We are Yixing Wencheng Chemical Co., Ltd., a manufacturer specializing in polyols—including ethylene glycol (EG)—with over 30 years of experience in the production and sales of polyols and their derivatives. Ethylene glycol is synthesized through the hydrolysis of ethylene oxide under high temperature and high pressure; this process yields ethylene glycol as the primary product, with diethylene glycol and triethylene glycol as by-products. In a previous article, we discussed how triethylene glycol (TEG) serves as a specialized dehydrating agent for natural gas, oilfield gas, and refinery gas. Thanks to properties such as strong hydrophilic adsorption, low volatility, thermal stability, and the ability to undergo high-temperature regeneration, TEG has become the standard solvent for natural gas purification worldwide. As for ethylene glycol itself—the main product of this synthesis process—approximately 70% of the global supply is consumed by the polyester industry, where it is polymerized with purified terephthalic acid (PTA) to produce polyethylene terephthalate (PET). Drawing on our domestic and international sales experience as well as practical field insights, I would like to share some of our knowledge in the hope that it proves helpful to those in the industry.

Polyethylene terephthalate, commonly known as PET plastic, is produced through a two-step process involving the esterification and polycondensation of terephthalic acid (PTA) and ethylene glycol (EG). PET is a high-quality plastic characterized by resistance to acids, alkalis, and oils, as well as excellent insulation properties and recyclability. In large-scale industrial production, the feed ratio of PTA to EG is critical. An insufficient proportion of EG leads to a low conversion rate of BHET, resulting in an inability to achieve the desired molecular weight during polycondensation, as well as low chip viscosity and poor strength. Conversely, an excess of EG lowers the system's boiling point, slows down water removal, increases energy consumption, places a heavier load on recovery systems, and leads to an increase in the byproduct diethylene glycol (DEG). Precise temperature control is also essential; excessively high temperatures cause significant EG volatilization and a surge in DEG byproducts, leading to a drop in the PET melting point and reduced heat resistance. Conversely, temperatures that are too low result in slow esterification and prolonged residence times, thereby reducing production efficiency. Naturally, the quality of raw materials is paramount; polyester-grade (≥99.9% purity) ethylene glycol must be used. Therefore, producing high-quality PET requires not only process control but also premium raw materials. Yixing Wencheng Chemical Co., Ltd. is a leading manufacturer of ethylene glycol, offering a product with a purity of ≥99.9%.

We also recommend utilizing the by-products generated throughout the entire PET polymerization process. These by-products fall into four main categories—liquid-phase alcohols (DEG, TEG, EG), gaseous acetaldehyde, solid-phase oligomers, waste polyester, and esterification wastewater—all of which can be recovered for value, thereby reducing specific raw material consumption and pollutant emissions. Diethylene glycol (DEG) is the liquid-phase by-product with the highest output; it can be separated sequentially into EG (recycled as feedstock to the unit), DEG, and TEG through multi-column vacuum distillation.

There are four major grades of polyethylene terephthalate (PET), each with distinct properties and applications.

1. Fiber-grade PET (accounts for the largest share of production capacity)

Characteristics: Low-to-medium intrinsic viscosity; good melt flowability.

Applications: Filament and staple fibers are used in clothing, home textiles, curtains, and tents; industrial yarns are used in seatbelts, conveyor belts, tire cords, and filter fabrics.

2. Bottle grade PET slicing

Features: high viscosity, low acetaldehyde, low precipitation, food safety grade; most of them are equipped with solid phase thickening SSP process.

Application: drinking water, carbonated drinks, juice bottles; plastic bottles for edible oil and condiments; disposable water cups, cosmetic containers.

3. Film-grade BOPET

Characteristics: Biaxially oriented and heat-set; high strength and high transparency.

Applications: Composite packaging films, high-transparency optical films, solar backsheets, motor insulation films, release films, and printing films.

4. Modified Engineering PET

Characteristics: Glass fiber reinforced; flame-retardant; toughened; hydrolysis-resistant.

Applications: Automotive structural parts, lamp bases, electronic connectors, sockets, and home appliance housings.

Our company offers a high-quality series of polyols—including ethylene glycol (EG)—characterized by stable performance and superior quality. Exported to numerous countries worldwide, these products are widely used in sectors such as polyester manufacturing, antifreeze and coolant production, and chemical intermediates. With thirty years of deep industry experience, we remain steadfast in our commitment to quality and production stability, and we warmly welcome customers from all sectors to contact us for consultations and partnership opportunities.