1. Basic process
Along with the rapid development of modern industry, especially the chemical industry, there are many kinds of rubber products, but the production process is basically the same. The product is made of general solid rubber (raw rubber), and its production process mainly includes:
Raw material preparation→Mastication→Kneading→forming→vulcanization→resting→testing
2. Raw material preparation
The main materials of rubber products are raw rubber, compounding agent, fiber material and metal material. The raw rubber is the basic material; the compounding agent is an auxiliary material added to improve certain properties of the rubber product; the fiber material (cotton, hemp, wool and various rayon, synthetic fiber) and the metal material (steel wire, copper wire) It is used as a skeleton material for rubber products to enhance mechanical strength and limit product modification.
In the preparation of raw materials, the ingredients must be weighed according to the formula. In order to allow the raw rubber and the compounding agent to be uniformly mixed with each other, some materials need to be processed:
The raw rubber should be softened in a 60--70 ° C oven, then cut into rubber and broken into small pieces;
Bulk compounding agents such as paraffin, stearic acid, rosin, etc. should be crushed;
If the powdery complexing agent contains mechanical impurities or coarse particles, it needs to be removed by screening;
Liquid compounding agent (pine tar, coumarone) needs to heat, melt, evaporate water, and filter impurities;
The compounding agent should be dried, otherwise it is easy to agglomerate and mix and disperse when it is not uniformly dispersed, and bubbles are generated during vulcanization, thereby affecting product quality;
Raw rubber is elastic and lacks the necessary properties (plasticity) during processing, so it is not easy to process. In order to improve its plasticity, the raw rubber is plasticized; thus, the compounding agent is easily dispersed uniformly in the raw rubber during the kneading; at the same time, it also contributes to the improvement of the permeability of the rubber during the calendering and molding process (infiltration) Inside the fiber fabric) 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 the process of shortening the degradation of long-chain rubber molecules and changing from a highly elastic state to a plastic state by the mechanical extrusion and friction of the plasticizer at a relatively low temperature. Thermoplasticing is the introduction of hot compressed air into the raw rubber. Under the action of heat and oxygen, the degradation of long-chain molecules is shortened, thereby obtaining plasticity.
In order to adapt to various use conditions, obtain various properties, and also to improve the performance of rubber products and reduce costs, it is necessary to add different compounding agents to the raw rubber. Mixing is a process in which the raw rubber after mastication is mixed with a compounding agent, placed in a rubber mixing machine, and mechanically mixed to completely and uniformly disperse the compounding agent in the raw rubber. Mixing is an important process in the production of rubber products. If the mixing is not uniform, the effects of rubber and compounding agents cannot be fully exerted, which affects the performance of the products. 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 purchaser can directly form and vulcanize the rubber compound. Rubber products needed. Depending on the formula, the mix has a range of different grades and varieties with different properties and offers a choice.
In the production process of rubber products, a variety of various shapes and different sizes of processes are preliminarily formed by a calender or an extruder, which is called forming. The molding methods are:
Calendering 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 textile products (such as tires, tapes, hoses, etc.) used in textile fiber materials must be coated with a thin layer of glue (also called glue or glue on the fiber), and the glue coating process is generally completed on the calender. The fiber material needs to be dried and dipped before calendering. The purpose of drying is to reduce the water content of the fiber material (to avoid evaporation of water and foam) and to increase the temperature of the fiber material to ensure the quality of the calendering process. Dipping is a necessary process before hanging glue, in order to improve the bonding properties of fiber materials and rubber compounds.
Extrusion molding For more complex rubber products, such as tire tread, hose, and wire surface coating, it needs to be manufactured by extrusion molding. It is to put a certain plasticity of the rubber into the hopper of the extruder, and squeeze it out by a variety of mouth shapes (also called templates) under the extrusion of the screw. Previously, the compound had to be preheated to make the rubber soft and easy to extrude, resulting in a rubber product with a smooth surface and accurate dimensions.
Molding It is also possible to use a molding method to manufacture rubber products of various shapes (such as cups and seals), and to form the rubber in a mold by means of a molded female and male mold.
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 (in the vulcanization tank), in the specified Heating and heat preservation at a temperature causes the linear molecules of the raw rubber to crosslink each other to form a network structure by forming a "sulfur bridge", thereby making the plastic compound into 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, there are many varieties of vulcanizing agents, in addition to sulfur, organic polysulfides, peroxides, and metal oxides. Wait. Therefore, the process of converting the plastic rubber of the linear structure into the elastic rubber of the three-dimensional network structure is called vulcanization. Any substance that can "bridge" in the rubber material is called "vulcanizing agent".
Vulcanized elastic rubber is called vulcanized rubber, also known as soft rubber. It is commonly called "rubber". Vulcanization is one of the most important processes in rubber processing. Various rubber products must be vulcanized to obtain the desired performance. Unvulcanized rubber has no use value in use, but low sulfur (not enough degree of vulcanization, insufficient vulcanization time, failure to achieve optimum conditions) and persulfurization (exceeding vulcanization time, performance is significantly reduced) Rubber performance is degraded. Therefore, the vulcanization time must be strictly controlled during the production process to ensure the best performance and longest service life of the vulcanized rubber products.
7. Auxiliary measures
In order to achieve performance, additional measures should be added to the production process:
7.1 increase the strength - with hard carbon black, mixed with phenolic resin;
7.2 Increase wear resistance - with hard carbon black;
7.3 High air tightness requirements - use less volatile components;
7.4 increase heat resistance - using a new vulcanization process;
7.5 increase the cold resistance - through the inlaid setting of raw rubber, reduce the tendency of crystallization, use low temperature resistant plasticizer;
7.6 Increased flame resistance - no flammable additives, less softeners, flame retardants (eg antimony trioxide)
7.7 increase the oxygen resistance and ozone resistance - the use of p-diamine protective agent;
7.8 Improve electrical insulation - use high-structure filler or metal powder with antistatic agent;
7.9 Improve magnetic properties - use strontium iron oxide powder, aluminum nickel iron powder, iron strontium powder, etc. as a filler;
7.10 Improve water resistance - use lead oxide or resin vulcanization system, with low water absorption filler (such as barium sulfate, clay);
7.11 Improve oil resistance - fully cross-linking, less plasticizer;
7.12 Improve the acid and alkali resistance - multi-purpose filler;
7.13 Improve high vacuum - use low-volatility additives;
7.14 Reduce hardness - a large amount of filling softener