resistant glass steel pipeline, which comprises a pipeline body, a heat insulation layer, a buffer layer, a protective layer and a fireproof layer arranged in sequence from inside to outside; the pipeline body is formed by impregnating glass fibers with glue and then curing under heating, the glue comprises epoxy resin, phenolic epoxy resin, brominated epoxy resin, phosphate ester flame retardant, toughening agent and leveling agent, and the heat insulation layer is hard polyurethane foam; the buffer layer is made of chloroprene rubber. The application also provides a pipeline preparation method. The pipeline body has certain flame retardance, so that even if the glass steel body contacts open flame, the pipeline body will not be affected, and the fire resistance of the glass steel pipeline is improved, so that the pipeline can keep stable performance and be used normally even under long-term high temperature. Furthermore, each layer has fire resistance, and the layers cooperate with each other, so that the 5-layer structure can achieve stronger ablation resistance, the number of protective layers on the outside of the pipeline is small, the overall structure is simple, the production efficiency is high, and the pipeline is convenient to install and mass-produce.

Description

Technical Field

[0001] This invention relates to the field of fiberglass pipe technology, and in particular to an ablation-resistant fiberglass pipe and its preparation method. Background Technology

[0002] Fiberglass reinforced plastic (FRP) is generally made of unsaturated polyester resin, epoxy resin, or phenolic resin as the matrix material, and glass fiber as the reinforcing material. With continuous economic progress and development, FRP's applications are becoming increasingly widespread due to its unique properties compared to other materials, including good corrosion resistance, light weight, high strength, and strong design flexibility. However, this type of resin has poor flame retardancy, and the resin matrix can burn under open flame, easily causing combustion or explosion accidents. Furthermore, the resin matrix is ​​prone to melting or performance degradation under high-temperature environments.

[0003] In existing technologies, fire-resistant fiberglass pipes have more than six layers of material on their outer layer, sometimes even reaching ten layers. This results in complex, time-consuming, inefficient, and low-tolerance manufacturing processes. Currently, polystyrene foam is commonly used for insulation, but polystyrene foam has poor flame retardancy and low strength, making it prone to detachment and cracking over prolonged use. Overall, current fire-resistant fiberglass pipes suffer from these problems, necessitating a solution that addresses the urgent need for an ablation-resistant fiberglass pipe. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the object of the present invention is:

[0005] Firstly, an ablation-resistant fiberglass pipe is provided, the key feature of which is that it includes a pipe body, a heat insulation layer, a buffer layer, a protective layer and a fireproof layer arranged sequentially from the inside to the outside.

[0006] The pipe body is formed by impregnating glass fiber with an adhesive and then heating and curing it. The adhesive includes flame retardant resin, phosphate ester flame retardant, toughening agent, and leveling agent. The flame retardant resin includes epoxy resin, phenolic epoxy resin, and brominated epoxy resin.

[0007] The insulation layer is rigid polyurethane foam;

[0008] The buffer layer is made of neoprene rubber;

[0009] The protective layer is made of corrosion-resistant metal;

[0010] The fireproof layer is formed by coating with a solvent-free two-component paint.

[0011] In conjunction with the first aspect, in one implementation, the components of the adhesive are mixed in the following parts by weight: 85-95 parts of epoxy resin, 5-20 parts of phenolic epoxy resin, 2-10 parts of brominated epoxy resin, 15-20 parts of phosphate ester flame retardant, 8-12 parts of toughening agent, and 0.01-0.2 parts of leveling agent.

[0012] In conjunction with the first aspect, in one implementation, a curing agent is also added to the adhesive, wherein the curing agent is an aromatic amine curing agent, and the amount added is 25 to 30 parts by weight.

[0013] In conjunction with the first aspect, in one implementation, the insulation layer is made by foaming a phthalic anhydride-type polyurethane foam composite with a flame retardant.

[0014] In conjunction with the first aspect, in one implementation, the thickness of the pipe body is 7-10 mm.

[0015] In conjunction with the first aspect, in one implementation, the thickness of the insulation layer is 30-40 mm.

[0016] In conjunction with the first aspect, in one implementation, the thickness of the buffer layer is 4-8 mm.

[0017] In conjunction with the first aspect, in one implementation, the thickness of the protective layer is 2-4 mm.

[0018] In conjunction with the first aspect, in one implementation, the thickness of the fireproof layer is 4-8 mm.

[0019] Secondly, a method for preparing the ablation-resistant fiberglass pipe described in any implementation of the first aspect is characterized by the following steps:

[0020] S1. Prepare the pipe body by mixing epoxy resin, phenolic epoxy resin, brominated epoxy resin, flame retardant, toughening agent, leveling agent and curing agent evenly according to the weight parts, impregnating alkali-free glass fiber, and then winding it onto the mold. After heating and curing, it is formed.

[0021] S2. First, the formed buffer layer is placed on the outside of the pipe body, and a casting gap is left between the buffer layer and the pipe body.

[0022] S3. Pour rigid polyurethane foam raw material into the pouring gap for foaming. After curing and molding, a heat insulation layer is formed between the buffer layer and the pipe body.

[0023] S4. A protective layer in the shape of a steel tube made of anti-corrosion metal is placed over the buffer layer, and then a fireproof layer is coated on the outside of the protective layer.

[0024] As described above, the ablation-resistant fiberglass pipe and its preparation method of the present invention have at least the following beneficial effects: First, the pipe body is manufactured using refractory resin, wherein phenolic epoxy resin and flame retardant are mixed and used. Excessive flame retardant can reduce pipe performance, but the phenolic structure in the phenolic epoxy resin can compensate for the shortcomings of the flame retardant, giving the pipe body a certain degree of flame retardancy. Even if the fiberglass body comes into contact with an open flame, it will not affect the pipe body. Simultaneously, it improves the fire resistance of the fiberglass pipe, maintaining stable performance and normal use under long-term high temperatures. Furthermore, each layer has a fire-resistant effect, and the layers work together. Only five layers are needed to achieve a stronger ablation resistance effect. The pipe has fewer external protective layers, a simple overall structure, high production efficiency, and is easy to install and mass-produce. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the ablation-resistant fiberglass pipe of the present invention;

[0026] Figure 2 This is a cross-sectional view of the ablation-resistant fiberglass pipe of the present invention;

[0027] Figure 3 This is a graph showing the change in glass transition temperature of the ablation-resistant fiberglass pipe in Embodiment 1 of the present invention.

[0028] Figure 4 This is a graph showing the change in glass transition temperature of the ablation-resistant fiberglass pipe in Comparative Example 1 of the present invention.

[0029] Figure 5 This is a graph showing the change in glass transition temperature of the ablation-resistant fiberglass pipes in Embodiment 2 and Comparative Example 2 of the present invention.

[0030] Attached diagram labels: 1 represents the pipe body, 2 represents the insulation layer, 3 represents the buffer layer, 4 represents the protective layer, and 5 represents the fireproof layer. Detailed Implementation

[0031] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for illustrating the present invention and not for limiting the scope of protection of the present invention.

[0032] It should be noted that the raw materials used in the technical solution of this invention, including epoxy resin, phenolic epoxy resin, brominated epoxy resin, flame retardant, toughening agent, leveling agent, curing agent, rigid polyurethane foam, chloroprene rubber, anti-corrosion metal, and fireproof coating, are all commercially available products.

[0033] First, the technical solution of the present invention provides an ablation-resistant fiberglass pipe, comprising a pipe body 1, a heat insulation layer 2, a buffer layer 3, a protective layer 4, and a fireproof layer 5 arranged sequentially from the inside to the outside.

[0034] The pipe body 1 is formed by impregnating glass fiber with an adhesive and then heating and curing it. The adhesive includes flame retardant resin, phosphate ester flame retardant, toughening agent, and leveling agent. The flame retardant resin includes epoxy resin, phenolic epoxy resin, and brominated epoxy resin.

[0035] The insulation layer 2 is rigid polyurethane foam.

[0036] The buffer layer 3 is made of neoprene rubber. Neoprene rubber has high temperature resistance, high flame retardancy, and a large number of polar bonds in its structure, resulting in strong intermolecular forces. Therefore, it has good mechanical properties and will not break or be damaged during prolonged high-temperature use.

[0037] The protective layer 4 is made of corrosion-resistant metal, such as stainless steel.

[0038] The fireproof layer 5 is coated with a solvent-free two-component paint, such as an intumescent fireproof coating. The fireproof coating is applied to the surface of the protective layer 4. This fireproof coating carbonizes and expands when heated during an external fire, preventing heat from being transferred inwards. Through the insulation effect of each layer of material, the temperature is lower when heat reaches the pipe body 1, thus protecting the pipe.

[0039] In summary, the pipe body 1, made of fiberglass material, possesses a certain degree of flame retardancy, ensuring that even if the fiberglass body comes into contact with an open flame, it will not be affected. Furthermore, the fiberglass pipe exhibits improved temperature resistance, maintaining stable performance and normal operation under prolonged high temperatures. Each layer protecting the pipe body 1 also possesses a certain degree of flame retardancy, guaranteeing the pipe's safety even if damage occurs in the middle. The fireproof layer 5 carbonizes and expands upon exposure to external fire, preventing heat from transferring inwards. Through the insulation effect of each layer of material, heat reaches the fiberglass pipe at a lower temperature, thus protecting the pipe.

[0040] In some embodiments, the insulation layer 2 is made by foaming a phthalic anhydride-based polyurethane foam composite with a flame retardant. A phthalic anhydride resin polyol with good flame retardancy is used, and a phosphate ester flame retardant is added to the formulation to further improve the material's flame retardancy. Simultaneously, the foam made from phthalic anhydride polyester has high strength, good mechanical properties, good adhesion to other materials, and will not detach during prolonged high-temperature use.

[0041] Currently, adding common flame retardants can help pipes achieve a certain flame-retardant effect. However, simply adding flame retardants results in poor flame-retardant effect with small amounts and high flame-retardant effect with large amounts, but the overall performance of the pipe will decrease. Therefore, in some embodiments of this invention, the adhesive uses the following components in parts by weight: 85-95 parts epoxy resin, 5-20 parts phenolic epoxy resin, 2-10 parts brominated epoxy resin, 15-20 parts phosphate ester flame retardant, 8-12 parts toughening agent, and 0.01-0.2 parts leveling agent. Using phosphate ester flame retardants and flame-retardant resins in combination, along with phenolic epoxy resin, can reduce pipe performance due to the high amount of phosphate ester flame retardant. However, the phenolic structure in a certain amount of phenolic epoxy resin can compensate for the shortcomings of phosphate ester flame retardants. However, excessive phenolic epoxy will increase the resin viscosity, affecting the production process and altering the pipe's performance.

[0042] In some embodiments, the curing agent is an aromatic amine curing agent, such as DL-50, and the amount added is 25 to 30 parts by weight.

[0043] In some embodiments, the pipe body 1 has a thickness of 7-10 mm. The heat insulation layer 2 has a thickness of 30-40 mm. The buffer layer 3 has a thickness of 4-8 mm. The protective layer 4 has a thickness of 2-4 mm. The fireproof layer 5 has a thickness of 4-8 mm.

[0044] Secondly, a method for preparing the ablation-resistant fiberglass pipe described in any of the above embodiments is also provided, which is carried out according to the following steps:

[0045] S1. Prepare the pipe body 1 by mixing epoxy resin, phenolic epoxy resin, brominated epoxy resin, flame retardant, toughening agent, leveling agent and curing agent evenly according to the weight parts, impregnating alkali-free glass fiber, and then winding it onto the mold. After heating and curing, it is formed.

[0046] S2. First, the formed buffer layer 3 is fitted over the pipe body 1, and a casting gap is left between the buffer layer 3 and the pipe body 1.

[0047] S3. Pour rigid polyurethane foam raw material into the pouring gap for foaming. After curing and molding, a heat insulation layer 2 is formed between the buffer layer 3 and the pipe body 1.

[0048] S4. A protective layer 4 made of corrosion-resistant metal in the shape of a steel tube is placed over the buffer layer 3, and then a fireproof layer 5 is coated on the outside of the protective layer 4.

[0049] The present invention will be described in detail below through specific examples and embodiments. It should also be understood that the following embodiments are only for specific illustration of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below.

[0050] Example 1

[0051] S1. Prepare the pipe body 1 by mixing 85 parts of epoxy resin, 20 parts of phenolic-epoxy resin, 5 parts of brominated epoxy resin, 15 parts of phosphate ester flame retardant, 27 parts of amine curing agent, 10 parts of toughening agent and 0.1 parts of leveling agent evenly, impregnating alkali-free glass fiber, and then winding it onto a mold with a winding thickness of 8 mm. After heating and curing, the pipe body 1 is formed.

[0052] S2. A 6mm thick tube body made of neoprene rubber is used as a buffer layer 3. The buffer layer 3 is first fitted over the pipe body 1, and a 35mm casting gap is left between the buffer layer 3 and the pipe body 1.

[0053] S3. Pour phthalic anhydride-type polyurethane foam mixture and flame retardant into the pouring gap and foam together. After curing, a 35mm heat insulation layer 2 is formed between the buffer layer 3 and the pipe body 1.

[0054] S4. Use a 3mm thick stainless steel pipe as a protective layer 4, put the stainless steel pipe over the buffer layer 3, and then coat the outside of the stainless steel pipe with a solvent-free two-component coating to form a 5mm fireproof layer 5.

[0055] Example 2

[0056] S1. Prepare the pipe body 1 by mixing 90 parts of epoxy resin, 10 parts of phenolic-epoxy resin, 8 parts of brominated epoxy resin, 18 parts of phosphate ester flame retardant, 25 parts of amine curing agent, 8 parts of toughening agent and 0.15 parts of leveling agent evenly, impregnating alkali-free glass fiber, and then winding it onto a mold with a winding thickness of 8mm. After heating and curing, the pipe body 1 is formed.

[0057] S2. A 6mm thick tube body made of neoprene rubber is used as a buffer layer 3. The buffer layer 3 is first fitted over the pipe body 1, and a 35mm casting gap is left between the buffer layer 3 and the pipe body 1.

[0058] S3. Pour phthalic anhydride-type polyurethane foam mixture and flame retardant into the pouring gap and foam together. After curing, a 35mm heat insulation layer 2 is formed between the buffer layer 3 and the pipe body 1.

[0059] S4. Use a 3mm thick stainless steel pipe as a protective layer 4, put the stainless steel pipe over the buffer layer 3, and then coat the outside of the stainless steel pipe with a solvent-free two-component coating to form a 5mm fireproof layer 5.

[0060] Example 3

[0061] S1. Prepare the pipe body 1 by mixing 85 parts of epoxy resin, 15 parts of phenolic-epoxy resin, 7 parts of brominated epoxy resin, 20 parts of phosphate ester flame retardant, 26 parts of amine curing agent, 9 parts of toughening agent, and 0.12 parts of leveling agent evenly, impregnating the mixture with alkali-free glass fiber, and then winding it onto a mold with a winding thickness of 8 mm. After heating and curing, the pipe body 1 is formed.

[0062] S2. A 6mm thick tube body made of neoprene rubber is used as a buffer layer 3. The buffer layer 3 is first fitted over the pipe body 1, and a 35mm casting gap is left between the buffer layer 3 and the pipe body 1.

[0063] S3. Pour phthalic anhydride-type polyurethane foam mixture and flame retardant into the pouring gap and foam together. After curing, a 37mm heat insulation layer 2 is formed between the buffer layer 3 and the pipe body 1.

[0064] S4. Use a 3mm thick stainless steel pipe as a protective layer 4, put the stainless steel pipe over the buffer layer 3, and then coat the outside of the stainless steel pipe with a solvent-free two-component coating to form a 5mm fireproof layer 5.

[0065] Example 4

[0066] S1. Prepare the pipe body 1 by mixing 95 parts of epoxy resin, 5 parts of phenolic-epoxy resin, 2 parts of brominated epoxy resin, 15 parts of phosphate ester flame retardant, 25 parts of amine curing agent, 8 parts of toughening agent, and 0.01 parts of leveling agent evenly, impregnating the mixture with alkali-free glass fiber, and then winding it onto a mold with a winding thickness of 10 mm. After heating and curing, the pipe body 1 is formed.

[0067] S2. A 4mm thick tube body made of neoprene rubber is used as a buffer layer 3. The buffer layer 3 is first fitted over the pipe body 1, and a 40mm casting gap is left between the buffer layer 3 and the pipe body 1.

[0068] S3. Pour phthalic anhydride-type polyurethane foam mixture and flame retardant into the pouring gap and foam together. After curing, a 40mm heat insulation layer 2 is formed between the buffer layer 3 and the pipe body 1.

[0069] S4. Use a 2mm thick stainless steel pipe as a protective layer 4, put the stainless steel pipe over the buffer layer 3, and then coat the outside of the stainless steel pipe with a solvent-free two-component coating to form a 4mm fireproof layer 5.

[0070] Example 5

[0071] S1. Prepare the pipe body 1 by mixing 86 parts of epoxy resin, 20 parts of phenolic-epoxy resin, 10 parts of brominated epoxy resin, 15 parts of phosphate ester flame retardant, 30 parts of amine curing agent, 12 parts of toughening agent and 0.2 parts of leveling agent evenly, impregnating the mixture with alkali-free glass fiber, and then winding it onto a mold with a winding thickness of 7 mm. After heating and curing, the pipe body 1 is formed.

[0072] S2. A pipe body with a thickness of 8mm made of neoprene rubber is used as a buffer layer 3. The buffer layer 3 is first fitted over the pipe body 1, and a casting gap of 30mm is left between the buffer layer 3 and the pipe body 1.

[0073] S3. Pour phthalic anhydride-type polyurethane foam mixture and flame retardant into the pouring gap and foam together. After curing, a 30mm heat insulation layer 2 is formed between the buffer layer 3 and the pipe body 1.

[0074] S4. Use a 4mm thick stainless steel pipe as a protective layer 4, put the stainless steel pipe over the buffer layer 3, and then coat the outside of the stainless steel pipe with a solvent-free two-component coating to form an 8mm fireproof layer 5.

[0075] Comparative Example 1

[0076] S1. Prepare pipe body 1 by mixing 110 parts of epoxy resin, 15 parts of phosphate ester flame retardant, 27 parts of amine curing agent, 10 parts of toughening agent and 0.1 parts of leveling agent evenly, impregnating alkali-free glass fiber, and then winding it onto a mold with a winding thickness of 8mm. After heating and curing, pipe body 1 is formed.

[0077] S2. A 6mm thick tube body made of neoprene rubber is used as a buffer layer 3. The buffer layer 3 is first fitted over the pipe body 1, and a 35mm casting gap is left between the buffer layer 3 and the pipe body 1.

[0078] S3. Pour phthalic anhydride-type polyurethane foam mixture and flame retardant into the pouring gap and foam together. After curing, a 35mm heat insulation layer 2 is formed between the buffer layer 3 and the pipe body 1.

[0079] S4. Use a 3mm thick stainless steel pipe as a protective layer 4, put the stainless steel pipe over the buffer layer 3, and then coat the outside of the stainless steel pipe with a solvent-free two-component coating to form a 5mm fireproof layer 5.

[0080] Comparative Example 2

[0081] S1. Prepare the pipe body 1 by mixing 90 parts of epoxy resin, 10 parts of phenolic-epoxy resin, 8 parts of brominated epoxy resin, 8 parts of toughening agent, and 0.15 parts of leveling agent evenly, impregnating the mixture with alkali-free glass fiber, and then winding it onto a mold with a winding thickness of 8 mm. After heating and curing, the pipe body 1 is formed.

[0082] S2. A 6mm thick tube body made of neoprene rubber is used as a buffer layer 3. The buffer layer 3 is first fitted over the pipe body 1, and a 20mm casting gap is left between the buffer layer 3 and the pipe body 1.

[0083] S3. Pour phthalic anhydride-type polyurethane foam mixture and flame retardant into the pouring gap and foam together. After curing, a 20mm heat insulation layer 2 is formed between the buffer layer 3 and the pipe body 1.

[0084] S4. Use a 3mm thick stainless steel pipe as a protective layer 4, put the stainless steel pipe over the buffer layer 3, and then coat the outside of the stainless steel pipe with a solvent-free two-component coating to form a 5mm fireproof layer 5.

[0085] Comparative analysis:

[0086] Two sets of comparative performance tests were conducted based on Examples 1 and 2 and Comparative Examples 1 and 2, as shown in the table below and appendix. Figure 3 , 4 As shown in Figure 5:

[0087]

[0088] Analysis of experimental results:

[0089] 1. Compared with Comparative Example 1, Example 1 is further analyzed in conjunction with the table above and appendix. Figure 3 and 4 As shown, Comparative Example 1 has a higher oxygen index, lower tensile strength, and lower glass transition. This is mainly because the phosphate ester flame retardant added to the resin system of Comparative Example 1 is similar to a plasticizer and does not participate in the reaction between the resin and the curing agent, which reduces the interaction between molecular chains and thus reduces the mechanical properties of the entire resin system. This results in slight leakage of the pipe body during the fire resistance test. Furthermore, no phenolic resin or brominated epoxy resin was added, so its oxygen index is higher than that of Example 1.

[0090] 2. Compared with Comparative Example 2, Example 2 is further analyzed in conjunction with the table above and appendix. Figure 5As shown, Example 2 and Comparative Example 2 use the same resin system and have the same glass transition temperature. However, in the fire resistance test, the water temperature inside the pipe of Comparative Example 2 is significantly higher than that of Example 2. This is because in Comparative Example 2, the insulation layer is thinner, allowing more heat to be transferred to the interior, resulting in an increase in the temperature of the pipe itself and the water inside, which in turn causes slight leakage in the pipe.

[0091] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A fiberglass reinforced plastic (FRP) pipe resistant to ablation, characterized in that, It consists of the pipe body, insulation layer, buffer layer, protective layer and fireproof layer arranged from the inside out; The pipe body is formed by impregnating glass fiber with an adhesive and then curing it with heat. The adhesive is composed of flame-retardant resin, phosphate ester flame retardant, toughening agent, leveling agent and aromatic amine curing agent. The flame-retardant resin is composed of epoxy resin, phenolic epoxy resin and brominated epoxy resin. The components of the adhesive are mixed in the following weight parts: 85-95 parts epoxy resin, 5-20 parts phenolic epoxy resin, 2-10 parts brominated epoxy resin, 15-20 parts phosphate ester flame retardant, 8-12 parts toughening agent, 0.01-0.2 parts leveling agent and 25-30 parts aromatic amine curing agent. The insulation layer is rigid polyurethane foam, which is made by foaming phthalic anhydride-type polyurethane foam composite material together with a flame retardant. The buffer layer is made of neoprene rubber; The protective layer is made of corrosion-resistant metal; The fireproof layer is formed by coating with a solvent-free two-component paint.

2. The ablation-resistant fiberglass pipe according to claim 1, characterized in that: The thickness of the pipe body is 7-10mm.

3. The ablation-resistant fiberglass pipe according to claim 1, characterized in that: The thickness of the insulation layer is 30-40mm.

4. The ablation-resistant fiberglass pipe according to claim 1, characterized in that: The thickness of the buffer layer is 4-8 mm.

5. The ablation-resistant fiberglass pipe according to claim 1, characterized in that: The thickness of the protective layer is 2-4 mm.

6. The ablation-resistant fiberglass pipe according to claim 1, characterized in that: The thickness of the fireproof layer is 4-8mm.

7. A method for preparing an ablation-resistant fiberglass pipe according to any one of claims 1 to 6, characterized in that... Follow these steps: S1. Prepare the pipe body by mixing epoxy resin, phenolic epoxy resin, brominated epoxy resin, flame retardant, toughening agent, leveling agent and curing agent evenly according to the weight parts, impregnating alkali-free glass fiber, and then winding it onto the mold. After heating and curing, it is formed. S2. First, the formed buffer layer is placed on the outside of the pipe body, and a casting gap is left between the buffer layer and the pipe body. S3. Pour rigid polyurethane foam raw material into the pouring gap for foaming. After curing and molding, a heat insulation layer is formed between the buffer layer and the pipe body. S4. A protective layer in the shape of a steel tube made of anti-corrosion metal is placed over the buffer layer, and then a fireproof layer is coated on the outside of the protective layer.

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