Development and application of the hottest SiOx co

2022-10-14
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Development and application of SiO x coating packaging materials (Part 1)

the production technology of SiO x coating packaging materials takes plastic film or paper as the base material, evaporates non-metallic inorganic substances (such as SiO x, SiO 2, etc.) under high vacuum conditions, and makes them accumulate on the surface of the base material to form a dense, uniform and firmly bonded film, which plays a good barrier layer role. Before use, it is compounded with other substrates such as paper and plastic to form a new type of high barrier packaging material. In recent years, industrial developed countries have invested a lot of human and material resources in the research and development of this new type of high barrier packaging material

1 research and development background of SiO x coating packaging materials

traditional packaging materials include paper, plastic, glass, metal, wood and other five categories. Plastic has become one of the most widely used packaging materials in the packaging field of food, medicine, cosmetics and so on because of its excellent performance. The plastic used for packaging accounts for 26% of the total output every year. In 2000, the consumption of plastic packaging in China reached nearly 3 million tons. With the development of society and the improvement of people's living standards, the commodity economy is becoming more and more developed. In order to improve the circulation cycle and shelf life of commodities, the role of commodity packaging is becoming increasingly important, especially for a class of commodities that are easy to deteriorate, such as food, drugs, cosmetics, etc., the use of high barrier packaging materials is often the most effective means. The traditional production methods of high barrier packaging materials mainly include composite processing, multi-layer coextrusion, surface coating, etc. at the same time, they can also be made into packaging materials with excellent performance and wider applicability by vacuum aluminum plating or compounding with aluminum foil and other materials. The basic properties of the main flexible packaging materials currently used for packaging are shown in Table 1

since the 1990s, the rapid development of microwave heating technology has put forward new requirements for microwave food packaging and the packaging of a class of commodities that need to be sterilized by microwave, that is, packaging materials should not only have excellent barrier properties, but also have high temperature resistance, good microwave permeability and other characteristics. As can be seen from table 1, traditional packaging materials are difficult to fully possess these characteristics. Therefore, in recent years, Japan, Germany, Britain, Italy, Canada, the United States and other industrial developed countries have invested a lot of human and material resources in the research and development of new high barrier packaging materials - SiO x and other non-metallic oxide coating composite packaging materials, so as to occupy a favorable position in the future technology and material market. In addition to the barrier performance comparable to that of aluminum-plastic composites, this kind of material also has the advantages that the micro calibration should be 5-point wave, good permeability, high temperature resistance, transparency, and less affected by ambient temperature and humidity. Especially in terms of commodity fragrance preservation, the effect is the same as that of glass bottle packaging. After long-term storage or high-temperature treatment, it will not produce peculiar smell. It can be widely used in the packaging of food, drugs, cosmetics, medical devices and other commodities with high requirements for safety and health performance and long shelf life; It is especially suitable as a kind of commodity packaging material for the application of microwave heating technology

statistics show that the output and consumption of SiO x coating packaging materials in the international market are gradually increasing, and now it is close to the scale of tens of thousands of tons; Among them, Japan's output ranks first in the world; Followed by the European Union and the United States. Experts predict that with the continuous improvement of SiOx coating technology and the further reduction of product costs, SiOx coating packaging materials will have a very broad application prospect. In most packaging fields, it will replace the traditional multi-layer coextrusion, aluminum-plastic composite, vacuum aluminum plating processing high barrier materials, and become the most widely used new composite packaging materials. The technical properties of SiO x coating packaging materials are shown in Table 2

2 production technology of SiO x coating packaging materials

the large continuous vacuum coating machine used for the production of SiO x coating packaging materials is much more complex than ordinary vacuum aluminum plating equipment. At the same time, the requirements for evaporation substrate, evaporation raw materials and evaporation technology are more stringent

2.1 evaporation of substrate

sio x coating, the higher gasification temperature of evaporation raw materials and evaporation can lead to higher temperature in the evaporation process, and a large amount of radiant heat makes the substrate absorb excessive heat energy and the temperature rise; At the same time, the heat released by gasification molecules, ions and other particles when they condense into a film on the surface of the substrate causes the substrate temperature to be too high and serious thermal deformation occurs. After thermal deformation, the substrate wrinkles, resulting in uneven coating or cracking, which can not achieve the effect of improving barrier performance. The evaporation effect of plastic film with low softening point and melting point is poor. Experiments show that only PP, pet, PA and other materials can be more suitable for oxide coating processing

(1) polypropylene (PP)

polypropylene film is odorless, tasteless, non-toxic, non absorbent, good chemical stability, stable to acid and alkali, thermal deformation temperature 100 ~ 120 ℃, and can be used continuously at 110 ~ 120 ℃. Theoretically, it is a good SiO x non-metallic coating substrate. Due to the high gasification point and evaporation energy of SiO and SiO 2, the evaporation power is large, and the composite film after evaporation has obvious thermal deformation. In addition, polypropylene materials have poor low-temperature adaptability, and the impact strength decreases sharply below - 5 ℃. In order to obtain satisfactory use effect, the resin model should be strictly selected and modified before plastic film forming processing

(2) polyester (PET)

polyester is polyethylene terephthalate, which has high strength, good dimensional stability, low water absorption, non-toxic, resistant to weak acids and organic solvents, stable chemical properties, thermal deformation temperature as high as 200 ℃, and can be used for a long time at 120 ℃. Using SiOx, SiO2, etc. as evaporation raw materials, as long as other conditions are properly controlled, the substrate will not have obvious thermal deformation, and the coating has high adhesion fastness. It is an ideal SiOx non-metallic coating substrate

(3) nylon (PA)

nylon has good low temperature resistance and can be used at - 30 ℃ to - 60 ℃. Stable chemical properties, oil resistance, solvent resistance, salt water resistance, non-toxic, tasteless; Good heat resistance, heat deformation temperature up to 141 ℃, can be used continuously at 180 ℃, high strength at high temperature, good dimensional stability. When SiO x and SiO 2 are used as evaporation raw materials, no obvious thermal deformation of nylon base film is observed even at high evaporation power. Among the tested substrates, its dimensional stability is the best. In the application of nylon film in vacuum evaporation technology, the orders of extruder enterprises will rise significantly. The only defect is that its moisture content is significantly higher than that of other plastic films, which can exceed 1% at the highest. On the one hand, under high vacuum and high temperature conditions, trace moisture evaporation leads to a significant decline in vacuum, which reduces the working stability of the electron gun. In order to eliminate the influence of water vapor evaporated from the substrate on the vacuum degree, it is necessary to increase the power and efficiency of the vacuum system, or degassing the film in the vacuum chamber first, and then vacuum coating processing, which has a certain negative impact on the production speed and cost. On the other hand, its surface moisture also affects the firmness of the coating. The comparative experiments before and after degassing have proved that considerable economic and social benefits have been created

2 2 evaporation raw materials

Si, SiO x, SiO 2 or other oxides can be used as evaporation raw materials. Other oxides such as Al2O3, MgO, Y 2O 3, TiO2 and Gd 2O 3 can also be used. Their main properties are shown in Table 3. (omitted)

(to be continued)

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