High-barrier surface nano-coating technology

High barrier function is one of the basic functional elements of plastic packaging. Polyethylene terephthalate (PET) is the preferred material for beverage packaging. PET has many advantages such as good transparency, stable chemical properties, relatively good barrier properties, light weight, low cost, and recyclability. Wide range of applications. However, as a beer bottle, the gas barrier property of PET is still not high enough. Therefore, improving the gas barrier properties of polyester bottles is a primary solution to the problem of plasticization of beer packaging. Among the numerous process technologies, the nano-surface coating method is one of the effective methods in the surface coating technology. It uses a variety of high barrier coating and corresponding coating technology, in the form of a very thin barrier coating inside and outside the PET bottle, cut off the gas in and out, to beer preservation and extend the life of the goods.
Plasma Nanotechnology
Among the various surface coating technologies, plasma nano coating technology has the greatest market potential, and it is also a hot spot for development. The research of plasma nano-surface treatment began in the late 20th century. It is a vacuum dry treatment process, which has the advantages of simple operation, cleanness, high efficiency, safety, and no pollution, and meets the requirements of environmental protection. The plasma surface treatment coating has a nanometer-scale thickness, and the physical properties of the material interface are significantly improved while ensuring that the material substrate is not adversely affected.
Amorphous nano-carbon coating The amorphous nano-carbon coating technology (ACTIS) developed by Sidel of France is a new high-barrier treatment technology. The technical method is to agglomerate plasma acetylene on the inner wall of a PET bottle to form a highly hydrogenated amorphous carbon uniform nano solid film with a thickness of 20-150 nm. The oxygen barrier performance of PET bottles treated with the ACTIS process was 30 times higher than that of ordinary PET bottles, and the barrier to CO2 was increased by more than 7 times, and the penetration resistance of acetaldehyde was increased by 6 times. Six months after storage of this PET bottled beer, the carbon dioxide loss rate was only 6%, which is lower than the current standard of 10% carbonation loss in the beer industry. The safety of the coating to food has been approved by the EU safety agency and approved by the US FDA for food packaging.
The PET bottles processed by the ACTIS process have a strong advantage in recycling. Due to the small amount of coating material and the structure similar to that of the polymer, the fibers produced from recycled ACTIS bottles have no negative effect on physical properties and color. Mixing with other uncoated materials does not affect the final package characteristics and conversion process.
According to reports, the first batch of production equipment ACTIS 20 produced by France's Sidel can process 10,000 0.6L PET bottles per hour. Such equipment has been sold to the United States, Japan, Austria, EU member states, etc. Market prospects good.
Diamond-type nano-carbon coating Japan Nippon-Nippon ASB cooperated with Japan Kirin Beer Corporation, Mitsubishi Corporation and Youtec Corporation to jointly develop a diamond-type nanocarbon coating process (DLC). The DLC process uses high-frequency vacuum discharge, so that ionized carbon and hydrogen form a fine coating with a thickness of 20 to 40 nm and a diamond-like carbon structure on the inner surface of the PET bottle. The PET bottle is more than 20 times more resistant to oxygen than normal PET bottles, 7 times more resistant to CO2, 8 times more resistant to water vapor, and also significantly improved in UV resistance. The nano-coating is not only highly transparent, the coating is not easy to crack, but also has good acid and alkali resistance. These companies are cooperating to develop industrial production equipment and plan to first promote it to the Southeast Asian market.
Silicon Oxide Nanocoating US COCA-COLA, in cooperation with Essen University, Krones and Leybold Systems of Germany, has developed silica nano-treated PET bottles with improved barrier properties. The technique is to use SiOx for vacuum physical vapor deposition treatment under high vacuum plasma conditions, with the treatment layer at the bottom of the PET bottle. According to reports, PET bottles treated with this process can increase barrier properties by a factor of 4 and extend shelf life by at least 6 months without affecting the odor of beer. According to Germany's Krones company, the processing cost of this method is lower than that of using PEN bottles or multi-layer bottles. In cooperation with Leybold, the company has installed a production line at a Coca-Cola bottling plant in Germany and has already put it into use.
According to foreign reports, Tetra Pak packaging company in Switzerland has developed a technology for plasma-coated nano-SiOx coating on the inner wall of PET bottles. This process can form a glass-like barrier coating with a thickness of 50 to 100 nm on the inner wall of the bottle. Filling beer or juice with this bottle, the shelf life can be extended to 12 months. The system can handle 18,000 PET bottles below 2L per hour and has been applied by Spendrups in Sweden. The market prospects are good.
Other nano-coating technologies According to incomplete reports, Italy's Sipa Corporation has developed an epoxy polyurethane outer coating PET bottle. This process uses the epoxy polyurethane barrier coating of PPG Company of the United States to form a bright abrasion resistance and scratch resistance barrier coating. Swiss Instant Surface Technology has developed a plasma coating technology at atmospheric pressure to deposit a barrier layer on the inner wall of a PET bottle. It is said that this technology does not require expensive equipment and simplifies the coating process, and the oxygen barrier of the coated PET bottle is 10 times higher than that of the conventional bottle. In addition, TetraPak Corporation has also introduced a new barrier coating technology that achieves the desired barrier effect by adjusting the thickness of the barrier layer. The barrier layer is a Dow Chemical Company's thermoplastic epoxy resin, both high transparency and excellent gas barrier properties.
Recently, DuPont Polyester (DUPONT) has developed a new two-stage overcoating technology to increase the barrier properties of PET bottles to O2 and CO2 by up to 30 times, and the primer can be separated by water. Very convenient. Another external coating technology developed by DuPont, called “transparent aluminum”, can increase the barrier properties of PET bottles by 30 to 40 times. This technology is close to commercialization.
Nonetheless, the coating barrier provided by the surface coating technology may be affected by the specific surface area of ​​the bottle. In addition, the inner coating has the problem of food safety and must be approved by a safety agency. In addition, some of the coatings are less flexible, and the SiOx coating is relatively brittle and easy to peel off. However, other methods also have more or less problems, which must be further improved.
The development of new surface coating technology and the overall improvement of the barrier properties of PET bottles have a long way to go in the packaging industry and a great deal of work needs to be done.