Polycarbonate Production Process.

Polycarbonate is usually a colorless transparent solid with a glass-like luster and high light transmittance (up to 88 to 90 percent), making it very popular in applications where transparency is required. The melting point of polycarbonate is generally between 230-260°C, and it has good thermal stability.

 

Polycarbonate is well tolerant to many chemicals, such as oils and alkaline solutions, but is not resistant to strong acids and certain organic solvents, especially ketones and benzenes. At room temperature, the water absorption of polycarbonate is low, but in a high humidity environment, its physical properties may be affected.

 

Polycarbonate is easy to process by injection molding, extrusion and thermoforming, and is widely used in electronics, appliances, automotive, construction and medical fields. Common products include clear goggles, lamp shades, optical discs, car windshields, and clear roofs and protective screens. Polycarbonate's high impact resistance and excellent UV resistance make it an ideal choice for safety shields and transparent partitions.

 

1.Transesterification method

Transesterification is one of the main processes for the production of polycarbonate (PC). In this process, bisphenol A reacts with dimethyl carbonate at high temperatures to form polycarbonate and release small molecules of methanol. The reaction usually takes place at 200-250°C and is driven towards the polymer by removing the resulting methanol. 

Features:

• mature process, simple operation, suitable for large-scale production.
• The produced polycarbonate has good transparency and mechanical properties and is widely used in optical and electronic products.
• The reaction conditions are relatively mild and the energy consumption is low.
• The efficient removal of methanol from the reaction is required to improve the polymerization efficiency, which can increase the complexity and cost of the operation.
• The purity of raw materials is required, and impurities may affect the quality of the final product.
   

2. Carbonate polymerization method

The polymerization of cyclic carbonates (such as cyclic dimethyl carbonate) is a new method for the production of polycarbonate. In this process, cyclic carbonates are ring-opening polymerized under the action of catalysts to produce linear polycarbonate.

Features:

• The process allows for mild conditions and is suitable for the production of high molecular weight polymers.
• The resulting polycarbonate has high purity and stable performance, making it suitable for high-end applications.
• In the process of reaction, the selection and control of catalysts are required, which increases the complexity of the process.
• Compared with other processes, the industrial production experience is relatively small, and it needs to be further improved.
   

3. Direct polymerization method 

Direct polymerization is A method of synthesizing polycarbonate by reacting a diphenol (such as bisphenol A) with a diisocyanate. Under the condition of high temperature and catalyst, bisphenol A is reacted with diisocyanate (such as toluene diisocyanate) to form polycarbonate. In this way, polycarbonates with specific properties can be prepared, which is suitable for some special functional polymer applications.

Features:

• Polycarbonate with specific properties can be prepared to meet the needs of some special functional polymers.
• The polymer produced by the reaction has excellent physical and chemical properties.
• The reaction conditions are complex, the operation requirements are high, and the corrosion resistance and stability of the equipment are required.
• By-products may be produced, which need to be treated to improve the purity of the final product.
   

4. Solution polymerization

Solution polymerization is a process of synthesizing polycarbonate (PC) in solvent. In this process, bisphenol A is mixed with carbonate in an appropriate organic solvent, and then polycarbonate is formed by polymerization.

Features:

• The reaction conditions are easy to control, which can optimize the molecular weight and structure of the polymer and improve the performance.
• Helps to obtain specific properties of polycarbonate, suitable for small batch or specialty polymer production.
• The selection and recovery process of solvents is complex, resulting in increased production costs.
• Production efficiency is relatively low, not suitable for large-scale commercial production.

Summary
Polycarbonate (PC) is a rapidly growing engineering plastic, global production capacity to maintain the growth trend, the main growth momentum from Northeast Asia, especially China. China has become the world's largest PC producer and consumer, and national policy support and production technology progress have promoted the development of the PC industry.

 

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