Overview of Fluorine Product Manufacturing

Fluorine products play a pivotal role across various industries due to their exceptional chemical properties. As a highly reactive and electronegative element, fluorine is widely used in the production of a diverse range of commercial products, including refrigerants, chemicals, pharmaceuticals, and polymers. Herein, we firstly outline the manufacturing process of several classes of fluorine products, and then focus on the manufacture of fluoropolymers.

Overview of Fluorine Product Manufacturing

Extraction of Fluorine
Fluorine is most commonly extracted from fluorite (CaF₂), a naturally occurring mineral. Processing fluorite involves hydrofluoric acid (HF) production through the reaction of fluorspar with concentrated sulfuric acid. Subsequently, the produced HF is purified using distillation or membrane-based methods to obtain the desired purity required for specific applications.

• Organic Fluorine Compounds
  Organic fluorine compounds are integral to multiple industries, including pharmaceuticals, agrochemicals, and polymers. The manufacturing process generally involves fluorination reactions and can be achieved through various methods, including halogen exchange, nucleophilic fluorination, electrophilic fluorination, and fluorination with fluorinating reagents.
• Inorganic Fluoride Compounds
  Inorganic fluoride compounds, such as hydrogen fluoride (HF) and sodium fluoride (NaF), are commonly used in various industrial applications. A common method for synthesizing inorganic fluoride compounds is through the reaction of a metal oxide or hydroxide with a source of fluoride ions, such as hydrofluoric acid (HF) or ammonium fluoride (NH₄F). For example, the synthesis of sodium fluoride (NaF) can be achieved by reacting sodium hydroxide (NaOH) with hydrofluoric acid.

Typical Fluoropolymer Manufacturing

• • Synthesis of Fluoropolymers
    Monomers used to produce fluoropolymers are shown in the figure. Fluoropolymers are typically synthesized industrially using a method called free-radical polymerization. This process mainly involves water-based reactions, utilizing either aqueous suspension or aqueous emulsion polymerization. Fluorinated emulsifiers, like ammonium perfluorooctanoate, are added during this process. To ensure successful polymerization without thermal decomposition of the gaseous monomers, the reactions are commonly conducted at low temperatures ranging from 0 to 100°C. Water-soluble peroxides, such as ammonium persulfate, KMnO₄, or a trialylboron catalyst, are typically utilized as initiators for the polymerization. Occasionally, small amounts of additives (< 0.1%) are incorporated to facilitate crosslinking or to slightly modify the properties of the fluoroplastics. This synthetic approach is employed in the commercial production of all fluoroplastics.

• Processing of Fluoropolymers
  Apart from PTFE and PVF, the majority of fluoroplastics can be shaped using conventional melt processing methods like injection, blow molding, rotational molding or extrusion. However, the processing of PTFE and PVF is distinct as they are not easily melt-processable like other fluoropolymers. In the case of PVF, due to its instability above its melting point, it is first dissolved in a latent solvent before being extruded into a film. On the other hand, PTFE resins are typically processed using compression molding or stamp extrusion, necessitating the use of a specific type of pelletized resin for each process.