A weather-resistant polyethylene composition for mulch film, its preparation method and application

Abstract

This invention discloses a polyethylene composition for weather-resistant mulch film, its preparation method, and its application. The polyethylene composition contains polyethylene, an antioxidant, a light stabilizer, a composite additive, and calcium carbonate. The composite additive is formed by loading a polyethylene nucleating agent onto the surface of spherical or near-spherical cross-linked rubber particles. The polyethylene is selected from linear low-density polyethylene. Based on mass parts, relative to 1000 parts of polyethylene, the content of the composite additive in the polyethylene composition is 0.5-3 parts, the content of calcium carbonate is 5-20 parts, and the content of the light stabilizer is 0.5-5 parts. Using the polyethylene composition of this invention provides stability in the LLDPE blown film process, results in neater winding, and eliminates the "knife sticking" problem.

Description

Technical Field

[0001] This invention relates to a special material for polyolefins, and more specifically to a polyethylene composition for weather-resistant mulch film, its preparation method, and its application. Background Technology

[0002] The widespread application of polyethylene blown agricultural ground cover film (hereinafter referred to as mulch film) has made significant contributions to increasing agricultural production and farmers' income due to its functions such as moisture retention, temperature increase, and water conservation, and has become an indispensable means of agricultural production. However, due to recycling issues, residual film accumulates over time, seriously affecting the sustainable development of agriculture.

[0003] Data from the National Bureau of Statistics shows that in 2015, my country's plastic film mulching area reached 275 million mu (approximately 18.3 million hectares), with a usage of 1.455 million tons. It is predicted that by 2024, my country's plastic film mulching area will reach 330 million mu (approximately 22.7 million hectares), with usage exceeding 2 million tons. Such large-scale use of plastic film has both advantages and disadvantages. On the one hand, it has played a significant role in improving agricultural quality and efficiency; on the other hand, it has caused serious damage to the soil environment, transforming the "white revolution" into "white pollution." Discarded plastic film fragments enter the soil, affecting permeability, reducing water content, weakening drought resistance, causing secondary salinization, resulting in soil compaction and decreased fertility, hindering crop water absorption and root growth, and gradually deteriorating the quality of arable land, causing serious damage to the agricultural ecological environment. Residual film discarded in fields and along roadsides is blown by the wind to areas around houses, treetops, rivers, and ponds, impacting the environment and causing "white pollution." While keeping the thickness of the mulch film basically unchanged, improving the weather resistance and mechanical properties of the mulch film, especially the longitudinal / transverse tensile load, nominal strain at break and right-angle tear load, is the key to improving the recycling rate of waste mulch film.

[0004] LLDPE has a lower melt strength than LDPE and a higher viscosity than HDPE, which poses significant challenges to film blow molding processes, especially when producing films with high blow-up ratios (>2.5), often resulting in production disruptions due to poor bubble stability. While blending with LDPE can solve the blown film production process problems, it reduces the film's mechanical strength. Furthermore, weather-resistant additives in recyclable mulch films often reduce some of the film's mechanical properties, further posing challenges to the development of resin raw material technology for mulch films.

[0005] Therefore, how to solve the problems of unstable film bubbles and uneven winding in the blown film process, as well as the "sticking to the knife" phenomenon, while maintaining or not reducing the mechanical strength of the film, are the technical problems that need to be solved. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention develops a special LLDPE weather-resistant mulch film material using LLDPE as the base resin and adding antioxidants, light stabilizers, composite additives, calcium carbonate particles, and other additives. While the composite additives can improve issues like unstable film bubbles and uneven winding in the blown film process, they require reduced production load and still occasionally cause "knife sticking," resulting in discontinuous production. Extensive experimental research revealed that, surprisingly, the addition of calcium carbonate, especially when the polyethylene composition contains antioxidants, light stabilizers, composite additives, and calcium carbonate, even at high blow-up ratios (>2.5), ensures a stable LLDPE blown film process: stable film bubbles and neat winding. More significantly, the addition of calcium carbonate maintains a production capacity similar to that of the compounded raw materials, thus guaranteeing production efficiency. Based on the above, the LLDPE mulch film of the present invention has high tensile load, nominal strain at break and right angle tear load, and maintains high physical and mechanical properties after artificial climate aging or actual use, effectively ensuring the mechanical properties during mulch film recycling. It can be widely used for mechanical recycling of mulch film and improve the mulch film recycling rate.

[0007] The first aspect of the present invention is to provide a polyethylene composition comprising polyethylene, an antioxidant, a light stabilizer, a composite additive, and calcium carbonate; wherein the composite additive is a composite additive formed by loading a polyethylene nucleating agent onto the surface of spherical or nearly spherical cross-linked rubber particles, and the polyethylene is selected from linear low-density polyethylene; based on parts by weight, relative to 1000 parts of polyethylene, the content of the composite additive in the polyethylene composition is 0.5-3 parts, the content of calcium carbonate is 5-20 parts, and the content of the light stabilizer is 0.5-5 parts.

[0008] As mentioned above, based on extensive experimental research, the inventors have discovered that the addition of calcium carbonate, particularly antioxidants, light stabilizers, composite additives, and calcium carbonate in the polyethylene composition significantly improves the stability of the LLDPE film production process, while only slightly reducing the film's physical and mechanical properties. This solves the problem of unstable blown film production of LLDPE resin and further addresses processing issues such as unstable film bubbles and uneven winding when using LLDPE mulch film materials to blow-dry mulch films with high blow-up ratios (>2.5). More significantly, it increases output without affecting production load, thus simplifying mulch film production, increasing efficiency, and lowering costs.

[0009] In a preferred embodiment of the present invention, the calcium carbonate is derived from at least one of the following calcium carbonates and / or at least one of the following calcium carbonates combined with polyethylene masterbatch: ordinary calcium carbonate, activated calcium carbonate.

[0010] In a preferred embodiment of the present invention, the calcium carbonate has a mesh size of 800-4000, preferably 1000-3000.

[0011] In this invention, the preferred amount of calcium carbonate added, based on parts by weight, is 5-20 parts per 1000 parts of polyethylene, more preferably 5-15 parts per 1000 parts of polyethylene. In polyolefin modification technology, calcium carbonate is generally used as a filler, and its addition amount is relatively high to reduce resin costs. Surprisingly, adding a small amount of calcium carbonate particles to LLDPE raw materials can significantly improve the processing stability of blown films, and only slightly reduce the mechanical properties of the film, effectively ensuring the continuity of film production. This solves the problem of difficult blown film processing caused by the high viscosity and low melt strength of LLDPE itself.

[0012] According to the present invention, the polyethylene nucleating agent can be selected from a wide range. In a preferred embodiment of the present invention, the polyethylene nucleating agent is selected from at least one of organic nucleating agents and inorganic nucleating agents, preferably at least one of organic carboxylic acid nucleating agents, organic carboxylate nucleating agents, and organic phosphate nucleating agents, and more preferably at least one of nucleating agent NA11, nucleating agent NA21, and nucleating agent 20E.

[0013] According to the present invention, the crosslinked rubber particles can be selected from a wide range. In a preferred embodiment of the present invention, the crosslinked rubber particles are at least one of the following crosslinked rubber particles:

[0014] At least one of crosslinked ethylene-vinyl acetate, crosslinked styrene-butadiene rubber, crosslinked carboxylated styrene-butadiene rubber, crosslinked acrylonitrile rubber, crosslinked carboxylated acrylonitrile rubber, crosslinked acrylate rubber, and crosslinked acrylate-butadiene rubber; preferably at least one of crosslinked ethylene-vinyl acetate, crosslinked styrene-butadiene rubber, crosslinked carboxylated styrene-butadiene rubber, and crosslinked acrylonitrile rubber; more preferably at least one of crosslinked ethylene-vinyl acetate and crosslinked styrene-butadiene rubber particles.

[0015] In a preferred embodiment of the present invention, the content of cross-linked rubber particles in the composite additive is 10-80 wt%, preferably 20-50 wt%.

[0016] The cross-linked rubber particles of this invention can be prepared using the method described in patent CN1402752. This involves adding a cross-linking agent such as TMPTA to a rubber latex containing uncross-linked rubber particles with a particle size of 20-2000 nm, irradiating it with a high-energy ray source, and then spray-drying it. The resulting cross-linked rubber particles are easily dispersed and can act as carriers, assisting in the more uniform dispersion of nucleating agents and light stabilizers into the matrix resin, significantly improving the overall mechanical properties of the resin composition and meeting application requirements.

[0017] In this invention, the nucleating agent and the rubber particles with cross-linked structures can be added to the resin composition as separate raw materials, or commercially available products containing both can be used.

[0018] In a more preferred embodiment of the present invention, the composite additive is selected from at least one of VP101B, VP101C, and VP801E.

[0019] According to the present invention, the light stabilizer can be selected from a wide range. In a preferred embodiment of the present invention, the light stabilizer is one or more of hindered amine light stabilizers and ultraviolet absorbers; preferably:

[0020] The hindered amine light stabilizer is selected from at least one of light stabilizer 770, light stabilizer 944, light stabilizer 622, and light stabilizer 3346; and / or,

[0021] The ultraviolet absorber is selected from at least one of UV-0, UV-9, UV-531, UV-P, UV-234, UV-326, and UV-327 ultraviolet absorbers.

[0022] In this invention, the light stabilizer models are as follows: bis(2,2,6,6-tetramethylpiperidinol) sebacic acid (hindered amine light stabilizer 770); poly{[6-[(1,1,3,3-tetramethylbutyl)amino]]-1,3,5-triazine-2,4-bis[(2,2,6,6,-tetramethyl-piperidinyl)imino]-1,6-hexanediamine[(2,2,6,6-tetramethyl-4-piperidinyl)imino] [Amino]} (hindered amine light stabilizer 944); Poly(4-hydroxy-2,2,6,6-tetramethyl-1-piperidinol) ester (hindered amine light stabilizer 622); Poly{(6-morpholino-5-triazine-2,4-diyl)(2,2,6,6-tetramethylpiperidinyl)imino-hexamethylene[(2,2,6,6-tetramethylpiperidinyl)-imino]} (hindered amine light stabilizer 3346).

[0023] In this invention, the ultraviolet absorber models are as follows: 2,4-dihydroxybenzophenone (UV absorber UV-0); 2-hydroxy-4-methoxybenzophenone (UV absorber UV-9); 2-hydroxy-4-n-octyloxybenzophenone (UV absorber UV-531); 2-(2'-hydroxy-5'-methylphenyl)benzotriazole (UV absorber UV-P); 2-(2-hydroxy-3,5-bis(a,a-dimethylbenzyl)phenyl)benzotriazole (UV absorber UV-234); 2-(2-hydroxy-3-tert-butyl-5-methylphenyl)-5-chlorobenzotriazole (UV absorber UV-326); 2-(2'-hydroxy-3',5'-di-tert-phenyl)-5-chlorobenzotriazole (UV absorber UVP-327).

[0024] In a preferred embodiment of the present invention, the linear low-density polyethylene is a copolymer of ethylene and α-olefin, preferably the α-olefin being at least one selected from butene-1, hexene-1, and octene-1. In a more preferred embodiment of the present invention, the melt mass flow rate of the linear low-density polyethylene at a temperature of 190±5℃ and a load of 2.16kg is less than 3g / 10min, preferably less than 2g / 10min.

[0025] According to the present invention, the antioxidant can be selected from a wide range. In a preferred embodiment of the present invention, the antioxidant includes a primary antioxidant and a secondary antioxidant. Preferably:

[0026] Based on parts by weight, relative to 1000 parts of polyethylene, the content of the primary antioxidant in the polyethylene composition is 0.3 to 3 parts, preferably 0.3 to 2 parts, more preferably 0.5 to 1 part; the content of the secondary antioxidant is 0.3 to 3 parts, preferably 0.3 to 2 parts; and / or,

[0027] The main antioxidants are hindered phenols, including pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (antioxidant 1010), octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (antioxidant 1076), 1,3,5-trimethyl-2,4,6-(3,5-di-tert-butyl-4-hydroxyphenylmethyl)benzene (antioxidant 1330), and 1,3,5-tris(3 At least one of the following: 5-di-tert-butyl-4-hydroxybenzyl)isocyanuric acid (antioxidant 3114), β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate isooctyl ester (antioxidant 1135), and 1,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)-1,3,5-triazine-2,4,6-(1H,3H,5H)-trione (antioxidant 1790); and / or,

[0028] Co-antioxidants include phosphites and thioesters, with phosphites being preferred, including at least one of the following: tris(nonylphenyl) phosphite (TNPP), tris(2,4-di-tert-butylphenyl) phosphite (antioxidant 168), bis(octadecyl) pentaerythritol diphosphite (antioxidant 618), pentaerythritol bis(2,4-tert-butylphenyl) diphosphite (antioxidant 626), bis(2,6-di-tert-butyl-4-tolyl) pentaerythritol phosphite (PEP-36), tetrakis(2,4-di-tert-butyloctaalkoxy-4,4'-biphenyl) phosphate, and 2,2-ethylidene bis(4,6-di-tert-butylphenyl) fluorophosphite (antioxidant 398).

[0029] According to the present invention, based on parts by weight, relative to 1000 parts of polyethylene, the content of the composite additive in the polyethylene composition is 0.5 to 3 parts, preferably 0.5 to 1.2 parts; and / or, the content of calcium carbonate is 5 to 20 parts, preferably 5 to 15 parts; and / or, the content of light stabilizer is 0.5 to 5 parts, preferably 1 to 3 parts.

[0030] The additives described in this invention may also include commonly used additives in plastic processing, such as antistatic agents, acid absorbers, and slip agents, the dosage of which is the conventional dosage or may be adjusted according to actual requirements.

[0031] A second aspect of the present invention is to provide a method for preparing the polyethylene composition described in the first aspect, comprising melt-blending raw materials including the polyethylene, the antioxidant, the light stabilizer, the composite additive, and the calcium carbonate to obtain the polyethylene composition; preferably, the method includes the following steps:

[0032] Step 1: Premix the raw materials including the polyethylene, the antioxidant, the light stabilizer, the composite additive, and the calcium carbonate; or, prepare an additive composition by preparing the additives including the antioxidant, the light stabilizer, the composite additive, and the calcium carbonate, and then premix the additive composition with the polyethylene.

[0033] Step 2: The premixed mixture obtained in Step 1 is melt-blended to obtain the polyethylene composition.

[0034] During the preparation process, the blending temperature of the materials corresponds to the typical processing temperature of the matrix resin, linear low-density polyethylene, and should be selected within a range that ensures complete melting of the matrix resin without causing its decomposition. Furthermore, appropriate amounts of conventional additives can be added to the blended materials according to processing requirements. During the blending process, the components can be simultaneously added to a melt blending device via metering or other methods for melt blending; alternatively, the components can be pre-mixed uniformly using general-purpose mixing equipment, and then melt-blended and extruded in a rubber-plastic blending device to obtain the modified resin composition.

[0035] The rubber-plastic blending equipment used in the preparation method of this invention can be an open mill, internal mixer, single-screw extruder, twin-screw extruder, or twin-rotor extruder, etc. The material mixing equipment is selected from commonly used mechanical mixing equipment in the art, such as high-speed mixers and kneaders.

[0036] A third aspect of the present invention is to provide a polyethylene film, wherein the polyethylene film is made of the polyethylene composition described in the first aspect or the polyethylene composition prepared by the preparation method described in the second aspect;

[0037] Preferably, the polyethylene film is obtained by blow molding, and more preferably, the blow-up ratio is >2.5.

[0038] A fourth aspect of the present invention is to provide a method for preparing a polyethylene film as described in the third aspect, comprising the step of blow molding a polyethylene composition as described in the first aspect or a polyethylene composition obtained by the preparation method as described in the second aspect, preferably with a blow-up ratio > 2.5.

[0039] The LLDPE weather-resistant mulch film material of this invention produces mulch films with high transverse / longitudinal tensile load, nominal strain at break, and right-angle tear load. Even with a large blow-out ratio (>2.5), the blown film process remains stable, the film bubble is stable, and the winding is neat. The mulch film produced by this weather-resistant mulch film material has good weather resistance, and after mulching, its mechanical properties are well retained, meeting the requirements for mulch film recycling and reuse. This solves the problem of white pollution caused by mulch film and enables the reuse of recycled mulch film. Significantly, this weather-resistant mulch film material avoids the need for downstream customers to compound it with other additives and resins to meet the mechanical properties and processing stability requirements of mulch film, thereby simplifying the production process and improving product stability.

[0040] The fifth aspect of the present invention is to provide the application of the polyethylene composition described in the first aspect or the polyethylene composition prepared by the preparation method described in the second aspect, or the polyethylene film described in the third aspect or the polyethylene film prepared by the preparation method described in the fourth aspect, in mulch film.

[0041] The advantage of this invention is that,

[0042] By specifically proportioning LLDPE, antioxidants, light stabilizers, composite additives, and calcium carbonate in the polyethylene composition, processing problems such as unstable film bubbles, high knife sticking frequency, and uneven winding during the blowing of high blow-up ratio (>2.5) mulch films using LLDPE mulch film materials can be solved. Mulch films produced using this material have higher tensile load, nominal strain at break, and right-angle tear load. Their physical and mechanical properties remain high even after artificial climate aging or actual use, effectively ensuring the mechanical properties during mulch film recycling. This allows for widespread use in the mechanical recycling of mulch films, improving the recycling rate and maintaining the strength and aging performance of approximately 10-micron thick mulch films. More importantly, compared to compounded materials, this mulch film-specific material can meet the stability requirements of the blown film process without reducing production output, resulting in more uniform winding, avoiding "knife sticking," and ensuring stable production. Attached Figure Description

[0043] Figure 1 These are isothermal crystallization diagrams of the resins from Comparative Example 1, Comparative Example 2, and Example 3 at 110°C.

[0044] Figure 2These are two-dimensional WAXD images of Comparative Example 1 and Example 3.

[0045] Figure 1 The figures show the isothermal DSC curves of the resins from Comparative Examples 1, 2, and 3 at 110°C. The test results indicate that the addition of the composite additive shifted the second exothermic peak on the DSC isothermal crystallization curve to the left, where it overlapped with the first exothermic peak to form a single exothermic peak. This indicates a significant increase in the crystallization rate of the special material. Further addition of a small amount of calcium carbonate particles resulted in a further significant leftward shift of the overlapping exothermic peak, indicating an even further increase in the crystallization rate.

[0046] Furthermore, after adding the composite additive, the second exothermic peak during isothermal crystallization shifted to the left and overlapped with the first exothermic peak, forming a single exothermic peak. Upon further addition of calcium carbonate, a second exothermic peak appeared, similar to the first, significantly shifted to the left and largely overlapping with it. This indicates a new nucleation process occurring during crystallization. Increased crystallization rate improves the mechanical properties of blown film bubbles, thereby enhancing bubble stability, while also reducing adhesion between films, significantly improving the stability of the blown film process. More significantly, the addition of a small amount of calcium carbonate prevents "knife sticking."

[0047] Figure 2 The two-dimensional WXRD spectra of the blown films from Comparative Example 1 and Example 3 are shown. The test results indicate that the molecules in both the transverse and longitudinal directions of the film are oriented, with a lower degree of orientation in the transverse direction than in the longitudinal direction. Significantly, the addition of calcium carbonate particles significantly improves both the transverse and longitudinal molecular orientations of the film, thus correspondingly increasing the mechanical strength of the film in both directions, which is more conducive to the stability of film processing. In summary, based on the raw materials of this invention, the addition of calcium carbonate particles further improves the crystallization rate and transverse / longitudinal molecular orientation, thereby maintaining the mechanical properties of the film, improving film stability, stabilizing production, and avoiding the "sticking" problem during production. Detailed Implementation

[0048] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0049] The present invention is further described below with reference to embodiments. The scope of the claims is not limited to these embodiments, but is set forth in the appended claims.

[0050] The experimental data in this embodiment were measured using the following instruments and methods:

[0051] The test specimens for tensile load and nominal strain at break were tested in accordance with the national standard GB / T1040.3-2006 and the local standard of Xinjiang Uygur Autonomous Region DB65 3189-2014. The specimens were type 2, with a width of 10 mm and an initial mark distance of 50 mm between the fixtures. The test speed (no load) was 500 mm / min. The specimens were stretched until they broke, and the maximum tensile load was measured to an accuracy of 0.01 N.

[0052] Right-angle tear load testing was conducted according to the national standard GB / T1130-1991 and the Xinjiang Uygur Autonomous Region local standard DB65 3189-2014. Single-piece specimens were used, with an initial mark distance of 55 mm between the fixtures, and a test speed (no load) of 200 mm / min. The arithmetic mean of the experimental results was taken.

[0053] Artificial climate aging tests were conducted in accordance with GB / T 9345.1-2008 and Xinjiang Uygur Autonomous Region local standard DB653189-2014. Specific ultraviolet aging conditions were as follows: Type II lamps (UV-A340) were used, with a wavelength of 340 nm and an irradiance of 0.76 W / m². 2 •nm, light temperature 60℃, radiation time 4h (bright); condensation temperature 50℃, condensation time 4h (dark), alternating cycles for 240 hours.

[0054] The melt flow index was measured at a temperature of 190±5℃ and a load of 2.16kg.

[0055] Bubble instability refers to the occurrence of at least one of the following phenomena within two hours during the production process: stretching resonance of the bubble, spiral instability, condensation line oscillation, bubble sagging, bubble tremor, and bubble contraction, which leads to production difficulties.

[0056] Uneven winding refers to a deviation of more than 30mm at the end face of the film roll or the occurrence of bursting veins in the film roll.

[0057] The "knife sticking" phenomenon refers to the phenomenon in film production where the film-breaking knife comes out from between the two layers of film to be broken. The frequency of "knife sticking" is calculated based on the number of times "knife sticking" occurs during an eight-hour continuous production process.

[0058] Melt blending and mulch film preparation

[0059] The initial mixing and melt blending process of the materials is as follows: First, all materials are weighed according to the proportion and initially mixed in a high-speed mixer for 20 seconds. Then, a twin-screw extruder (Coperon (Nanjing) Machinery Co., Ltd., length-to-diameter ratio 30:1, screw diameter 30 mm) is used for melt blending and granulation. The speed is 200 r / min, and the temperature is set to 170℃, 180℃, 190℃, 200℃, 200℃, and 200℃, with a feed rate of 14. The resulting granules are placed in a tray and treated in a 70℃ oven for 4 hours to remove moisture.

[0060] The mulch film was prepared using a single-layer blow molding method. The blow molding machine was a German company, Kölin. The temperature settings of the blow molding machine were: 160℃, 180℃, 200℃, 210℃, 210℃, 210℃, and 210℃ for each section. The blown film width was 31cm, the nominal thickness was 10µm, and the blow-up ratio was 2.9.

[0061] VP-801E refers to VP801E produced by Sinopec Beijing Research Institute of Chemical Industry. VP801E contains nucleating agent NA11 and EVA rubber particles with a cross-linked structure. The average particle size of the rubber particles is 0.2 micrometers, and the gel content of the rubber particles is 90 wt%. The mass ratio of the rubber particles to the nucleating agent is 3:7. The average particle size of VP-801E is 0.3 micrometers.

[0062] Example 1:

[0063] Weigh the LLDPE resin powder (Chemical Branch of Zhongtian Hechuang Energy Co., Ltd., melt index: 1.0 g / 10 min, density: 0.918 g / cm³). 3 2000.0g of antioxidant 1010 (Yingkou Fengguang New Materials Co., Ltd.), 1.0g of primary antioxidant 1010, 1.2g of secondary antioxidant 168 (Yingkou Fengguang New Materials Co., Ltd.), 6.0g of hindered amine light stabilizer 944 (Beijing Tiangang Additives Co., Ltd.), 1.0g of composite additive (Yanshan Petrochemical High-Tech Co., Ltd. VP-801E), and 10.0g of calcium carbonate (Lingshou County Guanghui Mineral Products Processing Co., Ltd., mesh size 2000) were dispersed evenly in a high-speed mixer, then melt-blended and granulated using a twin-screw extruder. The blown mulch film had a nominal thickness of 10 micrometers and a blow-up ratio of 2.9. The longitudinal / transverse tensile load, nominal strain at break, and right-angle tear load of the mulch film were tested before and after aging.

[0064] Example 2:

[0065] Weigh the LLDPE resin powder (Chemical Branch of Zhongtian Hechuang Energy Co., Ltd., melt index: 1.0 g / 10 min, density: 0.918 g / cm³). 32000.0g of antioxidant 1010 (Yingkou Fengguang New Materials Co., Ltd.), 1.0g of auxiliary antioxidant 168 (Yingkou Fengguang New Materials Co., Ltd.), 1.2g of hindered amine light stabilizer 944 (Beijing Tiangang Additives Co., Ltd.), 2.0g of composite additive (Yanshan Petrochemical High-Tech Co., Ltd. VP-801E), and 16.0g of calcium carbonate (Lingshou County Guanghui Mineral Products Processing Co., Ltd., mesh size 2000) were dispersed evenly in a high-speed mixer, then melt-blended and granulated using a twin-screw extruder. The blown mulch film had a nominal thickness of 10 micrometers and a blow-up ratio of 2.9. The longitudinal / transverse tensile load, nominal strain at break, and right-angle tear load of the mulch film were tested before and after aging.

[0066] Example 3:

[0067] Weigh the LLDPE resin powder (Chemical Branch of Zhongtian Hechuang Energy Co., Ltd., melt index: 1.0 g / 10 min, density: 0.918 g / cm³). 3 2000.0g of antioxidant 1010 (Yingkou Fengguang New Materials Co., Ltd.), 1.0g of primary antioxidant 1010 (Yingkou Fengguang New Materials Co., Ltd.), 1.2g of secondary antioxidant 168 (Yingkou Fengguang New Materials Co., Ltd.), 6.0g of hindered amine light stabilizer 944 (Beijing Tiangang Additives Co., Ltd.), 1.6g of composite additive (Yanshan Petrochemical High-Tech Co., Ltd. VP-801E), and 20.0g of calcium carbonate (Lingshou County Guanghui Mineral Products Processing Co., Ltd., mesh size 3000) were dispersed evenly in a high-speed mixer, then melt-blended and granulated using a twin-screw extruder. The blown mulch film had a nominal thickness of 10 micrometers and a blow-up ratio of 2.9. The longitudinal / transverse tensile load, nominal strain at break, and right-angle tear load of the mulch film were tested before and after aging.

[0068] Example 4:

[0069] Weigh the LLDPE resin powder (Chemical Branch of Zhongtian Hechuang Energy Co., Ltd., melt index: 1.0 g / 10 min, density: 0.918 g / cm³). 3 2000.0g of antioxidant 1010 (Yingkou Fengguang New Materials Co., Ltd.), 1.0g of primary antioxidant 1010 (Yingkou Fengguang New Materials Co., Ltd.), 1.2g of secondary antioxidant 168 (Yingkou Fengguang New Materials Co., Ltd.), 6.0g of hindered amine light stabilizer 622 (Beijing Tiangang Additives Co., Ltd.), 2.0g of composite additive (Yanshan Petrochemical High-Tech Co., Ltd. VP-801E), and 20g of calcium carbonate (Lingshou County Guanghui Mineral Products Processing Co., Ltd., mesh size 1000) were dispersed evenly in a high-speed mixer, then melt-blended and granulated using a twin-screw extruder. The blown mulch film had a nominal thickness of 10 micrometers and a blow-up ratio of 2.9. The longitudinal / transverse tensile load, nominal strain at break, and right-angle tear load of the mulch film were tested before and after aging.

[0070] Example 5:

[0071] Weigh the LLDPE resin powder (Chemical Branch of Zhongtian Hechuang Energy Co., Ltd., melt index: 1.0 g / 10 min, density: 0.918 g / cm³). 3 2000.0g of antioxidant 1010 (Yingkou Fengguang New Materials Co., Ltd.), 1.0g of primary antioxidant 1010 (Yingkou Fengguang New Materials Co., Ltd.), 1.2g of secondary antioxidant 168 (Yingkou Fengguang New Materials Co., Ltd.), 6.0g of synergistic compound light stabilizer HS-362 (Beijing Tiangang Additives Co., Ltd.), 2.0g of composite additive (Yanshan Petrochemical High-Tech Co., Ltd. VP-801E), and 20.0g of calcium carbonate masterbatch (Hangzhou Kaijie Plastics Technology Co., Ltd., CM-01, calcium carbonate mesh 1250) were dispersed evenly in a high-speed mixer, then melt-blended and granulated using a twin-screw extruder. The blown mulch film had a nominal thickness of 10 micrometers and a blow-up ratio of 2.9. The longitudinal / transverse tensile load, nominal strain at break, and right-angle tear load of the mulch film were tested before and after aging.

[0072] Comparative Example 1:

[0073] Weigh the LLDPE resin powder (Chemical Branch of Zhongtian Hechuang Energy Co., Ltd., melt index: 1.0 g / 10 min, density: 0.918 g / cm³). 3 2000.0g of antioxidant 1010 (Yingkou Fengguang New Materials Co., Ltd.), 1.0g of primary antioxidant 1010, 1.2g of secondary antioxidant 168 (Yingkou Fengguang New Materials Co., Ltd.), 6.0g of hindered amine light stabilizer 944 (Beijing Tiangang Additives Co., Ltd.), and 2.0g of composite additive (Yanshan Petrochemical High-Tech Co., Ltd. VP-801E) were dispersed evenly in a high-speed mixer, then melt-blended and granulated using a twin-screw extruder. The blown mulch film had a nominal thickness of 10 micrometers and a blow-up ratio of 2.9. The longitudinal / transverse tensile load, nominal strain at break, and right-angle tear load of the mulch film were tested before and after aging.

[0074] Comparative Example 2:

[0075] Weigh the LLDPE resin powder (Chemical Branch of Zhongtian Hechuang Energy Co., Ltd., melt index: 1.0 g / 10 min, density: 0.918 g / cm³). 3 2000.0 g of antioxidant 1010 (Yingkou Fengguang New Materials Co., Ltd.), 1.0 g of primary antioxidant 1010, 1.2 g of secondary antioxidant 168 (Yingkou Fengguang New Materials Co., Ltd.), and 6.0 g of hindered amine light stabilizer 944 (Beijing Tiangang Additives Co., Ltd.) were dispersed evenly in a high-speed mixer, then melt-blended and granulated using a twin-screw extruder. The blown mulch film had a nominal thickness of 10 micrometers and a blow-up ratio of 2.9. The longitudinal and transverse tensile loads, nominal strain at break, and right-angle tear load of the mulch film were tested before and after aging.

[0076] Comparative Example 3:

[0077] Weigh 2000.0 g of LLDPE resin powder (Chemical Branch of Zhongtian Hechuang Energy Co., Ltd., melt index: 1.0 g / 10 min, density: 0.918 g / cm3), 1.0 g of main antioxidant 1010 (Yingkou Fengguang New Materials Co., Ltd.), 1.2 g of auxiliary antioxidant 168 (Yingkou Fengguang New Materials Co., Ltd.), 6.0 g of synergistic compound light stabilizer HS-362 (Beijing Tiangang Additives Co., Ltd.), 10 g of composite additive (Yanshan Petrochemical High-Tech Co., Ltd. VP-801E), and 60 g of calcium carbonate masterbatch (Hangzhou Kaijie Plastics Technology Co., Ltd., CM-01, calcium carbonate mesh 1250). After being evenly dispersed in a high-speed mixer, the mixture is melt-blended and granulated by a twin-screw extruder.

[0078] Table 1. Physical and mechanical properties of the 10-micron thick mulch film prepared from special materials and the blown film process status.

[0079]

[0080] Table 2 Physical and mechanical properties of plastic film after artificial climate aging

[0081]

[0082] Comparative Example 1 contains only four components: the LLDPE matrix, antioxidant, light stabilizer, and composite additives of the present invention, without the addition of calcium carbonate.

[0083] Comparative Example 2 contains only three components: the LLDPE matrix, antioxidant, and light stabilizer of the present invention, without the addition of composite additives and calcium carbonate.

[0084] Examples 1-5 all contain an LLDPE resin matrix and an antioxidant; the types and contents of light stabilizers, calcium carbonate, and VP801E are varied.

[0085] As shown in Table 1, the examples with added VP801E and calcium carbonate components exhibited stable film bubbles, low frequency of blade sticking, and neater winding during processing.

[0086] As shown in Table 2, after aging, the longitudinal and transverse tensile loads of Examples 1-5 were significantly better than those of Comparative Example 2 without the addition of composite additives and calcium carbonate, demonstrating an excellent balance between mechanical properties and processing performance.

[0087] In Comparative Example 3, in addition to the matrix and antioxidant of this invention, a suitable light stabilizer and composite particles and calcium carbonate in amounts exceeding those of this invention were added. During the extrusion blow molding process, the product of this comparative example exhibited significantly reduced melt strength due to the excessive additives in the matrix. During unidirectional traction film formation, the film bubbles were highly unstable, resulting in too many film breakages and preventing normal blow molding of the film.

[0088] Comparative Example 1 contained only four components: the matrix of this invention, antioxidant, light stabilizer, and composite additives, without the addition of calcium carbonate. While the addition of calcium carbonate improves processing performance during ultrathin film processing, it can also create defects in the film, leading to a decrease in tensile load. Therefore, Tables 1 and 2 show that Comparative Example 1 exhibits relatively higher tensile load and nominal strain at break before and after aging, but the film bubble is unstable during processing, resulting in high frequency of blade sticking and uneven winding. Examples 1-5 all added composite additives and calcium carbonate. Although the tensile load was slightly lower than that of Comparative Example 1, their processing performance was superior, allowing for the successful preparation of weather-resistant mulch films without the addition of HDPE or LDPE.

[0089] Verification has shown that, using other linear low-density polyethylene raw materials, other light stabilizers, other composite additives, and other calcium carbonates as described in this invention, and modifying one or more of the above factors, the resulting embodiments, verified using the same method as in Example 1, all exhibited stable film bubbles, low knife sticking frequency, and neat winding during processing. The longitudinal and transverse tensile loads after aging were significantly better than those of the comparative example without the addition of composite additives and calcium carbonate under the same conditions, demonstrating an excellent balance between mechanical and processing properties.

[0090] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

[0091] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0092] When this specification uses the prefixes “known to those skilled in the art,” “prior art,” or similar terms to derive materials, substances, methods, steps, apparatus, or components, the objects derived from such prefixes cover those commonly used in the art at the time of this application, but also include those that are not currently commonly used but will become generally recognized in the art as suitable for similar purposes.

[0093] The endpoints and any values ​​of the ranges disclosed in this application are not limited to the precise ranges or values; such ranges or values ​​should be understood to include values ​​close to them. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In principle, various technical solutions can be combined with each other to obtain new technical solutions, which should also be considered as specifically disclosed herein.

[0094] In the context of this specification, except where expressly stated otherwise, any matters or issues not mentioned shall apply directly to those known in the art without any modification.

[0095] Furthermore, any implementation described herein can be freely combined with one or more other implementations described herein, and the resulting technical solutions or technical ideas shall be regarded as part of the original disclosure or original record of the present invention, and should not be regarded as new content not disclosed or anticipated herein, unless those skilled in the art consider the combination to be obviously unreasonable.

Claims

1. A polyethylene composition comprising polyethylene, an antioxidant, a light stabilizer, a compounding agent, and calcium carbonate; wherein, The composite additive is a composite additive formed by loading a polyethylene nucleating agent onto the surface of spherical or nearly spherical cross-linked rubber particles, wherein the polyethylene is selected from linear low-density polyethylene. Based on parts by weight, relative to 1000 parts of polyethylene, the polyethylene composition contains 0.5-3 parts of composite additives, 5-20 parts of calcium carbonate, and 0.5-5 parts of light stabilizer. The content of cross-linked rubber particles in the composite additive is 10-80 wt%.

2. The polyethylene composition according to claim 1, characterized in that: The calcium carbonate is derived from at least one of the following calcium carbonates and / or at least one of the following calcium carbonates in a composite masterbatch with polyethylene: ordinary calcium carbonate, activated calcium carbonate; and / or, The calcium carbonate has a mesh size of 800-4000.

3. The polyethylene composition according to claim 1, characterized in that: The calcium carbonate has a mesh size of 1000~3000.

4. The polyethylene composition according to claim 1, characterized in that: The polyethylene nucleating agent is selected from at least one of organic nucleating agents and inorganic nucleating agents; and / or, The crosslinked rubber particles are at least one of the following crosslinked rubber particles: crosslinked ethylene-vinyl acetate, crosslinked styrene-butadiene rubber, crosslinked carboxylated styrene-butadiene rubber, crosslinked acrylonitrile butadiene rubber, crosslinked carboxylated acrylonitrile butadiene rubber, crosslinked acrylate rubber, crosslinked acrylate-butadiene rubber; and / or, The content of cross-linked rubber particles in the composite additive is 20-50 wt%; and / or, The composite additive is selected from at least one of VP101B, VP101C, and VP801E.

5. The polyethylene composition according to claim 1, characterized in that: The polyethylene nucleating agent is at least one of nucleating agent NA11, nucleating agent NA21, and nucleating agent 20E; and / or, The cross-linked rubber particles are at least one of the following cross-linked rubber particles: Crosslinked ethylene-vinyl acetate, crosslinked styrene-butadiene rubber, crosslinked carboxylated styrene-butadiene rubber, crosslinked nitrile rubber.

6. The polyethylene composition according to claim 1, characterized in that: The cross-linked rubber particles are at least one of the following cross-linked rubber particles: Cross-linked ethylene-vinyl acetate particles, cross-linked styrene-butadiene rubber particles.

7. The polyethylene composition according to claim 1, characterized in that: The light stabilizer is one or more of hindered amine light stabilizers and ultraviolet absorbers.

8. The polyethylene composition according to claim 7, characterized in that: The hindered amine light stabilizer is selected from at least one of light stabilizer 770, light stabilizer 944, light stabilizer 622, and light stabilizer 3346; and / or, The ultraviolet absorber is selected from at least one of UV-0, UV-9, UV-531, UV-P, UV-234, UV-326, and UV-327 ultraviolet absorbers.

9. The polyethylene composition according to claim 1, characterized in that: The linear low-density polyethylene is a copolymer of ethylene and α-olefin.

10. The polyethylene composition according to claim 9, characterized in that: The α-olefin is at least one of butene-1, hexene-1, and octene-1.

11. The polyethylene composition according to claim 1, characterized in that: The linear low-density polyethylene has a melt mass flow rate of less than 3 g / 10 min under the conditions of temperature 190±5℃ and load 2.16 kg.

12. The polyethylene composition according to claim 1, characterized in that: The linear low-density polyethylene has a melt mass flow rate of less than 2 g / 10 min under the conditions of temperature 190±5℃ and load 2.16 kg.

13. The polyethylene composition according to claim 1, characterized in that: The antioxidants include primary antioxidants and secondary antioxidants.

14. The polyethylene composition according to claim 13, characterized in that: Based on parts by weight, the content of the primary antioxidant in the polyethylene composition is 0.3 to 3 parts relative to 1000 parts of polyethylene; the content of the secondary antioxidant is 0.3 to 3 parts.

15. The polyethylene composition according to claim 13, characterized in that: Based on parts by weight, relative to 1000 parts of polyethylene, the content of the primary antioxidant in the polyethylene composition is 0.3 to 2 parts; the content of the secondary antioxidant is 0.3 to 2 parts.

16. The polyethylene composition according to claim 14, characterized in that: Based on parts by weight, the content of the primary antioxidant in the polyethylene composition is 0.5 to 1 part relative to 1000 parts of polyethylene.

17. The polyethylene composition according to any one of claims 1-16, characterized in that: Based on parts by weight, relative to 1000 parts of polyethylene, the polyethylene composition contains 0.5 to 1.2 parts of composite additives; and / or 5 to 15 parts of calcium carbonate; and / or 1 to 3 parts of light stabilizer.

18. A method for preparing a polyethylene composition according to any one of claims 1-17, comprising melt-blending raw materials including the polyethylene, the antioxidant, the light stabilizer, the composite additive and the calcium carbonate to obtain the polyethylene composition.

19. The method for preparing the polyethylene composition according to claim 18, characterized in that: Includes the following steps: Step 1: Premix the raw materials including the polyethylene, the antioxidant, the light stabilizer, the composite additive, and the calcium carbonate; or, prepare an additive composition by preparing the additives including the antioxidant, the light stabilizer, the composite additive, and the calcium carbonate, and then premix the additive composition with the polyethylene. Step 2: The premixed mixture obtained in Step 1 is melt-blended to obtain the polyethylene composition.

20. A polyethylene film, wherein the polyethylene film is made of the polyethylene composition of any one of claims 1-17 or the polyethylene composition prepared by the preparation method of claim 18 or 19.

21. The polyethylene film according to claim 20, characterized in that: The polyethylene film is obtained by blow molding.

22. The polyethylene film according to claim 21, characterized in that: Inflation ratio > 2.

5.

23. A method for preparing a polyethylene film according to any one of claims 20-22, comprising the step of blow molding a polyethylene composition according to any one of claims 1-17 or a polyethylene composition obtained by the preparation method according to claims 18 or 19.

24. The method for preparing a polyethylene film according to claim 23, characterized in that: Inflation ratio > 2.

5.

25. The use of a polyethylene composition according to any one of claims 1-17, or a polyethylene composition prepared by the preparation method according to claims 18 or 19, or a polyethylene film according to any one of claims 20-22, or a polyethylene film prepared by the preparation method according to claims 23 or 24, in mulch film.

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