Lead-free crystalline composition, glass and glass articles made from said composition

Abstract

The present invention relates to a lead-free crystalline glass composition comprising: 58-64 wt. % SiO2, 0-0.5 wt. % Al2O3, a mixture of alkali oxides and alkaline earth oxides; The glass composition comprises: 58-64 wt% SiO2, 0-0.5 wt% Al2O3, 13.8-18 wt% of a mixture of alkali oxides consisting of K2O and Na2O, and 9-15 wt% of a mixture of alkaline earth oxides consisting of BaO and SrO (the ratio of the mole percent of the mixture of alkali oxides to the mole percent of the mixture of alkaline earth oxides is about 2 to about 3), 6-10 wt% ZnO, 0-1.20 wt% Sb2O3, 0-0.5 wt% SO3, 0-6.8 wt% TiO2, and 0-6 wt% La2O3, and 0-10% colorant. The present invention also relates to glass materials based on this composition, and to articles made from or containing such glasses.

Description

[Technical Field]

[0001] [Subject of the Invention] The present invention relates to a substantially lead-free (i.e., substantially lead-free) crystallized glass composition, but the resulting glasses based on this composition, and articles made from such glasses, have properties and characteristics that are the same as or similar to those of lead crystallized glasses. [Background technology]

[0002] [Latest technology] Lead crystal glass articles, whether they are or are intended for use as tableware, decorative items, lighting fixtures, or jewelry, are generally made from compositions that include a vitreous base and at least a significant proportion of lead oxide, generally greater than 24% or 30% by weight of the total weight of the composition.

[0003] Typically, they are obtained by melting the components of the composition in a continuous casting furnace, tank furnace, batch casting furnace, or pot furnace, usually in the presence of recycled lead crystal glass, followed by various steps of hot working and hot forming to form an article, which is then subjected to various steps of cold working or machining, generally consisting of one or more steps of sawing, slitting, cutting, drilling, mechanical polishing, or any combination of the above steps. Typically, the article is also subjected to an acid polishing step, typically performed using a mixture of hydrofluoric acid (HF) and sulfuric acid (H2SO4), followed by rinsing to remove residual salts. Finally, a finishing step can be performed, for example, to decorate the surface of the article.

[0004] The percentages of lead used in lead crystal glass compositions help to lower their melting and working temperatures compared to lead-free compositions. These percentages also help to increase their malleability and achieve a viscosity that allows for processing and shaping of the crystals within the temperature range of 600°C to 1200°C. They also give lead crystal glasses a pliable texture that makes them easy to polish, engrave, or cold cut. 、It also helps to ensure a particular level of gloss, density and tone, as well as excellent chemical durability characterized by good hydrolysis resistance, all of which are characteristics of lead crystal.

[0005] Nevertheless, taking into account that lead is toxic and that there is a risk of it migrating into products that come into contact with the crystalline glass, so-called "alternative" crystalline compositions in which the proportion of lead oxide is reduced, or indeed even so-called "lead-free crystalline" compositions, have been proposed.

[0006] These alternative lead-free crystalline compositions generally comprise a vitreous base, which may be silica (SiO2)-based for silicate glasses, or silica and aluminum oxide (Al2O3)-based for aluminosilicate glasses, or silica, aluminum oxide and boron oxide (BO3)-based for aluminoborosilicate glasses, a set of modifier components for modifying the vitreous base, specific additives such as, for example, one or more fluxes, stabilizers, fining agents, and optionally a set of coloring or bleaching components that make it possible to approximate or reproduce the properties and characteristics of the crystalline composition and lead crystalline glass, especially with regard to processing or forming / shaping and thus hot viscosity, density, refractive index and audibility.

[0007] For example, U.S. Pat. No. 6,235,667 states that the density is 2.9 g / cm 3 This paper describes a silicate or aluminosilicate glass composition having a density greater than 1.001 and a refractive index greater than 1.545, which is lead-free and suitable for the manufacture of tableware and / or decorative crystallized glass articles. The composition contains, by weight, 50-58% SiO2 and 0-3% Al2O3, with lead being replaced by a mixture of zinc, barium, lanthanum, niobium, and bismuth, accounting for 26-33% by weight, zinc oxide being 16-30% by weight, barium and bismuth oxides being 0-13% by weight each, and the sum of these oxides excluding zinc being 7-14%. The composition further comprises: 12 to 18% by mass of potassium, sodium and lithium oxides; Sb2O3, As2O3, NiO, CoO, MnO2, Er2O3, Nd2O3 as clarifying and decolorizing agents; It contains one or more components selected from SeO and CeO2 in a total amount of less than 2% by mass, with Sb2O3 representing 0 to 1% by mass; and may contain zirconium oxide, yttrium oxide and titanium oxide in a combined total content of less than 6% by mass.

[0008] EP 1725502 describes a lead-free, barium-free crystalline composition that is an aluminoborosilicate glass having a refractive index of at least 1.55. The composition contains, by weight, 50-60% SiO2, 0.6-4% B2O3, 0.25-5% Al2O3, 0-3% K2O, 12-15% Na2O, 4-11% CaO, 0-2% MgO, 0-5% TiO2, and 8-16% ZnO. The total content of Pb, Ba, and As oxides is less than 0.1%, the total content of Ti and La oxides is less than 5%, the total content of Nb, Ta, Yb, Y, W, Bi, and Zr oxides is less than 5%, and the total content of Nb, Ta, and Yb oxides is less than 1%, and the total content of Y, W, Bi, and Zr oxides is less than 3%.

[0009] Chinese Patent No. 105837045 describes a glass having a refractive index of 1.545 or more and a glass thickness of 2.9 g / cm intended for the manufacture of tableware articles. 3 This document describes a lead-free or barium-free glass composition, which may be a silicate, borosilicate, or aluminosilicate glass, having a density of at least 1000 MPa, the composition comprising, by weight, 50-65% SiO2, 0-5% Al2O3, 0-5% B2O3, 0-3% Li2O, 0-15% Na2O, 0-10% K2O, 0-10% La2O3, and 0-15% SrO, with ZnO at least 8% but less than 16%.

[0010] While such lead-free crystallized glass compositions provide a means for obtaining glasses with densities and refractive indices comparable to those of lead-crystallized glasses, they exhibit several drawbacks during the melting process and subsequent steps involved in the manufacture of articles. The compositions may exhibit crystallization during hot working. Furthermore, during the hot forming of articles, the molten material has proven to be poorly, if at all, suitable for the manufacture of large parts weighing, for example, 1 kg to 50 kg, or parts having complex forms or shapes. Furthermore, compositions containing boron oxide and / or bismuth oxide, as well as high contents of alkali oxides, especially lithium oxide, interact strongly at high temperatures with refractory elements that form an integral part of the furnace in which the melting process takes place. This results in premature wear of these refractory elements, reducing the useful life of the furnace and potentially resulting in undesirable discoloration of the glass. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] U.S. Patent No. 6,235,667 [Patent Document 2] European Patent No. 1725502 [Patent Document 3] Chinese Patent No. 105837045 Summary of the Invention

[0012] [Objective of the Invention] It is an object of the present invention to provide a substantially lead-free crystallized glass composition, a substantially lead-free crystallized glass, and articles made from such glasses, all of which do not exhibit the drawbacks of the state of the art. The aim of the present invention is to provide an alternative to existing state-of-the-art solutions.

[0013] It is also an object of the present invention to provide a composition that ensures ease of use in operational practices, allows improved processability and workability at operating temperatures similar to those for lead crystal glass compositions, and imparts to the glass obtained therefrom and to the articles made therefrom similar or identical characteristics and properties to those of lead crystal glass or lead crystal glass articles.

[0014] The object of the present invention also relates to the use of the composition according to the invention for the production of lead-free crystallized glass and to lead-free crystallized glass articles which are substantially free of lead.

[0015] [Summary of the Invention] The object of the present invention is to provide a lead-free crystalline glass composition comprising 58-64 wt% SiO2, 0-0.5 wt% Al2O3, 13.8-18 wt% of a mixture of alkali oxides consisting of K2O and Na2O, and 9-15 wt% of a mixture of alkaline earth oxides consisting of BaO and SrO (the ratio of the mole percent of the mixture of alkali oxides to the mole percent of the mixture of alkaline earth oxides is about 2 to about 3), 6-10 wt% ZnO, 0-1.20 wt% Sb2O3, 0-0.5 wt% SO3, 0-6.8 wt% TiO2 and 0-6 wt% La2O3, and 0-10% colorant or decolorant.

[0016] According to some particular embodiments of the present invention, the compositions according to the present invention comprise at least one, or any suitable combination of, the following characteristic properties: the alkali oxide mixture consists of 8-10% by weight of K2O and 5.8-8% by weight of Na2O, the mixture of alkaline earth oxides consists of 8.5-12% by weight of BaO and 0.5-3% by weight of SrO; the ratio of the mole percent of the mixture of alkali oxides to the mole percent of the mixture of alkaline earth metal oxides is equal to about 2; The ratio of the mole percentage of the mixture of alkali oxides to the mole percentage of the mixture of alkaline earth oxides is equal to about 2.5.

[0017] The present invention also relates to the use of the composition according to the invention for the production of lead-free crystallized glass.

[0018] The present invention also relates to a lead-free crystalline glass material based on the above composition, preferably having a refractive index of 1.537 to 1.559 and a density of 2.77 to 3.03.

[0019] The present invention further relates to the use of the lead-free glass according to the invention for producing an article made of the lead-free glass according to the invention.

[0020] The present invention also relates to lead-free crystalline articles made from or comprising a glass according to the present invention, which in some particular embodiments are tableware articles, ornaments, pieces of jewellery, elements of lighting fixtures or luminaires. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a diagram showing a comparison of the viscosity of lead crystals and lead-free crystals. DETAILED DESCRIPTION OF THE INVENTION

[0022] [Detailed Description of the Invention] In the following sections of this specification and in the claims, the term "wt %" refers to the fact that the percentage given for a component relates to the total mass of the composition; similarly, the term "mol %" or "mole percentage" refers to the fact that the percentage given relates to the total number of moles in the composition. The term "trace amount" or "impurity" refers to the fact that the compound in question is found to be present in an amount of 0.05% by weight or less.

[0023] The compositions according to the invention are called "lead-free crystallized glass compositions" because the glasses based on and obtained from them have properties and characteristics that are the same as or similar to those of lead crystallized glasses, but are substantially free of lead. The compositions according to the invention are substantially free of lead oxide but exhibit properties and characteristics that are identical, similar or very close to those of lead crystal glass compositions, in particular in that they offer the possibility of melting and fining the compositions in the same way, in particular with regard to temperature, under the operating conditions usually used for lead crystal, and also exhibit suitability for being worked by hand to obtain pressed and blown articles, as well as suitability for being cold-formed very similar to those of lead crystal.

[0024] The composition according to the invention comprises a vitreous base containing silica but substantially free of boron or boron oxide, phosphorus or phosphorus oxide, or bismuth or bismuth oxide, except in trace amounts or as an impurity, and may optionally contain aluminum oxide, which offers the advantage of increasing the stability and durability of the glass.

[0025] The composition according to the invention is not a glass-ceramic glass composition: it does not contain a crystalline phase present in the form of crystals dispersed in a glassy phase.

[0026] The composition according to the invention contains by weight 58-64% SiO2 and, if present, less than 0.5% Al2O3.

[0027] The composition further comprises a mixture of alkali and alkaline earth oxides.

[0028] The alkali oxide mixture consists of 13.8-18 wt% of a mixture of potassium oxide (K2O) and sodium oxide (Na2O). No other alkali metal oxides are included, especially lithium and / or or contains no cesium oxides other than in trace amounts or as impurities. Preferably, K2O is present in an amount of 8-10 wt%, i.e., 6-9 mol%, and Na2O is present in an amount of 5.8-8 wt%, i.e., 6-9.2 mol%. Preferably, the ratio of the molar percentage of Na2O to the molar percentage of K2O is about 1.

[0029] Potassium oxide and sodium oxide are modifiers of the vitreous network and flux. In the combinations and proportions according to the invention, these oxides present the advantage of maximizing their effect on the thermal properties of the glass, lowering the melting temperature of the vitreous base, reducing the viscosity of the glass at high temperatures, and facilitating fining and homogenization, while limiting the corrosion during the melting step of the refractory elements that constitute an integral part of the furnace.

[0030] The alkaline earth oxide mixture comprises 9-15 wt. % of a mixture of barium oxide (BaO) and strontium oxide (SrO). It contains no other alkaline earth metal oxides, and in particular, it contains no calcium and / or magnesium oxides except in trace amounts or as impurities. Preferably, BaO is present in an amount of 8.5-12 wt. %, i.e., 4-6 mol. %, while SrO is present in an amount of 0.5-3 wt. %, i.e., 0.3-3 mol. %. Preferably, the ratio of the mol. % of BaO to the mol. % of SrO is about 2.7-11.5%.

[0031] Barium oxide and strontium oxide are heavier stabilizers than the conventionally used calcium oxide and magnesium oxide. They offer the advantage of increasing the hot viscosity while increasing both the density and refractive index of the resulting glass. Furthermore, they improve the hot workability of the composition, thereby ensuring a higher processing range. In the proportions according to the present invention, they offer the advantage of amplifying the effects of barium oxide and strontium oxide alone at such content levels without exhibiting any of their drawbacks.

[0032] The ratio of the sum of the mole percent of alkali oxides to the sum of the mole percent of alkaline earth oxides, i.e., (mol % KO + mol % NaO) / (mol % BaO + mol % SrO), is between about 2 and about 3. Preferably, this ratio is equal to about 2, 2.25, 2.5, 2.75, 2.79, or 3. Advantageously, this ratio is equal to 2.5.

[0033] Such a mixture of alkali and alkaline earth oxides modifies the viscosity profile of glass materials based on the compositions according to the invention compared to the viscosity profile of glass compositions such as crystalline or soda-lime glass compositions, particularly between the glass-forming temperature corresponding to a viscosity of 10 poise and the softening temperature corresponding to a viscosity of 10 poise, which provides the advantageous ability to obtain glasses that do not harden as rapidly, thus enhancing their hot workability (FIG. 1).

[0034] The composition further contains zinc oxide but does not contain any other oxides of the lead group other than tin oxide. In any case, it does not contain oxides of bismuth, gallium, and / or cadmium except in trace amounts or as impurities. Zinc oxide accounts for 6 to 10% by weight of the composition according to the invention. When tin oxide is present, it may be present in an amount of up to 2% by weight.

[0035] In the compositions according to the invention, zinc oxide plays a role similar to that of lead in lead crystallized glasses: it serves the purpose of stabilizing the glass at high temperatures, increasing its chemical durability at low temperatures, and increasing the refractive index of the resulting glass.

[0036] This combination of barium, strontium and zinc oxide offers the advantage of increasing the stability of the glass at high temperatures by limiting crystallization.

[0037] The composition may further contain antimony oxide, preferably presenting 0 to 1.20% by weight. This provides the advantage of obtaining a homogeneous glass without residual bubbles. Furthermore, during the melting process, excess oxygen is provided, which allows for an oxide glass to be obtained that is easier to control throughout the melting process, thereby providing, among other things, a certain degree of color stability.

[0038] Preferably, the composition may further comprise, in addition to antimony oxide, one or more sulfates, which offer the advantage of oxidizing the glass and extending the fining temperature range during the melting process beyond the simple action of antimony oxide, with the one or more sulfates being present in the form of precursors such as, for example, Na2SO4, K2SO4, SrSO4, BaSO4, and combinations thereof.

[0039] The composition may further contain a transition metal oxide, preferably titanium oxide, preferably in an amount of less than 1% by weight. This has the advantage of lowering the melting temperature of the glass and increasing the refractive index. Titanium oxide may also contribute to the coloring of the glass. In this case, its content may be up to 6.8% by weight.

[0040] The composition may further comprise 0-6% of an oxide of a lanthanide, preferably lanthanum oxide, which has the advantage of making the composition heavier and increasing the density of the glass while retaining a high refractive index and good processability.

[0041] The composition may further comprise a coloring or decoloring agent, preferably to mask the color imparted by impurities or to actually obtain colored glass. Preferably, the composition may comprise a metal oxide such as V2O5, Cr2O3, MnO, Fe2O3, CoO, NiO, CuO, SnO2, a lanthanide oxide such as CeO2, Pr2O3, Nd2O3, Er2O3, or a noble metal such as Ag or Au.

[0042] Preferably, the composition does not contain any other ingredients than those mentioned above. Thus, the composition consists of: 58-64% by weight of SiO2, 0-0.5% by weight of Al2O3, 5.8-8% by weight of Na2O, 8-10% by weight of K2O, 8.5-12% by weight of BaO, 0.5-3% by weight of SrO (the ratio of the sum of the molar percentages of Na2O and K2O to the sum of the molar percentages of BaO and SrO is 2-3); 6-10% by weight of ZnO, 0-1.2% by weight of Sb2O3, 0-0.5% by weight of SO3, 0-6.8% by weight of TiO2, 0-6% by weight of La2O3, 0-10% by weight of colorant (the sum of these components represents 100% of the total weight of the composition). Examples of compositions according to the present invention are shown in Tables 1 and 2 below.

[0043] [Table 1]

[0044] [Table 2]

[0045] The composition according to the present invention should be understood as the mixture of components or raw materials that constitute it and that are melted in a furnace. The molten mass, and thus the glass based on or obtained from the composition according to the present invention, no longer contains the raw materials of the composition itself, but rather their reaction products. Furthermore, the molten mass (melt) and glass may further contain contaminants, minerals, or mineral oxides resulting from contamination that occurs during the process of obtaining the molten mass and glass, for example, during the time spent in the furnace. For example, the resulting melt and glass may contain zirconium or zirconium oxide from the refractory elements of the furnace, which may account for up to 1% by weight of the total mass of the raw materials of the composition.

[0046] The compositions according to the invention present the advantage that they can be used with the techniques, tools, and in particular furnaces, used in the production of lead crystal glasses and lead crystal glass articles.

[0047] The composition according to the invention is used to produce the lead-free glass according to the invention. The lead-free glasses of the present invention are obtained from the compositions of the present invention. They may be silicate or aluminosilicate glasses, but are not aluminoborosilicate glasses. The glasses of the present invention exhibit the same, equivalent, or very similar physical and mechanical properties as lead crystal glasses, as well as comparable audibility.

[0048] The lead-free crystallized glass according to the present invention has a refractive index of 1.537 to 1.559 and an Abbe number of greater than 42, preferably 54 to 56, as measured by an Abbe refractometer.

[0049] It has a density of 2.77 to 3.03, preferably 2.70 to 2.90.

[0050] The lead-free crystallized glass of the present invention has a refractive index of 1.537 to 1.559 and a density of 2.77 to 3.03.

[0051] The lead-free glass of the present invention has a viscosity of 436 kg / mm 2 or more, preferably 526 to 549 kg / mm 2 The Vickers hardness is Hv0.1.

[0052] It has an elasticity characterized by a Young's modulus greater than 59 GPa, preferably between 66 and 69.5 GPa.

[0053] It has a resistance to hydrolysis, expressed as R2O, of 122-132 μg / g, measured according to the ISO 719 standard.

[0054] The lead-free crystal glass of the present invention is used to manufacture lead-free crystal products. The glass is processed / formed to impart a specific shape, surface texture, etching, or other specific marking features, determined based on the end use and / or final destination of the article. The lead-free crystal glass may also potentially be covered with one or more decorative elements. As a result of these modifications, the glass is transformed into a lead-free crystal glass article.

[0055] A lead-free glass article according to the present invention is made from or comprises lead-free glass according to the present invention and one or more coatings of metals and / or precious metals and / or polymers, one or more etchings or markings, one or more surface textures, or combinations thereof, deposited on a substrate made from or comprising glass according to the present invention.

[0056] The lead-free crystal glass article according to the invention is preferably an element of prosthetics; tableware, for example ceramics; decorative items; lighting fixture elements; or decorative and ornamental articles.

Claims

1. A lead-free crystalline glass composition comprising: 58 to 64% by weight of SiO ２ and, 0 to 0.5 wt. % Al ２ O ３ and; A mixture of alkali oxides and alkaline earth oxides :-K ２ O and Na ２ a mixture of alkali and alkaline earth oxides consisting of 13.8 to 18 weight percent of a mixture of alkali oxides consisting of O and 9 to 15 weight percent of a mixture of alkaline earth oxides consisting of BaO and SrO, wherein the ratio of the mole percent of the mixture of alkali oxides to the mole percent of the mixture of alkaline earth oxides is from about 2 to about 3; 6 to 10 wt. % ZnO; 0 to 1.20 wt. % Sb ２ O ３ and, 0 to 0.5 wt. % SO ３ and, 0 to 6.8 wt. % TiO ２ and, 0 to 6 wt.% La ２ O ３ ,and A composition comprising 0-10% coloring or bleaching agent.

2. The mixture of alkali oxides contains 8 to 10 wt. % K ２ O and 5.8 to 8% by weight of Na ２ The composition of claim 1 consisting of O.

3. 3. The composition of claim 1, wherein the mixture of alkaline earth oxides consists of 8.5 to 12 wt. % BaO and 0.5 to 3 wt. % SrO.

4. 4. The composition of claim 1, wherein the ratio of the mole percent of the mixture of alkali oxides to the mole percent of the mixture of alkaline earth metal oxides is equal to about 2.

5. 4. The composition of any one of claims 1 to 3, wherein the ratio of mole percent of said mixture of alkali oxides to said mole percent of said mixture of alkaline earth oxides is equal to about 2.

5.

6. Use of the composition according to any one of claims 1 to 5 for the production of lead-free crystallized glass.

7. A lead-free crystallized glass based on the composition according to any one of claims 1 to 5.

8. The lead-free crystallized glass according to claim 7, having a refractive index of 1.537 to 1.559 and a density of 2.77 to 3.

03.

9. 9. Use of the lead-free crystallized glass according to claim 7 or 8 for producing an article made from the lead-free crystallized glass.

10. A lead-free crystalline article made from or comprising the glass of claim 7 or 8.

11. The lead-free crystalline article 11. The lead-free crystalline article of claim 10, which is a tableware, ornament, jewelry, lighting fixture component, or lighting fixture.

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