MXPA98006312A - Lead-free glass composition, low temperat fusion - Google Patents

Abstract

The present invention relates to: low melting lead-free glass compositions, glass frits consisting of said composition and glass enamels made therefrom for cover glass, especially automotive glassware. The composition consists of (% by weight): 45-67% Bi2O3, 24-39% SiO2, 8 ~ -10% B203, 1-7% ~ Na2O, 0.5% A1203, 0-4% TiO2, 0, 3% TiO2, 0.3% Li2.0, 0.4% F-1. The glass composition exhibits good chemical durability and good anti-tack properties and avoids stresses in the cast enamel

Description

COMPOSITION OF LEAD-FREE GLASS, LOW TEMPERATURE FUSION This invention relates to low temperature melting lead-free glass compositions.

BACKGROUND OF THE INVENTION Lead-free glass compositions are known in the art. Illustrative are the following: Reinherz U.S. Patent No. 4,892,847 Francel U.S. Patent No. 4,554,258 Roberts U.S. Patent No. 5,252,521 Klimas U.S. Patent No. 4,970 .178 Clifford U.S. Patent No. 5,308,803 Murkens U.S. Patent No. 5,093,285 Ryan U.S. Patent No. 5,559,059 Ne man U.S. Patent No. 2,301,100 Can be formed additional discoveries of lead-free glass compositions in Francel et al., U.S. Patent No. 4,446,241, Francel et al., U.S. Patent No. 4,537,862, Reade, U.S. Patent No. 4,224 .074, Eppler, U.S. Patent No. 4,312,951, Eppler, REF .: 28035 U.S. Patent No. 4,376,169, Emlemdi, U.S. Pat. No. 5,504,045, Manaba et al. U.S. Patent No. 5,578,533 and Evans and others, Inter Application National No. PCT / EP94 / 00403. These glass compositions are generally used to form, in a well-known manner, glass frits which are in turn used to formulate glass enamel compositions. These glass enamel (or ceramic) compositions are known as useful for the formation of decorative coatings for glassware, porcelain articles, architectural glasses and the like. They are especially useful in forming colored edges around glass sheets used for automotive windshields, side lights and taillights. These colored edges enhance the appearance as well as prevent the UV degradation of the fundamental adhesives. In general, these enamel compositions consist essentially of a glass frit, a colorant and an organic carrier. They are applied to a desired substrate and subsequently ignited to burn the organic vehicle and melt the frit, thereby bonding the enamel coating to the substrate.

- Glass sheets for automotive use are generally coated with the ceramic enamel composition, and then subjected to a process of formation at elevated temperatures. During this treatment the enamel is fused and melted to the glass substrate, and the final desired shape is given to the glass. However, many prior art coatings exhibit a tendency to adhere to the materials covering the forming matrix, such as a matrix covered with metallic fiber or glass fiber, because these conventional glazes have a low viscosity after melting and stick to other materials at high temperature. Accordingly, these materials are not suitable for use in glass forming processes in which the heated enamel-coated glass is contacted with a forming die covered with material. Several approaches have been suggested to facilitate the formation of glass sheets with a ceramic enamel coated thereon, withstanding the high forming or bending temperatures, and the repeated contact of the glass sheet and the covered forming matrix without the enamel will adhere to the forming matrix. For example, U.S. Patent Nos. 4,596,590 and 4,770,685 (issued to Boaz) and EP 201241 propose the addition of a low valence metal oxide powder, eg, cuprous oxide, to the paint composition to provide a non-stick barrier between the coating and the glass fiber-covered forming matrix. U.S. Patent Nos. 4,684,389; 4,857,096 and 5,037,783 (granted to Boaz), propose the addition of finely divided zinc metal powder for a similar effect. The use of a metallic iron powder is proposed in U.S. Patent No. 4,983,196 (issued to Stotka). The use of other metal oxide powders, including formulations containing bismuth oxide, is proposed in U.S. Patent Nos. 4,029,605 (issued to Kosiorek); 4,098,949 (issued to Kosiorek); 4,892,847 (granted to Reinherz), 4,959,090 (granted to (granted to Klimas and others), 5,093,285 (granted to Murkene); 5,203,902 (granted to Murkens) and EP 370,693. bismuth-containing systems produce a weak glass, such as when lithium is present, and have poor silver bleed properties, as well as inadequate anti-scallop properties US Patent No. 4,828,596 proposes the introduction of copper sulphide or copper sulfate in the ceramic enamel composition as an anti-stick agent.Sulfides or sulfates of other metals have been proposed as anti-tack agents in U.S. Patent No. 4,892,396 (issued to Reinherz). U.S. Patent Nos. 5,153,150 and 5,208,191 (issued to Ruderer et al.) Propose a supposedly improved anti-stick ceramic glaze composition, wherein a seed powder containing Zn 2 Si 4 is introduced into an oxide composition with or without the presence of bismuth oxide. As another problem, a number of prior ceramic enamel systems employ a glass frit containing lead. Due to environmental considerations it is desirable to avoid the use of any system containing lead. Furthermore, while some of the enamel systems mentioned above may perform very well in conventional glass-forming processes, some are not satisfactory for use in the newly developed "deep bending" processes for the formation of automotive glass. Each of the previously known enamel compositions suffers from one or more of the deficiencies noted above, making it desirable to provide a composition that avoids these defects. The present invention provides such ceramic enamel compositions, a method for employing the compositions, and substrates coated therewith. The present invention provides a glass and glass frit composition produced therefrom, which can be used in the production of enamels having improved chemical durability properties to the molten enamel coating. Currently, the only lead-free glass frits suitable for automotive enamel use that pass the required sulfuric acid durability evaluation specification, for example, in Japan, use lithium ions. However, if it is not carefully controlled, the use of lithium can cause unwanted stresses and rupture of the substrates. The new glass compositions of this invention avoid this problem. These compositions also impart excellent anti-tack properties, DESCRIPTION OF THE INVENTION The present invention provides novel glass compositions from which glass frits containing bismuth borosilicate, having a higher boron oxide content and / or higher bismuth oxide, can be obtained. These systems do not require the use of zirconium oxide, titanium oxide or lithium oxide within the range of composition. The glass compositions of the present invention are as follows: The glass compositions are formed in a known manner, as for example, by combining the known starting materials and fusing at a temperature of about -1000 ° to 1300 ° C for about forty (40) minutes, to form a molten glass having the desired composition. The molten glass formed can then be tempered with water in a known manner to form a frit. The frit can then be milled using conventional grinding techniques, at a fine particle size, preferably between 2 and 6 microns. The invention also provides glass enamel (ceramic) compositions employing the glass frit compositions described above. These compositions comprise from about 25 to 90% by weight solids of a glass frit component. This component comprises the discovered glass frit compositions. This glass frit component can be a unique composition of the invention, or alternatively, it can be a mixture of these frits. Furthermore, at least one frit of the present invention can be combined with an additional low melting frit having a composition outside the scope of those of the invention, to the extent that this other frit does not impair the qualities of the enamel that results. Representatives of said other frit that can be used is one that has a composition that is shown below: Oxide Range% in Weight Si02 20 - 35 - - Bi203 10 - 50 ZnO 5 - 45 B203 5 - 15 Na20 1 - 7 CaO 0 - 10 Ti02 0 - - 2 A1203 0 - - 5 Zr02 0 • - 2 F2 0 - - 1 A method for making said frit is discovered in the U.S. Patent No. 5,346,651. These frits have a cooking temperature low enough to ensure adequate adhesion to the substrate, and also have low density characteristics. The enamel composition further contains from about 10 to 37% by weight solids of an oxide pigment or combinations of oxide pigments. Such pigments are known in the art and can be obtained commercially. Examples are those such as CuCr20, (Co, Fe) (Fe, Cr) 204 and the like. Illustrative are the pigments that can be obtained from Cerdee Corporation such as pigment * 2991, which is a pigment of black copper chromite, pigment * 2980 which is a pigment of cobalt chromium iron black and pigment * 2987 which It is a chromium black pigment made of nickel manganese iron. The enamel compositions further contain an organic vehicle. The vehicle to be employed in the compositions is selected based on its end-use application. It is essential that the vehicle adequately suspend the particulates and burn completely with the cooking of the composition on the substrate. The vehicles are typically organic, and include compositions based on pine oils, vegetable oils, mineral oils, low molecular weight petroleum fractions, tridecyl alcohol, natural and synthetic resins, and the like. Surfactants and / or other film forming modifiers may also be included. As appropriate, UV-based vehicles are equally applicable for use in the invention. Such UV-based vehicles are well known in the art, and in general are composed of polymerizable monomers and / or oligomers containing, for example, acrylate or methacrylate functional groups, together with photoinitiators and polymerization inhibitors. Representative systems are disclosed in U.S. Patent Nos. 4,306,012 and 4,649,062. How it is recognized, said systems are cured with ultraviolet radiation after application to the substrate. The specific vehicle and the amounts used are selected based on the specific components of the composition and the desired viscosity. In general, the amount of the vehicle is about 10 to about 40% by weight based on the total weight of the enamel composition. In general, the enamel compositions are viscous in nature, the viscosity depending on the method of application to be employed and the end use. For viscosity printing purposes, viscosities ranging from 10 N * s / m2 (10,000 cpoise) to 80 N * s / m2 (80,000 cpoise), and preferably 35 N * s / m2 (35,000 cpoise) to 65 are appropriate. N * s / m2 (65,000 cpoises) at 20 ° C, as determined on a Brookfield Viscometer, needle # 7 at 20 rpm. The enamels of the invention may additionally contain up to about 15% by weight solids of a commonly used filler, such as silica and alumina, and other conventional additives, such as iron, silicon, zinc and the like, to enhance the desired properties, such as resistance to silver bleeding. The filler may also be a refractory oxide filler, such as wollastonite and materials such as alumina-silicate materials, calcium silicate compounds, boron-alumina-silicate compounds, soda-calcium-alumina-silicate compounds, feldspar compounds, titanium and combinations of said oxides. The enamel compositions may also contain up to about 20% by weight solids of a crystalline seed material, such as bismuth silicate, which is disclosed in my co-pending United States Patent Application No. 08 / 569,905, filed on April 8, 1995. December 1995, which is incorporated herein by reference. Bismuth silicate seed materials include, but are not limited to, Bi? 2Si02cw Bi4 (Si04) 3 and Bi2Si05. The enamel compositions will generally contain from about 85 to about 60% by weight solids as described above, and about 15 to about 40% by weight of the suitable organic carrier. The viscosity of the composition is adjusted so that it can be screen printed, roller coated or sprayed onto the desired substrate. The invention further provides a substrate having an enamel composition of the invention fired thereon. Said substrates are illustrated by glass, ceramic or other non-porous substrate, and in particular an automotive glass substrate. Other substrates include architectural glass, appliances and beverage containers.

To prepare the enamel compositions of the invention, the required frit or chips are ground to a fine powder using conventional methods. The frit component is combined with the other solids components and the solids are mixed with the necessary vehicle. The viscosity is adjusted as desired. Once the enamel composition is ready, it can be applied to the substrate in a conventional manner, such as by screen printing, decal application, spraying, brushing, roller coating or the like. Sieve printing is preferred when the composition is applied to a glass substrate. After application of the composition to a substrate in a desired pattern, the applied coating is then baked to bond the enamel to the substrate. The cooking temperature in general is determined by the maturation temperature of the frit, and is preferably in a wide temperature range. Typically, the cooking range for a present composition is in the range of about 500 ° to 750 ° C, more preferably in the range of about 520 ° to 650 ° C, and more preferably about 530 ° to 620 ° C. .

EXAMPLES Low melting glass frit compositions are produced by mixing raw materials that are known in the art, and using methods known to those skilled in the art. The well-mixed raw material batch compositions are then fused at temperatures between 1000 to 1300 ° C, followed by a sudden cooling, again using methods known to those skilled in the art. The glass compositions are then milled to a fine particle size, preferably between 2 and 6 microns, using a ball mill. The finely ground powder frits are then used to form glass enamel compositions. The finely ground glass frit is combined with a mixed metal oxide pigment. In addition, the solids of the enamel compositions are dispersed and suspended in a vehicle selected for the end-use application. The evaluation is carried out by sieving the resulting frit or enamel paste on a microscope slide or automotive glass substrate. The automotive glass slides or substrate are then fired at various temperatures to determine the "cooking temperature", TC, or "minimum cooking temperature" CM. The TC is the temperature when the glass has enough time to flow and melt within a 15 minute firing and produce a smooth, shiny surface. The CM is the temperature where the enamel has enough time to flow and melt in a 4 minute firing and produce an enamel without interconnected porosity.

The preheating time is 10 and 6 minutes at 427 ° C for TC and CM respectively. The acid resistance is evaluated using ASTM C-724-91, using a 10% by weight solution of citric acid. The cooked tests are exposed to the solution for 15 minutes and classified based on the following: Grade 1 - No apparent attack Grade 2 - Iridescence or visible spotting on the exposed surface when viewed at a 45 ° angle, but not apparent when observed at angles less than 30 °. Grade 3 - A defined stain that does not blur the reflected images and is visible at angles less than 30 °. Grade 4 - Spotting defined with a large color change or surface "strongly iridescent visible at angles less than 30 ° and which can blur the reflected images." Grade 5 - Cloudy or matte surface with possible dusting.

- - Grade 6 - Significant removal of enamel with obvious tiny holes. Grade 7 - Complete removal of enamel in exposed area.

Formulation of glass frit (% by weight) Next follow black automotive enamel formulations, made with the frit of the examples given above.

Formulation of Black Enamel (% by weight) * 2991 is a copper chromium pigment and RD-2077 is a bismuth silicate material. Both materials can be obtained commercially from Cerdee Corporation, Drakenfeld Products, West Wylie Avenue, Washington, Pennsylvania. The anti-tack properties are evaluated by printing the enamels on a piece of 10. 15 cm x 10. 15 cm (4"x 4") of automotive glass substrate, cooking in a cooking cycle of the automotive type of 3 to 5 minutes, and pressing with a pad of commercially used material, while the hot enamel and the substrate are kept inside the oven.

It is noted that, in relation to this date, the best method known to the applicant to carry out the aforementioned invention is that which is clear from the present description of the invention.

Having described the invention as above, the content of the following is claimed as property.

Claims (17)

1 . A glass composition, characterized in that it consists essentially of:

2 . A glass composition according to claim 1, characterized in that it consists essentially of:

3 . A glass composition, characterized in that it consists essentially of:

Four . A glass frit produced from a glass composition, characterized in that it consists essentially of: -

5. A glass frit according to claim 4, wherein the glass composition consists essentially of

6. A glass frit according to claim 4, wherein the glass composition consists essentially of

7. A glass frit according to claim 4, characterized in that the glass composition consists essentially of

8. In a glass enamel composition comprising a glass frit component, an oxide pigment component and an organic vehicle, the refinement wherein the glass frit component comprises at least one glass frit produced from a glass composition which consists essentially of

9. A glass enamel composition according to claim 8, wherein the glass composition consists essentially of

10. A glass enamel composition according to claim 8, wherein the glass composition consists essentially of

11. A glass enamel composition according to claim 8, wherein the glass composition consists essentially of A1203 0.3 to 0 by weight Ti02 1.4 a or by weight Na20 4.3 Q.? by weight K; 0 0.6 0, 0 by weight

12. A glass enamel composition according to claim 8, wherein the solids content is about 85 to about 60% by weight.

13. A glass enamel composition according to claim 8, wherein the glass frit component further contains one or more other low temperature melting glass frits.

14. A glass enamel composition according to claim 8, which further contains up to about 20% by weight solids of a crystalline seed material.

15. A glass enamel composition according to claim 14, wherein the crystalline seed material is bismuth silicate. -

16. A non-porous substrate having a glass enamel composition as defined in claim 8 fired thereon.

17. A substrate according to claim 16, which is automotive glass.