A composition, resin and method for producing thin walled polyethylene drip irrigation pipe at high speed

Abstract

The application provides a composition, resin and preparation method thereof for high-speed production of thin-wall polyethylene drip irrigation pipe, and belongs to the technical field of polyethylene resin. The resin for high-speed production of thin-wall polyethylene drip irrigation pipe is prepared by mixing 60-70 parts of high-density polyethylene, 10-16 parts of linear low-density polyethylene, 18-25 parts of low-density polyethylene, 1-3 parts of carbon black masterbatch and 0.1-0.2 parts of ultraviolet absorption agent in a high-speed mixer, granulating and drying. Compared with common drip irrigation pipe resin, the resin can be produced at high speed (>250 m / min), and when the pipe wall thickness is reduced to 0.12 mm, the longitudinal retraction rate and static liquid pressure strength meet the standard requirements, and the resin has excellent rigidity and toughness balance, wherein the Charpy notched impact strength of the simple supported beam is >80 kJ / m 2 , the bending modulus is >600 MPa, the tensile yield stress is >18 MPa, the tensile fracture nominal strain is >800%, and the oxidation induction time is >18 min (210 DEG C).

Description

Technical Field

[0001] This invention belongs to the field of polyethylene resin technology, specifically relating to a composition, resin, and preparation method for high-speed production of thin-walled polyethylene drip irrigation pipes. Background Technology

[0002] With the increasing global imbalance between water supply and demand, water conservation has become a global focus and is directly related to the long-term goal of sustainable development for population, resources, and the environment. Currently, relatively mature agricultural water-saving engineering technologies with significant water-saving effects include: canal seepage prevention, low-pressure pipeline water conveyance, plastic pipe wells, sprinkler irrigation, and micro-drip irrigation. Micro-drip irrigation pipes are divided into on-pipe drip irrigation pipes and in-line drip irrigation pipes. The drippers used include pressure-compensated and labyrinth channel types. When the diameter of the main and branch pipes is below 63mm, polyethylene (PE) pipes are used.

[0003] Drip irrigation pipes deliver water to the roots of crops through orifices or drippers on capillary tubes with a diameter of approximately 10mm for localized irrigation. Water is dripped slowly and evenly, drop by drop, onto the soil near the crop roots through drippers or drip tubes with very small outflow orifices. Currently, in some domestic fields where lifespan requirements are not high, recycled polyethylene drip irrigation pipes are frequently used. However, these pipes are prone to cracking, leading to water waste and hindering the effective use of drip irrigation tape. Furthermore, existing blending methods or the direct use of recycled polyethylene in drip irrigation pipe production result in products with poor performance characteristics such as resistance to environmental stress cracking and flexibility, failing to meet usage requirements. Processing speeds are also low (typically <200m / min), impacting production efficiency, and the product thickness is >0.15mm.

[0004] Currently, there are very few patents and documents regarding the preparation methods of resins used in the high-speed production of thin-walled polyethylene drip irrigation pipes. For example, the invention patent CN 107337836 A (application number 201710570865.5), which discloses "An Oxidation-Resistant Polyethylene Drip Irrigation Tape and Its Preparation Method," relates to an oxidation-resistant polyethylene drip irrigation tape comprising the following components: carbon black, PPA processing aid, composite antioxidant, high-density polyethylene, and linear low-density polyethylene. The composite antioxidant is composed of antioxidant B215, UV absorber UV531, and low-density high-pressure polyethylene. The composite antioxidant used in this invention's oxidation-resistant polyethylene drip irrigation tape is primarily a high-molecular-weight organic material, which not only has good oxidation resistance but also good compatibility with the polyethylene polymer, reducing structural defects that may occur during drip irrigation tape preparation. Compared to ordinary drip irrigation tape, it provides higher strength oxidation resistance. To prevent side cracking of drip irrigation tape during outdoor use, this patent effectively enhances the oxidation resistance of ordinary polyethylene drip irrigation tape without added antioxidants, ensuring its service life and reducing the possibility of damage during use. This patent focuses on improving the oxidation resistance of polyethylene drip irrigation pipes and does not address high-speed production or reducing wall thickness.

[0005] The invention patent CN 106397903 A (application number 201610768093.1), disclosing "A Polyethylene Drip Irrigation Tape with High Tensile Strength," provides a polyethylene drip irrigation tape with high tensile strength, prepared from raw materials comprising the following parts by weight: 40-45 parts high-density polyethylene; 16-18 parts low-density polyethylene; 14-15 parts linear low-density polyethylene; 0.75-1.5 parts carbon black; 5-10 parts plasticizer; 0.25-0.5 parts PPA processing aid; and 5-10 parts glass fiber. The high-tensile-strength polyethylene drip irrigation tape of this invention incorporates glass fiber in its formulation. Glass fiber is a high-performance inorganic non-metallic material with good insulation, heat resistance, corrosion resistance, and high mechanical strength. Compared to ordinary drip irrigation tape, it provides higher tensile strength. However, adding glass fiber increases costs and makes it difficult to disperse glass fiber in polyethylene, which complicates the process. In addition, this patent does not cover high-speed production of drip irrigation pipes or thinning of wall thickness. Summary of the Invention

[0006] The purpose of this invention is to design a composition and resin for high-speed production of thin-walled polyethylene drip irrigation pipes. In particular, by adjusting the ratio of different types of polyethylene, carbon black masterbatch and UV absorber, a polyethylene drip irrigation pipe that can be used for high-speed production and achieves thinner wall thickness can be produced while ensuring the balance of rigidity and toughness of the material.

[0007] The first technical problem to be solved by the present invention is to provide a polyethylene drip irrigation pipe resin that has excellent rigidity-toughness balance, can be produced at high speed (>250m / min), and at the same time, after the pipe wall thickness is reduced to 0.12mm, the longitudinal shrinkage rate and hydrostatic strength meet the standard requirements.

[0008] The second technical problem to be solved by the present invention is to provide a method for preparing the above-mentioned polyethylene drip irrigation pipe resin, which is simple in process and easy to operate.

[0009] According to one aspect of the present invention, a polyethylene composition is provided comprising, by weight:

[0010]

[0011]

[0012] Optionally, the polyethylene composition comprises, by weight:

[0013]

[0014] Optionally, the high-density polyethylene has a melt index (190℃, 5kg) of 0.5–0.7 g / 10min and a density of 0.940–0.950 g / cm³. 3 .

[0015] Optionally, the linear low-density polyethylene has a melt index (190℃, 2.16kg) of 1.0–1.5 g / 10min and a density of 0.910–0.915 g / cm³. 3 .

[0016] Optionally, the low-density polyethylene has a melt index (190°C, 2.16 kg) of 1.3–1.8 g / 10 min and a density of 0.915–0.920 g / cm³. 3 .

[0017] Optionally, the carbon black masterbatch is used in this invention to achieve antioxidant purposes. The carbon black masterbatch is composed of linear low-density polyethylene base material and carbon black, wherein the carbon black component accounts for 40% to 60% by weight. This invention does not specifically limit the source of the carbon black masterbatch.

[0018] Optionally, the UV absorber includes UV absorbers manufactured by BASF with model numbers 2020 or 622.

[0019] According to another aspect of the present invention, a polyethylene resin is provided, the polyethylene resin comprising the above-described polyethylene composition.

[0020] Optionally, the notched impact strength of the simply supported beam of the polyethylene resin is >80 kJ / m. 2 .

[0021] Optionally, the flexural modulus of the polyethylene resin is >600 MPa.

[0022] Optionally, the tensile yield stress of the polyethylene resin is >18MPa.

[0023] Optionally, the nominal tensile strain at break of the polyethylene resin is >800%.

[0024] Optionally, the oxidation induction time of the polyethylene resin is >18 min (210°C).

[0025] According to another aspect of the present invention, a method for preparing the above-mentioned polyethylene resin is provided, comprising mixing the polyethylene composition and then granulating and drying it.

[0026] Optionally, the mixing conditions are as follows: first mix at a low speed of 500-1000 r / min for 1-2 minutes, then mix at a high speed of 1000-2000 r / min for 0.5-1 minutes.

[0027] Optionally, the granulation is performed using a twin-screw extruder, and the temperature of the twin-screw extruder from feeding to the die head is set as follows: 170℃~180℃, 180℃~190℃, 182℃~192℃, 185℃~195℃, 185℃~195℃, 180℃~190℃, 175℃~185℃, 170℃~180℃, 170℃~180℃.

[0028] According to another aspect of the present invention, a drip irrigation tube is provided, the drip irrigation tube comprising at least one of the above-described polyethylene composition, the above-described polyethylene resin, and the polyethylene resin prepared by the above-described preparation method.

[0029] Optionally, the wall thickness of the drip irrigation tube is ≥0.12mm.

[0030] Optionally, the longitudinal shrinkage rate of the drip irrigation tube is <8%.

[0031] And / or the hydrostatic pressure of the drip irrigation tube is >20 min (0.3 MPa).

[0032] As a specific embodiment of the present invention, the specifications of the drip irrigation tube are as follows:

[0033] According to another aspect of the present invention, a method for preparing the above-mentioned drip irrigation pipe is provided, comprising extruding resin particles using a pipe extruder.

[0034] Optionally, the production speed of the drip irrigation tube is >250m / min.

[0035] Optionally, the pipe extruder is a single-screw pipe extruder.

[0036] The present invention has the following beneficial effects:

[0037] Resins containing the polyethylene composition described in this invention exhibit excellent stiffness-toughness balance properties, with a notched impact strength of a simply supported beam >80 kJ / m. 2 The polyethylene resin exhibits a flexural modulus > 600 MPa, tensile yield stress > 18 MPa, nominal tensile strain at break > 800%, and oxidation induction time > 18 min (210℃). It can be used for high-speed (>250 m / min) production of thin-walled polyethylene drip irrigation pipes. Even after reducing the pipe wall thickness to 0.12 mm, the longitudinal shrinkage rate and hydrostatic strength still meet standard requirements. The polyethylene resin preparation method provided by this invention is simple and easy to operate. Detailed Implementation

[0038] The present invention will be further described below with reference to specific embodiments, but this does not constitute any limitation on the present invention.

[0039] In various embodiments of the present invention, the melt index parameters for high-density polyethylene are a temperature of 190°C and a load of 5kg, while the melt index parameters for linear low-density polyethylene and low-density polyethylene are a temperature of 190°C and a load of 2.16kg.

[0040] In the various embodiments of the present invention, the high-speed mixer used is manufactured by White Bear Company, model SHR-50L, and the twin-screw extruder is manufactured by Nanjing Ruya Company, model TSE-35A.

[0041] In each embodiment of the present invention, the mechanical properties of the resin are tested using national standards such as GB / T 1040.2-2006, GB / T 9341-2008, GB / T1043.1-2008 and GB / T 19466.6-2009, and the performance of the drip irrigation pipe is tested using national standards such as GB / T 6671-2001 and GB / T 6111-2003.

[0042] In the various embodiments of the present invention, the carbon black masterbatch used is Cabot's black masterbatch model PE6269, and the UV absorber is BASF's UV absorber model 2020.

[0043] Example 1

[0044] Expressed in parts by weight, 60 parts of a product with a melt index of 0.5 g / 10 min and a density of 0.940 g / cm³... 3High-density polyethylene, 16 parts melt index of 1.0 g / 10 min, density of 0.910 g / cm³ 3 Linear low-density polyethylene, with a melt index of 1.3 g / 10 min and a density of 0.915 g / cm³. 3 Low-density polyethylene, 3 parts carbon black masterbatch, and 0.1 parts UV absorber were added to a high-speed mixer and thoroughly mixed at 500 rpm for 2 minutes, followed by 1200 rpm for 1 minute. The mixture was then fed into a twin-screw extruder for granulation. During the granulation process, the temperatures of each section of the extruder from the feed port to the die head were: 170℃, 180℃, 182℃, 185℃, 185℃, 185℃, 180℃, 180℃, 175℃, and 170℃. The resin underwent mechanical property testing according to national standards.

[0045] Example 2

[0046] Expressed in parts by weight, 62 parts had a melt index of 0.6 g / 10 min and a density of 0.945 g / cm³. 3 High-density polyethylene, with a melt index of 1.2 g / 10 min and a density of 0.912 g / cm³. 3 Linear low-density polyethylene, with a melt index of 1.5 g / 10 min and a density of 0.920 g / cm³. 3 Low-density polyethylene, 2 parts carbon black masterbatch, and 0.12 parts UV absorber were added to a high-speed mixer and thoroughly mixed at 800 rpm for 1.5 minutes, followed by 1500 rpm for 0.5 minutes. The mixture was then fed into a twin-screw extruder for granulation. During the granulation process, the temperatures of each section of the extruder from the feed port to the die head were: 175℃, 185℃, 188℃, 190℃, 190℃, 180℃, 185℃, 175℃, 170℃, and 175℃. The resin underwent mechanical property testing according to national standards.

[0047] Example 3

[0048] Expressed in parts by weight, 67 parts had a melt index of 0.55 g / 10 min and a density of 0.948 g / cm³. 3 High-density polyethylene, 14 parts melt index 1.5 g / 10 min, density 0.915 g / cm³ 3 Linear low-density polyethylene, with a melt index of 1.6 g / 10 min and a density of 0.918 g / cm³. 3Low-density polyethylene, 1 part carbon black masterbatch, and 0.14 parts UV absorber were added to a high-speed mixer and thoroughly mixed at 1000 rpm for 1 minute, then at 1600 rpm for 1 minute. The mixture was then fed into a twin-screw extruder for granulation. During the granulation process, the temperatures of each section of the extruder from the feed port to the die head were: 180℃, 180℃, 192℃, 195℃, 180℃, 190℃, 190℃, 185℃, 180℃, 180℃. The resin underwent mechanical property testing according to national standards.

[0049] Example 4

[0050] Expressed in parts by weight, 61 parts had a melt index of 0.65 g / 10 min and a density of 0.950 g / cm³. 3 High-density polyethylene, melt index of 1.2 g / 10 min at 12 parts, density of 0.912 g / cm³ 3 Linear low-density polyethylene, with a melt index of 1.8 g / 10 min and a density of 0.915 g / cm³. 3 Low-density polyethylene, 2 parts carbon black masterbatch, and 0.16 parts UV absorber were added to a high-speed mixer and thoroughly mixed at 600 rpm for 1 minute, followed by 2000 rpm for 0.5 minutes. The mixture was then fed into a twin-screw extruder for granulation. During the granulation process, the temperatures of each section of the extruder from the feed port to the die head were: 170℃, 190℃, 185℃, 185℃, 185℃, 185℃, 180℃, 180℃, 175℃, and 170℃. The resin underwent mechanical property testing according to national standards.

[0051] Example 5

[0052] Expressed in parts by weight, 65 parts had a melt index of 0.7 g / 10 min and a density of 0.945 g / cm³. 3 High-density polyethylene, melt index of 1.4 g / 10 min, and density of 0.910 g / cm³. 3 Linear low-density polyethylene, with a melt index of 1.3 g / 10 min and a density of 0.916 g / cm³. 3 Low-density polyethylene, 1 part carbon black masterbatch, and 0.18 parts UV absorber were added to a high-speed mixer and thoroughly mixed at 800 rpm for 2 minutes, followed by 1800 rpm for 1 minute. The mixture was then fed into a twin-screw extruder for granulation. During the granulation process, the temperatures of each section of the extruder from the feed port to the die head were: 173℃, 185℃, 185℃, 185℃, 185℃, 180℃, 180℃, 175℃, 175℃. The resin underwent mechanical property testing according to national standards.

[0053] Example 6

[0054] Expressed in parts by weight, 66 parts had a melt index of 0.55 g / 10 min and a density of 0.950 g / cm³. 3 High-density polyethylene, with a melt index of 1.0 g / 10 min and a density of 0.915 g / cm³. 3 Linear low-density polyethylene, with a melt index of 1.5 g / 10 min and a density of 0.918 g / cm³. 3 Low-density polyethylene, 3 parts carbon black masterbatch, and 0.2 parts UV absorber were added to a high-speed mixer and thoroughly mixed at 500 rpm for 2 minutes, followed by 1200 rpm for 1 minute. The mixture was then fed into a twin-screw extruder for granulation. During the granulation process, the temperatures of each section of the extruder from the feed port to the die head were: 170℃, 180℃, 185℃, 185℃, 185℃, 185℃, 180℃, 180℃, 175℃, and 170℃. The resin underwent mechanical property testing according to national standards.

[0055] Example 7

[0056] Expressed in parts by weight, 70 parts of a product with a melt index of 0.65 g / 10 min and a density of 0.940 g / cm³... 3 High-density polyethylene, melt index of 1.5 g / 10 min, and density of 0.912 g / cm³. 3 Linear low-density polyethylene, with a melt index of 1.8 g / 10 min and a density of 0.920 g / cm³. 3 Low-density polyethylene, 1 part carbon black masterbatch, and 0.15 parts UV absorber were added to a high-speed mixer and thoroughly mixed at 600 rpm for 1.5 minutes, followed by 1500 rpm for 1 minute. The mixture was then fed into a twin-screw extruder for granulation. During the granulation process, the temperatures of each section of the extruder from the feed port to the die head were: 175℃, 180℃, 185℃, 185℃, 185℃, 185℃, 180℃, 175℃, 175℃. The resin underwent mechanical property testing according to national standards.

[0057] Example 8

[0058] Expressed in parts by weight, 69 parts had a melt index of 0.7 g / 10 min and a density of 0.945 g / cm³. 3 High-density polyethylene, melt index of 1.3 g / 10 min, and density of 0.910 g / cm³. 3 Linear low-density polyethylene, with a melt index of 1.3 g / 10 min and a density of 0.916 g / cm³. 3Low-density polyethylene, 1 part carbon black masterbatch, and 0.15 parts UV absorber were added to a high-speed mixer and thoroughly mixed at 800 rpm for 1 minute, followed by 2000 rpm for 0.5 minutes. The mixture was then fed into a twin-screw extruder for granulation. During the granulation process, the temperatures of each section of the extruder from the feed port to the die head were: 175℃, 180℃, 185℃, 190℃, 185℃, 185℃, 180℃, 180℃, 175℃, and 175℃. The resin underwent mechanical property testing according to national standards.

[0059] Example 9

[0060] Expressed in parts by weight, 65 parts of a product with a melt index of 0.55 g / 10 min and a density of 0.948 g / cm³... 3 High-density polyethylene, melt index of 1.5 g / 10 min, and density of 0.915 g / cm³. 3 Linear low-density polyethylene, with a melt index of 1.6 g / 10 min and a density of 0.918 g / cm³. 3 Low-density polyethylene, 1 part carbon black masterbatch, and 0.18 parts UV absorber were added to a high-speed mixer and thoroughly mixed at 800 rpm for 1 minute, followed by 2000 rpm for 0.5 minutes. The mixture was then fed into a twin-screw extruder for granulation. During the granulation process, the temperatures of each section of the extruder from the feed port to the die head were: 175℃, 180℃, 185℃, 190℃, 185℃, 185℃, 180℃, 180℃, 175℃, 175℃. The resin underwent mechanical property testing according to national standards.

[0061] Example 10

[0062] Expressed in parts by weight, 67 parts had a melt index of 0.55 g / 10 min and a density of 0.950 g / cm³. 3 High-density polyethylene, with a melt index of 1.5 g / 10 min and a density of 0.913 g / cm³. 3 Linear low-density polyethylene, 18 parts, melt index 1.6 g / 10 min, density 0.916 g / cm³ 3 Low-density polyethylene, 1 part carbon black masterbatch, and 0.14 parts UV absorber were added to a high-speed mixer and thoroughly mixed at 800 rpm for 1 minute, followed by 2000 rpm for 0.5 minutes. The mixture was then fed into a twin-screw extruder for granulation. During the granulation process, the temperatures of each section of the extruder from the feed port to the die head were: 175℃, 180℃, 185℃, 190℃, 185℃, 185℃, 180℃, 180℃, 175℃, and 175℃. The resin underwent mechanical property testing according to national standards.

[0063] Example 11

[0064] Expressed in parts by weight, 67 parts had a melt index of 0.6 g / 10 min and a density of 0.948 g / cm³. 3 High-density polyethylene, with a melt index of 1.2 g / 10 min and a density of 0.915 g / cm³. 3 Linear low-density polyethylene, 18 parts, melt index 1.4 g / 10 min, density 0.918 g / cm³ 3 Low-density polyethylene, 1 part carbon black masterbatch, and 0.14 parts UV absorber were added to a high-speed mixer and thoroughly mixed at 800 rpm for 1 minute, followed by 2000 rpm for 0.5 minutes. The mixture was then fed into a twin-screw extruder for granulation. During the granulation process, the temperatures of each section of the extruder from the feed port to the die head were: 175℃, 180℃, 185℃, 190℃, 185℃, 185℃, 180℃, 180℃, 175℃, and 175℃. The resin underwent mechanical property testing according to national standards.

[0065] Comparative Example 1

[0066] Expressed in parts by weight, 55 parts of a product with a melt index of 0.55 g / 10 min and a density of 0.948 g / cm³... 3 High-density polyethylene, 18 parts melt index of 1.5 g / 10 min, density of 0.915 g / cm³ 3 Linear low-density polyethylene, with a melt index of 1.6 g / 10 min and a density of 0.918 g / cm³, at 25 parts per cubic centimeter. 3 Low-density polyethylene, 2 parts carbon black masterbatch, and 0.14 parts UV absorber were added to a high-speed mixer and thoroughly mixed at 1000 rpm for 1 minute, then at 1600 rpm for 1 minute. The mixture was then fed into a twin-screw extruder for granulation. During the granulation process, the temperatures of each section of the extruder from the feed port to the die head were: 180℃, 180℃, 192℃, 195℃, 180℃, 190℃, 190℃, 185℃, 180℃, 180℃. The resin underwent mechanical property testing according to national standards.

[0067] Comparative Example 2

[0068] Expressed in parts by weight, 75 parts of a product with a melt index of 0.55 g / 10 min and a density of 0.948 g / cm³... 3 High-density polyethylene, melt index of 1.5 g / 10 min, and density of 0.915 g / cm³. 3 Linear low-density polyethylene, with a melt index of 1.6 g / 10 min and a density of 0.918 g / cm³. 3Low-density polyethylene, 2 parts carbon black masterbatch, and 0.14 parts UV absorber were added to a high-speed mixer and thoroughly mixed at 1000 rpm for 1 minute, then at 1600 rpm for 1 minute. The mixture was then fed into a twin-screw extruder for granulation. During the granulation process, the temperatures of each section of the extruder from the feed port to the die head were: 180℃, 180℃, 192℃, 195℃, 180℃, 190℃, 190℃, 185℃, 180℃, 180℃. The resin underwent mechanical property testing according to national standards.

[0069] Comparative Example 3

[0070] Expressed in parts by weight, 60 parts of a product with a melt index of 0.55 g / 10 min and a density of 0.948 g / cm³... 3 High-density polyethylene, with a melt index of 1.6 g / 10 min and a density of 0.918 g / cm³. 3 Low-density polyethylene, 2 parts carbon black masterbatch, and 0.14 parts UV absorber were added to a high-speed mixer and thoroughly mixed at 1000 rpm for 1 minute, then at 1600 rpm for 1 minute. The mixture was then fed into a twin-screw extruder for granulation. During the granulation process, the temperatures of each section of the extruder from the feed port to the die head were: 180℃, 180℃, 192℃, 195℃, 180℃, 190℃, 190℃, 185℃, 180℃, 180℃. The resin underwent mechanical property testing according to national standards.

[0071] Test Example 1

[0072] Performance test results of polyethylene drip irrigation pipe resin:

[0073] Table 1

[0074]

[0075] The above tests show that the test results of Examples 1 to 11 all met the expected design (notched impact strength of simply supported beam > 80 kJ / m). 2 The flexural modulus is greater than 600 MPa, the tensile yield stress is greater than 18 MPa, the nominal strain at tensile fracture is greater than 800%, and the oxidation induction time is greater than 18 min (210℃). The performance of some of the comparative examples 1 to 3 did not meet the design requirements.

[0076] Test Example 2

[0077] The polyethylene drip irrigation pipe resins prepared in Examples 1-11 and Comparative Examples 1-3 were used for pipe processing tests. The tests were conducted using a single-screw pipe extruder manufactured by Tianjin Huaxushengtai Technology Co., Ltd. The extruder had a screw diameter of 60 mm and a length-to-diameter ratio of 40:1. The specifications of the extruded pipes were as follows: The pipe wall thickness is 0.12-0.15 mm; the production speed is greater than 250 m / min.

[0078] Performance test results of polyethylene drip irrigation pipes:

[0079] Table 2

[0080]

[0081] Any numerical value mentioned in this invention, if there is only a two-unit interval between any minimum and any maximum value, includes all values ​​that increase by one unit each time from the minimum to the maximum value. For example, if the amount of a component, or the value of a process variable such as temperature, pressure, or time, is stated as 50-90, in this specification it means specifically listing values ​​such as 51-89, 52-88, ..., 69-71, and 70-71, etc. For non-integer values, it may be appropriately considered that a unit is 0.1, 0.01, 0.001, or 0.0001. These are merely some specifically specified examples. In this invention, in a similar manner, all possible combinations of numerical values ​​between the listed minimum and maximum values ​​are considered to have been disclosed.

[0082] 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.

Claims

1. A polyethylene composition, characterized in that, The polyethylene composition comprises, by weight parts: high density polyethylene 60~70 parts, linear low density polyethylene 10~16 parts, low density polyethylene 18~25 parts, carbon black masterbatch 1~3 parts, ultraviolet absorption agent 0.1~0.2 parts. The parameter condition corresponding to the high-density polyethylene melt index is temperature 190℃, load 5kg, the melt index of the high-density polyethylene is 0.5~0.7 g / 10min, and the density is 0.940~0.950 g / cm 3 ; The parameter condition corresponding to the melt index of the linear low density polyethylene is temperature 190℃, load 2.16kg, and the melt index of the linear low density polyethylene is 1.0-1.5 g / 10min, and the density is 0.910-0.915 g / cm 3 ; The parameter condition corresponding to the melt index of the low-density polyethylene is temperature 190 ℃, load 2.16 kg, and the melt index of the low-density polyethylene is 1.3-1.8 g / 10 min, and the density is 0.915-0.920 g / cm 3 ; The drip irrigation pipe prepared from the polyethylene composition has a wall thickness ≥0.12mm, a longitudinal shrinkage rate <8%, and a hydrostatic strength >20min. The polyethylene resin prepared from the polyethylene composition is extruded into a drip irrigation pipe by a pipe material extruder, and the production speed of the drip irrigation pipe is >250m / min.

2. The polyethylene composition according to claim 1, characterized in that, The polyethylene composition comprises, by weight parts: high density polyethylene 65~68 parts, linear low density polyethylene 12~14 parts, low density polyethylene 18~20 parts, carbon black masterbatch 1~2 parts, ultraviolet absorption agent 0.12~0.16 parts.

3. A polyethylene resin characterized in that, The polyethylene resin comprises the polyethylene composition of claim 1 or 2.

4. The polyethylene resin according to claim 3, characterized in that, the Charpy notched impact strength of the polyethylene resin is > 80 kJ / m 2 and / or the flexural modulus is > 600 MPa, and / or the tensile yield stress is > 18 MPa, and / or the tensile break nominal strain is > 800%, and / or the oxidation induction time at 210°C is > 18 min.

5. A process for the preparation of a polyethylene resin as claimed in claim 3 or 4, characterized in that, The polyethylene composition is mixed and granulated, and then dried.

6. The production method according to claim 5, characterized by, The mixing conditions are: first mixing at a low speed of 500~1000r / min for 1~2 minutes, and then mixing at a high speed of 1000~2000r / min for 0.5~1 minute.

7. The preparation method according to claim 5, characterized in that, The granulation is performed by a double screw extruder, and the temperature settings of the double screw extruder from the feeding to the die head are: 170℃~180℃, 180℃~190℃, 182℃~192℃, 185℃~195℃, 185℃~195℃, 180~190℃, 180℃~190℃, 175℃~185℃, 170℃~180℃, and 170℃~180℃.

8. A drip irrigation pipe characterized in that, The drip irrigation pipe comprises at least one of the polyethylene composition of any one of claims 1~2, the polyethylene resin of any one of claims 3~4, and the polyethylene resin prepared by the method of any one of claims 5~7.

9. The drip irrigation pipe according to claim 8, characterized in that, The drip irrigation pipe has a wall thickness ≥0.12mm, and / or a longitudinal shrinkage rate <8%, and / or a hydrostatic strength >20min under 0.3MPa.

10. A method of manufacturing a drip irrigation pipe according to claim 8 or 9, characterized in that, The resin particles are extruded and formed by a pipe material extruder. And / or, the production speed of the drip irrigation pipe is >250m / min.

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