Research on Packaging Materials--Other Functional Packaging Materials (II)

2. High barrier plastic packaging material

High-barrier plastic packaging materials are developed with the rapid development of the food industry, and have been rapidly developed and widely used in the packaging industry, especially in the food packaging industry. It plays a role in food preservation, preservation, flavor protection and shelf life extension. The technologies for preserving foods are varied, such as vacuum packaging, gas replacement packaging, encapsulated deoxidant packaging, food drying packaging, aseptic filling packaging, cooking packaging, liquid hot filling packaging, and so on. Many of these packaging technologies require the use of plastic packaging materials. Although they require a variety of properties, it is important that they all have good barrier properties. In the packaging industry, the more common high barrier film materials are as follows:

Nylon packaging materials. Nylon type packaging materials have been using "nylon 6" before. However, the tightness of "nylon 6" is not ideal. One type of nylon (MKD6) obtained by polycondensation of meta-dimethylamine and adipic acid is 10 times more leak-tight than "nylon 6", and also has good transparency and crack resistance. Mainly used for high barrier packaging film, used for high barrier properties of food flexible packaging. Its food hygiene has also been approved by the FDA. Its greatest feature as a thin film is that the barrier properties do not decrease with increasing humidity. In Europe, due to outstanding environmental protection issues, the use of MXD6 nylon as a replacement for PVDC films is significant. A biaxially extendable new film made of MXD6 nylon and EVOH as a high barrier nylon film. The composite method has a multi-layered composite, and there is also a method of blending and stretching MXD6 nylon and EVOH.

PVDC-type material (polyvinylidene chloride). Polyvinylidene chloride (PVDC) resin, as a composite or monomer material and co-extruded film sheet, is the most used high barrier packaging material in the packaging industry. Among them, the PVDC coated film used the most. The PVDC coating film uses polypropylene (OPP), polyethylene terephthalate (PET), or the like as a base material. However, due to the high softening temperature of pure PVDC, and its close to the decomposition temperature, and poor compatibility with common plasticizers, it is difficult and difficult to directly apply the heat molding. The actual PVDC films used are mostly vinylidene chloride (VDC) and vinyl chloride ( The copolymer of VC) and the better barrier property made by copolymerization with methyl acrylate (MA).

EVOH materials. EVOH has always been the most used high barrier material. In addition to the non-stretch type, the film type of this material includes a biaxially stretched type, an aluminum evaporated type, and a binder coated type. The biaxially stretched type also has a heat-resistant type for aseptic packaging products. The coextruded film of EBOH resin and other resins such as polyolefin and nylon is mainly used for packaging of animal products.

In recent years, the international community has become increasingly demanding for green packaging, but PVDC waste, which is widely used as a high-barrier packaging material, generates HCI during combustion and causes environmental pollution. Therefore, it is currently packaged in other packaging. Material substitution trends. For example, a so-called plating film obtained by plating SIOX (silicon oxide) on a thin film of other substrates has received attention, and in addition to a silicon oxide film, an aluminum oxide vapor-deposited film has been obtained. The same silicon oxide coating. At the same time, due to the rapid development of multi-layer compounding, blending, copolymerization and vapor deposition technologies, high barrier packaging materials such as copolymers EVOH, polyvinylidene chloride (PVDC), polyamine (PA), polyethylene terephthalate Polyester (PET) multilayer composites and silicon oxide vapor deposited films have been further developed. Among them, the following products are particularly noticeable: MXD6 polyamide packaging material, polyethylene naphthalate (PEN), Silicon oxide evaporated film.

3. New type of fresh-keeping packaging materials

Over the years, due to the specialization of agricultural production and people’s demands for improved quality of life, more and more long-distance transportation of fresh fruits and vegetables has resulted in more demand for fresh-keeping packaging materials that can increase the shelf life and shelf life of fresh fruits and vegetables. The bigger it is. A common feature of fresh fruits and vegetables is that they continue to breathe after harvesting, while breathing is accompanied by metabolism, water evaporation, and ethylene production, prompting fruit and vegetables to mature further and die. At the same time, this environment also makes bacteria easy to breed and reproduce rapidly, causing fruits and vegetables to decay quickly. In order to prolong the storage of fruits and vegetables and shelf life, research and development of new multi-functional fresh-keeping packaging materials have been intensified at home and abroad, and most of the preservation technologies are through micropores or improved film formulation structures to improve the atmosphere within the packaging bags (atmosphere ) and the use of oxygen scavenger and selective permeation membrane combination method to achieve the purpose of preservation, especially among the following products will receive greater attention.

Functional cling film. A Japanese company introduced a strong-sealing packaging bag, which is made of a plastic called “Cikron” and has an excellent anti-oxidation effect. It is used to package new rice, and the fresh-keeping effect is particularly good. It can keep the color, smell and taste of rice unchanged for a long time, and the carbon dioxide produced in the bag also has the function of preventing insects and mildew. Another paper-making company in Japan produces a fresh-keeping fruit box, which is a layer of polyethylene film on the corrugated liner of the corrugated carton, and then coated with a waterproof wax coating containing trace amounts of fruit disinfectant to prevent Fruit moisture evaporates and inhibits breathing for preservation purposes. Packing fruit in this kind of packing box keeps the fruit fresh within a month.

A U.S. company has launched a new type of plastic bags for fruit and vegetable preservation that can extend the shelf life of fruits and vegetables and reduce the loss of fruit and vegetables caused by excessive aging. This kind of packaging bag is made of a mixture of natural activated clay and polyethylene. It is like a very fine filter screen. The gas and moisture generated during the ripening process of fruits and vegetables can pass through the packaging bag. It is not easy for the fungus to grow in the bag. The freshness is extended by more than 1 time. In addition, a U.S. company developed a plastic bag that can last for up to 3 years. This storage bag is a layer of plastic film on the inside of a common plastic bag. The film contains an oxygen absorbent. It absorbs oxygen that enters the food packaging process. This causes microorganisms that cause food rot to be unable to survive due to lack of oxygen. .


(to be continued)

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