thermal insulator

Abstract

The invention relates to inorganic fibers having a composition comprising: 61.0 to 70.8 wt% SiO2; 27.0 to 38.9 wt% CaO; 0.10 to 2.0 wt% MgO; and optionally, an amount of other components providing the balance up to 100 wt%. The sum of SiO2 and CaO is greater than or equal to 97.8 wt%, and wherein the amount of said other components, when present, comprises no more than 0.80 wt% Al2O3.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to thermal insulation comprising a bio-soluble inorganic fiber composition, and more particularly, insulation materials comprising the fibers. The present disclosure also relates to the use of the fibers at temperatures up to and beyond 1200°C. BACKGROUND

[0002] The insulation industry has identified a desire to utilize fibers that are not persistent in physiological fluids in thermal, electrical, and acoustic insulation applications. That is, fiber compositions that are considered to have low bio-persistence in physiological fluids (i.e., bio-soluble).

[0003] While candidates have been proposed, silicate materials, the temperature use limitations of these materials are not high enough to accommodate many applications for high temperature resistant fibers. For example, such bio-soluble fibers exhibit high shrinkage at use temperatures and / or reduced mechanical strength when exposed to use temperatures ranging from 1000°C to 1500°C compared to the performance of refractory ceramic fibers.

[0004] High temperature resistant fibers should exhibit minimal shrinkage at the intended exposure temperature and after long term or continuous exposure to the intended use temperature to provide effective thermal protection to the item being insulated. In addition to bio-soluble and high temperature resistant, the fibers used in the resulting insulation material should also have low diameters and low shot content to have low density and thermal conductivity. The numerous demands do not end there, the fibers also need to not react with other materials in the insulation system they can form.

[0005] In 1987, the Manville Corporation developed a bio-soluble high temperature resistant fiber based on a calcium magnesium silicate chemistry (US 5,714,421). This material not only had a higher temperature capability than traditional glass wool, but also a higher solubility in body fluids than most aluminosilicate fibers used for high temperature insulation. US 5,714,421 taught the necessity of combining silica, calcium oxide, and magnesium oxide with a variety of other metal oxide additives to achieve the desired combination of fiber properties and form.

[0006] While there are many commercial examples of bio-soluble high temperature resistant fibers, they are derived from a magnesium oxide, calcium oxide, silica system, there remains a need for improved bio-soluble high temperature resistant fibers and insulation materials therefrom.

[0007] International application WO 87 / 05007 discloses inorganic fibers consisting essentially of Si02, CaO, and MgO and Al203 in the specified ranges, derived from metal oxides rather than compositionally variable crude by-product materials. It was observed that lower Al203 levels resulted in surprisingly high levels of bio-solubility.

[0008] International application WO 94 / 15883 discloses CaO / MgO / SiO2 fibres with additional components AI2O3, ZrO2 and TiO2 and studies their salt water solubility and refractoriness. The article states that salt water solubility appears to increase with increasing amounts of MgO, while ZrO2 and AI2O3 are detrimental to solubility. The presence of TiO2 (0.71-0.74 mol%) and AI2O3 (0.51-0.55 mol%) results in fibres that do not meet the standard of 3.5% or less shrinkage at 1260°C. The article further states that fibres with too high SiO2 are difficult to form or impossible to form and cites fibres with 70.04, 73.09, 73.28 and 78.07 wt% SiO2 as examples of compositions that cannot be fibre formed.

[0009] US 6,953,757 discloses inorganic high-silica fibre compositions comprising mainly silica, calcium oxide, magnesium oxide and zirconium oxide and optionally viscosity modifiers such as aluminium oxide and borax to fibre the product.

[0010] JP 2003003335 discloses inorganic fibres comprising silica and calcium oxide to avoid precipitation of cristobalite when the fibres are heated to temperatures of 1000°C or more. To avoid precipitation of cristobalite, the levels of Na2O, K2O, TiO2, Fe2O3 and MgO are reduced or Na2O, K2O, TiO2, Fe2O3 and MgO are not added, high purity calcium oxide and silica are used as raw materials.

[0011] US 2004 / 254056 claims CaO / SiO2 fibres comprising more than or equal to 72 wt% SiO2 or a total of SiO2 + ZrO2 + B2O3 + 5*P2O5 of more than 72 wt%. Such fibres have a lower tendency to react with aluminosilicate bricks, while fibres with lower SiO2 + ZrO2 + B2O3 + 5*P2O5 content tend to react adversely with aluminosilicate bricks.

[0012] Despite the advances made in the field, there remains a need for simplified fibre compositions that do not rely on a series of additives to achieve the desired combination of fibre properties and form. There is also a need for simplified fibre compositions that do not rely on high-impurity raw materials in their production, where the purification processes commonly used to produce such high-purity raw materials increase the carbon footprint of the resulting inorganic fibres. SUMMARY

[0013] Applicants have discovered, contrary to accepted wisdom in the field of refractory alkaline earth silicate fibres, that within a specified compositional range, refractory fibres with high utility can be produced without the addition of large amounts of additives (such as viscosity modifiers, solubility or refractoriness enhancers) to the SiO2-CaO system.

[0014] According to a first aspect of the disclosure, there is provided an inorganic fiber having a composition comprising:

[0015] 61.0 to 70.8 percent by weight Si02;

[0016] 27.0 to 38.9 percent by weight CaO;

[0017] 0.10 to 2.0 percent by weight MgO; and

[0018] optionally other components providing the balance up to 100 percent by weight,

[0019] wherein the sum of Si02and CaO is greater than or equal to 97.8 percent by weight, and wherein the other components, when present, comprise no more than 0.80 percent by weight Al203.

[0020] The following alternative expressions can also be used to define the first aspect of the disclosure, wherein the inorganic fiber has a composition comprising:

[0021] 61.0 to 70.8 percent by weight Si02;

[0022] greater than or equal to 97.8 percent by weight Si02+ CaO;

[0023] 0.10 to 2.0 percent by weight MgO; and

[0024] optionally other components providing the balance up to 100 percent by weight, wherein the other components, when present, comprise no more than 0.80 percent by weight Al203.

[0025] It has been discovered that a narrow composition window, in which a small amount of MgO unexpectedly inhibits the formation of large surface microcrystallites at high temperature, while not significantly affecting the high temperature performance of the fiber. Large surface microcrystallites on the fiber can lead to the creation of stress points, which have an adverse effect on the mechanical properties of the fiber at high temperature. Thus, it is desirable to minimize the size of the surface microcrystalline phase formed at high temperature when the fiber is in use.

[0026] The sum of Si02and CaO can be greater than or equal to 97.9 wt% or greater than or equal to 98.0 wt% or greater than or equal to 98.1 wt% or greater than or equal to 98.2 wt% or greater than or equal to 98.3 wt% or greater than or equal to 98.4 wt% or greater than or equal to 98.5 wt% or greater than or equal to 98.6 wt% or greater than or equal to 98.7 wt% or greater than or equal to 98.8 wt% or greater than or equal to 98.9 wt% or greater than or equal to 99.0 wt% or greater than or equal to 99.1 wt% or greater than or equal to 99.2 wt% or greater than or equal to 99.3 wt% or greater than or equal to 99.4 wt% or greater than or equal to 99.5 wt%. Higher proportions of Si02and CaO (and lower proportions of other components) are believed to reduce the propensity for surface microcrystals to form at high temperatures. The upper limit on purity can be constrained by the cost and availability of raw materials, particularly those with a relatively low carbon footprint such as materials that have not been chemically purified or otherwise processed. The upper limit on the sum of Si02and CaO can also be limited by the ability to manufacture inorganic fibers, particularly for fine fiber diameters (e.g., < 6 pm and / or less than 52 wt% tramp balls (< 45 pm)).

[0027] In some embodiments, the amount of MgO is configured to inhibit the formation of surface microcrystallites having an average microcrystal size in the range of 0.0 to 0.90 pm after heat treatment at 1100 °C for 24 hours.

[0028] In addition to the presence of small amounts of MgO, the target composition range can also be limited in the amount of other components, such as additives or incidental impurities. In particular, it is desirable to limit the amount of alumina, titania, and alkali oxides to avoid promoting the formation of large microcrystallites.

[0029] In some embodiments, the amount of other components is configured to inhibit the formation of surface microcrystallites having an average microcrystal size in the range of 0.0 to 0.90 pm after heat treatment at 1100 °C for 24 hours.

[0030] The inorganic fiber after heat treatment at 1100 °C for 24 hours can include surface microcrystallites having an average microcrystal size of 0.90 pm or less or 0.80 pm or less or 0.70 pm or less or 0.60 pm or less or 0.50 pm or less or less than 0.40 pm. Preferably, there are no surface microcrystallites (i.e., microcrystal size = 0.0 pm) or no detectable surface microcrystallites.

[0031] The amount of MgO and / or other components can also be configured such that the vacuum cast preform of the fiber has a shrinkage of 3.5% or less when exposed to 1200 °C or 1300 °C for 24 h.

[0032] In some embodiments, the fiber composition is configured to include both high temperature microcrystalline grain inhibition properties and low shrinkage properties.

[0033] The amount of other components is no more than 2.1 wt.%, and can be no more than 2.0 wt.% or no more than 1.9 wt.% or no more than 1.8 wt.% or no more than 1.7 wt.% or no more than 1.6 wt.% or no more than 1.5 wt.% or no more than 1.4 wt.% or no more than 1.3 wt.% or no more than 1.2 wt.% or no more than 1.1 wt.% or no more than 1.0 wt.% or no more than 0.9 wt.% or no more than 0.8 wt.% or no more than 0.7 wt.% or no more than 0.6 wt.%. Higher levels of other components can have a detrimental effect on the high temperature performance of the fiber. By being able to utilize raw materials with higher levels of impurities but within the prescribed range, greater natural resource utilization can be achieved without the need for further processing, including chemical purification. The other components typically comprise at least 0.2 wt.% or at least 0.3 wt.% or at least 0.4 wt.% or at least 0.5 wt.% of the inorganic fiber composition. While it is possible to use purer raw materials, this can be accompanied by an increase in carbon footprint and cost due to the need for additional purification processes. Furthermore, these other components with incidental impurities are believed to contribute to the fiberization of the components.

[0034] In some embodiments, a small amount of additives can be included to fine tune the properties of the fiber. The additive addition can be greater than 0.0 wt.% or greater than 0.10 wt.% or greater than 0.20 wt.% or greater than 0.30 wt.%. The additive addition can be less than 2.0 wt.% or 1.7 wt.% or 1.5 wt.% or 1.4 wt.% or 1.3 wt.% or 1.1 wt.% or 1.2 wt.% or 1.0 wt.% or 0.9 wt.% or 0.8 wt.% or 0.7 wt.% or 0.6 wt.% or 0.5 wt.% or 0.4 wt.% or 0.3 wt.% or 0.2 wt.% of the inorganic fiber composition.

[0035] The additives can be in the oxide or non-oxide form of one or more metals, including but not limited to bromides, chlorides, fluorides, phosphates, nitrates, nitrites, oxides, carbonates, and / or sulfates. The metals can include, for example, alkali metals, alkaline earth metals, transition metals, post-transition metals, and lanthanides. For the purposes of the present disclosure, metals can also include metalloids.

[0036] In some embodiments, the additives are added for one or more of the following purposes:

[0037] • to aid in fiberization (melt viscosity modifiers);

[0038] • to enhance high temperature performance;

[0039] • Helps to form finer fiber diameters while maintaining the desired bio-solubility and high temperature use characteristics.

[0040] The additive can include an oxide or non-oxide (e.g., fluoride) of one or more of a lanthanide (e.g., La, Ce), Li, Na, K, Sr, Ba, Cr, Fe, Zn, Y, Zr, Hf, Ca, B, P, or combinations thereof. In another embodiment, the other component includes one or more oxides or non-oxides of a lanthanide, Sr, Ba, Cr, Zr, or combinations thereof. The fiber composition can include 0.05 to 1.0 wt% of the additive or 0.10 to 0.80 wt% or 0.15 to 0.60 wt% of the additive. The additive is preferably derived from a naturally occurring deposit. It is particularly advantageous to add a viscosity modifier when added to a fiber composition having a Si02 content greater than 66.0 wt% or 67.0 wt% or 68.0 wt% or 69.0 wt%.

[0041] It has been discovered that within this compositional window, bio-soluble high temperature resistant fibers are melt formable. In addition, when the fiber composition has 65.7 wt% or more Si02, the fibers show no reaction at high temperatures in the presence of aluminum-based materials. Other network formers (e.g., Zr02) show a substitutability with Si02, and thus, fiber compositions having a total of 65.7 wt% or more of Si02+ Zr02are expected to also show no reaction at high temperatures in the presence of aluminum-based materials.

[0042] In some embodiments, the inorganic fiber does not react when contacted with an alumina composition (e.g., mullite) at 1200°C for 24 h. The alumina composition preferably includes a composition having at least 20 wt% Al203or at least 30 wt% Al203or at least 40 wt% Al203or at least 50 wt% Al203. However, depending on the atmosphere, temperature, and duration of exposure, the benefits of this higher silica content can still be present at lower alumina content levels.

[0043] In some embodiments, the other component includes or consists of incidental impurities in the raw materials used to make the inorganic fiber (including coal ash when coal is used as a source of energy to melt in the inorganic fiber precursor materials (e.g., silica sand and lime)).

[0044] In some embodiments, the primary impurity in the lime includes magnesium oxide. Other impurities can include aluminum oxide, iron oxide, and alkali metal oxides such as K20 and Na20.

[0045] In some embodiments, the sum of Si02and CaO and MgO is greater than or equal to 98.5 wt% or 98.8 wt% or 99.0 wt% or 99.1 wt% or 99.2 wt% or 99.3 wt% or 99.4 wt% or 99.5 wt% of the fiber composition.

[0046] In some embodiments, the inorganic fiber composition comprises less than 1.7 wt% or less than 1.5 wt% or less than 1.2 wt% or less than 1.0 wt% or less than 0.90 wt% or less than 0.88 wt% or less than 0.85 wt% or less than 0.82 wt% or less than 0.80 wt% or less than 0.75 wt% or less than 0.70 wt% or less than 0.60 wt% MgO or less than 0.50 wt% or less than 0.45 wt% MgO from incidental impurities. Higher MgO content has been found to adversely affect the thermal stability of the fiber at 1200°C or 1300°C. The composition preferably comprises at least 0.11 wt% or at least 0.12 wt% or at least 0.14 wt% or at least 0.16 wt% or at least 0.18 wt% or at least 0.20 wt% MgO.

[0047] In some embodiments, the sum of Si02+ CaO + MgO + AI2O3 is greater than or equal to 99.3 wt% or 99.4 wt% or 99.5 wt% or 99.6 wt% or 99.7 wt% of the inorganic fiber composition.

[0048] Preferably, the inorganic fiber composition comprises less than 0.80 wt% AI2O3or less than 0.79 wt% AI2O3or less than 0.78 wt% AI2O3or less than 0.77 wt% AI2O3or less than 0.76 wt% AI2O3or less than 0.75 wt% AI2O3or less than 0.74 wt% AI2O3or less than 0.73 wt% AI2O3or less than 0.72 wt% AI2O3or less than 0.71 wt% AI2O3or less than 0.70 wt% AI2O3or less than 0.69 wt% AI2O3or less than 0.68 wt% AI2O3or less than 0.67 wt% AI2O3or less than 0.66 wt% AI2O3or less than 0.65 wt% AI2O3or less than 0.64 wt% AI2O3or less than 0.63 wt% AI2O3or less than 0.62 wt% AI2O3or less than 0.61 wt% AI2O3or less than 0.60 wt% AI2O3or less than 0.55 wt% AI2O3or less than 0.50 wt% AI2O3or less than 0.45 wt% AI2O3or less than 0.40 wt% AI2O3or less than 0.35 wt% AI2O3or less than 0.30 wt% AI2O3or less than 0.25 wt% AI2O3, preferably the AI2O3is derived from incidental impurities. The amount of AI2O3is typically 0.0 wt% or more. In the current SiO2-CaO compositions, higher AI2O3levels have been found to adversely affect the bio-solubility and thermal stability of the inorganic fiber in addition to promoting microcrystalline growth at high temperatures.

[0049] In another embodiment, the sum of MgO and AI2O3in the inorganic fiber is no more than 2.0 wt% or no more than 1.80 wt% or no more than 1.50 wt% or no more than 1.20 wt% or no more than 1.10 wt% or no more than 1.00 wt% or no more than 0.90 wt% or no more than 0.80 wt% or no more than 0.70 wt% or no more than 0.60 wt%.

[0050] In other embodiments, the vacuum cast preform of inorganic fibers has a composition configured to obtain a shrinkage of 8.0% or less, 7.0% or less, 6.0% or less, 5.0% or less, 4.5% or less, 4.0% or less, 3.0% or less, 2.5% or less, or 2.0% or less when exposed to 1200°C for 24h. In another embodiment, the vacuum cast preform of inorganic fibers has a composition configured to obtain a shrinkage of 8.0% or less, 7.0% or less, 6.0% or less, 5.0% or less, 4.5% or less, 4.0% or less, 3.0% or less, 2.5% or less, or 2.0% or less when exposed to 1300°C for 24h.

[0051] The melting temperature of the inorganic fibers is preferably at least 1350°C or at least 1380°C or at least 1400°C or at least 1420°C.

[0052] To facilitate fiberization, particularly in the absence of additives, the Si02content of the inorganic fiber composition is preferably less than 70.7 wt% or less than 70.6 wt% or less than 70.5 wt% or less than 70.4 wt% or less than 70.2 wt% or less than 70.0 wt% or less than 69.8 wt% or less than 69.6 wt%, less than 69.4 wt% or less than 69.2 wt% or less than 69.0 wt% or less than 68.8 wt% or less than 68.5 wt% or less than 68.3 wt% or less than 68.1 wt% or less than 68.0 wt%. To facilitate resilience at high temperatures and to minimize reactivity with substrates containing alumina, the Si02content of the inorganic fiber composition is preferably at least 61.1 wt% or at least 61.2 wt% or at least 62.3 wt% or at least 62.4 wt% or at least 62.5 wt% or at least 62.6 wt%, at least 62.7 wt% or at least 62.8 wt% or at least 62.9 wt% or at least 63.0 wt% or at least 63.5 wt% or at least 64.0 wt% or at least 64.5 wt% or at least 65.0 wt% or at least 65.7 wt% or at least 65.8 wt% or at least 66.0 wt% or at least 66.2 wt% or at least 66.4 wt% or at least 66.6 wt% or at least 66.8 wt% or at least 67.0 wt% or at least 67.2 wt% or at least 67.4 wt%.

[0053] The CaO content of the inorganic fiber composition is preferably thus varied, with a lower limit of CaO preferably being at least 27.0 wt% or at least 27.2 wt% or at least 27.5 wt% or at least 28.0 wt% or at least 28.5 wt% or at least 29.0 wt% or at least 29.5 wt% or at least 30.0 wt%. The upper limit of the CaO content of the inorganic fiber composition is preferably no more than 38.5 wt% or no more than 38.0 wt% or no more than 37.5 wt% or no more than 37.0 wt% or no more than 36.5 wt% or no more than 36.0 wt% or no more than 35.5 wt% or no more than 35.0 wt% or no more than 34.5 wt% or no more than 34.0 wt% or no more than 33.5 wt% or no more than 33.0 wt% or no more than 32.5 wt% or no more than 32.0 wt%.

[0054] The MgO content of the inorganic fiber composition preferably includes MgO in the range of 0.1 to 1.7 wt%; or 0.11 wt% to 1.50 wt%; or 0.12 wt% to 1.30 wt%; or 0.1 to 1.0 wt%; or 0.11 wt% to 0.90 wt%; or 0.12 wt% to 0.85 wt%; or 0.13 wt% to 0.80 wt%; or 0.14 wt% to 0.75 wt%; or 0.17 wt% to 0.72 wt%; or 0.15 wt% to 0.70 wt%; or 0.15 wt% to 0.65 wt%; or 0.17 wt% to 0.60 wt%; or 0.18 wt% to 0.50 wt%; or 0.19 wt% to 0.45 wt%; or 0.20 wt% to 0.40 wt%.

[0055] In one embodiment, the other components include:

[0056] • 0 or 0.01 to 0.8 wt% AI2O3 or 0.10 to 0.60 wt% AI2O3 or 0.20 to 0.55 wt% AI2O3 or 0.23 to 0.50 wt% AI2O3 or 0.24 to 0.45 wt% AI2O3 or 0.25 to 0.40 wt% AI2O3 or 0.25 to 0.35 wt% AI2O3;

[0057] • 0 to 0.50 wt% alkali metal oxide or 0.01 to 0.45 wt% alkali metal oxide or 0.03 to 0.40 wt% alkali metal oxide or 0.04 to 0.35 wt% alkali metal oxide or 0.05 to 0.30 wt% alkali metal oxide or 0.06 to 0.25 wt% alkali metal oxide or 0.07 to 0.20 wt% alkali metal oxide or 0.08 to 0.18 wt% alkali metal oxide;

[0058] • 0 to 1.0 wt% Ti02or 0.05 to 0.8 wt% Ti02or 0.10 to 0.6 wt% Ti02or 0.15 to 0.4 wt% Ti02or 0 to 0.2 wt% Ti02; or

[0059] • 0 to 1.0 wt% Zr02or 0.05 to 0.8 wt% Zr02or 0.10 to 0.6 wt% Zr02or 0.15 to 0.4 wt% Zr02or 0 to 0.2 wt% Zr02;

[0060] In some embodiments, at least 80 wt% of the alkali metal oxide comprises Na20 or K20.

[0061] In one embodiment, other incidental impurities in the inorganic fiber range from:

[0062] BaO: 0 to 0.05 wt% or >0 to 0.01 wt%

[0063] B203: 0 to 0.1 wt% or >0 to 0.05 wt%

[0064] Cr203: 0 to 0.08 wt% or >0 to 0.03 wt%

[0065] Fe203: 0 to 0.25 wt% or >0 to 0.15 wt%

[0066] Hf02: 0 to 0.05 wt% or >0 to 0.01 wt%

[0067] La203: 0 to 0.1 wt% or >0 to 0.03 wt%

[0068] Mn304: 0 to 0.05 wt% or >0 to 0.01 wt%

[0069] Li20: 0 to 0.15 wt% or >0 to 0.08 wt%

[0070] Na20: 0 to 0.15 wt% or >0 to 0.08 wt%

[0071] K20: 0 to 0.5 wt% or >0 to 0.20 wt%

[0072] P2O5: 0 to 0.05 wt% or >0 to 0.01 wt%

[0073] SrO: 0 to 0.08 wt% or >0 to 0.03 wt%

[0074] TiO2: 0 to 0.08 wt% or >0 to 0.03 wt%

[0075] V2O5: 0 to 0.05 wt% or >0 to 0.01 wt%

[0076] SnO2: 0 to 0.05 wt% or >0 to 0.01 wt%

[0077] ZnO: 0 to 0.05 wt% or >0 to 0.01 wt%

[0078] ZrO2: 0 to 0.1 wt% or >0 to 0.02 wt%

[0079] The sum of BaO + Cr2O3+ Fe2O3+ HfO2+ La2O3+ Mn3O4+ Na2O + K2O + P2O5+ SrO + SnO2+ TiO2+ V2O5+ ZrO2+ ZnO is preferably less than 2.0 wt% or 1.8 wt% or 1.6 wt% or 1.4 wt% or 1.2 wt% or 1.0 wt% or 0.8 wt% or 0.6 wt% or 0.5 wt% or 0.4 wt% or 0.3 wt% or 0.25 wt% or 0.2 wt% of the total weight of the inorganic fiber. The sum of BaO + Cr2O3+ Fe2O3+ HfO2+ La2O3+ Mn3O4+ Na2O + K2O + P2O5+ SrO + SnO2+ TiO2+ V2O5+ ZrO2+ ZnO is typically at least 0.10 wt% or at least 0.20 wt% or at least 0.30 wt% of the total weight of the inorganic fiber.

[0080] In one embodiment, the silica level of the inorganic fiber is configured to suppress the reactivity of the inorganic fiber such that the inorganic fiber does not react when contacted with mullite at 1200 °C for 24 h.

[0081] In another embodiment, the inorganic fiber has a composition comprising:

[0082] 65.7 to 70.8 wt% SiO2;

[0083] 27.0 to 32.3 wt% CaO;

[0084] 0.10 to 2.0 wt% MgO; and

[0085] optional other components that provide the balance up to 100 wt%,

[0086] The sum of SiO2 and CaO is greater than or equal to 97.8% by weight, and the other components, when present, contain no more than 0.80% by weight of Al2O3.

[0087] The fibers of this embodiment are particularly suitable for insulation systems in which inorganic fibers are configured to contact refractory material components, such as mullite, including alumina.

[0088] In another embodiment, the inorganic fiber has a composition comprising the following:

[0089] 66.0 to 69.0% by weight or (65.7 to 69.0% by weight) of SiO2 or the sum of SiO2 and ZrO2;

[0090] 30.0 to 34.0% by weight of CaO or (30.0 to 34.2% by weight) of CaO;

[0091] 0.10 to 0.45 wt% (or 0.1 to 0.45 wt%; or 0.1 to 0.60 wt%) of MgO

[0092] 0 to 0.35 wt% (or 0.1 to 0.35 wt%; or 0 to 0.45 wt%; or 0 to 0.60 wt%) of Al2O3

[0093] 0 to 0.20 wt% (or 0.05 to 0.18 wt%) of alkali metal oxides, and

[0094] The total amount of SiO2 and CaO is greater than or equal to 99.0% by weight.

[0095] In some embodiments, the numerically average (or arithmetic average) fiber diameter is less than 6.0 μm, less than 5.0 μm, less than 4.5 μm, less than 4.0 μm, less than 3.5 μm, less than 3.3 μm, less than 3.0 μm, less than 2.8 μm, or less than 2.5 μm. The minimum numerically average fiber diameter is typically at least 1.5 μm or at least 2.0 μm to ensure sufficient mechanical strength of the fiber during use.

[0096] In some embodiments, the slag ball content (>45 μm) of the inorganic fiber is less than 51% by weight or less than 50% by weight or less than 49% by weight or less than 48% by weight or less than 47% by weight or less than 46% by weight or less than 45% by weight or less than 44% by weight or less than 43% by weight or less than 42% by weight or less than 41% by weight or less than 40% by weight or less than 39% by weight or less than 38% by weight or less than 37% by weight or less than 36% by weight or less than 35% by weight or less than 34% by weight or less than 33% by weight.

[0097] The combination of reduced fibre diameter and low shot content results in improved insulation properties.

[0098] The inorganic fibres can be incorporated into thermal insulation for applications preferably requiring sustained resistance to temperatures up to 1300°C or in some embodiments 1200°C or higher (e.g. classification temperature (EN 1094-1-2008) of 1100°C or 1150°C or 1200°C or 1260°C or 1300°C).

[0099] In some embodiments, the rate of dissolution of the fibres in the flow solubility test (pH 7.4) is preferably at least 130 ng / cm 2 h or at least 140 ng / cm 2 h or at least 150 ng / cm 2 h or at least 170 ng / cm 2 h or at least 200 ng / cm 2 h or at least 250 ng / cm 2 h.

[0100] In some embodiments, the tensile strength of the fibre blanket (128 kg / m 3 ) is at least 50 kPa or at least 55 kPa or at least 60 kPa. The fibre blanket strength can be determined according to EN 1094-1 (2008).

[0101] In some embodiments, the 128 kg / m 3 fibre blanket has a thermal conductivity at 1000°C of no more than 0.30 W.m -1 .K -1 or no more than 0.28 W.m -1 .K -1 or no more than 0.26 W.m -1 .K -1 or no more than 0.25 W.m -1 .K -1 The fibre blanket thermal conductivity can be determined according to ASTM C201-93 (2019).

[0102] The 128 kg / m 3 fibre blanket has a thermal conductivity at 1200°C preferably no more than 0.35 W.m -1 .K -1 or no more than 0.32 W.m -1 .K -1 or no more than 0.31 W.m -1 .K -1 or no more than 0.30 W.m -1 .K -1 or no more than 0.29 W.m -1 .K-1 .

[0103] In some embodiments, the resilience of the manufactured fibre is at least 80%. The resilience after 24h at 1100°C is preferably at least 70wt% or at least 75wt%. The resilience after 24h at 1150°C is preferably at least 63wt% or at least 67wt% or at least 70wt% or at least 72wt% or at least 74wt%. The resilience after 24h at 1200°C is preferably at least 60wt% or at least 63wt% or at least 67wt% or at least 70wt%.

[0104] By maintaining other components (such as incidental impurities) within the above limits, the inorganic fibres of the present disclosure are able to maintain excellent high temperature utility. While individual impurity levels can vary outside of their preferred ranges, by maintaining overall low levels of incidental impurities, the need to add additives (such as viscosity modifiers, solubility enhancers, refractory temperature stabilisers, etc.) to the calcium oxide and silica mixture can be avoided or minimised.

[0105] Fibresation techniques as taught in US 4,238,213 or US 2012 / 247156 can be used to form the fibres of the present disclosure. It can be preferred to use the apparatus and techniques disclosed in WO 2017 / 121770 (which is incorporated herein in its entirety by reference), particularly for compositions comprising higher silica contents (e.g. > 68wt% or > 69wt%).

[0106] In a second aspect of the present disclosure, there is provided an insulation or sealing system comprising:

[0107] a. a refractory component comprising a contact surface; and

[0108] b. an insulation or sealing material comprising inorganic fibres having a composition of the first aspect of the invention

[0109] wherein the insulation lining or sealing material is disposed against the contact surface.

[0110] In some embodiments, the inorganic fibres of the insulation system comprise (i) at least 65.7wt% Si02; (ii) at least 65.7wt% of the sum of Si02+ Zr02; or (iii) a composition wherein the inorganic fibres do not react when contacted with mullite at 1200°C for 24h. The skilled person will appreciate that the exact composition window which does not react with mullite can vary depending on the additives or incidental impurities present.

[0111] The refractory component can comprise alumina. The refractory component can comprise at least 20 wt% AI2O3or at least 30 wt% or at least 40 wt% AI2O3or at least 50 wt% AI2O3or at least 60 wt% or at least 70 wt% AI2O3. Examples of refractory component compositions include mullite, clay-based compositions or alumina-based compositions. The refractory component can comprise a refractory mortar, a refractory cement, a refractory cement, a refractory board, a refractory fibre or a refractory brick.

[0112] The sealing material is in the form of a mortar, a blanket or loose fibres. The insulating material can be in the form of a blanket, a module, a board or loose fibres.

[0113] The insulation or sealing system can form part of a kiln, an oven, a furnace or other high temperature equipment.

[0114] In a third aspect of the disclosure, there is provided a furnace, kiln or oven comprising:

[0115] a. a wall comprising an inner surface; and

[0116] b. an insulating material comprising inorganic fibres having a composition according to the first aspect of the disclosure,

[0117] wherein the insulating material is attached to the inner surface of the wall, the insulating material in use has a hot face facing the interior of the furnace, kiln or oven; and a cold face located at, facing or adjacent to the inner surface of the wall.

[0118] The inorganic fibres can form part or all of the cold face, it can be in contact with the wall. The inorganic fibres can also form part or all of the hot face. The inorganic fibres can be in the form of a blanket. The blanket can be formed into a brick configuration by folding the blanket back and forth.

[0119] The wall can have the same composition as the other refractory component as defined in the second aspect of the disclosure.

[0120] In a fourth aspect of the disclosure, there is provided a method for manufacturing inorganic fibres comprising:

[0121] a. selecting the composition and proportions of each of the following raw materials:

[0122] i. silica sand and

[0123] ii. lime, the lime comprising at least 0.10 wt% magnesium oxide; and

[0124] iii. optional additives

[0125] b. mixing the silica sand, lime and optional additives to form a mixture;

[0126] c. melting the mixture in a furnace;

[0127] d. forming the molten mixture into inorganic fibers,

[0128] wherein the raw material selection comprises a composition selection and a ratio selection of silica sand and lime to obtain an inorganic fiber composition comprising silica in the range of 61.0 wt.% to 70.8 wt.%; less than 2.0 wt.% of magnesium oxide; not more than 2.0 wt.% of metal oxides and / or metal non-oxides from incidental impurities and from said optional additives; wherein calcium oxide provides the balance up to 100 wt.% and wherein the inorganic fiber composition comprises not more than 0.80 wt.% of AI2O3 from incidental impurities and / or optional additives.

[0129] In one embodiment, the method produces the inorganic fiber composition of the first aspect of the disclosure.

[0130] Forming the molten mixture into inorganic fibers can comprise forming a strand of the molten mixture and quenching the molten mixture to solidify it.

[0131] In embodiments comprising the addition of additives, not more than 1.9 wt.% or not more than 1.8 wt.% or not more than 1.7 wt.% or not more than 1.6 wt.% or not more than 1.5 wt.% or not more than 1.4 wt.% or not more than 1.3 wt.% or not more than 1.2 wt.% or not more than 1.1 wt.% or not more than 1.0 wt.% or not more than 0.9 wt.% or not more than 0.8 wt.% of the metal oxides and / or metal non-oxides in the inorganic fiber composition are derived from said optional additives. The raw materials comprise the optional additives.

[0132] In one embodiment, the composition selection and the ratio selection of the raw materials are configured such that the amount of magnesium oxide in the inorganic fiber composition is sufficient to inhibit the formation of surface microcrystallites after heat treatment at 1100 °C for 24 hours, wherein the average microcrystallite size of said surface microcrystallites is 0.90 pm or less. The magnesium oxide content of the inorganic fiber composition can be at least 0.08 wt.% or at least 0.10 wt.%.

[0133] In some embodiments, the raw materials consist of silica sand and lime (i.e. no additives, but incidental impurities can be present). By limiting the number of raw materials, the carbon footprint of the method can be reduced. The lime is preferably selected such that the resulting fiber composition comprises MgO in the range of 0.10 to 2.0 wt.% and not more than 0.80 wt.% of AI2O3, or other alternatives as defined in the first aspect of the disclosure.

[0134] The composition selection and the ratio selection can be configured to obtain the inorganic fiber composition of the first aspect of the disclosure.

[0135] In one embodiment, the composition selection of the raw materials involves: doping an amount (e.g., up to 2.0 wt% or up to 3.0 wt%) of a selected incidental impurity into the raw materials to determine the shrinkage of the resulting inorganic fiber when exposed to 1300°C for 24 h; and using this information to determine a target composition selection range for the silica sand and lime. By determining the limit of the incidental impurity, a wider source of raw materials can be used without the need for additional chemical purification.

[0136] The composition of the silica sand and / or lime can be obtained by blending different batches of silica sand and / or lime to obtain a target composition. The target composition can be selected to control the shrinkage and / or microcrystalline grain size when the inorganic fiber is exposed to temperatures of 1100°C or greater.

[0137] The raw materials are preferably not chemically purified. Chemical purification includes chemical leaching or extraction techniques, but can not include water washing operations. Each raw material is preferably sourced from a natural deposit.

[0138] In one embodiment, the composition selection and ratio selection of the raw materials are configured to obtain a vacuum cast preform of inorganic fiber having a shrinkage of 6.0% or less (or 4.0% or less or 3.5% or less) when exposed to 1300°C for 24 h.

[0139] In one embodiment, the composition selection and ratio selection of the raw materials are configured to obtain an inorganic fiber content comprising at least 65.7 wt% silicon dioxide.

[0140] In some embodiments, the composition selection and ratio selection of the raw materials are configured such that the inorganic fiber comprises less than 2.0 wt% of incidental impurities or less than 1.5 wt% of incidental impurities, less than 1.0 wt% of incidental impurities or less than 0.8 wt% of incidental impurities or less than 0.6 wt% of incidental impurities. The selection of the fuel source can also be used to control the composition and ratio of the incidental impurities (e.g., coal ash levels).

[0141] In some embodiments, no more than 3.0 wt% or no more than 2.5 wt% or no more than 2.2 wt% or no more than 2.0 wt% or no more than 1.8 wt% or no more than 1.5 wt% or no more than 1.2 wt% of the inorganic fiber is derived from the sum of the incidental impurities and optional additives.

[0142] Preferably, the sum of the magnesium oxide and incidental impurities is greater than or equal to 0.3 wt% or greater than or equal to 0.4 wt%. The amount of magnesium oxide and incidental impurities is sufficient to reduce the melt viscosity of the composition and enable the formation of fibers as described in previous aspects of the disclosure.

[0143] In a fifth aspect of the disclosure, there is provided an inorganic fiber obtained or obtainable by the method according to the fourth aspect of the disclosure.

[0144] It should be understood that the use of the name of an oxide [e.g., alumina, silica, potassium] in the composition does not mean that the material is provided in this manner, but rather that the composition of the final fiber will express the relevant element as an oxide. The material in question can be provided in whole or in part as a mixed oxide, complexed with a temporary component [e.g., provided as a carbonate] or indeed as a non-oxide component [e.g., as a halide].

[0145] Incidental impurities are defined as impurities obtained from the raw materials, fuel sources, or other sources during the formation of the inorganic fiber. The material composition is determined on a dry weight basis. BRIEF DESCRIPTION OF DRAWINGS

[0146] Figure 1 SEM image of fiber of sample 24;

[0147] Figure 2 SEM image of fiber of prior art (sample 23);

[0148] Figure 3a and 3b SEM image of fiber of sample 19;

[0149] Figure 3c SEM image of fiber of sample 31;

[0150] Figure 3d SEM image of fiber of sample 29;

[0151] Figure 4a SEM image of fiber of sample 22;

[0152] Figure 4b SEM image of fiber of sample 20;

[0153] Figure 4c SEM image of fiber of sample 4;

[0154] Figure 4d SEM image of fiber of sample 36;

[0155] Figure 5a SEM image of fiber of sample 8;

[0156] Figure 5b SEM image of sample 26;

[0157] Figure 6 Schematic of a bake-hearth furnace seal system;

[0158] Figure 7 Schematic of a furnace having an inner lining of inorganic fiber of the present disclosure. DETAILED DESCRIPTION

[0159] The fibers according to the present disclosure and comparative fibers described herein were produced by spinning [made from melt by forming a molten stream and converting the stream into fibers by allowing the stream to contact one or more spin wheels] at the French production facility in Saint Marcellin, France; or by spinning or alternatively by blowing [fibers are made from melt by forming a molten stream and converting the stream into fibers by using a gas stream against the stream] at the applicant’s research facility in Bromborough, UK. The present disclosure is not limited to any particular method of forming fibers from melt and other methods [e.g., spin or centrifugal formation of fibers; drawing; air jet attenuation] can be used. The resulting fibers were then fed onto a conveyor belt and needled by a needle punch method as known in the art.

[0160] The raw materials used to produce the inorganic fibers of the preferred embodiments of the present disclosure are lime and silica sand. The chemical analysis (normalized) of the lime used is provided in Table 1 below. The incidental impurities (100 - CaO - SiO2) in the lime are typically less than 2.0 wt.%. The silica sand purity can be 98.5 wt.% or 99.0 wt.% or higher. Typically, the purity of the silica sand is greater than 99.5 wt.% silicon dioxide and less than 200 ppm Fe2O3; less than 1000 ppm Al2O3; less than 200 ppm TiO2, less than 100 ppm CaO and less than 100 ppm K2O.

[0161] Some of the compositions produced had high K2O levels due to the addition of fluxing agents in the experimental scale furnace in Bromborough, or due to cross-contamination from previous production in the Saint Marcellin furnace. Among these, samples P61-0481 and P61-0488 represent compositions produced only from raw materials silica sand and lime.

[0162] Table 1

[0163]

[0164] The fibers / blankets made therefrom were then evaluated using the test methods described:

[0165] Test Methods

[0166] The EN 1094-1-2008 standard was used for shrinkage, tensile strength and resilience tests.

[0167] Ball content

[0168] The shot content was determined by the jet sieve method as detailed in WO2017 / 121770, which is incorporated herein by reference.

[0169] Thermal stability (shrinkage)

[0170] The method for determining dimensional stability of refractory materials, including refractory glass fibre insulation materials, is based on EN ISO 10635. This method is a shrinkage test which measures the change in linear dimension of a flat sample after heat treatment.

[0171] The shrinkage test requires a relatively rigid sample so that the linear dimension can be accurately determined before and after heat treatment. In cases where needle punched fibre mat samples are not available, starch bonded vacuum formed plaques are prepared from glass fibre samples.

[0172] To prepare the vacuum formed plaques, the manufactured fibre material is shredded using a small industrial granulator and passed through a 6 mesh sieve (~3mm openings). The shredded fibre sample is lightly washed using a sieve to remove any debris and large glass residues. 40g of the shredded clean fibre is mixed in 500ml of a 5wt% concentration aqueous solution of potato starch to give a slurry. Subsequently, a 75x75mm plaque with a thickness of 10-15mm is produced using a vacuum former. The vacuum former consists of a sealed acrylic mould with a 100μm mesh on the bottom and a vacuum pump is used to remove the water from the slurry whilst the shape is manually compressed using a flat plate. The vacuum formed plaque is dried at 120°C.

[0173] To measure the permanent linear shrinkage, the linear dimension of the sample is measured using a travelling microscope with an accuracy of ±5μm. The sample is then placed in a furnace and ramped at a rate of 300°C / hour to a temperature 50°C below the test temperature (e.g. 1300°C) and then at a rate of 120°C / hour for the final 50°C until the test temperature and held for 24 hours. At the end of the heat treatment, the sample is allowed to cool naturally to room temperature. After heat treatment, the linear dimension of the sample is measured again using the same equipment to calculate the change in dimension. The shrinkage value is given as the average of 4 measurements.

[0174] Reactivity with mullite

[0175] In this test, needle punched fibre mat samples of approximately 50mm x 100mm in size are used. The mat sample is placed on a new mullite insulating firebrick (JM 28 IFB). The sample is heat treated at 1200°C for 24 hours with the IFB substrate to confirm reactivity after heat treatment. The sample and IFB are inspected for any signs of melting or reaction. Samples which do not react at all with the IFB are assessed as good (O). Samples which react with the IFB (sample adheres to the IFB or signs of melting are observed) are assessed as poor (X).

[0176] Biological solubility

[0177] The biologic solubility of fibrous materials can be estimated in systems in which the material is exposed to simulated body fluids in a flow-through apparatus (i.e., in vitro). This measure of solubility is defined as the rate of mass loss per unit surface area (Kdis). Although several attempts have been made to standardize this measurement, there is currently no international standard. Major protocol differences between laboratories include different simulated body fluid chemistries (and most notably different buffer and organic components), flow rates, mass and / or surface area of the sample, method of specific surface area determination, and determination of mass loss. Therefore, Kdis values should be considered as a relative estimate of chemical reactivity with simulated body fluids under the specific parameters tested, and not a measure of the absolute solubility of the fiber particles in the human lung. The flow dissolution test method used in this study was a 3-week dissolution test in pH 7.4 saline. Two passes of each unique sample were tested simultaneously. Samples of the saline solution flowing through the fibrous sample were taken after 1, 4, 7, 11, 14, 19, and 21 days. The saline samples were analyzed using ICP methods to measure the oxide dissolution levels in ppm levels. To validate the flow test results and calculate the final dissolution rate for each sample, the square root of the remaining fiber mass was plotted against the sampling time. Deviation from a linear trend can indicate problematic results. Good linear regression fits were observed in the flow test results conducted in this study. Based on historical data collected by the authors, a fiber typically needs a minimum of 150 ng / cm2 2 h dissolution rate to have exoneration potential. In the static dissolution test method, fibrous samples are agitated in a saline solution at 37°C to replicate conditions within the lung. The test monitors fiber dissolution after 24 hours using ICP methods. SiO2and CaO typically make up the majority of the dissolved material.

[0178] Rebound rate

[0179] Rebound test (EN 1094-1-2008) shows the ability of fibrous insulation products to rebound after being compressed to 50% of their original thickness. The samples for rebound testing in this article are in the form of needled blanket. The manufactured or heat treated blanket samples are cut into 100 mm x 100 mm squares and dried at 110°C ± 5°C for 12 hours to remove any absorbed moisture. The samples are then allowed to cool to room temperature and then immediately tested. Prior to the rebound test, the initial thickness of the blanket samples is measured using the pin and disk method. An Instron universal mechanical testing frame equipped with a 150 mm diameter flat platen is used for the rebound test. During the test, the sample is compressed at a rate of 2 mm / min to 50% of their original thickness and then the sample is held under compression for 5 minutes. Subsequently, the sample is allowed to rebound by lifting the compression platen until 725 Pa (for samples ≥ 96 kg / m 3 bulk density) or 350 Pa (for samples < 96 kg / m 3 bulk density) is recorded on the load cell and then held for another 5 minutes. After this test, the rebound value is calculated using the following formula:

[0180]

[0181] R = Rebound

[0182] d f = thickness after test

[0183] d0 = initial thickness

[0184] Tensile strength

[0185] The breaking strength of the blanket is determined by breaking the test piece at room temperature. The samples are cut using a template (230 ± 5 mm x 75 ± 2 mm). The samples are dried at 110°C to a constant mass, cooled to room temperature, then immediately measured and tested.

[0186] The width of the middle of the piece is measured using a steel ruler to the nearest 1 mm and the sample thickness is measured for each sample (both ends of the sample) using the EN 1094-1 needle method. A minimum of 4 samples are taken per test along the manufacturing direction.

[0187] The two ends of the sample are clamped by jaw grips comprising pairs of jaws having a gripping surface of at least 40 mm x 75 mm with a serrated gripping surface to prevent slippage during the test. These dimensions give an unclamped span of 150 ± 5 mm to test. The jaw grips are closed to 50% of the sample thickness (measured using a vernier caliper or ruler).

[0188] The jaws are installed in a tensile testing machine [e.g., an Instron 5582, 3365, or at least a machine with equivalent tensile strength testing functionality using a 1 kN load cell]. The crosshead speed of the tensile testing machine is constant at 100 mm / min throughout the test. Any measurements where the sample broke closer to the jaw face than the center of the sample are excluded.

[0189] The maximum load during the test is recorded to calculate the strength.

[0190] Tensile strength is given by the following equation:

[0191]

[0192] Where:

[0193] R(m) = Tensile strength (kPa)

[0194] F = Maximum force at break (N)

[0195] W = Initial width of the active part of the test piece (mm)

[0196] T = Initial thickness of the test piece (mm)

[0197] The results of the test are expressed as the average of these tensile strength measurements and the bulk density of the product.

[0198] Fiber diameter

[0199] Measurements of fibre diameter are made using a scanning electron microscope (SEM). SEM is a microanalysis technique used for high magnification observation of the microscopic details of materials. SEM uses a tungsten filament to generate an electron beam which is then rastered over a selected area of the sample and the signals generated by the sample are recorded by a detector and processed into an image display on a computer. A variety of detectors can be used to record the signals generated by the sample including secondary electron and backscattered electron detectors.

[0200] The specific SEM equipment used operates under vacuum and on electrically conductive samples. Therefore, all glass / ceramic samples need to be coated with gold or carbon prior to SEM analysis. An automated sputter coater is used to coat at approximately 20 nm. To prepare the fiber samples for diameter measurement, the fiber samples are crushed using a pneumatic press at 400 psi. The purpose of crushing is to ensure that the sample is crushed enough to disperse without affecting the fiber length, the crushing results in a length to diameter ratio of the fiber > 3:1. The crushed fiber samples are then coned and quartered to ensure representative sampling. The crushed and quartered fibers are dispersed in IPA. Typically, 50 pg of fiber is placed in a 50 mL centrifuge tube and 25 mL of IPA is added. The SEM sample stage is then placed in the center of a petri dish, the centrifuge tube is then shaken vigorously and poured into the petri dish containing the SEM sample stage. The petri dish is left to sit in a fume hood for 1 hour to allow the fibers to settle on the SEM sample stage. The SEM sample stage is then carefully coated with gold in preparation for SEM imaging.

[0201] Following this sample preparation step, the SEM sample stage is imaged at 1500x magnification using the automated software on the SEM equipment to capture 350 unique secondary electron images. Following the image capture step, the images are processed by the System to measure the fiber diameter. This process involves a manual check of the fibers measured in each image to ensure that only fiber particles with a length to diameter ratio greater than 3:1 are measured. The final fiber diameter distribution along with the number average / arithmetic average diameter is plotted.

[0202] Microcrystalline grain size

[0203] Scanning Electron Microscopy (SEM) is used to make microcrystallite size measurements on heat treated fiber materials. SEM is a microanalysis technique for high magnification observation of the microscopic details of materials. SEM uses a tungsten filament to generate an electron beam that is then raster scanned over a selected area of the sample and the signals generated by the sample are recorded by a detector and processed into an image display on a computer. A variety of detectors can be used to record the signals generated by the sample, including secondary electron and backscattered electron detectors.

[0204] The specific SEM equipment used operates under vacuum and on electrically conductive samples. Therefore, all glass / ceramic samples need to be coated with gold or carbon prior to SEM analysis. An automated sputter coater is used to coat at approximately 20 nm. To prepare the fiber samples for diameter measurement, the fiber samples are crushed using a pneumatic press at 400 psi. The purpose of crushing is to ensure that the sample is crushed enough to disperse without affecting the fiber length, the crushing results in a length to diameter ratio of the fiber > 3:1. The crushed fiber samples are then coned and quartered to ensure representative sampling. The crushed and quartered fibers are dispersed in IPA. Typically, 50 pg of fiber is placed in a 50 mL centrifuge tube and 25 mL of IPA is added. The SEM sample stage is then placed in the center of a petri dish, the centrifuge tube is then shaken vigorously and poured into the petri dish containing the SEM sample stage. The petri dish is left to sit in a fume hood for 1 hour to allow the fibers to settle on the SEM sample stage. The SEM sample stage is then carefully coated with gold in preparation for SEM imaging.

[0205] Following this sample preparation step, several unique secondary electron images of the SEM sample stage are acquired using a SEM device at an appropriate magnification (typically in the range of 5000-10000x) based on morphology. After the image acquisition step, these images are then processed using computer software programs (Olympus). Images are processed to measure grain size by drawing circles around visible grain boundaries in several SEM images. This process involves manually inspecting the fibers in each image to ensure that only fibers are in focus. The final grain size report is the numerical average of all measurements (preferably measurements from at least 10 representative crystals). Preferably, the crystallite size is determined by randomly selecting at least five fibers, from which measurements of the crystallite size of five representative grains are obtained. Fiber measurements that differ from the average by more than two standard deviations should be ignored. Due to limitations in SEM image magnification and resolution, the minimum measurable grain size is approximately 0.4 μm. Samples with even smaller crystallite sizes are reported as having an average grain size value < 0.4 μm.

[0206] Microcrystals differ from other surface defects in the regularity of their frequency and shape; their defining characteristic is that they protrude from the fiber surface, such as... Figures 4a to 4d The increased grain size indicates that surface defects include the formation of irregularly shaped small plates, such as... Figure 3b and 3d As shown.

[0207] Melting temperature

[0208] The melting temperature of the fiber was determined by DSC (10 kJ / min, temperature increased from 30 °C to 1500 °C). The melting temperature of sample 26b (50 mg of fine powder from fiber grinding) was 1435.3 °C.

[0209] Fiber composition

[0210] The fiber composition was determined using standard XRF methods. After analysis of SiO2, CaO, K2O, Al2O3, MgO, and the oxide components listed in Table 6, the results were normalized. Unnormalized results were discarded if the total weight of the composition exceeded the range of 98.0% to 102.0% by weight.

[0211] Effect of impurities

[0212] To assess the effect of incidental impurities in the raw materials, an ultrapure sample (C-24) was produced using silica (Si02: 99.951 wt%, AI2O3: 0.038 wt%, Fe203: 0.012 wt%) and calcium oxide (CaO: 99.935 wt%, Si02: 0.011 wt%, AI2O3: 0.012 wt%, Fe203: 0.011 wt%, SrO: 0.031 wt%). The remaining components were all less than the XRF detection limit (<0.01 wt%).

[0213] To assess the effect of impurities, additional amounts of AI2O3, MgO, Ti02, and Zr02were added to the existing incidental impurities. As shown in Table 4a, increasing amounts of MgO, Ti02, and AI2O3resulted in decreased thermal stability at 1300°C (24h) as measured by percent shrinkage. Example 34 is an approximate repeat of sample E-174 of US 5,332,699.

[0214] Table 2

[0215] Sample SiO2 CaO Al2O3 K2O MgO CaO + SiO2 <!-- 14 -->]] C-1 72.8 24.9 1.1 0.6 0.6 97.7 C-2 71.2 28.1 0.33 0.06 0.17 99.3 1 70.7 28.8 0.26 0.03 0.13 99.5 2 70.6 28.9 0.28 0.04 0.16 99.5 3 70.6 28.5 0.55 0.12 0.19 99.1 4 70.5 28.4 0.69 0.18 0.23 98.9 5 70.3 29.1 0.36 0.05 0.17 99.4 6 69.5 30.0 0.27 0.04 0.15 99.5 7 69.4 30.1 0.32 0.03 0.15 99.5 8 67.7 31.9 0.25 0.03 0.15 99.6 9 67.1 32.4 0.28 0.02 0.15 99.5 10 66.0 33.1 0.60 0.04 0.18 99.1 11 65.7 33.8 0.22 0.03 0.15 99.5 12 65.6 34.0 0.27 0.02 0.15 99.6 13 65.3 34.2 0.23 0.03 0.16 99.5 14 65.0 34.5 0.35 0.02 0.17 99.5 15 64.5 35.1 0.19 0.06 0.16 99.6 16 63.3 36.1 0.22 0.10 0.29 99.4 17 62.8 36.7 0.23 0.07 0.16 99.5 18 61.5 38.0 0.21 0.09 0.16 99.5 19 67.2 32.3 0.07 0.02 0.23 99.5 20 69.0 30.2 0.49 0.03 0.23 99.2 21 66.0 33.5 0.18 0.02 0.32 99.5 22 66.3 33.2 0.19 0.01 0.26 99.5 C-23 66.3 33.2 - 0.004 0.03 99.5 C-24 65.8 34.2 0.02 0.0 0.0 100.0 25 63.3 36.1 0.22 0.10 0.29 99.4 26 68.0 31.3 0.18 0.27 0.21 99.3 26b 67.1 32.4 0.23 0.10 0.15 99.5 P61-0488 66.2 33.3 0.15 0.01 0.26 99.5 P61-0481 65.9 33.5 0.15 0.01 0.39 99.4 C-3 60.7 38.9 0.26 0.07 0.17 99.6 C-4 64.9 29.8 0.15 0.01 5.2 94.7 C-5 60.7 38.8 0.23 0.12 0.17 99.5

[0216] Results

[0217] Referring to Tables 2 and 3, the compositions of the inorganic fibers in weight percent of the total composition are shown for Examples 1-26b, P61-0481, P61-0488, and Comparative Examples C1-C5, C-27, C-34-C-36. As shown in Table 3, inorganic fiber compositions with silica levels below 65.7 wt% were found to be incompatible with mullite-based bricks, adhering to the bricks after 24h at 1200°C. Inorganic fiber compositions with higher silica levels generally had higher globule contents and higher fiber diameters. The results for sample P50 indicate that Zr02may be able to partially replace Si02in the glassy network-forming species, and the samples with low Si02content were also compatible with mullite-based bricks. Incorporation of a small fraction (e.g., up to 2.0 wt% or up to 1.5 wt%) of Zr02within the glassy network can maintain the non-reactive nature of the composition to mullite-based bricks or other alumina-based compositions.

[0218] Table 3

[0219]

[0220] Shrinkage at 1300°C for 24 hours

[0221] The lowest shrinkage (best high temperature performance) was observed in samples 32 and 33. Sample 33 is the control sample without additives, while sample 32 has a slightly higher MgO level, but in both samples the sum of SiO2and CaO is greater than 99.0 wt.%. Sample 32 appears to be an anomaly in the correlation between shrinkage and magnesium oxide content for samples 30 through 33. Likewise, example 37 is also considered a questionable result, as shrinkage results below 4% were expected. The results indicate, in general, that higher CaO + SiO2levels correspond to improved high temperature stability of the fiber composition as measured by the shrinkage test.

[0222] Surface crystallite size

[0223] The ultra-pure raw materials were difficult to form into fibers, and when fibers were formed, the yield was low and the fiber diameter was large (e.g., > 500 μm). As shown in Figure 1 the fiber surface contained average crystallite sizes of approximately 5 μm, and cracks were also observed. The general presence of surface crystallites was also noted on prior art high purity samples (sample C-23) with average crystallite sizes of approximately 1 μm. Figure 2

[0224] Table 4a

[0225]

[0226] As shown in Table 4a, higher CaO + SiO2sums tend to correspond to higher high temperature performance and bioresorbability. Table 4b further discloses a correlation between high temperature performance and MgO content, with lower MgO content associated with lower shrinkage of the fiber at 1300°C.

[0227] Static solubility

[0228] As shown in Table 4a, increasing amounts of ZrO2(see samples C-32, P40 and C-P50) resulted in decreased bioresorbability of the fiber.

[0229] Table 4b

[0230]

[0231] The effect of adding MgO is shown in Figures 3a to 3d samples 19 Figure 3a and Figure 3b and sample 31 (Figure 4) represent compositions in which MgO is the predominant minor oxide component. Figure 3b and Figure 3d Examples of surface defects are also shown, including surface platelets, which are associated with Figure 2 ​The regularity and form of the crystallites varied. The results indicate that up to at least 4.3 wt% MgO can inhibit crystallite growth at 1100°C, but increasing levels of MgO also resulted in increased fiber shrinkage, with more than 2 wt% MgO content less suitable for continuous use applications at 1200°C or above (Table 5). The effect of increasing Al2O3 levels is shown in Table 5. Figures 4a to 4d where the average crystallite size was about 1 μm was obtained with 1.04 wt% Al2O3 (sample 36) and 98.6 wt% CaO + SiO2. The effect of K2O content is shown in Table 5. Figure 5a (sample 8) and Figure 5b (sample 26), increasing K2O content from 0.03 wt% (sample 8) to 0.27 wt% (sample 26) corresponded to a slight increase in crystallite size from less than the detection limit (<0.4 μm) to 0.54 μm. However, samples P42 and P47 indicate that increasing K2O levels to about 0.5 wt% can still result in low crystallite size (<0.4 μm) for their composition matrix.

[0232] Adding 0.66 wt% TiO2and 0.89 wt% MgO (P41) resulted in poor shrinkage performance at 1300°C, with the TiO2component appearing to contribute most to this result. The MgO content of P40 was similar to P41, but ZrO2had less effect on shrinkage performance at 1300°C than TiO2. While the effect of an additive / impurity or combination thereof can be specific to the additive / impurity, by testing the sensitivity of the additive / impurity, inorganic fiber compositions can be readily configured to achieve desired high temperature performance in terms of shrinkage and / or crystallite size.

[0233] Table 5

[0234]

[0235] The results confirm that too little or too much of a secondary component in the composition can result in increased crystallite size, which is associated with deterioration in high temperature mechanical properties. In particular, MgO has been shown to inhibit crystallite growth, while Al2O3 has been shown to promote crystallite growth. In addition to the major incidental impurities Al2O3, MgO and K2O, XRF analysis also measured the metal oxides listed in Table 6. The maximum and minimum incidental impurity levels are provided for each metal oxide. Typically, these secondary incidental impurities are less than 0.3 wt% or less than 0.25 wt% or less than 0.20 wt%; and at least 0.10 wt%.

[0236] The skilled artisan can readily determine the level of a particular group or particular other component that promotes microcrystal growth without undue experimentation. When other components that are detrimental to microcrystal growth, i.e., impurities, and thus control high temperature performance are to be kept at specified levels, raw materials having a variety of other component profiles can be used.

[0237] Thus, the inorganic fiber composition can be configured to obtain formation of surface microcrystalline grains having an average microcrystal size of 0.90 pm or less after heat treatment at 1100 °C for 24 hours.

[0238] Table 6

[0239] Impurities Maximum level (% weight) Minimum level (% weight) BaO 0.01 0.00 <![CDATA[Cr2O3]]> 0.02 0.00 Fe2O3 0.13 0.08 [HfO2] 0.00 0.00 La2O3 0.07 0.00 Mn304 0.00 0.00 Na2O 0.03 0.00 P2O5 0.00 0.00 SrO 0.03 0.00 TiO2 0.03 0.00 [V2O5] 0.01 0.00 <![CDATA[SnO2]]> 0.01 0.00 ZnO 0.00 0.00 ZrO2 0.03 0.00

[0240] Thermal conductivity of inorganic fiber body

[0241] The thermal conductivity of a melt-formed fiber body, such as a blanket or other product form, is determined by a number of factors, including, among others:

[0242] • fiber diameter; and

[0243] • "slug" (non-fiberized material) content

[0244] Fine diameter fibers provide a low thermal conductivity to a fiber body by reducing the conduction range through the solid and allowing for a finer inter-fiber porosity to increase the number of radiation absorption steps for heat to pass through radiation from one side of the body to the other.

[0245] The presence of slugs in a blanket increases the thermal conductivity of the blanket by increasing the conduction range through the solid. Slugs also increase the density of the blanket. All else being equal, the lower the slug content, the lower the thermal conductivity and density. For two bodies of the same fiber content and chemistry, the body with the lower slug content has a lower density and lower thermal conductivity.

[0246] Referring to Table 7, the fiber diameter of the inorganic fibers produced was approximately between 2.6 and 3.0 pm and the slug content was between 32 and 41 wt.%. From the data sets provided in Tables 7 and 8, although there is no clear correlation between fiber characteristics and thermal conductivity, the lowest thermal conductivity samples P61-0481 and P61-0488 were obtained from commercial production lines with lower slug levels and the fiber diameter was expected to be more consistent with about 3 pm diameter. As shown in Table 3, due to the high slug content and fiber diameter associated with these compositions, blankets derived from inorganic fibers with high Si02content were expected to have high thermal conductivities. As can be seen, the resilience of the inorganic fibers (Table 7) generally increased with increasing Si02amount.

[0247] Sample P61-0488 was produced at the Saint Marcellin site using commercial scale melt spinning technology, with production conditions optimized to reduce the level of dross that impacts the insulating properties of the fiber. The inorganic fiber can be formed into a needled mat. The produced mat has a density of at least 64 kg / m 3 , with standard commercial densities that can be produced, such as 64 kg / m 3 , 96 kg / m 3 , 128 kg / m 3 , 160 kg / m 3 . The inorganic fiber can also be formed into high density modules of up to 240 kg / m 3 . Table 9 illustrates the improvement in insulating properties of a 128 kg / m 3 mat compared to a mat produced from Comparative Example C-1. The disclosed composition of the present disclosure is able to form a low fiber diameter and has a low dross content, contributing to excellent high temperature thermal insulation properties.

[0248] Table 7

[0249]

[0250] Table 8

[0251]

[0252] Heat flow test (ASTM C680-19 heat flow)

[0253] The insulating properties of a 128 kg / m 3 200 mm thick mat made from the composition of samples P61-0488 and C-1, respectively, were determined. A heat source was applied to one side of the mat (hot face). The opposite side of the mat (cold face) was initially maintained at an ambient temperature of 27°C, without wind. After the hot face was heated to 1000°C, the opposite side of the mat (cold face) is reported in Table 9. The results indicate that the composition of the present disclosure achieved a 15% reduction in heat loss.

[0254] Table 9

[0255]

[0256] Biological solubility

[0257] Referring now to Table 10, the data from the biosolubility test are shown. The compositions shown in Table 10 underwent 21-day static solubility and long-term flow solubility tests in saline solution at pH 7.4. Two samples of each fiber composition were tested simultaneously, and the average results are reported. The saline samples were analyzed using ICP to measure the oxide dissolution level in ppm. The results confirmed that the fibers have very low biosolubility. Low biosolubility fiber compositions are considered to be those with a dissolution rate of at least 150 ng / cm³ in the flow solubility test. 2 h or at least 170 ng / cm 2 h or at least 200ng / cm 2 h.

[0258] Compared to prior art fiber compositions C1 and C2, the inorganic fibers of this disclosure have comparable or improved biosolubility. As indicated by specific surface area measurements, the fine fiber size contributes to the increased biosolubility.

[0259] Summary of results

[0260] The above results highlight that the fiber compositions of this disclosure can produce highly effective refractory fibers without the need for the deliberate addition of large amounts of additives to enhance one or more fiber properties. This unexpected result also allows refractory fibers to be produced with a lower carbon footprint because the amount of raw materials required for their production is reduced.

[0261] Table 10

[0262]

[0263] Insulation or sealing system

[0264] In some embodiments, the fibers of this disclosure can be used as insulation and / or sealing systems in kilns, ovens, heating furnaces, or other high-temperature environments. The insulation or sealing system may comprise a layer of alumina-rich material (such as mullite or refractory brick) and a layer of inorganic fibers (such as a blanket). The insulation system can be used in kilns for the following:

[0265] • Production of glass and ceramic products;

[0266] • Chemical and petrochemical processes;

[0267] Iron and steel production and conversion facilities; and

[0268] Non-ferrous metal production and conversion facilities

[0269] Fibers can also be used as insulation for heat shields and contamination devices such as catalytic converters, where the non-reactive nature of the fibers is advantageous.

[0270] refer toFigure 6 Figure 1 illustrates a sealing system from a carbon bake oven section, including a flue wall 100 and a head wall 110. A refractory mastic including the inorganic fiber of the present disclosure is used as a corner seal 120 to prevent coke from the bake pit (not shown) from entering a vertical expansion joint 130. In some embodiments, the corner seal can also include an inorganic fiber blanket of the present disclosure. The flue wall 100 and head wall 110 in contact with the inorganic fiber-based refractory mastic and blanket (when present) are made of hot face refractory brick having an alumina content ranging from at least 42 wt% alumina to at least 58 wt% alumina. The sealing system including the inorganic fiber of the present disclosure having a silica content greater than 65.7 wt% is particularly advantageous in this application due to the non-reactivity of the fiber with alumina and the low shrinkage characteristics of the fiber at high temperatures.

[0271] An example of a furnace insulation system is shown in Figure 7 where an insulation lining material 200 is attached to the interior surface of a furnace wall 210. The insulation material in use has a hot face 220 (facing the interior side of the furnace) and a cold face 230 (in contact with the furnace wall 210), which is made of refractory brick containing alumina. The insulation lining material includes inorganic fiber in the form of a blanket, folded blanket modules, or high density (such as up to 240 kg / m 3 ) modules (such as Pyro-Stack TM or Pyro- modules available from Morgan Advanced Materials).

[0272] Other potential uses

[0273] The fibers of the present disclosure can be used for any purpose for which fibrous inorganic materials (and in particular, alkaline earth silicate and alumino-silicate materials) have heretofore been used; and for future applications for which fibrous properties are suitable, subject to meeting relevant performance standards. The fibers of the present disclosure, and products derived therefrom, can be used for applications for which commercially available products are currently used, including but not limited to KNAUF INSULATION HT, KNAUF INSULATION TM XTRA KNAUF INSULATION INSULFRAX 1260, INSULFRAX 1300, INSULFRAX 1400, KNAUF INSULATION TM LTX TM FINEFLEX BIO TM , KCC CERAKWOOL New-BioTM 1300, MINYE

[0274] In the following reference is made to a number of patent documents relating to applications in which fibres can be used, provided that the relevant performance criteria for the application are met. The fibres of the present disclosure can be used to replace the fibres specified in any of these applications, provided that the relevant performance criteria are met. For example, these fibres can be used as:

[0275] • bulk materials;

[0276] • deshotted materials [WO2013 / 094113];

[0277] • in mastic or malleable compositions [WO2013 / 080455, WO2013 / 080456] or as part of a wet product [WO2012 / 132271];

[0278] • as components of needle-punched or other entangled assemblies of materials, for example in the form of a mat, a folded mat module or a high density fibre block [WO2013 / 046052];

[0279] • as components of non-needle-punched assemblies of materials, for example a felt, a vacuum-formed shape [WO2012 / 132469] or paper [WO2008 / 136875, WO2011 / 040968, WO2012 / 132329, WO2012 / 132327];

[0280] • as components of boards, bricks and more complex shapes (with fillers and / or binders) [WO2007 / 143067, WO2012 / 049858, WO2011 / 083695, WO2011 / 083696];

[0281] • as reinforcing components in composite materials (for example like fibre-reinforced cement, fibre-reinforced plastics) and as components of metal matrix composites;

[0282] • support structures for fuel cells [WO2020047036] or catalyst bodies in pollution control devices (for example automotive exhaust system catalytic converters and diesel particulate filters) [WO2013 / 015083] which include support structures comprising:

[0283] • edge protectors [WO2010 / 024920, WO2012 / 021270];

[0284] o Microcellular materials [WO2009 / 032147, WO2011019394, WO2011 / 019396];

[0285] o Organic binders and antioxidants [WO2009 / 032191];

[0286] o Intumescent materials [WO2009 / 032191];

[0287] o Nanofibrillated fibers [WO2012 / 021817];

[0288] o Microspheres [WO2011 / 084558];

[0289] o Colloidal materials [WO2006 / 004974, WO2011 / 037617];

[0290] o Layers of oriented fibers [WO2011 / 084475];

[0291] o Sections with different basis weight [WO2011 / 019377];

[0292] o Layers comprising different fibers [WO2012065052];

[0293] o Coated fibers [WO2010122337];

[0294] o Mats cut at specific angles [WO2011067598];

[0295] [Note that all the above features can be used for applications other than support structures for catalytic bodies]

[0296] • As components of catalyst bodies [WO2010 / 074711];

[0297] • As components of friction materials [e.g. for automotive brakes [JP56-16578]];

[0298] • As components in insulation, fireproofing or thermal runaway prevention materials in energy storage devices;

[0299] • For fire protection [WO2011 / 060421, WO2011 / 060259, WO2012 / 068427, WO2012 / 148468, WO2012 / 148469, WO2013074968];

[0300] • For example, as insulation;

[0301] o As insulation for ethylene cracking furnaces [WO2009 / 126593], hydrogen reforming equipment [US4690690];

[0302] o as insulation in heating furnaces for the heat treatment of metals, including iron and steel [US4504957];

[0303] o as insulation in equipment for the manufacture of ceramics.

[0304] The fibres can also be used in combination with other materials. For example, the fibres can be used in combination with polycrystalline (sol-gel) fibres [WO2012 / 065052] or with other bio-soluble fibres [WO2011 / 037634].

[0305] The bodies comprising the fibres can also be used in combination with bodies formed from other materials. For example, in insulation applications, a layer of material according to the present disclosure [e.g. a blanket or board] can be secured to an insulation layer [e.g. a blanket or board of alkaline earth silicate fibres] having a lower maximum continuous use temperature [WO2010 / 120380, WO2011133778]. Securing the layers together can be achieved by any known mechanism, for example anchoring the blanket within the blanket [US4578918], or passing ceramic screws through the blanket [see for example DE3427918-A1].

[0306] Treatment of fibers

[0307] During or after the formation of the fibres, they can be treated by applying materials to the fibres. For example:

[0308] • lubricants can be applied to the fibres to aid needling or other processing of the fibres;

[0309] • coatings can be applied to the fibres to act as a binder;

[0310] • coatings can be applied to the fibres to provide reinforcement or other effects, for example phosphates [WO2007 / 005836] metal oxides [WO2011159914] and colloidal materials such as alumina, silica and zirconia [WO2006 / 004974];

[0311] • binders can be applied to the fibres to bind the fibres together after incorporation into a body comprising such fibres.

[0312] Many variations, product forms, uses and applications of the fibres of the present disclosure will be apparent to those skilled in the art and are intended to be covered by the present disclosure.

[0313] By providing bio-soluble fibres having a maximum continuous use temperature higher than alkaline earth silicate fibres, the present disclosure extends the range of applications in which bio-soluble fibres can be used. This reduces the need for the use of non-bio-soluble fibres in many applications currently.

[0314] For the avoidance of doubt, it is noted that in this specification the term "comprising" in relation to a composition is to be taken to mean including, containing or encompassing, and to permit the presence of other components. The terms "comprises" and "comprising" are to be construed in the same manner. It is also to be noted that there is no composition claimed which has a total of components which exceeds 100%.

[0315] Where reference is made in this text to a patent or other document, the content of the referenced document is incorporated herein by reference to the extent permitted by law.

[0316] It is to be understood that the use of the term oxide in relation to a component in a composition does not mean that the material is provided in this form, but rather that the composition of the final fibre will express the relevant element as an oxide. The relevant material can be provided wholly or in part as a mixed oxide, mixed with a transient component (such as provided as a carbonate) or provided as a non-oxide component.

[0317] The term metal oxide and / or non-oxide includes all forms of the metal, including phosphates, sulphates, halides or sulphides.

Claims

1. Inorganic fibers comprising the following composition: 61.0 to 70.8% by weight of SiO2; 28.5 to 38.9% by weight of CaO; 0.10 to 2.0 wt% MgO; and A certain amount of other components, which provide the balance up to 100% by weight. The total content of SiO2 and CaO is greater than or equal to 98.2% by weight, and the certain amount of other components contains no more than 0.60% by weight of Al2O3. The other components are configured to inhibit the formation of surface microcrystals after heat treatment at 1100°C for 24 hours, wherein the average crystallite size of the surface microcrystals ranges from 0.0 to 0.90 μm.

2. The inorganic fiber according to claim 1, wherein the amount of MgO is configured to suppress the formation of surface microcrystals after heat treatment at 1100°C for 24 hours, wherein the average crystallite size of the surface microcrystals ranges from 0.0 to 0.90 μm.

3. The inorganic fiber according to claim 1 or 2, wherein the amount of other components is configured to inhibit the formation of surface microcrystals after heat treatment at 1100°C for 24 hours, wherein the average crystallite size of the surface microcrystals ranges from 0.0 to 0.60 μm.

4. The inorganic fiber according to claim 1 or 2, wherein the amount of SiO2 present is configured to suppress the reactivity of the inorganic fiber such that the inorganic fiber does not react with mullite when contacted at 1200°C for 24 h.

5. The inorganic fiber according to claim 1 or 2, wherein the sum of SiO2 and CaO is greater than or equal to 98.4% by weight.

6. The inorganic fiber according to claim 1 or 2, wherein the sum of SiO2 and CaO is greater than or equal to 98.6% by weight.

7. The inorganic fiber according to claim 1 or 2, wherein the composition comprises less than 1.0% by weight of MgO.

8. The inorganic fiber according to claim 1 or 2, wherein the composition comprises less than 0.90% by weight of MgO.

9. The inorganic fiber according to claim 1 or 2, wherein the composition comprises less than 0.85% by weight of MgO.

10. The inorganic fiber according to claim 1 or 2, wherein the other components comprise no more than 0.4% by weight of alkali metal oxides.

11. The inorganic fiber according to claim 1 or 2, wherein the other component comprises no more than 0.35% by weight of alkali metal oxide.

12. The inorganic fiber according to claim 1, wherein the other components comprise no more than 0.20% by weight of alkali metal oxides.

13. The inorganic fiber according to claim 1 or 2, wherein the other component accounts for at least 0.3% by weight of the composition of the inorganic fiber.

14. The inorganic fiber according to claim 1 or 2, wherein the total content of BaO, Cr2O3, Fe2O3, HfO2, La2O3, Mn3O4, Na2O, K2O, P2O5, SrO, SnO2, TiO2, V2O5, ZrO2 and ZnO in the other components is 0.1 to 1.4 by weight.

15. The inorganic fiber according to claim 1 or 2, wherein the total content of BaO, Cr2O3, Fe2O3, HfO2, La2O3, Mn3O4, Na2O, K2O, P2O5, SrO, SnO2, TiO2, V2O5, ZrO2 and ZnO in the other components is 0.1 to 1.2 by weight.

16. The inorganic fiber according to claim 1 or 2, wherein the total content of BaO, Cr2O3, Fe2O3, HfO2, La2O3, Mn3O4, Na2O, K2O, P2O5, SrO, SnO2, TiO2, V2O5, ZrO2 and ZnO in the other components is 0.1 to 1.0 by weight.

17. The inorganic fiber according to claim 1 or 2, wherein the total content of BaO, Cr2O3, Fe2O3, HfO2, La2O3, Mn3O4, Na2O, K2O, P2O5, SrO, SnO2, TiO2, V2O5, ZrO2 and ZnO in the other components is 0.1 to 0.8% by weight.

18. The inorganic fiber according to claim 1 or 2, wherein the other component accounts for no more than 1.2% by weight of the inorganic fiber.

19. The inorganic fiber according to claim 1 or 2, wherein the sum of SiO2, CaO and MgO is greater than or equal to 98.5% by weight.

20. The inorganic fiber according to claim 1 or 2, wherein the sum of SiO2, CaO and MgO is greater than or equal to 99.0% by weight.

21. The inorganic fiber according to claim 1 or 2, wherein the sum of SiO2, CaO and MgO is greater than or equal to 99.3% by weight.

22. The inorganic fiber according to claim 1 or 2, wherein the average arithmetic fiber diameter of the inorganic fiber is less than 4.0 µm.

23. The inorganic fiber according to claim 1 or 2, wherein the content of slag balls larger than 45 µm in the inorganic fiber is in the range of 0 to 41% by weight.

24. The inorganic fiber according to claim 1 or 2, wherein the amounts of MgO and other components are configured to obtain a vacuum-cast preform of the inorganic fiber, which has a shrinkage rate of 3.5% or less when exposed at 1300°C for 24 h.

25. The inorganic fiber according to claim 1 or 2, wherein, in a flow solubility test at pH 7.4, the dissolution rate of the inorganic fiber is at least 150 ng / cm³. 2 h.

26. The inorganic fiber according to claim 1 or 2, wherein the total amount of SiO2 and optionally ZrO2 in the composition is 65.7% by weight or more.

27. The inorganic fiber according to claim 1 or 2, wherein the inorganic fiber does not react when contacted with mullite at 1200°C for 24 h.

28. An insulation system comprising: a. Refractory components, including contact surfaces; and b. An insulating lining comprising the inorganic fibers according to claim 26 or 27, The insulating lining is disposed against the contact surface.

29. The insulation system of claim 28, wherein the refractory component comprises mullite.

30. The insulation system of claim 28 or 29, wherein the refractory component comprises at least 20% by weight of alumina.

31. The insulation system of claim 30, wherein the refractory component comprises at least 40% by weight of alumina.

32. The insulation system according to claim 28 or 29, wherein the refractory component comprises refractory mortar, refractory putty, refractory cement, refractory board, refractory fiber or refractory brick.

33. A sealing system comprising: a. Refractory components, including contact surfaces; and b. A sealing material comprising the inorganic fibers according to claim 26 or 27, The sealing material is disposed against the contact surface.

34. The sealing system of claim 33, wherein the refractory component comprises mullite.

35. The sealing system according to claim 33 or 34, wherein the refractory component comprises at least 20% by weight of alumina.

36. The sealing system of claim 35, wherein the refractory component comprises at least 40% by weight of alumina.

37. The sealing system according to claim 33 or 34, wherein the refractory component comprises refractory mortar, refractory putty, refractory cement, refractory board, refractory fiber or refractory brick.

38. An oven comprising an insulation system according to any one of claims 28 to 32 or a sealing system according to any one of claims 33 to 37.

39. A kiln comprising an insulation system according to any one of claims 28 to 32 or a sealing system according to any one of claims 33 to 37.

40. An insulating blanket comprising inorganic fibers according to any one of claims 1 to 27.

41. The insulating blanket of claim 40, wherein the inorganic fibers are configured for continuous use at temperatures up to 1300°C, and the blanket has a density of 64 kg / m³. 3 Or larger.

42. The insulating blanket according to claim 40 or 41, wherein the density is 128 kg / m³. 3 The thermal conductivity of the blanket at 1200℃ is no more than 0.32 W / mK.

43. The insulating blanket according to claim 40 or 41, wherein the density is 128 kg / m³. 3 The strength of the blanket is at least 60 kPa.

44. The insulating blanket according to claim 40 or 41, wherein the resilience value measured at 1150°C for 24 h is at least 63% by weight.

45. A method for manufacturing inorganic fibers, comprising: a. Select the composition and proportion of each of the following raw materials: i. Silica sand and ii. Lime, wherein the lime comprises at least 0.10% by weight of magnesium oxide; and iii. Optional additives b. Mix the silica sand, lime, and optional additives to form a mixture; c. Melt the mixture in a heating furnace; d. Shape the molten mixture into inorganic fibers. The selection of raw materials includes the selection of the composition and proportion of silica sand and lime to obtain an inorganic fiber composition comprising, in the range of 61.0 wt% to 70.8 wt% silica; 28.5 wt% to 38.9 wt% calcium oxide; less than 2.0 wt% magnesium oxide; incidental impurities; and no more than 2.0 wt% metal oxides and / or non-metal oxides derived from the optional additives, wherein the total of silica and calcium oxide is greater than or equal to 98.2 wt%, and wherein the inorganic fiber composition comprises no more than 0.60 wt% Al2O3 derived from incidental impurities and / or optional additives. The composition and proportion of the raw materials are configured such that the amount of magnesium oxide in the fiber composition is sufficient to suppress the formation of surface microcrystals after heat treatment at 1100°C for 24 hours, wherein the average crystallite size of the surface microcrystals is in the range of 0.0 to 0.90 µm.

46. ​​The method of claim 45, wherein the amount of magnesium oxide in the inorganic fiber composition is at least 0.10% by weight.

47. The method according to claim 45 or 46, wherein the inorganic fiber composition comprises no more than 1.5% by weight of metal oxides and / or metal nonoxides derived from the optional additives.

48. The method according to claim 45 or 46, wherein the composition and proportion selection of the raw materials are configured to obtain a vacuum-cast preform of the inorganic fibers, which has a shrinkage rate of 3.5% or less when exposed at 1300°C for 24 h.

49. The method of claim 45 or 46, wherein the selection of the composition of the raw material involves: doping the raw material with a selected amount of incidental impurities to determine the shrinkage value of the resulting inorganic fibers after exposure at 1300°C for 24 h; and using the shrinkage value to determine a target range of compositional selection for the silica sand and lime.

50. The method of claim 49, wherein the target composition is selected to control the shrinkage rate and / or microcrystal size when the inorganic fiber is exposed to a temperature of 1100°C or higher.

51. The method according to claim 45 or 46, wherein the composition and proportion selection of the raw materials are configured to produce inorganic fibers according to any one of claims 1 to 27.

52. Inorganic fibers obtained by the method according to any one of claims 45 to 51.

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