Multifunctional gelatin-based intelligent packaging film with full-temperature-zone temperature control function and preparation method of multifunctional gelatin-based intelligent packaging film

Abstract

The invention discloses a multifunctional gelatin-based intelligent packaging film with a full-temperature-zone temperature control function and a preparation method of the multifunctional gelatin-based intelligent packaging film. According to the method, firstly, polyethylene glycol and a silane coupling agent are subjected to hydrolytic condensation to synthesize hyperbranched polysiloxane with a phase change chain segment and a Si-O-Si structure, then the hyperbranched polysiloxane is blended with nano zinc oxide and gelatin, and the intelligent packaging film is prepared through film forming and drying. According to the film, through a dual mechanism of phase change energy storage regulation and passive radiation cooling, the temperature is regulated through phase change heat absorption of polyethylene glycol in the low-temperature stage of temperature rising when refrigerated food is exposed to the natural environment, after the temperature rises to the high temperature, the temperature is reduced through passive radiation cooling of Si-O-Si and nano-zinc oxide, and therefore temperature regulation of a whole temperature area is achieved; meanwhile, the film has good ultraviolet barrier, antibacterial and antioxidant properties. The technology is simple, convenient, environmentally friendly and suitable for the field of intelligent packaging of fresh food sensitive to temperature.

Description

Technical Field

[0001] This invention belongs to the field of packaging film preparation technology, specifically relating to a multifunctional gelatin-based smart packaging film with full-temperature-range temperature control and its preparation method. Background Technology

[0002] Temperature fluctuations not only accelerate food spoilage and nutrient loss but also severely impact its sensory quality. As the requirements for temperature stability and food safety in fresh food storage increase, traditional packaging materials, lacking temperature regulation capabilities, struggle to cope with frequent temperature fluctuations during logistics and transportation. Smart packaging films, as an emerging technology, can sense and respond to environmental changes through embedded functional components, demonstrating enormous potential in ensuring the safety of fresh food transportation and storage. Therefore, developing smart packaging materials that combine temperature control and preservation performance has become a crucial issue that urgently needs to be addressed.

[0003] Passive radiative cooling is a green cooling strategy that reduces the surface temperature of materials by efficiently reflecting sunlight in the 0.3 to 2.5 μm wavelength range and radiating long-wave infrared energy into outer space through atmospheric transparency windows in the 8 to 13 μm range. It is suitable for cooling in medium to high temperature environments. However, in the initial stage of temperature recovery for refrigerated food exposed to the natural environment, as the product slowly warms from a frozen state, the packaging material temperature is lower than the ambient temperature, lacking a sufficient effective radiative gradient. Heat is more easily transferred from the outside, rendering passive radiative cooling almost ineffective at this stage and failing to meet the temperature control requirements in low-temperature environments.

[0004] Phase change materials effectively regulate temperature changes and maintain a relatively stable internal temperature of the packaging by absorbing or releasing latent heat during the phase change process, thus providing temperature regulation in low-temperature environments. However, their cooling range is limited, making it difficult to achieve sustained cooling in high-temperature environments.

[0005] Furthermore, modern fresh food packaging not only needs temperature control but also demands higher levels of protection, including UV blocking, antibacterial properties, and antioxidant capabilities, to comprehensively extend shelf life and improve food safety. Existing single-function packaging materials are insufficient to meet these multi-functional requirements; therefore, there is an urgent need to develop a new type of intelligent packaging film that integrates full-temperature-range control and multi-functional protection. The full-temperature range refers to the temperature recovery range after refrigerated food exposure (-10℃ to 50℃). Summary of the Invention

[0006] To overcome the shortcomings of the prior art, the present invention provides a multifunctional gelatin-based smart packaging film with full-temperature-range temperature control and its preparation method.

[0007] The technical solution adopted in this invention is implemented according to the following steps: Step 1: Preparation of hyperbranched polysiloxanes: By mass, 30 parts of silane coupling agent and 120-200 parts of polyethylene glycol are added to a three-necked flask. After purging N2 to remove oxygen from the system, the mixture is reacted in an oil bath at 100-130 ℃ for 1-3 h. The temperature is then increased to 140-180 ℃ for 2-4 h. N2 is continuously purged during the reaction to avoid side reactions. Finally, a pale yellow transparent liquid product, hyperbranched polysiloxane, is obtained. Step 2: Preparation of a multifunctional gelatin-based smart packaging film with full-temperature-range temperature control: By weight, 20 parts of gelatin were first dispersed in 180 parts of deionized water and stirred continuously in a constant temperature water bath at 40-60 ℃ for 30-60 min to obtain a 20 wt% gelatin solution. 4-20 parts of hyperbranched polysiloxane were added dropwise to 200 parts of the gelatin solution, and the reaction was carried out at 40-80 ℃ for 1-4 h. After the reaction was completed, 0.1-1 parts of nano-zinc oxide were added, and the mixture was ultrasonically stirred at 40-60 ℃ for 30-60 min. Finally, the mixed solution was poured into a polytetrafluoroethylene mold and dried at room temperature to obtain a multifunctional gelatin-based smart packaging film with full-temperature temperature control.

[0008] The silane coupling agent in step one includes one or more combinations of γ-aminopropyltriethoxysilane, 3-glycidyl etheroxypropyltrimethoxysilane, and 3-methacryloyloxypropyltrimethoxysilane.

[0009] A multifunctional gelatin-based smart packaging film with full-temperature-range temperature control was prepared by the method described above.

[0010] The technical principle of this invention is as follows: In this film, the polyethylene glycol segments in the hyperbranched polysiloxane exhibit reversible solid-liquid phase transition properties. During the initial exposure of refrigerated food to ambient temperature, as the product slowly warms from a frozen state, the polyethylene glycol actively absorbs transferred heat, slowing the rapid temperature rise inside the packaging and thus achieving temperature regulation in the low-temperature range. Furthermore, the stretching vibrations of Si–O–Si and Si–O in the hyperbranched polysiloxane significantly enhance the film's radiative capacity in the mid-infrared band, contributing to heat radiation and achieving passive radiative cooling in high-temperature environments. Simultaneously, nano-zinc oxide possesses excellent solar reflectivity, particularly exhibiting good infrared radiation performance in the 8–13 μm atmospheric window range, further synergistically enhancing the material's radiative cooling effect in high-temperature environments. Through a dual mechanism of "passive radiative cooling and phase change energy storage regulation," this film can achieve adaptive temperature control across the entire temperature range from low to high temperatures. In terms of multifunctional protection, nano-zinc oxide can effectively absorb and scatter ultraviolet rays, inhibiting UV-induced food oxidation. It exerts a synergistic antibacterial effect by interacting with bacterial cell walls, releasing Zn²⁺ to interfere with metabolism, and generating reactive oxygen species under light to damage cell membranes, thus endowing the film with antibacterial properties. Simultaneously, the oxygen and zinc vacancies on the ZnO surface can capture free radicals, inhibiting oxidation chain reactions and further enhancing the material's antioxidant properties.

[0011] Compared with other existing technical solutions, the present invention has at least the following beneficial effects: Green and environmentally friendly materials: This invention uses gelatin, a biomass raw material, as the base material and adds environmentally friendly functional components. This not only reduces the consumption of non-renewable resources, but also results in a film with good biodegradability. It has sustainable development potential in the field of smart food packaging and meets the dual requirements of modern packaging for functionality and ecological safety.

[0012] Achieving full-temperature range control: This invention achieves full-temperature range control of the film through a dual mechanism of "passive radiative cooling and phase change energy storage regulation." In the low-temperature range, the internal temperature of the packaging is regulated through a phase change heat absorption mechanism. In high-temperature environments, passive radiative cooling is achieved through the synergy between the Si–O–Si and Si–O structures in the hyperbranched polysiloxane and nano-zinc oxide. This effectively regulates temperature fluctuations across the entire temperature range as refrigerated food is exposed to the natural environment and temperatures rise, overcoming the limitation of traditional materials that only have a single temperature range.

[0013] Multifunctional protective properties: By adding the functional component nano zinc oxide, this invention endows the film with excellent UV blocking properties, antibacterial and antioxidant properties, effectively delaying the oxidative spoilage process of food, extending the shelf life of products, and significantly improving the overall preservation performance of packaging materials. Attached Figure Description

[0014] Figure 1This is the synthetic route for the hyperbranched polysiloxane of the present invention.

[0015] Figure 2 The above is the 1H NMR spectrum of the hyperbranched polysiloxane in Example 1 of the present invention.

[0016] Figure 3 The temperature change inside the gelatin-based smart packaging film in Example 1 of the present invention is compared with that of PVC packaging film at different times. Detailed Implementation

[0017] The present invention will now be described in detail with reference to specific embodiments. These descriptions are only for further illustrating the features and advantages of the present invention and are not intended to limit the claims of the present invention.

[0018] Example 1 Step 1: Preparation of hyperbranched polysiloxanes: By mass fraction, 30 parts of γ-aminopropyltriethoxysilane and 160 parts of polyethylene glycol were added to a three-necked flask. After purging the system with N2 to remove oxygen, the mixture was reacted in an oil bath at 120 °C for 2 h. The temperature was then increased to 150 °C and reacted for another 3 h. N2 was continuously purged during the reaction to avoid side reactions. The final product, hyperbranched polysiloxane, was obtained as a pale yellow transparent liquid.

[0019] Step 2: Preparation of a multifunctional gelatin-based smart packaging film with full-temperature-range temperature control: By weight, 20 parts of gelatin were first dispersed in 180 parts of deionized water and stirred continuously in a 60 ℃ constant temperature water bath for 60 min to obtain a 20 wt% gelatin solution. 12 parts of hyperbranched polysiloxane were added dropwise to 200 parts of the gelatin solution, and the reaction was carried out at 60 ℃ for 2 h. After the reaction was completed, 0.8 parts of nano-zinc oxide were added, and the mixture was ultrasonically stirred at 40 ℃ for 30 min. Finally, the mixed solution was poured into a polytetrafluoroethylene mold and dried at room temperature to obtain a multifunctional gelatin-based smart packaging film with full-temperature temperature control.

[0020] Example 2 Step 1: Preparation of hyperbranched polysiloxanes: By mass fraction, 30 parts of γ-aminopropyltriethoxysilane and 200 parts of polyethylene glycol were added to a three-necked flask. After purging the system with N2 to remove oxygen, the mixture was reacted in an oil bath at 130 °C for 1 h, and then the temperature was increased to 180 °C for 2 h. N2 was continuously purged during the reaction to avoid side reactions. Finally, a pale yellow transparent liquid product, hyperbranched polysiloxane, was obtained.

[0021] Step 2: Preparation of a multifunctional gelatin-based smart packaging film with full-temperature-range temperature control: By weight, 20 parts of gelatin were first dispersed in 180 parts of deionized water and stirred continuously in a 50 ℃ constant temperature water bath for 50 min to obtain a 20 wt% gelatin solution. 20 parts of hyperbranched polysiloxane were then added dropwise to 200 parts of the gelatin solution, and the reaction was carried out at 80 ℃ for 1 h. After the reaction was completed, 1 part of nano-zinc oxide was added, and the mixture was ultrasonically stirred at 60 ℃ for 60 min. Finally, the mixed solution was poured into a polytetrafluoroethylene mold and dried at room temperature to obtain a multifunctional gelatin-based smart packaging film with full-temperature temperature control.

[0022] Example 3 Step 1: Preparation of hyperbranched polysiloxanes: By mass parts, 30 parts of γ-aminopropyltriethoxysilane and 120 parts of polyethylene glycol were added to a three-necked flask. After purging the system with N2 to remove oxygen, the mixture was reacted in an oil bath at 100 °C for 3 h. The temperature was then increased to 140 °C and reacted for another 4 h. N2 was continuously purged during the reaction to avoid side reactions. The final product was a pale yellow transparent liquid product, hyperbranched polysiloxane.

[0023] Step 2: Preparation of a multifunctional gelatin-based smart packaging film with full-temperature-range temperature control: By weight, 20 parts of gelatin were first dispersed in 180 parts of deionized water and stirred continuously in a 40 ℃ constant temperature water bath for 30 min to obtain a 20 wt% gelatin solution. Four parts of hyperbranched polysiloxane were added dropwise to 200 parts of the gelatin solution, and the reaction was carried out at 40 ℃ for 4 h. After the reaction was completed, 0.1 parts of nano-zinc oxide were added, and the mixture was ultrasonically stirred at 40 ℃ for 30 min. Finally, the mixed solution was poured into a polytetrafluoroethylene mold and dried at room temperature to obtain a multifunctional gelatin-based smart packaging film with full-temperature temperature control.

[0024] Example 4 Step 1: Preparation of hyperbranched polysiloxanes: By mass, 30 parts of 3-glycidyl etheroxypropyltrimethoxysilane and 160 parts of polyethylene glycol were added to a three-necked flask. After purging the system with N2 to remove oxygen, the mixture was reacted in an oil bath at 120 °C for 2 h, and then the temperature was increased to 150 °C for 3 h. N2 was continuously purged during the reaction to avoid side reactions. Finally, a pale yellow transparent liquid product, hyperbranched polysiloxane, was obtained.

[0025] Step 2: Preparation of a multifunctional gelatin-based smart packaging film with full-temperature-range temperature control: By weight, 20 parts of gelatin were first dispersed in 180 parts of deionized water and stirred continuously in a 60 ℃ constant temperature water bath for 60 min to obtain a 20 wt% gelatin solution. 12 parts of hyperbranched polysiloxane were added dropwise to 200 parts of the gelatin solution, and the reaction was carried out at 60 ℃ for 4 h. After the reaction was completed, 0.8 parts of nano-zinc oxide were added, and the mixture was ultrasonically stirred at 40 ℃ for 30 min. Finally, the mixed solution was poured into a polytetrafluoroethylene mold and dried at room temperature to obtain a multifunctional gelatin-based smart packaging film with full-temperature temperature control.

[0026] Example 5 Step 1: Preparation of hyperbranched polysiloxanes: By mass, 30 parts of 3-methacryloyloxypropyltrimethoxysilane and 160 parts of polyethylene glycol were added to a three-necked flask. After purging the system with N2 to remove oxygen, the mixture was reacted in an oil bath at 120 °C for 2 h. The temperature was then increased to 150 °C and reacted for another 3 h. N2 was continuously purged during the reaction to avoid side reactions. The final product was a pale yellow transparent liquid product, hyperbranched polysiloxane.

[0027] Step 2: Preparation of a multifunctional gelatin-based smart packaging film with full-temperature-range temperature control: By weight, 20 parts of gelatin were first dispersed in 180 parts of deionized water and stirred continuously in a 60 ℃ constant temperature water bath for 60 min to obtain a 20 wt% gelatin solution. 12 parts of hyperbranched polysiloxane were added dropwise to 200 parts of the gelatin solution, and the reaction was carried out at 60 ℃ for 4 h. After the reaction was completed, 0.8 parts of nano-zinc oxide were added, and the mixture was ultrasonically stirred at 40 ℃ for 30 min. Finally, the mixed solution was poured into a polytetrafluoroethylene mold and dried at room temperature to obtain a multifunctional gelatin-based smart packaging film with full-temperature temperature control.

[0028] Comparative Example 1 The only difference between this comparative example and Example 1 is that γ-aminopropyltriethoxysilane in step one is replaced with glycerol glycidyl ether; all other raw materials and processes are the same as in Example 1.

[0029] Comparative Example 2 The only difference between this comparative example and Example 2 is that polyethylene glycol is replaced with ethylene glycol in step one; all other raw materials and processes are the same as in Example 2.

[0030] Comparative Example 3 The only difference between this comparative example and Example 2 is that nano zinc oxide is not added in step two; all other raw materials and processes are the same as in Example 2.

[0031] The detection methods for each indicator of this invention are as follows: reflectivity The reflectance of the samples in the wavelength range of 0.2-2.5 μm was tested using a PerkinElmer UV-vis-NIR spectrophotometer (with integrating sphere accessory Lambda750S).

[0032] Infrared emissivity The emissivity in the mid-infrared band was measured using a Nicolet IS.50 Fourier transform infrared spectroscopy spectrometer equipped with an integrating sphere from Thermo Fisher Scientific, USA. The test method adopted the reflection method (according to Kirchhoff's law, due to the opacity of the object, emissivity = 1 - reflectivity - transmittance), and the test wavelength range was 2.5-25 μm.

[0033] enthalpy of fusion To evaluate the phase change thermal storage performance of polyethylene glycol (PEG) segments in the thin film, 3–5 mg of the film sample was weighed and placed in an aluminum crucible. Using a DSC-Q 2000 differential scanning calorimeter, the sample was heated from -70 °C to 110 °C at a heating rate of 10 °C / min under a nitrogen atmosphere. The enthalpy of fusion (ΔH) of PEG was calculated from the melting endothermic peak in the heat flow curve. m This reflects the thermal regulation capability of the thin film in low-temperature environments.

[0034] UV blocking rate The transmittance T of the membrane in the range of 200 to 400 nm was measured using a UV spectrophotometer. (λ) The UV protection performance of a film is reflected in its UV shielding rate, which is calculated using the following formula: Antioxidant test The antioxidant activity of the membrane was evaluated using the DPPH radical scavenging method. Specifically, a 0.1 mM DPPH solution was prepared using 2,2-biphenyl-2-picrylhydrazine and ethanol-water (ethanol:water = 1:1). 20 mg of the membrane sample was immersed in 4 mL of the 0.1 mM DPPH solution and reacted for 60 min under light-protected conditions. The absorbance was measured at 517 nm using a UV-Vis spectrophotometer. A DPPH solution without the added sample was used as a blank control. The radical scavenging rate was calculated according to Equation 2-3. In the formula: A c Indicates the absorbance of the DPPH solution without the thin film sample; A s This indicates the absorbance of the DPPH solution containing the thin film sample.

[0035] Antibacterial test Culture medium and PBS buffer were prepared according to national standard GB / T 21866-2008. Following ISO 22196:2011, the antibacterial activity of the membrane was evaluated using colony counting, with Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli as model strains.

[0036] Specifically, 10 μL of bacterial suspension was evenly spread onto the surface of the film sample, and the sample with bacterial suspension was incubated in a biochemical incubator at 37 °C and 90% RH for 2 h. Then, the sample was transferred to a container containing 10 mL of PBS buffer, and the bacterial suspension was obtained by shaking the container. The bacterial suspension was diluted a certain factor and then added dropwise to solidified culture medium. The culture dish was incubated in a biochemical incubator at 37 °C and 90% RH for 24 h. The inhibition rate was calculated according to formula 2-4. In the formula: N0—Number of cells in the control group; N1—The number of surviving cells in the sample group.

[0037] The film performance test results of the above embodiments and comparative examples are compared in Tables 1 and 2.

[0038] Table 1 Comparison of temperature control capabilities of gelatin-based smart packaging films Table 2 Comparison of the preservation performance of gelatin-based smart packaging films By comparing Examples 1-3, it can be found that within the technical framework of this invention, whether adjusting the ratio of silane coupling agent to polyethylene glycol in the synthesis of hyperbranched polysiloxanes or changing its addition amount in the gelatin system, gelatin-based smart packaging films with full-temperature range control capabilities and multifunctional protective properties can be successfully prepared. Although the specific properties of the films differ under different formulation conditions, they still exhibit good functionality overall, verifying the high feasibility of this invention and the flexibility of formulation design.

[0039] By comparing Example 1 with Examples 4-5, it was found that within the technical framework of this invention, even if the type of silane coupling agent used to synthesize the hyperbranched polysiloxane is changed, the resulting film still possesses similar temperature control function across the entire temperature range and multiple preservation properties. This result indicates that this invention has good raw material compatibility and process adaptability, which helps to broaden the optional raw material system and enhance the promotion value of this technology in practical applications.

[0040] The comparison between Example 1 and Comparative Example 1 highlights the crucial role of the Si–O–Si and Si–O structures in hyperbranched polysiloxanes in enhancing infrared radiation capability. Hyperbranched polymers synthesized using non-silane coupling agents (such as glycerol glycidyl ether) lack infrared-active groups, resulting in a significant decrease in the radiation capability of the prepared films in the mid-infrared band and unsatisfactory radiative cooling effect. However, the introduction of silane coupling agents leads to the formation of abundant Si–O–Si and Si–O bonds. The stretching vibrations of these groups significantly enhance the infrared emissivity of the film, significantly improving its passive cooling capability under high-temperature environments.

[0041] The comparison between Example 1 and Comparative Example 2 highlights the crucial role of polyethylene glycol monomers in constructing multifunctional gelatin-based smart packaging films with full-temperature-range temperature control. Replacing polyethylene glycol with ethylene glycol, which lacks phase change capability, resulted in a film with a melting enthalpy of 0, unable to achieve phase change heat absorption regulation, thus failing to release ambient heat at low temperatures. In contrast, the polyethylene glycol-containing film can absorb heat through its phase change behavior during the initial exposure of refrigerated food to room temperature, as the product slowly warms from a frozen state, thereby regulating the internal temperature of the packaging and achieving temperature control in low-temperature environments.

[0042] The comparison between Example 1 and Comparative Example 3 highlights the multiple functional contributions of nano-zinc oxide. The film without added nano-zinc oxide showed a significant decrease in solar reflectivity, UV blocking rate, antioxidant properties, and antibacterial performance. In contrast, nano-zinc oxide enhances the film's solar reflectivity and radiative cooling capacity through its excellent optical reflectivity. Simultaneously, its UV absorption, free radical scavenging, and antibacterial capabilities endow the film with excellent UV protection, antioxidant, and antibacterial properties, thereby effectively extending the shelf life of food. These comparative results systematically verify the scientific and technical rationality of this invention in terms of molecular structure design, functional mechanism construction, and multi-performance integration.

[0043] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. 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 a multifunctional gelatin-based smart packaging film with full-temperature-range temperature control, characterized in that, Includes the following steps: Step 1: Dissolve silane coupling agent and polyethylene glycol in methanol, add to a three-necked flask, purge with nitrogen to remove oxygen from the system, and heat at different temperatures to react. Nitrogen is continuously purged throughout the reaction to prevent side reactions, and finally hyperbranched polysiloxane is obtained. Step 2: The hyperbranched polysiloxane is added dropwise to a 20 wt% gelatin solution, heated to react, then nano zinc oxide is added, and ultrasonic reaction is carried out. Finally, the solution is poured into a polytetrafluoroethylene mold and dried at room temperature to obtain a multifunctional gelatin-based smart packaging film with full-temperature control.

2. The method for preparing a multifunctional gelatin-based smart packaging film with full-temperature-range temperature control according to claim 1, characterized in that, In step 1, the amounts of silane coupling agent and polyethylene glycol used are as follows, by mass: 30 parts of silane coupling agent and 120-200 parts of polyethylene glycol.

3. The method for preparing a multifunctional gelatin-based smart packaging film with full-temperature-range temperature control according to claim 1, characterized in that: In step 1, the heating reaction conditions are as follows: react in an oil bath at 100-130 ℃ for 1-3 h, and then continue to heat to 140-180 ℃ for 2-4 h.

4. The method for preparing a multifunctional gelatin-based smart packaging film with full-temperature-range temperature control according to claim 1, characterized in that: In step 1, the silane coupling agent is one or more combinations of γ-aminopropyltriethoxysilane, 3-glycidyl etheroxypropyltrimethoxysilane, and 3-methacryloyloxypropyltrimethoxysilane.

5. The method for preparing a multifunctional gelatin-based smart packaging film with full-temperature-range temperature control according to claim 1, characterized in that: In step 2, the gelatin, hyperbranched polysiloxane, and nano zinc oxide are in the following proportions by mass: 200 parts gelatin solution, 4-20 parts hyperbranched polysiloxane, and 0.1-1 parts nano zinc oxide.

6. The method for preparing a multifunctional gelatin-based smart packaging film with full-temperature-range temperature control according to claim 1, characterized in that: In step 2, the heating reaction conditions are: reacting at 40-80 ℃ for 1-4 h.

7. The method for preparing a multifunctional gelatin-based smart packaging film with full-temperature-range temperature control according to claim 1, characterized in that: In step 2, the ultrasonic reaction conditions are: ultrasonic stirring at 40-60 ℃ for 30-60 min.

8. A multifunctional gelatin-based smart packaging film with full-temperature-range temperature control, prepared by the method according to any one of claims 1-7.

Images