The main reasons for the "self-sulfur" during the placement of the compound are:
(1) Too many vulcanizing agents and accelerators are used;
(2) The glue loading capacity is large, the temperature of the rubber mixer is too high, and the film cooling is not enough;
(3) or prematurely adding sulfur, the uneven dispersion of the medicine causes the local concentration of accelerator and sulfur;
(4) Improper parking, that is, the temperature of the parking place is too high, and the air is not ventilated.

How to reduce the Mooney of rubber compound?

The Mooney of the rubber compound is M (1+4), that is, the torque of the rotor is preheated at 100 degrees for 1 minute and the rotor is rotated for 4 minutes, that is, the force that hinders the rotation of the rotor. Any force that can reduce the rotation of the rotor can reduce the Mooney. The raw materials of the formula include raw rubber: natural rubber and synthetic rubber. Choose natural rubber with low Mooney or add chemical peptizers to the natural rubber formula (physical plasticizers are not effective) It is a good choice. Synthetic rubber generally does not add peptizers. Usually, some lower molecular weight lipids such as dispersants or internal release agents can be added. If the hardness requirements are not strict, stearic acid or oil can also be added. If it is in the process, you can increase the top bolt pressure or appropriately increase the rubber discharge temperature. If the conditions allow, the cooling water temperature can also be reduced. The rubber compound Mooney can also be reduced.

Factors affecting the mixing effect of the internal mixer:

Compared with open-mixer mixing, internal mixer mixing has the advantages of short mixing time, high efficiency, high degree of mechanization and automation, good rubber quality, low labor intensity, safe operation, small flying loss of drugs, and good environmental sanitation conditions. However, it is difficult to dissipate heat in the mixing chamber of the internal mixer, and the mixing temperature is high and difficult to control, which limits the temperature-sensitive rubber compound and is not suitable for the mixing of light-colored compounds and compounds with frequent variety changes. In addition, the mixer needs to be equipped with a corresponding unloading device.

(1) Glue quantity
A reasonable amount of glue should be able to ensure that the rubber material is subjected to maximum friction and shearing in the mixing chamber, so that the compounding agent is evenly dispersed. The amount of glue loaded depends on the characteristics of the equipment and the characteristics of the rubber material. Generally, it is calculated according to the total volume of the mixing chamber and the filling factor, and the filling factor is 0. 55 to 0. 75. If the equipment has been used for a long time, due to the wear and tear of the mixing chamber, the filling factor can take a large value, and the amount of glue can be increased. If the pressure of the top bolt is large, or the plasticity of the rubber material is large, the amount of glue can also be increased accordingly.

(2) Top bolt pressure
Increasing the pressure of the top bolt can not only increase the glue loading capacity, but also make the rubber compound and the equipment and the parts inside the compound contact and squeeze each other faster and more effectively, and accelerate the mixing process of the compounding agent into the rubber, thereby It can shorten the mixing time, improve the production efficiency, reduce the sliding of the material on the contact surface of the equipment, increase the shear stress on the compound, improve the dispersion of the compounding agent, and improve the quality of the compound. Therefore, at present, measures to increase the diameter of the top bolt air duct or increase the air pressure are taken to improve the mixing efficiency of the internal mixer and the quality of the mixed rubber.

(3) Rotor speed and rotor structure shape
During the mixing process, the shear rate of the compound is proportional to the rotor speed. Increasing the shear speed of the rubber compound can shorten the mixing time and is the main measure to improve the efficiency of the mixer. At present, the speed of the internal mixer has been increased from 20 r/min to 40 r/min, 60 r/min, and the highest is 80 r/min, so that the dark mixing cycle has been shortened from 12 to 15 min to the shortest 1 to 1. 5 min. In recent years, in order to meet the requirements of the mixing process, multi-speed or variable-speed internal mixers have been used for mixing, and the speed can be changed at any time according to the characteristics of the rubber material and process requirements to achieve the best mixing effect. The structural shape of the mixer rotor has a significant impact on the mixing process. The oval rotor of the internal mixer has increased from two to four, which can play a more effective shearing and stirring effect. It can improve production efficiency by 25-30% and reduce energy consumption. In recent years, in addition to elliptical, there are also triangular, cylindrical and other rotor-shaped mixers used in production.

(4) Mixing temperature
During the mixing process of the internal mixer, the heat generation is large and the heat dissipation is difficult. Therefore, the rubber compound heats up quickly and the temperature is high. Generally, the mixing temperature is 100~130'C in the swamp, and 170~190'C high temperature i-kun mixing is also used. This process has been used in the mixing of synthetic rubber, and the discharge temperature during slow mixing is generally controlled. At 125 ~ 135 'C, the degumming temperature reaches 160 ℃ during fast mixing. C or higher. I Kunming, the temperature is too high will reduce the mechanical shearing effect on the rubber, make the mixing uneven, and will aggravate the thermal oxidation cracking of the rubber molecules, reduce the physical and mechanical properties of the rubber, and at the same time, will also promote the rubber and the rubber. There is too much chemical combination between carbon blacks to generate too much gel, which reduces the plasticity of the rubber compound, and the surface of the rubber compound is rough, making it difficult to calender and extrude.

(5) Dosing sequence
Plasticizing rubber and masterbatch should be added first to make it form a whole, and then other compounding agents should be added in sequence. Solid softeners and small medicines are added before fillers such as carbon black are added to ensure sufficient mixing time. The liquid softener must be added after the carbon black is added to avoid agglomeration of the carbon black and cause dispersion difficulties; the super-accelerator and sulfur are added after the cooling of the unloader, or in the internal mixer during the second-stage mixing, but its The debinding temperature should be controlled below 100'C.

(6) Mixing time
The mixing time depends on various factors such as the performance characteristics of the internal mixer, the amount of glue loaded and the formula of the compound. Mixing: As time increases, the dispersion of the compounding agent can be improved, but if the time is too long, it is easy to cause over-refining, and it will also affect the vulcanization characteristics of the rubber compound. At present, the mixing time of XM-2 50/20 type internal mixer is 10-12min.