The natural rubber has good elasticity and high mechanical strength. The plasticity increases greatly during mechanical kneading during the mixing process. The calorific value during the mixing process is small, and the compounding agent is easily dispersed evenly in the rubber compound, but the natural rubber mixing time is too long. If the mixing temperature is too high or the mixing sequence during mixing (the effect of the feeding sequence on the quality of the natural rubber compounding rubber is smaller than that of the synthetic rubber) is unreasonable and the process is improper, which will seriously affect the quality of the natural rubber compounding rubber, then the natural rubber. What issues should you pay attention to when mixing?
1. Pay attention to the mixing temperature.
Different rubber products enterprises have different rubber mixing equipment. Under normal circumstances, the roller temperature should be controlled between 50-60 °C when the natural rubber is mixed with the open mill. The front roller temperature is slightly higher than the rear roller temperature, and the difference is about 5 °C; When mixing with an internal mixer, a mixing method is used, and the discharge temperature is controlled below 150 °C.
2, pay attention to mixing time.
Natural rubber itself has good mixing performance, good roll-to-roll property, good plasticity, compatibility and infiltration of compounding agent, fast powder feeding, but natural rubber is very sensitive to mixing time: too short mixing time will make natural rubber Granular irregularities appear on the surface of the rubber compound, which makes the subsequent calendering process difficult; the mixing time will be too long, which will not only reduce the strength of the natural rubber vulcanizate, but also produce a cross-linking gel of some rubber compounds. The quality of rubber mixing is significantly reduced. Therefore, rubber product manufacturers must reasonably determine the mixing time according to the shape and thickness of natural rubber products.
3. Pay attention to the mixing sequence.
Natural rubber is often used in combination with other types of rubber in practical applications, such as reclaimed rubber, silicone rubber, styrene butadiene rubber, butadiene rubber, etc.; if natural rubber and reclaimed rubber are used together, if natural rubber is the main raw material, it can be After the refining plastics are finished, the natural rubber is thinned 3-5 times and then added to the plasticized reclaimed rubber for mixing. The natural rubber can be plasticized and then mixed with the reclaimed rubber. The high proportion is mixed with natural rubber. When the refinery is used in a small amount or without oil, it is necessary to pre-plasticize the natural rubber, and add appropriate amount of peptizer during mastication to increase the plasticizing speed of natural rubber and shorten the mixing time; if natural rubber is used together with silicone rubber Need to first add natural rubber plastic.
4. Pay attention to the timing of adding the compounding agent.
1 Carbon black is the most commonly used reinforcing agent in natural rubber products. For rubber materials with large carbon black filling and fast heating during mixing, multi-stage mixing is used as much as possible to prevent the rubber material from heating up too quickly during the mixing process. Too high, it can also ensure that the carbon black is fully dispersed, reducing the Mooney viscosity of the rubber; when filling the soft carbon black, the oil should be added in advance, and the mixing time should be extended appropriately to avoid the oil addition too late and affect the natural rubber mixing effect.
2 The low melting point and softening point of the compounding agent should be added when adding oil or lifting ruthenium. For example, the early addition of stearic acid will hinder the mixing of carbon black and natural rubber, and the simultaneous addition with carbon black can prolong the maximum mixing power. Time; the premature addition of anti-aging agents will affect the natural rubber plasticizing effect.
In addition, when using rubber to produce rubber products, it is necessary to clean the pressure at regular intervals during the end of the mixing to avoid the glue that sticks to the pressure due to the viscosity and affect the quality of the rubber; When natural rubber is used instead of natural rubber to produce rubber products, it is necessary to carry out a filter process and the like before mixing. The continuous development of synthetic rubber and reclaimed rubber still cannot replace the important position of natural rubber in the rubber products industry. At present, a large part of rubber products are still based on natural rubber, or a certain proportion of synthetic rubber or recycled in rubber compounding. Glue; therefore, more natural rubber mixing techniques are waiting for you to discover, explore and summarize.