A biaxially oriented polyethylene film with low heat shrinkage and a preparation method and application thereof

Abstract

This invention belongs to the technical field of flexible packaging materials, specifically a low-heat-shrinkage biaxially oriented polyethylene film, its preparation method, and its applications. The invention comprises a film body, which is composed of an upper corona layer, a sub-surface layer, an intermediate layer, a sub-inner layer, and a lower corona layer connected sequentially. The polyethylene film of this invention possesses excellent optical and mechanical properties, low high-temperature heat shrinkage, stable surface wetting tension, and uniform thickness, meeting the requirements of high-temperature, high-speed packaging bag forming.

Description

Technical Field

[0001] This invention belongs to the field of flexible packaging materials technology, and particularly relates to a low heat shrinkage biaxially oriented polyethylene film, its preparation method, and its application. Background Technology

[0002] In recent years, biaxially oriented polyethylene (BOPE) film has become increasingly popular in the packaging industry due to its excellent mechanical properties. This is because the high orientation of polyethylene in the machine direction and transverse direction enhances its mechanical properties and provides outstanding optical performance.

[0003] Polyethylene (PE) resin can be used in structural layers or base layers (not surface layers) to achieve polyethylene-rich film structures. When polyethylene is used as a surface or top layer, it typically imparts a smooth, glossy surface to the film. However, when multiple layers use polyethylene resin, the resin's melting point of around 120°C leads to a relatively high overall thermal shrinkage rate during high-speed packaging molding, causing problems such as bag wrinkling. This significantly limits its suitability for the widespread application of single-material recyclable materials today. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, this invention provides a low-heat-shrinkage biaxially oriented polyethylene film, its preparation method, and its applications. The polyethylene film of this invention exhibits low high-temperature heat shrinkage, stable surface wetting tension, and uniform thickness.

[0005] To achieve one of the above objectives, the present invention adopts the following technical solution:

[0006] A low-heat-shrinkage biaxially oriented polyethylene film includes a film body, which is composed of an upper corona layer, a sub-surface layer, an intermediate layer, a sub-inner layer, and a lower corona layer connected in sequence. The upper corona layer includes 92-99 parts by weight of a first low-pressure high-density polyethylene resin and 1-8 parts by weight of silica resin. The sub-surface layer includes 15-45 parts by weight of a second high-density polyethylene resin and 55-85 parts by weight of a first low-pressure high-density polyethylene resin. The intermediate layer includes 50-70 parts by weight of a second high-density polyethylene resin, 28.5-44.5 parts by weight of a first low-pressure high-density polyethylene resin, 1-3 parts by weight of polyphenylene sulfide resin, and 0.5-2.5 parts by weight of an antistatic resin. The sub-inner layer includes 15-45 parts by weight of a second high-density polyethylene resin and 55-85 parts by weight of a first low-pressure high-density polyethylene resin. The lower corona layer includes 92-99 parts by weight of a first low-pressure high-density polyethylene resin and 1-8 parts by weight of silica resin.

[0007] Preferably, the upper corona layer comprises 98.2 parts by mass of a first low-pressure high-density polyethylene resin and 1.8 parts by mass of a silica resin; the second surface layer comprises 20 parts by mass of a second high-density polyethylene resin and 80 parts by mass of a first low-pressure high-density polyethylene resin; the intermediate layer comprises 54.2 parts by mass of a second high-density polyethylene resin, 42 parts by mass of a first low-pressure high-density polyethylene resin, 2.2 parts by mass of a polyphenylene sulfide resin, and 1.6 parts by mass of an antistatic resin; the second inner layer comprises 20 parts by mass of a second high-density polyethylene resin and 80 parts by mass of a first low-pressure high-density polyethylene resin; and the lower corona layer comprises 97.8 parts by mass of a first low-pressure high-density polyethylene resin and 2.2 parts by mass of a silica resin.

[0008] Preferably, the density of the first low-pressure high-density polyethylene resin is 0.955 g / cm³. 3 The melt index is 1.5 g / 10min; the density of the silica resin is 0.93 g / cm³. 3 The melt index is 3.5 g / 10min; the density of the second high-density polyethylene resin is 0.953 g / cm³. 3 The melt index is 3.0 g / 10min; the density of the polyphenylene sulfide resin is 1.3 g / cm³. 3 The melt index is 7.8 g / 10min; the density of the antistatic resin is 0.912 g / cm³. 3 The melt index was 2.8 g / 10min.

[0009] Preferably, the thickness of the film body is 20-45 μm, the thickness of the upper corona layer is 0.5-3 μm, the thickness of the subsurface layer is 0.5-3 μm, the thickness of the intermediate layer is 8-41 μm, the thickness of the subinner layer is 0.5-3 μm, and the thickness of the lower corona layer is 0.5-3 μm.

[0010] Preferably, the thickness of the film body is 25 μm, the thickness of the upper corona layer is 1.5 μm, the thickness of the subsurface layer is 1.5 μm, the thickness of the intermediate layer is 19 μm, the thickness of the subinner layer is 1.5 μm, and the thickness of the lower corona layer is 1.5 μm.

[0011] To achieve the second objective mentioned above, the present invention provides a method for preparing a low heat shrinkage biaxially oriented polyethylene film. The specific steps are as follows: weigh the materials contained in the upper corona layer, subsurface layer, intermediate layer, subinner layer and lower corona layer of the film body, add them to a five-layer co-extrusion biaxially oriented production line, and obtain the biaxially oriented polyethylene film body by co-extrusion biaxial stretching molding in both longitudinal and transverse directions.

[0012] To achieve the third objective mentioned above, the present invention provides an application of a low-heat-shrinkage biaxially oriented polyethylene film, comprising the following steps:

[0013] S1. The matte varnish is gravure-printed onto the corona layer of the film body, dried and cured to form a matte varnish layer;

[0014] S2. The benzene-free ink is reverse-printed onto the lower corona layer of the film body, dried and cured to form an ink layer;

[0015] S3. Using a gluing roller, apply the composite adhesive evenly to the ink layer through dry lamination or solvent-free lamination. After being heated and pressed by a bonding roller, an adhesive layer is formed. The adhesive layer is then laminated with a blown polyethylene film to obtain a biaxially oriented polyethylene composite film with low heat shrinkage.

[0016] Preferably, the polyethylene composite film is composed of a matte varnish layer, a film body, an ink layer, an adhesive layer, and a blown polyethylene film connected in sequence; wherein, the thickness of the film body is 20-45μm, the thickness of the ink layer is 0.5-2μm, the thickness of the adhesive layer is 1.5-3μm, and the thickness of the blown polyethylene film is 50-100μm; the blown polyethylene film is a blown polyethylene film with a sealing temperature of 80℃-100℃.

[0017] Preferably, in steps S1 and S2, the printing speed is 200-350 m / min and the drying temperature is 60-80℃.

[0018] Preferably, the adhesive layer is formed by curing a two-component polyurethane adhesive resin, which includes a polyurethane base agent and a curing agent, wherein the mass ratio of the base agent to the curing agent is 20:4, and the manufacturer is Beijing Gaomeng.

[0019] The advantages of this invention are:

[0020] (1) The polyethylene film of the present invention has excellent optical and mechanical properties, low high-temperature heat shrinkage rate, stable surface wetting tension value, and uniform thickness. It can meet the requirements of high-temperature and high-speed packaging bag forming, presenting a very good bag forming effect, flat bag body, no wrinkles in heat-sealed area, and greatly improving the production efficiency of all PE material packaging materials.

[0021] (2) The upper and lower corona layers, as well as the subsurface and subinner layers of the polyethylene film of the present invention, are designed with high-density polyethylene resin and additives. The density and molecular weight of each layer are similar, which can reduce the temperature difference between each layer, thereby making the shrinkage rate of each layer tend to be consistent. After heating, the polyethylene chain molecules of each layer become entangled due to hydrogen bonding and oxidation interaction, which improves its thermal stability. A low proportion of polyphenylene sulfide resin is added to the middle layer of the polyethylene film. This resin has strong molecular regularity and good compatibility with polyethylene resin. Oxygen bridging and cross-linking are formed between adjacent macromolecules, resulting in outstanding thermal stability. The biaxially oriented polyethylene film can stably maintain its shape at high temperatures, has a low thermal shrinkage rate and excellent optical properties, and good mechanical properties such as tensile strength. It can meet the requirements of high-temperature bag making and there is no phenomenon of high-temperature wrinkling or warping.

[0022] (3) The polyethylene film of the present invention has uniform thickness, which is conducive to printing ink and reverse matte varnish. The overprinting tension is stable during the post-processing, and the color reproduction is high, which can effectively reduce the frequency of appearance quality defects in the film.

[0023] (4) The present invention obtains biaxially oriented polyethylene film by five-layer co-extrusion and biaxial stretching, and then produces composite film by dry lamination or solvent-free lamination. It has high thermal adhesion strength, low sealing temperature and wide heat sealing processing window, which can meet the requirements of increasingly high-speed packaging molding equipment, meet the use of various food and daily chemical products, and meet the national requirements for carbon reduction, low carbon and environmental protection for plastic flexible packaging materials. The use of biaxially oriented polyethylene film can reduce the amount of petrochemical polyethylene resin used, which is conducive to the recycling and disposal of products after the packaging cycle. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of the present invention.

[0025] The meanings of the symbols in the diagram are as follows:

[0026] 1-Polyethylene composite film, 2-Film body, 3-Matte varnish layer, 4-Upper corona layer, 5-Secondary surface layer, 6-Intermediate layer, 7-Secondary inner layer, 8-Lower corona layer, 9-Adhesive layer, 10-Blown polyethylene film, 11-Ink layer. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0028] like Figure 1As shown, a low heat shrinkage biaxially oriented polyethylene film includes a film body 2, which is composed of an upper corona layer 4, a sub-surface layer 5, an intermediate layer 6, a sub-inner layer 7, and a lower corona layer 8 connected sequentially. The upper corona layer 4 comprises 92-99 parts by weight of a first low-density polyethylene resin (HDPE) and 1-8 parts by weight of silica resin (SiO2). The sub-surface layer 5 comprises 15-45 parts by weight of a second high-density polyethylene resin (LHDPE) and 55-85 parts by weight of the first low-density polyethylene resin (HDPE). The intermediate layer 6 comprises 50-70 parts by weight of the second high-density polyethylene resin (LHDPE). The inner layer 7 comprises 28.5-44.5 parts by weight of first low-pressure high-density polyethylene resin (HDPE), 1-3 parts by weight of polyphenylene sulfide resin (PPS), and 0.5-2.5 parts by weight of antistatic resin (ATPE). The innermost layer 7 comprises 15-45 parts by weight of second high-density polyethylene resin (HDPE) and 55-85 parts by weight of first low-pressure high-density polyethylene resin (HDPE). The lower corona layer 8 comprises 92-99 parts by weight of first low-pressure high-density polyethylene resin (HDPE) and 1-8 parts by weight of silica resin (SiO2).

[0029] The density of the first low-pressure high-density polyethylene resin is 0.955 g / cm³. 3 The melt index is 1.5 g / 10min; the density of the silica resin is 0.93 g / cm³. 3 The melt index is 3.5 g / 10min; the density of the second high-density polyethylene resin is 0.953 g / cm³. 3 The melt index is 3.0 g / 10min; the density of the polyphenylene sulfide resin is 1.3 g / cm³. 3 The melt index is 7.8 g / 10min; the density of the antistatic resin is 0.912 g / cm³. 3 The melt index was 2.8 g / 10min.

[0030] The thickness of the film body 2 is 20-45 μm, the thickness of the upper corona layer 4 is 0.5-3 μm, the thickness of the subsurface layer 5 is 0.5-3 μm, the thickness of the intermediate layer 6 is 8-41 μm, the thickness of the subinner layer 7 is 0.5-3 μm, and the thickness of the lower corona layer 8 is 0.5-3 μm.

[0031] A method for preparing a low heat shrinkage biaxially oriented polyethylene film includes the following steps: weighing the materials contained in the upper corona layer 4, subsurface layer 5, intermediate layer 6, subinner layer 7, and lower corona layer 8 of the film body 2, and adding them to a five-layer co-extrusion biaxially oriented production line; obtaining the biaxially oriented polyethylene film body 2 by co-extrusion biaxial stretching molding in both longitudinal and transverse directions. The specific processing technology is shown in Table 1 below.

[0032] Table 1

[0033]

[0034] The application of a low heat shrinkage biaxially oriented polyethylene film includes the following steps:

[0035] S1. The matte varnish is gravure-printed onto the corona layer 4 of the film body 2, dried and cured to form the matte varnish layer 3.

[0036] S2. The benzene-free ink is reverse-printed onto the lower corona layer 8 of the film body 2, dried and cured to form the ink layer 11;

[0037] S3. Using a gluing roller, the composite adhesive is evenly applied to the ink layer 11 through dry lamination or solventless lamination. After being heated and pressed by a bonding roller, an adhesive layer 9 is formed. The adhesive layer 9 is then laminated with the blown polyethylene film 10 to obtain a biaxially oriented polyethylene composite film 1 with low heat shrinkage.

[0038] Specifically, the ink layer 11 has a thickness of 0.5-2μm, the adhesive layer 9 has a thickness of 1.5-3μm, and the blown polyethylene film 10 has a thickness of 50-100μm; the blown polyethylene film 10 is a blown polyethylene film with a sealing temperature of 80℃-100℃.

[0039] In steps S1 and S2, the printing speed is 200-350 m / min and the drying temperature is 60-80℃.

[0040] The adhesive layer 9 is formed by curing a two-component polyurethane adhesive resin, which includes a polyurethane base agent and a curing agent, wherein the mass ratio of the base agent to the curing agent is 20:4, and the manufacturer is Beijing Gaomeng.

[0041] Example 1

[0042] A low heat shrinkage biaxially oriented polyethylene film is prepared according to the above preparation method. The formulation of polyethylene film 1 is shown in Table 2 below.

[0043] Example 2

[0044] A low heat shrinkage biaxially oriented polyethylene film is prepared according to the above preparation method. The formulation of polyethylene film 2 is shown in Table 2 below.

[0045] Example 3

[0046] A low-heat-shrinkage biaxially oriented polyethylene film is prepared according to the above preparation method. The formulation of polyethylene film 3 is shown in Table 2 below.

[0047] Example 4

[0048] A low heat shrinkage biaxially oriented polyethylene film is prepared according to the above preparation method. The formulation of polyethylene film 4 is shown in Table 2 below.

[0049] Table 2

[0050]

[0051] Comparative Example 1

[0052] 25μm biaxially oriented polyethylene film (produced by Huangshan Yongxin).

[0053] The performance of the polyethylene films 1-4 prepared in Examples 1-4 and the biaxially oriented polyethylene film of Comparative Example 1 were tested, and the results are shown in Table 3 below:

[0054] Table 3

[0055]

[0056] As shown in Table 3, the biaxially oriented polyethylene films produced in Examples 1-4 all exhibited lower longitudinal and transverse high-temperature heat shrinkage rates than those of Comparative Example 1. The 20 μm thick film of Example 3 showed a 39.6% lower longitudinal and transverse high-temperature heat shrinkage rate than the 25 μm thick film of Comparative Example 1, indicating that the polyethylene film prepared by this invention possesses excellent heat resistance under high-temperature conditions. After one month of storage, the corona wetting tension of the polyethylene films in Examples 1-4 remained stable at 42 mN / m, which was higher than that of Comparative Example 1. After six months of storage, the corona wetting tension of the polyethylene films in Examples 1-4 remained stable at 40 mN / m, which was also higher than that of Comparative Example 1. Stable wetting tension effectively improves the adhesion of the film after subsequent printing and metallization coating. Examples 1-4, due to the rational design of different polyethylene resin and polyphenylene sulfide resin blends, demonstrated superior thermal and corona performance compared to Comparative Example 1.

[0057] The biaxially oriented polyethylene film of this invention has a stable surface wetting tension value and good printing effect, which can meet the requirements of high-speed printing machines in packaging companies, with a printing speed of 200-350m / min.

[0058] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A biaxially oriented polyethylene film with low heat shrinkage, characterized in that: The film body (2) comprises an upper corona layer (4), a subsurface layer (5), an intermediate layer (6), a subinner layer (7), and a lower corona layer (8) connected in sequence. The upper corona layer (4) comprises 92-99 parts by weight of a first low-pressure high-density polyethylene resin and 1-8 parts by weight of silica resin. The subsurface layer (5) comprises 15-45 parts by weight of a second high-density polyethylene resin and 55-85 parts by weight of a first low-pressure high-density polyethylene resin. The intermediate layer (6) comprises 50 parts by weight of a second high-density polyethylene resin and 50 parts by weight of a first low-pressure high-density polyethylene resin. -70 parts by weight of second high-density polyethylene resin, 28.5-44.5 parts by weight of first low-pressure high-density polyethylene resin, 1-3 parts by weight of polyphenylene sulfide resin and 0.5-2.5 parts by weight of antistatic resin, the innermost layer (7) includes 15-45 parts by weight of second high-density polyethylene resin and 55-85 parts by weight of first low-pressure high-density polyethylene resin, the lower corona layer (8) includes 92-99 parts by weight of first low-pressure high-density polyethylene resin and 1-8 parts by weight of silica resin; The first low pressure high density polyethylene resin has a density of 0.955 g / cm 3 and a melt index of 1.5 g / 10 min; the second high density polyethylene resin has a density of 0.953 g / cm 3 and a melt index of 3.0 g / 10 min.

2. The low heat shrinkage biaxially oriented polyethylene film according to claim 1, characterized in that: The upper corona layer (4) comprises 98.2 parts by mass of a first low-pressure high-density polyethylene resin and 1.8 parts by mass of a silica resin; the subsurface layer (5) comprises 20 parts by mass of a second high-density polyethylene resin and 80 parts by mass of a first low-pressure high-density polyethylene resin; the intermediate layer (6) comprises 54.2 parts by mass of a second high-density polyethylene resin, 42 parts by mass of a first low-pressure high-density polyethylene resin, 2.2 parts by mass of a polyphenylene sulfide resin and 1.6 parts by mass of an antistatic resin; the subinner layer (7) comprises 20 parts by mass of a second high-density polyethylene resin and 80 parts by mass of a first low-pressure high-density polyethylene resin; and the lower corona layer (8) comprises 97.8 parts by mass of a first low-pressure high-density polyethylene resin and 2.2 parts by mass of a silica resin.

3. A low-heat-shrinkage biaxially oriented polyethylene film according to claim 1 or 2, characterized in that: The density of the silicone resin is 0.93 g / cm 3 , the melt index is 3.5 g / 10 min; the density of the polyphenylene sulfide resin is 1.3 g / cm 3 , the melt index is 7.8 g / 10 min; the density of the antistatic resin is 0.912 g / cm 3 , the melt index is 2.8 g / 10 min.

4. The low heat shrinkage biaxially oriented polyethylene film according to claim 1, characterized in that: The thickness of the film body (2) is 20-45 μm, the thickness of the upper corona layer (4) is 0.5-3 μm, the thickness of the subsurface layer (5) is 0.5-3 μm, the thickness of the intermediate layer (6) is 8-41 μm, the thickness of the subinner layer (7) is 0.5-3 μm, and the thickness of the lower corona layer (8) is 0.5-3 μm.

5. A low-heat-shrinkage biaxially oriented polyethylene film according to claim 1 or 4, characterized in that: The thickness of the film body (2) is 25 μm, the thickness of the upper corona layer (4) is 1.5 μm, the thickness of the subsurface layer (5) is 1.5 μm, the thickness of the intermediate layer (6) is 19 μm, the thickness of the subinner layer (7) is 1.5 μm, and the thickness of the lower corona layer (8) is 1.5 μm.

6. A method for preparing a low-heat-shrinkage biaxially oriented polyethylene film as described in any one of claims 1-5, characterized in that, The specific steps are as follows: Weigh the materials contained in the upper corona layer (4), subsurface layer (5), middle layer (6), subinner layer (7) and lower corona layer (8) of the film body (2), add them to the five-layer co-extrusion biaxial stretching production line, and obtain the biaxially stretched polyethylene film body (2) by co-extrusion longitudinal and transverse biaxial stretching molding.

7. An application of a low-heat-shrinkage biaxially oriented polyethylene film as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. The matte varnish is gravure printed onto the corona layer (4) of the film body (2), dried and cured to form a matte varnish layer (3). S2. The benzene-free ink is reverse-printed onto the lower corona layer (8) of the film body (2) and dried and cured to form an ink layer; S3. Apply the composite adhesive evenly to the ink layer using a glue roller through dry lamination or solventless lamination. After heating and pressing by a bonding roller, an adhesive layer (9) is formed. The adhesive layer (9) is then laminated with a blown polyethylene film to obtain a biaxially stretched polyethylene composite film (1) with low heat shrinkage.

8. The application of a low heat shrinkage biaxially oriented polyethylene film according to claim 7, characterized in that, The polyethylene composite film (1) is composed of a matte oil layer (3), a film body (2), an ink layer, an adhesive layer (9), and a blown polyethylene film connected in sequence; wherein, the thickness of the film body (2) is 20-45μm, the thickness of the ink layer is 0.5-2μm, the thickness of the adhesive layer (9) is 1.5-3μm, and the thickness of the blown polyethylene film is 50-100μm.

9. The application of a low heat shrinkage biaxially oriented polyethylene film according to claim 7, characterized in that, In steps S1 and S2, the printing speed is 200-350 m / min and the drying temperature is 60-80℃.

10. The application of a low heat shrinkage biaxially oriented polyethylene film according to claim 7, characterized in that, The adhesive layer (9) is formed by curing a two-component polyurethane adhesive resin, which includes a polyurethane base agent and a curing agent, wherein the mass ratio of the base agent and the curing agent is 20:4.

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