EVOH is an ethylene-vinyl alcohol copolymer. It is colorless and transparent. It is an excellent barrier material. Its permeability is very low in the state of dryness or relative humidity (RH<60%), and its gas barrier property is better than that of nylon. Excellent 10 to 50 times or more, second only to the barrier properties of aluminum foil. Regarding the use of flexible packaging, taking into account the material's processability and physical properties, the use of 10-20 times EVOH as a barrier layer can effectively prevent oxygen and water vapor from entering the package; it can also effectively block the aroma of the contents, liquid juice, Solvent extravasation, thus solving the problem of content (liquid, gas) dissolved composite layer glue. The barrier layer made of EVOH as a composite product is used to package foods, beverages, and articles that are easily oxidized by oxygen to extend the shelf life of the packaged articles. EVOH is excellent in oil resistance, organic solvent resistance and fragrance retention, can maintain the fragrance of the contents for a long period of time, and can prevent the infiltration of undesirable gases. At the same time, EVOH has the advantages of easy recovery and no harmful gases after incineration, and is known as a green environmental protection material. It is increasingly being taken seriously by countries and shows the growth trend with the most market potential.
Since EVOH copolymers contain alcohols, they have high moisture sensitivity, block after moisture absorption, and drop in enthalpy. Therefore, they are generally used as intermediate layers, and they are usually composed of a composite material with small moisture-absorbing polyolefin. Domestic companies adopt international advanced equipment and adopt the latest coextrusion casting process to produce high barrier coextrusion cast film with EVOH barrier layer, which not only solves the problem of moisture absorption, but also makes the material economical and its structure. For LLDPE/EVOH/LLDPE or PPOH/EVOH/PPCO, product thickness is 50μm-100μm, the product is tested according to ASTM D3985 (20°C, 65%RH) standard and ASTME96 (40°C, 90%RH) standard, respectively. : Oxygen transmission rate <10cc/m2.24hr; water vapor transmission rate is 4-6g/m2.24hr, such low transmission rate can only be achieved by using metal aluminum foil or vapor deposited metal polyester. The film has low adsorptivity to various active ingredients and high barrier to prevent the loss of active ingredients; it is excellent in oxygen barrier properties and can prevent oxidative deterioration of active ingredients; it has excellent transparency and is therefore widely used for oxygen-sensitive articles and powders. Products, meat, oxygen-sensitive liquid products, and odor-sensitive items. It is used to package whole milk powder in foreign countries, and the storage period is up to one year (packaging radiation sterilization). It is used to process meat packaging, can be used for quality preservation, freshness preservation, and greatly extended storage period. It is used as liquid packaging and used as "in box The bag's packaging method has been successfully used for packaging alcoholic beverages, fruit juices, tomato sauces, fresh milk and toothpaste aluminum-plastic composite pipes. Other aspects are also used to package high-grade foods to prevent intrusion of other odors and fragrances of soaps and fragrances, packaging of herbs, pesticides, olive oil, etc. (EVOH = 7 μm in the packaging structure).
Since EVOH high-barrier co-extruded cast film has both high-impedance and high transparency, the packaged articles have the effect of returning to nature, and there is a tendency to gradually replace metallized films, aluminum foils, and rigid containers in certain fields. According to related data, the annual growth rate of EVOH coextruded films in flexible packaging in the United States will reach 15%. With the increasing demand for packaging materials, environmental protection issues are increasingly important, EVOH coextrusion cast film can fully meet the requirements of gas barrier, flavor protection, fragrance preservation, transparency, resistance to cooking, extended shelf life and environmental protection. A wide market space for packaging materials.
