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
  • C03C10/00—Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition
• • 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
  • C03C1/00—Ingredients generally applicable to manufacture of glasses, glazes, or vitreous enamels
  • C03C1/10—Ingredients generally applicable to manufacture of glasses, glazes, or vitreous enamels to produce uniformly-coloured transparent products
• • 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
  • C03C10/00—Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition
  • C03C10/0018—Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition containing SiO2, Al2O3 and monovalent metal oxide as main constituents
  • C03C10/0027—Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition containing SiO2, Al2O3 and monovalent metal oxide as main constituents containing SiO2, Al2O3, Li2O as main constituents
• • 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
  • C03C3/083—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound
  • C03C3/085—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound containing an oxide of a divalent metal
• • 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
  • C03C3/095—Glass compositions containing silica with 40% to 90% silica, by weight containing rare earths
• • 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
  • C03C4/02—Compositions for glass with special properties for coloured glass

Definitions

• the present invention relates to /?-quartz glass-ceramic materials, articles comprising them and processes for making them.
• the present invention relates to /?-quartz glass-ceramic materials having a blue color, articles comprising such materials and processes for making them.
• the present invention is useful, e.g., in making cooktop plates.
• Transparent glass-ceramics with low thermal expansion coefficient which contain a solid ⁇ -quartz solution as main crystalline phase
• Said glass-ceramics are generally obtained from a precursor glass (more conventionally a mixture of the constituents of said glass) whose composition is of Li 2 O-Al 2 O 3 -SiO 2 type (LAS).
• Said composition may contain several secondary constituents, such as:
• alkaline-earth oxides and phosphates or fluorides to optimise fusion and microstructure in particular
• At least one fining agent generally As 2 O 3 and/or Sb 2 O 3 , to eliminate gaseous inclusions from the molten glass mass.
• Said glass-ceramics are obtained by heat treating the precursor glass or mixture of constituents of said glass (the term mineral filler can be used, mineral filler itself precursor of said glass).
• the manufacture of articles in ⁇ -quartz glass ceramic conventionally comprises the three main successive steps recalled below: a first fusion step to melt a mineral glass or a filler, precursor of such a glass, generally conducted at between 1550 and 1700 0 C, - a second cooling and forming step of the molten glass obtained, and a third crystallization or ceramming step of the cooled, formed glass carrying out a suitable heat treatment.
• Said glass-ceramics find application in numerous areas and in particular as glass substrate for fireplaces, cook-tops, protective lenses, security glass. It would be interesting to develop a /?-quartz glass-ceramic material exhibiting a blue coloration.
• a first aspect of the present invention relates to a process for producing a transparent blue glass-ceramic material comprising / ⁇ -quartz solid solution as a main crystalline phase, comprising:
• a lithium aluminosilicate precursor glass comprising TiO 2 as a nucleating agent and at least one glass reducing agent
• the precursor glass comprises at least one metal sulphide as glass reducing agent.
• the step of providing a lithium aluminosilicate precursor glass article comprises: melting a batch mixture of the precursor glass, comprising TiO 2 precursor, to form the precursor glass; - shaping the precursor glass into the desired shape, and the process is characterized in that at least one metal sulphide is included in the batch mixture of the precursor glass.
• said the at least one metal sulphide is selected from among MgS, ZnS and their mixtures.
• the precursor glass comprises at least 0.02 weight % sulphur expressed in terms of ZnS, or in that said batch mixture comprises 0.5 to 3 weight %, advantageously 1 to 2 weight %, ZnS, of the total weight of the batch mixture.
• said glass or said batch mixture comprises at least one oxidant. In certain embodiments of the process of the present invention, said glass or said batch mixture comprises: up to 0.6 wt. % SnO 2 ; and/or up to 1 wt. % CeO 2 ; and/or - up to 1 wt. % WO 3 . In certain embodiments of the process of the present invention, said glass or said batch mixture is essentially free of arsenic oxide and antimony oxide.
• a second aspect of the present invention relates to a blue, transparent Li 2 O-Al 2 O 3 - SiO 2 type glass-ceramic material comprising ⁇ -quartz solid solution as a main crystalline phase, obtainable by a process described summarily above, having a composition: comprising TiO 2 , sulphur, at least one metal oxide, advantageously MgO and/or
• the glass-ceramic material of the present invention has a composition, expressed in terms of weight percentages on the basis of oxides, comprising:
• the composition of the glass-ceramic material further comprises an oxidant.
• the composition of the glass-ceramic material comprises: up to 0.6 wt. % SnO 2 ; and/or - up to 1 wt.% CeO 2 ; and/or - up to 1 wt.% WO 3 .
• the glass-ceramic can have a low coefficient of thermal expansion; second, the glass-ceramic can have a blue color with various intensity.
• the present invention lies in the area of ⁇ -quartz glass-ceramics having a blue colour, of greater or lesser darkness.
• the subject of the invention is more particularly: a process for producing transparent blue glass-ceramics containing a solid ⁇ -quartz solution as main crystalline phase; a process for producing articles in said glass-ceramics; novel transparent blue glass-ceramics containing a solid ⁇ -quartz solution as main crystalline phase; articles in said novel glass-ceramics; and precursor glass for said novel glass-ceramics.
• the present invention is based on the action of original compounds, within the compositions of said glass-ceramics, to impart the blue colour.
• the blue colour persons skilled in the art know that while Ti + ions are essentially colourless, i.e. do not impart colour to the substrate (liquids, glass..) containing the same, Ti 3+ ions impart a blue colouring to said substrate due to d ⁇ d electronic transitions (Phys. Chem. Glass. 42 (2001) 231-239). Therefore one known manner to generate the blue colour within a glass or glass ceramic containing titanium consists of reducing the Ti 4+ ions.
• said reducing is conducted through the action of a reducing agent chosen from among a hydrogen-containing phosphate, Ti 2 O 3 and/or a chloride. Said chloride action raises problems:
• the inventor can be credited with proposing an original route of particular interest to obtain transparent blue glass ceramics with low thermal expansion coefficient.
• Samples 1 mm thick of said glass ceramics generally have the values given below for the parameters L* (lightness), a* and b* (colour coordinates) in the colour space laid down by "CIE 1976 Lab” (International Commission on Illumination):
• the glass-ceramics of the invention also generally have a thermal expansion coefficient (measured at 25-700 0 C) of between -15 x 10 "7 K “1 and +20 x 10 "7 K “1 .
• the first subject of the invention relates to an original process for producing a transparent blue glass-ceramic, containing a solid ⁇ -quartz solution as main crystalline phase (said solid ⁇ -quartz solution representing at least two thirds of the crystalline phase).
• Said process conventionally comprises heat treatment of a lithium aluminosilicate glass (LAS glass) or of a filler, itself a precursor of such a glass, under conditions which ensure ceramming; said glass or said filler including TiO 2 , or a source of TiO 2 , as nucleating agent and at least one glass reducing agent.
• LAS glass lithium aluminosilicate glass
• filler itself a precursor of such a glass
• At least one metal sulphide is used as glass reducing agent; advantageously a single metal sulphide is used as single glass reducing agent.
• the second subject of the present invention concerns a process for producing an article in a transparent blue glass-ceramic containing a solid ⁇ -quartz solution as main crystalline phase (said solid ⁇ -quartz solution representing at least two thirds of the crystalline phase).
• Said process conventionally, comprises: melting a lithium aluminosilicate glass (LAS glass) or an inorganic filler, itself a precursor of such a glass, - cooling the molten glass obtained, and simultaneously forming it into the required shape for the intended end article, and ceramming said formed glass; said glass or said filler including TiO 2 or a source of TiO 2 as nucleating agent, and at least one glass reducing agent.
• LAS glass lithium aluminosilicate glass
• an inorganic filler itself a precursor of such a glass
• said glass or said filler including TiO 2 or a source of TiO 2 as nucleating agent
• at least one glass reducing agent characteristically, for the implementation of said process, at least one metal
• At least one metal sulphide is used in original, characteristic manner as glass reducing agent.
• Said metal sulphide may be used alone or in combination with another metal sulphide and/or with at least one other glass reducing agent of another type (see above).
• a reducing agent of another type is not used.
• a single metal sulphide is used as single glass reducing agent.
• said at least one metal sulphide is generally chosen from among MgS, ZnS and their mixtures.
• the use of Na 2 S is also possible.
• ZnS is advantageously used and most advantageously used as single glass reducing agent.
• the blue colour is characteristically obtained through the addition of at least one metal sulphide to the composition to be cerammed.
• the obtaining of said blue colour is based a priori on the reaction:
• said at least one metal sulphide is or is not a single glass reducing agent; it is added to a filler or is present in a precursor glass, previously formed; it is desired to obtain a blue of greater or lesser darkness.
• the adjustment and optimisation under consideration is within the reach of persons skilled in the art.
• ZnS is used as single glass reducing agent in the meaning of the invention, to implement the process of the invention, use is generally made of: a glass containing at least 0.02 wt.% sulphur, expressed in ZnS; or - a filler containing 0.5 to 3 wt.%, advantageously 1 to 2 wt.%, of ZnS.
• the precursor glass or precursor filler may contain at least one oxidant.
• Said oxidant is suitable for attenuating the reducing action of said at least one metal sulphide, and can thereby enable "controlling" of the final blue colouring of greater or lesser darkness.
• Said oxidant can be chosen in particular from among SnO 2 , CeO 2 , WO 3 and their mixtures.
• Said glass or said precursor filler may in particular contain: up to 0.6 wt.% SnO 2 ; and/or up to 1 wt.% CeO 2 ; and/or - up to 1 wt.% WO 3 .
• the ceramming processes of the invention - implemented in manner known per se, using an original reducer for the probable reducing of at least part of the Ti 4+ ions to Ti + ions - generally include fining the molten glass before the actual ceramming step.
• the inventor has found that the at least one metal sulphide, used under the invention, optionally in combination with at least one oxidant, acts as a fining agent via the formation of SOx (SO 2 and/or SO 3 ). It is therefore possible to minimize, even to cancel out, the presence of conventional fining agents such as As 2 O 3 , Sb 2 O 3 and halides, when implementing the processes of the invention.
• the glass or precursor filler, precursor of the glass-ceramic or article in glass-ceramic concerned does not contain any arsenic oxide (As 2 O 3 ) or antimony oxide (Sb 2 O 3 ), with the exception of unavoidable traces thereof.
• the third subject of the invention concerns transparent blue glass-ceramics which may be obtained using the above-described process (first subject of the said invention).
• the fourth subject of the present invention concerns articles in a transparent blue glass-ceramic which may be obtained using the above-described process ( second subject of the present invention).
• Said glass-ceramics and articles in glass-ceramic carry the signature of the process used to obtain the same: their composition includes the oxide of the at least one metal used as sulphide i.e. at least one metal oxide; it therefore generally includes the oxide of magnesium and/or zinc, advantageously zinc oxide.
• the zinc oxide content generally lies between 0.5 and 4 weight percent; their composition includes sulphur.
• the sulphur content is not substantial owing to the volatility of SO 2 and/or SO 3 , but it is not a zero content owing to the action of said at least one metal sulphide.
• composition is also free of arsenic oxide and antimony oxide, with the exception of unavoidable traces thereof.
• Other fining agents are able to be used, and even better the at least one metal sulphide included for the blue colour is itself able to ensure the function of fining agent.
• the joint use is not excluded of said at least one metal sulphide with at least one other fining agent of another type, different from the arsenic oxide or antimony oxide.
• the articles in a blue glass-ceramic of the invention may be of different types. They may in particular be cook-tops, cooking utensils, plates of microwave ovens, fireplace windows, fire doors or windows, view windows for pyrolysis or catalysis ovens, lenses or tableware items. This is not an exhaustive list.
• the present invention especially concerns transparent blue glass-ceramics containing a solid ⁇ -quartz solution as main crystalline phase whose composition, expressed in weight percentage of oxides, essentially consists of:
• TiO 2 0.4 - 5 whose composition also contains sulphur, expressed in SO 3 , in a quantity of at least 0.01 weight percent, and is halide- and phosphate-free with the exception of unavoidable traces thereof.
• composition "essentially consists" of the given percentages of oxides. This means that in the glass-ceramics the sum of the oxides listed represents at least 95 weight %, generally at least 98 weight %. It is actually not excluded that other compounds may be found in small quantities in said glass-ceramics such as
• La 2 O 3 , Gd 2 O 3 , Y 2 O 3 and colour agents such as Nd 2 O 3 and Er 2 O 3 to act on the blue tints.
• the glass-ceramics under consideration are of LAS type. They contain Li 2 O, SiO 2 and Al 2 O 3 as essential constituents of the solid ⁇ -quartz solution, imparting transparency and a low thermal expansion coefficient thereto.
• TiO 2 is used as nucleating agent at a content of between 0.4 and 5 weight %. It is advantageously used at a content of between 2 and 3 weight %, most advantageously at a content of between 2.1 and 2.8 weight %. If the quantity of TiO 2 is too low, crystallization will not be homogeneous, crystal size will be increased and opalescence occurs. To obtain the blue colour, generally 0.1 to 10 % of titanium is reduced to Ti 3+
• the glass-ceramics contain ZrO 2 as other nucleating agent.
• the content of ZrO 2 is advantageously less than 2 weight %.
• the dissolution of ZrO 2 in the molten glass may give rise to problems.
• the alkaline-earth oxides are used to improve fusion properties, to stabilise the glass phase and to act on the microstructure of the glass-ceramic. If they are used in excessive quantity, thermal expansion may reach detrimental values.
• Small quantities of MgO preferably less than 1 weight %, even less than 0.7 weight %, and further preferably less than 0.5 weight %, have proved to be capable of reducing dispersion by reducing the size of the crystallites.
• BaO and SrO may be used to exert an influence on the microstructure, on the refractive index of the residual glass and on the coefficient of thermal expansion.
• Alkaline oxides, other than Li 2 O, i.e. Na 2 O and K 2 O are used as flow agents and to increase thermal expansion.
• the glass-ceramics of the invention advantageously have a K 2 O and Na 2 O content of between O and 1 weight %. Advantageously, they do not contain Na 2 O.
• the glass-ceramics of the invention contain sulphur (due to the action of ZnS and optionally of at least one other sulphide, whether or not used as reducing agent during the production process). They generally contain little thereof (due to the volatility of SO 2 and SO 3 ).
• the sulphur content, expressed in SO 3 is at least 0.01 weight %. It can be indicated, but in no way limited thereto, that said sulphur content generally ranges from 0.01 to 0.25 weight %.
• the glass-ceramics of the invention do not contain halides and phosphates, with the exception of unavoidable traces thereof.
• Said glass-ceramics may also contain at least one oxidant. It has been seen that in the event that at least one said oxidant is used, the percentages are advantageously: - up to 0.6 wt.% SnO 2 ; and/or up to 1 wt.% CeO 2 ; and/or - up to 1 wt.% WO 3 .
• the glass- ceramics whose composition is specified above, also advantageously have a composition that is free of arsenic oxide and antimony oxide with the exception of unavoidable traces thereof.
• the present invention particularly concerns articles in a transparent blue glass-ceramic containing a solid ⁇ -quartz solution as main crystalline phase, whose composition is as indicated above.
• Said articles may in particular consist of cook-tops, cooking utensils, plates of microwave ovens, fireplace windows, fire doors or windows, view windows of pyrolysis or catalysis ovens, lenses or tableware items. This list is evidently non-exhaustive.
• the present invention concerns lithium aluminosilicate glass, precursors of the glass-ceramics whose composition is given above. Said glass has the indicated composition.
• example C is given as comparative example, and examples 1 to 4 illustrate the said invention.
• the appended figure shows transmission (expressed in %) in relation to wavelength (expressed in nanometres) for glass-ceramic samples of examples C, 1 and 4,
• the crucibles were then removed from the furnace and the molten glass was poured onto a pre-heated steel plate. It was rolled to a thickness of 4 mm. Glass slabs approximately 20 cm x 30 cm were obtained. They were annealed at 65O 0 C and then cooled gently.
• the colour of the glass slabs obtained varied from light yellow to dark violet. Said glass slabs were then subjected to ceramming (crystallization) at temperatures ranging from 660 to 900 0 C, more precisely:
• the glass-ceramics obtained had the tints and properties indicated in the second part of Table 1 below.
• ZnS (no sulphur); those corresponding to examples 1, 2 and 4 respectively contain 1.6, 2 and 1.8 weight % ZnS; the batch corresponding to example 3 contains 2 weight % ZnS and 0.1 weight
• the glass-ceramic in example C has the yellow colour usually obtained for this type of glass-ceramic (LAS glass ceramic [Li 2 O-Al 2 O 3 -SiO 2 ] containing TiO 2 ). Its transmission spectrum (340 to 2000nm) is shown in appended figure 1.
• the glass-ceramic of the invention has a dark blue colour. Its transmission spectrum (340 to 2000nm) is shown in appended figure 1. The (total) sulphur content (expressed in SO 3 ) was taken to be the content determined by humic method after glass melting (method known per se) and was compared with the content of the glass-ceramic in example C.
• the glass-ceramic in example 2 has a different blue to the glass-ceramic in example 1. Said blue is very dark.
• the glass-ceramic in example 3 has a lighter blue than the glass-ceramic in example 2, insofar as an oxidant (CeO 2 ) is used.
• the glass-ceramic in example 4 has a lighter blue than the one in example 2, insofar as less ZnS is used. Its transmission spectrum (340 to 2000nm) is shown in appended figure 1.

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• Geochemistry & Mineralogy (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Ceramic Engineering (AREA)
• Crystallography & Structural Chemistry (AREA)
• Dispersion Chemistry (AREA)
• Glass Compositions (AREA)

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• 2006
  • 2006-10-27 FR FR0654585A patent/FR2907776B1/fr not_active Expired - Fee Related
• 2007
  • 2007-10-25 WO PCT/EP2007/061452 patent/WO2008049873A2/en not_active Ceased
  • 2007-10-25 KR KR1020097010874A patent/KR101398337B1/ko not_active Expired - Fee Related
  • 2007-10-25 CN CN2007800428169A patent/CN101631753B/zh not_active Expired - Fee Related
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  • 2007-10-25 ES ES07821815T patent/ES2339406T3/es active Active
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• 2015
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