| 摘要 |
A method for producing expandable thermoplastic microspheres by polymerisation in a reaction vessel of an ethylenically unsaturated monomer or a mixture of monomers in an aqueous suspension in the presence of a condensed propellant. In the method, the monomer or monomer mixture is suspended in the aqueous medium in the presence of a powder stabiliser which consists of a salt or hydroxide of any of the metals Ca, Mg, Ba, Fe, Zn, Ni or Mn. The powder stabiliser is insoluble in the aqueous medium at the pH the aqueous medium has at the polymerisation. The aqueous medium may also contain a co-stabiliser. The method further comprises the step of washing off the powder stabiliser from the microspheres after the polymerisation by lowering the pH of the aqueous medium by the addition of acid. Alternatively, amphoteric hydroxides can also be dissolved by a pH increase. The invention also relates to microspheres produced according to the method of the invention, and to the use thereof. |
