Synthetic materials are important members of new materials.
Different from natural materials, synthetic materials not only have more sufficient sources, but also control the synthesis process to achieve various required material properties.
Most raw materials for synthetic materials come from petroleum. After the petroleum is refined, basic chemical raw materials are obtained, and then converted into chemical intermediates through a series of chemical devices, and then continue to polymerize to obtain various synthetic resins.
Only after further processing and molding of the resin will the synthetic material be finally obtained and put into various application fields such as construction, transportation and daily use.
The industrial chain of rayon is a typical case.
In this industry chain, the existence of EDWARDS can be found everywhere, including resin production, extrusion degassing, masterbatch blending, film sheet, vacuum forming, EPS foam, etc. We will serialize 6 articles to introduce the above applications, and explain in detail how the vacuum expert EDWARDS can assist the development of the new material industry.
Resin and materials
The formation mechanism of resin can be understood as that small molecules form long chain macromolecules through polymerization reaction. In this process, small molecules in the gaseous or liquid state continue to polymerize, and the molecular weight gradually increases, eventually forming a solid or viscous polymer, that is, a resin. According to different polymerization reactions, resins can also be roughly classified into polyolefins (addition reaction) or polyesters (condensation reaction).
The resin is generally pelletized by an extrusion process to form granules for transportation, storage or reprocessing.
Synthetic materials are usually the products of synthetic resin processing. As the matrix of the material, the performance of the resin often determines the basic properties of the material, such as mechanical strength, heat resistance, transparency and so on. It can be said that a resin with excellent performance is a prerequisite for obtaining high-performance materials. Therefore, the production process that affects the performance of the resin is particularly important.
Process at a glance
For polyolefins, gaseous raw materials such as ethylene are introduced into the reactor via vacuum. The polymerization reaction is initiated by a solid catalyst and proceeds continuously in the reactor. After the polymerization is complete, the product is removed from the reactor and degassed. In the degassing tank, the deactivator is first introduced to deactivate the catalyst; then the unreacted monomers in the product are removed by the vacuum system (which will be recovered to the reactor to recycle the reaction). Afterwards, the product enters the purge tank and uses vacuum-driven circulating nitrogen to remove most of the water and volatile gases. Finally, the product forms a powder and is fed into the extruder together with the additives. After gradually melting in the extruder, the melt removes the volatile gas through the vacuum port, and then builds pressure, and then cools and forms the finished pellet.
The production process of polyester is similar to this. It also requires a vacuum system to remove unreacted monomers or by-products after polymerization, and it is often granulated or modified by an extrusion process.
It can be seen that a suitable and stable vacuum is a key process in resin production, which determines the key specifications of resin viscosity and color.
In the above process, the medium extracted by the vacuum system inevitably contains organic solvents or compounds. These chemicals are usually flammable, corrosive, or toxic. In addition, oligomers with a certain molecular weight are also easily pumped with vacuum. If the vacuum system cannot handle the above impurities safely and effectively, it will inevitably lead to abnormal processes, damage to the pump body and even safety accidents.
In addition, the vacuum and temperature need to be kept stable for a long time to avoid frequent fluctuations resulting in unqualified products or line maintenance.
EDWARDS has complete and complete vacuum products. The classic liquid ring pump can continuously replenish the working fluid, making the pump temperature almost constant to room temperature. In this way, combustible or explosive gases can be handled safely. In addition, the working fluid can also wash away the oligomers in the pump, avoiding the risk of the pump body becoming stuck.
The new type dry pump has a unique sealing technology, an efficient cooling system, and a sensitive temperature control function, making the pump body a stable temperature sealed cavity. In this way, the corrosive or toxic medium remains as dry gas in and out of the pump body, thereby avoiding corrosion or contamination diffusion of the pump body.
Whether it is wet (liquid ring, rotary vane, steam spray, diffusion) or dry product (screw, claw, mechanical roots), EDWARDS can use professional knowledge and application experience to select and design the most suitable for customers Vacuum system solution.
Typical vacuum system components include: vacuum pump (or Roots pump vacuum pump combination), inlet condenser, inlet separation tank (optional with filter), inlet gas / solvent flushing, outlet condenser / receiving tank.
What can the EDWARDS solution bring to customers?
Mature technology and explosion-proof certified vacuum system will reliably process various chemical media to meet safety and environmental requirements.
The customized system of the fitting process will achieve stable production with optimized pumping speed and vacuum degree. This will result in longer uptime and overhaul intervals, which means higher production efficiency and lower operating costs.