Emulsion polymerization is a polymerization method widely used in copolymer rubbers (including latex polybutylene, butyronitrile, chloroprene, etc.) containing butadiene or a derivative thereof (e.g., chloroprene). The early emulsion polymerization into rubber uses a higher polymerization temperature (40~50 °C), and the obtained synthetic rubber is commonly called “hot butyl benzene”. The disadvantage is that the molecular chain branching degree is high, resulting in a large gel content, high raw rubber viscosity, plastic Difficulties in refining, not ideal in liquidity. As a result, not only the process performance is poor, but also the performance is disadvantageous.
Later, the product obtained by the low temperature (5 ° C) polymerization was called “low temperature butadiene benzene, and the above problems were solved. Now the domestic low temperature styrene butadiene rubber is taken as an example to introduce the polymerization process as follows.
The main raw material is fresh butadiene (content 99.5% or more) and recovered butadiene (content 84% or more) is formulated into a mixed butadiene having a concentration of 95%. The purity requirement of styrene is the same as that of butadiene.
The emulsifier is prepared from rosin acid and sodium fatty acid soap (high temperature styrene butadiene rubber is used as an emulsifier).
The polymerization process is as follows.
1 Emulsification is carried out by adding water and an emulsifier in a proportionate mixture of monomeric butadiene and styrene.
2 The emulsified emulsion is sent to a polymerization vessel to start the polymerization reaction. The polymerization temperature is controlled at 5~10 °C
2 When the conversion rate reaches 60%, the terminator is added to terminate the reaction.
3 Post-treatment, including heating and dehydration, is roughly the same as solution polymerization. Since the low-temperature polymerization of styrene-butadiene rubber was put into production, it has been well received by the rubber processing industry. The reason is that low temperature styrene butadiene rubber is superior to high temperature styrene butadiene rubber in terms of processing properties or performance after product manufacture. Low-temperature polymerized styrene-butadiene rubber has a low raw rubber viscosity (no need for long-term mechanical mastication, no need for long-term thermal plasticization); no gel or even low content, so you can save many thin passes or The energy, manpower and precious time wasted by the use of thermoplastics.