CN114196101B

CN114196101B - Polyethylene heavy packaging film and preparation method thereof

Info

Publication number: CN114196101B
Application number: CN202111558393.4A
Authority: CN
Inventors: 岳雅娟; 王俊; 周珉; 李永波; 张俊红; 侯胜岗
Original assignee: Shijiazhuang Zhonghui Medicine Packaging Co ltd
Current assignee: Shijiazhuang Zhonghui Medicine Packaging Co ltd
Priority date: 2021-12-18
Filing date: 2021-12-18
Publication date: 2023-02-28
Anticipated expiration: 2041-12-18
Also published as: CN114196101A

Abstract

The application relates to the technical field of packaging films, and particularly discloses a polyethylene heavy packaging film and a preparation method thereof, wherein the polyethylene heavy packaging film comprises an inner layer, a middle layer and an outer layer, and the inner layer, the middle layer and the outer layer are sequentially co-extruded to prepare the polyethylene heavy packaging film; the inner layer and the outer layer are respectively prepared from the following raw materials in parts by weight: 20-30% of low-density polyethylene, 30-45% of linear low-density polyethylene, 15-20% of methacrylic acid copolymer, 3.5-9% of maleic anhydride grafted polypropylene, 3-10% of heat-sealing auxiliary agent, 1-7% of erucamide, 1-5% of polyester type polyurethane and 1-4% of antistatic agent; the middle layer is prepared from the following raw materials in parts by weight: 52-66% of metallocene polyethylene, 15-19% of high-density polyethylene, 7.5-9.5% of low-density polyethylene, 3-15% of ethylene-ethyl acrylate copolymer and 1-8% of color master batch. The heat seal strength of the heavy packaging film can reach 33.8N/15mm at most, and the heavy packaging film has excellent heat seal performance.

Description

Polyethylene heavy packaging film and preparation method thereof

Technical Field

The application relates to the field of packaging films, in particular to a polyethylene heavy packaging film and a preparation method thereof.

Background

At present, the packaging film capable of carrying 10-50kg of solid particles or powdery materials is generally referred to as a heavy packaging film. The heavy packaging film has excellent wear resistance and strength, so that the heavy packaging film is widely applied and mainly used for packaging plastic raw materials, fertilizers, catalysts and the like.

In the related technology, the polyethylene repackaging film is prepared by co-extruding an inner layer, a middle layer and an outer layer, wherein the inner layer and the middle layer contain LLDPE and m-LLDPE, and the outer layer contains LLDPE, LDPE and m-LLDPE.

The heavy packaging film has excellent mechanical property, but the heat sealing property is weaker, and the sealing quality is closely related to the heat sealing property. The heat sealing performance is weak, so that the packaging film is easy to leak in the links of production, transportation, shelf sale and the like after the packaging film is filled with contents; it also can occur that the repackaging film leaks air, causing deterioration and mildew of the contents that are sensitive to oxygen and water vapor.

Disclosure of Invention

In order to improve the heat sealing performance of the polyethylene heavy packaging film, the application provides the polyethylene heavy packaging film and the preparation method thereof.

In a first aspect, the present application provides a polyethylene heavy packaging film, which adopts the following technical scheme:

the polyethylene heavy packaging film comprises an inner layer, a middle layer and an outer layer, wherein the inner layer, the middle layer and the outer layer are sequentially co-extruded to form the polyethylene heavy packaging film;

the inner layer and the outer layer are both prepared from the following raw materials in percentage by weight: 20-30% of low-density polyethylene, 30-45% of linear low-density polyethylene, 15-20% of methacrylic acid copolymer, 3.5-9% of maleic anhydride grafted polypropylene, 3-10% of heat-sealing auxiliary agent, 1-7% of erucamide, 1-5% of polyester type polyurethane and 1-4% of antistatic agent;

the middle layer is prepared from the following raw materials in percentage by weight: 52-66% of metallocene polyethylene, 15-19% of high-density polyethylene, 7.5-9.5% of low-density polyethylene, 3-15% of ethylene-ethyl acrylate copolymer and 1-8% of color master batch.

By adopting the technical scheme, the excellent heat sealing performance of the heavy packaging film is mainly reflected in the three aspects of high heat sealing strength, strong inclusion heat sealing performance and good heat resistance. The low density polyethylene added into the inner layer and the outer layer has good chemical stability, the melting point of the low density polyethylene is between 105 ℃ and 120 ℃, and the heat sealing property is good. The linear low-density polyethylene has the advantages of strong heat resistance and strong inclusion heat sealability, and can still have good heat seal strength under the condition that the surface of the inner layer or the outer layer of the heavy packaging film is stained with dust, grease or impurities and the like. The methacrylic acid copolymer is a copolymer of methyl methacrylate and methacrylic acid which are completely polymerized, has good inclusion heat sealability, and can further improve the heat seal strength of the polyethylene heavy packaging film by adding the methacrylic acid copolymer.

The maleic anhydride grafted polypropylene is characterized in that a strong polar side group of maleic anhydride is introduced into a nonpolar molecular main chain of polypropylene, so that the surface of the polypropylene is modified, and the dispersibility of the polypropylene in a system is improved; and the maleic anhydride grafted polypropylene can also be used as a compatilizer to be added into the system, so that the compatibility of all raw materials in the system is improved. In addition, after the maleic anhydride grafted polypropylene is blended with the linear low density polyethylene, the heat seal strength of the linear low density polyethylene can be improved.

The erucamide can be used as an opening agent and a slipping agent, can improve the antistatic property of the heavy packaging film, effectively prevents the absorption and sticking between films of the heavy packaging film, can increase the smoothness of the surface of the film, prevents dust from being deposited on the surface of the film, and improves the heat sealability of inclusions, thereby improving the heat sealability of the heavy packaging film. However, the addition of erucamide tends to cause migration from the interior of the film to the skin layers, thereby reducing the heat seal strength of the repackaged film. But the surface of the erucamide dead weight packaging film can be better prevented from being separated out by adding the polyester polyurethane, and the polyester polyurethane can also be used as an adhesive to improve the viscosity and the mechanical stability of the dead weight packaging film.

When the antistatic agent is added to the raw material of the heavy packaging film in a molten state, the molecules of the antistatic agent can form a dense orientation arrangement at the interface between the resin and the air or between the resin and the machine, wherein the lipophilic groups extend to the inside of the resin and the hydrophilic groups extend to the outside of the resin. After the resin is cured, the hydrophilic groups on the molecules of the antistatic agent are arranged towards the air side to form a monomolecular conductive layer. During processing and use, the molecular layer of the antistatic agent on the surface of the material is damaged through stretching, rubbing, washing and the like, and the antistatic performance is reduced. After a period of time, the antistatic agent molecules in the material continuously migrate to the surface, so that the defect part is recovered and the antistatic effect is displayed again. In addition, the antistatic agent can prevent powder materials from being adsorbed at the bag mouth, and improve the heat seal strength of the heavy packaging film, thereby improving the heat seal performance of the heavy packaging film.

The metallocene polyethylene added in the middle layer has lower melting point and obvious melting zone, and the heat seal strength is superior to that of the traditional polyethylene. By adding the high-density polyethylene, the polyethylene heavy packaging film has higher heat seal strength. The ethylene ethyl acrylate copolymer is a polymer with thermoplasticity, extremely high cohesiveness and low clean crystallinity, has good thermal stability, and improves the heat sealing performance of the heavy packaging film.

Preferably, the method comprises the following steps: the inner layer and the outer layer are prepared from the following raw materials in percentage by weight: 22-27% of low-density polyethylene, 33-41% of linear low-density polyethylene, 17-18% of methacrylic acid copolymer, 5-8% of maleic anhydride grafted polypropylene, 4-8% of heat-sealing auxiliary agent, 2-4% of erucamide, 1.5-3% of polyester polyurethane and 1.5-5% of antistatic agent;

the middle layer is prepared from the following raw materials in percentage by weight: 52-59% of metallocene polyethylene, 17-18% of high-density polyethylene, 8-9% of low-density polyethylene, 6-10% of ethylene-ethyl acrylate copolymer and 1-6.5% of color master batch.

Preferably, the method comprises the following steps: the methacrylic acid copolymer is prepared from the following raw materials in parts by weight: 60-80 parts of methyl methacrylate, 25-30 parts of methacrylic acid, 1-5 parts of sodium dodecyl benzene sulfonate, 1-5 parts of pentaerythritol tetrapropionate, 1.5-2.5 parts of didodecyl thiodipropionate and 11-15 parts of potassium persulfate.

By adopting the technical scheme, the methacrylic acid copolymer is a copolymer completely polymerized by methyl methacrylate and methacrylic acid. The sodium dodecyl benzene sulfonate is used as an emulsifier, so that a uniform and stable dispersion system is formed in the methacrylic acid copolymer, and the effect of improving the heat sealing performance of the methacrylic acid copolymer is exerted more easily. The blending of pentaerythritol tetrapropionate and didodecyl thiodipropionate can improve the heat sealability of the heavy packaging film. Potassium persulfate is used as an initiator and can initiate the polymerization reaction of methyl methacrylate and methylacrylic acid, so that the methacrylic acid copolymer is obtained.

Preferably, the method comprises the following steps: the weight percentage of the methacrylic acid copolymer in the inner layer and the outer layer is 15-18.5%.

Preferably, the method comprises the following steps: the methacrylic acid copolymer is prepared by the following operation steps:

adding methyl methacrylate, methacrylic acid, sodium dodecyl benzene sulfonate, pentaerythritol tetrapropionate and didodecyl thiodipropionate into deionized water, and stirring for dissolving to obtain a monomer pre-emulsion;

adding potassium persulfate into deionized water, mixing and dissolving to obtain an initiator solution;

mixing the monomer pre-emulsion with an initiator solution, stirring and heating to 75-85 ℃, uniformly mixing, and reacting for 3-4h under the condition of nitrogen; cooling, demulsifying, washing and drying in sequence to obtain the methacrylic acid copolymer.

Preferably, the method comprises the following steps: the heat sealing auxiliary agent is ethylene-vinyl acetate copolymer.

By adopting the technical scheme, the ethylene-vinyl acetate copolymer has more vinyl acetate structural units, has the characteristics of high impact resistance, excellent flexibility and heat sealing performance and the like, and can improve the heat sealing performance of the heavy packaging film.

Preferably, the method comprises the following steps: the antistatic agent is ethoxylated aliphatic alkylamine.

By adopting the technical scheme, the ethoxylated aliphatic alkylamine is a nonionic surfactant, has high stability, is not easily influenced by the existence of strong electrolyte, has good antistatic performance, can prevent powder materials from being adsorbed at the bag mouth and improve the heat seal strength of the heavy packaging film.

Preferably, the following components: the weight ratio of the maleic anhydride grafted polypropylene to the linear low density polyethylene is 1: (8-10).

By adopting the technical scheme, the heat sealing performance of the heavy packaging film can be improved by optimizing the weight ratio of the maleic anhydride grafted polypropylene to the linear low-density polyethylene.

Preferably, the following components: the weight ratio of the polyester polyurethane to the erucamide is 1: (1.5-2.5).

By adopting the technical scheme, through the optimization of the weight ratio of the polyester polyurethane to the erucamide, the precipitation of the erucamide on the surface of the heavy packaging film can be reduced, and the heat sealing performance of the heavy packaging film is improved.

In a second aspect, the present application provides a method for preparing any one of the polyethylene heavy packaging films, which is specifically realized by the following technical scheme:

a preparation method of polyethylene repackaging film comprises the following operation steps:

preparing the inner and outer layer films: uniformly mixing low-density polyethylene, linear low-density polyethylene, methacrylic acid copolymer, maleic anhydride grafted polypropylene, heat-sealing auxiliary agent, erucamide, polyester type polyurethane and antistatic agent, and mixing at 170-190 ℃ under the conditions of 60-100r/min and processing pressure of 40-45MPa to obtain inner and outer layer molten materials;

preparing a middle-layer film: mixing metallocene polyethylene, high density polyethylene, low density polyethylene, ethylene-ethyl acrylate copolymer and color master batch, and mixing at 170-190 deg.C under 60-100r/min and processing pressure of 40-45MPa to obtain middle layer molten material;

respectively fusing and extruding the inner layer molten material, the outer layer molten material and the middle layer molten material to form a film bubble; cooling and forming, stabilizing the film bubble, and drawing and stretching to obtain a film strip; cooling the membrane strip to obtain a thin membrane;

coiling the cooled film to obtain a semi-finished film coil; and then sequentially carrying out unreeling, high-frequency electric spark treatment, printing, hot air drying and cold air drying to obtain the polyethylene heavy packaging film.

In summary, the present application includes at least one of the following beneficial technical effects:

(1) The heat seal strength of the polyethylene heavy packaging film can reach 33.8N/15mm at most, the heat seal performance of the heavy packaging film is effectively improved, and the heavy packaging film is found through inspection of a sample that the surface of the heavy packaging film is not adhered or melted under the conditions of applying 9.8N load and drying for 1h at 80 ℃, the heat resistance is excellent, and the peeling condition is not generated.

(2) The heat sealing performance of the heavy packaging film can be improved by using the methacrylic acid copolymer, the maleic anhydride grafted polypropylene, the antistatic agent, the erucamide, the ethylene-ethyl acrylate copolymer and the heat sealing auxiliary agent selected by the polyethylene heavy packaging film.

Detailed Description

The present application will be described in further detail with reference to specific examples.

The following raw materials are all commercially available products, and all the raw materials are fully disclosed in the application, and should not be understood as having a limiting effect on the sources of the raw materials, and specifically: low density polyethylene with density of 0.91g/cm ³ -0.93g/cm ³ (ii) a Linear low density polyethylene having a density of 0.932g/cm; maleic anhydride grafted polypropylene, type 350k; erucamide, content of active substance 99%; polyester polyurethane, model 575A; metallocene polyethylene, type 1018MF; high density polyethylene, model HHMTR-131; ethylene-ethyl acrylate copolymer, the effective concentration of ethyl acrylate is 16%; color master batch with the model of white 9302a; methyl methacrylate, the content of effective substances is 99.5 percent; methacrylic acid, with an active substance content of 99%; methacrylic acid copolymer, viscosity 100-200Pa.s.

The following are examples of the preparation of methacrylic acid copolymers in the present application:

preparation example 1

The methacrylic acid copolymer in certain embodiments of the present application is prepared by the following method:

according to the mixing amount shown in Table 1, methyl methacrylate, methacrylic acid, sodium dodecyl benzene sulfonate and pentaerythritol tetrapropionate were added to 15L of deionized water and stirred to dissolve, thereby obtaining a monomer pre-emulsion.

Adding potassium persulfate into 200mL of deionized water, mixing and dissolving to obtain an initiator solution.

And mixing the monomer pre-emulsion with an initiator solution, stirring, heating to 80 ℃, uniformly mixing, and reacting for 4 hours under the condition of nitrogen. And after cooling, demulsifying with 250mL of hydrochloric acid, washing with deionized water, and performing vacuum filtration and drying to obtain the methacrylic acid copolymer.

Preparation example 2

according to the mixing amount shown in Table 1, methyl methacrylate, methacrylic acid, sodium dodecyl benzene sulfonate and dilauryl thiodipropionate were added into 15L of deionized water, and stirred and dissolved to obtain a monomer pre-emulsion.

And mixing the monomer pre-emulsion with an initiator solution, stirring, heating to 80 ℃, uniformly mixing, and reacting for 4 hours under the condition of nitrogen. After cooling, demulsifying by using 15L hydrochloric acid, washing by using deionized water, and performing vacuum filtration and drying to obtain the methacrylic acid copolymer.

Preparation example 3

according to the mixing amount shown in Table 1, methyl methacrylate, methacrylic acid, sodium dodecyl benzene sulfonate, pentaerythritol tetrapropionate and didodecyl thiodipropionate were added to 15L of deionized water and stirred to dissolve, thereby obtaining a monomer pre-emulsion.

Preparation examples 4 to 7

The methacrylic acid copolymers of production examples 4 to 7 were prepared in the same manner as in production example 1 except that the raw material components were different, and the details are shown in Table 1.

TABLE 1 blending amounts (unit: g) of respective raw materials for methacrylic acid copolymers of preparation examples 1 to 7

Example 1

A polyethylene repackaging film prepared by the operations of:

according to the mixing amount of the table 2, the inner and outer layer film raw materials: uniformly mixing low-density polyethylene, linear low-density polyethylene, the methacrylic acid copolymer prepared in preparation example 1, maleic anhydride grafted polypropylene, a heat-sealing auxiliary agent ethylene-vinyl alcohol copolymer, erucamide, polyester type polyurethane and antistatic agent polyethylene glycol, and mixing at 245 ℃, 80r/min and the processing pressure of 45MPa to obtain an inner-layer molten material and an outer-layer molten material;

preparing a middle-layer film according to the doping amount in the table 3: mixing metallocene polyethylene, high-density polyethylene, low-density polyethylene, ethylene-ethyl acrylate copolymer and color master batch, and mixing at 245 ℃ and 80r/min under the condition that the processing pressure is 45MPa to obtain middle-layer molten material;

respectively fusing and extruding the raw materials of the inner layer film, the outer layer film and the middle layer film to form a film bubble, cooling and forming, stabilizing the film bubble, drawing and stretching, and cooling at the temperature of 5 ℃ to obtain a film;

and (4) coiling the cooled film, and sequentially carrying out shoulder insertion and embossing to obtain the polyethylene heavy packaging film.

Example 2

The polyethylene repackaging film of example 2 was prepared in exactly the same manner as in example 1, except that the methacrylic acid copolymer prepared in preparation example 2 was selected as the raw material for the inner and outer layers, as shown in table 2.

Example 3

The polyethylene repackaging film of example 3 was prepared in exactly the same manner as in example 1, except that the methacrylic acid copolymer prepared in preparation example 3 was selected as the raw material for the inner and outer layers, as shown in table 2.

Examples 4 to 7

The polyethylene repackaging films of examples 4 to 7 were prepared in the same manner and in the same types as those of example 3, except that the amounts of the respective materials of the inner layer, the middle layer and the outer layer were different, as shown in tables 2 and 3.

TABLE 2 blending amounts (unit: kg) of respective raw materials for inner and outer layers of polyethylene heavy packaging films of examples 1 to 7

Starting materials	Examples 1 to 3	Example 4	Example 5	Example 6	Example 7
						Low density polyethylene	20	22	25	27	30
Linear low density polyethylene	30	33	37	41	45
						Methacrylic acid copolymer	20	18	16	17	15
Maleic anhydride grafted polypropylene	8	9	5	7	4
						Ethylene-vinyl alcohol copolymer	10	8	6	4	3
Erucamide	3	7	4	2	1
						Polyester type polyurethane	5	2	5	1	1.5
Polyethylene glycol	4	1	2	1	1.5

TABLE 3 blending amounts (unit: kg) of respective raw materials of the middle layers of the polyethylene heavy packaging films of examples 1 to 7

Example 8

The polyethylene repackaging film of example 8 was produced in the same manner as in example 5, except that the heat-sealing auxiliary agent was ethylene-vinyl acetate copolymer, and the kinds and amounts of the other materials were the same as in example 5.

Example 9

The polyethylene repackaging film of example 9 was prepared in exactly the same manner as in example 8, except that the antistatic agent was ethoxylated aliphatic alkylamine and the remaining raw material types and amounts were the same as in example 9.

Examples 10 to 14

The polyethylene repackaging films of examples 10 to 14 were prepared in exactly the same manner as in example 9, except that the amounts of the respective raw materials for the inner and outer layers were different, as shown in table 4.

TABLE 4 blending amounts (unit: kg) of respective raw materials for inner and outer layers of polyethylene heavy packaging films of examples 10 to 14

Examples 15 to 19

The polyethylene repackaging films of examples 15-19 were prepared in exactly the same manner as in example 11, except that the amounts of the materials in the inner and outer layers were different, as detailed in Table 5.

TABLE 5 blending amounts (unit: kg) of respective raw materials for inner and outer layers of polyethylene heavy packaging films of examples 15 to 19

Examples 20 to 24

The polyethylene repackaging films of examples 20-24 were prepared in exactly the same manner as in example 16, except that the amounts of the materials in the inner and outer layers were different, as shown in Table 6.

TABLE 6 blending amounts (unit: kg) of respective raw materials of inner and outer layers of polyethylene heavy packaging films of examples 20 to 24

Examples 25 to 28

The polyethylene repackaging films of examples 25 to 28 were prepared in exactly the same manner as in example 21, except that the methacrylic acid copolymers prepared in preparation examples 4 to 7 were used as the raw materials for the inner and outer layers, respectively, and the kinds and amounts of the remaining raw materials were the same as in example 21.

Example 29

The polyethylene repackaging film of example 29 was produced in exactly the same manner as in example 26, except that the methacrylic acid copolymer used in the inner and outer layer materials was a commercially available methacrylic acid copolymer, and the other materials were the same in kind and amount as in example 26.

Comparative example 1

The polyethylene repackaging film of comparative example 1 was prepared exactly the same as example 1, except that: the methacrylic acid copolymer was replaced with an equivalent amount of styrene-butadiene-styrene block copolymer in the inner and outer layer raw materials, and the other raw materials and blending amounts were the same as in example 1.

Comparative example 2

The polyethylene repackaging film of comparative example 2 was prepared exactly the same as example 1, except that: the maleic anhydride grafted polypropylene was replaced with the same amount of polypropylene in the inner and outer layer raw materials, and the remaining raw materials and the blending amount were the same as in example 1.

Comparative example 3

The polyethylene repackaging film of comparative example 3 was prepared exactly the same as example 1, except that: the heat-sealing auxiliary agent ethylene-vinyl alcohol copolymer is not added in the raw materials of the inner layer and the outer layer, and the rest raw materials and the mixing amount are as follows: 20kg of low-density polyethylene, 35kg of linear low-density polyethylene, 20kg of methacrylic acid copolymer, 9kg of maleic anhydride grafted polypropylene, 7kg of erucamide, 5kg of polyester polyurethane and 4kg of antistatic agent polyethylene glycol, wherein the raw materials and the mixing amount of the middle layer are the same as those of the example 1.

Comparative example 4

The polyethylene repackaging film of comparative example 4 was prepared exactly the same as that of example 1, except that: erucamide is not added in the raw materials of the inner layer and the outer layer, and the rest raw materials and the mixing amount are as follows: 20kg of low-density polyethylene, 32kg of linear low-density polyethylene, 20kg of methacrylic acid copolymer, 9kg of maleic anhydride grafted polypropylene, 10kg of heat-sealing auxiliary agent ethylene-vinyl alcohol copolymer, 5kg of polyester polyurethane and 4kg of antistatic agent polyethylene glycol, wherein the raw materials and the mixing amount of the middle layer are the same as those of the example 1.

Comparative example 5

The polyethylene repackaging film of comparative example 5 was prepared exactly the same as example 1, except that: the linear low density polyethylene was replaced with the same amount of high density polyethylene in the inner and outer layer materials, and the other materials and blending amounts were the same as in example 1.

Comparative example 6

The polyethylene repackaging film of comparative example 6 was prepared exactly the same as example 1, except that: the middle layer material was replaced with the same amount of ethylene- α -olefin copolymer, and the other materials and the amounts thereof were the same as in example 1.

Performance detection

The detection method and the standard of BBT0058-2011 'multilayer co-extrusion heavy-duty film and bag for packaging' are adopted, the detection of the tensile strength and the nominal strain at break of the polyethylene heavy-duty packaging films in the examples 1, 9 and 26 is respectively carried out, and the longitudinal and transverse tensile strength and the elongation at break of each sample are detected; and at the height of 2m, the sample is subjected to drop test, and whether the polyethylene heavy packaging film is broken or not is observed.

TABLE 7 Performance test results for different polyethylene heavy packaging films

From the detection results in table 7, it can be seen that the polyethylene heavy packaging film of the present application has longitudinal and transverse tensile strengths of 35.1MPa and 33.3MPa or more, respectively, and longitudinal and transverse fracture nominal strains of 728% and 735% or more, respectively, has higher tensile strength and fracture nominal strain, and meets the requirements for physical and mechanical properties of the heavy packaging film in the use process.

The polyethylene heavy packaging films of examples 1-29 and comparative examples 1-6 were subjected to heat seal strength test using the test method and standard of BBT0058-2011 "multilayer co-extruded heavy-duty film and bag for packaging", respectively, and the heat resistance of each sample was observed, and finally the seal-lifting temperature of each sample was recorded, and the test results are shown in Table 8.

TABLE 8 Performance test results for different polyethylene heavy packaging films

The test results in Table 8 show that the polyethylene heavy packaging film of the present application has higher heat seal strength than the heavy packaging films of comparative examples 1-6, and the seal initiation temperature of the heavy packaging films of examples 1-29 is lower than that of the heavy packaging films of comparative examples 1-6 on the basis of satisfying the mechanical properties. The heat seal strength of the heavy packaging film can reach 33.8N/15mm at most, the heat seal performance of the heavy packaging film is effectively improved, and the heat resistance of the heavy packaging film under the conditions of 8.9N load and 80 ℃ drying is found to be excellent through inspection of samples, and the conditions of adhesion and weld marks do not occur.

In examples 1-6, the heat seal strength of the heavy packaging film of example 5 was 32.8N/15mm, which is higher than that of the heavy packaging films of examples 1-4 and examples 6-7; while the seal initiation temperature of the example 5 repackaged film was 81 deg.C, which was lower than the seal initiation temperature of the examples 1-4 and examples 6-7 repackaged films. The raw material weight parts of the heavy packaging film in example 5 are more appropriate, and the heat sealing performance of the heavy packaging film is effectively improved. Example 8 when the heat-seal adjuvant in the inner and outer layer materials of the heavy packaging film is ethylene-vinyl acetate copolymer, the heat-seal performance is better than that of the heavy packaging films of examples 1-6; example 9 when ethoxylated aliphatic alkylamine was used as the antistatic agent in the inner and outer layer materials of the heavy packaging film, the heat sealability was superior to that of the heavy packaging films of examples 1-6.

In examples 10-14, the heat seal strength of the heavy packaging film of example 11 was 33.2N/15mm, which is higher than that of the heavy packaging films of examples 10 and 12-14; while the seal initiation temperature of the example 11 repackaged film was 77 c, which was lower than the seal initiation temperature of the example 10 and examples 12-14 repackaged films. It is seen that when the weight ratio of the maleic anhydride grafted polypropylene to the linear low density polyethylene in the inner and outer layer raw materials of the heavy packaging film is 1:9, the surface of the heavy packaging film with heat sealability is more excellent.

In examples 15-19, the heat seal strength of the heavy packaging film of example 16 was 33.4N/15mm, both higher than the heat seal strength of the heavy packaging films of examples 15 and 17-19; while the seal initiation temperature for example 15 repackaged films was 75 deg.C, which was lower than the seal initiation temperature for example 15 and examples 17-19 repackaged films. Therefore, when the weight ratio of the polyester polyurethane to the erucamide in the raw materials of the inner layer and the outer layer of the heavy packaging film is 1:2, the surface of the heavy packaging film with heat sealing performance is more excellent.

In examples 20-24, the heat seal strength of example 21 repackaged films was 33.7N/15mm, both higher than those of example 20 and examples 22-24; while the resealing temperature of the example 21 repackaged film was 73 deg.C, which was lower than the resealing temperature of the examples 20 and 22-24 repackaged films. It is seen that when the methacrylic acid copolymer and other materials contained in the inner and outer layer materials of the heavy packaging film were 16.5% by weight, the heat-sealable surface of the heavy packaging film was more excellent.

In examples 25-28, the heat seal strength of the heavy packaging films of example 26 were 33.8N/15mm, respectively, which were higher than those of the heavy packaging films of examples 25 and 27-28; while the seal initiation temperature for example 26 repackaged films was 72 deg.C, which was lower than the seal initiation temperature for example 25 and examples 27-28 repackaged films. It is seen that, when the methacrylic acid copolymer prepared in preparation example 3 is more suitable in terms of the raw material weight parts, the surface of the heavy packaging film having heat sealability is more excellent. Example 29 the heat seal strength of the repackaged film was lower than that of example 26, indicating that the methacrylic copolymer prepared was more advantageous in improving the heat seal properties of the repackaged film.

In addition, the data of various indexes of comparative example 1 and comparative examples 1-6 show that the heat sealing performance of the heavy packaging film is obviously improved by adding methacrylic acid copolymer, maleic anhydride grafted polypropylene, antistatic agent, erucamide, ethylene-ethyl acrylate copolymer and heat sealing auxiliary agent.

The specific embodiments are only for explaining the present application and are not limiting to the present application, and those skilled in the art can make modifications to the embodiments without inventive contribution as required after reading the present specification, but all the embodiments are protected by patent law within the scope of the claims of the present application.

Claims

1. The polyethylene heavy packaging film is characterized by comprising an inner layer, a middle layer and an outer layer, wherein the inner layer, the middle layer and the outer layer are sequentially co-extruded to form the polyethylene heavy packaging film;

2. The polyethylene heavy packaging film according to claim 1, wherein the inner layer and the outer layer are prepared from the following raw materials in percentage by weight: 22-27% of low-density polyethylene, 33-41% of linear low-density polyethylene, 17-18% of methacrylic acid copolymer, 5-8% of maleic anhydride grafted polypropylene, 4-8% of heat-seal adjuvant, 2-4% of erucamide, 1.5-3% of polyester type polyurethane and 1.5-5% of antistatic agent;

3. The polyethylene heavy packaging film according to claim 1, wherein the methacrylic acid copolymer is prepared from the following raw materials in parts by weight: 60-80 parts of methyl methacrylate, 25-30 parts of methacrylic acid, 1-5 parts of sodium dodecyl benzene sulfonate, 1-5 parts of pentaerythritol tetrapropionate, 1.5-2.5 parts of didodecyl thiodipropionate and 11-15 parts of potassium persulfate.

4. The polyethylene repackaging film of claim 3, wherein the methacrylic acid copolymer of the inner and outer layers is present in an amount of 15 to 18.5% by weight.

5. The polyethylene repackaging film of claim 3, wherein said methacrylic acid copolymer is prepared by the following steps:

6. The polyethylene repackaging film of claim 1, wherein said heat-seal adjuvant is an ethylene-vinyl acetate copolymer.

7. The polyethylene repackaging film of claim 1, wherein the antistatic agent is an ethoxylated fatty alkylamine.

8. The polyethylene repackaging film of claim 1, wherein the weight ratio of the maleic anhydride grafted polypropylene to the linear low density polyethylene is 1: (8-10).

9. The polyethylene heavy packaging film according to claim 1, wherein the weight ratio of the polyester polyurethane to the erucamide is 1: (1.5-2.5).

10. A process for the preparation of polyethylene repackaging film according to any of claims 1 to 9, characterized in that it comprises the following operative steps:

preparing the inner and outer layer films: uniformly mixing low-density polyethylene, linear low-density polyethylene, methacrylic acid copolymer, maleic anhydride grafted polypropylene, heat-sealing auxiliary agent, erucamide, polyester polyurethane and antistatic agent, and mixing at 245-260 ℃ under the condition of 60-100r/min and processing pressure of 40-45MPa to obtain inner and outer layer molten materials;

preparing a middle-layer film: mixing metallocene polyethylene, high density polyethylene, low density polyethylene, ethylene-ethyl acrylate copolymer and color master batch, and mixing at 245-260 ℃, 60-100r/min and processing pressure of 40-45MPa to obtain middle layer molten material;

respectively fusing and extruding the inner layer molten material, the outer layer molten material and the middle layer molten material to form a film bubble; cooling and forming, stabilizing the film bubble, drawing and stretching, and cooling to obtain a film;