High-toughness high-strength combined polyether full-water foaming spray-winding polyurethane thermal insulation pipe and preparation method thereof

Abstract

This invention relates to a high-toughness, high-strength composite polyether all-water foamed spray-wrapped polyurethane insulation pipe and its preparation method. The insulation pipe is made by mixing composite polyether and isocyanate at a mass ratio of 1:1.3-1.5, and then spraying the mixture onto a rotating steel pipe under pressure using a spray gun, thereby forming a polyurethane insulation layer on the outer wall of the steel pipe. The composite polyether components include: 35-55 parts of highly active toughness-reinforced polyether, 15-35 parts of polyester polyol, 5-10 parts of composite crosslinking agent, 2.5-6 parts of synergistic catalyst, 1-2.5 parts of foam stabilizer, 8-15 parts of high-efficiency flame retardant, 0.8-2 parts of antioxidant, and 4-7 parts of water. In this invention, the main polyether is a toughness-modified polyether. Through the synergistic regulation of the composite crosslinking system and the catalysts before and after the process, the strength of the polyurethane insulation layer is ensured while maintaining a certain degree of toughness, making it suitable for pipeline insulation projects under complex conditions such as high pressure.

Description

Technical Field

[0001] This invention relates to the field of polyurethane insulation materials technology, specifically to a high-toughness, high-strength composite polyether water-foamed spray-wrapped polyurethane insulation pipe and its preparation method. Background Technology

[0002] Polyurethane insulated pipes, with their excellent insulation and reliability, have been widely used in many fields such as petrochemicals, municipal heating, and long-distance pipelines. As global environmental protection measures become increasingly stringent, traditional fluorinated foaming agents such as 141b are gradually being restricted due to their ozone-depleting and greenhouse effect properties. Meanwhile, all-water foaming technology, using water as a green foaming agent, boasts advantages such as being environmentally friendly, pollution-free, cost-effective, and having no ozone-depleting potential, making it a key research direction in polyurethane foaming technology.

[0003] However, the following drawbacks exist in the practical application of all-water-foamed polyurethane insulation layers. First, the reaction between water and isocyanate to generate carbon dioxide is quite intense, resulting in high internal heat and stress concentration, which easily leads to the collapse and shrinkage of internal cells. Second, the crosslinking density of the foam is difficult to control precisely, and its toughness is insufficient, making it prone to cracking during the spraying and winding of pipelines, as well as during subsequent transportation and construction. Finally, the compressive strength of traditional all-water-foamed foam is generally lower than 0.35 MPa, which is insufficient to meet the load-bearing capacity requirements of long-distance pipelines for the insulation layer structure.

[0004] In current water-sprayed spiral wound pipe technology, it is difficult to achieve a synergistic improvement in toughness and strength by simply adding toughening agents or adjusting the molecular weight of polyethers. This can easily lead to a decrease in thermal insulation performance and also affect the compatibility between the insulation layer and the steel pipe substrate. Therefore, developing a water-foamed polyurethane insulation pipe that combines high toughness, high strength, and excellent thermal insulation performance is of great significance for broadening its application areas. Summary of the Invention

[0005] To address the shortcomings of the existing technology, the present invention aims to provide a high-toughness, high-strength composite polyether all-water foamed spray-wrapped polyurethane insulation pipe. This pipe utilizes hydroxyl-terminated polyether grafted with hydrogenated nitrile butadiene rubber (NBR), introducing flexible NBR segments into the molecular chain to form a "rigid skeleton-flexible segment" composite structure. This structure ensures compatibility with the matrix through the full reaction of highly active hydroxyl-terminated polyethers with isocyanates, while the flexible segments alleviate internal stress concentration, significantly improving foam toughness. Simultaneously, the polyester polyol enhances mechanical strength, achieving a synergistic performance balance.

[0006] Another objective of this invention is to provide a method for preparing a high-toughness, high-strength composite polyether water-foamed spray-wrapped polyurethane insulation pipe. By adjusting the basic formula and improving the process, the toughness, strength and insulation performance are synergistically improved, thus broadening the application fields of the water-foamed polyurethane insulation pipe.

[0007] This invention is achieved using the following technical solution:

[0008] The high-toughness, high-strength composite polyether water-foamed spray-wrapped polyurethane insulation pipe includes a polyurethane foam insulation layer formed by water-foaming reaction, a core steel pipe, and a high-density polyethylene layer on the outside of the insulation layer; the polyurethane foam insulation layer comprises a water-foamed polyurethane insulation layer formed by the reaction and curing of composite polyether components and isocyanate components.

[0009] The polyether component comprises:

[0010] (a) A highly active toughness-enhancing polyether as a toughness matrix, the structure of which comprises a hydroxyl-terminated polyether grafted onto hydrogenated butadiene-acrylonitrile rubber segments;

[0011] (b) Polyester polyols as strength matrix;

[0012] (c) A composite crosslinking agent used to regulate the network structure, which is a compound of triethanolamine, glycerol and dimethylolpropionic acid;

[0013] (d) A synergistic catalyst used to regulate the reaction rate, which is a combination of amine catalysts, organometallic catalysts and delayed catalysts.

[0014] The combined polyether components, by weight, include:

[0015] Highly active toughness-reinforced polyether: 35-55 parts;

[0016] Polyester polyol: 15-35 parts;

[0017] Composite crosslinking agent: 5-10 parts;

[0018] Synergistic catalyst: 2.5-6 parts;

[0019] Water: 4-7 parts.

[0020] The highly active toughness-enhancing polyether has a hydroxyl value of 30-40 mgKOH / g, a functionality of 2.8-3.2, and a grafting rate of 18-28%.

[0021] The polyester polyol is an adipic acid-neopentyl glycol polyester polyol with a hydroxyl value of 90-130 mgKOH / g.

[0022] The polyether composition also includes at least one of a foam stabilizer, a high-efficiency flame retardant, and an antioxidant.

[0023] The foam stabilizer is a Si-C type water-resistant polyurethane silicone oil;

[0024] The high-efficiency flame retardant is a compound of TEP, TCEP, and TCPP, with a mass ratio of (2-3):1:1;

[0025] The antioxidant is one or more of antioxidant 1010, antioxidant 168 and triphenyl phosphite.

[0026] The isocyanate component is a compound of polymeric MDI and liquefied MDI, with an NCO content of 31-33% and a mass ratio of polymeric MDI to liquefied MDI of (3-4):1.

[0027] The composite crosslinking agent is a compound of triethanolamine, glycerol and dimethylolpropionic acid, in a mass ratio of (2-3):(3-4):1.

[0028] The amine catalyst is a mixture of N,N-dimethylcyclohexylamine and triethylenediamine; the organometallic catalyst is dibutyltin dilaurate or potassium isooctanoate; and the delayed catalyst is 2,2'-dimorpholinodiethyl ether.

[0029] The preparation method of the high-toughness, high-strength composite polyether water-foamed spray-wrapped polyurethane insulation pipe includes the following steps:

[0030] a. To prepare a combined polyether component comprising the highly active toughness-enhancing polyether, the polyester polyol, the composite crosslinking agent, and the synergistic catalyst;

[0031] b. The polyether component and isocyanate component obtained in step a are mixed using a high-pressure spraying device and sprayed onto the outer surface of the working steel pipe. The mixture is then cured by a full-water foaming reaction to form a polyurethane insulation layer.

[0032] The preparation method of the high-toughness and high-strength composite polyether water-foamed spray-wrapped polyurethane insulation pipe further includes: pre-treating the working steel pipe before step b and applying a polyurethane primer to its surface; and wrapping the polyurethane insulation layer with a composite outer protective pipe after step b; in step b, the mass ratio of the composite polyether component to the isocyanate component is 1:(1.3-1.5); and the spraying pressure is 18-25 MPa.

[0033] Specifically, the preparation method of high-toughness, high-strength composite polyether water-foamed polyurethane spray-coated and wound insulation pipe includes the following steps:

[0034] (1) Pretreatment of working steel pipe: The working steel pipe is shot blasted to remove rust and ultrasonically degreased. It is heated to a surface temperature of 40-50℃ by medium frequency heating, and a polyurethane primer is applied with a thickness of 8-15 μm. It is then cured at a constant temperature of 30-40℃ for 20-30 minutes.

[0035] (2) Preparation of polyether composition: Weigh out the high-activity toughness-enhancing polyether, polyester polyol, composite crosslinking agent, synergistic catalyst, foam stabilizer, high-efficiency flame retardant, and antioxidant by weight, and put them into a high-speed stirring kettle. Stir at 800~1200 r / min for 40-80 minutes at 30-40℃ to obtain a uniform polyether composition.

[0036] (3) High-pressure spraying foaming: The combined polyether component and isocyanate (a mixture of polymeric MDI and liquefied MDI) are heated to 30-35℃ respectively, and mixed at a mass ratio of 1:1.3-1.5 using a high-pressure spraying device. The spraying pressure is controlled at 18-25MPa, the spraying speed at 0.3-0.5m / s, the steel pipe rotation speed at 20s / r, and the equipment flow rate at 105g / s. A continuous and uniform foam layer is formed on the surface of the working steel pipe. The foaming and curing process takes 6-12 minutes to obtain a full water-foamed polyurethane insulation layer with a thickness of 70-85 mm.

[0037] (4) Composite outer protective pipe coating: HDPE resin and FRPP particles are mixed at a mass ratio of 3:1-4:1 and extruded through a twin-screw extruder to coat the surface of the foam insulation layer. The extrusion temperature is controlled at 170-200℃ and the coating pressure is 0.5-0.8 MPa. After water cooling and shaping, a high-toughness and high-strength composite polyether water spray wound insulation pipe is obtained.

[0038] In step (1), the polyurethane primer is a mixture of MDI-type prepolymer and toluene diisocyanate (TDI) in a mass ratio of 2:1 and a solid content ≥95%.

[0039] In step (3), the spraying environment temperature is 20-35℃ and the relative humidity is ≤75%; the mixing chamber temperature of the high-pressure spraying equipment is controlled at 32-35℃ and the mixing time is 0.5-1.0 seconds.

[0040] This invention employs graft modification of hydroxyl-terminated polyether with hydrogenated nitrile butadiene rubber (HNBR), introducing flexible hydrogenated nitrile butadiene rubber segments into the molecular chain to form a "rigid skeleton-flexible segment" composite structure. The polyether is prepared using an esterification grafting method, involving grafting followed by hydrogenation, resulting in a mild process with few byproducts. The first step involves preparing carboxylated nitrile butadiene rubber (XNBR) by copolymerizing butadiene, acrylonitrile, and a small amount of unsaturated acid emulsion to obtain XNBR containing active carboxyl groups (-COOH). The second step involves a grafting reaction, where XNBR is mixed with hydroxyl-terminated polyether (methoxylated polyethylene glycol with a molecular weight of 350-1000) in a specific ratio. Grafting is achieved through the esterification reaction of the carboxyl and hydroxyl groups, yielding grafted-modified XNBR. The third step is hydrogenation treatment, where the grafted product undergoes selective hydrogenation to convert it into hydroxyl-terminated polyether-grafted HNBR. It can fully react with isocyanate through highly active terminal hydroxyl groups to ensure compatibility with the matrix, and can also alleviate internal stress concentration through flexible chain segments to significantly improve foam toughness; at the same time, polyester polyol improves mechanical strength, and the two work together to achieve a performance balance.

[0041] A compound of glycerol, triethanolamine, and dimethylolpropionic acid is used as a crosslinking agent. Triethanolamine reacts with isocyanate to form a three-dimensional network structure, improving the dimensional stability of the foam; glycerol extends the length of the polyurethane molecular chain, improving mechanical properties; and dimethylolpropionic acid introduces hydrophilic groups and crosslinking structures, improving the water compatibility of the foaming system. These three components work synergistically to achieve a balance between high strength and high toughness in the polyurethane foam.

[0042] A combination of amine catalysts, organometallic catalysts, and delayed catalysts is employed. The amine catalysts accelerate the foaming reaction, the organometallic catalysts promote the gelation reaction, and the delayed catalysts regulate the reaction rate matching, avoiding uneven porosity caused by excessively rapid reactions and improving the density of the foam structure. A combination of polymeric MDI and liquefied MDI is also used. The polymeric MDI ensures mechanical strength, while the liquefied MDI enhances reactivity and compatibility. Their synergistic effect further optimizes the cross-linking structure of the polyurethane molecular chains.

[0043] By optimizing spraying pressure, temperature, and mixing time, thorough mixing of the polyether and isocyanate is ensured, forming a uniform and dense foam structure and avoiding performance defects caused by uneven mixing. Wrapping is performed when the insulation layer has cured to a Shore hardness of D=35-45, at which point the foam is in a semi-cured state, significantly improving interlayer bonding. A twin-screw extruder is used to achieve uniform mixing and coating of HDPE and FRPP, enhancing the mechanical strength and weather resistance of the outer protective tube and extending the service life of the insulation pipe.

[0044] Compared with the prior art, the beneficial effects of the present invention are:

[0045] (1) Through the innovative design of the high-activity toughness-enhancing polyether and polyester polyol enhancement-toughening synergistic system, the compressive strength of the insulation pipe is ≥0.45 MPa, the elongation at break is ≥25%, and there are no cracks when bending at room temperature. This solves the core pain points of poor toughness and low strength of all-water foamed polyurethane and meets the stringent mechanical requirements of long-distance transportation pipelines.

[0046] (2) With the precise ratio of synergistic composite catalyst and composite crosslinking agent, the dimensional stability (70℃, 24h) is ≤±0.8%, which effectively inhibits foam shrinkage and collapse and ensures the structural integrity of the insulation layer.

[0047] (3) It uses deionized water as the only foaming agent, ODP=0, and has no fluorine emissions, which complies with global environmental protection policies; the thermal conductivity is ≤0.023 W / (m·K), the closed-cell rate is ≥90%, the heat preservation effect is excellent, and the energy consumption of pipeline transportation can be reduced.

[0048] (4) The integrated process of high-pressure spraying, in-situ winding, and composite outer protective pipe covering has high construction efficiency, can be adapted to the insulation requirements of pipes of different specifications, and has a wide range of applications. Detailed Implementation

[0049] To make the objectives and technical solutions of this invention clearer, the invention will be further described in detail below.

[0050] Manufacturers of raw materials used in the examples and comparative examples:

[0051]

[0052] In the following examples and comparative examples, the synergistic catalyst is a mixture of N,N-dimethylcyclohexylamine and triethylenediamine in equal proportions, i.e., the mass ratio of the two is 1:1.

[0053] Example 1

[0054] The polyether composition (parts by weight) includes: 45 parts of high-activity toughness-reinforced polyether (hydroxyl value 35 mgKOH / g, functionality 3.0, grafting rate 22%), 35 parts of polyester polyol (adipic acid-neopentyl glycol system, hydroxyl value 110 mgKOH / g), 7 parts of composite crosslinking agent (triethanolamine: glycerol: dimethylolpropionic acid = 2.5: 3.5: 1), 4.5 parts of synergistic catalyst (equal proportion mixture of N,N-dimethylcyclohexylamine and triethylenediamine: dibutyltin dilaurate: 2,2'-dimorpholinodiethyl ether = 2: 0.5: 0.3), 2 parts of Si-C type water-resistant polyurethane silicone oil, 12 parts of high-efficiency flame retardant (TEP: TCEP: TCPP = 2.5: 1: 1), 1.2 parts of antioxidant (1010: 168: triphenyl phosphite = 1: 1: 0.5), and 5.5 parts of water.

[0055] Isocyanate component: a blend of polymeric MDI and liquefied MDI (mass ratio 3.5:1), NCO content 32%.

[0056] Add the above raw materials into a high-speed mixing vessel and stir at 1000 r / min for 60 minutes at 35 ℃ until they are evenly mixed and ready for use.

[0057] A method for preparing a high-toughness, high-strength composite polyether water-foamed polyurethane spray-coated and wound insulation pipe includes the following steps:

[0058] (1) Pretreatment of working steel pipe: Φ820×5 mm seamless steel pipe is selected. After shot blasting and ultrasonic degreasing, it is dried to a surface temperature of 45℃, and polyurethane primer (MDI type prepolymer: TDI=2:1) ​​is applied with a thickness of 10 μm. It is then cured at 35℃ for 25 minutes.

[0059] (2) High-pressure spraying foaming: The combined polyether component and polymeric MDI are heated to 32°C respectively, and mixed at a mass ratio of 1:1.40 through a high-pressure spraying device. The spraying pressure is 22 MPa, the spraying speed is 0.4 m / s, the mixing chamber temperature is 33°C, the mixing time is 0.8 seconds, and the foaming and curing time is 8 minutes to form a 75 mm thick all-water foamed polyurethane insulation layer with a peak foaming temperature of 105°C.

[0060] (3) Composite outer protective tube coating: HDPE resin and FRPP particles are mixed at a mass ratio of 3:1 and extruded and coated at 185°C using a twin-screw extruder with a coating pressure of 0.6 MPa. After cooling and shaping, the finished insulation pipe is obtained with an outer protective tube thickness of 7 mm.

[0061] Example 2

[0062] The polyether composition (parts by weight) is as follows: 35 parts of high-activity toughness-reinforced polyether (hydroxyl value 30 mgKOH / g, functionality 2.8, grafting rate 18%), 25 parts of polyester polyol (adipic acid-neopentyl glycol system, hydroxyl value 110 mgKOH / g), 5 parts of composite crosslinking agent (triethanolamine: glycerol: dimethylolpropionic acid = 2:3:1), 3.8 parts of synergistic catalyst (equal proportion mixture of N,N-dimethylcyclohexylamine and triethylenediamine: dibutyltin dilaurate: 2,2'-dimorpholinodiethyl ether = 2:0.4:0.2), 1 part of Si-C type water-resistant polyurethane silicone oil, 8 parts of high-efficiency flame retardant (TEP:TCEP:TCPP = 2:1:1), 0.8 parts of antioxidant (1010:168: triphenyl phosphite = 1:1:0.5), and 4 parts of water.

[0063] Isocyanate component: a blend of polymeric MDI and liquefied MDI (mass ratio 3:1), NCO content 31%.

[0064] Add the above raw materials into a high-speed mixing vessel and stir at 900 r / min for 50 minutes at 32°C until they are evenly mixed.

[0065] A method for preparing a high-toughness, high-strength composite polyether water-foamed polyurethane spray-coated and wound insulation pipe includes the following steps:

[0066] (1) Pretreatment of working steel pipe: Φ1020×6 mm seamless steel pipe, after pretreatment, apply a primer with a thickness of 12 μm, and cure at 32℃ for 22 minutes;

[0067] (2) High-pressure spraying foaming: The combined polyether and polymeric MDI are mixed at a mass ratio of 1:1.3, the spraying pressure is 20 MPa, the speed is 0.3 m / s, the mixing chamber temperature is 32℃, the mixing time is 0.7 seconds, the foaming and curing time is 7 minutes, the insulation layer thickness is 80 mm, and the peak temperature is 102℃.

[0068] (3) Composite outer sheath coating: HDPE to FRPP mass ratio 4:1, extrusion temperature 180℃, coating pressure 0.5 MPa, outer sheath thickness 8 mm, cooling and shaping to obtain the finished product.

[0069] Example 3

[0070] The polyether composition (parts by weight) is as follows: 55 parts of high-activity toughness-reinforced polyether (hydroxyl value 40 mgKOH / g, functionality 3.2, grafting rate 28%), 35 parts of polyester polyol (adipic acid-neopentyl glycol system, hydroxyl value 110 mgKOH / g), 10 parts of composite crosslinking agent (triethanolamine: glycerol: dimethylolpropionic acid = 3:4:1), 5.5 parts of synergistic catalyst (equal proportion mixture of N,N-dimethylcyclohexylamine and triethylenediamine: dibutyltin dilaurate: 2,2'-dimorpholinodiethyl ether = 2.1:0.6:0.4), 2.5 parts of Si-C type water-resistant polyurethane silicone oil, 15 parts of high-efficiency flame retardant (TEP:TCEP:TCPP = 3:1:1), 2 parts of antioxidant (1010:168: triphenyl phosphite = 1:1:0.5), and 7 parts of water.

[0071] Isocyanate component: a blend of polymeric MDI and liquefied MDI (mass ratio 4:1), NCO content 33%.

[0072] Add the above raw materials into a high-speed mixing vessel and stir at 1100 r / min for 70 minutes at 38°C until they are evenly mixed.

[0073] A method for preparing a high-toughness, high-strength composite polyether water-foamed polyurethane spray-coated and wound insulation pipe includes the following steps:

[0074] (1) Pretreatment of working steel pipe: Φ1220×8 mm seamless steel pipe is selected. After shot blasting and ultrasonic degreasing, it is dried to a surface temperature of 48℃, and polyurethane primer (MDI type prepolymer: TDI=2:1) ​​is applied with a thickness of 14 μm. It is then cured at 38℃ for 28 minutes.

[0075] (2) High-pressure spraying foaming: The combined polyether component and polymeric MDI are heated to 34°C respectively, and mixed at a mass ratio of 1:1.5 through a high-pressure spraying device. The spraying pressure is 24 MPa, the spraying speed is 0.5 m / s, the mixing chamber temperature is 34°C, the mixing time is 0.9 seconds, and the foaming and curing time is 10 minutes to form a full water foamed polyurethane insulation layer with a thickness of 85 mm and a peak foaming temperature of 108°C.

[0076] (3) Composite outer protective tube coating: HDPE resin and FRPP particles are mixed at a mass ratio of 3.5:1 and extruded and coated at 195°C using a twin-screw extruder with a coating pressure of 0.7 MPa. After cooling and shaping, the finished insulation pipe is obtained with an outer protective tube thickness of 9 mm.

[0077] Comparative Example 1

[0078] The polyether composition (parts by weight) is as follows: 80 parts of ordinary active polyether polyol (hydroxyl value 40 mgKOH / g, functionality 3.0), 7 parts of triethanolamine as a composite crosslinking agent, 4.5 parts of synergistic catalyst (a mixture of N,N-dimethylcyclohexylamine and triethylenediamine in equal proportions: dibutyltin dilaurate: 2,2'-dimorpholinodiethyl ether = 2:0.5:0.3), 2 parts of Si-C type water-resistant polyurethane silicone oil, 12 parts of high-efficiency flame retardant (TEP:TCEP:TCPP = 2.5:1:1), 1.2 parts of antioxidant (1010:168:triphenyl phosphite = 1:1:0.5), and 5.5 parts of water.

[0079] Isocyanate component: a blend of polymeric MDI and liquefied MDI (mass ratio 3.5:1), NCO content 32%.

[0080] Add the above raw materials into a high-speed mixing vessel and stir at 1000 r / min for 60 minutes at 35 ℃ until they are evenly mixed and ready for use.

[0081] The preparation method of the high-toughness and high-strength composite polyether water-foamed polyurethane spray-wrapped insulation pipe is the same as in Example 1.

[0082] Comparative Example 2

[0083] The polyether composition (parts by weight) is as follows: 45 parts of ordinary active polyether polyol (hydroxyl value 40 mgKOH / g, functionality 3.0), 35 parts of polyester polyol (adipic acid-neopentyl glycol system, hydroxyl value 110 mgKOH / g), 7 parts of composite crosslinking agent (triethanolamine: glycerol: dimethylolpropionic acid = 2.5: 3.5: 1), 4.5 parts of synergistic catalyst (equal proportion mixture of N,N-dimethylcyclohexylamine and triethylenediamine: dibutyltin dilaurate: 2,2'-dimorpholinodiethyl ether = 2: 0.5: 0.3), 2 parts of Si-C type water-resistant polyurethane silicone oil, 12 parts of high-efficiency flame retardant (TEP: TCEP: TCPP = 2.5: 1: 1), 1.2 parts of antioxidant (1010: 168: triphenyl phosphite = 1: 1: 0.5), and 5.5 parts of water.

[0084] Isocyanate component: a blend of polymeric MDI and liquefied MDI (mass ratio 3.5:1), NCO content 32%.

[0085] Add the above raw materials into a high-speed mixing vessel and stir at 1000 r / min for 60 minutes at 35 ℃ until they are evenly mixed and ready for use.

[0086] The preparation method of the high-toughness and high-strength composite polyether water-foamed polyurethane spray-wrapped insulation pipe is the same as in Example 1.

[0087] Comparative Example 3

[0088] The polyether composition (parts by weight) includes: 80 parts of high-activity toughness-reinforced polyether (hydroxyl value 35 mgKOH / g, functionality 3.0, grafting rate 22%), 7 parts of composite crosslinking agent (triethanolamine: glycerol: dimethylolpropionic acid = 2.5: 3.5: 1), 4.5 parts of synergistic catalyst (equal proportion mixture of N,N-dimethylcyclohexylamine and triethylenediamine: dibutyltin dilaurate: 2,2'-dimorpholinodiethyl ether = 2: 0.5: 0.3), 2 parts of Si-C type water-resistant polyurethane silicone oil, 12 parts of high-efficiency flame retardant (TEP: TCEP: TCPP = 2.5: 1: 1), 1.2 parts of antioxidant (1010: 168: triphenyl phosphite = 1: 1: 0.5), and 5.5 parts of water.

[0089] Isocyanate component: a blend of polymeric MDI and liquefied MDI (mass ratio 3.5:1), NCO content 32%.

[0090] Add the above raw materials into a high-speed mixing vessel and stir at 1000 r / min for 60 minutes at 35 ℃ until they are evenly mixed and ready for use.

[0091] The preparation method of the high-toughness and high-strength composite polyether water-foamed polyurethane spray-wrapped insulation pipe is the same as in Example 1.

[0092] The performance test results of Examples 1-3 are shown in Table 1.

[0093] The performance of the finished insulation pipes prepared in Implementation Cases 1-3 and Comparative Examples 1-3 was tested. The testing standards and results are shown in Table 1.

[0094] Table 1 Performance test results of Examples 1-3 and Comparative Examples 1-3

[0095]

[0096] As shown in Table 1, Examples 1-3 exhibit the best performance: compressive strength ≥ 0.46 MPa and elongation at break ≥ 26%, far exceeding the comparative examples, and demonstrating superior dimensional stability and bond strength. This confirms the synergistic effect of highly active toughness-enhancing polyether and polyester polyol, which, when combined with composite crosslinking agents and synergistic catalysts, achieve a balance between strength and toughness.

Claims

1. A high-toughness, high-strength composite polyether water-foamed spray-wrapped polyurethane insulation pipe, characterized in that, It includes a polyurethane foam insulation layer formed by a full water foaming reaction, a core steel pipe, and a high-density polyethylene layer on the outside of the insulation layer; the polyurethane foam insulation layer includes a full water foamed polyurethane insulation layer formed by the reaction and curing of a combination of polyether components and isocyanate components. The polyether component comprises: (a) The highly active toughness-enhancing polyether, which serves as the toughness matrix, is prepared by grafting carboxylated butadiene-acrylonitrile rubber and hydroxyl-terminated polyether through an esterification reaction, followed by hydrogenation treatment. (b) Polyester polyols as strength matrix; (c) A composite crosslinking agent used to regulate the network structure, which is a compound of triethanolamine, glycerol and dimethylolpropionic acid; (d) A synergistic catalyst used to regulate the reaction rate, which is a combination of amine catalysts, organometallic catalysts and delayed catalysts; The highly active toughness-enhancing polyether has a hydroxyl value of 30-40 mgKOH / g, a functionality of 2.8-3.2, and a grafting rate of 18-28%.

2. The high-toughness, high-strength composite polyether water-foamed spray-wrapped polyurethane insulation pipe according to claim 1, characterized in that, The combined polyether components, by weight, include: Highly active toughness-reinforced polyether: 35-55 parts; Polyester polyol: 15-35 parts; Composite crosslinking agent: 5-10 parts; Synergistic catalyst: 2.5-6 parts; Water: 4-7 parts.

3. The high-toughness, high-strength composite polyether water-foamed spray-wrapped polyurethane insulation pipe according to claim 1, characterized in that, The polyester polyol is an adipic acid-neopentyl glycol polyester polyol with a hydroxyl value of 90-130 mgKOH / g.

4. The high-toughness, high-strength composite polyether water-foamed spray-wrapped polyurethane insulation pipe according to claim 1, characterized in that, The polyether composition also includes at least one of a foam stabilizer, a high-efficiency flame retardant, and an antioxidant.

5. The high-toughness, high-strength composite polyether water-foamed spray-wrapped polyurethane insulation pipe according to claim 1, characterized in that, The isocyanate component is a compound of polymeric MDI and liquefied MDI, with an NCO content of 31-33% and a mass ratio of polymeric MDI to liquefied MDI of (3-4):

1.

6. The high-toughness, high-strength composite polyether water-foamed spray-wrapped polyurethane insulation pipe according to claim 1, characterized in that, The composite crosslinking agent is a compound of triethanolamine, glycerol and dimethylolpropionic acid, in a mass ratio of (2-3):(3-4):

1.

7. The high-toughness, high-strength composite polyether water-foamed spray-wrapped polyurethane insulation pipe according to claim 1, characterized in that, The amine catalyst is a mixture of N,N-dimethylcyclohexylamine and triethylenediamine; the organometallic catalyst is dibutyltin dilaurate or potassium isooctanoate; and the delayed catalyst is 2,2'-dimorpholinodiethyl ether.

8. A method for preparing a high-toughness, high-strength composite polyether water-foamed spray-wrapped polyurethane insulation pipe according to any one of claims 1-7, characterized in that, Includes the following steps: a. To prepare a combined polyether component comprising the highly active toughness-enhancing polyether, the polyester polyol, the composite crosslinking agent, and the synergistic catalyst; b. The polyether component and isocyanate component obtained in step a are mixed using a high-pressure spraying device and sprayed onto the outer surface of the working steel pipe. The mixture is then cured by a full-water foaming reaction to form a polyurethane insulation layer.

9. The method for preparing the high-toughness, high-strength composite polyether water-foamed spray-wrapped polyurethane insulation pipe according to claim 8, characterized in that, Also includes: Before step b, the working steel pipe is pretreated and a polyurethane primer is applied to its surface; And after step b, a composite outer protective tube is wrapped around the polyurethane insulation layer; in step b, the mass ratio of the combined polyether component to the isocyanate component is 1:(1.3-1.5); the spraying pressure is 18-25 MPa.

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