1. The basic technological process There are many types […]
1. The basic technological process There are many types of rubber products, but the production technological process is basically the same. The basic process of rubber products using general solid rubber-raw rubber as raw materials includes six basic processes: plasticizing, mixing, calendering, pressing, molding, and vulcanization. Of course, basic processes such as raw material preparation, finished product finishing, inspection and packaging are also indispensable. The process of rubber processing is mainly to resolve the contradiction between plastic and elastic properties. Through various technological means, the elastic rubber becomes plasticized rubber, and then various compounding agents are added to make semi-finished products, and then the plastic semi-finished products are turned into rubber products with high elasticity and good physical and mechanical properties through vulcanization. .
2. Raw material preparation
1. The main raw material of rubber products is raw rubber, and raw rubber grows on tropical and subtropical rubber trees and is collected by cutting the bark manually.
2. Various compounding agents are auxiliary materials added to improve certain properties of rubber products.
3. Fiber materials (cotton, hemp, wool and various man-made fibers, synthetic fibers and metal materials, steel wires) are used as the skeleton material of rubber products to enhance mechanical strength and limit product deformation. In the raw material preparation process, the ingredients must be accurately weighed according to the formula. In order to make the raw rubber and the compounding agent mix uniformly with each other, the material needs to be processed. The raw rubber should be dried in a 60-70℃ drying room before being cut and broken into small pieces. The compounding agent has a block shape. Such as paraffin, stearic acid, rosin, etc. must be crushed. If the powder contains mechanical impurities or coarse particles, it needs to be screened to remove the liquid, such as pine tar, coumarone, which needs to be heated, melted, evaporated, and filtered impurities. Air bubbles generated during uniform vulcanization will affect product quality.
3. Masticated raw rubber is elastic and lacks the necessary plastic properties during processing, so it is not easy to process. In order to improve its plasticity, it is necessary to masticate the raw rubber, so that the compounding agent is easy to be evenly dispersed in the raw rubber during mixing, and at the same time, it also helps to improve the permeability of the rubber material and penetrate 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 methods of plasticizing raw rubber: mechanical plasticizing and thermal plasticizing. Mechanical plasticization is the process of degrading and shortening long-chain rubber molecules from a highly elastic state to a plastic state through the action of mechanical extrusion and friction of the plasticizer at a not too high temperature. Thermoplastication is to pass hot compressed air into the raw rubber to degrade and shorten the long-chain molecules under the action of heat and oxygen to obtain plasticity.
4. Mixing In order to adapt to various use conditions, obtain various properties, and to improve the performance of rubber products and reduce costs, different compounding agents must be added to the raw rubber. Mixing is a process in which the plasticized raw rubber is mixed with the compounding agent and placed in a rubber mixer to make the compounding agent completely and uniformly dispersed in the raw rubber through mechanical mixing. Mixing is an important process in the production process of rubber products. If the mixing is not uniform, the role of rubber and compounding agents will not be fully exerted to affect the performance of the product. The rubber compound obtained after mixing is called compound rubber. It is a semi-finished material for the manufacture of various rubber products. Commonly known as rubber materials, they are usually sold as commodities. Buyers can use the rubber materials to directly process, shape and vulcanize to make the required rubber products. . According to different formulas, there are a series of different grades and varieties with different properties to choose from.
5. Molding In the production process of rubber products, the process of using a calender or extruder to make various shapes and sizes in advance is called molding. The molding methods are
1. Calendering is suitable for manufacturing simple sheet and plate products. It is a method of pressing the rubber compound into a film with a certain shape and a certain size through a calender, called calendering. Some rubber products, such as tires, rubber cloth, hoses and other textile fiber materials must be coated with a thin layer of glue. Gluing on the fiber is also called glue or rubbing glue. The glue coating process is usually completed on the calender. The purpose of drying and dipping the fiber material before calendering is to reduce the moisture content of the fiber material to prevent water from evaporating and foaming and to increase the temperature of the fiber material to ensure the quality of the calendering process. Glue dipping is a necessary process before hanging glue. The purpose is to improve the bonding performance of fiber materials and rubber materials.
2. Extrusion molding is used for more complex rubber products such as tire treads, hoses, metal wire surface coatings, which need to be manufactured by extrusion molding methods. It is a method in which the rubber compound with a certain degree of plasticity is put into the hopper of the extruder, and under the extrusion of the screw, the continuous molding is carried out through various mouth shapes, also called templates. Before extrusion, the rubber must be preheated to make the rubber soft and easy to extrude to obtain a rubber product with a smooth surface and accurate size.
3. Compression molding can also be used to make certain rubber products with complex shapes such as cups and sealing rings. The rubber material is placed in the mold for heating with the help of the formed female and male molds.
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 the semi-finished product made of raw rubber, and heat it at a specified temperature in a vulcanizing tank. , Thermal insulation makes the linear molecules of the raw rubber cross-link each other into a solid network structure through the formation of "sulfur bridges", so that the plastic rubber compound becomes a vulcanized rubber with high elasticity. Since the cross-linking bond is mainly composed of sulfur, it is called "vulcanization". With the rapid development of synthetic rubber, there are many types of vulcanizing agents in addition to sulfur, as well as organic polysulfides, peroxides, metal oxides and so on. Therefore, any process that can transform the linear structure of plastic rubber into a three-dimensional network structure of elastic rubber is called vulcanization. Any substance that can act as a "bridging" in the rubber material is called a "vulcanizing agent". Vulcanized elastic rubber is called vulcanized rubber or soft rubber, commonly known as "rubber". Vulcanization is one of the most important processes in rubber processing. Various rubber products must be vulcanized to obtain ideal performance. Unvulcanized rubber is of no use value in use, but the degree of under-sulfur vulcanization is not enough, the vulcanization time is not enough to reach the best state, the over-sulfur vulcanization time is exceeded, and the performance is significantly reduced, all of which reduce the rubber performance. Therefore, the vulcanization time must be strictly controlled during the production process? To ensure that the vulcanized rubber products have the best performance and the longest service life.
7. Auxiliary measures In order to achieve performance, auxiliary measures should be added to 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-less use of highly volatile components
4. Increase heat resistance-adopt a new vulcanization process
5. Increase cold resistance-through the unbranching of raw rubber, reduce the tendency of crystallization, use low temperature resistant plasticizer
6. Increase flame resistance-use no flammable additives, use less softeners, and use flame retardants such as antimony trioxide
7. Increase oxygen resistance and ozone resistance-use diamine protective agent
8.Improve electrical insulation-with high-structure filler or metal powder with antistatic agent
9. Improve magnetic properties-use strontium ferrite powder, aluminum nickel iron powder, iron barium powder, etc. as fillers
10. Improve water resistance-use lead oxide or resin vulcanization system with fillers with lower water absorption such as barium sulfate and clay
11.Improve oil resistance-fully crosslinked and use less plasticizer
12.Improve acid and alkali resistance-multi-purpose filler
13.Improve the high vacuum performance-with low volatile additives