Title of Invention

HONEYCOMB FILTER FOR CLARIFYING EXHAUST GAS AND METHOD FOR MANUFACTURE THEREOF

Abstract To provide a honeycomb filter for cleaning an exhaust gas, which is excellent in heat resistance and thermal shock resistance and has high thermal decomposition 5 resistance and high mechanical strength and which is thus capable of being used with stability at high and fluctuating temperatures, and a process for its production. A honeycomb filter for removing solid particles 10 containing carbon as the main component in an exhaust gas, characterised m that the material for the honeycomb filter is an aluminum titanate sintered product obtained by firing at from 1,250 to l,700°C a raw material mixture comprising 100 parts by mass of a mixture (component X) 15 comprising TiO2; and A12O3, in a molar ratio of the farmer/the latter being 40 to 6 0/6O tc 40, and from 1 to 10 -parts by mass of an alkali, feldspar represented by the empirical formula {NayKi-y)AlSi3O3 (wherein O<y<l) , an oxide having a spinel structure containing Mg, or MgO or 20 an Mg-containing compound which will be converted to MgO by faring (component Y)
Full Text 1
DESCRIPTION
HONEYCOMB FILTER FOR CLARIFYING EXHAUST GAS AND METHOD
FOR MANUFACTURE THEREOF
5
TECHNICAL FIELD
The present invention relates to a honeycomb filter
for cleaning an exhaust gas, to capture and remove fine
Solid particles (participates) containing carbon as the
10 main component, contained in an exhaust gas from e.g. a
Diesel engine, and a process for its production
BACKGROUND ART
In an exhaust gas from eg a Diesel engine of eg
15 an automobile, participates containing carbon as the main
component are contained in a substantial concentration
(from 150 to 25 0 mg/Nm3) and thus cause an environmental
problem together with nitrogen oxides, etc. Accordingly,
it is desired to remove them efficiently and economically
20 Heretofore, various filters have been proposed to capture
and remove such fine solid particles contained in exhaust
gases
For example, JP-A-57-35918 or JP-A-5-214922
discloses an exhaust gas filter wherein a plurality of
25 channels in a honeycomb filter are alternately plugged at
the upstream end or the downstream end A honeycomb
filter of this type has a structure such that a

2
combustion exhaust gaa to be cleaned, is supplied to
openings on the upstream side of the filter and permitted
to pass through partition walls of the filter, so that
particulates in the exhaust gas are captured and removed
5 by partition walls, and then, the exhaust gas after
cleaning is taken out from openings at the downstream
side of the filter.
On the other hand, the material for such a honeycomb
filter is required to have not only high heat reelstance
10 but also a small thermal expansion coefficient and high
thermal shock resistance, since it is exposed to a
rapidly heated or cooled environment, and. accordingly,
silicon carbide or cordiente material has been proposed
and practically used However, such, a material still has
15 no adequate properties as an exhaust gas filter.
Namely, with an exhaust gas filter, it is likely
that when captured non-combustion carbonaceous fine solid
particles are abnormally deposited, such carbon will
catch-fire and burn, whereby an abrupt tensperature rise
20 will take place so that the temperature locally reaches
from 1,400 to l,500 QC. In such a case, a filter made of
silicon carbide material will have a temperature
distribution at various places of the filter, and the
thennal expansion coefficient is about 4.2x10-6K-1 i.e.
25 not so small, whereby cracks are likely to form by the
thermal stress or thermal shock exerted to the material,
thus leading to partial breakage. On the other hand, in

3
the case of a filter made of cordierite material, the
thermal expansion coefficient is small at a level of from
0.6 to 1.2x10-6K-1 whereby the problem of cracks due to
thermal shock is less, but the melting point is not so
5 high at a level of from 1,400 to l,450°C, whereby a
problem of partial melting due to the above-mentioned
abnormal combustion of carbon becomes serious
Once defects are formed in the interior of an exhaust
gas filter by the breakage or melting of the filter as
10 described above, the efficiency of the filter for
capturing carbon decreases, and. at the same time, the
pressure of the exhaust gas exerted to the filter will be
an excessive load to the defective portions and thus
induce new breakage. Consequently, the entire exhaust
15 gas filter will fail to function.
As the material for such a honeycomb filter,
WOO 1/037971 proposes aluminum titanate as well as silicon
carbonate or cordierite. Aluminum titanate is a material
having beat resistance at a high temperature exceeding
20 l,700°C and a small thermal expansion coefficient and
excellent thermal shock resistance. However, on the
other hand, aluminum titanate has a serious problem that
since it has a decomposition region usually within a
temperature range of from 800 to l,2800 C, it can not be
25 used with, stability within a fluctuated temperature
region containing such a temperature range. Further, it
has a difficulty each that since the anistropy of its

4
crystal structure is substantial, slippage by a thermal
stress is likely to take place, and the mechanical
strength is not high enough Accordingly, it still has
had a problem in its use for the production of a
5 honeycomb having a thin wall thickness and a high cell
density or in its use as an exhaust gas filter to be
subjected to a load such as mechanical vibration at a
high temperature, as mounted on an automobile or the
like
10
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide
a honeycomb filter for cleaning an. ejdiaust gas, which is
excellent in heat resistance, has a email thermal
15 expansion coefficient and excellent thermal shock
resistance, is free from thermal decomposition even at a.
high and fluctuating temperature and has high mechanical
strength so that it can be used with stability for a long
period of time and which is capable of capturing and
20 removing, with high efficiency, particulates such as fine
carbon particles contained in an exhaust gas from e.g. a
Diesel engine, and a process for its production.
As a result of an extensive study to solve the
above-mentioned problems, the present invention has been
25 accomplished by paying attention to aluminum titanate, on
the basis of a discovery such that a honeycomb filter for
cleaning exhaust gas, employing an aluminum titanate

5
sintered product obtainable by firing a mixture having a.
specific alkali feldspar, an oxide having a spinel
structure containing Mg, or MgO or an Mg-containing
compound to be converted to MgO by firing, added in a
5 prescribed ratio to a mixture comprising TiO2 and Al203 in
a prescribed ratio to form aluminum titanate, has high
mechanical strength and thermal decomposition resistance,
as different from conventional aluminum titanate sintered
products, while maintaining the excellent heat resistance
10 and high thermal shock resistance due to the small
thermal expansion coefficient as inherent properties of
conventional aluminum titanate sintered products.
Thus, the present invention provides the following:
(1) A honeycomb filter for cleaning an exhaust gas which
15 is a honeycomb filter for removing solid particles
Containing carbon as their main component in an exhaust
gas, characterized in that the material for the honeycomb
filter is an aluminum titanate sintered product obtained
by firing at from 1,250 to l,700*C a raw material mixture
20 comprising
100 parts by mass of a mixture [component X)
comprising T1O2 and AI2O3 in a molar ratio of the
former/the latter being 40 to 60/60 to 40, and
from 1 to 10 parts by mass of an alkali feldspar
25 represented by the empirical formula [NayKI-V) AlSi3O3
(wherein 0 containing Mg, or MgO or an Mg-containing compound which

6
will be converted to MgQ by firing (component Y).
(2) The honeycomb filter for cleaning an exhaust gaa
according to the above (1), wherein component y is a
mature comprising the alkali feldspar represented by
5 (NayK1-Y)AlSi3Oa [wherein O structure containing Mg and/or MgO or the Mg-containing
compound which will be converted to MgO by firing,
(3] The honeycomb filter for cleaning an exhaust gas
according to the above (1}, wherein the honeycomb filter
10 has a wall thickness of from 0,1 to 0 6 mm and a cell
density of from 15 to 93 cells/cm2, wherein the porosity
of the partition wall is from 30 to 70%, and the thermal
expansion coefficient is at most 3.0x10-6K-1.
(4} A process for producing a honeycomb filter for
15 cleaning an exhaust gas, characterised by preparing a
mixture comprising
100 parts by mass of a mixture (component X]
comprising TiO2 and A12O3 in a molar ratio of the
former/the latter being 40 to 60/60 to 40, and
20 from 1 to 10 parts by mass of an alkali feldspar
represented by the empirical formula (NayKa-y)AlSi3O3
(wherein 0 containing Mg, or MgO or an Mg-containing compound which
will be converted to MgO by faring {component Y), adding
25 a molding assistant to the mixture, followed by kneading
to plasticine the mixture to make it extrusion-
processable, extrusion processing it into a honeycomb

7
structure, followed by firing at from l,250 to l,700°C.
(5) The process for producing a honeycomb filter for
cleaning an exhaust gas according to the above (4)(
wherein component y is a- mixture comprising the alkali.
b feldspar represented by (NayKi-y}AlSi3Qs [wherein O and the oxide of a spinel structure containing Mg and/or
MgO or the Mg-containing compound which will be converted
to MgO by firing.
(6} An apparatus for cleaning an exhaust gas,
lo characterised in that the honeycomb filter for cleaning
an exhaust gas as defined m any one of the above (1) to
(3) is accommodated in a can,
(7) The apparatus for cleaning art exhaust gas according
to the above (6), which is used for cleaning an exhaust
15 gas of an automobile having a diesel engine mounted
The reason as to why the honeycomb filter made of
the aluminium titauate sintered produce according to the
present invention, has high thermal decomposition
20 resistance and high mechanical strength while maintaining
the inherent high heat resistance, small thermal
expansion coefficient and excellent thermal shock
resistance as described above, is not clearly understood,
but may probably be as follows.
25 Namely, by the addition of the alkali feldspar to
the mixture to form aluminum titanate, the reaction to
farm alumina titanate takes place in a liquid phase,

8
since the alkali feldspar is present which becomes a
liquid phase in the vicinity of the temperature at which
aluminum titanate will be formed, whereby dense crystals
will be formed to improve the mechanical strength. And,
5 the S1 component contained in the alkali feldspar will be
solid-solubilized in the crystal lattice of the aluminum
titanate and: will be substituted for Al. Si has a
smaller ion radius than Al, whereby the bond distance
from the surrounding oxygen atoma will be shortened, and
10 the lattice constant tends to have a small value as
compared with pure aluminum titanate It is considered
that aa a result, "the sintered product thus obtained
shows a very high thermal stability as the crystal
structure is stabilized, and the thermal decomposition
15 resistance is substantially improved
Further, in a case where an oxide having a spinel
structure containing Mg, or MgO or an Mg-containing
compound which will be converted to MgO by firing, is
added to the mixture to form aluminum titanate, it is
20 possible to obtain a dense sintered product and to form a
sintered product having a very high mechanical strength
as compared with pure aluminum titanate
Further, in a case where the alkali feldspar, and
the oxide having a spinel structure and/or MgO or the Mg-
25 containing compound which will be converted to MgO by
firing, are simultaneously added to the mixture to form
an aluminum titanate, S1 contained in the alkali feldspar

9
and Mg contained in the oxide of the spinel structure
and/or MgO or the Mg-containing compound which, will be
converted to MgO by firing, will be substituted mainly at
Al sites in the aluminum titanate if these elements are
5 added alone, a bivalent (Mg} or tetravalent (Si) element
would be substituted at Al sites where the balance at
electric charge is maintained with trivalency-
Accordingly, in order for the sintered product to
maintain the balance of electric charge, it as considered
10 that when Mg is added, oxygen is discharged out of the
system to create oxygen deficiency to maintain the
balance of electric charge, and when S1 is added, since
S1 is tetravalent, the tetravalent T1 will he reduced to
trivalent to take the balance of electric charge
15 On the other hand, Mg is smaller by 1 in the
electric charge than Al, and Si is larger by 1 in. the
electric charge than Al. Thus, it ia considered possible
to take the balance of electric charge by simultaneously
adding the alkali feldspar and the oxide having a spinel
20 structure and/or MgO or the Mg-containing compound which
will be converted to MgO by firing, and it will be
possible to solid-solubilise them without presenting an
influence over other elements constituting the sintered
product.
21 It ia considered that especially when the alkali
fel&srpar, and the oxicte of spinel structure and/or MgO or
the Mg-containing compound which will be converted to MgO

10
by firing, are added in a ratio close to an equitmolar
ratio, tine additives can be present more stably as
compared With a case where they are added alone. It ie
considered that for these reasons, both act
5 synergistically to substantially improve the strength as
compared with a case where they are used alone, and it is
possible to form an aluminum titanate sintered product
which has a high mechanical strength without impairing
the low thermal expansion property inherent to aluminum
10 titanate and which at the same time has improved thermal
decomposition resistance
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a perspective view showing an. embodiment of
15 a honeycomb filter for cleaning an exhaust gas of the
present invention, as partly cut off
Fig. 2 is a diagrammatical View shoeing the end face
of the honeycomb filter in Fag 1
Fig. 3 is a cross-sectional diagrammatical view along
20 line A-A of the honeycomb filter in Fig. 2.
Fig. 4 shows the changes with time of the remaining
ratios £ of alummunium titanate with respect to the
sintered products in Examples 1 and 2 and Comparative
Example 2
25 MEANING OF SYMBOLS
1: honeycomb filter 2: partition wall
3:through-hole 4,5: blockers

11
BEST MODE FOR CARRYING OUT THE INVENTION
In the present invention, as the material for a
honey comb filter, an. aluminum titanate sintered product
is used which is obtained by fixing from 1,250 to l,7000C
5 a raw material fixture comprising 100 parts by mass of
component X comprising TiO2 and AL2O3- in a molar ratio of
the former/the latter being 40 to 60/60 to 40, and from l
to 10 parts by mass of component y
The above TiO2 and A12O3 to form aluminum titanate may
10 not necessarily be pure TiO2 and AI2O3 respectively, and
they are not particularly limited so long as they are
components capable of forming aluminum titanate by firing.
Usually, they are suitably selected for use among those
employed as raw materials for various ceramics, such as
15 alumina ceramics, titania. ceramics and aluminum titanate
Ceramics Yor example, double oxides; carbonates,
nitrates or sulfates containing Al and Ti as metal
components way also be used.
TiO2 and Al2O3 are used in a molar ratio of the
20 former/latter being 4 0 to 60/60 to 40, preferably 45 to
5 0/55 to 60. It is possible to avoid the eutectic point
of the fired product especially by adjusting the molar
ratio of Al2O3/TiO2 to be at least X within the above
range. In the present invention, Al2O3 and TiO3 are used
25 as a mixture, and an this invention, such a mixture may
sometimes be referred to as component X
In the case of the honeycomb filter ot the present

12
invention, it is necessary to add component Y as an
additive to the above component X, As the alkali
feldspar as one of component Y, one represented by the
empirical formula (NayK1-y)AlSi3O8 may be used. In the
5 formula, y satisfies 0≤y≤1, prsferably 0.1≤y≤1
particularly preferably 0 1≤y≤0 85 The alkali feldspar
having value y within this range his a low melting point
and is particularly effective for acceleration of the
sintering of aluminum titanate.
10 As the oxide having a spinel structure containing Mg
as another component y, MgAl2O4 or MgTi2O4 may, for
example, be used Such an oxide having a spinel
structure may be a natural mineral, or a material
containing MgO and Al203, a material containing MgO and
15 TiO2, or a spinel-form oxide obtained by firing such a
material Further, two or more oxides having different
types of spinel structures may be used in combination as
a. mixture. Further, as a MgO precursor, any material may
be used so long as it is capable of forming MgO by firling
20 and for example, MgCO3, Mg{NO3)2, MgSO4 or a mixture
thereof may be mentioned.
The ratio of the above components X and y is
important, and component Y is from 1 to 10 parts by mass
par 100 parts by mass of component x This is a ratio
25 where components X and y are oxides respesctively, and
when raw materials other than oxides are used, values
calculated as oxides will be employed. If component Y is

13
smaller than 1 part by mass per 100 parts by mass of
component X, the effect for improving the properties of
the sintered product by the effect of addition of
component Y, will be small On the other hand, if it
5 exceeds 10 parts by mass, such will exceeds the solid-
solubilization limit of the Si or Mg element in the
aluminum titanste crystals, and the excess component
added in excess will toe present in an independent oxide
an the altered product and tends to increase the thermal
10 expansion coefficient, such being undesirable It is
particularly preferred that component 1 ie from 3 to 7
parts by mass per 100 parts by mass of component X
Further, in the present invention, it is preferred
that as the above component y, the alkali feldspar
15 represented by the empirical formula (NayK1-y)AlSi3O8, and
the oxide having a spinel structure containing Mg arid/or
MgO or its precursor, are used in. combination as a
mixture. When such a, mixture is used, the above
mentioned synergistic functional improvement can be
20 obtained, The mixture of the above feldspar (former),
and the oxide having a spinel structure containing Mg
and/or MgO or its precursor flatter) preferably has a
mass ratio of the former/the latter being 2 0 to SO/SO to
40, particularly preferably 35 to 45/65 to 55 In the
25 above range, the ratio of Si/Mg will be equimolar, and j.f
the ratio is not within this range, the synergistic
effect by the simultaneous solid-solubilizaticn of Si and

14
Mg in aluminum titanate tends to be hardly obtainable,
such being undesirable.
In the preeent invention, in addition to the above
components X and Y, other sintering assistants may be
5 employed as the case requires, whereby the nature of the
obtainable sintered product can be improved As such
other sintering assistants, SiO2, Zno2, Fe3O3, CaO and Y2O3
may, for example, be mentioned
The raw material mixture comprising the above
10 components X and y is sufficiently mixed and pulverised
The mixing and pulverization of the raw material mixture
is not particularly limited and may be carried out by a
known method For example, they may be carried out by
irteans of e g. a ball mill or a medium-agitation mill.
15 The degree of pulverization of the raw material mixture
is not particularly limited, but the average particle
size is preferably at most 3 0 urn, particularly preferably
from S to 15 μn. The average particle size should better
be small so long as at is within a range where no
20 secondary particles "Will be formed
Molding assistant may preferably be incorporated to
the raw material mixture. As auch molding assistants,
known agents such as a binder, a pore-forming agent, a
release agent, a defearning agent and a peptiser may be
25 employed. As the binder, polyvinyl alcohol, microwax
emulsion, methyl cellulose or carboxymethyl cellulose may,
for example, be preferred. As the pore-forming agent,

15
activated carbon, coke, a polyethylene regin, starch or
graphite may, for example, be preferred As the release
agents a stearic acad emulsion may, for example, be
preferred, as the defoaming agent, n-octyl alcohol or
5 octylphenoxyethanol may, for example, be preferred, and
ag the peptizer, diethylamine or triethylanune may, for
example, be preferred
The amounts o£ the molding assistants are not
particularly limited. However, in the case of the
10 present invention, they are preferably within the
following ranges, respectively, as calculated as solid
contents, per 100 parts by maas o£ the total amount of
componetits X and V (as calculated as the respective
oxides) to bs used aa the starting waiterials. Namely, it
15 is preferred to use the binder in. an amount of from about
0 2 to 0,6 part by mass, the pore-forming agent in an
amount ot from about 40 to 60 parts by mass, the release
agent m an amount of from about 0 2 to 0 7 part by mass,
the defoaming agent in an amount of from about 0.5 to 1.5
20 parts by mass &nd the peptizer in an amount of from about
0.5 to 1.5 pares by mass.
The raw material mixture having such molding
assistants incorporated, is mixed, kneaded and
plasticized so that it is extruaion-procesgable, followed
25 by extrusion processing to form a honeycomb structure,
As the method for extrusion, a known method may be used,
and the shape of each cell of the honeycomb may be

15
circular, oval, tetragonal or triangular Further, the
entire configuration of the honeycomb molded product may
be either cylindrical or square tubular. The molded
honeycomb bady is preferably dried and then fired at from
5 1,250 to l,7000C, preferably from 1,300 to l,450°C. The
firing atmosphere is not particularly limited and is
preferably an oxygen-containing atmosphere such as in the
air which is commonly employed The firing time is not
particularly limited so long as the firing can be done
io until the sintering proceeds sufficiently, and it is
usually at a level of from 1 to 20 hours.
Also twith respect to the temperature raising rate or
the temperature lowering rate at the time of the above
firing, there is no particular restriction, and such
15 conditions may the suitably set so that no cracks will be
formed in the obtainable sintered product. For example,
it is preferred to gradually raise the temperature
without rapid rise of the temperatnre to sufficiently
remove the molding assistants such. as moisture., a. binder,
20 etc. contained in the raw material mixture, Further, if
necessary, prior to heatting at the above-mentioned firing
temperature, presintering may be carried out preferably
within a. temperature raiyge of from 500 to l,0000C for
from 10 to 30 hours by mild temperature raise, whereby
25 the etress in the sintered product which causes cracking
during the formation of aluminimum titemate, can be relaxed,
and formaticm of cracks in the sinteyed product can be

17
suppressed to obtain a uniform sintered product.
The sintered product thus obtainable will be one
having, as the basic component, aluminum titanate formed
from component X and having a Si component contained in
5 the alkali feldspar and the Mg component derived from the
oxide having a spinal structure containing Mg, MgO or the
Mg-containing compound which will be converted to MgO by
firing, as component Y, solid-solubilized in the crystal
lattice of the aluminum titanate Such a sintered
10 product has high mechanical strength and a low thermal
expansion coefficient and yet has a crystal structure
stabilised, as mentioned above, and will thus be a
sintered product having excellent heat decomposition
resistance
15 As a result, a honeycomb filter made of such a.
sintered product has a thin wall honeycomb structure
having a wall thickness of e g from 0.1 to 0.6 mm,
preferably from 0-3 to 0 48 mm and a cell density of eg
from IS to 93 cells/cm2 And, the porosity of the
20 partition wall is, for example, from 30 to 70%,
preferably from 40 to 60%, and the thermal expansion
coefficient 19 e.g. at most 3.0xl0-6K-1, preferably at
most 1.5xl0-6K-1. Such a honeycomb filter cart be used
with stability, from room temperature to l,600°C as the
25 thermal decomposition reaction of aluminum titanate is
suppressed even at a high temperature.
Fig. 1 is a. perspective view of an embodiment of the

16
honeycomb filter for cleaning an exhaust gas of the
present invention Fig. 2 is a diagrammatical view
showing the end face of the honeycomb filter in Example 1.
Fig. 3 is a diagrammatical view of the cross-section
5 along line A-A of the honeycomb filter in Fig. 2. In
these Figs , the honeycomb filter 1 for cleaning an
exhaust gas h&a both ends alternately plugged by blockers
4 and 5 at the upstream side and at the downstream side
of a honeycomb filter comprising through-holes 3
10 constituted by many partition walls 2. Namely, as shown
in Fig. 2, at the upstream or downstream eide end, the
throughw holes 3 are plugged with blockers 4 or 5 in a
lattice form, and with rfispect to each through-hole 3,
either the upstream or downstrearn side end is plugged
15 with a blocker 4 or 5, To such a honeycomb body, an
exhaust gas to be cleaned la supplied to through.-holes 3
on the upstream side of the honeycomb body and passed
through the partition walls 2 to have particulars in the
exhaust gas captured and removed by the partition walls 2,
20 and then, the exhaust gas after the cleaning is taken out
from the through-holea 3 on the downstream side.
The honeycomb product of the present invention
formed as a honeycomb filter for cleaning exhsmet gas is
preferably set in a can body by means of a s-uitable
25 supporting material and is "used "to capture and remove
fine solid particles (particulates) contaming carbon as
the main component, contained in an exhaiist g&s, With

13
respect to the type of the exhaust gas, any gas
discharged from a combustion source of either a
stationary body or a mobile body may be treated However,
as mentioned above, the honeycomb filter is particularly
5 useful for cleaning an exhaust gas from an automobile
having a Diesel engine mounted where the severest
properties are required
10 Now, the present invention will be described in
further detail with reference to Examples. However, it
should be understood that the present invention is by no
means thereby restricted
EXAMPLE 1
15 To 100 parts by mass of a. mixture comprising 56.1
mass% (50 mol%} of easily sinterable α-alumina and 439
mass% (50 nol%) of anatase-type titanium oxide( 4 parts
by mass of an alKali feldspar represented by
(Na0 6K0 4)AlS1jO8 6 parts by mass of a spinel compound
20 represented by a chemical formula MgAl2O4 0 25 parts by
mass of polyvinyl alcohol as a binder, 1 part by mass of
diethylamine as a peptizer, 0,5 part by mass of
polypropylene glycol as a defoaming agent, and 50 parts
by mass of activated carbon having a particle size of
25 from 50 to 80 μm ag a pore-forming agent, were added,
mixed for 3 hours in a ball mill and then dried in a
dryer at a temperature of 120°C for at least 13 hours to

20
obtain a raw material powder
The obtained raw material powder was pulverized to an
average particle size of at most 10 ΜM and farmed by a
vacuum forming machine (manufactured by Miyazaki Iron
5 Works Co , Ltd ) to obtain a honeycomb formed product.
This formed product was dried and then fired in the
atmosphere at l,500°C for 2 hours and then left to cool,
to obtain a totally cylindrical honeycomb filter having
cross-sectionally square cells, as shown in Figs 1 to 3.
10 The honeycomb filter had a wall thickness of 0.38 mm and
a cell density of 31 cells/cm2, and the outer diameter o£
tile cylindar was 144 mm and the length. was 152 mm
COMPARATIVE EXAMPLE 1
A honeycomb filter made of an aluminum titanate
is sintered product, was obtained in the same manner as in
Example 1 except that no alkali feldspar was used
EXAMPLE 2
To 10 0 parts by mass of a mixture comprising 56,1
mass% {50 mol%) of easily sinterable α-alumina and 43.9
20 mass%- (50 mol%) o£ anatase-type titanium oxide, 4 parts
by mass of an alkali feldspar represented by
(Na0 6K0 4)AlS1O8 6 parts by mass of a spinel compound
represented by a. chemical formula MgAl7O4 0 25 part by
tnasa of polyvinyl alcohol as a binder, i part by mass of
25 diethylamine as a peptizer, 0 5 part by mass of
polypropylene glycol as a deforming agent, and 50 parts
by mass of activated carbon having a particle size of

21
from 50 to 80 yon as a pore-forming agent, were added and
mixed for 3 hours in a ball mill and then dried in a
dryer at 120°C for at least 13 hours to obtain a raw
material powder,
5 Using the obtained raw material powder, pulverisation,
forming, drying and firing were carried out in the same
manner as in Example 1 to obtain a honeycomb filter
EXAMPLE 3
To 100 parts by mass of a mixture comprising 56.1
10 mass% (50 mol%} of easily sinterable α-alumina and 43 9
mass% (50 mol%) of anatase-type titanium oxide, 6 parts
by mass of a spinel compound represented by a chemical
formula MgAl2Q4 as an additive, 0.25 part by mass of
polyvinyl alcohol as a binder, 1 part by mass of
15 diethylamine as a peptizer, 05 part by mass of
polypropylene glycol as a defoaming agent, and 50 parts
by mass of activated carbon having a particle size of
from SO to 80 μm as a pore-forming agent, were added and
mixed for 3 hours in a ball mill and then dried, in a
20 dryer at 120°C for at least 12 hours to obtain a raw
material powder
Using the obtained raw material powder, pulverization,
forming, drying and firing were carried out in the same
manner as in Exainple 1 to obtain a honeycomb filter.
25 COMPARATIVE EXAMPLES 2 and 3
As materials for honeycomb filters, commercially
available silicon carbide powder (tradename SHOCERAM,

22
manufactured by SHOWA DENKO K K) and cordierite powder
(2MgO.2Al2O3.5SiO2)) were respectively used, and from these
materials, honeycomb filters were obtained by carrying
out the conventional methods respectively Here, the
s honeycomb made of silicon carhade will be referred to as
Comparative Example 2, and the honeycomb made of
cordiente as Comparative Example 3
FROPERTY TESTS WITH RESPECT TO HONEYCOMB SINTERED
PRODUCTS
10 With respect to the honeycomb filters obtained in the
above Examples l, 2 and 3 and Comparetive Examples 1, 2
and 3, the porosity (%), the thermal expansion
coefficient (xlO-6K-1) at from room temperature to 800°C,
the thermal shock resistance (0C) by art in-water dropping
15 method, the softening temperature {°C) and the
compression strength (MPa) were measured, and the results
are shown in Table 1 Here, the porosity was measured by
a method in accordance with JIS R1634, the thermal
expansion coefficient by a method in accordance with JIS
20 R1G18, the thermal shocK resistance by a method in
accordance with jIS Rl648f the softening temperature by a
method in accordance with JIS R22 09, and the coropression
Strength by a method an accordance with JIS R160S.
Further, with respect to the compression strength, from
25 each honeycomb filter, a square test specimen having
cross-sectionally 5x6 cells and a length of 15 mm, was
cut out, and this specimen was measured from three

23
directions i,e. (A) In the lengthwise axial direction
(axial) , (B) in the vertical direction (tangential) and
(C) in the direction inclined by 45° from the lengthwise
axis (diagonal).

TABLE 1

Porosity{%) Thermal expansion Thermal shock Softening temperature Compression strength
coefficient resistance CO (A) (C)
Example 1 43 1.2 950 1570 >5.0 >2.5 >! 2
Example 2 S3 1.5 3SD 1620 >8.3 >5 1 >1 0
Example 3 51 0 9 122 0 1680 >4 1 >1.9 >1 0
Comparativs Example 1 41 0.3 980 1680 >0.4 >0 1 >0 ,1
Comparative Example 2 42 4 0 400 - >6.0 >5 0 >1.5
Comparative Example 3 45 650 650 1320 >10 >1.3 >0.2

25
As is evident from Table l, each of the honeycombs in
Examples l) 2 and 3 and Comparative Examples 2 and 3, has
a porosity within a. range of from 40 to 60% and a high
compression strength sufficient tor mounting
5 Comparative Example 1 is inadequate for mounting
However, it is evident that each of the honeycombs in
Examples 1, 2 and 3 has a thermal expansion coefficient
very much smaller" than that in Comparative Example 2 and
has a softening temperature very much higher than that in.
10 Comparative Example 3, Further, it is evident that with,
respect to the thermal shock resistance, each of the
honeycomb sintered products in Example 1, 2 and 3 has a
property very much, higher than that in Comparative
Example 2 or 3
15 THERMAL DECOMPOSITION RESISTANCE TEST
From each of che honeycomb filters in Examples 1 and
2 and Comparative Example 1, a test specimen of 10 mm x
10 mm * 10 mm was cut out and held in a high temperature
atmosphere of l,000°C, whereby the change with time of
20 the remaining ratio 0 (%) of aluminum titanate was
investigated to carry out a thermal decomposition
resistance test
Here, the remaining ratio of aluminum titanate was
obtained by the following method from the spectrum of the
25 X-ray diffraction measurement (XRD)
Firstly, as A12O3 (corundum) and TiOs (rutile) are
formed when aluminum titanate undergoes thermal

26
decomposition, using the integrated intensity (Ifio2(mol)
of the diffraction peaK at the {110} face of rutile and
the integrated intensity (IAT (0231)) of the diffraction peak
at the (023) face of the aluminum titanate, the intensity
5 ratio r of aluminum titanate to rutile was obtained by
the following formula:
Farther, also with respect to the sintered product
before carrying out the thermal treatment at l.000 0C, the
10 intensity ratio r0 of aluminum titanate to rutile was
obtained in the same manner Then, uemg r and r0
obtained as described above, the remaining ratio 6(%) of
aluminum titanate was obtained by the following formula
P=(r/r0) * 100
15 With, respect to the respective honeycomb-shaped
sintered products in Examples 1 and 2 and Comparative
Example l, the changes with time of the remaining ratios
β of the respective crystals are shown by a graph in Fig.
4 As is evident from Fig. 4, Examples 1 and 2 are
20 superior in the thermal decomposition resistance, as the
remaining ratios are maintained at high levels over a
long time, as compared with Comparative Example 1.
Further, it is evident that while the remaining ratio in
Example 1 after expiration of 50 hours in. Fig- 4 is
25 slightly low, the remaining ratio in Example 2 is still
maintained at a high level and thus shows that the
thermal decomposition resistance is further improved over

27
Example 1.
INDUSTRIAL APPLICABILITY
The honeyscomb filter material made of an aluminum
5 titanate sintered product by the present invention, is
excellent in heat resistance and has high heat
decomposition resistance and high mechanical strength,
while maintaining a small thermal expansion coefficient
and heat: shock resistance, and thus has substantially
10 superior properties as compared, with conventional filter
materials. As a result, the honeycomb filter for exhaust
gas of the present invention is useful to remove fine
solid particles is. an exh&ust gae from a combust ion
source of either a stationary body or a mobile body,
15 Especially, as mentioned above, it is most suitable for
cleaning an exhaust gas froim an automobile having a
Diesel engine mounted, where the severest properties are
demanded -

28
CLAIMS
1. A honeycomb filter for cleaning an exhaust gas which
is a honeycomb filter for removing solid particles
containing carbon as their mam component in an exhaust
5 gas, characterised an that the material for the honeycomb
filter is an aluminum tita.na.te sintered product obtained
by firing at from 1,250 to l,700 0C a raw material mixture
comprising-
100 parts by mass of a mixture {component X)
10 comprising TiO2 and Al2O3 m a molar ratio of the
former/the latter being 40 to 6O/60 to 40, and
from 1 to 10 parts by mass of an alkali feldspar
represented by the empirical formula. (Nay K1 4)AlS1jO8
wherein 0 15 containing Mg, OT MgO or an Mg-containing compound which
will be converted to MgO by firing [component Y]
2. The honeycomb filter for cleaning an exhaust gas
according to Claim 1, wherein component Y is a mixture
comprising the alkali feldspar represented by {NayK1.
20 y)AlSi302 (wherein 0 structure containing Mg and/or MgO or the Mg-contailing
compound which will be converted to MgO by iiring
3 The honeycomb filter for cleaning an exhaust ga.s
according to Claim 1, wherein the honeycomb filter has a
25 wall thickness of from 0 1 to o 6 mm and a cell density
of from 15 to 93 cells/cm2, wherein the porosicy of Che
partition wall 13 from 3 0 to 704, and the thermal

29
expansion coefficient, is at most 3.0 x10-6 K-1,
4. A. process for producing a honeycomb filter for
cleaning an exhaust gas, characterized by preparing a
mixture comprising:
5 100 parts by iiass of a mixture (component X)
comprising TiOz and A12O3 in a, molar ratio of the
former/the latter being 40 to 60/60 to 40, and
from l to 10 parts by mass of an alkali feldspar-
represented by the empirical formula (NayKi-y)AlSi3O3
10 [wherein 0 containing Kg, or MgO or an Mg-containing compound which,
will be converted to MgO by firing {component Y) , adding
molding agsistants to the mixture, followed by kneading
to plasticize the mixture to make it extrusion-
15 proceasable, extrusaon processing it into a honeycomb
structure, followed by firing at from 1,250 to l,7000C.
5 - The process for producing a honeycomb filter for
cleaning an exhaust gas according to Claim 4, wherein
component Y is a mixture comprising the alkali feldspar
20 represented by (NayKi-v}AlSi3Os (wherein O oxide of a spinel structure containing Mg and/or Mgo or
the Mg-containing compound which will be converted to MgO
by firing
6. An apparatus for clesinang an exhaust gas,
25 characterised in that the honeycomb filter for cleaning
an exhaust gas as defined in any one of Claims 1 to 3 is
accommodated in a can

30
7 The apparatus for cleaning an exhaust gas according
to Claim 6, which is used to cleaning an exhaust gas of
an automobile having a diesel engine mounted.

To provide a honeycomb filter for cleaning an exhaust
gas, which is excellent in heat resistance and thermal
shock resistance and has high thermal decomposition
5 resistance and high mechanical strength and which is thus
capable of being used with stability at high and
fluctuating temperatures, and a process for its
production.
A honeycomb filter for removing solid particles
10 containing carbon as the main component in an exhaust
gas, characterised m that the material for the honeycomb
filter is an aluminum titanate sintered product obtained
by firing at from 1,250 to l,700°C a raw material mixture
comprising 100 parts by mass of a mixture (component X)
15 comprising TiO2; and A12O3, in a molar ratio of the
farmer/the latter being 40 to 6 0/6O tc 40, and from 1 to
10 -parts by mass of an alkali, feldspar represented by the
empirical formula {NayKi-y)AlSi3O3 (wherein O oxide having a spinel structure containing Mg, or MgO or
20 an Mg-containing compound which will be converted to MgO
by faring (component Y)

Documents:

00309-kolnp-2006-abstract.pdf

00309-kolnp-2006-claims.pdf

00309-kolnp-2006-description complete.pdf

00309-kolnp-2006-drawings.pdf

00309-kolnp-2006-form-1.pdf

00309-kolnp-2006-form-3.pdf

00309-kolnp-2006-form-5.pdf

00309-kolnp-2006-international publication.pdf

309-KOLNP-2006-(13-01-2012)-FORM-27.pdf

309-KOLNP-2006-CORRESPONDENCE.pdf

309-KOLNP-2006-FORM 27.pdf

309-KOLNP-2006-FORM-27.pdf

309-kolnp-2006-granted-abstract.pdf

309-kolnp-2006-granted-assignment.pdf

309-kolnp-2006-granted-claims.pdf

309-kolnp-2006-granted-correspondence.pdf

309-kolnp-2006-granted-description (complete).pdf

309-kolnp-2006-granted-drawings.pdf

309-kolnp-2006-granted-examination report.pdf

309-kolnp-2006-granted-form 1.pdf

309-kolnp-2006-granted-form 18.pdf

309-kolnp-2006-granted-form 3.pdf

309-kolnp-2006-granted-form 5.pdf

309-kolnp-2006-granted-gpa.pdf

309-kolnp-2006-granted-reply to examination report.pdf

309-kolnp-2006-granted-specification.pdf

309-kolnp-2006-granted-translated copy of priority document.pdf

abstract-00309-kolnp-2006.jpg


Patent Number 238262
Indian Patent Application Number 309/KOLNP/2006
PG Journal Number 05/2010
Publication Date 29-Jan-2010
Grant Date 28-Jan-2010
Date of Filing 13-Feb-2006
Name of Patentee OHCERA CO., LTD.
Applicant Address 1-19, UCHIHONMACHI 2-CHOME, CHUOU-KU, OSAKA-SHI, OSAKA
Inventors:
# Inventor's Name Inventor's Address
1 FUKUDA TSUTOMU 785-1, KUNIKANE, KAMISO-CHO, KAKOGAWA-SHI, HYOGO 6751213
2 FUKUDA MASAAKI 785-1, KUNIKANE, KAMISO-CHO, KAKOGAWA-SHI, HYOGO 6751213
3 YOKO TOSHIBOBU 31-1-120, TODOMONNOMAE, UJI-SHI, KYOTO 6110013
4 TAKAHASHI MASAHIDE KYODAI SHOKUINSHUKUSHA 1-113, GOKASHO KANYUCHI, UJI-SHI, KYOTO 6110011
5 FUKUDA MASAHIRO 94-1-603, OCHIAI, MAKISHIMA-CHO, UJI-SHI, KYOTO 6110041
PCT International Classification Number B01D 39/20
PCT International Application Number PCT/JP2004/012312
PCT International Filing date 2004-08-20
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 2003-208356 2003-08-22 Japan