The hottest EVOH helps to preserve the natural ele

EVOH helps to preserve the natural elements of food

food is very sensitive to gas and humidity. To prolong the storage life of food, more efforts must be made on packaging. Multilayer packaging materials have appeared in the market, but EVOH is an ideal material to further block gases. EVOH is widely used in the field of food packaging because of its high gas barrier and excellent processing formability. The global annual demand for EVOH is growing at a rate of 10%, which is mainly used to make films, sheets, bottles, etc. The structure of an EVOH bottle is different from that of other plastic materials. The function of EVOH is to completely seal the permeation barrier layer, which can prevent oxygen permeation. In this way, the shelf life of food can be extended. EVOH copolymer has excellent gas barrier, excellent solvent, chemical and hydrocarbon resistance, and can effectively block the penetration of odor and flavor. In most cases, EVOH copolymers are used in combination with other materials. It is combined with other polyolefins and adhesive layers to make multilayer films, which can enhance the barrier property of products. EVOH copolymer is bonded with nylon, which can effectively enhance the strength of the film. With different kinds and thicknesses of films, the film structure can be customized to meet the packaging needs of different uses, contents and secondary processing. At the same time, the type of material that can be used in combination with the film or packaging bottle can also be selected according to the required performance of the film or packaging bottle. In view of this, EVOH copolymer has found a broad application in the field of food packaging, especially fruit juice packaging. Fruit juice is packed with ordinary plastic, and oxygen will be sucked into the package, resulting in oxidation reaction, which will shorten the storage life and affect the taste and quality of fruit juice. If EVOH layer is added to the package, the permeability of non-conductive oxygen and other gases can be greatly reduced, thus extending the storage life. In fact, EVOH copolymer has excellent gas and flavor barrier properties, so it has potential applications in the field of fruit juice packaging containers. At the same time, this kind of copolymer can also be used as a veneer material to make it possible for trans isoprene rubber to be used in tread rubber and fuel-efficient tire manufacturing. It is coated on the inner surface of the polyethylene barrier packaging to prevent polyethylene from absorbing the taste of fruit juice. It is estimated that the global demand for EVOH in 2005 will reach 81260 metric tons. EVOH is mainly composed of carbon, oxygen and hydrogen, and will not release toxic gases during combustion. Therefore, the harm to the environment is very low. Now, many companies produce EVOH copolymers with different trade names, such as clarene, Eval, levasint, SELAR, soamol, etc. the components of EVOH materials are similar. Application field gas barrier: in the application field of gas filled packaging, nitrogen and carbon dioxide form a covering layer on the contents. EVOH copolymer effectively keeps the gas in the packaging because of its excellent gas barrier characteristics. Therefore, EVOH copolymers are often used in food packaging boxes that need gas preservation. Flavor preservation: the package containing EVOH copolymer can effectively maintain the flavor and retain the flavor of the contents in the package within the specified period. Used for packaging agricultural chemicals, drugs, cosmetics and gasoline. EVOH is resistant to oils and organic solvents, so it can also be used to produce oil tanks; At the same time, it is suitable for packaging oil food, edible oil, mineral oil and organic solvents. EVOH has weather aging resistance and excellent gas barrier properties. It is suitable for use as a building material in the production of floor heating pipes. EVOH can effectively prevent hazardous CFCs (chlorofluorocarbons) from diffusing into the atmospheric environment. EVOH molding conditions the key points of EVOH molding are the optimization of molding temperature and the selection of the most appropriate screw. EVOH steel trading enterprises have a large number of molding temperatures with a relatively narrow allowable range. Generally, the high ethylene content brand is 190 ° c~220 ° C, and the low ethylene content brand is 210 ° c~230 ° C. If the molding temperature is too high, the bridging reaction will occur with the decomposition reaction, resulting in crystal points, and further decomposition will produce foaming. The design concept of the screw is to try not to bring unnecessary heat to EVOH. It is recommended that the screw with l/d=, full screw type and compression ratio of 3.0~3.5. In recent years, users' requirements for packaging materials are multifaceted, such as lightweight, high barrier, cooking resistance, etc. Lightweight is to use materials with good mechanical properties as much as possible to meet the requirements of user's material lightness, so the probability of fire in the process of use will be very low and the design will be diversified. To improve the barrier property, it is required to develop EVOH with low ethylene content that is easy to process, inorganic evaporation, and newly developed coating materials. Cooking resistance is a higher level requirement for resin materials, and the growth of this market is just beginning. Especially when EVOH flexible packaging materials are used, the appearance will whiten and the heat sealing part will peel off. Although EVOH is not mature in processing technology, resulting in some defects, the overall demand will continue to grow. Soarnol is the EVOH brand of Japan Synthetic Chemical Industry Co., Ltd. After a long time, soarnol? Its viscosity changes little, and it has extrusion stability and long-term continuous processing stability. The material decomposes very little after heating, which is one of the reasons why it can maintain the stability of continuous processing for a long time. In addition, there is little gas generated, which can prevent the resin odor from transferring to the finished product. In order to verify the stability of EVOH to heat, synthetic chemical company used the extrusion temperature of 230 ° C to repeatedly extrude soar for 30 times. The results show that the material has strong heat resistance, and there is no deterioration at all. It can be seen that soarnol has strong heat resistance, relatively easy to use and high stability during processing

Kola Li has also recently developed a new EVOH resin based on eval. This new material is a functional resin. Its gas barrier effectiveness is the same as that of Eval, but its plasticity is better, and it can be easily mixed with resins such as pet and polypropylene, which solves the disadvantage that Eval cannot be mixed. With the increasing use of flexible packaging with gas barrier, this new EVOH barrier resin will find new applications in food packaging and industrial materials. At present, its uses mainly include shrink films and bags, deep support packaging materials, industrial materials for packaging, capping and inner padding, and auto parts

reprinted from: packaging Expo