EVOH: Star of Food Packaging Materials

Food and beverage safety has always been a topic of common concern for all humans. Packaging materials play an extremely important role in ensuring the quality of foods and beverages, and technological advancement and improvement of material properties have made EVOH (ethylene-vinyl alcohol copolymer) It is the first choice for high barrier performance packaging materials.
EVOH is a kind of crystalline polymer with a chain structure. It is a new type of barrier material that combines the good processability of ethylene polymer and the extremely high gas barrier property of vinyl alcohol polymer. Its gas barrier property is higher than that of PA. (Polyamide) is 100 times higher than PE and PP, and is tens of times higher than PVDC (polyvinylidene chloride), a commonly used high-barrier material. In addition, EVOH is excellent in transparency, gloss, mechanical strength, stretchability, abrasion resistance, cold resistance, and surface strength, and has the highest thermal stability in high-performance barrier resins. This property makes the waste produced during processing. Can be recycled.

EVOH is more and more widely used in packaging. It is used in aseptic packaging, hot canning and cooking bags in the food industry, packaging of dairy products, meats, canned fruit juices and condiments; in non-food products, for packaging solvents, Chemicals; can also be used to manufacture gasoline cans, petrol drum linings, and air-conditioning refrigerant containers and structural parts to reduce the leakage of hydrocarbons or HCFCs.

In food packaging, plastic containers made of EVOH can completely replace glass and metal containers. In particular, the current explosion of beer bottles has become a global problem. In recent years, PET/PEN has been used for polyethylene terephthalate/PET. The polyethylene naphthalate alloy beer bottle instead of glass bottles has entered the stage of industrialization and has good prospects for development. Among them, the most important way to improve the gas barrier property of the bottle is multi-layer composite. High barrier materials such as EVOH and PVDC are added in the middle layer to maintain the freshness of the beer and extend the shelf life of 6 to 9 months. The beer listed in the multi-layer bottle packaged with PET/EVOH/PET structure adopted by British company Bass Good results; US DuPont blends PEN with 15% EOVH to increase the oxygen barrier of PEN alloy by 2.7 times.

The use of ordinary plastics and high-barrier plastics to form multi-layered extruded composite films can significantly improve the barrier properties, and it is beneficial for the use of various components to obtain films with good overall performance and low cost. EVOH is a high-barrier material and is often extruded with a variety of resins for beverages, dairy products, fruit juices, beverages, and various foods. For example, many domestic seafood companies use PE/EVOH/PA for exporting seafood. /RVOH/PE five-layer co-extruded film vacuum packaging. In recent years, the average annual growth rate of high value-added, high-barrier, multi-layer co-extruded plastic films has been as high as 15%, which is rapidly growing.

A layer of polymer material with barrier properties is coated on the surface of the film to provide a high barrier performance on the surface of the film, which is commonly used in the international packaging industry, especially in the food packaging industry, in a variety of substrates such as PE, PP, PVC , Polystyrene, PET, PA, etc., the oxygen permeability after coating can be reduced to a few tens or even a thousandth of the substrate. According to the barrier effect requirements, the coating can be single-sided or double-sided. Multilayer coating can also be applied.

As a high-performance barrier packaging material, EVOH also has certain drawbacks, mainly in the case of high humidity, the barrier properties of its products will be reduced by a certain extent. In recent years, due to market demand and development prospects, new overseas product development has emerged in an endless stream. For example, the new STS brand launched by Japan Synthetic Chemical Co., Ltd. has not changed much due to humidity, and the fatigue resistance has improved significantly; Japan's Kuraray Corporation has produced XEP-400 At the same time, it developed two kinds of EVOH resin: RT film and HS film; DuPont Co., Ltd. adopts quartz filling method to modify EVOH resin, making the barrier property 3-5 times higher than traditional products; eval company in the United States has developed a new EVOH series product F100. And F151, with strong viscosity, and better compatibility with polyolefins, in recent years launched the third generation of EVOH resin XEP-567, lower than the second generation of oxygen permeability of about 50%, low carbon dioxide permeability About 50%.

While accelerating the development of EVOH composite membranes and new resins, EVOH stretching orientation has been studied abroad. In recent years, new EVOH membranes prepared by the tubular biaxial stretching process have been developed, and their gas barrier properties are currently high-performance non- Stretch EVOH film about 3 times.

Currently, the annual consumption of EVOH accounts for about 20% of the market for raw material consumption of high-barrier packaging materials, and industrial products have been applied abroad. The main manufacturers are Eval Corporation of USA, Japan Kuraray Corporation, Synthetic Chemical Industry Corporation, Belgium SOLVAY. Company etc. China's development and production of raw materials for plastic packaging materials, especially high-barrier packaging materials, is still in its infancy. PVDC and polyamide can only be produced in China, and the development and production of EVOH is in a blank position. In China, many plastic packaging materials, especially foods and medicines, cannot meet the requirements of high barrier properties, and they cannot participate in the international market competition. As a result, the application of high-barrier packaging materials in China is hindered. It is recommended that domestic authorities should accelerate the development of high-barrier packaging materials. The pace of raw materials EVOH meets the growing high resistance requirements of domestic food and beverage packaging.