Biaxially oriented polyethylene film with low thermal shrinkage rate as well as preparation method and application of biaxially oriented polyethylene film

Abstract

The invention belongs to the technical field of flexible packaging materials, and particularly relates to a low-thermal-shrinkage biaxially oriented polyethylene film as well as a preparation method and application thereof. The film comprises a film body, and the film body is composed of an upper corona layer, a secondary surface layer, a middle layer, a secondary inner layer and a lower corona layer which are connected in sequence. The polyethylene film has the advantages of excellent optical and mechanical properties, low high-temperature thermal shrinkage rate, stable surface wetting tension value and uniform thickness, and can meet the requirements of high-temperature and high-speed packaging bag-making molding.

Description

Technical Field

[0001] The invention belongs to the technical field of flexible packaging materials, and in particular relates to a low heat shrinkage biaxially stretched polyethylene film and a preparation method and application thereof. Background Art

[0002] In recent years, biaxially oriented polyethylene (BOPE) films have become increasingly popular in the packaging industry due to their excellent mechanical properties. This is because the high orientation of polyethylene in the machine and transverse directions gives it enhanced mechanical properties and outstanding optical properties.

[0003] Polyethylene (PE) resin can be used in the structural layer or base layer (non-surface layer) to achieve a polyethylene-rich film structure. When polyethylene is used for the surface or surface layer, it usually gives the film a smooth and shiny surface. When polyethylene resin is used in multiple layers, since the melting point of polyethylene resin itself is around 120°C, it will cause the overall thermal shrinkage rate of the film to be large during the high-speed packaging molding process, causing problems such as wrinkling of the bag body, which greatly limits its adaptability to the current widespread application of single material recyclability. Summary of the invention

[0004] In order to overcome the defects in the prior art, the present invention provides a low heat shrinkage biaxially stretched polyethylene film and a preparation method and application thereof. The polyethylene film of the present invention has low high temperature heat shrinkage, stable surface wetting tension value and uniform thickness.

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

[0006] A low heat shrinkage biaxially stretched polyethylene film comprises a film body, which is composed of an upper corona layer, a subsurface layer, an intermediate layer, a subinner layer and a lower corona layer connected in sequence, wherein the upper corona layer comprises 92-99 parts by weight of a low-pressure high-density polyethylene resin and 1-8 parts by weight of a silicon dioxide resin, the subsurface layer comprises 15-45 parts by weight of a linear high-density polyethylene resin and 55-85 parts by weight of a low-pressure high-density polyethylene resin, the intermediate layer comprises 50-70 parts by weight of a linear high-density polyethylene resin, 28.5-44.5 parts by weight of a low-pressure high-density polyethylene resin, 1-3 parts by weight of a polyphenylene sulfide resin and 0.5-2.5 parts by weight of an antistatic resin, the subinner layer comprises 15-45 parts by weight of a linear high-density polyethylene resin and 55-85 parts by weight of a low-pressure high-density polyethylene resin, and the lower corona layer comprises 92-99 parts by weight of a low-pressure high-density polyethylene resin and 1-8 parts by weight of a silicon dioxide resin.

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

[0008] Preferably, the density of the low pressure high density polyethylene resin is 0.955 g / cm 3 , the melt index is 1.5g / 10min; the density of silica resin is 0.93g / cm 3 , melt index is 3.5g / 10min; linear high density polyethylene resin. The density is 0.953g / cm 3 , melt index is 3.0g / 10min; density of polyphenylene sulfide resin is 1.3g / cm 3 , melt index is 7.8g / 10min; density of antistatic resin is 0.912g / cm 3 , the melt index is 2.8g / 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 middle 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 middle layer is 19 μm, the thickness of the sub-inner layer is 1.5 μm, and the thickness of the lower corona layer is 1.5 μm.

[0011] To achieve the second purpose above, the present invention provides a method for preparing a low heat shrinkage biaxially oriented polyethylene film, the specific steps of which are: weighing the materials contained in the upper corona layer, sub-surface layer, middle layer, sub-inner layer and lower corona layer of the film body, respectively adding them into a five-layer co-extrusion biaxially oriented production line, and preparing the biaxially oriented polyethylene film body by co-extrusion longitudinal and transverse biaxially oriented molding.

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

[0013] S1, gravure printing the matting oil on the upper corona layer of the film body, drying and curing the layer to form a matting oil layer;

[0014] S2, reverse printing the benzene-free ink on the lower corona layer of the film body, drying and curing the ink layer;

[0015] S3. Use a glue roller to evenly apply the composite glue on the ink layer through dry lamination or solvent-free lamination, form an adhesive layer after heating and pressing with a laminating roller, and laminate the adhesive layer with the blown polyethylene film to obtain a low heat shrinkage biaxially stretched polyethylene composite film.

[0016] Preferably, the polyethylene composite film is composed of a matte oil 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 20-45 μm, the thickness of the ink layer is 0.5-2 μm, the thickness of the adhesive layer is 1.5-3 μm, and the thickness of the blown polyethylene film is 50-100 μm; the blown polyethylene film is a blow-molded polyethylene film, and the sealing temperature is 80°C-100°C.

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

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

[0019] The advantages of the present invention are:

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

[0021] (2) The upper and lower corona layers, as well as the subsurface layer and the subinner layer of the polyethylene film of the present invention are designed with relatively high-density polyethylene resin and additives. The density and molecular weight of each layer are close, which can reduce the temperature difference between the layers, thereby making the shrinkage rate of each layer tend to be consistent; after heating, the polyethylene chain molecules of each layer are entangled with each other due to hydrogen bonds and oxidation interactions, thereby improving their thermal stability; a low proportion of polyphenylene sulfide resin is added to the middle layer of the polyethylene film, the resin has strong molecular weight regularity, has good compatibility with polyethylene resin, forms oxygen bridge branching and cross-linking between adjacent macromolecules, and has outstanding thermal stability; the biaxially oriented polyethylene film can stably maintain its shape at relatively high temperatures, has a relatively low thermal shrinkage rate and excellent optical properties, and has good mechanical properties such as tensile strength, which can meet the requirements of high-temperature bag making, and does not cause high-temperature wrinkling and curling.

[0022] (3) The polyethylene film of the present invention has uniform thickness, is conducive to printing ink and reverse matting oil, has stable overprint tension control during post-processing, has high color reproduction, and can effectively reduce the frequency of appearance quality problems of the film.

[0023] (4) The present invention obtains a biaxially oriented polyethylene film by a five-layer co-extrusion method of longitudinal and transverse biaxial stretching, and then produces a composite film by dry lamination or solvent-free lamination. The composite film has high hot adhesive strength, low sealing temperature, and a wide heat sealing processing window. It can adapt to the requirements of increasingly high-speed packaging molding equipment, meet the use of various food and daily chemical products, and meet the national carbon reduction, low carbon and environmental protection requirements for plastic flexible packaging materials. The use of biaxially oriented polyethylene film can reduce the use of petrochemical polyethylene resin, which is beneficial to the recovery and treatment of products after the packaging cycle. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0026] 1-polyethylene composite film, 2-film body, 3-matting oil layer, 4-upper corona layer, 5-subsurface layer, 6-middle layer, 7-subinner layer, 8-lower corona layer, 9-adhesive layer, 10-blown polyethylene film, 11-ink layer. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention.

[0028] like Figure 1As shown, a low heat shrinkage biaxially stretched polyethylene film comprises 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 in sequence, wherein the upper corona layer 4 comprises 92-99 parts by weight of a low-pressure high-density polyethylene resin (HDPE) and 1-8 parts by weight of a silicon dioxide resin (SiO2), the sub-surface layer 5 comprises 15-45 parts by weight of a linear high-density polyethylene resin (LHDPE) and 55-85 parts by weight of a low-pressure high-density polyethylene resin (HDPE), the intermediate layer 6 comprises 50-70 parts by weight of a linear high density polyethylene resin (LHDPE), 28.5-44.5 parts by mass of low pressure high density polyethylene resin (HDPE), 1-3 parts by mass of polyphenylene sulfide resin (PPS) and 0.5-2.5 parts by mass of antistatic resin (ATPE), the sub-inner layer 7 includes 15-45 parts by mass of linear high density polyethylene resin (LHDPE) and 55-85 parts by mass of low pressure high density polyethylene resin (HDPE), and the lower corona layer 8 includes 92-99 parts by mass of low pressure high density polyethylene resin (HDPE) and 1-8 parts by mass of silica resin (SiO2).

[0029] Among them, the density of low-pressure high-density polyethylene resin is 0.955g / cm 3 , the melt index is 1.5g / 10min; the density of silica resin is 0.93g / cm 3 , melt index is 3.5g / 10min; linear high density polyethylene resin. The density is 0.953g / cm 3 , melt index is 3.0g / 10min; density of polyphenylene sulfide resin is 1.3g / cm 3 , melt index is 7.8g / 10min; density of antistatic resin is 0.912g / cm 3 , the melt index is 2.8g / 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 middle layer 6 is 8-41 μm, the thickness of the sub-inner 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, the specific steps are: weighing the materials contained in the upper corona layer 4, the sub-surface layer 5, the middle layer 6, the sub-inner layer 7 and the lower corona layer 8 of the film body 2, respectively adding them into a five-layer co-extrusion biaxially oriented production line, and preparing the biaxially oriented polyethylene film body 2 by co-extrusion longitudinal and transverse biaxially oriented molding. The specific processing technology is shown in Table 1 below:

[0032] Table 1

[0033]

[0034]

[0035] An application of a low heat shrinkage biaxially stretched polyethylene film comprises the following steps:

[0036] S1, gravure printing the matting oil on the upper corona layer 4 of the film body 2, and drying and curing the resulting matting oil layer 3;

[0037] S2, reverse printing the benzene-free ink on the lower corona layer 8 of the film body 2, and drying and curing the ink layer 11;

[0038] S3. Use a glue roller to evenly apply the composite glue on the ink layer 11 through dry lamination or solvent-free lamination, and form an adhesive layer 9 after heating and pressing with a laminating roller. The adhesive layer 9 is compounded with the blown polyethylene film 10 to obtain a low heat shrinkage biaxially stretched polyethylene composite film 1.

[0039] Specifically, the thickness of the ink layer 11 is 0.5-2 μm, the thickness of the adhesive layer 9 is 1.5-3 μm, and the thickness of the blown polyethylene film 10 is 50-100 μm; the blown polyethylene film 10 is a blow-molded polyethylene film, and the sealing temperature is 80° C.-100° C.

[0040] In step S1 and step S2, the printing speed is 200-350 m / min, and the drying temperature is 60-80°C.

[0041] The adhesive layer 9 is formed by curing a two-component polyurethane glue resin. The two-component polyurethane glue includes a polyurethane main agent and a curing agent, wherein the mass ratio of the main agent to the curing agent is 20:4, and the manufacturer is Beijing Gaomeng.

[0042] Example 1

[0043] A low heat shrinkage biaxially stretched polyethylene film is prepared according to the above preparation method to obtain a polyethylene film 1, and the formula of the polyethylene film 1 is shown in Table 2 below.

[0044] Example 2

[0045] A low heat shrinkage biaxially stretched polyethylene film is prepared according to the above preparation method to obtain a polyethylene film 2, and the formula of the polyethylene film 2 is shown in Table 2 below.

[0046] Example 3

[0047] A low heat shrinkage biaxially stretched polyethylene film, a polyethylene film 3 is prepared according to the above preparation method, and the formula of the polyethylene film 3 is shown in Table 2 below.

[0048] Example 4

[0049] A low heat shrinkage biaxially stretched polyethylene film is prepared according to the above preparation method to obtain a polyethylene film 4, and the formula of the polyethylene film 4 is shown in Table 2 below.

[0050] Table 2

[0051]

[0052] Comparative Example 1

[0053] 25μm biaxially oriented polyethylene film (produced by Huangshan Yongxin).

[0054] The polyethylene films 1-4 prepared in Examples 1-4 and the biaxially oriented polyethylene film of Comparative Example 1 were tested for performance, and the results are shown in Table 3 below:

[0055] Table 3

[0056]

[0057]

[0058] As can be seen from Table 3, the biaxially oriented polyethylene films produced in Examples 1-4 have lower high-temperature heat shrinkage in the longitudinal and transverse directions than those in Comparative Example 1. The longitudinal and transverse high-temperature heat shrinkage in Example 3 with a thickness of 20 μm is 39.6% lower than that in Comparative Example 1 with a thickness of 25 μm, indicating that the polyethylene film prepared by the present invention has good heat resistance under high temperature environment. After storage for 1 month, the lower corona wetting tension of the polyethylene films of Examples 1-4 is stable at 42 mN / m, which is higher than the lower corona surface wetting tension of Comparative Example 1. After storage for 6 months, the lower corona wetting tension of the polyethylene films of Examples 1-4 is stable at 40 mN / m, which is higher than the lower corona surface wetting tension of Comparative Example 1. The stable wetting tension can effectively improve the adhesion of the film for post-processing printing composite aluminum plating coating. Since Examples 1-4 are reasonably designed to compound different polyethylene resins with polyphenylene sulfide resins, they are superior to Comparative Example 1 in terms of thermal performance and corona performance.

[0059] The biaxially stretched polyethylene film of the present invention has a stable surface wetting tension value and a good printing effect, and can meet the requirements of high-speed printing machines of packaging enterprises, and the printing speed can be 200-350 m / min.

[0060] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A low heat shrinkage biaxially oriented polyethylene film, characterized in that: The invention comprises a film body (2), wherein the film body (2) 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 in sequence, wherein the upper corona layer (4) comprises 92-99 parts by weight of a low-pressure high-density polyethylene resin and 1-8 parts by weight of a silicon dioxide resin, the sub-surface layer (5) comprises 15-45 parts by weight of a linear high-density polyethylene resin and 55-85 parts by weight of a low-pressure high-density polyethylene resin, the intermediate layer (6) comprises 5 0-70 parts by mass of linear high-density polyethylene resin, 28.5-44.5 parts by mass of low-pressure high-density polyethylene resin, 1-3 parts by mass of polyphenylene sulfide resin and 0.5-2.5 parts by mass of antistatic resin, the sub-inner layer (7) comprises 15-45 parts by mass of linear high-density polyethylene resin and 55-85 parts by mass of low-pressure high-density polyethylene resin, and the lower corona layer (8) comprises 92-99 parts by mass of low-pressure high-density polyethylene resin and 1-8 parts by mass of silica resin.

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 low-pressure high-density polyethylene resin and 1.8 parts by mass of a silicon dioxide resin, the sub-surface layer (5) comprises 20 parts by mass of a linear high-density polyethylene resin and 80 parts by mass of a low-pressure high-density polyethylene resin, the middle layer (6) comprises 54.2 parts by mass of a linear high-density polyethylene resin, 42 parts by mass of a 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 sub-inner layer (7) comprises 20 parts by mass of a linear high-density polyethylene resin and 80 parts by mass of a low-pressure high-density polyethylene resin, and the lower corona layer (8) comprises 97.8 parts by mass of a low-pressure high-density polyethylene resin and 2.2 parts by mass of a silicon dioxide resin.

3. A low heat shrinkage biaxially oriented polyethylene film according to claim 1 or 2, characterized in that: The density of the low-pressure high-density polyethylene resin is 0.955 g / cm 3 , the melt index is 1.5g / 10min; the density of silica resin is 0.93g / cm 3 , melt index is 3.5g / 10min; linear high density polyethylene resin. The density is 0.953g / cm 3 , melt index is 3.0g / 10min; density of polyphenylene sulfide resin is 1.3g / cm 3 , melt index is 7.8g / 10min; density of antistatic resin is 0.912g / cm 3 , the melt index is 2.8g / 10min.

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 sub-surface layer (5) is 0.5-3 μm, the thickness of the middle layer (6) is 8-41 μm, the thickness of the sub-inner 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 sub-surface layer (5) is 1.5 μm, the thickness of the middle layer (6) is 19 μm, the thickness of the sub-inner 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 according to any one of claims 1 to 5, characterized in that: The specific steps are as follows: weigh the materials contained in the upper corona layer (4), the secondary surface layer (5), the middle layer (6), the secondary inner layer (7) and the lower corona layer (8) of the film body (2), respectively add them into a 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 the low heat shrinkage biaxially oriented polyethylene film according to any one of claims 1 to 5, characterized in that: The steps include: S1, gravure printing the matting oil on the upper corona layer (4) of the film body (2), and drying and curing the resulting matting oil layer (3); S2, reverse printing the benzene-free ink on the lower corona layer (8) of the film body (2), drying and curing the ink layer; S3. Use a glue roller to evenly apply the composite glue on the ink layer through dry lamination or solvent-free lamination, and form an adhesive layer (9) after heating and pressing with a laminating roller. The adhesive layer (9) is laminated with a blown polyethylene film to obtain a low heat shrinkage biaxially stretched polyethylene composite film (1).

8. The use 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 which are connected in sequence; wherein the thickness of the film body (2) is 20-45 μm, the thickness of the ink layer is 0.5-2 μm, the thickness of the adhesive layer (9) is 1.5-3 μm, and the thickness of the blown polyethylene film is 50-100 μm.

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

10. The use 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 glue resin, wherein the two-component polyurethane glue comprises a polyurethane main agent and a curing agent, wherein the mass ratio of the main agent to the curing agent is 20:4.

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