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
  • C03C13/00—Fibre or filament compositions
  • C03C13/001—Alkali-resistant fibres
• • 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

Definitions

• the invention herein relates to alkaline- resistant glasses. While it pertains to glass bodies generally, it has particular pertinence to glasses which are fiberizable.
• the natural mineral zeolites are a group of hydrous alkali and/or alkaline earth aluminosilicates which have an open three-dimensional crystalline framework. While a large number of individual mineral zeolites are known and have been described in the literature, eleven (11) minerals make up the major group of mineral zeolites: analcime, chabazite, clinoptilolite, erionite, ferrierite, heulandite, iaumontite, mordenite, natrolite, phiilipsite and wairakite.
• Glasses are vitreous materials composed largely of silica. Because silica is a highly refractory material, however, substantial quantities of soda ash, lime or other fluxing materials are added to the silica to permit the glass-forming composition to be melted at reasonable temperatures. Small quantities of other materials, usually elemental materials or oxides, are commonly added to glass melts to provide particular properties such as color or chemical resistance to the finished glass. Heretofore, however, there has not been any report of significant usage of zeolites in glass matricles and particularly as the principal component of a glass matrix.
• zirconia and titania tend to add cost to the glass inasmuch as these are much more expensive materials than silica, soda, calcia and the usual components of soda lime silica glasses.
• calcia tends to lower the melting point of the glass composition
• a general admonition exists in the glass technology against using calcium oxide in soda lime silica glasses in quantities greater than about fifteen percent (15%) by weight of the glass body.
• Another object of the invention is to modify naturally occurring zeolite materials with readily available alkaline earth compounds.
• a further object of the invention is to form glass bodies from modified naturally occurring zeolites at relatively low temperatures.
• a still further object ot the invention is to form compositions having improved properties, in particular, fiberizability and/or alkaline resistance.
• the invention herein comprises glass compositions which have outstanding resistance to alkaline environments.
• Such glass compositions are characterized by a relatively high calcia content and a relatively low silica content and a very low iron oxide content.
• these glass compositions are derived from selected or treated naturally occurring zeolites to which alkaline earth compounds, especially calcium compounds or calcium and magnesium compounds are added to yield a low-silica, high-alkaline earth oxide, especially calcia, glass composition.
• glass bodies, particularly fibers, formed from the aforesaid glass composition are also included within the scope of the present invention.
• the present invention relates to low iron oxide, alkaline-resistant fiber glasses containing relatively high quantities of one or more alkaline earth oxides and particularly to glasses comprising silica, alumina, calcia and combinations of calcia and magnesia.
• a particularly useful alkaline-resistant glass has the following composition:
• glasses may be easily and inexpensively formed by melting a calcium compound, in the form of limestone, for example, or a calcium compound and a magnesium compound, such as found in dolomite, with a selected or treated naturally occurring zeolite.
• glasses of excellent resistance to alkaline attack may be formed by starting with conventional materials such as silica, soda ash, an aluminate, limestone and/or dolomite.
• Such glasses may be described as low-alumina, calcium silicate glasses inasmuch as the calcium, in many instances, is present in about the same quantity, on a weight basis, as is the silica.
• the alkaline-resistant glass composition may be readily formed by mixing calcium carbonate with a naturally occurring zeolite material.
• Many naturally occurring zeolite materials may be formed into glasses under appropriate conditions.
• the zeolites, as a glass- forming material have many advantages. Naturally occurring zeolites have already undergone reaction and the various elements are intimately mixed and reacted with one another. Also, the zeolite materials are particularly useful inasmuch as they have a very low sulphur content.
• very useful glass bodies may be formed by combining various quantities of calcia or calcia and magnesia combinations with a zeolite of the following compositional range:
• Naturally occurring, pre-reacted zeolites useful in the instant invention are those specially selected or treated to have a low iron oxide (FeO + Fe 2 O 3 + Fe 3 O 4 ) content.
• Preferred naturally occurring zeolites are those having an iron oxide content no greater than about 1.5% by weight and especially those with an iron oxide content less than about 1% by weight.
• Some deposits of naturally occurring zeolites contain less iron oxide than other deposits.
• zeolites with a low iron oxide content are preferred.
• the iron oxide content of naturally occurring zeolites may be lowered by chemical and/or mechanical treatment. Often iron oxide is present in deposits as magnetite, which may be separated by magnetic means.
• Naturally occurring zeolite materials are finely ground and conveyed over a magnetic separator to reduce the iron oxide content to a value less than about 1.5% by weight and preferrably below 1% by weight.
• a further means of treating the zeolite material involves dilution with very pure silica, alumina, and the like.
• glasses of various types may be formed from zeolite materials without addition of any other materials or by minor additions of selected materials to achieve certain properties in the resulting glass body.
• the zeolite material comprise less than about 50% of the batch materials.
• the zeolite proportion with respect to other materials present should be selected to be such that the iron oxide content of the resulting glass is about 0.5% by weight or less, and particularly preferably less than about 0.4% by weight.
• additions of from 30% to about 70% by weight, and in particular from about 30% to about- 60% by weight calcium carbonate mixed with a selected or treated zeolite results, after melting of the finely ground material, in a glass having excellent resistance to an alkaline environment.
• these glasses advantageously melt at temperatures from about 1250°C to about 1500°C.
• glasses formed by mixing a selected or treated zeolite with similar weight percentages of dolomite, i.e. about 30% to 70% by weight of dolomite result in glasses having comparable properties to those formed by addition of calcium carbonate.
• carbonates are preferred rea ⁇ tants, other salts or compounds of alkaline earth metals, especially calcium and magnesium, could be utilized.
• a glass-forming composition may be readily formed by mixing finely ground limestone with a finely ground zeolite material, such as the composition identified above.
• the zeolite material inasmuch as it is a pre-reacted crystalline material, largely calcium aluminum silicates, reacts readily and efficiently with the calcium carbonate of the limestone to form a glass composition having a high calcia loading.
• Calcia loadings of about 30% to 50% calcium carbonate tend to provide slightly lower melting points than loadings involving 60% to 70% by weight calcium carbonate, based upon a weight of 100% equalling the total weight of the zeolite and calcium carbonate in the glass batch materials.
• the glass material upon cooling, exhibits good physical properties, having strengths and other qualities substantiallyequivalent to a typical soda-lime silicate glass and having resistance to alkaline solutions from about ten-fold to twenty-fold better than a typical sodalime silicate window glass. Also, the resistance to alkaline materials tends to increase as the calcia content increases from about 30% to about 50% by weight of calcium carbonate in the mix and then tends to decrease slightly with loadings of 70% calcium carbonate contributing less resistance to dilute caustic soda than a glass with 30% loading.
• glasses having a relatively high calcia content have other advantages as well.
• the calcia addition tends to even out variances in the zeolite composition.
• Zeolites are naturally occurring materials and are not homogenous nor uniform in their composition.
• the zeolites contain iron which tends to contribute a brown color to the glass.
• Calcia tends to contribute a light green color, which for many purposes is preferable to brown colored glass.
• the zeolites contain relatively substantial quantities of water, that is, hydrated materials. Hydrated crystalline materials generally tend to melt at a lower temperature. Thus, there are further advantages to beginning the glass-forming operation with a prereacted zeolite, rather than initiating it with silica.
• the melting ranges of the calcia-modified aluminum silicate glasses of this invention come within a range, i.e. about 1250°C to about 1500°C, which permits the drawing of glass fibers through platinum dies.
• the glass fibers could also be formed by spinning or other techniques. However, formation of continuous strands is best accomplished by drawing through an orifice in a platinum or platinum-rhodium body.
• Fibers of the glass compositions of this invention are particularly useful inasmuch as they may be used to strengthen bodies which are highly alkaline in nature, for example, cement and plaster. Such fibers may also be used to strengthen organic matrices of various types.
• a glass composition was prepared utilizng silica, alumina, calcium carbonate, magnesium carbonate, soda, and potassia. Various amounts of iron oxide were added to this glass composition as indicated in Table I.
• the melting temperature for each glass composition was about 1400° C regardless of the minor quantities of iron oxide included in the batch.
• the melt stability of the glasses was generally acceptable so long as less than about 0.5% by weight iron oxide was present.
• the glass composition set forth in Table I is very similar to the composition obtained from a naturally occurring zeolite to which a substantial quantity of calcium carbonate and a small amount of magnesium carbonate have been added.
• the glasses set forth in Table II are somewhat more refractory than the glass composition of Example I. Alkaline resistance of these glasses diminished with increasing silica + alumina content and/or lower CaO plus MgO content. The alkali resistance of Glasses IIA and IIB was outstanding. Other adjustments in the proportions of oxides present in the resulting glass material may be made by utilizing different starting materials or by varying the proportions of ingredients in the glass-forming batch. Also, other ingredients may be added to alter the composition to be less refractory without adversely affecting fiberizability and stability of the glass melt. Such ingredients include fluxes such as soda, potassia and the like and boria.
• iron oxide may be tolerated in glasses formed into beverage containers and various other non-optical grade, non-fibrous uses.
• the presence of iron oxide as 0.5% by weight, and especially about 1.0% by weight, of a glass melt renders the melt relatively unstable and subject to spontaneous and rapid crystallization over a wide range of temperatures.
• Glasses of this invention, however, containing less than about 0.5% by weight, particularly less than about 0.4%, and especially less than about 0.25% by weight, are sufficiently stable that such molten glasses may be readily formed into continuous vitreous fibers.
• Preferred glass compositions for the purpose of the invention have a silica content of about 45% to about 60% by weight, and especially about 45% to about 55% by weight; an alumina content of about 10% to about 20% by weight, and especially about 12% to about 18% by weight; a calcia content of about 20% to about 35% by weight, and especially about 22% to about 35% by weight; a magnesia content of about 0% to about 10% by weight, and especially about 0% to about 5% by weight; wherein the CaO+MgO content is about 22% to about 35% by weight, and especially about 25% to about 30% by weight.
• Some glass compositions may be less affected by the presence of iron oxide than the glasses of the inven tion, which are characterized by a relatively high alkaline earth metal oxide content, especially a high calcia content. These glasses have excellent alkaline resistance and may be readily formed from naturally occurring, pre-reacted. zeolites modified with readily available materials such as limestone and dolomite.
• Glass fibers formed from glasses of this invention have particular utility as a reinforcement material for cementatious bodies, e.g. cement and concrete.
• Cementatious bodies exhibit enhanced strength when such bodies are reinforced with a minor amount of glass fiber, preferably from about 1% to about 10% by weight, and more preferably about 1.5% to about 7.5% by weight glass fibers of the type described herein.
• the fibers are included in cementatious bodies in sufficient amount to enhance the strength of such bodies.
• the glasses of this invention have excellent resistance to moisture degradation and do not degrade or deteriorate during normal or extended storage periods.
• the low sulfate content of naturally occurring zeolites is important in their utilization as ingredients in glass-forming processes. Sulfates tend to degrade during glass melting conditions, yielding sulfur dioxide and other objectionable sulfur compounds. Environmental concerns militate against use in glass-making processes of any raw material containing sulfates, sulfites and other sulfur compounds.
• Zeolite materials provide an excellent source of silica and minor quantities of alumina, calcia and the like.
• Very useful glasses may be formed from glass-forming batches having at least about 20% by weight of a zeolite material present. Frequently, 35% by weight up to about 70% by weight of a zeolite material may be advantageously included in a glass-forming batch.
• magnesium compounds particularly, magnesium carbonate may be substituted for at least some of the calcium carbonate in preparing a batch for melting into an alkaline-resistant glass.
• barium and strontium compounds may be substituted as well as beryllium compounds, many of which are naturally occurring materials found in the same geographic regions as zeolites.
• the oxides of alkaline earth metal elements are not considered glass formers, which is a term applied to elements having a valence greater than three, e.g. silicon, boron, andphosphorous, which may form three-dimensional networks with their oxides, namely, silica, boric oxide, and various oxides of phosphorous.
• Alkaline earth metal elements, being divalent, are more tightly bound in a glass than are alkali metal elements.
• Sources of alkaline earth metals to form oxides in the glasses of this invention are as follows: Alkaline Earth Metal Compound Source Calcium Carbonate Limestone
• Sources of calcium and magnesium carbonates are generally more plentiful and cheaper than sources of barium, strontium or beryllium compounds. Also, beryllium metal is considered toxic, although beryllium oxides bound within a glass body are not hazardous.
• the zeolite-derived glasses of this invention have good working properties and strength in addition to outstanding alkaline resistance.
• These glasses may be used in any form, e.g. containers, sheets, and the like, and especially as fibers.
• These low iron oxide glasses may be used as flakes, bubbles (microspheres), fibers and the like to reinforce organic or inorganic matrices, especially cement, plaster and the like.
• Aluminum may be included in the glass batch as alumina; aluminum silicates, e.g. from aluminosilicate glass cullet; or as naturally occurring materials such as kaolin, montmorillonite, and the like.
• Zirconia may optionally be present in the fiber glass. Minor quantities of zirconia in the glass may result from melting the glass in zirconia containing crucibles or through the addition of a zirconium component such as zircon or a zirconium silicate or zirconia containing glass cullet. Soda and potassia are often present in the glasses of the instant invention in amounts up to about 5% by weight of either, with amounts of about 1% to about 3% by weight of each being present and a combined amount of about 2% to about 5% by weight being usual. In instances that boria is present, the total soda, potassia, boria content is within the range of about 3% to about 10% by weight.

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• 1984
  • 1984-11-19 EP EP19850900314 patent/EP0164399A1/de not_active Withdrawn
  • 1984-11-19 WO PCT/US1984/001905 patent/WO1985002394A1/en unknown

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