Method for manufacturing sintered compact, sintered compact manufactured by the method and cell culture base formed from the sintered compact

Abstract

A method for manufacturing a sintered compact having high density, and a sintered compact manufactured by the manufacturing method are provided. The manufacturing method comprises the steps of preparing hydroxyapatite powder, molding a green compact, shaping the green compact, and sintering the green compact. Further, a method for manufacturing a sintered compact having high light permeability, and a sintered compact manufactured by the manufacturing method are provided. The manufacturing method comprises the steps of preparing hydroxyapatite powder, molding a green compact, shaping the green compact, primary sintering, and secondary sintering. Furthermore, a cell culture base formed from the sintered compact described above is provided, by which affinity of various cells with bone can be properly determined. Moreover, a cell culture base by which affinity of various cells with bone can be properly determined is provided. The cell culture base is mainly composed of a calcium phosphate based compound, and is highly compacted.

1 . A method for manufacturing a sintered compact, comprising the steps of:
 molding a green compact by compacting apatite powder with applying a pressure of 1 ton/cm 2  or higher thereto;   sintering the green compact by subjecting the green compact to primary sintering in an oxygen-containing atmosphere in a sintering furnace in which a volume ratio of oxygen in a gas existing in the sintering furnace is 50 vol % or more, thereby obtaining a sintered compact; and   subjecting the sintered compact to secondary sintering in an atmosphere with low level of activity.   
   
   
       2 . The method as claimed in  claim 1 , wherein the pressure is isotropically applied to the apatite powder in the step of producing the green compact. 
   
   
       3 . The method as claimed in  claim 2 , wherein the isotropic pressure is applied by hydrostatic pressing. 
   
   
       4 . The method as claimed in  claim 3 , wherein the hydrostatic pressing is carried out at a temperature in the range of 5 to 50° C. 
   
   
       5 . The method as claimed in  claim 1 , wherein the partial pressure of oxygen in the oxygen-containing atmosphere in the primary sintering step is 380 mmHg or higher. 
   
   
       6 . The method as claimed in  claim 1 , wherein the pressure of the oxygen-containing atmosphere in the primary sintering step is 900 mmHg or lower. 
   
   
       7 . The method as claimed in  claim 1 , wherein a temperature during sintering of the green compact in the primary sintering step is in the range of 850 to 1,350° C. 
   
   
       8 . The method as claimed in  claim 1 , wherein the atmosphere with low level of activity in the secondary sintering step is a nitrogen gas atmosphere or an inert gas atmosphere. 
   
   
       9 . The method as claimed in  claim 1 , wherein a temperature during sintering of the sintered compact in the secondary sintering step is in the range of 1,000 to 1,350° C. 
   
   
       10 . The method as claimed in  claim 1 , wherein the mean particle size of the apatite powder is 40 μm or less. 
   
   
       11 . The method as claimed in  claim 1 , wherein the primary and secondary sintering steps are carried out in the same sintering furnace by changing an atmosphere in the sintering furnace from the oxygen-containing atmosphere in the primary sintering step to the atmosphere with low level of activity in the secondary sintering step. 
   
   
       12 . The method as claimed in  claim 1 , wherein the apatite powder is hydroxyapatite powder. 
   
   
       13 . The method as claimed in  claim 12 , wherein the hydroxyapatite powder is prepared from a slurry which is obtained by reacting a calcium source with a phosphoric acid source using a wet synthesis method, in which at least one of the calcium source and the phosphoric acid source is used in a liquid form. 
   
   
       14 . The method as claimed in  claim 13 , wherein the calcium source contains calcium hydroxide or calcium oxide as a main ingredient, and the phosphoric acid source contains phosphoric acid as a main ingredient. 
   
   
       15 . The method as claimed in  claim 14 , wherein the slurry contains as a secondary reaction product tricalcium phosphate of 0.1 wt % or less. 
   
   
       16 . The method as claimed in  claim 15 , wherein the slurry satisfies the following condition A.
 The condition A: A part of the slurry is sampled and then subjected to compression molding at a molding pressure of 2 ton/cm 2  to form a sample green compact having a detection surface. The sample green compact is then sintered in an atmospheric air at 1,200° C. for 2 hours to obtain a sample sintered compact, and then substances which exist on the detection surface (having a surface roughness Ra of 10 μm) of the sample sintered compact are analyzed by x-ray diffraction. At this time, the intensity of a peak derived from hydroxyapatite is the largest among obtained peaks and a peak derived from tricalcium phosphate as a secondary reaction product is not observed.   
   
   
       17 . The method as claimed in  claim 14 , wherein the content of the calcium hydroxide or calcium oxide contained in the slurry is in the range of 0 to 3 wt %. 
   
   
       18 . The method as claimed in  claim 17 , wherein the slurry satisfies the following condition B.
 The condition B: A part of the slurry is sampled and then dried at 200° C. to obtain a sample. The sample is then sintered in an atmospheric air at 1,200° C. for 20 minutes to obtain a sintered sample, and then substances which exist in the sintered sample are analyzed by powder X-ray diffraction. At this time, when the intensity of a peak derived from hydroxyapatite is defined as X and the intensity of a peak derived from calcium oxide is defined as Y, X and Y satisfy the relation Y/X< 1/10.   
   
   
       19 . The method as claimed in  claim 1 , wherein the relative density of the sintered compact after the primary sintering is 99% or higher. 
   
   
       20 . The method as claimed in  claim 1 , wherein when the sintered compact is formed into a sheet form having a thickness of 0.5 mm and then thus obtained sheet form sintered compact is irradiated with light having wavelength of 300 nm, the transmittance of the light passing through the sintered compact is 10% or higher.