Alkali resistant glass compositions

• US 20060240967A1
• Filed: 02/24/2006
• Published: 10/26/2006
• Est. Priority Date: 02/24/2005
• Status: Active Grant

• Current Assignee: James Hardie Technology Limited (James Hardie Industries Plc)
• Original Assignee: James Hardie Technology Limited (James Hardie Industries Plc)
• Inventors: Hojaji, Hamid, Melmeth, David Leslie
• Granted Patent: US 7,744,689 B2
• Time in Patent Office: Days
• US Class Current: 501/33
• CPC Class Codes: C03C 11/002 Hollow glass particles
• CPC Class Codes: C03C 11/007 Foam glass, e.g. obtained by incorporating a blowing agent and heating
• CPC Class Codes: C03C 12/00 Powdered glass C03C8/02 takes precedence; Bead compositions
• CPC Class Codes: C03C 13/001 Alkali-resistant fibres
• CPC Class Codes: C03C 13/002 containing zirconium
• CPC Class Codes: C03C 2218/345 Surface crystallisation
• CPC Class Codes: C03C 2218/35 Exuding
• CPC Class Codes: C03C 23/00 Other surface treatment of glass not in the form of fibres or filaments
• CPC Class Codes: C03C 25/66 Chemical treatment, e.g. leaching, acid or alkali treatment dehydroxylation C03C25/64
• CPC Class Codes: C03C 3/087 containing calcium oxide, e.g. common sheet or container glass
• CPC Class Codes: C03C 4/20 for chemical resistant glass
• CPC Class Codes: C04B 14/22 Glass ; Devitrified glass
• CPC Class Codes: C04B 14/42 Glass
• CPC Class Codes: C04B 14/44 Treatment for enhancing alkali resistance composition of alkali resistant glass fibres C03C13/00; coating of glass fibres C03C25/10
• CPC Class Codes: C04B 20/0036 Microsized or nanosized
• CPC Class Codes: C04B 20/023 Chemical treatment
• CPC Class Codes: C04B 20/04 Heat treatment
• CPC Class Codes: C04B 20/1074 Silicates, e.g. glass
• CPC Class Codes: C04B 28/02 containing hydraulic cements other than calcium sulfates

Abstract

An alkali resistant glass composition having improved durability to withstand highly alkali environments at elevated temperatures, such as curing of cementitious products in an autoclave, is conveniently formed from economical and abundant materials. The glass composition includes increased levels of calcium and iron, and relatively low levels of alkali metals, as compared to many other alkali resistant glass products, and comprises essentially of, by weight, >35% Si₂O₃, 1-25% CaO, 1-15% Fe₂O₃, 1-10% R₂O, and an amount of Al₂O₃ such that the ratio of Si₂O₃:Al₂O₃ is greater than or equal to 1. Alkali resistance can be improved by forming a passivity layer on the surface of glass articles by treating the articles hydrothermally in a basic environment. Optionally zirconia and/or titania may be added to the composition to further improve alkali resistance.

Claims

1. An alkali resistant glass, comprising:

a silicate based glass body;

a passivity layer formed on an exterior surface of the silicate based glass body, wherein the passivity layer has a composition that is different than the composition of the glass body, said passivity layer comprises a substance that is native to the silicate based glass body, wherein the substance in combination with other substances in the passivity layer results in the passivity layer being substantially chemically inert in an alkaline environment.

2. The alkali resistant glass of claim 1, wherein the substance comprises calcium.

3. The alkali resistant glass of claim 1, wherein the substance comprises iron.

4. The alkali resistant glass of claim 1, wherein the passivity layer is enriched in iron oxide in comparison with the silicate based glass body.

5. The alkali resistant glass of claim 1, wherein the passivity layer is enriched in magnesium and/or calcium oxide in comparison with the silicate based glass body.

6. A cementitious article incorporating the alkali resistant glass of claim 1.

7. The alkali resistant glass of claim 1, wherein the composition of the glass body consists essentially of, by weight percent:

8. An alkali resistant glass, which consists essentially of, by weight percent:

9. The alkali resistant glass of claim 8, wherein the amount of Al₂O₃ is greater than or equal to about 4 wt. %.

10. The alkali resistant glass of claim 8, wherein the combination of all the iron oxides as expressed by Fe₂O₃ is greater than or equal to about 3 wt. %.

11. The alkali resistant glass of claim 8, wherein the combination of CaO and Fe₂O₃ is greater than or equal to about 10 wt. %.

12. The alkali resistant glass of claim 8, wherein the combination of SiO₂ and Al₂O₃ is between about 35-90 wt. %.

13. The alkali resistant glass of claim 8, further comprising a combination of ZrO₂ and TiO₂ up to about 15 wt. %.

14. The alkali resistant glass of claim 8, wherein the glass is formed as a fiber.

15. The alkali resistant glass of claim 8, wherein the glass is formed as one or more hollow spheres.

16. The alkali resistant glass of claim 15, wherein the hollow spheres are produced at a rate of greater than 1 kg per hour.

17. The alkali resistant glass of claim 8, wherein the glass comprises a passivity layer.

18. The alkali resistant glass of claim 17, wherein the passivity layer is enriched in iron oxide in comparison with the glass.

19. The alkali resistant glass of claim 17, wherein the passivity layer is enriched in magnesium and/or calcium oxide in comparison with the glass.

20. The alkali resistant glass of claim 8, wherein the molar ratio of CaO/R₂O is greater than unity.

21. A method of increasing the alkali resistance properties of glass, comprising:

providing a glass article consisting essentially of, by weight percent;

SiO₂ 

>

35%,CaO1-25%,Fe₂O₃1-15%,R₂O1-10%,

wherein R is selected from the group consisting of Na, K, and Li; and

treating the glass articles by exposing the glass articles to a basic environment to form a passivity layer over the surface of the glass articles thereby improving the alkali resistance of the glass articles.

22. The method of claim 21, wherein the treating the glass step is carried out at a temperature above 100°

C.

23. The method of claim 21, wherein the treating the glass step is carried out in an aqueous environment.

24. The method of claim 21, wherein the treating the glass step is carried out at a temperature below 100°

C.

25. A synthetic microsphere, comprising:

a synthetic, hollow, substantially spherical wall, the wall having an inner surface and an outer surface and a thickness therebetween; and

a passivity layer on the outer surface of the spherical wall.

26. The microsphere of claim 25, wherein the passivity layer substantially covers the outer surface of the spherical wall.

27. The microsphere of claim 25, wherein the passivity layer has a thickness less than about 10% of the spherical wall thickness.

28. The microsphere of claim 25, wherein the passivity layer is substantially chemically inert in a basic environment having a pH of about 12-14.

29. The microsphere of claim 25, wherein the passivity layer is formed through crystalline redeposition of leached glass elements.

30. The microsphere of claim 25, wherein the passivity layer is rich in silica and alumina in comparison with the spherical wall.

31. A cementitious composite article comprising:

a cementitious material;

a glass additive material, the glass comprising, by weight percent;

SiO₂ 

>

35%CaO1-25%Fe₂O₃1-15%R₂O1-10%,

and

an amount of Al₂O₃ such that SiO₂;

Al₂O₃≧

1.

32. The cementitious composite article of claim 31, wherein the glass additive material is a fiber.

33. The cementitious composite article of claim 31, wherein the glass additive material is a sphere.