Molding powder comprising agglomerated particles of PTFE compounds

Claim 2

An agglomerated powder suitable for use in a molding powder containing particles of a non-melt-fabricable tetrafluoroethylene polymer having a specific surface area of 0.5 to 4 m 2 /g as measured by the BET method the agglomerates thereof consisting of: (a) said tetrafluoroethylene polymer consisting of 0.001 to 1% by weight of copolymerized units of a perfluorinated vinyl ether of the formula CP.sub.2 ═CF--O--X in which X denotes a perfluoroalkyl radical having 1 to 4 C atoms or a radical of the formula ##STR2## and n is 0 to 1, and of copolymerized units of tetrafluoroethylene, (b) a particulate form having an average particle diameter d 50 of 150 to 1,000 μm which has been built up from primary particles having an average particle diameter d 50 of 20 to 80 μm and which possess a spheroidal form and a uniform, dense surface, and said agglomerated power having: (c) a bulk density of 800 to 1000 g/l, (d) a power flow time of 8.0 to 4.0 seconds/50 g at an average agglomerate diameter d 50 of 150 to 250 μm and of 4.0 to 1.5 seconds/50 g at an agglomerate diameter d 50 of 250 to 1,000 μm, (e) a particle stability of 8.0 to 4.0 seconds/50 g at an average agglomerate diameter d 50 of 150 to 250 μm and of 4.0 to 1.8 seconds/50 g at an agglomerate diameter d 50 of 250 to 1,000 μm, and (f) a proportion of 50 to 75% by weight of agglomerates with a particle size diameter which is at least 0.7 times and not more than 1.3 times the average particle diameter d 50 , (g) wherein a molded article prepared from said agglomerated powder has a welding factor of 0.6 to 1.0, and (h) the pore count, measured at a voltage of 5,000 V as electrical defects on a veneer-cut film 200 μm thick prepared from the agglomerated powder, is not more than 15 to 0 pores/m 2 .

Claim 3

An agglomerated powder as claimed in claim 1 in which said tetrafluoroethylene polymer consists of 0.01 to 0.5 % by weight of copolymerized units of a perfluorinated vinyl ether of the formula CF.sub.2 ═CF--O--X in which X denotes a perfluoroalkyl radical having 1 to 4 C atoms or a radical of the formula ##STR3## and n is 0 to 1, and of copolymerized units of tetrafluoroethylene.

Claim 4

An agglomerated powder as claimed in claim 1, the agglomerates of which have an average particle diameter d 50 of 150 to 800 μm which have been built up from primary particles having an average particle diameter d 50 of 20 to 80 μm and which possess a spheroidal form and a uniform, dense surface.

Claim 5

An agglomerated powder as claimed in claim 1, which has a flow time of 6.0 to 3.0 seconds/50 g at an average agglomerate diameter d 50 of 150 to 250 μm and of 3.0 to 1.5 seconds/50 g at an agglomerate diameter d 50 of 250 to 1,000 μm.

Claim 6

An agglomerated powder as claimed in claim 1 which has a particle stability of 6.0 to 3.0 seconds/50 g at an average agglomerate diameter d 50 of 150 to 250 μm and of 3.0 to 1.8 seconds/50 g at an agglomerate diameter of d 50 of 250 to 1,000 μm.

Claim 7

An agglomerated powder as claimed in claim 1, wherein a molded article prepared from said agglomerated powder has a welding factor of 0.8 to 1.0.

Claim 8

An agglomerated powder as claimed in claim 1, wherein the pore count, measured at a voltage of 5,000 V as electrical defects on a veneer-cut film 200 μm thick prepared from the agglomerated powder, is 6 to 0 pores/m 2 .

Claim 9

An agglomerated powder as claimed in claim 1, wherein the copolymerized units of the perfluorinated vinyl ether are units of perfuoro-(n-propyl-vinyl)ether.

Claim 10

An agglomerated tetrafluoroethylene co-polymer powder having a specific surface area as measured by the BET method, of 0.5 to 4 m 2 /g, suitable for use in a molding powder, the agglomerates of which were obtained by continuously introducing a polytetrafluorethylene co-polymer primary powder having an average particle diameter d 50 of 20 to 80 μm, together with a liquid medium into a staged cascade process in which (1) said primary powder is pre-agglomerated to an average particle diameter d 50 of about 100 to about 400 μm, (2) the resulting pre-agglomerated primary powder is passed through an agglomeration stage in which the resulting pre-agglomerated powder is further agglomerated to a tertiary powder having tertiary particles of an average diameter d 50 of 150 to 1000 μm, and (3) said tertiary powder is passed through and discharged continually from an after-treatment stage in which the final formation of the particle shape takes place without a further essential change in the average particle size; said agglomerates having said average particle diameter d 50 of 150 to 1000 μm, and being built up essentially from said primary powder, and possessing a spherical form and an uniform, dense surface; said co-polymer of said agglomerated tetrafluoroethylene copolymer powder having been obtained by copolymerizing polytetrafluoroethylene with 0.001 to 1% by weight of a perfluorinated vinyl ether of the formula CF.sub.2 ═CF--O--X in which X denotes a perfluoroalkyl radical having 1 to 4 C atoms or a radical of the formula ##STR4## and n is 0 to 1; and said agglomerated tetrafluoroethylene copolymer power having: (c) a bulk density of 800 to 1000 g/l, (d) a powder flow time of 8.0 to 4.0 seconds/50 g at an average agglomerate diameter d 50 of 150 to 250 μm and of 4.0 to 1.5 seconds/50 g at an agglomerate diameter d 50 of 250 to 1,000 μm, (e) a particle stability of 8.0 to 4.0 seconds/50 g at an average agglomerate diameter d 50 of 150 to 250 μm and of 4.0 to 1.8 seconds/50 g at an agglomerate diameter d 50 of 250 to 1,000 μm, and (f) a proportion of 50 to 75% by weight of agglomerates with a particle size diameter which is at least 0.7 times and not more than 1.3 times the average particle diameter d 50 , (g) wherein a molded article prepared from said agglomerated tetrafluoroethylene copolymer powder has a welding factor of 0.6 to 1.0, and (h) the pore count, measured at a voltage of 5,000 V as electrical defects on a veneer-cut film 200 μm thick prepared from the agglomerated tetrafluoroethylene copolymer powder, is not more than 15 to 0 pores/m 2 .

Claim 11

An agglomerated tetrafluoroethylene co-polymer powder having a specific surface area as measured by the BET method, of 0.5 to 4 m 2 /g, suitable for use in a molding powder, the agglomerates of which were obtained by continuously introducing a polytetrafluorethylene co-polymer primary powder having an average particle diameter d 50 of 20 to 80 μm, together with a liquid medium into a staged cascade process in which (1) said primary powder is pre-agglomerated to an average particle diameter d 50 of about 100 to about 400 μm, (2) the resulting pre-agglomerated primary powder is passed through an agglomeration stage in which the resulting pre-agglomerated powder is further agglomerated to a tertiary powder having tertiary particles of an average diameter d 50 of 150 to 1000 μm, and (3) said tertiary powder is passed through and discharged continually from an after-treatment stage in which the final formation of the particle shape takes place without a further essential change in the average particle size; said agglomerates having said average particle diameter d 50 of 150 to 1000 μm, and being built up essentially from said primary powder, and possessing a spherical form and an uniform, dense surface; said co-polymer of said agglomerated tetrafluoroethylene copolymer powder having been obtained by copolymerizing polytetrafluoroethylene with 0.001 to 1% by weight of a perfluorinated vinyl ether of the formula CF.sub.2 ═CF--O--X in which X denotes a perfluoroalkyl radical having 1 to 4 C atoms or a radical of the formula ##STR4## and n is 0 to 1; and said agglomerated tetrafluoroethylene copolymer power having: (c) a bulk density of 800 to 1000 g/l, (d) a powder flow time of 8.0 to 4.0 seconds/50 g at an average agglomerate diameter d 50 of 150 to 250 μm and of 4.0 to 1.5 seconds/50 g at an agglomerate diameter d 50 of 250 to 1,000 μm, (e) a particle stability of 8.0 to 4.0 seconds/50 g at an average agglomerate diameter d 50 of 150 to 250 μm and of 4.0 to 1.8 seconds/50 g at an agglomerate diameter d 50 of 250 to 1,000 μm, and (f) a proportion of 50 to 75% by weight of agglomerates with a particle size diameter which is at least 0.7 times and not more than 1.3 times the average particle diameter d 50 , (g) wherein a molded article prepared from said agglomerated tetrafluoroethylene copolymer powder has a welding factor of 0.6 to 1.0, and (h) the pore count, measured at a voltage of 5,000 V as electrical defects on a veneer-cut film 200 μm thick prepared from the agglomerated tetrafluoroethylene copolymer powder, is not more than 15 to 0 pores/m 2 .

Claim 12

A granular, agglomerated form of non-melt-fabricable polytetrafluoroethylene copolymer primary particles, said agglomerated form being useful in molding powders, said primary particles having been obtained by suspension polymerization of tetrafluorethylene adn 0.001 to 1% by weight of perfluorinated vinyl ether and having a specific surface area of 0.5 to 4 m 2 /g, as measured by the BET method, and a particle diameter d 50 of 20 to 80 μm, said perfluorinated vinyl ether having the formula CF.sub.2 ═CF--O--X in which X denotes a perfluoroalkyl radical having 1 to 4 C atoms or a radical of the formula ##STR5## the agglomerates of said granular, agglomerated form of the said primary particles having a spheroidal form and a uniform, dense surface, and a mass of the agglomerates having: (a) an average particle diameter d 50 of 150 to 1000 μm, the agglomerates of said average particle diameter d 50 having been built up from the primary particles having an average particle diameter d 50 of 20 to 80 μm; (b) a bulk density of 800 to 1000 g/l; (c) a powder flow time of 8.0 to 4.0 seconds/50 g at an average agglomerate diameter d 50 of 150 to 250 μm and of 4.0 to 1.5 seconds/50 g at an agglomerate diameter d 50 of 1,000 μm; (d) a particle stability of 8.0 to 4.0 seconds/50 g at an average agglomerate diameter d 50 of 150 to 250 μm and of 4.0 to 1.8 seconds/50 g at an agglomerate diameter d 50 to 1,000 μm; and (e) a proportion of 50 to 75% by weight of agglomerates with a particle size diameter which is at least 0.7 times and not more than 1.3 times the average particle diameter d 50 ; a molded article prepared from a molding powder consisting of said agglomerates having a welding factor of 0.6 to 1.0; and a veneer-cut film 200 μm thick prepared from a molding powder consisting of said agglomerates having a pore count, measured at a voltage of 5,000 v as electrical defects in said film, which is not more than 15 pores/m 2 to 0 pores/m 2 .

Claim 13

A granular, agglomerated form of non-melt-fabricable polytetrafluoroethylene copolymer primary particles, said agglomerated form being useful in molding powders, said primary particles having been obtained by suspension polymerization of tetrafluorethylene adn 0.001 to 1% by weight of perfluorinated vinyl ether and having a specific surface area of 0.5 to 4 m 2 /g, as measured by the BET method, and a particle diameter d 50 of 20 to 80 μm, said perfluorinated vinyl ether having the formula CF.sub.2 ═CF--O--X in which X denotes a perfluoroalkyl radical having 1 to 4 C atoms or a radical of the formula ##STR5## the agglomerates of said granular, agglomerated form of the said primary particles having a spheroidal form and a uniform, dense surface, and a mass of the agglomerates having: (a) an average particle diameter d 50 of 150 to 1000 μm, the agglomerates of said average particle diameter d 50 having been built up from the primary particles having an average particle diameter d 50 of 20 to 80 μm; (b) a bulk density of 800 to 1000 g/l; (c) a powder flow time of 8.0 to 4.0 seconds/50 g at an average agglomerate diameter d 50 of 150 to 250 μm and of 4.0 to 1.5 seconds/50 g at an agglomerate diameter d 50 of 1,000 μm; (d) a particle stability of 8.0 to 4.0 seconds/50 g at an average agglomerate diameter d 50 of 150 to 250 μm and of 4.0 to 1.8 seconds/50 g at an agglomerate diameter d 50 to 1,000 μm; and (e) a proportion of 50 to 75% by weight of agglomerates with a particle size diameter which is at least 0.7 times and not more than 1.3 times the average particle diameter d 50 ; a molded article prepared from a molding powder consisting of said agglomerates having a welding factor of 0.6 to 1.0; and a veneer-cut film 200 μm thick prepared from a molding powder consisting of said agglomerates having a pore count, measured at a voltage of 5,000 v as electrical defects in said film, which is not more than 15 pores/m 2 to 0 pores/m 2 .

Claim 14

A molding power consisting of said granular, agglomerated form of said primary particles as claimed in claim 10.

Claim 15

A molding powder consisting of the agglomerated powder of claim 1.

Claim 16

A molding powder consisting of the agglomerated tetrafluoroethylene copolymer powder of claim 9.