Since white carbon black has transparency, high reinforcing property, and good adhesion, it is widely used in the manufacture of rubber products such as transparent, translucent, light-colored, and colored. Especially in the footwear industry is an indispensable reinforcing material. However, since the white carbon black has the characteristics of adsorption and decomposition accelerators, it has a great trouble for the vulcanization stability in the rubber compounding process. Moreover, silica has different adsorption strengths for different operating temperatures and different accelerator types. Under certain operating time and temperature, the active agent zinc oxide and stearic acid will also have a certain interference reaction. Therefore, if the mixing process is not properly controlled, the vulcanization rate and physical properties of the silica composite will not be stabilized, and the stability of the product quality cannot be guaranteed. The mixing process is the most important process in the preparation of the silica composite. Process.
1. Open mill process
Advantages: low temperature and constant temperature during operation, it is easier to obtain an extremely stable vulcanization system.
Disadvantages: mixing white carbon black with open mill is the most easy to fly, serious environmental pollution, long mixing time, high energy consumption, poor dispersibility of compounding agent in rubber compound, especially high melting point resin, compounding agent, pigment, etc. Sex is worse.
The open mill operation usually has the following feeding sequence: (1) zinc oxide, stearic acid (2) accelerator (3) pigment, other small materials (4) white carbon black, active agent, coupling agent, and finally sulfur.
Although the silica has an adsorption effect on the accelerator, stearic acid, anti-aging agent, etc. during the kneading operation, the premature addition of zinc oxide may interfere with the modification of the polyphenol and the coupling agent to the white carbon black, but these reactions Mainly depends on temperature and time. Practice has proved that the white carbon black compound will decompose the accelerator during the mixing, the determining factor is mainly the temperature, and the action time at the lower temperature is a longer process. When ensuring that the opening temperature is low and the roll temperature is below 70 degrees, not only zinc oxide can be added in the initial stage of mixing, but also all the accelerators can be added, including TMTD as a secondary accelerator, which is generally not added with sulfur. It is very long when parked, and the effect on the vulcanization rate of the rubber is not very large. In order to ensure sufficient dispersion of the compounding agent in the rubber. The compound must be parked for the corresponding time.
Since the opener is the most easy to remove the roll when mixing the white carbon black compound, it is difficult to disperse the various compounding agents in general. In order to ensure the good physical properties of the rubber compound, the rubber must be parked after mastication and kneading, so that the rubber stress after the mastication is further eliminated, and the compounding agent after the kneading is further migrated and diffused. Therefore, the opening and refining process is still widely used in small and medium-sized enterprises.

2. Internal mixer process
In the shoe industry, the silica carbon compound mixing process has a relatively high operating temperature. The biggest problem is that at higher mixing temperatures, the temperature changes cause the adsorption and decomposition activities of the white carbon black to the accelerator. , thereby affecting the vulcanization rate. From the viewpoint of the sulfidation reaction mechanism, the first step of the sulfidation reaction is that zinc oxide reacts with stearic acid to form active stearic acid and then acts as a promoter (for example, decomposing into ZDC with thiura, and thiazole or sulfenamide). The class action decomposes MZ), which can decompose the accelerator.
Usually, the first step of the vulcanization reaction is carried out above the critical activation temperature of the accelerator, but since the white carbon black compound has a higher mixing temperature, it can promote the action of zinc oxide and stearic acid, and increase the zinc oxide. The solubility in the rubber, and activation, reduces the critical activation temperature of the accelerator. Relatively speaking, the lower the critical activation temperature, the easier it is to decompose at higher mixing temperatures. In the general mixing process, the super-speed accelerator and sulfur are finally added together or added to the open mill, mainly because the pre-disintegration of the accelerator during the kneading and the early vulcanization of the rubber are prevented. Since white carbon black has the characteristics of catalyzing the interaction between zinc oxide, stearic acid and accelerator, it must be adjusted according to different mixing temperature, formulation process and equipment condition. The general feeding procedure is: (1) rubber (2) white carbon black, oil, active agent, coupling agent (3) zinc oxide, stearic acid, other compounding agent (4) accelerator, sulfur.
Usually, whether it is a high-speed internal mixer or a low-speed internal mixer, it is rare to add an overspeed accelerator and sulfur during mixing. The low-speed mixing is due to the long mixing time, the large temperature variation, or the incomplete cooling device of the equipment. Generally, the sulfur and super-speed accelerator are added on the open mill, and the sulfur is added to the mixer, and the accelerator is added to the mill. of.

3. Mixing method
Zinc oxide is the most dispersible compounding agent in inorganic fillers. It produces the same-sex charge that is mutually exclusive with rubber during mixing and friction, especially when the particle size is small and the moisture content is high. In the formulation with light calcium, clay and low-structure carbon black, due to the small interaction between the fillers, the poor dispersion phenomenon will be more prominent. However, in the high-structure white carbon black compound formulation, this phenomenon is greatly improved due to the large interaction between the white carbon blacks, so zinc oxide is generally added in the middle and late stages of the kneading. Zinc oxide is susceptible to interference if it is added prematurely before the reaction of silica with a surfactant or silane coupling agent. Therefore, many processes use the inverse mixing method for mixing. The general feeding procedure is: (1) rubber (2) white carbon black, softener, active agent, silane (3) other filler, anti-aging agent, accelerator, zinc oxide. , stearic acid, other additives (4) speeding accelerator, sulfur.

4. Discharge temperature
The setting of the debinding temperature is an extremely important part of the mixing process. The debinding temperature is mainly determined by the optimal mixing temperature, but the effect of temperature on the vulcanization system and the dispersibility of various compounding agents should also be considered. The general debinding temperature is controlled between 100-110 degrees. Sometimes there is no high-melting point compounding agent or feeding bag in the formula, and if the amount of white carbon black is small and the formula hardness is low, it can be discharged below 90 degrees. Glue to ensure better vulcanization stability. When designing a compounding system with a high debinding temperature, it is best to use less accelerators such as accelerators TMTD, M and other critical activation temperatures. Generally, the active agents and accelerators are added at the late stage of mixing, or they can be mixed. Adding sulfur to the process of adding a promoter when the film is opened. Be sure to have a good rubber cooling system after draining.