The characteristics of internal mixer mixing

 

Put the plasticized rubber and various compounding agents into the high-temperature and high-pressure internal mixing chamber. After a short time of kneading, dispersion, and mixing, the mixed rubber required by the process can be obtained.

 

The mixing process is: lifting the top bolt → feeding → dropping the top bolt → pressure mixing → end of mixing → pulling the lower top bolt → turning over → discharging → turning back → closing the bottom top bolt.

 

The advantages of internal mixer mixing are:

 

①The mixing time is short, the production efficiency is high, and the quality of the mixed rubber is good;

 

②Large rubber filling capacity, high degree of automation for mixing and other operations, low labor intensity, and safe operation;

 

③Flying loss of compounding agent is small, pollution is small, and the workplace is hygienic.

 

The disadvantages of internal mixer mixing are:

 

①The internal mixer dissipates heat slowly, the mixing temperature is difficult to accurately control, and the temperature-sensitive rubber is prone to scorch when mixing, and the cooling water consumption is large;

 

②The shape of the compound is irregular and blocky, and supplementary processing such as tableting must be carried out;

 

③The internal mixer mixing is not suitable for the mixing of light-colored rubbers, special rubbers, rubbers with frequent varieties and temperature-sensitive rubbers.

 

Process method of internal mixer mixing

 

The process methods of internal mixer mixing include one-stage mixing method, two-stage mixing method, priming method and reverse mixing method.

 

(1) The working stage of internal mixer mixing. Internal mixer mixing is divided into three stages: wetting, dispersing and kneading.

 

(2) BIT value During the mixing process of the internal mixer, the two stages of wetting and dispersing play a leading role in the mixing. In production, to judge the mixing performance of the rubber compound, it is often measured by the time required for the compounding agent to be uniformly dispersed by the rubber compound. Generally, the second power peak on the mixing time-power diagram is used as the end time of dispersion. , Is called the BIT value of the carbon black mixing time. The smaller the BIT value, the better the mixing performance of the rubber compound, that is, the easier it is to mix.

 

(3) Cooling and parking

 

a. Cooling is to avoid scorching and mutual bonding caused by the high temperature of the rubber compound. Generally, it is forced to cool to below 35°C.

 

b. Parking can relax the stress of rubber molecules and reduce shrinkage. The compounding agent can also be dispersed continuously, and the carbon black can be further combined with the rubber to improve the physical-mechanical properties of the rubber compound.

 

Quick inspection of internal mixer

 

Controlling and ensuring the quality of the rubber compound is one of the key links in the production of rubber products. Quick inspection is to conduct a quick quality inspection on the rubber compound. The quick inspection method is to take a sample at each of the three parts of the front, middle, and back of each car after the compound is mixed to determine its plasticity, vulcanization characteristics, hardness, tensile strength, tensile strength, and tensile strength. Elongation at break, permanent deformation at break, density, etc., and compare the measured results with the specified standard values ​​to determine whether the quality meets the requirements.

 

Refer to the corresponding national standards for the inspection methods of related items.