Inorganic fibre mats

Abstract

A fibre mat, for example a monolith support mat or end cone insulator, the mat comprising inorganic fibres having a pressure retained value at 10 minutes at 900 C. of greater than 20 kPa; and preferably a binder. The inorganic fibres comprise X and Y and K.sub.2O, the sum of which is greater than 95 wt. % wherein X is the sum of SiO.sub.2 and ZrO.sub.2 and Y is the sum of Al.sub.2O.sub.3 and La.sub.2O.sub.3, wherein ZrO.sub.2 and La.sub.2O.sub.3 is each present in up to 10 wt. % of the total weight of the inorganic fibres.

Claims

1. A fibre mat for a monolith support mat or end cone insulator, the mat comprising: inorganic fibres having a pressure retained value at 10 minutes at 900 C. of greater than 20 kPa; and a binder, wherein the inorganic fibres comprise X and Y and K.sub.2O, the sum of which is greater than 95 wt. % wherein X is the sum of SiO.sub.2 and ZrO.sub.2 and Y is the sum of Al.sub.2O.sub.3 and La.sub.2O.sub.3, wherein ZrO.sub.2 and La.sub.2O.sub.3 each to 10 wt. % of the total weight of the inorganic fibres.

2. The mat according to claim 1, wherein the inorganic fibres are amorphous.

3. The mat according to claim 1, wherein the inorganic fibres have a dissolution rate of at least 150 ng/cm.sup.2/hr saline at pH 4.5.

4. The mat according to claim 1, wherein the sum of the wt. % of SiO.sub.2 and Al.sub.2O.sub.3 and K.sub.2O in the inorganic fibre is greater than 96.0 wt. %.

5. The mat according to claim 1, wherein the sum of the wt. % of CaO and MgO and Na.sub.2O in the inorganic fibre is less than or equal to 0.5 wt %.

6. The mat according to claim 1, wherein the pressure retained value at 10 minutes at 900 C. is greater than 30 kPa.

7. The mat according to claim 1, wherein the arithmetic mean diameter of the inorganic fibres is less than 10 m.

8. The mat according to claim 1, wherein the retained at 10 minutes at 900 C./(mean diameter of fibre).sup.2 is greater than 1.2.

9. The mat according to claim 1, further comprising an inorganic colloidal solution.

10. The mat according to claim 1, further comprising inorganic fillers or additives.

11. The mat according to claim 1, further comprising additional fibres selected from the group consisting of mullite, alumina, aluminosilicate or low biopersistent sol-gel fibres.

12. The mat according to claim 11, wherein the additional fibres are blended with the inorganic fibres.

13. The mat according to claim 11, wherein the additional fibres form a separate layer to the inorganic fibres.

14. A hybrid fibre mat, comprising a first mat according to claim 1, and a second mat formed from different inorganic fibres than the first mat.

15. A pollution control device further comprising a housing and a hybrid fibre according to claim 14 disposed therein, said hybrid fibre mat comprising a hot surface facing a heat source and a cool surface facing an opposing direction to the heat source, wherein the second mat forms part of the hot surface.

16. The pollution control device of claim 15, wherein the first mat forms part of the cool surface.

17. A catalytic converter comprising a housing, a catalytic converter element and, between the housing and the catalytic converter element a mat according to claim 1.

18. A pollution control device comprising a mat according to claim 1.

19. The fibre mat according to claim 1, wherein the inorganic fibres comprise 0 wt % each of La.sub.2O.sub.3 and ZrO.sub.2.

20. A fibre mat for a monolith support mat or end cone insulator, the mat comprising: melt formed amorphous inorganic fibres, with an arithmetic diameter of less than 10 m; and having a pressure retained value at 10 minutes at 900 C. of greater than 20 kPa; and a binder, wherein the inorganic fibres comprise X and Y and K.sub.2O, the sum of which is greater than 95 wt. % wherein X is the sum of SiO.sub.2 and ZrO.sub.2 and Y is the sum of Al.sub.2O.sub.3 and La.sub.2O.sub.3, wherein ZrO.sub.2 and La.sub.2O.sub.3 each i to 10 wt. % of the total weight of the inorganic fibres.

21. The fibre mat according to claim 20, wherein the inorganic fibres comprise 0 wt % each of La.sub.2O.sub.3 and ZrO.sub.2.

22. A fibre mat; for a monolith support mat or end cone insulator, the mat comprising: inorganic fibres having a strength per cross sectional area of greater than 1.2 kPa/m.sup.2; and a binder, wherein the inorganic fibres comprise X and Y and K.sub.2O, the sum of which is greater than 95 wt. % wherein X is the sum of SiO.sub.2 and ZrO.sub.2 and Y is the sum of Al.sub.2O.sub.3 and La.sub.2O.sub.3, wherein ZrO.sub.2 and La.sub.2O.sub.3 each to 10 wt. % of the total weight of the inorganic fibres and wherein the fibres have a dissolution rate of at least 150 ng/cm.sup.2/hr (saline at pH 4.5).

23. The fibre mat according to claim 22, wherein the inorganic fibres comprise 0 wt % each of La.sub.2O.sub.3 and ZrO.sub.2.

Description

(1) To further exemplify the disclosure, reference is made to the following non-limiting Examples, with reference to the accompanying drawings in which:

(2) FIG. 1 is an apparatus for fixed gap hot compression testing.

(3) Referring first to Table 1, there is shown the composition of inorganic fibres as % weight of the total composition according to Examples (1 to 13; 15-20) and Comparative Examples (CE1 to CE19) of the disclosure. The un-normalised results have been used.

(4) TABLE-US-00013 TABLE 1 Sample SiO.sub.2 Al.sub.2O.sub.3 K.sub.2O Na.sub.2O MgO CaO Total 1 40.6 37.2 22.3 0.2 0.0 0.0 100.3 2 40.4 36.4 21.8 0.2 0.0 0.0 98.8 3 40.8 38.2 20.4 0.2 0.0 0.0 99.6 4 40.9 36.1 22.4 0.2 0.0 0.0 99.7 5 43.0 34.0 19.7 0.2 0.0 0.1 96.9 6 44.7 34.6 20.3 0.3 0.0 0.2 99.9 7 43.5 35.3 20.6 0.2 0.0 0.1 99.6 8 42.0 35.5 22.0 0.2 0.0 0.1 99.8 9 41.3 36.0 21.2 0.2 0.0 0.0 100.1 10 40.5 35.2 22.3 0.2 0.0 0.0 98.2 11 40.7 36.5 22.4 0.2 0.0 0.0 99.9 12 39.9 37.1 22.3 0.3 0.0 0.0 99.5 13 45.5 35.6 18.8 0.3 0.0 0.0 100.2 15-16 41.2 36.3 22.6 0.3 0.0 0.0 100.6 17-20 40.7 36.7 22.1 0.2 0.0 0.0 99.6 C1 37.4 45.1 17.5 0.2 0.0 0.0 100.1 C2 30.4 52.0 17.3 0.2 0.0 0.0 99.9 C3 41.0 40.9 17.4 0.2 0.0 0.1 99.5 C4 37.6 42.9 19.3. 0.2 0.0 0.0 99.9 C5 31.4 49.5 18.9 0.2 0.0 0.0 100.0 C6 35.7 44.3 19.8 0.2 0.0 0.0 100.0 C7 25.6 53.9 20.0 0.2 0.0 0.0 99.6 C8 36.1 43.2 20.2 0.2 0.0 0.0 99.7 C9 30.6 50.1 19.4 0.2 0.0 0.0 100.4 C10 37.0 42.0 20.8 0.2 0.0 0.0 99.9 C11 42.5 41.3 15.1 0.2 0.1 0.0 99.1 C12 37.4 43.8 17.5 0.2 0.0 0.0 99.0 C13 38.7 40.8 19.5 0.2 0.0 0.0 99.2 C14 32.0 46.3 19.5 0.3 0.0 0.0 99.5 C15 31.9 47.0 20.7 0.3 0.0 0.0 99.9 C16 32.9 45.0 21.9 0.3 0.0 0.0 99.9 C17 38.5 38.2 21.9 0.2 0.0 0.0 98.8 C18 38.2 36.0 25.3 0.3 0.0 0.0 99.9 C19 46.4 35.8 17.7 0.3 0.0 0.0 100.1

(5) It is noted that some of the Comparative Examples are repeats of samples disclosed in U.S. Pat. No. 8,088,701 B2. Referring now to Table 2, there is shown the original inorganic fibre compositions disclosed in U.S. Pat. No. 8,088,701 B2 and the corresponding Comparative Examples disclosed in the present application.

(6) TABLE-US-00014 TABLE 2 Sample of U.S. Pat No. 8,088,701B2 SiO.sub.2 Al.sub.2O.sub.3 K.sub.2O Na.sub.2O Repeat KAS30 35.9 36.3 25.6 0.0 C18 KAS31 37.5 40.1 20.6 0.0 C13, C17 KAS33 45.4 36.7 17.4 0.0 C19

(7) Referring now to Table 3, there is shown the composition of inorganic fibres as % weight of the total composition according to Examples (14) and Comparative Examples (C20 to C25) of the disclosure. In these compositions, K.sub.2O is substituted for other cations to demonstrate effect of substitution and/or impurities levels on high temperature strength. The un-normalised results have been used and all other measured impurities (e.g. Fe.sub.2O.sub.3) 0.1 wt % or less.

(8) TABLE-US-00015 TABLE 3 K.sub.2O + Na.sub.2O + Sample SiO.sub.2 Al.sub.2O.sub.3 K.sub.2O Na.sub.2O MgO CaO Total CaO + MgO 14 42.0 35.5 22.2 0.2 0.0 0.1 99.6 22.5 C20 41.9 35.6 21.2 1.1 0.0 0.0 100.0 22.3 C21 41.7 36.5 20.0 2.2 0.0 0.0 100.4 22.2 C22 42.0 36.3 20.7 0.2 1.0 0.0 100.1 21.9 C23 41.2 36.4 20.0 0.1 2.1 0.0 100.3 22.2 C24 41.8 36.2 20.9 0.2 0.3 1.0 100.4 22.4 C25 42.6 35.9 20.1 0.2 0.1 1.7 100.7 22.1

(9) Referring now to Table 4, there is shown the composition of inorganic fibres as % weight of the total composition according to the prior art. There is shown the composition for an engineered refractory fibre (RCF) available from Morgan Advanced Materials, Isofrax from Unifrax Ltd, and Superwool Xtra (SW XT) from Morgan Advanced Materials.

(10) TABLE-US-00016 TABLE 4 Sample SiO.sub.2 Al.sub.2O.sub.3 K.sub.2O ZrO.sub.2 MgO Other Total RCF 48.7 51.4 0 0 0 0 100.1 Isofrax 70.0-80.0 0 0 0 >18.0-27.0 <4.0 SW XT 30 35 25.5 7 1.0 0.25 98.75

(11) The high temperature strength of the inorganic fibre of each of the Examples of the disclosure the Comparative Examples was tested using the fixed gap hot compression test. The results of this test provide a value (kPa) for the pressure retained at 10 minutes at 900 C. This provides a benchmark for the high temperature strength of each of the inorganic fibre compositions of the Examples and Comparative Examples.

(12) Referring now to FIG. 1, there is shown an apparatus 1 for fixed gap hot compression testing, which is adapted from the heated cyclic compression test disclosed in U.S. Pat. No. 5,736,109. There is shown a mechanical test frame 10 comprising a pair of water-cooled platens 11a, 11b, a furnace (not shown), a pair of quartz discs 12a, 12b, and a pair of quartz tubes 13a, 13b. There is further shown a sample S (e.g. Example 1) to be tested. The pair of quartz tubes 13a, 13b, are positioned between the pair of water-cooled platens 11a, 11b.

(13) During the test, the sample S (i.e. hand sheet sample) is located between the pair of quartz discs 12a, 12b.

(14) The mechanical test frame 10 was purchased from Instron of High Wycombe, Buckinghamshire, UK.

(15) The sample S was fabricated in the following procedure: Mix cleaned fibre (10.0 g) in water (600 mL). Using a 7575 mm vacuum forming mould with a 100 m screen mesh (the suction base being filled with water and the vacuum pump off), pour the fibre slurry into the mould and manually stir to ensure uniformity. Place the lid on top of the mix and turn the vacuum pump on slowly whilst pushing the lid down. Move the vacuum formed fibre mat onto a flat surface and use a heavy rolling pin (once in each direction) to improve the uniformity of the mat. Dry the resulting mat (7575 mm) at 120 C. Cut a 50 mm diameter round test sample from the centre of the vacuum formed mat to produce sample S, for use in the following high-temperature strength tests.

(16) The grammage of samples produced with this method was between 1500-1700 g/m.sup.2.

(17) The method of conducting the fixed gap hot compression test on a sample S using the apparatus 1 is described as follows: 1. Place the sample S between the pair of quartz discs 12a, 12b. 2. Apply pressure through the pair of quartz tubes 13a, 13b by compressing the sample S at a rate of 5 mm/min to 0.6 g/cm.sup.3 gap density at room temperature. Record as the initial pressure, the pressure produced as a result of resistance of the sample S to deformation at this density. 3. Initiate the heating cycle by heating the mechanical test frame 10 containing the sample from ambient temperature to 900 C. at a rate of 10 C./min followed by 10 minutes hold at 900 C., whilst maintaining the density/test gap of the sample S at a constant value through the heating cycle and 10 minute hold. 4. Record the pressure value produced (kPa) by the resistance of the sample S throughout the test, and specifically following the 10 minutes hold at 900 C.

(18) Referring now to Table 5, there is shown the results of the fixed gap hot compression test, which were performed as described above, to determine the high temperature strength measurement of each of the Examples of the disclosure, and of the Comparative Examples. There is also shown the arithmetic mean fibre diameter (m) for each of the Examples and Comparative Examples. The inorganic fibres according to the disclosure all exhibit a value for the pressure retained at 10 minutes at 900 C. of above 20 kPa and thus surprisingly show better high temperature resilience than fibres which fall outside of the current disclosure.

(19) TABLE-US-00017 TABLE 5 Pressured retained at Arithmetic mean Strength per Cross- 10 mins in fixed gap fibre diameter Sectional Area Example hot compression test (m) (Equation 1) 1 22 6.0 0.61 2 24 5-10 0.42* 3 25 6.3 0.63 4 38 1.9 10.53 5 63 5-10 1.12* 6 32 7.3 0.60 7 27 5-10 0.48* 8 64 5-10 1.14* 9 42 5-10 0.75* 10 33 5-10 0.59* 11 27 9.0 0.33 12 37 5-10 0.66* 13 40 5-10 0.71* 14 40 5-10 0.71* 15 111 6.7 2.5 16 79 6.7 1.8 17 36 4.6 1.7 18 53 4.6 2.5 19 60 4.6 2.8 20 44 4.6 2.1 C1 0 5-10 0 C2 2 2-5 0.1* C3 12 2-5 0.98* C4 18 4.2 1.02 C5 7 2-5 0.57* C6 0 <10 0 C7 0 2-5 0 C8 0 2-5 0 C9 20 5-10 0.36* C10 7 5-10 0.12* C11 0 2-5 0* C12 3 5-10 0.5* C13 8 4.2 0.45 C14 15 5-10 0.27* C15 4 5-10 0.07* C16 8 2-5 0.14* C17 14 4.9 0.58 C18 17 18.1 0.05 C19 2 5-10 0.04* C20 12 7.3 0.23 C21 0 5.5 0 C22 0 5.6 0 C23 0 4.0 0 C24 0 3.3 0 C25 0 4.5 0 RCF 36 1.65 13.22 Isofrax 0 4.0 0 SW XT 0 4.0 0 *estimate using mean diameter of estimated diameter range

(20) Therefore, the inorganic fibres of the present disclosure show improved temperature performance in comparison with compositions of the prior art.

(21) Moreover, the inorganic fibres of the present disclosure are able to produce comparable high performance as well as low biopersistence in comparison with the prior art.

(22) Referring now to Table 6, there is shown data for flow solubility testing.

(23) A 21 day long flow through solubility test in saline pH 4.5 was conducted on the compositions shown in Table 6. Two samples of each fibre composition were simultaneously tested, with the average results reported. The saline samples were analysed using the ICP method to measure the oxide dissolution levels in ppm level. The results confirm that the fibres have low biopersistence. A low biopersistence fibre composition is taken to be a fibre composition which has a dissolution rate, in the flow solubility test, of at least 100 ng/cm.sup.2 hr or at least 150 ng/cm.sup.2 hr or at least 170 ng/cm.sup.2 hr.

(24) TABLE-US-00018 TABLE 6 Specific Surface Area Dissolution rate Fibre Dissolution Example (m.sup.2/g) (ng/cm.sup.2hr) (% of initial mass) 1 0.443 190 36.9 C4 0.543 167 40.2 C9 0.328 214 31.8

(25) As will be appreciated, the above demonstrates that the fibres of the disclosure have desirable mechanical properties and low biopersistence. This is all the more surprising given that the fibres of the disclosure in mechanical testing were not heat treated and so are amorphous.

(26) Reference throughout this specification to one embodiment, certain embodiments, one or more embodiments or an embodiment, whether or not including the term exemplary preceding the term embodiment, means that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the certain exemplary embodiments of the present disclosure. Thus, the appearances of the phrases such as in one or more embodiments, in certain embodiments, in one embodiment or in an embodiment in various places throughout this specification are not necessarily referring to the same embodiment of the certain exemplary embodiments of the present disclosure.

(27) Furthermore, all publications and patents referenced herein are incorporated by reference in their entirety to the same extent as if each individual publication or patent was specifically and individually indicated to be incorporated by reference. Various exemplary embodiments have been described. These and other embodiments are within the scope of the following claims

(28) It will be appreciated by those skilled in the art that several variations to the aforementioned embodiments are envisaged without departing from the scope of the disclosure.

(29) It will also be appreciated by those skilled in the art that any number of combinations of the aforementioned features and/or those shown in the appended drawings provide clear advantages over the prior art and are therefore within the scope of the disclosure described herein.