Polyvinyl chloride resin (PVC for short) is one of the five major general plastics, ranking second in output after polyethylene. PVC resin powderThe main production process is the ethylene method and calcium carbide method. Depending on the process, the upstream industries are the ethylene industry and the calcium carbide industry respectively. In terms of downstream industries, PVC is widely used in construction, medical, automobile and other fields due to its corrosion resistance, electrical insulation, flame retardancy, light weight and high strength.
The production process of polyvinyl chloride resin is divided into petroleum route (ethylene method) and calcium carbide route (carbide method). The former uses petroleum and chlorine as raw materials, and the latter uses Coal and raw salt are used as raw materials. The commonality of the two processes is that vinyl chloride monomer (VCM) is finally produced and then polymerized to form polyvinyl chloride (PVC).
At present, the ethylene method is widely used in the PVC industry in Western Europe, North America, the Middle East and other regions, while the domestic calcium carbide method is developing rapidly, and the calcium carbide method PVC equipment production capacity accounts for the total domestic production capacity About 75%. Compared with the ethylene method using petroleum as raw material, the calcium carbide method has the advantages of less production investment, simple process and lower cost. At the same time, my country’s “poor oil and rich coal” energy structure and relatively mature calcium carbide production technology provide low-priced raw materials for the calcium carbide route.
PVC resin powderDaily models and uses
PVC is widely used in construction, medical, and automobiles due to its corrosion resistance, electrical insulation, flame retardancy, light weight, high strength, and ease of processing. and other fields. Among them, the construction industry accounts for about 60% of consumption, mainly using profiles, pipes and sheets made of general-purpose resins SG-5, SG-7, and SG-8 to replace traditional wood, metal, cement, etc.
Based on the difference in degree of polymerization, PVC can be divided into general-purpose resin (divided into eight models SG-1~SG-8) and special resin. Among them, the application scope of special resins is closely related to customer needs. General-purpose resin products can be divided into soft products and hard products
PVC resin powderDaily model span>
PVC models (hereinafter referred to as calcium carbide process brands), the most common one in my country is SG-5, followed by SG-3, SG-7, SG -8 etc.
In industry, the viscosity or K value is commonly used to represent the average molecular weight (or average degree of polymerization) of PVC, that is, the length of the PVC molecular chain, to determine and distinguish resin grades. and corresponding processing parameters. The molecular weight of the resin is related to the physical and mechanical properties of the product.
PVC is a non-crystalline linear polymer compound. The greater its relative molecular mass, the higher the viscosity and the higher the molecular weight. The tensile strength, The higher the impact strength and elastic modulus, but the fluidity and plasticity of the resin melt decrease. The viscosity number is usually used to express the molecular weight of the polymer and classify the polymer model.
Comparison of production requirements
VC has a wide range of applications, and different models are used due to different needs.
PVC resin powderSG5 is used in pipes, profiles, Plates etc.
PVC resin powderSG3 is mostly a soft product and is mostly used in the manufacture of hoses and wires Cables, films, shoe materials, toys, auto parts, conveyor belts, daily plastic products, etc.
SG7 and SG8 are mostly used for manufacturing pipe fittings, sheets, containers, etc. In principle, the higher the model, the harder the product.
Compared to SG5, the production of SG3 requires a long reaction time, high polymerization temperature, high requirements for the addition of excipients, and the production cost is higher than that of SG5. PVC resin powderSG3 type PVC should have high purity, fewer fish eyes, and is easy to absorb Plastic, with the characteristics of high temperature resistance, insulation and soft texture of products.
Comparison of SG-7/SG-8 and SG-5. The production processes of these three resins are basically the same, and the production equipment is exactly the same. The main difference lies in the additive formula, polymerization reaction temperature, reaction pressure, etc.
In terms of reaction temperature and reaction pressure. SG-8 resin has basically reached polymerizationThe working pressure limit of the kettle and the reaction requirements are more stringent. The requirements for operation, safety, technology, personnel quality, etc. are more stringent, and the resin quality is more difficult to control.
