Mixing of rubber is to disperse various compounds evenly in rubber with the help of mechanical force of rubber making machine, so as to form a multi-phase colloidal dispersion system with rubber as medium or a mixture of rubber and some compatible components (matching agent, other polymers) as medium, and incompatible matching agents (such as powder fillers, zinc oxide, pigments, etc.) as dispersed phase. process. The specific technical requirements of the compounding process are: uniform dispersal of the compounding agent, so that the best dispersion of the compounding agent, especially the reinforcing compounding agent such as carbon black, is achieved to ensure consistent performance of the rubber. The resulting rubber is called "compounding rubber" and its quality has an important influence on further processing and product quality.

1 - Compounding of neoprene

        Neoprene are emulsion polymerization method of production, the production process is mostly single kettle intermittent polymerization. Polymerization temperature is mostly controlled at 40-60 ℃, and the conversion rate is about 90%. Polymerization temperature, the final conversion rate is too high or polymerization process into the air will lead to a decline in product quality. The relative molecular mass is regulated by the sulfur-kiuram (tetraalkylmethylaminothiocarbonyldisulfide) system in production. The main disadvantage of the sulfur-kiuram system is the lack of stability of the sulfur bonds, which is one of the important reasons for the storage properties. If the relative molecular mass is adjusted with thiol can improve this performance. Neoprene is different from the general synthetic rubber, it does not use sulfur vulcanization, but with zinc oxide, magnesium oxide, etc. vulcanization.

The processing performance of neoprene depends on the viscoelastic behavior of unvulcanized rubber, and its viscoelastic behavior is related to the variety of neoprene and temperature. As the mixing is generally carried out in the elastic state to make use of the shear force of the elastic state of the rubber to make the filler well dispersed. Therefore, to avoid the influence of high temperature when mixing neoprene, the filler should be added as early as possible in order to achieve a certain degree of mixing in the elastic state. When mixing with open refiner, G-type neoprene is sensitive to temperature changes, and the roll temperature exceeds 70 ℃, it will be seriously sticky rolls, and is in a viscous flow state, and the filler is not easy to disperse. When mixing with a dense refiner, its capacity should be appropriately reduced, the general filling factor of 0.6 is appropriate, generally divided into two mixing, in order to minimize the mixing temperature. The discharge temperature should be lower than 100 ℃.

Neoprene in the use of open machine mixing disadvantage is the heat is large, easier to stick to the rollers, easy to scorch, with the agent dispersion is slow, so the mixing temperature should not be too high, the capacity should be small, the roller speed ratio should not be large. Due to the strong sensitivity to temperature, general-purpose neoprene at room temperature to 71 ℃, it will show the grain state, at this time the cohesion of raw rubber is weakened, not only serious sticky rollers, with the agent dispersion will also be very difficult. The elastic state temperature of non-sulfur-regulated neoprene is below 79 ℃, so the mixing process performance is better than sulfur-regulated, and the tendency of sticky rollers and scorching is smaller. Kneading with an open machine, in order to avoid sticky rollers, the roll temperature is generally controlled at 40 ~ 50 ℃ or less (the front roll is 5 ~ 10 ℃ lower than the rear roll temperature), and in the raw rubber kneading, the roll distance should be gradually adjusted from large to small. When mixing, first add acid absorbent magnesium oxide to prevent scorching, and finally add zinc oxide. In order to reduce the mixing heat, carbon black and liquid softeners can be added in batches alternately. Stearic acid and paraffin wax and other operating aids can be dispersed gradually added, so as to help dispersion, but also to prevent sticky rollers. Sulfur-regulated chloroprene rubber in the opener mixing time is generally 30% to 50% longer than natural rubber, non-sulfur-regulated mixing time can be about 20% shorter than sulfur-regulated. In order to avoid neoprene in the mixing machine in the opening of the temperature rise too fast, the speed ratio is less than 1:1.2 below, the cooling effect will be better. Reducing the refining capacity is also a way to ensure operational safety and good dispersion. At present, the domestic sulfur-regulated neoprene rubber refining capacity than natural rubber should be less than 20% to 30%, in order to operate normally. As neoprene is easy to scorch, so in the use of dense refining machine mixing is usually used in two mixing method. The mixing temperature should be lower (discharge temperature is generally controlled below 100 ℃), the loading capacity is lower than that of natural rubber (capacity factor is generally taken as 0.50 ~ 0.55), and zinc oxide is added to the press in the second mixing section. For the problem that chloroprene rubber mixing is easy to scorch and difficult to disperse, Leena refiner adopts the most advanced four-ring double rotor running in the same direction, combined with the "X" curve movement of the top bolt on the refiner, with good dispersion effect and short time, which can effectively reduce the scorching phenomenon of chloroprene rubber in the mixing process.

2 - Compounding of ethylene propylene rubber

       Ethylene propylene rubber can also be processed by ordinary rubber refining equipment, but because the plasticizing effect of ethylene propylene rubber is particularly poor, the lack of viscosity, rubber is not easy to wrap the roll, generally first use a narrow roll pitch, to form a continuous sheet and then widen the roll pitch for mixing processing. Roll temperature for the front roll 50 ~ 60 ℃, after the roll 60 ~ 70 ℃ is appropriate. EPDM rubber feeding order is generally: raw rubber cover roll-1/2 carbon black-1/2 carbon black-stearic acid-zinc oxide (or magnesium oxide)-promoter-crosslinker -Thin pass, lower sheet. Ethylene propylene rubber is not easily over-refined when mixing, and the compound is evenly dispersed, but the self-adhesive property is poor. Ethylene-propylene rubber mixing with an open refiner, generally first use a small roll moment to make it continuous after the roll, and then gradually relax the roll moment, add the compound, the roll temperature between 60 ~ 70 ℃. The mixing temperature is 150～160 ℃, which can help the dispersion of filler and softener and the improvement of mechanical properties. The loading capacity can be 10%~15% higher than other rubber materials.

3- Compounding of fluoroelastomer

      Fluorine rubber Menny viscosity is high, rigid, frictional heat generation, general mixing and processing is more difficult. When mixing fluorine rubber on the refining machine, to small roll distance, less capacity, roll temperature control at 50 ~ 60 ℃. Mixing begins, first make the rollers cool, add raw rubber thin pass about 10 times to form a uniform package roll rubber, adjust the roll moment to maintain a small amount of stacked rubber, and then add the compounding agent, mixing time is usually not strictly defined, but require as fast as possible. Fluorine rubber is more difficult to use the mixing machine mixing, but the meshing type of mixing machine cooling system is stronger, you can mix fluorine rubber. The compounded rubber should be parked for 24 hours before use, and must be refined before use to make the compound dispersed evenly and improve the fluidity and self-adhesiveness of the rubber.