CA1190945A - Moulded articles - Google Patents
Moulded articlesInfo
- Publication number
- CA1190945A CA1190945A CA000396255A CA396255A CA1190945A CA 1190945 A CA1190945 A CA 1190945A CA 000396255 A CA000396255 A CA 000396255A CA 396255 A CA396255 A CA 396255A CA 1190945 A CA1190945 A CA 1190945A
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- Prior art keywords
- weight
- parts
- bonding agent
- ceramic fibres
- mixture
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/34—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing cold phosphate binders
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B26/00—Compositions of mortars, concrete or artificial stone, containing only organic binders, e.g. polymer or resin concrete
- C04B26/02—Macromolecular compounds
- C04B26/22—Natural resins, e.g. rosin
- C04B26/24—Cellulosic waste liquor, e.g. sulfite lye
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
- F27D5/00—Supports, screens, or the like for the charge within the furnace
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Ceramic Engineering (AREA)
- Materials Engineering (AREA)
- Structural Engineering (AREA)
- Organic Chemistry (AREA)
- General Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Inorganic Chemistry (AREA)
- Mechanical Engineering (AREA)
- Compositions Of Oxide Ceramics (AREA)
- Ceramic Products (AREA)
- Lubricants (AREA)
- Porous Artificial Stone Or Porous Ceramic Products (AREA)
Abstract
ABSTRACT
MOULDED ARTICLES
A moulded article is made from a composition comprising a mixture of 100 parts by weight ceramic fibres or a mixture of at least 20% by weight ceramic fibres and up to 80% by weight of a fired bonded granular material comprising ceramic fibres, bonding agent and refractory materials with 2 to 20 parts by weight clay and/or other conventional refractory materials, 0 to 8 parts by weight phosphate bonding agent, 0 to 10 parts by weight organic bonding agent, there being at least two parts by weight bonding agent present, with water. The mixture is compressed whilst being moulded into the desired shape and then dried and/or fired.
The article has a density of 0.5 to 1.8 g/cm3 and a hot bending strength at 1000°C of at least 0.8 N/mm2.
MOULDED ARTICLES
A moulded article is made from a composition comprising a mixture of 100 parts by weight ceramic fibres or a mixture of at least 20% by weight ceramic fibres and up to 80% by weight of a fired bonded granular material comprising ceramic fibres, bonding agent and refractory materials with 2 to 20 parts by weight clay and/or other conventional refractory materials, 0 to 8 parts by weight phosphate bonding agent, 0 to 10 parts by weight organic bonding agent, there being at least two parts by weight bonding agent present, with water. The mixture is compressed whilst being moulded into the desired shape and then dried and/or fired.
The article has a density of 0.5 to 1.8 g/cm3 and a hot bending strength at 1000°C of at least 0.8 N/mm2.
Description
s 1. 238~3-111 MOULDED ARTICLES
The invention relates to moulded articles and is concerned with those articles whicll have a high mechanical stability at high temperatures and re-lates also to a process for the manufacture of such articles and their use.
Heat insulating ceramic fibre bodies comprising refractory fibres and organic or inorganic bonding agrent having either low strength and high compressi-bility or higrh values for their strength, density and cons~ancy of shape are known. Thus DE-AS 12 74 490 describes a combustion chamber for furnaces which is made by forming out a fibre mass mixed with bonding agent and in which the concentration of bonding agent decreases over the cross-section of the wall.
Clays, alkaline silicates, aluminium phosphate, colloidal silica with a proyor-tion by weight of 5 to 35%, optimally 10%, are named as a suitable bonding agent.
The fibre body is, however, not capable of adequately resisting high loads due to the fact that one wall surface is hard and compact whilst the opposing wall surface is soft and flexible.
In the process disclosed in DE-AS 27 32 387 a mineral fibre plate pre-bonded with an organic plastics bonding agent is supposed to be strengthened by soaking with an aqueous slurry of a bonding clay and subsequent ternpering.
It is an object of the invention to provide moulded articles which have improved mechanical and thermal properties and which, in particular, can serve as a replacement for light refractory plates.
According to the present invention there is provided a moulded article manufactured from the following composition:
100 parts by weight of either ceramic fibres or a mixture comprising at least 20% by weight ceramic fibres and up to 80% by weight of a fired, bonded, granular material comprising ceramic fibres, bonding agent and refractory material, PA 3124/A KXR/Sa/Le .~ .
- - \
The invention relates to moulded articles and is concerned with those articles whicll have a high mechanical stability at high temperatures and re-lates also to a process for the manufacture of such articles and their use.
Heat insulating ceramic fibre bodies comprising refractory fibres and organic or inorganic bonding agrent having either low strength and high compressi-bility or higrh values for their strength, density and cons~ancy of shape are known. Thus DE-AS 12 74 490 describes a combustion chamber for furnaces which is made by forming out a fibre mass mixed with bonding agent and in which the concentration of bonding agent decreases over the cross-section of the wall.
Clays, alkaline silicates, aluminium phosphate, colloidal silica with a proyor-tion by weight of 5 to 35%, optimally 10%, are named as a suitable bonding agent.
The fibre body is, however, not capable of adequately resisting high loads due to the fact that one wall surface is hard and compact whilst the opposing wall surface is soft and flexible.
In the process disclosed in DE-AS 27 32 387 a mineral fibre plate pre-bonded with an organic plastics bonding agent is supposed to be strengthened by soaking with an aqueous slurry of a bonding clay and subsequent ternpering.
It is an object of the invention to provide moulded articles which have improved mechanical and thermal properties and which, in particular, can serve as a replacement for light refractory plates.
According to the present invention there is provided a moulded article manufactured from the following composition:
100 parts by weight of either ceramic fibres or a mixture comprising at least 20% by weight ceramic fibres and up to 80% by weight of a fired, bonded, granular material comprising ceramic fibres, bonding agent and refractory material, PA 3124/A KXR/Sa/Le .~ .
- - \
2 to 20 parts by weight clay and/or A1203 ancl/or SiO2 and/or aluminium hydro-xides and/or magnesia and~or titanium dioxide and/or chromium oxide, 0 to 8 parts by weight phosphate bonding agent, calculated as P205, 0 to 10 parts by weight of an organic bonding agent, and 0 *o 10 parts by weight other refractory additivesl whereby, however, the composit:ion contains at least 2 parts by weight of a bond-ing agent, the article having a density of 0.5 to 1.8 g/cm3 and a hot bending strength at :L000 C of at leas-t 0.8 N/mm .
The invention relates also to a process for the manufacture of such an article and thus according l;o a further aspect of the present invention there is
The invention relates also to a process for the manufacture of such an article and thus according l;o a further aspect of the present invention there is
3.
provided a process for the manufacture of a moulded article including the following steps.
a) 100 parts by weight of either ceramic fibres or a mixture comprising at least 20% by weight ceramic 5. fibres and up to 80% by weight of a fired bonded granular material comprising ceramic fibres, - bonding agent and refractory material are thoroughly mixed with 2 to 20 parts by weight clay and/or A1203 and/or SiO2 and/or aluminium hydroxides and/or lOr magnesia and/or titanium dioxide and/or chromium o~ide, 0 to 8 parts by weight phosphate bonding agent, calculated as P205, 0 to 10 parts by weight of an organic bonding agent, whereby, however, at least 2 parts by weight o~ a bonding agent are 15. present, water and 0 to 10 parts by weight other refractory additivesj b) the mixture obtained in step a) is compressed by a minimum volume factor of 3 when only using ceramic fibres decreasing linearly to 1.5 when 20. using a mixture of 80 parts by weight of the bonded granular material and 20 parts by weight ceramic ~ibres whilst moulding the mixture to the desired shape , and c) the moulded article manufactured in step b) is dried 25. and/or tempered and/or fired.
The moulded articles in accordance with the invention can ~e used for many purposes, in particular as a replacement for known light refractory plates.
Their advantage is that they have a lower density than 30. such known plates and they have a very narrow pore
provided a process for the manufacture of a moulded article including the following steps.
a) 100 parts by weight of either ceramic fibres or a mixture comprising at least 20% by weight ceramic 5. fibres and up to 80% by weight of a fired bonded granular material comprising ceramic fibres, - bonding agent and refractory material are thoroughly mixed with 2 to 20 parts by weight clay and/or A1203 and/or SiO2 and/or aluminium hydroxides and/or lOr magnesia and/or titanium dioxide and/or chromium o~ide, 0 to 8 parts by weight phosphate bonding agent, calculated as P205, 0 to 10 parts by weight of an organic bonding agent, whereby, however, at least 2 parts by weight o~ a bonding agent are 15. present, water and 0 to 10 parts by weight other refractory additivesj b) the mixture obtained in step a) is compressed by a minimum volume factor of 3 when only using ceramic fibres decreasing linearly to 1.5 when 20. using a mixture of 80 parts by weight of the bonded granular material and 20 parts by weight ceramic ~ibres whilst moulding the mixture to the desired shape , and c) the moulded article manufactured in step b) is dried 25. and/or tempered and/or fired.
The moulded articles in accordance with the invention can ~e used for many purposes, in particular as a replacement for known light refractory plates.
Their advantage is that they have a lower density than 30. such known plates and they have a very narrow pore
4.
size distribution. Despite the compression in their man- ¦
ufact:ure, their thermal conductivity is of the same order as those shaped articles known per se including glass fibres which are not: compressed in their manufacture
size distribution. Despite the compression in their man- ¦
ufact:ure, their thermal conductivity is of the same order as those shaped articles known per se including glass fibres which are not: compressed in their manufacture
5. and which are manufactured by a vacuum suction process.
By comparison, the articles in accordance with the invention exhibit, however r a substantially higher strength.
By virtue of their high mechanical strength the artic:les in accordance with the invention are suitable 10. particularly as expansion joint fillers between the bricks of rotary tubular furnaces. For this purpose asbec;tos has long been used, however the use of asbestos is increasingly res:Lsted due to its adverse effect on the health, 15. The articles in accordance with the invention can incorporate all conventional ceramic fibres as the oryanic fibres r such as rock wool or r more preferably, fibres based on al~ninium silicate, preferably with an A120~ content of about ~0 to 95% by weight. The fibres 20. are, however, preferably based on A1203 and SiO2 with at least 40% by wei~ht A1203 and are preferably capable of being used at temperatures in excess of llO0CC. This will :Ln general exclude inorganic fibres basecl on, for instance, basalt, slag and glass and 25. natural asbestos fibres whose use temperature is below 1100 C, but such fibres may be, and preferably are, used as a subsidiary component in addition to those whose use temperature is above 1100Co The other refractory additives which may be used in 30. the articles in accordance with the invention are those 9~ .
adt-litives conventionally used in shaped fibre articles, suc:h as porcelain powder, fixe clay, hollow sphere corundum or vermicu].ite.
The phosphate bonding agents present in the 5. axt:icles in accordance with the invention may be conventional phosphate-containing bonding agents, - e.g. boron phosphate, aluminium phosphate or sodium polyphosphate with a degree of polymerisation n ~ 4, and particularly n = 6 to 10.
10. The organic bonding agents in the articles in accordance with the invention may be those bonding agents commonly usea in refractory or heat-resistant shaped articles such. as starch, sulphite lye or washings, molasses a.nd, in particular, methyl cellulose.
15. The given amount of bonding agent relates to solid organic bonding agent, i.e. disregarding any water.
Both the phosphate bonding.agent and the organic bonding agent can be added both in dissolved form and/o.r in solid form. When using methyl cellulose~
20. which is commonl.y used as a 5% by weight aqueous solution, a part of this methyl cellulose is however advantageously used in solid finely divided form, particularly when ad~ing larger quantities of methyl cellulose, since otherwise the quantity of water 25. introduced into the ,~omposition by such a bonding agent solut:ion would be too large The clay which ]nay be in the articles in accordance wit:h the invention may be a conventional bonding clay or a special clay such as bentonite. This and A1203 30. and SiO2 and magnesia, and titanium dioxide and s chromium oxide, all of which are preferably used in very finely divided form, and the aluminium hydroxideS
are components whose use is known in the refractory fielcl. The term "very finely divided" is used here 5. to mean that the cornponents are present in a very finely divided or in a col:loidal state. The very finely - - divided refractory rnaterials preferably have a gr~in size of less t:han 50 ~m, more preferably less than 10 ~m ParticUlarly when using such materials in the 10. colloidal state, suc:h as colloidal SiO2 or colloidal aluminium oxide, it is possible to use only small quantities of bonding agent, namely close to the lower thxeshold value of 2 parts by weight. The bonding agent can comprise only a phosphate bonding agent 15. or only an organic konding agent, advantageously however a mixture of both phosphate and organic bonding agents is used. The use of about the same parts by weight phosphate bonding agent and methyl ce:Llulose as the organic bonding agent is particularly 20. preferred.
Advantageously the composition o~ the articles in accordance with the invention contains 5 to 15 parts by weight clay and/or the other said components to ]00 parts by weight of the ceramic fibres or 25. ceramic fibre and granular material mi~tureO Particularly advantageous is the use of a mixture of clay, in particular of bentonite, and 1 to 3 parts by weight of one of the other components referred to above, particularly of colloidal silica.
30. When manufacturing the articles in accordance with s 7.
the invention, a mixture is produced of ceramic fibres or the mixture of ceramic fibres with the bonded granular material, and the clay and/or the other components referred to above, the phosphate bonding agent, if present, the other ref`ractory additives, if present, the organic bonding agent, if present, and water. If the pllosphate bonding agent and/or the organic bonding agent are added in the form of a solution, commonly an aqueous solution, the addition of further water may not be necessary. During the manufacture in step a) of the process there are preferably 5 to 25 parts by weight of water present to 100 parts by weight of the ceramic fibres. The phosphate bonding agents, such as sodium polyphosphate and monoaluminium pllosphate, as well as the organic bond-ing agents such as sulphite waste or methyl cellulose, can be used in solid ground form but it is also possible to add a portion of these bonding agents in the form of a solution and the remainder in solid form.
The bonded granular material used in the manufacture of the ar-ticles in accordance with the invention is preferably of the type described in more de-tail as follows. Its manufacture includes the following steps:
a) lO0 parts by weight ceramic: fibres, 2 to 15 parts by weight clay and/or Al2O3 and/or SiO2 and/or a]uminium hydroxides and/or titanium dioxide and/
or chromium oxide, optionally up to 10 parts by weight other refractory additives and 1 to 8 parts by weight phosphate bonding agent, / ,,~
s 8~
optionally with the addition of a plasticising agent, are thorou~hly mixed in a mixer with about 2 to 25, or in some cases 2 to 100, parts by weight water, . b~ the mixture obtained in step a) is compressed by a vol~ne factor of at least 3, and c) the product obtained in step b) is optionally dried and fired at temperatures of 800 to 1550C and subsequently comminuted, 10. The materials used in the manufacture of this granular material, i,e. ceramic fibres, clay or other components referred to, the refractory additives and the phosphate bonding agent correspond to the materials as described above~ ~ethyl cellulose 15. is preferably used as the plasticising agent. In the manufacture of the granular material the compression in step b) can be effected in an extruder, a rotary table press or a briquetting device. The mixing of the components in step a) in the manufacture oE this 20. fibre granulate can occur in any suitable mixer, Eor instance in a Drais mixer. Advantageously~loosened ceramic fibres are used in the manu-Eacture of such a granular material, as can also be used in the manufacture of the articles in accordance with the 25. invention. The comminution in step c) in thP manufacture of this granular material can be effected in any sultable device and the maximum yrain size is preferably 6 mm. This comminution can however be set to a predetermined ra~ge, for instance a product can 30. without difficulty be obtained with a grain size between 2 an~ 3 mm by comminution in conventional crushing devices and, if necessary, sieving out of the desired grain sizes. The granular material obtained thereby is found to have a clensity of 0.7 to 1.75 g/cm3 5. and a pore volume of the order of 35 - 75%.
The quantity of the plasticising agent which may be - - added in step a) depends on the compression device used in step b). For example, when using methyl cellulose and compressing in an extruder a quantity of 4 parts 10. by weight methyl cel.lulose is preferably added, whereby half of this methyl cellulose can be added as a 5% solution in water and the other half as dry methyl cellulose. The quantity of water added can also vary with the compression device so that whilst 15. normally 2 to 25 parts by weight water is adequate, if an extruder is used for the compression the water quantity may be up to lOO parts by weight.
The quantity of water used in the manufacture of the articles in accordance with the invention should 20. be kept as small as possible, advantageously only up to 15 parts by weight water are mixed in with 100 parts by weight of the ceramic fibres and particularly preferably only 10 parts by weight water so that a dough-like mass is obtained.
25. ~he advantage of using a mi~ture of ceramic fibr~s and a fired granular material comprising ceramic fibres, refraCtory material and bonding agent resides in that when manufacturing the shaped articles in accordance with the invention a smaller quantity of 30. wa~er is necessary. Thus the quantity of water -- ' '' ' 10 .
required depends on the proportion of ceramic fibres and fired granular material in the mixture. The use of a mixture of 50~ by weight ceramic fibres and 50%
by weight o~ the granular material has shown itself 5. tc be particularly a,dvantageous.
The dough-like mass obtained in step a) when - manufacturing the moulded articles is put into a suitable press in step b), for instance a plate press or a table press or even an isostatic press, and 10. pressed for a suitable period of time, this depending on the type of press used. In a plate press the pressing time is co~monly 5 to 20 seconds.
It is of importance when manufacturing the articles in step b) of the process in accordance with 15. the invention that the compression is effected by a volume factor of at least 3 when only using ceramic fibres or by a volume factor of at least 1.5 when using a mixkure of 80 parts by weight of the granular material and 20 parts by weight ceramic fibres.
20. when using a mixture of ceramic fibres and fired fibre granulate in other proportions this minimum compression factor varies proportionally between 3 and 1.5.
Advantageous values for the compression factor are between 5 and 8 when using only ceramic fibres and 25. 2.5 to ~ when using a mixture of 80 parts by weight granular material and 20 parts by weight ceramic fibres.
Naturally the advantageous compression factors lie between the values given above with other proportions of ceramic fibres and granular material.
30. The maximum volume factor of the compression is in practice about 12 to 14 when only using ceramic fibres and about 6 to 8 when using a mixture of 80 parts by weight granular material and 20 parts by weight ceramic fibres.
5. If the articles in accordance with the invention are in the form of plates these can have a thickness of 1 to 50 mm.
After pressing, the shaped articles are dried in step c) of the process, advantageously at between 10. 110 and 180 C, and/or they can be tempered, e.g. at temperatures between 250C and 600C and/or fired, e.g. at temperatures between 800C and 1650C.
The maximum firing temperature and also the maximum use temperature of the moulded articles depends, 15. however, primarily on the ceramic fibres used in the starting mixture and rather less on the other refractory additives possibly present.
When delivered, ceramic fibres are generally in the form of a loo;e wool which is, however, 20. partially strongly compressed. In order to enable a bett:er bonding of lhe fibres by the bonding agent used and a good wetting of the surface by liquids of low concentration, the fibres are advantageously separated or loosened before the moulding.
25. For this purpose mixing units can be used with rapidly rotating knif-e heads, so called impact mixers, wherehy larger agglomerates present in the fibres as delivered are loose~ed, without the fibres being thereby unacceptably strongly crushed.
30. If no granular material is used it is possible 12. - - -to carry out step a) of the process in such an impactmixer. This means that the loosening of the fibres is effected at the same time as the mixing with the comp-onents added in this step a), namely clay and/or the 5. other refractory components referred to and optionally an organic bonding agent. In this case, however, only dry solid materials are added in order adequately to achieve the loosening of the agglomerated fibres and also the homogeneous mixing in of the added 10. materials. Subsequently water and bonding agent, optionally in the form o~ a solution, are sprayed into the mixing container and mixed in.
Naturally it is, however, also possible to carry out the loosening of the ceramic fibres in an impact 15. mixer and then to add the other materials in another mixer, e.g. a Drais mixer or an Eirich mixer.
This mode of operation is particularly appropriate when using vermiculite or hollow sphere corundum as further refractory additives, since otherwise 20. a crushing of these ]naterials would occur, and also when starting with a mixture of ceramic fibres with the fired granular material.
~ he articles in accordance with the invention have the particular advantage that they have very good 25. thermal insulating properties due to the relatively high content of ceramic fibres but nevertheless a relatively good mechanical stability due to the compression during their manufacture. Furthermore their resistance to sudden changes of temperature, 30. that is to say their thermal shock resistance, i5 ~ ~r~ a/k ~9~
- 13.
excellent. This thermal shock resistance is preferably in excess of 25 air quenchings measured in accordance with German standard DIN 51068, part 2, on prismatic bodies of, e.g. 1~4 x 64 x 64 mm. The bodies are 5. repeatedly heated to 950 C and then quenched by blowing them with air at room temperature through an 8 rnm - nozzle. After cooling the bodies are tested with a bending stress of 0.3 N/mm2. The thermal shock resistance is the number of cycles before failure.
10. The invention will now be described in more detail with reierence to the following Examples.
In these Examples two types of ceramic ~ibres based on A1203 and SiO2 were used, that is to say fibres A with 47% A1203 and 53% SiO2 with a use 15. tempe:rature up to 1260 C and fibres B suitable for higher use temperatures with 95% A1203 and 5% SiO2.
The mixtures were partially produced in an impact mixer provided with a rapidly rotating knife head (3000 RPM). In this mixer the fibre material was 20. we:ll loosened and a pourable and fluid fibre material is produced which is uniformly mixed with the mixture components. The mixlure comprising the granular material leads on fw-ther processing in presses to fibre materials with low to high gross density and 25. a particularly homogeneous composition. If one uses a mixer which has mixing arms rotating with a relatively low velocity, e.g. an ~irich mixer, there is by contrast a less intensive loosening of the fibres and the resultant mixture is not so hornogeneous.
30. The 50% monoaluminium phosphate solution was introduced - 14.
into the mixer in the region of the rapidly rotating knife head as a spray. In this manner a complete wetting of the agglomerate surfaces was achieved with a minimum liquid volum~, e.g. 10% by weight 5. MAP - 6.6 litres. Water was subsequently sprayed in in a similar manner. The water dissolves any - dry methyl cellulose which may be present and thus brings about a good gre~n strength of the shaped article.
10. Manufacture of the fired granular material:
a) 100 parts ~y weight of ceramic fibres A), 10 parts by weight bonding clay with an A1203 content of 35% by weight and 1.5 parts by weight dry methyl cellulose in powder form were put 15. into an Eirich mixer and mixed together for 10 minutes. Then 10 parts by weight of 50% by weight monoaluminium phosphate solution and 2 parts by weight water were sprayed onto the mass in the mixer whilst continuing to mix and mixed in 20. for a further 30 minutes.
The product was taken out of the mixer and pressed at a pressing pressure of 30 N/mm in a plate press into a plate-shaped ,article with a thickness of 30 mm, whereby a compression by a factor of 5.5 was 25. ob~ained.
The plate-shaped article was substantially dried at 110 C for 24 hour,s in an oven and samples were then fired at different temperatures for 24 hours in each case and subsequently comminuted to a maximum grain 30. size of 3 mm.
15.
The gxanular ma.terials obtained had the following properties:
Table I
Firing temperature ( C) 800 1350 1510 5. Weight per unit volu.me, R, (g/cm ) 1.34 1.52 1.77 . . Specific weight, S, (g/cm3) 2.60 2.70 2.75 Pore volume, Pg, (Vol.~) 47.7 43.7 35.6 b) The method of m,anufacture of a) was repeated but 10. an impact mixer was used to loosen the fibres.
The pressing pressure in step b) was 10 and 15 N/mm on two different samples thereby achieving a compression by a factor of 4 and 5 respectively.
15. After firing at 1350C for 24 hours and comminution fibre granulates with the following properties were obtained:
Table II
Pressing pressure (N/mm ) 10 15 20. P~ (g/cm ) 0.7 1.02 Spec. weight (g/cm ) ~.7 2.7 Pg (Vol.%) 74 63 c) The method of manufacture a) was repeated but the proportion of monoaluminium phosphate solution 25. was increased to 15 parts by weight and the proportion of water to 5 parts by weight with the mixing time shortened to 20 minutes. After firing at 1350 C for 24 hours and comminution to the desired granulate this had the following properties:
119~39~5 16.
Table III
R (g/cm ) 1.29 S (g/cm3) 2.69 Pg (Vol.%) 53.8 5.
d) The method of mlanufacture a) was repeated but additionally 8 parts by weight fire clay--powder- --were added in the first step. Furthermore only 8.3 parts by weight of 50% by weight monoaluminium 10. phosphate solution but 4 parts by weight water were added in the mixing step.
The pressing pressure in the compression step b) wa~ 30 N/mm which resulted.in a compression by a volume factor of 5.2.
15.- The plate-shape article obtained was dried at 180C and samples were fired at the different temperatures given in the following Table IV. Subsequently the fired.product was comminuted to a maximum grain size of 3 mm.
20. The granular materials obtained had the followiny properties:
Table_IV
~rreatment temp. (C) 130 800 1200 1300 150-0 Weight per unit volume 25. R (g/cm3) 1.30 1.26 1.31 1.34 1.48 spec. weight (g/cm3) 2.60 2O60 2.65 2.68 2.72 Pg (Vol.%) 50.0 51.5 50.5 50.0 45.6 _nufacture of the moulded articles . Example 1 30. The following composition was used:
- 17.
Parts by weight Cexamic fibres A 100 Bonding clay (25% by weight A1203) 10 5- Dry methyl cellulosel 1O5 Monoaluminium phosphate - - - solution, 50% by weight :L0 Water 2 The ceramic fibres A were put into an Eirich 10. mixer with the bonding clay and the dry methyl cellulose and mixed for 20 min.utes thereby producing a homogeneous mixture. Then the monoaluminium phosphate solution and subsequently the water were sprayed in with the mixer continuing to run and thoroughly mixed in.
15. subsequently blocks were pressed out with dimensions 405 x 135 x 50 mm at a pressing pressure of 30 N/mm .
The compression factor was 6Ø
Subsequently the blocks were dried for 4 hours at 110 C and subsequently fired at differing temperatures 20. for different times.
The properties of the blocks after the firing wexe as follows:
S
18.
Table V
.
Te~mperature/
firing time800 C/8 h 1350 C/6 h1510 C/6h R (g/cm ) 1.34 1.52 1.77 5. P~ (~ol.%) 47.7 43.7 35.6 Deformation modulus (N/mm ) 1408 1303 5291 Cold bending strengt:h (N/ 2) 5.0 4~4 8.2 10. Thermal shock resist:ance > 25 > 25 > 25 Hot bending strength, 1000C (N/mm2) 4.7 6.6 11.6 Hot bending strength., 1200 C (N/mm2) 6.2 5.9 9.6 15.
Linear shrinkage % after 24 hours at 1400C -3.19 -1.89 1500C -6.94 -3.35 -0.16 20. 1600 C -10.3~ -7.70 -5.45 Chemical analysis:
A1203 (%) 44.7 25. SiO2 (%) 50.7 P205 (%) 2.95 Thermal conductivity (W/m K at 700~C) 0.45 ample 2 The same components were mixed in an impact mixer and moulded at lower pressing pressures. After firing at 1350 C blocks wit:h the following properites 5. were obtained (the properties at a pressing pressure of 30 N/mm from Table V are set out as well for - - comparison): -Table VI
Ex. 1 _ Ex. 2 10. Pressing pressure (N/mm ) 30 20 15 10 Compression factor 6.0 5.4 4.4 3.5 Firing temperature ( C) 1350 1350 1350 1350 Length of firing (h) 6 24 24 24 R (g/cm3) 1.52 1.34 1.02 0.7 15. Pg (Vol.%) 43.7 58.0 63.0 74.0 Cold bending strength, (N/mm ) 4,4 4.1 0.9 0.7 Hot bending strength, 1000 C (N/mm2) 6.6 - 2.0 0.8 20. Ho1 bending strength, 1200 C (N/mm2) 5.9 5.6 - _ Ho1: bending strength, 1400 C (N/mm2) _ _ 2.3 0.9 Thermal conductivity 25O (W/m K at 700C) 0.45 0O25 0.20 0.16 Example 3 The following composition was used:
20.
Parts by weight Ceramic fibres A 100 Bonding clay (35~ by weight A1203)10 5. Dry methyl cellulose 1.5 Monoaluminium phosphate - - solution, 50% by weight 15 l~ater 5 10. Firstly the dry components were put into an Eirich mixer and mixed for 10 minutes. Subsequently the monoaluminium phosphate solution and then the water were sprayed on. After further mixing for 20 minutes the composition was removed from the mixer.
15. As in Example 1 above, the mixture was pressed into blocks in a press at a pressing pressure of 30 N/mm2.
The compression factor was 5.2.
The pressed blocks were dried at 110C for 4 hours and subsequently fired for 6 hours at 1350C.
20. The properties of the blocks obtained were as follo~s:
Table VII
. _ R (g/cm ) 1.20 25. Pg (Vol.~) 53.8 Hot bending strength at 100 C (N/mm2) 2.1 Cold bending strength (N/mm ) 2.6 30. Thermal conductivity (W/m K at 700C) 0.35 9~ 1 21.
A comparison of the blocks produced in Examples 1 r 2 and 3 shows that when preparing the mixture in an impact mixer and using the same pressing pressure shaped articles can be obtained with a higher cold 5. bending strength. When using an Eirich mixer, i.e.
without loosening the ceramic fibres, it is convenient - - slightly to increase the proportion of phosphate bonding a~ent and also the proportion of water, the proportion of water being conveniently 8 to 10%.
10. Examples 4 and 5 The followingcorr.positions were used:
Parts by weight Ceramic fibres B 100 100 Bonding clay 15. (35~ by weight A1203) 10 10 Dry methyl cellulose 1.5 1.5 Monoaluminium phosphate solution, 50~ by weight 12 15 Water 3 5 20. The production of the composition in step a) occurred as in the method of Example 2, i.e. using an impact mixer.
Two portions of the mixture obtained in step a) were pressed in accordance with the method of Example 25. 2 at a pressing pressure of 9 and 20 N/mm respectively into blocks, subsequently dried for 4 hours at 110C
and then fired for 24 hours at 1350C. The properties of the blocks were as follows:
9~;
22.
Table VIII
Example _ 4 5 R (g/cm ) 0.52 1.0 Compression factor 3.5 6.7 5. Pg (Vol.%) 84.2 69.4 Cold bending strengt.h (N/mm2) 0.9 1.9 -- - Hot bending strength, 900 C (N/mm ) 3.4 Hot bending strength, 10. 1000 C (N/mm2) 0.8 Hot bending strength, 1400 C (N/mm ) 0.7 Thermal conductivity (W/m K at 700C) 0.19 0.35 15.
Examples 6 to 9 The following composition was used:
Parts b Ceramic fibres A) 25 20. Ceramic fibres B) 75 Bonding clay (35% by wei~ht Al203) 5 Very finely ground a:Lumina ~ 44 ~m 5 25. Dry methyl cellulose 1~5 Monoaluminium phosphate solltion, 50% by weight 10 Water 2 s 23.
The mixture of Example 6 was prepared in an impact mixer as in the method of Example 2 and pressed at the pressure given in the following Table IX into blocks as in the method of Example 1. An Eirich mixer 5. was used in Examplec; 7 to 9.
After drying at 110 C for 4 hours the blocks were fired for 24 hours at the different temperatures which are also given in the table. The properties of the block~ obtained are given in the table.
10. A portion of this mixture was also pressed into plates with dimensions 360 x 360 x 18 mm in a hydraulic plate press instead of into blocks with the dimensions given in Example 1. Such plates constitute an excellent firing aid, e.g. as a support 15. for fine-ceramic products or porcelain when being fired.
Table IX
ExamPle 6 _ 7 8 9 Pressing pressure 20. ~N/mm ) 8 30 30 30 Compression factor 3.8 5.3 5.3 5.3 Drying temperature ( C) 110 110 110 110 Firing temperature ( C) 1350 1520 1580 1620 Properties:
25. R (g/cm ) - 0O57 1.22 1.22 1.31 Pg (Vol.~) 79.9 62.1 6~.2 59.3 Cold bending strength (N/mm ) 0.4 3.5 3.6 4.2 Hot bending strength, 30. 1000 C (N/mm2) 0.8 Hot bending strength, 1400 C' (~J/~ ) 0.8 4.5 4.9 5.6 Thermal conductivity (W/m K at 700C) 0.22 0.47 0.49 0.53 --- - 24.
Example 10 The following composition was used:
Parts ~y weight Fix~dgranular material a) 80 Ceramic fibres B) 20 5. Bonding clay with 35% by weight Very finely ground alumina, < 44 ~m Very finely ground chromium oxide, 10. < ~4 ~m 2 Monoaluminium phosphate solution (50% by weight) 5 Solid sodium polyphosphate 0.5 Water 5 15.
rrhe fired granular material, the clay, the alumina and the chromium oxide were put with the solid sodium polyphosphate into an Eirich mixer, then 5 parts by we~ght water were sprayed on and mixed for 5 minutes.
20. subsequently the 20 parts by weight of ceramic fibres B) were added and mixed in for a further 10 minutes.
Then the monoaluminium phosphate solution was added and mlxed for a further 10 minutes. The mixture was removed from the mixer, pressed into plates of 25. 405 x 135 x 15 mm at a pressing pressure of 30 N/mm , subsec~uently dried for 24 hours at 110 C and then fired at 800C or 1350C for 8 hours. The following properties were cletermined on the product obtained:
- 25.
Table X
Firin.g temperature ~ C) 800 1350 R ~ / 3) 1.8 1.8 Compression factor 2.0 2.0 5. PcJ (Vol.%) 35.8 35~8 Cold bendlng strength (~/~m2) 2.65 6.4 Hc)t bending strength., 1000 C (N/mm ) 4.5 7,0 10. Thermal conductivity (W/m K at 700 C) 0.70 0.65 Example 11 The following composition was used:
15. Parts by wei~t Ceramic fibres A) 100 Hollow sphere corundum, < 3 mm 10 Clay with 35~ A12Q3 5 Magnesia 2 20. Solid boron phosphate ~ 5 Water g Irhe fibres were firstly loosened for 10 minutes in an impact mixer. The hollow sphere corundum, 25. the clay and the water were put into an Eirich mixer, mixed for 5 minutes and then the magnesia and the boron phosphate were added and mixed in for a further 5 minutes. Subseque:ntly the fibres loosened in the impact mixer were put into the Eirich mixer and mixed 30. for a further 20 minutes.
~3Lg~5 26.
~ lates were produced from the mixture in accordance with the method of Example 10. These were fired after drying at 120 C at 800C or 1350C. The following properties were determined on the products obtained:
5, Table XI
Firing temperature :( C) 800 1350 R (g/cm ) 1.15 1.18 Compression factor 4.1 4.1 Pg (Vol.%) 51.9 54.6 10. Hot bending strength, 1000 C (N/mm ) 2.8 4.1 Thermal conducti~ity (W/m K at 700C) 0.63 0.65 15. Example 12 The following composition was used:
Parts by weight Ceram:ic fibres A) 100 Bo:nding clay 10 20~ Dry sulphite waste 9 .
Water The ceramic fibres, the clay and the solid sulphite waste were mixed for 10 minutes in an Eirich mixer, then the water was sprayed on and mixing was finished 25. after a further 10 minutes. Blocks were pressed as in Example 1 at a pressing pressure of 30.N/mm . After drying at 110 C for 24 hours these blocks were fired at 800 C or 1350 C. The following properties were determined on the blocks:
Table_XII
Firing temperature (C) 800 1350 R (g/cm ) 1.18 1~28 Compression factor 5.1 5.1 5. p~ (Vol.~) 54.6 52.6 Hot bending strength, 1000 C (N/mm ) 1.5 2.
Thermal conductivity (W/m K at 700C) 0.27 0.28
By comparison, the articles in accordance with the invention exhibit, however r a substantially higher strength.
By virtue of their high mechanical strength the artic:les in accordance with the invention are suitable 10. particularly as expansion joint fillers between the bricks of rotary tubular furnaces. For this purpose asbec;tos has long been used, however the use of asbestos is increasingly res:Lsted due to its adverse effect on the health, 15. The articles in accordance with the invention can incorporate all conventional ceramic fibres as the oryanic fibres r such as rock wool or r more preferably, fibres based on al~ninium silicate, preferably with an A120~ content of about ~0 to 95% by weight. The fibres 20. are, however, preferably based on A1203 and SiO2 with at least 40% by wei~ht A1203 and are preferably capable of being used at temperatures in excess of llO0CC. This will :Ln general exclude inorganic fibres basecl on, for instance, basalt, slag and glass and 25. natural asbestos fibres whose use temperature is below 1100 C, but such fibres may be, and preferably are, used as a subsidiary component in addition to those whose use temperature is above 1100Co The other refractory additives which may be used in 30. the articles in accordance with the invention are those 9~ .
adt-litives conventionally used in shaped fibre articles, suc:h as porcelain powder, fixe clay, hollow sphere corundum or vermicu].ite.
The phosphate bonding agents present in the 5. axt:icles in accordance with the invention may be conventional phosphate-containing bonding agents, - e.g. boron phosphate, aluminium phosphate or sodium polyphosphate with a degree of polymerisation n ~ 4, and particularly n = 6 to 10.
10. The organic bonding agents in the articles in accordance with the invention may be those bonding agents commonly usea in refractory or heat-resistant shaped articles such. as starch, sulphite lye or washings, molasses a.nd, in particular, methyl cellulose.
15. The given amount of bonding agent relates to solid organic bonding agent, i.e. disregarding any water.
Both the phosphate bonding.agent and the organic bonding agent can be added both in dissolved form and/o.r in solid form. When using methyl cellulose~
20. which is commonl.y used as a 5% by weight aqueous solution, a part of this methyl cellulose is however advantageously used in solid finely divided form, particularly when ad~ing larger quantities of methyl cellulose, since otherwise the quantity of water 25. introduced into the ,~omposition by such a bonding agent solut:ion would be too large The clay which ]nay be in the articles in accordance wit:h the invention may be a conventional bonding clay or a special clay such as bentonite. This and A1203 30. and SiO2 and magnesia, and titanium dioxide and s chromium oxide, all of which are preferably used in very finely divided form, and the aluminium hydroxideS
are components whose use is known in the refractory fielcl. The term "very finely divided" is used here 5. to mean that the cornponents are present in a very finely divided or in a col:loidal state. The very finely - - divided refractory rnaterials preferably have a gr~in size of less t:han 50 ~m, more preferably less than 10 ~m ParticUlarly when using such materials in the 10. colloidal state, suc:h as colloidal SiO2 or colloidal aluminium oxide, it is possible to use only small quantities of bonding agent, namely close to the lower thxeshold value of 2 parts by weight. The bonding agent can comprise only a phosphate bonding agent 15. or only an organic konding agent, advantageously however a mixture of both phosphate and organic bonding agents is used. The use of about the same parts by weight phosphate bonding agent and methyl ce:Llulose as the organic bonding agent is particularly 20. preferred.
Advantageously the composition o~ the articles in accordance with the invention contains 5 to 15 parts by weight clay and/or the other said components to ]00 parts by weight of the ceramic fibres or 25. ceramic fibre and granular material mi~tureO Particularly advantageous is the use of a mixture of clay, in particular of bentonite, and 1 to 3 parts by weight of one of the other components referred to above, particularly of colloidal silica.
30. When manufacturing the articles in accordance with s 7.
the invention, a mixture is produced of ceramic fibres or the mixture of ceramic fibres with the bonded granular material, and the clay and/or the other components referred to above, the phosphate bonding agent, if present, the other ref`ractory additives, if present, the organic bonding agent, if present, and water. If the pllosphate bonding agent and/or the organic bonding agent are added in the form of a solution, commonly an aqueous solution, the addition of further water may not be necessary. During the manufacture in step a) of the process there are preferably 5 to 25 parts by weight of water present to 100 parts by weight of the ceramic fibres. The phosphate bonding agents, such as sodium polyphosphate and monoaluminium pllosphate, as well as the organic bond-ing agents such as sulphite waste or methyl cellulose, can be used in solid ground form but it is also possible to add a portion of these bonding agents in the form of a solution and the remainder in solid form.
The bonded granular material used in the manufacture of the ar-ticles in accordance with the invention is preferably of the type described in more de-tail as follows. Its manufacture includes the following steps:
a) lO0 parts by weight ceramic: fibres, 2 to 15 parts by weight clay and/or Al2O3 and/or SiO2 and/or a]uminium hydroxides and/or titanium dioxide and/
or chromium oxide, optionally up to 10 parts by weight other refractory additives and 1 to 8 parts by weight phosphate bonding agent, / ,,~
s 8~
optionally with the addition of a plasticising agent, are thorou~hly mixed in a mixer with about 2 to 25, or in some cases 2 to 100, parts by weight water, . b~ the mixture obtained in step a) is compressed by a vol~ne factor of at least 3, and c) the product obtained in step b) is optionally dried and fired at temperatures of 800 to 1550C and subsequently comminuted, 10. The materials used in the manufacture of this granular material, i,e. ceramic fibres, clay or other components referred to, the refractory additives and the phosphate bonding agent correspond to the materials as described above~ ~ethyl cellulose 15. is preferably used as the plasticising agent. In the manufacture of the granular material the compression in step b) can be effected in an extruder, a rotary table press or a briquetting device. The mixing of the components in step a) in the manufacture oE this 20. fibre granulate can occur in any suitable mixer, Eor instance in a Drais mixer. Advantageously~loosened ceramic fibres are used in the manu-Eacture of such a granular material, as can also be used in the manufacture of the articles in accordance with the 25. invention. The comminution in step c) in thP manufacture of this granular material can be effected in any sultable device and the maximum yrain size is preferably 6 mm. This comminution can however be set to a predetermined ra~ge, for instance a product can 30. without difficulty be obtained with a grain size between 2 an~ 3 mm by comminution in conventional crushing devices and, if necessary, sieving out of the desired grain sizes. The granular material obtained thereby is found to have a clensity of 0.7 to 1.75 g/cm3 5. and a pore volume of the order of 35 - 75%.
The quantity of the plasticising agent which may be - - added in step a) depends on the compression device used in step b). For example, when using methyl cellulose and compressing in an extruder a quantity of 4 parts 10. by weight methyl cel.lulose is preferably added, whereby half of this methyl cellulose can be added as a 5% solution in water and the other half as dry methyl cellulose. The quantity of water added can also vary with the compression device so that whilst 15. normally 2 to 25 parts by weight water is adequate, if an extruder is used for the compression the water quantity may be up to lOO parts by weight.
The quantity of water used in the manufacture of the articles in accordance with the invention should 20. be kept as small as possible, advantageously only up to 15 parts by weight water are mixed in with 100 parts by weight of the ceramic fibres and particularly preferably only 10 parts by weight water so that a dough-like mass is obtained.
25. ~he advantage of using a mi~ture of ceramic fibr~s and a fired granular material comprising ceramic fibres, refraCtory material and bonding agent resides in that when manufacturing the shaped articles in accordance with the invention a smaller quantity of 30. wa~er is necessary. Thus the quantity of water -- ' '' ' 10 .
required depends on the proportion of ceramic fibres and fired granular material in the mixture. The use of a mixture of 50~ by weight ceramic fibres and 50%
by weight o~ the granular material has shown itself 5. tc be particularly a,dvantageous.
The dough-like mass obtained in step a) when - manufacturing the moulded articles is put into a suitable press in step b), for instance a plate press or a table press or even an isostatic press, and 10. pressed for a suitable period of time, this depending on the type of press used. In a plate press the pressing time is co~monly 5 to 20 seconds.
It is of importance when manufacturing the articles in step b) of the process in accordance with 15. the invention that the compression is effected by a volume factor of at least 3 when only using ceramic fibres or by a volume factor of at least 1.5 when using a mixkure of 80 parts by weight of the granular material and 20 parts by weight ceramic fibres.
20. when using a mixture of ceramic fibres and fired fibre granulate in other proportions this minimum compression factor varies proportionally between 3 and 1.5.
Advantageous values for the compression factor are between 5 and 8 when using only ceramic fibres and 25. 2.5 to ~ when using a mixture of 80 parts by weight granular material and 20 parts by weight ceramic fibres.
Naturally the advantageous compression factors lie between the values given above with other proportions of ceramic fibres and granular material.
30. The maximum volume factor of the compression is in practice about 12 to 14 when only using ceramic fibres and about 6 to 8 when using a mixture of 80 parts by weight granular material and 20 parts by weight ceramic fibres.
5. If the articles in accordance with the invention are in the form of plates these can have a thickness of 1 to 50 mm.
After pressing, the shaped articles are dried in step c) of the process, advantageously at between 10. 110 and 180 C, and/or they can be tempered, e.g. at temperatures between 250C and 600C and/or fired, e.g. at temperatures between 800C and 1650C.
The maximum firing temperature and also the maximum use temperature of the moulded articles depends, 15. however, primarily on the ceramic fibres used in the starting mixture and rather less on the other refractory additives possibly present.
When delivered, ceramic fibres are generally in the form of a loo;e wool which is, however, 20. partially strongly compressed. In order to enable a bett:er bonding of lhe fibres by the bonding agent used and a good wetting of the surface by liquids of low concentration, the fibres are advantageously separated or loosened before the moulding.
25. For this purpose mixing units can be used with rapidly rotating knif-e heads, so called impact mixers, wherehy larger agglomerates present in the fibres as delivered are loose~ed, without the fibres being thereby unacceptably strongly crushed.
30. If no granular material is used it is possible 12. - - -to carry out step a) of the process in such an impactmixer. This means that the loosening of the fibres is effected at the same time as the mixing with the comp-onents added in this step a), namely clay and/or the 5. other refractory components referred to and optionally an organic bonding agent. In this case, however, only dry solid materials are added in order adequately to achieve the loosening of the agglomerated fibres and also the homogeneous mixing in of the added 10. materials. Subsequently water and bonding agent, optionally in the form o~ a solution, are sprayed into the mixing container and mixed in.
Naturally it is, however, also possible to carry out the loosening of the ceramic fibres in an impact 15. mixer and then to add the other materials in another mixer, e.g. a Drais mixer or an Eirich mixer.
This mode of operation is particularly appropriate when using vermiculite or hollow sphere corundum as further refractory additives, since otherwise 20. a crushing of these ]naterials would occur, and also when starting with a mixture of ceramic fibres with the fired granular material.
~ he articles in accordance with the invention have the particular advantage that they have very good 25. thermal insulating properties due to the relatively high content of ceramic fibres but nevertheless a relatively good mechanical stability due to the compression during their manufacture. Furthermore their resistance to sudden changes of temperature, 30. that is to say their thermal shock resistance, i5 ~ ~r~ a/k ~9~
- 13.
excellent. This thermal shock resistance is preferably in excess of 25 air quenchings measured in accordance with German standard DIN 51068, part 2, on prismatic bodies of, e.g. 1~4 x 64 x 64 mm. The bodies are 5. repeatedly heated to 950 C and then quenched by blowing them with air at room temperature through an 8 rnm - nozzle. After cooling the bodies are tested with a bending stress of 0.3 N/mm2. The thermal shock resistance is the number of cycles before failure.
10. The invention will now be described in more detail with reierence to the following Examples.
In these Examples two types of ceramic ~ibres based on A1203 and SiO2 were used, that is to say fibres A with 47% A1203 and 53% SiO2 with a use 15. tempe:rature up to 1260 C and fibres B suitable for higher use temperatures with 95% A1203 and 5% SiO2.
The mixtures were partially produced in an impact mixer provided with a rapidly rotating knife head (3000 RPM). In this mixer the fibre material was 20. we:ll loosened and a pourable and fluid fibre material is produced which is uniformly mixed with the mixture components. The mixlure comprising the granular material leads on fw-ther processing in presses to fibre materials with low to high gross density and 25. a particularly homogeneous composition. If one uses a mixer which has mixing arms rotating with a relatively low velocity, e.g. an ~irich mixer, there is by contrast a less intensive loosening of the fibres and the resultant mixture is not so hornogeneous.
30. The 50% monoaluminium phosphate solution was introduced - 14.
into the mixer in the region of the rapidly rotating knife head as a spray. In this manner a complete wetting of the agglomerate surfaces was achieved with a minimum liquid volum~, e.g. 10% by weight 5. MAP - 6.6 litres. Water was subsequently sprayed in in a similar manner. The water dissolves any - dry methyl cellulose which may be present and thus brings about a good gre~n strength of the shaped article.
10. Manufacture of the fired granular material:
a) 100 parts ~y weight of ceramic fibres A), 10 parts by weight bonding clay with an A1203 content of 35% by weight and 1.5 parts by weight dry methyl cellulose in powder form were put 15. into an Eirich mixer and mixed together for 10 minutes. Then 10 parts by weight of 50% by weight monoaluminium phosphate solution and 2 parts by weight water were sprayed onto the mass in the mixer whilst continuing to mix and mixed in 20. for a further 30 minutes.
The product was taken out of the mixer and pressed at a pressing pressure of 30 N/mm in a plate press into a plate-shaped ,article with a thickness of 30 mm, whereby a compression by a factor of 5.5 was 25. ob~ained.
The plate-shaped article was substantially dried at 110 C for 24 hour,s in an oven and samples were then fired at different temperatures for 24 hours in each case and subsequently comminuted to a maximum grain 30. size of 3 mm.
15.
The gxanular ma.terials obtained had the following properties:
Table I
Firing temperature ( C) 800 1350 1510 5. Weight per unit volu.me, R, (g/cm ) 1.34 1.52 1.77 . . Specific weight, S, (g/cm3) 2.60 2.70 2.75 Pore volume, Pg, (Vol.~) 47.7 43.7 35.6 b) The method of m,anufacture of a) was repeated but 10. an impact mixer was used to loosen the fibres.
The pressing pressure in step b) was 10 and 15 N/mm on two different samples thereby achieving a compression by a factor of 4 and 5 respectively.
15. After firing at 1350C for 24 hours and comminution fibre granulates with the following properties were obtained:
Table II
Pressing pressure (N/mm ) 10 15 20. P~ (g/cm ) 0.7 1.02 Spec. weight (g/cm ) ~.7 2.7 Pg (Vol.%) 74 63 c) The method of manufacture a) was repeated but the proportion of monoaluminium phosphate solution 25. was increased to 15 parts by weight and the proportion of water to 5 parts by weight with the mixing time shortened to 20 minutes. After firing at 1350 C for 24 hours and comminution to the desired granulate this had the following properties:
119~39~5 16.
Table III
R (g/cm ) 1.29 S (g/cm3) 2.69 Pg (Vol.%) 53.8 5.
d) The method of mlanufacture a) was repeated but additionally 8 parts by weight fire clay--powder- --were added in the first step. Furthermore only 8.3 parts by weight of 50% by weight monoaluminium 10. phosphate solution but 4 parts by weight water were added in the mixing step.
The pressing pressure in the compression step b) wa~ 30 N/mm which resulted.in a compression by a volume factor of 5.2.
15.- The plate-shape article obtained was dried at 180C and samples were fired at the different temperatures given in the following Table IV. Subsequently the fired.product was comminuted to a maximum grain size of 3 mm.
20. The granular materials obtained had the followiny properties:
Table_IV
~rreatment temp. (C) 130 800 1200 1300 150-0 Weight per unit volume 25. R (g/cm3) 1.30 1.26 1.31 1.34 1.48 spec. weight (g/cm3) 2.60 2O60 2.65 2.68 2.72 Pg (Vol.%) 50.0 51.5 50.5 50.0 45.6 _nufacture of the moulded articles . Example 1 30. The following composition was used:
- 17.
Parts by weight Cexamic fibres A 100 Bonding clay (25% by weight A1203) 10 5- Dry methyl cellulosel 1O5 Monoaluminium phosphate - - - solution, 50% by weight :L0 Water 2 The ceramic fibres A were put into an Eirich 10. mixer with the bonding clay and the dry methyl cellulose and mixed for 20 min.utes thereby producing a homogeneous mixture. Then the monoaluminium phosphate solution and subsequently the water were sprayed in with the mixer continuing to run and thoroughly mixed in.
15. subsequently blocks were pressed out with dimensions 405 x 135 x 50 mm at a pressing pressure of 30 N/mm .
The compression factor was 6Ø
Subsequently the blocks were dried for 4 hours at 110 C and subsequently fired at differing temperatures 20. for different times.
The properties of the blocks after the firing wexe as follows:
S
18.
Table V
.
Te~mperature/
firing time800 C/8 h 1350 C/6 h1510 C/6h R (g/cm ) 1.34 1.52 1.77 5. P~ (~ol.%) 47.7 43.7 35.6 Deformation modulus (N/mm ) 1408 1303 5291 Cold bending strengt:h (N/ 2) 5.0 4~4 8.2 10. Thermal shock resist:ance > 25 > 25 > 25 Hot bending strength, 1000C (N/mm2) 4.7 6.6 11.6 Hot bending strength., 1200 C (N/mm2) 6.2 5.9 9.6 15.
Linear shrinkage % after 24 hours at 1400C -3.19 -1.89 1500C -6.94 -3.35 -0.16 20. 1600 C -10.3~ -7.70 -5.45 Chemical analysis:
A1203 (%) 44.7 25. SiO2 (%) 50.7 P205 (%) 2.95 Thermal conductivity (W/m K at 700~C) 0.45 ample 2 The same components were mixed in an impact mixer and moulded at lower pressing pressures. After firing at 1350 C blocks wit:h the following properites 5. were obtained (the properties at a pressing pressure of 30 N/mm from Table V are set out as well for - - comparison): -Table VI
Ex. 1 _ Ex. 2 10. Pressing pressure (N/mm ) 30 20 15 10 Compression factor 6.0 5.4 4.4 3.5 Firing temperature ( C) 1350 1350 1350 1350 Length of firing (h) 6 24 24 24 R (g/cm3) 1.52 1.34 1.02 0.7 15. Pg (Vol.%) 43.7 58.0 63.0 74.0 Cold bending strength, (N/mm ) 4,4 4.1 0.9 0.7 Hot bending strength, 1000 C (N/mm2) 6.6 - 2.0 0.8 20. Ho1 bending strength, 1200 C (N/mm2) 5.9 5.6 - _ Ho1: bending strength, 1400 C (N/mm2) _ _ 2.3 0.9 Thermal conductivity 25O (W/m K at 700C) 0.45 0O25 0.20 0.16 Example 3 The following composition was used:
20.
Parts by weight Ceramic fibres A 100 Bonding clay (35~ by weight A1203)10 5. Dry methyl cellulose 1.5 Monoaluminium phosphate - - solution, 50% by weight 15 l~ater 5 10. Firstly the dry components were put into an Eirich mixer and mixed for 10 minutes. Subsequently the monoaluminium phosphate solution and then the water were sprayed on. After further mixing for 20 minutes the composition was removed from the mixer.
15. As in Example 1 above, the mixture was pressed into blocks in a press at a pressing pressure of 30 N/mm2.
The compression factor was 5.2.
The pressed blocks were dried at 110C for 4 hours and subsequently fired for 6 hours at 1350C.
20. The properties of the blocks obtained were as follo~s:
Table VII
. _ R (g/cm ) 1.20 25. Pg (Vol.~) 53.8 Hot bending strength at 100 C (N/mm2) 2.1 Cold bending strength (N/mm ) 2.6 30. Thermal conductivity (W/m K at 700C) 0.35 9~ 1 21.
A comparison of the blocks produced in Examples 1 r 2 and 3 shows that when preparing the mixture in an impact mixer and using the same pressing pressure shaped articles can be obtained with a higher cold 5. bending strength. When using an Eirich mixer, i.e.
without loosening the ceramic fibres, it is convenient - - slightly to increase the proportion of phosphate bonding a~ent and also the proportion of water, the proportion of water being conveniently 8 to 10%.
10. Examples 4 and 5 The followingcorr.positions were used:
Parts by weight Ceramic fibres B 100 100 Bonding clay 15. (35~ by weight A1203) 10 10 Dry methyl cellulose 1.5 1.5 Monoaluminium phosphate solution, 50~ by weight 12 15 Water 3 5 20. The production of the composition in step a) occurred as in the method of Example 2, i.e. using an impact mixer.
Two portions of the mixture obtained in step a) were pressed in accordance with the method of Example 25. 2 at a pressing pressure of 9 and 20 N/mm respectively into blocks, subsequently dried for 4 hours at 110C
and then fired for 24 hours at 1350C. The properties of the blocks were as follows:
9~;
22.
Table VIII
Example _ 4 5 R (g/cm ) 0.52 1.0 Compression factor 3.5 6.7 5. Pg (Vol.%) 84.2 69.4 Cold bending strengt.h (N/mm2) 0.9 1.9 -- - Hot bending strength, 900 C (N/mm ) 3.4 Hot bending strength, 10. 1000 C (N/mm2) 0.8 Hot bending strength, 1400 C (N/mm ) 0.7 Thermal conductivity (W/m K at 700C) 0.19 0.35 15.
Examples 6 to 9 The following composition was used:
Parts b Ceramic fibres A) 25 20. Ceramic fibres B) 75 Bonding clay (35% by wei~ht Al203) 5 Very finely ground a:Lumina ~ 44 ~m 5 25. Dry methyl cellulose 1~5 Monoaluminium phosphate solltion, 50% by weight 10 Water 2 s 23.
The mixture of Example 6 was prepared in an impact mixer as in the method of Example 2 and pressed at the pressure given in the following Table IX into blocks as in the method of Example 1. An Eirich mixer 5. was used in Examplec; 7 to 9.
After drying at 110 C for 4 hours the blocks were fired for 24 hours at the different temperatures which are also given in the table. The properties of the block~ obtained are given in the table.
10. A portion of this mixture was also pressed into plates with dimensions 360 x 360 x 18 mm in a hydraulic plate press instead of into blocks with the dimensions given in Example 1. Such plates constitute an excellent firing aid, e.g. as a support 15. for fine-ceramic products or porcelain when being fired.
Table IX
ExamPle 6 _ 7 8 9 Pressing pressure 20. ~N/mm ) 8 30 30 30 Compression factor 3.8 5.3 5.3 5.3 Drying temperature ( C) 110 110 110 110 Firing temperature ( C) 1350 1520 1580 1620 Properties:
25. R (g/cm ) - 0O57 1.22 1.22 1.31 Pg (Vol.~) 79.9 62.1 6~.2 59.3 Cold bending strength (N/mm ) 0.4 3.5 3.6 4.2 Hot bending strength, 30. 1000 C (N/mm2) 0.8 Hot bending strength, 1400 C' (~J/~ ) 0.8 4.5 4.9 5.6 Thermal conductivity (W/m K at 700C) 0.22 0.47 0.49 0.53 --- - 24.
Example 10 The following composition was used:
Parts ~y weight Fix~dgranular material a) 80 Ceramic fibres B) 20 5. Bonding clay with 35% by weight Very finely ground alumina, < 44 ~m Very finely ground chromium oxide, 10. < ~4 ~m 2 Monoaluminium phosphate solution (50% by weight) 5 Solid sodium polyphosphate 0.5 Water 5 15.
rrhe fired granular material, the clay, the alumina and the chromium oxide were put with the solid sodium polyphosphate into an Eirich mixer, then 5 parts by we~ght water were sprayed on and mixed for 5 minutes.
20. subsequently the 20 parts by weight of ceramic fibres B) were added and mixed in for a further 10 minutes.
Then the monoaluminium phosphate solution was added and mlxed for a further 10 minutes. The mixture was removed from the mixer, pressed into plates of 25. 405 x 135 x 15 mm at a pressing pressure of 30 N/mm , subsec~uently dried for 24 hours at 110 C and then fired at 800C or 1350C for 8 hours. The following properties were cletermined on the product obtained:
- 25.
Table X
Firin.g temperature ~ C) 800 1350 R ~ / 3) 1.8 1.8 Compression factor 2.0 2.0 5. PcJ (Vol.%) 35.8 35~8 Cold bendlng strength (~/~m2) 2.65 6.4 Hc)t bending strength., 1000 C (N/mm ) 4.5 7,0 10. Thermal conductivity (W/m K at 700 C) 0.70 0.65 Example 11 The following composition was used:
15. Parts by wei~t Ceramic fibres A) 100 Hollow sphere corundum, < 3 mm 10 Clay with 35~ A12Q3 5 Magnesia 2 20. Solid boron phosphate ~ 5 Water g Irhe fibres were firstly loosened for 10 minutes in an impact mixer. The hollow sphere corundum, 25. the clay and the water were put into an Eirich mixer, mixed for 5 minutes and then the magnesia and the boron phosphate were added and mixed in for a further 5 minutes. Subseque:ntly the fibres loosened in the impact mixer were put into the Eirich mixer and mixed 30. for a further 20 minutes.
~3Lg~5 26.
~ lates were produced from the mixture in accordance with the method of Example 10. These were fired after drying at 120 C at 800C or 1350C. The following properties were determined on the products obtained:
5, Table XI
Firing temperature :( C) 800 1350 R (g/cm ) 1.15 1.18 Compression factor 4.1 4.1 Pg (Vol.%) 51.9 54.6 10. Hot bending strength, 1000 C (N/mm ) 2.8 4.1 Thermal conducti~ity (W/m K at 700C) 0.63 0.65 15. Example 12 The following composition was used:
Parts by weight Ceram:ic fibres A) 100 Bo:nding clay 10 20~ Dry sulphite waste 9 .
Water The ceramic fibres, the clay and the solid sulphite waste were mixed for 10 minutes in an Eirich mixer, then the water was sprayed on and mixing was finished 25. after a further 10 minutes. Blocks were pressed as in Example 1 at a pressing pressure of 30.N/mm . After drying at 110 C for 24 hours these blocks were fired at 800 C or 1350 C. The following properties were determined on the blocks:
Table_XII
Firing temperature (C) 800 1350 R (g/cm ) 1.18 1~28 Compression factor 5.1 5.1 5. p~ (Vol.~) 54.6 52.6 Hot bending strength, 1000 C (N/mm ) 1.5 2.
Thermal conductivity (W/m K at 700C) 0.27 0.28
Claims (10)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A moulded article manufactured from the following composition:
100 parts by weight of either ceramic fibres or a mixture comprising at least 20% by weight ceramic fibres and up to 80% by weight of a fired, bonded, granular material comprising ceramic fibres, bonding agent and refractory ma-terial 2 to 20 parts by weight clay and at least one compound selected from Al2O3, SiO2, aluminium hydroxides, magnesia, titanium dioxide and chromium oxide, 0 to 8 parts by weight phosphate bonding agent, calculated as P2O5, 0 to 10 parts by weight of an organic bonding agent, and 0 to 10 parts by weight other refractory additives.
the composition containing at least 2 parts by weight of bonding agent, the article having a density of 0.5 to 1.8 g/cm3 and a hot bending strength at 1000°C of at least 0.8 N/mm2.
100 parts by weight of either ceramic fibres or a mixture comprising at least 20% by weight ceramic fibres and up to 80% by weight of a fired, bonded, granular material comprising ceramic fibres, bonding agent and refractory ma-terial 2 to 20 parts by weight clay and at least one compound selected from Al2O3, SiO2, aluminium hydroxides, magnesia, titanium dioxide and chromium oxide, 0 to 8 parts by weight phosphate bonding agent, calculated as P2O5, 0 to 10 parts by weight of an organic bonding agent, and 0 to 10 parts by weight other refractory additives.
the composition containing at least 2 parts by weight of bonding agent, the article having a density of 0.5 to 1.8 g/cm3 and a hot bending strength at 1000°C of at least 0.8 N/mm2.
2. An article as claimed in Claim 1 in which the clay is bentonite.
3. An article as claimed in Claim l or Claim 2 which contains porcelain powder, fire clay or hollow sphere corundum as a further refractory additive.
4. An article as claimed in Claim 1 in which the phosphate bonding agent is sodium polyphosphate or monoaluminium phosphate.
5. An article as claimed in Claim 1 in which the organic bonding agent is methyl cellulose.
6. A process for the manufacture of a moulded article including the following steps:
a) 100 parts by weight of either ceramic fibres or a mixture comprising at least 20% by weight ceramic fibres and up to 80% by weight of a fired bond-ed granular material comprising ceramic fibres, bonding agent and refractory material are thoroughly mixed with 2 to 20 parts by weight clay and at least one compound selected from Al2O3, SiO2, aluminium hydroxides, magnesia, titani-um dioxide and chromium oxide, 0 to 8 parts by weight phosphate bonding agent, calculated as P2O5, 0 to 10 parts by weight of an organic bonding agent, at least 2 parts by weight of bonding agent being present, water and 0 to 10 parts by weight other refractory additives, b) the mixture obtained in step a) is compressed by a minimum volume factor of 3 when only using ceramic fibres decreasing linearly to 1.5 when using a mixture of 80 parts by weight of the bonded granular material and 20 parts by weight ceramic fibres whilst moulding the mixture to the desired shape, and c) the moulded article manufactured in step b) is then treated by at least one of the steps of drying, tempering and firing.
a) 100 parts by weight of either ceramic fibres or a mixture comprising at least 20% by weight ceramic fibres and up to 80% by weight of a fired bond-ed granular material comprising ceramic fibres, bonding agent and refractory material are thoroughly mixed with 2 to 20 parts by weight clay and at least one compound selected from Al2O3, SiO2, aluminium hydroxides, magnesia, titani-um dioxide and chromium oxide, 0 to 8 parts by weight phosphate bonding agent, calculated as P2O5, 0 to 10 parts by weight of an organic bonding agent, at least 2 parts by weight of bonding agent being present, water and 0 to 10 parts by weight other refractory additives, b) the mixture obtained in step a) is compressed by a minimum volume factor of 3 when only using ceramic fibres decreasing linearly to 1.5 when using a mixture of 80 parts by weight of the bonded granular material and 20 parts by weight ceramic fibres whilst moulding the mixture to the desired shape, and c) the moulded article manufactured in step b) is then treated by at least one of the steps of drying, tempering and firing.
7. A process as claimed in Claim 6 in which the compression in step b) is carried out by a factor of 5 to 8 when only using ceramic fibres decreasing linearly to a factor of 2.5 to 4 when using a mixture of 80 parts by weight of the bonded granular material and 20 parts by weight ceramic fibres.
8. A process as claimed in Claim 6 in which the mixture is moulded into plates whilst compressing it in step b).
9. A process as claimed in Claim 6 in which the ceramic fibres are loosened ceramic fibres.
10. A method of using the moulded article as claimed in Claim 1 which comprises disposing said moulded article as a support for an object to be fired in a furnace, and then firing said object.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP3105534.6 | 1981-02-16 | ||
| DE3105534A DE3105534C2 (en) | 1981-02-16 | 1981-02-16 | Process for the production of a molded part and its use |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1190945A true CA1190945A (en) | 1985-07-23 |
Family
ID=6124956
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000396255A Expired CA1190945A (en) | 1981-02-16 | 1982-02-15 | Moulded articles |
Country Status (14)
| Country | Link |
|---|---|
| JP (1) | JPS57145084A (en) |
| BE (1) | BE892072A (en) |
| CA (1) | CA1190945A (en) |
| DD (1) | DD202135A5 (en) |
| DE (1) | DE3105534C2 (en) |
| FR (1) | FR2499972A1 (en) |
| GB (1) | GB2093009B (en) |
| IT (1) | IT8247787A0 (en) |
| NL (1) | NL8200598A (en) |
| NO (1) | NO820440L (en) |
| PL (1) | PL235102A1 (en) |
| SE (1) | SE8200858L (en) |
| YU (1) | YU31782A (en) |
| ZA (1) | ZA821007B (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3230253C2 (en) * | 1982-08-13 | 1987-03-19 | Didier-Werke Ag, 6200 Wiesbaden | Plastic fibre material for refractory applications and its use |
| EP0109241B1 (en) * | 1982-11-05 | 1990-07-18 | Donald Boden | Manufacture of composite of metal and synthetic inorganic fibrous material |
| JPS61168582A (en) * | 1985-01-18 | 1986-07-30 | 株式会社 興人 | Manufacture of inorganic formed body |
| DE3543311A1 (en) * | 1985-12-07 | 1987-06-11 | Didier Werke Ag | DEVICE FOR JOINING PARTS |
| JPH0627027B2 (en) * | 1986-12-18 | 1994-04-13 | 日本軽金属株式会社 | High-strength ceramic material manufacturing method |
| GB8906916D0 (en) * | 1989-03-28 | 1989-05-10 | Foseco Int | Refractory supports |
| NZ259123A (en) * | 1992-11-25 | 1997-02-24 | Khashoggi E Ind | Sheets having an inorganically filled matrix with a water dispersible organic polymer binder, fibrous material and an aggregate material |
| GB2290604A (en) * | 1994-06-14 | 1996-01-03 | Ea Tech Ltd | Apparatus and method for firing ceramic sheets |
| US5603760A (en) * | 1995-09-18 | 1997-02-18 | W. R. Grace & Co.-Conn. | Cement admixture capable of inhibiting drying shrinkage and method of using same |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3336716A (en) * | 1963-07-10 | 1967-08-22 | Johns Manville | Furnace combustion chamber with a transverse composition differential |
| GB1140734A (en) * | 1965-12-30 | 1969-01-22 | Johns Manville | Sag resistant mineral wool boards |
| DE2230429A1 (en) * | 1972-06-22 | 1974-01-10 | Vyzk Ustav Stavebnich Hmot V B | Large fibre-board prodn - using a starch-phosphoric acid react prod as binder |
| DE2618813C3 (en) * | 1976-04-29 | 1978-11-16 | Heinz Christian 6360 Friedberg Krebs | Spray-on composition containing inorganic fibers and binders for sound, heat and fire protection insulation |
| US4248664A (en) * | 1978-06-20 | 1981-02-03 | Turner & Newall Limited | Fibrous sheet materials |
-
1981
- 1981-02-16 DE DE3105534A patent/DE3105534C2/en not_active Expired
-
1982
- 1982-02-08 JP JP57017694A patent/JPS57145084A/en active Pending
- 1982-02-09 BE BE0/207264A patent/BE892072A/en not_active IP Right Cessation
- 1982-02-12 IT IT8247787A patent/IT8247787A0/en unknown
- 1982-02-12 SE SE8200858A patent/SE8200858L/en not_active Application Discontinuation
- 1982-02-12 DD DD82237378A patent/DD202135A5/en unknown
- 1982-02-15 YU YU00317/82A patent/YU31782A/en unknown
- 1982-02-15 GB GB8204313A patent/GB2093009B/en not_active Expired
- 1982-02-15 NO NO820440A patent/NO820440L/en unknown
- 1982-02-15 CA CA000396255A patent/CA1190945A/en not_active Expired
- 1982-02-15 FR FR8202453A patent/FR2499972A1/en active Granted
- 1982-02-16 NL NL8200598A patent/NL8200598A/en not_active Application Discontinuation
- 1982-02-16 PL PL23510282A patent/PL235102A1/xx unknown
- 1982-02-16 ZA ZA821007A patent/ZA821007B/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| NL8200598A (en) | 1982-09-16 |
| SE8200858L (en) | 1982-08-17 |
| ZA821007B (en) | 1983-01-26 |
| DD202135A5 (en) | 1983-08-31 |
| FR2499972B1 (en) | 1985-05-03 |
| YU31782A (en) | 1985-04-30 |
| DE3105534C2 (en) | 1985-07-11 |
| DE3105534A1 (en) | 1982-09-02 |
| FR2499972A1 (en) | 1982-08-20 |
| NO820440L (en) | 1982-08-17 |
| GB2093009A (en) | 1982-08-25 |
| IT8247787A0 (en) | 1982-02-12 |
| JPS57145084A (en) | 1982-09-07 |
| BE892072A (en) | 1982-05-27 |
| PL235102A1 (en) | 1982-10-11 |
| GB2093009B (en) | 1984-09-05 |
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