Fluorine is the most active and electronegative non-metal element. The introduction of fluorine into organic substances will significantly improve its physical and chemical properties.
- In the field of medicine, the introduction of fluorine atoms or fluorine-containing groups into drugs has a series of special properties such as mimicry effect, lipophilicity and stability, resulting in reduced toxicity, improved efficacy, enhanced metabolism, and long-lasting drug properties of fluorine-containing drugs.
- In the field of advanced functional materials, fluorine-containing polymer materials obtained from fluorine-containing intermediates can meet the extremely challenging needs of many industries for chemical corrosion resistance, electrical insulation, high thermal stability and low surface energy.
Application of Fluorointermediates
- Perfluoroalkyl vinyl ether
Perfluoroalkyl vinyl ethers are an important class of monomers. In addition to being widely used in copolymers with TFE and other monomers, they are also used as comonomers to modify the properties of homofluoropolymers. They can effectively inhibit the crystallization of PTFE, thereby imparting useful mechanical properties to lower molecular weight polytetrafluoroethylene polymers. The copolymer of PAVE and tetrafluoroethylene has the same thermal stability as PTFE homopolymer. Commercially important monomers are perfluoropropyl vinyl ether and perfluoromethyl vinyl ether (PMVE), which are used in the production of various perfluoroalkoxy resins.
Fluorinated epoxide, hexafluoropropylene oxide (HFPO), is a multifunctional fluorine-containing intermediate, which can be used to synthesize fluorine-containing monomers and fluorine-containing polymers, and add fluorine functional groups to various organic precursors middle. For example, hexafluoropropylene oxide is a key intermediate in the production of perfluoroalkoxy vinyl ethers, thereby further producing various commercial fluoropolymers.
- Halocarbon fluorointermediates
Chlorodifluoromethane is an important intermediate for the synthesis of fluorine-containing monomers. The manufacturing process of TFE includes the following four steps:
CaF2 + H2SO4 → CaSO4 + 2HF
CH4 + 3Cl2 → CHCl3 + 3HCl
CHCl3 + 2HF → CHClF2 + 2HCl
2CHClF2 ↔ CF2 = CF2 + 2HCl
In the third step, antimony fluoride (SbF3) is used as a catalyst to partially fluoride chloroform with hydrogen fluoride to chlorodifluoromethane. Finally, the chlorodifluoromethane undergoes pyrolysis and is converted into tetrafluoroethylene. Pyrolysis is a non-catalytic gas phase process carried out in a flow reactor at atmospheric pressure or below atmospheric pressure and temperatures from 590°C to 900°C (1094°F to 1652°F), with a yield of up to 95%. Due to the difficulty of handling monomers, this last step is usually carried out at the PTFE manufacturing site.[1]
Reference
- Gangal, S. V. in Kirk-Othmer, Encyclopedia of Chemical Technology, Vol.11, Third Edition, John Wiley & Sons, New York, p. 2 (1980).
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