Environment-friendly packaging material and preparation method thereof

Abstract

The application belongs to the technical field of packaging materials, and particularly relates to an environment-friendly packaging material and a preparation method thereof. The packaging material comprises an inner layer and a surface layer arranged in sequence; the inner layer comprises the following raw materials in parts by weight: low-density polyethylene 65-85 parts, metallocene linear low-density polyethylene 20-30 parts, ethylene-vinyl alcohol copolymer 5-10 parts, and nano-zinc oxide 1-2 parts; and the surface layer comprises the following raw materials in parts by weight: low-density polyethylene 20-25 parts, medium-density polyethylene 60-70 parts, modified montmorillonite 8-12 parts, and sedum aizoon extract 1-5 parts. The environment-friendly packaging material has good barrier property, antibacterial property, and excellent mechanical property.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of packaging materials, and particularly relates to an environment-friendly packaging material and a preparation method thereof. BACKGROUND

[0002] With the continuous progress of science and technology, high molecular materials such as plastic packaging are gradually applied to people's daily life, which brings great convenience to life. Among various plastic packaging materials, polyethylene is odorless, tasteless and non-toxic, and has high transparency and excellent processing performance, and can be made into plastic bags, preservative films and food bags and other articles. It can be seen that polyethylene has broad application prospects in the field of packaging materials.

[0003] However, it is found in actual application that the mechanical properties of the film packaging material obtained by taking polyethylene as the base material are poor, which cannot meet the impact of external forces such as impact during transportation of articles, and finally greatly reduces the packaging effect. Especially when applied to food packaging, the rupture of the packaging material will cause the food to be exposed to the air for a long time, leading to rapid corruption of the food, and the purpose of preserving the food cannot be achieved. In addition, the film packaging material obtained by taking polyethylene as the base material also has the problems of insufficient oxygen and water barrier ability and easy oxidation. Based on the above background, it is urgent to deeply explore the performance of the film packaging material taking polyethylene as the base material, so as to accelerate the application of polyethylene in the field of packaging materials. SUMMARY

[0004] The first object of the present application is to provide an environment-friendly packaging material which has good barrier properties, antibacterial properties and excellent mechanical properties.

[0005] The second object of the present application is to provide a preparation method of the environment-friendly packaging material, which is simple and easy to operate.

[0006] In order to achieve the above object, the technical scheme adopted by the present application is:

[0007] An environment-friendly packaging material, which comprises an inner layer and a surface layer arranged in sequence; the inner layer comprises the following raw materials in parts by weight: low-density polyethylene 65-85 parts, metallocene linear low-density polyethylene 20-30 parts, ethylene-vinyl alcohol copolymer 5-10 parts, and nano-zinc oxide 1-2 parts; and the surface layer comprises the following raw materials in parts by weight: low-density polyethylene 20-25 parts, medium-density polyethylene 60-70 parts, modified montmorillonite 8-12 parts, and sedum aizoon extract 1-5 parts.

[0008] Further, the preparation process of the modified montmorillonite is as follows:

[0009] (1) adding the pretreated montmorillonite into the aqueous ethanol solution, then adding the vinyl triethoxysilane to perform a heating stirring reaction, and obtaining the first modified montmorillonite after purification;

[0010] (2) adding the first modified montmorillonite in step (1) into DMF, then adding the polyethylene glycol methacrylate and azobisisobutyronitrile to perform a heating reaction, and obtaining the modified montmorillonite.

[0011] Further, the mass ratio of the first modified montmorillonite, the polyethylene glycol methacrylate and the azobisisobutyronitrile in step (2) is 1:(0.1-0.2):(0.008-0.012); the temperature of the heating reaction is 80-90℃, and the time of the heating reaction is 4-5h.

[0012] Further, the mass ratio of the pretreated montmorillonite and the vinyl triethoxysilane in step (1) is 1:(0.1-0.2); the temperature of the heating stirring reaction is 55-65℃, and the time of the heating stirring reaction is 3-4h; the volume ratio of ethanol and water in the aqueous ethanol solution is 1:(0.2-0.4).

[0013] Further, the preparation method of the pretreated montmorillonite is as follows:

[0014] According to the mass ratio of the montmorillonite, the sodium hydroxide solution and the manganese chloride solution being 1:(8-11):(1-3), the montmorillonite is added into the sodium hydroxide solution with a mass fraction of 6-9% to perform a heating reaction, then the manganese chloride solution with a mass fraction of 8-12% is added to perform stirring, and then filtration, washing, drying and calcination are performed to obtain the product.

[0015] Further, the temperature of the heating reaction is 65-75℃, the time of the heating reaction is 1.5-2.5h, the time of the stirring is 1.5-2.5h, and the temperature of the calcination is 300-400℃, and the time of the calcination is 4-5h.

[0016] Further, the melt index of the low-density polyethylene is 1.0-2.0g / 10min, the melt index of the metallocene linear low-density polyethylene is 3.0-4.0g / 10min, the melt index of the medium-density polyethylene is 0.18-0.22g / 10min, the molar content of ethylene in the ethylene-vinyl alcohol copolymer is 25-35%, and the weight average molecular weight of the ethylene-vinyl alcohol copolymer is (16-36)×10 4 g / moL.

[0017] Further, the thickness of the surface layer is 10-12μm, and the thickness of the inner layer is 20-30μm.

[0018] The preparation method of the above-mentioned environment-friendly packaging material comprises the following steps:

[0019] a. Preparing a surface layer: according to the weight ratio, the raw materials of the surface layer are uniformly mixed, and the surface layer is prepared by melt blending;

[0020] b. Preparing an inner layer: according to the weight ratio, the raw materials of the inner layer are uniformly mixed, and the inner layer is prepared by melt blending;

[0021] c. Preparing an environment-friendly packaging material: the surface layer prepared in step a and the inner layer prepared in step b are sequentially stacked and then hot-pressed to prepare the environment-friendly packaging material.

[0022] Further, the temperature of the melt blending in steps a and b is 160-170 DEG C.

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] 1. The environment-friendly packaging material provided by the present application comprises a surface layer and an inner layer, and the surface layer is added with modified montmorillonite, a Centella asiatica extract and other components. The modified montmorillonite has good dispersibility and compatibility in the matrix material, can form a network structure with the polyethylene matrix, improves the compactness of the material, and further improves the barrier properties of the material to water vapor and oxygen. The Centella asiatica extract can be adsorbed by the modified montmorillonite, thereby improving the dispersibility and stability of the Centella asiatica extract in the packaging material, so that the Centella asiatica extract can better play a bacteriostatic role. Further, the inner layer is added with the bacteriostatic component nano-zinc oxide, and the Centella asiatica extract and the nano-zinc oxide together improve the bacteriostatic properties of the material.

[0025] 2. The environment-friendly packaging material provided by the present application has good barrier properties and bacteriostatic properties, and also has excellent mechanical properties. DETAILED DESCRIPTION

[0026] The technical solutions of the present application are further described below in combination with specific embodiments. However, those skilled in the art should understand that the following examples are only used to illustrate the present application, and should not be regarded as limiting the present application. The specific conditions not mentioned in the examples are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used, such as those not specifically mentioned, are conventional products obtained through market channels.

[0027] The low-density polyethylene used in the embodiments of the present application is BASF 24200H, and the melt index is 1.0-2.0 g / 10 min; the metallocene linear low-density polyethylene is Exxon Mobil 3518PA, and the melt index is 3.0-4.0 g / 10 min; and the medium-density polyethylene is Nordic Chemical MDPE FB2230, and the melt index is 0.18-0.22 g / 10 min.

[0028] 1. Embodiment

[0029] Embodiment 1

[0030] Embodiment 1 provides an environmentally friendly packaging material, which comprises an inner layer and a surface layer arranged in sequence; the inner layer comprises the following raw materials in parts by weight: low-density polyethylene 72 parts, metallocene linear low-density polyethylene 26 parts, ethylene-vinyl alcohol copolymer 8 parts, nano zinc oxide 1.5 parts; the surface layer comprises the following raw materials in parts by weight: low-density polyethylene 22 parts, medium-density polyethylene 64 parts, modified montmorillonite 9 parts, and sedum sarmentosum extract 4 parts; wherein the molar content of ethylene in the ethylene-vinyl alcohol copolymer is 30%, and the weight average molecular weight of the ethylene-vinyl alcohol copolymer is 33 x 10 4 g / moL.

[0031] The preparation process of the modified montmorillonite is as follows:

[0032] (1) According to the mass ratio of montmorillonite, sodium hydroxide solution, and manganese chloride solution 1:10:2, the montmorillonite is added to a 8% sodium hydroxide solution, heated at 70°C for 2h, and then 9% manganese chloride solution is added and stirred for 2h; after filtration, washing, and drying, calcination at 350°C for 4.5h is performed to obtain the pretreated montmorillonite; according to the mass ratio of pretreated montmorillonite, vinyl triethoxysilane 1:0.15, the pretreated montmorillonite is added to an ethanol aqueous solution (volume ratio of ethanol to water 1:0.3), then vinyl triethoxysilane is added, heated and stirred at 60°C for 3.5h, filtered, washed, and dried to obtain the first modified montmorillonite;

[0033] (2) According to the mass ratio of the first modified montmorillonite, polyethylene glycol methacrylate, and azobisisobutyronitrile 1:0.15:0.01, the first modified montmorillonite of step (1) is added to DMF, then polyethylene glycol methacrylate and azobisisobutyronitrile are added, heated at 85°C for 4.5h, and after the reaction is completed, filtration, washing, and drying are performed to obtain the modified montmorillonite.

[0034] Embodiment 1 also provides a preparation method of the above-mentioned environmentally friendly packaging material, the specific process is as follows:

[0035] a. Preparation of the surface layer: according to the weight ratio, mix the raw materials of the surface layer uniformly, melt and blend at 165°C, then extrude the sheet layer through the extruder under the conditions of 165°C, screw rotation speed 20rpm, and pulling speed 15m / min, then adjust the pulling speed for stretching treatment at 145°C and set the temperature at 90°C, and finally cool it under the conditions of 30°C and wind speed 1.2m / s to obtain a surface layer with a thickness of 10μm;

[0036] b. Preparation of the inner layer: according to the weight ratio, the raw materials of the inner layer were mixed uniformly, melt blended at 165℃, then extruded into a sheet layer through an extruder at 165℃, screw speed 20rpm, and pulling speed 15m / min, followed by stretching treatment at 145℃ with adjusted pulling speed and setting at 90℃, and finally cooling at 30℃ with wind speed 1.2m / s to obtain the inner layer with a thickness of 28μm;

[0037] c. Preparation of the environmentally friendly packaging material: the surface layer prepared in step a and the inner layer prepared in step b were stacked in sequence, and then hot-pressed at 180℃ and 20bar to obtain the environmentally friendly packaging material.

[0038] Example 2

[0039] Example 2 provides an environmentally friendly packaging material, which comprises an inner layer and a surface layer arranged in sequence; the inner layer comprises the following raw materials by weight: low-density polyethylene 65 parts, metallocene linear low-density polyethylene 20 parts, ethylene-vinyl alcohol copolymer 5 parts, and nano-zinc oxide 1 part; the surface layer comprises the following raw materials by weight: low-density polyethylene 20 parts, medium-density polyethylene 60 parts, modified montmorillonite 8 parts, and sedum sarmentosum extract 1 part; wherein the molar content of ethylene in the ethylene-vinyl alcohol copolymer is 25%, and the weight average molecular weight of the ethylene-vinyl alcohol copolymer is 16×10 4 g / moL.

[0040] The preparation process of the modified montmorillonite is as follows:

[0041] (1) According to the mass ratio of montmorillonite, sodium hydroxide solution, and manganese chloride solution 1:8:1, the montmorillonite was added to a 6% sodium hydroxide solution, heated at 65℃ for 2.5h, then 8% manganese chloride solution was added and stirred for 2.5h; after filtration, washing, and drying, the pretreated montmorillonite was calcined at 300℃ for 5h to obtain the pretreated montmorillonite; according to the mass ratio of pretreated montmorillonite, vinyl triethoxysilane 1:0.1, the pretreated montmorillonite was added to an ethanol aqueous solution (volume ratio of ethanol to water 1:0.2), then vinyl triethoxysilane was added, heated and stirred at 55℃ for 4h, filtered, washed, and dried to obtain the first modified montmorillonite;

[0042] (2) According to the mass ratio of the first modified montmorillonite, polyethylene glycol methacrylate, and azobisisobutyronitrile 1:0.1:0.008, the first modified montmorillonite of step (1) was added to DMF, then polyethylene glycol methacrylate and azobisisobutyronitrile were added, and heated at 80℃ for 5h; after reaction, the modified montmorillonite was obtained by filtration, washing, and drying.

[0043] The embodiment 2 also provides a preparation method of the above-mentioned environment-friendly packaging material, and the specific process is as follows:

[0044] a. Preparation of the surface layer: according to the weight ratio, the raw materials of the surface layer are uniformly mixed, melt-blended at 160℃, and then extruded into a sheet layer through an extruder at 160℃, a screw rotation speed of 20 rpm and a pulling speed of 15 m / min. Subsequently, the pulling speed is adjusted at 145℃ for stretching treatment and heat setting at 90℃. Finally, the surface layer with a thickness of 11 μm is prepared by cooling at 30℃ and a wind speed of 1.2 m / s.

[0045] b. Preparation of the inner layer: according to the weight ratio, the raw materials of the inner layer are uniformly mixed, melt-blended at 160℃, and then extruded into a sheet layer through an extruder at 160℃, a screw rotation speed of 20 rpm and a pulling speed of 15 m / min. Subsequently, the pulling speed is adjusted at 145℃ for stretching treatment and heat setting at 90℃. Finally, the inner layer with a thickness of 20 μm is prepared by cooling at 30℃ and a wind speed of 1.2 m / s.

[0046] c. Preparation of the environment-friendly packaging material: the surface layer prepared in step a and the inner layer prepared in step b are stacked in sequence, and then hot-pressed and compounded at 180℃ and 20 bar to obtain the environment-friendly packaging material.

[0047] Embodiment 3

[0048] The embodiment 3 provides an environment-friendly packaging material, which comprises an inner layer and a surface layer arranged in sequence; the inner layer comprises the following raw materials in parts by weight: 85 parts of low-density polyethylene, 30 parts of metallocene linear low-density polyethylene, 10 parts of ethylene-vinyl alcohol copolymer and 2 parts of nano zinc oxide; the surface layer comprises the following raw materials in parts by weight: 25 parts of low-density polyethylene, 70 parts of medium-density polyethylene, 12 parts of modified montmorillonite and 5 parts of sedum aizoon extract; wherein the molar content of ethylene in the ethylene-vinyl alcohol copolymer is 35%, and the weight average molecular weight of the ethylene-vinyl alcohol copolymer is 36×10 4 g / moL.

[0049] The preparation process of the above-mentioned modified montmorillonite is as follows:

[0050] (1) According to the mass ratio of montmorillonite, sodium hydroxide solution, manganese chloride solution 1:11:3, the montmorillonite is added to the sodium hydroxide solution with a mass fraction of 9%, heated at 75°C for 1.5h, after the reaction is completed, 12% manganese chloride solution is added and stirred for 1.5h; after filtration, washing and drying, calcination at 400°C for 4h, the pretreated montmorillonite is obtained; according to the mass ratio of pretreated montmorillonite, vinyltriethoxysilane 1:0.2, the pretreated montmorillonite is added to the ethanol aqueous solution (volume ratio of ethanol to water 1:0.4), then vinyltriethoxysilane is added, heated and stirred at 65°C for 3h, after filtration, washing and drying, the first modified montmorillonite is obtained;

[0051] (2) According to the mass ratio of the first modified montmorillonite, polyethylene glycol methacrylate, azobisisobutyronitrile 1:0.2:0.012, the first modified montmorillonite of step (1) is added to DMF, then polyethylene glycol methacrylate and azobisisobutyronitrile are added, heated at 90°C for 4h, after the reaction is completed, filtration, washing and drying, the modified montmorillonite is obtained.

[0052] Example 3 also provides a preparation method of the above-mentioned environmentally friendly packaging material, and the specific process is as follows:

[0053] a. Preparation of the surface layer: according to the weight ratio, the raw materials of the surface layer are uniformly mixed, melt blended at 170°C, then extruded into a sheet layer through an extruder under the conditions of 170°C, screw rotation speed 20rpm, and pulling speed 15m / min, then stretched by adjusting the pulling speed at 145°C and heat setting at 90°C, and finally cooled at 30°C with a wind speed of 1.2m / s to form a surface layer with a thickness of 12μm;

[0054] b. Preparation of the inner layer: according to the weight ratio, the raw materials of the inner layer are uniformly mixed, melt blended at 170°C, then extruded into a sheet layer through an extruder under the conditions of 170°C, screw rotation speed 20rpm, and pulling speed 15m / min, then stretched by adjusting the pulling speed at 145°C and heat setting at 90°C, and finally cooled at 30°C with a wind speed of 1.2m / s to form an inner layer with a thickness of 30μm;

[0055] c. Preparation of the environmentally friendly packaging material: the surface layer prepared in step a and the inner layer prepared in step b are stacked in sequence, and then hot-pressed and compounded under the conditions of 180°C and 20bar to obtain the environmentally friendly packaging material.

[0056] 2. Comparative example

[0057] Comparative example 1

[0058] The difference between comparative example 1 and example 1 is that:

[0059] The surface layer comprises the following raw materials by weight: low density polyethylene 22 parts, medium density polyethylene 64 parts, and modified montmorillonite 9 parts.

[0060] Comparative Example 2

[0061] Comparative Example 2 differs from Example 1 in that:

[0062] Montmorillonite and polyethylene glycol methacrylate are used instead of modified montmorillonite, with a mass ratio of 1:0.15.

[0063] Comparative Example 3

[0064] Comparative Example 3 differs from Example 1 in that:

[0065] Firstly modified montmorillonite and polyethylene glycol methacrylate are used instead of modified montmorillonite, with a mass ratio of 1:0.15.

[0066] Comparative Example 4

[0067] Comparative Example 4 differs from Example 1 in that:

[0068] The surface layer comprises the following raw materials by weight: low density polyethylene 22 parts, medium density polyethylene 64 parts, and modified montmorillonite 9 parts.

[0069] 3. Test Example

[0070] The properties of the packaging materials obtained in Examples 1-3 and Comparative Examples 1-4 were detected, and the specific detection methods are as follows:

[0071] (1) Bacteriostatic property

[0072] According to QB / T 2591-2003 "Antibacterial plastics-antibacterial performance test method and antibacterial effect" (film method), the detection bacteria are Escherichia coli and Staphylococcus aureus. After each group of samples is placed at room temperature for 10 days, it is cleaned and dried before testing. The results are shown in Table 1.

[0073] (2) Barrier property

[0074] Oxygen transmission amount: The oxygen transmission rate was tested by the coulomb meter detection method of the standard "GB / T 19789-2005 Packaging materials, plastic film and sheet oxygen permeability test", and the results are shown in Table 2.

[0075] Water vapor transmission amount: The water vapor transmission of the film was tested according to the standard GB / T 21529-2008 standard, and the results are shown in Table 2.

[0076] (3) Mechanical property

[0077] Tensile strength: refer to standard GB / T 1040.1-2018, tensile speed is 50 mm / min, tensile force is 1000 N, refer to Table 3 for results;

[0078] Elongation at break: refer to standard GB / T 1040.1-2018, tensile speed is 50 mm / min, tensile force is 1000 N, refer to Table 3 for results.

[0079] Table 1

[0080] Packaging material / antibacterial rate (%) Escherichia coli Staphylococcus aureus Example 1 98.9 97.3 Example 2 98.6 97.1 Example 3 98.4 96.7 Comparative Example 1 97.2 95.2 Comparative Example 2 97.5 95.5 Comparative Example 3 97.9 96.1 Comparative Example 4 95.1 93.6

[0081] Table 2

[0082] Packaging material / barrier properties Oxygen transmission rate (cm 3 / m 2 / day / Pa)]]> Water vapor transmission (g / m 2 / day) Example 1 385 1.2 Example 2 390 1.3 Example 3 394 1.5 Comparative Example 1 497 6.3 Comparative Example 2 465 4.6 Comparative Example 3 448 3.7 Comparative Example 4 403 1.6

[0083] Table 3

[0084] Packaging material / mechanical properties Tensile strength / MPa Elongation at break / % Example 1 40.1 633 Example 2 39.5 625 Example 3 39.2 617 Comparative Example 1 22.4 522 Comparative Example 2 27.8 551 Comparative Example 3 31.3 574 Comparative Example 4 39.0 610

[0085] From Tables 1-3, it can be seen that the packaging materials obtained in Examples 1-3 have good barrier properties, antibacterial properties, and also have excellent mechanical properties.

[0086] From Table 1, it can be seen that, compared with Examples 1-3, the antibacterial property of the packaging material of Comparative Example 4 is significantly reduced due to the omission of the Centella asiatica extract. It is analyzed that the Centella asiatica extract can be adsorbed by the modified montmorillonite, thereby improving the dispersibility and stability of the Centella asiatica extract in the packaging material, so as to better play the antibacterial effect.

[0087] From Table 2, it can be seen that, compared with Examples 1-3, the barrier property of the packaging material of Comparative Example 1 is significantly reduced due to the omission of the modified montmorillonite; the barrier property of the packaging material of Comparative Example 2 is significantly reduced due to the use of montmorillonite and polyethylene glycol methacrylate instead of the modified montmorillonite; the barrier property of the packaging material of Comparative Example 3 is significantly reduced due to the use of the first modified montmorillonite and polyethylene glycol methacrylate instead of the modified montmorillonite. It is analyzed that the internal pores of the montmorillonite are increased after pretreatment, which can prolong the path of water and oxygen through the packaging material, and the increase of the specific surface area can also adsorb water and oxygen. The first modified montmorillonite, i.e., the montmorillonite after vinylization, can react with polyethylene glycol methacrylate, thereby further improving the dispersibility and compatibility of the montmorillonite in the matrix material, and the modified montmorillonite and the polyethylene matrix form a network structure, thereby improving the density of the material, and further improving the barrier property of the material to water vapor and oxygen.

[0088] Finally, it should be pointed out that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application. The basic principles and main features of the present application have been described above with specific embodiments, and some modifications or replacements can be made on the basis of the present application, but these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the present application.

Claims

1. An environmentally friendly packaging material, characterized by, The environment-friendly packaging material comprises an inner layer and a surface layer arranged in sequence; the inner layer comprises the following raw materials in parts by weight: low-density polyethylene 65-85 parts, metallocene linear low-density polyethylene 20-30 parts, ethylene-vinyl alcohol copolymer 5-10 parts, and nano zinc oxide 1-2 parts; the surface layer comprises the following raw materials in parts by weight: low-density polyethylene 20-25 parts, medium-density polyethylene 60-70 parts, modified montmorillonite 8-12 parts, and sedum aizoon extract 1-5 parts; and the modified montmorillonite is prepared by the following process: (1) adding pretreated montmorillonite into an ethanol aqueous solution, then adding vinyl triethoxysilane for heating and stirring reaction, and obtaining first modified montmorillonite after purification; (2) adding the first modified montmorillonite of step (1) into DMF, then adding polyethylene glycol methacrylate and azobisisobutyronitrile for heating reaction, and obtaining modified montmorillonite.

2. The environmentally friendly packaging material of claim 1, wherein In step (2), the mass ratio of the first modified montmorillonite, polyethylene glycol methacrylate and azobisisobutyronitrile is 1:(0.1-0.2):(0.008-0.012); the heating reaction is carried out at a temperature of 80-90℃ for 4-5h.

3. The environmentally friendly packaging material of claim 1, wherein In step (1), the mass ratio of the pretreated montmorillonite and vinyl triethoxysilane is 1:(0.1-0.2); the heating and stirring reaction is carried out at a temperature of 55-65℃ for 3-4h; and the volume ratio of ethanol to water in the ethanol aqueous solution is 1:(0.2-0.4).

4. The environmentally friendly packaging material of claim 3, wherein The pretreated montmorillonite is prepared by the following method: According to the mass ratio of montmorillonite, sodium hydroxide solution and manganese chloride solution being 1:(8-11):(1-3), the montmorillonite is added into a sodium hydroxide solution with a mass fraction of 6-9% for heating reaction, then a manganese chloride solution with a mass fraction of 8-12% is added for stirring, and then filtration, washing, drying and calcination are carried out to obtain the product.

5. The environmentally friendly packaging material of claim 4, wherein the polyethylene terephthalate is a copolymer of polyethylene terephthalate glycol. The heating reaction is carried out at a temperature of 65-75℃ for 1.5-2.5h; the stirring is carried out for 1.5-2.5h; and the calcination is carried out at a temperature of 300-400℃ for 4-5h.

6. The environmentally friendly packaging material of claim 1, wherein The low density polyethylene has a melt index of 1.0-2.0 g / 10 min; the metallocene linear low density polyethylene has a melt index of 3.0-4.0 g / 10 min; the medium density polyethylene has a melt index of 0.18-0.22 g / 10 min; the ethylene-vinyl alcohol copolymer has a molar content of ethylene of 25-35%; and the ethylene-vinyl alcohol copolymer has a weight average molecular weight of (16-36) x 10 4 g / moL.

7. The environmentally friendly packaging material of claim 1, wherein The thickness of the surface layer is 10-12μm, and the thickness of the inner layer is 20-30μm.

8. The method for preparing the environmentally friendly packaging material as described in claim 1, characterized in that, The following steps are included: a. preparing the surface layer: the raw materials of the surface layer are uniformly mixed according to the weight ratio, and the surface layer is prepared by melt blending; b. preparing the inner layer: the raw materials of the inner layer are uniformly mixed according to the weight ratio, and the inner layer is prepared by melt blending; c. preparing the environment-friendly packaging material: the surface layer prepared in step a and the inner layer prepared in step b are stacked in sequence and then hot-pressed to obtain the environment-friendly packaging material.

9. The method of claim 8, wherein the environment-friendly packaging material is prepared by coating a surface of a base material with a coating solution containing the water-soluble polymer and the water-soluble inorganic salt, and drying the coated base material. In steps a and b, the melt blending is carried out at a temperature of 160-170℃.