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Ceramic forming process
| Details |
Inventors: Jarcho, Michael; Rossetti, Michael;
Assignee: Sterling Drug Inc. (New York, NY)
Primary Examiner: Parrish; John
Assistant Examiner:
Attorney, Agent or Firm: Dupont; Paul E., Wyatt; B. Woodrow
A novel process is disclosed for producing a fracture-free shaped ceramic green body which comprises casting an aqueous suspension of hydroxylapatite, whitlockite or a mixture of these having a high water content and high drying shrinkage in an impervious mold, the cavity surfaces of which are coated with an inert water-immiscible lubricant; drying the casting under controlled conditions of temperature and humidity and removing adsorbed lubricant from the resulting dried green body. |
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DETAILED DESCRIPTION OF THE INVENTION INCLUSIVE OF THE PREFERRED EMBODIMENTS The invention sought to be patented resides in a process for forming a shaped, ceramic green body comprising a calcium phosphate selected from hydroxylapatite, whitlockite or a mixture of hydroxylapatite and whitlockite which comprises the steps of: casting an aqueous slurry of said calcium phosphate in an impervious mold, the cavity surfaces of which are coated with an inert, water-immiscible lubricant having a viscosity such that a liquid film of lubricant is formed between the mold surface and the slurry at the drying temperature of the slurry; drying the resulting molded slurry at a temperature and relative humidity such that the rate of evaporation of water from the surface of the slurry is approximately equal to the rate of diffusion of water from the interior of the slurry to the surface thereof; and removing adsorbed lubricant from the resulting dried green body.
In one of its preferred aspects the invention resides in a process for forming a fracture-free, shaped, ceramic green body comprising hydroxylapatite or a mixture of hydroxylapatite and whitlockite which can be sintered to produce a shaped article in the form of a substantially fully dense, polycrystalline ceramic as described in Jarcho U.
S.
Pat.
No.
4,097,935.
In another of its preferred aspects the present invention resides in a process for forming a fracture-free, shaped, ceramic green body comprising whitlockite which can be sintered to produce a shaped article in the form of a substantially fully dense, polycrystalline, whitlockite ceramic.
The mineral raw material for the present process, that is, a calcium phosphate either as hydroxylapatite, whitlockite or a mixture of these, is prepared as a gelatinous precipitate from aqueous solution in accordance with the procedures described hereinafter.
The precipitate is isolated from the reaction medium, usually by centrifugation followed by decantation of the supernatant, and the water content of the residual gelatinous calcium phosphate is adjusted to afford a pourable slurry or casting slip
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Liquid Purification 
