Composite pipe and preparation method thereof

Abstract

The invention discloses a composite pipe and a preparation method thereof. The composite pipe is prepared from 80 to 120 parts of low-density polyethylene, 5 to 15 parts of high-density polyethylene, 20 to 40 parts of ethylene-vinyl alcohol copolymer, 1 to 10 parts of maleic anhydride grafted polyethylene, 5 to 10 parts of reinforcing agent, 5 to 20 parts of wear-resistant agent and 0.1 to 1 part of antioxidant. The invention also provides a preparation method of the composition. Compared with the prior art, the prepared composite pipe has the advantages of being high in barrier capacity, good in mechanical property, good in antibacterial property and the like.

Description

Technical Field

[0001] The invention relates to the technical field of pipe production, and in particular to a composite pipe and a preparation method thereof. Background Art

[0002] The outer packaging materials of products are key factors to ensure that the contents are not easy to leak or deteriorate, including packaging materials such as packaging bags, packaging boxes, and packaging hoses. Packaging hoses are relatively low in cost and have been widely used in the packaging of daily chemical products, food, etc. in our lives after more than ten years of rapid development. At present, packaging hoses are still prone to deformation and damage due to repeated extrusion by external forces for a long time, resulting in leakage of contents, or the quality of contents is affected by the long-term infiltration of water vapor and oxygen in a humid environment. Therefore, it is very necessary to provide a composite pipe with good barrier effect, repeated extrusion by external forces, and antibacterial properties.

[0003] CN108623915A discloses a modified white graphene composite polypropylene pipe and a preparation method thereof, wherein the polypropylene composite pipe is composed of 1-3 parts of barium sulfate whisker, 3-12 parts of flame retardant, 10-16 parts of antistatic agent, 4-8 parts of modified white graphene, 6-12 parts of impact modifier, 0.6-1.2 parts of antioxidant, 0.6-1.2 parts of dispersant, 0.5-1 parts of nano calcium carbonate, 0.7-1.4 parts of nano ceramic powder, 0.2-0.5 parts of lubricant, 0.4-0.8 parts of surfactant, and 60-120 parts of polypropylene to improve mechanical properties. However, adding a lot of inorganic components to the modified formula may cause the pipe to have greater rigidity and poor extrusion resistance during use.

[0004] CN1357702A discloses a plastic composite hose for packaging. The hose body of the present invention comprises a composite aluminum foil inner layer, an adhesive layer and a plastic outer layer. The composite aluminum foil inner layer is a roll-welded structure, and the adhesive layer and the plastic outer layer are co-extruded structures. The aluminum foil layer plays a barrier role in the composite structure of the present invention, and mainly relies on this layer to block the penetration of various molecules inside and outside the hose, especially the mutual penetration between oxygen molecules in the air outside the hose and molecules in the content of the hose. Although the aluminum foil layer of the present invention can play a barrier role, this type of aluminum-plastic hose packaging material is opaque, has poor recyclability, is not conducive to environmental protection, and has poor extrusion resistance. Summary of the invention

[0005] In view of the above-mentioned defects of the prior art, the object of the present invention is to provide a composite tube having good antibacterial properties, mechanical properties, and good barrier properties, which can be used for packaging cosmetics and toothpaste.

[0006] One of the purposes of the present invention is to provide a composite pipe, wherein the raw material components include, by weight: 80-120 parts of low-density polyethylene, 5-15 parts of high-density polyethylene, 20-40 parts of ethylene-vinyl alcohol copolymer, 1-10 parts of maleic anhydride grafted polyethylene, 5-10 parts of reinforcing agent, 5-20 parts of anti-wear agent, and 0.1-1 part of antioxidant;

[0007] Or, 80-120 parts of low-density polyethylene, 5-15 parts of high-density polyethylene, 20-40 parts of ethylene-vinyl alcohol copolymer, 1-10 parts of maleic anhydride grafted polyethylene, 5-20 parts of anti-wear agent, and 0.1-1 part of antioxidant.

[0008] Preferably, the antioxidant is at least one of 2,6-di-tert-butyl-4-methylphenol, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and antioxidant 168.

[0009] Preferably, the preparation method of the enhancer comprises the following steps, calculated by weight:

[0010] Step 1, dissolving 1-5 parts of tetracycline and 10-20 parts of citric acid in 10-50 parts of water, and then transferring to an autoclave to react at 180-220° C. for 6-10 hours; after naturally cooling to room temperature, centrifuging at 8000-12000 rpm for 5-15 minutes, and removing larger particles in the supernatant with a 0.22 mm microporous membrane filter to obtain a carbon dot stock solution;

[0011] Step 2, dissolving 1-5 parts of melamine and 5-15 parts of ammonium chloride in 20-40 parts of water, and then calcining at 500-700°C for 2-4 hours to obtain modified graphite carbon nitride; 1-5 parts of modified graphite carbon nitride and 10-20 parts of the carbon dot stock solution prepared in the above step 1 are mixed evenly, transferred to a reactor, and reacted at 160-200°C for 16-24 hours; after naturally cooling to room temperature, centrifuging at 8000-12000rpm for 5-15 minutes, using a 0.22mm microporous membrane filter to remove larger particles in the supernatant, and then freeze-drying for 16-36 hours to obtain a composite material of carbon dots loaded on graphite carbon nitride;

[0012] Step 3, 5-10 parts of the modifier, 10-20 parts of 2-(7-azobenzotriazole)-N,N,N',N'-tetramethyluronium hexafluorophosphate and 50-100 parts of N,N-dimethylformamide are mixed evenly, and 1-5 parts of the composite material prepared in the above step 2 loaded on graphite carbon nitride are added, and the mixture is reacted at 40-60°C and 1000-2000rpm for 10-16h, and then filtered, and the filter residue is washed with water 2-4 times, and dried at 40-60°C for 4-6h to obtain a reinforcing agent.

[0013] More preferably, the modifier in step 3 is at least one of chitosan, polylysine, and N-ethyl-2-nitroaniline.

[0014] Carbon dots are a new type of carbon nanomaterial with a particle size less than 10nm. 2 Hybrid or amorphous sp 3 Hybrid carbon cores are polymerized with organic functional groups to form nano-scale particles with a large specific surface area and rich functional groups on the surface, such as carboxyl, carbonyl and hydroxyl. These functional groups make them water-soluble and easier to surface modify and couple. Some carbon dots have positive charges on their surfaces and can be adsorbed on the negatively charged bacterial cell membrane surface through electrostatic action, thereby destroying the integrity of the cell membrane, causing the leakage of intracellular substances and leading to bacterial death. Under light or specific conditions, carbon dots can produce reactive oxygen species, such as singlet oxygen, hydroxyl free radicals and superoxide anions. These highly oxidizing substances can oxidize bacterial cell walls, cell membranes and intracellular biomacromolecules, thereby inhibiting bacterial growth or directly killing bacteria. They may interact with biomacromolecules such as enzymes and proteins in bacterial cells, interfere with the normal metabolic process of bacteria, and affect bacterial growth and reproduction.

[0015] In the preparation step of the enhancer of the present invention, modified graphite carbon nitride is synthesized by high-temperature calcination of melamine and ammonium chloride. It has a graphite-like layered structure, and is connected by triazine or units through covalent bonds in the plane to form a two-dimensional plane network. These planes are stacked by van der Waals forces to form a three-dimensional structure. This unique structure gives it higher chemical stability. Compared with the common melamine calcined synthetic graphite carbon nitride, the present invention can synthesize modified graphite carbon nitride with a higher specific surface area through the joint action of melamine and ammonium chloride, and has better light absorption capacity. Graphite carbon nitride absorbs photon energy under light conditions, and its valence band electrons transition to the conduction band to form photogenerated electrons and holes. The photogenerated electrons react with oxygen adsorbed on the surface of the material to generate superoxide anion radicals, and the holes react with water molecules on the surface to generate hydroxyl radicals. These highly oxidizing active oxygen species can attack the cell wall and cell membrane of bacteria, resulting in increased permeability and leakage of contents, thereby destroying the cell structure of bacteria and killing bacteria, and have excellent antibacterial properties.

[0016] Based on this, the present invention synthesizes a composite material of carbon dots supported on graphite carbon nitride by mixing carbon dot materials and modified graphite carbon nitride, that is, in step 2 of the process of preparing the enhancer of the present invention, the carbon dot stock solution prepared in step 1 and the modified graphite carbon nitride in step 2 are combined. The present invention forms an enhancer with high reaction activity with the matrix by forming a stable chemical bond through an amide condensation reaction between the composite material of carbon dots supported on graphite carbon nitride and the modifier. The enhancer prepared by the present invention has good photocatalytic performance, and the overlap of the ultraviolet-visible absorption of the graphite carbon nitride in its structure and the up-conversion emission spectrum of the carbon dots produces a strong spectral coupling, inducing a broadband photocatalytic response from the ultraviolet to the NIR region, which can further improve the antibacterial effect. The reinforcing agent prepared by the present invention is introduced into the preparation process of the composite pipe. Since the surface of the carbon dots in the reinforcing agent structure is rich in functional groups such as hydroxyl and carboxyl, maleic anhydride can be grafted onto polyethylene to react to form stable chemical bonds, and the reinforcing agent has high reaction activity with the matrix. The carbon dots and modifiers introduced into the reinforcing agent can chemically react or physically crosslink with the polyethylene molecular chains to form a three-dimensional crosslinked network. At the same time, the graphite carbon nitride in the reinforcing agent has good mechanical effects, which can enhance the mechanical effects of the composite material and increase the dispersibility of the composite material to improve the antibacterial effect.

[0017] Preferably, the step of adding the anti-wear agent comprises the following steps, calculated by weight:

[0018] Dissolve 1-5 parts of γ-aminopropyltriethoxysilane in dichloromethane to obtain a mass fraction of 1-5%, add 20-40 parts of ultra-high molecular weight polyethylene, ultrasonically extract for 5-10 minutes, filter, and dry the filter cake to obtain solid a, dissolve 1-5 parts of solid a in 10-50 parts of white oil, add 1-10 parts of wear-resistant particles, and react at 40-60°C for 2-4 hours to obtain a wear-resistant agent.

[0019] Further preferably, the wear-resistant particles are nano-silicon dioxide.

[0020] As a further illustration of the present invention, in the preparation process of the wear-resistant agent, the present invention ultrasonically extracts γ-aminopropyl triethoxysilane and ultra-high molecular weight polyethylene to obtain solid a, the cavitation effect of ultrasound can accelerate the material exchange between the solvent and the solid, the components in the γ-aminopropyl triethoxysilane solution may interact with the ultra-high molecular weight polyethylene, the amino group and other functional groups in the molecule may be adsorbed or chemically reacted with the active sites on the surface of the ultra-high molecular weight polyethylene, thereby introducing γ-aminopropyl triethoxysilane into the ultra-high molecular weight polyethylene, and obtaining an ultra-high molecular weight polyethylene containing amino groups and hydroxyls on the surface, i.e., solid a; then the solid a is mixed with the wear-resistant particles, and the amino groups on its surface may react with the hydroxyls on the surface of the nano-silicon dioxide by condensation reaction or other active sites by adsorption, thereby preparing the wear-resistant agent. The wear-resistant agent prepared by the present invention is introduced into the preparation process of the composite pipe, and the amino groups, alkoxy groups, silanol groups, etc. on the surface of the wear-resistant agent may react chemically with the oxygen-containing functional groups of the reinforcing agent and the functional groups on the maleic anhydride grafted polyethylene during the melt mixing process to form a cross-linked network, further increasing the wear resistance and mechanical properties.

[0021] The second object of the present invention is to provide a method for preparing the composite pipe, the method comprising the following steps:

[0022] Step 1, mixing low-density polyethylene, high-density polyethylene, ethylene-vinyl alcohol copolymer, maleic anhydride grafted polyethylene, wear-resistant agent, and reinforcing agent (if any) at 140-220° C. for 5-15 minutes to obtain a mixture;

[0023] Step 2, extruding and granulating the mixture to obtain a masterbatch;

[0024] Step 3: Melt the masterbatch and the antioxidant to form a tube to obtain a composite tube.

[0025] Preferably,

[0026] In the step 2, the granulation temperature is 140-220° C., the die head temperature is 140-230° C., and the screw speed is 10-30 r / min.

[0027] Preferably, in the step 3, the tube drawing process parameters are as follows: the upper drawing temperature is 120-180°C, the temperature inside the table is 140-180°C, and the temperature outside the table is 165-190°C.

[0028] Beneficial effects of the present invention:

[0029] 1. Compared with the prior art, the present invention prepares a composite pipe by reasonably proportioning the raw materials, utilizing the interaction between the raw materials, and optimizing the preparation process. The composite pipe prepared by the present invention not only has a good barrier effect, but also has good mechanical properties, mechanical effects and antibacterial properties, and can be used in the packaging of cosmetics, toothpaste, etc.

[0030] 2. Compared with the prior art, the present invention can improve the mechanical effect and antibacterial performance, and further improve the barrier performance by introducing a reinforcing agent and an anti-wear agent into the preparation process of the composite pipe. In the preparation process of the composite pipe, the reinforcing agent of the present invention can react with the anti-wear agent and the maleic anhydride grafted polyethylene to form a chemical bond, which is beneficial to improving the mechanical effect of the composite pipe. At the same time, the reinforcing agent and the anti-wear agent may also produce synergistic synergy through electrostatic adsorption, further improving the antibacterial effect. DETAILED DESCRIPTION

[0031] The parameters and sources of some substances in the examples are as follows:

[0032] Low-density polyethylene, grade 2426K, from Maoming Petrochemical;

[0033] High-density polyethylene, brand: 9007, from Taiwan Plastics;

[0034] Ethylene-vinyl alcohol copolymer, brand: 3201, from Sinopec Sichuan Wei;

[0035] Maleic anhydride grafted polyethylene, sourced from Nanjing Feiteng New Materials Technology Co., Ltd.;

[0036] Ultra-high molecular weight polyethylene, brand: U-PE350, from Yuyao Jiuding;

[0037] Nano-silicon dioxide, particle size 50nm;

[0038] Nano calcium carbonate, particle size 40-80nm;

[0039] Nano zinc oxide, particle size 30-80nm;

[0040] Chitosan, deacetylation degree ≥ 95%, viscosity 150mPa.s.

[0041] Example 1

[0042] A method for preparing a composite pipe comprises the following steps:

[0043] Step 1: Mix 100 g of low-density polyethylene, 10 g of high-density polyethylene, 30 g of ethylene-vinyl alcohol copolymer, 5 g of maleic anhydride grafted polyethylene, and 15 g of anti-wear agent at 200° C. for 10 min to obtain a mixture;

[0044] Step 2: Extruding and granulating the mixture to obtain master batches; wherein the granulation temperature is 190° C., the die temperature is 200° C., and the screw speed is 20 r / min.

[0045] Step 3: Melt the masterbatch and 0.5 g of 2,6-di-tert-butyl-4-methylphenol to form a tube to obtain a composite tube, wherein the tube drawing process parameters are: an upper drawing temperature of 160° C., a table inner temperature of 170° C., and a table outer temperature of 175° C.

[0046] The preparation method of the anti-wear agent comprises the following steps:

[0047] Dissolve 3g of γ-aminopropyltriethoxysilane in dichloromethane to obtain a mass fraction of 3%, add 30g of ultra-high molecular weight polyethylene, ultrasonically extract for 8min, filter, and dry the filter cake to obtain solid a. Dissolve 3g of solid a in 30g of white oil, add 5g of nano-silicon dioxide, and react at 50°C for 3h to obtain an anti-wear agent.

[0048] Example 2

[0049] A method for preparing a composite pipe comprises the following steps:

[0050] Step 1: Mix 100 g of low-density polyethylene, 10 g of high-density polyethylene, 30 g of ethylene-vinyl alcohol copolymer, 5 g of maleic anhydride grafted polyethylene, 8 g of reinforcing agent, and 15 g of anti-wear agent at 200° C. for 10 min to obtain a mixture;

[0051] Step 2: Extruding and granulating the mixture to obtain master batches; wherein the granulation temperature is 190° C., the die temperature is 200° C., and the screw speed is 20 r / min.

[0052] Step 3: Melt the masterbatch and 0.5 g of 2,6-di-tert-butyl-4-methylphenol to form a tube to obtain a composite tube, wherein the tube drawing process parameters are: an upper drawing temperature of 160° C., a table inner temperature of 170° C., and a table outer temperature of 175° C.

[0053] The preparation method of the enhancer comprises the following steps:

[0054] Step 1, 3 g of tetracycline and 15 g of citric acid were dissolved in 40 g of water, and then transferred to an autoclave for reaction at 200 ° C for 8 h. After naturally cooling to room temperature, the mixture was centrifuged at 10000 rpm for 10 min, and the larger particles in the supernatant were removed with a 0.22 mm microporous membrane filter to obtain a carbon dot stock solution;

[0055] Step 2, 3g of melamine and 10g of ammonium chloride are dissolved in 30g of water, dried, mixed and then calcined at 600°C for 3h to obtain modified graphite carbon nitride, 3g of modified graphite carbon nitride is evenly mixed with 15g of the carbon point stock solution prepared in the above step 1, transferred to a reactor, reacted at 180°C for 20h, and after naturally cooling to room temperature, centrifuged at 10000rpm for 10min, and the larger particles in the supernatant are removed with a 0.22mm microporous membrane filter, and then freeze-dried for 24h to obtain a composite material of carbon dots loaded on graphite carbon nitride;

[0056] Step 3, 8g of chitosan, 15g of 2-(7-azobenzotriazole)-N,N,N',N'-tetramethyluronium hexafluorophosphate and 80g of N,N-dimethylformamide were mixed evenly, and 3g of the composite material of carbon dots loaded on graphite carbon nitride prepared in the above step 2 was added, and the mixture was reacted at 50°C and 1500rpm for 14h, and then filtered. The filter cake was washed with water 3 times and dried at 50°C for 5h to obtain a reinforcing agent.

[0057] The preparation method of the wear-resistant agent is consistent with that of Example 1.

[0058] Example 3

[0059] A method for preparing a composite pipe, which is different from Example 2 in that the method for preparing the reinforcing agent comprises the following steps:

[0060] Step 1, 3 g of tetracycline and 15 g of citric acid were dissolved in 40 g of water, and then transferred to an autoclave for reaction at 200 ° C for 8 h. After naturally cooling to room temperature, the mixture was centrifuged at 10000 rpm for 10 min, and the larger particles in the supernatant were removed with a 0.22 mm microporous membrane filter to obtain a carbon dot stock solution;

[0061] Step 2, 3g of melamine and 10g of ammonium chloride are dissolved in 30g of water and then calcined at 600°C for 3h to obtain modified graphite carbon nitride, 3g of modified graphite carbon nitride is mixed evenly with 15g of the carbon dot stock solution prepared in the above step 1, transferred to a reactor, reacted at 180°C for 20h, and after naturally cooling to room temperature, centrifuged at 10000rpm for 10min, and the larger particles in the supernatant are removed with a 0.22mm microporous membrane filter, and then freeze-dried for 24h to obtain a composite material of carbon dots loaded on graphite carbon nitride;

[0062] Step 3, 8g of N-ethyl-2-nitroaniline, 15g of 2-(7-azobenzotriazole)-N,N,N',N'-tetramethyluronium hexafluorophosphate and 80g of N,N-dimethylformamide were mixed evenly, and 3g of the composite material of carbon dots loaded on graphite carbon nitride prepared in the above step 2 was added, and the mixture was reacted at 50°C and 1500rpm for 14h, and then filtered. The filter cake was washed 3 times with water and dried at 50°C for 5h to obtain a reinforcing agent.

[0063] Example 4

[0064] A method for preparing a composite pipe, which is different from Example 2 in that the method for preparing the reinforcing agent comprises the following steps:

[0065] Step 1, 3 g of tetracycline and 15 g of citric acid were dissolved in 40 g of water, and then transferred to an autoclave for reaction at 200 ° C for 8 h. After naturally cooling to room temperature, the mixture was centrifuged at 10000 rpm for 10 min, and the larger particles in the supernatant were removed with a 0.22 mm microporous membrane filter to obtain a carbon dot stock solution;

[0066] Step 2, 3g of melamine and 10g of ammonium chloride are dissolved in 30g of water and then calcined at 600°C for 3h to obtain modified graphite carbon nitride, 3g of modified graphite carbon nitride is mixed evenly with 15g of the carbon dot stock solution prepared in the above step 1, transferred to a reactor, reacted at 180°C for 20h, and after naturally cooling to room temperature, centrifuged at 10000rpm for 10min, and the larger particles in the supernatant are removed with a 0.22mm microporous membrane filter, and then freeze-dried for 24h to obtain a composite material of carbon dots loaded on graphite carbon nitride;

[0067] Step 3, 8g of polylysine, 15g of 2-(7-azobenzotriazole)-N,N,N',N'-tetramethyluronium hexafluorophosphate and 80g of N,N-dimethylformamide were mixed evenly, and 3g of the composite material of carbon dots loaded on graphite carbon nitride prepared in the above step 2 was added, and the mixture was reacted at 50°C and 1500rpm for 14h, and then filtered. The filter cake was washed 3 times with water and dried at 50°C for 5h to obtain a reinforcing agent.

[0068] Comparative Example 1

[0069] A method for preparing a composite pipe comprises the following steps:

[0070] Step 1: Mix 100 g of low-density polyethylene, 10 g of high-density polyethylene, 30 g of ethylene-vinyl alcohol copolymer, and 5 g of maleic anhydride-grafted polyethylene at 200° C. for 10 minutes to obtain a mixture;

[0071] Step 2: Extruding and granulating the mixture to obtain master batches; wherein the granulation temperature is 190° C., the die temperature is 200° C., and the screw speed is 20 r / min.

[0072] Step 3: Melt the masterbatch and 0.5 g of 2,6-di-tert-butyl-4-methylphenol to form a tube to obtain a composite tube, wherein the tube drawing process parameters are: an upper drawing temperature of 160° C., a table inner temperature of 170° C., and a table outer temperature of 175° C.

[0073] Comparative Example 2

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

[0075] Step 1: Mix 100 g of low-density polyethylene, 10 g of high-density polyethylene, 30 g of ethylene-vinyl alcohol copolymer, 5 g of maleic anhydride grafted polyethylene, and 8 g of a reinforcing agent at 200° C. for 10 min to obtain a mixture;

[0076] Step 2: Extruding and granulating the mixture to obtain master batches; wherein the granulation temperature is 190° C., the die temperature is 200° C., and the screw speed is 20 r / min.

[0077] Step 3: Melt the masterbatch and 0.5 g of 2,6-di-tert-butyl-4-methylphenol to form a tube to obtain a composite tube, wherein the tube drawing process parameters are: an upper drawing temperature of 160° C., a table inner temperature of 170° C., and a table outer temperature of 175° C.

[0078] The preparation method of the enhancer is consistent with that of Example 4.

[0079] Comparative Example 3

[0080] A method for preparing a composite pipe, which is different from Example 4 in that the method for preparing the reinforcing agent comprises the following steps:

[0081] 3 g of tetracycline and 15 g of citric acid were dissolved in 40 g of water, and then transferred to an autoclave to react at 200°C for 8 h. After naturally cooling to room temperature, the mixture was centrifuged at 10,000 rpm for 10 min. A 0.22 mm microporous membrane filter was used to remove larger particles in the supernatant to obtain a carbon dot stock solution, which was then freeze-dried for 24 h to obtain an enhancer.

[0082] Comparative Example 4

[0083] A method for preparing a composite pipe, which is different from Example 4 in that the method for preparing the wear-resistant agent comprises the following steps:

[0084] Dissolve 3g of γ-aminopropyltriethoxysilane in dichloromethane to obtain a mass fraction of 3%, add 30g of ultra-high molecular weight polyethylene, ultrasonically extract for 8min, filter, and dry the filter cake to obtain solid a. Dissolve 3g of solid a in 30g of white oil, add 5g of nano calcium carbonate, and react at 50°C for 3h to obtain a wear-resistant agent.

[0085] Comparative Example 5

[0086] A method for preparing a composite pipe, which is different from Example 4 in that the method for preparing the wear-resistant agent comprises the following steps:

[0087] Dissolve 3g of γ-aminopropyltriethoxysilane in dichloromethane to obtain a mass fraction of 3%, add 30g of ultra-high molecular weight polyethylene, ultrasonically extract for 8min, filter, and dry the filter cake to obtain solid a. Dissolve 3g of solid a in 30g of white oil, add 5g of nano zinc oxide, and react at 50°C for 3h to obtain a wear-resistant agent.

[0088] Test Example 1

[0089] Performance Testing

[0090] The composite pipes prepared in Examples 1-4 and Comparative Examples 1-5 of the present invention were respectively tested for performance. The oxygen permeability of each embodiment and comparative example was tested according to GB / T 19789-2021 Coulometer test method for oxygen permeability of plastic films and sheets for packaging materials; the water vapor permeability of each embodiment and comparative example was tested according to GB 1037-2021 Cup weight gain and weight loss method for water vapor permeability of plastic films and sheets; the tensile strength and elongation at break of each embodiment and comparative example were tested according to GB / T 1040.2-2022 Determination of tensile properties of plastics Part II: Test conditions for molded and extruded plastics; the wear resistance of each embodiment and comparative example was tested according to GB / T 3960-2016 Test method for sliding friction and wear of plastics, and the wear resistance of each embodiment and comparative example was tested according to the mass loss rate of each sample before and after the wear test;

[0091] The specific test results are shown in Table 1;

[0092] Table 1 Performance test

[0093]

[0094] By comparing Examples 1-4 with Comparative Examples 1-5, it can be found that the mass loss rate of Example 4 is only 0.15%, and the oxygen permeability is only 0.015 cm 3 / m 2 ·24h·0.1Mpa, water vapor transmission rate is only 0.083g / m 2·24h, tensile strength reaches 41.2MPa, elongation at break reaches 351%, and comprehensive performance is the best. Analysis The reason may be that Example 4 adds both reinforcing agent and anti-wear agent. In Example 4 of the present invention, tetracycline and citric acid are reacted to obtain carbon dot stock solution, and then melamine and ammonium chloride are calcined and reacted with carbon dot stock solution, and finally polylysine is introduced to react to form a reinforcing agent with high reactivity; the prepared reinforcing agent may form more effective chemical bonding or interaction with the matrix such as ethylene-vinyl alcohol copolymer and maleic anhydride grafted polyethylene with excellent barrier properties to form a cross-linked three-dimensional network, which is beneficial to reduce the permeability of water vapor and oxygen; and the graphite carbon nitride part in the reinforcing agent has high chemical stability and unique layered structure. The layered structure of graphite carbon nitride can play a role of physical barrier to gas and water vapor molecules, which may cooperate with the molecular structure of ethylene-vinyl alcohol copolymer to further improve the overall barrier performance. At the same time, the anti-wear agent can form a wear-resistant protective film on the surface of the pipe. When the pipe is subjected to friction or external force, the nano-silicon dioxide in the anti-wear agent can bear part of the friction force, reducing the wear of the pipe base material, thereby reducing the mass loss rate. In addition, the anti-wear agent is mixed with the reinforcing agent, and there may be a synergistic effect between the two. The surface functional groups of the carbon dots in the reinforcing agent react with polylysine to form chemical bonds. At the same time, polylysine reacts chemically or physically cross-links with the polyethylene molecular chain to form a three-dimensional cross-linked network structure. During the stretching process, the polymer molecular chain can be limited to slip, so that the molecular chains can be synergistically stressed, which improves the material's ability to resist tensile deformation, thereby improving the tensile strength. In addition, the formed cross-linked structure can, to a certain extent, make the material yield and oriented during the stretching process, thereby further increasing the elongation at break.

[0095] By comparing Example 4 with Comparative Examples 4-5, it can be found that Example 4 has the best performance. The reason may be that the wear-resistant particles added in Comparative Example 4 are nano-calcium carbonate, and the wear-resistant particles added in Example 5 are nano-zinc oxide. The reactive groups on the surfaces of nano-calcium carbonate and nano-zinc oxide are few and cannot react well to form chemical bonds. The bonding ability is weaker and the effect is weaker than that of nano-silicon dioxide.

[0096] Test Example 2

[0097] Antimicrobial properties

[0098] Examples 2-4 and Comparative Example 3 were tested for their antibacterial properties according to the test method provided in the reference standard "GB / T 31402-2023 Determination of antibacterial activity on the surface of plastics and other non-porous materials"; experimental bacteria: Escherichia coli (commercially available, CGMCC 1.2463), Staphylococcus aureus (commercially available, CGMCC 1.2910); the test results are shown in Table 2.

[0099] Table 2 Antibacterial properties

[0100]

[0101] By comparing Examples 2-4 with Comparative Example 3, it can be found that the antibacterial rates of Examples 2-4 against Escherichia coli and golden Steroids are higher than those of Comparative Example 3, showing excellent antibacterial effects; by comparing Examples 2-4, it can be found that Example 4 has the highest antibacterial rates against Escherichia coli and golden Steroids, with the Escherichia coli inhibition rate reaching 95.3% and the golden Steroids inhibition rate reaching 94.9%. The reason may be that the modifier added during the preparation of the enhancer in Example 4 is polylysine, and the polylysine molecular chain carries a large amount of positive charge, which can be adsorbed on the surface of the negatively charged bacterial cell membrane through electrostatic action to produce a sterilization effect. In addition, polylysine can react chemically with the composite material in which carbon dots are loaded on graphite carbon nitride and the matrix such as maleic anhydride grafted polyethylene, which can synergistically enhance the antibacterial effect. In addition, the overlap of the ultraviolet-visible absorption of the graphite carbon nitride in the enhancer and the upconversion emission spectrum of the carbon dots produces a strong spectral coupling, inducing a broadband photocatalytic response from the ultraviolet to the NIR region, which can further improve the antibacterial effect.

[0102] By comparing Examples 2-4 and Comparative Example 3, it can be found that Example 4 has the highest antibacterial rate. The reason for the analysis may be that the modifier added in the preparation process of the enhancer in Example 2 is chitosan, which is similar to the polylysine in structure in Example 4 and also has a certain antibacterial effect, but it may be because the positive charge is lower than that of polylysine in promoting the antibacterial effect of the composite material loaded with carbon dots on graphite carbon nitride; the modifier added in the preparation process of the enhancer in Example 3 is N-ethyl-2-nitroaniline, which can produce chemical reactions, but the molecular chain length and the reaction activity with the matrix are weaker than chitosan and polylysine, and the antibacterial effect of the composite material loaded with carbon dots on graphite carbon nitride is also low, so the antibacterial effect produced is low; the enhancer in Comparative Example 3 is carbon dots, although the carbon dots have antibacterial effects, but there is no synergistic enhancement of modified graphite carbon nitride to promote the antibacterial effect, so the antibacterial rate is low.

Claims

1. A composite pipe, characterized in that: The raw material components include, by weight: 80-120 parts of low-density polyethylene, 5-15 parts of high-density polyethylene, 20-40 parts of ethylene-vinyl alcohol copolymer, 1-10 parts of maleic anhydride grafted polyethylene, 5-20 parts of anti-wear agent, and 0.1-1 part of antioxidant; Or, 80-120 parts of low-density polyethylene, 5-15 parts of high-density polyethylene, 20-40 parts of ethylene-vinyl alcohol copolymer, 1-10 parts of maleic anhydride grafted polyethylene, 5-10 parts of reinforcing agent, 5-20 parts of anti-wear agent, 0.1-1 part of antioxidant.

2. The composite pipe according to claim 1, characterized in that: The preparation method of the enhancer comprises the following steps, calculated by weight: Step 1, dissolving 1-5 parts of tetracycline and 10-20 parts of citric acid in 10-50 parts of water, and then transferring to an autoclave to react at 180-220° C. for 6-10 hours; after naturally cooling to room temperature, centrifuging at 8000-12000 rpm for 5-15 minutes, and removing larger particles in the supernatant with a 0.22 mm microporous membrane filter to obtain a carbon dot stock solution; Step 2, dissolving 1-5 parts of melamine and 5-15 parts of ammonium chloride in 20-40 parts of water, and then calcining at 500-700°C for 2-4 hours to obtain modified graphite carbon nitride; 1-5 parts of modified graphite carbon nitride and 10-20 parts of the carbon dot stock solution prepared in the above step 1 are mixed evenly, transferred to a reactor, and reacted at 160-200°C for 16-24 hours; after naturally cooling to room temperature, centrifuging at 8000-12000rpm for 5-15 minutes, using a 0.22mm microporous membrane filter to remove larger particles in the supernatant, and then freeze-drying for 16-36 hours to obtain a composite material of carbon dots loaded on graphite carbon nitride; Step 3, 5-10 parts of the modifier, 10-20 parts of 2-(7-azobenzotriazole)-N,N,N',N'-tetramethyluronium hexafluorophosphate and 50-100 parts of N,N-dimethylformamide are mixed evenly, and 1-5 parts of the composite material prepared in the above step 2 loaded on graphite carbon nitride are added, and the mixture is reacted at 40-60°C and 1000-2000rpm for 10-16h, and then filtered, and the filter residue is washed with water 2-4 times, and dried at 40-60°C for 4-6h to obtain a reinforcing agent.

3. The composite pipe according to claim 2, characterized in that: In step 3, the modifier is selected from at least one of chitosan, polylysine, and N-ethyl-2-nitroaniline.

4. The composite pipe according to claim 1, characterized in that: The preparation method of the anti-wear agent comprises the following steps, calculated by weight: Dissolve 1-5 parts of γ-aminopropyltriethoxysilane in 100 parts of dichloromethane, add 20-40 parts of ultra-high molecular weight polyethylene, and ultrasonically extract for 5-10 minutes; filter, and dry the filter cake to obtain solid a; dissolve 1-5 parts of solid a in 10-50 parts of white oil, add 1-10 parts of wear-resistant particles, and react at 40-60°C for 2-4 hours to obtain a wear-resistant agent.

5. The composite pipe according to claim 4, characterized in that: The wear-resistant particles are nano silicon dioxide.

6. The composite pipe according to claim 1, characterized in that: The antioxidant is selected from at least one of 2,6-di-tert-butyl-4-methylphenol, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and antioxidant 168.

7. The method for preparing a composite pipe according to any one of claims 1 to 6, characterized in that: The steps include: Step 1, mixing low-density polyethylene, high-density polyethylene, ethylene-vinyl alcohol copolymer, maleic anhydride grafted polyethylene, wear-resistant agent and reinforcing agent at 140-220° C. for 5-15 minutes to obtain a mixture; Step 2, extruding and granulating the mixture to obtain a masterbatch; Step 3: Melt the masterbatch and the antioxidant to form a tube to obtain a composite tube.

8. The method for preparing the composite pipe according to claim 7, characterized in that: In the step 2, the granulation temperature is 140-220° C., the die temperature is 140-230° C., and the screw speed is 10-30 r / min.

9. The method for preparing a composite pipe according to claim 7, characterized in that: The tube drawing process parameters in step 3 are as follows: the upper drawing temperature is 120-180°C, the temperature inside the table is 140-180°C, and the temperature outside the table is 165-190°C.

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