At present, polyester bottles (PET) have gradually become the preferred material in the field of beverage packaging. Because of its advantages such as good transparency, stable chemical properties, relatively good barrier properties, light weight and low cost, and being recyclable, it is very useful. widely. However, as beer packaging, the gas barrier properties of PET bottles still do not meet the requirements. Therefore, continuously improving the gas barrier properties of polyester bottles is the current major research direction. China is a big country of beer production in the world and a big beer sales country. It is of great significance to research and develop high barrier polyester packaging materials for beer.
1. Copolymerization modification
In order to improve the barrier properties of polyester (PET), glycols, dicarboxylic acids, or NDC (dimethyl-2,6-naphthalate) are commonly used as copolymerization carriers to copolymerize and modify polyesters. Recently, the copolyester B010 developed by Japan’s Mitsui Petroleum Co., Ltd. is a polymer made of terephthalic acid, isophthalic acid, ethylene glycol and a special diol. In the case of PET blends, the copolymers can be shaped and processed under the same conditions as PET, with better gas barrier properties than PET. The products are mainly used in the small plastic container market. In addition, American Amoco Company has also begun to produce a transparent copolyester Amosorb 3000 with stable oxygen bonds. Beer bottles made from this copolyester can not only block the oxygen passing through the container walls, but also eliminate the presence of containers in the production process. The oxygen at the top.
2, blend modification
Other materials such as LCP, MAX6, PEN, nano/inorganic/particles, etc. can be added to polyester (PET) and can be blended and modified. Modified PET is now entering the market for sales. The beverage bottle made of PET not only improves the heat-resisting temperature, gas barrier property, and UV resistance, but also can perform high-temperature cleaning and filling the beverage under high temperature conditions. In addition, it meets the requirements of environmental protection and can be reused. It is the ideal polymer packaging material to replace glass beer bottles in the future. At present, foreign countries are researching and manufacturing PET bottles, liquid crystal polymers (LCPs), and polyethylene naphthalate (PEN) blends to produce thinner and more barrier-free packaging containers. LCP has excellent barrier properties. In PET/LCP blends, LCP particles are biaxially stretched, the molecules form a structure resembling a sheet, and the lamellar structure is arranged in a staggered manner, with a similar “maze†to gas permeation. The effect can effectively prevent gas penetration. In addition, the PET/LCP multiphase structure is opaque and is an ideal protective packaging for light-sensitive dairy products.
3, multi-layer composite modification
In order to increase the gas barrier performance of polyester (PET), most beer bottles on the foreign market are made of PET by a surface coating method or a multilayer composite method. . The representative multilayer bottle is a PET/EVOH/PET/EVOH/PET five-layer bottle made of co-extruded blown EVOH and PET (adhesive layer in the middle) and a PET/MXD6 nylon five-layer bottle. Recently, Superex polymer company in the United States has used LCP as a laminated barrier material for PET to develop beer bottles. The effect is better than coating PET bottles coated with EVOH and PVDC, and can also be made into food trays for microwave processed food packaging. . Pechiney, France, specializes in packaging and aluminum products. Recently, it has also developed a multi-layer plastic beer bottle consisting of three layers of plastic composites. Two of them are PET and the other is a copolymer of ethylene and vinyl, which can be stored. Beer time is 12 weeks. Five-layer PET bottles with modified nylon layer as barrier layer have also been listed on Altoplast-Claropack, Switzerland. In 2000, 900,000 bottles were put on the market, each weighing 28 bottles.
Grams, with a volume of 500 ml, and a bottled beer with a shelf life of 4 months. In addition, U.S. Plastipak Packaging and Husky Injection Molding in Canada have jointly developed a new method for producing multi-layered preforms for PET barrier bottles. The gas barrier layer is formed by co-extrusion blow-moulding and final parison separation. be made of.
4, surface coating modification
The surface coating method is also a frequently used and economical method to increase the gas barrier properties of polyester (PET). Most plastic beer bottles on foreign markets are products that have PET treated with a surface coating method. PPG USA has successfully developed a gas barrier coating technology for PET bottles that can be removed when waste bottles are recycled. The coating consists of a two-component epoxy-amine. The thermosetting coating has toughness and moisture resistance. For a 0.5-liter PET bottle, the coating thickness is 4-19 micrometers, and the barrier property to oxygen can be increased by 2 -12 times that of the coating. Not only does it not affect the transparency of the bottle, but it also improves the degree of tuckiness of PET bottles. In addition, the hard carbon film coating (DIC) application technology developed by Nissei ASB Machinery Co., Ltd., the Actill inner surface amorphous carbon processing technology developed by the French company Sidel, the Glaskin process and the Sealica process of the Swiss company Tetrapak, and development by Tetra Pak. The purpose of coating 20-meter SiOx coating technology on PET beer bottles is to target the oxygen-sensitive food packaging market, such as tomato sauce, jam and beer bottles.
5, nano composite modification
In the 1990s, the world material science entered the nano era. Therefore, nano-composite modification (using nano-particles, nano-materials) has become the main route and success path for the preparation of advanced packaging materials. Among them, the surface nano-coating method is the most widely studied and most frequently used new technology. It mainly uses a variety of high-barrier coatings and various coating techniques to form a very thin barrier coating on the inner and outer surfaces of PET bottles. It is an important means to improve the gas barrier properties of polyester bottles by blocking the inflow and outflow of gases, thus achieving beer preservation and extending the shelf life. The United States, Japan, and Europe have begun to use. For example, the United States Eastman Chemical Co. and Nanocor Nano Co. have jointly developed a nano-composite packaging material based on PET for the past two years, greatly improving the barrier properties, heat resistance, and other properties. Beverage packaging. The Institute of Chemistry of the Chinese Academy of Sciences in cooperation with Yanshan Petrochemical Company conducted research and research on PET/MT nanocomposites (montmorillonite) and their applications. Translucent beer bottle samples have been produced and it is said that the barrier properties are higher than those of PET bottles. 4 times, the heat resistance has also been improved, and the application prospect is good. At present, some influencing factors, such as the specific surface area of ​​the bottle, the toughness of the coating, and food safety, etc., may be further studied in the nano-surface coating.
In short, the research and development of new processes for the surface coating of polyester bottles (PET) and the overall improvement of the barrier properties of PET bottles have many twists and turns. There is still a lot of work to be done.