A puncture resistant linear low density polyethylene composition and film

Abstract

This invention belongs to the field of polyethylene film technology and discloses a puncture-resistant linear low-density polyethylene composition and film. The polyethylene composition contains component A and component B, wherein component A is metallocene linear low-density polyethylene with a density of 0.90-0.92 g / cm³. 3 Component B: Linear low-density polyethylene, whose comonomer distribution, as determined by temperature leaching curve analysis, exhibits peaks above 93°C, and the proportion of molecules leached above 93°C is not less than 75%; based on the total weight of components A and B, the weight content of component B is 10-30 wt%. The polyethylene composition and film of the present invention exhibit excellent puncture resistance.

Description

A puncture-resistant linear low-density polyethylene composition and film Technical Field

[0001] This invention belongs to the field of polyethylene film technology, specifically relating to a puncture-resistant linear low-density polyethylene composition and a film containing the polyethylene composition. Background Technology

[0002] With the improvement of living standards and the development of the logistics industry, people have access to an extremely wide variety of goods, and their requirements for the quality of packaging are also increasing. Puncture resistance is one of the important mechanical properties of packaging films. Linear low-density polyethylene (LLDPE) is often used in packaging films due to its excellent tear and puncture resistance.

[0003] Existing patent literature achieves the desired puncture resistance by adding linear low-density polyethylene (LLDPE) to the raw materials, especially by using metallocene LLDPE. For example, patent literature CN110733218A discloses a high puncture-resistant polyethylene film and its preparation method. The key technical point is a high puncture-resistant polyethylene film, comprising an inner layer, a middle layer, and an outer layer; the middle layer raw material includes a melt index of 0.5 g / 10 min and a density of 0.916 g / cm³. 3 The m-LLDPE has a melt index of 0.8 g / 10 min and a density of 0.913 g / cm³. 3 The m-LLDPE has a melt index of 0.25 g / 10 min and a density of 0.9225 g / cm³. 3 The film contains LDPE, 0.5-2 parts slip agent, and 1-3 parts PPA additive; Patent document CN111806014B discloses a low-temperature puncture-resistant polyethylene packaging film and its preparation method. The puncture-resistant packaging film, from the outside to the inside in cross-section, consists of layers A, B, C, D, E, F, and G. Layers A and C are identical in composition (nylon), layers B and D are identical in composition (adhesive resin), layer E is low-density polyethylene, and layer F is metallocene polyethylene with a density of 0.865–0.915 g / cm³. 3 The melt flow index is 1.0 to 3.0 g / 10 min, and the G layer is a heat-sealing layer.

[0004] However, there is still a need to improve the puncture resistance of films that simply use linear low-density polyethylene through composition design. Summary of the Invention

[0005] In view of the above, the purpose of this invention is to provide a puncture-resistant linear low-density polyethylene composition and film, which have excellent puncture resistance.

[0006] A first aspect of the present invention provides a puncture-resistant linear low-density polyethylene composition, the polyethylene composition comprising component A and component B, wherein,

[0007] Component A: Metallocene linear low-density polyethylene, with a density of 0.90-0.92 g / cm³. 3 ;

[0008] Component B: Linear low-density polyethylene. When its comonomer distribution is determined by temperature rinsing curve, there is a peak above 93℃, and the proportion of molecules leached above 93℃ is not less than 75%.

[0009] Based on the total weight of components A and B, the weight content of component B is 10-30 wt%.

[0010] A second aspect of the present invention provides a film comprising at least one polyethylene layer formed from the above-described puncture-resistant linear low-density polyethylene composition.

[0011] The linear low-density polyethylene composition and film of the present invention have higher puncture resistance than component A or component B, with an increase in puncture strength of more than 5%. This technology can be used to further improve the puncture resistance of metallocene linear low-density polyethylene films.

[0012] Other features and advantages of the present invention will be described in detail in the following detailed description section. Detailed Implementation

[0013] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0014] According to a first aspect of the present invention, a puncture-resistant linear low-density polyethylene composition is provided, the polyethylene composition comprising component A and component B, wherein,

[0015] Component A: Metallocene linear low-density polyethylene, with a density of 0.90-0.92 g / cm³. 3 ;

[0016] Component B: Linear low-density polyethylene. When its comonomer distribution is determined by temperature rinsing curve, there is a peak above 93℃, and the proportion of molecules leached above 93℃ is not less than 75%.

[0017] Based on the total weight of components A and B, the weight content of component B is 10-30 wt%.

[0018] In a preferred embodiment, the weight content of component B is 10-20 wt%, based on the total weight of component A and component B.

[0019] In this invention, the method for preparing the polyethylene composition includes: mixing component A and component B, and then extruding and granulating to obtain the polyethylene composition.

[0020] Preferably, component A and component B are mixed using a high-speed mixer for a mixing time of 0.5-5 minutes. High-speed mixer is a well-established trade term with clear industry manufacturing standards.

[0021] According to the present invention, extrusion granulation can be carried out using a twin-screw extruder, and the extrusion granulation temperature is 190-240℃.

[0022] According to a second aspect of the present invention, a film is provided, the film comprising at least one polyethylene layer formed of the above-described puncture-resistant linear low-density polyethylene composition.

[0023] The polyethylene layer of the present invention can be prepared by any method in the prior art, such as casting, blow molding, etc., and the parameters of each preparation method can be conventionally selected as needed.

[0024] Preferably, the film is cast from the above-mentioned puncture-resistant linear low-density polyethylene composition. Casting conditions may include: cast extruder temperature 180-240°C, screw speed 10-50 r / min, cold roll temperature 10-60°C, and winding traction speed 2-5 m / min.

[0025] The thickness of the film can be 10-50 μm, preferably 10-30 μm.

[0026] The substances and parameters not limited in this invention can be selected according to existing technology, which is a conventional technical means in this field.

[0027] The present invention will be further described below with reference to embodiments. However, the invention is not limited to these embodiments.

[0028] In the following examples and comparative examples, the data were obtained using the following test methods:

[0029] 1. Temperature-elution profile: A TREF300 temperature-elution analyzer from Polymer Char (Spain) was used. 60 mg of sample was placed in a metal container, and 20 mL of 1,2,4-trichlorobenzene solvent (containing 0.25 mg / mL of the antioxidant 2,6-di-tert-butyl-p-cresol) was injected. Under N2 protection, the temperature was rapidly increased to 150 °C and stirred at 200 rpm for 60 min to ensure complete sample dissolution. 0.3 mL of the solution was transferred to a stainless steel cylinder filled with inert gas and held at 95 °C for 45 min. The temperature was then slowly decreased to 35 °C at a rate of 0.1 °C / min and maintained for 30 min, during which the sample gradually crystallized and precipitated. Subsequently, the temperature was increased to 130 °C at a rate of 1.0 °C / min, and the column was eluted with 1,2,4-trichlorobenzene solvent at a flow rate of 0.5 mL / min. The crystallized polymer was fractionated along with the 1,2,4-trichlorobenzene elution. The content of fractions in the eluent was analyzed using an infrared detector IR4 to obtain the fraction content under different temperature conditions. After normalization, the temperature-increasing leaching curves of the resin were obtained. The relationship between the leaching ratio Y and the leaching temperature T in the temperature-increasing leaching curves is defined as Y = f(T). The proportion of molecules leached above 93℃ in the temperature-increasing leaching curves is...

[0030] 2. Puncture Performance Test: The test was conducted using an Instron 5965 tensile tester according to the method specified in ASTM D4833-07. The puncture rate was 100 mm / min. The stainless steel needle used for puncture had a hemispherical conical tip with a radius of 1.5 mm and a cone angle of 11.4°. The puncture strength was calculated by dividing the puncture force before rupture by the thickness, in mN / μm. The distance the needle traveled before the film broke was the puncture distance, in mm.

[0031] The films in the following examples and comparative examples were prepared using a CR136-E20T casting machine from COLLIN GmbH, Germany. The casting extruder temperature was 200°C, the screw speed was 30 r / min, the cold roll temperature was 25°C, and the winding traction speed was 3 m / min.

[0032] Example 1

[0033] Component A (metallocene linear low-density polyethylene, density 0.918 g / cm³) 3 The resin was mixed in a high-speed mixer at a weight ratio of 90:10 for 1 min with component B (linear low-density polyethylene, with a peak position of 99.7℃ in the temperature rise washing curve and a leaching ratio of 77% above 93℃, and component 22F, manufactured by Sinopec Qilu Petrochemical). The mixture was then extruded and granulated at 200℃ using a twin-screw extruder to obtain resin particles of the composite. These particles were then added to a casting extruder and cast into a film with a thickness of 25 μm. The puncture performance of the film was tested, and the results are shown in Table 1.

[0034] Example 2

[0035] Component A (metallocene linear low-density polyethylene, density 0.918 g / cm³) 3 The resin was mixed in a high-speed mixer for 1 minute at a weight ratio of 80:20 with component B (linear low-density polyethylene, with a peak position of 99.7℃ in the temperature rise washing curve and a leaching ratio of 77% above 93℃, and component B (22F, manufactured by Sinopec Qilu Petrochemical) and component C (linear low-density polyethylene, with a peak position of 99.7℃ in the temperature rise washing curve and a leaching ratio of 77% above 93℃). The resulting granules were obtained by extrusion granulation at 200℃ using a twin-screw extruder. The granules were then added to a casting extruder and cast into a film with a thickness of 25μm. The puncture performance of the film was tested, and the results are shown in Table 1.

[0036] Example 3

[0037] Component A (metallocene linear low-density polyethylene, density 0.918 g / cm³) 3 The resin was mixed in a high-speed mixer for 1 minute at a weight ratio of 70:30 with component B (linear low-density polyethylene, with a peak position of 99.7℃ in the temperature rise washing curve and a leaching ratio of 77% above 93℃, and component B (22F, manufactured by Sinopec Qilu Petrochemical) and component C (linear low-density polyethylene, with a peak position of 99.7℃ in the temperature rise washing curve and a leaching ratio of 77% above 93℃). The resulting granules were obtained by extrusion granulation at 200℃ using a twin-screw extruder. The granules were then added to a casting extruder and cast into a film with a thickness of 25μm. The puncture performance of the film was tested, and the results are shown in Table 1.

[0038] Example 4

[0039] Component A (metallocene linear low-density polyethylene, density 0.902 g / cm³) 3 The resin was mixed in a high-speed mixer for 1 minute at a weight ratio of 80:20 with component B (linear low-density polyethylene, with a peak position of 99.7℃ in the temperature washing curve and a leaching ratio of 77% above 93℃, brand name 22F, manufacturer of Sinopec Qilu Petrochemical). The mixture was then extruded and granulated at 200℃ using a twin-screw extruder to obtain resin particles. These particles were then added to a casting extruder and cast into a film with a thickness of 25μm. The puncture performance of the film was tested, and the results are shown in Table 1.

[0040] Comparative Example 1

[0041] Component A (metallocene linear low-density polyethylene, density 0.918 g / cm³) 3The product (brand name 23F, manufactured by Sinopec Qilu Petrochemical) was added to the casting extruder and cast into a film with a thickness of 25μm. The puncture performance of the film was tested, and the results are shown in Table 1.

[0042] Comparative Example 2

[0043] Component A (metallocene linear low-density polyethylene, density 0.918 g / cm³) 3 The resin was mixed in a high-speed mixer for 1 minute at a weight ratio of 60:40. The mixture was then extruded and granulated at 200°C using a twin-screw extruder to obtain resin particles. These particles were then added to a casting extruder and cast into a 25 μm thick film. The puncture performance of the film was tested, and the results are shown in Table 1.

[0044] Comparative Example 3

[0045] Component B (linear low-density polyethylene, with a peak position of 99.7℃ in the temperature washing curve and a leaching ratio of 77% above 93℃, grade 22F, manufactured by Sinopec Qilu Petrochemical) was added to a casting extruder to cast a film with a thickness of 25μm. The puncture performance of the film was tested, and the results are shown in Table 1.

[0046] Comparative Example 4

[0047] Component A (metallocene linear low-density polyethylene, density 0.918 g / cm³) 3 The resin was mixed in a high-speed mixer for 1 minute at a weight ratio of 70:30. The mixture was then extruded and granulated at 200°C using a twin-screw extruder to obtain resin particles. These particles were then added to a casting extruder and cast into a 25 μm thick film. The puncture performance of the film was tested, and the results are shown in Table 1.

[0048] Comparative Example 5

[0049] Component A (metallocene linear low-density polyethylene, density 0.902 g / cm³) 3 The material (brand name Engage8480, manufactured by Dow Chemical Company, USA) was added to a casting extruder and cast into a film with a thickness of 25 μm. The puncture performance of the film was tested, and the results are shown in Table 1.

[0050] Table 1

[0051] Number | Puncture Intensity (mN / μm) | Example 1 | 2 | 4 | 8 | Example 2 | 2 | 3 | 6 | Example 3 | 2 | 2 | 8 | Example 4 | 2 | 6 | 1 | Comparative Example 1 | 2 | ...6 | Comparative Example 3 | 2 | 2 | 0 | Comparative Example 4 | 2 | surface

[0052] As shown in Table 1, the special crystalline interaction between the components in the linear low-density polyethylene composition of the present invention enables the crystalline-amorphous structure of the film to resist higher puncture force. The prepared film has higher puncture resistance than the film prepared by using only component A (metallocene linear low-density polyethylene) or component B (linear low-density polyethylene), with an improvement of more than 5%, achieving unexpected results.

[0053] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A puncture-resistant linear low-density polyethylene composition, characterized in that, This polyethylene composition contains component A and component B, wherein component A is metallocene linear low-density polyethylene with a density of 0.90-0.92 g / cm³. 3 Component B: Linear low-density polyethylene. When its comonomer distribution is determined by temperature rinsing curve, there is a peak above 93℃, and the proportion of molecules leached above 93℃ is not less than 75%. Based on the total weight of components A and B, the weight content of component B is 10-30wt%.

2. The puncture-resistant linear low-density polyethylene composition according to claim 1, wherein, Based on the total weight of components A and B, the weight content of component B is 10-20 wt%.

3. The puncture-resistant linear low-density polyethylene composition according to claim 1 or 2, wherein, The preparation method of the polyethylene composition includes: mixing component A and component B, and then extruding and granulating to obtain the polyethylene composition.

4. The puncture-resistant linear low-density polyethylene composition according to claim 3, wherein, Mixing is carried out using a high-speed mixer, with a mixing time of 0.5-5 minutes.

5. The puncture-resistant linear low-density polyethylene composition according to claim 3, wherein, Extrusion granulation is carried out using a twin-screw extruder, with an extrusion granulation temperature of 190-240℃.

6. A thin film, characterized in that, The film contains at least one polyethylene layer formed from the puncture-resistant linear low-density polyethylene composition according to any one of claims 1-5.

7. The film according to claim 6, wherein, The film is cast from the puncture-resistant linear low-density polyethylene composition according to any one of claims 1-5.

8. The film according to claim 7, wherein, The conditions for casting include: casting extruder temperature 180-240℃, screw speed 10-50r / min, cold roll temperature 10-60℃, and winding traction speed 2-5m / min.

9. The film according to claim 7, wherein, The thickness of the film is 10-50 μm.

10. The thin film according to claim 9, wherein, The thickness of the film is 10-30 μm.