A high-impact polyethylene composite modified plastic

Abstract

This invention relates to a high-impact polyethylene composite modified plastic and its preparation method, belonging to the field of polyethylene plastics technology. The invention involves creating a self-made modifier and using this modifier to modify chlorinated polyethylene to obtain modified chlorinated polyethylene. This modified chlorinated polyethylene is then blended with polyethylene and silica to obtain a composite modified plastic. The siloxane groups at the end of the modifier can combine with the hydroxyl groups on the silica surface, improving the interfacial bonding between the filler and the polymer, and enhancing the mechanical properties of the material. The pyridine ring forms a stable conjugated π-electron system with benzotriazole, synergistically expanding the ultraviolet absorption range of the material, thereby enhancing its ultraviolet absorption performance. The quaternary ammonium salt structure formed by the combination of the modifier and chlorinated polyethylene can form ion-conducting channels in the polymer matrix, reducing surface charge accumulation and lowering surface resistivity, thus endowing the material with excellent antistatic properties.

Description

Technical Field

[0001] This invention belongs to the field of polyethylene plastics technology, specifically, it relates to a high-impact polyethylene composite modified plastic and its preparation method. Background Technology

[0002] Polyethylene, as one of the most widely used general-purpose plastics, is widely used in packaging, pipes, automotive parts, and other fields due to its excellent chemical stability and processing performance. However, it also has some inherent defects that severely limit its application in high-end fields. First, polyethylene is prone to photo-oxidative degradation under ultraviolet radiation, leading to a sharp decline in the material's mechanical properties and poor weather resistance; second, high-density polyethylene has poor impact toughness and is prone to brittle fracture.

[0003] To improve the UV resistance and aging resistance of polyethylene, the most common practice is to add small-molecule UV absorbers or light stabilizers during processing. However, these small-molecule additives have limited compatibility with the polyethylene matrix, and their small molecular weight and high migration rate make them prone to migration, volatilization, and precipitation onto the product surface during processing and use. This not only leads to a rapid decline in UV resistance, failing to provide long-term protection, but also causes surface contamination. To improve the toughness of polyethylene, physical toughening methods such as blending with elastomers are commonly used. Chlorinated polyethylene, as an important polymer modifier, is widely used for toughening modification of polyethylene. However, this modification often comes at the cost of sacrificing the material's rigidity and tensile strength, and its functionality is limited to improving toughness, failing to address other inherent defects of polyethylene.

[0004] Based on this, the present invention provides a method for preparing high-impact polyethylene composite modified plastic. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing high-impact polyethylene composite modified plastics to solve the problems mentioned in the background art.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A method for preparing a high-impact polyethylene composite modified plastic includes the following steps:

[0008] Step 1: Add 3-nitropyridine, hydroxybenzotriazole, potassium carbonate and N-methylpyrrolidone to a three-necked flask, attach a condenser and thermometer, turn on magnetic stirring, and react at 70-90℃ for 3-5 hours. After the reaction is complete, cool the reaction solution to room temperature, then transfer it to water. After the solid precipitates, filter it, wash the obtained solid with water and dry it, then elute it by silica gel column chromatography to obtain the ultraviolet absorber.

[0009] Step 2: Add the ultraviolet absorber, silane coupling agent, potassium carbonate and acetonitrile to a three-necked flask, attach a condenser and thermometer, turn on magnetic stirring, and react at 65-75℃ for 2-3 hours. After the reaction is complete, cool to room temperature and filter to remove the solid. The remaining filtrate is rotary evaporated to remove the solvent, then extracted with ethyl acetate and the organic phase is retained. The organic phase is washed with water and dried to obtain the modifier.

[0010] The third step involves adding the modifier and chlorinated polyethylene into a torque rheometer and mixing them thoroughly. After melt grafting at 160–180°C for 8–12 minutes, modified chlorinated polyethylene is obtained.

[0011] Step 4: After mixing high-density polyethylene, polyolefin elastomer, modified chlorinated polyethylene, silica, antioxidant and lubricant evenly, the mixture is transferred to a screw extruder for melt extrusion, and then cooled and granulated to obtain polyethylene composite modified plastic.

[0012] Furthermore, the hydroxybenzotriazole in the first step is one of 4-hydroxybenzotriazole and 5-hydroxybenzotriazole.

[0013] Furthermore, the mass ratio of 3-nitropyridine, hydroxybenzotriazole, potassium carbonate and N-methylpyrrolidone is 12.5–14.5:15–17:27.5–41.5:200–240.

[0014] Furthermore, the silane coupling agent in the second step is at least one of (2-chloroethyl)triethoxysilane, (3-chloropropyl)triethoxysilane, and (3-chloropropyl)trimethoxysilane.

[0015] Furthermore, in the second step, the mass ratio of the ultraviolet absorber, silane coupling agent, potassium carbonate, and acetonitrile is 18–21:20–24:10–15:200–240.

[0016] Furthermore, in the third step, the mass ratio of the modifier to chlorinated polyethylene is 20–25:40–50.

[0017] Furthermore, the lubricant in the fourth step is at least one of polyethylene wax and oxidized polyethylene wax.

[0018] Furthermore, the antioxidant in the fourth step is at least one of antioxidant 1010, antioxidant 1076, and antioxidant 168.

[0019] Furthermore, the temperature of melt extrusion in the fourth step is 160–180°C.

[0020] Furthermore, in the fourth step, the mass ratio of high-density polyethylene, polyolefin elastomer, modified chlorinated polyethylene, silica, antioxidant, and lubricant is 80–85:15–20:15–20:10–15:1–3:1–3.

[0021] A high-impact polyethylene composite modified plastic is prepared by any of the above preparation steps.

[0022] The beneficial effects of this invention are:

[0023] This invention uses 3-nitropyridine and hydroxybenzotriazole as raw materials to carry out a nucleophilic substitution reaction to obtain an ultraviolet absorber. Then, the ultraviolet absorber and a silane coupling agent are used to carry out a nucleophilic substitution reaction to obtain a modifier. The modifier is used to modify chlorinated polyethylene. The quaternary ammonium salt reaction between the modifier and chlorinated polyethylene is used to improve the compatibility between the modifier and chlorinated polyethylene. Finally, high-density polyethylene, polyolefin elastomer, modified chlorinated polyethylene, silica, antioxidant and lubricant are used as raw materials for melt blending and granulation to obtain polyethylene composite modified plastic.

[0024] The siloxane groups at the end of the modifier of this invention undergo cross-linking during processing to form a cross-linked network that connects polymer macromolecules together, restricting the slippage of molecular chains. These siloxane groups can also combine with the hydroxyl groups on the surface of silica filler, greatly improving the interfacial bonding and adhesion between the filler and the polymer, and also making the filler more uniformly dispersed in the system. At the same time, the quaternary ammonium salt reaction between the modifier and chlorinated polyethylene gives them good compatibility, thus significantly improving the overall mechanical properties of the material.

[0025] The modifier of this invention introduces an additional pyridine ring into the benzotriazole conjugated system, forming a new conjugated π-electron system. This synergistically expands the UV absorption range of the polyethylene composite modified plastic, enhances its UV absorption performance, and effectively prevents UV damage to the material. Subsequent modification of chlorinated polyethylene with the modifier ensures that the modified plastic maintains good anti-aging properties even after long-term exposure to sunlight.

[0026] The quaternary ammonium salt reaction between the modifier and chlorinated polyethylene in this invention creates quaternary ammonium salt ions in the system. These quaternary ammonium salt ions can form ion-conducting channels in the polymer matrix, reduce the accumulation of surface static charge, and lower the surface resistivity, thereby endowing the modified plastic with antistatic properties and effectively avoiding product damage and safety hazards caused by static electricity. Detailed Implementation

[0027] The technical solutions of the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments in this application specification, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection claimed in this application.

[0028] The raw materials used in this invention are not particularly restricted in terms of their source; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0029] Example 1

[0030] A method for preparing a high-impact polyethylene composite modified plastic includes the following steps:

[0031] Step 1: Add 12.5g of 3-nitropyridine, 15g of 4-hydroxybenzotriazole, 27.5g of potassium carbonate and 200g of N-methylpyrrolidone to a three-necked flask, attach a condenser and thermometer, turn on magnetic stirring, and react at 70℃ for 5h. After the reaction is complete, cool the reaction solution to room temperature, then transfer it to water. After the solid precipitates, filter it, wash the obtained solid with water and dry it, then elute it by silica gel column chromatography to obtain the ultraviolet absorber.

[0032] Step 2: Add 18g of ultraviolet absorber, 20g of (2-chloroethyl)triethoxysilane, 10g of potassium carbonate and 200g of acetonitrile to a three-necked flask, attach a condenser and thermometer, turn on magnetic stirring, and react at 65℃ for 3h. After the reaction is complete, cool to room temperature and filter to remove the solid. Remove the solvent from the remaining filtrate by rotary evaporation, extract with ethyl acetate and retain the organic phase. Wash the organic phase with water and dry to obtain the modifier.

[0033] The third step is to add 20g of modifier and 40g of chlorinated polyethylene into a torque rheometer and mix them evenly. After melting and grafting at 160℃ for 12 minutes, modified chlorinated polyethylene is obtained.

[0034] Step 4: Mix 80g of high-density polyethylene, 20g of polyolefin elastomer, 15g of modified chlorinated polyethylene, 10g of silica, 1g of antioxidant 1010 and 1g of polyethylene wax evenly, transfer the mixture to a screw extruder and melt extrude at 160℃, and then cool and granulate to obtain polyethylene composite modified plastic.

[0035] A high-impact polyethylene composite modified plastic is prepared by the above preparation steps.

[0036] Example 2

[0037] A method for preparing a high-impact polyethylene composite modified plastic includes the following steps:

[0038] Step 1: Add 13.5g of 3-nitropyridine, 16g of 5-hydroxybenzotriazole, 34.5g of potassium carbonate and 220g of N-methylpyrrolidone to a three-necked flask, attach a condenser and thermometer, turn on magnetic stirring, and react at 80℃ for 4h. After the reaction is complete, cool the reaction solution to room temperature, then transfer it to water. After the solid precipitates, filter it, wash the obtained solid with water and dry it, then elute it by silica gel column chromatography to obtain the ultraviolet absorber.

[0039] Step 2: Add 19.5g of UV absorber, 22g of (3-chloropropyl)triethoxysilane, 12.5g of potassium carbonate and 220g of acetonitrile to a three-necked flask, attach a condenser and thermometer, turn on magnetic stirring, and react at 70℃ for 2.5h. After the reaction is complete, cool to room temperature and filter to remove the solid. Remove the solvent from the remaining filtrate by rotary evaporation, extract with ethyl acetate and retain the organic phase. Wash the organic phase with water and dry to obtain the modifier.

[0040] The third step involves adding 22.5g of modifier and 45g of chlorinated polyethylene to a torque rheometer and mixing them evenly. After melting and grafting at 170°C for 10 minutes, modified chlorinated polyethylene is obtained.

[0041] Step 4: Mix 82.5g of high-density polyethylene, 17.5g of polyolefin elastomer, 17.5g of modified chlorinated polyethylene, 12.5g of silica, 2g of antioxidant 1076 and 2g of oxidized polyethylene wax evenly, transfer the mixture to a screw extruder and melt extrude at 170°C, and then cool and granulate to obtain polyethylene composite modified plastic.

[0042] A high-impact polyethylene composite modified plastic is prepared by the above preparation steps.

[0043] Example 3

[0044] A method for preparing a high-impact polyethylene composite modified plastic includes the following steps:

[0045] Step 1: Add 14.5g of 3-nitropyridine, 17g of 4-hydroxybenzotriazole, 41.5g of potassium carbonate and 240g of N-methylpyrrolidone to a three-necked flask, attach a condenser and thermometer, turn on magnetic stirring, and react at 90℃ for 3h. After the reaction is complete, cool the reaction solution to room temperature, then transfer it to water. After the solid precipitates, filter it, wash the obtained solid with water and dry it, then elute it by silica gel column chromatography to obtain the ultraviolet absorber.

[0046] Step 2: Add 21g of ultraviolet absorber, 24g of (3-chloropropyl)trimethoxysilane, 15g of potassium carbonate and 240g of acetonitrile to a three-necked flask, attach a condenser and thermometer, turn on magnetic stirring, and react at 75℃ for 2h. After the reaction is complete, cool to room temperature and filter to remove the solid. Remove the solvent from the remaining filtrate by rotary evaporation, extract with ethyl acetate and retain the organic phase. Wash the organic phase with water and dry to obtain the modifier.

[0047] The third step is to add 25g of modifier and 50g of chlorinated polyethylene into a torque rheometer and mix them evenly. After melting and grafting at 180℃ for 8 minutes, modified chlorinated polyethylene is obtained.

[0048] Step 4: Mix 85g of high-density polyethylene, 15g of polyolefin elastomer, 20g of modified chlorinated polyethylene, 15g of silica, 3g of antioxidant 168 and 2g of polyethylene wax evenly, transfer the mixture to a screw extruder and melt extrude at 180°C, and then cool and granulate to obtain polyethylene composite modified plastic.

[0049] A high-impact polyethylene composite modified plastic is prepared by the above preparation steps.

[0050] Comparative Example 1

[0051] The difference between this comparative example and Example 2 is that the modifier is replaced with commercially available benzotriazole UV absorber UV-P, and the polyvinyl chloride is not modified; it is directly melt-blended. The other raw materials and preparation steps remain unchanged.

[0052] Experimental Example 1

[0053] The plastics in Examples 1-3 and Comparative Example 1 were subjected to performance tests. The tensile strength and elongation at break of each group of plastics were tested according to GB / T1845.2-2021 "Plastics - Molded and Extruded Polyethylene Materials". The tensile strength retention rate and elongation at break of each group of plastics after exposure to a xenon arc lamp were tested according to GB / T16422.2-2022 "Plastics - Laboratory Light Source Exposure Test Method". The surface resistivity of each group of plastics was tested according to GB / T31838.3-2019 "Dielectric and Resistance Properties of Solid Insulating Materials". The test results are shown in Table 1.

[0054]

[0055] As can be seen from Table 1, Examples 1-3 have higher tensile strength, elongation at break, tensile strength retention rate, elongation at break retention rate, and surface resistivity compared with Comparative Example 1. This indicates that the mechanical properties, anti-aging properties, and antistatic properties of Examples 1-3 are all superior to those of Comparative Example 1. Combined with Comparative Example 1, it can be seen that the mechanical properties, anti-aging properties, and antistatic properties of the composite modified plastic can be effectively improved by modifying polyvinyl chloride with a modifier and then blending it with polyethylene.

[0056] The descriptions of the above embodiments are merely illustrative of the methods and core ideas of the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a high-impact polyethylene composite modified plastic, characterized in that, Includes the following steps: Preparation of modified chlorinated polyethylene: A UV absorber is obtained by nucleophilic substitution reaction of 3-nitropyridine with hydroxybenzotriazole, and a modifier is obtained by nucleophilic substitution reaction of the UV absorber with a silane coupling agent. Finally, the chlorinated polyethylene is modified by the modifier through a quaternary ammonium salt reaction to obtain modified chlorinated polyethylene. Preparation of polyethylene composite modified plastic: High-density polyethylene, polyolefin elastomer, modified chlorinated polyethylene, fumed silica, antioxidant, and lubricant are blended, and then melt-extruded and granulated to obtain polyethylene composite modified plastic; The preparation of modified chlorinated polyethylene includes the following steps: Step 1: Add 3-nitropyridine, hydroxybenzotriazole, potassium carbonate and N-methylpyrrolidone to a three-necked flask, attach a condenser and a thermometer, turn on magnetic stirring, and react at 70-90℃ for 3-5 hours to obtain an ultraviolet absorber. The second step involves adding the ultraviolet absorber, silane coupling agent, potassium carbonate, and acetonitrile to a three-necked flask, attaching a condenser and a thermometer, turning on the magnetic stirrer, and reacting at 65–75°C for 2–3 hours to obtain the modifier. The third step is to add the modifier and chlorinated polyethylene into a torque rheometer and mix them evenly. After melting and grafting at 160-180℃ for 8-12 minutes, modified chlorinated polyethylene is obtained. The mass ratio of 3-nitropyridine, hydroxybenzotriazole, potassium carbonate, and N-methylpyrrolidone is 12.5–14.5:15–17:27.5–41.5:200–240. The mass ratio of ultraviolet absorber, silane coupling agent, potassium carbonate and acetonitrile is 18-21:20-24:10-15:200-240; The mass ratio of modifier to chlorinated polyethylene is 20-25:40-50; The mass ratio of high-density polyethylene, polyolefin elastomer, modified chlorinated polyethylene, silica, antioxidant and lubricant is 80-85:15-20:15-20:10-15:1-3:1-3.

2. The method for preparing a high-impact polyethylene composite modified plastic according to claim 1, characterized in that, Hydroxybenzotriazole is one of 4-hydroxybenzotriazole and 5-hydroxybenzotriazole.

3. The method for preparing a high-impact polyethylene composite modified plastic according to claim 1, characterized in that, The silane coupling agents are (2-chloroethyl)triethoxysilane, (3-chloropropyl)triethoxysilane, and (3-chloropropyl)trimethoxysilane.

4. The method for preparing a high-impact polyethylene composite modified plastic according to claim 1, characterized in that, The lubricant is at least one of polyethylene wax and oxidized polyethylene wax.

5. The method for preparing a high-impact polyethylene composite modified plastic according to claim 1, characterized in that, The antioxidant is at least one of antioxidant 1010, antioxidant 1076, and antioxidant 168.

6. The method for preparing a high-impact polyethylene composite modified plastic according to claim 1, characterized in that, The temperature for melt extrusion is 160–180℃.

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