Method for producing a lithium silicate glass blank and a lithium silicate glass-ceramic blank

Patent metadata

Field	Value
Publication number	US-9701572-B2
Application number	US-201514671253-A
Country	US
Kind code	B2
Filing date	Mar 27, 2015
Priority date	Mar 28, 2014
Publication date	Jul 11, 2017
Grant date	Jul 11, 2017

Abstract

The invention relates to a method for producing a blank of lithium silicate glass a starting composition of at least 8 wt-% of a stabilizer selected from the group consisting of ZrO 2 , HfO 2 , and mixtures thereof, wherein the method includes the steps of mixing the raw materials comprising the stabilizer in powder form, wherein the powder of the stabilizer has a particle size d 50 =x with 0.3 μm≦x≦1.5 μm, melting the raw materials in a crucible at a temperature T AU and storing the melt in the crucible for a time t H , pouring the homogenized melt into molds, wherein the melt flows out of the crucible with a discharge temperature T AB being T AU ≧T AB , wherein the filling of the molds and the molding of the melt in the molds takes place with a cooling rate A.

First claim

The invention claimed is:

1. A method for producing a lithium silicate glass blank with a composition of at least 8 wt-% of a stabilizer selected from the group consisting of ZrO 2 , HfO 2 , and mixtures thereof, comprising the method steps of:
mixing the raw materials comprising the stabilizer in powder form, wherein the powder of the stabilizer has a particle size d 50 =x with 0.3 μm≦x≦1.5 μm,
melting the raw materials in a crucible at a temperature T AU and storing the melt in the crucible for a time t H ,
pouring the homogenized melt into molds, wherein the melt flows out of the crucible with a discharge temperature T AB being T AU ≧T AB , wherein the filling of the molds and the molding of the melt in the molds takes place with a cooling rate A.

2. The method according to claim 1 , wherein 5 K/sec≦A≦100 K/sec up to a temperature T M with T M ≧600° C.

3. The method according to claim 1 , wherein the melt flows out of the crucible with a discharge temperature T AB with T AU −Y° C.=T AB with 150° C.≦Y≦350° C.

4. The method according to claim 3 , wherein the melt has a temperature T B with 1150° C.≦T B <T AB when melt is filled into the molds.

5. The method according to claim 1 , wherein the melting of the raw materials takes place at a temperature T AU with 1450° C.≦T AU ≦1600° C.

6. The method according to claim 1 , wherein the powder of the stabilizer has a particle size d 10 =0.5·x, d 90 =1.5·x, or both d 10 =0.5·x and d 90 =1.5·x, with 0.3 μm≦x≦1.5 μm.

7. The method according to claim 1 , wherein the melt in the crucible is homogenized by convection and the melt is cooled in the crucible during the homogenization.

8. The method according to claim 1 , wherein the melt is cooled in the discharge region of the crucible to a temperature T AB with 1200° C.≦T AB ≦1300° C.

9. The method according to claim 8 , wherein the first heat treatment W1 is carried out in two steps having a first step at a temperature T St1 with 630° C.≦T St1 ≦690° C. and a second step at a temperature T ST2 with 720° C.≦T St2 ≦780° C.

10. The method according to claim 1 , wherein the stabilizer comprises more than 90 wt-% ZrO 2 .

11. The method according to claim 10 , wherein the lithium silicate glass-ceramic blank is subjected to a second heat treatment W2 at a temperature T W2 for a time t w2 after the first heat treatment W1, with 800° C.≦T W2 <1040° C. and 5 min≦t W2 ≦200 min.

12. The method according to claim 1 , wherein after melting and homogenizing the raw materials in the crucible by convection, the melt is immediately poured into the molds.

13. The method according to claim 1 , wherein the melt in the crucible is cooled to a temperature T M with T M ≧600° C. with a cooling rate A with 5 K/sec≦A≦100 K/sec.

14. The method according to claim 1 , wherein the composition of the blank comprises (data in % by weight):

SiO 2
46.0-72.0

Li 2 O
10.0-25.0

ZrO 2
 8.0-20.0

Al 2 O 3
 0.1-8.0

K 2 O
 0.1-5.0

CeO 2
 0.0-4.0

B 2 O 3
 0.0-4.0

Na 2 O
 0.0-4.0

Tb 4 O 7
 0.0-2.5

at least one nucleating agent 1.0-10.0, and
0.0 to 4.0 of at least one additive,
wherein the additive is at least an oxide selected from the group consisting of BaO, CaO, MgO, MnO, Er 2 O 3 , Pr 6 O 11 , Sm 2 O 3 , TiO 2 , V 2 O 5 , and Y 2 O 3 , and
the total sum is 100 wt-%.

15. The method according to claim 1 , wherein the composition of the blank comprises (data in % by weight):

SiO 2
  58-60

Li 2 O
13.5-20.5

ZrO 2
 9.0-12.5

nucleating agent,
 3.0-7.5, particularly P2O5,

Al 2 O 3
 0.5-6.0

K 2 O
 0.5-3.5

CeO 2
 0.5-2.5

B 2 O 3
  0-3

Na 2 O
  0-3

Tb 4 O 7
  0-1.5,

wherein the total sum is 100 wt-%.

16. A method for producing a lithium silicate glass-ceramic blank by using the lithium silicate glass blank according to claim 1 , wherein the melt is poured into one or more molds and cooled in the one or more molds, being subjected to at least a first heat treatment W1 at a temperature T W1 for a period of time t W1 , with 620° C.≦T W1 ≦800° C. and 1 min≦t W1 ≦200 min.

17. The method according to claim 1 , wherein the melt has a discharge temperature T B with 1150° C.≦T B <T AB when the melt is filled into the one or more molds.

18. The method according to claim 1 , wherein the raw materials and/or the melt is made of the raw materials stored in the crucible at the temperature T AU for the time t H with t H ≧1 h.

19. A dental product made of a lithium silicate glass-ceramic blank according claim 8 .

20. A method for producing a lithium silicate glass blank with a composition of at least 8 wt-% of a stabilizer selected from the group consisting of ZrO 2 , HfO 2 , and mixtures thereof, comprising the method steps of:
mixing the raw materials comprising the stabilizer in powder form, wherein the powder of the stabilizer has a particle size d 50 =x with 0.3 μm≦x≦1.5 μm,
melting the raw materials in a crucible at a temperature T AU and storing the melt in the crucible for a time t H ,
pouring

Assignees

• Dentsply Int Inc

Inventors

• Vollmann Markus
• Schusser Udo

Classifications

• A61K6/833

  Glass-ceramic composites · CPC title

• A61K6/818 Primary

  comprising zirconium oxide · CPC title

• C03B32/02

  Thermal crystallisation, e.g. for crystallising glass bodies into glass-ceramic articles {(C03B27/012 takes precedence)} · CPC title

• C03B19/02

  by casting {molten glass, e.g. injection moulding} · CPC title

• A61C13/0022

  Blanks or green, unfinished dental restoration parts · CPC title