High-barrier modified polyethylene

Abstract

The invention relates to the technical field of high polymer materials, in particular to high-barrier modified polyethylene which comprises high-density polyethylene, vinyl silane, montmorillonite, alkali, an antioxidant, nano silicon dioxide, a polyolefin grafted compound, a plasticizer and a stabilizer. According to the invention, additives such as vinyl silane, modified montmorillonite and the like are introduced into high-density polyethylene, and an irradiation crosslinking process is adopted, so that the gas barrier property and the mechanical property of polyethylene are remarkably improved; through surface modification of the montmorillonite, the compatibility of the montmorillonite and a polyethylene matrix is improved, so that the polyethylene matrix is more uniform in microstructure, and the barrier effect is effectively enhanced; by adopting an irradiation crosslinking technology, not only is the barrier property of polyethylene improved, but also the heat resistance and the mechanical strength of the polyethylene are enhanced, so that the material can keep stable performance in a harsh environment; compared with a traditional modification method, the method has the advantages that the production process is simplified, and the dependence on chemical additives is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and particularly relates to a high-barrier modified polyethylene. Background Art

[0002] As a common plastic material, high-density polyethylene (HDPE) is widely used in packaging, pipelines, storage containers, etc. due to its excellent chemical stability, relatively high strength, and low cost. However, although HDPE exhibits good mechanical properties in many applications, its gas barrier property is poor. Especially in fields with high requirements for gas barrier properties such as oxygen and carbon dioxide, for example, in food packaging, pharmaceutical packaging, and certain special industrial applications, the gas barrier property of HDPE cannot meet the requirements. In addition, HDPE also faces some challenges in heat resistance and mechanical properties. Especially in high-temperature environments, the material is prone to deformation or loss of its original strength, thus limiting its use in some high-end applications.

[0003] In the prior art, although HDPE has been partially modified by adding various fillers, plasticizers, or modifiers, etc., and certain gas barrier effects have been achieved, these methods often have problems such as insignificant modification effects, high costs, or difficulty in large-scale production. Summary of the Invention

[0004] Based on the above purpose, the present invention provides a high-barrier modified polyethylene.

[0005] A high-barrier modified polyethylene includes high-density polyethylene, vinyl silane, montmorillonite, alkali, antioxidant, nano-silica, polyolefin graft compound, plasticizer, and stabilizer. The specific preparation of this high-barrier modified polyethylene includes the following steps: S1: Weigh high-density polyethylene, vinyl silane, montmorillonite, alkali, antioxidant, nano-silica, polyolefin graft compound, plasticizer, and stabilizer in proportion and set aside. S2: Mix montmorillonite with alkali and conduct surface modification to obtain modified montmorillonite. S3: Conduct a graft reaction between vinyl silane and modified montmorillonite to obtain montmorillonite filler with vinyl silane grafted on its surface. S4: Put the montmorillonite filler together with the high-density polyethylene, nano-silica, polyolefin graft compound, plasticizer, antioxidant, and stabilizer weighed in S1 into a high-speed mixer for dry mixing to obtain mixture A. S5: Feed mixture A into a melt extruder and conduct melt extrusion at a predetermined temperature to obtain a polyethylene substrate. S6: Conduct irradiation cross-linking treatment on the polyethylene substrate obtained in S5. S7: Cool the crosslinked polyethylene substrate to room temperature and cut it into pellets by a pelletizer to obtain the finished product of high-barrier modified polyethylene.

[0006] Optionally, the components of the high-barrier modified polyethylene are in the following mass percentages: High-density polyethylene accounts for 68% - 84%; Vinyl silane accounts for 6% - 10%; Montmorillonite accounts for 3% - 6%; Base accounts for 1% - 3%; Antioxidant accounts for 0.5% - 1%; Nano-silica accounts for 2% - 4%; Polyolefin graft compound accounts for 1% - 2%; Plasticizer accounts for 2% - 4%; Stabilizer accounts for 0.5% - 2%.

[0007] Optionally, the vinyl silane is vinyltrimethoxysilane; the base is selected from sodium hydroxide or potassium hydroxide; the antioxidant is selected from BHT or antioxidant 1000; the polyolefin graft compound is selected from acrylic acid or butenoic acid; the plasticizer is selected from dioctyl phthalate or diisooctyl phthalate; the stabilizer is selected from UV-328 or UV-9.

[0008] Optionally, the S2 specifically includes: S21: Mix the base and deionized water at a mass ratio of 1:10 to 1:25 to obtain a base solution with a concentration of 1 - 2.5 mol / L; S22: Add montmorillonite to the base solution and stir it with a high-speed stirrer at a speed of 300 - 500 rpm for 30 - 60 minutes; S23: Transfer the mixture obtained in S22 to a reaction kettle, heat it to 50 - 60 °C, and keep it for 30 - 60 minutes for surface modification reaction; S24: After the reaction, let the mixture stand and settle for 60 minutes, discard the upper clear liquid, and retain the settled solid as the modified montmorillonite; S25: Vacuum-dry the filtered modified montmorillonite at a temperature controlled at 60 - 80 °C for 12 - 24 hours until the water content of the modified montmorillonite is lower than 5%.

[0009] Optionally, the S3 specifically includes: S31: Mix the vinyl silane with the modified montmorillonite according to the mass ratio to form mixture B; S32: Add mixture B to the reaction solvent, and the reaction solvent is deionized water, and the solvent volume is 5 - 10 times the total mass of mixture B; S33: While stirring, heat the solution to 60 - 80 °C and react for 2 - 4 hours; S34: After the reaction ends, remove the unreacted vinyl silane and solvent from the reaction mixture B by filtration to obtain a modified montmorillonite filler with vinyl silane grafted on its surface; S35: Vacuum dry the filtered filler at a temperature controlled at 60 - 80 °C for 12 - 24 hours until its moisture content is less than 5%.

[0010] Optionally, the specific steps of S4 are as follows: S41: Put the montmorillonite filler, the high - density polyethylene, nano - silica, polyolefin graft compound, plasticizer, antioxidant, and stabilizer weighed in S1 into a high - speed mixer in proportion; S42: Start the high - speed mixer, set the mixing speed at 300 - 600 rpm, and the mixing time at 10 - 20 minutes; S43: During the mixing process, add an appropriate amount of deionized water, and the volume of deionized water is 1% - 3% of the total material mass; S44: After mixing, check the uniformity of mixture A to ensure that all components are fully dispersed and there is no obvious particle agglomeration.

[0011] Optionally, the specific steps of S5 are as follows: S51: Uniformly add mixture A to the feed inlet of the melt extruder at a feed rate of 50 - 100 kg / h; S52: Set multiple heating zones in the melt extruder to ensure that the temperature gradually increases from the feed end to the extrusion end. Among them, the temperature at the feed end is controlled at 180 - 190 °C, the temperature in the middle heating zone is controlled at 200 - 210 °C, and the temperature at the discharge end is controlled at 210 - 220 °C; S53: Control the melting process of the material by the screw speed, and set the screw speed at 100 - 150 rpm; S54: During the melting process, maintain a constant pressure, and control the extrusion pressure at 15 - 25 MPa; S55: After the melt extrusion is completed, cool the polyethylene substrate through a die at a cooling rate of 2 - 4 °C / min until the polyethylene substrate solidifies.

[0012] Optionally, the specific steps of S6 are as follows: S61: Uniformly place the polyethylene substrate obtained in S5 into the irradiation chamber of the irradiation equipment to ensure that there is no obvious stacking between the substrates; S62: Set the irradiation dose of the irradiation equipment at 8 - 12 kGy, and control the irradiation time at 30 - 60 minutes; S63: During the irradiation process, the irradiation equipment adopts the electron beam irradiation method, and the acceleration voltage of the irradiation accelerator is set to 1 - 3 MeV; and during the irradiation process, the substrate temperature is controlled at 20 - 30 °C.

[0013] Optionally, the S7 specifically includes: S71: Place the polyethylene substrate after irradiation crosslinking in the cooling zone, control the temperature of the cooling zone at 20 - 30 °C, and use natural air circulation for cooling; S72: The cooling time is 1 - 2 hours until the temperature of the polyethylene substrate drops to room temperature.

[0014] Optionally, the S7 further includes: S73: Feed the polyethylene substrate cooled to room temperature into a pelletizer, and adjust the tool gap of the pelletizer to 3 - 5 mm; S74: Cut the polyethylene substrate into pellets through the pelletizer, and the cutting speed is 50 - 100 kg / h; S75: Screen the cut pellets, and the particle size of the screened pellets is 1 - 3 mm, thereby obtaining the finished product of high-barrier modified polyethylene.

[0015] Advantages of the present invention: In the present invention, by introducing additives such as vinyl silane and modified montmorillonite into high-density polyethylene and adopting the irradiation crosslinking process, the gas barrier performance and mechanical properties of polyethylene are significantly improved; by surface-modifying montmorillonite, the compatibility with the polyethylene matrix is enhanced, making the polyethylene substrate more uniform in microstructure, thereby effectively enhancing the barrier effect; especially in application fields with high requirements for the gas barrier properties of gases such as oxygen and carbon dioxide.

[0016] In the present invention, by adopting the irradiation crosslinking technology, not only the barrier performance of polyethylene is improved, but also its heat resistance and mechanical strength are enhanced, enabling the material to maintain stable performance in more demanding environments; compared with traditional modification methods, the production process is simplified, the dependence on chemical additives is reduced, the production cost is lowered, and it has good environmental friendliness. Description of the drawings

[0017] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following-described drawings are only those of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0018] Figure 1 It is a schematic diagram of the preparation method of high-barrier modified polyethylene according to an embodiment of the present invention. Detailed implementation manners

[0019] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted here that in order to make the embodiments more detailed, the following embodiments are the best and preferred embodiments. For some well-known technologies, those skilled in the art can also adopt other alternative methods for implementation; moreover, the accompanying drawings are only for more specifically describing the embodiments, and are not intended to specifically limit the present invention.

[0020] It should be noted that in the specification, references to "an embodiment", "embodiment", "exemplary embodiment", "some embodiments", etc. indicate that the described embodiments may include specific features, structures, or characteristics, but not necessarily every embodiment includes such specific features, structures, or characteristics. Additionally, when combining embodiments to describe specific features, structures, or characteristics, implementing such features, structures, or characteristics in combination with other embodiments (whether explicitly described or not) should be within the knowledge of those skilled in the relevant art.

[0021] Generally, terms can be understood at least in part from their use in context. For example, at least in part depending on the context, the term "one or more" as used herein can be used to describe any feature, structure, or characteristic in a singular sense, or can be used to describe a combination of features, structures, or characteristics in a plural sense. Additionally, the term "based on" can be understood as not necessarily intended to convey a set of exclusive factors, but rather can alternatively, at least in part depending on the context, allow for the existence of other factors that may not be explicitly described.

[0022] Embodiment 1 As Figure 1 shown, a high-barrier modified polyethylene includes high-density polyethylene, vinyl silane, montmorillonite, alkali, antioxidant, nano-silica, polyolefin graft compound, plasticizer, and stabilizer; the specific preparation of the high-barrier modified polyethylene includes the following steps: S1: Weigh high-density polyethylene, vinyl silane, montmorillonite, alkali, antioxidant, nano-silica, polyolefin graft compound, plasticizer, and stabilizer in proportion and set aside for later use; S2: Mix montmorillonite and alkali and perform surface modification to obtain modified montmorillonite; S3: Carry out a graft reaction between vinyl silane and the modified montmorillonite to obtain montmorillonite filler with vinyl silane grafted on its surface; S4: Put the montmorillonite filler together with the high-density polyethylene, nano-silica, polyolefin graft compound, plasticizer, antioxidant, and stabilizer weighed in S1 into a high-speed mixer for dry mixing to obtain mixture A; S5: Feed mixture A into a melt extruder and perform melt extrusion at a predetermined temperature to obtain a polyethylene substrate; S6: The polyethylene substrate obtained in S5 is subjected to radiation cross-linking treatment, which improves the barrier property and mechanical properties of polyethylene. S7: The cross-linked polyethylene substrate is cooled to room temperature and cut into particles by a pelletizer to obtain the finished product of high-barrier modified polyethylene.

[0023] The components of the high-barrier modified polyethylene are as follows by mass percentage: High-density polyethylene accounts for 76.2%; Vinyl silane accounts for 8%; Montmorillonite accounts for 4%; Base accounts for 2%; Antioxidant accounts for 0.8%; Nano-silica accounts for 3%; Polyolefin graft compound accounts for 1.5%; Plasticizer accounts for 3%; Stabilizer accounts for 1.5%.

[0024] The vinyl silane is vinyltrimethoxysilane; the base is selected from sodium hydroxide; the antioxidant is selected from BHT; the polyolefin graft compound is selected from acrylic acid; the plasticizer is selected from dioctyl phthalate; the stabilizer is selected from UV-328.

[0025] S2 specifically includes: S21: The base and deionized water are mixed at a mass ratio of 1:18 to obtain a base solution with a concentration of 1.4 mol / L. S22: Montmorillonite is added to the base solution and stirred at a speed of 400 rpm by a high-speed stirrer for 45 minutes to ensure that the montmorillonite is fully dispersed. S23: The mixture obtained in S22 is transferred to a reaction kettle, heated to 55 °C and maintained for 45 minutes for surface modification reaction. S24: After the reaction, the mixture is allowed to stand and settle for 60 minutes, the supernatant is discarded, and the settled solid is retained as modified montmorillonite. S25: The filtered modified montmorillonite is vacuum dried at a temperature controlled at 70 °C for 18 hours until the moisture content of the modified montmorillonite is lower than 5%.

[0026] S3 specifically includes: S31: The vinyl silane is mixed with the modified montmorillonite according to a mass ratio to form mixture B. S32: Mixture B is added to a reaction solvent, which is deionized water, and the solvent volume is 7 times the total mass of mixture B. S33: Under stirring, the solution is heated to 75 °C and the reaction time is 3 hours. S34: After the reaction is completed, the reaction mixture B is filtered to remove unreacted vinylsilane and the solvent, obtaining a modified montmorillonite filler with vinylsilane grafted on its surface; S35: The filtered filler is dried under vacuum at a temperature controlled at 75 °C for 18 hours until its moisture content is lower than 5%.

[0027] S4 specifically includes: S41: The montmorillonite filler, the high-density polyethylene, nano-silica, polyolefin graft compound, plasticizer, antioxidant, and stabilizer weighed in S1 are put into a high-speed mixer in proportion; S42: Start the high-speed mixer, set the mixing speed at 400 rpm and the mixing time at 15 minutes to ensure that all components are evenly mixed; S43: During the mixing process, deionized water is added in an appropriate amount, and the volume of deionized water is 2% of the total material mass, to help improve the fluidity of the material and prevent heat generation due to excessive friction; S44: After the mixing is completed, check the uniformity of mixture A to ensure that all components are fully dispersed and there is no obvious particle agglomeration.

[0028] S5 specifically includes: S51: Evenly add mixture A to the feed inlet of the melt extruder at a feed rate of 80 kg / h; S52: Set multiple heating zones in the melt extruder to ensure that the temperature gradually increases from the feed end to the extrusion end, where the temperature at the feed end is controlled at 185 °C, the temperature in the middle heating zone is controlled at 205 °C, and the temperature at the discharge end is controlled at 215 °C; S53: Control the melting process of the material by the screw rotation speed, and the screw rotation speed is set at 120 rpm to ensure that the material is fully melted and has good fluidity; S54: During the melting process, maintain a constant pressure, and the extrusion pressure is controlled at 20 MPa to ensure that the material has stable fluidity during extrusion; S55: After the melt extrusion is completed, cool the polyethylene substrate through a die at a cooling rate of 2 - 4 °C / min until the polyethylene substrate is cured.

[0029] S6 specifically includes: S61: Evenly place the polyethylene substrate obtained in S5 into the irradiation chamber of the irradiation equipment, ensuring that there is no obvious stacking between the substrates so as to be evenly irradiated; S62: Set the irradiation dose of the irradiation equipment at 10 kGy and control the irradiation time at 45 minutes to ensure that the crosslinking degree of the substrate reaches the predetermined level; S63: During the irradiation process, the irradiation equipment adopts the electron beam irradiation method, and the acceleration voltage of the irradiation accelerator is set to 2 MeV; and during the irradiation process, the substrate temperature is controlled at 25 °C to avoid thermal degradation of the material due to excessive temperature.

[0030] S7 specifically includes: S71: Place the irradiated cross-linked polyethylene substrate in the cooling zone, control the temperature of the cooling zone at 25 °C, and use natural air circulation for cooling; S72: The cooling time is 1.5 hours until the temperature of the polyethylene substrate drops to room temperature.

[0031] S7 also includes: S73: Feed the polyethylene substrate cooled to room temperature into the granulator, and adjust the tool gap of the granulator to 4 mm to ensure uniform particle size; S74: Cut the polyethylene substrate into particles by the granulator at a cutting speed of 70 kg / h to ensure smooth particle surface and neat cutting; S75: Screen the cut particles, and the particle size of the screened particles is 2 mm, and then obtain the finished product of high-barrier modified polyethylene.

[0032] Example 2 Formulation and proportion: High-density polyethylene 84%; Vinyl silane 6%; Montmorillonite 3%; Alkali (potassium hydroxide) 1%; Antioxidant (1000 antioxidant) 0.5%; Nano-silica 2%; Polyolefin graft compound (butenoic acid) 1%; Plasticizer (diisooctyl phthalate) 2%; Stabilizer (UV-9) 0.5%.

[0033] Preparation steps: S1: Weigh high-density polyethylene, vinyl silane, montmorillonite, alkali, antioxidant, nano-silica, polyolefin graft compound, plasticizer and stabilizer according to the formulation and proportion for standby; S2: Mix sodium hydroxide and deionized water at a mass ratio of 1:10 to obtain an alkali solution with a concentration of 2.5 mol / L. Add montmorillonite to the alkali solution and stir with a high-speed stirrer at a speed of 300 rpm for 30 minutes; Subsequently, transfer the mixture to a reaction kettle, heat it to 50 °C and keep it for 30 minutes for surface modification reaction; After the reaction is completed, let the mixture stand and settle for 60 minutes, discard the supernatant, and retain the settled solid as modified montmorillonite; Vacuum dry the filtered modified montmorillonite, control the drying temperature at 60 °C, and the drying time is 12 hours until the moisture content is lower than 5%; S3: Mix vinyl silane with modified montmorillonite in a mass ratio to form mixture A; add mixture A to deionized water with a volume 5 times that of mixture A, stir and heat to 60 °C, and react for 2 hours; after the reaction, filter the mixture to remove unreacted vinyl silane and solvent to obtain modified montmorillonite filler with vinyl silane grafted on its surface; subject the filtered filler to vacuum drying at a drying temperature of 60 °C and a drying time of 12 hours until the moisture content is lower than 5%; S4: Put the montmorillonite filler, weighed high-density polyethylene, nano-silica, polyolefin graft compound, plasticizer, antioxidant, and stabilizer into a high-speed mixer in proportion, set the mixing speed at 300 rpm, and mix for 10 minutes; add deionized water during the mixing process, with the water volume being 1% of the total material mass; after mixing, check the uniformity of the mixture to ensure that all components are fully dispersed; S5: Uniformly add the mixture to a melt extruder at a feeding speed of 50 kg / h; set the temperature to gradually increase from the feeding end to the extrusion end, with the feeding end temperature controlled at 180 °C, the middle temperature at 200 °C, and the discharging end temperature at 210 °C; control the melting of the material through the screw rotation speed, with the screw rotation speed at 100 rpm; control the extrusion pressure at 15 MPa, and after the melt extrusion is completed, cool the polyethylene substrate through a die at a cooling speed of 2 °C / min to finally obtain the polyethylene substrate; S6: Uniformly place the polyethylene substrate into an irradiation device, set the irradiation dose at 8 kGy, control the irradiation time at 30 minutes, and during the irradiation process, set the acceleration voltage of the irradiation accelerator at 1 MeV and control the substrate temperature at 20 °C; S7: After irradiation, cool the polyethylene substrate to room temperature, control the temperature in the cooling zone at 20 °C, and the cooling time at 1 hour; use a pelletizer to cut the cooled polyethylene substrate into pellets, adjust the tool gap of the pelletizer to 3 mm, the cutting speed at 50 kg / h, and control the pellet particle size at 1 mm.

[0034] Example 3 Formulation and proportion: High-density polyethylene 68%; vinyl silane 10%; montmorillonite 6%; alkali (sodium hydroxide) 3%; antioxidant (BHT) 1%; nano-silica 4%; polyolefin graft compound (acrylic acid) 2%; plasticizer (dioctyl phthalate) 4%; stabilizer (UV-328) 2%.

[0035] Preparation steps: S1: Weigh and reserve high-density polyethylene, vinyl silane, montmorillonite, alkali, antioxidant, nano-silica, polyolefin graft compound, plasticizer, and stabilizer according to the formulation and proportion; S2: Mix sodium hydroxide and deionized water at a mass ratio of 1:25 to obtain an alkali solution with a concentration of 1 mol / L. Add montmorillonite to the alkali solution and stir it with a high-speed stirrer at a speed of 500 rpm for 60 minutes. Subsequently, transfer the mixture to a reaction kettle, heat it to 60 °C and maintain it for 60 minutes for surface modification reaction. After the reaction, let the mixture stand and settle for 60 minutes, discard the supernatant, and retain the settled solid as modified montmorillonite. Vacuum-dry the filtered modified montmorillonite, control the drying temperature at 80 °C, and the drying time at 24 hours until the moisture content is lower than 5%. S3: Mix vinyl silane with modified montmorillonite at a mass ratio to form mixture A. Add mixture A to deionized water with a volume 10 times that of mixture A, stir and heat it to 80 °C, and the reaction time is 4 hours. After the reaction, filter the mixture to remove unreacted vinyl silane and solvent to obtain modified montmorillonite filler with vinyl silane grafted on the surface. Vacuum-dry the filtered filler at a drying temperature of 80 °C and a drying time of 24 hours until the moisture content is lower than 5%. S4: Put the montmorillonite filler, weighed high-density polyethylene, nano-silica, polyolefin graft compound, plasticizer, antioxidant, and stabilizer into a high-speed mixer in proportion, set the mixing speed at 600 rpm, and the mixing time at 20 minutes. Add deionized water during the mixing process, and the volume of water is 3% of the total material mass. After mixing, check the uniformity of the mixture to ensure that all components are fully dispersed. S5: Uniformly add the mixture into a melt extruder with a feeding speed of 100 kg / h. Set the temperature to gradually increase from the feeding end to the extrusion end, control the feeding end temperature at 190 °C, the middle temperature at 210 °C, and the discharging end temperature at 220 °C. Control the melting of the material by the screw rotation speed, and the screw rotation speed is 150 rpm. Control the extrusion pressure at 25 MPa. After the melt extrusion is completed, cool the polyethylene substrate through a die, and the cooling speed is 4 °C / min to finally obtain the polyethylene substrate. S6: Uniformly place the polyethylene substrate into an irradiation device, set the irradiation dose at 12 kGy, control the irradiation time at 60 minutes. During the irradiation process, set the acceleration voltage of the irradiation accelerator at 3 MeV and control the substrate temperature at 30 °C. S7: After irradiation, cool the polyethylene substrate to room temperature, control the cooling zone temperature at 30 °C, and the cooling time at 2 hours. Use a pelletizer to cut the cooled polyethylene substrate into particles, adjust the tool gap of the pelletizer to 5 mm, the cutting speed is 100 kg / h, and control the particle size at 3 mm.

[0036] Comparative Example 1 Formulation: 100% high-density polyethylene Preparation steps: S1: Weigh high-density polyethylene in proportion for standby. Usually, pure high-density polyethylene is used without the need for additional additives; S2: Directly add the weighed high-density polyethylene into the extruder for melt extrusion. Set the temperature at 200°C, the screw speed at 80 rpm, and keep the melt pressure at 13 MPa; S3: Cool and form the molten polyethylene substrate through a mold at a cooling rate of 3°C / min to finally obtain polyethylene particles.

[0037] Table 1 Comparison table of finished product performance parameters

[0038] As can be seen from Table 1 above, the tensile strength of Example 1 (high-barrier modified polyethylene) is the highest, significantly better than that of conventional polyethylene (18 MPa), indicating that this modified polyethylene has stronger mechanical properties; in terms of elongation at break, Example 1 shows the best performance, meaning that the modified polyethylene has better toughness; Example 1 has higher antioxidant performance, better than conventional polyethylene, indicating stronger antioxidant ability; the melt flow index of conventional polyethylene is the highest, indicating better fluidity, but the modified polyethylene still maintains good fluidity, meeting the application requirements; Example 1 has the highest high-temperature resistance performance, with better heat resistance stability compared to conventional polyethylene; the thermal stability of Example 1 is 25 minutes, showing the best performance, far higher than that of conventional polyethylene, indicating a longer service life of the modified material in high-temperature environments; the ultraviolet resistance performance of Example 1 is the highest, significantly improved compared to conventional polyethylene, which helps to improve the durability of polyethylene in outdoor or light environments; generally speaking, the modified polyethylene of Example 1 is superior to conventional polyethylene in multiple performance aspects, especially in terms of tensile strength, elongation at break, and ultraviolet resistance performance, and is suitable for applications with higher performance requirements.

[0039] Table 2 Comparison table of other performance parameters

[0040] As can be seen from Table 2 above, the density of Example 1 is 0.96 g / cm³, slightly higher than that of conventional polyethylene, and is more suitable for applications requiring higher density and strength; the hardness of Example 1 is 70 Shore D, higher than 60 Shore D of conventional polyethylene, showing better hardness and being suitable for applications that can withstand greater pressure; the impact strength of Example 1 is 13 kJ / m², significantly higher than that of conventional polyethylene, indicating that it has stronger impact resistance and is applicable to more complex environments; the corrosion resistance of Example 1 is 0.15 mmpy, superior to 0.25 mmpy of conventional polyethylene, meaning that it has stronger stability in harsh environments; the water absorption rate of Example 1 is 0.02%, much lower than 0.05% of conventional polyethylene, indicating that it has higher stability in humid environments; the coefficient of thermal expansion of Example 1 is , lower than that of conventional polyethylene , showing better thermal stability; the oxygen transmission rate of Example 1 is 2.5 cm³ / m²·day, significantly lower than that of conventional polyethylene (5.0 cm³ / m²·day), indicating that it has excellent oxygen barrier performance; through the above comparison, it can be seen that the high-barrier modified polyethylene of Example 1 has obvious advantages over conventional polyethylene in many aspects and is applicable to application fields with higher performance requirements.

[0041] Comparative Example 2: Vinyl silane was not added Formulation and proportion: High-density polyethylene 84.2%; Montmorillonite 4%; Alkali (sodium hydroxide) 2%; Antioxidant (BHT) 0.8%; Nano-silica 3%; Polyolefin graft compound (acrylic acid) 1.5%; Plasticizer (dioctyl phthalate) 3%; Stabilizer (UV-328) 1.5%; Preparation steps: S1: Weigh each component (without vinyl silane) according to the above formula and set aside; S2: Mix sodium hydroxide and deionized water at a mass ratio of 1:18 to obtain an alkali solution with a concentration of 1.4 mol / L; add montmorillonite to this solution and stir at 400 rpm for 45 minutes; then heat to 55 °C and maintain the reaction for 45 minutes, filter after completion and dry in vacuum at 70 °C for 18 hours to obtain modified montmorillonite; S3: In this example, vinyl silane was not introduced, so the graft reaction step was skipped; S4: Put the modified montmorillonite, high-density polyethylene, nano-silica, graft compound, plasticizer, antioxidant and stabilizer into a high-speed mixer, with a mixing speed of 400 rpm and a time of 15 minutes. During the mixing process, add deionized water (the amount of water is 2% of the total mass); S5: Feed the mixture into a melt extruder at a feeding rate of 80 kg / h, set the heating zone temperatures at 185 / 205 / 215 °C, the screw rotation speed at 120 rpm, the pressure control at 20 MPa, and the die cooling rate at 3 °C / min to obtain a polyethylene substrate; S6: Irradiate with an electron beam of 10 kGy for 45 minutes at a voltage of 2 MeV and control the temperature at 25 °C; S7: Set the cooling temperature at 25 °C for 1.5 hours, then use a pelletizer (knife gap 4 mm, speed 70 kg / h) to pelletize, and control the screening particle size at 2 mm.

[0042] Comparative Example 3: Montmorillonite was not added Formulation and proportion: High-density polyethylene 82.2%; Vinyl silane 8%; Antioxidant (BHT) 0.8%; Nano-silica 3%; Polyolefin graft compound (acrylic acid) 1.5%; Plasticizer (dioctyl phthalate) 3%; Stabilizer (UV-328) 1.5%; Preparation steps: S1: Weigh each component according to the above formulation (without montmorillonite) for standby; S2: In this example, montmorillonite was not introduced, so the alkali solution modification process was skipped; S3: Directly add vinyl silane to deionized water with a volume 7 times its mass, stir and heat it to 75 °C for 3 hours without contact with a polyethylene carrier to form a free grafting solution (with a low grafting degree); after the reaction, filter and vacuum dry (75 °C, 18 hours); S4: Put the treated vinyl silane residue together with high-density polyethylene, nano-silica, polyolefin graft compound, plasticizer, antioxidant and stabilizer into a high-speed mixer at a mixing speed of 400 rpm for 15 minutes, and add 2% water; S5: Set the melt extrusion temperature at 185 / 205 / 215 °C, the feeding rate at 80 kg / h, the screw rotation speed at 120 rpm, the extrusion pressure at 20 MPa, and the cooling rate at 3 °C / min to obtain a polyethylene substrate; S6: Conduct irradiation of 10 kGy at a voltage of 2 MeV for 45 minutes and control the temperature at 25 °C; S7: After cooling, pelletize at a speed of 70 kg / h with a knife gap of 4 mm and control the particle size at 2 mm.

[0043] Comparative Example 4: Irradiation crosslinking was not carried out Formulation and proportion: High-density polyethylene 76.2%; vinyl silane 8%; montmorillonite 4%; alkali (sodium hydroxide) 2%; antioxidant (BHT) 0.8%; nano-silica 3%; polyolefin graft compound (acrylic acid) 1.5%; plasticizer (dioctyl phthalate) 3%; stabilizer (UV-328) 1.5%; Preparation steps: S1: Weigh each component according to the ratio in Example 1 for standby; S2: Mix sodium hydroxide with water at a ratio of 1:18 to obtain an alkali solution with a concentration of 1.4 mol / L. Stir montmorillonite at 400 rpm for 45 minutes, heat at 55 °C and maintain the reaction for 45 minutes, filter and dry at 70 °C for 18 hours; S3: React vinyl silane with the dried modified montmorillonite in deionized water (the volume is 7 times its mass), maintain at 75 °C for 3 hours, and dry after the reaction; S4: Mix the filler and other components at high speed (400 rpm, 15 minutes, with a water addition of 2%); S5: Feed into an extruder at temperatures of 185 / 205 / 215 °C, a feeding speed of 80 kg / h, a screw rotation speed of 120 rpm, a pressure of 20 MPa, and a die cooling rate of 3 °C / min to obtain a polyethylene substrate; S6: In this example, no irradiation cross-linking treatment is carried out; S7: The cooling temperature is 25 °C, the time is 1.5 hours, the pelletizing speed is 70 kg / h, the tool gap is 4 mm, and the particle size is 2 mm.

[0044] Table 3 Comparative table of performance data for the comparative examples

[0045] As can be seen from Table 3 above, for the case of the absence of vinyl silane (Comparative Example 2), the tensile strength decreased from 30.5 MPa to 25.8 MPa; at the same time, the oxygen transmission rate increased to 4.8 cm³ / m²·day; this clearly shows that vinyl silane participated in the construction of the cross-linking network and interface enhancement, and its absence directly led to the decline of mechanical and barrier properties; for the case of the absence of montmorillonite (Comparative Example 3), the high-temperature resistance decreased to 198 °C, and the thermal stability was only 17 minutes; the oxygen transmission rate increased to 4.3; this shows the significant role of modified montmorillonite in constructing the inorganic barrier layer, and its absence will weaken the thermal barrier and denseness; for the case of no irradiation cross-linking (Comparative Example 4), the elongation at break decreased significantly to 370%, and the high-temperature resistance was only 180 °C; the mechanical flexibility and thermal stability decreased significantly, indicating that irradiation cross-linking is crucial for the molecular structure stability.

[0046] The present invention covers any alternatives, modifications, equivalent methods, and solutions made to the essence and scope of the present invention. To enable the public to have a thorough understanding of the present invention, specific details are described in detail in the following preferred embodiments of the present invention, and those skilled in the art can fully understand the present invention without the description of these details. In addition, well-known methods, processes, procedures, components, and circuits are not described in detail to avoid unnecessary confusion to the essence of the present invention.

[0047] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A high-barrier modified polyethylene, characterized in that, It includes high-density polyethylene, vinyl silane, montmorillonite, alkali, antioxidant, nano-silica, polyolefin graft compound, plasticizer and stabilizer; The specific preparation of the high-barrier modified polyethylene includes the following steps: S1: Weigh high-density polyethylene, vinyl silane, montmorillonite, alkali, antioxidant, nano-silica, polyolefin graft compound, plasticizer and stabilizer in proportion and set aside; S2: Mix montmorillonite with alkali and conduct surface modification to obtain modified montmorillonite; S3: Conduct grafting reaction between vinyl silane and modified montmorillonite to obtain montmorillonite filler with vinyl silane grafted on the surface; S4: Put the montmorillonite filler together with the high-density polyethylene, nano-silica, polyolefin graft compound, plasticizer, antioxidant and stabilizer weighed in S1 into a high-speed mixer for dry mixing to obtain mixture A; S5: Send mixture A into a melt extruder and conduct melt extrusion at a predetermined temperature to obtain a polyethylene substrate; S6: Conduct irradiation cross-linking treatment on the polyethylene substrate obtained in S5; S7: Cool the cross-linked polyethylene substrate to room temperature and cut it into particles through a pelletizer to obtain the finished product of high-barrier modified polyethylene.

2. The high-barrier modified polyethylene according to claim 1, wherein The components of the high-barrier modified polyethylene are in mass percentages as follows: High-density polyethylene accounts for 68% - 84%; Vinyl silane accounts for 6% - 10%; Montmorillonite accounts for 3% - 6%; Alkali accounts for 1% - 3%; Antioxidant accounts for 0.5% - 1%; Nano-silica accounts for 2% - 4%; Polyolefin graft compound accounts for 1% - 2%; Plasticizer accounts for 2% - 4%; Stabilizer accounts for 0.5% - 2%.

3. A high-barrier modified polyethylene according to claim 1, characterized in that, The vinyl silane is vinyltrimethoxysilane; the alkali is selected from sodium hydroxide or potassium hydroxide; the antioxidant is selected from BHT or antioxidant 1000; the polyolefin graft compound is selected from acrylic acid or butenoic acid; the plasticizer is selected from dioctyl phthalate or diisooctyl phthalate; the stabilizer is selected from UV-328 or UV-9.

4. A high-barrier modified polyethylene according to claim 1, wherein The specific steps of S2 include: S21: Mix alkali and deionized water in a mass ratio of 1:10 to 1:25 to obtain an alkali solution with a concentration of 1 - 2.5 mol / L; S22: Add montmorillonite to the alkali solution and stir it with a high-speed stirrer at a speed of 300 - 500 rpm for 30 - 60 minutes; S23: Transfer the mixture obtained in S22 to a reaction kettle, heat it to 50 - 60 °C, and keep it for 30 - 60 minutes for surface modification reaction; S24: After the reaction, let the mixture stand and settle for 60 minutes, discard the upper clear liquid, and retain the settled solid as the modified montmorillonite; S25: Conduct vacuum drying on the filtered modified montmorillonite, control the temperature at 60 - 80 °C, and the drying time is 12 - 24 hours until the moisture content of the modified montmorillonite is lower than 5%.

5. A high-barrier modified polyethylene according to claim 1, characterized in that, The specific steps of S3 include: S31: Mix vinyl silane with modified montmorillonite in a mass ratio to form mixture B; S32: Add mixture B into a reaction solvent, and the reaction solvent is deionized water, and the solvent volume is 5 - 10 times the total mass of mixture B; S33: While stirring, heat the solution to 60 - 80 °C, and the reaction time is 2 - 4 hours; S34: After the reaction ends, remove the unreacted vinylsilane and solvent from the reaction mixture B by filtration to obtain the modified montmorillonite filler with vinylsilane grafted on the surface; S35: Vacuum dry the filtered filler at a temperature controlled at 60 - 80 °C for 12 - 24 hours until its moisture content is lower than 5%.

6. A high-barrier modified polyethylene according to claim 1, characterized in that, The specific steps of S4 are as follows: S41: Put the montmorillonite filler, the high - density polyethylene weighed in S1, nano - silica, polyolefin graft compound, plasticizer, antioxidant and stabilizer into a high - speed mixer in proportion; S42: Start the high - speed mixer, set the mixing speed at 300 - 600 rpm, and the mixing time at 10 - 20 minutes; S43: During the mixing process, add deionized water in an appropriate amount, and the volume of deionized water is 1% - 3% of the total material mass; S44: After the mixing ends, check the uniformity of mixture A to ensure that all components are fully dispersed and there is no obvious particle agglomeration.

7. A high-barrier modified polyethylene according to claim 1, wherein The specific steps of S5 are as follows: S51: Uniformly add mixture A to the feed inlet of the melt extruder at a feed rate of 50 - 100 kg / h; S52: Set multiple heating zones in the melt extruder to ensure that the temperature gradually increases from the feed end to the extrusion end. Among them, the temperature at the feed end is controlled at 180 - 190 °C, the temperature in the middle heating zone is controlled at 200 - 210 °C, and the temperature at the discharge end is controlled at 210 - 220 °C; S53: Control the melting process of the material by the screw rotation speed, and set the screw rotation speed at 100 - 150 rpm; S54: During the melting process, maintain a constant pressure, and control the extrusion pressure at 15 - 25 MPa; S55: After the melt extrusion is completed, cool the polyethylene substrate through a mold at a cooling rate of 2 - 4 °C / min until the polyethylene substrate solidifies.

8. A high-barrier modified polyethylene according to claim 1, characterized in that, The specific steps of S6 are as follows: S61: Uniformly place the polyethylene substrate obtained in S5 into the irradiation chamber of the irradiation equipment, ensuring that there is no obvious stacking between the substrates; S62: Set the irradiation dose of the irradiation equipment at 8 - 12 kGy, and control the irradiation time at 30 - 60 minutes; S63: During the irradiation process, the irradiation equipment adopts the electron beam irradiation method, and set the acceleration voltage of the irradiation accelerator at 1 - 3 MeV; and control the substrate temperature at 20 - 30 °C during the irradiation process.

9. A high-barrier modified polyethylene according to claim 1, wherein The specific steps of S7 are as follows: S71: Place the irradiated and cross - linked polyethylene substrate in the cooling zone, control the temperature of the cooling zone at 20 - 30 °C, and use natural air circulation for cooling; S72: The cooling time is 1 - 2 hours until the temperature of the polyethylene substrate drops to room temperature.

10. A high-barrier modified polyethylene according to claim 9, characterized in that, S7 also includes: S73: Feed the polyethylene substrate cooled to room temperature into a pelletizer, and adjust the tool gap of the pelletizer to 3 - 5 mm; S74: Cut the polyethylene substrate into pellets by the pelletizer at a cutting speed of 50 - 100 kg / h; S75: Screen the cut pellets, and the particle size of the screened pellets is 1 - 3 mm, thus obtaining the finished product of high - barrier modified polyethylene.

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