| US 7,387,834 B2 | ||
| Polytetrafluoroethylene fine powder of particular specific standard gravity, polytetrafluoroethylene formed article prepared from the same and method for preparation of the same | ||
| Tetsuo Shimizu, Settsu (Japan); Michio Asano, Settsu (Japan); Makoto Ono, Settsu (Japan); Yoshinori Nanba, Settsu (Japan); Shunji Kasai, Settsu (Japan); Shinichi Yano, Settsu (Japan); and Hiroyuki Yoshimoto, Settsu (Japan) | ||
| Assigned to Daikin Industries, Ltd., Osaka (Japan) | ||
| Appl. No. 10/485,352 PCT Filed Aug. 01, 2002, PCT No. PCT/JP02/07845 § 371(c)(1), (2), (4) Date Jan. 30, 2004, PCT Pub. No. WO03/014197, PCT Pub. Date Feb. 20, 2003. |
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| Claims priority of application No. 2001/234947 (JP), filed on Aug. 02, 2001. | ||
| Prior Publication US 2004/0197566 A1, Oct. 07, 2004 | ||
| Int. Cl. B32B 5/16 (2006.01); B05D 7/00 (2006.01) | ||
| U.S. Cl. 428—403 [427/212] | 15 Claims |
| 1. A polytetrafluoroethylene fine powder having a standard specific gravity of 2.180 to 2.225, which is obtained by contacting
polytetrafluoroethylene fine powder having a standard specific gravity of 2.180 to 2.225 with a fluorine radical source; wherein
tanδ of a sample film prepared from said fluorinated polytetrafluoroethylene fine powder at 12 GHz, which is measured by the
following method using a sample film prepared under the following conditions, is at most 2.0×10−4:(Conditions for preparing sample film)
Said PTFE fine powder is compression molded into a cylinder; A film having a thickness of 0.5 mm which is cut out from said
cylinder is baked by heating at 380° C. for 5 minutes in a convection electric furnace; Immediately thereafter, said film
is taken out into air of room temperature (25° C.) and stood to cool to room temperature at 5 to 50° C./second, to prepare
a sample film:
(Measurement method of tanδ)
Changes in resonance frequency and Q value of said prepared film are measured by a cavity resonator using a network analyzer
and tanδ at 12 GHz is calculated from the following equation:
 Symbols in the equations represent the following:
D: diameter of cavity resonator (mm)
M: length of cavity resonator (mm)
L: length of sample (mm)
c: light velocity (m/s)
ID: amount of decay (dB)
F0: resonance frequency (Hz)
F1: upper frequency when the amount of decay from the resonance point is 3dB (Hz)
F2: lower frequency when the amount of decay from the resonance point is 3dB (Hz)
ε0: dielectric constant of vacuum (H/m)
εr: specific dielectric constant of sample
μ0: magnetic permeability of vacuum (H/m)
Rs: effective surface resistance considering surface roughness of conductor cavity (Ω)
J0: −0.402759
J1: 3.83171, and
wherein said standard specific gravity is measured pursuant to ASTM D4895-89 by water displacement of a molded article formed
from the polytetrafluoroethylene fine powder.
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