Title of Invention	CERAMIC PRODUCT BASED UPON LITHIUM ALUMINIUM SILICATE
Abstract	A ceramic product, particularly one for handling molten aluminium, which contains at least 70 % lithium aluminium silicate on a mass per mass basis is disclosed as well as a method of improving the non-wettability of the product.

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FROM 2 original IN/PCT/2001/00287/MUM 13-03-2001 THE PATENTS ACT 1970 [39 OF 1970] COMPLETE SPECIFICATION [SEE SECTION 10] 1 TITLE CERAMIC PRODUCT BASED UPON LITHIUM ALUMINIUM SILICATE 2 APPLICANT NAME ADDRESS DAKOT CC 22 SIYAYI AVENUE, 3867 MTUNZINI KWAZULU, NATAL REPUBLIC OF SOUTH AFRICA NATIONALITY REPUBLIC OF SOUTH AFRICA The following specification particularly describes the nature of the invention and the manner in which it is to be performed: technical Field This invention relates to a ceramic product, and then particularty on© for handling molten aluminium. In this specification the term "ceramic product refers to a product which has been formed by firing a ceramic raw material to a suitable temperature. 10 Background Art Molten aluminium, which has a relatively low melting point of approximataly 700°C, is difficult to handle and far this reason the apparatus used usually comprises a product that has a high thermal shock resistance, a high 15 resistance to wettability, a low thermal conductivity/capacity, and high strength. Nona of the products which has hitherto been used for the aforesaid purpose, amongst others aluminium trtanate; tused silica; cast iron and fibrous ceramic board, has ideal properties in this regard. 20 Object of the invention It is en object of this Invention to provide a ceramic product which the applicant believes has advantages over the known arrangements. 2 Disclosure of the invention According to the invention a ceramic product is provided which contains at least 70% lithium aluminium silicate on a mass per mass basis. 5 lithium aluminium silicate (hereafter referred to as LAS) occurs naturally as the mineral petalte, and is used in small quantities in ceramic formulation® instead of feldspar in order to decrease fire thermal expansion of such formulations, and hence improve their resistance to thermal shock. It is also used in glass 10 compositions for stove tope and oven ware. Applicant has now found that an LAS-ceramic product according to the || invention has extremely low thermal expansion and can hence as such be used in any apparatus subjected to any form of heat exposure, such as for example, 15 that occurring in the handling of molten aluminium. SUCH an LAS-ceramic product can be manufactured by forming a suitable quantity of finely divided petalfte in any of the conventional methods such as slip castjng; extrusion or injection moulding; and wet or dry pressing and then 20 fifing it at a temperature in the order of between 11500C and 12100C. For use in the aluminium Industry, such an LAS-ceramic product does not have to be fired to full density- ft has been found that fired densities of the order of 3 60 to 70% of the theoretical are obtained when firing eft between 1150 and 1210°C. At these densities, the product shows no dimensional changes, no thermal expansion, adequate strength. a tow- thermal conductivity and thermal capacity, and also takes an excellent coating whan 5 painted with protective materials such as boron nitride, as is normal practice* in the aluminium industry. Jt can furthermore be impregnated with liquid substances intended for enhancing the metallurgical properties of the product if required, the density of the LAS-ceramic product can be lowered by the 10 addition of fly ash microspheres and/or a suitable combustible materia!. Further according to the invention the LAS-ceramic product according to the invention Includes a non-wetting agent which has been incorporated in the fired LAS-ceramic product 15 The reason lor such incorporation is that the inherent wettability of IAS by molten aluminium poses severe problems when the protective coating usually provided on the LAS-cararmic product is removed, which may, for example, happen during use of the ceramic product, 20 It has furthermore been found that such wettability cannot be reduced by the incorporation of Known non-wetting agents in the ceramic formulation of the product according to the invention, because such agents tend to react with the 4 LAS during the firing process causing them to tree their abality as non-wettlng agents. Furthermore, by incorporating the non-wetting agent in the fired LAS-ceramic 5 product, the thermal expansion properties of the ceramic product are not adversely affected, Further according to the Invention the non-wetting agent comprises barium sulphate (BaSQ4). which is a well known non-wetting agent in the ceramic 10 industry, Further according to the invention a method ror improving the non-wettability of an LAS-ceramic product is provided which includes the step of providing a suitable non-wetting agent such as BaSO4 in the fired LAS-ceramic product 15 In one form of the invention the BaSo4 may be provided in the fired LAS-ceramic product by impregnating the semi-porous tired LAS-ceramic product with a saturated aqueous eofution of barium sulphide (BaS) which, after drying, te oxidised in situ to BaSO4. 20 &ugh oxklalion may be effected by calcining the dried product to 600 - 8000C in an oxidising atmosphere. 5 Commercial BaS can be used, or Bas can be prepared by the reduction of BaS04 with carbon at 1190°C, orwith ammonia at 1000"C. in another form of the invention the Baso4 may be provided by impregnating 5 the semi-porous fired LAS-ceramic product with a solution of BaCl2, and then treating the product wtth sulphuric add to cause BaSQ4 to precipitate inside the pores of the ceramic product Preferably file BaCl2- solutionis a substantially saturated one, and the sulphuric to acid comprises diluted sulphuric acid. The BaCl2 - solution can either be prepared by dissolving BaCl3 In water, or by treating BaC03 with hydrochloric acid. 15 In a preferred form of the invention the ceramic product according to the invention comprises substantiafly_10Q% LAS (mass per mass). best mod* for carrying out the Invention A semi-porous LAS-ceramic product according to the Invention comprising 20 100% (mass per mass) LAS is provided by forming a suitable quantity of petafite in finely divided form by means of any one of the conventional methods such as slip casting; extrusion of injection moulding; or wet or dry pressing, and firing the formed product at & temperature of between 1150*C and 1210"C. 6 Preferably said finely divided petalite comprises a mixture of two fractions: a first one having an average particle size in the order of 1 micrometer, used in a concentration from 50 to 100% (mass per mass); and 6 - a second one having a particle size finar than 75 micrometer used in a concentration of from 0 - 50% (mass per mass). The non-wettability of said LAS-ceramic product is Improved according to the invesntion by incorporating BaSo4 as non-wettfng agent in the product in any 10 on© of the following two methods: 1- Bas-Impregnation (i) A solution of BaS is prepared by intimately mixing one mass part of BaSo4 with half a mass part of carbon, end firing the mixture at 16 1190*C for 2 hours; (ii) One mass part of the product of step (I) is added to four mass parts water: boiled for 12 hours; and the solids filtered off; (Hi) The solution resulting from step (ii) is kept at boiling point, and the semi-porous LAS-ceramic product Immersed in the boiling 20 solution for 15 minutes; (iv) The impregnated product is air-dried and then calcined at 500 -800 for 3 hours. 7 2 Bacl2- Impregnation 0} A saturated solution of BaCI2 is prepared by dissolving 59g BaCl2 in 100m( H2O at 100°C. (Alternatively 1 kg BaCo3 0,95kg H2O is treated with 1,11kg HCI (33% concentration by volume)to form & a saturated solution of BaCl2 00 A dfluted solutfon of H2So4 (concentiaBon not critical, say 50% (volume by volume) is prepared; to (in) A cooled down seml-porous as tired LAS ceiarnic product is impregnated with the boiling BaCl2 - solution; (iv) the ceramic product is cooled down to cause Bacl2 out in the pores of the ceramic product; 15 (v) Any excess water is removed from the oersmio product under vacuum (vi) The ceramic body is impregnated with the diluted H2SO4 which 20 reacts with the BaCl2to cause BaSO4 to precipitate inside the pores of the ceramic product; (vii) The ceramic product is dried and calcined to 700°c to remove all volalites. In both instances an LAS-ceramic product is formed which is substantially norv-5 wettabte with molten aluminium. It will be appreciated that the invention aiso inductee within its scope an LAS-ceramic product of which the non-wettabilfty had been improved by 1h© inoQrporation therein of BaSc4 by any one of the aforesaid two methods. 10 15 Results obtained with a product according to the Invention The following results were obtained comparing em LAS-ceramic product according to the invention with products conventionally used in the handling of molten aluminium. In completing these results, the importance to the process of the relevant refractory property is rated from 1 -10. and then multiplied by the rafing (1 -10) of the specific ceramic material in terms of trie property, m order to generate n normalised rank lor the different materials in terms of their total performance. 20 9 Competitive products, Aluminium Titanate (AT) Fused Silica (FS) Cast Iron (CI) Fibrous Ceramic BoanJ (CS) Ceramic LAS - Product (LAS) Weighted properties Thermal Shock Resistance (10) Resistant to Wetfing (8) tharmal conductivity Capacity (5) Strength (5) Material ratings 3.1 tharmal Shock(x 1) AT 10 (100) FS 10 (100) CI 10 (100) CB 6 (SO) LAS 10 (100) 10 -It Wettability(x B) AT 10 (80) FS 4 (32) CI 0 (0) CB 10 (BO) LAS 10 (80) thermal conductivity capacity (x AT 3 (15) FS 8 (40) cl 0 (0) CB 10 (50) LAS 10 (50) AT 10 (60) FS 6 (30) CI 10 (50) CB 2 (10) LAS 10 (50) 11 it is clear from the above resute that when used lor the handling of molten aluminium, an LAS-ceramic product according to the invention has much better 10 overall properties than those of the aforementioned known products. It will also be appreciated that there are no doubt many variations in detail possible with a ceramic product according to the invention without departing from the scope of the claims. 15 12 WE CLAIM: 1. A ceramic product characterised in that it contains at least 70% lithium aluminium silicate (LAS) on a mass per mass basis; and a non-wetting agent. 2. The ceramic product as claimed in claim 1, wherein the lithium aluminium silicate comprises petalite in finely divided form which has been fired to a temperature in the order between 1150°C and 1210°C. 3. The ceramic product as claimed in claim 1 or 2, wherein the lithium aluminium silicate is present in an amount of substantially 100% on a mass per mass basis. 4. The ceramic product as claimed in preceding claim, wherein the-non-wetting agent is incorporated in the fired LAS ceramic product after being fired. 5. The ceramic product as claimed in claim 4, wherein the non-wettting agent comprises barium sulphate. 6. A method for the manufacture of a ceramic product of claim 1 to 5 with improved non-wettability, wherein non-wetting agent such as bariumsulphate is incorporated in the. fired LAS-ceramic product after being fired. 7. The method as claimed in claim /6 wherein the barium sulphate is provided in the fired LAS-ceramic product by impregnating the semiporous fired LAS ceramic product with a saturated aqueous solution of barium sulphide (BaS) which, after drying, is oxidised into BaS04. 8. The method as claimed in claim7wherein the oxidation is effected by calcining the dried product to 500-800°C in an oxidising atmosphere. 9. The method as claimed in claim 6 wherein the BaS04 is provided by impregnating the semi-porous fired LAS-ceramic product with a solution of BaC12, and then treating the 13 product with sulphuric acid to cause BaS04 to precipitate inside the pores of the ceramic product. 10. The method as claimed in claim 9, wherein the BaC12-solution is a substantially saturated one, and the sulphuric acid comprises diluted sulphuric acid. 11. A method of forming the ceramic product of any one of claims 1 to 6 wherein the petalite in finely divided form is fired to a temperature in the order of between 1150°C and 1210° C and impregnating the fired product impregnated with a non-wetting agent 12. The method as claimed in claim 11, wherein the product is formed by means of any one of the following methods: slip casting; extrusion or injection moulding; wet or dry pressing. 13. The method as claimed in any one of claims 11 or 12, wherein the finely divided petalite may comprises a mixture of two fractions: a first one having an average particle size in the order of 1 micrometer, used in a concentration from 50 to 100% (mass per mass); and a second one having an average particle size in the order of 75 micrometer, used in a concentration of from 0 - 50% (mass per mass). Dated this 12 day of March 2001 DAKOT CC by its Attorneys Shyam Sunder Iyer Patent Agent TAS & CO.

Documents:

in-pct-2001-00287-mum-abstract(14-01-2005).doc

in-pct-2001-00287-mum-abstract(14-5-2004).pdf

in-pct-2001-00287-mum-cancelled pages(14-5-2004).pdf

in-pct-2001-00287-mum-claims(granted)-(14-01-2005).doc

in-pct-2001-00287-mum-claims(granted)-(14-5-2004).pdf

in-pct-2001-00287-mum-correspondence(ipo).pdf

in-pct-2001-00287-mum-correspondence.pdf

in-pct-2001-00287-mum-form 19(7-10-2003).pdf

in-pct-2001-00287-mum-form 1a(14-5-2004).pdf

in-pct-2001-00287-mum-form 2(granted)-(14-01-2005).doc

in-pct-2001-00287-mum-form 2(granted)-(14-5-2004).pdf

in-pct-2001-00287-mum-form 3(12-3-2001).pdf

in-pct-2001-00287-mum-form 5(12-3-2001).pdf

in-pct-2001-00287-mum-form pct-ipea-409(13-3-2001).pdf

in-pct-2001-00287-mum-form pct-isa-210(13-3-2001).pdf

in-pct-2001-00287-mum-petition under rule 138(13-1-2005).pdf

in-pct-2001-00287-mum-power of authority(14-5-2004).pdf