A high water-resistance, antibacterial and mechanical property composite film material and a preparation method thereof

Abstract

This invention relates to the field of packaging materials technology, specifically to a composite film material and its preparation method with high water resistance, antibacterial properties, and mechanical strength, comprising the following components by weight percentage: 60-75% matrix polymer, 10-20% nano-reinforcing filler, 1-10% antibacterial active ingredient, 5-15% plasticizer, and 0.5-5% crosslinking agent; the matrix polymer comprises chitosan and gelatin, with a weight ratio of chitosan to gelatin of 1:0.5-1.5; the nano-reinforcing filler is carboxylated cellulose nanofibers and ZnO nanoparticles, with a weight ratio of carboxylated cellulose nanofibers to ZnO nanoparticles of 1.5-2.5:1; the crosslinking agent is calcium chloride; this invention possesses high water resistance, long-lasting antibacterial properties, and enhanced mechanical strength.

Description

Technical Field

[0001] This invention relates to the field of packaging materials technology, specifically to a composite film material with high water resistance, antibacterial properties and mechanical properties, and its preparation method. Background Technology

[0002] Packaging film materials play a crucial role in ensuring the quality and safety of goods (especially food and pharmaceuticals) and extending their shelf life. Currently, the most widely used packaging films on the market are primarily made of petroleum-based polymers such as polyethylene (PE) and polypropylene (PP). While these materials possess good processing properties and mechanical strength, they still have some significant drawbacks in practical applications: 1. Limited water barrier performance: The water vapor barrier performance of traditional polyolefin films is difficult to meet the packaging requirements of high humidity environments or products that are extremely sensitive to moisture.

[0003] 2. Lack of long-lasting antibacterial function: Ordinary packaging materials do not have active antibacterial capabilities. During packaging, storage and transportation, once microbial contamination occurs, it is very easy for microorganisms to grow and multiply on the product surface, leading to spoilage and even safety issues.

[0004] 3. Difficulty in achieving synergistic performance: Modifications made to improve a certain property (such as barrier properties or strength) (such as adding inorganic nanoparticles) often sacrifice other properties of the material (such as flexibility, transparency or processability), making it difficult to achieve a balance between comprehensive properties such as high barrier properties, high strength and good toughness.

[0005] 4. Environmental burden: The extensive use of petroleum-based materials has led to an increasingly serious problem of "white pollution." Although bio-based biodegradable materials (such as chitosan and gelatin) have attracted attention, their mechanical properties, water resistance, and functionality are generally insufficient, making it difficult to directly replace traditional plastics.

[0006] Currently, some technologies have attempted to partially improve the performance of thin films by adding nanofillers (such as montmorillonite and nano-SiO2) or directly blending antibacterial agents (such as silver ions and essential oils). However, these methods often suffer from problems such as uneven dispersion and easy aggregation of nanofillers, easy volatility and poor stability of antibacterial agents, impact on the bulk properties of the material, and poor overall process compatibility with continuous industrial production.

[0007] Therefore, developing a composite packaging film material that is structurally dense, possesses excellent barrier, antibacterial, and mechanical properties in synergy, and is suitable for continuous industrial production has significant application value and market demand. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a composite thin film material with high water resistance, antibacterial properties and mechanical properties, and a preparation method thereof.

[0009] This invention provides a composite film material with high water resistance, antibacterial properties, and mechanical properties, comprising the following components by mass percentage: 60-75% matrix polymer, 10-20% nano-reinforcing filler, 1-10% antibacterial active ingredient, 5-15% plasticizer, and 0.5-5% crosslinking agent; The matrix polymer comprises chitosan and gelatin, with a weight ratio of chitosan to gelatin of 1:0.5-1.5; the nano-reinforcing filler comprises carboxylated cellulose nanofibers and ZnO nanoparticles, with a weight ratio of carboxylated cellulose nanofibers to ZnO nanoparticles of 1.5-2.5:1; and the crosslinking agent is calcium chloride.

[0010] Preferably, the composition includes the following components by weight percentage: 70% matrix polymer, 15% nano-reinforcing filler, 5% antibacterial active ingredient, 8% plasticizer, and 2% crosslinking agent.

[0011] Preferably, the weight ratio of chitosan to gelatin is 1:1; and the weight ratio of carboxylated cellulose nanofibers to ZnO nanoparticles is 2:1.

[0012] Preferably, the antibacterial active ingredient is a microencapsulated product of a natural antibacterial substance, and more preferably, the natural antibacterial substance is thymol. Microencapsulation effectively protects the antibacterial active substance from the processing environment, achieving its long-term stable existence and sustained-release function within the film.

[0013] Preferably, the plasticizer is at least one of glycerol, sorbitol, citrate, and epoxidized soybean oil.

[0014] Preferably, the plasticizer is glycerin.

[0015] This invention provides a method for preparing the composite thin film material, comprising the following steps: 1) Dissolve the matrix polymer in a solvent to form a homogeneous matrix solution; 2) Add nano-reinforced filler to the matrix solution and disperse it uniformly to obtain a dispersion system; 3) Add the antibacterial active ingredient and plasticizer to the dispersion system, mix well, and obtain a mixed solution; 4) The mixed solution is applied to the surface of the substrate (by means of scraping, casting or spraying, etc., applied to a flat substrate (such as glass plate, polytetrafluoroethylene plate, release film, etc.), the film thickness is controlled, and then dried (such as 40-60℃ forced air drying) to obtain the initial film; 5) The nascent film is subjected to crosslinking treatment to obtain the composite film material.

[0016] Preferably, in step 1), the solvent is water, acetic acid solution, or ethanol solution; In step 2), uniform dispersion is achieved by ultrasonic dispersion, with a power of 300W-500W and a duration of 15-60 minutes.

[0017] Preferably, in step 5), the crosslinking treatment involves immersing the nascent film in a solution containing a crosslinking agent for ionic crosslinking, with a treatment time of 1-30 minutes.

[0018] The beneficial effects of this invention are that it uses a combination of chitosan and gelatin, which can form a more stable and uniform network structure through intermolecular hydrogen bonds and other interactions, providing a good carrier for other functional components. The combination of carboxylated cellulose nanofibers and ZnO nanoparticles can provide a high aspect ratio and abundant carboxyl functional groups, exhibiting nanoscale effects and potential auxiliary antibacterial and UV shielding functions. The two work synergistically to construct a physically-chemically enhanced and barrier network. This invention uses calcium chloride as a crosslinking agent, where calcium ions can simultaneously react with the amino groups (-NH3) of chitosan. + ) forms ionic bonds with the carboxyl groups (-COO) in carboxylated cellulose nanofibers or alginate groups. - It can form ionic bonds and also interact with gelatin molecular chains to achieve efficient "ion bridge" cross-linking.

[0019] This invention possesses excellent comprehensive performance: By carefully selecting each component and optimizing their synergistic effect, the composite thin film material obtained by this invention simultaneously possesses the following properties: High water resistance: Through the synergistic effect of nanofillers with surface functional groups (such as -COOH) (such as carboxylated cellulose nanofibers) and ionic crosslinking agents, a tortuous and dense physical / chemical barrier network is constructed in the polymer matrix, which significantly reduces the water vapor permeability.

[0020] Long-lasting antibacterial properties: By using microencapsulation technology to load essential oils and other natural antibacterial agents, the drawbacks of volatility and instability are overcome, and the antibacterial components are slowly released, thus giving the film long-term, stable, and broad-spectrum antibacterial properties.

[0021] Enhanced mechanical properties: The good interfacial bonding between the nanofiller and the matrix, the multi-point cross-linking network constructed by the ionic cross-linking agent, and the regulation of molecular chain motion by the plasticizer synergistically improve the tensile strength and elongation at break of the film, achieving a "stiffness-toughness balance".

[0022] This invention emphasizes the compatibility and synergistic effect of components. For example, the matrix polymer is preferably a charged biomacromolecule (such as chitosan, which is positively charged, and gelatin and carboxylated cellulose nanofibers, which are partially negatively charged), capable of interacting efficiently with specific ionic crosslinking agents. The selection of fillers takes into account both physical barrier and interfacial reinforcement.

[0023] The entire preparation process of this invention uses aqueous solution as the main medium (particularly suitable for bio-based / degradable substrates), eliminating the need for large amounts of toxic and harmful organic solvents. The process steps are simple, the conditions are mild (room temperature or low temperature), and it is easy to scale up and achieve continuous industrial production (such as coating and impregnation continuous production lines).

[0024] This invention flexibly utilizes a large number of bio-based, biodegradable or renewable raw materials (such as chitosan, gelatin, etc.), reducing dependence on petroleum resources and environmental burden, which is in line with the development trend of green packaging. Detailed Implementation

[0025] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the technical solutions of this invention will be further described in detail below with reference to specific embodiments. It should be understood that the embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this invention.

[0026] Example 1 A composite thin film material with high water resistance, antibacterial properties, and mechanical properties, comprising the following raw materials (by mass percentage): Matrix polymer: chitosan 35g, gelatin 35g; Nano-reinforced filler: 10g carboxylated cellulose nanofibers (CNF), 5g ZnO nanoparticles; Antibacterial active ingredient: 5g of thymol microcapsules; Plasticizer: 8g glycerin; Crosslinking agent: 2g of calcium chloride.

[0027] The preparation method of composite thin film materials includes the following steps: 1) Preparation of matrix solution: Chitosan powder was slowly added to a 1% (v / v) aqueous acetic acid solution and magnetically stirred for 6 hours at room temperature until completely dissolved; gelatin particles were added to deionized water at 50°C and stirred until dissolved. The two solutions were mixed and stirred for another 2 hours to obtain a homogeneous matrix solution.

[0028] 2) Nano-reinforced filler dispersion: Carboxylated cellulose nanofibers (CNF) and ZnO nanoparticle powder were added to the above matrix solution. The mixture was placed in an ultrasonic cell disruptor and ultrasonically treated at 400W power for 30 minutes to obtain a uniformly dispersed mixture.

[0029] 3) Introduction of antibacterial active ingredients: Add thymol microcapsules and glycerin to the mixture in step 2), and continue stirring with mechanical stirring (500 rpm) for 1 hour to ensure that all components are fully mixed.

[0030] 4) Film Formation and Drying: Pour the final mixture onto a flat polytetrafluoroethylene (PTFE) plate and coat it into a uniform wet film (approximately 0.3 mm thick) using an automatic coating machine. Then, transfer the coated plate into a 45°C forced-air drying oven and dry it continuously for 12 hours. Peel off the nascent film to obtain the nascent film.

[0031] 5) Crosslinking treatment: Prepare a 2 wt% CaCl2 aqueous solution. Cut the nascent film to a suitable size and immerse it in the CaCl2 solution for 5 minutes to perform ionic crosslinking. After removal, gently rinse the film surface with deionized water to remove residual CaCl2, and then place it again in a 45°C forced-air drying oven for 2 hours to obtain the finished composite film material.

[0032] Comparative Example 1 The nano-reinforced filler in Example 1 was replaced with 10g of montmorillonite and 5g of TiO2 nanoparticles. The rest was the same as in Example 1.

[0033] Comparative Example 2 Replace the 2g calcium chloride ionic crosslinking agent in Example 1 with 2g glutaraldehyde chemical crosslinking agent. The rest is the same as in Example 1.

[0034] Comparative Example 3 The carboxylated cellulose nanofibers in Example 1 were replaced with cellulose nanocrystals, while the ZnO nanoparticles remained unchanged. Everything else was the same as in Example 1.

[0035] Comparative Example 4 The matrix polymer in Example 1 was replaced with 35g of chitosan and 35g of alginate. The rest was the same as in Example 1.

[0036] Comparative Example 5 The nano-reinforcing filler in Example 1 was replaced with 7.5g of carboxylated cellulose nanofibers (CNF) and 7.5g of ZnO nanoparticles. The rest was the same as in Example 1.

[0037] The performance of the composite thin film materials prepared in Example 1 and the comparative example was tested, and the specific results are shown in the table below.

[0038] Table 1

[0039] Comparative Example 1, failing to form a multi-level dense barrier network like in Example 1, exhibited improved tensile strength but severely deteriorated water resistance, making it unsuitable for packaging in high-humidity environments. Comparative Example 2 possessed high strength but was brittle, suitable for rigid packaging but not for flexible applications. Comparative Example 3, lacking additional ionic crosslinking sites provided by carboxyl groups, resulted in a looser barrier path with the matrix and crosslinking agent, leading to decreased ductility and making it unsuitable for films requiring flexibility. Comparative Example 4, with its alginate system, exhibited poor barrier properties but good biocompatibility, making it suitable for low-humidity, short-shelf-life products. Comparative Example 5, with its reduced filler ratio, weakened the reinforcing effect, verifying that 10g CNF + 5g ZnO was the optimal ratio. These examples and comparative examples fully demonstrate the innovation and synergistic effect of the component selection, combination, and preparation method of this invention.

[0040] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of protection of this application is limited to these examples; within the framework of this application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of one or more embodiments of this application as described above, which are not provided in detail for the sake of brevity.

[0041] One or more embodiments in this application are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of this application. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of one or more embodiments in this application should be included within the protection scope of this application.

Claims

1. A composite thin film material with high water resistance, antibacterial properties, and mechanical properties, characterized in that, It includes the following components by weight percentage: matrix polymer 60-75%, nano-reinforcing filler 10-20%, antibacterial active ingredient 1-10%, plasticizer 5-15%, and crosslinking agent 0.5-5%; The matrix polymer comprises chitosan and gelatin, with a weight ratio of chitosan to gelatin of 1:0.5-1.5; the nano-reinforcing filler comprises carboxylated cellulose nanofibers and ZnO nanoparticles, with a weight ratio of carboxylated cellulose nanofibers to ZnO nanoparticles of 1.5-2.5:1; and the crosslinking agent is calcium chloride.

2. The composite thin film material according to claim 1, characterized in that, It comprises the following components by weight percentage: 70% matrix polymer, 15% nano-reinforcing filler, 5% antibacterial active ingredient, 8% plasticizer, and 2% crosslinking agent.

3. The composite thin film material according to claim 1, characterized in that, The weight ratio of chitosan to gelatin is 1:1; the weight ratio of carboxylated cellulose nanofibers to ZnO nanoparticles is 2:

1.

4. The composite thin film material according to claim 1, characterized in that, The antibacterial active ingredient is a microencapsulated product of natural antibacterial substances.

5. The composite thin film material according to claim 4, characterized in that, The natural antibacterial substance is thymol.

6. The composite thin film material according to claim 1, characterized in that, The plasticizer is at least one of glycerol, sorbitol, citrate, and epoxidized soybean oil.

7. The composite thin film material according to claim 6, characterized in that, The plasticizer is glycerin.

8. A method for preparing a composite thin film material as described in any one of claims 1-7, characterized in that, Includes the following steps: 1) Dissolve the matrix polymer in a solvent to form a homogeneous matrix solution; 2) Add nano-reinforced filler to the matrix solution and disperse it uniformly to obtain a dispersion system; 3) Add the antibacterial active ingredient and plasticizer to the dispersion system, mix well, and obtain a mixed solution; 4) The mixed solution is coated onto the surface of the substrate, the film thickness is controlled, and then dried to obtain the initial film; 5) The nascent film is subjected to crosslinking treatment to obtain the composite film material.

9. The preparation method according to claim 8, characterized in that, In step 1), the solvent is water, acetic acid solution, or ethanol solution; In step 2), uniform dispersion is achieved by ultrasonic dispersion, with a power of 300W-500W and a duration of 15-60 minutes.

10. The preparation method according to claim 8, characterized in that, In step 5), the crosslinking treatment involves immersing the nascent film in a solution containing a crosslinking agent for ionic crosslinking, with a treatment time of 1-30 minutes.

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