Fine fluoropolymer powders
A polymer and fine powder technology, applied in the field of condensed fine powder, can solve the problems that the dispersion is difficult to condense, cannot be used to obtain condensed fine powder, and cannot be condensed
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Embodiment 1
[0124] emulsion polymerization
[0125] 11 g of an aqueous solution of ammonium perfluorooctanoate at a concentration of 100 g / l and 31 l of precisely degassed deionized water were fed into a 50 l autoclave equipped with a mechanical stirrer and a pre-set vacuum. In the reactor, 140 grams of paraffin wax with a softening point of 52°C-54°C was added in advance. The autoclave was kept mechanically stirred and pressurized with TFE to 20 bar at a temperature of 68°C. At this time, 500ml (NH 4 ) 2 S 2 o 8 (APS) and disuccinylated peroxygen (DSAP) solutions were fed into the autoclave.
[0126]When the pressure in the reactor dropped by 0.5 bar, the feed of TFE through the compressor was started, so as to maintain a constant pressure of 20 bar in the reactor. Simultaneously, the temperature inside the reactor was increased to 78°C at a rate of 0.5°C / min. During the reaction, 50.6 g of a 100 g / l aqueous solution of ammonium perfluorooctanoate were fed into the autoclave. The...
Embodiment 2
[0130] Preparation of acrylic polyelectrolyte (Craymul 8212 - Cray Valley ) in aqueous solution. Starting from a commercial sample of an aqueous dispersion in 40% by weight of an acrylic polyelectrolyte (Craymul 8212) with a pH of 3.0-4.0, with a molecular weight of about 100,000 and an equivalent weight of about 450, a transparent and uniform 5% by weight solution was obtained by adding water and an aqueous ammonia solution under stirring conditions. The pH of the solution was about 9.
Embodiment 3
[0132] From 40 kg of the dispersion obtained according to Example 1 (the pH of which was adjusted to about 9 with an aqueous ammonia solution) and the Craymul® obtained according to Example 2 Starting from an aqueous solution of 8212, a mixture containing 0.25% Craymul by weight based on PTFE was prepared by stirring in a glass reactor equipped with a discharge valve at the bottom. A dispersion sample of 8212. The PTFE content of the sample thus obtained was equal to 29.6% by weight. To the sample was added 5% by weight of the ion exchange resin Amberjet, based on the weight of the sample 4400 OH. The mixture was kept under gentle stirring with a dual-blade mechanical stirrer for 8 hours. At the end, the dispersion showed no fluoropolymer coagulum, and the dispersion was separated from the resin by filtration through a 150 μm mesh screen. The PFTE content of the resulting dispersion was equal to 29.6% by weight. Based on PTFE content, PFOA content is less than 5ppm.
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