Polyethylene composition for weather-resistant mulching film as well as preparation method and application of polyethylene composition

Abstract

The invention discloses a polyethylene composition for a weather-resistant mulching film as well as a preparation method and application of the polyethylene composition, and the polyethylene composition contains polyethylene, an antioxidant, a light stabilizer, a compound additive and calcium carbonate, wherein the composite additive is compounded by loading a polyethylene nucleating agent on the surfaces of spherical or approximately spherical cross-linked rubber particles, and polyethylene is selected from linear low-density polyethylene; relative to 1000 parts by mass 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. By adopting the polyethylene composition disclosed by the invention, the stability of an LLDPE (Linear Low Density Polyethylene) film blowing process is improved, the winding is more tidy, and the problem of'knife sticking 'is eliminated.

Description

Technical Field

[0001] The invention relates to a special polyolefin material, and more specifically to a polyethylene composition for weather-resistant ground film, and a preparation method and application thereof. Background Art

[0002] The promotion and application of polyethylene blown agricultural ground covering film (referred to as ground film) has become an indispensable means of production for agricultural production due to its functions of moisture retention, temperature increase and water saving. However, due to recycling problems, residual film accumulates over time.

[0003] Under the premise of keeping the thickness of the mulch basically unchanged, improving the weather resistance and mechanical properties of the mulch, especially the longitudinal / transverse tensile load, nominal strain at break and right-angle tear load, is the key to increasing the recycling rate of waste mulch.

[0004] In order to meet the requirements of mulch film recycling and reach national / local standards, mulch film manufacturers in Xinjiang or supplying mulch film to Xinjiang generally use mixed materials, compounding a variety of polyethylene raw materials and additives to improve the stability of the film blowing process and produce mulch film performance to meet national and local standards. However, this often leads to higher mulch film costs, more complicated production processes, and unstable product quality. Therefore, it is urgent to develop a special material for weather-resistant mulch film for use by mulch film manufacturers.

[0005] The melt strength of LLDPE is lower than that of high-pressure polyethylene (LDPE), and the viscosity is higher than that of high-density polyethylene (HDPE), which brings great difficulties to the film blowing process, especially when producing films with high blow-up ratios (>2.5), the production is often not normal due to poor bubble stability. Although blending with LDPE can solve the problem of film blowing production process, it reduces the mechanical strength of the film and makes it difficult to meet the indicators of Xinjiang local standards. In addition, the weathering additives added to recyclable mulch films often reduce some of the mechanical properties of the mulch films, which also brings challenges to the technical development of resin raw materials for mulch films.

[0006] Therefore, how to solve the problems of unstable film bubbles and uneven winding in the ground film blowing process, as well as the "knife sticking" phenomenon, and maintain or not reduce the mechanical strength of the film, is a technical problem that needs to be solved at present. Summary of the invention

[0007] In view of the above technical problems, the present invention uses LLDPE as the base resin, and adds antioxidants, light stabilizers, composite additives, calcium carbonate particles and other additives to develop a special material for LLDPE weather-resistant ground film. Although the composite additives in the additives can also improve the problems of unstable film bubbles and uneven winding in the ground film blowing process, it is necessary to reduce the production load, and there is still an occasional "sticky knife" phenomenon, resulting in discontinuous production. Through a large number of experimental studies, it is found that when the polyethylene composition contains antioxidants, light stabilizers, composite additives and calcium carbonate, especially the addition of calcium carbonate, it is unexpected that even under high blowing ratios (>2.5), the LLDPE film blowing process is still stable: the film bubbles are stable and the winding is neat. More importantly, the addition of calcium carbonate can still maintain a production capacity similar to that of the compounded raw materials, thereby ensuring production efficiency. On the basis of the above, the LLDPE mulch film of the present invention has higher tensile load, nominal strain at break and right-angle tear load, and its physical and mechanical properties after artificial weather aging or actual use remain high, which effectively ensures the mechanical properties of the mulch film during recycling, and can be widely used in mechanical recycling of mulch film to improve the mulch film recycling rate.

[0008] The first aspect of the present invention is to provide a polyethylene composition, comprising polyethylene, an antioxidant, a light stabilizer, a composite auxiliary agent and calcium carbonate; wherein the composite auxiliary agent is a composite auxiliary agent formed by loading a polyethylene nucleating agent on the surface of spherical or approximately spherical cross-linked rubber particles, and the polyethylene is selected from linear low-density polyethylene; in parts by mass, relative to 1000 parts of polyethylene, the content of the composite auxiliary agent 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.

[0009] As mentioned above, based on a large number of experimental studies, the inventors found that when the polyethylene composition contains antioxidants, light stabilizers, composite additives and calcium carbonate, especially the addition of calcium carbonate, the stability of the LLDPE film production process can be significantly improved, and the physical and mechanical properties of the film are only slightly reduced. This solves the problem of unstable film blowing of LLDPE resin, and further solves the processing problems such as unstable film bubbles and uneven winding of LLDPE special materials for mulch film when blowing mulch with a high blow-up ratio (>2.5). More importantly, it does not affect the production load and increases the output. This makes the mulch film production simpler, more efficient and less costly.

[0010] In a preferred embodiment of the present invention, the calcium carbonate is derived from at least one of the following calcium carbonates and / or a composite masterbatch of at least one of the following calcium carbonates and polyethylene: ordinary calcium carbonate, activated calcium carbonate.

[0011] In a preferred embodiment of the present invention, the mesh size of the calcium carbonate is 800-4000, preferably 1000-3000.

[0012] In the present invention, the amount of calcium carbonate added is preferably 5 to 20 parts by mass, more preferably 5 to 15 parts, relative to 1000 parts of polyethylene. In polyolefin modification technology, calcium carbonate is generally used as a filler, and the amount added is relatively high to reduce the cost of the resin. Surprisingly, adding a small amount of calcium carbonate particles to the LLDPE raw material can significantly improve the stability of the blown film processing, and only slightly reduce the mechanical properties of the film, effectively ensuring the continuity of film production. This solves the problem of the difficulty of the film blowing process caused by the high viscosity and low melt strength of LLDPE itself.

[0013] According to the present invention, the polyethylene nucleating agent can be selected in a wide range. In a preferred embodiment of the present invention, the polyethylene nucleating agent is selected from at least one of an organic nucleating agent and an inorganic nucleating agent, preferably at least one of an organic carboxylic acid nucleating agent, an organic carboxylate nucleating agent, and an organic phosphate nucleating agent, and more preferably at least one of nucleating agent NA11, nucleating agent NA21, and nucleating agent 20E.

[0014] According to the present invention, the cross-linked rubber particles can be selected from a wide range. In a preferred embodiment of the present invention, the cross-linked rubber particles are at least one of the following cross-linked rubber particles:

[0015] At least one of cross-linked ethylene-vinyl acetate, cross-linked styrene-butadiene rubber, cross-linked carboxylated styrene-butadiene rubber, cross-linked nitrile rubber, cross-linked carboxylated nitrile rubber, cross-linked acrylic rubber, and cross-linked acrylate-butadiene rubber; preferably at least one of cross-linked ethylene-vinyl acetate, cross-linked styrene-butadiene rubber, cross-linked carboxylated styrene-butadiene rubber, and cross-linked nitrile rubber; more preferably at least one of cross-linked ethylene-vinyl acetate and cross-linked styrene-butadiene rubber particles.

[0016] In a preferred embodiment of the present invention, the content of the cross-linked rubber particles in the composite auxiliary agent is 10-80wt%, preferably 20-50wt%.

[0017] The rubber particles with cross-linked structure described in the present invention can be prepared by the method of patent CN1402752, which is prepared by adding a cross-linking agent such as TMPTA to a rubber latex containing uncross-linked rubber particles with a particle size of 20-2000nm, irradiating with a high-energy ray source, and spray drying. The obtained cross-linked rubber particles are easy to disperse and can be used as a carrier to help the nucleating agent and the light stabilizer to be more evenly dispersed in the matrix resin, significantly improving the comprehensive mechanical properties of the resin composition and meeting the application requirements.

[0018] In the present invention, the nucleating agent and the rubber particles having a cross-linked structure may be added to the resin composition as separate raw materials, or a commercial product containing both may be used.

[0019] In a more preferred embodiment of the present invention, the composite auxiliary agent is selected from at least one of VP101B, VP101C, and VP801E.

[0020] 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 a hindered amine light stabilizer and an ultraviolet absorber; preferably:

[0021] 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,

[0022] 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.

[0023] In the present invention, the light stabilizer models correspond to the following: bis-2,2,6,6-tetramethylpiperidinol sebacate (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-piperidinylethanol) succinate (hindered amine light stabilizer 622); poly {(6-morpholinyl-5-triazine-2,4-diyl)(2,2,6,6-tetramethylpiperidinyl)iminohexamethylene [(2,2,6,6-tetramethylpiperidinyl)-imino]} (hindered amine light stabilizer 3346).

[0024] In the present invention, the ultraviolet absorber models correspond to the following: 2,4-dihydroxybenzophenone (ultraviolet absorber UV-0); 2-hydroxy-4-methoxybenzophenone (ultraviolet absorber UV-9); 2-hydroxy-4-n-octyloxybenzophenone (ultraviolet absorber UV-531); 2-(2'-hydroxy-5'-methylphenyl)benzotriazole (ultraviolet absorber UV-P); 2-(2-hydroxy-3,5-bis(a,a-dimethylbenzyl)phenyl)benzotriazole (ultraviolet absorber UV-234); 2-(2-hydroxy-3-tert-butyl-5-methylphenyl)-5-chlorobenzotriazole (ultraviolet absorber UV-326); 2-(2'-hydroxy-3',5'-di-tert-phenyl)-5-chlorobenzotriazole (ultraviolet absorber UVP-327).

[0025] In a preferred embodiment of the present invention, the linear low-density polyethylene is a copolymer of ethylene and α-olefin, and preferably the α-olefin is at least one of 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°C and a load of 2.16 kg is less than 3 g / 10 min, preferably less than 2 g / 10 min.

[0026] 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:

[0027] In parts by mass, 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,

[0028] The main antioxidants are hindered phenols, including pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate (antioxidant 1010), β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate octadecyl alcohol (antioxidant 1076), 1,3,5-trimethyl-2,4,6-(3,5-di-tert-butyl-4-hydroxyphenylmethyl)benzene (antioxidant 1330), 1,3,5-tri(3 ,5-di-tert-butyl-4-hydroxybenzyl) isocyanuric acid (antioxidant 3114), β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate (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,

[0029] Auxiliary antioxidants include phosphites and thioesters, etc., preferably phosphites, including 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, 2,2-ethylenebis(4,6-di-tert-butylphenyl)fluorophosphite (antioxidant 398), etc.

[0030] According to the present invention, in parts by mass, relative to 1000 parts of polyethylene, the content of the composite auxiliary agent 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 the light stabilizer is 0.5 to 5 parts, preferably 1 to 3 parts.

[0031] The additives of the present invention may also include additives commonly used in plastic processing, such as antistatic agents, acid absorbers, lubricants, etc., and the amounts used are conventional amounts or may be adjusted according to actual requirements.

[0032] The second aspect of the present invention is to provide a method for preparing the polyethylene composition of the first aspect, comprising melt blending raw materials including the polyethylene, the antioxidant, the light stabilizer, the composite auxiliary agent and the calcium carbonate to obtain the polyethylene composition; preferably, comprising the following steps:

[0033] Step 1, premixing the raw materials including the polyethylene, the antioxidant, the light stabilizer, the composite auxiliary agent, and the calcium carbonate, or preparing an auxiliary agent composition with the auxiliary agent including the antioxidant, the light stabilizer, the composite auxiliary agent, and the calcium carbonate, and then premixing the auxiliary agent composition with the polyethylene;

[0034] Step 2: melt-blending the pre-mixed mixture obtained in step 1 to obtain the polyethylene composition.

[0035] During the preparation process, the blending temperature of the materials corresponds to the usual processing temperature of the matrix resin linear low-density polyethylene, and should be selected within a range that ensures that the matrix resin is completely melted and does not decompose. In addition, according to processing requirements, an appropriate amount of conventional additives can be added to the blended materials. During the blending process, the components can be added to the melt blending equipment at the same time by metering or the like for melt blending; or the components can be pre-mixed uniformly by a general mixing equipment, and then melt blended and extruded once through a rubber and plastic blending equipment to obtain a modified resin composition.

[0036] The rubber and plastic blending equipment used in the preparation method of the present invention can be an open mixer, internal mixer, single screw extruder, twin screw extruder or twin rotor extruder, etc. The material mixing equipment is selected from mechanical mixing equipment such as high-speed mixers and kneaders commonly used in the art.

[0037] The third aspect of the present invention is to provide a polyethylene film, wherein the material of the polyethylene film is the polyethylene composition described in the first aspect or the polyethylene composition prepared by the preparation method described in the second aspect;

[0038] Preferably, the polyethylene film is obtained by blow molding, and more preferably the blow-up ratio is greater than 2.5.

[0039] The fourth aspect of the present invention is to provide a method for preparing the polyethylene film described in the third aspect, comprising the step of blow molding the polyethylene composition described in the first aspect or the polyethylene composition prepared by the preparation method described in the second aspect, preferably with a blow ratio greater than 2.5.

[0040] The mulch produced by the LLDPE weather-resistant mulch special material of the present invention has a high transverse / longitudinal tensile load, nominal strain at break and right-angle tear load. Even if the inflation ratio is relatively large (>2.5), the film blowing process is still smooth, the film bubble is stable, and the winding is neat. The mulch produced by the weather-resistant mulch special material has good weather resistance. After being used for covering the ground, its mechanical property retention rate is high, which can meet the recycling and reuse of the mulch, which not only solves the problem of white pollution caused by the mulch, but also realizes the reuse of the recycled mulch. It is very meaningful that the weather-resistant mulch special material avoids the need for downstream customers to compound with other additives and resins to meet the mechanical properties and processing stability of the mulch, thereby simplifying the production process and improving product stability.

[0041] The fifth aspect of the present invention is to provide an 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 ground film.

[0042] The advantages of the present invention are:

[0043] By specially proportioning LLDPE, antioxidant, light stabilizer, composite additive and calcium carbonate in the polyethylene composition, the processing problems of LLDPE special materials for mulch film, such as unstable film bubbles, high frequency of sticking to the knife, and uneven winding, can be solved during the processing of blowing mulch film with high blowing ratio (>2.5). The mulch film produced by the special materials has high tensile load, nominal strain at break and right-angle tear load, and the physical and mechanical properties after artificial climate aging or actual use are kept high, which effectively guarantees the mechanical properties of the mulch film during recycling. It can be widely used in mechanical recycling of mulch film, improve the recycling rate of mulch film, and maintain the strength and aging performance of mulch film with a thickness of about 10 microns. Compared with compound ingredients, more importantly, the special materials for mulch film can meet the stability of the film blowing process without reducing the production output, make the winding more neat, avoid the "sticking to the knife" phenomenon, and ensure stable production. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is the isothermal crystallization diagram of the resins of Comparative Example 1, Comparative Example 2 and Example 3 at 110°C;

[0045] Figure 2These are the two-dimensional WAXD images of Comparative Example 1 and Example 3.

[0046] Figure 1 The isothermal DSC curves of the resins of Comparative Example 1, Comparative Example 2 and Example 3 at 110°C show that with the addition of the composite additive, the second exothermic peak on the DSC isothermal crystallization curve shifts to the left and overlaps with the first exothermic peak to form an exothermic peak, which indicates that the crystallization rate of the special material is significantly increased. When a small amount of calcium carbonate particles is added, the overlapping exothermic peaks further shift to the left, indicating that the crystallization rate is further increased.

[0047] Moreover, after adding the composite additive, the second exothermic peak of isothermal crystallization shifted to the left and overlapped with the first exothermic peak to form an exothermic peak. After adding calcium carbonate, a second exothermic peak appeared, which was significantly shifted to the left like the first exothermic peak, and most of it overlapped with the first exothermic peak, indicating that a new nucleation process occurred during the crystallization process. The increase in crystallization rate helps the mechanical properties of the blown film bubble, thereby improving the stability of the bubble, while reducing the adhesion between the films, thereby significantly improving the stability of the blown film process. More importantly, the addition of a small amount of calcium carbonate avoids "sticking to the knife".

[0048] Figure 2 The two-dimensional WXRD spectra of the blown films of Comparative Example 1 and Example 3 are shown. The test results show that the transverse / vertical molecules of the film are oriented, and the transverse orientation is lower than the longitudinal orientation. It is significant that the addition of calcium carbonate particles significantly improves the transverse / vertical molecular orientation of the film at the same time, so the mechanical strength of the film in the transverse / vertical direction is also improved accordingly, which is more conducive to the stability of film processing. In short, based on the raw materials of the present invention, due to the addition of calcium carbonate particles, the crystallization rate and the transverse / vertical molecular orientation are further improved, thereby maintaining the mechanical properties of the film, improving the stability of the film, stabilizing production, and avoiding the problem of "sticking knife" during the production process. DETAILED DESCRIPTION

[0049] The present invention is described in detail below in conjunction with specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the contents of the present invention still fall within the scope of protection of the present invention.

[0050] The present invention is further described below in conjunction with the embodiments. The scope of the claims of the present invention is not limited by these embodiments, and the scope of the claims of the present invention is set forth in the appended claims.

[0051] The experimental data in the examples were measured using the following equipment and methods:

[0052] The test specimens for tensile load and nominal strain at break are tested in accordance with the national standard GB / T1040.3-2006 and the Xinjiang Uygur Autonomous Region local standard DB65 3189-2014. The specimen is type 2, with a width of 10 mm, an initial marking distance of 50 mm between the fixtures, a test speed (no load) of 500 mm / min, and the specimen is stretched until it breaks, and the maximum tensile load is measured with an accuracy of 0.01 N.

[0053] The right-angle tearing load is carried out in accordance with the national standard GB / T1130-1991 and the Xinjiang Uygur Autonomous Region local standard DB653189-2014. A single specimen is used, the initial marking distance between the fixtures is 55mm, and the test speed (no load) is 200mm / min. The arithmetic mean of the experimental results is taken.

[0054] The artificial weathering test was carried out in accordance with GB / T 9345.1-2008 and Xinjiang Uygur Autonomous Region local standard DB653189-2014. The specific conditions of ultraviolet aging are as follows: the experimental lamp uses a type II lamp (UV-A340), with a wavelength of 340nm and an irradiance of 0.76W / m 2 ·nm, illumination temperature 60℃, irradiation time 4h (light); condensation temperature 50℃, condensation time 4h (dark) cycle alternately for 240 hours.

[0055] The melt index test temperature is 190±5°C and the measurement is carried out under the conditions of a load of 2.16kg.

[0056] Bubble instability refers to the occurrence of the following phenomena at least once within two hours during the production process: bubble stretching resonance, spiral instability, condensation line oscillation, bubble sagging, bubble vibration and bubble fluttering, which leads to production difficulties.

[0057] Uneven winding means that the end surface deviation of the film roll exceeds 30mm or the film roll has ribs.

[0058] The "sticky knife" phenomenon refers to the phenomenon that during the film production process, the film-breaking knife comes out from between the two layers of film to be broken. The frequency of "sticky knife" is calculated by the number of times "sticky knife" occurs during eight hours of continuous production.

[0059] Melt blending and film preparation

[0060] The process of initial mixing and melt blending of materials is as follows: first weigh all materials according to the proportion, perform preliminary mixing in a high-speed mixer for 20 seconds, and then use a twin-screw extruder (Coperion (Nanjing) Machinery Co., Ltd., aspect ratio 30:1, screw diameter 30 mm) for melt blending and granulation, the speed is 200r / min, the temperature is set to 170℃, 180℃, 190℃, 200℃, 200℃, 200℃, and the feed amount is 14; the obtained pellets are placed in a tray and treated in an oven at 70℃ for 4 hours to remove moisture.

[0061] The ground film is prepared by a single-layer blow molding method. The film blowing machine is a German Colin. The temperature settings of the film blowing machine are: each section temperature is set at 160℃, 180℃, 200℃, 210℃, 210℃, 210℃, 210℃, the film blowing width is 31cm, the nominal thickness is 10um, and the blowing ratio is 2.9.

[0062] VP-801E refers to VP801E produced by Sinopec Beijing Research Institute of Chemical Industry, wherein 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 microns, and the gel content of the rubber particles is 90wt%; the mass ratio of the rubber particles to the nucleating agent is 3:7; the average particle size of VP-801E is 0.3 microns.

[0063] Embodiment 1:

[0064] Weigh the LLDPE resin powder (Chemical Branch of Zhongtian Hechuang Energy Co., Ltd., melt index: 1.0g / 10min, density: 0.918g / cm 3 ) 2000.0g, primary antioxidant 1010 (Yingkou Fengguang New Materials Co., Ltd.) 1.0g, secondary antioxidant 168 (Yingkou Fengguang New Materials Co., Ltd.) 1.2g, hindered amine light stabilizer 944 (Beijing Tiangang Auxiliary Co., Ltd.) 6.0g, composite additive (VP-801E of Yanshan Petrochemical High-tech Technology Co., Ltd.) 1.0g, calcium carbonate (Lingshou County Guanghui Mineral Products Processing Co., Ltd., mesh number 2000) 10.0g, after being dispersed evenly by a high-speed mixer, melt blended and granulated by a twin-screw extruder. Blown mulch: nominal thickness 10 microns, blowing ratio 2.9. Test the longitudinal / transverse tensile load, nominal strain at break and right-angle tear load of the mulch before / after aging.

[0065] Embodiment 2:

[0066] Weigh the LLDPE resin powder (Chemical Branch of Zhongtian Hechuang Energy Co., Ltd., melt index: 1.0g / 10min, density: 0.918g / cm 3) 2000.0g, primary antioxidant 1010 (Yingkou Fengguang New Materials Co., Ltd.) 1.0g, secondary antioxidant 168 (Yingkou Fengguang New Materials Co., Ltd.) 1.2g, hindered amine light stabilizer 944 (Beijing Tiangang Auxiliary Co., Ltd.) 6.0g, composite additive (VP-801E of Yanshan Petrochemical High-tech Technology Co., Ltd.) 2.0g, calcium carbonate (Lingshou County Guanghui Mineral Products Processing Co., Ltd., mesh number 2000) 16.0g, dispersed evenly by high-speed mixer, melt blended and granulated by twin screw. Blown mulch: nominal thickness 10 microns, blowing ratio 2.9. Test the longitudinal / transverse tensile load, nominal strain at break and right-angle tear load of the mulch before / after aging.

[0067] Embodiment 3:

[0068] Weigh the LLDPE resin powder (Chemical Branch of Zhongtian Hechuang Energy Co., Ltd., melt index: 1.0g / 10min, density: 0.918g / cm 3 ) 2000.0g, primary antioxidant 1010 (Yingkou Fengguang New Materials Co., Ltd.) 1.0g, secondary antioxidant 168 (Yingkou Fengguang New Materials Co., Ltd.) 1.2g, hindered amine light stabilizer 944 (Beijing Tiangang Auxiliary Co., Ltd.) 6.0g, composite additive (VP-801E of Yanshan Petrochemical High-tech Technology Co., Ltd.) 1.6g, calcium carbonate (Lingshou County Guanghui Mineral Products Processing Co., Ltd., mesh number 3000) 20.0g, after being dispersed evenly by a high-speed mixer, melt blended and granulated by a twin-screw extruder. Blown mulch: nominal thickness 10 microns, blowing ratio 2.9. Test the longitudinal / transverse tensile load, nominal strain at break and right-angle tear load of the mulch before / after aging.

[0069] Embodiment 4:

[0070] Weigh the LLDPE resin powder (Chemical Branch of Zhongtian Hechuang Energy Co., Ltd., melt index: 1.0g / 10min, density: 0.918g / cm 3 ) 2000.0g, primary antioxidant 1010 (Yingkou Fengguang New Materials Co., Ltd.) 1.0g, secondary antioxidant 168 (Yingkou Fengguang New Materials Co., Ltd.) 1.2g, hindered amine light stabilizer 622 (Beijing Tiangang Auxiliary Co., Ltd.) 6.0g, composite additive (VP-801E of Yanshan Petrochemical High-tech Technology Co., Ltd.) 2.0g, calcium carbonate (Lingshou County Guanghui Mineral Products Processing Co., Ltd., mesh number 1000) 20g, after being dispersed evenly by a high-speed mixer, melt blended and granulated by a twin-screw extruder. Blown mulch: nominal thickness 10 microns, blow-up ratio 2.9. Test the longitudinal / transverse tensile load, nominal strain at break and right-angle tear load of the mulch before / after aging.

[0071] Embodiment 5:

[0072] Weigh the LLDPE resin powder (Chemical Branch of Zhongtian Hechuang Energy Co., Ltd., melt index: 1.0g / 10min, density: 0.918g / cm 3 ) 2000.0 g, main antioxidant 1010 (Yingkou Fengguang New Materials Co., Ltd.) 1.0 g, auxiliary antioxidant 168 (Yingkou Fengguang New Materials Co., Ltd.) 1.2 g, synergistic compound light stabilizer HS-362 (Beijing Tiangang Auxiliary Co., Ltd.) 6.0 g, composite additive (Yanshan Petrochemical High-Tech Co., Ltd. VP-801E) 2.0 g, calcium carbonate masterbatch (Hangzhou Kaijie Plastic Technology Co., Ltd., CM-01, calcium carbonate mesh 1250) 20.0 g, after being dispersed evenly by a high-speed mixer, melt blended and granulated by a twin-screw extruder. Blown mulch: nominal thickness 10 microns, blow-up ratio 2.9. Test the longitudinal / transverse tensile load, nominal strain at break and right-angle tear load of the mulch before and after aging.

[0073] Comparative Example 1:

[0074] Weigh the LLDPE resin powder (Chemical Branch of Zhongtian Hechuang Energy Co., Ltd., melt index: 1.0g / 10min, density: 0.918g / cm 3 ) 2000.0g, primary antioxidant 1010 (Yingkou Fengguang New Materials Co., Ltd.) 1.0g, secondary antioxidant 168 (Yingkou Fengguang New Materials Co., Ltd.) 1.2g, hindered amine light stabilizer 944 (Beijing Tiangang Auxiliary Co., Ltd.) 6.0g, composite additive (VP-801E of Yanshan Petrochemical High-tech Technology Co., Ltd.) 2.0g, dispersed evenly by high-speed mixer, melt blended and granulated by twin screw. Blown mulch: nominal thickness 10 microns, blow-up ratio 2.9. Test the longitudinal / transverse tensile load, nominal strain at break and right-angle tear load of the mulch before / after aging.

[0075] Comparative Example 2:

[0076] Weigh the LLDPE resin powder (Chemical Branch of Zhongtian Hechuang Energy Co., Ltd., melt index: 1.0g / 10min, density: 0.918g / cm 3 ) 2000.0g, primary antioxidant 1010 (Yingkou Fengguang New Materials Co., Ltd.) 1.0g, auxiliary antioxidant 168 (Yingkou Fengguang New Materials Co., Ltd.) 1.2g, hindered amine light stabilizer 944 (Beijing Tiangang Auxiliary Co., Ltd.) 6.0g, after being dispersed evenly by a high-speed mixer, melt blended and granulated by a twin-screw extruder. Blown mulch: nominal thickness 10 microns, blow-up ratio 2.9. Test the longitudinal / transverse tensile load, nominal strain at break and right-angle tear load of the mulch before / after aging.

[0077] Comparative Example 3:

[0078] Weigh 2000.0 grams of LLDPE resin powder (Chemical Branch of Zhongtian Hechuang Energy Co., Ltd., melt index: 1.0g / 10min, density: 0.918g / cm3), 1.0 grams of primary antioxidant 1010 (Yingkou Fengguang New Materials Co., Ltd.), 1.2 grams of auxiliary antioxidant 168 (Yingkou Fengguang New Materials Co., Ltd.), 6.0 grams of synergistic compound light stabilizer HS-362 (Beijing Tiangang Additive Co., Ltd.), 10 grams of composite additive (VP-801E of Yanshan Petrochemical High-Tech Co., Ltd.), 60 grams of calcium carbonate masterbatch (Hangzhou Kaijie Plastic Technology Co., Ltd., CM-01, calcium carbonate mesh number 1250), and after uniform dispersion in a high-speed mixer, use a twin-screw melt blending and granulation.

[0079] Table 1 Physical and mechanical properties test and film blowing process status of nominally 10 μm thick ground film prepared by special materials

[0080]

[0081]

[0082] Table 2 Physical and mechanical properties test of ground film after artificial climate aging

[0083]

[0084] Comparative Example 1 only contains four components, namely, the LLDPE matrix of the present invention, an antioxidant, a light stabilizer and a composite auxiliary agent, without adding calcium carbonate.

[0085] Comparative Example 2 only contains three components, namely, the LLDPE matrix of the present invention, an antioxidant, and a light stabilizer, without adding composite additives and calcium carbonate.

[0086] Examples 1-5 all contain an LLDPE resin matrix and an antioxidant; the type and content of the light stabilizer, the type and content of calcium carbonate, and the content of VP801E are changed.

[0087] As can be seen from Table 1, in the embodiment in which VP801E and calcium carbonate components are added, the film bubbles are stable during processing, the frequency of sticking to the knife is low, and the winding is more neat.

[0088] It can be seen from Table 2 that after aging, the longitudinal and transverse tensile loads of Examples 1-5 are significantly better than those of Comparative Example 2 in which no composite additive and calcium carbonate are added, showing an excellent balance between mechanical properties and processing properties.

[0089] In Comparative Example 3, in addition to the matrix and antioxidant of the present invention, a suitable light stabilizer and composite particles and calcium carbonate exceeding the content of the present invention are added. During the extrusion blow molding process, the melt strength of the comparative example formula product is greatly reduced due to the excessive additives in the matrix. During the unidirectional traction film forming process, the film bubble is very unstable and the film is broken too many times, so the film cannot be blown normally.

[0090] Comparative Example 1 only contains four components, namely, the matrix of the present invention, antioxidant, light stabilizer and composite auxiliary agent, without adding calcium carbonate. In the process of ultra-thin film processing, the addition of calcium carbonate can improve the processing performance, but it will form defects in the film, resulting in a decrease in the tensile load. Therefore, in Tables 1 and 2, it is shown that the tensile load and nominal strain at break of Comparative Example 1 before and after aging are relatively high, but the film bubble is unstable during processing, the frequency of knife sticking is high, and the winding is uneven. Composite auxiliary agents and calcium carbonate are added to Examples 1-5. Although the tensile load is slightly lower than that of Comparative Example 1, its processing performance is better, and weather-resistant ground film can be successfully prepared without adding HDPE or LDPE.

[0091] It has been verified that the examples obtained by changing one or more of the above factors using other linear low-density polyethylene raw materials, other light stabilizers, other composite additives and other calcium carbonate described in the present invention, and verifying them using the same method as Example 1, all show that the film bubbles are stable during processing, the frequency of sticking to the knife is low, and the winding is neat. The longitudinal and transverse tensile loads after aging are significantly better than the comparative examples without adding composite additives and calcium carbonate under the same conditions, showing an excellent balance between mechanical properties and processing properties.

[0092] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to 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 words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

[0093] 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 conventionally understood by those skilled in the art. In the event of a conflict, the definition in this specification shall prevail.

[0094] When this specification uses the prefix "well-known to those skilled in the art", "prior art" or similar terms to introduce materials, substances, methods, steps, devices or components, etc., the objects introduced by the prefix cover those commonly used in the art when this application is filed, but also include those that are not commonly used at present but will become recognized in the art as being suitable for similar purposes.

[0095] The endpoints and any values ​​of the scope disclosed in the present application document are not limited to the precise scope or value, and these scopes or values ​​should be understood to include values ​​close to these scopes or values. For numerical ranges, between the endpoint values ​​of each scope, between the endpoint values ​​of each scope and a separate point value, and between separate point values, one or more new numerical ranges can be combined with each other, and these numerical ranges should be considered as specifically disclosed in this article. Hereinafter, in principle, each technical solution can be combined with each other to obtain a new technical solution, which should also be considered as specifically disclosed in this article.

[0096] In the context of the present specification, any matters or items not mentioned are directly applicable to those known in the art without any changes except those explicitly stated.

[0097] Moreover, any embodiment described in this document may be freely combined with one or more other embodiments described in this document, and the technical solutions or technical ideas formed thereby are deemed to be part of the original disclosure or original record of the present invention, and should not be regarded as new content that has not been disclosed or anticipated in this document, unless a person skilled in the art considers that the combination is obviously unreasonable.

Claims

1. A polyethylene composition comprising polyethylene, an antioxidant, a light stabilizer, a composite auxiliary agent and calcium carbonate; in, The composite auxiliary agent is a composite auxiliary agent formed by loading a polyethylene nucleating agent on the surface of spherical or approximately spherical cross-linked rubber particles, and the polyethylene is selected from linear low-density polyethylene; In parts by mass, relative to 1000 parts of polyethylene, the content of the composite auxiliary agent 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.

2. The polyethylene composition according to claim 1, Features: The calcium carbonate is derived from at least one of the following calcium carbonates and / or a composite masterbatch of at least one of the following calcium carbonates and polyethylene: ordinary calcium carbonate, activated calcium carbonate; and / or, The mesh size of the calcium carbonate is 800-4000, preferably 1000-3000.

3. The polyethylene composition according to claim 1, Features: The polyethylene nucleating agent is selected from at least one of an organic nucleating agent and an inorganic nucleating agent, preferably at least one of an organic carboxylic acid nucleating agent, an organic carboxylate nucleating agent, and an organic phosphate nucleating agent, and more preferably 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: At least one of cross-linked ethylene-vinyl acetate, cross-linked styrene-butadiene rubber, cross-linked carboxylated styrene-butadiene rubber, cross-linked nitrile rubber, cross-linked carboxylated nitrile rubber, cross-linked acrylic rubber, and cross-linked acrylate-butadiene rubber; preferably at least one of cross-linked ethylene-vinyl acetate, cross-linked styrene-butadiene rubber, cross-linked carboxylated styrene-butadiene rubber, and cross-linked nitrile rubber; more preferably at least one of cross-linked ethylene-vinyl acetate particles and cross-linked styrene-butadiene rubber particles; and / or, The content of the cross-linked rubber particles in the composite auxiliary agent is 10-80wt%, preferably 20-50wt%; and / or, Preferably, the composite auxiliary agent is selected from at least one of VP101B, VP101C, and VP801E.

4. The polyethylene composition according to claim 1, Features: The light stabilizer is one or more of a hindered amine light stabilizer and an ultraviolet absorber; preferably: 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.

5. The polyethylene composition according to claim 1, Features: The linear low-density polyethylene is a copolymer of ethylene and α-olefin, preferably the α-olefin is at least one of butene-1, hexene-1 and octene-1; and / or, The linear low-density polyethylene has a melt mass flow rate of less than 3 g / 10 min, preferably less than 2 g / 10 min, under the conditions of a temperature of 190±5° C. and a load of 2.16 kg.

6. The polyethylene composition according to claim 1, Features: The antioxidant includes a primary antioxidant and a secondary antioxidant, preferably: In parts by mass, 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.

7. The polyethylene composition according to any one of claims 1 to 6, Features: In parts by mass, relative to 1000 parts of polyethylene, the content of the composite auxiliary agent in the polyethylene composition is 0.5 to 1.2 parts; and / or the content of calcium carbonate is 5 to 15 parts; and / or the content of the light stabilizer is 1 to 3 parts.

8. A method for preparing the polyethylene composition according to any one of claims 1 to 7, comprising melt blending raw materials including the polyethylene, the antioxidant, the light stabilizer, the composite auxiliary agent and the calcium carbonate to obtain the polyethylene composition; preferably, comprising the following steps: Step 1, premixing the raw materials including the polyethylene, the antioxidant, the light stabilizer, the composite auxiliary agent, and the calcium carbonate, or preparing an auxiliary agent composition with the auxiliary agent including the antioxidant, the light stabilizer, the composite auxiliary agent, and the calcium carbonate, and then premixing the auxiliary agent composition with the polyethylene; Step 2: melt-blending the pre-mixed mixture obtained in step 1 to obtain the polyethylene composition.

9. A polyethylene film, wherein the polyethylene film is made of the polyethylene composition according to any one of claims 1 to 7 or the polyethylene composition prepared by the preparation method according to claim 8; Preferably, the polyethylene film is obtained by blow molding, and more preferably the blow-up ratio is greater than 2.

5.

10. A method for preparing the polyethylene film according to claim 9, comprising the step of blow molding the polyethylene composition according to any one of claims 1 to 7 or the polyethylene composition obtained by the preparation method according to claim 8, preferably with a blow-up ratio of >2.

5.

11. Use of the polyethylene composition according to any one of claims 1 to 7, or the polyethylene composition obtained by the preparation method according to claim 8, or the polyethylene film according to claim 9, or the polyethylene film obtained by the preparation method according to claim 10 in ground film.

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