METHOD OF MANUFACTURING S-GLASS FIBERS IN A DIRECT MELT OPERATION AND PRODUCTS FORMED THEREFROM

Abstract

A method of forming high strength glass fibers in a refractory-lined glass melter, products made there from and batch compositions suited for use in the method are disclosed. The glass composition for use in the method of the present invention is up to about 64-75 weight percent SiO.sub.2, 16-24 weight percent Al.sub.2O.sub.3, 8-12 weight percent MgO and 0.25-3 weight percent R.sub.2O, where R.sub.2O equals the sum of Li.sub.2O and Na.sub.2O, has a fiberizing temperature less than about 2650 F., and a T of at least 80 F. By using oxide-based refractory-lined furnaces the cost of production of glass fibers is substantially reduced in comparison with the cost of fibers produced using a platinum-lined melting furnace. High strength composite articles including the high strength glass fibers are also disclosed.

Claims

1-29. (canceled)

30. A high strength article comprising: glass fibers formed from a glass batch composition comprising: 64-75 weight percent SiO.sub.2; 16-24 weight percent Al.sub.2O.sub.3; 8-11 weight percent MgO; 0.25-3 weight percent Li.sub.2O; and no more than 2.0 weight percent CaO; and a polymer matrix material, wherein said glass fibers have a strength of greater than about 700 KPsi.

31. The high strength article of claim 30, wherein the glass batch composition comprises: 17-22 weight percent Al.sub.2O.sub.3; 9-11 weight percent MgO; and 1.75-3 weight percent Li.sub.2O.

32. The high strength article of claim 30, wherein the glass batch composition comprises: 68-69 weight percent SiO.sub.2; 20-22 weight percent Al.sub.2O.sub.3; 9-10 weight percent MgO; 1-3 weight percent Li.sub.2O; and no more than 2.0 weight percent CaO.

33. The high strength article of claim 30, wherein the glass batch comprises: less than 5 weight percent total of compounds selected from the group consisting of P.sub.2O.sub.3, ZnO, ZrO.sub.2, SrO, BaO, SO.sub.3, F.sub.2, B.sub.2O.sub.3, TiO.sub.2 and Fe.sub.2O.sub.3.

34. The high strength article of claim 30, wherein said glass batch comprises Li.sub.2O in an amount from about 1.75 to 3.0 weight percent.

35. The high strength article of claim 30, wherein said glass batch composition has a fiberizing temperature of less than about 2650 F. and a liquidus temperature, wherein the difference (T) between the fiberizing temperature and the liquidus temperature is at least 80 F.

36. The high strength article of claim 35, wherein said glass batch composition has a fiberizing temperature less than about 2600 F.

37. The high strength article of claim 30, wherein said glass batch composition is meltable in a refractory-lined melter.

38. The high strength article of claim 30, wherein said glass batch composition comprises 2.0-3.0 weight percent Li.sub.2O.

39. The high strength article of claim 30, wherein said glass batch composition comprises less than 1.0 weight percent CaO.

40. The high strength article of claim 30, wherein said glass fibers have a density of 2.434 g/cc to 2.486 g/cc.

41. The high strength article of claim 30, wherein said glass fibers have a measured modulus greater than 12.6 MPsi.

42. The high strength article of claim 30, wherein said glass fibers have strength in excess of about 730 KPsi.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 is a cross-sectional longitudinal view of a glass melting furnace useful with the method of the present invention;

[0014] FIG. 2 is a cross-sectional plan view of the glass melting furnace of FIG. 1 taken along line 2-2;

[0015] FIG. 3 is a cross-sectional view of the glass melting furnace of FIG. 1 taken along line 3-3 illustrating two burners adjacent the upstream end wall of the furnace;

[0016] FIG. 4 is an alternate cross-sectional plan view of the glass melting furnace of FIG. 1 taken along line 3-3 illustrating one burner adjacent the upstream end wall of the furnace; and

[0017] FIG. 5 is a side view, partially in cross section, of a bushing assembly/support structure arrangement for producing continuous glass filaments useful in the method of the present invention.

DETAILED DESCRIPTION AND PREFERRED EMBODIMENTS OF THE INVENTION

[0018] Fiberizing properties of the glass composition used to form the glass fibers of the present invention include the fiberizing temperature, the liquidus, and delta-T. The fiberizing temperature is defined as the temperature that corresponds to a viscosity of 1000 Poise. As discussed in more detail below, a lowered fiberizing temperature reduces the production cost of the fibers, allows for a longer bushing life, increases throughput, permits the glass to be melted in a refractory-lined melter, and reduces energy usage. For example, at a lower fiberizing temperature, a bushing operates at a cooler temperature and does not sag as quickly. Sag is a phenomenon that occurs in bushings that are held at an elevated temperature for extended periods of time. By lowering the fiberizing temperature, the sag rate of the bushing may be reduced and the bushing life can be increased. In addition, a lower fiberizing temperature allows for a higher throughput since more glass can be melted in a given period at a given energy input. As a result, production cost is reduced. In addition, a lower fiberizing temperature will also permit glass formed with the inventive method and composition to be melted in a refractory-lined melter since both its melting and fiberizing temperatures are below the upper use temperatures of many commercially available refractories.

[0019] The liquidus is defined as the highest temperature at which equilibrium exists between liquid glass and its primary crystalline phase. At all temperatures above the liquidus, the glass is free from crystals in its primary phase. At temperatures below the liquidus, crystals may form.

[0020] Another fiberizing property is delta-T (T), which is defined as the difference between the fiberizing temperature and the liquidus. A larger T offers a greater degree of flexibility during the formation of the glass fibers and helps to inhibit devitrification of the glass (that is, the formation of crystals within the melt) during melting and fiberizing. Increasing the T also reduces the production cost of the glass fibers by allowing for a greater bushing life and by providing a wider process window for forming fibers.

[0021] The glass compositions employed in the present invention are advantageously suitable for melting in traditional, commercially available refractory-lined glass melters. Starting batch components typically include SiO.sub.2 (ground silica sand), and Al.sub.2O.sub.3 (calcined alumina), Li.sub.2CO.sub.3 (lithium carbonate), H.sub.3BO.sub.3 (boric acid), NaCaB.sub.5O.sub.9. 8H.sub.2O (ulexite), 2CaO-3B.sub.2O.sub.3-5h.sub.2O (colmanite) as well as chain modifiers from source materials such as MgCO.sub.3 (magnesite), CaCO.sub.3 (limestone), SrCO.sub.3 (strontianite), BaCO.sub.3 (witherite), ZrSiO.sub.4 (zircon), and Na.sub.2CO.sub.3 (natrite).

[0022] FIGS. 1-4 depict a glass melting furnace 10 useful in the method of forming the glass fibers described herein and set forth in the examples and claims below. It may also be desirable to use oxygen-fired heating within the melting furnace, as disclosed in U.S. patent application Ser. No. 10/116,432 entitled OXYGEN-FIRED FRONT END FOR GLASS FORMING OPERATION, inventors David J Baker et al., and published as U.S. Published Application No. 2003/0188554, herein incorporated in its entirety by reference. The glass melting furnace 10 provides molten glass to a glass forehearth 12. The molten glass is preferably composed of about 64-75 weight % SiO.sub.2, 16-24 weight % Al.sub.2O.sub.3, 8-12 weight % MgO and 0.25 to 3.0 weight % R.sub.2O where R.sub.2O is the sum of Li.sub.2O and Na.sub.2O. In certain embodiments, the composition does not contain more than about 5.0 weight % of oxides or compounds such as CaO, P.sub.2O.sub.5, ZnO, ZrO.sub.2, SrO, BaO, SO.sub.3, F.sub.2, B.sub.2O.sub.3, TiO.sub.2 and Fe.sub.2O.sub.3.

[0023] In addition, a fiber formed in accordance with the method and composition of the present invention will have a fiberizing temperature of less than 2650 F., and in certain embodiments less than about 2625 F., in other embodiments less than about 2600 F. and in certain embodiments less than about 2575 F. and a liquidus temperature that is below the fiberizing temperature in certain embodiments by at least 80 F., and in other embodiments by at least about 120 F., and in yet other embodiments by at least about 150 F. Further, the glass fibers of the present invention, in certain embodiments, will have a pristine fiber strength in excess of 680 KPSI, and in certain other embodiments a strength in excess of about 700 KPSI, and in yet other embodiments a strength in excess of about 730 KPSI. Further, the glass fibers will advantageously have a modulus greater than 12.0 MPSI, and in certain embodiments greater than about 12.18 MPSI, and in some embodiments greater than about 12.6 MPSI.

[0024] The method of the present invention is preferably performed using the glass melting furnace 10, which includes an elongated channel having an upstream end wall 14, a downstream end wall 16, side walls 18, a floor 20, and a roof 22. Each of the components of the glass melting furnace 10 are made from appropriate refractory materials such as alumina, chromic oxide, silica, alumina-silica, zircon, zirconia-alumina-silica, or similar oxide-based refractory materials. The roof 22 is shown generally as having an arcuate shape transverse to the longitudinal axis of the composition the channel; however, the roof may have any suitable design. The roof 22 is typically positioned between about 3-10 feet above the surface of the glass batch composition 30. The glass batch material 30 is a mixture of raw materials used in the manufacture of glass in the accordance with the present invention. The glass melting furnace 10 may optionally include one more bubblers 24 and/or electrical boost electrodes (not shown). The bubblers 24 and/or electrical boost electrodes increase the temperature of the bulk glass and increase the molten glass circulation under the batch cover.

[0025] In addition, the glass melting furnace 10 may include two successive zones, an upstream melting zone 26 and a downstream refining zone 28. In the melting zone 26, the glass batch composition 30 may be charged into the furnace using a charging device 32 of a type well-known in the art.

[0026] In one suitable melter configuration, the glass batch material 30 forms a batch layer of solid particles on the surface of the molten glass in the melting zone 26 of the glass melting furnace 10. The floating solid batch particles of the glass batch composition 30 are at least partially melted by at least one burner 34 having a controlled flame shape and length mounted within the roof 22 of the glass melting furnace 10.

[0027] In one preferred embodiment, as shown in FIG. 1, the glass melting furnace 10 includes three burners 34. A single burner 34 is positioned upstream of two adjacently positioned downstream burners 34. However, it will be appreciated that any number of burners 34 may be positioned at any suitable location in the roof 22 of the furnace 10 over the batch to melt the glass batch composition 30. For example, two burners 34 may be positioned in a side-by-side relationship (FIG. 3) or a single burner may be used (FIG. 4).

[0028] Other conventional melters may be used without departing from the present invention. Conventional melters include Air-Gas melters, Oxygen-Gas melters, electrically fired melters, or any fossil fuel fired melter. It is possible to add electric boost or bubblers to any of the melting processes. It is also possible to include a separate refining zone (as shown in FIG. 1) or incorporate the refining zone into the main tank of the melter.

[0029] As shown in FIG. 5, a bushing assembly 100 includes a bushing 110 and a bushing frame 210. The bushing 110 includes a bushing main body 120 with sidewalls 122 and a tip plate 124 extending between the sidewalls 122. The main body 120 is positioned below a bushing block 300 that, in turn, is positioned beneath a forehearth 310.

[0030] In practicing the method of the present invention, a stream of molten glass is received by the main body 120 from the forehearth 310.l The forehearth 310 receives the molten glass from a melter 10 (shown in FIG. 1). A delivery channel 40 is positioned between the melter 10 and the forehearth 310 to deliver the molten glass batch composition 30 from the melter 10 to the forehearth 310. The forehearth 310 and bushing block 300 may be conventional in construction and may be formed from refractory materials.

[0031] The tip plate 124 contains a plurality of nozzles 124a (also referred to as orifices) through which a plurality of streams of molten glass may be discharged. The streams of molten material may be mechanically drawn from the tip plate 124 to form continuous filaments 125 via a conventional winder device 400. The filaments 125 may be gathered into a single continuous strand 125a after having received a protective coating of a sizing composition from a sizing applicator 410. The continuous filaments 125a may be wound onto a rotating collet 402 of the winder device 400 to form a package 125b. The continuous filaments 125 may also be processed into other desired composite glass materials including, without limitation, wet use chopped strand fibers, dry use chopped strand fibers, continuous filament mats, chopped strand mats, wet formed mats or air laid mats.

[0032] High strength articles of the present invention use the formed fibers described above as glass fiber reinforcement within a polymer matrix material. Typical matrix materials include epoxies, phenolic resins, vinylesters, and polyesters. The articles may be formed by any suitable manufacturing technique including compression molding, laminating, spray up, hand laying, prefabricated lay-up (prepreg), compression molding, vacuum bag molding, pressure bag molding, press molding, transfer molding, vacuum assisted resin transfer molding, pultrusion molding, filament winding, casting, autoclave molding, centrifugal casting resin transfer and continuous casting.

[0033] Having generally described this invention, a further understanding can be obtained by reference to certain specific examples illustrated below which are provided for purposes of illustration only and are not intended to be all inclusive or limiting unless otherwise specified.

EXAMPLES

[0034] The glasses in the examples listed in Tables IIA-IIC were melted in platinum crucibles or in a continuous platinum-lined melter for determining the mechanical and physical properties of the glass and fibers produced there from. The units of measurement for the physical properties are: Viscosity ( F.), Liquidus temperature ( F.) and T ( F.). In some examples the glasses were fiberized and Strength (KPsi), Density (g/cc), and Modulus (MPsi) were measured.

[0035] The fiberizing temperature was measured using a rotating spindle viscometer. The fiberizing viscosity is defined as 1000 Poise. The liquidus was measured by placing a platinum container filled with glass in a thermal gradient furnace for 16 hours. The greatest temperature at which crystals were present was considered the liquidus temperature. The modulus was measured using the sonic technique on a single fiber of glass. The tensile strength was measured on a pristine single fiber.

TABLE-US-00006 TABLE II-A Glass Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 SiO.sub.2 67.2 69 67 70 70 65 Al.sub.2O.sub.3 20 22 22 17 17 21 MgO 9.8 9 11 11 10 11 Li.sub.2O 3 0 0 2 3 3 Measured 2531 2761 2648 2557 2558 2461 Viscosity( F.) 1.sup.st Measured 2313 2619 2597 2332 2302 2296 Liquidus ( F.) 2.sup.nd Measured 2302 2620 2614 2346 2308 2318 Liquidus ( F.) T ( F.) 218 142 51 225 256 165 Measured 2.459 2.452 2.481 2.450 2.441 2.482 Density (g/cc)

TABLE-US-00007 TABLE II-B Glass Ex. 7 Ex. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 12 SiO.sub.2 70 69 70 65 66 65 Al.sub.2O.sub.3 18 17 21 22 22 22 MgO 9 11 9 11 9 10 Li.sub.2O 3 3 0 2 3 3 Measured 2544 2496 2752 2525 2523 2486 Viscosity ( F.) 1.sup.st Measured 2311 2234 2597 2468 2391 2361 Liquidus ( F.) 2.sup.nd Measured 2324 2343 2603 2462 2394 2382 Liquidus ( F.) T ( F.) 233 262 155 57 132 125 Measured 2.434 2.455 2.443 2.486 2.460 2.474 Density (g/cc)

TABLE-US-00008 TABLE II-C Glass Ex. 13 Ex. 14 Ex. 15 Ex. 16 Ex. 17 Ex. 18 SiO.sub.2 70 67.32 67.57 68.27 68.02 67.76 Al.sub.2O.sub.3 19 20.49 20.49 20.10 20.10 20.10 MgO 11 10.00 10.00 9.69 9.69 9.69 Li.sub.2O 0 2.00 1.75 1.75 2.00 2.25 Measured 2679 2563 2584 2598 2578 2547 Viscosity ( F.) 1.sup.st Measured 2596 2456 2486 2446 2431 2399 Liquidus ( F.) 2.sup.nd Measured 2582 2447 2469 2469 2437 2406 Liquidus ( F.) T ( F.) 83 111.5 106.5 140.5 144 144.5 Measured 2.453 2.461 2.452 Density (g/cc)

[0036] The composition of the present invention may also include chain modifiers such as Na.sub.2O, CaO and B.sub.2O.sub.3. Such compositions are shown in Table II-D (below).

TABLE-US-00009 TABLE II-D Glass Ex. 19 Ex. 21 Ex. 22 Ex. 22 Ex. 23 Ex. 24 SiO.sub.2 75 66 65 65 66 74 Al.sub.2O.sub.3 15 20 20 24 19 15 MgO 8 9 8 8 9 8 Li.sub.2O 1 1 2 0 0 0 Na.sub.2O 1 2 1 1 2 3 CaO 2 4 B.sub.2O.sub.3 2 4 Measured 2765 2607 2469 2669 2809 Viscosity ( F.) 1.sup.st Measured 2422 2729 2614 2630 2680 Liquidus ( F.) T ( F.) 343 122 55 129

[0037] The fibers of the present invention have superior modulus and strength characteristics. The fibers of Example 1 have a Measured Modulus of 12.71 MPsi and a Measured Strength of 688 KPsi. The fibers of Example 3 have a Measured Modulus of 12.96 MPsi and a Measured Strength of 737 KPsi. The fibers of Example 17 have a Measured Modulus of 12.75 MPsi and a Measured Strength of 734 KPsi.

[0038] As is understood in the art, the above exemplary inventive compositions do not always total 100% of the listed components due to statistical conventions (such as, rounding and averaging) and the fact that some compositions may include impurities that are not listed. Of course, the actual amounts of all components, including any impurities, in a composition always total 100%. Furthermore, it should be understood that where small quantities of components are specified in the compositions, for example, quantities on the order of about 0.05 weight percent or less, those components may be present in the form of trace impurities present in the raw materials, rather than intentionally added.

[0039] Additionally, components may be added to the batch composition, for example, to facilitate processing, that are later eliminated, thereby forming a glass composition that is essentially free of such components. Thus, for instance, minute quantities of components such as fluorine and sulfate may be present as trace impurities in the raw materials providing the silica, lithia, alumina, and magnesia components in commercial practice of the invention or they may be processing aids that are essentially removed during manufacture.

[0040] As is apparent from the above examples, glass fiber compositions of the invention have advantageous properties, such as low fiberizing temperatures and wide differences between the liquidus temperatures and the fiberizing temperatures (high T values). Other advantages and obvious modifications of the invention will be apparent to the artisan from the above description and further through practice of the invention). The high-performance glass of the present invention melts and refines at relatively low temperatures, has a workable viscosity over a wide range of relatively low temperatures, and a low liquidus temperature range.

[0041] The invention of this application has been described above both generically and with regard to specific embodiments. Although the invention has been set forth in what is believed to be the preferred embodiments, a wide variety of alternatives known to those of skill in the art can be selected within the generic disclosure. Other advantages and obvious modifications of the invention will be apparent to the artisan from the above description and further through practice of the invention, The invention is not otherwise limited, except for the recitation of the claims set forth below.