GLASS POWDER COMPOSITE, AND METHOD OF PRODUCING GLASS POWDER COMPOSITE

Abstract

A glass powder composite includes a first glass powder, and a second glass powder having a different solubility from that of the first glass powder depending on pH, wherein both the first glass powder and the second glass powder have ion sustained-release properties.

Claims

1. A glass powder composite comprising: a first glass powder; and a second glass powder having a different solubility from that of the first glass powder depending on pH, wherein both the first glass powder and the second glass powder have ion sustained-release properties.

2. The glass powder composite according to claim 1, wherein the first glass powder is a powder of silicate glass, and the second glass powder is a powder of phosphate glass.

3. The glass powder composite according to claim 1, wherein both the first glass powder and the second glass powder contain at least one element selected from Li, Ca, Sr, Cu, Ag, Zn, B, Ga, and F.

4. The glass powder composite according to claim 1, wherein at least one of elements contained in the first glass powder is same as at least one of elements contained in the second glass powder.

5. The glass powder composite according to claim 1, wherein at least one of elements contained in the first glass powder is different from elements contained in the second glass powder, and wherein at least one of the elements contained in the second glass powder is different from the elements contained in the first glass powder.

6. The glass powder composite according to claim 5, wherein the second glass powder has a higher dissolution rate in a neutral pH region than a dissolution rate in an acidic pH region.

7. A method of producing a glass powder composite comprising, mixing a first glass powder and a second glass powder having a different solubility from that of the first glass powder depending on pH, wherein both the first glass powder and the second glass powder have ion sustained-release properties.

Description

EXAMPLES

[0074] The present invention will be described below with further examples. Various tests and evaluations are conducted according to the following methods.

Silicate Glass

[0075] The raw material of silicate glass was weighed, mixed in a mortar for 10 minutes, placed in a platinum crucible, melted at 1350° C. for 1 hour, and the melt was water-cooled to vitrify. The resulting glass was collected, dried at 110° C. for 5 hours and ground in a planetary mill (15 mm alumina ball, 150 rpm) for 30 minutes to 1 hour to obtain glass components S1 to S5. Commercially available quartz glass fillers (hereinafter referred to as QG) were also used.

Phosphate Glass

[0076] The raw material of the phosphate glass was weighed, mixed in a mortar for 10 minutes, placed in a platinum crucible, melted at 1100° C. for 1 hour, and the melt was cooled by iron-pressing. The resulting product was ground by a ball mill for 30 minutes (ethanol wet grinding, 40 mm alumina ball, 100 rpm) and further ground by a ball mill for 30 minutes (ethanol wet grinding, 5 mm alumina ball, 100 rpm). The glass powder was then collected by centrifugation and dried under reduced pressure (−0.1 MPa, 40° C.) to evaporate the remaining ethanol to obtain glass components P1, P2, PA1, and PA2.

Glass Composition

[0077] Using X-ray fluorescence analysis device (ZSX Primus IV, manufactured by Rigaku), the glass powder (formed with PVC billing) was analyzed to determine the composition of the glass powder. Tables 1 and 2 indicate the evaluation results of the glass powder composition (unit: % by mass).

Particle Size Distribution

[0078] A laser diffraction/scattering particle size analyzer (Partica LA-960 V2, manufactured by Horiba Ltd.) was used to measure the silicate glass dispersed in distilled water and to measure the phosphate glass dispersed in ethanol. Both glass powders were confirmed to be D(50): 10±2 μm.

Amount Dissolved (Glass Only)

[0079] 0.1 g of glass powder was put into a 10 ml of acetic acid-sodium acetate buffer of pH 4.5 and hydroxyethyl piperazine ethanesulfonic acid (HEPES) buffer of pH 7.5, and the mixture was stored at 37° C. for one day with stirring at 10 rpm. Then, the residue was filtered through a glass filter paper and the dissolution rate was calculated from the weight of the residue using the following formula.

Dissolution rate (%)=[(weight before immersing in the buffer)−(weight after immersing in the buffer)]×100/weight before immersing in the buffer.

[0080] Table 1 indicates the dissolution rate of the silicate glass (Glass components S1 to S5, QG). Table 2 indicates the dissolution rate of the phosphate glass (Glass components P1, P2, PA1, and PA2).

TABLE-US-00001 TABLE 1 Glass components/% by mass S1 S2 S3 S4 S5 QG P.sub.2O.sub.5 6.2 8.2 Na.sub.2O 6.7 6.6 6.5 5.6 9.4 CaO 9.7 3.5 9.8 9.0 SiO.sub.2 38.7 24.5 24.3 24.7 24.9 SrO Al.sub.2O.sub.3 7.2 31.8 27.8 100  ZnO 34.4 30.3 35.0 Ga.sub.2O.sub.3 La.sub.2O.sub.3 31.8 31.2 F 3.3 3.3 3.0 21.9 20.7 pH 4.5 Dissolution rate (%) 11 21 24 12.4 4.9 0 Amount of eluted Zn.sup.2+ 533 564 567 — — — ion (ppm) Ca.sup.2+ — — — 113 57 — Sr.sup.2+ — — — — — — Ga.sup.3+ — — — — — — F.sup.− 66 2 2 111 111 — pH 7.5 Dissolution rate (%) 5 6 4 4.6 4.2 0 Amount of eluted Zn.sup.2+ 8 10 10 — — — ion (ppm) Ca.sup.2+ — — — 10 11 — Sr.sup.2+ — — — — — — Ga.sup.3+ — — — — — — F.sup.− 7 3 2 12 20 —

TABLE-US-00002 TABLE 2 Glass components/% by mass PN1 PN2 PA1 PA2 P.sub.2O.sub.5 65.1 55.7 54.8 54.6 Na.sub.2O 14.8 9.5 7.8 6.6 CaO SiO.sub.2 SrO 34.8 33.9 33.3 Al.sub.2O.sub.3 3.9 3.5 5.5 ZnO Ga.sub.2O.sub.3 16.2 La.sub.2O.sub.3 F pH 4.5 Dissolution rate (%) 29 45 15 17 Amount of eluted Zn.sup.2+ — — — — ion (ppm) Ca.sup.2+ — — — — Sr.sup.2+ — 958 464 373 Ga.sup.3+ 185 — — — F.sup.− — — — — pH 7.5 Dissolution rate (%) 40 61 5 6 Amount of eluted Zn.sup.2+ — — — — ion (ppm) Ca.sup.2+ — — — — Sr.sup.2+ — 1684 66 53 Ga.sup.3+ 427 — — — F.sup.− — — — — Acid < Neutral Acid < Neutral Acid > Neutral Acid > Neutral

Amount of Eluted Ions (Glass Only)

[0081] 0.1 g of glass powder was put into 10 ml of acetate-sodium acetate buffer of pH 4.5 and HEPES buffer of pH 7.5, and the mixture was stored at 37° C. for one day with stirring at 10 rpm. Then, the mixture was centrifuged at 2,000 rpm for 10 minutes, and this was repeated twice. In the solution filtered through a 0.2 μm membrane filter, the concentrations of Zn.sup.2+, Sr.sup.2+, Ca.sup.2+, and Ga.sup.3+ were measured with an inductively coupled plasma optical emission spectrometer (ICP-OES) (iCAP 7200 Duo, manufactured by Thermo Fisher) and the concentration of F− was measured with a fluorine electrode. Table 1 indicates the amount of eluted ion of silicate glass. Table 2 indicates the amount of eluted ion of phosphate glass.

Amount of Eluted Ion (A Combination of Glass)

[0082] Two kinds of glass powders (in any amount) were put into 10 ml of acetate-sodium acetate buffer of pH 4.5 and HEPES buffer of pH 7.5, and the mixture was stored at 37° C. for one day with stirring at 10 rpm. Then, the mixture was centrifuged at 2,000 rpm for 10 minutes, and this was repeated twice. In the solution filtered through a 0.2 μm membrane filter, the concentrations of Zn.sup.2+, Sr.sup.2+, Ca.sup.2+, and Ga.sup.3+ were measured using ICP-OES and the concentration of F− was measured using a fluorine electrode.

[0083] Table 3 indicates the components and the amount of eluted ions in Examples 1 to 5. Table 4 indicates the components and the amount of eluted ions in Comparative Examples 1 to 5.

TABLE-US-00003 TABLE 3 Example 1 Example 2 Example 3 Example 4 Example 5 Components (g) Silicate glass S1 —   0.1 — — — S2 — —   0.1 — — S3 0.1 — — — — S4 — — —   0.1 — S5 — — — —   0.1 Non-eluted glass QG — — — — — Phosphate glass PN1 0.5   0.1 —   0.1 — PN2 — —   0.1 —   0.1 PA1 — — — — — PA2 — — — — — Amount of eluted pH 4.5 Zn.sup.2+ 625 431  497  — — ion (ppm) Ca.sup.2+ — 95 56 124  33 Sr.sup.2+ — — 40 — 81 Ga.sup.3+ 0  1 —  0 — F.sup.− 8 48  2 146  61 pH 7.5 Zn.sup.2+ 281 66 110  — — Ca.sup.2+ — 13 14 12  9 Sr.sup.2+ — — 525  — 1228  Ga.sup.3+ 166 43 — 367  — F.sup.− 17 14 18 12 14

TABLE-US-00004 TABLE 4 Comparative Comparative Comparative Comparative Comparative Example 1 Example 2 Example 3 Example 4 Example 5 Components (g) Silicate glass S1 — — — — — S2 — — — — — S3 —   0.1 — — — S4 — — — — — S5 — —   0.1 — — Non-eluted glass QG — — — —    0.1 Phosphate glass PN1 — — — — — PN2 0.1 — —    0.1    0.1 PA1 0.1 —   0.1 — — PA2 —   0.9 —    0.1 — Amount of eluted pH 4.5 Zn.sup.2+ — 445  — — — ion (ppm) Ca.sup.2+ — 225  134  — — Sr.sup.2+ 305 — 53 832 950 Ga.sup.3+ 72 — — — — F.sup.− — — 132  — — pH 7.5 Zn.sup.2+ — 14 — — — Ca.sup.2+ — 33 66 — — Sr.sup.2+ 540 — 15 1759  1681  Ga.sup.3+ 214 — — — — F.sup.− — —  7 — —

[0084] From Tables 1, 2, and 3, in Examples 1 to 5, at least one or more ions eluted differently from other ions regarding whether increased or decreased in acidic versus neutral conditions, indicating acidity (pH) responsiveness (the property that the amount of dissolved ions varies depending on the acidity (pH) of the solution). On the other hand, from Tables 1, 2 and 4, in Comparative Examples 1 to 5, the elution of all ions is greater at neutral than acidic or smaller at neutral than acidic and therefore does not show an acidity (pH) responsiveness.

[0085] From these results, it was found that the glass powder composite contains the first glass powder and the second glass powder having different solubility from that of the first glass powder depending on pH, and both the first glass powder and the second glass powder have ion sustained-release, so that the ion sustained-release can be changed according to the changes in acidity.

[0086] As described above, the embodiment of the present invention is not limited to a specific embodiment, and various modifications and corrections are possible within the scope of the invention described in the claims.