WO1996006052A1 - Opal glass - Google Patents

Opal glass Download PDF

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Publication number
WO1996006052A1
WO1996006052A1 PCT/SE1995/000948 SE9500948W WO9606052A1 WO 1996006052 A1 WO1996006052 A1 WO 1996006052A1 SE 9500948 W SE9500948 W SE 9500948W WO 9606052 A1 WO9606052 A1 WO 9606052A1
Authority
WO
WIPO (PCT)
Prior art keywords
weight
glass
content
opal
approximately
Prior art date
Application number
PCT/SE1995/000948
Other languages
French (fr)
Inventor
Bo Jonson
Lars Gunnar Johansson
Original Assignee
Glasforskningsinstitutet
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Glasforskningsinstitutet filed Critical Glasforskningsinstitutet
Priority to AU33584/95A priority Critical patent/AU3358495A/en
Publication of WO1996006052A1 publication Critical patent/WO1996006052A1/en

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C3/00—Glass compositions
    • C03C3/04—Glass compositions containing silica
    • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
    • C03C3/097—Glass compositions containing silica with 40% to 90% silica, by weight containing phosphorus, niobium or tantalum
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C4/00—Compositions for glass with special properties
    • C03C4/005—Compositions for glass with special properties for opaline glass

Definitions

  • the opal glass prefer ⁇ ably has the following composition 56-60% by weight of Si0 2 3-5% by weight of A1 2 0 3 12-14% by weight of Na 2 0
  • P 2 0 5 content of the glass in the form of sodium tripolyphosphate instead of adding the P 2 0 5 content of the glass in the form of sodium tripolyphosphate, one may, in accordance with the invention, resort to other suitable P 2 0 5 sources, such as Ca 3 (P0 4 ) 2 , NaH 2 P0 4 , and Na 2 HP0 4 -2H 2 0.
  • P 2 0 5 sources such as Ca 3 (P0 4 ) 2 , NaH 2 P0 4 , and Na 2 HP0 4 -2H 2 0.
  • the finished opal glass had the following, theoretical composition in % by weight: 57.9% Si0 2 4.1% A1 2 0 3 13.3% Na 2 0 5.8% CaO 0.6% BaO 3.5% ZnO 4.3% B 2 0 3 8.7% P 2 0 5 1.2% Li 2 0 0.6% Sb 2 0 3
  • the resulting opal glass was white and contained no crystals that could be perceived with the naked eye.
  • the light transmission was below 0.5%.
  • the transformation temperature (Tg) of the glass was 518°C, and the thermal expansion coefficient ⁇ of the glass was 9.65 x 10 "6 °C "1 .

Abstract

Fluorine-free opal glass has the following composition, based on the oxides of the ingredients: 55-65 % by weight of SiO2, 2-6 % by weight of Al2O3, 10-17 % by weight of Na2O, 2-10 % by weight of CaO, 0.1-6 % by weight of BaO, 0.1-6 % by weight of ZnO, 1-8 % by weight of B2O3, 4-12 % by weight of P2O5, 0.1-3 % by weight of Li2O, 0.1-3 % by weight of Sb2O3, 0-4 % by weight of MgO, the total of the weight quantities of the ingredients amounting to 100 %. In the temperature range of 20-300 °C, the opal glass has a thermal expansion coefficient of 8-11 x 10-6 °C-1, enabling it to be combined with some other translucent glass, such as clear glass, and be melted in electrically-heated furnaces.

Description

OPAL GLASS
This invention relates to opal glass, i.e. glass which, owing to the presence of crystals, is non-trans¬ parent but translucent, and which usually is white. Opal glass is used in many different fields, for instance in art glassware, tableware and illuminating glass. Fre¬ quently, opal glass is combined with some other trans¬ parent glass (clear glass), for instance when used in lamps.
It is known to produce white opal glass by adding various fluorine compounds to the glass. As a result of the fluorine addition, the melted glass has a low vis¬ cosity as well as good forming properties within a fairly broad composition range.
However, the use of fluorine compounds involves health hazards as well as environmental hazards. In view of these hazards as well as the increasingly strict re¬ quirements placed by the authorities on the emission of fluorine, there is a widespread demand for reducing or eliminating the fluorine content of opal glass. Apart from the undesirable fluorine emission, the evaporation of fluorine from melted fluorine-containing opal glass entails that the opacity of the glass fades away after a brief period when the glass is maintained at working temperature. This instability results in produc- tion losses for opal glass.
Another drawback is that fluorine-containing opal glass cannot be melted in furnaces that are heated by means of electric heating elements. As a result of its fluorine content, the melt is highly corrosive, and the corrosion to which the electric heating elements are exposed shortens their service life to an unacceptable extent.
Despite the above drawbacks of fluorine-containing opal glass, it is, however, not possible to reduce or eliminate the fluorine content just like that, since the compatibility of opal glass with other sorts of glass, especially clear glass, must be taken into consideration. The thermal expansion coefficient (α) of the glass is of special importance to this compatibility, and the thermal expansion coefficient of clear glass, for instance lead- free crystal glass, is approximately 8-11 x 10"6°C"1 in the temperature range of 20-300°C. In order that two types of glass should be regarded as sufficiently compatible, the thermal expansion coefficients should not differ by more than 0.15 x 10"6°C"1, at the very most.
US-A-3,498,801 and SU-A-772,979 teach the use of phosphorus compounds instead of fluorine compounds as opacity-imparting component in the production of glass. The types of glass described in these specifications have other compositions than the inventive opal glass, and these specifications further do not disclose the thermal expansion coefficient which characterises the inventive opal glass and enables good compatibility with other sorts of glass, such as clear glass. In addition, the glass disclosed in SU-A-772,979 has a high light-trans¬ mission, and thus is really no opal glass, but opaline.
This invention aims at reducing or obviating the drawbacks of the prior art by providing fluorine-free opal glass having a suitable thermal expansion coeffi- cient.
According to the invention, this aim is achieved by the opal glass containing, as opacity-imparting compo¬ nent, phosphorus compounds instead of fluorine compounds and having optimal contents of the remaining ingredients. To be more specific, the present invention provides opal glass which is characterised in that it has the following composition, based on the oxides of the ingre¬ dients. 55-65% by weight of Si02 2-6% by weight of A1203 10-17% by weight of Na20 2-10% by weight of CaO 0.1-6% by weight of BaO 0.1-6% by weight of ZnO 1-8% by weight of B203 4-12% by weight of P205 0.1-3% by weight of Li20 0.1-3% by weight of Sb203 0-4% by weight of MgO the total of the weight quantities of the ingredients amounting to 100%, and that the opal glass has a thermal expansion coefficient of 8-11 x lO'^C'1 in the temperature range of 20-300°C.
According to the invention, the opal glass prefer¬ ably has the following composition 56-60% by weight of Si02 3-5% by weight of A1203 12-14% by weight of Na20
4-8% by weight of CaO 0.1-2% by weight of BaO 2-5% by weight of ZnO 3-6% by weight of B203 7-10% by weight of P205
0.5-1.5% by weight of Li20 0.1-1% by weight of Sb203 0.5-3% by weight of MgO The invention thus provides opal glass having a thermal expansion coefficient of 8-11 x 10" "C"1 in the temperature range of 20-300°C, i.e. a thermal expansion coefficient which agrees well with that of clear glass. The opal glass according to the invention is thus highly compatible with clear glass, which is an essential qua- lity, especially in the production of illuminating glass. Owing to a complete lack of fluorine, the opal glass according to the invention is not corrosive, as is con- ventional fluorine-containing opal glass. Thus, the in¬ ventive glass can be melted in electrically-heated fur¬ naces, which is a great advantage.
Further distinctive features and advantages of the invention will appear from the following description, as well as the appended claims.
The following description focuses on the ingredients of the glass and their qualities.
The main ingredient of the glass, i.e. Si02, is a glass former which constitutes the network of the glass structure. The glass according to the invention has an Si02 content of approximately 55-65% by weight, prefer¬ ably approximately 56-60% by weight. If the Si02 content falls below the lower limit of the general content range, the chemical resistance and the hot-forming properties of the glass will suffer. Should the Si02 content, on the other hand, exceed the upper limit of the general content range, the viscosity of the glass will increase to an undesirable extent, such that the glass becomes difficult to melt. For these reasons, the Si02 content should fall within the given range.
Both Na20 and Li20 affect the viscosity and the ther¬ mal expansion coefficient α of the glass and, to a cer¬ tain extent, the crystal growth. Should the content of these substances be too low, the viscosity of the glass is increased, thus impairing the melting and forming pro¬ perties of the glass. Furthermore, the thermal expansion coefficient α is reduced, such that the opal glass cannot be combined with standard crystal glass. Should, on the other hand, the content of these substances be too high, the viscosity of the glass will be reduced to an undesir¬ able extent, resulting in corrosive glass and insuffi¬ cient crystal growth. For these reasons, the Na02 content is, according to the invention, approximately 10-17% by weight, preferably approximately 12-14% by weight, while the Li20 content is approximately 0.1-3% by weight, pre¬ ferably approximately 0.5-1.5% by weight. A1203 increases the chemical resistance and the vis¬ cosity of the glass. However, too low an A1203 content impairs the crystal growth as well as the chemical resis¬ tance, whereas too high an Al203 content results in an undesirably high viscosity and an impaired meltability of the glass. For these reasons, the A1203 content of the inventive glass is approximately 2-6% by weight, prefer¬ ably approximately 3-5% by weight.
Moreover, CaO, BaO and ZnO affect the crystallinity of the glass; CaO affecting the crystal form, BaO affect¬ ing the crystal size, and ZnO affecting the crystallisa¬ tion rate. According to the invention, these parameters are favourable when the CaO content is approximately 2-10% by weight, preferably approximately 4-8% by weight, the BaO content is approximately 0.1-6% by weight, pre¬ ferably approximately 0.1-2% by weight, and the ZnO con¬ tent is approximately 0.1-6% by weight, preferably appro¬ ximately 2-5% by weight. By striking a balance between the respective weights of these components, the above parameters (crystal form, crystal size and crystallisa¬ tion rate) may, in addition, be optimised. Preferably, the weight ratio CaO:BaO:ZnO is approximately 8-12:0.5- 1:3-7, more preferred approximately 10:1:5.
In a preferred embodiment, the opal glass according to the invention contains MgO as well. As indicated above with respect to CaO, BaO and ZnO, MgO affects the crys¬ tallinity of the glass, and to be more specific improves the control of the crystallisation process at working temperature. According to the invention, the MgO content does not exceed approximately 4% by weight, i.e. the MgO content generally is 0-4% by weight, and it is preferred that this content is approximately 0.5-3% by weight. When present in the inventive glass, MgO is included in the CaO content in the above weight ratio. If so, the weight ratio (CaO+MgO) :BaO:ZnO is approximately 8-12:0.5-1:3-7. Also B203 has a certain effect on the crystal growth of the glass, but primarily affects the thermal expansion coefficient α. Too low a B203 content impairs the control of the meltability and crystal size of the glass, where¬ as too high a B203 content results in too low a thermal expansion coefficient. As mentioned in the foregoing, the opal glass according to the invention should have a ther¬ mal expansion coefficient of approximately 8-11 x 10"6°C"1 if it is to be combined with clear glass. For these rea¬ sons, the B203 content of the inventive glass is approxi¬ mately 1-8% by weight, preferably approximately 3-6% by weight.
P205, which is a key ingredient of the glass accord¬ ing to the invention, is the main ingredient replacing the fluorine-containing ingredient found in prior-art opal glass. Should the content of P205, which is the main component of the opaque crystals of the glass, be too low, the crystals rendering the glass opaque will not form. Should, on the other hand, the P205 content be too high, the chemical resistance of the glass will suffer. For these reasons, the P205 content of the glass according to the invention is approximately 4-12% by weight, pre¬ ferably approximately 7-10% by weight.
Finally, the glass according to the invention con¬ tains also Sb203, which is a fining agent that, when the glass is being melted, hastens the departure of gas, counteracts gas inclusions in the glass and contributes to the creation of homogeneous glass. If the Sb203 content is too low, no fining effect is achieved, i.e. gas inclu¬ sions form in the glass. On the other hand, the Sb203 con¬ tent should not be too high, not only because such a high content does not result in any additional fining effect, but also because Sb203 is not a completely non-toxic com¬ ponent. For these reasons, the Sb203 content of the glass according to the invention is approximately 0.1-3% by weight, preferably approximately 0.1-1% by weight. The invention will now be further elucidated with the aid of two non-restricting Examples. Example 1
A glass batch of the following composition ( in parts by weight) was introduced into an electrically-heated pot furnace: 100.0 parts of Si02 (sand)
10.7 parts of A1(0H)3 (aluminium hydrate) 12.3 parts of Na2C03 (soda) 18.0 parts of CaC03 (lime) 1.3 parts of BaC03 (barium carbonate) 6.0 parts of ZnO (zinc oxide)
20.2 parts of Na2B407«10H20 (borax) 26.2 parts of Na5P3O10 (sodium tripolyphosphate) 4.9 parts of Li2C03 (lithium carbonate) 1.0 parts of Sb203 (antimony oxide) 5.0 parts of NaN03 (sodium nitrate).
Instead of adding the P205 content of the glass in the form of sodium tripolyphosphate, one may, in accordance with the invention, resort to other suitable P205 sources, such as Ca3(P04)2, NaH2P04, and Na2HP04-2H20. The glass batch introduced into the pot furnace was melted to glass at a temperature of 1420°C, and samples of the melted glass were taken. The finished opal glass had the following, theoretical composition in % by weight: 57.9% Si02 4.1% A1203 13.3% Na20 5.8% CaO 0.6% BaO 3.5% ZnO 4.3% B203 8.7% P205 1.2% Li20 0.6% Sb203 The resulting opal glass was white and contained no crystals that could be perceived with the naked eye. The light transmission was below 0.5%. The transformation temperature (Tg) of the glass was 518°C, and the thermal expansion coefficient α of the glass was 9.65 x 10"6°C"1.
After the glass had been melted, the pot furnace was examined, but no abnormal corrosion of the electric heat- ing elements could be found. Example 2
A glass batch of the following composition (in parts by weight) was introduced into an electrically-heated pot furnace: 100.0 parts of Si02 (sand)
17.6 parts of Na2C03 (soda) 10.4 parts of CaC03 (lime)
8.3 parts of CaMg(C03)2 (dolomite)
1.4 parts of BaC03 (barium carbonate) 6.0 parts of ZnO (zinc oxide)
19.9 parts of Na2B4O7«10H2O (borax) 4.8 parts of Li2C03 (lithium carbonate)
10.7 parts of A1(0H)3 (aluminium hydrate)
26.1 parts of Na5P3O10 (sodium tripolyphosphate) 5.0 parts of NaN03 (sodium nitrate)
1.0 parts of Sb203 (antimony oxide) The glass batch introduced into the pot furnace was melted to glass at a temperature of 1420°C, and samples were taken of the melted glass. The finished opal glass had the following, theoretical composition in % by weight:
57.0% Si02 4.0% A1203 14.8% Na20 4.7% CaO 1.0% MgO 0.6% BaO 3.4% ZnO 4.2% B203 1.1% Li20 8.5% P205 0.6% Sb205 The opal glass was white and contained no crystals that could be perceived with the naked eye. The light transmission was below 0.5%. The transformation tempera¬ ture (Tg) of the glass was 470°C, and the thermal expan- sion coefficient α of the glass was 10.5 x 10" °C~ .
After the glass had been melted, the pot furnace was examined, but no abnormal corrosion of the electric heat¬ ing elements could be found.

Claims

1. Opal glass, c h a r a c t e r i s e d in that it has the following composition, based on the oxides of the ingredients,
55-65% by weight of Si02 2-6% by weight of A1203 10-17% by weight of Na20 2-10% by weight of CaO 0.1-6% by weight of BaO 0.1-6% by weight of ZnO 1-8% by weight of B203 4-12% by weight of P205 0.1-3% by weight of Li20 0.1-3% by weight of Sb203 0-4% by weight of MgO the total of the weight quantities of the ingredients amounting to 100%, and that the opal glass has a thermal expansion coefficient of 8-11 x 10" °C" in the temperature range of 20-300°C.
2. Opal glass as set forth in claim 1, c h a r ¬ a c t e r i s e d in that it has the following composi¬ tion 55-60% by weight of Si02
3-5% by weight of Al203
12-14% by weight of Na20
4-8% by weight of CaO
0.1-2% by weight of BaO 2-5% by weight of ZnO
3-6% by weight of B203
7-10% by weight of P205
0.5-1.5% by weight of Li20
0.1-1% by weight of Sb203 0.5-3% by weight of MgO
PCT/SE1995/000948 1994-08-24 1995-08-21 Opal glass WO1996006052A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU33584/95A AU3358495A (en) 1994-08-24 1995-08-21 Opal glass

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE9402832-1 1994-08-24
SE9402832A SE502937C2 (en) 1994-08-24 1994-08-24 opal Glass

Publications (1)

Publication Number Publication Date
WO1996006052A1 true WO1996006052A1 (en) 1996-02-29

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ID=20395018

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/SE1995/000948 WO1996006052A1 (en) 1994-08-24 1995-08-21 Opal glass

Country Status (3)

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AU (1) AU3358495A (en)
SE (1) SE502937C2 (en)
WO (1) WO1996006052A1 (en)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1997047562A1 (en) * 1996-06-14 1997-12-18 Saint-Gobain Emballage Opal glass compositions
CN104556688A (en) * 2014-12-25 2015-04-29 河北省沙河玻璃技术研究院 Emulsion opal glass and preparation method thereof
WO2018086639A1 (en) * 2016-11-09 2018-05-17 Tomas Bata University In Zlin Ecological alabaster glass
FR3068034A1 (en) * 2017-06-27 2018-12-28 Societe Nouvelle Vermont Financement OPAL GLASS, METHOD FOR MANUFACTURING OPAL GLASS, BULBS AND SHADED TUBES OBTAINED WITH SUCH A GLASS.
WO2023101863A1 (en) * 2021-11-30 2023-06-08 Corning Incorporated Light diffusing glass ceramics

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3498801A (en) * 1965-08-17 1970-03-03 Saint Gobain Phosphate opal glass

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3498801A (en) * 1965-08-17 1970-03-03 Saint Gobain Phosphate opal glass

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
DERWENT'S ABSTRACT, No. 49334D/27, Week 8127; & SU,A,772 979 (GLASS RES INST), 23 October 1980. *

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1997047562A1 (en) * 1996-06-14 1997-12-18 Saint-Gobain Emballage Opal glass compositions
FR2749842A1 (en) * 1996-06-14 1997-12-19 Saint Gobain Emballage COMPOSITIONS OF OPALINE GLASSES
US6001754A (en) * 1996-06-14 1999-12-14 Saint-Gobain Emballage Opal glass compositions
CN104556688A (en) * 2014-12-25 2015-04-29 河北省沙河玻璃技术研究院 Emulsion opal glass and preparation method thereof
CN104556688B (en) * 2014-12-25 2017-05-10 河北省沙河玻璃技术研究院 Emulsion opal glass and preparation method thereof
WO2018086639A1 (en) * 2016-11-09 2018-05-17 Tomas Bata University In Zlin Ecological alabaster glass
FR3068034A1 (en) * 2017-06-27 2018-12-28 Societe Nouvelle Vermont Financement OPAL GLASS, METHOD FOR MANUFACTURING OPAL GLASS, BULBS AND SHADED TUBES OBTAINED WITH SUCH A GLASS.
WO2023101863A1 (en) * 2021-11-30 2023-06-08 Corning Incorporated Light diffusing glass ceramics

Also Published As

Publication number Publication date
SE9402832L (en) 1996-02-25
SE502937C2 (en) 1996-02-26
AU3358495A (en) 1996-03-14
SE9402832D0 (en) 1994-08-24

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