Application and development trend of the hottest p

2022-08-17
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Application and development trend of polyester in packaging field

polyester is the general term of thermoplastic saturated polyester represented by pet, including PBT, pen, PCT and their copolymers. Among them, pet is the polyester product with the earliest development, the largest output and the widest application. In recent years, carbonated soft drinks, pure water, fruit juice and other beverages in China have increased by more than 20%, so the demand for polyester bottles for beverage packaging has also increased by double digits. At the same time, the demand for bottle grade polyester in cosmetics, medicine and other fields is also quietly increasing

polyester can be divided into fiber and non fiber according to its purpose, and the latter includes film, container and engineering plastics. In the early stage of development, polyester is mainly used to manufacture synthetic fibers (accounting for about 70% of pet consumption). Polyester is also used to make insulating materials, tape bases, film or photographic film bases and vacuum packaging. Another major application field of polyester non fiber is the manufacture of hollow containers for filling beverages, food, etc. Secondly, polyester is also used as an engineering plastic in electronics, electrical appliances and other fields, such as meter cases, hot air masks and so on. Among them, the development of packaging containers is the most eye-catching. Now more than 20% of pet is used as packaging materials, and it is increasing year by year. Packaging industry has become the second largest user of pet, second only to synthetic fiber

because pet can easily obtain pet products that are basically amorphous, highly transparent and easy to stretch through rapid cooling, when used as packaging materials, pet can be made into biaxial stretching packaging film, and can also be made into high-strength and highly transparent stretch blow molding bottles from amorphous bottle blanks, and can also be directly extruded or blown into non stretched hollow containers. PET film has the properties of transparency, oil resistance, fragrance retention, sanitation and reliability, and a wide range of application temperatures (both high-temperature cooking and frozen packaging), but its thermal sealing property is poor, so it must be used in combination with other films (thermal sealing layer), and its price is higher than that of general plastic film, which limits the application of PET film in packaging. PET hollow containers, especially stretch blow molding bottles, give full play to the performance of pet, have a good display effect on the contents, and the cost is low. Therefore, when pet is used as packaging material, it is basically formed by stretch blow molding, among which the most widely used are small bottles with a volume of tens of milliliters to 2 liters, as well as large bottles with a capacity of 30 liters

beverage packaging. In beverage packaging, carbonated soft drinks (CSD), such as coke and Sprite, are the most successful in the application of polyester bottles. CSD bottles have accounted for 1/3 of the total PET bottles. PET bottles have beautiful appearance, flexible design, high strength, good sealing to carbon dioxide and reliable hygiene, making polyester bottles an ideal packaging container for CSD and widely used by CSD industry. The statistics of China Beverage Industry Association in 1998 showed that PET bottles accounted for 574% of CSD packaging in China, followed by cans and glass bottles, accounting for 31% and 7% respectively

edible oil packaging. PET bottles are oil-resistant, transparent, non-toxic, tasteless, not easy to break, good barrier to oxygen, and good shielding against ultraviolet rays. The industry will reach 500000 people to protect edible oil from oxidation and deterioration for a long time. It has been successfully applied abroad, and the domestic demand for this aspect has been rising in recent years

packaging of seasoning commodities. Liquid condiments such as soy sauce are a huge potential market for polyester bottles. PET bottles have the advantages of good fragrance retention, light weight and not easy to be broken. As early as 1995, Japan's application in this area has exceeded 30000 tons, accounting for 13% of the total consumption of PET bottles. In China, such goods are still mainly packaged in glass bottles, and the application of polyester bottles is still in its infancy

beer packaging. In the world, the use of plastic bottles instead of glass bottles for beer packaging is still in the development and trial stage, and the relevant departments and enterprises in China are also paying more and more attention to the development of beer plastic packaging

packaging of pesticides, pharmaceuticals and daily chemical products. Polyester bottles can be used for some pesticide packaging. Low cost PET produced with polyester is not only in line with the market, but also pesticide bottles have been put into production in China. PET bottles are safe, hygienic, and have good moisture-proof, oxygen isolation and display functions, which makes PET bottles applied in the field of the development of pharmaceutical packaging bending testing machine. Cosmetics, detergents and other daily chemical products are also a huge market for the application of polyester bottles. The good chemical resistance, fragrance retention, high transparency, UV shielding and shape design flexibility of PBT and pen bottles are the expected characteristics of cosmetics and other daily chemical products. Therefore, polyester bottles are widely used in the packaging of daily chemical products, especially the new gas blocking and UV shielding pen resin bottles will occupy a place in the packaging of perfume and cosmetics

With its superior performance, relatively low cost and adaptability to environmental protection, PET bottles have developed rapidly in the competition with other packaging materials (glass, tinplate, PE, PVC, etc.), but its heat resistance and gas resistance are poor, which limits its application in hot filling and occasions requiring high air tightness, and has attracted great attention. In the process of improving its performance, polyester packaging has achieved new development

first, improve heat resistance. Ordinary PET bottles cannot be used for the packaging of fruit juice, tea and other items that need hot filling. At present, through research, three kinds of practical heat-resistant polyester bottles have been developed: thermosetting bottles, which can meet the requirements of 85 ℃ filling; PET/pen alloy bottles, pen has high heat resistance. Bottles that meet the requirements of hot filling above 80 ℃ can be made on ordinary injection, drawing and blowing equipment. If heat setting treatment is carried out again, the hot filling temperature can reach above 90 ℃; It is made into multi-layer composite bottles with heat-resistant polyarylate to avoid high-temperature scalding, so as to improve heat resistance

the second is to improve the gas resistance. Although the gas barrier property of pet is much higher than that of polyethylene, polypropylene, polystyrene and other plastics, it still cannot meet the requirements for beer, Baijiu, perfume and other products with strict requirements for freshness preservation and flavor preservation. There are three main ways to improve gas resistance. First, multi-layer composite, mainly pet, is added with PVDC, EVOH, MXD6, pen and other materials with good air tightness to make 3-layer or 5-layer bottles. Second, special treatment methods are adopted, such as coating epoxy barrier layer inside or outside the PET bottle, or plasma treatment (ACTIS Technology). Third, it is formed with other barrier resins, using pen or the copolymerization or blend of pen and pet as raw materials, which not only improves the gas resistance of the bottle, but also improves the heat resistance of the bottle, which can meet the requirements of beer storage for 3 ~ 6 months, but also can be washed and disinfected by alkali and reused, so as to reduce the cost. Because the first two methods have problems such as poor transparency, difficult recovery and treatment, complex process, special equipment requirements and so on, and although the air tightness is improved, the heat resistance is poor, so they can only adapt to sterile filling occasions. China's beer industry mostly adopts the pasteurization technology after filling, so using pen or copolymerization and blending with pet as raw materials and molding through the current pet bottle blowing equipment and process is the development direction of beer plastic packaging suitable for China's national conditions, which deserves the attention of relevant departments and enterprises

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