One-stage mixing method
The one-stage mixing method refers to the method of preparing the compound rubber by adding all the compounding agents at one time. It is often used to prepare those compounds with good scorch performance and no or only a small amount of active compounding agents. 50% rubber. In order to prevent the temperature of the rubber compound from rising too fast during mixing, a slow mixer is generally used. A two-speed internal mixer can also be used.In the early stage of mixing, the masterbatch except sulphur and super accelerator can be completed quickly and shortly. Then use a slow speed to cool the rubber and then add sulphur and then discharge. The next film is cooled and parked. Generally, a low-speed mixing is performed in the internal mixer.
The feeding sequence of the one-stage mixing method is:
Raw rubber (including various synthetic rubber, plasticized rubber, recycled rubber, masterbatch) → small materials (solid softener, active agent, accelerator, antioxidant) → reinforcing fillers (carbon black, white carbon black) → Liquid softening agent → The top plug drops to start the mixing → The end of the mixing → Discharge to the open mill or tablet press → Add super accelerator and sulfur in the tablet press → Turn the glue → Cool out (or cooling water) ) → Slicing standby
The mixing period of a one-step mixing method depends on the rubber properties and the rotor speed. During the one-stage mixing, vulcanizing agent and accelerator are generally added within about 60s before the end of the mixer, or vulcanizing agent and accelerator are added to the opener after the discharge of the next sheet. However, no matter which method is used to add the vulcanizing agent and accelerator, the temperature of the mixed rubber during operation must be controlled below 110 degrees (sulfur and accelerator system) or 120 degrees (DCP vulcanization system) to prevent scorching of the rubber. And should be adjusted according to different curing systems. Non-dispersible complexing agents or complexing agents with small amounts can usually be prepared into various masterbatch particles or ointment-like mixtures for easy addition and rapid mixing into the gum.
The one-stage mixing method must strictly follow the requirements of the process conditions such as the order of adding the compounding agent, the mixing temperature, and the mixing time. At the same time, the pressure of the upper plug and the position of the upper plug in the mixing process must be paid attention to. Compared with the two-stage or multi-stage mixing method, the tabletting, cooling and parking time between each stage is saved, the production efficiency is improved, and the manufacturing cost of the compounded rubber is reduced. However, the premise is that the performance of the mixer (mainly cooling capacity, speed regulation capacity and temperature control capacity) is high, and sufficient mixing time is required to achieve the required degree of dispersion.
The disadvantages of the one-stage mixing method are: the prepared rubber compound has low plasticity (high Mooney viscosity), carbon black and other compounding agents are sometimes difficult to disperse uniformly, and it is easy to cause scorch danger. The physical and mechanical properties of the vulcanizate are relatively low.
The one-stage mixing method is only suitable for general purpose (relatively slow vulcanization speed) compound rubber preparation. It should be used cautiously for large mixers, and it must also be used cautiously for the preparation of high-fill, high-viscosity or high-hardness compound rubbers. . As an improvement, the rubber compound discharged from the internal mixer can be sufficiently cooled on the lower tablet opener before adding a vulcanizing agent and an accelerator.