Viscosity control for reduced fluorosurfactant aqueous fluoropolymer dispersions by the addition of cationic surfactant
a technology of aqueous fluoropolymer and surfactant, which is applied in the field of viscosity control of the resulting dispersions, can solve the problems of long-term stability problems, unacceptably high cost of anionic fluorosurfactants, and high cost of some end uses, so as to reduce the viscosity of the dispersion, reduce the content of fluorosurfactants, and reduce the viscosity of stabilized fluorosurfa
Inactive Publication Date: 2006-06-22
EI DU PONT DE NEMOURS & CO
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AI Technical Summary
Benefits of technology
The present invention provides a way to make a stable dispersion of fluoropolymer particles in water that has very low amounts of fluorosurfactant and a cationic surfactant. The cationic surfactant helps to reduce the viscosity of the dispersion. By reducing the fluorosurfactant content and adding cationic surfactant, the viscosity of the dispersion can be reduced and the dispersion can be used in various applications. This invention also provides a process for reducing the viscosity of a stabilized fluorosurfactant-containing aqueous fluoropolymer dispersion by reducing the fluorosurfactant content and adding cationic surfactant.
Problems solved by technology
Because of environmental concerns and because anionic fluorosurfactants are expensive, processes have been developed for the removal of anionic fluorosurfactants from aqueous fluoropolymer dispersions.
In concentrated aqueous fluoropolymer dispersions which have reduced levels of anionic fluorosurfactant, the viscosity levels can be higher than in dispersions containing fluorosurfactant and can be unacceptably high for some end uses.
The presence of residues from such species can produce objectionable color in films and coatings and may give rise to long term stability problems.
Method used
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Fluoropolymer Dispersion
[0007] The stabilized fluorosurfactant-containing aqueous fluoropolymer dispersion for treatment in accordance with the present invention is made by dispersion polymerization (also known as emulsion polymerization). The aqueous fluoropolymer dispersion is a stabilized fluorosurfactant-containing aqueous fluoropolymer dispersion which means that it contains sufficient nonionic surfactant to prevent coagulation of the dispersion when the fluorosurfactant content is reduced. As will be explained in more detail hereinafter, depending upon when the process of the invention is employed, the nonionic surfactant may already be present or may be added for stabilization prior to treatment according to the invention. After concentration, aqueous fluoropolymer dispersions are useful in coating or impregnating compositions and to make cast films.
[0008] Fluoropolymer dispersions are comprised of particles of polymers made from monomers wherein at least one of the monome...
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Abstract
A stabilized aqueous fluoropolymer dispersion comprising fluoropolymer particles, wherein the dispersion contains less that about 300 ppm fluorosurfactant based on the weight of the dispersion and a cationic surfactant. The cationic surfactant aids in reducing the viscosity of the dispersion and preferred cationic surfactants are volatile in coating or film casting operations involving drying and sintering of the dispersion.
Description
FIELD OF THE INVENTION [0001] This invention relates to removing fluorosurfactant from aqueous fluoropolymer dispersions and more particularly relates to controlling of the viscosity of the resulting dispersions. BACKGROUND OF THE INVENTION [0002] Aqueous fluoropolymer dispersions are typically manufactured in an aqueous dispersion polymerization employing anion fluorosurfactants as a polymerization aid, the fluorosurfactants functioning as a non-telogenic dispersing agent. For example, an early description of this use of anionic fluorosurfactants is found in U.S. Pat. No. 2,559,752 (Berry). After polymerization, the dispersions are usually subjected to a concentration step to increase the fluoropolymer solids concentration in the dispersion. In one type of dispersion concentration operation, the dispersion is concentrated with the aid of a nonionic surfactant as taught in Marks et al., U.S. Pat. No. 3,037,953, and in Holmes, U.S. Pat. No. 3,704,272 to raise the solids from nominall...
Claims
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IPC IPC(8): C08L27/12
CPCC08F6/16C08K5/19C09D127/18C08L27/12C08L27/18
Inventor CAVANAUGH, ROBERT JOHN
Owner EI DU PONT DE NEMOURS & CO