A PPR pipe and its preparation method and application

Abstract

The present invention belongs to the field of pipes, and specifically discloses a PPR pipe, a preparation method thereof, and an application thereof. The present invention adds a silane coupling agent modified inorganic filler containing layered hydrotalcite, hexagonal boron nitride, and modified active silicon powder to the fiber reinforcement layer and the flame retardant layer of the PPR pipe, so that the flame retardancy, mechanical strength, and pressure resistance of the PPR pipe can be significantly improved, so that the PPR pipe has excellent flame retardancy, antibacterial, pressure resistance, and mechanical properties; in addition, the preparation process of the PPR pipe of the present invention is simple, the cost is low, and the application prospect is broad.

Description

Technical Field

[0001] The invention belongs to the field of pipes, and in particular relates to a PPR pipe and a preparation method and application thereof. Background Art

[0002] During long-term use, the metal pipes of fire-fighting pipes are prone to corrosion, especially in humid and highly corrosive environments, which can cause the pipe walls to become thinner, perforated, or even leak, affecting the normal operation of the pipe system and causing the sprinkler system to be unable to work effectively when needed, thus posing potential hazards to the fire-fighting system.

[0003] PPR (random copolymer polypropylene) pipes have many advantages such as corrosion resistance, high pressure resistance, long life, easy installation and maintenance, and low construction cost. However, PPR itself has insufficient flame retardancy and is easy to burn when exposed to fire, which is very prone to fire. Although its flame retardancy can be increased by adding a small amount of traditional halogen flame retardants, the presence of halogen flame retardants will cause smoke of toxic gases such as hydrogen halides, carbon monoxide, and carbon dioxide to be produced when it burns, which not only affects the smooth progress of disaster relief work, but also causes a "second disaster" to life and property. With the continuous improvement of global environmental awareness, halogen-free flame retardant materials have gradually become recognized environmentally friendly materials and have been used more and more widely. However, a large amount of halogen-free materials must be added to obtain good flame retardancy. The compatibility of halogen-free materials with substrates is poor, which will significantly affect the strength, pressure resistance and other mechanical properties of the material itself, which is not conducive to the practical application and promotion of PPR flame retardant pipe products. Summary of the invention

[0004] In view of the problem that the halogen-free flame-retardant PPR pipes involved in the above-mentioned prior art cannot have both good flame retardancy and mechanical properties, the present invention will provide a PPR pipe and a preparation method and application thereof.

[0005] To achieve the above purpose, the following technical solutions are specifically included:

[0006] On the one hand, the present invention provides a PPR pipe material, which includes an antibacterial layer, a fiber reinforcement layer, and a flame retardant layer from the inside to the outside;

[0007] The antibacterial layer comprises the following components in parts by weight: 100 parts of random copolymer polypropylene and 2-4 parts of antibacterial agent;

[0008] The fiber reinforcement layer comprises the following components in parts by weight: 60-80 parts of random copolymer polypropylene, 20-30 parts of fiber, 5-10 parts of compatibilizer, 0.1-1 parts of antioxidant, and 3-15 parts of silane coupling agent modified inorganic filler;

[0009] The flame retardant layer comprises the following components in parts by weight: 60-80 parts of random copolymer polypropylene, 10-15 parts of halogen-free flame retardant, 5-10 parts of compatibilizer, 5-20 parts of silane coupling agent modified inorganic filler, and 0.1-1 parts of antioxidant;

[0010] In the silane coupling agent modified inorganic filler of the fiber reinforced layer and the flame retardant layer, the inorganic filler includes layered hydrotalcite, hexagonal boron nitride and modified active silicon powder.

[0011] PPR pipes have an internal hollow structure. From the inside to the outside, the pipes include an inner layer, a middle layer, and an outer layer, which correspond to the antibacterial layer, the fiber-reinforced layer, and the flame-retardant layer, respectively. All three layers use random copolymer polypropylene as the base resin, and corresponding additives are added to achieve their specific functions. Among them, antibacterial agents are added to the inner layer of the pipe to effectively prevent bacterial growth and ensure the hygiene and cleanliness of the pipe; the addition of fibers in the fiber layer not only reduces the linear expansion coefficient of the pipe and improves the mechanical properties of the pipe, but also improves the flame retardant ability of the pipe; the addition of halogen-free flame retardants in the flame retardant layer can increase its flame retardant properties. In particular, the PPR pipe of the present invention has added silane coupling agent modified inorganic filler in both the fiber reinforcement layer and the flame retardant layer, which can have good dispersibility in the resin matrix and play a lubricating and flame retardant role: on the one hand, the layered hydrotalcite and hexagonal boron nitride are both lamellar structures, which are easy to peel and slip between layers when external force is applied, and therefore have a lubricating effect, can greatly reduce the friction coefficient in the system, improve melt fluidity and formability, avoid polymer decomposition caused by high shear heat due to the addition of flame retardants or fibers, reduce processing costs, and have a unique lamellar structure; at the same time, the surface of the modified active silicon powder has an organic system affinity group, which can improve compatibility with the resin and has The internal lubrication performance improves the processing performance between the components, and the modified silicon micropowder has increased cross-linking, which can further increase the wear resistance of the pipe; the layered hydrotalcite, hexagonal boron nitride and modified active silicon micropowder are combined as a whole inorganic filler, which cooperate with each other to synergistically improve the appearance and wear resistance of the pipe; on the other hand, the layered hydrotalcite and boron nitride nanosheets absorb a large amount of heat during the flame retardant process, which is beneficial to reduce the high temperature generated during combustion, and can be used as a halogen-free high smoke suppression synergist. At the same time, the lamellar structure has a flame retardant effect, which inhibits the volatilization of combustibles during the decomposition of the polymer and prevents the entry of external oxygen. At the same time, it is compounded with halogen-free flame retardants and has excellent flame retardant effects.

[0012] Preferably, in the PPR pipe, the thickness of the fiber-reinforced layer accounts for no less than 30% of the thickness of the PPR pipe, and more preferably 30-45%.

[0013] Preferably, in the fiber-reinforced layer, the weight portion of the silane coupling agent-modified inorganic filler is 5-10 parts.

[0014] Preferably, in the PPR pipe, the thickness of the flame retardant layer accounts for no less than 30% of the thickness of the PPR pipe, and more preferably 30-45%.

[0015] Preferably, in the flame retardant layer, the weight portion of the silane coupling agent modified inorganic filler is 10-15 parts.

[0016] Preferably, in the silane coupling agent modified inorganic filler, the mass ratio of silane coupling agent, layered hydrotalcite, hexagonal boron nitride and modified active silicon micropowder is silane coupling agent: layered hydrotalcite: hexagonal boron nitride: modified active silicon micropowder = 1: (0.5-3): (0.5-3): (0.5-3).

[0017] Preferably, the preparation method of the silane coupling agent modified inorganic filler comprises the following steps:

[0018] (1) mixing hexagonal boron nitride and hydrogen peroxide solution, stirring and performing a hydroxylation reaction to obtain hydroxylated hexagonal boron nitride;

[0019] (2) dispersing ammonium chloride, sodium hydroxide and hydroxylated hexagonal boron nitride in water to obtain a premix; adding the premix to an aqueous solution of magnesium chloride and aluminum chloride, and reacting under the assistance of ultrasound to obtain a composite of layered hydrotalcite and hexagonal boron nitride;

[0020] (3) adding the modified active silicon micropowder and the silane coupling agent into ethanol and performing ultrasonic stirring; then adding the composite of the layered hydrotalcite and hexagonal boron nitride, reacting under the assistance of ultrasound, and vacuum drying to obtain the silane coupling agent modified inorganic filler.

[0021] Further preferably, in step (1), when the boron nitride and the hydrogen peroxide solution are mixed, the dosage of the boron nitride is 0.05-0.5 kg / L, and the mass percentage of hydrogen peroxide in the hydrogen peroxide solution is 10-30%.

[0022] Further preferably, in step (1), the stirring time is 12-48 hours, and the stirring rate is 300-800 rpm.

[0023] Further preferably, in step (1), the temperature of the hydroxylation reaction is 90-120° C., and the time of the hydroxylation reaction is 12-48 h.

[0024] Further preferably, in step (2), the reaction time is 3-5 h.

[0025] Further preferably, in step (2), the mass ratio of ammonium chloride, sodium hydroxide and hydroxylated hexagonal boron nitride is (20-40): (5-15): (10-25).

[0026] Further preferably, in step (2), the mass ratio of the hydroxylated hexagonal boron nitride to water is (10-25): (100-200).

[0027] Further preferably, in step (2), the mass ratio of the hydroxylated hexagonal boron nitride, magnesium chloride and aluminum chloride is (10-25): (5-15): (15-20). Further preferably, in step (3), the ultrasonic stirring time is 5-7 hours, and the reaction time is 3-5 hours.

[0028] Further preferably, in step (3), the mass ratio of the modified active silicon powder, the silane coupling agent and ethanol is (10-20): (10-20): (80-150).

[0029] Further preferably, in step (3), the mass ratio of the modified active silicon powder to the composite of layered hydrotalcite and hexagonal boron nitride is (10-20):(30-45).

[0030] Preferably, in the silane coupling agent modified inorganic filler, the silane coupling agent includes at least one of γ-aminopropyltriethoxysilane and γ-glycidyloxypropyltrimethoxysilane;

[0031] Preferably, the modified active silicon micropowder is active silicon micropowder modified by at least one of epoxy modification, acyloxy modification and vinyl modification.

[0032] Preferably, in the antibacterial layer, the density of the random copolymer polypropylene is 0.895-0.915 g / cm 3 , and its melt flow rate is 0.2-0.5g / 10min; the antibacterial agent includes a silver ion antibacterial agent, and the carrier of the silver ion antibacterial agent includes at least one of zeolite, zirconium phosphate, calcium zinc phosphate, and soluble glass.

[0033] Preferably, in the fiber reinforced layer, the density of the random copolymer polypropylene is 0.895-0.915 g / cm 3 , its melt flow rate is 0.2-0.5g / 10min

[0034] Preferably, the fibers include basalt fibers and / or surface-treated alkali-free continuous basalt chopped fibers, the average length of the fibers is 2-4 mm, and the average diameter of the fibers is 6-15 μm.

[0035] Preferably, in the fiber-reinforced layer and the flame-retardant layer, the compatibilizer comprises polypropylene grafted maleic anhydride, and the density of the polypropylene grafted maleic anhydride is 0.9-1.0 g / cm 3, its melt flow rate is 5-10g / 10min, and its grafting rate is 1-1.5%.

[0036] Preferably, in the fiber-reinforced layer and the flame-retardant layer, the antioxidant is independently selected from at least one of 2,6-di-tert-butyl-p-cresol, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, triphenyl phosphite and tributyl sulfite.

[0037] Preferably, in the flame retardant layer, the density of the random copolymer polypropylene is 0.895-0.915 g / cm 3 , and its melt flow rate is 0.2-0.5g / 10min.

[0038] Preferably, the flame retardant includes at least one of aluminum diethylphosphinate, melamine cyanurate, and piperazine pyrophosphate.

[0039] On the other hand, the present invention provides a method for preparing the PPR pipe, comprising the following steps:

[0040] (1) The raw materials of the antibacterial layer, the fiber reinforced layer, and the flame retardant layer are mixed uniformly, and the raw materials are melted, extruded, and granulated to obtain granules of the antibacterial layer, the fiber reinforced layer, and the flame retardant layer respectively;

[0041] (2) The antibacterial layer, the fiber-reinforced layer, and the flame-retardant layer pellets are respectively extruded through a three-layer co-extrusion die, shaped, cooled, pulled, and cut to obtain the PPR pipe.

[0042] Preferably, in step (1), the melting temperature is 170-190°C.

[0043] Preferably, in step (2), the extrusion temperature is 190-210°C.

[0044] In addition, the present invention also provides an application of the PPR pipe in the preparation of fire protection pipelines.

[0045] Compared with the prior art, the present invention has the following beneficial effects: the present invention can significantly improve the flame retardancy, mechanical strength and pressure resistance of the PPR pipe by adding a silane coupling agent-modified inorganic filler containing layered hydrotalcite, hexagonal boron nitride and modified active silicon micropowder to the fiber reinforcement layer and the flame retardant layer of the PPR pipe, so that the PPR pipe has excellent flame retardancy, antibacterial, pressure resistance and mechanical properties; in addition, the PPR pipe preparation process of the present invention is simple, the cost is low, and the application prospect is broad. DETAILED DESCRIPTION

[0046] In order to better illustrate the purpose, technical scheme and advantages of the present invention, the present invention will be further described below through specific examples. The test methods used in the examples and / or comparative examples are conventional methods unless otherwise specified; the materials, reagents, etc. used can be obtained from commercial channels unless otherwise specified.

[0047] raw material:

[0048] PPR: 4220 Beijing Yanshan Branch of China Petrochemical Corporation;

[0049] Glass carrier antibacterial agent: JDSKM-PE3 Jinda Nano Technology Co., Ltd.;

[0050] Zinc calcium phosphate carrier antibacterial agent: PPR15-6P0114P011C Fuji, Japan;

[0051] Zirconium phosphate carrier antibacterial agent: JDSKM-PP25 Jinda Nano Technology Co., Ltd.;

[0052] Basalt fiber: Changzhou Bochao Engineering Materials Co., Ltd.;

[0053] Compatibilizer Polypropylene grafted with maleic anhydride: 18722 SK General Chemical;

[0054] Modified active silica powder: epoxy modified active silica powder, HY-GA-2, Shenzhen Haiyang Powder;

[0055] Hexagonal boron nitride: BN, Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0056] Flame retardant: aluminum diethylphosphinate, Shouguang Puer Chemical Co., Ltd.;

[0057] Antioxidant: 2,6-di-tert-butyl-p-cresol, Shanghai Aladdin Biochemical Technology Co., Ltd.

[0058] Silane coupling agent: γ-aminopropyltriethoxysilane, Shanghai Aladdin Biochemical Technology Co., Ltd.

[0059] Filler 1: The silane coupling agent modified inorganic filler is self-made, and the following examples and comparative examples all use this silane coupling agent modified inorganic filler. The self-made preparation method includes the following steps:

[0060] (1) 0.1 kg / L of hexagonal boron nitride powder and 30% hydrogen peroxide solution were mixed, stirred at 600 rpm / min for 24 hours, and then the mixture was placed in a reactor and reacted at 100°C for 24 hours. After the reaction, the mixture was centrifuged and washed three times with deionized water, and then ultrasonicated in an ultrasonic cleaning machine for 2 hours, and finally vacuum dried at 50°C to obtain hydroxylated hexagonal boron nitride.

[0061] (2) dispersing 35 parts by weight of ammonium chloride, 10 parts by weight of sodium hydroxide and 17 parts by weight of hydroxylated hexagonal boron nitride in 150 parts by weight of deionized water to obtain a premix; slowly adding the premix into an aqueous solution of 11 parts by weight of magnesium chloride and 17 parts by weight of aluminum chloride, and reacting for 4 hours under ultrasound assistance to obtain a composite of layered hydrotalcite and hexagonal boron nitride;

[0062] (3) 20 parts by weight of modified active silicon powder and 20 parts by weight of silane coupling agent are added to 100 parts by weight of ethanol, and ultrasonic stirring is performed for 6 hours; then 40 parts by weight of the composite of layered hydrotalcite and hexagonal boron nitride are added, reacted under ultrasonic assistance for 2.5 hours, and vacuum dried to obtain the silane coupling agent modified inorganic filler.

[0063] Filler 2: The preparation method of the mixture of hexagonal boron nitride and modified active silicon powder used in Comparative Example 3 refers to the preparation method of the silane coupling agent modified inorganic filler mentioned above, and specifically includes the following steps:

[0064] (1) 0.1 kg / L of hexagonal boron nitride powder and 30% hydrogen peroxide solution were mixed, stirred at 600 rpm / min for 24 hours, and then the mixture was placed in a reactor and reacted at 100°C for 24 hours. After the reaction, the mixture was centrifuged and washed three times with deionized water, and then ultrasonicated in an ultrasonic cleaning machine for 2 hours, and finally vacuum dried at 50°C to obtain hydroxylated hexagonal boron nitride.

[0065] (2) 20 parts by weight of modified active silicon micropowder and 20 parts by weight of silane coupling agent are added to 100 parts by weight of ethanol, and ultrasonic stirring is performed for 6 hours; then 40 parts by weight of a mixture of hydroxylated hexagonal boron nitride is added, and the mixture is reacted under ultrasonic assistance for 2.5 hours, and vacuum dried to obtain a mixture of hexagonal boron nitride and modified active silicon micropowder.

[0066] Filler 3: The preparation method of the mixture of layered hydrotalcite and modified active silicon powder used in Comparative Example 4 refers to the preparation method of the silane coupling agent modified inorganic filler mentioned above, and specifically includes the following steps:

[0067] (2) dispersing 35 parts by weight of ammonium chloride and 10 parts by weight of sodium hydroxide in 150 parts by weight of deionized water to obtain a premix; slowly adding the premix into an aqueous solution of 11 parts by weight of magnesium chloride and 17 parts by weight of aluminum chloride, and reacting for 4 hours under the assistance of ultrasound to obtain a layered hydrotalcite;

[0068] (3) 20 parts by weight of modified active silica powder and 20 parts by weight of silane coupling agent were added to 100 parts by weight of ethanol, and ultrasonic stirring was performed for 6 hours; then 40 parts by weight of the layered hydrotalcite mixture was added, and the mixture was reacted under ultrasonic assistance for 2.5 hours, and vacuum dried to obtain a mixture of the layered hydrotalcite and modified active silica powder.

[0069] Filler 4: The preparation method of the silane coupling agent-modified layered hydrotalcite and hexagonal boron nitride mixture (lacking modified active silicon powder) used in Comparative Example 5 refers to the preparation method of the silane coupling agent-modified inorganic filler described above, and specifically includes the following steps:

[0070] (1) 0.1 kg / L of hexagonal boron nitride powder and 30% hydrogen peroxide solution were mixed, stirred at 600 rpm / min for 24 hours, and then the mixture was placed in a reactor and reacted at 100°C for 24 hours. After the reaction, the mixture was centrifuged and washed three times with deionized water, and then ultrasonicated in an ultrasonic cleaning machine for 2 hours, and finally vacuum dried at 50°C to obtain hydroxylated hexagonal boron nitride.

[0071] (2) dispersing 35 parts by weight of ammonium chloride, 10 parts by weight of sodium hydroxide and 17 parts by weight of hydroxylated hexagonal boron nitride in 150 parts by weight of deionized water to obtain a premix; slowly adding the premix into an aqueous solution of 11 parts by weight of magnesium chloride and 17 parts by weight of aluminum chloride, and reacting for 4 hours under the assistance of ultrasound;

[0072] (3) adding 20 parts by weight of a silane coupling agent to 100 parts by weight of ethanol, and performing ultrasonic stirring for 6 hours; then adding 40 parts by weight of the mixture of the layered hydrotalcite and hexagonal boron nitride, reacting under ultrasonic assistance for 2.5 hours, and vacuum drying to obtain the layered hydrotalcite and hexagonal boron nitride mixture.

[0073] Examples 1-6 and Comparative Examples 1-5

[0074] A method for preparing a PPR pipe comprises the following steps:

[0075] (1) According to the formula in Table 1-3, the raw materials of the antibacterial layer, the fiber reinforced layer and the flame retardant layer are mixed evenly, respectively, melted, extruded and granulated by a twin-screw extruder, and the temperature is set at 170-190° C. to obtain pellets of the antibacterial layer, the fiber reinforced layer and the flame retardant layer, respectively;

[0076] (2) Controlling the process, the pellets of the antibacterial layer, the fiber reinforced layer, and the flame retardant layer are respectively passed through a single screw extruder and extruded through a three-layer co-extrusion die head so that the thickness of the antibacterial layer, the fiber reinforced layer, and the flame retardant layer are 30%, 35%, and 35%, respectively. The pipe is then passed through a die, shaped, cooled, pulled, and cut to obtain the PPR pipe. The temperature of the single screw extruder is set at 190-210°C.

[0077] Table 1 Antibacterial layer (parts by weight)

[0078]

[0079] Table 2 Fiber reinforcement layer (parts by weight)

[0080]

[0081] Table 3 Flame retardant layer (parts by weight)

[0082]

[0083] The PPR pipes prepared in the above embodiments and comparative examples were subjected to the following performance tests:

[0084] (1) Mechanical strength (MPa): tested according to GB / T 8804;

[0085] (2) Oxygen index: tested according to GB / T 2406-1993;

[0086] (3) Flame retardant grade: tested in accordance with the requirements of GB8624-2012, the flame retardant grades are divided into A, B1, B2, and B3, and the flame retardant performance decreases in sequence;

[0087] (4) Pipe bursting pressure (MPa): Tested according to GB / T 18742.2-2017, where pipe specifications are indicated as: d n 20×e n 3.4, the test time is 1h, the test temperature is 22℃;

[0088] (5) Axial linear expansion coefficient (mm / m×℃): tested according to CJ / T 258-2014;

[0089] (6) Antibacterial rate (%): tested according to GB / T 17219-1998;

[0090] The test results are shown in Table 4.

[0091] Table 4

[0092]

[0093] Compared with the above-mentioned Example 1 and Comparative Examples 1-2, there is no filler in Comparative Example 1, but it contains the same total weight of filler and flame retardant as in Example 1; in Comparative Example 2, both the fiber reinforcement layer and the flame retardant layer lack silane coupling agent modified inorganic filler, and PP is used to make up the number. It can be seen from Example 1 and Comparative Example 1 that when a certain amount of flame retardant already exists in the PPR pipe, the flame retardant is only added on this basis. Due to the poor compatibility between the flame retardant and the matrix, the flame retardant effect does not continue to increase, and it will also cause the mechanical strength and the bursting pressure of the pipe to decrease. Combining the analysis of Example 1 and Comparative Examples 1 and 2, it can be seen that adding silane coupling agent modified inorganic filler to the PPR pipe can not only significantly increase the flame retardant performance, but also significantly improve the mechanical strength and the bursting pressure of the pipe. It can be seen that the PPR pipe of the present invention has added silane coupling agent modified inorganic filler in both the fiber reinforcement layer and the flame retardant layer, which can have good dispersibility in the resin matrix and also have lubricating and flame retardant effects, so that the PPR pipe can have good mechanical strength, compressive resistance and flame retardant properties.

[0094] Compared with Comparative Examples 2-5, in Example 1, both the fiber-reinforced layer and the flame-retardant layer lack silane coupling agent-modified inorganic fillers in Comparative Example 2, and PP is used to make up the number of parts; in Comparative Examples 3-5, the fillers of the fiber-reinforced layer and the flame-retardant layer lack one of the layered hydrotalcite, hexagonal boron nitride and modified active silicon micropowder. In the silane coupling agent-modified inorganic filler of the present invention, the layered hydrotalcite, hexagonal boron nitride and modified active silicon micropowder work synergistically, and the whole has good dispersibility in the resin matrix, plays a lubricating and flame-retardant role, and can significantly improve the mechanical strength, compressive resistance and flame-retardant properties of the PPR pipe.

[0095] It can be seen from Examples 1-5 that, compared with Example 1, Example 2 replaces 5 parts of flame retardant in the flame retardant layer with silane coupling agent modified inorganic filler, and Example 3 replaces 5 parts of silane coupling agent modified inorganic filler in the flame retardant layer with flame retardant; Example 4 adds 10 parts of basalt fiber and 5 parts of silane coupling agent modified inorganic filler to the fiber reinforced layer, and Example 5 adds 5 parts of silane coupling agent to the fiber reinforced layer. It can be seen that the silane coupling agent modified inorganic filler of the present invention has a better effect than the traditional flame retardant, which not only improves the mechanical properties of the pipe, but also improves the flame retardant properties of the pipe.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A PPR pipe, characterized in that: From inside to outside, it includes an antibacterial layer, a fiber reinforcement layer, and a flame retardant layer; The antibacterial layer comprises the following components in parts by weight: 100 parts of random copolymer polypropylene and 2-4 parts of antibacterial agent; The fiber reinforcement layer comprises the following components in parts by weight: 60-80 parts of random copolymer polypropylene, 20-30 parts of fiber, 5-10 parts of compatibilizer, 0.1-1 parts of antioxidant, and 3-15 parts of silane coupling agent modified inorganic filler; The flame retardant layer comprises the following components in parts by weight: 60-80 parts of random copolymer polypropylene, 10-15 parts of halogen-free flame retardant, 5-10 parts of compatibilizer, 5-20 parts of silane coupling agent modified inorganic filler, and 0.1-1 parts of antioxidant; In the silane coupling agent modified inorganic filler of the fiber reinforcement layer and the flame retardant layer, the inorganic filler includes layered hydrotalcite, hexagonal boron nitride and modified active silicon micropowder; the modified active silicon micropowder is epoxy-modified active silicon micropowder; The preparation method of the silane coupling agent modified inorganic filler comprises the following steps: (1) mixing hexagonal boron nitride and a hydrogen peroxide solution, stirring and subjecting the mixture to a hydroxylation reaction to obtain hydroxylated hexagonal boron nitride; (2) dispersing ammonium chloride, sodium hydroxide and hydroxylated hexagonal boron nitride in water to obtain a premix; adding the premix to an aqueous solution of magnesium chloride and aluminum chloride, and reacting under the assistance of ultrasound to obtain a composite of layered hydrotalcite and hexagonal boron nitride; (3) adding the modified active silicon micropowder and the silane coupling agent into ethanol and performing ultrasonic stirring; then adding the composite of the layered hydrotalcite and hexagonal boron nitride, reacting under the assistance of ultrasound, and vacuum drying to obtain the silane coupling agent modified inorganic filler.

2. The PPR pipe according to claim 1, characterized in that: In the silane coupling agent modified inorganic filler, the silane coupling agent includes at least one of γ-aminopropyltriethoxysilane and γ-glycidyloxypropyltrimethoxysilane.

3. The PPR pipe according to claim 1, characterized in that: In the silane coupling agent modified inorganic filler, the mass ratio of silane coupling agent, layered hydrotalcite, hexagonal boron nitride and modified active silicon micropowder is silane coupling agent: layered hydrotalcite: hexagonal boron nitride: modified active silicon micropowder = 1: (0.5-3): (0.5-3): (0.5-3).

4. The PPR pipe according to claim 1, characterized in that: In the antibacterial layer, the density of the random copolymer polypropylene is 0.895-0.915 g / cm 3 , its melt flow rate is 0.2-0.5g / 10min; And / or, the antibacterial agent includes a silver ion antibacterial agent, and the carrier of the silver ion antibacterial agent includes at least one of zeolite, zirconium phosphate, calcium zinc phosphate, and soluble glass.

5. The PPR pipe according to claim 1, characterized in that: In the fiber-reinforced layer, the density of the random copolymer polypropylene is 0.895-0.915 g / cm 3 , its melt flow rate is 0.2-0.5g / 10min; And / or, the fibers include basalt fibers and / or surface-treated alkali-free continuous basalt chopped fibers, the average length of the fibers is 2-4 mm, and the average diameter of the fibers is 6-15 μm.

6. The PPR pipe according to claim 1, characterized in that: In the fiber reinforced layer and the flame retardant layer, the compatibilizer includes polypropylene grafted maleic anhydride, and the density of the polypropylene grafted maleic anhydride is 0.9-1.0 g / cm 3 , its melt flow rate is 5-10g / 10min, and its grafting rate is 1-1.5%; And / or, in the fiber-reinforced layer and the flame-retardant layer, the antioxidant is independently selected from at least one of 2,6-di-tert-butyl-p-cresol, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, triphenyl phosphite and tributyl sulfite.

7. The PPR pipe according to claim 1, characterized in that: In the flame retardant layer, the density of the random copolymer polypropylene is 0.895-0.915 g / cm 3 , its melt flow rate is 0.2-0.5g / 10min; And / or, the flame retardant includes at least one of aluminum diethylphosphinate, melamine cyanurate, and piperazine pyrophosphate.

8. A method for preparing a PPR pipe according to any one of claims 1 to 7, characterized in that: The steps include: (1) The raw materials of the antibacterial layer, the fiber reinforced layer, and the flame retardant layer are mixed uniformly, and the raw materials are melted, extruded, and granulated to obtain granules of the antibacterial layer, the fiber reinforced layer, and the flame retardant layer respectively; (2) The antibacterial layer, the fiber-reinforced layer, and the flame-retardant layer pellets are respectively extruded through a three-layer co-extrusion die, shaped, cooled, pulled, and cut to obtain the PPR pipe.

9. Use of the PPR pipe according to any one of claims 1 to 7 in the preparation of fire protection pipes.

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