Working principle of internal mixer

##Introduction to Internal Mixer

An internal mixer is a mechanical device equipped with a pair of specific shaped and relatively rotating rotors that intermittently plastic and mix polymer materials in a closed state with adjustable temperature and pressure. Mainly used for kneading, dispersing, mixing, and plasticizing various rubber, plastic raw materials, engineering modified materials, metal powder, ceramic powder, and other raw materials.

##The purpose of the mixer

Mainly used for the molding and mixing of rubber, but also for the mixing of raw materials for rubber and plastic products such as EVA, PVC, TPR, PE, PP, PC, metal powder, ceramic powder, functional masterbatch, rubber additives, shoe materials, rubber tires, sealing miscellaneous parts, electronic products, wires and cables, automotive products, etc.

##Principle of Internal Mixer

During the rubber mixing process of the internal mixer, after raw rubber or other materials are added from the feeding hopper, they first fall into the upper part of two relatively rotating rotors, and are brought into the gap between the two rotors under the pressure of the top bolt and the friction force, which is subjected to kneading. The rubber material is divided into two parts by the protruding edges of the lower top bolt, and as the rotor rotates, it passes through the gap between the surface of the rotor and the front wall of the mixing chamber. After being subjected to strong mechanical shear and kneading, it reaches the upper part of the mixing chamber. Under the influence of different speeds of the rotor, two strands of rubber converge at different speeds on the upper part of the two rotors and enter the gap between the two rotors repeatedly. Throughout the entire operation of the internal mixer, raw rubber is subjected to both strong mechanical stress and thermal oxidative cracking during molding, thus achieving the required plasticity in a short period of time.

##Structure and function of internal mixer

An internal mixer generally consists of an internal mixing chamber, two relatively rotating rotors, an upper top bolt, a lower top bolt, a temperature measurement system, a heating and cooling system, an exhaust system, a safety device, a discharge device, and a recording device.

-Mixing part: The mixing part mainly consists of rotors, mixing chambers, sealing devices, etc.

-Feeding section: It mainly consists of a feeding chamber, a bucket shaped feeding port, and a flap door (feeding door) 11, which is mainly used for feeding and instant storage.

-Material pressing part: It mainly consists of an upper top bolt 9 and a cylinder 14 that drives the upper top bolt to move up and down reciprocally. Its main function is to provide a certain pressure to the rubber material, accelerate the rubber mixing process, and improve the rubber mixing effect.

-Discharging device part: mainly composed of the lower top bolt 3 and the lower top bolt locking mechanism 2 installed below the mixing chamber. Its main function is to discharge the rubber material after the mixing is completed, which is unloading. The lower top bolt can be cooled by cooling water, and the surface of the lower top bolt in contact with the material should be welded with wear-resistant alloy to increase its wear resistance.

-Transmission device part: mainly composed of motor 22, elastic coupling 21, reducer 20, and toothed coupling 19, installed on the transmission base, its function is to transmit power, make the rotor overcome working resistance and rotate, thus completing the rubber mixing operation.

-Base: Mainly composed of a base, some are divided into a host base and a transmission base. Its function is to provide for the use of the internal mixer, where the components of the main engine and transmission system are installed.

-Heating and cooling system: mainly composed of pipelines and distributors, in order to circulate cooling water or steam into the cavities of the mixing chamber, rotor, upper and lower top bolts, etc., in order to control the temperature of the rubber material. The heating and cooling system of the internal mixer imported from abroad is equipped with a temperature control device, which uses constant temperature Water heating heating for cooling. The function is to control the temperature of the rubber material during the mixing process according to the process requirements.

-Hydraulic system: mainly composed of a dual vane oil pump 15, rotating oil cylinder 17, reciprocating oil cylinder 16, pipelines, oil tank, etc. It is the power supply part of the unloading mechanism. Used to control the opening and closing of the lower top bolt and the locking mechanism of the lower top bolt.

-Pressure system: mainly composed of cylinder 14, piston 13, cylinder of feeding valve, air valve, pipeline and compressed air. It is the power supply part of the feeding and pressing mechanism. Used to control the lifting, pressurization, and opening and closing of the top bolt.

-Electric control system: It is mainly composed of control box, operating console and various electrical instruments. It is the Action Center of the whole console.

-Lubrication system: mainly composed of oil pumps, oil separators, and pipelines, with the aim of reducing friction and increasing service life of various rotating parts (such as rotating shafts, bearings, sealing ring friction surfaces of sealing devices, etc.) by injecting lubricating oil into these friction surfaces.

##Advantages and disadvantages of internal mixer

The internal mixer has the following advantages:

-It can accelerate the process of rubber plasticization and improve production efficiency.

-The effect of rubber plasticization can be achieved to be relatively uniform, improving the quality of rubber products.

-The ingredients of rubber can be blended to produce rubber that is more suitable for production needs.

-It can control the temperature during the rubber processing to prevent incomplete plasticization of the rubber.

-Other auxiliary materials such as fillers can be added (note that fillers should be added before rubber plasticization).

The internal mixer also has the following drawbacks:

-The equipment is large and requires a certain amount of space and cost.

-The requirements for workers are relatively high, and they need to understand the operation and maintenance of machines.

-Long operation time and high labor required.

-Some internal mixers may cause certain pollution to the environment.