Note: Descriptions are shown in the official language in which they were submitted.
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LOW SIDESTREAM SMOKE
CIGARETTE WITH COMBUSTIBLE PAPER
HAVING A MODIFIED ASH
FIELD OF THE INVENTION
The invention relates to sidestream smoke reduction in burning
cigarettes and other smoking products. More particularly, the invention
relates
to cigarette paper, cigarette wrapper, or a wrapper for a cigar or other like
tobacco products for reducing visible sidestream smoke while providing a
modified ash.
BACKGROUND OF THE INVENTION
Various attempts have been made to reduce or eliminate sidestream
smoke emanating from a burning cigarette. The applicant developed various
approaches to cigarette sidestream smoke control systems as described in its
Canadian patents 2,054,735 and 2,057,962; U.S. patents 5,462,073 and
5,709,228 and published PCT applications WO 96/22031; WO 98/16125 and
WO 99/53778.
Other sidestream smoke control systems have been developed which use
filter material or adsorptive material in the tobacco, filter or paper
wrapper.
Examples of these systems are described in U.S. Patents 2,755,207, 4,108,151
and 4,225,636; EP patent applications 0 740 907 and 0 251 254; and WO
97/27831 and WO 99/53778. U.S. Patent 2,755,207 describes a low sidestream
smoke cigarette paper. The cigarette paper on burning yields a smoke
substantially free of obnoxious components. The cigarette paper is cellulosic
material in fibre form. It has intimately associated therewith a finely
divided
mineral type siliceous catalyst material. The cigarette paper which is
essentially non-combustible and refractory remains substantially unchanged
during combustion of the cigarette paper and functions like a catalyst in
modifying the combustion of the paper. Suitable siliceous catalysts include
acid-treated clays, heat-treated montmorillonite and natural and synthetic
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silicates containing some hydrogen atoms which are relatively mobile.
Suitable mixed silica oxides include silica oxides with alumina, zirconia,
titania, chromium oxide and magnesium oxide. Other silicas include the oxides
of silicon and aluminum in a weight ratio of 9:1 of silica to alumina.
U.S. Patent 4,108,151 describes the use of a gamma alumina filler for
cigarette paper which selectively reduces the organic vapor phase constituents
in tobacco smoke. There is at least 50% by weight of alumina filler in the
cigarette paper for reducing the organic vapor phase constituents, in a
tobacco
smoke. As a result there is a reduction in the visible sidestrearn smoke
emanating from a burning cigarette. The gamma alumina is most commonly
known as activated alumina which is finely pulverized to pass through a 300-
mesh screen.
U.S. Patent 4,225,636 describes the use of carbon in the cigarette paper
to reduce organic vapour phase components and total particulate matter found
in sidestream smoke. In addition, the carbon results in a substantial
reduction
in visible sidestream smoke emitting from a burning cigarette. Activated
carbon is preferred as the carbon source. The use of the activated carbon
results
in a slight drop in visible sidestream smoke. Up to 50% of the cigarette paper
may be finely divided carbon. The carbon-coated papers may be used as the
inner wrap for the tobacco rod in combination with a conventional cigarette.
European patent application 0 740 907 published November 6, 1996
describes the use of zeolites in the tobacco of the cigarette to alter the
characteristics of the mainstream smoke and in particular remove various
components from the mainstream smoke such as some of the tars. The zeolite
as provided in the tobacco, also apparently change the characteristics of the
sidestream smoke. The zeolites used were of a particle size between 0.5 mm to
1.2 mm.
European application 0 251 254 describes the use of a high superficial
surface area filler in cigarette paper. The fillers are generally crystals and
solids having surface areas of at least 20 m2/g. The fillers are preferably,
peroxides, carbonates, phosphates, sulphates, aluminates and silicates. It is
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taught that porous fillers such as zeolites are not preferred in cigarette
paper
and are taught as functioning similarly to conventional chalk.
Published PCT patent application WO 97/27831 describes the use of a
dealuminated zeolite for absorbing nonpolar or weakly polar molecules form a
polar liquid or gas. Effective amounts of the powered dealuminated zeolite
may be incorporated in cigarette paper to reduce the carbon monoxide in
sidestream smoke. The step of dealuminating aluminous zeolite renders the
zeolite hydrophobic so 'as to affect absorption and removal of the nonpolar
and
weakly polar molecules which even happens in the present of water.
Published PCT patent application WO 99/53778 describes a non-
combustible sheet of treatment material for reducing sidestream smoke
emissions. The sheet is used as a wrap and is applied over conventional
cigarette paper of a conventional cigarette. The wrap has a very high porosity
to allow the cigarette to bum at or close -to conventional free-bum rates
while at
the same time reduce visible sidestream smoke emissions. The non-
combustible wrap includes non-combustible ceramic fibres, non-combustible
activated carbon fibres as well as other standard materials used in making the
wrap. The wrap also includes zeolites or other similar sorptive materials and
an oxygen donor/oxygen storage metal oxide oxidation catalyst. The non-
combustible wrap provides an acceptable degree of sidestream smoke control,
however, due to the non-combustible nature of the wrap, a charred tube
remains.
U.S. Patents 4,433,697 and 4,915,117 describe the incorporation of
ceramic fibres in a cigarette paper manufacture. U.S. Patent 4,433,697
describes at least 1 % by weight of certain ceramic fibres in the paper
furnish in
combination with magnesium oxide and/or magnesium hydroxide fillers to
reduce visible sidestream smoke emanating from the burning cigarette. The
furnish of fibre pulp, ceramic fibres and fillers are used to make a paper
sheet
on conventional paper making machines. The ceramic fibres may be selected
from the group of polycrystalline alumina, aluminum-silicate and amorphous
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alumina. A filler of magnesium hydroxide or magnesium oxide is used and is
coated on or applied to the fibres of the sheet.
Ito, U.S. Patent 4,915,117 describes a non-combustible sheet for holding
tobacco. The thin sheet is formed from ceramic materials which upon burning
produces no smoke. The ceramic sheet comprises a woven or non-woven
fabric of ceramic fibre or a mixture of paper and ceramics thermally
decomposed at high temperature. The ceramic fibre may be selected from
inorganic fibres such as silica fibre, silica-alumina fibre, alumina fibre,
zirconia
fibre, or alumino borosilicate and glass fibre. The ceramic sheet is formed by
binding these materials by inorganic binders such as silica gel or alumina
gel.
The fibres are preferably 1 to 10 micrometers in diameter.
Published PCT patent application WO 01/41590 describes the use of
ceramic materials in cigarette wrappers to reduce sidestream smoke. The
ceramic filler which is incorporated in the cigarette wrapper using a binder
has
particle size in range of 2-90 m. The ceramic filler is of a predefined shape
which is spherical or substantially spherical, oval or substantially oval or
another irregular shape approximating thereto. The ceramic filler may be
alumina, silica, an alumino-silicate, silicon carbide, stabilised or un-
stabilised
zirconium oxide, zircon, garnet, feldspar and the like. The ceramic filler is
provided in the cigarette wrapper at greater than 40% by weight of the dry
materials in the slurry that is used to produce the wrapper. The binder may be
an alginate, a gum, cellulose, pectin, starch or Group I or II metal salts of
these
binders. The resultant wrapper has a porosity usually less than 200 Coresta
Units and is preferably in the range of 2-100 Coresta Units. The wrapper has a
density of 0.5-3.0 g/cm3. The wrapper is preferably used as an overwrap for a
porous non-smokeable plugwrap tobacco rod having porosities of about 12,000
Coresta Units.
Sol gels have been applied to conventional cigarette paper in order to
reduce sidestream smoke, particularly sol gels made from a magnesium
aluminate, calcium aluminate, titania, zirconia and aluminum oxide, as
described in Canadian Patent 1,180,968 and Canadian Patent application
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2,010,575. Canadian Patent 1,180,968 describes the application of magnesium
hydroxide in the form of an amorphous gel as a cigarette paper filler
component to improve ash appearance and sidestream smoke reduction. The
magnesium hydroxide gel is coated on or applied to the fibres of the sheet of
the cigarette paper. Canadian patent application 2,010,575 describes the use
of
gels produced by a solution gelation or sol-gel process for controlling the
combustion of wrappers for smoking articles. The gels may be applied as
coatings to paper fibres before the paper is formed into wrappers. The
wrappers are useful for reducing visible sidestream smoke. The metal oxides
for the sol gels may be oxides of aluminum, titanium, zirconium, sodium,
potassium or calcium.
Published German patent application DE 3508 127 describes a novelty
type cigarette which produces a shower of sparks when smoked. This is
achieved by incorporating a granular misch metal in the form of cerium ferrite
or silico-cerium in the cigarette paper. When the cigarette is smoked
particularly in dark spaces the burning cigarette gives off sparks along with
a
bright light effect. The cerium ferrite particles incorporated in the
cigarette
paper usually have a particle size of about 20 m.
Catalysts have also been directly applied to cigarette paper, such as
described in Canadian Patent 604,895 and U.S. Patent 5,386,838. Canadian
Patent 604,895 describes the use of platinum, osmium, iridium, palladium,
rhodium and rhuthenium in the cigarette paper. These metals function as
oxidation catalysts to treat vapours arising from combustion of the paper
wrapper. Optimum catalytic effect has been provided by the metal palladium.
The metal particles in a suitable medium are dispersed onto the face of a
paper
wrapper before it is applied to the cigarette.
U.S. Patent 5,386,838 describes the use of a sol solution comprising a
mixture of iron and magnesium as a smoke suppressive composition. The
smoke suppressive composition is made by co-precipitating iron and
magnesium from an aqueous solution in the presence of a base. The iron
magnesium composition demonstrates high surface area of approximately 100
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m2/g to approximately 225 m2/g when heated to a temperature between 100 C
and approximately 500 C. The iron magnesium composition may be added to
paper pulp which is used to make smoke suppressive cigarette paper. The iron
magnesium composition apparently functions as an oxidation catalyst and
reduces the amount of smoke produced by the burning cigarette. The catalyst
may also be applied to the tobacco, for example, as described in U.S. Patent
4,248,251, palladium, either in metallic form or as a salt, may be applied to
the
tobacco. The presence of palladium in tobacco reduces the polycyclic aromatic
hydrocarbons in the mainstream smoke. Palladium is used in combination with
an inorganic salt or nitric or nitrous acid. Such nitrates include lithium,
sodium, potassium, rubidium, cesium, magnesium, calcium, strontium,
lanthanum, cerium, neodymium, samarium, europium, gadolinium, terbium,
dysprosium, erbium, scandium, manganese, iron, rhodium, palladium, copper,
zinc, aluminum, gallium, tin, bismuth, hydrates thereof and mixtures thereof.
Catalysts have also been used in tubes to reduce sidestream smoke such as
described in published PCT application WO 98/16125.
U.S. patent 6 228 799 describes a composition comprising cerium oxide
and zirconium oxide in particulate form and having a high surface area usually
in excess of 35 m2/g. The composition is made by co-precipitating cerium and
zirconium species from a solution at an elevated temperature, which is then
separated and dried at temperatures between 80-300 C and then calcined at
temperatures between 200 and 1,200 C.
Catalytic materials have been used in aerosol types of cigarettes which
do not produce sidestream or mainstream smoke per se, but instead a flavoured
aerosol. Examples of these aerosol cigarettes include those described in U.S.
patents 5,040,551, 5,137,034 and 5,944,025, which use catalysts to provide the
necessary heat generation to develop the aerosol. Such catalyst systems
include oxides of cerium, palladium or platinum.
A variety of sidestream smoke control systems have been contemplated
in the prior art but none of them contemplate a combustible cigarette paper
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which burns like a normal cigarette without appreciably affecting cigarette
taste
and has an acceptable ash.
SUMMARY OF THE INVENTION
In accordance with various aspects of this invention, cigarette paper,
cigarette wrapper, wrapper for a cigar or other like tobacco products is
provided for reducing visible sidestream smoke with an improved or modified
ash.
In accordance with an aspect of the invention, in a low sidestream
smoke cigarette having a conventional tobacco rod and a combustible treatment
paper, said treatment paper having a sidestream smoke treatment composition
comprising an oxygen storage and donor metal oxide oxidation catalyst and an
essentially non-combustible finely divided particulate adjunct for said
catalyst,
the improvement comprising the use of a solid solution of particulate mixed
metal oxides as said catalyst and said adjunct.
The oxygen storage and donor metal oxide oxidation catalyst as part of
the solid solution is preferably selected from the group consisting of
lanthinum
oxide, cerium oxide, praseodymium oxide, neodymium oxide and mixtures
thereof. The adjunct which is also part of the solid solution is preferably
selected from the group of metal oxides consisting of zirconium oxide,
aluminum oxide, magnesium oxide, titanium oxide and mixtures thereof.
The solid solution of mixed metal oxides may further include in the
solid solution metal catalyst selected from the group consisting of palladium,
platinum, rhodium, tin oxide, copper oxide, iron oxide, manganese oxide and.
mixtures thereof. Preferred mixed oxides of the solid solution are
cerium/lanthinum mixed oxide, cerium/zirconium mixed oxide, cerium/
zirconium/lanthinum mixed oxide, cerium/zirconium/ praseodynium mixed
oxide, cerium/zirconium/ lanthinum/praseodynium mixed oxide,
cerium/zirconium/neodymium mixed oxide and mixtures thereof.
In accordance with another aspect of the invention, a low sidestream
smoke cigarette comprises a conventional tobacco rod and a combustible
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treatment paper having a sidestream smoke treatment composition, the
treatment composition comprises an oxygen storage and donor metal oxide
oxidation catalyst, an essentially non-combustible adjunct for said catalyst
and
a metal oxide for modifying ash characteristics.
In accordance with another aspect of the invention, the adjunct may
comprise a mixed metal oxide or carbonate filler used in conjunction with a
zeolite based material. The zeolite based material is preferably in an amount
ranging from about 0.1% to 35% by weight of the total dry weight of the
composition, although the amount could be higher. The mixture of metal
oxides may include mixtures of zirconium oxide, tin oxide, titanium oxide,
magnesium oxide, alumina, cerium oxide tin oxide, iron oxide, manganese
oxide, calcium carbonate, zirconium carbonate, magnesium carbonate and
mixtures thereof. The metal oxides may be of various surface areas and most
preferably either low surface area in the range of about 5 to 15 m2/g and high
surface area of over 20 m2/g. A cerium oxide hydrate sol may be applied to the
adjunct, for example, the metal oxides to provide increase catalytic activity.
In accordance with another aspect of the invention, the oxygen storage
and donor metal oxide oxidation catalyst material preferably include lanthinum
oxide, cerium oxide, praseodymium oxide, neodymium oxide and mixtures
thereof. Oxidation catalyst of the precious metal and transition metal type
may
also be included such a palladium, platinum, rhodium, tin oxide, copper oxide,
iron oxide, manganese oxide and mixtures thereof. These catalyst may also be
fixed on the adjunct or the ash modification material or as part of the solid
solution of the mixed oxides.
The sidestream smoke treatment composition may be incorporated in the
combustible treatment paper, coated on the combustible treatment paper,
impregnated into treatment paper or a combination of the above steps. The
treatment paper may be double wrapped and be of the same or different
compositions. One of the double wraps may be conventional paper.
Alternatively, one of the double wraps may have a composition directed
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primarily to sidestream smoke reduction and the other double wrap paper
include a composition directed towards ash modification.
In accordance with another aspect of the invention, a low sidestream
smoke cigarette comprises a conventional tobacco rod and a combustible
treatment paper having a sidestream smoke treatment composition. The
treatment composition comprises an oxygen storage and donor metal oxide
oxidation catalyst and an essentially non-combustible high surface area
adsorptive adjunct for the catalyst incorporated in said treatment paper. A
coating of calcium carbonate is provided on an exterior surface of the
treatment
paper to modify ash characteristics.
In accordance with a further aspect of the invention, a low sidestream
smoke cigarette comprising a conventional tobacco rod and a combustible
treatment paper having a sidestream smoke treatment composition, said
treatment composition comprising an oxygen storage and donor metal oxide
oxidation catalyst, an essentially non-combustible particulate adjunct for
said
catalyst and a metal oxide or carbonate for modifying ash characteristics.
In accordance with another aspect of the invention, a low sidestream
smoke cigarette comprising a conventional tobacco rod and a combustible
treatment paper having a sidestream smoke treatment composition, said
treatment composition comprising an oxygen storage and donor metal oxide
oxidation catalyst, an essentially non-combustible high surface area adjunct
for
said catalyst incorporated in said treatment paper and a coating of calcium
carbonate on an exterior surface of said treatment paper to modify ash
characteristics.
For ease of description, whenever the term cigarette is used, it is
understood to not only include smokable cigarettes but as well any form of
wrapped smokable tobacco product, such as cigars, or the like. Whenever the
term treatment paper is used, it is understood to encompass combustible
wrappers and the like which may be used on cigarettes, cigars, and the like.
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The wrapper may be used as a single layer of cigarette paper or multiple layer
of cigarette paper. The wrapper may be applied as the sole layer of cigarette
paper or as a wrap over conventional cigarette paper of a cigarette. The
treatment paper may include as its substrate conventional cigarette paper or
similar combustible product with a wide range of porosities. The conventional
tobacco rod encompasses tobacco compositions normally used in smokable
cigarettes. These rods are to be distinguished from tobacco components used
in aerosol cigarette.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the invention are shown in the drawings
wherein:
Figure 1 is a schematic view of a spray technique for applying the
treatment composition to a cigarette paper;
Figure 2 is a schematic view of extruding a film of the treatment
composition onto the cigarette paper;
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Figure 3 is a schematic view of roll coating the treatment composition
on cigarette paper;
Figure 4 is a schematic view of the impregnation of a coating of the
treatment composition into the cigarette paper;
Figure 5 is a schematic view of mixing the treatment composition with
the paper pulp in the manufacture of cigarette paper;
Figure 6 is a perspective view of a tobacco rod having the treatment
paper of this invention applied thereto;
Figure 7 shows an alternative embodiment of Figure 6;
Figure 8 is a perspective view of a tobacco rod having the treatment
composition sandwiched between two layers of cigarette paper as applied to the
tobacco rod; and
Figure 9 is a perspective view of a double wrap for the tobacco rod
where treatment paper is applied over conventional cigarette paper.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In accordance with an aspect of this invention, the sidestream smoke
treatment composition provides the desired degree of visible sidestream smoke
control while at the same time providing a suitable ash of desired
characteristics. The sidestream smoke treatment composition of this invention
comprises, an oxygen storage and donor metal oxide oxidation catalyst used in
combination with a non-combustible finely divided porous particulate adjunct
for the catalyst. As taught in applicant's co-pending U.S. Patent Serial No.
6,799,578 filed September 18, 2001, it was unexpectantly found that when
these two components are used in combination either alone or with other
constituents, a very surprising degree of visible sidestream smoke control is
provided. It has been found that with certain types of catalytic material
and/or
adjuncts, ash characteristics, such as, appearance can sometimes be less than
acceptable due to, for example, discolouration, delamination and defoliation.
In accordance with this invention, enhancements have been made to the
composition and in particular to the catalyst and/or adjunct to modify ash
characteristics to provide for example an acceptable appearance, acceptable
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strength, colour, integrity and reduction or elimination of ash defoliation,
delamination and the like.
The adjunct may be any suitable essentially non-combustible, finely
divided particulate material which does not affect the flavour and taste of
the
mainstream smoke and does not give off any undesirable odours in the
sidestrearn vapours. The particulate material is physically stable at the
elevated
temperatures of the burning cigarette coal. The adjunct may have a low surface
area usually less than 20 m2/g and preferably 1 m2/g to 15 m2/g and most
preferably 3 m2/g to 10 m2/g. It is understood for the low surface area
materials the particulates are finely ground and are usually not porous.
However, as the surface area increases towards 20 m2/g it is understood that
the
particles may be porous. Conversely the adjunct may also have a high surface
area usually greater than 20 m2/g and at this level of surface area usually
the
particulate material is porous. The porous adjunct may have pores with an
average diameter of less than 100 nm (1000A). More preferably, the pores
have an average diameter of less than 20 nm (200 A) and even more preferred
are pores with an average diameter of 0.5 to lOnm (5-100 A). With zeolite
based materials, the pores have an average diameter in the range of about 0.5
to
1.3 nm (5-131).
The particulate adjunct may have an average particle size of less than
about 30 m, more preferably less than about 20 m and most preferably
ranging from about 1 m up to about 10 m. Non-combustible materials may be
porous clays of various categories commonly used in cigarette paper
manufacture, such as the bentonite clays or treated clays having high surface
areas. Non-combustible carbon materials may also be used including milled
porous carbon fibres and particulates. Various metal oxides and/or carbonates
may be used such as porous monolithic mineral based materials such as
zirconium oxide, titanium oxides, magnesium oxide, aluminum oxide, cerium
oxide, tin oxide, iron oxide, manganese oxide, calcium carbonate, zirconium
carbonate, magnesium carbonate and mixtures thereof, metal oxide fibres such
as zirconium fibres and other ceramics such as milled porous ceramic fibres
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and mixtures thereof. In respect of cerium oxide, it has been found that it is
capable of functioning as a finely divided adjunct and as an oxygen storage
and
donor cerium oxide oxidation catalyst. Other adjunct materials include high
surface area materials such as activated carbon and zeolites.
The adjunct may also comprise high surface area highly sorptive
materials which are non-combustible, inorganic finely divided particulate,
such
as molecular sieves which include zeolites and may also comprise amorphous
materials such as silica/alumina, zirconium oxide, zirconium hydroxide and the
like. Zeolites such as silicalite zeolites, faujasites X, Y and L zeolites,
beta
zeolites, Mordenite zeolites and ZSM zeolites are acceptable. Preferred
zeolites include hydrophobic zeolites and mildly hydrophobic zeolites which
have affinity for hydrophobic and mildly hydrophobic organic compounds of
such sidestream smoke whereby water vapour is avoided. The zeolite materials
provide a highly porous structure which selectively absorbs and adsorbs
components of sidestream smoke. The highly porous structure generally
comprise macropores amongst the particles and micropores within the particles
which branch off of the macropores. It is believed that the captured
components in the macropores and micropores in presence of the cerium oxide
or other suitable oxidation catalysts at the high temperature of the burning
cigarette, converts such captured components into oxidized compounds which
continue to be trapped in the adsorbent material or are released as invisible
gases which have sufficiently low tar and nicotine levels so that the
sidestream
is invisible or at a low desired level.
The zeolite materials may be characterized by the following formula:Mm
M',,M"p[aA102 = b Si02 = cTO2]
wherein
M is a monovalent cation,
M' is a divalent cation,
M" is a trivalent cation,
a, b, c, n, in, and p are numbers which reflect the stoichiometric
proportions,
c, in, n or p can also be zero,
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Al and Si are tetrahedrally coordinated Al and Si atoms, and
T is a tetrahedrally coordinated metal atom being able to replace Al or Si,
wherein the ratio of b/a of the zeolite or the zeolite-like material, has a
value of about 5 to 300 and the micropore size is within the range of about
0.5 to 1.3 nm (5 to 13A).
Preferred zeolites of the above formula, have the specific formulas of
faujasites ((Na2, Ca, Mg)29[A158Si134O384] - 240 H2O; cubic), (3-zeolites
(Nan[AlnSi64-nO128] with n<7; tetragonal), Mordenite zeolites (Na8[Al8Si4oO96]
24 H2O; orthorhombic), ZSM zeolites (Nan[AlnSi96-nO192] - 16 H2O with n<27;
orthorhombic), and mixtures thereof.
It is appreciated that various grades of the sorptive material may be
used. This is particularly true with gradients of zeolites which can be custom
designed to selectively adsorb, for example, high boiling point materials, mid
boiling point materials and low boiling point materials. This can lead to
layers
of the zeolite composition where the cerium oxide or other suitable catalyst
contemplated by this invention is preferably dispersed throughout these
layers.
The layers may then be bound on cigarette paper for the tobacco rod by using a
binder or an adhesive which may be, for example, polyvinylacetate, polyvinyl
alcohol, carboxy methyl cellulose (CMC), starches and casein or soya proteins,
and mixtures thereof
The oxygen donor and oxygen storage metal oxide oxidation catalyst
may be selected from the transition metal oxides, rare earth metal oxides,
(such
as scandium, yttrium, and lanthanide metal series, i.e. lanthanum) and
mixtures
thereof. It is appreciated that the catalyst may be in its metal oxide form or
a
precursor of the metal oxide which, at the temperature of the burning
cigarette,
is converted to a metal oxide to perform its catalytic activities. The
transition
metal oxides may be selected from oxides of the group of metals from the
Periodic Table consisting of groups IVB, VB, VIB, VIIB, VIII and IB metals
and mixtures thereof. Preferred metals from the transition metal group are
oxides of iron, copper, silver, manganese, titanium, zirconium, vanadium and
tungsten and from the rare earth group are oxides of lanthanide metals such as
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oxides of lanthinum, cerium, praseodymium, neodymium and mixtures thereof.
For example, cerium may be used in admixture with any one of the transition
metals such as Ce/Zr mixed oxide. It is appreciated that other metal oxide
oxidation catalysts may be used with the oxygen storage and oxygen donor
type of catalyst. Such other metal catalysts include precious metals and
metals
from groups IIA, IVA and mixtures thereof. Examples include palladium,
platinum, rhodium, tin oxide, copper oxide, iron oxide, manganese oxide and
mixtures thereof.
The cerium catalyst precursor may be in the form of a cerium salt such
as a cerium nitrate or other dispersible forms of cerium such as a cerium sol
made up of a cerium oxide hydrate or as it is also refired to as a cerium
hydroxide which is applied in solution or sol to the sorptive material or to a
paper as a coating and which is converted to cerium oxide at the high
temperature of the burning cigarette to then function as a catalyst. It is
understood that the sol may be a low nitrate cerium oxide hydrate sol. For
purposes of describing the invention, the term catalyst is intended to include
any catalyst precursor.
The catalyst such as, cerium oxide, is used in combination with the
adjunct material. It has been found that when the two are used separate from
one another or in spaced apart, non- adjacent layers, the ability to control
sidestream smoke is greatly reduced. Although in certain arrangements, some
sidestream smoke control can be achieved. Preferably the catalyst is
substantially adjacent the adjunct material. This can be achieved by co-
mingling the particulate catalyst, in admixture with the adjunct, contacting a
layer of the adjunct with a catalyst layer, coating the catalyst on the
adjunct or
impregnating the catalyst within or on the porous surfaces of the adjunct, to
bring about the desired surprising sidestream smoke control properties. It
should be appreciated that many other constituents may be used in addition to
the combination of the oxygen storage and oxygen donor metal oxide oxidation
catalyst and the adjunct. Additional additives may be used to further enhance
the treatment of the sidestream smoke or alter other characteristics of the
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cigarette. Such additional additives may be mixed in with the treatment
composition or used elsewhere in the cigarette construction, providing of
course that such additives do not appreciably impact negatively on the ability
of the treatment composition to treat the sidestream smoke.
The composition may be formulated in a variety of ways which achieve
co-mingling of the cerium with the adsorptive material. For example, the
adsorptive material may be sprayed with or dipped in a cerium salt solution
such as cerium nitrate or cerium oxide hydrate sol to impregnate the surface
of
the adsorptive material with cerium material. Cerium oxide may be prepared
as a separate fine powder which is mixed with the fine powder of the
adsorptive material. It is particularly preferred that the catalyst powders
have
an average particle size of less than about 30 m and preferably less than 20 m
and most preferably about 1.0 to 10 m and more preferably 6 to 10 m to
ensure intimate mixing and co-mingling of the materials.
15. As a general guide to selecting catalyst particle size and surface area,
it
is appreciated by one skilled in the art that the selected catalyst has a
surface
area which is such to ensure that the catalyst active sites are available to
the
migrating sidestream smoke components. This may result in catalyst particle
size being greater than 30 m in certain embodiments, if the catalyst particles
are properly distributed to achieve the necessary degree of sidestream smoke
component oxidation.
It has been surprisingly found that the cerium oxide, particularly high
surface area cerium oxide, is one of the few metal oxides which can perform
both functions of the invention, namely as the oxygen storage and oxygen
donor catalyst and as well as the adjunct. The porous cerium oxide particles
can be made with the high surface areas and an average particle size required
for the adjunct. The cerium oxide is used with the cigarette paper in a first
amount as the catalyst and a second amount as the adjunct in the treatment
composition. Such amounts of the cerium oxide correspond generally with the
amounts used for the catalyst and adjunct in accordance with other aspects of
the invention to make up the total loading. Alternatively the high surface
area
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cerium oxides can be used with adjuncts such as zeolites or other high surface
metal oxides such as zirconium oxide or zirconium hydroxide.
The cerium may be formulated as a solution dispersion, such as cerium
oxide sol, or the like and applied to the sorptive material such as zeolite.
It is
then dried and fired to provide cerium oxide particles fixed on the surfaces
of
the adsorptive material. When the cerium oxide particles are fixed to adjunct
surfaces such as surfaces of zeolite, the average particle size may be less
than
about 1.0 m. The relative amounts of cerium oxide fixed to the zeolite may
range from about 1% to 75% by weight based on the total equivalent cerium
oxide and zeolite content. The preferred relative amounts of cerium oxide
fixed
to the zeolite may range from about 5% to 70% by weight based on the total
equivalent cerium oxide and zeolite content.
One possible method for making the combination product of cerium
oxide fixed on the surfaces of the zeolite is described in PCT International
Patent Application No. WO 03/024595, entitled A Process For Making Metal
Oxide-Coated Microporous Materials, filed on September 12, 2002.
The method generally involves making a catalytic cerium oxide-coated
zeolite particulate material having at least 1 % by weight of cerium oxide
coated
on outer surfaces of the zeolite particulate material, based on the total
equivalent cerium oxide and zeolite content. In one aspect, the method
generally comprises the steps of:
i) combining an amount of a colloidal dispersion of cerium
oxide hydrate (cerium hydroxide) with a compatible zeolite particulate
material
to form a slurry, the amount of the colloidal dispersion being sufficient to
provide, when heat treated as per step (ii), greater than 20% by weight of the
cerium oxide, the zeolite particulate material having an average pore size of
less than 20A and the colloidal dispersion having an average particle size of
at
least 20A, to position thereby, the colloidal dispersion on the outer surfaces
of
the zeolite; and
ii) heat treating the slurry firstly, at temperatures below about
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200 C and secondly, above about 400 C, to fix the resultant cerium oxide on
the outer surfaces of the zeolite particulate material, to provide a free
flowing
bulk particulate.
Some of the combinations for the treatment composition can result in
what could be considered as unacceptable ash appearance. Unacceptable ash
appearance characteristics include delamination, defoliation, ash smear, oily
appearance and color. It was thought that various ash modifiers could be added
to the paper to improve ash appearance. Such ash modifiers include metal
oxides and/or carbonates such as zirconium oxide, titanium oxides, magnesium
oxide, aluminum oxide, cerium oxide, tin oxide, iron oxide, manganese oxide,
calcium carbonate, zirconium carbonate, magnesium carbonate and mixtures
thereof.
It is been found that the treatment composition may require
modifications to improve ash characteristics. Such modifications may include
selection of a particular chemical or physical type of oxygen donor/oxygen
storage catalyst and/or of the type of adjunct. In particular to enhance the
color
of the ash so that it is more a white or gray rather than a dark coal color,
it has
been found that reduced amounts of zeolite base material for the adjunct is
appropriate. The reduce amount of zeolite material based on the dry weight of
the paper is preferably less than 35% by weight and more preferably less than
25% by weight and most preferably less than 15% by weight. It is appreciated
that other types of fillers have to be added to compensate for the reduced
amount of zeolite based adjunct. Suitable substitute metal oxides and/or
carbonates include zirconium oxide, titanium oxides, magnesium oxide,
aluminum oxide, cerium oxide, tin oxide, iron oxide, manganese oxide,
calcium carbonate, zirconium carbonate, magnesium carbonate and mixtures
thereof. Low or high surface area cerium/zirconium mixed oxides as a solid
solution are preferred. Such adjuncts may be made for example by co-
precipitating zirconium and cerium species, drying the precipitate and then
firing to form a crystalline solid solution product of high surface area
cerium
oxide and zirconium oxide. The ratio of cerium oxide to zirconium oxide in
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this crystalline structure may range from about 5:95 through to 95:5.
Alternatively, the ratio may range from about 20:80 to 80:20 and most
preferred ranging from about 50:50 to 80:20. This material in its high surface
area form also has catalytic properties and also provides for oxygen storage
and donor properties where the zirconium oxide functions as the adjunct for
the
cerium oxide.
In respect of the catalyst selection, there has also found that
combinations with cerium oxide contribute to a better ash appearance. For
example cerium oxide may be deposited on high surface area cerium oxide,
cerium oxide hydrate deposited on high surface area cerium/zirconium oxides,
cerium oxide hydrate deposit and dried on a high surface area cerium oxide
particle. Furthermore, oxidation catalyst of the aforementioned precious metal
or transition metal types may be combined with the cerium based materials
such as palladium, platinum, rhodium, tin oxide, copper oxide, iron oxide,
manganese oxide, and mixtures thereof.
Solid solutions of mixed metal oxides are particularly preferred as the
oxygen donor catalyst because of an improved lighter colour ash. The solid
solution of the mixed metal oxides includes the oxygen donor oxygen storage
oxidation catalyst and the adjunct. Preferred metal oxides in a solid solution
as
the oxygen donor oxygen storage material include lanthinum oxide, cerium
oxide, praseodymium oxide, neodymium oxide and mixtures thereof. The
preferred metal oxides as adjuncts include zirconium oxide, aluminum oxide,
magnesium oxide, titanium oxide and mixtures thereof. Examples of these
solid solutions include cerium/lanthinum mixed oxide, cerium/zirconium mixed
oxide, cerium/zirconium/lanthinum mixed oxide, cerium/zirconium/
praseodynium mixed oxide, cerium/zirconium/lanthinum/praseodynium mixed
oxide, cerium/zirconium/neodymium mixed oxide. These solid solutions of
mixed oxides and other mixed oxides are readily available as commercial grade
catalyst and are available from any of a number of catalyst suppliers. Other
alternatives to the solid solutions include physical mixtures of zirconium
oxide,
aluminum oxide, magnesium oxide, titanium oxide with a solid solution for
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example cerium/zirconium mixed oxide solid solution. Other solid solutions
and mixed oxides contemplated by this invention include cerium/aluminum
mixed oxide, cerium/magnesium mixed oxide, cerium/titanium mixed oxide.
The oxidation catalysts which maybe included in the solid solutions are
usually present in trace amounts. Such catalyst include palladium, platinum,
rhodium, tin oxide, copper oxide, iron oxide, manganese oxide and mixtures
thereof. They are usually included in the solid solutions at levels less than
1%
by weight of the total solid solution. A preferred combination and in respect
of
the solid solution with trace amounts of other oxidation catalyst is a
combination of the above catalyst with a solid solution of cerium/zirconium
mixed oxide. It is preferred that the above oxidation catalyst either
individually or, mixtures thereof be included in the solid solution. Although
alternatively it is understood that the above catalyst or mixtures thereof
maybe
applied to the surfaces of the cerium/zirconium mixed oxide solid solution
particulate material.
Multiple purpose solid solution of mixed oxides include ceria/
zirconia/magnesia/titania/ where ceria makes up about 5% to about 75% of the
solid solution.
It has also been found that a coating on the wrapper of particulate
calcium carbonate is useful in improving ash characteristics. As previously
described the treatment composition maybe incorporated or coated on a
wrapper which is the sole wrapper for the tobacco rod. As noted above, one
approach to improving ash is to reduce the amount of the absorptive adjunct
such a zeolites and substitute therefor a selected metal oxide. Alternatively
it
has been found that particularly with single wrappers having incorporation of
the treatment composition, a coating of calcium carbonate on the exterior of
the
wrapper greatly improves the ash particularly from the stand point of
appearance. It is quite surprising that a coating of particulate calcium
carbonate could have this effect on improving the ash characteristics. Perhaps
the calcium carbonate chemically or physically binds constituents in the
wrapper to produce a more uniform light to gray coloured ash. The particulate
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calcium carbonate maybe slurried with a suitable binder for coating on the
wrapper. Suitable binders include those commonly used in coating calcium
carbonate on wrapper materials such a polyvinlylalcohols, starches, CMC,
casein, soya, binding clays and other acceptable binders or glues. The
particulate calcium carbonate has a particle size of that normally associated
with its use as a filler in manufacture of cigarette paper. The particle size
is
therefore usually below 10 gm and preferably above 3 m. Although some
grades of calcium carbonate less than 1 gm may also be useful.
The surprising activity of the sidestream smoke treatment composition
permits its use in cigarette papers having a wide range of porosities. It has
also
been found that the composition does not have to be used in cigarette papers
that just have high porosities. The treatment composition works equally well
in
papers with very low porosities of about 0.5 through to very high porosities
of
about 1,000 Coresta units. Preferred porosities are usually less than 200
Coresta units and most preferred porosities are usually in the range of about
15
to 60 Coresta units. It is appreciated that the paper may be used as a double
or
multiple wrap. The paper may be applied as an outer wrap over a cigarette
having conventional cigarette paper. It is appreciated that depending upon the
porosity, certain combinations of the catalyst and adjunct may work better
than
others.
The composition may be simply sprayed onto either side or both sides of
the cigarette paper and absorbed into the paper. As shown in Figure 1, the
paper 10 is conveyed in the direction of arrow 12. The treatment composition
14 as a slurry is sprayed by spray nozzle 16 onto the paper 10 to provide a
coating 18 which is dried on the paper. Alternatively, the composition may be
extruded as a film to the surface of the paper and may be used as a single or
multiple wrap. As shown in Figure 2, a film coating device 20 contains the
slurried treatment composition 14. The film coater 20 lays a thin film 22 on
the
paper 10 which is conveyed in the direction of arrow 12. The film is dried to
provide a coating 36 on the paper 10. With these arrangements, it is quite
surprising that the visual sidestream smoke from a burning cigarette virtually
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disappears. The treatment composition may be applied to a conventional
cigarette on the exterior of the cigarette paper.
Coating may be achieved by a roller applicator 26, as shown in Figure 3.
The treatment composition 14 is applied as a layer 28 on the roller 30. A
doctor knife 32 determines the thickness of a layer 34 which is then laid onto
the paper 10 which is conveyed in the direction of arrow 12. The layer is then
dried to form a coating 36 on the paper 10.
Impregnation is achieved by using the coating roller 24 of Figure 4 and
the coating 36 with paper 10 is passed in the direction of arrow 12 through
pressure rollers 38 and 40 which force the layer of material into the paper 10
to
thereby impregnate constituents of the treatment composition into the paper.
It is also understood by one of skill in the art that various other coating
processes including transfer coating processes, may be used for making the
treatment paper of the invention. In the transfer coating process, MylarTM
sheet
or other suitable continuous sheet may be used to transfer a coating
composition from the MylarTM sheet to the surface of the cigarette paper. This
type of transfer coating is useful when the substrate sheet may not readily
accept the roll coating of a composition due to physical strength
characteristics
of the paper or the like.
A further alternative is to incorporate the treatment composition into the
manufacture of paper. The composition may be introduced to the paper furnish
as a slurry. With reference to Figure 5, the treatment composition in the
furnish 42 is stirred by stirrer 44 to form a slurry in the tank 46. The
slurry is
transferred in the conventional paper making manner and is laid as a layer 48
on a moving conveyor 50 to form the resultant cigarette paper 52. As a result
the treatment composition is incorporated in the final paper product.
Another alternative is to sandwich the treatment composition between
paper layers to form a double cigarette paper wrap on tobacco rods. For
example, the composition may be applied such as by the spraying technique of
Figure 1 on the interior of the outer paper and/or the exterior of the inner
paper.
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Once the two papers are applied to the tobacco rod the composition as a layer
is
sandwiched between the two papers. Each paper maybe of half of the
thickness of conventional cigarette paper so that the double wrap does not add
appreciably to the overall diameter of the cigarette as is readily handled by
cigarette making machines.
With reference to Figure 6, the tobacco rod 54 has, for example, the
cigarette paper 10 wrapped therearound with the coating 18 on the outside of
the paper. Conversely, as shown in Figure 7, the cigarette paper 10 can be
applied with the coating 18 on the inner surface of the paper adjacent the
tobacco rod 54.
Another alternative, as shown in Figure 8, is to sandwich the coating 18
between cigarette papers 56 and 58. The papers 56 and 58 with the
intermediate coating 18 may be formed as a single cigarette wrapper which is
applied to the tobacco rod 54. A further alternative is shown in Figure 9
where
the tobacco rod 54 is covered with conventional cigarette paper 60. Over the
conventional paper 60 is the cigarette paper 52 of Figure 5 with the treatment
composition incorporated therein. It is also appreciated that paper 52 with
the
treatment composition incorporated therein may be applied directly to the
tobacco rod 54.
In yet another alternative embodiment of the invention, various
combinations for the sidestream smoke treatment paper may be provided in a
double wrap configuration for example, a coated paper of Figure 7 could be
used as the inner layer of paper and a different paper could be used as the
outer
layer of the double wrap which could be conventional paper. The inner layer
paper could also be a paper having the treatment composition incorporated
therein such as that of Figure 9. The inner layer paper could be designed to
provide for sidestream smoke reduction by including all the necessary
components of the composition such an oxygen storage and donor metal oxide
oxidation catalyst and the non-combustible adjunct for the catalyst. Preferred
examples of this type of composition includes a high surface area,
cerium/zirconium mixed oxide with zeolite and optionally enhanced with an
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oxidation catalyst such as platinum or palladium. In a double wrap system, the
amount of zeolite may exceed 30% and may be in the range for example of
50% to 60% by weight.
The outer layer of the double wrap may have a different composition
and be designed to provide for ash modifications to achieve desired
characteristics. For example, the outer paper may be designed to enhance not
only ash appearance but as well modify the burn rate of the cigarette and also
minimized if not eliminate flare ups on lightning and puffing of the
cigarette.
The outer layer may include, for example, metal oxides such as low surface
area cerium oxide, solid solution of cerium oxide/zirconium oxide, alumina,
zirconium oxide, titanium oxide, tin oxide and the like. In addition cerium
oxide hydrate may be coated on the metal oxide materials of the outer layer to
ensure sufficient oxygen is present to support combustion of the outer layer
of
the cigarette. The two layers when combined as a double wrap provide
effective control of visible sidestream smoke. The adjacent papers burn evenly
to produce desired ash and the outer paper may function to minimize or
eliminate the highly active oxygen donor material from causing flare ups.
The double wrap feature of the invention provides significant flexibility
in the design of a low sidestream smoke cigarette. The individual sheets of
the
double wrap design has the selected treatment composition impregnated, coated
or incorporated in the respective sheet. Alternatively sheets that have a
treatment composition incorporated therein may also be coated with the same
or different treatment composition to further enhance the sidestream smoke
control and/or ash modification. To demonstrate such flexibility in the design
of the low sidestream smoke cigarette, exemplary treatment composition for
the inner and outer papers are as follows:-
Outer paper
i) High surface area of cerium/zirconium mixed oxide
(75:25) + low surface area zirconium oxide;
ii) High surface area alumina coated with cerium hydrate;
iii) Low surface area cerium oxide coated with cerium hydrate;
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iv) High surface area zirconium oxide coated with cerium hydrate;
or
v) High surface area cerium/zirconium mixed oxide (25:75).
Inner paper
i) High surface area of cerium/zirconium mixed oxide
(75:25) enhanced with palladium catalyst + zeolite
enhance with palladium catalyst;
ii) High surface area of cerium/zirconium mixed oxide
(75:25) + zeolite enhanced with palladium;
iii) High surface area of cerium/zirconium mixed oxide
(75:25) + zeolite where the cerium/zirconium mixed
oxide is enhanced with palladium catalyst; or
iv) High surface area of cerium/zirconium mixed oxide (75:25)
+ zeolite where the cerium/zirconium mixed oxide is enhanced
with platinum and tin catalyst.
These various compositions for the inner and outer papers may be
combined in various combinations to provide for sidestream smoke control and
ash improvement.
The preferred combination is a solid solution of high surface area
cerium/zirconium mixed oxide (75:25) and zirconium oxide for the outer paper.
For the inner paper the preferred treatment composition is a solid solution of
high surface area cerium/zirconium mixed oxide (75:25) enhanced with
palladium catalyst plus zeolite enhanced with palladium catalyst. On a dry
weight basis in the outer paper coating formulation has 25% of high surface
area cerium/zirconium mixed oxide and 75% of low surface area zirconium
oxide. The inner paper on a dry weight basis has about 44% of high surface
area cerium/zirconium mixed oxide and 56% of zeolite both enhanced with
palladium.
As is appreciated by one of skill in the art, the aforementioned
procedures for providing the sidestream smoke treatment composition within or
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CA 02476971 2009-10-19
onto a desired cigarette paper may be varied with respect to the loadings
provided and the number of wraps used on a tobacco rod. For example, two or
more papers with various loadings of the composition, on both sides of the
papers, may be used such that the loading to one side is reduced, making the
coating application easier.
With any of these combinations, it has been surprisingly found that
visible sidestream smoke is virtually eliminated. At the same time, the
cigarette paper demonstrates conventional ashing characteristics. It is
particularly surprising that the simple application of the composition to the
exterior of the cigarette paper can minimize to an almost undetectable level,
visible sidestream smoke.
It is appreciated that depending upon the manner in which the
composition is used and applied to a cigarette, various processing aids and
mixtures thereof may be required to facilitate the particular application of
the
treatment composition. Such processing aids include laminating materials such
as polyvinylalcohol, starches, CMC, casein, soya and other types of acceptable
glues, various types of binding clays, inert fillers, whiteners, viscosity
modying
agents, inert fibrous material such as zirconium fibres and zirconium/cerium
fibres, such as described in PCT International Patent Application No.
WO 03/023096 entitled Zirconium/Metal Oxide Fibres, filed September 12,
2002.
Penetrating agents may also be employed to carry the composition into
the paper. Suitable diluents such as water are also used to dilute the
composition so that it may be spray coated, curtain coated, air knife coated,
rod
coated, blade coated, print coated, size press coated, roller coated, slot die
coated, technique of transfer coating and the like onto a conventional
cigarette
paper.
Desirable loadings of the treatment composition onto or into the
cigarette paper, wrapper or the like is preferably in the range of from about
2.5
g/m2 to about 125 g/m2. Most preferably the loading is in the range of about
2.5g/m2 to about 100 g/m2. Expressed as a percent by weight, the paper may
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have from about 10% to 500% by weight and most preferably about 10% to
400% by weight of the treatment composition. While these loadings are
representative for single paper, it is understood by one skilled in the art
that
these total loadings may be provided with the use of two or more papers.
The sidestream smoke reduction composition is used normally as a
water slurry of the composition. The make up of the dry composition which
can be made into a slurry, may vary depending on its use as a paper coating,
incorporation or impregnation. For example the incorporation formulation may
contain by weight from about 10% to 33% of a cerium based catalyst, 20% to
62% of an adjunct and 10% to 75% of an ash modifier. Another alternative
may contain by weight about 10% to 25% of a cerium based catalyst, 40% to
55% of an adjunct and 20% to 50% of a zeolite which is other than the adjunct.
The slurry may be incorporated in the furnish of the paper in the paper
making process, or is coated onto the paper by various coating processes or
impregnated into the paper by various impregnating methods. The preferred
average particle size of the catalyst and adjunct for the slurry is in the
range of
about 1 m to about 30 m and most preferably about 1 m to about 10 m.
The preferred relative amounts of catalyst fixed to the adjunct may range from
about 1% to 75% for cerium, more preferably from about 10% to 70%, and
even more preferably from about 20% to 70% by weight based on the total
equivalent catalyst and adjunct content. Less than 1 % of other catalyst such
as
precious metal catalyst may be fixed to the adjunct.
Although preferred embodiments of the invention have been described
herein in detail, it will be understood by those skilled in the art that
variations
may be made thereto without departing from the spirit of the invention or the
scope of the appended claims.
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