Method to increase the strength of a form body of a lithium silicate glass ceramic

Patent metadata

Field	Value
Publication number	US-11370702-B2
Application number	US-201615160432-A
Country	US
Kind code	B2
Filing date	May 20, 2016
Priority date	May 22, 2015
Publication date	Jun 28, 2022
Grant date	Jun 28, 2022

Abstract

The invention relates to a method to derive a medical form body of lithium silicate glass ceramic. To increase its strength it is proposed that in the form body comprising lithium silicate glass or containing lithium silicate glass the lithium ions are replaced by alkali ions of greater diameter to generate a surface compressive stress. To this end the form body is covered with a melt containing an alkali metal for which an aliquoted quantity of salt containing the alkali metal is used.

First claim

The invention claimed is:

1. A method to increase the strength of a form body of lithiumlithiun silicate glass ceramic, or a part thereof comprising the steps of:
preparing the form body from a glass melt which comprises at least the following as starting components: SiO 2 , Al 2 O 3 , Li 2 O, K 2 O, at least one nucleating agent and at least one stabilizer, wherein the stabilizer is ZrO2 in the range of 6 to 14% by weight of the starting components;
forming a blank from the glass melt during cooling or following cooling to room temperature, said blank then being subject to at least one first heat treatment W1 at a temperature T W1 for a time t W1 , wherein 620° C.≤T W1 ≤800° C., and 1 minute≤t W1 ≤200 minutes to obtain a crystallization having metasilicate crystals, disilicate crystal, or a combination of metasilicate and disilicate crystals;
providing a melt including a first salt of an alkali metal phosphate salt and a second salt of a number of alkali metals with ions of greater diameter than lithium ions, wherein the ions of greater diameter than lithium ions is selected from the group consisting of Na, K, Cs, Rb and combinations thereof ions; and wherein an aliquoted quantity of the first salt and the second salt is used for the melt;
laying the form body in a first receptacle having perforations, and then
(i) immersing the first receptacle with the form body in the melt or
(ii) introducing the first receptacle with the form body into the salt and the salt is then melted or
(iii) laying the first receptacle with the form body on the salt or the salt body and the salt is melted at the same time as immersion of the form body in the melt that is forming;
annealing the at least a portion of the form body that is in contact with the melt for a time t at a temperature T where 620° C.≤T≤800° C. and 0.5 hours≤t≤10 hours;
replacing lithium ions of the form blank with the ions of greater diameter than lithium ions selected from the group consisting of Na, K, Cs, Rb and combinations thereof ions to generate a surface compressive stress to a depth of at least 20 microns in the form body of lithium silicate glass ceramic through the replacement of lithium ions by the number of alkali metal ions of greater diameter, wherein the replaced lithium ions from the form blank are bound to the alkali metal phosphate salt to reduce the lithium ion content in the melt by precipitating lithium phosphate; and
removing the melt from the at least a portion of the form body.

2. The method according to claim 1 , further comprising the step of enveloping the form body by a heat-resistant foil that includes a portioned quantity of salt and then melting the salt.

3. The method according to claim 2 , wherein the portioned salt is made available in a second receptacle with a closure that can be removed.

4. The method according to claim 3 , further comprising the step of melting the salt in the second receptacle and then immersing the form body in the melt.

5. The method according to claim 3 , further comprising the step of immersing the form body with a third receptacle having perforations in the melt present in the second receptacle.

6. The method according to claim , further comprising the step of laying the form body on the salt before melting of the salt.

7. The method according to claim 1 , wherein the melt includes one or more elements that color the form body.

8. The method according to claim 7 , wherein the one or more coloring elements are one or more lanthanides with the atomic number or numbers in the range 58 to 70.

9. The method according to claim 7 , wherein at least one of the one or more coloring elements is an element selected from the group consisting of vanadium, manganese, iron, yttrium, and antimony.

10. The method according to claim 7 , further comprising the step of dissolving the one or more coloring elements in the melt containing alkali ions.

11. The method according to claim 1 , wherein the step of annealing, the form body in is annealed in the melt, the melt including potassium ions or sodium ions, or a mixture of potassium ions and sodium ions.

12. The method according to claim 1 , wherein the glass melt includes at least one coloring metal oxide.

13. The method according to claim 1 , wherein the form body or a blank from which the form body is manufactured, is prepared from a glass melt that includes the following components in percentage by weight:
SiO 2 50-80,
a nucleating agent 0.5-11,
Al 2 O 3 0-10,
Li 2 O 10-25,
K 2 O 0-13,
Na 2 O 0-1,
ZrO 2 8-12,
CeO 2 0-10,
Tb 4 O 7 0-8,
optionally an oxide or a number of oxides of an earth alkali metal or a number of earth alkali metals selected from the group consisting of magnesium, calcium, strontium, barium, and any combination thereof 0-20,
optionally one or more additives selected from the group consisting of B 2 O 3 , MnO 2 , Fe 2 O 3 , V 2 O 5 , TiO 2 , Sb 2 O 3 , ZnO, SnO 2 , fluorides and any combination thereof 0-6,
optionally one or more oxides of the rare earth metals with the atomic numbers 57, 59-64, 66-71, 0-5.

14. The method according to claim 1 , wherein the glass melt contains the following as starting components in percentage by weight
SiO 2 58.1±2.0
P 2 O 5 5.0±1.5
Al 2 O 3 4.0±2.5
Li 2 O 16.5±4.0
K 2 O 2.0±0.2
ZrO 2 10.0±0.5
CeO 2 0-3,
Tb 4 O 7 0-3,
Na 2 O 0-0.5.

15. The method according to claim 1 , wherein the blank is formed from the glass melt in the course of cooling or following cooling to room temperature, said blank then being subject to at least one first heat treatment W1 at a temperature T W1 for a time t W1 , wherein 620° C.≤T W1 ≤800° C., and/or 1 minute≤t W1 ≤200 minutes.

16. The method according to claim 15 , wherein the first heat treatment W1 is carried out in two steps, wherein in a first step, a temperature T St1 is set where 630° C.≤T St1 ≤690° C. and/or in a second step a temperature T St2 where 720° C.≤T St2 ≤780° C. and/or the heating rate A St1 up to the temperature T St1 is 1.5 K/minute≤A St1 ≤2.5 K/minute and/or the heating rate A St2 up to the temperature T St2 is 8 K/minute≤T St2 ≤12 K/minute.

17. The method according to dawn 15 , wherein after the first and/or second heat treatment step, the form body is prepared from the blank through grinding and/or milling or pressing, wherein the heat treatment step or steps is/are carried out during or after pressing.

18. Use of a capsule filled with at least one alkali metal salt to create a surface stress in a form body of a lithium silicate ceramic material through the replacement of lithium ions by a number of alkali metal ions of greater diameter than the lithium ions, in that the form body is covered by a salt of alkali metal phosphate ions and the number of alkali metals ions of greater diameter than the lithium ions melted in the capsule, wherein the number of alkali metal ions of greater diameter than lithium ions is selected from the group consisting of Na, K, Cs, Rb and combinations thereof ions and wherein:
(i) the form body is prepared from a glass melt which comprises at least the following as starting components: SiO 2 , Al 2 O 3 , K 2 O, at least one nucleating agent and at least one stabilizer, wherein the stabilizer is ZrO2 in the range of 6 to 14% by weight of the starting components;
(ii) the blank is formed from the glass melt during cooling or following cooling to room temperature, said blank then being subject to at least one first heat treatment W1 at a temperature T W1 for a time t W1 , wherein 620° C.≤T W1 ≤800° C., and/or 1 minute≤t W1 ≤200 mi

Assignees

• Dentsply Sirona Inc

Inventors

• Fecher Stefan
• Völkl Lothar

Classifications

• A61K6/853

  Silicates · CPC title

• A61K6/818

  comprising zirconium oxide · CPC title

• C03C3/097

  containing phosphorus, niobium or tantalum · CPC title

• A61K6/822

  comprising rare earth metal oxides · CPC title

• C03C21/002 Primary

  to perform ion-exchange between alkali ions (C03C21/005 takes precedence) · CPC title