A PE film and its preparation method

Abstract

This invention discloses a PE film and its preparation method, belonging to the field of polymer materials technology. The prepared PE film comprises a three-layer structure from top to bottom: a hydrophobic antibacterial upper layer, an oleophobic antibacterial layer, and a hydrophobic antibacterial lower layer. The raw materials for the hydrophobic antibacterial upper / lower layer include: 80-100 parts of polyethylene resin, 3-12 parts of organic antibacterial agent, 8-20 parts of modified shell powder, and 10-25 parts of polysilane hydrophobic agent. The raw materials for the oleophobic antibacterial layer include: 80-100 parts of polyethylene resin, 3-12 parts of organic antibacterial agent, 8-20 parts of modified shell powder, and 8-20 parts of modified chitosan. The combination of the good antibacterial activity of modified shell powder and modified chitosan improves the antibacterial performance of the PE film. Furthermore, the three-layer structure achieves hydrophobic and antibacterial properties on both the upper and lower surfaces of the film. In the oleophobic antibacterial layer, the macromolecular chains of modified chitosan are intertwined with the molecular chains of polyethylene resin, forming a denser film structure that prevents grease penetration.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a PE film and its preparation method. Background Technology

[0002] Polyethylene film, a widely used plastic film material, is a film material made primarily from polyethylene (PE). PE film possesses excellent physical properties, such as high tensile strength, good elongation, and a high modulus of elasticity. These properties allow PE film to maintain good shape stability under external forces, making it less prone to breakage or deformation. Furthermore, PE film exhibits good low-temperature resistance, maintaining good flexibility even at low temperatures. PE film also possesses excellent chemical stability, resisting the erosion of various acids, alkalis, and salts. This allows PE film to maintain good performance stability in various environments, extending its service life.

[0003] Polyethylene film has excellent processing properties and can be manufactured into films of different thicknesses and for different applications through various processes such as blown film, casting, and calendering. Polyethylene film has high transparency and gloss, making it widely used in the packaging industry; it also possesses certain barrier properties, effectively preventing the penetration of substances such as moisture and oxygen. This barrier property makes polyethylene film widely used in food packaging, moisture protection, and other fields.

[0004] As a food packaging material, PE film has gaps between polyethylene molecules, which allow oil molecules in food to pass through, causing oil seepage and affecting the food's portability. In order to keep food fresh, packaging materials should have certain antibacterial properties during long-term storage. Therefore, improving the antibacterial and oil-proof properties of PE film is more conducive to its widespread application in the food packaging field. Summary of the Invention

[0005] The purpose of this invention is to provide a PE film and its preparation method, which improves the antibacterial and oil-proof properties of the PE film.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] This invention provides a PE film, which comprises, from top to bottom, a hydrophobic and antibacterial upper layer, an oleophobic and antibacterial layer, and a hydrophobic and antibacterial lower layer;

[0008] The raw materials of the hydrophobic and antibacterial upper layer include, by weight, 80-100 parts of polyethylene resin, 3-12 parts of organic antibacterial agent, 8-20 parts of modified shell powder, and 10-25 parts of polysilane hydrophobic agent.

[0009] The raw materials of the oleophobic and antibacterial layer include, by mass parts: 80-100 parts of polyethylene resin, 3-12 parts of organic antibacterial agent, 8-20 parts of modified shell powder, and 8-20 parts of modified chitosan.

[0010] The raw material of the hydrophobic and antibacterial lower layer is the same as that of the hydrophobic and antibacterial upper layer.

[0011] The antibacterial properties of PE film as food packaging are enhanced by combining the antibacterial properties of shell powder and organic antibacterial agents. After modification, the shell powder has better compatibility with resin and is more evenly dispersed.

[0012] The amino groups on the chitosan molecular chain are protonated under acidic conditions, becoming positively charged, while fats or lipids are usually negatively charged. Therefore, through electrostatic adsorption, chitosan can prevent the transfer of fats or lipids, thus achieving an oil-repellent effect. Furthermore, chitosan has significant antibacterial properties, which can further enhance the antibacterial properties of the film.

[0013] Furthermore, the organic antibacterial agent is one of vanillin and ethyl vanillin compounds.

[0014] Furthermore, the preparation steps of the modified seashell powder are as follows:

[0015] Shells of mollusks are washed, dried, and pulverized to obtain shell powder with a particle size of 10-30 μm. The powder is then placed in a crucible and calcined at 900-1000℃ for 2-4 hours to obtain calcined powder. The calcined powder is added to deionized water at 10-20 wt%, heated to 60-90℃, and sodium stearate is added. The mixture is then reacted at a constant temperature for 30-60 minutes. After the reaction is completed, the mixture is filtered and dried to obtain modified shell powder.

[0016] The main component of calcined shell powder is active calcium oxide, which has good antibacterial effect and excellent antifungal properties. Due to the large surface energy of shell powder particles, the powder agglomeration phenomenon is obvious, resulting in poor dispersion performance in polymers. After modification with sodium stearate, long-chain sodium stearate molecules exist on the surface, which weakens the surface polarity of particles and reduces the agglomeration phenomenon of shell powder.

[0017] Furthermore, the high-temperature calcination temperature is 1000℃, and the calcination time is 2 hours.

[0018] Furthermore, the calcined powder is added to deionized water at 10 wt%, the heating temperature is 80°C, and the reaction time is 50 min.

[0019] Furthermore, the shellfish is at least one of hard clams, mussels, and razor clams.

[0020] Furthermore, the amount of sodium stearate added is 1-3% of the mass of the calcined powder. In the embodiments of the present invention, it is preferred that the amount of sodium stearate added is 2% of the mass of the calcined powder. At this time, the sodium stearate molecules are partially present on the surface of the shell powder, and the activation degree of the shell powder is the highest.

[0021] Furthermore, the polysilane hydrophobic agent is one of polydimethylsiloxane and hexadecyltrimethylsilane.

[0022] Polysilane hydrophobic agents improve the hydrophobicity of films, promote the untangling of long polyethylene (PE) macromolecular chains, and act as a lubricant between macromolecular chains, making polyethylene materials easier to process and mold.

[0023] Furthermore, the preparation steps of the modified chitosan are as follows:

[0024] Chitosan was dissolved in acetic acid solution with a volume fraction of 1-2% at a mass fraction of 0.5-2.5 wt%. After heating, cerium ammonium nitrate initiator (CAN) was added, and N-vinylimidazol was added under nitrogen. The mixture was stirred at a constant temperature of 40-80℃ for 2-3 hours. After the reaction was completed, the mixture was poured into acetone and stirred to precipitate. After filtration and washing, the mixture was extracted with ethanol and dried to obtain modified chitosan.

[0025] The reaction equations for the above reactions are as follows:

[0026]

[0027] Modified chitosan obtained by grafting N-vinylimidazol onto chitosan exhibits higher antibacterial activity, and the π-π interaction between the imidazole group and polyethylene resin can improve the dispersibility of modified chitosan in polyethylene resin.

[0028] Furthermore, the cerium ammonium nitrate initiator is added at a concentration of 0.1-0.35 mol / L.

[0029] Further, the N-vinylimidazole is added at a concentration of 0.1-0.3 mol / L.

[0030] The present invention also provides a method for preparing the PE film as described above, comprising the following steps:

[0031] The raw materials with three layers are mixed and melted at a melting temperature of 150-200℃ to obtain a three-layer melt. The melt is then co-extruded and blown into a PE film.

[0032] The beneficial effects of this invention are:

[0033] (1) The antibacterial properties of PE film are improved by combining the good antibacterial activity of modified shell powder and modified chitosan. Through the three-layer structure, the upper and lower surfaces of the film are hydrophobic and antibacterial, while the middle oleophobic and antibacterial layer can prevent the penetration of oil.

[0034] (2) The dispersibility of shell powder and chitosan in polyethylene resin is improved by surface modification. N-vinylimidazolium-modified chitosan can enhance its antibacterial activity. Moreover, the macromolecular chains of modified chitosan are intertwined with the molecular chains of polyethylene resin to form a denser membrane structure, which enhances the oil-proof performance. Detailed Implementation

[0035] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0036] Example 1

[0037] Preparation of modified seashell powder:

[0038] After washing and drying the shells of the razor clam, the shell powder with a particle size of 10-30 μm was obtained. The powder was placed in a crucible and calcined at 1000℃ for 2 hours to obtain calcined powder. The calcined powder was added to deionized water at 10 wt%, heated to 80℃, and sodium stearate was added at 2% of the mass of the calcined powder. The reaction was carried out at a constant temperature for 50 minutes. After the reaction was completed, the shell powder was obtained by filtration and drying.

[0039] Example 2

[0040] Preparation of modified chitosan:

[0041] Chitosan was dissolved in acetic acid solution with a mass fraction of 1.0 wt% at a volume fraction of 1%, and after heating, cerium ammonium nitrate initiator (CAN) was added at a concentration of 0.25 mol / L. N-vinylimidazol was added at a concentration of 0.2 mol / L under nitrogen conditions. The reaction was carried out at a constant temperature of 70 °C with stirring for 3 h. After the reaction was completed, the mixture was poured into acetone and stirred to precipitate. After filtration and washing, the mixture was extracted with ethanol and dried to obtain modified chitosan.

[0042] Example 3

[0043] This embodiment provides a PE film, which includes, from top to bottom, a hydrophobic and antibacterial upper layer, an oleophobic and antibacterial layer, and a hydrophobic and antibacterial lower layer;

[0044] The raw materials for the hydrophobic and antibacterial upper layer, by weight, include: 100 parts polyethylene resin, 12 parts vanillin, 8 parts modified shell powder, and 25 parts polydimethylsiloxane.

[0045] The raw materials for the oleophobic and antibacterial layer, by weight, include: 100 parts polyethylene resin, 12 parts vanillin, 8 parts modified shell powder, and 8 parts modified chitosan.

[0046] The raw materials of the hydrophobic and antibacterial lower layer are the same as those of the hydrophobic and antibacterial upper layer.

[0047] The raw materials with three layers are mixed and melted at a melting temperature of 150-200℃ to obtain a three-layer melt. The melt is then co-extruded and blown into a PE film.

[0048] Example 4

[0049] The difference from Example 3 is that the mass fraction of modified shell powder in the raw material of the hydrophobic and antibacterial upper layer is adjusted to 15 parts, and correspondingly, the mass fraction of modified shell powder in the raw materials of the oleophobic and antibacterial layer and the hydrophobic and antibacterial lower layer is also adjusted to 15 parts. Other steps and conditions are the same as in Example 3.

[0050] Example 5

[0051] The difference from Example 3 is that the mass fraction of modified shell powder in the raw material of the hydrophobic and antibacterial upper layer is adjusted to 20 parts, and the mass fraction of modified shell powder in the raw materials of the oleophobic and antibacterial layer and the hydrophobic and antibacterial lower layer is also adjusted to 20 parts. Other steps and conditions are the same as in Example 3.

[0052] Example 6

[0053] The difference from Example 4 is that the mass fraction of modified chitosan in the raw material of the oleophobic and antibacterial layer is adjusted to 16 parts, while the other steps and conditions are the same as in Example 4.

[0054] Example 7

[0055] The difference from Example 4 is that the mass fraction of modified chitosan in the raw material of the oleophobic and antibacterial layer is adjusted to 20 parts, while the other steps and conditions are the same as in Example 4.

[0056] Examples 8-9

[0057] The difference from Example 6 is that the mass ratio of raw materials in each layer is different, while the other steps and conditions are the same as in Example 6. The specific raw material ratios are shown in Table 1.

[0058] Table 1

[0059]

[0060] Comparative Example 1

[0061] Compared to Example 3, the only difference in this comparative example is that modified shell powder is not added to the raw materials of each layer; the other steps and conditions are the same as in Example 3.

[0062] Comparative Example 2

[0063] Compared to Example 3, the only difference in this comparative example is that modified chitosan is not added to the oleophobic and antibacterial layer raw material; the other steps and conditions are the same as in Example 3.

[0064] Comparative Example 3

[0065] Compared to Example 3, the PE film of this comparative example has only one layer structure, and its raw materials include, by mass parts: 100 parts of polyethylene resin, 12 parts of vanillin, 8 parts of modified shell powder, and 25 parts of polydimethylsiloxane.

[0066] The raw materials are mixed and melted at a temperature of 150-200℃ to obtain a melt. The melt is then extruded and blown to obtain a PE film.

[0067] The performance of the PE films prepared in Examples 3-9 and Comparative Examples 1-3 was tested, and the results are shown in Table 2:

[0068] The antibacterial rate and antifungal performance were tested in accordance with the "QBT2591-2003 Test Methods and Antibacterial Effects of Antibacterial Plastics".

[0069] Oil resistance performance testing reference KIT test: The oil resistance level is tested using the Oil Kit Test TAPPI 559pm-96 test method.

[0070] Table 2

[0071]

[0072] As shown in Table 1, in Examples 3-5, the antibacterial performance of the PE film significantly improved with the increase of the modified shell powder content. However, due to the influence of shell powder on the surface roughness of the PE film, the hydrophobic performance decreased slightly. Examples 6 and 7, based on Example 4, increased the modified chitosan content, resulting in improved antibacterial performance and significantly enhanced oil-repellent properties. In Comparative Example 1, without modified shell powder, the PE film exhibited poor antibacterial performance, especially with an antifungal performance level of only 2. In Comparative Example 2, without modified chitosan, the oil-repellent and antibacterial performance was significantly lower than that of Example 3. Compared to Example 3, Comparative Example 3 consisted of only one layer; without the oleophobic and antibacterial layer, the PE film exhibited poor oil-repellent performance.

[0073] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0074] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A PE film, characterized in that, The PE film comprises, from top to bottom, a hydrophobic and antibacterial upper layer, an oleophobic and antibacterial layer, and a hydrophobic and antibacterial lower layer; The raw materials of the hydrophobic and antibacterial upper layer include, by weight, 80-100 parts of polyethylene resin, 3-12 parts of organic antibacterial agent, 8-20 parts of modified shell powder, and 10-25 parts of polysilane hydrophobic agent. The raw materials of the oleophobic and antibacterial layer include, by weight, 80-100 parts of polyethylene resin, 3-12 parts of organic antibacterial agent, 8-20 parts of modified shell powder, and 8-20 parts of modified chitosan. The raw material of the hydrophobic and antibacterial lower layer is the same as that of the hydrophobic and antibacterial upper layer; The preparation steps of the modified seashell powder are as follows: Shells of mollusks are washed, dried, and pulverized to obtain shell powder with a particle size of 10-30 μm. The powder is placed in a crucible and calcined at 900-1000℃ for 2-4 hours to obtain calcined powder. The calcined powder is added to deionized water at 10-20 wt%, heated to 60-90℃, and sodium stearate is added. The mixture is reacted at a constant temperature for 30-60 minutes. After the reaction is completed, the mixture is filtered and dried to obtain modified shell powder. The polysilane hydrophobic agent is one of polydimethylsiloxane and hexadecyltrimethylsilane; The preparation steps of the modified chitosan are as follows: Chitosan was dissolved in acetic acid solution with a mass fraction of 1-2% at a mass fraction of 0.5-2.5 wt%. After heating, cerium ammonium nitrate initiator was added, and N-vinylimidazolium was added under nitrogen atmosphere. The mixture was stirred at a constant temperature of 40-80℃ for 2-3 hours. After the reaction was completed, the mixture was poured into acetone and stirred to precipitate. After filtration and washing, the mixture was extracted with ethanol and dried to obtain modified chitosan.

2. The PE film according to claim 1, characterized in that, The organic antibacterial agent is one of vanillin and ethyl vanillin compounds.

3. The PE film according to claim 1, characterized in that, The shellfish is at least one of the following: hard clam, mussel, and razor clam.

4. A PE film according to claim 1, characterized in that, The amount of sodium stearate added is 1-3% of the mass of the calcined powder.

5. A PE film according to claim 1, characterized in that, The cerium ammonium nitrate initiator is added at a concentration of 0.1-0.35 mol / L.

6. A PE film according to claim 1, characterized in that, The N-vinylimidazole was added at a concentration of 0.1-0.3 mol / L.

7. A method for preparing a PE film as described in any one of claims 1-6, characterized in that, Includes the following steps: The raw materials with three layers are mixed and melted at a melting temperature of 150-200℃ to obtain a three-layer melt. The melt is then co-extruded and blown into a PE film.

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