An environmentally friendly, moisture-resistant, flame-retardant PPR pipe and its preparation method

Abstract

This invention discloses an environmentally friendly, moisture-resistant, and flame-retardant PPR pipe and its preparation method, belonging to the field of PPR pipe technology. The invention utilizes the synergistic effect of adding a moisture-resistant flame retardant and a flame-retardant synergist to achieve more significant flame-retardant performance. Combined with the effect of a hydrophobic additive, it significantly improves the flame-retardant durability and stability of the pipe in humid environments while ensuring excellent flame-retardant performance. Furthermore, it provides a hydrophobic additive system composed of hydrophobic nano-silica and low-viscosity polyolefin, which can form a hydrophobic barrier on the surface and inside of the pipe, effectively inhibiting moisture penetration and adsorption, thereby improving the long-term reliability of the pipe in high-humidity environments and helping to maintain flame-retardant and mechanical properties. Overall, the pipe possesses multiple functions including antibacterial, high strength, flame retardancy, and moisture resistance, meeting the comprehensive performance requirements of complex usage environments and expanding the application range of PPR pipes in high-safety-standard locations.

Description

Technical Field

[0001] This invention relates to the field of PPR pipe manufacturing technology, and more specifically, to an environmentally friendly, moisture-resistant, and flame-retardant PPR pipe and its manufacturing method. Background Technology

[0002] Random copolymer polypropylene (PPR) pipes are widely used in building hot and cold water systems and heating systems due to their advantages such as heat resistance, pressure resistance, corrosion resistance, and easy installation. However, ordinary PPR pipes have a low limiting oxygen index, making them flammable materials. Furthermore, they produce molten droplets during combustion, which can easily ignite other materials and accelerate the spread of fire. This severely limits their application in fire sprinkler systems, high-rise buildings, and locations with special fire safety requirements.

[0003] To improve the flame retardant properties of PPR pipes, existing technologies typically employ the addition of flame retardants. While traditional flame retardants can enhance the flame retardant performance of materials, they generally suffer from poor environmental friendliness, require large dosages, and can easily lead to a decline in the material's mechanical properties. With increasing environmental awareness and the growing scarcity of petroleum resources, developing green, sustainable, and efficient flame-retardant materials has become an important direction for the industry. Currently, intumescent flame retardants are widely used in the flame-retardant modification of PP due to their halogen-free, high-efficiency, and cost-controllable characteristics.

[0004] However, existing intumescent flame retardants are prone to absorbing moisture and leaching in high humidity environments. This not only significantly reduces their flame retardant performance but also affects the long-term stability and mechanical strength of composite materials, limiting their reliability in humid environments (such as underground pipes, bathrooms, and kitchens). Furthermore, poor moisture resistance also leads to a decline in flame retardant performance. After prolonged use or storage in humid environments, the pipes will absorb moisture from the environment. This moisture will evaporate prematurely during high-temperature processing or the initial stages of a fire, not only consuming some of the effective components of the flame retardant (decomposition endothermic) but also disrupting the process of forming a dense char layer during combustion, resulting in a significant decrease in flame retardant efficiency or even complete failure.

[0005] Therefore, developing a PP-R pipe that combines environmental friendliness, moisture resistance, and high flame retardancy has become an urgent technical problem to be solved in this field. Summary of the Invention

[0006] In view of this, in order to solve one of the above-mentioned technical problems, the present invention provides an environmentally friendly, moisture-resistant, and flame-retardant PPR pipe and its preparation method, the specific technical solution of which is as follows:

[0007] An environmentally friendly, moisture-resistant, and flame-retardant PPR pipe, comprising at least one flame-retardant layer, wherein the flame-retardant layer comprises the following raw materials in parts by weight: 100 parts PPR resin, 1 to 15 parts composite flame retardant, 1 to 7 parts hydrophobic additive, 0.5 to 3 parts silane coupling agent, 1 to 3 parts compatibilizer, 0.5 to 1 part antioxidant, and 0.5 to 1 part lubricant; The composite flame retardant is obtained by mixing a moisture-resistant flame retardant and a flame retardant synergist in a mass ratio of (5~9):(1~5); The hydrophobic additive is obtained by mixing hydrophobic nano-silica with low-viscosity polyolefin in a mass ratio of (1~2):(3~5).

[0008] Furthermore, the preparation method of the moisture-resistant flame retardant includes the following steps: a. Phytic acid was dispersed in anhydrous methanol and ultrasonically dispersed. Then zinc nitrate hexahydrate was added and dispersed evenly. The mixture was stirred at 50℃~65℃ to obtain a Zn-AP mixture. b. Add 2-methylimidazole to anhydrous methanol. After it is fully dissolved, slowly add it to the Zn-AP mixture. After it is completely added, continue stirring and reacting. Allow it to stand, filter it, and obtain the crude product. c. The crude product is washed and dried to obtain a moisture-resistant flame retardant.

[0009] Furthermore, in step a, the ultrasonic dispersion treatment lasts for 10 to 20 minutes; the stirring reaction time is 10 to 15 hours. Further, in step a, the ratio of phytic acid, anhydrous methanol, and zinc nitrate hexahydrate added is (8~12) g: 100 mL: (1~3) g.

[0010] Furthermore, in step b, the temperature of the stirring reaction is 50℃~65℃, the time is 30min~35min, and the settling time is 20h~24h.

[0011] Furthermore, the flame retardant synergist is a metal oxide supported on a porous molecular sieve.

[0012] Furthermore, the hydrophobic nano-silica has a particle size of 20nm~50nm.

[0013] Furthermore, the low-viscosity polyolefin is a maleic anhydride-grafted polyolefin, with a melt flow rate of 5-15 g / 10 min at 230°C and 2.16 kg load.

[0014] Furthermore, the compatibilizer is maleic anhydride-grafted polypropylene with a grafting rate of 0.8% to 1.5%.

[0015] In addition, the present invention also provides a method for preparing environmentally friendly, moisture-resistant, and flame-retardant PPR pipes, the method comprising the following steps: S1. Add the raw materials for the preparation of the antibacterial layer to a twin-screw extruder, melt extrude, granulate, and obtain the antibacterial layer masterbatch; S2. Add the raw materials for preparing the reinforcing layer to a twin-screw extruder, melt extrude, granulate, and obtain the reinforcing layer masterbatch; S3. Add the raw materials for the preparation of the flame retardant layer to a twin-screw extruder, melt extrude, granulate, and obtain the flame retardant layer masterbatch; S4. The antibacterial layer masterbatch, reinforcing layer masterbatch, and flame retardant layer masterbatch are respectively added to the corresponding barrels of the three-layer co-extrusion extruder, and after melt co-extrusion, shaping, cooling, and cutting, environmentally friendly, moisture-resistant, and flame-retardant PPR pipes are obtained.

[0016] Compared with existing technologies, its beneficial effects include: 1. This invention uses a phytic acid-based moisture-resistant flame retardant, which is relatively environmentally friendly in terms of raw material source and has mild reaction conditions. It avoids the use of harmful flame retardant systems such as those containing halogens, which is in line with the development direction of green building materials. In addition, by compounding the moisture-resistant flame retardant with a flame retardant synergist, a composite flame retardant is formed. The synergistic effect can exert a more significant flame retardant performance. Combined with the role of hydrophobic additives, while ensuring excellent flame retardant performance, it significantly improves the flame retardant durability and stability of the pipe in a humid environment, overcoming the problem of the flame retardant effect of traditional flame-retardant PPR pipes decreasing in a wet state.

[0017] 2. This invention provides a hydrophobic additive system composed of hydrophobic nano-silica and low-viscosity polyolefin, which can form a hydrophobic barrier on the surface and inside of the pipe, effectively inhibiting moisture penetration and adsorption, thereby improving the long-term reliability of the pipe in high humidity environments, and helping to maintain flame retardant and mechanical properties.

[0018] 3. This invention optimizes the composition of the flame-retardant layer and enhances the interfacial bonding between the inorganic flame-retardant components, nano-silica, and the PPR matrix through the combined use of a silane coupling agent and a maleic anhydride-grafted polypropylene compatibilizer. This ensures uniform dispersion of all functional components, avoids performance inconsistencies or interfacial defects, and guarantees the overall structural stability of the pipe. Furthermore, the three-layer co-extrusion process enables a composite structure design of the antibacterial layer, reinforcing layer, and flame-retardant layer, giving the pipe multiple functions including antibacterial properties, high strength, flame retardancy, and moisture resistance. This meets the comprehensive performance requirements of complex operating environments and expands the application range of PPR pipes in high-safety-standard locations. Attached Figure Description

[0019] The invention will be further understood from the following description taken in conjunction with the accompanying drawings. The components in the drawings are not necessarily drawn to scale, but rather the emphasis is on illustrating the principles of the embodiments. In different views, the same reference numerals designate corresponding parts.

[0020] Figure 1This is a schematic diagram of the preparation process of the moisture-resistant flame retardant in Example 1 of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to its embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the scope of protection of the invention.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0023] An embodiment of the present invention provides an environmentally friendly, moisture-resistant, and flame-retardant PPR pipe, comprising at least one flame-retardant layer, wherein the flame-retardant layer comprises the following raw materials in parts by weight: 100 parts PPR resin, 1 to 15 parts composite flame retardant, 1 to 7 parts hydrophobic additive, 0.5 to 3 parts silane coupling agent, 1 to 3 parts compatibilizer, 0.5 to 1 part antioxidant, and 0.5 to 1 part lubricant; The composite flame retardant is obtained by mixing a moisture-resistant flame retardant and a flame retardant synergist in a mass ratio of (5~9):(1~5); The hydrophobic additive is obtained by mixing hydrophobic nano-silica with low-viscosity polyolefin in a mass ratio of (1~2):(3~5).

[0024] In one embodiment, the method for preparing the moisture-resistant flame retardant includes the following steps: a. Phytic acid was dispersed in anhydrous methanol and ultrasonically dispersed. Then zinc nitrate hexahydrate was added and dispersed evenly. The mixture was stirred at 50℃~65℃ to obtain a Zn-AP mixture. b. Add 2-methylimidazole to anhydrous methanol. After it is fully dissolved, slowly add it to the Zn-AP mixture. After it is completely added, continue stirring and reacting. Allow it to stand, filter it, and obtain the crude product. c. The crude product is washed and dried to obtain a moisture-resistant flame retardant.

[0025] In one embodiment, in step a, the ultrasonic dispersion treatment lasts for 10 to 20 minutes; the stirring reaction time is 10 to 15 hours. In one embodiment, in step a, the ratio of phytic acid, anhydrous methanol, and zinc nitrate hexahydrate added is (8~12)g:100mL:(1~3)g.

[0026] In one embodiment, in step b, the temperature of the stirring reaction is 50°C to 65°C, and the time is 30 min to 35 min; the settling time is 20 h to 24 h.

[0027] In one embodiment, in step b, the ratio of 2-methylimidazole to anhydrous methanol is (1~3) g: 50 mL.

[0028] In one embodiment, in step c, anhydrous methanol is used, and the mixture is centrifuged and washed three times at a speed of 5000 rpm, and then dried to constant weight at 75℃~85℃.

[0029] In one embodiment, the flame retardant synergist is a metal oxide supported on a porous molecular sieve.

[0030] In one embodiment, the porous molecular sieve is of type ZSM-5 or type SBA-15.

[0031] In one embodiment, the metal oxide is at least one of tin oxide, cerium oxide, and antimony trioxide.

[0032] In one embodiment, the metal oxide loaded on the porous molecular sieve is 5% to 9% of the weight of the molecular sieve. The addition of molecular sieve-loaded metal oxide as a flame retardant synergist not only prevents the agglomeration of metal oxide particles and synergistically retards flames, but also adsorbs molten polymers and degrades combustible gases during combustion, thus delaying combustion.

[0033] In one embodiment, the hydrophobic nano-silica has a particle size of 20 nm to 50 nm.

[0034] In one embodiment, the low-viscosity polyolefin is a maleic anhydride-grafted polyolefin with a melt flow rate of 5-15 g / 10 min at 230°C and 2.16 kg load.

[0035] In one embodiment, the silane coupling agent is at least one selected from vinyltrimethoxysilane, vinyltriethoxysilane, alkyltrimethoxysilane, and alkyltriethoxysilane.

[0036] In one embodiment, the compatibilizer is maleic anhydride-grafted polypropylene with a grafting rate of 0.8% to 1.5%.

[0037] In one embodiment, the antioxidant is at least one of β-octadecyl malonate, pentaerythritol ester, and tris(2,4-di-tert-butylphenyl) phosphite.

[0038] In one embodiment, the lubricant is at least one of polyethylene wax, paraffin wax, stearic acid, calcium stearate, and zinc stearate.

[0039] In addition, the present invention also provides a method for preparing environmentally friendly, moisture-resistant, and flame-retardant PPR pipes, the method comprising the following steps: S1. Add the raw materials for the preparation of the antibacterial layer to a twin-screw extruder, melt extrude, granulate, and obtain the antibacterial layer masterbatch; S2. Add the raw materials for preparing the reinforcing layer to a twin-screw extruder, melt extrude, granulate, and obtain the reinforcing layer masterbatch; S3. Add the raw materials for the preparation of the flame retardant layer to a twin-screw extruder, melt extrude, granulate, and obtain the flame retardant layer masterbatch; S4. The antibacterial layer masterbatch, reinforcing layer masterbatch, and flame retardant layer masterbatch are respectively added to the corresponding barrels of the three-layer co-extrusion extruder, and after melt co-extrusion, shaping, cooling, and cutting, environmentally friendly, moisture-resistant, and flame-retardant PPR pipes are obtained.

[0040] In one embodiment, the raw materials for preparing the antibacterial layer include, by weight, 100 parts of PPR resin, 1 to 5 parts of antibacterial agent, 1 to 3 parts of dispersant, 0.5 to 3 parts of coupling agent, and 0.1 to 0.3 parts of lubricant.

[0041] In one embodiment, the coupling agent in the antibacterial layer is a hydrophobic coupling agent, which is at least one of methylsilane coupling agent, chlorosilane coupling agent, aminosilane coupling agent, perfluoroalkylsilane coupling agent, trimethylchlorosilane, and methyltrimethoxysilane.

[0042] In one embodiment, the antibacterial agent is at least one of nano zinc oxide, silver-loaded zirconium phosphate, and silver-loaded zeolite.

[0043] In one embodiment, the dispersant in the antibacterial layer is at least one of sodium dodecyl sulfate, ethylene bis-stearamide, and sodium methylene bisnaphthalene sulfonate.

[0044] In one embodiment, the lubricant in the antibacterial layer is at least one selected from polyethylene wax, paraffin wax, stearic acid, calcium stearate, and zinc stearate.

[0045] In one embodiment, the method for preparing the antibacterial masterbatch is as follows: PPR resin, antibacterial agent, coupling agent, dispersant and lubricant are mixed at high speed for 5 min to 10 min, then added to a twin-screw extruder, the temperature is set to 170℃ to 200℃, melt extruded, granulated, and the antibacterial masterbatch is obtained.

[0046] In one embodiment, the raw materials for preparing the reinforcing layer include, by weight, 100 parts of PPR resin, 3 to 7 parts of alkali-free chopped glass fiber, 0.5 to 1 part of coupling agent, and 0.1 to 0.3 parts of lubricant.

[0047] In one embodiment, the length of the alkali-free chopped glass fiber is 3mm to 6mm.

[0048] In one embodiment, the coupling agent in the reinforcing layer is γ-aminopropyltriethoxysilane.

[0049] In one embodiment, the lubricant in the reinforcing layer is at least one selected from polyethylene wax, paraffin wax, stearic acid, calcium stearate, and zinc stearate.

[0050] In one embodiment, the method for preparing the reinforcing layer is as follows: PPR resin, alkali-free chopped glass fiber, coupling agent and lubricant are mixed at high speed for 5 min to 10 min, then added to a twin-screw extruder, the temperature is set to 175℃ to 210℃, melt extruded, granulated, and the reinforcing layer masterbatch is obtained.

[0051] In one embodiment, the flame retardant layer is prepared by mixing PPR resin, composite flame retardant, hydrophobic additive, silane coupling agent, compatibilizer, antioxidant and lubricant at high speed for 5 min to 10 min, then adding it to a twin-screw extruder, setting the temperature to 175℃ to 220℃, melting and extruding, granulating to obtain flame retardant layer masterbatch.

[0052] In one embodiment, the processing temperature of the three-layer co-extrusion extruder is 180°C to 220°C.

[0053] In one embodiment, the thickness ratio of the antibacterial layer, the reinforcing layer, and the flame-retardant layer is 1:1:(1~2.5).

[0054] After component optimization, the above-mentioned scheme can produce environmentally friendly, moisture-resistant, and flame-retardant PPR pipes. Through a three-layer co-extrusion process, a composite structure design of antibacterial, reinforcing, and flame-retardant layers can be achieved, enabling the pipes to simultaneously possess multiple functions such as antibacterial, high strength, flame retardancy, and moisture resistance. This meets the comprehensive performance requirements of complex usage environments and expands the application range of PPR pipes in high-safety-standard locations.

[0055] The implementation schemes of the present invention will now be described in detail with reference to specific embodiments.

[0056] Example 1: A method for preparing environmentally friendly, moisture-resistant, and flame-retardant PPR pipe includes the following steps: S1. By weight, mix 100 parts PPR resin, 3 parts nano zinc oxide, 1 part sodium dodecyl sulfate, 0.5 parts methyltrimethoxysilane and 0.2 parts polyethylene wax at high speed for 10 minutes, then add to a twin-screw extruder, set the temperature to 170℃~200℃, melt extrude, granulate to obtain antibacterial masterbatch. S2. By weight, mix 100 parts PPR resin, 5 parts alkali-free chopped glass fiber, 0.5 parts γ-aminopropyltriethoxysilane and 0.2 parts polyethylene wax at high speed for 10 min, then add to a twin-screw extruder, set the temperature to 175℃~210℃, melt extrude, granulate, and obtain reinforcing layer masterbatch. S3. Mix 100 parts PPR resin, 12 parts composite flame retardant, 5 parts hydrophobic additive, 0.5 parts vinyltrimethoxysilane, 3 parts maleic anhydride grafted polypropylene with a grafting rate of 1.2%, 0.5 parts β-malonic acid octadecyl ester, and 0.5 parts polyethylene wax at high speed for 10 minutes, then add to a twin-screw extruder, set the temperature to 175℃~220℃, melt extrude, granulate, and obtain flame retardant layer masterbatch; The composite flame retardant is obtained by mixing a moisture-resistant flame retardant and a flame retardant synergist in a mass ratio of 7:3; the preparation method of the moisture-resistant flame retardant includes the following steps: a. Disperse 20g of phytic acid in 200mL of anhydrous methanol, sonicate for 15min, then add 2.22g of zinc nitrate hexahydrate, continue dispersing for 10min, and stir at 55℃ for 12h to obtain a Zn-AP mixture; b. Add 2.46 g of 2-methylimidazole to 50 mL of anhydrous methanol. After it is fully dissolved, slowly add it to the Zn-AP mixture. After it is completely added, continue to stir the reaction at 50 °C for 30 min, let it stand for 24 h, filter it, and obtain the crude product. c. The crude product was centrifuged and washed three times with anhydrous methanol at 5000 rpm, and then dried at 80°C to constant weight to obtain a moisture-resistant flame retardant. The flame retardant synergist is antimony trioxide supported on ZSM-5 porous molecular sieve, with a loading amount of 7% of the weight of ZSM-5 porous molecular sieve; The hydrophobic additive is obtained by mixing hydrophobic nano-silica and low-viscosity polyolefin in a mass ratio of 2:3, and the particle size of the hydrophobic nano-silica is 35nm. The low-viscosity polyolefin is a maleic anhydride-grafted polyolefin with a melt flow rate of 12g / 10min at 230℃ and 2.16kg load. S4. The antibacterial layer masterbatch, reinforcing layer masterbatch, and flame retardant layer masterbatch are added to the corresponding barrels of the three-layer co-extrusion extruder, and the processing temperature is set to 180℃~220℃. After melt co-extrusion, shaping, cooling, and cutting, environmentally friendly, moisture-resistant, and flame-retardant PPR pipes are obtained.

[0057] Example 2: A method for preparing environmentally friendly, moisture-resistant, and flame-retardant PPR pipe includes the following steps: S1. By weight, mix 100 parts PPR resin, 4 parts nano zinc oxide, 1 part sodium dodecyl sulfate, 0.6 parts methyltrimethoxysilane and 0.3 parts polyethylene wax at high speed for 10 minutes, then add to a twin-screw extruder, set the temperature to 170℃~200℃, melt extrude, granulate to obtain antibacterial masterbatch. S2. By weight, mix 100 parts of PPR resin, 6 parts of alkali-free chopped glass fiber, 0.6 parts of γ-aminopropyltriethoxysilane and 0.2 parts of polyethylene wax at high speed for 10 minutes, then add to a twin-screw extruder, set the temperature to 175℃~210℃, melt extrude, granulate, and obtain the reinforcing layer masterbatch. S3. Mix 100 parts PPR resin, 13 parts composite flame retardant, 6 parts hydrophobic additive, 0.5 parts vinyltrimethoxysilane, 3 parts maleic anhydride grafted polypropylene with a grafting rate of 1.2%, 0.5 parts β-malonic acid octadecyl ester, and 0.5 parts polyethylene wax at high speed for 10 minutes, then add to a twin-screw extruder, set the temperature to 175℃~220℃, melt extrude, granulate, and obtain flame retardant layer masterbatch; The composite flame retardant is obtained by mixing a moisture-resistant flame retardant and a flame retardant synergist in a mass ratio of 7:3; the preparation method of the moisture-resistant flame retardant includes the following steps: a. Disperse 20g of phytic acid in 200mL of anhydrous methanol, sonicate for 15min, then add 2.22g of zinc nitrate hexahydrate, continue dispersing for 10min, and stir at 55℃ for 12h to obtain a Zn-AP mixture; b. Add 2.46 g of 2-methylimidazole to 50 mL of anhydrous methanol. After it is fully dissolved, slowly add it to the Zn-AP mixture. After it is completely added, continue to stir the reaction at 55 °C for 30 min, let it stand for 24 h, filter it, and obtain the crude product. c. The crude product was centrifuged and washed three times with anhydrous methanol at 5000 rpm, and then dried at 80°C to constant weight to obtain a moisture-resistant flame retardant. The flame retardant synergist is antimony trioxide supported on ZSM-5 porous molecular sieve, with a loading amount of 7% of the weight of ZSM-5 porous molecular sieve; The hydrophobic additive is obtained by mixing hydrophobic nano-silica and low-viscosity polyolefin in a mass ratio of 2:3, and the particle size of the hydrophobic nano-silica is 35nm. The low-viscosity polyolefin is a maleic anhydride-grafted polyolefin with a melt flow rate of 12g / 10min at 230℃ and 2.16kg load. S4. The antibacterial layer masterbatch, reinforcing layer masterbatch, and flame retardant layer masterbatch are added to the corresponding barrels of the three-layer co-extrusion extruder, and the processing temperature is set to 180℃~220℃. After melt co-extrusion, shaping, cooling, and cutting, environmentally friendly, moisture-resistant, and flame-retardant PPR pipes are obtained.

[0058] Example 3: A method for preparing environmentally friendly, moisture-resistant, and flame-retardant PPR pipe includes the following steps: S1. By weight, mix 100 parts PPR resin, 5 parts nano zinc oxide, 2 parts sodium dodecyl sulfate, 0.8 parts methyltrimethoxysilane and 0.2 parts polyethylene wax at high speed for 10 min, then add to a twin-screw extruder, set the temperature to 170℃~200℃, melt extrude, granulate to obtain antibacterial masterbatch; S2. By weight, mix 100 parts of PPR resin, 7 parts of alkali-free chopped glass fiber, 0.8 parts of γ-aminopropyltriethoxysilane and 0.3 parts of polyethylene wax at high speed for 10 minutes, then add to a twin-screw extruder, set the temperature to 175℃~210℃, melt extrude, granulate, and obtain the reinforcing layer masterbatch. S3. Mix 100 parts of PPR resin, 14 parts of composite flame retardant, 7 parts of hydrophobic additive, 1 part of vinyltrimethoxysilane, 3 parts of maleic anhydride-grafted polypropylene with a grafting rate of 1.2%, 0.6 parts of β-octadecyl malonate and 0.6 parts of polyethylene wax at high speed for 10 min, then add to a twin-screw extruder, set the temperature to 175℃~220℃, melt extrude, granulate, and obtain flame retardant layer masterbatch; The composite flame retardant is obtained by mixing a moisture-resistant flame retardant and a flame retardant synergist in a mass ratio of 7:3; the preparation method of the moisture-resistant flame retardant includes the following steps: a. Disperse 20g of phytic acid in 200mL of anhydrous methanol, sonicate for 15min, then add 2.22g of zinc nitrate hexahydrate, continue dispersing for 10min, and stir at 60℃ for 11h to obtain Zn-AP mixture; b. Add 2.46 g of 2-methylimidazole to 50 mL of anhydrous methanol. After it is fully dissolved, slowly add it to the Zn-AP mixture. After it is completely added, continue to stir the reaction at 55 °C for 30 min, let it stand for 24 h, filter it, and obtain the crude product. c. The crude product was centrifuged and washed three times with anhydrous methanol at 5000 rpm, and then dried at 80°C to constant weight to obtain a moisture-resistant flame retardant. The flame retardant synergist is antimony trioxide supported on ZSM-5 porous molecular sieve, with a loading amount of 7% of the weight of ZSM-5 porous molecular sieve; The hydrophobic additive is obtained by mixing hydrophobic nano-silica and low-viscosity polyolefin in a mass ratio of 2:3, and the particle size of the hydrophobic nano-silica is 35nm. The low-viscosity polyolefin is a maleic anhydride-grafted polyolefin with a melt flow rate of 12g / 10min at 230℃ and 2.16kg load. S4. The antibacterial layer masterbatch, reinforcing layer masterbatch, and flame retardant layer masterbatch are added to the corresponding barrels of the three-layer co-extrusion extruder, and the processing temperature is set to 180℃~220℃. After melt co-extrusion, shaping, cooling, and cutting, environmentally friendly, moisture-resistant, and flame-retardant PPR pipes are obtained.

[0059] Comparative Example 1: The difference between Comparative Example 1 and Example 3 is that no moisture-resistant flame retardant was added to the flame retardant layer of Comparative Example 1, while the rest is the same as Example 3.

[0060] Comparative Example 2: The difference between Comparative Example 2 and Example 3 is that the flame retardant synergist in the flame retardant layer of Comparative Example 2 is antimony trioxide, that is, antimony trioxide is directly added and used, without ZSM-5 porous molecular sieve for loading. Otherwise, it is the same as Example 3.

[0061] Comparative Example 3: The difference between Comparative Example 3 and Example 3 is that no flame retardant synergist was added to the flame retardant layer of Comparative Example 3, but otherwise it is the same as Example 3.

[0062] Comparative Example 4: The difference between Comparative Example 4 and Example 3 is that no hydrophobic additive was added to the flame retardant layer of Comparative Example 4, but otherwise it is the same as Example 3.

[0063] Comparative Example 5: Compared with Example 3, Comparative Example 5 uses a conventional flame retardant (a mixture of ammonium polyphosphate, pentaerythritol and melamine in a mass ratio of 3:2:1) instead of the moisture-resistant flame retardant in this invention. Otherwise, it is the same as Example 3.

[0064] I. The PPR pipes prepared in Examples 1-3 and Comparative Examples 1-5 were subjected to the performance tests shown in Table 1. The results are shown in Table 1 below. The oxygen index was determined according to GB / T2406-1993. The pipes underwent damp heat treatment followed by flame retardancy testing. The damp heat treatment conditions were: temperature 40℃, humidity 90%, duration 72h. The flame retardancy rating was determined according to GB8624-2012, which classifies flame retardancy into A, B1, B2, and B3, with flame retardancy decreasing sequentially. The antibacterial rate test was conducted according to JC / T939-2004. Products with an antibacterial rate of not less than 90% can be reported as having antibacterial effects, and products with an antibacterial rate of not less than 99% can be reported as having strong antibacterial effects.

[0065] Table 1: Performance Test Results

[0066] Analysis of the data in Table 1 shows that the pipes prepared in Examples 1-3 of this invention all exhibit excellent flame-retardant properties, with a flame-retardant rating of B1, meeting the high standards required for building fireproof materials. This is attributed to the composite flame retardant, which, through the synergistic effect of a moisture-resistant flame retardant with a hydrophobic zeolite-like imidazole skeleton-8 (ZIF-8) in situ grown in phytic acid (PA) molecules and a flame-retardant synergist supported on a molecular sieve, achieves superior flame-retardant performance. Furthermore, the moisture-resistant flame retardant also synergistically interacts with the hydrophobic additive, significantly improving hydrophobic properties and enhancing the effectiveness of the composite flame retardant in humid environments. Compared to Example 3, Comparative Example 1 did not add a moisture-resistant flame retardant, resulting in a weakened flame-retardant synergistic effect and reduced hydrophobicity, leading to a significant decrease in flame-retardant performance. The changes in the flame-retardant synergists in Comparative Examples 2 and 3 also weakened the synergistic flame-retardant effect. Comparative Example 4 did not add a hydrophobic additive, causing the hydrophobic moisture-resistant flame retardant to lose its synergistic hydrophobic effect with the hydrophobic additive, resulting in pipes with lower hydrophobic properties than in Example 3. After damp heat treatment, it failed to achieve the optimal flame-retardant effect. Comparative Example 5 used a conventional flame retardant to replace the moisture-resistant flame retardant of this application. Since conventional flame retardants lack moisture resistance, damp heat treatment affected their effectiveness in humid environments, resulting in pipes with lower flame-retardant performance than in Example 3. This demonstrates that through component optimization, the synergistic effect between components in this application achieves a synergistic effect greater than the sum of its parts (1+1>2), resulting in better performance.

[0067] II. To further verify the performance of the pipe of the present invention, the following performance tests were also conducted, and the test results are shown in Table 2. Among them, the water contact angle test was conducted using a K12 contact angle meter from KRUSS GmbH, Germany. The diameter of the deionized water droplet was approximately 1.5 mm. The droplet was applied to the inner wall surface of the pipe using a micro-syringe, and the average value of the measurements at three different locations was taken as the measured contact angle. The oxygen permeability was referenced to GB / T34437-2017; the hydrostatic pressure was referenced to GB / T18742.2-2017; and the hot and cold water circulation was referenced to GB / T19993-2005.

[0068] Table 2: Performance Test Results

[0069] Analysis of the data in Table 2 shows that, by optimizing the composition of the pipe, the pipe maintains good structural integrity and pressure resistance under long-term pressure, and the water contact angle is higher than 125°, indicating that the addition of hydrophobic additives can form an effective hydrophobic barrier, and the surface of the pipe has obvious hydrophobic properties. Compared with Example 3, Comparative Example 1 did not add a moisture-resistant flame retardant, resulting in the inability to form a dense char layer, and the flame retardant effect was significantly worse than that of Example 3. In the moisture-resistant flame retardant, the hydrophobic zeolite-like imidazole framework-8 (ZIF-8) was grown in situ in phytic acid (PA) molecules. Since this structure itself also has a certain degree of hydrophobicity, the lack of synergistic effect of the moisture-resistant flame retardant resulted in a hydrophobic effect that was not as good as that of Example 3. In the flame retardant layer of Comparative Example 2, the flame retardant synergist was antimony trioxide, which affected its synergistic effect with the moisture-resistant flame retardant. The main impact on flame retardant effect was observed in Example 3, which passed the hydrostatic test. Example 4, lacking a hydrophobic additive, exhibited poorer hydrophobicity than Example 3 due to water adsorption and penetration, affecting the effectiveness of the composite flame retardant in humid environments and resulting in inferior flame retardant performance of the pipe after humid heat treatment compared to Example 3. Example 5 used a conventional flame retardant without a hydrophobic structure, failing to synergize with the hydrophobic additive, thus affecting hydrophobic performance. Therefore, this invention optimizes the composition and proportions, achieving synergistic flame retardancy between the moisture-resistant flame retardant and the synergistic flame retardant. This ensures the flame retardant effect of the composite flame retardant while simultaneously inhibiting moisture penetration and reducing its impact on the pipe, thus minimizing pipe loss in humid environments. Through extrusion molding, a PPR pipe with improved flame retardancy and moisture resistance, along with antibacterial properties, is achieved.

[0070] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0071] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. An environment-friendly moisture-resistant flame-retardant PPR pipe material, characterized in that, The environmentally friendly, moisture-resistant, and flame-retardant PPR pipe includes at least one flame-retardant layer, wherein the flame-retardant layer comprises the following raw materials in parts by weight: 100 parts PPR resin, 1 to 15 parts composite flame retardant, 1 to 7 parts hydrophobic additive, 0.5 to 3 parts silane coupling agent, 1 to 3 parts compatibilizer, 0.5 to 1 part antioxidant, and 0.5 to 1 part lubricant; The composite flame retardant is obtained by mixing a moisture-resistant flame retardant and a flame retardant synergist in a mass ratio of (5~9):(1~5); The hydrophobic additive is obtained by mixing hydrophobic nano-silica with low-viscosity polyolefin in a mass ratio of (1~2):(3~5).

2. The environment-friendly wet-resistant flame-retardant PPR pipe according to claim 1, characterized in that, The preparation method of the moisture-resistant flame retardant includes the following steps: a. Phytic acid was dispersed in anhydrous methanol and ultrasonically dispersed. Then zinc nitrate hexahydrate was added and dispersed evenly. The mixture was stirred at 50℃~65℃ to obtain a Zn-AP mixture. b. Add 2-methylimidazole to anhydrous methanol. After it is fully dissolved, slowly add it to the Zn-AP mixture. After it is completely added, continue stirring and reacting. Allow it to stand, filter it, and obtain the crude product. c. The crude product is washed and dried to obtain a moisture-resistant flame retardant.

3. The environment-friendly wet-resistant flame-retardant PPR pipe according to claim 2, characterized in that, In step a, ultrasonic dispersion is performed for 10 to 20 minutes; the stirring reaction time is 10 to 15 hours.

4. The environment-friendly wet-resistant flame-retardant PPR pipe according to claim 2, characterized in that, In step a, the ratio of phytic acid, anhydrous methanol, and zinc nitrate hexahydrate added is (8~12)g:100mL:(1~3)g.

5. The environmentally friendly, moisture-resistant, flame-retardant PPR pipe according to claim 2, characterized in that, In step b, the stirring reaction is carried out at a temperature of 50℃~65℃ for 30min~35min; the settling time is 20h~24h.

6. The environmentally friendly, moisture-resistant, flame-retardant PPR pipe according to claim 1, characterized in that, The flame retardant synergist is a metal oxide supported on a porous molecular sieve.

7. The environmentally friendly, moisture-resistant, flame-retardant PPR pipe according to claim 1, characterized in that, The hydrophobic nano-silica has a particle size of 20nm~50nm.

8. The environmentally friendly, moisture-resistant, flame-retardant PPR pipe according to claim 1, characterized in that, The low-viscosity polyolefin is a maleic anhydride-grafted polyolefin, with a melt flow rate of 5-15 g / 10 min at 230°C and 2.16 kg load.

9. The environmentally friendly, moisture-resistant, flame-retardant PPR pipe according to claim 1, characterized in that, The compatibilizer is maleic anhydride-grafted polypropylene with a grafting rate of 0.8% to 1.5%.

10. A method for preparing environmentally friendly, moisture-resistant, and flame-retardant PPR pipe, characterized in that, The preparation method includes the following steps: S1. Add the raw materials for the preparation of the antibacterial layer to a twin-screw extruder, melt extrude, granulate, and obtain the antibacterial layer masterbatch; S2. Add the raw materials for preparing the reinforcing layer to a twin-screw extruder, melt extrude, granulate, and obtain the reinforcing layer masterbatch; S3. Add the raw materials for the preparation of the flame retardant layer to a twin-screw extruder, melt extrude, granulate, and obtain the flame retardant layer masterbatch; S4. The antibacterial layer masterbatch, reinforcing layer masterbatch, and flame retardant layer masterbatch are respectively added to the corresponding barrels of the three-layer co-extrusion extruder, and after melt co-extrusion, shaping, cooling, and cutting, environmentally friendly, moisture-resistant, and flame-retardant PPR pipes are obtained.

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