| 摘要 |
<p>Finely ground polytetrafluoroethylene (PTFE) moulding powder with average particle dia. 100, pref. 20-50 mu m, is agglomerated by subjecting it to high speed agitation in the presence of a water/hydrophobic organic liq. medium at a volumetric ratio of 2:1-1:2. The hydrophobic liq. is one of which 15 wt.% is miscible with water at the agglomeration temp. 0.5-1 litre of medium is used per kg powder. The peripheral speed of the agitating blades is pref. >5 m/sec and the agglomeration temp. 40 degrees C. They hydrophobic liq. pref. has a surface tension 45 dyne/cm at 23 degrees C and a b.pt. of 40-200 degrees C. The PTFE can have a hydrophobic filler, partic. carbon fibre of length 100-200 um, glass fibre surface treated with polyphenylene sulphide, carbon black, or chromium oxide surface treated with PTFE. The filler content is pref. 10-50 wt.%. The method can give agglomerates of average dia. 300-600 um, and with 10 wt.% having dias. >2000 mu m, and with an angle of repose 45 degrees. The agglomerated PTFE has excellent powder flowability and bulk density and gives good moulded products, being advantageously used in automatic moulding processes.</p> |
