When using reclaimed rubber to produce rubber products, mixing in the internal mixer is conducive to the uniform mixing of the reclaimed rubber and the compounding agent, which can effectively avoid the problems of uneven mixing, local scorching and blistering that may occur when using the open mixer. However, when the reclaimed rubber is mixed in the internal mixer, it is easy to scorch due to the difficulty in controlling the mixing temperature; This problem can be avoided with proper handling and recipe adjustments. In actual production, there are five main factors that affect the mixing effect of reclaimed rubber in the internal mixer.
1. Glue loading capacity
Glue loading capacity is an important factor affecting the mixing effect. When the reclaimed rubber is mixed in the internal mixer, the large or too small glue loading capacity will lead to uneven mixing of the rubber and affect the physical and mechanical properties of the reclaimed rubber vulcanized rubber; The mixing capacity is usually controlled at 60% to 70% of the total effective volume of the mixing chamber. The reasonable filling capacity or filling coefficient needs to be determined according to the type of reclaimed rubber, the characteristics of the rubber formula, the characteristics of the equipment and the degree of wear, and the pressure of the upper jacking bolt.
2. Upper top bolt pressure
When the reclaimed rubber is mixed in the internal mixer, the pressure of the upper jacking bolt is very important to the shear effect of the rubber compound. Appropriately increasing the pressure of the upper jacking bolt can reduce the internal void of the rubber compound, increase the friction and shear force, improve the mixing effect, and shorten the mixing time. The pressure of the top bolt on the mixer is generally controlled at 0.3-0.6MPa. It should be noted that excessive pressure on the top bolt of the internal mixer will cause the mixing temperature to rise sharply, which is not conducive to the dispersion of the compounding agent; Insufficient pressure is easy to form a dead angle at the charging port, which affects the mixing quality.
3. Rotor speed and mixing time
The increase of rotor speed can significantly increase the shear speed of the rubber compound, shorten the mixing time, and improve the production capacity. Although prolonging the mixing time can improve the dispersion of the compounding agent, too long a time will reduce the production efficiency and damage the physical and mechanical properties of the vulcanized rubber. At present, the speed of the internal mixer has been increased from 20r/min to more than 80r/min, and the mixing cycle has been shortened to 1 to 1.5 minutes.
4. Mixing temperature
The mixing temperature of the internal mixer directly affects the plastic flow and deformation of the reclaimed rubber compound and the mixing of the compounding agent. The appropriate mixing temperature is conducive to the dispersion of fillers and the processing of rubber compounds. If the mixing temperature of the internal mixer is too high, the rubber may become soft, weaken the mechanical shear effect, and accelerate the thermal-oxygen cracking E4LYY429 of the rubber, thereby reducing the physical and mechanical properties of the reclaimed rubber vulcanized rubber. If the mixing temperature is too low, it is easy to cause the problem of rubber dispersion, and it cannot be kneaded. Therefore, when the reclaimed rubber is mixed in the internal mixer, the temperature should be strictly controlled during the mixing process to avoid scorching.
5. Rubber feeding sequence
Reasonable rubber feeding sequence has a significant impact on the mixing efficiency and quality of reclaimed rubber. When the reclaimed rubber is mixed by internal mixer, the general feeding sequence is: reclaimed rubber → active agent, solid softener, antioxidant, ordinary accelerator→ carbon black→ liquid softener→ sulfur and overspeed accelerator; It helps to reduce mixing time, improve mixing efficiency, and ensure uniform dispersion of compounding agents.
The internal mixer has a large capacity and is suitable for large-scale production; The mixing process is carried out under fast, high temperature and high pressure conditions, which can shorten the mixing time and improve production efficiency. When mixing reclaimed rubber in the internal mixer, reasonable control of the rubber loading capacity, upper top bolt pressure, rotor speed, mixing temperature and rubber feeding sequence can significantly improve the mixing efficiency and product quality.
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