Synthesis of fluorine surfactants and surface treatment agents

Synthesis of Fluorine Surfactants and Treatment Agents:

The synthesis of fluorinated surfactants generally involves three steps: first, synthesizing fluorocarbon compounds containing 6-10 carbon atoms, then preparing fluorinated intermediates that are easy to introduce various hydrophilic groups, and finally introducing various hydrophilic groups to produce various fluorinated surfactants. The synthesis of fluorinated alkyl groups is the key to preparing fluorinated surfactants. The industrial production methods of fluorinated alkyl groups mainly include electrolytic fluorination, fluorinated olefin polymerization, and fluorinated olefin oligomerization.

1. Electrolytic fluorination method

Electrolytic fluorination is the process of dissolving or dispersing fluorinated substances in anhydrous hydrogen fluoride and electrolyzing them at a DC voltage below 8V. Hydrogen gas is generated at the cathode during electrolysis, and organic matter is fluorinated at the anode. In this process route, acyl chloride or sulfonyl chloride of hydrocarbon chain alkyl can be directly replaced with corresponding perfluoroalkyl fluoride or sulfonyl fluoride products. Starting from them, various fluorinated surfactants can be prepared using ordinary methods (see the following formula).

Due to the intense reaction of electrolytic fluorination, C-C chain breakage is prone to occur. During the reaction, in addition to producing perfluorinated compounds with the same number of carbon atoms as the raw material, short chain perfluorinated compounds and other types of by-products are also generated, resulting in a lower overall product yield.

2-fluoroolefin polymerization method

The fluoroolefin polymerization method was first proposed by Professor HaszeldineRH in the UK, which uses perfluoroalkyl iodine and other substances as end groups to regulate the polymerization of fluorinated monomers such as tetrafluoroethylene to obtain low polymerization degree fluorinated alkene based modulators. In 1951, he discovered an industrial production route in which trifluoroiodomethane can undergo regulated polymerization reactions with ethylene and tetrafluoroethylene. Subsequently, DuPont Company in the United States developed a polymerization reaction using iodine pentafluoride and tetrafluoroethylene to produce perfluoroalkyl sulfonates. C2F5I+nCF2=CF2C2F5 (CF2CF2) nI Although the yield of this reaction is high, the final product is a mixture of different chain lengths (with a wide distribution of n numbers). Choose a good reaction process appropriately, control the reaction process conditions, and ensure that n numbers are within the required range (n: 24) to terminate the continuous development of the reaction. To reduce the generation of unwanted high boiling substances (n>6) in large quantities. There are many other substances used as modifiers, and a large number of patents have been published in this research field, with their respective reaction formulas

3-fluoroolefin oligomerization method

The fluoroolefin oligomerization method was developed by ICI in the UK from 1965 to 1969. It uses fluoroolefins to undergo oligomerization reaction in non protonic solvents to obtain perfluoroalkene oligomers with high branching and low polymerization degree. The most commonly used methods include tetrafluoroethylene oligomerization, hexafluoropropylene oligomerization, and hexafluoroepoxypropane oligomerization. The tetrafluoroethylene oligomerization method yields oligomers with a polymerization degree mainly ranging from 4 to 6, with pentamers accounting for the largest proportion, approximately 65% of the entire mixture. Due to the fact that the fluorine atom on the double bonded carbon atom is easily replaced by nucleophilic reagents, this reaction can be used to introduce the required linking group. The fluorine atoms directly connected to the double bond atoms in tetrafluoroethylene pentamer molecules can undergo substitution reactions with nucleophilic reagents such as phenol in alkaline media, thereby synthesizing a series of fluorine-containing surfactants.

Hexafluoroepoxypropane can easily undergo oligomerization reaction under the action of fluoride ions. The oligomers of hexafluoroepoxypropane contain acyl fluorine functional groups, which can undergo various reactions and yield various fluorinated surfactants.

The synthesis of fluorine surface treatment agents is generally similar to that of surfactants, except that short chain fluorine is introduced as a polymer bond, such as vinyl and propionyloxy groups, to enable the synthesis of polymers. At the same time, functional monomers, such as hydrophilic monomers, are introduced during the polymerization process to achieve surface treatment and other functions.