Porous material

Abstract

A porous material of a medical implant material, the material body of which is a hierarchical porous material with multilevel pore cavities graded according a pore size of the material. The permeability of the hierarchical porous material is more than 0.5×10.sup.−9 m.sup.2. The hierarchical porous material can fully ensure blood flow, achieve transmission of adequate nutrients and growth factors, migration of cells, and remove cell fragments and stimulate tissue growth, and has various functions, thus fully satisfying the requirements of human tissue regeneration.

Claims

1. A porous material, comprising: a material body, wherein the material body is a hierarchical porous material with pore cavities at multilevel graded according to a pore size of the porous material; and wherein the material body of the hierarchical porous material is constituted by the pore cavities at each level graded according to the pore size of the porous material and cavity walls at each level surrounding to form the pore cavities; wherein a cavity wall of an upper-level pore cavity formed by surrounding a three-dimensional space is constituted by a porous material of a lower-level pore cavity such that the lower-level pore cavity are positioned within the cavity wall of the upper-level pore cavity, wherein porous materials at each same level of the material body is a continuous structure, and a maximum outer boundary of the continuous structure formed by the same level of porous material is equivalent to a maximum space boundary of the entire material body; and the permeability of the porous material is more than 0.7×10.sup.−9 m.sup.2; and wherein the porous material is porous tantalum.

2. The porous material according to claim 1, wherein pore cavities of the porous material at each same level in the hierarchical porous material are uniform in size and are uniformly distributed in the material body; and the permeability of the hierarchical porous material is more than 0.76×10.sup.−9 m.sup.2.

3. The porous material according to claim 1, wherein when a number of the levels of the hierarchical porous material is three, a pore size of smallest-level pore cavities is a nanoscale, and a pore size of second-level pore cavities is between a pore size of largest-level pore cavities and the pore size of the smallest-level pore cavities; the permeability of the hierarchical porous material is more than 1.5×10.sup.−9 m.sup.2.

4. The porous material according to claim 1, wherein the porous material is used as a medical implant material, wherein porous materials at each same level of the material body is a continuous structure, and a maximum outer boundary of the continuous structure formed by the same level of porous material is equivalent to a maximum space boundary of the entire material body; and the permeability of the hierarchical porous material is more than 0.7×10.sup.−9 m.sup.2.

5. The porous material according to claim 4, wherein pore cavities of the porous material at each same level in the hierarchical porous material are uniform in size and are uniformly distributed in the material body; and the permeability of the hierarchical porous material is more than 0.76×10.sup.−9 m.sup.2.

6. The porous material according to claim 5, wherein when a number of the levels of the hierarchical porous material is three, a pore size of smallest-level pore cavities is a nanoscale, and a pore size of second-level pore cavities is between a pore size of largest-level pore cavities and the pore size of the smallest-level pore cavities; the permeability of the hierarchical porous material is more than 1.5×10.sup.−9 m.sup.2.

Description

DETAILED DESCRIPTION

(1) The embodiments of the present invention will be described below. On the premise of the technical solution of the present invention, the detailed implementation and specific operation process are given by the embodiments. However, the scope of the present invention is not limited to the following embodiments.

(2) Embodiments of the present invention are described in detail below.

Embodiment 1

(3) The porous material of this embodiment is porous β-tricalcium phosphate ceramic with a secondary pore structure. An average pore size of large pore cavities is 200 μm, an average pore size of small pore cavities is 560 nm, and the total porosity is 75%. The porosity formed by the large pore cavities is 66% and the porosity formed by the small pore cavities is 9%. The method for preparing porous β-tricalcium phosphate ceramic includes the following steps: mixing the ρ-tricalcium phosphate ceramic powder with an average particle size of 160 nm, urea with an average particle size of 710 nm, and ethyl cellulose with an average particle size of 280 μm according to a volume ratio of 25:10:72 to obtain a mixture, pressing the mixture into a compact green body, performing a vacuum sintering, and then carrying out conventional subsequent treatment according to a β-tricalcium phosphate ceramic process to obtain a porous β-tricalcium phosphate ceramic with secondary structure.

(4) According to National Standard GB/T 1969-1996 method for testing permeability of porous ceramic, a water flow exhaust device is used, and a cylindrical porous β-tricalcium phosphate ceramic sample with a thickness of 10 mm and a cross-sectional diameter of 10 mm is used to be tested at 20° C. The kinematic viscosity of water is 1.006×10.sup.−6 (m.sup.2/s). The sample is placed in a clamp to compress the sample, water is introduced from the bottom of the clamp to exhaust the gas inside the clamp completely, the sample clamp is placed in a container with an overflow port. After the water flows out of the overflow port and reaches stability, the time and flow rate will be recorded. The permeability μ is calculated according to the formula μ=4Qηδ/(πd.sup.2tΔP), where Q is the amount of water that has permeated the sample during the test, η is the viscosity of the test water, d is the diameter of the cylindrical sample, δ is the thickness of the cylindrical sample, t is the test time, and ΔP is the pressure difference between two sides of the sample. The permeability of the above-mentioned porous β-tricalcium phosphate with secondary pores is measured to be 0.51×10.sup.−9 m.sup.2. The material is used as a bone implant material.

Embodiment 2

(5) The porous material of this embodiment is porous carbonyl apatite with a secondary pore structure. The pore sizes of large pore cavities and small pore cavities thereof are the same as those in Embodiment 1, and the total porosity is 78%. The porosity formed by the large pore cavities is 68% and the porosity formed by the small pore cavities is 10%. The preparation method is similar to that of Embodiment 1.

(6) A flat sample having the size of 20 mm×20 mm×1 mm is prepared from the above-mentioned porous carbonyl apatite sample with secondary pores. A FEINova Nano SEM 400 field emission scanning electron microscope is used for observation. 40 pore cavities are selected randomly from each of the two levels of poles, the interconnection conditions of the pore cavities on the prepared plane with surrounding pore cavities and the interconnection conditions of the internal of the pore cavities with the lower pore cavities are observed. The number of each pore cavity interconnecting adjacent pore cavities is recorded. A result shows that the number of large pore cavities that interconnect more than four adjacent pore cavities is 36 (accounting for 90% of the pore cavities of this level) and the number of small pore cavities that interconnect more than four adjacent pore cavities is 35 (accounting for 87.5% of the pore cavities of this level).

(7) The permeability of the porous carbonyl apatite is measured to be 0.53×10.sup.−9 m.sup.2 using the same method as that in Embodiment 1.

(8) Due to the proper proportion of the pore-forming agent, the interconnectivity of each level of pore cavities is ensured, and the effect that the proportion of the pore cavities interconnecting more than four adjacent pore cavities is more than 85% in the pore cavities in this level is achieved, so that the material has a higher permeability index.

(9) The material is used as a bone implant material.

Embodiment 3

(10) The porous material of this embodiment is porous f-tricalcium phosphate ceramic, with a secondary pore structure. The average pore size of large pore cavities is 250 μm, the average pore size of small pore cavities is 600 nm, and the total porosity is 82%. The porosity formed by the large pore cavities is 73% and the porosity formed by the small pore cavities is 9%. The small pore cavities are positioned on the cavity walls of the large pore cavities, and the preparation method is as follows:

(11) (1) Material Preparation

(12) Using β-tricalcium phosphate ceramic powder with an average particle size of 160 nm as a raw material, using urea with an average particle size of 690 nm as a pore-forming agent for the smallest level of pore cavities of the porous β-tricalcium phosphate ceramic to be prepared, and using biological glass powder with an average particle size of 690 nm as a binder, and preparing a slurry according to the volume ratio of β-tricalcium phosphate ceramic powder:urea:biological glass powder:distilled water of 1:3:1:13.

(13) Using polyester foam with a pore size of 600 μm-950 μm, filling the slurry in the polyester foam uniformly by a foam impregnation method to form a green body, drying the green body, and then crushing the green body to obtain mixed grains with a grain size of 50 μm-70 μm containing the raw material, the pore-forming agent and the polyester foam.

(14) (2) Mixing the mixed grains and ethyl cellulose with an average particle size of 330 μm according to a volume ratio of 1:3.5 to obtain a mixture, putting the mixture into a closed mould and pressing the mixture into a compact green body.

(15) (3) Vacuum sintering the compact green body, carrying out a conventional subsequent treatment according to a β-tricalcium phosphate ceramic process on the sintered green body to obtain the porous β-tricalcium phosphate ceramic with a secondary structure.

(16) The crushed polyester foam particles in the mixed grains form channels during sintering, which increases the interconnectivity of the material.

(17) The interconnectivity is tested by the same method as the method in Embodiment 2. Results show that the number of large pore cavities that interconnect more than four adjacent pore cavities is 37 (accounting for 92.5% of the pore cavities of this level) and the number of small pore cavities that interconnect more than four adjacent pore cavities is 36 (accounting for 90% of the pore cavities of this level).

(18) The permeability of the porous β-tricalcium phosphate is measured to be 0.55×10.sup.−9 m.sup.2 using the same method as that in Embodiment 1.

(19) The material is used as a bone implant material.

Embodiment 4

(20) The porous material of this embodiment is porous carbonyl apatite with a secondary pore structure. The structure and preparing method are similar to those in Embodiment 3. The average pore size of large pore cavities is 310 μm, the average pore size of small pore cavities is 700 nm, and the total porosity is 86%. The porosity formed by the large pore cavities is 77% and the porosity formed by the small pore cavities is 9%. The interconnectivity is tested by the same method as the method in embodiment 2. Results show that the number of large pore cavities that interconnect more than four adjacent cavities is 37 (accounting for 92.5% of the pore cavities of this level) and the number of small pore cavities that interconnect more than four adjacent cavities is 36 (accounting for 90% of the pore cavities of this level).

(21) The permeability of the porous carbonyl apatite is measured to be 0.58×10.sup.−9 m.sup.2 using the same method as that in Embodiment 1. The material is used as a bone implant material.

Embodiment 5

(22) The porous material of this embodiment is porous titanium with a secondary pore structure, which is similar in structure and preparation method to that of Embodiment 3, and the porous materials at each level is a continuous structure, and a maximum outer boundary of the porous material at each level is equivalent to the space boundary of the entire material body. The average pore size of large pore cavities is 600 μm, the average pore size of small pore cavities is 750 nm, and the total porosity is 86%. The porosity formed by the large pore cavities is 76% and the porosity formed by the small pore cavities is 10%. The preparation method is as follows:

(23) (1) Material Preparation

(24) Using titanium powder with an average particle size of 110 nm as a raw material, using methylcellulose with an average particle size of 830 nm as a pore-forming agent for the smallest level of pore cavities of porous titanium to be prepared, using starch with an average particle size of 830 nm as a binder, preparing a slurry according to the volume ratio of titanium powder:methylcellulose:starch:distilled water of 1:3.5:1:13.

(25) Using polyester foam with a pore size of 550 μm-850 μm, filling the slurry in the polyester foam uniformly by a foam impregnation method to form a green body, drying the green body, and then crushing the green body to obtain mixed grains with a grain size of 40 μm-60 μm containing the raw material, the pore-forming agent and the polyester foam.

(26) (2) Mixing the mixed grains and ethyl cellulose with an average particle size of 680 μm according to a volume ratio of 1:4 uniformly to obtain a mixture, putting the mixture into a closed mould and pressing the mixture into a compact green body.

(27) (3) Vacuum sintering the compact green body; carrying out a conventional subsequent treatment according to a titanium process on the sintered green body to obtain the porous titanium with a secondary structure.

(28) The interconnectivity is tested by the same method as the method in Embodiment 2. Results show that the number of large pore cavities that interconnect more than four adjacent cavities is 37 (accounting for 92.5% of the pore cavities of this level) and the number of small pore cavities that interconnect more than four adjacent cavities is 36 (accounting for 90% of the pore cavities of this level).

(29) The permeability of the above-mentioned porous titanium with secondary pores is measured to be 0.71×10.sup.−9 m.sup.2 using the same method as that in Embodiment 1. The material is used as a bone implant material.

Embodiment 6

(30) The medical implant porous material of this embodiment is porous titanium with a secondary pore structure, which is similar to that of Embodiment 4, the difference is that during preparation, the particle size error of the methylcellulose and the ethyl cellulose is controlled within 10%, so that the prepared porous titanium has a uniform pore size and small error. The mixed grains and ethyl cellulose are repeatedly stirred, fully and uniformly mixed, so that the pore cavities are uniformly distributed. The interconnectivity is tested by the same method as the method in Embodiment 2. Results show that the number of large pore cavities that interconnect more than four adjacent cavities is 37 (accounting for 92.5% of the pore cavities of this level) and the number of small pore cavities that interconnect more than four adjacent cavities is 37 (accounting for 92.5% of the pore cavities of this level).

(31) The permeability of the porous titanium with secondary pores is measured to be 0.77×10.sup.−9 m.sup.2 using the same method as that in Embodiment 1. The material is used as a bone implant material.

Embodiment 7

(32) The medical implant porous material of this embodiment is porous tantalum with a tertiary pore structure, the cavity walls of the first-level pore cavities (i.e., the largest-level pore cavities) are provided with second-level pore cavities which are distributed evenly and interconnected, and the cavity walls of the second-level pore cavities are provided with third-level pore cavities (i.e., the smallest-level pore cavities) which are distributed evenly and interconnected. The pore cavities at each level are interconnected. The porous tantalum at each level is a continuous structure, and a maximum outer boundary of the porous tantalum at each level is equivalent to the space boundary of the entire material body. An average pore size of third-level pore cavities is 64 nm, an average pore size of second-level pore cavities is 96 μm, an average of first-level pore cavities is 600 μm, and the total porosity is 93%. The porosity formed by the first-level pore cavities is 80%, the porosity formed by the second-level pore cavities is 8%, and the porosity formed by the third-level pore cavities is 5%.

(33) The preparation method is:

(34) (1) Material Preparation

(35) Using tantalum powder with an average particle size of 20 nm as a raw material, using starch with an average particle size of 75 nm as a pore-forming agent for the smallest level of pore cavities of porous tantalum to be prepared, using stearate with an average particle size of 75 nm as a binder, preparing a slurry according to the volume ratio of tantalum powder:starch:stearate:distilled water of 1:4:1:11.

(36) Using polyester foam with a pore size of 550 μm-820 μm, filling the slurry in the polyester foam uniformly by a foam impregnation method to form a green body, drying the green body, and then crushing the green body to obtain mixed grains with a grain size of 60 μm-80 μm containing the raw material, the pore-forming agent and the polyester foam.

(37) (2) fully and uniformly mixing the mixed grains and ammonium chloride with an average particle size of 110 μm according to a volume ratio of 1:4 to obtain a mixture, pouring the mixture into a three-dimensional interconnecting polyester foam with an average strut diameter of 710 μm and an average pore size of 670 μm, and then putting the polyester foam into a closed mould to press the polyester foam into a compact green body.

(38) (3) Vacuum sintering the compact green body, carrying out a conventional subsequent treatment according to tantalum material process on the sintered green body to obtain the porous tantalum with a tertiary structure.

(39) The interconnectivity is tested by the same method as the method in Embodiment 2. Results show that the number of pore cavities that interconnect more than four adjacent cavities is as follows. The number of the first-level pore cavities is 38 (accounting for 95% of the pore cavities of this level), the number of the second-level pore cavities is 37 (accounting for 92.5% of the pore cavities of this level), and the number of the third-level pore cavities is 37 (accounting for 92.5% of the pore cavities of this level).

(40) The permeability of the above-mentioned porous tantalum with tertiary pores is measured to be 1.52×10.sup.−9 m.sup.2 using the same method as that in Embodiment 1. The material is used as a bone implant material.

Embodiment 8

(41) The medical implant porous material of this embodiment is porous tantalum with a tertiary pore structure, which is similar to that of Embodiment 8, but during preparation, in step (2), a three-dimensional interconnecting polyester foam with an average pore size of 600 μm is used, and the total porosity of the prepared porous tantalum is 95%, the porosity formed by the first-level pore cavities is 82%, the porosity formed by the second-level pore cavities is 8%, and the porosity formed by the third-level pore cavities is 5%.

(42) The interconnectivity is tested by the same method as the method in Embodiment 2. Results show that the number of pore cavities that interconnect more than four adjacent cavities is as follows. The number of the first-level pore cavities is 38 (accounting for 95% of the pore cavities of this level), the number of the second-level pore cavities is 38 (accounting for 95% of the pore cavities of this level), and the number of the third-level pore cavities is 37 (accounting for 92.5% of the pore cavities of this level). The permeability of the porous tantalum is measured to 1.57×10.sup.−9 m.sup.2 using the same method as that in Embodiment 1. The material is used as a bone implant material.