Special material for middle-layer resin of cold-drawn sleeve packaging film as well as preparation method and application of special material

Abstract

The invention belongs to the technical field of polyolefin film materials, and relates to a special material for middle-layer resin of a cold-drawing sleeve packaging film as well as a preparation method and application of the special material. The special material is prepared from the following raw materials in parts by weight: 50 to 90 parts of LLDPE (Linear Low Density Polyethylene), 15 to 30 parts of mLLDPE (Linear Low Density Polyethylene), 1 to 5 parts of UHMWPE (Ultra High Molecular Weight Polyethylene), 2 to 5 parts of EVA (Ethylene Vinyl Acetate) and 0.01 to 0.1 part of chain dispersion driving agent, the LLDPE is linear low density polyethylene resin, and the linear low density polyethylene resin comprises HD-LLDPE and LD-LLDPE. Through optimized raw material components and raw material ratio, under the condition that the use amount of imported mLLDPE raw materials is reduced, the retraction rate and tensile strength of the film are effectively improved, and the appearance performance of the film is improved. And meanwhile, the production cost can be reduced, and the sustainable development principle is met.

Description

Technical Field

[0001] The invention belongs to the technical field of polyolefin film materials, and relates to a special material for middle-layer resin of a cold-stretched sleeve packaging film, a preparation method and application thereof. Background Art

[0002] Cold stretch sleeve packaging film is mainly used for secondary containerization of synthetic resin granule products, aiming to simplify the storage and transportation process and protect the primary packaging from dust and rain. Cold stretch sleeve packaging film usually adopts a three-layer composite blown film structure. The tensile strength and transverse shrinkage rate of the film are mainly determined by the aggregate structure of polyethylene. Imported metallocene linear low-density polyethylene (mLLDPE) is usually used as the main raw material of the film, so the cost is relatively high.

[0003] As a global leader in synthetic resin production, China's demand for stretch hood packaging films continues to grow. In order to reduce costs and meet the market's demand for lighter, thinner and more efficient packaging films, traditional resin substrates can no longer meet the performance requirements of modern packaging films, which are "thin and shrinking" and "thin and strong". At present, the middle layer of stretch hood packaging films mainly uses mLLDPE resin to ensure that the film has good lateral shrinkage and sufficient strength. However, mLLDPE is expensive, which directly increases the production cost of the final product. In addition, as the film continues to thin, the stretch shrinkage rate and strength of the finished film also decrease, which may cause damage during storage and transportation, thereby affecting the effect of the secondary packaging.

[0004] Therefore, finding new materials and technologies that are more economical and efficient and can maintain or improve film performance has become an important issue in the current industry. This will not only help reduce production costs, but also further improve the comprehensive performance of packaging films to meet the growing market demand. Summary of the invention

[0005] The invention aims at the deficiencies of cold-stretch sleeve packaging films in the prior art and provides a special middle-layer resin material for cold-stretch sleeve packaging films and a preparation method thereof.

[0006] One object of the present invention is achieved by the following technical solutions:

[0007] The invention discloses a special material for middle layer resin of cold stretch sleeve packaging film, which is prepared from the following raw materials in parts by weight: 50-90 parts of LLDPE, 15-30 parts of mLLDPE, 1-5 parts of UHMWPE, 2-5 parts of EVA and 0.01-0.1 parts of chain dispersion driver.

[0008] Preferably, the LLDPE is a linear low-density polyethylene resin, including HD-LLDPE and LD-LLDPE.

[0009] Further preferably, the special material for the middle layer resin of the cold stretch sleeve packaging film is prepared from the following raw materials in parts by weight: 30 to 50 parts of HD-LLDPE, 15 to 30 parts of mLLDPE, 20 to 40 parts of LD-LLDPE, 1 to 5 parts of UHMWPE, 2 to 5 parts of EVA and 0.01 to 0.1 parts of chain dispersion driver.

[0010] Preferably, the HD-LLDPE is a high-density linear low-density polyethylene resin, which is copolymerized with 1-hexene and LLDPE and has a density of 0.922 to 0.926 g / cm 3 More preferably, it is 0.922 to 0.924 g / cm 3 .

[0011] Preferably, the HD-LLDPE is in powder form, and the particle size of the powder is 100 to 1000 μm, more preferably 200 to 500 μm.

[0012] Preferably, the HD-LLDPE has a melt flow rate (MFR) of 0.6 to 3.0 g / 10 min at 190° C. and 2.16 kg, and more preferably 1.0 to 2.0 g / 10 min.

[0013] MFR (Melt Flow Rate) is a method used to measure the melt fluidity of thermoplastics under specific conditions. Here, the MFR value refers to the mass of polymer melt flowing through a capillary of standard diameter and length within 10 minutes at a temperature of 190°C and a pressure of 2.16Kg. MFR is an important quality control parameter in the plastics industry because it is directly related to the processing performance and some mechanical properties of plastics.

[0014] Preferably, the LD-LLDPE is a low-density linear low-density polyethylene resin, which is copolymerized with 1-butene and LLDPE and has a density of 0.910 to 0.919 g / cm 3 More preferably, it is 0.914 to 0.917 g / cm 3 .

[0015] Preferably, the LD-LLDPE is a melt-granulated granular particle with a size of φ2-3 mm and L2-4 mm. Here, the diameter of the LD-LLDPE particle is 2-3 mm and the length is about 2-4 mm, which is the size of the melt-granulated granular particle recognized by the industry.

[0016] Preferably, the melt flow rate MFR value of the LD-LLDPE at 190° C. and 2.16 kg is 0.8 to 1.5 g / 10 min.

[0017] Preferably, the mLLDPE is metallocene linear low-density polyethylene resin powder, and the powder particle size is 10 to 500 μm, more preferably 100 to 300 μm.

[0018] Preferably, the mLLDPE has a melt flow rate MFR value of 0.8 to 3.0 g / 10 min at 190°C and 2.16 kg, and a density of 0.910 to 0.930 g / cm 3 .

[0019] More preferably, the mLLDPE has a melt flow rate MFR value of 0.8 to 1.5 g / 10 min at 190° C. and 2.16 kg, and a density of 0.918 to 0.922 g / cm 3 .

[0020] Preferably, the UHMWPE is an ultra-high molecular weight polyethylene resin powder, and the particle size of the powder is 50 to 500 μm, more preferably 100 to 300 μm.

[0021] Preferably, the weight average molecular weight Mw of the UHMWPE is 1.2 to 2 million, and the density is 0.920 to 0.924 g / cm 3 .

[0022] Further preferably, the UHMWPE is prepared by solvent-free tableting and is a low-entanglement ultra-high molecular weight polyethylene resin powder. Since the molecular weight of UHMWPE is very high, the material becomes very viscous and difficult to flow during processing. The low-entanglement UHMWPE used in the present invention is prepared by solvent-free tableting, and the interaction between the molecular chains of the material is weak during processing, making the material easier to flow and form.

[0023] Preferably, the VA content in the EVA is 5 to 20 wt %, and the melt flow rate MFR value at 190° C. and 2.16 kg is 1.0 to 6.0 g / 10 min.

[0024] More preferably, the VA content in the EVA is 8 to 15 wt %, and the melt flow rate MFR value at 190° C. and 2.16 kg is 2.0 to 4.0 g / 10 min.

[0025] Preferably, the chain dispersion driver comprises low molecular weight polyethylene glycol (LMWPEG) and low molecular weight polylactic acid (LMWPLA), and the weight average molecular weight Mw of the chain dispersion driver is 1000 to 8000. More preferably, the weight average molecular weight Mw is 3000 to 6000.

[0026] Preferably, in the chain dispersion driver, the ratio of low molecular weight polyethylene glycol to low molecular weight polylactic acid is (1-5):(5-1), and more preferably (1-2):(3-1).

[0027] The second object of the present invention is achieved by the following technical solutions:

[0028] A method for preparing a special material for a middle layer resin of a cold stretch sleeve packaging film, the method comprising the following steps: adding HD-LLDPE and UHMWPE into a mixer for primary mixing, then adding a chain dispersing driver, mLLDPE, EVA and LD-LLDPE for secondary mixing, and finally mixing and granulating to obtain the special material for a middle layer resin of a cold stretch sleeve packaging film.

[0029] Preferably, the first mixing time is 1 to 10 minutes, and the second mixing time is 1 to 10 minutes.

[0030] Preferably, the kneading and granulation are carried out in a twin-screw kneading and granulating machine, and the melt temperature is 180 to 210°C, more preferably 190 to 200°C.

[0031] The third object of the present invention is achieved by the following technical solutions:

[0032] The invention discloses an application of a special material for middle layer resin of a cold stretch sleeve packaging film in preparing the cold stretch sleeve packaging film.

[0033] Preferably, the cold stretch sleeve packaging film is a three-layer co-extruded composite film, including an inner layer, a middle layer and an outer layer. The raw materials for preparing the middle layer film include the above-mentioned cold stretch sleeve packaging film middle layer resin special material, and its blown film processing melt temperature is 185-195°C.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. In the special material for the middle layer resin of the cold-stretch sleeve packaging film provided by the present invention, the aggregate structure of polyethylene is optimized by selecting the raw materials: HD-LLDPE is used to provide more crystallization sites, which can be used as anchor points in the film structure and help form a more stable crystallization region; the introduction of LD-LLDPE and mLLDPE increases the number of molecular folding chains in the amorphous region, and the connection between the molecular chains is enhanced through the interaction between the crystallization sites and the folded molecular chains in the amorphous region. This enhanced lacing effect can significantly improve the lateral shrinkage rate of the film.

[0036] 2. In the special material for the middle layer resin of a cold-stretch sleeve packaging film provided by the present invention, by introducing UHMWPE molecular chains, the number of cross-crystalline chains and the degree of entanglement of the molecular chains are increased, thereby improving the tensile strength of the film. Due to its extremely high molecular weight, the UHMWPE molecular chain can form a more complex structure during the processing process, increasing the interaction force between molecules. These long-chain molecules can form more cross-crystalline chains between the crystalline region and the amorphous region, thereby improving the overall strength and toughness of the film. At the same time, the length of the UHMWPE molecular chain makes it easier for them to entangle with each other during the processing process, enhancing the interaction between the molecular chains, and improving the resistance of the film when subjected to external forces, thereby improving the tensile strength.

[0037] 3. A small amount of EVA and chain dispersion driver are introduced into the middle layer resin special material of the cold stretch sleeve packaging film provided by the present invention to promote the dispersion of the UHMWPE resin molecular chain and obtain a better reinforcement effect. At the same time, it helps the UHMWPE molecular chain to be better dispersed in the matrix resin, avoid agglomeration, reduce the generation of crystal points, and improve the appearance performance of the film.

[0038] 4. In the special material for the middle layer resin of the cold-stretch sleeve packaging film provided by the present invention, the powdered matrix resin is used for mixing and granulation, which is conducive to the uniform dispersion of low-entanglement UHMWPE in the matrix resin in molecular form, thereby obtaining the maximum reinforcement effect. This method effectively avoids the agglomeration of UHMWPE molecular chains, eliminates the crystal point phenomenon, and improves the processing performance and appearance quality of the film.

[0039] 5. The special resin material for the middle layer of the cold-stretch sleeve packaging film provided by the present invention reduces the use of imported mLLDPE raw materials. The prepared cold-stretch sleeve packaging film can effectively increase the transverse shrinkage rate and tensile strength of the film while maintaining the same thickness, thereby improving the performance of the film. Even when the film is thinned, it can still meet the requirements of national standards, which not only helps to reduce production costs, but also conforms to the concept of green development, reduces resource consumption and environmental impact, and embodies the principle of sustainable development. DETAILED DESCRIPTION

[0040] The technical solution of the present invention is further described below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

[0041] The preparation method of the cold stretch sleeve packaging film in the following examples and comparative examples comprises the following steps: feeding the raw materials for preparing the inner layer, middle layer and outer layer of the cold stretch sleeve packaging film into a three-layer co-extrusion film blowing machine for film blowing according to a thickness of 1:3:1 to prepare a three-layer composite film, and obtaining the cold stretch sleeve packaging film after cooling;

[0042] Among them, the basic formula of the inner layer film is mLLDPE / LLDPE of 30 / 70, and the melt temperature of blown film processing is 175°C; the basic formula of the outer layer film is mLLDPE / LLDPE of 65 / 35, and the melt temperature of blown film processing is 185°C; the formula of the middle layer film adopts the materials provided in the following embodiments and comparative examples, and the melt temperature of blown film processing is 190°C.

[0043] In the following examples and comparative examples, UHMWPE was prepared by solvent-free tabletting, and rheological analysis confirmed that it was low-entanglement ultra-high molecular weight polyethylene resin powder.

[0044] Example 1

[0045] The special resin material for the middle layer of the cold stretch sleeve packaging film of this embodiment is prepared from the following raw materials in parts by weight: 30 parts of HD-LLDPE, 15 parts of mLLDPE, 40 parts of LD-LLDPE, 1 part of UHMWPE, 5 parts of EVA and 0.1 parts of chain dispersion driver.

[0046] Among them, the MFR (190℃, 2.16kg) value of HD-LLDPE is 1.0g / 10min, and the density is 0.922g / cm 3 , the average particle size of the powder is 200μm;

[0047] The MFR (190°C, 2.16kg) value of mLLDPE is 0.8g / 10min, and the density is 0.918g / cm 3 , the average particle size of the powder is 100μm;

[0048] The MFR (190°C, 2.16kg) value of LD-LLDPE is 0.8g / 10min and the density is 0.914g / cm 3 , particle size is φ2mm, L3mm;

[0049] The Mw of UHMWPE is 2 million and the density is 0.924 g / cm 3 , the average particle size of the powder is 100μm;

[0050] The VA content in EVA is 15wt%, and the MFR (190℃, 2.16kg) value is 4.0g / 10min;

[0051] The chain dispersion driver is a compound of LMWPEG and LMWPLA in a mass ratio of 2:1, and has a Mw of 1000.

[0052] The preparation method of the special material for the middle layer resin of the cold stretch sleeve packaging film in this embodiment comprises the following steps: adding HD-LLDPE and UHMWPE into a high-speed mixer and mixing for 1 minute, then adding a chain dispersion driver, mLLDPE, EVA and LD-LLDPE and continuing to mix for 1 minute, and finally mixing and granulating in a twin-screw compounding and granulating machine with a melt temperature of 190-200°C to obtain the special material for the middle layer resin of the cold stretch sleeve packaging film.

[0053] The middle layer resin special material of the cold stretch sleeve packaging film in this embodiment was used as the middle layer film formula to prepare the cold stretch sleeve packaging film, and the obtained film thickness was 122 μm.

[0054] Example 2

[0055] The special resin material for the middle layer of the cold stretch sleeve packaging film of this embodiment is prepared from the following raw materials in parts by weight: 50 parts of HD-LLDPE, 30 parts of mLLDPE, 20 parts of LD-LLDPE, 5 parts of UHMWPE, 2 parts of EVA and 0.02 parts of chain dispersion driver.

[0056] Among them, the MFR (190℃, 2.16kg) value of HD-LLDPE is 1.6g / 10min, and the density is 0.923g / cm 3 , the average particle size of the powder is 400μm;

[0057] The MFR (190°C, 2.16kg) value of mLLDPE is 1.0g / 10min, and the density is 0.919g / cm 3 , the average particle size of the powder is 200μm;

[0058] The MFR (190°C, 2.16kg) value of LD-LLDPE is 1.2g / 10min and the density is 0.915g / cm 3 , particle size is φ2mm, L3mm;

[0059] The Mw of UHMWPE is 1.7 million and the density is 0.922 g / cm 3 , the average particle size of the powder is 200μm;

[0060] The VA content in EVA is 12wt%, and the MFR (190℃, 2.16kg) value is 3.0g / 10min;

[0061] The chain dispersion driver is a compound of LMWPEG and LMWPLA in a mass ratio of 1:1, and has a Mw of 6000.

[0062] The preparation method of the special resin material for the middle layer of the cold stretch sleeve packaging film in this embodiment is the same as that in Example 1.

[0063] The middle layer resin special material of the cold stretch sleeve packaging film in this embodiment was used as the middle layer film formula to prepare the cold stretch sleeve packaging film, and the obtained film thickness was 122 μm.

[0064] Example 3

[0065] The special resin material for the middle layer of the cold stretch sleeve packaging film of this embodiment is prepared from the following raw materials in parts by weight: 40 parts of HD-LLDPE, 20 parts of mLLDPE, 30 parts of LD-LLDPE, 2.5 parts of UHMWPE, 4 parts of EVA and 0.06 parts of chain dispersion driver.

[0066] Among them, the MFR (190℃, 2.16kg) value of HD-LLDPE is 2.0g / 10min, and the density is 0.924g / cm 3 , the average particle size of the powder is 500μm;

[0067] The MFR (190°C, 2.16kg) value of mLLDPE is 1.5g / 10min, and the density is 0.918g / cm 3 , the average particle size of the powder is 300μm;

[0068] The MFR (190°C, 2.16kg) value of LD-LLDPE is 1.5g / 10min and the density is 0.917g / cm 3 , particle size is φ2mm, L3mm;

[0069] The Mw of UHMWPE is 1.2 million and the density is 0.920 g / cm 3 , the average particle size of the powder is 100μm;

[0070] The VA content in EVA is 8wt%, and the MFR (190℃, 2.16kg) value is 2.0g / 10min;

[0071] The chain dispersion driver is a compound of LMWPEG and LMWPLA in a mass ratio of 1:3, and has a Mw of 5000.

[0072] The preparation method of the special resin material for the middle layer of the cold stretch sleeve packaging film in this embodiment is the same as that in Example 1.

[0073] The middle layer resin special material of the cold stretch sleeve packaging film in this embodiment was used as the middle layer film formula to prepare the cold stretch sleeve packaging film, and the obtained film thickness was 122 μm.

[0074] Example 4

[0075] The special resin material for the middle layer of the cold stretch sleeve packaging film of this embodiment is prepared from the following raw materials in parts by weight: 35 parts of HD-LLDPE, 15 parts of mLLDPE, 40 parts of LD-LLDPE, 5 parts of UHMWPE, 5 parts of EVA and 0.02 parts of chain dispersion driver.

[0076] Among them, the MFR (190℃, 2.16kg) value of HD-LLDPE is 0.6g / 10min, and the density is 0.922g / cm 3 , the average particle size of the powder is 100μm;

[0077] The MFR (190°C, 2.16kg) value of mLLDPE is 0.8g / 10min, and the density is 0.918g / cm 3 , the average particle size of the powder is 10μm;

[0078] The MFR (190°C, 2.16kg) value of LD-LLDPE is 0.8g / 10min and the density is 0.914g / cm 3 , particle size is φ2mm, L3mm;

[0079] The Mw of UHMWPE is 1.2 million and the density is 0.920 g / cm 3 , the average particle size of the powder is 50μm;

[0080] The VA content in EVA is 5wt%, and the MFR (190℃, 2.16kg) value is 1.0g / 10min;

[0081] The chain dispersion driver is a compound of LMWPEG and LMWPLA in a mass ratio of 1:5, and has a Mw of 1000.

[0082] The preparation method of the special resin material for the middle layer of the cold stretch sleeve packaging film in this embodiment is the same as that in Example 1.

[0083] The middle layer resin special material of the cold stretch sleeve packaging film in this embodiment is used as the middle layer film formula to prepare the cold stretch sleeve packaging film, and the obtained film thickness is 125 μm.

[0084] Example 5

[0085] The special resin material for the middle layer of the cold stretch sleeve packaging film of this embodiment is prepared from the following raw materials in parts by weight: 43 parts of HD-LLDPE, 30 parts of mLLDPE, 20 parts of LD-LLDPE, 5 parts of UHMWPE, 2 parts of EVA and 0.04 parts of chain dispersion driver.

[0086] Among them, the MFR (190℃, 2.16kg) value of HD-LLDPE is 3.0g / 10min, and the density is 0.926g / cm 3 , the average particle size of the powder is 1000μm;

[0087] The MFR (190°C, 2.16kg) value of mLLDPE is 3.0g / 10min, and the density is 0.922g / cm 3 , the average particle size of the powder is 500μm;

[0088] The MFR (190°C, 2.16kg) value of LD-LLDPE is 1.5g / 10min and the density is 0.917g / cm 3 , particle size is φ2mm, L3mm;

[0089] The Mw of UHMWPE is 1.2 million and the density is 0.924 g / cm 3 , the average particle size of the powder is 500μm;

[0090] The VA content in EVA is 8wt%, and the MFR (190℃, 2.16kg) value is 2.0g / 10min;

[0091] The chain dispersion driver is a compound of LMWPEG and LMWPLA in a mass ratio of 1:3, and has a Mw of 3000.

[0092] The preparation method of the special resin material for the middle layer of the cold stretch sleeve packaging film in this embodiment is the same as that in Example 1.

[0093] The special resin material for the middle layer of the cold stretch sleeve packaging film of this embodiment was used as the middle layer film formula to prepare the cold stretch sleeve packaging film, and the obtained film thickness was 123 μm.

[0094] Example 6

[0095] The special resin material for the middle layer of the cold stretch sleeve packaging film of this embodiment is prepared from the following raw materials in parts by weight: 34 parts of HD-LLDPE, 30 parts of mLLDPE, 40 parts of LD-LLDPE, 1 part of UHMWPE, 5 parts of EVA and 0.07 parts of chain dispersion driver.

[0096] Among them, the MFR (190℃, 2.16kg) value of HD-LLDPE is 2.0g / 10min, and the density is 0.922g / cm3 , the average particle size of the powder is 500μm;

[0097] The MFR (190°C, 2.16kg) value of mLLDPE is 1.5g / 10min, and the density is 0.918g / cm 3 , the average particle size of the powder is 300μm;

[0098] The MFR (190°C, 2.16kg) value of LD-LLDPE is 0.8g / 10min and the density is 0.916g / cm 3 , particle size is φ2mm, L3mm;

[0099] The Mw of UHMWPE is 1.5 million and the density is 0.922 g / cm 3 , the average particle size of the powder is 300μm;

[0100] The VA content in EVA is 15wt%, and the MFR (190℃, 2.16kg) value is 4.0g / 10min;

[0101] The chain dispersion driver is a compound of LMWPEG and LMWPLA in a mass ratio of 5:1, and has a Mw of 5000.

[0102] The preparation method of the special resin material for the middle layer of the cold stretch sleeve packaging film in this embodiment is the same as that in Example 1.

[0103] The middle layer resin special material of the cold stretch sleeve packaging film in this embodiment was used as the middle layer film formula to prepare the cold stretch sleeve packaging film, and the obtained film thickness was 124 μm.

[0104] Example 7

[0105] The special resin material for the middle layer of the cold stretch sleeve packaging film of this embodiment is prepared from the following raw materials in parts by weight: 32 parts of HD-LLDPE, 27 parts of mLLDPE, 35 parts of LD-LLDPE, 2.5 parts of UHMWPE, 3.5 parts of EVA and 0.06 parts of chain dispersion driver.

[0106] Among them, the MFR (190℃, 2.16kg) value of HD-LLDPE is 1.5g / 10min, and the density is 0.923g / cm 3 , the average particle size of the powder is 350μm;

[0107] The MFR (190°C, 2.16kg) value of mLLDPE is 2.3g / 10min, and the density is 0.918g / cm 3 , the average particle size of the powder is 200μm;

[0108] The MFR (190°C, 2.16kg) value of LD-LLDPE is 1.2g / 10min and the density is 0.915g / cm 3 , particle size is φ2mm, L3mm;

[0109] The Mw of UHMWPE is 1.7 million and the density is 0.922 g / cm 3 , the average particle size of the powder is 200μm;

[0110] The VA content in EVA is 12wt%, and the MFR (190℃, 2.16kg) value is 3.0g / 10min;

[0111] The chain dispersion driver is a compound of LMWPEG and LMWPLA in a mass ratio of 1:1, and has a Mw of 6000.

[0112] The preparation method of the special resin material for the middle layer of the cold stretch sleeve packaging film in this embodiment is the same as that in Example 1.

[0113] The middle layer resin special material of the cold stretch sleeve packaging film in this embodiment was used as the middle layer film formula to prepare the cold stretch sleeve packaging film, and the obtained film thickness was 122 μm.

[0114] Example 8

[0115] The raw materials and preparation method of the special material for the middle layer resin of the cold stretch sleeve packaging film in this embodiment are the same as those in Example 1.

[0116] The special resin material for the middle layer of the cold stretch sleeve packaging film of this embodiment is used as the middle layer film formula to prepare the cold stretch sleeve packaging film, and the obtained film thickness is 133 μm.

[0117] Comparative Example 1

[0118] The comparative example cold stretch sleeve packaging film adopts conventional materials as the basic formula of the middle layer film to prepare the cold stretch sleeve packaging film, and the obtained film thickness is 133 μm. Among them, the basic formula of the middle layer film is mLLDPE / LLDPE is 70 / 30.

[0119] Comparative Example 2

[0120] The difference between the middle layer resin material of the cold stretch hood packaging film in this comparative example and that in Example 1 is that all LLDPE materials are LD-LLDPE, and the other materials are the same as those in Example 1.

[0121] The middle layer resin material of the cold stretch sleeve packaging film of this comparative example is prepared from the following raw materials in parts by weight: 15 parts of mLLDPE, 70 parts of LD-LLDPE, 1 part of UHMWPE, 5 parts of EVA and 0.1 parts of chain dispersion driver. The raw material parameters are the same as those in Example 1.

[0122] The preparation method of the middle layer resin material of the cold stretch sleeve packaging film in this comparative example comprises the following steps: mLLDPE, LD-LLDPE, UHMWPE, EVA and a chain dispersion driver are added into a high-speed mixer and mixed for 1 minute, and then sent into a twin-screw compounding and granulating machine for compounding and granulating, the melt temperature is 190-200°C, and the middle layer resin material of the cold stretch sleeve packaging film is obtained.

[0123] The middle layer resin material of the cold stretch sleeve packaging film of this comparative example was used as the middle layer film formula to prepare the cold stretch sleeve packaging film, and the obtained film thickness was 122 μm.

[0124] Comparative Example 3

[0125] The difference between the middle layer resin material of the cold stretch hood packaging film in this comparative example and that in Example 1 is that HD-LLDPE is used in all LLDPE materials, and the other materials are the same as those in Example 1.

[0126] The middle layer resin material of the cold stretch sleeve packaging film of this comparative example is prepared from the following raw materials in parts by weight: 70 parts of HD-LLDPE, 15 parts of mLLDPE, 1 part of UHMWPE, 5 parts of EVA and 0.1 parts of chain dispersion driver. The raw material parameters are the same as those in Example 1.

[0127] The preparation method of the middle layer resin material of the cold stretch sleeve packaging film in this comparative example comprises the following steps: adding HD-LLDPE and UHMWPE into a high-speed mixer and mixing for 1 minute, then adding a chain dispersion driver, mLLDPE and EVA and continuing to mix for 1 minute, and finally mixing and granulating in a twin-screw compounding granulator with a melt temperature of 190 to 200°C to obtain the middle layer resin material of the cold stretch sleeve packaging film.

[0128] The middle layer resin material of the cold stretch sleeve packaging film of this comparative example was used as the middle layer film formula to prepare the cold stretch sleeve packaging film, and the obtained film thickness was 122 μm.

[0129] Comparative Example 4

[0130] The difference between the middle layer resin material of the cold stretch sleeve packaging film in this comparative example and that in Example 1 is that UHMWPE is not added to the material, and the other materials are the same as those in Example 1.

[0131] The middle layer resin material of the cold stretch sleeve packaging film of this comparative example is prepared from the following raw materials in parts by weight: 30 parts of HD-LLDPE, 15 parts of mLLDPE, 40 parts of LD-LLDPE, 5 parts of EVA and 0.1 parts of chain dispersion driver. The raw material parameters are the same as those in Example 1.

[0132] The preparation method of the middle layer resin material of the cold stretch sleeve packaging film in this comparative example comprises the following steps: adding HD-LLDPE, mLLDPE, LD-LLDPE, EVA and a chain dispersion driver into a high-speed mixer and mixing for 1 minute, and then sending the mixture into a twin-screw compounding and granulating machine for compounding and granulating, with the melt temperature being 190 to 200° C., to obtain the middle layer resin material of the cold stretch sleeve packaging film.

[0133] The middle layer resin material of the cold stretch sleeve packaging film of this comparative example was used as the middle layer film formula to prepare the cold stretch sleeve packaging film, and the obtained film thickness was 122 μm.

[0134] Comparative Example 5

[0135] The difference between the middle layer resin material of the cold stretch hood packaging film in this comparative example and that in Example 1 is that EVA is not added to the material, and the other materials are the same as those in Example 1.

[0136] The middle layer resin material of the cold stretch sleeve packaging film of this comparative example is prepared from the following raw materials in parts by weight: 30 parts of HD-LLDPE, 15 parts of mLLDPE, 40 parts of LD-LLDPE, 1 part of UHMWPE and 0.1 part of chain dispersion driver. The raw material parameters are the same as those in Example 1.

[0137] The preparation method of the middle layer resin material of the cold stretch sleeve packaging film in this comparative example comprises the following steps: adding HD-LLDPE and UHMWPE into a high-speed mixer and mixing for 1 minute, then adding a chain dispersion driver and mLLDPE and continuing to mix for 1 minute, and finally mixing and granulating in a twin-screw compounding and granulating machine with a melt temperature of 190 to 200°C to obtain the middle layer resin material of the cold stretch sleeve packaging film.

[0138] The middle layer resin material of the cold stretch sleeve packaging film of this comparative example was used as the middle layer film formula to prepare the cold stretch sleeve packaging film, and the obtained film thickness was 122 μm.

[0139] Comparative Example 6

[0140] The difference between the middle layer resin material of the cold stretch hood packaging film in this comparative example and that in Example 1 is that no chain dispersing agent is added to the material, and the other materials are the same as those in Example 1.

[0141] The middle layer resin material of the cold stretch sleeve packaging film of this comparative example is prepared from the following raw materials in parts by weight: 30 parts of HD-LLDPE, 15 parts of mLLDPE, 40 parts of LD-LLDPE, 1 part of UHMWPE and 5 parts of EVA. The raw material parameters are the same as those in Example 1.

[0142] The preparation method of the middle layer resin material of the cold stretch sleeve packaging film in this comparative example comprises the following steps: adding HD-LLDPE and UHMWPE into a high-speed mixer and mixing for 1 minute, then adding mLLDPE and EVA and continuing to mix for 1 minute, and finally mixing and granulating in a twin-screw compounding granulator with a melt temperature of 190 to 200°C to obtain the middle layer resin material of the cold stretch sleeve packaging film.

[0143] The middle layer resin material of the cold stretch sleeve packaging film of this comparative example was used as the middle layer film formula to prepare the cold stretch sleeve packaging film, and the obtained film thickness was 122 μm.

[0144] Comparative Example 7

[0145] The difference between the middle layer resin material of the cold stretch sleeve packaging film in this comparative example and that in Example 1 is that only LMWPEG is used in the chain dispersion driver, and the remaining raw material portions and parameters, as well as the material preparation method are the same as in Example 1.

[0146] The middle layer resin material of the cold stretch sleeve packaging film of this comparative example was used as the middle layer film formula to prepare the cold stretch sleeve packaging film, and the obtained film thickness was 122 μm.

[0147] Comparative Example 8

[0148] The difference between the middle layer resin material of the cold stretch hood packaging film in this comparative example and that in Example 1 is that only LMWPLA is used in the chain dispersion driver, and the remaining raw material portions and parameters, as well as the material preparation method are the same as in Example 1.

[0149] The middle layer resin material of the cold stretch sleeve packaging film of this comparative example was used as the middle layer film formula to prepare the cold stretch sleeve packaging film, and the obtained film thickness was 122 μm.

[0150] The cold stretch hood packaging films prepared in the above examples and comparative examples were tested using national standards, and the testing method is as follows:

[0151] The tensile strength is measured in accordance with GB / T1040.3-2006;

[0152] The elongation at break is measured in accordance with GB / T1040.3-2006;

[0153] The right-angle tear strength is measured according to QB / T1130;

[0154] The dart impact strength is measured in accordance with GB / T9639.1-2008;

[0155] The elastic recovery rate is measured according to the method specified in 5.6.6 of T / ZZB1008-2019 standard;

[0156] The specific test results are shown in Table 1.

[0157] Table 1 Performance test data of cold stretch hood packaging film

[0158]

[0159]

[0160] As shown in Table 1, it can be seen from the examples and comparative example 1 that a variety of materials are introduced into the middle layer resin special material of the cold stretch sleeve packaging film of the present invention. When applied to the preparation of the cold stretch sleeve packaging film, the amount of imported mLLDPE raw materials used is reduced compared with conventional films, and the industry standard requirements can be met even when the thickness is reduced.

[0161] It can be seen from Example 8 and Comparative Example 1 that, when the film is blown at the same thickness as a conventional film, the use of the special resin material for the middle layer of the cold stretch sleeve packaging film of the present invention can significantly improve the shrinkage rate and comprehensive mechanical properties of the cold stretch sleeve packaging film.

[0162] It can be seen from Examples 1 to 7 that the special material for the middle layer resin of the stretch sleeve packaging film prepared by using the further preferred material in the technical solution of the present invention can further improve the comprehensive performance of the stretch sleeve packaging film.

[0163] It can be seen from Example 1 and Comparative Examples 2 to 8 that the comprehensive mechanical properties of the stretch hood packaging film prepared without using the raw material ratio within the scope of the technical solution of the present invention, such as the strength and shrinkage rate of the film, are significantly lower than those of the examples, which further illustrates the importance and effectiveness of the technical solution of the present invention in improving the comprehensive performance of the stretch hood packaging film.

[0164] The various aspects, embodiments, and features of the present invention should be considered to be illustrative in all aspects and not limiting of the present invention, the scope of which is defined solely by the claims. Other embodiments, modifications, and uses will be apparent to those skilled in the art without departing from the spirit and scope of the claimed invention.

[0165] In the preparation method of the present invention, the order of each step is not limited to the order listed. For those skilled in the art, without creative work, the order of each step is also within the protection scope of the present invention. In addition, two or more steps or actions can be performed simultaneously.

[0166] Finally, it should be noted that the specific embodiments described herein are merely examples of the present invention, and are not intended to limit the implementation methods of the present invention. A person skilled in the art of the present invention may make various modifications or supplements to the specific embodiments described, or replace them in a similar manner. It is not necessary and impossible to provide all examples of all implementation methods here. However, these obvious changes or modifications derived from the essential spirit of the present invention still fall within the scope of protection of the present invention, and interpreting them as any additional limitation is contrary to the spirit of the present invention.

Claims

1. A special material for middle layer resin of cold stretch sleeve packaging film, characterized in that: The middle layer resin special material of the cold stretch sleeve packaging film is prepared from the following raw materials in parts by weight: 50-90 parts of LLDPE, 15-30 parts of mLLDPE, 1-5 parts of UHMWPE, 2-5 parts of EVA and 0.01-0.1 parts of chain dispersion driver; The LLDPE is a linear low-density polyethylene resin, including HD-LLDPE and LD-LLDPE.

2. The special resin material for the middle layer of the cold stretch hood packaging film according to claim 1, characterized in that: The cold stretch sleeve packaging film middle layer resin special material is prepared from the following raw materials in parts by weight: 30-50 parts of HD-LLDPE, 15-30 parts of mLLDPE, 20-40 parts of LD-LLDPE, 1-5 parts of UHMWPE, 2-5 parts of EVA and 0.01-0.1 parts of chain dispersion driver.

3. The special resin material for the middle layer of the cold stretch hood packaging film according to claim 1, characterized in that: The HD-LLDPE is a high-density linear low-density polyethylene resin, which is copolymerized with 1-hexene and LLDPE, and has a density of 0.922-0.926 g / cm 3 ; And / or, the HD-LLDPE is in powder form, and the powder particle size is 100 to 1000 μm; And / or, the HD-LLDPE has a melt flow rate (MFR) value of 0.6 to 3.0 g / 10 min at 190° C. and 2.16 kg.

4. The special resin material for the middle layer of the cold stretch hood packaging film according to claim 1, characterized in that: The LD-LLDPE is a low-density linear low-density polyethylene resin, which is copolymerized with 1-butene and LLDPE, and has a density of 0.910-0.919 g / cm 3 ; and / or, the LD-LLDPE is in the form of melt-granulated granules with a size of φ2 to 3 mm and L2 to 4 mm; And / or, the melt flow rate MFR value of the LD-LLDPE at 190° C. and 2.16 kg is 0.8 to 1.5 g / 10 min.

5. The special resin material for the middle layer of the cold stretch hood packaging film according to claim 1, characterized in that: The mLLDPE is a metallocene linear low-density polyethylene resin powder, and the powder particle size is 10 to 500 μm; And / or, the mLLDPE has a melt flow rate MFR value of 0.8 to 3.0 g / 10 min at 190° C. and 2.16 kg, and a density of 0.910 to 0.930 g / cm 3 .

6. The special material for middle layer resin of cold stretch hood packaging film according to claim 1, characterized in that: The UHMWPE is an ultra-high molecular weight polyethylene resin powder with a particle size of 50 to 500 μm, a weight average molecular weight Mw of 1.2 to 2 million, and a density of 0.920 to 0.924 g / cm 3 ; And / or, the VA content in the EVA is 5-20wt%, and the melt flow rate MFR value at 190°C and 2.16Kg is 1.0-6.0g / 10min.

7. The special resin material for the middle layer of the cold stretch hood packaging film according to claim 1, characterized in that: The chain dispersion driver comprises low molecular weight polyethylene glycol and low molecular weight polylactic acid, the weight average molecular weight Mw of the chain dispersion driver is 1000-8000; the ratio of the low molecular weight polyethylene glycol to the low molecular weight polylactic acid is (1-5): (5-1).

8. A method for preparing a special resin material for the middle layer of a cold stretch hood packaging film according to any one of claims 1 to 7, characterized in that: The preparation method comprises the following steps: adding HD-LLDPE and UHMWPE into a mixer for primary mixing, then adding a chain dispersing driver, mLLDPE, EVA and LD-LLDPE for secondary mixing, and finally mixing and granulating to obtain a special material for the middle layer resin of a cold stretch sleeve packaging film.

9. The preparation method according to claim 8, characterized in that: The first mixing time is 1 to 10 minutes, and the second mixing time is 1 to 10 minutes; And / or, the mixing and granulation is carried out in a twin-screw mixing and granulating machine, and the melt temperature is 180-210°C.

10. Use of the special resin material for the middle layer of a cold stretch hood packaging film according to any one of claims 1 to 7 in the preparation of a cold stretch hood packaging film.

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