PE film and preparation method thereof

Abstract

The invention discloses a PE film and a preparation method thereof, and belongs to the technical field of high polymer materials, and the prepared PE film comprises a hydrophobic antibacterial upper layer, an oleophobic antibacterial layer and a hydrophobic antibacterial lower layer from top to bottom. The hydrophobic antibacterial upper layer / hydrophobic antibacterial lower layer is prepared from the following raw materials: 80 to 100 parts of polyethylene resin, 3 to 12 parts of organic antibacterial agent, 8 to 20 parts of modified shell powder and 10 to 25 parts of polysilane hydrophobic agent; the oleophobic antibacterial layer is prepared from the following raw materials: 80 to 100 parts of polyethylene resin, 3 to 12 parts of organic antibacterial agent, 8 to 20 parts of modified shell powder and 8 to 20 parts of modified chitosan. The antibacterial performance of the PE film is improved by combining the good antibacterial activity of the modified shell powder and the modified chitosan, the hydrophobic and antibacterial effects of the upper surface and the lower surface of the film are achieved through the arrangement of the three-layer structure, meanwhile, a more compact film structure is formed based on mutual entanglement of macromolecular chains of the modified chitosan in the oleophobic antibacterial layer and molecular chains of polyethylene resin, and the antibacterial performance of the film is improved. And grease permeation is prevented.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and in particular relates to a PE film and a preparation method thereof. Background Art

[0002] Polyethylene film, as a widely used plastic film material, is a film material made of polyethylene (PE) as the main raw material. Polyethylene film has excellent physical properties, such as high tensile strength, good elongation, and large elastic modulus. These properties enable the polyethylene film to maintain good shape stability when subjected to external forces and is not easy to break or deform. In addition, the polyethylene film also has good low-temperature resistance and can maintain good flexibility even at lower temperatures. Polyethylene film has excellent chemical stability and can resist erosion by a variety of acids, alkalis, salts and other chemical substances. This allows the polyethylene film to maintain good performance stability in a variety of environments and extend its service life.

[0003] Polyethylene film has good processing properties and can be made into films of different thicknesses and for different purposes through various processes such as film blowing, casting, and calendering. Polyethylene film has high transparency and glossiness, which makes it widely used in the packaging field; it has certain barrier properties and can effectively block the penetration of moisture, oxygen and other substances. This barrier property makes polyethylene film widely used in food packaging, moisture-proof and other fields.

[0004] As a PE film used for food packaging, due to the gaps between polyethylene molecules, the "oil molecules" in the food can pass through these gaps, causing oil seepage, affecting the carrying of food. In order to ensure that the food remains fresh, the packaging material should have certain antibacterial properties during long-term storage. Therefore, improving the antibacterial and anti-oil seepage properties of PE film is more conducive to its widespread application in the field of food packaging. Summary of the invention

[0005] The object of the present invention is to provide a PE film and a preparation method thereof, so as to improve the antibacterial property and anti-oil seepage property of the PE film.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

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

[0008] The raw materials of the hydrophobic 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 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.

[0010] The raw material of the hydrophobic antibacterial lower layer is the same as that of the hydrophobic 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 the resin and is more evenly dispersed.

[0012] The amino groups on the chitosan molecular chain will be protonated under acidic conditions and carry a positive charge, while fats or lipids usually carry a negative charge. Therefore, through electrostatic adsorption, chitosan can prevent the transfer of fats or lipids, thereby achieving an oil-proof effect. Chitosan also has a significant antibacterial effect, 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 shell powder are as follows:

[0015] The shells of shellfish are washed, dried and crushed to obtain shell powder with a particle size of 10-30 μm, which is placed in a crucible and calcined at 900-1000° C. for 2-4 hours to obtain calcined powder, the calcined powder is added into deionized water at 10-20 wt%, heated to 60-90° C., sodium stearate is added thereto, and the reaction is carried out at a constant temperature for 30-60 minutes. After the reaction is completed, the shell powder is filtered and dried to obtain the modified shell powder.

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

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

[0018] Furthermore, the calcined powder is added into 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 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, the amount of sodium stearate added is preferably 2% of the mass of the calcined powder. At this time, part of the sodium stearate molecules exist 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] While improving the hydrophobicity of the film, the polysilane hydrophobic agent promotes the disentanglement of the long chains of polyethylene (PE) macromolecules and acts as a lubricant between the macromolecular chains, making the polyethylene material easy to process and shape.

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

[0024] Chitosan is dissolved in an acetic acid solution with a volume fraction of 1-2% at a mass fraction of 0.5-2.5wt%, and an initiator of cerium ammonium nitrate (CAN) is added after heating. N-vinyl imidazole is added under nitrogen conditions, and the reaction is stirred at a constant temperature of 40-80°C for 2-3h. After the reaction is completed, the mixture is poured into acetone and stirred for precipitation, filtered and washed, extracted with ethanol and dried to obtain modified chitosan.

[0025] The reaction equation for the above reaction is as follows:

[0026]

[0027] Modified chitosan obtained by grafting N-vinyl imidazole on chitosan has higher antibacterial activity, and there is a π-π interaction between the imidazole group and the polyethylene resin, which can improve the dispersibility of the modified chitosan in the polyethylene resin.

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

[0029] Furthermore, 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 above-mentioned PE film, comprising the following steps:

[0031] The raw materials of the three-layer structure are mixed separately and then melted at a melting temperature of 150-200° C. to obtain a three-layer melt, and the melt is subjected to three-layer co-extrusion film blowing to obtain a PE film.

[0032] Beneficial effects of the present invention:

[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 oleophobic antibacterial layer in the middle can prevent the penetration of grease.

[0034] (2) The dispersibility of shell powder and chitosan in polyethylene resin was improved by surface modification. N-vinyl imidazole-modified chitosan could enhance its antibacterial activity. The macromolecular chains of modified chitosan were entangled with the molecular chains of polyethylene resin to form a denser membrane structure, thus enhancing the anti-oil permeability performance. DETAILED DESCRIPTION

[0035] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] Example 1

[0037] Preparation of modified shell powder:

[0038] The shells of Sinonovacula constricta are washed and dried, and then crushed to obtain shell powder with a particle size of 10-30 μm. The shell powder is placed in a crucible and calcined at 1000° C. for 2 h to obtain calcined powder. The calcined powder is added into deionized water at 10 wt %, heated to 80° C., and sodium stearate is added in an amount of 2% of the mass of the calcined powder. The reaction is carried out at a constant temperature for 50 min. After the reaction is completed, the shell powder is filtered and dried to obtain the modified shell powder.

[0039] Example 2

[0040] Preparation of modified chitosan:

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

[0042] Example 3

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

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

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

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

[0047] The raw materials of the three-layer structure are mixed separately and then melted at a melting temperature of 150-200° C. to obtain a three-layer melt, and the melt is subjected to three-layer co-extrusion film blowing to obtain a PE film.

[0048] Example 4

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

[0050] Example 5

[0051] The difference from Example 3 is that the mass fraction of modified shell powder in the raw materials of the hydrophobic antibacterial upper layer is adjusted to 20 parts, and correspondingly the mass fractions of modified shell powder in the raw materials of the oleophobic antibacterial layer and the hydrophobic antibacterial lower layer are both adjusted to 20 parts, and the other steps and conditions are the same as 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 antibacterial layer is adjusted to 16 parts, and the other steps and conditions are the same as 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 antibacterial layer is adjusted to 20 parts, and the other steps and conditions are the same as Example 4.

[0056] Embodiment 8-9

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

[0058] Table 1

[0059]

[0060] Comparative Example 1

[0061] Compared with Example 3, the only difference of this comparative example is that no modified shell powder is added to the raw materials of each layer, and the other steps and conditions are the same as Example 3.

[0062] Comparative Example 2

[0063] Compared with Example 3, the only difference of this comparative example is that no modified chitosan is added to the raw materials of the oleophobic and antibacterial layer, and the other steps and conditions are the same as those of Example 3.

[0064] Comparative Example 3

[0065] Compared with Example 3, the PE film of this comparative example has only one layer structure, and its raw materials include, by mass: 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 melting temperature of 150-200° C. to obtain a melt, which is then extruded and blown to obtain a PE film.

[0067] The performance tests were performed on the PE films prepared in Examples 3 to 9 and Comparative Examples 1 to 3. The results are shown in Table 2:

[0068] The antibacterial rate and antifungal performance tests were conducted with reference to "QBT2591-2003 Test Methods and Antibacterial Effects of Antibacterial Plastics".

[0069] Reference KIT test for oil seepage prevention performance detection: Use Oil Kit Test TAPPI 559pm-96 test method to detect oil resistance level.

[0070] Table 2

[0071]

[0072] As can be seen from Table 1, in Examples 3 to 5, as the proportion of modified shell powder increases, the antibacterial performance of the PE film is significantly improved, and due to the influence of shell powder on the surface roughness of the PE film, the hydrophobic performance is slightly reduced. In Examples 6 and 7, the proportion of modified chitosan is increased on the basis of Example 4, and the antibacterial performance is improved while the oil-proof performance is greatly enhanced. In Comparative Example 1, no modified shell powder is added, and the antibacterial performance of the PE film is poor, especially the antifungal performance is only level 2. In Comparative Example 2, no modified chitosan is added, and its oil-proof and antibacterial performance is significantly lower than that of Example 3. Compared with Example 3, Comparative Example 3 is only a one-layer structure, and without the oleophobic antibacterial layer, the oil-proof performance of the PE film is poor.

[0073] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

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

Claims

1. A PE film, characterized in that: The PE film includes, from top to bottom, a hydrophobic antibacterial upper layer, an oleophobic antibacterial layer and a hydrophobic antibacterial lower layer; The raw materials of the hydrophobic 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 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 antibacterial lower layer is the same as that of the hydrophobic antibacterial upper layer.

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

3. A PE film according to claim 1, characterized in that: The preparation steps of the modified shell powder are as follows: The shells of shellfish are washed, dried and crushed to obtain shell powder with a particle size of 10-30 μm, which is placed in a crucible and calcined at 900-1000° C. for 2-4 hours to obtain calcined powder, the calcined powder is added into deionized water at 10-20 wt%, heated to 60-90° C., sodium stearate is added thereto, and the reaction is carried out at a constant temperature for 30-60 minutes. After the reaction is completed, the shell powder is filtered and dried to obtain the modified shell powder.

4. A PE film according to claim 3, characterized in that: The shellfish is at least one of clams, mussels and razor clams.

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

6. A PE film according to claim 1, characterized in that: The polysilane hydrophobic agent is one of polydimethylsiloxane and hexadecyltrimethylsilane.

7. A PE film according to claim 1, characterized in that: The preparation steps of the modified chitosan are as follows: Chitosan is dissolved in an acetic acid solution with a volume fraction of 1-2% at a mass fraction of 0.5-2.5wt%, and an initiator of ammonium cerium nitrate is added after heating. N-vinyl imidazole is added under nitrogen conditions, and the reaction is stirred at a constant temperature of 40-80°C for 2-3h. After the reaction is completed, the mixture is poured into acetone and stirred for precipitation, filtered and washed, extracted with ethanol and dried to obtain modified chitosan.

8. A PE film according to claim 7, characterized in that: The ammonium cerium nitrate initiator is added at a concentration of 0.1-0.35 mol / L.

9. A PE film according to claim 7, characterized in that: The N-vinylimidazole is added at a concentration of 0.1-0.3 mol / L.

10. A method for preparing a PE film according to any one of claims 1 to 9, characterized in that: The steps include: The raw materials of the three-layer structure are mixed separately and then melted at a melting temperature of 150-200° C. to obtain a three-layer melt, and the melt is subjected to three-layer co-extrusion film blowing to obtain a PE film.

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