Foamable polyvinylidene fluoride and methods

Claim 1

A method for producing a foamable polyvinylidene fluoride material suitable for forming foamed electrical wire insulation having a dielectic constant of less than about 5.0, comprising: (a) blending in an intensive powder blender a mixture of (i) a polymer selected from the group of polymers consisting essentially of a homopolymer of polyvinylidene fluoride, copolymers or terpolymers containing a major portion of vinylidene fluoride with at least one copolymerizable monomer selected from the group consisting essentially of hexafluoropropylene, trifluoroethylene, chlorotrifluoroethylene and tetrafluoroethylene and mixtures of the homopolymer, copolymer, and terpolymer; (ii) 0.05 to 5.0 percent by weight of the polymer of (i) of a nucleating agent of discreet, insoluble particles having a size distribution whose average length in the longest dimension of less than about 5 microns; (iii) 0.05 to 5.0 percent by weight of the polymer of (i) of a blowing agent having an activation temperature that is above the melting point of said polymer but below the decomposition temperature of said polymer; (iv) 0.05 to 5.0 percent by weight of the polymer of (i) of a dispersing aid selected from the group consisting of dialkyl phthalate, dibutoxyethyl phthalate, diisononyl phthalate, ditridecyl phthalate, dicyclohexyl phthalate, diphenyl alkyl adipate, methyl phthalyl ethyl glycolate, and diethylene glycol monobutyl ether; to provide a substantially homogeneous powdered mixture; (b) melt compounding the substantially homogeneous powdered mixture of (a) with high shear melt compounding means while maintaining the temperature of the mixture below the activation temperature of the blowing agent to provide a substantially homogeneous melted blend of the mixture of (a); and then (c) extruding and quenching the melted mixture of (b) to provide the foamable polyvinylidene fluoride material.

Claim 2

A method for producing a foamable polyvinylidene fluoride material suitable for forming foamed electrical wire insulation having a dielectic constant of less than about 5.0, comprising: (a) blending in an intensive powder blender a mixture of (i) a polymer selected from the group of polymers consisting essentially of a homopolymer of polyvinylidene fluoride, copolymers or terpolymers containing a major portion of vinylidene fluoride with at least one copolymerizable monomer selected from the group consisting essentially of hexafluoropropylene, trifluoroethylene, chlorotrifluoroethylene and tetrafluoroethylene and mixtures of the homopolymer, copolymer, and terpolymer; (ii) 0.05 to 5.0 percent by weight of the polymer of (i) of a nucleating agent of discreet, insoluble particles having a size distribution whose average length in the longest dimension of less than about 5 microns; (iii) 0.05 to 5.0 percent by weight of the polymer of (i) of a blowing agent having an activation temperature that is above the melting point of said polymer but below the decomposition temperature of said polymer; (iv) 0.05 to 5.0 percent by weight of the polymer of (i) of a dispersing aid selected from the group consisting of dialkyl phthalate, dibutoxyethyl phthalate, diisononyl phthalate, ditridecyl phthalate, dicyclohexyl phthalate, diphenyl alkyl adipate, methyl phthalyl ethyl glycolate, and diethylene glycol monobutyl ether; to provide a substantially homogeneous powdered mixture; (b) melt compounding the substantially homogeneous powdered mixture of (a) with high shear melt compounding means while maintaining the temperature of the mixture below the activation temperature of the blowing agent to provide a substantially homogeneous melted blend of the mixture of (a); and then (c) extruding and quenching the melted mixture of (b) to provide the foamable polyvinylidene fluoride material.