High-strength polyethylene wrapping film and preparation method and application thereof

Abstract

A high strength polyethylene wrapping film is formed from a five layer composite structure of ABCBC, wherein layer A comprises linear low density polyethylene, tackifying masterbatch, and elastomer; layer B comprises linear low density polyethylene, metallocene polyethylene, and low density polyethylene; and layer C comprises linear low density polyethylene. By optimizing the ratio of linear low density polyethylene to additives between the layers, and by increasing the vacuum level of the manufacturing process and the cooling speed of the melt film on the chill roll, the resulting polyethylene film has superior tensile strength in both the machine direction and the cross direction than existing films. The high strength polyethylene wrapping film can be used in the field of heavy weight packaging.

Description

Technical Field

[0001] This invention relates to a high-strength polyethylene wrapping film, its preparation method, and its application, belonging to the field of polymer films. Background Technology

[0002] Polyethylene stretch film, due to its good flexibility, low cost, and oil and moisture resistance, is widely used in various product packaging and logistics packaging. However, with the expansion of applications, in some special situations such as heavy-duty packaging, the mechanical strength of mainstream polyethylene stretch film currently on the market is insufficient. This is because the composition of polyethylene stretch film is relatively simple, resulting in limited tensile and tear strength. The specific mechanical strength of polyethylene stretch film varies with the raw material formulation and production process. Using a multi-layer co-extrusion production process, by incorporating a certain proportion of modified masterbatch, metallocene, and other materials, is an effective way to improve the mechanical properties of the film. However, the influence of the ratio of each layer component, including low-density polyethylene and metallocene, as well as the cooling time of the vacuum system and cooling rollers in the processing technology, on the final mechanical properties of the film remains unclear. Summary of the Invention

[0003] To address the above problems, the present invention aims to provide a high-strength polyethylene stretch film, its preparation method, and its application. The preparation method provided by the present invention is suitable for large-scale application. Furthermore, thanks to the material properties of metallocene polyethylene and low-density polyethylene, as well as the rapid cooling design of vacuum adsorption and low-temperature forming rollers in the processing technology, the prepared high-strength polyethylene stretch film has significant high-strength characteristics.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0005] A high-strength polyethylene stretch film is characterized by having a multi-layer composite structure, consisting of five layers (ABCBC) distributed sequentially from the surface layer to the bottom layer.

[0006] Preferably, layer A comprises linear low-density polyethylene, tackifying masterbatch, and elastomer.

[0007] Preferably, the B layer comprises linear low-density polyethylene, metallocene polyethylene, or low-density polyethylene.

[0008] Preferably, the C layer is linear low-density polyethylene.

[0009] A method for preparing high-strength polyethylene stretch film includes the following steps:

[0010] (1) Weigh the raw materials of different layers ABCBC according to the proportion, pour them into the mixer and stir evenly to obtain raw materials of different film layers;

[0011] (2) Pour the well-stirred film material into the feeder corresponding to different extrusion layers, heat and melt it in stages, and obtain a multi-layer composite melt film by casting extrusion according to the distribution order of ABCBC.

[0012] (3) The molten adhesive film is vacuum-adsorbed onto a forming roller with water circulation and cooled into a thin film to finally obtain a high-strength polyethylene wrapping film.

[0013] Preferably, the raw material ratio of the high-strength wrapping film A layer is: 88-93% linear low-density polyethylene, 4-7% tackifying masterbatch, and 3-5% elastomer.

[0014] Preferably, the raw material ratio of the high-strength wrapping film B layer is: 50-80% linear low-density polyethylene, 17-40% metallocene polyethylene, and 3-10% low-density polyethylene.

[0015] Preferably, the high-strength wrapping film C layer is composed of linear low-density polyethylene.

[0016] Preferably, the thickness ratio of the different layers ABCBC of the high-strength wrapping film is 2:7:2:7:2, and the total thickness of the wrapping film is 15-25μm.

[0017] Preferably, the linear low-density polyethylene has a melt index of 1.95-2 g / 10 min, the low-density polyethylene has a melt index of 1.9-2 g / 10 min, the metallocene polyethylene has a melt index of 1-1.2 g / 10 min, the tackifying masterbatch has a melt index of 15-20 g / 10 min, and the elastomer has a melt index of 1.4-3.7 g / 10 min.

[0018] Preferably, the high-strength wrapping film is heated and melted in four stages: the first stage temperature is 160-180℃, the second stage temperature is 180-210℃, the third stage temperature is 210-230℃, and the fourth stage temperature is 230-260℃.

[0019] Preferably, the die temperature of the high-strength wrapping film casting extrusion process is 230-260℃.

[0020] Preferably, the vacuum degree of the high-strength wrapping film vacuum adsorbed onto the forming roller is 4-5 mbar, and the surface temperature of the forming roller is 23-25℃.

[0021] The present invention also provides a high-strength polyethylene wrapping film prepared by the preparation method described above, comprising a 5-layer structure distributed in the order ABCBC. By utilizing the material properties of metallocene polyethylene and low-density polyethylene, combined with the rapid cooling effect of vacuum adsorption and low-temperature forming rollers, the polyethylene wrapping film has high strength characteristics.

[0022] The present invention also provides the application of the above-mentioned high-strength polyethylene film in the field of heavy object packaging.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The multi-layer structure design in this invention maximizes the material properties of low-density polyethylene, linear low-density polyethylene, and metallocene polyethylene. In addition, by increasing the vacuum level, this invention reduces the time for the molten film extruded from the die to be adsorbed onto the forming roller. Combined with a water circulation cooling system, this accelerates the cooling speed of the molten film, resulting in a significant improvement in film strength. Detailed Implementation

[0025] Example 1

[0026] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, provides a high-strength polyethylene stretch film, its preparation method, and its applications. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0027] (1) Weigh the raw materials of different layers according to the proportions, pour them into the mixer and stir evenly to obtain raw materials of different film layers; the high-strength polyethylene stretch film includes two A-layer compositions, two B-layer compositions, and one C-layer composition, and is composed in the order of ABCBA, wherein the A-layer includes 90 parts of linear low-density polyethylene, 5 parts of tackifying masterbatch, and 5 parts of elastomer; the B-layer is 70 parts of linear low-density polyethylene, 25 parts of metallocene polyethylene, and 5 parts of low-density polyethylene; the C-layer is 100 parts of linear low-density polyethylene. The thickness ratio of the different layers ABCBC of the high-strength stretch film is 2:7:2:7:2, and the total thickness of the stretch film is 20μm.

[0028] (2) Pour the well-stirred film material into the feeders corresponding to different extrusion layers, and heat and melt it in stages (the temperature of the first stage is 160℃, the temperature of the second stage is 180℃, the temperature of the third stage is 210℃, the temperature of the fourth stage is 230℃, and the die head temperature is 230℃). Extrusion casting is used to obtain a multi-layer composite molten adhesive film.

[0029] (3) The molten adhesive film is vacuum adsorbed onto a forming roller with water circulation and cooled into a thin film. The vacuum degree is set to 5 mbar and the surface temperature of the forming roller is 23°C. Finally, a high-strength polyethylene wrapping film is obtained.

[0030] Tests showed that the longitudinal and transverse tensile strengths of the wrapping film without vacuum adsorption were 40 MPa and 17 MPa, respectively, and the longitudinal and transverse elongation at break were 626% and 822%, respectively. The high-strength polyethylene wrapping film prepared in this embodiment had longitudinal and transverse tensile strengths of 55 MPa and 20 MPa, respectively, and the longitudinal and transverse elongation at break were 378% and 826%, respectively.

[0031] Example 2

[0032] This embodiment provides a method for preparing high-strength polyethylene stretch film, including the following steps:

[0033] (1) Weigh the raw materials of different layers according to the proportions, pour them into the mixer and stir evenly to obtain raw materials of different film layers; the high-strength polyethylene stretch film includes two A-layer compositions, two B-layer compositions, and one C-layer composition, and is composed in the order of ABCBA, wherein the A-layer includes 90 parts of linear low-density polyethylene, 5 parts of tackifying masterbatch, and 5 parts of elastomer; the B-layer is 70 parts of linear low-density polyethylene, 25 parts of metallocene polyethylene, and 5 parts of low-density polyethylene; the C-layer is 100 parts of linear low-density polyethylene. The thickness ratio of the different layers ABCBC of the high-strength stretch film is 2:7:2:7:2, and the total thickness of the stretch film is 20μm.

[0034] (2) Pour the well-stirred film material into the feeders corresponding to different extrusion layers, and heat and melt it in stages (the temperature of the first stage is 160℃, the temperature of the second stage is 180℃, the temperature of the third stage is 210℃, the temperature of the fourth stage is 230℃, and the die head temperature is 230℃). Extrusion casting is used to obtain a multi-layer composite molten adhesive film.

[0035] (3) The molten adhesive film is vacuum adsorbed onto a forming roller with water circulation and cooled into a thin film. The vacuum degree is set to 4.8 mbar and the surface temperature of the forming roller is 23°C. Finally, a high-strength polyethylene wrapping film is obtained.

[0036] Tests showed that the longitudinal and transverse tensile strengths of the wrapping film without vacuum adsorption were 40 MPa and 17 MPa, respectively, and the longitudinal and transverse elongation at break were 626% and 822%, respectively. The high-strength polyethylene wrapping film prepared in this embodiment had longitudinal and transverse tensile strengths of 47 MPa and 24 MPa, respectively, and the longitudinal and transverse elongation at break were 447% and 755%, respectively.

[0037] Example 3

[0038] This embodiment provides a method for preparing high-strength polyethylene stretch film, including the following steps:

[0039] (1) Weigh the raw materials of different layers according to the proportions, pour them into the mixer and stir evenly to obtain raw materials of different film layers; the high-strength polyethylene stretch film includes two A-layer compositions, two B-layer compositions, and one C-layer composition, and is composed in the order of ABCBA, wherein the A-layer includes 92 parts of linear low-density polyethylene, 5 parts of tackifying masterbatch, and 3 parts of elastomer; the B-layer is 80 parts of linear low-density polyethylene, 17 parts of metallocene polyethylene, and 3 parts of low-density polyethylene; the C-layer is 100 parts of linear low-density polyethylene. The thickness ratio of the different layers ABCBC of the high-strength stretch film is 2:7:2:7:2, and the total thickness of the stretch film is 25μm.

[0040] (2) Pour the well-stirred film material into the feeders corresponding to different extrusion layers, and heat and melt it in stages (the temperature of the first stage is 180℃, the temperature of the second stage is 200℃, the temperature of the third stage is 220℃, the temperature of the fourth stage is 240℃, and the die head temperature is 245℃). Extrusion casting is used to obtain a multi-layer composite molten adhesive film.

[0041] (3) The molten adhesive film is vacuum adsorbed onto a forming roller with water circulation and cooled into a thin film. The vacuum degree is set to 4.5 mbar, and finally a high-strength polyethylene wrapping film is obtained.

[0042] Tests showed that the longitudinal and transverse tensile strengths of the wrapping film without vacuum adsorption were 36 MPa and 20 MPa, respectively, and the longitudinal and transverse elongation at break were 552% and 706%, respectively. The high-strength polyethylene wrapping film prepared in this embodiment had longitudinal and transverse tensile strengths of 48 MPa and 19 MPa, respectively, and the longitudinal and transverse elongation at break were 439% and 755%, respectively.

[0043] Example 4

[0044] This embodiment provides a method for preparing high-strength polyethylene stretch film, including the following steps:

[0045] (1) Weigh the raw materials of different layers according to the proportions, pour them into the mixer and stir evenly to obtain raw materials of different film layers; the high-strength polyethylene stretch film includes two A-layer compositions, two B-layer compositions, and one C-layer composition, and is composed in the order of ABCBA, wherein the A-layer includes 88 parts of linear low-density polyethylene, 7 parts of tackifying masterbatch, and 5 parts of elastomer; the B-layer is 65 parts of linear low-density polyethylene, 30 parts of metallocene polyethylene, and 5 parts of low-density polyethylene; the C-layer is 100 parts of linear low-density polyethylene. The thickness ratio of the different layers ABCBC of the high-strength stretch film is 2:7:2:7:2, and the total thickness of the stretch film is 18μm.

[0046] (2) Pour the well-stirred film material into the feeders corresponding to different extrusion layers, and heat and melt it in stages (the temperature of the first stage is 160℃, the temperature of the second stage is 190℃, the temperature of the third stage is 210℃, the temperature of the fourth stage is 245℃, and the die head temperature is 250℃). Extrusion casting is used to obtain a multi-layer composite molten adhesive film.

[0047] (3) The molten adhesive film is vacuum adsorbed onto a forming roller with water circulation and cooled into a thin film. The vacuum degree is set to 4.4 mbar and the surface temperature of the forming roller is 24°C. Finally, a high-strength polyethylene wrapping film is obtained.

[0048] Tests showed that the longitudinal and transverse tensile strengths of the wrapping film without vacuum adsorption were 51 MPa and 21 MPa, respectively, and the longitudinal and transverse elongation at break were 546% and 713%, respectively. The high-strength polyethylene wrapping film prepared in this embodiment had longitudinal and transverse tensile strengths of 52 MPa and 22 MPa, respectively, and the longitudinal and transverse elongation at break were 453% and 823%, respectively.

[0049] Example 5

[0050] This embodiment provides a method for preparing high-strength polyethylene stretch film, including the following steps:

[0051] (1) Weigh the raw materials of different layers according to the proportions, pour them into the mixer and stir evenly to obtain raw materials of different film layers; the high-strength polyethylene stretch film includes two A-layer compositions, two B-layer compositions, and one C-layer composition, and is composed in the order of ABCBA, wherein the A-layer includes 90 parts of linear low-density polyethylene, 4 parts of tackifying masterbatch, and 6 parts of elastomer; the B-layer consists of 65 parts of linear low-density polyethylene, 30 parts of metallocene polyethylene, and 5 parts of low-density polyethylene; the C-layer consists of 100 parts of linear low-density polyethylene. The thickness ratio of the different layers ABCBC of the high-strength stretch film is 2:7:2:7:2, and the total thickness of the stretch film is 15μm.

[0052] (2) Pour the well-stirred film material into the feeders corresponding to different extrusion layers, and heat and melt it in stages (the temperature of the first stage is 165℃, the temperature of the second stage is 200℃, the temperature of the third stage is 220℃, the temperature of the fourth stage is 250℃, and the die head temperature is 250℃). Extrusion casting is used to obtain a multi-layer composite molten adhesive film.

[0053] (3) The molten adhesive film is vacuum adsorbed onto a forming roller with water circulation and cooled into a thin film. The vacuum degree is set to 4 mbar and the surface temperature of the forming roller is 24°C. Finally, a high-strength polyethylene wrapping film is obtained.

[0054] Tests showed that the longitudinal and transverse tensile strengths of the wrapping film without vacuum adsorption were 50 MPa and 19 MPa, respectively, and the longitudinal and transverse elongation at break were 386% and 631%, respectively. The high-strength polyethylene wrapping film prepared in this embodiment had longitudinal and transverse tensile strengths of 54 MPa and 20 MPa, respectively, and the longitudinal and transverse elongation at break were 437% and 833%, respectively.

Claims

1. A method for preparing a high-strength polyethylene stretch film, characterized in that, Includes the following steps: (1) Weigh the raw materials of different layers ABCBC according to the proportion, pour them into the mixer and stir evenly to obtain raw materials of different film layers; (2) Pour the uniformly stirred film material into the feeder corresponding to different extrusion layers, heat and melt it in stages, and obtain a multi-layer composite melt film by casting extrusion according to the distribution order of ABCBC. (3) The molten adhesive film is vacuum adsorbed onto a forming roller with water circulation and cooled into a thin film to finally obtain a high-strength polyethylene wrapping film; wherein, the raw material ratio of the A layer of the high-strength wrapping film is: 88-93% linear low-density polyethylene, 4-7% tackifying masterbatch, and 3-5% elastomer; the raw material ratio of the B layer of the high-strength wrapping film is: 50-80% linear low-density polyethylene, 17-40% metallocene polyethylene, and 3-10% low-density polyethylene; the C layer of the high-strength wrapping film is composed of linear low-density polyethylene.

2. The preparation method according to claim 1, characterized in that, The thickness ratio of the different layers of the high-strength stretch film ABCBC is 2:7:2:7:2, and the total thickness of the stretch film is 15-25μm.

3. The preparation method according to claim 1, characterized in that, The linear low-density polyethylene has a melt index of 1.95-2 g / 10 min, the low-density polyethylene has a melt index of 1.9-2 g / 10 min, the metallocene polyethylene has a melt index of 1-1.2 g / 10 min, the tackifying masterbatch has a melt index of 15-20 g / 10 min, and the elastomer has a melt index of 1.4-3.7 g / 10 min.

4. The preparation method according to claim 1, characterized in that, The high-strength wrapping film undergoes a zoned heating and melting process, which is divided into four stages: the first stage temperature is 160-180℃, the second stage temperature is 180-210℃, the third stage temperature is 210-230℃, and the fourth stage temperature is 230-260℃.

5. The preparation method according to claim 1, characterized in that, The die temperature of the high-strength wrapping film casting extrusion process is 230-260℃.

6. The preparation method according to claim 1, characterized in that, The high-strength wrapping film is vacuum-adsorbed onto the forming roller at a vacuum level of 4-5 mbar, and the surface temperature of the forming roller is 23-25℃.

7. The high-strength winding film prepared by any one of the preparation methods of claims 1-6 comprises a 5-layer structure, distributed in the order ABCBC. Utilizing the material properties of metallocene polyethylene and low-density polyethylene, and combined with vacuum adsorption and rapid cooling by a low-temperature forming roller, the polyethylene winding film exhibits high strength characteristics. Layer A comprises linear low-density polyethylene, tackifying masterbatch, and elastomer; layer B comprises linear low-density polyethylene, metallocene polyethylene, and low-density polyethylene; and layer C is linear low-density polyethylene.

8. The application of the high-strength polyethylene stretch film according to claim 7 in the field of heavy object packaging.