Tetrafluoroethylene polymer dispersions stabilized with aliphatic non-ionic surfactants

An aqueous dispersion comprising a tetrafluoroethylene core-shell polymer and at least one non-fluorinated non-ionic surfactant corresponding to the formula:

• R1O—[CH2CH2O]n—[R2O]m—R3 (I)
• wherein R1 is (R′)(R″)HC- and wherein R′ and R″ are the same or different, linear or branched alkyl groups wherein at least one of R′ and R″ is a branched alkyl group and wherein R1 has at least 6 carbon atoms, R2 represents an alkylene unit having 3 or 4 carbon atoms, R3 represents hydrogen, a C1-C3 alkyl group, or a C1-C3 hydroxyalkyl group, n has a value of 0 to 40, m has a value of 0 to 40 and the sum of n+m is at least 2,
• wherein the core-shell polymer contains an outer shell that has a greater molecular weight than the core and wherein the dispersion is essentially free of fluorinated emulsifiers corresponding to the formula
• Y—Rf—Z-M
• wherein Y represents hydrogen, Cl or F;
• Rf represents a linear or branched perfluorinated or partially fluorinated alkylene wherein the alkylene chain may be interrupted once or more than once by oxygen atoms;
• Z represents an acid anion or a plurality thereof, and M represents a counter cation or a plurality thereof and wherein essentially free means an amount of less than 50 ppm and including 0 ppm based on the weight of the dispersion;
• and
• wherein the aqueous dispersion comprises 1 to 12 percent by weight of the non-fluorinated non-ionic surfactant(s) based on the weight of the dispersion and has a shear stability of at least 360 seconds.