An inorganic nanocomposite material, its preparation method, and its application in fruit and vegetable preservation.

Abstract

This invention belongs to the field of fruit and vegetable preservation technology, specifically relating to an inorganic nanocomposite material, its preparation method, and its application in fruit and vegetable preservation. The inorganic nanocomposite material provided by this invention includes a porous structure carrier, which is an acid-activated porous silicate material; and a first coating layer and a second coating layer loaded on the surface of the pores of the porous structure carrier. The first coating layer is in contact with the surface of the pores of the porous structure carrier, and the first coating layer is composed of nano-yttrium oxide and nano-titanium oxide layers, while the second coating layer is composed of nano-silver layers. The inorganic nanocomposite material provided by this invention can simultaneously and efficiently regulate humidity and atmosphere, decompose ethylene, and provide antibacterial and antifungal effects. It can significantly delay the decline in fruit and vegetable quality and spoilage caused by self-ripening and microbial invasion, exhibiting a significant preservation effect, wide application, and suitability for large-scale industrial application.

Description

Technical Field

[0001] This invention belongs to the field of fruit and vegetable preservation technology, specifically relating to an inorganic nanocomposite material, its preparation method, and its application in fruit and vegetable preservation. Background Technology

[0002] Domestically and internationally, there are two main categories of preservation methods for fruits and vegetables: physical and chemical. Physical methods refer to using isolation methods such as plastic wrap and airtight containers to preserve fruits and vegetables, or employing temperature-controlled equipment such as cold storage. Chemical methods, on the other hand, refer to spraying chemical preservatives onto the surface of fruits and vegetables to prevent spoilage and maintain freshness. While different preservation methods have different focuses, they all revolve around regulating three key elements that play a crucial role in maintaining freshness: first, controlling the aging process of fruits and vegetables, generally achieved through temperature and respiration control; second, controlling microorganisms, mainly through controlling spoilage bacteria; and third, controlling internal moisture evaporation, mainly through controlling relative humidity and the structuring of water within cells.

[0003] Currently reported advanced preservation technologies include: ozone modified atmosphere preservation, critical low temperature and high humidity preservation, low-dose radiation pretreatment preservation and ultraviolet preservation, coating preservation, genetic engineering preservation, modified atmosphere preservation, and preservation bags or films. Table 1 shows the analysis and comparison results of various existing preservation technologies.

[0004] Table 1 Comparison of domestic and international preservation technologies

[0005]

[0006] As shown in Table 1, current domestic and international preservation technologies mainly control certain single aspects that affect the spoilage of fruits and vegetables. The methods are limited and lack flexibility, and cannot provide personalized services for fruit and vegetable preservation. In many cases, the varieties and origins of fruits and vegetables vary significantly, and the preservation effect is not ideal. Summary of the Invention

[0007] The purpose of this invention is to provide an inorganic nanocomposite material, its preparation method, and its application in fruit and vegetable preservation. The inorganic nanocomposite material provided by this invention can simultaneously and efficiently regulate humidity and atmosphere, decompose ethylene, and have antibacterial and antifungal effects. It can significantly delay the decline in fruit and vegetable quality and spoilage caused by self-ripening and microbial invasion, resulting in a remarkable preservation effect.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] This invention provides an inorganic nanocomposite material, comprising a porous structure carrier, wherein the porous structure carrier is an acid-activated porous silicate material;

[0010] The first coating layer and the second coating layer are loaded on the surface of the porous structure carrier pores. The first coating layer is in contact with the surface of the porous structure carrier pores. The first coating layer is a nano-yttrium oxide and nano-titanium oxide layer, and the second coating layer is a nano-silver layer.

[0011] Preferably, the particle size of the nano-silver is 10~35nm.

[0012] This invention provides a method for preparing the inorganic nanocomposite material described above, comprising the following steps:

[0013] Porous silicate materials are activated by immersing them in a strong acid solution to obtain activated porous materials.

[0014] Yttrium oxide sol, metatitanic acid solution, activated porous material and grinding beads are mixed and subjected to a first grinding process to obtain a coated porous material. The coated porous material is a porous silicate material whose pores are coated with a yttrium oxide sol and a metatitanic acid layer.

[0015] The coated porous material, nano silver hydrosol and grinding beads are mixed and then subjected to a second grinding to obtain a double-layer coated porous material. The double-layer coated porous material is a porous silicate material whose pores are sequentially coated with yttrium oxide sol, metatitanic acid layer and nano silver hydrosol layer.

[0016] The double-layer coated porous material is calcined to obtain the inorganic nanocomposite material.

[0017] Preferably, the porous silicate material is clinoptilolite, and the average particle size of the porous silicate material is <0.6 μm;

[0018] The strong acid solution is an aqueous nitric acid solution, and the mass content of the strong acid solution is 5-6%.

[0019] The acid activation temperature is 20~35℃, and the time is 12~15h.

[0020] Preferably, the method for preparing the yttrium oxide sol includes the following steps: mixing yttrium nitrate and hydrogen peroxide solution, and subjecting the resulting mixture to an oxidation reaction to obtain yttrium oxide sol; wherein the mass content of yttrium nitrate in the mixture is 6%, and the mass content of the hydrogen peroxide solution is 3%.

[0021] Preferably, the mass content of the metatitanic acid solution is 12%; the volume ratio of the yttrium oxide sol to the metatitanic acid solution is 1:1; and the first grinding speed is 2000~3000 rpm, and the time is 3~4 hours.

[0022] Preferably, the content of silver nanoparticles in the nano-silver hydrosol is 12000ppm; the second grinding speed is 2000~3000rpm and the time is 3~4h.

[0023] This invention provides the application of the inorganic nanocomposite material described in the above technical solution or the inorganic nanocomposite material prepared by the preparation method described in the above technical solution in fruit and vegetable preservatives.

[0024] This invention provides a method for preparing nano-preservative blocks, comprising the following steps:

[0025] The inorganic nanocomposite material described in the above technical solution or the inorganic nanocomposite material prepared by the preparation method described in the above technical solution is mixed with hydroxypropyl cellulose to obtain a mixture.

[0026] The mixture is pressed into shape to obtain nano-preservation blocks.

[0027] This invention provides a method for preparing nano-preservative plastic masterbatch, comprising the following steps:

[0028] The inorganic nanocomposite material described in the above technical solution or the inorganic nanocomposite material prepared by the preparation method described in the above technical solution, polyolefin resin and organic coupling agent are heated and mixed to obtain a mixture.

[0029] The mixture is extruded by a screw extruder and then granulated to obtain nano-preservative plastic masterbatch.

[0030] This invention provides an inorganic nanocomposite material, comprising a porous structure carrier, wherein the porous structure carrier is an acid-activated porous silicate material; and a first coating layer and a second coating layer loaded on the surface of the pores of the porous structure carrier, the first coating layer being in contact with the surface of the pores of the porous structure carrier, the first coating layer being a nano-yttrium oxide and nano-titanium oxide layer, and the second coating layer being a nano-silver layer. The inorganic nanocomposite material provided by this invention uses an acid-activated porous silicate material as the inorganic porous carrier (e.g.,...). Figure 1As shown, yttrium oxide and titanium dioxide nanoparticles are adsorbed onto the pore surface of an inorganic porous carrier via physical adsorption, forming a first coating layer. Due to the strong van der Waals forces resulting from the inherently large specific surface area of ​​nanoparticles, they exhibit a strong affinity for porous silicates, allowing for the firm adsorption of yttrium oxide and titanium dioxide nanoparticles onto the surface of the porous carrier pores. Then, through the chemical bonding between titanium dioxide and nano-silver, uniformly dispersed silver nanoparticles are formed on the surface of the first coating layer, creating a second coating layer. Compared to directly loading silver nanoparticles onto the porous silicate pore surface, this invention utilizes chemical bonding, resulting in a more robust silver nanoparticle load. It also prevents titanium dioxide nanoparticles (high-efficiency photocatalysts) from being exposed on the outermost layer. Furthermore, the use of both yttrium oxide and titanium dioxide as the first coating layer ensures that the silver nanoparticle-to-titanium dioxide coating is not dense, thus minimizing the obstruction of small-molecule ethylene gas contact with titanium dioxide. The inorganic nanocomposite material provided by this invention offers the following advantages in fruit and vegetable preservation:

[0031] (1) Acid-activated porous silicate materials have significantly improved moisture absorption performance. Their porous structure has the functions of moisture absorption, moisture permeation and moisture replenishment, which can maintain and regulate the moisture of the microenvironment for fruit and vegetable storage, and prevent fruit and vegetable from losing water and wilting.

[0032] (2) The porous structure of porous silicate materials can regulate the carbon dioxide concentration in the microenvironment for fruit and vegetable preservation. The porous structure provides air permeability, so that the microenvironment for fruit and vegetable preservation has a certain degree of air permeability without causing water loss too quickly. It plays a role in self-regulating the carbon dioxide content in the microenvironment for fruit and vegetable preservation, preventing fruit and vegetable poisoning and rotting due to excessive accumulation and high concentration of carbon dioxide, and can also retain a certain amount of carbon dioxide gas to inhibit the aging of fruit and vegetables.

[0033] (3) The porous structure of acid-activated silicate materials has excellent physical adsorption capacity for ethylene. The adsorbed ethylene can also be released into the external microenvironment of fruit and vegetable preservation through the pore structure of silicate materials. At the same time, ethylene and rare earth yttrium atoms entering the silicate channels can form complexes and be adsorbed by chemical adsorption. The effect of chemical adsorption is not only much greater than that of physical adsorption, but the chemically adsorbed ethylene can also be quickly decomposed by the nearby titanium dioxide and nano silver catalysts, and the yttrium complex active center can continue to work.

[0034] (4) The silver and titanium active centers catalyze the decomposition of ethylene gas adsorbed on the surface. The process of decomposing ethylene is as follows: gaseous ethylene (in the storage environment) — adsorption (silicate and yttrium oxide adsorption sites) — oxidation (silver / titanium catalytic sites) — oxidation products (ethanol, acetaldehyde, carbon dioxide, water, etc.). Since the ethylene content in the fruit and vegetable environment is very low, about 0.1~10 ppm, the composite material provided by this invention has high efficiency in adsorbing and removing ethylene. The chemical substances produced by the reaction are simple, low in concentration, and harmless to humans, fruits and vegetables, and the environment. In the composite material provided by this invention, the ethylene adsorption sites and ethylene decomposition active centers are designed together. The arrangement of the reaction sites is conducive to the efficient removal of ethylene, thereby reducing the ethylene content in the environment and reducing self-ripening and aging.

[0035] (5) The outermost layer of the composite material provided by the present invention is silver nanoparticles. The silver nanoparticles release a large number of silver ions, which have strong antibacterial and antifungal effects. The nano-titanium dioxide also has the ability to photocatalytically decompose organic matter (under ultraviolet light). Moreover, the antibacterial and antifungal effect of the silver nanoparticles relies on the principle of contact antibacterial. In the composite material provided by the present invention, the silver nanoparticles are located on the outermost layer of the material, which can exert the maximum antibacterial efficiency.

[0036] In summary, the inorganic nanocomposite material provided by this invention can simultaneously and efficiently regulate humidity and atmosphere, decompose ethylene, and provide antibacterial and antifungal effects. It can significantly delay the decline in quality and spoilage of fruits and vegetables caused by self-ripening and microbial invasion, resulting in a remarkable preservation effect. The inorganic nanocomposite material provided by this invention can be directly applied to fruit and vegetable preservation by forming nano-preservation blocks, or it can be further processed by adding the nano-preservative to resins such as polyethylene (PE) and polypropylene (PP) using plastic processing technology to produce preservation plastic products (preservation bags, preservation blocks, preservation films, and preservation boxes). Its applications are wide-ranging and suitable for large-scale industrial application.

[0037] This invention provides a method for preparing the inorganic nanocomposite material described in the above-mentioned technical solution. The preparation method first activates porous silicate material with a strong acid solution. Then, yttrium oxide sol is used as a precursor for nano-yttrium oxide particles, and metatitanic acid solution is used as a precursor for nano-titanium oxide particles. These particles firmly adhere to the surface of the pores in the porous silicate material. Next, through chemical bonding between nano-silver hydrosol and the hydroxyl groups of metatitanic acid, nano-silver particles are uniformly distributed on the surface of the metatitanic acid. Finally, after calcination and shaping, the nano-yttrium oxide particles and nano-titanium oxide particles generated from the yttrium oxide sol and metatitanic acid are firmly adsorbed in the channels of the porous silicate material by strong van der Waals forces. Simultaneously, the nano-silver particles are chemically bonded to the surface of the titanium oxide particles (e.g., ...). Figure 3As shown in the figure, an inorganic nanocomposite material was prepared, which showed strong stability. The three types of nanoparticles were evenly and layered on the surface of the pores of the silicate material. The porous structure of the three types of nanoparticles and silicate complemented and reinforced each other, achieving the best fruit and vegetable preservation effect. Attached Figure Description

[0038] Figure 1 The image shows the electron microscope morphology of the inorganic nanocomposite material prepared in Example 1 of this invention.

[0039] Figure 2 This is a schematic diagram of the structure of the porous silicate material used in Embodiment 1 of the present invention;

[0040] Figure 3 This is a schematic diagram of the structure of the inorganic nanocomposite material prepared in Example 1 of the present invention;

[0041] Figure 4 Electron micrographs of the nano-yttrium oxide and nano-titanium oxide layers prepared in Example 1 of this invention. Detailed Implementation

[0042] This invention provides an inorganic nanocomposite material, comprising a porous structure carrier, wherein the porous structure carrier is an acid-activated porous silicate material;

[0043] The first coating layer and the second coating layer are loaded on the surface of the porous structure carrier pores. The first coating layer is in contact with the surface of the porous structure carrier pores. The first coating layer is a nano-yttrium oxide and nano-titanium oxide layer, and the second coating layer is a nano-silver layer.

[0044] In this invention, unless otherwise specified, all raw materials / components used in the preparation are commercially available products well known to those skilled in the art.

[0045] A schematic diagram of the structure of the inorganic nanocomposite material provided by this invention is shown below. Figure 3 As shown below, in conjunction with Figure 3 The inorganic nanocomposite material provided by this invention will be described in detail.

[0046] like Figure 2 The schematic diagram shows that the inorganic nanocomposite material provided by this invention includes a porous structure carrier. The porous structure carrier is an acid-activated porous silicate material. The porous silicate material is clinoptilolite.

[0047] The inorganic nanocomposite material provided by this invention includes a first coating layer loaded on the surface of the pores of the porous structure carrier. The first coating layer is composed of nano-yttrium oxide and nano-titanium oxide (…). Figure 3 (The yellow layer represents the substance shown in the image). In this invention, nano-yttrium oxide particles and nano-titanium oxide particles are uniformly coated on the surface of the pores by van der Waals forces.

[0048] The inorganic nanocomposite material provided by this invention includes a second coating layer loaded on the surface of the first coating layer. The second coating layer is a nano-silver layer (…). Figure 3 (The substance is indicated by black in the image). The silver nanoparticles are chemically bonded to the surface of the titanium dioxide nanoparticles. In this invention, the preferred particle size of the silver nanoparticles is 10-35 nm, and the preferred average particle size is 20 nm.

[0049] In this invention, the nano-silver layer is a mixed layer formed by nano-silver and nano-silver oxide. The content of nano-silver oxide in the nano-silver layer is less than that of nano-silver.

[0050] The presence of a small amount of nano-silver oxide in the nano-silver layer does not affect the effectiveness of the inorganic nanocomposite material of this invention. The small mass percentage of nano-silver oxide in the nano-silver layer is readily apparent from the light grayish-white appearance of the inorganic nanocomposite product. Experimental practice has shown that a higher proportion of nano-silver oxide results in an inorganic nanocomposite material that appears dark yellow, brownish-red, brown, or even black.

[0051] In the coating structure of the inorganic nanocomposite material provided by this invention, nano-silver particles are uniformly distributed on the active sites of the nano-titanium dioxide surface. This not only ensures good bonding between the nano-silver and the matrix material but also prevents the titanium dioxide particles from being exposed on the outermost layer. Nano-titanium dioxide is a highly efficient photocatalyst that can decompose not only ethylene but also polyethylene. If exposed on the surface of the composite material and added to a polyethylene film, the film will also be catalytically oxidized and decomposed, causing the packaging bag to lose its mechanical strength and usability. Silver has a very weak decomposition effect on polyethylene. On the other hand, the coating layer of nano-silver particles on titanium dioxide is not dense, thus not significantly hindering the contact of small molecule ethylene gas with titanium dioxide.

[0052] This invention provides a method for preparing the inorganic nanocomposite material described above, comprising the following steps:

[0053] Porous silicate materials are activated by immersing them in a strong acid solution to obtain activated porous materials.

[0054] Yttrium oxide sol, metatitanic acid solution, activated porous material and grinding beads are mixed and subjected to a first grinding process to obtain a coated porous material. The coated porous material is a porous silicate material whose pores are coated with a yttrium oxide sol and a metatitanic acid layer.

[0055] The coated porous material, nano silver hydrosol and grinding beads are mixed and then subjected to a second grinding to obtain a double-layer coated porous material. The double-layer coated porous material is a porous silicate material whose pores are sequentially coated with yttrium oxide sol, metatitanic acid layer and nano silver hydrosol layer.

[0056] The double-layer coated porous material is calcined to obtain the inorganic nanocomposite material.

[0057] This invention involves immersing a porous silicate material in a strong acid solution for acid activation, thereby obtaining an activated porous material. In this invention, the porous silicate material is preferably clinoptilolite, and the average particle size of the porous silicate material is preferably <0.6 μm. The strong acid solution is preferably an aqueous nitric acid solution, and the mass content of the strong acid solution is preferably 5-6%, more preferably 6%. The mass ratio of the porous silicate material to the volume of the strong acid solution is preferably 1 g:10 mL. The acid activation temperature is preferably 20-35°C, and the time is preferably 12-15 h, more preferably 12 h. In this invention, the effect of acid activation is to improve the adsorption activity and selectivity of the mesoporous channels of the porous silicate material.

[0058] After obtaining the activated porous material, the present invention mixes yttrium oxide sol, metatitanic acid solution, activated porous material, and grinding beads (hereinafter referred to as the first mixture) and performs a first grinding to obtain a coated porous material. The coated porous material is a porous silicate material whose pores are coated with a yttrium oxide sol and a metatitanic acid layer. In the present invention, the preparation method of the yttrium oxide sol preferably includes the following steps: mixing yttrium nitrate and hydrogen peroxide solution, and subjecting the resulting mixture to an oxidation reaction to obtain yttrium oxide sol; wherein the mass content of yttrium nitrate in the mixture is preferably 6%, the mass content of the hydrogen peroxide solution is preferably 3%, and the mass content of the metatitanic acid solution is preferably 12%. In the present invention, the yttrium ions and hydrogen peroxide in the mixture react slowly to form a hydrosol, which is a high-purity yttrium oxide dispersion system in water, exhibiting good light transmittance, low impurity content, and good stability.

[0059] The preparation method of the metatitanic acid solution includes the following steps: mixing titanium sulfate, water, and sodium hydroxide, and heating to hydrolyze the mixture to obtain a metatitanic acid solution. The preferred mass ratio of titanium sulfate to sodium hydroxide is 10:1. The preferred hydrolysis temperature is 70-80℃, and the preferred time is 80-120 min. The grinding beads are preferably zirconia beads. The preferred diameter of the grinding beads is 0.5 mm. The preferred volume ratio of yttrium oxide sol to metatitanic acid solution is 1:1. The preferred volume ratio of yttrium oxide sol to the mass ratio of the activated porous material (or silicate material) is 2500 mL: 1000 g. The preferred mass ratio of the activated porous material (or silicate material) to the grinding beads is 1.2: 1.0. The preferred order of the first mixing is: adding yttrium oxide sol and metatitanic acid solution to the activated porous material and mixing, then adding the mixture to the grinding beads before the first grinding. The first grinding is performed in a sand mill. The preferred grinding speed for the first grinding is 2000-3000 rpm, more preferably 2500 rpm; the preferred grinding time is 3-4 hours, more preferably 3.5 hours. The abrasive obtained from the first grinding is directly mixed with the nano-silver hydrosol for the second grinding, without the need for post-processing.

[0060] After obtaining the coated porous material (the abrasive obtained from the first grinding), the present invention mixes the coated porous material, nano silver hydrosol and abrasive beads (hereinafter referred to as the second mixture) and performs a second grinding to obtain a double-layer coated porous material. The double-layer coated porous material is a porous silicate material whose pores are sequentially coated with yttrium oxide sol, metatitanic acid layer and nano silver hydrosol layer.

[0061] In this invention, the nano-silver hydrosol is preferably prepared according to the method disclosed in Chinese Patent CN103691967A, the specific method including:

[0062] A: Add 0.2-5 parts by weight of water-soluble silver salt and 30-40 parts by weight of water to a mixing tank, and stir at 20-60℃ for 5-20 minutes to completely dissolve the silver salt, obtaining a uniform and transparent solution for later use; the water-soluble silver salt is at least one of silver nitrate, silver acetate, or silver ammonia solution; the water is deionized water or distilled water.

[0063] B: First, add 0.5-10 parts by weight of oxime reducing agent, 0.3-15 parts by weight of polymeric dispersant, and 30-69 parts by weight of water to the reactor. The oxime reducing agent is acetone oxime. Stir at 400-800 rpm for 10-20 minutes at 20-60℃ to form a uniform and transparent solution. Then, add the silver salt solution obtained in step A in 3-5 batches over 20-60 minutes, and continue the reaction at 20-60℃ for 60-120 minutes. Finally, raise the temperature to 65-80℃ while maintaining the same stirring speed. Simultaneously, the reactor is evacuated for 30-60 minutes to remove and recover volatile components from the reaction system; the oxime reducing agent is at least one of acetaldehyde oxime, acetone oxime, or butanone oxime; the polymeric dispersing agent is at least one of water-soluble starch, polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), polyvinyl alcohol (PVA), sodium carboxymethyl cellulose (CMC), or carboxymethyl chitosan; the weight ratio of the water-soluble silver salt, oxime reducing agent, and polymeric dispersing agent is (0.5-1):(2-2.5):(1-3).

[0064] C: Release the transparent and uniform liquid obtained in step B, seal and package it to complete the preparation of nano silver hydrosol.

[0065] In this invention, the content of silver nanoparticles in the nano-silver hydrosol is preferably 12000 ppm. The particle size of the nano-silver particles in the nano-silver hydrosol is preferably 10-35 nm, and the average particle size is preferably 20 nm. The mass ratio of the coated porous material (or silicate material) to the volume of the nano-silver hydrosol is preferably 1000 g: 2000 mL. The grinding beads used in the second grinding are preferably the grinding beads used in the first grinding. The second mixing is preferably: the nano-silver hydrosol is added dropwise to the coated porous material. The second grinding is carried out in a sand mill. The rotation speed of the second grinding is preferably 2000-3000 rpm, more preferably 2500 rpm; the time is preferably 2-3 h, more preferably 2.5 h. After the second grinding, this invention preferably separates the grinding beads by sieving the obtained grinding material to obtain a mixed slurry; the mixed slurry is dried to obtain a double-layer coated porous material. The mesh size of the sieve used for sieving is preferably 325 mesh. The drying process is preferably spray drying, which is preferably carried out in a rotary spray dryer, and the rotation speed of the rotary spray dryer is preferably 600 rpm.

[0066] After obtaining the double-layer coated porous material, the present invention calcines the double-layer coated porous material to obtain the inorganic nanocomposite material. In the present invention, the calcination temperature is preferably 350~600℃, and the calcination time is preferably 90~180min. The calcination is carried out in air. The calcination temperature of 350~600℃ used in the present invention, and the pore structure of the silicate material has a protective effect on the nano-silver, preventing a large amount of nano-silver from being oxidized to nano-silver oxide during the calcination process. The present invention controls the calcination temperature, preserves the pore structure of the silicate, and avoids a large amount of nano-silver from being oxidized to silver oxide.

[0067] In this invention, after the calcination is completed, the obtained inorganic nanocomposite material is preferably pulverized to obtain inorganic nanocomposite material powder. The pulverization is preferably performed using an air jet mill. The particle size D of the inorganic nanocomposite material powder is... 97 ≤1.2μm.

[0068] This invention provides the application of the inorganic nanocomposite material described in the above technical solution or the inorganic nanocomposite material prepared by the preparation method described in the above technical solution in fruit and vegetable preservatives.

[0069] The inorganic nanocomposite material provided by this invention integrates various functions required for fruit and vegetable preservation into one material, so that the functional points cooperate and complement each other to achieve the maximum fruit and vegetable preservation effect. Specifically, it is manifested in: (1) The silicate porous structure in the inorganic nanocomposite material can adsorb ethylene gas, and its pores provide channels for the flow of oxygen and carbon dioxide, while playing a role in moisturizing and permeability. (2) The inorganic nanocomposite material is designed with the active centers for ethylene adsorption (physical adsorption sites of silicate and chemical complex adsorption sites of yttrium oxide) and decomposition (silver / titanium catalytic sites) together, which is conducive to the efficient removal of ethylene. (3) The synergistic effect of silver-based antibacterial agents and photocatalysis and the design of the structure make it exhibit a good inhibitory effect on various types of microorganisms in the fruit and vegetable environment, without damaging the strength of the polyethylene preservation bag with nano-titanium dioxide.

[0070] In this invention, when the above-mentioned inorganic nanocomposite materials are used in fruit and vegetable preservatives, they are preferably used in the form of nanopreservative powder, nanopreservative blocks, nanopreservative bags, nanopreservative films, or nanopreservative boxes.

[0071] This invention utilizes various forms of nano-preservatives for packaging in post-harvest storage and distribution. By employing functional packaging materials, it maximizes the delay of the aging process and maintains the quality of fruits and vegetables. The nano-preservatives provided by this invention achieve excellent preservation effects by efficiently regulating humidity and atmosphere, decomposing ethylene, and providing antibacterial and antifungal properties.

[0072] In this invention, the nano-preservative powder is preferably an inorganic nanocomposite material powder obtained by pulverizing an inorganic nanocomposite material. The particle size D of the nano-preservative powder is... 97 ≤1.2μm, MIC≤350ppm, safe, non-toxic, and non-irritating. MIC stands for Minimum Inhibitory Concentration, which is the lowest concentration of a drug that can significantly inhibit the growth of a certain microorganism after 24 hours of incubation under specific conditions. It is used to quantitatively determine in vitro antibacterial activity.

[0073] This invention provides a method for preparing nano-preservative blocks, comprising the following steps:

[0074] The inorganic nanocomposite powder described in the above technical solution or the inorganic nanocomposite powder prepared by the preparation method described in the above technical solution is mixed with hydroxypropyl cellulose to obtain a mixture;

[0075] The mixture is pressed into shape to obtain nano-preservation blocks.

[0076] This invention involves mixing the inorganic nanocomposite powder described in the above-described technical solution or the inorganic nanocomposite powder prepared by the above-described preparation method with hydroxypropyl cellulose to obtain a mixture. The viscosity of the hydroxypropyl cellulose is preferably 20 mPa·s. The mass ratio of the inorganic nanocomposite material to hydroxypropyl cellulose is preferably 100:(2~5). The mixing is preferably carried out in a high-speed mixer, and the mixing preferably includes sequential premixing and final mixing. The premixing speed is preferably 800~1200 rpm, and the time is preferably 1~5 min. The final mixing speed is preferably 600~1000 rpm, and the time is preferably 2~10 min.

[0077] After obtaining the mixture, the present invention presses the mixture into a shape to obtain nano-preservative blocks. In the present invention, it is preferable to load the mixture into a mold before pressing. The mold is preferably a cubic mold. The pressing is preferably carried out in a basket-type tablet press. The ratio of pressing pressure to the volume of the nano-preservative block is preferably (0.5~5) kN: (1~125) cm³. 3 .

[0078] This invention provides a method for preparing nano-preservative plastic masterbatch, comprising the following steps:

[0079] The inorganic nanocomposite powder described in the above technical solution or the inorganic nanocomposite powder prepared by the preparation method described in the above technical solution, polyolefin resin and organic coupling agent are heated and mixed to obtain a mixture;

[0080] The mixture is extruded by a screw extruder and then granulated to obtain nano-preservative plastic masterbatch.

[0081] This invention involves heating and mixing the inorganic nanocomposite powder described in the above-described technical solution, or the inorganic nanocomposite powder prepared by the above-described preparation method, polyolefin resin, and an organic coupling agent to obtain a mixture. In this invention, the polyolefin resin is preferably polyethylene resin particles (LDPE) or polypropylene resin particles (PP). The organic coupling agent is preferably a commercially available ethylene bis(fatty acid) amide-type BAB block copolymer with the anchoring group in the center, produced by Suzhou Xingtai Optoelectronic Chemical Additives Co., Ltd., with the common designation TAS-2A. The preferred mass ratio of the inorganic nanocomposite material to the polyolefin resin is (0.4~5):100. The preferred mass ratio of the organic coupling agent to the polyolefin resin is (0.1~2):100. The mixing is preferably carried out in a high-speed kneader. The preferred heating temperature is 95~100℃, the preferred mixing speed is 300~500 rpm, and the preferred mixing time is 10~20 min. In this invention, the preferred heating temperature is 95-100°C. The organic coupling agent is completely melted by shear heat under high-speed mixing, allowing the inorganic nanocomposite material to adhere uniformly to the surface of the polyolefin resin particle carrier. The organic coupling agent used in this invention is based on ethylene bis(fatty acid) amide with structural adjustments, introducing polar groups (anchoring groups). These groups have a strong binding affinity to carbon black inorganic pigments, fillers, talc, and other material particles. The main chain molecule consists of solvated segment lipophilic groups, exhibiting a certain degree of compatibility with the resin. This invention uses the organic coupling agent to form a compatibility layer between the inorganic nanocomposite material particles and the matrix resin plastic particles. Simultaneously, it can also form a protective layer on the surface of the inorganic nanocomposite powder material particles. When solid particles containing dispersing groups interact due to van der Waals forces, the spatial barriers between the adsorption layers cause the particles to repel each other, thereby achieving stable dispersion of the solid particles in the resin. The organic coupling agent used in this invention is a regular copolymer with a structure similar to a BAB-type block copolymer where the anchoring group is located in the center. The anchoring group is on the same side of the dispersant molecular chain, and the adsorption shape is similar to tail-shaped adsorption. This significantly reduces steric hindrance, preventing bridging and flocculation, and thus providing excellent dispersant properties. Plastics treated with this organic coupling agent exhibit a significantly increased melt index, making it also a good lubricant.

[0082] After obtaining the mixture, the present invention granulates the mixture by extruding it through a screw extruder to obtain nano-preservative plastic masterbatch. The screw extruder is preferably a twin-screw extruder. The twin-screw extruder is preferably a co-rotating twin-screw extruder. The screw diameter of the co-rotating twin-screw extruder is preferably Φ35 or Φ65, the length-to-diameter ratio (L / D) is 40:1, and the granulation temperature is preferably 150~210℃.

[0083] In this invention, the preferred method for preparing the nano-preservation bag includes the following steps: preparing the nano-preservation plastic masterbatch prepared above using a blown film method to obtain the nano-preservation bag. The preparation of the nano-preservation bag is completed on a conventional bag-making machine. The preferred processing temperature of the nano-preservation bag is 150~190℃.

[0084] Compared with unpackaged or pre-packaged products, the nano-preservation bags prepared by this invention extend the shelf life of fruits and vegetables by more than 100%, while reducing the vitamin C and sugar content in the fruits and vegetables by more than 30%.

[0085] In this invention, the preferred method for preparing the nano-preservative film includes the following steps: preparing the nano-preservative plastic masterbatch prepared above using a casting method to obtain the nano-preservative film. The preparation of the nano-preservative film is completed on a conventional film-making machine. The preferred processing temperature of the nano-preservative film is 150~190℃.

[0086] The nano-preservative film prepared by this invention has an O2 permeability ≥ 5000 cm⁻¹ 3 / m 2 •d·bar, CO2 permeability ≥18000cm 3 / m 2 ·d·bar, antibacterial rate ≥99%, mildew prevention level 1.

[0087] In this invention, the preferred method for preparing the nano-preservation box includes the following steps: preparing the nano-preservation plastic masterbatch as described above using an injection molding method to obtain the nano-preservation box. The preparation of the nano-preservation box is completed on a conventional injection molding machine. The preferred processing temperature for the nano-preservation box is 180~230℃.

[0088] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0089] Example 1

[0090] (1) A nano-silver hydrosol was prepared according to Example 1 disclosed in Chinese Patent CN103691967A. The nano-silver particles in the nano-silver hydrosol had a particle size of 10~35nm, an average particle size of 20nm, and a nano-silver particle content of 12000ppm.

[0091] (2) First, 1000 g of ultrafine mesoporous silicate powder (clinopyrite, average particle size less than 0.6 μm) was activated at 25 °C for 12 hours using 10000 mL of 6.0% nitric acid aqueous solution. A 6% yttrium nitrate hydrogen peroxide aqueous solution (containing 3% hydrogen peroxide) was prepared to obtain yttrium oxide sol. 120 g of titanium sulfate and 1000 g of water were mixed, 12 g of sodium hydroxide was added, and the mixture was heated at 80 °C for 120 min to prepare metatitanic acid solution.

[0092] Then, 1200g of yttrium oxide sol and 1200g of metatitanic acid solution were slowly added to 900g of activated active mesoporous silicate, stirred at high speed, and ground at 2500rpm for 3.5h in a high-speed sand mill (with 200g of 0.5mm zirconia beads pre-placed in the barrel) to fully coat the surface of the mesoporous silicate pores with metatitanic acid and yttrium oxide sol, thus obtaining a slurry of coated porous material. Figure 4 Electron micrographs of the nano-yttrium oxide and nano-titanium oxide layers prepared in this embodiment.

[0093] (3) The nano-silver hydrosol was slowly dripped into the slurry of the porous material, and the milling speed was controlled at 3000 rpm for 2.5 h. Then, the zirconium oxide beads were separated by a 325 mesh sieve. The suspension of nano-silver / titanium / yttrium composite multi-component silicate formed at this time was spray-dried in a rotary spray dryer at 600 rpm and then calcined at high temperature (600℃) to obtain the inorganic nanocomposite material.

[0094] (4) The inorganic nanocomposite material was pulverized by air jet mill to obtain a particle size D. 97 Nanoparticle preservative powder with a diameter of ≤1.2μm. Figure 1 The image shows the electron micrograph of the nano-preservative powder prepared in this embodiment. The nano-preservative powder prepared in this embodiment can be directly used for fruit and vegetable preservation. Table 2 introduces the functional features of the nano-preservative powder prepared in Example 1.

[0095] Table 2. Functional features of the nano-preservative powder prepared in Example 1.

[0096]

[0097]

[0098]

[0099] Example 2

[0100] 100 parts of the nano-preservative powder prepared in Example 1 and 5 parts of low solution viscosity (20 mPa) hydroxypropyl cellulose were mixed in a high-speed mixer at low speed (800 rpm) for 5 min and then at high speed (1200 rpm) for 10 min until fully mixed. The mixture was then added to the cubic mold box of a basket press and pressed into 125 cm cubes using a pressure of 5 kN. 3 Cube-shaped nano-preservation blocks.

[0101] Example 3

[0102] 100 parts of polyethylene resin granules (LDPE), 2.0 parts of organic coupling agent, and 2.0 parts of the nano-preservative powder prepared in Example 1 were mixed in a 100L high-speed kneader for 20 minutes. When the temperature of the mixing machine reached 100°C, the organic coupling agent was completely melted by shear heat under high-speed mixing, so that the nano-preservative powder was uniformly adhered to the surface of the resin carrier. The mixture was then discharged and granulated in a Φ35 co-rotating twin-screw extruder at 210°C to prepare plastic granules with preservation function. The prepared plastic granules were then processed in a bag making unit at a processing temperature of 190°C to prepare nano-preservative bags by blown film method.

[0103] Example 4

[0104] 100 parts of polyethylene resin granules (LDPE), 2.0 parts of organic coupling agent, and 2.0 parts of the nano-preservative powder prepared in Example 1 were mixed in a 100L high-speed kneader for 20 minutes. When the temperature of the kneader reached 100°C, the organic coupling agent was completely melted by shear heat under high-speed mixing, so that the nano-preservative powder was uniformly adhered to the surface of the resin carrier. The mixture was then discharged and granulated in a Φ65 co-rotating twin-screw extruder at 210°C to prepare plastic granules with preservation function. The prepared plastic granules were then processed in a film-making unit at a processing temperature of 190°C to prepare nano-preservative film by casting.

[0105] Example 5

[0106] 100 parts of polyethylene resin granules (LDPE), 2.0 parts of organic coupling agent, and 2.0 parts of the nano-preservative powder prepared in Example 1 were mixed in a 100L high-speed kneader for 20 minutes. When the temperature of the kneader reached 100°C, the organic coupling agent was completely melted by shear heat under high-speed mixing, so that the nano-preservative powder was uniformly adhered to the surface of the resin carrier. The mixture was then discharged and granulated in a Φ65 co-rotating twin-screw extruder at 210°C to prepare plastic granules with preservation function. The prepared plastic granules were then processed in an injection molding machine at a processing temperature of 230°C to prepare nano-preservative boxes.

[0107] Test case

[0108] The preservation performance of the nano-preservation bags prepared in Example 3 was tested, and the results are shown in Tables 3-6. The experimental results show that the preservation bags prepared in Example 3 have good preservation effects on various fruits and vegetables, significantly improving both their appearance, commercial value, and internal nutritional elements. The ordinary bag used was a commercially available ordinary polyethylene plastic bag.

[0109] Table 3 Comparison of the preservation effects of food storage bags and ordinary bags on several fruits and vegetables.

[0110]

[0111] As shown in Table 3, the preservation bag prepared in Example 3 can help fruits and vegetables retain higher levels of vitamins, chlorophyll, and other nutrients.

[0112] Table 4. Nutritional composition and good fruit rate of fruits and vegetables after packaging in food storage bags

[0113]

[0114] As shown in Table 4, composite nanoparticle materials in PE plastic film can be used to package and preserve some fruits and vegetables, such as apples, papayas, mangoes, grapes, cucumbers, green peppers, eggplants, and green beans. It has been successfully used for the distribution and seasonal storage of tropical fruits in Hainan, agricultural bases in Fujian, and vegetables in Heilongjiang, as well as for fruit and vegetable storage inside naval submarines. Nearly 5 tons of various sizes of preservation bags have been sold cumulatively.

[0115] The inorganic composite nanomaterials provided by this invention are rationally arranged into an integrated structure, enabling each functional site to have a synergistic effect and improving its ethylene decomposition efficiency. Compared to existing food preservation bags, which have a generally poor preservation effect on certain fruits and vegetables, such as bok choy and snow peas, the nano-preservation bag provided in Example 3 of this invention has a highly efficient preservation effect, as shown in Table 5.

[0116] Table 5. Nutritional composition and percentage of good fruit after fruits and vegetables are packaged in food storage bags.

[0117]

[0118] The inorganic composite nanomaterials provided in this invention, used as preservatives, create fruit and vegetable preservation bags that integrate three functions: gas regulation, antibacterial properties, and inhibition of post-ripening. These bags offer exceptional preservation effects, suitable for long-term storage and long-distance transportation of fresh fruits and vegetables—a characteristic unavailable in ordinary preservation bags. Furthermore, their use in supermarket and shopping mall fruit and vegetable packaging effectively extends shelf life. The preservation principle is as follows: First, it regulates the ratio of nitrogen, carbon dioxide, and oxygen within the bag to maintain gas balance and prevent gas corrosion; second, it inhibits the respiration of fruits and vegetables after harvest to prevent rotting; third, it inhibits the growth of various microorganisms to prevent rotting; and fourth, the bag's excellent breathability facilitates moisture evaporation, extending preservation time. Practical experiments have proven that these preservation bags can preserve various vegetables, fruits, and edible fungi, and show good storage effects on various dried products (shiitake mushrooms, rice, and flour). For ordinary vegetables, the preservation time can be extended by 1-2 times at 8-12℃, and for 7-20 days at room temperature (15-20℃). Vegetables and fruits that are stored in a way that allows for better preservation will stay fresh longer. The results of the preservation experiment on 90% ripe papayas using a food storage bag versus a regular polyethylene plastic bag are shown in Table 6 below.

[0119] Table 6. Results of preservation experiments on 90% ripe papaya using preservation bags and ordinary bags (preservation temperature 10-12℃, experiment quantity 100 kg).

[0120]

[0121] Table 6 shows that the preservation bag prepared in Example 3 of the present invention did not significantly change the sweetness, ripeness, taste, and vitamin content of the papaya; while under the same conditions, the quality of the papaya decreased significantly when using ordinary polyethylene plastic bags.

[0122] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing an inorganic nanocomposite material, characterized in that, Includes the following steps: Porous silicate materials are activated by immersing them in a strong acid solution to obtain activated porous materials. Yttrium oxide sol, metatitanic acid solution, activated porous material and grinding beads are mixed and subjected to a first grinding process to obtain a coated porous material. The coated porous material is a porous silicate material whose pores are coated with a yttrium oxide sol and a metatitanic acid layer. The coated porous material, nano silver hydrosol and grinding beads are mixed and then subjected to a second grinding to obtain a double-layer coated porous material. The double-layer coated porous material is a porous silicate material whose pores are sequentially coated with yttrium oxide sol, metatitanic acid layer and nano silver hydrosol layer. The double-layer coated porous material is calcined to obtain the inorganic nanocomposite material; The inorganic nanocomposite material includes a porous structure carrier, which is an acid-activated porous silicate material; The first coating layer and the second coating layer are loaded on the surface of the porous structure carrier pores. The first coating layer is in contact with the surface of the porous structure carrier pores. The first coating layer is a nano-yttrium oxide and nano-titanium oxide layer, and the second coating layer is a nano-silver layer.

2. The preparation method according to claim 1, characterized in that, The particle size of nano-silver is 10~35nm.

3. The preparation method according to claim 1, characterized in that, The porous silicate material is clinoptilolite, and the average particle size of the porous silicate material is <0.6μm; The strong acid solution is an aqueous nitric acid solution, and the mass content of the strong acid solution is 5-6%. The acid activation temperature is 20~35℃, and the time is 12~15h.

4. The preparation method according to claim 1, characterized in that, The preparation method of the yttrium oxide sol includes the following steps: mixing yttrium nitrate and hydrogen peroxide solution, and subjecting the resulting mixture to an oxidation reaction to obtain yttrium oxide sol; the mass content of yttrium nitrate in the mixture is 6%, and the mass content of hydrogen peroxide solution is 3%.

5. The preparation method according to claim 1 or 4, characterized in that, The mass content of the metatitanic acid solution is 12%; the volume ratio of the yttrium oxide sol to the metatitanic acid solution is 1:1; the first grinding speed is 2000~3000 rpm, and the time is 3~4 hours.

6. The preparation method according to claim 1, characterized in that, The content of silver nanoparticles in the nano-silver hydrosol is 12000ppm; the second grinding speed is 2000~3000rpm, and the time is 3~4h.

7. The application of the inorganic nanocomposite material prepared by the preparation method according to any one of claims 1 to 6 in fruit and vegetable preservatives.

8. A method for preparing a nano-preservative block, characterized in that, Includes the following steps: Porous silicate materials are activated by immersing them in a strong acid solution to obtain activated porous materials. Yttrium oxide sol, metatitanic acid solution, activated porous material and grinding beads are mixed and subjected to a first grinding process to obtain a coated porous material. The coated porous material is a porous silicate material whose pores are coated with a yttrium oxide sol and a metatitanic acid layer. The coated porous material, nano silver hydrosol and grinding beads are mixed and then subjected to a second grinding to obtain a double-layer coated porous material. The double-layer coated porous material is a porous silicate material whose pores are sequentially coated with yttrium oxide sol, metatitanic acid layer and nano silver hydrosol layer. The double-layer coated porous material was calcined to obtain an inorganic nanocomposite material; The inorganic nanocomposite material and hydroxypropyl cellulose are mixed to obtain a mixture; The mixture is pressed into shape to obtain nano-preservation blocks.

9. A method for preparing a nano-preservative plastic masterbatch, characterized in that, Includes the following steps: Porous silicate materials are activated by immersing them in a strong acid solution to obtain activated porous materials. Yttrium oxide sol, metatitanic acid solution, activated porous material and grinding beads are mixed and subjected to a first grinding process to obtain a coated porous material. The coated porous material is a porous silicate material whose pores are coated with a yttrium oxide sol and a metatitanic acid layer. The coated porous material, nano silver hydrosol and grinding beads are mixed and then subjected to a second grinding to obtain a double-layer coated porous material. The double-layer coated porous material is a porous silicate material whose pores are sequentially coated with yttrium oxide sol, metatitanic acid layer and nano silver hydrosol layer. The double-layer coated porous material was calcined to obtain an inorganic nanocomposite material; The inorganic nanocomposite material, polyolefin resin, and organic coupling agent are heated and mixed to obtain a mixture. The mixture is extruded by a screw extruder and then granulated to obtain nano-preservative plastic masterbatch.

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