United States Patent (15) 3,663,245 Bryson (45) May 16, 1972

54 FOREHEARTH COLOR CONCENTRATE Primary Examiner-Tobias E. Levow 72) Inventor: Robert O. Bryson, Euclid, Ohio is farO.S.E (73) Assignee: Ferro Corporation, Cleveland, Ohio (22) Filed: Oct. 31, 1969 (57) ABSTRACT (21) Appl. No.:- 873,129 glassForehearth in a glass color furnace concentrates forehearth for coloring after melting molten and clear fining, base comprising a non-smelted interspersion of a flux and colorant. (52) U.S. Cl...... 106752 Suitable fluxes are those materials which are compatible with (51) Int, Cl...... C03c.3/04, CO3c. 1700, CO3c 1/10 the glass and which promote the fusion and dispersion of the 58 Field of Search...... 106752, colorant. Suitable fluxes include the alkali borates, boric acid, 313| 89. 252 alkali phosphates, orthophosphoric acid, alkali silicates, fluosilic acid, alkali fluorides, alkali salts, alkali hydroxides, 56 References Cited mixtures and reaction products of said fluxes. Alkali silicates UNITED STATES PATENTS and particularly sodium silicates are preferred. Suitable 106752 colorants include color indicating metals, color inducing 3,364,0413,024, 21 3/19621/1968 HagedornSwain, Jr. et al...... a ------w ------106752f metal oxideoxides or compounds which contain a color inducing 3,498,806 3/1970 Hammer et al...... 106/52 3,513,003 5, 1970 Hammer et al...... 106/52 8 Claims, No Drawings 3,663,245 2 FOREHEARTH COLOR CONCENTRATE monium phosphate, diammonium phosphate, monocalcium phosphate, dicalcium phosphate, tricalcium phosphate, sodi This invention relates to forehearth color concentrates, to a um acid pyrophosphate, tetrasodium pyrophosphate, method for their preparation and to a method for coloring tetrapotassium pyrophosphate, calcium pyrophosphate, sodi container glasses. um tripolyphosphate, potassium tripolyphosphate, calcium The manufacture of colored glass by the addition of a color tripolyphosphate, potassium metaphosphate, sodium enriched frit glass to a molten colorless base glass flowing trimetaphosphate, sodium monofluorophosphate, calcium through a forehearth from a melting tank is commonly em monofluorophosphate and sodium tetrametaphosphate. Suita ployed. This process makes possible the manufacture of both ble alkali silicates include sodium silicate, potassium silicate, colored glass items and colorless glass items from a single sodium fluosilicate and calcium fluosilicate. Suitable alkali melting furnace having multiple forehearths. In the forehearth fluorides include sodium aluminum fluoride, calcium fluoride, coloration process, a frit glass is metered into the molten base lithium fluoride, anhydrous potassium fluoride, potassium glass after the base glass flows from the fining zone of the fur fluoride dihydrate, potassium bifluoride and sodium fluoride. nace into the forehearth. Generally a vibratory feeder is used. Suitable alkali salts include sodium carbonate and barium car One of the difficulties encountered heretofore, however, is 5 bonate. Suitable alkali hydroxides include sodium hydroxide, that colored frit could not be manufactured containing more lithium hydroxide and potassium hydroxide. than a minor amount of color inducing metal (normally the The preferred fluxes however are the alkali silicates formed metal oxide) or the metal oxide would not be taken into solu from alkali metals such as potassium, lithium and sodium. The tion in the molten glass color and consequently would ag alkali metal silicates are preferred because they generally will glomerate or precipitate and appear in the frit, and sub combine with larger amounts of colorant than the other fluxes sequently in the glass to be colored, as inclusions or specks. and are readily dispersed when added to the forehearth. The amount of metal oxide which could be taken into solution Moreover these silicates are compatible with most commer in the frit varied depending on the metal oxide. For example, cial glasses. although about 25% CuO can be taken into solution in the frit smelt, only about 2% CrO can be taken into solution. 25 Of the alkalisilicates, the silicate of sodium is preferred. It has now been discovered however, that a forehearth color The color concentrates will generally contain from about 50 concentrate can be prepared which contains color inducing to about 99.9 percent by weight of flux and about 0.1 to about metal oxides, compounds which contain a color inducing 50 percent by weight of colorant. Any of the commonly em metal oxide or color inducing metals (all of which are alterna ployed color inducing metal oxides can be employed in the tively referred to herein as colorants) in substantially greater 30 concentrate. Illustrative of suitable color inducing metals are amounts than previously employed color frits and which ob chromium, copper, iron, cobalt, manganese, vanadium, viates the need for employing frits. nickle, uranium, cerium and cerium-titanium and some rare For example, in accordance with this invention, a color con earth oxides such as neodymium oxide, praseodymium oxide centrate can be prepared having no agglomerated metal ox and mixtures which are usually added in the form of their ox ides which contains more than 20% of the less soluble color in 35 ides. Selenium is exemplary of a color inducing metal which ducing metal oxides such as CrOs. In addition, whereas previ need not be added in the form of its oxide. ous color inducing metal oxides were taken into solution in a The concentrate is preferably a bound or intimate admix glass frit by smelting with a blend of glass-formers and fluxes ture of flux and colorant. A powder concentrate can be em at a temperature in the range of 2,250–2,600 F. and then the ployed but it is not generally preferred because of the dust molten mix fed from the smelter to a body of water to break 40 problem. That is the powder contaminates the plant equip up the frit into granulated form, or quenched through water ment and other products being processed, and tends to be cooled rolls to form a ribbon which was subsequently broken blown back out of the glass tank by convection currents result to form flakes, the concentrate of the invention can be ing from the extremely high glass tank temperatures. blended at room temperature. Moreover the concentrate of The color concentrate can be prepared by blending the the invention is more quickly and completely dispersed and 45 colorant and flux with a commercial high speed blender or ball dissolved when added to the molten base glass than the previ mill. When an aqueous alkali silicate is employed as the flux, ously employed frits. the mixture can be blended until a complete viscous syrupy mixture results, and then dried to form a tacky dough-like More particularly the invention forehearth color concen mixture by subjecting the mixture to heat lamps or an oven at trate comprises a non-smelted intimate admixture of inter 50 spersion of a flux or fluxes, with one or more colorants relatively low temperatures of between about 100 F. and (usually a metal oxide). about 500 F. for a time between about 1 minute and about For the purposes of this invention the flux can be defined as hour. Alternatively, however the concentrate can be spray any substance which is compatible with the glass and which dried and then formed into pellets or shots and the like by em promotes the fusion and dispersion of the colorant. The flux 55 ploying conventional equipment. The dry fluxes can be acts to locally and temporarily reduce the fusion temperature formed into shot or pellets and the like by conventional between the colorant and the glass batch for a time sufficient methods. For example, a Komarek-Greaves Compacter can be to permit rapid and thorough dispersement of the colorant used to form the powder into briquets, using a small amount of through the glass batch with the flux subsequently being water or other suitable substance as a binder. dispersed and diluted within the glass so that it does not alter 60 Another method of producing the concentrate in commer the glass's basic characteristics. cial form when an alkali silicate is employed as the flux is to Suitable fluxes include alkali borates, boric acid, alkali lower the pH of the aqueous silicate-colorant dispersion by ad phosphates, orthophosphoric acid, alkali silicates, fluosilic dition of a suitable acid such as boric acid, phosphoric acid or acid, alkali fluorides, alkali salts, alkali hydroxides and mix hydrochloric acid. This method results in the formation of a tures. 65 non-sticky agglomerate which can then be dehydrated and Suitable alkalications include the alkali metals such as sodi compacted if desired. um, potassium and lithium and the alkaline earth metals such Any of the conventional silica type base glasses are adapta as calcium, magnesium and barium. ble to be colored with the color concentrate of the invention. Suitable alkali borates which can be employed as fluxes in The silica type glasses generally contain the following oxides the invention include borax, potassium pentaborate, potassi 70 in the indicated percentages. um metaborate, potassium tetraborate and calcium borate. Among the alkali phosphates which can be employed are TABLE 1. hemisodium phosphate, monosodium phosphate, disodium Oxide Percent by Weight phosphate, trisodium phosphate, monopotassium phosphate, dipotassium phosphate, tripotassium phosphate, monoam 75 SiO, 60-75

453 3,663,245 4 AlOs 0.3-10 CaO +MgO 6-15 Glass disks prepared from the aforesaid compositions in ac NaO 12-18 cordance with the procedure of Example 1 were transparent KO O-5 and free of inclusions, indicating through dispersion of the BaO 0-5 metal oxides. Fe .00025-.0035 EXAMPLE 4 A composition comprising 3,000 parts of an aqueous sodi Other suitable glasses are reported in Kirk-Othmer; En cyclopedia of Chemical Technology, 2nd Edition, Volume 10, um silicate (29.6% SiO.), 20.5 grams sodium selenate and O 36.3 grams of black nickle oxide were blended in a Cowles Table 3, Pages 542-3. As is readily apparent to one skilled in Dissolver for 20 minutes and then placed in a gas muffle fur the art, however, not all of the fluxes of the invention are nace for approximately 15 minutes at 1,000 F. The resultant suitable for every type of glass. Thus the particular flux foam like material was milled in a ball mill for one-half hour selected will depend on its compatibility with the particular and then pelletized in a Komarek-Greaves Compacter. The components of the base glass. 15 pellets were then added to a commercial glass tank forehearth The following examples will serve to illustrate the invention through which a conventional clear glass was being run, and and its preferred embodiments. Unless otherwise indicated, all the concentrate was quickly melted and dispersed in the clear percentages and parts are by weight. base glass, which was of conventional composition. Discs EXAMPLE1 prepared from the resultant salmon colored glass in ac 20 cordance with the aforesaid procedure were free of inclusions. 400 grams of sodium silicate containing 9.1% NaO and The following examples will illustrate compositions employ 29.6% SiO, (NaO:SiO, ratio of 1:3.25) was blended with 25 ing concentrates which were prepared by dry mixing the flux grams of pigment grade CrOa in an Osterizer blender at high and color inducing metal oxides. speed. The mixture was then dried under an infrared lamp for approximately 5 minutes and then rolled into balls and dried 25 EXAMPLE 5 at a temperature of about 230 F. for 30 minutes, until the material was no longer tacky. The color concentrate balls (30 A concentrate consisting of 25.8 parts of dry frit grade sodi grams) were then added to 500 grams of a molten glass com um silicate (75.8% SiO,), 1.26 parts sodium selenate, and 1.5 prising the following oxides in the percentages indicated, parts black nickle oxide was milled 2 hours in a ball mill, and 30 pelletized with a Komarek-Greaves Compacter. The pellets SiO, 7.53% were then added to a forehearth as in Example 4, and the con BO 0.48 centrate was quickly melted and dispersed in the clear base NaO 13.30 glass. Discs prepared from the resultant salmon colored glass KO 0.40 in accordance with the aforesaid procedure were free of inclu CaO 96 S.S. F 0.6 35 Al2O 1.83 BaO 0.60 EXAMPLE 6 MgO 2.43 AsO. 0.2 In accordance with the procedure of Example 5 glass discs 40 were prepared from the following ingredients in the indicated and the color concentrate containing 13.9% CrO3 was proportions and the discs were free of inclusions. completely melted and dispersed in about 2 minutes. The glass was then formed into flat colored disks approximately one Ingredients Parts By Weight eighth inch thick and 5 inches in diameter by pressing the mol ten glass. No inclusions or undissolved crystalline materials 45 Sodium Silicate 360 360 360 360 were noted in the glass indicating that thorough dispersion of Nickel Oxide 10 30 60 6) the CrO3 was achieved. Sodium Selenate 5 15 () 30

EXAMPLE 2 EXAMPLE 7 50 In accordance with the procedure of Example 1,500 grams In accordance with the procedure of Example 5 the follow of sodium silicate and 50 grams of pigment grade calcined ing compositions containing approximately 10 percent urani CrO were blended and dried and 10 grams of the concen um dioxide were prepared, and no inclusions were noted. trate added to 500 grams of the aforesaid base glass. The con centrate (containing 20.5% CrO3) was quickly melted and dispersed in the base glass and a glass disk prepared from the 55 Ingredients Parts by Weight colored glass was free of inclusions. Sodium Silicate 360 360 360 360 EXAMPLE 3 Uranium Dioxide 46 46 46 46 Nickel Oxide - 0. - In accordance with the procedure of Example 1, color con 60 Sodium Selenate -- m --- 5 centrates were made from the following ingredients. Amnonium Nitrate 20 20 20 20

% EXAMPLE 8 Composition Color pigment in concentrate based on total solids In accordance with the procedure of Example 5 discs were 65 prepared from the following ingredients containing approxi 1. 250 grams sodium silicate Blue-Green 34O1 mately 6.25% CrO3 and no inclusions were noted. 50 grams CuO 2. 250 grams sodium silicate Brown 33.33 Ingredients Parts by Weight 50 grams NiO, 3.250 grams sodium silicate Blue 9.35 70 10 grams CoOa Sodium Silicate 375 - - - 4. 250 grams sodium silicate Green 34, Frit Makers Borax - 37 - - 50 grams FeOa Sodium Nitrate - - 375 - Sodium Nitrite - - - 375 75 CrOs. 25 2S 25 25

463. 3,663,245 5 6 EXAMPLES 9 - 12 As is known to those skilled in the art, smelting is the melt In accordance with the procedure of Example 5 the follow ing of glass raw materials in a melting furnace around 2,500 ing compositions were prepared employing respectively, lithi F. The raw materials which have been first thoroughly mixed um carbonate, boric acid, potassium carbonate and lithium are loaded into the smelter and allowed to remain there until metasilicate as the flux and containing approximately 12.5% thoroughly and uniformly melted. This melting process CrOs. No inclusions were noted when glass discs were made requires from one to 3 hours time. The molten glass then runs incorporating these compositions. from the furnace in a white hot stream and the contact with the cold water in the quenching tank shatters the glass into ingredients Parts By Weight millions of friable pieces which are known as frit. But in ac O cordance with the aforesaid invention, the expensive and time Lithium Carbonate 877 - - - consuming operation of smelting a fritted color concentrate, Anhydrous Boric Acid - 35 --- - for subsequently coloring container glass in the forehearth, Potassium Carbonate - - 519 --- has been obviated. Lithium Metasilicate - - - 350 At the same time, a much higher concentration of coloring CrOs 50 50 So 50 15 oxide is possible in the color concentrate of this invention than could ever be achieved in a fritted concentrate. EXAMPLES 13 - 16 The results of this invention being totally unexpected as it in accordance with the procedure of Example 5 the follow hadides heretoforeas CrOs could been not the possibly belief that be sucheffectively refractory dispersed color inox a ing brown compositions were prepared employing dry sodium 20 glass, without the intermediate step of first dissolving them in silicate, sodium carbonate, sodium nitrate, borax and caustic a frit, prior to their introduction into a forehearth. soda as the fluxes. All were free of inclusions when made into What is claimed is: glass discs. 1. A forehearth color concentrate consisting essentially of, as a non-smelted pelletized interspersion, a colorant oxide and ingredients Parts By Weight 25 a flux in from about 50.0 weight percent to about 99.9 weight percent flux, and a forehearth soluble amount of colorant ox Anhydrous Boric Acid 52 (10% ide, to a maximum of 50.0 weight percent thereof, dispersed BOs) - 52 456 throughout said interspersion as discrete, unreacted particles, Red Iron Oxide 1 (2.25% FeO) 11 said colorant oxide consisting essentially of CrO3, and said Nickel Carbonate 68 (8.50% 30 flux consisting essentially of an alkali silicate. NiO) 68 68 68 2. A forehearth color concentrate consisting essentially of, Sodium Silicate 396 ------Sodium Carbonate - 572 - - as a non-smelted pelletized interspersion, a colorant oxide and Sodium Nitrate -- 100 - -- a flux, in from about 0.1 weight percent to about 20.5 weight Borax -- 77 - - percent colorant oxide, and from about 79.5 weight percent to Caustic Soda --- - 512 --- 35 about 99.9 weight percent flux, said colorant oxide consisting essentially of CrO3 dispersed throughout said interspersion as discrete, unreacted particles, and said flux consisting essen EXAMPLE 1.7 tially of an alkali silicate. In accordance with the procedure of Example 5 brown 3. The color concentrate of claim 2 wherein said colorant colored glasses were prepared from a concentrate comprising 40 oxide is present in from about 0.1 to about 13.9 weight per dry sodium silicate, nickie carbonate and sodium selenate cent, and said flux is present in from about 86.1 to about 99.9 wherein the nickle was present in concentrations of from 4 to weight percent. about 8 percent. Lavender blue glasses prepared from dry 4. The color concentrate of claim 2 wherein said colorant sodium silicate and potassium permanganate (KMO); and oxide is present in from about 0.1 to about 6.25 weight per black glasses prepared from dry sodium silicate, manganese 45 cent, and said flux is present in from about 93.75 to about 99.1 dioxide (M.O.) and sodium dichromate (Na,CrO2H2O) weight percent. were prepared and likewise found to have no inclusions. 5. The color concentrate of claim 2 wherein said alkali is Other suitable fluxes include tetrapotassium sodium. pyrophosphate, fluosilic acid, calcium fluoride, and monoam 6. The color concentrate of claim 3 wherein said alkali is monium phosphate. 50 sodium. When the aforesaid color concentrates of the invention are 7. The color concentrate of claim 4 wherein said alkali is added to a body of molten clear glass in a glass furnace sodium. forehearth after melting and fining of the clear glass, the con 8. The color concentrate of claim 1 wherein said alkali is centrates are readily dispersed and the resultant colored glass sodium. free of inclusions. 55

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