An Introduction to PVC Calcium Carbide and Ethylene Processes

The calcium carbide method is a production method for preparing polyvinyl chloride (PVC) with calcium carbide as a raw material. Calcium carbide is obtained by melting limestone and coke at a high temperature (approximately 2000 degrees Celsius). Subsequently, calcium carbide reacts with water to generate acetylene and hydrogen chloride, ultimately synthesizing chloroethylene. China's main synthetic PVC production bases are located in Xinjiang, Inner Mongolia, Shaanxi, Shandong, and other regions.

In industrial applications, polyvinyl chloride is typically categorized into three types: SG-3, SG-5, and SG-8.

SG-3: Primarily used for the production of soft PVC products, such as pipes, cable sheathing, boots, raincoats, etc. Due to its relatively low molecular weight, SG-3 PVC products exhibit softer and more cold-resistant characteristics.

SG-5: A general-purpose PVC resin used for the production of rigid PVC products, including pipes, door and window frames, films, sheets, etc. Its relatively higher molecular weight makes SG-5 PVC products harder and more stable.

SG-8: Mainly used for the production of rigid, high-strength PVC products, such as window frames, pipes, etc. Due to its higher molecular weight, SG-8 PVC products typically have stronger mechanical properties and weather resistance.

It is important to note that the quality of PVC resin powder produced by the calcium carbide method is comparable to that produced by the ethylene method. It is a common misconception that the use of the calcium carbide method implies lower product quality.

Polyvinyl chloride produced by the ethylene method is mainly derived from ethylene as a raw material, undergoing chlorination polymerization to obtain PVC resin.

Ethylene is sourced from petrochemicals, natural gas, and coal chemicals, and must be purified first. PVC resin produced by the ethylene method is typically named using two methods: one based on the K value, representing the relative molecular weight of the polymer (e.g., s65, s70), and the other based on average polymerization degree (e.g., s1000, s700, s1300), corresponding to SG-3, SG-5, and SG-8 in the calcium carbide method, respectively.

PVC Calcium Carbide