Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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
.~ .
- - \
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
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
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
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~ .
- ---- 5
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
A123 5
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
