Antibacterial high-barrier starch-based plastic bottle and preparation method thereof

Abstract

The invention provides an antibacterial high-barrier starch-based plastic bottle and a preparation method thereof.The preparation method comprises the steps that firstly, titanate generates nano titanium dioxide in situ in starch through acid catalysis, starch is subjected to in-situ hybridization modification, and nano titanium dioxide in-situ hybridization starch is prepared; then adding nano inorganic barrier powder, and then adding a long-chain silane coupling agent to modify the nano titanium dioxide in-situ hybridized starch and the nano inorganic barrier powder to obtain a modified starch compound; performing vacuum kneading and drying until the water content is lower than 0.5%, and adding an antibacterial lubricant for plasticizing to obtain a plasticized material; and finally, carrying out melt blending and granulation with polyolefin resin, and carrying out extrusion blow molding. The environment-friendly and low-cost starch-based material is kept, meanwhile, the comprehensive performance of the product is remarkably improved, the surface contact angle of the product is 110 degrees or above, the antibacterial rate is 97% or above, and the oxygen permeation amount and the water vapor permeation amount are 100 cm / (m.24h. Atm) and 4 g / (m.24h) or below respectively.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of bio-based composite materials, in particular to an antibacterial high-barrier starch-based plastic bottle and a preparation method thereof. BACKGROUND

[0002] Polypropylene (PP) and polyethylene (PE) have become the most widely used plastic bottle manufacturing materials in daily life due to their excellent mechanical properties, processing adaptability and cost advantages. In response to the problems of tight oil resources and environmental pollution such as white pollution, it has become an important development direction to replace traditional petrochemical plastics with renewable biomass resources. Among them, starch-based polypropylene bottles or starch-based polyethylene bottles are prepared by melt blending modification of natural starch and polypropylene (PP) or polyethylene (PE), and then blow molding process. To some extent, this kind of bio-based plastic bottle inherits the strength and toughness of traditional plastic. At the same time, because renewable starch components are used, it not only helps to reduce the cost of raw materials, but also meets the current safety requirements of food contact materials, and is beneficial to reducing carbon emissions and saving oil resources in the whole life cycle, which has significant environmental benefits and sustainable development prospects.

[0003] However, starch, as a natural polysaccharide, has a large number of hydrophilic hydroxyl groups (-OH) on its molecular chain, which brings a severe challenge to the practical application of starch-based plastic bottles: First, poor mildew resistance and antibacterial property. Due to the strong hygroscopicity of starch, starch-based plastic bottles are prone to absorb moisture from the environment when stored or used in humid environments. This not only may cause the size of the bottle to be unstable and the mechanical properties to decrease, but more importantly, it provides a breeding ground for mold, bacteria and other microorganisms, leading to problems such as mildew, discoloration, odor generation and the like of the packaging bottle, which seriously damages the appearance and hygiene safety of the product.

[0004] Second, poor barrier performance. Starch has hydrophilic properties and poor compatibility with hydrophobic polyolefin matrix, which allows small molecules such as oxygen and water vapor to pass through the bottle wall more quickly. Poor oxygen barrier property will accelerate the oxidation and rancidity of the contents (especially oil-based foods), and poor water vapor barrier property cannot effectively maintain the moisture of the contents or prevent external water vapor from entering, leading to drying or dampening of the food, which easily causes the packaged food to spoil and deteriorate in advance, greatly shortening the shelf life.

[0005] To address these issues, existing technologies typically employ physical blending to add antibacterial agents or nanofillers (such as montmorillonite). However, simple blending of antibacterial agents results in poor compatibility with the matrix, posing a risk of migration and precipitation, impacting food safety, and lacking sufficient antibacterial durability. Nanofillers, due to their high surface energy, tend to aggregate within the polymer matrix, making uniform dispersion difficult and thus failing to fully realize their potential to enhance barrier effects. Furthermore, existing technologies lack a solution for synergistically improving the hydrophobicity, antibacterial properties, and barrier properties against oxygen and water vapor in starch-based plastic bottles.

[0006] Therefore, developing a method for preparing starch-based plastic bottles that can improve the hydrophilicity of starch and integrate antibacterial and high barrier functions has become a key technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] To address the aforementioned technical problems, this application provides an antibacterial high-barrier starch-based plastic bottle and its preparation method.

[0008] In a first aspect, this application provides a method for preparing an antibacterial, high-barrier starch-based plastic bottle, comprising the following steps: S1: Under the catalysis of an acid catalyst, titanate esters are used to generate nano-titanium dioxide in situ in starch, and the starch is then modified in situ by hybridization to obtain nano-titanium dioxide in situ hybridized starch. Then, nano-inorganic barrier powder is added, mixed evenly, and then long-chain silane coupling agent is added to modify the in-situ hybridized starch of nano-titanium dioxide and nano-inorganic barrier powder to obtain modified starch complex. S2: Place the modified starch compound in a kneader and knead it to ensure that the moisture content of the modified starch compound is less than 0.5%; add antibacterial lubricant and knead again to obtain plasticized material; S3: The plasticizer is blended with polyolefin resin, melt-extruded and granulated through a twin-screw extruder to obtain antibacterial high-barrier starch-based injection molding compound; S4: The antibacterial high-barrier starch-based injection molding compound is extruded and blow-molded to obtain the antibacterial high-barrier starch-based plastic bottle.

[0009] Furthermore, step S1 is carried out under an inert atmosphere in an anhydrous alcohol solvent; the acid catalyst is a 5% aqueous solution of glacial acetic acid; the reaction temperature is 25-45℃, and the reaction time is 1-2 hours.

[0010] Furthermore, the reaction temperature for modifying nano-titanium dioxide in-situ hybrid starch and nano-inorganic barrier powder with long-chain silane coupling agent in step S1 is 60-80℃.

[0011] Further, in step S2, the modified starch complex is placed in a kneader and kneaded at a speed of 30-50 rpm and a temperature of 80-100℃.

[0012] Furthermore, in step S2, the modified starch complex is placed in a kneader and kneaded while simultaneously undergoing dehydration to ensure that the moisture content of the modified starch complex is below 0.5%; preferably, the dehydration process is performed using vacuum, with the vacuum degree controlled at -0.09 to 0.098 MPa.

[0013] Furthermore, in step S2, an antibacterial lubricant is added, and the mixture is kneaded for 15-30 minutes.

[0014] Furthermore, in step S3, the temperature of the twin-screw extruder from the feed inlet to the die head is set at 165-195℃, the screw speed is 120-300 r / min, and the pelletizer speed is 250-350 r / min.

[0015] Furthermore, in step S4, extrusion blow molding is performed using extrusion blow molding equipment, with the temperature from the feed inlet to the die set at 160-175℃ and the screw speed at 80-150 r / min.

[0016] Furthermore, based on 100 parts by weight of starch, the amounts of each component in steps S1 and S2 are as follows: 5-15 parts of titanate; 10-30 parts of acid catalyst; 3-10 parts of nano-inorganic barrier powder; 3-8 parts of long-chain silane coupling agent; and 0.5-2 parts of antibacterial lubricant.

[0017] Furthermore, the anhydrous alcohol solvent is anhydrous ethanol; based on 100 parts by weight of starch, the amount of anhydrous alcohol solvent used is 200-300 parts.

[0018] Furthermore, in step S3, the mass ratio of plasticizer to polyolefin resin is (15-40):(60-85).

[0019] Furthermore, the starch is at least one of corn starch, tapioca starch, or potato starch.

[0020] Furthermore, the titanate is at least one of tetraethyl titanate, tetrabutyl titanate, tetra-n-propyl titanate, or tetraisopropyl titanate.

[0021] Furthermore, the nano-inorganic barrier powder is a nano-inorganic material with a layered structure, including at least one of nano-montmorillonite, graphene nanosheets, graphene oxide nanosheets, or layered double hydroxides.

[0022] Furthermore, the long-chain silane coupling agent is an alkyltrialkoxysilane with a carbon chain length of C8-C18; preferably, the long-chain silane coupling agent is at least one of isooctyltriethoxysilane, dodecyltrimethoxysilane, hexadecyltrimethoxysilane, octadecyltrimethoxysilane or octadecyltriethoxysilane.

[0023] Furthermore, the antibacterial lubricant is glyceryl monolaurate.

[0024] Furthermore, the polyolefin resin is polypropylene or polyethylene, and the melt flow index of the polyolefin resin is 0.5-4 g / 10 min.

[0025] The melt flow index of the polyolefin resin is the melt flow index under the conditions of 230℃ and 2.16Kg load, in accordance with standard GB / T 3682.1-2018.

[0026] Secondly, this application provides an antibacterial high-barrier starch-based plastic bottle, which is prepared by the method for preparing the antibacterial high-barrier starch-based plastic bottle described in the first aspect.

[0027] Furthermore, the surface contact angle of the antibacterial high-barrier starch-based plastic bottle is above 110°, the antibacterial rate is above 97%, the oxygen permeability is below 100 cm³ / (m²·24h·atm), and the water vapor permeability is below 4 g / (m²·24h).

[0028] 100 cm³ / (m²·24h·atm) means 100 cubic centimeters per square meter per 24 hours per standard atmosphere.

[0029] 4 g / (m²·24h) means 4 grams per square meter per 24 hours.

[0030] Thirdly, this application provides an antibacterial high-barrier starch-based injection molding compound, which is prepared according to steps S1-S3 of the first aspect.

[0031] Compared with existing technologies, this application includes the following beneficial technical effects: This application constructs a material system with a clearly defined function and synergistic efficiency by carefully selecting raw materials. Starch, as a biomass matrix, is a carrier for achieving environmental friendliness and cost advantages. Titanate undergoes a sol-gel reaction under acid catalysis, and its core role is to generate highly active, high specific surface area nano-titanium dioxide (TiO2) particles in situ within the starch, achieving high antibacterial properties. Nano-inorganic barrier powders (such as montmorillonite, layered double hydroxides, etc.) possess unique layered nanostructures. Oxygen or water vapor molecules cannot pass through the material in a straight line, but are forced to bypass these layered barriers and travel along highly tortuous paths. This greatly extends the effective diffusion path length of penetrating molecules, thereby significantly reducing the permeation rate and significantly improving the barrier performance against oxygen and water vapor. Long-chain alkylsilane coupling agents (C8-C18) are simultaneously grafted onto nano-titanium dioxide and nano-inorganic barrier powders through chemical bonding. On the one hand, the introduction of strongly hydrophobic long-chain alkyl groups greatly enhances the surface hydrophobicity of the materials. On the other hand, the molecular structure of long-chain alkylsilane coupling agents possesses amphiphilic chemical groups. The siloxane groups (-Si(OR)3) of the long-chain alkylsilane coupling agents, after hydrolysis, react with the hydroxyl groups (-OH) on the surface of titanium dioxide to form Si-O-Ti covalent bonds. Simultaneously, they react with the hydroxyl groups (-OH) or other active groups on the surface of the barrier powder to form Si-O-Si (for montmorillonite) or Si-OM (where M is a metal ion in LDH, such as Mg, Al), etc., covalent bonds, which firmly bind to the surface of inorganic nanoparticles. Furthermore, the long-chain alkylsilane coupling agents, through their long-chain alkyl groups (C8-C18),... The long-chain alkylsilane coupling agent exhibits strong hydrophobic interactions and segmental compatibility with the polyolefin (PP / PE) molecular chains. Its amphiphilic structure perfectly resolves the inherent interfacial incompatibility between the hydrophilic inorganic nanophase and the hydrophobic organic polymer matrix, establishing a stable, primarily chemically bonded connection between the inorganic nanophase (nano-titanium dioxide and nano-inorganic barrier powder) and the organic polymer phase (polyolefin matrix). As a food-grade additive, glyceryl laurate possesses both antibacterial and lubricating functions. It not only synergistically works with titanium dioxide to provide a second layer of antibacterial protection, consolidating the antibacterial effect, but also effectively improves the melt flowability of the composite system during processing. Finally, the polyolefin resin (PP / PE) provides the necessary mechanical strength, toughness, and a mature blow molding process foundation for the entire composite material.

[0032] The core of the preparation process in this application is the simultaneous modification of the in-situ hybrid starch with titanium dioxide and the nano-inorganic barrier powder by the long-chain silane coupling agent. First, under acid catalysis, titanium ester is reacted in-situ in starch to generate nano-titanium dioxide, achieving a strong and uniform combination of antibacterial components and starch. Then, without separating the intermediate products, the nano-barrier powder and the long-chain silane coupling agent are directly added for simultaneous modification, ensuring that the newly generated nano-titanium dioxide and the added barrier powder are uniformly and hydrophobically modified in the same reaction environment, laying the interfacial foundation for their subsequent dispersion in the polyolefin matrix. The second step involves deep drying of the modified composite during kneading under vacuum conditions. Controlling moisture content helps maintain the stability of the in-situ hybrid starch structure composed of nano-titanium dioxide. The bond between the in-situ hybridized titanium dioxide and starch is formed through hydrogen bonds and coordination bonds, and the interface region is hydrophilic. Excessive moisture will invade this interface, weakening the connection between titanium dioxide and starch. Under the shear force of subsequent kneading, plasticizing, and melt blending processes, titanium dioxide particles are more likely to peel off, detach, and agglomerate from the starch surface, resulting in poor dispersibility and a significant decrease in the effective antibacterial surface area. Moisture vaporizes during high-temperature processing, first at the weak interfaces inside the hybrid starch, thus directly destroying this core functional unit structurally and causing structural defects during high-temperature processing. Therefore, controlling the moisture content to below 0.5% is a key prerequisite for ensuring smooth processing and meeting performance standards. The second step involves blending lauric acid monoglyceride to ensure uniform dispersion of the antibacterial lubricant. This achieves synergistic antibacterial action with titanium dioxide and further provides processing lubrication, giving the plasticizer good processability and interfacial compatibility. This ensures that even with a high starch content, the plasticizer can still be successfully processed into plastic bottles with good appearance and performance through kneading, extrusion, and blow molding processes. The third step utilizes the strong shearing and mixing action of a twin-screw extruder to uniformly disperse the plasticizer in the polyolefin melt, completing the preparation of the antibacterial high-barrier starch-based injection molding compound. Finally, through an extrusion blow molding process, the high-performance antibacterial high-barrier starch-based injection molding compound is transformed into a solid plastic bottle with regular shape and consistent performance. The preparation process of this application is interconnected, achieving efficient and controllable transformation from molecular design to macroscopic product.

[0033] In summary, this application, while maintaining the green and low-cost nature of starch-based plastic bottles, significantly improves the hydrophobicity, antibacterial properties, and barrier properties against oxygen and water vapor through the synergistic design of various raw material components and preparation processes. This results in a surface contact angle of over 110°, an antibacterial rate of over 97%, and oxygen and water vapor permeability of less than 100 cm³ / (m²·24h·atm) and 4 g / (m²·24h), respectively. Attached Figure Description

[0034] The present application will be described in further detail below with reference to the accompanying drawings and preferred embodiments. However, those skilled in the art will understand that these drawings are drawn only for the purpose of explaining the preferred embodiments and therefore should not be construed as limiting the scope of this disclosure. Furthermore, unless specifically indicated, the drawings are only schematic representations of the composition or structure of the described objects and may contain exaggerated depictions, and the drawings are not necessarily drawn to scale.

[0035] Fig. 1 Example 4: Transmission electron microscopy image of in-situ hybridized starch with nano-titanium dioxide.

[0036] Fig. 2 Water droplet contact angle test diagrams of antibacterial high-barrier starch-based plastic bottles prepared in Examples 2, 4, and 3; wherein, A is the water droplet contact angle test diagram of the antibacterial high-barrier starch-based plastic bottle prepared in Example 2; B is the water droplet contact angle test diagram of the antibacterial high-barrier starch-based plastic bottle prepared in Example 4; and C is the water droplet contact angle test diagram of the antibacterial high-barrier starch-based plastic bottle prepared in Comparative Example 3. Detailed Implementation

[0037] The following is in conjunction with the appendix Figs. 1-2 This application will be described in detail.

[0038] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this disclosure.

[0039] Unless otherwise specified, all other reagents used in the embodiments of this application are from conventional commercially available products.

[0040] Detection methods Contact angle The measurement was performed according to GB / T 30693-2014, the method for measuring the contact angle between plastic film and water.

[0041] Antibacterial properties According to the international standard ISO 22196:2011, the method for evaluating the antimicrobial properties of plastic products, the test species was Escherichia coli.

[0042] Oxygen permeability Plastic films and sheets were tested according to GB / T 19789-2021, with the following test conditions: temperature 23.0℃±0.5℃ and relative humidity 50%±2%.

[0043] Water vapor transmission rate Plastic films and sheets were tested according to GB / T 1037-2021, with the following test conditions: temperature 23℃±0.5℃ and relative humidity 50%±2%.

[0044] The specific implementation method of this application is as follows.

[0045] Example 1 100 parts corn starch, 5 parts tetraethyl titanate, and 200 parts anhydrous ethanol were placed in a reaction vessel and stirred until homogeneous. Over 0.5 hours, 10 parts of a 5% (w / w) aqueous solution of glacial acetic acid were added dropwise to the reaction vessel. Under nitrogen protection, the reaction was carried out at 25°C for 2 hours to obtain in-situ hybridized nano-titanium dioxide starch. Then, 6 parts of layered double hydroxides were added to the reaction vessel and stirred until homogeneous. The temperature was raised to 60°C, and over 0.5 hours, 4 parts of dodecyltrimethoxysilane were slowly added dropwise. The reaction was stirred for 0.5 hours, filtered, and washed once with anhydrous ethanol to obtain the modified starch composite.

[0046] The modified starch complex was placed in a kneader at a speed of 30 rpm, a temperature of 80°C, and a vacuum of -0.098 MPa. The mixture was kneaded and dried until the moisture content was below 0.5%. Then, 2 parts of monoglyceride laurate were added, and the mixture was kneaded for another 15 minutes to obtain the plasticized material.

[0047] Take 15 parts of plasticizer and 85 parts of polypropylene and mix them evenly. Granulate the mixture using a twin-screw extruder to obtain antibacterial high-barrier starch-based injection molding compound. The temperature of the twin-screw extruder from the feed inlet to the die head is set as follows: 165℃, 185℃, 195℃, 195℃, 195℃, 195℃, 190℃, 190℃, 190℃. The screw speed is 300 r / min and the pelletizer speed is 350 r / min.

[0048] Antibacterial high-barrier starch-based injection molding compound was added to an extrusion blow molding machine. The temperatures from the feed inlet to the die head were set to 160℃, 175℃, 175℃, 175℃, 175℃, and 160℃, respectively. The screw speed was 150 r / min. Extrusion blow molding was performed to obtain antibacterial high-barrier starch-based plastic bottles.

[0049] Example 2 100 parts of cassava starch, 8 parts of tetrabutyl titanate, and 250 parts of anhydrous ethanol were placed in a reaction vessel and stirred until homogeneous. Over 1 hour, 15 parts of a 5% (w / w) aqueous solution of glacial acetic acid were added dropwise to the reaction vessel. Under nitrogen protection, the reaction was carried out at 30°C for 1.5 hours to obtain in-situ hybridized starch with nano-titanium dioxide. Then, 3 parts of graphene oxide nanosheets were added to the reaction vessel and stirred until homogeneous. The temperature was raised to 65°C, and 3 parts of isooctyltriethoxysilane were slowly added dropwise over 0.5 hours. The reaction was stirred for 0.5 hours, filtered, and washed twice with anhydrous ethanol to obtain the modified starch composite.

[0050] The modified starch complex was placed in a kneader at a speed of 40 rpm, a temperature of 85°C, and a vacuum of -0.09 MPa. The mixture was kneaded and dried until the moisture content was below 0.5%. Then, 0.8 parts of monoglyceride laurate were added, and the mixture was kneaded for another 15 minutes to obtain the plasticized material.

[0051] Take 20 parts of plasticizer and 80 parts of polyethylene and mix them evenly. Granulate the mixture using a twin-screw extruder to obtain antibacterial high-barrier starch-based injection molding compound. The temperature of the twin-screw extruder from the feed inlet to the die head is set as follows: 165℃, 185℃, 190℃, 190℃, 190℃, 190℃, 185℃, 185℃, 190℃. The screw speed is 250 r / min and the pelletizer speed is 300 r / min.

[0052] Antibacterial high-barrier starch-based injection molding compound was added to an extrusion blow molding machine. The extruder temperature from the feed inlet to the die head was set to 160℃, 170℃, 170℃, 170℃, 170℃, and 160℃ respectively. The screw speed was 125 r / min. Extrusion blow molding was performed to obtain antibacterial high-barrier starch-based plastic bottles.

[0053] Example 3 100 parts of potato starch, 10 parts of tetrapropyl titanate, and 200 parts of anhydrous ethanol were placed in a reaction vessel and stirred until homogeneous. Over 1 hour, 20 parts of a 5% (w / w) aqueous solution of glacial acetic acid were added dropwise to the reaction vessel. Under nitrogen protection, the reaction was carried out at 40°C for 1.5 hours to obtain in-situ hybridized starch with nano-titanium dioxide. Then, 5 parts of graphene nanosheets were added to the reaction vessel and stirred until homogeneous. The temperature was raised to 70°C, and 6 parts of hexadecyltrimethoxysilane were slowly added dropwise over 0.5 hours. The reaction was stirred for 1 hour, filtered, and washed twice with anhydrous ethanol to obtain the modified starch composite.

[0054] The modified starch compound was placed in a kneader at a speed of 50 rpm, a temperature of 90°C, and a vacuum of -0.096 MPa. The mixture was kneaded and dried until the moisture content was below 0.5%. Then, 1 part of monoglyceride laurate was added, and the mixture was kneaded for another 20 minutes to obtain the plasticized material.

[0055] Take 30 parts of plasticizer and 70 parts of polypropylene and mix them evenly. Granulate the mixture using a twin-screw extruder to obtain antibacterial high-barrier starch-based injection molding compound. The temperature of the twin-screw extruder from the feed inlet to the die head is set as follows: 165℃, 185℃, 190℃, 190℃, 190℃, 190℃, 185℃, 185℃, 190℃. The screw speed is 200 r / min and the pelletizer speed is 250 r / min.

[0056] Antibacterial high-barrier starch-based injection molding compound was added to an extrusion blow molding machine. The extruder temperature from the feed inlet to the die head was set to 160℃, 165℃, 165℃, 165℃, 165℃, and 160℃, respectively. The screw speed was 100 r / min. Extrusion blow molding was performed to obtain antibacterial high-barrier starch-based plastic bottles.

[0057] Example 4 100 parts of cassava starch, 15 parts of tetraethyl titanate, and 300 parts of anhydrous ethanol were placed in a reaction vessel and stirred until homogeneous. Over 1 hour, 30 parts of a 5% (w / w) aqueous solution of glacial acetic acid were added dropwise to the reaction vessel. Under nitrogen protection, the reaction was carried out at 45°C for 2 hours to obtain in-situ hybridized nano-titanium dioxide starch. Then, 10 parts of montmorillonite were added to the reaction vessel and stirred until homogeneous. The temperature was raised to 80°C, and over 1 hour, 8 parts of octadecyltriethoxysilane were slowly added dropwise. The reaction was stirred for 1 hour, filtered, and washed three times with anhydrous ethanol to obtain the modified starch composite.

[0058] The modified starch compound was placed in a kneader at a speed of 50 rpm, a temperature of 100°C, and a vacuum of -0.098 MPa. The mixture was kneaded and dried until the moisture content was below 0.5%. Then, 0.5 parts of monoglyceride laurate were added, and the mixture was kneaded for another 30 minutes to obtain the plasticized material.

[0059] Take 35 parts of plasticizer and 65 parts of polyethylene and mix them evenly. Granulate the mixture using a twin-screw extruder to obtain antibacterial high-barrier starch-based injection molding compound. The temperature of the twin-screw extruder from the feed inlet to the die head is set as follows: 165℃, 185℃, 190℃, 190℃, 190℃, 190℃, 185℃, 185℃, 190℃. The screw speed is 150 r / min and the pelletizer speed is 250 r / min.

[0060] Antibacterial high-barrier starch-based injection molding compound was added to an extrusion blow molding machine. The extruder temperature from the feed inlet to the die head was set to 160℃, 165℃, 165℃, 165℃, 165℃, and 160℃, respectively. The screw speed was 80 r / min. Extrusion blow molding was performed to obtain antibacterial high-barrier starch-based plastic bottles.

[0061] Example 5 100 parts corn starch, 7 parts tetraethyl titanate, and 200 parts anhydrous ethanol were placed in a reaction vessel and stirred until homogeneous. Over 0.5 hours, 15 parts of a 5% (w / w) aqueous solution of glacial acetic acid were added dropwise to the reaction vessel. Under nitrogen protection, the reaction was carried out at 40°C for 1 hour to obtain in-situ hybridized starch with nano-titanium dioxide. Then, 7 parts of graphene oxide nanosheets were added to the reaction vessel and stirred until homogeneous. The temperature was raised to 75°C, and 7 parts of octadecyltrimethoxysilane were slowly added dropwise over 1 hour. The reaction was stirred for 1 hour, filtered, and washed twice with anhydrous ethanol to obtain the modified starch composite.

[0062] The modified starch complex was placed in a kneader at a speed of 40 rpm, a temperature of 95°C, and a vacuum of -0.09 MPa. The mixture was kneaded and dried until the moisture content was below 0.5%. Then, 1.5 parts of monoglyceride laurate were added, and the mixture was kneaded for another 30 minutes to obtain the plasticized material.

[0063] Take 40 parts of plasticizer and 60 parts of polypropylene and mix them evenly. Granulate the mixture using a twin-screw extruder to obtain antibacterial high-barrier starch-based injection molding compound. The temperature of the twin-screw extruder from the feed inlet to the die head is set as follows: 165℃, 185℃, 195℃, 195℃, 195℃, 195℃, 190℃, 190℃, 190℃. The screw speed is 200 r / min and the pelletizer speed is 300 r / min.

[0064] The obtained antibacterial high-barrier starch-based injection molding compound is added to an extrusion blow molding machine. The extruder temperature from the feed port to the die head is set to 160℃, 170℃, 170℃, 170℃, 170℃, and 160℃ respectively, and the screw speed is 120 r / min. The extrusion blow molding process is used to obtain an antibacterial high-barrier starch-based plastic bottle.

[0065] Example 6 100 parts of potato starch, 12 parts of tetrabutyl titanate, and 300 parts of anhydrous ethanol were placed in a reaction vessel and stirred until homogeneous. Over 1 hour, 25 parts of a 5% (w / w) aqueous solution of glacial acetic acid were added dropwise to the reaction vessel. Under nitrogen protection, the reaction was carried out at 45°C for 1.5 hours to obtain in-situ hybridized nano-titanium dioxide starch. Then, 8 parts of layered double hydroxides were added to the reaction vessel and stirred until homogeneous. The temperature was raised to 70°C, and 5 parts of isooctyltriethoxysilane were slowly added dropwise over 1 hour. The reaction was stirred for 1 hour, filtered, and washed twice with anhydrous ethanol to obtain the modified starch complex.

[0066] The modified starch complex was placed in a kneader at a speed of 50 rpm, a temperature of 100℃, and a vacuum of -0.096 MPa. The mixture was kneaded and dried until the moisture content was below 0.5%. Then, 1.2 parts of monoglyceride laurate were added, and the mixture was kneaded for another 30 minutes to obtain the plasticized material.

[0067] 45 parts of plasticizer and 55 parts of polypropylene were mixed evenly and granulated using a twin-screw extruder to obtain antibacterial high-barrier starch-based injection molding compound. The temperatures of the twin-screw extruder from the feed inlet to the die head were set to 165℃, 185℃, 185℃, 190℃, 190℃, 190℃, 190℃, 190℃, and 190℃, respectively. The screw speed was 120 r / min and the pelletizer speed was 250 r / min.

[0068] The obtained antibacterial high-barrier starch-based injection molding compound is added to an extrusion blow molding machine. The extruder temperature from the feed port to the die head is set to 160℃, 165℃, 165℃, 165℃, 165℃, and 160℃ respectively, and the screw speed is 100 r / min. The extrusion blow molding process produces an antibacterial high-barrier starch-based plastic bottle.

[0069] Example 7 100 parts of potato starch, 12 parts of tetrabutyl titanate, and 300 parts of anhydrous ethanol were placed in a reaction vessel and stirred until homogeneous. Over 1 hour, 25 parts of a 5% (w / w) aqueous solution of glacial acetic acid were added dropwise to the reaction vessel. Under nitrogen protection, the reaction was carried out at 45°C for 1.5 hours to obtain in-situ hybridized nano-titanium dioxide starch. Then, 8 parts of layered double hydroxides were added to the reaction vessel and stirred until homogeneous. The temperature was raised to 70°C, and 5 parts of isooctyltriethoxysilane were slowly added dropwise over 1 hour. The reaction was stirred for 1 hour, filtered, and washed twice with anhydrous ethanol to obtain the modified starch complex.

[0070] The modified starch complex was placed in a kneader at a speed of 50 rpm, a temperature of 100°C, and a vacuum of -0.096 MPa. The mixture was kneaded and dried until the moisture content was below 0.5%. Then, 1.2 parts of monoglyceride laurate were added, and the mixture was kneaded for another 30 minutes to obtain the plasticized material.

[0071] Take 40 parts of plasticizer and 60 parts of polypropylene and mix them evenly. Granulate the mixture using a twin-screw extruder to obtain antibacterial high-barrier starch-based injection molding compound. The temperature of the twin-screw extruder from the feed inlet to the die head is set to 165℃, 185℃, 185℃, 190℃, 190℃, 190℃, 190℃, 190℃, 190℃, respectively. The screw speed is 120 r / min and the pelletizer speed is 250 r / min.

[0072] Antibacterial high-barrier starch-based injection molding compound was added to an extrusion blow molding machine. The extruder temperature from the feed inlet to the die head was set to 160℃, 165℃, 165℃, 165℃, 165℃, and 160℃, respectively. The screw speed was 100 r / min. Extrusion blow molding was performed to obtain antibacterial high-barrier starch-based plastic bottles.

[0073] Comparative Example 1 The difference between Comparative Example 1 and Example 4 is that tetraethyl titanate was not added, meaning that the starch was not modified in situ with titanium dioxide. Comparative Example 1 is detailed below: Take 100 parts of cassava starch, 10 parts of montmorillonite and 200 parts of anhydrous ethanol and put them into a reaction vessel. Stir well. Add 12 parts of 5% glacial acetic acid aqueous solution to the reaction vessel dropwise over 1 hour. Under nitrogen protection, heat to 80°C and slowly add 8 parts of octadecyltriethoxysilane dropwise over 1 hour. Stir the reaction for 1 hour, filter, and wash twice with anhydrous ethanol.

[0074] The preparation processes of the modified starch compound, plasticizer, starch-based injection molding compound, and starch-based plastic bottle in Comparative Example 1 were the same as those in Example 4.

[0075] Comparative Example 2 The difference between Comparative Example 2 and Example 4 is that no nano-inorganic barrier powder montmorillonite was added, while the other components and amounts, and the preparation parameters were the same as in Example 4.

[0076] Comparative Example 3 The difference between Comparative Example 3 and Example 4 is that a conventional aluminate coupling agent was used instead of octadecyltriethoxysilane in Example 4.

[0077] This application performed transmission electron microscopy (TEM) scanning on the in-situ hybrid starch made of nano-titanium dioxide obtained in Example 4, as follows: Fig. 1 As shown. By Fig. 1 As can be seen, uniformly sized nano-sized titanium dioxide particles (dark spots in the figure) were successfully generated in situ and uniformly distributed in starch, forming a tightly bound hybrid structure, indicating the successful preparation of nano-titanium dioxide in situ hybrid starch.

[0078] This application conducted performance tests on the antibacterial high-barrier starch-based plastic bottles prepared in Examples 1-7 and Comparative Examples 1-3. The test results are shown in Table 1.

[0079] Table 1. Performance test results of antibacterial high-barrier starch-based plastic bottles prepared in Examples 1-7 and Comparative Examples 1-3

[0080] As shown in Table 1, the antibacterial high-barrier starch-based plastic bottles prepared in Examples 1-7 exhibit excellent performance, with antibacterial rates all exceeding 97%. The in-situ hybridization of nano-titanium dioxide and the synergistic effect of the antibacterial lubricant lauric acid monoglyceride provide stable and efficient antibacterial protection. They also demonstrate excellent barrier properties, with oxygen permeability consistently below 97 cm³ / (m²·24h·atm). The synergistic effect of the nano-inorganic barrier powder and long-chain silane constructs a highly efficient oxygen barrier. Water vapor permeability is also below 3.8 g / (m²·24h). The strong hydrophobicity imparted by the long-chain silane coupling agent, combined with the layered structure of the nano-inorganic barrier powder, achieves superior moisture-proof performance. Furthermore, the bottles exhibit good hydrophobicity, with contact angles all above 110°, reaching a maximum of 137°. This indicates that the surface of the antibacterial high-barrier starch-based plastic bottles is strongly hydrophobic, which stems from the hydrophobic modification by the long-chain alkyl silane coupling agent. Example 4 achieves the best balance in four properties: contact angle, antibacterial properties, oxygen barrier properties, and moisture barrier properties, and is the optimal example.

[0081] Analysis of the contact angle test data from Examples 1-7 showed that the antibacterial high-barrier starch-based plastic bottle prepared in Example 4 had the highest contact angle (137°). Fig. 2As shown in Figure B, the water droplet is highly spherical with the largest contact angle, exhibiting excellent hydrophobicity. The antibacterial high-barrier starch-based plastic bottle prepared in Example 2 has a relatively low contact angle (112°), as... Fig. 2 As shown in Figure A, the contact angle is slightly smaller. The antibacterial high-barrier starch-based plastic bottle prepared in Example 3 has a contact angle of 126°. This is attributed to the silane alkyl chain length and amount of the silane coupling agent. In Example 4, the silane coupling agent has a chain length of C18 and an amount of 8 parts. In Example 2, the silane coupling agent has a chain length of C8 and an amount of 3 parts. In Example 3, the silane coupling agent has a chain length of C16 and an amount of 6 parts. The longer the silane alkyl chain and the more sufficient the amount, the more significant the hydrophobic effect.

[0082] Analysis of the test data on the antibacterial properties of Examples 1-7 showed that the antibacterial rate of all examples was above 97%, with Examples 4 and 6 reaching 99%. The antibacterial performance was mainly attributed to the in-situ generation of nano-titanium dioxide and the synergistic antibacterial effect with the antibacterial lubricant laurate monoglyceride. In Example 4, the amount of titanate was 15 parts, and in Example 6, the amount of titanate was 12 parts, ensuring the generation of sufficient and highly active titanium dioxide.

[0083] Analysis of the oxygen permeability test data for Examples 1-7 showed that Example 4 exhibited the best oxygen barrier performance, Example 2 had slightly higher oxygen barrier performance, and Examples 6 and 7 had slightly lower oxygen barrier performance than Example 4. This is mainly attributed to the amount of nano-inorganic barrier powder used; increasing the amount of nano-inorganic barrier powder helps to form a denser barrier network, thereby providing a lower oxygen permeability. Example 4 used 10 parts montmorillonite, Example 2 used 1 part graphene oxide nanosheets, and Examples 6 and 7 used 8 parts layered double hydroxides. The superior data of Example 4 is partly due to its higher loading of effective barrier components.

[0084] Analysis of the test data on water vapor transmission in Examples 1-7 showed that Example 4 had the best moisture barrier properties, while Example 2 had relatively lower moisture barrier properties. Moisture barrier properties were positively correlated with the hydrophobicity of the prepared antibacterial high-barrier starch-based plastic bottle. Hydrophobicity was reflected by the contact angle. Example 4 had the strongest hydrophobicity and the best moisture barrier properties, while Example 2 had relatively lower hydrophobicity and moisture barrier properties. This indicates that the high hydrophobicity brought by long-chain silanes is the key to obtaining high moisture barrier properties.

[0085] In summary, the contact angle mainly depends on the chain length and amount of long-chain silane coupling agent; the antibacterial rate is dominated by in-situ generated nano-titanium dioxide, and maintains high antibacterial activity with the synergistic effect of monoglyceride laurate; oxygen barrier properties are mainly determined by the amount of nano-inorganic barrier powder used; while water vapor barrier properties are strongly positively correlated with the hydrophobicity (contact angle) of the material.

[0086] Table 1 shows that Comparative Example 1, without the addition of titanate ester and without in-situ titanium dioxide hybridization of starch, exhibited a decrease in antibacterial rate of approximately 50%, while the contact angle and oxygen and water vapor barrier properties remained acceptable. This indicates that the inorganic barrier powders montmorillonite and octadecyltriethoxysilane still play a role. Comparative Example 1 demonstrates that in-situ generated nano-titanium dioxide is the core and necessary condition for high antibacterial activity, and its antibacterial effect cannot be replaced by other components.

[0087] As shown in Table 1, Comparative Example 2, without the addition of nano-inorganic barrier powder, exhibited significantly reduced barrier performance, with a surge in oxygen permeability reaching 213 cm³ / (m²·24h·atm) and water vapor permeability reaching 23 g / (m²·24h). Nano-inorganic barrier powder forms the physical framework for constructing high barrier performance; without it, oxygen and water vapor cannot be blocked.

[0088] Table 1 shows that Comparative Example 3, which uses conventional aluminate esters instead of long-chain silane coupling agents, has a contact angle of only 85° for its antibacterial high-barrier starch-based plastic bottle. Fig. 2 As shown in Figure C, the water droplets spread out, have a very small contact angle, are highly hydrophilic, and have reduced hydrophobicity; the oxygen permeability is 152 cm³ / (m²·24h·atm), and the water vapor permeability is 12 g / (m²·24h·atm). 2 •day), barrier properties are significantly reduced. Long-chain alkylsilane coupling agents with specific structures are key to achieving deep hydrophobicity, improving interfacial compatibility, and enhancing barrier performance, effects that conventional coupling agents cannot achieve.

[0089] In summary, the superior performance of the antibacterial high-barrier starch-based plastic bottles prepared in Examples 1-7 is not a simple summation of the functions of each component. Comparative Example 3 shows that even with in-situ modification of starch with nano-titanium dioxide to achieve highly efficient antibacterial properties and the use of barrier materials, theoretically possessing good barrier performance, high hydrophobicity and excellent barrier performance cannot be obtained if the interface modifier silane coupling agent is not a long-chain silane coupling agent. This indicates that the in-situ titanium dioxide hybrid modified starch, nano-inorganic barrier powder, and long-chain silane coupling agent constitute a closely synergistic and interdependent functional system, and the synergistic effect is not a simple additive result.

[0090] The present application has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present application. The descriptions of the embodiments above are only for the purpose of helping to understand the present disclosure and its core ideas. It should be noted that those skilled in the art can make several improvements and modifications to the present application without departing from the principles of the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims

1. A method for preparing an antibacterial, high-barrier starch-based plastic bottle, characterized in that, Includes the following steps: S1: Under the catalysis of an acid catalyst, titanate esters are used to generate nano-titanium dioxide in situ in starch, and the starch is then modified in situ by hybridization to obtain nano-titanium dioxide in situ hybridized starch. Then, nano-inorganic barrier powder is added, mixed evenly, and then long-chain silane coupling agent is added to modify the in-situ hybridized starch of nano-titanium dioxide and nano-inorganic barrier powder to obtain modified starch complex. S2: Place the modified starch compound in a kneader and knead it to ensure that the moisture content of the modified starch compound is less than 0.5%; add antibacterial lubricant and knead again to obtain plasticized material; S3: The plasticizer is blended with polyolefin resin, melt-extruded and granulated through a twin-screw extruder to obtain antibacterial high-barrier starch-based injection molding compound; S4: The antibacterial high-barrier starch-based injection molding compound is extruded and blow-molded to obtain the antibacterial high-barrier starch-based plastic bottle.

2. The method for preparing the antibacterial high-barrier starch-based plastic bottle as described in claim 1, characterized in that, Step S1 is carried out under an inert atmosphere in an anhydrous alcohol solvent; the acid catalyst is a 5% aqueous solution of glacial acetic acid; the reaction temperature is 25-45℃ and the reaction time is 1-2 hours. Alternatively, the reaction temperature for modifying nano-titanium dioxide in-situ hybrid starch and nano-inorganic barrier powder with long-chain silane coupling agent in step S1 is 60-80℃.

3. The method for preparing the antibacterial high-barrier starch-based plastic bottle as described in claim 1, characterized in that, Step S2: Place the modified starch complex in a kneader and knead it at a speed of 30-50 rpm and a temperature of 80-100℃. Alternatively, in step S2, the hydrophobic modified composite powder is placed in a kneader and kneaded while simultaneously undergoing dehydration to ensure that the moisture content of the modified starch composite is below 0.5%. Alternatively, in step S2, add an antibacterial lubricant and knead for 15-30 minutes.

4. The method for preparing the antibacterial high-barrier starch-based plastic bottle as described in claim 1, characterized in that, In step S3, the temperature of the twin-screw extruder from the feed inlet to the die head is set at 165-195℃, the screw speed is 120-300 r / min, and the pelletizer speed is 250-350 r / min. Alternatively, in step S4, extrusion blow molding is performed using an extrusion blow molding machine, with the temperature from the feed inlet to the die set at 160-175℃ and the screw speed at 80-150 r / min.

5. The method for preparing the antibacterial high-barrier starch-based plastic bottle as described in claim 1, characterized in that, Based on 100 parts by weight of starch, the amounts of each component in steps S1 and S2 are as follows: 5-15 parts of titanate; 10-30 parts of acid catalyst. 3-10 parts of nano-inorganic barrier powder; 3-8 parts of long-chain silane coupling agent; 0.5-2 parts of antibacterial lubricant.

6. The method for preparing the antibacterial high-barrier starch-based plastic bottle as described in claim 1, characterized in that, In step S3, the mass ratio of plasticizer to polyolefin resin is (15-40):(60-85).

7. The method for preparing the antibacterial high-barrier starch-based plastic bottle as described in claim 1, characterized in that, The starch is at least one of corn starch, tapioca starch, or potato starch. Alternatively, the titanate ester is at least one of tetraethyl titanate, tetrabutyl titanate, tetra-n-propyl titanate, or tetraisopropyl titanate; Alternatively, the nano-inorganic barrier powder is a nano-inorganic material with a layered structure, including at least one of nano-montmorillonite, graphene nanosheets, graphene oxide nanosheets, or layered double hydroxides. Alternatively, the long-chain silane coupling agent is an alkyltrialkoxysilane with a carbon chain length of C8-C18; preferably, the long-chain silane coupling agent is at least one of isooctyltriethoxysilane, dodecyltrimethoxysilane, hexadecyltrimethoxysilane, octadecyltrimethoxysilane, or octadecyltriethoxysilane. Alternatively, the antibacterial lubricant is glyceryl monolaurate; Alternatively, the polyolefin resin may be polypropylene or polyethylene, with a melt flow index of 0.5-4 g / 10 min.

8. An antibacterial high-barrier starch-based plastic bottle, wherein the antibacterial high-barrier starch-based plastic bottle is prepared by the preparation method of any one of claims 1-7.

9. The antibacterial high-barrier starch-based plastic bottle as described in claim 8, characterized in that, The surface contact angle of the antibacterial high-barrier starch-based plastic bottle is above 110°, the antibacterial rate is above 97%, the oxygen permeability is below 100 cm³ / (m²·24h·atm), and the water vapor permeability is below 4 g / (m²·24h).

10. An antibacterial high-barrier starch-based injection molding compound, wherein the antibacterial high-barrier starch-based injection molding compound is prepared according to steps S1-S3 of claim 1.

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