Polyethylene Terephthalate (PET) is a plastic polymer widely used in the field of chemical production. Due to its excellent mechanical properties, chemical resistance, high transparency and other advantages, it is widely used in packaging, fiber, engineering plastics and other fields. In this paper, the manufacturing method of polyethylene terephthalate will be described in detail.
I. Raw material preparation
1. Terephthalic Acid (TPA): as one of the main raw materials of PET, TPA is usually supplied in powder or granule form.
2. Ethylene Glycol (EG for short): another main raw material, ethylene glycol is usually supplied in liquid form.
2. Esterification Reaction
In an esterification reactor, terephthalic acid and ethylene glycol under the action of a catalyst carry out an esterification reaction to produce bis(2-ethylene-terephthalate) (BHET). Commonly used catalysts include acetate and ascorbic acid. The reaction process requires strict control of temperature, pressure, pH and other parameters to ensure the smooth progress of the reaction.
Three, polycondensation reaction
In the polycondensation reactor, diethylene glycol terephthalate further undergoes polycondensation reaction to produce high molecular weight polyethylene glycol terephthalate. The polycondensation reaction process requires the elimination of by-product water to facilitate the reaction. Commonly used polycondensation catalysts include titanium and antimony catalysts. Four, melt conveying and granulation
After the polycondensation reaction of PET melt needs to be transported through the melt conveying system to the granulator for granulation. In the process of granulation, the melt is cut into particles of a certain length and undergoes cooling, drying and other processes to obtain the final PET granule product.
V. Quality Control and Packaging
The PET granules produced need to go through strict quality control, including the testing of various indexes such as molecular weight, viscosity, color, melting point and so on. Qualified products can be warehoused or sent to downstream customers after packaging.
Above is the basic manufacturing method of polyethylene terephthalate. In the actual production process, depending on 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 follow the operating procedures and pay close attention to the changes in various process parameters. At the same time, it is also necessary to carry out regular maintenance and repair of the production equipment to ensure the normal operation of the equipment.
In terms of environmental protection, the production process of polyethylene terephthalate will produce a certain amount of wastewater, exhaust gas and other pollutants. Therefore, enterprises need to take corresponding environmental protection measures, such as wastewater treatment, exhaust gas recycling and so on, in order to reduce the pollution of the environment.
In short, the manufacture of polyethylene terephthalate requires strict process control and quality management to ensure product quality and performance. At the same time, companies also need to pay attention to environmental protection and sustainable development to promote green development in the field of chemicals production.
