Preservative film and preparation method thereof

Abstract

The invention belongs to the technical field of food fresh-keeping materials, and particularly relates to a fresh-keeping film and a preparation method thereof.The fresh-keeping film comprises a resin base film, an ethylene regulation and control composite functional layer and a selective breathable protective layer which are sequentially stacked; the ethylene regulation and control composite functional layer is composed of porous polymer microspheres of a core-shell structure, the porous polymer microspheres comprise a porous core body, an ethylene removal active component is loaded in the porous core body, and a functional shell layer is arranged on the outer surface of the porous core body; the porous polymer microspheres with the core-shell structure are used for loading the ethylene removal active component, so that the stability and the utilization efficiency of the ethylene removal component are improved, and the ethylene concentration in the package can be continuously reduced; the polyvinylidene fluoride microfiltration membrane is used as a functional shell layer, migration of active components is effectively limited, and the use safety is improved; antibacterial active components are introduced into the ethylene regulation and control composite functional layer and have an inhibition effect on microorganisms on the surfaces of fruits and vegetables and in a packaging environment.

Description

Technical Field

[0001] This invention belongs to the field of food preservation materials technology, specifically referring to a preservation film and its preparation method. Background Technology

[0002] Fresh fruits and vegetables continue to respire and release ethylene gas during post-harvest storage and distribution. As an endogenous plant hormone, ethylene, when it reaches a certain concentration, significantly accelerates the ripening and senescence process of fruits and vegetables, leading to softening, rotting, and a decline in quality, thereby shortening their shelf life.

[0003] Most existing food preservation films are made of a single resin material, primarily serving a physical barrier function. They lack the ability to effectively regulate ethylene gas, easily leading to the accumulation of ethylene concentration inside the packaging and accelerating the spoilage of fruits and vegetables. Simultaneously, microorganisms present on the surface of fruits and vegetables and in the packaging environment can also cause spoilage, further affecting food safety and preservation effectiveness.

[0004] To address these issues, existing technologies have attempted to introduce ethylene adsorbents or antibacterial components into preservation materials, but these methods suffer from drawbacks such as easy migration of active components, insufficient stability, and limited duration of action. Summary of the Invention

[0005] To address the aforementioned problems, this invention proposes a food preservation film and its preparation method.

[0006] The technical solution adopted by the present invention is as follows: The present invention provides a food preservation film, comprising a resin base film, an ethylene regulation composite functional layer and a selective air permeable protective layer stacked in sequence; the ethylene regulation composite functional layer is composed of core-shell structured porous polymer microspheres, the porous polymer microspheres include a porous core, the porous core is loaded with ethylene removal active components, and the outer surface of the porous core is provided with a functional shell layer.

[0007] Furthermore, the active components for ethylene removal include potassium permanganate, methylcyclopropene, and a metal oxide catalyst; the mass percentages of potassium permanganate, methylcyclopropene, and the metal oxide catalyst are 40-55%, 15-30%, and 15-35%, respectively.

[0008] Furthermore, the porous core is made of one of the following materials: acrylate copolymers, polylactic acid, and bio-based polymers.

[0009] Furthermore, the functional shell layer is a polyvinylidene fluoride microporous filter membrane.

[0010] Furthermore, the ethylene-regulated composite functional layer also includes antibacterial active components, which include nano-silver, zinc oxide, and natural antibacterial substances; the mass percentages of the nano-silver, the zinc oxide, and the natural antibacterial substances are 5-20%, 20-45%, and 35-60%, respectively.

[0011] Furthermore, the selectively breathable protective layer is made of expanded polytetrafluoroethylene, which allows ethylene and oxygen to pass through while blocking liquid water and solid particles.

[0012] Furthermore, the resin-based film has a thickness of 8–20 μm, the ethylene-regulated composite functional layer has a thickness of 1–6 μm, and the selectively breathable protective layer has a thickness of 1–5 μm.

[0013] This solution also discloses a method for preparing plastic wrap, which mainly includes the following steps: Step 1: Using one of acrylate copolymers, polylactic acid, or bio-based polymers, porous polymer microspheres with interconnected pore structures are prepared via emulsion polymerization to serve as porous cores; Step 2: Potassium permanganate, methylcyclopropene, and metal oxide catalyst are mixed in proportion and dispersed in deionized water medium to form a uniform dispersion system; porous core is added to the dispersion system and impregnated under stirring conditions to allow the ethylene removal active component to attach and fix in the pore structure of the porous core, thereby obtaining a porous core loaded with the ethylene removal active component. Step 3: Place the porous core loaded with ethylene to remove the active components in a film-forming solution containing polyvinylidene fluoride. Through a phase separation process, a polyvinylidene fluoride microporous filter membrane is formed on the outer surface of the porous core loaded with ethylene to remove the active components, thus obtaining a core-shell structured porous polymer microsphere. Step 4: Mix the core-shell structured porous polymer microspheres with antibacterial active components to obtain a mixture, wherein the antibacterial active components include nano-silver, zinc oxide and natural antibacterial substances; uniformly coat the mixture on the surface of the resin base film and dry it to form an ethylene-regulated composite functional layer; Step 5: Expanded polytetrafluoroethylene material is coated on the ethylene-regulated composite functional layer, and a selectively breathable protective layer is formed by hot pressing to obtain the food preservation film.

[0014] The beneficial effects achieved by the present invention using the above structure are as follows: (1) By loading ethylene removal active components onto porous polymer microspheres with a core-shell structure, the stability and utilization efficiency of ethylene removal components are improved, which can continuously reduce the ethylene concentration inside the packaging.

[0015] (2) Polyvinylidene fluoride microporous filter membrane serves as a functional shell layer, effectively restricting the migration of active components and improving safety in use.

[0016] (3) Antibacterial active components are introduced into the ethylene-regulated composite functional layer, which have an inhibitory effect on microorganisms on the surface of fruits and vegetables and in the packaging environment.

[0017] (4) The selectively breathable protective layer can block liquid water and solid particles while ensuring gas exchange, which is conducive to maintaining the normal breathing environment of fruits and vegetables.

[0018] (5) The structure is reasonable and the technology is mature, which is suitable for large-scale production and can significantly extend the shelf life of fruits and vegetables. Detailed Implementation

[0019] The following are specific embodiments of the present invention, which further describe the technical solution of the present invention. However, the scope of protection of the present invention is not limited to these embodiments. All changes or equivalent substitutions that do not depart from the concept of the present invention are included within the scope of protection of the present invention.

[0020] Example 1 A food preservation film, the raw material ratio is as follows: including a resin base film, an ethylene-regulating composite functional layer and a selectively breathable protective layer stacked in sequence; the ethylene-regulating composite functional layer is composed of core-shell structured porous polymer microspheres, the porous polymer microspheres include a porous core, the porous core is loaded with ethylene removal active components, and the outer surface of the porous core is provided with a functional shell layer.

[0021] The active components for ethylene removal include potassium permanganate, methylcyclopropene, and a metal oxide catalyst; the mass percentages of potassium permanganate, methylcyclopropene, and the metal oxide catalyst are 40%, 30%, and 30%, respectively.

[0022] The porous core is made of an acrylate copolymer.

[0023] The functional shell is a polyvinylidene fluoride microporous filter membrane.

[0024] The ethylene-regulated composite functional layer also includes antibacterial active components, including nano-silver, zinc oxide, and natural antibacterial substances; the mass percentages of nano-silver, zinc oxide, and natural antibacterial substances are 5%, 45%, and 50%, respectively.

[0025] The selectively breathable protective layer is made of expanded polytetrafluoroethylene (ePTFE), which allows ethylene and oxygen to pass through while blocking liquid water and solid particles.

[0026] The resin-based film has a thickness of 8 μm, the ethylene-regulated composite functional layer has a thickness of 6 μm, and the selectively breathable protective layer has a thickness of 5 μm.

[0027] Preparation process: Step 1: Using acrylate copolymers, porous polymer microspheres with interconnected pore structures are prepared by emulsion polymerization to serve as porous cores; Step 2: Potassium permanganate, methylcyclopropene, and metal oxide catalyst are mixed in proportion and dispersed in deionized water medium to form a uniform dispersion system; porous core is added to the dispersion system and impregnated under stirring conditions to allow the ethylene removal active component to attach and fix in the pore structure of the porous core, thereby obtaining a porous core loaded with the ethylene removal active component. Step 3: Place the porous core loaded with ethylene to remove the active components in a film-forming solution containing polyvinylidene fluoride. Through a phase separation process, a polyvinylidene fluoride microporous filter membrane is formed on the outer surface of the porous core loaded with ethylene to remove the active components, thus obtaining a core-shell structured porous polymer microsphere. Step 4: Mix the core-shell structured porous polymer microspheres with antibacterial active components to obtain a mixture, wherein the antibacterial active components include nano-silver, zinc oxide and natural antibacterial substances; uniformly coat the mixture on the surface of the resin base film and dry it to form an ethylene-regulated composite functional layer; Step 5: Expanded polytetrafluoroethylene material is coated on the ethylene-regulated composite functional layer, and a selectively breathable protective layer is formed by hot pressing to obtain the food preservation film.

[0028] Example 2 A food preservation film, the raw material ratio is as follows: including a resin base film, an ethylene-regulating composite functional layer and a selectively breathable protective layer stacked in sequence; the ethylene-regulating composite functional layer is composed of core-shell structured porous polymer microspheres, the porous polymer microspheres include a porous core, the porous core is loaded with ethylene removal active components, and the outer surface of the porous core is provided with a functional shell layer.

[0029] The active components for ethylene removal include potassium permanganate, methylcyclopropene, and a metal oxide catalyst; the mass percentages of potassium permanganate, methylcyclopropene, and the metal oxide catalyst are 55%, 15%, and 30%, respectively.

[0030] The porous core is made of polylactic acid.

[0031] The functional shell is a polyvinylidene fluoride microporous filter membrane.

[0032] The ethylene-regulated composite functional layer also includes antibacterial active components, including nano-silver, zinc oxide, and natural antibacterial substances; the mass percentages of nano-silver, zinc oxide, and natural antibacterial substances are 20%, 20%, and 60%, respectively.

[0033] The selectively breathable protective layer is made of expanded polytetrafluoroethylene (ePTFE), which allows ethylene and oxygen to pass through while blocking liquid water and solid particles.

[0034] The resin-based film has a thickness of 10 μm, the ethylene-regulated composite functional layer has a thickness of 5 μm, and the selectively breathable protective layer has a thickness of 4 μm.

[0035] Preparation process: Step 1: Using polylactic acid, porous polymer microspheres with interconnected pore structures are prepared through emulsion polymerization to serve as porous cores; Step 2: Potassium permanganate, methylcyclopropene, and metal oxide catalyst are mixed in proportion and dispersed in deionized water medium to form a uniform dispersion system; porous core is added to the dispersion system and impregnated under stirring conditions to allow the ethylene removal active component to attach and fix in the pore structure of the porous core, thereby obtaining a porous core loaded with the ethylene removal active component. Step 3: Place the porous core loaded with ethylene to remove the active components in a film-forming solution containing polyvinylidene fluoride. Through a phase separation process, a polyvinylidene fluoride microporous filter membrane is formed on the outer surface of the porous core loaded with ethylene to remove the active components, thus obtaining a core-shell structured porous polymer microsphere. Step 4: Mix the core-shell structured porous polymer microspheres with antibacterial active components to obtain a mixture, wherein the antibacterial active components include nano-silver, zinc oxide and natural antibacterial substances; uniformly coat the mixture on the surface of the resin base film and dry it to form an ethylene-regulated composite functional layer; Step 5: Expanded polytetrafluoroethylene material is coated on the ethylene-regulated composite functional layer, and a selectively breathable protective layer is formed by hot pressing to obtain the food preservation film.

[0036] Example 3 A food preservation film, the raw material ratio is as follows: including a resin base film, an ethylene-regulating composite functional layer and a selectively breathable protective layer stacked in sequence; the ethylene-regulating composite functional layer is composed of core-shell structured porous polymer microspheres, the porous polymer microspheres include a porous core, the porous core is loaded with ethylene removal active components, and the outer surface of the porous core is provided with a functional shell layer.

[0037] The active components for ethylene removal include potassium permanganate, methylcyclopropene, and a metal oxide catalyst; the mass percentages of potassium permanganate, methylcyclopropene, and the metal oxide catalyst are 45%, 20%, and 35%, respectively.

[0038] The porous nucleus is made of a bio-based polymer.

[0039] The functional shell is a polyvinylidene fluoride microporous filter membrane.

[0040] The ethylene-regulated composite functional layer also includes antibacterial active components, including nano-silver, zinc oxide, and natural antibacterial substances; the mass percentages of nano-silver, zinc oxide, and natural antibacterial substances are 15%, 35%, and 50%, respectively.

[0041] The selectively breathable protective layer is made of expanded polytetrafluoroethylene (ePTFE), which allows ethylene and oxygen to pass through while blocking liquid water and solid particles.

[0042] The resin-based film has a thickness of 8 μm, the ethylene-regulated composite functional layer has a thickness of 6 μm, and the selectively breathable protective layer has a thickness of 5 μm.

[0043] Preparation process: Step 1: Using bio-based polymers, porous polymer microspheres with interconnected pore structures are prepared through emulsion polymerization to serve as porous cores; Step 2: Potassium permanganate, methylcyclopropene, and metal oxide catalyst are mixed in proportion and dispersed in deionized water medium to form a uniform dispersion system; porous core is added to the dispersion system and impregnated under stirring conditions to allow the ethylene removal active component to attach and fix in the pore structure of the porous core, thereby obtaining a porous core loaded with the ethylene removal active component. Step 3: Place the porous core loaded with ethylene to remove the active components in a film-forming solution containing polyvinylidene fluoride. Through a phase separation process, a polyvinylidene fluoride microporous filter membrane is formed on the outer surface of the porous core loaded with ethylene to remove the active components, thus obtaining a core-shell structured porous polymer microsphere. Step 4: Mix the core-shell structured porous polymer microspheres with antibacterial active components to obtain a mixture, wherein the antibacterial active components include nano-silver, zinc oxide and natural antibacterial substances; uniformly coat the mixture on the surface of the resin base film and dry it to form an ethylene-regulated composite functional layer; Step 5: Expanded polytetrafluoroethylene material is coated on the ethylene-regulated composite functional layer, and a selectively breathable protective layer is formed by hot pressing to obtain the food preservation film.

[0044] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A type of food preservation film, characterized in that: It includes a resin-based film, an ethylene-regulating composite functional layer, and a selectively breathable protective layer stacked in sequence; the ethylene-regulating composite functional layer is composed of porous polymer microspheres with a core-shell structure, the porous polymer microspheres include a porous core, the porous core is loaded with an ethylene removal active component, and a functional shell layer is provided on the outer surface of the porous core.

2. The food preservation film according to claim 1, characterized in that: The active components for ethylene removal include potassium permanganate, methylcyclopropene, and a metal oxide catalyst; the mass percentages of potassium permanganate, methylcyclopropene, and the metal oxide catalyst are 40-55%, 15-30%, and 15-35%, respectively.

3. The food preservation film according to claim 2, characterized in that: The porous core is made of one of the following materials: acrylate copolymers, polylactic acid, or bio-based polymers.

4. The food preservation film according to claim 3, characterized in that: The functional shell is a polyvinylidene fluoride microporous filter membrane.

5. A food preservation film according to claim 4, characterized in that: The ethylene-regulated composite functional layer further includes antibacterial active components, which include nano-silver, zinc oxide, and natural antibacterial substances; the mass percentages of the nano-silver, the zinc oxide, and the natural antibacterial substances are 5-20%, 20-45%, and 35-60%, respectively.

6. A food preservation film according to claim 5, characterized in that: The selectively breathable protective layer is made of expanded polytetrafluoroethylene, which allows ethylene and oxygen to pass through while blocking liquid water and solid particles.

7. A food preservation film according to claim 6, characterized in that: The resin-based film has a thickness of 8–20 μm, the ethylene-regulated composite functional layer has a thickness of 1–6 μm, and the selectively breathable protective layer has a thickness of 1–5 μm.

8. A method for preparing a food preservation film, wherein the food preservation film is prepared according to claim 7, characterized in that, The main steps include the following: Step 1: Using one of acrylate copolymers, polylactic acid, or bio-based polymers, porous polymer microspheres with interconnected pore structures are prepared via emulsion polymerization to serve as porous cores; Step 2: Potassium permanganate, methylcyclopropene, and metal oxide catalyst are mixed in proportion and dispersed in deionized water medium to form a uniform dispersion system; porous core is added to the dispersion system and impregnated under stirring conditions to allow the ethylene removal active component to attach and fix in the pore structure of the porous core, thereby obtaining a porous core loaded with the ethylene removal active component. Step 3: Place the porous core loaded with ethylene to remove the active components in a film-forming solution containing polyvinylidene fluoride. Through a phase separation process, a polyvinylidene fluoride microporous filter membrane is formed on the outer surface of the porous core loaded with ethylene to remove the active components, thus obtaining a core-shell structured porous polymer microsphere. Step 4: Mix the core-shell structured porous polymer microspheres with antibacterial active components to obtain a mixture, wherein the antibacterial active components include nano-silver, zinc oxide and natural antibacterial substances; uniformly coat the mixture on the surface of the resin base film and dry it to form an ethylene-regulated composite functional layer; Step 5: Expanded polytetrafluoroethylene material is coated on the ethylene-regulated composite functional layer, and a selectively breathable protective layer is formed by hot pressing to obtain the food preservation film.