Polymer film, preparation method thereof and application of polymer film in hygienic product absorption pad

Abstract

The invention relates to the technical field of hygienic product absorption pads, and particularly discloses a polymer film, a preparation method thereof and application of the polymer film in the hygienic product absorption pads. The polymer film is formed by blending and processing polylactic acid and chitosan, the preparation method of the polymer film comprises the steps of preparing a chitosan solution, preparing a polylactic acid emulsion, preparing a chitosan / polylactic acid mixed solution and forming a film, the raw materials are rich, easy to obtain and low in price, the adopted raw materials are easy to degrade, the cost is low, and the polymer film is environment-friendly. And the polymer film can be effectively biodegraded, so that the later treatment of sanitary pad waste materials is facilitated, the environment is not influenced, and a good application prospect is achieved. The polymer film provided by the invention has obvious antibacterial ability, good antibacterial broad-spectrum property, and obvious antibacterial activity on candida albicans and escherichia coli, reduces bacterial breeding, improves the ability of a user to resist various gynecological diseases in the menstrual period, and ensures female health.

Description

TECHNICAL FIELD

[0001] The embodiment of the present application belongs to the technical field of sanitary product absorbent pad, and particularly relates to a polymer film, a preparation method thereof and application of the polymer film to a sanitary product absorbent pad. BACKGROUND

[0002] With the improvement of people's living standards and the enhancement of health awareness, the demand for personal hygiene products, especially sanitary napkins, is increasing. As a necessity in women's life, sanitary napkins play a crucial role in protecting women's reproductive health, and their antibacterial performance, air permeability and other characteristics directly affect the comfort and health of users. During the menstrual period, women have relatively weak resistance, while the environment where the sanitary napkin is located is warm, humid and rich in nutrients, which is very suitable for the breeding of bacteria. If the sanitary napkin does not have good antibacterial performance, the large number of bacteria may cause the female external genitalia to itch and become red and swollen, and even cause gynecological diseases such as vaginitis and cervicitis. Therefore, the sanitary napkin needs to use antibacterial layer technology to reduce bacterial breeding and protect women's health. The material science background of the sanitary napkin antibacterial layer technology involves antibacterial mechanism, material classification, key performance requirements, etc., and the core is to achieve the balance between efficient antibacterial, safety and functionality through material design.

[0003] In the prior art, according to the source and chemical structure of the material, the antibacterial layer material includes inorganic antibacterial material, organic antibacterial material, natural antibacterial material, etc. However, the antibacterial layer materials existing on the market all have problems such as low antibacterial effect, low safety and economy. In addition, some sanitary napkin antibacterial layer materials prepared by using modified polymer materials, natural extracts or composite antibacterial agents and other components may contain formaldehyde and organic solvents, and inferior products may cause skin allergy or contact dermatitis. The main problems include chemical reagent risk, low antibacterial durability, poor use experience, etc. Moreover, most polymer materials (such as PE and PP) are petroleum-based plastics and are difficult to degrade naturally, which may cause environmental pollution after being discarded.

[0004] Therefore, the prior art in the above has the following defects: the antibacterial layer material of the sanitary napkin absorbent pad or the existing design of the antibacterial layer in the prior art has the problems of high cost, low antibacterial spectrum and difficulty in natural degradation. Therefore, it is of great significance to develop a sanitary product absorbent pad antibacterial layer material with low cost, good antibacterial performance and natural degradation for ensuring women's menstrual health and avoiding environmental pollution. SUMMARY

[0005] The embodiment of the present application aims to provide a polymer film, a preparation method thereof and application of the polymer film to a sanitary product absorbent pad, so as to solve the problems of high cost, low antibacterial spectrum and difficulty in natural degradation of the antibacterial layer material of the sanitary napkin absorbent pad or the existing design of the antibacterial layer in the prior art proposed in the background.

[0006] To achieve the above objectives, the embodiments of the present invention provide the following technical solutions:

[0007] A polymer film, wherein the polymer film is formed by blending polylactic acid and chitosan, wherein the chitosan has a molecular weight of 50-190 kDa and a degree of deacetylation ≥85%.

[0008] In this embodiment of the invention, polylactic acid particles with an intrinsic viscosity of 0.8-1.2 dL / g are selected.

[0009] Another objective of this invention is to provide a method for preparing a polymer film, comprising the following steps:

[0010] (1) Preparation of chitosan solution: Measure the acetic acid solution and transfer it into an Erlenmeyer flask. Then weigh the chitosan powder for later use. Place the Erlenmeyer flask on a magnetic stirrer and slowly add the weighed chitosan powder while stirring continuously until the solution is transparent, uniform and free of particles and bubbles. This gives you the chitosan solution.

[0011] (2) Preparation of polylactic acid emulsion: Weigh a certain amount of polylactic acid and add it to chromatographic grade chloroform. Stir and dissolve it in a water bath at 35-45℃ to obtain polylactic acid / chloroform solution. At the same time, prepare polyvinyl alcohol solution. Dissolve polyvinyl alcohol in deionized water, filter and set aside. Slowly add the polylactic acid / chloroform solution to the polyvinyl alcohol solution for emulsification and concentration to obtain polylactic acid emulsion.

[0012] (3) Preparation of chitosan / polylactic acid mixed solution: Take the polylactic acid emulsion and chitosan solution prepared in the above steps and mix them until the solution is uniformly milky white and there is no phase separation. The mixing process is carried out in a glass container with a lid to prevent solvent evaporation, and chitosan / polylactic acid mixed solution is obtained.

[0013] (4) Control the ambient temperature to 23-27℃ and the ambient humidity to 45-55%RH. Place the chitosan / polylactic acid mixed solution prepared in step (3) into a mold, adjust the film thickness using an automatic coating machine, and cast and dry to obtain a polymer film.

[0014] In step (4), if the polymer film material cracks, it can be solved by reducing the drying rate or adding a plasticizer; and ultrasonic degassing of the chitosan / polylactic acid mixed solution before casting helps to solve the bubble problem.

[0015] Preferably, step (1) of preparing the chitosan solution is as follows: 100 mL of acetic acid solution is transferred to a 250 mL conical flask, and then 2 g of chitosan powder is weighed for later use. The conical flask is placed on a magnetic stirrer, and the speed is set to 450-550 rpm. During continuous stirring, the weighed chitosan powder is slowly added. The temperature is controlled at 23-27℃ throughout the stirring process, and the stirring is carried out for 2-3 hours.

[0016] Preferably, the chitosan solution prepared in step (1) has a pH value of 4-5, and the prepared chitosan solution is stored at 4°C and used up within 24 hours to ensure the freshness of the chitosan solution and thus guarantee the antibacterial properties of the polymer film.

[0017] The preparation of polylactic acid emulsion in step (2) is as follows: Weigh 5g of polylactic acid and add it to 100mL of chromatographic grade chloroform. Place it in a water bath at 35-45℃ and stir to dissolve to obtain a polylactic acid / chloroform solution. At the same time, prepare a polyvinyl alcohol solution by dissolving 2g of polyvinyl alcohol in 100mL of deionized water at 75-85℃ and stirring magnetically at 350-450rpm for 1-2 hours until completely dissolved. After the solution is cooled to room temperature, filter it through a 0.4-0.5μm filter membrane for later use. Slowly add the polylactic acid / chloroform solution to the polyvinyl alcohol solution for emulsification and concentration to obtain a polylactic acid emulsion.

[0018] Preferably, during emulsification, a high-shear dispersing emulsifier with a rotation speed of 8000-12000 rpm is used to slowly add the polylactic acid / chloroform solution to the polyvinyl alcohol solution at a rate of 1-1.5 mL / min, maintaining the emulsification temperature at 24-26℃ throughout the process. After the addition is completed, emulsification is continued for 25-35 min. The concentration process uses rotary evaporation, with the water bath temperature set at 30-40℃, the rotation speed at 120 rpm, and the vacuum degree at 200 mbar. Concentration is considered complete when the emulsion volume decreases to 50 mL. The polyvinyl alcohol used is polyvinyl alcohol with a degree of alcoholysis of 88%.

[0019] In step (3), a mother liquor is prepared by mixing polylactic acid emulsion and chitosan solution. 80 mL of polylactic acid emulsion and 20 mL of chitosan solution are mixed to prepare a basic mother liquor. Then, a chitosan / polylactic acid mixed solution containing different concentrations of chitosan is prepared by gradient dilution.

[0020] It should be noted that a base stock solution was prepared by mixing 80 mL of polylactic acid (PLA) emulsion with 20 mL of chitosan solution, labeled as 20% chitosan / PLA. To obtain mixed solutions with different amounts of chitosan, a gradient dilution method can be used: mix 50 mL of the base stock solution with 50 mL of PLA emulsion (by adding PLA emulsion to dilute the concentration of the base stock solution, labeled as 10% chitosan / PLA); mix 25 mL of the base stock solution with 75 mL of PLA emulsion (further increasing the amount of PLA emulsion to dilute the concentration of the base stock solution, labeled as 5% chitosan / PLA). The gradient dilution method improves the accuracy and repeatability of experiments due to its precise concentration control, ease of operation, and wide applicability.

[0021] Another objective of this invention is to provide an application of a polymer film in absorbent pads for sanitary products. Preferably, the absorbent pads include sanitary napkins, diapers, disposable underwear, and panty liners. Its unique feature lies in the fact that chitosan is a natural high-molecular-weight polysaccharide, chemically named polyglucosamine (1-4)-2-amino-BD-glucose, obtained from chitin through deacetylation. Chitin is widely found in the shells of crustaceans (such as shrimp and crab), insect epidermis, and fungal cell walls, and is the second largest natural polysaccharide after cellulose. The positive charge of chitosan can adsorb onto the negatively charged surface of bacteria, disrupting bacterial cell membranes and inhibiting bacterial metabolism; simultaneously, it promotes platelet aggregation and accelerates coagulation. This invention uses the natural polymer material chitosan and biodegradable polylactic acid to develop a film material with antibacterial, absorbent, and biodegradable properties. Its application in the field of sanitary products, particularly the antibacterial layer of sanitary napkins, effectively inhibits the metabolism of Candida albicans and Escherichia coli, exhibiting good broad-spectrum antibacterial activity.

[0022] Compared with the prior art, the beneficial effects of the embodiments of the present invention are:

[0023] The raw materials used in this invention are abundant, readily available, and inexpensive, offering good economic prospects. Furthermore, the polymer film, made from easily degradable raw materials, is effectively biodegradable, facilitating the disposal of waste sanitary pad materials and minimizing environmental impact.

[0024] The preparation method of the polymer film in this invention is simple and easy to operate, making it suitable for mass production. Furthermore, the polymer film possesses significant antibacterial capabilities and exhibits good broad-spectrum antibacterial activity, showing significant inhibitory effects against Candida albicans and Escherichia coli, reducing bacterial growth, improving users' ability to resist various gynecological diseases during menstruation, and ensuring consumer health. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention.

[0026] Figure 1 The images show the appearance of the polymer films prepared in Examples 1, 2, and 3 of this invention, as well as the polylactic acid film prepared in Comparative Example 1.

[0027] Figure 2 The images show the surface morphology of the polymer films prepared in Examples 1, 2, and 3 of this invention, as well as the polylactic acid film prepared in Comparative Example 1, using scanning electron microscopy (SEM).

[0028] Figure 3 Microscopic images of the polymer films prepared in Examples 1, 2, and 3 of this invention on day 0 and day 30 after being buried in soil.

[0029] Figure 4 The graphs show the quantitative analysis of the biodegradation of the polymer films prepared in Examples 1, 2, and 3 of this invention, and the polylactic acid film prepared in Comparative Example 1, after being buried in soil on day 0 and day 30.

[0030] Figure 5 The results of mechanical property tests are given for the polymer films prepared in Examples 1, 2, and 3 of this invention and the polylactic acid film prepared in Comparative Example 1.

[0031] Figure 6 The results of water absorption performance tests are shown for the polymer films prepared in Examples 1, 2, and 3 of this invention and the polylactic acid film prepared in Comparative Example 1. Detailed Implementation

[0032] To make the technical problems, technical solutions, and beneficial effects of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the following embodiments will help those skilled in the art to further understand the embodiments of this invention, but do not limit the embodiments of this invention in any way. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the embodiments of this invention. These all fall within the protection scope of the embodiments of this invention.

[0033] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0034] First, it's important to clarify that existing antibacterial layers in sanitary napkins utilize a variety of technologies, primarily including: traditional antibacterial technology, nanomaterial antibacterial technology, and composite material antibacterial technology. Traditional antibacterial technology for sanitary napkins is relatively simple, mainly involving the addition of traditional antibacterial agents such as quaternary ammonium salts and phenols to the sanitary napkin material. Composite material antibacterial technology typically uses antibacterial layers made from polymeric materials, natural extracts, or compound antibacterial agents. Polymer antibacterial materials, through chemical modification or the addition of antibacterial agents, are a core component of the antibacterial layer in sanitary napkins. Common types include: 1. Polyethylene (PE) / polypropylene (PP) composite fibers treated with antibacterial agents (such as silver ions, copper ions, etc.) can achieve an antibacterial effect by contacting bacteria and disrupting their cell membranes or inhibiting enzyme activity. This provides long-lasting antibacterial protection, is washable, and inhibits common bacteria such as Escherichia coli and Staphylococcus aureus. 2. Polyester fiber modified materials, through copolymerization or coating processes, introduce antibacterial groups (such as quaternary ammonium salt compounds), which disrupt bacterial structures through charge adsorption. It is designed for use on skin-friendly surfaces, has a soft texture, and reduces friction and irritation. It has high antibacterial efficiency and also has a certain inhibitory effect on fungi (such as Candida albicans).

[0035] However, research has found that formaldehyde and organic solvents may remain during the modification process of polymer materials. Inferior products may cause skin allergies or contact dermatitis. The main problems with polymer antibacterial materials include the risk of chemical reagents, low antibacterial durability, and poor user experience. Most polymer materials (such as PE and PP) are petroleum-based plastics, which are difficult to degrade naturally and may cause environmental pollution after disposal. In addition, in polymer antibacterial layers modified with nanomaterials, nano-sized antibacterial particles (such as nano-silver) may release microplastics as the product wears down and enter the water cycle system, posing an ecological safety hazard.

[0036] Furthermore, the main problems with polymeric antibacterial materials include the risks associated with chemical reagents, low antibacterial durability, and poor user experience. Potential risks of some antibacterial agents include: quaternary ammonium compounds (such as benzalkonium chloride) may disrupt the vaginal microecological balance, and long-term use may increase the risk of gynecological inflammation. Metal ions (such as silver and copper ions), if not properly controlled for sustained release, may be absorbed through the mucous membrane, raising concerns about bioaccumulation toxicity. Formaldehyde and organic solvents (such as DMF) may remain during the modification process of polymeric materials; inferior products may cause skin allergies or contact dermatitis.

[0037] Furthermore, surface-coated antibacterial agents (such as silver ion coatings) are easily rubbed off by friction and menstrual blood, and their antibacterial effectiveness typically only lasts for 2-4 hours, requiring frequent changes of sanitary napkins. In hot and humid environments (such as summer), polymer materials may degrade, leading to the inactivation of antibacterial groups. They also lack broad-spectrum activity: their inhibitory effect on fungi (such as Candida albicans) and viruses (such as HPV) is limited, failing to address the complex microbial environment during menstruation. Moreover, most of these antibacterial layers offer a poor user experience. Modified polypropylene (PP) fibers, while antibacterial, have poor breathability, easily causing stuffiness and increasing menstrual discomfort. Polyester fiber (polyester) antibacterial layers have weak moisture absorption, posing a higher risk of menstrual blood backflow and affecting dryness. Multi-layered composite structures (such as antibacterial layer + diversion layer + absorbent layer) require special bonding processes, potentially increasing product thickness or hardness and reducing softness. Most polymer materials (such as PE and PP) are petroleum-based plastics, difficult to degrade naturally, and may cause environmental pollution after disposal. Furthermore, in polymeric antibacterial layers modified with nanomaterials, nanoscale antibacterial particles (such as nano-silver) may release microplastics as the product wears down, entering the water circulation system and posing an ecological safety hazard. Some plant-derived antibacterial materials, such as volatile oils (e.g., tea tree oil, peppermint oil), are prone to volatilization due to light and high temperatures, and their antibacterial effect rapidly diminishes after opening, requiring cold chain storage or special packaging. Polyphenols (such as tea polyphenols) are easily oxidized and inactivated in the alkaline menstrual blood environment and have a narrow pH adaptability. Moreover, plant extracts may react chemically with polymer matrices (such as PVA), leading to darkening of color and the development of odors, affecting the product's sensory appeal. The main problems include: poor stability of antibacterial components, limited broad-spectrum activity, and complex processing techniques. Therefore, developing a low-cost, high-performance, and biodegradable antibacterial layer material for hygiene products is an urgent problem to be solved, and is of great significance for ensuring women's menstrual health and avoiding environmental pollution.

[0038] Therefore, in order to solve the problems of high cost, low antibacterial spectrum, and difficulty in natural degradation of the existing antibacterial layer materials or designs of sanitary napkin absorbent pads, the present invention provides a polymer film and its preparation method and its application in sanitary absorbent pads. The polymer film is made by blending polylactic acid and chitosan. The chitosan has a molecular weight of 50-190kDa and a degree of deacetylation ≥85%.

[0039] In another preferred embodiment of the present invention, the polylactic acid is selected from polylactic acid particles with an intrinsic viscosity of 0.8-1.2 dL / g.

[0040] This invention also provides a method for preparing a polymer film, comprising the following steps:

[0041] (1) Preparation of chitosan solution: Measure the acetic acid solution and transfer it into an Erlenmeyer flask. Then weigh the chitosan powder for later use. Place the Erlenmeyer flask on a magnetic stirrer and slowly add the weighed chitosan powder while stirring continuously until the solution is transparent, uniform and free of particles and bubbles. This gives you the chitosan solution.

[0042] (2) Preparation of polylactic acid emulsion: Weigh a certain amount of polylactic acid and add it to chromatographic grade chloroform. Stir and dissolve it in a water bath at 35-45℃ to obtain polylactic acid / chloroform solution. At the same time, prepare polyvinyl alcohol solution. Dissolve polyvinyl alcohol in deionized water, filter and set aside. Slowly add the polylactic acid / chloroform solution to the polyvinyl alcohol solution for emulsification and concentration to obtain polylactic acid emulsion.

[0043] (3) Preparation of chitosan / polylactic acid mixed solution: Take the polylactic acid emulsion and chitosan solution prepared in the above steps and mix them until the solution is uniformly milky white and there is no phase separation. The mixing process is carried out in a glass container with a lid to prevent solvent evaporation, and chitosan / polylactic acid mixed solution is obtained.

[0044] (4) Control the ambient temperature to 23-27℃ and the ambient humidity to 45-55%RH. Place the chitosan / polylactic acid mixed solution prepared in step (3) into a mold, adjust the film thickness using an automatic coating machine, and cast and dry to obtain a polymer film.

[0045] In another preferred embodiment of the present invention, step (1) of preparing the chitosan solution is as follows: 100 mL of acetic acid solution is transferred to a 250 mL Erlenmeyer flask, and then 2 g of chitosan powder is weighed for later use. The Erlenmeyer flask is placed on a magnetic stirrer, and the speed is set to 450-550 rpm. During continuous stirring, the weighed chitosan powder is slowly added. The temperature is controlled at 23-27°C throughout the stirring process, and the stirring is carried out for 2-3 hours. Furthermore, the pH value of the prepared chitosan solution is 4-5, and the prepared chitosan solution is stored at 4°C and used within 24 hours to ensure the freshness of the chitosan solution and to guarantee the antibacterial properties of the polymer film.

[0046] As another preferred embodiment of the present invention, step (2) of preparing polylactic acid emulsion is as follows: 5g of polylactic acid is weighed and added to 100mL of chromatographic grade chloroform, and stirred and dissolved in a water bath at 35-45℃ to obtain a polylactic acid / chloroform solution. At the same time, a polyvinyl alcohol solution is prepared by dissolving 2g of polyvinyl alcohol in 100mL of deionized water at 75-85℃ and stirring magnetically at 350-450rpm for 1-2 hours until completely dissolved. After the solution is cooled to room temperature, it is filtered through a 0.4-0.5μm filter membrane for later use. The polylactic acid / chloroform solution is slowly added dropwise to the polyvinyl alcohol solution for emulsification and concentration to obtain a polylactic acid emulsion.

[0047] In another preferred embodiment of the present invention, during emulsification, a high-shear dispersing emulsifier with a rotation speed of 8000-12000 rpm is used to slowly add the polylactic acid / chloroform solution to the polyvinyl alcohol solution at a rate of 1-1.5 mL / min, maintaining the emulsification temperature at 24-26℃ throughout the process. After the addition is completed, emulsification is continued for 25-35 min. The concentration process adopts the rotary evaporation method, setting the water bath temperature to 30-40℃, the rotation speed to 120 rpm, and the vacuum degree to 200 mbar. The concentration is completed when the emulsion volume decreases to 50 mL. The polyvinyl alcohol used is polyvinyl alcohol material with a degree of alcoholysis of 88%.

[0048] In another preferred embodiment of the present invention, step (3) involves mixing 80 mL of polylactic acid emulsion with 20 mL of chitosan solution to prepare a basic stock solution, labeled as 20% chitosan / polylactic acid. To obtain mixed solutions with different amounts of chitosan, a gradient dilution method can be used: 50 mL of the basic stock solution is mixed with 50 mL of polylactic acid emulsion (the concentration of the basic stock solution is diluted by adding polylactic acid emulsion, labeled as 10% chitosan / polylactic acid); 25 mL of the basic stock solution is mixed with 75 mL of polylactic acid emulsion (the amount of polylactic acid emulsion is further increased to dilute the concentration of the basic stock solution, labeled as 5% chitosan / polylactic acid). The gradient dilution method improves the accuracy and repeatability of the experiment due to its precise concentration control, ease of operation, and wide applicability.

[0049] This invention also provides a polymer film material prepared by the above-described preparation method.

[0050] The present invention also provides an application of the above-mentioned polymer film material in absorbent pads for sanitary products, particularly the application of the polymer film in the antibacterial absorbent pads of sanitary napkins, diapers, disposable underwear, and panty liners.

[0051] It should be noted that the preparation method used in this invention is simple to operate. When applied to feminine sanitary pads, it can reduce the manufacturing cost of antibacterial sanitary napkins. The polymer film has obvious antibacterial ability and good broad-spectrum antibacterial properties. It has significant antibacterial performance against Candida albicans and Escherichia coli, thereby improving the antibacterial performance of sanitary pads. Furthermore, it is easy to integrate with other layers of sanitary napkins, which is conducive to its widespread application.

[0052] The technical effects of the polymer film of the present invention will be further illustrated below by listing specific embodiments. The specific preparation process of the polymer film of the present invention is as follows:

[0053] (1) Preparation of chitosan solution

[0054] Prepare a calibrated electronic balance with an accuracy of 0.01 g; prepare chitosan powder with a molecular weight of 50-190 kDa and a degree of deacetylation ≥85%. The specific operating steps are as follows: Accurately measure 100 mL of 1% (v / v) acetic acid solution into a 250 mL Erlenmeyer flask using a graduated cylinder. Then, accurately weigh 2.00 g of chitosan powder using an analytical balance. Place the Erlenmeyer flask on a magnetic stirrer, set the speed to 500 rpm, and slowly add the weighed chitosan powder while continuously stirring. Maintain the temperature at 25 ± 2℃ throughout the stirring process. After continuous stirring for 2 hours, the solution should be transparent, homogeneous, and free of particles and bubbles. Use a pH meter to check the pH value of the solution; the normal value is approximately 4.5. If dissolution is incomplete, extend the stirring time to 3 hours. Store the prepared solution at 4℃ and use it within 24 hours.

[0055] (2) Preparation of polylactic acid emulsion

[0056] During the experiment, PLA particles with an intrinsic viscosity of 0.8-1.2 dL / g should be selected, and the operation should be carried out in a fume hood using glass containers. Accurately weigh 5.00±0.05g of PLA and add it to 100mL of chromatographic grade chloroform. Place the solution in a 40℃ water bath and stir at 300rpm to promote dissolution, which takes approximately 30 minutes. Simultaneously prepare the PVA solution: Select PVA material with a degree of alcoholysis of 88%, add 2.00g of PVA to 100mL of 80℃ deionized water, and magnetically stir at 400rpm for approximately 1 hour until completely dissolved. After the solution cools to room temperature, filter it through a 0.45μm filter membrane for later use. For emulsification, use a high-shear dispersing emulsifier (10000rpm) to slowly add the PLA-chloroform solution dropwise to the PVA solution at a rate of 1mL / min, maintaining the emulsification temperature within the range of 25±1℃ throughout the process. After the addition is complete, continue emulsification for 30 minutes. The subsequent concentration process employed rotary evaporation, with parameters set at 35°C water bath, 120 rpm rotation speed, and 200 mbar vacuum. The concentration endpoint was determined by observing the emulsion volume decrease to approximately 50 mL (at which point the solid content was approximately 10%). Strict control of all process parameters was necessary throughout the entire operation to ensure the accuracy and reproducibility of the experimental results.

[0057] (3) Preparation of chitosan / polylactic acid mixed solution

[0058] A base stock solution was prepared by mixing 80 mL of polylactic acid (PLA) emulsion with 20 mL of chitosan solution, labeled as 20% chitosan / PLA. To obtain mixed solutions with different amounts of chitosan, a gradient dilution method can be used: 50 mL of the base stock solution was mixed with 50 mL of PLA emulsion (the concentration of the base stock solution was diluted by adding PLA emulsion, labeled as 10% chitosan / PLA); 25 mL of the base stock solution was mixed with 75 mL of PLA emulsion (further increasing the amount of PLA emulsion to dilute the concentration of the base stock solution, labeled as 5% chitosan / PLA). After each dilution, vortexing for 1 minute was required to ensure uniform mixing. The mixing process was carried out in a covered glass container to prevent solvent evaporation, with a stirring speed of 400 ± 50 rpm and a mixing time of 30 ± 5 minutes. The endpoint of mixing was determined when the solution was a homogeneous milky white color without phase separation.

[0059] (4) Film forming process

[0060] The experiment used a 10×10cm polytetrafluoroethylene mold. The mold was pre-cleaned with ethanol and thoroughly dried. Alternatively, silanization treatment can be used to improve demolding efficiency. During casting, the casting volume was controlled at 20mL / 100cm. ² An automatic coating machine was used to precisely adjust the doctor blade gap to 500 μm to ensure uniform film thickness. After casting, the film was allowed to stand for 10 minutes to eliminate air bubbles. The drying process consisted of two stages: first, drying at 25℃ and 50% relative humidity for 12 hours, followed by treatment in a 40℃ vacuum drying oven for 6 hours. The drying endpoint was determined by a film weight change rate of less than 0.5% / h. After film formation, the thickness was measured at multiple points using a micrometer, with the average thickness controlled within the range of 100±10 μm and the coefficient of variation (CV) less than 5%. All operations involving organic solvents were performed in an explosion-proof fume hood. The temperature and humidity of the experimental environment were controlled (maintained at 25±2℃, 50±5%RH). Phase separation could be improved by adding 0.1% Tween 80; film cracking could be addressed by reducing the drying rate or adding a plasticizer; ultrasonic degassing before casting resolved the air bubble problem.

[0061] It should be noted that the polymer film preparation method of this invention uses a solvent method.

[0062] Example 1

[0063] A method for preparing a polymer film includes the following steps:

[0064] (1) Preparation of chitosan solution: Measure 100 mL of acetic acid solution and transfer it to a 250 mL conical flask. Then weigh 2 g of chitosan powder for later use. Place the conical flask on a magnetic stirrer and set the speed to 500 rpm. Slowly add the weighed chitosan powder during continuous stirring. The temperature is controlled at 25℃ throughout the stirring process. Stir for 2 hours. The pH value of the chitosan solution is 4.5. If the dissolution is incomplete, extend the stirring time to 3 hours. Store the prepared chitosan solution at 4℃ and use it within 24 hours.

[0065] (2) Preparation of polylactic acid emulsion: During the experiment, glass containers were used in a fume hood. 5g of polylactic acid was weighed and added to 100mL of chromatographic grade chloroform. The mixture was placed in a 40℃ water bath and stirred at 300rpm to promote dissolution, resulting in a polylactic acid / chloroform solution. Simultaneously, a polyvinyl alcohol solution was prepared using polyvinyl alcohol with a degree of hydrolysis of 88%. 2g of polyvinyl alcohol was dissolved in 100mL of 80℃ deionized water and magnetically stirred at 400rpm for 1.5h until completely dissolved. After the solution cooled to room temperature, it was filtered through a 0.45μm filter membrane for later use. The acid / chloroform solution was slowly added dropwise to the polyvinyl alcohol solution for emulsification. During emulsification, a high-shear dispersing emulsifier with a rotation speed of 10,000 rpm was used to slowly add the polylactic acid / chloroform solution to the polyvinyl alcohol solution at a rate of 1 mL / min. The emulsification temperature was maintained at 25°C throughout the process. After the addition was completed, the emulsification process was continued for 30 min. After the emulsification was completed, the solution was concentrated. The subsequent concentration process used the rotary evaporation method, with the water bath temperature set at 35°C, the rotation speed at 120 rpm, and the vacuum degree at 200 mbar. The concentration was completed when the emulsion volume decreased to 50 mL, and a polylactic acid emulsion was obtained.

[0066] (3) Preparation of chitosan / polylactic acid mixed solution: Take 80 mL of polylactic acid emulsion and mix it with 20 mL of chitosan solution to prepare a basic stock solution (labeled as 20% chitosan / polylactic acid). The mixing process is carried out in a glass container with a lid to prevent solvent evaporation. The stirring speed is set to 400 rpm and the mixing time is 30 minutes. The mixing endpoint is judged when the solution is uniformly milky white and there is no phase separation, thus obtaining the chitosan / polylactic acid mixed solution;

[0067] (4) Control the temperature and humidity of the experimental environment (maintain at 25℃, 50%RH). Use a 10×10cm polytetrafluoroethylene mold. The mold should be cleaned with ethanol and thoroughly dried beforehand. Silanization treatment can also be used to improve the demolding effect. Control the casting volume to 20mL / 100cm during the casting process. ²An automatic coating machine was used to precisely adjust the doctor blade gap to 500 μm to ensure uniform film thickness. After casting, the film was allowed to stand for 10 minutes to eliminate air bubbles. The drying process consisted of two stages: first, drying at 25℃ and 50% relative humidity for 12 hours, followed by treatment in a 40℃ vacuum drying oven for 6 hours. The drying endpoint was determined by a film weight change rate of less than 0.5% / h. After film formation, the thickness was measured at multiple points using a micrometer, with the average thickness controlled within the range of 100±10 μm and the coefficient of variation (CV) less than 5%. All operations involving organic solvents were performed in an explosion-proof fume hood, ultimately yielding a polymer film.

[0068] Example 2

[0069] Compared with Example 1, everything is the same except for step (3).

[0070] In step (3) of this embodiment, a chitosan / polylactic acid (PLA) mixed solution is prepared: 80 mL of PLA emulsion is mixed with 20 mL of chitosan solution to prepare a base stock solution (labeled as 20% chitosan / PLA). To obtain mixed solutions with different amounts of chitosan, a gradient dilution method can be used: 50 mL of base stock solution is mixed with 50 mL of PLA emulsion (the concentration of the base stock solution is diluted by adding PLA emulsion, labeled as 10% chitosan / PLA); 25 mL of base stock solution is mixed with 75 mL of PLA emulsion (the amount of PLA emulsion is further increased to dilute the concentration of the base stock solution, labeled as 5% chitosan / PLA). After dilution, vortexing is required for 1 minute to ensure uniform mixing. The mixing process is carried out in a glass container with a lid to prevent solvent evaporation. The stirring speed is set to 400 rpm, and the mixing time is 30 minutes. The solution is kept uniformly milky white without phase separation to obtain the chitosan / PLA mixed solution.

[0071] Example 3

[0072] Compared with Example 1, everything is the same except for step (3).

[0073] In step (3) of this embodiment, a chitosan / polylactic acid (PLA) mixed solution is prepared: 80 mL of PLA emulsion is mixed with 20 mL of chitosan solution to prepare a base stock solution (labeled as 20% chitosan / PLA). To obtain mixed solutions with different amounts of chitosan, a gradient dilution method can be used: 50 mL of base stock solution is mixed with 50 mL of PLA emulsion (the concentration of the base stock solution is diluted by adding PLA emulsion, labeled as 10% chitosan / PLA); 25 mL of base stock solution is mixed with 75 mL of PLA emulsion (the amount of PLA emulsion is further increased to dilute the concentration of the base stock solution, labeled as 5% chitosan / PLA). After dilution, vortexing is required for 1 minute to ensure uniform mixing. The mixing process is carried out in a glass container with a lid to prevent solvent evaporation. The stirring speed is set to 400 rpm, and the mixing time is 30 minutes. The solution is kept uniformly milky white without phase separation to obtain the chitosan / PLA mixed solution.

[0074] Comparative Example 1

[0075] Compared with Example 1, except that chitosan is not added to the raw materials, all other steps and methods and the amount of raw materials are the same.

[0076] I. To record the morphology of the polymer films, the polymer films prepared in Examples 1, 2, 3, and Comparative Example 1 were compared. First, the appearance of the polymer films prepared in Examples 1, 2, 3, and Comparative Example 1 was photographed and recorded, as follows: Figure 1 As shown, the polymer film was then characterized using a scanning electron microscope. The image shows a SEM image of the prepared polymer film. Figure 2 SEM images show the surface morphology of chitosan / polylactic acid films containing different amounts of chitosan.

[0077] II. To verify the biodegradability, the polymer films prepared in Examples 1, 2, 3 and Comparative Example 1 were subjected to biodegradability verification.

[0078] The polymer films prepared in Examples 1, 2, 3, and Comparative Example 1 were buried in soil under the same conditions (humidity, temperature, depth, light, etc.). The experimental conditions were: room temperature 25±5 degrees Celsius, 50±5%RH, depth 70 cm, and natural indoor light. The polymer films were characterized by optical microscopy on day 0 (before burial) and day 30. Figure 3Microscopic images of the polymer film are shown on day 0 (before burial) and day 30 after burial. Optical microscope images reveal the biodegradation of polymer films containing different amounts of chitosan. The images generally indicate that biodegradation occurs in polymer films with varying chitosan content, such as reduced surface smoothness, cracking, and structural disintegration in some areas. The experimental results suggest that the polymer film may be effectively degraded by microorganisms in the natural environment.

[0079] Next, we quantitatively analyzed the degree of biodegradation. The polymer films from different time points in the above landfill experiment were retrieved, and the samples were washed with soil, dried, and finally their mass was measured. The experimental results are as follows: Figure 4 As shown in the figure. Experimental results indicate that the pure PLA polymer film exhibited the highest degree of degradation, with only approximately 50.65 mg remaining after 30 days of landfill (from an initial mass of 93.55 mg). Chitosan / polylactic acid polymer films containing different amounts of chitosan all showed varying degrees of mass reduction: the 5% chitosan / polylactic acid polymer film had approximately 60.3 mg remaining after 30 days; the 20% chitosan / polylactic acid film showed the lowest degree of degradation, still retaining approximately 72.30 mg remaining after 30 days. Although the incorporation of chitosan reduced the degree of biodegradation, the biodegradation effect could be controlled by adjusting the chitosan ratio, and the biodegradation rates of several chitosan / polylactic acid polymers were close to those of pure PLA. These experimental results demonstrate that chitosan / polylactic acid films can be effectively biodegraded and have the potential to solve the problem of future sanitary pad waste material disposal.

[0080] III. In order to verify the antibacterial properties and broad-spectrum activity, the polymer films prepared in Examples 1, 2, 3 and Comparative Example 1 were tested for antibacterial properties and broad-spectrum activity.

[0081] Next, the antibacterial properties of the chitosan / polylactic acid film were determined experimentally. The film samples were cut into 1 cm wide rectangular strips, each weighing approximately 0.4 g. Before analysis, the film surface was sterilized by irradiating with ultraviolet light for 20 seconds. The bacterial standard strain was inoculated into trypsin-based soybean broth (TSB) and incubated at 37°C for 24 hours. The bacterial concentration was adjusted to approximately 1.5 × 10⁻⁶ using the McFarland turbidimetric method. 8 The concentration was calculated as CFU / mL, then diluted to the required concentration with a peptone aqueous solution (25g peptone / 1L water). The test concentration for Candida albicans and Escherichia coli was 10. 5 CFU / mL. The antibacterial activity test for each film sample was performed in duplicate. Pre-sterilized PLA-PG-CH composite film samples were immersed in a solution containing 10 mL TSB medium and 0.1 mL of bacterial suspension (1×10⁻⁶ CFU / mL). 5The bacterial culture was incubated in test tubes containing (CFU / mL) at 37°C for 24 hours. After incubation, the bacterial culture that had been in contact with the membrane was serially diluted with 0.9% sodium chloride solution. The diluted samples were then inoculated onto agar plates and incubated at 37°C for another 24 hours. After incubation, the colony-forming units (CFU) of each plate were counted. The CFU / mL value was calculated by multiplying the average colony count of the plate by the dilution factor and dividing by the inoculation volume (mL). The quantitative reduction in bacteria by the sample was finally calculated using the following formula: R = log(B / A), where A and B represent the average viable count of the test sample and the control sample after 24 hours of incubation at 37°C, respectively. The test results are shown in Table 1.

[0082] Table 1. Test results of antibacterial properties of different materials

[0083]

[0084] It should be noted that PLA in the instructions refers to polylactic acid, and PVA refers to polyvinyl alcohol. *E. coli: Escherichia coli (ATCC: 11775); C. albicans: Candida albicans (ATCC: 90028); purchased from Shanghai Baolu Biotechnology.

[0085] Table 1 shows the antibacterial test results. The results indicate that the chitosan / polylactic acid polymer film containing chitosan has significant antibacterial ability, and its antibacterial ability is significantly correlated with the amount of chitosan contained in the film. Furthermore, the chitosan / polylactic acid film has good broad-spectrum antibacterial properties and has significant antibacterial performance against Candida albicans and Escherichia coli.

[0086] IV. To test the changes in mechanical properties, tensile tests were conducted on the polymer films prepared in Examples 1, 2, 3, and Comparative Example 1. The experimental results are as follows: Figure 5 As shown.

[0087] like Figure 5The stress-strain curves of chitosan / polylactic acid polymer films and pure polylactic acid with different chitosan addition amounts are shown in the figure. As can be seen from the figure, the tensile strength of pure polylactic acid is 32.50 MPa, and the fracture strain is only 1.7%, exhibiting obvious brittle characteristics. When 5% chitosan is added, the tensile strength of the polymer film material increases to 35.90 MPa, and the fracture strain increases to 6.0%, showing some improvement in mechanical properties. When 10% chitosan is added, the tensile strength further increases to 38.74 MPa, and the fracture strain is 7.0%. When the chitosan addition reaches 20%, the tensile strength reaches 44.86 MPa, and the fracture strain is 7.1%. This indicates that the introduction of chitosan can effectively strengthen and toughen polylactic acid materials. With the increase of chitosan addition, the tensile strength of the polymer film composite material shows an upward trend, and the fracture strain also increases, which to some extent improves the inherent brittleness of polylactic acid and enhances the overall mechanical properties of the material. This change in mechanical properties not only makes chitosan / polylactic acid polymer film materials easier to process and adapt to the needs of different products, but also enables chitosan / polylactic acid polymer film materials to adapt to low-intensity or even moderate-intensity daily activities for feminine hygiene products.

[0088] V. To test the changes in water absorption performance, the polymer films prepared in Examples 1, 2, 3, and Comparative Example 1 were subjected to a mass change test after water absorption. The experimental results are as follows: Figure 6 As shown.

[0089] Figure 6 The figures show the water absorption test results for chitosan / polylactic acid polymer film materials with different chitosan addition amounts and pure polylactic acid. As can be seen from the figure, only the polylactic acid group has the lowest water absorption rate, close to 0, indicating that pure polylactic acid material itself has poor hydrophilicity and weak water absorption capacity. When chitosan is added to polylactic acid, the water absorption rate of the composite material significantly increases. The water absorption rate of the 5% chitosan / polylactic acid group increases to approximately 15%; as the chitosan addition amount continues to increase, the water absorption rates of the 10% chitosan / polylactic acid group and the 20% chitosan / polylactic acid group further increase, with the 20% chitosan / polylactic acid group having a relatively higher water absorption rate (approximately 25%). This indicates that the introduction of chitosan can impart a certain degree of hydrophilicity to polylactic acid materials, and the water absorption rate of the polymer film composite material increases with the increase of chitosan addition amount. This is presumably because chitosan molecules contain a large number of polar groups (such as amino and hydroxyl groups), which can enhance the interaction between the material and water, thereby improving water absorption capacity. This gives chitosan / polylactic acid polymer film materials a strong ability to absorb liquids, keeping the skin surface dry and further reducing bacterial growth.

[0090] Example 4

[0091] Compared with Example 1, except that the chitosan / polylactic acid mixed solution prepared in step (3) has a chitosan content of 1% chitosan / polylactic acid, everything else is the same.

[0092] Example 5

[0093] Compared with Example 1, except that the chitosan / polylactic acid mixed solution prepared in step (3) has a chitosan content of 2% chitosan / polylactic acid, everything else is the same.

[0094] Example 6

[0095] Compared with Example 1, except that the chitosan / polylactic acid mixed solution prepared in step (3) has a chitosan content of 3% chitosan / polylactic acid, everything else is the same.

[0096] Example 7

[0097] Compared with Example 1, except that the chitosan / polylactic acid mixed solution prepared in step (3) has a chitosan content of 15% chitosan / polylactic acid, everything else is the same.

[0098] Example 8

[0099] Compared with Example 1, except that the chitosan / polylactic acid mixed solution prepared in step (3) has a chitosan content of 25% chitosan / polylactic acid, everything else is the same.

[0100] Example 9

[0101] In this embodiment, the amounts of each raw material and the chitosan content in the prepared chitosan / polylactic acid mixed solution are the same as in Example 1. Other differences include the following preparation method:

[0102] (1) Preparation of chitosan solution: Prepare a calibrated electronic balance with an accuracy of 0.01g; prepare chitosan powder with a molecular weight of 50kDa and a degree of deacetylation ≥85%, measure 100mL of acetic acid solution and transfer it to a 250mL conical flask, then weigh 2g of chitosan powder for later use, place the conical flask on a magnetic stirrer, set the speed to 450rpm, and slowly add the weighed chitosan powder during continuous stirring. The temperature is controlled at 23℃ throughout the stirring process, and the stirring is carried out for 2h. The pH value of the prepared chitosan solution is 4, and the prepared chitosan solution is stored at 4℃ and used up within 24 hours to ensure the freshness of the chitosan solution and to ensure the antibacterial properties of the polymer film;

[0103] (2) Preparation of polylactic acid emulsion: First, polylactic acid particles with an intrinsic viscosity of 0.8 dL / g should be selected. Weigh 5g of polylactic acid and add it to 100mL of chromatographic grade chloroform. Place it in a 35℃ water bath and stir to dissolve to obtain a polylactic acid / chloroform solution. At the same time, prepare a polyvinyl alcohol solution by dissolving 2g of polyvinyl alcohol in 100mL of 75℃ deionized water and stirring magnetically at 350rpm for 1h until completely dissolved. After the solution cools to room temperature, filter it through a 0.4μm filter membrane for later use. Slowly add the polylactic acid / chloroform solution dropwise. The polylactic acid / chloroform solution was emulsified and concentrated in a polyvinyl alcohol solution. During emulsification, a high-shear dispersing emulsifier with a rotation speed of 8000 rpm was used. The polylactic acid / chloroform solution was slowly added dropwise to the polyvinyl alcohol solution at a rate of 1 mL / min, and the emulsification temperature was maintained at 24°C throughout the process. After the addition was completed, the emulsification process was continued for 25 min. The concentration process was carried out by rotary evaporation, with the water bath temperature set at 30°C, the rotation speed at 120 rpm, and the vacuum degree at 200 mbar. The concentration was completed when the emulsion volume decreased to 50 mL, and a polylactic acid emulsion was obtained.

[0104] (3) Preparation of chitosan / polylactic acid mixed solution: Except that the mixing process is carried out in a covered glass container to prevent solvent evaporation, the stirring speed is set to 400 rpm and the mixing time is 25 minutes, the other steps are the same as in step (3) of Example 1.

[0105] (4) This step is the same as in Example 1.

[0106] Example 10

[0107] In this embodiment, the amounts of each raw material and the chitosan content in the prepared chitosan / polylactic acid mixed solution are the same as in Example 1. Other differences include the following preparation method:

[0108] (1) Preparation of chitosan solution: Prepare a calibrated electronic balance with an accuracy of 0.01g; prepare chitosan powder with a molecular weight of 190kDa and a degree of deacetylation ≥85%, measure 100mL of acetic acid solution and transfer it to a 250mL conical flask, then weigh 2g of chitosan powder for later use, place the conical flask on a magnetic stirrer, set the speed to 550rpm, and slowly add the weighed chitosan powder during continuous stirring. The temperature is controlled at 27℃ throughout the stirring process, and the stirring is carried out for 3h. The pH value of the prepared chitosan solution is 5, and the prepared chitosan solution is stored at 4℃ and used up within 24 hours to ensure the freshness of the chitosan solution and to ensure the antibacterial properties of the polymer film;

[0109] (2) Preparation of polylactic acid emulsion: First, polylactic acid particles with an intrinsic viscosity of 1.2 dL / g should be selected. Weigh 5g of polylactic acid and add it to 100mL of chromatographic grade chloroform. Place it in a 45℃ water bath and stir to dissolve to obtain a polylactic acid / chloroform solution. At the same time, prepare a polyvinyl alcohol solution by dissolving 2g of polyvinyl alcohol in 100mL of 85℃ deionized water and stirring magnetically at 450rpm for 2h until completely dissolved. After the solution cools to room temperature, filter it through a 0.5μm filter membrane for later use. Slowly add the polylactic acid / chloroform solution dropwise to the polylactic acid emulsion. Emulsification and concentration were carried out in a polyvinyl alcohol solution. During emulsification, a high-shear dispersing emulsifier with a rotation speed of 12000 rpm was used to slowly add the polylactic acid / chloroform solution to the polyvinyl alcohol solution at a rate of 1.5 mL / min. The emulsification temperature was maintained at 26°C throughout the process. After the addition was completed, the emulsification process was continued for 35 min. The concentration process adopted the rotary evaporation method, with the water bath temperature set at 40°C, the rotation speed at 120 rpm, and the vacuum degree at 200 mbar. The concentration was completed when the emulsion volume decreased to 50 mL, thus obtaining a polylactic acid emulsion.

[0110] (3) Preparation of chitosan / polylactic acid mixed solution: Except that the mixing process is carried out in a covered glass container to prevent solvent evaporation, the stirring speed is set to 450 rpm and the mixing time is 5 minutes, the other steps are the same as in step (3) of Example 1.

[0111] (4) This step is the same as in Example 1.

[0112] In summary, the core of this invention lies in the fact that the polymer film produced by blending polylactic acid and chitosan in the above embodiments of the invention is made from abundant and readily available raw materials at low prices, resulting in high economic efficiency in preparation. Both polylactic acid and chitosan used have biodegradable properties, enabling the polymer film to be effectively biodegraded. This has the potential to solve the problem of waste disposal of sanitary pads in the future, eliminating the need to consider waste disposal or environmental pollution issues, and has broad market prospects.

[0113] The preparation method of the polymer film in this invention is simple. The polymer film has significant antibacterial ability, and its antibacterial ability is significantly correlated with the amount of chitosan contained in the film. Furthermore, the chitosan / polylactic acid polymer film has good broad-spectrum antibacterial properties, with significant antibacterial performance against Candida albicans and Escherichia coli. Using the polymer film in the absorbent pad of sanitary napkins can not only reduce the manufacturing cost of antibacterial sanitary napkins, but also play a role in cleaning the vulva and preventing gynecological diseases. Applying this polymer film to the antibacterial layer of the absorbent pad of sanitary napkins improves the antibacterial performance of the sanitary napkins, and it is easy to integrate with other layers of sanitary napkins in manufacturing. It is practical and easy to promote and apply.

[0114] Finally, it should be noted that PLA in the instructions refers to polylactic acid, and PVA refers to polyvinyl alcohol. *E. coli: Escherichia coli (ATCC: 11775); C. albicans: Candida albicans (ATCC: 90028); purchased from Shanghai Baolu Biotechnology.

[0115] The preferred embodiments of the present invention have been described in detail above, outlining the basic principles, main features, and advantages of the invention. However, those skilled in the art should understand that the embodiments of the present invention are not limited to the above-described embodiments. The embodiments and descriptions in the specification are merely preferred examples of the present invention and are not intended to limit the invention. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the embodiments of the present invention. It is neither necessary nor possible to exhaustively describe all embodiments here. However, obvious changes or modifications derived therefrom are still within the protection scope of the embodiments of the present invention.

Claims

1. A polymer film, characterized in that, The polymer film is made by blending polylactic acid and chitosan, wherein the chitosan has a molecular weight of 50-190 kDa and a degree of deacetylation ≥85%.

2. The polymer film according to claim 1, characterized in that, The polylactic acid used is polylactic acid particles with an intrinsic viscosity of 0.8-1.2 dL / g.

3. A method for preparing a polymer film as described in any one of claims 1-2, characterized in that, Includes the following steps: (1) Preparation of chitosan solution: Measure the acetic acid solution and transfer it into an Erlenmeyer flask. Then weigh the chitosan powder for later use. Place the Erlenmeyer flask on a magnetic stirrer and slowly add the weighed chitosan powder while stirring continuously until the solution is transparent, uniform and free of particles and bubbles. This gives you the chitosan solution. (2) Preparation of polylactic acid emulsion: Weigh a certain amount of polylactic acid and add it to chromatographic grade chloroform. Stir and dissolve it in a water bath at 35-45℃ to obtain polylactic acid / chloroform solution. At the same time, prepare polyvinyl alcohol solution. Dissolve polyvinyl alcohol in deionized water, filter and set aside. Slowly add the polylactic acid / chloroform solution to the polyvinyl alcohol solution for emulsification and concentration to obtain polylactic acid emulsion. (3) Preparation of chitosan / polylactic acid mixed solution: Take the polylactic acid emulsion and chitosan solution prepared in the above steps and mix them until the solution is uniformly milky white and there is no phase separation. The mixing process is carried out in a glass container with a lid to prevent solvent evaporation and obtain chitosan / polylactic acid mixed solution. (4) Control the ambient temperature to 23-27℃ and the ambient humidity to 45-55%RH. Place the chitosan / polylactic acid mixed solution prepared in step (3) into a mold, adjust the film thickness using an automatic coating machine, and cast and dry to obtain a polymer film.

4. The method for preparing the polymer film according to claim 3, characterized in that, The preparation of chitosan solution in step (1) is as follows: 100 mL of acetic acid solution is transferred to a 250 mL conical flask, and then 2 g of chitosan powder is weighed for later use. The conical flask is placed on a magnetic stirrer and the speed is set to 450-550 rpm. During the continuous stirring process, the weighed chitosan powder is slowly added. The temperature is controlled at 23-27℃ throughout the stirring process, and the stirring is carried out for 2-3 hours.

5. The method for preparing the polymer film according to claim 4, characterized in that, The chitosan solution prepared in step (1) has a pH value of 4-5, and the prepared chitosan solution is stored at 4°C.

6. The method for preparing the polymer film according to claim 3, characterized in that, The preparation of polylactic acid emulsion in step (2) is as follows: Weigh 5g of polylactic acid and add it to 100mL of chromatographic grade chloroform. Place it in a water bath at 35-45℃ and stir to dissolve to obtain a polylactic acid / chloroform solution. At the same time, prepare a polyvinyl alcohol solution by dissolving 2g of polyvinyl alcohol in 100mL of deionized water at 75-85℃ and stirring magnetically at 350-450rpm for 1-2 hours until completely dissolved. After the solution is cooled to room temperature, filter it through a 0.4-0.5μm filter membrane for later use. Slowly add the polylactic acid / chloroform solution to the polyvinyl alcohol solution for emulsification and concentration to obtain a polylactic acid emulsion.

7. The method for preparing the polymer film according to claim 6, characterized in that, During emulsification, a high-shear dispersing emulsifier with a rotation speed of 8000-12000 rpm is used to slowly add the polylactic acid / chloroform solution dropwise to the polyvinyl alcohol solution at a rate of 1-1.5 mL / min, maintaining the emulsification temperature at 24-26℃ throughout the process. After the addition is completed, emulsification is continued for 25-35 min. The concentration process uses rotary evaporation, with the water bath temperature set at 30-40℃, rotation speed at 120 rpm, and vacuum at 200 mbar. Concentration is complete when the emulsion volume decreases to 50 mL. The polyvinyl alcohol used is polyvinyl alcohol with a degree of alcoholysis of 88%.

8. The method for preparing the polymer film according to claim 3, characterized in that, In step (3), a basic mother liquor is prepared by mixing polylactic acid emulsion and chitosan solution. 80 mL of polylactic acid emulsion and 20 mL of chitosan solution are mixed to prepare the basic mother liquor. Then, a chitosan / polylactic acid mixed solution containing different amounts of chitosan is prepared by gradient dilution.

9. The use of a polymer film as described in claim 1, 2, 3, 4, 5, 6, 7, or 8 in a sanitary absorbent pad.

10. The application according to claim 9, characterized in that, The sanitary absorbent pads include at least one of sanitary napkins, diapers, disposable underwear, and panty liners.

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