Current situation and development of the hottest p

2022-08-20
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Current situation and development of plastic flexible packaging (Part I)

nowadays, with the continuous development of science and technology, people have higher and higher requirements for the quality of life. High performance and multifunctional plastic flexible packaging materials are becoming a hot development packaging materials

high barrier plastic packaging materials

high barrier plastic packaging materials have developed with the rapid development of the food industry. High barrier packaging materials have been rapidly developed and widely used in the packaging industry, especially in the food packaging industry. It plays a role in ensuring the quality, freshness, flavor and prolonging the shelf life of food. There are various technologies for preserving food, such as vacuum packaging, gas replacement packaging, sealed deoxidizer packaging, food drying packaging, sterile filling packaging, cooking packaging, liquid heat filling packaging, and so on. Many of these packaging technologies use plastic packaging materials. Although they are required to have a variety of properties, it is important to have good barrier properties

the common high barrier film materials are as follows:

PVDC materials (polyvinylidene chloride) are cleaned on the surface of the experimental machine. Polyvinylidene chloride (PVDC) resin, often used as composite or monomer materials and coextrusion film sheets, is the most used high barrier packaging material. Among them, PVDC coating film is used in a large amount. PVDC coating film uses polypropylene (OPP), polyethylene terephthalate (PET) and other materials as substrates. Due to the high softening temperature of pure PVDC, which is close to its decomposition temperature, and poor compatibility with general plasticizers, it is difficult to heat forming and direct application. PVDC films used in practice are mostly copolymers of vinylidene chloride (VDC) and vinyl chloride (2. Shear test: VC) and films with particularly good barrier properties made by copolymerization with methyl acrylate (MA)

nylon packaging materials. Nylon packaging materials used to use "nylon 6". But the air tightness of "nylon 6" is not ideal. There is a nylon (mkd6) polycondensated from m-dimethylamine and adipic acid. Its air tightness is 10 times higher than that of "nylon 6", and it also has good transparency and puncture resistance. It is mainly used for high barrier packaging film and soft food packaging with high barrier requirements. Its food hygiene has also been approved by FDA. As a film, its greatest feature is that its barrier property does not decrease with the rise of humidity. In Europe, due to outstanding environmental protection issues, as a substitute for PVDC films, MXD6 nylon is used in a large amount, with a sales revenue of 15billion yuan. A new film with bi-directional extensibility, which is compounded by MXD6 nylon and EVOH, is a nylon film with high barrier. The methods of compounding include multilayer compounding and blending and stretching MXD6 nylon and EVOH

evoh materials. EVOH has been the most widely used high barrier material. In addition to the non stretching type, the film type of this material also includes biaxial stretching type, aluminum evaporation type, adhesive coating type, etc. Biaxial stretching type and heat-resistant type are used for sterile packaging products. The film produced by CO extrusion of eboh resin with polyolefin, nylon and other resins is mainly used for the packaging of livestock products

inorganic oxide coated film

PVDC, which is widely used as a high barrier packaging material, has the trend of being replaced by other packaging materials because its waste will produce HCI during combustion treatment, resulting in environmental pollution. For example, the so-called coating film made after SiOx (silicon oxide) is plated on the film of other substrates has received attention. In addition to the silicon oxide coating, there is also the aluminum oxide evaporation film, whose air tightness is the same as that of the silicon oxide coating obtained by the same method

in recent years, the technology of multilayer compounding, blending, copolymerization and evaporation has developed very rapidly. High barrier packaging materials, such as multilayer composites of copolymer EVOH, polyvinylidene chloride (PVDC), polyamine (PA), polyethylene terephthalate (PET) and siloxane evaporation films, have been further developed, especially the following products: MXD6 polyamide packaging materials, polyethylene naphthalate (pen), silicon oxide evaporation films, etc

new fresh-keeping film

due to the specialization of agricultural production, more and more long-distance transportation, long-distance transportation of fresh fruits and vegetables, and people's requirements for improving the quality of life, there is an increasing demand for fresh-keeping films that can prolong the storage life and shelf life of fresh fruits and vegetables. A common feature of fresh fruits and vegetables is that they continue to breathe after picking, and breathing is accompanied by metabolism, water evaporation and ethylene production, which promotes the further maturation of fruits and vegetables until they decline. At the same time, this environment also makes bacteria easy to breed and multiply rapidly, leading to the rapid decay of fruits and vegetables. In order to prolong the storage and shelf life of fruits and vegetables, the research and development of new multifunctional fresh-keeping films have been strengthened at home and abroad

fresh food packaging attaches great importance to the permeability of gas, and uses this to choose different plastic materials. With the development of food industry and the progress of material science, as food packaging materials, it is not only required to have high gas resistance, but also further required to develop the function of selective permeability, that is, according to the requirements of the packaging contents, only the necessary (or unnecessary) gas molecules are allowed to pass through, so as to establish a suitable climate control environment. This kind of selective permeable packaging materials has entered the practical stage abroad, mainly including films with dissolved gas substances, films with porous zeolite or silica powder, and films with γ X-ray irradiation changes the properties of the films, and the dependence of diffusion coefficient on water content, the introduction of films containing hydroxyl groups and amide groups, etc. This needs to be replaced in a few years. In addition, some antibacterial agents and preservatives can be added to the film to inhibit the growth and reproduction of bacteria and molds

in recent years, the preservation technology that has attracted much attention is to improve the formula structure of the film through micropores, improve the controlled atmosphere environment (atmosphere) in the packaging bag, and use the combination of Deaerator and selective permeation of the film, especially the following products will receive greater attention

functional fresh-keeping film. A Japanese company has introduced a kind of strong sealing packaging bag, which is made of a kind of plastic called "chicron", which has excellent anti-oxidation effect. Using it to package new rice has a particularly good fresh-keeping effect, which can keep the color, aroma and taste of rice unchanged for a long time, and the carbon dioxide produced in the bag also has the effects of insect prevention and mold prevention. (to be continued)

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