Development status of the hottest plastic flexible

Development status of plastic flexible packaging materials

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

I. at the same time, it is also used in markets such as printed circuit boards and industrial special yarns. 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:

1, PVDC materials (polyvinylidene chloride). 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 (VC), and films with particularly good barrier properties made by copolymerization with methyl acrylate (MA)

2. 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, as a substitute for PVDC films, MXD6 nylon is used in a large amount due to outstanding environmental protection problems. 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

3. 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

second, 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 multi-layer composites of copolymer EVOH, polyvinylidene chloride (PVDC), polyamine (PA), polyethylene terephthalate (PET), silicone evaporation film 1, graphene, etc. have been further developed, especially the following products are more eye-catching: MXD6 polyamide packaging materials, polyethylene naphthalate (pen), silicon oxide evaporation film, etc

III. 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 film 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 selects different plastic materials as the mainstay of high-strength steel automotive 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. 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

a Japanese paper company produces a fruit fresh-keeping packaging box. It is to add a layer of polyethylene film on the corrugated paper liner of the corrugated box, and then apply a waterproof wax coating containing a trace of fruit disinfectant to prevent the evaporation of fruit moisture and inhibit respiration, so as to achieve the purpose of fresh preservation. The fruit packed in this packing box can keep fresh for a month

in order to keep fruits and vegetables fresh during transportation, an American company invented a new method to reduce oxygen content and increase nitrogen content in packaging boxes to keep fruits and vegetables fresh. This method uses a new type of packing box with air conditioning performance in transportation. This kind of packing has a special film, which can absorb oxygen molecules and let nitrogen pass through. In this way, after the air enters the packaging box through the film, the nitrogen content in the box can be up to more than 98%, so as to slow down the respiration of fruits and vegetables and achieve the purpose of keeping fresh for a long time

an American company has launched a new type of fresh-keeping plastic bag for fruits and vegetables, which can prolong the fresh-keeping period of fruits and vegetables and reduce the loss of fruits and vegetables caused by too fast ripening. This kind of packaging bag is made of natural activated clay and polyethylene, which is like a very fine filter screen. The gas and water produced by fruits and vegetables in the ripening process can pass through the packaging bag, and it is not easy to breed fungi in the bag, which can prolong the freshness of fruits and vegetables by more than one time

an American company has developed a plastic fresh-keeping bag with a fresh-keeping time of up to 3 years. This kind of fresh-keeping bag is attached with a layer of plastic film inside the ordinary plastic bag. The film contains oxygen getter, which can absorb the oxygen entering in the process of food packaging, which makes the microorganisms that cause food decay unable to survive due to lack of oxygen

silicon window modified atmosphere fresh-keeping bag. Silicon window modified atmosphere fresh-keeping bag is to put silicone rubber film with appropriate area on the plastic film bag. Silicone rubber film can selectively penetrate oxygen, carbon dioxide and nitrogen. This kind of silicon window modified atmosphere fresh-keeping bag has achieved good results in fruit storage. Using it, under certain storage conditions, determine the appropriate silicon window area, and after closing for a certain time, the concentration of oxygen and carbon dioxide in the package can be automatically adjusted to the level required automatically. Generally, 1000 kg apples are stored, and a silicon window with an area of 0.6 square meters is set to maintain oxygen and carbon dioxide at an appropriate level. Excessive carbon dioxide generated by respiration can be discharged through the silicon window. When the oxygen in the bag is insufficient, it can be penetrated through the silicon window. The key of silicon window controlled atmosphere technology is to select silicon window film and determine the appropriate storage capacity and storage temperature of silicon window surface under the support of National Natural Science Foundation program, 973 program, 863 program, international cooperation program and other projects

IV. sterile and antibacterial plastic packaging materials

sterile packaging can retain the original nutritional components and flavor of food to the greatest extent under sterile conditions without adding preservatives at room temperature. It can prolong the shelf life and facilitate transportation and storage. Aseptic packaging is mainly used in food, condiments, medicine, cosmetics and other fields. The flexible packaging materials used are paper, plastic, aluminum-plastic composite films, multi-layer co extruded sterile packaging sheets containing high barrier plastics, etc

antibacterial plastic packaging materials give certain antibacterial properties to plastic packaging materials. Now a brand-new masterbatch with silver ion as inorganic antibacterial agent has been developed. Silver ion has significant antibacterial effect, which is characterized by long-lasting antibacterial effect, will not be high due to gasification and migration, and will not pollute the environment. The film made from the added masterbatch containing silver ion (content 1% ~ 3%) or the container with a layer of this film on the surface has been tested. It has been shown that the film containing 1% silver ion masterbatch can completely kill the bacteria that will cause food poisoning in 1 ~ 2 days without nutrient source, and is widely used in the packaging of cooked meat, aquatic products and liquid food. In addition, films with extracts from some plants as antibacterial agents have also been produced abroad, which are mainly used for the packaging of newly picked vegetables and fruits

v. high heat resistant plastic packaging materials

heat resistant plastic flexible packaging materials used to be resistant to cooking and sterilization, which meet the packaging requirements of cooking and sterilization. Under the condition of 120 ℃, 10 ~ 20 minutes of cooking and sterilization or heating, there is no obvious change in appearance, shape and quality, and the packaged food will not produce container damage, content leakage, secondary microbial pollution, light and heat deterioration during storage. Cooking bags are mostly made of multilayer composite cooking films with shading aluminum foil as the middle layer, high barrier plastics PA and pet as the outer layer, and heat sealing PE and PP as the inner layer. Some new multilayer composites containing high barrier materials such as EVOH, PVDC, MXD6 and silicon oxide evaporation film are also increasingly used

with the increasing popularity of the use of electromagnetic cookers and microwave ovens, it is suitable for the use of electromagnetic cookers and microwave ovens