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[Chemical Knowledge]：Manufacturing method and process of polyethylene terephthalate

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Polyethylene terephthalate (Polyethylene Terephthalate, PET) is a plastic polymer widely used in the field of chemical production. Because of its excellent mechanical properties, chemical corrosion resistance, high transparency and other advantages, it is widely used in packaging, fiber, engineering plastics and other fields. This article will introduce the manufacturing method of polyethylene terephthalate in detail.

1. Raw Material Preparation

1. Terephthalic acid (Terephthalic Acid, referred to as TPA): As one of the main raw materials of PET, terephthalic acid is usually supplied in the form of powder or granules.
2. Ethylene glycol (Ethylene Glycol, EG): Another major raw material, ethylene glycol is usually supplied in liquid form.

2. Esterification Reaction

In an esterification reactor, terephthalic acid and ethylene glycol undergo an esterification reaction under the action of a catalyst to produce terephthalic acid diethylene glycol ester (BHET). Commonly used catalysts include acetate, ascorbic acid, and the like. The temperature, pressure, pH value and other parameters need to be strictly controlled in the reaction process to ensure the smooth progress of the reaction.

3. Polycondensation Reaction

In the polycondensation reactor, the diethylene glycol terephthalate further undergoes polycondensation reaction to produce high molecular weight polyethylene terephthalate. During the polycondensation reaction, it is necessary to eliminate the by-product water to promote the reaction. Commonly used polycondensation catalysts include titanium-based and antimony-based catalysts.

4. Melt Conveying and Granulation

The PET melt obtained after the polycondensation reaction needs to be transported to a granulator for granulation through a melt conveying system. In the granulation process, the melt is cut into particles of a certain length, and after cooling, drying and other processes, the final PET pellet product is obtained.

5. quality control and packaging

production of PET particles need to undergo strict quality control, including molecular weight, viscosity, chroma, melting point and other indicators of the detection. After qualified products are packaged, they can be put into storage or sent to downstream customers.

or more is a basic production method of polyethylene terephthalate. In the actual production process, according to different production equipment and process conditions, the specific operation steps and parameter control may be different. In order to ensure product quality and production efficiency, the production process needs to strictly abide by the operating procedures and pay close attention to the changes of various process parameters. At the same time, regular maintenance and maintenance of production equipment are required to ensure the normal operation of the equipment.

In terms of environmental protection, the production process of polyethylene terephthalate will produce certain pollutants such as waste water and waste gas. Therefore, enterprises need to take corresponding environmental protection measures, such as wastewater treatment, waste gas recovery, etc., to reduce environmental pollution.

In short, the manufacture of polyethylene terephthalate requires strict process control and quality management to ensure product quality and performance. At the same time, enterprises also need to pay attention to environmental protection and sustainable development, and promote the green development of chemical production.

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