Amorphous glass fiber modified zein composite film and preparation method thereof

Abstract

The present application relates to a kind of amorphous glass fiber modified zein composite film and its preparation method.The present application utilizes the influence of biological microcrystalline glass on the structure of Zein in the condensation process and the high strength of microcrystalline glass itself to modify Zein film, effectively reduces the porosity of the film, and improves the mechanical properties and barrier properties of the film.The present application uses Zein as raw material to prepare Zein / amorphous glass fiber composite film, which not only increases the commercial value of Zein, but also provides a new idea for the research and development of degradable composite film, which is conducive to the development of degradable plastic industry in the future.

Description

Technical Field

[0001] This invention relates to biodegradable green packaging film preparation technology, and specifically to an amorphous glass fiber modified zein composite film and its preparation method. Background Technology

[0002] Biodegradable bioplastics refer to environmentally friendly plastics that are degradable and renewable, based on natural materials such as starch. Zein, a major byproduct of corn starch production, is a promising raw material for biodegradable plastic films. Zein is insoluble in water but soluble in 60%–95% (v / v) aqueous solutions of alcohols. As the solvent evaporates, protein molecules in the Zein solution self-assemble and aggregate through disulfide bonds, hydrophobic bonds, and hydrogen bonds to form a network-like film. Zein is widely available and possesses characteristics such as safety, non-toxicity, high barrier properties, degradability, and recyclability, gradually replacing petroleum-based plastic film products. However, pure zein films are brittle and have low strength, limiting their further application in industries such as packaging. Therefore, modification by adding cross-linking agents and high-strength mineral raw materials can meet practical application requirements. When crosslinking agents are added during the production of Zein films, the reactive ends of the crosslinking agents can react with specific functional groups of zein to form new chemical bonds, improving the spatial structure of the Zein film and enhancing its toughness and strength. However, most crosslinking agents are non-degradable petroleum-based polymers, which, while improving the strength of zein films, also introduce new forms of environmental pollution. When modifying Zein films using mineral raw materials, the mineral raw materials can improve the strength of zein films through dispersion strengthening. Although mineral raw materials are environmentally friendly, the mixing of mineral raw materials and zein is often a simple mechanical process, resulting in very limited strength improvement. Therefore, it is necessary to explore new modification methods to prepare biodegradable Zein composite films. Summary of the Invention

[0003] To address the issues of high brittleness and low strength in zein films, this invention provides an amorphous glass fiber modified zein film and its preparation method. The preparation method of this invention can improve the strength and toughness of zein. The resulting amorphous glass fiber modified zein film has low porosity and good mechanical and barrier properties.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows:

[0005] In a first aspect, the present invention provides a method for preparing an amorphous glass fiber modified zein film, comprising the following steps:

[0006] (1) Propyl orthosilicate, triethyl phosphate and calcium fluoride were added to deionized water in sequence, and acetic acid solution was added as a hydrolysis catalyst. The mixture was stirred until dissolved to obtain a modified sol.

[0007] (2) Add zein to an aqueous ethanol solution to obtain a zein ethanol solution;

[0008] (3) Add the modified sol to the zein ethanol solution, mix thoroughly, keep warm at a certain temperature to prepare a film solution, and dry to obtain the zein / amorphous glass fiber composite film.

[0009] Furthermore, in the modified sol raw material, the molar percentage of propyl orthosilicate is 55-70%; the molar percentage of calcium fluoride is 18-46%; and the molar percentage of triethyl phosphate is 4-12%.

[0010] Furthermore, the total concentration of Si, Ca, and P in the modified sol is 1 mol / L.

[0011] Furthermore, in the modified sol, the concentration of the acetic acid solution is 0.1–0.5 mol / L.

[0012] Furthermore, in the aqueous ethanol solution, the volume percentage of ethanol is 80% v / v.

[0013] Furthermore, zein powder is added to the ethanol aqueous solution at a ratio of 1:10 g / mL.

[0014] Furthermore, the volume percentage of the modified sol added to the zein ethanol solution is 5-30%.

[0015] Furthermore, the film-forming solution is spread out and dried to obtain an amorphous glass fiber modified zein film.

[0016] Furthermore, the heating temperature is 60–90°C and the heating time is 20–40 min.

[0017] Furthermore, the drying temperature is 45–55°C.

[0018] Secondly, the present invention provides an amorphous glass fiber modified zein membrane prepared by the above preparation method.

[0019] Thirdly, the present invention provides an application of amorphous glass fiber modified zein film in packaging and / or as a substitute for traditional plastic products.

[0020] This invention not only utilizes the high strength of the amorphous glass fibers, the product of Zein-modified sol hydrolysis, to strengthen Zein membranes, but also leverages the ability of the modified sol to alter the self-assembly process and final structure of Zein protein molecules during coagulation. This enhancement is achieved by affecting the Zein protein polypeptide chains, thereby improving Zein membrane performance. Propyl orthosilicate and triethyl phosphate in the modified sol hydrolyze to form silicon and phosphorus oxides and alcohols. During drying, silicon, phosphorus, and calcium atoms covalently or ionicly bond with oxygen atoms, forming an irregular spatial network structure, ultimately resulting in amorphous glass fibers. These amorphous glass fibers possess high strength and toughness, improving the strength and toughness of Zein membranes. Furthermore, the coagulation of the modified sol to form amorphous glass fibers also affects the unfolding degree of the Zein protein polypeptide chains. Free silicon, phosphorus, and calcium atoms can penetrate the protein interior, causing the Zein protein to unfold, exposing hydrophobic groups, and enhancing hydrophobic interactions. This allows zein molecules to self-assemble into structures with higher strength and plasticity. Meanwhile, the long silicon-oxygen chains in amorphous glass fibers can connect with the carboxyl groups of Zein protein molecules to form a more stable spatial network structure. Phosphorus-oxygen bonds can bond with the nitrogen atoms in the amino groups of Zein protein, enhancing molecular electrostatic repulsion and improving the mechanical properties of the film. Calcium atoms can bond with silicon and phosphorus atoms in the glass fibers and nitrogen atoms in the Zein protein molecules through oxygen atoms, effectively connecting the glass fibers and Zein protein. Furthermore, the large radius of calcium atoms themselves provides excellent dispersion strengthening, resulting in a significant strengthening effect on the Zein film.

[0021] The beneficial effects of this invention are as follows:

[0022] (1) This invention utilizes the influence of biocrystalline glass on the Zein structure during the condensation process and the high strength of the microcrystalline glass itself to modify the Zein film, effectively reducing the porosity of the film and improving the mechanical and barrier properties of the film.

[0023] (2) This invention uses zein as raw material to prepare a zein / amorphous glass fiber composite film, which not only increases the commercial value of zein, but also puts forward a new idea for the research and development of biodegradable composite films, which is conducive to the future development of the biodegradable plastics industry. Attached Figure Description

[0024] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0025] Figure 1 Tensile strength and elongation at break of amorphous glass fiber modified zein films with different Si, Ca, and P molar ratios were studied.

[0026] Figure 2 Oxygen permeability of amorphous glass fiber modified zein membranes with different Si, Ca, and P molar ratios;

[0027] Figure 3 Figure showing the effect of modified sol addition amount on the tensile strength of Zein film;

[0028] Figure 4 The effect of modified sol addition on the elongation at break of Zein. Detailed Implementation

[0029] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0030] This invention discovers that modifying zein films with amorphous glass fibers improves the strength and plasticity of the films, enhances their barrier properties, and solves the problem of insufficient strength and toughness in zein films. This invention proposes an amorphous glass fiber modified zein film, its preparation method, and its application.

[0031] A typical embodiment of the present invention provides a method for preparing an amorphous glass fiber modified zein membrane. The method involves adding zein to an aqueous ethanol solution to prepare a dispersion, adding a silicon-calcium-phosphorus modified sol to the dispersion and mixing them, heating the mixture at a certain temperature to react and prepare a film-forming solution, and then heating and drying the film-forming solution to obtain an amorphous glass fiber modified zein membrane.

[0032] In some embodiments of this implementation, propyl orthosilicate, triethyl phosphate, and calcium fluoride are added sequentially to a certain amount of deionized water in a certain proportion, and the mixture is stirred continuously with a magnetic stirrer until completely dissolved to obtain a zein-modified sol. The total molar amount of propyl orthosilicate, triethyl phosphate, and calcium fluoride is mixed with deionized water to a concentration of 1 mol / L to prepare the modified sol.

[0033] In some embodiments of this implementation, the molar percentage of propyl orthosilicate in the modified sol raw material is 55–70 mol.%. Experiments show that the content of propyl orthosilicate affects the membrane performance; when the molar percentage of propyl orthosilicate is 58–65 mol.%, the membrane strength is higher and the elongation at break is greater. When the molar percentage of propyl orthosilicate is 60–62 mol.%, the membrane strength is even higher.

[0034] In some embodiments of this implementation, the molar percentage of calcium fluoride in the modified sol raw material is 18–46 mol.%. Experiments have shown that the calcium fluoride content also affects the membrane performance; when the molar percentage of calcium fluoride is 27–35%, the membrane strength is higher and the elongation at break is greater. When the molar percentage of calcium fluoride is 30–33 mol.%, the membrane strength is even higher.

[0035] In some embodiments of this implementation, the molar percentage of triethyl phosphate in the modified sol raw material is 4–12 mol.%. Experiments have shown that the content of triethyl phosphate also affects the membrane performance; when the molar percentage of triethyl phosphate is 6–10 mol.%, the membrane strength is higher and the elongation at break is greater. When the molar percentage of triethyl phosphate is 8–9 mol.%, the membrane strength is even higher.

[0036] In some embodiments of this implementation, the volume percentage of Zein-modified sol added to the zein ethanol solution is 5-30%. When the volume percentage of Zein-modified sol is 5-30%, the film exhibits good tensile and barrier properties; when the volume percentage of Zein-modified sol is 10-15%, the film exhibits optimal tensile and barrier properties.

[0037] In some embodiments of this implementation, the heating reaction temperature is 60–90°C. A heating reaction temperature of 75–85°C results in better tensile properties of the film, while a heating reaction temperature of 79–81°C produces the best tensile properties.

[0038] In some embodiments of this implementation, the heating reaction time is 20 to 40 minutes.

[0039] In some embodiments of this implementation, the drying temperature is 45–55°C.

[0040] Another embodiment of the present invention provides an amorphous glass fiber modified zein membrane, obtained by the above preparation method.

[0041] A third embodiment of the present invention provides an application of the above-mentioned amorphous glass fiber modified zein film in packaging and / or as a substitute for traditional plastic products.

[0042] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0043] Material:

[0044] Propyl orthosilicate and triethyl phosphate were purchased from Tianjin Kemeo Chemical Reagent Co., Ltd.; zein (99%, molecular weight 164.2 kDa) and calcium fluoride were purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; and ethanol and acetic acid were purchased from Sinopharm Chemical Reagent Co., Ltd.

[0045] Performance testing methods:

[0046] (1) Tensile property test

[0047] The tensile properties of Zein film were tested using a ZQ-990LA electric tensile and compressive testing machine (ZQ, Dongguan) according to the standard test method for tensile properties of plastics (ASTM-D882-09). Tensile test samples were prepared as 10mm × 7mm squares, and the tensile speed was set to 500mm / min.

[0048] (2) Test of oxygen permeability

[0049] Oxygen permeability was determined using a VAC-V1 differential pressure permeability tester. The test was conducted in a standard environment (23℃, 50% relative humidity) according to GB / T 2918-1998, with the following experimental parameters set: proportional mode 5%, upper and lower degassing time 4h, GTR > 1.

[0050] Example 1:

[0051] (1) According to the modified sol raw material ratio shown in Table 1, weigh out propyl orthosilicate, triethyl phosphate and calcium fluoride respectively, and add them to a certain amount of deionized water in sequence to prepare a solution with a total concentration of Si, Ca and P of 1 mol / 1 L. Add acetic acid solution as a hydrolysis catalyst according to a concentration of 0.1 mol / L, and stir continuously with a magnetic stirrer until the solute is dissolved to obtain zein modified sol.

[0052] (2) Prepare an ethanol aqueous solution with a volume fraction of 80% v / v using deionized water as solvent. Add zein powder to the above ethanol solution at a ratio of 1:10 g / ml and stir magnetically at room temperature until completely dissolved to obtain zein ethanol solution.

[0053] (3) Add 10% by volume of Zein modified sol to the zein ethanol solution, stir and react for 30 minutes in a magnetic stirrer at 80°C, and prepare a film solution after thorough mixing.

[0054] (4) Cool the film-forming solution to room temperature, then pour the film-forming solution into a square petri dish and place it in a preheated drying oven at 50°C for 3 hours to obtain an amorphous glass fiber modified zein film.

[0055] Table 1. Proportioning of Modified Sol Raw Materials

[0056]

[0057]

[0058] Figure 1 The tensile strength and elongation at break of zein films modified with amorphous glass fibers of different Si, Ca, and P molar ratios were investigated. The Zein film, a pure Zein film without modified sol, exhibited a tensile strength of only 4.58 MPa and an elongation at break of 1.52%. The addition of modified sols with different Si, Ca, and P molar ratios significantly improved both tensile strength and elongation at break. The film with Z3 sol (Si:Ca:P molar ratio of 60%:32%:8%) showed the highest tensile strength, reaching 25.35 MPa. This strength improvement is attributed to the inherent high strength of the amorphous glass fibers and the influence of the modified sol on the self-assembly process of Zein protein molecules during aggregation, thus improving the Zein film performance. Although the addition of modified sols increased the tensile strength of the films, the most ideal strength improvement was observed when the Si content in the modified sol was 60–65%, the Ca content was 27–35%, and the P content was 8–10%.

[0059] When the molar ratio of Si, Ca, and P in the sol is within a suitable range, the strength of the amorphous glass fiber itself and its influence on the Zein protein structure can reach the ideal state, resulting in a good modification effect on the Zein film. However, when the ratio deviates significantly, the strength of the amorphous glass fiber itself will decrease substantially, and its influence on the Zein protein structure will also weaken. Among them, Ca has a large atomic radius and can play a good role in dispersion reinforcement of the film, but excessively high or low contents will reduce this dispersion effect; P atoms can interact with amino groups in Zein protein to enhance the electrostatic repulsion of protein molecules, but when the P content is too high, it tends to exist in the form of phosphate, weakening its reinforcing ability; Si is the most important element in constituting the glass fiber network structure and is the most important additive element for film modification and reinforcement, but excessively high silicon content will reduce the content of other elements and weaken their reinforcing effects.

[0060] Based on the results of the elongation at break of amorphous glass fiber modified zein films with different Si, Ca, and P molar ratios, increasing the molar ratio of Si and P in the modified sol helps to improve the elongation at break of the film. This is because Si atoms readily form silicon-oxygen tetrahedra with oxygen and expand to form a spatial network structure, while P atoms readily bond with N atoms in the amino groups of zein protein, promoting long-chain bonding of protein molecules, thereby improving the plasticity and elongation at break of the film.

[0061] Figure 2 The figures show the oxygen permeability test results for amorphous glass fiber-modified zein films with different Si, Ca, and P molar ratios. As can be seen from the figures, the oxygen permeability of the amorphous glass fiber-modified zein films is lower than that of the Zein films. This is because the addition of the modified sol makes the film structure more compact, and the Zein molecular structure forms a good oxygen barrier under the enhanced polar forces, indicating that amorphous glass fibers can improve the barrier performance of the film.

[0062] Example 2

[0063] (1) Prepare the modified sols Z3, Z4, Z5 and Z6 shown in Table 1 according to the preparation method of Zein modified sol in Implementation Case 1.

[0064] (2) Prepare an ethanol aqueous solution with a volume fraction of 80% v / v using deionized water as solvent. Add zein powder to the above ethanol solution at a ratio of 1:10 g / ml and stir magnetically at room temperature until completely dissolved to obtain zein ethanol solution.

[0065] (3) Add 5%, 10%, 15%, 20%, 25%, and 30% Zein modified sol to the zein ethanol solution by volume, stir and react for 30 minutes in a magnetic stirrer at 80°C, and prepare a film solution after thorough mixing.

[0066] (4) Cool the film-forming solution to room temperature, then pour the film-forming solution into a square petri dish and place it in a preheated drying oven at 50°C for 3 hours to obtain an amorphous glass fiber modified zein film.

[0067] Figure 3 and Figure 4 The tensile strength and elongation at break of Zein films modified with different amounts of modified sol are shown. The addition of the four modified sol components exhibits the same trend in affecting the tensile strength and elongation at break of the films: with increasing sol content, both tensile strength and elongation at break initially increase and then decrease. Furthermore, when the addition amount is 30%, the strength and elongation at break of the four types of films tend to be consistent. When the addition amount is 10–15%, the sol has a better modification effect on the films.

[0068] Example 3

[0069] (1) Weigh out propyl orthosilicate, triethyl phosphate and calcium fluoride in a molar ratio of 60:32:8 and add them to a certain amount of deionized water to prepare a solution with a total concentration of Si, Ca and P of 1 mol / L. Add a small amount of acetic acid solution as a hydrolysis catalyst and stir continuously with a magnetic stirrer until the solute is dissolved to obtain zein modified sol.

[0070] (2) Prepare an ethanol aqueous solution with a volume fraction of 80% v / v using deionized water as solvent. Add zein powder to the above ethanol solution at a ratio of 1:10 g / ml and stir magnetically at room temperature until completely dissolved to obtain zein ethanol solution.

[0071] (3) Add 10% Zein modified sol to the zein ethanol solution by volume, and stir in a magnetic stirrer at temperatures of 60℃, 70℃, 80℃ and 90℃ for 30 minutes to prepare a film solution after thorough mixing.

[0072] (4) Cool the film-forming solution to room temperature, then pour the film-forming solution into a square petri dish and place it in a preheated drying oven at 50°C for 3 hours to obtain an amorphous glass fiber modified zein film.

[0073] The tensile properties of films prepared under different reaction temperatures are shown in Table 2. At low temperatures, the modified sol cannot fully react with Zein protein, resulting in lower tensile strength. The reaction effect is better at a reaction temperature of 80℃, and the tensile strength of the film is the highest. The elongation at break of the Zein film is less affected by temperature changes, but the maximum elongation at break also occurs at 80℃. Therefore, in this invention, the ideal reaction temperature is 80℃, but it can be varied within the range of 75–85℃.

[0074] Table 2 Effect of different reaction temperatures on film tensile properties

[0075]

[0076] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing an amorphous glass fiber modified zein film, characterized in that, Includes the following steps: (1) Propyl orthosilicate, triethyl phosphate and calcium fluoride were added to deionized water in sequence, and acetic acid solution was added as a hydrolysis catalyst. The mixture was stirred until dissolved to obtain a modified sol. (2) Add zein to an aqueous ethanol solution to obtain a zein ethanol solution; (3) Add the modified sol to the zein ethanol solution, mix thoroughly, keep warm at a certain temperature to prepare the film solution, and dry to obtain the zein / amorphous glass fiber composite film; In the modified sol raw material, the molar percentage of propyl orthosilicate is 55-70%; the molar percentage of calcium fluoride is 18-46%; the molar percentage of triethyl phosphate is 4-12%; and the total concentration of Si, Ca, and P in the modified sol is 1 mol / L. Add zein powder to the ethanol-water solution at a ratio of 1:10 g / mL; The volume percentage of the modified sol added to the zein ethanol solution is 5-30%. The heating reaction temperature is 60~90℃ and the heating reaction time is 20~40 min; the drying temperature is 45~55℃.

2. The preparation method according to claim 1, characterized in that, In the modified sol, the concentration of acetic acid solution is 0.1~0.5 mol / L.

3. The preparation method according to claim 1, characterized in that, In an aqueous ethanol solution, the volume percentage of ethanol is 80%.

4. The amorphous glass fiber modified zein membrane prepared by the preparation method according to any one of claims 1-3.

5. The application of the amorphous glass fiber modified zein film as described in claim 4 in replacing traditional plastic products.

6. The application of the amorphous glass fiber modified zein film as described in claim 5 in the packaging field.

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