Polyethylene composition, polyethylene composite and method for producing a polyethylene composite

Abstract

The present application relates to a kind of polyethylene composition, polyethylene composite material and the preparation method of polyethylene composite material, the polyethylene composition includes polyethylene and light stabilizer composition, antioxidant and lubricant;The light stabilizer composition includes light screen, ultraviolet absorber and modified light stabilizer;The modified light stabilizer includes hindered amine light stabilizer intercalation LDH;The weight ratio of the polyethylene and the light stabilizer composition is 100: (1.5-6.5) ;The weight ratio of the light screen, the ultraviolet absorber and the modified light stabilizer is 1: (1-4) : (5-10).The polyethylene composition of the present application can avoid the migration failure of hindered amine light stabilizer by using intercalation fixed modified light stabilizer, improves the long-term aging resistance of polyethylene composition.

Description

Technical Field

[0001] This invention belongs to the field of polymers, specifically relating to a polyethylene composition, a polyethylene composite material, and a method for preparing the polyethylene composite material. Background Technology

[0002] Polyethylene (PE) is lightweight, wear-resistant, and corrosion-resistant, and also possesses electrical insulation properties, making it widely used in automotive parts, electronic products, and electrical equipment. However, PE products are prone to aging when exposed to high temperatures and air for extended periods. For example, prolonged exposure to air allows oxygen to react with PE, causing the PE molecular chains to break and cross-link, leading to a decline in the performance of the PE products.

[0003] To improve the anti-aging ability of polyethylene compositions, CN115197491A discloses a marine-grade aging-resistant high-strength polyethylene composition, its preparation method, and its application. The raw materials of this polyethylene composition include, by weight, 80-100 parts of high-density polyethylene, 10-20 parts of low-density polyethylene, 5-10 parts of linear low-density polyethylene, 1-7 parts of chlorosulfonated polyethylene, 10-50 parts of carbon black polyethylene masterbatch, 5-20 parts of UV polyethylene masterbatch, 1-10 parts of nano-silicon nitride, 1-10 parts of nano-boron nitride, 5-20 parts of polyethylene wax, and 2-10 parts of antioxidant. The resulting polyethylene composition has good flowability and processability, as well as good strength, impact resistance, and environmental stress resistance, and excellent thermal stability and aging resistance.

[0004] CN112876760A discloses a controlled-release polymer composite material with extended photoaging performance. In this composite material, inorganic fillers coat the light stabilizer on the surface through electrostatic interaction or physical adsorption. The light stabilizer is released in a controlled manner during production, storage, transportation, and use, thus extending the effective time of the light stabilizer while ensuring the photoaging performance of the composite material, thereby extending the photoaging performance of the composite material and allowing the performance of the composite material to be maintained for a longer period of time. The light stabilizer used is a hindered amine light stabilizer and an ultraviolet absorber.

[0005] Existing technologies mainly improve the anti-aging properties or weather resistance of materials by introducing anti-aging additives; however, the mechanical properties of the materials still need further improvement. Summary of the Invention

[0006] The purpose of this invention is to further improve the mechanical properties of polyethylene compositions, so as to balance the aging resistance and mechanical properties of the material.

[0007] To achieve the above objectives, a first aspect of the present invention provides a polyethylene composition comprising polyethylene and a light stabilizer composition, an antioxidant, and a lubricant; wherein the light stabilizer composition comprises a light shielding agent, an ultraviolet absorber, and a modified light stabilizer. The modified light stabilizer includes hindered amine light stabilizer intercalated LDH; The weight ratio of the polyethylene to the light stabilizer composition is 100:(1.5-6.5). The weight ratio of the light-shielding agent, the ultraviolet absorber, and the modified light stabilizer is 1:(1-4):(5-10).

[0008] Optionally, the light-shielding agent is selected from one or more of carbon black, silicon dioxide, titanium dioxide, and zinc oxide; the ultraviolet absorber is selected from benzotriazole absorbers.

[0009] Optionally, the modified light stabilizer contains 50-70 wt% hindered amine light stabilizer; the hindered amine light stabilizer is selected from one or more of light stabilizers UV944, UV 770, UV4050, and UV3853; optionally, the modified light stabilizer is prepared by a method comprising the following steps: intercalating a hindered amine light stabilizer into a layered composite metal hydroxide; the metal ions in the layered composite metal hydroxide include Ca. 2+ And Al 3+ .

[0010] Optionally, the polyethylene comprises metallocene linear low-density polyethylene and metallocene medium-density polyethylene; the weight ratio of the metallocene linear low-density polyethylene to the metallocene medium-density polyethylene is 1:(3-5); wherein the metallocene linear low-density polyethylene has a melt index of 3.5-4.5 g / min and a density of 0.915-0.92 g / cm³ at 190 ℃ / 2.16 kg. 3 The metallocene medium-density polyethylene described above has a melt index of 3.5-5 g / min and a density of 0.925-0.938 g / cm³ at 190 ℃ / 2.16 kg. 3 .

[0011] Optionally, the weight ratio of the polyethylene, lubricant, and antioxidant is 100:(0.5-2):(0.1-1.0); the lubricant is selected from one or more of polyethylene wax, stearic acid, zinc stearate, and calcium stearate; and / or, the antioxidant is a composition comprising a primary antioxidant and a secondary antioxidant; the weight ratio of the primary antioxidant to the secondary antioxidant is 1:(0.5-1); the primary antioxidant is selected from one or more of antioxidant 1010 and antioxidant 1330; and the secondary antioxidant is selected from one or more of antioxidant 168 and antioxidant DSTP.

[0012] A second aspect of the present invention provides a method for preparing a polyethylene composition, the method comprising: The polyethylene composition described in the first aspect of the present invention is mixed, and the mixed material is melt-blended and granulated to obtain a polyethylene composition; optionally, the temperature of the melt-blending and granulation is 150-190 °C.

[0013] A third aspect of the present invention provides a polyethylene composite material comprising a polyethylene outer layer and a polyethylene inner layer compoundly formed inside the polyethylene outer layer, wherein the polyethylene inner layer is crosslinkable polyethylene, and the polyethylene outer layer is obtained by rotational molding of a polyethylene composition prepared by the polyethylene composition described in the first aspect of the present invention or a polyethylene composition prepared by the method described in the second aspect of the present invention.

[0014] Optionally, the ratio of the thickness of the polyethylene outer layer to the thickness of the polyethylene inner layer is (0.35-1.0):1; preferably, the thickness of the polyethylene composite material is 4-12 mm.

[0015] A fourth aspect of the present invention provides a method for preparing a polyethylene composite material, the method comprising: The polyethylene composition described in the first aspect of the present invention or the polyethylene composition prepared by the method described in the second aspect of the present invention is added to a rotational molding mold for a first rotational molding process to obtain a polyethylene outer layer. After the polyethylene outer layer has cooled and solidified, cross-linkable polyethylene is added to the rotational molding mold for a second rotational molding process, so as to form a polyethylene inner layer on the inner surface of the polyethylene outer layer.

[0016] Optionally, the weight ratio of the polyethylene composition to the crosslinkable polyethylene is (0.35-1):1; the conditions for the first rotational molding include: a molding temperature of 240-280 ℃ and a molding time of 8-15 min; the conditions for the second rotational molding include: a molding temperature of 270-290 ℃ and a molding time of 25-35 min; optionally, the melt index of the matrix material of the crosslinkable polyethylene at 190℃ / 2.16 kg is 4-15 g / min; the density of the crosslinkable polyethylene is 0.93-0.95 g / cm³. 3 Optionally, the degree of crosslinking of the crosslinkable polyethylene is 60-80%.

[0017] Through the above technical solution, the present invention uses an intercalated and fixed modified light stabilizer to avoid the migration and failure of hindered amine light stabilizers, thereby improving the long-term aging resistance of the polyethylene composition; at the same time, the light stabilizer composition of the present invention is obtained by compounding a light shielding agent, an ultraviolet absorber and a modified light stabilizer. The light shielding agent and the ultraviolet absorber work together to make the polyethylene composition have excellent anti-aging properties in the early stage.

[0018] Other features and advantages of the present invention will be described in detail in the following detailed description section. Detailed Implementation

[0019] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0020] A first aspect of the present invention provides a polyethylene composition comprising polyethylene and a light stabilizer composition, an antioxidant, and a lubricant; said light stabilizer composition comprising a light shielding agent, an ultraviolet absorber, and a modified light stabilizer; The modified light stabilizer includes hindered amine light stabilizer intercalated LDH; The weight ratio of the polyethylene to the light stabilizer composition is 100:(1.5-6.5). The weight ratio of the light-shielding agent, the ultraviolet absorber, and the modified light stabilizer is 1:(1-4):(5-10).

[0021] Through the above technical solutions, on the one hand, the present invention uses an intercalated modified light stabilizer to avoid the migration and failure of hindered amine light stabilizers, thereby improving the long-term aging resistance of the polyethylene composition; on the other hand, the present invention uses a light stabilizer obtained by compounding a light shielding agent, an ultraviolet absorber and a modified light stabilizer. The light shielding agent and the ultraviolet absorber work together to make the polyethylene composition have excellent anti-aging properties in the early stage.

[0022] Typically, light stabilizers are physically mixed with plastics for composite modification and highly dispersed in plastic products to fully utilize their ability to scavenge reactive free radicals, reduce photo-oxidative degradation of plastics, and extend their service life. However, small-molecule organic light stabilizers suffer from drawbacks such as volatility, migration, and poor thermal stability. This invention addresses this issue by inserting hindered amine light stabilizers into layered composite metal hydroxides (LDHs). Based on the tunable nature of the LDH's structure and function, hindered amine light stabilizers can be stabilized, thereby leveraging their excellent long-term anti-aging properties.

[0023] In this invention, the light-shielding agent can reflect ultraviolet light, reducing the amount of ultraviolet light penetrating the material. By adding an appropriate amount of light-shielding agent, the problem of poor interfacial compatibility between polyethylene and the light-shielding agent can be reduced, thereby improving the mechanical properties of the polyethylene composition. In some embodiments of this invention, the light-shielding agent may be selected from one or more of carbon black, silicon dioxide, titanium dioxide, and zinc oxide.

[0024] In this invention, the ultraviolet absorber is used to absorb unshielded ultraviolet light, thereby improving the material's initial resistance to ultraviolet aging. In some embodiments of this invention, the ultraviolet absorber is selected from benzotriazole absorbers.

[0025] In this invention, by selecting modified stabilizers, the hindered amine light stabilizers can promptly scavenge active free radicals generated by ultraviolet light irradiation, preventing further degradation of material properties caused by active free radicals and improving the material's resistance to ultraviolet aging. By inserting the hindered amine light stabilizers into layered composite metal hydroxides (LDHs), the hindered amines can be immobilized, preventing the migration and failure of hindered amine small molecule anti-aging agents, thereby improving the material's long-term resistance to ultraviolet aging.

[0026] In some embodiments of the present invention, the content of hindered amine light stabilizer in the modified light stabilizer is 50-70 wt%. This ensures that the modified light stabilizer contains an appropriate amount of hindered amine light stabilizer, which can promptly remove reactive free radicals generated by ultraviolet light irradiation.

[0027] In some embodiments of the present invention, the hindered amine light stabilizer is selected from one or more of the light stabilizers UV 944, UV 770, UV4050 and UV 3853.

[0028] In some embodiments of the present invention, the modified light stabilizer is prepared by a method comprising the following steps: Intercalation of hindered amine light stabilizers into layered composite metal hydroxides; The metal ions in the layered composite metal hydroxide include Ca. 2+ And Al 3+ .

[0029] In this invention, the hydrogen bonds and electrostatic interactions between the host and guest components in the calcium-aluminum based LDH structure, as well as the covalent bonds on the host layer, endow the LDH with a certain thermal stability, resulting in hindered amine intercalated LDH with excellent anti-aging properties.

[0030] In some embodiments of the present invention, the polyethylene comprises metallocene linear low-density polyethylene and metallocene medium-density polyethylene; the weight ratio of the metallocene linear low-density polyethylene to the metallocene medium-density polyethylene is 1:(3-5). By using metallocene linear low-density polyethylene and metallocene medium-density polyethylene in combination, it is beneficial to obtain polyethylene with suitable flowability and viscosity, and the material can maintain high impact resistance and high modulus.

[0031] The metallocene linear low-density polyethylene has a melt index of 3.5-4.5 g / min and a density of 0.915-0.92 g / cm³ at 190 ℃ / 2.16 kg. 3 .

[0032] The metallocene medium-density polyethylene described herein has a melt index of 3.5-5 g / min and a density of 0.925-0.938 g / cm³ at 190 ℃ / 2.16 kg. 3 .

[0033] In some embodiments of the present invention, the weight ratio of the polyethylene, lubricant, and antioxidant is 100:(0.5-2):(0.1-1.0). By adding a suitable antioxidant, the antioxidant properties of the polyethylene material can be improved, and its anti-aging properties can be further enhanced.

[0034] The antioxidant is a composition comprising a primary antioxidant and a secondary antioxidant, wherein the primary antioxidant is selected from one or more of antioxidant 1010 and antioxidant 1330; the secondary antioxidant is selected from one or more of antioxidant 168 and antioxidant DSTP; and the weight ratio of the primary antioxidant to the secondary antioxidant is 1:(0.5-1).

[0035] The lubricant is selected from one or more of polyethylene wax, stearic acid, zinc stearate and calcium stearate.

[0036] The polyethylene composition obtained by this invention has long-term resistance to ultraviolet aging, with a tensile yield strength ≥16.7MPa, an elongation at break ≥300%, and a tensile yield strength ≥17.2MPa and an elongation at break ≥250% after 100kW ultraviolet irradiation.

[0037] A second aspect of the present invention provides a method for preparing a polyethylene composition, the method comprising: The above-mentioned polyethylene composition is mixed, and the mixed material is melt-blended and granulated to obtain a polyethylene composition.

[0038] In some embodiments of the present invention, the temperature of the melt blending granulation is 150-190 °C.

[0039] Specifically, the melt blending granulation is carried out using a twin-screw extruder, with the operating temperature of the melt blending process being 150-190 ℃ and the screw speed being 100-250 rpm.

[0040] In some embodiments of the present invention, the method further includes grinding the product obtained by melt blending and granulation into a powder of about 30 mesh, thereby obtaining a polyethylene composition that can be used for rotational molding. In some specific embodiments, the grinding is carried out in a grinding mill, and the material temperature of the grinding mill is controlled at 40-55 °C during the grinding process.

[0041] A third aspect of the present invention provides a polyethylene composite material comprising a polyethylene outer layer and a polyethylene inner layer formed therein within the polyethylene outer layer, wherein the polyethylene inner layer is crosslinkable polyethylene, and the polyethylene outer layer is obtained by rotational molding of the aforementioned polyethylene composition.

[0042] The polyethylene composite material of the present invention has long-term resistance to ultraviolet aging and excellent mechanical properties: room temperature drop impact strength ≥24.5 J / mm, drop impact strength after 100kw ultraviolet irradiation ≥21.6 J / mm, and performance retention rate ≥88%.

[0043] In some embodiments of the present invention, the thickness ratio of the outer polyethylene layer to the inner polyethylene layer can be (0.35-1.0):1. By controlling the thickness ratio of the outer polyethylene layer to the inner polyethylene layer within a certain range, the polyethylene composite material possesses both good anti-aging properties and impact resistance.

[0044] The thickness of the polyethylene composite material can be 4-12 mm.

[0045] A fourth aspect of the present invention provides a method for preparing a polyethylene composite material, the method comprising: The above-mentioned polyethylene composition is added to a rotational molding mold for a first rotational molding process to obtain a polyethylene outer layer; After the polyethylene outer layer has cooled and solidified, cross-linkable polyethylene is added to the rotational molding mold for a second rotational molding process, so as to form a polyethylene inner layer on the inner surface of the polyethylene outer layer.

[0046] In the above method, the present invention first performs rotational molding of a polyethylene composition to form a polyethylene outer layer, and then introduces a crosslinkable polyethylene composition for a second rotational molding to form a polyethylene inner layer. This step-by-step molding avoids the hindered amine light stabilizer from capturing free radicals in the crosslinkable polyethylene composition, thus preventing interference with its crosslinking process. The fully crosslinked inner layer, however, possesses excellent mechanical properties. The polyethylene outer layer can reduce the impact of ultraviolet light on the product through light shielding, ultraviolet absorption, and free radical capture, thereby ensuring that the polyethylene composite material has good UV aging resistance.

[0047] In some embodiments of the present invention, the weight ratio of the polyethylene composition to the crosslinkable polyethylene is (0.35-1):1. By adjusting the thickness ratio of the inner and outer layers, the product exhibits long-term resistance to ultraviolet aging and excellent mechanical properties.

[0048] In some embodiments of the present invention, the conditions for the first rotational molding include: a molding temperature of 240-280 °C and a molding time of 8-15 min.

[0049] In some embodiments of the present invention, the conditions for the second rotational molding include: a molding temperature of 270-290 °C and a molding time of 25-35 min.

[0050] In some embodiments of the present invention, the melt flow index of the crosslinkable polyethylene matrix material at 190°C / 2.16 kg is 4-15 g / min; the density of the crosslinkable polyethylene is 0.93-0.95 g / cm³. 3 The degree of crosslinking of the crosslinkable polyethylene is 60-80%.

[0051] By using cross-linkable polyethylene to form the inner layer of polyethylene, the polyethylene transforms from a linear structure to a network structure after cross-linking, which can absorb and disperse the energy of external impacts and exhibit higher impact resistance.

[0052] The present invention will be further described in detail below through embodiments, but the invention is not limited thereto. All raw materials used in the embodiments are commercially available.

[0053] Among them, metallocene linear low-density polyethylene is 5220G; Metallocene medium-density polyethylene is R335HL; The ultraviolet absorber is benzotriazole absorber UVA-326; The light-shielding agent is titanium dioxide with a particle size of 10,000 mesh; The lubricant is polyethylene wax, brand name AC316; The antioxidants include Irganox 1010 and Irgafos 168 in a weight ratio of 1:1. The crosslinkable polyethylene composition is a commercially available product, brand name SLHI1006; The hindered amine light stabilizer is a commercially available product, brand name UV 944.

[0054] The modified light stabilizers in the following examples and comparative examples were prepared by a method including the following steps: (1) Ca(NO3)2·4H2O and Al(NO3)3·9H2O were mixed in a molar ratio of (4-1):1 and dissolved in an appropriate amount of water-alcohol solution to obtain Al 3+ Solution I with a concentration of 0.2-0.6 mol / L; (2) The hindered amine light stabilizer and NaOH were mixed and dissolved in an aqueous alcohol solution at a molar ratio of 1:(1-3) to obtain solution II with an anion concentration of 0.4-1 mol / L of hindered amine light stabilizer; (3) Under nitrogen protection, solution II was added dropwise to solution I, and the pH of the resulting mixed solution was controlled at 8-12 during the dropwise addition. The mixture was magnetically stirred at room temperature for 24 h, and the stirring speed was controlled at 500-1000 rpm. After the reaction was completed, the product was centrifuged and washed, and then freeze-dried for 24 h to obtain the modified light stabilizer.

[0055] The calcium-aluminum base layer composite metal hydroxides (LDHs) have a particle size of 10-100 nm; the content of hindered amine light stabilizers in the obtained hindered amine intercalated LDHs is 50-70 wt%.

[0056] Example 1 This embodiment illustrates the preparation method of the polyethylene composition of the present invention, including the following steps: S1. Weigh each component of the polyethylene composition and add it to a high-speed mixer until it is mixed evenly. The evenly mixed material is then melt-blended and granulated using a low-shear twin-screw extruder to prepare a light-resistant polyethylene composition. The twin-screw extruder has a screw length-to-diameter ratio of 26 / 1, a screw speed of 100 rpm, and an extrusion blending temperature of 170°C. The polyethylene composition comprises, by weight, 80 parts of metallocene medium-density polyethylene, 20 parts of metallocene low-density polyethylene, 1.5 parts of modified light stabilizer (60% of which is hindered amine light stabilizer), 0.4 parts of ultraviolet absorber, 0.2 parts of light shielding agent, 0.5 parts of lubricant, and 0.2 parts of antioxidant. S2. Grind the obtained light-resistant polyethylene composition into powder of about 30 mesh using a grinding mill.

[0057] Example 2 The method for preparing the polyethylene composition in this embodiment is basically similar to that in Example 1, except that: In step S1, the ethylene composition comprises, by weight parts: 80 parts by weight of metallocene medium-density polyethylene, 20 parts by weight of metallocene low-density polyethylene, 1 part by weight of modified light stabilizer, 0.4 parts by weight of ultraviolet absorber, 0.2 parts by weight of light shielding agent, 0.5 parts by weight of lubricant and 0.2 parts by weight of antioxidant.

[0058] Example 3 The method for preparing the polyethylene composition in this embodiment is basically similar to that in Example 1, except that: In step S1, the ethylene composition comprises, by weight parts: 80 parts by weight of metallocene medium-density polyethylene, 20 parts by weight of metallocene low-density polyethylene, 2 parts by weight of modified light stabilizer, 0.4 parts by weight of ultraviolet absorber, 0.2 parts by weight of light shielding agent, 0.5 parts by weight of lubricant and 0.2 parts by weight of antioxidant.

[0059] Example 4 The method for preparing the polyethylene composition in this embodiment is basically similar to that in Example 1, except that: In step S1, the ethylene composition comprises, by weight parts: 80 parts by weight of metallocene medium-density polyethylene, 20 parts by weight of metallocene low-density polyethylene, 3 parts by weight of modified light stabilizer, 0.4 parts by weight of ultraviolet absorber, 0.4 parts by weight of light shielding agent, 0.5 parts by weight of lubricant and 0.2 parts by weight of antioxidant.

[0060] Example 5 The method for preparing the polyethylene composition in this embodiment is basically similar to that in Example 1, except that: In step S1, the ethylene composition comprises, by weight parts: 80 parts by weight of metallocene medium-density polyethylene, 20 parts by weight of metallocene low-density polyethylene, 4.5 parts by weight of modified light stabilizer, 0.6 parts by weight of ultraviolet absorber, 0.6 parts by weight of light shielding agent, 0.5 parts by weight of lubricant and 0.2 parts by weight of antioxidant.

[0061] Comparative Example 1 The method for preparing the polyethylene composition in this comparative example is basically similar to that in Example 1, except that: In step S1, the ethylene composition comprises, by weight parts: 80 parts by weight of metallocene medium-density polyethylene, 20 parts by weight of metallocene low-density polyethylene, 0.4 parts by weight of ultraviolet absorber, 0.2 parts by weight of light shielding agent, 0.5 parts by weight of lubricant and 0.2 parts by weight of antioxidant.

[0062] Comparative Example 2 The method for preparing the polyethylene composition in this comparative example is basically similar to that in Example 1, except that: In step S1, the ethylene composition comprises, by weight parts: 80 parts by weight of metallocene medium-density polyethylene, 20 parts by weight of metallocene low-density polyethylene, 1.5 parts by weight of modified light stabilizer, 0.4 parts by weight of ultraviolet absorber, 0.5 parts by weight of lubricant and 0.2 parts by weight of antioxidant.

[0063] Comparative Example 3 The method for preparing the polyethylene composition in this comparative example is basically similar to that in Example 1, except that: In step S1, the ethylene composition comprises, by weight parts: 80 parts by weight of metallocene medium-density polyethylene, 20 parts by weight of metallocene low-density polyethylene, 1.5 parts by weight of modified light stabilizer, 0.4 parts by weight of ultraviolet absorber, 0.8 parts by weight of light shielding agent, 0.5 parts by weight of lubricant and 0.2 parts by weight of antioxidant.

[0064] Comparative Example 4 The method for preparing the polyethylene composition in this comparative example is basically similar to that in Example 1, except that: In step S1, the ethylene composition comprises, by weight parts: 80 parts of metallocene medium-density polyethylene, 20 parts of metallocene low-density polyethylene, 0.4 parts of hindered amine light stabilizer, 0.4 parts of ultraviolet absorber, 0.8 parts of light shielding agent, 0.5 parts of lubricant, and 0.2 parts of antioxidant.

[0065] Comparative Example 5 The method for preparing the polyethylene composition in this comparative example is basically similar to that in Example 1, except that: In step S1, the ethylene composition comprises, by weight parts: 80 parts by weight of metallocene medium-density polyethylene, 20 parts by weight of metallocene low-density polyethylene, 2.5 parts by weight of modified light stabilizer, 0.4 parts by weight of ultraviolet absorber, 0.2 parts by weight of light shielding agent, 0.5 parts by weight of lubricant and 0.2 parts by weight of antioxidant.

[0066] The polyethylene composition powders obtained in Examples 1-5 and Comparative Examples 1-5 were used to prepare test samples by molding. The results of notched impact strength, tensile elongation at break, tensile yield strength and UV aging resistance tests on the samples are shown in Table 1.

[0067] The notched impact strength of the cantilever beam was tested according to GB / T 1843-2008; the tensile elongation at break, tensile yield strength, elongation at break after irradiation, and tensile yield strength after irradiation were tested according to GB / T1040.2-2022.

[0068] Table 1

[0069] As can be seen from the data in the table above, the UV aging resistance of the polyethylene polymer provided by the present invention is significantly improved compared with the polyethylene composition in the comparative example.

[0070] In Comparative Example 1, the polyethylene composition does not contain a light stabilizer, and in Comparative Example 2, the polyethylene composition does not contain a light shielding agent. Neither of them can reflect ultraviolet light or remove active free radicals generated by ultraviolet light in a timely manner, resulting in performance degradation after long-term ultraviolet radiation and poor resistance to ultraviolet aging.

[0071] In Comparative Example 3, due to the excessively high content of light-shielding agent, the light-shielding agent material is prone to forming defects at the interface with polyethylene, resulting in low notched impact strength, low elongation at break, and poor mechanical properties of the polyethylene composition.

[0072] Comparative Example 4, due to the use of ordinary light stabilizers, could not reflect ultraviolet light or remove active free radicals generated by ultraviolet light in time, resulting in performance degradation after long-term ultraviolet radiation and poor resistance to ultraviolet aging.

[0073] Example 6 This embodiment illustrates the preparation method of the polyethylene composite material of the present invention, including the following steps: Weigh 2 kg of the polyethylene composition obtained in Example 1 and add it to a rotational molding mold. Heat at 280 °C for 8 minutes to perform the first rotational molding to obtain the polyethylene outer layer. Add 2 kg of crosslinkable polyethylene composition to the feed port of the rotational molding die, continue heating at 280 °C for 25 minutes to perform a second rotational molding, and then cool for 25 minutes to obtain the rotational molded product.

[0074] In the rotational molding product, the thickness of the inner polyethylene layer is 2 mm, and the thickness of the outer polyethylene layer is 2 mm.

[0075] Example 7 The method for preparing the polyethylene composite material in this embodiment is basically similar to that in Example 6, except that: The conditions for the first rotational molding process include: a temperature of 280 ℃ and a time of 11 minutes; The conditions for the second rotational molding process include: a temperature of 280 ℃ and a time of 28 minutes; The amount of polyethylene composition used is 3 kg, and the amount of crosslinkable polyethylene composition used is 4 kg.

[0076] The thickness of the inner polyethylene layer in the obtained rotational molding product is 4 mm, and the thickness of the outer polyethylene layer is 3 mm.

[0077] Example 8 The method for preparing the polyethylene composite material in this embodiment is basically similar to that in Example 6, except that: The conditions for the first rotational molding process include: a temperature of 280 ℃ and a time of 11 minutes; The conditions for the second rotational molding process include: a temperature of 280 ℃ and a time of 32 minutes; The amount of polyethylene composition used is 3 kg, and the amount of crosslinkable polyethylene composition used is 8 kg.

[0078] The thickness of the inner polyethylene layer in the obtained rotational molding product is 8 mm, and the thickness of the outer polyethylene layer is 3 mm.

[0079] Example 9 The method for preparing the polyethylene composite material in this embodiment is basically similar to that in Example 6, except that: The conditions for the first rotational molding process include: a temperature of 280 ℃ and a time of 15 minutes; The conditions for the second rotational molding process include: a temperature of 280 ℃ and a time of 35 minutes; The amount of polyethylene composition used is 4 kg, and the amount of crosslinkable polyethylene composition used is 8 kg.

[0080] The thickness of the inner polyethylene layer in the obtained rotational molding product is 8 mm, and the thickness of the outer polyethylene layer is 4 mm.

[0081] Example 10 The method for preparing the polyethylene composite material in this embodiment is basically similar to that in Example 6, except that: The material used to prepare the polyethylene outer layer is the polyethylene composition prepared in Example 2.

[0082] Example 11 The method for preparing the polyethylene composite material in this embodiment is basically similar to that in Example 6, except that: The material used to prepare the polyethylene outer layer is the polyethylene composition prepared in Example 3.

[0083] Example 12 The method for preparing the polyethylene composite material in this embodiment is basically similar to that in Example 6, except that: The material used to prepare the polyethylene outer layer is the polyethylene composition prepared in Example 4.

[0084] Example 13 The method for preparing the polyethylene composite material in this embodiment is basically similar to that in Example 6, except that: The material used to prepare the polyethylene outer layer is the polyethylene composition prepared in Example 5.

[0085] Comparative Example 6 The method for preparing polyethylene material in this comparative example is the same as in Example 6, except that: The material used for the second rotational molding was the polyethylene composition prepared in Example 1.

[0086] Comparative Example 7 The method for preparing polyethylene material in this comparative example is the same as in Example 6, except that: The material used for the second rotational molding was metallocene medium-density polyethylene R335HL powder (30 mesh).

[0087] Comparative Example 8 The method for preparing polyethylene material in this comparative example is the same as in Example 6, except that: The material used for the first rotational molding is a cross-linkable polyethylene composition.

[0088] Comparative Example 9 The method for preparing polyethylene material in this comparative example is the same as in Example 6, except that: When performing the first rotational molding, the amount of the polyethylene composition obtained in Example 1 was 1 kg; When performing the second rotational molding, the amount of crosslinkable polyethylene composition used is 3 kg.

[0089] The thickness of the inner polyethylene layer in the obtained rotational molding product is 3 mm, and the thickness of the outer polyethylene layer is 1 mm.

[0090] The inner layer crosslinking degree, drop hammer impact strength and UV aging resistance of the rotational molded products prepared in Examples 6-13 and Comparative Examples 6-9 were tested respectively. The results are shown in Table 2.

[0091] The degree of cross-linking of the inner layer was tested in accordance with GB / T 18474-2001; the drop hammer impact strength and the post-irradiation impact strength were tested in accordance with GB / T39933-2021.

[0092] Table 4

[0093] As can be seen from the results in the table above, compared with comparative examples 6-9, the polyethylene composite material of the present invention can simultaneously possess better mechanical and UV aging resistance properties.

[0094] In Comparative Example 6, because both the inner and outer layers use an aging-resistant polyethylene composition, a cross-linked network cannot be formed to absorb impact energy. Therefore, the resulting product is easily damaged by external impacts, exhibiting low drop-weight impact strength and poor impact resistance. In Comparative Example 7, because the inner layer uses a common polyethylene composition, a cross-linked network cannot be formed to absorb impact energy. Consequently, the resulting product is easily damaged by external impacts, exhibiting low drop-weight impact strength and poor performance. In Comparative Example 8, because the outer layer uses a cross-linkable polyethylene composition, it cannot resist material degradation caused by ultraviolet light aging. The resulting product exhibits low drop-weight impact strength after ultraviolet irradiation and poor anti-aging performance. In Comparative Example 9, because the outer light-aging-resistant polyethylene layer is thin, it cannot completely protect the inner layer from ultraviolet light, resulting in low drop-weight impact strength and decreased anti-aging performance after ultraviolet irradiation.

[0095] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0096] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0097] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A polyethylene composition, characterized in that, The polyethylene composition comprises polyethylene and a light stabilizer composition, an antioxidant, and a lubricant; the light stabilizer composition comprises a light shielding agent, an ultraviolet absorber, and a modified light stabilizer. The modified light stabilizer includes hindered amine light stabilizer intercalated LDH; The weight ratio of the polyethylene to the light stabilizer composition is 100:(1.5-6.5). The weight ratio of the light shielding agent, the ultraviolet absorber, and the modified light stabilizer is 1:(1-4):(5-10).

2. The polyethylene composition according to claim 1, wherein, in, The light-shielding agent is selected from one or more of carbon black, silicon dioxide, titanium dioxide, and zinc oxide; The ultraviolet absorber is selected from benzotriazole absorbers.

3. The polyethylene composition according to claim 1 or 2, wherein, The modified light stabilizer contains 50-70 wt% hindered amine light stabilizers. The hindered amine light stabilizer is selected from one or more of the light stabilizers UV 944, UV 770, UV 4050 and UV 3853; Optionally, the modified light stabilizer is prepared by a method comprising the following steps: Intercalation of hindered amine light stabilizers into layered composite metal hydroxides; The metal ions in the layered composite metal hydroxide include Ca. 2+ And Al 3+ .

4. The polyethylene composition according to claim 1, wherein, The polyethylene includes metallocene linear low-density polyethylene and metallocene medium-density polyethylene; the weight ratio of the metallocene linear low-density polyethylene to the metallocene medium-density polyethylene is 1:(3-5). The metallocene linear low-density polyethylene described herein has a melt index of 3.5-4.5 g / min and a density of 0.915-0.92 g / cm³ at 190 ℃ / 2.16 kg. 3 ; The metallocene medium-density polyethylene has a melt index of 3.5-5 g / min and a density of 0.925-0.938 g / cm³ at 190 ℃ / 2.16 kg. 3 .

5. The polyethylene composition according to claim 1, wherein, The weight ratio of the polyethylene, lubricant, and antioxidant is 100:(0.5-2):(0.1-1.0). The lubricant is selected from one or more of polyethylene wax, stearic acid, zinc stearate, and calcium stearate; and / or, The antioxidant is a composition comprising a primary antioxidant and a secondary antioxidant; the weight ratio of the primary antioxidant to the secondary antioxidant is 1:(0.5-1). The primary antioxidant is selected from one or more of antioxidant 1010 and antioxidant 1330; the secondary antioxidant is selected from one or more of antioxidant 168 and antioxidant DSTP.

6. A method for preparing a polyethylene composition, characterized in that, The method includes: Mix the polyethylene composition according to any one of claims 1-5, and then melt-blend and granulate the mixed material to obtain the polyethylene composition. Optionally, the temperature of the melt blending granulation is 150-190 °C.

7. A polyethylene composite material, characterized in that, The polyethylene composite material includes a polyethylene outer layer and a polyethylene inner layer formed inside the polyethylene outer layer, wherein the polyethylene inner layer is crosslinkable polyethylene, and the polyethylene outer layer is obtained by rotational molding of a polyethylene composition according to any one of claims 1-5 or a polyethylene composition prepared by the method of claim 6.

8. The polyethylene composite material according to claim 7, wherein, The ratio of the thickness of the outer polyethylene layer to the thickness of the inner polyethylene layer is (0.35-1.0):1; Preferably, the thickness of the polyethylene composite material is 4-12 mm.

9. A method for preparing polyethylene composite materials, characterized in that, The method includes: The polyethylene composition according to any one of claims 1-5 or the polyethylene composition prepared by the method according to claim 6 is added to a rotational molding mold for a first rotational molding process to obtain a polyethylene outer layer. After the polyethylene outer layer has cooled and solidified, cross-linkable polyethylene is added to the rotational molding mold for a second rotational molding process, so as to form a polyethylene inner layer on the inner surface of the polyethylene outer layer.

10. The method according to claim 9, wherein, The weight ratio of the polyethylene composition to the crosslinkable polyethylene is (0.35-1):1; The conditions for the first rotational molding include: molding temperature of 240-280 ℃ and molding time of 8-15 min; The conditions for the second rotational molding include: a molding temperature of 270-290 ℃ and a molding time of 25-35 min; Optionally, the melt index of the crosslinkable polyethylene matrix material at 190 °C / 2.16 kg is 4-15 g / min; the density of the crosslinkable polyethylene is 0.93-0.95 g / cm³. 3 ; Optionally, the degree of crosslinking of the crosslinkable polyethylene is 60-80%.

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