A polylactic acid antibacterial film containing tangerine peel essential oil and a preparation method thereof

Abstract

The present invention relates to a polylactic acid antibacterial film containing tangerine peel essential oil, which comprises the following components: polylactic acid, a ternary polylactic acid copolymer, modified nano-silica, tangerine peel essential oil, and an additive; wherein, the ternary polylactic acid block copolymer is a product obtained by polymerizing lactide, glycolide, and RNS-E, and the modified nano-silica is a blend of hydroxylated nano-silica and ordinary nano-silica. For the polylactic acid antibacterial film containing tangerine peel essential oil of the present invention, with the increase of the content of the ternary polylactic acid copolymer, the thermal stability and tensile strength of the film gradually increase, and the added modified nano-silica further enhances the film stability and dispersibility, enabling the film to have good thermal stability, mechanical properties, and also good antibacterial properties.

Description

Technical Field

[0001] The present invention relates to the field of packaging material processing, and particularly to a polylactic acid antibacterial film containing tangerine peel essential oil and a preparation method thereof. Background Art

[0002] The polylactic acid (PLA) film is a new type of biodegradable material. In recent years, it has been widely used in the fields of packaging, agriculture, biomedicine, and textiles. With its unique biocompatibility and environmental safety, it has become an important force in promoting green development. Major scientific research institutions and companies around the world have increased their investment in the research and production of polylactic acid films.

[0003] Currently, adding antibacterial agents to polylactic acid films to endow the films with antibacterial properties is a new development direction. However, in the commonly used preparation methods for large-scale industrial production, during the preparation of polylactic acid films with antibacterial properties, inorganic particles and other fillers are usually added. However, the compatibility between inorganic particles and polylactic acid or other organic substances is poor, and the inorganic particles cannot be evenly dispersed in polylactic acid or other organic substances. This leads to a decrease in the mechanical properties of the polylactic acid film with antibacterial properties. For example, the tensile strength decreases, making the polylactic acid film with antibacterial properties prone to being torn under external force. If the polylactic acid film with antibacterial properties is used in an extremely high-temperature environment, its thermal stability will decrease, and it is more likely to decompose, ultimately resulting in the inability to continue using the polylactic acid film with antibacterial properties.

[0004] Therefore, it is urgent to develop a polylactic acid antibacterial film with better performance. Summary of the Invention

[0005] Based on this, the present invention provides a polylactic acid antibacterial film containing tangerine peel essential oil and a preparation method thereof to overcome the deficiencies of the prior art.

[0006] One object of the present invention is to provide a polylactic acid antibacterial film containing tangerine peel essential oil, and the polylactic acid antibacterial film containing tangerine peel essential oil comprises the following components in parts by mass:

[0007]

[0008] Among them, the triblock polylactic acid copolymer is a product polymerized from lactide, glycolide, and RNS-E, and the modified nano-silica is a blend of hydroxylated nano-silica and ordinary nano-silica.

[0009] Further, the particle size of the modified nano-silica is 15 - 25 nm.

[0010] Further, the auxiliary agent is selected from one or more of a dispersant, a plasticizer, an antioxidant, a lubricant, and a film-forming agent.

[0011] Further, the dispersant is selected from one or more of stearic acid, zinc stearate, and white oil.

[0012] Further, the plasticizer is selected from PEG200.

[0013] The present invention also provides a method for preparing the polylactic acid antibacterial film containing tangerine peel essential oil, comprising the following steps:

[0014] S1. Blend lactide, glycolide, and RNS-E, add a catalyst under an inert atmosphere protection, heat and react, and perform recrystallization to obtain a ternary polylactic acid copolymer;

[0015] S2. Hydroxylate nano-silica to obtain hydroxylated nano-silica, and add common nano-silica for blending to obtain modified nano-silica;

[0016] S3. Blend the ternary polylactic acid copolymer, modified nano-silica, polylactic acid, tangerine peel essential oil, and additives, put them into a screw extruder, heat and extrude into a film to obtain a polylactic acid antibacterial film containing tangerine peel essential oil.

[0017] Further, the mass ratio of lactide, glycolide, and RNS-E is 1:(1 - 10):(0.02 - 0.05).

[0018] Further, the mass ratio of hydroxylated nano-silica to common nano-silica is 1:(1 - 2).

[0019] Further, the RNS-E is nano-silica with epoxy groups, and the particle size is 15 - 25 nm.

[0020] Further, the catalyst is selected from stannous octoate.

[0021] Further, the addition amount of the catalyst is 0.5 - 2% of the total mass of lactide, glycolide, and RNS-E.

[0022] Further, the temperature of the heating reaction is 130 - 150 °C.

[0023] Further, the temperature of the heating extrusion is 145 - 175 °C.

[0024] The present invention has the following beneficial effects:

[0025] The polylactic acid antibacterial film containing dried orange peel essential oil of the present invention adopts ternary polylactic acid copolymer as component, and this component is reacted with the polymer of lactide and glycolide through RNS-E, so that RNS-E is grafted with polymer chain segment, thus the effect of compatibilizer is brought into play, and the affinity between silicon dioxide and polylactic acid resin can be improved, so as to improve the dispersion effect of inorganic filler, and silicon dioxide has more active groups after hydroxylation modification, and increases the crosslinking degree between components after compounding with ternary polylactic acid copolymer, so that molecules are closely combined, and stability is enhanced. In addition, the hydroxyl group in modified nano silicon dioxide can form hydrogen bonds with ternary polylactic acid copolymer and polylactic acid, so as to form a stable network, improve material strength, and can also form hydrogen bonds with groups such as amino, ester group, hydroxyl group in dried orange peel essential oil, further improve stability, and promote the improvement of multiple performances.

[0026] Therefore, in summary, the polylactic acid antibacterial film containing tangerine peel essential oil of the present invention has good thermal stability and mechanical properties, and also has good antibacterial properties. DETAILED DESCRIPTION

[0027] In order to more clearly illustrate the technical solution of the present invention, the following examples are listed. Unless otherwise stated, the raw materials, reactions and post-treatment methods shown in the examples are common raw materials on the market and technical methods well known to those skilled in the art.

[0028] It should be understood that, except in any operating examples, or where otherwise indicated, all numbers expressing, for example, the amounts of ingredients used in the specification and claims should be understood to be modified in all cases by the term "about". Therefore, unless indicated to the contrary, the numerical parameters set forth in the following specification and the appended claims are approximate values ​​that vary depending on the desired properties to be obtained by the present invention.

[0029] In the following examples, unless otherwise specified, all preparations and tests took place at 25°C.

[0030] Polylactic acid, brand 4032D, was purchased from Dongguan Yingde Plastic Raw Materials Co., Ltd.

[0031] Tangerine peel essential oil was purchased from Jiangxi Chuanhui Herbal Biotechnology Co., Ltd.

[0032] White oil, dispersant, was purchased from Maoming Petrochemical Shihua Co., Ltd.

[0033] RNS-E, nano-silica with epoxy groups, with a particle size of 15-25 nm, was purchased from Xi'an Qiyue Biotechnology Co., Ltd.

[0034] Example 1

[0035] A polylactic acid antibacterial film containing tangerine peel essential oil, comprising the following components in parts by mass:

[0036]

[0037] The preparation method of the polylactic acid antibacterial film containing tangerine peel essential oil comprises the following steps:

[0038] S1. Lactide, glycolide, and RNS-E are added to a container in a mass ratio of 1:10:0.04. After vacuum pumping and nitrogen purging, a toluene solution of stannous octoate (1.0 wt%, and the mass of stannous octoate is 2% of the total mass of the reaction system) is added. Then, vacuum pumping and nitrogen purging are repeated three times. The container is sealed and then placed in an oil bath heated to 135 °C for reaction for 24 h. The solid product is dissolved in dichloromethane, and then an excessive amount of methanol is added for precipitation. Then, suction filtration is carried out, and drying is performed for 24 h to obtain a ternary polylactic acid copolymer;

[0039] S2. Nano-silica is added to a mixed solution of concentrated sulfuric acid and hydrogen peroxide (the concentration of hydrogen peroxide is 30 wt%, and the mass ratio of concentrated sulfuric acid to hydrogen peroxide is 7:3). The mixture is heated to 70 °C and reacted for 1 h to obtain hydroxylated nano-silica. Modified nano-silica is obtained by blending with ordinary nano-silica (the mass ratio of hydroxylated nano-silica to ordinary nano-silica is 1:1);

[0040] S3. According to the above parts by mass, the ternary polylactic acid copolymer, modified nano-silica, polylactic acid, tangerine peel essential oil, and white oil are blended and put into a twin-screw extruder (the temperatures of the 1st - 7th zones of the twin-screw extruder are 145, 155, 160, 165, 175, 175, 175 °C respectively, and the rotation speed is 45 r / min) for heating and extrusion. After extrusion, a film bubble is blown by a blower. After the size of the film bubble is stable, the blow-up ratio is adjusted to 3.0 to make the width of the film reach 1 m. By adjusting the main machine rotation speed and the traction rate, the film thickness is adjusted to 15 μm to obtain a polylactic acid antibacterial film containing tangerine peel essential oil.

[0041] Example 2

[0042] A polylactic acid antibacterial film containing tangerine peel essential oil, comprising the following components in parts by mass:

[0043]

[0044] The preparation method of the polylactic acid antibacterial film containing tangerine peel essential oil comprises the following steps:

[0045] S1. Add lactide, glycolide, and RNS-E into a container at a mass ratio of 1:10:0.04. After evacuating and purging with nitrogen, add a toluene solution of stannous octoate (1.0 wt%, and the mass of stannous octoate is 2% of the total mass of the reaction system). Then evacuate and purge with nitrogen again, repeating three times. Seal the container and then place it in an oil bath heated to 135 °C for reaction for 24 h. Dissolve the solid product with dichloromethane, add excessive methanol for sedimentation, then filter by suction, and dry for 24 h to obtain a ternary polylactic acid copolymer;

[0046] S2. Add nano-silica into a mixed solution of concentrated sulfuric acid and hydrogen peroxide (the concentration of hydrogen peroxide is 30 wt%, and the mass ratio of concentrated sulfuric acid to hydrogen peroxide is 7:3). Heat to 70 °C and react for 1 h to obtain hydroxylated nano-silica. Add common nano-silica (the mass ratio of hydroxylated nano-silica to common nano-silica is 1:1) for blending to obtain modified nano-silica;

[0047] S3. According to the above mass parts, blend the ternary polylactic acid copolymer, modified nano-silica, polylactic acid, tangerine peel essential oil, and white oil, and put them into a twin-screw extruder (the temperatures of the 1st - 7th zones of the twin-screw extruder are 145, 155, 160, 165, 175, 175, 175 °C respectively, and the rotation speed is 45 r / min) for heating and extrusion. After extrusion, blow a film bubble through a blower. After the size of the film bubble is stable, adjust the blow-up ratio to 3.0 to make the width of the film reach 1 m. Adjust the thickness of the film to 15 μm by adjusting the main machine rotation speed and the traction rate to obtain a polylactic acid antibacterial film containing tangerine peel essential oil.

[0048] Example 3

[0049] A polylactic acid antibacterial film containing tangerine peel essential oil, comprising the following components in mass parts:

[0050]

[0051] The preparation method of the polylactic acid antibacterial film containing tangerine peel essential oil comprises the following steps:

[0052] S1. Add lactide, glycolide, and RNS-E into a container at a mass ratio of 1:10:0.04. After evacuating and purging with nitrogen, add a toluene solution of stannous octoate (1.0 wt%, and the mass of stannous octoate is 2% of the total mass of the reaction system). Then evacuate and purge with nitrogen again, repeating three times. Seal the container and then place it in an oil bath heated to 135 °C for reaction for 24 h. Dissolve the solid product with dichloromethane, add excessive methanol for sedimentation, then filter by suction, and dry for 24 h to obtain a ternary polylactic acid copolymer;

[0053] S2. Add nano-silica into the mixed solution of concentrated sulfuric acid and hydrogen peroxide (the concentration of hydrogen peroxide is 30 wt%, and the mass ratio of concentrated sulfuric acid to hydrogen peroxide is 7:3), heat to 70 °C, react for 1 h to obtain hydroxylated nano-silica, and add common nano-silica (the mass ratio of hydroxylated nano-silica to common nano-silica is 1:1) for blending to obtain modified nano-silica;

[0054] S3. According to the above mass parts, blend the ternary polylactic acid copolymer, modified nano-silica, polylactic acid, tangerine peel essential oil, and white oil, and put them into a twin-screw extruder (the temperatures of the 1st - 7th zones of the twin-screw extruder are 145, 155, 160, 165, 175, 175, 175 °C respectively, and the rotation speed is 45 r / min) for heating and extrusion. After extrusion, blow a film bubble through a blower. After the size of the film bubble is stable, adjust the blow-up ratio to 3.0 to make the width of the film reach 1 m. Adjust the thickness of the film to 15 μm by adjusting the main machine rotation speed and the traction rate to obtain a polylactic acid antibacterial film containing tangerine peel essential oil.

[0055] Comparative Example 1

[0056] The difference between this comparative example and Example 1 is that: Step S1 is deleted, and the ternary polylactic acid copolymer is replaced with an equal mass of: adding lactide, glycolide, and RNS-E into a container in a mass ratio of 1:10:0.02 and stirring the obtained mixture evenly.

[0057] Comparative Example 2

[0058] The difference between this comparative example and Example 1 is that: Step S2 is deleted, and the modified nano-silica is replaced with unmodified nano-silica in an equal mass.

[0059] Test Example 1

[0060] Conduct mechanical property tests on the film samples of Examples 1 - 3 and Comparative Examples 1 - 2.

[0061] Test method:

[0062] Conduct tensile strength and elongation at break property tests on the film samples of Examples 1 - 3 and Comparative Examples 1 - 2 according to the ASTM D638 plastic tensile property test standard.

[0063] The test results are shown in Table 1.

[0064] Table 1 Mechanical property test results of the film samples of Examples 1 - 3 and Comparative Examples 1 - 2

[0065]

[0066]

[0067] As can be seen from Table 1, the polylactic acid antibacterial films containing tangerine peel essential oil in Examples 1-3 have good mechanical properties, and the tensile strength and elongation at break are significantly better than those in Comparative Examples 1-2. In Comparative Example 1, due to the replacement of the ternary polylactic acid copolymer, the compatibility and stability between components are significantly reduced, and the ideal synergistic effect cannot be achieved, resulting in a significant reduction in strength; in Comparative Example 2, the modified nano-silica is replaced, and the synergistic effect between components also decreases, and the strength weakens.

[0068] Test Example 2

[0069] The antibacterial properties of the film samples of Examples 1-3 and Comparative Examples 1-2 were tested.

[0070] Test method:

[0071] The antibacterial properties of the film samples of Examples 1-3 and Comparative Examples 1-2 were tested according to the ASTM E2180-07 standard.

[0072] The test results are shown in Table 2.

[0073] Table 2 Antibacterial property test results of the film samples of Examples 1-3 and Comparative Examples 1-2

[0074]

[0075] As can be seen from Table 2, Examples 1-3 have excellent antibacterial properties, and the antibacterial rates against Escherichia coli and Staphylococcus aureus both reach over 99%. However, the stability of Comparative Examples 1-2 with replaced components decreases, and the antibacterial properties also decline, and the ideal performance improvement cannot be obtained.

[0076] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention.

[0077] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A polylactic acid antibacterial film containing tangerine peel essential oil, characterized in that: The polylactic acid antibacterial film containing tangerine peel essential oil comprises the following components in parts by weight: Wherein, the ternary polylactic acid block copolymer is a product of polymerization of lactide, glycolide and RNS-E; The modified nano-silicon dioxide is a blend of hydroxylated nano-silicon dioxide and common nano-silicon dioxide; The RNS-E is nano-silicon dioxide with epoxy groups; The particle size of the modified nano-silicon dioxide is 15-25 nm; The auxiliary agent is selected from one or more of a dispersant, a plasticizer, an antioxidant, a lubricant, and a film-forming agent.

2. The method for preparing the polylactic acid antibacterial film containing tangerine peel essential oil according to claim 1, characterized in that: The preparation method of the polylactic acid antibacterial film containing tangerine peel essential oil is: S1, blending lactide, glycolide and RNS-E, adding a catalyst under inert atmosphere protection, heating for reaction, and recrystallization to obtain a ternary polylactic acid copolymer; S2, hydroxylating the nano-silicon dioxide to obtain hydroxylated nano-silicon dioxide, and adding ordinary nano-silicon dioxide to blend to obtain modified nano-silicon dioxide; S3, blending the ternary polylactic acid copolymer, modified nano-silica, polylactic acid, tangerine peel essential oil, and additives, putting them into a screw extruder, heating and extruding them into a film, and obtaining a polylactic acid antibacterial film containing tangerine peel essential oil.

3. The method for preparing the polylactic acid antibacterial film containing tangerine peel essential oil according to claim 2, characterized in that: The mass ratio of lactide, glycolide and RNS-E is 1:(1-10):(0.02-0.05).

4. The method for preparing the polylactic acid antibacterial film containing tangerine peel essential oil according to claim 2, characterized in that: The mass ratio of the hydroxylated nano-silicon dioxide to the common nano-silicon dioxide is 1:(1-2).

5. The method for preparing the polylactic acid antibacterial film containing tangerine peel essential oil according to claim 2, characterized in that: The RNS-E particle size is 15-25 nm.

6. The method for preparing the polylactic acid antibacterial film containing tangerine peel essential oil according to claim 2, characterized in that: The catalyst is selected from organotin catalysts.

7. The method for preparing the polylactic acid antibacterial film containing tangerine peel essential oil according to claim 2, characterized in that: The temperature of the heating reaction is 130-150°C.

8. The method for preparing the polylactic acid antibacterial film containing tangerine peel essential oil according to claim 2, characterized in that: The temperature of the heated extrusion is 145-175°C.

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