Claims
- 1. A process for preparing a stable inorganic pigment which comprises adding an aqueous solution of sodium silicate having a concentration of sodium silicate of from 1 to 10 wt % as SiO.sub.2 and an aqueous solution of one or more compounds simultaneously to an aqueous slurry of pigment having a pigment concentration of about 50 to 300 g/l to react the two solutions and thereby form and deposit a continuous non-porous coating of amorphous silica on the surface of said pigment, wherein said reaction is carried out at a temperature of at least about 60.degree. C. to 100.degree. C. for 1 to 6 hours such that the pH of the slurry is controlled constant at a predetermined pH within the range of from 7 to 11, said compounds having a solubility of at least about 0.01 g/100 g water at 20.degree. C., providing a pH of at least about 1.0 in a 3.0 wt % aqueous solution and being selected from the group consisting of aliphatic carboxylic acids, oxycarboxylic acids, an ester or aldehyde of said above acids, a sodium salt of hydrogen sulfate or hydrogen carbonate, and ammonium salt of a halogen acid or a sulfurous oxyacid and ethylene carbonate, wherein said pigment is selected from the group consisting of ultramarine and bronze powder.
- 2. The process of claim 1, wherein said ammonium salt is ammonium chloride, ammonium sulfate, ammonium hydrogen sulfate, ammonium sulfite or ammonium hydrogen sulfite.
- 3. The process of claim 1, wherein said pH of the slurry does not vary more than .+-.0.5 from said predetermined pH.
- 4. The process of claim 1, wherein said predetermined pH is within the range of 8 to 11.
- 5. The process of claim 1, wherein said reaction is completed within 1 to 4 hours.
- 6. The process of claim 1, wherein the compound which reacts with the sodium silicate solution to form a silica sol is selected from the group consisting of ethylene glycol diacetate, ethylene glycol monoacetate, methyl acrylate, glutardialdehyde, acetic acid and tartaric acid.
Priority Claims (8)
Number |
Date |
Country |
Kind |
53-162203 |
Dec 1978 |
JPX |
|
53-162204 |
Dec 1978 |
JPX |
|
54-20876 |
Feb 1979 |
JPX |
|
54-20877 |
Feb 1979 |
JPX |
|
54-42563 |
Apr 1979 |
JPX |
|
54-42564 |
Apr 1979 |
JPX |
|
54-46085 |
Apr 1979 |
JPX |
|
54-46086 |
Apr 1979 |
JPX |
|
Parent Case Info
This is a continuation of application Ser. No. 108,609, filed Dec. 31, 1979.
US Referenced Citations (13)
Foreign Referenced Citations (2)
Number |
Date |
Country |
46-9555 |
Mar 1971 |
JPX |
49-8019 |
Mar 1974 |
JPX |
Non-Patent Literature Citations (1)
Entry |
Iler, R. K.-The Colloid Chemistry of Silica and Silicates-Pub. by Cornell Univ., N.Y. (1955), pp. 91-92. |
Continuations (1)
|
Number |
Date |
Country |
Parent |
108609 |
Dec 1979 |
|