An antibacterial, barrier, and flame-retardant polylactic acid film, its preparation method and application

Abstract

This invention belongs to the field of bio-based thin film technology, specifically relating to an antibacterial, barrier, and flame-retardant polylactic acid (PLA) film, its preparation method, and its application. The method includes the following steps: 1) Calcining clay minerals to obtain calcined clay; mixing the calcined clay with a strong acid; heating and reacting the mixture; filtering; washing; and drying to obtain acid-treated calcined clay; 2) Mixing the acid-treated calcined clay with essential oil until homogeneous; then drying under negative pressure to obtain a modified clay composite; 3) Mixing a PVA aqueous solution and the modified clay composite until homogeneous; coating the surface of the modified PLA film; and drying to obtain an antibacterial, barrier, and flame-retardant PLA film. This invention significantly improves the antibacterial, barrier, and flame-retardant properties.

Description

Technical Field

[0001] This invention belongs to the field of bio-based thin film technology, specifically relating to an antibacterial, barrier, and flame-retardant polylactic acid film, its preparation method, and its application. Background Technology

[0002] With the rapid development of the new materials industry, especially the widespread use of packaging materials in daily life, most of these materials are not easily degraded. Therefore, it is crucial to develop bio-based biodegradable packaging materials.

[0003] Bio-based biodegradable packaging materials have poor barrier properties, lack antibacterial properties, and are highly flammable, limiting their wider application. Therefore, it is crucial to enhance the application range of these materials by imbuing them with barrier, flame-retardant, and antibacterial properties.

[0004] Polylactic acid (PLA) is an important member of bio-based polymer materials and has been widely used and researched in recent years. To overcome its poor barrier properties and flammability, surface coating technology is used to improve the barrier, flame retardant, and antibacterial properties of PLA. This has important practical significance for the further research and industrialization of modified PLA films in the field of plastic packaging. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an antibacterial, barrier, and flame-retardant polylactic acid film, its preparation method and application, which significantly improves the antibacterial, barrier and flame-retardant properties.

[0006] This invention provides a method for preparing an antibacterial, barrier, and flame-retardant polylactic acid film, comprising the following steps: 1) Clay minerals are calcined to obtain calcined clay. The calcined clay is mixed with a strong acid, heated to react, filtered, washed, and dried to obtain acid-treated calcined clay. 2) The acid-treated calcined clay and essential oil are mixed evenly, and then dried under negative pressure to obtain a modified clay composite. 3) Mix the PVA aqueous solution and the modified clay composite evenly, coat the surface of the modified PLA film, and dry to obtain an antibacterial, barrier, and flame-retardant polylactic acid film.

[0007] Preferably, in step 1), the clay mineral is kaolin, and the calcination temperature is 600-700℃.

[0008] Preferably, in step 1), the strong acid is sulfuric acid with a concentration of 3-5 mol / L, and the weight-to-volume ratio of clay mineral to strong acid is 1 g: 8-12 mL.

[0009] Preferably, in step 1), the temperature of the heating reaction is 80-90℃.

[0010] Preferably, the essential oil is one or more of the following: rosemary essential oil, tea tree essential oil, clove essential oil, thyme essential oil, peppermint essential oil, lavender essential oil, and marjoram essential oil.

[0011] Preferably, the essential oil is tea tree oil.

[0012] Preferably, the weight-to-volume ratio of acid-treated calcined clay to essential oil is 1g:8-12mL.

[0013] Preferably, the concentration of the PVA aqueous solution is 4-6%, and the weight ratio of the PVA aqueous solution to the modified clay composite is 10:0.1-0.3.

[0014] This invention provides an antibacterial, barrier, and flame-retardant polylactic acid film, which is prepared using the aforementioned preparation method.

[0015] This invention provides an application of the antibacterial, barrier, and flame-retardant polylactic acid film, which is used to prepare packaging materials.

[0016] The beneficial effects of this invention are that the antibacterial, barrier, and flame-retardant polylactic acid film of this invention can not only play a flame-retardant role by introducing clay minerals and plant essential oils on the surface (clay minerals mainly form a barrier layer to prevent the substrate from exchanging substances with the external environment; plant essential oils contain benzene rings or hydroxyl groups to play a role in char formation, etc.); the coating has the film-forming function of PVA and the barrier function of clay minerals to achieve a barrier effect; the plant essential oils in the coating also have antibacterial function, and the essential oils that enter the nanopores can also enhance their slow-release function and high-temperature resistance (at high temperatures such as 120°C, most of the essential oils will evaporate completely at this time). Attached Figure Description

[0017] Figure 1 The graph shows the change in oxygen permeability over time for PLA and antibacterial, barrier, and flame-retardant polylactic acid films.

[0018] Figure 2 The graph shows the release rate of PLA and antibacterial, barrier, and flame-retardant polylactic acid films over time. Detailed Implementation

[0019] The present invention will be further described below with reference to the embodiments to facilitate understanding of the technical solution of the present invention, but it should not be construed as the scope of the present invention being limited to the following implementation examples.

[0020] Example 1 A method for preparing an antibacterial, barrier, and flame-retardant polylactic acid film includes the following steps: 1) Dissolve an appropriate amount of PEI in deionized water to prepare an aqueous solution with a concentration of 5 mg / mL to obtain a PEI solution; 2) Immerse the cleaned and dried PLA film in PEI solution for 5 minutes, then remove it to make its surface positively charged, and dry it to obtain the modified PLA film. 3) Take an appropriate amount of clay mineral (kaolin), calcine it at 650℃ for 2 hours, and then cool it to obtain calcined kaolin; 4) Add 20g of calcined kaolin to a round-bottom flask, then add 200ml of 4mol / L H2SO4 to the flask. React at 90℃ for 6 hours, then filter, wash, and dry. 5) Take 5g of the product from step 4) and place it in a beaker, then add 50ml of tea tree oil and stir well; 6) Place the product from step 5) in a vacuum drying oven (room temperature), form a negative pressure (-0.1 MPa), maintain it for 3 minutes, then restore it to normal pressure. Repeat the above process 3 times (this helps essential oil molecules enter the clay pores, improves thermal stability, and the acidified clay pores contain hydroxyl groups, which also helps chelate essential oils and improve thermal stability). Take it out to obtain the modified clay complex. 7) Prepare a 5% (w / w) aqueous solution of PVA (polyvinyl alcohol); 8) Take 10g of PVA aqueous solution and place it in a beaker. Then take 0.3g of modified clay composite from step 6), stir and mix it, and then coat it onto the surface of the modified PLA film from step 2). After drying, an antibacterial, barrier, and flame-retardant polylactic acid film is obtained.

[0021] Example 2 The difference between Example 2 and Example 1 is that the modified clay composite in step 8) is 0.2g. Everything else is the same as in Example 1.

[0022] Example 3 The difference between Example 3 and Example 1 is that the modified clay composite in step 8) is 0.1g. Everything else is the same as in Example 1.

[0023] Example 4 Oxygen permeability test: The test was conducted according to the test method published in GB / T1038-2000 "Test method for gas permeability of plastic films and sheets - differential pressure method"; Flame retardant performance test: The test was conducted using a cone calorimeter according to the ISO 5660 test method. Antimicrobial performance test: The test was conducted according to the test method published in GB / T31402-2015 / ISO22196:2007 "Plastics - Test method for antimicrobial properties of plastic surfaces".

[0024] The performance results, as tested experimentally, are as follows: Figure 1 , Figure 2 The results are shown in Table 1.

[0025] Table 1. Antibacterial properties, oxygen permeability, and heat release rate of PLA and its modified films.

[0026] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of protection of this application is limited to these examples; within the framework of this application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of one or more embodiments of this application as described above, which are not provided in detail for the sake of brevity.

[0027] One or more embodiments in this application are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of this application. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of one or more embodiments in this application should be included within the protection scope of this application.

Claims

1. A method for preparing an antibacterial, barrier, and flame-retardant polylactic acid film, characterized in that, Includes the following steps: 1) Clay minerals are calcined to obtain calcined clay. The calcined clay is mixed with a strong acid, heated to react, filtered, washed, and dried to obtain acid-treated calcined clay. 2) The acid-treated calcined clay and essential oil are mixed evenly, and then dried under negative pressure to obtain a modified clay composite. 3) Mix the PVA aqueous solution and the modified clay composite evenly, coat the surface of the modified PLA film, and dry to obtain an antibacterial, barrier, and flame-retardant polylactic acid film.

2. The preparation method according to claim 1, characterized in that, In step 1), the clay mineral is kaolin, and the calcination temperature is 600-700℃.

3. The preparation method according to claim 1, characterized in that, In step 1), the strong acid is sulfuric acid with a concentration of 3-5 mol / L, and the weight-to-volume ratio of clay minerals to strong acid is 1 g: 8-12 mL.

4. The preparation method according to claim 1, characterized in that, In step 1), the temperature of the heating reaction is 80-90℃.

5. The preparation method according to claim 1, characterized in that, The essential oil is one or more of the following: rosemary essential oil, tea tree essential oil, clove essential oil, thyme essential oil, peppermint essential oil, lavender essential oil, and marjoram essential oil.

6. The preparation method according to claim 5, characterized in that, The essential oil is tea tree oil.

7. The preparation method according to claim 1, characterized in that, The weight-to-volume ratio of acid-treated calcined clay to essential oil is 1g:8-12mL.

8. The preparation method according to claim 1, characterized in that, The concentration of the PVA aqueous solution is 4-6%, and the weight ratio of the PVA aqueous solution to the modified clay composite is 10:0.1-0.

3.

9. An antibacterial, barrier, and flame-retardant polylactic acid film, characterized in that, It is prepared by the preparation method described in any one of claims 1-8.

10. An application of the antibacterial, barrier, and flame-retardant polylactic acid film as described in claim 9, characterized in that, The antibacterial, barrier, and flame-retardant polylactic acid film is used to prepare packaging materials.

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