Temperature-resistant flame-retardant antibacterial composite polypropylene pipe for water supply

Abstract

The invention discloses a temperature-resistant flame-retardant antibacterial composite polypropylene pipe for water supply, and belongs to the technical field of polypropylene pipes. The pipe is prepared by blending and extruding the following components in parts by weight: 70-80 parts of polypropylene random copolymer, 3-8 parts of modified organosilicon copolymer, 5-15 parts of maleic anhydride grafted polypropylene, 8-15 parts of polyolefin thermoplastic elastomer, an initiator, talcum powder, aluminum hydroxide, nano silicon dioxide, a lubricant, an antioxidant and the like. The modified organic silicon copolymer is prepared through specific steps, and the structure of the modified organic silicon copolymer contains a rigid oxa-phospho-spiro ring, a flexible organic silicon chain segment and a terminal guanidyl group. The rigid structure of the modified organic silicon copolymer is combined with the flexible chain segment, the temperature resistance and low-temperature toughness are improved, the flame retardant effect is achieved through cooperation of the oxa-phospho-spiro ring, the aluminum hydroxide and the organic silicon chain segment, and the molten drop tendency is reduced; guanidyl at the tail end endows long-acting antibacterial performance; vinyl double bonds of the organosilicone chain segment react with polypropylene to form a cross-linked network, so that the high-temperature stability and the creep resistance are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of polypropylene pipes, and in particular relates to a heat-resistant, flame-retardant and antibacterial composite polypropylene pipe for water supply. Background Art

[0002] Random copolymer polypropylene (RP) is a modified polypropylene resin formed by copolymerizing propylene with a small amount of ethylene or other α-olefins under specific temperature and pressure conditions. In its molecular structure, the comonomer is randomly distributed within the PP chain. This disrupts the orderly arrangement of the PP crystals, resulting in reduced crystallinity and smaller spherulite size, significantly improving its performance compared to homopolymer polypropylene. Compared to homopolymer polypropylene, random copolymer polypropylene has a lower melting point and exhibits superior transparency and impact resistance: its impact resistance is significantly improved, its rigidity is significantly enhanced, and it also offers excellent heat resistance—maximum operating temperature up to 95°C, typically 70°C at 1.0 MPa pressure, and a service life of up to 50 years, fully meeting the requirements of general pipeline applications. Furthermore, while improving on the low-temperature brittleness of homopolymer polypropylene, random copolymer polypropylene also offers higher-temperature creep resistance, high transparency, good strength, rigidity, and elasticity. Its applicable temperature range is 0-80°C, and its low-temperature impact resistance is typically 0°C.

[0003] Thanks to these excellent properties, random copolymer polypropylene pipes, as environmentally friendly and energy-saving green products, have been widely used in industrial building water supply and drainage, hot and cold water pipes, and floor heating systems, showing significant development prospects in modern civil construction and piping systems. However, random copolymer polypropylene still has certain performance limitations: it is prone to brittleness and poor toughness at low temperatures, which makes installation and use in northern winter construction difficult. Its high coefficient of thermal expansion in high-temperature environments significantly reduces the thermal stability, creep resistance, and dimensional retention of existing random copolymer polypropylene pipes when the medium temperature is high, posing safety risks and shortening its service life. Furthermore, polypropylene is inherently flammable and has a low oxygen index, so when it burns, it melts and drips, releasing large amounts of heat and smoke. Its lack of flame retardancy is a significant drawback in its application within buildings, especially in areas with strict fire protection requirements, posing a risk of fire spread. Furthermore, as a water supply pipe, its inner surface is prone to the growth of bacteria, mold, and other microorganisms over long-term use, forming biofilms that can contaminate water quality and affect water hygiene and safety. Summary of the Invention

[0004] In view of the above situation, in order to overcome the defects of the prior art, the present invention uses the synergistic effect of components such as random copolymerized polypropylene, modified silicone copolymer and maleic anhydride grafted polypropylene polyolefin thermoplastic elastomer to make a composite pipe through blending and extrusion, which significantly improves the temperature resistance, flame retardancy and antibacterial properties of the pipe.

[0005] In order to achieve the above-mentioned purpose, the following technical scheme is adopted: The present invention provides a heat-resistant, flame-retardant and antibacterial composite polypropylene pipe for water supply, which is made of the following components in parts by mass: 70-80 parts of random copolymer polypropylene, 3-8 parts of modified silicone copolymer, 5-15 parts of maleic anhydride grafted polypropylene, 8-15 parts of polyolefin thermoplastic elastomer, 0.1-0.5 parts of initiator, 3-5 parts of talc powder, 3-5 parts of aluminum hydroxide, 2-6 parts of nano-silicon dioxide, 0.5-1.5 parts of lubricant, and 0.3-0.8 parts of antioxidant.

[0006] Furthermore, the preparation of the polypropylene pipe comprises the following steps: S1. Blending: Dry the random copolymer polypropylene, maleic anhydride grafted polypropylene, and polyolefin thermoplastic elastomer at 80° C. for 4 h, add the dried base resin, modified silicone copolymer, initiator, antioxidant, and lubricant into a high-speed mixer, and premix at 500-800 rpm for 5 min. Then, add talc, aluminum hydroxide, and nano-silica, and continue mixing for 10 min until uniformly dispersed to obtain a premix; S2. Extrusion: The premix is ​​fed into a twin-screw extruder, and the temperature gradient is set as follows: zone 1: 170-180°C, zone 2: 180-190°C, zone 3: 190-200°C, die head: 200-210°C, the screw speed is controlled to 200-300 rpm, and the melt pressure is maintained at 15-25 MPa. The extruded tube is cooled and shaped to obtain a polypropylene pipe.

[0007] Furthermore, the modified organosilicon copolymer is prepared by the following steps: (1) Pentaerythritol and phosphorus oxychloride were heated to 80-90°C under nitrogen protection and refluxed for 4 hours. After the reaction, unreacted phosphorus oxychloride was removed by distillation under reduced pressure, cooled to room temperature, filtered, washed with dichloromethane, filtered again, and dried to obtain intermediate A as a white crystal. (2) Add acetyl propanol and triethylamine to dichloromethane, place in an ice-water bath and stir for 10 minutes, slowly add intermediate A, then remove the ice-water bath, stir and react at 30°C for 48 hours. After the reaction is completed, separate the liquids, wash with deionized water, dry the organic phase with anhydrous sodium sulfate, filter, remove dichloromethane with rotary evaporation, and recrystallize and dry with anhydrous ethanol to obtain polymer monomer A; (3) After mixing hydroxyl-terminated methyl vinyl silicone oil and 3-aminopropyltriethoxysilane, dibutyltin dilaurate was added under nitrogen protection, the temperature was raised to 80-90°C, the reaction was carried out for 5-6 hours, the alcohol and unreacted raw materials were removed by vacuum distillation, and the mixture was cooled to room temperature to obtain amino-terminated methyl vinyl silicone oil, which is the polymer monomer B; (4) Under nitrogen protection, monomer B and hexamethylenediamine were added to dimethyl sulfoxide, mixed evenly, and then monomer A was added. The temperature was raised to 65-75°C and stirred for 10-12 hours. After the reaction, the system was cooled to room temperature and ether was added in an amount 3-4 times the volume of the system to dilute it. After stirring for 30 minutes, the system was allowed to stand for precipitation, filtered, washed with anhydrous ethanol, and dried to obtain a copolymer product. Under nitrogen protection, the copolymer product and p-guanidine benzoic acid are added to N,N-dimethylformamide, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide are added, and nitrogen protection is introduced. After stirring at room temperature for 30 minutes, the temperature is raised to 40-50°C and the reaction is continued for 5-6 hours. Then, the system is poured into 5-10 times the volume of deionized water, filtered, and the precipitate is washed with 50% mass fraction ethanol aqueous solution and dried to obtain a modified silicone copolymer.

[0008] The preparation formula of the modified silicone copolymer is as follows: .

[0009] Furthermore, in step (1), the feeding ratio of pentaerythritol to phosphorus oxychloride is 1 g: 3.2-3.5 mL.

[0010] Furthermore, in step (2), the feeding ratio of acetyl propanol, triethylamine, intermediate A, and dichloromethane is 1 mL: 1.8-2.2 mL: 2.1-2.3 g: 25.6-38.5 mL.

[0011] Furthermore, in step (3), the feeding ratio of hydroxyl-terminated methyl vinyl silicone oil to 3-aminopropyltriethoxysilane is 10 g:1.3-1.5 mL, and the added amount of dibutyltin dilaurate is 0.1%-0.3% of the total mass of hydroxyl-terminated methyl vinyl silicone oil and 3-aminopropyltriethoxysilane.

[0012] Furthermore, in step (4), the feeding ratio of polymer monomer B, polymer monomer A, hexamethylenediamine and dimethyl sulfoxide is 35g: 2-3g: 3-8g: 45mL-60mL.

[0013] Furthermore, in the step (4), the feeding ratio of the copolymerization product, p-guanidinobenzoic acid and N,N-dimethylformamide is 3-5 g:1 g:25-40 mL, and the addition amounts of the 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide are 2%-3% and 1%-2% of the total mass of the copolymerization product and p-guanidinobenzoic acid, respectively.

[0014] Furthermore, the initiator is at least one of dicumyl peroxide and hydroxycumyl peroxide.

[0015] Furthermore, the lubricant is at least one of calcium stearate and zinc stearate.

[0016] Furthermore, the antioxidant is at least one of antioxidant 1010 , antioxidant 168 , antioxidant 330 and antioxidant 1076 .

[0017] The beneficial effects of the present invention are: The present invention makes composite pipes through the synergistic effect of random copolymerized polypropylene, modified silicone copolymer and maleic anhydride grafted polypropylene polyolefin thermoplastic elastomer, and then blends and extrude them, which significantly improves the heat resistance, flame retardancy and antibacterial properties of the pipes. The modified organic copolymer is obtained by firstly reacting a carbonyl-containing monomer and an amino-containing monomer through a Schiff base condensation reaction, and then reacting the amino groups at both ends with guanidinobenzoic acid.

[0018] The rigid oxyphosphorus spiro ring structure in the modified silicone copolymer can effectively limit the high-temperature movement of the polymer molecular chain and reduce the thermal expansion coefficient. At the same time, the flexible silicone chain segment introduced by amino-terminated methyl vinyl silicone oil can improve the low-temperature toughness of the matrix and broaden the operating temperature range of the pipe. Maleic anhydride grafted polypropylene is used as a compatibilizer to enhance the interfacial bonding strength between the random copolymer polypropylene matrix and the modified silicone copolymer, POE elastomer and other inorganic components, thereby inhibiting deformation caused by thermal expansion differences between components at high temperatures and improving the long-term thermal stability of the pipe.

[0019] The oxygen-phosphorus-spiro ring structure in the modified silicone copolymer can be used as a highly efficient gas-phase-condensed phase flame retardant. It releases phosphorus-containing free radicals when decomposed at high temperature, captures active free radicals in the combustion chain reaction, and exerts a gas-phase flame retardant effect. At the same time, it promotes carbonization in the condensed phase to form a dense, oxygen-isolated protective carbon layer. The aluminum hydroxide in the pipe component serves as an inorganic flame-retardant filler. It decomposes under heat to release crystalline water, absorbs a large amount of heat and dilutes the combustible gas and oxygen concentration. Its decomposition product, aluminum oxide, cooperates with the carbon layer promoted by the modified silicone copolymer to form a strong, heat-insulating physical barrier. The introduced silicone chain segment itself also has certain flame retardancy, which can enhance the strength and stability of the carbon layer. In addition, silicone can improve the fluidity of the melt and reduce the tendency of dripping during combustion.

[0020] The guanidine group introduced at the end of the modified silicone copolymer carries a strong positive charge and can strongly adsorb and penetrate the negatively charged bacterial cell membrane through electrostatic action, destroying its integrity, causing leakage of intracellular substances, and achieving efficient contact sterilization. The guanidine functional group is chemically bonded to the main chain of the modified silicone copolymer and is not easy to dissolve or migrate, avoiding the problem of traditional additive antibacterial agents being easily lost and causing the effect to attenuate, and giving the pipe long-lasting and stable antibacterial properties.

[0021] Through the vinyl double bonds on the main chain of amino-terminated methyl vinyl silicone oil, under the action of initiators during the blending and extrusion process, these double bonds can undergo free radical reactions with random copolymer polypropylene to form chemical crosslinking points. This crosslinking network can effectively limit the movement of molecular chains at high temperatures, significantly improve the high-temperature dimensional stability, creep resistance and long-term heat aging performance of the pipe, and reduce the thermal expansion coefficient at high temperatures. The silicone chain segments in the modified silicone copolymer also have excellent lubricity and low surface energy, which can improve the melt fluidity of the blending system, reduce extrusion torque and melt pressure, contribute to the dispersion of inorganic fillers and the smoothness of the pipe surface, and synergistically optimize the processing performance of the pipe with the lubricant. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The modified organosilicon copolymer prepared in Example 4 of the present invention 1 HNMR spectrum.

[0023] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present invention are clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art. Furthermore, any methods and materials similar or equivalent to those described herein can be applied to the present invention. The preferred embodiments and materials described herein are for illustrative purposes only and are not intended to limit the scope of this application.

[0026] The experimental methods in the following examples, unless otherwise specified, are all conventional methods, and the experimental materials used in the following examples, unless otherwise specified, are all purchased from commercial channels.

[0027] Example 1: A heat-resistant, flame-retardant and antibacterial composite polypropylene pipe for water supply is made from the following components in parts by mass: 70 parts of random copolymer polypropylene, 3 parts of modified silicone copolymer, 5 parts of maleic anhydride grafted polypropylene, 8 parts of polyolefin thermoplastic elastomer, 0.1 part of initiator, 3 parts of talc powder, 3 parts of aluminum hydroxide, 2 parts of nano-silicon dioxide, 0.5 part of lubricant, and 0.3 part of antioxidant.

[0028] The initiator is dicumyl peroxide, the lubricant is calcium stearate, and the antioxidant is a combination of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1.

[0029] The preparation of the polypropylene pipe comprises the following steps: S1. Blending: Dry the random copolymerized polypropylene, maleic anhydride grafted polypropylene, and polyolefin thermoplastic elastomer at 80° C. for 4 h, add the dried base resin, modified silicone copolymer, initiator, antioxidant, and lubricant into a high-speed mixer, and premix at 500 rpm for 5 min. Then, add talc, aluminum hydroxide, and nano-silica, and continue mixing for 10 min until uniformly dispersed to obtain a premix. S2. Extrusion: The premix is ​​fed into a twin-screw extruder, and the temperature gradient is set as follows: zone 1: 170°C, zone 2: 180°C, zone 3: 190°C, die head: 200°C, the screw speed is controlled to 200 rpm, the melt pressure is maintained at 15 MPa, and the extruded tube is cooled and shaped to obtain a polypropylene pipe.

[0030] The modified silicone copolymer is prepared by the following steps: (1) 1 g of pentaerythritol and 3.2 mL of phosphorus oxychloride were heated to 80°C under nitrogen protection and refluxed for 4 h. After the reaction, unreacted phosphorus oxychloride was removed by distillation under reduced pressure, cooled to room temperature, filtered, washed with dichloromethane, filtered again, and dried to obtain intermediate A as a white crystal. (2) Add 1 mL of acetyl-n-propanol and 1.8 mL of triethylamine to 25.6 mL of dichloromethane, place in an ice-water bath and stir for 10 min, slowly add 2.1 g of intermediate A, then remove the ice-water bath, stir and react at 30°C for 48 h. After the reaction is completed, separate the liquids, wash with deionized water, dry the organic phase with anhydrous sodium sulfate, filter, remove dichloromethane by rotary evaporation, and recrystallize and dry with anhydrous ethanol to obtain polymer monomer A; (3) 10 g of hydroxyl-terminated methyl vinyl silicone oil was mixed with 1.3 mL of 3-aminopropyltriethoxysilane, and then 0.1% of the total mass of dibutyltin dilaurate was added under nitrogen protection. The mixture was heated to 80°C and reacted for 5 h. The alcohol and unreacted raw materials were removed by vacuum distillation and cooled to room temperature to obtain amino-terminated methyl vinyl silicone oil, which was polymerized monomer B. (4) Under nitrogen protection, 35 g of polymer monomer B and 3 g of hexamethylenediamine were added to 45 mL of dimethyl sulfoxide, mixed evenly, and then 2 g of polymer monomer A was added. The temperature was raised to 65 ° C and stirred for 10 h. After the reaction, the system was cooled to room temperature and diluted with ether 3 times the volume of the system. After stirring for 30 min, the system was allowed to stand and precipitate was precipitated. The precipitate was filtered, washed with anhydrous ethanol, and dried to obtain a copolymer product. Under nitrogen protection, 3 g of the copolymer product and 1 g of p-guanidinobenzoic acid were added to 25 mL of N,N-dimethylformamide, and 2% of the total mass of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and 1% of the total mass of N-hydroxysuccinimide were added. Nitrogen protection was introduced, and the mixture was stirred at room temperature for 30 minutes. The temperature was raised to 40°C and the reaction was continued for 5 hours. The system was then poured into 5 times the volume of deionized water, filtered, and the precipitate was washed with 50% mass fraction of ethanol aqueous solution and dried to obtain a modified silicone copolymer.

[0031] Example 2: A heat-resistant, flame-retardant and antibacterial composite polypropylene pipe for water supply is made from the following components in parts by mass: 80 parts of random copolymer polypropylene, 8 parts of modified silicone copolymer, 15 parts of maleic anhydride grafted polypropylene, 15 parts of polyolefin thermoplastic elastomer, 0.5 parts of initiator, 5 parts of talc powder, 5 parts of aluminum hydroxide, 6 parts of nano-silicon dioxide, 1.5 parts of lubricant, and 0.8 parts of antioxidant.

[0032] The initiator is cumene peroxide, the lubricant is zinc stearate, and the antioxidant is a combination of antioxidant 330 and antioxidant 1076 in a mass ratio of 1:1.

[0033] The preparation of the polypropylene pipe comprises the following steps: S1. Blending: Dry the random copolymerized polypropylene, maleic anhydride grafted polypropylene, and polyolefin thermoplastic elastomer at 80° C. for 4 h, add the dried base resin, modified silicone copolymer, initiator, antioxidant, and lubricant into a high-speed mixer, and premix at 800 rpm for 5 min. Then, add talc, aluminum hydroxide, and nano-silica, and continue mixing for 10 min until uniformly dispersed to obtain a premix. S2. Extrusion: The premix is ​​fed into a twin-screw extruder, and the temperature gradient is set as follows: zone 1: 180°C, zone 2: 190°C, zone 3: 200°C, die head: 210°C, the screw speed is controlled to 300 rpm, the melt pressure is maintained at 25 MPa, and the extruded tube is cooled and shaped to obtain a polypropylene pipe.

[0034] The modified silicone copolymer is prepared by the following steps: (1) 1 g of pentaerythritol and 3.5 mL of phosphorus oxychloride were heated to 90°C under nitrogen protection and refluxed for 4 h. After the reaction, unreacted phosphorus oxychloride was removed by distillation under reduced pressure, cooled to room temperature, filtered, washed with dichloromethane, filtered again, and dried to obtain intermediate A as a white crystal. (2) Add 1 mL of acetyl-n-propanol and 2.2 mL of triethylamine to 38.5 mL of dichloromethane, place in an ice-water bath and stir for 10 min, slowly add 2.3 g of intermediate A, then remove the ice-water bath, stir and react at 30°C for 48 h. After the reaction is completed, separate the liquids, wash with deionized water, dry the organic phase with anhydrous sodium sulfate, filter, remove dichloromethane by rotary evaporation, and recrystallize and dry with anhydrous ethanol to obtain polymer monomer A; (3) After mixing 10 g of hydroxyl-terminated methyl vinyl silicone oil with 1.5 mL of 3-aminopropyltriethoxysilane, dibutyltin dilaurate (0.3% of the total weight of hydroxyl-terminated methyl vinyl silicone oil and 3-aminopropyltriethoxysilane) was added under nitrogen protection, the temperature was raised to 90 ° C, the reaction was carried out for 6 h, the alcohol and unreacted raw materials were removed by vacuum distillation, and the mixture was cooled to room temperature to obtain amino-terminated methyl vinyl silicone oil, which is the polymerization monomer B; (4) Under nitrogen protection, 35 g of polymer monomer B and 8 g of hexamethylenediamine were added to 60 mL of dimethyl sulfoxide, mixed evenly, and then 3 g of polymer monomer A was added. The temperature was raised to 75 ° C and stirred for 12 h. After the reaction, the system was cooled to room temperature and diluted with ether 4 times the volume of the system. After stirring for 30 min, the system was allowed to stand and precipitate was precipitated. The precipitate was filtered, washed with anhydrous ethanol, and dried to obtain a copolymer product. Under nitrogen protection, 5 g of the copolymer product and 1 g of p-guanidinobenzoic acid were added to 40 mL of N,N-dimethylformamide, and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (3% of the total mass of the copolymer product and guanidinobenzoic acid) and N-hydroxysuccinimide (2% of the total mass) were added. Nitrogen protection was introduced, and after stirring at room temperature for 30 minutes, the temperature was raised to 50°C and the reaction was continued for 6 hours. The system was then poured into 10 times the volume of deionized water, filtered, and the precipitate was washed with 50% mass fraction of ethanol aqueous solution and dried to obtain a modified silicone copolymer.

[0035] Example 3: A heat-resistant, flame-retardant and antibacterial composite polypropylene pipe for water supply is made from the following components in parts by mass: 75 parts of random copolymer polypropylene, 5.5 parts of modified silicone copolymer, 10 parts of maleic anhydride grafted polypropylene, 11.5 parts of polyolefin thermoplastic elastomer, 0.3 parts of initiator, 4 parts of talc powder, 4 parts of aluminum hydroxide, 4 parts of nano-silicon dioxide, 1.0 parts of lubricant, and 0.55 parts of antioxidant.

[0036] The initiator is a combination of dicumyl peroxide and hydroxycumyl peroxide in a mass ratio of 1:1, the lubricant is a combination of calcium stearate and zinc stearate in a mass ratio of 1:1, and the antioxidant is a combination of antioxidant 1010, antioxidant 168, and antioxidant 330 in a mass ratio of 2:1:1.

[0037] The preparation of the polypropylene pipe comprises the following steps: S1. Blending: Dry the random copolymerized polypropylene, maleic anhydride grafted polypropylene, and polyolefin thermoplastic elastomer at 80° C. for 4 h, add the dried base resin, modified silicone copolymer, initiator, antioxidant, and lubricant into a high-speed mixer, and premix at 650 rpm for 5 min. Then, add talc, aluminum hydroxide, and nano-silica, and continue mixing for 10 min until uniformly dispersed to obtain a premix. S2. Extrusion: The premix is ​​fed into a twin-screw extruder, and the temperature gradient is set as follows: zone 1: 175°C, zone 2: 185°C, zone 3: 195°C, die head: 205°C. The screw speed is controlled to 250 rpm, and the melt pressure is maintained at 20 MPa. The extruded tube is cooled and shaped to obtain a polypropylene pipe.

[0038] The modified silicone copolymer is prepared by the following steps: (1) 1 g of pentaerythritol and 3.4 mL of phosphorus oxychloride were heated to 85°C under nitrogen protection and refluxed for 4 h. After the reaction, unreacted phosphorus oxychloride was removed by distillation under reduced pressure, cooled to room temperature, filtered, washed with dichloromethane, filtered again, and dried to obtain intermediate A as a white crystal. (2) Add 1 mL of acetyl-n-propanol and 2 mL of triethylamine to 32 mL of dichloromethane, place in an ice-water bath and stir for 10 min, slowly add 2.2 g of intermediate A, then remove the ice-water bath, stir and react at 30°C for 48 h. After the reaction is completed, separate the liquids, wash with deionized water, dry the organic phase with anhydrous sodium sulfate, filter, remove dichloromethane with rotary evaporation, and recrystallize and dry with anhydrous ethanol to obtain polymer monomer A; (3) 10 g of hydroxyl-terminated methyl vinyl silicone oil was mixed with 1.4 mL of 3-aminopropyltriethoxysilane, and then dibutyltin dilaurate (0.2% by weight of the total weight of hydroxyl-terminated methyl vinyl silicone oil and 3-aminopropyltriethoxysilane) was added under nitrogen protection. The mixture was heated to 85°C and reacted for 5.5 h. The alcohol and unreacted raw materials were removed by vacuum distillation, and the mixture was cooled to room temperature to obtain amino-terminated methyl vinyl silicone oil, which was polymerized monomer B. (4) Under nitrogen protection, 35 g of polymer monomer B and 5.5 g of hexamethylenediamine were added to 52.5 mL of dimethyl sulfoxide, mixed evenly, and then 2.5 g of polymer monomer A was added. The temperature was raised to 70 ° C and stirred for 11 h. After the reaction, the system was cooled to room temperature and diluted with 3.5 times the volume of ether. After stirring for 30 min, the system was allowed to stand and precipitate was precipitated. The precipitate was filtered, washed with anhydrous ethanol, and dried to obtain a copolymer product. Under nitrogen protection, 4 g of the copolymer product and 1 g of p-guanidinobenzoic acid were added to 30 mL of N,N-dimethylformamide, and 2.5% of the total mass of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and 1.5% of the total mass of N-hydroxysuccinimide were added. Nitrogen protection was introduced, and the mixture was stirred at room temperature for 30 minutes. The temperature was raised to 45°C and the reaction was continued for 5.5 hours. The system was then poured into 7.5 times the volume of deionized water, filtered, and the precipitate was washed with 50% mass fraction of ethanol aqueous solution and dried to obtain a modified silicone copolymer.

[0039] Example 4: A heat-resistant, flame-retardant and antibacterial composite polypropylene pipe for water supply is made from the following components in parts by mass: 74 parts of random copolymer polypropylene, 6.5 parts of modified silicone copolymer, 10 parts of maleic anhydride grafted polypropylene, 11.5 parts of polyolefin thermoplastic elastomer, 0.4 part of initiator, 4 parts of talc powder, 4 parts of aluminum hydroxide, 5 parts of nano-silicon dioxide, 1.2 parts of lubricant, and 0.5 part of antioxidant.

[0040] The initiator is a combination of dicumyl peroxide and hydroxycumyl peroxide in a mass ratio of 2:1, the lubricant is a combination of calcium stearate and zinc stearate in a mass ratio of 1:1, and the antioxidant is a combination of antioxidant 1010, antioxidant 168, antioxidant 330 and antioxidant 1076 in a mass ratio of 2:1:1:1.

[0041] Comparative Example 1: A polypropylene pipe, which differs from Example 3 in that no modified silicone copolymer is added, and the remaining components and amounts are the same as those in Example 3.

[0042] Comparative Example 2: A polypropylene pipe, which differs from Example 3 in that the modified silicone copolymer is replaced by a copolymer product without grafted guanidine groups, i.e., no reaction with p-guanidine benzoic acid is performed in step (4), and the remaining components and amounts are the same as those in Example 3.

[0043] Result Analysis The modified organosilicon copolymer prepared in Example 4 of the present invention was characterized by hydrogen nuclear magnetic resonance spectroscopy, and its image is shown in FIG. Figure 1The multiplet at 3.85 ppm is the proton peak of the methylene group on the spirocyclic structure, the multiplet at 4.05 ppm is the proton peak of the methylene group connected to the phosphorus-oxygen bond, the multiplets at 0.15 ppm and 0.20 ppm are the proton peaks of the methyl group connected to silicon, the multiplets at 5.22 ppm and 5.46 ppm are the proton peaks of the double bond introduced by the hydroxyl-terminated methyl vinyl silicone oil, and the multiplets in the range of 1.25 ppm-1.65 ppm are the proton peaks of the alkyl chain segment introduced by hexamethylenediamine, indicating that monomer A, monomer B, and hexamethylenediamine are successfully polymerized to form a copolymer. Among them, the proton peaks at 6.65 ppm, 7.85 ppm, and 8.96 ppm are the proton peaks of the primary amine, imine, and secondary amine on the guanidine group, respectively, the proton peaks at 6.95 ppm and 7.55 ppm are the proton peaks on the benzene ring, and the proton peak at 8.45 ppm is the proton peak on the amide bond, indicating that p-guanidinobenzoic acid successfully capped both ends of the copolymer, thereby successfully preparing a modified silicone copolymer.

[0044] The mechanical properties, temperature change resistance, flame retardancy and antibacterial properties of the polypropylene pipes prepared in the embodiments of the present invention and the comparative examples were tested, and the test results are shown in Figure 1.

[0045] Mechanical property tests include tensile and impact resistance tests. The specific test methods are as follows: the tensile property test refers to GB / T 1040.2-2006, the specimen is a dumbbell-shaped specimen, the conditions are 23±2℃, 50% RH, and the tensile rate is 50 mm / min, and the tensile strength and elongation at break are measured; the impact property test refers to GB / T 1843-2008, the specimen is a notched cantilever beam impact specimen with a V-notch depth of 2 mm, and the conditions are -20℃ and 23℃, and the impact strength at different temperatures is tested.

[0046] The temperature change resistance performance refers to GB / T 1633-2000, under the conditions of load 10 N, heating rate 50℃ / h, and Vicat softening point (VST) is measured.

[0047] Flame retardant properties include tests for limiting oxygen index and vertical burning grade. The limiting oxygen index refers to GB / T 2406.2-2009, and the vertical burning grade is classified according to UL94.

[0048] The antibacterial performance test refers to ISO 22196-2011 and measures the antibacterial rate of each group of pipes against Escherichia coli and Staphylococcus aureus.

[0049] As can be seen from Table 1, the pipes prepared in various embodiments of the present invention have high strength and excellent ductility, and exhibit excellent impact strength at both low temperatures of -20°C and 23°C, solving the low-temperature embrittlement problem of traditional polypropylene pipes. The toughness is also better than that of ordinary pipes. The Vicat softening points are all over 150°C, indicating that the high-temperature dimensional stability is significantly improved. The vertical burning grade of Comparative Example 1 without the addition of the modified silicone copolymer only reaches V-1, while the examples with the addition of the copolymer all reach V-0, indicating that the flame retardant effect is significantly improved. The antibacterial rates against Escherichia coli and Staphylococcus aureus are both >98%, indicating excellent antibacterial properties.

[0050] Table 1 Comparison of performance test results of each group of polypropylene pipes

[0051] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

[0052] The present invention and its embodiments are described above. Such description is not restrictive. The embodiment shown in the embodiment is only one embodiment of the present invention, and actual application is not limited thereto. In short, if a person skilled in the art is inspired by the above, and does not deviate from the purpose of the invention, without creatively designing methods and embodiments similar to the technical solution, they shall fall within the scope of protection of the present invention.

Claims

1. A heat-resistant, flame-retardant, and antibacterial composite polypropylene pipe for water supply, characterized by: The invention is prepared from the following components in parts by weight: 70-80 parts of random copolymerized polypropylene, 3-8 parts of modified silicone copolymer, 5-15 parts of maleic anhydride grafted polypropylene, 8-15 parts of polyolefin thermoplastic elastomer, 0.1-0.5 parts of initiator, 3-5 parts of talc, 3-5 parts of aluminum hydroxide, 2-6 parts of nano-silicon dioxide, 0.5-1.5 parts of lubricant, and 0.3-0.8 parts of antioxidant. The preparation of the polypropylene pipe comprises the following steps: S1. Blending: Dry the random copolymer polypropylene, maleic anhydride grafted polypropylene, and polyolefin thermoplastic elastomer at 80° C. for 4 h, add the dried base resin, modified silicone copolymer, initiator, antioxidant, and lubricant into a high-speed mixer, and premix at 500-800 rpm for 5 min. Then, add talc, aluminum hydroxide, and nano-silica, and continue mixing for 10 min until uniformly dispersed to obtain a premix; S2, extrusion: the premix is ​​fed into a twin-screw extruder, and the temperature gradient is set as follows: zone 1: 170-180°C, zone 2: 180-190°C, zone 3: 190-200°C, die head: 200-210°C, the screw speed is controlled to 200-300 rpm, the melt pressure is maintained at 15-25 MPa, and the extruded tube is cooled and shaped to obtain a polypropylene pipe; Wherein, the modified organosilicon copolymer has the following structure: 。 2. The heat-resistant, flame-retardant, and antibacterial composite polypropylene pipe for water supply according to claim 1, characterized in that: The modified silicone copolymer is prepared by the following steps: (1) Pentaerythritol and phosphorus oxychloride were heated to 80-90°C under nitrogen protection and refluxed for 4 hours. After the reaction, unreacted phosphorus oxychloride was removed by distillation under reduced pressure, cooled to room temperature, filtered, washed with dichloromethane, filtered again, and dried to obtain intermediate A as a white crystal. (2) Add acetyl propanol and triethylamine to dichloromethane, place in an ice-water bath and stir for 10 minutes, slowly add intermediate A, then remove the ice-water bath, stir and react at 30°C for 48 hours. After the reaction is completed, separate the liquids, wash with deionized water, dry the organic phase with anhydrous sodium sulfate, filter, remove dichloromethane with rotary evaporation, and recrystallize and dry with anhydrous ethanol to obtain polymer monomer A; (3) After mixing hydroxyl-terminated methyl vinyl silicone oil and 3-aminopropyltriethoxysilane, dibutyltin dilaurate was added under nitrogen protection, the temperature was raised to 80-90°C, the reaction was carried out for 5-6 hours, the alcohol and unreacted raw materials were removed by vacuum distillation, and the mixture was cooled to room temperature to obtain amino-terminated methyl vinyl silicone oil, which is the polymer monomer B; (4) Under nitrogen protection, monomer B and hexamethylenediamine were added to dimethyl sulfoxide, mixed evenly, and then monomer A was added. The temperature was raised to 65-75°C and stirred for 10-12 hours. After the reaction, the system was cooled to room temperature and ether was added in an amount 3-4 times the volume of the system to dilute it. After stirring for 30 minutes, the system was allowed to stand for precipitation, filtered, washed with anhydrous ethanol, and dried to obtain a copolymer product. Under nitrogen protection, the copolymer product and p-guanidine benzoic acid are added to N,N-dimethylformamide, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide are added, and nitrogen protection is introduced. After stirring at room temperature for 30 minutes, the temperature is raised to 40-50°C and the reaction is continued for 5-6 hours. Then, the system is poured into 5-10 times the volume of deionized water, filtered, and the precipitate is washed with 50% mass fraction ethanol aqueous solution and dried to obtain a modified silicone copolymer.

3. The heat-resistant, flame-retardant, and antibacterial composite polypropylene pipe for water supply according to claim 2, characterized in that: In step (1), the feeding ratio of pentaerythritol to phosphorus oxychloride is 1 g: 3.2-3.5 mL.

4. The heat-resistant, flame-retardant, and antibacterial composite polypropylene pipe for water supply according to claim 2, characterized in that: In step (2), the feeding ratio of acetyl propanol, triethylamine, intermediate A, and dichloromethane is 1 mL: 1.8-2.2 mL: 2.1-2.3 g: 25.6-38.5 mL.

5. The heat-resistant, flame-retardant, and antibacterial composite polypropylene pipe for water supply according to claim 2, characterized in that: In the step (3), the feeding ratio of hydroxyl-terminated methyl vinyl silicone oil and 3-aminopropyltriethoxysilane is 10 g:1.3-1.5 mL, and the added amount of dibutyltin dilaurate is 0.1%-0.3% of the total mass of hydroxyl-terminated methyl vinyl silicone oil and 3-aminopropyltriethoxysilane.

6. The heat-resistant, flame-retardant, and antibacterial composite polypropylene pipe for water supply according to claim 2, characterized in that: In the step (4), the feeding ratio of the polymer monomer B, the polymer monomer A, hexamethylenediamine and dimethyl sulfoxide is 35g: 2-3g: 3-8g: 45mL-60mL.

7. The heat-resistant, flame-retardant, and antibacterial composite polypropylene pipe for water supply according to claim 2, characterized in that: In the step (4), the feeding ratio of the copolymerization product, p-guanidinobenzoic acid and N,N-dimethylformamide is 3-5 g:1 g:25-40 mL, and the addition amount of the 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide is 2%-3% and 1%-2% of the total mass of the copolymerization product and p-guanidinobenzoic acid, respectively.

8. The heat-resistant, flame-retardant, and antibacterial composite polypropylene pipe for water supply according to claim 1, characterized in that: The initiator is at least one of dicumyl peroxide and hydroxycumyl peroxide.

9. The heat-resistant, flame-retardant, and antibacterial composite polypropylene pipe for water supply according to claim 1, characterized in that: The lubricant is at least one of calcium stearate and zinc stearate.

10. The heat-resistant, flame-retardant, and antibacterial composite polypropylene pipe for water supply according to claim 1, characterized in that: The antioxidant is at least one of antioxidant 1010 , antioxidant 168 , antioxidant 330 and antioxidant 1076 .

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