An antibacterial bio-based composite film and its preparation method

Abstract

The present invention relates to the field of thin film technology, and discloses an antibacterial bio-based composite thin film and a preparation method thereof. The present invention uses formaldehyde, 3-aminopropyltriethoxysilane, and p-hydroxyphenylacetic acid as raw materials, and through the Mannich reaction, intermediate 1 is obtained. Intermediate 1 is subjected to an acyl chlorination reaction with thionyl dichloride to obtain intermediate 2, which is then subjected to dehydration condensation with nano-titanium dioxide to obtain intermediate 3. Under the action of pyridine, intermediate 3 and tea polyphenols are subjected to an esterification reaction to obtain nano-titanium dioxide modified tea polyphenols. Finally, polylactic acid and nano-titanium dioxide modified tea polyphenols are stirred and dispersed, and cast and scraped to obtain an antibacterial bio-based composite thin film. The composite thin film prepared by the present invention has good antibacterial properties, mechanical properties, and the characteristics of being green and environmentally friendly.

Description

Technical Field

[0001] The invention relates to the technical field of thin films, in particular to an antibacterial bio-based composite film and a preparation method thereof. Background Art

[0002] Polylactic acid is a material with good biodegradability and biocompatibility. It is renewable, has high gloss and good transparency. It can be degraded into carbon dioxide and water under the action of microorganisms and acids. However, its antibacterial properties are not good, and the antibacterial properties of the bio-based film prepared from it are also not good. In recent years, the safety issues caused by microbial contamination have affected people's health. The development of bio-based films with antibacterial properties is the focus of current research.

[0003] Tea polyphenols are a safe and non-toxic green compound with excellent antibacterial and antioxidant properties. They are widely used in the food processing industry, the medical field, and the daily necessities field. Nano titanium dioxide, also known as nano titanium dioxide, has a small particle size and can reduce oxygen in water to produce highly oxidizing hydrogen peroxide and free radicals, which can decompose the cell outer membrane, followed by chaos in the cytoplasm and cell membrane until the cell dies, thereby achieving an antibacterial effect. However, due to its small particle size, it is easy to agglomerate. Therefore, how to improve the dispersion of nano titanium dioxide and thus improve the antibacterial effect is a hot topic of research. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies of the above-mentioned prior art and to provide a bio-based composite film which is both antibacterial and green and environmentally friendly and a preparation method thereof.

[0005] To achieve the above object, the technical solution adopted by the present invention is: an antibacterial bio-based composite film, the composite film comprises the following components in parts by weight: 100 parts of polylactic acid, 1-5 parts of nano-titanium dioxide modified tea polyphenols;

[0006] The preparation method of the antibacterial bio-based composite film is as follows:

[0007] Polylactic acid and nano-titanium dioxide modified tea polyphenols are added to chloroform, fully stirred and dispersed, poured onto a smooth glass plate, and cast and scraped using a scraping machine, and dried to obtain an antibacterial bio-based composite film.

[0008] Furthermore, the preparation method of the nano-titanium dioxide modified tea polyphenols is:

[0009] (1) Add formaldehyde and chloroform into a flask, stir to disperse, heat to 55 - 65 °C, add 3 - aminopropyltriethoxysilane to it, then raise the temperature to 75 - 85 °C, add p - hydroxyphenylacetic acid to it, stir and react for 1 - 3 h. After the reaction is completed, cool to room temperature and evaporate the solvent to obtain intermediate 1; the dosage ratio of formaldehyde, 3 - aminopropyltriethoxysilane, and p - hydroxyphenylacetic acid is (0.4 - 0.5) g : (1.5 - 2) g : 1 g;

[0010] Mannich reaction occurs among formaldehyde, 3 - aminopropyltriethoxysilane, and p - hydroxyphenylacetic acid to obtain intermediate 1, and the reaction process is as follows:

[0011]

[0012] (2) Add intermediate 1 and chloroform into a flask, stir to disperse, then add thionyl chloride to it, heat to 60 - 65 °C, react for 2 - 5 h. After the reaction is completed, perform atmospheric distillation and drying to obtain intermediate 2; the dosage ratio of intermediate 1 and thionyl chloride is 1 g : (0.25 - 0.35) g;

[0013] The carboxyl group on the molecule of intermediate 1 undergoes an acylation reaction with thionyl chloride to obtain intermediate 2, and the reaction process is as follows:

[0014]

[0015] (3) Add dry nano - titanium dioxide and ethanol into a flask, disperse by ultrasonic wave, add intermediate 2 to it, react ultrasonically at 35 - 45 °C for 2 - 4 h. After the reaction is completed, centrifuge, wash with ethanol, centrifuge again, repeat 2 - 3 times, and dry to obtain intermediate 3; the dosage ratio of nano - titanium dioxide and intermediate 2 is 1 g : (1.5 - 4) g;

[0016] The siloxane bond of intermediate 2 undergoes hydrolysis to generate silanol groups, which undergo dehydration condensation with the hydroxyl groups on nano - titanium dioxide to obtain intermediate 3, and the reaction process is as follows;

[0017] Among them is nano - titanium dioxide;

[0018] (4) Add tea polyphenols and ethyl acetate into a flask, stir to dissolve, then add pyridine and intermediate 3 to it, react at 65 - 75 °C for 6 - 10 h. After the reaction is completed, wash with deionized water, perform extraction and liquid separation, rotary evaporation, and drying to obtain nano - titanium dioxide - modified tea polyphenols; the dosage ratio of tea polyphenols, pyridine, and intermediate 3 is 1 g : (0.1 - 0.2) mL : (2.5 - 5) g;

[0019] Under the action of pyridine, the -COCl2 on the intermediate 3 molecule undergoes an esterification reaction with the hydroxyl group on the tea polyphenol molecule to obtain nano-titanium dioxide modified tea polyphenols. The reaction process is as follows:

[0020]

[0021] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0022] 1. The bio-based composite film prepared by the present invention contains inorganic nanoparticles such as titanium dioxide, which has good photocatalytic antibacterial effects. However, it is prone to agglomeration. In the present invention, it reacts with intermediate 2 to reduce the degree of agglomeration, increase its compatibility with organic substances, and can be uniformly dispersed in the matrix. When subjected to external forces, it can cause cracks in the matrix, while hindering and passivating the expansion of matrix cracks, ultimately preventing the cracks from continuing to develop, thereby improving the mechanical properties of the film.

[0023] 2. The tea polyphenols used in the present invention are natural antibacterial substances. However, tea polyphenols are prone to volatilization during application, resulting in low utilization rates. In the present invention, it reacts with intermediate 3 to reduce the volatility and improve the utilization rate of tea polyphenols. It interacts with nano-titanium dioxide to jointly improve the antibacterial performance and mechanical properties of the bio-based composite film. The composite film prepared by the present invention has excellent antibacterial performance, mechanical properties, and the advantages of being green and environmentally friendly. Detailed implementation manners

[0024] To better illustrate the purpose, technical solutions, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0025] Example 1

[0026] (1) Add 3 g of formaldehyde and 100 mL of chloroform to a flask, stir and disperse, heat to 60 °C, add 14 g of 3-aminopropyltriethoxysilane to it, then raise the temperature to 80 °C, add 7.6 g of p-hydroxyphenylacetic acid to it, stir and react for 2 h. After the reaction is completed, cool to room temperature and evaporate the solvent to obtain intermediate 1.

[0027] (2) Add 20 g of intermediate 1 and 100 mL of chloroform to a flask, stir and disperse, then add 6 g of thionyl chloride to it, heat to 60 °C, and react for 4 h. After the reaction is completed, perform atmospheric distillation and drying to obtain intermediate 2.

[0028] (3) Add 2 g of dry nano-titanium dioxide and 200 mL of ethanol to a flask, ultrasonically disperse, add 8 g of intermediate 2 to it, react ultrasonically at 40 °C for 4 h. After the reaction is completed, centrifuge, wash with ethanol, centrifuge again, repeat 2 times, and dry to obtain intermediate 3.

[0029] (4) Add 2 g of tea polyphenols and 100 mL of ethyl acetate to a flask, stir to dissolve, then add 0.2 mL of pyridine and 10 g of intermediate 3 thereto, and react at 75 °C for 8 h. After the reaction is completed, wash with deionized water, extract and separate the liquid, rotary evaporate, and dry to obtain nano-titanium dioxide modified tea polyphenols.

[0030] (5) Add 20 g of polylactic acid and 0.2 g of nano-titanium dioxide modified tea polyphenols to 100 mL of chloroform, stir well to disperse, pour it on a smooth glass plate, use a film casting machine to cast and film, and dry to obtain an antibacterial bio-based composite film.

[0031] Example 2

[0032] (1) Add 3.8 g of formaldehyde and 100 mL of chloroform to a flask, stir to disperse, heat to 65 °C, add 11.4 g of 3-aminopropyltriethoxysilane thereto, then raise the temperature to 85 °C, add 7.6 g of p-hydroxyphenylacetic acid thereto, stir and react for 1 h. After the reaction is completed, cool to room temperature, evaporate the solvent to obtain intermediate 1.

[0033] (2) Add 20 g of intermediate 1 and 100 mL of chloroform to a flask, stir to disperse, then add 7 g of thionyl chloride thereto, heat to 65 °C, and react for 2 h. After the reaction is completed, distill at atmospheric pressure and dry to obtain intermediate 2.

[0034] (3) Add 2 g of dry nano-titanium dioxide and 200 mL of ethanol to a flask, ultrasonically disperse, add 4 g of intermediate 2 thereto, react ultrasonically at 45 °C for 2 h. After the reaction is completed, centrifuge, wash with ethanol, centrifuge again, repeat 3 times, and dry to obtain intermediate 3.

[0035] (4) Add 2 g of tea polyphenols and 100 mL of ethyl acetate to a flask, stir to dissolve, then add 0.3 mL of pyridine and 6 g of intermediate 3 thereto, and react at 65 °C for 10 h. After the reaction is completed, wash with deionized water, extract and separate the liquid, rotary evaporate, and dry to obtain nano-titanium dioxide modified tea polyphenols.

[0036] (5) Add 20 g of polylactic acid and 0.4 g of nano-titanium dioxide modified tea polyphenols to 100 mL of chloroform, stir well to disperse, pour it on a smooth glass plate, use a film casting machine to cast and film, and dry to obtain an antibacterial bio-based composite film.

[0037] Example 3

[0038] (1) Add 3.5 formaldehyde and 100 mL of chloroform to a flask, stir to disperse, heat to 55 °C, add 15.2 g of 3-aminopropyltriethoxysilane to it, then raise the temperature to 75 °C, add 7.6 g of p-hydroxyphenylacetic acid to it, stir and react for 3 h. After the reaction is completed, cool to room temperature and evaporate the solvent to obtain Intermediate 1.

[0039] (2) Add 20 g of Intermediate 1 and 100 mL of chloroform to a flask, stir to disperse, then add 5 g of thionyl chloride to it, heat to 65 °C, react for 5 h. After the reaction is completed, perform atmospheric distillation and drying to obtain Intermediate 2.

[0040] (3) Add 2 g of dry nano-titanium dioxide and 200 mL of ethanol to a flask, ultrasonically disperse, add 7 g of Intermediate 2 to it, react ultrasonically at 40 °C for 3 h. After the reaction is completed, centrifuge, wash with ethanol, centrifuge again, repeat 3 times, and dry to obtain Intermediate 3.

[0041] (4) Add 2 g of tea polyphenols and 100 mL of ethyl acetate to a flask, stir to dissolve, then add 0.4 mL of pyridine and 5 g of Intermediate 3 to it, react at 70 °C for 6 h. After the reaction is completed, wash with deionized water, extract and separate, rotary evaporate, and dry to obtain nano-titanium dioxide modified tea polyphenols.

[0042] (5) Add 20 g of polylactic acid and 0.6 g of nano-titanium dioxide modified tea polyphenols to 100 mL of chloroform, stir well to disperse, pour it on a smooth glass plate, use a film casting machine to cast and film, and dry to obtain an antibacterial bio-based composite film.

[0043] Example 4

[0044] (1) Add 3.8 g of formaldehyde and 100 mL of chloroform to a flask, stir to disperse, heat to 65 °C, add 12 g of 3-aminopropyltriethoxysilane to it, then raise the temperature to 85 °C, add 7.6 g of p-hydroxyphenylacetic acid to it, stir and react for 3 h. After the reaction is completed, cool to room temperature and evaporate the solvent to obtain Intermediate 1.

[0045] (2) Add 20 g of Intermediate 1 and 100 mL of chloroform to a flask, stir to disperse, then add 5 g of thionyl chloride to it, heat to 65 °C, react for 4 h. After the reaction is completed, perform atmospheric distillation and drying to obtain Intermediate 2.

[0046] (3) Add 2 g of dry nano-titanium dioxide and 200 mL of ethanol to a flask, ultrasonically disperse, add 3 g of Intermediate 2 to it, react ultrasonically at 35 °C for 3 h. After the reaction is completed, centrifuge, wash with ethanol, centrifuge again, repeat 3 times, and dry to obtain Intermediate 3.

[0047] (4) Add 2 g of tea polyphenols and 100 mL of ethyl acetate to a flask, stir to dissolve, then add 0.3 mL of pyridine and 8 g of intermediate product 3 thereto, and react at 75 °C for 8 h. After the reaction is completed, wash with deionized water, extract and separate the liquid, rotary evaporate, and dry to obtain nano-titanium dioxide modified tea polyphenols.

[0048] (5) Add 20 g of polylactic acid and 0.8 g of nano-titanium dioxide modified tea polyphenols to 100 mL of chloroform, stir well to disperse, pour it on a smooth glass plate, use a film casting machine to cast and film, and dry to obtain an antibacterial bio-based composite film.

[0049] Example 5

[0050] (1) Add 3.6 g of formaldehyde and 100 mL of chloroform to a flask, stir to disperse, heat to 60 °C, add 14 g of 3-aminopropyltriethoxysilane thereto, then raise the temperature to 80 °C, add 7.6 g of p-hydroxyphenylacetic acid thereto, stir and react for 2 h. After the reaction is completed, cool to room temperature and evaporate the solvent to obtain intermediate product 1.

[0051] (2) Add 20 g of intermediate product 1 and 100 mL of chloroform to a flask, stir to disperse, then add 6 g of thionyl chloride thereto, heat to 65 °C, and react for 4 h. After the reaction is completed, distill at atmospheric pressure and dry to obtain intermediate product 2.

[0052] (3) Add 2 g of dry nano-titanium dioxide and 200 mL of ethanol to a flask, ultrasonically disperse, add 6 g of intermediate product 2 thereto, react ultrasonically at 45 °C for 2 h. After the reaction is completed, centrifuge, wash with ethanol, centrifuge again, repeat 2 times, and dry to obtain intermediate product 3.

[0053] (4) Add 2 g of tea polyphenols and 100 mL of ethyl acetate to a flask, stir to dissolve, then add 0.3 mL of pyridine and 7 g of intermediate product 3 thereto, and react at 75 °C for 10 h. After the reaction is completed, wash with deionized water, extract and separate the liquid, rotary evaporate, and dry to obtain nano-titanium dioxide modified tea polyphenols.

[0054] (5) Add 20 g of polylactic acid and 1 g of nano-titanium dioxide modified tea polyphenols to 100 mL of chloroform, stir well to disperse, pour it on a smooth glass plate, use a film casting machine to cast and film, and dry to obtain an antibacterial bio-based composite film.

[0055] Comparative Example 1

[0056] Add 20 g of polylactic acid and 0.2 g of nano-titanium dioxide to 100 mL of chloroform, stir well to disperse, pour it on a smooth glass plate, use a film casting machine to cast and film, and dry to obtain an antibacterial bio-based composite film.

[0057] Comparative Example 2

[0058] 20 g of polylactic acid and 0.2 g of tea polyphenols were added to 100 mL of chloroform, fully stirred and dispersed, poured onto a smooth glass plate, and cast and scraped using a scraper, and dried to obtain an antibacterial bio-based composite film.

[0059] Determination of antibacterial rate: According to QB / T2591-2003, the bio-based composite film was cut into a standard size of 50mm×50mm, and a 40mm×40mm polyethylene film was used as a covering film. A pipette was used to take 200μL of bacterial solution on the antibacterial film, and the sterilized polyethylene film was covered on it. The film was cultured at 37°C for 24h, and then the film was taken out and the bio-based composite film and polyethylene film were washed with eluent. After the mixture was shaken thoroughly, 100μL was inoculated in nutrient agar medium and cultured at 37°C for 24h. According to GB / T4789.2, the number of viable bacteria was tested and the antibacterial rate was calculated. The test bacteria were Escherichia coli and Staphylococcus aureus.

[0060] Table 1:

[0061]

[0062] It can be seen from the table that the bio-based composite film prepared by the present invention has excellent antibacterial effect, and the highest antibacterial rate against Escherichia coli and Staphylococcus aureus can reach 99.9%.

[0063] The tensile properties of the bio-based composite film were tested according to GB / T1040-2006. The film size was 15 mm × 15 mm and the tensile rate was 50 mm / min.

[0064]

[0065]

[0066] It can be seen from the table that the bio-based composite film prepared by the present invention has good mechanical properties, and the maximum tensile strength can reach 40.3 MPa.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. An antibacterial bio-based composite film, characterized in that, The composite film comprises the following components in parts by weight: 100 parts of polylactic acid and 1-5 parts of nano-titanium dioxide modified tea polyphenols; The preparation method of the antibacterial bio-based composite film is as follows: Add polylactic acid and nano-titanium dioxide modified tea polyphenols into chloroform, fully stir and disperse, pour onto a smooth glass plate, use a film scraping machine to cast the film, and dry to obtain an antibacterial bio-based composite film; The preparation method of the nano-titanium dioxide modified tea polyphenols is: (1) Add formaldehyde and chloroform into a flask, stir and disperse, heat to 55-65°C, add 3-aminopropyltriethoxysilane, then heat to 75-85°C, add p-hydroxyphenylacetic acid, stir and react for 1-3 hours. After the reaction is completed, cool to room temperature, evaporate the solvent, and obtain intermediate 1. The reaction process is as follows: ； (2) Add the intermediate product 1 and chloroform into a flask, stir and disperse, then add dichlorothionyl, heat to 60-65°C, react for 2-5 hours, and after the reaction is completed, distill under normal pressure and dry to obtain the intermediate product 2. The reaction process is as follows: ； (3) Add dried nano-titanium dioxide and ethanol to a flask, disperse by ultrasonication, add intermediate product 2, and react by ultrasonication at 35-45°C for 2-4 hours. After the reaction is completed, centrifuge, wash with ethanol, centrifuge again, repeat 2-3 times, and dry to obtain intermediate product 3. The reaction process is as follows: , where is nano-titanium dioxide; (4) Tea polyphenols and ethyl acetate are added to a flask, stirred to dissolve, and then pyridine and intermediate product 3 are added thereto. Under the action of pyridine, -COCl2 on the intermediate product 3 molecule reacts with the hydroxyl group on the tea polyphenol molecule through esterification reaction at 65-75°C for 6-10 hours. After the reaction is completed, the mixture is washed with deionized water, extracted, separated, rotary evaporated, and dried to obtain nano-titanium dioxide modified tea polyphenols.

2. The antibacterial bio-based composite film according to claim 1, characterized in that, In the above (1), the usage ratio of formaldehyde, 3-aminopropyltriethoxysilane and p-hydroxyphenylacetic acid is (0.4-0.5) g: (1.5-2) g: 1 g.

3. The antibacterial bio-based composite film according to claim 1, characterized in that, In the above (2), the usage ratio of the intermediate product 1 and dichlorothionyl is 1g:(0.25-0.35)g.

4. The antibacterial bio-based composite film according to claim 1, wherein In the above (3), the usage ratio of nano titanium dioxide and intermediate product 2 is 1g:(1.5-4)g.

5. The antibacterial bio-based composite film according to claim 1, characterized in that, In the above (4), the usage ratio of tea polyphenols, pyridine and intermediate product 3 is 1 g: (0.1-0.2) mL: (2.5-5) g.

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