Nucleating agents for thermoplastic resins

Claim 1

In an improved process for producing a foam of a thermoplastic resin composition, the improvement characterized in that the process is carried out with an effective amount of the nucleating agent of the formula [Z(CF.sub.2).sub.x (CF.sub.2 CFX).sub.p (R').sub.y (CH.sub.2).sub.z RO.sub.3 ].sub.n M wherein: Z is CCl 3 , CCl 2 H, H, F, Cl or Br; each X, independently, is selected from H, F or Cl; R is sulfur or phosphorus; M is H or a metallic, ammonium, substituted ammonium or quaternary ammonium cation; x is an integer and is 0 to 10; p is an integer and is 0 to 6; y is 0 or 1; z is an integer and is 0 to 10; x+y+z+p is a positive integer or, if x+y+z+p is 0, Z is CCl 3 or CCl 2 H; n is the valence of M; and R' is a C 1-16 straight or branched chain perfluoroalkylene diradical containing a perfluorinated alicyclic ring; a C 1-16 perfluorinated aliphatic polyether diradical with repeat units selected from [CF 2 O], [CF 2 CF 2 O] and [CF 2 CF(CF 3 )O]; or, when z is 0, an aromatic diradical; so as to produce a foam having uniformity of cell size, small cell size, and high void content.