Production technology and market overview of the h

Polyester film production technology and market overview (I)

since 1948, British Imperial Chemical Company (i.c.i) and American DuPont company (DuPont) produced polyester film, and the industrial production of biaxially stretched polyester film was realized in 1953. Biaxially stretched polyester film (BOPET) has excellent physical and chemical properties, and is widely used in electronics, electrical appliances, magnetic recording, packaging, decoration, plate making and printing, photosensitive materials, etc. it is more and more used in the domestic market, especially in China's plastic packaging products industry, which is developing rapidly, far higher than the growth rate of GDP, It is expected that the annual growth rate of plastic packaging products' GDP will remain above 10% in the next few years. With the development of high-grade packaging, the output and consumption of BOPET film have increased significantly, and packaging film is the application field with the fastest growth in BOPET film demand. As of 2003, the output of polyester for film in China was 200000 tons, which basically met the demand of domestic BOPET manufacturers for raw materials. The users of film polyester chips are mainly distributed in Guangdong, Jiangsu, Shanghai, Henan and other regions. Most of the direct production of film processing, bronzing, composite, aluminum plating and other packaging materials leave the factory. The manufacturers that can produce film grade chips in China mainly include Yizheng Chemical fiber, Liaohua, Yanhua, Tianhua and other enterprises, with an annual output of about 250000 tons. Polyester for film has become an important direction for the development of non fiber polyester

polyester film is a high-grade film made of high-quality fiber grade polyester chips (viscosity 0.64) as the main raw material, using advanced process formula, through drying, melting, extrusion, casting and stretching

biaxial stretching of polyester film can be divided into one-time stretching and two-time stretching, and the latter is mostly used, that is, extrusion vertical and horizontal successive stretching method. The stretching temperature is usually above the glass transition temperature and below the melting point temperature of polyester. After stretching, the film is heat set, so that the molecular arrangement is called fixed, which is called setting film; If the molecular arrangement is not fixed without heat setting, it is a shrink film, which can shrink rapidly when heated. According to the different raw materials and stretching processes used in the production of polyester film, it can be divided into the following two kinds:

1. Biaxially stretched polyester film (BOPET) is a high-grade film that uses bright materials (also known as bright materials, that is, adding titanium dioxide to the raw material polyester chips, and then drying, melting, extrusion, casting and vertical and horizontal stretching. It is widely used.

2. Uniaxially stretched polyester film (CPET), It is a film made of semi matting material (the raw material polyester chip is not added with titanium dioxide), which has been dried, melted, extruded, cast and longitudinally stretched. It has the lowest grade and price in polyester film, and is mainly used for the packaging of pharmaceutical tablets. Due to less usage and less manufacturers, large-scale production accounts for about 5% of the polyester film field. Chinese enterprises also import less, with a standard thickness of 150 μ m。

according to the similarities and differences of orientation and properties, polyester film can be divided into balanced film and reinforced film. The horizontal and vertical orientations of the equilibrium film are basically the same, and the tensile strength and relative thermal shrinkage are the same; Usually, when the tensile strength in both directions reaches 2.7 ~ 3Mpa, it is called super balanced film. The strengthening film is called strengthening film, in which the orientation degree in one direction is greater than that in the other direction in both vertical and horizontal aspects, and the tensile strength in this direction is greater than 2.6MPa; If the tensile strength is greater than 4MPa, it is called super strengthened film

polyester film has different uses due to its characteristics. Polyester films for different purposes have different requirements for raw materials, additives and processing technology, and their thickness and technical indicators are also different; In addition, only BOPET has multiple uses, so the films classified according to their uses are BOPET. It can be divided into the following:

1. Electrical insulating film. Due to its good electrical, mechanical, thermal and chemical inertness, good insulation performance and high puncture resistance voltage, it is specially used for electronic and electrical insulation materials. The commonly used standard thickness is: 25 μ m、36 μ m、40 μ m、48 μ m、50 μ m、70 μ m、75 μ m、80 μ m、100 μ M and 125 μ M (microns). Including wire and cable insulation film (thickness: μ m) And touch switch insulating film（ μ m）。

2. Capacitor film. It has the characteristics of high tensile strength, high dielectric constant, low loss factor, good thickness uniformity, good electrical performance, large electrical resistance and so on. It has been widely used in capacitor dielectric and insulation barrier. The common standard thickness is 3.5 μ m、3.8 μ m、4 μ m、4.3 μ m、4.8 μ m、5 μ m、6 μ m、8 μ m、9 μ m、9.8 μ m、10 μ m、12 μ m。

3. Protective film. It has good transparency, high stiffness, good thermal stability, excellent winding performance with flat surface, uniform longitudinal and transverse tensile performance, and excellent properties such as waterproof, oil proof and chemical proof. It is specially used for the protective packaging of pictures, certificates, documents and office supplies, so that it is flat and beautiful after hot stamping as a protective film, and can maintain the clarity and deformation of the original. The common standard thickness is 10.75 μ m、12 μ m、15 μ m、25 μ m、28 μ m、30 μ m、36 μ m. 45 support fuzzy query μ m、

55 μ m、65 μ m、70 μ m. Of which 15 μ M above is mainly used as laser anti-counterfeiting base film or high-grade card protection film

4. Universal membrane. With excellent strength, dimensional stability, cold resistance and chemical stability, it is widely used in composite packaging, photosensitive film, metal evaporation, audio and video recording and other substrates. Specifically, there are the following:

① semi reinforced membrane. The main feature is that it has high longitudinal tensile strength and is not easy to break under large tensile force. It is mainly used for packaging seals of boxed items. The common standard thickness is 20 μ m、28 μ m、30 μ m、36 μ m、50 μ m。

② bronzing film. It is characterized by good tensile strength and transparency, stable thermal performance and low adhesion with some resins. It is mainly suitable for small size change during high-temperature processing or as a transfer carrier. The normal standard thickness is 9 μ m、12 μ m、15 μ m、19 μ m、25 μ m、36 μ m。

③ printing composite packaging film. The main characteristics are good transparency, good penetration resistance, excellent chemical resistance, temperature resistance and moisture resistance. It is suitable for the packaging of frozen food, food, medicine, industrial products and cosmetics. The common standard thickness is 12 μ m、15 μ m、23 μ m、36 μ m。

④ aluminum coating. The main characteristics are high strength, good temperature resistance, good chemical resistance, good processing and aging resistance. Proper corona treatment makes the adhesion of aluminum layer and film more firm. After aluminizing, it can be widely used in the packaging of tea, milk powder, candy, biscuits and so on, and can also be used as decorative film, such as string flower crafts and Christmas trees; At the same time, it is also suitable for printing lamination or paperboard lamination. The conventional standard thickness is 12 μ m、16 μ m、25 μ m、36 μ m。

⑤ magnetic recording film. It has the characteristics of good dimensional stability, uniform thickness and high tensile strength. Suitable for base film and special packaging film of magnetic recording materials. Including audio and video tape base (common standard thickness is μ m) And black film (common standard thickness is μ m）。

different manufacturers can have different classification names according to the quality of polyester film. Chinese manufacturers are generally divided into excellent products, first-class products and qualified products, while foreign manufacturers are generally divided into class a products, class B products and class C products. Generally, grade a products account for%, grade B products only account for%, and grade C products are unqualified products, which cannot be sold in the circulation field. The main reason is the high price of raw materials. Generally, manufacturers return them to the furnace and reuse them as raw materials, or sell them as staple fibers to textile mills as textile raw materials. Foreign manufacturers sometimes sell the films in stock every quarter or half a year as class B products with large travel. This practice is the consistent practice of some manufacturers in Southeast Asian countries to reduce inventory

polyester film is usually colorless, transparent, shiny, and has good strength, toughness and elasticity. Compared with other plastic films, it has the characteristics of high relative density, high tensile strength, moderate elongation, high impact strength, low permeability, good heat resistance and high transparency

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