The internal and external coating technology of plastic hollow products is mainly to improve the barrier properties of PET bottles and greatly prolong the shelf life of beer and beverages in PET bottles, so that they can replace glass bottles. High-barrier packaging bottle technology is a relatively difficult technology. This article only makes some introductions to the principles and industrial applications of these two coating technologies.
Polyester (PET) is one of the main raw materials in the field of food or pharmaceutical packaging. It has many advantages such as good transparency, stable chemical properties, relatively good barrier properties, light weight and low price, and recyclability. However, as a beer packaging bottle with hollow processing technology, the gas barrier properties of PET are still not high enough. Therefore, improving the gas barrier properties of PET bottles is a major research direction for beer plasticized packaging. Among them, the surface coating method is one of the earliest and most researched processes, and it has become an important means to improve the gas barrier properties of PET bottles.
The key to beer packaging is to control the inhalation of air during storage, because oxygen in the air can promote premature aging and spoilage of the beer. To avoid this situation, coating PET beer bottles to prevent air infiltration and carbon dioxide leakage is an indispensable process. The so-called surface coating method is to use various high-barrier materials and various coating technologies to form a thin barrier layer on the inner and outer surfaces of the PET bottle to isolate the gas from entering and leaving, so as to achieve the purpose of keeping beer fresh and extending shelf life. The coating technologies that have been developed so far include: one is to deposit a very thin layer of material such as carbon or silicon on the surface of the bottle by vacuum or plasma technology; the other is to spray liquid organic materials onto the outer surface of the bottle by atomic spraying . These coating materials have good aging resistance and adhesion, can significantly enhance the barrier properties of containers, especially food safety has been widely proven.
Inner coating scheme
The GLASKIN PET bottle coating machine is used in the industrial production of silicon treatment coating coating in PET bottles. The gas separation layer in the bottle is tasteless and odorless, and will not have any chemical effect with the substances in the bottle, which can ensure the quality of the substances in the bottle. Quality and taste. GLASKIN PET (PET processed with GLASKIN machine) bottle is covered with a layer of silicon oxide similar to glass material, which covers the inner wall of the plastic bottle, which can effectively prevent external oxygen from entering the bottle, and the carbon dioxide gas in the bottle will not leak from the bottle. , thus playing a very good role in gas isolation.
In addition, because the separator is inside the bottle, damage during storage is avoided, allowing the product to achieve a longer shelf life. Tests have shown that this plastic bottle has achieved good results in maintaining product quality and preserving taste, and can make the product shelf life range from 4 to 12 months in accordance with customer requirements for product shelf life.
Through continuous improvement, the application of GLASKIN technology can now enable the PET plastic bottle packaging system to continuously coat 0.2~2L plastic bottles with a productivity of up to 6000~180000/h. GLASKIN PET bottles are also environmentally friendly. During the recycling process, the thin layer of silicon oxide is separated from the plastic bottles, and the PET plastic can be recycled into new plastic bottles or faux fleece fabrics. In addition, GLASKIN PET bottles are lighter than glass bottles and should not be broken, which can reduce the pollution caused by product transportation.
Another inner coating technology uses a plastic bottle inner wall amorphous carbon coating machine, which is a device that uses a carbon source gas to form plasma under microwave excitation to deposit an amorphous carbon film on the inner wall of the bottle. Its structure is controlled by a vacuum system, which can create a vacuum state in the inner cavity of the plastic bottle. The microwave generated by a microwave generating system acts on the plastic bottle, so that the carbon source gas generated in the inner cavity of the plastic bottle forms a plasma resonance cavity. The system can complete the injection of carbon source gas into the inner cavity of the plastic bottle by communicating with the carbon source gas injection system. The plastic bottle processed by this coating machine can effectively control the loss of gas in the bottle from the bottle wall, or the infiltration of gas outside the bottle from the bottle wall.
Outer coating scheme
In an industrial scale production line for PET bottle topcoat application, a BESTPET coater can be used. In previous years, PET bottles whose barrier properties have been enhanced by the silica treatment of the BESTPET coater were mainly used for filling non-alcoholic soft drinks. But recently this new craft bottle can also be used to fill beer, and the beer in this bottle can be tested to ensure that it will not spoil for 6 months.
The overcoating process with BESTPET immediately following the stretch blow molding machine and the filling plant is a high technology, which is characterized by:
(1) The bottle has good barrier properties;
(2) The bottle is as transparent as glass;
(3) It is economical and efficient to combine beer or beverage filling with coating application;
(4) Can be widely used in the beverage industry;
(5) Continuous online coating can be realized.
Because of the outer coating, the product does not come into direct contact with the coating, thus avoiding off-flavor and shortened shelf life caused by the outer coating coming into direct contact with the ingredients of the beer or beverage. This is the biggest benefit of exterior coatings. In addition, the risk of peeling and melting of the inner coating that may occur is also avoided.