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Mechanical smelting of rubber products

Edit: John 2020-02-17 Mobile

Mechanical smelting of rubber products Tags:Rubber Mixers 

  Since the basic principle of rubber mixing is to reduce the molecular weight of the solid raw rubber, that is, the degradation reaction of the rubber molecules, all processes related to reducing the molecular weight of the raw rubber can be used as the plasticizing method of the raw rubber. However, in the manufacture of rubber products and abrasive tools, the most commonly used are mechanical plasticizing method and thermal oxidation plasticizing method. Mechanical plastic smelting method The equipment used for mechanical plastic smelting of rubber products includes open mixers, sealed mixers, spiral mixers, and four-roller mixers. Open rubber mills are mainly used in the manufacture of rubber product binder abrasive tools. Not only the rubber products, but also the preparation of abrasive molding materials and roll forming can be carried out on this equipment.

  

  The main working part of the open mill is two hollow rollers rotating at different speeds. When the rubber material is added to the two opposite rotating rollers, the rubber material is brought into the gap between the two rollers under the effect of the friction between the rubber material and the surface of the roller. Due to the squeezing action of the roller, the cross section of the rubber material gradually decreases. At this time, under the action of the speed gradient caused by different roller speeds, the rubber compound is subjected to strong frictional shear and chemical action. This is repeated many times to achieve the purpose of mixing. During the rubber mixing process, there should be an appropriate amount of accumulated rubber on the two rollers. The accumulated glue is continuously brought into the nip by the rotating roller, and new glue is continuously formed. This is beneficial to improve the rubber mixing effect, especially to improve the radial mixing effect during the mixing process. However, the accumulation of glue on the roller cannot be too much, otherwise there will be a part of the accumulation of glue that can only shake or rotate on the roller pitch, and cannot enter the roll gap in time, thereby reducing the effect of rubber mixing.

  1. Plasticizing method of open rubber mixer

  Use an open rubber mill to mechanically plasticize natural rubber products. The specific operation methods are: roll plastic or thin-pass plastic smelting; one-time plastic smelting or segmental plastic smelting; pure plastic smelting or plasticizer. And other methods.

  The roll-roll plastic smelting method puts the raw rubber block one by one above the roll gap near one end of the roll. After passing through the roll gap, it is wrapped on the surface of the slow front roll, and it is continuously rolled until it reaches the requirements. Time.

  The thin-pass plastic smelting method uses the minimum roll distance (0.5 ~ 1.0mm). When the raw rubber passes through the roll gap, it is not covered with rolls, let it fall directly on the receiving tray, and then repeat this method multiple times until specified. Times or times.

  Segmented plasticizing method When the solid raw rubber is strongly rolled on the roller, it will self-heat due to repeated stretching and deformation. Therefore, no matter whether it is a roll plasticizing or a thin-pass plasticizing, one continuous plasticizing can obtain High plasticity is impossible. In order to achieve high plasticity, it should be used multiple times, that is, the segmented plasticizing method, that is, plasticizing for a certain time each time, and then taking off and cooling for 4 ~ 8h, and then performing the second or third and fourth plasticizing Refining.

  Plasticizing agent plastic smelting method Plastic smelting method that simply makes the raw rubber subject to rollers can be called pure rubber plastic smelting method. In the rubber products industry, in order to improve the plasticization, some chemicals are often added to speed up the process during the roll plasticization. These chemicals are called "peptides".

  2.Influencing factors of open mixing

  Gentle plasticizing time of rollers The plasticizing of open mill belongs to low-temperature mechanical plasticizing, and the plasticizing temperature is generally below 55 ℃. The lower the temperature, the greater the plasticizing effect. Therefore, during the plasticizing process, the roller must be cooled as much as possible to control the temperature of the roller below 45 ~ 55 ° C. One of the purposes of adopting thin-pass plasticizing and segmental plasticizing is to reduce the temperature of the rubber compound.

  In the first 10 to 15 minutes of the beginning of the plasticizer, the plasticity of the rubber compound increased rapidly, and then stabilized. This is because with the extension of the plasticizing time, the temperature of the rubber compound increases and the mechanical plasticizing effect decreases. In order to improve the mechanical plasticizing effect. After the rubber is plasticized for a certain period of time, the rubber must be allowed to cool down for a certain period of time, and then re-molded to fully play the plasticizing effect of the equipment and obtain greater plasticity. This is the fundamental purpose of segmented plastics.

  Roller distance and speed ratio When the roller speed ratio is constant, the smaller the roller distance, the greater the friction and shear between the rollers. At the same time, because the film is thinner and easier to cool, the mechanical plastification is further strengthened. Effect, the greater the plasticizing effect. Botong Plastic Smelting is based on this principle.

  The greater the speed ratio between the rollers, the greater the shearing effect that the rubber material undergoes when passing through the roll gap, and the greater the plasticizing effect; otherwise, the opposite is true. Therefore, in the plasticizing process, the plasticizing effect of the rubber material is closely related to the speed ratio of the roller. The speed ratio of the open mill roll used for plasticizing processing is generally 1: 1.5 to 1: 1.27. The speed ratio cannot be too large, because the excessively intense friction will actually cause the rubber to generate too much heat and the temperature will rise sharply, but it will reduce the plasticizing effect of the machine and increase the power consumption. Therefore, the speed ratio must be selected reasonably.

  The amount of rubber installed The size of the open rubber mixer depends on the size and type of the rubber mixer, and is generally determined by empirical formulas. In order to increase the output, the amount of glue can be increased appropriately. However, if the amount of glue is too large, the accumulation of glue on the roller will be too much and it will be difficult to enter the roll gap, and the heat of the rubber will be difficult to radiate, which will reduce the effect of mechanical molding and increase the labor intensity. Synthetic rubber products have high heat-generating properties, so the amount of rubber should be appropriately reduced.

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