Polyester is a general term for thermoplastic linear saturated polyesters represented by PET, including PBT, PEN, PCT, and copolymers thereof. PET is the earliest developed, the largest production, the most widely used polyester products, people are most familiar with.
First, performance and use The use of polyester can be divided into two major categories of fiber and non-fiber, the latter including films, containers and engineering plastics. In the early stages of polyester development, it was mainly used for the production of synthetic fibers (about 70% of PET consumption). Polyesters are also used to make 3-350μm films, insulating materials, tape bases, film or photographic film bases, and vacuum packaging. Another major area of ​​polyester non-fiber applications is the manufacture of hollow containers filled with beverages, foods, and the like. Secondly, polyester is also used as engineering plastics in electronics, electrical appliances and other fields, such as connectors, instrument housings, and hot air masks, among which the development of packaging containers has attracted attention. More than 20% of PET is now used as a packaging material, and there is an upward trend. Packaging has become PET's second largest user, second only to synthetic fiber.
Second, the application of the packaging 1, polyester packaging types and characteristics of PET can be easily achieved by the rapid cooling method is basically in amorphous, highly transparent, easy to stretch PET products, so when the packaging material is PET can be The biaxially stretched packaging film can be made to obtain a high-strength, high-transparency stretch blow-molded bottle from an amorphous preform, and can also be directly extruded or blown into a non-stretched hollow container.
PET film has the properties of transparency, oil resistance, fragrance protection, hygienic reliability and wide range of operating temperature (high temperature cooking and frozen packaging are all possible), but its heat sealing property is poor and must be used in combination with other films (heat sealing layer), and the price is lower The high general plastic film limits the use of PET film on packaging. PET hollow containers, especially stretch blow-molded bottles, give full play to PET performance, have a good display effect on the contents, and the performance and cost are in competition with other hollow containers. Therefore, PET as a packaging material is basically formed by stretch blow molding, of which the most widely used are small bottles of tens of milliliters to 2 liters, and large bottles of 30 liters in capacity.
2. Application examples (1) Beverage packaging In beverage packaging, the most successful PET bottle application is carbonated soft drink (CSD), such as Coke, Sprite, etc. CSD bottles account for 1/3 of the total number of PET bottles. The PET bottle has a beautiful appearance, flexible design, high strength, sealing to CO2 (carbon dioxide) and reliable hygienic properties, making the PET bottle an ideal packaging container for CSD, and is the only widely used plastic container for CSD beverages to date. Statistical data from the China Beverage Industry Association in 1998 showed that PET bottles in China's CSD beverage packaging accounted for 57.4%, followed by cans and glass bottles, which accounted for 31% and 7%, respectively.
(2) Edible oil packaging PET bottles are oil-resistant, transparent, non-toxic, odorless, non-breakable, have good barrier properties to O2 (oxygen), and also have good barrier properties to ultraviolet rays, and can protect edible oils from oxidation for a long time. , not deterioration. Foreign countries have been successfully applied, and domestic demand in this area is still rising.
(3) Seasoning Packaged sauces and other sauces are a huge potential market for polyester bottles. PET bottles have good properties such as good fragrance protection, light weight, and unbreakable properties, which are favorable conditions for their application in this field. As early as 1995, Japan's application in this area has exceeded 30,000 tons. It accounts for 13% of the total consumption of PET bottles. China's such products are still mainly used glass packaging, the application of polyester bottles is still in its infancy.
(4) Beer packaging The world uses plastic bottles instead of glass bottles. Beer packaging is still in the research and development trial phase. Relevant departments and enterprises in China are also increasingly concerned about the development of beer plastic packaging.
(5) Pesticides, medicines, and daily chemical product packaging PET bottles can be used for partial pesticide packaging. Low-cost PET pesticide bottles blown with recycled materials have been put into production in China. PET bottles are safe, hygienic, and have good moisture-proof, oxygen-proof, and display functions, making PET bottles used in the field of pharmaceutical packaging. Cosmetics, detergents and other daily chemical products are also a huge market for polyester bottles. The good chemical resistance, fragrance retention, high transparency, and high gloss of the PBT and PEN bottles, as well as the flexibility of the UV rays, and the flexibility of the design, are the desirable characteristics of cosmetic products such as cosmetics. Therefore, polyester bottles are widely used in daily chemical product packaging. In particular, the new PEN resin bottles with gas barrier and ultraviolet shielding will occupy a place in the packaging of perfumes and cosmetics.
3. New developments in polyester packaging PET bottles have been competitive with other packaging materials (glass, tin, PE, PVC, etc.) for their superior performance, low cost, and adaptability to environmental protection. Rapid development, but its low heat resistance, poor gas barrier property limits its application in hot canning and high air tightness applications, and has attracted great attention. In the process of improving and improving its performance, polyester packaging has gained new development.
(1) Improved heat resistance Normal PET bottles cannot be used for the packaging of juices, teas and other hot-potted items. Through research, three types of practical heat-resistant polyester bottles have been developed:
1 Heat-set bottles, capable of reaching 85°C canned requirements;
2 PET/PEN alloy bottle, PEN has high heat resistance. In the universal injection stretch blow-molding equipment, the bottle that meets the hot-canned requirements above 80°C can be produced. If the heat setting treatment is performed, the hot-canned temperature can reach above 90°C. ;
3 Multi-layer composite bottle made of heat-resistant polyarylate, etc. to improve heat resistance.
(2) Improve gas barrier Although PET gas barrier is much higher than polyethylene, polypropylene, polystyrene and other plastics. However, products that require more stringent preservation and taste protection, such as beer, liquor, and perfume, still cannot meet the requirements. There are three main methods for improving gas barrier properties.
1 multi-layer composite. Mainly PET, add PVDC, EVOH, MXD6, PEN and other airtight materials made of 3 or 5 bottles.
2 Use special treatment methods, such as applying an epoxy barrier layer in the PET bottle or outer layer, or plasma treatment (ACTIS technology).
3 Formed with other barrier resins, copolymer or blend of PEN or PEN and PET is used as raw material, which not only improves the gas barrier property of the bottle, but also improves the heat resistance of the bottle, which can meet the beer preservation for 3-6 months. The requirements can also be alkali-washed and reused to reduce costs.
Because the first two methods are poor transparency, difficult recycling process, complicated process, and special equipment requirements, and even though the airtightness is improved, the heat resistance is not enough. It can only adapt to the occasion of aseptic filling. Most of the beer industry in China Canned pasteurized technology. Therefore, the use of PEN or PRT copolymer, blends as raw materials, through the current PET bottle blowing equipment and process for molding, is suitable for China's national conditions of beer plastic packaging development direction, it is worth causing the attention of relevant departments and businesses.
III. Development Prospects Polyester packaging materials are the most dynamic and promising materials in all types of packaging materials, and they are also the fastest-growing areas in many polyester applications. Polyesters such as PET and PEN have become the mainstream materials for beverage packaging such as CSD, water, and fruit juices, and will also become one of the packaging materials for beer, edible oils, and cosmetics.
The development of China's polyester non-fiber use started in the 1980s, bottle-grade polyester and polyester bottles started late, but China's polyester packaging industry is developing rapidly. China's CSD, pure water, fruit juice and other beverages have grown at a rate of more than 20%. Therefore, the demand for beverage packaging PET bottles has also increased at a double-digit rate. At the same time, bottle grade polyesters are used in non-food packaging markets (such as cosmetics, medicine, and The demand for pesticides, etc., is also increasing quietly. In 1996, the consumption of bottle-grade polyester in China was 120,000 tons, and in 1998 it was 180,000 tons. It is estimated that it will reach 300,000 tons in 2000. It can be seen that China has the largest potential market for bottle grade polyester and polyester packaging. China's packaging non-fibre polyester has great development prospects, and the polyester packaging industry will continue to develop rapidly.
Application of Polyester in Packaging
August 31 14:07:01, 2024
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