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Process for removing fluorosurfactant from aqueous fluoropolymer dispersions and reducing scum formation

一种表面活性剂、聚合物的技术，应用在去除含氟表面活性剂领域，能够解决不能防止红色浮渣等问题

Inactive Publication Date: 2007-12-12
THE CHEMOURS CO FC LLC
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  • Summary
  • Abstract
  • Description
  • Claims
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AI Technical Summary

Problems solved by technology

Citric acid has been used as this agent but does not prevent red scum: (1) if added after ammonium hydroxide is added, (2) if the iron content is too high relative to the amount of citric acid added or ( 3) If other chemicals present complex with citrate and compete with iron

Method used

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Embodiment Construction

[0007] As mentioned above, it is known to prevent the formation of red scum by treating the aqueous fluoropolymer dispersion with citric acid or ethylenediaminetetraacetic acid (EDTA) before adding ammonia to increase the pH to at least about 9 to prevent bacterial growth. . EDTA or citric acid acts as a chelating agent that complexes with iron ions in the solution and prevents the formation of insoluble iron hydroxide, which floats to the top of the dispersion as a visible red scum.

[0008] However, when the dispersion is treated with a strongly basic anion exchange resin in the hydroxide form to reduce the fluorosurfactant, it is undesirable to add a chelating agent before adding ammonia. Treating the dispersion in this way can significantly increase the pH to cause scum formation even before the addition of ammonia.

[0009] According to the present invention, in order to reduce the content of fluorosurfactant and prevent the formation of scum, a chelating agent should be adde...

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Abstract

A method for reducing the fluorosurfactant content of a stable fluorosurfactant-containing aqueous fluoropolymer dispersion containing iron ions comprising: exchanging the fluoropolymer dispersion with a strongly basic anion contacting the resin to reduce the content of the fluorosurfactant to a predetermined level, the anion exchange resin is in the hydroxide form, separating the dispersion from the anion exchange resin, and adding an effective amount of Chelating agents are used to complex iron ions to prevent scum formation, said chelating agents having an equilibrium constant of at least 1018 when complexing iron.

Description

Invention field [0001] The present invention relates to a method for removing fluorosurfactant from aqueous fluoropolymer dispersion by using anion exchange resin. Background of the invention [0002] In the process of forming an aqueous fluoropolymer dispersion, it has long been recognized that a small amount of iron (iron ion) in the dispersion can cause a pollution problem called "red scum". Red scum is a term applied to a dispersion containing an insoluble iron hydroxide layer floating on the surface of the dispersion. Iron can be incorporated into the dispersion by adding iron compounds to the fluoropolymer formulation or from metal equipment used to polymerize or process polymers. In the acidic state of polymerization, the iron present is soluble. However, in order to prevent bacterial growth, the dispersion is usually made alkaline by adding a compound such as ammonium hydroxide or sodium hydroxide. When the dispersion is made alkaline, the iron becomes insoluble. Eventual...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C08F6/16C08F14/18
CPCC08F6/16C08F6/02C08F14/18C08F14/26C08F214/18C08L27/12C08F2/20
Inventor D·W·约翰逊R·J·卡瓦诺
Owner THE CHEMOURS CO FC LLC
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