A multi-layer composite polyethylene film material and its preparation method

Abstract

The present invention belongs to the technical field of packaging films, and particularly relates to a multi-layer composite polyethylene film material and a preparation method thereof. The multi-layer composite polyethylene film material comprises a surface layer and an inner layer arranged in sequence; the surface layer comprises the following raw materials in parts by weight: 90-100 parts of high-density polyethylene, 10-15 parts of modified biochar, and 3-8 parts of chitosan; the inner layer comprises the following raw materials in parts by weight: 30-40 parts of low-density polyethylene and 70-85 parts of linear low-density polyethylene; wherein, the preparation process of the modified biochar is as follows: the biochar obtained after pretreatment of biomass is added to an ethanol aqueous solution, and then a silane coupling agent is added for heating reaction. After the reaction is completed, it is purified to obtain amino-functionalized biochar; it is added to DMF, and then gallic acid and triethylamine are added for heating reaction. After the reaction is completed, it is purified to obtain modified biochar. The polyethylene film material has excellent antioxidant performance and mechanical properties.

Description

Technical Field

[0001] The present invention belongs to the technical field of packaging films, and particularly relates to a multi-layer composite polyethylene film material and a preparation method thereof. Background Art

[0002] With the development of the plastics industry, plastic films are widely used as packaging films in the fields of food, medicine, chemical industry, electrical appliances, etc. Commonly used packaging materials on the market include polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polycarbonate (PC), etc. Polyethylene films have the characteristics of semi-transparency, low cost, non-toxicity, luster, and soft texture. At the same time, they also have good chemical stability, heat sealability, and low temperature resistance, so they are widely used. However, the existing polyethylene films have problems such as poor mechanical strength and easy oxidation, which to a certain extent limit their application scope.

[0003] To improve the barrier properties of packaging films, composite packaging films are usually used. For example, Chinese Patent CN115556455A discloses a fully plastic transparent high-barrier coated composite film and a preparation method thereof. This patent discloses a composite film prepared by laminating a high-oxygen-barrier BOPET film and a high-water-barrier PE film, which has oxygen barrier properties. Nevertheless, the antioxidant performance of this composite film still needs to be further improved. Based on this, it is necessary to conduct a deeper study on the properties of polyethylene films. Summary of the Invention

[0004] The first object of the present invention is to provide a multi-layer composite polyethylene film material, which has excellent antioxidant performance and mechanical properties.

[0005] The second object of the present invention is to provide a preparation method of the multi-layer composite polyethylene film material, and the steps are simple.

[0006] To achieve the above objects, the technical solution adopted by the present invention is:

[0007] A multi-layer composite polyethylene film material, the multi-layer composite polyethylene film material includes a surface layer and an inner layer arranged in sequence; the surface layer includes the following raw materials in parts by weight: 90-100 parts of high-density polyethylene, 10-15 parts of modified biochar, and 3-8 parts of chitosan; the inner layer includes the following raw materials in parts by weight: 30-40 parts of low-density polyethylene and 70-85 parts of linear low-density polyethylene;

[0008] The preparation process of the modified biochar is as follows:

[0009] (1) Add the biochar obtained by pretreating biomass to an ethanol aqueous solution, then add a silane coupling agent and carry out a heating reaction. After the reaction is completed, purification is carried out to obtain amino-functionalized biochar;

[0010] (2) Add the aminated biochar obtained in step (1) to DMF, then add gallic acid and triethylamine and carry out a heating reaction. After the reaction is completed, purification is carried out to obtain the modified biochar.

[0011] Further, in step (1), the mass ratio of the biochar to the silane coupling agent is 1:(0.05 - 0.1); the silane coupling agent is KH550; the concentration of the ethanol aqueous solution is 70 - 75%.

[0012] Further, in step (1), the temperature of the heating reaction is 50 - 55 °C, and the time of the heating reaction is 5 - 6 h.

[0013] Further, the process of the biomass pretreatment in step (1) is as follows: under a nitrogen atmosphere, pyrolyze the biomass material powder at 400 - 600 °C for 3 - 4 h; the biomass material powder is peanut straw powder.

[0014] Further, in step (2), the mass ratio of the aminated biochar, gallic acid, and triethylamine is 1:(0.05 - 0.1):(0.2 - 0.3).

[0015] Further, in step (2), the temperature of the heating reaction is 80 - 90 °C, and the time of the heating reaction is 3 - 4 h.

[0016] Further, the melt index of the high-density polyethylene is 0.15 - 0.2 g / 10 min; the melt index of the low-density polyethylene is 1.0 - 2.0 g / 10 min; the melt index of the linear low-density polyethylene is 1.5 - 2.0 g / 10 min.

[0017] Further, the thickness of the surface layer is 10 - 15 μm, and the thickness of the inner layer is 30 - 40 μm.

[0018] The preparation method of the above multi-layer composite polyethylene film material includes the following steps:

[0019] a. Prepare the surface layer: Mix the raw materials of the surface layer evenly according to the weight ratio, and make the surface layer by melt blending.

[0020] b. Prepare the inner layer: Mix the raw materials of the inner layer evenly according to the weight ratio, and make the inner layer by melt blending.

[0021] c. Prepare the multi-layer composite polyethylene film material: Stack the surface layer obtained in step a and the inner layer obtained in step b in sequence and then carry out hot pressing and compounding to prepare the multi-layer composite polyethylene film material.

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

[0023] Compared with the prior art, the beneficial effects of the present invention mainly lie in:

[0024] 1. The biochar obtained after biomass pretreatment of the present invention has a high porosity, and these pores provide a large adsorption area, making the biochar have a large specific surface area; the biochar is modified with KH550, and then reacted with gallic acid and triethylamine. After the amide reaction between the amino group on the biochar and the carboxyl group in gallic acid, on the one hand, the antioxidant functional groups of gallic acid are introduced on the biochar surface, and the antioxidant property of the material is improved by capturing free radicals. On the other hand, a stable structure composed of amide bonds is formed on the biochar surface, which can further reduce the damage of the internal structure of the biochar and achieve the purpose of improving the material stability. The modified biochar is mixed with chitosan, and the rich hydroxyl groups on the surface of the modified biochar interact with the amino groups on the chitosan molecular chain to form hydrogen bonds, and the hydrogen bond interaction makes the combination between the two closer, thereby improving the overall mechanical properties of the material.

[0025] 2. The multi-layer composite polyethylene film material of the present invention has excellent mechanical properties, antioxidant properties and thermal stability. Specific embodiments

[0026] The technical solutions of the present invention will be further described below in conjunction with specific embodiments. However, those skilled in the art should understand that the following examples are only used to illustrate the present invention and should not be regarded as a limitation of the present invention. The specific conditions not specified in the examples are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used, unless otherwise specified, are all conventional products obtained through commercial channels.

[0027] In the embodiments of the present invention, the linear low-density polyethylene is Daqing Petrochemical 9047 with a melt index of 1.5 - 2.0 g / 10 min; the high-density polyethylene is Saudi Phillips 50100 with a melt index of 0.15 - 0.2 g / 10 min; the low-density polyethylene is BASF 24200H with a melt index of 1.0 - 2.0 g / 10 min.

[0028] 1. Embodiments

[0029] Example 1

[0030] A multi-layer composite polyethylene film material, which includes a surface layer and an inner layer arranged in sequence; the surface layer includes the following raw materials in parts by weight: 95 parts of high-density polyethylene, 12 parts of modified biochar, and 6 parts of chitosan; the inner layer includes the following raw materials in parts by weight: 34 parts of low-density polyethylene and 76 parts of linear low-density polyethylene. Among them, the preparation process of the modified biochar is as follows:

[0031] (1) Dry and grind peanut straw to obtain peanut straw powder; under a nitrogen atmosphere, pyrolyze the peanut straw powder at 500 °C for 3.5 h to obtain biochar; according to the mass ratio of biochar to KH550 of 1:0.07, add the obtained biochar to an ethanol aqueous solution with a concentration of 72%, then add KH550, and react at 53 °C for 5.5 h. After the reaction is completed, filter, wash, and dry to obtain amino-functionalized biochar;

[0032] (2) According to the mass ratio of amino-functionalized biochar, gallic acid, and triethylamine of 1:0.06:0.25, add the amino-functionalized biochar in step (1) to DMF, then add gallic acid and triethylamine, and react at 85 °C for 3.5 h. After the reaction is completed, filter, wash, and dry to obtain modified biochar.

[0033] The preparation method of the above multi-layer composite polyethylene film material is as follows:

[0034] a. Prepare the surface layer: Mix the raw materials of the surface layer evenly according to the stated weight ratio, and melt-blend them to form a surface layer with a thickness of 12 μm, where the temperature of the melt-blending is 165 °C;

[0035] b. Prepare the inner layer: Mix the raw materials of the inner layer evenly according to the stated weight ratio, and melt-blend them to form an inner layer with a thickness of 33 μm, where the temperature of the melt-blending is 165 °C;

[0036] c. Prepare the multi-layer composite polyethylene film material: Stack the surface layer prepared in step a and the inner layer prepared in step b in sequence, and then hot-press and laminate them under the conditions of 180 °C and 20 bar to obtain the multi-layer composite polyethylene film material.

[0037] Example 2

[0038] A multi-layer composite polyethylene film material, which includes a surface layer and an inner layer arranged in sequence; the surface layer includes the following raw materials in parts by weight: 90 parts of high-density polyethylene, 10 parts of modified biochar, and 3 parts of chitosan; the inner layer includes the following raw materials in parts by weight: 30 parts of low-density polyethylene and 70 parts of linear low-density polyethylene.

[0039] Among them, the preparation process of the modified biochar is as follows:

[0040] (1) Dry and grind peanut straw to obtain peanut straw powder; under a nitrogen atmosphere, pyrolyze the peanut straw powder at 400 °C for 4 h to obtain biochar; according to the mass ratio of biochar to KH550 of 1:0.05, add the obtained biochar to an ethanol aqueous solution with a concentration of 70%, then add KH550, and react at 50 °C for 6 h. After the reaction is completed, filter, wash, and dry to obtain amino-functionalized biochar;

[0041] (2) According to the mass ratio of aminated biochar, gallic acid, and triethylamine of 1:0.05:0.2, add the aminated biochar obtained in step (1) to DMF, then add gallic acid and triethylamine, react at 80 °C for 4 h, and after the reaction is completed, filter, wash, and dry to obtain modified biochar.

[0042] The preparation method of the above multi-layer composite polyethylene film material is as follows:

[0043] a. Prepare the surface layer: Mix the raw materials of the surface layer evenly according to the stated weight ratio, and melt-blend them to form a surface layer with a thickness of 10 μm, where the temperature of the melt-blending is 160 °C;

[0044] b. Prepare the inner layer: Mix the raw materials of the inner layer evenly according to the stated weight ratio, and melt-blend them to form an inner layer with a thickness of 30 μm, where the temperature of the melt-blending is 160 °C;

[0045] c. Prepare the multi-layer composite polyethylene film material: Stack the surface layer obtained in step a and the inner layer obtained in step b in sequence, and then hot-press and composite them under the conditions of 180 °C and 20 bar to obtain the multi-layer composite polyethylene film material.

[0046] Example 3

[0047] A multi-layer composite polyethylene film material, which includes a surface layer and an inner layer arranged in sequence; the surface layer includes the following raw materials in parts by weight: 100 parts of high-density polyethylene, 15 parts of modified biochar, and 8 parts of chitosan; the inner layer includes the following raw materials in parts by weight: 40 parts of low-density polyethylene and 85 parts of linear low-density polyethylene.

[0048] Among them, the preparation process of the modified biochar is as follows:

[0049] (1) Dry and grind peanut straw to obtain peanut straw powder; under a nitrogen atmosphere, pyrolyze the peanut straw powder at 600 °C for 3 h to obtain biochar; according to the mass ratio of biochar to KH550 of 1:0.1, add the obtained biochar to an ethanol aqueous solution with a concentration of 75%, then add KH550, react at 55 °C for 5 h, and after the reaction is completed, filter, wash, and dry to obtain aminated biochar;

[0050] (2) According to the mass ratio of aminated biochar, gallic acid, and triethylamine of 1:0.1:0.3, add the aminated biochar obtained in step (1) to DMF, then add gallic acid and triethylamine, react at 90 °C for 3 h, and after the reaction is completed, filter, wash, and dry to obtain modified biochar.

[0051] The preparation method of the above multi-layer composite polyethylene film material is as follows:

[0052] a. Preparation of the surface layer: According to the weight ratio, the raw materials of the surface layer are mixed evenly and made into a surface layer with a thickness of 15 μm by melt blending, where the temperature of the melt blending is 170 °C;

[0053] b. Preparation of the inner layer: According to the weight ratio, the raw materials of the inner layer are mixed evenly and made into an inner layer with a thickness of 40 μm by melt blending, where the temperature of the melt blending is 170 °C;

[0054] c. Preparation of the multi-layer composite polyethylene film material: The surface layer obtained in step a and the inner layer obtained in step b are stacked in sequence and then hot-pressed and compounded under the conditions of 180 °C and 20 bar to obtain the multi-layer composite polyethylene film material.

[0055] 2. Comparative examples

[0056] Comparative example 1

[0057] The difference between Comparative example 1 and Example 1 is that:

[0058] Biochar is used to replace the modified biochar, and the rest is the same as Example 1.

[0059] Comparative example 2

[0060] The difference between Comparative example 2 and Example 1 is that:

[0061] Aminated biochar is used to replace the modified biochar, and the rest is the same as Example 1.

[0062] Comparative example 3

[0063] The difference between Comparative example 3 and Example 1 is that:

[0064] 11.9 parts of biochar and 0.1 part of gallic acid are used to replace the modified biochar, and the rest is the same as Example 1.

[0065] Performance detection test

[0066] The polyethylene films prepared in Examples 1-3 and Comparative examples 1-3 are made into specimens with a length of 50 mm, a width of 4 mm, and a thickness of 0.15 mm. The performance of each of the above specimens is detected, and the specific test process is as follows:

[0067] (1) Tensile strength and elongation at break: Refer to the standard GB / T 1040.1-2018, the tensile speed is 50 mm / min, and the tensile force is 1000 N. The results are shown in Table 1;

[0068] (2) Oxygen permeability: The oxygen permeability was tested by the coulometer detection method with reference to the standard "GB / T 19789-2005 Test Method for Oxygen Permeability of Packaging Materials, Plastic Films and Sheets". The results are shown in Table 2;

[0069] (3) DPPH radical scavenging rate: The samples of Examples 1-3 and Comparative Examples 1-3 were punched to obtain discs with a diameter of 10 mm. Each disc was placed in 10 mL of 0.02 mg / mL DPPH ethanol solution and magnetically stirred at room temperature for 35 min. Then, the supernatant of each group was taken to detect the absorbance value at 517 nm, and a DPPH solution control group was set. The calculation formula for the DPPH radical scavenging rate is as follows: DPPH radical scavenging rate = (absorbance value of the control group - absorbance value of the test group) / absorbance value of the test group × 100%. The results are shown in Table 2;

[0070] (4) Thermal stability: The above-mentioned samples were respectively cut to obtain small pieces of samples with a weight of 10 mg for thermogravimetric testing. The testing conditions were as follows: under a nitrogen atmosphere, the temperature was raised from room temperature to 600 °C at a heating rate of 10 °C / min. The results are shown in Table 3.

[0071] Table 1

[0072]

[0073]

[0074] Table 2

[0075] Grouping <![CDATA[Oxygen transmission rate (cm 3 / m 2 / day / Pa)]]> DPPH free radical scavenging rate / % Example 1 407 98.21 Example 2 415 97.75 Example 3 426 97.42 Comparative Example 1 561 87.54 Comparative Example 2 534 91.68 Comparative Example 3 503 94.39

[0076] Table 3

[0077] Grouping Weight retention rate at 200 °C (%) Weight retention rate at 300 °C (%) Weight retention rate at 600 °C (%) Example 1 99.8 95.6 65.4 Example 2 99.7 95.2 64.1 Example 3 99.7 94.9 63.5 Comparative Example 1 91.4 83.6 49.7 Comparative Example 2 94.1 87.3 55.0 Comparative Example 3 96.6 89.7 58.3

[0078] It can be seen from Tables 1-2 that compared with Comparative Examples 1-3, the multi-layer composite polyethylene film materials of Examples 1-3 of the present invention have excellent mechanical properties and antioxidant properties. The modified biochar used in the surface layer of the composite film of the present invention can improve the antioxidant property of the composite film by capturing free radicals due to the gallic acid part in its structure. The close interaction between the modified biochar and chitosan and the wear resistance and weather resistance of high-density polyethylene itself make the composite film have excellent mechanical properties.

[0079] It can be seen from Table 3 that the weight retention rates of the multi-layer composite polyethylene film materials of Examples 1-3 of the present invention at different temperatures are better than those of Comparative Examples 1-3. The above results show that the polyethylene film material of the present invention has excellent thermal stability. The stable amide bond structure formed on the surface of the modified biochar of the present invention can reduce the destruction of the internal structure of the biochar, thereby improving the thermal stability of the material.

[0080] Further analysis shows that in Comparative Example 1, biochar was used to replace the modified biochar to prepare the polyethylene film material; in Comparative Example 2, aminated biochar was used to replace the modified biochar to prepare the polyethylene film material; in Comparative Example 3, biochar and gallic acid were used to replace the modified biochar to prepare the polyethylene film material. The above results indicate that adjusting the formulation of the present invention will lead to a decrease in the various properties of the polyethylene film material.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. The basic principles and main features of the present invention have been described with specific implementation schemes above. On the basis of the present invention, some modifications or substitutions can be made, but these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the scope of protection required by the present invention.

Claims

1. A multi-layer composite polyethylene film material, characterized in that, The multi-layer composite polyethylene film material comprises a surface layer and an inner layer arranged in sequence; the surface layer comprises the following raw materials in parts by weight: 90-100 parts of high-density polyethylene, 10-15 parts of modified biochar, and 3-8 parts of chitosan; the inner layer comprises the following raw materials in parts by weight: 30-40 parts of low-density polyethylene and 70-85 parts of linear low-density polyethylene; The preparation process of the modified biochar is as follows: (1) Add the biochar obtained by pretreating biomass to an ethanol aqueous solution, then add a silane coupling agent and carry out a heating reaction. After the reaction is completed, purify to obtain amino-functionalized biochar; (2) Add the amino-functionalized biochar obtained in step (1) to DMF, then add gallic acid and triethylamine and carry out a heating reaction. After the reaction is completed, purify to obtain modified biochar.

2. The multi-layer composite polyethylene film material according to claim 1, wherein In step (1), the mass ratio of the biochar to the silane coupling agent is 1:(0.05-0.1); the silane coupling agent is KH550; the concentration of the ethanol aqueous solution is 70-75%.

3. The multi-layer composite polyethylene film material according to claim 1, characterized in that, In step (1), the temperature of the heating reaction is 50-55°C, and the time of the heating reaction is 5-6 h.

4. The multi-layer composite polyethylene film material according to claim 1, wherein The process of pretreating the biomass in step (1) is: under a nitrogen atmosphere, pyrolyze the biomass material powder at 400-600°C for 3-4 h; the biomass material powder is peanut straw powder.

5. The multi-layer composite polyethylene film material according to claim 1, characterized in that, In step (2), the mass ratio of the amino-functionalized biochar, gallic acid, and triethylamine is 1:(0.05-0.1):(0.2-0.3).

6. The multi-layer composite polyethylene film material according to claim 1, wherein In step (2), the temperature of the heating reaction is 80-90°C, and the time of the heating reaction is 3-4 h.

7. The multi-layer composite polyethylene film material according to claim 1, characterized in that, The melt index of the high-density polyethylene is 0.15-0.2 g / 10 min; the melt index of the low-density polyethylene is 1.0-2.0 g / 10 min; the melt index of the linear low-density polyethylene is 1.5-2.0 g / 10 min.

8. The multilayer composite polyethylene film material according to claim 1, characterized in that, The thickness of the surface layer is 10-15 μm, and the thickness of the inner layer is 30-40 μm.

9. The preparation method of the multi-layer composite polyethylene film material according to any one of claims 1-8, characterized in that, Comprises the following steps: a. Prepare the surface layer: Mix the raw materials of the surface layer evenly according to the above-mentioned parts by weight ratio, and make the surface layer by melt blending; b. Prepare the inner layer: Mix the raw materials of the inner layer evenly according to the above-mentioned parts by weight ratio, and make the inner layer by melt blending; c. Prepare the multi-layer composite polyethylene film material: Stack the surface layer obtained in step a and the inner layer obtained in step b in sequence, and then carry out hot pressing and compounding to obtain the multi-layer composite polyethylene film material.

10. The preparation method of the multilayer composite polyethylene film material according to claim 9, characterized in that, In steps a and b, the temperature of the melt blending is 160-170°C.

Images