A method for low-temperature high-speed blow molding of polylactic acid drainage bags

Abstract

This invention discloses a low-temperature, high-speed blow molding method for polylactic acid (PLA) drainage bags, relating to the field of polymer materials technology. The method first involves blending PLA with plasticizers and lubricants, melting and granulating the mixture at a specific low-temperature window, and then blow molding it to obtain a substrate. Subsequently, the substrate is pretreated with a silver ion solution and then subjected to in-situ oxidative polymerization with a dispersion containing functionalized pyrrole derivative monomers and silver phosphate microcapsules loaded with perfluorinated monomers, constructing a composite functional coating on the substrate surface. This invention effectively inhibits the thermal degradation of PLA by strictly controlling the low-temperature process parameters of blow molding, ensuring the safety of the substrate; simultaneously, by embedding microcapsules into the coating through in-situ polymerization, it achieves a synergistic effect of antibacterial and hydrophobic functions.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically a low-temperature high-speed blow molding method for polylactic acid drainage bags. Background Technology

[0002] Polylactic acid (PLA), as a bio-based biodegradable polymer, has shown great potential in the manufacture of medical products as a replacement for traditional petroleum-based plastics due to its excellent biocompatibility and complete degradability. Among these, drainage bags, as commonly used clinical medical devices, have stringent requirements for the biosafety of materials; using PLA to manufacture drainage bags aligns with the development trend of green healthcare.

[0003] However, the inherent heat sensitivity and brittleness of polylactic acid (PLA) pose significant challenges to its blow molding process. In traditional blow molding, high processing temperatures are typically required to achieve sufficient melt flow, which easily triggers thermal degradation of the PLA molecular chains, leading to a decrease in molecular weight, deterioration of mechanical properties, and potential generation of small molecule impurities such as oligomers, thereby compromising the biosafety of the final product. On the other hand, if excessively low processing temperatures are used to avoid thermal degradation, the melt strength is insufficient, making stable high-speed molding difficult, and the resulting product is highly brittle and cannot meet the flexibility requirements for use. Therefore, balancing the contradictions between processing temperature, production efficiency, and material safety in the manufacture of PLA drainage bags has become a difficult technical challenge.

[0004] Furthermore, polylactic acid (PLA) alone is insufficient to meet the stringent clinical requirements for the antibacterial properties of drainage bag surfaces. Bacterial colonization and biofilm formation on the bag surface are major risks leading to catheter-related infections. Current common surface modification methods, such as simply applying antibacterial coatings, often suffer from weak adhesion, easy loss of antibacterial components, and poor functional durability, failing to provide stable and reliable protection during long-term use.

[0005] To address the aforementioned problems, this invention provides a low-temperature, high-speed blow molding method for polylactic acid drainage bags. Summary of the Invention

[0006] The purpose of this invention is to provide a low-temperature, high-speed blow molding method for polylactic acid drainage bags to solve the problems raised in the prior art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A low-temperature, high-speed blow molding method for a polylactic acid drainage bag includes the following steps: Step 1: Mechanically blend polylactic acid, plasticizer, and lubricant, extrude and granulate, water cool, and cut into pellets to obtain polylactic acid filler; dry the polylactic acid filler, blow mold it, and cool it after molding to obtain a drainage bag; Step 2: Immerse the drainage bag in silver nitrate aqueous solution, add the dispersion containing microcapsules, and stir continuously to react; after the reaction is completed, remove the drainage bag, vacuum dry and solidify to obtain polylactic acid drainage bag.

[0008] Furthermore, in step one, the extrusion granulation conditions are set as follows: Zone 1: 120–130℃, Zone 2: 150–160℃, Zone 3: 160–170℃, Zone 4: 170–175℃, Zone 5: 170–175℃, Zone 6: 170–175℃, Zone 7: 170–175℃, Die head: 170–175℃, Screw speed: 150–220 rpm.

[0009] Furthermore, in step one, the blow molding settings are as follows: Zone 1 temperature: 155~158℃, Zone 2: 165~170℃, Zone 3: 165~172℃, Zone 4: 165~175℃, Zone 5: 160~165℃; Mold body: 160~170℃; Mold opening: 160~170℃; Screw speed: 100~220rpm, Traction speed: 15~25m / min, Blow-up ratio: 2~6.

[0010] Furthermore, in step two, the preparation process of the dispersion containing microcapsules is as follows: weigh 1-2g of N-(2-hydroxyethyl)pyrrole, add it to deionized water, add functionalized microcapsules and ultrasonically disperse for 15-25min to obtain a dispersion containing microcapsules.

[0011] Furthermore, the preparation process of the functionalized microcapsules is as follows: sorbitan oleate and octylphenol polyoxyethylene ether are mixed, cyclohexane is added, and the mixture is stirred until homogeneous to obtain an oil phase; perfluorooctyl ethyl acrylate is mixed with deionized water, sodium phosphate is added, and the mixture is ultrasonically dispersed to obtain an aqueous phase; under stirring, the aqueous phase is slowly added dropwise to the oil phase, and emulsification is continued after the addition is complete to obtain an emulsion; silver nitrate ethanol solution is added dropwise to the above emulsion, and the reaction is continued by heating; after the reaction is completed, anhydrous ethanol is added to break the emulsion, and the mixture is centrifuged, washed, and vacuum dried to obtain the functionalized microcapsules.

[0012] Furthermore, the weight ratio of perfluorooctyl ethyl acrylate to deionized water to sodium phosphate is (0.9-1):10:(0.1-0.15).

[0013] Furthermore, in step two, the soaking parameters are: constant temperature at 50-55℃ for 15-20 minutes.

[0014] Furthermore, in step two, the concentration of the silver nitrate aqueous solution is 0.04-0.06 mol / L.

[0015] Furthermore, in step two, the parameters for continuous stirring of the reaction are: reaction at 28-35℃ for 60-90 min.

[0016] Furthermore, the polylactic acid filler comprises the following components, in parts by weight: 10-25 parts polylactic acid, 2-4 parts plasticizer, and 0.5-2 parts lubricant.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention controls the temperature of the core plasticizing zone in polylactic acid blow molding within a low-temperature window of 165 to 172 degrees Celsius, and matches it with a dual-vent gradient cooling process. This is because the combination of process parameters can maximally suppress the thermal degradation and thermal oxidation reactions of polylactic acid molecular chains during processing, greatly improving the safety and stability of the resulting drainage bag substrate, thereby further enhancing the mechanical properties of the drainage bag.

[0018] 2. This invention employs the method of co-dispersing silver phosphate microcapsules loaded with perfluorinated monomers with N-(2-hydroxyethyl)pyrrole monomers, followed by in-situ oxidative polymerization on a substrate pretreated with silver ions. The weight ratio of perfluorooctyl ethyl acrylate to deionized water to sodium phosphate is (0.9-1):10:(0.1-0.15). This precise ratio ensures stable performance of the functionalized microcapsules, providing a long-lasting antibacterial effect through the sustained release of silver ions via silver phosphate. Simultaneously, the perfluorooctyl ethyl acrylate segments grafted onto the surface impart hydrophobic properties to the microcapsules. The in-situ polymerization of N-(2-hydroxyethyl)pyrrole monomers under silver ion oxidation forms a polypyrrole structure, which, upon curing, forms a protective coating. The hydroxyethyl side chains on this monomer enhance the interaction between the polymer, the polylactic acid matrix, and the microcapsules, improving the coating's adhesion stability and biocompatibility. Detailed Implementation

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments, and all described quantities are by weight. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] The sources and types of substances involved in this invention are not particularly limited. Exemplary examples include the following raw materials: polylactic acid: type: PLA LX930, which can be purchased from Shanghai Nuochen New Materials Co., Ltd.; octylphenol polyoxyethylene ether: item number: HY-207, which can be purchased from Hangzhou Jessica Chemical Co., Ltd. Example

[0021] Step 1: Mechanically blend 10 parts polylactic acid, 2 parts plasticizer acetylated tributyl citrate, and 0.5 parts lubricant ethylene bis-stearamide for 5 minutes. Add the mixed raw material to a twin-screw extruder. The extrusion granulation conditions are as follows: Twin-screw extruder set temperature: Zone 1: 120℃, Zone 2: 150℃, Zone 3: 160℃, Zone 4: 170℃, Zone 5: 170℃, Zone 6: 170℃, Zone 7: 170℃, Die head: 170℃, Screw speed: 150 rpm. After melt extrusion, water cooling, and pelletizing, polylactic acid filler is obtained. The polylactic acid filler was dried in a constant temperature oven at 80°C for 5 hours, and then added to a blown film machine for blow molding. The set temperature of the blown film machine is: Zone 1: 155℃, Zone 2: 165℃, Zone 3: 165℃, Zone 4: 165℃, Zone 5: 160℃; Mold body: 160℃; Mold opening: 160℃; Screw speed: 100 rpm, traction speed: 15 m / min, inflation ratio: 2, cooling method: adopts a dual-air-outlet cooling ring, upper air outlet temperature: 20℃, lower air outlet temperature: 10℃, rapid cooling to obtain the drainage bag; Step 2: Mix sorbitan oleate and octylphenol polyoxyethylene ether at a weight ratio of 8:1, add 100 mL of cyclohexane, and stir and mix evenly at 45°C to obtain the oil phase; Perfluorooctyl ethyl acrylate was mixed with deionized water at a weight ratio of 0.9:10, and sodium phosphate was added at a total weight of 1.0 wt% of the deionized water. The mixture was ultrasonically dispersed in an ice-water bath for 25 min to obtain the aqueous phase. While stirring at 400 rpm, the aqueous phase was slowly added dropwise to the oil phase. After the addition was complete, emulsification was continued for 25 minutes to obtain an emulsion. Prepare a 0.15 mol / L silver nitrate ethanol solution, slowly add the silver nitrate ethanol solution dropwise to the above emulsion, then heat the system to 40℃ and continue the reaction for 4-5 hours; After the reaction was completed, 50 mL of anhydrous ethanol was added to break the emulsion, centrifuged, washed, and vacuum dried at 45 °C for 22 h to obtain functionalized microcapsules. Step 3: Weigh 1g of N-(2-hydroxyethyl)pyrrole, add it to 50mL of deionized water, add 0.4g of functionalized microcapsules; sonicate for 15min to obtain a dispersion containing microcapsules; Prepare a 0.04 mol / L silver nitrate aqueous solution, immerse the polylactic acid drainage bag in it, and soak at 50℃ for 15 min. While stirring at 200 rpm, slowly pour in the dispersion containing microcapsules, and continue stirring at 28℃ for 60 min. After the reaction is complete, remove the drainage bag, rinse with deionized water, and dry in a vacuum oven at 50℃ for 2 h to allow the coating to fully cure, thus obtaining the polylactic acid drainage bag. Example

[0022] Step 1: Mechanically blend 15 parts polylactic acid, 3 parts plasticizer acetylated tributyl citrate, and 1 part lubricant ethylene bis-stearamide for 8 minutes. Add the mixed raw material to a twin-screw extruder. The extrusion granulation conditions are as follows: Twin-screw extruder set temperature: Zone 1: 125℃, Zone 2: 155℃, Zone 3: 165℃, Zone 4: 172℃, Zone 5: 172℃, Zone 6: 172℃, Zone 7: 172℃, Die head: 172℃, Screw speed: 180 rpm. After melt extrusion, water cooling, and pelletizing, polylactic acid filler is obtained. The polylactic acid filler was dried in a constant temperature oven at 90°C for 5.5 hours, and then added to a blown film machine for blow molding. The set temperature of the blown film machine is: Zone 1: 156℃, Zone 2: 168℃, Zone 3: 170℃, Zone 4: 170℃, Zone 5: 163℃; Mold body: 165℃; Mold opening: 165℃; Screw speed: 180 rpm, traction speed: 20 m / min, inflation ratio: 4, cooling method: adopts a dual-air-outlet cooling ring, with an upper air outlet temperature of 23℃ and a lower air outlet temperature of 12℃, to quickly cool and obtain the drainage bag; Step 2: Mix sorbitan oleate and octylphenol polyoxyethylene ether at a weight ratio of 8:1, add 100 mL of cyclohexane, and stir and mix evenly at 45-50℃ to obtain the oil phase; Perfluorooctyl ethyl acrylate was mixed with deionized water at a weight ratio of 0.95:10, and sodium phosphate at a weight of 1.3 wt% of the total weight of deionized water was added. The mixture was ultrasonically dispersed in an ice-water bath for 28 min to obtain an aqueous phase. While stirring at 450 rpm, the aqueous phase was slowly added dropwise to the oil phase. After the addition was complete, emulsification was continued for 28 minutes to obtain an emulsion. Prepare a 0.20 mol / L silver nitrate ethanol solution, slowly add the silver nitrate ethanol solution dropwise to the above emulsion, then heat the system to 42℃ and continue the reaction for 4.5 h; After the reaction was completed, 50 mL of anhydrous ethanol was added to break the emulsion, centrifuged, washed, and vacuum dried at 45-50 °C for 23 h to obtain functionalized microcapsules. Step 3: Weigh 1.5g of N-(2-hydroxyethyl)pyrrole, add it to 80mL of deionized water, add 0.6g of functionalized microcapsules; sonicate for 20min to obtain a dispersion containing microcapsules; Prepare a 0.05 mol / L silver nitrate aqueous solution, immerse the polylactic acid drainage bag in it, and soak it at 52℃ for 18 min. While stirring at 300 rpm, slowly pour in the dispersion containing microcapsules and continue stirring at 30℃ for 75 min. After the reaction is complete, remove the drainage bag, rinse it with deionized water, and dry it in a vacuum drying oven at 60℃ for 3 h to allow the coating to fully cure, thus obtaining the polylactic acid drainage bag. Example

[0023] Step 1: Mechanically blend 25 parts of polylactic acid, 4 parts of plasticizer acetylated tributyl citrate, and 2 parts of lubricant ethylene bis-stearamide for 10 minutes. Add the mixed raw material to a twin-screw extruder. The extrusion granulation conditions are as follows: Twin-screw extruder set temperature: Zone 1: 130℃, Zone 2: 160℃, Zone 3: 170℃, Zone 4: 175℃, Zone 5: 175℃, Zone 6: 175℃, Zone 7: 175℃, Die head: 175℃, Screw speed: 220 rpm. After melt extrusion, water cooling, and pelletizing, polylactic acid filler is obtained. The polylactic acid filler was dried in a constant temperature oven at 800℃ for 6 hours, and then added to a blown film machine for blow molding. The set temperature of the blown film machine is: Zone 1: 158℃, Zone 2: 170℃, Zone 3: 172℃, Zone 4: 175℃, Zone 5: 165℃; Mold body: 170℃; Mold opening: 170℃; Screw speed: 220 rpm, traction speed: 25 m / min, inflation ratio: 6, cooling method: adopts dual-air-outlet cooling ring, upper air outlet temperature: 25℃, lower air outlet temperature: 15℃, rapid cooling to obtain the drainage bag; Step 2: Mix sorbitan oleate and octylphenol polyoxyethylene ether at a weight ratio of 8:1, add 100 mL of cyclohexane, and stir at 50 °C until homogeneous to obtain the oil phase; Perfluorooctyl ethyl acrylate was mixed with deionized water at a weight ratio of 1:10, and sodium phosphate was added at a total weight of 1.5 wt% of the deionized water. The mixture was ultrasonically dispersed in an ice-water bath for 30 min to obtain the aqueous phase. While stirring at 500 rpm, the aqueous phase was slowly added dropwise to the oil phase. After the addition was complete, emulsification was continued for 30 minutes to obtain an emulsion. Prepare a 0.25 mol / L silver nitrate ethanol solution, slowly add the silver nitrate ethanol solution dropwise to the above emulsion, then heat the system to 45℃ and continue the reaction for 5 h; After the reaction was completed, 50 mL of anhydrous ethanol was added to break the emulsion, centrifuged, washed, and vacuum dried at 50 °C for 24 h to obtain functionalized microcapsules. Step 3: Weigh 2g of N-(2-hydroxyethyl)pyrrole, add it to 100mL of deionized water, add 0.8g of functionalized microcapsules; sonicate for 25min to obtain a dispersion containing microcapsules; Prepare a 0.06 mol / L silver nitrate aqueous solution, immerse the polylactic acid drainage bag in it, and soak it at 55℃ for 20 min. While stirring at 400 rpm, slowly pour in the dispersion containing microcapsules and continue stirring at 35℃ for 90 min. After the reaction is complete, remove the drainage bag, rinse it with deionized water, and dry it in a vacuum drying oven at 70℃ for 4 h to allow the coating to fully cure, thus obtaining the polylactic acid drainage bag.

[0024] Comparative Example 1: In the preparation of the microcapsules, the weight ratio of perfluorooctyl ethyl acrylate to deionized water to sodium phosphate was changed, and the proportion of sodium phosphate was reduced to 1.2:10:0.08. The rest was the same as in Example 1. Step 1: Mechanically blend 10 parts polylactic acid, 2 parts plasticizer acetylated tributyl citrate, and 0.5 parts lubricant ethylene bis-stearamide for 5 minutes. Add the mixed raw material to a twin-screw extruder. The extrusion granulation conditions are as follows: Twin-screw extruder set temperature: Zone 1: 120℃, Zone 2: 150℃, Zone 3: 160℃, Zone 4: 170℃, Zone 5: 170℃, Zone 6: 170℃, Zone 7: 170℃, Die head: 170℃, Screw speed: 150 rpm. After melt extrusion, water cooling, and pelletizing, polylactic acid filler is obtained. The polylactic acid filler was dried in a constant temperature oven at 80°C for 5 hours, and then added to a blown film machine for blow molding. The set temperature of the blown film machine is: Zone 1: 155℃, Zone 2: 165℃, Zone 3: 165℃, Zone 4: 165℃, Zone 5: 160℃; Mold body: 160℃; Mold opening: 160℃; Screw speed: 100 rpm, traction speed: 15 m / min, inflation ratio: 2, cooling method: adopts a dual-air-outlet cooling ring, upper air outlet temperature: 20℃, lower air outlet temperature: 10℃, rapid cooling to obtain the drainage bag; Step 2: Mix sorbitan oleate and octylphenol polyoxyethylene ether at a weight ratio of 8:1, add 100 mL of cyclohexane, and stir and mix evenly at 45°C to obtain the oil phase; Perfluorooctyl ethyl acrylate was mixed with deionized water at a weight ratio of 1.2:10, and sodium phosphate was added at a total weight of 0.8 wt% of the deionized water. The mixture was ultrasonically dispersed in an ice-water bath for 25 min to obtain the aqueous phase. While stirring at 400 rpm, the aqueous phase was slowly added dropwise to the oil phase. After the addition was complete, emulsification was continued for 25 minutes to obtain an emulsion. Prepare a 0.15 mol / L silver nitrate ethanol solution, slowly add the silver nitrate ethanol solution dropwise to the above emulsion, then heat the system to 40℃ and continue the reaction for 4-5 hours; After the reaction was completed, 50 mL of anhydrous ethanol was added to break the emulsion, centrifuged, washed, and vacuum dried at 45 °C for 22 h to obtain functionalized microcapsules. Step 3: Weigh 1g of N-(2-hydroxyethyl)pyrrole, add it to 50mL of deionized water, add 0.4g of functionalized microcapsules; sonicate for 15min to obtain a dispersion containing microcapsules; Prepare a 0.04 mol / L silver nitrate aqueous solution, immerse the polylactic acid drainage bag in it, and soak at 50℃ for 15 min. While stirring at 200 rpm, slowly pour in the dispersion containing microcapsules, and continue stirring at 28℃ for 60 min. After the reaction is complete, remove the drainage bag, rinse with deionized water, and dry in a vacuum oven at 50℃ for 2 h to allow the coating to fully cure, thus obtaining the polylactic acid drainage bag.

[0025] Comparative Example 2: No microcapsule structure was introduced into the solution; only silver nitrate was added. The rest of the process was the same as in Example 1. Step 1: Mechanically blend 10 parts polylactic acid, 2 parts plasticizer acetylated tributyl citrate, and 0.5 parts lubricant ethylene bis-stearamide for 5 minutes. Add the mixed raw material to a twin-screw extruder. The extrusion granulation conditions are as follows: Twin-screw extruder set temperature: Zone 1: 120℃, Zone 2: 150℃, Zone 3: 160℃, Zone 4: 170℃, Zone 5: 170℃, Zone 6: 170℃, Zone 7: 170℃, Die head: 170℃, Screw speed: 150 rpm. After melt extrusion, water cooling, and pelletizing, polylactic acid filler is obtained. The polylactic acid filler was dried in a constant temperature oven at 80°C for 5 hours, and then added to a blown film machine for blow molding. The set temperature of the blown film machine is: Zone 1: 155℃, Zone 2: 165℃, Zone 3: 165℃, Zone 4: 165℃, Zone 5: 160℃; Mold body: 160℃; Mold opening: 160℃; Screw speed: 100 rpm, traction speed: 15 m / min, inflation ratio: 2, cooling method: adopts a dual-air-outlet cooling ring, upper air outlet temperature: 20℃, lower air outlet temperature: 10℃, rapid cooling to obtain the drainage bag; Step 2: Weigh 1g of N-(2-hydroxyethyl)pyrrole, add it to 50mL of deionized water, add 0.4g of functionalized microcapsules; sonicate for 15min to obtain a dispersion containing N-(2-hydroxyethyl)pyrrole; Prepare a 0.04 mol / L silver nitrate aqueous solution, immerse the polylactic acid drainage bag in it, and soak it at 50°C for 15 min. While stirring at 200 rpm, slowly pour in the dispersion containing N-(2-hydroxyethyl)pyrrole, and continue stirring at 28°C for 60 min. After the reaction is complete, remove the drainage bag, rinse it with deionized water, and dry it in a vacuum oven at 50°C for 2 h to allow the coating to fully cure, thus obtaining the polylactic acid drainage bag.

[0026] Comparative Example 3: No hydrophobic perfluorooctyl ethyl acrylate group was added to the microcapsules; all other aspects were the same as in Example 1. Specifically: Step 1: Mechanically blend 10 parts polylactic acid, 2 parts plasticizer acetylated tributyl citrate, and 0.5 parts lubricant ethylene bis-stearamide for 5 minutes. Add the mixed raw material to a twin-screw extruder. The extrusion granulation conditions are as follows: Twin-screw extruder set temperature: Zone 1: 120℃, Zone 2: 150℃, Zone 3: 160℃, Zone 4: 170℃, Zone 5: 170℃, Zone 6: 170℃, Zone 7: 170℃, Die head: 170℃, Screw speed: 150 rpm. After melt extrusion, water cooling, and pelletizing, polylactic acid filler is obtained. The polylactic acid filler was dried in a constant temperature oven at 80°C for 5 hours, and then added to a blown film machine for blow molding. The set temperature of the blown film machine is: Zone 1: 155℃, Zone 2: 165℃, Zone 3: 165℃, Zone 4: 165℃, Zone 5: 160℃; Mold body: 160℃; Mold opening: 160℃; Screw speed: 100 rpm, traction speed: 15 m / min, inflation ratio: 2, cooling method: adopts a dual-air-outlet cooling ring, upper air outlet temperature: 20℃, lower air outlet temperature: 10℃, rapid cooling to obtain the drainage bag; Step 2: Mix sorbitan oleate and octylphenol polyoxyethylene ether at a weight ratio of 8:1, add 100 mL of cyclohexane, and stir and mix evenly at 45°C to obtain the oil phase; Add 1.0 wt% sodium phosphate to deionized water and ultrasonically disperse in an ice-water bath for 25 min to obtain the aqueous phase. While stirring at 400 rpm, the aqueous phase was slowly added dropwise to the oil phase. After the addition was complete, emulsification was continued for 25 minutes to obtain an emulsion. Prepare a 0.15 mol / L silver nitrate ethanol solution, slowly add the silver nitrate ethanol solution dropwise to the above emulsion, then heat the system to 40℃ and continue the reaction for 4-5 hours; After the reaction was completed, 50 mL of anhydrous ethanol was added to break the emulsion, centrifuged, washed, and vacuum dried at 45 °C for 22 h to obtain functionalized microcapsules. Step 3: Weigh 1g of N-(2-hydroxyethyl)pyrrole, add it to 50mL of deionized water, add 0.4g of functionalized microcapsules; sonicate for 15min to obtain a dispersion containing microcapsules; Prepare a 0.04 mol / L silver nitrate aqueous solution, immerse the polylactic acid drainage bag in it, and soak at 50℃ for 15 min. While stirring at 200 rpm, slowly pour in the dispersion containing microcapsules. Continue stirring and react at 28℃ for 60 min. After the reaction is complete, remove the drainage bag, rinse with deionized water, and dry in a vacuum oven at 50℃ for 2 h to allow the coating to fully cure, thus obtaining the polylactic acid drainage bag.

[0027] Experiment: The antibacterial and hydrophobic effects of the polylactic acid drainage bags prepared in Examples 1-3 and Comparative Examples 1-3 were tested.

[0028] (1) In the antibacterial effect test, Escherichia coli was used as the strain. The polylactic acid drainage bag was placed in a container with Escherichia coli cultured. After 24 hours, the bacterial growth on the surface of the polylactic acid drainage bag was observed, and the proportion of the area on the packaging paper surface where no bacteria grew was recorded.

[0029] (2) In the hydrophobicity test, the water contact angle of the polylactic acid drainage bag was measured. (3) Referring to GB / T1040, the tensile strength of the polylactic acid drainage bag was tested under the condition of a tensile rate of 50 mm / min; the data obtained are shown in Table 1 below:

[0030] Conclusion: The test data above show that the polylactic acid drainage bag prepared by the coating technology of this invention forms a stable functional coating on its surface, exhibiting excellent antibacterial properties, with an antibacterial rate of ≥99.0% after 24 hours and very high hydrophobic properties, with a water contact angle ≥150°. This indicates that the product of this invention can effectively inhibit bacterial colonization and has excellent liquid anti-adhesion capabilities, thus providing antibacterial and hydrophobic properties for the drainage bag. Simultaneously, the tensile properties are generally excellent, indicating that the low-temperature, high-speed blow molding process improves the mechanical properties of the drainage bag.

[0031] In Comparative Example 1, the proportion of perfluorooctyl ethyl acrylate was significantly increased while the proportion of sodium phosphate was decreased during the preparation of microcapsules. Compared to Example 1, the coating surface prepared in Comparative Example 1 exhibited excellent hydrophobic properties due to the higher density of fluorinated groups. However, due to insufficient sodium phosphate content, the silver ions in the solution were not fully precipitated and fixed into stable silver phosphate, resulting in a significant reduction in the effective antibacterial load of the microcapsules.

[0032] Comparative Example 2 involved directly adding silver nitrate to the coating without preparing it into a microcapsule structure. Compared to Example 1, both its antibacterial and hydrophobic effects were significantly reduced. This indicates that the direct addition method cannot achieve uniform dispersion and long-lasting release of the antibacterial agent, and also lacks an effective hydrophobic structure.

[0033] Although Comparative Example 3 prepared a silver-containing microcapsule coating, no hydrophobic groups were introduced into the microcapsules. Compared with Example 1, although it maintained good antibacterial properties, its hydrophobic properties decreased significantly. This comparison proves that hydrophobic groups reduce the initial adhesion of bacteria to the surface, while the antibacterial microcapsules achieve highly efficient antibacterial activity against a small number of attached bacteria, thereby achieving a comprehensive protective effect.

[0034] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A low-temperature, high-speed blow molding method for a polylactic acid drainage bag, characterized in that: Includes the following steps: Step 1: Mechanically blend polylactic acid, plasticizer, and lubricant, extrude and granulate, water cool, and cut into pellets to obtain polylactic acid filler; dry the polylactic acid filler, blow mold it, and cool it after molding to obtain a drainage bag; Step 2: Immerse the drainage bag in silver nitrate aqueous solution, add the dispersion containing microcapsules, and stir continuously to react; after the reaction is completed, remove the drainage bag, vacuum dry and solidify to obtain polylactic acid drainage bag.

2. The low-temperature high-speed blow molding method for polylactic acid drainage bags according to claim 1, characterized in that: In step one, the extrusion granulation conditions are set as follows: Zone 1: 120-130℃, Zone 2: 150-160℃, Zone 3: 160-170℃, Zone 4: 170-175℃, Zone 5: 170-175℃, Zone 6: 170-175℃, Zone 7: 170-175℃, Die head: 170-175℃, Screw speed: 150-220 rpm.

3. The low-temperature high-speed blow molding method for polylactic acid drainage bags according to claim 1, characterized in that: In step one, the blow molding settings are as follows: Zone 1 temperature: 155~158℃, Zone 2: 165~170℃, Zone 3: 165~172℃, Zone 4: 165~175℃, Zone 5: 160~165℃; Mold body: 160~170℃. Die opening: 160~170℃; screw speed: 100~220rpm; traction speed: 15~25m / min; inflation ratio: 2~6.

4. The low-temperature high-speed blow molding method for polylactic acid drainage bags according to claim 1, characterized in that: In step two, the preparation process of the dispersion containing microcapsules is as follows: weigh 1-2g of N-(2-hydroxyethyl)pyrrole, add it to deionized water, add functionalized microcapsules and ultrasonically disperse for 15-25min to obtain a dispersion containing microcapsules.

5. The low-temperature high-speed blow molding method for polylactic acid drainage bags according to claim 4, characterized in that: The preparation process of the functionalized microcapsules is as follows: sorbitan oleate and octylphenol polyoxyethylene ether are mixed, cyclohexane is added, and the mixture is stirred until homogeneous to obtain an oil phase; perfluorooctyl ethyl acrylate is mixed with deionized water, sodium phosphate is added, and the mixture is ultrasonically dispersed to obtain an aqueous phase; under stirring, the aqueous phase is slowly added dropwise to the oil phase, and emulsification is continued after the addition is complete to obtain an emulsion; silver nitrate ethanol solution is added dropwise to the above emulsion, and the reaction is continued by heating; after the reaction is completed, anhydrous ethanol is added to break the emulsion, and the mixture is centrifuged, washed, and vacuum dried to obtain the functionalized microcapsules.

6. The low-temperature high-speed blow molding method for polylactic acid drainage bags according to claim 5, characterized in that: The weight ratio of the perfluorooctyl ethyl acrylate to deionized water to sodium phosphate is (0.9-1): 10：（0.1-0.15）。 7. The low-temperature high-speed blow molding method for polylactic acid drainage bags according to claim 1, characterized in that: In step two, the soaking parameters are: constant temperature at 50-55℃ for 15-20 minutes.

8. The low-temperature high-speed blow molding method for polylactic acid drainage bags according to claim 1, characterized in that: In step two, the concentration of the silver nitrate aqueous solution is 0.04-0.06 mol / L.

9. The low-temperature high-speed blow molding method for polylactic acid drainage bags according to claim 1, characterized in that: In step two, the parameters for the continuous stirring reaction are: reaction at 28-35℃ for 60-90 minutes.

10. The low-temperature high-speed blow molding method for polylactic acid drainage bags according to claim 1, characterized in that: The polylactic acid filler comprises the following components, in parts by weight: 10-25 parts polylactic acid, 2-4 parts plasticizer, and 0.5-2 parts lubricant.

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