A method for preparing a cottonseed protein film for labels

Abstract

This invention discloses a method for preparing a cottonseed protein film for labeling, comprising: dissolving cottonseed protein in a protein denaturant solution and stirring until homogeneous to obtain a cottonseed protein-protein denaturant dispersion; mixing the cottonseed protein-protein denaturant dispersion with a cationic solution and stirring until homogeneous to obtain a cottonseed protein-protein denaturant-cationic mixed solution; and drying the cottonseed protein-protein denaturant-cationic mixed solution using physical means to form a film, thereby obtaining a cottonseed protein film for labeling. The cottonseed protein film prepared by this invention exhibits good film-forming properties, mechanical properties, and surface adhesion properties, and can be directly used as a label material. Furthermore, the cottonseed protein raw material is renewable, and the product is biodegradable, demonstrating good environmental friendliness and sustainable development advantages.

Description

Technical Field

[0001] This invention belongs to the field of bio-based materials and green adhesives technology. More specifically, this invention relates to a method for preparing a cottonseed protein film for labeling. Background Technology

[0002] In industries such as packaging, logistics, food, and daily necessities, labels serve as crucial carriers of information transmission and product management, widely applied in various stages including product identification, anti-counterfeiting traceability, logistics sorting, brand promotion, and user instructions. With the continuous improvement of modern supply chain systems and the rapid development of e-commerce, labels not only fulfill basic identification functions but also play an increasingly important role in information management, intelligent identification, and quality and safety tracking. Therefore, the performance stability, adhesion reliability, and environmental adaptability of label materials have become critical factors influencing product performance and corporate image.

[0003] Currently, most label materials on the market are based on petroleum-based polymers, such as polypropylene (PP), polyester (PET), and polyvinyl chloride (PVC), combined with acrylic or rubber-based synthetic adhesives. These materials possess excellent mechanical properties, heat resistance, and water resistance, maintaining good structural integrity and adhesion even in complex environments, thus enjoying long-term and widespread application in industrial production. However, petroleum-based polymers rely on non-renewable fossil resources, and their production processes are energy-intensive and generate significant carbon emissions, contradicting the current trend of low-carbon economy and green manufacturing. Furthermore, these materials are difficult to degrade in the natural environment, easily forming persistent solid waste after disposal, placing a long-term burden on soil, water bodies, and ecosystems. In addition, traditional synthetic adhesives often involve volatile organic compounds (VOCs) such as formaldehyde, benzene, and ketones during production and use. These substances may be released into the air during use, posing a potential threat to the health of operators, causing environmental pollution, and affecting indoor air quality and ecological safety. In the food packaging and daily necessities labeling sectors, the migration risk of these chemicals is particularly significant. Therefore, against the backdrop of increasingly stringent environmental regulations and rising consumer health awareness worldwide, developing safe, environmentally friendly, and sustainable labeling materials and adhesive systems has become an inevitable trend in the industry.

[0004] With the continuous advancement of green chemistry concepts and sustainable development strategies, bio-based materials with renewable and biodegradable sources have gradually become a research hotspot. Among them, plant protein materials have attracted much attention due to their wide availability, abundant resources, and good environmental compatibility. Cottonseed protein, as a byproduct of cottonseed processing, has advantages such as high yield, low price, and high utilization rate, making it a natural polymer resource with great development potential. As a major cotton producer, my country has abundant cottonseed resources. Utilizing these resources at high value not only helps improve the comprehensive utilization rate of agricultural byproducts but also helps reduce resource waste and achieve circular economy development. Cottonseed protein molecules contain abundant active functional groups such as amino, carboxyl, and hydroxyl groups, possessing certain film-forming ability and adhesion potential, while also exhibiting good biodegradability and environmental friendliness. However, due to the relatively compact molecular structure of natural cottonseed protein, and the strong hydrogen bonds and hydrophobic interactions within and between molecules, its solubility and dispersibility in water are limited. This makes it difficult for the molecular chains to fully unfold and rearrange during film formation, resulting in films with high brittleness and insufficient strength. In addition, natural protein-based adhesives are also insufficient in terms of water resistance, heat resistance and long-term stability, making it difficult to meet the comprehensive requirements for adhesive strength, environmental resistance and service life in label applications.

[0005] To address the aforementioned issues, modifying cottonseed protein through structural regulation and chemical modification has become a key approach to improve its performance. On the one hand, physical modification or enzymatic hydrolysis can open up the protein's spatial structure, enhancing the flexibility and reactivity of the molecular chains. On the other hand, appropriate cross-linking agents or functionalized small molecules can be introduced to form a three-dimensional network structure through chemical cross-linking, thereby improving the material's mechanical strength and water resistance. Furthermore, blending or compounding with other bio-based polymers (such as starch, chitosan, or cellulose derivatives) can also help improve film-forming properties and interfacial adhesion properties, achieving synergistic performance enhancement. Therefore, developing a modified cottonseed protein-based adhesive system to construct a structurally tunable and performance-controllable bio-based adhesive material can not only effectively improve its film-forming, mechanical, and adhesive properties, meeting the requirements for strength, stability, and environmental adaptability in label applications, but also reduce dependence on petroleum-based materials and lower environmental pollution risks. This research direction has significant theoretical and practical value for promoting the industrial application of green labeling materials, facilitating the high-value utilization of agricultural by-product resources, and achieving sustainable development in the field of materials science. Summary of the Invention

[0006] One object of the present invention is to solve at least the above-mentioned problems and / or defects, and to provide at least the advantages described below.

[0007] To achieve these objectives and other advantages of the present invention, a method for preparing a cottonseed protein film for labeling is provided, comprising the following steps: Step 1: Dissolve cottonseed protein in a protein denaturant solution and stir until homogeneous to obtain a cottonseed protein-protein denaturant dispersion. Step 2: Mix the cottonseed protein-protein denaturant dispersion with the cationic solution and stir until homogeneous to obtain a mixed solution of cottonseed protein-protein denaturant-cationic solution; Step 3: The cottonseed protein-protein denaturant-cationic mixed solution is dried by physical means to form a film, which is used for labeling.

[0008] Preferably, in step one, the mass of cottonseed protein is 7-15% of the mass of the protein denaturant solution.

[0009] Preferably, in step one, the protein denaturant in the protein denaturant solution is one of sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, sodium N-dodecyl sarcosinate, or bile salt; and the concentration of the protein denaturant solution is 50~400 mmol / L.

[0010] Preferably, in step one, the stirring time is 1 to 3 hours.

[0011] Preferably, in step two, the cationic solution is one of hexadecyltrimethylammonium bromide solution, benzalkonium chloride solution, polyethyleneimine solution, dioctadecyldimethylammonium chloride solution, copper ammonia solution, copper sulfate solution, and ferric chloride solution; the mass fraction of the cationic solution is 5-50%.

[0012] Preferably, in step two, the cationic solution is a modified polyethyleneimine solution; the preparation method of the modified polyethyleneimine solution is as follows: S1. According to the weight parts, add 1~3 parts of protocatechuic acid to 50~200 parts of water and stir until dissolved. Then add 1~3 parts of DMTMM-methanol solution. The mass ratio of DMTMM to methanol in the DMTMM-methanol solution is 10~30:100. Stir at 100~200 r / min in the dark for 10~20 min at room temperature to obtain a mixture. S2. Add 1-2 parts of chitosan to 80-150 parts of 0.5% acetic acid solution and stir until dissolved. Adjust the pH to 5.5-6.0 with 0.1 mol / L sodium hydroxide solution. Then add the mixture and stir at 100-200 r / min in the dark for 1-4 h under nitrogen protection at room temperature. After the reaction is complete, dialyze with deionized water for 24-72 h to obtain modified chitosan solution. S3. Slowly add 5-10 parts of polyethyleneimine solution to the modified chitosan solution, stir until uniformly mixed, and then stir and react at 50-70℃ for 4-10 hours. After the reaction is completed, continue to concentrate at 50-70℃ until the solid content is 5-50% to obtain the modified polyethyleneimine solution.

[0013] Preferably, in step two, the mass ratio of the cationic solution to the cottonseed protein-protein denaturant dispersion is 1 to 5:1.

[0014] Preferably, in step two, the stirring time is 1 to 3 hours.

[0015] Preferably, in step three, the physical means include one of the following: casting, spin coating, drop coating, hot pressing, and blow molding coating; the drying temperature is 60~80℃, and the drying time is 30~120 min.

[0016] The present invention also provides a cottonseed protein film for labeling prepared according to the above preparation method.

[0017] The present invention also provides the application of a cottonseed protein film for labeling prepared according to the above preparation method in a label.

[0018] This invention offers at least the following beneficial effects: It utilizes a protein denaturant to structurally unfold cottonseed protein, improving the accessibility and dispersibility of the protein molecular chains and providing reaction sites for subsequent cross-linking. By introducing a cationic solution for cross-linking modification, intermolecular interactions are enhanced, improving film strength and adhesion. The prepared cottonseed protein-protein denaturant-cationic membrane exhibits excellent film-forming properties, mechanical properties, and surface adhesion, and can be directly used as a labeling material. The cottonseed protein raw material is renewable, and the product is biodegradable, offering significant environmental and sustainable development advantages.

[0019] This invention also provides a method for preparing a modified polyethyleneimine solution. The method involves activating the carboxyl groups on protocatechuic acid using 4-(4,6-dimethoxytriazine-2-yl)-4-methylmorpholine hydrochloride (DMTMM) as a condensing agent. The activated protocatechuic acid is then amidated with the amino groups on chitosan, grafting a catechol structure onto the chitosan to obtain modified chitosan, thus improving its adhesion properties. The modified chitosan is then compounded with polyethyleneimine to obtain a modified polyethyleneimine solution. When this modified polyethyleneimine solution is used for protein crosslinking modification, it can improve film-forming properties and interfacial adhesion properties, thereby enhancing the adhesion and performance of cottonseed protein films.

[0020] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0021] Figure 1 Infrared images of the cottonseed protein membrane prepared in Example 10 and Comparative Example 1, and the cottonseed protein obtained in Comparative Example 2, respectively. Figure 2 Peel force diagrams of cottonseed protein membrane prepared in Example 10 of this invention on different substrate surfaces; Figure 3 This is a graph showing the solid content of the cottonseed protein membrane prepared in Example 10 of the present invention. Detailed Implementation

[0022] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0023] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0024] Example 1 A method for preparing a cottonseed protein film for labeling includes the following steps: Step 1: Dissolve cottonseed protein in a 150 mmol / L sodium dodecyl sulfate solution. The mass of cottonseed protein is 8% of the mass of sodium dodecyl sulfate solution. Stir for 2 hours to obtain a cottonseed protein-protein denaturant dispersion. Step 2: Mix the cottonseed protein-protein denaturant dispersion with a 10% (w / w) polyethyleneimine solution. The mass ratio of the cottonseed protein-protein denaturant dispersion to the polyethyleneimine solution is 2:1. Stir for 2 hours to obtain a cottonseed protein-protein denaturant-cationic mixed solution. Step 3: Pour the cottonseed protein-protein denaturant-cationic mixed solution into a mold, cast it into a liquid film, and then dry it in an 80°C oven for 50 minutes to obtain a cottonseed protein film for labeling.

[0025] Example 2 A method for preparing a cottonseed protein film for labeling includes the following steps: Step 1: Dissolve cottonseed protein in a 150 mmol / L sodium dodecyl sulfate solution. The mass of cottonseed protein is 10% of the mass of sodium dodecyl sulfate solution. Stir for 2 hours to obtain a cottonseed protein-protein denaturant dispersion. Step 2: Mix the cottonseed protein-protein denaturant dispersion with a 10% (w / w) polyethyleneimine solution. The mass ratio of the cottonseed protein-protein denaturant dispersion to the polyethyleneimine solution is 3:1. Stir for 2 hours to obtain a cottonseed protein-protein denaturant-cationic mixed solution. Step 3: Pour the cottonseed protein-protein denaturant-cationic mixed solution into a mold, cast it into a liquid film, and then dry it in an 80°C oven for 50 minutes to obtain a cottonseed protein film for labeling.

[0026] Example 3 A method for preparing a cottonseed protein film for labeling includes the following steps: Step 1: Dissolve cottonseed protein in a 150 mmol / L sodium dodecyl sulfate solution. The mass of cottonseed protein is 12% of the mass of sodium dodecyl sulfate solution. Stir for 2 hours to obtain a cottonseed protein-protein denaturant dispersion. Step 2: Mix the cottonseed protein-protein denaturant dispersion with a 10% (w / w) polyethyleneimine solution. The mass ratio of the cottonseed protein-protein denaturant dispersion to the polyethyleneimine solution is 4:1. Stir for 2 hours to obtain a cottonseed protein-protein denaturant-cationic mixed solution. Step 3: Pour the cottonseed protein-protein denaturant-cationic mixed solution into a mold, cast it into a liquid film, and then dry it in an 80°C oven for 50 minutes to obtain a cottonseed protein film for labeling.

[0027] Example 4 A method for preparing a cottonseed protein film for labeling includes the following steps: Step 1: Dissolve cottonseed protein in a 175 mmol / L sodium dodecyl sulfate solution. The mass of cottonseed protein is 8% of the mass of sodium dodecyl sulfate solution. Stir for 2 hours to obtain a cottonseed protein-protein denaturant dispersion. Step 2: Mix the cottonseed protein-protein denaturant dispersion with a 10% (w / w) polyethyleneimine solution. The mass ratio of the cottonseed protein-protein denaturant dispersion to the polyethyleneimine solution is 3:1. Stir for 2 hours to obtain a cottonseed protein-protein denaturant-cationic mixed solution. Step 3: Pour the cottonseed protein-protein denaturant-cationic mixed solution into a mold, cast it into a liquid film, and then dry it in an 80°C oven for 50 minutes to obtain a cottonseed protein film for labeling.

[0028] Example 5 A method for preparing a cottonseed protein film for labeling includes the following steps: Step 1: Dissolve cottonseed protein in a 175 mmol / L sodium dodecyl sulfate solution. The mass of cottonseed protein is 10% of the mass of sodium dodecyl sulfate solution. Stir for 2 hours to obtain a cottonseed protein-protein denaturant dispersion. Step 2: Mix the cottonseed protein-protein denaturant dispersion with a 10% (w / w) polyethyleneimine solution. The mass ratio of the cottonseed protein-protein denaturant dispersion to the polyethyleneimine solution is 4:1. Stir for 2 hours to obtain a cottonseed protein-protein denaturant-cationic mixed solution. Step 3: Pour the cottonseed protein-protein denaturant-cationic mixed solution into a mold, cast it into a liquid film, and then dry it in an 80°C oven for 50 minutes to obtain a cottonseed protein film for labeling.

[0029] Example 6 A method for preparing a cottonseed protein film for labeling includes the following steps: Step 1: Dissolve cottonseed protein in a 175 mmol / L sodium dodecyl sulfate solution. The mass of cottonseed protein is 12% of the mass of sodium dodecyl sulfate solution. Stir for 2 hours to obtain a cottonseed protein-protein denaturant dispersion. Step 2: Mix the cottonseed protein-protein denaturant dispersion with a 10% (w / w) polyethyleneimine solution. The mass ratio of the cottonseed protein-protein denaturant dispersion to the polyethyleneimine solution is 2:1. Stir for 2 hours to obtain a cottonseed protein-protein denaturant-cationic mixed solution. Step 3: Pour the cottonseed protein-protein denaturant-cationic mixed solution into the mold, cast it into a liquid film, and then dry it in an 80°C oven for 50 minutes to obtain the cottonseed protein film for labeling.

[0030] Example 7 A method for preparing a cottonseed protein film for labeling includes the following steps: Step 1: Dissolve cottonseed protein in a 200 mmol / L sodium dodecyl sulfate solution. The mass of cottonseed protein is 8% of the mass of sodium dodecyl sulfate solution. Stir for 2 hours to obtain a cottonseed protein-protein denaturant dispersion. Step 2: Mix the cottonseed protein-protein denaturant dispersion with a 10% (w / w) polyethyleneimine solution. The mass ratio of the cottonseed protein-protein denaturant dispersion to the polyethyleneimine solution is 4:1. Stir for 2 hours to obtain a cottonseed protein-protein denaturant-cationic mixed solution. Step 3: Pour the cottonseed protein-protein denaturant-cationic mixed solution into a mold, cast it into a liquid film, and then dry it in an 80°C oven for 50 minutes to obtain a cottonseed protein film for labeling.

[0031] Example 8 A method for preparing a cottonseed protein film for labeling includes the following steps: Step 1: Dissolve 10% cottonseed protein in a 200 mmol / L sodium dodecyl sulfate solution. The mass of cottonseed protein is 10% of the mass of sodium dodecyl sulfate solution. Stir for 2 hours to obtain a cottonseed protein-protein denaturant dispersion. Step 2: Mix the cottonseed protein-protein denaturant dispersion with a 10% (w / w) polyethyleneimine solution. The mass ratio of the cottonseed protein-protein denaturant dispersion to the polyethyleneimine solution is 2:1. Stir for 2 hours to obtain a cottonseed protein-protein denaturant-cationic mixed solution. Step 3: Pour the cottonseed protein-protein denaturant-cationic mixed solution into a mold, cast it into a liquid film, and then dry it in an 80°C oven for 50 minutes to obtain a cottonseed protein film for labeling.

[0032] Example 9 A method for preparing a cottonseed protein film for labeling includes the following steps: Step 1: Dissolve cottonseed protein in a 200 mmol / L sodium dodecyl sulfate solution. The mass of cottonseed protein is 12% of the mass of sodium dodecyl sulfate solution. Stir for 2 hours to obtain a cottonseed protein-protein denaturant dispersion. Step 2: Mix the cottonseed protein-protein denaturant dispersion with a 10% (w / w) polyethyleneimine solution. The mass ratio of the cottonseed protein-protein denaturant dispersion to the polyethyleneimine solution is 3:1. Stir for 2 hours to obtain a cottonseed protein-protein denaturant-cationic mixed solution. Step 3: Pour the cottonseed protein-protein denaturant-cationic mixed solution into a mold, cast it into a liquid film, and then dry it in an 80°C oven for 50 minutes to obtain a cottonseed protein film for labeling.

[0033] Example 10 A method for preparing a cottonseed protein film for labeling includes the following steps: Step 1: Dissolve cottonseed protein in a 200 mmol / L sodium dodecyl sulfate solution. The mass of cottonseed protein is 10% of the mass of sodium dodecyl sulfate solution. Stir for 2 hours to obtain a cottonseed protein-protein denaturant dispersion. Step 2: Mix the cottonseed protein-protein denaturant dispersion with a 10% (w / w) polyethyleneimine solution. The mass ratio of the cottonseed protein-protein denaturant dispersion to the polyethyleneimine solution is 3:1. Stir for 2 hours to obtain a cottonseed protein-protein denaturant-cationic mixed solution. Step 3: Pour the cottonseed protein-protein denaturant-cationic mixed solution into a mold, cast it into a liquid film, and then dry it in an 80°C oven for 50 minutes to obtain a cottonseed protein film for labeling.

[0034] Example 11 This embodiment is basically the same as Embodiment 10, except that in step two, the 10% polyethyleneimine solution by mass is replaced with a modified polyethyleneimine solution. The method for preparing the modified polyethyleneimine solution is as follows: S1. According to the weight parts, add 1 part of protocatechuic acid to 60 parts of water and stir until dissolved. Then add 1 part of DMTMM-methanol solution. The mass ratio of DMTMM to methanol in the DMTMM-methanol solution is 15:100. Stir at 150 r / min in the dark for 15 min at room temperature to obtain a mixture. S2. Add 1 part of chitosan to 90 parts of 0.5wt% acetic acid solution and stir until dissolved. Adjust the pH to 5.5 with 0.1 mol / L sodium hydroxide solution. Then add the mixture and stir at 150 r / min in the dark for 2 h under nitrogen protection at room temperature. After the reaction is complete, dialyze with deionized water for 48 h to obtain modified chitosan solution. S3. Slowly add 10 parts of a 10% polyethyleneimine solution to the modified chitosan solution, stir until uniformly mixed, and then stir and react at 55°C for 8 hours. After the reaction is completed, continue to concentrate at 55°C until the solid content is 10% to obtain the modified polyethyleneimine solution.

[0035] Example 12 This embodiment is basically the same as Embodiment 10, except that in step two, the 10% polyethyleneimine solution by mass is replaced with a modified polyethyleneimine solution. The method for preparing the modified polyethyleneimine solution is as follows: By weight, 1 part chitosan was added to 90 parts of 0.5 wt% acetic acid solution and stirred until dissolved. Then, 10 parts of 10% polyethyleneimine solution were slowly added and stirred until evenly mixed. The mixture was then stirred at 55°C for 8 hours. After the reaction was completed, the mixture was further concentrated at 55°C until the solid content was 10% to obtain the modified polyethyleneimine solution.

[0036] Comparative Example 1 A method for preparing a cottonseed protein membrane includes the following steps: Step 1: Dissolve cottonseed protein in a 200 mmol / L sodium dodecyl sulfate solution. The mass of cottonseed protein is 10% of the mass of sodium dodecyl sulfate solution. Stir for 2 hours to obtain a cottonseed protein-protein denaturant dispersion. Step 2: Pour the cottonseed protein-protein denaturant dispersion into a mold, cast it into a liquid film, and then dry it in an oven at 80°C for 50 minutes to obtain a cottonseed protein film.

[0037] Comparative Example 2 This comparative example did not add sodium dodecyl sulfate solution, but replaced it with water. The remaining steps were the same as in Comparative Example 1. The cottonseed protein membrane was not obtained, and the cottonseed protein was obtained after drying.

[0038] The cottonseed protein films prepared in Examples 1-12 and Comparative Example 1 were subjected to 90° maximum peel force and overlap shear tests. The method was to conduct the 90° maximum peel force and overlap shear tests using a universal testing machine. The results are shown in Table 1.

[0039] Table 1 Table 1 shows that the orthogonal experiments of Examples 1-9 indicate the following factors affecting the maximum 90° peel force: cottonseed protein > sodium dodecyl sulfate > polyethyleneimine. The maximum peel film formation condition was found in Example 7, with a sodium dodecyl sulfate concentration of 200 mmol / L, a cottonseed protein content of 8%, and a cottonseed protein-sodium dodecyl sulfate dispersion:polyethyleneimine solution ratio of 4, resulting in a maximum peel force of 0.263 N. Range analysis of Examples 1-9 shows the following factors affecting overlap shear: polyethyleneimine > cottonseed protein > sodium dodecyl sulfate. The maximum overlap shear film formation condition was found in Example 10, with a sodium dodecyl sulfate concentration of 200 mmol / L, a cottonseed protein content of 10%, and a cottonseed protein-sodium dodecyl sulfate dispersion:polyethyleneimine solution ratio of 3. Under these conditions, the overlap shear strength was 7.356 kPa, the maximum value. Compared to Example 10, Examples 11-12 showed further increases in maximum peel force and overlap shear strength. This was due to the modification of the polyethyleneimine solution. By combining chitosan with polyethyleneimine, the film-forming properties and interfacial adhesion of the polyethyleneimine-crosslinked modified cottonseed protein were improved. Furthermore, in Example 11, the modification of chitosan further enhanced its adhesive properties, resulting in a cottonseed protein film with greater maximum peel force and overlap shear strength than that of Example 12. The test results show that the cottonseed protein films prepared in Examples 1-12 can all be used as labels. The resulting cottonseed protein film products are mainly used as temporary labels and can be quickly removed after getting wet. In contrast, the cottonseed protein film prepared in Comparative Example 1 has almost no adhesiveness and very weak overlap shear strength.

[0040] Figure 1 Infrared spectra of cottonseed protein membranes prepared in Example 10 (CPI-SDS-PEI), Comparative Example 1 (CPI-SDS), and Comparative Example 2 (CPI) obtained. A typical protein characteristic band was observed in the spectrum and identified as amide I (1655 cm⁻¹). -1 ), 1650cm -1The peak of the amide I band initially strengthens and then weakens. The stretching vibration of the carbonyl group indicates a process of initial deformation and unfolding followed by hydrophobic aggregation of cottonseed protein. This indirectly suggests that the cottonseed protein was successfully modified by sodium dodecyl sulfate, resulting in a change in protein structure. (IR 2918 cm⁻¹) -1 and 2845cm -1 The weakening of the peak at 3280 cm⁻¹ indicates a decrease in the number of methylene groups; -1 The leftward shift of the peak indicates a weakening of hydrogen bonding. The red shift of the sulfonate characteristic peak indicates that the negative charge on the modified cottonseed protein binds to polyethyleneimine.

[0041] Figure 2 This is a peel force diagram of the cottonseed protein film prepared in Example 10 of the present invention on different substrate surfaces. The peel force test results show that the cottonseed protein-sodium dodecyl sulfate-polyethyleneimine film exhibits relatively high peel force on high surface energy substrates such as aluminum, tin foil, glass, and paper, while its peel force is lower on low surface energy substrates such as plastics, rubber, stainless steel, and PTFE. However, it still meets basic adhesion requirements, and the overall peel force level meets the requirements for everyday label use.

[0042] Figure 3 This is a graph showing the solid content of the cottonseed protein film prepared in Example 10 of the present invention. The solid content analysis results show that the cottonseed protein film has a solid content of approximately 12%. This low solid content gives the film good flexibility and spreadability, which is beneficial for initial adhesion and avoids the problem of residual adhesive caused by long-term adhesion. The membrane-state cottonseed protein-sodium dodecyl sulfate-polyethyleneimine achieves controllable peeling behavior while ensuring adhesion to multiple substrates, demonstrating its potential application value in the field of peelable, short-term use labels.

[0043] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for preparing a cottonseed protein film for labeling, characterized in that, Includes the following steps: Step 1: Dissolve cottonseed protein in a protein denaturant solution and stir until homogeneous to obtain a cottonseed protein-protein denaturant dispersion. Step 2: Mix the cottonseed protein-protein denaturant dispersion with the cationic solution and stir until homogeneous to obtain a mixed solution of cottonseed protein-protein denaturant-cationic solution; Step 3: The cottonseed protein-protein denaturant-cationic mixed solution is dried by physical means to form a film, which is used for labeling.

2. The method for preparing the cottonseed protein film for labeling as described in claim 1, characterized in that, In step one, the mass of cottonseed protein is 7-15% of the mass of the protein denaturant solution.

3. The method for preparing the cottonseed protein film for labeling as described in claim 1, characterized in that, In step one, the protein denaturant in the protein denaturant solution is one of sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, sodium N-dodecyl sarcosinate, or bile salt; the concentration of the protein denaturant solution is 50~400 mmol / L.

4. The method for preparing the cottonseed protein film for labeling as described in claim 1, characterized in that, In step one, the stirring time is 1 to 3 hours.

5. The method for preparing the cottonseed protein film for labeling as described in claim 1, characterized in that, In step two, the cationic solution is one of the following: hexadecyltrimethylammonium bromide solution, benzalkonium chloride solution, polyethyleneimine solution, dioctadecyldimethylammonium chloride solution, copper ammonia solution, copper sulfate solution, and ferric chloride solution; the mass fraction of the cationic solution is 5-50%.

6. The method for preparing the cottonseed protein film for labeling as described in claim 1, characterized in that, In step two, the mass ratio of the cationic solution to the cottonseed protein-protein denaturant dispersion is 1~5:

1.

7. The method for preparing the cottonseed protein film for labeling as described in claim 1, characterized in that, In step two, the stirring time is 1 to 3 hours.

8. The method for preparing the cottonseed protein film for labeling as described in claim 1, characterized in that, In step three, the physical means include one of the following: casting, spin coating, drop coating, hot pressing, and blow molding coating; the drying temperature is 60~80℃, and the drying time is 30~120 min.

9. A cottonseed protein film for labeling prepared by the preparation method according to any one of claims 1-8.

10. The application of a cottonseed protein film for labeling prepared by any one of claims 1-8 in a label.

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