darvan 1 naphtalenesulfonic acid formaldehyde condensate sodium salt 30 g finely ground antimony oxide ultrafine grade with typical average particle size of 0 2 u03bcm 0 4 u03bcm ao 750 g was slowly added under fast stirring 400 600 rpm the stirrer was slowed 50 150 rpm and a 1 5 solution of rhodopol 23 xanthan gum cas n o 11138 66 2 with preserving agents u2014 1 methyl paraben methyl 4 hydroxybenzoate cas n o 99 76 3 and 0 5 propyl paraben propyl 4 hydroxybenzoate cas n o 94 13 3 were added 115 ml the mixed pbbma ao suspension was prepared as follows to a slowly stirred 40 rpm suspension of pbbma 750 ml at 25 u00b0 c 30 u00b0 c obtained as described in example 1 was added the ao suspension 250 ml as described above after five minutes stirring was stopped yielding a homogeneous mixture in a 0 5 l 4 necked round bottom flask fitted with mechanical stirrer reflux condenser thermometer dropping funnel and nitrogen inlet were charged 1 4 gr sds sodium dodecyl sulfate and 100 ml of water the flask was immersed in an oil bath and heated to 70 u00b0 c with continuous stirring 250 rpm nitrogen was introduced under the surface of the liquid after 1 hr the nitrogen inlet was raised above the surface of the liquid and 0 15 gr of k 2 s 2 o 8 were added five minutes later.