The basic process of rubber production

- Oct 23, 2019-

First, the basic process

There are many kinds of rubber products, but the production process is basically the same. The basic process of rubber products using general solid rubber-raw rubber as raw materials includes six basic processes of mastication, mixing, calendering, extrusion, molding and vulcanization. Of course, basic processes such as raw material preparation, finished product finishing, and inspection and packaging are also indispensable. The rubber processing process is mainly to solve the contradiction process of plasticity and elastic properties. Through various processes, the elastic rubber is transformed into a plasticized plastic compound, and then various compounding agents are added to make a semi-finished product, and then the semi-finished product having plasticity is turned into a rubber product with high elasticity and good physical and mechanical properties by vulcanization. .


Second, raw material preparation

1. The main raw material of rubber products is raw rubber as the basic material, while raw rubber is grown in the tropical, subtropical rubber trees collected by artificially cutting the bark.

2. Various compounding agents are auxiliary materials added to improve certain properties of rubber products.

3. Fiber materials (cotton, hemp, wool and various rayon, synthetic fiber and metal materials, steel wire) are used as a skeleton material for rubber products to enhance mechanical strength and limit product modification. In the raw material preparation process, the ingredients must be weighed accurately according to the formula. In order to allow the raw rubber and the compounding agent to be uniformly mixed with each other, the material needs to be processed. The raw rubber should be softened in a 60--70 ° C drying room, then cut into pieces, broken into small pieces, and the compounding agent has a block shape. Such as paraffin, stearic acid, rosin, etc. to be crushed. If powdery contains mechanical impurities or coarse particles, it is necessary to screen and remove liquid such as pine tar. Gumaron needs heating, melting, evaporating water, and filtering impurities. If the compounding agent is dried, it will be easy to agglomerate and if it is not dispersed during mixing. Air bubbles generated during uniform vulcanization can affect product quality.


Third, mastication

Raw rubber is elastic and lacks the plasticity properties necessary for processing, so it is not easy to process. In order to improve the plasticity, the raw rubber is masticated, so that the compounding agent is easily dispersed uniformly in the raw rubber during the kneading, and also helps to improve the permeability of the rubber into the fiber fabric during the calendering and molding process. And molding fluidity. The process of degrading the long-chain molecules of raw rubber to form plasticity is called mastication. There are two kinds of raw plastic mastication methods: mechanical mastication and thermoplastic refining. Mechanical mastication is a process in which the degradation of long-chain rubber molecules is shortened from a highly elastic state to a plastic state by mechanical extrusion and friction of a plasticizer at a relatively low temperature. Thermoplasticing is the introduction of hot compressed air into the raw rubber to shorten the degradation of long-chain molecules under heat and oxygen to obtain plasticity.


Fourth, mixing

In order to adapt to various conditions of use, to obtain various properties, and to improve the performance of rubber articles and to reduce costs, it is necessary to add different compounding agents to the raw rubber. Mixing is a process in which the raw rubber after the mastication is mixed with the compounding agent and placed in the rubber mixing machine to completely and uniformly disperse the compounding agent in the raw rubber by mechanical mixing. Mixing is an important process in the production of rubber products. If the mixing is not uniform, the effects of rubber and compounding agents can not be fully exerted. The compound obtained after mixing is called rubber compound. It is a semi-finished material for manufacturing various rubber products. It is commonly known as rubber compound. It is usually sold as a commodity. The rubber product can be directly processed and vulcanized by the rubber. . Depending on the recipe, the mix has a range of different grades and varieties with different properties.


Five, molding

In the production process of rubber products, a variety of different shapes and sizes of processes are prepared in advance by using a calender or an extruder. The method of molding has

Calendering

It is suitable for the manufacture of simple sheet and plate products. It is a method of pressing a rubber compound into a certain shape and a certain size by a calender, which is called calender molding. Some rubber products, such as tires, tapes, hoses, etc., must be coated with a thin layer of glue. The glue on the fibers is also called glue or glue. The glue application process is also generally done on the calender. The purpose of the fiber material to be dried and dipped before calendering is to reduce the water content of the fiber material to prevent evaporation of water and to increase the temperature of the fiber material to ensure the quality of the calendering process. Dipping is a necessary process before the glue is applied to improve the bonding properties of the fiber material and the rubber compound.

2. Extrusion molding

For more complex rubber products, such as tire tread, hose, wire surface coating needs to be made by extrusion molding. It is a method of putting a certain plasticity into a hopper of an extruder under the extrusion of a screw through a variety of mouth shapes, also called a template. Before the extrusion, the rubber must be preheated to make the rubber soft and easy to extrude to obtain a rubber product with smooth surface and accurate size.

3. Molding

It is also possible to use a molding method to manufacture certain rubber products having complicated shapes such as cups and seals, and to place the rubber in the mold by means of a molded female and male mold.


Six, vulcanization

The process of converting plastic rubber into elastic rubber is called vulcanization. It is to add a certain amount of vulcanizing agent such as sulfur, vulcanization accelerator, etc. to a semi-finished product made of raw rubber, and heat and heat the temperature at a predetermined temperature in a vulcanization tank. The linear molecules of the raw rubber crosslink each other by forming a "sulfur bridge" to form a network structure of the body, so that the plastic compound becomes a vulcanizate having high elasticity. Since the cross-linking bond is mainly composed of sulfur, it is called "vulcanization". With the rapid development of synthetic rubber, many varieties of vulcanizing agents include organic polysulfides, peroxides, and metal oxides in addition to sulfur. Therefore, any process that converts the plastic rubber of the linear structure into a three-dimensional network structure is called a vulcanizing agent. Any substance that can "bridge" in the rubber material is called a "vulcanizing agent". The vulcanized elastic rubber is called vulcanized rubber, which is also called soft rubber. Vulcanization is one of the most important processes in rubber processing. Various rubber products must be vulcanized to achieve the desired performance. Unvulcanized rubber has no use value in use, but the degree of sulfur vulcanization is not enough. The vulcanization time is not enough to achieve the best condition and the sulfur vulcanization time is exceeded, and the performance is significantly degraded, which causes the rubber performance to decrease. Therefore, the vulcanization time must be strictly controlled during the production process to ensure that the vulcanized rubber product has the best performance and the longest service life.


Seven, auxiliary measures

In order to achieve the performance, it is also necessary to add auxiliary measures in the production process.

1. Increase the strength - with hard carbon black mixed with phenolic resin

2. Increase wear resistance - with hard carbon black

3. High air tightness requirements - use less volatile components

4. Increase heat resistance - using a new vulcanization process

5. Increase cold resistance - through the inlaid setting of raw rubber to reduce the tendency of crystallization? Use low temperature resistant plasticizer

6. Increase flame resistance - no flammable additives, less softeners, use of flame retardants such as antimony trioxide

7. Increased oxygen and ozone resistance - using p-diamine protectants

8. Improve electrical insulation - use high-structure filler or metal powder with antistatic agent

9. Improve magnetic properties - using barium iron oxide powder, aluminum nickel iron powder, iron powder, etc. as a filler

10. Improve water resistance - use lead oxide or resin vulcanization system with low water absorption filler such as barium sulfate, clay

11. Improve oil resistance - fully cross-linking, less plasticizer

12. Improve acid and alkali resistance - multi-purpose filler

13. Improve high vacuum - with low volatility additives