Fluid highly conc. stable calcium and/or magnesium hydroxide slurry - for producing micro-flakes and granules, obtd. by slaking oxide with aq. acid and adding polyanion

摘要

Ca(OH)2 and/or Mg(OH)2 slurry (I) contg. over 60% dry substance contains an inorg. acid (poly)anion (II) and a polyanion (III) to give (I) a viscosity less than 1500, pref. 500-1500 cP. Also claimed are: (a) Ca(OH)2 and/or Mg(OH)2 microflakes (IA) with a thickness less than 0.5, pref. less than 0.3 micron and parallel upper and lower sides with an area less than 200, pref. less than 100 micron 2; and (b) Ca(OH)2 and/or Mg(OH)2 granules or granulate (IB) in the form of a mixt. of (IA). (II) is pref. SO3-. SO4(2-) or Cl(-) and (III) is derived from a (co)polymer with anionic gps. of (meth)acrylic, vinylbenzylsulphonic or acrylamino-2-methylpropanesulphonic acid or salt or 2-sulphoethyl methacrylate or salt gps. opt. with (meth)acrylate ester(s) as comonomer. The concs. are 1-50, pref. 6-50, pref. 6-50, esp. 6-30 g/l (II) and 1-50, pref. 5-30 g/l (III). In (I), at least 20%, pref. at least 30% of the Ca(OH)2 particles have a grain size of over 100 microns and over 80% a grain size of over 20 microns. (I) contains less than 5, pref. less than 1% Mg(OH)2 w.r.t. Ca(OH)2+ Mg(OH)2. (IB) has an average grain size of over 20, pref. over 50 microns, with over 80% of the particles larger than 20 microns and esp. a grain size of over 100, partic. over 250 microns. (I) is prepd. by slaking CaO and/or MgO with an aq. soln. contg. (II) and adding (III) before, during or at the end of the slaking reaction. The reaction mixt. is stirred and kept below 30, pref. below 20 deg. C. Its viscosity is regulated, pref. by adding CaO to a viscosity of 300-1200 cP; or by slaking with aq. (II) soln. until the viscosity is 300-1200 cP, adding (III) to reduce the viscosity and then adding CaO and/or MgO to a viscosity of 300-1200 cP. (IA) are produced by sepg. the medium into a solid and liq. phase and opt. drying, milling and opt. drying the solid; and (IB) by sepg. the phases and opt. drying. ADVANTAGE - In spite of its very high solids content, (I) has good stability, i.e. high resistance to sedimentation, which facilitates transport and use.