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

Abstract

The invention relates to a high-strength polyethylene wrapping film, which is composed of an ABCBC five-layer composite structure, the A layer comprises linear low-density polyethylene, tackifying master batch and an elastomer; the layer B comprises linear low-density polyethylene, metallocene polyethylene and low-density polyethylene; and the layer C is made of linear low-density polyethylene. By optimizing the ratio of the linear low-density polyethylene to the additive among the layers, the vacuum degree of the preparation process and the cooling speed of the molten adhesive film on a cooling roller are improved, and the longitudinal and transverse tensile strength of the prepared polyethylene film is superior to that of the existing film. The prepared high-strength polyethylene wrapping film can be used in the field of heavy object packaging.

Description

Technical Field

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

[0002] Polyethylene stretch film is widely used in packaging of various items and logistics packaging due to its good flexibility, low cost, oil-proof and moisture-proof properties. With the expansion of application scenarios, in some special occasions such as packaging of heavy objects, the mechanical strength of the mainstream polyethylene stretch film on the market cannot meet the requirements. This is because the composition of polyethylene stretch film is relatively single, resulting in limited tensile strength and tear strength. The specific mechanical strength of polyethylene stretch film varies with changes in raw material formula and production process. The use of a multi-layer co-extrusion production process, combined with a certain proportion of modified masterbatch, metallocene and other materials, is an effective way to effectively improve the mechanical properties of the film. However, the ratio of each layer of components, including low-density polyethylene and metallocene, as well as the influence of the vacuum system and cooling roller cooling time in the processing technology on the final mechanical properties of the film are still unclear. Summary of the invention

[0003] In view of the above problems, the purpose of the present invention is to provide a high-strength polyethylene stretch film and a preparation method and application thereof. The preparation method provided by the present invention is suitable for large-scale application. At the same time, thanks to the material properties of metallocene polyethylene and low-density polyethylene, as well as the vacuum adsorption and rapid cooling design of the low-temperature forming roller in the processing technology, the prepared high-strength polyethylene stretch film has significant high-strength characteristics.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0005] A high-strength polyethylene wrapping film is characterized by having a multi-layer composite structure, with five layers of ABCBC distributed in sequence from the surface layer to the bottom layer.

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

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

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

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

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

[0011] (2) pouring the uniformly stirred film layer raw materials into feeders corresponding to different extrusion layers respectively, heating and melting them in stages, and then obtaining a multi-layer composite molten adhesive film by cast extrusion according to the distribution order of ABCBC;

[0012] (3) The molten film is vacuum-adsorbed onto a forming roller with water circulation to be cooled into a film, thereby finally obtaining a high-strength polyethylene wrapping film.

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

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

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

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

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

[0018] Preferably, the zoned heating and melting process of the high-strength wrapping film is divided into four stages, the temperature of the first stage is 160-180°C, the temperature of the second stage is 180-210°C, the temperature of the third stage is 210-230°C, and the temperature of the fourth stage is 230-260°C.

[0019] Preferably, the die head temperature of the high-strength stretch film cast extrusion process is 230-260°C.

[0020] Preferably, the vacuum degree of the high-strength stretch film vacuum adsorbed to the forming roller is 4-5 mbar, and the surface temperature of the forming roller is 23-25°C.

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

[0022] The present invention also provides application of the 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 the present invention gives full play to the material properties of low-density polyethylene, linear low-density polyethylene and metallocene polyethylene. In addition, the present invention improves the vacuum degree, reduces the time for the molten film extruded from the die to be adsorbed to the forming roller, and cooperates with the water circulation cooling system to accelerate the cooling speed of the molten film, thereby achieving a significant improvement in the strength of the film. DETAILED DESCRIPTION

[0025] Example 1

[0026] In order to further illustrate the present invention, a high-strength polyethylene wrapping film provided by the present invention and its preparation method and application are described in detail below in conjunction with embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0027] (1) The raw materials of different layers are weighed in proportion, poured into a mixer and stirred evenly to obtain raw materials of different film layers; the high-strength polyethylene wrapping film includes two layers of A layer composition, two layers of B layer composition, and one layer of 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; 5 parts of low-density polyethylene; and the C layer is 100 parts of linear low-density polyethylene. The thickness ratio of different layers of the high-strength wrapping film ABCBC is 2:7:2:7:2, and the total thickness of the wrapping film is 20 μm.

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

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

[0030] After testing, 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 elongations 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 elongations at break were 378% and 826%, respectively.

[0031] Example 2

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

[0033] (1) The raw materials of different layers are weighed in proportion, poured into a mixer and stirred evenly to obtain raw materials of different film layers; the high-strength polyethylene wrapping film includes two layers of A layer composition, two layers of B layer composition, and one layer of 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; 5 parts of low-density polyethylene; and the C layer is 100 parts of linear low-density polyethylene. The thickness ratio of different layers of the high-strength wrapping film ABCBC is 2:7:2:7:2, and the total thickness of the wrapping film is 20 μm.

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

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

[0036] After testing, 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 elongations 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 elongations at break were 447% and 755%, respectively.

[0037] Example 3

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

[0039] (1) The raw materials of different layers are weighed in proportion, poured into a mixer and stirred evenly to obtain raw materials of different film layers; the high-strength polyethylene wrapping film includes two layers of A layer composition, two layers of B layer composition, and one layer of 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; 3 parts of low-density polyethylene; and the C layer is 100 parts of linear low-density polyethylene. The thickness ratio of different layers of the high-strength wrapping film ABCBC is 2:7:2:7:2, and the total thickness of the wrapping film is 25 μm.

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

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

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

[0043] Example 4

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

[0045] (1) The raw materials of different layers are weighed in proportion, poured into a mixer and stirred evenly to obtain raw materials of different film layers; the high-strength polyethylene wrapping film includes two layers of A layer composition, two layers of B layer composition, and one layer of 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; 5 parts of low-density polyethylene; and the C layer is 100 parts of linear low-density polyethylene. The thickness ratio of different layers of the high-strength wrapping film ABCBC is 2:7:2:7:2, and the total thickness of the wrapping film is 18 μm.

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

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

[0048] After testing, 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 elongations 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 elongations at break were 453% and 823%, respectively.

[0049] Example 5

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

[0051] (1) The raw materials of different layers are weighed in proportion, poured into a mixer and stirred evenly to obtain raw materials of different film layers; the high-strength polyethylene wrapping film includes two layers of A layer composition, two layers of B layer composition, and one layer of 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 is 65 parts of linear low-density polyethylene, 30 parts of metallocene polyethylene; 5 parts of low-density polyethylene; and the C layer is 100 parts of linear low-density polyethylene. The thickness ratio of different layers of the high-strength wrapping film ABCBC is 2:7:2:7:2, and the total thickness of the wrapping film is 15 μm.

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

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

[0054] After testing, 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 elongations 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 elongations at break were 437% and 833%, respectively.

Claims

1. A method for preparing a high-strength polyethylene stretch film, characterized in that: The following steps are involved: (1) weighing the raw materials of different layers of ABCBC according to the proportion, pouring them into a mixer and stirring them evenly to obtain raw materials of different film layers; (2) pouring the uniformly stirred film layer raw materials into feeders corresponding to different extrusion layers respectively, heating and melting them in stages, and then obtaining a multi-layer composite molten adhesive film by cast extrusion according to the distribution order of ABCBC; (3) The molten film is vacuum-adsorbed onto a forming roller with water circulation to be cooled into a film, thereby finally obtaining a high-strength polyethylene wrapping film.

2. The preparation method according to claim 1, characterized in that: The raw material ratio of the A layer of the high-strength wrapping film is as follows: 88-93% of linear low-density polyethylene, 4-7% of tackifying masterbatch, and 3-5% of elastomer.

3. The preparation method according to claim 1, characterized in that: The raw material ratio of the high-strength wrapping film layer B is: 50-80% of linear low-density polyethylene, 17-40% of metallocene polyethylene, and 3-10% of low-density polyethylene.

4. The preparation method according to claim 1, characterized in that: The high-strength wrapping film layer C is made of linear low-density polyethylene.

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

6. The preparation method according to claim 1, characterized in that: The linear low-density polyethylene melt index is 1.95-2g / 10min, the low-density polyethylene melt index is 1.9-2g / 10min, the metallocene polyethylene melt index is 1-1.2g / 10min, the viscosity-enhancing masterbatch melt index is 15-20g / 10min, and the elastomer melt index is 1.4-3.7g / 10min.

7. The preparation method according to claim 1, characterized in that: The high-strength wrapping film zone heating and melting process is divided into four stages, the temperature of the first stage is 160-180°C, the temperature of the second stage is 180-210°C, the temperature of the third stage is 210-230°C, and the temperature of the fourth stage is 230-260°C.

8. The preparation method according to claim 1, characterized in that: The die head temperature of the high-strength stretch film cast extrusion process is 230-260°C.

9. The preparation method according to claim 1, characterized in that: The vacuum degree of the high-strength stretch film vacuum adsorbed to the forming roller is 4-5 mbar, and the surface temperature of the forming roller is 23-25°C.

10. The high-strength stretch film prepared by the preparation method according to any one of claims 1 to 10 comprises a 5-layer structure, the distribution order is ABCBC, and the polyethylene stretch film has high strength characteristics by virtue of the material properties of metallocene polyethylene and low-density polyethylene, combined with vacuum adsorption and rapid cooling of low-temperature forming rollers, wherein layer A comprises linear low-density polyethylene, a tackifier masterbatch, and an elastomer; layer B comprises linear low-density polyethylene, metallocene polyethylene, and low-density polyethylene; and layer C is linear low-density polyethylene.

11. Use of the high-strength polyethylene wrapping film according to claim 11 in the field of heavy object packaging.