Preparation method of chlorinated polyvinyl chloride

Solvent method

The solvent method is the earliest method to prepare CPVC. The West German AG method is the first to be produced by our company using the solvent method. The process is relatively mature, and its main process is to dissolve the PVC resin in chloroform or carbon tetrachloride solvent and then chlorinate it.

Suspension method

In the early 1960s, the Goodrich Company of the United States first adopted the aqueous phase suspension method to produce CPVC. The process was to suspend the powdered PVC resin in a hydrogen chloride solution, and react with chlorine in the presence of additives. The reaction proceeds according to the free radical reaction mechanism, where the chlorination conversion rate is controlled by diffusion. In order to facilitate the diffusion of chlorine in the polymer phase and improve the uniformity of chlorination, the early process required the addition of a swelling agent, such as chloroform or CCl4, to the water phase to increase the contact area between chlorine and PVC. .

Gas-solid method

The West German Laurent Company first reported the gas-solid phase chlorination method in 1958. The gas-solid phase chlorination method is to put the PVC resin into a reactor or a fluidized bed in a dry state under normal pressure, and directly chlorinate it. reaction. The loose particles can be chlorinated by treating them with diluted oxygen in a fluidized bed at 55°C. The gas flow can be composed of a mixed gas containing 50% chlorine (volume fraction), 0.75% fluorine (volume fraction) and 49.25% nitrogen (volume fraction). After 100 minutes of reaction, 64% chlorine (volume fraction) and 0.6 fluorine can be obtained. % (Volume fraction) of CPVC. Light can catalyze chlorination, but trace oxygen can also have a catalytic effect when there is no light.