Silane self-crosslinked polyethylene pipe with antibacterial property and preparation method thereof

Abstract

The invention discloses a silane self-crosslinked polyethylene pipe with antibacterial performance and a preparation method thereof, and belongs to the technical field of high polymer materials. A small amount of nano-silver is loaded on the surface of titanium dioxide, a coating layer is formed on the surface of the titanium dioxide through a high polymer material, the titanium dioxide is applied to preparation of the pipe, the pipe can be endowed with remarkable and durable antibacterial performance, the high polymer coating layer on the surface of the titanium dioxide can form excellent chemical bonding effect with a polyethylene system, and the service life of the pipe is prolonged. And moreover, a cross-linked three-dimensional network structure is adopted, so that effective antibacterial components are not easy to separate out and migrate, and the antibacterial durability is further improved. Besides, the material A and the material B are prepared in advance, the material A is grafted with silane, the catalyst is added into the material B, and then the water producing agent and the modified antibacterial powder are added, so that the silane crosslinking reaction is controllably and uniformly carried out, the processing difficulty caused by premature crosslinking is avoided, the water producing agent can react in the self-crosslinking treatment process, water molecules are provided, meanwhile, the water producing agent participates in the crosslinking reaction process, and the anti-bacterial effect is achieved. Certain moisture is provided for basic internal cross-linking, the cross-linking rate is increased, a three-dimensional network structure is formed, and the mechanical strength and environmental stress cracking resistance of the pipe are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and more specifically, to a silane self-crosslinking polyethylene pipe with antibacterial properties and its preparation method. Background Technology

[0002] Silane cross-linked polyethylene (PEX-B) pipes are widely used in building hot and cold water supply and heating systems due to their excellent temperature and pressure resistance, flexibility, and long service life. With increasing demands for healthy drinking water quality, it is of great significance to endow pipes with higher antibacterial properties to inhibit the growth of microorganisms such as bacteria and mold on the inner walls of pipes.

[0003] Currently, the molding of PEX-B pipes relies on the cross-linking reaction of silane hydrolysis and condensation. According to standard processes, the molded pipes need to undergo a long-term "hydrolysis cross-linking" process in a high-temperature and high-humidity environment to achieve a cross-linking degree of over 65% as required by standards, thus ensuring their mechanical properties. Existing technologies also include new silane-crosslinked polyethylene technologies that can complete cross-linking at room temperature. For example, CN107936441A discloses a two-step method for silane-crosslinked polyethylene. This method utilizes a novel catalyst to address the issue that while previous silane cross-linking processes could be carried out at low temperatures and with insufficient moisture, they failed to solve the problem of antibacterial agent migration in polyethylene pipes.

[0004] To enhance antibacterial properties while maintaining cross-linked mechanical properties, antibacterial agents need to be added. Current technologies often involve adding antibacterial masterbatches to the polyethylene matrix to impart antibacterial properties to pipes, forming an antibacterial functional layer within the pipe through co-extrusion. These antibacterial masterbatches typically contain inorganic antibacterial agents such as silver and zinc ions. When using the conventional "high-temperature water boiling cross-linking" process to treat PEX-B pipes containing such antibacterial masterbatches, the following problems arise: a. To achieve sufficient cross-linking, current processes generally use a high-temperature water bath of 90-95℃ for prolonged cross-linking. This increases the activity of the antibacterial agents, making them prone to migration and precipitation at this high temperature, leading to a decrease in the pipe's antibacterial properties and compromising long-term antibacterial durability. b. Conventional processes lower the water boiling cross-linking temperature to ensure antibacterial properties, which significantly reduces the rate of silane hydrolysis and cross-linking reactions, affecting cross-linking performance and increasing post-processing costs.

[0005] Therefore, there is a lack of PEX-B pipes and their preparation methods that can achieve efficient cross-linking while maintaining long-lasting antibacterial properties in the existing technology. Summary of the Invention

[0006] In view of this, in order to solve one of the above-mentioned technical problems, the present invention provides a silane self-crosslinking polyethylene pipe with antibacterial properties and a method for preparing the same, the specific technical solution of which is as follows:

[0007] A silane self-crosslinking polyethylene pipe with antibacterial properties, the silane self-crosslinking polyethylene pipe comprising the following raw materials in parts by weight: 70-99 parts of material A, 1-30 parts of material B, 1-8 parts of water-generating agent, and 1-5 parts of modified antibacterial powder; The A material comprises the following raw materials in parts by weight: 100 parts of polyethylene, 1 to 5 parts of silane crosslinking agent, and 0.05 to 3 parts of initiator; Material B comprises the following raw materials in parts by weight: 100 parts polyethylene, 0.1 to 5 parts catalyst, and 0.01 to 5 parts other additives.

[0008] Preferably, the modified antibacterial powder is prepared by dispersing nano-titanium dioxide in water, then adding silver nitrate, hexamethyltetramine and hexadecyltrimethylammonium bromide, stirring under certain conditions, washing, and drying to obtain mixture A; Sodium dodecyl sulfate and ammonium persulfate were dissolved in deionized water and stirred until homogeneous. Then, polyethyleneimine was added and the mixture was circulated and milled for 10 to 20 minutes to obtain mixture B. Mixture A is slowly added to mixture B. After the reaction is complete, the mixture is washed, dried, and ball-milled to obtain modified antibacterial powder.

[0009] Preferably, the polyethylene in both material A and material B is at least one of low-density polyethylene and high-density polyethylene; The low-density polyethylene has a molecular weight of 80,000 to 150,000, and the high-density polyethylene has a molecular weight of 70,000 to 150,000.

[0010] Preferably, in material A, the silane crosslinking agent is at least one of vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(2-methoxyethoxy)silane, and mercaptopropyltriethoxysilane.

[0011] Preferably, in material A, the initiator is at least one of organic peroxide, 2-hydroxy-methylphenylpropane-1-one, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methylpropanone, dicumyl peroxide, di-tert-butyl peroxide, 1-bis(tert-butyl peroxide)cyclohexane, and di-tert-butyl hydroperoxide.

[0012] Preferably, in the B material, the catalyst is at least one selected from ammonium persulfate, dibutyltin dilaurate, dibutyltin maleate, dibutyltin maleate, and dioctyltin dilaurate.

[0013] Preferably, in the B material, the other additives are at least one of antioxidants, light stabilizers, UV absorbers, and lubricants.

[0014] Preferably, the water-producing agent is prepared from citric acid, pentaerythritol and a catalyst in a weight ratio of (1~3):(1~3):(0.01~0.05).

[0015] In addition, the present invention also provides a method for preparing silane self-crosslinking polyethylene pipe with antibacterial properties, the preparation method comprising the following steps: S1. Silane mixed liquid and polyethylene resin are fed into a twin-screw extruder in proportion using an automatic metering scale / pump. The first shear zone and the melt section of the twin-screw extruder are equipped with exhaust holes and a vacuum is drawn. After blending, reaction grafting, extrusion granulation and drying, material A is obtained. S2. Add the raw materials for preparing material B to a high-speed mixer for mixing, then add them to a twin-screw extruder for melt extrusion, granulation, and drying to obtain material B; S3. Mix material A, material B, water-producing agent and modified antibacterial powder evenly, then melt extrude, cool and shape to obtain tube blank; S4. The tube blank is subjected to self-crosslinking treatment to obtain silane self-crosslinked polyethylene pipe.

[0016] Preferably, the temperature of the self-crosslinking treatment is 50℃~75℃, and the time is 10h~48h.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention loads a small amount of nano-silver onto the surface of titanium dioxide and forms a coating layer on its surface using polymer materials. When applied to the preparation of pipes, it not only endows the pipes with significant and durable antibacterial properties, but the polymer coating layer on its surface can also form excellent chemical bonds with the polyethylene system, resulting in better compatibility and dispersibility. Furthermore, the cross-linked three-dimensional network structure makes it difficult for effective antibacterial components to precipitate and migrate, further increasing the durability of antibacterial properties.

[0018] 2. This invention pre-prepares material A and material B, grafting silane onto material A and adding a catalyst to material B, followed by the addition of a water-generating agent and modified antibacterial powder. This allows the silane crosslinking reaction to proceed in a controllable and uniform manner, avoiding processing difficulties caused by premature crosslinking. The water-generating agent reacts during the self-crosslinking process, providing water molecules while participating in the crosslinking reaction, providing a certain amount of moisture for the basic internal crosslinking, increasing the crosslinking rate, and forming a three-dimensional network structure. This significantly increases the mechanical strength and resistance to environmental stress cracking of the pipe. Attached Figure Description

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

[0020] Figure 1 This is a schematic flowchart of a method for preparing a silane self-crosslinking polyethylene pipe with antibacterial properties according to Embodiment 1 of the present invention. Detailed Implementation

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

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

[0023] An embodiment of the present invention provides a silane self-crosslinking polyethylene pipe with antibacterial properties, wherein the silane self-crosslinking polyethylene pipe comprises the following raw materials in parts by weight: 70-99 parts of material A, 1-30 parts of material B, 1-8 parts of water-generating agent, and 1-5 parts of modified antibacterial powder. The A material comprises the following raw materials in parts by weight: 100 parts of polyethylene, 1 to 5 parts of silane crosslinking agent, and 0.05 to 3 parts of initiator; Material B comprises the following raw materials in parts by weight: 100 parts polyethylene, 0.1 to 5 parts catalyst, and 0.01 to 5 parts other additives.

[0024] In one embodiment, the modified antibacterial powder is prepared by dispersing nano-titanium dioxide in water, then adding silver nitrate, hexamethyltetramine and hexadecyltrimethylammonium bromide, stirring under certain conditions, washing, and drying to obtain mixture A; Sodium dodecyl sulfate and ammonium persulfate were dissolved in deionized water and stirred until homogeneous. Then, polyethyleneimine was added and the mixture was circulated and milled for 10 to 20 minutes to obtain mixture B. Mixture A is slowly added to mixture B. After the reaction is complete, the mixture is washed, dried, and ball-milled to obtain modified antibacterial powder.

[0025] In one embodiment, the weight ratio of the nano-titanium dioxide, water, silver nitrate, hexamethyltetramine and hexadecyltrimethylammonium bromide is (5~20):(20~30):(0.01~0.09):(0.5~2):(1~3).

[0026] In one embodiment, the specific conditions are: temperature of 60℃~85℃, stirring rate of 20r / min~50r / min, and stirring time of 30min~60min.

[0027] In one embodiment, the weight ratio of sodium dodecyl sulfate, deionized water, ammonium persulfate, and polyethyleneimine is (4~10):(20~35):(1~2):(5~9).

[0028] In one embodiment, the weight ratio of mixture A to mixture B is (5~7):(3~5).

[0029] In one embodiment, mixture A is slowly added to mixture B, and the mixture is reacted at a temperature of 60°C to 75°C and a speed of 20 r / min to 100 r / min for 1 h to 2 h.

[0030] In one embodiment, the modified antibacterial powder has an average particle size of 20 nm to 100 nm.

[0031] In one embodiment, the polyethylene in both material A and material B is at least one of low-density polyethylene and high-density polyethylene; The low-density polyethylene has a molecular weight of 80,000 to 150,000, and the high-density polyethylene has a molecular weight of 70,000 to 150,000.

[0032] In one embodiment, the silane crosslinking agent in material A is at least one of vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(2-methoxyethoxy)silane, and mercaptopropyltriethoxysilane.

[0033] In one embodiment, the initiator in material A is at least one of organic peroxide, 2-hydroxy-methylphenylpropane-1-one, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methylpropanone, dicumyl peroxide, di-tert-butyl peroxide, 1-bis(tert-butyl peroxide)cyclohexane, and di-tert-butyl hydroperoxide.

[0034] In one embodiment, the catalyst in material B is at least one of ammonium persulfate, dibutyltin dilaurate, dibutyltin maleate, dibutyltin maleate laurate, and di-n-octyltin dilaurate.

[0035] In one embodiment, the other additives in material B are at least one of antioxidants, light stabilizers, UV absorbers, and lubricants.

[0036] In one embodiment, the antioxidant is one or a mixture of more than one of butylated hydroxyanisole, tris(2,4-di-tert-butylphenol) phosphite, tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] pentanediol ester, antioxidant 1076, antioxidant 168, and antioxidant 1035.

[0037] In one embodiment, the light stabilizer is at least one of light stabilizer 622, light stabilizer 944, light stabilizer 3853, light stabilizer 123, UV-236, and UV-237.

[0038] In one embodiment, the UV absorber is at least one of 2,4-dihydroxybenzophenone and 2-hydroxy-4-n-octyloxybenzophenone.

[0039] In one embodiment, the lubricant is at least one of zinc stearate and pentylenetetrate stearate.

[0040] In one embodiment, the water-producing agent is prepared from citric acid, pentaerythritol and a catalyst in a weight ratio of (1~3):(1~3):(0.01~0.05).

[0041] In one embodiment, the water-generating agent is obtained by uniformly mixing citric acid, pentaerythritol and p-toluenesulfonic acid in a weight ratio of (1~3):(1~3):(0.01~0.05).

[0042] In addition, the present invention also provides a method for preparing silane self-crosslinking polyethylene pipe with antibacterial properties, the preparation method comprising the following steps: S1. Silane mixed liquid and polyethylene resin are fed into a twin-screw extruder in proportion using an automatic metering scale / pump. The first shear zone and the melt section of the twin-screw extruder are equipped with exhaust holes and a vacuum is drawn. After blending, reaction grafting, extrusion granulation and drying, material A is obtained. S2. Add the raw materials for preparing material B to a high-speed mixer for mixing, then add them to a twin-screw extruder for melt extrusion, granulation, and drying to obtain material B; S3. Mix material A, material B, water-producing agent and modified antibacterial powder evenly, then melt extrude, cool and shape to obtain tube blank; S4. The tube blank is subjected to self-crosslinking treatment to obtain silane self-crosslinked polyethylene pipe.

[0043] In one embodiment, in step S1, the temperature of the first zone of the melt extrusion is 130°C to 150°C, the temperature of the second zone is 150°C to 170°C, the temperature of the third zone is 170°C to 190°C, the temperature of the fourth zone is 190°C to 200°C, and the temperature of the die head is 200°C to 210°C.

[0044] In one embodiment, in step S2, the temperature of the first zone of the melt extrusion is 130℃~150℃, the temperature of the second zone is 150℃~170℃, the temperature of the third zone is 170℃~190℃, the temperature of the fourth zone is 190℃~200℃, and the temperature of the die head is 200℃~210℃.

[0045] In one embodiment, in step S3, the temperature of the first zone of the melt extrusion is 130°C to 140°C, the temperature of the second zone is 140°C to 150°C, the temperature of the third zone is 140°C to 150°C, the temperature of the fourth zone is 150°C to 160°C, and the temperature of the die head is 170°C to 190°C.

[0046] In one embodiment, the self-crosslinking treatment is performed at a temperature of 50°C to 75°C for a time of 10 hours to 48 hours.

[0047] In one embodiment, the ambient humidity of the self-crosslinking treatment is 40% to 60%.

[0048] The silane self-crosslinking polyethylene pipe prepared by the above method has significant and lasting antibacterial properties. During the self-crosslinking process, a certain amount of moisture is generated inside, which can promote the self-crosslinking rate and help increase the mechanical properties of the pipe, making it more valuable for application.

[0049] The implementation schemes of the present invention will now be described in detail with reference to specific embodiments.

[0050] Example 1: A method for preparing a silane self-crosslinking polyethylene pipe with antibacterial properties, the method comprising the following steps: S1. By weight, 100 parts of high-density polyethylene, 2 parts of vinyltrimethoxysilane and 0.08 parts of 2-hydroxy-methylphenylpropane-1-one are added to a high-speed mixer and mixed. Then, the mixture is added to a twin-screw extruder and melt-extruded. The temperature of the first zone of the melt extrusion is 135°C, the temperature of the second zone is 155°C, the temperature of the third zone is 175°C, the temperature of the fourth zone is 190°C, and the temperature of the die head is 200°C. The mixture is then granulated and dried to obtain material A. S2. By weight, 100 parts of high-density polyethylene, 3 parts of dibutyltin maleate, 1 part of butylated hydroxyanisole, 0.3 parts of light stabilizer 622 and 1 part of zinc stearate are added to a high-speed mixer and mixed. Then, the mixture is added to a twin-screw extruder and melt-extruded. The temperature of the first zone of the melt extrusion is 130°C, the temperature of the second zone is 155°C, the temperature of the third zone is 175°C, the temperature of the fourth zone is 195°C, and the temperature of the die head is 200°C. The mixture is then granulated and dried to obtain material B. S3. By weight, mix 94 parts of material A, 6 parts of material B, 5 parts of water-generating agent and 3 parts of modified antibacterial powder evenly, and then perform melt extrusion. The temperature of the first zone of melt extrusion is 135℃, the temperature of the second zone is 145℃, the temperature of the third zone is 150℃, the temperature of the fourth zone is 155℃, the temperature of the die head is 170℃, and then cool and solidify to obtain the tube blank. The water-producing agent is obtained by uniformly mixing citric acid, pentaerythritol and p-toluenesulfonic acid in a weight ratio of 2:3:0.04. The modified antibacterial powder is prepared as follows: 13 parts by weight of nano titanium dioxide are dispersed in 30 parts of water, and then 0.03 parts of silver nitrate, 1 part of hexamethyltetramine and 1 part of hexadecyltrimethylammonium bromide are added. The mixture is stirred for 45 minutes at a temperature of 65°C and a stirring rate of 20 r / min. After washing and drying, mixture A is obtained. Dissolve 7 parts sodium dodecyl sulfate and 2 parts ammonium persulfate in 30 parts deionized water by weight, stir well, then add 7 parts polyethyleneimine, and circulate and mill for 15 minutes to obtain mixture B. By weight, 6 parts of the mixture A were slowly added to 4 parts of the mixture B, and the mixture was reacted at 65°C and 50 r / min for 1 h. After washing, drying, and ball milling, the modified antibacterial powder was obtained. S4. The tube blank is subjected to self-crosslinking treatment at 55°C for 25 hours in an environment with 45% humidity to obtain silane self-crosslinking polyethylene pipe.

[0051] Example 2: A method for preparing a silane self-crosslinking polyethylene pipe with antibacterial properties, the method comprising the following steps: S1. By weight, 100 parts of high-density polyethylene, 3 parts of vinyltrimethoxysilane and 0.08 parts of 2-hydroxy-methylphenylpropane-1-one are added to a high-speed mixer and mixed. Then, the mixture is added to a twin-screw extruder and melt-extruded. The temperature of the first zone of the melt extrusion is 135°C, the temperature of the second zone is 155°C, the temperature of the third zone is 175°C, the temperature of the fourth zone is 190°C, and the temperature of the die head is 200°C. The mixture is then granulated and dried to obtain material A. S2. By weight, 100 parts of high-density polyethylene, 4 parts of dibutyltin maleate, 1 part of butylated hydroxyanisole, 0.3 parts of light stabilizer 622 and 1 part of zinc stearate are added to a high-speed mixer and mixed. Then, the mixture is added to a twin-screw extruder and melt-extruded. The temperature of the first zone of the melt extrusion is 130°C, the temperature of the second zone is 155°C, the temperature of the third zone is 175°C, the temperature of the fourth zone is 195°C, and the temperature of the die head is 200°C. The mixture is then granulated and dried to obtain material B. S3. By weight, mix 95 parts of material A, 5 parts of material B, 4 parts of water-generating agent and 3 parts of modified antibacterial powder evenly, and then perform melt extrusion. The temperature of the first zone of melt extrusion is 135℃, the temperature of the second zone is 145℃, the temperature of the third zone is 150℃, the temperature of the fourth zone is 155℃, the temperature of the die head is 170℃, and then cool and shape to obtain the tube blank. The water-producing agent is obtained by uniformly mixing citric acid, pentaerythritol and p-toluenesulfonic acid in a weight ratio of 2:3:0.04. The modified antibacterial powder is prepared as follows: 15 parts by weight of nano titanium dioxide are dispersed in 30 parts of water, and then 0.04 parts of silver nitrate, 1.5 parts of hexamethyltetramine and 2 parts of hexadecyltrimethylammonium bromide are added. The mixture is stirred for 45 minutes at a temperature of 70°C and a stirring rate of 20 r / min. After washing and drying, mixture A is obtained. Dissolve 8 parts sodium dodecyl sulfate and 2 parts ammonium persulfate in 30 parts deionized water by weight, stir evenly, then add 8 parts polyethyleneimine, and circulate and mill for 20 minutes to form mixture B. According to the weight ratio, 6 parts of the mixture A were slowly added to 4 parts of the mixture B, and the mixture was reacted at 70°C and 50 r / min for 1 h. After washing, drying, and ball milling, the modified antibacterial powder was obtained. S4. The tube blank is subjected to self-crosslinking treatment at 60°C for 22 hours in an environment with 45% humidity to obtain silane self-crosslinking polyethylene pipe.

[0052] Example 3: A method for preparing a silane self-crosslinking polyethylene pipe with antibacterial properties, the method comprising the following steps: S1. By weight, 100 parts of high-density polyethylene, 2 parts of vinyltrimethoxysilane and 0.08 parts of 2-hydroxy-methylphenylpropane-1-one are added to a high-speed mixer and mixed. Then, the mixture is added to a twin-screw extruder and melt-extruded. The temperature of the first zone of the melt extrusion is 135°C, the temperature of the second zone is 160°C, the temperature of the third zone is 175°C, the temperature of the fourth zone is 195°C, and the temperature of the die head is 200°C. The mixture is then granulated and dried to obtain material A. S2. By weight, 100 parts of high-density polyethylene, 5 parts of dibutyltin maleate, 1 part of butylated hydroxyanisole, 0.3 parts of light stabilizer 622 and 1 part of zinc stearate are added to a high-speed mixer and mixed. Then, the mixture is added to a twin-screw extruder and melt-extruded. The temperature of the first zone of the melt extrusion is 130°C, the temperature of the second zone is 155°C, the temperature of the third zone is 175°C, the temperature of the fourth zone is 195°C, and the temperature of the die head is 200°C. The mixture is then granulated and dried to obtain material B. S3. By weight, mix 96 parts of material A, 4 parts of material B, 3 parts of water-producing agent and 5 parts of modified antibacterial powder evenly, and then perform melt extrusion. The temperature of the first zone of melt extrusion is 135℃, the temperature of the second zone is 145℃, the temperature of the third zone is 150℃, the temperature of the fourth zone is 155℃, the temperature of the die head is 175℃, and then cool and shape to obtain the tube blank. The water-producing agent is obtained by uniformly mixing citric acid, pentaerythritol and p-toluenesulfonic acid in a weight ratio of 2:3:0.05. The modified antibacterial powder is prepared as follows: 15 parts by weight of nano titanium dioxide are dispersed in 30 parts of water, and then 0.03 parts of silver nitrate, 2 parts of hexamethyltetramine and 2 parts of hexadecyltrimethylammonium bromide are added. The mixture is stirred for 50 minutes at a temperature of 80°C and a stirring rate of 20 r / min. After washing and drying, mixture A is obtained. Dissolve 10 parts sodium dodecyl sulfate and 2 parts ammonium persulfate in 30 parts deionized water by weight, stir evenly, then add 9 parts polyethyleneimine, and circulate and mill for 20 minutes to form mixture B. According to the weight, 6 parts of the mixture A were slowly added to 4 parts of the mixture B, and reacted at 75°C and 50 r / min for 1 h. After washing, drying, and ball milling, the modified antibacterial powder was obtained. S4. The tube blank is subjected to self-crosslinking treatment at 60°C and 45% humidity for 21 hours to obtain silane self-crosslinking polyethylene pipe.

[0053] Comparative Example 1: The difference between Comparative Example 1 and Example 3 lies in the preparation method of the pipe material. However, the preparation methods of the water-generating agent and modified antibacterial powder are the same as in Example 3. The preparation method of the pipe material in Comparative Example 1 is as follows: 100 parts of high-density polyethylene, 7 parts of vinyltrimethoxysilane, 6 parts of 2-hydroxy-methylphenylpropane-1-one, 5 parts of dibutyltin maleate, 1 part of butylated hydroxyanisole, 0.3 parts of light stabilizer 622, 1 part of zinc stearate, 15 parts of water-generating agent, and 15 parts of modified antibacterial powder were added to a high-speed mixer and mixed. Then, melt extrusion was carried out with the following temperatures: Zone 1: 135°C, Zone 2: 155°C, Zone 3: 165°C, Zone 4: 175°C, and Die: 200°C. After cooling and shaping, a tube blank was obtained. The tube blank was subjected to self-crosslinking treatment at 60°C for 21 hours in an environment with 45% humidity to obtain silane self-crosslinking polyethylene pipe.

[0054] In Comparative Example 1, the blank tube was prepared by a one-step method. However, in actual production, there were many defects, and the resulting blank tube had poor formability and was even difficult to form.

[0055] Comparative Example 2: The difference between Comparative Example 2 and Example 3 is that no water-producing agent was added in Comparative Example 2, while the rest is the same as in Example 3.

[0056] Comparative Example 3: The difference between Comparative Example 3 and Example 3 is that nano-titanium dioxide was used directly as an antibacterial agent in Comparative Example 3, that is, nano-titanium dioxide was used to replace the modified antibacterial powder in Example 3. Everything else was the same as in Example 3.

[0057] Comparative Example 4: The difference between Comparative Example 4 and Example 3 is that the preparation method of the modified antibacterial powder in Comparative Example 4 is different; otherwise, it is the same as Example 3. The preparation method of the modified antibacterial powder in Comparative Example 4 is as follows: The modified antibacterial powder in Comparative Example 4 was prepared as follows: 15 parts by weight of nano-titanium dioxide were dispersed in 30 parts of water, and then 0.03 parts of silver nitrate, 2 parts of hexamethyltetramine and 2 parts of hexadecyltrimethylammonium bromide were added. The mixture was stirred for 50 min at a temperature of 80℃ and a stirring rate of 20 r / min. After washing and drying, the modified antibacterial powder was obtained.

[0058] Comparative Example 5: The difference between Comparative Example 5 and Example 3 is that the preparation method of the modified antibacterial powder in Comparative Example 5 is different; otherwise, it is the same as Example 3. The preparation method of the modified antibacterial powder in Comparative Example 5 is as follows: The preparation method of the modified antibacterial powder in Comparative Example 5 is as follows: 10 parts by weight of sodium dodecyl sulfate and 2 parts by weight of ammonium persulfate are dissolved in 30 parts by weight of deionized water and stirred evenly. Then, 9 parts by weight of polyethyleneimine are added and the mixture is circulated and milled for 20 min. Then, 15 parts by weight of nano titanium dioxide are added and the mixture is stirred at 75°C and 50 r / min for 1 h. After washing, drying, and ball milling, the modified antibacterial powder is obtained.

[0059] Comparative Example 6: The difference between Comparative Example 6 and Example 3 is that no modified antibacterial powder was added in Comparative Example 6, but otherwise it is the same as Example 3.

[0060] Comparative Example 7: Compared with Example 3, Comparative Example 7 differs in that, in step S4 of Comparative Example 7, a self-crosslinking treatment was performed at a temperature of 90°C for 21 hours, while the rest was the same as in Example 3.

[0061] I. The crosslinking degree of the pipe samples prepared in Examples 1-3 and the comparative pipe samples prepared in Comparative Examples 1-7 was tested. The crosslinking degree was referenced to the standards GB / T 18992.2 and GB / T 18474. Samples were taken from the outer wall of the pipe and the center of the inner wall of the pipe to test the crosslinking degree. The results are shown in Table 1.

[0062] Table 1: Crosslinking Degree Test Results

[0063] II. Mechanical properties were tested on the pipe samples prepared in Examples 1-3 and the comparative pipe samples prepared in Comparative Examples 1-6. The tensile properties were tested according to GB / T1040.1-2018; the flexural modulus of elasticity was tested according to GB / T9341-2008; and the impact strength was tested according to GB / T1843-2008. The results are shown in Table 2 below.

[0064] Table 2: Mechanical Performance Test Results

[0065] Analysis of Tables 1 and 2 shows that the present invention, through optimization of composition and process, can effectively improve the degree of crosslinking, and the difference between the degree of crosslinking at the edge and the center is small, indicating that a uniform and efficient crosslinking reaction can be achieved, promoting silane hydrolysis and condensation, so that the degree of crosslinking meets the application requirements of pipe materials (≥65%). In addition, the mechanical properties of the pipe material are excellent and meet the mechanical requirements for use. Compared with Example 3, the order of feeding and preparation method in Comparative Example 1 are different. The material is mixed and melt-extruded in one go, resulting in poorer uniformity of crosslinking and increased defects. Due to the difficulty in molding and the overlapping of molding shapes, its strength was not further tested. In Comparative Example 2, no water-generating agent was added, which failed to achieve the effect of promoting crosslinking as described in the present invention, resulting in mechanical properties that are not as good as those in Example 3. This shows that adding a certain amount of the water-generating agent of this application can effectively increase the crosslinking effect and mechanical properties. Comparative Example 3 directly uses nano-titanium dioxide as an antibacterial agent, which has poor surface compatibility with the polyethylene matrix, also affecting the crosslinking effect. In addition, the lack of a surface-coated polymer layer results in poor chemical bonding and a deteriorated crosslinking structure during application, affecting the mechanical properties of the pipe material. Comparative Example 4, without coating treatment, exhibited poor chemical bonding and a deteriorated cross-linking structure, affecting the mechanical properties of the pipe. Comparative Examples 3 and 4 demonstrate that the coating treatment of the material in this invention significantly improves its compatibility and cross-linking properties within the polyethylene matrix. Comparative Example 5, lacking silver ion loading, had little impact on cross-linking properties and mechanical properties, but did have some influence on antibacterial durability. Comparative Example 6, without modified antibacterial powder, had little impact on mechanical properties, but due to the lack of polymer cross-linking on the surface of the modified antibacterial powder, the degree of cross-linking decreased slightly. While Comparative Example 7 achieved a degree of cross-linking and mechanical properties close to those of Example 3, the high temperature in Comparative Example 7 increased production costs, indicating that this application, after optimizing the composition and ingredient ratios, can achieve a lower-temperature cross-linking effect.

[0066] III. The antibacterial properties of the pipe samples prepared in Examples 1-3 and the comparative pipe samples prepared in Comparative Examples 1-6 were tested using the film-coating method, referring to the antibacterial performance test of plastic pipes in JC / T 939-2004. The test bacteria were commercially available *Escherichia coli* and *Codonopsis aureus*. The samples were incubated at 37°C for 24 hours, based on a 1.44 cm... 2 The antibacterial rate was calculated based on the number of colonies grown on the surface, and the results are shown in Table 3 below.

[0067] Table 3: Results of Antibacterial Performance Test

[0068] Analysis of the data in Table 3 shows that the present invention, by loading silver ions onto nano-titanium dioxide and coating it, exhibits better compatibility with the polyethylene matrix, improved dispersion, and better chemical bonding. The polymer coating layer forms chemical bonds with the polyethylene system, making the modified antibacterial powder less prone to precipitation and migration, thus ensuring the pipe's durable antibacterial properties. Compared to Example 3, Comparative Example 1, due to poor crosslinking, affected the distribution of the modified antibacterial powder, which had a certain impact on antibacterial stability. Comparative Example 2, without the addition of a water-generating agent, resulted in a low degree of crosslinking, leading to a loose pipe structure and affecting antibacterial durability. The nano-titanium dioxide in Comparative Example 3, without modification, easily migrated and precipitated, affecting antibacterial durability. Comparative Example 4, lacking the crosslinking coating treatment of polyethyleneimine, had poorer compatibility with the polyethylene matrix than Example 3, and its migration resulted in poor antibacterial properties. Comparative Example 5, without silver ion loading, lacked the synergistic antibacterial properties of silver ions, thus affecting its antibacterial performance. In Comparative Example 6, no modified antibacterial powder was added, resulting in poor antibacterial performance of the pipe. This demonstrates that the modified antibacterial powder of the present invention has significant antibacterial properties and excellent antibacterial durability. In Comparative Example 7, the self-crosslinking temperature was increased to 90°C. Under high temperature conditions, the modified antibacterial powder showed slight migration and precipitation. Although the degree of crosslinking was relatively excellent, the antibacterial effect decreased. At the same time, the high temperature increased the cost. In contrast, the preferred self-crosslinking treatment temperature of this application is 50°C to 75°C, which still achieves a significant and durable antibacterial effect.

[0069] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0070] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A silane self-crosslinking polyethylene pipe with antibacterial properties, characterized in that, The silane self-crosslinking polyethylene pipe comprises the following raw materials in parts by weight: 70-99 parts of material A, 1-30 parts of material B, 1-8 parts of water-generating agent, and 1-5 parts of modified antibacterial powder. The A material comprises the following raw materials in parts by weight: 100 parts of polyethylene, 1 to 5 parts of silane crosslinking agent, and 0.05 to 3 parts of initiator; Material B comprises the following raw materials in parts by weight: 100 parts polyethylene, 0.1 to 5 parts catalyst, and 0.01 to 5 parts other additives.

2. The silane self-crosslinking polyethylene pipe according to claim 1, characterized in that, The modified antibacterial powder is prepared by dispersing nano-titanium dioxide in water, then adding silver nitrate, hexamethyltetramine and hexadecyltrimethylammonium bromide, stirring under certain conditions, washing, and drying to obtain mixture A; Sodium dodecyl sulfate and ammonium persulfate were dissolved in deionized water and stirred until homogeneous. Then, polyethyleneimine was added and the mixture was circulated and milled for 10 to 20 minutes to obtain mixture B. Mixture A is slowly added to mixture B. After the reaction is complete, the mixture is washed, dried, and ball-milled to obtain modified antibacterial powder.

3. The silane self-crosslinking polyethylene pipe according to claim 1, characterized in that, The polyethylene in both material A and material B is at least one of low-density polyethylene and high-density polyethylene. The low-density polyethylene has a molecular weight of 80,000 to 150,000, and the high-density polyethylene has a molecular weight of 70,000 to 150,000.

4. The silane self-crosslinking polyethylene pipe according to claim 1, characterized in that, In material A, the silane crosslinking agent is at least one of vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(2-methoxyethoxy)silane, and mercaptopropyltriethoxysilane.

5. The silane self-crosslinking polyethylene pipe according to claim 1, characterized in that, In material A, the initiator is at least one of organic peroxide, 2-hydroxy-methylphenylpropane-1-one, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methylpropanone, dicumyl peroxide, di-tert-butyldicumyl peroxide, 1-bis(tert-butylperoxide)cyclohexane, and di-tert-butyl hydroperoxide.

6. The silane self-crosslinking polyethylene pipe according to claim 1, characterized in that, In the material B, the catalyst is at least one of ammonium persulfate, dibutyltin dilaurate, dibutyltin maleate, dibutyltin maleate, and dioctyltin dilaurate.

7. The silane self-crosslinking polyethylene pipe according to claim 1, characterized in that, In the B material, the other additives are at least one of antioxidants, light stabilizers, UV absorbers, and lubricants.

8. The silane self-crosslinking polyethylene pipe according to claim 1, characterized in that, The water-producing agent is prepared from citric acid, pentaerythritol and a catalyst in a weight ratio of (1~3):(1~3):(0.01~0.05).

9. A method for preparing a silane self-crosslinking polyethylene pipe with antibacterial properties, characterized in that, The preparation method is used to prepare the silane self-crosslinking polyethylene pipe according to any one of claims 1 to 8, and the preparation method includes the following steps: S1. Silane mixed liquid and polyethylene resin are fed into a twin-screw extruder in proportion using an automatic metering scale / pump. The first shear zone and the melt section of the twin-screw extruder are equipped with exhaust holes and a vacuum is drawn. After blending, reaction grafting, extrusion granulation and drying, material A is obtained. S2. Add the raw materials for preparing material B to a high-speed mixer for mixing, then add them to a twin-screw extruder for melt extrusion, granulation, and drying to obtain material B; S3. Mix material A, material B, water-producing agent and modified antibacterial powder evenly, then melt extrude, cool and shape to obtain tube blank; S4. The tube blank is subjected to self-crosslinking treatment to obtain silane self-crosslinked polyethylene pipe.

10. The preparation method according to claim 9, characterized in that, The self-crosslinking treatment is performed at a temperature of 50℃ to 75℃ for a time of 10h to 48h.

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