A cold drawn sleeve packaging film and a method of making the same

Abstract

The present application relates to the technical fields of polyolefin film material, and relates to a cold-stretching sleeve packaging film and a preparation method thereof.The present application discloses a cold-stretching sleeve packaging film, which is composed of an inner layer, a middle layer and an outer layer.The raw material of the inner layer comprises 30-60 wt% of metallocene linear low-density polyethylene (mLLDPE) and 40-70 wt% of linear low-density polyethylene (LLDPE).The raw material of the middle layer comprises 20-70 wt% of metallocene linear low-density polyethylene (mLLDPE), 10-30 wt% of linear low-density polyethylene (LLDPE) and 1-40 wt% of a pre-dispersed component.The raw material of the outer layer comprises 10-60 wt% of metallocene linear low-density polyethylene (mLLDPE), 10-40 wt% of linear low-density polyethylene (LLDPE) and 1-40 wt % of a pre-dispersed component.The pre-dispersed component is prepared by high-speed mixing and pre-mixing of metallocene linear low-density polyethylene (mLLDPE) virgin powder, non-tangled ultra-high molecular weight polyethylene (UHMWPE) virgin powder and a low-melting-point dispersant.The low-melting-point dispersant is polyethylene wax and polyethylene glycol.

Description

Technical Field

[0001] This invention belongs to the field of polyolefin film material technology, and relates to a cold-stretched sleeve packaging film and its preparation method. Background Technology

[0002] In synthetic resin manufacturing plants, products are typically packaged in 25 kg heavy-duty packaging bags. After packaging, the goods are stacked on pallets, usually one or two tons per pallet. To prevent contamination of the primary packaging bags during handling and storage, and also to protect against rain, cold-stretch sleeve packaging film is used for secondary containerization of the products.

[0003] The performance requirements of cold-stretch sleeve packaging film mainly include three aspects: First, the shrinkage rate, which determines the tightness of the stacked goods after packaging; second, the tensile strength, which relates to the stability of the packaging; and third, the inner wall friction coefficient, which affects the smoothness of the packaging process.

[0004] Currently, cold-stretch tubing packaging films are mainly produced using a three-layer composite blown film process. The main raw materials include a mixture of mLLDPE and LLDPE, along with some additives. In accepted formulations, LLDPE typically accounts for 20% to 60% of the total raw materials, while mLLDPE accounts for 40% to 80%. Cold-stretch tubing packaging films produced using this formulation require a relatively thick film to meet the requirements for tensile strength and lateral shrinkage, resulting in higher film costs.

[0005] In order to reduce costs and achieve lightweight and green packaging, the thickness of cold-stretched tubing packaging film has been continuously reduced. This has led to a decrease in the tensile strength and lateral shrinkage rate of the cold-stretched tubing packaging film. This not only affects the effect of secondary containerization packaging, but also causes damage to goods and slippage of bags during storage and transportation. Summary of the Invention

[0006] The purpose of this invention is to address the aforementioned problems in the prior art by proposing a cold-stretched tubing packaging film that achieves thinning of the cold-stretched tubing packaging film while ensuring its mechanical properties.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] A cold-stretched tubular packaging film, comprising an inner layer, a middle layer, and an outer layer;

[0009] The inner layer is made of 30-60 wt% metallocene linear low-density polyethylene mLLDPE and 40-70 wt% linear low-density polyethylene LLDPE.

[0010] The raw materials for the middle layer include 20-70 wt% metallocene linear low-density polyethylene mLLDPE, 10-30 wt% linear low-density polyethylene LLDPE, and 1-40 wt% pre-dispersed components.

[0011] The outer layer consists of 10-60 wt% metallocene linear low-density polyethylene mLLDPE, 10-40 wt% linear low-density polyethylene LLDPE, and 1-40 wt% pre-dispersed components.

[0012] The pre-dispersed component is prepared by high-speed mixing and pre-mixing of metallocene linear low-density polyethylene mLLDPE raw powder, non-entanglement ultra-high molecular weight polyethylene UHMWPE raw powder and low-melting-point dispersant in a mass ratio of (60-90):(10-40):(1-30).

[0013] The low-melting-point dispersant is polyethylene wax and polyethylene glycol in a mass ratio of 1:(1-5).

[0014] Preferably, the inner layer is made of 30-50 wt% metallocene linear low-density polyethylene or 50-70 wt% linear low-density polyethylene.

[0015] The raw materials for the middle layer are 50-80 wt% metallocene linear low-density polyethylene, 10-50 wt% linear low-density polyethylene, and 1-20 wt% pre-dispersed components.

[0016] The outer layer is made of 40-70 wt% metallocene linear low-density polyethylene, 30-50 wt% linear low-density polyethylene, and 1-20 wt% pre-dispersed components.

[0017] Preferably, the amount of low-melting-point dispersant added to the pre-dispersed component is 20-60 wt% of the mass of the metallocene linear low-density polyethylene (mLLDPE) raw powder.

[0018] Preferably, the density of the metallocene linear low-density polyethylene (mLLDPE) raw powder is 0.918–0.922 g / cm³. 3 The melt flow rate is 1.5–4.5 g / 10 min (190℃ / 2.16 kg), and the particle size is 100–800 μm;

[0019] The density of linear low-density polyethylene (LLDPE) is 0.916–0.920 g / cm³. 3 The melt flow rate is 0.5–2.5 g / 10 min (190℃ / 2.16 kg).

[0020] Further preferably, the density of the metallocene linear low-density polyethylene (mLLDPE) raw material is 0.918–0.922 g / cm³.3 The melt flow rate is 1.5–2.5 g / 10 min (190℃ / 2.16 kg).

[0021] Preferably, the metallocene linear low-density polyethylene (mLLDPE) has a density of 0.918–0.922 g / cm³. 3 The melt flow rate is 1.5–4.5 g / 10 min (190℃ / 2.16 kg).

[0022] Preferably, the pre-dispersed component contains unentangled ultra-high molecular weight polyethylene (UHMWPE) raw material with a molecular weight of 1 million to 5 million, a particle size of 30 to 200 μm, and a density of 0.924 to 0.928 g / cm³. 3 .

[0023] Further optimization revealed that the molecular weight of the entanglement-free ultra-high molecular weight polyethylene raw material is 1 million to 2 million, and the particle size is 50 to 150 μm.

[0024] Further optimization yields unentangled ultra-high molecular weight polyethylene (UHMWPE) raw material with a molecular weight of 1.2 to 1.5 million and a particle size of 70 to 120 μm.

[0025] Further preferably, the particle size of the metallocene linear low-density polyethylene raw material is 200-400 μm.

[0026] Preferably, the metallocene linear low-density polyethylene in the inner, middle, and outer layers has the same or different melt flow rate and density as the metallocene linear low-density polyethylene raw material in the pre-dispersed component.

[0027] Further preferably, the metallocene linear low-density polyethylene in the inner / middle / outer layer has the same melt flow rate and density as the metallocene linear low-density polyethylene raw material in the pre-dispersed component.

[0028] Preferably, the thickness of the cold-stretched sleeve packaging film is 120±2μm.

[0029] A method for preparing a cold-stretched sleeve packaging film, the method comprising:

[0030] The various raw materials of the pre-dispersed components are placed in a twin-screw compounding extruder for pre-mixing at a processing temperature of 190–210℃. Then, the inner layer raw materials, middle layer raw materials, and outer layer raw materials are placed in a blown film extruder for blown film processing. The processing temperature of the inner layer blown film is 160–190℃, the processing temperature of the middle layer blown film is 170–210℃, and the processing temperature of the outer layer blown film is 165–200℃.

[0031] Preferably, the length-to-diameter ratio of the twin-screw compounding extruder is (25-35):1.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. The present invention adds pre-dispersed components to the middle and outer layers of the cold-stretched tubing packaging film to improve the lateral shrinkage rate and tensile strength of the cold-stretched tubing packaging film, thereby obtaining a relatively thin cold-stretched tubing packaging film with excellent comprehensive performance.

[0034] 2. In the pre-dispersed component of the present invention, a low-melting-point dispersant is added to the unentangled ultra-high molecular weight polyethylene (UHMWPE) raw powder and mLLDPE raw powder. This ensures that the UHMWPE molecular chains are more dispersed at the molecular level in the mLLDPE matrix. The low-melting-point dispersant acts as a lubricant for the molecular chains, promoting the movement of the UHMWPE molecular chains in the molten mixed state and promoting dispersion. It also avoids the formation of crystal points in the film due to the entanglement of UHMWPE molecular chains, which would affect the film reinforcement effect.

[0035] 3. By adjusting the formulations of the inner, middle, and outer layers, this invention achieves thinning of the cold-stretched tubing packaging film while ensuring its mechanical properties. Detailed Implementation

[0036] The following are specific embodiments of the present invention, which further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0037] Unless otherwise specified, the materials used in this invention are commercially available products, and the methods used are conventional technical means.

[0038] In this invention, the raw materials include:

[0039] Metallocene linear low-density polyethylene (mLLDPE): In-house prepared by copolymerizing ethylene and 1-hexene using a metallocene catalyst. MFR value: 2.1 ± 0.3 g / 10 min; density: 0.920 ± 0.002 g / cm³. 3 Linear low-density polyethylene with an average particle size of 310 μm;

[0040] Metallocene linear low-density polyethylene (mLLDPE) raw material: self-made, produced by copolymerization with metallocene catalyst and 1-hexene, with an MFR value of 2.1±0.3 g / 10 min and a density of 0.920±0.002 g / cm³. 3 Linear low-density polyethylene with an average particle size of 310 μm;

[0041] Linear low-density polyethylene (LLDPE): Guangzhou Petrochemical, model DFDA7068;

[0042] Untangled ultra-high molecular weight polyethylene (UHMWPE) raw material: self-made, polymerized via titanium-based catalyst slurry method, molecular weight 1.4 million, average particle size 100μm, density 0.926±0.002g / cm³ 3 .

[0043] In this invention, metallocene linear low-density polyethylene mLLDPE raw powder and non-entangled ultra-high molecular weight polyethylene UHMWPE raw powder can be replaced by commercially available products that meet the requirements of this invention.

[0044] In this invention, the target thickness of the cold-stretched sleeve packaging film is 120 μm, and the actual thickness is ±2 μm.

[0045] In this invention, the cold-stretched sleeve packaging film is tested according to the T / ZZB 1008-2019 standard, and the specific test method is as follows:

[0046] Tensile strength was tested in accordance with GB / T 1040.3-2006.

[0047] The elongation at break was tested in accordance with GB / T 1040.3-2006.

[0048] Right-angle tear strength shall be tested in accordance with QB / T1130.

[0049] The impact strength of the dart was tested in accordance with GB / T 9639.1-2008.

[0050] The elastic recovery rate was tested in accordance with GB / T 1040.3-2006.

[0051] Example 1

[0052] In this embodiment, the thickness of the cold-stretched sleeve packaging film is 121 μm, and the film thickness ratio of the inner layer / middle layer / outer layer is 1 / 3 / 1;

[0053] Preparation of the pre-dispersed component: Weigh 90 parts of metallocene linear low-density polyethylene (mLLDPE) raw powder, 10 parts of non-entanglement ultra-high molecular weight polyethylene (UHMWPE) raw powder, and 2 parts of low-melting-point dispersant (polyethylene wax and polyethylene glycol in a mass ratio of 1:2); mix the metallocene linear low-density polyethylene (mLLDPE) raw powder, non-entanglement ultra-high molecular weight polyethylene (UHMWPE) raw powder, and low-melting-point dispersant at high speed for 2 minutes, and then perform mixing and extrusion on a twin-screw compounding granulator at a melt temperature of 190-210℃ to obtain the pre-dispersed component, which is then directly added to the middle and outer film extruders of the composite film.

[0054] The inner layer consists of 40 parts of metallocene linear low-density polyethylene mLLDPE and 60 parts of linear low-density polyethylene LLDPE.

[0055] The raw materials for the middle layer include 70 parts of metallocene linear low-density polyethylene mLLDPE, 30 parts of linear low-density polyethylene LLDPE, and 20 parts of pre-dispersed components.

[0056] The outer layer consists of 60 parts of metallocene linear low-density polyethylene mLLDPE, 40 parts of linear low-density polyethylene LLDPE, and 10 parts of pre-dispersed components.

[0057] The preparation method of cold-stretched tubular packaging film includes: placing the inner layer raw material, middle layer raw material, and outer layer raw material into the hoppers of the inner layer, middle layer, and outer layer blown film extruders, respectively; simultaneously, metering the pre-dispersed components into the middle layer and outer layer blown film extruders for blown film processing; the inner layer blown film extrusion processing temperature is 175±5℃, the middle layer blown film extrusion processing temperature is 185±5℃, and the outer layer blown film extrusion processing temperature is 180±5℃; thus obtaining the cold-stretched tubular packaging film.

[0058] The specific performance of the cold-stretched tubing packaging film in this embodiment is shown in Table 1. It can be seen that the performance of the cold-stretched tubing packaging film meets the requirements of T / ZZB 1008-2019.

[0059] Example 2

[0060] In this embodiment, the thickness of the cold-stretched sleeve packaging film is 119 μm, and the film thickness ratio of the inner layer / middle layer / outer layer is 1 / 3 / 1;

[0061] Preparation of pre-dispersed components: Weigh 60 parts of metallocene linear low-density polyethylene mLLDPE raw powder, 40 parts of non-entangled ultra-high molecular weight polyethylene UHMWPE raw powder, and 24 parts of low-melting-point dispersant (polyethylene wax and polyethylene glycol in a mass ratio of 1:2); other preparation methods are the same as in Example 1.

[0062] The inner layer consists of 40 parts of metallocene linear low-density polyethylene mLLDPE and 60 parts of linear low-density polyethylene LLDPE.

[0063] The raw materials for the middle layer include 70 parts of metallocene linear low-density polyethylene mLLDPE, 30 parts of linear low-density polyethylene LLDPE, and 5 parts of pre-dispersed components.

[0064] The outer layer consists of 60 parts of metallocene linear low-density polyethylene mLLDPE, 40 parts of linear low-density polyethylene LLDPE, and 2.5 parts of pre-dispersed components.

[0065] Preparation method of cold-stretched sleeve packaging film: same as in Example 1.

[0066] The specific performance of the cold-stretched tubing packaging film in this embodiment is shown in Table 1. It can be seen that the performance of the cold-stretched tubing packaging film meets the requirements of T / ZZB 1008-2019.

[0067] Example 3

[0068] In this embodiment, the thickness of the cold-stretched sleeve packaging film is 120μm, and the film thickness ratio of the inner layer / middle layer / outer layer is 1 / 3 / 1;

[0069] Preparation of pre-dispersed components: Weigh 80 parts of metallocene linear low-density polyethylene mLLDPE raw powder, 20 parts of non-entangled ultra-high molecular weight polyethylene UHMWPE raw powder, and 7 parts of low-melting-point dispersant (polyethylene wax and polyethylene glycol in a mass ratio of 1:2); other preparation methods are the same as in Example 1.

[0070] The inner layer consists of 40 parts of metallocene linear low-density polyethylene mLLDPE and 60 parts of linear low-density polyethylene LLDPE.

[0071] The raw materials for the middle layer include 70 parts of metallocene linear low-density polyethylene mLLDPE, 30 parts of linear low-density polyethylene LLDPE, and 10 parts of pre-dispersed components.

[0072] The outer layer consists of 60 parts of metallocene linear low-density polyethylene mLLDPE, 40 parts of linear low-density polyethylene LLDPE, and 5 parts of pre-dispersed components.

[0073] Preparation method of cold-stretched sleeve packaging film: same as in Example 1.

[0074] The specific performance of the cold-stretched tubing packaging film in this embodiment is shown in Table 1. It can be seen that the performance of the cold-stretched tubing packaging film meets the requirements of T / ZZB 1008-2019.

[0075] Example 4

[0076] In this embodiment, the thickness of the cold-stretched sleeve packaging film is 122 μm, and the film thickness ratio of the inner layer / middle layer / outer layer is 1 / 3 / 1;

[0077] Preparation of pre-dispersed components: Weigh 75 parts of metallocene linear low-density polyethylene mLLDPE raw powder, 25 parts of non-entangled ultra-high molecular weight polyethylene UHMWPE raw powder, and 11 parts of low-melting-point dispersant (polyethylene wax and polyethylene glycol in a mass ratio of 1:2); other preparation methods are the same as in Example 1.

[0078] The inner layer consists of 40 parts of metallocene linear low-density polyethylene mLLDPE and 60 parts of linear low-density polyethylene LLDPE.

[0079] The raw materials for the middle layer include 70 parts of metallocene linear low-density polyethylene mLLDPE, 30 parts of linear low-density polyethylene LLDPE, and 10 parts of pre-dispersed components.

[0080] The outer layer consists of 60 parts of metallocene linear low-density polyethylene mLLDPE, 40 parts of linear low-density polyethylene LLDPE, and 5 parts of pre-dispersed components.

[0081] Preparation method of cold-stretched sleeve packaging film: same as in Example 1.

[0082] The specific performance of the cold-stretched tubing packaging film in this embodiment is shown in Table 1. It can be seen that the performance of the cold-stretched tubing packaging film meets the requirements of T / ZZB 1008-2019.

[0083] Example 5

[0084] In this embodiment, the thickness of the cold-stretched sleeve packaging film is 118 μm, and the film thickness ratio of the inner layer / middle layer / outer layer is 1 / 3 / 1;

[0085] Preparation of pre-dispersed components: Weigh 70 parts of metallocene linear low-density polyethylene mLLDPE raw powder, 30 parts of non-entangled ultra-high molecular weight polyethylene UHMWPE raw powder, and 15 parts of low-melting-point dispersant (polyethylene wax and polyethylene glycol in a mass ratio of 1:2); other preparation methods are the same as in Example 1.

[0086] The inner layer consists of 40 parts of metallocene linear low-density polyethylene mLLDPE and 60 parts of linear low-density polyethylene LLDPE.

[0087] The raw materials for the middle layer include 70 parts of metallocene linear low-density polyethylene mLLDPE, 30 parts of linear low-density polyethylene LLDPE, and 8 parts of pre-dispersed components.

[0088] The outer layer consists of 60 parts of metallocene linear low-density polyethylene mLLDPE, 40 parts of linear low-density polyethylene LLDPE, and 5 parts of pre-dispersed components.

[0089] Preparation method of cold-stretched sleeve packaging film: same as in Example 1.

[0090] The specific performance of the cold-stretched tubing packaging film in this embodiment is shown in Table 1. It can be seen that the performance of the cold-stretched tubing packaging film meets the requirements of T / ZZB 1008-2019.

[0091] Comparative Example 1

[0092] In this comparative example, the thickness of the cold-stretched sleeve packaging film is 133 μm, and the film thickness ratio of the inner layer / middle layer / outer layer is 1 / 3 / 1;

[0093] The inner layer consists of 40 parts of metallocene linear low-density polyethylene mLLDPE and 60 parts of linear low-density polyethylene LLDPE.

[0094] The raw materials for the middle layer include 70 parts of metallocene linear low-density polyethylene mLLDPE and 30 parts of linear low-density polyethylene LLDPE.

[0095] The outer layer consists of 60 parts of metallocene linear low-density polyethylene mLLDPE and 40 parts of linear low-density polyethylene LLDPE.

[0096] Preparation method of cold-stretched sleeve packaging film: same as in Example 1.

[0097] The specific performance of the cold-stretched sleeve packaging film in this comparative example is shown in Table 1.

[0098] In this comparative example, the cold-stretched tubing packaging film is the commonly used cold-stretched tubing packaging film on the market, which meets the performance requirements, but has a relatively large thickness.

[0099] Comparative Example 2

[0100] Compared with Comparative Example 1, the difference is that the thickness of the cold-stretched sleeve packaging film in this comparative example is 120 μm, and the film thickness ratio of the inner layer / middle layer / outer layer is 1 / 3 / 1.

[0101] The specific performance of the cold-stretched sleeve packaging film in this comparative example is shown in Table 1.

[0102] Comparative Example 3

[0103] The difference compared to Example 4 is that no low-melting-point dispersant is added to the pre-dispersed component.

[0104] In this comparative example, the pre-dispersed component raw materials include 75 parts of metallocene linear low-density polyethylene (mLLDPE) raw powder and 25 parts of non-entangled ultra-high molecular weight polyethylene (UHMWPE) raw powder.

[0105] The specific performance of the cold-stretched sleeve packaging film in this comparative example is shown in Table 1.

[0106] Comparative Example 4

[0107] Compared with Example 4, the difference is that no pre-dispersed component is added to the raw materials in the middle layer.

[0108] In this comparative example, the inner layer raw materials include 40 parts of metallocene linear low-density polyethylene mLLDPE and 60 parts of linear low-density polyethylene LLDPE.

[0109] The raw materials for the middle layer include 70 parts of metallocene linear low-density polyethylene mLLDPE and 30 parts of linear low-density polyethylene LLDPE.

[0110] The outer layer consists of 60 parts of metallocene linear low-density polyethylene mLLDPE, 40 parts of linear low-density polyethylene LLDPE, and 10 parts of pre-dispersed components.

[0111] The specific performance of the cold-stretched sleeve packaging film in this comparative example is shown in Table 1.

[0112] Comparative Example 5

[0113] Compared with Example 4, the difference is that no pre-dispersed component is added to the raw materials of the outer layer.

[0114] In this comparative example, the inner layer raw materials include 40 parts of metallocene linear low-density polyethylene mLLDPE and 60 parts of linear low-density polyethylene LLDPE.

[0115] The raw materials for the middle layer include 70 parts of metallocene linear low-density polyethylene mLLDPE, 30 parts of linear low-density polyethylene LLDPE, and 20 parts of pre-dispersed components.

[0116] The outer layer consists of 60 parts of metallocene linear low-density polyethylene mLLDPE and 40 parts of linear low-density polyethylene LLDPE.

[0117] The specific performance of the cold-stretched sleeve packaging film in this comparative example is shown in Table 1.

[0118] Comparative Example 6

[0119] Compared with Example 4, the difference is that metallocene linear low-density polyethylene mLLDPE raw powder is not added to the pre-dispersed component.

[0120] In this comparative example, the pre-dispersed component raw materials include 25 parts of unentangled ultra-high molecular weight polyethylene (UHMWPE) raw powder and 11 parts of low melting point dispersant.

[0121] The specific performance of the cold-stretched sleeve packaging film in this comparative example is shown in Table 1.

[0122] Comparative Example 7

[0123] Compared with Example 4, the difference is that no unentangled ultra-high molecular weight polyethylene (UHMWPE) raw material is added to the pre-dispersed component.

[0124] In this comparative example, the pre-dispersed component raw materials include 75 parts of metallocene linear low-density polyethylene (mLLDPE) raw powder and 11 parts of low-melting-point dispersant.

[0125] The specific performance of the cold-stretched sleeve packaging film in this comparative example is shown in Table 1.

[0126] Comparative Example 8

[0127] Compared with Example 4, the difference is that the pre-dispersed component is made only from a low-melting-point dispersant (polyethylene wax and polyethylene glycol in a mass ratio of 1:2); the film thickness ratio of the inner layer / middle layer / outer layer is 1 / 3 / 1.

[0128] The specific performance of the cold-stretched sleeve packaging film in this comparative example is shown in Table 1.

[0129] Comparative Example 9

[0130] Compared with Example 4, the difference is that ordinary linear low-density polyethylene mLLDPE is used instead of unentangled ultra-high molecular weight polyethylene UHMWPE raw powder in the pre-dispersion component.

[0131] In this comparative example, the pre-dispersed component raw materials include 75 parts of metallocene linear low-density polyethylene mLLDPE, 25 parts of linear low-density polyethylene LLDPE (DFDA7042), and 11 parts of low-melting-point dispersant.

[0132] The specific performance of the cold-stretched sleeve packaging film in this comparative example is shown in Table 1.

[0133] Comparative Example 10

[0134] Compared with Example 4, the difference is that the thickness of the cold-stretched sleeve packaging film in this comparative example is 122 μm, and the film thickness ratio of the inner layer / middle layer / outer layer is 1 / 2 / 1.

[0135] The specific performance of the cold-stretched sleeve packaging film in this comparative example is shown in Table 1.

[0136] Comparative Example 11

[0137] The difference compared to Example 4 is that the raw material formula of the middle layer of the cold-stretched sleeve packaging film is adjusted.

[0138] The inner layer consists of 40 parts of metallocene linear low-density polyethylene mLLDPE and 60 parts of linear low-density polyethylene LLDPE.

[0139] The raw materials for the middle layer include 60 parts of metallocene linear low-density polyethylene mLLDPE, 40 parts of linear low-density polyethylene LLDPE, and 10 parts of pre-dispersed components.

[0140] The outer layer consists of 60 parts of metallocene linear low-density polyethylene mLLDPE, 40 parts of linear low-density polyethylene LLDPE, and 5 parts of pre-dispersed components.

[0141] The specific performance of the cold-stretched sleeve packaging film in this comparative example is shown in Table 1.

[0142] Table 1. Performance Data of Cold-Stretched Tubing Packaging Film

[0143]

[0144] As shown in the table above, the performance of the cold-stretched sleeve packaging films prepared in Examples 1 to 5 of the present invention all meet the requirements of T / ZZB 1008-2019.

[0145] Comparative Example 1 uses a conventional 130μm thick cold-stretched tubing packaging film, whose performance meets the requirements of T / ZZB 1008-2019; while in Comparative Example 2, the film thickness is reduced to 120μm, and all performance characteristics are significantly reduced, and it does not meet the requirements of T / ZZB 1008-2019.

[0146] The overall performance of the cold-stretched tubing packaging film in Examples 3 and 4 of this invention is superior to that of the cold-stretched tubing packaging film in Comparative Example 1. It is evident that this invention achieves thinning of the cold-stretched tubing packaging film while maintaining its mechanical properties, and further enhances these properties by adjusting the formulation.

[0147] In summary, this invention achieves thinning of the cold-stretch tubing packaging film while maintaining its mechanical properties by adjusting the formulations of the inner, middle, and outer layers. By adding pre-dispersed components to the middle and outer layers of the cold-stretch tubing packaging film, the lateral shrinkage rate and tensile strength of the film are improved, thereby obtaining a relatively thin cold-stretch tubing packaging film with excellent overall performance.

[0148] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A cold-stretched sleeve packaging film, characterized in that, It consists of an inner layer, a middle layer, and an outer layer; The inner layer is made of 30-50 wt% metallocene linear low-density polyethylene and 50-70 wt% linear low-density polyethylene. The middle layer is made of 50-80 wt% metallocene linear low-density polyethylene, 10-50 wt% linear low-density polyethylene, and 1-20 wt% pre-dispersed components. The outer layer is made of 40-70 wt% metallocene linear low-density polyethylene, 30-50 wt% linear low-density polyethylene, and 1-20 wt% pre-dispersed components. The pre-dispersed component is prepared by high-speed mixing and pre-mixing of metallocene linear low-density polyethylene mLLDPE raw powder, non-entangled ultra-high molecular weight polyethylene UHMWPE raw powder and low-melting-point dispersant in a mass ratio of (60~90):(10~40):(1~30). The low-melting-point dispersant is polyethylene wax and polyethylene glycol in a mass ratio of 1:(1~5).

2. The cold-stretched sleeve packaging film according to claim 1, characterized in that, The density of the metallocene linear low-density polyethylene (mLLDPE) raw powder is 0.918~0.922 g / cm³. 3 The melt flow rate is 1.5~4.5 g / 10 min (190℃ / 2.16 kg), and the particle size is 100~800 μm; The linear low-density polyethylene (LLDPE) has a density of 0.916~0.920 g / cm³. 3 The melt flow rate is 0.5~2.5g / 10min (190℃ / 2.16kg).

3. The cold-stretched sleeve packaging film according to claim 1, characterized in that, The density of the metallocene linear low-density polyethylene (mLLDPE) is 0.918~0.922 g / cm³. 3 The melt flow rate is 1.5~4.5 g / 10 min (190℃ / 2.16 kg).

4. The cold-stretched sleeve packaging film according to claim 1, characterized in that, The unentangled ultra-high molecular weight polyethylene (UHMWPE) raw material has a molecular weight of 1 million to 5 million, a particle size of 30 to 200 μm, and a density of 0.924 to 0.928 g / cm³. 3 .

5. The cold-stretched sleeve packaging film according to claim 1, characterized in that, The metallocene linear low-density polyethylene in the inner, middle, and outer layers may have the same or different melt flow rate and density as the metallocene linear low-density polyethylene raw material in the pre-dispersed component.

6. The cold-stretched sleeve packaging film according to claim 1, characterized in that, The thickness of the cold-stretched sleeve packaging film is 120±2μm.

7. A method for preparing a cold-stretched sleeve packaging film as described in claim 1, characterized in that, The preparation method includes: placing various raw materials of the pre-dispersed components into a twin-screw compounding extruder for pre-mixing at a processing temperature of 190~210℃; then placing the inner layer raw material, middle layer raw material, and outer layer raw material into a blown film machine for blown film processing at a processing temperature of 160~190℃ for the inner layer, 170~210℃ for the middle layer, and 165~200℃ for the outer layer.

8. The method for preparing the cold-stretched sleeve packaging film according to claim 7, characterized in that, The length-to-diameter ratio of the twin-screw compounding extruder is (25~35):1.

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