Dispersing calcium carbonate in water at high pH - by addn. of an organic phosphonate and an amino organic phosphonate

摘要

Dispersion of CaCO3 in an aq. system at a pH 9 comprises adding to the system an effective amt. of (i) an organic phosphonate (MO)2-PO-R1-PO-(MO)2 in which R1 = 1-3C alkyl gp. opt. substd. by OH and/or 1-3C alkyl, and M = water soluble cation; and (ii) an amino-organic phosphonate contg. the gp. >N-CH2-PO3M2, esp. a cpd. (R3)(R4)N-CN2-PO-(OM)2 in which R3 = H or -CH3-PO3M2 and R4 = -CH2-PO3M2 if R3 = -CH2-PO3M2 or R4 = -(-(CH2)n-N)m-(PO3M2)2 if R3 = H; m = 1-3 and n = 1-6. Generally the phosphonate cpds. are added at 0.5-500 ppm to the water at a pH of 10-14, with a wt. ratio phosphonates (i):(ii) = 1:6 to 6:1. The phosphonate mixts. are esp. useful for keeping CaCO3 in suspension in aq. systems at high pH, and esp. to prevent scale formation and encrusting e.g. of appts. used in papermaking and wood pulp mfr., esp. the evaporators used for black liquor and wood pulp digestion units used in the Kraft process, etc.