Claims
- 1. 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.sup.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 .dbd.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.sub.50 of 150 to 1,000 .mu.m which has been built up from primary particles having an average particle diameter d.sub.50 of 20 to 80 .mu.m 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.sub.50 of 150 to 250 .mu.m and of 4.0 to 1.5 seconds/50 g at an agglomerate diameter d.sub.50 of 250 to 1,000 .mu.m,
- (e) a particle stability of 8.0 to 4.0 seconds/50 g at an average agglomerate diameter d.sub.50 of 150 to 250 .mu.m and of 4.0 to 1.8 seconds/50 g at an agglomerate diameter d.sub.50 of 250 to 1,000 .mu.m, 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.sub.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 .mu.m thick prepared from the agglomerated powder, is not more than 15 to 0 pores/m.sup.2.
- 2. 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 .dbd.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.
- 3. An agglomerated powder as claimed in claim 1, the agglomerates of which have an average particle diameter d.sub.50 of 150 to 800 .mu.m which have been built up from primary particles having an average particle diameter d.sub.50 of 20 to 80 .mu.m and which possess a spheroidal form and a uniform, dense surface.
- 4. 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.sub.50 of 150 to 250 .mu.m and of 3.0 to 1.5 seconds/50 g at an agglomerate diameter d.sub.50 of 250 to 1,000 .mu.m.
- 5. 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.sub.50 of 150 to 250 .mu.m and of 3.0 to 1.8 seconds/50 g at an agglomerate diameter of d.sub.50 of 250 to 1,000 .mu.m.
- 6. 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.
- 7. 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 .mu.m thick prepared from the agglomerated powder, is 6 to 0 pores/m.sup.2.
- 8. 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.
- 9. An agglomerated tetrafluoroethylene co-polymer powder having a specific surface area as measured by the BET method, of 0.5 to 4 m.sup.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.sub.50 of 20 to 80 .mu.m, 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.sub.50 of about 100 to about 400 .mu.m, (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.sub.50 of 150 to 1000 .mu.m, 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.sub.50 of 150 to 1000 .mu.m, 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 .dbd.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.sub.50 of 150 to 250 .mu.m and of 4.0 to 1.5 seconds/50 g at an agglomerate diameter d.sub.50 of 250 to 1,000 .mu.m,
- (e) a particle stability of 8.0 to 4.0 seconds/50 g at an average agglomerate diameter d.sub.50 of 150 to 250 .mu.m and of 4.0 to 1.8 seconds/50 g at an agglomerate diameter d.sub.50 of 250 to 1,000 .mu.m, 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.sub.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 .mu.m thick prepared from the agglomerated tetrafluoroethylene copolymer powder, is not more than 15 to 0 pores/m.sup.2.
- 10. 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.sup.2 /g, as measured by the BET method, and a particle diameter d.sub.50 of 20 to 80 .mu.m, said perfluorinated vinyl ether having the formula
- CF.sub.2 .dbd.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.sub.50 of 150 to 1000 .mu.m, the agglomerates of said average particle diameter d.sub.50 having been built up from the primary particles having an average particle diameter d.sub.50 of 20 to 80 .mu.m;
- (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.sub.50 of 150 to 250 .mu.m and of 4.0 to 1.5 seconds/50 g at an agglomerate diameter d.sub.50 of 1,000 .mu.m;
- (d) a particle stability of 8.0 to 4.0 seconds/50 g at an average agglomerate diameter d.sub.50 of 150 to 250 .mu.m and of 4.0 to 1.8 seconds/50 g at an agglomerate diameter d.sub.50 to 1,000 .mu.m; 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.sub.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 .mu.m 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.sup.2 to 0 pores/m.sup.2.
- 11. A molding power consisting of said granular, agglomerated form of said primary particles as claimed in claim 10.
- 12. A molding powder consisting of the agglomerated powder of claim 1.
- 13. A molding powder consisting of the agglomerated tetrafluoroethylene copolymer powder of claim 9.
Priority Claims (1)
Number |
Date |
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Kind |
3135598 |
Sep 1981 |
DEX |
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Parent Case Info
This is a continuation of our copending application Ser. No. 885,247, filed July 14, 1986, which is a continuation of application Ser. No. 738,532, filed May 24, 1985 abandoned, which is a continuation of application Ser. No. 563,357, filed Dec. 20, 1983 abandoned, which is a division of application Ser. No. 413,716 filed Sept. 1, 1982 now U.S. Pat. No. 4,439,385.
US Referenced Citations (2)
Number |
Name |
Date |
Kind |
4379900 |
Sulzbach |
Apr 1983 |
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4408007 |
Kuhls |
Oct 1983 |
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Divisions (1)
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Number |
Date |
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Parent |
413716 |
Sep 1982 |
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Continuations (3)
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Number |
Date |
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885247 |
Jul 1986 |
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Parent |
738532 |
May 1985 |
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Parent |
563357 |
Dec 1983 |
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