Halogenated butyl rubber is a modified elastomer obtained by introducing halogen atoms into the butyl rubber molecular chain. Its production process uses butyl rubber as the base raw material and imparts higher vulcanization activity, adhesion, and compatibility with other rubbers through halogenation reactions. The entire process encompasses raw material preparation, halogenation reaction, neutralization and washing, devolatilization and drying, and finished product processing. Precise control of each step directly determines the uniformity of the product's molecular structure, halogen content, and overall performance.
Production begins with the dissolution of high-purity butyl rubber. Typically, alkane solvents (such as hexane or cyclohexane) are used to prepare a solution of solid butyl rubber at a certain concentration. Simultaneously, the moisture and metal ion content are strictly controlled to avoid inhibiting the catalyst in the subsequent halogenation reaction. The solvent needs to undergo dehydration and distillation to ensure the system's cleanliness meets the reaction requirements.
The halogenation reaction is the core process, and it is divided into two routes: chlorination and bromination, depending on the target product. Chlorination typically uses chlorine gas as the halogenating agent, proceeding under free radical initiation or Lewis acid catalysis. The reaction temperature is generally maintained between -10°C and 40°C. The degree of chlorine substitution is controlled by adjusting the chlorine gas introduction rate and reaction time to avoid over-substitution leading to chain breakage or cross-linking. Bromination uses bromine or bromides (such as N-bromosuccinimide) under mild conditions, exhibiting high selectivity and yielding uniform bromine-substituted structures at lower temperatures. During the reaction, real-time monitoring of halogen content and solution color changes is necessary to assess the reaction progress and prevent localized over-reaction.
After halogenation, a neutralization and washing stage follows. Residual halogenating agents and generated acidic byproducts are neutralized using an alkaline solution (such as dilute sodium carbonate or sodium hydroxide). Subsequently, multi-stage water washing or dilute acid washing removes soluble salts and unreacted halogens, ensuring product purity and reducing corrosivity. The washing temperature and number of washes in this stage need to be optimized based on halogen content and solvent system to improve separation efficiency and reduce solvent loss.
Volatile removal and drying are crucial in determining the product's form and stability. Solvents and low-molecular-weight byproducts are removed by vacuum distillation or stripping, followed by hot air circulation or vacuum drying to reduce the moisture content of the rubber granules to extremely low levels. For products requiring granulation, extrusion and pelletizing can be performed in the molten state, followed by cooling to obtain uniform granules for easy subsequent processing and metering. Strict control of drying temperature is essential to prevent thermal degradation of rubber molecular chains or secondary cross-linking caused by high temperatures.
Quality control is maintained throughout the entire process, including halogen content determination, molecular weight distribution analysis, volatile matter and ash content detection, and vulcanization characteristic evaluation, to ensure that the product meets the performance indicators for different applications. In recent years, process optimization has trended towards continuous halogenation reactor configurations, online halogen content monitoring, and closed-loop control systems to improve batch stability and reduce energy consumption and waste emissions.
Overall, the production process of halogenated butyl rubber centers on butyl rubber solution halogenation, combined with meticulous neutralization washing, devolatilization drying, and granulation molding, forming a scalable and controllable manufacturing system. The coordination and precise control of each link not only ensures the uniformity of product structure and performance, but also provides high-quality basic materials for downstream fields such as tires, seals, pharmaceuticals and chemical protection.