The order of addition of the compounding agent during NBR mixing is one of the most important factors affecting the mixing operation and the quality of the mixing. Improper feeding sequence may cause the rubber material to be unrolled, unable to operate smoothly, prolong the mixing time, prone to scorch and over-refining, and reduce the quality of the rubber compound.

The NBR feeding sequence is an accumulation and summary of long-term production practice. The general principle is that the compounding agent with less dosage and large effect, such as accelerator, active agent, anti-aging agent and anti-scorching agent, should be added first because the mixing uniformity is high, firstly, it is beneficial to mix evenly, anti-aging agent Early addition can also inhibit the aging of the rubber compound during mixing; the compounding agent which is difficult to disperse in the rubber compound, such as ZnO and solid softener, should also be added early; the critical temperature is low, the chemical activity is large, and the temperature sensitivity is large. Mixing agents such as sulfur and speeding accelerators should be added in the late stage of mixing; vulcanizing agents and accelerators must be added separately. If the accelerator is added to the accelerator, the vulcanizing agent is added at the end, or vice versa. The general feeding order of natural rubber formula opener mixing is: raw rubber, plastic rubber, masterbatch, reclaimed rubber → solid softener (such as coumarone resin, rosin, solid paraffin, etc.) → accelerator, active agent , anti-aging agent and anti-cavity agent → filler (carbon black, clay, calcium carbonate, etc.) → liquid oil (paraffin oil, naphthenic oil and aromatic oil, etc.) → sulfur.

When the amount of liquid softener is small, it can also be added before the filler. Synthetic rubber formula fillers and oils are used in a high proportion, and the oil can only be added after the filler or alternately batched with the filler.

Some special Buna-N formulations can be adjusted for the order of addition. For example, the hard rubber formula has the most sulfur content, and should be added before other compounding agents to ensure uniform mixing; when the sponge rubber compound is mixed, the oil should be added after adding sulfur, otherwise the compounding agent is difficult to disperse evenly.