Multilayer composite polyethylene film material and preparation method thereof

Abstract

The 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 which are arranged in sequence, the surface layer is prepared from the following raw materials in parts by weight: 90 to 100 parts of high-density polyethylene, 10 to 15 parts of modified charcoal and 3 to 8 parts of chitosan; the inner layer is prepared from the following raw materials in parts by weight: 30 to 40 parts of low-density polyethylene and 70 to 85 parts of linear low-density polyethylene; wherein the preparation process of the modified biochar comprises the following steps: adding biochar obtained after biomass pretreatment into an ethanol aqueous solution, then adding a silane coupling agent, carrying out a heating reaction, and after the reaction is completed, carrying out purification to obtain aminated biochar; the preparation method comprises the following steps: adding the activated carbon into DMF (Dimethyl Formamide), then adding gallic acid and triethylamine, carrying out a heating reaction, and purifying after the reaction is completed, so as to obtain the modified biochar. The polyethylene film material has excellent oxidation resistance and mechanical properties.

Description

Technical Field

[0001] The invention belongs to the technical field of packaging films, and in particular 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 are translucent, low cost, non-toxic, glossy, and soft in texture. They also have good chemical stability, heat sealing, and low temperature resistance, so they are widely used. However, existing polyethylene films have problems such as poor mechanical strength and easy oxidation, which to a certain extent limits their scope of application.

[0003] In order 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 its preparation method. The patent discloses a composite film made by compounding a high oxygen barrier BOPET film and a high water barrier PE film, which has oxygen barrier properties. Nevertheless, the antioxidant properties of the composite film still need to be further improved. Based on this, a deeper study on the performance of polyethylene films is needed. 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 anti-oxidation performance and mechanical properties.

[0005] The second object of the present invention is to provide a method for preparing a multi-layer composite polyethylene film material with simple steps.

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

[0007] A multi-layer composite polyethylene film material, comprising 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;

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

[0009] (1) adding the biochar obtained after biomass pretreatment to an ethanol aqueous solution, then adding a silane coupling agent for heating reaction, and purifying after the reaction is completed to obtain the amino biochar;

[0010] (2) Adding the amination biochar of step (1) to DMF, and then adding gallic acid and triethylamine to carry out heating reaction, and purifying after the reaction is completed to obtain modified biochar.

[0011] Furthermore, 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; and the concentration of the ethanol aqueous solution is 70-75%.

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

[0013] Furthermore, the biomass pretreatment process in step (1) is: pyrolyzing the biomass material powder at 400-600° C. for 3-4 hours under a nitrogen atmosphere; the biomass material powder is peanut straw powder.

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

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

[0016] Furthermore, 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; and the melt index of the linear low-density polyethylene is 1.5-2.0 g / 10 min.

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

[0018] The method for preparing the above-mentioned multi-layer composite polyethylene film material comprises the following steps:

[0019] a. Preparation of the surface layer: According to the weight ratio, the raw materials for the surface layer are uniformly mixed and the surface layer is formed by melt blending;

[0020] b. Preparation of the inner layer: According to the weight ratio, the raw materials for the inner layer are uniformly mixed and the inner layer is formed by melt blending;

[0021] c. Preparation of a multi-layer composite polyethylene film material: The surface layer obtained in step a and the inner layer obtained in step b are sequentially stacked and hot-pressed to obtain a multi-layer composite polyethylene film material.

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

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

[0024] 1. The biochar obtained after the biomass pretreatment of the present invention has a high porosity. These pores provide a large amount of adsorption area, so that the biochar has a large specific surface area; the biochar is modified with KH550, and then reacted with gallic acid and triethylamine. After the amino groups on the biochar and the carboxyl groups in the gallic acid undergo amidation reaction, on the one hand, the antioxidant functional groups of gallic acid are introduced on the surface of the biochar, and the antioxidant property of the material is improved by capturing free radicals. On the other hand, a layer of stable structure composed of amide bonds is formed on the surface of the biochar, which can further reduce the damage to the internal structure of the biochar and achieve the purpose of improving the stability of the material. The modified biochar is mixed with chitosan. The surface of the modified biochar contains abundant hydroxyl groups that interact with the amino groups on the chitosan molecular chain to form hydrogen bonds. The hydrogen bonding effect 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. DETAILED DESCRIPTION

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

[0027] In the embodiment 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. Embodiment

[0029] Example 1

[0030] A multi-layer composite polyethylene film material, comprising a surface layer and an inner layer arranged in sequence; the surface layer comprises 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 comprises the following raw materials in parts by weight: 34 parts of low-density polyethylene and 76 parts of linear low-density polyethylene. The preparation process of the modified biochar is as follows:

[0031] (1) Drying and grinding peanut straw to obtain peanut straw powder; pyrolyzing the peanut straw powder at 500°C for 3.5 hours under a nitrogen atmosphere to obtain biochar; adding the obtained biochar to a 72% ethanol aqueous solution according to a mass ratio of biochar to KH550 of 1:0.07, then adding KH550, reacting at 53°C for 5.5 hours, filtering, washing, and drying after the reaction is completed to obtain amino-treated biochar;

[0032] (2) According to the mass ratio of amination biochar, gallic acid and triethylamine of 1:0.06:0.25, the amination biochar of step (1) was added to DMF, and then gallic acid and triethylamine were added, and the mixture was reacted at 85°C for 3.5 hours. After the reaction was completed, the mixture was filtered, washed and dried to obtain modified biochar.

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

[0034] a. Preparation of the surface layer: According to the weight ratio, the raw materials for the surface layer are uniformly mixed, and a surface layer having a thickness of 12 μm is prepared by melt blending, wherein the melt blending temperature is 165 ℃;

[0035] b. Preparation of the inner layer: According to the weight ratio, the raw materials for the inner layer were uniformly mixed, and the inner layer having a thickness of 33 μm was prepared by melt blending, wherein the melt blending temperature was 165 ℃;

[0036] c. Preparation of a multilayer 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 laminated at 180° C. and 20 bar to obtain a multilayer composite polyethylene film material.

[0037] Example 2

[0038] A multilayer composite polyethylene film material comprises a surface layer and an inner layer which are arranged in sequence; the surface layer comprises 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 comprises 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 modified biochar is as follows:

[0040] (1) Drying and grinding peanut straw to obtain peanut straw powder; pyrolyzing the peanut straw powder at 400°C for 4 hours under a nitrogen atmosphere to obtain biochar; adding the obtained biochar to a 70% ethanol aqueous solution according to a mass ratio of biochar to KH550 of 1:0.05, then adding KH550, reacting at 50°C for 6 hours, filtering, washing, and drying after the reaction is completed to obtain amino-treated biochar;

[0041] (2) According to the mass ratio of amination biochar, gallic acid and triethylamine of 1:0.05:0.2, the amination biochar of step (1) was added to DMF, and then gallic acid and triethylamine were added, and the mixture was reacted at 80°C for 4 hours. After the reaction was completed, the mixture was filtered, washed and dried to obtain modified biochar.

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

[0043] a. Preparation of the surface layer: According to the weight ratio, the raw materials for the surface layer are uniformly mixed, and a surface layer having a thickness of 10 μm is prepared by melt blending, wherein the melt blending temperature is 160 ℃;

[0044] b. Preparation of the inner layer: According to the weight ratio, the raw materials for the inner layer were uniformly mixed, and the inner layer having a thickness of 30 μm was prepared by melt blending, wherein the melt blending temperature was 160 ℃;

[0045] c. Preparation of a multilayer 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 laminated at 180° C. and 20 bar to obtain a multilayer composite polyethylene film material.

[0046] Example 3

[0047] A multilayer composite polyethylene film material comprises a surface layer and an inner layer which are arranged in sequence; the surface layer comprises 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 comprises 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 modified biochar is as follows:

[0049] (1) Drying and grinding peanut straw to obtain peanut straw powder; pyrolyzing the peanut straw powder at 600°C for 3 hours under a nitrogen atmosphere to obtain biochar; adding the obtained biochar to a 75% ethanol aqueous solution according to a mass ratio of biochar to KH550 of 1:0.1, then adding KH550, reacting at 55°C for 5 hours, filtering, washing, and drying after the reaction is completed to obtain amino-treated biochar;

[0050] (2) According to the mass ratio of amination biochar, gallic acid and triethylamine of 1:0.1:0.3, the amination biochar of step (1) was added to DMF, and then gallic acid and triethylamine were added, and the mixture was reacted at 90° C. for 3 h. After the reaction was completed, the mixture was filtered, washed and dried to obtain modified biochar.

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

[0052] a. Preparation of the surface layer: According to the weight ratio, the raw materials for the surface layer are uniformly mixed, and a surface layer having a thickness of 15 μm is prepared by melt blending, wherein the melt blending temperature is 170 ℃;

[0053] b. Preparation of the inner layer: According to the weight ratio, the raw materials for the inner layer were uniformly mixed, and the inner layer having a thickness of 40 μm was prepared by melt blending, wherein the melt blending temperature was 170 ℃;

[0054] c. Preparation of a multilayer 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 laminated at 180° C. and 20 bar to obtain a multilayer composite polyethylene film material.

[0055] 2. Comparative Example

[0056] Comparative Example 1

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

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

[0059] Comparative Example 2

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

[0061] Amination biochar was used to replace the modified biochar, and the rest was the same as in 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 parts of gallic acid were used to replace the modified biochar, and the rest was the same as in Example 1.

[0065] Performance testing

[0066] The polyethylene films obtained in Examples 1-3 and Comparative Examples 1-3 were made into samples, and the sample dimensions were 50 mm in length, 4 mm in width, and 0.15 mm in thickness. The properties of the above samples were tested, and the specific test process was as follows:

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

[0068] (2) Oxygen permeability: The oxygen permeability test was conducted according to the coulometric test method of GB / T 19789-2005 Oxygen permeability test for 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, respectively. Each disc was placed in 10 mL of 0.02 mg / mL DPPH ethanol solution, and magnetically stirred at room temperature for 35 min. The supernatant of each group was taken to detect the absorbance of each group of discs at 517 nm, and a DPPH solution control group was set. The scavenging rate of DPPH radicals was calculated as follows: scavenging rate of DPPH radicals = (absorbance value of control group - absorbance value of test group) / absorbance value of test group × 100%, and the results are shown in Table 2;

[0070] (4) Thermal stability: The above samples were cut into small pieces weighing 10 mg each for thermogravimetric testing. The test conditions were: heating from room temperature to 600°C at a heating rate of 10°C / min in a nitrogen atmosphere. 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 200℃ weight retention (%) 300℃ weight retention (%) 600℃ weight retention (%) 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 Table 1-2 that compared with Comparative Examples 1-3, the multilayer composite polyethylene film materials of Examples 1-3 of the present invention have excellent mechanical properties and antioxidant properties. The gallic acid part in the structure of 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. The close interaction between the modified biochar and chitosan and the wear resistance and weather resistance of the 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 multilayer 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 damage to the internal structure of the biochar, thereby improving the thermal stability of the material.

[0080] Further analysis shows that comparative example 1 uses biochar to replace modified biochar to prepare polyethylene film materials; comparative example 2 uses amination biochar to replace modified biochar to prepare polyethylene film materials; comparative example 3 uses biochar and gallic acid to replace modified biochar to prepare polyethylene film materials. The above results show that adjusting the formula of the present invention will lead to a decrease in the performance 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 them. The basic principles and main features of the present invention have been described above with specific implementation schemes. On the basis of the present invention, some modifications or replacements may be made thereto, but these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of protection claimed by the present invention.

Claims

1. A multi-layer composite polyethylene film material, characterized in that: The multilayer composite polyethylene film material comprises a surface layer and an inner layer which are 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) adding the biochar obtained after biomass pretreatment to an ethanol aqueous solution, then adding a silane coupling agent for heating reaction, and purifying after the reaction is completed to obtain the amino biochar; (2) Adding the amination biochar of step (1) to DMF, and then adding gallic acid and triethylamine to carry out heating reaction, and purifying after the reaction is completed to obtain modified biochar.

2. The multi-layer composite polyethylene film material according to claim 1, characterized in that: The mass ratio of the biochar to the silane coupling agent in step (1) is 1:(0.05-0.1); the silane coupling agent is KH550; and 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: The temperature of the heating reaction in step (1) is 50-55° C., and the heating reaction time is 5-6 hours.

4. The multi-layer composite polyethylene film material according to claim 1, characterized in that: The biomass pretreatment process in step (1) is: pyrolyzing the biomass material powder at 400-600° C. for 3-4 hours under a nitrogen atmosphere; the biomass material powder is peanut straw powder.

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

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

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; and the melt index of the linear low-density polyethylene is 1.5-2.0 g / 10 min.

8. The multi-layer 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 method for preparing the multi-layer composite polyethylene film material according to any one of claims 1 to 8, characterized in that: The following steps are involved: a. Preparation of the surface layer: According to the weight ratio, the raw materials for the surface layer are uniformly mixed and the surface layer is formed by melt blending; b. Preparation of the inner layer: According to the weight ratio, the raw materials for the inner layer are uniformly mixed and the inner layer is formed by melt blending; c. Preparation of a multi-layer composite polyethylene film material: The surface layer obtained in step a and the inner layer obtained in step b are sequentially stacked and hot-pressed to obtain a multi-layer composite polyethylene film material.

10. The method for preparing a multi-layer composite polyethylene film material according to claim 9, characterized in that: The temperature of melt blending in step a and step b is 160-170°C.

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