Cold drawing sleeve packaging film and preparation method thereof

Abstract

The invention relates to the technical field of polyolefin film materials, in particular to a cold drawing sleeve packaging film and a preparation method thereof. The invention discloses a cold drawing sleeve packaging film which is composed of an inner layer, a middle layer and an outer layer. The inner layer is prepared from the following raw materials in percentage by weight: 30 to 60 percent of metallocene linear low density polyethylene (mLLDPE) and 40 to 70 percent of linear low density polyethylene (LLDPE); the middle layer is prepared from the following raw materials in percentage by weight: 20 to 70 percent of metallocene linear low density polyethylene (mLLDPE), 10 to 30 percent of linear low density polyethylene (LLDPE) and 1 to 40 percent of pre-dispersion component; the outer layer is prepared from the following raw materials in percentage by weight: 10 to 60 percent of metallocene linear low density polyethylene (mLLDPE), 10 to 40 percent of linear low density polyethylene (LLDPE) and 1 to 40 percent of pre-dispersed component; the pre-dispersed component is prepared from an original ecological powder material of metallocene linear low density polyethylene (mLLDPE), an original ecological powder material of non-entanglement ultra-high molecular weight polyethylene (UHMWPE) and a low-melting-point dispersing agent through high-speed mixing and pre-mixing; the low-melting-point dispersing agent is polyethylene wax and polyethylene glycol.

Description

Technical Field

[0001] The invention belongs to the technical field of polyolefin film materials and relates to a cold-stretched sleeve packaging film and a preparation method thereof. Background Art

[0002] In synthetic resin production enterprises, products are usually packaged in 25 kg heavy packaging film bags, and then the goods are stacked on pallets, usually one ton or two tons per pallet. In order to prevent the primary packaging bags from being contaminated by dust during transportation and storage, and also to prevent rain, cold stretch sleeve packaging film is used for secondary container packaging of 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 is related to the stability of the packaging; and third, the inner wall friction coefficient, which affects the smoothness of the packaging process.

[0004] At present, the cold stretch sleeve packaging film is mainly produced by the three-layer composite blown film process, and its main raw materials include a mixture of mLLDPE and LLDPE and some additives. In the recognized formula, LLDPE usually accounts for 20% to 60% of the total raw materials, while mLLDPE accounts for 40% to 80%. The cold stretch sleeve packaging film produced by this formula can only meet the requirements of tensile strength and transverse shrinkage rate under the condition of thicker film, resulting in high film cost.

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

[0006] The purpose of the present invention is to solve the above problems in the prior art and to provide a cold stretch sleeve packaging film, which can reduce the thickness of the cold stretch sleeve packaging film while ensuring its mechanical properties.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] A cold stretch sleeve packaging film, which consists of an inner layer, a middle layer and an outer layer;

[0009] The raw materials of the inner layer include 30-60wt% of metallocene linear low-density polyethylene mLLDPE and 40-70wt% of linear low-density polyethylene LLDPE;

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

[0011] The raw materials of the outer layer include 10-60 wt% of metallocene linear low-density polyethylene mLLDPE, 10-40 wt% of linear low-density polyethylene LLDPE, and 1-40 wt% of pre-dispersed components;

[0012] The pre-dispersed component is prepared by high-speed mixing and pre-mixing of metallocene linear low-density polyethylene mLLDPE original powder, entanglement-free ultra-high molecular weight polyethylene UHMWPE original powder and a 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 raw material of the inner layer is 30-50wt% of metallocene linear low-density polyethylene and 50-70wt% of linear low-density polyethylene;

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

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

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

[0018] Preferably, the density of the original metallocene linear low-density polyethylene mLLDPE powder is 0.918-0.922 g / cm 3 , melt flow rate is 1.5-4.5 g / 10 min (190°C / 2.16 kg), particle size is 100-800 μm;

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

[0020] More preferably, the density of the original metallocene linear low-density polyethylene mLLDPE powder is 0.918-0.922 g / cm3 , melt flow rate is 1.5~2.5g / 10min(190℃ / 2.16kg),

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

[0022] Preferably, the molecular weight of the entanglement-free ultra-high molecular weight polyethylene UHMWPE original powder in the pre-dispersed component is 1 million to 5 million, the particle size is 30 to 200 μm, and the density is 0.924 to 0.928 g / cm 3 .

[0023] More preferably, the molecular weight of the entanglement-free ultra-high molecular weight polyethylene original powder is 1 to 2 million, and the particle size is 50 to 150 μm.

[0024] More preferably, the molecular weight of the entanglement-free ultra-high molecular weight polyethylene UHMWPE original powder is 1.2 to 1.5 million, and the particle size is 70 to 120 μm.

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

[0026] Preferably, the melt flow rate and density of the metallocene linear low-density polyethylene in the inner layer, the middle layer and the outer layer are the same as or different from the original metallocene linear low-density polyethylene powder in the pre-dispersed component.

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

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

[0029] A method for preparing a cold stretch 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°C; then the inner layer raw materials, the middle layer raw materials, and the outer layer raw materials are respectively placed in a film blowing machine for film blowing processing, the inner layer film blowing processing temperature is 160-190°C, the middle layer film blowing processing temperature is 170-210°C, and the outer layer film blowing processing temperature is 165-200°C.

[0031] Preferably, the aspect 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 layer and the outer layer of the cold-stretch sleeve packaging film to improve the transverse shrinkage rate and tensile strength of the cold-stretch sleeve packaging film, thereby obtaining a relatively thin cold-stretch sleeve packaging film with excellent comprehensive performance.

[0034] 2. In the pre-dispersed components of the present invention, a low melting point dispersant is added to the entanglement-free ultra-high molecular weight polyethylene UHMWPE original powder and mLLDPE original powder, which can ensure that the UHMWPE molecular chains are more dispersed at the molecular level in the mLLDPE matrix. The low melting point dispersant plays a role in lubricating the molecular chains, promoting the movement of the UHMWPE molecular chains in the molten mixed state, and promoting dispersion; avoiding the formation of crystal points in the film due to the entanglement of the UHMWPE molecular chains, thereby affecting the film strengthening effect.

[0035] 3. The present invention adjusts the formula of the inner layer, the middle layer and the outer layer to achieve the thinning of the cold-stretch sleeve packaging film while ensuring its mechanical properties. DETAILED DESCRIPTION

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

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

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

[0039] Metallocene linear low-density polyethylene mLLDPE: homemade, made by copolymerizing ethylene and 1-hexene using a metallocene catalyst, MFR value 2.1±0.3g / 10min, density 0.920±0.002g / cm 3 Linear low-density polyethylene with an average particle size of 310 μm;

[0040] Metallocene linear low-density polyethylene mLLDPE original powder: homemade, produced by metallocene catalyst and 1-hexene copolymerization, MFR value 2.1±0.3g / 10min, density 0.920±0.002g / cm 3 Linear low-density polyethylene with an average particle size of 310 μm;

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

[0042] Entanglement-free ultra-high molecular weight polyethylene UHMWPE original powder: homemade, polymerized by titanium catalyst slurry method, molecular weight 1.4 million, average particle size 100μm, density 0.926±0.002g / cm 3 .

[0043] In the present invention, the original powder of metallocene linear low-density polyethylene mLLDPE and the original powder of entanglement-free ultra-high molecular weight polyethylene UHMWPE can be replaced by commercial products that meet the requirements of the present invention.

[0044] In the present invention, the target thickness of the stretch hood packaging film is 120 μm, and the actual thickness is ±2 μm.

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

[0046] The tensile strength is tested in accordance with GB / T 1040.3-2006.

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

[0048] The right-angle tear strength is tested in accordance with QB / T1130.

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

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

[0051] Example 1

[0052] In this embodiment, the thickness of the cold stretch 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 pre-dispersed components: Weigh 90 parts of metallocene linear low-density polyethylene mLLDPE original powder, 10 parts of entanglement-free ultra-high molecular weight polyethylene UHMWPE original powder, and 2 parts of low-melting point dispersant (polyethylene wax and polyethylene glycol in a mass ratio of 1:2) respectively; mix the metallocene linear low-density polyethylene mLLDPE original powder, entanglement-free ultra-high molecular weight polyethylene UHMWPE original powder and low-melting point dispersant at high speed for 2 minutes, and then put them on a twin-screw compounding granulator for compounding and extrusion at a melt temperature of 190-210°C to obtain a pre-dispersed component which is directly added to the middle layer and outer layer film extruders of the composite film.

[0054] The raw materials of the inner layer include 40 parts of metallocene linear low-density polyethylene mLLDPE and 60 parts of linear low-density polyethylene LLDPE;

[0055] The raw materials of 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 raw materials of the outer 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;

[0057] The preparation method of the cold-stretch sleeve packaging film comprises: placing the inner layer raw material, the middle layer raw material and the outer layer raw material in the inner layer, middle layer and outer layer film blowing machine hoppers respectively, and simultaneously adding the pre-dispersed components into the middle layer and outer layer film blowing extruders by metering, and performing film blowing processing, wherein the inner layer film blowing extrusion processing temperature is 175±5°C, the middle layer film blowing extrusion processing temperature is 185±5°C, and the outer layer film blowing extrusion processing temperature is 180±5°C; and a cold-stretch sleeve packaging film is obtained.

[0058] The properties of the cold stretch sleeve packaging film in this embodiment are specifically shown in Table 1. It can be seen that the performance of the cold stretch sleeve packaging film meets the requirements of T / ZZB 1008-2019.

[0059] Example 2

[0060] The thickness of the cold stretch sleeve packaging film in this embodiment 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 original powder, 40 parts of entanglement-free ultra-high molecular weight polyethylene UHMWPE original powder, and 24 parts of low-melting point dispersant (polyethylene wax and polyethylene glycol in a mass ratio of 1:2) respectively; other preparation methods are the same as Example 1.

[0062] The raw materials of the inner layer include 40 parts of metallocene linear low-density polyethylene mLLDPE and 60 parts of linear low-density polyethylene LLDPE;

[0063] The raw materials of 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 raw materials of the outer layer include 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 stretch sleeve packaging film: same as Example 1.

[0066] The properties of the cold stretch sleeve packaging film in this embodiment are specifically shown in Table 1. It can be seen that the performance of the cold stretch sleeve packaging film meets the requirements of T / ZZB 1008-2019.

[0067] Example 3

[0068] In this embodiment, the thickness of the cold stretch sleeve packaging film is 120 μm, 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 original powder, 20 parts of entanglement-free ultra-high molecular weight polyethylene UHMWPE original powder, and 7 parts of low-melting point dispersant (polyethylene wax and polyethylene glycol in a mass ratio of 1:2) respectively; other preparation methods are the same as Example 1.

[0070] The raw materials of the inner layer include 40 parts of metallocene linear low-density polyethylene mLLDPE and 60 parts of linear low-density polyethylene LLDPE;

[0071] The raw materials of 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 raw materials of the outer layer include 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 stretch sleeve packaging film: same as Example 1.

[0074] The properties of the cold stretch sleeve packaging film in this embodiment are specifically shown in Table 1. It can be seen that the performance of the cold stretch sleeve packaging film meets the requirements of T / ZZB 1008-2019.

[0075] Example 4

[0076] In this embodiment, the thickness of the cold stretch 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 original powder, 25 parts of entanglement-free ultra-high molecular weight polyethylene UHMWPE original powder, and 11 parts of low-melting point dispersant (polyethylene wax and polyethylene glycol in a mass ratio of 1:2) respectively; other preparation methods are the same as Example 1.

[0078] The raw materials of the inner layer include 40 parts of metallocene linear low-density polyethylene mLLDPE and 60 parts of linear low-density polyethylene LLDPE;

[0079] The raw materials of 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 raw materials of the outer layer include 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 stretch sleeve packaging film: same as Example 1.

[0082] The properties of the cold stretch sleeve packaging film in this embodiment are specifically shown in Table 1. It can be seen that the performance of the cold stretch sleeve packaging film meets the requirements of T / ZZB 1008-2019.

[0083] Example 5

[0084] In this embodiment, the thickness of the cold stretch 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 original powder, 30 parts of entanglement-free ultra-high molecular weight polyethylene UHMWPE original powder, and 15 parts of low-melting point dispersant (polyethylene wax and polyethylene glycol in a mass ratio of 1:2) respectively; other preparation methods are the same as Example 1.

[0086] The raw materials of the inner layer include 40 parts of metallocene linear low-density polyethylene mLLDPE and 60 parts of linear low-density polyethylene LLDPE;

[0087] The raw materials of 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 raw materials of the outer layer include 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 stretch sleeve packaging film: same as Example 1.

[0090] The properties of the cold stretch sleeve packaging film in this embodiment are specifically shown in Table 1. It can be seen that the performance of the cold stretch sleeve packaging film meets the requirements of T / ZZB 1008-2019.

[0091] Comparative Example 1

[0092] The thickness of the cold stretch hood packaging film in this comparative example is 133 μm, and the film thickness ratio of the inner layer / middle layer / outer layer is 1 / 3 / 1;

[0093] The raw materials of the inner layer include 40 parts of metallocene linear low-density polyethylene mLLDPE and 60 parts of linear low-density polyethylene LLDPE;

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

[0095] The raw materials of the outer layer include 60 parts of metallocene linear low-density polyethylene mLLDPE and 40 parts of linear low-density polyethylene LLDPE;

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

[0097] The properties of the cold stretch hood packaging film in this comparative example are specifically shown in Table 1.

[0098] The cold stretch sleeve packaging film in this comparative example is a common cold stretch sleeve packaging film currently on the market, which can meet 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 stretch hood 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 properties of the cold stretch hood packaging film in this comparative example are specifically shown in Table 1.

[0102] Comparative Example 3

[0103] Compared with Example 4, the difference is that no low melting point dispersant is added to the pre-dispersed components.

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

[0105] The properties of the cold stretch hood packaging film in this comparative example are specifically 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 of the middle layer.

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

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

[0110] The raw materials of the outer 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.

[0111] The properties of the cold stretch hood packaging film in this comparative example are specifically 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 raw materials of the inner layer include 40 parts of metallocene linear low-density polyethylene mLLDPE and 60 parts of linear low-density polyethylene LLDPE;

[0115] The raw materials of 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 raw materials of the outer layer include 60 parts of metallocene linear low-density polyethylene mLLDPE and 40 parts of linear low-density polyethylene LLDPE.

[0117] The properties of the cold stretch hood packaging film in this comparative example are specifically shown in Table 1.

[0118] Comparative Example 6

[0119] Compared with Example 4, the difference is that no original powder of metallocene linear low-density polyethylene mLLDPE is added to the pre-dispersed component.

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

[0121] The properties of the cold stretch hood packaging film in this comparative example are specifically shown in Table 1.

[0122] Comparative Example 7

[0123] Compared with Example 4, the difference is that no entanglement-free ultra-high molecular weight polyethylene UHMWPE original powder is added to the pre-dispersed components.

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

[0125] The properties of the cold stretch hood packaging film in this comparative example are specifically shown in Table 1.

[0126] Comparative Example 8

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

[0128] The properties of the cold stretch hood packaging film in this comparative example are specifically 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 in the pre-dispersed component instead of the entanglement-free ultra-high molecular weight polyethylene UHMWPE original powder.

[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 properties of the cold stretch hood packaging film in this comparative example are specifically shown in Table 1.

[0133] Comparative Example 10

[0134] Compared with Example 4, the difference is that the thickness of the cold stretch hood 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 properties of the cold stretch hood packaging film in this comparative example are specifically shown in Table 1.

[0136] Comparative Example 11

[0137] Compared with Example 4, the difference is that: the raw material formula of the middle layer of the cold stretch sleeve packaging film is adjusted.

[0138] The raw materials of the inner layer include 40 parts of metallocene linear low-density polyethylene mLLDPE and 60 parts of linear low-density polyethylene LLDPE;

[0139] The raw materials of 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 raw materials of the outer layer include 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 properties of the cold stretch hood packaging film in this comparative example are specifically shown in Table 1.

[0142] Table 1. Performance data of cold stretch hood packaging film

[0143]

[0144] According to the above table, the performance of the cold stretch 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 is a conventional 130 μm thick cold-stretch sleeve packaging film, and its performance meets the requirements of T / ZZB 1008-2019; while in Comparative Example 2, the film thickness is reduced to 120 μm, and various performances are significantly reduced, and do not meet the requirements of T / ZZB 1008-2019.

[0146] The comprehensive performance of the cold stretch hood packaging film in Examples 3 and 4 of the present invention is better than the comprehensive performance of the cold stretch hood packaging film in Comparative Example 1. It can be seen that the present invention can achieve the thinning of the cold stretch hood packaging film while ensuring its mechanical properties, and can further improve the mechanical properties by adjusting the formula.

[0147] In summary, the present invention adjusts the formula of the inner layer, the middle layer and the outer layer to achieve the thinning of the cold stretch sleeve packaging film while ensuring its mechanical properties; adds pre-dispersed components to the middle layer and the outer layer of the cold stretch sleeve packaging film to improve the lateral shrinkage rate and tensile strength of the cold stretch sleeve packaging film, thereby obtaining a relatively thin cold stretch sleeve packaging film with excellent comprehensive performance.

[0148] The specific embodiments described herein are merely examples of the spirit of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, but they will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A cold stretch hood packaging film, characterized in that: It consists of an inner layer, a middle layer, and an outer layer; The raw materials of the inner layer include 30-60wt% of metallocene linear low-density polyethylene mLLDPE and 40-70wt% of linear low-density polyethylene LLDPE; The raw materials of the middle layer include 20-70 wt% of metallocene linear low-density polyethylene mLLDPE, 10-30 wt% of linear low-density polyethylene LLDPE, and 1-40 wt% of pre-dispersed components; The raw materials of the outer layer include 10-60 wt% of metallocene linear low-density polyethylene mLLDPE, 10-40 wt% of linear low-density polyethylene LLDPE, and 1-40 wt% of pre-dispersed components; The pre-dispersed component is prepared by high-speed mixing and pre-mixing of metallocene linear low-density polyethylene mLLDPE original powder, entanglement-free ultra-high molecular weight polyethylene UHMWPE original powder and a 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 stretch hood packaging film according to claim 1, characterized in that: The raw materials of the inner layer are 30-50wt% of metallocene linear low-density polyethylene and 50-70wt% of linear low-density polyethylene; The raw materials of the middle layer are 50-80wt% of metallocene linear low-density polyethylene, 10-50wt% of linear low-density polyethylene, and 1-20wt% of pre-dispersed components; The raw materials of the outer layer are 40-70 wt% of metallocene linear low-density polyethylene, 30-50 wt% of linear low-density polyethylene and 1-20 wt% of pre-dispersed components.

3. The stretch hood packaging film according to claim 1, characterized in that: The amount of the low melting point dispersant added in the pre-dispersed component is 20-60wt% of the original powder of the metallocene linear low density polyethylene mLLDPE.

4. The stretch hood packaging film according to claim 1, characterized in that: The density of the original metallocene linear low-density polyethylene mLLDPE powder is 0.918-0.922 g / cm 3 , melt flow rate is 1.5-4.5 g / 10 min (190°C / 2.16 kg), particle size is 100-800 μm; The density of the linear low-density polyethylene LLDPE is 0.916-0.920 g / cm 3 , the melt flow rate is 0.5~2.5g / 10min(190℃ / 2.16kg).

5. The stretch hood 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 / cm 3 , the melt flow rate is 1.5~4.5g / 10min(190℃ / 2.16kg).

6. The stretch hood packaging film according to claim 1, characterized in that: The entanglement-free ultra-high molecular weight polyethylene UHMWPE original ecological powder 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 / cm 3 .

7. The stretch hood packaging film according to claim 1, characterized in that: The melt flow rate and density of the metallocene linear low-density polyethylene in the inner layer, the middle layer and the outer layer are the same as or different from the original metallocene linear low-density polyethylene powder in the pre-dispersed component.

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

9. A method for preparing a stretch hood packaging film according to claim 1, characterized in that: The preparation method comprises: placing various raw materials of pre-dispersed components in a twin-screw mixing extruder for pre-mixing at a processing temperature of 190-210°C; then placing the inner layer raw materials, the middle layer raw materials and the outer layer raw materials in a film blowing machine for film blowing processing, the inner layer film blowing processing temperature is 160-190°C, the middle layer film blowing processing temperature is 170-210°C, and the outer layer film blowing processing temperature is 165-200°C.

10. The method for preparing a stretch hood packaging film according to claim 9, characterized in that: The aspect ratio of the twin-screw compounding extruder is (25-35):1.

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