Views: 0 Author: Site Editor Publish Time: 2023-08-13 Origin: Site
After chloroprene rubber is wrapped around the rolls, the state of the rubber material, like natural rubber, changes with temperature . Chloroprene rubber phase changes at different temperatures.... By the temperature-induced changes in the rubber between the three states is reversible, in the plastic state of the rubber, if the temperature is reduced, can make it return to the elastic state. Using the shear force of the elastic state, the filler can be well dispersed. When the processing temperature of chloroprene rubber is higher than 90 ℃, part of the chloroprene rubber is transformed into the plastic state, constituting the coexistence of the elastic state and the plastic state, i.e., the granular state. As the elastic state temperature of chloroprene rubber is lower than that of natural rubber, so its mixing operation temperature should be lower than that of natural rubber. In the actual operation of the factory, the mixing temperature of the rubber is generally very high, so it should be as early as possible to join the filler, so that the filler in the elastic state to achieve a certain degree of mixing, in order to improve the hardness of the rubber mixing, increase the shear force, so that it is in the plastic state of the mixing, but also can be well dispersed.
( I ) open-machine mixing
chloroprene rubber mixing heat than natural rubber, so the batch of chloroprene rubber mixing to be slightly smaller.
Until the addition of hard filler, should be cooled roller, to ensure that the elastic state can be added. But magnesium oxide in too cold roller will be agglomerated, easy to cause poor dispersion, so the roller temperature of 50 ℃ is appropriate. Reinforcing filler can only be added in small quantities one by one, and softener can be added at the same time with soft filler. Adhesion is too big rubber, add a small amount of stearate, the effect is better.
Stopping cutting and rolling before the filler has reached full mixing is the cause of poor dispersion. High mixing temperatures can lead to sticky rolls, uneven dispersion of the powder and even scorching.
( II ) Banbury mixer mixing
Chloroprene rubber due to mixing heat, so its capacity should be slightly reduced. The loading factor is generally set at 60%.
(1)Mixer mixing time is generally between 5 to 15 minutes. In order to make good dispersion. Mixing time needs to be a little longer, in the actual production and processing, chloroprene rubber mixer mixing, can be divided into the following two methods. (1) mixing of high-quality rubber, due to the high rubber content, but also requires good dispersion, so the mixing should be the same as with the opening machine mixing, filler to be added gradually.
(2) mixing of low-quality rubber, or the rotor of the refiner and the chamber wall of the gap is large, you can put a lot of filler at the same time.
Banbury mixer mixing points have two points:
One is to knead the mixed rubber material into a ball;
The second is the effective use of shear, so that it is well dispersed.
If the performance of the banbury mixer is good, can be well kneaded rubber, you can only consider the problem of good dispersion. If the rotor of the refiner and the chamber wall of the gap is large, or mixing low rubber content formula, then knead the rubber is the first place, well-dispersed is the second place. At this time, the loading factor should be increased to 65 ~ 70%, while the filler can be added to take the method similar to the "reverse mixing" method. That is, after the addition of chloroprene rubber, magnesium oxide, antioxidant, half of all filler at the same time. If the rubber is loose and can not be pinched into a ball, you can also add half of the oil and so on. In short, we must try to make the rubber pinched into a ball.
It should be noted that magnesium oxide, when added alone, tends to agglomerate and stick if the rotor is cold. If softener and filler are added at the same time, it is also easy to agglomerate. Add oil after dispersing the filler, or add filler after dispersing the oil, the dispersing effect is good. In addition, when using carbon black with large oil absorption value, it is better to let the carbon black absorb oil first before adding it to the rubber. In the case of good kneading of the rubber into a group, the softener is added last, then the dispersion is good, and can reduce the temperature of the rubber. When mixing with the banbury mixer, in order to prevent the production of carbon black gel or scorching, should try to use low-temperature mixing. But the exception is clay, calcium carbonate and other inorganic fillers, due to its moisture content is more, resulting in poor dispersion, if the rubber temperature is increased to about 100 ℃ for mixing, to reduce the water, the dispersion is good. Add zinc oxide, accelerator in the refiner, the discharge temperature control in 105 a 110 ℃, not in the refiner when added, the discharge temperature should be lower than 125 ℃. Zinc oxide and accelerator is best added in the form of mother refining rubber. Recently, due to the rotor speed of the smelter has been accelerated, chloroprene rubber is easy to burn, generally tend to take in the smelting in a short period of time mixing, fast discharge, in the opening of the smelter to add zinc oxide, and then with the press and so on into the two-stage mixing The two-stage mixing method of additional processing.