TWI487684B - Method for preparing a hardened calcium sulfate dihydrate block and use thereof - Google Patents

Description

Preparation method of calcium sulfate dihydrate hardened block and use thereof

The present invention relates to a method for preparing a calcium sulphate dihydrate from a paste of calcium sulphate hemihydrate powder and an aqueous solution, and relates to the use of the hardened dihydrate in orthopedic treatment or dental treatment (for example, root canal treatment) Method of calcium sulfate.

For many orthopedic applications, calcium sulfate dihydrate is not an ideal graft material due to its insufficient compressive strength and/or too high dissolution rate compared to calcium phosphate graft materials. Furthermore, one of the major drawbacks of calcium sulphate hemihydrate cement is that it has traditionally been short and unworkable during working hours and curing times. Therefore, researchers have tried a number of different methods (but have not succeeded) to develop calcium sulphate hemihydrate cement having a suitable working time and cure time and the resulting calcium sulphate dihydrate having the desired compressive strength.

The main object of the present invention is to provide a bone cement formulation comprising a calcium sulphate hemihydrate powder as a main powder portion and an aqueous solution to make the paste formed from the formulation suitable for work and from the paste. The calcium sulphate dihydrate block has improved mechanical strength.

Another object of the present invention is to provide a method of preparing a calcium sulphate dihydrate using the bone cement formulation of the present invention.

Another object of the present invention is to provide a method of treating a patient in need of orthopedic treatment or root canal treatment.

Preferred embodiments of the invention include, but are not limited to, the following items:

A method of preparing a hard block of calcium sulphate dihydrate comprising mixing a calcium sulphate hemihydrate powder with an aqueous solution containing a phosphate ion to form a paste, wherein the aqueous solution has a pH of less than 10.

2. The method according to item 1, wherein the alkaline compound is not added to the aqueous solution, the calcium sulfate hemihydrate powder or a paste thereof to adjust the pH thereof.

3. The method of item 1, wherein the aqueous solution has a temperature below 50 °C prior to the mixing.

4. The method of item 3, wherein the mixing is carried out at a temperature below 50 °C.

5. The method of item 3, wherein the powder and the paste of the aqueous solution have a temperature of less than 50 °C.

6. The method of item 1, wherein the aqueous solution, the calcium sulphate hemihydrate powder or the paste thereof is not heated to raise the temperature to be equal to or higher than 50 °C.

7. The method of item 6, wherein the aqueous solution has a phosphate ion concentration of less than 1.0 M.

8. The method of item 7, wherein the concentration is from 0.01 M to 0.5 M.

9. The method of item 1, wherein the mixing is carried out at a liquid to powder ratio of from 0.20 cc/g to 0.60 cc/g.

10. The method of item 9, wherein the liquid to powder ratio is from 0.30 cc/g to 0.50 cc/g.

11. The method of item 1, wherein the aqueous solution is (NH ₄ ) ₃ PO ₄ , (NH ₄ ) ₂ HPO ₄ , NH ₄ H ₂ PO ₄ , K ₃ PO ₄ , K ₂ HPO ₄ , KH ₂ PO ₄ An aqueous solution of Na ₃ PO ₄ , Na ₂ HPO ₄ , NaH ₂ PO ₄ , H ₃ PO ₄ or a mixture thereof.

12. The method of item 11, wherein the aqueous solution is an aqueous solution of (NH ₄ ) ₃ PO ₄ , (NH ₄ ) ₂ HPO ₄ , NH ₄ H ₂ PO ₄ or a mixture thereof.

13. The method of item 1, wherein the aqueous solution or the calcium sulphate hemihydrate powder additionally comprises living cells, growth factors or drugs.

14. The method of item 1, wherein the calcium sulphate hemihydrate powder is an alpha-type calcium sulphate hemihydrate powder.

15. The method of clause 1, further comprising introducing the paste to a hole or cavity and allowing the paste to solidify in situ to form a calcium sulphate dihydrate block in the hole or cavity.

16. The method of item 1, further comprising shaping the paste in a mold and removing the mold to form a hard block of calcium sulfate dihydrate.

17. The method of clause 16, further comprising pressurizing the paste in the mold to cure a portion of the liquid from the paste prior to curing of the paste, such that the liquid to powder ratio of the paste is reduced .

18. The method of item 17, wherein the pressure applied to the paste in the mold is from about 1 MPa to 500 MPa, preferably from 100 MPa to 500 MPa.

19. The method of item 16, further comprising impregnating the lumps with an immersion liquid for a period of time such that the compressive strength of the resulting impregnated mass removed from the immersion liquid is increased as compared to the compressive strength of the lumps not subjected to the immersion treatment. .

20. The method of item 19, wherein the immersion liquid is a phosphate-containing solution.

21. The method of item 20, wherein the phosphate-containing solution is (NH ₄ ) ₃ PO ₄ , (NH ₄ ) ₂ HPO ₄ , NH ₄ H ₂ PO ₄ , K ₃ PO ₄ , K ₂ HPO ₄ , KH An aqueous solution of ₂ PO ₄ , Na ₃ PO ₄ , Na ₂ HPO ₄ , NaH ₂ PO ₄ or H ₃ PO ₄ .

22. The method of clause 20, wherein the phosphate-containing solution has a phosphate concentration of from about 0.1 M to about 6 M, preferably from about 1 M to about 3 M.

23. The method of item 20, wherein the impregnation is carried out at a temperature of about 0 °C.

24. The method of item 1, further comprising mixing a pore former with the powder or with the paste; forming the paste in a mold; removing the mold to form the pore former buried therein a slab of calcium sulphate dihydrate; and a hard block of calcium sulphate dihydrate embedded in the porogen is immersed in the immersion liquid to dissolve the porogen in the immersion liquid, and pores are generated in the slab of calcium sulphate dihydrate, so that A porous lumps are formed.

25. The method of item 24, wherein the pore former is selected from the group consisting of LiCl, KCl, NaCl, MgCl ₂ , CaCl ₂ , NaIO ₃ , KI, Na ₃ PO ₄ , K ₃ PO ₄ , Na ₂ CO ₃ , amino acid-sodium salt, amino acid-potassium salt, glucose, polysaccharide, fatty acid-sodium salt, fatty acid-potassium salt, potassium acid tartrate (KHC ₄ H ₄ O ₆ ), Potassium carbonate, potassium glucuronide (KC ₆ H ₁₁ O ₇ ), potassium tartrate-sodium (KNaC ₄ H ₄ O ₆ ‧ ₄ H ₂ O), potassium sulfate (K ₂ SO ₄ ), sodium sulfate, sodium lactate and mannose alcohol.

26. The method of item 24, wherein the immersion liquid is an acidic aqueous solution, an alkaline aqueous solution, a physiological solution, an organic solvent or water.

27. The method of clause 26, wherein the immersion solution has a phosphate-containing solution having a phosphate concentration of from about 0.1 M to about 6 M, preferably from about 1 M to about 3 M.

28. The method of item 27, wherein the phosphate-containing solution is (NH ₄ ) ₃ PO ₄ , (NH ₄ ) ₂ HPO ₄ , NH ₄ H ₂ PO ₄ , K ₃ PO ₄ , K ₂ HPO ₄ , KH An aqueous solution of ₂ PO ₄ , Na ₃ PO ₄ , Na ₂ HPO ₄ , NaH ₂ PO ₄ or H ₃ PO ₄ .

29. The method of item 27, wherein the immersion liquid is water.

30. The method of item 24, further comprising impregnating the porous lumps with an immersion liquid for a period of time such that the compressive strength of the impregnated porous lumps removed from the immersion liquid and the compression of the porous lumps not subjected to the immersion treatment The strength is improved compared to the strength.

31. The method of item 30, wherein the immersion liquid is a phosphate-containing solution.

32. The method of item 31, wherein the phosphate-containing solution is (NH ₄ ) ₃ PO ₄ , (NH ₄ ) ₂ HPO ₄ , NH ₄ H ₂ PO ₄ , K ₃ PO ₄ , K ₂ HPO ₄ , KH An aqueous solution of ₂ PO ₄ , Na ₃ PO ₄ , Na ₂ HPO ₄ , NaH ₂ PO ₄ or H ₃ PO ₄ .

33. The method of clause 31, wherein the phosphate-containing solution has a phosphate concentration of from about 0.1 M to about 6 M, preferably from about 1 M to about 3 M.

34. The method of clause 27, further comprising impregnating the porous lumps in a suspension of living cells or a solution of growth factors or drugs to deposit the living cells, growth factors or drugs on the porous lumps.

The method of item 24, wherein the porous lumps have a porosity of 50 to 90% by volume.

36. A method of treating a patient comprising mixing a calcium sulphate hemihydrate powder with an aqueous solution containing phosphate ions to form a paste; and filling the bone of the patient with the paste as needed for the treatment In a hole or hole, the paste solidifies in the hole or cavity.

37. The method of clause 36, wherein the treatment is orthopedic or dental treatment.

38. A method of treating a patient comprising mixing a calcium sulphate hemihydrate powder with an aqueous solution containing phosphate ions to form a paste; forming a lumps of calcium sulphate dihydrate from the syrup; and The lumps are implanted into the patient.

39. The method of clause 38, wherein the treatment is orthopedic or dental treatment.

40. The method of clause 39, wherein the implanting comprises breaking the lumps into crumbs and filling the holes or holes in the bone of the patient with the crumbs.

41. The method of clause 39, wherein the forming of the calcium sulphate dihydrate comprises forming the paste in a mold and removing the mold to form a calcium sulphate dihydrate.

42. The method of clause 41, wherein the forming of the calcium sulphate dihydrate block further comprises pressurizing the paste in the mold to cure a portion of the liquid from the paste prior to curing of the paste, such that the paste The liquid to powder ratio is reduced.

43. The method of item 42, wherein the pressure applied to the paste in the mold is from about 1 MPa to 500 MPa, preferably from 100 MPa to 500 MPa.

44. The method of item 41, wherein the forming of the calcium sulphate dihydrate syrup further comprises impregnating the lumps with the immersion liquid for a period of time such that the resulting impregnated mass removed from the immersion liquid has a compressive strength and a lumps that have not undergone the immersion treatment. The compressive strength is improved compared to that.

45. The method of item 44, wherein the immersion liquid is a phosphate-containing solution.

46. The method of item 45, wherein the phosphate-containing solution is (NH ₄ ) ₃ PO ₄ , (NH ₄ ) ₂ HPO ₄ , NH ₄ H ₂ PO ₄ , K ₃ PO ₄ , K ₂ HPO ₄ , KH An aqueous solution of ₂ PO ₄ , Na ₃ PO ₄ , Na ₂ HPO ₄ , NaH ₂ PO ₄ or H ₃ PO ₄ .

47. The method of clause 45, wherein the phosphate-containing solution has a phosphate concentration of from about 0.1 M to about 6 M, preferably from about 1 M to about 3 M.

48. The method of item 45, wherein the impregnation is carried out at a temperature of about 0 °C.

49. The method of clause 38, further comprising mixing a pore former with the powder or with the paste, wherein the forming of the calcium sulphate dihydrate comprises forming the paste in a mold; removing the mold Forming the hard block of calcium sulphate dihydrate buried in the pore-forming agent; and immersing the hard block of calcium sulphate dihydrate in which the pore-forming agent is buried in the immersion liquid to dissolve the pore-forming agent in the immersion liquid, The pores are formed in the calcium sulphate hard block to form a porous lumps, and the implant contains the porous lumps implanted into the patient under the treatment.

50. The method of clause 49, wherein the implanting comprises crushing the porous lumps into crumbs and filling the holes or holes in the bones of the patient with the crumbs.

51. The method of item 50, wherein the pore former is selected from the group consisting of LiCl, KCl, NaCl, MgCl ₂ , CaCl ₂ , NaIO ₃ , KI, Na ₃ PO ₄ , K ₃ PO ₄ , Na ₂ CO ₃ , amino acid-sodium salt, amino acid-potassium salt, glucose, polysaccharide, fatty acid-sodium salt, fatty acid-potassium salt, potassium acid tartrate (KHC ₄ H ₄ O ₆ ), Potassium carbonate, potassium glucuronide (KC ₆ H ₁₁ O ₇ ), potassium tartrate-sodium (KNaC ₄ H ₄ O ₆ ‧ ₄ H ₂ O), potassium sulfate (K ₂ SO ₄ ), sodium sulfate, sodium lactate and mannose alcohol.

52. The method of item 50, wherein the immersion liquid is an acidic aqueous solution, an alkaline aqueous solution, a physiological solution, an organic solvent or water.

53. The method of clause 52, wherein the immersion fluid is a phosphate-containing solution having a phosphate concentration of from about 0.1 M to about 6 M, preferably from about 1 M to about 3 M.

54. The method of item 53, wherein the phosphate-containing solution is (NH ₄ ) ₃ PO ₄ , (NH ₄ ) ₂ HPO ₄ , NH ₄ H ₂ PO ₄ , K ₃ PO ₄ , K ₂ HPO ₄ , KH An aqueous solution of ₂ PO ₄ , Na ₃ PO ₄ , Na ₂ HPO ₄ , NaH ₂ PO ₄ or H ₃ PO ₄ .

55. The method of item 53, wherein the immersion liquid is water.

56. The method of item 50, further comprising impregnating the lumps with an immersion liquid for a period of time such that the compressive strength of the impregnated porous lumps removed from the immersion liquid is comparable to the compressive strength of the porous lumps not subjected to the immersion treatment. More than that.

57. The method of item 56, wherein the immersion liquid is a phosphate-containing solution.

58. The method of item 57, wherein the phosphate-containing solution is (NH ₄ ) ₃ PO ₄ , (NH ₄ ) ₂ HPO ₄ , NH ₄ H ₂ PO ₄ , K ₃ PO ₄ , K ₂ HPO ₄ , KH An aqueous solution of ₂ PO ₄ , Na ₃ PO ₄ , Na ₂ HPO ₄ , NaH ₂ PO ₄ or H ₃ PO ₄ .

59. The method of clause 57, wherein the phosphate-containing solution has a phosphate concentration of from about 0.1 M to about 6 M, preferably from about 1 M to about 3 M.

60. The method of clause 49, further comprising impregnating the porous lumps in a suspension of living cells or a solution of growth factors or drugs to deposit the living cells, growth factors or drugs on the porous lumps.

The method of item 49, wherein the porous lumps have a porosity of 50 to 90% by volume.

The present invention provides a technique for extending the working time and curing time of a calcium sulphate hemihydrate paste by mixing a calcium sulphate hemihydrate powder and an aqueous solution containing a phosphate ion, so that the paste is suitable for operation and The calcium sulphate dihydrate obtained from the paste has improved mechanical strength. The bone cement formulation provided in accordance with the present invention consists of calcium sulfate hemihydrate powder, an aqueous solution containing phosphate ions, and one or more optional functional components such as living cells, growth factors, drugs or pore forming agents.

The invention will be better understood by the following examples, which are merely illustrative and are not intended to be limited in any way.

Example: Chemicals used in the examples:

Preparation of calcium sulfate cement paste

The calcium sulfate cement paste is prepared by mixing an appropriate amount of CSH powder and a hardening solution (for example, diammonium phosphate or dipotassium hydrogen phosphate) by a suitable liquid/powder ratio (for example, 0.35 cc/g). ) prepared.

Preparation of dense block of calcium sulfate

The appropriate amount of CSH powder and hardening solution are uniformly mixed in a ball mill at a suitable L/P ratio to form a calcium sulfate cement paste.

Prior to complete hardening, the paste is placed in a mold under a suitable pressure (for example, 450 Kgf) to extrude a portion of the hardening solution from the paste to form a hardened dense mass. After removing from the mold, a set of hardened samples were placed in a moisture-proof container for 1 day. Another set of samples is immersed in an impregnation solution (for example, (NH ₄ ) ₂ HPO ₄ or K ₂ HPO ₄ ) at a suitable temperature (for example, 37 ° C) for a period of time (for example, 1 day) Then, it was dried in an oven at 50 ° C for 1 day.

Preparation of calcium sulphate porous lumps

Mixing the appropriate amount of CSH powder, powder, and the appropriate KCl/CSH ratio (for example, 1:1 or 1.5:1 by weight) and a suitable liquid/powder ratio (for example, 0.35 cc/g) The pore-forming particles (for example, KCl) and the hardening solution are formed to form a KCl/CSH cement paste.

Prior to complete hardening, the KCl/CSH cement paste is placed in a mold under a suitable pressure (for example, 450 Kgf) to squeeze a portion of the hardening solution out of the paste to form a hardened dense mass. After the removal from the mold, the hardened dense block sample is immersed in deionized water for a period of time (for example, 3 days) to enable the pore-forming particles to be washed out of the dense block to form a porous slab of calcium sulfate. It was then dried in an oven at 50 ° C for 1 day.

A set of porous hard block samples are further immersed in an impregnation solution (for example, (NH ₄ ) ₂ HPO ₄ or K ₂ HPO ₄ ) at a suitable temperature (for example, 37 ° C or 4 ° C) for a period of time to make the porous The strength of the lumps was increased and then dried in an oven at 50 ° C for 1 day. To remove the remaining impregnation solution from within the pores, the impregnated porous sample is rinsed in deionized water for a period of time (for example, 3 days).

Further, another set of samples was treated by immersing in a CaCl ₂ solution for a period of time (for example, 3 days) to further enhance the strength of the porous samples.

Compressive strength (CS) test

In order to measure the CS of the hardened cement, after mixing for 1 minute, the cement paste was placed in a 6 mm diameter, 12 mm deep cylindrical stainless steel mold for 30 minutes under a pressure of 0.7 MPa. After removal from the mold, the hardened cement sample was immersed in a Hanks' physiological solution maintained at 37<0>C and agitated daily to assist in maintaining a uniform ion concentration. After immersion, the sample was removed from the solution for the CS test if the sample was still wet. The CS test was performed using a desktop mechanical tester (Shimadzu AGS-500D, Tokyo, Japan) at a crosshead speed of 1.0 mm/min. The test method is in accordance with ASTM 451-99a.

Working time (WT) / curing time (ST) measurement

The working time of the cement paste is determined when the cement paste is no longer processable. The curing time of the cement paste was measured according to the standard method described in ISO 1566 for zinc phosphate cement for teeth. The cement was considered to be cured when a 400 gm weight on a Vical needle with a 1 mm diameter tip could not cause a perceptible circular indentation on the cement surface.

pH measurement

The pH change at the initial stage (during curing) was measured using a pH acidity meter (Suntex Instruments SP20004, Taipei, Taiwan), and the pH acidity meter was buried in the cement paste immediately after the powder and the solidified liquid were mixed. The first degree was taken 1 minute after mixing. Continue to measure until the paste is almost cured. The degree is collected every 30 seconds until 30 minutes after mixing. The degree is then collected every 60 seconds.

The pH change of the Hanks' solution immersed in the cement paste sample was monitored using the same pH acidity meter. After the powder and the solidified solution were mixed for 5 minutes, 2 g of a cement paste was taken, and the cement paste was immersed in 20 ml of a Hanks' solution having a pH of 7.05. The solution was maintained at 37 ° C throughout the test and continued to stir to help maintain a uniform ion concentration of the solution.

Composition of Hanks' solution (Hench, 1971)

Porosity measurement

The porosity of a plurality of different samples was measured according to the method of ASTM C830-00 (2006), "Standard Test Methods for Apparent Porosity, Liquid Absorption, Apparent Specific Gravity, and Bulk Density of Refractory Shapes by Vacuum Pressure".

result Group A - Paste Table A-1. Working time, curing time and CS (n=6) of calcium sulfate cement prepared from acid hardening solution (L/P=0.35)

Table A-2. Working time, curing time and CS (n=6) of calcium sulfate cement prepared from alkaline hardening solution (L/P=0.35)

Summary (Tables A-1 and A-2):

1. All solutions containing phosphate (whether acidic or basic) result in moderate WT/ST (about 5 to 10 minutes), while all solutions that do not contain phosphate (whether acidic or basic) cause too short WT/ST (for surgical treatment of paste injection).

(Note: too short WT/ST does not have enough time for preparation and/or surgical treatment)

2. All solutions containing phosphate (whether acidic or basic) are much higher than the CS-free solution.

3. The phosphate concentration of 0.0375 M results in the highest CS value, but the CS values obtained from all three concentrations (0.01875 to 0.075 M) are acceptable.

Table A-3. Effect of (NH ₄ ) ₂ concentration of HPO ₄ hardening solution on WT and ST of calcium sulfate cement

* Increase the L/P ratio to promote mixing

Table A-4. Effect of concentration of K ₂ HPO ₄ hardening solution on WT and ST of calcium sulfate cement

* Increase the L/P ratio to promote mixing

Summary (Tables A-3 and A-4):

1. (NH ₄ ) ₂ HPO ₄ solution containing a phosphate concentration of up to 1.0 M gives moderate WT/ST.

2. A moderately WT/ST was obtained with a K ₂ HPO ₄ solution containing a phosphate concentration of at most 0.1 M. When the concentration of K ₂ HPO ₄ is higher than 0.1 M, WT/ST becomes too long (in terms of surgical treatment of paste injection).

(Note: too long WT/ST indicates low initial strength and the paste is easily dispersed by contact with body fluid/blood before hardening).

Table A-5. Effect of (NH ₄ ) ₂ concentration of HPO ₄ hardening solution on CS of calcium sulfate cement (L/P=0.35) (n=6)

* Increase the L/P ratio to 0.40 to promote mixing

to sum up:

1. The phosphate concentration of 0.0375 M results in the highest CS value, but a moderate CS can still be obtained at a phosphate concentration of 0.1 M.

2. When the phosphate concentration is 0.75 M, the CS value becomes lower than half of the CS value of 0.0375 M.

Table A-6. Effect of pH on WT and ST of calcium sulfate cement (n=6)

to sum up:

1. The WT/ST value is very sensitive to the pH of the hardening solution.

2. When a phosphate-containing solution (whether (NH ₄ ) ₂ HPO ₄ or K ₂ HPO ₄ ) has a pH above about 11, the WT/ST will be significantly reduced and become unacceptable.

Table A-7. Effect of pH on CS of Calcium Sulfate Cement [Note: (NH ₄ ) ₂ HPO ₄ concentration: 0.0375 M, pH = 7.9; K ₂ HPO ₄ concentration: 0.0375 M, pH = 8.4. Add HCl to lower the pH and add NaOH to increase the pH) (n=6)

to sum up:

1. The CS value is very sensitive to the pH of the hardening solution.

2. When the (NH ₄ ) ₂ HPO ₄ hardening solution has a pH above about 11, the CS value is greatly reduced. When its pH reached 13.0, the CS value was reduced by 68% from its highest CS.

3. When the K ₂ HPO ₄ hardening solution has a pH above about 12.0, the CS value is greatly reduced. When its pH reached 13.0, the CS value was reduced by 67% from its highest CS.

Table A-8. Initial pH Changes of Calcium Sulfate Cement Paste Prepared from 0.0375 M(NH ₄ ) ₂ HPO ₄ Hardening Solution

to sum up:

After 15 minutes of mixing, the pH of the paste (mixed CSH and 0.0375 M(NH ₄ ) ₂ HPO ₄ ) was slowly increased to a range between 6.5 and 7.0, tissue/cell acceptable range.

Table A-9. pH change of Hanks' solution in which calcium sulfate cement prepared from a 0.0375 M(NH ₄ ) ₂ HPO ₄ hardening solution was immersed.

to sum up:

The pH of the Hanks' solution is always between 6 and 7, with a tissue/cell acceptable range. After 14 days, the pH became nearly neutral.

Table A-10. CS change from deionized water, 0.0375 M(NH ₄ ) ₂ HPO ₄ and 0.0375 MK ₂ HPO ₄ hardening solution, followed by immersion in Hanks' solution over several periods of calcium sulfate cement (n=6 ).

to sum up:

1. The calcium sulfate cement prepared from deionized water has a CS value that is much lower than the other two phosphate-containing hardening solutions.

2. The CS value of the calcium sulfate cement prepared from the phosphate-containing hardening solution is moderately and slowly attenuated when stored in the Hanks' solution for a long period of time.

3. The calcium sulfate cement prepared from the (NH ₄ ) ₂ HPO ₄ hardening solution is particularly excellent in terms of maintaining the CS value when stored in the Hanks' solution. After 30 days, its CS value decreased by less than 20% compared to the 1-day value.

Table A-11. Effect of tartaric acid addition on CS of calcium sulphate cement prepared from 0.0375 M(NH ₄ ) ₂ HPO ₄ hardening solution

to sum up:

1. The calcium sulfate cement prepared from the (NH ₄ ) ₂ HPO ₄ /tartaric acid hardening solution has a CS value 18% higher than the CS value of the calcium sulfate cement prepared from (NH ₄ ) ₂ HPO ₄ .

Group B - dense block [Note: For pre-formed lumps, “WT/ST” is no longer a problem and K ₂ HPO ₄ is chosen as the hardening solution for the study] Table B-1. Sclerosing solution concentration of K ₂ HPO ₄ to block object densified calcium sulphate (L / P = 0.35) Effect of CS

to sum up:

1. A calcium sulfate dense block prepared from a K ₂ HPO ₄ hardening solution containing a phosphate concentration of 0.01875 M to 0.15 M has a high CS value. When the concentration is higher than 0.20 M, CS drops to an unacceptably low value.

2. The concentration of 0.075 M results in the highest CS value.

Table B-2. CS values of calcium sulfate dense block samples prepared by 0.075 MK ₂ HPO ₄ hardening solution (L/P = 0.35) followed by immersion treatment in different impregnation solutions for 1 day. (n=6)

to sum up:

1. A dense block sample prepared from a 0.075 MK ₂ HPO ₄ hardening solution has a much higher CS value in a phosphate-containing solution than after immersion in a phosphate-free solution for 1 day. [Note: HANKS' solution is a phosphate-containing solution]

2. Whether the impregnation solution is a Hanks' solution or a K ₂ HPO ₄ solution, a lower impregnation temperature (0 ° C) results in a higher CS than the impregnation temperature (37 ° C).

Table B-3. CS variation of calcium sulfate dense block samples prepared from 0.075 MK ₂ HPO ₄ hardening solution (L/P = 0.35) and then immersed in Hanks' solution for different periods. (n=6)

to sum up:

1. When immersed in Hanks' solution, CS of dense block samples prepared by K ₂ HPO ₄ hardening solution (regardless of concentration of 0.0375 M or 0.075 M) moderately decays slowly. After immersion for 16 days, these CS values still maintained about 70% of their original CS value.

Group C - porous lumps Preparation of calcium sulphate porous lumps

The calcium sulphate porous lumps used in the study were prepared by mixing CSH and KCl powder (1:1 by weight) with 0.075 MK ₂ HPO ₄ hardening solution at an L/P ratio of 0.35 cc/g to form KCl/CSH. Cement paste. Prior to complete hardening, the KCl/CSH cement paste was placed in a mold under a pressure of 450 Kgf to extrude a portion of the hardening solution out of the paste to form a hardened dense mass. After the removal from the mold, the hardened dense block sample is immersed in deionized water for 3 angels. The pore-forming particles can be washed out of the dense block to form a porous slab of calcium sulfate, followed by drying in an oven at 50 ° C. day. The X-ray diffraction results indicated that the KCl phase was completely dissolved after 3 days of immersion in deionized water at 37 ° C or 4 ° C (the KCl peak disappeared from the XRD pattern).

A set of porous lumps samples were further immersed in an impregnation solution ((NH ₄ ) ₂ HPO ₄ or K ₂ HPO ₄ ) at 37 ° C or 4 ° C for a period of time to increase the strength of the porous lumps, followed by 50 ° C Dry in an oven for 1 day.

Another set of samples was further treated by immersing in a CaCl ₂ solution for 1 to 3 days to further enhance the strength of the porous samples.

Table C-1. CS values of calcium sulfate porous lumps samples prepared by immersing in deionized at 37 ° C or 4 ° C to remove KCl particles.

to sum up:

1. The CS value of the porous lumps sample immersed in 4 ° C deionized water (4.8 MPa) was 71% higher than the CS value of the porous lumps sample immersed in 37 ° C deionized water (2.8 MPa).

Table C-2. CS values of the impregnated porous lumps under different impregnation conditions. (The KCl particles are dissolved by immersing in deionized water at 4 ° C for 3 days)

to sum up:

1. In both impregnation solutions, the CS value increases significantly as the concentration of the impregnation solution increases.

2. After 1 day of immersion, CS was increased by 46% in 2M (NH ₄ ) ₂ HPO ₄ and by 29% in 2M K ₂ HPO ₄ impregnation solution. After 3 days of immersion, the CS increased by as much as 113% in the 2M K ₂ HPO ₄ impregnation solution.

Further enhance CS through CaCl ₂ treatment

In order to further enhance the strength of the porous hard block samples, a calcium sulfate porous hard block sample having a CS value of 5.0 MPa (control) was immersed in a CaCl ₂ solution under different conditions.

Table C-3. CS values of porous slab samples of calcium sulphate treated by immersion in a CaCl ₂ solution under different conditions.

result:

1. After treatment with CaCl ₂ , the CS is greatly improved under all conditions.

Found that the maximum lift of the CS process 2. 3 days 2M CaCl ₂ (from 5.0 MPa to 21.1 MPa, 322% increase), and 3M CaCl ₂ in 3 days (from 5.0 MPa to 25.1 MPa, 402% increase).

Claims (26)

A method for preparing a hard block of calcium sulphate dihydrate, characterized in that a calcium sulphate hemihydrate powder and an aqueous solution containing phosphate ions are mixed to form a paste, wherein the aqueous solution has a pH lower than 10, wherein the aqueous solution has The phosphate ion concentration of 0.01 M to 1.0 M, and the mixing is carried out at a liquid to powder ratio of 0.20 cc/g to 0.60 cc/g. The method of claim 1, wherein the alkaline compound is not added to the aqueous solution, the calcium sulfate hemihydrate powder or a paste thereof during, before or after the mixing. The method of claim 1, wherein the aqueous solution or the calcium sulfate hemihydrate powder has a temperature of less than 50 ° C before the mixing, and the mixing is carried out at a temperature lower than 50 ° C. The method of claim 3, wherein the aqueous solution has a phosphate ion concentration of less than 0.5M. The method of claim 1, wherein the liquid to powder ratio is from 0.30 cc/g to 0.50 cc/g. The method of claim 1, wherein the aqueous solution is (NH ₄ ) ₃ PO ₄ , (NH ₄ ) ₂ HPO ₄ , NH ₄ H ₂ PO ₄ , K ₃ PO ₄ , K ₂ HPO ₄ , KH ₂ PO _4. An aqueous solution of Na ₃ PO ₄ , Na ₂ HPO ₄ , NaH ₂ PO ₄ , H ₃ PO ₄ or a mixture thereof. The method of claim 6, wherein the aqueous solution is an aqueous solution of (NH ₄ ) ₃ PO ₄ , (NH ₄ ) ₂ HPO ₄ , NH ₄ H ₂ PO ₄ or a mixture thereof. The method of claim 1, wherein the calcium sulphate hemihydrate powder is an alpha-type calcium sulphate hemihydrate powder. The method of claim 1, further comprising introducing the paste to a hole or cavity and allowing the paste to solidify in situ to form a calcium sulphate dihydrate block in the hole or cavity. The method of claim 1, further comprising forming the paste in a mold and removing the mold to form a calcium sulphate dihydrate. The method of claim 10, further comprising pressurizing the paste in the mold to cure a portion of the liquid from the paste prior to curing of the paste, such that the paste has a liquid to powder ratio The pressure applied to the paste in the mold is reduced from 1 MPa to 500 MPa. The method of claim 10, further comprising impregnating the lumps with the immersion liquid for a period of time such that the compressive strength of the impregnated block obtained by removing the immersion liquid is compared with the compressive strength of the lumps not subjected to the immersion treatment. improve. The method of claim 12, wherein the immersion liquid is a phosphate-containing solution having a phosphate concentration of 0.1 M to 6 M. The method of claim 13, wherein the phosphate-containing solution is (NH ₄ ) ₃ PO ₄ , (NH ₄ ) ₂ HPO ₄ , NH ₄ H ₂ PO ₄ , K ₃ PO ₄ , K ₂ HPO ₄ , An aqueous solution of KH ₂ PO ₄ , Na ₃ PO ₄ , Na ₂ HPO ₄ , NaH ₂ PO ₄ or H ₃ PO ₄ . The method of claim 12, wherein the impregnation is carried out at a temperature of 0 °C. The method of claim 1, further comprising mixing a pore former with the powder or the paste; forming the paste in a mold; removing the mold to form the pore former buried therein a hard block of calcium sulphate dihydrate; and immersing the hard block of calcium sulphate dihydrate in which the pore former is buried in the immersion liquid to dissolve the porogen in the immersion liquid, and producing fine pores in the slab of calcium sulphate dihydrate, In order to form a porous hard block having a porosity of 50 to 90% by volume. The method of claim 16, wherein the pore former is selected from the group consisting of LiCl, KCl, NaCl, MgCl ₂ , CaCl ₂ , NaIO ₃ , KI, Na ₃ PO ₄ , K ₃ PO ₄ , Na ₂ CO ₃ , amino acid-sodium salt, amino acid-potassium salt, glucose, polysaccharide, fatty acid-sodium salt, fatty acid-potassium salt, potassium acid tartrate (KHC ₄ H ₄ O ₆ ) , potassium carbonate, potassium glucuronide (KC ₆ H ₁₁ O ₇ ), potassium tartrate-sodium (KNaC ₄ H ₄ O ₆ . ₄ H ₂ O), potassium sulfate (K ₂ SO ₄ ), sodium sulfate, sodium lactate and nectar Sugar alcohol. The method of claim 16, wherein the immersion liquid is a phosphate-containing solution having a phosphate concentration of 0.1 M to 6 M. The method of claim 18, wherein the phosphate-containing solution is (NH ₄ ) ₃ PO ₄ , (NH ₄ ) ₂ HPO ₄ , NH ₄ H ₂ PO ₄ , K ₃ PO ₄ , K ₂ HPO ₄ , An aqueous solution of KH ₂ PO ₄ , Na ₃ PO ₄ , Na ₂ HPO ₄ , NaH ₂ PO ₄ or H ₃ PO ₄ . The method of claim 16, wherein the immersion liquid is water. The method of claim 16, further comprising impregnating the porous lumps with an immersion liquid for a period of time such that the compressive strength of the impregnated porous lumps obtained from the immersion liquid is removed from the porous lumps that have not undergone the immersion treatment. The compression strength is improved. The method of claim 21, wherein the immersion liquid is a phosphate-containing solution having a phosphate concentration of 0.1 M to 6 M. The method of claim 22, wherein the phosphate-containing solution is (NH ₄ ) ₃ PO ₄ , (NH ₄ ) ₂ HPO ₄ , NH ₄ H ₂ PO ₄ , K ₃ PO ₄ , K ₂ HPO ₄ , An aqueous solution of KH ₂ PO ₄ , Na ₃ PO ₄ , Na ₂ HPO ₄ , NaH ₂ PO ₄ or H ₃ PO ₄ . For example, the method of claim 10, which additionally includes the hard block Crushed into scraps. The method of claim 16, further comprising crushing the porous lumps into chips. A method for preparing a hard block of calcium sulphate dihydrate comprising mixing a calcium sulphate hemihydrate powder and an aqueous solution containing a phosphate ion to form a paste, wherein the aqueous solution has a pH of less than 10, and the aqueous solution has a 0.01 M to 1.0 The phosphate ion concentration of M and the mixture were carried out at a liquid to powder ratio of 0.20 cc/g to 0.60 cc/g and all of the calcium sulphate powder was used.