Polyethylene film and method for producing the same

Abstract

This application provides a polyethylene film comprising a three-layer co-extruded layer formed by three-layer co-extrusion blown film. The three-layer co-extruded layer includes an inner layer, a middle layer, and an outer layer. The inner layer is composed of HDPE-MH602 and MLLDPE-1327CA; the middle layer is composed of HDPE-MH602, HDPE-7000F, and MLLDPE-1327CA; and the outer layer is composed of HDPE-MH602, HDPE-HHMTR144, and MLLDPE-1327CA. This application also provides a method for preparing the polyethylene film and garbage bags obtained from the film. The film provided by this application has better material mechanical properties, which facilitates appropriate reduction of film thickness and thus helps reduce resource waste.

Description

Technical Field

[0001] This invention relates to the technical field of films for garbage bags, and specifically to a polyethylene film and its preparation method. Background Technology

[0002] Currently, garbage bags must be thicker than 8µm to ensure their material mechanical properties meet usage requirements. Increasing bag thickness also leads to increased raw material consumption, and since garbage bags are a non-recyclable resource, increased material consumption results in increased resource waste. Summary of the Invention

[0003] In order to overcome the shortcomings of the prior art, the purpose of this invention is to provide a polyethylene film with better material mechanical properties, which is conducive to appropriately reducing the thickness of the film and thus reducing resource waste.

[0004] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0005] A polyethylene film includes a three-layer co-extruded layer formed by three-layer co-extrusion blown film. The three-layer co-extruded layer includes an inner layer, a middle layer, and an outer layer. The inner layer is composed of HDPE-MH602 and MLLDPE-1327CA. The middle layer is composed of HDPE-MH602, HDPE-7000F, and MLLDPE-1327CA. The outer layer is composed of HDPE-MH602, HDPE-HHMTR144, and MLLDPE-1327CA.

[0006] In some possible implementations, the inner layer component consists of 70% HDPE-MH602 and 30% MLLDPE-1327CA by weight percentage;

[0007] The middle layer is composed of 35% HDPE-MH602, 35% HDPE-7000F and 30% MLLDPE-1327CA by weight percentage.

[0008] The outer layer is composed of 35% HDPE-MH602, 35% HDPE-HHMTR144 and 30% MLLDPE-1327CA by weight percentage.

[0009] In some possible implementations, the thickness of the inner layer is 30% of the total thickness of the film, the thickness of the middle layer is 40% of the total thickness of the film, and the thickness of the outer layer is 30% of the total thickness of the film.

[0010] In some possible implementations, the thickness of the polyethylene film is less than 8 μm and greater than or equal to 5 μm.

[0011] This application also provides a method for preparing a polyethylene film, the method comprising the following steps:

[0012] The components of the inner layer are mixed evenly and added to the inner hopper of the three-layer co-extrusion blown film machine;

[0013] The components of the middle layer are mixed evenly and added to the middle layer hopper of the three-layer co-extrusion blown film machine;

[0014] The components of the outer layer are mixed evenly and added to the outer hopper of the three-layer co-extrusion blown film machine;

[0015] The three-layer co-extrusion blown film machine melts and extrudes the components in each hopper through the extrusion screws to the die head to be blown into the film.

[0016] In some possible implementations, the inner screw barrel temperature is 175-185°C, the middle screw barrel temperature is 185-195°C, the outer screw barrel temperature is 180-190°C, the die head runner temperature is 190-200°C, and the die opening temperature is 195°C.

[0017] In some possible implementations, the air-cooling temperature is 20-25°C.

[0018] In some possible implementations, the inflation ratio is 1:2.5 to 1:3.

[0019] In some possible implementations, the operating frequency of the cooling fan is greater than or equal to 40Hz.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] In this application, the polyethylene film blown by mixing polyethylene raw materials with different physical properties has better material mechanical properties, which is conducive to appropriately reducing the thickness of the film and thus reducing resource waste.

[0022] The present invention will be further described in detail below with reference to specific embodiments. Detailed Implementation

[0023] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0025] The following describes some embodiments of the present invention in detail. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0026] A polyethylene film includes a three-layer co-extruded layer formed by three-layer co-extrusion blown film. The three-layer co-extruded layer includes an inner layer, a middle layer, and an outer layer. The inner layer is composed of HDPE-MH602 and MLLDPE-1327CA. The middle layer is composed of HDPE-MH602, HDPE-7000F, and MLLDPE-1327CA. The outer layer is composed of HDPE-MH602, HDPE-HHMTR144, and MLLDPE-1327CA.

[0027] HDPE-MH602 is the abbreviation for high-density polyethylene with the model number MH602. MLLDPE-1327CA is the abbreviation for metallo-modified linear low-density polyethylene with the model number 1327CA. HDPE-7000F is the abbreviation for high-density polyethylene with the model number 7000F. HDPE-HHMTR144 is the abbreviation for high-density polyethylene with the model number HHMTR144.

[0028] HDPE-MH602 is branded by Shanghai Petrochemical, with a melt index of 0.2 g / 10 min and a density of 0.946 g / cm³. 3 The melting point is 131℃. MLLDPE-1327CA is from ExxonMobil, with a melt index of 1.3 g / 10 min and a melting point of 122℃. HDPE-7000F is from Thailand, with a melt index of 4 g / 10 min and a density of 0.956 g / cm³. 3 The melting point is 129℃. The brand of HDPE-HHMTR144 is Maoming Petrochemical, with a melt index of 0.2 g / 10 min and a density of 0.956 g / cm³. 3 Its melting point is 130℃.

[0029] The inner layer component consists of 70% HDPE-MH602 and 30% MLLDPE-1327CA by weight percentage.

[0030] The middle layer is composed of 35% HDPE-MH602, 35% HDPE-7000F and 30% MLLDPE-1327CA by weight percentage.

[0031] By mass percentage, the outer layer consists of 35% HDPE-MH602, 35% HDPE-HHMTR144, and 30% MLLDPE-1327CA. The selection of these component proportions ensures that the polyethylene film exhibits good mechanical properties even at a micrometer thickness of 5 μm.

[0032] The polyethylene film provided in this application can be blown into film using a three-layer co-extrusion top-blown method.

[0033] The thickness of the inner layer is 30% of the total thickness of the film, the thickness of the middle layer is 40% of the total thickness of the film, and the thickness of the outer layer is 30% of the total thickness of the film.

[0034] The thickness of the polyethylene film is less than 8 μm and greater than or equal to 5 μm. The film provided in this application can further reduce the thickness, thereby helping to reduce resource waste.

[0035] Another embodiment of this application provides a method for preparing a polyethylene film. It is understood that the raw materials used in this method are derived from the components of each layer of the polyethylene film in corresponding proportions, and therefore will not be described in detail here. The preparation method includes the following steps:

[0036] The components of the inner layer are mixed evenly and added to the inner layer hopper of the three-layer co-extrusion blown film machine. The temperature of the inner layer screw barrel is set to 175-185℃.

[0037] Mix the components of the middle layer evenly and add them to the middle layer hopper of the three-layer co-extrusion blown film machine. Set the temperature of the middle layer screw barrel to 185-195℃.

[0038] The components of the outer layer are mixed evenly and added to the outer layer hopper of the three-layer co-extrusion blown film machine. The temperature of the outer layer screw barrel is set to 180-190℃.

[0039] The three-layer co-extrusion blown film mill uses extrusion screws to melt and extrude the components in each hopper to the die head for blown film formation. Specifically, the screw corresponding to the inner hopper extrudes the material from the inner hopper, the screw corresponding to the middle hopper extrudes the material from the middle hopper, and the screw corresponding to the outer hopper extrudes the material from the outer hopper. The die head runner temperature is 190-200℃, and the die opening temperature is 195℃. These temperature settings stabilize the film bubble while ensuring adequate cooling efficiency, thus guaranteeing film forming quality. The air cooling temperature is 20-25℃, which reduces energy consumption while providing good cooling for the formulation. The blow-up ratio is 1:2.5-1:3, which helps improve film quality. The cooling fan operates at a frequency greater than or equal to 40Hz. Existing equipment can be used for the three-layer co-extrusion blown film mill, so its specific structure will not be described in detail.

[0040] The film provided in this application has a transverse tensile strength ≥15 Newtons, a longitudinal tensile strength ≥16 Newtons, a transverse elongation at break ≥600%, and a longitudinal elongation at break ≥550% when the thickness is 0.6C (6 micrometers).

[0041] In this application, the polyethylene film blown by mixing polyethylene raw materials with different physical properties has better material mechanical properties, which is conducive to appropriately reducing the thickness of the film and thus reducing resource waste.

[0042] In addition, the selection of interlayer raw materials is crucial. Different types of raw materials require different temperatures in each temperature zone. High temperatures can cause the film bubble to become unstable and make cooling more difficult, while low temperatures can result in insufficient temperature. Calculating the temperature based on the melt index is not practical and requires testing and repeated testing.

[0043] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a polyethylene film, characterized in that, The preparation method includes the following steps: The components of the inner layer are mixed evenly and added to the inner layer hopper of the three-layer co-extrusion blown film machine. By mass percentage, the inner layer components consist of 70% HDPE-MH602 and 30% MLLDPE-1327CA. The components of the middle layer are mixed evenly and added to the middle layer hopper of the three-layer co-extrusion blown film machine. By mass percentage, the components of the middle layer consist of 35% HDPE-MH602, 35% HDPE-7000F and 30% MLLDPE-1327CA. The components of the outer layer are mixed evenly and added to the outer layer hopper of the three-layer co-extrusion blown film machine. By mass percentage, the components of the outer layer consist of 35% HDPE-MH602, 35% HDPE-HHMTR144 and 30% MLLDPE-1327CA. The three-layer co-extrusion blown film machine melts and extrudes the components in each hopper through the extrusion screws to the die head for blown film formation. The inner screw barrel temperature is 175-185℃, the middle screw barrel temperature is 185-195℃, the outer screw barrel temperature is 180-190℃, the die head runner temperature is 190-200℃, the die opening temperature is 195℃, and the blown film ratio is 1:2.5-1:

3.

2. The preparation method according to claim 1, characterized in that, The air-cooled temperature is 20-25℃.

3. The preparation method according to claim 1, characterized in that, The operating frequency of the cooling fan is greater than or equal to 40Hz.

4. The preparation method according to claim 1, characterized in that, The thickness of the inner layer is 30% of the total thickness of the film, the thickness of the middle layer is 40% of the total thickness of the film, and the thickness of the outer layer is 30% of the total thickness of the film.

5. The polyethylene film as described in claim 1, characterized in that, The thickness of the polyethylene film is less than 8 μm and greater than or equal to 5 μm.