High-barrier intelligent antibacterial degradable agricultural mulching film and preparation method thereof

Abstract

The invention relates to a high-barrier intelligent antibacterial degradable agricultural mulching film and a preparation method thereof, and belongs to the field of degradable agricultural mulching films. The problems that an existing bio-based material for the degradable film is not ideal in mechanical property and barrier property and lacks antibacterial property are solved. The agricultural mulching film provided by the invention comprises the following components: 20-30 parts of deionized water; 2-5 parts of a bacterial cellulose membrane; 20-30 parts of nano cellulose, 3-5 parts of montmorillonite and 10-15 parts of coconut oil; and 5-10 parts of natural polyphenol. According to the agricultural mulching film disclosed by the invention, the stabilization and temperature-sensitive controlled release behaviors of volatile active polyphenols are realized by utilizing the self-coupling effect of natural polyphenols under an ultrasonic condition based on the high adsorption performance of nano-montmorillonite and the heated phase change behavior of coconut oil, and the composite film is endowed with responsive antibacterial performance under a heating condition; the mechanical property of the material is greatly improved by utilizing the three-dimensional reticular microporous structure of the bacterial cellulose membrane and enhancing intermolecular high-density hydrogen bond connection through nanocellulose.

Description

Technical Field

[0001] The present invention belongs to the technical field of degradable agricultural films, and particularly relates to a high-barrier, intelligent antibacterial degradable agricultural film and a preparation method thereof. Background Art

[0002] With the continuous development of agricultural technology in China, the application of agricultural films has been continuously popularized, which has enabled the rapid development of the agricultural film market in China. For this reason, the long-term and large-scale use of agricultural films, and the current lack of effective recycling and treatment, have further exacerbated the "white pollution" phenomenon in China. Therefore, the development of high-barrier, intelligent antibacterial degradable agricultural films and their preparation technologies has practical significance for the development of related industries in China.

[0003] Bio-based materials are an important part of degradable films, and their selection plays an important role in various properties of degradable film materials. However, bio-based degradable agricultural films, such as PLA, PBAT, etc., usually face bottleneck problems such as high cost, unsatisfactory mechanical properties, and uncontrollable degradation period, and their comprehensive performance is difficult to rival that of commercial petroleum-based agricultural films. Therefore, the development of high-barrier and intelligent antibacterial degradable agricultural films is of great significance for the sustainable development of the industry.

[0004] At present, there have been literature reports on introducing dehydrogenases with rich hydroxyl groups such as LDH into PBAT films (Yang Zeya, Li Biao, Li Shuangde, Dou Yibo, Han Jingbin, Layered double hydroxide / PBAT hybrid film with high barrier and degradability, Chemical Engineering Science, 280th volume, 2023, 119016, ISSN 0009-2509). These bio-based enzymes can improve the barrier properties of the film by capturing diffused water molecules. However, due to the insufficient hydrogen bond density in the system, the mechanical properties are unsatisfactory, and at the same time, the antibacterial property is lacking. There is an urgent need to develop methods to enhance the mechanical properties and antibacterial properties of degradable films. Summary of the Invention

[0005] The present invention aims to solve the technical problems in the prior art that the mechanical properties, barrier properties of bio-based materials for degradable films are unsatisfactory and lack antibacterial properties, and provides a high-barrier, intelligent antibacterial degradable agricultural film and a preparation method thereof. The present invention utilizes the self-coupling effect of natural polyphenols under ultrasonic conditions, based on the high adsorption performance of nano-montmorillonite and the heat-induced phase change behavior of coconut oil, to achieve the stabilization and temperature-sensitive controlled release behavior of volatile active polyphenols, endowing the composite film with responsive antibacterial properties under heating conditions. At the same time, by using the high filling of montmorillonite and the temperature-sensitive phase change characteristics of coconut oil, a montmorillonite-coconut oil nanofluid is prepared to achieve high barrier and high fluidization of the degradable film, solving the material processing problem; by using the three-dimensional network microporous structure of bacterial cellulose membrane to enhance the high-density hydrogen bond connection between molecules through nano-cellulose, a significant improvement in the mechanical properties of the material is achieved.

[0006] To solve the above technical problems, the technical solution of the present invention is as follows:

[0007] A high-barrier, intelligent antibacterial and degradable agricultural film, which is composed of the following components in parts by weight:

[0008]

[0009] In the above technical solution, preferably, the montmorillonite is modified montmorillonite.

[0010] In the above technical solution, preferably, the coconut oil is coconut oil fatty acid.

[0011] In the above technical solution, preferably, the natural polyphenol is at least one of thymol, tea polyphenol, catechin, and thymol.

[0012] A preparation method of a high-barrier, intelligent antibacterial and degradable agricultural film includes the following steps:

[0013] (1) Take bacterial cellulose membranes according to parts by weight and dissolve them in an appropriate amount of deionized water, and wait for the bacterial cellulose membranes to absorb water and swell completely;

[0014] (2) After the bacterial cellulose membranes swell completely, freeze-dry the bacterial cellulose membranes until they are completely dry to obtain bacterial cellulose membranes in the form of aerogels;

[0015] (3) Blend nanocellulose and deionized water according to the parts by weight ratio to obtain a nanocellulose solution, put the bacterial cellulose membranes obtained in step (2) into the nanocellulose solution for infiltration, and after complete infiltration, dry to obtain a bacterial cellulose composite film;

[0016] (4) Blend montmorillonite and coconut oil according to the parts by weight ratio and grind to obtain a suspension;

[0017] (5) Add natural polyphenols to the suspension obtained in step (4) according to the parts by weight ratio and stir until the suspension particles disappear;

[0018] (6) Ultrasonic the solution obtained in step (5) to obtain a montmorillonite-coconut oil nanofluid;

[0019] (7) Put the bacterial cellulose composite film obtained in step (3) into the montmorillonite-coconut oil nanofluid obtained in step (6) for infiltration, and after complete infiltration, press the obtained composite film into a sheet to obtain a high-barrier, intelligent antibacterial and degradable agricultural film.

[0020] In the above technical solution, preferably, the drying in step (3) is normal temperature drying for 30 min - 5 h.

[0021] In the above technical solution, preferably, the grinding time in step (4) is 5 min.

[0022] In the above technical solution, preferably, the stirring time in step (5) is 5 min.

[0023] In the above technical solution, preferably, the ultrasonic time in step (6) is 3 - 5 h.

[0024] The beneficial effects of the present invention are as follows:

[0025] (1) Aiming at the problem of unsatisfactory mechanical properties of biobased materials, the present invention uses a biobased bacterial cellulose membrane with high mechanical properties, and utilizes its unique three-dimensional reticulated microporous structure to enhance the high-density hydrogen bond connection between molecules through nanofibrillated cellulose, thereby greatly improving the mechanical properties of the material.

[0026] (2) Aiming at the key problems of unsatisfactory small molecule barrier property, low added value, and lack of antibacterial ability of biodegradable thin film materials, the present invention develops a key filler preparation technology for high barrier, temperature-sensitive controlled release antibacterial. By using the self-coupling effect of natural polyphenols under ultrasonic conditions, based on the high adsorption performance of nanometer montmorillonite and the heat-induced phase change behavior of coconut oil, the stabilization and temperature-sensitive controlled release behavior of volatile active polyphenols are realized, endowing the composite film with responsive antibacterial performance under heating conditions. At the same time, by using the high filling of montmorillonite and the temperature-sensitive phase change characteristics of coconut oil, montmorillonite-coconut oil nanofluid is prepared, solving the problem that it is difficult to balance the practical performance and degradability of the material, and realizing the intelligent antibacterial effect of the thin film at the same time.

[0027] (3) Aiming at the problems of cumbersome process and difficult processing in the preparation of high-barrier, antibacterial and biodegradable thin films, the present invention uses montmorillonite and coconut oil under the regulation of small molecules of natural polyphenols such as thymol, and prepares montmorillonite-coconut oil nanofluid through repeated grinding and continuous ultrasonic technology, solving the problem of difficult processing of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0029] Figure 1 FIG. is the characterization diagram of the bacterial cellulose membrane of Example 1 at different magnification factors, where the left figure has a magnification factor of 40 times and the right figure has a magnification factor of 100 times.

[0030] Figure 2 FIG. is the characterization diagram of the aerogel-like bacterial cellulose membrane of Example 1 at different magnification factors, where the left figure has a magnification factor of 40 times and the right figure has a magnification factor of 100 times.

[0031] Figure 3Characterization diagrams of the high-barrier, intelligent antibacterial and degradable agricultural film prepared in Example 1 at different magnifications. The left figure has a magnification of 40 times, and the right figure has a magnification of 100 times. Detailed implementation mode

[0032] The inventive concept of the present invention is as follows: In order to solve the technical problems of unsatisfactory mechanical properties, barrier properties and lack of antibacterial properties of bio-based materials used in degradable films in the prior art, a montmorillonite-coconut oil nanofluid technology with natural polyphenol thermosensitive controlled release regulation is developed to achieve high barrier and intelligent antibacterial properties of degradable agricultural films, which is of great significance to the sustainable development of the industry. Some natural polyphenols have amphiphilicity and can act as coupling agents. Through high-density interfacial crosslinking and micro-nano assembly structures, the mechanical properties of degradable films can be enhanced efficiently. At the same time, their antibacterial characteristics can inhibit the growth of microorganisms and protect the films from pollution, meeting the current trend of environmental protection and sustainable development. By introducing key components such as montmorillonite and coconut oil, montmorillonite-coconut oil nanofluids are prepared, which are expected to achieve the synergistic improvement of barrier properties and antibacterial properties and solve the problem of difficult processing, showing broad application prospects.

[0033] For the high-barrier, intelligent antibacterial and degradable agricultural film of the present invention and its preparation method, montmorillonite and coconut oil are ground. The fatty acids and glycerol contained in coconut oil react with the hydroxyl groups on the surface of montmorillonite to obtain a suspension. After adding natural polyphenols, a large number of phenolic hydroxyl groups in the polyphenols react with the fatty acids in coconut oil. Through stirring and continuous ultrasonic treatment, they are uniformly dispersed in the layered structure of montmorillonite to prepare montmorillonite-coconut oil nanofluids. By using a bio-based, high-mechanical property bacterial cellulose membrane and utilizing its unique three-dimensional network microporous structure to enhance the high-density hydrogen bond connection between molecules through nanocellulose, a significant improvement in the mechanical properties of the material is achieved.

[0034] The high-barrier, intelligent antibacterial and degradable agricultural film of the present invention is composed of the following parts by weight of materials:

[0035]

[0036] Preferably, the montmorillonite is modified montmorillonite; the coconut oil is a mixture of coconut oil fatty acids and glycerol; the natural polyphenol is at least one of thymol, tea polyphenols, catechins, and thymol. Further preferably, the natural polyphenol is thymol.

[0037] A preparation method of a high-barrier, intelligent antibacterial and degradable agricultural film includes the following steps:

[0038] (1) Take the bacterial cellulose membrane according to the parts by weight and dissolve it in an appropriate amount of deionized water, and wait for the bacterial cellulose membrane to absorb water and swell completely;

[0039] The deionized water used in this step is used to swell the bacterial cellulose membrane, and the amount of this part of deionized water is not included in the weight of deionized water contained in the high-barrier, intelligent antibacterial and degradable agricultural film of the present invention;

[0040] (2) After the bacterial cellulose membrane is completely swollen, place the bacterial cellulose membrane in a freeze-dryer for drying until it is completely dry to obtain a bacterial cellulose membrane in the form of an aerogel;

[0041] (3) Blend nanocellulose and deionized water in a beaker according to the weight ratio to obtain a nanocellulose solution. Place the bacterial cellulose membrane obtained in step (2) in the nanocellulose solution for infiltration. After complete infiltration, dry it at room temperature for 30 min - 5 h to obtain a bacterial cellulose composite film;

[0042] (4) Blend montmorillonite and coconut oil according to the weight ratio, put them in a mortar, and grind for 5 min. Then transfer the obtained suspension to a beaker;

[0043] (5) Add natural polyphenols to the suspension obtained in step (4) according to the weight ratio and stir at room temperature for 5 min until the suspension particles disappear;

[0044] (6) Place the solution obtained in step (5) in an ultrasonic machine and perform continuous ultrasonic treatment for 3 - 5 h to obtain a montmorillonite-coconut oil nanofluid;

[0045] (7) Place the bacterial cellulose composite film obtained in step (3) in the montmorillonite-coconut oil nanofluid obtained in step (6) for infiltration. After complete infiltration, press the obtained composite film into a sheet to obtain a high-barrier, intelligent antibacterial and degradable agricultural film.

[0046] The present invention will be specifically described below through examples. It is necessary to point out here that the following examples only further illustrate the present invention and should not be construed as limiting the protection scope of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above content.

[0047] The coconut oil used in the following examples is coconut oil fatty acid, purchased from: Shandong Yousuo Chemical Technology Co., Ltd.; the commercial model of the modified montmorillonite is: DK-32B, purchased from: Zhejiang Feihong New Materials Co., Ltd.

[0048] Example 1:

[0049] (1) Preparation of bacterial cellulose composite film

[0050] Take 2.0 g of bacterial cellulose membrane (see the structure diagram in Figure 1) Dissolve it in an appropriate amount of deionized water. After the bacterial cellulose membrane absorbs water and swells, put it into a freeze dryer for drying to obtain an aerogel-like bacterial cellulose membrane (the structural diagram is as shown in Figure 2 ). Blend 20 g of nanocellulose and 20 g of deionized water in proportion, soak the bacterial cellulose membrane with the obtained solution. After soaking is completed, dry it at room temperature for 30 min to obtain a bacterial cellulose composite membrane.

[0051] (2) Preparation of montmorillonite-coconut oil nanofluid

[0052] Take 3.0 g of modified montmorillonite and 10.0 g of coconut oil and blend them. Pour them into a mortar and grind continuously for 5 min. Transfer the obtained suspension to a beaker, add 5 g of thymol to the suspension, stir for 5 min. After the suspended particles dissolve, place the obtained solution in an ultrasonic machine and ultrasonicate continuously for 3 h to obtain a montmorillonite-coconut oil nanofluid.

[0053] (3) Preparation of high-barrier, intelligent antibacterial and degradable agricultural film

[0054] Pour the prepared montmorillonite-coconut oil nanofluid into the bacterial cellulose composite membrane. After the composite membrane is completely soaked, put the composite membrane into a tablet press and press it into shape at 180 °C and 50 MPa to obtain a high-barrier, intelligent antibacterial and degradable agricultural film (as shown in Figure 3 ).

[0055] Example 2:

[0056] 1) Preparation of bacterial cellulose composite membrane

[0057] Take 5.0 g of bacterial cellulose membrane and dissolve it in an appropriate amount of deionized water. After the bacterial cellulose membrane absorbs water and swells, put it into a freeze dryer for drying to obtain an aerogel-like bacterial cellulose membrane. Blend 30 g of nanocellulose and 30 g of deionized water in proportion, soak the bacterial cellulose membrane with the obtained solution. After soaking is completed, dry it at room temperature for 30 min to obtain a bacterial cellulose composite membrane.

[0058] (2) Preparation of montmorillonite-coconut oil nanofluid

[0059] Take 5.0 g of modified montmorillonite and 15.0 g of coconut oil and blend them. Pour them into a mortar and grind continuously for 5 min. Transfer the obtained suspension to a beaker, add 10 g of thymol to the suspension, stir for 5 min. After the suspended particles dissolve, place the obtained solution in an ultrasonic machine and ultrasonicate continuously for 3 h to obtain a montmorillonite-coconut oil nanofluid.

[0060] (3) Preparation of high-barrier, intelligent antibacterial and degradable agricultural film

[0061] Pour the prepared montmorillonite-coconut oil nanofluid into the bacterial cellulose composite film. After the composite film is completely infiltrated, put the composite film into a tablet press and press it into shape at 180 °C and 50 MPa to obtain a high-barrier, intelligent antibacterial and degradable agricultural film.

[0062] Example 3:

[0063] (1) Preparation of bacterial cellulose composite film

[0064] Take 3.0 g of bacterial cellulose membrane and dissolve it in an appropriate amount of deionized water. After the bacterial cellulose membrane absorbs water and swells, put it into a freeze dryer for drying to obtain an aerogel-like bacterial cellulose membrane. Mix 30 g of nanocellulose and 30 g of deionized water in proportion, infiltrate the bacterial cellulose membrane with the obtained solution, and after infiltration, dry it at room temperature for 30 min to obtain a bacterial cellulose composite film.

[0065] (2) Preparation of montmorillonite-coconut oil nanofluid

[0066] Take 5.0 g of modified montmorillonite and 15.0 g of coconut oil and mix them. Pour them into a mortar and grind continuously for 5 min. Transfer the obtained suspension to a beaker, add 10 g of tea polyphenols to the suspension, stir for 5 min, and after the suspension particles dissolve, place the obtained solution in an ultrasonic machine and ultrasonicate continuously for 3 h to obtain a montmorillonite-coconut oil nanofluid.

[0067] (3) Preparation of high-barrier, intelligent antibacterial and degradable agricultural film

[0068] Pour the prepared montmorillonite-coconut oil nanofluid into the bacterial cellulose composite film. After the composite film is completely infiltrated, put the composite film into a tablet press and press it into shape at 180 °C and 50 MPa to obtain a high-barrier, intelligent antibacterial and degradable agricultural film.

[0069] Example 4:

[0070] (1) Preparation of bacterial cellulose composite film

[0071] Take 3.0 g of bacterial cellulose membrane and dissolve it in an appropriate amount of deionized water. After the bacterial cellulose membrane absorbs water and swells, put it into a freeze dryer for drying to obtain an aerogel-like bacterial cellulose membrane. Mix 20 g of nanocellulose and 20 g of deionized water in proportion, infiltrate the bacterial cellulose membrane with the obtained solution, and after infiltration, dry it at room temperature for 30 min to obtain a bacterial cellulose composite film.

[0072] (2) Preparation of montmorillonite-coconut oil nanofluid

[0073] Take 3.0 g of modified montmorillonite and 10.0 g of coconut oil, blend them, pour them into a mortar, and continuously grind for 5 min. Transfer the obtained suspension to a beaker, add 5 g of catechin to the suspension, stir for 5 min. After the suspended particles dissolve, place the obtained solution in an ultrasonic machine and ultrasonicate continuously for 3 h to obtain montmorillonite-coconut oil nanofluid.

[0074] (3) Preparation of high-barrier, intelligent antibacterial and degradable agricultural film

[0075] Pour the prepared montmorillonite-coconut oil nanofluid into the bacterial cellulose composite film. After the composite film is completely infiltrated, put the composite film into a tablet press and press it into shape at 180 °C and 50 MPa to obtain a high-barrier, intelligent antibacterial and degradable agricultural film.

[0076] Comparative Example 1:

[0077] Take 2.5 g of montmorillonite and 8.0 g of coconut oil, blend them, pour them into a mortar, and continuously grind for 5 min. Transfer the obtained suspension to a beaker, add 0.8 parts of tea polyphenol to the suspension, stir until the suspended particles dissolve, place the obtained solution in an ultrasonic machine and ultrasonicate continuously for 3 h to obtain montmorillonite-coconut oil nanofluid.

[0078] Comparative Example 2:

[0079] Take 3.0 g of montmorillonite and 10.0 g of coconut oil, blend them, pour them into a mortar, and continuously grind for 5 min. Transfer the obtained suspension to a beaker, add 1.0 part of catechin to the suspension, stir until the suspended particles dissolve, place the obtained solution in an ultrasonic machine and ultrasonicate continuously for 3 h to obtain montmorillonite-coconut oil nanofluid.

[0080] Perform performance tests on the specimens obtained in Examples 1-4 and Comparative Examples 1 and 2 above. The obtained results are shown in the following table:

[0081] Table 1 Detection results

[0082]

[0083] As can be seen from the above table, the montmorillonite-coconut oil nanofluid prepared in Example 1 of the present invention has a significant improvement in water vapor barrier performance compared with the high-filled materials in Comparative Examples 1 and 2 without any treatment (without any treatment: that is, not infiltrating the fluid into the bacterial cellulose membrane), and its comprehensive mechanical properties are significantly higher than those of commonly used petroleum-based films. Examples 2-4 of the present invention also have improvements in water vapor barrier performance and comprehensive mechanical properties compared with the comparative examples.

[0084] In summary, the present invention first proposes to develop the technology of montmorillonite nanofluids. Based on the self-coupling and antibacterial performance characteristics of natural polyphenols and the three-dimensional network structure of bacterial cellulose, the comprehensive performance of the degradable composite film material is significantly improved, which is expected to realize the replacement of petroleum-based films with bio-based degradable films, and effectively promote the upgrading of the film market and sustainable development.

[0085] Obviously, the above embodiments are merely examples given for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or variations can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. And the obvious changes or variations derived therefrom are still within the protection scope of the present invention.

Claims

1. A high barrier, intelligent antibacterial and degradable agricultural mulch film, characterized in that: It is composed of the following materials in parts by weight:

2. The high barrier, intelligent antibacterial and degradable agricultural mulch film according to claim 1, characterized in that: The montmorillonite is modified montmorillonite.

3. The high barrier, intelligent antibacterial and degradable agricultural mulch film according to claim 1, characterized in that: The coconut oil is coconut oil fatty acid.

4. The high barrier, intelligent antibacterial and degradable agricultural mulch film according to claim 1, characterized in that: The natural polyphenol is at least one of thymol, tea polyphenols, catechins and thymol.

5. A method for preparing the high-barrier, intelligent antibacterial and degradable agricultural mulch film according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) taking a bacterial cellulose membrane according to weight, dissolving it in an appropriate amount of deionized water, and waiting for the bacterial cellulose membrane to absorb water and swell completely; (2) After the bacterial cellulose membrane is completely swollen, freeze-drying the bacterial cellulose membrane until it is completely dried to obtain a bacterial cellulose membrane in the form of an aerogel; (3) mixing nanocellulose and deionized water in parts by weight to obtain a nanocellulose solution, and infiltrating the bacterial cellulose film obtained in step (2) into the nanocellulose solution, and drying after the infiltration is complete to obtain a bacterial cellulose composite film; (4) blending montmorillonite and coconut oil in proportion by weight, grinding, and obtaining a suspension; (5) adding natural polyphenols to the suspension obtained in step (4) according to a weight ratio, and stirring until the suspended particles disappear; (6) subjecting the solution obtained in step (5) to ultrasonication to obtain montmorillonite-coconut oil nanofluid; (7) The bacterial cellulose composite film obtained in step (3) is immersed in the montmorillonite-coconut oil nanofluid obtained in step (6). After complete infiltration, the obtained composite film is pressed into a sheet to obtain a high-barrier, intelligent antibacterial and degradable agricultural mulch film.

6. The method for preparing the high-barrier, intelligent antibacterial and degradable agricultural mulch film according to claim 5, characterized in that: The drying in step (3) is performed at room temperature for 30 min-5 h.

7. The method for preparing the high-barrier, intelligent antibacterial and degradable agricultural mulch film according to claim 5, characterized in that: The grinding time in step (4) is 5 min.

8. The method for preparing the high-barrier, intelligent antibacterial and degradable agricultural mulch film according to claim 5, characterized in that: The stirring time in step (5) is 5 min.

9. The method for preparing the high-barrier, intelligent antibacterial and degradable agricultural mulch film according to claim 5, characterized in that: The ultrasonication time in step (6) is 3 to 5 hours.

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