| 摘要 |
PROBLEM TO BE SOLVED: To provide lead cyanamide with a remarkable rustproofing power while keeping the concn. of nitrogen components in waste water, which is a problem in enveironmental protection, at 120 mg/l or lower. SOLUTION: A rustproof pigment contg. crystalline lead cyanamide as the effective component, of which the relative strength (R) of two diffraction line patterns of Cu-KαX-ray diffraction spectrum defined by R=I2 /I1 (wherein R is the relative strength; I1 is the diffraction line strength at an interplanar spacing d1 of 4.99±0.05Å; and I2 , that at an interplanar spacing d2 of 2.92±0.03Å) is in the range of 0.2-2.0, can be produced at a nitrogen components concn. in waste water of 120 mg/l or lower through a process comprising the step of slurry preparation wherein a slurry of lead oxide is finely divided by a strong shearing treatment and the step of a solid-liquid reaction of the resultant slurry with an aq. calcium cyanamide soln.
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