Microwave vulcanization technology of rubber

- May 08, 2019 -

1. Microwave Rubber vulcanization Technical Principles and Advantages:

1. Rubber vulcanization principle and advantages of microwave rubber vulcanization

raw rubber is softened by heat, hardened and brittle by cold, difficult to form, easy to wear and tear, soluble in organic solvents such as gasoline, with double bonds in molecules, easy to initiate additive reaction and easy to aging. In order to improve the properties of rubber products, production is essential. The raw rubber is processed in a series of ways. Under certain conditions, the raw rubber in the compound reacts with the vulcanizing agent, making it cross-linked from the linear macromolecule to the three-dimensional network macromolecule, so that the compound has high strength, high elasticity, high wear resistance, corrosion resistance and other excellent properties. This process is called rubber vulcanization. Generally, the vulcanization process is divided into four stages: induction-pre-sulfur-positive sulfur-super-sulfur. In order to achieve this reaction, it is necessary to add energy to make it reach a certain vulcanization temperature, and then rubber insulation in the vulcanization temperature range to complete the whole vulcanization reaction. Various methods can be used for vulcanization of rubber

. The traditional method is to use steam or far infrared heating vulcanization process. But because the heating temperature is slowly conducting from the outside to the inside of the medium, because the rubber material is a bad heat conducting material, for rubber, heating depends on the surface of the material to the inner layer of the heat transfer rate is very slow, most of the time spent on making the rubber reach the vulcanization temperature. Therefore, the heating time is long, the efficiency is low, and the uniformity of vulcanization is not good. Particularly, magnesium silicate (talc powder) was used in the old process to eliminate rubber adhesion, resulting in dust diffuse in rubber production workshop, and dust content in the air far exceeded the national environmental protection department standards. Moreover, the overall vulcanization state of rubber is not ideal, because, in the case of conventional heat conduction, the surface temperature of vulcanized rubber varies with the time of the inner layer, resulting in the phenomenon of non-uniform vulcanization.

p>strong>microwave heating is totally different from the traditional heating method. It is the microwave energy penetrating into the heated medium for the whole heating directly. Therefore, the heating is fast, efficient and energy-saving, which greatly shortens the vulcanization time of rubber, makes the heating uniformity better and the vulcanization quality higher. In a short time, it can go beyond the induction stage of rubber adhesion and enter the pre-sulfur stage. The operation of talc powder used in the old process can be removed to meet the environmental protection requirements. The production process can make most of the production processes concentrate on one production line, with high automation, low energy consumption, saving manpower, stable production, uniform product quality and so on. It has greatly improved. Labor conditions of production.

2. The application status of microwave rubber vulcanization technology:

Microwave rubber vulcanization technology has been rapidly promoted since its advent in the 1970s, especially the application of microwave rubber continuous vulcanization production line in the production of rubber extrusion products. Its rapid development is unprecedented. Japan is a country with rapid development of microwave continuous vulcanization technology. Up to now, more than 450 microwave continuous vulcanization production lines have been produced, and more than 100 microwave continuous vulcanization production lines have been exported to countries all over the world. Microwave vulcanization technology has become a common mode of production in foreign industrialized countries. It is not only widely used for vulcanization preheating of various extruded rubber strips and hoses, but also for vulcanization preheating of various tires. China has introduced dozens of continuous vulcanization production lines of microwave sealing strips from Germany, Japan, Spain, Britain and other countries. But the imported microwave vulcanization production line also has many problems, such as high price, high maintenance cost, unreasonable design of microwave cabinet, low microwave efficiency, and insufficient automation of control. With the development of microwave energy application technology in China, a number of equipment using microwave vulcanization technology have been modified and modified in succession. Some imported equipment manufacturers, in cooperation with microwave energy application manufacturers, began to reform the existing problems of imported rubber vulcanization equipment, so that the product quality and output have been greatly improved. Since 2000, with the successful development of multi-tube microwave vulcanization equipment, the cost of equipment and the difficulty of maintenance have been reduced. At present, the technology of rubber microwave vulcanization has become more and more mature, and the equipment has been continuously improved. Efforts have been made in the direction of high automation, energy saving and environmental pollution reduction to meet the increasing needs of users. It has great potential and broad market.

2, microwave rubber vulcanization equipment and production process:

At present, the most practical basic technological process of microwave rubber vulcanization is: the extruded products from the extruder are conveyed through conveyor belt or roller, and enter the microwave vulcanization device, where the rubber is heated rapidly to the vulcanization temperature, and then enter the hot air trough of secondary vulcanization. Rubber is vulcanized at a certain temperature in the hot air trough. The foaming and vulcanization process of the product can be completed within a certain period of time. At this time, if the hot air trough is not used, the vulcanization is all carried out in the microwave trough, which wastes too much energy, and combined with the hot air trough, it is more economical. The composition of microwave rubber vulcanization production line includes extruder, high temperature setting equipment, microwave vulcanization equipment, hot air vulcanization equipment, cooling section, tractor, cutting machine and punching machine.

Extruder: Used to extrude rubber raw materials into the required shape and structure. The extruded rubber can be divided into single layer rubber (sponge or solid core rubber), two layer composite rubber (sponge and solid core rubber), three layer composite rubber (steel core, sponge and solid core rubber), four layer composite rubber, and so on. The structure and performance of the extruder used for different rubber types and specifications are also different.

High-temperature setting equipment: It is mainly used to vulcanize the surface of rigidly extruded rubber rapidly at high temperature to prevent its deformation or adhesion with conveyor belt from destroying its surface.

Microwave vulcanization equipment: It only takes tens of seconds to one or two minutes to use microwave heating speed to heat the whole to the temperature needed for vulcanization. Hot-air vulcanization equipment:

keeps the rubber strip in the temperature range needed for vulcanization and continues to vulcanize.

cooling section: used to cool the rubber strip to a temperature that can be cut and collected.

Tractor: Provides power for rubber bars to move forward.

above is only the basic configuration of vulcanized rubber strips. When vulcanizing rubber strip with skeleton, the front section of extruder is equipped with steel core supply equipment, and in the back section, drilling machine, steel core forming machine and other equipment are also equipped as required; when vulcanizing non-strip continuous products, no cutting machine is needed. Microwave heating equipment is the core of the whole microwave vulcanization process. Uniform heat design of microwave heating equipment is particularly important. Uniform heat design of microwave heater is the premise of uniform vulcanization of rubber. In addition, the composition ratio, color depth and surface finish of rubber compound will affect the microwave absorption performance. It is necessary to consider appropriate coordination in microwave heating process to meet the requirements of the process.

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